JP3289314B2 - Aqueous coating composition - Google Patents

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, and more specifically, the present invention is excellent in coating workability such as coating and printing, and has excellent adhesion to various film substrates. The present invention relates to an aqueous coating composition having a water-resistant and hot-water resistance, and particularly useful as a printing ink for laminating food packaging materials capable of boiling and retorting.

[0002]

2. Description of the Related Art Conventionally, as an aqueous coating composition, a composition comprising a coloring agent such as a pigment, a binder resin, water, a solvent and additives such as a surfactant and a wax has been known.
Pigments are usually added to the composition as a thick ground base. The binder resin used for the 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 an emulsion containing a large amount of a water-soluble resin or a water-soluble resin is often used as the resin for pigment wool. These water-soluble resins are generally required as a component of the ink composition because they have excellent wettability with the pigment, provide glossy printed matter, and improve printability. However, these water-soluble resins have a low molecular weight and contain a large amount of polar groups such as carboxyl groups, so that they have poor water resistance and insufficient adhesion to various film substrates.

[0003] In addition to being water-soluble, aqueous binder resins
There are water dispersible and emulsion forms. Water dispersibility and emulsions can have low viscosity and high non-volatile content despite the fact that the resin generally has a higher molecular weight than water solubility,
Water resistance added to the composition as a letdown resin,
Improvements in drying properties, adhesiveness, and non-volatile content are achieved.

[0004]

However, the aqueous coating composition as described above leaves a large amount of hydrophilic groups and low molecular weight components in the film, so that its adhesion to various plastic films is still insufficient. In particular, the adhesive strength after immersion in hot water is significantly reduced. Therefore, it was impossible to use it as a laminating ink for food packaging materials requiring high lamination strength, boil resistance and retort resistance.

The present invention is intended to improve the adhesiveness and hot water resistance by making the hydrophilic groups react during the process of forming the 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 which can be sufficiently used as a laminating ink.

[0006]

The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, completed the present invention.

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

[0008] The aqueous coating composition of the present invention has good hot water resistance and good adhesiveness after immersion in hot water because it is contained in the core portion of the core-shell type water-dispersible resin in the film forming process. It is considered that the epoxy group reacts with the carboxyl group in the polyurethane of the shell portion and the carboxyl group-containing aqueous resin to reduce the carboxyl group which is a hydrophilic group, and to eliminate the low molecular weight component of the carboxyl group-containing aqueous resin by crosslinking.

The core-shell type water-dispersible resin having an epoxy group-containing copolymer as a core and a carboxyl group-containing polyurethane as a shell used in the aqueous coating composition of the present invention is prepared by preparing an aqueous dispersion of a carboxyl group-containing polyurethane. And copolymerizable unsaturated monomers having an α, β-ethylenically unsaturated monomer having an epoxy group as 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-emulsified or self-dispersed. In order to prepare such a polyurethane, for example, a polyol component is reacted with a polyisocyanate component, and the thus obtained urethane prepolymer is chain-extended with a chain extender comprising a low molecular weight compound having two or more active hydrogen atoms. In the method for producing a polyurethane, the reactivity with an isocyanate is at least part of the polyol component and / or the chain extender.
A compound containing a carboxyl group which is more inactive than two or more active hydrogen atoms may be used, and a carboxyl group may be introduced into a side chain or a terminal of the polyurethane according to another known and commonly used method.

The carboxyl group-containing polyurethane has an acid value of 10 per solid content of the polyurethane.
The range of 200 to 200, preferably the range of 15 to 100 is appropriate. If less than 10,
It is difficult to ensure the stability at the time of polymerization, and the storage stability of the aqueous resin dispersion finally obtained tends to be poor. On the other hand, when it exceeds 200, the strength, water resistance and / or solvent resistance are inevitably increased. In any case, it is not possible to improve the physical properties such as properties.

Polyols such as dicarboxylic acids (eg, adipic acid, azelaic acid, sebacic acid, succinic acid, glutaric acid, maleic acid, fumaric acid) may be mentioned as particularly typical polyol components of the polyurethane. , Phthalic acid, isophthalic acid,
Terephthalic acid, etc.) and glycols (ethylene glycol, propylene glycol, 1,4-butanediol,
1,3-butanediol, 1,6-hexanediol,
1,8-octamethylenediol, neopentyl glycol, bishydroxymethylcyclohexane, bishydroxyethylbenzene, alkyl dialkanolamine, etc.), for example, 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 weight glycols (ethylene glycol, propylene glycol, 1,4-butanediol, etc.) (Alkylene oxides having 2 to 4 carbon atoms, such as ethylene oxide, propylene oxide and butylene oxide) Additives and ring-opening polymers of the above-mentioned alkylene oxides, specifically, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol and mixtures of two or more of these. On the other hand, those particularly representative as polyisocyanate components To name 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 diisocyanate 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 low molecular glycols.

