![Introduction to Detergents 3
4. Personal cleansing products. These include products for hand and body washing
as well as shampoos, conditioners, and toothpastes. They are marketed primarily
in bar, gel, and liquid forms. A major consideration in formulation of such
products is the desired consumer aesthetic such as lather, skin feel, rinsability,
smell, and taste. Formulations designed for cleaning may also provide moistur-
izing benefits, disinfectancy, conditioning, and styling effects.
Within each of these categories products are formulated with specific ingredients selected
on the basis of their ability to perform the desired function and deliver “consumer pre-
ferred” aesthetics while meeting specific cost constraints, environmental regulations, and
human safety guidelines.
In addition to these familiar consumer products, detergent formulations are used in
a number of other applications and industries. These include:
1. Environmental remediation. Surfactant systems have been developed to aid in
the clean up of contaminated groundwater supplies [1].
2. Enhanced oil recovery. Micellar and surfactant “floods” are among the most
successful methods of enhancing recovery of oil from depleted reservoirs [2].
3. Nanoegineering. Researchers have used the phase behavior of surfactants to
generate self-assembling nanosystems [3].
4. Formulation of paints and printing inks. Paints and inks comprise formulations
wherein a pigment is dispersed into a liquid phase. The dispersion is typically
achieved with surfactants and/or dispersing polymers [4].
5. Preparation and application of synthetic polymers. Emulsion polymerization
and the preparation of latexes represent one of the largest uses for surfactants
outside the cleaning arena [5].
6. Industrial/metal parts cleaning. Detergent compositions based on a CO2 bulk
phase have application in the cleaning of microelectronic components [1].
7. Medical applications. Mimics of human lung surfactants have been developed
to treat respiratory distress syndrome in premature infants [1].
8. Lubricants. While highly diverse, lubricant formulations utilize the same basic
additives: surfactants, dispersants, antiwear actives, antioxidants, corrosion
inhibitors, and viscosity modifiers.
9. Textile processing. Detergent formulations are used to clean fibers prior to
manufacture into finished textiles as well as lubricate the fibers during spinning
and weaving.
10. Agricultural preparations. Pesticide and herbicide preparations are often formu-
lated as aqueous dispersions with specific functional actives to promote even
distribution of the active during application and fast penetration of the active
upon contact with plants [6].
This diversity of application of detergents presents a rather formidable challenge when
compiling a volume such as this on detergent formulations. Accordingly, rather than try
to cover authoritatively all aspects of detergent formulations—a monumental task in its
own right— I have elected instead in this chapter to provide some general background on
detergency, the common ingredients used in detergent formulations, and general
approaches to detergent processing or manufacture. This should provide a solid framework
for the more in-depth discussions found in later chapters of this book. In addition, there
are several good reference books available on the topic of detergent formulations [7– 9].
© 2006 by Taylor & Francis Group, LLC](https://image.slidesharecdn.com/51715-250226095935-4839376d/85/Handbook-of-Detergents-Part-D-Formulation-Surfactant-Science-1st-Edition-Michael-Showell-27-320.jpg)
![4 Showell
II. COMMON DETERGENT INGREDIENTS
Modern detergents can comprise 20 or more ingredients depending on what benefits
the detergent is meant to deliver. It is not within the scope of this chapter to provide an
extensive review of the myriad ingredients used in detergent formulations. Rather, the intent
of this section is to provide a general overview of the more common elements— surfactants,
dispersing polymers, builders and chelants, bleaching systems, solvents, and performance
enhancing minors — in order to familiarize the reader with the general chemistry of detergent
formulation. Subsequent chapters will provide significantly more detail on many of these
ingredients and there are several reference books available on the topic [6–12].
A. Surfactants
Surfactants are arguably the most common ingredient of the detergent formulations
described in this book. Their primary function is to modify the interface between two or
more phases in order to promote the dispersion of one phase into another. In cleaning
formulations, for example, surfactants serve to wet surfaces and reduce the interfacial
tension between soil and water such that the soil is removed from the surface to be cleaned
and dispersed in the aqueous phase. The ability of surfactants to concentrate at interfaces
derives from their amphiphilic character—the combination of hydrophilic and hydrophobic
moieties within the same molecule.
Generally, surfactants are classified according to their hydrophilic component as
nonionic, anionic, cationic, or amphoteric. The nonionic surfactants have a hydrophilic
component that is not ionized. Typical nonionic groups consist of polyoxyethylene, poly-
oxypropylene, alkanolamides, or sugar esters. As the name implies, the hydrophilic com-
ponent of anionic surfactants comprises an anionic group, typically a sulfate, sulfonate,
or carboxylate moiety. Likewise, the cationic surfactants comprise molecules containing
a positively charged group such as a quaternary amine. The amphoteric surfactants are
perhaps the most unique in that they comprise a hydrophilic group containing both anionic
and cationic character such as the amino acids.
Typical hydrophobes for surfactants are the alkyl chains between C10 and C20.
However, in some specialty surfactants the hydrophobe may consist of polysiloxane or
Until the 1940s detergents were formulated principally with the sodium or potassium
salts of C12–C18 chain length fatty acids. The synthesis of surfactants from petroleum
feed stocks in the late 1940s spurred the development of soap-free synthetic detergents
that proved much more effective for cleaning in cooler wash temperatures and in hard
water. Today, the linear alkyl benzene sulfonates, alkyl sulfates, alkyl ethoxy sulfates, and
alkyl ether ethoxylates are the workhorse surfactants for most detergent formulations.
Alkyl polyglucosides, alkyl glucosamides, and methyl ester sulfonates are also widely
used [13]. Recent attention has been given to the use of internal methyl branched alkyl
chains as the hydrophobe for certain anionic surfactants [14]. Such branching promotes
improved solubility, particularly in cold, hard water.
For systems where water is not the continuous phase a variety of specialty surfactants
are used. Examples include the polydimethylsiloxane-based surfactants for use in highly
hydrophobic media and the acrylate-polystyrene co-polymers designed by DiSimone and
colleagues for applications in cleaning systems utilizing condensed phase CO2 [15].
B. Dispersing Polymers
The suspension of solids or liquids in a continuous phase is a critical aspect in the
formulation of paints, inks, coatings, and agricultural products such as herbicides.
Suspension of soil after removal from a surface is important in cleaning applications to
© 2006 by Taylor & Francis Group, LLC
perfluorocarbon backbones. Examples of common surfactants are shown in Table 1.](https://image.slidesharecdn.com/51715-250226095935-4839376d/85/Handbook-of-Detergents-Part-D-Formulation-Surfactant-Science-1st-Edition-Michael-Showell-28-320.jpg)
![Introduction to Detergents 5
avoid redeposition of the soil back onto the cleaned surface. Generally speaking, the
particles to be suspended are sufficiently large that definite surfaces of separation exist
between the dispersed phase and the dispersion medium [16]. In order to keep the
dispersed phase stable it is important to adsorb functional actives at these surfaces to
prevent aggregation. This is one of the critical functions of surfactants. However, another
class of detergent actives has been developed to assist in particle suspension—the
polymeric dispersants.
Table 1 Common Surfactants Used in Detergent Formulations
O
CH3-CH2-(CH2)nCO-CH3
SO3
Na
Methyl ester sulfonate
O
CH3-(CH2)nCONa
Fatty Acid Soap
CH3-(CH2)n-O-(CH2-CH2-O)xSO3Na
Alkyl Ether Sulfate
CH3-(CH2)n-CH-(CH2)m-CH3
SO3Na
Paraffinsulfonate
CH3-(CH2)n-CH-(CH2)m-CH3
Linear Alkyl Benzene Sulfonate
Anionic
Structure
Type
OH OH
CH3-(CH2)n-C-N-CH2-CH-CH-CH-CH-CH2OH
O CH3 OH OH
N-methylglucosamide
CH3-(CH2)n-C-NH-CH2-CH2OH
Alkyl monoethanolamide
CH3-(CH2)n-N(CH3)2 O
Amine oxide
CH3-(CH2)n-O-(CH2-CH2O)nH
Fatty alcohol ethoxylate
Nonionic
CH3-(CH2)n-N+(CH3)3Cl-
Quaternary
monoalkylammonium
chloride
Cationic
O
CH3-(CH2)n-N+(CH3)2-CH2-CH-CH2-SO3
-
OH
Alkyl sulfobetaine
CH3-(CH2)n-C-NH-(CH2)3-N+(CH3)2-CH2-C-O-
O O
Amidopropyl betaine
Amphoteric
SO3Na
© 2006 by Taylor & Francis Group, LLC](https://image.slidesharecdn.com/51715-250226095935-4839376d/85/Handbook-of-Detergents-Part-D-Formulation-Surfactant-Science-1st-Edition-Michael-Showell-29-320.jpg)
![6 Showell
In general two types of polymeric dispersants are used in detergent formula-
tions—polymers comprising ionically charged groups and nonionic polymers. Typical of
the ionic dispersing polymers are the homopolymers of acrylic acid and copolymers of
acrylic and maleic acids which are widely used in laundry detergent formulations:
where Z is either hydrogen, in the case of homopolymers of acrylic acid, or a carboxyl
group in the case where the monomer unit is maleic acid. Polymers of this type are
commonly found in powdered laundry detergent formulations where they assist in cleaning
by acting as a dispersant for soil and inorganic salts, provide alkalinity control, and serve
as crystal growth inhibitors [17].
Anionic dispersing polymers comprising carboxyl and sulfonate groups in the same
backbone have been developed for use in water treatment where they act to prevent
formation of inorganic scale. The polymers are generally of the following hybrid type:
The key features are A and B. A, the sulfonated monomers, include the following
groups:
H H
C C
Z COOH n
Sulfonated
monomer(s)
Optional
neutral
monomer(s)
Optional
charged
monomer(s)
A B C D
Carboxylate
monomer(s)
SO3H
O
N
H
R
SO3H
R1
R2
SO3H
O
O
O
n
AMPS
SO3H
N
H
SO3H
SMS
O
q
(OR)nSO3H
(OR)qSO3H
(CH2)nSO3H
SO3H
O
OH
AHPS
OH
HO3S
SO3H
O
R
SPMS
SSS
© 2006 by Taylor & Francis Group, LLC](https://image.slidesharecdn.com/51715-250226095935-4839376d/85/Handbook-of-Detergents-Part-D-Formulation-Surfactant-Science-1st-Edition-Michael-Showell-30-320.jpg)
![Introduction to Detergents 7
B usually comprises maleic, acrylic, or methacrylic acid. C and D are optional but can
include acrylamide, vinyl acetate (alcohol), acrylate esters, cationics, or phosphonates [18].
Carboxymethylcellulose is another example of an anionic dispersing polymer widely
used in laundry detergent applications
Considerable attention has been paid over the years to the preparation of biodegrad-
able dispersants [19–21]. Examples include polyamino acid polymers such as polyaspartate
prepared from the catalytic condensation of polyaspartic acid [22] and functionalized
polysaccharides such as oxidized starches [23]. Recently, a novel process was reported
for the preparation of functionalized polyaspartic acid polymers that expands the utility
of these materials as dispersants for a variety of applications [24].
Cationic dispersants are less commonly used although some amphiphilic structures
have been described as effective dispersants in high salt content media [25]:
Amphoteric dispersing polymers of the types shown below have also been reported
to be good clay and particulate dispersants in certain laundry detergent formulations [26]:
O
OH
O
O
OH
n
CH2OCH2COO−
[CH CH]m
C
N
C O
O
CH2
N+
CH3
CH3
H3C
[CH2-CH]n
Cl−
(CH2CH2O)24SO3Na CH3
NaO3S-(OCH2CH2)24N N-(CH2CH2O)24SO3Na
(CH2CH2O)24SO3Na
+ Cl−
+ Cl−
CH3
(CH2CH2O)20SO3Na (CH2CH2O)20SO3Na
NaO3S(OCH2CH2)20-N N-(CH2CH2O)20SO3Na
+
Cl−
+
Cl−
+
Cl−
(CH2CH2O)20SO3Na
N
© 2006 by Taylor & Francis Group, LLC](https://image.slidesharecdn.com/51715-250226095935-4839376d/85/Handbook-of-Detergents-Part-D-Formulation-Surfactant-Science-1st-Edition-Michael-Showell-31-320.jpg)
![8 Showell
Nonionic polymers include polyethylene glycol, polyvinyl alcohol, and random and
block ethoxy propoxy copolymers. Graft copolymers of polyalkylene oxide and vinyl
acetate are reported to be effective antiredeposition agents for hydrophobic surfaces like
polyester fabric [27].
C. Builders and Chelants
Metal ion control is a common need in many detergent formulations. For example, in
aqueous cleaning applications the presence of Ca2+ in the water can lead to the precipitation
of anionic surfactant reducing the effective concentration available for cleaning. Fatty
acids can precipitate as calcium soaps resulting in the formation of soap scum on hard
surfaces, and many soils, especially inorganic clays, will precipitate with calcium leading
to redeposition of the soil onto the surface being cleaned. Builders—a generic term used
to refer to any number of materials whose primary function is the removal of Ca2+ and
Mg2+ ions from aqueous solutions—and chelants are widely used in the formulation of
various detergents.
Sodium tripolyphosphate (STPP) is among the best known and widely used detergent
builder. In laundry detergent formulations it serves not only as an extremely effective
calcium control agent but also provides dispersion, suspension, and anti-encrustation
benefits. However, environmental concerns associated with large-scale release of phos-
phates into the environment lead to the development of a number of substitutes. Citric
acid and sodium nitrilotriacetate are representative of soluble detergent builders
Sodium carbonates and noncrystalline sodium silicate form sparingly soluble
precipitates with calcium and are frequently used in powdered detergent formulations
where they also provide a source of alkalinity. However, to avoid encrustation of the
calcium carbonate/silicate onto surfaces these building agents generally are co-for-
mulated with a dispersing polymer like the polyacrylate/maleic acid copolymers
described above and crystal growth inhibitors like HEDP (1-hydroxyethane diphos-
phonic acid).
Insoluble builders include the zeolites and layered silicates, which bind calcium via
an ion exchange mechanism [28]. Zeolite A, Na12(AlO2)12(SiO2)12∑27H2O, is the principal
alternative to phosphate as a detergent builder. The Na+ ions are exchangeable for Ca2+
while the larger hydration shell around Mg2+ tends to impede exchange.
Citric acid is also an excellent chelant for metal ions other than calcium and can
be employed where the removal of transition metals such as copper, zinc, and iron is
important. Other commonly used detergent chelants include ethylenediaminetetraacetate
(EDTA)
CH2COOH
HO C COOH
CH2COOH
CH2COONa
N CH2COONa
CH2COONa
Citric Acid Sodium nitrilotriacetate
© 2006 by Taylor & Francis Group, LLC](https://image.slidesharecdn.com/51715-250226095935-4839376d/85/Handbook-of-Detergents-Part-D-Formulation-Surfactant-Science-1st-Edition-Michael-Showell-32-320.jpg)
![10 Showell
generate peracetic acid. NOBS reacts in much the same way but generates the more
hydrophobic pernonanoic acid.
A frequently studied approach to bleaching involves the use of transition metal
catalysts [29]. Complexes of metals like Mn, Fe, Cu, and Co with certain organic ligands
can react with peroxygen compounds to form reactive intermediates, which can poten-
tially result in powerful bleaching action. Typical of these systems are the structures
shown below:
E. Solvents
The selection of solvents for use in detergent formulation depends on the nature of the
actives being formulated, the intended application of the detergent, and economics. Water
is the dominant solvent in most household and industrial cleaning formulations. Generally
speaking, water-based detergents are less toxic, more environmentally friendly, cheaper,
more surface compatible, and easier to handle than petroleum-based solvents. However,
many common detergent actives have limited solubility in water requiring formulation of
a co-solvent and/or hydrotrope. Typical co-solvents used in household cleaning formula-
tions include ethanol, glycerol, and 1,2-propanediol.
A hydrotrope, also called a “coupling agent,” is an organic compound that increases
the ability of water to dissolve other molecules. Hydrotropes are commonly used in
aqueous-based detergent formulations containing high concentrations of surfactant in order
to achieve a shelf-stable, clear, isotropic fluid. Common hydrotropes are sodium xylene
sulfonate, sodium toluene sulfonate, and sodium cumene sulfonate. A typical liquid dish-
aqueous-based detergent system comprising both a co-solvent (in this case ethanol) and
a hydrotrope (sodium cumene sulfonate):
Of course there are applications where water must be avoided. Perhaps the most
recognizable of these is in the dry cleaning of fine textiles like silk and wool. Historically,
this process has used volatile organic solvents like perchloroethylene as the bulk cleaning
fluid. Concerns that such solvents may represent human and environmental safety hazards
has recently lead to the development of alternative processes utilizing condensed phase
CO2 [30] and certain silicone oils like cyclic decamethylpentasiloxane, D5 [31]. Detergent
formulations for use in such systems will typically comprise a solvent compatible with
the bulk phase (e.g., polydimethylsiloxane in the case of the D5 system) and capable of
solublizing the cleaning actives to be introduced into the bulk phase.
