JPH042633B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an aqueous printing ink composition, and particularly to an ink composition that has excellent adhesion to corona discharge treated polyolefin film and is suitable for lamination. Conventionally, polyolefin film has been widely used as a food packaging material because it has excellent hygiene properties, heat-sealability, and is inexpensive. However, since polyolefin film has poor polarity, it does not have adhesion with printing ink. Therefore, the adhesion can be improved by kneading a filler into the polyolefin in advance or by applying corona discharge treatment to the film surface. In particular, corona discharge treatment is the most advantageous in terms of cost. As printing inks used for corona discharge treated polyolefin film, organic solvent type inks such as nitrified cotton/polyamide based, nitrated cotton/maleic acid resin based, nitrated cotton/polyurethane based, and chlorinated polypropylene based inks are used. In addition, organic solvents such as hydrocarbons, esters, and ketones are added to dissolve the resin, resulting in problems with residual solvents, hygiene issues, and the volatilization of organic solvents into the atmosphere. Water-based printing inks are desired from the standpoint of saving resources and energy, and some are being put into practical use. Conventional vehicles for water-based printing inks include silica, rosin-modified maleic acid resin, styrene-acrylic acid resin, acrylic ester-acrylic acid resin, hydroxyethyl cellulose, and water-soluble polyester. Although the ink adheres to expensive modified polyolefin film, it has poor adhesion to relatively inexpensive corona discharge treated polyolefin film, and it also causes plate clogging in gravure printing.
There are problems such as a lack of printability such as plate fog, a lack of printing effects such as curvature of printed matter, and a lack of stability during ink storage. Conventionally, back-printed composite films have been used as transparent flexible packaging materials for ramen noodles, confectionery, etc. In other words, front packaging materials such as polypropylene film (OPP) / printing ink / adhesive / polypropylene film (CPP) or polyethylene film, etc. Many films are processed by dry lamination or extrusion lamination such as packaging material/printing ink/anchor coating agent/polyethylene melt coating, and currently there is no known water-based printing ink that can withstand this process. The present invention was completed as a result of intensive research to solve the above-mentioned problems, and the first purpose is to obtain a water-based printing ink with excellent printing effects and printability. The purpose of the present invention is to obtain a water-based printing ink that has sufficient adhesive strength to corona discharge treated polyolefin film, and a third purpose is to obtain a water-based printing ink that can withstand lamination. That is, the present invention comprises 1 to 10% by weight of a carboxyl group-containing vinyl monomer (1) containing the following formula in the molecule. (However, in the formula, R is a hydrogen atom or a methyl group, and n is an integer of 2 to 50.) Contains 3 to 40% by weight of a vinyl monomer (B) containing a polyalkylene oxide group, and other hydroxyl groups. Ammonia or amine is added to an acrylic copolymer obtained by solution polymerizing a monomer mixture consisting of 0 to 30% by weight of a vinyl monomer (C), and the remainder is another copolymerizable vinyl monomer (D), and The present invention provides an aqueous printing ink composition whose vehicle component is a resin solution dissolved in . The carboxyl group-containing vinyl monomer (A) in the present invention includes acrylic acid, methacrylic acid, itaconic acid, crotonic acid, etc., and is used in an amount of 1 to 10% by weight, preferably 3 to 7% by weight.
If the amount used is too small, it will be difficult to water-solubilize it, and if it is too large, the adhesive strength during extrusion lamination will be reduced. Examples of the vinyl monomer (B) containing a polyalkylene oxide group in the molecule include polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, N-
(Polyoxyalkylene)-(meth)acrylamide or alkyl etherified products thereof, etc. Those in which n in the general formula is 2 to 50, preferably 4 to 25 are used, and the amount used is 3 to 40. % by weight, preferably in the range 5-25% by weight. If the amount used is too small, it will cause a decrease in adhesion to the corona-treated polyolefin film, a decrease in the printing effect, and a decrease in suitability for lamination, and if it is too large, no increase in the effect can be expected and the cost will increase, which is undesirable. As a vinyl monomer (C) containing a hydroxyl group,
2-hydroxyethyl (meth)acrylate, 2
-Hydroxypropyl (meth)acrylate, etc., used in an amount of 0 to 30% by weight, preferably 1 to 30% by weight
In the range of 20 parts by weight. If too much is used, the flexibility of the ink film will decrease, resulting in insufficient adhesive strength when laminated, but the adhesive strength will increase due to reaction with the adhesive (urethane type) during dry lamination. Therefore, it is preferable to use 1% by weight or more. Other copolymerizable vinyl monomers (D) include:
(Meth)acrylic acid alkyl esters having an alkyl group having 1 to 8 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, 2- Examples include ethylhexyl (meth)acrylate, styrene, vinyltoluene, vinyl acetate, and N-methylol (meth)acrylamide. In the present invention, solution polymerization of the above monomer mixture may be carried out by a method known per se, for example, iso-propyl alcohol or the like in the presence of an initiator that generates a radical group such as azobisisobutyronitrile or benzoyl peroxide. polymerize in an organic solvent. The amines necessary for neutralizing the obtained acrylic copolymer include dimethylethanolamine, diethylethanolamine, and morpholine, and then, if necessary, part of the organic solvent during polymerization is distilled off. Dissolve the resin in an aqueous medium. The polyalkylene oxide group-containing vinyl monomer (B) used in the present invention has also been attempted to be used as an emulsifier during emulsion polymerization, but if such emulsion is used as a vehicle for aqueous printing ink, plate clogging may occur. Cause. On the other hand, in the present invention, since solution polymerization is performed, the molecular weight is relatively small, and the resin solution differs in certain respects, and no deterioration in printing suitability such as plate clogging occurs. The aqueous printing ink composition according to the present invention is obtained by adding a coloring agent such as a pigment, a filler, and other necessary additives and kneading the composition as is known in the art. This printing ink is applied to paper, plastic, metal boxes, etc., and exhibits superior effectiveness compared to known water-based inks when applied to corona discharge treated polyolefin film and lamination processing applications. It is. The present invention will be explained in more detail below using specific examples. The middle part of the example shows parts by weight. Example 1 In a four-necked flask equipped with a stirrer, a thermometer, and a nitrogen gas inlet tube, add 150% iso-propyl alcohol.
heat to 83°C and maintain this temperature. Next, 4 parts of the monomer mixture and polymerization initiator shown in Table 1 were added dropwise over 2 hours, and then 3 parts of the polymerization initiator were added dropwise over 2 hours.
Continue the time reaction. After that, 136 parts of ammonia water and water shown in Table 1 were added, azeotropically distilled off a part of the iso-propyl alcohol, and water/iso-
A vehicle was obtained in which the proportion of propyl alcohol was 8/2 (weight ratio) and the resin solid content (40% by weight).

