JPH09111172A - Water-based printing ink composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a water-based printing ink compsn. which possesses excellent adhesion to various films, resistance to blocking to these films, and laminate strength. SOLUTION: An aq. polyurethane graft copolymer (A) comprising an aq. polyurethane as a backbone polymer component and a polymer, comprising a polymerizable unsatd. monomer as graft chain component, and a water- dispersible polyurethane resin (B) are incorporated as a binder in a component (A) to component (B) wt. ratio of (80:20) to (20:80).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a water-based printing ink composition, and more particularly to a water-based printing ink composition having excellent adhesion to various plastic films, blocking resistance and laminate strength.

[0002]

2. Description of the Related Art Conventionally, various kinds of organic solvent type inks have been used as inks for gravure printing and flexographic printing according to their respective requirements. Above all, a urethane resin or the like is contained as a binder for a plastic film. Things are widely used. However, in recent years, there has been an increasing demand for water-based printing inks due to environmental problems, fire hazards, and occupational health and safety problems.

Further, with the recent improvement in the performance of packaging materials,
There is also an increasing demand for printing inks that are suitable for laminating. Here, the laminating process is to perform dry laminating process or extrusion process after printing, the former is a process method of sticking a film via an adhesive, and the latter is a molten state via an anchor coating agent. It is a processing method of laminating a polymer.

In response to such a demand, various types of water-based printing inks have already been proposed. For example, a water-based printing ink composition using a water-based polyurethane resin (JP-A-5-1).
No. 71091), a water-based printing ink composition for lamination using a water-soluble polyurethane resin and a water-dispersible ethylene-acrylic acid copolymer (JP-A-5-27159), and a water-based printing ink using a modified urethane resin. Composition (JP-A-6-80930, JP-A-7-82456)
No. gazettes) are proposed.

[0005]

However, the binders of water-based printing ink compositions that are known today are not necessarily used for various plastic films, especially treated polypropylene (O).
PP) film, vinylidene chloride coat (K coat) film that is often used for packaging materials that require gas shielding, adhesion to nylon and blocking resistance to these films are not sufficient, and effective laminate strength is also obtained. I couldn't. That is, the water-based polyurethane resin alone had good adhesiveness to OPP and polyethylene terephthalate (PET), but insufficient adhesiveness to the vinylidene chloride coat (K coat) film. Further, this is inferior in anti-plocking property and is not preferable in terms of cost.

Further, in the combined system of the water-soluble polyurethane resin and the water-dispersible ethylene-acrylic acid type copolymer, although the blocking resistance is improved, the adhesion to PET and nylon is insufficient and the laminate strength is also high. Was also insufficient.

Further, although the modified urethane resin shows a well-balanced adhesion to various plastic films, it cannot be said to be sufficient as a whole and the laminating strength is insufficient.

Therefore, an object of the present invention is to provide an aqueous printing ink composition having excellent adhesion to various films including OPP and PET, nylon, and K coat, blocking resistance to these films, and laminate strength. .

[0009]

As a result of intensive studies to solve the above problems, the present inventor has found that a modified urethane resin (A) having a good blocking property and a water-dispersible polyurethane resin (B) having a good laminate strength are used. The present invention has been completed by discovering that by admixing) in a predetermined ratio, good adhesion to all general-purpose films such as PET, OPP, nylon, and K coat film, and sufficient laminate strength can be obtained. Came to do.

That is, the aqueous printing ink composition of the present invention comprises an aqueous polyurethane graft copolymer (A) comprising an aqueous polyurethane as a trunk polymer component and a polymer comprising a polymerizable unsaturated monomer as a graft chain component. The water-dispersible polyurethane resin (B) is contained as a binder in a weight ratio of 80:20 to 20:80.

Preferably, the weight ratio is 60:40 to.
It is 40:60.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The aqueous polyurethane graft copolymer (A) used in the present invention is reported in JP-A-7-82456, and a polyfunctional hydrazide compound,
It is used in the form of a room temperature curable aqueous resin composition comprising an organic solvent miscible with water and water. The trunk polymer component in the graft copolymer is (a) a hydroxyl group-containing monomer having an α, β-ethylenic double bond, (b)
A polyhydroxy compound having at least one carboxyl group and two or more hydroxyl groups, (c) a polyhydroxy compound having two or more hydroxyl groups,
(D) An aqueous polyurethane composed of a polyol-isocyanate polyaddition reaction product composed of (a) to (d) which is an isocyanate compound having two or more isocyanate groups as essential components and a mixed amine of monoamine and diamine. The graft chain component in the graft copolymer is composed of a polymerizable unsaturated monomer group containing a polymerizable unsaturated monomer containing a ketone group or an aldehyde group as an essential component.

