Aqueous pigment dispersion and applications thereof

Abstract

Disclosed are an aqueous pigment dispersion containing at least a pigment, water, a high-molecular dispersant, and an alkali. The high-molecular dispersant is a diblock polymer having a formula (1) of A-B or a triblock polymer having a formula (2) of A-B-C. The diblock or triblock polymer is a diblock or triblock polymer obtained by polymerizing addition-polymerizable monomers with a radical generator while using an organic iodide as a polymerization initiating compound and an organic phosphorus compound, organic nitrogen compound or organic oxygen compound as a catalyst. Also disclosed are a production method and use of the aqueous pigment dispersion. With the high-molecular dispersant obtained by a simple living radical polymerization process free of the problems of conventional living radical polymerization and having a precisely-controlled molecular structure, the aqueous pigment dispersion can be obtained with the pigment dispersed in it.

1 . An aqueous pigment dispersion comprising at least a pigment, water, a high-molecular dispersant, and an alkali, wherein:
 the high-molecular dispersant is a diblock polymer having a formula (1) of A-B or a triblock polymer having a formula (2) of A-B-C, and the diblock or triblock polymer is a diblock or triblock polymer obtained by polymerizing addition-polymerizable monomers with a radical generator while using an organic iodide as a polymerization initiating compound and an organic phosphorus compound, organic nitrogen compound or organic oxygen compound as a catalyst; and   in the formulas (1) and (2), A, B and C each represent a polymer block of at least one of the addition-polymerizable monomers, the A and C blocks may be the same or different, the A and C blocks are each a polymer block which is formed from at least one monomer having an acid group and has an acid value of from 40 to 300 mgKOH/g, and the B block is a polymer block of a hydrophobic monomer.   
     
     
         2 . The aqueous pigment dispersion according to  claim 1 , wherein the organic phosphorus compound is an iodine-containing phosphorus halide, phosphite compound or phosphinate compound, the organic nitrogen compound is an imide compound or hydantoin compound, and the organic oxygen compound is a phenolic compound, iodoxyphenyl compound or vitamin. 
     
     
         3 . The aqueous pigment dispersion according to  claim 1 , wherein the diblock or triblock polymer has an overall acid value of from 20 to 250 mgKOH/g, and a content of the A block or a total content of the A and C blocks in the diblock or triblock polymer amounts to at least 20 wt % of the entire diblock or triblock polymer. 
     
     
         4 . The aqueous pigment dispersion according to  claim 1 , wherein the diblock or triblock polymer has a number average molecular weight of from 1,000 to 20,000, and the B block in the diblock or triblock polymer has a total number average molecular weight of not greater than 80% of the overall number average molecular weight of the corresponding block polymer. 
     
     
         5 . The aqueous pigment dispersion according to  claim 1 , wherein the monomer having the acid group is (meth)acrylic acid, and the hydrophobic monomer comprises benzyl(meth)acrylate or cyclohexyl (meth)acrylate. 
     
     
         6 . A process for treating a pigment, comprising mixing at least the pigment, water, an organic solvent, an alkali and a high-molecular dispersant to disperse the pigment in the water to form a liquid mixture, and then adding an acid to the liquid mixture such that the high-molecular dispersant dissolved in the liquid mixture is caused to precipitate to coat the pigment with the high-molecular dispersant wherein:
 the high-molecular dispersant is a diblock polymer having a formula (1) of A-B or a triblock polymer having a formula (2) of A-B-C, and the diblock or triblock polymer is a diblock or triblock polymer obtained by polymerizing addition-polymerizable monomers with a radical generator while using an organic iodide as a polymerization initiating compound and an organic phosphorus compound, organic nitrogen compound or organic oxygen compound as a catalyst; and   in the formulas (1) and (2), A, B and C each represent a polymer block of at least one of the addition-polymerizable monomers, the A and C blocks may be the same or different, the A and C blocks are each a polymer block which is formed from at least one monomer having an acid group and has an acid value of from 40 to 300 mgKOH/g, and the B block is a polymer block of a hydrophobic monomer.   
     
     
         7 . A treated pigment obtained by the process according to  claim 6  and having a pigment content of from 20 to 95 wt %. 
     
     
         8 . A method for producing an aqueous pigment dispersion, which comprises dispersing the treated pigment according to  claim 7  in an alkaline aqueous medium. 
     
     
         9 . A paint, ink, coating formulation, toner or stationery comprising the aqueous pigment dispersion obtained by the method according to  claim 8 . 
     
     
         10 . A process for treating a pigment, comprising kneading at least the pigment and a high-molecular dispersant to form a kneaded mixture, and then adding the kneaded mixture to a poor solvent for the high-molecular dispersant such that the pigment is coated with the high-molecular dispersant, wherein:
 the high-molecular dispersant is a diblock polymer having a formula (1) of A-B or a triblock polymer having a formula (2) of A-B-C, and the diblock or triblock polymer is a diblock or triblock polymer obtained by polymerizing addition-polymerizable monomers with a radical generator while using an organic iodide as a polymerization initiating compound and an organic phosphorus compound, organic nitrogen compound or organic oxygen compound as a catalyst; and   in the formulas (1) and (2), A, B and C each represent a polymer block of at least one of the addition-polymerizable monomers, the A and C blocks may be the same or different, the A and C blocks are each a polymer block which is formed from at least one monomer having an acid group and has an acid value of from 40 to 300 mgKOH/g, and the B block is a polymer block of a hydrophobic monomer.   
     
     
         11 . A treated pigment obtained by the process according to  claim 10  and having a pigment content of from 20 to 95 wt %. 
     
     
         12 . A method for producing an aqueous pigment dispersion, which comprises dispersing the treated pigment according to  claim 11  in an alkaline aqueous medium. 
     
     
         13 . A paint, ink, coating formulation, toner or stationery comprising the aqueous pigment dispersion obtained by the method according to  claim 12 .