JP2007106896A - Water-based ink composition and printed matter using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based ink composition capable of obtaining coating film properties excellent in water resistance, alkali resistance and the like and excellent in redissolvability, and to provide printed matters using the composition. <P>SOLUTION: The water-based ink composition comprises a water-soluble resin comprising an (α-methyl)styrene-(meth)acrylic acid-(meth)acrylic ester copolymer and a base, wherein the copolymer comprises 50-65 wt.% (α-methyl)styrene, 0.1-15 wt.% (meth)acrylic ester having a 12-18C long chain alkyl and 5-25 wt.% (meth)acrylic ester having nonionic alkylene oxide and has 50-150 mgKOH/g acid value and 5,000-30,000 weight-average molecular weight. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a water-based ink composition having excellent water resistance, alkali resistance, and the like, and having excellent re-solubility and a printed product thereof.

  Printing inks are roughly classified into oil-based inks and water-based inks depending on the solvent used. Oil-based inks use organic solvents such as toluene and xylene as solvents, and water-based inks use water and alcohol. The organic solvent used for the oil-based ink improves the fluidity, transferability, and drying properties of the ink. However, since the solvent discharged from the factory discharges organic chemical substances, it generates a bad odor around the factory, a problem of the working environment, etc., and has an adverse effect on the global environment and the human body. On the other hand, water-based inks do not emit organic chemical substances, improve the working environment, and protect the global environment and prevent adverse effects on the human body, and are excellent in productivity. For these reasons, in recent years, the printing industry has been required to use water-based ink.

  However, water-soluble resins used in conventional water-based inks require an acid value of 200 mgKOH / g or more in order to obtain good pigment dispersibility and printability, and the water resistance and alkali resistance of the coating film (printed matter). Etc. were inferior. Conventionally, water-based inks using water-soluble styrene- (meth) acrylic resins have a high styrene compounding ratio of 60 wt% or more in order to improve the water resistance of the coating film, but the styrene compounding ratio is high. As a result, the hydrophobicity of the resin became strong, and in order to make it water-soluble, it had to be produced with a high acid value of 200 mgKOH / g or more, and the alkali resistance of the coating film was inferior. In addition, the water-soluble resin having a low acid value (100 to 200 mgKOH / g) with improved water resistance and alkali resistance of the coating film (printed material) has a weight average molecular weight of 4,500 to 10,000 for water solubility. As a result, the pigment dispersibility was poor.

  In addition, in order to improve the water resistance, alkali resistance, etc. of the coating film (printed material), the water-dispersible resin is added to the high-concentration pigment dispersion in which the pigment is dispersed using a water-soluble resin or a water-dispersible resin. However, since water-based inks are manufactured, the use of different resins raises the viscosity of the inks, which causes a problem in storage stability.

  In order to solve the above storage stability problem, the alkali-soluble water-soluble resin is 3 to 20% by weight as the solid content, the water-dispersible resin is 5 to 30% by weight as the solid content, and the number average molecular weight is 2,000 or more. A water-based ink composition containing 0.5 to 5% by weight of polyoxyethylene alkylphenyl ether as a solid content is disclosed (see Patent Document 1).

  Also, after kneading the pigment with a water-dispersible styrene- (meth) acrylic acid alkyl ester- (meth) acrylic acid resin, a water-dispersible ethylene- (meth) acrylic acid resin is added to form an aqueous printing ink. Techniques have been disclosed that can easily produce water-based printing inks that are manufactured and form a coating film excellent in water resistance, solvent resistance, alkali resistance, etc., and excellent in storage stability (Patent Documents). 2).

An aqueous acrylic resin comprising α-methylstyrene, methyl methacrylate, and an ethylenically unsaturated compound having a carboxyl group as essential components, wherein the amount of α-methylstyrene and methyl methacrylate in all constituent monomers is 60 to 80% by weight. And a water-based printing ink composition comprising an aqueous acrylic resin having a ratio of α-methylstyrene / methyl methacrylate = 5/95 to 30/70 and a carbodiimide-based curing agent. (See Patent Document 3).
Japanese Patent No. 3301267 (page 1-5) JP 07-041719 A (page 1-4) JP 2003-26980 A (pages 1-8)

  However, in Japanese Patent No. 3301267, it is necessary to blend an alkali-soluble water-soluble resin, a water-dispersible resin, and polyoxyethylene alkylphenyl ether. The water resistance tended to be inferior. In addition, since JP 07-041719 A uses a water-dispersible resin, an anilox roll after ink transfer or an ink that has remained in a semi-dried state on the surface of a plate during flexographic printing or gravure printing will be used next time. There is a problem that the re-dissolvability of the ink is inferior when the ink is dissolved again by the ink supplied at the time of rotation. JP-A-2003-26980 also proposes a method of improving the durability of a coating film by dispersing a pigment using a water-soluble resin or a water-dispersible resin and then adding a crosslinking agent having a carbodiimide group. However, there are problems in the durability of the effect of the additive and the storage stability of the ink.

