JP2023137669A - Pigment dispersant, method for producing pigment dispersant, pigment dispersion liquid, and uv-curable ink - Google Patents

Abstract

To provide a pigment dispersant that makes it possible to prepare a pigment dispersion liquid with excellent pigment dispersibility, and low viscosity and high storage stability.SOLUTION: A pigment dispersant has a structure represented by general formula (1). (R1, R2, and R3 each represent a pentadecyl group or the like, R4, R5, and R6 independently represent H, a group represented by formula (2), or a group represented by formula (3), at least one of R4, R5, and R6 represents the group represented by formula (2), and n represents a number selected from 1-10. * represents a bond position, R7 represents an ethylene group or a methyl ethylene group, and m represents a number selected from 14-68. A represents an alkyl group, a dialkylamino alkyl group, a pyridinyl alkyl group, an imidazolyl alkyl group, a pyridinyl group, or an imidazolyl group, and R8 represents H or an alkyl group.)SELECTED DRAWING: None

Description

The present invention relates to a pigment dispersant, a method for producing a pigment dispersant, a pigment dispersion, and an ultraviolet curable ink.

Common coating fluids such as paints, inks, and coating agents contain organic solvents. For this reason, since the organic solvent evaporates after application of these coating liquids, the burden on the environment is relatively high. Therefore, as environmentally friendly coating liquids that do not substantially contain organic solvents, water-based inks and coating liquids that use water as the main liquid medium, powder coatings using colored resin powder, etc. have been proposed. Furthermore, coating liquids using vinyl-based, epoxy-based, and oxetane-based monomers in place of organic solvents have also been proposed. These coating fluids are of the type that apply heat or light after application to polymerize monomers to form polymers, so they are suitable for ultraviolet curing inks and electronic inks that do not substantially contain volatile components. It is used as active energy ray-curable ink such as line-curable ink.

In recent years, ultraviolet curable inkjet inks (UVIJ inks) containing pigments as colorants have been proposed, which can record vivid images on demand on base materials such as packaging materials and containers. UVIJ inks are required to exhibit ejection properties suitable for high-speed printing, have excellent pigment dispersion stability, and further have lower viscosity. That is, there is a need for a pigment dispersion liquid for UVIJ ink in which the pigment is finely dispersed and which has excellent pigment dispersion stability.

A pigment dispersant is usually used when preparing a pigment dispersion. As the pigment dispersant, a low molecular weight dispersant such as a surfactant, a polymer type dispersant, etc. are used. Among these, from the viewpoint of fine dispersibility and dispersion stability of pigments, polymer type dispersants such as vinyl polymers obtained by polymerizing vinyl monomers are frequently used. Incidentally, such pigment dispersants such as vinyl polymers are usually used in the form of a solution diluted with an organic solvent (Patent Documents 1 and 2).

JP 2019-157077 Publication JP2013-177580A

As mentioned above, general polymer-type pigment dispersants are used in a state dissolved in an organic solvent. Therefore, UVIJ ink prepared using such a pigment dispersant also contains organic solvents, which reduces the superiority of UVIJ ink, which is ``contains virtually no volatile components and is environmentally friendly.'' easily damaged. Therefore, there has been a demand for the development of a polymer-based pigment dispersant that does not substantially contain volatile components, has a solid content of 100%, and is easy to handle.

A polymer-based pigment dispersant containing substantially no volatile components can be produced, for example, by removing the organic solvent from an organic solvent solution of a polymer produced by solution polymerization or the like. However, there are problems in that the solid content (polymer) obtained by removing the organic solvent is not necessarily easy to handle, and the manufacturing process becomes complicated. Furthermore, the function of the obtained polymer as a pigment dispersant was not necessarily good, and there was room for further improvement.

The present invention was made in view of the problems of the prior art, and its object is to provide a pigment dispersion that has good pigment dispersibility, low viscosity, and excellent storage stability. The object of the present invention is to provide a pigment dispersant that can be used to prepare a liquid.

Further, the object of the present invention is to provide a simple method for producing the above-mentioned pigment dispersant, and a method that uses the above-mentioned pigment dispersant to achieve good pigment dispersibility, low viscosity, and excellent storage stability. An object of the present invention is to provide a pigment dispersion liquid with a high quality pigment. Furthermore, it is an object of the present invention to provide pigments with good dispersibility, low viscosity and excellent storage stability, which contain substantially volatile organic compounds, using the above-mentioned pigment dispersant. The purpose of the present invention is to provide an ultraviolet curable ink for inkjet printing that does not require any heat treatment.

That is, according to the present invention, the following pigment dispersant is provided.
[1] A pigment dispersant having a structure represented by the following general formula (1).

（前記一般式（１）中、Ｒ_１、Ｒ_２、及びＲ_３は、相互に独立に、ペンタデシル基、７－ペンタデセニル基、７，１０－ペンタデカジエニル基、又は７，１０，１４－ペンタデカトリエニル基を示し、Ｒ_４、Ｒ_５、及びＲ_６は、相互に独立に、水素原子、下記一般式（２）で表される基、又は下記一般式（３）で表される基を示すとともに、Ｒ_４、Ｒ_５、及びＲ_６のうちの１以上は下記一般式（２）で表される基であり、ｎは１～１０の数を示す）

(In the general formula (1), R ₁ , R ₂ , and R ₃ are each independently a pentadecyl group, a 7-pentadecenyl group, a 7,10-pentadecadienyl group, or a 7,10,14- It represents a pentadecatrienyl group, and R ₄ , R ₅ , and R ₆ are each independently a hydrogen atom, a group represented by the following general formula (2), or a group represented by the following general formula (3). group, and one or more of R ₄ , R ₅ , and R ₆ is a group represented by the following general formula (2), and n represents a number from 1 to 10)

（前記一般式（２）中、＊は結合位置を示し、Ｒ_７はエチレン基又はメチルエチレン基を示し、ｍは１４～６８の数を示す）

(In the general formula (2), * indicates a bonding position, R ₇ indicates an ethylene group or a methylethylene group, and m indicates a number from 14 to 68)

（前記一般式（３）中、＊は結合位置を示し、Ａはアルキル基、ジアルキルアミノアルキル基、ピリジニルアルキル基、イミダゾリルアルキル基、ピリジニル基、又はイミダゾリル基を示し、Ｒ_８は水素原子又はアルキル基を示す）

(In the general formula (3), * indicates a bonding position, A indicates an alkyl group, dialkylaminoalkyl group, pyridinyl alkyl group, imidazolylalkyl group, pyridinyl group, or imidazolyl group, and R ₈ is a hydrogen atom or alkyl group)

Further, according to the present invention, the following method for producing a pigment dispersant is provided.
[2] The method for producing a pigment dispersant according to [1] above, which includes a reaction step of reacting a polyepoxy compound represented by the following general formula (4) with a polyalkylene glycol monomethyl ether monoamine. Method for manufacturing the agent.

