| 摘要 |
PROBLEM TO BE SOLVED: To prepare a highly expanded polyolefin having uniform, fine bubbles. SOLUTION: This preparation process comprises the first process wherein a polyolefin (polypropylene or polyethylene), a decomposition blowing agent and a gaseous or low-boiling solvent are mixed, heated and expanded by a gaseous or low-boiling solvent and the second process wherein they are heated to a temperature higher than that in the first process and expanded by the decomposition blowing agent. Preferably, the expansion ratio in the first process is 2/3 times the expansion ratio in the second process or lower. |
