| 摘要 |
PROBLEM TO BE SOLVED: To obtain a foam having excellent environmental compatibility, a high closed-cell rate and excellent heat-insulation properties and outer appearance by using a blowing agent comprising 1,1-dfluoro-1-chloroethane (HCFC 142b), a hydrocarbon and an alkyl chloride in a specified ratio in the extrusion foaming of an alkenylaromatic resin. SOLUTION: The alkenylaromatic resin is desirably a polystyrene resin. The content of HCFC 142b in the blowing agent is 30-75wt.%. The hydrocarbon which constitutes the blowing agent is an aliphatic hydrocarbon having a boiling point of -90 to 85 deg.C (e.g. propane). The alkyl chloride which constitutes the blowing agent is selected from methyl chloride and ethyl chloride. Especially, ethyl chloride is more desirable because it has an allowable concentration in a working environment, is high as compared with that of methyl chloride and exerts less load on the working environment. The amount of the blowing agent used should be 0.1 to below 0.18mol per 100g of the alkenylaromatic resin. The amount of HCFC 142b contained in the foam should be 0.02-0.17mol. |
