JP2001294777A - Grafted pigment and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grafted pigment exhibiting good dispersion stability in an organic solvent-based or aqueous medium and a method for producing the same. A grafted pigment having a structure in which a radical generated from a compound having a maleimide group is chemically bonded to the surface of the pigment. A method for producing a grafted pigment, in which a mixture of a compound having a maleimide group, a pigment, and an organic solvent is irradiated with energy rays, and radicals generated from the compound having a maleimide group are chemically bonded to the surface of the pigment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pigment useful for applications such as paints, fiber treatment agents, printing inks, inks used in recording devices such as ink jet printers, and a method for producing the same. The present invention relates to a pigment exhibiting good dispersion stability in an organic solvent-based or aqueous medium and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, organic pigments and carbon black have been
Since its surface is hydrophobic, it is difficult to disperse in an aqueous medium, and its dispersion stability is not sufficient. Such physical properties have caused various problems. Also,
Even with an organic solvent-based medium, when fine pigment dispersion is required, there is a problem in obtaining sufficient dispersion stability suitable for the purpose.

As means for solving these problems, a number of methods have been proposed for modifying the pigment surface by graft polymerizing the pigment surface with a polymer, increasing the affinity for the medium, and improving the dispersion stability of the pigment. I have.

For example, Japanese Patent Publication No. 1-49369 discloses a method in which carbon black is treated with a peroxide to form a graft reaction site on the surface of the carbon black, and then a monomer is polymerized in the presence of a radical initiator. ,
A method has been proposed for improving the dispersion stability of carbon black in an aqueous medium.

Japanese Patent Application Laid-Open No. 11-335602 discloses that carbon black having a functional group generated by thermal decomposition of a radical generator composed of a polymer containing an azo group is chemically bonded to the surface of the radical generator. A method for improving the dispersion stability of the used ink has been proposed.

[0006]

However, in the method described in Japanese Patent Publication No. 49369/94, the generated radicals are trapped by the carbon black, so that a polymerization delay phenomenon occurs or the carbon black itself is inhibited from being polymerized. Phenomena such as acting as an agent cannot be completely suppressed, and therefore, there has been a problem that graft efficiency is poor and pigment dispersion stability is hardly obtained. Furthermore, when the ink is finally formed into an ink or the like, it contains a large amount of impurities such as a radical polymerization initiator and fragments thereof, unreacted monomers, and a polymer that is not grafted on carbon black, which adversely affects dispersion stability. There were also points.

The method described in Japanese Patent Application Laid-Open No. 11-335602 has the disadvantage that the graft ratio is low due to a radical reaction due to heat, and furthermore, the pigment is agglomerated by heating during the reaction. there were.

[0008] An object of the present invention is to provide a grafted pigment exhibiting good dispersion stability in an organic solvent-based or aqueous medium and a method for producing the same.

[0009]

In order to solve the above problems, the present invention provides (I) a grafted pigment having a structure in which a radical generated from a compound having a maleimide group is chemically bonded to the surface of the pigment.

In order to solve the above-mentioned problems, the present invention is directed to (II) irradiating a mixture comprising a compound having a maleimide group, a pigment and an organic solvent with an energy ray to generate a radical generated from the compound having a maleimide group. Provided is a method for producing a grafted pigment which is chemically bonded to the surface of a pigment.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The compound having a maleimide group used in the present invention can be used without particular limitation as long as it has 1 to 6 maleimide groups in one molecule. As a compound having such a maleimide group, for example,
General formula (1)

[0012]

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Wherein m and n are each independently 1
Represents an integer of 5 to 5, and the sum of m and n is an integer of 2 to 6. R ₁ represents a divalent hydrocarbon bond selected from the group consisting of an alkylene group, a cycloalkylene group, an arylalkylene group and a cycloalkylalkylene group. G
₁ represents an ester bond represented by -C (= O) O- or -OC (= O)-. R ₂₁ has an average molecular weight of 100 to
Represents a (poly) ether or (poly) ester linkage in the range of 100,000. A) a compound represented by the general formula (2)

[0014]

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(Wherein m and n are each independently 1
Represents an integer of 5 to 5, and the sum of m and n is an integer of 2 to 6. R ₁ represents a divalent hydrocarbon bond selected from the group consisting of an alkylene group, a cycloalkylene group, an arylalkylene group and a cycloalkylalkylene group. G
₂ is -NHC (= O) O- or -OC (= O) NH-
Represents a urethane bond represented by R ₂₂ represents a range of average molecular weight from 100 to 100,000 (poly) urethane connecting chain. A) a compound represented by the general formula (3)

[0016]

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(Wherein, R ₁ represents a divalent hydrocarbon bond selected from the group consisting of an alkylene group, a cycloalkylene group, an arylalkylene group and a cycloalkylalkylene group. G ₁ represents —C (＝ O) O -Or -OC (=
O)-represents an ester bond represented by-. R ₂₁ represents a (poly) ether-linked chain or a (poly) ester-linked chain having an average molecular weight in the range of 100 to 100,000.
R ₃ represents an alkyl group having 1 to 4 carbon atoms. And the like, and the like.

