| 摘要 |
PROBLEM TO BE SOLVED: To easily produce prefoamed granules having a low density, uniform granule size and foamed density, and an excellent moldability at a low cost by granulating a resin compsn. contg. an ethylene-propylene random copolymer, impregnating the resultant granules with a mixed blowing agent comprising isobutane and an alicyclic hydrocarbon, and foaming the impregnated granules. SOLUTION: A resin compsn. contg. an ethylene-propylene random copolymer is kneaded, melted, and granulated; the resultant granules are dispersed in an aq. medium, and while being kept dispersed in the medium, the granules are impregnated with a mixed blowing agent comprising isobutane and an alicyclic hydrocarbon in an enclosed system under heating and pressure; then, the aq. medium is removed while the system is being kept pressurized to give foamable granules contg. 5-12 wt.% isobutane and 0.3-3 wt.% alicyclic hydrocarbon; and the impregnated granules are foamed by steam heating while the pressurized state is being kept. Examples of the alicyclic hydrocarbon are 4-8C cycloalkanes. |
