| 摘要 |
A polyether precondensate made by mixing polypropylene glycol (12 parts) with toluene diisocyanate (1 part) plus stannous octoate (0.1 part) (resistant phase) is mixed with a similar precondensate which has no accelerator and in which the proportions of glycol to diisocyanate is 12 to 3 1/2 (fragile phase). A film extruded from the heterogeneous mixture is heated to 50 DEG C. to effect curing of the resistant phase, and then treated with steam at 100 DEG C., which causes foaming of the fragile phase by liberation of CO2. |
