Patent ID: 8097659

Claim:
A method of producing a flexible polyurethane foam having an open cell structure, according to which a raw material containing polyols, a cross-linking agent, and a polyisocyanate compound is made to react in the presence of a catalyst, a blowing agent, and an auxiliary blowing agent, and thereby, a flexible polyurethane foam is obtained, wherein a hydroxyl value of the polyols is 50 mg KOH/g to 60 mg KOH/g, wherein the polyols are polyether polyols having three hydroxyl groups; wherein when the polyurethane is obtained, the raw material is discharged onto a conveyer belt to foam and harden while moving on the conveyer belt, wherein the isocyanate index of said polyisocyanate compound is 112 to 120, wherein the blowing agent is water and the amount of the blowing agent mixed in is 1.5 mass parts to 3.0 mass parts relative to 100 mass parts of polyols, wherein the auxiliary blowing agent is a liquefied carbon dioxide, wherein the content of the liquefied carbon dioxide in said raw material is 1.5 mass parts to 6.0 mass parts relative to 100 mass parts of the polyols, wherein the amount of water is equal to or less than the content of the liquefied carbon dioxide, wherein, when a foaming reaction between the polyisocyanate compound and water proceeds in the presence of the liquefied carbon dioxide as the auxiliary blowing agent, generation of an amine compound (—R—NH 2 ) is suppressed and thus generation of urea bonds is suppressed, and wherein the density of the resulting foam is 20-41 kg/m 3 ; wherein the load required for compressing said flexible polyurethane foam to 25% of the initial thickness is 30 N to 70 N; wherein the flexible polyurethane foam is cut in plate form and has an open cell structure, wherein the compression deflection coefficient, which is calculated by dividing the load for compressing the flexible polyurethane foam to 65% of the initial thickness by the load required for compressing the foam to 25% of the initial thickness is 3.0 to 4.0, and wherein x/y is greater than 1 and no greater than 1.5 in cells, where the length in the rising direction of the thickness of the foam is represented by x and the length in the direction of a plane of the foam is represented by y, and wherein the liquefied carbon dioxide is dissolved in the polyols under a pressure of 5 MPa to 7 MPa and a temperature of −12° C. to −20° C.