Soft silicone medical devices
View Patent ↗The invention is related to a method for producing silicone medical devices, in particular, silicone contact lenses, having consistent mechanical properties in a cost-effective manner. The invention is also related to a silicone medical device, especially a soft silicone contact lens.
1. A method for producing a silicone medical device, comprising the steps of:
(1) obtaining a polymerizable silicone composition which comprises
(a) (i) from about 70% to about 97% by weight of one or more first polydiorganosiloxanes each having at least two (meth)acryloylamido groups, and (ii) from about 2% to about 15% by weight of one or more second polydiorganosiloxanes each having at least two (meth)acryloyloxy groups, wherein each of the first and second polydiorganosiloxanes has an averaged molecular weight of at least about 2000 Daltons,
(b) from about 1.0% to about 20.0% by weight of one or more third polydiorganosiloxanes each having at least two thiol groups and an averaged molecular weight of at least about 2000 Daltons, and
(c) from about 0.1% to about 3% by weight of a free-radical initiator,
provided that components (a) to (c) listed above and any additional polymerizable components present in the polymerizable silicone composition add up to 100% by weight;
(2) introducing the polymerizable silicone composition into a mold for making a silicone medical device; and
(3) curing thermally or actinically the polymerizable silicone composition in the mold to form the silicone medical device,
wherein the formed silicone medical device has an elastic modulus of about 1.2 M Pa or less and an elongation at break of about 200% or larger.
2. The method of claim 1 , wherein the first, second, and third polydiorganosiloxanes independent of one another are a linear polydiorganosiloxane.
3. The method of claim 1 , wherein the first, second, and third polydiorganosiloxanes independent of one another are a linear polydimethylsiloxane.
4. The method of claim 3 , wherein the free-radical initiator is a thermal initiator.
5. The method of claim 3 , wherein the free-radical initiator is a photoinitiator.
6. The method of claim 5 , wherein the polymerizable silicone composition comprises a UV-absorbing vinylic monomer.
7. The method of claim 1 , wherein the medical device is a silicone contact lens.
8. The method of claim 2 , wherein the polymerizable silicone composition comprises from about 75% to about 95% by weight of the first polydiorganosiloxanes.
9. The method of claim 2 , wherein the polymerizable silicone composition comprises from about 80% to about 93% by weight of the first polydiorganosiloxanes.
10. The method of claim 1 , wherein the first and second polydiorganosiloxanes independent of one another have an average molecular weight of from about 6000 to about 200000 Daltons.
11. The method of claim 8 , wherein the first and second polydiorganosiloxanes independent of one another have an average molecular weight of from about 6000 to about 200000 Daltons.
12. The method of claim 9 , wherein the first and second polydiorganosiloxanes independent of one another have an average molecular weight of from about 6000 to about 200000 Daltons.
13. The method of claim 10 , wherein the third polydiorganosiloxanes have an average molecular weight of from about 4000 to about 150000 Daltons.
14. The method of claim 11 , wherein the third polydiorganosiloxanes have an average molecular weight of from about 4000 to about 150000 Daltons.
15. The method of claim 12 , wherein the third polydiorganosiloxanes have an average molecular weight of from about 4000 to about 150000 Daltons.
16. The method of claim 6 , wherein the first and second polydiorganosiloxanes independent of one another have an average molecular weight of from about 6000 to about 200000 Daltons, wherein the third polydiorganosiloxanes have an average molecular weight of from about 4000 to about 150000 Daltons.
17. The method of claim 6 , wherein the polymerizable silicone composition comprises from about 75% to about 95% by weight of the first polydiorganosiloxanes, wherein the first and second polydiorganosiloxanes independent of one another have an average molecular weight of from about 6000 to about 200000 Daltons, wherein the third polydiorganosiloxanes have an average molecular weight of from about 4000 to about 150000 Daltons.
18. The method of claim 6 , wherein the polymerizable silicone composition comprises from about 80% to about 93% by weight of the first polydiorganosiloxanes, wherein the first and second polydiorganosiloxanes independent of one another have an average molecular weight of from about 6000 to about 200000 Daltons, wherein the third polydiorganosiloxanes have an average molecular weight of from about 4000 to about 150000 Daltons.
19. The method of claim 18 , wherein the medical device is a silicone contact lens.