JP2023096902A - Coated paper, and package or container including the coated paper - Google Patents

Abstract

To provide coated paper that can substitute for a polyethylene film without causing a decrease in paper recycling efficiency, the coated paper excelling in all of oil resistance, water resistance, and safety.SOLUTION: Coated paper comprises a paper substrate with its one side comprising a printed layer and an overcoating layer laminated on in this order, the printed layer being composed of an ink that can be brought into contact with food without concern about safety, and the overcoating layer comprising a styrene acryl copolymer composed of a copolymer of a styrene and a methacrylate,.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to coated paper and packages or containers using the coated paper.

In food packaging, when paper or paperboard is used as a material that comes into direct contact with food, it is necessary to have functions such as oil resistance and water resistance depending on the food and to satisfy high safety. Therefore, a material obtained by laminating a polyethylene film, a polypropylene film, or the like, which is obtained by extruding a polyethylene resin, a polypropylene resin, or the like into a film shape, to a paper substrate is often used. Designability can also be enhanced by using paper in which these films are laminated on paper provided with printing ink (having a printing layer).

However, since the laminated polyethylene film does not dissolve in the alkaline solution used in the paper recycling process, it must be physically removed, leading to a decrease in recycling efficiency. In addition, marine pollution due to the outflow of plastic waste into the ocean has become a global problem. A target of the Sustainable Development Goals (SDGs) is to "By 2025 prevent and significantly reduce marine pollution of all kinds, especially pollution from land-based activities, including marine debris and eutrophication." It has become an important global theme, with agreements to strengthen efforts at summits (summer meetings of major countries). Therefore, there is a demand for a paper-made material that does not use a plastic film and that is oil-resistant, water-resistant, safe to the human body, and safe to the environment.

On the other hand, in order to satisfy high safety, development of printing inks that can come into direct contact with food is underway. For example, Patent Document 1 discloses a food contactable printing ink composed of ingredients recognized as food additives.

JP 2005-220144 A

However, in applications where the printing ink comes into direct contact with food for a long period of time, there is a concern that the components of the printing ink may migrate into the food, so higher safety is required. For example, chocolate paperboard is often printed in the same color as chocolate, but is often stored in the package for a relatively long period of time, so higher safety is required.

The present invention has been made in view of the above circumstances, and is a coated paper that does not reduce paper recycling efficiency and is a substitute for polyethylene film, and is excellent in all of oil resistance, water resistance, and safety. The purpose is to provide a coated paper.

As a result of intensive studies by the present inventors to solve the above problems, a printing layer is formed using ink that can come into contact with food, and a styrene-acrylic copolymer having excellent oil resistance and water resistance is formed on this printing layer. The inventors have found that the above problems can be solved by providing an overcoating coating layer containing coalescence, and have completed the present invention.
That is, the present invention includes the following aspects.
[1] A printed layer and an overcoating layer are laminated in this order on one side of the paper substrate,
The printed layer is formed of ink that can come into contact with food,
Coated paper, wherein the overcoating layer contains a styrene-acrylic copolymer comprising a copolymer of styrenes and (meth)acrylate.
[2] The coated paper according to [1], wherein the styrene-acrylic copolymer contained in the overcoating layer is a styrene-acrylic copolymer of styrene, α-methylstyrene and (meth)acrylate.
[3] The styrene-acrylic copolymer contained in the overcoating coating layer is a styrene-acrylic copolymer of styrene, α-methylstyrene, and (meth)acrylate, and (meth)acrylic acid and (meth)acrylate. The coated paper according to [2], which is a styrene-acrylic copolymer consisting of a copolymer.
[4] The coated paper according to any one of [1] to [3], wherein the styrene-acrylic copolymer contained in the overcoating coating layer is a styrene-acrylic copolymer having a core-shell structure.
[5] The coated paper according to any one of [1] to [4], wherein the overcoating layer further contains wax.
[6] The coated paper of [5], wherein the wax exists within the core-shell structure of the styrene-acrylic copolymer.
[7] The coated paper according to any one of [1] to [6], wherein the food-contactable ink is an ink composed of raw materials approved as food ingredients or food contact ingredients.
[8] The coated paper according to any one of [1] to [7], wherein the printed layer and the overcoating layer are printed and coated in-line [9] Any of [1] to [8] A package or container using the coated paper as described in (1).

