| 摘要 |
PURPOSE:To obtain a packing for a bottle crown cap made of finely expanded uniform foam, having smooth surface and improved hold-on pressure, by molding an expandable ethylenic copolymer containing a blowing agent of a decomposable compound, followed by crosslinking and expansion. CONSTITUTION:An expandable ethylenic copolymer consisting of (A) 100 parts by wt. of an (crosslinkable with metallic ions) ethylenic copolymer made from ethylene and a vinyl monomer shown by the formula (R1 and R2 are H or alkyl) and (B) 0.3-2 parts by wt. of a blowing agent of a decomposable compound whose decomposing rate is controllable with ease without causing pungent odor and contamination in the decomposed residue is molded into a bottle crown cap having a thickness of 0.5-1.5 mm to form a layer, which is irradiated by an ultraviolet light having a wave length of 1800-3200 Angstrom to be crosslinked to a degree of crosslinking of not more than 30 %, and heated at a temperature higher than a decomposing temperature of the blowing agent, followed by expansion. |
