JP7330038B2 - Water-based gravure printing ink composition for paper containers - Google Patents

Description

The present invention relates to an aqueous gravure printing ink composition for paper containers.

From the standpoint of environmental issues, resource saving, occupational safety, disaster prevention, etc., water-based printing inks that use as few organic solvents as possible are used.

For example, in Patent Document 1, a water-based printing ink composition containing a pigment and a water-based binder resin varnish as main components further contains a specific water-soluble or water-dispersible dimethylpolysiloxane alkylene oxide adduct in the ink composition. Aqueous printing ink compositions are disclosed which are characterized by containing 0.005 to 5% by weight.

Further, for example, in Patent Document 2, at least one aqueous binder resin selected from the group consisting of polyurethane resins, acrylic resins, styrene-maleic acid resins, and ethylene-acrylic acid resins is added as an emulsifier and/or Or an aqueous binder resin varnish obtained by dissolving or dispersing in water in the presence of a basic compound, and an aqueous printing ink composition containing a pigment as a main component, further comprising a fluoroalkyl (meth) acrylate monomer and other A water-based printing ink composition characterized by containing 0.01 to 5% by weight of a fluorine-containing acrylic copolymer resin obtained by copolymerizing a polymerizable monomer as a solid content in the ink composition. disclosed.

Further, for example, Patent Document 3 discloses an aqueous gravure printing ink composition for paper containers containing a colorant, an alkali-soluble water-soluble resin and an aqueous medium, wherein the solid content concentration is 15 to 30% by mass, Disclosed is an aqueous gravure printing ink composition for paper containers, wherein the alkali-soluble water-soluble resin and the aqueous medium satisfy specific conditions.

In recent years, water-based printing inks have been required to be compatible with bar code printing.
When printing barcodes, it is necessary that the line width is narrower than that of normal fine characters and that the characters are not thickened or smeared in order to be read accurately by a barcode reader.

The water-based printing inks described in Patent Documents 1 to 3 do not discuss suitability for barcodes as described above, and there is room for further improvement.

JP-A-10-158564 JP-A-10-158565 JP 2013-35967 A

Therefore, the present invention is intended to solve the above-mentioned problems, and it is a bar code that can be printed with a line width thinner than normal fine characters and does not cause thickening or bleeding in the printed image. An object of the present invention is to provide a suitable water-based gravure printing ink composition for paper containers.

In order to solve the above problems, the present inventors have made intensive studies, and found that the colorant, the alkali-soluble water-soluble resin, the high acid value polymer resin, and the aqueous medium contain the alkali-soluble water-soluble The above-mentioned problems can be solved by having the organic resin, the high-acid-value polymer resin, and the aqueous medium satisfy the predetermined conditions 1 to 3 and containing the high-acid-value polymer resin in a predetermined amount. The inventors have found that and completed the present invention.

That is, the present invention provides an aqueous gravure printing ink composition for paper containers containing a colorant, an alkali-soluble water-soluble resin, a high acid value polymer resin, and an aqueous medium,
The solid content concentration is 15 to 30% by mass, and the high acid value polymer resin has a solid content concentration of 0.2 to 1.8% by mass with respect to the total mass of the aqueous gravure printing ink composition for paper containers. A water-based gravure printing ink composition for paper containers, wherein the alkali-soluble water-soluble resin satisfies the following condition 1, and the high acid value polymer resin satisfies the following condition 2. It is a thing.
Condition 1
The alkali-soluble water-soluble resin is a styrene-maleic acid half ester copolymer resin having an acid value of 100 to 210 mgKOH/g, and is a monomer component of the styrene-maleic acid half ester copolymer resin. The maleic acid half ester is at least one type containing an isobutyl maleic acid half ester and an ethoxyethoxyethyl maleic acid half ester in a molar ratio ranging from 100/0 to 55/45.
Condition 2
The high acid value polymer resin has a weight average molecular weight of 30,000 to 150,000 and an acid value of 120 to 250 mgKOH/g.

The water-based gravure printing ink composition for paper containers of the present invention preferably has a solid content concentration of 20 to 30% by mass and further contains an emulsion-type water-based resin that satisfies condition 3 below.
Condition 3
The emulsion-type aqueous resin has an acid value of 30 to 80 mgKOH/g and a glass transition temperature of 15 to 60°C.
The aqueous medium preferably satisfies condition 4 below.
Condition 4
The aqueous medium comprises water, 2-ethyl-1,3-hexanediol, and a lower alcohol having 1 to 4 carbon atoms, and the lower alcohol having 1 to 4 carbon atoms in the water-based gravure printing ink composition for paper containers. is 30% by mass or less, and the content of 2-ethyl-1,3-hexanediol in the aqueous gravure printing ink composition for paper containers is 0.1 to 2.5% by mass.
Hereinafter, the water-based gravure printing ink composition for paper containers of the present invention will be specifically described.

The water-based gravure printing ink composition for paper containers of the present invention contains a colorant, an alkali-soluble water-soluble resin, a high acid value polymer resin, and an aqueous medium.
Each component will be described below.

<Colorant>
The coloring agent is not particularly limited, and conventionally known pigments usually used in water-based printing inks can be used.
Specifically, examples of inorganic pigments include titanium oxide, red iron oxide, antimony red, cadmium yellow, cobalt blue, Prussian blue, ultramarine blue, carbon black, and graphite.
Examples of organic pigments include soluble azo pigments, insoluble azo pigments, azo lake pigments, condensed azo pigments, copper phthalocyanine pigments, and condensed polycyclic pigments.

As the coloring agent, black, indigo, or blue coloring agents are preferable, and carbon black and phthalocyanine pigments are particularly preferable, from the viewpoint of readability when used as a bar code.

