| 摘要 |
PURPOSE:To obtain a hard urethane foam with delaying the initial reaction stage but without delaying the subsequent curing reaction by using an N-substd. imidazole as a catalyst. CONSTITUTION:In a method for preparing a hard urethane foam from an org. polyisocyanate, a polyol, a foaming agent, a catalyst and other auxiliaries, N-substd. imidazoles of the formula are used as a catalyst. For foaming-in-place of a hard urethane foam in the other shell of a refrigerator, a urethane stock soln. is simultaneously poured thereinto from one or two opening and foam is filled in a gap by the foaming and curing reaction. In the conventional method, the foam density in the extended part of the foam is remarkably higher than that in the neighborhood of the opening. On the other hand, when N-substd. imidazoles are used as the catalyst, the poured urethane stock soln. is spread over a wide area before the foaming and curing reaction takes place. Difference in the foam density can be thereby decreased. |