From US Patent 5, 798, 326 From US Patent 5, 246, 612
Cl
NH3
NH3
NH3
H3N Co
NH3
Me
N
Me
Me
Me Me
(PF6
−
)2
N
N N
O
O
O
MnIV MnIV
Me
N
N
2+
© 2006 by Taylor & Francis Group, LLC
washing formulation, shown below in Table 2, is a good example of a surfactant-rich](https://image.slidesharecdn.com/51715-250226095935-4839376d/85/Handbook-of-Detergents-Part-D-Formulation-Surfactant-Science-1st-Edition-Michael-Showell-34-320.jpg)
![Introduction to Detergents 11
Other areas where water is not a suitable solvent include the cleaning of certain
metal parts and electronic circuit boards. Here chlorinated hydrocarbons like perchloro-
ethylene or methylene chloride, or volatile organics like methyl ethyl ketone have histor-
ically been used but regulatory pressure has resulted in a shift to more environmentally
friendly solvents like terpenes and dibasic esters.
F. Performance Enhancing Minor Ingredients
Depending upon the end use of the detergent formulation and the benefits to be delivered
a number of performance enhancing minor ingredients may be used. These include:
1. Enzymes. Used primarily in cleaning formulations enzymes promote soil
removal by the catalytic breakdown of specific soil components. Proteases
(enzymes that degrade protein) are the most common of all the detergent
enzymes but amylases (starch degrading), lipases (lipid degrading), and cellu-
lases (cellulase degrading) are also used [32].
2. Brighteners/fabric whitening actives. These materials enhance the visual appear-
ance of white surfaces, typically cotton fabrics, by absorbing ultraviolet (UV)
radiation and emitting via fluorescence in the visible portion of the spectrum.
Typical whitening actives are built from direct linkage or ethylenic bridging of
aromatic or heteroaromatic moieties.Among the most commonly used whiteners
in laundry detergents are the derivatives of 4,4-diaminostilbene-2,2-disulfonic
acid.
3. Foam boosters. In some applications, most notably hand dishwashing and sham-
poos; it is desirable for the detergent formulation to generate a large-volume,
stable foam. While most surfactants are capable of generating and sustaining
foam in the absence of soil, these foams rapidly collapse in the presence of soil,
especially particulate and fatty soils. In applications where foam must be main-
tained throughout the course of detergent use, specific boosters may be added.
Proteins have been shown to promote foaming in certain systems [33] especially
in food and beverage applications [34]. Alkanolamides, particularly mono- and
diethanolamides, are effective foam stabilizers used in dishwashing liquids and
Table 2 Typical Hand Dishwash Formulation
Ingredient Weight %
C12-C13 Alkyl ethoxy (E1.4) sulfate 33
C12-C14 Polyhydroxy fatty acid amide 4
C14 Amine oxide 5
C11 Alcohol ethoxylate E9 1
MgCl2 0.7
Calcium citrate 0.4
Polymeric suds booster 0.5
Ethanol 1
Sodium cumene sulfonate 0.5
Minors and water Balance
© 2006 by Taylor & Francis Group, LLC](https://image.slidesharecdn.com/51715-250226095935-4839376d/85/Handbook-of-Detergents-Part-D-Formulation-Surfactant-Science-1st-Edition-Michael-Showell-35-320.jpg)
![12 Showell
shampoos [7]. Polymeric foam boosters of the type shown below have also
proved effective in hand dish wash applications [35]:
4. Antifoam agents. In many applications it is desirable to minimize foam gener-
ation. For example, in automatic dishwashing foam generation can interfere
with rotation of the spray arm leading to degradation in the performance of the
dishwasher. Antifoam agents act to reduce or eliminate foams. They either
prevent formation of the foam or accelerate its collapse. Alkyl ethoxylate non-
ionic surfactants are commonly used as foam control agents in detergents where
application temperatures exceed the cloud point of the surfactant—the temper-
ature at which the surfactant becomes insoluble. The insoluble nonionic-rich
surfactant phase acts to break foam lamella promoting foam collapse.
Hydrophobic particulate antifoam agents physically break foams by lodging
in the foam film promoting rapid localized draining in the region of the film in
contact with the particles. The calcium soaps of long-chain fatty acids are
effective at foam control as are hydrophobic silica particles. Particularly effec-
tive antifoams are comprised of colloidal hydrophobic silica particles suspended
in a silicone oil like polydimethyl siloxane. The hydrophobic oil promotes
spreading of the particles at the air-water interface thereby ensuring entrapment
in the foam film and subsequent foam disruption [7].
5. Thickeners. It is often desirable to modify the rheology of a detergent formu-
lation to fit a particular application. For example, gel-type automatic dishwash-
ing detergents are thickened to help suspend phosphate and other solids that
would otherwise separate out from the liquid phase. Thickening can be achieved
through the use of inorganic electrolytes, e.g., NaCl; clays, such as laponite or
hectorite; or a high-molecular-weight polymer like carboxymethylcellulose,
guar, or xanthan gum. The Carbopol“ series of polymers from Noveon, homo-
and copolymers of acrylic acid cross linked with polyalkenyl polyether, are
particularly effective thickeners for household cleaning detergent formulations.
6. Soil release polymers. Soil release refers to the enhanced removal of soil from
a surface as a result of modification of that surface with a specific agent, typically
a polymer that alters surface polarity thereby decreasing adherence of soil. Used
primarily in laundry detergent formulations soil release polymers provide sig-
nificant changes in surface energy, which in turn can lead to dramatic improve-
ments in the removal of soils. Carboxymethyl cellulose (CMC) is the
archetypical soil release polymer. CMC absorbs onto cotton fabric owing to the
similarity in structure between the cellulose backbone of CMC and the cellulose
polymer of cotton fibers. Once absorbed, the carboxyl moiety creates a high
net negative charge on the fabric surface effectively repelling negatively charged
soils, especially clays [7].
n
O
N
O
© 2006 by Taylor & Francis Group, LLC](https://image.slidesharecdn.com/51715-250226095935-4839376d/85/Handbook-of-Detergents-Part-D-Formulation-Surfactant-Science-1st-Edition-Michael-Showell-36-320.jpg)
![Introduction to Detergents 13
Other soil release polymers used in detergents are derivatives of polyester-polyether
block copolymers that are capped with nonionic (ethoxylates), anionic (typically sul-
fonates), or cationic (typically quaternary amines) groups to achieve deposition and release
from specific formulations [36].
III. REPRESENTATIVE DETERGENT FORMULATIONS
This section provides examples of detergent formulations comprising the ingredients
discussed in Section II. This is by no means an exhaustive compilation. Rather, the intent
is to illustrate the variety of detergent formulations and how the composition of the
formulation varies depending on the intended use. Subsequent chapters of this book will
provide more detail on detergent formulations for specific applications.
A. Laundry Detergent Formulations
B. Dishwash Detergent Formulations
Examples of granular detergent formulations for use in automatic dishwashing
C. Hard Surface Cleaning Formulations
D. Personal Care Detergent Formulations
E. Oral Care Detergent Formulations
In the toothpaste formulations illustrated in Table 11 note the use of silica as an
abrasive cleaning agent.
F. Agricultural Detergent Formulations
Herbicidal compositions typically comprise an aqueous emulsion of the active with appro-
priate surfactants to insure effective spreading and penetration of the herbicide into plants.
Typical compositions comprising the well-known herbicidal active glyphosphate are illus-
G. Automobile Detergent Formulations
A variety of detergent compositions are used in the care and maintenance of automobiles.
finish to the exterior of automobiles.
A formulation designed to remove grease from automobile engines and engine
© 2006 by Taylor & Francis Group, LLC
Examples of granular laundry detergent formulations are shown in Table 3.
Table 4 illustrates typical liquid laundry detergent formulations.
Examples of typical liquid hand dishwash formulations are provided in Table 5.
applications are illustrated in Table 6.
Examples of liquid hard surface cleaning formulations are illustrated in Table 7.
Table 8 provides examples of typical shampoo formulations.
Examples of body washes are provided in Table 9.
An oral mouthwash formulation is illustrated in Table 10.
Examples of Toothpaste formulations are provided in Table 11.
trated in Table 12.
composition in Table 13 illustrates a formulation designed to clean and provide a waxed
compartments is illustrated in Table 14.
Chapter 8 provides an extensive review of the components used in such formulations. The](https://image.slidesharecdn.com/51715-250226095935-4839376d/85/Handbook-of-Detergents-Part-D-Formulation-Surfactant-Science-1st-Edition-Michael-Showell-37-320.jpg)
![Introduction to Detergents 21
mediated removal of soil from a surface. Soil removal mechanisms can be considered to
comprise several steps:
1. Surfactant transport to an interface. This can occur with the surfactant in the
monomeric form, in which case kinetics of transport are fairly rapid (10–5
cm2/sec), or with the surfactant in aggregated or micellar form in which case
the kinetics of transport are relatively slow (10–7 cm2/sec). The kinetics of
surfactant transport and adsorption at the interface can be measured via dynamic
interfacial tensiometry [37–41].
2. Adsorption of surfactant at the solution/soil interface, solution/atmosphere inter-
face, and surface/solution interface. This step results in lowering of the interfa-
Table 16 Enzymatic Based Detergents for Cleaning Food Processing Equipment
Ingredients Weight %
Examples A B C D
Triethanolamine 2 2 2 2
Sodium metabisulfite 1 1 1 1
Propylene glycol 12 12 15 15
Sodium xylene sulfonate 20 20 20 20
Ethoxylated propoxylated nonionic 25 25 25 25
Protease 6.3 6.3 3.1 3.1
Water Balance Balance Balance Balance
Source: From U.S. Patent 6,197,739 B1 to Ecolab Inc.
Table 17 Representative Aqueous-Based Metal Cleaning Detergents
Ingredients Weight %
Examples A B C D
Sodium carbonate 3 3 3 3
Borax 0.3 0.3 0.3 0.3
N-octylpyrrolidone — — — 2
1,2,3-Benzotriazole 0.3 0.3 0.3 0.3
C9-C11 Alcohol ethoxylate (E2.5) 2 — — 2
C9-C11 Alcohol ethoxylate (E6) 2 — — 2
C12-C15 Alcohol ethoxylate (E9) — 4 — —
C14-C15 Alcohol ethoxylate (E7) — — 4 —
Acrylic acid polymer 0.5 0.5 0.5 0.5
NaOH 0.5 0.5 0.5 0.5
Sodium silicate 2 2 2 2
Sodium nonanoate 6.5 6.5 6.5 6.5
Water Balance Balance Balance Balance
Source: From U.S. Patent 6,124,253 to Church & Dwight Co.
© 2006 by Taylor & Francis Group, LLC](https://image.slidesharecdn.com/51715-250226095935-4839376d/85/Handbook-of-Detergents-Part-D-Formulation-Surfactant-Science-1st-Edition-Michael-Showell-45-320.jpg)
![22 Showell
cial energies at each of these interfaces. Adsorption is driven by the surfactant
packing parameter (P = V/aoI) where V is the volume described by the hydro-
phobic portion (alkyl chain) of the surfactant, ao is the mean cross-sectional
area of the surfactant head group, and l is the all trans alkyl chain length of the
hydrophobe (alkyl chain) [42]. Surfactants with 0 < P < 1/3 form micelles in
aqueous solution. Surfactants with 1/3 < P < 1/2 form wormlike micelles and
surfactants with 1/2 < P < 1 display vesicle formation. Controlling the surfactant
packing parameter close to 1 (flat surfactant film) promotes strong adsorption
and delivers very low-soil/bulk phase equilibrium interfacial tensions.
3. Formation of a surfactant:soil complex. This typically is represented as surfac-
tant coating the soil to be removed either in a monolayer, or, at high enough
surfactant concentrations with bilayer structures. During this step surfactant can
promote solid soil softening and liquifaction. This is a critical step to promote
roll-up or emulsification that takes place only with liquid soils.
4. Desorption of the surfactant:soil complex. For oily soils this occurs either via
the classical roll-up mechanism or by solubilization of the oil into micellar
surfactant aggregates. In the case of liquid soil, the energy required to remove
the soil can be expressed as gow (1+cosq) where gow is the soil/solution interfacial
tension and q is the soil/substrate contact angle. For large contact angle (180o)
roll-up of the soil occurs. For small contact angles emulsification via low gow is
the major mechanism of soil removal.
5. Transport of the surfactant:soil complex away from the surface. In the case of
greasy soils that have lower density than the bulk solution, the soil simply floats
to the surface. In other cases, mechanical energy or agitation is critical to move
the surfactant:soil complex away from the interface.
6.
The work, WR, to move soil (o) from the surface (s) to the bulk phase (w) can be
directly related to the interfacial tensions of the various interfaces through the following
[7]:
WR = gsw + gow - gos (1)
where gsw is the interfacial tension between the surface and bulk phase, gow is the interfacial
tension between the soil and the bulk phase, and gos is the interfacial tension between the
soil and the surface. From this equation it can be seen that the work required to remove
soil from a surface is reduced when the interfacial tensions between the surface and bulk
phase and soil and bulk phase are minimized and the interfacial tension of the soil-surface
is increased. This is exactly the effect that surfactants have. By adsorbing at the surface,
bulk-phase, and soil interfaces surfactant lowers interfacial energies, decreasing the free
energy associated with moving the soil from the surface into the bulk phase. Surfactant
adsorption causes the surface/bulk phase (gsw ) and soil/bulk phase (gow) interfacial tensions
to drop while the interfacial tension between soil and surface (gos) increases thereby
facilitating movement of the soil into the bulk phase.
One aspect of the above that is often ignored is step one, transport of surfactant to
the various interfaces. The presence of monomeric surfactant is critical to rapid transport
of surfactant to the interface and rapid lowering of the interfacial tensions (IFT). However,
solubilization is dependent on the presence of micelles. As surfactant concentration in
solution is raised aggregates (micelles) form and at a certain concentration (critical micelle
concentration, CMC) the monomer concentration of surfactant remains constant and addi-
© 2006 by Taylor & Francis Group, LLC
Stabilization of the dispersed soil to prevent redeposition (see Section IV B).](https://image.slidesharecdn.com/51715-250226095935-4839376d/85/Handbook-of-Detergents-Part-D-Formulation-Surfactant-Science-1st-Edition-Michael-Showell-46-320.jpg)
![Introduction to Detergents 23
tional surfactant resides in micelles. The formation of micelles reduces the capacity of the
surfactant to adsorb at the interface and reduce IFT that is critical in step 2. Therefore,
there is an optimum CMC that must be achieved in order to optimize steps 1 and 2 above
while still allowing efficient solubilization. This optimum is dependent on the nature of
the soil being removed, the substrate (hydrophobicity), and the surfactant system used.
The mechanism outlined above is generally applicable for oily soils. For particulate
soils consideration of the electrostatic and van der Waals forces of attraction between the
particle and the surface need to be considered because most particulate dirt and most
surfaces tend to be charged due to the presence of surface exposed silicic acid, hydroxyl,
or carboxyl groups [43]. .
Again, the process can be described in a series of steps [44]. In the first step a soil
particle, P, adhering to a surface, S, is removed a distance d with no penetration of liquid
between the soil and the surface. The process requires work input, w1, to overcome the
van der Waals attraction between P and S. Then detergent solution penetrates the space
between P and S, allowing surfactant to adsorb at the solution-particle interface and the
surface-solution interface, and a net sum of work, w2 , is obtained. The total work done
in this first step is:
W1 = w1 - w2 (2)
In the second step the particle is removed from the surface to a distance large enough
that there are effectively no forces of interaction between P and S. The work for this
second step, W2, is composed of contributions from van der Waals attractions and the
electrostatic repulsions between P and S, and is equal to the total potential energy of the
system at the distance d such that W2 = -jd and the work done for the total process of
removing an adhering particle, P, from surface S is equal to the sum of W1 and W2 or:
SW = W1 + W2 = w1 - w2 - jd (3)
The work, w2, created when surfactant adsorbs onto the particle and the surface can,
in the first approximation, be described as the sum of various interfacial energies, similar
to Eq. (1):
w2 = gsp - gsw - gpw (4)
where gpw is the interfacial tension between the particle and the solution phase.
According to Eq. (3) the removal of particulate soil becomes easier as the total work to
remove the particle, SW, becomes smaller. The addition of surfactant reduces both gsw and
gpw such that w2 increases, which helps to lower the total work of removal. In addition,
the total potential energy of the system jd is the sum of the attractive van der Waals
interactions, jd,A, and the repulsive interactions, jd,R, due to surface charges. The adsorp-
tion of surfactant, especially anionic surfactant, at the surface-solution and particle-solution
interfaces serves to decrease the attractive force and increase the repulsive force thereby
promoting removal to a distance where there are no longer any attractive forces between
particle and surface.