The content of the coloring agent is preferably 4 to 11% by mass with respect to the total mass of the aqueous gravure printing ink composition for paper containers of the present invention.
If the content of the coloring agent is less than 4% by mass, it may not be possible to obtain a printed matter having a printing density.
On the other hand, when the content of the coloring agent exceeds 11% by mass, the resulting aqueous gravure printing ink composition for paper containers tends to have a high viscosity.

A dispersant may be contained for the purpose of improving the dispersibility of the colorant.
The dispersant is not particularly limited, and conventionally known dispersants used for improving the dispersibility of pigments and the like in water-based printing inks can be mentioned.
In the present invention, since the specific styrene-maleic acid half ester copolymer resin described below is used, an extender pigment is not essential to improve drying and fluidity, but performance does not deteriorate. Extender pigments can also be used to some extent.
Specific examples of the extender pigment include calcium carbonate, kaolin, barium sulfate, aluminum hydroxide, clay and talc.

<Alkali-soluble water-soluble resin>
The alkali-soluble water-soluble resin constituting the water-based gravure printing ink composition for paper containers of the present invention satisfies Condition 1 below.
By satisfying condition 1 below, the water-based gravure printing ink composition for paper containers of the present invention can exhibit performance such as bar code suitability.
(Condition 1)
It is a styrene-maleic acid half ester copolymer resin having an acid value of 100 to 210 mgKOH/g. and maleic acid ethoxyethoxyethyl half ester in a molar ratio range of 100/0 to 55/45.

If the acid value of the styrene-maleic acid half ester copolymer resin is less than 100 mgKOH/g, the solubility in the aqueous medium described above is lowered.
On the other hand, when the acid value of the styrene-maleic acid half ester copolymer resin exceeds 210 mgKOH/g, the water resistance of the resulting printed material is lowered.
A preferable lower limit of the acid value of the alkali-soluble water-soluble resin is 120 mgKOH/g, and a preferable upper limit thereof is 200 mgKOH/g.

The above styrene-maleic acid half ester copolymer resin comprises, as monomer components, a maleic acid half ester, which is an ethylenically unsaturated monomer containing an acid group, a styrene monomer, and, if necessary, other copolymers. A styrene-maleic acid half ester copolymer resin that is obtained by copolymerizing an ethylenically unsaturated monomer and is soluble in water in the presence of a basic compound, specifically, It is a styrene-maleic acid half ester copolymer resin.
In the case of containing other copolymerizable ethylenically unsaturated monomers, specific examples include alkali-soluble water-soluble resins such as styrene-acrylic-maleic acid half ester copolymer resins. .

The above maleic acid half ester is an isobutyl maleic acid half ester and an ethyl carbitol maleic acid half ester in a molar ratio (isobutyl maleic acid half ester/ethyl carbitol maleic acid half ester) in the range of 100/0 to 55/45. It is at least one kind to contain.
By using such a specific maleic acid half ester, leveling properties and printability are improved.
In the maleic acid half ester, if the molar ratio of the maleic acid ethyl carbitol half ester to the maleic acid isobutyl half ester exceeds 45 moles, the water resistance tends to decrease.

Examples of the styrene-based monomer include styrene-based monomers such as styrene, α-methylstyrene, vinyltoluene, and derivatives thereof.

Examples of other copolymerizable ethylenically unsaturated monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) ) acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, 2-hydroxystearyl (meth)acrylate and the like.

The content of the alkali-soluble water-soluble resin is preferably 5 to 25% by mass with respect to the total mass of the aqueous gravure printing ink composition for paper containers of the present invention.
If the content of the alkali-soluble water-soluble resin is less than 5% by mass, the dispersibility of the pigment tends to deteriorate.
On the other hand, if the content of the alkali-soluble water-soluble resin exceeds 25% by mass, it may become difficult to design the aqueous gravure printing ink composition for paper containers of the present invention.

The alkali-soluble water-soluble resin is usually used as a water-soluble resin varnish by dissolving it in water in the presence of a basic compound.
Examples of basic compounds used for dissolving the alkali-soluble water-soluble resin in water include ammonia, organic amines, alkali metal hydroxides, and the like. Specifically, examples of the organic amine include alkylamines such as diethylamine, triethylamine and ethylenediamine, and alkanolamines such as monoethanolamine, ethylethanolamine, diethylethanolamine, diethanolamine and triethanolamine.
Examples of the alkali metal hydroxide include sodium hydroxide and potassium hydroxide. Among them, in order to improve the drying property, it is preferable to use those which are easily volatilized at room temperature or slightly heated.

The water-based gravure printing ink composition for paper containers of the present invention may further contain a water-based binder resin varnish other than the alkali-soluble water-soluble resin, such as water-based shellac varnish, water-based Casein varnish, water-based rosin-maleic acid resin varnish, water-based polyester resin varnish, water-soluble cellulose varnish and the like may be contained.

In this specification, the acid value is used to obtain 1 g of a polymer (styrene-maleic acid half ester copolymer resin, high acid value polymer resin described later, emulsion-type aqueous resin, polymer emulsifier, etc.). A theoretical amount of potassium hydroxide (KOH) for neutralization is determined for the amount of each monomer theoretically required for the above, and the total amount in mg of the neutralized amount is regarded as the acid value of the polymer.

<High acid value polymer resin>
The high acid value polymer resin constituting the water-based gravure printing ink composition for paper containers of the present invention satisfies the following condition 2.
(Condition 2)
The high acid value polymer resin has a weight average molecular weight of 30,000 to 150,000 and an acid value of 120 to 250 mgKOH/g.
In the water-based gravure printing ink composition for paper containers of the present invention, by containing the above-mentioned high acid value polymer resin, not only bar code suitability but also doctor sharpness can be imparted.

