Patent ID: 7854871

Claim:
A method for producing a polyolefin-based resin crosslinked foamed sheet, comprising the steps of using, as one set of a roll pair, one pair of rolls which have different circumferential speeds, and are rotated so that rotating directions on facing surfaces are the same direction, supplying sequentially a foamed sheet with closed cells, comprising a polyolefin-based resin, to a gap between rolls of each roll of a roll group in which two or more sets of the roll pairs are sequentially disposed, and applying a compression force and a shear stress to the foamed sheet with closed cells simultaneously to rupture a part of closed cells of the foamed sheet with closed cells to communicate closed cells into open cells, wherein rolls having a greater circumferential speed of respective roll pairs are disposed on opposite sides, putting the foamed sheet with closed cells therebetween, in arbitrary two sets of roll pairs adjacent to each other among the roll group, wherein two sets of roll pairs adjacent to each other among a roll group, a circumferential speed V 1 of a roll R 1 having a smaller circumferential speed and a circumferential speed V 2 of a roll R 2 having a greater circumferential speed among a roll pair on a rear side, and a circumferential speed V 3 of a roll R 3 having a smaller circumferential speed and a circumferential speed V 4 of a roll 4 having a greater circumferential speed among a roll pair on a front side satisfy the following conditions, a roll R 1 and a roll R 4 are disposed on the same side of the foamed sheet with closed cells and, at the same time, a roll R 2 and a roll R 3 are disposed on the same side of the foamed sheet with closed cells, and circumferential speed V 2 > circumferential speed V 1 , circumferential speed V 4 > circumferential speed V 3 , circumferential speed V 3 > circumferential speed V 1 .