B. Suspension Mechanisms
Once material is removed from a surface it must be suspended in the bulk phase to avoid
redeposition. For hydrophobic liquid soils in aqueous media, suspension is typically
accomplished by entrapment of the soil within the surfactant micelle or vesicle. For
particulate soils suspension is often best achieved by adsorption of a charged polymer
onto the surface of the particle thereby increasing electrostatic repulsion between particle-
© 2006 by Taylor & Francis Group, LLC](https://image.slidesharecdn.com/51715-250226095935-4839376d/85/Handbook-of-Detergents-Part-D-Formulation-Surfactant-Science-1st-Edition-Michael-Showell-47-320.jpg)
![24 Showell
particle and particle-surface interactions. There are two general mechanisms for suspend-
ing soil in solution— electrostatic repulsion and steric stabilization.
In polar media, most substances will acquire a surface electric charge as a result of
ionization of surface chemical groups, ion adsorption, and ion dissolution [16]. In aqueous
solutions most surfaces and most soil particles are negatively charged. As a result both
soil and surface possess an electrical double layer. The electrical double layer is comprised
of a compact layer of ions of opposite charge to the surface and a more diffuse double
layer comprised of counter- and co-ions distributed in a diffuse manner in the polar
medium. As described in Section IV A, the total potential energy for a system comprised
of a particle at some distance, d, from a surface is the sum of the attractive force, jd,A,
and the repulsive force jd,R. When two particles of the same net surface charge approach
one another, or when a particle approaches a charged surface, they repel each other as
their double layers start to overlap. The particles have to overcome this electrical barrier
in order to get close enough for van der Waals attraction to take over. When the potential
energy barrier jd,R is high particles tend to stay dispersed in the bulk phase. However, if
the electrical double layer is compressed by high ionic strength or shielded by adsorption
of an organic layer coalescence and aggregation can occur resulting in redeposition of soil
particles back onto the surface. Electrostatic repulsion is best achieved in low ionic strength
media where the electrical double layer on particles and surfaces is diffuse. An alternative
strategy is to adsorb a charged polymer, such as the acrylic acid polymers described in
Section II B, or a charged surfactant onto the surface.
When particles having adsorbed layers (polymer or surfactant) collide, their adsorbed
layers may be compressed without penetrating. This results in reduced configurations
available to the adsorbed layer. In thermodynamic terms the reduction in potential con-
figurations is expressed as a decrease in entropy for the system or an increase in free
energy. This increased free energy of stabilization results from the “elastic” effect of
colliding adsorbed layers and is referred to as steric stabilization. The positive free energy
change is related to both the enthalpy and entropy change by DG = DH – TDS. Stabilization
can therefore come either as a result of a positive change in enthalpy or a decrease in
entropy. A positive DH reflects the release of bound solvent from the polymer chains as
they interact and a negative DS results from the loss of configurational freedom of the
polymer [16]. Steric stabilizers are usually block copolymers that make up a hydrophobic
part (e.g., polyethyleneterepthalate) which attaches to the particle surface and a hydrophilic
part (e.g., polyethylene glycol) which trails out into the bulk solution.
Effective detergency results when the detergent formulation is designed to maximize
four basic properties; penetration, wetting, dispersion, and emulsification. These four
factors combined determine the ultimate effectiveness of the detergent formulation. Sub-
sequent chapters of this book provide significantly more detail on how to design effective
detergents for a variety of specific applications.
ACKNOWLEDGMENTS
I thank each of the authors of the individual chapters in this work for their effort and
dedication in bringing the vision to life. Thanks to all of my friends and colleagues at
Procter & Gamble who contributed their time and expertise to review and critique of the
contributions.
© 2006 by Taylor & Francis Group, LLC](https://image.slidesharecdn.com/51715-250226095935-4839376d/85/Handbook-of-Detergents-Part-D-Formulation-Surfactant-Science-1st-Edition-Michael-Showell-48-320.jpg)
![28 Ashrawi and Smith
In the trial-and-error approach, component variations are usually fairly small, which
limits the composition space that is investigated to small perturbations around the starting
formulation. Because responses are optimized one at a time, one is never quite sure that
all properties and performance responses have been optimized. Furthermore, one is not
sure if the observed optimum is local within the small composition space that was inves-
tigated, or global within a much larger composition space. Finally, since this approach
does not yield maps of performance over the composition space, it is not possible to predict
the behavior of new formulations without continuous tweaking.
An alternative, and more informative, approach is the use of statistical experimental
design to optimize formulations. We have used various types of statistically designed
experiments in our laboratories to help develop and optimize formulations for different
applications [1,2]. Factorial screening designs are extremely helpful in identifying the vital
factors or components that affect the desired product. Response surface designs are useful
in locating the ideal criteria or process settings that yield optimum performance. And
finally, mixture designs yield performance maps over a defined composition space,
enabling us to discover the optimum formulation and to predict performance in other
regions of the defined composition space.
Figure 1 describes the framework of our statistical experimental approach to formu-
lation development. Beginning with a well-defined goal of achieving certain performance
criteria, physical properties, and cost, we conduct screening experiments to determine the
components that would be vital to achieving our goal. Once the trial mixtures are prepared
and the desired property or performance response is measured, the results can be analyzed
Figure 1 Framework for formulation development using statistical experimental design.
Model
Generation
& Validation
Goal Definition
Screening Design
Mixture Design
Properties
Optimization
Data Analysis
Scenario
Analysis
Performance
© 2006 by Taylor & Francis Group, LLC](https://image.slidesharecdn.com/51715-250226095935-4839376d/85/Handbook-of-Detergents-Part-D-Formulation-Surfactant-Science-1st-Edition-Michael-Showell-52-320.jpg)
![Statistical Mixture Design for Optimization of Detergent Formulations 29
to determine how each component affects a particular response as the amount of that
component is changed. Next, we use the components that most affect the measured
response to develop a suitable mixture design. The mixture design trial formulations are
prepared and the physical properties and performance responses are measured and
recorded. A model that best fits the data is then generated and validated by exploring its
statistical significance. With a good-fit model, one can then proceed to optimization of the
composition to meet the required performance criteria.
The authors have used mixture design experiments to optimize different types of
cleaning formulations. Examples include laundry liquids, dishwashing liquids, and hard
surface cleaners. Many times the results indicate that improvements in one property come
at the expense of another. By measuring multiple responses it is possible to optimize the
formulation to get the best overall performance for a wide variety of performance factors.
Mixture design experiments can also be used to optimize formulation robustness. This
allows us to obtain a product that can be easily manufactured on a commercial scale.
II. MIXTURE DESIGN EXPERIMENTS
It is not the purpose of this chapter to delve into all the mathematical details of mixture
design experiments. Our intent is to present only the major salient points to better under-
stand the basic assumptions behind the technique. For a more complete discussion of
statistics as applied to mixture designs, the reader is invited to peruse the pertinent literature
[3–5]. In a mixture design experiment, two or more individual ingredients are blended
together to produce a final product or formulation. Measurements of the physical properties
and the performance for several different trial blends are made and the results used to find
the best overall result. The measured properties depend only on the relative proportions
of the individual ingredients and not on the total amount present.
The defining feature of a mixture design is that the proportions of the ingredients
sum to unity. In mathematical terms, if the number of ingredients in the system is given
by q, and the proportion of the ith component is given by xi
Because of the restrictions imposed by Eqs. (1) and (2), the experimental region of
interest is a (q-1) dimensional space. For q = 2, the dimensional space is a straight line
and can be represented on a conventional x-y plot. For q = 3, the dimensional space is an
equilateral triangle and can be represented in triangular coordinates. For q = 4, the
dimensional space is a tetrahedron. Since the proportions sum to unity, the xi are con-
strained variables; varying the proportion of one component will change the proportion
of at least one other component in the mixture.
In mixture design experiments, the experimental data are defined in a quantitative
fashion, the purpose of which is to model the mixture behavior using some form of a
mathematical equation. This allows for predictions of the response for any combination
of ingredients and allows for a measure of the influence for each component or combination
of components on the measured response.
For and (1)
(2)
xi ≥ 0 i q
= 1 2
, ,...,
χ χ χ χ
i q
i
q
= + + + =
=
∑ 1 2
1
1
.....
© 2006 by Taylor & Francis Group, LLC](https://image.slidesharecdn.com/51715-250226095935-4839376d/85/Handbook-of-Detergents-Part-D-Formulation-Surfactant-Science-1st-Edition-Michael-Showell-53-320.jpg)
![30 Ashrawi and Smith
The data from a mixture design experiment are modeled in the following fashion.
Assuming that the response factor η depends only on the proportions of the individual
components:
(3)
We assume that the function is continuous for all χi, and can be represented by a
first- or second-order polynomial. Only on rare occasions is a third-degree (cubic) poly-
nomial necessary to represent the data.
In actual practice, it is convenient to use a canonical form for the polynomial fitting
equation. This acts to reduce the number of fitting parameters compared to a standard
power series polynomial expression. Canonical polynomial expressions were developed
by Henri Scheffé in the early 1950s specifically for mixture design experiments [6,7]. The
Scheffé quadratic polynomial for two components is given by
(4)
The Scheffé form of the fitting equation is also easy to interpret. The coefficients
for the main effects are responses for the pure components. The coefficients for the
mixed terms give a measure of positive or negative deviation from the response
predicted for ideal mixing of the individual components.
Up until this point, we have not discussed the experimental error associated with
the measured responses. Experimental error can arise from various sources including
sample preparation, analytical methodology, mechanical noise, and equipment problems.
In an experimental program consisting of N trials, the observed value of the response in
the uth trial is given by yu and is assumed to vary about the mean of η with a common
variance σ2. The observed response value contains experimental error εu
(5)
where the errors are assumed to be independent with a common variance. The
Scheffé expression for two components becomes
(6)
With N 2 observations collected on yu, we can obtain the estimates b1 and b2 of
the parameters and , respectively. The parameters of Eq. (6) can be replaced by their
respective estimates to give the approximating equation
(7)
where is the predicted value of for given values of x1 and x2. The estimated
parameters contain the main effects plus any error associated with measurement of the
response variables.
In practice, the magnitude of error associated with the measured responses can be
determined by replicating some of the trial blends. Differences in the response values of
the replicate samples are taken as a measure of the experimental error. Lack of fit tests
η χ χ χ
= f q
( , ,..... )
1 2
η β χ β χ χ
= + ∑
∑
∑ i i ij i j
j
q
i
q
i
q
βi
( )
βij
( )
yu u
= +
η ε 1 ≤ ≤
u N
yu u
= + +
β χ β χ ε
1 1 2 2
≥
β1 β2
ˆ( )
y x b b
= +
1 1 2 2
χ χ
ˆ( )
y x η
© 2006 by Taylor & Francis Group, LLC](https://image.slidesharecdn.com/51715-250226095935-4839376d/85/Handbook-of-Detergents-Part-D-Formulation-Surfactant-Science-1st-Edition-Michael-Showell-54-320.jpg)
Handbook of Detergents Part D Formulation Surfactant Science 1st Edition Michael Showell
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- 6. HANDBOOK OF DETERGENTS Part D: Formulation © 2006 by Taylor & Francis Group, LLC
- 7. DANIEL BLANKSCHTEIN Department of Chemical Engineering Massachusetts Institute of Technology Cambridge, Massachusetts S. KARABORNI Shell International Petroleum Company Limited London, England LISA B. QUENCER The Dow Chemical Company Midland, Michigan JOHN F. SCAMEHORN Institute for Applied Surfactant Research University of Oklahoma Norman, Oklahoma P. SOMASUNDARAN Henry Krumb School of Mines Columbia University New York, New York ERIC W. KALER Department of Chemical Engineering University of Delaware Newark, Delaware CLARENCE MILLER Department of Chemical Engineering Rice University Houston, Texas DON RUBINGH The Procter & Gamble Company Cincinnati, Ohio BEREND SMIT Shell International Oil Products B.V. Amsterdam, The Netherlands JOHN TEXTER Strider Research Corporation Rochester, New York SURFACTANT SCIENCE SERIES FOUNDING EDITOR MARTIN J. SCHICK 1918–1998 SERIES EDITOR ARTHUR T. HUBBARD Santa Barbara Science Project Santa Barbara, California ADVISORY BOARD © 2006 by Taylor & Francis Group, LLC
- 8. 1. Nonionic Surfactants, edited by Martin J. Schick (see also Volumes 19, 23, and 60) 2. Solvent Properties of Surfactant Solutions, edited by Kozo Shinoda (see Volume 55) 3. Surfactant Biodegradation, R. D. Swisher (see Volume 18) 4. Cationic Surfactants, edited by Eric Jungermann (see also Volumes 34, 37, and 53) 5. Detergency: Theory and Test Methods (in three parts), edited by W. G. Cutler and R. C. Davis (see also Volume 20) 6. Emulsions and Emulsion Technology (in three parts), edited by Kenneth J. Lissant 7. Anionic Surfactants (in two parts), edited by Warner M. Linfield (see Volume 56) 8. Anionic Surfactants: Chemical Analysis, edited by John Cross 9. Stabilization of Colloidal Dispersions by Polymer Adsorption, Tatsuo Sato and Richard Ruch 10. Anionic Surfactants: Biochemistry, Toxicology, Dermatology, edited by Christian Gloxhuber (see Volume 43) 11. Anionic Surfactants: Physical Chemistry of Surfactant Action, edited by E. H. Lucassen-Reynders 12. Amphoteric Surfactants, edited by B. R. Bluestein and Clifford L. Hilton (see Volume 59) 13. Demulsification: Industrial Applications, Kenneth J. Lissant 14. Surfactants in Textile Processing, Arved Datyner 15. Electrical Phenomena at Interfaces: Fundamentals, Measurements, and Applications, edited by Ayao Kitahara and Akira Watanabe 16. Surfactants in Cosmetics, edited by Martin M. Rieger (see Volume 68) 17. Interfacial Phenomena: Equilibrium and Dynamic Effects, Clarence A. Miller and P. Neogi 18. Surfactant Biodegradation: Second Edition, Revised and Expanded, R. D. Swisher 19. Nonionic Surfactants: Chemical Analysis, edited by John Cross 20. Detergency: Theory and Technology, edited by W. Gale Cutler and Erik Kissa 21. Interfacial Phenomena in Apolar Media, edited by Hans-Friedrich Eicke and Geoffrey D. Parfitt 22. Surfactant Solutions: New Methods of Investigation, edited by Raoul Zana 23. Nonionic Surfactants: Physical Chemistry, edited by Martin J. Schick 24. Microemulsion Systems, edited by Henri L. Rosano and Marc Clausse © 2006 by Taylor & Francis Group, LLC
