PURPOSE: To obtain a foamed crosslinked polyolefin having excellent heat resistance and flexibility, by specifying rate of dimensional change on heating and Young's modulus.
CONSTITUTION: A foamed crosslinked polyolefin for a pipe cover has a rate of dimensional change on heating according to JIS K 6767 (heating temperature: 110°C) of 5% or below and a Young's modulus of 12-25kg/cm2. If the rate of dimensional change on heating is more than 5%, there arises the problem that, in use of the foamed polyolefin as a pipe cover for a piping through which a heat medium is circulated, the cover is welded to the surface of the piping when the piping surface temperature is raised to about 120°C. That is, lowering in heat resistance is caused. A foamed crosslinked polyolefin with a Young's modulus of less than 12kg/cm2 shows poor moldability in molding into a pipe cover, whereas a foamed crosslinked polyolefin with a Young's modulus of more than 25kg/cm2 exhibits lowered flexibility. The foamed crosslinked polyolefin can be produced by blending various polyolefins with a crosslinking agent and a foaming agent in predetermined amounts to prepare a polyolefin resin composition, and subjecting the composition to crosslinking and foaming.
ONO TATSUYA
OKADA MITSUNORI
