Abstract: An apparatus is described for forming a web (N) that is permeable to liquids and designed to separate two environments and to allow the liquid to flow in one direction from one of said environments to the other, in which said web is caused to pass between two contra-rotating cylinders (5, 7) that are pressed against each other, one of said cylinders (7) having a surface provided with projections which cause perforations in said web (N). The cylinder (7) with the projections is turned at a peripheral speed greater than the peripheral speed of the other cylinder (5), with a consequent relative slipping action between the surfaces of the two cylinders (5, 7).

Abstract: There is described a three-dimensional membrane generally of a thin plastic film which has apertures therein created by simultaneously perforating the film and pushing the material from the holes to one side of the apertures and piling it up to create an overall membrane thickness which is at least 10 times the original thickness of the film. It has particular application as a topsheet for sanitary napkins and the like.

Abstract: A method for forming a web (N) that is permeable to liquids and designed to separate two environments and to allow the liquid to flow in one direction from one of said environments to the other. The web is caused to pass between two contra-rotating cylinders (5, 7) that are pressed against each other, one of said cylinders (7) having a surface provided with projections which cause perforations in said web (N). The cylinder (7) with the projections is turned at a peripheral speed greater than the peripheral speed of the other cylinder (5), with a consequent relative slipping action between the surfaces of the two cylinders (5, 7).