| 摘要 |
PROBLEM TO BE SOLVED: To obtain a prefoamed particle of a polyolefin resin having desirable characteristics without using a conventional blowing agent such as a volatile blowing agent or carbon dioxide. SOLUTION: A prefoamed particle having an apparent expansion ratio of from 5 to 60 fold, a closed cell percentage of from 80 to 100% and an average cell size of from 50 to 500μm is prepared by dispersing a particle comprising a polyolefin resin composition which comprises 100 pts.wt. crystalline polyolefin resin and from 0.1 to 10 pts.wt. hydrophilic, low-molecular-weight organic compound and has a water content at a temperature equal to the melting point of the polyolefin resin and under a pressure equal to the water vapor pressure at this temperature of from 1 to 50 wt.%, in an aqueous disperse medium in a sealed vessel. Then, it is heated to a temperature equal to the softening point or higher to obtain a water-containing particle having a water content of from 1 to 50 wt.%, which is then released into a low pressure atmosphere, and the water containing particle is allowed to expand.
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