| 摘要 |
Carbohydrate ether mixtures, suitable for the production of polymerizable solutions, consist of at least one unsaturated polymerizable carbohydrate ether, at least one non-polymerizable high molecular weight substance and at least one polymerization catalyst. The non-polymerizable material acts as a catalyst-carrier and is at least partly soluble in the same solvent as the unsaturated carbohydrate ether. Suitable polymerizable carbohydrate ethers are allyl or crotyl ethers, which may also contain alkyl, hydroxyalkyl, carboxymethyl or ethane sulphonic acid ether groups. Preferred ethers include allyl, hydroxalkyl-allyl or carboxymethyl-allyl ethers of p cellulose, starch, amylose, amylopectin or carob bean flour. Watersoluble non-polymerizable substances for use with polymerizable carbohydrates having a low degree of substitution include polyethylene glycols, polyacrylates, polyvinyl alcohol, dextrin, dextran, tragacanth, carob bean flour and ethers of starch or cellulose. Non-polymerizable substances soluble in organic solvents, for use with highly substituted polymerizable carbohydrate ethers, include ethyl, acetyl or nitrocelluloses, polyvinyl acetate and polyvinyl acetal. The polymerization catalyst may be a percompound, possibly incorporated into a redox system, or an azo compound or other radical former. Preferred catalysts are potassium persulphate, sodium sulphite/potassium persulphate, percarbamide and cyclohexanone peroxide. 1 part by weight of catalyst may be added to 1 to 20 parts by weight of carrier. 5 to 15 parts by weight of the mixture may then be mixed with 100 parts by weight of polymerizable, unsaturated carbohydrate ether, in a similar state of comminution. The dry mixtures so obtained may be stored for several months without deterioration. Their aqueous or non-aqueous solutions polymerize to form gels or water-insoluble films of reduced swellability. |