In the general formulas (1) and (2), m and n each represent an integer in the range of 1 to 5. In the general formulas (1) and (2), when a compound having a large sum (m + n) of m and n is used,
In the course of the reaction, the generation of a gelled product composed of a compound having maleimide as a by-product increases more than the chemical bond with the pigment, so that the general formulas (1) and (2)
In the above, a compound in which m + n is an integer of 2 or more and 6 or less is preferable, and a compound in which m + n is an integer of 2 or more and 4 or less is particularly preferable.

In the general formulas (1), (2) and (3), R ₁ is a hydrocarbon bond selected from the group consisting of an alkylene group, a cycloalkylene group, an arylalkylene group and a cycloalkylalkylene group. Represents Here, the alkylene group may be linear or branched, and the cycloalkylalkylene group may have an aryl group or a cycloalkyl group in a main chain or a branched chain. Although the number of carbon atoms of R ₁ is not particularly limited, it is not particularly necessary that the number of carbon atoms is large, and the number of carbon atoms may be in the range of 1 to 20.

The general formula (1), as R ₁ in the general formula (2) and the general formula (3), for example, methylene group, ethylene group, trimethylene group, such as a straight-chain alkylene group hexamethylene group; 1- A branched alkylene group such as a methylethylene group or a 2-methyltetramethylene group; a cycloalkylene group such as a cyclopentylene group or a cyclohexylene group; a cycloaryl group in a main chain or a side chain such as a benzylene group or a 1-phenyl-ethylene group. And an arylalkylene group having a group.

In the general formulas (1) and (2),
Each R in the compound represented ₁Are all the same
Or a different one.

In the general formulas (1) and (3), G ₁ represents —C (＝ O) O— or —OC (＝ O) —
Represents an ester bond represented by In this case, R ₂₁ in the general formulas (1) and (3) represents a (poly) ether-linked chain or a (poly) ester-linked chain.

The (poly) ether linking chain or (poly) ester linking chain is, for example, a linear alkylene group having 1 to 24 carbon atoms, a branched alkylene group, an alkylene group having a hydroxyl group, a cycloalkylene group, an aryl group. And an at least one organic group selected from the group consisting of an arylalkylene group and an ether alkylene group.

R ₂₁ may be a connecting chain composed of an oligomer or polymer in which these connecting chains are repeated as one unit, and those having an average molecular weight of 100 to 100,000 can be used. Molecular weight 10
Those having a range of 0 to 10,000 are preferred in terms of grafting efficiency.

Specific examples of the connecting chain representing R ₂₁ include: (a) a linear alkylene group having 1 to 24 carbon atoms, a branched alkylene group having 1 to 24 carbon atoms, a cycloalkylene group and an aryl group; At least one selected from the group consisting of
One hydrocarbon group having one or a repeating unit thereof linked by an ether bond has an average molecular weight of 100 to
A linking chain composed of 100,000 (poly) ether (poly) ol residues;

(B) at least one hydrocarbon group selected from the group consisting of a linear alkylene group having 1 to 24 carbon atoms, a branched alkylene group having 1 to 24 carbon atoms, a cycloalkylene group and an aryl group; A connecting chain composed of (poly) ester (poly) ol residues having an average molecular weight of 100 to 100,000 and having one or a repeating unit thereof bonded by an ester bond;

(C) at least one hydrocarbon group selected from the group consisting of a linear alkylene group having 1 to 24 carbon atoms, a branched alkylene group having 1 to 24 carbon atoms, a cycloalkylene group, and an aryl group; Ester of (poly) ether (poly) ol having an average molecular weight of 100 to 100,000 having one or a repeating unit thereof bonded by an ether bond and di-hexa-carboxylic acid (hereinafter abbreviated as polycarboxylic acid) (Poly) carboxylic acid whose terminal is a polycarboxylic acid residue (poly)
A linking chain composed of ether (poly) ol ester;

(D) at least one hydrocarbon group selected from the group consisting of a linear alkylene group having 1 to 24 carbon atoms, a branched alkylene group having 1 to 24 carbon atoms, a cycloalkylene group, and an aryl group; A polycarboxylic acid terminal obtained by esterifying a (poly) ether (poly) ol having an average molecular weight of 100 to 100,000 having one or a repeating unit thereof bonded by an ether bond and an ester bond, and a polycarboxylic acid, A connecting chain composed of (poly) carboxylic acid {(poly) ester (poly) ol} ester, which is an acid residue;

(E) at least one hydrocarbon group selected from the group consisting of a linear alkylene group having 1 to 24 carbon atoms, a branched alkylene group having 1 to 24 carbon atoms, a cycloalkylene group and an aryl group; A linking chain obtained by ring-opening a (poly) epoxide having an average molecular weight of 100 to 100,000 having one or a repeating unit thereof bonded by an ether bond; and the like, but is not limited thereto. .

