JP2577848B2 - Aqueous printing ink composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aqueous printing ink composition for a plastic film. More specifically, the present invention relates to an aqueous printing ink for lamination suitable for performing a boil and retort sterilization step after lamination.

[0002]

2. Description of the Related Art Today, polyethylene, polypropylene,
Plastic films such as polyester and nylon are widely used as various kinds of packaging materials, and printing on these plastic films is performed by a printing method called gravure or flexo. Conventionally, solvent-based inks using an organic solvent such as toluene, ethyl acetate, methyl ethyl ketone, or isopropyl alcohol as a medium have been exclusively used for such uses. In recent years, however, there has been a risk of air pollution, fire, and environmental problems during work. There is an increasing demand for water-based inks that do not use organic solvents due to hygiene considerations.
On the other hand, cosmetics and functionality are pursued in packaging materials using plastic films. Especially in the case of packaging containing foods for cooking, the contents must be preserved for a long period of time in order to prevent spoilage and deterioration of the contents. After filling and sealing, the use of boil sterilization at 80 to 100 ° C or retort sterilization at 120 to 135 ° C is increasing.

After printing and laminating using an aqueous printing ink for lamination using a (meth) acrylic copolymer resin having a carboxyl group, a polyurethane resin or a polyester resin as a binder, a boil and retort process are generally used. If this is done, peeling may occur between the ink film and the plastic film base material to be printed, or the cross section of the ink film at the end of the packaging material may be directly exposed to hot water or high-temperature steam during boil or retort processing, Is eluted and destroyed, which is completely unsuitable for this application. This is due to the hydrophilicity of the carboxyl groups present in the binder resin of these aqueous printing inks. Therefore, when using a low acid value aqueous resin to reduce the hydrophilicity,
The solubility and dispersion state in water are reduced, and in the extreme case, the aqueous resin vehicle in the emulsion state cannot provide the pigment dispersion, appropriate viscosity, transferability, and the like, which are requirements as a printing ink,
It has been extremely difficult to provide a practical printing ink.

[0004]

SUMMARY OF THE INVENTION The present inventors have conducted intensive studies to solve the problems of the prior art, and as a result, have found that aqueous printing using an aqueous resin based on a carboxyl group as a mono- and / or polycarbodiimide compound as a binder. The present invention was found to have an effect of imparting boil and retort processing resistance by being mixed under specific conditions with the ink, and thus the present invention was achieved.

[0005]

According to the present invention, there is provided an aqueous resin containing a (meth) acrylic copolymer resin, a polyester resin or a polyurethane resin as a binder. An aqueous printing ink composition for lamination comprising a printing ink mixed with a mono- and / or polycarbodiimide compound and subjected to a boil-retort treatment. Further, the acid value based on the carboxyl group of the aqueous resin is in the range of 30 to 200 KOH mg / g, and the ratio of the compounded mono- and / or polycarbodiimide compound is in the range of carboxyl group / carbodiimide group = 0.3 to 3.0. An aqueous printing ink composition for lamination.

[0006] The mono- and / or polycarbodiimide compounds must be kept in a substantially uniform dispersed state at the time of blending with the aqueous printing ink, and are disclosed in JP-A-59-187029 and JP-A-63-91356. As described, an emulsion obtained by emulsifying a polycarbodiimide solution dissolved in an organic solvent having no active hydrogen with an appropriate emulsifier, JP-A-63-172718 and JP-A-63-172718 As described in JP-A-264128, the ink is blended with the ink in the form of a self-emulsified product in which a hydrophilic polyoxyethylene chain is added to the molecular structure of the polycarbodiimide compound.

The monocarbodiimide compounds include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, dodecylisopropylcarbodiimide, diphenylcarbodiimide, di-tolylcarbodiimide, dip-tolylcarbamide, The
Examples thereof include t-butylcarbodiimide, 1,3-bis (trimethylsilyl) carbodiimide, di-β-naphthylcarbodiimide, and benzylisopropylcarbodiimide. As monocarbodiimide which is easily available industrially, dicyclohexylcarbodiimide and diisopropylcarbodiimide are preferable.

