| 摘要 |
Prepn. of a polyurethane polymer having a density of 100-1000 kg/m3 comprises intimately contacting under reaction conditions (A) an active hydrogen contg. substance with (B) an isocyanate compsn. having an NCO equiv. wt. of 180-300 and comprising at least 50 wt.% of an NCO-terminated prepolymer, in the presence of a blowing agent comprising water in an amt. sufficient to provide for at least 50 mole% of the total blowing requirement. The prepolymer is obtd. by reacting an organic polyisocyanate comprising at least 70 wt.% 4,4'-methylene diphenylisocyanate (4,4'-MDI) with an NCO-reactive compsn. comprising (a) a branched diol or triol having a mol.wt. of 60-300; and (b) a polyoxyalkylene polyol(s) having an ave. functionality, based on that of its initiator, of 2-4 NCO-reactive H atoms/mol. and a mol.wt. of 3000-12000, wherein the wt. ratio of (a):(b) is 0.01:1-0.25:1 and wherein (B) is present in an amt. providing 0.8-1.3 NCO gps. per NCO-reactive H of the polyether glycol and water present. |
