TWI596151B - Pigment dispersant and pigment dispersion composition including the same - Google Patents

Description

Pigment dispersant and pigment dispersion composition containing same

The present invention relates to a pigment dispersant and a pigment dispersion composition comprising the same.

In the ink of a printer or the like, there are a dye ink obtained by dissolving a dye as a coloring material in an aqueous medium, and a pigment ink obtained by finely dispersing a pigment as a coloring material in an aqueous medium. Since dye inks have problems of light resistance and water resistance, the use of pigment inks is advantageous for applications requiring light resistance and water resistance.

However, when a pigment is used as a coloring material, if the pigment particles are not dispersed in a fine form and stabilized, the pigment may be poorly dispersed. When used as an ink, the coloring force is lowered and the pores are reduced. The lack of ink characteristics such as clogging and deterioration of storage stability due to viscosity increase results in dispersion stability of the pigment.

In particular, an ink jet printer is a printing method in which an ink droplet is ejected from a fine nozzle to record an image, so that the ink used in the application does not clog the nozzle, thereby achieving high dispersion stability of the pigment. Further, even in the case where the nozzle is clogged due to long-term deactivation, it is required to re-dissolve the causative substance by a simple cleaning operation, thereby immediately recovering.

Therefore, Patent Document 1 proposes a polymer compound dispersing agent obtained by copolymerizing an N-vinylpyrrolidone derivative with an acrylic acid derivative. Further, Patent Document 2 proposes the use of a polymer dispersant comprising a hydrophilic block and a hydrophobic block containing benzyl methacrylate or cyclohexyl methacrylate.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 9-59554

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2012-21120

However, since the dispersing agent disclosed in Patent Document 1 copolymerizes N-vinylpyrrolidone as a hydrophilic monomer with a hydrophilic monomer, solubility in an aqueous medium is high, and dispersibility of the pigment is not full. Further, the dispersant disclosed in Patent Document 2 has a pigment derivative as an essential component, and there is a problem in that the use of the pigment derivative causes a decrease in the properties of the pigment and causes problems such as penetration during printing.

An object of the present invention is to provide a pigment dispersant which can be used as a pigment dispersion composition excellent in dispersion stability, storage stability and resolubility, and a pigment dispersion composition containing the same.

The present invention provides the following pigment dispersant and pigment dispersion composition.

Item 1 A pigment dispersant having an A block comprising a structural unit derived from an N-vinyl indoleamine monomer, and a structural unit derived from an alkyl (meth)acrylate and derived from The B block of the structural unit of the acid group vinyl monomer and the block polymer having an acid value of 20 to 140 mgKOH/g.

Item 2 The pigment dispersant according to Item 1, wherein the A block comprises 80% by mass to 100% by mass of the structural unit derived from the N-vinyl decylamine monomer.

The pigment dispersant according to Item 1 or Item 2, wherein the B block comprises 50% by mass to 90% by mass of the structural unit derived from the alkyl (meth)acrylate.

The pigment dispersing agent according to any one of item 1, wherein the mass ratio of the A block to the B block (the mass of the A block: the mass of the B block) is 10:90 to 70: 30.

The pigment dispersant of any one of items 1 to 4, wherein the block polymer has a molecular weight distribution of less than 2.

The pigment dispersant according to any one of items 1 to 5, which comprises the diblock polymer of the above A block and the above block B.

Item 7 A pigment dispersion composition comprising the pigment dispersant of Item 6, a pigment, and an aqueous solvent.

Item 8. The pigment dispersion composition of Item 7, which is used for ink jetting.

According to the present invention, a pigment dispersion composition excellent in dispersion stability, storage stability, and resolubility can be obtained.

Hereinafter, an example of a preferred embodiment of the present invention will be described. However, the following embodiments are merely illustrative. The present invention is not limited to the following embodiments.

<Pigment Dispersant>

The pigment dispersant of the present invention has an A block comprising a structural unit derived from an N-vinyl indoleamine monomer, and a structural unit derived from an alkyl (meth)acrylate and derived from an acid group. The B block of the structural unit of the vinyl monomer and the block polymer having an acid value of 20 to 140 mgKOH/g. In the present invention, "(meth)acrylic acid" means at least one of acrylic acid and methacrylic acid. For example, "(meth)acrylic acid" means "at least one of acrylic acid and methacrylic acid". Further, in the present invention, the vinyl monomer means a monomer having a radically polymerizable carbon-carbon double bond in the molecule.

Hereinafter, various constituent components and the like of the block copolymer will be described.

(A block)

The A block is a polymer block containing a structural unit derived from an N-vinyl decylamine monomer. The structural unit derived from an N-vinyl decylamine monomer refers to an N-vinyl fluorene. A structural unit formed by radical polymerization of an amine-based monomer, specifically, a structural unit of a N-vinyl decylamine-based monomer capable of undergoing radical polymerization of a carbon-carbon double bond to become a carbon-carbon single bond .

The N-vinylnamidamide-based monomer is not particularly limited as long as it is a vinyl monomer having a lactam ring skeleton. For example, a compound represented by the following formula (1) can be exemplified.

[where n is an integer from 2 to 12]

In the formula (1), n is preferably from 2 to 8, more preferably from 3 to 4. Further, the group represented by -(CH ₂ ) _n - constituting the ring may have a substituent, and examples of the substituent include an alkyl group having 1 to 6 carbon atoms, preferably an alkyl group having 1 to 2 carbon atoms.

Specific examples of the N-vinyl decylamine-based monomer include N-vinyl-2-pyrrolidone, N-vinylcaprolactam, and N-vinyl-4-butylpyrrolidone. , N-vinyl-4-propylpyrrolidone, N-vinyl-4-ethylpyrrolidone, N-vinyl-4-methyl-5-ethylpyrrolidone, N-vinyl- 4-methyl-5-propylpyrrolidone, N-vinyl-5-methyl-5-ethylpyrrolidone, N-vinyl-5-propylpyrrolidone, N-vinyl-5 -butylpyrrolidone, N-vinyl-4-methylcaprolactam, N-vinyl-6-methylcaprolactam, N-vinyl-6-propylcaprolactam, N -vinyl-7-butyl caprolactam or the like. Among these, N-vinyl-2-pyrrolidone and N-vinyl caprolactam are preferred.

One type or two or more types of N-vinyl decylamine monomers can be used.

The A block may be only a structural unit derived from an N-vinyl decylamine monomer, and may also contain other structural units. In the case where other structural units are contained in the A block, the other structural units may be contained in any of a random copolymerization or a block copolymerization.

