Abstract: The invention relates to a process for producing foamed polyolefin-based plastics blocks by first crosslinking a matrix comprising a) from 51 to 97% by weight of one or more polyolefins, selected from the group consisting of polyethylene and ethylene copolymer, b) from 3 to 20% by weight of a foaming agent, using &bgr;-radiation of energy >6 MeV. The thickness of the matrix is from 25 to 45 mm. The radiation dose is from 20 to 150 kJ/kg. During the irradiation, atmospheric oxygen is at least substantially prevented from reaching the surface of the matrix. After crosslinking, the crosslinked matrix is foamed by heating to a temperature >160° C. and decomposing the blowing agent.

Abstract: A process for producing an expanded or foamed polyolefin panel with a decorative surface wherein a polyolefin or a mixture of a polyolefin with rubber and/or a synthetic resin miscible therewith is blended homogeneously with a crosslinking agent and a blowing agent and shaped into a panel-like matrix below the decomposition temperature of the blowing agent and the activation temperature of the crosslinking agent; a film of a thermoplastic synthetic resin, imprinted in accordance with a pattern with printing ink on one surface side, is applied unilaterally or bilaterally to the matrix, with the imprinted surface side facing the matrix; and then the matrix, with the film applied, is crosslinked and expanded by heating to a temperature above the activation of the crosslinking agent and the decomposition temperature of the blowing agent.