| 摘要 |
PROBLEM TO BE SOLVED: To obtain a low-density, thick-walled foam with uniform foam structure by subjecting a styrene-based resin to extrusion foam molding by using carbon dioxide and water as foaming agents with a nonionic surfactant having a specific HLB. SOLUTION: A nonionic surfactant having an HLB of 12-18 is used. Carbon dioxide and water as foaming agents and the nonionic surfactant having an HLB of 12-18 are added to a styrene-based resin in a molten state, mixed, and subjected to extrusion foam molding to prepare this styrene-based foam. Preferably, 2.0-6.0 pts.wt. of carbon dioxide, 0.5-2.0 pts.wt. of water (with the proviso that carbon dioxide is present more than water) and 0.1-1.0 pts.wt. of the nonionic surfactant are blended with 100 pts.wt. of the styrene-based resin. The foam preferably has a density of 0.025-0.050 g/cm3, especially 0.040 g/cm3 or less, a thickness of 10-120 mm, especially 15 mm or more and an average bubble diameter of 0.10-0.80 mm.
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