CN116390960A - (meth) acrylic copolymer, (meth) acrylic copolymer composition and ink - Google Patents

Abstract

The present invention relates to a (meth) acrylic copolymer having good solubility in alkaline water, storage stability of ink, and good masking property in film printing; a (meth) acrylic copolymer composition containing the (meth) acrylic copolymer; and an ink containing the (meth) acrylic copolymer composition. The (meth) acrylic copolymer of the present invention has a chemical structure derived from a structural unit of an alkyl (meth) acrylate having 1 to 8 carbon atoms in the alkyl group, a structural unit derived from a vinyl compound containing an acid group, and a thiol derived from a trifunctional or higher thiol; the (meth) acrylic copolymer composition of the present invention contains: the (meth) acrylic copolymer, water, and an alkaline compound; the ink of the present invention contains the (meth) acrylic copolymer composition.

Description

(meth)acrylic copolymer, (meth)acrylic copolymer composition and ink

technical field

The invention relates to a (meth)acrylic copolymer, a (meth)acrylic copolymer composition and ink.

This application claims priority based on Japanese Patent Application No. 2020-192003 filed with the Japan Patent Office on November 18, 2020, and the contents thereof are incorporated herein by reference.

Background technique

Water-based inks (also called water-based inks) are different from solvent-based inks in that they can reduce the amount of volatile organic compounds (VOC), and can reduce the risk of fire and toxicity such as mutagenicity. Therefore, water-based inks are widely used in applications such as gravure printing. Among them, (meth)acrylic polymers and (meth)acrylic copolymers containing structural units derived from alkyl (meth)acrylates and structural units derived from (meth)acrylic acid have high transparency, Pigments have good color rendering properties, so they are widely used in water-based inks.

In addition to good solubility in alkaline water, (meth)acrylic polymers and (meth)acrylic copolymers for water-based inks also require that the total amount of VOC during dissolution can be controlled at a low level. The storage stability of the ink and the masking property at the time of film printing are good.

Patent Document 1 describes a method of condensing a polycarboxylic acid resin and a polyol resin produced by solution polymerization using a polyfunctional mercaptan in a solvent different from the polymerization solvent, and then neutralizing with an amine at 95° C. Dispersed in deionized water to produce a water-dilutable resin for coatings.

Patent Document 2 describes a method of introducing a hydrophobic moiety and a hydrophilic moiety into a polyfunctional thiol produced in a solution to obtain an aqueous pigment dispersion having high storage stability.

prior art literature

patent documents

Patent Document 1: Japanese Patent Application Laid-Open No. 04-304277

Patent Document 2: International Publication No. 2019/065604

Contents of the invention

The problem to be solved by the invention

However, in the method described in Patent Document 1, it is necessary to repeatedly perform the solvent devolatilization process. In addition, in order to melt the resin at a high temperature of about 95°C during resin condensation, amine neutralization is required, so the solubility of the resin in alkaline water is low. In addition, there are problems in that the total amount of energy required to obtain an aqueous dispersion is large, and the solvent used in the polymerization step and the condensation step remains in the final composition.

In the method of Patent Document 2, since the hydrophobic moiety and the hydrophilic moiety are separately introduced through a multi-stage polymerization process, the entire polymerization process is long and the productivity is poor. In addition, the (meth)acrylic copolymer obtained in the polymerization step needs to be neutralized with an alkali at a high temperature of 70°C. Therefore, there is a problem that the solubility of the (meth)acrylic copolymer in alkaline water is low.

The object of the present invention is to provide a (meth)acrylic copolymer having good solubility in alkaline water, storage stability of ink and good masking property in film printing; containing said (meth)acrylic copolymer A (meth)acrylic copolymer composition; and an ink containing the (meth)acrylic copolymer composition.

Technical solution to the problem

The present invention has the following modes:

[1] A (meth)acrylic copolymer having a structural unit derived from an alkyl (meth)acrylate having an alkyl group having 1 to 8 carbon atoms and a unit derived from an acid group-containing vinyl compound. The structural unit and the chemical structure derived from a trifunctional or higher mercaptan, the (meth)acrylic copolymer is a particulate solid.

[2] A (meth)acrylic copolymer having a structural unit derived from an alkyl (meth)acrylate having an alkyl group having 1 to 8 carbon atoms and a unit derived from an acid group-containing vinyl compound. A structural unit and a chemical structure derived from a trifunctional or higher thiol, and the (meth)acrylic copolymer further has a chemical structure derived from a monofunctional thiol and a chemical structure derived from a bifunctional thiol More than one chemical structure in .

[3] The (meth)acrylic copolymer according to [1] or [2], wherein the (meth)acrylic copolymer has a secondary glass transition temperature of 35° C. or higher.

[4] The (meth)acrylic copolymer according to any one of [1] to [3], further comprising a structural unit derived from a compound having two or more polymerizable double bonds.

[5] The (meth)acrylic copolymer according to any one of [1], [3], and [4], which further has a chemical structure selected from monofunctional thiol-derived and bifunctional One or more chemical structures among the chemical structures of thiols.

[6] The (meth)acrylic copolymer according to any one of [1] to [5], wherein the (meth)acrylic copolymer has a mass average particle diameter of 20 to 2000 μm.

[7] The (meth)acrylic copolymer according to any one of [1] to [6], wherein the water content of the (meth)acrylic copolymer is 0.01 to 10% by mass.

[8] The (meth)acrylic copolymer according to any one of [1] to [7], wherein the (meth)acrylic copolymer has an acid value of 20 to 140 mgKOH/g.

[9] The (meth)acrylic copolymer according to any one of [1] to [8], wherein the (meth)acrylic copolymer has a weight average molecular weight of 15,000 to 80,000.

[10] A (meth)acrylic copolymer composition comprising: the (meth)acrylic copolymer according to any one of [1] to [9], water, and a basic compound.

[11] The (meth)acrylic copolymer composition according to [10], further comprising a pigment.

[12] An ink comprising the (meth)acrylic copolymer composition of [10] or [11].

Invention effect

According to the present invention, it is possible to provide a (meth)acrylic copolymer having good solubility in alkaline water, good storage stability of ink, and good masking property in film printing, and a (meth)acrylic copolymer containing the above-mentioned (meth)acrylic copolymer. The (meth)acrylic copolymer composition and the ink containing the (meth)acrylic copolymer composition.

Detailed ways

Next, the present invention will be described in detail. The following embodiments are merely examples for explaining the present invention, and are not intended to limit the present invention to these embodiments. This invention can be implemented in various forms unless it deviates from the summary.

In this specification, "(meth)acrylic acid" is a generic term for acrylic acid and methacrylic acid. "(Meth)acrylic" is a general term for acrylic and methacrylic. The "(meth)acrylic copolymer" refers to a copolymer having, for example, at least one of an acryloyl group and a methacryloyl group.

In this specification, "(meth)acrylate" is a generic term for acrylate and methacrylate.

In this specification, the ratio of each structural unit of a (meth)acryl-type copolymer and the ratio of the chemical structure originating in a thiol are calculated from the mass ratio of each monomer used for a polymerization raw material, and a thiol.

In this specification, "room temperature" refers to a temperature within the range of 23°C±2°C unless otherwise specified.

[(meth)acrylic copolymer]

<The (meth)acrylic copolymer of the first embodiment>

The (meth)acrylic copolymer of the first aspect of the present invention has an alkyl (meth)acrylate derived from an alkyl group having 1 to 8 carbon atoms (hereinafter also referred to as "monomer (a)") A structural unit derived from an acid group-containing vinyl compound (hereinafter, also referred to as "monomer (b)"), and a chemical structure derived from a trifunctional or more functional thiol.

The (meth)acrylic copolymer of the first aspect preferably further has at least one chemical structure selected from the chemical structure derived from a monofunctional thiol and the chemical structure derived from a bifunctional thiol. In addition, the (meth)acrylic copolymer may have a structural unit derived from other monomers (hereinafter also referred to as "monomer (c)") other than the monomer (a) and the monomer (b). .

