GB736413A - Improvements in and relating to the manufacture of sebacic acid - Google Patents

Abstract

Sebacic acid is obtained by reacting an alkali metal soap of ricinoleic acid, if desired in the presence of added water, at elevated temperature with caustic alkali, the mixture being dissolved in a fatty acid alkali metal soap which is liquid at said elevated temperature. The ricinoleic acid soap may be formed in situ from castor oil and the caustic alkali. If castor oil is used it is preferred to add an amount of water corresponding to that which would be formed if free ricinoleic acid had been used instead, by neutralization of the acid with the caustic alkali. The preferred caustic alkalis are caustic soda and caustic potash. Suitable fatty acid alkali metal soaps are those of soap forming natural or synthetic fatty acids having straight or branched chain structures. These soaps may be made in the course of the reaction either by alkaline oxidation of the corresponding alcohol or by alkaline degradation of unsaturated hydroxyl-group-free fatty acids, allowance being made for the alkali consumption involved. The reaction may be carried out at 200-350 DEG C. and is preferably carried out in the presence of cadmium or a cadmium compound or in a cadmium coated autoclave. In examples the reaction components are heated with stirring in a copper-lined steel autoclave and at the end of the reaction the pressure is released and the contents dissolved in or diluted with water. The pH of the resulting solution is adjusted to a value of 6 to precipitate monobasic fatty acids and the octanol formed is driven off with steam. After removing the precipitated fatty acids the solution is acidified and cooled to yield sebacic acid. In the three examples given the starting materials are (1) and (2) castor oil, soyabean fatty acids, caustic soda, water and cadmium oxide; (3) castor oil, a mixture of fatty alcohols from whale oil, caustic soda, water, and cadmium oxide. In each case the ricinoleic acid alkali metal salt and the fatty acid alkali metal soap are formed during the reaction. Specification 698,154 is referred to.