[0008] Polycarbodiimide compounds are disclosed in
Known methods described in 187029, for example, mono,
The di, triisocyanate compound is heated in a non-reactive organic solvent in the presence of a suitable catalyst, for example, 3-methyl-1-phenyl-2-phosphorate oxide, and decarboxylation converts the isocyanate group to a carbodiimide group. Manufactured.
Organic diisocyanate which is a raw material for synthesizing the polycarbodiimide compound is an aromatic diisocyanate, an aliphatic diisocyanate, an alicyclic diisocyanate or a mixture thereof, for example, 1,5-naphthylene diisocyanate, 4,4-diphenylmethane diisocyanate, 4-diphenyldimethylmethane diisocyanate, 4,4-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene diisocyanate,
Butane-1,4-diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, cyclohexane-
1,4-diisocyanate, xylylene diisocyanate,
Examples include isophorone diisocyanate, dicyclohexylmethane-4,4-diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, methylcyclohexane diisocyanate, m-tetramethylxylylene diisocyanate, and dimeryl diisocyanate. In order to adjust the carbodiimide group concentration in the molecule, an organic monoisocyanate compound such as phenyl isocyanate and butyl isocyanate is used.

The aqueous resin used as the binder is
It is selected from any of a (meth) acrylic copolymer resin containing a carboxyl group and capable of being neutralized with a basic substance, a polyester resin or a polyurethane resin. The above-mentioned aqueous resin can be mixed as required, and a resin obtained by modifying the resin by a grafting method or the like may be used. Further, various natural resins known as water-based resins, modified products thereof, and other dispersed resins can be used in combination as long as the object of the present application is not hindered.

The concentration of the carboxyl group contained in the aqueous resin must be 30 to 200 KOH mg / g in terms of acid value. If the acid value is less than 30 KOHmg / g, the solubility gradually decreases when mono- and / or polycarbodiimide compounds are blended, and the ink composition remaining during or after printing thickens, separates pigments and gels. Etc. are not preferred. On the other hand, if the acid value exceeds 200 KOHmg / g, the hydrophilic group is likely to remain in the dried film, so the suitability for boiling and retorting becomes insufficient, and the compounding amount of the required mono- and / or polycarbodiimide compound increases. It is not economically favorable.

Examples of the (meth) acrylic copolymer resin containing a carboxyl group include polymerizable unsaturated carboxylic acids such as (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid and anhydrides thereof. , Methyl (meth) acrylate, ethyl (meth) acrylate,
Butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate,
(Meth) acrylates such as 2-hydroxypropyl (meth) acrylate, (meth) acrylamide,
(Meth) acrylic monomers other than (meth) acrylic acid such as acrylontrile and, if necessary, α-methylstyrene, vinyl acetate, etc., are copolymerized by a polymerization method such as milk polymerization, solution polymerization, or bulk polymerization. The obtained acrylic resin is mentioned.

The polyester resin containing a carboxyl group is, for example, a polyester resin obtained by extending the chain of a glycol or a polyester glycol having a hydroxyl group at the end with a tetracarboxylic dianhydride by a selective monoesterification reaction. Can be Further, as the polyurethane resin containing a carboxyl group, for example, an isocyanate compound, a carboxyl group-containing polyol and / or an amino acid and a carboxyl group-containing urethane prepolymer obtained from a polyol, a solvent and / or water A polyurethane-based resin obtained by reacting with a basic organic compound and an elongating agent in the presence of, followed by removing the solvent under reduced pressure.

The ratio of the mono- and / or polycarbodiimide compound to be blended must be carbodiimide group / carboxyl group = 0.3 to 3.0. If less than 0.3,
Since the carboxyl group that is hydrophilic remains in the dried film, it cannot withstand boil and retort processing.
Decomposition products of low molecular weight polycarbodiimide remain,
It will not be able to withstand boiling and retorting.

