JPH08269381A - Water-based printing ink - Google Patents

Abstract

PURPOSE: To prepare a water-based printing ink for polypropylene(PP) films, etc., suitable for a lamination-processing of PP films after printing by allowing to contain a chlorinated polypropylene in a water-based ink containing a water soluble or a water dispersible resin as a vehicle. CONSTITUTION: This water-based ink suitable for gravure or flexography on polypropylene films and a successive lamination processing of the polypropylene films is obtained by blending 2.0-100.0wt.% chlorinated polypropylene (based on the solid resin in the ink) having 5000-200000 weight average molecular weight and 10-40wt.% chlorine content to a water-based printing ink prepared by mixing a water soluble and/or a water dispersible resin [e.g.; a styrene-(meth) acrylic acid copolymer resin, etc.] used as a vehicle with a pigment such as titanium oxide, phthalocyanine blue, etc., and water etc., and diluting the blended mixture with a mixture of water with the same volume of isopropyl alcohol.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based printing ink suitable for laminating after gravure or flexographic printing on a polypropylene film, and more specifically, after printing on a corona discharge treated stretched polypropylene film, an anchor coat is applied on the printing surface. It relates to a water-based printing ink suitable for melt extrusion and lamination of polypropylene without agents.

[0002]

2. Description of the Related Art In recent years, various plastic films have been developed as a packaging material in accordance with the diversification of packaging objects and the sophistication of packaging technology, so that a material suitable for the packaging object can be appropriately selected and used. It has become to. Further, when plastic films are used as packaging materials, they are printed for decoration or surface protection of the plastic films, and the printing ink for such printing has high performance and quality for these various plastic films. It is becoming required. In particular, for printing inks, a wide range of adhesiveness to various composite films and further post-processing suitability such as suitability for laminating, suitability for boil, suitability for retort and the like have become necessary for making packaging containers more beautiful and sophisticated.

Further, in order to improve the performance of the packaging material, dry laminating or extrusion laminating may be performed after printing. In this case, an adhesive such as urethane is used for dry laminating, and an anchor coating agent is used for extrusion laminating. Further, an aluminum foil may be interposed in the middle so that the packaging material can be boiled or retort processed. Although strength up to retort processing is not required, in the field of packaging materials based on transparent substrates, corona discharge treated stretched polypropylene (OPP) is used as the substrate film and directly coated with molten polypropylene without using an anchor coating agent. A laminating method (PP direct laminating) is also used.

In order to carry out such post-processing, it is required that the printing ink used in the preceding step has not only the adhesiveness to various substrate films and printability but also the suitability for each post-processing. It Solvent-based printing inks using a chlorinated polyolefin having a relatively high degree of chlorination such as chlorinated polypropylene as a binder are mainly used for the polyolefin to be subjected to PP direct lamination. However, since these solvent-based inks contain a large amount of organic solvent in the ink and in the diluting solvent, solvent vapors will be present in the printing work environment, which may have an unfavorable effect on health for workers. Not only is it given, but there is also the danger of fire, which is not desirable. Further, when a solvent-based ink is used, an organic solvent harmful to the human body remains in the laminate, and when used in food packaging, the residual solvent easily migrates to the food, which is not preferable in food hygiene.

Therefore, practical application of an aqueous printing ink containing no harmful organic solvent has been studied. Conventional shellac,
Shellac modified styrene resin, styrene- (meth) acrylic acid copolymer resin, (meth) acrylic acid alkyl ester- (meth) acrylic acid copolymer resin, styrene-
(Meth) acrylic acid alkyl ester- (meth) acrylic acid copolymer resin, urethane resin or a water-based printing ink having a resin made of a mixture thereof as a vehicle, a dry lamination process using a urethane adhesive, and an anchor coat It is general that the composition has the suitability for extrusion lamination using the agent.

Japanese Patent Laid-Open No. 2-169797 discloses a printed matter containing finely pulverized polyethylene and / or oxidized polyethylene having a molecular weight of 300 to 3000 with respect to an aqueous ink and having an average particle diameter of about 20 μ or less. Ink compositions having improved surface performance are disclosed. Further, in Japanese Patent Laid-Open No. 4-366180, 1,000 to 1
Having a molecular weight of 50,000 and an acid value of 20 to 100,
Printing using a corona discharge-treated stretched polypropylene as a base film by using an aqueous ink containing polypropylene oxide having a softening point of 100 to 200 ° C. in an amount of 1.0 wt% to 10.0 wt% with respect to the ink solid content. A method of melt extruding and laminating polypropylene without an anchor coating agent on the surface is disclosed, but the laminating strength is insufficient and it cannot be used for an untreated polypropylene film.

[0007]

DISCLOSURE OF THE INVENTION As a result of intensive studies, the present inventors have made a polypropylene base material by incorporating chlorinated polypropylene into an aqueous printing ink containing a water-soluble and / or water-dispersible resin as a vehicle. In the PP direct laminating process in which the printed surface is directly laminated with molten polypropylene without using an anchor coating agent after gravure and / or flexographic printing, it was found that high laminating strength can be imparted, and the present invention was achieved. The invention provides a water-based printing ink having an improved PP direct laminating suitability by improving the drawbacks of the conventional water-based printing ink.

