Weak bronsted acid derivatives for improving dimensional stability of polyurethane flexible foams

In a method for preparing a flexible polyurethane foam which comprises reacting an organic diisocyanate with a polyester or polyether polyol in the presence of urethane catalyst, water or water and HCFC as the blowing agent, optionally a silicone surfactant cell stabilizer, and a cell opener, the improvement for reducing shrinkage and/or the force-to-crush of the flexible foam which comprises as the cell opener an active methylene- or methine-group containing compound selected from the group consisting of .beta.-dicarbonyl compounds, esters of cyanoacetic acid, esters of 1,3-acetone dicarboxylic acid, 2-acyl-1,3-diketones, 2-acyl-1,3-keto esters, and esters of substituted-acetic acids in which the substituents are electron-withdrawing groups, the cell opener present at 0.001-2.5 pphpp.

In a flexible polyurethane foam having a density of 0.6-25 lb/ft.sup.3 (10-400 kg/m.sup.3) prepared by reacting a composition comprising the following components in parts by weight (pbw):

• ______________________________________ Polyol 20-100 Polymer Polyol 80-0 Silicone Surfactant 0.5-2.5 Stabilizer/Cell Opener 0.05-3 Water 1-8 Auxiliary Blowing Agent 0-4.5 Crosslinker 0.5-2 Catalyst Composition 0.1-5 Isocyanate Index 70-115 ______________________________________
• the improvement for reducing shrinkage and/or the force-to-crush of the flexible foam which comprises as the stabilizer/cell opener an active methylene- or methine-group containing compound selected from the group consisting of -dicarbonyl compounds, esters of cyanoacetic acid, esters of 1,3-acetone dicarboxylic acid, 2-acyl-1,3-diketones, 2-acyl-1,3-keto esters, and esters of substituted-acetic acids in which the substituents are electron-withdrawing groups.