| 摘要 |
PURPOSE:To produce the title foam having fine and homogeneous cells and a low density by quenching a thermoplastic polyester resin foam, which is just after being foamed and still at a high temp., below the glass transition point of the resin and then heating the foam. CONSTITUTION:A thermoplastic polyester resin is dried by exposing the resin to air at about 160 deg.C for about 4 hr, the air having a dew point of about -30 deg.C. The dried polyester resin is impregnated with a blowing agent (e.g. hexane) under pressure and then foamed to give a foam with a thickness of 10 mm or lower, which is quenched below the glass transition point of the resin, thereby giving a foam of a degree of crystallization of 30% or lower. The foam is allowed to stand for at least 24 hr, and heated to 60 deg.C or higher to foam (secondary foaming). |