Examples of the (poly) ether (poly) ol constituting the linking chain (a) include polyalkylene glycols such as polyethylene glycol, polypropylene glycol, polybutylene glycol and polytetramethylene glycol; Propanediol, propylene glycol, tetramethylene glycol, pentamethylene glycol, hexanediol, neopentyl glycol, glycerin, trimethylolpropane, pentaerythritol, diglycerin,
Modified ethylene oxide, propylene oxide, butylene oxide, and tetrahydrofuran of alkylene glycols such as ditrimethylolpropane and dipentaerythritol. Of these, various modified alkylene glycols are preferable. Further, the (poly) ether (poly) ol constituting the linking chain (a) includes a copolymer of ethylene oxide and propylene oxide, a copolymer of propylene glycol and tetrahydrofuran, a copolymer of ethylene glycol and tetrahydrofuran, Hydrocarbon polyols such as polyisoprene glycol, hydrogenated polyisoprene glycol, polybutadiene glycol, and hydrogenated polybutadiene glycol; and polyhydric hydroxyl compounds such as polytetramethylene hexaglyceryl ether (tetrahydrofuran-modified hexaglycerin). Is not limited to these.

Examples of the (poly) ester (poly) ol constituting the linking chain (b) include polyalkylene glycols such as polyethylene glycol, polypropylene glycol, polybutylene glycol and polytetramethylene glycol; Propanediol, propylene glycol, tetramethylene glycol, pentamethylene glycol, hexanediol, neopentyl glycol, glycerin, trimethylolpropane, pentaerythritol, diglycerin,
Alkylene glycols such as ditrimethylolpropane and dipentaerythritol, ε-caprolactone modified, γ-butyrolactone modified, δ-valerolactone modified or methylvalerolactone modified; aliphatic dicarboxylic acids such as adipic acid and dimer acid And an aliphatic polyester polyol which is an esterified product of a polyol such as neopentyl glycol and methylpentanediol; an aromatic polyester polyol which is an esterified product of an aromatic dicarboxylic acid such as terephthalic acid and a polyol such as neopentyl glycol. Polyhydric hydroxyl compounds such as polyester polyols, polycarbonate polyols, acrylic polyols, polytetramethylene hexaglyceryl ether (tetrahydrofuran modified hexaglycerin) Esterification with dicarboxylic acids such as glycerol, fumaric acid, phthalic acid, isophthalic acid, itaconic acid, adipic acid, sebacic acid and maleic acid; transesterification reaction between polyhydric hydroxyl-containing compounds such as glycerin and fatty acid esters of animals and plants And the like, but not limited thereto.

Examples of the (poly) carboxylic acid {(poly) ether (poly) ol} ester having a carboxylic acid at the terminal constituting the linking chain (c) include (1) succinic acid, adipic acid and phthalic acid , Hexahydrophthalic acid,
Polycarboxylic acids such as tetrahydrophthalic acid, fumaric acid, isophthalic acid, itaconic acid, sebacic acid, maleic acid, trimellitic acid, pyromellitic acid, benzenehexacarboxylic acid and citric acid; and (2) the above (a) (Poly) carboxylic acid {(poly) ether (poly) ol} ester whose terminal is a carboxylic acid obtained by esterification with (poly) ether (poly) ol, but not limited thereto. Absent.

The (poly) carboxylic acid {(poly) ester (poly) ol} ester having a carboxylic acid at the terminal constituting the linking chain (d) includes, for example, (1) succinic acid, adipic acid, phthalic acid , Hexahydrophthalic acid,
Polycarboxylic acids such as tetrahydrophthalic acid, fumaric acid, isophthalic acid, itaconic acid, sebacic acid, maleic acid, trimellitic acid, pyromellitic acid, benzenehexacarboxylic acid and citric acid; (Poly) carboxylic acid {(poly) ester (poly) ol} ester having a carboxylic acid at the end obtained by esterification with (poly) ester (poly) ol, but not limited thereto. Absent.