  The present invention aims to solve the above-mentioned problems, and (α-methyl) styrene- (meth) acrylic acid having a weight average molecular weight of 5,000 to 30,000 blended at a predetermined ratio. By using a water-soluble resin obtained by neutralizing a (meth) acrylic acid ester copolymer with ammonia or amine, it not only reduces environmental burden and improves the working environment, but also has excellent productivity and excessively high ink viscosity. The water-based ink composition excellent in re-dissolvability is obtained, and the coating film of the printed material obtained by the water-based ink composition of the present invention proposes a printed material excellent in printability, water resistance, alkali resistance, etc. is there.

  The present invention relates to (α-methyl) styrene 50 to 65% by weight, (meth) acrylic acid ester 0.1 to 15% by weight having a long-chain alkyl group having 12 to 18 carbon atoms, nonionic alkylene oxide group (Α-methyl) styrene having an acid value of 50 to 150 mgKOH / g and a weight average molecular weight of 5,000 to 30,000, comprising 5 to 25% by weight of (meth) acrylic acid ester having A water-based ink composition comprising a (meth) acrylic acid- (meth) acrylic acid ester copolymer and a water-soluble resin comprising a base.

  Moreover, it is a printed matter printed on a base material with a water-based ink composition.

  In the water-based ink using the water-soluble styrene- (meth) acrylic resin of the present invention, the blending ratio of styrene is set to 50 to 65% by weight, the water resistance of the coating film is improved, and a carboxyl group is included for water-solubilization. By copolymerizing (meth) acrylic acid ester having nonionic alkylene oxide in addition to (meth) acrylic acid, a water-soluble resin having a low acid value of 50 to 150 mgKOH / g can be produced. Accordingly, an aqueous ink composition that is excellent in productivity, low ink viscosity, and excellent re-dissolvability as well as environmental load reduction and work environment improvement can be obtained.

  The coating film of the printed matter obtained by the water-based ink composition of the present invention is excellent in printability, and a printed matter excellent in water resistance, alkali resistance and the like is obtained.

  The best mode for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the best mode for carrying out the invention described below, and includes various other embodiments within the scope of the technical idea described in the scope of claims.

  The present invention is a water-based ink composition containing a pigment, a water-soluble resin, alcohol and / or water and an additive. The water-soluble styrene- (meth) acrylic resin, which is a water-soluble resin, is an (α-methyl) styrene- (meth) acrylic acid- (meth) having an acid value of 50 to 150 mgKOH / g and a weight average molecular weight of 5,000 to 30,000. ) A pH 8.0-10.0 aqueous solution obtained by neutralizing an acrylate copolymer with a base. (Α-methyl) styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer had (α-methyl) styrene 50 to 65% by weight and a long chain alkyl group having 12 to 18 carbon atoms (meth) It is obtained by including 0.1 to 15% by weight of an acrylate ester and 5 to 25% by weight of a (meth) acrylate ester having a nonionic alkylene oxide group.

  The styrene- (meth) acrylic resin has a high copolymerization ratio of styrene of 50 to 65% by weight, a (meth) acrylic ester A having 12 to 18 carbon atoms as a long-chain alkyl group, and a hydrophilic functional group. A low acid value water-soluble resin containing (meth) acrylic acid ester B having a nonionic alkylene oxide group is used.

  Styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer is prepared from 50 to 65% by weight of styrene, 6 to 13% by weight of (meth) acrylic acid, and 22 to 44% by weight of (meth) acrylic acid ester. did. The (meth) acrylic acid ester is a (meth) acrylic acid ester A having 12 to 18 carbon atoms as a long-chain alkyl group, and a (meth) acrylic acid ester having a nonionic alkylene oxide group as a hydrophilic functional group B and (meth) acrylic acid ester C.

