Method for making porous polyurethane foams

Claim 1

IN A PROCESS FOR MAKING A FLEXIBLE POLYURETHANE FOAM BY REACTING A POLYHYDROXYL-CONTAINING ORGANIC COMPOUND HAVING AN OH EQUIVALENT WEIGHT OF AT LEAST 500 WITH AN ORGANIC POLYISOCYANATE IN THE PRESENCE OF AN AMINE CATALYST AND A STANNOUS SALT OF A FATTY ACID CATALYST, THE IMPROVEMENT FOR MAKING A FLEXIBLE POLYURETHANE FOAM CONTAINING PREDOMINANTLY OPEN AND INTERCONNECTING CELLS WHICH COMPRISES CARRYING OUT THE REACTION OF (1) A POLYETHER POLYOL HAVING AN OH EQUIVALENT WEIGHT OF AT LEAST 500 AND CONSISTING PRINCIPALLY OF THE REACTION PRODUCT OF (I) PROPYLENE OXIDE OR PROPYLENE OXIDE AND A MINOR PROPORTION OF ETHYLENE OXIDE, WITH (II) AN ALIPHATIC POLYOL HAVING FROM 2 TO 8 HYDROXYL GROUPS IN THE MOLECULE, AND (2) AN APPROXIMATE CHEMICALLY EQUIVALENT AMOUNT OF AN ORGANIC POLYISOCYANATE IN ADMIXTURE WITH (A) FROM 6 TO 12 PARTS BY WEIGHT OF WATER, (B) FROM 20 TO 120 PARTS BY WEIGHT OF AN INERT VOLATILE ORGANIC FLUID BLOWING AGENT BOILING BELOW 110*C., AND (C) FROM 1 TO 8 PARTS BY WEIGHT OF A SILICONE SURFACTANT, PER 100 PARTS BY WEIGHT OF SAID POLYETHER POLYOL STARTING MATERIAL, SAID POLYISOCYANATE BEING WITHIN THE RANGE OF FROM 0.90 TO 1.10 NCO GROUPS PER CHEMICALLY EQUIVALENT HYDROGEN AND OH GROUPS IN THE POLYETHER POLYOL AND WATER STARTING MATERIALS AND WITH THE PROVISO THAT SAID MIXTURE OF STARTING MATERIALS (1), (2) AND (A), (B), AND (C) ABSENT SAID CATALYSTS, HAS AN ABSOLUTE VISCOSITY BETWEEN ABOUT 20 AND ABOUT 40 CENTIPOISES AT 25*C.