JPH0128786B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a water-based printing ink that is used in plastic film bags, flexible packaging materials, etc., and has an excellent balance between printability, printing effect, processability, water resistance, and alkali resistance. Conventionally, printing inks for flexible packaging materials have been organic solvent-type gravure using a vehicle in which nitrified cotton/polyamide resin or nitrated cotton/maleic acid resin is dissolved in an organic solvent such as toluene, ethyl acetate, methyl ethyl ketone, or isopropyl alcohol. Printing ink was used, but organic solvents remain in the packaging material after printing, and there are concerns about the problem of migration into food in food packaging, so great efforts are being made to reduce residual organic solvents. However, no fundamental solution had been reached. Further, even during printing operations, the organic solvent vapor is unfavorable in terms of hygiene control, and there is a risk of ignition, which poses problems in terms of the working environment. Therefore, the practical use of water-based inks has been considered because they do not contain harmful organic solvents, are not flammable, and have the disadvantage of conserving resources. For example, it consists of Sierra Tsuk, Sierra Tsuk modified styrene resin, rosin modified maleic acid resin, styrene-acrylic acid resin, acrylic ester-acrylic acid resin, styrene-maleic acid resin, hydroxyethyl cellulose, hydroxypropyl cellulose, etc., or a mixture thereof. Although printing inks use resin as a binder, none of them have sufficient water resistance or alkali resistance, and when applied to plastic films such as polyethylene, polypropylene, and polyester, they have poor adhesion and lack sufficient adhesive strength. could not be maintained and could not be put to practical use. The inventors of the present invention have conducted intensive studies to eliminate the drawbacks of conventional printing inks for flexible packaging materials as described above, and have found that there is no problem in terms of hygiene, such as reduction of residual solvents and residual monomers, and that the printing inks are compatible with plastic films. It has good adhesion, excellent water resistance and alkali resistance, and printability (processing speed, plate binding, transferability), printing effects (gloss, pigment color development), and various printing ink film physical properties (abrasion resistance, We discovered a vehicle for water-based printing ink that has excellent scratch resistance, heat resistance, kneading resistance, and bending resistance.
This completes the present invention. That is, the present invention provides a copolymer obtained by radical polymerization of a monomer mixture containing 10 to 50% by weight of a hydroxyl group-containing ethylenically unsaturated monomer and 0.5 to 3% by weight of an ethylenically unsaturated carboxylic acid based on the total monomer components. Alternatively, the present invention relates to an aqueous printing ink characterized by using as a vehicle component an aqueous resin dispersion whose solid content has an acid value of 3 to 16, which is obtained by neutralizing with organic amines. Examples of the hydroxyl group-containing ethylenically unsaturated monomer in the present invention include β-hydroxyethyl (meth)acrylate, β-hydroxypropyl (meth)acrylate, and the like. The amount of the hydroxyl group-containing ethylenically unsaturated monomer used is 10 to 50% by weight based on the total monomer mixture. If it is used in an amount less than 10% by weight, the stability of the resulting aqueous dispersion will decrease. On the other hand, if more than 50% by weight is used, water resistance and alkali resistance will decrease. In the present invention. As the ethylenically unsaturated carboxylic acid, one or more types are appropriately selected and used from monobasic acids such as acrylic acid, methacrylic acid, and crotonic acid, dibasic acids such as fumaric acid, itaconic acid, and maleic acid, and their anhydrides. can do.
