JPH061940A - Water-base coating composition - Google Patents

Abstract

PURPOSE:To provide a water-base coating composition usable as a laminating ink for a food-packaging material requiring high lamination strength, boil resistance and retort resistance. CONSTITUTION:The objective water-base coating composition contains a colorant, a carboxyl-containing water-base resin and a core-shell-type water- dispersible resin containing an epoxy-containing copolymer as the core and a carboxyl-containing polyurethane as the shell.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous coating composition. More specifically, the present invention is excellent in coating workability such as painting and printing, and the obtained film has excellent adhesiveness to various film substrates. And an aqueous coating composition having hot water resistance and being particularly useful as a printing ink for laminating food packaging materials that can be boiled or retorted.

[0002]

2. Description of the Related Art Conventionally, an aqueous coating composition has been known which comprises a colorant such as a pigment, a binder resin, water, a solvent, and an additive such as a surfactant or wax.
Pigments are usually added to the composition as a thick, ground meat base. The binder resin used for the ground meat base is generally a water-soluble resin or an aqueous resin containing a large amount thereof. For example, in a water-based ink, a styrene-acrylic copolymer resin in the form of water-soluble or an emulsion containing a large amount of a water-soluble resin is often used as a resin for pigment milling. These water-soluble resins generally have excellent wettability with pigments, provide glossy printed matter, and improve printability, and are therefore necessary as components of the ink composition. However, since these water-soluble resins have a small molecular weight and contain a large amount of polar groups such as carboxyl groups, they have poor water resistance and insufficient adhesiveness to various film substrates.

In addition to the water-soluble binder resin,
There are water dispersible and emulsion forms. Water-dispersible and emulsions have low viscosity and high non-volatile content although the molecular weight of resin is generally larger than water-soluble.
Water resistance added to the composition as a letdown resin
The drying property, the adhesion property and the non-volatile content are increased.

[0004]

However, the aqueous coating composition as described above leaves a large amount of hydrophilic groups in the film and also has a low molecular weight component, so that the adhesiveness to various plastic films is still insufficient. In particular, the adhesive strength after dipping in hot water significantly decreases. Therefore, it cannot be used as a laminating ink for a food packaging material that requires a high degree of laminating strength and resistance to boiling and retort.

The present invention is intended to improve adhesiveness and hot water resistance by allowing hydrophilic groups to react in the process of forming a film and reducing the hydrophilic groups and low molecular weight components in the film. It is an object of the present invention to provide an aqueous coating composition that can be sufficiently used as a laminating ink.

[0006]

Means for Solving the Problems The present inventors have completed the present invention as a result of intensive studies to solve the above problems.

That is, the present invention comprises a core-shell type water-dispersible resin containing a colorant and a carboxyl group-containing aqueous resin, an epoxy group-containing copolymer as a core, and a carboxyl group-containing polyurethane as a shell. The present invention relates to an aqueous coating composition characterized by:

The aqueous coating composition of the present invention has good hot water resistance and good adhesion after hot water immersion because it is contained in the core portion of the core-shell type water-dispersible resin during the film formation process. It is considered that the epoxy group reacts in the polyurethane of the shell portion and with the carboxyl group of the carboxyl group-containing aqueous resin to reduce the hydrophilic carboxyl group and eliminates the low molecular weight component of the carboxyl group-containing aqueous resin by crosslinking.

A core-shell type water-dispersible resin having an epoxy group-containing copolymer used in the aqueous coating composition of the present invention as a core and a carboxyl group-containing polyurethane as a shell is used in an aqueous dispersion of a carboxyl group-containing polyurethane. , An epoxy group-containing α, β-ethylenically unsaturated monomer can be obtained by copolymerizing copolymerizable unsaturated monomers having an essential component.