（前記一般式（４）中、Ｒ_１、Ｒ_２、及びＲ_３は、相互に独立に、ペンタデシル基、７－ペンタデセニル基、７，１０－ペンタデカジエニル基、又は７，１０，１４－ペンタデカトリエニル基を示し、Ｒ_９、Ｒ_１０、及びＲ_１１は、相互に独立に、水素原子又は２，３－エポキシプロピル基を示すとともに、Ｒ_９、Ｒ_１０、及びＲ_１１のうちの１以上は２，３－エポキシプロピル基であり、ｎは１～１０の数を示す）

(In the general formula (4), R ₁ , R ₂ , and R ₃ are each independently a pentadecyl group, a 7-pentadecenyl group, a 7,10-pentadecadienyl group, or a 7,10,14- represents a pentadecatrienyl group, R ₉ , R ₁₀ , and _{R 11 each} independently _represent a hydrogen atom or a 2,3-epoxypropyl group _; 1 or more is a 2,3-epoxypropyl group, and n represents a number from 1 to 10)

[3] The method for producing a pigment dispersant according to [2] above, wherein the compound represented by the general formula (4) is a formalin condensate of cardanol.
[4] The reaction step is a step of further reacting the polyepoxy compound with at least one amine compound selected from the group consisting of a primary organic amine, a secondary organic amine, and a polyamine compound, and the The method for producing a pigment dispersant as described in [2] or [3] above, wherein the polyamine compound is a compound having a primary amino group or a secondary amino group and a tertiary amino group.
[5] The polyamine compound is a group consisting of dimethylaminopropylamine, diethylaminopropylamine, dibutylaminopropylamine, 4-aminopyridine, 4-(2-aminoethyl)pyridine, and 1-(3-aminopropyl)imidazole. The method for producing a pigment dispersant according to the above [4], which is at least one selected from the following.

Furthermore, according to the present invention, the following pigment dispersion is provided.
[6] A pigment dispersion containing a pigment, a solvent, and a pigment dispersant for dispersing the pigment in the solvent, wherein the pigment dispersant is the pigment dispersant described in [1] above. liquid.
[7] The pigment dispersion according to the above [6], further containing a pigment derivative having at least one acidic group selected from the group consisting of a carboxy group, a phosphoric acid group, and a sulfonic acid group.
[8] The pigment dispersion according to [6] or [7], wherein the solvent is an ultraviolet/electron beam curable monomer or an ultraviolet/electron beam curable oligomer having one or more unsaturated bonds.

Further, according to the present invention, the following ultraviolet curable ink is provided.
[9] An ultraviolet curing ink for inkjet use containing the pigment dispersion according to [8] above.

According to the present invention, it is possible to provide a pigment dispersant that allows the preparation of a pigment dispersion having good pigment dispersibility, low viscosity, and excellent storage stability.

Further, according to the present invention, there is provided a simple method for producing the above-mentioned pigment dispersant, and a pigment dispersion using the above-mentioned pigment dispersant that has good pigment dispersibility, low viscosity, and excellent storage stability. liquid can be provided. Furthermore, according to the present invention, an inkjet inkjet product that uses the above-described pigment dispersant, has good pigment dispersibility, low viscosity, and excellent storage stability, and does not substantially contain volatile organic compounds. UV curable ink can be provided.

<Pigment dispersant>
Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments. One embodiment of the pigment dispersant of the present invention is a compound (polymer) represented by the following general formula (1). The details of the pigment dispersant of this embodiment will be explained below.

（前記一般式（１）中、Ｒ_１、Ｒ_２、及びＲ_３は、相互に独立に、ペンタデシル基、７－ペンタデセニル基、７，１０－ペンタデカジエニル基、又は７，１０，１４－ペンタデカトリエニル基を示し、Ｒ_４、Ｒ_５、及びＲ_６は、相互に独立に、水素原子、下記一般式（２）で表される基、又は下記一般式（３）で表される基を示すとともに、Ｒ_４、Ｒ_５、及びＲ_６のうちの１以上は下記一般式（２）で表される基であり、ｎは１～１０の数を示す）

(In the general formula (1), R ₁ , R ₂ , and R ₃ are each independently a pentadecyl group, a 7-pentadecenyl group, a 7,10-pentadecadienyl group, or a 7,10,14- It represents a pentadecatrienyl group, and R ₄ , R ₅ , and R ₆ are each independently a hydrogen atom, a group represented by the following general formula (2), or a group represented by the following general formula (3). group, and one or more of R ₄ , R ₅ , and R ₆ is a group represented by the following general formula (2), and n represents a number from 1 to 10)

（前記一般式（２）中、＊は結合位置を示し、Ｒ_７はエチレン基又はメチルエチレン基を示し、ｍは１４～６８の数を示す）

(In the general formula (2), * indicates a bonding position, R ₇ indicates an ethylene group or a methylethylene group, and m indicates a number from 14 to 68)

（前記一般式（３）中、＊は結合位置を示し、Ａはアルキル基、ジアルキルアミノアルキル基、ピリジニルアルキル基、イミダゾリルアルキル基、ピリジニル基、又はイミダゾリル基を示し、Ｒ_８は水素原子又はアルキル基を示す）

(In the general formula (3), * indicates a bonding position, A indicates an alkyl group, dialkylaminoalkyl group, pyridinyl alkyl group, imidazolylalkyl group, pyridinyl group, or imidazolyl group, and R ₈ is a hydrogen atom or alkyl group)

In general formula (1), the aromatic ring and the long-chain hydrocarbon groups represented by R ₁ , R ₂ , and R ₃ are moieties that impart affinity to pigments. Further, 7-pentadecenyl group, 7,10-pentadecadienyl group, and 7,10,14-pentadecatrienyl group, which are groups having unsaturated bonds, are all groups capable of generating radicals. Therefore, by using the pigment dispersant of this embodiment having these groups in an ultraviolet curable ink, these groups can react with the curing component in the ink.