- 9. 25. Biosurfactants and Biotechnology, edited by Naim Kosaric, W. L. Cairns, and Neil C. C. Gray 26. Surfactants in Emerging Technologies, edited by Milton J. Rosen 27. Reagents in Mineral Technology, edited by P. Somasundaran and Brij M. Moudgil 28. Surfactants in Chemical/Process Engineering, edited by Darsh T. Wasan, Martin E. Ginn, and Dinesh O. Shah 29. Thin Liquid Films, edited by I. B. Ivanov 30. Microemulsions and Related Systems: Formulation, Solvency, and Physical Properties, edited by Maurice Bourrel and Robert S. Schechter 31. Crystallization and Polymorphism of Fats and Fatty Acids, edited by Nissim Garti and Kiyotaka Sato 32. Interfacial Phenomena in Coal Technology, edited by Gregory D. Botsaris and Yuli M. Glazman 33. Surfactant-Based Separation Processes, edited by John F. Scamehorn and Jeffrey H. Harwell 34. Cationic Surfactants: Organic Chemistry, edited by James M. Richmond 35. Alkylene Oxides and Their Polymers, F. E. Bailey, Jr., and Joseph V. Koleske 36. Interfacial Phenomena in Petroleum Recovery, edited by Norman R. Morrow 37. Cationic Surfactants: Physical Chemistry, edited by Donn N. Rubingh and Paul M. Holland 38. Kinetics and Catalysis in Microheterogeneous Systems, edited by M. Grätzel and K. Kalyanasundaram 39. Interfacial Phenomena in Biological Systems, edited by Max Bender 40. Analysis of Surfactants, Thomas M. Schmitt (see Volume 96) 41. Light Scattering by Liquid Surfaces and Complementary Techniques, edited by Dominique Langevin 42. Polymeric Surfactants, Irja Piirma 43. Anionic Surfactants: Biochemistry, Toxicology, Dermatology. Second Edition, Revised and Expanded, edited by Christian Gloxhuber and Klaus Künstler 44. Organized Solutions: Surfactants in Science and Technology, edited by Stig E. Friberg and Björn Lindman 45. Defoaming: Theory and Industrial Applications, edited by P. R. Garrett 46. Mixed Surfactant Systems, edited by Keizo Ogino and Masahiko Abe 47. Coagulation and Flocculation: Theory and Applications, edited by Bohuslav Dobiás © 2006 by Taylor & Francis Group, LLC
- 10. 48. Biosurfactants: Production Properties Applications, edited by Naim Kosaric 49. Wettability, edited by John C. Berg 50. Fluorinated Surfactants: Synthesis Properties Applications, Erik Kissa 51. Surface and Colloid Chemistry in Advanced Ceramics Processing, edited by Robert J. Pugh and Lennart Bergström 52. Technological Applications of Dispersions, edited by Robert B. McKay 53. Cationic Surfactants: Analytical and Biological Evaluation, edited by John Cross and Edward J. Singer 54. Surfactants in Agrochemicals, Tharwat F. Tadros 55. Solubilization in Surfactant Aggregates, edited by Sherril D. Christian and John F. Scamehorn 56. Anionic Surfactants: Organic Chemistry, edited by Helmut W. Stache 57. Foams: Theory, Measurements, and Applications, edited by Robert K. Prud’homme and Saad A. Khan 58. The Preparation of Dispersions in Liquids, H. N. Stein 59. Amphoteric Surfactants: Second Edition, edited by Eric G. Lomax 60. Nonionic Surfactants: Polyoxyalkylene Block Copolymers, edited by Vaughn M. Nace 61. Emulsions and Emulsion Stability, edited by Johan Sjöblom 62. Vesicles, edited by Morton Rosoff 63. Applied Surface Thermodynamics, edited by A. W. Neumann and Jan K. Spelt 64. Surfactants in Solution, edited by Arun K. Chattopadhyay and K. L. Mittal 65. Detergents in the Environment, edited by Milan Johann Schwuger 66. Industrial Applications of Microemulsions, edited by Conxita Solans and Hironobu Kunieda 67. Liquid Detergents, edited by Kuo-Yann Lai 68. Surfactants in Cosmetics: Second Edition, Revised and Expanded, edited by Martin M. Rieger and Linda D. Rhein 69. Enzymes in Detergency, edited by Jan H. van Ee, Onno Misset, and Erik J. Baas 70. Structure-Performance Relationships in Surfactants, edited by Kunio Esumi and Minoru Ueno 71. Powdered Detergents, edited by Michael S. Showell 72. Nonionic Surfactants: Organic Chemistry, edited by Nico M. van Os 73. Anionic Surfactants: Analytical Chemistry, Second Edition, Revised and Expanded, edited by John Cross © 2006 by Taylor & Francis Group, LLC
- 11. 74. Novel Surfactants: Preparation, Applications, and Biodegradability, edited by Krister Holmberg 75. Biopolymers at Interfaces, edited by Martin Malmsten 76. Electrical Phenomena at Interfaces: Fundamentals, Measurements, and Applications, Second Edition, Revised and Expanded, edited by Hiroyuki Ohshima and Kunio Furusawa 77. Polymer-Surfactant Systems, edited by Jan C. T. Kwak 78. Surfaces of Nanoparticles and Porous Materials, edited by James A. Schwarz and Cristian I. Contescu 79. Surface Chemistry and Electrochemistry of Membranes, edited by Torben Smith Sørensen 80. Interfacial Phenomena in Chromatography, edited by Emile Pefferkorn 81. Solid–Liquid Dispersions, Bohuslav Dobiás, Xueping Qiu, and Wolfgang von Rybinski 82. Handbook of Detergents, editor in chief: Uri Zoller Part A: Properties, edited by Guy Broze 83. Modern Characterization Methods of Surfactant Systems, edited by Bernard P. Binks 84. Dispersions: Characterization, Testing, and Measurement, Erik Kissa 85. Interfacial Forces and Fields: Theory and Applications, edited by Jyh-Ping Hsu 86. Silicone Surfactants, edited by Randal M. Hill 87. Surface Characterization Methods: Principles, Techniques, and Applications, edited by Andrew J. Milling 88. Interfacial Dynamics, edited by Nikola Kallay 89. Computational Methods in Surface and Colloid Science, edited by Malgorzata Borówko 90. Adsorption on Silica Surfaces, edited by Eugène Papirer 91. Nonionic Surfactants: Alkyl Polyglucosides, edited by Dieter Balzer and Harald Lüders 92. Fine Particles: Synthesis, Characterization, and Mechanisms of Growth, edited by Tadao Sugimoto 93. Thermal Behavior of Dispersed Systems, edited by Nissim Garti 94. Surface Characteristics of Fibers and Textiles, edited by Christopher M. Pastore and Paul Kiekens 95. Liquid Interfaces in Chemical, Biological, and Pharmaceutical Applications, edited by Alexander G. Volkov 96. Analysis of Surfactants: Second Edition, Revised and Expanded, Thomas M. Schmitt 97. Fluorinated Surfactants and Repellents: Second Edition, Revised and Expanded, Erik Kissa 98. Detergency of Specialty Surfactants, edited by Floyd E. Friedli © 2006 by Taylor & Francis Group, LLC
- 12. 99. Physical Chemistry of Polyelectrolytes, edited by Tsetska Radeva 100. Reactions and Synthesis in Surfactant Systems, edited by John Texter 101. Protein-Based Surfactants: Synthesis, Physicochemical Properties, and Applications, edited by Ifendu A. Nnanna and Jiding Xia 102. Chemical Properties of Material Surfaces, Marek Kosmulski 103. Oxide Surfaces, edited by James A. Wingrave 104. Polymers in Particulate Systems: Properties and Applications, edited by Vincent A. Hackley, P. Somasundaran, and Jennifer A. Lewis 105. Colloid and Surface Properties of Clays and Related Minerals, Rossman F. Giese and Carel J. van Oss 106. Interfacial Electrokinetics and Electrophoresis, edited by Ángel V. Delgado 107. Adsorption: Theory, Modeling, and Analysis, edited by József Tóth 108. Interfacial Applications in Environmental Engineering, edited by Mark A. Keane 109. Adsorption and Aggregation of Surfactants in Solution, edited by K. L. Mittal and Dinesh O. Shah 110. Biopolymers at Interfaces: Second Edition, Revised and Expanded, edited by Martin Malmsten 111. Biomolecular Films: Design, Function, and Applications, edited by James F. Rusling 112. Structure–Performance Relationships in Surfactants: Second Edition, Revised and Expanded, edited by Kunio Esumi and Minoru Ueno 113. Liquid Interfacial Systems: Oscillations and Instability, Rudolph V. Birikh,Vladimir A. Briskman, Manuel G. Velarde, and Jean-Claude Legros 114. Novel Surfactants: Preparation, Applications, and Biodegradability: Second Edition, Revised and Expanded, edited by Krister Holmberg 115. Colloidal Polymers: Synthesis and Characterization, edited by Abdelhamid Elaissari 116. Colloidal Biomolecules, Biomaterials, and Biomedical Applications, edited by Abdelhamid Elaissari 117. Gemini Surfactants: Synthesis, Interfacial and Solution-Phase Behavior, and Applications, edited by Raoul Zana and Jiding Xia 118. Colloidal Science of Flotation, Anh V. Nguyen and Hans Joachim Schulze 119. Surface and Interfacial Tension: Measurement, Theory, and Applications, edited by Stanley Hartland © 2006 by Taylor & Francis Group, LLC
- 13. 120. Microporous Media: Synthesis, Properties, and Modeling, Freddy Romm 121. Handbook of Detergents, editor in chief: Uri Zoller Part B: Environmental Impact, edited by Uri Zoller 122. Luminous Chemical Vapor Deposition and Interface Engineering, HirotsuguYasuda 123. Handbook of Detergents, editor in chief: Uri Zoller Part C: Analysis, edited by Heinrich Waldhoff and Rüdiger Spilker 124. Mixed Surfactant Systems: Second Edition, Revised and Expanded, edited by Masahiko Abe and John F. Scamehorn 125. Dynamics of Surfactant Self-Assemblies: Micelles, Microemulsions, Vesicles and Lyotropic Phases, edited by Raoul Zana 126. Coagulation and Flocculation: Second Edition, edited by Hansjoachim Stechemesser and Bohulav Dobiás 127. Bicontinuous Liquid Crystals, edited by Matthew L. Lynch and Patrick T. Spicer 128. Handbook of Detergents, editor in chief: Uri Zoller Part D: Formulation, edited by Michael S. Showell © 2006 by Taylor & Francis Group, LLC
- 14. HANDBOOK OF DETERGENTS Edited by Michael S. Showell Procter & Gamble Company Cincinnati, Ohio, U.S.A. Boca Raton London New York Singapore A CRC title, part of the Taylor & Francis imprint, a member of the Taylor & Francis Group, the academic division of T&F Informa plc. Part D: Formulation © 2006 by Taylor & Francis Group, LLC
- 15. Published in 2006 by CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2006 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group No claim to original U.S. Government works Printed in the United States of America on acid-free paper 10 9 8 7 6 5 4 3 2 1 International Standard Book Number-10: 0-8247-0350-2 (Hardcover) International Standard Book Number-13: 978-0-8247-0350-9 (Hardcover) This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. A wide variety of references are listed. Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use. No part of this book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers. For permission to photocopy or use material electronically from this work, please access www.copyright.com (http://www.copyright.com/) or contact the Copyright Clearance Center, Inc. (CCC) 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400. CCC is a not-for-profit organization that provides licenses and registration for a variety of users. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Library of Congress Cataloging-in-Publication Data Catalog record is available from the Library of Congress Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com Taylor & Francis Group is the Academic Division of T&F Informa plc. © 2006 by Taylor & Francis Group, LLC
- 16. iii Preface We are all familiar with the most common form of detergent formulations—household cleaners, laundry detergents, dishwashing detergents, shampoos, body washes, bar soaps, toothpastes, etc. While pervasive in developed markets in a variety of forms for a variety of uses, even developing markets offer an array of such products for consumer use. However, detergents, a term applied to any material which either aids in the removal of foreign matter from surfaces or promotes the dispersion and stabilization of one or more ingredients in a bulk matrix, are widely used in a number of applications and industries not generally familiar to the public (the reader is referred to Volume C of this series: Applications). These include additives to lubricants to aid the removal of deposits from internal surfaces of engines, formulations to aid in the cleanup of, or to enhance the biodegradation of, oil spills and other environmental contaminants, paper and textile processing aids, and as components in the formulation of paints, inks, and colorants. The purpose of this volume, Part D in the Handbook of Detergents series, is to provide an overview of the full range of detergent formulations used today, from common household products to the more esoteric specialty applications. Detergents, although thousands of years old, continue to evolve, providing the end user with an array of benefits and services. In their most common form, as aids in household cleaning and personal care, detergents generally offer not only a basic cleaning benefit but also a range of ancillary benefits intended to better meet the needs of the consumer. For example, today’s laundry detergents provide good general cleaning of fabrics while delivering additional benefits like increased fabric wear, color rejuvenation, and long- lasting fresh scent. The increasing complexity of detergent formulations, which combine surface-active agents, builders, sequestering agents, bleaches, enzymes, and other compo- nents, places a high demand for creativity and innovation on the part of the detergent formulator. Furthermore, economic constraints and an increasing expectation that detergent formulations meet the ever-increasing demands of sustainability place even more demand on, and require more responsibility from, the formulator. This, in turn, requires that the formulator be knowledgeable of the conditions under which the product will be used, stored, and shipped as well as the end user’s needs and constraints so that formulations are designed which are shelf stable, have acceptable consumer aesthetics, and provide the intended benefit with each particular use. In addition, the increasing volume of detergents and their use across a range of product segments, categories, and industries increases the load on the environment to which they are eventually released. This makes it necessary for the detergent formulator to consider the use of environmentally friendly, and ultimately biodegradable, raw materials whenever possible, creating additional formulation chal- lenges. © 2006 by Taylor & Francis Group, LLC
- 17. iv Preface This volume of the Handbook of Detergents series provides a review of the process and chemical technologies involved in producing various detergent formulations. Attention is given to formulations in the consumer products area—laundry detergents, dishwashing products, and household cleaning formulations (Chapters 3–7) as well as a number of specialty areas like Auto Care and Industrial/Institutional Products (Chapter 8), Textile Processing (Chapter 9), Separation Science (Chapter 10), Oil Recovery (Chapter 11), Environmental Cleanup (Chapter 12), Paints and Colorants (Chapter 13), Polymerization Processes (Chapter 14), and Lubricants (Chapter 15). Formulations based on N-alkyl amide sulfates are covered in Chapter 16. A major aim of this book is to provide the reader with some general guidance on formulation approaches. To that end, Chapter 2 provides an overview of the use of statistical mixture design in detergent formulations. This book should serve as a useful reference for scientists, engineers, technicians, managers, policymakers, and students having an interest in detergents and emerging technology trends and formulations that will sustain the industry for years to come. I would like to thank the contributing authors for their time in preparing the highly authoritative individual chapters for this volume, Dr. Uri Zoller for his helpful suggestions and guidance, and Helena Redshaw for her patience, encouragement, and support. Michael S. Showell © 2006 by Taylor & Francis Group, LLC
- 18. v About the Editor Michael S. Showell joined Procter & Gamble in 1984 in the Packaged Soap Division and has had various assignments with increasing responsibilities within P&G’s laundry and cleaning product research and development community. He currently is associate director of R&D in the Fabric & Home Care Technology Division at P&G’s Miami Valley Inno- vation Center in Cincinnati, Ohio. His research interests include: enzymes and their application in laundry and cleaning products, enzyme/detergent interactions, protein engi- neering to improve enzymes for use in consumer product applications, enzymatic synthesis of detergent ingredients, bioremediation, bioprocessing, and detergents. He is author or coauthor of a number of articles, book chapters, and presentations on the use of enzymes in laundry and cleaning products. In 1999 he was one of the recipients of the American Chemical Society award for Team Innovation. Mike received a B.S. in chemistry from Willamette University in 1978, and M.S. and Ph.D. degrees in physical chemistry from Purdue University in 1980 and 1983, respectively. © 2006 by Taylor & Francis Group, LLC
- 20. vii Contributors Thanaa Abdel-Moghny, Application Department, Egyptian Petroleum Research Insti- tute, Cairo, Egypt Achim Ansmann, Cognis Deutschland GmbH & Co. KG, Düsseldorf, Germany Shoaib Arif, Noveon, Inc., Cleveland, Ohio Samir S. Ashrawi, Surface Sciences Division, The Austin Laboratories, Huntsman Cor- poration, Austin, Texas Alessandra Bianco Prevot, Dipartimento di Chimica Analitica. Università di Torino, Torino, Italy Jean-François Bodet, Brussels Technical Center, Procter & Gamble Eurocor NV, Strombeek-Bever, Belgium Peter Busch, Cognis Deutschland GmbH & Co. KG, Düsseldorf, Germany Jeffrey H. Harwell, School of Chemical Engineering and Materials Science and The Institute for Applied Surfactant Research, The University of Oklahoma, Norman, Okla- homa and Surbec-ART Environmental, LLC, Norman, Oklahoma Hermann Hensen, Cognis Deutschland GmbH & Co. KG, Düsseldorf, Germany Karlheinz Hill, Cognis Deutschland GmbH & Co. KG, Monheim, Germany Krister Holmberg, Department of Applied Surface Chemistry, School of Chemical and Biological Engineering, Chalmers University of Technology, Göteborg, Sweden Tze-Chi Jao, Research & Development Department,Afton Chemical Corporation, Rich- mond, Virginia Glenn T. Jordan, Fabric & Home Care Technology Division, Miami Valley Innovation Center, The Procter & Gamble Company, Cincinnati, Ohio Robert C. Knox, School of Chemical Engineering and Materials Science and The Insti- tute for Applied Surfactant Research, The University of Oklahoma, Norman, Oklahoma and Surbec-ART Environmental, LLC, Norman, Oklahoma Hans-Udo Krächter, Cognis Deutschland GmbH & Co. KG, Düsseldorf, Germany Hiromoto Mizushima, Material Development Research Laboratories, Kao Corporation, Wakayama, Japan Felix Mueller, Degussa AG Goldschmidt Home Care, Essen, Germany Michael Müller, Cognis Deutschland GmbH & Co. KG, Düsseldorf, Germany © 2006 by Taylor & Francis Group, LLC
