Method for preparing a latex with photochromic properties and uses thereof, particularly in ophthalmology
View Patent ↗This invention relates to a method for preparing a photochromic latex, photochromic thin films obtained therefrom, and articles coated with such thin films, in particular photochromic ophthalmic lenses.
1. A method for preparing a latex with photochromic properties comprising:
preparing an aqueous emulsion (I) of a composition A comprising:
at least one organic monomer Z, wherein said at least one monomer is further defined as comprising a C═C group and being capable of free-radical polymerization, and
one or more organic photochromic compounds containing a nucleus of formula:
polymerizing composition A in the presence of a water-soluble initiator to obtain particles of an at least partially polymerized latex with photochromic properties;
adding to the particles of an at least partially polymerized latex a second aqueous emulsion (II) containing a composition B comprising at least one organic monomer capable of free-radical polymerization; and
polymerizing the composition B to obtain a latex comprising at least biphasic photochromic particles.
2. The method of claim 1 , wherein composition A comprises only one type of organic monomer Z.
3. The method of claim 1 , wherein composition A comprises more than one type of organic polymer Z.
4. The method of claim 1 , wherein the latex is a fully polymerized latex.
5. The method of claim 1 , wherein the biphasic latex is further defined as comprising a core/skin structure.
6. The method of claim 1 , wherein the water-soluble initiator is introduced progressively to the aqueous emulsion I, during the polymerization.
7. The method of claim 1 , wherein the water-soluble initiator and the aqueous emulsion (I) are each introduced progressively into a reaction medium throughout polymerization.
8. The method of claim 1 , wherein the water-soluble initiator is an alkali or ammonium persulfate.
9. The method of claim 8 , wherein the water-soluble initiator is potassium or sodium persulfate.
10. The method of claim 1 , wherein the percentage by weight of the initiator with respect to total organic weight of monomer or monomers capable of free-radical polymerization used for the preparation of the latex is between 0.1 and 1%.
11. The method of claim 1 , wherein the organic monomer Z is an alkyl (meth)acrylate monomer.
12. The method of claim 1 , wherein composition A is further defined as comprising at least one monomer Z which is further defined as a low Tg monomer which leads to a homopolymer whose glass transition temperature is less than or equal to 0° C.
13. The method of claim 12 , wherein the low Tg monomer represents at least 40% by weight of the monomers capable of free-radical polymerization.
14. The method of claim 1 , wherein the particles of the latex are further defined as having a diameter of 50 to 400 nm.
15. The method of claim 1 , wherein a dry extract of the latex represents from 30 to 50% of the total weight of the latex.
16. The method of claim 1 , wherein the pH of the latex is between 5 and 7.
17. A latex with photochromic properties, further defined as comprising particles of a polymer material resulting from the free-radical polymerization of at least one monomer Z with a C═C group comprising one or more organic photochromic compound comprising a nucleus of formula:
the particles of said polymer material having an average size of between 50 and 400 nm and a biphasic structure of the core/skin type, and
wherein the organic photochromic compound is further defined as not containing an indoline ring.
18. The latex of claim 17 , wherein the particles are further defined as having an average size of between 80 and 300 nm.
19. The latex of claim 18 , wherein the particles are further defined as having an average size between 150 and 250 nm.
20. The latex of claim 17 , wherein the organic photochromic compound is contained in the core of the particles.
21. The latex of claim 17 , wherein a dry extract of the latex represents from 30 to 50% of the total weight of the latex.
22. A substrate comprising a dry latex film with photochromic properties, the latex further defined as comprising particles of a polymer material resulting from the free-radical polymerization of at least one monomer Z with a C═C group comprising one or more organic photochromic compound comprising a nucleus of formula:
the particles of said polymer material having an average size of between 50 and 400 nm and a biphasic structure of the core/skin type, and
wherein the organic photochromic compound is further defined as not containing an indoline ring.
23. The substrate of claim 22 , wherein the film has a thickness of between 3 and 20 μm.
24. The substrate of claim 22 , further defined as comprising an anti-abrasion coating.
25. The substrate of claim 22 , further defined as comprising an anti-reflection coating.
26. The substrate of claim 22 , further defined as comprising an anti-abrasion coating on the latex film and an anti-reflection coating on the anti-abrasion coating.
27. The substrate of claim 22 , further defined as an ophthalmic lens.
28. The method of claim 14 , wherein the particles of the latex are further defined as having an average size of between 80 and 300 nm.
29. The method of claim 28 , wherein the particles are further defined as having an average size between 150 and 250 nm.
30. The method of claim 1 , wherein the organic photochromic compound is further defined as not containing an indoline ring.
31. The method of claim 30 , wherein the particles of polymer material have a biphasic structure of the core/skin type.
32. The method of claim 31 , wherein the organic photochromic compound is contained in the core of the particles.
33. The method of claim 1 , wherein the latex is further defined as a dry latex film.
34. The method of claim 33 , wherein the dry latex film has a thickness of between 3 and 20 μm.
35. The method of claim 1 , wherein a substrate comprises the latex.
36. The method of claim 35 , wherein the substrate further comprises an anti-abrasion coating.
37. The method of claim 35 , wherein the substrate further comprises an anti-reflection coating.
38. The method of claim 35 , wherein the substrate comprises an anti-abrasion coating on the latex film and an anti-reflection coating on the anti-abrasion coating.
39. The method of claim 35 , wherein the substrate is further defined as an ophthalmic lens.
40. A method for preparing a latex with photochromic properties comprising:
preparing an aqueous emulsion (I) of a composition A comprising:
at least one organic monomer Z, wherein said at least one monomer is further defined as comprising a C═C group and being capable of free-radical polymerization, and
one or more organic photochromic compounds containing a nucleus of formula:
polymerizing composition A in the presence of a water-soluble initiator to obtain particles of an at least partially polymerized latex with photochromic properties,
wherein the particles have a biphasic structure of the core/skin type, and
wherein the organic photochromic compound is further defined as not containing an indoline ring.
41. The method of claim 40 , wherein the organic photochromic compound is contained in the core of the particles.