Pigment Dispersant Composition, Method for Producing the Same, Pigment Dispersion Liquid, and Actinic Energy Ray-Curable Inkjet Ink

Abstract

Provided is an environmentally conscious pigment dispersant composition that is relatively easy to manufacture. Although it contains a pigment dispersant having a structural unit mainly derived from a vinyl-based monomer, the content of volatile components is significantly reduced, and a pigment dispersion liquid and ink with excellent pigment dispersibility can be prepared. The pigment dispersant composition contains a polyglycol component and a polymer component. The polymer component has a structural unit (1) derived from a macromonomer represented by the general formula (1) (R represents a hydrogen atom or a methyl group, R1 represents CH2CH2 or CH2CH2OCH2CH2, m + n = 20 to 100) and a structural unit (2) derived from a functional group-containing vinyl-based monomer. The polyglycol component is a polyalkylene glycol or the like. Among them, the content of organic compounds having a boiling point of 250°C or lower is 1% by mass or less.

Description

Technical Field

[0001] The present invention relates to a pigment dispersant composition, a method for producing the same, a pigment dispersion, and an active energy ray-curable inkjet ink. Background Art

[0002] Products such as inks, paints, and coating agents are usually coating liquids containing organic solvents. Therefore, since the organic solvents volatilize after coating these products, there is a technical problem of high environmental load. To solve such a technical problem, environmentally conscious products that substantially do not contain organic solvents have been proposed. For example, aqueous coating liquids having water as a main medium, powder coatings based on colored resin powders, and the like. Further, coating liquids using vinyl-based, epoxy-based, or oxetane-based monomers instead of organic solvents, and active energy ray-curable inks such as ultraviolet-curable inks or electron beam-curable inks that form a coating film by polymerizing the monomers by heat or light after coating and substantially do not contain volatile components have also been proposed.

[0003] In recent years, an ultraviolet-curable inkjet ink (UVIJ ink) using a pigment as a colorant has been developed, which can use a packaging material or a container as a printing substrate, directly send an image from a personal computer, and obtain a printed matter with vivid colors on demand. In order to cope with high-speed printing, this UVIJ ink needs to improve characteristics such as ejection property and dispersion stability of the pigment. That is, a pigment dispersion for UVIJ ink in which the pigment is stably microdispersed is required.

[0004] To obtain such a pigment dispersion, in addition to low-molecular-weight pigment dispersants such as surfactants, polymer-type high-molecular-weight pigment dispersants are also used. Among them, from the viewpoint of improving the dispersibility and dispersion stability of the pigment, polymer-type pigment dispersants obtained by polymerizing vinyl-based monomers are frequently used. It should be noted that such polymer-type pigment dispersants are usually used in a state of a solution dissolved and diluted in an organic solvent (Patent Documents 1 and 2).

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2019-157077

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2013-177580 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] Since the pigment dispersion liquid prepared using the pigment dispersant proposed in Patent Documents 1 and 2 etc. contains an organic solvent, the UV ink prepared using this pigment dispersion liquid also contains an organic solvent. In order to obtain an environmentally conscious pigment dispersant that substantially does not contain volatile components such as organic solvents, an operation such as removing the organic solvent from the polymer solution obtained by solution polymerization etc. through distillation etc. is required. Therefore, there are defects such as the need for a process for removing the organic solvent etc., which complicates and makes the process cumbersome.

[0011] In addition, there are pigment dispersants such as polyesters and polyamides obtained by polymerization without using an organic solvent. However, it is difficult to polymerize and manufacture a pigment dispersant having a vinyl-based monomer as a main structural unit without using a liquid medium such as an organic solvent. Further, although polymerization can also be carried out in a state of 100% solid content, since a special kneader such as an extruder capable of withstanding high pressure and high temperature conditions is required, there is a problem of lack of versatility.

[0012] The present invention has been completed in view of these problems in the prior art, and the technical problem thereof is to provide an environmentally conscious pigment dispersant composition that is relatively easy to manufacture. Although this pigment dispersant composition contains a pigment dispersant having a structural unit derived from a vinyl-based monomer as a main body, the content of volatile components is significantly reduced, and a pigment dispersion liquid and an ink having excellent dispersibility of the pigment can be prepared. In addition, the technical problem of the present invention is to provide a method for manufacturing the above pigment dispersant composition, as well as a pigment dispersion liquid and an active energy ray-curable inkjet ink obtained using the above pigment dispersant composition.

[0013] Means for Solving the Problems

[0014] That is, according to the present invention, a pigment dispersant composition as shown below can be provided.

[0015] [1]A pigment dispersant composition containing a polyglycol component and a polymer component. The polyglycol component has at least one alkylene chain selected from the group consisting of CH2CH2, CH2CH(CH3), and CH2CH2CH2CH2, and has a molecular weight of 1000 or more and 4000 or less. The polymer component has 50 to 80% by mass of a structural unit (1) derived from a macromonomer having a molecular weight of 1000 to 4000 represented by the following general formula (1), 5 to 25% by mass of a structural unit (2) derived from at least one functional group-containing vinyl monomer selected from the group consisting of carboxyl group-containing vinyl monomers and amino group-containing vinyl monomers, and 0 to 45% by mass of a structural unit (3) derived from other monomers, and has a number average molecular weight of 5000 to 20000. The polyglycol component is at least one selected from the group consisting of polyalkylene glycol, polyalkylene glycol monoalkyl (1 to 18 carbon atoms) ether, and polyalkylene glycol dialkyl (1 to 4 carbon atoms) ether. In the pigment dispersant composition, the content of organic compounds having a boiling point of 250°C or lower is 1% by mass or less.

[0016]

[0017] (In the general formula (1), R represents a hydrogen atom or a methyl group, R1 represents CH2CH2 or CH2CH2OCH2CH2, and m + n = 20 to 100)

[0018] [2]The pigment dispersant composition according to [1] above, wherein, based on the total of the structural unit (1), the structural unit (2), and the structural unit (3), the polymer component further has a structural unit (4) derived from a chain transfer agent in an amount of 5% by mass or less.

[0019] [3]The pigment dispersant composition according to [2] above, wherein the chain transfer agent is at least one selected from the group consisting of iodine, dodecyl mercaptan, and thioglycerol, and based on the total of the structural unit (1), the structural unit (2), and the structural unit (3), the content of the structural unit (4) in the polymer component is 0.5 to 3% by mass.

[0020] [4] The pigment dispersant composition according to any one of [1] to [3] above, wherein the carboxyl group-containing vinyl monomer is at least one selected from the group consisting of (meth)acrylic acid, 2-(meth)acryloyloxyethyl succinate, 1-(meth)acryloyloxyphthalate, and 1-(meth)acryloyloxy-1,2,4-benzenetricarboxylate, the amino group-containing vinyl monomer is at least one selected from the group consisting of dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, 2-vinylpyridine, 4-vinylpyridine, and vinylimidazole, and the other monomer is α-methylstyrene.

[0021] [5] The pigment dispersant composition according to any one of [1] to [4] above, wherein the polyglycol component is a liquid having an oxypropylene unit content of 30% by mass or more and a viscosity at 25°C of 2 Pa·s or less.

