Resin particle dispersion

Abstract

To provide a resin particle dispersion capable of creating a printed material with superior finger rub resistance even upon printing on substrates with low water absorption, a water-based ink comprising the resin particle dispersion, and a method for producing the resin particle dispersion.SOLUTION: The present invention provides [1] a resin particle dispersion comprising resin particles dispersed in a water-based medium, wherein the resin particles comprise (A) a copolymer comprising a constitutional unit derived from (a-1) a (meth)acrylate which is an ester of a C6-7 alcohol and (meth)acrylic acid and a constitutional unit derived from (a-2) a (meth)acrylamide monomer, and a carboxy group-terminated butadiene / acrylonitrile copolymer (B), [2] a water-based ink comprising the resin particle dispersion set forth in [1], and [3] a method for producing the resin particle dispersion set forth in [1].SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a resin particle dispersion. [Background technology]

[0002] In today's printing industry, there is a growing awareness of working environments, printing environments, and workplace environments, leading to a demand for water-based inks, where water accounts for the largest proportion of the vehicle component, from the perspectives of low odor and safety. However, for low-water-absorbent printing substrates such as resin films, further improvements in print quality are required. In particular, there is a need to improve the adhesion between the ink film formed by water-based ink and the printing substrate. To meet these demands, water-based inks containing resin particles have been proposed.

[0003] For example, Patent Document 1 discloses a resin particle dispersion containing core-shell type resin particles and water, for the purpose of providing a resin particle dispersion that can be used as an aqueous ink with excellent substrate adhesion, etc., wherein the shell resin of the core-shell type resin particles contains constituent units derived from a specific (meth)acrylic acid ester, the core resin of the core-shell type resin particles contains a specific amount of constituent units derived from a specific acrylamide monomer, and the glass transition temperature of the core resin and the acid value of the core-shell type resin particles are within a specific range. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-84977 [Overview of the project] [Problems that the invention aims to solve]

[0005] Patent Document 1 states that printed materials printed on a polyolefin resin film substrate exhibit excellent adhesion to the substrate as determined by tape peeling tests. However, Patent Document 1 revealed that while the adhesion to the substrate improved in tape peeling tests, the durability of the ink coating against finger rubbing (hereinafter also referred to as "finger rubbing durability") was insufficient, especially when printing on low-water-absorbent printing substrates such as polyolefin resin films. Therefore, in recent years, there has been a demand for products with excellent finger rubbing durability. The present invention aims to provide a resin particle dispersion, a water-based ink containing the resin particle dispersion, and a method for producing the resin particle dispersion, which enable the production of printed materials with excellent finger-rubbing resistance even when printed on low-water-absorbent printing substrates. [Means for solving the problem]

[0006] The present inventors have found that the above problem can be solved by a resin particle dispersion in which resin particles are dispersed in an aqueous medium, wherein the resin particles are copolymers containing structural units derived from (meth)acrylic acid esters, which are esters of a C6 or C7 alcohol and (meth)acrylic acid, and structural units derived from (meth)acrylamide monomers, and resin particle dispersions containing carboxy-terminated butadiene / acrylonitrile copolymers.

[0007] In other words, the present invention provides the following [1] to [3]. [1] A resin particle dispersion in which resin particles are dispersed in an aqueous medium, A resin particle dispersion comprising a copolymer (A) containing structural units derived from a (meth)acrylic acid ester (a-1), which is an ester of a carbon-6 or carbon-7 alcohol with (meth)acrylic acid, and structural units derived from a (meth)acrylamide monomer (a-2), and a carboxyl-terminated butadiene / acrylonitrile copolymer (B). [2] A water-based ink containing the resin particle dispersion described in [1] above. [3] A method for producing a resin particle dispersion as described in [1] above, A method for producing a resin particle dispersion, comprising the step of adding an aqueous medium to an organic solvent solution containing copolymer (A) and copolymer (B) to perform phase inversion emulsification. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a resin particle dispersion, a water-based ink containing the resin particle dispersion, and a method for producing the resin particle dispersion, which enable the production of printed materials with excellent finger-rubbing durability even when printing on low-water-absorbent printing substrates. [Modes for carrying out the invention]

[0009] [Resin particle dispersion] The resin particle dispersion of the present invention is a resin particle dispersion in which resin particles are dispersed in an aqueous medium, wherein the resin particles contain a copolymer (A) comprising structural units derived from (meth)acrylic acid ester (a-1), which is an ester of a carbon-6 or carbon-7 alcohol and (meth)acrylic acid, and structural units derived from (meth)acrylamide monomer (a-2), and a carboxyl-terminated butadiene / acrylonitrile copolymer (B). In the present invention, "aqueous medium" means a liquid component contained in a resin particle dispersion in which water accounts for the largest proportion by mass. Furthermore, "water-based ink" means that water accounts for the largest proportion by mass of the liquid components contained in the ink. In the present invention, "(meth)acrylic acid" refers to acrylic acid and / or methacrylic acid, and "(meth)acrylamide monomer" refers to a monomer having an acrylamide structure and / or a monomer having a methacrylamide structure. Furthermore, "low water absorption" is a concept that includes both low water absorption and non-water absorption, and the amount of water absorbed by the printing substrate during a contact time of 100 milliseconds with pure water is 0 g / m². 2 More than 10g / m 2 This means the following: Furthermore, "high water absorption" means that the amount of water absorbed by the printing substrate during a 100 m / s contact time with pure water is 10 g / m². 2 It means "super." The resin particle dispersion of the present invention can be used as a water-based ink to obtain printed materials with excellent finger-rubbing resistance, and can be further used as a water-based ink for printing, particularly for gravure printing and inkjet printing, by adding pigments or the like. Furthermore, if the resin particle dispersion of the present invention does not contain pigments, it can be used as a clear ink.

[0010] According to the present invention, even when printing on low-water-absorbent printing substrates, it is possible to obtain printed materials with excellent finger-rubbing resistance, which is a remarkable effect. The reason for this is not entirely clear, but it is presumed to be as follows. In the present invention, by including a monomer component (meth)acrylic acid ester (a-1) of copolymer (A) that contains a group derived from an alcohol having 6 or 7 carbon atoms, and by including a structural unit derived from acrylonitrile in copolymer (B), a resin particle dispersion with good dispersibility can be obtained. Furthermore, the resin particles according to the present invention contain a copolymer (A) that includes constituent units derived from a (meth)acrylamide monomer (a-2) having an amide structure. Since the amide structure has a large dipole moment, it exhibits strong cohesive force (intermolecular interaction) between the resin particles, resulting in an ink coating that can resist strong peeling forces. Therefore, it is believed that the resistance to physical deformation of low water-absorbent printing substrates can be improved, and the durability against finger rubbing can be enhanced. Furthermore, the resin particles according to the present invention also contain a carboxyl-terminated butadiene / acrylonitrile copolymer (B). Copolymer (B) has a form in which acrylonitrile is copolymerized with butadiene, and since this acrylonitrile also has a large dipole moment, it is thought to contribute to improved finger-rubbing durability, similar to the constituent units derived from (meth)acrylamide monomer (a-2). However, it is also presumed that a high level of interaction is exhibited between copolymer (A) and the constituent units derived from (meth)acrylamide monomer (a-2), and it is thought that the synergistic effect of these is what results in excellent finger-rubbing durability. In addition, copolymer (B) can also exhibit good flexibility because the constituent units derived from butadiene act as sites that can exhibit flexibility, and it is thought that this can improve finger-rubbing durability by flexibly deflecting the stress acting on the ink coating film.

