WO2015072333A1

WO2015072333A1 - Pigment dispersant and pigment-dispersed composition containing same

Info

Publication number: WO2015072333A1
Application number: PCT/JP2014/078862
Authority: WO
Inventors: 光梅本
Original assignee: 大塚化学株式会社
Priority date: 2013-11-12
Filing date: 2014-10-30
Publication date: 2015-05-21
Also published as: TWI596151B; CN105722922B; JP6189183B2; TW201527397A; JP2015093917A; CN105722922A; KR101917483B1; KR20160083873A

Abstract

Provided are: a pigment dispersant which enables the production of a pigment-dispersed composition having excellent dispersion stability, storage stability and resolubility; and a pigment-dispersed composition containing the pigment dispersant. The pigment dispersant is characterized by being a block polymer, wherein the block polymer comprises a block (A) containing a structural unit derived from an N-vinyllactam-type monomer and a block (B) containing a structural unit derived from a (meth)acrylic acid alkyl ester and a structural unit derived from a vinyl monomer containing an acid group and has an acid value of 20 to 140 mgKOH/g.

Description

Pigment dispersant and pigment dispersion composition containing the same

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

Ink for printers and the like includes a dye ink in which a dye is dissolved in an aqueous medium as a colorant, and a pigment ink in which a pigment is finely dispersed in an aqueous medium as a colorant. Since dye ink has problems of light resistance and water resistance, it is advantageous to use a pigment ink for applications requiring light resistance and water resistance.

However, when pigment is used as a colorant, poor pigment dispersion occurs unless pigment particles are dispersed and stabilized, and when used as an ink, coloring power decreases and pore clogging occurs. In view of the lack of ink characteristics such as deterioration in storage stability due to thickening, pigment dispersion stability is required.

Particularly, since an ink jet printer is a printing method in which ink droplets are ejected from fine nozzles to record an image, the ink used in this application is required to have high pigment dispersion stability in order not to clog the nozzles. Furthermore, even when nozzle clogging occurs during a long period of rest, it is also required that the causative substance be redissolved by a simple cleaning operation and recovered immediately.

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

JP-A-9-59554 JP 2012-21120 A

However, since the dispersant disclosed in Patent Document 1 is obtained by copolymerizing a hydrophilic monomer with the hydrophilic monomer N-vinylpyrrolidone, it has high solubility in an aqueous medium and has sufficient dispersibility of the pigment. is not. In addition, the dispersant disclosed in Patent Document 2 has a pigment derivative as an essential component, and the use of the pigment derivative may cause problems such as poor properties as a pigment and bleeding during printing. is there.

An object of the present invention is to provide a pigment dispersant that can be a pigment dispersion composition excellent in dispersion stability, storage stability, and re-dissolution property, and a pigment dispersion composition containing the same.

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

Item 1: A block containing a structural unit derived from an N-vinyl lactam monomer, and a B block containing a structural unit derived from a (meth) acrylic acid alkyl ester and a structural unit derived from an acid group-containing vinyl monomer A pigment dispersant which is a 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 contains 80% by mass to 100% by mass of a structural unit derived from an N-vinyl lactam monomer.

Item 3. The pigment dispersant according to Item 1 or Item 2, wherein the B block contains 50 mass% to 90 mass% of a structural unit derived from a (meth) acrylic acid alkyl ester.

Item 4 The pigment according to any one of Items 1 to 3, wherein a mass ratio of the A block to the B block (A block mass: B block mass) is 10:90 to 70:30. Dispersant.

Item 5. The pigment dispersant according to any one of Items 1 to 4, wherein the molecular weight distribution of the block polymer is less than 2.

Item 6. The pigment dispersant according to any one of Items 1 to 5, which is a diblock polymer composed of the A block and the block B.

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

Item 8. The pigment dispersion composition according to Item 7, which is for inkjet.

According to the present invention, a pigment dispersion composition having excellent dispersion stability, storage stability, and re-dissolvability can be obtained.

Hereinafter, an example of a preferable embodiment in which the present invention is implemented will be described. However, the following embodiment is merely an example. The present invention is not limited to the following embodiments.

<Pigment dispersant>
The pigment dispersant of the present invention includes an A block containing a structural unit derived from an N-vinyl lactam monomer, a structural unit derived from a (meth) acrylic acid alkyl ester, and a structural unit derived from an acid group-containing vinyl monomer. A block polymer having a B block and an acid value of 20 to 140 mgKOH / g. In the present invention, “(meth) acryl” means “at least one of acryl and methacryl”. For example, “(meth) acrylic acid” means “at least one of acrylic acid and methacrylic acid”. In the present invention, the vinyl monomer means a monomer having a carbon-carbon double bond capable of radical polymerization in the molecule.

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

(Block A)
The A block is a polymer block containing a structural unit derived from an N-vinyl lactam monomer. The structural unit derived from the N-vinyl lactam monomer means a structural unit formed by radical polymerization of the N-vinyl lactam monomer. Specifically, the carbon can be radically polymerized from the N-vinyl lactam monomer. A structural unit in which a carbon double bond is a carbon-carbon single bond.

As the N-vinyl lactam monomer, any vinyl monomer having a lactam ring skeleton can be used without particular limitation, and examples thereof include compounds represented by the following general formula (1).