[0022] In addition, according to the present invention, a method for producing the pigment dispersant composition shown below can be provided.

[0023] [6] A method for producing the pigment dispersant composition according to any one of [1] to [5] above, the method for producing the pigment dispersant composition comprising the following step: using the polyglycol component as a polymerization solvent, polymerizing a monomer component containing the macromonomer and the functional group-containing vinyl monomer in the presence of a radical initiator at a temperature of 50°C or higher.

[0024] Furthermore, according to the present invention, a pigment dispersion liquid and an active energy ray-curable inkjet ink shown below can be provided.

[0025] [7] A pigment dispersion liquid for producing an active energy ray-curable inkjet ink, the pigment dispersion liquid containing the pigment dispersant composition according to any one of [1] to [5] above, a pigment, and a photopolymerizable monomer.

[0026] [8] An active energy ray-curable inkjet ink containing the pigment dispersion liquid according to [7] above and a photoinitiator.

[0027] Effects of the Invention

[0028] According to the present invention, an environmentally conscious pigment dispersant composition that is relatively easy to manufacture can be provided. Although the pigment dispersant contains a structural unit derived from a vinyl monomer as a main component, the content of volatile components is significantly reduced, and a pigment dispersion liquid and an ink having excellent pigment dispersibility can be prepared. In addition, according to the present invention, a method for producing the above pigment dispersant composition, and a pigment dispersion liquid and an active energy ray-curable inkjet ink obtained by using the above pigment dispersant composition can be provided. Detailed Description

[0029] <Pigment Dispersant Composition>

[0030] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. One embodiment of the pigment dispersant composition of the present invention contains a polyglycol component having a molecular weight of 1000 or more and 4000 or less, and a polymer component having a number average molecular weight of 5000 to 20000. The polyglycol component is at least one selected from the group consisting of polyalkylene glycols, polyalkylene glycol monoalkyl (1 to 18 carbon atoms) ethers, and polyalkylene glycol dialkyl (1 to 4 carbon atoms) ethers having at least one alkylene chain selected from the group consisting of CH2CH2, CH2CH(CH3), and CH2CH2CH2CH2. In addition, the polymer component has structural units (1) derived from a macromonomer having a molecular weight of 1000 to 4000 represented by the following general formula (1) in an amount of 50 to 80% by mass, structural units (2) derived from at least one functional group-containing vinyl monomer selected from the group consisting of carboxyl group-containing vinyl monomers and amino group-containing vinyl monomers in an amount of 5 to 25% by mass, and structural units (3) derived from other monomers in an amount of 0 to 45% by mass. Moreover, in the pigment dispersant composition of the present embodiment, the content of organic compounds having a boiling point of 250°C or lower is 1% by mass or less, preferably 0.5% by mass or less. Hereinafter, the pigment dispersant composition of the present embodiment will be described in detail.

[0031]

[0032] (In the general formula (1), R represents a hydrogen atom or a methyl group, R1 represents CH2CH2 or CH2CH2OCH2CH2, and m + n = 20 to 100)

[0033] (Polyglycol Component)

[0034] The pigment dispersant composition of the present embodiment is a composition that can be obtained by polymerizing a specific monomer in a polyglycol component (hereinafter, also referred to as "polymer (1)") to form a polymer component (hereinafter, also referred to as "polymer (2)"), contains a polyglycol component and a polymer component that functions as a pigment dispersant, and preferably contains substantially only a polyglycol component and a polymer component. That is, the polyglycol component (polymer (1)) functions as a polymerization solvent, while improving the wettability of the pigment, the leveling property, the softness of the coating film, and the pigment dispersibility, and can function as a pigment dispersion aid. Since polymer (1) is a component that can also function as a polymerization solvent, it is preferably liquid in the range of room temperature (25 °C) to the polymerization temperature, and at the same time has a viscosity that is easily mixed and stirred even in a state containing the polymer component (polymer (2)). Specifically, the viscosity of polymer (1) at 25 °C is preferably 10 Pa·s or less.

[0035] Polymer (1) is a polyglycol component having at least one alkylene chain selected from the group consisting of CH2CH2, CH2CH(CH3), and CH2CH2CH2CH2, with a molecular weight of 1000 or more and 4000 or less, preferably 2000 to 3000. When the molecular weight of polymer (1) is less than 1000, there may be cases where volatile components with a small molecular weight are contained. On the other hand, when the molecular weight of polymer (1) is greater than 4000, there may be cases where the viscosity becomes too high, and at the same time, there may be cases where it does not become liquid in the range of room temperature (25 °C) to the polymerization temperature. The molecular weight of polymer (1) refers to the number average molecular weight calculated based on the hydroxyl value of polymer (1).

[0036] Polymer (1) is at least one selected from the group consisting of polyalkylene glycols, polyalkylene glycol monoalkyl (1 to 18 carbon atoms) ethers, and polyalkylene glycol dialkyl (1 to 4 carbon atoms) ethers. Examples of polyalkylene glycols include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene glycol-polypropylene glycol random copolymer, polyethylene glycol-polytetramethylene glycol random copolymer, polypropylene glycol-polytetramethylene glycol random copolymer, polyethylene glycol-polypropylene glycol-polytetramethylene glycol random copolymer, polyethylene glycol-polypropylene glycol block copolymer, polypropylene glycol-polyethylene glycol-polypropylene glycol triblock copolymer, polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer, etc.

[0037] The polyalkylene glycol monoalkyl (1 to 18 carbon atoms) ether is formed by etherifying the hydroxyl group at one end of the above polyalkylene glycol with an alkyl group having 1 to 18 carbon atoms. Examples of the alkyl group having 1 to 18 carbon atoms include methyl, ethyl, propyl, butyl, hexyl, octyl, 2-ethylhexyl, nonyl, decyl, dodecyl, hexadecyl, octadecyl, docosyl, etc.

[0038] The polyalkylene glycol dialkyl (1 to 4 carbon atoms) ether is formed by etherifying the hydroxyl groups at both ends of the above polyalkylene glycol with alkyl groups having 1 to 4 carbon atoms. The alkyl groups having 1 to 4 carbon atoms at both ends may be the same or different. Examples of the alkyl group having 1 to 4 carbon atoms include methyl, ethyl, propyl, butyl, etc.

[0039] The polyglycol component (polymer (1)) is preferably a liquid containing 30% by mass or more of oxypropylene units, more preferably a liquid containing 50 to 80% by mass. In addition, the polyglycol component (polymer (1)) is preferably a liquid having a viscosity of 2 Pa·s or less at 25°C, more preferably a liquid having a viscosity of 2 Pa·s or less. Since a polymer (1) having a large content of oxyethylene units or oxytetramethylene units is likely to be cured, there is a tendency for the processability to deteriorate. On the other hand, since a polymer (1) having a large content of oxypropylene units is not easily cured, it is easily in a liquid state even at room temperature and has excellent processability. The viscosity of the polyglycol component (polymer (1)) at 25°C is a value measured by using a B-type viscometer and a rotor matching the viscosity.

