Silicone hydrogel reactive mixtures comprising borates
Disclosed in this specification is a method for forming a silicone hydrogel material that is useful for forming contact lens materials. The method includes using an effective amount of a borate additive to reduce the gel time of the silicone hydrogel reactive mixture and/or enhance the optical properties of the resulting cured material.
1. A method of forming a silicone hydrogel material comprising the steps of:
providing a mixture of polymerizable components that includes at least one hydrophilic component and at least one silicone component, wherein at least one of the polymerizable components contains a hydroxyl group, the mixture further including a sufficient amount of a borate to reduce cure time compared to an identical mixture that lacks the borate, the borate being selected from either boric anhydride or a borate represented by formula:
where wherein R 1 , R 2 and R 3 are independently selected from the group consisting of hydrogen; C1-C16 alkyl groups; C1-C16 alkyl groups substituted with O, Cl, N, or Br; polymerizable groups; ester groups, amide groups, ether groups, silicone components and hydrophilic components, with the proviso that R 1 , R 2 , and R 3 comprise at most one hydroxyl group;
curing the mixture to form a cured material.
2. The method as recited in claim 1 , wherein R 1 , R 2 and R 3 are monovalent.
3. The method as recited in claim 1 , wherein at least two of R 1 , R 2 and R 3 are divalent and, taken together, form a cyclic borate ester.
4. The method as recited in claim 1 , wherein at least one of R 1 , R 2 and R 3 comprises a polymerizable group.
5. The method as recited in claim 1 , wherein R 1 , R 2 and R 3 are the same.
6. The method as recited in claim 1 , wherein the borate is selected from the group consisting of a borate ester of methanol, ethanol, propanol, t-amyl alcohol, 3-methyl-3-pentanol, 3,7-dimethyl-3-octanol, 2-hydroxyethylmethacrylate, tri(propylene glycol) methyl ether, 2-propenoic acid, 2-methyl-,2-hydroxy-3-[3-[1,3,3,3-tetramethyl-1-[(trimethylsilyl)oxy]disiloxanyl]propoxy]propyl ester (SiGMA), mono-(3-methacryloxy-2-hydroxypropyloxy)propyl terminated, mono-butyl terminated polydimethylsiloxane (OHmPDMS); and combinations thereof.
7. The method as recited in claim 5 , wherein R 1 , R 2 and R 3 are selected from the group consisting of n-propyl, iso-propyl, butyl and tert-butyl.
8. The method as recited in claim 1 , wherein the borate is selected from the group consisting of trimethyl borate and triethyl borate.
9. The method as recited in claim 1 , wherein the borate is boric acid.
10. The method as recited in claim 1 , wherein the step of curing the mixture has a borate content of between 2 M % OH and 50 M % OH.
11. The method as recited in claim 1 , wherein the mixture has a viscosity that is at least 10% greater than that of the identical mixture that lacks the borate.
12. The method as recited in claim 1 , further comprising the step of removing at least half of the borate from the cured contact lens material.
13. The method as recited in claim 1 , wherein the cure time is reduced by at least 10% relative to the identical mixture that lacks the borate.
14. The method as recited in claim 1 , wherein the cure time is reduced by at least 25% relative to the identical mixture that lacks the borate.
15. The method as recited in claim 1 , wherein the cure time is reduced by at least 50% relative to the identical mixture that lacks the borate.
16. A method of forming an optically clear material comprising the steps of:
providing a mixture of polymerizable components that includes at least one hydrophilic component and at least one silicone component wherein at least one of the polymerizable components contains a hydroxyl group, the mixture further including a sufficient amount of a borate to render the resulting cured material more optically clear compared to a cured material formed from an identical mixture that lacks the borate, the borate being selected from either boric anhydride or a borate represented by formula:
wherein R 1 , R 2 , and R 3 are independently selected from the group consisting of hydrogen; C1-C16 alkyl groups; C1-C16 alkyl groups substituted with O, Cl, N, or Br; polymerizable groups; ester groups, amide groups, ether groups, silicone components and hydrophilic components, with the proviso that R 1 , R 2 , and R 3 comprise at most one hydroxyl group;
curing the mixture to form a cured, optically clear material.