The above-mentioned carboxyl group-containing polyurethane must be neutralized with a basic substance such as amine or ammonia, ionized in water and self-emulsifying or self-dispersing. To prepare such a polyurethane, for example, a polyol component is reacted with a polyisocyanate component, and the urethane prepolymer thus obtained is chain-extended with a chain extender composed of a low molecular weight compound having two or more active hydrogen atoms. In the method for producing a polyurethane, the reactivity with isocyanate is at least 2% as at least a part of the polyol component and / or the chain extender.
A compound containing a carboxyl group that is more inactive than one or more active hydrogen atoms may be used, or a carboxyl group may be introduced into the side chain or terminal of the polyurethane according to other known and commonly used methods.

The acid value of the above-mentioned carboxyl group-containing polyurethane is 10 per solid content of the polyurethane.
Is suitable within the range of -200, preferably within the range of 15-100. If it is less than 10,
It is difficult to ensure stability during polymerization, and the storage stability of the finally obtained aqueous resin dispersion tends to be poor. On the other hand, when it exceeds 200, the strength, water resistance and / or solvent resistance are inevitable. In any case, it is not preferable because improvement of various physical properties such as properties cannot be expected.

As only the polyol component of the above-mentioned polyurethane, only typical polyester polyols such as dicarboxylic acids (adipic acid, azelaic acid, sebacic acid, succinic acid, glutaric acid, maleic acid, fumaric acid) are listed. , Phthalic acid, isophthalic acid,
Terephthalic acid) and glycols (ethylene glycol, propylene glycol, 1,4-butanediol,
1,3-butanediol, 1,6-hexanediol,
1,8-octamethylenediol, neopentyl glycol, bishydroxymethylcyclohexane, bishydroxyethylbenzene, alkyldialkanolamine, etc.), such as polyethylene adipate, polybutylene adipate, polyhexamethylene adipate , Polyethylene / propylene adipate; polylactone diols by ring-opening polymerization of lactones, such as polycaprolactone diol, polyvalerolactone diol, and polyether polyols, such as low-molecular glycols (ethylene glycol, propylene glycol, 1,4-butane diol, etc.) Alkylene oxides of 2 to 4 carbon atoms such as ethylene oxide, propylene oxide and butylene oxide Additives and ring-opening polymerization products of the above alkylene oxides, specifically, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol and mixtures of two or more kinds thereof, on the other hand, particularly representative ones as the polyisocyanate component. Only to mention only, aliphatic diisocyanates such as 1,6-hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, hydrogenated 4,4′-diphenylmethane diisocyanate, methyl Alicyclic diisocyanates such as cyclohexylene diisocyanate, isopropylidene dicyclohexyl-4,4'-diisocyanate or 4,4'-diphenylmethane diisocyanate, xylylene Diisocyanate, tetramethylxylylene diisocyanate,
Aromatic diisocyanates such as tolylene diisocyanate and urethane prepolymers obtained by reacting these with the low molecular weight glycols.

Further, only specific examples of the above-mentioned active hydrogen atom-containing low molecular weight compound used as a chain extender are exemplified, and ethylene glycol, propylene glycol, 1,4-butanediol, 1, Low molecular weight glycols such as 6-hexanediol and aliphatic diamines such as ethylenediamine, hexamethienediamine, 2,2,4-trimethylhexamethylenediamine and isophoronediamine, dicyclohexylmethane-4,
4'-diamine, isopropylidenedicyclohexyl-
Examples are alicyclic diamines such as 4,4′-diamine and 1,4-diaminocyclohexane.

Then, only those compounds which are particularly representative as the compound containing a carboxyl group which is more reactive with isocyanate than the other two or more active hydrogen atoms are given below. Dimethylolpropionic acid,
2,5-diaminohexanoic acid and the like can be mentioned.

The chain extension reaction of the above polyurethane may be carried out in a solvent-free system, but a solvent is usually used. When a solvent is used, examples of the solvent used include alcohols such as ethanol, isopropanol, and n-butyl alcohol; ketones such as acetone, methyl ethyl ketone and cyclohexanone; ethers such as dioxane and tetrahydrofuran; aromatic hydrocarbons such as toluene. Amides such as dimethylformamide and dimethylacetamide; halogenated hydrocarbons such as chlorobenzene, trichlene and perclen; esters such as ethyl acetate and butyl acetate, and mixtures of two or more of these, from the viewpoint of solubility and economy, Preferably isopropanol, n
-Butyl alcohol, acetone, methyl ethyl ketone,
Ethyl acetate, toluene and mixtures of two or more of these.