- 21. viii Contributors Charles A. Passut, Research & Development Department,Afton Chemical Corporation, Richmond, Virginia Jörg Peggau, Degussa AG Goldschmidt Home Care, Essen, Germany Gianmarco Polotti, Lamberti SpA, Albizzate, Italy Edmondo Pramauro, Dipartimento di Chimica Analitica, Università di Torino,Torino, Italy Kenneth N. Price, Global Household Care Technology Division, Miami Valley Innova- tion Center, The Procter & Gamble Company, Cincinnati, Ohio David A. Sabatini, School of Civil Engineering and Environmental Science, and School of Chemical Engineering and Materials Science, and The Institute for Applied Surfactant Research, The University of Oklahoma, Norman, Oklahoma and Surbec-ART Environ- mental, LLC, Norman, Oklahoma William M. Scheper, Fabric & Home Care Technology Division, Miami Valley Inno- vation Center, The Procter & Gamble Company, Cincinnati, Ohio Stefano Scialla, Italia SpA, Pescara Technical Center, The Procter & Gamble Company, Pescara, Italy Jichun Shi, Fabric & Home Care Technology Division, Miami Valley Innovation Center, The Procter & Gamble Company, Cincinnati, Ohio Ben Shiau, Surbec-ART Environmental, LLC, Norman, Oklahoma Michael S. Showell, Fabric & Home Care Technology Division, Miami Valley Innova- tion Center, The Procter & Gamble Company, Cincinnati, Ohio Mark R. Sivik, Fabric & Home Care Technology Division, Miami Valley Innovation Center, The Procter & Gamble Company, Cincinnati, Ohio George A. Smith, Surface Sciences Division, The Austin Laboratories, Huntsman Cor- poration, Austin, Texas Brian X. Song, Home Care Product Development, Ivorydale Innovation Center, The Procter & Gamble Company, Cincinnati, Ohio Oreste Todini, Household Care, Bruxelles Innovation Center, The Procter & Gamble Company, Bruxelles, Belgium Jiping Wang, Fabric & Home Care Technology Division, The Procter & Gamble Com- pany, Cincinnati, Ohio Randall A. Watson, Beijing Technical Center, The Procter & Gamble Company, Beijing, P.R. China Yong Zhu, Fabric & Home Care Technology Division, The Procter & Gamble Company, Cincinnati, Ohio © 2006 by Taylor & Francis Group, LLC
- 22. ix Table of Contents 1. Introduction to Detergents 1 Michael S. Showell 2. Statistical Mixture Design for Optimization of Detergent Formulations 27 Samir S. Ashrawi and George A. Smith 3 . Laundry Detergent Formulations 51 Randall A. Watson 4 . Dishwashing Detergents for Household Applications 105 Jichun Shi, William M. Scheper, Mark R. Sivik, Glenn T. Jordan, Jean-François Bodet, and Brian X. Song 5. The Formulation of Liquid Household Cleaners 153 Stefano Scialla 6. Liquid Bleach Formulations 179 Stefano Scialla and Oreste Todini 7. Personal Care Formulations 207 Achim Ansmann, Peter Busch, Hermann Hensen, Karlheinz Hill, Hans-Udo Krächter, and Michael Müller 8. Special Purpose Cleaning Formulations: Auto Care and Industrial/Institutional Products 261 Felix Mueller, Jörg Peggau, and Shoaib Arif 9. Surfactant Applications in Textile Processing 279 Jiping Wang and Yong Zhu 10. Detergent Formulations in Separation Science 305 Edmondo Pramauro and Alessandra Bianco Prevot 11. Surfactant Formulations in Enhanced Oil Recovery 325 Thanaa Abdel-Moghny © 2006 by Taylor & Francis Group, LLC
- 23. x Table of Contents 12. Surfactant-Based Systems for Environmental Remediation 347 David A. Sabatini, Robert C. Knox, Jeffrey H. Harwell, and Ben Shiau 13. Paints and Printing Inks 369 Krister Holmberg 14. Surfactant Formulations in Polymerization 387 Gianmarco Polotti 15. Detergent Formulations in Lubricants 437 Tze-Chi Jao and Charles A. Passut 16. N-Alkyl Amide Sulfates 473 Hiromoto Mizushima 17. Future Outlook for Detergent Formulations 483 Kenneth N. Price © 2006 by Taylor & Francis Group, LLC
- 25. 1 1 Introduction to Detergents Michael S. Showell CONTENTS I. Introduction ............................................................................................................... 2 II. Common Detergent Ingredients................................................................................ 4 A. Surfactants ..................................................................................................... 4 B. Dispersing Polymers ..................................................................................... 4 C. Builders and Chelants ................................................................................... 8 D. Bleaching Systems ........................................................................................ 9 E. Solvents ....................................................................................................... 10 F. Performance Enhancing Minor Ingredients................................................ 11 III. Representative Detergent Formulations ................................................................. 13 A. Laundry Detergent Formulations................................................................ 13 B. Dishwash Detergent Formulations.............................................................. 13 C. Hard Surface Cleaning Formulations ......................................................... 13 D Personal Care Detergent Formulations....................................................... 13 E Oral Care Detergent Formulations.............................................................. 13 F. Agricultural Detergent Formulations.......................................................... 13 G. Automobile Detergent Formulations........................................................... 13 H. Detergent Formulations for Cleaning Food Processing Equipment .......... 14 I. Detergent Formulations for Metal Component Cleaning........................... 15 IV. Detergency Theory and Mechanisms...................................................................... 15 A. Removal Mechanisms ................................................................................. 19 B. Suspension Mechanisms ............................................................................. 23 Acknowledgments............................................................................................................. 24 References......................................................................................................................... 25 © 2006 by Taylor & Francis Group, LLC
- 26. 2 Showell I. INTRODUCTION Generally, the term “detergents” is applied to materials and/or products that provide the following functions: 1. Promote removal of material from a surface, e.g., soil from a fabric, food from a dish, or soap scum from a hard surface; 2. Disperse and stabilize materials in a bulk matrix, e.g., suspension of oil droplets in a mobile phase like water. The ability of a detergent to perform either of these functions depends on the composition of the formulation, the conditions of use, the nature of the surfaces being treated, the nature of the substance to be removed and/or dispersed, and the nature of the bulk phase. Accordingly, detergent formulation is a complex process driven by the specific needs of the end user, economics, environmental considerations, and the availability of specific “actives” that can provide the required functionality. By far the most common and familiar detergents are those used in household cleaning and personal care. These products can be grouped into four general categories: 1. Laundry detergents and laundry aids. These comprise mainframe laundry deter- gents in powder, liquid, tablet, gel, and bar form, fabric conditioner products typically in liquid or sheet form, and an array of specialty products like pre- treaters (as sticks, gels, sprays, bars), presoaks (liquids, powders), and bleaches (liquids, powders). Typical laundry detergents are formulated to provide general cleaning, which includes removal of soils and stains as well as the ability to maintain whiteness and brightness. In addition, many premium laundry deter- gents offer additional benefits like fabric softening, dye lock, fiber protection, and disinfectancy. 2. Dishwashing products. These include detergents for hand and machine dishwash- ing and are typically provided in liquid, gel, powder, or tablet form. Hand dish wash products are formulated to remove and suspend food soils from a variety of surfaces. They also must deliver long-lasting suds, even at high soil loads, and they must be mild to skin. Products designed for automatic dishwashing must provide soil removal and suspension, control of water hardness and sheeting of water off dish surfaces in order to achieve a spot- and film-free finish, and produce little or no suds that would otherwise interfere with the operation of the machine. Rinse aids are specialty detergent formulations for automatic dishwashing designed to promote drainage of water from surfaces via lowering of surface tension. This helps minimize spotting and filming during drying. 3. Household cleaning products. Because no single product can provide the range of cleaning required on the various surfaces found in the home a broad range of household cleaning products are currently marketed. These are typically formulated either in liquid or powder form although gel, solid, sheet, and pad products are also available. So-called “all-purpose” cleaners are designed to penetrate and loosen soil, control water hardness, and prevent soil from rede- positing onto clean surfaces. Many of these products also contain low levels of antibacterial actives like Triclosan to sustain disinfectancy claims. Powdered abrasive cleaners remove heavy accumulations of soil via the use of mineral or metallic abrasive particles. Some of these products may also bleach and disinfect through the incorporation of a bleach precursor like sodium perborate, sodium percabonate, or sodium dichloroisocyanurate. © 2006 by Taylor & Francis Group, LLC
- 27. Introduction to Detergents 3 4. Personal cleansing products. These include products for hand and body washing as well as shampoos, conditioners, and toothpastes. They are marketed primarily in bar, gel, and liquid forms. A major consideration in formulation of such products is the desired consumer aesthetic such as lather, skin feel, rinsability, smell, and taste. Formulations designed for cleaning may also provide moistur- izing benefits, disinfectancy, conditioning, and styling effects. Within each of these categories products are formulated with specific ingredients selected on the basis of their ability to perform the desired function and deliver “consumer pre- ferred” aesthetics while meeting specific cost constraints, environmental regulations, and human safety guidelines. In addition to these familiar consumer products, detergent formulations are used in a number of other applications and industries. These include: 1. Environmental remediation. Surfactant systems have been developed to aid in the clean up of contaminated groundwater supplies [1]. 2. Enhanced oil recovery. Micellar and surfactant “floods” are among the most successful methods of enhancing recovery of oil from depleted reservoirs [2]. 3. Nanoegineering. Researchers have used the phase behavior of surfactants to generate self-assembling nanosystems [3]. 4. Formulation of paints and printing inks. Paints and inks comprise formulations wherein a pigment is dispersed into a liquid phase. The dispersion is typically achieved with surfactants and/or dispersing polymers [4]. 5. Preparation and application of synthetic polymers. Emulsion polymerization and the preparation of latexes represent one of the largest uses for surfactants outside the cleaning arena [5]. 6. Industrial/metal parts cleaning. Detergent compositions based on a CO2 bulk phase have application in the cleaning of microelectronic components [1]. 7. Medical applications. Mimics of human lung surfactants have been developed to treat respiratory distress syndrome in premature infants [1]. 8. Lubricants. While highly diverse, lubricant formulations utilize the same basic additives: surfactants, dispersants, antiwear actives, antioxidants, corrosion inhibitors, and viscosity modifiers. 9. Textile processing. Detergent formulations are used to clean fibers prior to manufacture into finished textiles as well as lubricate the fibers during spinning and weaving. 10. Agricultural preparations. Pesticide and herbicide preparations are often formu- lated as aqueous dispersions with specific functional actives to promote even distribution of the active during application and fast penetration of the active upon contact with plants [6]. This diversity of application of detergents presents a rather formidable challenge when compiling a volume such as this on detergent formulations. Accordingly, rather than try to cover authoritatively all aspects of detergent formulations—a monumental task in its own right— I have elected instead in this chapter to provide some general background on detergency, the common ingredients used in detergent formulations, and general approaches to detergent processing or manufacture. This should provide a solid framework for the more in-depth discussions found in later chapters of this book. In addition, there are several good reference books available on the topic of detergent formulations [7– 9]. © 2006 by Taylor & Francis Group, LLC
- 28. 4 Showell II. COMMON DETERGENT INGREDIENTS Modern detergents can comprise 20 or more ingredients depending on what benefits the detergent is meant to deliver. It is not within the scope of this chapter to provide an extensive review of the myriad ingredients used in detergent formulations. Rather, the intent of this section is to provide a general overview of the more common elements— surfactants, dispersing polymers, builders and chelants, bleaching systems, solvents, and performance enhancing minors — in order to familiarize the reader with the general chemistry of detergent formulation. Subsequent chapters will provide significantly more detail on many of these ingredients and there are several reference books available on the topic [6–12]. A. Surfactants Surfactants are arguably the most common ingredient of the detergent formulations described in this book. Their primary function is to modify the interface between two or more phases in order to promote the dispersion of one phase into another. In cleaning formulations, for example, surfactants serve to wet surfaces and reduce the interfacial tension between soil and water such that the soil is removed from the surface to be cleaned and dispersed in the aqueous phase. The ability of surfactants to concentrate at interfaces derives from their amphiphilic character—the combination of hydrophilic and hydrophobic moieties within the same molecule. Generally, surfactants are classified according to their hydrophilic component as nonionic, anionic, cationic, or amphoteric. The nonionic surfactants have a hydrophilic component that is not ionized. Typical nonionic groups consist of polyoxyethylene, poly- oxypropylene, alkanolamides, or sugar esters. As the name implies, the hydrophilic com- ponent of anionic surfactants comprises an anionic group, typically a sulfate, sulfonate, or carboxylate moiety. Likewise, the cationic surfactants comprise molecules containing a positively charged group such as a quaternary amine. The amphoteric surfactants are perhaps the most unique in that they comprise a hydrophilic group containing both anionic and cationic character such as the amino acids. Typical hydrophobes for surfactants are the alkyl chains between C10 and C20. However, in some specialty surfactants the hydrophobe may consist of polysiloxane or Until the 1940s detergents were formulated principally with the sodium or potassium salts of C12–C18 chain length fatty acids. The synthesis of surfactants from petroleum feed stocks in the late 1940s spurred the development of soap-free synthetic detergents that proved much more effective for cleaning in cooler wash temperatures and in hard water. Today, the linear alkyl benzene sulfonates, alkyl sulfates, alkyl ethoxy sulfates, and alkyl ether ethoxylates are the workhorse surfactants for most detergent formulations. Alkyl polyglucosides, alkyl glucosamides, and methyl ester sulfonates are also widely used [13]. Recent attention has been given to the use of internal methyl branched alkyl chains as the hydrophobe for certain anionic surfactants [14]. Such branching promotes improved solubility, particularly in cold, hard water. For systems where water is not the continuous phase a variety of specialty surfactants are used. Examples include the polydimethylsiloxane-based surfactants for use in highly hydrophobic media and the acrylate-polystyrene co-polymers designed by DiSimone and colleagues for applications in cleaning systems utilizing condensed phase CO2 [15]. B. Dispersing Polymers The suspension of solids or liquids in a continuous phase is a critical aspect in the formulation of paints, inks, coatings, and agricultural products such as herbicides. Suspension of soil after removal from a surface is important in cleaning applications to © 2006 by Taylor & Francis Group, LLC perfluorocarbon backbones. Examples of common surfactants are shown in Table 1.
