Process for producing plastic foam

Abstract

A process for producing a foam comprising subjecting a foaming composition to foaming conditions, said foaming composition comprising (A) from 1 to 99% by weight, based on the total weight of (A) and (B), of a random copolymer comprising units derived from propylene, from 0.1 to 15 mol % of units derived from a non-conjugated diene represented by formula (I): ##STR1## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 each independently represents a hydrogen atom or an alkyl group having from 1 to 8 carbon atoms; and n represents a number of from 2 to 10, and, if desired, up to 4 mol % of units derived from ethylene, said random copolymer having a degree of crystallinity of at least 20% as measured by X-ray diffractometry, a melt flow rate of from 0.01 to 200 g/10 min as measured according to ASTM D1238-1986, and an elastic modulus of from 1,000 to 15,000 kg/cm.sup.2 as measured according to JIS K-7203, and (B) from 99 to 1% by weight, based on the total weight of (A) and (B), of a homopolymer of an .alpha.-olefin having from 3 to 12 carbon atoms or a copolymer mainly comprising said .alpha.-olefin, wherein the melting point of the minor resin component (A) or (B) is less than 15.degree. C. higher than that of the major resin component (A) or (B), and the ratio of the melt flow rate of resin component (A) to that of (B) is between 0.02 and 50, utilizes a foaming composition having a low melt viscosity and provides a uniform foam having a uniform cell size and a high foaming rate.