The polyurethane solution thus obtained is dispersed in water together with ammonia or a volatile amine for neutralizing a part or all of the acid component present in the resin. The method is to contain an alkali. It may be a method of gradually adding and dispersing this resin solution while stirring water, or conversely by a method of gradually adding water containing an alkali to this resin solution and performing phase inversion emulsification. Good.

Generally, about 50 parts of polyurethane resin solution is added.
The method of heating to -100 ° C and gradually agitating the water containing the alkali while stirring well to carry out the phase inversion emulsification is to obtain a stable polyurethane resin dispersion having a fine particle size. It is more preferable because it makes it easier.

Ammonia and volatile amines are suitable as the basic substance used for neutralizing and ionizing the carboxyl groups in the resin.
Grade, secondary or tertiary alkylamines, representative examples being methylamine, ethylamine, propylamine, butylamine, amylamine, dimethylamine,
Diethylamine, dipropylamine, dibutylamine,
Trimethylamine, triethylamine, tripropylamine, morpholine; primary, secondary or tertiary alkanolamines, representative examples of which include monoethanolamine, diethanolamine, dimethylethanolamine and diethylethanolamine. Among these amines, diethylamine, triethylamine and dimethylethanolamine, which have good dispersibility and are hard to remain in the coating film and have high volatility, are preferable. The above ammonia and amine may be used alone or in combination of two or more. The amount of the neutralizing agent used is generally 0.1 to 2.0 equivalents, preferably 0.3 to 1.2 equivalents, relative to the carboxyl groups in the resin.

The polyurethane resin dispersion thus obtained, which is to be the shell part of the core-shell emulsion used in the present invention, can be used as it is for the next step, that is, emulsion polymerization of the core part. In order to carry out the process more smoothly, it is suitable to remove a part or all of the organic solvent contained in the dispersion liquid. A method using a film can be considered to remove the organic solvent,
It can also be easily carried out by distillation under normal pressure or reduced pressure, preferably under reduced pressure in order not to impair the stability of the dispersion system,
It is suitable to carry out at a low temperature of 60 ° C. or lower.

The core-shell emulsion used in the present invention is prepared by using the above-mentioned aqueous dispersion of polyurethane resin as an emulsifying dispersant, and by using a radical polymerization initiator, an α, β-ethylenically unsaturated monomer having an epoxy group as an essential component. It is carried out by copolymerizing the copolymerizable unsaturated monomers described below.

The α, β-ethylenically unsaturated monomers having the above-mentioned epoxy group are only representatively exemplified, and unsaturated compounds such as glycidyl acrylate, glycidyl methacrylate or allyl glycidyl ether. Examples thereof include glycidyl compounds.

On the other hand, as the other copolymerizable monomers having no epoxy group, of course, any one can be used as long as it is copolymerizable with the unsaturated glycidyl compound as described above. However, if only to exemplify only typical ones among them, acrylic acid esters such as methyl acrylate, butyl acrylate or 2-ethylhexyl acrylate; methyl methacrylate, ethyl methacrylate, Methacrylic acid esters such as butyl methacrylate; diethyl maleate, dibutyl fumarate,
Or unsaturated dicarboxylic acid diesters such as diethyl itaconic acid; vinyl esters such as vinyl acetate, vinyl propionate or vinyl tertiary carboxylic acid; styrene, α-methylstyrene, chlorostyrene, pt
aromatic vinyl compounds such as ert-butylstyrene or vinyltoluene; heterocyclic vinyl compounds such as vinylpyrrolidone; vinylidene chloride, vinylidene bromide or vinylidene halide compounds such as vinylidene bromide; α-such as ethylene or propylene. Olefins; dienes such as butadiene; silane compounds such as vinyltrichlorosilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane or γ-methacryloxypropylmethoxysilane; acrylonitrile, acrolein, vinylmethylketone, vinylethyl There are various α, β-ethylenically unsaturated monomers such as ketones, vinyl butyl ketone, diacetone acrylate or acetonitrile acrylate, and if desired, acrylamide , Amides of α, β-ethylenically unsaturated acids such as methacrylamide, maleic acid amide;
Substituted amides of unsaturated carboxylic acids such as N-methylol acrylamide or methacrylamide, diacetone acrylamide; diallyl phthalate, divinylbenzene,
A monomer having two or more unsaturated bonds in one molecule such as allyl acrylate and trimethylolpropane trimethacrylate can also be used.

When using various typical unsaturated monomers such as those listed above, the ratio of the above-mentioned aqueous polyurethane to the unsaturated monomers is the same as the solid content conversion ratio. A suitable range is 10 to 500 parts by weight, preferably 25 to 300 parts by weight of the aqueous polyurethane based on 100 parts by weight of the saturated monomers. When it deviates from this range, the polymerization stability is inevitably deteriorated, and the strength and durability are deteriorated, which is not preferable in any case.

In the present invention, the use of a surfactant such as an emulsifier is not always necessary because such an aqueous polyurethane can serve as a reaction site for unsaturated monomers.
It may be used in an amount of 0 to 20 parts by weight based on 100 parts by weight of the unsaturated monomers.

As only specific examples of such surfactants (emulsifiers), various anionic emulsifiers such as sodium dodecylbenzenesulfate, sodium dodecylbenzenesulfonate or alkylaryl polyether sulfates are given. Various non-ionic emulsifiers such as polyoxyethylene lauryl ether, polyoxyethylene nonylphenyl ether or polyoxyethylene-polyoxypropylene block copolymers; what are called reactive emulsifiers, ie sulfate groups or sulfones as hydrophilic groups Having an ionic group such as a group or a nonionic group such as a polyoxyethylene group and having an ethylenically unsaturated bond in the same molecule, for example, an alkenylbenzenesulfonic acid (sulfate such as sodium styrenesulfonate) Salts); (meth) acrylic acid ester sulfonic acid (sulfate) salts; ionic reactive emulsifiers such as itaconic acid, fumaric acid, and reactive emulsifiers having a maleic acid skeleton; polyoxyethylene Non-ionic reactive emulsifiers such as (or propylene) alkenyl (phenyl) ether derivatives are mentioned. These may be appropriately selected and used within the range of conventional doses.

It is needless to say that a water-soluble oligomer can be used as a dispersant instead of such an emulsifier or in the form of combined use with an emulsifier.

Further, a water-soluble polymer substance such as polyvinyl alcohol or hydroxyethyl cellulose is used in combination with the above-mentioned emulsifier to carry out a copolymerization reaction, or after the copolymerization reaction, it is added to an aqueous resin dispersion liquid. It is also effective to do. The total amount of the emulsifier, water-soluble oligomer and / or water-soluble polymer substance used is 0 to 100 parts by weight of the unsaturated monomers.
A range of 20 parts by weight is suitable.

If the amount is more than the above range, the water resistance is inevitably lowered when the water is scattered to form a film, which is not preferable.

On the other hand, as the radical polymerization initiators used in the copolymerization reaction, only typical ones will be exemplified. Potassium persulfate, ammonium persulfate,
Alternatively, azobisbutyronitrile or its hydrochloride, and an organic peroxide such as cumene hydroperoxide or tert-butyl hydroperoxide can be used, if necessary.

Furthermore, these persulfates and peroxides are used in combination with a metal ion such as iron ion or a reducing agent such as sodium sulfoxylate formaldehyde, sodium pyrosulfite or L-ascorbic acid. So-called redox type initiators can also be used.

From the practical point of view, the concentration of the aqueous resin dispersion during the copolymerization reaction should be finally set to a solid content of 25 to 65% by weight.
The unsaturated monomers and radical polymerization initiator to the reaction system are
Of course, any known method such as a batch charging method, a continuous dropping method or a divided addition method may be used.

The reaction temperature at the time of the copolymerization reaction is also within the range that is used in the known emulsion polymerization reaction, for example, 50 to 8
The temperature may be 0 ° C., and the copolymerization reaction is carried out under normal pressure or under pressure for the gaseous unsaturated monomers.