The group represented by general formula (2) has a hydroxyl group and an amino group. In addition, as the methoxypolyalkylene glycol chain represented by "(R ₇ O) _m CH ₃ ", methoxypolyethylene glycol chain, methoxypolypropylene glycol chain, methoxypolyethylene glycol polypropylene glycol random structure chain, methoxypolyethylene glycol polypropylene glycol diblock Examples include a methoxypolyethylene glycol polypropylene glycol polyethylene glycol triblock structural chain, and a methoxypolyethylene glycol polypropylene glycol polyethylene glycol triblock structural chain.

In general formula (2), m is 14 to 68, and the molecular weight of the methoxypolyalkylene glycol chain represented by "(R ₇ O) _m CH ₃ " is preferably 1,000 to 3,000. From the viewpoint of raw material availability and marketability, the methoxypolyalkylene glycol chain represented by "(R ₇ O) _m CH ₃ " is preferably a methoxypolyethylene glycol polypropylene glycol random structure chain, and ethylene oxide The molar ratio of (EO) to propylene oxide (PO) is preferably in the range of EO/PO=6 to 58/3 to 29. In general formula (1), one or more of R ₄ , R ₅ , and R ₆ is a group represented by general formula (2), and more than half of the repeating units are represented by general formula (2). It is preferable that the groups are bonded, and all of R ₄ , R ₅ and R ₆ may be groups represented by general formula (2).

In general formula (3), examples of the alkyl group represented by R ₈ include a methyl group, an ethyl group, a butyl group, a hexyl group, and the like. In general formula (3), the dialkylaminoalkyl group represented by A includes dimethylaminoethyl group, dimethylaminopropyl group, diethylaminoethyl group, diethylaminopropyl group, dibutylaminopropyl group, dibutylaminobutyl group, etc. be able to. Among these, dimethylaminopropyl group, diethylaminopropyl group, and dibutylaminopropyl group are preferred because they have high basicity and good reactivity.

In general formula (3), the pyridinyl alkyl group represented by A includes a 2-pyridinylmethyl group, a 4-pyridinylmethyl group, a 1-(2-pyridinyl)ethyl group, a 2-(2-pyridinyl)ethyl group, Examples include 1-(4-pyridinyl)ethyl group and 2-(4-pyridinyl)ethyl group. Among these, a 4-pyridinyl group and a 2-(4-pyridinyl)ethyl group having a basic nitrogen at the 4-position are preferred. In general formula (3), examples of the imidazolylalkyl group represented by A include 2-imidazolylethyl group, 3-imidazolylpropyl group, and 4-imidazolylbutyl group. Among these, 3-imidazolylpropyl group is preferred from the viewpoint of easy availability of raw materials.

In general formula (1), n represents a number from 1 to 10, preferably a number from 2 to 4. If n is 0, the adsorbed portion of the main chain is small and will be detached from the pigment, resulting in a decrease in the dispersion stability of the pigment. On the other hand, if n is more than 10, the molecular weight will be too large and the viscosity of the resulting pigment dispersion will become excessively high.

The polystyrene equivalent number average molecular weight (Mn) of the pigment dispersant measured by gel permeation chromatography (GPC) is preferably 1,000 or more and 20,000 or less, and 3,000 or more and 10,000 or less. It is even more preferable that there be.

<Production method of pigment dispersant>
The above-mentioned pigment dispersant can be manufactured by the method shown below.
That is, one embodiment of the method for producing a pigment dispersant of the present invention is a method for producing the above-mentioned pigment dispersant, in which polyalkylene glycol monomethyl ether monoamine is added to a polyepoxy compound represented by the following general formula (4). It has a reaction step of reacting.

（前記一般式（４）中、Ｒ_１、Ｒ_２、及びＲ_３は、相互に独立に、ペンタデシル基、７－ペンタデセニル基、７，１０－ペンタデカジエニル基、又は７，１０，１４－ペンタデカトリエニル基を示し、Ｒ_９、Ｒ_１０、及びＲ_１１は、相互に独立に、水素原子又は２，３－エポキシプロピル基を示すとともに、Ｒ_９、Ｒ_１０、及びＲ_１１のうちの１以上は２，３－エポキシプロピル基であり、ｎは１～１０の数を示す）

(In the general formula (4), R ₁ , R ₂ , and R ₃ are each independently a pentadecyl group, a 7-pentadecenyl group, a 7,10-pentadecadienyl group, or a 7,10,14- represents a pentadecatrienyl group, R ₉ , R ₁₀ , and _{R 11 each independently} represent a hydrogen atom or a 2,3-epoxypropyl group _; 1 or more is a 2,3-epoxypropyl group, and n represents a number from 1 to 10)

R ₁ , R ₂ , and R ₃ in general formula (4) have the same meanings as R ₁ , R ₂ , and R ₃ in general formula (1) described above. In general formula (4), one or more of R ₉ , R ₁₀ , and R ₁₁ is a 2,3-epoxypropyl group (hereinafter also simply referred to as an "epoxy group"), preferably two or more repeating units. It is less than or equal to n+2.

As the polyepoxy compound represented by the general formula (4), it is preferable to use a formalin condensate of cardanol. Cardanol has an aromatic ring with a long chain hydrocarbon group. Since cardanol is a plant-derived raw material, it is a raw material that contributes to reducing carbon dioxide from a carbon neutral standpoint. Examples of commercially available formalin condensates of cardanol include "Cardolite NC-547" (trade name) manufactured by Caedolite.

In the reaction step, the polyepoxy compound is reacted with polyalkylene glycol monomethyl ether monoamine. Examples of polyalkylene glycol monomethyl ether monoamines include methoxypolyethylene glycol monoamine, methoxypolypropylene glycol monoamine, methoxypolyethylene glycol polypropylene glycol random structure monoamine, methoxypolyethylene glycol polypropylene glycol diblock structure monoamine, methoxypolyethylene glycol polypropylene glycol polyethylene glycol triblock structure monoamine, Examples include methoxypolyethylene glycol polypropylene glycol polyethylene glycol triblock structure monoamine. Among these, methoxypolyethylene glycol polypropylene glycol random structure monoamine is preferred. Examples of commercially available polyalkylene glycol monomethyl ether monoamines include the "Jeffamine M-" series manufactured by Huntsman and the "Genamine" manufactured by Clariant.

