Patent ID: 7504523

Claim:
A method of producing a uretonimine-modified isocyanate composition, said method comprising: providing a polyisocyanate composition having two or more isocyanate groups and comprising 4,4′-diphenylmethane diisocyanate (MDI); reacting the polyisocyanate composition at a first temperature in a range of from about 80° C. to about 130° C. and in the presence of a catalyst such that the isocyanate groups form carbodiimides available for forming uretonimines and uretonimine oligomers; partially quenching the reaction of the polyisocyanate composition with a first quenching agent having a pKa of greater than about −8.0 to inhibit formation of carbodiimides thereby inhibiting additional formation of uretonimine and uretonimine oligomers at the first temperature; reducing the temperature of the partially quenched reaction of polyisocyanate composition to a second temperature lower than the first temperature; and quenching the reaction of the polyisocyanate composition with a second quenching agent having a pKa of less than about −8.0 and different than the first quenching agent to further inhibit formation of carbodiimides thereby further inhibiting additional formation of uretonimines and uretonimine oligomers.