<The (meth)acrylic copolymer of the second embodiment>

The (meth)acrylic copolymer of the second aspect of the present invention has a structural unit derived from the monomer (a), a structural unit derived from the monomer (b), and a chemical structure derived from a trifunctional or higher thiol, The (meth)acrylic copolymer further has one or more chemical structures selected from a chemical structure derived from a monofunctional thiol and a chemical structure derived from a bifunctional thiol. Moreover, the (meth)acrylic-type copolymer of a 2nd aspect may have the structural unit derived from a monomer (c).

<Alkyl (meth)acrylate having an alkyl group having 1 to 8 carbon atoms>

The (meth)acrylic copolymers of the first and second aspects of the present invention have a structural unit derived from an alkyl (meth)acrylate having an alkyl group having 1 to 8 carbon atoms, that is, a unit derived from a monomer ( a) Structural unit.

Examples of the monomer (a) in the (meth)acrylic copolymers of the first aspect and the second aspect include: methyl (meth)acrylate, ethyl (meth)acrylate, (meth) n-propyl acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate.

Among these, methyl (meth)acrylate, n-butyl (meth)acrylate, acrylic acid, etc. -2-Ethylhexyl ester.

These may be used alone or in combination of two or more.

Among the (meth)acrylic copolymers of the first embodiment and the second embodiment, in a total of 100 mass % of the structural unit derived from the monomer (a) and the structural unit derived from the monomer (b), The proportion of the structural unit of (a) is preferably 60 to 97% by mass, more preferably 80 to 95% by mass. The lower and upper limits of these numerical ranges may be combined arbitrarily.

When the proportion of the structural unit derived from the monomer (a) is within the above-mentioned range, the film-forming properties and water resistance of the ink will become favorable.

<Vinyl compounds containing acid groups>

The (meth)acrylic copolymers of the first aspect and the second aspect of the present invention have a structural unit derived from an acid group-containing vinyl compound, that is, a structural unit derived from a monomer (b).

As a monomer (b), the vinyl compound etc. which have acid groups, such as carboxylic acid and sulfonic acid, are mentioned, for example.

Specific examples of vinyl compounds having carboxylic acid groups in the (meth)acrylic copolymers of the first and second aspects include monobasic acids such as (meth)acrylic acid and crotonic acid; fumaric acid; , maleic acid, itaconic acid and other dibasic acids; partial esters of these dibasic acids, etc.

Specific examples of the vinyl compound having a sulfonic acid group include vinylsulfonic acid, 2-acrylamide-2-methylpropanesulfonic acid, and the like.

Among these, vinyl compounds having a carboxylic acid group are preferable, and (meth)acrylic acid is more preferable from the viewpoint that the water solubility of the (meth)acrylic copolymer becomes favorable.

These may be used alone or in combination of two or more.

Among the (meth)acrylic copolymers of the first embodiment and the second embodiment, in a total of 100 mass % of the structural unit derived from the monomer (a) and the structural unit derived from the monomer (b), The proportion of the structural unit of (b) is preferably 3 to 40% by mass, more preferably 5 to 20% by mass. The lower and upper limits of these numerical ranges may be combined arbitrarily.

When the proportion of the structural unit derived from the monomer (b) is within the above range, the solubility of the (meth)acrylic copolymer in alkaline water and the solubility in other solvents will become better.

With respect to the total mass of all structural units constituting the (meth)acrylic copolymer, the structural unit derived from the monomer (a) and the unit derived from the (meth)acrylic copolymer of the first embodiment and the second embodiment The total ratio of the structural units of the body (b) is preferably 70 to 99.9% by mass, more preferably 80 to 99% by mass, and still more preferably 85 to 95% by mass. The lower and upper limits of these numerical ranges may be combined arbitrarily.

When the total ratio of the structural unit derived from the monomer (a) and the structural unit derived from the monomer (b) is within the above range, the solubility in alkaline water becomes very good.

In this specification, the ratio derived from the chemical structure of the mercaptan mentioned later is also included in the gross mass of all the structural units which comprise the (meth)acryl-type copolymer of a 1st aspect and a 2nd aspect.

<thiol>

The (meth)acrylic copolymers of the first aspect and the second aspect have a chemical structure derived from a trifunctional or more functional thiol.

The details will be described later. When producing the (meth)acrylic copolymers of the first embodiment and the second embodiment, by using a trifunctional or higher mercaptan as a chain transfer agent in the polymerization reaction, the trifunctional or higher mercaptan becomes polymerized. The initiation point, derived from the chemical structure of trifunctional or more mercaptan, was introduced into the (meth)acrylic copolymer.

The more than trifunctional thiol is a compound having three or more mercapto groups in a single molecule.

Examples of the trifunctional or more functional thiol in the (meth)acrylic copolymers of the first and second aspects include 1,2,3-trimercaptopropane, 2,2-bis(mercaptomethyl )-1-mercaptobutane, 1,2,3,4-tetramercaptobutane, 2,2-bis(mercaptomethyl)-1,3-dimercaptopropane, tris(3-mercaptopropionic acid)glyceride , trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptopropionate), dipentaerythritol hexa(3-mercaptopropionate), tri(thioglycolate) glyceride, trimethylol Trimethylolpropane tris(thioglycolate), Pentaerythritol tetrakis(thioglycolate), Dipentaerythritol hexa(thioglycolate), Trimethylolpropane tris(2-mercaptobutyrate), Pentaerythritol tetrakis(2-mercaptobutyrate) ester, dipentaerythritol hexa(2-mercaptobutyrate), etc.

Among these, trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetra( 3-mercaptopropionic acid) ester, pentaerythritol tetrakis (mercaptoacetic acid) ester.

These may be used alone or in combination of two or more.

In the (meth)acrylic copolymers of the first aspect and the second aspect, sulfur derived from trifunctional or higher is relative to a total of 100 parts by mass of structural units constituting all monomers derived from the (meth)acrylic copolymer. The ratio of the chemical structure of alcohol is preferably 0.1 to 20 parts by mass, more preferably 1 to 6 parts by mass. The lower and upper limits of these numerical ranges may be combined arbitrarily.

When the ratio of the chemical structure derived from the trifunctional or more functional mercaptan is more than the said lower limit, the solubility to alkaline water of a (meth)acryl-type copolymer will become more favorable. The odor of a (meth)acrylic-type copolymer will be suppressed as the ratio of the chemical structure originating in the trifunctional or more functional thiol is below the said upper limit.

The (meth)acrylic copolymer of the first aspect preferably has a chemical structure derived from a monofunctional thiol and a bifunctional sulfur derived from a chemical structure derived from a trifunctional or higher thiol, in addition to a chemical structure derived from a trifunctional or higher thiol. One or more of the chemical structures of alcohols. When the (meth)acrylic copolymer of the first aspect further has one or more chemical structures selected from a chemical structure derived from a monofunctional thiol and a chemical structure derived from a bifunctional thiol, When dissolved in alkaline water, the viscosity becomes lower, making it easier to mix in pigments, etc.

The (meth)acrylic copolymer of the second aspect has a chemical structure derived from a trifunctional or higher thiol, in addition to having a chemical structure derived from a trifunctional or higher thiol, and has a chemical structure derived from One or more chemical structures derived from the chemical structure of the monofunctional thiol and the chemical structure of the bifunctional thiol. Therefore, according to the (meth)acrylic copolymer of the second aspect, the viscosity at the time of dissolution in alkaline water becomes low, and it becomes easier to mix a pigment and the like.

A monofunctional thiol is a compound having one mercapto group in a single molecule.

Examples of the monofunctional thiol in the (meth)acrylic copolymers of the first and second aspects include n-octyl mercaptan, n-dodecyl mercaptan, and t-dodecyl mercaptan Alcohol, n-butylmercaptan, thioglycolic acid, 3-mercaptopropionic acid, 2-mercaptoethanol, 2-ethylhexyl 3-mercaptopropionic acid, 2-ethylhexyl thioglycolic acid, 3-mercaptopropionic acid Isooctyl ester, isooctyl mercaptoacetate, 2-methoxybutyl 3-mercaptopropionate, etc.

These may be used alone or in combination of two or more.

In the (meth)acrylic copolymers of the first aspect and the second aspect, the monofunctional thiol-derived The proportion of the chemical structure is preferably 0.1 to 20 parts by mass, more preferably 1 to 6 parts by mass. The lower and upper limits of these numerical ranges may be combined arbitrarily.

