JP5515762B2 - Water based gravure ink composition for paper containers - Google Patents

Description

The present invention relates to an aqueous gravure printing ink composition for paper containers. More specifically, the present invention relates to a water-based ink composition for paper containers that has a good printing effect when gravure printing is performed on various printing papers, and is suitable for obtaining a printed matter of excellent quality.

From the viewpoint of environmental problems such as air pollution caused by organic solvents, safety and health problems in the work environment, and disaster prevention, removal of organic solvents and water-based solutions have long been studied in the field of printing inks and paints.
However, water-based gravure ink compositions that have been put to practical use may contain a large amount of alcohol in the printing ink composition due to printing effects (solid portion formation, halftone dot reproducibility) due to leveling properties. It is almost.
In addition, due to the enforcement of the Air Pollution Control Act in 2010, the emission concentration of volatile organic compounds is limited, and each printing manufacturer is forced to take measures. Accordingly, reduction of the volatile organic compounds contained in the aqueous gravure ink composition has been demanded.

Japanese Patent Laid-Open No. 08-144191 JP 2005-290078 A JP 07-316492 A

The present invention is a solvent composition that contains as little or no volatile organic compound as possible, and has a good printing effect when gravure printing is performed on various printing papers, and obtains an excellent quality printed matter. It is in obtaining the water-based ink composition for paper containers suitable for.

That is, in the present invention, the shell is copolymerizable with polyethylene glycol (meth) acrylate (a) 1 to 6% by weight, (meth) acrylic acid (b) 2 to 8% by weight, and (a) and (b). (Meth) acrylate (c) 25 to 70% by weight, core is styrene (d) 15 to 40% by weight, and glass point transfer point is −50 to −70 ° C. (meth) acrylate (e) 10 to 30% by weight (( an acrylic having a core / shell structure in which the sum of a) to (e) is 100% by weight), and the weight% M of (a) and the weight% N of (b) are within the range represented by the formula (1) The present invention relates to an aqueous ink composition for paper containers characterized by being an emulsion, a colorant, water, and a water-soluble organic solvent.

Formula (1) 0.3 <M / N <2
Further, the ethylene oxide addition number of the polyethylene glycol (meth) acrylate (a) is 20 to 50, and the core / shell ratio of the acrylic emulsion is 30:70 to 60:40. The present invention relates to a water-based ink composition.
In addition, the present invention relates to a printed matter obtained by printing an ink composition on a printing paper substrate.

The water-based ink composition for paper containers of the present invention has a good printing effect when gravure printing is performed on various printing papers even in a solvent composition containing as little or no volatile organic compound as possible. It has become possible to obtain a paper-based water-based ink composition suitable for obtaining an excellent quality printed matter.

Examples of the polyethylene glycol (meth) acrylate (a) that can form the acrylic emulsion constituting the aqueous ink composition of the present invention include polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, alkoxy polyethylene glycol acrylate, alkoxy polyethylene glycol methacrylate, and phenoxy polyethylene glycol. Examples thereof include acrylate and phenoxypolyethylene glycol methacrylate. Examples of commercially available products include Blenmer AE90 (ethylene oxide addition number: about 2), Blemmer AE200 (about 4.5), Blenmer AE400 (about 10) as polyethylene glycol monoacrylate having a hydroxyl group at the end. Examples of polyethylene glycol monomethacrylate having a hydroxyl group at the end include Blemmer PE90 (addition number of ethylene oxide: about 2), Blemmer PE200 (about 4.5), Blenmer PE350 (about 8). Examples of polyethylene glycol monomethacrylate having a methoxy terminal include Blemmer PME100 (addition number of ethylene oxide: about 2), Blemmer PME200 (about 4), Blemmer PME400 (about 9), Blemmer PME1000 (about 23), Blemmer PME4000 ( 90) (manufactured by Nippon Oil & Fats Co., Ltd.), light ester D41MA (ethylene oxide addition number of about 30, manufactured by Kyoeisha) and the like. The number of ethylene oxide additions is preferably 20-50. Between 20 and 50, there is little viscosity lowering property when the ink is diluted, and leveling property is also good.

