Method for producing battery separator sheet

Claim 1

A PROCESS FOR CONTINUOUSLY PRODUCING A POROUS SHEET MEMBRANE SUITABLE FOR CONVERSION INTO A BATTERY SEPARATOR AND HAVING TWO PRINCIPAL OPPOSITE SURFACES ONE OF WHICH HAS SHORT PROJECTIONS THEREON AND THE OTHER OF WHICH HAS HIGHER PROJECTIONS THEREON COMPRISING EXTRUDING A SELF SUPPORTING EASILY DEFORMABLE RELATIVELY PLAIN SHEET OF THERMOPLASTIC MATERIAL, SAID THERMOPLASTIC MATERIAL BEING OIL FILLED TO ABOVE 30% BY VOLUME CALENDER MOLDING SAID SHEET BETWEEN TWO CALENDERING ROLLS SYNCHRONIZED SURFACE SPEEDS ON OF SAID CALENDERING ROLLS HAVING SHALLOW DEPPRESSION THAT ARE INTERRUPTED CIRCUMFERENTIALLY AND SPACED AROUND THE CIRCUMFERENCE THEREOF AND BEING HOT AND THE OTHER OF SAID CALENDERING ROLLS HAVING DEEPER DEPRESSION THAT ARE INTERRUPTED CIRCUMFERENTIALLY AND SPACED AROUND THE CIRCUMFERENCE THEREOF AND BEING WARM, SAID SHEET SURFACE HAVING SAID SHORT PROJECTION BEING FORMED AGAINST SAID CALENDERING ROLL HAVING SAID SHALLOW DEPRESSIONS AND SAID SHEET SURFACE HAVING SAID HIGHER PROJECTION BEING FORMED ON SAID CALENDERING ROLL HAVING SAID DEEPER DEPRESSIONS FORMING A BANK OF SAID OIL FILLED MATERIAL FROM SAID EXTRUDED SHEET AT THE NIP OF SAID CALENDERING ROLLS AND MAINTAINING SAID BANK AT SAID NIP TRANSPORTING THE CALENDERED SHEET AROUND AT LEAST 20% OF THE CIRCUMFERENCE OF SAID CALENDERING ROLL HAVING SAID DEEPER DEPRESSIONS AND PARTIALLY SETTING SAID CALENDERED SHEET INCLUDING SAID PRROJECTING WITHDRAWING SAID PARTIALLY SET HIGHER PROJECTIONS FROM SAID DEEPER DEPRESSIONS SUBSTANTIALLY STRAIGHT OUT OF SAID DEEPER DEPRESSIONS AND AT A RATE OF TAKEAWAY SLIGHTLY GREATER THAN THE SPEED AT WHICH SAID CALENDERED SHEET IS TRANSPORTED BY SAID CALENDERING ROLL HAVING SAID DEEPER DEPRESSIONS TO PREVENT PICKING OF SAID HIGHER POJECTION STRUCTURE BEFORE SAID SHEET HAS ENTIRELY SET ENGAGING THE SIDE THEREOF HAVING SAID SHORT PROJECTIONS WITH A TRANSPORTING ROLL AND PASSING SAID SHEET ACROSS A SIZING ROLL AND THE SAME SURFACE SPEED AS SAID TRANSPORTING ROLL AND TRAPPING SAID SHEET IN A PRESET SIZING GAP BETWEEN SAID SIZING ROLL AND SAID TRANSPORTING ROLL WITH SAID SIZING ROLL IMPINGING AGAINST THE TOP OF SAID HIGH PROJECTIONS AND PUSHING AGAINST THE TOP OF SAID HIGH PROJECTIONS AND PERMANENTLY DEFORMING SAID HIGHER PROJECTION AND REDUCING THEIR HEIGHT AND THEREBY SETTING THE FINAL THICKNESS OF SAID SHEET THEREAFTER FURTHER COOLING SAID SHEET TO COMPLETE ITS SET AND THEREAFTER LEACHING AT LEAST ENOUGH OF SAID OIL FROM SAID SHEET TO MAKE SAID SHEET POROUS.

Claim 5

A method for continuously producing a sheet suitable for conversion into a battery separator and having two principal opposite surfaces with series of spaced apart projections thereon comprising delivering a mass of readily deformable plastic material to the nip of two opposed calendering rolls having depressions that are interrupted circumferentially and spaced around their respective circumferences, one of said calender rolls being warm and having deeper depressions and the other of said calender rolls being hot and having shallower depressions; forming said plastic material between said two calendering rolls and in said depressions producing a sheet with projections thereof, the projections on the side of the sheet molded by said roll with said deeper depressions being higher than the projections on the side of the sheet molded by said roll with said shallower depressions which projections are short; and passing said formed sheet between two sizing rolls that have a preset sizing gap therebetween pressing said projections inwardly of said sheet to set the final thickness of said sheet, the sizing roll engaging the higher projections being heated.

Claim 6

A method for continuously producing a sheet suitable for conversion into a battery separator and having two principal opposite surfaces with series of spaced apart projections thereon comprising delivering a mass of readily deformable plastic material to the nip of two opposed calendering rolls having depressions that are interrupted circumferentially and spaced around their respective circumferences, one of said calender rolls being warm and having deeper depressions and the other of said calender rolls being hot and having shallower depressions; forming said plastic material between said two calendering rolls and in said depressions producing a sheet with projections thereof, the projections on the side of the sheet molded by said roll with said deeper depressions being higher than the projections on the side of the sheet molded by said roll with said shallower depressions which projections are short; and passing said formed sheet between two sizing rolls that have a preset sizing gap therebetween pressing said projections inwardly of said sheet to set the final thickness of said sheet, the sizing roll engaging the higher projections being heated.