[0040] The polymer (1) can be produced by a conventionally known method. For example, by using a pressure-resistant container, etc., in the presence of an initiator and a catalyst, monomers such as ethylene oxide, propylene oxide, and tetrahydrofuran are polymerized while cooling at room temperature (25°C) to 200°C, and the polymer (1) can be obtained. As the initiator, ethylene glycol, propylene glycol, etc. can be used. As the catalyst, alkali metals such as sodium hydroxide and potassium methoxide can be used.

[0041] (Polymer component)

[0042] The polymer component (polymer (2)) is a component that functions as a pigment dispersant for dispersing pigments in a liquid medium, and has structural units (1) derived from the macromonomer represented by the general formula (1) in an amount of 50 to 80% by mass, preferably 55 to 75% by mass. Since the polymer (2) contains a large amount of structural units (1) derived from a macromonomer having a structure similar to that of the polymer (1), it is easily compatible with the polymer (1), and a pigment dispersant composition in the form of a uniform mixed solution can be prepared. In addition, the polymer (2) includes a main chain having a functional group such as a carboxyl group or an amino group, and a graft chain formed by structural units (1) derived from the macromonomer grafted to the main chain. The main chain having a functional group adsorbs on the pigment, and at the same time, the graft chain dissolves in the dispersion medium, thereby repelling the pigment particles and improving the storage stability of the pigment dispersion, ink, etc. In addition, since the polymer (2) contains a large amount of structural units (1) derived from the macromonomer, the density of the graft chain is high, and the dispersion stability of the pigment can be improved by steric repulsion.

[0043] The macromonomer is a monomer represented by the following general formula (1) with a molecular weight of 1,000 to 4,000, preferably a molecular weight of 2,000 to 3,500.

[0044]

[0045] (In the general formula (1), R represents a hydrogen atom or a methyl group, R1 represents CH2CH2 or CH2CH2OCH2CH2, and m + n = 20 to 100)

[0046] In the general formula (1), m + n = 20 to 100, preferably m + n = 30 to 75. When the value of m + n is less than 20, sufficient steric hindrance cannot be obtained, and it is difficult to improve the dispersion stability of the pigment. On the other hand, when the value of m + n is greater than 100, due to the excessive molecular weight, the viscosity of the pigment dispersant composition or the pigment dispersion obtained using the same is likely to increase excessively, and the processability will decrease. The ratio of m to n is not particularly limited, and preferably satisfies the relationship of m > n, that is, relatively more oxypropylene units are contained. Since the macromonomer satisfying the relationship of m > n is likely to be liquid, the processability will be improved.

[0047] The macromonomer can be produced by a conventionally known method. For example, it can be produced by reacting a (meth)acrylate monomer having an isocyanate group with a polyalkylene glycol monomethyl ether having an amino group at one end. Examples of the (meth)acrylate monomer having an isocyanate group include acryloyloxyethyl isocyanate, methacryloyloxyethyl isocyanate, acryloyloxyethoxyethyl isocyanate, methacryloyloxyethoxyethyl isocyanate, and the like. Since the resulting macromonomer will substantially contain no low-boiling solvent, the above reaction is preferably carried out under solvent-free conditions.

[0048] The polymer (2) has a structural unit (2) derived from at least one functional group-containing vinyl-based monomer selected from the group consisting of a carboxyl group-containing vinyl-based monomer and an amino group-containing vinyl-based monomer in an amount of 5 to 25% by mass, preferably 10 to 20% by mass. The polymer chain having a functional group containing this structural unit (2) is adsorbed on the pigment particles to be dispersed. When the content of the structural unit (2) in the polymer (2) is less than 5% by mass, the amount of the functional group is insufficient, and the adsorption property to the pigment will decrease. On the other hand, when the content of the structural unit (2) in the polymer (2) is greater than 25% by mass, due to the excessive amount of the functional group, the chemical resistance such as water resistance, acid / alkali resistance, etc. will decrease.

[0049] Examples of the carboxyl group-containing vinyl-based monomers include vinylbenzoic acid, (meth)acrylic acid, acrylic acid dimer, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxypropyl succinate, 2-(meth)acryloyloxybutyl phthalate, 2-(meth)acryloyloxyethyl maleate, 1-(meth)acryloyloxyphthalate, 1-(meth)acryloyloxy-1,2,4-benzenetricarboxylate, 1-(meth)acryloyloxy-1,2,4-naphthalenetricarboxylate, and the like. Among them, from the viewpoints of versatility, ease of acquisition / synthesis, and affinity with pigments, as the carboxyl group-containing vinyl-based monomers, (meth)acrylic acid, 2-(meth)acryloyloxyethyl succinate, 1-(meth)acryloyloxyphthalate, and 1-(meth)acryloyloxy-1,2,4-benzenetricarboxylate are preferred.

[0050] Examples of the amino group-containing vinyl-based monomers include dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, tert-butylaminoethyl (meth)acrylate, 2-vinylpyridine, 4-vinylpyridine, vinylimidazole, dimethylaminopropyl (meth)acrylamide, and the like. Among them, from the viewpoints of versatility, ease of acquisition / synthesis, and affinity with pigments, as the amino group-containing vinyl-based monomers, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, 2-vinylpyridine, 4-vinylpyridine, and vinylimidazole are preferred.

[0051] As the functional group-containing vinyl-based monomers, only the carboxyl group-containing vinyl-based monomers may be used, or only the amino group-containing vinyl-based monomers may be used. Further, the carboxyl group-containing vinyl-based monomers and the amino group-containing vinyl-based monomers may be used in combination.

[0052] The polymer (2) preferably has structural units (3) derived from other monomers other than the macromonomer and the functional group-containing vinyl monomer in an amount of 0 to 45% by mass, more preferably 5 to 40% by mass. Examples of other monomers include monofunctional (meth)acrylates having substituents such as methyl, ethyl, propyl, butyl, pentyl, 2-ethylhexyl, isooctyl, nonyl, dodecyl, hexadecyl, octadecyl, isostearyl, docosyl, cyclohexyl, trimethylcyclohexyl, tert-butylcyclohexyl, benzyl, methoxyethyl, butoxyethyl, phenoxyethyl, nonylphenoxyethyl, glycidyl, isobornyl, dicyclopentanyl, dicyclopentenyl, dicyclopentenyl oxyethyl, 2-hydroxyethyl, 2-hydroxypropyl, 4-hydroxybutyl; polymer-type (meth)acrylates of macromonomers such as poly(n≥2)alkylene (2 to 4 carbon atoms) glycol mono(meth)acrylate, poly(n≥2)alkylene (2 to 4 carbon atoms) glycol monoalkyl (1 to 22 carbon atoms) mono(meth)acrylate, poly(n≥2)hydroxyalkanoic acid (5 to 18 carbon atoms) mono(meth)acrylate; vinyl monomers such as styrene, vinyltoluene, vinylpyridine, vinylcaprolactone, α-methylstyrene, 2,4-diphenyl-1-butene, 2,4-diphenyl-4-methyl-1-pentene, vinyl acetate, etc.

