Production of product sheets having waved marginal portions

摘要

Sheet products having a waved marginal portion are prepared by passing a sheet of a plastic material through and compressing the sheet between shaped circumferential rollers which are positioned and configured to provide therebetween a plurality of differing nip clearance gap distances and to compress the sheet to form an intermediate sheet portion flanked by a marginal waved flanking portion and a second flanking portion, wherein the intermediate portion has a thickness greater than the second portion which, in turn, has a thickness greater than the marginal waved portion.