| 摘要 |
The present invention is directed to a simple process for preparing a 4,4'-diisocyanato dicyclohexylmethane containing at least 90% by weight of the trans,trans-isomer. More particularly, the process comprises: (a) melting a mixture of 4,4'-diisocyanato dicyclohexylmethane isomers containing at least 30% by weight, and preferably from 45 to 55% by weight, of the trans,trans-isomer, (b) cooling the melted mixture to a temperature of from about 20 to about 25 DEG C to form: (1) a liquid phase which contains from about 18 to about 25% by weight of the trans,trans-isomer, and (2) a solid phase which contains from about 70 to about 85% by weight of the trans,trans-isomer, (c) removing said liquid phase, (d) dissolving said solid phase in a solvent to form a 4,4'-diisocyanato dicyclohexylmethane-containing solution, (e) allowing said solution to remain at room temperature for a time sufficient to form: (1) a solid phase containing at least 90% by weight, and preferably at least 98% by weight of the trans,trans-isomer, and (2) a liquid phase containing said solvent and a mixture of 4,4'-diisocyanato dicyclohexylmethane isomers containing from 30 to 70% by weight, and preferably from 45 to 55% by weight of the trans,trans-isomer, and (f) removing said solid phase (e)(1). b |
