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1. (US20040012002) Method for preparing a photochromic polyurethane latex and application to ophthalmic optics
Nota: Texto obtenido mediante procedimiento automático de reconocimiento óptico de caracteres.
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Claims

1. Method for preparing a photochromic polyurethane latex, characterized in that it comprises:
a) forming a hydrophilic polyurethane prepolymer with isocyanate end groups, by the polyaddition reaction of at least one polyol and at least one polyisocyanate in the presence of at least one internal emulsifying agent;
b) mixing the polyurethane prepolymer obtained in step (a) with a photochromic agent;
c) adding water or a mixture of water and solvent, under agitation, to the mixture of the polyurethane prepolymer and the photochromic agent, to form an emulsion; and
d) adding at least one chain extension agent to the emulsion and performing a chain extension reaction to give the final photochromic polyurethane latex.
2. Method according to claim 1, characterized in that the internal emulsifying agent is an ionic emulsifying agent.
3. Method according to claim 2, characterized in that the ionic internal emulsifying agent is an anionic internal emulsifying agent.
4. Method according to claim 3, characterized in that the internal emulsifying agent is selected from the diamine and diol sulfonates and the dihydroxycarboxylic acids.
5. Method according to claim 4, characterized in that the internal emulsifying agent is α,α-dimethylolpropionic acid.
6. Method according to any. one of claims 2 to 5, characterized in that it comprises, before the step (b) of mixing the photochromic agent, a step of neutralization of the polyurethane prepolymer obtained in step (a).
7. Method according to claim 6, characterized in that the neutralization step comprises the addition of a tertiary amine.
8. Method according to any one of the preceding claims, characterized in that the polyol is selected from the polyols of low molecular weight, the polyester polyols, the polyether polyols, the polyols containing amide, groups, the polyacrylic polyols, the epoxypolyols, the polyvinyl polyols, the urethane polyols, and their mixtures.
9. Method according to claim 8, characterized in that the polyol is selected from the polycaprolactone diols.
10. Method according to any one of the preceding claims, characterized in that the polyisocyanate is a diisocyanate.
11. Method according to claim 10, characterized in that the diisocyanate is selected from toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, diphenylmethane-4,4′-diisocyanate, diphenylmethane-2,4′-diisocyanate, paraphenylene diisocyanate, biphenyldiisocyanate, 3,3′-dimethyl-4,4′-diphenylene diisocyanate, tetramethylene-1,4-diisocyanate, hexamethylene-1,6-diisocyanate, 2,2,4-trimethyl hexane-1,6-diisocyanate, lysine methyl ester diisocyanate, bis(isocyanatoethyl)fumarate, isophorone diisocyanate, ethylene diisocyanate, dodecane-1,12-diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, methylcyclohexyl diisocyanate, hexahydrotoluene-2,4-diisocyanate, hexahydrotoluene-2,6-diisocyanate, hexahydrophenylene-1,3-diisocyanate, hexahydrophenylene-1,4-diisocyanate, perhydrodiphenyl-methane-2,4′-diisocyanate, perhydrophenylmethane-4,4′-diisocyanate, and their mixtures.
12. Method according to claim 11 characterized in that the diisocyanate is isophorone diisocyanate.
13. Method according to any one of the preceding claims, characterized in that the relative quantities of polyol and diisocyanate component in step (a) are such that the molar ratio OH groups/NCO groups is 1/2.
14. Method according to any one of the preceding claims, characterized in that the quantity of internal emulsifying agent present in step (a) is from 3 to 5% by weight with respect to the total weight of polyol, polyisocyanate and internal emulsifying agent.
15. Method according to any. one of the preceding claims, characterized in that the photochromic agent is selected from chromene and compounds thereof, oxazine compounds, the fulgides, the fulgimides, and metallic salts of dithizonate.
16. Method according to any one of the preceding claims, characterized in that the quantity of the photochromic agent added represents 0.1 to 15%, and preferably 2 to 10% by weight with respect to the total weight of polyol, polyisocyanate, internal emulsifying agent and photochromic agent used.
17. Method according to any one of the preceding claims, characterized in that the photochromic agent is added in the form of a solution in a solvent.
18. Method according to claim 17, characterized in that the solvent is N-methylpyrrolidone.
19. Method according to any one of the preceding claims, characterized in that it comprises the addition of a solvent during step (a).
20. Method according to claim 19, characterized in that the solvent is N-methylpyrrolidone.
21. Method according to any one of the preceding claims, characterized in that the chain extension agent is selected from the aliphatic and cycloaliphatic diamines, triamines and tetramines and their mixtures.
22. Method according to claim 21, characterized in that the chain extension agent is selected from ethylenediamine, diethylenetriamine and tris(2-aminoethyl)amine.
23. Method according to any one of the preceding claims, characterized in that the molar ratio prepolymer/chain extension agent is between 0.2 and 2.
24. Method according to any one of the preceding claims, characterized in that the-final polyurethane latex has a concentration in solids of at least 30% by weight, preferably 30 to 35% by weight.
25. Method according to any one of the preceding claims, characterized in that the final polyurethane latex has a particle size of from 50 to 300 nm, preferably 150 to 250 nm.
26. Ophthalmic article comprising an organic or inorganic glass substrate. with a surface coated with a film of photochromic material, characterized in that the film of photochromic material results from depositing and drying a photochromic polyurethane latex obtained according to any one of claims 1 to 25.
27. Article according to claim 26, characterized in that the film of photochromic material has a glass transition temperature ≦0° C., preferably lower than −55° C.
28. Article according to one of claims 26 or 27, characterized in that the article is an ophthalmic lens.