A process for the preparation of a polyurethane soft foam.

摘要

PURPOSE:To obtain the subject foamed material having decreased density without lowering the physical properties of the foamed material by carrying out one-shot reaction process using water as a foaming agent and using a mixture having a specific composition as an organic polyisocyanate compound. CONSTITUTION:An active hydrogen-containing component consisting of (A) an active hydrogen compound, (B) water acting as a foaming agent and (C) an additive is made to react with (D) an organic polyisocyanate compound consisting of a mixture having a 4,4'-diphenylmethane diisocyanate (MDI) content of 60wt.% and produced by mixing (i) MDI containing 20-50wt.% of a mixture of 2,2'- and 2,4'-isomers and (ii) a polyphenylmethane diisocyanate having an MDI content of 35wt.%, an average number of functional groups of =2.9 and a content of 2,2'- and 2,4'-isomer mixture in the MDI of 2wt.%. The mixing ratio of the component (i) to the component (ii) is =1.