JP7088457B2 - Resin emulsion and water-based ink - Google Patents

Description

The present invention relates to a resin emulsion and a water-based ink containing the resin emulsion.

In fields such as commercial label printing used for product packaging printing and advertising, resin printing media such as PET (polyethylene terephthalate), PVC (polyvinyl chloride), PE (polyethylene), PP (polypropylene), NY (nylon), etc. On the other hand, as a printing method using water-based ink, utilization of an inkjet printing method and a flexographic printing method is required from the viewpoints of reduction of environmental load, energy saving, safety and the like.
In particular, the inkjet printing method is a printing method in which ink droplets are directly ejected from a very fine nozzle onto a printing medium and adhered to the printed matter to obtain a printed matter in which characters and images are recorded. The inkjet printing method is remarkably popular because it is easy to make full color, inexpensive, and has many advantages such as non-contact with the printed matter. As ink for inkjet printing, various inks containing pigments, water-based media and polymers have been proposed.

For example, Patent Document 1 describes a polymer compound obtained by polymerizing a monomer giving an aromatic functional group and a monomer giving a carboxyl group as a recording liquid having excellent water resistance due to friction. A recording solution composed of an aqueous liquid medium, a pigment, a polymer compound and a compound forming a salt is described.
Patent Document 2 contains a resin and a surfactant as ink for inkjet recording, which improves the scratch resistance of the recorded material and exhibits excellent ejection characteristics in which the landing point of the ink on the recording medium does not shift. Inkjet ink, the acid value of the resin is 100 mgKOH / g or more and 220 mgKOH / g or less, the weight average molecular weight of the resin is 3,000 or more and 10,000 or less, and the surfactant is specified. Inkjet inks having the above structure are described.

Japanese Unexamined Patent Publication No. 5-287227 Japanese Unexamined Patent Publication No. 2009-7556

However, Patent Document 1 has a problem of water resistance due to running water and friction when printed on plain paper, and Patent Document 2 has a problem of scratch resistance when printed on PPC paper. Therefore, the techniques of these patented documents are insufficient in fixability to a resin printing medium and document offset resistance under high humidity. Therefore, it is required to improve the fixability to the resin printing medium and the document offset resistance.
An object of the present invention is to provide a resin emulsion having excellent fixability to a resin printing medium and document offset resistance under high humidity when blended in an ink and printing, and a water-based ink containing the resin emulsion. And.
In the present specification, "printing" is a concept including printing and printing for recording characters and images, and "printed matter" is a concept including printed matter and printed matter on which characters and images are recorded. .. Further, the "water system" means that water occupies the largest proportion in the medium contained in the ink.

The present inventors have found that a resin emulsion containing specific polymer particles can solve the above-mentioned problems.
That is, the present invention provides the following [1] and [2].
[1] A resin emulsion containing polymer (A) particles.
A resin emulsion in which the polymer (A) contains a structural unit derived from itaconic acid (a-1) and a structural unit derived from a hydrophobic monomer (a-2), and at least a part of the acid group is neutralized. ..
[2] A water-based ink containing the resin emulsion according to the above [1] and a colorant.

According to the present invention, there is provided a resin emulsion having excellent fixability to a resin printing medium and document offset resistance under high humidity when blended in an ink and printing, and a water-based ink containing the resin emulsion. Can be done.

[Resin emulsion]
The resin emulsion of the present invention is a resin emulsion containing polymer (A) particles, wherein the polymer (A) is derived from a structural unit derived from itaconic acid (a-1) and a hydrophobic monomer (a-2). It contains a structural unit and is further neutralized with at least a portion of the acid group.

The resin emulsion of the present invention has fixability to a resin printing medium (hereinafter, also simply referred to as "fixability") and document offset resistance under high humidity (hereinafter, simply "resistant" when blended in ink and printed. It has an excellent effect (also called "document offset property"). The reason is not clear, but it can be considered as follows.
In the present invention, the polymer (A) contains a structural unit derived from itaconic acid (a-1) and a structural unit derived from the hydrophobic monomer (a-2). Therefore, in the polymer chain, a hydrophilic portion having a locally high acid group density is formed by itaconic acid (a-1) and a hydrophobic portion is formed by the hydrophobic monomer (a-2), and the polymer chain is pro-hydrophobic. Distribution bias occurs. This bias is more pronounced than in the case of one acid group contained in the hydrophilic monomer, and the hydrophilic portion enhances the dispersibility of the polymer (A) particles in the resin emulsion and is hydrophobic. The moiety is considered to improve the fixability to the resin printing medium and the document offset resistance between printed matter under high humidity.
In particular, as compared with the case where a hydrophilic monomer having one acid group is used, the structural unit derived from itaconic acid (a-1) is locally a hydrophilic portion having a high acid group density, so that the degree of neutralization is high. It is considered that sufficient dispersive power can be obtained even under low conditions, that is, conditions with low ionicity. Further, it is considered that the continuous phase of the printed layer formed of the polymer (A) particles is less susceptible to the influence of humidity and the like because of its low neutralization degree, and the document offset between printed matter can be suppressed even under high humidity. ..

<Polymer (A) particles>
Polymer (A) The polymer (A) constituting the particles (hereinafter, also simply referred to as “polymer (A)”) is derived from itaconic acid (a-1) (hereinafter, also simply referred to as “monomer (a-1)”). It contains the structural unit of the above and the structural unit derived from the hydrophobic monomer (a-2) (hereinafter, also simply referred to as “monomer (a-2)”), and further, at least a part of the acid group is neutralized.

[Itaconic acid (a-1)]
The monomer (a-1) is itaconic acid. Itaconic anhydride can also be used as the monomer (a-1).
Moreover, in recent years, in the environmental protection problem, the conversion from the conventional petroleum-derived raw materials to plant-derived raw materials is being promoted. Since itaconic acid can be derived from plants, the dependence on petroleum can be reduced.

[Hydrophobic monomer (a-2)]
The monomer (a-2) is used as a monomer component of the polymer (A) from the viewpoint of improving fixability and document offset resistance.
In the present invention, "hydrophobicity" means that the amount of the monomer soluble in 100 g of ion-exchanged water at 25 ° C. is less than 10 g. The amount of the hydrophobic monomer dissolved in 100 g of ion-exchanged water at 25 ° C. is preferably 5 g or less, more preferably 1 g or less, from the viewpoint of improving fixability and document offset resistance.
The monomer (a-2) has at least a hydrophobic group and a polymerizable group in its structure. Examples of the hydrophobic group include one or more selected from an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group, and preferably selected from an aliphatic hydrocarbon group and an aromatic hydrocarbon group. It is one or more kinds. Examples of the polymerizable group include one or more selected from a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, a propenyl group, a vinylidene group, and a vinylene group, which are groups having an unsaturated double bond capable of radically polymerizable. It is preferably a vinyl group.

Examples of the monomer (a-2) include aromatic group-containing monomers and (meth) acrylic acid alkyl esters.
Examples of the aromatic group-containing monomer include compounds having an aromatic ring and a polymerizable group. The aromatic group-containing monomer is preferably a vinyl monomer having an aromatic group having 6 or more and 22 or less carbon atoms, which may have a substituent containing a heteroatom, and is preferably a styrene-based monomer or an aromatic group-containing (meth) acrylic. Acid esters are more preferred. The molecular weight of the aromatic group-containing monomer is preferably less than 500.
The styrene-based monomer is preferably one or more selected from styrene, 2-methylstyrene, α-methylstyrene and divinylbenzene, and more preferably styrene.
The aromatic group-containing (meth) acrylic acid ester is preferably one or more selected from benzyl (meth) acrylate and phenoxyethyl (meth) acrylate, and more preferably benzyl (meth) acrylate.
Here, "(meth) acrylic acid" means one or more selected from acrylic acid and methacrylic acid. "(Meta) acrylate" means one or more selected from acrylates and methacrylates.

As the (meth) acrylic acid alkyl ester, those having an alkyl group having 1 or more and 22 or less carbon atoms are preferable, and those having an alkyl group having 6 or more and 18 or less carbon atoms are more preferable. For example, methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, (iso or tertiary) butyl (meth) acrylate, (iso) amyl (meth) acrylate, cyclohexyl (meth) acrylate, Examples thereof include 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, and stearyl (meth) acrylate.
In addition, in this specification, "(iso or tertiary)" and "(iso)" mean both the case where these prefixes exist and the case where these prefixes do not exist, and when these prefixes do not exist , Indicates the normal.

