| 摘要 |
PROBLEM TO BE SOLVED: To obtain an yellowing-resistant foam showing no degradation and no generation of crack by making the foam contain an acidic component derived from hydrolysis of a hydrolyzable polyester used as a raw material component of the subject polyurethane foam and show pH in an acidic region. SOLUTION: A hydrolyzable polyester is added to a polyol, a polyisocyanate, water and an amine catalyst, and the mixture is foamed to form a polyurethane foam, which becomes yellowing-resistant when the polyester is automatically hydrolyzed to shift pH to an acidic range. When the foam is immersed in 100 times by weight of distilled water for 30 minutes, the water shows pH of not more than 6. The hydrolyzable polyester shows pH in the range of 7.4<=pH<=6.5 and the rate of hydrolysis of the polyester is such that the foaming reaction is allowed to proceed before pH of the mixed material comes in an acidic range. The hydrolyzable polyesters to be used are a phosphite such as triphenylphosphite, triethylphophite, and the like, and an electron-attractive carboxylate such as trichloroacetate, nitroacetate, and the like. |