The A block preferably contains 80% by mass to 100% by mass of the structural unit derived from the N-vinyl decylamine-based monomer, more preferably 90% by mass to 100% by mass, and even more preferably 95% by mass. ~100% by mass.

The A block preferably does not have a structural unit derived from a hydrophobic monomer. Examples of the hydrophobic monomer include aromatic group-containing vinyl monomers such as styrene, α-methylstyrene, benzyl (meth)acrylate, and vinylnaphthalene. When the structural unit derived from the hydrophobic monomer is contained in the A block, the content ratio in the A block is preferably 1% by mass or less.

(B block)

The B block is a polymer block comprising a structural unit derived from an alkyl (meth) acrylate and a structural unit derived from an acid group-containing vinyl monomer. The structural unit derived from an alkyl (meth) acrylate refers to a structural unit formed by radical polymerization of an alkyl (meth) acrylate, and specifically refers to an alkyl (meth) acrylate. A carbon-carbon double bond in which radical polymerization is carried out becomes a structural unit of a carbon-carbon single bond. The structural unit derived from the acid group-containing vinyl monomer refers to a structural unit formed by radical polymerization of an acid group-containing vinyl monomer, and specifically refers to an acid group-containing vinyl monomer. A structural unit in which a carbon-carbon double bond of radical polymerization is changed into a carbon-carbon single bond.

The (meth)acrylic acid alkyl ester is not particularly limited as long as it is a hydrophobic monomer, and examples thereof include a compound represented by the following formula (2).

[Chemical 2]

[wherein R ¹ is a hydrogen atom or a methyl group. R ² is an alkyl group having 1 to 10 carbon atoms]

In the R ² of the formula (2), specific examples of the alkyl group having 1 to 10 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, and the like. a cyclic alkyl group such as a straight or branched alkyl group such as a dibutyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a decyl group or a fluorenyl group; or a cyclohexyl group; R ^{2 is} preferably an alkyl group having 1 to 5 carbon atoms.

Specific examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, and n-butyl (meth)acrylate. Isobutyl (meth)acrylate, second butyl (meth)acrylate, tert-butyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc. . Among these, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, and n-butyl (meth)acrylate are preferable.

The alkyl (meth)acrylate may be used alone or in combination of two or more.

The B block preferably contains 50% by mass to 90% by mass, more preferably 60% by mass to 90% by mass, and more preferably 65% by mass to 90% by mass of the structural unit derived from the alkyl (meth) acrylate. quality%.

The vinyl group containing an acid group is not particularly limited and can be used as long as it is hydrophilic. The acid group may, for example, be a carboxyl group, a sulfonic acid group or a phosphoric acid group, and is preferably a carboxyl group.

As the acid group-containing vinyl monomer, a conventionally known one can be mentioned. As a carboxyl group Specific examples of the vinyl monomer include (meth)acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, vinylbenzoic acid, and (meth)acrylic acid 2- A monomer obtained by reacting a hydroxyalkyl (meth) acrylate such as hydroxyethyl or 4-hydroxybutyl (meth)acrylate with maleic anhydride, succinic anhydride or phthalic anhydride. Examples of the monomer having a sulfonic acid group include styrenesulfonic acid, (meth)acrylamide, dimethyl sulfonate, ethyl sulfonate, and ethyl sulfonate. ) acrylamide, vinyl sulfonic acid, and the like. Examples of the monomer having a phosphoric acid group include methacryloxyethyl phosphate and the like. Among these, (meth)acrylic acid is preferred.

The acid group-containing vinyl monomer may be used alone or in combination of two or more.

The B block preferably contains 10% by mass to 50% by mass of the structural unit derived from the acid group-containing vinyl monomer, more preferably 10% by mass to 40% by mass, and even more preferably 10% by mass to 35% by mass. quality%.

The B block may be only a structural unit derived from an alkyl (meth) acrylate and a structural unit derived from an acid group-containing vinyl monomer, and may also contain other structural units. Each structural unit of the B block may be contained in any form such as random copolymerization or block copolymerization.

(block polymer)

In the block polymer, the mass ratio of the A block to the B block (A block: B block) is preferably from 10:90 to 70:30, more preferably from 30:70 to 50:50.

The acid value of the block polymer is 20 to 140 mgKOH/g. It is preferred that the B block contains a structural unit derived from an acid group-containing vinyl monomer in such a manner that the acid value of the block polymer is in this range. The lower limit of the acid value of the block polymer is preferably 40 mgKOH/g, and the upper limit is preferably 130 mgKOH/g. When the acid value is less than 20 mgKOH/g, the solubility in an aqueous solvent is inferior. When the acid value is more than 140 mgKOH/g, the solubility in an aqueous solvent is too high, and the dispersibility of the pigment is deteriorated.

The lower limit of the weight average molecular weight (Mw) of the block polymer is preferably 6,000, more preferably 10,000. The upper limit of the weight average molecular weight (Mw) of the block polymer is preferably 50000, more preferably 30,000.

The block polymer preferably has a molecular weight distribution (PDI) of less than 2, more preferably less than 1.5, and even more preferably less than 1.3. Further, in the present invention, the molecular weight distribution (PDI) is determined based on (weight average molecular weight (Mw) of the block polymer) / (number average molecular weight (Mn) of the block polymer), and PDI is more When it is small, the molecular weight of the polymer having a narrow molecular weight distribution is uniform, and when the value is 1.0, the width of the molecular weight distribution is the narrowest. Conversely, if the PDI is larger, it contains a smaller molecular weight than the molecular weight of the designed polymer, or a larger molecular weight, resulting in poor dispersibility of the pigment. The reason for this is that the solubility of the molecular weight is too small in an aqueous solvent is too high, and if the molecular weight is too large, the solubility in an aqueous solvent is deteriorated.

In the prior block polymer type dispersant in which a block having a hydrophobic substituent is used as a pigment adsorption group, wettability to a pigment is insufficient due to formation of a micelle having a pigment adsorption group as a core in an aqueous solution. . On the other hand, the block polymer of the present invention is presumed to have a block of an N-vinyl indoleamine group having excellent hydrophilicity as a pigment adsorbing group, and rapidly wets the pigment in an aqueous solution, thereby promoting the pigment. Dispersed.

Further, it is presumed that the dispersion can be stabilized by electrostatic repulsion or steric repulsion by the other block having an acid group. Moreover, excellent resolubility is exhibited by the overall structure having high hydrophilicity. Therefore, in the case of use for ink for inkjet, nozzle clogging can be suppressed. Therefore, the block polymer having an N-vinyl indoleamine group can be suitably used as a dispersing agent for a pigment in an aqueous medium. Further, by using the above block polymer as a pigment dispersant, the dried precipitate formed of the pigment dispersion composition can be easily redissolved.

