Process for finishing a nonwoven film-fibril sheet

Claim 1

A process for preparing a bonded nonwoven sheet of polyethylene film-fibrils, said sheet having high delamination strength and uniformity of appearance, said process comprising 1. providing a lightly consolidated, non-woven, film-fibril sheet having a basis weight of from about 34-119 g/m 2 (1-3.5 oz/yd 2 ), a coefficient of variation in basis weight, normalized to a 68 g/m 2 (2 oz/yd 2 ) basis weight, of from about 8 - 15%, and a density of from about 0.2-0.4 g/cc; 2. passing the lightly consolidated sheet through a nip formed between two rolls while applying a nip loading sufficient to provide an average nip pressure of from about 1.7-6.2 MPa (250-900 psi); one of said rolls having a multiplicity of bosses over practically its entire surface and extending from the surface of the roll to a height of from about 50-100% of the thickness of the lightly consolidated sheet, said bosses having tips which have at least one dimension being less than 0.64 cm (0.25 in) and the most prominent of which, in aggregate, form an area which is from about 1-50% of the area of the surface of the roll; the other roll having a surface with a durometer hardness of from about 55-80 as measured on the Shore D scale;