The polyalkylene glycol monomethyl ether monoamine can be reacted with all epoxy groups in the polyepoxy compound. By reacting the epoxy group with the amino group in the polyalkylene glycol monomethyl ether monoamine, the epoxy group opens to form a hydroxyl group and an amino group, making it possible to obtain a pigment dispersant having the desired structure. . The polyalkylene glycol monomethyl ether monoamine may be reacted so as to leave some epoxy groups in the polyepoxy compound. It is also preferable to further react the remaining epoxy groups with an amine compound to introduce amino groups. The polyalkylene glycol monomethyl ether monoamine is preferably reacted with 50 mol% or more of the epoxy groups in the polyepoxy compound.

The amine compound to be reacted with the remaining epoxy group may be at least one selected from the group consisting of primary organic amines, secondary organic amines, and polyamine compounds. That is, the reaction step is preferably a step of further reacting the polyepoxy compound with at least one amine compound selected from the group consisting of primary organic amines, secondary organic amines, and polyamine compounds. In addition, it is preferable that the said polyamine compound is a compound which has a primary amino group or a secondary amino group, and a tertiary amino group.

Examples of primary organic amines include methylamine, ethylamine, butylamine, octylamine, and hydroxyethylamine. Examples of secondary organic amines include dimethylamine, diethylamine, dibutylamine, and dihydroxyethylamine.

Among polyamine compounds, compounds having a primary amino group and a tertiary amino group include dimethylaminoethylamine, dimethylaminopropylamine, diethylaminoethylamine, diethylaminopropylamine, dibutylaminopropylamine, 4-aminopyridine, 4-(2- Examples include aminoethyl)pyridine and 1-(3-aminopropyl)imidazole. Further, among polyamine compounds, examples of compounds having a secondary amino group and a tertiary amino group include diethylaminoethylmethylamine and bis(dimethylaminoethyl)amine.

The polyamine compound is selected from the group consisting of dimethylaminopropylamine, diethylaminopropylamine, dibutylaminopropylamine, 4-aminopyridine, 4-(2-aminoethyl)pyridine, and 1-(3-aminopropyl)imidazole. Preferably, it is at least one type.

The desired pigment dispersant can be obtained by reacting a polyepoxy compound with a polyalkylene glycol monomethyl ether monoamine and further reacting with an amine compound as needed. In the reaction step, for example, the epoxy group and the amino group are reacted by heating, preferably at 60° C. or higher, more preferably at 80° C. or higher, in the presence of an organic solvent that does not have reactivity with the epoxy group or amino group. Thereafter, by distilling off the organic solvent as necessary, a pigment dispersant having a solid content of about 100% can be obtained. Polyepoxy compounds are usually liquids with relatively low viscosity under conditions of room temperature to 40°C. For this reason, it is preferable to heat and react in bulk without using a solvent (in the absence of a solvent).

The progress of the reaction can be determined by measuring the infrared absorption spectrum (IR) and confirming the disappearance of absorption near 910 cm ^-1 derived from epoxy groups and the generation of absorption near 3,200 cm ^-1 derived from hydroxyl groups. can be grasped. Further, the progress of the reaction can also be grasped by measuring the epoxy equivalent according to a conventionally known method and confirming the disappearance of the epoxy group. Furthermore, the progress of the reaction can be grasped by confirming the increase in molecular weight by gel permeation chromatography or by measuring the amine value according to a conventionally known method. Note that even if the reaction does not proceed completely, as long as the pigment dispersant of this embodiment having a specific structure is produced, it can be used as a dispersant for dispersing pigments.

<Pigment dispersion>
One embodiment of the pigment dispersion of the present invention contains a pigment, a solvent, and a pigment dispersant that disperses the pigment in the solvent. This pigment dispersant is the aforementioned pigment dispersant.

As the pigment, conventionally known pigments can be used. As a pigment, C. I. Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 94, 95, 97, 109, 110, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 175, 180, 181, 185, 191; C. I. Pigment Orange 16, 36, 43, 51, 55, 59, 61, 64, 71, 73; C. I. Pigment Red 4, 5, 9, 23, 48, 49, 52, 53, 57, 97, 112, 122, 123, 144, 146, 147, 149, 150, 166, 168, 170, 176, 177, 180, 184,185,192,202,207,214,215,216,217,220,221,223,224,226,227,228,238,240,242,254,255,264,269,272;C. I. Pigment Violet 19, 23, 29, 30, 37, 40, 50; C. I. Pigment Blue 15, 15:1, 15:3, 15:4, 15:6, 22, 60, 64; C. I. Pigment Green 7, 36, 58; C. I. Pigment Black 7; C. I. Pigment White 6; and the like.

When these pigments are used as a mixture, any of the following methods may be used: a method of mixing powder pigments, a method of mixing paste-like pigments, or a method of mixing them at the time of pigment formation to form a solid solution. Further, fillers such as zinc oxide, zirconium oxide, silica, and mica can also be used. Furthermore, carbon nanotubes, graphite, graphene, carbon nanohorns, carbon nanoribbons, carbon fullerenes, carbon-based quantum dots, nanodiamonds, and the like can also be used.

From the viewpoints of color development, dispersibility, weather resistance, etc., pigments suitable for inkjet inks include C.I. I. Pigment Yellow 74, 83, 109, 128, 139, 150, 151, 154, 155, 180, 181, 185; C.I. I. Pigment Red 122, 170, 176, 177, 185, 269; C. I. Pigment Violet 19, 23; C.I. I. Pigment Blue 15:3, 15:4, 15:6; C. I. Pigment Black 7; C. I. Pigment White 6; and the like.

The pigment may be an untreated pigment, a self-dispersing pigment with a functional group introduced onto its surface, or a pigment that has been surface-treated with a surface treatment agent such as a coupling agent or an activator, or a polymer, etc. or encapsulated treated pigments. Further, unless a hiding power is required, it is preferable to use organic fine particle pigments. Furthermore, when high definition and transparency are required, it is preferable to use a pigment that has been finely divided by wet grinding such as salt milling or dry grinding. In consideration of suppressing nozzle clogging during printing, it is preferable to remove pigments with a particle diameter of more than 1.0 μm. The average particle size of the organic pigment is preferably 0.2 μm or less, and the average particle size of the inorganic pigment is preferably 0.4 μm or less.

