FOERFARANDE FOER FRAMSTAELLNING AV TVAERBUNDNA POLYOLEFINSKUMPRODUKTER

1. Process for preparing cross-linked polyolefin foamed articles with closed cells, in which a cross-linkable, expandable composition is heated under pressure for a preset period of time and subsequently heated again at atmospheric pressure for a preset period of time, characterised in that a composition containing in 100 parts by weight polyolefin with a melt ---flow rate (MFR) ranging ---from 0.1 to 5.0 g/10 min 0.2 to 1.0 parts by weight of a cross-linking agent, 10 to 30 parts by weight of a blowing agent and 0 to 0.6 parts by weight of an auxiliary foaming agent, is filled into a closed mould and heated therein for 20 to 70 min at temperatures ranging from 120 to 160 degrees C at a pressure of more than 10 bar and moulded into a shape corresponding to the mould, in which case a crosslinked, essentially unfoamed product with a gel content of approximately 10 to 70% and a degree of expansion ranging from 1 to 3 times the original volume is obtained, and subsequently this cross-linked, unfoamed product is foamed by heating at atmospheric pressure in a mould, which is not gas-tight, which corresponds to a desired shape, in which case a thick, tough foamed article with uniform, fine cells is obtained.