The method for producing the block polymer is not particularly limited. The block polymer is obtained, for example, by a block polymerization using a living radical polymerization method or the like to sequentially carry out a polymerization reaction of a monomer. The A block can be firstly polymerized by polymerization of the monomer, and the monomer of the B block can be polymerized on the A block. The B block can be first produced to polymerize the monomer of the A block onto the B block. . Further, in the case of producing a block polymer, the A block and the B block may be separately produced by a polymerization reaction of a monomer, and then the A block and the B block may be coupled.

The block polymer is preferably a diblock polymer comprising an A block and a B block, and usually comprises a bond such as an A block-B block or a B block-A block. The living radical polymerization method is a polymerization method which maintains the simplicity and versatility of radical polymerization and can precisely control the molecular structure. In the living radical polymerization method, a method of using a transition metal catalyst (ATRP (Atom Transfer Radical Polymerization)) or a sulfur-based reversible chain is used depending on the method of stabilizing the polymerization growth terminal. Method for transferring a transfer agent (RAFT (Reversible Addition-Fragmentation Chain Transfer Polymerization)), a method using an organic ruthenium compound (TERP (Telluride-Mediated Polymerization)) . Among these methods, a method using an organic ruthenium compound (TERP) is preferred from the viewpoint of the diversity of monomers that can be used and the molecular weight control of the polymer region.

The TERP method is a method of polymerizing a radically polymerizable compound using an organic ruthenium compound as a polymerization initiator, and is, for example, a method described in International Publication No. 2004/14848 and International Publication No. 2004/14962.

Specifically, (a) an organic hydrazine compound represented by the general formula (3), (b) a mixture of an organic hydrazine compound represented by the general formula (3) and an azo polymerization initiator, and (c) a general formula (3) a mixture of the organic hydrazine compound represented by the formula and the organic quinone compound represented by the formula (4), or (d) an organic hydrazine compound represented by the formula (3), an azo polymerization initiator, and a pass. a mixture of organic diterpene compounds represented by formula (4)

Aggregate by any of them.

[Chemical 3]

(wherein R ³ represents an alkyl group having 1 to 8 carbon atoms, an aryl group or an aromatic heterocyclic group; and R ⁴ and R ⁵ represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms; and R ⁶ represents a carbon number of 1 to 8; 8 alkyl, aryl, aromatic heterocyclic, fluorenyl, decyl, oxycarbonyl or cyano)

(R ³ Te) ₂ (4)

(wherein R ³ represents an alkyl group having 1 to 8 carbon atoms, an aryl group or an aromatic heterocyclic group).

Specifically, the organic hydrazine compound represented by the formula (3) can be exemplified by (methylmethylmethyl)benzene, (methylmethylmethyl) naphthalene, and 2-methyl-2-methylindenyl- Ethyl propionate, 2-methyl-2-n-butyl decyl-ethyl propionate, (2-trimethyldecyloxyethyl)-2-methyl-2-methylindolyl-propionic acid Ester, (2-hydroxyethyl)-2-methyl-2-methylindolyl-propionate, (3-trimethyldecylpropargyl)-2-methyl-2-methylindenyl - Propionate, etc.

Specifically, the compound represented by the formula (4) can be exemplified by dimethyl ditelluride, diethyl ditelluride, di-n-propyl ditelluride, diisopropyl ditelluride, and dicyclopropyl group. Di-telluride, di-n-butyl ditelluride, di-tert-butyl ditelluride, di-tert-butyl ditelluride, dicyclobutyl ditelluride, diphenyl ditelluride, bis-(pair Oxyphenyl) ditelluride, bis-(p-aminophenyl) ditelluride, bis-(p-nitrophenyl) ditelluride, bis-(p-cyanophenyl) ditelluride, double- (p-sulfonylphenyl) ditelluride, dinaphthyl ditelluride, dipyridyl ditelluride, and the like.

The azo polymerization initiator is not particularly limited as long as it is a azo polymerization initiator used in usual radical polymerization. For example, 2,2'-azobis(isobutyronitrile) (AIBN), 2,2'-azobis(2-methylbutyronitrile) (AMBN), 2,2'-azobis ( 2,4-Dimethylvaleronitrile) (ADVN), 1,1'-azobis(1-cyclohexanecarbonitrile) (ACHN), 2,2'-azobisisobutyrate Dimethyl methacrylate (MAIB), 4,4'-azobis(4-cyanovaleric acid) (ACVA), 1,1'-azobis(1-ethenyloxy-1-phenylethane ), 2,2'-azobis(2-methylbutylguanamine), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70) , 2,2'-azobis(2-methylamidopropane) dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2, 2'-Azobis[2-methyl-N-(2-hydroxyethyl)propanamide], 2,2'-azobis(2,4,4-trimethylpentane), 2- Cyano-2-propylazomethamine, 2,2'-azobis(N-butyl-2-methylpropionamide), 2,2'-azobis(N-cyclohexyl- 2-methylpropanamide) and the like.

The amount of the compound of the formula (3) to be used may be appropriately adjusted depending on the physical properties of the target polymer. Usually, the compound of the formula (3) is preferably 0.05 to 50 mmol based on 1 mol of the monomer.

In the case where the compound of the formula (3) and the azo polymerization initiator are used in combination, it is usually preferred to set the azo polymerization initiator to 0.01 to 10 mol based on 1 mol of the compound of the formula (3). .

When a compound of the formula (3) and a compound of the formula (4) are used in combination, it is usually preferred to set the compound of the formula (4) to 0.01 to 100 mol based on 1 mol of the compound of the formula (3). .

When a compound of the formula (3), a compound of the formula (4), and an azo polymerization initiator are used in combination, it is usually preferred to be a compound of the formula (3) and a compound of the formula (4). The total amount of the compounds is 1 mol, and the azo polymerization initiator is 0.01 to 100 mol.

The polymerization can be carried out without a solvent, but it can be carried out by using an organic solvent or an aqueous solvent generally used in radical polymerization, and stirring the above mixture. The organic solvent which can be used is, for example, benzene, toluene, N,N-dimethylformamide (DMF), dimethyl hydrazine (DMSO), acetone, 2-butanone (methyl ethyl ketone), two Alkane, hexafluoroisopropanol, chloroform, carbon tetrachloride, tetrahydrofuran (THF), ethyl acetate, trifluoromethylbenzene, and the like. Further, examples of the aqueous solvent include water, methanol, ethanol, isopropanol, n-butanol, ethyl cellosolve, butyl cellosolve, 1-methoxy-2-propanol, and diacetone alcohol.