(A) needs to be contained in an amount of 1 to 6% by weight in the total amount of (a) to (e) constituting the acrylic emulsion. If it is less than 1% by weight, the stability as an emulsion and the viscosity as a printing ink are lowered, and the printability is poor. Even if it is contained in an amount of more than 6% by weight, the effect simply added to the printability cannot be obtained.
Examples of (meth) acrylic acid (b) include acrylic acid and methacrylic acid. The usage-amount of (meth) acrylic acid (b) needs to be 2-8 weight% among the total amount of (a)-(e). If it is less than 2% by weight or more than 8% by weight, the print gloss is lowered.
(A), (b) copolymerizable (meth) acrylate (c) is methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meta) ) (Meth) acrylate having an alkyl chain such as acrylate and stearyl (meth) acrylate, (meth) acrylate having a hydroxyl group such as 2-hydroxyethyl (meth) acrylate and 2-hydroxybutyl (meth) acrylate. Examples include (meth) acrylates having an alicyclic structure such as cyclohexyl (meth) acrylate, and these can be used alone or in combination of two or more. The amount of (meth) acrylate (c) used needs to be 25 to 70% by weight. When the amount is less than 25% by weight, the gloss of the printed matter is lowered. When the amount is more than 70% by weight, the film formation is poor and the wear resistance as the printed matter is deteriorated.
Examples of styrene (d) include styrene and α-methylstyrene, and these can be used alone or in combination. It is necessary to use 15 to 40% by weight of styrene (d). If it is less than 15% by weight, drying failure occurs during gravure printing, and if it exceeds 40% by weight, the re-dissolvability is deteriorated and good halftone dot reproducibility cannot be obtained. Examples of (meth) acrylate (e) having a glass point transfer of −50 to −70 ° C. include butyl acrylate and 2-ethylhexyl acrylate. It is necessary to use 10 to 30% by weight as the (meth) acrylate (e). When the amount is less than 10% by weight, the gloss of the printed matter is lowered. When the amount is more than 30% by weight, film formation is poor and the wear resistance of the printed matter is deteriorated.
In the present invention, the acrylic emulsion needs to have a core / shell structure, and (a) to (c) are used as the shell and (d) and (e) are used as the core. In particular, (a) to (c) used for the shell are important for determining the aging stability and viscosity of the emulsion. Among them, polyethylene glycol (meth) acrylate (a) is an important (meth) acrylate that determines the viscosity of a printing ink composition containing an emulsion and the retention of viscosity against dilution, as well as having an aqueous ability.
The weight% M of polyethylene glycol (meth) acrylate (a) and the weight% N of (meth) acrylic acid (b) in the monomer capable of forming the copolymer of acrylic emulsion constituting the aqueous ink composition of the present invention are It is necessary to be within the range represented by the formula (1).

