| 摘要 |
1382243 Thermoplastic polyurethanes IMPERIAL CHEMICAL INDUSTRIES Ltd 8 March 1972 [30 March 1971] 8160/71 Heading C3R Thermoplastic polyurethane elastomers are prepared by (1) reacting a substantially linear polypropylene glycol of M.W. greater than 800 with an excess of an organic diisocyanate to form a prepolymer, (2) reacting the prepolymer with a diol of M.W. at most 250 in such proportions that (a) the ratio of NCO groups in the prepolymer to hydroxyl groups in the diol is at most 1 : 1 and (b) there is produced a polyurethane which is insoluble in dimethylformamide, (3) heating the insoluble product until a dimethylformamide-soluble product is obtained, (4) dissolving the product in dimethylformamide and (5) removing the dimethylformamide to produce a solid polyurethane product. Step (3) of the process is preferably carried out by heating the insoluble product to a temperature of 180‹ to 220‹ C., suitably with mechanical working thereof. The mechanical working may be achieved by injection moulding techniques or by passing the product through a heated barrel by means of a screwed or scrolled axially rotatable shaft. The finally formed dimethylformamide-soluble product is suitably used as a textile coating. |