The carboxyl group-containing aqueous resin used in the aqueous coating composition of the present invention is not particularly limited, and various conventionally known and commonly used various types of resins having an acid value of 20 to 250 are applied. Among these resins, polyester resin,
Polyamide resin, shellac or modified shellac, rosin derivative, unsaturated acid-based copolymer and the like can be mentioned, and among them, particularly preferable one is unsaturated acid-based copolymer.

The above-mentioned unsaturated acid acid-based copolymer is a polymerizable acid monomer such as acrylic acid, methacrylic acid, itaconic acid or maleic acid, and other monomers copolymerizable therewith, such as acrylic acid esters. , Methacrylic acid esters, styrene, α-methylstyrene,
It can be obtained by copolymerizing vinyltoluene, acrylonitrile and the like by a known and commonly used method. In order to make it alkali-soluble, it is necessary to use an acid monomer in such an amount that the resin acid value becomes approximately 30 or more. These unsaturated acid-based copolymers may be water-soluble ones themselves, and further, these water-soluble resins containing a large amount of polar groups are used as protective colloids for styrene, α-methylstyrene, vinyltoluene, acrylonitrile, acrylic acid esters. An emulsion obtained by emulsion-polymerizing non-polar monomers such as methacrylic acid esters can be preferably used.

As the colorant used in the aqueous coating composition of the present invention, pigments and dyes may be used alone or in combination, for example, organic pigments such as soluble or insoluble azo type, phthalocyanine type and naphthol type, titanium oxide, valves. Examples thereof include patterns, carbon black, inorganic pigments such as calcium carbonate and barium sulfate, and organic dyes such as metal complex salts, which may be used alone or as a mixture. The colorant may be a dry powder, but a press cake containing water may be used.

The aqueous coating composition of the present invention may be prepared by any method, for example, it can be prepared according to the following formulation. That is, the colorant of the press cake or dry powder is usually an ordinary kneading machine such as a media mill such as a ball mill, a sand mill or the like, together with a carboxyl group-containing aqueous resin and optionally a neutralizing agent, a defoaming agent or a surfactant. The kneaded meat is dispersed in the mixture to form a colorant base. The colorant base is mixed with other resin components including the above core-shell type water-dispersible resin and, if necessary, water, a solvent, a neutralizing agent, a defoaming agent, and other additives, and the desired aqueous coating composition. It is finally prepared as a product.

[0037]

EXAMPLES Next, the present invention will be described in more detail with reference to Reference Examples, Examples and Comparative Examples. In the following, all parts and% are based on weight unless otherwise specified.

Reference Example 1 (Preparation Example of Carboxyl Group-Containing Aqueous Acrylic Resin) A four-necked flask equipped with a stirrer, a thermometer, a dropping funnel and a nitrogen gas inlet was charged with 600 parts of isopropyl alcohol to start stirring. In a nitrogen stream, raise the temperature to 80 ° C,
In advance, 36 parts acrylic acid, 300 methyl methacrylate
Part, butyl methacrylate 132 parts, butyl acrylate 132 parts and azobisisobutyronitrile 12 parts were prepared and the monomer mixture liquid was added dropwise over 3 hours. The reaction temperature at this time was maintained at 80 ° C ± 3 ° C.

After the completion of dropping, the temperature was kept in the same temperature range for 2 hours, and then 1.2 parts of azobisisobutyronitrile was added,
The reaction was continued under stirring for another 2 hours.

After the reaction was completed, the reaction mixture was cooled to 40 ° C., 46 parts of dimethylethanolamine was added, and then 600 parts of ion-exchanged water was added to make it water-soluble.

Next, the transparent reaction product thus obtained was distilled under reduced pressure at 60 ° C. to remove isopropyl alcohol, and then ion-exchanged water was added to adjust the concentration. A water-soluble acrylic resin was obtained.

The property value of this product is 32.1% of nonvolatile content.
Viscosity at 25 ° C (Brook at 60 rpm
The field viscosity ... The same hereinafter) was 340 cps, the pH was 7.3, and the solid content acid value was 47.