The monomer (a-2) is preferably one or more selected from an aromatic group-containing monomer and a (meth) acrylic acid alkyl ester from the viewpoint of improving fixability and document offset resistance, and more preferably aromatic. It contains a group-containing monomer, and is more preferably one or more selected from a styrene-based monomer and an aromatic group-containing (meth) acrylic acid ester, more preferably a styrene-based monomer, and further preferably styrene.

The polymer (A) may further contain structural units derived from other monomers other than the monomers (a-1) and (a-2).
Examples of other monomers include acid monomers other than itaconic acid and itaconic anhydride, and nonionic monomers containing a hydroxy group or a polyalkylene glycol chain. Specifically, ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid and maleic acid; hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate and 3-hydroxypropyl (meth) acrylate; polyethylene glycol. Polyalkylene glycol (meth) such as (meth) acrylate (n = 2 to 30, n indicates the average number of moles of oxyalkylene group added; the same applies hereinafter), polypropylene glycol (n = 2 to 30) (meth) acrylate, and the like. Acrylate; Acrylic polyalkylene glycol (meth) acrylate such as methoxypolyethylene glycol (n = 1 to 30) (meth) acrylate; Phenoxy (ethylene glycol-propylene glycol copolymerization) (n = 1 to 30, ethylene glycol in it: n = 1-29) (meth) acrylate and the like can be mentioned.

The total content of the structural units derived from the monomers (a-1) and (a-2) in the total amount of the monomer units constituting the polymer (A) is preferably from the viewpoint of improving the fixability and the document offset resistance. It may consist of 80% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, still more preferably 100% by mass, that is, only the structural units derived from the monomers (a-1) and (a-2). preferable.

The content of each monomer in the monomer mixture at the time of producing the polymer (A) (content as an unneutralized amount; the same applies hereinafter) or the monomer (a-1) in the total amount of the monomer units constituting the polymer (A). The contents of the constituent unit derived from the constituent unit and the constituent unit derived from the monomer (a-2) are as follows from the viewpoint of improving the fixability and the document offset resistance.
The content of the monomer (a-1) is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, still more preferably 20% by mass or more, still more preferably 25% by mass. And more preferably 50% by mass or less, more preferably 45% by mass or less, still more preferably 40% by mass or less, still more preferably 35% by mass or less.
The content of the monomer (a-2) is preferably 50% by mass or more, more preferably 55% by mass or more, still more preferably 60% by mass or more, still more preferably 65% by mass or more, and preferably 95% by mass or more. It is mass% or less, more preferably 90% by mass or less, still more preferably 85% by mass or less, still more preferably 80% by mass or less, still more preferably 75% by mass or less.

Since itaconic acid (a-1) is used in the present invention, sufficient dispersion is sufficient even if the content of the constituent unit derived from the hydrophilic monomer in the polymer is low as compared with the case where a hydrophilic monomer having one acid group is used. Polymer particles having properties are obtained. Further, since the content of the structural unit derived from the hydrophobic monomer can be increased, the proportion of the hydrophobic portion in the polymer chain can be increased, and the fixability can be improved. From this point of view, the mass ratio [(a-1) / (a-2)] of the structural unit derived from the monomer (a-1) and the structural unit derived from the monomer (a-2) in the polymer (A) is preferable. Is 5/95 or more, more preferably 10/90 or more, still more preferably 15/85 or more, still more preferably 20/80 or more, still more preferably 25/75 or more, and preferably 50/50 or less. , More preferably 45/55 or less, still more preferably 40/60 or less, still more preferably 35/65 or less.

(Manufacturing of resin emulsion)
[Synthesis of polymer (A')]
In the resin emulsion of the present invention, the polymer (A') is obtained from a monomer mixture containing the monomers (a-1) and (a-2) constituting the polymer (A), and then at least one of the acid groups is used with a neutralizing agent. It is preferably obtained by a method of neutralizing the part and emulsifying it in an aqueous medium. The polymer (A') is produced by copolymerizing a monomer mixture by a known polymerization method such as a massive polymerization method, a solution polymerization method, a suspension polymerization method, or an emulsion polymerization method. Among these polymerization methods, the solution polymerization method is preferable.
In the present specification, the polymer (A) before neutralization is referred to as "polymer (A')".

The solvent used in the solution polymerization method is not limited, but a polar organic solvent such as an aliphatic alcohol having 1 or more and 3 or less carbon atoms, ketones, ethers, and esters is preferable. Specific examples thereof include 1,4-dioxane, methanol, ethanol, acetone and methyl ethyl ketone, and among these, 1,4-dioxane is preferable.
At the time of polymerization, a polymerization initiator or a polymerization chain transfer agent can be used, but as the polymerization initiator, an azo compound is preferable, and 2,2'-azobis (isobutyronitrile) is more preferable. As the polymerization chain transfer agent, mercaptans are preferable, and 3-mercaptopropionic acid is more preferable.
Preferred polymerization conditions vary depending on the type of polymerization initiator and the like, but the polymerization temperature is preferably 50 ° C. or higher and 90 ° C. or lower, and the polymerization time is preferably 1 hour or longer and 20 hours or lower. The polymerization atmosphere is preferably a nitrogen gas atmosphere or an inert gas atmosphere such as argon.
After completion of the polymerization reaction, the produced polymer (A') can be isolated from the reaction solution by a known method such as reprecipitation and solvent distillation. Further, in the obtained polymer (A'), unreacted monomers and the like can be removed by reprecipitation, membrane separation, chromatographic method, extraction method and the like.

The acid value of the polymer (A') is preferably 50 mgKOH / g or higher, more preferably 100 mgKOH / g or higher, still more preferably 150 mgKOH / g or higher, even more preferably 180 mgKOH / g or higher, and preferably 350 mgKOH / g or higher. It is g or less, more preferably 300 mgKOH / g or less, still more preferably 250 mgKOH / g or less, still more preferably 230 mgKOH / g or less.
As described in the examples, the acid value of the polymer (A') is based on the method of JIS K 0070, and only the measurement solvent is a mixture of acetone and toluene from the mixed solvent of ethanol and ether specified in JIS K 0070. It is measured by a method changed to a solvent (acetone: toluene = 4: 6 (volume ratio)). The acid value can also be calculated from the ratio of the monomer components during the synthesis of the polymer (A'), but if the polymer (A') has poor solubility in the solvent for measuring the acid value, the inside of the polymer chain It is considered that there is a structural unit derived from the monomer (a-1) that is taken in and does not come out to the outside, and the measured value by the above method tends to show a lower value than the calculated value.

The number average molecular weight of the polymer (A') is preferably 500 or more, more preferably 1,000 or more, still more preferably 1,000 or more, from the viewpoint of improving the dispersibility of the polymer particles and improving the fixability and document offset resistance. Is 1,300 or more, and is preferably 100,000 or less, more preferably 50,000 or less, still more preferably 10,000 or less, still more preferably 8,000 or less, still more preferably 6,000 or less. , More preferably 2,000 or less. The number average molecular weight of the polymer (A') can be adjusted by the amount of the polymerization chain transfer agent.
The number average molecular weight can be measured by the method described in Examples.

[Emulsification]
The resin emulsion of the present invention is preferably produced by a method of adding a neutralizing agent to the polymer (A') and emulsifying it in an aqueous medium. As a result, at least a part of the acid groups contained in the structural unit derived from the monomer (a-1) is neutralized with a neutralizing agent, and at least a part of the acid groups form a salt, and a resin emulsion having excellent dispersibility Can be obtained.
The water-based medium contains water as a main component. The content of water in the aqueous medium is preferably 80% by mass or more, more preferably 90% by mass or more, and 100% by mass or less from the viewpoint of improving the dispersibility of the polymer particles and the environmental safety. It is more preferably 100% by mass. As the water, deionized water, ion-exchanged water or distilled water is preferably used. Examples of the components other than water include alcohol solvents such as methanol, ethanol, isopropanol and butanol; ketone solvents such as acetone and methyl ethyl ketone; and organic solvents such as ether solvents such as tetrahydrofuran.