[Where n is an integer from 2 to 12. ]

In the general formula (1), n is preferably 2 to 8, and more preferably 3 to 4. Further, the group represented by — (CH ₂ ) n— constituting the ring may have a substituent, and the substituent is an alkyl group having 1 to 6 carbon atoms, preferably 1 to 2 carbon atoms. An alkyl group is mentioned.

Specific examples of N-vinyllactam monomers include N-vinyl-2-pyrrolidone, N-vinylcaprolactam, N-vinyl-4-butylpyrrolidone, N-vinyl-4-propylpyrrolidone, N-vinyl-4-ethyl Pyrrolidone, N-vinyl-4-methyl-5-ethylpyrrolidone, N-vinyl-4-methyl-5-propylpyrrolidone, N-vinyl-5-methyl-5-ethylpyrrolidone, N-vinyl-5-propylpyrrolidone, Examples thereof include N-vinyl-5-butylpyrrolidone, N-vinyl-4-methylcaprolactam, N-vinyl-6-methylcaprolactam, N-vinyl-6-propylcaprolactam, N-vinyl-7-butylcaprolactam and the like. Among these, N-vinyl-2-pyrrolidone and N-vinylcaprocaprolactam are preferable.

N-vinyl lactam monomers can be used alone or in combination of two or more.

The A block may be only a structural unit derived from an N-vinyl lactam monomer, or may contain other structural units. When another structural unit is contained in the A block, the other structural unit may be contained in any form such as random copolymerization or block copolymerization.

The A block preferably contains 80% by mass to 100% by mass of structural units derived from N-vinyl lactam monomers, more preferably 90% by mass to 100% by mass, and 95% by mass to 100% by mass. Is more preferable.

It is preferable that the A block 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 A block has a structural unit derived from a hydrophobic monomer, the content in the A block is preferably 1% by mass or less.

(B block)
The B block is a polymer block including 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 (meth) acrylic acid alkyl ester is a structural unit formed by radical polymerization of (meth) acrylic acid alkyl ester. Specifically, radical polymerization of (meth) acrylic acid alkyl ester is possible. A structural unit in which a carbon-carbon double bond becomes a carbon-carbon single bond. The structural unit derived from an acid group-containing vinyl monomer refers to a structural unit formed by radical polymerization of an acid group-containing vinyl monomer. Specifically, a carbon-carbon duplex capable of radical polymerization of an acid group-containing vinyl monomer. A structural unit in which the bond is a carbon-carbon single bond.

The (meth) acrylic acid alkyl ester can be used without particular limitation as long as it is a hydrophobic monomer, and examples thereof include compounds represented by the following general formula (2).

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

Specific examples of the alkyl group having 1 to 10 carbon atoms in R ² of the general formula (2) include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group. A tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group or a linear alkyl group such as a cyclohexyl group, or a cyclic alkyl group such as a cyclohexyl group. R ² is preferably an alkyl group having 1 to 5 carbon atoms.

Specific examples of (meth) acrylic acid alkyl esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, and (meth) acrylic acid. Examples include isobutyl, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, cyclohexyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. Among these, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and n-butyl (meth) acrylate are preferable.

(Meth) acrylic acid alkyl ester can be used alone or in combination of two or more.

The B block preferably contains 50 mass% to 90 mass%, more preferably 60 mass% to 90 mass%, and more preferably 65 mass% to 90 mass% of a structural unit derived from an alkyl (meth) acrylate. It is further preferable to include it.

The acid group-containing vinyl monomer can be used without particular limitation as long as it is hydrophilic. Examples of the acid group include a carboxyl group, a sulfonic acid group, and a phosphoric acid group, and a carboxyl group is preferable.

Examples of the acid group-containing vinyl monomer include conventionally known ones. Specific examples of the carboxyl group-containing vinyl monomer include (meth) acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, vinyl benzoic acid, (meth) acrylic acid 2-hydroxyethyl and (meth) acrylic acid 4- Examples include monomers obtained by reacting hydroxyalkyl (meth) acrylate such as hydroxybutyl with maleic anhydride, succinic anhydride, and phthalic anhydride. Examples of the monomer having a sulfonic acid group include styrene sulfonic acid, dimethylpropyl sulfonic acid (meth) acrylamide, ethyl sulfonate (meth) acrylate, ethyl sulfonate (meth) acrylamide, and vinyl sulfonic acid. Examples of the monomer having a phosphoric acid group include methacryloyloxyethyl phosphate ester. Among these, (meth) acrylic acid is preferable.

One or more acid group-containing vinyl monomers can be used.

The B block preferably contains 10 mass% to 50 mass% of structural units derived from the acid group-containing vinyl monomer, more preferably 10 mass% to 40 mass%, and more preferably 10 mass% to 35 mass%. Further preferred.

The B block may be a structural unit derived from a (meth) acrylic acid alkyl ester and a structural unit derived from an acid group-containing vinyl monomer, or may 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 10:90 to 70:30, and more preferably 30:70 to 50:50.