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a coated paper that can be used as a polyethylene film substitute without reducing paper recycling efficiency, and that is excellent in all of oil resistance, water resistance, and safety.

The present invention will be described in detail below. It should be noted that the description of the constituent elements described below is an example for describing the present invention, and the present invention is not limited to these contents.

[Coated paper]
In the coated paper of the present invention, a printed layer and an overcoating layer are laminated in this order on one side of a paper substrate.
The printed layer is made of ink that can come into contact with food.
The overcoating layer contains a styrene-acrylic copolymer comprising a copolymer of styrenes and (meth)acrylate.

(Layer structure)
Examples of the layer structure of the coated paper of the present invention include the following aspects. Specifically, a printed layer is provided on one side of the paper substrate, and an overcoating layer is provided thereon.
・Paper substrate - printed layer - overcoating coating layer

In addition, the coated paper of the invention may be provided with two or more overcoating layers.
When two or more overcoating layers are provided, preferred embodiments of the coated paper of the present invention include, for example, coated paper having the following layer structure.
・Overcoating coating layer - paper substrate - printing layer - overcoating coating layer

The coated paper of the invention is preferably provided with a primer layer (anchor layer) adjacent to the printed layer in order to improve adhesion of the printed layer.
In the case of having a primer layer (anchor layer), preferred embodiments of the coated paper of the present invention include, for example, coated paper having the following layer structure.
・Paper substrate - primer layer (anchor layer) - printing layer - overcoating coating layer ・Overcoating coating layer - paper substrate - primer layer (anchor layer) - printing layer - overcoating coating layer

A preferred embodiment of the coated paper of the present invention is coated paper further laminated with a heat seal layer.
The heat seal layer is preferably provided on the other side of the paper substrate (the side opposite to the side of the paper substrate on which the printed layer is provided).
When the paper has a heat-seal layer, preferred embodiments of the coated paper of the present invention include, for example, coated paper having the following layer structure.
・Heat seal layer - paper base - primer layer (anchor layer) - print layer - overcoating coating layer ・Heat seal layer - overcoating coating layer - paper base - primer layer (anchor layer) - print layer - over Coating layer

The coated paper of the present invention has a printed layer formed with ink that can come into contact with food. Accordingly, the coated paper of the present invention is excellent in safety. Moreover, the overcoating coating layer according to the present invention contains a styrene-acrylic copolymer and has high oil resistance and water resistance. As a result, the coated paper of the present invention is a coated paper that can be used as a substitute for polyethylene film without lowering paper recycling efficiency, and is excellent in oil resistance and water resistance.
That is, the coated paper of the present invention is a coated paper that can be used as a polyethylene film substitute without reducing paper recycling efficiency, and is excellent in all of oil resistance, water resistance, and safety.
Each layer constituting the coated paper of the present invention will be described in detail below.

(Print layer)
The printed layer is a layer formed by printing ink. The printed layer contains characters, numbers, patterns, figures, symbols, patterns, etc. for decoration, display of contents, display of expiration date, display of manufacturer, seller, etc. It is a layer that forms any desired printed pattern.
The printing layer is preferably located on the outer surface side of the paper substrate, and as described above, it is preferable that the printing layer and the overcoating layer are laminated in this order on one side of the paper substrate. preferable. Moreover, the printed layer may be provided on the entire surface, or may be provided partially.

The number of printed layers may be one or multiple layers. In order to print in a plurality of colors and improve designability, it is preferable to have a printing layer consisting of a plurality of layers.
The printed layer can be formed using a conventionally known method, the formation method is not particularly limited, and can be appropriately selected according to the purpose.

<Ink>
The ink forming the printed layer is a food-contactable ink. As a result, it is highly safe in applications where it is in direct contact with food for a long period of time. Food contactable inks include, for example, inks composed of ingredients approved as food ingredients or food contact ingredients.