[0011] <Resin particles> The resin particles contained in the resin particle dispersion of the present invention include a copolymer (A) (hereinafter also simply referred to as "polymer (A)") comprising structural units derived from an ester (a-1) of an alcohol having 6 or 7 carbon atoms and (meth)acrylic acid (hereinafter also simply referred to as "(meth)acrylic acid ester (a-1)") and structural units derived from a (meth)acrylamide monomer (a-2), and a carboxyl-terminated butadiene / acrylonitrile copolymer (B) (hereinafter also simply referred to as "polymer (B)").

[0012] [Copolymer (A)] The copolymer (A) according to the present invention comprises a structural unit derived from an ester (a-1) of an alcohol having 6 or 7 carbon atoms and (meth)acrylic acid, and a structural unit derived from a (meth)acrylamide monomer (a-2), and preferably a vinyl polymer comprising a structural unit derived from an ester (a-1) of an alcohol having 6 or 7 carbon atoms and (meth)acrylic acid, and a structural unit derived from a (meth)acrylamide monomer (a-2).

[0013] ((meth)acrylic acid ester (a-1)) (Meta)acrylic acid ester (a-1) is not particularly limited as long as it is an ester composed of an alcohol having 6 or 7 carbon atoms and (meta)acrylic acid. In the present invention, the alcohol having 6 or 7 carbon atoms that constitutes the (meta)acrylic acid ester (a-1) may have other functional groups containing heteroatoms such as oxygen and nitrogen. When the alcohol has other functional groups containing heteroatoms, the carbon atoms of the other functional groups containing heteroatoms are also included in the carbon number of the alcohol. In the present invention, from the viewpoint of the finger-rubbing durability of the printed matter, it is preferable that the alcohol does not have other functional groups containing heteroatoms.

[0014] (Meta)acrylic acid ester (a-1) may have any of a linear structure, a branched structure, and a cyclic structure. The cyclic structure may be either an alicyclic structure or an aromatic ring structure. Among these, from the viewpoint of improving the finger-rubbing durability of the obtained printed matter, the alcohol preferably has a cyclic structure. Further, the alcohol having 6 or 7 carbon atoms that constitutes the (meta)acrylic acid ester (a-1) may be any of a primary alcohol, a secondary alcohol, and a tertiary alcohol. Among these, the alcohol having 6 or 7 carbon atoms that constitutes the (meta)acrylic acid ester (a-1) is preferably one or more selected from the group consisting of primary alcohols and secondary alcohols. Examples of the alcohol having 6 or 7 carbon atoms that constitutes the (meta)acrylic acid ester (a-1) preferably include those having an n-hexyl group, an n-heptyl group, a 4-methyl-2-pentyl group, a cyclohexyl group, a 4-methylcyclohexyl group, a hexahydrobenzyl group, or a benzyl group. Among these, the alcohol having 6 or 7 carbon atoms that constitutes the (meta)acrylic acid ester (a-1) more preferably has a cyclohexyl group or a benzyl group. (Meta)acrylic acid ester (a-1) can be used alone or in combination of two or more.

[0015] As (meth)acrylic acid ester (a-1), one or more selected from the group consisting of n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, 4-methyl-2-pentyl (meth)acrylate, cyclohexyl (meth)acrylate, 4-methylcyclohexyl (meth)acrylate, hexahydrobenzyl (meth)acrylate, and benzyl (meth)acrylate are preferred. Among these, from the viewpoint of improving the finger-rubbing durability of the resulting printed material, one or more selected from the group consisting of cyclohexyl (meth)acrylate and benzyl (meth)acrylate are preferred. The content of constituent units derived from (meth)acrylic acid ester (a-1) in copolymer (A) according to the present invention is preferably 30% by mass or more, more preferably 45% by mass or more, even more preferably 55% by mass or more, and preferably 75% by mass or less, more preferably 70% by mass or less, and even more preferably 67% by mass or less, from the viewpoint of increasing the affinity of copolymer (A) to copolymer (B), ensuring good dispersibility of resin particles, and improving the finger-rubbing durability of the resulting printed material.

[0016] ((meth)acrylamide monomer (a-2)) There are no particular restrictions on the (meth)acrylamide monomer (a-2), but from the viewpoint of improving the finger-rubbing durability of printed materials, the solubility parameter (hereinafter also referred to as "SP value") of the (meth)acrylamide monomer (a-2) should be 17 (MPa). 0.5 The above is 23 MPa. 0.5 The following is preferable: When the SP value of the (meth)acrylamide monomer (a-2) is within this range, it is thought that it imparts appropriate polarity to copolymer (A), and through the interaction between copolymer (A) and copolymer (B), the interaction between resin particles containing copolymer (A) and copolymer (B) and resin film, particularly polyolefin resin film, can be made to be well expressed, thereby improving the finger-rubbing durability of printed materials. In this invention, the solubility parameter (SP value) is the Hansen solubility parameter (HSP value), and the value calculated using the calculation software "Hansen Solubility Parameter in Practice (HSPiP) Version 5.2.02" is used. The unit of the solubility parameter in this invention is "(MPa) 0.5 "

[0017] Examples of (meth)acrylamide monomers (a-2) include N-tert-octylacrylamide (SP value: 17.9), N-dodecylacrylamide (SP value: 18.5), N-(2-ethylhexyl)acrylamide (SP value: 19.4), Nn-octylacrylamide (SP value: 19.8), N-tert-butylacrylamide (SP value: 20.2), Nn-heptylacrylamide (SP value: 20.3), and N-hexylacrylamide (S Examples include N-alkyl(meth)acrylamides having linear, branched, or cyclic alkyl groups such as N-cyclohexylmethacrylamide (SP value: 20.6); aromatic group-containing (meth)acrylamides such as N,N-dibenzylacrylamide (SP value: 20.4); N-alkoxymethyl(meth)acrylamides such as N-isobutoxymethylacrylamide (SP value: 20.8); and diacetone acrylamide (SP value: 22.0). Among these, (meth)acrylamide monomer (a-2) is preferably one or more selected from the group consisting of N-alkyl(meth)acrylamide and diacetone acrylamide having a linear, branched, or cyclic alkyl group, more preferably one or more selected from the group consisting of N-alkyl(meth)acrylamide and diacetone acrylamide having a branched alkyl group, and even more preferably one or more selected from the group consisting of N-tert-octylacrylamide, N-tert-butylacrylamide, and diacetone acrylamide, in order to improve the interaction between copolymer (A) and copolymer (B) and improve the finger-rubbing durability of printed materials. (Meth)acrylamide monomers (a-2) can be used individually or in combination of two or more.

[0018] The content of constituent units derived from (meth)acrylamide monomer (a-2) in copolymer (A) is preferably 5% by mass or more, more preferably 8% by mass or more, even more preferably 10% by mass or more, even more preferably 15% by mass or more, and preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 23% by mass or less, from the viewpoint of increasing affinity with copolymer (B) constituting the resin particles, ensuring good dispersibility of the resin particles, and improving the finger-rubbing durability of the resulting printed material.

