SOAPS & DETERGENTS
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Soaps are made by reacting fats or oils with a strong alkali like sodium hydroxide. Detergents are similar cleansing agents but use synthetic surfactants instead of fats/oils and do not form scum with hard water. The manufacturing process for soaps involves saponification of fats/oils, glycerin removal, purification, and finishing. Detergent production uses petrochemical raw materials and involves slurry making and spray drying. Both have advantages like cleaning ability but can harm aquatic environments if not properly treated in wastewater.
SOAPS & DETERGENTS
- 2. Soap Definition: Soaps are water soluble sodium or potassium salts of fatty acids. Soaps are made from fats and oils, or their fatty acids, by treating them chemically with a strong alkali. OR Soap is a cleansing agent created by the chemical reaction of a fatty acid with an alkali metal hydroxide. Soap has general chemical formula “RCOOX”.
- 3. Raw Material: 1) Fats and Oils: Fats & Oil are used in soap-making come from animal or plant sources. Each fat or oil is made up of a distinctive mixture of several different triglycerides. In a triglyceride molecule, three fatty acid molecules are attached to one molecule of glycerine. There are many types of triglycerides; each type consists of its own particular combination of fatty acids. Fatty acids are the components of fats and oils that are used in making soap. They are weak acids composed of two parts: A carboxylic acid group consisting of one hydrogen (H) atom, two oxygen (O) atoms, and one carbon (C) atom, plus a hydrocarbon chain attached to the carboxylic acid group. Generally, it is made up of a long straight chain of carbon (C) atoms each carrying two hydrogen (H) atoms. 2) Alkali: • An alkali is a soluble salt of an alkali metal like sodium or potassium. Originally, the alkalis used in soap-making were obtained from the ashes of plants, but they are now made commercially. Today, the term alkali describes a substance that chemically is a base (the opposite of an acid) and that reacts with and neutralizes an acid. • The common alkalis used in soap-making are sodium hydroxide (NaOH), also called caustic soda; and potassium hydroxide (KOH), also called caustic potash.
- 4. Soap Manufacturing Process Soaps are the product of the reaction between a fat and sodium hydroxide. fat + 3NaOH → glycerine + 3 soap Soaps are produce industrially in four basic steps. 1. Saponification The chemical reaction between any fat and sodium hydroxide is a saponification reaction. OR The process of making soap by the hydrolysis of fats and oils with alkalies. In saponification, a mixture of tallow (animal fat) and coconut oil is mixed with sodium hydroxide and heated. The soap produced is the salt of a long chain carboxylic acid. 2. Glycerine Removal Glycerine is more valuable than soap, so most of it is removed. Some is left in the soap to help make it soft and smooth. Soap is not very soluble in salt water, whereas glycerine is, so salt is
- 5. added to the wet soap causing it to separate out into soap and glycerine in salt water. 3. Soap Purification Any remaining sodium hydroxide is neutralized with a weak acid such as citric acid and two thirds of the remaining water removed. 4. Finishing Additives such as preservatives, colour and perfume are added and mixed in with the soap and it is shaped into bars for sale.
- 7. ANCILLIARY PROCESSES Glycerine Recovery As has already been stated, glycerine is more valuable than the soap itself, and so as much of it as possible is extracted from the soap. This is done in a three step process. Step: 1 - (Soap Removal) The spent lye contains a small quantity of dissolved soap which must be removed before the evaporation process. This is done by treating the spent lye with ferrous chloride. Step: 2 - (Salt Removal) Water is removed from the lye in a vacuum evaporator, causing the salt to crystallize out as the solution becomes supersaturated. This is removed in a centrifuge, dissolved in hot water and stored for use as fresh lye. When the glycerine content of the solution reaches 80 - 85% it is pumped to the crude settling tank where more salt separates out.