The reaction temperature and the reaction time may be appropriately adjusted depending on the molecular weight or molecular weight distribution of the obtained polymer, and are usually stirred at 0 to 150 ° C for 1 minute to 100 hours. The TERP process achieves higher yields and precise molecular weight distributions even at lower polymerization temperatures and shorter polymerization times.

After completion of the polymerization reaction, the target polymer can be separated from the obtained reaction mixture by a usual separation and purification method.

<Pigment Dispersion Composition>

The pigment dispersion composition of the present embodiment contains a pigment dispersant containing the above block polymer, a pigment, and an aqueous solvent.

Hereinafter, various constituent components and the like of the pigment dispersion composition will be described.

The pigment dispersant of the present invention is preferably used by neutralizing an acid group. By neutralizing an acid group, it is possible to obtain a pigment dispersion composition in which the dispersion state of the pigment is stable and the long-term storage stability is more excellent. At the time of neutralization, for example, an alkali metal hydroxide such as potassium hydroxide or sodium hydroxide, ammonia, dimethylamine, diethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine or dimethylethanolamine can be used. Such as organic amines and the like. The ratio of the acid group to be neutralized is preferably from 30 to 100%, more preferably from 80 to 100%.

The blending amount of the pigment dispersing agent in the pigment dispersion composition of the present invention is preferably 5 parts by mass to 100 parts by mass, preferably 10 parts by mass to 70 parts by mass, more preferably 10% by mass based on 100 parts by mass of the pigment. ~50 parts by mass. When the amount of the pigment dispersant is too small, the pigment cannot be sufficiently dispersed. If the amount of the pigment dispersant is too large, the pigment dispersant which is not adsorbed to the pigment may be present in the liquid, which is not preferable.

The pigment used in the present invention is not particularly limited, and any of an organic pigment and an inorganic pigment can be used, and examples thereof include various kinds of red pigment, yellow pigment, orange pigment, blue pigment, green pigment, violet pigment, and black pigment. Color pigments. Examples of the organic pigments include azo-based pigments such as monoazo-based, diazo-based, and condensed diazo-based dyes, diketopyrrolopyrrole-based, phthalocyanine-based, isoindolinone-based, and iso-porphyrin-based. , quinacridone, indigo, sulphur blue, quinophthalone, two Polycyclic pigments such as lanthanum, lanthanide, lanthanide, and lanthanide. Examples of the inorganic pigment include carbon black pigments such as furnace black, lamp black, acetylene black, and chimney black.

The pigment contained in the pigment dispersion composition is preferably used in accordance with the purpose, and the type, particle diameter, and type of treatment of the pigment are selected. Further, the pigment contained in the pigment dispersion composition may be one type or plural types.

Specific examples of the pigment include CI Pigment Red 7, CI Pigment Red 9, CI Pigment Red 14, CI Pigment Red 41, CI Pigment Red 48: 1, CI Pigment Red 48: 2, and CI Pigment Red. 48:3, CI Pigment Red 48:4, CI Pigment Red 81:1, CI Pigment Red 81:2, CI Pigment Red 81:3, CI Pigment Red 122, CI Pigment Red 123, CI Pigment Red 146, CI Pigment Red 149, CI Pigment Red 168, CI Pigment Red 177, CI Pigment Red 178, CI Pigment Red 179, CI Pigment Red 187, CI Pigment Red 200, CI Pigment Red 202, CI Pigment Red 208, CI Pigment Red 210, CI Pigment Red 215, CI Pigment Red 224, CI Pigment Red 254, CI Pigment Red 255, CI Pigment Red 264 and other red pigments; CI Pigment Yellow (Pigment Yellow) 1, CI Pigment Yellow 3, CI Pigment Yellow 5, CI Pigment Yellow 6, CI Pigment Yellow 14, CI Pigment Yellow 55, CI Pigment Yellow 60, CI Pigment Yellow 61, CI Pigment Yellow 62, CI Pigment Yellow 63, CI Pigment Yellow 65, CI Pigment Yellow 73, CI Pigment Yellow 74, CI Pigment Yellow 77, CI Pigment Yellow 81, CI Pigment Yellow 93, CI Pigment Yellow 97, CI Pigment Yellow 98, CI Pigment Yellow 104, CI Pigment 108, CI Pigment Yellow 110, CI Pigment Yellow 128, CI Pigment Yellow 138, CI Pigment Yellow 139, CI Pigment Yellow 147, CI Pigment Yellow 150, CI Pigment Yellow 151, CI Pigment Yellow 154, CI Pigment Yellow 155, CI Pigment Yellow 166, CI Pigment Yellow 167, CI Pigment Yellow 168, CI Pigment Yellow 170, CI Pigment Yellow 180, CI Pigment Yellow 188, CI Pigment Yellow 193, CI Pigment Yellow 194, CI Pigment Yellow 213, etc. Yellow Pigment; CI Pigment Orange (Pigment) Orange) 36, CI Pigment Orange 38, CI Pigment Orange 43 and other orange pigments; CI Pigment Blue (Pigment Blue) 15, CI Pigment Blue 15:2, CI Pigment Blue 15:3, CI Pigment Blue 15:4, CI Pigment Blue 15:6, CI Pigment Blue 16. CI pigment blue 22, CI pigment blue 60 and other blue pigments; CI pigment green (Pigment Green) 7, CI pigment green 36, CI pigment green 58 and other green pigments; CI pigment purple (Pigment Violet) 19, CI pigment purple 23, purple pigment such as CI Pigment Violet 32, CI Pigment Violet 50; black pigment such as CI Pigment Black (Pigment Black) 7. Among these, CI Pigment Red 122; CI Pigment Yellow 74, CI Pigment Yellow 128, CI Pigment Yellow 155; CI Pigment Blue 15:3, CI Pigment Blue 15:4, CI Pigment Blue 15:6; CI Green 7, CI Green 36; CI Pigment Violet 19; CI Pigment Black 7 and the like.

The concentration of the pigment in the pigment dispersion composition of the present invention is not particularly limited as long as it imparts a sufficient coloring concentration to the object to be recorded, and is preferably 1% by mass to 30% by mass, more preferably 1% by mass to 20% by mass. % is further preferably from 1% by mass to 10% by mass. If it exceeds 30% by mass, the density of the pigment in the liquid increases, and there is a possibility that agglomeration due to the free movement of the pigment particles is caused.