[0019] (Ionic monomer (a-3)) From the viewpoint of ensuring good dispersibility of resin particles and improving the finger-rubbing durability of the resulting printed material, copolymer (A) preferably further contains structural units derived from ionic monomer (a-3) in addition to structural units derived from (meth)acrylic acid ester (a-1) and structural units derived from (meth)acrylamide monomer (a-2), and more preferably copolymer (A) is a vinyl polymer having structural units derived from (meth)acrylic acid ester (a-1), structural units derived from (meth)acrylamide monomer (a-2), and structural units derived from ionic monomer (a-3). Examples of ionic monomers (a-3) include anionic monomers and cationic monomers, with anionic monomers being preferred. Examples of anionic monomers include carboxylic acid monomers, sulfonic acid monomers, and phosphate monomers. Among these, carboxylic acid monomers are more preferred as ionic monomers (a-3) from the viewpoint of improving the dispersibility of resin particles. Examples of carboxylic acid monomers include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethylsuccinic acid, but one or more selected from the group consisting of acrylic acid and methacrylic acid are preferred, with acrylic acid being more preferred.

[0020] The content of constituent units derived from ionic monomer (a-3) in copolymer (A) is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 13% by mass or more, even more preferably 15% by mass or more, and preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 32% by mass or less, from the viewpoint of ensuring good dispersibility of resin particles and improving the finger-rubbing durability of the resulting printed material.

[0021] Copolymer (A) may contain other monomers other than (meth)acrylic acid ester (a-1), (meth)acrylamide monomer (a-2), and ionic monomer (a-3), as long as the effects of the present invention are not impaired. Specific examples of such other monomers include esters of (meth)acrylic acid with alcohols other than C6 or C7 alcohols; aromatic compounds having addition polymerizable functional groups such as styrene; vinyl esters such as vinyl acetate; and compounds with an SP value of 17 (MPa). 0.5 Less than or 23 (MPa) 0.5 Examples include (meth)acrylamide monomers exceeding [a certain value].

[0022] The content of constituent units derived from monomers other than (meth)acrylic acid ester (a-1), (meth)acrylamide monomer (a-2), and ionic monomer (a-3) in copolymer (A) is preferably 50% by mass or less, more preferably 25% by mass or less, even more preferably 10% by mass or less, even more preferably 5% by mass or less, even more preferably 1% by mass or less, and even more preferably substantially 0% by mass. Here, "substantially 0% by mass" means that it is permissible for the copolymer (A) to contain impurity components present in the (meth)acrylic acid ester (a-1), (meth)acrylamide monomer (a-2), and ionic monomer (a-3).

[0023] The weight-average molecular weight of copolymer (A) is preferably 5,000 or more, more preferably 7,000 or more, and even more preferably 9,000 or more, from the viewpoint of ensuring good dispersibility of resin particles and improving the finger-rubbing durability of the resulting printed material, and also preferably 50,000 or less, more preferably 30,000 or less, even more preferably 25,000 or less, and even more preferably 20,000 or less, from the same viewpoint as above. The weight-average molecular weight of copolymer (A) can be measured by the method described in the examples.

[0024] The acid value of copolymer (A) is preferably 100 mg KOH / g or more, more preferably 130 mg KOH / g or more, even more preferably 150 mg KOH / g or more, from the viewpoint of ensuring good dispersibility of resin particles and improving the finger-rubbing durability of the resulting printed material, and also preferably 360 mg KOH / g or less, more preferably 300 mg KOH / g or less, even more preferably 270 mg KOH / g or less, and even more preferably 250 mg KOH / g or less. The acid value of copolymer (A) can be calculated from the mass ratio of its constituent monomers.

[0025] The method for producing copolymer (A) is not particularly limited, and copolymer (A) can be obtained by polymerizing the raw material monomers (a) that constitute copolymer (A) by any known polymerization method. Among these, solution polymerization is preferred. There are no restrictions on the organic solvent used in solution polymerization, but polar organic solvents such as aliphatic alcohols with 1 to 3 carbon atoms, ketones with 3 to 8 carbon atoms, ethers, and esters are preferred. Specific examples of polar organic solvents include methanol, ethanol, acetone, and methyl ethyl ketone, with methyl ethyl ketone being more preferred among these. Polymerization initiators and polymerization chain transfer agents can be used during polymerization. Azo compounds are preferred as polymerization initiators, with 4,4'-azobis(4-cyanovaleric acid) and 2,2'-azobis(2,4-dimethylvaleronitrile) being more preferred. Mercaptans are preferred as polymerization chain transfer agents, with 3-mercaptopropionic acid and 2-mercaptoethanol being more preferred. The preferred polymerization conditions vary depending on the type of polymerization initiator, but a polymerization temperature of 50°C to 90°C is preferred. Furthermore, the polymerization atmosphere is preferably an inert gas atmosphere such as nitrogen gas or argon. After the polymerization reaction is complete, the resulting copolymer (A) can be isolated from the reaction solution by known methods such as reprecipitation and solvent removal. Furthermore, the obtained copolymer (A) can be isolated by reprecipitation and membrane separation. Unreacted monomers and other substances can be removed by separation, chromatography, extraction, etc. From the viewpoint of improving the productivity of resin particle dispersions, it is preferable to use copolymer (A) as a solution of copolymer (A) without removing the solvent used in the polymerization reaction.

[0026] [Carboxyterminated butadiene / acrylonitrile copolymer (B)] The resin particles contained in the resin particle dispersion of the present invention contain copolymer (A) and a carboxy-terminated butadiene / acrylonitrile copolymer (B) (polymer (B)). Copolymer (B) is a copolymer of butadiene and acrylonitrile, and is not particularly limited as long as it has a carboxyl group at the end of its molecular chain. As mentioned above, copolymer (B) is thought to contribute to improving the finger-rubbing durability of the resin particle dispersion of the present invention due to the large dipole moment derived from acrylonitrile and the flexibility derived from butadiene.

[0027] The content of acrylonitrile-derived structural units in copolymer (B) is not particularly limited, but from the viewpoint of ensuring good dispersibility of resin particles and improving the finger-rubbing durability of the resulting printed material, it is preferably 5% by mass or more, more preferably 7% by mass or more, even more preferably 10% by mass or more, and preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and even more preferably 27% by mass or less.

[0028] The number-average molecular weight of copolymer (B) is preferably 2,000 or more, more preferably 2,500 or more, even more preferably 3,000 or more, and preferably 5,000 or less, and more preferably 4,000 or less, from the viewpoint of ensuring good dispersibility of resin particles and improving the finger-rubbing durability of the resulting printed material.

[0029] Copolymer (B) has carboxyl groups at the ends of its molecular chains. The carboxyl groups of copolymer (B) are thought to contribute to improved dispersibility of resin particles through interaction with copolymer (A). The acid value of copolymer (B) is preferably 20 mg KOH / g or more, more preferably 25 mg KOH / g or more, even more preferably 28 mg KOH / g or more, and preferably 40 mg KOH / g or less, more preferably 38 mg KOH / g or less, and even more preferably 35 mg KOH / g or less, from the viewpoint of ensuring good dispersibility of resin particles and improving the finger-rubbing durability of the resulting printed material.

[0030] Copolymer (B) may be produced by known methods or a commercially available product may be used. Commercially available copolymers (B) include "Hypro 1300X13 CTBN", "Hypro 1300X8 CTBN", "Hypro 1300X31 CTBN", "Hypro 1300X9 CTBNX", and "Hypro 1300X18 CTBNX" from Huntsman.

