Process for the Post-Modification of Homo and Copolymers Prepared by Controlled Free Radical Polymerization Processes

Abstract

The instant invention pertains to the preparation of polymers or copolymers wherein in a first step a controlled free radical polymerization process is carried out and in a second step the resulting polymer is modified by transesterification reactions. The final modified polymer or copolymer is useful as a dispersant for pigments. Further aspects of the invention are the thus prepared polymers or copolymers, a pigment concentrate containing the polymer or copolymer and a coating material containing the pigment concentrate.

1 . A process for the preparation of a modified polymer or copolymer comprising the steps
 a1) polymerizing in a first step one or more ethylenically unsaturated monomers in the presence of at least one nitroxylether having the structural element   
     
       
         
         
             
             
         
       
     
     wherein X represents a group having at least one carbon atom and is such that the free radical X• derived from X is capable of initiating polymerization; or
 a2) polymerizing in a first step one or more ethylenically unsaturated monomers in the presence of at least one stable free nitroxyl radical 
 
     
       
         
         
             
             
         
       
     
     and a free radical initiator; wherein at least one monomer used in the steps a1) or a2) is a C 1 -C 6  alkyl or hydroxy C 1 -C 6  alkyl ester of acrylic or methacrylic acid; and a second step
 b) comprising the modification of the polymer or copolymer prepared under a1) or a2) by a transesterification reaction, an amidation, hydrolysis or anhydride modification or a combination thereof. 
 
   
   
       2 . A process according to  claim 1  wherein the first polymerization step is carried out according to a1). 
   
   
       3 . A process according to  claim 1  wherein the second step b) is a transesterification reaction. 
   
   
       4 . A process according to  claim 1  wherein step a1 or a2 is carried out twice and a block copolymer is obtained wherein in the first or second radical polymerization step the monomer or monomer mixture contains 50 to 100% by weight, based on total monomers, of a C 1 -C 6  alkyl ester of acrylic or methacrylic acid and in the second or first radical polymerization step respectively, the ethylenically unsaturated monomer or monomer mixture contains at least a monomer without primary or secondary ester bond. 
   
   
       5 . A process according to  claim 4  wherein in the first polymerization step the monomer or monomer mixture contains from 50 to 100% by weight based on total monomers of a C 1 -C 6  alkyl ester of acrylic or methacrylic acid and in the second polymerization step the ethylenically unsaturated monomer or monomer mixture comprises 4-vinyl-pyridine or pyridinium-ion, 2-vinyl-pyridine or pyridinium-ion, vinyl-imidazole or imidazolinium-ion, dimethylacrylamide, 3-dimethylaminopropylmethacrylamide, styrene, α-methyl styrene, p-methyl styrene or p-tert-butyl-styrene. 
   
   
       6 . A process according to  claim 1  wherein the polymer or copolymer is a gradient block copolymer. 
   
   
       7 . A process according to  claim 1  wherein the structural element 
     
       
         
         
             
             
         
       
     
     is a structural element of formula (I) 
     
       
         
         
             
             
         
       
       wherein 
       G 1 , G 2 , G 3 , G 4  are independently C 1 -C 6 alkyl or G 1  and G 2  or G 3  and G 4 , or G 1  and G 2  and G 3  and G 4  together form a C 5 -C 12 cycloalkyl group; 
       G 5 , G 6  independently are H, C 1 -C 18 alkyl, phenyl, naphthyl or a group COOC 1 -C 18 alkyl; 
       X is selected from the group consisting of —CH 2 -phenyl, CH 3 CH-phenyl, (CH 3 ) 2 C-phenyl, (C 5 -C 6 cycloalkyl) 2 CCN, (CH 3 ) 2 CCN, 
     
     
       
         
         
             
             
         
       
     
     —CH 2 CH═CH 2 , CH 3 CH—CH═CH 2  (C 1 -C 4 alkyl)CR 20 —C(O)-phenyl, (C 1 -C 4 )alkyl-CR 20 —C(O)—(C 1 -C 4 )alkoxy, (C 1 -C 4 )alkyl-CR 20 —C(O)—(C 1 -C 4 )alkyl, (C 1 -C 4 )alkyl-CR 20 —C(O)—N-di(C 1 -C 4 )alkyl, (C 1 -C 4 )alkyl-CR 20 —C(O)—NH(C 1 -C 4 )alkyl and (C 1 -C 4 )alkyl-CR 20 —C(O)—NH 2 , wherein R 20  is hydrogen or (C 1 -C 4 )alkyl and
 * denotes a valence. 
 
