JP6762889B2 - Water-based ink - Google Patents

Description

The present invention relates to a water-based ink and a printing method using the water-based ink.

In fields such as commercial label printing used for product packaging printing and advertising, resin printing such as PET (polyethylene terephthalate), PVC (polyvinyl chloride), PE (polyethylene), PP (polypropylene), NY (nylon), etc. From the viewpoints of reducing environmental load, energy saving, safety, etc., the medium is required to utilize an inkjet printing method or a flexo printing method as a printing method using water-based ink. In particular, the inkjet printing method is a printing method in which ink droplets are directly ejected onto a printing medium from a very fine nozzle and adhered to obtain a printed matter on 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. Therefore, an attempt is being made to utilize the inkjet printing method for the resin printing medium.

For example, Patent Document 1 describes the first as a two-component water-based ink set for inkjet recording, which has excellent scratch resistance immediately after printing without image distortion such as bleeding and intercolor bleeding even when printed on a plastic film. The ink contains a coloring material, an olefin resin having a hydroxy group and / or a carboxy group, a water-soluble solvent and / or water, and the second ink contains an acid-type anionic surfactant, a water-soluble solvent and / or water. A water-based ink set for inkjet recording including is described.
Patent Document 2 describes that as a water-based coating material having water resistance and adhesion to various substrates such as PET film and polypropylene plate, the content of unsaturated hydrocarbon having 3 to 6 carbon atoms is 50 to 98% by mass and unsaturated. A water-based paint containing a polyolefin resin containing 0.5 to 20% by mass of a carboxylic acid unit,, if necessary, another resin, and a pigment or dye is described.

Japanese Unexamined Patent Publication No. 2014-24945 International Publication No. 2004/1004090

However, in Patent Documents 1 and 2, the fixability to a print medium having low polarity and the water resistance of the printed matter are not sufficient, and further improvement of the fixability and the water resistance is required.
An object of the present invention is to provide a water-based ink having excellent fixability to a print medium having low polarity and water resistance of a printed matter, and a printing method using the water-based ink.
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, "water-based" means that water occupies the largest proportion in the medium contained in the ink.

The present inventors have found that the above-mentioned problems can be solved by a water-based ink containing a polycarboxylic acid-modified propylene-based polymer having a specific structure and an organic solvent.
That is, the present invention provides the following [1] and [2].
[1] A polycarboxylic acid-modified propylene-based polymer containing a structural unit derived from one or more monomers (a-1) selected from unsaturated carboxylic acids and their anhydrides and a structural unit derived from a propylene monomer (a-2). A water-based ink containing A) and an organic solvent (B).
The polymer (A) is formed by acid-denaturing a propylene-based polymer (A') having a mmmm fraction of 5 mol% or more and 50 mol% or less in a pentad sequence, and has a structure represented by the following general formula (I). Is a polymer containing
A water-based ink in which the content of the polymer (A) in the water-based ink is 5% by mass or more and 15% by mass or less as a solid content.

(In the general formula (I), X ¹ represents a structural unit derived from one or more monomers (a-1) selected from unsaturated carboxylic acids and their anhydrides, p and q are integers, and n is an integer. It is an integer of 2 or more.)
[2] A printing method for printing on a printing medium using the water-based ink according to the above [1], wherein the printing medium is a polyolefin film.

According to the present invention, it is possible to provide a water-based ink having excellent fixability to a print medium having low polarity and water resistance of a printed matter, and a printing method using the water-based ink.

Using the polycarboxylic acid-modified propylene-based polymer A1 used in Example 1 as a measurement sample, a DSC curve obtained under the measurement conditions described in Example is shown using a differential scanning calorimeter (DSC). Using the polycarboxylic acid-modified propylene-based polymer AC2 used in Comparative Example 3 as a measurement sample, a DSC curve obtained under the measurement conditions described in Examples is shown using a differential scanning calorimeter (DSC).

[Water-based ink]
The water-based ink of the present invention (hereinafter, also simply referred to as “ink”) is a structural unit derived from one or more monomers (a-1) selected from unsaturated carboxylic acids and their anhydrides (hereinafter, simply “monomers (a”). -1) Unit ") and a polymer containing a propylene monomer (a-2) -derived structural unit (hereinafter, also simply referred to as" propylene monomer (a-2) unit "or" monomer (a-2) unit "). A water-based ink containing a carboxylic acid-modified propylene-based polymer (A) (hereinafter, also simply referred to as "acid-modified propylene-based polymer (A)" or "polymer (A)") and an organic solvent (B). The polymer (A) is obtained by acid-modifying a propylene-based polymer (A') having a mmmm fraction of 5 mol% or more and 50 mol% or less in a pentad sequence, and has a structure represented by the following general formula (I). The content of the polymer (A) in the aqueous ink is 5% by mass or more and 15% by mass or less as a solid content.

(In the general formula (I), X ¹ represents a structural unit derived from one or more monomers (a-1) selected from unsaturated carboxylic acids and their anhydrides, p and q are integers, and n is an integer. It is an integer of 2 or more.)

The water-based ink of the present invention has excellent effects on fixability to a print medium having low polarity (hereinafter, also simply referred to as “fixability”) and water resistance of printed matter (hereinafter, also simply referred to as “water resistance”). The reason is not clear, but it can be considered as follows.
The acid-modified propylene-based polymer (A) contained in the water-based ink of the present invention has n in the general formula (I) with respect to the propylene-based polymer segment of the main chain, as represented by the general formula (I). Since the segment [(X ¹ ) _n ] composed of a plurality of monomer (a-1) units having a value of 2 or more exists in a graft manner, the functions are separated from the structural features of the two segments. Therefore, when the ink adheres to a low-polarity printing medium such as a polyolefin film (hereinafter, also simply referred to as “low-polarity printing medium”), the propylene-based polymer segment is oriented and adsorbed on the low-polarity printing medium, and the fixability is improved. It is thought that it will improve. Further, it is considered that the segment [(X ¹ ) _n ] composed of the monomer (a-1) unit is oriented and adsorbed on the ink side, and the ink is firmly fixed on the surface of the low-polarity printing medium.
After the ink is dried, the propylene-based polymer segment is oriented on the image surface, that is, the interface with the hydrophobic air, and the segment [(X ¹ ) _n ] composed of the monomer (a-1) unit is hydrogen-bonded or ionic-bonded. It is considered that the water resistance of the printed matter is improved because of the physical cross-linking.
On the other hand, in the polycarboxylic acid-modified propylene-based polymer having the same acid modification rate and the structure of the following general formula (II), the segment consisting of the monomer (a-1) unit grafted is the monomer (a-1). The number of units is as short as one, and the number of acid modification points of the propylene-based polymer segment increases. Therefore, the propylene-based polymer segment between the adjacent graft joints is also shortened, the above-mentioned functional separation cannot be performed, and the physical cross-linking is not sufficient, so that it is considered that good fixability and water resistance cannot be obtained.

(In the general formula (II), X ¹ is the same as the general formula (I), and r and s are integers.)

Further, the acid-modified propylene-based polymer (A) according to the present invention has a structure in which a polycarboxylic acid oligomer is graft-bonded and modified as represented by the general formula (I). Compared with the case where only one monomer (a-1) is graft-bonded and modified as in the general formula (II) at the same acid modification rate, p in the general formulas (I) and (II) r, q and s have a relationship of q <s with p> r. Therefore, the acid-modified propylene-based polymer (A) has a specific stereoregularity in which the propylene-based polymer segment between adjacent graft joints is long and has low crystallinity, and the melting start temperature is low. As a result, it is considered that the fixability is further improved.
On the other hand, the polycarboxylic acid-modified propylene-based polymer represented by the general formula (II) in which the monomer (a-1) is graft-bonded and modified has a short propylene-based polymer segment between adjacent graft-bonded portions. It is considered that the isotactic fraction is locally high, the crystallinity is high, and good fixability cannot be obtained.
In the present invention, the acid modification modified with a polycarboxylic acid oligomer in which n is an integer of 2 or more as in the general formula (I) is referred to as "oligomer graft modification", as in the general formula (II). Acid modification modified with one monomer is called "monomer graft modification".

<Colorant>
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.
The clear ink is a colorless and transparent ink that does not contain a colorant.
The ink of the present invention may further contain a colorant. Examples of the colorant include pigments and dyes, and pigments are preferable from the viewpoint of improving water resistance and weather resistance of printed matter.
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.
The pigment is preferably contained in the water-based ink as a self-dispersing pigment, a pigment dispersed with a polymer dispersant, or polymer particles containing the pigment.

In the present invention, a self-dispersing pigment can also be used. The self-dispersing 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 resin by binding 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 acids such as nitric acid, sulfuric acid, peroxodisulfuric acid, hypochlorous acid, and chromic acid, and a method of binding a hydrophilic functional group using a coupling agent are preferable.
The above pigments can be used alone or in admixture of two or more at any ratio.

<Polycarboxylic acid-modified propylene polymer (A)>
The acid-modified propylene-based polymer (A) according to the present invention contains one or more monomer (a-1) units and propylene monomer (a-2) units selected from unsaturated carboxylic acids and anhydrides thereof, and is a pentad. It is a polymer obtained by acid-modifying a propylene-based polymer (A') having a mmmm fraction of 5 mol% or more and 50 mol% or less in the sequence, and containing a structure represented by the following general formula (I).
It has a structure represented by the following general formula (I) in which a propylene-based polymer segment as a main chain and a segment [(X ¹ ) _n ] consisting of a monomer (a-1) unit as a side chain are graft-bonded. As a result, the functions can be separated and the fixability and water resistance can be improved.

(In the general formula (I), X ¹ represents one or more monomer (a-1) units selected from unsaturated carboxylic acids and their anhydrides, p and q are integers, and n is 2 or more. It is an integer.)

