Polyurethane hydrogel contact lens

1. A prepolymer, which is an isocyanate terminated prepolymer, is free of unreacted hydroxyl groups and is prepared by reacting a mixture comprising:

(a) at least one multifunctional compound containing three or more amine or isocyanate groups,

(b) at least one diisocyanate, and

(c) at least one diol,

wherein said diol has a weight average molecular weight of at most 7000,

said prepolymer has a viscosity of at most 100,000 cps at 70° C., and

said prepolymer, when reacted with an excess of water, forms a hydrogel polymer.

2. The prepolymer of claim 1 , wherein component (a) is at least one triisocyanate compound selected from the group consisting of the isocyanurate trimer of hexamethylene diisocyanate, 2,4,6-toluene triisocyanate, p,p′,p″-triphenylmethane triisocyanate, the isocyanurate of isophorone diisocyanate, and the trifunctional biuret of hexamethylene diisocyanate.

3. A prepolymer, prepared by reacting a mixture comprising:

(a) at least one triisocyanate,

(b) at least one diisocyanate, and

(c) at least one polyalkylene oxide having two terminal hydroxyl groups,

wherein a molar ratio of (a):(b):(c) in said mixture is 0.9-1.1:1.8-3.3:1.8-3.3,

said at least one polyalkylene oxide has weight average molecular weight of at most 7000, and

said prepolymer, when reacted with an excess water, forms a hydrogel polymer.

4. The prepolymer of claim 3 , wherein said molar ratio of (a):(b):(c) in said mixture is 0.97-1.03:1.94-2.06:1.94-2.06, and

said at least one polyalkylene oxide has a weight average molecular weight of 1000-2000.

5. The prepolymer of claim 4 , wherein said prepolymer has a viscosity of 1000 to 50,000 cps at 70° C.

6. The prepolymer of claim 3 , wherein the triisocyanate is the isocyanurate trimer of hexamethylene diisocyanate, 2,4,6-toluene triisocyanate, p,p′,p″-triphenylmethane triisocyanate, the isocyanurate of isophorone diisocyanate, or the trifunctional biuret of hexamethylene diisocyanate.

7. The prepolymer of claim 3 , wherein the diisocyanate is methylen dicyclohexyl diisocyanate, hexamethylene diisocyanate, isophrone diisocyanate, toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, ethylene diisocyanate, ethylidene diisocyanate, propylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, ethylene diisocyanate, ethylidene diisocyanate, propylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, m-phenylene diisocyanate, 3,3″-diphenyl-4,4″-biphenylene diisocyanate, 4,4″-biphenylene diisocyanate, 4,4″-diphenylmethane diisocyanate, 3,3″-dichloro-4,4″-biphenylene diisocyanate, 1,6-hexamethylene diisocyante, 1,4-tetramethylene diisocyante, 1,10-decamethylene diisocyanate, cumene-2,4-diisocyanate, 1,5-naphthalene diisocyante, 1,4-cyclohexylene diisocyanate, p-tetramethyl xylylene diisocyanate, p-phenylene diisocyante, 4-methoxy-1,3-phenylene diisocyante, 4-chloro-1,3-phenylene diisocyanate, 4-bromo-1,3-phenylene diisocyanate, 4-ethoxy-1,3-phenylene diisocyanate, 2,4-dimethyl-1,3-phenylene diisocyanate, 5,6-dimethyl-1,3-phenylene diisocyanate, 2,4-diisocyanatodiphenylether, 4,4″-diisocyanatodiphenylether, benzidine diisocyanate, 4,6-dimethyl-1,3-phenylene diisocyanate, 9,10-anthracene diisocyanate, 4,4′-diisocyanatodibenzyl, 3,3′-dimethyl-4,4′-diisocyanatodiphenylmethane, 2,6-dimethyl-4,4′-diisocyanatodiphenyl, 2,4-diisocyanatostilbene, 3,3′-dimethoxy-4,4′-diisocyanatodiphenyl, 1,4-anthracenediisocyanate, 2,5-fluorenediisocyanate, 1,8-naphthalene diisocyanate, 2,6-diisocyanatobenzfuran, xylylen diisocyanate, or m-tetramethyl xylylene diisocyanate.

