	US 7,608,207 B2
	Method for preparing a photochromic polyurethane latex and application to ophthalmic optics
Nathaly Vassal, Paris (France); Jean-Pierre Vairon, Bourg la Reine (France); Bernadette Charleux, Vincennes (France); Pascale Tardieu, Paris (France); Sylvette Maisonnier, Moisselles (France); and Jean-Paul Cano, Chennevieres sur Marne (France)
Assigned to Essilor International Compagnie Generale d'Optique, Charenton-le-Pont (France)
Appl. No. 10/332,287 PCT Filed Jul. 06, 2001, PCT No. PCT/EP01/07771 § 371(c)(1), (2), (4) Date Jul. 25, 2003, PCT Pub. No. WO02/04535, PCT Pub. Date Jan. 17, 2002.
Claims priority of application No. 00 08937 (FR), filed on Jul. 07, 2000.
Prior Publication US 2004/0012002 A1, Jan. 22, 2004
Int. Cl. G02B 5/23 (2006.01); G03C 1/72 (2006.01)

U.S. Cl. 252—586 [252/182.2; 359/4; 430/339]

28 Claims

1. A method of preparing a photochromic polyurethane latex comprising:

forming a hydrophilic polyurethane prepolymer with isocyanate end groups, by polyaddition of at least one polyol and at least one polyisocyanate in the presence of at least one internal emulsifying agent, wherein the quantities of the polyol and polyisocyanate are such that the molar ratio of OH groups/NCO groups is about 1/2;

mixing the polyurethane prepolymer with a photochromic agent;

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

adding at least one chain extension agent to the emulsion and performing a chain extension reaction to give a final photochromic polyurethane latex.