[0014]

The present invention will be described below with reference to examples. In the examples, “parts” means “parts by weight” and “%” means “% by weight”. Production Example-1 Isopropyl alcohol was placed in a four-necked flask equipped with a stirrer, a reflux condenser, a temperature controller, and a nitrogen gas inlet tube.
150 parts were charged and heated to 83 ° C., and this temperature was maintained. Then, a mixture of 8 parts of acrylic acid, 30 parts of acrylic t-butyl, 36 parts of n-butyl acrylate, 22 parts of polyethylene glycol methacrylate, and 80 parts of a solution of azobisisobutyronitrile / isopropyl alcohol = 1/20 = 80 parts for 2 hours. After the addition, the reaction was continued for 3 hours under reflux. Further, 28% aqueous ammonia and 250 parts of water were added, and the entire amount of isopropyl alcohol was distilled off under azeotropic distillation, to obtain an aqueous acrylic resin solution having a resin solid content of 30% and an acid value of 62 KOHmg / g.

Production Example 2 29.6 parts of dimethyl-5-sodium sulfoisophthalic acid, 155.2 parts of dimethyl terephthalic acid, 86.8 parts of ethylene glycol were placed in a reactor equipped with a stirrer, a rectification column, a temperature controller and a nitrogen gas inlet tube. 104 parts of neopentyl glycol was charged together with 0.1 part of zinc acetate, and transesterification was carried out at 160 to 220 ° C. for 8 hours. Then isophthalic acid 1
82.6 parts were added and the reaction was carried out at 190 to 240 ° C. for 10 hours while removing water to obtain a polyester glycol having a molecular weight of 1,600 and a hydroxyl value of 70 KOHmg / g. In the same reactor as above,
100 parts of the polyester glycol obtained above and 14 parts of pyromellitic anhydride were charged and reacted at 170 ° C. for 3 hours. As a result, a carboxyl group-containing polyester resin having an average molecular weight of 12,000 and an acid value of 63.2 KOHmg / g was obtained. 80 parts of the carboxyl group-containing polyester obtained above and 120 parts of methyl ethyl ketone were charged into a container, and stirred at 70 ° C. for about 3 hours to obtain a uniform and viscous solution.
After slowly adding a mixture of 5.5 parts of 28% aqueous ammonia and 294.5 parts of water, the entire amount of methyl ethyl ketone was distilled off under azeotropic distillation to obtain a polyester resin aqueous dispersion having a resin solid content of 30%.

Production Example 3 A 1,000 ml four-necked flask equipped with a thermometer, a stirrer, and a nitrogen inlet tube was charged with 2,000 molecular weight polycaprolactone.
, 29.3 parts of dimethylolpropionic acid and 150 parts of methyl ethyl ketone, and the temperature was raised to 50 ° C while introducing nitrogen to dissolve the contents. Next, 97.3 parts of isophorone diisocyanate was added, and the mixture was heated to keep the internal temperature at 80 to 90 ° C., reacted for 4 hours, cooled, and diluted with 100 parts of acetone to obtain a prepolymer. A mixed solvent of 3.2 parts of dibutylamine, 24.1 parts of isophoronediamine, 220 parts of acetone and 50 parts of water was maintained at 30 ° C., and the prepolymer 52 obtained above was obtained.
By dropping and reacting 2.7 parts, a polyurethane resin solution was obtained. The obtained polyurethane resin solution was neutralized by adding 465 parts of deionized water containing 2.7 parts of 28% aqueous ammonia, and the solvent was removed (methyl ethyl ketone, acetone). Finally, the nonvolatile content was 26.8%, and the acid value was 41 KOHmg. / g, pH 7.
A urethane-based resin aqueous solution having a viscosity of 400 cps / 25 ° C. was obtained.

