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
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
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 again
