GB607721A - Continuous process for neutralizing fatty acids - Google Patents

Abstract

Soap is made by a continuous process in which fatty acids and an aqueous solution of neutralising agent are intimately mixed to give a product containing 12-27 per cent water, the temperature of the reactants being regulated so that the soap as formed is in a pumpable condition, and the mixing being carried out in close proximity to a heat-absorbing medium adapted to minimise local overheating arising from the exothermic reaction. One method of providing such a heat-absorbing medium is by pre-cooling the fatty acids so that a substantial proportion of them are in the form of crystals which are suspended as a slurry in a mother liquid of unsolidified fatty acids. A substantial proportion of the heat of reaction is thus used in melting the fatty acid crystals. Another method is by conducting the neutralisation reaction within an efficient continuous cooling device, such as the cooling and agitating device illustrated in Specification 555,034. A third method is by recirculating through the mixing zone, where the fatty acids and alkali solution meet, a large quantity of the fluid soap previously made by the neutralisation reaction. The soap thus re-circulated may be used at the temperature at which it is formed or it may be cooled before it is brought back to the mixing zone. If desired, one of the proportioned streams of reactants (preferably the stream of fatty acids) may be merged with the re-circulated stream of soap ahead of the point at which the proportioned stream of the other reactant enters the process. The fluid soap to be re-circulated may be cooled by passing through a continuous cooling device in contact with which the reactants flow. More than one of the methods of providing a heat-absorbing medium referred to may be employed. The soap-making process may be carried out according to Specification 555,034 so that the beta phase of the soap is made or it may be carried out in such a way that the beta phase is not formed. Fatty acids which may be employed are those derived from tallow, hog grease or lard, waste greases, palm oil, olive oil, olive oil foots, coconut oil, palm kernel oil, hydrogenated fish oils and marine animal oils, hydrogenated cottonseed and soybean oils, foots or soapstock from the caustic refining of crude vegetable oils, rosin, and synthetic fatty acids derived from petroleum and other organic sources. The neutralising agent may be sodium hydroxide, potassium hydroxide, ammonium hydroxide, the alkylamine and alkanolamine hydroxides, carbonates of alkalies such as sodium carbonate, and mixtures of these alkaline materials. Adjuvants such as glycerin, salt, free alkali, sodium silicate, sodium carbonate, sodium phosphate, other soap builders, preservatives, colouring matter, perfume, or air may be introduced at any convenient point in the process. In the examples: (1) an aqueous solution of caustic soda containing common salt is mixed with a melted mixture of tallow fatty acids and coconut oil fatty acids containing crystals of fatty acids, with re-circulation of the soap formed if desired; (2) caustic soda solution is mixed with a molten mixture of tallow fatty acids, cottonseed foots fatty acids and rosin, while perfume, preservative and sodium silicate solution are also introduced into the mixer which is cooled; the soap formed may be re-circulated if desired; (3) an aqueous solution of sodium and potassium hydroxides is mixed with a mixture of tallow fatty acids, palm oil fatty acids and fatty acids of hydrogenated vegetable oil, with re-circulation of the soap formed, and (4) an aqueous solution of sodium and potassium hydroxides containing common salt is mixed with a mixture of commercial distilled oleic acid and fatty acids of tallow, with re-circulation of the soap formed after cooling. Mention is made of the production of soap granules by passing the soap formed in the examples to the spray-drying tower of U.S.A. Specification 1,985,987, of the production of soap bars by passing the soap to the bar soap former of U.S.A. Specification 1,416,483, and of the introduction of perfume and preservative into the soap in the continuous crutcher of U.S.A. Specification 2,024,425.