Examples of the neutralizing agent include alkali metal hydroxides, ammonia, organic amines and the like, and among these, alkali metal hydroxides are preferable. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide and cesium hydroxide, with sodium hydroxide being preferred. Examples of the organic amine include trimethylamine, ethylamine, diethylamine, triethylamine, triethanolamine and the like.
The neutralizing agent is preferably used as an aqueous solution of the neutralizing agent from the viewpoint of sufficiently and uniformly promoting neutralization. From the above viewpoint, the concentration of the neutralizing agent aqueous solution is preferably 3% by mass or more, more preferably 10% by mass or more, further preferably 15% by mass or more, and preferably 30% by mass or less, more preferably 25% by mass or less. It is less than mass%.

Since itaconic acid (a-1) has two acid groups, the dispersibility of the polymer particles is high even under the condition of low neutralization degree, and the fixability and fixability are improved as compared with the case where a hydrophilic monomer having one acid group is used. Document resistance can be improved. From this point of view, the degree of neutralization of the polymer (A) is preferably 10 mol% or more, more preferably 15 mol% or more, still more preferably 20 mol% or more, still more preferably 25 mol% or more, and It is preferably 50 mol% or less, more preferably 45 mol% or less, still more preferably 40 mol% or less, still more preferably 35 mol% or less, still more preferably 30 mol% or less.
Here, the degree of neutralization is a value obtained by dividing the number of molar equivalents of the neutralizing agent by the number of molar equivalents of the acid groups of the polymer (A) (polymer (A')) before neutralization, that is, "molar of neutralizing agent". It is a value of "equivalent number / molar equivalent number of acid groups of the polymer (A')". Originally, the degree of neutralization does not exceed 100 mol%, but in the present invention, since it is calculated from the number of molar equivalents of the neutralizing agent, it exceeds 100 mol% when the neutralizing agent is excessively used.

The emulsification method is not particularly limited, and it is preferable to control the average particle size of the polymer (A) particles to a desired particle size by using a known stirrer, mixer or the like. The emulsifying temperature is preferably less than 100 ° C, more preferably 95 ° C or lower.
The average particle size of the polymer (A) particles is preferably 20 nm or more, more preferably 30 nm or more, still more preferably 40 nm or more, from the viewpoint of reducing coarse particles and improving fixability and document offset resistance. And, preferably 400 nm or less, more preferably 300 nm or less, still more preferably 200 nm or less, still more preferably 100 nm or less, still more preferably 80 nm or less, still more preferably 60 nm or less.
The average particle size is measured by the method described in Examples.

[Crosslink]
The resin emulsion of the present invention is preferably crosslinked polymer particles obtained by cross-linking polymer (A) particles from the viewpoint of improving fixability and document offset resistance.
The crosslinked polymer particles are formed by cross-linking the polymer (A) particles with a cross-linking agent.
The cross-linking agent is preferably a compound having at least two reactive groups in the molecule that react with the acid group from the viewpoint of improving the fixing property and the document offset resistance. The molecular weight of the cross-linking agent is preferably 120 or more, more preferably 150 or more, and preferably 2,000 or less, more preferably 1,500, from the viewpoint of improving reactivity, fixing property and document offset resistance. Below, it is more preferably 1,000 or less, and even more preferably 500 or less.
The number of reactive groups contained in the cross-linking agent is preferably 2 or more and 4 or less, more preferably 2 or more and 3 or less, and further preferably 2 from the viewpoint of efficiently carrying out the cross-linking reaction. Examples of the reactive group include an epoxy group, an oxazoline group, a hydroxy group, an amino group, an isocyanate group and the like, and among these, an epoxy group is preferable.

The cross-linking agent having an epoxy group is preferably a polyhydric alcohol glycidyl ether, and a cross-linking agent having a group derived from the polyhydric alcohol is preferable.
The carbon number of the polyhydric alcohol is preferably 2 or more, more preferably 4 or more, still more preferably 6 or more, and preferably 14 or less, more preferably 14 or less, from the viewpoint of improving fixability and document offset resistance. Is 10 or less, more preferably 8 or less.
Examples of the polyhydric alcohol include alkylene glycols such as ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol and polypropylene glycol; 1,4-butanediol, 1,6-hexanediol and 1,4-cyclohexanedimethanol. , Alcandiols such as neopentyl glycol; trimethylolpropane; pentaerythritol and the like.

Specific examples of the cross-linking agent include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and 1,4-butanediol. Diglycidyl ether, 1,6-hexanediol diglycidyl ether, 1,8-octanediol diglycidyl ether, 1,10-decanediol diglycidyl ether, 1,12-dodecanediol diglycidyl ether, 1,14-tetradecanediol Dihydric alcohol diglycidyl ether such as diglycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, neopentyl glycol diglycidyl ether; trihydric alcohol polyglycidyl ether such as trimethylolpropane polyglycidyl ether; pentaerythritol polyglycidyl ether Examples thereof include tetravalent alcohol polyglycidyl ether and the like. Among these, one or more selected from 1,6-hexanediol diglycidyl ether and trimethylolpropane polyglycidyl ether are preferable, and 1,6-hexanediol diglycidyl ether is more preferable.

Specific examples of commercially available polyhydric alcohol glycidyl ether type cross-linking agents include Denacol EX-810 (ethylene glycol diglycidyl ether), Denacol EX-811 (ethylene glycol diglycidyl ether), and Denacol EX-911 (. Propropylene glycol diglycidyl ether), Denacol EX-850 (diethylene glycol diglycidyl ether), Denacol EX-851 (diethylene glycol diglycidyl ether), Denacol EX-941 (polypropylene glycol diglycidyl ether, n = 2 (catalog value)), Denacol EX-920 (polyprepylene glycol diglycidyl ether, n = 3 (catalog value)), Denacol EX-212 (1,6-hexanediol diglycidyl ether), Denacol EX-216 (1,4-cyclohexanedimethanol dimethanol). Glycidyl ether), Denacol EX-211 (neopentyl glycol diglycidyl ether), Denacol EX-321 (trimethylol propanepolyglycidyl ether), and their L series (low chlorine products) (all manufactured by Nagase ChemteX Corporation). , Epolite 40E (ethylene glycol diglycidyl ether), Epolite 100E (diethylene glycol diglycidyl ether), Epolite 1600 (1,6-hexanediol diglycidyl ether) (all manufactured by Kyoeisha Chemical Co., Ltd.), Ricaresin DME-100 (1, 4-Cyclohexanedimethanol diglycidyl ether) (manufactured by Shin Nihon Rika Co., Ltd.) and the like can be mentioned.

When the polymer (A) particles are crosslinked polymer particles, the average particle size of the polymer (A) particles is preferably 20 nm or more from the viewpoint of reducing coarse particles and improving fixability and document offset resistance. It is more preferably 30 nm or more, further preferably 40 nm or more, and preferably 400 nm or less, more preferably 300 nm or less, still more preferably 200 nm or less, still more preferably 100 nm or less, still more preferably 80 nm or less, still more preferable. Is 60 nm or less.
The average particle size is measured by the method described in Examples.

The non-volatile component concentration (solid content concentration) of the resin emulsion of the present invention is preferably 10% by mass or more, more preferably 20% by mass, from the viewpoint of improving the dispersibility of the polymer particles and facilitating the preparation of the water-based ink. The above, and preferably 40% by mass or less, more preferably 30% by mass or less.
The solid content concentration of the resin emulsion is measured by the method described in Examples.

[Water-based ink]
The water-based ink of the present invention (hereinafter, also simply referred to as “ink”) contains the resin emulsion.
The color of the ink of the present invention is not particularly limited, and is a chromatic color such as C (cyan), M (magenta), Y (yellow), special color (S); K (black), W (white), CL ( Achromatic colors such as clear) can be mentioned. Clear ink is a colorless and transparent ink that does not contain a colorant.

