GB729823A - Improvements in or relating to alkali cellulose preparation - Google Patents

Abstract

Comminuted cellulose having a particle size sufficiently small to pass through a 35-mesh sieve is slurried and agitated in a medium consisting of a saturated monohydric alcohol having from 2 to 5 carbon atoms in the molecule, dioxane, tetrahydrofuran or a mixture thereof, together with caustic alkali and water, the slurry containing up to 20 per cent by weight of cellulose based on the weight of the total slurry (calculated as moisture-free), and 0.2-1.8 parts of caustic alkali and 0.5-8.0 parts of water for each part of moisture-free cellulose. The cellulose may be derived from any suitable source such as cotton, cotton linters or wood pulp. Alcohols which may be used include ethyl alcohol, n- and iso-propyl alcohols, n-, secondary, iso-, and tertiary butyl alcohols, methyl propyl carbinol, diethyl carbinol, methyl isopropyl carbinol, tertiary amyl alcohol, fusel oil and pentasol (a mixture of amyl alcohols); isopropyl and tertiary butyl alcohols are preferred. The slurrying medium may be anhydrous or may contain water, e.g. ir may be an azeotropic mixture, but the water content is taken into account in calculating the water-cellulose ratio of the system. Similarly any water added with the caustic alkali is taken into account. The alkali-cellulose formed may be etherified without addition of more alkali or water to give cellulose ethers such as alkali-soluble and water-soluble carboxymethyl cellulose, hydroxyethyl cellulose, carboxyethyl cellulose, sulphoethyl cellulose, hydroxyethyl carboxymethyl cellulose, sulphoethyl hydroxyethyl cellulose, sulphoethyl carboxymethyl cellulose and cyanoethyl cellulose. In an example (all parts by weight), 30 parts of purified air-dry wood-pulp containing 5 per cent of moisture and cut to pass a standard 40-mesh sieve are added with agitation to 566.4 parts of isopropanol containing 1.5 per cent of water and 65 parts additional water. Then 31 parts of 49.7 per cent aqueous sodium hydroxide are added and agitation is continued, the temperature being kept at 18-25 DEG C. The so-formed alkali cellulose is etherified to form a carboxy methyl cellulose without further addition of alkali or water.