<<Ink composed of food ingredients>>
The ink composed of food ingredients is not particularly limited, and known edible inks can be used. Edible inks include, for example, an edible ink composition described in JP-A-2010-248356, an edible ink for ink jet printing described in JP-A-2010-185030, and an edible ink described in JP-A-2008-285533. Emulsion ink, ink composition described in JP-A-2007-177132, edible ink described in JP-A-2005-320528, raw materials and composition used for food jet ink described in JP-A-2000-507820, etc. can be used.
Alternatively, commercially available edible ink (for example, Rio Fresh 1377 manufactured by Toyo Ink Mfg. Co., Ltd.) may be used.
An example of the composition of the ink composed of food ingredients is shown below.

The ink may contain, for example, an edible resin as a resin. Edible resins include binder components such as shellac, dammar, copal, mystic, rosin and soybean protein. These can be used singly or in combination.

The ink may contain, for example, an edible coloring material as a coloring material. Synthetic coloring agents and/or natural coloring agents can be used as edible coloring agents. Examples of synthetic colorants include azo dyes Yellow No. 5, Red No. 505, etc., xanthene dyes Red No. 213, Red No. 230, etc., quinoline dyes Yellow No. 204, etc., triphenyl There are methene dyes such as Blue No. 1, anthraquinone dyes such as Green No. 201, and indigo dyes, as well as organic coloring agents (tar pigments) such as Risol Rubin BCA, Lake Red CBA, Risol Red, and Risol Red CA. , Risol Red BA, Risol Red SR, Tetrachlortetrabromofluorescein, Brilliant Lake Red R, Deep Maroon, Toluidine Red, Tetrabromofluorescein, Sudan III, Herringdon Pink CN, Permerton Red, Dibromofluorescein, Permanent Orange, Bench Gin Orange G, Diiodofluorescein, Quinoline Yellow SS, Benzidine Yellow G, Quinizarin Green SS, Indigo, Calvinthrene Blue, Alizurin Purple SS, Brilliant Fast Scarlet, Permanent Red F5R, Medicinal Scarlet, Oil Red XO, Hansa Orange , Orange SS, Hansa Yellow, Yellow AB, Yellow OB, Sudan Blue B, and Phthalocyanine Blue. Natural coloring agents include paprika pigment, carotene pigment, carrot carotene pigment, rosewood pigment (sandalwood pigment), guaiazulene, red cabbage pigment, red rice pigment, annatto pigment, squid ink pigment, turmeric pigment, paprika pigment, krill pigment, and persimmon. Pigment, caramel pigment, corn pigment, onion pigment, tamarind pigment, spirulina pigment, safflower yellow pigment, safflower red pigment, gardenia yellow pigment, gardenia blue pigment, gardenia red pigment, whole buckwheat pigment, cherry pigment, seaweed pigment, hibiscus pigment , grape juice pigment, marigold pigment, purple potato pigment, purple yam pigment, lac pigment, rutin, butterfly bean blue pigment, carminic acid, laccaic acid, brasilin, crocin, carotene, cochineal, and Linablue (registered trademark). These can be used singly or in combination.

The ink may contain, for example, an edible solvent as a solvent. Edible solvents include water, ethanol, glycerin, propylene glycol and the like. These can be used singly or in combination.

The ink may contain additives such as edible dispersants. Edible dispersants include glycerin fatty acid ester, sucrose fatty acid ester, lecithin and the like. These can be used singly or in combination.

<<Inks composed of raw materials approved as food contact ingredients>>
Next, inks composed of raw materials approved as food contact components (hereinafter also referred to as "direct contact food inks") will be described.

