Patent GB-644358-A (GB)
Title: Improvements in or relating to the continuous production of soap
IPC: C11D13/04
Filed: 1946-10-21
Abstract: <PICT:0644358/III/1> A process for the continuous manufacture of neat soap comprises forming an emulsion of the water-in-oil type between a glyceride mixture at a temperature slightly above the melting point and an alkaline lye, the lye being at a concentration high enough to lead to the production of a soap having a water content corresponding to neat soap and in quantity in excess of that necessary for complete saponification, homogenizing and initiating saponification by a momentary application of heat near the entrance of the saponification chamber to bring the temperature at that point to about 100 DEG  C., after which the temperature is maintained by the heat evolved by the exothermic reaction.  The neat soap is washed at a temperature of about 100 DEG  C. by an electrolytic solution such as brine, at a concentration near the critical concentration below which soap may be dissolved, and then by an alkaline lye, followed by neutralization of the major portion of the alkali contained in the soap by a fatty acid.  The process is automatically controlled by a testing device responsive to the presence of unsaponified material at the termination of the saponification stage, and by another testing device responsive to alkalinity situated at the delivery point of the final product.  A diagrammatic view of the plant is shown in Fig. 1. Melted tallow at a temperature of 45 DEG  C. from a tank 1 is mixed with 40 per cent NaOH from a tank 2 by a metering pump 5 such as described in Specification 623,051, [Group XVIII]. materials are emulsified by an agitator 9 and then pass to a homogenizer 10, the temperature still being low.  They then enter a saponification chamber 11 at the entrance of which is a heater 12 arranged to raise the temperature of the walls at that point to 100 DEG  C. to cause saponification to start, after which the heater can be cut out as saponification proceeds automatically.  The saponified mixture then passes through mixing devices m3,m2 and settling devices s3, s2 in counter current to brine from the tanks r3, r2.  The soap is then freed from salt by two washings in countercurrent with 12 per cent NaOH from the tanks r1, r0, and the excess caustic soda is removed by treatment with cocoa-nut fat from a tank d  by homogenizing it and conducting it at 100 DEG  C. through a saponification chamber 13. The last trace of alkali is removed by a buffer mixture, or free fatty acid, or by free or dispersed rosin, for example a mixture of lauric acid and acidic triethylolamine sulphoricinate from a tank e . The soap finally passes through a homogenizer 14 to cooling rollers 15 for drying, milling or other treatment.  The automatic control of the saponification stage is effected by withdrawing a small quantity of soap at b , dissolving it in boiling distilled water in a long sinuous tube, Fig. 2, and passing the solution through a glass tank 16 having blackened walls on one side and a source of light S at the end.  If the solution is cloudy owing to unchanged fat, a photo-electric cell P receives light by diffusion and stops the apparatus.  The alkalinity of the final soap product is similarly checked at g  by wiping a continuous band of alcoholic phenol phthalein solution across the sheet of soap on the roller 15.  A beam of light is caused to fall on the thus moistened area of the soap and is reflected into a photo-electric cell provided with a monochromatic blue screen.  The cell is arranged to stop the apparatus should a red colouring appear. Specification 636,945 also is referred to.