Preparation of a cured polyurethane cellular material

Claim 1

PROCESS FOR PREPARING A CURED POLYURETHANE CELLULAR MATERIAL WHICH COMPRISES PASSING AN ORGANIC LIQUID AND AN INERT GAS TOGETHER THROUGH A FROTHING ZONE CONSISTING ESSENTIALLY OF AT LEAST ONE PERFORATED PLATE HAVING A PLURALITY OF OPENINGS WHOSE NUMBER-AVERAGE SIZE IS SUCH THAT THE AVERAGE MINOR AXIS OF ANY OPENING IS NOT LESS THAN 10 MICRONS AND THE AVERAGE MAJOR AXIS OF ANY OPENING IS NOT GREATER THAN 2000 MICRONS, THEREBY CAUSING AT LEAST A PORTION OF SAID ORGANIC LIQUID AND INERT GAS TO FORM A FROTH CONSISTING ESSENTIALLY OF A PLURALITY OF BUBBLES HAVING A NUMBER-AVERAGE PARTICLE SIZE RANGING FROM ABOUT ONE TO 2000 MICRONS; REDUCING THE PRESSURE OVER SAID FROTH TO LESS THAN THE PRESSURE AT WHICH IT WAS FORMED, THEREBY CAUSING EXPANSION OF SAID FROTH; AND CURING SAID EXPANDED FROTH TO YIELD A CURED, TACK-FREE POLYURETHANE CELLULAR MATERIAL; SAID ORGANIC LIQUID BEING A PRECURSOR FOR SAID CURED POLYURETHANE CELLULAR MATERIAL AND HAVING A BROOKFIELD VISCOSITY AT THE TEMPERATURE AT WHICH SAID FROTH IS FORMED OF FROM ABOUT 500 TO 20,000 CENTIPOISE; THE RATIO IN CU. FT./LB. OF SAID INERT GAS TO SAID ORGANIC LIQUID AS THEY ENTER SAID FROTHING ZONE HAVING A VALUE RANGING FROM ABOUT 30:1 TO 120:1; WITH THE PROVISO THAT WHEN MORE THAN ONE PERFORATED PLATE IS EMPLOYED, THE NUMBER-AVERAGE DISTANCE BETWEEN THE ADJACENT SURFACES OF SAID PLATES SHALL BE SUCH THAT THE RATIO OF THE DISTANCE BETWEEN SAID ADJACENT SURFACES TO THE TOTAL AREA OF ONE OF SAID SURFACES HAVE A VALUE GREATER THAN ABOUT 0.014.