Silicone hydrogels comprising N-alkyl methacrylamides and contact lenses made thereof
The present invention relates to silicone hydrogels exhibiting desired combinations of physical and mechanical properties, formed from a reactive monomer mixture comprising at least one N-alkyl methacrylamide, and at least one silicone-containing component. These silicone hydrogels may also contain hydrophilic components, crosslinking agents and toughening monomers. These silicone hydrogels are useful in preparing biomedical devices, ophthalmic lenses, and contact lenses.
1. A process for making a composite contact lens, comprising:
(a) dosing a first silicone hydrogel formulation containing at least one N-alkyl methacrylamide and at least one silicone-containing component into a first mold,
(b) partially curing the first silicone hydrogel formulation into a gel,
(c) dosing a second silicone hydrogel formulation into the first mold
(d) allowing time for the second silicone hydrogel formulation to imbibe into the gel,
(e) placing a second mold on top of the first mold, and
(f) fully curing the combination to form the composite contact lens,
wherein the composite contact lens contains a central region comprised of a first silicone hydrogel derived from the first silicone hydrogel formulation and a peripheral region comprised of a second silicone hydrogel derived from the second silicone hydrogel formulation, and
wherein the first silicone hydrogel has a modulus of at least about 1000 psi and a water content of at least about 10%.
2. A process for making a composite contact lens, comprising:
(a) dosing a first silicone hydrogel formulation containing at least one N-alkyl methacrylamide and at least one silicone-containing component into a first mold,
(b) partially curing the first silicone hydrogel formulation into a gel,
(c) dosing a second silicone hydrogel formulation into the first mold
(d) allowing time for the second silicone hydrogel formulation to imbibe into the gel,
(e) placing a second mold on top of the first mold, and
(f) fully curing the combination to form the composite contact lens,
wherein the composite contact lens contains a central region comprised of a first silicone hydrogel that is a non-ionic silicone hydrogel derived from the first silicone hydrogel formulation and a peripheral region comprised of a second silicone hydrogel derived from the second silicone hydrogel formulation, and wherein the first silicone hydrogel has a modulus of about 140 to about 2000 psi and a water content of about 20 to about 50%.
3. The process of any one of claims 1 to 2 wherein the peripheral region exhibits a lower modulus than the central region.
4. The process of claim 1 wherein the central region exhibits a modulus between about 10,000 psi and about 200,000 psi and the peripheral region exhibits a modulus between about 50 psi and about 300 psi.
5. The process of claim 3 wherein the first and second silicone hydrogels comprise water contents within about 5 weight percent of one another.
6. The process of claim 3 wherein the central region is encapsulated by the peripheral region.