GB231809A - Manufacture of new cellulose derivatives - Google Patents

Abstract

Cellulose derivatives soluble in aqueous alkalies, and which are precipitated as products insoluble in water by the addition of alcohol to the solutions in aqueous alkalies, are prepared by carrying out the treatment of cellulose or a cellulose conversion product insoluble in alkali, with a monohalogen fatty acid, or a salt or ester of such acid, and alkali, in the absence of alcohol or in the presence of not more than 20 parts of alcohol for each 100 parts of water present; the process is conducted so that the maximum quantity of halogen fatty acid &c. is inversely proportional to the strength of the alkali solution. Other conditions are:-the halogen fatty acid should not be used in more than 18/a molecular proportions to each molecular proportion of caustic alkali, where a represents the percentage strength of the alkali lye; for each molecular proportion of caustic alkali, if this is used as a solution of not more than 25 per cent strength, there should be used not more than 180 (n + 1)/a molecular proportions of halogen fatty acid (a being the percentage strength of the alkali lye, and n the number of parts of alkali lye used to each part of cellulose), or, if the alkali lye is of more than 25 per cent strength, not more than 60/a (n + 1) molecular equivalents of halogen fatty acid, or generally, with lye up to 25 per cent strength, not more than 0.75-1 molecular proportions of halogen fatty acid, and with stronger lye, not more than 0.5-0.6 molecular equivalents, although smaller amounts than these are usually sufficient; and there should be used not more than one molecular equivalent of halogen fatty acid to one molecular proportion of cellulose. The cellulose &c. to be treated may be soaked in an excess of alkali lye, the surplus being subsequently removed, or it may be mixed or kneaded with the required quantity of lye, or with solid caustic alkali, or with a mixture of solid caustic alkali and saturated lye; the reaction is carried out at room temperature or below, or with the application of heat; and contact substances such as copper, iron, silver, and benzoyl superoxide may be added. Suitable halogen fatty acids &c. are:-monochloracetic acid, methyl or ethyl chloracetate, a-bromopropionic acid, bromosuccinic acid, a-bromo-isobutyric acid and their salts and esters. The products are isolated from the reaction mixtures by the addition of an acid, an acid salt, &c., or by treating with alcohol. When precipitated in the form of threads and films from their solutions, they give solid, flexible, and transparent products. The cellulose derivatives may be employed in the manufacture of artificial fibres, films, plastic compositions, coatings, dressings for fabrics, sizes, thickening-agents for textile printing, agents for fixing pigments, &c. Specifications 138,116, 177,810, 203,346, and 203,347 are referred to.