Examples of the (poly) epoxide constituting the linking chain (e) include, for example, epichlorohydrin-modified bisphenol type synthesized from (methyl) epichlorohydrin and bisphenol A or bisphenol F and ethylene oxide or propylene oxide modified products thereof. Epoxy resin; epichlorohydrin-modified hydrogenated bisphenol-type epoxy resin synthesized from (methyl) epichlorohydrin and hydrogenated bisphenol A or hydrogenated bisphenol F, ethylene oxide-modified product, propylene oxide-modified product thereof, epoxy novolak resin; phenol, biphenol Reaction products of (e) and (methyl) epichlorohydrin; aromatic epoxy resins such as glycidyl ester of terephthalic acid, isophthalic acid and pyromellitic acid; adipic acid, Glycidyl esters of carboxylic acids such as sulfonic acid, maleic acid and itaconic acid; glycidyl ethers of polyester polyols with polyhydric alcohols and polycarboxylic acids; copolymers of glycidyl (meth) acrylate and methyl glycidyl (meth) acrylate Examples include, but are not limited to:

Among these, R ₂₁ is (I) a linear alkylene group having 2 to 24 carbon atoms,
A branched alkylene group having 2 to 2 carbon atoms having a hydroxyl group
A (poly) ether linking chain having an average molecular weight of 100 to 100,000 and consisting of a repeating unit containing an alkylene group and / or an aryl group of 4, or (II) having 2 carbon atoms.
Average molecular weight of 100 to 100,000 consisting of a repeating unit containing a linear alkylene group having 2 to 24 carbon atoms, a branched alkylene group having 2 to 24 carbon atoms, an alkylene group having 2 to 24 carbon atoms and / or an aryl group having a hydroxyl group. And (III) a linear alkylene group having 2 to 24 carbon atoms, a branched alkylene group having 2 to 24 carbon atoms or 2 carbon atoms having a hydroxyl group. Average molecular weight of 100 to 100,000 consisting of a repeating unit containing from 24 to 24 alkylene groups
Or (IV) a linear alkylene group having 2 to 24 carbon atoms, a branched alkylene group having 2 to 24 carbon atoms, or a carbon atom having 2 to 2 carbon atoms having a hydroxyl group.
It is preferably a (poly) ester linked chain having an average molecular weight of 100 to 100,000 and comprising a repeating unit containing 4 alkylene groups.

Most preferred are (poly) ether linked chains of the polytetramethylene glycol residues among the above. It is very preferable in that the reaction proceeds rapidly without requiring an initiator.

As a specific method for synthesizing such a compound having a maleimide group, a known method as described in JP-A-11-124403 can be mentioned.

When the compound having a maleimide group is monofunctional as represented by the general formula (3), one end of the (poly) ether-linked chain or the (poly) ester-linked chain has a (poly) ether-linked chain. Is an alkanol group having 1 to 4 carbon atoms, and in the case of a (poly) ester linking chain, it is esterified with an alkyl group having 1 to 4 carbon atoms.

G ₂ in the general formula (2) is -NHC
It represents a urethane bond represented by (= O) O- or -OC (= O) NH-. In this case, R ₂₂ in the general formula (2) is a (poly) urethane linking chain.

This (poly) urethane linking chain is, for example,
At least one organic group selected from the group consisting of a linear alkylene group having 1 to 24 carbon atoms, a branched alkylene group, an alkylene group having a hydroxyl group, a cycloalkylene group, an aryl group and an arylalkylene group is connected by a urethane bond. It is a thing.

R ₂₂ may be an oligomer in which these connecting chains are repeated as one unit of repetition or a connecting chain composed of a polymer, and have an average molecular weight of 100 to 1
000, but having an average molecular weight of 100
From 10,000 to 10,000 are preferred in terms of grafting efficiency.

[0042] When showing the linking chain representing the R ₂₂ Specifically, for example, (f) a straight-chain alkylene group having 1 to 24 carbon atoms, branched alkylene groups having 1 to 24 carbon atoms, cycloalkylene and aryl At least one selected from the group consisting of
One hydrocarbon group having one or a repeating unit thereof linked by an ether bond has an average molecular weight of 100 to
Urethaneized (poly) of 100,000 (poly) ether (poly) ol and organic (poly) isocyanate
A linking chain composed of ether (poly) isocyanate;

(G) at least one hydrocarbon group selected from the group consisting of a linear alkylene group having 1 to 24 carbon atoms, a branched alkylene group having 1 to 24 carbon atoms, a cycloalkylene group and an aryl group; (Poly) ester (poly) isocyanate obtained by urethanizing a (poly) ester (poly) ol having an average molecular weight of 100 to 100,000 and having one or a repeating unit thereof bonded by an ester bond and an organic (poly) isocyanate However, the present invention is not limited thereto.

Among these, (poly) ether (poly)
A connecting chain (f) composed of all and an organic (poly) isocyanate is preferred.

Examples of the (poly) ether (poly) isocyanate constituting the linking chain (f) include aliphatic diisocyanate compounds such as methylene diisocyanate and hexamethylene diisocyanate; 2,4-tolylene diisocyanate, p-xylene Aromatic diisocyanate compound such as diisocyanate; polyisocyanate such as alicyclic diisocyanate such as isophorone diisocyanate and 4,4'-methylenebis (cyclohexyl isocyanate) are obtained by urethanization reaction with (poly) ether (poly) ol (poly ) Ether (poly) isocyanate and the like, but are not limited thereto.