  The water-soluble (α-methyl) styrene- (meth) acrylic resin in the water-based ink composition of the present invention is characterized in that the acid value is in the range of 50 to 150 mgKOH / g, and the acid value is lower than 50 mgKOH / g. If the resin has insufficient solubility, and the acid value exceeds 150 mgKOH / g, the resin has high solubility, and the water resistance and alkali resistance of the printed matter are lowered.

  The water-soluble (α-methyl) styrene- (meth) acrylic resin in the water-based ink composition of the present invention is characterized in that the weight average molecular weight is in the range of 5,000 to 30,000, and the molecular weight is from 5,000. If it is small, the water resistance and friction resistance of the printed matter will deteriorate, and if the molecular weight exceeds 30,000, the resin will not have sufficient solubility and the printability will deteriorate. The water-soluble (α-methyl) styrene- (meth) acrylic resin in the water-based ink composition of the present invention is characterized in that the copolymerization ratio of (α-methyl) styrene is 50 to 65% by weight, from 50% by weight If the amount is too small, the hydrophobicity of the resin will be lowered, and sufficient water resistance of the printed matter will not be obtained. If the copolymerization ratio of (α-methyl) styrene exceeds 65% by weight, the hydrophobicity of the resin will become strong, and the low acid value will be low. The solubility in the ink becomes poor, and the printing color density of the printed matter decreases.

  The (meth) acrylic acid ester A having 12 to 18 carbon atoms as the long-chain alkyl group of the water-soluble (α-methyl) styrene- (meth) acrylic resin in the water-based ink composition of the present invention is 0.1 to 15 Used for copolymerization in the range of% by weight. When the copolymerization ratio of the (meth) acrylic ester A is less than 0.1% by weight, the pigment dispersibility is deteriorated in ink preparation, and the printing color density of the printed matter is lowered. On the other hand, when the copolymerization ratio of (meth) acrylic acid ester A exceeds 15% by weight, the hydrophobicity of the aqueous resin is too high, the solubility becomes poor, and the printing color density of the printed matter is lowered. In the present invention, the copolymerization ratio of (meth) acrylic acid ester A is preferably in the range of 5 to 10% by weight.

  Examples of the (meth) acrylic acid ester A include lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, and the like.

  The water-based ink composition of the present invention has a nonionic alkylene oxide group (ethylene oxide (EO) or propylene oxide (PO)) as a hydrophilic functional group of the water-soluble (α-methyl) styrene- (meth) acrylic resin. The (meth) acrylic acid ester B is used for copolymerization in the range of 5 to 25% by weight. If the copolymerization ratio of (meth) acrylic ester B is less than 5% by weight, the resin is water-solubilized and the hydrophilicity is inferior, so that the pigment dispersibility is deteriorated and the printing color density of the printed matter is lowered. On the other hand, when the copolymerization ratio of the (meth) acrylic acid ester B exceeds 25% by weight, the hydrophilicity of the aqueous resin is too high, and the water resistance of the printed matter is lowered. In the present invention, the copolymerization ratio of (meth) acrylic acid ester B is preferably in the range of 10 to 20% by weight.

  (Meth) acrylic acid ester B is (meth) acrylic acid-2-methoxyethyl, (meth) acrylic acid-2-ethoxyethyl, (meth) acrylic acid ethyl carbitol, (meth) acrylic acid methoxytriethylene glycol, Examples include (meth) acrylic acid methoxytetraethylene glycol, (meth) acrylic acid phenoxydiethylene glycol, (meth) acrylic acid methoxydipropylene glycol, and (meth) acrylic acid methoxytripropylene glycol. Absent.

  (Meth) acrylic acid ester C is (meth) acrylic acid methyl, (meth) acrylic acid ethyl, (meth) acrylic acid propyl, butyl acrylate, (meth) acrylic acid isobutyl, (meth) acrylic acid normal octyl, ( (Meth) acrylic acid-2-ethylhexyl etc. can be mentioned.

  Examples of the base used for neutralizing the carboxyl group of the water-soluble (α-methyl) styrene- (meth) acrylic resin in the water-based ink composition of the present invention include ammonia or dimethylamine, trimethylamine, diethylamine, triethylamine, N, N -Examples include, but are not limited to, dimethylethanolamine, N, N-diethylethanolamine, monoethanolamine, triethanolamine, morpholine, and triethylenediamine.