[0053] When using the polymer (1) as a polymerization solvent and polymerizing specific monomers in the polymer (1) to synthesize the polymer (2), if the molecular weight of the resulting polymer (2) is too large, the viscosity of the obtained pigment dispersant composition becomes too high and it is sometimes prone to curing. In addition, there are also cases where the polymerization rate is too fast, low molecular weight monomers polymerize preferentially, and macromonomers are likely to remain. Here, when using α-methylstyrene as other monomers, it is preferred because the polymerizability can be appropriately suppressed and controlled.

[0054] When polymerizing the polymer (2), it is preferred to use a chain transfer agent. By using a chain transfer agent, the polymerization reaction can be controlled and the excessive increase in the molecular weight of the resulting polymer (2) can be suppressed.

[0055] As the chain transfer agent, conventionally known chain transfer agents can be used. Examples of chain transfer agents include thiol compounds such as hydroxyethyl mercaptan, octyl mercaptan, dodecyl mercaptan, stearyl mercaptan, thiodiglycerol; α-substituted acrylate compounds such as bromomethyl acrylate, ethyl bromomethyl acrylate, ethyl benzyl methacrylate; halogen compounds such as trichloroiodomethane, iodine; trithiocarbonates such as S,S-dibenzyl trithiocarbonate, methyl cyanoisopropyl trithiocarbonate; thioesters such as 2-cyanopropyl dithiobenzoate. Among them, iodine, dodecane mercaptan, and thiodiglycerol with weak odor and high boiling point are preferred.

[0056] When polymerizing the polymer (2), by using a chain transfer agent, the polymer (2) will contain a structural unit (4) derived from the chain transfer agent. Based on the total of the structural unit (1), the structural unit (2), and the structural unit (3), the content of the structural unit (4) in the polymer (2) is preferably 5% by mass or less, more preferably 0.5 to 3% by mass, and particularly preferably 1 to 2.5% by mass. When the content of the structural unit (4) derived from the chain transfer agent in the polymer (2) is excessive, the molecular weight of the polymer (2) may become too small. In addition, odor or coloring may tend to occur.

[0057] The number average molecular weight of the polymer component (polymer (2)) is 5,000 to 20,000, preferably 7,000 to 15,000. When the number average molecular weight of the polymer (2) is less than 5,000, the dispersion stability of the pigment may be insufficient. On the other hand, when the number average molecular weight of the polymer (2) is greater than 20,000, the viscosity of the pigment dispersant composition or the pigment dispersion may become too high, and the processability may deteriorate. The number average molecular weight of the polymer (2) is a value in terms of polystyrene measured by gel permeation chromatography (GPC). It should be noted that the content of the polymer component (polymer (2)) in the pigment dispersant composition is preferably 30 to 70% by mass, more preferably 40 to 70% by mass.

[0058] <Method for producing pigment dispersant composition>

[0059] One embodiment of the method for producing the pigment dispersant composition of the present invention is a method for producing the pigment dispersant composition in which the content of an organic compound having a boiling point of 250°C or lower is 1% by mass or less, preferably substantially free, and includes the following step (polymerization step): using a polyglycol component (polymer (1)) as a polymerization solvent, polymerizing a monomer component containing a macromonomer and a functional group-containing vinyl monomer in the presence of a radical initiator at a temperature of 50°C or higher.

[0060] In the polymerization step, using the polymer (1) as a polymerization solvent, polymerize a monomer component containing a macromonomer and a functional group-containing vinyl monomer. By polymerizing the monomer component, a polymer component (polymer (2)) is formed, and a target pigment dispersant composition containing the polymer (1) and the polymer (2) and having a content of an organic compound having a boiling point of 250°C or lower of 1% by mass or less can be obtained. As the monomer component, other monomers or a chain transfer agent can be used as needed. It should be noted that the polymerization reaction system containing the polymer (1) as a polymerization solvent and the monomer component is in a liquid state.

[0061] As a radical initiator, an azo-based radical initiator such as azobisisobutyronitrile; peroxides such as benzoyl peroxide, etc. can be used. The reaction solution containing the polymer (1), the monomer component, and the radical initiator is heated to a temperature above the decomposition temperature of the radical initiator and a temperature at which the reaction solution can be easily stirred, specifically, heated to 50 °C or higher for polymerization. When the temperature during polymerization is less than 50 °C, since the decomposition rate of the radical initiator becomes slow, the molecular weight of the obtained polymer component (polymer (2)) becomes too large, and at the same time, the monomer component is likely to remain. In addition, sometimes the viscosity of the reaction solution is too high and it is difficult to stir. The temperature during polymerization is preferably set to 60 to 100 °C.

[0062] The content of the monomer component in the reaction solution is preferably set to 30 to 70% by mass, and more preferably set to 40 to 70% by mass. By setting the content of the monomer component in the reaction solution within the above range, it is easy to effectively stir the reaction solution, and at the same time, the amount of the remaining monomer component can be reduced.

[0063] Among the components that may be contained in the obtained pigment dispersant composition, a part of the residual monomer belongs to organic compounds having a boiling point of 250 °C or lower. In the manufacturing method of the pigment dispersant composition of the present embodiment, control is performed so that the polymerization reaction proceeds sufficiently, and no organic compounds having a boiling point of 250 °C or lower such as residual monomers remain. For example, the polymerization reaction can be carried out while monitoring the amount of the residual monomer in the reaction solution by gas chromatography (GC) or the like. Thereby, a target pigment dispersant composition with the content of organic compounds having a boiling point of 250 °C or lower reduced as much as possible can be obtained. It should be noted that when the polymer (1) and the polymer (2) are water-soluble polymers, the pigment dispersant composition can also be diluted with water. Thereby, an environmentally friendly aqueous pigment dispersant composition that substantially does not contain organic compounds having a boiling point of 250 °C or lower can be prepared.

[0064] The pigment dispersant composition of the present embodiment is useful as a pigment dispersant for manufacturing various products such as coatings, inks such as aqueous inkjet inks, gravure inks, coating agents, etc. Among them, since it substantially does not contain volatile components, the pigment dispersant composition of the present embodiment is suitable as a pigment dispersant for manufacturing active energy ray-curable inks such as ultraviolet-curable inks or electron beam-curable inks that all become coating film components. In particular, since it can finely disperse the pigment and has high storage stability, the pigment dispersant composition of the present embodiment is suitable as a pigment dispersant for manufacturing active energy ray-curable inkjet inks.

[0065] <Pigment dispersion liquid>

[0066] The pigment dispersion liquid as an embodiment of the present invention is a pigment dispersion liquid for manufacturing an active energy ray-curable inkjet ink, and contains the pigment dispersant composition, a pigment, and a photopolymerizable monomer.

[0067] As the pigment, in terms of the Color Index (C.I.) number, examples include 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, etc.

[0068] Among them, from the viewpoints of color rendering property, dispersibility, weather resistance, etc., yellow pigments such as C.I. Pigment Yellow 74, 83, 109, 128, 139, 150, 151, 154, 155, 180, 181, 185, etc.; red pigments such as C.I. Pigment Red 122, 170, 176, 177, 185, 269, C.I. Pigment Violet 19, 23, etc.; blue pigments such as C.I. Pigment Blue 15:3, 15:4, 15:6, etc.; black pigments such as C.I. Pigment Black 7, etc.; white pigments such as C.I. Pigment White 6, etc. are suitable as pigments for inkjet ink.