Examples of the (poly) ether (poly) ol used in the reaction with the polyisocyanate include polyalkylene glycols such as polyethylene glycol, polypropylene glycol, polybutylene glycol and polytetramethylene glycol;
Ethylene oxide-modified alkylene glycols such as propanediol, propylene glycol, tetramethylene glycol, pentamethylene glycol, hexanediol, neopentyl glycol, glycerin, trimethylolpropane, pentaerythritol, diglycerin, ditrimethylolpropane, and dipentaerythritol; Modified propylene oxide, modified butylene oxide, modified tetrahydrofuran, and the like.
Among these, various modified products of alkylene glycols are preferable.

Further, (poly) ether (poly) ol used for the reaction with polyisocyanate includes, for example,
A copolymer of ethylene oxide and propylene oxide, a copolymer of propylene glycol and tetrahydrofuran,
A copolymer of ethylene glycol and tetrahydrofuran,
Hydrocarbon polyols such as polyisoprene glycol, hydrogenated polyisoprene glycol, polybutadiene glycol, and hydrogenated polybutadiene glycol; and polyhydric hydroxyl compounds such as polytetramethylene hexaglyceryl ether (tetrahydrofuran-modified hexaglycerin). However, the present invention is not limited to these.

The (poly) ester (poly) isocyanate constituting the linking chain (g) may be, for example, a polyisocyanate described for the linking chain (f) and a urethanization of the (poly) ester (poly) ol. The resulting (poly) ester (poly) isocyanate may be mentioned, but is not limited thereto.

The (poly) ester (poly) ol used for the reaction with the polyisocyanate includes, for example, ethylene glycol, propanediol, propylene glycol, tetramethylene glycol, pentamethylene glycol, hexanediol, neopentyl glycol, glycerin, trimethylol Of alkylene glycols such as propane, pentaerythritol, diglycerin, ditrimethylolpropane, and dipentaerythritol,
Modified ε-caprolactone, modified γ-butyrolactone, modified δ-valerolactone, modified methylvalerolactone; adipic acid, aliphatic dicarboxylic acids such as dimer acid, and polyols such as neopentyl glycol and methylpentanediol Aliphatic polyester polyols which are esterified products; polyester polyols such as aromatic polyester polyols which are esterified products of aromatic dicarboxylic acids such as terephthalic acid and polyols such as neopentyl glycol; polycarbonate polyols; acrylic polyols; polytetramethylene hexaglyceryl A polyvalent hydroxyl compound such as ether (a tetrahydrofuran modified product of hexaglycerin), fumaric acid,
Esterified products with dicarboxylic acids such as phthalic acid, isophthalic acid, itaconic acid, adipic acid, sebacic acid and maleic acid; compounds containing polyhydric hydroxyl groups such as glycerin and animals
Examples include, but are not limited to, polyhydric hydroxyl group-containing compounds such as monoglycerides obtained by transesterification with plant fatty acid esters.

Among them, R ₂₂ is a group consisting of (V) a linear alkylene group having 2 to 24 carbon atoms, a branched alkylene group having 2 to 24 carbon atoms and a cycloalkylene group having 6 to 24 carbon atoms. It is preferable that at least one organic group selected from the group consisting of (poly) ether having an average molecular weight of 100 to 100,000 be a urethane-bonded linking chain.
The 000 (poly) ether is selected from the group consisting of a straight chain alkylene group having 2 to 24 carbon atoms, a branched alkylene group having 2 to 24 carbon atoms and an alkylene group having 2 to 24 carbon atoms having a hydroxyl group. Those which are (poly) ethers having a repeating unit are particularly preferred.

R ₂₁ and R ₂₂ can be selected and used according to the polarity of the dispersion medium.

As a specific method for synthesizing such a compound having a maleimide group, a known method described in JP-A-11-124404 can be mentioned.

As the pigment used in the present invention, generally used organic pigments and carbon black can be used.

Examples of organic pigments include azo pigments; polycyclic pigments such as phthalocyanine pigments, perylene pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments; nitro pigments and nitroso pigments.
Examples of the carbon black include known carbon blacks such as furnace black, acetylene black, and channel black. Among these, the use of carbon black is preferred.

The method for producing the above grafted pigment is as follows:
The compound having the maleimide group, the mixture of the above-described pigment and the organic solvent is irradiated with energy rays, and the radical generated from the compound having the maleimide group is chemically bonded to the surface of the pigment, and at the same time, the compound having the maleimide group Is polymerized. As the energy beam, an electron beam or an ultraviolet ray can be used.

The reaction solvent used in the production method of the present invention does not inhibit the generation of radicals, and preferably uses an organic solvent having an affinity for the compound having a maleimide group. In particular, when the compound having a maleimide group is a solid, a compound that can be dissolved is selected. When the compound having a maleimide group is a low-viscosity liquid, the affinity with the organic solvent does not particularly affect the reaction, but when the affinity is low, the oligomer or polymer as a by-product is not dissolved and precipitates as a solid, Removal after the reaction becomes difficult. In this respect, it is preferable to use one showing a certain degree of affinity.