- 29. Introduction to Detergents 5 avoid redeposition of the soil back onto the cleaned surface. Generally speaking, the particles to be suspended are sufficiently large that definite surfaces of separation exist between the dispersed phase and the dispersion medium [16]. In order to keep the dispersed phase stable it is important to adsorb functional actives at these surfaces to prevent aggregation. This is one of the critical functions of surfactants. However, another class of detergent actives has been developed to assist in particle suspension—the polymeric dispersants. Table 1 Common Surfactants Used in Detergent Formulations O CH3-CH2-(CH2)nCO-CH3 SO3 Na Methyl ester sulfonate O CH3-(CH2)nCONa Fatty Acid Soap CH3-(CH2)n-O-(CH2-CH2-O)xSO3Na Alkyl Ether Sulfate CH3-(CH2)n-CH-(CH2)m-CH3 SO3Na Paraffinsulfonate CH3-(CH2)n-CH-(CH2)m-CH3 Linear Alkyl Benzene Sulfonate Anionic Structure Type OH OH CH3-(CH2)n-C-N-CH2-CH-CH-CH-CH-CH2OH O CH3 OH OH N-methylglucosamide CH3-(CH2)n-C-NH-CH2-CH2OH Alkyl monoethanolamide CH3-(CH2)n-N(CH3)2 O Amine oxide CH3-(CH2)n-O-(CH2-CH2O)nH Fatty alcohol ethoxylate Nonionic CH3-(CH2)n-N+(CH3)3Cl- Quaternary monoalkylammonium chloride Cationic O CH3-(CH2)n-N+(CH3)2-CH2-CH-CH2-SO3 - OH Alkyl sulfobetaine CH3-(CH2)n-C-NH-(CH2)3-N+(CH3)2-CH2-C-O- O O Amidopropyl betaine Amphoteric SO3Na © 2006 by Taylor & Francis Group, LLC
- 30. 6 Showell In general two types of polymeric dispersants are used in detergent formula- tions—polymers comprising ionically charged groups and nonionic polymers. Typical of the ionic dispersing polymers are the homopolymers of acrylic acid and copolymers of acrylic and maleic acids which are widely used in laundry detergent formulations: where Z is either hydrogen, in the case of homopolymers of acrylic acid, or a carboxyl group in the case where the monomer unit is maleic acid. Polymers of this type are commonly found in powdered laundry detergent formulations where they assist in cleaning by acting as a dispersant for soil and inorganic salts, provide alkalinity control, and serve as crystal growth inhibitors [17]. Anionic dispersing polymers comprising carboxyl and sulfonate groups in the same backbone have been developed for use in water treatment where they act to prevent formation of inorganic scale. The polymers are generally of the following hybrid type: The key features are A and B. A, the sulfonated monomers, include the following groups: H H C C Z COOH n Sulfonated monomer(s) Optional neutral monomer(s) Optional charged monomer(s) A B C D Carboxylate monomer(s) SO3H O N H R SO3H R1 R2 SO3H O O O n AMPS SO3H N H SO3H SMS O q (OR)nSO3H (OR)qSO3H (CH2)nSO3H SO3H O OH AHPS OH HO3S SO3H O R SPMS SSS © 2006 by Taylor & Francis Group, LLC
- 31. Introduction to Detergents 7 B usually comprises maleic, acrylic, or methacrylic acid. C and D are optional but can include acrylamide, vinyl acetate (alcohol), acrylate esters, cationics, or phosphonates [18]. Carboxymethylcellulose is another example of an anionic dispersing polymer widely used in laundry detergent applications Considerable attention has been paid over the years to the preparation of biodegrad- able dispersants [19–21]. Examples include polyamino acid polymers such as polyaspartate prepared from the catalytic condensation of polyaspartic acid [22] and functionalized polysaccharides such as oxidized starches [23]. Recently, a novel process was reported for the preparation of functionalized polyaspartic acid polymers that expands the utility of these materials as dispersants for a variety of applications [24]. Cationic dispersants are less commonly used although some amphiphilic structures have been described as effective dispersants in high salt content media [25]: Amphoteric dispersing polymers of the types shown below have also been reported to be good clay and particulate dispersants in certain laundry detergent formulations [26]: O OH O O OH n CH2OCH2COO− [CH CH]m C N C O O CH2 N+ CH3 CH3 H3C [CH2-CH]n Cl− (CH2CH2O)24SO3Na CH3 NaO3S-(OCH2CH2)24N N-(CH2CH2O)24SO3Na (CH2CH2O)24SO3Na + Cl− + Cl− CH3 (CH2CH2O)20SO3Na (CH2CH2O)20SO3Na NaO3S(OCH2CH2)20-N N-(CH2CH2O)20SO3Na + Cl− + Cl− + Cl− (CH2CH2O)20SO3Na N © 2006 by Taylor & Francis Group, LLC
- 32. 8 Showell Nonionic polymers include polyethylene glycol, polyvinyl alcohol, and random and block ethoxy propoxy copolymers. Graft copolymers of polyalkylene oxide and vinyl acetate are reported to be effective antiredeposition agents for hydrophobic surfaces like polyester fabric [27]. C. Builders and Chelants Metal ion control is a common need in many detergent formulations. For example, in aqueous cleaning applications the presence of Ca2+ in the water can lead to the precipitation of anionic surfactant reducing the effective concentration available for cleaning. Fatty acids can precipitate as calcium soaps resulting in the formation of soap scum on hard surfaces, and many soils, especially inorganic clays, will precipitate with calcium leading to redeposition of the soil onto the surface being cleaned. Builders—a generic term used to refer to any number of materials whose primary function is the removal of Ca2+ and Mg2+ ions from aqueous solutions—and chelants are widely used in the formulation of various detergents. Sodium tripolyphosphate (STPP) is among the best known and widely used detergent builder. In laundry detergent formulations it serves not only as an extremely effective calcium control agent but also provides dispersion, suspension, and anti-encrustation benefits. However, environmental concerns associated with large-scale release of phos- phates into the environment lead to the development of a number of substitutes. Citric acid and sodium nitrilotriacetate are representative of soluble detergent builders Sodium carbonates and noncrystalline sodium silicate form sparingly soluble precipitates with calcium and are frequently used in powdered detergent formulations where they also provide a source of alkalinity. However, to avoid encrustation of the calcium carbonate/silicate onto surfaces these building agents generally are co-for- mulated with a dispersing polymer like the polyacrylate/maleic acid copolymers described above and crystal growth inhibitors like HEDP (1-hydroxyethane diphos- phonic acid). Insoluble builders include the zeolites and layered silicates, which bind calcium via an ion exchange mechanism [28]. Zeolite A, Na12(AlO2)12(SiO2)12∑27H2O, is the principal alternative to phosphate as a detergent builder. The Na+ ions are exchangeable for Ca2+ while the larger hydration shell around Mg2+ tends to impede exchange. Citric acid is also an excellent chelant for metal ions other than calcium and can be employed where the removal of transition metals such as copper, zinc, and iron is important. Other commonly used detergent chelants include ethylenediaminetetraacetate (EDTA) CH2COOH HO C COOH CH2COOH CH2COONa N CH2COONa CH2COONa Citric Acid Sodium nitrilotriacetate © 2006 by Taylor & Francis Group, LLC
- 33. Introduction to Detergents 9 and diethylenetriaminepentaacetate (DTPA) D. Bleaching Systems Bleaches are common components of laundry, automatic dish wash, and hard surface cleaning detergent formulations where they act to destroy chromophoric groups responsible for color in soils via oxidative attack. Four basic technology approaches have been taken to deliver bleaching in these products—chlorine-based bleaches, peroxide-based bleaches, activated peroxide systems, and metal catalysts. Chlorine-based systems are common in some powdered abrasive hard surface clean- ers and automatic dishwashing products. Typically, hypochlorite bleach is delivered via precursor like sodium dichloroisocyanurate according to the reaction: Peroxide-based bleaches either use hydrogen peroxide directly or appropriate pre- cursors like perborate monohydrate, which generate peroxide according to the reaction: (NaBO2H2O2)2 Æ Æ Æ Æ H2O2NaBO2 + 2H2O2 + H2O Activated peroxide systems rely on perhydrolysis of a precursor molecule (generally referred to as an “activator” to generate a peracid bleach in situ: RCO2H + H2O2 Æ RCO3H + H2O The two most common activators used in laundry detergents are N¢N≤-tetraacetyl ethylene diamine (TAED) and nonanoyloxybenzene sulfonate (NOBS). In an aqueous environment TAED undergoes perhydrolysis with the perhydroxyl anion from peroxide to NaOOCCH2 CH2COONa N-CH2CH2-N NaOOCCH2 CH2COONa NaOOCCH2 CH2COONa N-CH2CH2-N-CH2CH2-N NaOOCCH2 CH2COONa CH2COONa Na Na N N C C 2HClO + C C N N N O O N O O Cl H Cl H O O H2O © 2006 by Taylor & Francis Group, LLC
- 34. 10 Showell generate peracetic acid. NOBS reacts in much the same way but generates the more hydrophobic pernonanoic acid. A frequently studied approach to bleaching involves the use of transition metal catalysts [29]. Complexes of metals like Mn, Fe, Cu, and Co with certain organic ligands can react with peroxygen compounds to form reactive intermediates, which can poten- tially result in powerful bleaching action. Typical of these systems are the structures shown below: E. Solvents The selection of solvents for use in detergent formulation depends on the nature of the actives being formulated, the intended application of the detergent, and economics. Water is the dominant solvent in most household and industrial cleaning formulations. Generally speaking, water-based detergents are less toxic, more environmentally friendly, cheaper, more surface compatible, and easier to handle than petroleum-based solvents. However, many common detergent actives have limited solubility in water requiring formulation of a co-solvent and/or hydrotrope. Typical co-solvents used in household cleaning formula- tions include ethanol, glycerol, and 1,2-propanediol. A hydrotrope, also called a “coupling agent,” is an organic compound that increases the ability of water to dissolve other molecules. Hydrotropes are commonly used in aqueous-based detergent formulations containing high concentrations of surfactant in order to achieve a shelf-stable, clear, isotropic fluid. Common hydrotropes are sodium xylene sulfonate, sodium toluene sulfonate, and sodium cumene sulfonate. A typical liquid dish- aqueous-based detergent system comprising both a co-solvent (in this case ethanol) and a hydrotrope (sodium cumene sulfonate): Of course there are applications where water must be avoided. Perhaps the most recognizable of these is in the dry cleaning of fine textiles like silk and wool. Historically, this process has used volatile organic solvents like perchloroethylene as the bulk cleaning fluid. Concerns that such solvents may represent human and environmental safety hazards has recently lead to the development of alternative processes utilizing condensed phase CO2 [30] and certain silicone oils like cyclic decamethylpentasiloxane, D5 [31]. Detergent formulations for use in such systems will typically comprise a solvent compatible with the bulk phase (e.g., polydimethylsiloxane in the case of the D5 system) and capable of solublizing the cleaning actives to be introduced into the bulk phase. From US Patent 5, 798, 326 From US Patent 5, 246, 612 Cl NH3 NH3 NH3 H3N Co NH3 Me N Me Me Me Me (PF6 − )2 N N N O O O MnIV MnIV Me N N 2+ © 2006 by Taylor & Francis Group, LLC washing formulation, shown below in Table 2, is a good example of a surfactant-rich
- 35. Introduction to Detergents 11 Other areas where water is not a suitable solvent include the cleaning of certain metal parts and electronic circuit boards. Here chlorinated hydrocarbons like perchloro- ethylene or methylene chloride, or volatile organics like methyl ethyl ketone have histor- ically been used but regulatory pressure has resulted in a shift to more environmentally friendly solvents like terpenes and dibasic esters. F. Performance Enhancing Minor Ingredients Depending upon the end use of the detergent formulation and the benefits to be delivered a number of performance enhancing minor ingredients may be used. These include: 1. Enzymes. Used primarily in cleaning formulations enzymes promote soil removal by the catalytic breakdown of specific soil components. Proteases (enzymes that degrade protein) are the most common of all the detergent enzymes but amylases (starch degrading), lipases (lipid degrading), and cellu- lases (cellulase degrading) are also used [32]. 2. Brighteners/fabric whitening actives. These materials enhance the visual appear- ance of white surfaces, typically cotton fabrics, by absorbing ultraviolet (UV) radiation and emitting via fluorescence in the visible portion of the spectrum. Typical whitening actives are built from direct linkage or ethylenic bridging of aromatic or heteroaromatic moieties.Among the most commonly used whiteners in laundry detergents are the derivatives of 4,4-diaminostilbene-2,2-disulfonic acid. 3. Foam boosters. In some applications, most notably hand dishwashing and sham- poos; it is desirable for the detergent formulation to generate a large-volume, stable foam. While most surfactants are capable of generating and sustaining foam in the absence of soil, these foams rapidly collapse in the presence of soil, especially particulate and fatty soils. In applications where foam must be main- tained throughout the course of detergent use, specific boosters may be added. Proteins have been shown to promote foaming in certain systems [33] especially in food and beverage applications [34]. Alkanolamides, particularly mono- and diethanolamides, are effective foam stabilizers used in dishwashing liquids and Table 2 Typical Hand Dishwash Formulation Ingredient Weight % C12-C13 Alkyl ethoxy (E1.4) sulfate 33 C12-C14 Polyhydroxy fatty acid amide 4 C14 Amine oxide 5 C11 Alcohol ethoxylate E9 1 MgCl2 0.7 Calcium citrate 0.4 Polymeric suds booster 0.5 Ethanol 1 Sodium cumene sulfonate 0.5 Minors and water Balance © 2006 by Taylor & Francis Group, LLC
- 36. 12 Showell shampoos [7]. Polymeric foam boosters of the type shown below have also proved effective in hand dish wash applications [35]: 4. Antifoam agents. In many applications it is desirable to minimize foam gener- ation. For example, in automatic dishwashing foam generation can interfere with rotation of the spray arm leading to degradation in the performance of the dishwasher. Antifoam agents act to reduce or eliminate foams. They either prevent formation of the foam or accelerate its collapse. Alkyl ethoxylate non- ionic surfactants are commonly used as foam control agents in detergents where application temperatures exceed the cloud point of the surfactant—the temper- ature at which the surfactant becomes insoluble. The insoluble nonionic-rich surfactant phase acts to break foam lamella promoting foam collapse. Hydrophobic particulate antifoam agents physically break foams by lodging in the foam film promoting rapid localized draining in the region of the film in contact with the particles. The calcium soaps of long-chain fatty acids are effective at foam control as are hydrophobic silica particles. Particularly effec- tive antifoams are comprised of colloidal hydrophobic silica particles suspended in a silicone oil like polydimethyl siloxane. The hydrophobic oil promotes spreading of the particles at the air-water interface thereby ensuring entrapment in the foam film and subsequent foam disruption [7]. 5. Thickeners. It is often desirable to modify the rheology of a detergent formu- lation to fit a particular application. For example, gel-type automatic dishwash- ing detergents are thickened to help suspend phosphate and other solids that would otherwise separate out from the liquid phase. Thickening can be achieved through the use of inorganic electrolytes, e.g., NaCl; clays, such as laponite or hectorite; or a high-molecular-weight polymer like carboxymethylcellulose, guar, or xanthan gum. The Carbopol“ series of polymers from Noveon, homo- and copolymers of acrylic acid cross linked with polyalkenyl polyether, are particularly effective thickeners for household cleaning detergent formulations. 6. Soil release polymers. Soil release refers to the enhanced removal of soil from a surface as a result of modification of that surface with a specific agent, typically a polymer that alters surface polarity thereby decreasing adherence of soil. Used primarily in laundry detergent formulations soil release polymers provide sig- nificant changes in surface energy, which in turn can lead to dramatic improve- ments in the removal of soils. Carboxymethyl cellulose (CMC) is the archetypical soil release polymer. CMC absorbs onto cotton fabric owing to the similarity in structure between the cellulose backbone of CMC and the cellulose polymer of cotton fibers. Once absorbed, the carboxyl moiety creates a high net negative charge on the fabric surface effectively repelling negatively charged soils, especially clays [7]. n O N O © 2006 by Taylor & Francis Group, LLC
- 37. Introduction to Detergents 13 Other soil release polymers used in detergents are derivatives of polyester-polyether block copolymers that are capped with nonionic (ethoxylates), anionic (typically sul- fonates), or cationic (typically quaternary amines) groups to achieve deposition and release from specific formulations [36]. III. REPRESENTATIVE DETERGENT FORMULATIONS This section provides examples of detergent formulations comprising the ingredients discussed in Section II. This is by no means an exhaustive compilation. Rather, the intent is to illustrate the variety of detergent formulations and how the composition of the formulation varies depending on the intended use. Subsequent chapters of this book will provide more detail on detergent formulations for specific applications. A. Laundry Detergent Formulations B. Dishwash Detergent Formulations Examples of granular detergent formulations for use in automatic dishwashing C. Hard Surface Cleaning Formulations D. Personal Care Detergent Formulations E. Oral Care Detergent Formulations In the toothpaste formulations illustrated in Table 11 note the use of silica as an abrasive cleaning agent. F. Agricultural Detergent Formulations Herbicidal compositions typically comprise an aqueous emulsion of the active with appro- priate surfactants to insure effective spreading and penetration of the herbicide into plants. Typical compositions comprising the well-known herbicidal active glyphosphate are illus- G. Automobile Detergent Formulations A variety of detergent compositions are used in the care and maintenance of automobiles. finish to the exterior of automobiles. A formulation designed to remove grease from automobile engines and engine © 2006 by Taylor & Francis Group, LLC Examples of granular laundry detergent formulations are shown in Table 3. Table 4 illustrates typical liquid laundry detergent formulations. Examples of typical liquid hand dishwash formulations are provided in Table 5. applications are illustrated in Table 6. Examples of liquid hard surface cleaning formulations are illustrated in Table 7. Table 8 provides examples of typical shampoo formulations. Examples of body washes are provided in Table 9. An oral mouthwash formulation is illustrated in Table 10. Examples of Toothpaste formulations are provided in Table 11. trated in Table 12. composition in Table 13 illustrates a formulation designed to clean and provide a waxed compartments is illustrated in Table 14. Chapter 8 provides an extensive review of the components used in such formulations. The
- 38. 14 Showell H. Detergent Formulations for Cleaning Food Processing Equipment Processing of food contaminates surfaces with lipids, carbohydrates, and proteins. A variety of detergent formulations have been developed specifically for cleaning food utilizing high alkalinity as the major detersive component: More user friendly and environmentally compatible formulations can be built around enzyme technology to facilitate the removal of protein bound to surfaces. Examples are Table 3 Representative Granular Laundry Detergent Formulations Ingredients Weight % Examples A B C C11-C13 Linear alkyl benzene sulfonate 8 10 — C12-C16 Alkyl ethoxy (E2) sulfate — — 5.3 C14-C16 Secondary alkyl sulfate 2 — — C14-C15 Alkyl sulfate — 7 — C16-C18 Alkyl sulfate 2 — — C14-C15 Alkyl ethoxy (E2) sulfate — 1 — C12-C15 Alcohol ethoxylate E7 3.4 — — C14-C15 Alcohol ethoxylate E7 — 1 3.3 STPP — — 10.7 Zeolite A 18 22 10.7 Carbonate 13 19 6 Silicate 1.4 1 7 Sodium sulfate 26 10 40 Na perborate tetrahydrate 9 — 5 Na perborate monohydrate — 1 — TAED 1.5 — 0.5 NOBS — 4 — HEDP 0.3 — — DTPA — 0.4 — Proteasea 0.8 0.3 0.3 Amylasea 0.8 0.1 0.1 Lipasea 0.2 — 0.2 Cellulasea 0.15 — 0.3 Acrylic/maleic copolymer 0.3 1 0.8 CMC 0.2 — 0.2 Polyester-based soil release polymer 0.2 0.4 — Minors Balance Balance Balance aEnzymes are added in granulated form where typical enzyme level in the granulate ranges from 1 to about 8% by weight of the granulate formulation. Source: From U.S. Patents 6,326,348 B1 and 6,376,445 B1. © 2006 by Taylor & Francis Group, LLC processing and preparation equipment. Table 15 provides an example of one such detergent illustrated in Table 16.