When the ratio of the chemical structure derived from a monofunctional mercaptan is more than the said lower limit, the solubility to alkaline water of a (meth)acryl-type copolymer will become more favorable. The odor of a (meth)acrylic-type copolymer will be suppressed as the ratio of the chemical structure originating in a monofunctional mercaptan is below the said upper limit.

Difunctional thiols are compounds that have two mercapto groups in a single molecule.

Examples of the bifunctional thiol in the (meth)acrylic copolymers of the first aspect and the second aspect include: 1,4-dimercaptobutane, 3-oxo-1,5-pentanediene Mercaptan, 3-thia-1,5-pentanedithiol, ethylene glycol bis(3-mercaptopropionate), bis(thioglycolate)-1,4-butylene glycol, etc.

These may be used alone or in combination of two or more.

In the (meth)acrylic copolymers of the first aspect and the second aspect, the bifunctional thiol-derived The proportion of the chemical structure is preferably 0.1 to 20 parts by mass, more preferably 1 to 6 parts by mass. The lower and upper limits of these numerical ranges may be combined arbitrarily.

When the ratio of the chemical structure derived from a bifunctional mercaptan is more than the said lower limit, the solubility to alkaline water of a (meth)acryl-type copolymer will become more favorable. The odor of a (meth)acrylic-type copolymer will be suppressed as the ratio of the chemical structure originating in a bifunctional mercaptan is below the said upper limit.

<other monomers>

The (meth)acrylic copolymers of the first aspect and the second aspect may have, in addition to the structural unit derived from the monomer (a) and the structural unit derived from the monomer (b), other monomers (the structural unit of the monomer (c)).

Examples of the monomer (c) in the (meth)acrylic copolymers of the first and second aspects include compounds having one polymerizable double bond (hereinafter also referred to as "monomer (c1) ”), a compound having two or more polymerizable double bonds (hereinafter also referred to as “monomer (c2)”), and the like. Among these, monomer (c2) is preferable as monomer (c). That is, the (meth)acrylic copolymer preferably has a structural unit derived from the monomer (c2) in addition to the structural unit derived from the monomer (a) and the structural unit derived from the monomer (b).

Examples of the monomer (c1) in the (meth)acrylic copolymers of the first aspect and the second aspect include styrene, o-methylstyrene, m-methylstyrene, and p-methylstyrene , α-methylstyrene, o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, 4-(tert-butyl)styrene, p-(tert-butoxy)styrene, 1 -Vinylnaphthalene, 2-vinylnaphthalene, phenyl (meth)acrylate, benzyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate ester, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, etc.

These may be used alone or in combination of two or more.

In the (meth)acrylic copolymers of the first aspect and the second aspect, in the (meth)acrylic copolymers of the first aspect and the second aspect, the monomer-derived The ratio of the structural unit of (c1) is preferably 0.1 to 20 parts by mass, more preferably 1 to 6 parts by mass. The lower and upper limits of these numerical ranges may be combined arbitrarily.

When the proportion of the structural unit derived from the monomer (c1) is more than the above lower limit, the storage stability of the ink tends to be better. When the ratio of the structural unit derived from the monomer (c1) is below the above-mentioned upper limit, the viscosity of the ink can be reduced, and the workability at the time of printing becomes favorable.

Examples of the monomer (c2) in the (meth)acrylic copolymers of the first and second aspects include ethylene glycol di(meth)acrylate, 1,2-propanediol di(methyl) ) acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,4-cyclohexanedimethanol di(meth)acrylate , neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1,3-propanediol di(meth)acrylate, trimethylolpropane di(meth)acrylate , trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, bisphenol A di(meth)acrylate, 2,2-bis{4 -[2-(acryloyloxy)ethoxy)]phenyl}propane, 2,2-bis{4-[2-(methacryloyloxy)ethoxy)]phenyl}propane, tri Cyclodecanedimethanol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, dipropylene glycol di(meth)acrylate, glycerol tri(meth)acrylate, ethoxy Modified isocyanuric acid tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-divinylbenzene, 1,3,5-trivinylbenzene, etc.

Among these, ethylene glycol diacrylate and 1,6-hexanediol di(meth)acrylate are preferable from the viewpoint of lower viscosity when dissolved in alkaline water and easier mixing of pigments, etc. , Trimethylolpropane tri(meth)acrylate.

These may be used alone or in combination of two or more.

In the (meth)acrylic copolymers of the first aspect and the second aspect, in the (meth)acrylic copolymers of the first aspect and the second aspect, the monomer-derived The ratio of the structural unit of (c2) is preferably 0.1 to 20 parts by mass, more preferably 1 to 6 parts by mass. The lower and upper limits of these numerical ranges may be combined arbitrarily.

When the ratio of the structural unit derived from the monomer (c2) is more than the above-mentioned lower limit, the storage stability of the ink tends to become better. When the ratio of the structural unit derived from the monomer (c2) is below the above-mentioned upper limit, the viscosity of the ink can be reduced, and the workability at the time of printing becomes favorable.

<Physical properties>

The (meth)acrylic copolymer of the first aspect is solid at room temperature. Since the (meth)acrylic copolymer of the first aspect is solid at room temperature, VOC when dissolved in alkaline water can be reduced. In addition, since the increase in volume can be suppressed compared with the state dissolved in water (aqueous solution) and the state dispersed in water (dispersion liquid), it is also suitable for transportation and storage.

It is also preferable that the (meth)acrylic copolymer of the second aspect is solid at room temperature. When the (meth)acrylic copolymer of the second aspect is solid at room temperature, it can reduce VOC when dissolved in alkaline water. In addition, since the increase in volume can be suppressed compared with the state dissolved in water (aqueous solution) and the state dispersed in water (dispersion liquid), it is also suitable for transportation and storage.

As a specific shape of a solid (meth)acryl-type copolymer, powdery, plate-like, flake-like, spherical, particle-like, granular, pellet-like solid, etc. are mentioned. Among these, solids in the form of powders, flakes, spheres, granules, and granules are preferable from the viewpoint of ease of handling when dissolved in a solvent or alkaline water.

The (meth)acrylic copolymers of the first aspect and the second aspect can be easily dissolved in water or a mixed solvent of water and an auxiliary solvent described later by being neutralized with a basic compound described later.

The secondary glass transition temperature (Tg) of the (meth)acrylic copolymers of the first aspect and the second aspect is preferably 35°C or higher, more preferably 40°C or higher, even more preferably 45°C or higher. The secondary glass transition temperature (Tg) of the (meth)acrylic copolymers of the first aspect and the second aspect is preferably 70°C or lower, more preferably 60°C or lower, even more preferably 55°C or lower. These lower limit values and upper limit values may be combined arbitrarily.

If the secondary glass transition temperature (Tg) of the (meth)acrylic copolymers of the first aspect and the second aspect is within the above-mentioned range, the aggregation between the copolymer particles when dissolved in alkaline water is suppressed, and the Solubility in water becomes better.

The secondary glass transition temperature (Tg) of the (meth)acrylic copolymer of the first mode and the second mode can be measured using a differential scanning calorimeter (DSC), and its specific measurement method is as in the example item described in the record.

The mass average particle diameter of the (meth)acrylic copolymers of the first aspect and the second aspect is preferably 20 to 2000 μm, more preferably 50 to 850 μm, still more preferably 80 to 700 μm, particularly preferably 150 to 600 μm. The lower and upper limits of these numerical ranges may be combined arbitrarily.

Blending work becomes easy as the mass average particle diameter of a (meth)acryl-type copolymer is more than the said lower limit. Moreover, when the mass average particle diameter of a (meth)acrylic-type copolymer is below the said upper limit, the dissolution time in alkaline water will shorten.

The mass average particle diameter of the (meth)acrylic copolymer can be calculated by shaking and sieving 20 g of the granular resin for 5 minutes using a standard sieve.

The water content of the (meth)acrylic copolymers of the first embodiment and the second embodiment is preferably 0.01 to 10% by mass, more preferably 0.02 to 8.0% by mass, and even more preferably 0.1% by mass relative to the total mass of the acrylic copolymer. ~5.0% by mass, particularly preferably 0.5-5.0% by mass. The lower and upper limits of these numerical ranges may be combined arbitrarily.

