Improvements in or relating to preparation of cellulose acetate sorbate

摘要

Cellulose acetate sorbate having a total acyl degree of substitution (D.S.) of 2.2-2.9, the sorboyl D.S. being 0.01-0.35, is obtained by completely acylating cellulose, in the presence of a substantial amount of methylene chloride and a minimum effective catalytic amount of sulphuric acid, with an anhydride mixture of acetic and sorbic acids in which the sorbic acid amounts to 0.0023 to 0.13 mole. fraction of the organic acids and the anhydride value of the mixture amounts to at least 3 moles. anhydride per anhydroglucose unit, and partially hydrolysing the completely acylated cellulose by heating on the average at 50 DEG -55 DEG C., but not exceeding 65 DEG C., in the presence of 5-15 per cent (based on the weight of the cellulose) of either p-toluene sulphonic acid, benzene sulphonic acid, methane- or ethane-sulphonic acid or methionic acid as hydrolysis catalyst and with no more sulphuric acid than that used in the esterification step and in the presence of aqueous acetic acid containing 5-30 per cent of water. The sulphuric acid used is preferably below 1.5 per cent based on the weight of the cellulose. The acylation may take place at 20-60 DEG C. The products obtained are stable against degradation by heat. They may be rendered insoluble in organic solvents by subjecting them to the action of actinic light or by heating them in the presence of peroxides or other oxidizing agents. Such treatment appears to effect polymerization and cross-linking of the molecules. To avoid premature cross-linking, hydroquinone, catechol, pyrogallol, t-butyl catechol, di-t-butyl hydroquinone, hydroquinone benzyl ether, a -naphthylamine, diphenylamine, phenyl-b -naphthylamine or other anti-oxidant may be added to the solution of the cellulose ester during the hydrolysis step. The anhydride mixture used for the esterification may be a mixture of acetic acid and sorbic anhydride, acetic anhydride and sorbic acid, or a mixed anhydride. The cellulose acetate sorbate may be used for making filaments, films, lacquers and moulded articles. Bristle-like filaments for use in paint brushes may be produced. Benzoyl peroxide may be incorporated in the solution or composition from which filaments, films or lacquers are formed, or it may be incorporated in a moulding powder before or after grinding. Filaments or films may be insolubilized by heating them in boiling water, or an aqueous solution of acetone, alcohol or other organic liquid in the presence of benzoyl peroxide, hydrogen peroxide, potassium persulphate or other oxidizing agent, or in presence of actinic light. The cellulose acetate sorbate may be used in printing inks or in laminated structures comprising paper, wood, metals, glass, leather or textile fibres or fabrics. It may be used for coating wire and for impregnating porous materials.