JP3028680B2 - Water-based printing ink for plastic film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

This invention relates to aqueous printing inks. More specifically, the present invention relates to an aqueous printing ink having good wettability in various printing processes for various plastic film substrates and excellent adhesiveness and suitability for laminating.

[0002]

2. Description of the Related Art Today, polyethylene, polypropylene,
Plastic films such as polyester and nylon are widely used as various packaging materials, and printing on these plastic films is performed by a gravure or flexographic printing method. Conventionally, solvent inks using an organic solvent such as toluene, ethyl acetate, or isopropyl alcohol as a medium have been exclusively used for such applications. In recent years, however, air pollution, fire danger, work hygiene, etc. In view of the above, there is an increasing interest in aqueous inks that do not use organic solvents.

[0003] When a permeable paper is used as a printing medium, there are few problems of drying of the aqueous ink and uniform wetting of the substrate, and it is relatively easy to secure various performances such as adhesion.
Practical application is progressing. On the other hand, when a non-penetrable plastic film is used as the printing medium, in addition to the drying property of the aqueous ink, uniform wettability and adhesion to the substrate, and applicability to post-processing such as various laminating processes. The problem had not been solved, and practical application was extremely difficult.

[0004] Regarding wetting, aqueous inks containing water as a main solvent have a high surface tension, and can be used for corona discharge-treated polyolefin films (surface tension of 36 to 38 dyne / cm) which are most commonly used for packaging. However, even when an alcohol having a surface tension lowering effect is used in combination during printing, sufficient wetting could not be achieved, repelling of the obtained printing surface was remarkable, and it was difficult to obtain a uniform and smooth printing surface. As a means of improving wetting, attempts have been made to introduce various additives for lowering the surface tension and to increase the alcohol ratio to be used. However, sufficient effects cannot be achieved. Not preferred.

In the industry of printing on plastic films, in recent years, smaller lots and diversification of varieties have progressed, and in order to cope with this, so-called general-purpose inks that can be adhered to various plastic films and adapted to various uses are used. The use of such inks has been aimed at improving work efficiency and economic efficiency, and there is a demand for a technique for bonding aqueous inks to various substrates.

As an attempt to improve the adhesion to a plastic film, Japanese Patent Application Laid-Open No. 61-19676 discloses a method in which an alkali solution of a styrene acrylic copolymer is mixed with an acrylic emulsion having a specific glass transition temperature range. A water-based printing ink that imparts adhesion to various plastic substrates and suitability for lamination processing by adding a rosin ester as a tackifier in the form of an aqueous dispersion is disclosed. Further, JP-A-3-7783 discloses a composition used for an aqueous ink or the like, which comprises an aqueous dispersion containing a rosin component in a polymer composed of an aqueous acrylic copolymer or polyurethane. I have.

However, the addition of an aqueous dispersion such as rosin improves the wettability of a generally used corona-discharged polyolefin film even when the adhesion strength to various film substrates is improved. There was a drawback that a smooth printed surface could not be obtained.

[0008]

The inventors of the present invention have conducted intensive studies to solve such a problem, and as a result, have obtained an acid value of 80 to 330.
(KOH mg / g) rosin-modified maleic acid resin is neutralized with an alkali, and is uniformly dissolved in water or a water / alcohol mixed solvent, and is contained in the printing ink at a specific compounding ratio. at the same time make increase adhesion to corona discharge treated polyolefin, a laminate strength,
Significantly lower the surface tension of the printing ink, corona discharge treatment
The present inventors have found that they have an effect of improving the wettability of the treated polyolefin film , and have reached the present invention.

[0009]

That is, the present invention provides:
(B) An acid value of 80 to 80 contained in the aqueous binder resin
330 (KOH mg / g) alkali of rosin-modified maleic resin
An aqueous printing ink for a plastic film , wherein the neutralized product is in the range of 2 to 20% by weight of (b) .

Examples of the rosin component of the rosin-modified maleic acid resin include tall oil rosin, gum rosin and wood rosin containing abietic acid, dehydroabietic acid, neoabietic acid, parastolic acid, pimaric acid and isopimaric acid as main components. Rosin-modified maleic resin is an adduct of these rosin and maleic anhydride by Diels-Alder reaction and glycerin, pentaerythritol,
It is an esterified product with a polyhydric alcohol such as ethylene glycol, and the acid value is determined by the mixing ratio of the raw materials and the degree of esterification.

The acid value of the rosin-modified maleic resin is 80 to 33.
A range of 0 (KOH mg / g) can be used, but 100-300
(KOH mg / g) is more preferred. When the acid value is less than 80 (KOH mg / g), the alkali-neutralized product has insufficient water solubility,
Poor wetting of low surface tension plastic substrates. On the other hand, if the acid value exceeds 330 (KOH mg / g), the hydrophilicity is too strong, and the water resistance of the obtained ink film is remarkably reduced, which is a practical problem.

The alkali used for neutralizing the rosin-modified maleic resin is not particularly limited as long as it is neutralized and can be uniformly dissolved in water or a mixed solvent of water / alcohol, and examples thereof include ammonia, organic amines and inorganic alkalis. However, the use of ammonia or a volatile organic amine is preferred for maintaining the water resistance of the dried film of the ink composition.