Next, a four-necked flask equipped with a stirrer, a thermometer, a dropping funnel and a nitrogen gas inlet was charged with 8.3 parts of ion-exchanged water and 208.7 parts of the above water-soluble acrylic resin solution, and stirring was started. Then, the temperature was raised to 70 ° C. in a nitrogen stream, 0.07 part of a 0.75% copper (II) sulfate aqueous solution was added, and further 11 parts of styrene, 22 parts of butyl acrylate and 0.03 parts of tert-dodecyl mercaptan in advance.
A mixed solution prepared by using 2 parts of the above solution, 2.64 parts of a 5% sodium thiosulfate aqueous solution and 0.66 parts of a 5% potassium persulfate solution were added dropwise over 3 hours. The reaction temperature at this time was maintained at 70 ° C ± 3 ° C.

After completion of the dropping, the reaction was continued under stirring while maintaining the same temperature range for 1 hour, then cooled and the pH was adjusted to 7.5 to 8.5 with 5% aqueous ammonia. did. An aqueous resin dispersion having a nonvolatile content of 39.7%, a Brookfield viscosity at 25 ° C. of 540 cps, and a pH of 8.3 was obtained. This is abbreviated as (A-1).

Reference Example 2 (Preparation Example of Aqueous Polyurethane) 294 parts of terephthalic acid, 294 parts of isophthalic acid, 131 parts of ethylene glycol and 223 parts of diethylene glycol.
After the parts were mixed and heated at 180 to 230 ° C. for 8 hours to perform an esterification reaction, a condensation reaction was performed at 230 ° C. for 6 hours until the acid value became smaller than 1. .

Next, dehydration treatment was carried out under reduced pressure at 120 ° C., and after cooling to 90 ° C., 263 parts of methyl ethyl ketone was added and stirred to sufficiently dissolve, and the acid value was 0.7. A polyester polyol having a hydroxyl value of 50 was obtained. Thereafter, 226 parts of this polyester polyol and 44 parts of isophorone diisocyanate were sufficiently stirred at 75 ° C., 13 parts of 2,2-dimethylolpropionic acid was added as a chain extender, and the mixture was heated at 70 ° C. for 12 hours. I reacted for a while.

After completion of the reaction, after cooling to 40 ° C., 5
35 parts of% ammonia water was added to make it water soluble.

Then, from the thus obtained transparent reaction product, methyl ethyl ketone was removed at 60 ° C. under reduced pressure, and ion-exchanged water was added to adjust the concentration to obtain a translucent aqueous polyurethane. Was given. Hereinafter, this is abbreviated as aqueous polyurethane (U), but the physical properties of this are as follows: non-volatile content 22.5%, Brookfield viscosity at 25 ° C. 18 cps, pH 7.
In 3, the acid value of the solid content was 19.

Reference Example 3 (Synthesis of core-shell type water-dispersed resin B-1 for letdown) In a four-necked flask equipped with a stirrer, thermometer, dropping funnel and nitrogen gas inlet, Rebenol WZ (manufactured by Kao Corporation). 8 parts of anionic emulsifier; solid content = 25%), 17.5 parts of ion-exchanged water, and 222.2 parts of the aqueous polyurethane (U) shown in Reference Example 2 were charged, stirring was started, and the mixture was placed in a nitrogen stream. At 70 ° C., then add 0.6 parts of ammonium persulfate, and then add 75 parts of ethyl acrylate beforehand.
Parts, n-butyl acrylate 10 parts, acrylonitrile 5
Part and 100 parts of unsaturated monomers consisting of 10 parts of glycidyl methacrylate, 6 parts of rebenol WZ, and 30 parts of ion-exchanged water were added dropwise to the mixed emulsion prepared over 3 hours. The reaction temperature at this time was maintained at 70 ° C ± 3 ° C.

After completion of the dropping, the reaction was continued under stirring while maintaining the same temperature range for 1 hour, then cooled and the pH was adjusted to 6.5 to 7.5 with 25% aqueous ammonia. However, it has a nonvolatile content of 39.6% and a viscosity at 25 ° C. of 44.
An aqueous resin dispersion having a cps and a pH of 6.7 was obtained. This is abbreviated as let-down resin (B-1).