Solubility in alkaline water becomes favorable as the water content of a (meth)acryl-type copolymer is more than the said lower limit. Moreover, when the water content of a (meth)acrylic-type copolymer is below the said upper limit, the water resistance of a printed matter will become high. Moreover, when the water content of a (meth)acryl-type copolymer exists in the said range, the handling property of a copolymer becomes favorable when obtaining a particulate-form (meth)acryl-type copolymer.

The specific measurement method of the water content of the (meth)acrylic copolymer is as described in the item of the embodiment.

The acid value of the (meth)acrylic copolymers of the first aspect and the second aspect is preferably 20 to 140 mgKOH/g, more preferably 50 to 100 mgKOH/g, and still more preferably 55 to 90 mgKOH/g. The lower and upper limits of these numerical ranges may be combined arbitrarily.

Solubility in alkaline water becomes more favorable as the acid value of a (meth)acryl-type copolymer is more than the said lower limit. If the acid value of the (meth)acrylic copolymer is not more than the above-mentioned upper limit, the amount of the basic compound required for neutralization and dissolution can be reduced, and the water resistance of printed matter will also become favorable.

The acid value of a (meth)acrylic-type copolymer means the value which shows the mass of potassium hydroxide required to neutralize 1 g of (meth)acrylic-type copolymers by the number of milligrams. The acid values of the (meth)acrylic copolymers of the first aspect and the second aspect can be measured by neutralization titration of a potassium hydroxide solution based on the phenolphthalein discoloration point. The specific assay method is as described in the item of embodiment.

The weight average molecular weight (Mw) of the (meth)acrylic copolymers of the first aspect and the second aspect is preferably 15,000 to 80,000, more preferably 15,000 to 60,000, still more preferably 20,000 to 60,000, particularly preferably 25,000 to 60,000, Most preferably, it is 25,000 to 40,000. The lower and upper limits of these numerical ranges may be combined arbitrarily.

When the weight average molecular weight of a (meth)acrylic-type copolymer is more than the said lower limit, the storage stability of an ink will become more favorable. When the weight average molecular weight of a (meth)acrylic-type copolymer is below the said upper limit, the viscosity of an ink will fall and film-forming property will become favorable.

The weight average molecular weight (Mw) of the (meth)acrylic copolymer of a 1st aspect and a 2nd aspect is the weight average molecular weight (in terms of polystyrene) measured by gel permeation chromatography (GPC). The specific assay method is as described in the item of embodiment.

The number average molecular weight (Mn) of the (meth)acrylic copolymers of the first aspect and the second aspect is preferably 5,000 to 120,000, more preferably 8,000 to 80,000, still more preferably 12,000 to 70,000, particularly preferably 15,000 to 60,000, Most preferably, it is 20,000 to 50,000. The lower and upper limits of these numerical ranges may be combined arbitrarily.

When the number average molecular weight of the (meth)acrylic copolymer is more than the above-mentioned lower limit, the storage stability of the ink tends to become better. When the number average molecular weight of a (meth)acryl-type copolymer is below the said upper limit, the viscosity of an ink will fall and film-forming property will become favorable.

The number average molecular weights (Mn) of the (meth)acrylic copolymers of the first aspect and the second aspect are number average molecular weights (in terms of polystyrene) measured by gel permeation chromatography (GPC). The specific assay method is as described in the item of embodiment.

<Manufacturing method>

The (meth)acrylic copolymers of the first aspect and the second aspect can be produced by known polymerization methods such as bulk polymerization, suspension polymerization, and emulsion polymerization. Among these polymerization methods, bulk polymerization and suspension polymerization are preferable from the viewpoint of easily obtaining powdery, spherical, and granular copolymers that are easy to handle.

<Manufacturing method by suspension polymerization>

The production methods of the (meth)acrylic copolymers of the first aspect and the second aspect by suspension polymerization preferably include a suspension polymerization step, a first dehydration step, a washing step, a second dehydration step, and a drying step.

(suspension polymerization process)

In the suspension polymerization step, the above-mentioned monomer (a) and monomer (b) and, if necessary, monomer (c) are dispersed in water and polymerized in the presence of a trifunctional or higher thiol to obtain the first embodiment and the second embodiment. The process of the (meth)acrylic copolymer of the mode.

As the method of suspension polymerization, known methods can be employed. As a method of suspension polymerization, for example, the following method can be mentioned: in the presence of a polymerization auxiliary agent in a reactor having a polymerization temperature control function and a stirring function, the monomer (a) and the monomer (b) are mixed according to There is a need for a method of polymerizing monomer (c) in water.

As a polymerization auxiliary agent which can be used for manufacture of the (meth)acrylic-type copolymer of a 1st aspect and a 2nd aspect, a polymerization initiator, a chain transfer agent, a dispersant, a dispersion auxiliary agent, etc. are mentioned. However, at least the above-mentioned trifunctional or higher functional thiol is used as a chain transfer agent.

By using a trifunctional or more functional thiol as the polymerization auxiliary agent, the (meth)acrylic copolymers of the first embodiment and the second embodiment having a chemical structure derived from a trifunctional or more functional thiol can be obtained.

Examples of polymerization initiators that can be used in the production of the (meth)acrylic copolymers of the first and second aspects include 2,2'-azobisbisisobutyronitrile, 2,2' -Azobis(2-methylbutyronitrile), benzoyl peroxide, lauroyl peroxide, tert-butyl peroxy-2-ethylhexanoate, tert-amylhydroxy-2-ethylhexanoate, tert-hexyl peroxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, etc.

These may be used alone or in combination of two or more.

As the chain transfer agent which can be used in the production of the (meth)acrylic copolymers of the first aspect and the second aspect, at least a trifunctional or higher mercaptan is used.

In addition, as the chain transfer agent, in addition to the trifunctional or higher functional thiol, at least one of the above-mentioned monofunctional thiol and bifunctional thiol may be used in combination.

Furthermore, in addition to these mercaptans, diphenyl disulfide, dibenzyl disulfide, and α-methylstyrene dimer can be further used in combination.

These may be used alone or in combination of two or more.

As a dispersant which can be used for manufacture of the (meth)acryl-type copolymer of a 1st aspect and a 2nd aspect, the surfactant which disperses a monomer stably in water is mentioned, for example. Specifically, a copolymer of sodium 2-ethanesulfonate methacrylate, potassium methacrylate, and methyl methacrylate, sodium 3-propylsulfonate methacrylate, and methyl methacrylate Copolymers of sodium methacrylate and methacrylic acid, polyvinyl alcohol, polyvinylpyrrolidone, hydroxyethyl cellulose, hydroxypropyl cellulose, etc.

These may be used alone or in combination of two or more.

Examples of dispersing aids that can be used in the production of the (meth)acrylic copolymers of the first and second aspects include sodium sulfate, sodium carbonate, sodium dihydrogen phosphate, disodium hydrogen phosphate, chlorine Potassium chloride, calcium acetate, magnesium sulfate, manganese sulfate, etc.

These may be used alone or in combination of two or more.

The (meth)acrylic copolymers of the first embodiment and the second embodiment are obtained in a slurry state by suspension polymerization. By dehydrating the slurry, generally spherical (meth)acrylic copolymer particles are obtained.

(1st dehydration process, 2nd dehydration process)

The first dehydration step is a step of dehydrating the slurry after suspension polymerization with a dehydrator or the like to separate the (meth)acrylic copolymer particles of the first embodiment and the second embodiment from the reaction liquid.

The second dehydration step is a step of dehydrating the (meth)acrylic copolymer particles after the washing step with a dehydrator or the like to separate the (meth)acrylic copolymer particles from the washing liquid.

Various dehydrators can be used in each dehydration step, for example, a centrifugal dehydrator, a device with a mechanism for suctioning and removing water on a porous belt, etc. can be appropriately selected and used.

One dehydrator can be used, or two of the same model can be prepared and used in each dehydration process, and dehydrators of various models can also be used. From the viewpoints of product quality, equipment investment costs, productivity, and operating costs, it is possible to appropriately select a model that suits the purpose. In the case of emphasizing the balance between product quality and production speed, it is preferable to use a dedicated dehydrator in each dehydration process.

