Method of making a microporous sheet material

Claim 1

THE METHOD OF MANUFACTURING A MICROPOROUS LAYER OF PLASTICIZED VINYL CHLORIDE POLYMER RESIN COMPRISING THE STEPS OF SPREADING FINE GRANULES OF SAID RESIN IN A UNIFORM LAYER ON THE SURFACE OF ONE OF TWO SHEETS COVERING THE EXPOSED SURFACE OF SAID UNIFORM LAYER WITH THE OTHER OF SAID SHEETS, AT LEAST ONE OF THE SURFACES OF SAID SHEETS ADJACENT TO SAID LAYER BEING COATED WITH 0.5 TO 5 GRAMS PER SQUARE FOOT OF AN AIR PERMEABLE, RESINOUS MATERIAL CONTAINING AS A FILM-FORMING INGREDIENT A MEMBER SELECTED FROM THE GROUP CONSISTING OF POLYVINYL CHLORIDE AND ACRYLIC RESINS HAVING A FILM-FORMING TEMPERATURE ABOVE 300*F. AND BEING DRIED AT A TEMPERATURE BELOW SAID FILM-FORMING TEMPERATURE, PASSING THE RESULTANT ASSEMBLY BETWEEN HEATED PLATES DEFINING A PASSAGEWAY DIMINISHING IN THICKNESS FROM A THICKNESS AT THE ENTRY TO THE PASSAGEWAY APPROXIMATING THE INTIAL THICKNESS OF SAID ASSEMBLY TO A THICKNESS LESS THAN SAID INITIAL THICKNESS AT THE EXIT OF SAID PASSAGEWAY, SAID HEATED PLATES BEING AT A TEMPERATURE OF FROM ABOUT 200* TO ABOUT 400*F. AND SUPPLYING HEAT AND PRESSURE TO SAID ASSEMBLY TO SINTER THE RESIN GRANULES TOGETHER INTO A MICROPOROUS LAYER AND AT THE SAME TIME TO TRANSFER SAID COATING FROM SAID SHEET AND BOND IT TO THE SURFACE OF SAID LAYER, COOLING SAID ASSEMBLY AND STRIPPING THE SHEETS FROM THE COATED MICROPOROUS RESIN LAYER.

Claim 2

THE METHOD OF MANUFACTURING A MICROPOROUS LAYER OF PLASTICIZED VINYL CHLORIDE POLYMER RESIN COMPRISING THE STEPS OF SPREADING FINE GRANULES OF SAID RESIN IN A UNIFORM LAYER ON THE SURFACE OF ONE OF TWO SHEETS COVERING THE EXPOSED SURFACE OF SAID UNIFORM LAYER WITH THE OTHER OF SAID SHEETS, AT LEAST ONE OF THE SURFACES OF SAID SHEETS ADJACENT TO SAID LAYER BEING COATED WITH 0.5 TO 5 GRAMS PER SQUARE FOOT OF AN AIR PERMEABLE, RESINOUS MATERIAL CONTAINING AS A FILM-FORMING INGREDIENT A MEMBER SELECTED FROM THE GROUP CONSISTING OF POLYVINYL CHLORIDE AND ACRYLIC RESINS HAVING A FILM-FORMING TEMPERATURE ABOVE 300*F. AND BEING DRIED AT A TEMPERATURE BELOW SAID FILM-FORMING TEMPERATURE, PASSING THE RESULTANT ASSEMBLY BETWEEN HEATED PLATES DEFINING A PASSAGEWAY DIMINISHING IN THICKNESS FROM A THICKNESS AT THE ENTRY TO THE PASSAGEWAY APPROXIMATING THE INTIAL THICKNESS OF SAID ASSEMBLY TO A THICKNESS LESS THAN SAID INITIAL THICKNESS AT THE EXIT OF SAID PASSAGEWAY, SAID HEATED PLATES BEING AT A TEMPERATURE OF FROM ABOUT 200* TO ABOUT 400*F. AND SUPPLYING HEAT AND PRESSURE TO SAID ASSEMBLY TO SINTER THE RESIN GRANULES TOGETHER INTO A MICROPOROUS LAYER AND AT THE SAME TIME TO TRANSFER SAID COATING FROM SAID SHEET AND BOND IT TO THE SURFACE OF SAID LAYER, COOLING SAID ASSEMBLY AND STRIPPING THE SHEETS FROM THE COATED MICROPOROUS RESIN LAYER.