Preparation of a photochromic ink

Abstract

The present invention relates to a photochromic ink, the process for its preparation which is based on a spiropyran powder obtainable by melting, cooling and crushing, and to a new form of a spiropyran obtainable thereby. Said process to prepare a photochromic ink comprises the steps of a) heating and melting the spiropyran at a temperature below 250° C., b) cooling the melt to obtain a solidified spiropyran, c) crushing the solidified spiropyran to obtain a powder, d) optionally adding the powder to a binder providing the basis for the photochromic ink.

1 . A process to prepare a photochromic ink comprising the steps of
 a) heating and melting a spiropyran at a temperature below 250° 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.   
     
     
         2 . A photochromic ink obtainable according to the process of  claim 1 . 
     
     
         3 . A process according to  claim 1  wherein the binder is water-soluble or water-dispersible acrylic polymer. 
     
     
         4 . A process according to  claim 1  wherein the spiropyran is a compound of the formula I: 
       
         
           
           
               
               
           
         
         wherein 
         R 1  is hydrogen, —C 1 -C 18  alkoxy, —C 1 -C 18  alkylthio, halogen, —C 1 -C 18  alkyl, —NO 2 or a phenyl radical 
         R 2  is hydrogen, —C 1 -C 18  alkoxy or NO 2 ; 
         R 3  is NO 2  or halogen; 
         R 4  is hydrogen, —C 1 -C 18  alkoxy or halogen; 
         R 5  is hydrogen, halogen, —C 1 -C 18  alkoxy, —COOH, —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 —C 1 -C 6  alkyl; 
         R b  is hydrogen or —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 —CH 2 —COO—C 1 -C 18 alkyl or —CH 2 —COOH or —CH 2 —CO—N(R 10 )—R 9 ; or —CH 2 —CO—N(R 10 )-L-N(R 10 )CO—CH 2 —; wherein 
         R 9  is hydrogen, C 1 -C 18 alkyl, phenyl, mesityl, phenyl once or more than once substituted by halogen, —CF 3 , C 1 -C 6 alkyl, —C 1 -C 6  alkoxy, carboxy, —COO—C 1 -C 6 alkyl, —S-phenyl or —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, —CF 3 , C 1 -C 18 alkyl, —C 1 -C 18  alkoxy, carboxy, —CONH 2 , —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, —CF 3 , —C 1 -C 18  alkoxy, carboxy, —CONH 2 , —CON(C 1 -C 18 alkyl) 2 , nitro. 
       
     
     
         5 . A process according to  claim 4 , wherein the spiropyran is a compound of the formula I wherein
 R 1  is hydrogen, —C 1 -C 18  alkoxy, —C 1 -C 18  alkylthio, halogen, —C 1 -C 18  alkyl, or NO 2 ,   R 2  is hydrogen or —C 1 -C 18  alkoxy,   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 —CH 2 —COO—C 1 -C 18 alkyl or —CH 2 —COOH or —CH 2 —CO—N(R 10 )—R 9 ; or —CH 2 —CO—N(R 10 )-L-N(R 10 )CO—CH 2 —; wherein R 9 , R 10  and L are as defined in  claim 4 , and the remaining substituents are as defined in  claim 4 .   
     
     
         6 . A process according to  claim 4 , wherein the spiropyran is a compound of the formula I wherein
 Y is   
       
         
           
           
               
               
           
         
         R 1  is C 1 -C 6 alkoxy, R 2  is hydrogen, 
         R 3  is NO 2 , 
         R 4  is hydrogen, 
         R 5  is hydrogen or C 1 -C 6 alkoxy, 
         R 6  is hydrogen, 
         R 7  is hydrogen, 
         R a  is methyl, 
         R b  is methyl, 
         R 100  is NO 2 , bromine, fluorine or CF 3 , 
         R  200  is hydrogen or fluorine. 
       
     
     
         7 . A process according to  claim 4 , wherein the spiropyran is a compound of the formula 
       
         
           
           
               
               
           
         
       
     
     
         8 . A process according to  claim 4 , wherein the spiropyran is a compound of the formula I wherein
 Y is —CH 2 —COR   R 1  is C 1 -C 6 alkoxy or C 1 -C 6 alkylthio   R is —C 1 -C 6 alkoxy or —NHR 9  wherein R 9  is phenyl, phenyl once or more than once substituted by halogen, —CF 3 , C 1 -C 6 alkyl, —C 1 -C 6  alkoxy, —S-phenyl or —CO-phenyl   R 2  is hydrogen,   R 3  is NO 2      R 4  is hydrogen,   R 5  is hydrogen,   R 6  is hydrogen,   R 7  is hydrogen,   R a  is methyl.   R b  is methyl.   
     
     
         9 . A photochromic spiropyran in the form of a powder which, after dispersion in a printing ink, has at least the double color strength than known forms of the same spiropyran, said powder being obtainable by
 d) carefully heating a photochromic spiropyran until it has melted,   e) cooling the melt to obtain a solidified spiropyran, and   f) crushing the solidified spiropyran to obtain a powder.   
     
     
         10 . A spiropyran according to  claim 9  having the formula I 
       
         
           
           
               
               
           
         
         wherein 
         R 1  is hydrogen, —C 1 -C 18  alkoxy, —C 1 -C 18  alkylthio, halogen, —C 1 -C 18  alkyl, —NO 2  or a phenyl radical 
         R 2  is hydrogen, —C 1 -C 18  alkoxy or NO 2 ; 
         R 3  is NO 2  or halogen; 
         R 4  is hydrogen, —C 1 -C 18  alkoxy or halogen; 
         R 5  is hydrogen, halogen, —C 1 -C 18  alkoxy, —COOH, —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 —C 1 -C 6  alkyl; 
         R b  is hydrogen or —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 —CH 2 —COO—C 1 -C 18 alkyl or —CH 2 —COOH or —CH 2 —CO—N(R 10 )—R 9 ; or —CH 2 —CO—N(R 10 )-L-N(R 10 )CO—CH 2 —; wherein
 R 9  is hydrogen, C 1 -C 18 alkyl, phenyl, mesityl, phenyl once or more than once substituted by halogen, —CF 3 , C 1 -C 6 alkyl, -C 1 -C 6  alkoxy, carboxy, —COO—C 1 -C 6 alkyl, —S-phenyl or —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, —CF 3 , —C 1 -C 18  alkoxy, carboxy, —COO—C 1 -C 18 alkyl, —CONH 2 , —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, —CF 3 , —C 1 -C 18  alkoxy, carboxy, —CONH 2 , —CON(C 1 -C 18 alkyl) 2 , nitro.