(pigment derivative)
Preferably, the pigment dispersion of the present embodiment further contains a pigment derivative having at least one acidic group selected from the group consisting of a carboxy group, a phosphoric acid group, and a sulfonic acid group. A pigment derivative having an acidic group imparts an acidic group to the surface of the pigment by adsorbing to the surface of the pigment. Then, the provided acidic group and the amino group of the pigment dispersant form an ionic bond, so that the pigment dispersant is more firmly adsorbed on the surface of the pigment and prevented from being desorbed. Therefore, by further containing a pigment dispersant having an acidic group, aggregation and sedimentation of the pigment can be suppressed, and a pigment dispersion liquid with even better dispersion stability can be obtained.

As the pigment derivative, conventionally known pigment derivatives can be used. Specifically, a compound in which at least one acidic group of a carboxyl group, a phosphoric acid group, and a sulfonic acid group is bonded to an organic dye skeleton can be used as a pigment derivative. The acidic group is preferably sulfonic acid. Examples of the organic dye skeleton include an azo dye skeleton, an anthraquinone dye skeleton, a quinacridone dye skeleton, a phthalocyanine dye skeleton, a diketopyrrolopyrrole dye skeleton, and an isoindoline dye skeleton. It is preferable that one acidic group is bonded to the organic dye skeleton, and two or more acidic groups may be bonded to the organic dye skeleton.

Examples of pigment derivatives having an azo dye skeleton include compounds represented by the following formula (A). Examples of pigment derivatives having an anthraquinone dye skeleton include compounds represented by the following formula (B). Examples of pigment derivatives having a quinacridone dye skeleton include compounds represented by the following formulas (C) and (D). Examples of pigment derivatives having a phthalocyanine dye skeleton include compounds represented by the following formula (E). Examples of pigment derivatives having a diketopyrrolopyrrole dye skeleton include compounds represented by the following formula (F). Examples of pigment derivatives having an isoindoline dye skeleton include compounds represented by the following formula (G).

The pigment derivative may be blended when producing the pigment dispersion, or may be treated on the surface of the pigment in advance. Methods for surface treating pigments with pigment derivatives include, for example, adding the pigment to the pigment after synthesis and filtering it; mixing the pigment with a pigment derivative in which the acidic group is a sodium salt, and then acidifying the pigment to make the pigment derivative water-insoluble. Examples include a method in which pigments are milled together when they are made into fine particles; and a method in which pigments are milled together. The amount of the pigment derivative relative to 100 parts by weight of the pigment is preferably 0.5 to 20 parts by weight, more preferably 1 to 10 parts by weight.

(solvent)
The solvent is a liquid such as an organic solvent used as a dispersion medium for dispersing the pigment. Examples of organic solvents include hydrocarbon solvents such as hexane, toluene, and xylene; alcohol solvents such as methanol, ethanol, isopropanol, butanol, and dodecanol; ketone solvents such as acetone, methyl ethyl ketone, diethyl ketone, and isobutyl methyl ketone; ethyl acetate. , butyl acetate, amyl acetate, dimethyl succinate, dimethyl adipate, methyl lactate, dimethyl lactate, and other ester solvents; dipropyl ether, tetrahydrofuran, dioxane, and other ether solvents; dimethyl carbonate, ethylene carbonate, propylene carbonate, and other carbonates System solvent: Amides such as N,N-dimethylformamide, N,N-dimethylacetamide, pyrrolidone, N-methylpyrrolidone, 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, etc. Solvents: Urea solvents such as tetramethylurea and dimethylimidazolidinone; Sulfoxide solvents such as dimethyl sulfoxide; Ethylene glycol, propylene glycol, diethylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, diethylene glycol methyl ether, diethylene glycol monobutyl ether, Glycol monoether solvents such as ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether; ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, etc. Glycol diether solvents; glycol ether monoether ester solvents such as ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monobutyl ether acetate; 1,2-dimethyl-3-propylimidazolium Ionic liquids such as bis(trifluoromethylsulfonyl)imide; etc. can be mentioned. Moreover, water can also be used as a solvent if necessary.

When the pigment dispersion is used to prepare an ultraviolet curable ink, the solvent must be an ultraviolet/electron beam curable monomer or an ultraviolet/electron beam curable oligomer having one or more unsaturated bonds. is preferred. Since these solvents are cured by irradiation with ultraviolet rays or the like, they do not substantially contain volatile components such as organic solvents. Therefore, by using these solvents, it is possible to obtain a pigment dispersion liquid from which an environmentally friendly ink can be prepared.

Examples of the ultraviolet/electron beam curable monomer and oligomer include curing components such as monofunctional monomers, polyfunctional monomers, photocurable oligomers, and photocurable polymers. Monofunctional monomers include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, and hexyl (meth)acrylate. Acrylate, cyclohexyl (meth)acrylate, trimethylcyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, Isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, adamantyl (meth)acrylate, adamantylmethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl ( meth)acrylate, glycidyl(meth)acrylate, dimethylaminoethyl(meth)acrylate, diethylaminoethyl(meth)acrylate, polyethylene glycol mono(meth)acrylate, polyethylene glycol monomethyl ether(meth)acrylate, 2-ethoxyethyl(meth)acrylate , tetrahydrofurfuryl (meth)acrylate, allyl (meth)acrylate, vinyloxyethoxyethyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phthalic anhydride and 2-hydroxyethyl (meth)acrylate. Examples include adducts and radically polymerizable monomers such as acryloylmorpholine.

Polyfunctional monomers and photocurable oligomers include neopentyl glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, poly(n=2 or more) ethylene glycol di(meth)acrylate, polypropylene glycol(n=2 or more) ) di(meth)acrylate, polybutylene glycol (n=2 or more) di(meth)acrylate, 2,2-bis(4-(meth)acryloxyethoxyphenyl)propane, 2,2-bis(4-(meth) ) acryloxydiethoxyphenyl)propane, trimethylolpropane diacrylate, bis(2-(meth)acryloxyethyl)-hydroxyethyl-isocyanurate, trimethylolpropane tri(meth)acrylate, tris(2-(meth)acrylate) (oxyethyl) isocyanurate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, bisphenol Epoxy poly(meth)acrylate such as epoxy di(meth)acrylate made by reacting Type A diepoxy with (meth)acrylic acid, and 2-hydroxyethyl(meth)acrylate reacted with a trimer of 1,6-hexamethylene diisocyanate. urethane tri(meth)acrylate, urethane di(meth)acrylate obtained by reacting isophorone diisocyanate with 2-hydroxypropyl (meth)acrylate, urethane hexa(meth)acrylate obtained by reacting isophorone diisocyanate with pentaerythritol tri(meth)acrylate, Urethane di(meth)acrylate made by reacting dicyclohexyl diisocyanate and 2-hydroxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate is added to the urethane reaction product of dicyclohexyl diisocyanate and poly(n=6-15)tetramethylene glycol. Urethane poly(meth)acrylate such as reacted urethane di(meth)acrylate, polyester(meth)acrylate obtained by reacting trimethylolethane with succinic acid and (meth)acrylic acid, trimethylolpropane, succinic acid, and ethylene glycol. , and polyester poly(meth)acrylate such as polyester(meth)acrylate reacted with (meth)acrylic acid.