Reference Example 4 (Synthesis of let-down core-shell type water-dispersed resin B-2) The unsaturated monomers were 70 parts of ethyl acrylate, 10 parts of n-butyl acrylate, 5 parts of acrylonitrile and 15 glycidyl methacrylate. Except that the total amount of the non-volatile components is 100 parts, the synthesis is performed in the same manner as in Reference Example 3.
An aqueous resin dispersion having a viscosity of 9.4%, a viscosity at 25 ° C. of 51 cps, and a pH of 6.7 was obtained. This is abbreviated as let-down resin (B-2).

Reference Example 5 (Synthesis of let-down core-shell type water-dispersed resin B-3) The unsaturated monomers were ethyl acrylate 65 parts, n-butyl acrylate 10 parts, acrylonitrile 5 parts, and glycidyl methacrylate. Unsaturated monomers 100 consisting of 20 parts
Synthesis was carried out in the same manner as in Reference Example 3 except for the parts, and the nonvolatile content was 39.1% and the viscosity at 25 ° C was 73%.
An aqueous resin dispersion having a cps and a pH of 6.7 was obtained. This is abbreviated as let-down resin (B-3).

Reference Example 6 (Synthesis of core-shell type water-dispersed resin B-4 for letdown) In a four-necked flask equipped with a stirrer, a thermometer, a dropping funnel and a nitrogen gas inlet, Rebenol WZ (manufactured by Kao Corporation). Anionic emulsifier (solid content = 25%) 12.0 and 444.4 parts of the aqueous polyurethane (U) shown in Reference Example 2 were charged, stirring was started, and the temperature was raised to 70 ° C. in a nitrogen stream. Then, after adding 0.6 part of ammonium persulfate, 75 parts of ethyl acrylate and 1 part of n-butyl acrylate were previously prepared.
A mixed emulsion prepared by using 100 parts of unsaturated monomers consisting of 0 part, 5 parts of acrylonitrile and 10 parts of glycidyl methacrylate, 8 parts of Rebenol WZ and 21.3 parts of ion-exchanged water is used for 3 hours. It was dripped over. The reaction temperature at this time was maintained at 70 ° C ± 3 ° C.

After completion of the dropping, the reaction was continued under stirring while maintaining the same temperature range for 1 hour, then cooled and the pH was adjusted to 6.5 to 7.5 with 25% aqueous ammonia. However, it has a nonvolatile content of 34.8% and a viscosity at 25 ° C. of 87.
An aqueous resin dispersion having a cps and a pH of 6.7 was obtained. This is abbreviated as let-down resin (B-4).

Reference Example 7 (Synthesis of let-down core-shell type water-dispersed resin B-5) The unsaturated monomers were ethyl acrylate 65 parts, n-butyl acrylate 10 parts, acrylonitrile 5 parts, and glycidyl methacrylate. Unsaturated monomers 100 consisting of 20 parts
All were synthesized in the same manner as in B-4 except that the content was 3 parts, the nonvolatile content was 34.6%, and the viscosity at 25 ° C was 90%.
An aqueous resin dispersion having a cps and a pH of 6.7 was obtained. This is abbreviated as let-down resin (B-5).

Reference Example 8 (Synthesis of let-down core-shell type water-dispersed resin B-6) The unsaturated monomer comprises 75 parts of ethyl acrylate, 15 parts of n-butyl acrylate and 10 parts of acrylonitrile. Synthesis was carried out in the same manner as in Reference Example 3 except that the amount of the monomers was 100 parts.
An aqueous resin dispersion liquid having a viscosity at 32 ° C. of 32 cps and a pH of 6.7 was obtained. This is abbreviated as let-down resin (B-6).

The characteristics of the let-down resin used in Table 1 are shown.