As the aqueous solvent to be used in the present invention, water or a water-soluble organic solvent may be used, or one or two or more of these may be mixed. As the water, pure water or ion-exchanged water (deionized water) is preferably used. As the water-soluble organic solvent, alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, second butanol, and third butanol; ethylene glycol, propylene glycol, butanediol, and triethylene glycol can be used. Alcohol, 1,2,6-hexanetriol, thiobisethanol, hexanediol, diethylene glycol and other glycols; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol methyl ether, a glycol ether such as diethylene glycol diethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether or triethylene glycol monobutyl ether; a polyhydric alcohol such as glycerin; N-methyl-2-pyrrolidone; A nitrogen-containing compound such as 2-pyrrolidone or 1,3-dimethyl-2-imidazolidinone is preferably 0 to 100 parts by mass based on 100 parts by mass of water.

As a method of dispersing a pigment or the like using the pigment dispersant of the present invention, a conventionally known method can be applied, and it is not particularly limited. For example, it is obtained by mixing a base-neutralized pigment dispersant of the present invention, a pigment, and an aqueous solvent by using a mixing disperser such as a paint shaker, a bead mill, a ball mill, a dissolver, or a kneader.

The pigment dispersion composition of the present invention may also contain other additives as needed. Examples of the other additives include a viscosity modifier, a surface tension adjuster, a penetrating agent, a pigment derivative, an antioxidant, an ultraviolet absorber, a preservative, and an antifungal agent.

The pigment dispersant of the present invention imparts excellent dispersion stability and storage stability to pigments in an aqueous medium, and is excellent in resolubility. Here, the term "resolubility" means the solubility in the solvent in the pigment dispersion composition and the solubility of the dried dried precipitate in the solvent. Therefore, the pigment dispersion composition containing the pigment dispersant of the present invention can be preferably used as an ink for inkjet.

[Examples]

Hereinafter, the present invention will be described in detail based on specific examples. The present invention is not limited to the following examples, and may be appropriately modified without departing from the spirit and scope of the invention. Further, the weight ratio, weight average molecular weight (Mw), molecular weight distribution (PDI), and acid value of the pigment dispersant and the pigment dispersion composition, and the viscosity, storage stability, and resolubility of the pigment dispersion composition are as follows: The method is measured or evaluated.

(polymerization rate)

¹ H-NMR was measured by NMR (Nuclear Magnetic Resonance) (trade name: AVANCE 500, manufactured by Bruker BioSpin Co., Ltd.), and the polymerization ratio was calculated from the area ratio of the vinyl group and the polymer peak of the monomer.

(weight average molecular weight (Mw) and molecular weight distribution (PDI))

GPC (gel permeation chromatography) (trade name: HPLC 11 series, manufactured by Agilent Technologies, Inc.), column (trade name: Shodex GPC LF-804, manufactured by Showa Denko Co., Ltd.), Mobile phase: 10 mM LiBr/N-methylpyrrolidone solution) and calibrated using polystyrene as a standard material (molecular weight 1,090,000, 775,000, 427,000, 190,000, 96,400, 37,900, 10,200, 2,630, 440, 92) The curve was measured for a weight average molecular weight (Mw) and a number average molecular weight (Mn). Calculate the molecular weight distribution based on the measured values (PDI).

(acid value (effective solids composition conversion))

A sample dissolved in tetrahydrofuran (hereinafter referred to as "THF") was titrated with a 0.1 M potassium hydroxide / 2-propanol solution using a potentiometric titration apparatus (trade name: GT-200, manufactured by Mitsubishi Chemical Corporation). The inflection point of the titrated pH curve was taken as the end point of the titration, and the acid value was calculated according to the following formula.

A=56.11×Vs×0.1×f/w

A: Acid value (mgKOH/g)

Vs: the amount of 0.1M potassium hydroxide/2-propanol solution required for titration (mL)

f: the price of 0.1M potassium hydroxide/2-propanol solution

w: measurement sample weight (g) (solid content conversion)

(viscosity)

The E-type viscometer (trade name: TVE-22L, manufactured by Toki Sangyo Co., Ltd.) was used, and a cone rotor of 0.8° × R24 was used, and the measurement was performed at 25 ° C at a rotor rotation number of 60 rpm.

(save stability)

The viscosity before and after storage of the pigment dispersion composition at 70 ° C for one week was measured, and the viscosity change rate calculated by the following formula was evaluated as an index (storability) of storage stability. The closer the viscosity change rate is to 100%, the higher the storage stability is determined.

Viscosity change rate (%) = {(viscosity after storage) / (pre-preservation viscosity)} × 100

(resolubility)

25 μl of the pigment dispersion composition was dropped on a glass petri dish using a micropipette, and dried at a temperature of 60 ° C and a humidity of 40% using a constant temperature and humidity chamber (trade name: Platinous S PR-2SP, manufactured by Tabai Espec Co., Ltd.). hour. After taking out the culture dish, it was cooled to room temperature. 2 ml of deionized water was added to the dried precipitate on the culture dish, and the re-dissolved state of the dried precipitate was visually observed and evaluated based on the following criteria.

○: No residue, and the precipitate was dried and dissolved.

△: Some residue remained, but most of it was redissolved.

×: There are many residues, and almost no redissolution.

<Polymerization initiator>

(Synthesis Example 1): 2-methyl-2-n-butyl decyl-ethyl propionate (hereinafter referred to as "BTEE")

6.38 g (50 mmol) of metal ruthenium (trade name: Tellurium (-40 mesh), manufactured by Aldrich Co., Ltd.) was suspended in 50 ml of THF, and n-butyllithium (manufactured by Aldrich Co., Ltd., 1.6 M) was slowly added dropwise thereto at room temperature. Hexane solution) 34.4 ml (55 mmol) (10 min). The reaction solution was stirred until the metal ruthenium completely disappeared (20 minutes). To the reaction solution, 10.7 g (55 mmol) of ethyl 2-bromoisobutyrate was added at room temperature, and the mixture was stirred for 2 hours. After completion of the reaction, the solvent was concentrated under reduced pressure, and then evaporated under reduced pressure to give y.

<Pigment Dispersant>

(Example 1): Pigment Dispersant A

N-vinylpyrrolidone (manufactured by Nippon Shokubai Co., Ltd., hereinafter referred to as "VP") 3.60 g, deionized water 1.94 g, BTEE 0.360 g, 2, 2 were added to a flask equipped with an argon introduction tube and a stir bar. '-Azobis(4-methoxy-2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd., hereinafter referred to as "V-70"), 0.0259 g, was reacted at 30 ° C for 24 hours. The polymerization rate was 100%, the Mw was 3,450, and the PDI was 1.17.