As photocurable polymers, multiple (meth)acryloyloxy groups, which are radically polymerizable groups, are introduced into the terminals or side chains of polymers such as poly(meth)acrylate, polyurethane, polyester, polyamide, polyimide, and polyepoxy resin. Examples include polymers such as Furthermore, a photocurable polymer having alkali developability and having a carboxyl group or the like introduced therein may also be used.

(Additive)
The pigment dispersion can contain various additives. Specific examples of additives include light stabilizers such as nitroxide compounds, antioxidants such as hindered phenols, dyes, optical brighteners, leveling agents to improve the physical properties and coatability of the coating, and antifoaming agents. , lubricant, thickener, antistatic agent, surfactant, silane coupling agent, antioxidant, anti-yellowing agent, bluing agent, infrared absorber, adhesion promoter, antifouling agent, water repellent, curing Examples thereof include a chemical catalyst, an inorganic filler such as silica, and fine metal particles.

Furthermore, the pigment dispersion may contain a photopolymerization initiator. As a photopolymerization initiator, benzoin, benzoin monomethyl ether, benzoin isopropyl ether, acetoin, benzyl, benzophenone, p-methoxybenzophenone, diethoxyacetophenone, benzyl dimethyl ketal, 2,2-diethoxyacetophenone, 1-hydroxycyclohexylphenyl ketone , methylphenylglyoxylate, carbonyl compounds such as 2-hydroxy-2-methyl-1-phenylpropan-1-one; sulfur compounds such as tetramethylthiuram monosulfide, tetramethylthiuram disulfide; 2,4,6-trimethyl Benzoyl diphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4 , 4-trimethyl-pentylphosphine oxide; 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone-1; camphorquinone; and the like.

A pigment dispersion can be prepared according to a conventionally known method. For example, the pigment dispersion of this embodiment can be prepared by using a solvent as a dispersion medium and dispersing the pigment in the solvent using a pigment dispersant. The content of the organic pigment in the pigment dispersant is preferably 1 to 30% by mass, more preferably 10 to 25% by mass. Further, the inorganic pigment content in the pigment dispersion is preferably 5 to 70% by mass, more preferably 30 to 50% by mass.

First, a mixture of pigment, pigment dispersant, and solvent is processed using a paint shaker, ball mill, attritor, sand mill, horizontal media mill, colloid mill, roll mill, etc. to finely disperse the pigment with a predetermined particle size. At the same time, a dispersion liquid adjusted to a predetermined liquid chromaticity is obtained. After that, it is preferable to remove coarse particles from the obtained dispersion using a centrifuge or a filter. Next, a pigment dispersion can be prepared by adding various additives as necessary.

The viscosity of the pigment dispersion may be adjusted to suit the properties of the pigment and the application method. The viscosity at 25° C. of a pigment dispersion using an organic pigment is preferably 2 to 100 mPa·s. Further, the viscosity at 25° C. of a pigment dispersion using an inorganic pigment is preferably 5 to 200 mPa·s.

The pigment dispersion of this embodiment is useful as a pigment dispersion in applications such as paints, gravure inks, coating agents, and stationery. In addition, in general formula (2), if the proportion of ethylene oxide (EO) in the methoxypolyalkylene glycol chain represented by "(R ₇ O) _m CH ₃ " is 50 mol% or more, the methoxypolyalkylene glycol chain Since the water solubility of the ink is improved, it can also be used in water-based inks.

<Ultraviolet curable ink>
The aforementioned pigment dispersants are preferably substantially free of volatile components. Therefore, the pigment dispersant of the present embodiment does not substantially contain volatile components and is useful as a material for constructing ultraviolet curable ink or electron beam curable ink in which most of the components form a coating film. . Moreover, when the pigment dispersant of this embodiment is used, the pigment can be stably and finely dispersed in a medium, and the resulting dispersion has high storage stability. Therefore, the pigment dispersant and pigment dispersion liquid of this embodiment are suitable as materials used in ultraviolet curable ink for inkjet. That is, the ultraviolet curable ink of this embodiment is an inkjet inkjet inkjet inkjet inkjet inkjet ink containing the above-mentioned pigment dispersion using an ultraviolet ray/electron beam curable monomer or an ultraviolet ray/electron beam curable oligomer as a solvent and which does not substantially contain volatile components. This is an ink for.

The ultraviolet curable ink of this embodiment contains a pigment dispersion, the above-mentioned photopolymerization initiator used as necessary, an ultraviolet/electron beam curable monomer, an ultraviolet/electron beam curable oligomer, and various additives. contains. After mixing and sufficiently stirring each component, an ultraviolet curable ink can be obtained by, for example, filtering the mixture with a filter if necessary. The content of the photopolymerization initiator in the ultraviolet curable ink is preferably 3 to 12% by mass. If the content of the photopolymerization initiator is less than 3% by mass, poor curing may occur. On the other hand, if the content of the photopolymerization initiator exceeds 12% by mass, an excessive amount of the photopolymerization initiator may remain or the image may be colored by the photopolymerization initiator.

By using the ultraviolet curable ink of this embodiment, various images (printed films) with high chroma and excellent durability such as color development, adhesion, and abrasion resistance can be created using general inkjet recording methods. It can be recorded (printed) on the base material. Examples of the substrate include paper, photographic paper, glossy photographic paper, plastic film, fabric, ceramics, metal, and the like.

Hereinafter, the present invention will be specifically explained based on Examples, but the present invention is not limited to these Examples. Note that "parts" and "%" in Examples and Comparative Examples are based on mass unless otherwise specified.