Production Example-4 80 parts of dicyclohexylcarbodiimide and 15 parts of propylene glycol monomethyl ether acetate were mixed, and 2.5 parts of polyoxyethylene polystyrylphenyl ether (HLB 14.4) and 2.5 parts of polyoxyethylene polystyrylphenylether sulfate were used as emulsifiers. The mixture was mixed and mixed with a stirrer at 1,000 rpm for 1 minute. Using a homogenizer, this mixture was stirred at a high speed of 3,000 rpm to remove 60 parts of water.
The mixture was gradually added over 5 minutes to obtain a 50% aqueous dispersion of dicyclohexylcarbodiimide.

Examples 1 to 7 and Comparative Examples 1 to 13 Using the aqueous resins obtained in Production Examples 1 to 3, commercially available acrylic resins and commercially available polyester resins, the compositions shown in Table 1 were used. A water-based printing ink was produced by a conventional method. The obtained water-based printing ink is applied with Zahn Cup # 3 (manufactured by Rigosha).
Diluted with a mixed solvent of water / isopropyl alcohol = 1/1 to 18 seconds (25 ° C) and printed on a corona discharge treated polyethylene terephthalate film (PET) with a gravure proofing machine equipped with a 25 µm deep gravure plate. 40-50
It dried at ° C and obtained a printed matter. Polyurethane anchor coating agent "EL443A, EL443B" on the printed surface of the obtained printed matter
(Manufactured by Toyo Morton Co., Ltd.), and extrusion lamination was performed on the coated surface with low-density polyethylene "Yukaron LK30" (manufactured by Mitsubishi Yuka) to evaluate the suitability of the laminate for boiling at 90 ° C. .

The suitability for boiling was evaluated by heat sealing with the polyethylene film side of the obtained laminate inside, filling the obtained bag with water as the contents, and boiling the mixture at 90 ° C. for 30 minutes to observe the appearance. Was evaluated. ○: No abnormality, ×: Delamination or blister
Those with some abnormalities are indicated by △. The appearance of the laminate of the ink containing the polyurethane resin was filled with oil as the content and boiled at 90 ° C. for 30 minutes to visually evaluate the appearance. Table 1 shows the evaluation results. Further, the obtained ink was stored in a constant temperature bath at 40 ° C. for one week, and the storage stability was evaluated. The viscosity after storage is 1 to 1.
A sample of 5 times is indicated by 、, a sample of 1.5 to 2 times is indicated by Δ, and a sample of 2 times or more is indicated by ×. Table 1 shows the evaluation results.

[0020]

[Table 1]

* 1 Rutile type titanium oxide manufactured by Furukawa Kogyo Co., Ltd. * 2 Allied Coro Acrylic Colloidal Dispersion Id Co., Ltd. Acid value 25KOHmg / g, solid content 48% * 3 Toyobo Co., Ltd. polyester resin water dispersion Solid content 15 % * 4 Acetylene glycol (isopropyl alcohol solution) manufactured by Nissin Chemical Co., Ltd. Active ingredient 50% * 4 Union car polycarbodiimide solution (Ruether acetate solution manufactured by propylene glycol monomethybyte) Solid component 50
%

[0022]

According to the present invention, an aqueous solution having excellent boiling and retort suitability can be obtained by the reduction of hydrophilicity due to the reaction between a hydrophilic carboxyl group and a carbodiimide group and the contribution of a crosslinking reaction between resins when a polycarbodiimide compound is blended. A printing ink composition was obtained.

Claims (2)

(57) [Claims] 1. An aqueous resin containing a carboxyl group and capable of being neutralized, a (meth) acrylic copolymer resin, a polyester resin or a polyurethane resin as an aqueous printing ink having a binder as a mono- and / or poly- An aqueous printing ink composition for lamination, which is subjected to a boil / retort treatment containing a carbodiimide compound. 2. The acid value based on the carboxyl group of the aqueous resin is in the range of 30 to 200 KOH mg / g, and the ratio of the compounded mono- and / or polycarbodiimide compound is carbodiimide group / carboxyl group = 0.3 to 3.0. The aqueous printing ink composition for a laminate according to claim 1, wherein the composition is in the range of: