GB447530A - Improvements in or relating to the production of cellulose esters - Google Patents

Abstract

Cellulose is esterified in presence of a polybasic inorganic acid or acid derivative thereof as catalyst, the ester is ripened in the esterification solution, a salt of basic character containing a metal of Groups 2--4 of the Periodic Table, or two or more substances which react to form such a salt, is added in amount at least sufficient to neutralize inorganic acid present, and the cellulose ester is precipitated from the solution by means of a non-solvent. The catalyst may be sulphuric acid, sodium bisulphate, methyl sulphate or a mixture of these with each other, or with any other catalyst such as zinc chloride. The basic salt may be basic aluminium acetate, sodium aluminate, sodium stannate, calcium acetate, barium acetate, zinc acetate, or mixtures of aluminium chloride and sodium acetate, or aluminium acetate, lime, acetic acid, and aluminium sulphate, or zinc chloride and sodium acetate. The solution may be heated after addition of the salt and before precipitation of the ester. The process is applicable to the production of cellulose formate, acetate, propionate, or butyrate. The products are free from sulphur compounds and have high stability to light and heat. They may be used for the production of artificial filaments. The ripening may be effected in the presence of metal halides. The catalyst may be neutralized by an ammonium salt of an organic acid or by an alkali metal carbonate. In an example, ripened cellulose acetate solution is mixed with basic aluminium acetate, the solution is heated for several hours, and the cellulose acetate is then precipitated. In another example, sodium acetate is added to a ripened cellulose acetate solution to neutralize the sulphuric acid present. The solution is heated and zinc chloride dissolved in glacial acetic acid is added. After several hours the solution is cooled and the cellulose acetate is precipitated. Specification 446,723 is referred to.