Formula (1) 0.3 <M / N <2
M and N% by weight determine the aqueous ability and viscosity stability of the acrylic emulsion, especially the viscosity retention with respect to dilution. The viscosity stability balanced by the ratio N / M of both, viscosity retention during dilution. Properties and leveling properties, water resistance of the ink film, etc. are manifested. In the present invention, since the emulsion shell has polyethylene glycol (meth) acrylate, the viscosity decrease when the ink is diluted is less than that of the emulsion not using polyethylene glycol (meth) acrylate, and printing is performed. The range of dilution rate at the time is wide and can be suitably used for printing. This seems to be due to the high water hydration ability, hydration ability, and hydrogen bonding ability of the polyethylene glycol chain extending from the emulsion surface into the solution. In particular, even when a solvent such as alcohol is not used, the decrease in viscosity due to dilution is low. M / N needs to be 0.3 <M / N <2. When M / N is less than 0.3, the decrease in viscosity due to dilution becomes large, or the leveling property decreases. On the other hand, when the ratio is more than 2, the water resistance of the ink film is lowered and the viscosity of the ink is increased.
The acrylic emulsion in the water-based ink composition used in the present invention was obtained by copolymerizing the polyethylene glycol (meth) acrylate (a), (meth) acrylic acid (b), and (meth) acrylate (c). An acrylic emulsion having a core / shell structure obtained by emulsion polymerization of copolymerizable styrene (d) and (meth) acrylate (e) in the presence of a polymer emulsifier. The core / shell ratio of the acrylic emulsion is preferably 30:70 to 60:40. When the core is 30 or less, the physical properties of the film are liable to deteriorate, and when it is 60 or more, the stability over time as an acrylic emulsion tends to be inferior. The glass transition point of the acrylic emulsion is preferably 10 to 30 ° C. If it is 10 ° C. or less, the blocking resistance, friction resistance, etc. of the printed matter tend to decrease, and if it is 30 ° C. or more, film-forming properties and gloss are liable to decrease.
As the neutralizing agent used for the synthesis of the acrylic emulsion, ammonia, organic amine, alkali metal hydroxide and the like can be used. Examples of the organic amine include diethylamine, triethylamine, monoethanolamine, dimethylethanolamine, diethylethanolamine and the like. Examples of the alkali metal hydroxide include sodium hydroxide and potassium hydroxide. An organic amine is preferable, and dimethylethanolamine is more preferable.
In starting the polymerization reaction, a water-soluble pyrolytic polymerization initiator such as a persulfate such as potassium persulfate or ammonium persulfate or an azobis cation salt or a hydroxyl adduct can be used.
A redox initiator can also be used.
Redox initiators include combinations of organic peroxides such as t-butyl hydroperoxide, benzoyl peroxide, cumene hydroperoxide and reducing agents such as Rongalite, sodium metabisulfite, or potassium persulfate, ammonium persulfate and A combination with Rongalite, sodium thiosulfate, or the like, or a combination of hydrogen peroxide and ascorbic acid is used.
The aqueous printing ink composition for paper containers of the present invention comprises an acrylic emulsion, a pigment and a solvent. In order to obtain good gloss and dryness when gravure printing is performed on various printing papers, it is important to contain 5-50% by weight of an emulsion type resin in the ink composition as a solid content. When the amount is small, sufficient gloss and drying properties cannot be obtained. When the amount is more than 50% by weight, it is difficult to obtain sufficient fluidity and leveling properties.
Next, examples of the pigment include organic and inorganic pigments and dyes used in general inks, paints, and recording agents. Organic pigments include azo, phthalocyanine, anthraquinone, perylene, perinone, quinacridone, thioindigo, dioxazine, isoindolinone, quinophthalone, azomethine azo, dictopyrrolopyrrole, and isoindoline pigments Is mentioned. Indigo ink contains copper phthalocyanine, and transparent yellow ink uses C.I. I. Pigment Yellow No. 83 is preferably used.
Examples of the inorganic pigment include carbon black, titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, bengara, aluminum, kaolin clay, talc, mica (mica) and the like. From the viewpoints of cost and coloring power, it is preferable to use titanium oxide for white ink, carbon black for black ink, aluminum for silver ink, and mica for pearl ink.
The pigment is preferably contained in an amount sufficient to ensure the concentration and coloring power of the ink, that is, in a proportion of 1 to 50% by weight based on the total weight of the ink. The colorants can be used alone or in combination of two or more.
As the solvent, water and, if necessary, an organic solvent soluble in water can be used. Examples of such solvents include alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, and N-propyl alcohol, glycols such as ethylene glycol and propylene glycol, butyl cellosolve, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, and diethylene glycol monoethyl ether. And glycol ethers such as diethylene glycol monobutyl ether. The weight ratio of water to the water-soluble organic solvent is preferably 100/0 to 90/10 from the viewpoint of drying properties. Moreover, when using alcohol, it is preferable that the weight ratio of water and alcohol is 100 / 0-60 / 40 from a viewpoint of discharge | emission amount of a volatile organic compound.
In the aqueous printing ink of the present invention, in addition to the above-mentioned constituent materials, if necessary, bases such as ammonia, triethylamine, aminomethylpropanol, monoethanolamine, diethylaminoethanol, sodium hydroxide, potassium hydroxide, gas phase Additives such as silica, wet silica, organic silica, alumina silica, etc., polyethylene wax, antifoaming agent, leveling agent, tackifier, antiseptic, antibacterial agent, rust inhibitor can do.
The ink composition obtained from the above materials and production method can be diluted with water and, if necessary, a diluting solvent comprising a water-soluble organic solvent and printed on various printing papers by a gravure printing method. For example, there are art paper, coated paper, high-quality paper, and the like. Specifically, the dilutable solvent that can be used is a mixed solvent of water and alcohol, and the weight ratio is preferably 100: 0 to 60:40 from the viewpoint of the discharge amount of volatile organic compounds.
Furthermore, the printed matter obtained by printing by the gravure printing machine is post-processed according to various uses and used for packaging of products such as food.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited to these Examples. In the examples, “parts” and “%” represent “parts by weight” and “% by weight”.
<Synthesis of acrylic emulsion>
First, core / shell type acrylic emulsions used in Examples and Comparative Examples were synthesized. The “part” in the synthesis example is the same as described above.
(Synthesis Example 1)
A four-necked flask purged with nitrogen gas was charged with 100 parts of isopropyl alcohol, the temperature was raised to 80-82 ° C., and then a polyethylene glycol monoacrylate A (Blemmer AE400, ethylene oxide addition number of about 10, Japan) charged in a dropping funnel. A mixture of 2 parts manufactured by Yushi Co., Ltd., 2 parts acrylic acid, 40 parts methyl methacrylate, 12 parts butyl acrylate, and 1 part benzoyl peroxide was added dropwise over 2 hours. After completion of the dropwise addition, 0.5 part of benzoyl peroxide was added, and the mixture was further reacted for 2 hours. The temperature was lowered to 40 ° C., and dimethylaminoethanol and ion exchange water were added. Thereafter, the temperature of the reaction flask was raised to 80 to 82 ° C., stripping was performed, and finally a water-soluble resin using 30% solid water as a solvent was obtained.
The water-soluble resin obtained above and 10 parts of ion-exchanged water were charged into a reaction flask, the temperature was raised to 80 ° C. to 82 ° C., 0.8 part of potassium persulfate was added, 24 parts of styrene, 2-ethylhexyl acrylate 16 parts of the mixture was added dropwise over 2 hours. After completion of dropping, 0.2 part of potassium persulfate was added and reacted for 2 hours. The acrylic emulsion (resin 1) thus obtained had a solid content of 40%.
(Synthesis Examples 2 to 16)
About the synthesis examples 2-16, it superposed | polymerized by the method similar to the synthesis example 1, and obtained the resin 2-resin 16 which is an acrylic emulsion. Tables 1 and 2 show the blending of these monomers.
In addition, the following were used as other polyethylene glycol (meth) acrylates.

