| 摘要 |
PURPOSE:To produce a foam having a high expansion ratio free from occurrence of harmful cracks in the interior of the foam with a small amount of a blowing agent. CONSTITUTION:A foamable composition comprising a vinyl chloride based-resin, a solvent and a blowing agent is packed into a mold, heated under pressure, the vinyl chloride-based resin is gelatinized and the contents in the mold are cooled until the contents show rubber elasticity. The cooled gelatinized material is taken out from the mold, a primary foam having a foamable cell nucleus is made, the primary foam is made to have water on its surface and heated. Consequently, a gas pressure of the remaining blowing agent in the cells of the primary foam and vapor pressure of the remaining solvent are increased, the primary foam is secondarily expanded and the solvent is removed. |