N in the general formula (I) is the number of repeating units of the monomer (a-1) unit, and is an integer of 2 or more from the viewpoint of improving fixability and water resistance.
The monomer (a-1) is one or more selected from unsaturated carboxylic acids and their anhydrides. Examples of the monomer (a-1) include unsaturated carboxylic acids such as (meth) acrylic acid; unsaturated dicarboxylic acids such as fumaric acid and citraconic acid; and unsaturated carboxylic acids such as maleic acid, itaconic acid, aconitic acid, and nadic acid. And their anhydrides; methyl fumarate, ethyl fumarate, propyl fumarate, butyl fumarate, dimethyl fumarate, diethyl fumarate, dipropyl fumarate, dibutyl fumarate, methyl maleate, ethyl maleate, propyl maleate, Unsaturated dicarboxylic acid esters such as butyl maleate, dimethyl maleate, diethyl maleate, dipropyl maleate, dibutyl maleate; methyl (meth) acrylate, ethyl (meth) acrylate, cyclohexyl (meth) acrylate, lauryl (meth) acrylate , Benzyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate and other unsaturated carboxylic derivatives. Compounds having at least one carboxy group or acid anhydride group in the molecule, such as unsaturated dicarboxylic acid half esters and half amides, can also be used. Among these, at least one selected from (meth) acrylic acid and maleic anhydride is preferable from the viewpoint of ease of introduction into a propylene-based polymer, and from the viewpoint of improving fixability and water resistance. Maleic anhydride is preferred.
In addition, "(meth) acrylic acid" means one or more kinds selected from acrylic acid and methacrylic acid. Further, "(meth) acrylate" means one or more selected from acrylate and methacrylate. These are also synonymous in the following.

P and q in the general formula (I) are the number of repeating units of the propylene monomer (a-2) unit. The acid-modified propylene-based polymer (A) is obtained by acid-modifying the monomer (a-1) with the propylene-based polymer (A'), and p and q are the molecular weights of the raw material propylene-based polymer (A'). It is a value determined by the content of the propylene monomer (a-2) unit, the modification method, and the modification rate. The r and s in the general formula (II) are also values determined by the molecular weight of the propylene-based polymer (A') as a raw material, the content of the propylene monomer (a-2) unit, the modification method, and the modification rate.

The acid-modified propylene-based polymer (A) is a structural unit derived from one or more monomers (a-3) selected from ethylene and α-olefin having 4 or more and 20 or less carbon atoms (hereinafter, from the viewpoint of improving fixability). , Simply referred to as “monomer (a-3) unit”), and from the viewpoint of ease of production and improvement of fixability and water resistance, the main chain of the propylene-based polymer segment is a propylene monomer ( In addition to the a-2) unit, one or more monomer (a-3) units selected from ethylene and α-olefin having 4 or more and 20 or less carbon atoms may be further contained.
The number of carbon atoms of the α-olefin is preferably 4 or more and 10 or less, more preferably 4 or more and 8 or less, and further preferably 4 or more and 6 or less. Examples of the α-olefin include 1-butene, isobutene, 1-pentene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-hexene, 1-octene and the like.
The monomer (a-3) is preferably one or more selected from ethylene, 1-butene and isobutene, more preferably ethylene and 1 from the viewpoint of ease of production and improvement of fixability and water resistance. -One or more selected from -butene, more preferably 1-butene, and ethylene and 1-butene may be used in combination.
The monomer (a-3) can be used alone or in combination of two or more.

The contents of the monomer (a-2) unit and the monomer (a-3) unit in the propylene-based polymer segment are as follows from the viewpoint of improving fixability and water resistance.
The content of the monomer (a-2) unit is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass in the propylene-based polymer segment from the viewpoint of improving fixability and water resistance. As mentioned above, it is more preferably 80% by mass or more, and preferably 100% by mass or less, more preferably 98% by mass or less, still more preferably 95% by mass or less.
The content of the monomer (a-3) unit is preferably 2% by mass or more, more preferably 5% by mass or more in the propylene-based polymer segment, and is preferably from the viewpoint of improving fixability and water resistance. It is 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.
When ethylene and 1-butene are used in combination, the mass ratio of ethylene units to 1-butene units [ethylene units / 1-butene units] is preferably 1 or more, more preferably 1.5 or more, still more preferably 2 or more. Yes, and preferably 6 or less, more preferably 5.5 or less, still more preferably 4 or less, still more preferably 4.5 or less.

The mmmm fraction of the propylene-based polymer (A') in the pentad sequence is 5 mol% or more and 50 mol% or less from the viewpoint of improving fixability and water resistance. As a result, the crystallinity of the acid-modified propylene-based polymer (A) is lowered, the melting start temperature is lowered, and the fixability is improved. From this point of view, the mmmm fraction is preferably 10 mol% or more, more preferably 20 mol% or more, still more preferably 30 mol% or more, even more preferably 35 mol% or more, and preferably 48 mol% or more. Below, it is more preferably 46 mol% or less, still more preferably 45 mol% or less. The mmmm fraction of the polymer does not change due to acid denaturation, and the mmmm fraction of the acid-modified propylene-based polymer (A) is the same as that of the propylene-based polymer (A') which is the raw material before acid denaturation. The preferred embodiment of the mmmm fraction of (A) is also the same as that of the propylene-based polymer (A').
The mmmm fraction is the ratio of the propylene unit at the center of the chain in which five propylene monomer units are continuously mesobonded to the total propylene unit as a percentage. Pentad is usually determined by ¹³ C-NMR, specifically measured by the method described in the Examples. Most of the commercially available acid-modified propylene-based polymers have a mmmm fraction of less than 5 mol%.

The weight average molecular weight of the propylene-based polymer (A') is preferably 5,000 or more, more preferably 10,000 or more, still more preferably 10,000 or more, from the viewpoint of improving dispersion stability in the ink, fixability and water resistance. It is 20,000 or more, preferably 150,000 or less, more preferably 100,000 or less, still more preferably 50,000 or less.
The weight average molecular weight can be measured by the method described in Examples.

(Production of Polycarboxylic Acid-Modified Propylene Polymer (A))
The acid-modified propylene-based polymer (A) is preferably modified by graft-polymerizing the monomer (a-1) to the propylene-based polymer (A'). In the present invention, the propylene-based polymer (A') refers to the polymer before acid denaturation. The propylene-based polymer (A') contains a monomer (a-2) unit, and may further contain a monomer (a-3) unit. The content of the monomer (a-2) unit and the (a-3) unit in the propylene-based polymer (A') is the monomer (a) in the above-mentioned propylene-based polymer segment from the viewpoint of improving fixability and water resistance. -2) The content is the same as that of the unit and the unit (a-3). The monomer (a-1) unit may form a salt in part or in whole.
Graft polymerization is, for example, a melting method in which a propylene-based polymer (A') and a monomer (a-1) are heated and melted above the melting point of the propylene-based polymer (A') in the presence of a radical generator and reacted. Alternatively, it can be carried out by a solution method in which the propylene-based polymer (A') is dissolved in an organic solvent and then heated and stirred in the presence of a radical generator to react. Among these, the solution method is preferable from the viewpoint of controlling n in the general formula (I).
Examples of the radical generator used for graft polymerization include di-t-butyl peroxide, dicumyl peroxide, t-butyl hydroperoxide, t-butyl cumyl peroxide, benzoyl peroxide, dilauryl peroxide, and cumenhydro. Organic radicals such as peroxide, t-butylperoxybenzoate, ethylethylketone peroxide, di-t-butyldiperphthalate; azonitriles such as azobisisobutyronitrile can be mentioned. These can be appropriately selected depending on the reaction temperature.
The reaction temperature of the graft polymerization is preferably 80 ° C. or higher, more preferably 100 ° C. or higher, further preferably 120 ° C. or higher, and preferably 200 ° C. or lower, more preferably 180 ° C. or lower, still more preferably 160 ° C. or lower. Is preferable.
The reaction time is preferably 30 minutes or more, more preferably 1 hour or more, and preferably 5 hours or less, more preferably 4 hours or less, still more preferably 3 hours or less.

The acid modification rate of the polycarboxylic acid-modified propylene-based polymer (A) is represented by the following formula (1).
Acid denaturation rate (% by mass) = [mass of structural unit derived from monomer (a-1) in the polymer (A) / mass of the polymer (A)] × 100 (1)
From the viewpoint of improving fixability and water resistance, the acid denaturation rate is preferably 1% by mass or more, more preferably 3% by mass or more, further preferably 5% by mass or more, and preferably 30% by mass or less. It is more preferably 25% by mass or less, still more preferably 20% by mass or less, still more preferably 15% by mass or less, still more preferably 10% by mass or less.
The acidity is measured by the method described in Examples.

The weight average molecular weight of the acid-modified propylene-based polymer (A) is preferably 5,000 or more, more preferably 10,000 or more, still more preferably 10,000 or more, from the viewpoint of improving dispersion stability in ink, fixability and water resistance. Is 20,000 or more, and preferably 150,000 or less, more preferably 100,000 or less, still more preferably 50,000 or less.
The weight average molecular weight can be measured by the method described in Examples.

The acid-modified propylene-based polymer (A) is preferably contained in the ink as an aqueous dispersion dispersed in water.
The aqueous dispersion of the acid-modified propylene-based polymer (A) can be obtained by adding water to the acid-modified propylene-based polymer (A).
Further, a neutralizing agent may be added from the viewpoint of obtaining an aqueous dispersion having good dispersion stability. As a result, a part or all of the carboxy group or the acid anhydride group contained in the monomer (a-1) unit of the acid-modified propylene-based polymer (A) forms a salt, and the dispersion stability of the aqueous dispersion is improved. .. Examples of the neutralizing agent include alkali metal hydroxides, ammonia, organic amines and the like. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide, but potassium hydroxide is preferable.
The non-volatile component concentration (solid content concentration) of the aqueous dispersion of the acid-modified propylene-based polymer (A) is preferably 10% by mass or more from the viewpoint of improving the dispersion stability and facilitating the preparation of the aqueous ink. It is preferably 20% by mass or more, preferably 40% by mass or less, and more preferably 30% by mass or less.
The solid content concentration of the aqueous dispersion is measured by the method described in Examples.

The average particle size of the aqueous dispersion of the acid-modified propylene-based polymer (A) is preferably 40 nm or more, more preferably 50 nm or more, still more preferably 60 nm or more, and preferably 150 nm from the viewpoint of reducing coarse particles. Below, it is more preferably 120 nm or less, still more preferably 100 nm or less.
The average particle size in the aqueous dispersion is measured by the method described in Examples.

<Organic solvent (B)>
The water-based ink of the present invention contains an organic solvent (B) from the viewpoint of improving fixability and water resistance. The boiling point of the organic solvent (B) 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. Is 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 (B), the boiling point of the organic solvent (B) is a weighted average value weighted by the content (mass%) of each organic solvent.

The organic solvent (B) 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-Hexanediol (boiling point 223 ° C.), etc .; 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 (boilage 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-butanetriol (boiling point 190 ° C.), 1, , 2,3-Butantriol (boiling point 175 ° C.), petriol (boiling point 216 ° C.), glycerin (boiling point 290 ° C.) and the like.
From the viewpoint of improving fixability and water resistance, the polyhydric alcohol is preferably 1,2-alkanediol having 2 or more and 6 or less carbon atoms, and more preferably propylene glycol.
In addition, 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.