The high acid value polymer resin preferably contains an acrylate-based monomer, a methacrylic-based monomer, an olefin-based monomer, and a carboxylic acid monomer as monomer components.
The above-mentioned high acid value polymer resin can be obtained by polymerizing the above-mentioned monomer components by the polymerization method described below.

Specific examples of the acrylate monomer include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, t-butyl acrylate, amyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, tert-octyl acrylate, 2-chloroethyl acrylate, 2-bromoethyl acrylate, 4-chlorobutyl acrylate, cyanoethyl acrylate, 2-acetoxyethyl acrylate, benzyl acrylate, methoxybenzyl acrylate, 2-chloro cyclohexyl acrylate, cyclohexyl acrylate, furfuryl acrylate, tetrahydrofurfuryl acrylate, phenyl acrylate, 5-hydroxypentyl acrylate, 2,2-dimethyl-3-hydroxypropyl acrylate, 2-methoxyethyl acrylate, 3-methoxybutyl acrylate, 2- ethoxyethyl acrylate, 2-butoxyethyl acrylate, 2-(2-methoxyethoxy)ethyl acrylate, 2-(2-butoxyethoxy)ethyl acrylate, glycidyl acrylate, 1-bromo-2-methoxyethyl acrylate, 1,1-dichloro -2-ethoxyethyl acrylate, 2,2,2-tetrafluoroethyl acrylate, 1H,1H,2H,2H-perfluorodecyl acrylate and the like.

Specific examples of the methacrylic monomers include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, amyl methacrylate, hexyl methacrylate, Cyclohexyl methacrylate, benzyl methacrylate, chlorobenzyl methacrylate, octyl methacrylate, stearyl methacrylate, 2-(3-phenylpropyloxy)ethyl methacrylate, furfuryl methacrylate, tetrahydrofurfuryl methacrylate, phenyl methacrylate, cresyl methacrylate, naphthyl methacrylate, 2-hydroxy Ethyl methacrylate, 4-hydroxybutyl methacrylate, triethylene glycol monomethacrylate, dipropylene glycol monomethacrylate, 2-methoxyethyl methacrylate, 3-methoxybutyl methacrylate, 2-ethoxyethyl methacrylate, 2-iso-propoxyethyl methacrylate, 2-butoxy ethyl methacrylate, 2-(2-methoxyethoxy)ethyl methacrylate, 2-(2-ethoxyethoxy)ethyl methacrylate, 2-(2-butoxyethoxy)ethyl methacrylate, 2-acetoxyethyl methacrylate, 2-acetoacetoxyethyl methacrylate, allyl methacrylate, glycidyl methacrylate, 2,2,2-tetrafluoroethyl methacrylate, 1H,1H,2H,2H-perfluorodecyl methacrylate, etc.

Specific examples of the olefinic monomer include dicyclopentadiene, ethylene, propylene, 1-butene, 1-pentene, vinyl chloride, vinylidene chloride, isoprene, chloroprene, butadiene, 2,3-dimethylbutadiene, and styrenes. , for example, styrene, methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, isopropylstyrene, chloromethylstyrene, methoxystyrene, acetoxystyrene, chlorostyrene, dichlorostyrene, bromostyrene, vinyl benzoic acid methyl ester, and the like. Specifically, dicyclopentadiene, ethylene, propylene, 1-butene, 1-pentene, vinyl chloride, vinylidene chloride, isoprene, chloroprene, butadiene, 2,3-dimethylbutadiene, etc., styrenes such as styrene, methylstyrene , dimethylstyrene, trimethylstyrene, ethylstyrene, isopropylstyrene, chloromethylstyrene, methoxystyrene, acetoxystyrene, chlorostyrene, dichlorostyrene, bromostyrene, vinyl benzoic acid methyl ester, and the like.

Examples of the carboxylic acid monomer include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, crotonic acid, monoalkyl itaconate (e.g., monomethyl itaconate, monoethyl itaconate, monobutyl itaconate, etc.). ), maleic acid monoalkyl esters (eg, monomethyl maleate, monoethyl maleate, monobutyl maleate, etc.), and the like.

If necessary, the high acid value polymer resin may contain, in addition to the above monomers, vinyl ester-based monomers, acrylamide-based monomers, methacrylamide-based monomers, vinyl ether-based monomers, sulfonic acid-based monomers, and the like. .

The polymerization method and the like for the high acid value polymer resin are not particularly limited, and known polymerization methods, solvents, polymerization initiators, and the like can be used.
Examples of the polymerization method include bulk radical polymerization, solution radical polymerization, and non-aqueous dispersion radical polymerization.
The obtained high acid value polymer resin is preferably neutralized with alkanolamine or the like from the viewpoint of odor and doctor cutting property.

The compounding ratio of the monomers when polymerizing the high acid value polymer resin is preferably contained in the following amounts, for example.
It is preferable that the total amount of the acrylate-based monomer and the methacrylic-based monomer is 20 to 80 parts by mass based on the total mass of the monomers. It is preferable that the amount of the olefinic monomer is 1 to 50 parts by mass based on the total mass of the monomers.
It is preferable that the amount of the carboxylic acid monomer is 5 to 30 parts by mass based on the total mass of the monomers.
By satisfying the blending ratio of the above monomers, the doctor sharpness can be improved more suitably.

