JP5858320B1 - Alkali-resistant water-based ink composition - Google Patents

Abstract

Alkali-resistant water-based ink composition using an ethylene-acrylic acid copolymer as a resin component does not depend on the type of pigment, and even if a special surfactant is not used, the pigment dispersibility is good and alkali resistance An ink composition is provided. A pigment is dispersed in an aqueous dispersion obtained by neutralizing an acrylic acid copolymer having an SP value of 20.4 to 20.7 (J / cm 3) 1/2 in turbidity titration method with ammonia and / or alkanolamine. And an alkali-resistant water-based ink composition containing an aqueous dispersion obtained by neutralizing an ethylene-acrylic acid copolymer with an alkanolamine.

Description

  The present invention relates to a water-based ink composition having high alkali resistance and excellent printability and workability, particularly an ink composition suitable for water-based ink use for gravure printing and flexographic printing, and a method for producing the composition About.

  In recent years, water-based printing inks in the field of gravure printing and flexographic printing have been promoted to prevent air pollution and improve the working environment. Styrene-acrylic acid copolymers that have a track record in the field have poor printing surface resistance, particularly alkali resistance, and a method using a crosslinking agent such as an aziridine compound is known, but there are problems such as mutagenicity. It is not preferable for the health of workers. Moreover, since it becomes an aqueous | water-based 2 liquid type, it hydrolyzed in a comparatively short time, and there existed a problem in workability | operativity and economical efficiency, such as short pot life.

  Therefore, an ethylene-acrylic acid copolymer is known as a new resin component that solves these problems. A method of blending a special surfactant (acetylene diols) at a specific ratio (for example, Patent Document 1) when dispersing the pigment in the resin component has been proposed and exhibits a certain effect, but the type of pigment changes. However, the dispersion effect is reduced, and when the pigment concentration is increased, the pigment is settled and the function is not sufficiently exhibited.

JP2011-144335

  Accordingly, the object of the present invention is to use an alkali-resistant water-based ink composition using an ethylene-acrylic acid copolymer as a resin component, without depending on the type of pigment, and without using a special surfactant. An object of the present invention is to provide an alkali-resistant ink composition having good pigment dispersibility.

  As a result of intensive studies to solve the above problems, the present inventor has obtained a pigment dispersion using a neutralized aqueous dispersion of a basic compound of an acrylic acid copolymer having a specific SP value, and ethylene-acrylic. The present invention was completed by finding that the dispersion stability of an ink composition containing an acid copolymer was good.

That is, the present invention relates to water obtained by neutralizing an acrylic acid copolymer having an SP value of 20.4 to 20.7 (J / cm ³ ) ^1/2 in turbidity titration method with ammonia and / or alkanolamine. Provided is an alkali-resistant water-based ink composition containing a water dispersion obtained by dispersing a pigment in a dispersion and then neutralizing an ethylene-acrylic acid copolymer with an alkanolamine.

  The present invention also provides an alkali-resistant water-based ink composition in which the acrylic acid copolymer is a copolymer of an aromatic compound having a vinyl group, a (meth) acrylic acid ester, and (meth) acrylic acid. .

  The present invention also provides an alkali-resistant water-based ink composition containing a (meth) acrylic acid ester having 12 to 18 carbon atoms in an alcohol constituting the ester group of the (meth) acrylic acid ester.

  Furthermore, the present invention also provides an alkali-resistant water-based ink composition in which the acrylic acid copolymer has an acid value of 50 mgKOH / g or more.

  Since the alkali-resistant water-based ink composition according to the present invention is excellent in dispersibility between the pigment and the ethylene-acrylic acid copolymer, the obtained ink is excellent in stability and printability, and the printed matter is excellent in alkali resistance. .

The acrylic acid copolymer used for dispersing the pigment used in the alkali-resistant water-based ink composition of the present invention has an SP value of 20.4 to 20.7 (J / cm ³ ) ^{1/2 in} the turbidity titration method. There is no particular limitation as long as it is an aqueous dispersion of acrylic acid copolymer neutralized with ammonia.
The SP value is measured by the turbidity titration method as described in K.A. W. Suh, D.H. H. The method is proposed by Clarke et al. In the following [Document 1], [Document 2], and the like.

