| 摘要 |
Carboxyalkyl-polysaccharide-ethers or mixed ethers which are weakly substd. and have an average carboxyalkyl substitution (ACS) of 0.25-0.75, are prepd. by alkalinisation of a polysaccharide raw material in finely divided state with an excess alkali at low temp. followed by reaction with carboxy alkylating agents (I) and opt. other etherification agents, at a molar ratio (A) I/anhydroglucose unit of 0.4-1.1. In view of improving the solubility of the reaction prods., the excess alkali of the alkalinisation step is adjusted according to the subsequent molar ratio (A), by using an excess of alkali which is all the more higher as the required ACS is lower, and the amt. of excess alkali used (referred each time to 2 (A)) is 3-20 mole% for (A) of value 1.1 and 80-120 moles% for (A) of value 0.4. The prods. are also claimed. A simplified process is provided which gives carboxyalkyl polysaccharides with the lowest possible substitution (partic. CMC or CMS), and with very very good solubility in cold water for low turbidity indices, the solns. having a smooth structure.
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