The acid value of the block polymer is 20 to 140 mgKOH / g. It is preferable that the B block contains a structural unit derived from an acid group-containing vinyl monomer so that the acid value of the block polymer falls within 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 poor, and 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 6000, and more preferably 10,000. The upper limit of the weight average molecular weight (Mw) of the block polymer is preferably 50000, and more preferably 30000.

The molecular weight distribution (PDI) of the block polymer is preferably less than 2, more preferably less than 1.5, and even more preferably less than 1.3. In the present invention, the molecular weight distribution (PDI) is determined by (weight average molecular weight (Mw) of block polymer) / (number average molecular weight (Mn) of block polymer). The smaller the PDI, the molecular weight distribution. The polymer has a narrow molecular weight and a uniform molecular weight. When the value is 1.0, the molecular weight distribution has the narrowest width. On the contrary, the larger the PDI, the smaller the molecular weight and the larger the molecular weight of the designed polymer, and the worse the dispersibility of the pigment. If the molecular weight is too small, the solubility in an aqueous solvent is too high, and if the molecular weight is too large, the solubility in an aqueous solvent becomes poor.

The conventional block polymer type dispersant using a block having a hydrophobic substituent as a pigment adsorbing group has insufficient wettability to the pigment due to the formation of micelles having the pigment adsorbing group as a core in an aqueous solution. On the other hand, in the block polymer of the present invention, the block having an N-vinyl lactam group having excellent hydrophilicity acts as a pigment adsorbing group, and the wetting to the pigment proceeds rapidly in an aqueous solution to promote the dispersion of the pigment. I guess that.

Furthermore, it is presumed that the dispersion can be stabilized by electrostatic repulsion and steric repulsion by the other block having an acid group. Moreover, the excellent resolubility is expressed by the highly hydrophilic whole structure. For this reason, when used for ink jet ink, nozzle clogging can be suppressed. Therefore, the block polymer having an N-vinyl lactam group can be suitably used as a pigment dispersant in an aqueous medium. Furthermore, by using the block polymer as a pigment dispersant, the dried precipitate formed from the pigment dispersion composition can be easily redissolved.

The method for producing the block polymer is not particularly limited. The block polymer can be obtained by, for example, sequentially polymerizing monomers by block polymerization using a living radical polymerization method or the like. According to the polymerization reaction of the monomer, the A block may be produced first, the B block monomer may be polymerized into the A block, or the B block may be produced first, and the A block monomer may be polymerized into the B block. . In the production of the block polymer, the A block and the B block may be separately produced by the polymerization reaction of the monomers, and then the A block and the B block may be coupled.

The block polymer is preferably a diblock polymer composed of 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 that enables precise control of the molecular structure while maintaining the simplicity and versatility of radical polymerization. The living radical polymerization method includes a method using a transition metal catalyst (ATRP), a method using a sulfur-based reversible chain transfer agent (RAFT), and a method using an organic tellurium compound depending on the method for stabilizing the polymerization growth terminal. There are methods such as (TERP). Among these methods, it is preferable to use a method (TERP) using an organic tellurium compound from the viewpoint of diversity of usable monomers and molecular weight control in the polymer region.

The TERP method is a method of polymerizing a radical polymerizable compound using an organic tellurium compound as a polymerization initiator, and is, for example, a method described in International Publication Nos. 2004/14848 and 2004/14962.

In particular,
(A) an organic tellurium compound represented by the general formula (3),
(B) a mixture of an organic tellurium compound represented by the general formula (3) and an azo polymerization initiator,
(C) a mixture of an organic tellurium compound represented by the general formula (3) and an organic ditellurium compound represented by the general formula (4), or (d) an organic tellurium compound represented by the general formula (3), an azo type A mixture of a polymerization initiator and an organic ditellurium compound represented by the general formula (4);
Polymerization is carried out using any of the above.

(In the formula, R ³ represents an alkyl group having 1 to 8 carbon atoms, an aryl group, or an aromatic heterocyclic group. R ⁴ and R ⁵ represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. R ⁶ represents an alkyl group having 1 to 8 carbon atoms, an aryl group, an aromatic heterocyclic group, an acyl group, an amide group, an oxycarbonyl group or a cyano group.

(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.)

Specific examples of the organic tellurium compound represented by the general formula (3) include (methylterranylmethyl) benzene, (methylterranylmethyl) naphthalene, ethyl-2-methyl-2-methylterranyl-propionate, and ethyl-2-methyl. -2-n-butylterranyl-propionate, (2-trimethylsiloxyethyl) -2-methyl-2-methylterranyl-propionate, (2-hydroxyethyl) -2-methyl-2-methylterranyl-propionate, (3-trimethylsilylpropargyl) Examples include -2-methyl-2-methylterranyl-propinate.

Specific examples of the compound represented by the general formula (4) include dimethyl ditelluride, diethyl ditelluride, di-n-propyl ditelluride, diisopropyl ditelluride, dicyclopropyl ditelluride, di-n. -Butylditelluride, di-s-butylditelluride, di-t-butylditelluride, dicyclobutylditelluride, diphenylditelluride, bis- (p-methoxyphenyl) ditelluride, bis- (p-aminophenyl) ditelluride, bis- ( Examples thereof include p-nitrophenyl) ditelluride, bis- (p-cyanophenyl) ditelluride, bis- (p-sulfonylphenyl) ditelluride, dinaphthylditelluride, and dipyridylditelluride.