The optimum organic solvent is appropriately selected depending on the compound having a maleimide group to be used. Examples thereof include tetrahydrofuran (THF) and isopropanol (IP
A) and the like.

The concentration of the pigment with respect to the solvent in the production method of the present invention is preferably in the range of 1 to 20%, and preferably 2 to 10%.
Is particularly preferred.

The ratio of the compound having a maleimide group to the pigment used in the production method of the present invention is such that the concentration of the compound having a maleimide group per 1 g of the pigment is 0.2 to 0.2%.
A range of 4 mmol is preferred, and a range of 0.4 to 3 mmol is particularly preferred.

In the production method of the present invention, radicals are generated from a compound having a maleimide group dispersed or dissolved in a reaction solvent by irradiation with energy rays, and radicals are generated at the same time, such as carbon black dispersed in the reaction solvent. A reaction that chemically bonds to the pigment surface is used. The generation of radicals by energy beam irradiation is rapid, and the generated radicals may be bonded to carbon black or the like as a single molecule, or radicals formed of oligomers or polymers by a plurality of molecules may be bonded to carbon black or the like. obtain.

When the grafted pigment obtained by such a method is used, depending on the structure of R ₂₁ or R _{22 in} the general formulas (1), (2) and (3), an organic solvent-based pigment or Affinity for aqueous media can be controlled, and pigment aggregation in these media is suppressed, resulting in a pigment dispersion exhibiting sufficient dispersion stability for applications such as paints and inks.

That is, when the structure of R ₂₁ or R _{22 in} the above general formulas (1), (2) and (3) is a polyester structure having a low polarity, the organic solvent or the resin It has an effect of increasing affinity and improving dispersion stability in an organic solvent system. Conversely, when the structure of R ₂₁ or R _{22 in} the general formulas (1), (2) and (3) is a highly polar polyether, the affinity for an aqueous medium or an aqueous resin is low. Growing,
It has the effect of improving the dispersion stability in aqueous systems.

In the production method of the present invention, the reaction proceeds sufficiently without using a polymerization initiator or a photosensitizer. However, in some cases, they can be used together according to the purpose, and there is no problem.

The energy beam that can be used in the production method of the present invention is an electron beam or an ultraviolet ray. Among them, an ultraviolet ray having a wavelength of 180 to 500 nm is preferable. These energy rays may be obtained by known means, for example,
Sources of ultraviolet light having a wavelength of 180 to 500 nm include a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, a chemical lamp, a mercury-xenon lamp, a short arc lamp, a helium / cadmium laser, an argon laser, an excimer laser, Sun light,
And the like.

The production method of the present invention is preferably performed while blowing an inert gas such as nitrogen. Regarding the reaction temperature and pressure, the reaction proceeds without any particular problem under the conditions of normal temperature and normal pressure, so there is no need for special heating and pressurization.On the contrary, excessive heating tends to cause pigment aggregation and the like. This is not preferred. Needless to say, appropriate heating such that the pigment does not agglomerate may be used.

The irradiation time of active light in the production method of the present invention is preferably in the range of 30 minutes to 4 hours. Irradiation with actinic rays longer than 4 hours is not particularly problematic, but is uneconomical.

After the irradiation with the actinic ray, the by-product oligomers and the like can be removed by washing with an organic solvent. As the organic solvent to be used, an organic solvent in which the compound having a maleimide group is dissolved, and the washing method is stirring washing,
A commonly used method such as Soxhlet extraction may be used. Further, as these separation methods, generally performed operations such as centrifugation and filtration can be applied.

After washing, the obtained grafted pigment does not necessarily have to be dried, and can be used as it is in the form of a wet cake. In the case of drying, any method may be used as long as it is a usual drying operation.

The grafted pigment thus obtained can be easily and easily mixed with an aqueous medium or an organic solvent medium.
It can be stably dispersed.

Further, even when a dispersing resin is used, the grafted pigment of the present invention has a high affinity for the dispersing resin, so that it can be easily and stably dispersed.

[0071]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the scope of these Examples.

<Example 1><Preparation of grafted carbon black>
"Carbon black # 45L" (Mitsubishi Chemical Industries, Ltd.)
6 parts by weight, "MIA-250" (general formula (4) manufactured by Dainippon Chemical Industries, Ltd.)

[0073]

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3 parts by weight (0.92 mmol) of a maleimide derivative represented by the formula (wherein x represents 3 to 4)
And 200 parts by weight of tetrahydrofuran, stirred and mixed by a three-one motor, and irradiated with ultraviolet rays for 3 hours using a high-pressure mercury lamp while passing nitrogen. After irradiating with ultraviolet rays, the solid content was washed with methyl ethyl ketone and dried with a reduced-pressure drier to obtain a target grafted carbon black (A).