<Colorant>
The ink of the present invention preferably contains the resin emulsion and a colorant. Examples of the colorant include pigments, hydrophobic dyes, water-soluble dyes (acid dyes, reactive dyes, direct dyes, etc.) and the like. From the viewpoint of improving the water resistance and weather resistance of the printed matter, at least one selected from pigments and hydrophobic dyes, more preferably pigments.
The pigment may be either an inorganic pigment or an organic pigment. In addition, if necessary, they can be used in combination with extender pigments.
Examples of the inorganic pigment include carbon black and metal oxides, and carbon black is particularly preferable for black ink. Examples of carbon black include furnace black, thermal lamp black, acetylene black, and channel black.
Examples of the organic pigment include azo pigment, diazo pigment, phthalocyanine pigment, quinacridone pigment, isoindolinone pigment, dioxazine pigment, perylene pigment, perinone pigment, thioindigo pigment, anthraquinone pigment, quinophthalone pigment and the like.
The hue is not particularly limited, and any chromatic pigment such as yellow, magenta, cyan, blue, red, orange, and green can be used.
Specific examples of preferable organic pigments include C.I. I. Pigment Yellow, C.I. I. Pigment Red, C.I. I. Pigment Orange, C.I. I. Pigment Violet, C.I. I. Pigment Blue, and C.I. I. One or more product numbers selected from Pigment Green can be mentioned.
Examples of the extender pigment include silica, calcium carbonate, talc and the like.

In the present invention, a self-dispersing pigment can also be used. The self-dispersion pigment is a direct one or more of hydrophilic functional groups (hydrophilic groups having anionic properties such as carboxy group and sulfonic acid group, or hydrophilic groups having cationic properties such as quaternary ammonium group). Alternatively, it means a pigment that can be dispersed in an aqueous medium without using a surfactant or a polymer dispersant by being bonded to the surface of the pigment via another atomic group. Here, examples of other atomic groups include an alkanediyl group having 1 or more and 12 or less carbon atoms, a phenylene group, a naphthylene group, and the like.
In order to make the pigment a self-dispersing pigment, for example, the required amount of hydrophilic functional groups may be chemically bonded to the pigment surface by a conventional method. More specifically, a method of liquid phase oxidation with an acid such as nitric acid, sulfuric acid, peroxodisulfuric acid, hypochloric acid, chromic acid or the like, or a method of binding a hydrophilic functional group using a coupling agent is preferable.

The hydrophobic dye means a dye having a solubility in 100 g of water at 20 ° C. of less than 6 g / 100 gH ₂ O. Examples of the hydrophobic dye include oil-soluble dyes and disperse dyes.
The colorants may be used alone or in admixture of two or more at any ratio.

<Water-insoluble polymer (B)>
The ink of the present invention is a water-insoluble polymer (B) (hereinafter, simply referred to as a water-insoluble polymer) from the viewpoint of improving the dispersion stability of the colorant in the ink, improving the image density of the ink, and improving the fixability and the document offset resistance. It is preferably contained (also referred to as "polymer (B)") and the colorant is dispersed in the polymer (B). The polymer (B) has a function as a dispersant for a colorant.
Here, "water-insoluble" means that the amount of the polymer that has reached a constant weight after being dried at 105 ° C. for 2 hours is less than 10 g when dissolved in 100 g of water at 25 ° C. until saturated. This means that the dissolved amount is preferably 5 g or less, more preferably 1 g or less. When the polymer (B) is an anionic polymer, the amount of dissolution thereof is the amount of dissolution when the anionic group of the polymer is 100% neutralized with sodium hydroxide. When the polymer (B) is a cationic polymer, the amount of dissolution thereof is the amount of dissolution when the cationic group of the polymer is 100% neutralized with hydrochloric acid.
Examples of the polymer (B) include vinyl-based polymers, polyesters, polyurethanes and the like. Among these, from the viewpoint of improving the dispersion stability of the colorant, and from the viewpoint of improving the fixability and document offset resistance, it is preferably obtained by addition polymerization of a vinyl monomer (vinyl compound, vinylidene compound, vinylene compound). It is a vinyl-based polymer that is used.

As a vinyl-based polymer, the polymer (B) contains a structural unit derived from the ionic monomer (b-1) from the viewpoint of improving the dispersion stability of the colorant and improving the fixability and the document offset resistance. Those containing a structural unit derived from the hydrophobic monomer (b-2) are preferable.

The ionic monomer (b-1) is preferably an anionic monomer from the viewpoint of improving the dispersion stability of the colorant in the ink. Examples of the anionic monomer include a carboxylic acid monomer, a sulfonic acid monomer, and a phosphoric acid monomer. Examples of the carboxylic acid monomer include acrylic acid, methacrylic acid, maleic acid, fumaric acid, 2-methacryloyloxymethylsuccinic acid and the like.
Among the anionic monomers, at least one selected from a carboxylic acid monomer, more preferably acrylic acid and methacrylic acid, from the viewpoint of improving the dispersion stability of the colorant in the ink.
The content of the structural unit derived from the ionic monomer (b-1) is preferably 2% by mass or more, more preferably 5 in the polymer (B) from the viewpoint of improving the dispersion stability of the colorant in the ink. It is by mass or more, more preferably 8% by mass or more, and preferably 40% by mass or less, more preferably 30% by mass or less, still more preferably 25% by mass or less.

The hydrophobic monomer (b-2) is more preferably 1 or more and 22 or less carbon atoms from the viewpoint of improving the dispersion stability of the colorant in the ink and improving the fixability and the document offset resistance. Alkyl (meth) acrylate having an alkyl group having 6 to 18 carbon atoms; styrene-based monomer such as styrene, 2-methylstyrene, divinylbenzene; containing aromatic groups such as benzyl (meth) acrylate and phenoxyethyl (meth) acrylate. Examples thereof include (meth) acrylate, and styrene and benzyl (meth) acrylate are preferable.
The content of the structural unit derived from the hydrophobic monomer (b-2) is the polymer (B) from the viewpoint of improving the dispersion stability of the colorant in the ink and improving the fixability and the document offset resistance. Among them, it is preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 98% by mass or less, more preferably 80% by mass or less.

From the viewpoint of improving the dispersion stability of the colorant in the ink, the polymer (B) further has a polymerizable functional group such as a (meth) acryloyloxy group at one end and has a number average molecular weight of 500 or more and 100,000 or less. It may contain a macromer, a nonionic monomer having a polyoxyalkylene glycol chain, and the like.
The amounts of the macromer and the nonionic monomer component are preferably 1% by mass or more, more preferably 5% by mass or more, respectively, in the polymer (B) from the viewpoint of improving the dispersion stability of the colorant in the ink. And, preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, still more preferably 20% by mass or less.

As the monomer component of the polymer (B), one kind may be used alone or two or more kinds may be used in combination.
The weight average molecular weight of the polymer (B) is preferably 5,000 or more, more preferably 10,000 or more, still more preferably 20,000 or more, from the viewpoint of improving the dispersion stability of the colorant in the ink. And, preferably 500,000 or less, more preferably 400,000 or less, still more preferably 300,000 or less, still more preferably 200,000 or less. The weight average molecular weight can be measured by the method described in Examples.

The polymer (B) is produced by copolymerizing a monomer mixture by a known polymerization method. As a polymerization method, for example, a solution polymerization method in which the monomer mixture is heated and polymerized in a solvent together with a polymerization initiator, a polymerization chain transfer agent and the like can be mentioned as a preferable example.
After completion of the polymerization reaction, the produced polymer may be isolated and purified by a known method such as reprecipitation or solvent distillation from the reaction solution.

The present form of the polymer (B) in the ink includes a state in which the polymer (B) is adsorbed on the colorant, a state in which the colorant is contained, and a state in which the colorant is not adsorbed. Among these, from the viewpoint of improving the dispersion stability of the colorant, and from the viewpoint of improving the fixability and the document offset resistance, the polymer particles containing the colorant are preferable.
Hereinafter, the polymer (B) particles containing the colorant will be described.