To the reaction liquid, n-butyl acrylate (manufactured by Nippon Shokubai Co., Ltd., hereinafter referred to as "BA"), 6.86 g, and acrylic acid (manufactured by Sigma-Aldrich Japan Co., Ltd., hereinafter referred to as "AA") 1.54 were added to the reaction liquid. g, 2,2'-azobis(2,4-dimethylvaleronitrile) (manufactured by Otsuka Chemical Co., Ltd., hereinafter referred to as "ADVN"), a mixed solution of 0.0596 g, THF 8.00 g, and methanol 3.59 g, at 45 The reaction was carried out at ° C for 39 hours. The polymerization rate was 98% for both BA and AA.

After the reaction was completed, 48.00 g of THF was added to the reaction solution, and the mixture was poured under stirring. Heptane in 300 ml. The pigment dispersant A is obtained by suction filtration and drying of the precipitated polymer. The Mw was 11,000, the PDI was 1.27, and the acid value was 108 mgKOH/g.

(Example 2): Pigment Dispersant B

To a flask equipped with an argon introduction tube and a stirrer, 6.00 g of VP, 3.23 g of deionized water, 0.360 g of BTEE, and 0.0259 g of V-70 were added, and the mixture was reacted at 30 ° C for 8 hours. The polymerization rate was 98%, the Mw was 6,100, and the PDI was 1.17.

To the reaction mixture, a mixed solution of 4.46 g of BA, AA 1.54 g, ADVN 0.0596 g, THF 7.11 g, and methanol 4.03 g, which had been previously replaced with argon gas, was added, and the mixture was reacted at 45 ° C for 38 hours. The polymerization rates were 97% for BA and 96% for AA.

After completion of the reaction, 48.00 g of THF was added to the reaction solution, and the mixture was poured into 300 ml of heptane under stirring. The pigment dispersant A is obtained by suction filtration and drying of the precipitated polymer. The Mw was 11,300, the PDI was 1.24, and the acid value was 98 mgKOH/g.

(Example 3): Pigment Dispersant C

To a flask equipped with an argon introduction tube and a stirrer, 6.00 g of VP, 3.23 g of deionized water, 0.360 g of BTEE, and 0.0259 g of V-70 were added, and the mixture was reacted at 30 ° C for 8 hours. The polymerization rate was 98%, the Mw was 6,100, and the PDI was 1.17.

A mixed solution of BA 5.34 g, AA 0.660 g, ADVN 0.0596 g, THF 7.10 g, and MeOH 4.94 g which had been previously replaced with argon gas was added to the above reaction solution, and the mixture was reacted at 45 ° C for 38 hours. The polymerization rates were 97% for BA and 96% for AA.

After completion of the reaction, 48.00 g of THF was added to the reaction solution, and the mixture was poured into 300 ml of heptane under stirring. The precipitated polymer was subjected to suction filtration and dried to obtain a pigment dispersant C. The Mw was 10,800, the PDI was 1.23, and the acid value was 42 mgKOH/g.

(Example 4): Pigment Dispersant D

To a flask equipped with an argon introduction tube and a stirrer, 6.00 g of VP, 3.23 g of deionized water, 0.360 g of BTEE, and 0.0259 g of V-70 were added, and the mixture was reacted at 30 ° C for 8 hours. The polymerization rate was 98%, the Mw was 6,100, and the PDI was 1.17.

A mixed solution of 4.90 g of BA, AA 1.10 g, AD96N of 0.0596 g, 7.11 g of THF, and 4.03 g of methanol, which had been previously replaced with argon gas, was added to the above reaction solution, and the mixture was reacted at 45 ° C for 38 hours. The polymerization rates were 97% for BA and 96% for AA.

After completion of the reaction, 48.00 g of THF was added to the reaction solution, and the mixture was poured into 300 ml of heptane under stirring. The precipitated polymer was subjected to suction filtration and dried to obtain a pigment dispersant D. The Mw was 10,600, the PDI was 1.22, and the acid value was 73 mgKOH/g.

(Example 5): Pigment Dispersant E

To a flask equipped with an argon introduction tube and a stirrer, VP 6.00 g, 3.23 g of deionized water, 0.360 g of BTEE, and 0.0259 g of V-70 were added, and the mixture was reacted at 30 ° C for 12 hours. The polymerization rate was 100%, the Mw was 6,100, and the PDI was 1.17.

A mixed solution of BA 4.07 g, AA 1.93 g, ADVN 0.0596 g, THF 7.11 g, and MeOH 4.03 g which had been previously replaced with argon gas was added to the above reaction solution, and the mixture was reacted at 45 ° C for 40 hours. The polymerization rates were 97% for BA and 100% for AA.

After completion of the reaction, 48.00 g of THF was added to the reaction solution, and the mixture was poured into 300 ml of heptane under stirring. The precipitated polymer was subjected to suction filtration and dried to obtain a pigment dispersant E. The Mw was 11,600, the PDI was 1.17, and the acid value was 125 mgKOH/g.

(Example 6): Pigment Dispersant F

To a flask equipped with an argon introduction tube and a stirrer, 3.60 g of VP, 1.94 g of deionized water, 0.360 g of BTEE, and 0.0259 g of V-70 were added, and the mixture was reacted at 30 ° C for 24 hours. The polymerization rate was 100%, the Mw was 3,450, and the PDI was 1.17.

To the reaction solution, 2-ethylhexyl acrylate (manufactured by Nippon Shokubai Co., Ltd., hereinafter referred to as "EHA"), 6.86 g, AA 1.54 g, ADVN 0.0596 g, THF 8.05 g, and methanol 5.33 were added to the reaction liquid. The mixed solution of g was reacted at 45 ° C for 39 hours. The polymerization rates were 97% for EHA and 97% for AA.

After completion of the reaction, 48.00 g of THF was added to the reaction solution, and the mixture was poured into 300 ml of heptane under stirring. The precipitated polymer is subjected to suction filtration and drying to obtain pigment dispersion. Agent F. The Mw was 8,610, the PDI was 1.25, and the acid value was 115 mgKOH/g.

(Example 7): Pigment Dispersant G

To a flask equipped with an argon introduction tube and a stirrer, 3.60 g of VP, 1.94 g of deionized water, 0.360 g of BTEE, and 0.0259 g of V-70 were added, and the mixture was reacted at 30 ° C for 24 hours. The polymerization rate was 100%, the Mw was 3,450, and the PDI was 1.17.