<Preparation of Aqueous Dispersion (W) of Acrylic Resin>
100 parts of methyl ethyl ketone (MEK) is placed in a reaction vessel, and styrene 50
, A mixture consisting of 20 parts of acrylic acid, 30 parts of butyl acrylate, and 8 parts of "Perbutyl O" (a polymerization initiator manufactured by NOF Corporation) was dropped over 2 hours. After completion of the dropwise addition, the reaction was continued at the same temperature for another 20 hours. In the course of the reaction, a polymerization initiator was added as needed while checking the consumption of the raw materials.

Ten parts of the resin solution thus obtained was neutralized with carboxyl groups in the resin by 100% with respect to the measured acid value using sodium hydroxide, and 20 parts of pure water was added thereto to disperse. After that, MEK was distilled off to obtain an aqueous dispersion (W) of an acrylic resin.

<Preparation of Aqueous Dispersion of Grafted Carbon Black> 4 parts by weight of grafted carbon black (A), equivalent to 2 parts by weight of resin solid content of aqueous dispersion of acrylic resin (W), and 20 parts by weight of distilled water Parts (including 20 parts by weight of water of an aqueous dispersion of acrylic resin) in 100 parts by weight.
zirconia beads (“Treceram” φ1.25 mm manufactured by Toray Industries, Inc.)
After adding 60 g, the mixture was stirred with a paint conditioner for 3 hours to obtain an aqueous dispersion of grafted carbon black (A).

<Example 2><Preparation of grafted carbon black>
"Carbon black # 850" (Mitsubishi Chemical Industries, Ltd.)
6 parts by weight, general formula (5)

[0079]

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(In the formula, y represents 4 to 6) 4.2 parts by weight (1.85 mmol) of a maleimide derivative represented by the following formula and 200 parts by weight of isopropanol are added, and the mixture is stirred and mixed by a three-one motor, and nitrogen is aerated. Then, ultraviolet rays were irradiated for 3 hours using a high-pressure mercury lamp. After irradiation with ultraviolet light, the solid content is washed with methyl ethyl ketone,
After drying with a reduced pressure drier, a target grafted carbon black (B) was obtained.

<Preparation of Aqueous Dispersion> 4 parts by weight of grafted carbon black (B), 14 parts by weight of distilled water and 8 parts by weight of diethylene glycol were blended in a 100 ml polyethylene pot, and 160 g of zirconia beads were added. Stir for 3 hours with a conditioner,
An aqueous dispersion of the grafted carbon black (B) was obtained.

<Comparative Example 1><Preparation of aqueous dispersion>"Carbon black # 45L"
4 parts by weight (manufactured by Mitsubishi Kasei Kogyo Co., Ltd.), equivalent to 2 parts by weight as a resin solid content of an aqueous dispersion of acrylic resin (W) and 20 parts by weight of distilled water (20 parts by weight of acrylic resin The dispersion (including water) was mixed in a 100 ml polyethylene pot, and 160 g of zirconia beads were further added. The mixture was stirred with a paint conditioner for 3 hours to obtain an aqueous dispersion of carbon black.

<Comparative Example 2><Preparation of aqueous dispersion>"Carbon black # 850"
4 parts by weight (manufactured by Mitsubishi Kasei Kogyo Co., Ltd.), 14 parts by weight of distilled water and 8 parts by weight of diethylene glycol were blended in a 100 ml polyethylene pot.
After adding 0 g, the mixture was stirred for 3 hours with a paint conditioner to obtain an aqueous dispersion of carbon black.

The aqueous dispersion of carbon black obtained in Comparative Example 2 was unstable. After the completion of stirring, the carbon black precipitated immediately, and a colorless and transparent supernatant layer was formed.

The dispersion stability of the aqueous dispersions obtained in Examples 1 and 2 and Comparative Examples 1 and 2 was evaluated, and the results are shown in Table 1.

As a method for evaluating the dispersion stability of the aqueous dispersion, each of the aqueous dispersions was placed in a 10 ml centrifugal sedimentation tube, and subjected to 20 centrifugation at 15000 rpm using a commercially available centrifuge.
After treating for 1 minute, the supernatant was diluted 4000 times with distilled water, and the absorbance at 500 nm was measured. The sample having a change in absorbance before and after centrifugation of less than 30% is indicated by ○, the sample having a change of 30% or more and less than 50% is indicated by △, and the sample having a change of 50% or more is indicated by ×.

[0087]

[Table 1]

From the results shown in Table 1, it is clear that the grafted pigment of the present invention shows good dispersion stability.

[0089]

The grafted pigment having a structure in which the radical generated from the compound having a maleimide group according to the present invention is chemically bonded to the surface of the pigment has excellent dispersion stability. Therefore, the grafted pigment of the present invention is useful as a pigment used in applications such as paints, fiber treatment agents, printing inks, inks used in recording devices such as ink jet printers, and the like.

