MANUFACTURE OF SOAP:
Soap is sodium or potassium salt of fatty acids, mainly oleic, stearic, palmttic, lauric and myristic.
Fat is the primary greasy material in cleanser making.. It contains mixed glycerides obtained from the solid fat of cattle. This solid fat is digested with steam. The tallow forms a layer above water and is easily removed. Tallow is usually mixed with coconut oil to increase the solubility of soap. Greases are also used as raw materials for soap making. These are important sources of glycerides of fatty acids. The soap made from coconut oil lathers well. Inorganic chemicals added to soap are called builders e.g., soda ash, sodium tripolyphosphate, tatrasodium pyrophosphate.
Soap is manufactured by saponification of glycerides of fatty acids. The basic chemical reaction in soap making is saponification of fat.
The following two steps are involved in soap making:
The fat is hydrolyzed to get fatty acids and glycerine. The fatty acid is neutralized with caustic soda solution to form soap.
The fatty oil is deaerated under vacuum to prevent darkening by oxidation during processing. It is charged at a controlled rate to the bottom of the hydrolyzing tower, which breaks the fat into droplets. These are about 20 m high and 60 cm in diameter and are made of stainless steel. At the same time deaerated, demineralised water is fed to the top of contacting section to separated glycerine from fatty phase. They fatty acids are discharged from the top of the hydrolyser to a decanter and glycerine _ water solution from the s bottom. The molten fatty acid is run into pans and neutralized with 50 % caustic soda to get soap.
The neat soap is discharged at 93 ºC into blending tank and extruded, milled flake or spray – dried. The soap is heated at about 200 ºC under high pressure steam exchanger. The heated soap is released to a flash tank at atmosphere pressure, where partial drying takes place. The soap is cooled from 105 ºC to about 65 and cut into bar lengths.
The main classes of soap are toilet and industrial soaps. All soaps contain 10 – 30ºC water. If soap is anhydrous, It would be to hard to dissolve it. Toilet soaps contain 10-10 % moisture and have perfume and a fraction of a percent of titanium dioxide as a whitening agent shaving soaps are potassium salts of mainly stearic acid.