- 8. Step: 3 - (Glycerine Purification) A small amount of caustic soda is added to the crude glycerine and the solution then distilled under vacuum in a heated still. Two fractions are taken off - one of pure glycerine and one of glycerine and water. The glycerine thus extracted is bleached with carbon black then transferred to drums for sale, while the water/glycerine fraction is mixed with the incoming spent lye and repeats the treatment cycle.
- 9. Classification of Soap • Run and Glued Up Soaps • Curd Soap • Sulphur Soap • Tar Soap • Carbolic Soap • Peroxide Soap • Mercury Soap • Castile Soap • Transparent Soap • Shaying Soap • Pumice/ Sand Soap • Liquid Soap • Textile Soap.
- 10. Advantages & Disadvantages of Soap Advantages: • Very effective as a bactericide. • It will form gels, emulsify oil and lower the surfaces tension of water. • Excellent everyday cleaning agent. • Good biodegradability Disadvantages: • Oils and perfume are immiscible in water and if spilled create havoc, although the oils do solidify at room temperature. • When used in hard water, soap can produced a scum. Note:- Soaps, will react with metal ions in the water and can form insoluble precipitates (soap scum).
- 11. Detergents Definition: A water-soluble cleansing agent which combines with impurities and dirt to make them more soluble, and differs from soap in not forming a scum with the salts in hard water. OR • Detergents are the sodium salts of long chain benzene sulphuric acids. • It is used in both, Powder and Liquid form, and sold as laundry powders, hard surface cleansers, dish washing liquids, fabric conditioners etc.
- 12. Raw Material Petrochemicals are utilized as a raw material for the manufacturing of detergents. Explanation: Primarily surfactants, which could be produced easily from petrochemicals. Surfactants lower the surface tension of water, essentially making it 'wetter' so that it is less likely to stick to itself and more likely to interact with oil and grease. (SURFACTANTS - SURFACE ACTIVE AGENTS)
- 13. Detergent Manufacturing Process • Step 1 - Slurry Making The solid and liquid raw ingredients are dropped into a large tank known as a slurry mixer. As the ingredients are added the mixture heats up as a result of two exothermic reactions: the hydration of sodium tripolyphosphate and the reaction between caustic soda and linear alkylbenzenesulphonic acid. The mixture is then further heated to 85oC and stirred until it forms a homogeneous slurry. • Step 2 - Spray Drying The slurry is deaerated in a vacuum chamber and then separated by an atomiser into finely divided droplets. These are sprayed into a column of air at 425 C, where they dry instantaneously. The resultant powder is known as 'base powder', and its exact treatment from this point on depends on the product being made.
- 14. • Step 3 - Post dosing Other ingredients are now added, and the air blown through the mixture in a fluidiser to mix them into a homogeneous powder. Typical ingredients are listed in the following table.
- 16. Advantages & Disadvantages of Detergent Advantages: • Biodegradable . • Detergents do not decompose in acidic medium. • As detergents are derived from petroleum they save on natural vegetable oils. Disadvantages: • Their elimination from municipal wastewaters by the usual treatments is a problem. • It has tendency to produce stable foams in rivers that extend over several hundred meters of the river water. • It is dangerous to aquatic life. • Some surfactants are incompletely broken down with conventional treatment processes • It an inhibitor oxidation. Wastes: • Phosphate Builders • Excess of detergent foam • Effluent • Excess chemicals
- 17. Soap & Detergents Products Four General Categories: • Personal Cleansing – include bar soaps, gels, liquid soaps and heavy duty hand cleaners. • Laundry – available as liquids, powders, gels, sticks, spray pumps, sheets and bars Personal Cleansing laundry dishwashing Household Cleaning
- 18. • Dishwashing – include detergents for hand and machine dishwashing as well as some specialty products. (liquids, gels, powders, solids) • Household Cleaning – available as liquids, gels, powders, sheets and pads for use on painted, plastic, metal, porcelain, glass and other surfaces, and on washable floor coverings.