Examples of the organic solvent other than the polyhydric alcohol include glycol ethers, alcohols other than the polyhydric alcohols, alkyl ethers of the alcohols, nitrogen-containing heterocyclic compounds such as N-methyl-2-pyrrolidone, amides, amines, and sulfur-containing compounds. And so on. Among these, glycol ethers having a boiling point of 90 ° C. or higher are preferable from the viewpoint of improving fixability and water resistance. The organic solvent other than the polyhydric alcohol can be used alone or in combination of two or more.

Specific examples of the glycol ether include alkylene glycol monoalkyl ether and alkylene glycol dialkyl ether from the viewpoint of improving fixability and water resistance, but alkylene glycol monoalkyl ether is preferable. The alkyl group of the alkylene glycol monoalkyl ether preferably has 1 or more carbon atoms, more preferably 2 or more carbon atoms, still more preferably 3 or more carbon atoms, and preferably 6 or less, more preferably 4 or less carbon atoms. The alkyl group of the alkylene glycol monoalkyl ether may be a straight chain or a branched chain.
Specific examples of the alkylene glycol monoalkyl ether include ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, and diethylene glycol mono. Ethylene glycol monoalkyl ethers such as isobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoisobutyl ether, tetraethylene glycol monomethyl ether; propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether, tripropylene glycol Examples thereof include propylene glycol monoalkyl ethers such as monomethyl ether and tripropylene glycol monobutyl ether.
Among these, ethylene glycol monoalkyl ether is preferable, and one or more selected from ethylene glycol monoisopropyl ether, ethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether and diethylene glycol monoisopropyl ether are preferable. There, more preferably one or more selected from diethylene glycol monoisobutyl ether and diethylene glycol monoisopropyl ether.

The organic solvent (B) is preferably one or more selected from polyhydric alcohols and glycol ethers, and more preferably one or more selected from diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monoisopropyl ether, and propylene glycol. It is more preferably one or more selected from diethylene glycol monoisobutyl ether, diethylene glycol monoisopropyl ether, and propylene glycol, and even more preferably propylene glycol.

<Polymer (C)>
The water-based ink of the present invention preferably further contains a polymer (C) other than the acid-modified propylene-based polymer (A). The polymer (C) has at least one function as a pigment dispersant that exhibits a pigment-dispersing action when the water-based ink contains a pigment and a function as a fixing agent on a printing medium, and is preferable. It is a water-insoluble polymer.
Here, "water-insoluble" means that when a polymer that has reached a constant weight after being dried at 105 ° C. for 2 hours is dissolved in 100 g of water at 25 ° C., the dissolved amount is 10 g or less. The dissolved amount is preferably 5 g or less, more preferably 1 g or less. When the water-insoluble polymer is an anionic polymer, the dissolved amount is the dissolved amount when the anionic group of the polymer is 100% neutralized with sodium hydroxide. When the water-insoluble polymer is a cationic polymer, the dissolved amount is the dissolved amount when the cationic group of the polymer is 100% neutralized with hydrochloric acid.
When the water-based ink contains a pigment, the present form of the polymer (C) in the ink is a state in which it is adsorbed on the pigment, a state in which the pigment is contained (capsule), and a state in which the pigment is adsorbed. There is a form that is not. Among these, from the viewpoint of the dispersion stability of the pigment, the form of the polymer particles containing the pigment is preferable, and the pigment-encapsulating state containing the pigment is more preferable.
Examples of the polymer (C) include acrylic polymers, polyesters, polyurethanes and the like. Among these, an acrylic polymer is preferable from the viewpoint of improving fixability and water resistance.

[Acrylic polymer]
The acrylic polymer preferably contains a structural unit derived from (meth) acrylic acid and a structural unit derived from a hydrophobic monomer.
The (meth) acrylic acid is preferably methacrylic acid from the viewpoint of improving the dispersion stability in the ink.
The hydrophobic monomer is used as a monomer component of the acrylic polymer from the viewpoint of improving the dispersion stability in the ink. Examples of the hydrophobic monomer include an alkyl (meth) acrylic acid ester and an aromatic group-containing monomer.
As the alkyl (meth) acrylic acid 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 (iso) stearyl (meth) acrylate.
In addition, "(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, it indicates a normal. Here, the "(meth) acrylic acid ester" means one or more selected from an acrylic acid ester and a methacrylic acid ester.

As the aromatic group-containing monomer, 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, is preferable, and a styrene-based monomer and 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.
As the styrene-based monomer, styrene, 2-methylstyrene, and divinylbenzene are preferable, and styrene is more preferable.
Further, as the aromatic group-containing (meth) acrylic acid ester, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate and the like are preferable, and benzyl (meth) acrylate is more preferable.
The hydrophobic monomer is preferably an aromatic group-containing monomer, more preferably one or more selected from a styrene-based monomer and an aromatic group-containing (meth) acrylic acid ester, and more preferably an aromatic group-containing (meth) group. ) Acrylic acid ester, more preferably benzyl (meth) acrylate.
As the hydrophobic monomer, two or more of the above-mentioned monomers may be used, or a styrene-based monomer and an aromatic group-containing (meth) acrylic acid ester may be used in combination.

The macromonomer is a compound having a polymerizable functional group at one end and having a number average molecular weight of 500 or more and 100,000 or less, and may be used as a monomer component of an acrylic polymer from the viewpoint of improving dispersion stability in ink. .. As the polymerizable functional group present at one end, an acryloyloxy group or a methylenedioxy group is preferable, and a methylenedioxy group is more preferable.
The number average molecular weight of the macromonomer is preferably 1,000 or more and 10,000 or less. The number average molecular weight is measured by a gel permeation chromatography method using chloroform containing 1 mmol / L dodecyldimethylamine as a solvent, using polystyrene as a standard substance.
As the macromonomer, an aromatic group-containing macromonomer and a silicone-based macromonomer are preferable, and an aromatic group-containing macromonomer is more preferable, from the viewpoint of improving dispersion stability in the ink.
Examples of the aromatic group-containing monomer constituting the aromatic group-containing macromonomer include the aromatic group-containing monomer described in the hydrophobic monomer, and styrene and benzyl (meth) acrylate are preferable, and styrene is more preferable.
Specific examples of the styrene-based macromonomer include AS-6 (S), AN-6 (S), HS-6 (S) (trade name of Toagosei Co., Ltd.) and the like.
Examples of the silicone-based macromonomer include organopolysiloxane having a polymerizable functional group at one end.

The acrylic polymer preferably further contains a structural unit derived from a nonionic monomer from the viewpoint of improving dispersion stability in the ink.
Examples of the nonionic monomer include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate and 3-hydroxypropyl (meth) acrylate; polypropylene glycol (m = 2 to 30, m is the average molar addition of oxyalkylene groups). The numbers are shown below. The same applies hereinafter. Polyalkylene glycol mono (meth) acrylates such as mono (meth) acrylate and polyethylene glycol (m = 2 to 30) mono (meth) acrylate; methoxypolyethylene glycol (m = 1 to 30) (meth). ) Alkoxypolyalkylene glycol (meth) acrylate such as acrylate; Phenoxy (ethylene glycol-propylene glycol copolymerization) (m = 1 to 30, ethylene glycol in it: m = 1-29) (meth) acrylate and the like. .. Among these, polyalkylene glycol mono (meth) acrylate is preferable, and polypropylene glycol (m = 2 to 30) mono (meth) acrylate is more preferable.
Specific examples of commercially available nonionic monomers include NK ester M-20G, 40G, 90G, 230G, etc. (these are trade names of Shin-Nakamura Chemical Industry Co., Ltd.), Blemmer PE-90, and the same. 200, 350, etc., PME-100, 200, 400, etc., PP-500, 800, 1000, etc., AP-150, 400, 550, etc., 50PEP-300, 50POEP-800B, 43PAPE-600B Etc. (above, the trade name of NOF CORPORATION).
The above-mentioned monomers of the acrylic polymer can be used alone or in combination of two or more.

The content of each monomer in the monomer mixture (content as an unneutralized amount; the same applies hereinafter) or the content of the structural unit derived from each monomer in the acrylic polymer during the production of the acrylic polymer is dispersed in the ink. From the viewpoint of improving stability, it is as follows.
The content of (meth) acrylic acid is preferably 3% by mass or more, more preferably 5% by mass or more, further preferably 7% by mass or more, still more preferably 10% by mass or more, and preferably 30% by mass. % Or less, more preferably 25% by mass or less, still more preferably 20% by mass or less, still more preferably 15% by mass or less.
The content of the hydrophobic monomer is preferably 20% by mass or more, more preferably 30% by mass or more, further preferably 40% by mass or more, still more preferably 50% by mass or more, and preferably 70% by mass or less. , More preferably 65% by mass or less, still more preferably 60% by mass or less.
The content of the macromonomer is preferably 3% by mass or more, more preferably 5% by mass or more, further preferably 7% by mass or more, and preferably 25% by mass or less, more preferably 20% by mass or less, further. It is preferably 15% by mass or less.
The content of the nonionic monomer is preferably 5% by mass or more, more preferably 10% by mass or more, further preferably 15% by mass or more, and preferably 35% by mass or less, more preferably 30% by mass or less. More preferably, it is 25% by mass or less.

(Manufacturing of acrylic polymer)
The acrylic polymer 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. Of these polymerization methods, the solution polymerization method is preferable.
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 methanol, ethanol, acetone and methyl ethyl ketone, and among these, methyl ethyl ketone 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 (2,4-dimethylvaleronitrile) is more preferable. .. As the polymerization chain transfer agent, mercaptans are preferable, and 2-mercaptoethanol 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 acrylic polymer can be isolated from the reaction solution by a known method such as reprecipitation and solvent distillation. In addition, unreacted monomers and the like can be removed from the obtained acrylic polymer by reprecipitation, membrane separation, chromatographic method, extraction method and the like.
When the acrylic polymer is used as a polymer constituting the pigment-containing polymer particles, the solvent used in the polymerization reaction is not removed from the viewpoint of improving the productivity of the aqueous dispersion of the pigment-containing polymer particles described later. Since the contained organic solvent is used as the organic solvent used in step I described later, it may be used as it is as a solution of the acrylic polymer.
The solid content concentration of the acrylic polymer solution is preferably 30% by mass or more, more preferably 40% by mass or more, and preferably 70 from the viewpoint of improving the productivity of the aqueous dispersion of the pigment-containing polymer particles. It is mass% or less, more preferably 65 mass% or less.