The high acid value polymer resin has a weight average molecular weight of 30,000 to 150,000.
If the weight average molecular weight of the high acid value polymer resin is less than 30,000, the printed image will be thickened.
On the other hand, when the weight average molecular weight of the high acid value polymer resin exceeds 150,000, it becomes difficult to print with a fine line width.
The preferred lower limit of the weight average molecular weight of the high acid value polymer resin is 40,000, the preferred upper limit is 130,000, the more preferred lower limit is 50,000, and the more preferred upper limit is 110,000.
As the weight average molecular weight, the high acid value polymer resin is dissolved to prepare a 0.02% by mass solution, and a filter (GL chromatodisc manufactured by GL Sciences, water system 25A, pore size 0.2 μm ), size exclusion chromatography and an alliance (manufactured by Nippon Waters Co., Ltd.) consisting of a refractive index detector can be used for measurement under the following conditions.
Column: pLgel mixed D (manufactured by Agilent) × 2 serially connected detector: alliance (manufactured by Japan Waters)
Eluent: THF
Flow rate: 1.0 ml/min
Injection volume: 100 μl

The high acid value polymer resin has an acid value of 120 to 250 mgKOH/g.
When the acid value of the high acid value polymer resin is less than 120 mgKOH/g, bleeding occurs during drying.
On the other hand, when the acid value of the high acid value polymer resin exceeds 250 mgKOH/g, it becomes difficult to print with a narrow line width.
A preferred lower limit of the acid value of the high acid value polymer resin is 130 mgKOH/g, a preferred upper limit is 240 mgKOH/g, a more preferred lower limit is 140 mgKOH/g, and a more preferred upper limit is 230 mgKOH/g.

The high acid value polymer resin is contained in a solid content concentration of 0.2 to 1.8% by mass based on the total mass of the aqueous gravure printing ink composition for paper containers of the present invention.
When the content of the high acid value polymer resin is less than 0.2% by mass, it becomes difficult to print narrow lines.
On the other hand, when the content of the high acid value polymer resin exceeds 1.8% by mass, the printed image may become thick.
A preferable lower limit of the content of the high acid value polymer resin is 0.5% by mass, and a preferable upper limit is 1.6% by mass in terms of solid content concentration.

<Aqueous medium>
The aqueous medium constituting the water-based gravure printing ink composition for paper containers of the present invention preferably satisfies condition 4 below.
(Condition 4)
It consists of water, 2-ethyl-1,3-hexanediol, and a lower alcohol having 1 to 4 carbon atoms, and the content of the lower alcohol having 1 to 4 carbon atoms in the water-based gravure printing ink composition for paper containers is 30. % by mass or less, and the content of 2-ethyl-1,3-hexanediol in the aqueous gravure printing ink composition for paper containers is 0.1 to 2.5% by mass.
That is, in the aqueous gravure printing ink composition for paper containers of the present invention, the aqueous medium contains 2-ethyl-1,3-hexanediol. As a result, it is possible to improve the drying property and leveling property of the water-based gravure printing ink composition for paper containers of the present invention, and to improve the printability when printing by the gravure printing method.

When the content of the 2-ethyl-1,3-hexanediol is less than 0.1% by mass with respect to the total mass of the aqueous gravure printing ink composition for paper containers of the present invention, the content of the lower alcohol is When it is suppressed, drying property and leveling property are lowered.
On the other hand, when the content of 2-ethyl-1,3-hexanediol exceeds 2.5% by mass, the stability over time of the aqueous gravure printing ink composition for paper containers tends to decrease.
Since the water-based gravure printing ink composition for paper containers of the present invention has better drying properties and leveling properties, the preferred lower limit of the content of 2-ethyl-1,3-hexanediol is 0.5% by mass, which is preferred. The upper limit is 2.0% by mass.

The lower alcohol having 1 to 4 carbon atoms is not particularly limited as long as it is conventionally used in aqueous coating compositions, such as methanol, ethanol, n-propanol, isopropanol, n-butanol and sec-butanol. , tert-butanol, isobutanol, and the like.
Further, when the content of the lower alcohol having 1 to 4 carbon atoms exceeds 30% by mass in the aqueous gravure printing ink composition for paper containers of the present invention, the VOC emission concentration increases. The content of the lower alcohol is preferably 15 to 30% by mass, more preferably 15 to 25% by mass, in the aqueous gravure printing ink composition for paper containers of the present invention. If it is less than 15% by mass, the printability may deteriorate.

The water-based gravure printing ink composition for paper containers of the present invention can contain 2-ethyl-1,3-hexanediol as described above, and can also contain a specific styrene-maleic acid half ester copolymer described later. Since the coalescing resin is contained, the content of the lower alcohol, which is a volatile organic compound, can be reduced as much as possible, and excellent printability, leveling properties, and drying properties can be obtained.

In the aqueous gravure printing ink composition for paper containers of the present invention, the aqueous medium contains water. By appropriately adjusting the content of the water, the content of the 2-ethyl-1,3-hexanediol and the lower alcohol having 1 to 4 carbon atoms in the aqueous medium is adjusted within the above range. can be done.

<Emulsion type aqueous resin>
In addition, in the present invention, it is preferable to incorporate an emulsion-type water-based resin as appropriate depending on the type of the colorant or in the case of a water-based gravure printing ink composition for paper containers having a high solid content concentration.
As the emulsion-type water-based resin, the above-described styrene-based monomer and ethylenically unsaturated monomer (preferably, ethylene having a glass transition temperature of −50° C. or less of the polymer obtained when polymerized alone ethylenically unsaturated monomers such as 2-ethylhexyl (meth)acrylate, butyl acrylate, etc.) are emulsion-polymerized in the presence of a polymer emulsifier. The obtained resin, styrene-acrylic water-based resin, styrene-maleic acid-based water-based resin, styrene-acrylic-maleic acid-based water-based resin, and the like are preferable.