[0013] Further, only typical examples of the above-mentioned active hydrogen atom-containing low molecular weight compound used as a chain extender include ethylene glycol, propylene glycol, 1,4-butanediol, Low molecular weight glycols such as 6-hexanediol and ethylenediamine, aliphatic diamines such as 2,2,4-trimethylhexamethylenediamine and isophoronediamine, dicyclohexylmethane-4,
4'-diamine, isopropylidenedicyclohexyl-
Alicyclic diamines such as 4,4'-diamine and 1,4-diaminocyclohexane;

[0014] If only a typical example of a compound containing a carboxyl group which is more inactive than the other two or more active hydrogen atoms in reactivity with the isocyanate is mentioned, only 2,2 -Dimethylolpropionic acid,
2,5-diaminohexanoic acid and the like.

The above-mentioned chain extension reaction of polyurethane may be carried out without a solvent, 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, tricrene and perchrene; esters such as ethyl acetate and butyl acetate; and mixtures of two or more thereof. 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. This resin solution may be gradually added and dispersed while stirring the water, or conversely, a method of gradually adding alkali-containing water to the resin solution to cause phase inversion emulsification. Good.

In general, about 50 polyurethane resin solutions are used.
The method of heating to 100 ° C. and gradually dropping water containing an alkali with good stirring to cause phase inversion emulsification gives a stable polyurethane resin dispersion having a fine particle diameter. It is more preferable because it is easy.

As the basic substance used to neutralize and ionize the carboxyl groups in the resin, ammonia and volatile amines are suitable.
Primary, secondary or tertiary alkylamines, typically methylamine, ethylamine, propylamine, butylamine, amylamine, dimethylamine,
Diethylamine, dipropylamine, dibutylamine,
Trimethylamine, triethylamine, tripropylamine, morpholine; primary, secondary or tertiary alkanolamines, typical examples of which include monoethanolamine, diethanolamine, dimethylethanolamine, diethylethanolamine and the like. Among these amines, diethylamine, triethylamine and dimethylethanolamine, which have good dispersibility and high volatility which hardly remain in the coating film, are preferred. The above-mentioned 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, based on the carboxyl group in the resin.

The polyurethane resin dispersion to be used as the shell portion of the core-shell emulsion used in the present invention thus obtained can be used as it is in the next step of emulsion polymerization of the core portion. For smoother operation, it is preferable to remove part or all of the organic solvent contained in the dispersion. The removal of the organic solvent may be a method using a membrane,
Distillation at normal pressure or reduced pressure can be easily performed, preferably under reduced pressure, so as not to impair the stability of the dispersion system,
It is appropriate to carry out at a low temperature of 60 ° C. or less.

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

Only the typical α, β-ethylenically unsaturated monomers having an epoxy group described above are exemplified. Unsaturated monomers such as glycidyl acrylate, glycidyl methacrylate and allyl glycidyl ether can be used. Glycidyl compounds are exemplified.

On the other hand, other copolymerizable monomers having no epoxy group can be used as long as they are copolymerizable with the unsaturated glycidyl compound as described above. However, if only typical examples are exemplified, acrylates such as methyl acrylate, butyl acrylate or 2-ethylhexyl acrylate; methyl methacrylate, ethyl methacrylate, Methacrylates such as butyl methacrylate; diethyl maleate, dibutyl fumarate,
Or unsaturated dicarboxylic acid diesters such as diethyl itaconate; vinyl esters such as vinyl acetate, vinyl propionate or vinyl tertiary carboxylate; styrene, α-methylstyrene, chlorostyrene, pt
aromatic vinyl compounds such as tert-butylstyrene or vinyltoluene; heterocyclic vinyl compounds such as vinylpyrrolidone; vinylidene halide compounds such as vinylidene chloride, vinylidene bromide or vinylidene fluoride; α-vinyl compounds 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 Various α, β-ethylenically unsaturated monomers such as ketone, vinyl butyl ketone, diacetone acrylate or acetonitrile acrylate, and, if desired, acrylamide Amides of α, β-ethylenically unsaturated acids, such as methacrylamide, maleic amide and the like;
Substituted amides of unsaturated carboxylic acids such as N-methylol acrylamide or methacrylamide, diacetone acrylamide; diallyl phthalate, divinyl benzene,
Monomers having two or more unsaturated bonds in one molecule such as allyl acrylate and trimethylolpropane trimethacrylate can also be used.