To the reaction liquid, 7.35 g of Cyclohexyl Acrylate (hereinafter referred to as "CHA" manufactured by Osaka Organic Chemical Industry Co., Ltd.), AA 1.14 g, ADVN 0.0596 g, THF 8.05 g, and methanol 2.01 g were added to the reaction solution. The solution was mixed and reacted at 45 ° C for 39 hours. The polymerization rates were 95% for CHA and 99% for AA.

After completion of the reaction, 48.00 g of THF was added to the reaction solution, and the mixture was poured into 300 ml of heptane under stirring. The precipitated polymer was subjected to suction filtration and dried to obtain a pigment dispersant G. The Mw was 9,020, the PDI was 1.25, and the acid value was 77 mgKOH/g.

(Example 8): Pigment Dispersant H

To a flask equipped with an argon introduction tube and a stirrer, VP 6.00 g, 3.23 g of deionized water, 0.180 g of BTEE, and 0.0259 g of V-70 were added, and the mixture was reacted at 30 ° C for 15 hours. The polymerization rate was 100%, the Mw was 11,400, and the PDI was 1.15.

To the reaction mixture, a mixed solution of 4.46 g of BA, AA 1.54 g, ADVN 0.0745 g, THF 7.11 g, and methanol 4.03 g, which had been previously replaced with argon gas, was added, and the mixture was reacted at 45 ° C for 46 hours. The polymerization rates were 99% for BA and 95% for AA.

After completion of the reaction, 48.00 g of THF was added to the reaction solution, and the mixture was poured into 300 ml of heptane under stirring. The precipitated polymer was subjected to suction filtration and dried to obtain a pigment dispersant H. The Mw was 21,000, the PDI was 1.19, and the acid value was 99 mgKOH/g.

(Comparative Example 1): Pigment Dispersant I

To a flask equipped with an argon introduction tube and a stirrer, VP 6.00 g, 3.23 g of deionized water, 0.360 g of BTEE, and 0.0259 g of V-70 were added, and the mixture was reacted at 30 ° C for 12 hours. The polymerization rate was 100%, the Mw was 6,100, and the PDI was 1.17.

A mixed solution of 3.69 g of BA, AA 2.31 g, 0.059 g of ADVN, 7.11 g of THF, and 4.03 g of methanol, which had been previously replaced with argon gas, was added to the above reaction liquid, and the mixture was reacted at 45 ° C for 40 hours. The polymerization rates were 97% for BA and 100% for AA.

After completion of the reaction, 48.00 g of THF was added to the reaction solution, and the mixture was poured into 300 ml of heptane under stirring. The precipitated polymer was subjected to suction filtration and dried to obtain a pigment dispersant I. The Mw was 11,900, the PDI was 1.16, and the acid value was 148 mgKOH/g.

(Comparative Example 2): Pigment Dispersant J

To a flask equipped with an argon introduction tube and a stirrer, VP 6.00 g, 3.23 g of deionized water, 0.360 g of BTEE, and 0.0259 g of V-70 were added, and the mixture was reacted at 30 ° C for 15 hours. The polymerization rate was 100%, the Mw was 5,700, and the PDI was 1.13.

To the reaction mixture, a mixed solution of BA 6.00 g, ADVN 0.0894 g, THF 7.11 g, and methanol 4.03 g, which had been previously replaced with argon gas, was added, and the mixture was reacted at 45 ° C for 40 hours. The polymerization rate was 97%.

After completion of the reaction, 48.00 g of THF was added to the reaction solution, and the mixture was poured into 300 ml of heptane under stirring. The precipitated polymer was subjected to suction filtration and dried to obtain a pigment dispersant J. The Mw is 10,200 and the PDI is 1.17.

(Comparative Example 3): Pigment Dispersant K

To a flask equipped with an argon introduction tube and a stirrer, 11.77 g of VP, 6.34 g of deionized water, 0.405 g of BTEE, and 0.0416 g of V-70 were added, and the mixture was reacted at 30 ° C for 15 hours. The polymerization rate was 98%, the Mw was 10,200, and the PDI was 1.13.

A mixed solution of 1.73 g of AA previously replaced with argon gas, 0.0335 g of ADVN, 6.27 g of THF, and 3.56 g of MeOH was added to the reaction mixture, and the mixture was reacted at 45 ° C for 46 hours. Further, 0.0333 g of AIBN was added and reacted at 60 ° C for 27 hours. The polymerization rate was 86%.

After completion of the reaction, 56.00 g of THF was added to the reaction solution, and the mixture was poured into 350 ml of heptane under stirring. The precipitated polymer is subjected to suction filtration and drying to obtain a pigment component. Powder K. The Mw was 12,400, the PDI was 1.15, and the acid value was 94 mgKOH/g.

(Comparative Example 4): Pigment Dispersant L

Into a flask equipped with an argon gas introduction tube, a stirrer, and a cooling tube, 300 g of methyl ethyl ketone and 20.0 g of 2,2'-azobisisobutyronitrile (hereinafter referred to as "AIBN" manufactured by Otsuka Chemical Co., Ltd.) were added. Replace with argon, heat to 78 ° C (reflux) and stir. VP 50.0 g, BA 34.2 g, and AA 12.8 g were mixed therein, and the argon gas was replaced by dropwise addition over 3 hours. Further, AIBN 2.0 g was added and reacted at 78 ° C for 2 hours. The polymerization rate was 96% for VP, 100% for BA, and 100% for AA.

After completion of the reaction, the reaction solution was poured into a liquid in which 0.7 L of ethyl acetate and 0.7 L of heptane were mixed. The precipitated polymer was subjected to suction filtration and dried to obtain a pigment dispersant L. The Mw was 8,730, the PDI was 1.61, and the acid value was 108 mgKOH/g.

(Comparative Example 5): Pigment Dispersant M

VP 12.00 g, 6.46 g of deionized water, 0.360 g of BTEE, and 0.0370 g of V-70 were placed in a flask equipped with an argon introduction tube and a stirrer, and reacted at 30 ° C for 8 hours. The polymerization rate was 98%.

After completion of the reaction, 48.00 g of THF was added to the reaction solution, and the mixture was poured into 300 ml of heptane under stirring. The precipitated polymer was subjected to suction filtration and dried to obtain a pigment dispersant M. The Mw is 12,400 and the PDI is 1.18.

<Pigment Dispersion Composition>

(Example 9)

Potassium hydroxide in an amount of 95% of the acid group of the neutralizing pigment dispersant was dissolved in water, and then the pigment dispersant A was added to prepare a 15% by mass aqueous solution of the pigment dispersant.