(Colorant-containing polymer (B) particles)
The colorant-containing polymer (B) particles (hereinafter, also simply referred to as “colorant-containing polymer (B) particles”) are, for example, a colorant, a polymer (B), an organic solvent, water, and, if necessary, medium. A colorant mixture containing a Japanese agent, a surfactant, etc. is dispersed to obtain a dispersion of colorant-containing polymer (B) particles, and then the organic solvent is removed from the dispersion to contain the colorant. It can be produced by a method for obtaining a colorant aqueous dispersion of polymer (B) particles.
The organic solvent for dissolving the polymer (B) is not limited, but aliphatic alcohols having 1 or more and 3 or less carbon atoms, ketones, ethers, esters and the like are preferable, and the wettability to a colorant and the wettability of the polymer (B) From the viewpoint of improving the solubility and the adsorptivity of the polymer (B) to the colorant, a ketone having 4 or more and 8 or less carbon atoms is more preferable, a methyl ethyl ketone and a methyl isobutyl ketone are further preferable, and a methyl ethyl ketone is further preferable.
When the polymer (B) is synthesized by the solution polymerization method, the solvent used in the polymerization may be used as it is.

When the polymer (B) is an anionic polymer, a neutralizing agent may be used to neutralize the anionic groups in the polymer (B). When a neutralizing agent is used, it is preferable to neutralize the pH so that the pH is 7 or more and 11 or less.
Examples of the neutralizing agent include alkali metal hydroxides, ammonia, organic amines and the like.
Further, the polymer (B) may be neutralized in advance.

(Contents of each component in the colorant mixture)
The content of the colorant in the colorant mixture is preferably 10% by mass or more, more preferably 12% by mass or more, and further, from the viewpoint of improving the dispersion stability of the colorant aqueous dispersion and increasing the image density. It is preferably 14% by mass or more, preferably 30% by mass or less, more preferably 25% by mass or less, and further preferably 20% by mass or less.
The content of the polymer (B) in the colorant mixture is preferably 2% by mass or more, more preferably 3% by mass or more, from the viewpoint of improving the dispersion stability of the colorant aqueous dispersion and increasing the image density. It is more preferably 4% by mass or more, preferably 15% by mass or less, more preferably 10% by mass or less, still more preferably 7% by mass or less.

The mass ratio of the colorant to the polymer (B) in the colorant mixture [colorant / polymer (B)] is preferably from the viewpoint of improving the dispersion stability of the colorant aqueous dispersion and increasing the image density. 30/70 or more, more preferably 40/60 or more, still more preferably 50/50 or more, still more preferably 60/40 or more, even more preferably 70/30 or more, and preferably 90/10 or less. It is more preferably 85/15 or less, still more preferably 80/20 or less.

There are no particular restrictions on the method of dispersing the colorant mixture. It is preferable to control the average particle size of the colorant-containing polymer (B) particles to a desired particle size by using a known kneader, disperser or the like.
By removing the organic solvent from the obtained dispersion by a known method, an aqueous dispersion of the colorant-containing polymer (B) particles (colorant aqueous dispersion) can be obtained.
Further, if necessary, the dispersion can be heat-stirred before distilling off the organic solvent.
The colorant aqueous dispersion is one in which solid polymer (B) particles containing a colorant are dispersed in a medium containing water as a main medium. Here, the form of the colorant-containing polymer (B) particles is not particularly limited, and at least the particles may be formed by the colorant and the polymer (B). For example, a particle morphology in which a colorant is contained in the polymer (B), a particle morphology in which the colorant is uniformly dispersed in the polymer (B), a particle morphology in which the colorant is exposed on the particle surface of the polymer (B), and the like. Is included, and a mixture of these is also included.

The concentration of the non-volatile component (solid content concentration) of the aqueous colorant dispersion is preferably 10% by mass or more, more preferably 10% by mass or more, from the viewpoint of improving the dispersion stability of the aqueous colorant dispersion and facilitating the preparation of ink. It is 15% by mass or more, preferably 30% by mass or less, and more preferably 25% by mass or less.
The solid content concentration of the aqueous colorant dispersion is measured by the method described in Examples.

The average particle size of the colorant-containing polymer (B) particles in the colorant aqueous dispersion is preferably 40 nm or more, more preferably 40 nm or more, from the viewpoint of reducing coarse particles and improving fixability and document offset resistance. It is 60 nm or more, more preferably 75 nm or more, still more preferably 100 nm or more, and preferably 300 nm or less, more preferably 200 nm or less, still more preferably 150 nm or less.
The average particle size of the colorant-containing polymer (B) particles in the colorant aqueous dispersion is measured by the method described in Examples.
Further, it is preferable that the colorant-containing polymer (B) particles in the ink do not swell or shrink, or aggregate between the particles, and the average particle size of the colorant-containing polymer (B) particles in the ink is , Colorant It is preferable that the particle size is the same as the average particle size in the aqueous dispersion. The preferred aspect of the average particle size of the colorant-containing polymer (B) particles in the ink is the same as the preferred aspect of the average particle size in the aqueous colorant dispersion. The average particle size of the colorant-containing polymer (B) particles in the ink is also measured by the method described in Examples.

The colorant constituting the colorant-containing polymer (B) particles is preferably a pigment and a hydrophobic dye from the viewpoint of improving the dispersion stability of the colorant aqueous dispersion and improving the fixability and document offset resistance. At least one selected from, more preferably a pigment.

(Organic solvent (C))
The ink of the present invention preferably further contains an organic solvent (C) from the viewpoint of improving fixability and document offset resistance. The boiling point of the organic solvent (C) is preferably 90 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 150 ° C. or higher, still more preferably 180 ° C. or higher, and preferably less than 250 ° C., more preferably. It is preferably 240 ° C. or lower, more preferably 230 ° C. or lower, and even more preferably 220 ° C. or lower.
When two or more kinds of organic solvents are used in combination as the organic solvent (C), the boiling point of the organic solvent (C) is a weighted average value weighted by the content (mass%) of each organic solvent.

The organic solvent (C) preferably contains a polyhydric alcohol having a boiling point of 90 ° C. or higher. The polyhydric alcohol is preferably a compound having a boiling point of less than 250 ° C.
Examples of polyhydric alcohols having a boiling point of 90 ° C. or higher include ethylene glycol (boiling point 197 ° C.), propylene glycol (boiling point 188 ° C.), 1,2-butanediol (boiling point 193 ° C.), and 1,2-pentanediol (boiling point 206 ° C.). ), 1,2-Alcoholdiol (boiling point 223 ° C.); diethylene glycol (boiling point 244 ° C.), polyethylene glycol, dipropylene glycol (boiling point 232 ° C.), 1,3-propanediol (boiling point 210 ° C.) ℃), 1,3-butanediol (boiling point 208 ℃), 1,4-butanediol (boiling point 230 ℃), 3-methyl-1,3-butanediol (boiling point 203 ℃), 1,5-pentanediol (boiled point 203 ℃) Boiling point 242 ° C.), 2-Methyl-2,4-pentanediol (boiling point 196 ° C.), 1,2,6-hexanetriol (boiling point 178 ° C.), 1,2,4-butantriol (boiling point 190 ° C.), 1 , 2,3-Butantriol (boiling point 175 ° C.), Petriol (boiling point 216 ° C.) and the like.
Further, compounds having a boiling point of 250 ° C. or higher, such as 1,6-hexanediol (boiling point 250 ° C.), triethylene glycol (boiling point 285 ° C.), tripropylene glycol (boiling point 273 ° C.), and glycerin (boiling point 290 ° C.), can be used. May be used in combination with a compound having a temperature below 250 ° C.

The organic solvent (C) is an organic solvent other than the polyhydric alcohol, such as glycol ether, an alcohol other than the polyhydric alcohol, an alkyl ether of the alcohol, a nitrogen-containing heterocyclic compound such as N-methyl-2-pyrrolidone, and an amide. , Amine, sulfur-containing compounds and the like may be contained. The organic solvent other than the polyhydric alcohol may be used alone or in combination of two or more.

The content of the polyhydric alcohol having a boiling point of 90 ° C. or higher in the organic solvent (C) is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably, from the viewpoint of improving fixability and document offset resistance. Is 100% by mass.
The organic solvent (C) is preferably a polyhydric alcohol from the viewpoint of improving fixability and document offset resistance, and more preferably one or more selected from diethylene glycol, propylene glycol and glycerin.

(Other ingredients)
In addition to the above components, the ink of the present invention includes various commonly used surfactants, moisturizers, wetting agents, penetrants, viscosity modifiers, defoaming agents, preservatives, fungicides, rust preventives and the like. Additives can be added.