The graft copolymer (A) is produced, for example, by the following method. That is, first, a diisocyanate compound, a diol compound, a diol compound containing a carboxyl group, and a hydroxyl compound containing a polymerizable unsaturated group are subjected to a urethane reaction in an organic solvent to prepare a prepolymer. As the diisocyanate compound used at this time, various known aromatic, aliphatic or alicyclic diisocyanates can be used.

As the organic solvent used for urethanization, acetone, methyl ethyl ketone and the like which are inert to isocyanate groups and miscible with water are preferable. Further, examples of the neutralizing agent include amines such as ammonia and trimethylamine, and examples of the chain extender include various known diamines such as ethylenediamine and propylenediamine.

As the molecular weight of the aqueous polyurethane of the present invention, Mw (weight average molecular weight) in terms of polystyrene by gel permeation chromatography is 3,000 to 100,
000, more preferably 5,000 to 50,000.

The acid value of the aqueous polyurethane resin of the present invention is
It is preferably in the range of 10 mg-KOH / g to 200 mg-KOH / g, more preferably 15 to 100 m.
It is in the range of g-KOH / g.

A typical polymerizable unsaturated monomer that is polymerized in the presence of an aqueous polyurethane emulsion having a polymerizable unsaturated bond in its side chain is a vinyl monomer, preferably acrylic acid. Acrylic esters such as methyl, ethyl acrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, and methacrylic acid such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, and glycidyl methacrylate. A monomer mixture containing acid esters and styrene as a main component is selected.

Examples of vinyl monomers having a ketone group include diacetoacrylamide, acrolein and vinyl methyl ketone. Two or more of these monomers having a ketone group may be contained in the graft chain. The amount of the ketone group-containing vinyl monomer used is 0.5 to 30 with respect to the total dry weight of the graft polymer.
% By weight, preferably 1 to 20% by weight. As a method for polymerizing the vinyl-based monomer, radical polymerization is preferable.

Further, examples of the polyfunctional hydrazide compound used as the crosslinking agent include polyhydric carboxylic acid polyhydrazide having 2 to 30 carbon atoms in one molecule, and preferably adipic acid dihydrazide. , Isophthalic acid dihydrazide and 1,3-bis (hydrazinocarboethyl) -5-isopropylhydantoin (VDH). 0.02 to 1 equivalent, preferably 0.4 to 0.6 equivalent of hydrazide group is used per equivalent of the carbonyl group contained in the graft copolymer.

Furthermore, the water-miscible organic solvent is effective in improving the wettability to a substrate such as plastic and the volatility of the solvent when forming a coating film from the ink. Preferred is isopropyl alcohol,
It is ethyl alcohol.

Next, the water-dispersible polyurethane resin (B) used in the present invention will be described. The water-dispersible polyurethane resin (B) is an organic diisocyanate compound,
It is an alkali-soluble or self-emulsifying aqueous polyurethane resin obtained by reacting a polyol with a chain extender and having a carboxyl group in the molecule for aqueousization. Such an aqueous polyurethane resin is produced, for example, by the following method.

Ammonia or 3 of urethane prepolymer having carboxyl group and terminal isocyanate group
In an aqueous polyurethane composition comprising a neutralized product of a primary amine and a chain extender, the urethane prepolymer is reacted with a polyol having a carboxyl group and a diisocyanate.

Alternatively, the urethane prepolymer is reacted with a mixture of polyols having carboxyl groups and other polyols and diisocyanates.

When the urethane prepolymer does not have a carboxyl group, a chain extender having a free carboxyl group can be used to obtain an aqueous polyurethane composition.

As the organic diisocyanate compound, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate,
Aromatic diisocyanates such as tetramethylxylylene diisocyanate and 4,4-diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate,
Examples thereof include aliphatic or alicyclic diisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, and 4,4-dicyclohexylmethane diisocyanate.

As the polyols, known ones which are usually used for producing urethane resins can be used. For example, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3. -Butylene glycol, tetramethylene glycol, hexamethylene glycol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, hydrogenated bisphenol A, ethylene oxide or propylene oxide adduct of bisphenol A, dimethylolpropion Acids, dimethylol butyric acid, polyester polyols, polyether polyols, polycaprolactam polyols, polybutadiene diols, polythioether polyols and polyacetal polyols. Lumpur, and trimethylol ethane, pentaerythritol, trimethylolpropane, polyoxyethylene triol, polyoxypropylene triol, tris-hydroxyethyl isocyanurate, one or a mixture of two or more such as polyoxyethylene tetrols and the like.

