| 摘要 |
The solubility in water of a water-soluble or unlimitedly water-swellable macromolecular carbohydrate or derivative thereof, especially of a cellulose ether, or of a polyvinyl alcohol or derivative thereof, is improved by treatment at elevated temperature with a dialdehyde polysaccharide in a proportion of 0.1-5% by weight, especially 0.3-5% by weight. Specified materials include cellulose ethers and esters, especially methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose and mixed ethers of cellulose, starch ethers and esters, modified starches, vegetable gums, e.g. gum tragacanth and their derivatives, alginates, polyvinyl alcohol and its derivatives, especially partially etherified or esterified polyvinyl alcohols, e.g. polyvinyl acetate. Specified dialdehyde polysaccharides include dialdehyde starch, and the dialdehyde forms of cellulose, dextran and galactomannan. In general, the process is performed in a neutral medium and the mixture of the dialdehyde polysaccharide and macromolecular substance is heated to 60-130 DEG C., especially 90-110 DEG C., suitably by drying the mixture in air at these temperatures. The dialdehyde polysaccaride may be mixed with the macromolecular compound in the dry state and the mixture moistened with solvent and/or water, or an aqueous solution of the dialdehyde polysaccharide may be employed which is dropped or sprayed on the macromolecular compound. Various techniques are described, including the treatment of cellulose ethers while the latter are being converted from fibrous to particulate form. Examples are given. |
