GB604282A - Improvements in or relating to process for the manufacture of soap - Google Patents

Abstract

<PICT:0604282/III/1> Saponifiable matter such as animal or vegetable fat or oil is converted into soap by heating it with an aqueous solution of a saponifying agent in presence of a relatively large amount of inert organic diluent having a solvent action on the saponifiable material, the proportion of inert diluent being sufficient to render the reaction mixture flowable and to enable the saponification reaction to be carried out at a temperature below that at which the soap would be molten when the volatile matter is removed. The proportion of diluent is preferably at least 50 per cent, and preferably is between 75 and 150 per cent by weight of the saponifiable material so as to render the mixture fluid below the melting point of the pure soap. The diluent is preferably miscible with the soap product as well as the saponifiable matter. It may be a petroleum fraction of boiling range 450 DEG -500 DEG F., or kerosene, naphtha, gas oil, toluene, xylene, trichlorbenzene, or tetrachlorethane. The process may be carried out as a continuous operation and the soap may be obtained in powder form. The saponifying agent may be caustic soda or potash and it may be used in a concentration of 50 per cent or less, but preferably not below 25 per cent. The mixture may be emulsified before effecting saponification. The saponification may be carried out at 300 DEG to 350 DEG F. In an example, 100 parts of tallow are dissolved in 114 parts of a petroleum fraction of boiling range 450-500 DEG F. and the solution is emulsified with a 51 per cent caustic soda solution in the proportion of 12.9 parts of caustic solution to 100 parts of the fat-diluent solution. The emulsion is passed through a saponification coil under 100 pounds per sq. in. pressure and at 400 DEG F. As shown in Fig. 1, a solution of saponifiable material in an inert diluent is placed in tank 10, and caustic soda solution is placed in tank 13. The two solutions are drawn by a proportioning pump 18 and fed to a homogenizer 20. The emulsion passes to a mixer 23 and is pumped to saponification coil 28 which is heated by a burner 29 or oil bath. The temperature of saponification may be 400 DEG F. for a seven minute reaction period. It is preferably substantially below the melting point of the soap when anhydrous. The pressure within the coil may be 100 pounds per square inch. The fluid product of saponification passes through a preheating coil 31 and is then sprayed into a flash chamber 35 which is maintained at low pressure. The volatile constituents, including inert diluent and glycerine are volatilzed. Solid soap particles settle as a fine powder at the bottom of the chamber and are continuously removed by a screw conveyer 40. The vapours are passed to a condenser and the inert diluent is separated from the glycerine and water. The glycerine and water are separated by fractional distillation. If desired, the temperature and pressure of the reaction mixture may be such that a substantial amount of the water is vaporized prior to entry of the mixture into the flash chamber.