   
   
       8 . A process according to  claim 1  wherein the structural element 
     
       
         
         
             
             
         
       
     
     is a structural element of formula (II) 
     
       
         
         
             
             
         
       
       wherein 
       G 1 , G 2 , G 3 , G 4  are independently C 1 -C 6 alkyl or G 1  and G 2  or G 3  and G 4 , or G 1  and G 2  and G 3  and G 4  together form a C 5 -C 12 cycloalkyl group; 
       G 5 , G 6  independently are H, C 1 -C 18 alkyl, phenyl, naphthyl or a group COOC 1 -C 18 alkyl. 
     
   
   
       9 . A process according to  claim 7  wherein the structural element of formula (I) is a compound of formula (O1) 
     
       
         
         
             
             
         
       
     
   
   
       10 . A process according to  claim 1  wherein the monomer in step a1 or a2 is selected from isoprene, 1,3-butadiene, α-C 5 -C 18 alkene, 4-vinyl-pyridine, 4-vinyl-pyridinium-ion, 2-vinyl-pyridine, 2-vinyl-pyridinium-ion, vinyl-imidazole, vinyl-imidazolinium-ion, dimethylacrylamide, 3-dimethylaminopropylmethacrylamide, styrene, α-methyl styrene, p-methyl styrene, p-tert-butyl-styrene and a compound of formula CH 2 ═C(R a )—(C=Z)-R b , wherein R a  is hydrogen or methyl, R b  is NH 2 , O − (Me + ), unsubstituted C 1 -C 18 alkoxy, C 2 -C 100 alkoxy interrupted by at least one N and/or O atom, or hydroxy-substituted C 1 -C 18 alkoxy, unsubstituted C 1 -C 18 alkylamino, di(C 1 -C 18 alkyl)amino, hydroxy-substituted C 1 -C 18 alkylamino, —O—CH 2 —CH 2 —N(CH 3 ) 2  or —O—CH 2 —CH 2 —N + H(CH 3 ) 2  An − ;
 An −  is a anion of a monovalent organic or inorganic acid;   Me is a monovalent metal atom or the ammonium ion and   Z is oxygen or sulfur.   
   
   
       11 . A process according to  claim 1  wherein step b comprises transesterification with an alcohol which alcohol is an unsubstituted linear or branched C 8 -C 36 alkyl mono alcohol or a mono alcohol derived from ethyleneoxide, propyleneoxide or mixtures thereof with up to 100 C atoms. 
   
   
       12 . A process according to  claim 11  wherein in step b the alcohol is an ethoxylate of formula (A)
   R A —[O—CH 2 —CH 2 —] n —OH  (A)   
     wherein R A  is saturated or unsaturated, linear or branched chain alkyl with 1-22 carbon atoms, or alkylaryl or dialkylaryl with up to 24 carbon atoms and n is 1 to 150. 
   
   
       13 . A process according to  claim 11 , wherein the alcohol is an unsubstituted linear or branched C 8 -C 36 alkyl mono alcohol. 
   
   
       14 . A process according to  claim 1  wherein step b comprises transesterification with an alcohol which alcohol is a polydimethylsilicone oligomer of formula (B) 
     
       
         
         
             
             
         
       
     
     wherein R B  is C 1 -C 18 alkyl, phenyl or C 7 -C 15 aralkyl; n is 1 to 50 and R′ is a linking group with 1 to 20 carbon atoms. 
   
   
       15 . A process according to  claim 1  wherein step b comprises transesterification with an alcohol which alcohol is a partly or fully fluorinated primary alcohol. 
   
   
       16 . A polymer or copolymer obtained by a process according to  claim 1 . 
   
   
       17 . (canceled) 
   
   
       18 . A pigment concentrate comprising
 a) a pigment and   b) a polymer or copolymer prepared according to the process of  claim 1 .   
   
   
       19 . A composition comprising
 a) a thermoplastic, chemically crosslinked or structurally crosslinked polymer and   b) a polymer or copolymer prepared according to the process of  claim 1 .   
   
   
       20 . A composition according to  claim 19  wherein component a) is a film forming binder material. 
   
   
       21 . A composition according to  claim 19 , which contains in addition organic or inorganic pigments or mixtures thereof.