[0058]

[Table 1]

Preparation of Printing Ink Base In a plastic container, 28 parts of the aqueous acrylic resin dispersion (A-1) shown in Reference Example 1, 30 parts of titanium oxide, 6 parts of industrial ethanol, 4 parts of ion-exchanged water and ceramic beads were used. Add 136 parts and add 30 with paint conditioner
The mixture was kneaded for a minute to obtain a printing ink base (C-1).

Examples 1 to 5 and Comparative Example 1 Examples shown in Table 2 in which ion-exchanged water and let-down water dispersion resins (B-1) to (B-5) were added to the printing ink base (C-1). 1 to 5 printing inks were obtained. Further, as Comparative Example 1, similarly, a letdown water-dispersed resin (B-
A printing ink using 6) was prepared.

Lamination Test Method and Results As an adhesive, 9 parts of Dick Dry Lx-901 (a main agent manufactured by Dainippon Ink and Chemicals, Inc.) and Dick Dry K were used.
Prepare a solution of 1 part of W75 (hardening agent) and 7.5 parts of ethyl acetate, and use drawdown rod # 12 to prepare a solution of 15 μm.
After coating the untreated surface of the aluminum foil and volatilizing the solvent, it is laminated with a linear low-density polyethylene film (thickness 60 μ, hereinafter abbreviated as LLDPE) and laminated using a pressure roll of 80 kg / cm ² pressure. went.

Each of the printing inks of Examples 1 to 5 and Comparative Example 1 was applied to a 12μ surface-treated polyester film (hereinafter abbreviated as PET) using a drawdown rod # 7, and dried with a dryer for 30 seconds. The above adhesive is similarly applied thereto using the draw down rod # 12, and the solvent is volatilized, and then the above aluminum / LLD is used.
The aluminum surface of the PE laminate was overlaid and laminated with a pressure roll.

On the other hand, each of the printing inks of Examples 1 to 5 and Comparative Example 1 was applied to a 15μ surface-treated nylon film (hereinafter abbreviated as ON) using a drawdown rod # 7 and dried with a dryer for 30 seconds. Let The above adhesive was similarly applied thereto by using the draw down rod # 12, the solvent was volatilized, LLDPE was overlapped and laminated with a pressure roll.

The laminate thus obtained was aged for 72 hours in a constant temperature bath at 50 ° C.
The tape was cut into a tape having a width of mm and Tensilon RTM-25 manufactured by Orientec Co., Ltd. was used, and the peel strength of the T-type peel of the ink layer at a speed of 300 mm / min (unit: g /
15 mm width) was measured (normal peel strength). In addition, a bag of 12 cm × 12 cm was prepared from the laminate, and the bag filled with water was immersed in a boiling water bath for 40 minutes. Immediately thereafter, the peel strength of the laminate was measured in the same manner as described above (peel strength after immersion in hot water). The measurement results of these peel strengths are shown in Table 2 together with the printing ink formulations.

[0065]

[Table 2]

As is clear from Table 2, the aqueous coating composition according to the present invention has remarkably improved hot water resistance and can be suitably used as a laminating ink which requires boil / retort resistance.

[0067]

In the aqueous coating composition according to the present invention, the core-shell type water-dispersible resin particles are fused in the process of forming a film, and the epoxy group contained in the core is a shell portion and a carboxyl group-containing aqueous resin. As a result of the reaction with the carboxyl groups of (1), the hydrophilic groups and low molecular weight components in the coating are reduced, whereby the adhesiveness and hot water resistance of the coating are significantly improved. As a result, it is possible to provide an aqueous coating composition that can be sufficiently used as a laminating ink that requires boil retort resistance in particular.

Claims (2)

[Claims] 1. A core-shell type water-dispersible resin containing a colorant and a carboxyl group-containing aqueous resin, having an epoxy group-containing copolymer as a core, and a carboxyl group-containing polyurethane as a shell. Aqueous coating composition. 2. The ratio of the epoxy group (B) of the core portion of the core-shell type water-dispersible resin to the carboxyl group (A) of the shell portion of the carboxyl group-containing aqueous resin and the core-shell type water-dispersible resin is an equivalent ratio (A). ) / (B) = 3
It is / 1-1 / 2, The composition for aqueous coatings of Claim 1 characterized by the above-mentioned.