The emulsion-type aqueous resin preferably has an acid value of 30 to 80 mgKOH/g and a glass transition temperature of 15 to 60°C. When the acid value of the emulsion-type water-based resin is less than 30 mgKOH/g, the re-solubility tends to be lowered, and when the acid value is greater than 80 mgKOH/g, the drying property tends to be lowered, which is not preferable.
If the glass transition temperature of the emulsion-type water-based resin is less than 15°C, the blocking property may deteriorate, and if it exceeds 60°C, the abrasion resistance of the printed matter may deteriorate.

Moreover, the content of the emulsion-type water-based resin is preferably in the range of 60% by mass or less in the solid content contained in the water-based gravure printing ink composition for paper containers.
Further, in order to obtain an aqueous gravure printing ink composition for paper containers having a high solid content concentration, the content of the emulsion-type aqueous resin is 30 to 60% by mass in the solid content contained in the aqueous gravure printing ink composition for paper containers. is preferably in the range of

As the polymer emulsifier, a carboxyl group-containing α,β-monoethylenically unsaturated monomer, an ethylenically unsaturated monomer (A) having a highly hydrophobic aromatic ring, and, if necessary, Copolymer resins having an acid value of 100 to 200 mgKOH/g obtained by copolymerizing other copolymerizable ethylenically unsaturated monomers (B) can be mentioned.
Examples of the carboxyl group-containing α,β-monoethylenically unsaturated monomer include (meth)acrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic anhydride, maleic acid, and maleic acid monoester. can.
If the acid value of the polymer emulsifier is less than 100 mgKOH/g, the solubility of the polymer emulsifier in water may decrease. If it exceeds 200 mgKOH/g, the water resistance of the resulting printed matter may deteriorate. More preferably, the acid value is 150-200 mgKOH/g.

A basic compound can be used to dissolve or disperse the polymer emulsifier in water. Examples of the basic compound include those similar to those described above.

The glass transition temperature of the emulsion-type water-based resin can be obtained by the following method.

<Glass transition temperature>
In the present specification, the glass transition temperature is a theoretical glass transition temperature determined by the following Wood's formula.
Wood's formula: 1/Tg=W1/Tg1+W2/Tg2+W3/Tg3+...+Wx/Tgx
(Wherein, Tg1 to Tgx are the monomers 1, 2, 3, . Each mass fraction of 3, .

The glass transition temperature of the emulsion-type water-based resin is obtained when all the ethylenically unsaturated monomers used in the emulsion polymerization are copolymerized at once without being divided into the core portion and the shell portion. It represents the glass transition temperature of the copolymer.

<Other additives>
The water-based gravure printing ink composition for paper containers of the present invention may contain optional components as appropriate depending on the intended use. Examples of the optional components include various additives such as surfactants, waxes, wetting agents, antifoaming agents, pH adjusters, viscosity modifiers, drying modifiers, brightening agents, and cross-linking agents.

A method for producing the water-based gravure printing ink composition for paper containers of the present invention using the constituent materials described above will now be described.
First, a coloring agent, an alkali-soluble water-soluble resin, and a dispersing agent to be added as necessary are mixed, and stirred and mixed using a normal ink manufacturing device (for example, a ball mill, an attritor, a sand mill, etc.). After kneading, an alkali-soluble water-soluble resin, an aqueous medium such as 2-ethyl-1,3-hexanediol, and, if necessary, an emulsion-type water-based resin, wax, an antifoaming agent, etc. are added and mixed. method.

The aqueous gravure printing ink composition for paper containers of the present invention thus produced has a solid content concentration of 15 to 30% by mass. When it is less than 15% by mass, the drying property tends to be lowered, and when it exceeds 30% by mass, the viscosity tends to be increased. % by mass, more preferably 25 to 30% by mass. When the solid content concentration is within this range, it becomes possible to use a shallow printing plate in gravure printing.
The solid content concentration is the solid content concentration when gravure printing is performed using the water-based gravure printing ink composition for paper containers of the present invention.

A method for printing with the water-based gravure printing ink composition for paper containers of the present invention will be described.
As a method of using the water-based gravure printing ink composition for paper containers of the present invention for high-quality printing, a method of printing the water-based gravure printing ink composition for paper containers on a paper substrate such as coated paper by a gravure printing method can be exemplified. .

Considering the production efficiency of printed matter, the printing speed is preferably 150 m/min or more. Moreover, in order to achieve the above printing speed, a drying process using various heat drying devices may be included after printing.
During printing, the viscosity of the water-based gravure printing ink composition for paper containers is preferably such that the Zahn cup N0.3 outflow time is about 15 to 19 seconds. When it is less than 15 seconds, the leveling property tends to be lowered, and when it exceeds 19 seconds, the printability tends to be lowered.

In general, the water-based gravure printing ink composition for paper containers of the present invention is stored in a concentrated state and diluted with a diluent at the time of printing. The above dilution is within a range where the solid content concentration in the water-based gravure printing ink composition for paper containers at the time of printing is 15 to 30% by mass as described above. From the viewpoint of printability and printability, the solid content concentration in the aqueous gravure printing ink composition for paper containers at the time of printing is 20 to 30% by mass, more preferably 25 to 30% by mass.

Furthermore, the printing method will be specifically described.
A printed matter printed using the aqueous gravure printing ink composition for paper containers of the present invention may be coated with an aqueous overprint varnish composition for paper containers. The step of printing using the water-based gravure printing ink composition for paper containers of the present invention and the step of applying the water-based overprint varnish composition for paper containers may be carried out in a series of steps, and may be carried out on separate occasions. may be carried out by dividing the process into
In addition, for example, in the case of a 6-can pack package, post-processing such as punching is performed after the printed material is manufactured. You may divide a process into an opportunity and may be performed.

