Abstract: The present invention relates to a process for the preparation of low-density flexible polyurethane foams comprising reacting, in a closed mold, a mixture comprising polyisocyanates; compounds containing at least two isocyanate-reactive hydrogen atoms and having a molecular weight in the range from about 400 to about 10,000; water as blowing agent; optionally, compounds containing at least two isocyanate-reactive hydrogen atoms and having a molecular weight in the range from 32 to 399 as chain-extending and crosslinking agents; and optionally, one or more known auxiliaries and additives, wherein one or more of the reaction mixture components is heated before foaming to a temperature of at least 40.degree. C.

Abstract: A deformable and durable polyurethane foam molding is made from the reaction product of a polyether polyol component and a polyisocyanate component. The polyether polyol component is a polyether having at least two hydroxyl groups, a molecular weight of from 400 to 10,000 and at least 10 wt. % hydroxyl groups which are primary hydroxyl groups. The polyisocyanate component is a mixture of from 60-90 wt. % 4,4'-diphenyl methane diisocyanate and from 3-30 wt. % 2,4'-diphenyl methane diisocyanate. Such reaction mixture is prepared in each of at least two mixing heads. The index of reaction mixture is different from that in the other mixing head. The mixture is then introduced into associated zones of a mold cavity where the mixture is allowed to foam. The molding is subsequently removed from the mold cavity. These polyurethane foam moldings are particularly useful in making seat cushions.