Patent ID: 6653363
Filing Date: 2003-11-25
Classification: B29C,B29K,C08G

Abstract:
A method for producing a viscoelastic polyurethane foam, comprising:(1) preparing a reaction mixture comprising: (a) a polyol mixture of (i) about 30 to 95 percent by weight total polyols of a polyether polyol, and having a hydroxyl number in the range of about 180 to 280 and a functionality from 2.7 to 3.3, and (ii) about 5 to 70 percent by weight total polyols of a graft polyol having a hydroxyl number in the range of about 25 to 50 and a functionality from 2.5 to 3.0; (b) an organic polyisocyanate selected from the group consisting of toluene diisocyanate and methylene diisocyanate mixed with toluene diisocyanate, wherein at least 50 percent of the methylene diisocyanate is 4, 4â€² methylene diisocyanate, wherein if a mixture of methylene diisocyanate and toluene diisocyanate is used, the polyisocyanate mixture comprises from about 5 to 20 percent by weight toluene diisocyanate and about 80 to 95 percent by weight methylene diisocyanate, and wherein the isocyanate index is below about 120; and (c) from about 1.5 to 3.0 parts per hundred parts polyol of water as a blowing agent; and (2) allowing said reaction mixture to react while held at a pressure of about 1.05 to 1.5 bar (absolute) so as to form the viscoelastic polyurethane foam, wherein the viscoelastic polyurethane foam at room temperature has a density of at least 2.0 pounds per cubic foot, a ball rebound of at least 9%, and an IFD25 in the range of about 20 to 60 lbf, and wherein the viscoelastic foam has a temperature sensitivity such that when the foam is heated from room temperature to about 100Â° F. (38Â° C.) the IFD25 is reduced by 25% or more from the room temperature IFD25 value.