WATER-BLOWN POLYURETHANE SEALING DEVICES AND COMPOSITIONS FOR PRODUCING SAME

摘要

Disclosed as a particular isocyanate prepolymer composition particularly suitable for use in polyurethane compositions having particular applicability for producing microcellular molded polyurethane articles particularly suitable for use as sealing devices. In particular, the isocyanate prepolymer composition is the result of reacting an isocyanate blend (a) having (i) 0 to 10 pbw 2,4'-diphenylmethane diisocyanate; (ii) 40 to 90 pbw 4,4'-diphenylmethane diisocyanate; (iii) 1 to 10 pbw 3-ring oligomers of polymethylene polyphenyl polyisocyanate; (iv) 1 to 20 pbw of n-ring oligomers of polymethylene polyphenyl polyisocyanate (n being greater than 3); and (v) 1 to 10 pbw of a mixture of uretonimine with from 5 to 50 parts by weight of a propoxylated propylene glycol (b) having a number average molecular weight of between 2000 and 6000, and a hydroxyl number of between 10 to 75. The resulting isocyanate prepolymer (I) has a free NCO of from 20 to 30 and a viscosity of from 50 to 500 cPs.