GB737263A - Process for the production of alkyl-cellulose compositions in a finely pulverisable form - Google Patents

Abstract

Alkyl-celluloses soluble in cold water and insoluble in hot water are converted into a finely pulverizable form by mixing an aqueous solution of the alkyl cellulose with a water-soluble salt having a precipitating action in sufficient concentration to precipitate the alkyl cellulose, and filtering and drying the precipitate. The salt may be added in solid form or as a concentrated aqueous solution and may be a salt of an alkali metal or alkaline earth metal, e.g. sodium chloride or sulphate. After the addition of the salt the mixture is preferably heated to about 50-100 DEG C. before filtration. The alkyl cellulose may be a methyl cellulose or an alkyl cellulose containing some oxyalkyl groups, e.g. ethyl-oxyethyl-cellulose. In an example 10 parts by weight of a methyl cellulose soluble in cold water are stirred in 200 parts by volume of water at 60 DEG C., the resulting suspension is mixed with 200 parts by volume of cold water, and the mixture is cooled to 25 DEG C. Four additions of 100 parts by volume of a saturated aqueous solution of sodium chloride are made at intervals of a few minutes, whereby a flocculent precipitate is formed which is stirred for a further hour. The mixture is then heated to 90 DEG C. by introducing steam, and filtered with suction. The filter cake is partially dried by suction or pressure and the drying is then completed by exposing the material spread out in loose form to a current of air at 90-100 DEG C. A granular material is obtained which contains 20-30 per cent of sodium chloride and can be easily ground to fine powder in a percussion mill. In other examples, sodium sulphate and magnesium sulphate respectively are used as precipitating salts.