(washing process)

The washing step is a step of washing the (meth)acrylic copolymer particles separated from the reaction liquid.

Components other than the (meth)acrylic copolymer are removed through the washing step to obtain the (meth)acrylic copolymers of the first embodiment and the second embodiment.

As a washing method, for example, a method of adding a washing liquid to the (meth)acrylic copolymer particles dehydrated in the first dehydration step, and re-slurrying the (meth)acrylic copolymer and stirring and mixing Method; after the dehydration process is carried out in a dehydrator with washing function, the method of continuing to add washing liquid for washing, etc. In addition, these washing methods may be combined for washing.

The type and amount of the washing liquid should be selected to achieve the purpose of the washing process. Examples of the washing solution include water (ion-exchanged water, distilled water, purified water, etc.), an aqueous solution in which a sodium salt is dissolved, a buffer solution that can be adjusted to an arbitrary pH, methanol, and the like.

(drying process)

The drying step is a step of drying the (meth)acrylic copolymer particles of the first embodiment and the second embodiment after the second dehydration step.

Water remains on the surface of the (meth)acrylic copolymer particles after the second dehydration step. In addition, the inside of the (meth)acrylic copolymer is in a state close to saturation with water absorption. Therefore, drying is preferably performed so as to further reduce the water content of the (meth)acrylic copolymers of the first embodiment and the second embodiment.

Various dryers can be used for drying, for example, dryers that dry by heating under reduced pressure; dryers that dry (meth)acrylic copolymer particles while being air-transported in a tube using heated air. A dryer; a dryer that dries the (meth)acrylic copolymer particles on the upper side while blowing heated air from the lower side of the perforated plate, and the like.

It is preferable to carry out a drying process so that the moisture content of the (meth)acrylic-type copolymer of the 1st aspect and 2nd aspect after a drying process may be 0.01-10 mass %.

<Manufacturing method by bulk polymerization>

It is preferable that the manufacturing method by bulk polymerization of a (meth)acrylic-type copolymer has a bulk polymerization process and a pulverization process. A devolatilization step may be provided between the bulk polymerization step and the pulverization step.

(Bulk polymerization process)

In the bulk polymerization step, the above-mentioned monomer (a) and monomer (b) and, if necessary, monomer (c) are polymerized in the presence of a trifunctional or higher mercaptan to obtain the (a) of the first embodiment and the second embodiment. base) acrylic copolymer process.

As a method of bulk polymerization, known methods can be employed. As a method of bulk polymerization, for example, the method of making monomer (a) and monomer (b) and, if necessary, monomer (c) A method of carrying out the polymerization.

As a polymerization auxiliary agent, a polymerization initiator, a chain transfer agent, etc. are mentioned. However, as at least a chain transfer agent, the above-mentioned trifunctional or higher mercaptan is used.

As a polymerization initiator, what was exemplified in the description of the suspension polymerization process previously is mentioned.

Examples of the chain transfer agent include the chain transfer agents exemplified in the description of the suspension polymerization step.

The shape of the reactor used in the bulk polymerization step is optional. For example, as a method at the laboratory level, a glass tank in which a rubber tube connected at both ends in a ring shape is sandwiched between two tempered glass plates and the four corners are fixed with clamps can be used as a reactor. Moreover, the airtight container which has a stirring mechanism is mentioned as an industrially usable reactor.

Regarding the polymerization temperature control function, for example, when using the above-mentioned glass tank as a reactor, a commercially available constant temperature water tank may be used. In the case of using an airtight container having a stirring mechanism, temperature control can be performed by exchanging heat with the temperature-regulated heating medium and cooling medium from the outer surface of the reaction container.

(Devolatilization process)

The devolatilization step is to remove (devolatilize) volatile components (such as unreacted monomers, water, etc.) contained in the (meth)acrylic copolymers of the first embodiment and the second embodiment obtained in the bulk polymerization step process.

As a devolatilization method, a known method can be used. As a devolatilization method, the method of processing a (meth)acryl-type copolymer using the extruder with a vent hole etc. are mentioned, for example.

The set temperature of the extruder may be determined in consideration of the boiling point and the like of the volatile components to be removed.

(crushing process)

The pulverization step is a step of pulverizing the (meth)acrylic copolymers of the first embodiment and the second embodiment subjected to a devolatilization treatment as necessary to a desired particle size.

As the pulverization method, any pulverization method corresponding to the desired particle diameter can be adopted.

From the viewpoint of forming a slurry with water during neutralization and dissolution in water, the maximum diameter of the pulverized particles is preferably 5 mm or less, more preferably 2 mm or less.

<Effect>

The (meth)acrylic copolymers of the first and second aspects of the present invention described above have excellent solubility and powder properties, and therefore have good solubility in various solvents, especially alkaline water. Furthermore, the compositions and inks containing the (meth)acrylic copolymers according to the first aspect and the second aspect of the present invention are excellent in paintability, storage stability, and masking properties in film printing, so they are not easy to be printed. Pitting and uneven printing occur.

In addition, the (meth)acrylic copolymers of the first aspect and the second aspect of the present invention are also excellent in productivity.

<purpose>

The (meth)acrylic copolymers of the first and second aspects of the present invention can be used, for example, as raw materials for inks and paints. It is especially suitable as a raw material for water-based ink.

[(meth)acrylic copolymer composition]

The (meth)acrylic copolymer composition of the present invention contains: one selected from the (meth)acrylic copolymer of the first aspect of the present invention and the (meth)acrylic copolymer of the second aspect. more than one species, water, alkaline compounds.

The (meth)acrylic copolymer composition may contain a pigment and a solvent other than water (hereinafter, also referred to as "auxiliary solvent").

Hereinafter, the (meth)acrylic copolymer composition containing a pigment is also specifically called a "pigment-containing composition".

The content of the (meth)acrylic copolymer is preferably 10 to 60% by mass, more preferably 15 to 50% by mass based on the total mass of the (meth)acrylic copolymer composition. The lower and upper limits of these numerical ranges may be combined arbitrarily. Film-forming properties will become favorable as content of a (meth)acryl-type copolymer is more than the said lower limit, and the texture at the time of printing on a base material will become favorable. When content of a (meth)acryl-type copolymer is below the said upper limit, film-forming property will become favorable, and the favorable printing performance to various base materials will be shown.

The water content is preferably 20 to 80% by mass, more preferably 30 to 70% by mass based on the total mass of the (meth)acrylic copolymer composition. The lower and upper limits of these numerical ranges may be combined arbitrarily. Mixability with a pigment will become favorable as content of water is more than the said lower limit. When content of water is below the said upper limit, the viscosity after dissolving a (meth)acryl-type polymer will be low, and the miscibility with other materials will become favorable.

The basic compound acts to neutralize the solid (meth)acrylic copolymer and dissolve it in water or a mixed solvent of water and an auxiliary solvent.

As a basic compound, an alkali metal hydroxide, ammonia, ammonia water, an amine compound etc. are mentioned, for example.

As an alkali metal hydroxide, lithium hydroxide, sodium hydroxide, potassium hydroxide etc. are mentioned, for example.

As the amine compound, for example, triethylamine, 1-propylamine, diethylamine, triisopropylamine, dibutylamine, pentylamine, 1-octylamine, 2-(dimethylamino)ethanol, 2-(ethylamino) Amino)ethanol, 2-(diethylamino)ethanol, 1-amino-2-propanol, 2-amino-1-propanol, 3-amino-1-propanol, 1-(dimethylamino)-2- Propanol, 3-(dimethylamino)-1-propanol, 2-(propylamino)ethanol, bis(3-ethoxypropyl)amine, aminobenzyl alcohol, morpholine, N-methylmorpholine, Tetrabutylammonium hydroxide, etc.

Among them, the number of amines per unit usage is high, the amount of amine required for neutralization can be reduced, and the low VOC of the ink can be achieved, and it is easy to volatilize after the printed matter is dried, and it is difficult to remain on the printed matter. , preferably triethylamine, 2-(dimethylamino)ethanol.

These may be used alone or in combination of two or more.

