| 摘要 |
There is now provided a closed cell rigid polyisocyanate based foam blown with a C1-C4 hydrofluorocarbon and formic acid as blowing agents, which possesses a uniform density gradient varying by not more than 10 percent. There is also now provided a polyol composition and a froth foaming mixture having good flow by employing a polyol and formic acid in the presence of a C1-C4 hydrofluorocarbon having a boiling point of 300 K or less as co-blowing agents. The polyol composition advantageously has an average OH number of less than 400 and an average functionality of greater than 4, which when reacted with the isocyanate in the presence of a C1-C4 hydrofluorocarbon, yields a rigid closed cell polyisocyanate based dimensionally stable foam having a fine cell structure.
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