Further, according to the method for producing a grafted pigment of the present invention, a pigment having excellent dispersion stability can be easily produced.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J011 AC04 CA02 CA06 CA10 QA19 QA36 QA39 QB13 QB15 UA01 UA03 VA05 WA02 WA05 4J026 AC00 BA40 BA50 DB36 GA08 4J037 AA02 AA30 CC24 CC25 CC29 EE03 EE24 EE28 EE43 FF15

Claims (7)

[Claims] 1. A grafted pigment having a structure in which radicals generated from a compound having a maleimide group are chemically bonded to the surface of the pigment. 2. A compound having a maleimide group is represented by the general formula (1): (In the formula, m and n each independently represent an integer of 1 to 5, and the sum of m and n is an integer of 2 to 6. R ₁ represents an alkylene group, a cycloalkylene group, an arylalkylene group, G ₁ represents a divalent hydrocarbon bond selected from the group consisting of cycloalkylalkylene groups, and G ₁ represents —C (=
O) represents an ester bond represented by O- or -OC (= O)-. R ₂₁ has an average molecular weight of 100 to 100,00
(Poly) ether linked chains or (poly) in the range of 0
Represents an ester linking chain. A compound represented by the general formula (2): (In the formula, m and n each independently represent an integer of 1 to 5, and the sum of m and n is an integer of 2 to 6. R ₁ represents an alkylene group, a cycloalkylene group, an arylalkylene group, G ₂ represents a divalent hydrocarbon bond selected from the group consisting of cycloalkylalkylene groups, and G ₂ represents —NHC
It represents a urethane bond represented by (= O) O- or -OC (= O) NH-. R ₂₂ is an average molecular weight from 100 to 10
Represents a (poly) urethane linking chain in the range of 000. And a compound represented by the general formula (3): (In the formula, R ₁ represents a divalent hydrocarbon bond selected from the group consisting of an alkylene group, a cycloalkylene group, an arylalkylene group, and a cycloalkylalkylene group.
G ₁ is -C (= O) O- or -OC (= O) - represents an ester bond represented by. R ₂₁ has an average molecular weight of 100
Represents a (poly) ether linked chain or a (poly) ester linked chain in the range of 100,000. R ₃ represents an alkyl group having 1 to 4 carbon atoms. The grafted pigment according to claim 1, which is one or more compounds selected from the group consisting of compounds represented by the formula (1). 3. The pigment according to claim 1, wherein the pigment is carbon black.
Or the grafted pigment according to 2. 4. A mixture comprising a compound having a maleimide group, a pigment and an organic solvent is irradiated with energy rays,
A method for producing a grafted pigment, wherein a radical generated from a compound having a maleimide group is chemically bonded to the surface of the pigment. 5. The compound having a maleimide group is represented by the general formula (1): (In the formula, m and n each independently represent an integer of 1 to 5, and the sum of m and n is an integer of 2 to 6. R ₁ represents an alkylene group, a cycloalkylene group, an arylalkylene group, G ₁ represents a divalent hydrocarbon bond selected from the group consisting of cycloalkylalkylene groups, and G ₁ represents —C (=
O) represents an ester bond represented by O- or -OC (= O)-. R ₂₁ has an average molecular weight of 100 to 100,00
(Poly) ether linked chains or (poly) in the range of 0
Represents an ester linking chain. A) a compound represented by the general formula (2): (In the formula, m and n each independently represent an integer of 1 to 5, and the sum of m and n is an integer of 2 to 6. R ₁ represents an alkylene group, a cycloalkylene group, an arylalkylene group, G ₂ represents a divalent hydrocarbon bond selected from the group consisting of cycloalkylalkylene groups, and G ₂ represents —NHC
It represents a urethane bond represented by (= O) O- or -OC (= O) NH-. R ₂₂ is an average molecular weight from 100 to 10
Represents a (poly) urethane linking chain in the range of 000. And a compound represented by the general formula (3): (In the formula, R ₁ represents a divalent hydrocarbon bond selected from the group consisting of an alkylene group, a cycloalkylene group, an arylalkylene group, and a cycloalkylalkylene group.
G ₁ is -C (= O) O- or -OC (= O) - represents an ester bond represented by. R ₂₁ has an average molecular weight of 100
Represents a (poly) ether linked chain or a (poly) ester linked chain in the range of 100,000. R ³ represents an alkyl group having 1 to 4 carbon atoms. 5. The method for producing a grafted pigment according to claim 4, wherein the compound is one or more compounds selected from the group consisting of compounds represented by the formula (1). 6. The pigment according to claim 4, wherein the pigment is carbon black.
Or the manufacturing method of 5. 7. The method according to claim 4, wherein the energy rays are ultraviolet rays.
7. The production method according to 5 or 6.