A raw material approved as a food contact ingredient may be, for example, a raw material approved under the positive list system or the negative list system of the regulations or standards shown below.
・“European Regulation (EC) No. 1935/2004 (promulgated in October 2011, enforced in December 2011)” in the European Union
・"European Regulation (EC) No. 10/2011 (promulgated in January 2011, enforced in May)" in the European Union
・In the Swiss Confederation, "RS 817.023.21 Federal Order of the Ministry of the Interior on Materials and Products Decree of 23 November 2005"
・"BfR Recommendations for substances in contact with food" of the German Federal Institute for Risk Assessment (BfR) in the Federal Republic of Germany
・"Food Sanitation Law (Ministry of Health and Welfare Notification No. 370)" in Japan
・In Japan, the positive list of food containers and containers and packaging posted by partial revision of the above "Food Sanitation Law (Ministry of Health and Welfare Notification No. 370)" (revised Food Sanitation Law)
・"Article 21 of the Federal Regulations (CFR Article 21) Part 170-190" in the United States
・In the People's Republic of China, "Compulsory National Standard GB 9685-2016 "Hygienic Standards for the Use of Additives in Food Containers and Packaging Materials" and "Compulsory National Standard GB 4806.1-2016 General Safety Requirements for Food Contact Materials and Products" ”

The direct food contact ink according to the present invention may be composed of raw materials that satisfy the above rules or standards, but it is preferable to use the direct food contact ink described in WO 2021/007422.
Commercially available direct contact food inks (eg, SunPak Organic DFC from Sun Chemical, SunVistro Aquasafe Food Contact Ink from Sun Chemical, etc.) may also be used.

The ink that can come into contact with food may be the ink described above or ink composed of the raw materials described above, but from the viewpoint of higher safety, all the raw materials that make up the ink must be approved as food ingredients. is particularly preferred. Moreover, from the viewpoint of higher safety, it is particularly preferable that the raw materials constituting the ink are plant-derived and do not contain mineral oil and bisphenol A. Furthermore, from the viewpoint of not drying due to oxidation, it is particularly preferred that the raw materials constituting the ink do not contain drying catalysts based on heavy metals such as cobalt and manganese.

Examples of inks include inks used for offset printing, flexographic printing, gravure printing, and the like. When these printing methods are used, the printing of ink that can come into contact with food for image formation on paper, etc., and the adhesion of the ink to the paper, etc. after printing depend on fluid ink constituents such as ethanol. It is preferable that printing is performed on paper or the like, ethanol is dried and evaporated on the printed material, and the edible resin and pigment components are fixed and dried on the surface or inside of the printed paper or the like.
Since the method of printing is the same as the method of manufacturing ordinary printed matter, it is the same as ordinary printing except that the ink is an ink that can come into contact with food.
The printing layer according to the present invention can contain raw materials used in conventional offset printing, flexographic printing, gravure printing, etc. described below within a range that does not impair the effects of the present invention. These raw materials are also preferably composed of raw materials approved as food contact ingredients and selected from non-toxic raw materials.
Printing ink compositions used in conventional offset printing, flexographic printing, gravure printing and the like are described below.

[Offset printing]
Offset printing is a printing method that utilizes the repulsion of water and oil. The printing plate consists of a part that repels water and repels ink, and a part that repels water and accepts ink. The latter is the drawing area.
Offset printing inks include oxidation polymerization offset printing inks, thermosetting offset printing inks, and active energy ray-curable offset printing inks. For example, general oxidation polymerization offset printing inks used in offset printing consists of a composition containing pigment, varnish, vegetable oil, organic solvent, extender, drying accelerator and the like.

<Coloring pigment>
Examples of color pigments include yellow pigments such as disazo yellow (Pigment Yellow 12, Pigment Yellow 13, Pigment Yellow 17, and Pigment Yellow 1) and Hansa Yellow, and magenta pigments such as brilliant carmine 6B, lake red C, watching red and the like. Examples of cyan pigments include phthalocyanine blue, phthalocyanine green, and alkali blue, and examples of black pigments include carbon black such as furnace carbon black and channel black, and aniline black.

<Varnish>
The varnish used in the printing ink composition contains at least a rosin-modified phenolic resin, and the varnish to be used can be obtained by a known method. and/or the transesterification reaction and/or the aluminum chelation reaction. Other resins that can be used in combination with the rosin-modified phenolic resin include petroleum resins, alkyd resins, rosin-modified alkyd resins, petroleum resin-modified alkyd resins, rosin ester resins, and the like. It can also be adjusted by changing the type of vegetable oil component used in the production of the varnish and the temperature of the transesterification reaction.