The azo polymerization initiator can be used without particular limitation as long as it is an azo polymerization initiator used in normal 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), dimethyl-2,2′-azobisisobutyrate (MAIB), 4,4′-azobis (4-cyanovaleric acid) (ACVA), 1,1′-azobis (1-acetoxy-1-phenylethane), 2,2′-azobis (2-methylbutyramide), 2,2′-azobis (4-methoxy-2,4- Dimethylvaleronitrile) (V-70), 2,2′-azobis (2-methylamidinopropane) dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propyl Pan], 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], 2,2′-azobis (2,4,4-trimethylpentane), 2-cyano-2-propyl Examples thereof include azoformamide, 2,2′-azobis (N-butyl-2-methylpropionamide), 2,2′-azobis (N-cyclohexyl-2-methylpropionamide) and the like.

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

When the compound of the general formula (3) and the azo polymerization initiator are used in combination, it is usually preferable to use 0.01 to 10 mol of the azo polymerization initiator with respect to 1 mol of the compound of the general formula (3).

When the compound of the general formula (3) and the compound of the general formula (4) are used in combination, the amount of the compound of the general formula (4) is usually 0.01 to 100 mol with respect to 1 mol of the compound of the general formula (3). Good.

When the compound of the general formula (3), the compound of the general formula (4) and the azo polymerization initiator are used in combination, the total amount of the compound of the general formula (3) and the compound of the general formula (4) is usually 1 mol. The azo polymerization initiator is preferably 0.01 to 100 mol.

The polymerization reaction can be performed without a solvent, but is performed by stirring the above mixture using an organic solvent or an aqueous solvent generally used in radical polymerization. Examples of organic solvents that can be used include benzene, toluene, N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetone, 2-butanone (methyl ethyl ketone), dioxane, hexafluoroisopropaol, chloroform, carbon tetrachloride. , Tetrahydrofuran (THF), ethyl acetate, trifluoromethylbenzene, and the like. Examples of the aqueous solvent include water, methanol, ethanol, isopropanol, n-butanol, ethyl cellosolve, butyl cellosolve, 1-methoxy-2-propanol, diacetone alcohol and the like.

The reaction temperature and reaction time may be appropriately adjusted depending on the molecular weight or molecular weight distribution of the polymer to be obtained, but are usually stirred at 0 to 150 ° C. for 1 minute to 100 hours. The TERP method can obtain a high yield and a precise molecular weight distribution even at a low polymerization temperature and a short polymerization time.

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

<Pigment dispersion composition>
The pigment dispersion composition according to this embodiment includes a pigment dispersant composed of the block polymer, a pigment, and an aqueous solvent.

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

The pigment dispersant of the present invention is preferably used after neutralizing acid groups. By neutralizing and using the acid group, the dispersion state of the pigment becomes stable, and a pigment dispersion composition having excellent long-term storage stability can be obtained. Neutralization includes, for example, alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, organic amines such as ammonia, dimethylamine, diethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, and dimethylethanolamine. Etc. can be used. The ratio of acid groups to be neutralized is preferably 30 to 100%, more preferably 80 to 100%.

The blending amount of the pigment dispersant in the pigment dispersion composition of the present invention is preferably 5 parts by mass to 100 parts by mass with respect to 100 parts by mass of the pigment, and preferably 10 parts by mass to 70 parts by mass. More preferably, it is 50 parts by mass. If the blending amount of the pigment dispersant is too small, the pigment cannot be sufficiently dispersed, and if the blending amount of the pigment dispersant is too large, a pigment dispersant not adsorbed on the pigment is present in the liquid. Absent.

As the pigment used in the present invention, any of organic pigments and inorganic pigments can be used without particular limitation, and examples thereof include red, yellow, orange, blue, green, purple, and black pigments. It is done. Organic pigments include monoazo, diazo, and condensed diazo pigments, diketopyrrolopyrrole, phthalocyanine, isoindolinone, isoindoline, quinacridone, indigo, thioindigo, and quinophthalone. And dioxazine-based, anthraquinone-based, perylene-based and perinone-based polycyclic pigments. Examples of inorganic pigments include carbon black pigments such as furnace black, lamp black, acetylene black, and channel black.

It is desirable to use the pigment contained in the pigment dispersion composition by selecting the pigment type, particle size, and treatment type according to the purpose. Moreover, only one type of pigment may be contained in the pigment dispersion composition, or a plurality of types may be used.

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

The pigment concentration in the pigment dispersion composition of the present invention is not particularly limited as long as it provides a sufficient coloring concentration to the recording material, but is preferably 1% by mass to 30% by mass, and preferably 1% by mass to 20%. More preferably, it is more preferably 1% by mass to 10% by mass. If it exceeds 30% by mass, the density of the pigment in the liquid becomes high, which may cause a problem of aggregation due to hindering free movement of the pigment particles.