The preferred number average molecular weight of such a polyol is 500 to 3000. If the average molecular weight is less than 500, the strength of the resulting polyurethane will be insufficient, while if it exceeds 3,000, the stability of the polyurethane will be poor.

The above-mentioned reaction between the organic diisocyanate compound and the polyols can be carried out without solvent or in an organic solvent. However, it is preferable to carry out the reaction in an organic solvent, and the organic solvent used is N-methyl-2. Pyrrolidone,
Water-soluble organic solvents such as acetone and methyl ethyl ketone are preferred.

The carboxyl groups in the prepolymer can be neutralized by adding ammonia or a tertiary amine such as triethylamine or triethanolamine to the solution of the urethane prepolymer. Such addition can be done directly or as an aqueous solution.

When the urethane prepolymer composed of the above-mentioned organic diisocyanate compound and polyol compound already contains a free carboxyl group necessary for water-solubilization, the following chain extension conventionally used is used. Agents can be used. That is, glycols such as ethylene glycol and propylene glycol, glycerin, aliphatic polyols such as 1,2,3-trimethylolpropane and pentaerythritol, alicyclic polyols such as 1,3,5-cyclohexanetriol, and hydrazine. , Ethylenediamine, 1,4-butanediamine,
Aliphatic polyamines such as aminoethylethanolamine, diethylenetriamine, triethylenetetramine,
Alternatively, they are alicyclic amines such as isophoronediamine.

On the other hand, when the urethane prepolymer does not have a free carboxyl group, it is necessary to use a chain extender containing at least a free carboxyl group.
With a chain extender containing a free carboxyl group, dimethylolpropionic acid, dimethylolbutyric acid, dimethylolvaleric acid or phthalic acid, pyromellitic acid, aromatic carboxylic acids such as trimellitic acid and its anhydride, and lower polyols. Specific examples thereof include aromatic carboxylic acid-containing polyols obtained by reacting

The method of adding the chain extender to the urethane prepolymer is preferably a method of adding an aqueous solution of the chain extender to an organic solvent solution of the neutralized product of the urethane prepolymer, but the chain extender alone is used. Water may be added after synthesizing a polyurethane having a high molecular weight in addition to the organic solvent solution of the neutralized product of the above, or water may be added to the organic solvent solution of the neutralized product of the urethane prepolymer to obtain the urethane prepolymer. After dispersing in water, a chain extender may be added. The amount of water to be added is preferably such that the solid content concentration of the final product of the aqueous polyurethane composition, that is, the aqueous polyurethane emulsion is about 30 to 50% by weight.

In the polyurethane resin obtained by reacting the above compounds, the content of the free carboxyl group necessary for water solubilization is such that the acid value of the polyurethane resin is 20 to 20.
It is preferable that the amount is 100 to 100, and it is particularly preferable that the acid value of the polyurethane resin is 30 to 60. If the acid value is lower than 20, it will be difficult for the resulting aqueous polyurethane resin to maintain a stable dissolved or dispersed state in an aqueous system. On the other hand, if the acid value exceeds 100, the resulting resin film will have water resistance. It becomes low and hard, and good film properties cannot be obtained.

In the water-based printing ink composition of the present invention, the weight ratio of the water-based polyurethane graft copolymer (A) to the water-dispersible polyurethane resin (B) is 80: 20-2.
It is contained as a binder at 0:80. When the amount of the graft copolymer (A) is less than the above weight ratio, the adhesion to the OPP and K coat film becomes weak, and the blocking resistance to all films is lowered. On the other hand, when the amount of the resin (B) is small, sufficient laminating strength cannot be obtained. The weight ratio is preferably 60:40 to 40:60, most preferably 50:50.

[0035]

The present invention will be described below in more detail with reference to examples and comparative examples. A water-dispersible polyurethane resin (B) was prepared in each of Synthesis Examples 1 and 2 below. [Preparation of Water-Dispersible Polyurethane Resin (B)] Synthesis Example 1: 250 g of polytetramethylene glycol (number average molecular weight 2000) and dimethylolpropionic acid 17 were placed in a reactor equipped with a thermometer, a stirrer, and a cooling tube.
g, 65 g of isophorone diisocyanate and 50 g of methyl ethyl ketone were charged, and while introducing nitrogen gas, 7
The reaction was carried out at 0 to 75 ° C for 8 hours. 16 g of triethylamine in the urethane prepolymer solution obtained in the above reaction
Was added and neutralized, 800 g of distilled water in which 4 g of ethylenediamine was dissolved was added with stirring, and then methyl ethyl ketone was removed under reduced pressure to obtain an aqueous polyurethane resin solution ((B) -1). The resulting aqueous polyurethane resin solution had a nonvolatile content of 30% and a viscosity of 320 cps.

