| 摘要 |
PURPOSE:To obtain the title foam excellent in flame retardancy and dimensional stability and useful as a construction material, by mixing a specified oxyalkylated novolak phenolic resin with a polyisocyanate, a catalyst, a blowing agent and a foam stabilizer and foaming the mixture. CONSTITUTION:A novolak phenolic resin (a) of a number-average MW of 250-550, a weight-average MW of 350-980, a dispersity index <=2.0 and a free phenol content <=2.5wt% is obtained by reacting a phenol with an aldehyde substance at a molar ratio of 1:0.51-0.70 under reflux at 90-105 deg.C for 60-120min in the presence of an acidic catalyst. This resin (a) is reacted with an alkylene oxide (b) at 80-160 deg.C in the presence of an alkali metal hydroxide catalyst to effect addition of 1-4mol of the alkylene oxide to the hydroxyl groups to obtain an oxyalkylated novolak phenolic resin (A) of an hydroxyl value of 150-450mg KOH. Component A is mixed with a polyisocyanate (B) at an equivalent ratio in the range of 2<=NCO/OH<=15, a catalyst (C) such as a metal carboxylate, a blowing agent (D) and a foam stabilizer (E), and the mixture is foamed.
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