| 摘要 |
PROBLEM TO BE SOLVED: To obtain a rigid polyurethane foam excellent in adhesiveness by mixing a mixture of polyphenylmethane polyisocyanate and diphenylmethane diisocyanate in a specified wt. ratio, a mixture of polyether polyols having different functionalities and hydroxyl values, and water and allowing the resultant mixture to foam. SOLUTION: Polyphenylmethane polyisocyanate contg. 0.1-30wt.% isomers other than 4,4'-diphenylmethane diisocyanate is mixed with diphenylmethane diisocyanate having an isomer content of 0.1-70wt.% in a wt. ratio of 0.5-25 to give a polyisocyanate mixture. A polyether polyol having a functionality of 3.5-4.5 and a hydroxyl value of 300-400mgKOH/g and a polyether polyol having a functionality of 2 or 3 and a hydroxyl value of 20-120mgKOH/g are mixed in a wt. ratio of (100/20)-(100/60) to give a polyol mixture. The polyisocyanate mixture and the polyol mixture are mixed in an equivalent ratio of NCO group to active hydrogen group of 0.5-2, together with water, a catalyst, etc., and then allowed to foam. |