[Reference 1] K.K. W. Suh, D .; H. Clarke, J .; Polym. Sci. , 1671, 1967
[Reference 2] K.K. W. Suh, J .; M.M. Corbett. J. et al. Appl. Poym. Sci. , 2359, 1968

If the measurement procedure according to this method is illustrated, it will measure according to the following procedure, for example.
Procedure 1. Solidification of aqueous resin (Preparation of SP value measurement sample)
(1) Add 300 ml of ion-exchanged water to a 500 ml beaker and dissolve 20 g of the aqueous dispersion resin while magnetically stirring.
(2) Concentrated hydrochloric acid is added dropwise until the pH of the aqueous solution becomes 4.
(3) The resin component is isolated by filtration under reduced pressure, and washed with ion exchange water until the waste liquid pH becomes 7.
(4) The washed resin component powder is vacuum dried at 40 ° C. for 8 hours.
Procedure 2. Measurement of SP value (1) Weigh 0.500 g + −0.005 g of the solid resin sample into a 50 ml Erlenmeyer flask.
(2) Dissolve the sample with 10 ml of THF.
(3) While maintaining the sample solution at 25 ° C. by water cooling or the like, titrate the cloud point (Lml) with n-hexane while magnetically stirring. The cloud point is determined when the flask containing the titration sample is placed on a printed material while being kept at 25 ° C. and viewed from above, and when the liquid layer becomes cloudy, the type is blurred and cannot be read.
(4) Titrate the cloud point (Hml) of ion-exchanged water in the same procedure.
(5) Calculation The SP value δ [(J / cm ³ ) ^1/2 ] of the sample is obtained by the following formula.

here,
L: Titration amount of low polarity solvent (n-hexane) (cm ³ )
H: titration of highly polar solvent (water) (cm ³ )
φ _SL : Volume fraction of dissolved solvent (THF) with respect to the sum of dissolved solvent (THF) and titration solvent (n-hexane) φ _L : Titration solvent with respect to the sum of dissolved solvent (THF) and titration solvent (n-hexane) ( n-Hexane) volume fraction φ _SH : volume fraction of dissolving solvent (THF) with respect to the sum of dissolving solvent (THF) and titration solvent (ion exchange water) φ _H : dissolving solvent (THF) and titration solvent (ion) Volume fraction of titration solvent (ion exchange water) with respect to the sum of exchange water) V _S : molecular volume [ml / mol] of dissolution solvent (THF) = 81
V _L : Molecular volume of titration solvent (n-hexane) [ml / mol] = 132
V _H : Molecular volume of titration solvent (ion exchange water) [ml / mol] = 18
δ _S : SP value of dissolved solvent (THF) [(J / cm ³ ) ^1/2 ] = 19.5
δ _L : SP value of titration solvent (n-hexane) [(J / cm ³ ) ^1/2 ] = 14.8
δ _H : SP value of titration solvent (ion exchange water) [(J / cm ³ ) ^1/2 ] = 48.1
δ: SP value of sample [(J / cm ³ ) ^1/2 ] (turbidity titration method)

Conventionally, the unit of the SP value (cal / cm ³ ) ^1/2 has been widely used. However, in recent years, (J / cm ³ ) ^1/2 has been used due to the introduction of the SI unit. 1 (cal / cm ³ ) ^1/2 in the conventional unit corresponds to 2.045 (J / cm ³ ) ^1/2 .

  On the other hand, by calculating the SP value of the copolymer from the SP value of the monomer constituting the acrylic acid copolymer and its mole fraction, the calculated SP value can be known. In addition, an approximate copolymer composition can be determined before preparing an acrylic acid copolymer. Therefore, it is possible to theoretically design the outline of the acrylic acid copolymer composition having a specific SP value used in the present invention.

