Patent ID: 8287776

Claim:
A process to prepare a photochromic ink comprising the steps of: a) heating and melting a spiropyran at a temperature below 250Â° C., b) cooling the melt to obtain a solidified spiropyran, c) crushing the solidified spiropyran to obtain a powder, and d) adding the powder to a binder providing the basis for the photochromic ink, wherein the spiropyran is a compound of the formula I: wherein R 1 is hydrogen, â€”C 1 -C 18 alkoxy, â€”C 1 -C 18 alkylthio, halogen, â€”C 1 -C 18 alkyl, â€”NO 2 or a phenyl radical, R 2 is hydrogen, â€”C 1 -C 18 alkoxy or NO 2 ; R 3 is NO 2 or halogen; R 4 is hydrogen, â€”C 1 -C 18 alkoxy or halogen; R 5 is hydrogen, halogen, â€”C 1 -C 18 alkoxy, â€”COOH, â€”COOâ€”C 1 -C 18 alkyl, â€”CF 3 or phenyl; R 6 is hydrogen or R 6 and R 7 form together a phenyl ring; R 7 is hydrogen; R a is hydrogen or â€”C 1 -C 6 alkyl; R b is hydrogen or â€”C 1 -C 6 alkyl, or together with R a form a 5-6 membered ring; Y is phenyl or benzyl wherein the phenyl or benzyl group may be substituted by one or more groups selected from NO 2 fluorine, bromine, chlorine, CF 3 or phenyl or Y is â€”CH 2 â€”COOâ€”C 1 -C 18 alkyl or â€”CH 2 â€”COOH or â€”CH 2 â€”COâ€”N(R 10 )â€”R 9 ; or â€”CH 2 â€”COâ€”N(R 10 )-L-N(R 10 ) COâ€”CH 2 â€”; wherein R 9 is hydrogen, C 1 -C 18 alkyl, phenyl, mesityl, phenyl once or more than once substituted by halogen, â€”CF 3 , C 1 -C 6 alkyl, â€”C 1 -C 6 alkoxy, carboxy, â€”COOâ€”C 1 -C 6 alkyl, â€”S-phenyl or â€”CO-phenyl; R 10 is hydrogen, C 1 -C 18 alkyl; L is 1,3 phenylene or 1,4 phenylene wherein the phenylene linker is optionally substituted by once or more than once by halogen, â€”CF 3 , C 1 -C 18 alkyl, â€”C 1 -C 18 alkoxy, carboxy, â€”COOâ€”C 1 -C 18 alkyl, â€”CONH 2 , â€”CON(C 1 -C 18 alkyl) 2 , nitro; or L is naphthalene, biphenylene or phenylene-O-phenylene wherein the naphthalene, biphenylene or phenylene-O-phenylene linker is optionally substituted once or more than once by halogen, â€”CF 3 , C 1 -C 18 alkyl, â€”C 1 -C 18 alkoxy, carboxy, â€”COOâ€”C 1 -C 18 alkyl, â€”CONH 2 , â€”CON(C 1 -C 18 alkyl) 2 , nitro.