Polyethylene glycol methacrylate B: Blemmer PME1000 (terminated with methoxy group, ethylene oxide addition number about 23, manufactured by NOF Corporation)
Polyethylene glycol methacrylate C: Light ester D41MA (terminal is methoxy group, ethylene oxide addition number is about 30, manufactured by Kyoeisha)
Further, as the neutralizing agent in the synthesis of the shell layer resin, dimethylethanolamine is used in Synthesis Examples 1 to 3, 5, and 7 to 10, and ammonia water is used in Synthesis Examples 4 and 6, and distillation by stripping is also considered. Finally, the carboxyl group was neutralized by 110%.
<Example 1>
For the dispersion obtained by dispersing 20 parts (solid 40%) of the acrylic emulsion (resin 1), 20 parts of pigment (phthalocyanine blue) and 20 parts of water obtained in Synthesis Example 1 for 60 minutes with a paint conditioner, the acrylic emulsion 30 Parts (solid 40%), polyethylene wax 2.5 parts, silicone-based antifoaming agent 0.01 parts, water 17.49 parts, and further dispersed in a paint conditioner for 10 minutes to obtain an aqueous gravure ink composition ( 1) was obtained.
The water-based gravure ink composition (1) is adjusted to 15 to 18 seconds with Zahn Cup No. 3 (manufactured by Raigo Co., Ltd.) with water. A gravure printing machine was used to print using a sculpture gradation plate, and printing effects (gloss, leveling properties, halftone dot reproducibility) were evaluated.
<Examples 2 to 10 and Comparative Examples 1 to 6>
A water-based gravure ink composition (2) to a water-based ink composition (16) were obtained by the same formulation as in Example 1. Next, a printed matter was obtained in the same manner as in Example 1.
The printing effects (gloss, leveling property, halftone dot reproducibility) of Examples 1 to 10 and Comparative Examples 1 to 6 were evaluated. Evaluation methods and criteria are as follows.
Judgment criteria are also shown. The results are shown in Table 2.
<Evaluation>
Gloss: The gloss value of 100% part of the gradation was measured at 60 ° -60 ° by “Haze-Gloss Reflectometer” [Bic Chemie Japan Co., Ltd.].
Judgment criteria: ○ Gloss value of 40 or more
△ Gloss value 30-40
X Gloss value less than 30 Leveling property: Swim 100% part of gradation, visually determine the degree of color unevenness.