[0031] The resin particles contained in the resin particle dispersion of the present invention contain copolymer (A) and copolymer (B) within a single particle. The content of copolymer (B) relative to the total content of copolymer (A) and copolymer (B) in the resin particles is arbitrary as long as it does not impair the effects of the present invention, but from the viewpoint of ensuring good dispersibility of the resin particles and improving the finger-rubbing durability of the resulting printed material, it is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, even more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, even more preferably 25 parts by mass or more, and preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 45 parts by mass or less, and even more preferably 35 parts by mass or less.

[0032] The resin particles contained in the resin particle dispersion of the present invention may contain other components besides copolymer (A) and copolymer (B), as long as the effects of the present invention are not impaired. Specific examples of such other components include other polymers other than copolymer (A) and copolymer (B), and organic solvents with low affinity to aqueous media. Such organic solvents may be dispersed in an aqueous media while contained within the resin particles. In the resin particle dispersion of the present invention, the content of components other than copolymer (A) and copolymer (B) relative to the total content of copolymer (A) and copolymer (B) is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, and even more preferably substantially 0% by mass. Here, "substantially 0% by mass" means that copolymer (A) and copolymer (B) may contain components that are not intended to be used, so-called impurities. The total content of copolymer (A) and copolymer (B) in the resin particles contained in the resin particle dispersion of the present invention is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 99% by mass or more, and even more preferably substantially 100% by mass. Here, "substantially 100% by mass" means that copolymer (A) and copolymer (B) may contain components that are not intended to be used, so-called impurities.

[0033] The content of constituent units derived from (meth)acrylamide monomer (a-2) in the resin particles contained in the resin particle dispersion of the present invention is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 8% by mass or more, even more preferably 10% by mass or more, and even more preferably 13% by mass or more, and from the viewpoint of ensuring good dispersibility of the resin particles and improving the finger-rubbing durability of the resulting printed material, and also preferably 20% by mass or less, more preferably 18% by mass or less, even more preferably 16% by mass or less, and even more preferably 15% by mass or less.

[0034] The content of acrylonitrile-derived constituent units in the resin particles contained in the resin particle dispersion of the present invention is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, and even more preferably 5% by mass or more, from the viewpoint of ensuring good dispersibility of the resin particles and improving the finger-rubbing durability of the resulting printed material, and also preferably 20% by mass or less, more preferably 17% by mass or less, even more preferably 12% by mass or less, even more preferably 11% by mass or less, and even more preferably 9% by mass or less.

[0035] The acid value of the resin particles contained in the resin particle dispersion of the present invention is preferably 50 mg KOH / g or more, more preferably 70 mg KOH / g or more, even more preferably 90 mg KOH / g or more, even more preferably 100 mg KOH / g or more, and preferably 240 mg KOH / g or less, more preferably 200 mg KOH / g or less, even more preferably 180 mg KOH / g or less, even more preferably 160 mg KOH / g or less, and even more preferably 140 mg KOH / g or less, from the viewpoint of ensuring good dispersibility of the resin particles and improving the finger-rubbing durability of the resulting printed material. The acid value of the resin particles contained in the resin particle dispersion of the present invention is calculated based on the acid value of copolymer (A) and copolymer (B), as well as the ratio of copolymer (A) and copolymer (B).

[0036] From the viewpoint of improving the finger-rubbing durability of the resulting printed material, the average particle diameter of the resin particles in the resin particle dispersion of the present invention is preferably 5 nm or more, more preferably 8 nm or more, even more preferably 10 nm or more, even more preferably 15 nm or more, even more preferably 20 nm or more, and preferably 100 nm or less, more preferably 50 nm or less, even more preferably 40 nm or less, even more preferably 35 nm or less, and even more preferably 32 nm or less. The average particle size of resin particles in a resin particle dispersion can be measured by the method described in the examples.

[0037] The aqueous medium of the resin particle dispersion of the present invention contains water in the largest possible proportion by mass, but may contain other components besides water as long as it does not impair the effects of the present invention. Examples of such other components include water-soluble organic solvents that can be miscible with water in any proportion. Furthermore, while the resin particle dispersion of the present invention contains resin particles and an aqueous medium, it may also contain other components besides resin particles and an aqueous medium. Specific examples of such other components include preservatives, humectants, viscosity modifiers, and surfactants.

[0038] [Method for manufacturing resin particle dispersions] The resin particle dispersion of the present invention is obtained by dispersing resin particles containing copolymer (A) and copolymer (B) within a single particle in an aqueous medium. A specific example of the method for producing the resin particle dispersion of the present invention is a method in which copolymer (A) and copolymer (B) are mixed and dispersed in the presence of an aqueous medium. Furthermore, when mixing copolymer (A) and copolymer (B) and dispersing them, it is more preferable to use an organic solvent for mixing copolymer (A) and copolymer (B) and then distill off the organic solvent after the dispersion. The mixing of copolymer (A) and copolymer (B) may be done by stirring alone, or it may be done using a disperser such as an ultrasonic homogenizer or a high-pressure homogenizer. Among these methods, from the viewpoint of ease of operation, it is more preferable to prepare an organic solvent solution containing copolymer (A) and copolymer (B) by dissolving copolymer (A) and copolymer (B) in an organic solvent that dissolves both copolymer (A) and copolymer (B), and then adding an aqueous medium to the organic solvent solution to perform phase inversion emulsification, or to add the organic solvent solution to an aqueous medium to perform phase inversion emulsification, and even more preferable to add an aqueous medium to the organic solvent solution to perform phase inversion emulsification.

[0039] As the organic solvent for dissolving copolymer (A) and copolymer (B), dialkyl ketones having an alkyl group with 1 to 3 carbon atoms, such as acetone and methyl ethyl ketone, are preferred, and methyl ethyl ketone is more preferred, from the viewpoint of dissolving copolymer (A) and copolymer (B) and easily removing them from the emulsion. Before dissolving in the organic solvent, copolymer (A) and copolymer (B) may be mixed beforehand and then added to the organic solvent. Alternatively, copolymer (A) and copolymer (B) may be dissolved separately in the organic solvent, and then the organic solvent solution of copolymer (A) and the organic solvent solution of copolymer (B) may be mixed. The mass ratio of the organic solvent to copolymer (A) and copolymer (B) [organic solvent / (copolymer (A) and copolymer (B)] is preferably 30 / 100 or more, more preferably 40 / 100 or more, even more preferably 50 / 100 or more, and preferably 500 / 100 or less, more preferably 300 / 100 or less, even more preferably 200 / 100 or less, and even more preferably 100 / 100 or less, from the viewpoint of dissolving the resin and facilitating phase inversion to an aqueous medium, and from the viewpoint of improving the dispersibility of the resin particle dispersion, and is also preferably 500 / 100 or less, more preferably 300 / 100 or less, even more preferably 200 / 100 or less, and even more preferably 100 / 100 or less. The dissolution of copolymer (A) and copolymer (B) in organic solvents, and the addition of basic compounds in the neutralization step described later, are usually carried out at temperatures below the boiling point of the organic solvent.

