| abstract |
Polyurethane foams formed under vacuum (below atmospheric pressure) conditions using methylene diisocyanate or a specific mixture of polyisocyanate and with a major portion of methylene diisocyanate (MDI) with a specific mixture of polyether and graft polyols produces cushioning foams with lower density (1.4 to 1.8 pounds per cubic foot) and higher support factor (above 2.4). The foam-forming ingredients are mixed together and foamed under controlled pressures in the range 0.5 to 0.9 bar (absolute), preferably 0.6 to 0.8 bar (absolute). A major portion of the MDI is 4,4' methylene diisocyanate. |