It is preferable that content of a basic compound is 0.1-10 mass % with respect to the gross mass of a (meth)acryl-type copolymer composition, and it is more preferable that it is 2-5 mass %. The lower and upper limits of these numerical ranges may be combined arbitrarily. The solubility of a (meth)acrylic polymer composition becomes favorable that content of a basic compound is more than the said lower limit. Water resistance after printing will become favorable as content of a basic compound is below the said upper limit.

Examples of pigments include titanium oxide, carbon black, phthalocyanine blue, phthalocyanine green, chrome yellow, cadmium yellow, lead chromate, cobalt blue, chrome green, cobalt green, benzidine yellow, and zinc white. In addition, any commercially available pigments can also be used.

These may be used alone or in combination of two or more.

When the (meth)acrylic copolymer composition contains a pigment, the content of the pigment is preferably 20 to 60% by mass, more preferably 20 to 50% by mass relative to the total mass of the (meth)acrylic copolymer composition. quality%. The lower and upper limits of these numerical ranges may be combined arbitrarily. When content of a pigment is more than the said lower limit, the shielding property with respect to a base material will improve and the color development of a coating film will become favorable. When content of a pigment is below the said upper limit, the ink which disperse|distributed a pigment can be adjusted uniformly, and it becomes a coating film with little pitting.

The (meth)acrylic copolymer composition of the present invention contains water as a solvent, but may contain a solvent other than water as an auxiliary solvent as needed.

Examples of the auxiliary solvent include water-soluble organic solvents among alcohols, glycols, ethers, ketones, esters, and carbitols.

These may be used alone or in combination of two or more.

When the (meth)acrylic copolymer composition contains an auxiliary solvent, the content of the auxiliary solvent is preferably 1 to 40% by mass, more preferably 2% by mass relative to the total mass of the (meth)acrylic copolymer composition. ~30% by mass. The lower and upper limits of these numerical ranges may be combined arbitrarily. The leveling property in a (meth)acryl-type copolymer composition can be improved more that content of an auxiliary solvent is more than the said lower limit. The quantity of the volatile organic compound (VOC) contained in a (meth)acryl-type copolymer composition can be reduced as content of an auxiliary solvent is below the said upper limit.

The (meth)acrylic copolymer composition can be obtained, for example by dissolving a (meth)acrylic copolymer in water or a mixed solvent of water and an auxiliary solvent together with a basic compound. At this time, pigments may also be added as needed. As a specific manufacturing method, the method of mixing and stirring the component which comprises a (meth)acryl-type copolymer composition using the stirrer used normally is mentioned.

The (meth)acrylic copolymer composition of the present invention described above is excellent in paintability, storage stability, and masking properties in film printing, and thus hardly causes pitting and printing unevenness during printing.

[ink]

The ink of the present invention contains the above-mentioned (meth)acrylic copolymer composition.

When the (meth)acrylic copolymer composition does not contain a pigment, the ink further preferably contains a pigment in addition to the (meth)acrylic copolymer composition.

When the (meth)acrylic copolymer composition is a pigment-containing composition, the pigment-containing composition itself may be used as an ink, and may be further diluted with water or an auxiliary solvent.

In addition, according to various purposes, the ink may further contain auxiliary solvents, binders, other auxiliary agents, and the like as necessary.

The content of the (meth)acrylic copolymer according to the first aspect and the second aspect of the present invention contained in the ink is preferably 5 to 30% by mass, more preferably 10 to 25% by mass based on the total mass of the ink. The lower and upper limits of these numerical ranges may be combined arbitrarily. Aggregation of pigment primary particles can be suppressed as content of a (meth)acryl-type copolymer is more than the said lower limit. When content of a (meth)acryl-type copolymer is below the said upper limit, it will become ink with low viscosity and easy handling.

The content of water contained in the ink is preferably 20 to 60% by mass, more preferably 25 to 50% by mass, based on the total mass of the ink. The lower and upper limits of these numerical ranges may be combined arbitrarily. When content of water is more than the said lower limit, it will become ink with low viscosity and easy printing. The drying property of a printed matter becomes favorable that content of water is below the said upper limit.

The content of the basic compound contained in the ink is preferably 0.1 to 10% by mass, more preferably 2 to 5% by mass, based on the total mass of the ink. The lower and upper limits of these numerical ranges may be combined arbitrarily. The film-forming property of ink becomes favorable that content of a basic compound is more than the said lower limit. When content of a basic compound is below the said upper limit, the image with favorable water resistance can be formed.

Examples of the pigment include those exemplified above in the description of the (meth)acrylic copolymer composition.

The content of the pigment contained in the ink is preferably 10 to 50% by mass, more preferably 20 to 40% by mass, based on the total mass of the ink. The lower and upper limits of these numerical ranges may be combined arbitrarily. When content of a pigment is more than the said lower limit, it will become the ink excellent in the shielding property of a base material. When the content of the pigment is not more than the above-mentioned upper limit, generation of aggregates during printing is suppressed, and an ink with little color unevenness is obtained.

The ink of the present invention contains water as a solvent, but may contain a solvent other than water as an auxiliary solvent if necessary.

As an auxiliary solvent, the auxiliary solvent exemplified above in the description of the (meth)acrylic copolymer composition can be mentioned.

When the ink contains an auxiliary solvent, the content of the auxiliary solvent is preferably 0.1 to 30% by mass, more preferably 1 to 25% by mass, based on the total mass of the ink. The lower and upper limits of these numerical ranges may be combined arbitrarily. The leveling property in aqueous ink can be improved more that content of an auxiliary solvent is more than the said lower limit. When the content of the auxiliary solvent is not more than the above upper limit, the amount of volatile organic compounds (VOC) contained in the ink can be reduced.

The ink of the present invention may contain a binder for the purpose of supplementing the substrate adhesion of the ink.

Examples of binders include: polyurethane dispersion (PUD), polyurethane-acrylate composite dispersion (PUA), acrylic emulsion, polyester dispersion, polyolefin dispersion, polyolefin-acrylate composite dispersion, Polyolefin-polyester dispersions, etc.

These may be used alone or in combination of two or more.

As another auxiliary agent, an antifoamer, a leveling agent, a pigment dispersant, a film-forming auxiliary agent, an adhesiveness imparting agent, etc. are mentioned, for example.

These may be used alone or in combination of two or more.

The ink is obtained, for example, by adding and mixing a pigment and, if necessary, one or more of auxiliary solvents, binders, and other auxiliary agents to a (meth)acrylic copolymer composition. At this time, a pigment dispersion treatment may be performed as needed. In addition, it can be further diluted with water as needed.

As the method of the pigment dispersion treatment, any dispersion treatment method using a commercially available rocker shaker, planetary bead mill, batch stirring bead mill, continuous stirring bead mill, or the like can be employed.

The ink of the present invention described above is excellent in paintability, storage stability, and excellent masking properties in film printing, so it is less prone to pitting and printing unevenness during printing.

Example

Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited thereto.

Various measurement and evaluation methods in the following examples and comparative examples are as follows.

In addition, in the following description, unless otherwise specified, "part" means a mass part, and "%" means a mass %.

[measurement/evaluation method]

<Measurement of Secondary Glass Transition Temperature (Tg)>

Using a differential scanning calorimeter (manufactured by Seiko Instruments, Inc., "EXSTAR DSC-6200"), the temperature of 5 mg of the (meth)acrylic copolymer was raised and lowered under the following temperature sweep conditions. When the DSC data measured in step (3) of the following temperature scanning conditions are plotted with the horizontal axis as the temperature (°C) and the vertical axis as the DSC measured value (Mw), the rate of change in the slope of the graph is 0 Draw a tangent line on the low temperature side of the points, and the temperature (°C) corresponding to the intersection point of the tangent line and the tangent line at the point (inflection point) where the rate of change of the slope of the graph is the largest (inflection point) is used as the secondary glass of (meth)acrylic copolymer Transformation temperature (Tg).

(temperature sweep condition)

• Step (1): Stabilize at -10°C for 5 minutes, then raise the temperature to 110°C.

• Step (2): Cool to -10°C.

· Step (3): heat up to 110°C again.

• Step (4): Cool to room temperature.

·Heating rate: +10°C/min.

·Cooling rate: -10°C/min.