When the typical various unsaturated monomers as described above are used, the ratio of the aqueous polyurethane to the unsaturated monomer is determined by the solid content conversion ratio. The appropriate amount is from 10 to 500 parts by weight of the aqueous polyurethane, preferably from 25 to 300 parts by weight, based on 100 parts by weight of the saturated monomers. If the ratio is outside the above range, the polymerization stability is inevitably deteriorated and the strength and durability are lowered.

In the present invention, the use of a surfactant such as an emulsifier is not always necessary since such an aqueous polyurethane can act as a reaction site for unsaturated monomers.
It can be used in the range of 0 to 20 parts by weight with respect to 100 parts by weight of the unsaturated monomer.

Examples of such surfactants (emulsifiers) include various anionic emulsifiers such as sodium dodecylbenzenesulfate, sodium dodecylbenzenesulfonate and alkylaryl polyether sulfate. Various nonionic emulsifiers such as polyoxyethylene lauryl ether, polyoxyethylene nonylphenyl ether or polyoxyethylene-polyoxypropylene block copolymer; those called reactive emulsifiers, ie, sulfate groups or sulfones as hydrophilic groups. Those 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, alkenylbenzenesulfonic acid such as sodium styrenesulfonate (sulfuric acid) Salt); (meth) acrylic acid ester sulfonic acid (sulfate) salt; ionic reactive emulsifier such as reactive emulsifier having itaconic acid, fumaric acid, maleic acid skeleton such as allyl alkyl itaconate sulfate, and polyoxyethylene Non-ionic reactive emulsifiers such as (or propylene) alkenyl (phenyl) ether derivatives are included. These may be selected and used in an appropriate amount within the range of a conventional dose.

It is a matter of course that a water-soluble oligomer can be used as a dispersant instead of such an emulsifier or in combination with an emulsifier.

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

If the amount is larger than this, it is not preferable because water is scattered and the water resistance or the like when forming a film is remarkably reduced.

On the other hand, as typical radical polymerization initiators used in the copolymerization reaction, only typical ones are exemplified. Potassium persulfate, ammonium persulfate,
Or azobisbutyronitrile or a hydrochloride thereof, and an organic peroxide such as cumene hydroperoxide or tert-butyl hydroperoxide can be used as needed.

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

From the practical point of view, the concentration of the aqueous resin dispersion during the copolymerization reaction is preferably adjusted so as to finally have a solid content of 25 to 65% by weight.
Unsaturated monomers and radical polymerization initiator to the reaction system,
Of course, any known and commonly used system such as a batch charging system, a continuous dropping system, or a divided addition system may be used.

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

The carboxyl group-containing aqueous resin to be used in the aqueous coating composition of the present invention is not particularly limited, and various types of conventionally known and commonly used resins having an acid value of 20 to 250 are applied. If only representative ones of these resins are exemplified, polyester resins,
Examples thereof include a polyamide resin, shellac or modified shellac, a rosin derivative, and an unsaturated acid-based copolymer. Of these, an unsaturated acid-based copolymer is particularly preferred.

The above-mentioned unsaturated acid-based copolymers include polymerizable acid monomers such as acrylic acid, methacrylic acid, itaconic acid and maleic acid, and other monomers copolymerizable therewith, such as acrylic acid esters. , Methacrylates, 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 the resin soluble in alkali, it is necessary to use an acid monomer in such an amount that the resin acid value becomes about 30 or more. These unsaturated acid-based copolymers may be water-soluble in themselves, but furthermore, these water-soluble resins containing a large amount of polar groups may be used as protective colloids in styrene, α-methylstyrene, vinyltoluene, acrylonitrile, acrylates and the like. Emulsions obtained by emulsion polymerization of non-polar monomers such as methacrylates can be suitably used.

As the colorant used in the aqueous coating composition of the present invention, pigments and dyes each alone or as a mixture, for example, organic pigments such as soluble or insoluble azo, phthalocyanine and naphthol, titanium oxide, valve Patterns, inorganic pigments such as carbon black, calcium carbonate, barium sulfate, etc., and organic dyes of metal complex salts may be used alone or in combination. As the colorant, a dry powder may be used, but a press cake containing water may also 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 formula. That is, the colorant of the press cake or the dry powder is usually mixed with a carboxyl group-containing aqueous resin and, if necessary, a neutralizing agent, an antifoaming agent or a surfactant together with a conventional milling machine such as a ball mill, a sand mill or another media mill. And the mixture is dispersed to make a colorant base. The colorant base is mixed with other resin components including the core-shell type water-dispersible resin and, if necessary, water, a solvent, a neutralizing agent, an antifoaming agent, and other additives to form a desired aqueous coating composition. Final preparation.