The SP value of the copolymer is represented by the following formula.

here,
δ _copolym : SP value of copolymer [(J / cm ³ ) ^1/2 ]
Mi: indicates the mole fraction of the monomer component i component, and ΣMi = 1
_δ unit_i: SP value of the monomer units i component ^{[(J /} cm ^{3) 1/2]}

The acrylic acid copolymer used for dispersing the pigment used in the alkali-resistant water-based ink composition of the present invention has an SP value in the turbidity titration method of 20.4 to 20.7 (J / cm ³ ) ^1/2. The SP value (δ unit — _i ) of the constituent monomer of the acrylic acid copolymer and the unit component thereof is, for example, styrene [18.4], α-methylstyrene. [17.4], acrylic acid [24.5], methacrylic acid [22.9], methyl acrylate [20.5], ethyl acrylate [19.4], butyl acrylate [18.4], acrylic Acid (2-ethylhexyl) [18.5], ethyl carbitol acrylate [42.5], methyl methacrylate [19.4], ethyl methacrylate [18.0], n-butyl methacrylate [18.0] ], Methacrylic acid i o-Butyl [14.7], lauryl methacrylate [16.8], stearyl methacrylate “16.0”, hydroxyethyl methacrylate [27.5], and the like can be used. The calculated SP value can be known in advance from the fraction.

  In addition, the SP value of the monomer unit component that does not exist as a literature value can be estimated by the Fedors method described in [Document 3] below.

  [Reference 3] R.A. F. Fedors, Polym. Eng. Sci. , 14 [2], 145-154, 1974

  However, the SP value calculated from the calculation cannot be applied to the present invention as it is because the SP value of each monomer is slightly different depending on the literature. In order to carry out the present invention, it is necessary to determine the SP value by the turbidity titration method described above.

  As described above, the constituent monomer of the acrylic acid copolymer used in the alkali-resistant water-based ink composition of the present invention includes, for example, styrene, α-methylstyrene, 2-methylstyrene as the vinyl group-containing aromatic. 3-methylstyrene, 4-methylstyrene, 4-propylstyrene, 4-t-butylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 2,4 , 6-trimethylstyrene, 2-ethyl-4-benzylstyrene, 4- (phenylbutyl) styrene, 1-vinylnaphthalene, 2-vinylnaphthalene, vinylanthracene, N, N-diethyl-4-aminoethylstyrene, vinylpyridine 4-methoxystyrene, monochlorostyrene, dichlorostyrene and divini Benzene, and the like. These aromatic vinyl compounds may be used alone or in combination of two or more. Of these, styrene and α-methylstyrene are preferable.

  Examples of other constituent monomers (meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, ( N-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, capryl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, (meth) acrylic acid Myristyl, cetyl (meth) acrylate, stearyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, (meth) acrylic Isobornyl acid, glycidyl (meth) acrylate, tetrahydrofur (meth) acrylate Ryl, allyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, (meth) Examples thereof include acrylates such as cyclohexyl acrylate and polyalkylene glycol esters of (meth) acrylic acid. These (meth) acrylic acid esters may be used alone or in combination of two or more.

  As shown above, from the SP value (δunit_i) of the constituent monomer component of (meth) acrylic acid ester, the SP value increases when the carbon number is small, and the SP value tends to decrease when the carbon number is large. There is. From this, (meth) acrylic acid lauryl, (meth) acrylic acid tridecyl, (meth) acrylic acid myristyl, (meth) wherein the alcohol constituting the ester group of (meth) acrylic acid ester has 12 to 18 carbon atoms. When cetyl acrylate, stearyl (meth) acrylate, and (meth) acrylic acid ester are included, it is preferable because the SP value and acid value of the acrylic copolymer are easily balanced.

On the other hand, it is practical and preferable to use mainly acrylic acid and methacrylic acid as the (meth) acrylic acid monomer. Of course, these may be used alone or in combination of two or more.
The amount of the (meth) acrylic acid monomer used at that time is affected by the type of organic solvent and the ratio of the organic solvent to water in the aqueous process, but the solid content acid value ( mgKOH / g) can be made aqueous if it is about 20 or more, but from the viewpoint of reducing the amount of the organic solvent, the amount which becomes at least 50 with such an acid value is preferably the same acid. An amount that is 80 or more is appropriate.
The constituent components of these acrylic acid copolymers are not limited to the exemplified monomers, and other monomers may be added at all.