  The water-soluble (α-methyl) styrene- (meth) acrylic resin in the present invention is produced by a conventionally known polymerization method such as bulk polymerization, solution polymerization, emulsion polymerization and suspension polymerization, and neutralized with a base. It is done.

  In the water-based ink composition of the present invention, a water-soluble or water-dispersible resin can be used in combination as necessary as long as the function is not inhibited.

  The water-soluble (α-methyl) styrene- (meth) acrylic acid- (meth) acrylic acid ester resin in the water-based ink composition of the present invention has a base added so that the resin solid content is 20 to 30% by weight. By neutralizing, an aqueous resin solution having a pH of 8.0 to 10.0 is prepared. When the pH is lower than 8.0, an emulsion-like resin solution is obtained, and the pigment dispersibility is lowered.

  The water-based ink composition of the present invention includes the water-soluble (α-methyl) styrene- (meth) acrylic acid- (meth) acrylic ester resin, a base, a colorant such as a pigment, and an antifoaming agent as necessary. Etc. are added by a known method.

  As the pigment, an inorganic pigment, an organic pigment, an extender pigment, or the like can be used. Moreover, an additive can be mixed with the water-based ink composition of the present invention as necessary. Examples of additives include pigment dispersants, antifoaming agents, leveling agents, and friction resistance improvers such as polyethylene wax.

  Viscosity can be adjusted by mixing water and / or alcohol with the water-based ink composition of the present invention. Examples of alcohol used for viscosity adjustment include, but are not limited to, methanol, ethanol, 1-propanol, 2-propanol and the like.

  The water-based ink composition can be printed by water-based gravure printing, water-based flexographic printing, water-based ink jet printing, commercial printing, securities printing, or the like. A printed film having excellent water resistance, alkali resistance and the like can be obtained. In particular, the water-based ink composition of the present invention is preferably used as a water-based gravure printing ink composition from the viewpoint of ink characteristics.

  The base material printed with the water-based ink composition of the present invention is not particularly limited, and examples thereof include paper sheets, plastics, and vinyl.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, the content of this invention is not limited to the range of these Examples.

(Examples 1-7)
A (α-methyl) styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer was prepared with the monomer composition ratio shown in Table 1, neutralized with ammonia water as a base, and an aqueous resin solution (solid content) 25% by weight). Next, a planetary ball mill (Fritsch) containing 64% by weight of the resin aqueous solution, 16% by weight of 1-propanol and 20% by weight of phthalocyanine blue pigment (Fastgen Blue FGF, manufactured by Dainippon Ink & Chemicals, Inc.). P-5 type) was kneaded for 1 hour to prepare a mill base of a high concentration pigment dispersion. Then, 80% by weight of the mill base, 16% by weight of the water-soluble (α-methyl) styrene- (meth) acrylic acid- (meth) acrylic acid ester resin aqueous solution (resin solid content 25% by weight), and 4% by weight of alcohol. %, 2% by weight of antifoaming agent and 3% by weight of wax were mixed and stirred well to prepare a water-based ink composition.

(Comparative Examples 1-7)
A styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer was prepared with the monomer composition ratio shown in Table 2, neutralized with ammonia water as a base, and an aqueous resin solution (solid content 25 wt%). Got. Next, a planetary ball mill (Fritsch) containing 64% by weight of the resin aqueous solution, 16% by weight of 1-propanol and 20% by weight of phthalocyanine blue pigment (Fastgen Blue FGF, manufactured by Dainippon Ink & Chemicals, Inc.). P-5 type) was kneaded for 1 hour to prepare a mill base of a high concentration pigment dispersion. Then, 80% by weight of the mill base, 16% by weight of the aqueous water-soluble styrene- (meth) acrylic acid- (meth) acrylic acid ester resin aqueous solution (resin solid content 25% by weight), 4% by weight of alcohol, and defoaming A water-based ink composition was prepared by mixing 2% by weight of the agent and 3% by weight of the wax and stirring well.