As the aqueous solvent used in the present invention, water or a water-soluble organic solvent can be used, and these may be used alone or in combination. As water, it is preferable to use pure water or ion exchange water (deionized water). Water-soluble organic solvents include alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol; ethylene glycol, propylene glycol, butylene glycol, tri Glycols such as ethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, triethylene glycol monomethyl ether , Triethylene glycol monoethyl ether, triethylene glycol monobutyl ether Glycol ethers such as glycerin, polyhydric alcohols such as glycerin, nitrogen-containing compounds such as N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, etc. The amount is preferably 0 to 100 parts by mass with respect to 100 parts by mass of water.

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

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

The pigment dispersant of the present invention can give excellent dispersion stability and storage stability to a pigment in an aqueous medium, and is excellent in re-solubility. Here, the re-solubility means the ease of dissolution when the solvent in the pigment dispersion composition is volatilized and the dried dried precipitate is dissolved again in the solvent. Therefore, the pigment dispersion composition containing the pigment dispersant of the present invention can be suitably used as an inkjet ink.

Hereinafter, the present invention will be described in further detail based on specific examples. The present invention is not limited to the following examples, and can be implemented with appropriate modifications without departing from the scope of the invention. The weight ratio, weight average molecular weight (Mw), molecular weight distribution (PDI) and acid value of the pigment dispersant and pigment dispersion composition, and the viscosity, storage stability and resolubility of the pigment dispersion composition are as follows. Measured or evaluated according to

(Polymerization rate)
¹ H-NMR was measured using NMR (trade name: AVANCE500, manufactured by Bruker BioSpin Corporation), and the polymerization rate was calculated from the area ratio between the vinyl group of the monomer and the polymer peak.

(Weight average molecular weight (Mw) and molecular weight distribution (PDI))
Standard using GPC (trade name: HPLC 11Series, manufactured by Agilent Technologies), column (trade name: Shodex GPC LF-804, manufactured by Showa Denko KK), mobile phase: 10 mM LiBr / N-methylpyrrolidone solution) A calibration curve was prepared using polystyrene (molecular weight 1,090,000, 775,000, 427,000, 190,000, 96,400, 37,900, 10,200, 2,630, 440, 92) as a substance. The weight average molecular weight (Mw) and the number average molecular weight (Mn) were measured. Molecular weight distribution (PDI) was calculated from these measured values.

(Acid value (effective solid content 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 titrator (trade name: GT-200, manufactured by Mitsubishi Chemical Corporation). The acid value was calculated by the following formula using the inflection point of the titration pH curve as the titration end point.

A = 56.11 × Vs × 0.1 × f / w
A: Acid value (mgKOH / g)
Vs: Amount of 0.1 M potassium hydroxide / 2-propanol solution used for titration (mL)
f: Potency of 0.1M potassium hydroxide / 2-propanol solution w: Weight of sample to be measured (g) (solid content conversion)

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

(Storage stability)
The viscosity before and after storage when the pigment dispersion composition was stored at 70 ° C. for 1 week was measured, and the rate of change in viscosity calculated by the following formula was evaluated as an index of storage stability (storability). The closer the viscosity change rate is to 100%, the higher the storage stability.

Viscosity change rate (%) = {(viscosity after storage) / (viscosity before storage)} × 100

(Re-solubility)
25 μl of the pigment dispersion composition is dropped on a glass petri dish with a micropipette and dried for 4 hours at a temperature of 60 ° C. and a humidity of 40% in a constant temperature and humidity chamber (trade name: Platinum SPR-2SP, manufactured by Tabai Espec). After removing the petri dish, cool to room temperature. 2 ml of deionized water was added dropwise to the dried precipitate on the petri dish, and the redissolved state of the dried precipitate was visually observed and evaluated according to the following criteria.

○: The dry precipitate is re-dissolved without any residue.
Δ: A little residue remains but almost dissolves.
X: The residue is large and hardly re-dissolves.

<Polymerization initiator>
(Synthesis Example 1): Ethyl-2-methyl-2-n-butylterranyl-propionate (hereinafter referred to as “BTEE”)
6.38 g (50 mmol) of metal tellurium (trade name: Tellurium (-40 mesh), manufactured by Aldrich) was suspended in 50 ml of THF, and 34.4 ml of n-butyllithium (manufactured by Aldrich, 1.6 M hexane solution) was added thereto. 55 mmol) was slowly added dropwise at room temperature (10 minutes). The reaction solution was stirred until the metal tellurium disappeared completely (20 minutes). To this reaction solution, 10.7 g (55 mmol) of ethyl-2-bromo-isobutyrate was added at room temperature and stirred for 2 hours. After completion of the reaction, the solvent was concentrated under reduced pressure, followed by distillation under reduced pressure to obtain 8.98 g (yield 59.5%) of BTEE as a yellow oil.

<Pigment dispersant>
(Example 1): Pigment dispersant A
In a flask equipped with an argon gas introduction tube and a stirrer, 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′-azobis 0.0259 g of (4-methoxy-2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd., hereinafter referred to as “V-70”) was charged and reacted at 30 ° C. for 24 hours. The polymerization rate was 100%, Mw was 3,450, and PDI was 1.17.

