Polyisocyanate compositions for the preparation of flexible polyurethane foams

An isocyanate prepolymer composition, capable of reacting with a compound containing a least two isocyanate-reactive hydrogen atoms to form a foam, the composition comprising the result of combining:

• (a.) about 50 to 90% by wt, based on the total isocyanate composition, of an isocyanate blend comprising:
• (i) 55 to 75% by wt of 4,4'-diphenylmethane diisocyanate;
• (ii) 17 to 27% by wt of 2,4'-diphenylmethane diisocyanate;
• (iii) 1 to 10% by wt of 3-ring oligomers of
• (iv) 1 to 15% by wt of n-ring oligomers of polymethylene polyphenyl polyisocyanate (n being greater than 3) the weights of (i) to (iv), being based on the weight of blend (a);
• (b.) about 5 to 30% by wt, based on the total isocyanate composition, of a polyhydroxy containing polyol having a molecular weight of from 700 to about 6000;
• and
• (c.) about 5 to 15% by wt, based on the total isocyanate composition, of toluene diisocyanate;
• and
• wherein the resulting isocyanate prepolymer composition has a free NCO content of from about 20 to 40% by wt.