[0037]

Next, the present invention will be described more specifically with reference examples, examples and comparative examples. In the following, all parts and percentages are by 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, and stirring was started. The temperature was raised to 80 ° C in a nitrogen stream,
36 parts of acrylic acid and 300 parts of methyl methacrylate
Parts, butyl methacrylate 132 parts, butyl acrylate 132 parts and azobisisobutyronitrile 12 parts, a monomer mixture prepared dropwise was added dropwise over 3 hours. At this time, the reaction temperature was kept at 80 ° C. ± 3 ° C.

After completion of the dropwise addition, the mixture was maintained at the same temperature range for 2 hours, and 1.2 parts of azobisisobutyronitrile was added.
The reaction was maintained for another 2 hours, and the reaction was continued with stirring.

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

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

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

Next, 8.3 parts of ion-exchanged water and 208.7 parts of the above water-soluble acrylic resin solution were charged into a four-necked flask equipped with a stirrer, a thermometer, a dropping funnel and a nitrogen gas inlet, and stirring was started. Then, the temperature was raised to 70 ° C. in a nitrogen stream, 0.07 part of a 0.75% aqueous solution of copper (II) sulfate was added, and 11 parts of styrene, 22 parts of butyl acrylate and 0.03 part of tert-dodecyl mercaptan were added in advance.
The mixture prepared in the above-mentioned manner, 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. At this time, the reaction temperature was maintained at 70 ° C. ± 3 ° C.

After completion of the dropwise addition, the reaction is continued under stirring while maintaining the same temperature range for one hour, and then cooled and the pH is 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 diethylene glycol 223
After the parts were mixed and heated at 180 to 230 ° C. for 8 hours to perform the esterification reaction, the condensation reaction was performed at 230 ° C. for 6 hours until the acid value became smaller than 1. .

Then, after dehydrating at 120 ° C. under reduced pressure, cooling to 90 ° C., adding 263 parts of methyl ethyl ketone, stirring, and sufficiently dissolving, the acid value is 0.7. A polyester polyol having a hydroxyl value of 50 was obtained. Thereafter, after 226 parts of the 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. For a while.

After completion of the reaction, the mixture is cooled to 40 ° C.
35% aqueous ammonia was added to make the mixture water-soluble.

Next, 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, whereby a translucent aqueous polyurethane was obtained. Was done. Hereinafter, this is abbreviated as aqueous polyurethane (U), which has a property value of 22.5% of non-volatile content, a Brookfield viscosity at 25 ° C. of 18 cps, and a pH of 7.
At 3 the solid content acid number was 19.

Reference Example 3 (Synthesis of core-shell water-dispersible resin B-1 for letdown) In a four-necked flask equipped with a stirrer, thermometer, dropping funnel and nitrogen gas inlet, Levenol 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 stirred and started to be stirred in a nitrogen stream. At 70 ° C., and then 0.6 parts of ammonium persulfate was added.
Parts, n-butyl acrylate 10 parts, acrylonitrile 5
And a mixed emulsion prepared using 100 parts of an unsaturated monomer consisting of 10 parts of glycidyl methacrylate, 6 parts of Levenol WZ and 30 parts of ion-exchanged water, was added dropwise over 3 hours. At this time, the reaction temperature was maintained at 70 ° C. ± 3 ° C.

After completion of the dropwise addition, the reaction was continued under stirring while maintaining the same temperature range for one hour, and then cooled and the pH was adjusted to 6.5 to 7.5 with 25% aqueous ammonia. Having a non-volatile 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-dispersible resin B-2) 70 parts of ethyl acrylate, 10 parts of n-butyl acrylate, 5 parts of acrylonitrile and 15 parts of glycidyl methacrylate were used. The synthesis was carried out in the same manner as in Reference Example 3 except that 100 parts
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-dispersible resin B-3) The unsaturated monomers were 65 parts of ethyl acrylate, 10 parts of n-butyl acrylate, 5 parts of acrylonitrile, and glycidyl methacrylate. 20 parts of unsaturated monomers 100
Parts, all of which were synthesized in the same manner as in Reference Example 3 and had a nonvolatile content of 39.1% and a viscosity at 25 ° C. of 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-dispersible resin B-4 for letdown) In a four-necked flask equipped with a stirrer, thermometer, dropping funnel and nitrogen gas inlet, Levenol WZ (manufactured by Kao Corporation) 12.0 and 444.4 parts of the aqueous polyurethane (U) shown in Reference Example 2 were stirred, stirring was started, and the temperature was raised to 70 ° C. in a nitrogen stream. Then, after adding 0.6 parts of ammonium persulfate, 75 parts of ethyl acrylate and 1 part of n-butyl acrylate were added in advance.
A mixed emulsion prepared using 0 parts, 100 parts of an unsaturated monomer composed of 5 parts of acrylonitrile and 10 parts of glycidyl methacrylate, 8 parts of Levenol WZ and 21.3 parts of ion-exchanged water was used for 3 hours. Was dropped. At this time, the reaction temperature was maintained at 70 ° C. ± 3 ° C.