The weight average molecular weight of the acrylic polymer is preferably 5,000 or more, more preferably 10,000 or more, still more preferably 20,000, from the viewpoint of improving dispersion stability in ink and improving fixability. The above, 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, still more preferably 100,000 or less, still more preferable. Is less than 50,000.
The weight average molecular weight can be measured by the method described in Examples.

The acrylic polymer may be contained in the ink as a dispersion of acrylic polymer particles containing no pigment. Examples of commercially available dispersions of the acrylic polymer particles include "Neocryl A-1127" (manufactured by DSM Coating Resins, anionic self-crosslinked water-based vinyl resin), "John Krill 390", "John Krill 7100", and "John Krill 7100". Acrylic resins such as "John Krill 734" and "John Krill 538" (manufactured by BASF Japan Co., Ltd.), and emulsions of vinyl chloride-acrylic resin such as "Viniblanc 701" (manufactured by Nisshin Chemical Industry Co., Ltd.) are listed. Be done.

[Manufacture of pigment-containing polymer particles]
When the water-based ink of the present invention contains a pigment as a colorant, the polymer (C) is preferably contained in the ink as polymer particles containing the pigment (hereinafter, also referred to as "pigment-containing polymer particles"). ..
The pigment-containing polymer particles can be efficiently produced by a method having the following steps I and II as an aqueous dispersion.
Step I: A mixture containing the polymer (C), an organic solvent, a pigment, and water (hereinafter, also referred to as "pigment mixture") is dispersed to obtain a dispersion of pigment-containing polymer particles. Step II: Step I A step of removing the organic solvent from the dispersion obtained in (1) to obtain an aqueous dispersion of pigment-containing polymer particles (hereinafter, also referred to as "pigment aqueous dispersion").

(Step I)
In step I, first, the polymer (C) is dissolved in an organic solvent to obtain an organic solvent solution of the polymer (C), and then a pigment, water, and if necessary, a neutralizing agent, a surfactant, or the like are added to the solution. In addition to the above, a method of mixing to obtain an oil-in-water type dispersion is preferable. The order in which the polymer (C) is added to the organic solvent solution is not limited, but water, the neutralizing agent, and the pigment are preferably added in this order.
The organic solvent for dissolving the polymer (C) is not limited, but aliphatic alcohols having 1 to 3 carbon atoms, ketones, ethers, esters and the like are preferable, and wettability to pigments and dissolution of the polymer (C) are preferable. From the viewpoint of improving the properties and the adsorptivity of the polymer (C) to the pigment, a ketone having 4 or more carbon atoms and 8 or less carbon atoms is more preferable, methyl ethyl ketone and methyl isobutyl ketone are further preferable, and methyl ethyl ketone is even more preferable.
When the polymer (C) is synthesized by the solution polymerization method, the solvent used in the polymerization may be used as it is.

(Neutralization)
When the polymer (C) is an anionic polymer, a neutralizing agent may be used to neutralize the anionic groups in the polymer (C). 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. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide, but sodium hydroxide is preferable. Examples of the organic amine include trimethylamine, ethylamine, diethylamine, triethylamine, triethanolamine and the like.
From the viewpoint of improving the ejection stability of the ink, the neutralizing agent is preferably an alkali metal hydroxide or ammonia, and more preferably a combination of sodium hydroxide and ammonia. Further, the polymer (C) may be neutralized in advance.

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. It is 25% by mass or less.
The degree of neutralization of the anionic group of the polymer (C) is preferably 30 mol% or more, more preferably 40 mol% or more, from the viewpoint of improving the dispersion stability of the pigment-containing polymer particles in the pigment aqueous dispersion and the ink. , More preferably 50 mol% or more, and preferably 300 mol% or less, more preferably 200 mol% or less, still more preferably 150 mol% or less.
Here, the degree of neutralization is obtained by dividing the molar equivalent of the neutralizing agent by the molar amount of the anionic group of the polymer (C).

(Content of each component in pigment mixture)
The content of the pigment in the pigment mixture in step I 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 pigment dispersion and improving the printing quality and increasing the printing density. It is 12% by mass or more, more preferably 14% by mass or more, preferably 30% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less.
The content of the polymer (C) in the pigment mixture is preferably 2% by mass or more, more preferably 2% by mass or more, from the viewpoint of improving the dispersion stability of the aqueous pigment dispersion and improving the printing quality and increasing the printing density. It is 4% by mass or more, more preferably 5% by mass or more, preferably 15% by mass or less, more preferably 12% by mass or less, still more preferably 10% by mass or less.
The content of the organic solvent in the pigment mixture is preferably 10% by mass or more, more preferably 12% by mass or more, still more preferably 12% by mass or more, from the viewpoint of improving the wettability to the pigment and the adsorptivity of the polymer (C) to the pigment. Is 15% by mass or more, preferably 35% by mass or less, more preferably 30% by mass or less, still more preferably 25% by mass or less.
The content of water in the pigment mixture is preferably 40% by mass or more, more preferably 45% by mass or more, still more preferably 45% by mass or more, from the viewpoint of improving the dispersion stability of the pigment aqueous dispersion and improving the productivity. It is 50% by mass or more, preferably 70% by mass or less, more preferably 65% by mass or less, and further preferably 63% by mass or less.

The mass ratio of the pigment to the polymer (C) in the pigment mixture [pigment / polymer (C)] improves the dispersion stability of the aqueous pigment dispersion, as well as the ejection stability and print quality, and improves the print density. From the viewpoint of enhancing, it is preferably 30/70 or more, more preferably 40/60 or more, still more preferably 50/50 or more, even more preferably 60/40 or more, and preferably 90/10 or less, more preferably 90/10 or more. It is 80/20 or less, more preferably 78/22 or less.

(Dispersion treatment of pigment mixture)
In step I, the pigment mixture is dispersed to obtain a dispersion of pigment-containing polymer particles. There is no particular limitation on the dispersion method for obtaining the dispersion. Although it is possible to atomize the average particle size of the pigment particles to a desired particle size only by the main dispersion, preferably, after the pigment mixture is pre-dispersed, the main dispersion is further applied by applying shear stress to perform the main dispersion of the pigment particles. It is preferable to control the average particle size of the above to a desired particle size.
The temperature in the preliminary dispersion of step I is preferably 0 ° C. or higher, and preferably 40 ° C. or lower, more preferably 30 ° C. or lower, still more preferably 25 ° C. or lower, and the dispersion time is preferably 0.5 hours. As described above, it is more preferably 0.8 hours or more, preferably 30 hours or less, more preferably 10 hours or less, and further preferably 5 hours or less.
When the pigment mixture is pre-dispersed, a commonly used mixing and stirring device such as an anchor blade and a discharge blade can be used, and a high-speed stirring and mixing device is particularly preferable.

Examples of means for applying the shear stress of this dispersion include a kneader such as a roll mill and a kneader, a high-pressure homogenizer such as a microfluidic (manufactured by Microfluidic), and a media type disperser such as a paint shaker and a bead mill. Examples of commercially available media-type dispersers include Ultra Apex Mill (manufactured by Kotobuki Industry Co., Ltd.) and Pico Mill (manufactured by Asada Iron Works Co., Ltd.). A plurality of these devices can be combined. Among these, it is preferable to use a high-pressure homogenizer from the viewpoint of reducing the particle size of the pigment.
When the main dispersion is performed using a high-pressure homogenizer, the pigment can be controlled to have a desired particle size by controlling the processing pressure and the number of passes.
From the viewpoint of productivity and economy, the treatment pressure is preferably 60 MPa or more, more preferably 100 MPa or more, further preferably 130 MPa or more, and preferably 200 MPa or less, more preferably 180 MPa or less.
The number of passes is preferably 3 or more, more preferably 10 or more, and preferably 30 or less, more preferably 25 or less.

(Step II)
In step II, an aqueous dispersion of pigment-containing polymer particles (pigment aqueous dispersion) can be obtained by removing the organic solvent from the dispersion obtained in step I by a known method. It is preferable that the organic solvent in the obtained aqueous pigment dispersion is substantially removed, but it may remain as long as the object of the present invention is not impaired. The amount of the residual organic solvent is preferably 0.1% by mass or less, more preferably 0.01% by mass or less.
Further, if necessary, the dispersion can be heat-stirred before distilling off the organic solvent.
The obtained pigment aqueous dispersion is one in which solid polymer particles containing a pigment are dispersed in a medium containing water as a main medium. Here, the form of the pigment-containing polymer particles is not particularly limited, and at least the particles may be formed by the pigment and the polymer (C). For example, a particle form in which the pigment is encapsulated in the polymer (C), a particle form in which the pigment is uniformly dispersed in the polymer (C), a particle form in which the pigment is exposed on the particle surface of the polymer (C), and the like are included. , A mixture of these is also included.
The pigment aqueous dispersion preferably contains the pigment as particles of the polymer (C) containing the pigment.

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

The average particle size of the pigment-containing polymer particles in the pigment aqueous dispersion is preferably 40 nm or more, more preferably 60 nm or more, still more preferably 75 nm or more, from the viewpoint of reducing coarse particles and improving the ejection stability of the water-based ink. It is preferably 150 nm or less, more preferably 120 nm or less, and further preferably 110 nm or less.
The average particle size of the pigment-containing polymer particles in the aqueous pigment dispersion is measured by the method described in Examples.
Further, it is preferable that the pigment-containing polymer particles in the water-based ink do not swell or shrink, or aggregate between the particles, and the average particle size of the pigment-containing polymer particles in the water-based ink is in the pigment aqueous dispersion. It is preferable that the particle size is the same as that of. The preferred aspect of the average particle size of the pigment-containing polymer particles in the water-based ink is the same as the preferred aspect of the average particle size in the pigment aqueous dispersion. The average particle size of the pigment-containing polymer particles in the water-based ink is also measured by the same method as the average particle size of the pigment-containing polymer particles in the pigment aqueous dispersion described in Examples.

(Manufacture of polymer particles containing no pigment)
The polymer (C) may be contained in the ink as pigment-free polymer particles.
The pigment-free polymer particles can be efficiently produced as an aqueous dispersion by a method having the following steps (I') and (II').
Step (I'): A step of dispersing a mixture containing the polymer (C), an organic solvent, a neutralizing agent, and water to obtain a dispersion. Step (II'): Dispersion obtained in the step (I'). Step of removing the organic solvent from the liquid to obtain an aqueous dispersion of the polymer particles containing no pigment In the above steps (I') and (II'), the pigment was used in the above-mentioned production of the pigment-containing polymer particles. It is the same as the above steps (I) and (II) except that it is not used.
In the above method, the polymer (C), the organic solvent, the neutralizing agent, and water are mixed in the order of mixing the polymer (C) and the organic solvent in advance, preferably dissolving the polymer (C) in the organic solvent. Next, it is preferable to add a neutralizing agent and add water with stirring. As the neutralizing agent, the same neutralizing agent as that used in the step (I) is preferable.
When mixing the polymer (C), the organic solvent, the neutralizing agent, and water, it is preferable to use a dispersion method similar to the method for producing an aqueous dispersion of pigment-containing polymer particles.