<Vegetable oil>
Vegetable oils include oils such as soybean oil, linseed oil, rice oil, paulownia oil, castor oil, dehydrated castor oil, corn oil, safflower oil, tung oil, canol oil, and thermally polymerized and oxidatively polymerized oils thereof. In addition, linseed oil fatty acid methyl ester, linseed oil fatty acid ethyl ester, linseed oil fatty acid propyl ester, linseed oil fatty acid butyl ester, soybean oil fatty acid methyl ester, soybean oil fatty acid ethyl ester, soybean oil fatty acid propyl ester, soybean oil fatty acid butyl ester, Palm oil fatty acid methyl ester, palm oil fatty acid ethyl ester, palm oil fatty acid propyl ester, palm oil fatty acid butyl ester, castor oil fatty acid methyl ester, castor oil fatty acid ethyl ester, castor oil fatty acid propyl ester, castor oil fatty acid butyl ester, tung oil ester, Vegetable oil fatty acid esters such as isobutyl laurate and n-butyl laurate can also be used. Recycled vegetable oil can also be used as the vegetable oil component. Recycled vegetable oil is vegetable oil that has been recovered from oils used for cooking or the like and regenerated.

<Organic solvent>
The organic solvent used heretofore is a conventionally known solvent having naphthene as a main component and having low odor, low aromaticity, and low toxicity. It is preferable that the initial boiling point obtained by the distillation test described in JIS K2254 is 230°C or higher and the end point is 350°C or lower.

<Extender pigment>
As the extender pigment, one or two or more known pigments such as clay such as pyrophyllite clay, talc, barium sulfate, calcium carbonate, ground calcium carbonate, barium carbonate, magnesium carbonate, silica, bentonite, titanium oxide, etc. may be used. can be done. These extender pigments may be surface-treated with rosin acid or the like, or may be untreated. Moreover, it is preferable that the primary particle diameter is 30 nm or more and 150 nm or less.

<Drying accelerator>
A drying accelerator (dryer) is added for the purpose of improving the drying property of the ink coating film. and metal soaps which are salts with carboxylic acids of.

[Flexographic printing, gravure printing]
Gravure printing and flexographic printing are printing methods that use letterpress or intaglio printing plates. Printing inks used for these printing methods are roughly classified into organic solvent-based liquid printing inks containing organic solvents as the main solvent and water-based liquid printing inks containing water as the main solvent.

<Organic solvent liquid printing ink>
Organic solvent-based liquid printing inks are obtained by dispersing a mixture containing a coloring agent, a binder resin, an organic solvent medium, a dispersant, an antifoaming agent, etc., which will be described later, with a disperser to obtain a pigment dispersion. It can be obtained by adding a resin, an aqueous medium, and, if necessary, an additive such as a leveling agent to the obtained pigment dispersion, and stirring and mixing. As a dispersing machine, a bead mill, eiger mill, sand mill, gamma mill, attritor, etc. generally used for the production of gravure and flexographic printing inks are used.

The ink viscosity of the organic solvent-based liquid printing ink is 10 mPa·s or more from the viewpoint of preventing sedimentation of the pigment and appropriately dispersing it, whether it is used as a gravure ink or a flexographic ink. It is preferably in the range of 1000 mPa·s or less from the viewpoint of workability efficiency during ink production and printing. The above viscosity is measured at 25° C. with a B-type viscometer manufactured by Tokimec.

The viscosity of the ink can be adjusted by appropriately selecting the types and amounts of raw materials used, binder resins, pigments, organic solvents, and the like. Also, the viscosity of the ink can be adjusted by adjusting the particle size and particle size distribution of the pigment in the ink.

Organic solvent-based liquid printing ink has excellent adhesion to substrates such as paper and synthetic paper, and is suitable for gravure printing using gravure printing plates such as electronic engraving intaglio, or flexographic printing using flexographic printing plates such as resin plates. It is useful as an ink for
The film thickness of the printing ink formed by the gravure printing method or the flexographic printing method using the organic solvent type liquid printing ink is, for example, 10 μm or less, preferably 5 μm or less.