As an apparatus capable of performing such gravure printing, coating, and post-processing at once, for example, there is a Bobst Champlain Ramanic gravure rotary punching machine.
Specifically, a paper substrate is supplied to a paper feeder, and after printing with the water-based gravure printing ink composition for paper containers of the present invention from the paper feeder by a gravure printing method, the water-based overprint varnish composition for paper containers is applied. can be printed and coated at a printing/coating speed of 150 to 200 m/min, followed by a punching step to obtain the desired printed matter.
Furthermore, after printing the water-based gravure printing ink composition for paper containers of the present invention and after coating the water-based overprint varnish composition for paper containers, printing efficiency and coating efficiency are improved by using a hot air drying device for drying. , the production efficiency of the whole printed matter is increased.

Since it is necessary to reduce the VOC emission concentration to 700 ppmC, the water-based overprint varnish composition for paper containers used in the above printing method contains an aqueous medium and an emulsion-type water-based resin as essential components. Preference is given to using compositions.

As the aqueous medium, an aqueous medium comprising water and 2-ethyl-1,3-hexanediol is preferably used.
The aqueous medium may further contain a lower alcohol having 1 to 4 carbon atoms in an amount of 30% by mass or less in the water-based overprint varnish composition for paper containers, if necessary, and a lower alcohol having 1 to 4 carbon atoms is used. When doing so, it is preferable to reduce it as much as possible in order to reduce the VOC emission concentration. Examples of the lower alcohol having 1 to 4 carbon atoms are the same as those described in connection with the aqueous gravure printing ink composition for paper containers of the present invention.

The content of 2-ethyl-1,3-hexanediol is preferably 0.1 to 2.5% by mass in the aqueous overprint varnish composition for paper containers. If the content is less than 0.1% by mass, drying properties and leveling properties may deteriorate. On the other hand, when it exceeds 2.5% by mass, the stability over time of the water-based overprint varnish composition for paper containers tends to decrease.

Next, the water-based resin constituting the water-based overprint varnish composition for paper containers will be described.
The water-based resin is an emulsion-type water-based resin. As the emulsion-type water-based resin, specifically, in the presence of a polymer emulsifier, ethylenically unsaturated monomer A having an aromatic ring is mainly used in order to impart drying properties and obtain a tough coating film. The ethylenically unsaturated monomer as a component is emulsion-polymerized to form the core portion, and then the ethylenically unsaturated monomer obtained by polymerizing alone has a glass transition temperature of −50° C. or less. It is a resin obtained by polymerizing B to form a shell portion, and preferably has an acid value of 50 to 70 mgKOH/g and a glass transition temperature of 40 to 70°C.

As the polymer emulsifier, a carboxyl group-containing α,β-monoethylenically unsaturated monomer, an ethylenically unsaturated monomer A having a highly hydrophobic aromatic ring, and, if necessary, other co- A copolymer resin having an acid value of 100 to 200 mgKOH/g obtained by copolymerizing a polymerizable ethylenically unsaturated monomer can be mentioned.

Examples of the ethylenically unsaturated monomer A having an aromatic ring include styrene-based monomers such as styrene, α-methylstyrene, vinyltoluene, derivatives thereof, benzyl (meth)acrylate, and (meth)acrylic Naphthyl acid and the like can be mentioned.

Examples of the ethylenically unsaturated monomer B, the glass transition temperature of which is −50° C. or lower when polymerized alone, include 2-ethylhexyl (meth)acrylate and butyl acrylate.

Examples of the carboxyl group-containing α,β-monoethylenically unsaturated monomer include (meth)acrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic anhydride, maleic acid, and maleic acid monoester. can.

Examples of other copolymerizable ethylenically unsaturated monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) ) acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, 2-hydroxystearyl (meth)acrylate and the like.

The polymer emulsifier preferably has an acid value of 100 to 200 mgKOH/g. If the acid value is less than 100 mgKOH/g, the solubility of the polymer emulsifier in water may decrease. If the acid value exceeds 200 mgKOH/g, the water resistance of the resulting printed matter may be lowered.

A basic compound can be used to dissolve or disperse the polymer emulsifier in water. Examples of the above-mentioned basic compound include those similar to those explained in the water-based gravure printing ink composition for paper containers of the present invention.

An aqueous resin having such a core-shell structure can be obtained, for example, by using a power feed polymerization method under the following polymerization conditions.
Polymerization conditions (first stage)
Formation of nucleus (core part) For example, using the above-mentioned monomer A and the above-mentioned monomer B as copolymerization components, the above-mentioned monomer A is added to the above-mentioned monomer B in the presence of a polymer emulsifier. By adding at an addition rate longer than the time and emulsifying, the core portion containing the monomer A as a main component is formed.
(Second stage)
After the completion of the reaction in the first step, the formed core portion is used as a seed, and the monomer B is added to carry out emulsion polymerization, thereby attaching a soft polymer that forms a flexible film to the surface of the core portion. , to form a shell portion composed of a polymer of the above monomer B to obtain an emulsion having a two-layer structure. In addition, it is preferable that the soft polymer forming the flexible film is polymerized so as to be localized on the surface of the core portion.

In addition, multistage polymerization methods such as a seed polymerization method and a core-shell polymerization method can be used as a method for producing the aqueous resin having the core-shell structure.
By containing such an emulsion-type water-based resin having both a core portion that contributes to rigidity and film strength and a shell portion that contributes to film-forming properties and durability, an aqueous overprint varnish composition for paper containers can be obtained. As a result, it exhibits excellent performance.

The content of the emulsion-type water-based resin is preferably 20 to 45% by mass in terms of solids concentration in the water-based overprint varnish composition for paper containers, and from the viewpoint of drying property, the higher the solids concentration, the more preferable. .