The concentration of the non-volatile component (solid content concentration) of the aqueous dispersion of the obtained pigment-free polymer particles is preferably 10% by mass or more from the viewpoint of improving dispersion stability and facilitating the preparation of water-based ink. It is more preferably 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 dispersion is measured by the method described in Examples.

The average particle size of the pigment-free polymer particles is preferably 40 nm or more, more preferably 60 nm or more, still more preferably 75 nm or more, and from the viewpoint of reducing coarse particles and improving the ejection stability of the water-based ink. It is preferably 150 nm or less, more preferably 120 nm or less, and further preferably 110 nm or less.
The average particle size of the pigment-free polymer particles in the aqueous dispersion is measured by the method described in Examples.
Further, it is preferable that the pigment-free polymer particles in the water-based ink do not swell or shrink the particles or agglomerate between the particles, and the average particle size of the pigment-free polymer particles in the water-based ink is the pigment. It is preferable that the average particle size of the polymer particles containing no is the same as the average particle size in the aqueous dispersion. The preferred aspect of the average particle size of the pigment-free polymer particles in the water-based ink is the same as the preferred aspect of the average particle size in the aqueous dispersion. The average particle size of the pigment-free polymer particles in the water-based ink is also measured by the same method as the average particle size of the pigment-free polymer particles in the aqueous dispersion described in Examples.

(Other ingredients)
In addition to the above components, the water-based ink of the present invention contains commonly used surfactants, moisturizers, wetting agents, penetrants, dispersants, viscosity regulators, defoamers, preservatives, fungicides, and rust preventives. Various additives such as agents can be added.

(Surfactant)
The water-based ink of the present invention preferably further contains a surfactant from the viewpoint of improving fixability and water resistance. Examples of the surfactant include nonionic surfactants, silicone-based surfactants, fluorine-based surfactants 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 to 30 carbon atoms and acetylene glycol-based surfactants. One or more selected ones are more preferable, and from the viewpoint of improving fixability and water resistance, a surfactant of an alcohol alkylene oxide adduct having 6 to 30 carbon atoms and an acetylene glycol-based surfactant are used in combination. Is more preferable.

[Manufacturing method of water-based ink]
In the water-based ink of the present invention, an acid-modified propylene-based polymer (A), an organic solvent (B), a colorant, a polymer (C), a surfactant, water and other components are mixed and stirred, if necessary. Can be obtained by
The content and physical properties of each component of the water-based ink according to the present invention are as follows.

(Content of polycarboxylic acid-modified propylene polymer (A))
The content of the acid-modified propylene-based polymer (A) in the water-based ink is 5% by mass or more, preferably 5.5% by mass or more, and more preferably 6% by mass from the viewpoint of improving fixability and water resistance. From the same viewpoint as above, it is 15% by mass or less, preferably 12% by mass or less, more preferably 10% by mass or less, and further preferably 8% by mass or less.

(Content of organic solvent (B))
The content of the organic solvent (B) in the water-based ink is preferably 1% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, still more, from the viewpoint of improving fixability and water resistance. It is preferably 20% by mass or more, more preferably 25% by mass or more, and from the same viewpoint as described above, preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 35% by mass or less. Even more preferably, it is 30% by mass or less.

(Content of polymer (C))
The content of the polymer (C) in the water-based ink is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.15% by mass, from the viewpoint of improving fixability and water resistance. % Or more, more preferably 0.2% by mass or more, and from the same viewpoint as described above, preferably 5% by mass or less, more preferably 4% by mass or less, still more preferably 3% by mass or less, still more. It is preferably 2% by mass or less, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less.

(Content of colorant)
The content of the colorant in the water-based ink is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, still more preferably 0.3% by mass or more, still more, from the viewpoint of improving the printing density. It is preferably 0.5% by mass or more, and 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, still more preferably 3% by mass. % Or less, more preferably 1% by mass or less.

(Total content of colorant and polymer (C))
The total content of the pigment and the polymer (C) in the water-based ink is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 0, from the viewpoint of improving the dispersibility of the pigment. It is .7% by mass or more, and from the viewpoint of improving discharge stability, it is preferably 20% by mass or less, more preferably 15% by mass or less, still more preferably 10% by mass or less, still more preferably 5% by mass or less. , More preferably 3% by mass or less.

(Surfactant content)
The content of the surfactant in the water-based ink is preferably 0.3% by mass or more, more preferably 0.5% by mass or more, still more preferably 0.7% by mass or more, from the viewpoint of improving the print quality. From the same viewpoint as described above, it is preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less.

(Water content)
The content of water in the water-based 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 85% by mass or less, more preferably 80% by mass or more. Below, it is more preferably 75% by mass or less, and even more preferably 70% by mass or less.

(Water-based ink physical properties)
The viscosity of the water-based ink at 25 ° C. is preferably 2.0 mPa · s or more, more preferably 3.0 mPa · s or more, further preferably 4.0 mPa · s or more, and preferably 12 mPa · s or more. It is s or less, more preferably 9.0 mPa · s or less, further preferably 7.0 mPa · s or less, and even more preferably 6.0 mPa · s or less.
The viscosity of the water-based ink is measured by the method described in Examples.

The pH of the water-based ink at 25 ° C. is preferably 7.0 or more, more preferably 8.0 or more, still more preferably 8.5 or more, from the viewpoint of increasing the printing density. Further, from the viewpoint of member resistance and skin irritation, the pH is preferably 11.0 or less, more preferably 10.0 or less, and further preferably 9.5 or less.
The pH of the water-based ink is measured by the method described in Examples.

[Printing method]
The printing method of the present invention is a printing method for printing on a printing medium using the water-based ink. The water-based ink can be used as a water-based ink for flexo printing, gravure printing, or inkjet printing because a printed matter having excellent fixability and water resistance can be obtained even when printed on a low-polarity printing medium. Since it is also excellent in fixability and water resistance in inkjet printing, it is preferably used as a water-based ink for inkjet printing.
In the inkjet printing method using the water-based 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 printing media such as synthetic resin film. Among these, a synthetic resin film is preferable from the viewpoint of improving fixability and water resistance, and a polyolefin film such as a polyethylene film or a polypropylene film is more preferable as a low-polarity printing medium, and a polypropylene film is further preferable. Further, a water-absorbent printing medium such as plain paper or high-quality paper can also be used as the printing medium.

The amount of the water-based ink adhered to the print medium is preferably 0.1 g / m ² or more, more preferably 1 g / m ² or more, and further preferably 5 g / m as a solid content from the viewpoint of improving print quality and printing speed. It is m ² or more, more preferably 10 g / m ² or more, and preferably 25 g / m ² or less, more preferably 20 g / m ² or less, still more preferably 15 g / m ² or less.
The inkjet printing method preferably includes a step of ejecting ink droplets onto a printing medium for printing, and then drying the ink droplets that have landed on the printing medium.
In the drying step, the surface temperature of the printing medium is preferably 25 ° C. or higher, more preferably 30 ° C. or higher, still more preferably 40 ° C. or higher, still more preferably 50 ° C. or higher, still more preferably, from the viewpoint of improving print quality. Is 60 ° C. or higher, more preferably 65 ° C. or higher, and preferably 200 ° C. or lower, more preferably 150 ° C. or lower, still more preferably 120 ° C. or lower, from the viewpoint of suppressing deformation of the print medium due to heat and reducing energy. , More preferably 90 ° C. or lower.

Regarding the above-described embodiment, the present invention further discloses the following water-based ink and printing method.
<1> A polycarboxylic acid-modified propylene-based polymer containing a structural unit derived from one or more monomers (a-1) selected from unsaturated carboxylic acids and their anhydrides and a structural unit derived from a propylene monomer (a-2). A water-based ink containing A) and an organic solvent (B).
The polymer (A) is formed by acid-denaturing a propylene-based polymer (A') having a mmmm fraction of 5 mol% or more and 50 mol% or less in a pentad sequence, and has a structure represented by the following general formula (I). Is a polymer containing
A water-based ink in which the content of the polymer (A) in the water-based ink is 5% by mass or more and 15% by mass or less as a solid content.

(In the general formula (I), X ¹ represents a structural unit derived from one or more monomers (a-1) selected from unsaturated carboxylic acids and their anhydrides, p and q are integers, and n is an integer. It is an integer of 2 or more.)

<2> The polycarboxylic acid-modified propylene-based polymer (A) further contains a structural unit derived from one or more monomers (a-3) selected from ethylene and an α-olefin having 4 to 20 carbon atoms. The water-based ink according to 1>.
<3> The water-based ink according to <2>, wherein the α-olefin has 4 or more and 10 or less carbon atoms, preferably 4 or more and 8 or less, and more preferably 4 or more and 6 or less.
<4> The monomer (a-3) is at least one selected from ethylene, 1-butene and isobutene, preferably at least one selected from ethylene and 1-butene, and more preferably 1-butene. The water-based ink according to <2> or <3> above.
<5> The monomer (a-1) is at least one selected from acrylic acid, methacrylic acid, and maleic anhydride, and is preferably maleic anhydride, according to any one of <1> to <4>. The water-based ink described.

<6> The content of the structural unit derived from the propylene monomer (a-2) in the propylene-based polymer segment which is the main chain of the polycarboxylic acid-modified propylene-based polymer (A) is 50% by mass or more, preferably 60% by mass. Above, more preferably 70% by mass or more, further preferably 80% by mass or more, and 100% by mass or less, preferably 98% by mass or less, more preferably 95% by mass or less. The water-based ink according to any one of 5>.
<7> The content of the structural unit derived from the monomer (a-3) in the propylene-based polymer segment which is the main chain of the polycarboxylic acid-modified propylene-based polymer (A) is 2% by mass or more, preferably 5% by mass. The above, and according to any one of <2> to <6> above, which is 50% by mass or less, preferably 40% by mass or less, more preferably 30% by mass or less, and further preferably 20% by mass or less. Water-based ink.