- 39. Introduction to Detergents 15 I. Detergent Formulations for Metal Component Cleaning Industries involved in repair and replacement of mechanical parts often require that those parts be cleaned prior to inspections, repair, or replacement. Generally, mechanical parts have been exposed to a wide variety of contaminants including dirt, oil, ink, and grease that must be removed for effective repair or service. A variety of metal cleaners have been developed to clean such surfaces. For example, solvent-based cleaners containing either halogenated or nonhalogenated hydrocarbons are common. However, the use of these cleaners carries certain environmental and worker safety issues. Where appropriate, aque- provides example formulations of aqueous-based metal cleaning formulations: IV. DETERGENCY THEORY AND MECHANISMS As noted in the introduction the two major functions of detergents are to remove materials from surfaces and keep materials suspended in a bulk phase. Each function requires work Table 4 Representative Liquid Laundry Detergent Formulations Ingredients Weight % Examples A B C C11-C13 Linear alkyl benzene sulfonate 12 — 28 C12-C15 Alkyl sulfate — 18 — C14-C15 Alkyl sulfate — — 14 C14-C15 Alkyl ethoxy (E2.5) sulfate 12 2 — C12-C13 Alcohol ethoxylate (E7) 3 4 — C11-C13 Alcohol ethoxylate (E8) — — 3 C16-C18 Alkyl N-methyl glucamide — 8 2 C12-C14 Fatty acids 2 11 — Oleic acid — 3.4 Citric acid 3 5 5.4 Sodium cumene sulfonate 4 — — NaOH 6 — 0.4 Ethanol — 3 7 1,2 propanediol 3 10 6 Monoethanolamine 3 9 17 Proteasea 0.8 0.8 1 Amylasea — 0.3 — Lipasea — 0.1 — Cellulasea — 0.1 — Polyester-based soil release polymer 0.2 0.2 — Water + minors Balance Balance Balance aEnzymes are added from liquid stocks where typical enzyme levels in the stock ranges from 1 to about 8% by weight of the liquid stock formulation. Source: From U.S. Patent 6,376,445 B1. © 2006 by Taylor & Francis Group, LLC ous-based cleaners are preferred for cost, safety, and environmental concerns. Table 17
- 40. 16 Showell Table 5 Representative Liquid Hand Dishwash Detergent Formulations Ingredients Weight % Examples A B C C12-C13 Alkyl ethoxy (E3.5) carboxylate 22 — — C11-C17 Alkyl ethoxy (E2.5) sulfate — 29 34 C12-C13 Alcohol ethoxylate (E3.5) 1.3 — — Polyhydroxy fatty acid amide — — 7 C12-C13 Alkyl sulfate 6 — — C12-C14 Amidopropyl diemethyl betaine 3 0.9 2 C14 Amine oxide 3 3 3 MgCl2 0.6 3.3 — Mg(OH)2 — — 2 Methyldiethanol amine 10 — — Ethanol 9 4 9 Xylene sulfonate — 2 2 Water + minors Balance Balance Balance Source: From U.S. Patents 5,376,310 and 6,376,445 B1. Table 6 Representative Granular Automatic Dishwashing Detergent Compositions Ingredients Weight % Examples A B STPP 54 30 Carbonate 14 31 Silicate 15 7.4 Sodium perborate monohydrate 8 4.4 Alcohol ethoxylate 2 1.2 Metal bleach catalyst 0.01 — TAED — 1 Proteasea 2 2.5 Amylasea 0.3 0.5 Sulfate 5 23.4 Minors Balance Balance aEnzymes are added in granulated form where typical enzyme level in the granulate ranges from 1 to about 8% by weight of the granulate formulation. Source: From U.S. Patent 6,376,445 B1. © 2006 by Taylor & Francis Group, LLC
- 41. Introduction to Detergents 17 Table 7 Representative Liquid Hard Surface Cleaning Compositions Ingredients Weight % Examples A B C Hydrogen peroxide 7 — — C10 Alkyl sulfate 2 — — Na octyl sulfate — 2 — Na dodecyl sulfate — 4 — C12-C13 Alcohol ethoxylate (E3) 2 — — C9-C11 Alcohol ethoxylate (E10) 2 — — Betaine — — 0.8 Butyl octanol 0.5 — — Butyl carbitol — 4 — Isopropanol — — 30 Butoxypropanol — — 15 Sodium hydroxide — 0.8 — Silicate — 0.04 — Monoethanolamine — — 2.5 Quaternary ammonium disinfectant — — 0.5 Tartaric acid — — 0.1 Water + minors Balance Balance Balance Source: From U.S. Patents 6,277,805 and 6,376,445. Table 8 Representative Shampoo Formulations Ingredients Weight % Examples A B C D Ammonium lauryl sulfate 14 12.5 48 50 Isostearamidopropyl morpholine lactate — — 3 6 Cocoamidopropylbetaine 2.7 4.2 — — Sodium cocosulfate — — 4 3 Polyquaternium-10 0.3 0.3 — — Trimethylolpropane caprylate caprate 0.3 0.3 — — Cocamide MEA 0.8 — — — Cetyl alcohol — 0.4 — — Stearyl alcohol — 0.2 — — Glycerol stearate — — 1.5 1.5 Ethylene glycol distearate 1.5 1.5 — — Dimethicone 1 1 — — EDTA — — — 0.4 Water + minors Balance Balance Balance Balance Source: From U.S. Patent 6,007,802 and HAPPI, February 2001. © 2006 by Taylor & Francis Group, LLC
- 42. 18 Showell (W) to be done on the system. In the case of removal that work, defined here as WR, is a measure of the energy required to move a substance from a surface into the bulk phase. In general, surface-active agents like surfactants promote removal from surfaces by low- ering the interfacial energy between the substrate and the bulk phase. In the case of suspension, the work, WS, to suspend in the bulk phase is a measure of the energy required to keep materials from aggregating, flocculating, or adhering to a surface. Generally, suspension is achieved either by electrostatic repulsive effects or steric stabilization. Subsequent chapters of this book provide extensive detail on how to remove and suspend materials via chemical means. The purpose of this section is to provide a general thermo- dynamic underpinning to the phenomena of soil removal and particulate suspension so that the reader can better understand the mechanisms by which detergent chemicals function. Table 9 Representative Body Wash Formulations Ingredients Weight % Examples A B Sodium cocoamphoacetate 5 14 Cocaminopropyl betaine 10 10 Disodium lauryl sulfosuccinate — 30 Disodium oleamido MEA sulfosuccinate 5 — Disodium laureth sulfosuccinate 5 — Sodium laureth sulfate 17 — Isostearamidopropyl morpholine lactate 2 6 Hydrolyzed wheat protein derivative 1 — Polyquaternium–7 2 3 Glycol distearate — 3.5 Sodium chloride — 3 Water + minors Balance Balance Source: Courtesy of T. Schoenberg, The McIntyre Group Ltd. Table 10 Oral Mouthwash Formulation Ingredients Weight % tb 10 Glycerine 10 Betaine 1.4 Ethanol 10 Propylene glycol 7 Flavoring 0.2 Triclosan 0.06 Water Balance Source: From U.S. Patent 5,681,548. © 2006 by Taylor & Francis Group, LLC
- 43. Introduction to Detergents 19 A. Removal Mechanisms For simplicity, in the following discussion, materials to be removed from a surface will be generically referred to as soils. The basic concept illustrated here will be for surfactant- Table 11 Representative Toothpaste Formulations Ingredients Weight % Examples A B C Glycerin 27 29 29 Polyethylene glycol 2 1 3 Xanthan gum 0.3 0.4 0.3 CMC 0.2 0.2 0.2 Water 5 7 5 Sodium saccharin 0.5 0.4 0.5 Sodium fluoride 0.2 0.2 0.2 Xylitol 10 10 10 Poloxamer 2 3 — Sodium alkyl sulfate 6 4 4 Cocamidopropyl betaine — — 2 Flavoring 1.1 1 1 Sodium carbonate 2.6 3 3 Titanium dioxide 1 1 1 Silica 20 20 20 Sodium bicarbonate 1.5 1 1 Propylene glycol 15 11 12 Tetrasodium pyrophosphate 5 7 7 Calcium peroxide 0.5 1 1 Source: From U.S. Patent 5,849,269. Table 12 Representative Herbicidal Formulations Ingredients Weight % Examples A B C Butyl stearate 18 1 7.5 Span 80 3 — 3 Tween 20 5 — 5 C12-15 Alcohol ethoxylate (E20) — 10 — Glyphosphate (as g a.e./liter) 100 163 160 Water Balance Balance Balance Note: a.e. = active ether Source: From U.S. Patent 6,479,434. © 2006 by Taylor & Francis Group, LLC
- 44. 20 Showell Table 13 Detergent Formulation for Cleaning and Care of Automobile Exteriors Ingredients Weight % Micronized polymer wax 6 Amino functional silicone 3 Polydimethylsiloxane 1 Paraffinic hydrocarbon solvent 15 Alkyl alcohol ethoxylate 0.5 Fluoroamide polymer 0.2 Water Balance Source: From U.S. Patent 5,782,962. Table 14 Automobile Engine Cleaner Ingredients Weight % Dodecyl oxydibenzene disulfonate 6 Nonylphenol-9 ethoxylate 1.2 Sodium orthosilicate 1.2 Tetra potassium pyrophosphate 8 C18 tall oil 9.5 Heavy aromatic naphtha 14 Water Balance Source: From U..S Patent 3,717,590. Table 15 Detergents for Cleaning Food Processing Equipment Examples A B C Sodium hydroxide 15 15 15 Sodium polyacrylate 2.7 2.7 2.7 1,2,4 Tricarboxylic acid 0.8 — — 1-Hydroxyethylidene-1,1-disphosphonic acid — 0.3 0.8 Sodium hypochlorite 2 3 3 Water Balance Balance Balance Source: From U.S. Patent 4,935,065 to Ecolab Inc. © 2006 by Taylor & Francis Group, LLC
- 45. Introduction to Detergents 21 mediated removal of soil from a surface. Soil removal mechanisms can be considered to comprise several steps: 1. Surfactant transport to an interface. This can occur with the surfactant in the monomeric form, in which case kinetics of transport are fairly rapid (10–5 cm2/sec), or with the surfactant in aggregated or micellar form in which case the kinetics of transport are relatively slow (10–7 cm2/sec). The kinetics of surfactant transport and adsorption at the interface can be measured via dynamic interfacial tensiometry [37–41]. 2. Adsorption of surfactant at the solution/soil interface, solution/atmosphere inter- face, and surface/solution interface. This step results in lowering of the interfa- Table 16 Enzymatic Based Detergents for Cleaning Food Processing Equipment Ingredients Weight % Examples A B C D Triethanolamine 2 2 2 2 Sodium metabisulfite 1 1 1 1 Propylene glycol 12 12 15 15 Sodium xylene sulfonate 20 20 20 20 Ethoxylated propoxylated nonionic 25 25 25 25 Protease 6.3 6.3 3.1 3.1 Water Balance Balance Balance Balance Source: From U.S. Patent 6,197,739 B1 to Ecolab Inc. Table 17 Representative Aqueous-Based Metal Cleaning Detergents Ingredients Weight % Examples A B C D Sodium carbonate 3 3 3 3 Borax 0.3 0.3 0.3 0.3 N-octylpyrrolidone — — — 2 1,2,3-Benzotriazole 0.3 0.3 0.3 0.3 C9-C11 Alcohol ethoxylate (E2.5) 2 — — 2 C9-C11 Alcohol ethoxylate (E6) 2 — — 2 C12-C15 Alcohol ethoxylate (E9) — 4 — — C14-C15 Alcohol ethoxylate (E7) — — 4 — Acrylic acid polymer 0.5 0.5 0.5 0.5 NaOH 0.5 0.5 0.5 0.5 Sodium silicate 2 2 2 2 Sodium nonanoate 6.5 6.5 6.5 6.5 Water Balance Balance Balance Balance Source: From U.S. Patent 6,124,253 to Church & Dwight Co. © 2006 by Taylor & Francis Group, LLC
- 46. 22 Showell cial energies at each of these interfaces. Adsorption is driven by the surfactant packing parameter (P = V/aoI) where V is the volume described by the hydro- phobic portion (alkyl chain) of the surfactant, ao is the mean cross-sectional area of the surfactant head group, and l is the all trans alkyl chain length of the hydrophobe (alkyl chain) [42]. Surfactants with 0 < P < 1/3 form micelles in aqueous solution. Surfactants with 1/3 < P < 1/2 form wormlike micelles and surfactants with 1/2 < P < 1 display vesicle formation. Controlling the surfactant packing parameter close to 1 (flat surfactant film) promotes strong adsorption and delivers very low-soil/bulk phase equilibrium interfacial tensions. 3. Formation of a surfactant:soil complex. This typically is represented as surfac- tant coating the soil to be removed either in a monolayer, or, at high enough surfactant concentrations with bilayer structures. During this step surfactant can promote solid soil softening and liquifaction. This is a critical step to promote roll-up or emulsification that takes place only with liquid soils. 4. Desorption of the surfactant:soil complex. For oily soils this occurs either via the classical roll-up mechanism or by solubilization of the oil into micellar surfactant aggregates. In the case of liquid soil, the energy required to remove the soil can be expressed as gow (1+cosq) where gow is the soil/solution interfacial tension and q is the soil/substrate contact angle. For large contact angle (180o) roll-up of the soil occurs. For small contact angles emulsification via low gow is the major mechanism of soil removal. 5. Transport of the surfactant:soil complex away from the surface. In the case of greasy soils that have lower density than the bulk solution, the soil simply floats to the surface. In other cases, mechanical energy or agitation is critical to move the surfactant:soil complex away from the interface. 6. The work, WR, to move soil (o) from the surface (s) to the bulk phase (w) can be directly related to the interfacial tensions of the various interfaces through the following [7]: WR = gsw + gow - gos (1) where gsw is the interfacial tension between the surface and bulk phase, gow is the interfacial tension between the soil and the bulk phase, and gos is the interfacial tension between the soil and the surface. From this equation it can be seen that the work required to remove soil from a surface is reduced when the interfacial tensions between the surface and bulk phase and soil and bulk phase are minimized and the interfacial tension of the soil-surface is increased. This is exactly the effect that surfactants have. By adsorbing at the surface, bulk-phase, and soil interfaces surfactant lowers interfacial energies, decreasing the free energy associated with moving the soil from the surface into the bulk phase. Surfactant adsorption causes the surface/bulk phase (gsw ) and soil/bulk phase (gow) interfacial tensions to drop while the interfacial tension between soil and surface (gos) increases thereby facilitating movement of the soil into the bulk phase. One aspect of the above that is often ignored is step one, transport of surfactant to the various interfaces. The presence of monomeric surfactant is critical to rapid transport of surfactant to the interface and rapid lowering of the interfacial tensions (IFT). However, solubilization is dependent on the presence of micelles. As surfactant concentration in solution is raised aggregates (micelles) form and at a certain concentration (critical micelle concentration, CMC) the monomer concentration of surfactant remains constant and addi- © 2006 by Taylor & Francis Group, LLC Stabilization of the dispersed soil to prevent redeposition (see Section IV B).