(Surfactant)
The ink of the present invention preferably further contains a surfactant from the viewpoint of improving fixability and document offset resistance. Examples of the surfactant include nonionic surfactants, silicone-based surfactants, fluorine-based active agents and the like, but nonionic surfactants are more preferable.
The nonionic surfactant may be any one that can be used for water-based inks, for example, a polyoxyalkylene alkyl ether type surfactant, an acetylene glycol type surfactant, a polyhydric alcohol type surfactant, and a fatty acid alkanol. Examples include amides. Among these, polyoxyalkylene alkyl ether type surfactants, acetylene glycol-based surfactants are preferable, and from alkylene oxide adducts of alcohols having 6 or more and 30 or less carbon atoms, and acetylene glycol-based surfactants. One or more selected ones are more preferable, and from the viewpoint of improving fixability and document offset resistance, a surfactant of an alcohol alkylene oxide adduct having 6 or more and 30 or less carbon atoms and an acetylene glycol-based surfactant are used in combination. It is more preferable to do so.

(Manufacturing of water-based ink)
The ink of the present invention can be obtained by mixing and stirring the resin emulsion, water, if necessary, the colorant, the polymer (B), the organic solvent (C), the surfactant, and other components. Can be done. The content of each component of the ink of the present invention and the physical characteristics of the ink are as follows.

(Content of resin emulsion)
The content of the resin emulsion in the ink is preferably 1% by mass or more, more preferably 2% by mass or more, still more preferably 3% by mass in terms of solid content, from the viewpoint of improving fixability and document offset resistance. As mentioned above, it is more preferably 4% by mass or more, and preferably 15% by mass or less, more preferably 12% by mass or less, still more preferably 10% by mass or less, still more preferably 8% by mass or less.

(Contents of colorant)
The content of the colorant in the ink is preferably 1% by mass or more, more preferably 2% by mass or more, still more preferably 3% by mass or more, and fixability and document offset resistance from the viewpoint of image density. From the viewpoint of improvement, it is preferably 15% by mass or less, more preferably 10% by mass or less, still more preferably 7% by mass or less, still more preferably 5% by mass or less.

(Total content of colorant and polymer (B))
The total content of the colorant and the polymer (B) in the ink is preferably 2% by mass or more, more preferably 3% by mass or more, still more preferably 4% by mass from the viewpoint of improving fixability and document offset resistance. % Or more, preferably 20% by mass or less, more preferably 15% by mass or less, still more preferably 12% by mass or less, still more preferably 10% by mass or less, still more preferably 7% by mass or less.

(Mass ratio [colorant / polymer (B)])
The mass ratio of the colorant to the polymer (B) in the ink [colorant / polymer (B)] is preferably 30/70 or more, more preferably 40/60 or more, from the viewpoint of improving fixability and document offset resistance. , More preferably 50/50 or more, even more preferably 60/40 or more, even more preferably 70/30 or more, and preferably 90/10 or less, more preferably 85/15 or less, still more preferably 80. It is 20 or less.

(Content of organic solvent (C))
The content of the organic solvent (C) in the ink is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and more, from the viewpoint of improving fixability and document offset resistance. It is more preferably 20% by mass or more, and preferably 40% by mass or less, more preferably 35% by mass or less, still more preferably 30% by mass or less.

(Surfactant content)
The content of the surfactant in the ink is preferably 0.5% by mass or more, more preferably 1% by mass or more, still more preferably 2% by mass or more, from the viewpoint of improving fixability and document offset resistance. And, preferably 5% by mass or less, more preferably 4% by mass or less, still more preferably 3% by mass or less.

(Water content)
The content of water in the ink is preferably 40% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, and preferably 60% by mass or more, from the viewpoint of improving fixability and document offset resistance. Is 80% by mass or less, more preferably 75% by mass or less, still more preferably 70% by mass or less.

The polymer (A) particles preferably do not swell or shrink, or aggregate between the particles, and the average particle size of the polymer (A) particles in the ink is the same as the average particle size in the resin emulsion. It is preferable to have. The preferred embodiment of the average particle size of the polymer (A) particles in the ink is the same as the preferred embodiment of the average particle size in the resin emulsion. The average particle size of the polymer (A) particles in the ink is also measured by the same method as described in Examples.

(Physical characteristics of water-based ink)
The viscosity of the ink at 25 ° C. is preferably 2.0 mPa · s or more, more preferably 3.0 mPa · s or more, still more preferably 4.0 mPa · s or more, and preferably 12 mPa · s or less, more preferably. Is 9.0 mPa · s or less, more preferably 7.0 mPa · s or less, still more preferably 6.0 mPa · s or less.
The viscosity of the ink is measured by the method described in Examples.

The pH of the ink at 25 ° C. is preferably 7.0 or higher, more preferably 7.5 or higher, from the viewpoint of improving fixability and document offset resistance. Further, from the viewpoint of member resistance and skin irritation, the pH is preferably 11.0 or less, more preferably 10.0 or less, still more preferably 9.5 or less.
The pH of the ink is measured by the method described in Examples.

(Inkjet printing method)
Since the ink of the present invention can obtain a printed matter having excellent fixability and document offset resistance even when printed on a resin printing medium, it should be used as a water-based ink for flexo printing, gravure printing, or inkjet printing. Therefore, it is preferable to use it as a water-based ink for inkjet printing because it is excellent in fixing property and document offset resistance in inkjet printing.

In the inkjet printing method using the ink, a serial head method, a line head method, or the like can be used, but it is preferable to use an inkjet recording device having a line head type recording head. The line head type recording head is a long recording head about the width of the printing medium. The recording head is fixed, the printing medium is moved in the transport direction, and the printing medium is moved from the nozzle opening of the recording head in conjunction with this movement. An image or the like can be recorded by ejecting ink droplets and adhering them to a printing medium.
Examples of the printing medium include low water-absorbent printing media such as art paper and coated paper, and non-water-absorbent resin printing media such as synthetic resin film. Among these, a resin printing medium is preferable from the viewpoint of improving fixability and document offset resistance. Further, a water-absorbent printing medium such as plain paper or high-quality paper can also be used as the printing medium.

Examples of the resin printing medium include a polyester film such as a polyethylene terephthalate film; a polyvinyl chloride film; a polyolefin film such as a polypropylene film and a polyethylene film; and a synthetic resin film such as a polyamide film such as a nylon film. These films may be biaxially stretched films, uniaxially stretched films, and non-stretched films. Among these, a polyester film is preferable, and a polyethylene terephthalate film is more preferable.
The thickness of the resin printing medium is not particularly limited, and a thin film having a thickness of 1 μm or more and less than 20 μm may be used. It is more preferably 80 μm or more, and preferably 200 μm or less, more preferably 170 μm or less, still more preferably 150 μm or less.
Commercially available synthetic resin films include Lumirror P60, Lumirror T60 (above, Toray Co., Ltd., polyethylene terephthalate), Taiko FE2001 (Futamura Chemical Co., Ltd., corona-treated polyethylene terephthalate), PVC80B P (Lintec Co., Ltd., chloride). Vinyl), Kinus KEE70CA (polyethylene manufactured by Lintec Co., Ltd.), YUPO SG90 PAT1 (polypropylene manufactured by Lintec Co., Ltd.), Bonnil RX (manufactured by Kojin Film & Chemicals Co., Ltd., nylon) and the like.

In the following preparation examples, synthesis examples, production examples, examples and comparative examples, "%" is "mass%" unless otherwise specified.
Each physical property was measured by the following method.

[Acid value of polymer (A')]
The acid value of the polymer (A') was measured according to the method of JIS K 0070. However, only the measurement solvent was changed from the mixed solvent of ethanol and ether specified in JIS K 0070 to the mixed solvent of acetone and toluene (acetone: toluene = 4: 6 (volume ratio)).

[Measurement of weight average molecular weight and number average molecular weight of polymer (A') and polymer (B)]
A gel permeation chromatography method [GPC apparatus "HLC-8120GPC" (GPC apparatus "HLC-8120GPC") using 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, as an eluent. (Made by Toso Co., Ltd.) Two columns "TSK-GEL, α-M" (manufactured by Toso Co., Ltd.), flow velocity: 1 mL / min], and the measurement was performed using polystyrene having a known molecular weight as a standard substance.