After completion of the dropwise addition, the reaction was continued under stirring while maintaining the same temperature range for one hour, and then cooled and the pH was adjusted to 6.5 to 7.5 with 25% aqueous ammonia. Having a non-volatile 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 core-shell type water-dispersible resin B-5 for let down) 65 parts of ethyl acrylate, 10 parts of n-butyl acrylate, 5 parts of acrylonitrile, and glycidyl methacrylate 20 parts of unsaturated monomers 100
Parts, except that they are parts, the synthesis was carried out in the same manner as in B-4.
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 core-shell type water-dispersible resin B-6 for letdown) An unsaturated monomer containing 75 parts of ethyl acrylate, 15 parts of n-butyl acrylate and 10 parts of acrylonitrile was used. Synthesis was carried out in the same manner as in Reference Example 3 except that the monomers were 100 parts, and the non-volatile content was 39.6%,
An aqueous resin dispersion 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).

Table 1 shows the characteristics of the letdown resin used.

[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 Add 136 parts and use paint conditioner for 30
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 were obtained by adding ion-exchanged water and water dispersion resins for letdown (B-1) to (B-5) to the printing ink base (C-1). 1 to 5 printing inks were obtained. Further, as Comparative Example 1, the water dispersion resin for let down (B-
A printing ink using 6) was prepared.

Laminating Test Method and Results As an adhesive, 9 parts of Dick Dry Lx-901 (main agent manufactured by Dainippon Ink and Chemicals, Inc.), 9 parts of Dick Dry K
A solution of 1 part of W75 (the same curing agent) and 7.5 parts of ethyl acetate was prepared, and 15 μm was drawn using a drawdown rod # 12.
After coating on the untreated surface of the aluminum foil and evaporating the solvent, it is overlaid 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 12 μ surface-treated polyester film (hereinafter abbreviated as PET) using a drawdown rod # 7 and dried with a dryer for 30 seconds. The above adhesive was similarly applied using a draw-down rod # 12, and after the solvent was volatilized, the above-mentioned aluminum / LLD
The aluminum surface of the PE laminate was stacked 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 15 μ surface-treated nylon film (hereinafter abbreviated as “ON”) using a drawdown rod # 7 and dried with a drier for 30 seconds. I let it. The above adhesive was similarly applied using a drawdown rod # 12, and after the solvent was volatilized, LLDPE was overlaid and laminated with a pressure roll.

The thus obtained laminate 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 the peeling strength of the T-peeling of the ink layer at a speed of 300 mm / min (unit: g / g) using Tensilon RTM-25 manufactured by Orientec Co., Ltd.
15 mm width) (normal peel strength). In addition, a bag of 12 cm × 12 cm was prepared from the laminate, and a bag filled with water was immersed in a boiling water bath for 40 minutes. Thereafter, the peel strength of the laminate was measured immediately in the same manner as above (peel strength after immersion in hot water). The results of measuring the 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 a remarkably improved hot water resistance and can be suitably used as a laminating ink requiring 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 the film, and the epoxy group contained in the core is converted into the shell portion and the aqueous resin containing a carboxyl group. The reaction with the carboxyl group of the above reduces the number of hydrophilic groups and low molecular weight components in the film, so that the adhesion and hot water resistance of the film are remarkably improved. This makes it possible to provide an aqueous coating composition which can be sufficiently used especially as a laminating ink requiring boil retort resistance.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C09D 11/10 C08G 18/00-18/87

Claims (2)

(57) [Claims] 1. A core-shell type water-dispersible resin containing a colorant and a carboxyl group-containing aqueous resin, and having an epoxy group-containing copolymer as a core and a carboxyl group-containing polyurethane as a shell. Lamine
Preparative aqueous coating composition. 2. The equivalent 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 (A) ) / (B) = 3
/ 1-1 / 2 laminate for aqueous coating composition according to claim 1 it is.