[0040] As for the aqueous medium, it is preferable that water constitutes the largest proportion by mass. Other components include aliphatic alcohols having 1 to 5 carbon atoms such as methanol, ethanol, isopropanol, and butanol; dialkyl ketones having alkyl groups with 1 to 3 carbon atoms such as acetone and methyl ethyl ketone; and organic solvents that dissolve in water such as cyclic ethers such as tetrahydrofuran. From the viewpoint of ensuring good dispersibility of resin particles, the water content in the aqueous medium is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 100% by mass. Ion-exchanged water or distilled water is preferred. The temperature at which an aqueous medium is added to an organic solvent solution containing copolymer (A) and copolymer (B) is preferably 10°C or higher, more preferably 20°C or higher, even more preferably 25°C or higher, and preferably 80°C or lower, more preferably 75°C or lower, from the viewpoint of ensuring good dispersibility of the resin particle dispersion. From the viewpoint of ensuring good dispersibility of the resin particles, the addition rate of the aqueous medium is preferably 0.5 parts by mass / min or more, more preferably 1 part by mass / min or more, even more preferably 3 parts by mass / min or more, and even more preferably 5 parts by mass / min or more, and preferably 100 parts by mass / min or less, more preferably 50 parts by mass / min or less, and even more preferably 30 parts by mass / min or less, based on 100 parts by mass of the total amount of copolymer (A) and copolymer (B) constituting the resin particles, until the phase inversion is completed. After the phase inversion, there are no restrictions on the addition rate of the aqueous medium after the resin particles have been obtained. From the viewpoint of improving the productivity of the resin particle dispersion, the amount of aqueous medium added is preferably 100 parts by mass or more, more preferably 300 parts by mass or more, even more preferably 500 parts by mass or more, and preferably 1500 parts by mass or less, more preferably 1000 parts by mass or less, and even more preferably 700 parts by mass or less, based on 100 parts by mass of the total amount of copolymer (A) and copolymer (B) constituting the resin particles.

[0041] In the method for producing the resin particle dispersion of the present invention, it is preferable to include a neutralization step in which a portion of the carboxyl groups contained in copolymer (B), and, if copolymer (A) contains constituent units derived from ionic monomer (a-3) and the ionic group of the ionic monomer (a-3) is an anionic group, a portion of the anionic group is neutralized. That is, it is preferable that the resin particle dispersion further contains a neutralizing agent. The neutralization step of copolymer (A) and copolymer (B) is preferably carried out using a basic compound that can react with the ionic groups in copolymer (A) and the carboxyl groups in copolymer (B) as a neutralizing agent. The basic compound is preferably one or more selected from the group consisting of alkali metal hydroxides and water-soluble amines.

[0042] The resin particles of the present invention preferably contain a copolymer (A) comprising structural units derived from (meth)acrylic acid ester (a-1), which is an ester of a C6 or C7 alcohol and (meth)acrylic acid, and structural units derived from (meth)acrylamide monomer (a-2), and a carboxylate-terminated butadiene acrylonitrile copolymer (B), wherein some of the carboxyl groups of copolymer (B) are carboxylate anions. More preferably, the resin particles contain a copolymer (A) comprising structural units derived from (meth)acrylic acid ester (a-1), which is an ester of a C6 or C7 alcohol and (meth)acrylic acid, structural units derived from (meth)acrylamide monomer (a-2), and structural units derived from ionic monomer (a-3), and a carboxylate-terminated butadiene acrylonitrile copolymer (B), wherein some of the ionic groups of the structural units derived from ionic monomer (a-3) and some of the carboxyl groups of copolymer (B) are carboxylate anions.

[0043] The ratio of the number of moles of the neutralizing agent to the total number of moles of ionic groups of copolymer (A) and carboxyl groups of copolymer (B) in the resin particle dispersion of the present invention, i.e., the degree of neutralization of the resin particles, is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 70 mol% or more, and even more preferably 80 mol% or more, and from the viewpoint of ensuring good dispersibility of the resin particles and improving the finger-rubbing durability of the resulting printed material, and also preferably 200 mol% or less, more preferably 150 mol% or less, even more preferably 140 mol% or less, and even more preferably 130 mol% or less. In the resin particle dispersion of the present invention, the neutralizing agent is treated as neither a "component other than resin particles in the resin particle dispersion" nor a "component constituting the aqueous medium of the resin particle dispersion."

[0044] The solid content concentration of the resin particle dispersion of the present invention is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, from the viewpoint of improving the finger-rubbing durability of the resulting printed material, and preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, from the viewpoint of the dispersibility of the resin particles. The solid content concentration can be measured by the method described in the examples.

[0045] [Water-based ink] The resin particle dispersion of the present invention, when incorporated into printing inks, becomes a component of water-based inks. That is, the water-based ink of the present invention (hereinafter also referred to as "the ink of the present invention" or "water-based ink") contains the resin particle dispersion of the present invention. From the viewpoint of improving the finger-rubbing durability of the resulting printed material, the content of the resin particle dispersion in the ink of the present invention is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, even more preferably 4% by mass or more, even more preferably 5% by mass or more, even more preferably 6% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, even more preferably 9% by mass or less, and even more preferably 8% by mass or less.

[0046] <Pigments> The ink of the present invention may contain a pigment. The type of pigment may be either an inorganic pigment or an organic pigment. Examples of inorganic pigments include carbon black and metal oxides. For black inks, carbon black is preferred as the pigment. Examples of carbon black include furnace black, thermal black, acetylene black, and channel black. For white inks, examples of pigments include titanium dioxide, zinc oxide, silica, alumina, and metal oxides such as magnesium oxide. Among these, titanium dioxide is preferred. Examples of organic pigments include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthraquinone pigments, and quinophthalone pigments. Organic pigments are preferred for chromatic inks. The hue is not particularly limited, and any chromatic pigment such as yellow, magenta, cyan, red, blue, orange, and green can be used. Pigments can be used individually or in mixtures of two or more types.

[0047] The pigments used in the present invention are preferably in the form of one or more pigments selected from the group consisting of self-dispersing pigments and pigments dispersed with polymer dispersants. Among these, pigments dispersed with polymer dispersants are preferred. That is, the ink of the present invention preferably contains pigments dispersed with polymer dispersants. Self-dispersing pigments are pigments that are dispersed without the use of dispersants. Examples of self-dispersing pigments include pigments that can be dispersed in aqueous media without the use of dispersants such as surfactants and polymer dispersants by directly bonding one or more hydrophilic functional groups (anionic hydrophilic groups such as carboxyl groups and sulfonic acid groups, or cationic hydrophilic groups such as quaternary ammonium groups) to the surface of the pigment, or via other atomic groups such as alkanediyl groups having 1 to 12 carbon atoms.

[0048] The pigment content in the ink of the present invention is preferably 2% by mass or more, more preferably 4% by mass or more, and even more preferably 5% by mass or more, from the viewpoint of ensuring the image density of the resulting printed material. Furthermore, from the viewpoint of reducing the viscosity of the water-based ink, improving continuous ejection performance, obtaining a good printed material without color transfer or deformation of the printing medium, and improving the finger-rubbing durability of the resulting printed material, the pigment content is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, and even more preferably 10% by mass or less.