The amount of the ethylenically unsaturated carboxylic acid used is 0.5 to 2% by weight based on the total monomer mixture, and if it is used in an amount less than 0.5% by weight, it will interfere with the fluidity and water dilutability of the printing ink. When the amount exceeds % by weight, the water resistance and alkali resistance of the printing ink film, especially the alkali resistance, tend to deteriorate significantly. In addition to the above-mentioned functional group-containing monomers, (meth)
Methyl acrylate, ethyl (meth)acrylate,
Acrylic acid or methacrylic acid esters such as propyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, azinidyl (meth)acrylate, styrene, α-methylstyrene, etc. The styrene monomer, acrylamide and its derivatives, 2- and 4-vinylpyridine, N-vinyl 2-pyrrolidone, etc. can be appropriately selected and used. Among the monomer components mentioned above, (meth)acrylic acid ester and styrene monomer are particularly important as components forming the skeleton of the aqueous resin dispersion, and in order to control the hardness of the dispersion,
It is preferable to use a combination of a so-called hard component and a soft component. In addition, monomers selected from acrylamide and its derivatives, vinylpyridine, and N-vinyl 2-pyrrolidone are effective in improving the pigment color development and water dispersion stability of the ink, and the monomers selected from acrylamide and its derivatives, vinylpyridine, and N-vinyl 2-pyrrolidone are effective in improving the pigment color development and water dispersion stability of the ink. % or less is preferable. The copolymer of the present invention is prepared by adding a monomer mixture of di-t-butyl peroxide, benzoyl peroxide, 2,2' - It can be obtained by radical polymerization in the presence of a radical polymerization initiator such as azobisisobutyronitrile. The copolymer obtained by radical polymerization can be neutralized with ammonia or organic amines such as trimethylamine, triethylamine, dimethylethanolamine, diethylethanolamine, etc. to a pH range of 6 to 11 to obtain an aqueous resin dispersion. . The water-based resin dispersion according to the present invention is produced by blending general inorganic pigments and organic pigments as coloring agents using a kneading machine such as a ball mill, attritor, or sand mill, and using water and water as solvents. Alternatively, the desired aqueous printing ink is produced by blending the lower alcohols mentioned above, blending wax and other additives as an anti-wear agent as necessary, and kneading. The acid value of the solid content of the aqueous resin dispersion in the present invention, that is, the number of mg of potassium hydroxide necessary to neutralize the organic acid contained in 1 g of the resin solid content is 3 to 16, and within this range, the present invention The desired excellent performance of the water-based printing ink is demonstrated. In terms of weight average molecular weight, a weight average molecular weight of 3,000 to 80,000 is preferable in terms of physical properties, and can be adjusted within the above range by selecting the type of polymerization initiator, the method of use, and the selection of a solvent with an appropriate chain transfer constant. At the time of printing with the obtained aqueous printing ink, the viscosity can be adjusted to be suitable for printing methods such as the gravure method and the flexo method using water and/or the above-mentioned lower alcohols. Examples will be described below. In the examples, parts indicate parts by weight. Example 1 Monomer component (a) Acrylic acid 0.5 parts Methyl methacrylate 30 parts Ethyl acrylate 39.5 parts Diacetone acrylamide 10 parts β-hydroxyethyl acrylate 20 parts 100 parts of isopropyl alcohol in a four-necked flask saturated with nitrogen gas Prepare at 80-82℃,
Monomer components put into the dropping funnel while stirring and mixing
(a) Add the entire amount and 2 parts of 2,2'-azobisisobutyronitrile (hereinafter abbreviated as AIBN) dropwise over 2 hours, and then add 0.5 parts of AIBN every hour. The reaction was continued for 2 hours and for an additional 2 hours. After lowering the reaction system to about 40℃ and adding about 15 parts of 25% aqueous ammonia and stirring well, about 60 parts of isopropyl alcohol is distilled out while blowing nitrogen gas into the solution at 80 to 82℃, and the same parts by weight of ions are distilled out. After adding exchanged water and lowering the temperature of the reaction system to 40°C, the pH was adjusted to 8.5 with 25% aqueous ammonia. Resin solid content 30%, acid value of solid content 4, viscosity 600 cps
(25℃) water-based resin dispersion (referred to as vehicle (A))
I got it. Next, a printing ink was obtained using the following recipe and operation. Vehicle (A) 10 parts Styrene-acrylic acid copolymer (30% solution) 10 parts Phthalocyanine blue 9 parts Polyethylene powder wax 2 parts Isopropyl alcohol 5 parts Water 10 parts The above ingredients were placed in a pepple ball mill and ground for 16 hours. Thereafter, 40 parts of vehicle (A), 5 parts of n-propyl alcohol, and 19 parts of water were blended to obtain a water-based printing ink with a viscosity of 40 seconds (Zahnkapp #3, the same applies to the following examples). Add this printing ink to a viscosity of 30 seconds with water/
Surface tension: 47 dyn
cm, 25μ thick reinforced polyethylene film (Trademark HIZEX 7000 manufactured by Mitsui Petrochemical Co., Ltd., Masterbatch 10020 White 3% manufactured by Toyo Ink Manufacturing Co., Ltd.)