[0069] The pigment can be an untreated pigment, a self-dispersing pigment with functional groups introduced on its surface, or a treated pigment whose surface has been treated with a surface treatment agent such as a coupling agent or an active agent, or a polymer, or a capsuleized pigment. Additionally, except in cases where hiding power is required, organic particulate pigments are preferred. Further, when recording a high-definition and highly transparent image, it is preferable to use pigments that have been micronized by wet grinding such as salt grinding or dry grinding. Considering avoiding nozzle clogging during printing, etc., it is preferable to use pigments from which large particles with a particle size greater than 1.0 μm have been removed, and whose average particle size is 0.2 μm or less, or 0.4 μm or less in the case of inorganic pigments.

[0070] As the photopolymerizable monomer, curing components such as monofunctional monomers, polyfunctional monomers, photocurable oligomers, and photocurable polymers can be used. Examples of monofunctional monomers include (meth)acrylic acid methyl ester, (meth)acrylic acid ethyl ester, (meth)acrylic acid butyl ester, (meth)acrylic acid n-butyl ester, (meth)acrylic acid isobutyl ester, (meth)acrylic acid tert-butyl ester, (meth)acrylic acid hexyl ester, (meth)acrylic acid cyclohexyl ester, (meth)acrylic acid trimethylcyclohexyl ester, (meth)acrylic acid tert-butylcyclohexyl ester, (meth)acrylic acid 2-ethylhexyl ester, (meth)acrylic acid isodecyl ester, (meth)acrylic acid lauryl ester, (meth)acrylic acid stearyl ester, (meth)acrylic acid isobornyl ester, (meth)acrylic acid dicyclopentenyl ester, (meth)acrylic acid adamantyl ester, (meth)acrylic acid adamantyl methyl ester, (meth)acrylic acid 2-hydroxyethyl ester, (meth)acrylic acid 2-hydroxypropyl ester, (meth)acrylic acid 4-hydroxybutyl ester, (meth)acrylic acid glycidyl ester, (meth)acrylic acid dimethylaminoethyl ester, (meth)acrylic acid diethylaminoethyl ester, polyethylene glycol mono(meth)acrylate, polyethylene glycol monomethyl ether (meth)acrylate, (meth)acrylic acid 2-ethoxyethyl ester, (meth)acrylic acid tetrahydrofurfuryl ester, (meth)acrylic acid allyl ester, (meth)acrylic acid vinyloxyethoxyethyl ester, (meth)acrylic acid benzyl ester, (meth)acrylic acid phenoxyethyl ester, an adduct of phthalic anhydride and (meth)acrylic acid 2-hydroxyethyl ester, acryloylmorpholine, and other free-radical polymerizable monomers.

[0071] Examples of the polyfunctional monomer and the photocurable oligomer include neopentyl glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, poly(n ≥ 2)ethylene glycol di(meth)acrylate, polypropylene glycol (n ≥ 2) di(meth)acrylate, polybutylene glycol (n ≥ 2) di(meth)acrylate, 2,2-bis(4-(meth)acryloyloxyethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxydiethoxyphenyl)propane, trimethylolpropane diacrylate, bis(2-(meth)acryloyloxyethyl)-hydroxyethyl-isocyanurate, trimethylolpropane tri(meth)acrylate, tris(2-(meth)acryloyloxyethyl) isocyanurate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, epoxy poly(meth)acrylate such as epoxy di(meth)acrylate obtained by reacting bisphenol A type diepoxide with (meth)acrylic acid, urethane tri(meth)acrylate obtained by reacting 2-hydroxyethyl (meth)acrylate with a trimer of 1,6-hexamethylene diisocyanate, 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 obtained by reacting dicyclohexyl diisocyanate with 2-hydroxyethyl (meth)acrylate, urethane poly(meth)acrylate such as urethane di(meth)acrylate obtained by reacting 2-hydroxyethyl (meth)acrylate with a urethanized product of dicyclohexyl diisocyanate and poly(n = 6 - 15) tetramethylene glycol, polyester poly(meth)acrylate such as polyester (meth)acrylate obtained by reacting trimethylolethane with succinic acid and (meth)acrylic acid, polyester poly(meth)acrylate such as polyester (meth)acrylate obtained by reacting trimethylolpropane with succinic acid, ethylene glycol and (meth)acrylic acid, and the like.

[0072] Examples of the photocurable polymer include polymers in which a plurality of (meth)acryloyloxy groups as free radical polymerizable groups are introduced into the terminals or side chains of polymers such as poly(meth)acrylate, polyurethane, polyester, polyamide, polyimide, and polyepoxy resin. Further, a photocurable polymer having alkali developability such as a polymer having a carboxyl group or the like can also be used.

[0073] Regarding the content of the pigment in the pigment dispersion, when it is an organic pigment, it is preferably 1 to 30% by mass, more preferably 10 to 25% by mass. In addition, when it is an inorganic pigment, it is preferably 5 to 70% by mass, more preferably 30 to 50% by mass. In the pigment dispersion, the content of the polymer component (polymer (2)) is preferably 5 to 100 parts by mass, more preferably 7.5 to 50 parts by mass, relative to 100 parts by mass of the pigment. When the content of the polymer (2) is less than 5 parts by mass relative to 100 parts by mass of the pigment, the dispersion stability of the pigment may sometimes become insufficient. On the other hand, when the content of the polymer (2) is greater than 100 parts by mass relative to 100 parts by mass of the pigment, the viscosity tends to increase excessively, and at the same time, the ejectability of the inkjet ink is likely to decrease, and the physical properties or durability of the formed coating film may sometimes decrease.

[0074] The pigment dispersion of the present embodiment can be produced by a conventionally known method. For example, a mixture containing a pigment, a pigment dispersant composition, and a photopolymerizable monomer can be added to a paint mixer, a ball mill, a grinder, a sand mill, a horizontal media mill, a colloid mill, a roll mill, etc. to finely disperse the pigment, thereby preparing the pigment dispersion. It should be noted that it is preferable to remove coarse particles using a centrifuge or a filter. If necessary, other additives can also be added.

[0075] The viscosity of the pigment dispersion can be appropriately adjusted in consideration of the properties of the pigment, the viscosity of the active energy ray-curable inkjet ink to be produced, etc. Specifically, when using an organic pigment, the viscosity of the pigment dispersion is preferably 2 to 50 mPa·s. In addition, when using an inorganic pigment, the viscosity of the pigment dispersion is preferably 5 to 100 mPa·s.

[0076] <Active energy ray-curable inkjet ink>

[0077] The active energy ray-curable inkjet ink (hereinafter, also simply referred to as "ink") according to an embodiment of the present invention contains the above-mentioned pigment dispersion and a photoinitiator.

[0078] Examples of the photopolymerization initiator include carbonyl compounds such as benzoin, benzoin monomethyl ether, benzoin isopropyl ether, acetone, benzil, benzophenone, p-methoxybenzophenone, diethoxyacetophenone, benzil dimethyl ketal, 2,2 - diethoxyacetophenone, 1 - hydroxycyclohexyl phenyl ketone, methyl benzoylformate, 2 - hydroxy - 2 - methyl - 1 - phenylpropan - 1 - one; sulfur compounds such as tetramethylthiuram monosulfide and tetramethylthiuram disulfide; phosphoric acid compounds such as 2,4,6 - trimethylbenzoyl diphenylphosphine oxide, 2,4,6 - trimethylbenzoyl phenylethoxyphosphine 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)butan - 1 - one; camphorquinone, etc. The type of the photopolymerization initiator can be selected according to the wavelength of the irradiated light.

[0079] The ink may further contain components other than the pigment dispersion and the photopolymerization initiator (other additives). Examples of the other additives include light stabilizers such as nitroxide radical compounds, antioxidants such as hindered phenols, dyes, fluorescent brighteners, leveling agents, defoaming agents, lubricants, tackifiers, antistatic agents, surfactants, silane coupling agents, yellowing inhibitors, bluing agents, infrared absorbers, adhesion promoters, antifouling agents, water repellents, curable catalysts, inorganic fillers such as silica, and metal fine particles. However, it is preferable not to use organic compounds having a boiling point of 250 °C or lower as the other additives.

[0080] Examples

[0081] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. It should be noted that, unless otherwise specified, "parts" and "%" in the examples and comparative examples are based on mass.

[0082] <Manufacture of Pigment Dispersant Composition>

[0083] (Example 1)

[0084] (a) Synthesis of Macromonomer

[0085] 100 parts (0.05 mol) of a mono - terminal amino - modified polypropylene glycol polyethylene glycol (PPG / PEG) monomethyl ether copolymer (trade name “JEFFAMINE M2005”, manufactured by Huntsman Corporation, amine value (measured value) 28.05 mgKOH / g) (M2005) was added to a reaction vessel. While cooling 7.76 parts (0.05 mol) of 2 - isocyanatoethyl methacrylate (trade name “Karenz MOI”, manufactured by Showa Denko K.K.) (MOI) with water, it was added dropwise into the reaction vessel over 30 minutes. After the dropwise addition, a part of the reaction solution was sampled, and by infrared spectroscopy (IR), it was confirmed that the isocyanate groups derived from MOI almost completely disappeared and urea bonds were formed. Thus, it was confirmed that the macromonomer MA - 1 shown by the general formula (1) was formed. The number - average molecular weight (Mn) of the macromonomer MA - 1 in terms of polystyrene measured by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as the developing solvent was 3500, and the dispersity (PDI = Mw (weight - average molecular weight) / Mn (number - average molecular weight)) was 1.19. In addition, the amine value of the macromonomer MA - 1 could not be measured by an automatic potentiometric titrator using a 0.1 mol / L 2 - propanol hydrochloric acid solution.

[0086] (b) Synthesis of pigment dispersant (polymer (2))

[0087] 139.6 parts of a polypropylene glycol polyethylene glycol monobutyl ether copolymer (trade name “UNILUBE50MB - 11”, manufactured by NOF Corporation, hydroxyl value 56.1 mgKOH / g, molecular weight calculated from the hydroxyl value 1000) (50MB - 11), 20.0 parts of methyl methacrylate (MMA), 10.0 parts of methacrylic acid (MAA), and 1.5 parts of 1 - thioglycerol (TGL) were added to the above - mentioned reaction vessel. After heating to 70 °C while bubbling nitrogen, 0.2 part of 2,2’ - azobis(isobutyronitrile) (trade name “V - 601”, manufactured by FUJIFILM Wako Pure Chemical Corporation) (V - 601) was added and polymerization was carried out for 4 hours. Further, 0.1 part of V - 601 was added and polymerization was carried out at 70 °C for 4 hours to form the polymer (2) as a pigment dispersant, and a pigment dispersant composition COV - 1 with a content of the pigment dispersant (polymer (2)) of 50% was obtained. The Mn of the formed polymer (2) was 13500 and the PDI was 2.10. The contents of the residual monomers (MMA, MAA) quantified by headspace - gas chromatography - mass spectrometry (HS - GCMS) were both less than 0.2%, and the content of other organic compounds with a boiling point of 250 °C or lower was less than 0.1%. The residual monomers were quantified by the measurement method based on ISO17895 related to the measurement of volatile organic compounds in coatings. The acid value of the polymer (2) measured by neutralization titration using a 0.1 mol / L ethanolic potassium hydroxide solution was 46.5 mgKOH / g.

[0088] (Examples 2 to 5)

[0089] Except for using the compounding shown in Table 1, pigment dispersant compositions COV-2 to 5 were obtained in the same manner as in Example 1. For any of the pigment dispersant compositions, it was confirmed that the content of organic compounds having a boiling point of 250°C or lower was 1% or less. The meanings of the abbreviations in Table 1 are as follows.

[0090] ·MB-38: Polypropylene glycol monobutyl ether, trade name "UNILUBE MB-38", manufactured by NOF Corporation

[0091] ·DMPEG: Dimethyl polyethylene glycol

[0092] ·STE: Polypropylene glycol polyethylene glycol monostearyl ether, trade name "BLAUNON SA-30 / 702000R", manufactured by Aoki Yushi Co., Ltd.

[0093] ·50MB-72: Polypropylene glycol polyethylene glycol monobutyl ether, trade name "UNILUBE50MB-72", manufactured by NOF Corporation

[0094] ·M41: Mono-terminally amino-modified polypropylene glycol polyethylene glycol monomethyl ether copolymer, trade name "Genamin M41 / 2000", manufactured by Clariant Ltd.

[0095] ·BzMA: Benzyl methacrylate

[0096] ·CHMA: Cyclohexyl methacrylate

[0097] ·HOMS: 2-Methacryloyloxyethyl succinate

[0098] ·PAMA: 1-Methacryloyloxyethyl phthalate

[0099] ·TMA: Addition reaction product of trimellitic anhydride and 2-hydroxyethyl methacrylate

[0100] Table 1

[0101]

[0102] (Comparative Examples 1 and 2)

[0103] Except for using the compounding shown in Table 2, pigment dispersant compositions H-1 and H-2 were obtained in the same manner as in Example 1. For any of the pigment dispersant compositions, it was confirmed that the content of organic compounds having a boiling point of 250°C or lower was 1% or less. The meanings of the abbreviations in Table 2 are as follows.

[0104] ·DMFDG: Dipropylene Glycol Ether Dimethyl Ether, manufactured by Nippon Emulsifier Co., Ltd.

[0105] Table 2

[0106]

[0107] (Example 6)

[0108] Synthesize the macromonomer MA-1 in the same manner as in Example 1. Subsequently, add 159.6 parts of 50MB-11, 15.0 parts of MMA, 35.0 parts of 2-(dimethylamino)ethyl methacrylate (DMAEMA), and 1.5 parts of α-methylstyrene (αMS) to the reaction vessel. After heating to 70 °C while bubbling nitrogen, add 0.2 part of V-601 and polymerize for 4 hours. Further add 0.1 part of V-601 and polymerize at 70 °C for 4 hours to form the polymer (2) as a pigment dispersant, and obtain the pigment dispersant composition COV-6 with a content of the pigment dispersant (polymer (2)) of 50%. The Mn of the formed polymer (2) is 9500, the PDI is 1.91, and the amine value is 78.4 mgKOH / g. In addition, confirm that the content of the organic compound with a boiling point of 250 °C or lower is 1% or less.

[0109] (Example 7)

[0110] (a) Synthesis of Macromonomer

[0111] Add 100 parts (0.05 mol) of M2005 to the reaction vessel. Add 148.3 parts of polyethylene glycol monolauryl ether (trade name “BLAUNON EL-1530”, manufactured by Aoki Yushi Co., Ltd., molecular weight approximately 1500) (EL1530) heated to melt it, stir to homogenize it, and then cool to room temperature. While cooling 7.76 parts (0.05 mol) of MOI with water, add it dropwise to the reaction vessel over 30 minutes. After the dropwise addition, take a part of the reaction solution as a sample, and confirm by IR that the isocyanate groups derived from MOI have almost completely disappeared and a urethane bond has been formed. Thus, confirm that the macromonomer MA-4 represented by the general formula (1) has been formed. The Mn of the macromonomer MA-4 is 3300, the PDI is 1.15, and the amine value could not be measured.

[0112] (b) Synthesis of Pigment Dispersant (Polymer (2))

[0113] 15.0 parts of MMA, 35.0 parts of DEAEMA, and 1.5 parts of α-MS were added to the above reaction vessel. After heating to 70 °C while bubbling nitrogen, 0.2 parts of V-601 was added and polymerization was carried out for 4 hours. Further, 0.1 part of V-601 was added and polymerization was carried out at 70 °C for 4 hours to form a polymer (2) as a pigment dispersant, and a pigment dispersant composition COV-7 having a content of the pigment dispersant (polymer (2)) of 50% was obtained. The Mn of the formed polymer (2) was 8700, the PDI was 1.88, and the amine value was 49.0 mgKOH / g. In addition, it was confirmed that the content of organic compounds having a boiling point of 250 °C or lower was 1% or less.

[0114] (Examples 8 to 10)

[0115] Except for using the compounding shown in Table 3, the pigment dispersant compositions COV-8 to 10 were obtained in the same manner as in Example 6. For any of the pigment dispersant compositions, it was confirmed that the content of organic compounds having a boiling point of 250 °C or lower was 1% or less. The meanings of the abbreviations in Table 3 are as follows.

[0116] ·MB-370: Polypropylene glycol monobutyl ether, trade name "UNILUBE MB-370", manufactured by NOF Corporation

[0117] ·D-1200: Polypropylene glycol, trade name "UNIOL D-1200", manufactured by NOF Corporation

[0118] ·50MB-26: Polypropylene glycol polyethylene glycol monobutyl ether, trade name "UNILUBE 50MB-26", manufactured by NOF Corporation

[0119] ·EHMA: 2-Ethylhexyl methacrylate

[0120] ·2-VP: 2-Vinylpyridine

[0121] ·4-VP: 4-Vinylpyridine

[0122] ·1-VI: 1-Vinylimidazole

[0123] Table 3

[0124]

[0125] (Comparative Examples 3 and 4)

[0126] Except for using the compounding shown in Table 4, the pigment dispersant compositions H-3 and H-4 were obtained in the same manner as in Example 6. For any of the pigment dispersant compositions, it was confirmed that the content of organic compounds having a boiling point of 250 °C or lower was 1% or less. The meanings of the abbreviations in Table 4 are as follows.

[0127] · M600: Mono - terminal amino - modified polypropylene glycol polyethylene glycol monomethyl ether copolymer, trade name "JEFFAMINE M600", manufactured by Huntsman Corporation

[0128] Table 4

[0129]

[0130] <Pigment dispersion liquid for ultraviolet - curable inkjet ink>

[0131] (Examples 11 - 15, Comparative Examples 5 and 6)

[0132] (a) Preparation of pigment dispersion liquid

[0133] Mix the components of the types and amounts (parts) shown in Table 5 and stir with a dissolution device for 2 hours. After confirming that there are no pigment lumps, perform a dispersion treatment using a horizontal media disperser to prepare pigment dispersion liquids of various colors (yellow (Y), magenta (M), cyan (C), black (Bk), and white (W)). In Table 5, "Synergist 1", "Synergist 2", and "Synergist 3" are pigment derivatives with basic groups represented by the following formulas (I) - (III) respectively. In addition, the meanings of the abbreviations in Table 5 are as follows.

[0134] · PY - 150: Trade name " Yellow", manufactured by LANXESS

[0135] · PR - 122: Manufactured by Dainichi Seika Kogyo Co., Ltd.

[0136] · PB - 15:4: Manufactured by Dainichi Seika Kogyo Co., Ltd.

[0137] · Carbon black: MB - 1000, manufactured by Mitsubishi Chemical Corporation

[0138] · Titanium oxide: Trade name "JR - 405", manufactured by TAYCA Co., Ltd.

[0139] · BzA: Benzyl acrylate

[0140] · IBXA: Isobornyl acrylate

[0141] · PEA: 2 - Phenylethyl acrylate

[0142] · TBCHA: 4 - tert - Butylcyclohexyl acrylate

[0143]

[0144] Table 5 (unit: parts)

[0145]

[0146] (b) Evaluation of the pigment dispersion

[0147] Measure the initial particle size of the pigment in the pigment dispersion and the initial viscosity of the pigment dispersion. In addition, store the pigment dispersion at 70 °C for 1 week, and measure the particle size of the pigment and the viscosity of the pigment dispersion after storage. The results are shown in Table 6. The particle size of the pigment was measured using a dynamic light scattering particle size distribution tester (trade name "SZ-100", manufactured by HORIBA) as the median particle size (D 50 ).

[0148] Table 6

[0149]

[0150] Put the W-color pigment dispersion-1 prepared in Example 15 into a light-shielded glass bottle and store it in a constant temperature bath set at 60 °C for 1 month. The particle size of the pigment in the pigment dispersion after storage was 237 nm, and the viscosity of the pigment dispersion after storage was 42.1 mPa·s. From this, it can be seen that after storage, the physical properties hardly changed, and a high degree of dispersion stability was maintained. In addition, almost no supernatant was observed in the pigment dispersion after storage. It should be noted that although a very small amount of slightly viscous sediment was confirmed, after shaking, it returned to the state of the original pigment dispersion. The particle size of the pigment in the pigment dispersion after shaking was 240 nm. From the above, it can be seen that although the particle size of the pigment increased slightly due to sedimentation, the sediment was easily redispersed and returned to a good dispersion state.

[0151] (Examples 16 to 20, Comparative Examples 7 and 8)

[0152] (a) Preparation of the pigment dispersion

[0153] Except for using the types and amounts (parts) of each component shown in Table 7, prepare the pigment dispersions of each color in the same manner as in Examples 11 to 15 and Comparative Examples 5 and 6. In Table 7, "Synergist 4", "Synergist 5", and "Synergist 6" are pigment derivatives having acidic groups represented by the following formulas (IV) to (VI), respectively.