[Average particle size of polymer (A) particles in resin emulsion]
The cumulant average particle size was measured under the following measurement conditions using a dynamic light scattering type particle size measuring machine "Zetasizer Nano ZS" (manufactured by Malvern). The average cumulant particle size obtained was taken as the average particle size of the polymer (A) particles in the resin emulsion.
(Measurement condition)
Solid content concentration: 0.1%
Measurement temperature: 25 ° C
Medium: Water Measurement cell: Glass Cuvette
Laser specifications: He-Ne, 4mW, 633nm
Detection optical system: NIBS, 173 ° C
Number of measurements: 10 times Isothermal time: 5 minutes Analysis software: Zeta Sizer Software 6.2
Analysis method: General Purpose Mode (cumulant method)

[Concentration of solid content of resin emulsion]
Using an infrared moisture meter "FD-230" (manufactured by Ketsuto Kagaku Kenkyusho Co., Ltd.), 5 g of resin emulsion is dried at a drying temperature of 150 ° C. and measured mode 96 (monitoring time 2.5 minutes / fluctuation range 0.05%). The water content (%) of the resin emulsion was measured. The solid content concentration was calculated according to the following formula.
Solid content concentration (%) = 100-M
M: Moisture (%) of the resin emulsion = [(W-W ₀ ) / W] x 100
W: Sample mass before measurement (initial sample mass)
W ₀ : Sample mass after measurement (absolute dry mass)

[Measurement of solid content concentration of aqueous dispersion (colorant aqueous dispersion) of colorant-containing polymer (B) particles]
Weigh 10.0 g of sodium sulfate homogenized in a desiccator into a 30 mL container, add about 1.0 g of a sample to the container, mix, weigh accurately, and maintain at 105 ° C. for 2 hours. Volatile components were removed, and the mixture was left in a desiccator for 15 minutes to measure the mass. The mass of the sample after removing the volatile matter was taken as the solid content and divided by the mass of the added sample to obtain the solid content concentration.

[Measurement of average particle size of colorant-containing polymer (B) particles]
The average particle size of the cumulant obtained by measurement using the laser particle analysis system "ELS-8000" (Otsuka Electronics Co., Ltd., cumulant analysis) was taken as the average particle size of the colorant-containing polymer (B) particles. A dispersion diluted with water was used so that the concentration of the particles to be measured was about 5 × 10 ^-3 %. The measurement conditions were a temperature of 25 ° C., an angle of 90 ° between the incident light and the detector, and 100 times of integration, and the refractive index of water (1.333) was input as the refractive index of the dispersion solvent.

[Measurement of viscosity of water-based ink]
The viscosity was measured at 25 ° C. using an E-type viscometer "TV-25" (manufactured by Toki Sangyo Co., Ltd., standard cone rotor 1 ° 34'x R24 used, rotation speed 50 rpm).

[Measurement of pH of water-based ink]
The pH of the water-based ink at 25 ° C. was measured using a desktop pH meter "F-71" (manufactured by HORIBA, Ltd.) using a pH electrode "6337-10D" (manufactured by HORIBA, Ltd.).

(Preparation of aqueous dispersion of colorant-containing polymer (B) particles)
Preparation Example 1
(1) Synthesis of polymer (B) 91 g of methacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd.), 399 g of benzyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd.), methoxypolyethylene glycol methacrylate "M-230G" (Shin Nakamura Chemical Industry Co., Ltd.) A monomer mixed solution of 770 g was prepared by mixing 140 g of ethylene oxide having an average addition molar number of 23) and 140 g of styrene macromer "AS-6S" (manufactured by Toa Synthetic Co., Ltd., solid content 50%).
In the reaction vessel, 15.75 g of methyl ethyl ketone, 0.35 g of a polymerization chain transfer agent (2-mercaptoethanol), and 10% (77 g) of the above-mentioned monomer mixture were put and mixed, and nitrogen gas substitution was performed.
Separately, 80% (616 g) of the monomer mixture, 2.45 g of the polymerization chain transfer agent, 173.25 g of the methyl ethyl ketone and the polymerization initiator "V-65" (manufactured by Wako Pure Chemical Industries, Ltd., 2,) are added to the dropping funnel. A mixture of 5.6 g of 2'-azobis (2,4-dimethylvaleronitrile) was added, and the temperature was raised to 75 ° C. while stirring the mixed solution in the reaction vessel under a nitrogen atmosphere, and the mixture was mixed in the dropping funnel. The solution was added dropwise over 4.5 hours. Then, the remaining 10% (77 g) of the monomer mixture, 0.7 g of the polymerization chain transfer agent, 126 g of the methyl ethyl ketone and 1.4 g of the polymerization initiator were placed in a dropping funnel at 75 ° C. for 1.7 hours. And dropped. After completion of the dropping, 2.1 g of the polymerization initiator was mixed, the temperature was raised to 80 ° C., and the mixture was stirred for 1.5 hours. By further mixing, raising the temperature, and stirring the polymerization initiator twice, a polymer solution of the acrylic polymer (B1) (weight average molecular weight of the polymer (B1): 26,000) was obtained.

(2) Preparation of water dispersion (colorant water dispersion) of colorant-containing polymer (B) particles 20 g of the polymer (B1) obtained by drying the polymer solution obtained in the above (1) under reduced pressure is methyl ethyl ketone 62. Dissolve in 0.8 g, add 5.01 g of neutralizing agent 5N sodium hydroxide aqueous solution, 1.13 g of 25% ammonia water, and 236.5 g of ion-exchanged water, and use a disper blade at 10 to 15 ° C. 2, Stirring and mixing were performed at 000 rpm for 15 minutes. Subsequently, as a colorant, a magenta pigment [C. I. Pigment Violet 19 "Inkjet Magenta E5B02" (manufactured by Clariant) 45g and C.I. I. Pigment Red 122 "6111T" (manufactured by Dainichiseika Kogyo Co., Ltd.) 25 g] was added, and the mixture was stirred and mixed at 7,000 rpm for 3 hours at 10 to 15 ° C. using a disper blade to obtain a colorant mixture. The obtained colorant mixture was filtered by 200 mesh and subjected to 20-pass dispersion treatment at a pressure of 150 MPa using a microfluidics "M-110K" (high-pressure homogenizer manufactured by Microfluidics) to obtain a colorant-containing polymer (B1). A dispersion of particles was obtained.
Methyl ethyl ketone was removed from the obtained dispersion at 60 ° C. under reduced pressure, a part of water was further removed, the mixture was centrifuged, and the liquid layer portion was filtered through a filter (manufactured by Sartorius Stedim Biotech) having a pore size of 5 μm to obtain coarse particles. The particles were removed to obtain an aqueous dispersion. Further, in 80 g of this aqueous dispersion, 5.0 g of glycerin (manufactured by Kao Co., Ltd.), 0.2 g of 1,2-benzoisothiazole-3 (2H) -on "Proxel XL2" (manufactured by Abyssia Co., Ltd.), ion-exchanged water 14 After mixing 0.8 g and sterilizing at 70 ° C. for 1 hour, the mixture was cooled to room temperature and filtered through the filter having a pore size of 5 μm to obtain an aqueous dispersion of colorant-containing polymer (B1) particles [solid content]. A concentration of 20% and an average particle size of 133 nm] were obtained.

(Synthesis of polymer (A'))
Synthesis example 1
In a 200 mL two-necked round-bottom flask equipped with a thermometer and a reflux device, itaconic acid 9 g, styrene 21 g, 1,4-dioxane (solvent) 45 g, 2,2-azobis (isobutyronitrile) (Wako Pure Chemical Industries, Ltd.) 0.50 g of a polymerization initiator (manufactured by Tokyo Kasei Kogyo Co., Ltd.) and 0.30 g of 3-mercaptopropionic acid (a polymerization chain transfer agent manufactured by Tokyo Kasei Kogyo Co., Ltd.) were added and mixed with a magnetic stirrer. The mixture was bubbled with nitrogen for 10 minutes, then heated to 77 ° C. in a water bath and stirred for 30 minutes. Then, the temperature was kept at 77 ° C. for 16 hours to terminate the reaction. Then, after distilling off the solvent at 70 ° C. and 20 kPa, the mixture was dried at 70 ° C. and 8 kPa for 8 hours to obtain a polymer (A'1) having an acid value of 220 mgKOH / g and a number average molecular weight of 1,600.