[Table] Next, using each vehicle obtained in this way, each printing ink was kneaded according to the following recipe in a conventional manner, and water and ethyl alcohol were mixed in equal amounts in a Zahn cup #3 for 17 seconds (25°C). It was diluted with a solvent and gravure printed on a corona discharge-treated polypropylene film (Torejuan #2535, trade name manufactured by Toray Industries, Inc.), and tested for inkability, adhesion, bending resistance, and printing effect 24 hours after printing. , the results are shown in Table 2. Vehicle 45 Lionol Blue KLH 15 (phthalocyanine pigment manufactured by Toyo Ink Manufacturing Co., Ltd.,
Trademark name) Industrial ethyl alcohol 20 Water 10 Isopropyl alcohol 10 In addition, each printed material is treated with a polyethyleneimine anchor coating agent and then coated with polyethylene, and each printed material is coated with an adhesive (Toyo Morton Co., Ltd.). A polyethylene film was dry laminated after applying Adcoat (trade name) manufactured by Manufacturer Co., Ltd., and the strength was measured after aging at 40°C for 2 days. The results are shown in Table 2. Suitability for making ink is determined by fluidity, adhesion is determined by the peeling strength of cellophane adhesive tape, bending resistance is determined by the peeling state when the print is rubbed, and printing effect is determined by the gradation reproducibility of the printed material and the ink. Judgments were made based on the state of color development.

[Table] The evaluations in Table 2 are as follows: ◯: good, △: slightly poor, ×: poor.

Claims (1)

[Claims] 1 Carboxyl group-containing vinyl monomer (A) 1 to 10
Weight%, the following formula in the molecule (In the formula, R is a hydrogen atom or a methyl group, n is 2
Indicates an integer between ~50. ) Vinyl monomer (B) containing a polyalkylene oxide group represented by 3~
Ammonia or amine is added to an acrylic copolymer prepared by solution polymerizing a monomer mixture of 40% by weight, 1 to 20% by weight of a hydroxyl group-containing vinyl monomer (C), and the balance of other copolymerizable vinyl monomers (D). A water-based printing ink composition for corona discharge treated OPP that is used for lamination processing, which contains a resin solution added and dissolved in an aqueous medium as a vehicle component.