[0154]

[0155] Table 7 (unit: part)

[0156]

[0157] (b) Evaluation of the pigment dispersion

[0158] Measure the initial particle size of the pigment in the pigment dispersion and the initial viscosity of the pigment dispersion. In addition, store the pigment dispersion at 70 °C for 1 week, and measure the particle size of the pigment and the viscosity of the pigment dispersion after storage. The results are shown in Table 8.

[0159] Table 8

[0160]

[0161] <UV-curable inkjet ink>

[0162] (Examples 21 to 25, Comparative Example 9)

[0163] Mix the components of the types and amounts (parts) shown in Formulation Table 9, and stir well using a dissolution apparatus. Filter successively through membrane filters with pore sizes of 10 μm and 5 μm to obtain a UV-curable inkjet ink. In Table 9, “Lucirin TPO”, “Irgacure819”, and “Irgacure 127” are all trade names of photoinitiators manufactured by BASF Corporation. None of the inks were gelled or sedimented.

[0164] Formulation Table 9 (unit: part)

[0165]

[0166] (Examples 26 to 30)

[0167] Except for using the components of the types and amounts (parts) shown in Formulation Table 10, obtain a UV-curable inkjet ink in the same manner as in Examples 21 to 25 and Comparative Example 9. None of the inks were gelled or sedimented.

[0168] Formulation Table 10 (unit: part)

[0169]

[0170] <Evaluation of UV-curable inkjet ink>

[0171] Fill the prepared various inks into ink cartridges respectively, and install them in an inkjet printer (trade name “EB100”, manufactured by KonicaMinolta, Inc.). Using this inkjet printer, print a solid image continuously on a polyethylene terephthalate (PET) film for 1 hour. As a result, none of the inks clogged the nozzles of the recording head, and printing was carried out smoothly. In addition, no streaks or misregistration were observed at all, and the ejection stability was good.

[0172] In addition, using the above inkjet printer, solid images were also printed on a surface-treated polypropylene (OPP) film. Further, ultraviolet rays were irradiated onto the images printed on the PET film and the OPP film using a UV lamp to cure the coating films, thereby obtaining cured images of various colors. A transparent tape (trade name "Cellulose Tape (registered trademark)", manufactured by NICHIBAN) was firmly pressed onto the cured images of various colors and then peeled off. The peelability of the images was visually observed, and the adhesion of the images was evaluated according to the evaluation criteria shown below. The results are shown in Table 11.

[0173] ◎: The image was not peeled off at all.

[0174] ○: The image was slightly peeled off.

[0175] △: The peeled area was smaller than the unpeeled area.

[0176] ×: The peeled area was larger than the unpeeled area.

[0177] Table 11

[0178]

[0179] Industrial Applicability

[0180] The pigment dispersant composition and the pigment dispersion of the present invention are useful as materials for preparing a pigment dispersion for an environmentally conscious active energy ray-curable inkjet ink. In addition, the active energy ray-curable inkjet ink of the present invention is suitable as an ink for printing food packaging, electronic component packaging, labels, and the like.

Claims

1. A pigment dispersant composition containing a polyglycol component and a polymer component, The polyglycol component has at least one alkylene chain selected from the group consisting of CH2CH2, CH2CH(CH3), and CH2CH2CH2CH2, and has a molecular weight of 1000 or more and 4000 or less; The polymer component has 50 to 80% by mass of a structural unit (1) derived from a macromonomer having a molecular weight of 1000 to 4000 represented by the following general formula (1), 5 to 25% by mass of a structural unit (2) derived from at least one functional group-containing vinyl monomer selected from the group consisting of a carboxyl group-containing vinyl monomer and an amino group-containing vinyl monomer, and 0 to 45% by mass of a structural unit (3) derived from other monomers, and has a number average molecular weight of 5000 to 20000; The polyglycol component is at least one selected from the group consisting of polyalkylene glycol, polyalkylene glycol monoalkyl ether, and polyalkylene glycol dialkyl ether, wherein, In the polyalkylene glycol monoalkyl ether, the number of carbon atoms of the monoalkyl group is 1 to 18, and in the polyalkylene glycol dialkyl ether, the number of carbon atoms of the dialkyl group is 1 to 4. The carboxyl group-containing vinyl monomer is selected from any one or more of the group consisting of vinyl benzoic acid, (meth)acrylic acid, acrylic acid dimer, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxypropyl succinate, 2-(meth)acryloyloxybutyl phthalate, 2-(meth)acryloyloxyethyl maleate, 1-(meth)acryloyloxyphthalate, 1-(meth)acryloyloxy-1,2,4-benzenetricarboxylate, and 1-(meth)acryloyloxy-1,2,4-naphthalenetricarboxylate; The other monomer is one or more selected from the group consisting of a monofunctional (meth)acrylate having a substituent, a polymeric (meth)acrylate, and a vinyl monomer; In the pigment dispersant composition, the content of an organic compound having a boiling point of 250°C or lower is 1% by mass or less. In the general formula (1), R represents a hydrogen atom or a methyl group, R1 represents CH2CH2 or CH2CH2OCH2CH2, and m + n = 20 to 100.

2. The pigment dispersant composition according to claim 1, wherein, Based on the sum of the structural unit (1), the structural unit (2), and the structural unit (3), the polymer component further has a structural unit (4) derived from a chain transfer agent in an amount of 5% by mass or less.

3. The pigment dispersant composition according to claim 2, wherein, The chain transfer agent is at least one selected from the group consisting of iodine, dodecyl mercaptan, and thioglycerol. Based on the sum of the structural unit (1), the structural unit (2), and the structural unit (3), the content of the structural unit (4) in the polymer component is 0.5 to 3% by mass.

4. The pigment dispersant composition according to any one of claims 1 to 3, wherein, The carboxyl group-containing vinyl monomer is at least one selected from the group consisting of (meth)acrylic acid, 2-(meth)acryloyloxyethyl succinate, 1-(meth)acryloyloxyphthalate, and 1-(meth)acryloyloxy-1,2,4-benzenetricarboxylate; The amino group-containing vinyl monomer is at least one selected from the group consisting of dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, 2-vinylpyridine, 4-vinylpyridine, and vinylimidazole. The other monomer is α-methylstyrene.

5. The pigment dispersant composition according to any one of claims 1 to 3, wherein, The polyglycol component is a liquid containing 30% by mass or more of oxypropylene units and having a viscosity of 2 Pa·s or less at 25°C.

6. The pigment dispersant composition according to claim 4, wherein The polyglycol component is a liquid containing 30% by mass or more of oxypropylene units and having a viscosity of 2 Pa·s or less at 25°C.

7. A method for producing a pigment dispersant composition according to any one of claims 1 to 6, the method for producing the pigment dispersant composition comprising the following steps: Using the polyglycol component as a polymerization solvent, polymerizing a monomer component containing the macromonomer and the functional group-containing vinyl monomer in the presence of a radical initiator at a temperature of 50°C or higher.

8. A pigment dispersion for producing an active energy ray-curable inkjet ink The pigment dispersion contains the pigment dispersant composition according to any one of claims 1 to 6, a pigment, and a photopolymerizable monomer.

9. An active energy ray-curable inkjet ink containing the pigment dispersion according to claim 8 and a photoinitiator.

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