<Measurement of acid value>

Accurately weigh about 0.5 g (A(g)) of the (meth)acrylic copolymer in a beaker, and add 50 mL of a mixed solution of toluene and ethanol (mass ratio 1:1). Add a few drops of phenolphthalein and titrate with 0.05 N KOH solution (solvent: ethanol). (Titration = B (mL), potency of KOH solution = f). Similarly, blank measurement (titration = C (mL)) was performed, and calculated according to the following formula.

Acid value (mgKOH/g)={(B-C)×0.05×56.11×f}/A

<Measurement of Weight Average Molecular Weight (Mw) and Number Average Molecular Weight (Mn)>

The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the (meth)acrylic copolymer were measured by gel permeation chromatography (GPC), and a calibration curve of standard polystyrene was used as a value converted to polystyrene to calculate. The measurement conditions of GPC are as follows.

(GPC measurement conditions)

- Apparatus: "HLC-8220GPC" manufactured by Tosoh Corporation.

”和“GMHXL-L/>

”串联连接而成。・Column: "TSKgel G5000HXL" manufactured by Tosoh Corporation

" and "GMHXL-L/>

" connected in series.

• Eluent: tetrahydrofuran.

• Sample concentration: 0.4%.

· Measurement temperature: 40°C.

• Injection volume: 100 μL.

• Flow rate: 1.0 mL/min.

·Detector: RI (inside the device), UV (Tosoh UV-8220).

<Measurement of Moisture Content>

The water content of the (meth)acrylic copolymer is 0% when the (meth)acrylic copolymer is dried at 105° C. for 2 hours. ) is calculated from the drying loss of the weight of the acrylic copolymer.

<Evaluation of Solubility in Alkaline Water>

Put 65.5 g of water and 30.0 g of a (meth)acrylic copolymer together with a stirrer into a glass bottle (manufactured by Boyang Glass Co., Ltd., "M-225"), close the lid, and adjust the temperature to 30° C. Agitate in a water bath for 10 minutes to make a slurry. 4.5 g of 2-(dimethylamino)ethanol was added to the obtained slurry, and the solubility after further stirring at 30° C. for 3 hours was checked visually for the state of the solution. When there was a precipitate in the solution, stirring was added for 3 hours, and the solubility in alkaline water was evaluated according to the following evaluation criteria.

A: After stirring for the first 3 hours, no precipitate was visually confirmed, and the solubility was excellent.

A-: After stirring for the first 3 hours, a precipitate was visually confirmed, but the precipitate disappeared after additional stirring for 3 hours, and the solubility was excellent.

B: After stirring for 6 hours, insoluble matter precipitated obviously, and the solubility was poor.

<Evaluation of Storage Stability and Shading Properties>

(Preparation of (meth)acrylic copolymer composition)

Put 65.5 g of water and 30.0 g of a (meth)acrylic copolymer together with a stirrer into a glass bottle (manufactured by Boyang Glass Co., Ltd., "M-225"), close the lid, and stir at room temperature for 10 minutes to prepare into slurry. Add 4.5 g of 2-(dimethylamino)ethanol to the obtained slurry, further place it in a water bath at 60° C., and stir until no residue is dissolved to obtain a (meth)acrylic copolymer composition. ) The concentration of the acrylic copolymer is 30%.

(preparation of ink)

50 g of the obtained (meth)acrylic copolymer composition, 30 g of titanium oxide CR-90 (manufactured by Ishihara Sangyo Co., Ltd.), 20 g of 2-propanol, and 60 g of glass beads were mixed in a container, and then mixed with a rocking shaker Disperse for 1 hour. Next, the glass beads were removed from the obtained mixture to obtain a pigment paste.

To 60 g of the obtained pigment paste, 11 g of 2-propanol and 13 g of water were added and diluted to obtain an aqueous ink. Using the obtained water-based ink, the storage stability of the ink and the hiding property of the printed matter were evaluated.

(Evaluation of storage stability)

The ink was left to stand at room temperature for 3 days, the presence or absence of pigment sedimentation was visually checked, and the storage stability was evaluated according to the following evaluation criteria.

A: After 3 days, the pigment was also dispersed in the ink.

B: Part or all of the pigment in the ink precipitated when 3 days passed.

(evaluation of concealment)

Ink was set on a gravure printing machine (manufactured by RK PRINTCOAT INSTRUMENTS, "GP-100"), and printing was performed. A 150 line/inch plate was used for printing. In addition, an acrylic film (manufactured by Toyobo Co., Ltd., "PYLEN (registered trademark) Film OT P2108") was used as a substrate to be printed.

About the coating film after printing, the color difference of transmitted light was measured using the spectrophotometer (Konica Minolta Corporation, "CM-5"). Then, the ΔL value was obtained by subtracting 100 from the actual measurement value of the L ^* value (brightness), and the masking properties were evaluated according to the following evaluation criteria. The smaller the ΔL value, the better the hiding property of the printed matter.

A: ΔL value≦-22.5.

B: ΔL value > -22.5.

[Manufacture of dispersant (1)]

Add 1230 g of deionized water, 60 g of sodium methacrylate 2-ethanesulfonate, 10 g of potassium methacrylate, and 12 g of methyl methacrylate into a polymerization device equipped with a stirrer, a cooling pipe, and a thermometer. Nitrogen replacement was carried out, while raising the temperature to a polymerization temperature of 50°C, 0.08 g of 2,2'-azobis(2-methylpropylimid) dihydrochloride was added as a polymerization initiator, and the temperature was further raised to a polymerization temperature of 60°C. While adding the polymerization initiator, use a dripping pump to continuously drop methyl methacrylate for 75 minutes at a speed of 0.24 g/min, keep it at a polymerization temperature of 60° C. for 6 hours, then cool to room temperature to obtain a dispersant ( 1). The obtained dispersant (1) had a solid content of 7.5%.

[Example 1]

In a polymerization device equipped with a stirrer, a cooling tube, and a thermometer, add 40 parts of methyl methacrylate, 40 parts of n-butyl methacrylate, 5 parts of n-butyl acrylate, 15 parts of methacrylic acid, trihydroxy 1.2 parts of monomer mixture of methyl propane trimethacrylate, 0.4 parts of 2,2'-azobis(2-methylbutyronitrile), 2 parts of 2-ethylhexyl 3-mercaptopropionate, three 2 parts of methylolpropane tris(3-mercaptopropionate) and 2 parts of pentaerythritol tetra(mercaptoacetic acid) ester, stir and mix until uniform. Furthermore, the liquid which uniformly mixed 160 parts of pure water, 0.1 part of sodium sulfate, and 0.6 parts of dispersing agents (1) was added, and nitrogen substitution was performed, stirring. Then, the temperature in the flask was controlled at 80° C. to initiate suspension polymerization, and after the polymerization exothermic peak was detected, it was treated at 90° C. for 30 minutes to obtain a slurry-like (meth)acrylic copolymer (suspension polymerization step).

After the polymerization, the inside of the tank was cooled to normal temperature, and the resulting slurry was dehydrated with a centrifugal dehydrator (first dehydration step).

The obtained (meth)acrylic copolymer and pure water as a washing solution were placed in a washing tank at a mass ratio ((meth)acrylic copolymer:washing solution) of 1:2, and stirred and mixed for 20 minutes. After washing for 10 minutes (washing process), dehydrate with a centrifugal dehydrator (second dehydration process).

After dehydration, put the dehydrated (meth)acrylic copolymer into a fluidized tank dryer with an internal temperature set at 40° C., and dry it so that the moisture content of the (meth)acrylic copolymer particles 10% or less (drying process).

For the obtained particulate solid (meth)acrylic copolymer particles, measure the secondary glass transition temperature (Tg), acid value, weight average molecular weight (Mw) and number average molecular weight (Mn), and evaluate the solubility. In addition, water-based ink was prepared by the above-mentioned method, and the storage stability of the ink and the hiding property of the printed matter were evaluated. The results are shown in Table 1.

[Examples 2, 3, 5, 6; Comparative Examples 1-7]

Except having adopted the compounding composition shown in Table 1, 2, it carried out similarly to Example 1, produced the particulate-form solid (meth)acryl-type copolymer particle, and performed various measurement and evaluation. The results are shown in Table 1.