The water-based overprint varnish composition for paper containers may appropriately contain optional components such as waxes and antifoaming agents, depending on the intended use.
Moreover, examples of the method for producing the water-based overprint varnish composition for paper containers include a method in which the constituent materials are uniformly stirred with a stirring device such as a disper.

The water-based gravure printing ink composition for paper containers of the present invention can be printed with a line width narrower than that of ordinary fine characters, and has bar code suitability such that the printed image does not thicken or bleed.

FIG. 1 shows a picket barcode used for barcode suitability evaluation in the example.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited only to these Examples. Unless otherwise specified, "%" means "% by mass" and "parts" means "mass parts". In addition, the number of the amount of each material in the table is also "mass part".

<Water-based gravure printing ink composition for paper containers>
Constituent material (colored pigment)
Blue pigment (Pigment Blue 15:3)
Black pigment (carbon black)
(aqueous medium)
Water isopropanol, 2-ethyl-1,3-hexanediol (antifoaming agent)
BYK-028#C (trade name, manufactured by BYK-Chemie)
(wax)
Chemipearl-400W (trade name, manufactured by Mitsui Chemicals, polyethylene wax)

(Production example of alkali-soluble water-soluble resin)
<Alkali-soluble water-soluble resin 1>
22 parts by mass of styrene, 6 parts by mass of α-methylstyrene, 6 parts by mass of methacrylic acid, 28 parts by mass of methyl methacrylate, and 34 parts by mass of isobutanol half ester of maleic anhydride were synthesized by a conventional polymerization method, and the acid value was 150 mgKOH. /g and a copolymer having a weight average molecular weight of 19,000 was obtained. This copolymer resin was neutralized with aqueous ammonia to obtain an alkali-soluble water-soluble resin 1 having a solid concentration of 20.2%.

<Alkali-soluble water-soluble resin 2>
In the production example of the alkali-soluble water-soluble resin 1, the procedure is the same as that of the alkali-soluble water-soluble resin 1, except that the maleic anhydride isobutanol half ester is changed to the maleic anhydride n-butanol half ester. Thus, an alkali-soluble water-soluble resin 2 having a solid concentration of 20.2% was obtained.

(Preparation of ink base for aqueous gravure printing)
According to the formulation in Table 1, pigments (blue: pigment blue 15:3, black: carbon black), alkali-soluble water-soluble resins 1 and 2, and a mixture of water were mixed in a bead mill, and then the remaining materials were added and mixed. Thus, blue and black ink bases A and B for water-based gravure printing were obtained.

(Production example of high acid value polymer resin)
<High acid value polymer resin 1>
10 parts by mass of styrene, 20 parts by mass of acrylic acid, 50 parts by mass of methyl methacrylate, and 20 parts by mass of hexyl acrylate were synthesized by a conventional polymerization method to obtain a copolymer having an acid value of 150 mgKOH/g and a weight average molecular weight of 70,000.
This copolymer resin was neutralized with dimethylethanolamine to obtain a high acid value polymer resin 1 having a solid concentration of 20%.

<High acid value polymer resin 2>
10 parts by mass of styrene, 20 parts by mass of acrylic acid, 50 parts by mass of methyl methacrylate, and 20 parts by mass of hexyl acrylate were synthesized by a conventional polymerization method to obtain a copolymer having an acid value of 150 mgKOH/g and a weight average molecular weight of 100,000. This copolymer resin was neutralized with dimethylethanolamine to obtain a high acid value polymer resin 2 having a solid concentration of 20%.

<High acid value polymer resin 3>
10 parts by mass of styrene, 25 parts by mass of acrylic acid, 50 parts by mass of methyl methacrylate, and 20 parts by mass of hexyl acrylate were synthesized by a conventional polymerization method to obtain a copolymer having an acid value of 187 mgKOH/g and a weight average molecular weight of 70,000. This copolymer resin was neutralized with dimethylethanolamine to obtain a high acid value polymer resin 3 having a solid concentration of 20%.

<High acid value polymer resin 4>
10 parts by mass of styrene, 20 parts by mass of acrylic acid, 50 parts by mass of methyl methacrylate, and 20 parts by mass of hexyl acrylate were synthesized by a conventional polymerization method to obtain a copolymer having an acid value of 150 mgKOH/g and a weight average molecular weight of 20,000. This copolymer resin was neutralized with dimethylethanolamine to obtain a high acid value polymer resin 4 having a solid concentration of 20%.

<High acid value polymer resin 5>
10 parts by mass of styrene, 15 parts by mass of acrylic acid, 50 parts by mass of methyl methacrylate, and 20 parts of hexyl acrylate were synthesized by a conventional polymerization method to obtain a copolymer having an acid value of 112 mgKOH/g and a weight average molecular weight of 70,000. This copolymer resin was neutralized with dimethylethanolamine to obtain a high acid value polymer resin 5 having a solid concentration of 20%.

The acid value of the alkali-soluble water-soluble resin and the acid value of the high-acid-value polymer resin are the amounts of potassium hydroxide ( KOH) was theoretically neutralized, and the total mg of the neutralized amount was regarded as the acid value.

The weight average molecular weight of the high acid value polymer resin is obtained by dissolving the high acid value polymer resin to prepare a solution of 0.02% by mass, filter (GL Sciences Co., GL Chromatodisk, aqueous 25A, pore size 0.2 μm), and then measured under the following conditions using an alliance (manufactured by Nippon Waters Co., Ltd.) consisting of size exclusion chromatography and a refractive index detector.
Column: pLgel mixed D (manufactured by Agilent) × 2 serially connected detector: alliance (manufactured by Japan Waters)
Eluent: THF
Flow rate: 1.0 ml/min
Injection volume: 100 μl

(Emulsion-type aqueous resin production example)
<Emulsion 1>
A dimethylethanolamine aqueous solution of an alkali-soluble resin composed of 13 parts by mass of acrylic acid, 65 parts by mass of methyl methacrylate, and 22 parts by mass of butyl acrylate was prepared as a polymer emulsifier. 19 parts by mass of 2-ethylhexyl acrylate and 28 parts by mass of styrene were added to 53 parts by mass of the resin solid content of this polymer emulsifier, and emulsion polymerization was performed by a conventional method to give an acid value of 53 mgKOH/g, a glass transition temperature of 22°C, and a solid. Emulsion 1 was obtained with a concentration of 40%.

