GB231810A - Manufacture of cellulose derivatives - Google Patents

Abstract

Cellulose derivatives insoluble in water but soluble in aqueous alkalies are obtained by treating cellulose or an alkali-in-soluble cellulose conversion product, with a monohalogen fatty acid or a salt, ester or other derivative thereof, in the presence of caustic alkali and an aliphatic alcohol, the molecular proportions of halogen fatty acid to free caustic alkali being not more than 0.5 : 1, for instance, not more than 0.3 : 1. The stronger the caustic alkali solution, the less halogen fatty acid is necessary, according to the rule that 8/a molecular proportions of halogen fatty acid are used with each molecular proportion of caustic alkali, where a is the percentage strength of the caustic alkali solution, allowance being made for any water to be added with the halogen fatty acid and for alkali consumed in neutralizing the acid. The products are precipitated from their solutions in alkalies by reagents that will neutralize the alkali, even while the mixture is still alkaline in reaction; and also by the addition of alcohol. The products obtained when in the form of threads or films are strong, flexible, and transparent; they may therefore be used for the manufacture of artificial threads, films, plastic compositions, coatings, finishes, sizes, thickening-agents for textile printing, and fixing-agents for pigments. The halogen fatty acid may be in the dissolved or undissolved condition; the reaction may be carried out at ordinary temperature or at a raised or lower temperature; the alkali may be first incorporated with the cellulose either as a solution or in the solid state, or partly as a solid and partly as a saturated solution; the alcohol may be added with the caustic alkali, or with the halogen fatty acid. The reaction mixture may be worked up into technical products, as a solution after the addition of water or dilute caustic alkali solution; or the derivative may be isolated, for instance, after neutralization or acidification, or the derivative may be first brought to solution by the addition of water or caustic alkali solution, and afterwards precipitated by acid, an ammonium salt or other reagent that will fix alkali. Suitable mono-halogen fatty acids are monochloracetic acid, a -bromo- or a -chloro-propionic acid, b -iodapropionic acid, bromosuccinic acid, and a -bromisobutyric acid.