<8> The mmmm fraction of the propylene-based polymer (A') in the pentad sequence is 10 mol% or more, preferably 20 mol% or more, more preferably 30 mol% or more, still more preferably 35 mol% or more. The water-based ink according to any one of <1> to <7> above, which is 48 mol% or less, preferably 46 mol% or less, more preferably 45 mol% or less.
<9> The weight average molecular weight of the propylene-based polymer (A') is 5,000 or more, preferably 10,000 or more, more preferably 20,000 or more, and 150,000 or less, preferably 100,000. The water-based ink according to any one of <1> to <8>, which is more preferably 50,000 or less.
<10> The acid modification rate of the polycarboxylic acid-modified propylene-based polymer (A) represented by the following formula (1) is 1% by mass or more, preferably 3% by mass or more, and more preferably 5% by mass or more. The above <1> to <9>, which are 30% by mass or less, preferably 25% by mass or less, more preferably 20% by mass or less, still more preferably 15% by mass or less, still more preferably 10% by mass or less. The water-based ink described in either.
Acid denaturation rate (% by mass) = [mass of structural unit derived from monomer (a-1) in the polymer (A) / mass of the polymer (A)] × 100 (1)
<11> The weight average molecular weight of the polycarboxylic acid-modified propylene-based polymer (A) is 5,000 or more, preferably 10,000 or more, more preferably 20,000 or more, and 150,000 or less, preferably 150,000 or less. The water-based ink according to any one of <1> to <10>, which is 100,000 or less, more preferably 50,000 or less.
<12> The polycarboxylic acid-modified propylene-based polymer (A) is contained in the aqueous ink as an aqueous dispersion, and the average particle size of the aqueous dispersion of the polymer (A) is 40 nm or more, preferably 50 nm or more, more preferably. The water-based ink according to any one of <1> to <11> above, wherein is 60 nm or more, 150 nm or less, preferably 120 nm or less, and more preferably 100 nm or less.

<13> The boiling point of the organic solvent (B) is 90 ° C. or higher, preferably 120 ° C. or higher, more preferably 150 ° C. or higher, further preferably 180 ° C. or higher, and lower than 250 ° C., preferably 240 ° C. or lower. The water-based ink according to any one of <1> to <12>, more preferably 230 ° C. or lower, still more preferably 220 ° C. or lower.
<14> The organic solvent (B) is at least one selected from polyhydric alcohols and glycol ethers, preferably one or more selected from diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monoisopropyl ether, and propylene glycol. The above <1> to <13>, wherein one or more selected from diethylene glycol monoisobutyl ether, diethylene glycol monoisopropyl ether, and propylene glycol is more preferable, and propylene glycol is more preferable. Water-based ink.

<15> The water-based ink further contains a polymer (C) other than the polycarboxylic acid-modified propylene-based polymer (A), and the polymer (C) is preferably one or more selected from an acrylic polymer, polyester, and polyurethane. The water-based ink according to any one of <1> to <14> above, which is more preferably an acrylic polymer.
<16> The water-based ink according to <15>, wherein the polymer (C) is contained in the ink as polymer particles containing a pigment.
<17> The water-based ink according to <15>, wherein the polymer (C) is contained in the ink as polymer particles containing no pigment.

<18> The content of the polycarboxylic acid-modified propylene-based polymer (A) in the water-based ink is 5.5% by mass or more, preferably 6% by mass or more, and 12% by mass or less, preferably 10% by mass. The water-based ink according to any one of <1> to <17>, which is more preferably 8% by mass or less.
<19> The content of the organic solvent (B) in the water-based ink is 1% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 20% by mass or more, still more preferably. Any of the above <1> to <18>, which is 25% by mass or more, and 50% by mass or less, preferably 40% by mass or less, more preferably 35% by mass or less, and further preferably 30% by mass or less. Water-based ink described in.
<20> The water-based ink further contains a polymer (C) other than the polycarboxylic acid-modified propylene-based polymer (A), and the content of the polymer (C) in the water-based ink is preferably 0.05% by mass or more. Is 0.1% by mass or more, more preferably 0.15% by mass or more, still more preferably 0.2% by mass or more, and 5% by mass or less, preferably 4% by mass or less, more preferably 3% by mass. The water-based ink according to any one of <1> to <19>, wherein more preferably 2% by mass or less, still more preferably 1% by mass or less, and even more preferably 0.5% by mass or less.

<21> The water-based ink according to any one of <1> to <20>, wherein the water-based ink further contains a colorant.
<22> The water-based ink according to <21>, wherein the colorant is a pigment and the form of the polymer (C) is polymer particles containing the pigment.
<23> The content of the colorant in the water-based ink is 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.3% by mass or more, still more preferably 0.5% by mass or more. And, 15% by mass or less, preferably 10% by mass or less, more preferably 7% by mass or less, still more preferably 5% by mass or less, still more preferably 3% by mass or less, still more preferably 1% by mass or less. The water-based ink according to <21> or <22>.
<24> The water-based ink further contains a surfactant, and the content of the surfactant in the water-based ink is 0.3% by mass or more, preferably 0.5% by mass or more, more preferably 0. The water-based ink according to any one of <1> to <23>, which is 7% by mass or more, and 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less.
<25> The content of water in the water-based ink is 40% by mass or more, preferably 50% by mass or more, more preferably 60% by mass or more, and 85% by mass or less, preferably 80% by mass or less. The water-based ink according to any one of <1> to <24>, which is more preferably 75% by mass or less, still more preferably 70% by mass or less.

<26> The water-based ink according to any one of <1> to <25>, wherein the water-based ink is for flexographic printing, gravure printing, or inkjet printing, and is preferably for inkjet printing.
<27> A printing method for printing on a printing medium using the water-based ink according to any one of <1> to <26>, wherein the printing medium is selected from art paper, coated paper, and synthetic resin film. A printing method, preferably one or more, preferably a synthetic resin film, more preferably a polyolefin film, and even more preferably a polypropylene film.
<28> Use of the water-based ink according to any one of <1> to <26> for flexographic printing, gravure printing, or inkjet printing, preferably for inkjet printing.

In the following production examples, examples and comparative examples, "parts" and "%" are "parts by mass" and "% by mass" unless otherwise specified.

(1) Average particle size of pigment aqueous dispersion of pigment-containing polymer particles, aqueous dispersion of pigment-free polymer particles, and aqueous dispersion of polycarboxylic acid-modified propylene-based polymer (A) [medium volume particle size (1) D ₅₀ )]
The volume median particle size (D ₅₀ ) measured under the following measurement conditions using a dynamic light scattering type particle size measuring machine "ZETASIZERNANO ZS" (manufactured by Malvern) was used as the average particle size of each aqueous dispersion.
(Measurement condition)
Solid content concentration: 0.1%
Measurement temperature: 25 ° C
Medium: Water Measurement cell: Glass Cuvette
Laser specifications: He-Ne, 4mW, 633nm
Detection optics: 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)

(2) Measurement of weight average molecular weight of propylene-based polymer (A') and polycarboxylic acid-modified propylene-based polymer (A) Gel permeation chromatography using chloroform as an eluent [GPC apparatus "HLC-8120 GPC" (Tosoh Corporation) (Manufactured by) Two columns "TSK-GEL, α-M" (manufactured by Tosoh Corporation), flow velocity: 1 mL / min], using polystyrene having a known molecular weight as a standard substance was used for measurement.

(3) Measurement of solid content concentration of pigment aqueous dispersion of pigment-containing polymer particles, aqueous dispersion of pigment-free polymer particles, aqueous dispersion of polycarboxylic acid-modified propylene-based polymer (A), and ink in a 30 mL container Weigh 10.0 g of sodium sulfate homogenized in a desiccator, add about 1.0 g of a sample to it, mix, weigh accurately, and maintain at 105 ° C. for 2 hours to remove volatiles. Then, it was left in a desiccator for 15 minutes, and the mass was measured. 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.

(4) Measurement of mmmm fraction 1 g of powder polymer sample of propylene polymer (A') was dissolved in 3 g of deuterated chloroform at room temperature, ¹³ C-NMR was measured under the following measurement conditions, and mm mm fraction in the pentad sequence was measured. The rate (mol%) was calculated.
(Measurement condition)
Measuring machine: Mercury-400 (manufactured by VARIAN)
Observation nucleus: 13C
Polymer sample: 1g
Measurement solvent: CDCl ₃ 3g
Magnetic field strength: 14.09637 [T] (600 [MHz])
Number of scans: 6400
Relaxation time: 45 seconds Measurement temperature: Room temperature

(5) Confirmation of modified structure The modified structure of the acid-modified propylene-based polymer (A) is, for example, by Koji Miyauchi and Keiji Saito, Analytical Chemistry (Bunseki Kagaku), Vol.55, No.8, pp.547-554 ( ¹ H-NMR was measured and confirmed according to the method described in 2006).

(6) Measurement of acid denaturation rate 1 g of powder polymer sample of acid-modified propylene-based polymer (A) was dissolved in 10 g of deuterated chloroform at room temperature, and ¹³ C-NMR was measured under the following measurement conditions to determine the acid denaturation rate. It was.
The acid denaturation rate is represented by the following formula (1).
Acid denaturation rate (% by mass) = [mass of structural unit derived from monomer (a-1) in the polymer (A) / mass of the polymer (A)] × 100 (1)
(Measurement condition)
Measuring machine: Mercury-400 (manufactured by VARIAN)
Observation nucleus: 13C
Polymer sample: 1g
Measuring solvent: CDCl ₃ 10 g
Magnetic field strength: 14.09637 [T] (600 [MHz])
Number of scans: 8
Relaxation time: 10 seconds Measurement temperature: Room temperature

(7) DSC measurement of polycarboxylic acid-modified propylene-based polymer (A) Sample 0.01 using a differential scanning calorimeter (DSC) "Q-100" (manufactured by TA Instruments Japan Co., Ltd.) ~ 0.02 g was weighed in an aluminum pan, the temperature was raised to 200 ° C., and then cooled from that temperature to −50 ° C. at a lowering rate of 10 ° C./min. Next, the calorific value was measured while raising the temperature to 200 ° C. at a heating rate of 10 ° C./min to obtain a DSC curve. The DSC curves of Example 1 and Comparative Example 3 are shown in FIGS. 1 and 2, respectively.

(8) Measurement of Weight Average Molecular Weight of Polymer (C) Gel 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. The molecular weight is known as a standard substance by permeation chromatography [GPC apparatus manufactured by Tosoh Corporation (HLC-8120 GPC), column manufactured by Tosoh Corporation (TSK-GEL, α-M x 2), flow velocity: 1 mL / min]. It was measured using monodisperse polystyrene.