<Manufacture of pigment dispersant>
(Example 1)
In a reaction apparatus, 75 parts of cardanol novolak type polyepoxy resin (NC-547), one-end aminated polypropylene glycol polyethylene glycol monomethyl ether copolymer (trade name "Jeffamine M2005", manufactured by Huntsman, PPG/PEG = 29) /6 (molar ratio), measured amine value: 26.1 mgKOH/g, molecular weight calculated from amine value: 2,151) (M2005) 215 parts (0.1 mol) were added. As the cardanol novolak type polyepoxy resin, the trade name "Cardlite NC-547" (manufactured by Cardlite, epoxy equivalent: 750 g/mol) was used. Cardanol has a structure in which a pentadecyl group, 7-pentadecenyl group, 7,10-pentadecadienyl group, and 7,10,14-pentadecatrienyl group are bonded to the 4-position of the phenol skeleton. The mixture was heated to 80° C. while bubbling with nitrogen and reacted for 8 hours to obtain pigment dispersant NCA-1. A portion of the reaction solution was sampled and the infrared absorption spectrum (IR) was measured, and it was found that the absorption of epoxy groups (904 cm ^-1 ) had almost completely disappeared, and the absorption of hydroxyl groups (3,500 cm ^-1 ) had disappeared. It was confirmed that there was an increase. The number average molecular weight (Mn) of the pigment dispersant NCA-1 measured by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a developing solvent in terms of polystyrene is 2,700, and the degree of dispersion (PDI = weight average molecular weight) is 2,700. (Mw)/number average molecular weight (Mn)) was 6.13. Almost no peaks derived from NC-547 and M2005 used as raw materials were observed. The amine value of the pigment dispersant NCA-1 measured by an automatic potentiometric titrator using a 0.1 mol/L isopropanolic hydrochloric acid solution was 20.9 mgKOH/g. The solid content of the heated residue (measured using a moisture meter), which reached a constant weight at 180° C., was approximately 100%.

(Example 2 and 3)
Pigment dispersants NCA-2 and 3 were obtained in the same manner as in Example 1 above, except that the formulations shown in Table 1 were used. The meanings of the abbreviations in Table 1 are shown below.
・M1000: One-end aminated polypropylene glycol polyethylene glycol monomethyl ether copolymer, trade name "Jeffamine M1000", manufactured by Huntsman ・M41: one-end aminated polypropylene glycol polyethylene glycol monomethyl ether copolymer, trade name "Genamine M41"/2000'', manufactured by Clariant

(Example 4)
75 parts of NC-547, 158.2 parts (0.074 mol) of M41, and 2.67 parts (0.026 mol) of 3-dimethylaminopropylamine (DMAPA) were placed in the reactor. The reaction mixture was heated to 80° C. while bubbling nitrogen and reacted for 8 hours to obtain pigment dispersant NCA-4. A portion of the reaction solution was sampled and IR was measured, and it was confirmed that the absorption of epoxy groups had almost completely disappeared and that the absorption of hydroxyl groups had increased. The pigment dispersant NCA-4 measured by GPC had an Mn of 2,100 and a PDI of 4.09, and almost no peaks derived from NC-547 and M41 used as raw materials were observed. Further, the amine value of the pigment dispersant NCA-4 was 31.3 mgKOH/g, and the solid content was 99.3%.

(Examples 5 and 6)
Pigment dispersants NCA-5 and 6 were obtained in the same manner as in Example 4 above, except that the formulations shown in Table 2 were used. The meanings of the abbreviations in Table 2 are shown below.
・AEP: 2-(2-aminoethyl)pyridine ・API: 1-(3-aminopropyl)imidazole

(Comparative production example 1)
Into a reaction apparatus, 17.6 parts of a phenol novolac type polyepoxy resin (trade name "Araldite EPN 1180", manufactured by Huntsman, epoxy equivalent: 176 g/mol) (EPN1180) and 214 parts (0.1 mol) of M41 were placed. Ta. While bubbling nitrogen, the mixture was heated to 80°C and reacted for 8 hours to obtain pigment dispersant H-1. A portion of the reaction solution was sampled and IR was measured, and it was confirmed that the absorption of epoxy groups had almost completely disappeared and that the absorption of hydroxyl groups had increased. Pigment dispersant H-1 measured by GPC had an Mn of 1,800, a PDI of 4.22, and almost no peaks derived from EPN1180 and M41 used as raw materials were observed. Further, the amine value of pigment dispersant H-1 was 24.5 mgKOH/g, and the solid content was 99.5%.

(Comparative production example 2)
(a) Synthesis of acrylic polyepoxy compound 98.2 parts of propylene glycol monomethyl ether acetate (PGMAc) was charged into a reaction apparatus, heated to 65°C while bubbling with nitrogen, and then 2,2'-azobis(2 , 3.4 parts of 4-dimethylvaleronitrile (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) (V65) were added. Glycidyl methacrylate 51.2 parts (0.36 mol), styrene 37.5 parts (0.36 mol), and 1-thioglycerol (trade name "Blenmar TGL", manufactured by NOF Corporation) 4.3 parts (0.04 mol) A solution prepared by mixing was added dropwise over 1 hour. After polymerizing for 1 hour at 65°C, 0.9 part of V65 was added. Furthermore, after polymerizing at 65° C. for 2 hours, 0.9 part of V65 was added and polymerization was performed for 4 hours to obtain a PGMAc solution of an acrylic polyepoxy compound. When IR was measured, absorption of epoxy groups could be confirmed. The Mn of the acrylic polyepoxy compound measured by GPC was 2,800, and the PDI was 2.49. Further, the epoxy equivalent was 273 g/mol, and the solid content was 50.1%.

(b) Production of pigment dispersant A reaction apparatus was charged with 54.5 parts of a PGMAc solution of an acrylic polyepoxy compound, 0.1 part of 4-methoxyphenol, and 214 parts (0.1 mol) of M41. While bubbling nitrogen, the mixture was heated to 80°C and reacted for 8 hours to obtain pigment dispersant H-2. A portion of the reaction solution was sampled and IR was measured, and it was confirmed that the absorption of epoxy groups had almost completely disappeared and that the absorption of hydroxyl groups had increased. The Mn of pigment dispersant H-2 measured by GPC was 3,500, the PDI was 3.05, and almost no peaks derived from the acrylic polyepoxy compound used as a raw material and M41 were observed. Further, the amine value of pigment dispersant H-2 was 23.8 mgKOH/g, and the solid content was 89.8%.