[0049] <Polymer dispersant> As the polymer dispersant, it is preferable to use one described in paragraphs

[0015] and

[0016] of International Publication No. 2017 / 138438, and more preferably a vinyl polymer obtained by addition polymerization of vinyl monomers (vinyl compounds, vinylidene compounds, vinylene compounds). As for pigments dispersed with a polymer dispersant, from the viewpoint of improving the storage stability of the water-based ink and improving the finger-rubbing durability of the resulting printed material, it is preferable that the polymer dispersant is crosslinked with a crosslinking agent, that is, that the pigment is dispersed with a polymer dispersant having a crosslinked structure (hereinafter also referred to as "crosslinked polymer dispersant"). In other words, it is more preferable that the ink of the present invention contains a pigment dispersed with a crosslinked polymer dispersant. Examples of crosslinking agents include compounds having two or more functional groups that can react with the functional groups of the polymeric dispersant. For example, when the polymeric dispersant has a carboxyl group, polyglycidyl ether compounds of polyhydric alcohols are preferred as crosslinking agents. The content of the polymer dispersant (crosslinked polymer dispersant) in the ink of the present invention is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 2.5% by mass or more, and preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 5% by mass or less, from the viewpoint of improving the finger-rubbing durability of the resulting printed material.

[0050] <organic solvents> The ink of the present invention preferably contains an organic solvent. Preferably, the organic solvent is one described in paragraphs

[0020] to

[0023] of International Publication No. 2017 / 138438, and more preferably one or more selected from the group consisting of polyhydric alcohols and glycol ethers. Preferred glycol ethers include alkylene glycol monoalkyl ethers and alkylene glycol dialkyl ethers. Organic solvents can be used individually or in combination of two or more. From the viewpoint of improving the continuous discharge performance of the water-based ink, the content of the organic solvent in the ink of the present invention is preferably 15% by mass or more, more preferably 20% by mass or more, even more preferably 25% by mass or more, and preferably 45% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less.

[0051] <Surfactants> The ink of the present invention preferably contains a surfactant. Examples of surfactants include those described in paragraphs

[0024] to

[0026] of International Publication No. 2017 / 138438. Among these, one or more selected from the group consisting of acetylene glycol-based surfactants and polyether-modified silicone-based surfactants are preferred, and a combination of acetylene glycol-based surfactants and polyether-modified silicone-based surfactants is more preferred. Surfactants can be used individually or in combination of two or more types. Examples of acetylene glycol-based surfactants include the Surfinol series manufactured by Nisshin Chemical Industry Co., Ltd. and Air Products & Chemicals. Specific examples of polyether-modified silicone surfactants include the KF series manufactured by Shin-Etsu Chemical Co., Ltd., Silface SAG005 manufactured by Nisshin Chemical Industry Co., Ltd., and BYK-348 manufactured by BIC Chemie Japan Co., Ltd. From the viewpoint of obtaining good finger-rubbing durability, the surfactant content in the ink of the present invention is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, and preferably 3% by mass or less, more preferably 2.5% by mass or less, and even more preferably 2% by mass or less.

[0052] From the viewpoint of obtaining good finger-rubbing durability, the water content in the ink of the present invention is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 45% by mass or more, and even more preferably 50% by mass or more, and preferably 70% by mass or less, more preferably 65% ​​by mass or less, and even more preferably 60% by mass or less.

[0053] The ink of the present invention can be manufactured by adding, as necessary, pigments, polymer dispersants, organic solvents, surfactants, water, etc., to the resin particle dispersion of the present invention. The pigment is preferably used as a dispersion of pigment dispersed in an aqueous medium with a polymer dispersant (hereinafter also referred to as "pigment dispersion"). Here, "aqueous medium" means a medium in which water accounts for the largest proportion by mass of the liquid components contained in the pigment dispersion. In the production of the ink of the present invention, any known production method or production apparatus can be used.

[0054] (Printing method) The present invention relates to a printing method using a water-based ink, which involves printing onto a printing substrate using the water-based ink. There are no particular restrictions on the printing substrate used in the printing method using the water-based ink of the present invention, and both low-water-absorbent and high-water-absorbent printing substrates can be used. Examples of printing substrates include plain paper, foam paper, coated paper, photographic paper, and resin film. Among these, low-water-absorbent printing substrates are preferred from the viewpoint of finger-rubbing resistance. The low water-absorbent printing substrate is preferably one or more selected from the group consisting of coated paper and resin film, and more preferably a resin film. The resin film is preferably one or more selected from the group consisting of polyolefin resin film, polyester resin film, polyvinyl chloride resin film, and nylon resin film, and more preferably a polyolefin resin film. Polypropylene resin film is preferred as the polyolefin resin film. These films may be biaxially oriented films, uniaxially oriented films, or unoriented films. Furthermore, the resin film is preferably corona treated. Among these, the printing substrate is more preferably a biaxially oriented polypropylene resin film that has undergone surface treatment such as corona discharge treatment.

[0055] The printing method using the aqueous ink of the present invention is preferably one or more selected from the group consisting of gravure printing methods and inkjet printing methods, and more preferably an inkjet printing method. In the aforementioned inkjet printing method, it is preferable to print water-based ink onto a printing substrate using a piezo-type inkjet recording device. The piezo method minimizes heating and evaporation of the ink during printing, and allows printing without damaging the composition of the water-based ink. [Examples]

[0056] In the following manufacturing examples, embodiments, and comparative examples, "parts" refers to "parts by mass" unless otherwise specified. The various physical properties were measured using the following methods.

[0057] (1) Measurement of the weight-average molecular weight of copolymer (A) The results were obtained by gel permeation chromatography. The measurement conditions are shown below. GPC device: Tosoh Corporation "HLC-8320GPC" Columns: "TSKgel SuperAWM-H", "TSKgel SuperAW3000", and "TSKgel guardcolumn Super AW-H" manufactured by Tosoh Corporation. Eluent: A solution prepared by dissolving phosphoric acid and lithium bromide in N,N-dimethylformamide at concentrations of 60 mmol / L and 50 mmol / L, respectively Flow rate: 0.5 mL / min Standard substances: Monodisperse polystyrene kits with known molecular weights, "PStQuick B (F-550, F-80, F-10, F-1, A-1000)" and "PStQuick C (F-288, F-40, F-4, A-5000, A-500)" (both manufactured by Tosoh Corporation) Measurement sample: 0.1 g of copolymer (A) was mixed with 10 mL of the above eluent in a glass vial, stirred with a magnetic stirrer at 25 °C for 10 hours, and filtered through a syringe filter "DISMIC-13HP" (membrane filter material: hydrophilic PTFE, pore size 0.2 μm, manufactured by Advantec Co., Ltd.).

[0058] (2) Measurement of the average particle diameter of resin particles in the resin particle dispersion Cumulant analysis was performed and measured using a laser particle analysis system "ELS-8000" (manufactured by Otsuka Electronics Co., Ltd.). The measurement conditions were a temperature of 25 °C, an angle of 90° between the incident light and the detector, and an integration count of 100 times. The refractive index of water (1.333) was input as the refractive index of the dispersion solvent, and the obtained cumulant average particle diameter was taken as the average particle diameter of the resin particles. For the measurement sample, a dispersion diluted with water so that the concentration of the resin particles to be measured was approximately 5×10 -3 mass% was used.

