Process of making a porous, coated material

Claim 1

THE METHOD OF PROCESSING A POROUS BASE WEB COATED ON ONE SURFACE WITH A NORMALLY NON-POROUS LAYER OF UNDISSOLVED HEAT-SOFTENABLE RESINOUS PLASTIC MATERIAL WHICH COMPRISES RENDERING SAID NON-POROUS LAYER SUBSTANTIALLY POROUS BY PASSING THE COATED BASE WEB IN DIRECT CONTACT WITH A HEATED CONTINUOUSLY MOVING SURFACE, THE WEB AND HEATED SURFACE BEING SO ORIENTED THAT SAID LAYER OF NORMALLY NON-POROUS MATERIAL IS IN DIRECT CONTACT WITH SAID HEATED SURFACE, MAINTAINING SAID COATED WEB IN CONTACT WITH SAID HEATED SURFACE FOR A PREDETERMINED PERIOD OF SHORT DURATION TO HEAT SAID RESINOUS PLASTIC MATERIAL TO BUT NOT SUBSTANTIALLY BEYOND ITS TACKY STATE BY CAUSING SAID COATED WEB TO PASSS AROUND A PREDETERMINED PORTION OF SAID CONTINUOUS SURFACE, MAINTAINING THE SURFACE SPEEDS OF SAID HEATED SURFACE AND SAID WEB SUBSTANTIALLY EXACTLY EQUAL DURING SAID PREDETERMINED PERIOD, AND WITHDRAWING SAID WEB FROM SAID HEATED SURFACE WHEREBY SAID LAYER OF PLASTIC MATERIAL IS RENDERED POROUS, SAID HEATED SURFACE CONSTITUTING THE SOLE EFFECTIVE HEAT SOURCE OPERATIVE IN THE STEP OF RENDERING SAID RESINOUS PLASTIC MATERIAL SUBSTANTIALLY POROUS.