Flexible cycloaliphatic diisocyanate trimers

1. An allophanate-modified, partially trimerized cycloaliphatic diisocyanate which is characterized by a low T g , and which comprises the reaction product of:

(1) organic diisocyanate having cycloaliphatically bound isocyanate groups, with

(2) an hydroxyl-functional organic compound having a molecular weight of 200 to 2,000 and a functionality of greater than 1 to less than or equal to 2.9, in the presence of

(3) at least one suitable catalyst,

wherein the organic diisocyanate component (1) is free of diisocyanates which have aliphatically bound isocyanate groups and/or of diisocyanates which have aromatically bound isocyanate groups, and wherein the T g of the resultant product ranges from about −30° C. to about 40° C. and is measured after the removal of an unreacted excess monomer from the resultant product.

2. The allophanate-modified, partially trimerized cycloaliphatic diisocyanate of claim 1 , wherein

(1) said organic diisocyanate is 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl cyclohexane,

and

(2) said hydroxyl-functional organic compound is selected from the group consisting of polyester diols, and caprolactone based polyester diols.

3. The allophanate-modified, partially trimerized cycloaliphatic diisocyanate of claim 1 , wherein the T g . ranges from about −20° C. and to about 30° C.

4. A process for preparing an allophanate-modified, partially trimerized cycloaliphatic diisocyanate which is characterized by a T g from about −30° C. to about 40° C. measured after the removal of an unreacted excess monomer from the resultant product, such process comprising:

(A) providing an organic diisocyanate having cycloaliphatically bound isocyanate groups,

(B) trimerizing a portion of the isocyanate groups of an organic diisocyanate having cycloaliphatically bound isocyanate groups in the presence of a suitable catalyst,

(C) terminating the trimerization reaction at the desired degree of trimerization, and

(D) removing unreacted excess diisocyanate from the resultant product such that the product has the free monomer content of the diisocyanate is less than 0.5% by weight;

wherein prior to step (D), the process additionally comprises adding at least one hydroxyl-functional organic compound having a molecular weight of 200 to 2,000 and a functionality of greater than 1 to less than or equal to 2.9, and allowing the reaction to continue until the desired quantity of allophanate groups are formed and wherein the organic diisocyanate component in step (B) is free of diisocyanates which have aliphatically bound isocyanate groups and/or of diisocyanates which have aromatically bound isocyanate groups.

5. The process of claim 4 , wherein

(1) said organic diisocyanate is 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl cyclohexane,

and

(2) said hydroxyl-functional organic compound is selected from the group consisting of polyester diols, and caprolactone based polyester diols.

6. The process of claim 4 , wherein the T g ranges from about −20° C. and to about 30° C.

7. The process of claim 4 , in which the trimerization and the allophanatization reactions occur simultaneously.

8. The process of claim 4 , in which the trimerization reaction occurs first, followed by the allophanatization reaction.

9. The process of claim 4 , in which the allophanatization reaction occurs first, followed by the trimerization reaction.

10. A coating composition comprising:

(A) the allophanate-modified, partially trimerized cycloaliphatic diisocyanate of claim 1 ,

and

(B) at least one compound that contains isocyanate-reactive groups.