[0059] (3) Measurement of the solid content concentration of the resin particle dispersion Using an infrared moisture meter (manufactured by Kett Science Laboratory Co., Ltd., product name: FD-230), 5 g of the resin particle dispersion was dried under the conditions of a drying temperature of 150 °C and a measurement mode of 96 (monitoring time 2.5 minutes / variation width 0.05%) to measure the moisture (mass%) of the resin particle dispersion. The solid content concentration was calculated according to the following formula. Solid content concentration (mass%) = 100 - moisture (mass%) of the resin particle dispersion

[0060] (4) Measurement of the solid content concentration of the solution of copolymer (A) and the pigment dispersion Approximately 10 g of sodium sulfate, which had been stabilized in a desiccator, was weighed into a 30 mL polypropylene container (φ=40 mm, height=30 mm), and the combined mass of the container and sodium sulfate (denoted as mass M1) was accurately weighed. Approximately 1 g of the sample was added and thoroughly mixed, and the combined mass of the container, sodium sulfate, and sample (denoted as mass M2) was accurately weighed. The mixture was maintained at 105°C for 2 hours to remove volatile components, and after being left in a desiccator for another 15 minutes, the mass (denoted as mass M3) was accurately weighed. The mass of the sample after removal of volatile components was taken as the solid content, and the solid content concentration was calculated according to the following formula. Solid concentration (mass%) = [(mass M3 - mass M1) / (mass M2 - mass M1)] x 100

[0061] (Production of copolymer (A)) Manufacturing Example 1-1 59.4 parts of cyclohexyl methacrylate (constituent alcohol with 6 carbon atoms, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent), N-tert-butylacrylamide (manufactured by Mitsubishi Chemical Corporation, SP value: 20.2 (MPa)) 0.5 A monomer mixture was prepared by mixing 20.0 parts of () and 20.6 parts of acrylic acid. Five parts of methyl ethyl ketone (a reagent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., hereinafter referred to as "MEK"), 2.5 parts of 2-mercaptoethanol (a reagent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polymerization chain transfer agent, and 10% by mass of the monomer mixture were added to the reaction vessel and mixed, and the mixture was thoroughly purged with nitrogen gas. Separately, a dropping funnel was filled with a mixture consisting of the remainder of the monomer mixture (90% by mass of the monomer mixture), 2.25 parts of the polymerization chain transfer agent, 75 parts of MEK, and 2.0 parts of 2,2'-azobis(2,4-dimethylvaleronitrile) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as an azo radical polymerization initiator. Next, under a nitrogen atmosphere, the mixture in the reaction vessel was heated to 77°C while stirring, and the mixture in the dropping funnel was added dropwise over 5 hours. After the dropwise addition was complete, a solution of 0.5 parts of the polymerization initiator dissolved in 5 parts of MEK was added, and the reaction was continued at 77°C for another 2 hours. Finally, MEK was added to a solid content concentration of 40% by mass to obtain a MEK solution of copolymer A1. The acid value of copolymer A1 was 160 mgKOH / g, and the weight-average molecular weight was 11,000.

[0062] Manufacturing Example 1-2 A MEK solution of copolymer A2 was obtained using the same procedure as in Production Example 1-1, except that the amount of azo radical polymerization initiator added to the dropping funnel was changed from 2.0 parts to 2.5 parts, the heating temperature of the reaction vessel was changed from 77°C to 80°C, and the temperature at which the reaction was allowed to proceed for 2 hours after the dropping of the mixed solution in the dropping funnel was changed from 77°C to 82°C. The acid value of copolymer A2 was 160 mgKOH / g, and the weight-average molecular weight was 13,000.

[0063] Manufacturing Examples 1-3 to 1-9 and Comparative Manufacturing Examples 1-1 to 1-4 MEK solutions of copolymers A3-A9 and AC1-AC4 were obtained using the same procedure as in Production Example 1-1, except that the raw material monomer (a) was of the type and quantity listed in Table 1. The acid value and weight-average molecular weight of each copolymer are shown in Table 1.

[0064] [Table 1]

[0065] (Manufacturing of resin particle dispersions) Example 1-1 In a 1000 mL separable flask, 150 parts of a 40% by mass MEK solution of copolymer A1 was charged as copolymer (A). While stirring at 200 rpm with a stirring blade at room temperature, 64.3 parts of a 40% by mass MEK solution of pre-prepared carboxy-terminated butadiene / acrylonitrile copolymer B1 (Huntsman "Hypro 1300X13 CTBN") as copolymer (B) were added. Then, 40.6 parts of 5N sodium hydroxide aqueous solution (6.86 parts sodium hydroxide) were added dropwise, followed by the addition of 495.1 parts of deionized water at a rate of 10 mL / min. Subsequently, the solvent was removed using an evaporator, followed by phase inversion emulsification and further dehydration to obtain a resin particle dispersion EM1 with a solid content of 21% by mass. The average particle size of the resin particles in the resin particle dispersion is shown in Table 2.

[0066] Examples 1-2 to 1-11 and Comparative Example 1-1 In Example 1-1, the polymer (A), polymer (B), and sodium hydroxide were changed to the types or amounts shown in Table 2, and the amount of deionized water was adjusted so that the total amount was 750 parts. Except for these changes, the resin particle dispersions EM2-EM11 and EMC1 were obtained using the same procedure as in Example 1-1. The average particle size of the resin particles in the resin particle dispersions is shown in Table 2.

[0067] Comparative Examples 1-2 to 1-5 In Example 1-1, the procedure was the same as in Example 1-1, except that the types or amounts of copolymer (A), copolymer (B), and sodium hydroxide were changed to those listed in Table 2, and the amount of deionized water was adjusted so that the total amount was 750 parts, in an attempt to obtain resin particle dispersions EMC2 to EMC5. However, aggregation and phase separation occurred during the desolventing and dehydration operations using an evaporator, and it was not possible to obtain resin particle dispersions. Therefore, in Comparative Examples 1-2 to 1-5, the average particle size of the resin particles in the resin particle dispersions was not measured.

[0068] The copolymer (B) in Table 2 is as follows: Copolymer B1: Huntsman's "Hypro 1300X13 CTBN" (carboxylate-terminated butadiene / acrylonitrile copolymer, Mn: 3,150 (catalog value)) Copolymer B2: Huntsman's "Hypro 1300X8 CTBN" (carboxylate-terminated butadiene / acrylonitrile copolymer, Mn: 3,550 (catalog value)) Copolymer B3: Huntsman's "Hypro 1300X31 CTBN" (carboxylate-terminated butadiene / acrylonitrile copolymer, Mn: 3,800 (catalog value)) Polymer BC1: Huntsman's "Hypro 2000X162 CTB" (carboxylate-terminated butadiene polymer, Mn: 4,200 (catalog value))

[0069] [Table 2]

[0070] Comparative Examples 1-2 to 1-4 could not obtain a resin particle dispersion because the number of carbon atoms in the alcohol constituting the (meth)acrylic acid ester (a-1) was not 6 or 7. Comparative Example 1-5 could not obtain a resin particle dispersion because, instead of the carboxyl-terminated butadiene / acrylonitrile copolymer (B), a carboxyl-terminated butadiene polymer that did not contain acrylonitrile-derived constituent units was used. Water-based inks were prepared using the resin particle dispersions of Examples 1-1 to 1-11 and Comparative Example 1-1, and their finger-rubbing durability was evaluated as described below.