Printed using a gravure plate with a plate depth of 28μ. Table 1 shows the results of various performance tests of this ink. Example 2 Monomer component (b) Methacrylic acid 1.0 parts Methyl methacrylate 20 parts Styrene 5 parts N-vinyl 2-pyrrolidone 10 parts β-hydroxypropyl methacrylate 30 parts Butyl acrylate 34 parts The above monomer component (b) Example 1 except that instead of 3 parts of AIBN used in Example 1, 5 parts of benzoyl peroxide (hereinafter abbreviated as BPO) was added at a rate of 3 parts at first and 1 part every hour thereafter.
By the same operation as above, an aqueous resin dispersion solution (referred to as vehicle (B)) having a solid content of 30%, an acid value of solid content of 7, and a viscosity of 1200 (25°C) and PH8.4 was obtained. Next, the following ingredients were kneaded in exactly the same manner as in Example 1, and 30 parts of vehicle (B) and 5 parts of ethyl alcohol were added.
1 part and 8 parts of water to obtain a water-based printing ink with a viscosity of 30 seconds. Vehicle (B) 25 parts carbon black (Tokai Seast Co., Ltd.)
300) 10 parts polyethylene powder wax 2 parts isopropyl alcohol 5 parts water 15 parts This printing ink was diluted with a mixed solvent of water/isopropyl alcohol (1/1) to a viscosity of 17 seconds, and an easily adhesive polypropylene film with a thickness of 25μ was prepared. (Toray
Co., Ltd. YS-42) was used for gravure printing. Table 1 shows the results of various performance tests of this ink. Further, as a result of measuring the residual solvent in the printed matter obtained above, it was found that the amount of isopropyl alcohol was 50 ppm and the amount of ethyl alcohol was 30 ppm per 0.2 m ² of printed matter. Example 3 Monomer component (c) Itaconic acid 2.0 parts Methyl methacrylate 40 parts Partial sodium salt of aminomethylpropylacrylamide sulfonic acid 5 parts β-hydroxyethyl methacrylate 40 parts Butyl acrylate 13 parts Above monomer component (c) Using the same procedure as in Example 2 except that EPO used in Example 2 was replaced with AIBN, the solid content was 30% and the solid content was oxidized.
15. An aqueous resin dispersion solution (referred to as vehicle (C)) with a viscosity of 800 cps (25°C) and a pH of 8.5 was obtained. Next, the following ingredients were kneaded in exactly the same manner as in Example 1, and 30 parts of vehicle (C) and 4 parts of ethyl alcohol were added.
1 part and 8 parts of water to obtain a water-based printing ink with a viscosity of 45 seconds. Vehicle C 25 parts Phthalocyanine blue 16 parts Polyethylene powder wax 2 parts Isopropyl alcohol 5 parts Water 10 parts This printing ink was diluted with a mixture ratio of isopropyl alcohol/water (6/4) to a viscosity of 35 seconds, and processed using polyethylene treated for milk cartons. Flexo printing was performed on coated paper (manufactured by Wahauser Co., Ltd.). Table 1 shows the results of various performance tests of this ink. Comparative Example 1 Monomer component (d) Styrene 20 parts Ethyl acrylate 30 parts β-hydroxyethyl acrylate 50 parts Using the above monomer components, resin synthesis was carried out in the same manner as in Example 3, but the ammonia water was It was used only for pH adjustment. Solid content 30%, viscosity
An aqueous resin dispersion solution (referred to as vehicle (D)) of 1100 cps (25° C.) and pH 8.5 was obtained. Next, a water-based printing ink with a viscosity of 60 seconds was obtained by the same procedure as in Example 2, except that the same amount of vehicle (D) was used in place of the vehicle (B) used in Example 2. This printing ink was diluted to 17 seconds with a mixed solvent of water/isopropyl alcohol (1/1), and printing was carried out in the same manner as in Example 2, and its performance was comparatively tested. The results are shown in Table 1. Comparative Example 2 Monomer component (e) Methyl methacrylate 40 parts Acrylic acid 5 parts β-hydroxyethyl acrylate 20 parts Ethyl acrylate 35 parts Using the above monomer components, a solid content of 30% was prepared in the same manner as in Example 3. Solid content oxidation 39, viscosity 950cps
(25℃) PH8.4 aqueous resin dispersion solution (vehicle (E)
) was obtained. Next, a water-based printing ink with a viscosity of 50 seconds was obtained by the same operation as in Example 3, except that vehicle (B) was used in an equal amount in place of vehicle (C) used in Example 3. This printing ink was diluted with a mixed solvent of isopropyl alcohol/water (6/4) to a viscosity of 35 seconds and printed in the same manner as in Example 3, and its performance was comparatively tested. The results are shown in Table 1. Comparative Example 3 Monomer component (f) Methyl methacrylate 15 parts Acrylic acid 4 parts Hydroxyethyl diacetone acrylamide
15 parts β-hydroxyethyl methacrylate 48 parts Butyl methacrylate 20 parts Using the above monomer components, the same procedure as in Example 2 was performed to obtain a solid content of 30%, a solid content of oxidation of 32, and a viscosity of 930 cps.