8. A prepolymer, which is an isocyanate terminated prepolymer, is free of unreacted hydroxyl groups and is prepared by reacting a mixture comprising:

(a) at least one triol,

(b) at least one diisocyanate, and

(c) at least one polyalkylene oxide having two terminal hydroxyl groups,

wherein a molar ratio of (a):(b):(c) in said mixture is 0.9-1.1:4.5-5.5:1.8-2.2,

said at least one polyalkylene oxide has a weight average molecular weight of at most 7000, and

said prepolymer, when reacted with an excess water, forms a hydrogel polymer.

9. The prepolymer of claim 8 , wherein said molar ratio of (a):(b):(c) in said mixture is 0.97-1.03:4.85-5.15:1.94-2.06, and said at least one polyalkylene oxide has a weight average molecular weight of 1000-2000.

10. The prepolymer of claim 9 , wherein said prepolymer has a viscosity of 1000 to 50,000 cps at 70° C.

11. The prepolymer of claim 8 , wherein the triol is glycerol, trimethylol propane, or triethanolamine.

12. A prepolymer of formula I:

wherein X is a trivalent organic group containing 3-20 carbon atoms;

Y is a divalent organic group containing 3-20 carbon atoms;

Z is an oligomer consisting of monomer units selected from the group consisting of —(CH 2 —CH 2 —O)—, —(CH 2 —CH(CH 3 )—O)—, —(CH(CH 3 )—CH 2 —O)—, —(CH 2 —CH(CH 2 —CH 3 )—O)—, —(CH(CH 2 —CH 3 )—CH 2 —O)—, and —(CH(CH 3 )—CH(CH 3 )—O)—, and

Z has a weight average molecular weight of at most 7000.

13. The prepolymer of claim 12 , wherein

Y is a divalent aliphatic group,

Z has a weight average molecular weight of 1000-2000, and

Said prepolymer has a viscosity of 1000 to 50,000 cps at 70° C.

14. The prepolymer of claim 12 , wherein the trivalent organic group X contains heteroatoms selected from the group consisting of oxygen, nitrogen, sulfur, and halogens.

15. The prepolymer of claim 14 , wherein X is a saturated or unsaturated cyclic group or a saturated or unsaturated acyclic alkyl group.

16. The prepolymer of claim 15 , wherein X is a 6-membered cyclic group containing at least one nitrogen.

17. The prepolymer of claim 16 , wherein X is a group of formula (V)

18. The prepolymer of claim 12 , wherein Y is a group of Formula (VI) or (VII)

19. A prepolymer of formula II:

wherein X is trivalent organic group containing 3-20 carbon atoms;

Y is divalent organic group containing 3-20 carbon atoms;

Z is an oligomer consisting of monomer units selected from the group consisting of —(CH 2 —CH 2 —O)—, —(CH 2 —CH(CH 3 )—O)—, —(CH(CH 3 )—CH 2 —O)—, —(CH 2 —CH(CH 2 —CH 3 )—O)—, —(CH(CH 2 —CH 3 )—CH 2 —O)—, and —(CH(CH 3 )—CH(CH 3 )—O)—, and

Z has a weight average molecular weight of at most 7000.

20. The prepolymer of claim 1 , wherein

Y is a divalent aliphatic group,

Z has a weight average molecular weight of 1000-2000, and

Said prepolymer has a viscosity of 1000 to 50,000 cps at 70° C.

21. The prepolymer of claim 19 , wherein the trivalent organic group X contains heteroatoms selected from the group consisting of oxygen, nitrogen, sulfur, and halogens.

22. The prepolymer of claim 21 , wherein X is a saturated or unsaturated cyclic group or a saturated or unsaturated acyclic alkyl group.

23. The prepolymer of claim 22 , wherein X is a 6-membered cyclic group containing at least one nitrogen.

24. The prepolymer of claim 23 , wherein X is a group of formula (V)

25. The prepolymer of claim 19 , wherein Y is a group of Formula (VI) or (VII)