Patent ID: 6515164
Filing Date: 2003-02-04
Classification: B32B,C08G,C09J

Abstract:
A low-monomer polyurethane prepolymer containing free isocyanate groups obtained by reacting one or more polyhydric alcohols and two or more diisocyanates, wherein the polyhydric alcohol is first reacted with at least one non-symmetrical diisocyanate having a first NCO group which has a slower rate of reaction with the polyhydric alcohol than a second NCO group, wherein a ratio of a number of OH groups to a number of first and second NCO groups is form 4:1 to 0.55:1, to form a reaction product having free OH groups and free first NCO groups, and reacting the reaction product with at least one second diisocyanate having NCO groups which have a faster rate of reaction with the polyhydric alcohol than the first NCO groups wherein a ratio of a total number of first and second NCO groups of the non-symmetrical diisocyanate to a number of NCO groups of the second diisocyanate is greater than 6:1 and the second diisocyanate is added in an amount less than an equivalent of free OH groups in the reaction product.