The mass fraction of the aqueous solution of the above-prepared pigment dispersant was adjusted to 53 parts by mass, 20 parts by mass of pigment (CI Pigment Blue 15:3, trade name: CHROMOPHTAL BLUE 4GNP, manufactured by Ciba Specialty Chemicals Co., Ltd.), and 27 parts by mass of deionized water. To mix the composition, add 400 parts by mass of 0.3mm zirconia beads, and use a bead mill (trade name: DISPERMAT CA, manufactured by VMA-GETZMANN GmbH) was mixed for 5 hours to be sufficiently dispersed. After the completion of the dispersion, the beads were subjected to filtration separation to obtain a pigment dispersion (pigment composition).

30 parts by mass of the pigment dispersion obtained, 10 parts by mass of glycerin (manufactured by Kanto Chemical Co., Ltd.), 3 parts by mass of PEG 1540 (manufactured by Kanto Chemical Co., Ltd.), and 10 parts by mass of 2-pyrrolidone (manufactured by Tokyo Chemical Industry Co., Ltd.). 1,2-hexanediol (manufactured by Tokyo Chemical Industry Co., Ltd.), 2 parts by mass, hexanediol (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.35 parts by mass, Olfine E1004 (manufactured by Nissin Chemical Industry Co., Ltd.), 0.35 parts by mass, triethanolamine (Kanto An inkjet ink was prepared by dissolving a composition of 0.7 parts by mass, 0.05 parts by mass of Proxel GxL (S) (manufactured by Arch Chemicals Japan Co., Ltd.), and 44 parts by mass of deionized water.

The viscosity, storage stability, and resolubility of the obtained inkjet ink were evaluated and shown in Table 1.

(Embodiment 10)

The same procedure as in Example 9 was carried out except that the pigment dispersant was changed to the pigment dispersant B.

(Example 11)

The same procedure as in Example 9 was carried out except that the pigment dispersant was changed to the pigment dispersant C.

(Embodiment 12)

The same procedure as in Example 9 was carried out except that the pigment dispersant was changed to the pigment dispersant D.

(Example 13)

The same procedure as in Example 9 was carried out except that the pigment dispersant was changed to the pigment dispersant E.

(Example 14)

The same as Example 9, except that the pigment dispersant was changed to the pigment dispersant F. Shi.

(Example 15)

The same procedure as in Example 9 was carried out except that the pigment dispersant was changed to the pigment dispersant G.

(Embodiment 16)

The same procedure as in Example 9 was carried out except that the pigment dispersant was changed to the pigment dispersant B, and the pigment was changed to C.I. Pigment Yellow 74 (trade name: HANSA Yellow 5GX01, manufactured by Clariant Co., Ltd.).

(Example 17)

The same procedure as in Example 9 was carried out except that the pigment dispersant was changed to the pigment dispersant B, and the pigment was changed to C.I. Pigment Black 7 (trade name: Carbon Black MA-100, manufactured by Mitsubishi Chemical Corporation).

(Embodiment 18)

The pigment dispersant was changed to the pigment dispersant H, and the pigment was changed to CI Pigment Red 122 (trade name: Cinquasia Magenta D4550J, manufactured by BASF Corporation), and the amount of the aqueous solution of the pigment dispersant when the pigment dispersion was adjusted was changed to 27 The mass fraction was changed in the same manner as in Example 9 except that the amount of the deionized water used was changed to 53 parts by mass.

(Comparative Example 6)

The same procedure as in Example 9 was carried out except that the pigment dispersant was changed to the pigment dispersant I.

(Comparative Example 7)

The pigment dispersant J was added to water. However, the pigment dispersant J cannot be dissolved in water.

(Comparative Example 8)

Potassium hydroxide in an amount of 95% of the acid group of the neutralizing pigment dispersant was dissolved in water, and then a pigment dispersant K was added to prepare a 15% by mass aqueous solution of the pigment dispersant.

The mass fraction of the aqueous solution of the above-prepared pigment dispersant was adjusted to 53 parts by mass, 20 parts by mass of pigment (CI Pigment Blue 15:3, trade name: CHROMOPHTAL BLUE 4GNP, manufactured by Ciba Specialty Chemicals Co., Ltd.), and 27 parts by mass of deionized water. The composition was adjusted, and 400 parts by mass of 0.3 mm zirconia beads were added, and they were mixed by a bead mill (trade name: DISPERMAT CA, manufactured by VMA-GETZMANN GmbH) for 5 hours. However, the pigment cannot be dispersed.

(Comparative Example 9)

The same procedure as in Comparative Example 8 was carried out except that the pigment dispersant was changed to the pigment dispersant L. However, the pigment cannot be dispersed.

(Comparative Example 10)

A 15% by mass aqueous solution of a pigment dispersant was prepared by dissolving the pigment dispersant K in water.

The mass fraction of the aqueous solution of the above-prepared pigment dispersant was adjusted to 53 parts by mass, 20 parts by mass of pigment (CI Pigment Blue 15:3, trade name: CHROMOPHTAL BLUE 4GNP, manufactured by Ciba Specialty Chemicals Co., Ltd.), and 27 parts by mass of deionized water. The composition was adjusted, and 400 parts by mass of 0.3 mm zirconia beads were added, and they were mixed by a bead mill (trade name: DISPERMAT CA, manufactured by VMA-GETZMANN GmbH) for 5 hours. However, the pigment cannot be dispersed.

It is disclosed that in any of the examples, an ink having a low viscosity and a high storage stability and a good resolubility is obtained. From the results, it was confirmed that the pigment dispersant of the present invention is useful for general pigments used in inkjet inks.

Claims (8)

A pigment dispersant having an A block comprising a structural unit derived from an N-vinyl indoleamine monomer, and a structural unit derived from an alkyl (meth)acrylate and derived from an acid group The B block of the structural unit of the vinyl monomer and the block polymer having an acid value of 20 to 140 mgKOH/g. The pigment dispersant of claim 1, wherein the A block comprises 80% by mass to 100% by mass of the structural unit derived from the N-vinyl decylamine monomer. The pigment dispersant of claim 1 or 2, wherein the B block comprises 50% by mass to 90% by mass of the structural unit derived from the alkyl (meth)acrylate. The pigment dispersant of claim 1 or 2, wherein the mass ratio of the above A block to the above B block (the mass of the A block: the mass of the B block) is from 10:90 to 70:30. The pigment dispersant of claim 1 or 2, wherein the above block polymer has a molecular weight distribution of less than 2. A pigment dispersant according to claim 1 or 2, which comprises the above-mentioned A block and the above-mentioned block B diblock polymer. A pigment dispersion composition comprising the pigment dispersant of claim 6, a pigment, and an aqueous solvent. The pigment dispersion composition of claim 7, which is used for ink jetting.