Self-supporting photochromic polyurethane film, method of manufacturing the film, article comprising said film

A method for producing a self-supporting polymer film comprising between 3% and 12% by weight of a ketone based on the total weight of the self-supporting polymer film and further comprising at least one organic photochromic molecule comprising a chromophore, comprising the steps of:

• a. providing an aliphatic thermoplastic polyurethane film wherein the polyurethane is based on an aliphatic diisocyanate selected from 1,4-tetramethylene diisocyanate, 2,2,4-trimethyl-1,6-hexamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, 1-isocyanato-2-isocyanatomethyl cyclopentane, isophorone diisocyanate, 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethylcyclohexane, bis-(4-isocyanatocyclohexyl)-methane, 2,4′-dicyclohexylmethane diisocyanate, 1,3-bis(isocyanatometyl)-cyclohexane, 1,4-bis(isocyanatometyl)-cyclohexane, bis-(4-isocyanato-3-methylcyclohexyl)-methane, α,α,α′,α′-tetramethyl-1,3-xylylen diisocyanate, α,α, α′,α′-tetramethyl-1,4-xylylen diisocyanate, 1-isocyanato-1-methyl-4(3)-isocyanatomethyl cyclohexane, 2,4-hexahydrotoluylene diisocyanate, 2,6-hexahydrotoluylene diisocyanate, 4,4′-methylene dicyclohexyl diisocyanate, hexamethylene diisocyanate, or mixtures thereof, providing a ketone selected from propan-2-one, butan-2-one, 3-methylbutan-2-one, pentan-2-one, pentan-3-one, cyclopentanone, 2-methylpentan-3-one, 3-methylpentan-2-one, 4-methylpentan-2-one, 4-methylpent-3-en-2-one, pentane-2,4-dione, hexan-2-one, 3,5,5-trimethyl-2-cyclohexene-1-one, 5-methylhexan-2-one, 1-cyclohexylpropan-1-one, 1-cyclohexylethanone, cyclohexanone, heptan-2-one, heptan-4-one, 2,6-dimethyl-4-heptanon, octan-3-one, octan-2-one, octan-4-one, or a mixture thereof, and providing at least one organic photochromic molecule comprising a chromophore selected from a diarylethene, a spirooxazine and a naphthopyran, or a combination thereof;
• b. dissolving the at least one organic photochromic molecule comprising a chromophore of step a. in the ketone of step a. therewith providing a solution with a final concentration of the at least one organic photochromic molecule comprising a chromophore in the ketone of between 0.1% and 2.5% based on the weight of the solution;
• c. immersing the aliphatic thermoplastic polyurethane film of step a. with the solution of step b., for a time period of at least 5 seconds;
• and
• d. drying the immersed aliphatic thermoplastic polyurethane film obtained with step c. for a time period of between 1 minute and 16 hours, at a temperature of between 45° C. and 75° C., such that the self-supporting polymer film is obtained.