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

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

(Manufacture of aqueous dispersion of pigment-containing polymer particles)
Manufacturing example 1
(1) Synthesis of acrylic polymer C1 91 parts of methacrylic acid (manufactured by Kojunyaku Kogyo Co., Ltd.), 399 parts of benzyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd.), styrene macromer "AS-6S" (manufactured by Toa Synthesis Co., Ltd.) 140 parts (solid content 50%) and 140 parts of methoxypolyethylene glycol methacrylate "M-230G" (manufactured by Shin-Nakamura Chemical Industries, Ltd., average number of moles of ethylene oxide added 23) were mixed to prepare 770 parts of a monomer mixed solution.
In the reaction vessel, 15.75 parts of methyl ethyl ketone, 0.350 parts of the polymerization chain transfer agent (2-mercaptoethanol), and 10% (77 parts) of the monomer mixed solution were put and mixed, and nitrogen gas replacement was performed.
Separately, 80% (616 parts) of the monomer mixed solution, 2.45 parts of the polymerization chain transfer agent, 173.25 parts of methyl ethyl ketone and the polymerization initiator "V-65" (manufactured by Wako Pure Chemical Industries, Ltd., 2, 2). Put 5.6 parts of the mixed solution of'-azobis (2,4-dimethylvaleronitrile)) into the dropping funnel, raise the temperature to 75 ° C. while stirring the mixed solution in the reaction vessel under a nitrogen atmosphere, and in the dropping funnel. The mixed solution of was added dropwise over 4.5 hours. Then, the remaining 10% (77 parts) of the monomer mixed solution, 0.7 parts of the polymerization chain transfer agent, 126 parts of methyl ethyl ketone and 1.4 parts of the polymerization initiator were placed in a dropping funnel at 75 ° C. and 1 part. . Dropped over 7 hours. After completion of the dropping, 2.1 parts of the polymerization initiator was mixed, the temperature was raised to 80 ° C., and the mixture was stirred for 1.5 hours. A solution of the acrylic polymer C1 (weight average molecular weight of the acrylic polymer C1: 26,000) was obtained by further mixing, raising the temperature, and stirring the polymerization initiator twice.

(2) Production of an aqueous dispersion of pigment-containing acrylic polymer particles (Step I)
20 parts of the acrylic polymer C1 obtained by drying the polymer solution obtained in (1) above under reduced pressure was dissolved in 62.8 parts of methyl ethyl ketone, and 5.01 parts and 25 parts of a neutralizing agent 5N sodium hydroxide aqueous solution were dissolved therein. 1.13 parts of% ammonia water and 236.5 parts of ion-exchanged water were added, and stirring and mixing was carried out at 10 to 15 ° C. using a dispar blade at 2,000 rpm for 15 minutes. Subsequently, as a magenta pigment, C.I. I. Pigment Violet 19 "Inkjet Magenta E5B02" (manufactured by Clariant) 45 copies and C.I. I. 25 parts of Pigment Red 122 "6111T" (manufactured by Dainichiseika Kogyo Co., Ltd.) was added, and the mixture was stirred and mixed at 7,000 rpm for 3 hours at 10 to 15 ° C. using a dispar blade to perform predispersion. The obtained dispersion was filtered by 200 mesh and subjected to 20-pass dispersion treatment at a pressure of 150 MPa using a microfluidicizer "M-110K" (manufactured by Microfluidics, high pressure homogenizer) to obtain a dispersion.
(Step II)
Methyl ethyl ketone is removed from the obtained dispersion at 60 ° C. under reduced pressure, some water is further removed, the mixture is centrifuged, and the liquid layer portion is filtered through a filter (manufactured by Sartorius, trade name: Minisart) having a pore size of 5 μm. Then, the coarse particles were removed to obtain an aqueous dispersion of pigment-containing acrylic polymer C1 particles. Further, 80 parts of this aqueous dispersion contains 5.0 parts of glycerin (manufactured by Kao Co., Ltd.), 0.2 parts of 1,2-benzoisothiazole-3 (2h) -on "Proxel XL2" (manufactured by Abyssia Co., Ltd.), and ions. 14.8 parts of exchanged water was mixed, sterilized at 70 ° C. for 1 hour, cooled to room temperature, and filtered through the filter having a pore size of 5 μm to obtain an aqueous dispersion of pigment-containing acrylic polymer C1 particles. Solid content concentration 40%, average particle size 133 nm] was obtained.

(Manufacture of aqueous dispersion of polymer particles containing no pigment)
Manufacturing example 2
(Step I')
2. 20 parts of the acrylic polymer C1 obtained by drying the polymer solution obtained in the above (1) of Production Example 1 under reduced pressure was dissolved in 62.8 parts of methyl ethyl ketone, and a neutralizing agent 5N sodium hydroxide aqueous solution was dissolved therein. 01 part, 1.13 part of 25% ammonia water, and 115 part of ion-exchanged water were added, and the mixture was stirred and mixed at 2,000 rpm for 15 minutes at 10 to 15 ° C. using a disper blade to perform pre-dispersion. The obtained dispersion was filtered through 200 meshes and subjected to 20-pass dispersion treatment at a pressure of 150 MPa using a microfluidizer "M-110K" (manufactured by Microfluidics, a high-pressure homogenizer) to obtain a dispersion.
(Step II')
Methyl ethyl ketone is removed from the obtained dispersion at 60 ° C. under reduced pressure, some water is further removed, the mixture is centrifuged, and the liquid layer portion is filtered through a filter (manufactured by Sartorius, trade name: Minisart) having a pore size of 5 μm. Then, the coarse particles were removed to obtain an aqueous dispersion of the polymer C1 particles containing no pigment. Further, 80 parts of this aqueous dispersion contains 5.0 parts of glycerin (manufactured by Kao Co., Ltd.), 0.2 parts of 1,2-benzoisothiazole-3 (2h) -on "Proxel XL2" (manufactured by Abyssia Co., Ltd.), and ions. 14.8 parts of exchanged water is mixed, sterilized at 70 ° C. for 1 hour, cooled to room temperature, and filtered through the filter having a pore size of 5 μm to obtain pigment-free acrylic polymer C1 particles (anionic). An aqueous dispersion of polymer particles (solid content concentration 20%, average particle size 106 nm) was obtained.

(Production of Polycarboxylic Acid-Modified Propylene Polymer (A))
Production Example A-1
In a 1 L stainless steel reaction vessel, a propylene / 1-butene copolymer (90% propylene, 1-butene 10%, weight average molecular weight 30,000, mmmm ratio 45%, Unitica stock) as a propylene-based polymer (A'). 200 parts (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in a mixed solvent of 475 parts of toluene (manufactured by Wako Pure Chemical Industries, Ltd.) and 25 parts of acetone (manufactured by Wako Pure Chemical Industries, Ltd.). Next, 50 parts of maleic anhydride (manufactured by Wako Pure Chemical Industries, Ltd.) was added, and after heating at 145 ° C. for 1 hour to dissolve, 5 parts of di-t-butyl peroxide (manufactured by NOF CORPORATION) was added. did. After stirring for 5 hours while maintaining the temperature, the mixture was cooled to room temperature. After adding 3 L of acetone to the obtained polymer solution, the precipitated polymer component was suction-filtered and dried to obtain a polycarboxylic acid-modified propylene-based polymer A1 containing amorphous propylene / 1-butene modified with maleic anhydride. A polymer was obtained. The acid denaturation rate was 6%.
Next, 30 parts of the above polycarboxylic acid-modified propylene polymer A1, 70 parts of water, and 0.72 g of potassium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) were placed separately in a 500 mL stainless steel reaction vessel, and the mixture was stirred at 98 ° C. for 12 hours. did. Then, it was air-cooled with stirring and filtered through a 200-mesh wire mesh to obtain an aqueous dispersion of the polycarboxylic acid-modified propylene-based polymer A1. The solid content concentration of the aqueous dispersion was 30%, and the volume average particle diameter was 62 nm. It was confirmed by NMR measurement that the modified structure was an oligomer graft modification represented by the general formula (I). In addition, DSC measurement was performed to obtain the DSC curve shown in FIG.

Production Examples A-2, 3
In Production Example A-1, except that the propylene / 1-butene copolymer was changed to a propylene / ethylene / 1-butene copolymer (both manufactured by Unitica Co., Ltd.) as shown in Table 1, Production Example A- The same as No. 1 was produced to obtain aqueous dispersions of polycarboxylic acid-modified propylene-based polymers A2 and A3. The solid content concentration of these aqueous dispersions is 30%, and the volume average particle diameter is as shown in Table 1.

Production Example A-4
In Production Example A-1, the same production as in Production Example A-1 except that maleic anhydride was changed to 5 parts and the amount of potassium hydroxide was changed to 0.2 parts, and the polycarboxylic acid-modified propylene type was used. An aqueous dispersion of polymer A4 was obtained. The acid denaturation rate was 1%. The solid content concentration of the aqueous dispersion is 30%, and the volume average particle diameter is as shown in Table 1.

Production Example A-5
In Production Example A-1, the same production as in Production Example A-1 except that maleic anhydride was changed to 200 parts and the amount of potassium hydroxide was changed to 2.7 parts, and the polycarboxylic acid-modified propylene type was used. An aqueous dispersion of polymer A5 was obtained. The acid denaturation rate was 20%. The solid content concentration of the aqueous dispersion is 30%, and the volume average particle diameter is as shown in Table 1.

Production Example A-6
Water dispersion of acrylic acid-modified propylene polymer A6 in the same manner as in Production Example A-1 except that in Production Example A-1, 50 parts of acrylic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was changed instead of maleic anhydride. I got a body. The acid denaturation rate was 6%. The solid content concentration of the aqueous dispersion is 30%, and the volume average particle diameter is as shown in Table 1.

Comparative production example AC-1
As shown in Table 1, the styrene-modified propylene-based polymer AC1 was prepared in the same manner as in Production Example A-1 except that 50 parts of styrene (manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of maleic anhydride in Production Example A-1. Obtained. Then, 30 parts of the above styrene-modified propylene polymer AC, 70 parts of water, and 0.72 parts of potassium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) were placed separately in a 500 mL stainless steel reaction vessel, and the mixture was stirred at 98 ° C. for 12 hours. .. After that, it was air-cooled with stirring and filtered through a 200-mesh wire mesh, but all the solid content remained on the wire mesh and could not be emulsified.

