Patent ID: 7541397

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 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 uretonimine and/or uretonimine oligomers; quenching the reaction of the polyisocyanate composition with a quenching agent to inhibit formation of carbodiimides thereby inhibiting additional formation of additional uretonimine and/or uretonimine oligomers; and adding a color inhibitor having a pKB of greater than about 7 and having at least one hindered amine group.