GB369215A - A process of hydrolysing cellulose acetate - Google Patents

Abstract

Comprises the hydrolysis of fibrous or precipitated cellulose triacetate in presence of a solvent mixture of ethylene dichloride and an organic acid, preferably acetic acid. Ethylene chloride may constitute 75 per cent or more of the solvent mixture, but should be at least 25 per cent of the acetic acid. Hydrolysis is preferably conducted at a temperature of approximately 50 DEG C. for 18-24 hours. Suitable hydrolysing agents comprise alcohol or water and the usual acid or other catalyst. After hydrolysis, the solution is immersed in or preferably extruded into a hot precipitating medium, e.g. water, which is kept at a temperature well above the boiling point of ethylene chloride, whereas the latter is flashed out from the solution and the cellulose acetate is precipitated in a light, fluffy form and can be readily washed and dried. The ethylene chloride is recovered by suitable collecting and condensing means. In an example, 88 parts of fibrous or precipitated cellulose triacetate is dissolved in a bath containing 234 parts glacial acetic acid, 312 parts ethylene chloride, 26 parts water, 23 parts sodium acid sulphate monohydrate, 0,9 parts sulphuric acid, and 2,7 parts phosphoric acid; the solution is kept at 50 DEG C. for 18-22 hours, and the cellulose acetate is then precipitated in hot water. Specifications 337,366, [Class 2 (ii), Cellulose &c.], and 356,012, are referred to. The Specification as open to inspection under Sect. 91 (3) (a) refers also to hydrolysis applied directly to acetylation baths. This subject-matter does not appear in the Specification as accepted.