(Comparative Example 8)
38.4% by weight of an aqueous dispersible resin solution having an acid value of 87 and a weight average molecular weight of 100,000 to 200,000 (Johncrill 7001 resin solid content 42% by weight, pH 8.4, manufactured by Johnson Polymer Co., Ltd.) and 25 ion-exchanged water. 1.6% by weight, 16% by weight of 1-propanol, and 20% by weight of phthalocyanine blue pigment (Fastgen Blue FGF, manufactured by Dainippon Ink & Chemicals, Inc.) ) For 1 hour to prepare a mill base of a high concentration pigment dispersion. Further, 9.6% by weight of the above water-dispersible resin solution (Johncrill 7001 resin solid content 42% by weight, manufactured by Johnson Polymer Co., Ltd.), 6.4% by weight of ion-exchange water, and alcohol are added to 80% by weight of the mill base. A water-based ink composition was obtained by mixing 4% by weight, 2% by weight of an antifoaming agent and 3% by weight of a wax and stirring well.

(Comparative Example 9)
53.3% by weight of a water-soluble resin solution having an acid value of 213 and a weight average molecular weight of 1,2,500 (John Cryl 63 resin solid content 30% by weight, pH 8.5, manufactured by Johnson Polymer Co., Ltd.), 10.7% by weight of ion-exchanged water, Using a planetary ball mill (P-5 type manufactured by Fritsch) with a composition of 16% by weight of 1-propanol and 20% by weight of phthalocyanine blue pigment (Fastgen Blue FGF, manufactured by Dainippon Ink & Chemicals, Inc.) The mill base of the high concentration pigment dispersion was prepared by kneading for 1 hour. Then, 80% by weight of the mill base, 16% by weight of the aqueous water-soluble styrene- (meth) acrylic acid- (meth) acrylic acid ester resin aqueous solution (resin solid content 25% by weight), 4% by weight of alcohol, and defoaming 2% by weight of the agent and 3% by weight of the wax were mixed and stirred well to obtain a water-based ink composition.

  Each water-based ink composition of Examples 1 to 7 and Comparative Examples 1 to 9 was adjusted for viscosity by adding water and / or alcohol, and tested for gravure printing using an automatic engraving plate (250 lines / inch) on coated paper. Using a machine (Kumaya Riki Kogyo Co., Ltd.), printing was performed at a speed of 45 m / min to obtain each printed matter. Each printed product was evaluated for printing color density, water resistance and alkali resistance.

Re-solubility of ink: After printing with a printing machine, printing was stopped for 5 minutes and then printing again. The obtained printed material was compared with the printed material before stopping, and the reproducibility of the image line was visually determined.
(Double-circle): It is completely the same as before stopping.
○: Slightly rubbed immediately after stopping, but recovered immediately.
(Triangle | delta): The image line has rubbed a little.
X: The image line is rubbed.

Printing color density of printed matter: The printing color density was evaluated by visual observation of gray scale density and gradation reproducibility.
A: The printing color density is high and the gradation reproducibility is good.
○: The printing color density is slightly low, but the gradation reproducibility is good.
Δ: The printing color density is slightly low and rubbing.
X: The printing color density is low and the gradation reproducibility is poor.

Water resistance of printed matter: Using a friction tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.), the printed matter is rubbed 60 times with a friction piece (R-45 mm, 200 g) with a cotton cloth wetted with water. The degree of ink peeling was visually evaluated.
A: There is no ink peeling.
○: There is almost no ink peeling.
Δ: Ink is peeled off.
X: Ink peeling off remarkably.

Alkali resistance of printed matter: The printed product was immersed in a 1% strength caustic aqueous solution for 24 hours, washed with water and dried, and then the printed color density was visually evaluated.
A: No decrease in printing color density.
○: The printing color density slightly decreases.
Δ: The printing color density decreased.
X: The printing color density was remarkably lowered.

  According to the present invention, a water-based ink composition using a water-soluble (α-methyl) styrene- (meth) acrylic resin excellent in re-solubility and a printed matter excellent in water resistance and alkali resistance can be obtained.

Claims (2)

(Α-methyl) styrene 50 to 65 wt%, (meth) acrylic acid ester 0.1 to 15 wt% having a long-chain alkyl group having 12 to 18 carbon atoms, and a nonionic alkylene oxide group ( (Α-methyl) styrene- (meth) acrylic acid containing 5 to 25% by weight of (meth) acrylic acid and having an acid value of 50 to 150 mgKOH / g and a weight average molecular weight of 5,000 to 30,000 A water-based ink composition comprising an acid- (meth) acrylic acid ester copolymer and a water-soluble resin comprising a base. A printed matter printed on a substrate with the water-based ink composition according to claim 1.