N-butyl acrylate (Nihon Shokubai Co., Ltd., hereinafter referred to as “BA”) 6.86 g, acrylic acid (Sigma Aldrich Japan Co., Ltd., hereinafter referred to as “AA”) 1.54 g, 2. 2'-azobis (2,4-dimethylvaleronitrile) (manufactured by Otsuka Chemical Co., Ltd., hereinafter referred to as “ADVN”) 0.0596 g, THF 8.00 g, methanol 3.59 g mixed solution was added and reacted at 45 ° C. for 39 hours. I let you. The polymerization rate was 98% for both BA and AA.

After completion of the reaction, 48.00 g of THF was added to the reaction solution and poured into 300 ml of heptane with stirring. The pigment dispersant A was obtained by suction-filtering the polymer which precipitated and drying. Mw was 11,000, PDI was 1.27, and the acid value was 108 mgKOH / g.

(Example 2): Pigment dispersant B
A flask equipped with an argon gas introduction tube and a stirring bar was charged with 6.00 g of VP, 3.23 g of deionized water, 0.360 g of BTEE, and 0.0259 g of V-70, and reacted at 30 ° C. for 8 hours. The polymerization rate was 98%, Mw was 6,100, and PDI was 1.17.

A mixed solution of 4.46 g of BA, 1.54 g of AA, 0.0596 g of ADVN, 7.11 g of THF and 4.03 g of methanol was added to the reaction solution in advance, and the mixture was reacted at 45 ° C. for 38 hours. The polymerization rates were BA 97% and AA 96%, respectively.

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

(Example 3): Pigment dispersant C
A flask equipped with an argon gas introduction tube and a stirring bar was charged with 6.00 g of VP, 3.23 g of deionized water, 0.360 g of BTEE, and 0.0259 g of V-70, and reacted at 30 ° C. for 8 hours. The polymerization rate was 98%, Mw was 6,100, and 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 previously substituted with argon was added to the above reaction solution, and reacted at 45 ° C. for 38 hours. The polymerization rates were BA 97% and AA 96%, respectively.

After completion of the reaction, 48.00 g of THF was added to the reaction solution and poured into 300 ml of heptane with stirring. The pigment dispersant C was obtained by suction-filtering the polymer which precipitated and drying. Mw was 10,800, PDI was 1.23, and the acid value was 42 mgKOH / g.

(Example 4): Pigment dispersant D
A flask equipped with an argon gas introduction tube and a stirring bar was charged with 6.00 g of VP, 3.23 g of deionized water, 0.360 g of BTEE, and 0.0259 g of V-70, and reacted at 30 ° C. for 8 hours. The polymerization rate was 98%, Mw was 6,100, and PDI was 1.17.

A mixed solution of 4.90 g of BA, 1.90 g of AA, 0.0596 g of ADVN, 7.11 g of THF, and 4.03 g of methanol was added to the reaction solution in advance and reacted at 45 ° C. for 38 hours. The polymerization rates were BA 97% and AA 96%, respectively.

After completion of the reaction, 48.00 g of THF was added to the reaction solution and poured into 300 ml of heptane with stirring. The pigment dispersant D was obtained by suction-filtering the polymer which precipitated and drying. Mw was 10,600, PDI was 1.22, and the acid value was 73 mgKOH / g.

Example 5: Pigment dispersant E
A flask equipped with an argon gas introduction tube and a stirring bar was charged with 6.00 g of VP, 3.23 g of deionized water, 0.360 g of BTEE, and 0.0259 g of V-70, and reacted at 30 ° C. for 12 hours. The polymerization rate was 100%, Mw was 6,100, and PDI was 1.17.

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

After completion of the reaction, 48.00 g of THF was added to the reaction solution and poured into 300 ml of heptane with stirring. The pigment dispersant E was obtained by suction-filtering the polymer which precipitated and drying. Mw was 11,600, PDI was 1.17, and the acid value was 125 mgKOH / g.

Example 6: Pigment dispersant F
A flask equipped with an argon gas inlet tube and a stir bar was charged with 3.60 g of VP, 1.94 g of deionized water, 0.360 g of BTEE, and 0.0259 g of V-70, and reacted at 30 ° C. for 24 hours. The polymerization rate was 100%, Mw was 3,450, and PDI was 1.17.

A mixture of 2-ethylhexyl acrylate (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 g previously substituted with argon in the above reaction solution. The solution was added and reacted at 45 ° C. for 39 hours. The polymerization rates were EHA 97% and AA 97%, respectively.

After completion of the reaction, 48.00 g of THF was added to the reaction solution and poured into 300 ml of heptane with stirring. Pigment dispersant F was obtained by filtering the deposited polymer with suction and drying. Mw was 8,610, PDI was 1.25, and the acid value was 115 mgKOH / g.

Example 7: Pigment dispersant G
A flask equipped with an argon gas inlet tube and a stir bar was charged with 3.60 g of VP, 1.94 g of deionized water, 0.360 g of BTEE, and 0.0259 g of V-70, and reacted at 30 ° C. for 24 hours. The polymerization rate was 100%, Mw was 3,450, and PDI was 1.17.

Mixture of cyclohexyl acrylate (Osaka Organic Chemical Co., Ltd., hereinafter referred to as “CHA”) 7.35 g, AA 1.14 g, ADVN 0.0596 g, THF 8.05 g, and methanol 2.01 g previously substituted with argon in the above reaction solution. The solution was added and reacted at 45 ° C. for 39 hours. The polymerization rates were CHA 95% and AA 99%, respectively.