  In the present invention, the acrylic acid copolymer can be produced by a known method. For example, a two-stage method comprising a first step of producing an acrylic acid copolymer in an organic solvent and a second step of producing an aqueous resin is known.

  The production of the acrylic acid copolymer in the first step is obtained by so-called solution polymerization in which the monomer is polymerized in an organic solvent. The organic solvent herein is not particularly limited, but only a typical one among them is exemplified, and various aromatic organic solvents such as toluene and xylene, ethyl acetate, Various water-insoluble organic solvents such as various ester solvents such as butyl acetate; methanol, ethanol, normal (n-) propanol, iso (i-) propanol, n-butanol, isobutanol, tertiary ( tert-) various alcohol solvents such as butanol, 3-methoxybutanol, 3-methyl-3-methoxybutanol; various ketone solvents such as acetone, methyl ethyl ketone, isobutyl ketone, cyclohexanone; ethylene glycol, ethylene glycol monomethyl Ether, ethylene glycol monoethyl ether Various ethylene glycol solvents such as ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, cellosolve acetate; various diethylene glycol solvents such as methyl carbitol, ethyl carbitol, butyl carbitol; propylene glycol, propylene Various propylene glycol solvents such as glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol mono-tert-butyl ether; dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether, Various di- such as tripropylene glycol monobutyl ether Or a tripropylene glycol solvent, and various water-soluble organic solvents having good solubility in water, such as tetrahydrofuran, N-methylpyrrolidone, dimethylformamide, dimethyl sulfoxide, and sulfolane. However, in order to make it aqueous in the second step, it is desirable to use a water-soluble organic solvent as described above in view of its productivity and workability.

  As a polymerization means at that time, the radical solution polymerization method is the simplest polymerization method. If only typical examples of polymerization initiators that can be used in application using such radical solution polymerization method are exemplified, 2,2′-azobis (isobutyronitrile), 2,2′- Various azo compounds such as azobis (2,4-dimethylvaleronitrile) or 2,2′-azobis (2-methylbutyronitrile); or tert-butyl peroxypivalate, tert-butyl peroxybenzoate, tert-butylperoxy-2-ethylhexanoate, benzoyl peroxide, lauroyl peroxide, acetyl peroxide, di-tert-butyl peroxide, dicumyl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, Methyl ethyl ketone peroxide Such de or diisopropyl peroxycarbonate, various peroxides and the like.

  An acrylic acid copolymer can be produced by radical polymerization using various raw materials as listed above according to a known and commonly used method. Next, the acrylic acid copolymer thus obtained can be partially or completely neutralized with a basic compound and dissolved in an aqueous medium by adding water.

  In consideration of the physical properties when used and applied to the printing ink of the present invention, the basic compound to be used in that case is appropriate to use ammonia or organic amines, which is recommended and particularly representative. To illustrate only those, diethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, N, N-dimethylethanolamine, N, N-diethylethanolamine, N-isopropylethanolamine, N, N- Various organic amines such as diisopropanolamine, 2-amino-2-methylpropanol, 2- (dimethylamino) -2-methylpropanol, morpholine, N-methylmorpholine, N-ethylmorpholine; or ammonia It is done.

  As described above, a resin dissolved in an aqueous medium can be obtained. By removing the organic solvent under reduced pressure or normal pressure, the amount of the organic solvent contained in these resins can be reduced. Of course, it is possible. In addition, when a resin obtained by conducting a polymerization reaction using a water-insoluble organic solvent is used and applied, an operation such as addition of a water-soluble solvent or so-called solvent replacement with a water-soluble solvent is performed. In the same manner, a resin in a form dissolved in an aqueous medium can be obtained by performing the treatment before or after neutralization and aqueous formation.