- 47. Introduction to Detergents 23 tional surfactant resides in micelles. The formation of micelles reduces the capacity of the surfactant to adsorb at the interface and reduce IFT that is critical in step 2. Therefore, there is an optimum CMC that must be achieved in order to optimize steps 1 and 2 above while still allowing efficient solubilization. This optimum is dependent on the nature of the soil being removed, the substrate (hydrophobicity), and the surfactant system used. The mechanism outlined above is generally applicable for oily soils. For particulate soils consideration of the electrostatic and van der Waals forces of attraction between the particle and the surface need to be considered because most particulate dirt and most surfaces tend to be charged due to the presence of surface exposed silicic acid, hydroxyl, or carboxyl groups [43]. . Again, the process can be described in a series of steps [44]. In the first step a soil particle, P, adhering to a surface, S, is removed a distance d with no penetration of liquid between the soil and the surface. The process requires work input, w1, to overcome the van der Waals attraction between P and S. Then detergent solution penetrates the space between P and S, allowing surfactant to adsorb at the solution-particle interface and the surface-solution interface, and a net sum of work, w2 , is obtained. The total work done in this first step is: W1 = w1 - w2 (2) In the second step the particle is removed from the surface to a distance large enough that there are effectively no forces of interaction between P and S. The work for this second step, W2, is composed of contributions from van der Waals attractions and the electrostatic repulsions between P and S, and is equal to the total potential energy of the system at the distance d such that W2 = -jd and the work done for the total process of removing an adhering particle, P, from surface S is equal to the sum of W1 and W2 or: SW = W1 + W2 = w1 - w2 - jd (3) The work, w2, created when surfactant adsorbs onto the particle and the surface can, in the first approximation, be described as the sum of various interfacial energies, similar to Eq. (1): w2 = gsp - gsw - gpw (4) where gpw is the interfacial tension between the particle and the solution phase. According to Eq. (3) the removal of particulate soil becomes easier as the total work to remove the particle, SW, becomes smaller. The addition of surfactant reduces both gsw and gpw such that w2 increases, which helps to lower the total work of removal. In addition, the total potential energy of the system jd is the sum of the attractive van der Waals interactions, jd,A, and the repulsive interactions, jd,R, due to surface charges. The adsorp- tion of surfactant, especially anionic surfactant, at the surface-solution and particle-solution interfaces serves to decrease the attractive force and increase the repulsive force thereby promoting removal to a distance where there are no longer any attractive forces between particle and surface. B. Suspension Mechanisms Once material is removed from a surface it must be suspended in the bulk phase to avoid redeposition. For hydrophobic liquid soils in aqueous media, suspension is typically accomplished by entrapment of the soil within the surfactant micelle or vesicle. For particulate soils suspension is often best achieved by adsorption of a charged polymer onto the surface of the particle thereby increasing electrostatic repulsion between particle- © 2006 by Taylor & Francis Group, LLC
- 48. 24 Showell particle and particle-surface interactions. There are two general mechanisms for suspend- ing soil in solution— electrostatic repulsion and steric stabilization. In polar media, most substances will acquire a surface electric charge as a result of ionization of surface chemical groups, ion adsorption, and ion dissolution [16]. In aqueous solutions most surfaces and most soil particles are negatively charged. As a result both soil and surface possess an electrical double layer. The electrical double layer is comprised of a compact layer of ions of opposite charge to the surface and a more diffuse double layer comprised of counter- and co-ions distributed in a diffuse manner in the polar medium. As described in Section IV A, the total potential energy for a system comprised of a particle at some distance, d, from a surface is the sum of the attractive force, jd,A, and the repulsive force jd,R. When two particles of the same net surface charge approach one another, or when a particle approaches a charged surface, they repel each other as their double layers start to overlap. The particles have to overcome this electrical barrier in order to get close enough for van der Waals attraction to take over. When the potential energy barrier jd,R is high particles tend to stay dispersed in the bulk phase. However, if the electrical double layer is compressed by high ionic strength or shielded by adsorption of an organic layer coalescence and aggregation can occur resulting in redeposition of soil particles back onto the surface. Electrostatic repulsion is best achieved in low ionic strength media where the electrical double layer on particles and surfaces is diffuse. An alternative strategy is to adsorb a charged polymer, such as the acrylic acid polymers described in Section II B, or a charged surfactant onto the surface. When particles having adsorbed layers (polymer or surfactant) collide, their adsorbed layers may be compressed without penetrating. This results in reduced configurations available to the adsorbed layer. In thermodynamic terms the reduction in potential con- figurations is expressed as a decrease in entropy for the system or an increase in free energy. This increased free energy of stabilization results from the “elastic” effect of colliding adsorbed layers and is referred to as steric stabilization. The positive free energy change is related to both the enthalpy and entropy change by DG = DH – TDS. Stabilization can therefore come either as a result of a positive change in enthalpy or a decrease in entropy. A positive DH reflects the release of bound solvent from the polymer chains as they interact and a negative DS results from the loss of configurational freedom of the polymer [16]. Steric stabilizers are usually block copolymers that make up a hydrophobic part (e.g., polyethyleneterepthalate) which attaches to the particle surface and a hydrophilic part (e.g., polyethylene glycol) which trails out into the bulk solution. Effective detergency results when the detergent formulation is designed to maximize four basic properties; penetration, wetting, dispersion, and emulsification. These four factors combined determine the ultimate effectiveness of the detergent formulation. Sub- sequent chapters of this book provide significantly more detail on how to design effective detergents for a variety of specific applications. ACKNOWLEDGMENTS I thank each of the authors of the individual chapters in this work for their effort and dedication in bringing the vision to life. Thanks to all of my friends and colleagues at Procter & Gamble who contributed their time and expertise to review and critique of the contributions. © 2006 by Taylor & Francis Group, LLC
- 49. Introduction to Detergents 25 REFERENCES 1. INFORM, Vol. 13, pp. 682–695 (September 2002). 2. J. W. B. Gogarty, Petroleum Techn., pp. 1475–1483 (1976). 3. X. Zheng, Y. Xie, L. Zhu, X. Jiang, and A. Yan, Ultrasonics Sonochem., 9(6):311 (2002). 4. R. W. Bassemir, A. Bean, O. Wasilewski, D. Kline, W. Hills, C. Su, I.R. Steel, and W. E. Rusterholz, in: Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. 14, 4th ed., New York, Wiley, pp. 482–503 (1995). 5. H. Hendricks and C. Nootens, J. Eur. Coat., 6:710 (2003). 6. T. F. Tadros, Surfactants in Agrochemicals, Vol. 54, Marcel Dekker Surfactant Science Series, New York (1995). 7. L. H. Tan Tai, Formulating Detergents and Personal Care Products, AOCS Press, Cham- paign, Illinois (2000). 8. Liquid Detergents, Vol. 67, ed. K-Y. Lai, Marcel-Dekker Surfactant Science Series, New York (1997). 9. Powdered Detergents, Vol. 71, ed. M. S. Showell, Marcel-Dekker Surfactant Science Series, New York (1998). 10. Nonionic Surfactants, Vols. 1(1967) and 23 (1987), ed. M. J. Schick, Marcel Dekker Sur- factant Science Series, New York. 11. Anionic Surfactants: Organic Chemistry, ed. H. W. Stache, Vol. 56, Marcel Dekker Surfac- tant Science Series, New York (1995 ). 12. Novel Surfactants: Preparation, Applications, and Biodegradability, ed. K. Holmberg, Vol 74, Marcel Dekker Surfactant Science Series (1998). 13. Detergency of Specialty Surfactants, ed. F. E. Friedli, Vol. 98, Marcel Dekker Surfactant Science Series, New York (2001). 14. P. K. Vinson, P. R. Foley, T. A. Cripe, D. S. Connor, and K. W. Willman, U.S. Patent 6,326,348 to The Procter & Gamble Co. (2001). 15. J. B. McClain, D. E. Betts, D. A. Canelas, E. T. Samulski, J. M. DeSimone, J. D. Londono, H. D. Cochran, G. D. Wignall, D. Chillura-Martino, and R. Triolo, Science, 274:2049 (1996). 16. D. J. Shaw, Introduction to Colloid and Surface Chemistry, 3rd ed., Butterworth & Co. Ltd., London (1980). 17. G. Swift in Powdered Detergents, Vol. 71, ed. M. S. Showell, Marcel Dekker Surfactant Science Series, New York (1998). 18. (a) A. M. B. Austin, A. M. Carrier, and M. L. Standish, U.S. Patent 5547612 to National Starch and Chemical Investment Holding Corp. (1996); (b) A. M. B. Austin, A. M. Carrier, and M. L. Standish, U.S. Patent 5,698,512 to National Starch and Chemical Investment Holding Corp. (1997); (c) E. Penzel, G. Franzmann, A. Maximilian, J. Pakusch, and B. Schuler, U.S. Patent 5604272 to BASF Aktiengesellschaft (1997); (d) W. Denzinger, A. Kisternmadner, J. Perner, A. Funhoff, B. Potthoff-Karl, and H-J. Raubenheimer, U.S. Patent 5,658,993 to BASF Aktiengesellschaft (1997). 19. A. duVosel, F. Francalanci, and P. Maggiorotti, Eur. Patent Application 454,126-A1 to Montedipe S.r.l. (1991). 20. T. Cassata, U.S. Patent 5,219,986 to Cygnus Corporation (1993). 21. M. Kroner, G. Schornick, W. Denzinger, R. Baur, K. Alexander, B. Potthoff-Karl, V. Sch- wendemann, German Patent Application DE 4,308,426-A to BASF AG (1993). 22. M. B. Freeman, Am. Oil Chemists Soc. Annual Meeting, San Antonio, Texas (1995). 23. S. W. Heinzman and S. J. Dupont, Eur. Patent 542,496-B1 to The Procter & Gamble Company (1998). 24. S. C. Sikes, L. Ringsdorf, and G. Swift, U.S. Patent 6,495,658 to Folia, Inc. (2002). 25. D. T. Nzudie and C. Collette, U.S. Patent 6,221,957 to Elf Atochem S. A. (2001). 26. (a) K. N. Price, U.S. Patent 6,444,633 B2 to The Procter & Gamble Company (2002); (b) K. N. Price U.S. Patent 6,479,451 B2 to The Procter & Gamble Company (2002). 27. J. V. Boskamp, Eur. Patent Apps. 0358473-A2 and 0358472-A2 to Unilever NV (1990). © 2006 by Taylor & Francis Group, LLC
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- 51. 27 2 Statistical Mixture Design for Optimization of Detergent Formulations Samir S. Ashrawi and George A. Smith CONTENTS I. Introduction ............................................................................................................ 27 II. Mixture Design Experiments ................................................................................. 29 III. Examples of Mixture Design Experiments............................................................ 31 A. Heavy Duty Liquid Detergent Optimization ............................................. 32 B. Light Duty Liquid Detergent Optimization............................................... 39 C. Detergent Concentrate Robustness Study.................................................. 45 IV. Conclusions ............................................................................................................ 49 References........................................................................................................................ 49 I. INTRODUCTION Development of new cleaning formulations can be a very arduous and time-consuming task. The formulator must choose from literally hundreds of raw materials. The individual ingredients must be combined in the proper ratio to obtain the best cost performance while satisfying a myriad of physical property and stability criteria. The formulation must also be robust enough to be produced on a commercial scale with little or no rework required to meet product specifications. Traditionally, formulators of cleaning products have used a trial-and-error approach to arrive at cost-effective, robust formulations. The formulator selects ingredients based on experience, availability, and cost in order to develop an initial starting formulation. The starting formulation is tested against competitive products and the results are analyzed to determine which physical and performance properties need improvement. The formulation is then modified and the process repeated in an iterative fashion until acceptable perfor- mance is obtained. It is common to optimize the formulation components one at a time to avoid confounding the response with other variables. © 2006 by Taylor & Francis Group, LLC
- 52. 28 Ashrawi and Smith In the trial-and-error approach, component variations are usually fairly small, which limits the composition space that is investigated to small perturbations around the starting formulation. Because responses are optimized one at a time, one is never quite sure that all properties and performance responses have been optimized. Furthermore, one is not sure if the observed optimum is local within the small composition space that was inves- tigated, or global within a much larger composition space. Finally, since this approach does not yield maps of performance over the composition space, it is not possible to predict the behavior of new formulations without continuous tweaking. An alternative, and more informative, approach is the use of statistical experimental design to optimize formulations. We have used various types of statistically designed experiments in our laboratories to help develop and optimize formulations for different applications [1,2]. Factorial screening designs are extremely helpful in identifying the vital factors or components that affect the desired product. Response surface designs are useful in locating the ideal criteria or process settings that yield optimum performance. And finally, mixture designs yield performance maps over a defined composition space, enabling us to discover the optimum formulation and to predict performance in other regions of the defined composition space. Figure 1 describes the framework of our statistical experimental approach to formu- lation development. Beginning with a well-defined goal of achieving certain performance criteria, physical properties, and cost, we conduct screening experiments to determine the components that would be vital to achieving our goal. Once the trial mixtures are prepared and the desired property or performance response is measured, the results can be analyzed Figure 1 Framework for formulation development using statistical experimental design. Model Generation & Validation Goal Definition Screening Design Mixture Design Properties Optimization Data Analysis Scenario Analysis Performance © 2006 by Taylor & Francis Group, LLC
- 53. Statistical Mixture Design for Optimization of Detergent Formulations 29 to determine how each component affects a particular response as the amount of that component is changed. Next, we use the components that most affect the measured response to develop a suitable mixture design. The mixture design trial formulations are prepared and the physical properties and performance responses are measured and recorded. A model that best fits the data is then generated and validated by exploring its statistical significance. With a good-fit model, one can then proceed to optimization of the composition to meet the required performance criteria. The authors have used mixture design experiments to optimize different types of cleaning formulations. Examples include laundry liquids, dishwashing liquids, and hard surface cleaners. Many times the results indicate that improvements in one property come at the expense of another. By measuring multiple responses it is possible to optimize the formulation to get the best overall performance for a wide variety of performance factors. Mixture design experiments can also be used to optimize formulation robustness. This allows us to obtain a product that can be easily manufactured on a commercial scale. II. MIXTURE DESIGN EXPERIMENTS It is not the purpose of this chapter to delve into all the mathematical details of mixture design experiments. Our intent is to present only the major salient points to better under- stand the basic assumptions behind the technique. For a more complete discussion of statistics as applied to mixture designs, the reader is invited to peruse the pertinent literature [3–5]. In a mixture design experiment, two or more individual ingredients are blended together to produce a final product or formulation. Measurements of the physical properties and the performance for several different trial blends are made and the results used to find the best overall result. The measured properties depend only on the relative proportions of the individual ingredients and not on the total amount present. The defining feature of a mixture design is that the proportions of the ingredients sum to unity. In mathematical terms, if the number of ingredients in the system is given by q, and the proportion of the ith component is given by xi Because of the restrictions imposed by Eqs. (1) and (2), the experimental region of interest is a (q-1) dimensional space. For q = 2, the dimensional space is a straight line and can be represented on a conventional x-y plot. For q = 3, the dimensional space is an equilateral triangle and can be represented in triangular coordinates. For q = 4, the dimensional space is a tetrahedron. Since the proportions sum to unity, the xi are con- strained variables; varying the proportion of one component will change the proportion of at least one other component in the mixture. In mixture design experiments, the experimental data are defined in a quantitative fashion, the purpose of which is to model the mixture behavior using some form of a mathematical equation. This allows for predictions of the response for any combination of ingredients and allows for a measure of the influence for each component or combination of components on the measured response. For and (1) (2) xi ≥ 0 i q = 1 2 , ,..., χ χ χ χ i q i q = + + + = = ∑ 1 2 1 1 ..... © 2006 by Taylor & Francis Group, LLC
- 54. 30 Ashrawi and Smith The data from a mixture design experiment are modeled in the following fashion. Assuming that the response factor η depends only on the proportions of the individual components: (3) We assume that the function is continuous for all χi, and can be represented by a first- or second-order polynomial. Only on rare occasions is a third-degree (cubic) poly- nomial necessary to represent the data. In actual practice, it is convenient to use a canonical form for the polynomial fitting equation. This acts to reduce the number of fitting parameters compared to a standard power series polynomial expression. Canonical polynomial expressions were developed by Henri Scheffé in the early 1950s specifically for mixture design experiments [6,7]. The Scheffé quadratic polynomial for two components is given by (4) The Scheffé form of the fitting equation is also easy to interpret. The coefficients for the main effects are responses for the pure components. The coefficients for the mixed terms give a measure of positive or negative deviation from the response predicted for ideal mixing of the individual components. Up until this point, we have not discussed the experimental error associated with the measured responses. Experimental error can arise from various sources including sample preparation, analytical methodology, mechanical noise, and equipment problems. In an experimental program consisting of N trials, the observed value of the response in the uth trial is given by yu and is assumed to vary about the mean of η with a common variance σ2. The observed response value contains experimental error εu (5) where the errors are assumed to be independent with a common variance. The Scheffé expression for two components becomes (6) With N 2 observations collected on yu, we can obtain the estimates b1 and b2 of the parameters and , respectively. The parameters of Eq. (6) can be replaced by their respective estimates to give the approximating equation (7) where is the predicted value of for given values of x1 and x2. The estimated parameters contain the main effects plus any error associated with measurement of the response variables. In practice, the magnitude of error associated with the measured responses can be determined by replicating some of the trial blends. Differences in the response values of the replicate samples are taken as a measure of the experimental error. Lack of fit tests η χ χ χ = f q ( , ,..... ) 1 2 η β χ β χ χ = + ∑ ∑ ∑ i i ij i j j q i q i q βi ( ) βij ( ) yu u = + η ε 1 ≤ ≤ u N yu u = + + β χ β χ ε 1 1 2 2 ≥ β1 β2 ˆ( ) y x b b = + 1 1 2 2 χ χ ˆ( ) y x η © 2006 by Taylor & Francis Group, LLC
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- 56. AN ANECDOTE by Forrest J. Ackerman In the early days of science fiction when there were not many authors who wrote it and Amazing was chiefly a magazine of Verne- Wells-Poe reprints, Bob Olsen was writing and had a friend who thought he could too. Bob had two tales published in Amazing without mentioning the accomplishment to his friend who succeeded in having nothing accepted (he was not writing stf). Then, with the third story, Bob's name appeared on the cover, giving him quite a thrill. 'Stories by: H. G. Wells, Bob Olsen, Edgar Allan Poe', it read. "Uh, what do you think of that?" asked Bob proudly, now displaying his work, his name with Wells and Poe. The friend sized up a moment. Then, "They've got you just right, all right," he seemed to have to admit, Bob swelling with pride—"half way between a live one and a dead one!" Bob still thinks he was a little bit envious, tho. Tell your friends to read THE FANTASY FAN ALIER'S ALIBI by Mortimer Weisinger Years ago, when Hugo Gernsback's "Scientific Adventures of Baron Munchhausen" were appearing serially in the Electrical Experimenter, it occasionally transpired that an installment was omitted. At such intervals various ingenious excuses were offered to explain the
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