GB780628A - Improvements in or relating to improved water-soluble salts of carboxyalkyl cellulose ethers and method of converting into granular form - Google Patents

Abstract

In the process of the parent Specification, fibrous water-soluble salts of carboxyalkyl cellulose ethers are converted into free-flowing substantially granular powders by agitating a loose fibrous mass comprising a water-soluble salt of a carboxy-alkyl cellulose ether, moist with a mixture of water and a water-miscible alcohol in such proportions that the mass would normally dry to a loose fibrous product at below 100 DEG C., simultaneously introducing thereto a dispersed stream of water or an aqueous salt solution or an aqueous alcohol containing not more than 15 per cent of water-miscible alcohol, or wet or saturated steam, until the proportion of water introduced is sufficient to form with the alcohol present in the mass a powerful solvent for the ether salt, said solvent containing at least 67.5 per cent by weight of water and the total liquid content in the mass being below 4 per cent by weight based on the ether salt, and continuing agitation until the fibrous structure of the mass is substantially destroyed and the ether salt is converted into a mass of separate gel particles, which are then dried. This process is now modified in that the gel particles are classified to obtain in dry form substantially 100 per cent through a U.S.A. Standard series sieve No. 12 with not more than 20 per cent through a No. 100 U.S.A. sieve, whereby the product so converted, dried and classified, in addition to being a free-flowing substantially granular powder, is quickly soluble in water and substantially dust-free. The cellulose ether salt may also be classified when in the form of a granular powder, with or without preliminary grinding of the powder, or may be wet-screened while it is still in the form of wet gel particles, and before it has been dried, the wet screening being so carried out as to give a fraction which, when dried, has the specified particle size range. The cellulose ether salt may be an alkali-metal or ammonium salt of carboxy-methyl, -ethyl or -propyl cellulose and hydroxyethyl groups may also be present in the molecule. Specification 623,276 is referred to.