  On the other hand, the ethylene-acrylic acid copolymer used in the alkali-resistant water-based ink composition of the present invention is preferably 70 to 95% by weight of ethylene and 5 to 30% by weight of acrylic acid. . The molecular weight of the ethylene-acrylic acid resin is preferably 5,000 to 10,000, the glass transition point is 0 ° C. or lower, and the acid value is preferably 10 to 60.

  As the neutralizing agent for the ethylene-acrylic acid copolymer, alkylamine, alkanolamine and the like are preferable, and the carboxyl group of the copolymer is neutralized to obtain an aqueous dispersion. The added amount of the neutralizing agent is 0.8 equivalent or more with respect to 1 equivalent of the carboxyl group in the ethylene-acrylic acid copolymer, so that the dispersion stability of the copolymer and the re-solubility of the ink can be improved. It is preferable from the viewpoint of improvement, and is preferably 1.2 equivalents or less with respect to 1 equivalent of the carboxyl group in the ethylene-acrylic acid copolymer, because the drying property, water resistance, and alkali resistance of the ink are hardly impaired.

  Examples of the alkylamines include diethylamine and triethylamine. Examples of the alkanolamines include monoethanolamine, dimethylethanolamine, and diethylethanolamine. Dimethylethanolamine is preferred.

  In addition, as an aqueous dispersion of the ethylene-acrylic acid copolymer, from Sumitomo Seika Co., Ltd., depending on the neutralizing agent, there is a difference between sixene AC (ammonia neutralization), sixene L (dimethylethanolamine neutralization), sixene. N (sodium hydroxide neutralized) is commercially available as Finelex SG-2000 from Lead City.

  The acrylic acid copolymer used in the alkali-resistant water-based ink composition of the present invention is preferably 5% to 10% of the entire resin component contained in the ink. If it is less than this, it is difficult to disperse the pigment, so the pigment concentration must be reduced. On the other hand, if it exceeds this, the alkali resistance of the printed matter will be weakened.

In the water-based ink composition of the present invention, a colorant, a solvent, and other auxiliaries according to the purpose can be used.
As the colorant, inorganic pigments, organic pigments, extender pigments and the like used in general water-based ink compositions can be used.
As the solvent, water alone or an organic solvent miscible with water can be used. Examples of the organic solvent include alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol and n-propyl alcohol, polyhydric alcohols such as propylene glycol and glycerin, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and propylene glycol mono n. -Ethers such as propyl ether and ethyl carbitol.

  Other auxiliary ingredients include waxes such as paraffin wax, polyethylene wax, carnauba wax, oleic acid amide, stearic acid amide, erucic acid amide, etc. for imparting friction resistance, slipperiness, etc. Fatty acid amides, silicon-based and non-silicon-based antifoaming agents for suppressing foaming at the time of printing, various dispersants for improving pigment wetting, and the like can also be used as appropriate.

  The alkali-resistant water-based printing ink composition according to the present invention is produced using an Eiger mill, a sand mill, a gamma mill, an attritor or the like generally used for the production of gravure and flexographic printing inks.

  The alkali-resistant water-based printing ink according to the present invention can be printed on a plastic film, polyethylene-coated paper or the like by a printing method in which oil-based printing ink is generally used, that is, gravure printing, flexographic printing or the like.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. In the examples, “parts” and “%” are based on weight unless otherwise specified.

