Aliphatic polyisocyanate prepolymers and polyurethane resin coating compositions using the same

1. A polyurethane resin coating composition comprising

(a) an aliphatic polyisocyanate prepolymer

comprising the reaction product of an aliphatic isocyanurate group-containing polyisocyanate and a short-chain diol, having a urethane bond content of 4.5% by weight or more, based on the weight of the prepolymer, and a solubility parameter of 11.8 or more and wherein the short-chain diol is a diol having 2 to 7 carbon atoms

and

(b) a hydroxyl group-containing polyol having a hydroxyl group content of 5.0% by weight or more, based on the weight of the polyol.

2. The composition of claim 1 , wherein the aliphatic isocyanurate group-containing isocyanate is prepared from an aliphatic diisocyanate.

3. The composition of claim 2 , wherein the aliphatic diisocyanate is 1,6-hexamethylene diisocyanate.

4. The composition of claim 1 , wherein the short-chain diol has a carbon atom number of 2 to 4.

5. The composition of claim 1 , wherein the content of isocyanate group in the prepolymer is at least 16.5% by weight.

6. The composition as claimed in claim 1 , wherein the diol is ethylene glycol, propylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 1,2-butanediol, 1,5-pentanediol, 1,6-hexanediol, methylpentanediol, diethylene glycol or triethylene glycol.

7. The composition as claimed in claim 1 , wherein the diol contains 3 or 4 carbon atoms, and has a molecular weight up to 90.

8. The composition as claimed in claim 7 , wherein the solubility parameter of the diol is from 14.8 to 17.8.

9. The composition of claim 8 , wherein the content of isocyanate group in the prepolymer is at least 16.5% by weight.

10. The composition of claim 9 , wherein the aliphatic diisocyanate is 1,6-hexamethylene diisocyanate.

11. The composition as claimed in claim 1 , wherein the solubility parameter of the diol is 14.8 or more.

12. The composition as claimed in claim 1 , wherein the solubility parameter of the diol is from 14.8 to 17.8.

13. The composition as claimed in claim 1 , wherein the reaction product of an aliphatic isocyanurate group-containing polyisocyanate and a short-chain diol, has a urethane bond content of 5% by weight or more, based on the weight of the prepolymer.

14. The composition as claimed in claim 13 , wherein the hydroxyl group-containing polyol has a hydroxyl group content in the range of 7.5% by weight to 10% by weight based on the weight of the polyol.

15. The composition as claimed in claim 14 , which consists essentially of (a) and (b).

16. The composition as claimed in claim 14 , which consists of (a) and (b).

17. The composition as claimed in claim 1 , wherein the hydroxyl group-containing polyol has a hydroxyl group content of 7.0% by weight or more, based on the weight of the polyol.

18. The composition as claimed in claim 1 , wherein the hydroxyl group-containing polyol has a hydroxyl group content in the range of 7.5% by weight to 10% by weight based on the weight of the polyol.

19. The composition as claimed in claim 1 , which consists essentially of (a) and (b).

20. The composition as claimed in claim 1 , which consists of (a) and (b).