The aqueous binder resin (b) other than (a) is a water-soluble or water-dispersible resin, for example, a polymerizable resin such as (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, etc. Unsaturated carboxylic acids or their anhydrides, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, (meth) acrylic acid
(Meth) acrylates such as 2-ethylhexyl, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and (meth) acrylic acid other than (meth) acrylic acid such as (meth) acrylamide and acrylonitrile ) Acrylic resins, polyurethane resins, carboxyl groups and / or sulfones obtained by copolymerizing acrylic monomers and, if necessary, α-methylstyrene, vinyl acetate, etc. by a polymerization method such as emulsion polymerization, solution polymerization, or bulk polymerization. Polyester resin, shellac resin, polyamide resin and their modified products containing acid metal base, compatible with rosin-modified maleic resin, plastic
Any material that can produce a stable aqueous printing ink for a film may be used, and may be used alone or in combination.

(B) Aqueous binder in aqueous printing ink
(A) Log of acid value 80-330 (KOH mg / g) contained in resin
Weight percent of the alkali-neutralized product of the modified maleic acid resin
(B) in the range of 2 to 20% by weight, preferably 5 to 15%.
% By weight. If (a) is less than 2 wt%, wettability is insufficient with respect to the polyolefin film surface tension is subjected to weak corona discharge treatment of approximately 36 dyne / cm, with uniform and smooth printing surface can not be formed , Adhesion, and lamination strength when subjected to lamination are insufficient. (A) When more than 20% by weight, relative to the polyolefin film that has been subjected to weak have corona discharge treatment of approximately 36 dyne / cm, wettability and adhesion although improved, cohesion of the dried ink film is reduced Therefore, the lamination strength of the laminated product is weak, and the water resistance of the dried film is also lowered , which is not preferable.

In the printing ink, general inorganic and organic pigments can be used as a colorant. For example, soluble and insoluble organic pigments such as azo, phthalocyanine and naphthol, titanium oxide, carbon black, red iron oxide, calcium carbonate,
Inorganic pigments such as barium sulfate; Although water is used as the solvent, alcohols, preferably lower alcohols such as ethyl alcohol, isopropyl alcohol and normal propyl alcohol may be used in combination. In addition, a wax, an antifoaming agent, a dispersant, or the like may be used as the anti-wear agent.

The printing ink is manufactured by kneading the meat using an attritor, a sand mill, a high-speed stirrer, etc., which are usually used in the production of gravure and flexographic printing inks, and adjusting the viscosity to a predetermined value. Is done. The resulting printing ink is diluted with water until it has the proper viscosity during printing,
Printed on plastic film. As a diluent, alcohols and water can be mixed and used as needed for the purpose of drying adjustment.

[0017]

The present invention will be described below with reference to examples. In the examples, “parts” means “parts by weight” and “%” means “% by weight”.
100 parts of a mixture having the composition shown in Table 1 was kneaded with a ball mill for 24 hours to prepare an aqueous printing ink. Table 2 shows the ingredients
Put together.

[0018]

[Table 1]

[0019]

[Table 2]

The surface tension of the obtained aqueous printing ink at 25 ° C. was measured using KYOWACBVP SURFACE TENSI manufactured by Kyowa Kagaku Co., Ltd.
Measured by OMETER A1. Table 3 shows the measurement results.
Then, apply the aqueous printing ink to Cup No.
And diluted with water so that the temperature becomes 16 seconds at 25 ° C. Using a gravure printing machine (plate: electronic engraving plate 250 lines / inch), a corona discharge treated stretched polypropylene film with a surface tension of 38 dyne / cm (Toyobo Co., Ltd.) (Pyrene P2161 20μ) was printed at 50 m / min and dried with hot air at 60 ° C, and the smoothness, adhesion and water resistance of the obtained printed matter were evaluated.

Further, a polyethyleneimine-based anchor coat agent (EL420, manufactured by Toyo Morton Co., Ltd.) is applied on the printing surface of the obtained printed material, and low-density polyethylene (Yukaron LK30, manufactured by Mitsubishi Yuka Co., Ltd.) is applied on the coated surface. ) Was extrusion-laminated to a thickness of 40 μm, and the laminate strength of the obtained laminate was measured. Table 3 shows the measurement results.

Each evaluation was performed according to the following method. 1) Smoothness The surface condition of the printed matter was visually judged as follows. ：: No repelling or slipping out, forming a smooth surface state △: Slight repelling or slipping out, lacking in forming a smooth surface state ×: Repelling and slipping out, forming a smooth surface state Something not

2) Adhesion Peeling was performed using Nichiban cellophane tape 12 mm wide.
It was determined as follows. 5: No peeling when abruptly separated 3: Peeling when abruptly separating, but not peeling when gradually separating 1: 1: Peeling even when gradually separating

3) Water resistance The printed material was rubbed with absorbent cotton soaked in water and the number of times until the ink film disappeared was determined as follows. 5: 100 times or more 4: 60 to 100 times 3: 30 to 60 times 2: 10 to 30 times 1: 10 times or less 4) Extrusion lamination strength After leaving the obtained laminate for 2 days, cut into a 15 mm width. ,
The T-peel strength (g / 15 mm width) was measured using a tensile tester.

[0025]

[Table 3]

[0026]

According to the present invention, it has become possible to provide an aqueous printing ink which has good wettability to various plastic films, excellent adhesiveness, and excellent lamination strength when subjected to lamination.

Claims (2)

(57) [Claims] (B) contained in an aqueous binder resin
(A) Rosin-modified maleic acid with an acid value of 80 to 330 (KOH mg / g)
The alkali neutralized resin is in the range of 2 to 20% by weight of (b).
A water-based printing ink for plastic films , characterized in that: 2. An aqueous binder resin (b) other than (a)
The aqueous printing ink for a plastic film according to claim 1, wherein the component comprises at least one selected from an acrylic resin, a polyurethane resin, a polyester resin, and a shellac resin.