Reference Example 1 (Synthesis of acrylic acid copolymer aqueous solution)
In a reaction vessel equipped with a thermometer, a reflux condenser, a stirrer, a dropping funnel and a nitrogen introduction tube, 900 parts of isopropanol was charged, and the temperature was raised to 80 ° C. in an atmosphere of nitrogen gas.
Subsequently, at the same temperature, 70 parts of α-methylstyrene, 80 parts of methacrylic acid, 520 parts of methyl methacrylate, 250 parts of stearyl methacrylate, 50 parts of hydroxyethyl methacrylate, 30 parts of ethyl carbitol acrylate, 2,2′- A mixture of 90 parts of azobis (2-methylbutyronitrile) and 100 parts of isopropanol was added dropwise over 6 hours. After completion of the dropwise addition, the reaction was carried out at the same temperature for 15 hours, then the temperature was lowered to 60 ° C., a mixture consisting of 83 parts of dimethylethanolamine and 100 parts of water was added and stirred until uniform. . Next, 2900 parts of ion-exchanged water was added and stirred uniformly, and then most of the isopropanol was removed by distillation under reduced pressure. Dimethanolamine was added until the pH of the aqueous solution reached 8.0 to obtain an aqueous solution of acrylic acid copolymer having a nonvolatile content of 22%. When SP value of solid content was measured by the turbidity titration method, it was 20.6 (J / cm ³ ) ^1/2 , and the solid content acid value was 81 mgKOH / g.

Example 1
Mix 40 parts of the indigo pigment FASTOGEN BLUE LDB30 manufactured by DIC Corporation, 20 parts of the acrylic acid copolymer aqueous solution prepared in Reference Example 1, 4 parts of isopropyl alcohol, and 36 parts of water. Got. To 26 parts of this mill base was added 70 parts of an aqueous dispersion of ethylene-acrylic acid copolymer manufactured by Sumitomo Seika Co., Ltd., 3.8 parts of polyethylene wax, 3.8 parts of polyethylene wax, and 0.2 part of a silicone-based antifoaming agent. Cup No. 3 was adjusted by adding an aqueous diluent so as to be 16 seconds to obtain an aqueous ink.

(Example 2)
An acrylic acid copolymer aqueous solution was synthesized by the same operation as in Reference Example 1 except that the monomers and neutralizing agents shown in Table 1 were used. When the SP value of the solid content of the obtained acrylic acid copolymer was measured by the turbidity titration method and the turbidity titration method, it was 20.4 (J / cm ³ ) ^1/2 and the solid content acid value was 82 mgKOH / g. there were. Using this aqueous resin, a mill base and aqueous ink were obtained in the same manner as in Example 1.

(Example 3)
An acrylic acid copolymer aqueous solution was synthesized by the same operation as in Reference Example 1 except that the monomers and neutralizing agents shown in Table 1 were used. When the SP value of the solid content of the obtained acrylic acid copolymer was measured by turbidity titration method and turbidity titration method, it was 20.7 (J / cm ³ ) ^1/2 , and the solid content acid value was 50 mgKOH / g. there were. Using this aqueous resin, a mill base and aqueous ink were obtained in the same manner as in Example 1.

Example 4
A mill base was prepared in the same manner as in Example 1 except that the acrylic acid copolymer aqueous solution of Reference Example 1 was used and the pigment was changed to 40 parts of DIC Corporation yellow pigment SYMULER FAST YELLOW 5GF, and then an aqueous ink was obtained. .

(Comparative Example 1)
An acrylic acid copolymer aqueous solution was synthesized by the same operation as in Reference Example 1 except that the monomers and neutralizing agents shown in Table 1 were used. When the SP value of the solid content of the obtained acrylic acid copolymer was measured by turbidity titration method and turbidity titration method, it was 20.8 (J / cm ³ ) ^1/2 , and the solid content acid value was 85 mgKOH / g. there were. Using this aqueous resin, a mill-base ink was obtained in the same manner as in Example 1.
Next, adjustment of water-based ink was attempted in the same manner as in Example 1, but the ink was solidified immediately after the blending of Syxen L, and the ink could not be prepared.

(Comparative Example 2)
In the same manner as in Comparative Example 2, an acrylic acid copolymer aqueous solution was synthesized. When the SP value of the solid content of the obtained acrylic acid copolymer was measured by the turbidity titration method and the turbidity titration method, it was 20.3 (J / cm ³ ) ^1/2 , and the solid content acid value was 100 mgKOH / g. there were. Using this aqueous resin, a mill base was obtained in the same manner as in Example 1.
Next, adjustment of water-based ink was attempted in the same manner as in Example 1, but the ink was solidified immediately after the blending of Syxen L, and the ink could not be prepared.

