| 摘要 |
PURPOSE: To obtain a process for producing a synthetic resin foam whereby the defects in physical properties and foaming process of a phenol resin foam are eliminated and a heat-resistant foam is obtd. by using a heat- -resistant resin contg. dihydrobenzoxazine rings. CONSTITUTION: A resin compsn. comprising a heat-resistant resin having dihydrobenzoxazine rings and a blowing agent is heated to cause the ring- opening polymn. of the oxazine rings and the decomposition of the blowing agent, thereby giving a foam. The heat-resistant resin used contains structural units (A) represented by formula I and structural units (B) represented by formula II (wherein R<1> is methyl, cyclohexyl, or optonally substd. phenyl) in a molar ratio of (1/0.25)-(1/9), pref. units A being bonded to units B directly or through org. groups. The numbers of structural units in the molecule pref. satisfy the relations: m>=1, n>=1, and 10>=m+n>=2 (wherein m and n are the numbers of structural units A and B, respectively). The org. group is alkylene, xylylene, etc. The blowing agent is pref. of an org., thermally decomposable type. |
