Patent ID: 7608207
Filing Date: 2009-10-27
Classification: C08G,C08K,G02B

Abstract:
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.