(Preparation of aqueous gravure printing ink compositions for paper containers of Examples 1 to 6 and Comparative Examples 1 to 5)
The above black and blue water-based gravure printing ink base A, alkali-soluble water-soluble resin 1, high acid value polymer resins 1 to 5, antifoaming agent, wax, and isopropanol were mixed so as to have the composition shown in Table 2. , 2-ethyl-1,3-hexanediol, and water were stirred and mixed.
Then, diluent A, 70/30 isopropanol/water, was used to dilute Zahn cup no. In the range of 15 to 19 seconds in 3, the solid content concentration in the ink composition is 15 to 30% by mass, and the content of isopropanol is 13 to 24% by mass. 6 and Comparative Examples 1 to 5, blue Examples 1 to 6 and Comparative Examples 1 to 5 water-based gravure printing ink compositions for paper containers were obtained.

<Production of Printed Matter and Evaluation of Printed Matter of Water-Based Gravure Printing Ink Composition for Paper Containers>
Regarding the drying properties, leveling properties, and halftone dot reproducibility of the water-based gravure printing ink compositions for paper containers of each color according to Examples and Comparative Examples, each water-based gravure printing ink composition for paper containers was gravure-printed on coated paper under the following conditions. , evaluated for its prints.

(Barcode aptitude)
Under the following conditions, the picket bar code shown in FIG. 1 was printed under the following printing conditions and evaluated according to the following evaluation criteria.
<Printing conditions>
Paper: Coated paper (trade name: CRC230, manufactured by Rengo Co., Ltd.)
Printing machine: Gravure proofing machine Printing plate for printing ink: Helio 200 Line/inch
<Evaluation Criteria>
◯: Can be read by scanning once with a scanner.
Δ: Can be read by scanning multiple times.
×: Unreadable.

(Doctor sharpness)
After running idle for 40 minutes under the above printing conditions, continuous printing was performed on coated paper (trade name: CRC230, manufactured by Rengo Co., Ltd.), and the degree of contamination of the non-image areas at that time was judged according to the following evaluation criteria.
<Evaluation Criteria>
◯: There is no stain in the non-image area.
Δ: Some staining occurs in the non-image area.
x: The non-image area is stained and cannot be practically used.

In the examples using the water-based gravure printing ink composition for paper containers of the present invention, it has bar code aptitude and is excellent in doctor cutting property.
On the other hand, Comparative Example 1, in which the content of the high acid value polymer resin was too high, and Comparative Example 2, in which the content of the high acid value polymer resin was too low, were insufficient in bar code suitability and inferior in doctor cutting ability.
Moreover, Comparative Example 3, in which the weight-average molecular weight of the high-acid-value polymer resin is small, and Comparative Example 4, in which the acid value is small, were clearly inferior in barcode suitability.
Moreover, in Comparative Example 5, in which the half-ester portion of the alkali-soluble water-soluble resin did not satisfy the condition 1, the suitability for barcodes was clearly inferior.

The water-based gravure printing ink composition for paper containers of the present invention can be printed with a narrow line width and has bar code suitability such that the printed image does not thicken or bleed. It can be suitably used in boxes, multi-pack packages for alcoholic beverages and beverages, and the like.

Claims (3)

A water-based gravure printing ink composition for paper containers containing a colorant, an alkali-soluble water-soluble resin, a high acid value polymer resin, and an aqueous medium,
The solid content concentration is 15 to 30% by mass,
The high acid value polymer resin is contained in a solid content concentration of 0.2 to 1.8% by mass with respect to the total mass of the water-based gravure printing ink composition for paper containers,
A water-based gravure printing ink composition for paper containers, wherein the alkali-soluble water-soluble resin satisfies condition 1 below, and the high acid value polymer resin satisfies condition 2 below.
Condition 1
The alkali-soluble water-soluble resin is a styrene-maleic acid half ester copolymer resin having an acid value of 100 to 210 mgKOH/g, and is a monomer component of the styrene-maleic acid half ester copolymer resin. The maleic acid half ester is at least one type containing an isobutyl maleic acid half ester and an ethoxyethoxyethyl maleic acid half ester in a molar ratio ranging from 100/0 to 55/45.
Condition 2
The high acid value polymer resin has a weight average molecular weight of 30,000 to 150,000 and an acid value of 120 to 250 mgKOH/g. 2. The water-based gravure printing ink composition for paper containers according to claim 1, which has a solid content concentration of 20 to 30 mass % and further contains an emulsion-type water-based resin satisfying condition 3 below.
Condition 3
The emulsion-type aqueous resin has an acid value of 30 to 80 mgKOH/g and a glass transition temperature of 15 to 60°C. The water-based gravure printing ink composition for paper containers according to claim 1 or 2, wherein the water-based medium satisfies condition 4 below.
Condition 4
The aqueous medium comprises water, 2-ethyl-1,3-hexanediol, and a lower alcohol having 1 to 4 carbon atoms, and the lower alcohol having 1 to 4 carbon atoms in the water-based gravure printing ink composition for paper containers. is 30% by mass or less, and the content of 2-ethyl-1,3-hexanediol in the aqueous gravure printing ink composition for paper containers is 0.1 to 2.5% by mass.

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