| 摘要 |
PROBLEM TO BE SOLVED: To produce a polypropylenic resin foam having heat resistance and strengths high enough to withstand stamping molding and improved deep drawability by irradiating the surfaces of an expandable resin sheet comprising a polypropylenic resin, a heat-decomposable blowing agent, and a crosslinking agent, with an ionizing radiation in different dosages and expanding the sheet by heating. SOLUTION: 100 pts.wt. polypropylenic resin having a melt index of 0.3-10g/10min is mixed with 1-30 pts.wt. heat-decomposable blowing agent and 0.5-30wt.% crosslinking agent to obtain a composition. This composition is kneaded, optionally pelletized and molded to obtain an expandable resin sheet. The surfaces of this sheet are irradiated with an ionizing radiation in different dosages in the range of 1-50Mrad till the gel fraction of one surface reaches 30-40% and that of the other surface reaches 0-62%. The sheet is then expanded by heating to a temperature equal to or higher than the decomposition temperature of the blowing agent. |