<Production of pigment dispersion for ultraviolet curable ink>
(Examples 7 to 12, Comparative Examples 1 and 2)
The types and amounts of each component shown in Table 3 were blended. After stirring for 2 hours with a dissolver, it is dispersed using a horizontal media dispersion machine for use in ultraviolet curable inks of yellow (Y), magenta (M), cyan (C), and black (Bk) colors. A pigment dispersion was prepared. In Table 3, "Synergist 1", "Synergist 2", and "Synergist 3" are pigment derivatives having acidic groups represented by the following structural formulas (I) to (III), respectively. In Table 3, "PY-150" is Revasculin Yellow (manufactured by LANXESS), and "PR-122" and "PB-15:4" are both pigments manufactured by Dainichiseika Kagyo. In Table 3, "PEA" is 2-phenylethyl acrylate, and the carbon black used was the trade name "MB-1000" (manufactured by Mitsubishi Chemical Corporation).

<Evaluation of pigment dispersion>
The viscosity (initial viscosity) of the produced pigment dispersion and the particle diameter (initial particle diameter (median diameter; D ₅₀ )) of the pigment were measured. In addition, the viscosity after storing the pigment dispersion at 70° C. for one week (viscosity after storage) and the particle diameter of the pigment (particle diameter after storage (median diameter; D ₅₀ )) were measured. The measurement results are shown in Table 4. The particle size of the pigment was measured using a dynamic light scattering type particle size distribution measuring device (trade name "SZ-100", manufactured by Horiba, Ltd.).

As shown in Table 4, the M color pigment dispersion-3 produced in Comparative Example 2 showed some good dispersibility, but it contained PGMAc, which is a volatile component, and the volatile component was substantially removed. It is unsuitable as a pigment dispersion for ultraviolet curable ink containing no pigment.

<Preparation of ultraviolet curable ink>
(Examples 13 to 18, Comparative Example 3)
Using the types and amounts (parts) of each component shown in Table 5, an ultraviolet curing ink (pigment ink) for inkjet was prepared. Specifically, the types and amounts of each component shown in Table 5 were mixed, thoroughly stirred using a dissolver, and then filtered through a membrane filter with a pore size of 10 μm. It was further filtered through a 5 μm membrane filter to obtain a pigment ink. In Table 5, "Lucirin TPO", "Irgacure 819", and "Irgacure 127" are all trade names of photopolymerization initiators manufactured by BASF.

<Evaluation of ultraviolet curable ink>
The viscosity (initial viscosity) and pigment particle diameter (initial particle diameter (median diameter; D ₅₀ )) of the prepared ultraviolet curable ink (pigment ink) were measured. In addition, the viscosity of the pigment ink after it was stored at 70° C. for one week (viscosity after storage) and the particle size of the pigment (particle size (median diameter; D ₅₀ ) after storage) were measured. The measurement results are shown in Table 6.

<Example of ink usage>
(Usage examples 1 to 6)
The pigment inks of each color prepared in Examples 13 to 18 were filled into ink cartridges, and the cartridges were installed in an inkjet printer (trade name "EB100", manufactured by Konica Minolta, Inc.). Using this inkjet printer, a solid image was printed continuously for one hour on a polyethylene terephthalate (PET) film. As a result, no matter which pigment ink was used, printing could be performed smoothly without clogging the head. Furthermore, no problems such as streaks or twists occurred, and the discharge stability was good.

The pigment dispersant of the present invention is useful as a material for environmentally friendly ultraviolet curable inks, and is also useful as a pigment dispersion liquid for environmentally friendly printing inks, and is used in food packaging, electronic component packaging, and labels. It is suitable as a material for ink used in printing, etc.

Claims (9)

A pigment dispersant having a structure represented by the following general formula (1).

(In the general formula (1), R ₁ , R ₂ , and R ₃ are each independently a pentadecyl group, a 7-pentadecenyl group, a 7,10-pentadecadienyl group, or a 7,10,14- It represents a pentadecatrienyl group, and R ₄ , R ₅ , and R ₆ are each independently a hydrogen atom, a group represented by the following general formula (2), or a group represented by the following general formula (3). group, and one or more of R ₄ , R ₅ , and R ₆ is a group represented by the following general formula (2), and n represents a number from 1 to 10)

(In the general formula (2), * indicates a bonding position, R ₇ indicates an ethylene group or a methylethylene group, and m indicates a number from 14 to 68)

(In the general formula (3), * indicates a bonding position, A indicates an alkyl group, dialkylaminoalkyl group, pyridinyl alkyl group, imidazolylalkyl group, pyridinyl group, or imidazolyl group, and R ₈ is a hydrogen atom or alkyl group) A method for producing a pigment dispersant according to claim 1, comprising:
A method for producing a pigment dispersant, comprising a reaction step of reacting a polyepoxy compound represented by the following general formula (4) with a polyalkylene glycol monomethyl ether monoamine.

(In the general formula (4), R ₁ , R ₂ , and R ₃ are each independently a pentadecyl group, a 7-pentadecenyl group, a 7,10-pentadecadienyl group, or a 7,10,14- represents a pentadecatrienyl group, R ₉ , R ₁₀ , and _{R 11 each independently} represent a hydrogen atom or a 2,3-epoxypropyl group _; 1 or more is a 2,3-epoxypropyl group, and n represents a number from 1 to 10) The method for producing a pigment dispersant according to claim 2, wherein the compound represented by the general formula (4) is a formalin condensate of cardanol. The reaction step is a step of further reacting the polyepoxy compound with at least one amine compound selected from the group consisting of a primary organic amine, a secondary organic amine, and a polyamine compound,
The method for producing a pigment dispersant according to claim 2 or 3, wherein the polyamine compound is a compound having a primary amino group or a secondary amino group and a tertiary amino group. The polyamine compound is selected from the group consisting of dimethylaminopropylamine, diethylaminopropylamine, dibutylaminopropylamine, 4-aminopyridine, 4-(2-aminoethyl)pyridine, and 1-(3-aminopropyl)imidazole. The method for producing a pigment dispersant according to claim 4, which is at least one type of pigment dispersant. A pigment dispersion containing a pigment, a solvent, and a pigment dispersant for dispersing the pigment in the solvent,
A pigment dispersion, wherein the pigment dispersant is the pigment dispersant according to claim 1. The pigment dispersion according to claim 6, further comprising a pigment derivative having at least one acidic group selected from the group consisting of a carboxy group, a phosphoric acid group, and a sulfonic acid group. The pigment dispersion according to claim 6 or 7, wherein the solvent is an ultraviolet/electron beam curable monomer or an ultraviolet/electron beam curable oligomer having one or more unsaturated bonds. An ultraviolet curable ink for inkjet, comprising the pigment dispersion according to claim 8.