Molded polyurethane foam product, seat pad for vehicle, and method for molding polyurethane foam product
At least two urethane stock solutions capable of forming polyurethane foam segments having different physical characteristics are charged into a mold and foamed under a predetermined molding pressure P to mold a one-piece polyurethane product including at least two molded portions having different physical characteristics. During the foaming step, the amounts of urethane stock solutions charged are determined so that the predetermined molding pressure P is obtained at any molded portion.
1. A method for molding a one-piece polyurethane foam product, the product comprising at least two molded portions having different physical characteristics, the method comprising:
injecting at least two urethane stock solutions capable of forming polyurethane foam segments having different physical characteristics into a mold, each of the urethane stock solutions comprising a polyol-containing solution and an isocyanate component; and
foaming the urethane stock solutions at a predetermined molding pressure P, wherein the at least two urethane stock solutions are injected into the mold and foamed so that any molded portion has the predetermined molding pressure P during foaming based on a maximum internal pressure and volumes of molded portions formed with the respective urethane stock solutions.
2. The method for molding the polyurethane foam product according to claim 1 , wherein the one-piece polyurethane foam product comprising a first molded portion having a predetermined density and a second molded portion having a density different from that of the first molded portion is molded by injecting at least two urethane stock solutions capable of forming polyurethane foam segments having different densities into the mold and then foaming the urethane stock solutions at the predetermined molding pressure P.
3. The method for molding the one-piece polyurethane foam product according to claim 2 , wherein the amounts of urethane stock solutions injected are determined so that any molded portion has the predetermined molding pressure P during foaming, based on the densities of the polyurethane foam segments formed with the urethane stock solutions at the predetermined molding pressure and the volumes of molded portions formed with the respective urethane stock solutions.
4. The method for molding the one-piece polyurethane foam product according to claim 2 , wherein the one piece polyurethane foam product comprising the first molded portion having a predetermined hardness and density and the second molded portion having a density different from that of the first molded portion and having substantially the same hardness as that of the first molded portion is molded by injecting at least two urethane stock solutions capable of forming polyurethane form segments having different densities and substantially the same hardness into the mold and then foaming the urethane stock solutions at the predetermined molding pressure P.
5. The method for molding the one-piece polyurethane foam product according to claim 1 , wherein the at least two urethane stock solutions are injected into the mold at the same time.
6. The method for molding the one-piece polyurethane foam product according to claim 1 , wherein the at least two urethane stock solutions are injected into the mold with a time difference.
7. The method for molding the one-piece polyurethane foam product according to claim 1 , wherein the molded polyurethane foam product is a seat pad for a vehicle.
8. A molded polyurethane foam product produced by the method according to claim 1 .
9. A seat pad for a vehicle produced by the method according to claim 1 .
10. The seat pad for the vehicle according to claim 9 , said seat pad having a first molded portion consisting of an under-buttocks section and a second molded portion consisting of portions other than the under-buttocks section of a seating portion of the seat pad, wherein the second molded portion partly or wholly have a density lower than that of the under-buttocks section and has substantially the same hardness as that of the under-buttocks section.
11. The seat pad for the vehicle according to claim 10 , wherein a density of the second molded portion is 40 percent to 95 percent of a density of the first molded portion.
12. The seat pad for the vehicle according to claim 10 , wherein a volume of first molded portion comprises 20 percent to 70 percent of a total volume of the one-piece polyurethane product.
13. The seat pad for the vehicle according to claim 10 , wherein a 25% hardness of the first molded portion is 150 to 300 N.
14. The method for molding the one piece polyurethane foam product according to claim 1 , wherein the hardness of each portion is adjusted by adjusting an isocyanate index of a urethane solution for forming thereof.
15. The molded polyurethane product according to claim 8 , wherein the product has an interface between the molded portions being substantially in the same plane.