GB587522A - Improvements relating to the production of aluminium soaps - Google Patents

Abstract

In the manufacture of aluminium soaps having gelling power towards hydrocarbon oils by an aqueous precipitation process wherein a water soluble salt of aluminium is mixed with either a water-soluble salt of an organic acid reaction component or the organic acid itself in the presence of a water-soluble alkali hydroxide or carbonate under conditions of agitation and at a temperature compatible with a melted condition of the organic acid employed, the process is effected under conditions which are not substantially akaline, in the presence of a hydrophylic colloid dispersed in the bath, whereby a proportion of the colloid becomes incorporated with the precipitate so as to persist in the dried product. The organic acids are aliphatic or cycloaliphatic and contain not less than six carbon atoms in the molecule, specified reactants being caproic, lauric, stearic, palmitic, oleic, ricinoleic acids or naphthenic acid or mixtures of such acids. Specified protective colloids are: gelatine, glue, albumen, gum arabic, polyvinyl alcohol, methyl cellulose, isinglass, soluble starch, agar agar and saponin. Advantageously the bulk of the precipitation is effected under conditions of non-alkalinity of the bath, optionally in the presence of a buffer reagent such as sodium acetate. The precipitate at first formed is preferably allowed to mature, with continued agitation of the bath for a period of several hours before filtration, and meanwhile a part of the total quantity of alkali necessary may be added. The organic acid and alkali reactants are preferably added to an already prepared bath of the aluminium salt reactant, the addition being preferably in the form of a substantially neutralised aqueous solution of an alkali soap of the organic component. The product is desirably such as readily forms a gel when dissolved in pure benzene, containing a little phenol, by a specified procedure. When it is aluminium stearate it may suitably contain a proportion of free stearic acid. In an example, an aqueous solution of aluminium sulphate is treated with an aqueous glue solution at 60 DEG C. and to the stirred mixture at 60 DEG C. is added a soap solution formed by dissolving commercial stearic acid in an aqueous mixture of acetic acid and caustic soda, the pH being approximately 3.5-4.0 while the bulk of the precipitable hydrated alumina stearate is formed as a highly dispersed precipitate of fine granular texture. More but smaller quantities of precipitate are then formed by adding 10 per cent. aqueous soda ash until the pH is 5.2 and the stirring of the mixture is continued for about 5 hours at 60 DEG C. with periodic addition of further small quantities of soda ash to maintain the pH at 5.2 and below 5.3 until precipitation is complete. In further examples the same procedure is followed except in that the factors pH value and nature of colloid are varied within the scope of the invention. The Provisional Specification comprises the optional use of protective colloids in general, casein being additionally specified.