Comparative manufacturing example AC-2
200 parts of a propylene / 1-butene copolymer (propylene 90% by mass, 1-butene 10% by mass, weight average molecular weight 30,000, mmmm ratio 45%, Unitica Co., Ltd.) in a 1 L stainless steel reaction vessel. The temperature was raised to 200 ° C. and melted. Next, 50 parts of maleic anhydride (manufactured by Wako Pure Chemical Industries, Ltd.) was added. It was dissolved by heating at 200 ° C. for 5 hours. Next, 15 parts of di-t-butyl peroxide (manufactured by NOF CORPORATION) was added dropwise over 1 hour. After stirring for 5 hours while maintaining the temperature, the mixture was cooled to room temperature and pulverized. As the polycarboxylic acid-modified propylene-based polymer AC2, an amorphous propylene / 1-butene copolymer modified with maleic anhydride was obtained. The acid denaturation rate was 6%.
Next, 30 parts of the above polycarboxylic acid-modified propylene-based polymer, 70 parts of water, and 0.72 g of potassium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) were placed separately in a 500 mL stainless steel reaction vessel, and the mixture was stirred at 98 ° C. for 12 hours. .. Then, it was air-cooled with stirring and filtered through a 200-mesh wire mesh to obtain an aqueous dispersion of the polycarboxylic acid-modified propylene-based polymer AC2. The solid content concentration of the aqueous dispersion was 30%, and the volume average particle diameter was 51 nm. It was confirmed by NMR that the modified structure was the monomer graft modification represented by the general formula (II). In addition, DSC measurement was performed to obtain the DSC curve shown in FIG.

Comparative production example AC-3
In Production Example A-1, as shown in Table 1, a propylene / 1-butene copolymer (propylene 90% by mass, 1-butene 10% by mass, weight average molecular weight 30,000, mmmm ratio 3%, Unitica Co., Ltd.) An aqueous dispersion of a polycarboxylic acid-modified propylene-based polymer AC3 was obtained by producing in the same manner as in Production Example A-1 except that it was changed to The solid content concentration of the aqueous dispersion is 30%, and the volume average particle diameter is as shown in Table 1.

Comparative manufacturing example AC-4
In Production Example A-1, as shown in Table 1, a propylene / 1-butene copolymer (propylene 90% by mass, 1-butene 10% by mass, weight average molecular weight 30,000, mmmm ratio 55%, Unitica Co., Ltd.) It was produced in the same manner as in Production Example A-1 except that it was changed to A-1, and an aqueous dispersion of a polycarboxylic acid-modified propylene-based polymer AC4 was obtained. The solid content concentration of the aqueous dispersion is 30%, and the volume average particle diameter is as shown in Table 1.

Comparative manufacturing example AC-5
In Production Example A-1, as shown in Table 1, the propylene / 1-butene copolymer was used as an ethylene / 1-butene copolymer (ethylene 90% by mass, 1-butene 10% by mass, weight average molecular weight 28,000). , Unitica Co., Ltd.) was produced in the same manner as in Production Example A-1 to obtain an aqueous dispersion of a polycarboxylic acid-modified propylene-based polymer AC5. The solid content concentration of the aqueous dispersion is 30%, and the volume average particle diameter is as shown in Table 1.

(Manufacturing of water-based ink)
Example 1
60 parts of propylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.), 2 parts of Surfinol 104PG-50 (manufactured by Air Products and Chemicals, propylene glycol solution of acetylene glycol-based nonionic surfactant, effective content 50%), emalgen 1 part of 120 (polyoxyethylene lauryl ether manufactured by Kao Co., Ltd., ether-based nonionic surfactant) and 87.04 parts of ion-exchanged water were mixed, and the mixture was stirred with a magnetic stirrer at room temperature for 15 minutes. Next, 5 parts of an aqueous dispersion of the pigment-containing acrylic polymer C1 particles obtained in Production Example 1 was dropped by a dropper and charged. Next, 40 parts of an aqueous dispersion of the polycarboxylic acid-modified propylene-based polymer A1 obtained in Production Example A-1 was added dropwise with a dropper. Then, it was filtered through a membrane filter having a pore size of 1.2 μm to obtain an aqueous ink. The evaluation results are shown in Table 2.

Examples 2-12 and Comparative Examples 1-8
In Example 1, an aqueous ink was obtained in the same manner as in Example 1 except that the compounding compositions shown in Tables 2 and 3 were changed.

<Evaluation of water-based ink>
(1) Evaluation of Fixability The obtained water-based ink was filled in the ink inlet on the upper part of the head of the inkjet printer "IPSiOGX5000" (manufactured by Ricoh Co., Ltd.) via a silicon tube. A solid print pattern (width 204 mm x length 275 mm) is produced by Photoshop (registered trademark) (manufactured by Adobe), and the OPP film "P60" (Toray Co., Ltd.) has an adhesion amount of 14 g / m ^2. It was solidly printed on (manufactured by the company) and dried at a temperature of 25 ° C. and a relative humidity of 50% for 60 minutes to obtain a printed matter. The printed matter was rubbed 5 times by applying a load of 2 kg to the cellulose non-woven fabric "Bencot M3-II" (manufactured by Asahi Kasei Fibers Co., Ltd.) using the bottom surface of the weight (bottom area 78.5 cm ² ). The image density of the Bencott surface before and after rubbing was measured using a reflection densitometer "RD-915" (manufactured by Gretag Macbeth). The difference in image density before and after rubbing was calculated, and the calculated value was used to evaluate the fixability after ink drying. The smaller the value, the better the fixability. The evaluation results are shown in Tables 2 and 3.

(2) Evaluation of water resistance A solid printed matter of 200 mm × 200 mm was prepared under the same printing conditions as the above evaluation of fixability, dried in a vacuum dryer at 40 ° C. for 12 hours, and then the mass was measured. A cotton wool soaked with 20 g of water was placed on the entire surface of the printed matter and left for 1 hour. Next, the cotton wool was reciprocated 10 times with a load of 50 g using the bottom surface of the weight (bottom area of 7.1 cm ² ). After that, the moisture on the surface was wiped off with Kimwipe (Nippon Paper Crecia, trade name), left in a vacuum dryer at 40 ° C for 12 hours, and then the mass was measured, and the difference from the mass before the test (mg). Was calculated. The smaller the difference value, the better the water resistance. The evaluation results are shown in Tables 2 and 3.

The notations in Tables 2 and 3 are as follows.
* 1: The content of propylene polymer (a-2) units in the propylene polymer segment.
* 2: The content of the acid-modified propylene-based polymer (A) as a solid content in the ink.
* 3: The content (solid content) of the polymer (C) as pigment-containing polymer particles in the ink.
* 4: The content (solid content) of the polymer particles containing no pigment of the polymer (C) in the ink.
* 5: Comparative Example 1 could not be emulsified because it did not use the monomer (a-1). Therefore, the ink could not be produced.
PG: Propylene glycol iBDG: Diethylene glycol monoisobutyl ether iPDG: Diethylene glycol monoisopropyl ether The values in parentheses in Tables 2 and 3 are the solid content of the polymer (C) in the ink.

From Tables 2 and 3, it can be seen that Examples 1 to 12 are superior in fixability and water resistance as compared with Comparative Examples 1 to 8.
Comparative Example 2 is inferior in fixability and water resistance because it does not contain the organic solvent (B).
Comparative Example 3 is inferior in fixability and water resistance as compared with Example 1 having the same acid denaturation rate. This is because Comparative Example 3 is a monomer graft-modified propylene polycarboxylic acid polymer, while Example 1 is an oligomer graft-modified propylene polycarboxylic acid polymer (A). From these DSC curves, FIGS. 1 and 2, the melting start temperature in Example 1 is lower than that in Comparative Example 3. From this, the propylene polycarboxylic acid polymer (A) according to the present invention has a specific stereoregularity in which the propylene polymer segment between adjacent graft bonding portions is long and has low crystallinity, and melting starts. It is considered that the temperature was lowered, and as a result, the fixability was further improved.

The water-based ink of the present invention is excellent in fixability and water resistance. The water-based ink is a printing method for printing on a printing medium, and can be particularly preferably used for a printing method in which the printing medium is a polyolefin film.

Claims (11)

A polycarboxylic acid-modified propylene-based polymer (A) containing a structural unit derived from one or more monomers (a-1) selected from an unsaturated carboxylic acid and its anhydride and a structural unit derived from a propylene monomer (a-2). , A water-based ink containing an organic solvent (B).
The polymer (A) is formed by acid-denaturing a propylene-based polymer (A') having a mmmm fraction of 5 mol% or more and 50 mol% or less in a pentad sequence, and has a structure represented by the following general formula (I). Is a polymer containing
A water-based ink in which the content of the polymer (A) in the water-based ink is 5% by mass or more and 15% by mass or less as a solid content.

(In the general formula (I), X ¹ represents a structural unit derived from one or more monomers (a-1) selected from unsaturated carboxylic acids and their anhydrides, p and q are integers, and n is an integer. It is an integer of 2 or more.) The first aspect of claim 1, wherein the polycarboxylic acid-modified propylene-based polymer (A) further contains a structural unit derived from ethylene and one or more monomers (a-3) selected from α-olefins having 4 or more and 20 or less carbon atoms. Water-based ink. The water-based ink according to claim 1 or 2, wherein the monomer (a-1) is at least one selected from acrylic acid, methacrylic acid, and maleic anhydride. Any of claims 1 to 3, wherein the content of the structural unit derived from the propylene monomer (a-2) in the propylene-based polymer segment which is the main chain of the polycarboxylic acid-modified propylene-based polymer (A) is 70% by mass or more. Water-based ink described in Crab. The water-based ink according to any one of claims 1 to 4, wherein the polycarboxylic acid-modified propylene-based polymer (A) has an acid modification rate represented by the following formula (1) of 3% by mass or more and 15% by mass or less.
Acid denaturation rate (% by mass) = [mass of structural unit derived from monomer (a-1) in the polymer (A) / mass of the polymer (A)] × 100 (1) The water-based ink further contains a polymer (C) other than the polycarboxylic acid-modified propylene-based polymer (A), and the content of the polymer (C) in the water-based ink is 0.05% by mass or more and 5% by mass or less. , The water-based ink according to any one of claims 1 to 5. The water-based ink according to any one of claims 1 to 6, wherein the water-based ink further contains a colorant. The water-based ink according to claim 7, wherein the colorant is a pigment, and the form of the polymer (C) is polymer particles containing the pigment. The organic solvent (B) contains at least one selected from diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monoisopropyl ether, and propylene glycol, and the content of the organic solvent (B) in the aqueous ink is 1% by mass. The water-based ink according to any one of claims 1 to 8, which is the above. The water-based ink according to any one of claims 1 to 9, wherein the water-based ink is for inkjet printing. A printing method for printing on a printing medium using the water-based ink according to any one of claims 1 to 10, wherein the printing medium is a polyolefin film.