(Comparative Example 3)
An acrylic acid copolymer aqueous solution was synthesized in the same manner as in Comparative Example 1. When the SP value of the solid content of the obtained acrylic acid copolymer was measured by turbidity titration method and turbidity titration method, it was 21.6 (J / cm ³ ) ^1/2 and the solid content acid value was 220 mgKOH / g. there were. Using this aqueous resin, a mill-base ink was obtained in the same manner as in Example 1. Next, a water-based ink was obtained in the same manner as in Example 1, except that 40 parts of Joncrill 711, which is a styrene-acrylic copolymer aqueous resin, was used in place of Saixen L at the time of ink blending.

  The water-based ink thus obtained, and this ink were applied to a 25 μm-thick biaxially stretched polyethylene terephthalate film with a bar coater No. The performance of the coated film coated and dried in 4 was compared by the following test method.

  Each test method and evaluation criteria are as follows.

[1. Storage stability: Evaluation criteria)
The prepared ink was put into a 450 ml mayonnaise bottle and allowed to stand at room temperature for 1 week, and then mixed with a spatula to visually evaluate the state of the ink.
○: Uniform dispersion △: Precipitates, but homogenized when shaken ×: Precipitates, even if shaken, not uniformly dispersed

[2. Adhesion: Evaluation criteria)
The cellophane tape having a width of 18 mm was uniformly pressed against the coating surface of the coating film, and then the cellophane tape was quickly peeled off from the printing surface. At this time, the peeling state of the coating film from the film was visually evaluated.
○: almost no peeling of the coating film from the film Δ: about half of the coating film is peeling ×: the coating film is completely peeled off

[3. (Resolubility: Evaluation criteria)
After dropping one drop of the same ink used for coating on the coating surface of the coating film with a dropper, it was quickly wiped off with gauze. After wiping, the time until the coating film did not dissolve was evaluated.
○: The coating film dissolves within 3 seconds after dropping. Δ: The coating film dissolves within 5 seconds after dropping. X: It takes 5 seconds or more to dissolve the coating film after dropping.

[4. Alkali resistance: Evaluation criteria)
A sodium hydroxide aqueous solution of pH 11 was dropped on the coating film surface of the coating film, and after 5 minutes, 10 reciprocations were rubbed with a cotton swab, and the color fading of the coating film and the color transfer to the cotton swab were visually evaluated.
○: No color fading of the coating film and no color transfer to the cotton swab △: No significant color fading of the coating film is seen, but there is a color transfer to the cotton swab ×: The coating film is completely removed

  Table 1 shows the formulation of the acrylic acid copolymer aqueous solution on a weight basis.

  Table 2 shows the formulation of the mill base using each acrylic acid copolymer aqueous solution prepared on a weight basis.

Table 3 shows the formulation of water-based ink using each mill base produced on a weight basis.
Incidentally, after blending the ink, it was diluted with isopropyl alcohol: water = 40: 60 (volume ratio). The ink viscosity was adjusted to be 16 seconds at 3.

Table 4 shows the evaluation results of the water-based ink produced.
The water-based ink of the present invention is excellent in storage stability, adhesion, re-solubility and alkali resistance.

Claims (2)

Disperse the pigment in an aqueous dispersion obtained by neutralizing an acrylic acid copolymer having an SP value of 20.4 to 20.7 (J / cm ³ ) ^1/2 with a turbidity titration method with ammonia and / or alkanolamine. And an alkali-resistant water-based ink composition containing an aqueous dispersion obtained by neutralizing an ethylene-acrylic acid copolymer with an alkanolamine , wherein the acrylic acid copolymer has an aromatic compound having a vinyl group And (meth) acrylic acid ester and (meth) acrylic acid copolymer, wherein the alcohol constituting the ester group of the (meth) acrylic acid ester has 12 to 18 carbon atoms. Water-based ink composition.
Claim 1 Alkali aqueous ink composition according the acid value of the acrylic acid-based copolymer is 50 mg KOH / g or more.