Synthesis example 2-3
Polymers (A'2) and (A'3) were obtained in the same manner as in Synthesis Example 1 except that the amounts of itaconic acid and styrene were changed to the mass ratios shown in Table 1 in Synthesis Example 1.

Synthesis Examples 4-5
Polymers (A'4) and (A'5) were obtained in the same manner as in Synthesis Example 1 except that the amounts of 3-mercaptopropionic acid were changed to 0.10 g and 0.50 g, respectively, in Synthesis Example 1.

Synthesis example 6-7
Polymers (A'6) and (A'7) were obtained in the same manner as in Synthesis Example 1 except that styrene was replaced with the hydrophobic monomer shown in Table 1 in Synthesis Example 1.

Comparative synthesis example 1-2
Polymers (A'8) and (A'9) were obtained in the same manner as in Synthesis Example 1 except that itaconic acid was replaced with the hydrophilic monomer shown in Table 1 in Synthesis Example 1.

なお、表１中の各表記は下記のとおりである。
ＭＭＡ：メチルメタクリレート
ＢＡ：ブチルアクリレート

The notations in Table 1 are as follows.
MMA: Methyl Methacrylate BA: Butyl Acrylate

(Manufacturing of resin emulsion)
Production Example 1
15.4 g of the polymer (A'1) obtained in Synthesis Example 1, 1.5 g of a 5N sodium hydroxide aqueous solution, 23.1 g of ion-exchanged water and a stirrer bar were placed in a pressure-resistant glass bottle, and the mixture was closed. The mixture was stirred in a water bath at 90 ° C. for 1 hour and emulsified.
Then, the temperature was returned to room temperature, 1.1 g of Denacol EX-212L (trade name, Nagasechemtex Co., Ltd., 1,6-hexanediol diglycidyl ether) and 1.49 g of ion-exchanged water were added as a cross-linking agent, and the mixture was added at room temperature. The mixture was stirred for 30 minutes. Then, the mixture was stirred in a water bath at 70 ° C. for 3 hours and crosslinked to obtain a resin emulsion (A-1) containing crosslinked polymer particles [solid content concentration 30%, average particle size 46 nm].
The degree of neutralization was 30 mol%.

Production Examples 2-9 and Comparative Production Examples 1-2
Resin emulsions (A-2) to (A-11) were obtained in the same manner as in Production Example 1 except that the type of polymer (A') and the degree of neutralization were changed as shown in Table 2. rice field.
In Production Example 6, the emulsification time in a water bath at 90 ° C. in Production Example 1 was changed to 0.5 hours.

Example 1
Glycerin (manufactured by Kao Co., Ltd.) 8.67 g, diethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.) 15.0 g, Surfinol 104PG-50 (trade name, manufactured by Air Products and Chemicals, Inc., acetylene glycol-based nonionic surfactant) A mixture of 1.50 g of propylene glycol solution (effective content 50%), 1.50 g of Emargen 120 (trade name, manufactured by Kao Co., Ltd., polyoxyethylene lauryl ether, ether-based nonionic surfactant) and 29.96 g of ion-exchanged water. Then, the mixture was stirred at room temperature for 15 minutes using a magnetic stirrer to obtain a mixed solution.
Next, while stirring 26.67 g (4.0 g in terms of pigment content in 100 g of ink) of the aqueous dispersion of the colorant-containing polymer (B1) particles obtained in Preparation Example 1 with a magnetic stirrer, the mixed solution was mixed. Mixed. Further, the resin emulsion (A-1) obtained in Production Example 1 was stirred and mixed while dropping 16.7 g (5.0 g in terms of solid content in 100 g of ink) with a dropper.
Finally, the ink was obtained by filtering with a filter (manufactured by Sartorius) having a pore size of 1.2 μm. Table 2 shows the evaluation results of the obtained ink.

Examples 4 to 9 , Reference Examples 2 to 3, and Comparative Examples 1 to 2.
Ink was obtained in the same manner as in Example 1 except that the resin emulsion was changed to the resin emulsion shown in Table 2. Table 2 shows the evaluation results of the obtained ink.

<Evaluation of water-based ink>
[PET film fixability]
The obtained ink was filled in the ink inlet on the upper part of the head of the inkjet printer "IPSiO GX5000" (trade name, manufactured by Ricoh Co., Ltd.) via a silicon tube. A solid print print pattern (width 204 mm x length 275 mm) is produced by Photoshop (registered trademark) (manufactured by Adobe), and the PET film "Lumirror P60" (Toray) has a discharge rate of 14 g / m ² . It was solid-printed on (manufactured by Co., Ltd.) and dried at a temperature of 25 ° C. and a relative humidity of 30% for 60 minutes to obtain a printed matter. The printed matter was rubbed 10 times by applying a 1.5 kg load to the cellulose non-woven fabric "Bencot M-3II" (manufactured by Asahi Kasei Corporation) using the bottom surface of a weight (bottom area 78.5 cm ² ). The image density of the Bencott surface before and after scraping was measured using a reflection densitometer "RD-915" (manufactured by Gretag Macbeth). The difference in image density before and after scraping was calculated, and the fixability to the PET film was evaluated from the calculated value. The smaller the calculated value, the better the fixability to the PET film.

[Document offset resistance of PET printed matter under high humidity]
Under the above printing conditions, two solid printed matter 1 and 2 of 20 cm × 20 cm were prepared and dried in a vacuum dryer at 35 ° C. for 12 hours. After that, the two printed matter are superposed so that the printed surface of the printed matter 1 and the non-printed PET film surface (corona surface) of the printed matter 2 are in contact with each other, and the temperature is 25 ° C. and the humidity is 90 under a load of 50 g / cm ² . It was left for 5 days under the condition of%. After leaving it for 5 days, it was peeled off, and the mass of the printed matter 2 in contact with the printed surface was measured, and the difference (mg) from the mass before the test was calculated. The smaller the difference value, the better the document offset resistance under high humidity.

なお、表２中の各表記は下記のとおりである。
ＭＭＡ：メチルメタクリレート
ＢＡ：ブチルアクリレート

The notations in Table 2 are as follows.
MMA: Methyl Methacrylate BA: Butyl Acrylate

From Table 2, it can be seen that Examples 1 and 4 to 9 are superior in both fixing property and document offset resistance as compared with Comparative Examples 1 and 2.

The resin emulsion of the present invention is excellent in fixing property to a resin printing medium and document offset resistance by being contained in a water-based ink. The water-based ink containing the resin emulsion can be suitably used for inkjet printing.

Claims (8)

A resin emulsion containing polymer (A) particles.
The polymer (A) contains a structural unit derived from itaconic acid (a-1) and a structural unit derived from the hydrophobic monomer (a-2), and is derived from the itaconic acid (a-1) in the polymer (A). The mass ratio [(a-1) / (a-2)] of the structural unit to the structural unit derived from the hydrophobic monomer (a-2) is 15/85 or more and 40/60 or less, and further, the acid group At least part of it has been neutralized
A resin emulsion in which the polymer (A) particles are crosslinked polymer particles formed by cross-linking the polymer (A) particles with a polyhydric alcohol glycidyl ether . The resin emulsion according to claim 1, wherein the polymer (A) particles have an average particle size of 20 nm or more and 300 nm or less. The resin emulsion according to claim 1 or 2, wherein the degree of neutralization of the polymer (A) is 20 mol% or more and 50 mol% or less. The resin emulsion according to any one of claims 1 to 3, wherein the hydrophobic monomer (a-2) contains an aromatic group-containing monomer. The resin emulsion according to any one of claims 1 to 4, wherein the polyhydric alcohol glycidyl ether is at least one selected from 1,6-hexanediol diglycidyl ether and trimethylolpropane polyglycidyl ether. A water-based ink containing the resin emulsion according to any one of claims 1 to 5 and a colorant. The water-based ink according to claim 6 , wherein the colorant is dispersed in a water-insoluble polymer (B). The water-based ink according to claim 6 or 7 , wherein the water-based ink is for inkjet printing.