Synthesis Example 2: Polypropylene glycol (number average molecular weight of 200) was placed in the same reactor as in Synthesis Example 1 above.
0) 250 g, 1,4-butanediol 5 g, dimethylolpropionic acid 18 g, isophorone diisocyanate 73 g, and methyl ethyl ketone 60 g were charged, and the reaction was carried out at 70 to 75 ° C. for 5 hours while introducing nitrogen gas. To the urethane prepolymer solution obtained by the above reaction, 18 g of triethylamine was added and neutralized, and then 797 g of distilled water in which 4 g of ethylenediamine was dissolved was added with stirring.
Thereafter, methyl ethyl ketone was removed under reduced pressure to obtain an aqueous polyurethane resin solution ((B) -2). The obtained aqueous polyurethane resin solution has a nonvolatile content of 30% and a viscosity of 200c.
ps.

Regarding the aqueous polyurethane graft copolymer (A), trade names WEM 141M ((A) -1) and WEM 141B ((A) available from Taisei Kako Co., Ltd.
-2) was used.

[Preparation Method of Ink] Using the above-mentioned aqueous polyurethane graft copolymers (A) -1, (A) -2 and water-dispersible polyurethane resins (B) -1, (B) -2, Formulation examples shown in Table 1 (actual 1 to 6, ratio 1 to
According to 3), 100 g of glass beads, graft copolymer (A), resin (B), titanium oxide R-780 (Ishihara Sangyo Co., Ltd.), industrial ethanol, and deionized water were put in a predetermined amount in a glass bottle having a capacity of 225 ml. Then, dispersion treatment was carried out for 30 minutes with a red devil type disperser to prepare an aqueous ink composition for each laminate.

[0039]

[Table 1]

The evaluation test of the obtained ink composition was conducted as follows. (A) Adhesion PET (Toyobo Co., Ltd., trade name: E-5100, 12
μ), stretched OPP (Toyobo Co., Ltd., trade name: P-21
61, 20μ), nylon (Unitika Ltd., trade name:
Emblem, 12μ) and K coat film (TOCELLO Co., Ltd., trade name: OLE, 20μ) are coated with the sample ink with a gravure rotary press, and one day later, a Nichiban cellophane tape with a width of 24 mm is applied to the printing screen, and then instantly. Whether or not the ink was peeled off and removed was evaluated according to the following 5 grades. 5 Printing film does not peel at all 4 Printing film remains 80% or more 3 Printing film remains 50-80% 2 Printing film remains 30-50% 1 Printing film remains less than 30%

(B) Blocking resistance A printed matter was prepared using a test ink with a gravure rotary press.
Immediately after that, overlay the printed film and the non-printed side of the printed material,
Blocking tester (under conditions of 50 ° C and 80% humidity
5 kg / cm ²Test with a load of 24 hours)
After that, peel them off and remove the ink in the following 5 steps.
Evaluated. 5 Printing film does not peel at all 4 Printing film remains 80% or more 3 Printing film remains 50-80% 2 Printing film remains 30-50% 1 Printing film remains less than 30%

(C) Laminating Strength A printed matter was prepared by using a test ink with a gravure rotary press, a polyethyleneimine-based anchor coating agent was applied thereon, and molten polyethylene was laminated with an extrusion laminating machine. After 2 days, laminate
It was cut to a width of mm, the peel strength was measured, and the following criteria were evaluated. ○ The average peel strength has no practical problem. Fairly inferior in practical use. × Inferior in practical use. The results obtained are shown in Table 2 below.

[0043]

[Table 2]

[0044]

As described above, in the water-based printing ink composition of the present invention, the water-based polyurethane graft copolymer (A) and the water-dispersible polyurethane resin (B) are mixed in a predetermined ratio. , OPP, PET, nylon, and K coat have excellent adhesion to all films, and also have excellent blocking resistance to these films and excellent laminate strength.

Claims (2)

[Claims] 1. An aqueous polyurethane graft copolymer (A) comprising an aqueous polyurethane as a trunk polymer component and a polymer comprising a polymerizable unsaturated monomer as a graft chain component, and a water-dispersible polyurethane resin (B). Weight ratio 80: 20-2
A water-based printing ink composition containing 0:80 as a binder. 2. The aqueous printing ink composition according to claim 1, wherein the weight ratio is 60:40 to 40:60.