After completion of the reaction, 48.00 g of THF was added to the reaction solution and poured into 300 ml of heptane with stirring. The pigment dispersant G was obtained by suction-filtering the polymer which precipitated and drying. Mw was 9,020, PDI was 1.25, and the acid value was 77 mgKOH / g.

(Example 8): Pigment dispersant H
A flask equipped with an argon gas introduction tube and a stirring bar was charged with 6.00 g of VP, 3.23 g of deionized water, 0.180 g of BTEE, and 0.0259 g of V-70, and reacted at 30 ° C. for 15 hours. The polymerization rate was 100%, Mw was 11,400, and PDI was 1.15.

A mixed solution of 4.46 g of BA, 1.54 g of AA, 0.0745 g of ADVN, 7.11 g of THF, and 4.03 g of methanol was added to the reaction solution in advance and reacted at 45 ° C. for 46 hours. The polymerization rates were BA 99% and AA 95%, respectively.

After completion of the reaction, 48.00 g of THF was added to the reaction solution and poured into 300 ml of heptane with stirring. The pigment dispersant H was obtained by suction-filtering the polymer which precipitated and drying. Mw was 21,000, PDI was 1.19, and the acid value was 99 mgKOH / g.

(Comparative Example 1): Pigment dispersant I
A flask equipped with an argon gas introduction tube and a stirring bar was charged with 6.00 g of VP, 3.23 g of deionized water, 0.360 g of BTEE, and 0.0259 g of V-70, and reacted at 30 ° C. for 12 hours. The polymerization rate was 100%, Mw was 6,100, and PDI was 1.17.

A mixed solution of 3.69 g of BA, 2.31 g of AA, 0.0596 g of ADVN, 7.11 g of THF, and 4.03 g of methanol was added to the reaction solution in advance and reacted at 45 ° C. for 40 hours. The polymerization rates were BA 97% and AA 100%, respectively.

After completion of the reaction, 48.00 g of THF was added to the reaction solution and poured into 300 ml of heptane with stirring. The pigment dispersant I was obtained by suction filtration and drying the precipitated polymer. Mw was 11,900, PDI was 1.16, and the acid value was 148 mgKOH / g.

(Comparative Example 2): Pigment dispersant J
A flask equipped with an argon gas introduction tube and a stirring bar was charged with 6.00 g of VP, 3.23 g of deionized water, 0.360 g of BTEE, and 0.0259 g of V-70, and reacted at 30 ° C. for 15 hours. The polymerization rate was 100%, Mw was 5,700, and PDI was 1.13.

A mixed solution of BA 6.00 g, ADVN 0.0894 g, THF 7.11 g, and methanol 4.03 g previously substituted with argon was added to the above reaction solution, and 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 poured into 300 ml of heptane with stirring. The pigment dispersant J was obtained by suction-filtering the polymer which precipitated and drying. Mw was 10,200 and PDI was 1.17.

(Comparative Example 3): Pigment dispersant K
A flask equipped with an argon gas introduction tube and a stirring bar was charged with 11.77 g of VP, 6.34 g of deionized water, 0.405 g of BTEE, and 0.0416 g of V-70, and reacted at 30 ° C. for 15 hours. The polymerization rate was 98%, Mw was 10,200, and PDI was 1.13.

A mixed solution of AA 1.73 g, ADVN 0.0335 g, THF 6.27 g, and MeOH 3.56 g previously substituted with argon was added to the above reaction solution, and reacted at 45 ° C. for 46 hours. Furthermore, 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 poured into 350 ml of heptane with stirring. The pigment dispersant K was obtained by suction-filtering the polymer which precipitated and drying. Mw was 12,400, PDI was 1.15, and the acid value was 94 mgKOH / g.

(Comparative Example 4): Pigment dispersant L
A flask equipped with an argon gas introduction tube, a stirrer, and a cooling tube was charged with 300 g of methyl ethyl ketone and 10.0 g of 2,2′-azobisisobutyronitrile (Otsuka Chemical Co., Ltd., hereinafter referred to as “AIBN”) and purged with argon. , Heated to 78 ° C. (reflux) and stirred. A mixture of VP 50.0 g, BA 34.2 g, and AA 12.8 g and substituted with argon was added dropwise over 3 hours. Further, 2.0 g of AIBN was charged and reacted at 78 ° C. for 2 hours. The polymerization rates were VP 96%, BA 100%, AA 100%.

After completion of the reaction, the reaction solution was poured into a mixture of 0.7 L of ethyl acetate and 0.7 L of heptane. The pigment dispersant L was obtained by suction-filtering the polymer which precipitated and drying. Mw was 8,730, PDI was 1.61, and the acid value was 108 mgKOH / g.

(Comparative Example 5): Pigment dispersant M
A flask equipped with an argon gas inlet tube and a stirring bar was charged with 12.00 g of VP, 6.46 g of deionized water, 0.360 g of BTEE, and 0.0370 g of V-70, 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 poured into 300 ml of heptane with stirring. The pigment dispersant M was obtained by suction-filtering the polymer which precipitated and drying. Mw was 12,400 and PDI was 1.18.