[Example 4]

In a glass tank equipped with a thermometer, put 70 parts of methyl methacrylate, 5 parts of n-butyl acrylate, 12 parts of 2-ethylhexyl acrylate, 13 parts of methacrylic acid, trimethylolpropane triacrylate 1.2 parts, tert-butyl peroxy-2-ethylhexanoate (manufactured by NOF Corporation, "PERBUTYL O") 0.4 parts, 4 parts of 2-ethylhexyl 3-mercaptopropionate, pentaerythritol tetrakis (thioglycolic acid) ) a homogeneous mixture of 2 parts of ester, after airtight, control the temperature in the glass tank at 83°C in a water tank to initiate bulk polymerization, after detecting the polymerization exothermic peak, treat it at 90°C for 30 minutes, and obtain blocky solid (formazan base) acrylic copolymer (bulk polymerization process).

After the polymerization, the inside of the glass tank was cooled to normal temperature. The blocky solid (meth)acrylic copolymer is taken out from the tank, pulverized with Sanitary Crusher SC-01 (manufactured by Sanzhuang Industrial Co., Ltd.), then vibrated on a sieve with an aperture of 2mm, and the part passing through is collected to obtain Particulate solid (meth)acrylic copolymer (crushing process).

For the obtained particulate solid (meth)acrylic copolymer, measure the secondary glass transition temperature (Tg), acid value, weight average molecular weight (Mw) and number average molecular weight (Mn), and evaluate the Solubility. In addition, water-based ink was prepared by the above-mentioned method, and the storage stability of the ink and the hiding property of the printed matter were evaluated. The results are shown in Table 1.

[Example 5]

The particulate solid (meth)acrylic copolymer obtained in Example 4 was shaken on a sieve with a pore size of 1 mm for 5 minutes, and the part passing through was collected to obtain a particulate solid (meth)acrylic copolymer .

[Example 6]

The particulate (meth)acrylic copolymer obtained in Example 4 was shaken on a sieve with a pore size of 750 μm for 5 minutes, and the portion passing through was collected to obtain a particulate solid (meth)acrylic copolymer.

[Table 1]

[Table 2]

The abbreviations in the table are as follows. In addition, the blank column in a table|surface means that the said component was not compounded (the compounded amount is 0 part).

MMA: Methyl methacrylate.

n-BMA: n-butyl methacrylate.

n-BA: n-butyl acrylate.

2-EHA: 2-ethylhexyl acrylate.

· IBXMA: Isobornyl methacrylate.

· MAA: methacrylic acid.

TMPTMA: Trimethylolpropane trimethacrylate.

· HDDA: 1,6-hexanediol diacrylate.

· TMPTA: trimethylolpropane triacrylate.

· EHMP: 2-ethylhexyl 3-mercaptopropionate.

EGMP: Ethylene glycol bis(3-mercaptopropionate).

• TMPMP: trimethylolpropane tris(3-mercaptopropionate).

· PEMP: Pentaerythritol tetrakis(3-mercaptopropionate).

· PETG: pentaerythritol tetrakis (thioglycolate).

AMBN: 2,2'-azobis(2-methylbutyronitrile).

PERBUTYL O: tert-butyl peroxy-2-ethylhexanoate.

In addition, IBXMA is a substitute for monomer (a) (monomer (a')).

As can be seen from the results in Table 1, the (meth)acrylic copolymers obtained in Examples have good solubility in alkaline water. In addition, inks containing these (meth)acrylic copolymers have good storage stability, and are also excellent in hiding properties of printed matter in film printing.

On the other hand, as can be seen from the results in Table 2, when using a (meth)acrylic copolymer that does not have a chemical structure derived from a trifunctional or higher thiol but instead has a chemical structure derived from a monofunctional thiol, In the case of Comparative Examples 1 and 2, the storage stability of the ink and the hiding property of the printed matter were inferior.

It does not have a chemical structure derived from a trifunctional or higher thiol but has a chemical structure derived from a monofunctional thiol instead, but has a structure unit derived from a monomer (c2) derived from HDDA (1,6 The (meth)acrylic copolymer of Comparative Example 3, which is a structural unit of -hexanediol diacrylate), has poor solubility in alkaline water. In addition, in the case of Comparative Example 3, although a (meth)acrylic copolymer composition was obtained, its viscosity was very high, and since the dispersion treatment of the pigment could not be performed, the storage stability of the ink and the hiding property of the printed matter could not be improved. evaluation of.

Although it does not have a chemical structure derived from a trifunctional or more functional thiol, it has a chemical structure derived from a monofunctional thiol or a chemical structure derived from a bifunctional thiol instead, but the ratio is the same as that of Comparative Examples 1 and 2. The (meth)acrylic copolymers of Comparative Examples 4 and 5, which were relatively rare, were not dissolved in the eluent and could not be measured by GPC. In addition, the solubility in alkaline water is poor. Furthermore, in the case of Comparative Examples 4 and 5, although a (meth)acrylic copolymer composition was obtained, its viscosity was very high, and since the dispersion treatment of the pigment could not be performed, the storage stability of the ink and the quality of the printed matter could not be improved. Covered evaluation.

The (meth)acrylic copolymers of Comparative Examples 6 and 7 which did not have a structural unit derived from a monomer (a) or a structural unit derived from a monomer (b) had poor solubility in alkaline water. In addition, in the case of Comparative Examples 6 and 7, since the (meth)acrylic copolymer was not completely dissolved in alkaline water, the (meth)acrylic copolymer composition and the ink could not be prepared, so the storage of the ink could not be performed. Evaluation of Stability and Opacity of Prints.

Industrial availability

According to the present invention, it is possible to provide a (meth)acrylic copolymer having good solubility in alkaline water, good storage stability of ink, and good masking property in film printing, and a (meth)acrylic copolymer containing the above-mentioned (meth)acrylic copolymer. The (meth)acrylic copolymer composition and the ink containing the (meth)acrylic copolymer composition. Therefore, the (meth)acrylic copolymer of this invention can be used also in the field of the resin composition developable by aqueous alkali solution, and it is industrially very important.

Claims (12)

1. A (meth)acrylic copolymer, characterized in that, it has a structural unit derived from an alkyl (meth)acrylate having an alkyl carbon number of 1 to 8, and a ethylene compound derived from an acid group. The structural unit of the base compound and the chemical structure derived from a trifunctional or higher mercaptan, the (meth)acrylic copolymer is a particulate solid. 2. A (meth)acrylic copolymer, characterized in that it has a structural unit derived from an alkyl (meth)acrylate with an alkyl carbon number of 1 to 8, and a ethylene compound containing an acid group. The structural unit of the base compound and the chemical structure derived from a trifunctional or more thiol, the (meth)acrylic copolymer also has a chemical structure derived from a monofunctional thiol and a chemical structure derived from a bifunctional thiol More than one chemical structure in the chemical structure. 3. The (meth)acrylic copolymer according to claim 1 or 2, wherein the secondary glass transition temperature of the (meth)acrylic copolymer is 35° C. or higher. 4 . The (meth)acrylic copolymer according to claim 1 , further comprising a structural unit derived from a compound having two or more polymerizable double bonds. 5. The (meth)acrylic copolymer according to any one of claims 1, 3, 4, further having a chemical structure derived from a monofunctional thiol and a chemical structure derived from a bifunctional thiol More than one chemical structure in a chemical structure. 6 . The (meth)acrylic copolymer according to claim 1 , wherein the (meth)acrylic copolymer has a mass average particle diameter of 20 to 2000 μm. 7. The (meth)acrylic copolymer according to any one of claims 1 to 6, wherein the water content of the (meth)acrylic copolymer is 0.01 to 10% by mass. 8 . The (meth)acrylic copolymer according to claim 1 , wherein the (meth)acrylic copolymer has an acid value of 20 to 140 mgKOH/g. 9 . The (meth)acrylic copolymer according to claim 1 , wherein the (meth)acrylic copolymer has a weight average molecular weight of 15,000 to 80,000. A (meth)acrylic copolymer composition containing the (meth)acrylic copolymer according to any one of claims 1 to 9, water, and a basic compound. 11. The (meth)acrylic copolymer composition according to claim 10, further comprising a pigment. 12. An ink comprising the (meth)acrylic copolymer composition according to claim 10 or 11.