| 摘要 |
PROBLEM TO BE SOLVED: To produce a thick foam having a high foaming ratio and a high closed cell rate from a polypropylene resin. SOLUTION: This method for producing a thermoplastic resin foam comprises adding isoprene and a radical polymerization initiator to a polypropylene resin, melt-modifying the resin to impart a melt tension to the polymer, melting the modified polypropylene resin in an extruder without adding an organic decomposable foaming and nucleating agent capable of being thermally and chemically decomposed to generate carbon dioxide, nitrogen or oxygen, forcibly charging a physical flowing agent comprising an organic volatile compound into the melted resin, kneading and dissolving the mixture in the extruder, and subsequently extruding the melted mixture from a mold having a rectangular opening shape. Thus, the rectangular foam having a cross-sectional area of >=20 times that of the mold opening, a foaming ratio of >=30 times and a closed cell rate of >=60% is obtained. |
