| 摘要 |
PURPOSE:To obtain extremely highly expanded foam by one stage without using a complicated operation and a device, by expanding small peices of styrenic resin containing a specific volatile organic solvent, cooling naturally to shrink them, expanding and recovering them. CONSTITUTION:Small pieces of styrenic resin is blended with a blowing agent having <=30 deg.C boiling point consisting of one or a combination of a volatile organic blowing agent (e.g., butane, dichlorodifluoromethane) having a gas permeability rate to the base resin of <=1/10 that of air, or a mixed blowing agent of it and another blowing agent in such as way that the amount of a blowing agent component having <=30 deg.C boiling point is >= (0.11gmol/100g resin), and the small pieces are directly expanded under heating with steam at >=80 times expansion ratio, small piece foam is naturally cooled in the air, th volume of the foam is shrinked to <=1/2 of the maximum volume at the blowing, then expanded and recovered to give small piece foam having >=80 times expansion ratio.
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