| 摘要 |
PROBLEM TO BE SOLVED: To obtain the subject resin foam usable suitably as e.g. a cushioning or building material, having low density and high closed cell content by expanding a polypropylene-based resin having specific characteristics. SOLUTION: This resin foam comprises a polypropylene-based resin, as the base material resin which rapidly increases in tensile viscosity with increasing its strain, when measured in its molten state and has a semi-crystallization time of below 800s., when measured at its cold crystallization temperature plus 15 deg.C, density of 10-100kg/m<3> and closed cell content of >=60%. This resin foam is obtained, pref. by melting and kneading 100 pts.wt. of the polypropylene- based resin with 5-40 pts.wt. of a foaming agent, and then, by extruding the blended mixture under a reduced pressure to effect expansion. Thus, this resin foam is stable with respect to its appearance after expanded and is satisfactory without causing internal foam-breaking, even when the resin foam in the form of thick plate is produced. |