(25℃) PH8.5 aqueous resin dispersion solution (vehicle (F)
) was obtained. Next, a water-based printing ink with a viscosity of 34 seconds was obtained by the same operation as in Example 1, except that vehicle (F) was used in an equal amount in place of vehicle (A) used in Example 1. This printing ink was diluted with a mixed solvent of water/isopropyl alcohol (4/6) to a viscosity of 30 seconds and printed in the same manner as in Example 1, and its performance was comparatively tested. The results are shown in Table 1. Comparative example 4 Cierasch alcoholic aqueous solution (solid content 35%)
20 parts Phthalocyanine blue 9 parts Polyethylene powder wax 2 parts Isopropyl alcohol 7 parts Water 6 parts The conventional water-based ink shown in the above formulation was milled under the same conditions as in Example 1 to adjust it to a water-based printing ink with a viscosity of 30 seconds. Printing was performed using this printing ink in the same manner as in Example 1, and its performance was compared and tested. The results are shown in Table 1. Table 1 shows the results of examining the printing suitability and stability over time of the inks obtained in Examples 1 to 3 and Comparative Examples 1 to 4, the printing effect of the obtained printed matter, and various durability tests of the printing ink film. Indicated. As is clear from Table 1, the water-based printing ink of the present invention has an excellent balance of printability, printing effect, processability, water resistance, and alkali resistance.

[Table] Test method Adhesion Cellophane adhesive tape (Nichiban
Co., Ltd. (width 12 mm)) and rub it vigorously with your thumb 5 times. The degree of peeling of the ink and film was evaluated by gradually pulling apart the cellophane adhesive tape and then abruptly pulling it off halfway. Odor A certain amount of the printed material was placed in an odor bottle and placed in an oven at 50°C for 4 hours, after which the sensory odor was evaluated. Friction resistance Loaded using a Gakushin type friction resistance tester
The printed surface was rubbed with high-quality paper under the conditions of 500 gr and 30 times, and the degree of damage to the printed surface and the stain on the superior paper were evaluated. Water friction resistance Using a Gakushin type friction resistance tester,
The printed surface was rubbed with a hydrated calico under the conditions of 40 times of 500 g, and the degree of damage to the printed surface and the stain on the calico were evaluated. Alkali resistance Using the same test machine, with a weight of 500
The print was rubbed with a dial coated with 1% NaOH under the conditions of 40 g times, and the degree of damage to the printed surface and the stain on the dial coat were evaluated. Rub resistance The printed surface was rubbed with fingertips and the degree of ink peeling was evaluated. Scratch Resistance Scratch the printed surface with your fingertips to evaluate the occurrence of scratches on the printed surface. Bending resistance The printed surface was bent 3 to 5 times at 180° and the degree to which the ink peeled off was evaluated. Blocking resistance 60℃×60%RH×500g/ ^cm2
Overlap the surfaces at x8hr and evaluate the degree of blocking. All of the above are displayed in 5 levels, 5 (extremely good)
~1 (defective), and in practical terms it is 4 or more.

Claims (1)

[Claims] 1. A copolymer obtained by radical polymerization of a monomer mixture containing 10 to 50% by weight of a hydroxyl group-containing ethylenically unsaturated monomer and 0.5 to 3% by weight of an ethylenically unsaturated carboxylic acid based on the total monomer components. 1. An aqueous printing ink characterized by using as a vehicle component an aqueous resin dispersion whose solid content has an acid value of 3 to 16, which is obtained by neutralizing it with ammonia or organic amines. 2 The monomer mixture further comprises acrylamide and its derivatives, vinylpyridine, and N-
1 selected from the group consisting of vinyl 2-pyrrolidone
The water-based printing ink according to claim 1, which contains 10% by weight or less of one or more types of nitrogen-containing ethylenically unsaturated monomers.