[0071] (Manufacturing of pigment dispersions) Manufacturing Example 2-1 As a polymeric dispersant, 514.3 parts of styrene / acrylic acid copolymer (BASF's "JONCRYL 690", Mw 16,500, acid value 240 mg KOH / g) was added to a mixture of 262.4 parts of 5N sodium hydroxide aqueous solution (solid content concentration 16.9% by mass) (degree of neutralization of polymeric dispersant 50 mol%) and 4760 parts of deionized water. The mixture was heated at 90°C for 8 hours while stirring at 200 rpm. Then, 1200 parts of cyanide pigment (PB15:3, DIC Corporation, FASTOGEN BLUE TGR-SD) were added, and the mixture was stirred at 15°C and 6400 rpm for 1 hour using a homodisper manufactured by Primix Corporation to obtain the mixed solution. Next, using a microfluidizer manufactured by Microfluidics, the dispersion treatment was carried out in 10 passes at 15°C and a pressure of 150 MPa to obtain a pigment dispersion in which cyan pigment was dispersed with a polymer dispersant. Next, 123.4 parts (40 mol% crosslinking degree) of trimethylolpropane polyglycidyl ether (EX-321, manufactured by Nagase ChemteX Corporation, epoxy equivalent 140) was added as a crosslinking agent and mixed, and the mixture was heated at 90°C for 90 minutes while stirring at 200 rpm. After cooling to 25°C, the mixture was centrifuged, filtered through a 5 μm acetylcellulose membrane filter, and deionized water was added to obtain a pigment dispersion P1 in which cyanide pigment with a solid content of 25% by mass was dispersed in a crosslinking polymer dispersant.

[0072] (Manufacturing of water-based inks) Example 2-1 33.3 parts of the resin particle dispersion EM1 from Example 1-1 (resin particle content: 7 parts), 30.7 parts of the pigment dispersion P1 obtained in Production Example 2-1 (pigment content: 5 parts, crosslinked polymer dispersant content: 2.7 parts), 9 parts of diethylene glycol monoisobutyl ether (reagent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 19 parts of 1,2-propanediol (reagent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 1 part of the acetylene glycol-based surfactant "Surfinol 440" (ethylene oxide (3.5 mol) adduct of 2,4,7,9-tetramethyl-5-decine-4,7-diol, manufactured by Nisshin Chemical Industry Co., Ltd.), 1 part of the polyether-modified silicone-based surfactant "KF6011" (PEG-11 methyl ether dimethicone, manufactured by Shin-Etsu Chemical Co., Ltd.), and 6 parts of ion-exchanged water were mixed to obtain aqueous ink 1, so that the total volume of the aqueous ink was 100 parts. (Production of printed materials) In an environment with a temperature of 25±1℃ and a relative humidity of 30±5%, a printing evaluation device (manufactured by Trytech Co., Ltd.) equipped with an inkjet head "KJ4B-HD06MHG-STDV" (manufactured by Kyocera Corporation, piezo type) was filled with water-based ink 1. The head voltage was set to 26V, the frequency to 10kHz, the appropriate amount of ejected liquid to 12pL, the head temperature to 32℃, the resolution to 600dpi, the number of pre-ejection flushing cycles to 200, and the negative pressure to -4.0kPa. Corona discharge treated OPP film (FOR-AQ, #20 (thickness 20μm), manufactured by Futamura Chemical Co., Ltd.) was fixed to a transport table under reduced pressure as the printing substrate, with the longitudinal direction of the printing substrate being the same as the transport direction. A print command was transferred to the printing evaluation device, and a solid image (4cm x 4cm) with a duty cycle of 100% was printed. The printed material was then dried at 60℃ for 1 hour.

[0073] Examples 2-2 to 2-11 and Comparative Example 2-1 In Example 2-1, water-based inks 2-11 and C1 were obtained using the same procedure as in Example 1, except that resin particle dispersion EM1 was replaced with resin particle dispersions EM2-EM11 and EMC1, respectively, and then each printed material was obtained.

[0074] [evaluation] The finger-rubbing durability of each printed material obtained in the examples and comparative examples was evaluated using the following method.

[0075] [Finger rubbing durability (abrasion resistance test)] In an environment of 25°C, the solid image area of ​​each printed material obtained in the examples and comparative examples was pressed down with the tip of the thumb (fingerprint area), and the back side of the film of the solid image area (the side without the printed image) was pinched between the tip of the index finger (fingerprint area). The ink coating was then rubbed with the fingers, shifting the tip of the thumb (fingerprint area) and the tip of the index finger (fingerprint area) while applying strong pressure to the printed material in a finger snapping motion to peel off the ink coating. The abrasion resistance test of the ink coating was performed by observing whether or not the ink coating peeled off and evaluating the finger rubbing durability according to the following criteria. The results are shown in Table 3. A: There is absolutely no peeling of the ink coating. B: There is little to no peeling of the ink coating, or only fine, scratch-like peeling (the percentage of peeled area is less than 10%). C: There is peeling of the ink coating (the percentage of the peeled area is 10% or more). If the above evaluation is B, it can be used in applications where the ink coating of the printed material is not rubbed off much, and if the above evaluation is A, it can be used in applications where the ink coating of the printed material is rubbed off.

[0076] [Table 3]

[0077] Table 3 shows that the water-based inks in Examples 2-1 to 2-11 have superior resistance to finger rubbing compared to the water-based ink in Comparative Example 2-1.

Claims

1. A resin particle dispersion in which resin particles are dispersed in an aqueous medium, A resin particle dispersion comprising a copolymer (A) containing structural units derived from a (meth)acrylic acid ester (a-1), which is an ester of a carbon-6 or carbon-7 alcohol with (meth)acrylic acid, and structural units derived from a (meth)acrylamide monomer (a-2), and a carboxylate-terminated butadiene / acrylonitrile copolymer (B).

2. The resin particle dispersion according to claim 1, wherein the copolymer (A) further comprises a constituent unit derived from the ionic monomer (a-3).

3. The resin particle dispersion according to claim 2, wherein the resin particle dispersion further contains a neutralizing agent, and the ratio of the number of moles of the neutralizing agent to the total number of moles of ionic groups of copolymer (A) and carboxyl groups of copolymer (B) in the resin particle dispersion is 50 mol% or more and 200 mol% or less.

4. The resin particle dispersion according to claim 1, wherein the content of acrylonitrile-derived structural units in the copolymer (B) is 5% by mass or more and 50% by mass or less.

5. The resin particle dispersion according to claim 1, wherein the content of copolymer (B) in the resin particles is 5 parts by mass or more and 60 parts by mass or less, relative to the total content of copolymer (A) and copolymer (B) in 100 parts by mass.

6. The solubility parameter of (meth)acrylamide monomer (a-2) is 17 (MPa). 0.5 The above is 23 MPa. 0.5 The resin particle dispersion according to claim 1, which is as follows:

7. The resin particle dispersion according to claim 1, wherein the content of constituent units derived from (meth)acrylamide monomer (a-2) in the copolymer (A) is 5% by mass or more and 30% by mass or less.

8. A water-based ink containing a resin particle dispersion according to any one of claims 1 to 7.

9. A method for producing a resin particle dispersion according to any one of claims 1 to 7, A method for producing a resin particle dispersion, comprising the step of adding an aqueous medium to an organic solvent solution containing copolymer (A) and copolymer (B) to perform phase inversion emulsification.

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