Judgment criteria: ○ No swimming or color irregularity △ Slight swimming, color irregularity recognized
X Swim, remarkably uneven color halftone dot reproducibility: Ink fillability of 10 to 70% of gradation is visually determined.
Judgment criteria: ○ Good
△ Somewhat bad
X Defect results are shown in Tables 1 and 2. In the printing effect (solid formability, halftone dot reproducibility), ○ to Δ are practical ranges.

Claims (5)

The shell is polyethylene glycol (meth) acrylate (a) 1 to 6% by weight, (meth) acrylic acid (b) 2 to 8% by weight, and (meth) acrylate (c) copolymerizable with (a) and (b) ) 25-70% by weight,
(Meth) acrylate (e) having a core of 15 to 40% by weight of styrene (d) and glass transition point of −50 to −70 ° C. (e) of 10 to 30% by weight (the total of (a) to (e) is 100% by weight) ,
And a paper container comprising an acrylic emulsion having a core / shell structure in which the weight% M of (a) and the weight% N of (b) are within the range represented by the formula (1), a pigment, and a solvent Water-based ink composition.

Formula (1) 0.3 <M / N <2

However, the polyethylene glycol (meth) acrylate (a) is a polyethylene glycol mono (meth) acrylate or alkoxy polyethylene glycol mono (meth) acrylate having a hydroxyl group at the end, and has an ethylene oxide addition number of 2 to 90. The water-based ink composition for paper containers according to claim 1, wherein the ethylene oxide addition number of the polyethylene glycol (meth) acrylate (a) is 20 to 50. The water-based ink composition for paper containers according to claim 1 or 2, wherein the acrylic emulsion has a core / shell weight ratio of 30:70 to 60:40. The water-based ink composition for paper containers according to any one of claims 1 to 3, wherein the acrylic emulsion is neutralized with dimethylethanolamine. The printed matter for paper containers which printed the water-based ink composition for paper containers in any one of Claims 1-4 on the printing paper base material.