<Pigment dispersion composition>
Example 9
An amount of potassium hydroxide that neutralizes 95% of the acid groups of the pigment dispersant was dissolved in water, and then pigment dispersant A was added to prepare a 15% by mass aqueous solution of the pigment dispersant.

53 parts by mass of the aqueous pigment dispersant prepared above, 20 parts by mass of pigment (CI Pigment Blue 15: 3, trade name: CHROMOPHTAL BLUE 4GNP, manufactured by Ciba Specialty Chemicals), 27 parts by mass of deionized water The blending composition was adjusted so that 400 parts by weight of 0.3 mm zirconia beads was added, and mixed for 5 hours with a bead mill (trade name: DISPERMAT CA, VMA-GETZMANN GmbH) and sufficiently dispersed. After the dispersion was completed, the beads were filtered to obtain a pigment dispersion (pigment composition).

30 parts by mass of the obtained pigment dispersion, 10 parts by mass of glycerin (manufactured by Kanto Chemical Co., Inc.), 3 parts by mass of PEG 1540 (manufactured by Kanto Chemical Co., Ltd.), 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, hexyl glycol (manufactured by Tokyo Chemical Industry Co., Ltd.) 0.35 parts by mass, Olphine E1004 (manufactured by Nissin Chemical Industry Co., Ltd.) 0.35 parts by mass, triethanolamine (Kanto Chemical) Inkjet ink was prepared by blending 0.7 parts by mass of Proxel GxL (S) (manufactured by Arch Chemicals Japan) and 44 parts by mass of deionized water.

The viscosity, storage stability, and re-solubility of the obtained ink-jet ink were evaluated and are shown in Table 1.

(Example 10)
The same operation as in Example 9 was performed except that the pigment dispersant was changed to the pigment dispersant B.

(Example 11)
The same operation as in Example 9 was performed except that the pigment dispersant was changed to the pigment dispersant C.

Example 12
The same operation as in Example 9 was performed except that the pigment dispersant was changed to the pigment dispersant D.

(Example 13)
The same operation as in Example 9 was performed except that the pigment dispersant was changed to the pigment dispersant E.

(Example 14)
The same operation as in Example 9 was performed except that the pigment dispersant was changed to the pigment dispersant F.

(Example 15)
The same operation as in Example 9 was performed except that the pigment dispersant was changed to the pigment dispersant G.

(Example 16)
The pigment dispersant was changed to pigment dispersant B, and the pigment was changed to C.I. I. It implemented similarly to Example 9 except having changed to Pigment Yellow 74 (brand name: HANSA Yellow 5GX01, product made by Clariant).

(Example 17)
The pigment dispersant was changed to pigment dispersant B, and the pigment was changed to C.I. I. The same procedure as in Example 9 was performed except that Pigment Black 7 (trade name: Carbon Black MA-100, manufactured by Mitsubishi Chemical Corporation) was used.

(Example 18)
The pigment dispersant was changed to Pigment Dispersant H, and the pigment was changed to C.I. I. Changed to Pigment Red 122 (trade name: Cinquasia Magenta D4550J, manufactured by BASF) The same operation as in Example 9 was performed except that.

(Comparative Example 6)
The same operation as in Example 9 was performed except that the pigment dispersant was changed to the pigment dispersant I.

(Comparative Example 7)
Pigment dispersant J was added to water. However, the pigment dispersant J could not be dissolved in water.

(Comparative Example 8)
An amount of potassium hydroxide that neutralizes 95% of the acid groups of the pigment dispersant was dissolved in water, and then the pigment dispersant K was added to prepare a 15% by mass aqueous solution of the pigment dispersant.

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

(Comparative Example 10)
The pigment dispersant K was dissolved in water to prepare a 15% by mass aqueous solution of the pigment dispersant.

In any of the examples, it was shown that an ink having low viscosity, high storage stability, and good re-dissolvability can be obtained. From this result, it was confirmed that the pigment dispersant of the present invention is useful for general pigments used in inkjet inks.

Claims

A block containing a structural unit derived from an N-vinyl lactam monomer, a B block containing a structural unit derived from a (meth) acrylic acid alkyl ester and a structural unit derived from an acid group-containing vinyl monomer. A pigment dispersant which is a block polymer having a value of 20 to 140 mgKOH / g.
2. The pigment dispersant according to claim 1, wherein the A block contains 80% by mass to 100% by mass of a structural unit derived from an N-vinyl lactam monomer.
The pigment dispersant according to claim 1 or 2, wherein the B block contains 50 mass% to 90 mass% of a structural unit derived from an alkyl (meth) acrylate.
The pigment dispersant according to any one of claims 1 to 3, wherein a mass ratio of the A block to the B block (A block mass: B block mass) is 10:90 to 70:30. .
The pigment dispersant according to any one of claims 1 to 4, wherein the molecular weight distribution of the block polymer is less than 2.
The pigment dispersant according to any one of claims 1 to 5, which is a diblock polymer composed of the A block and the block B.
A pigment dispersion composition comprising the pigment dispersant according to claim 6, a pigment, and an aqueous solvent.
The pigment dispersion composition according to claim 7, which is for inkjet.