[0008]

According to the present invention, a water-soluble and / or water-dispersible resin and / or an intermediate hydrosol type resin is used as a vehicle component of a printing ink, and a resin solid component in the ink is used. Is a water-based printing ink for polypropylene, characterized in that the content of chlorinated polypropylene is 2.0 to 100.0% by weight.
The water-soluble and / or water-dispersible resin and / or the intermediate hydrosol type resin used in the present invention include (meth) acrylic acid, (meth) acrylic acid alkyl ester, and other monomers having a (meth) acrylic acid group. , Styrene, α-
(Meth) acrylic acid copolymer resin synthesized from unsaturated carboxylic acid esters such as methylstyrene, maleic acid and fumaric acid, styrene, α-methylstyrene, (meth) acrylic acid copolymer resin, water-soluble or , And natural,
A colloidal aqueous resin synthesized by using a synthetic water-soluble resin as a protective colloid, and styrene, α-methylstyrene,
Emulsion such as (meth) acrylic acid copolymer resin, or water-based polyurethane, water-based polyester resin or the like may be used as long as it has good adhesion to the treated polyolefin film and can produce a stable ink. Can be used.

The chlorinated polypropylene used in the present invention is generally represented by the formula 1 and has CH ₃ CHCH ₃ [CH ₂ C
H (CH ₃ )] m (CH ₂ Cl) n (formula 1) having an average weight molecular weight of 5,000 to 200,000, preferably 10.0.
00 to 100,000, a chlorine content of 10 to 40%, preferably 15 to 30%, and a softening point of 40 to 110 ° C, preferably 50 to 80 ° C are used. These are nonionic surfactants and A surfactant that is an anion activator,
Obtained by dispersing in water using a dispersant such as a water-soluble polymer. The content of chlorinated polypropylene with respect to the resin solid content in the ink is 2.0 to 100.0% by weight, preferably 5.0% by weight or more. If less than 2.0% by weight, PP
Wetting with molten polypropylene during direct lamination is reduced, and good laminating strength cannot be obtained.

The water-based printing ink according to the present invention is obtained by a known production method by adding a coloring material such as a pigment, a filler and other necessary additives. Further, in the water-based printing ink of the present invention, a shellac resin, a rosin-modified maleic acid resin, a carboxylated petroleum resin, a cellulosic resin, and a styrene-maleic acid resin may be used in combination as long as the function thereof is not impaired. Aqueous printing inks composed of these compositions,
It has the effect of increasing the affinity for molten polypropylene, which is necessary to obtain the PP direct laminating strength, and it is considered that stable laminating strength is obtained by this.

[0011]

The present invention will be described below with reference to examples. In the examples, “part” means “part by weight” and “%” means “% by weight”.
Mixture 1 having the composition shown in Table 1 as Examples and Comparative Examples
00 parts were kneaded to prepare an aqueous printing ink. The viscosity of each aqueous printing ink was measured with Zahn cup No. 4 and used as the finish viscosity. Each of the obtained water-based printing inks was diluted with an equal mixture of water and isopropyl alcohol, and the viscosity was adjusted to 16 seconds (25 ° C) with a Zahn cup No. 3 and the gravure printing machine (plate: Helio 200 lines / inch) was used. ) And printed on a corona discharge treated stretched polypropylene film (Pyrene P-2161 20μ manufactured by Toyobo) to evaluate the adhesiveness. In addition, on the printing surface of the obtained printed matter, extrusion lamination was carried out with polypropylene "Mitsubishi Polypro FL-25R" (manufactured by Mitsubishi Yuka Co., Ltd.) without an anchor coating agent, and the laminate strength of the obtained laminate was obtained. Was evaluated.

Each evaluation method is based on the method described below. 1. Adhesiveness After the printed matter was left for one day, a cellophane tape was stuck to the printed surface, and the appearance of the printed film when this was rapidly peeled was observed and evaluated. The evaluation results are shown in Table 2. ◎ ... It did not peel off at all. A: 80% or more of the printed film remained on the film. Δ: 50 to 80% of the printed film remained on the film. X: 50% or less of the printed film remained on the film. 2. PP Direct Lamination Strength The obtained laminate was left for 2 days and then cut into a width of 15 mm to measure T-type peel strength (g / 15 mm width). The evaluation results are shown in Table 2.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

According to the present invention, it is possible to provide a water-based printing ink suitable for extrusion-laminating molten polypropylene after printing on polypropylene without using an anchor coating agent.

Claims (3)

[Claims] 1. A water-based printing ink for polypropylene film, characterized in that a water-based printing ink containing a water-soluble and / or water-dispersible resin as a vehicle contains chlorinated polypropylene. 2. The chlorinated polypropylene has a weight average molecular weight of 5,000 to 200,000 and a chlorine content of 10.
The water-based printing ink according to claim 1, wherein the water-based printing ink is about 40% by weight. 3. The water-based printing ink according to claim 1, wherein the content of chlorinated polypropylene is 2.0 to 100.0% by weight based on the solid resin content of the ink.