<<binder resin>>
Binder resins for organic solvent-based liquid printing inks are not particularly limited, and include polyurethane resins, acrylic resins, vinyl chloride-vinyl acetate copolymer resins, vinyl chloride-acrylic copolymers, which are commonly used for liquid printing inks. Combined resin, chlorinated polypropylene resin, cellulose resin, polyamide resin, ethylene-vinyl acetate copolymer resin, vinyl acetate resin, styrene resin, dammar resin, styrene-maleic acid copolymer resin, polyester resin, alkyd resin, poly chloride Examples include vinyl resins, rosin-based resins, rosin-modified maleic acid resins, terpene resins, phenol-modified terpene resins, ketone resins, cyclized rubbers, chlorinated rubbers, butyral resins, polyacetal resins, petroleum resins, and modified resins thereof. . These resins can be used alone or in combination of two or more.
Among the above, polyurethane resins, cellulose resins, polyamide resins, vinyl chloride-vinyl acetate copolymer resins, vinyl chloride-acrylic copolymer resins, ethylene-vinyl acetate copolymer resins, vinyl acetate resins, acrylic resins, styrene resins , styrene-maleic acid copolymer resin, dammar resin, rosin-based resin, rosin-modified maleic acid resin, ketone resin and cyclized rubber.
The content of the binder resin is in the range of 1 to 50% by mass, more preferably 2 to 40% by mass, in terms of the solid content of the water-based liquid printing ink.

<<Organic solvent>>
Organic solvents for organic solvent-type liquid printing inks are not particularly limited, but examples include aromatic hydrocarbon organic solvents such as toluene, xylene, Solvesso #100 and Solvesso #150, hexane, methylcyclohexane, heptane, octane, Examples include aliphatic hydrocarbon-based organic solvents such as decane, and ester-based organic solvents such as methyl acetate, ethyl acetate, isopropyl acetate, normal-propyl acetate, butyl acetate, amyl acetate, ethyl formate, and butyl propionate. Water-miscible organic solvents include alcohols such as methanol, ethanol, propanol, butanol and isopropyl alcohol, ketones such as acetone, methyl ethyl ketone and cyclohaxanone, ethylene glycol (mono, di) methyl ether, and ethylene glycol (mono, di) ethyl. Ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, monobutyl ether, diethylene glycol (mono, di) methyl ether, diethylene glycol (mono, di) ethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, triethylene glycol (mono, Di)methyl ether, propylene glycol (mono, di)methyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol (mono, di)methyl ether, and other glycol ether organic solvents can be used. These may be used alone or in combination of two or more.

Organic solvent-based liquid printing inks may also contain waxes, chelate cross-linking agents, extender pigments, leveling agents, antifoaming agents, plasticizers, infrared absorbers, ultraviolet absorbers, fragrances, flame retardants, etc. can also

<<coloring agent>>
As the coloring agent, it is preferable to use a general natural food coloring from the viewpoint of safety even if it comes into direct contact with food. Representative examples of such pigments include carotenoids, chlorophyll, anthocyanins, and turmeric.
As the colorant, organic pigments and/or inorganic pigments used in general inks, paints, recording agents, etc. may be used.
Examples of organic pigments include soluble azo, insoluble azo, azo, phthalocyanine, halogenated phthalocyanine, anthraquinone, anthanthrone, dianthraquinonyl, anthrapyrimidine, perylene, perinone, quinacridone, Thioindigo-based, dioxazine-based, isoindolinone-based, quinophthalone-based, azomethineazo-based, flavanthrone-based, diketopyrrolopyrrole-based, isoindoline-based, indanthrone-based, and carbon black-based pigments can be used. Also, for example, Carmine 6B, Lake Red C, Permanent Red 2B, Disazo Yellow, Pyrazolone Orange, Carmine FB, Chromophtal Yellow, Chromophtal Red, Phthalocyanine Blue, Phthalocyanine Green, Dioxazine Violet, Quinacridone Magenta, Quinacridone Red, Indance Ron blue, pyrimidine yellow, thioindigo bordeaux, thioindigo magenta, perylene red, perinone orange, isoindolinone yellow, aniline black, diketopyrrolopyrrole red, daylight fluorescent pigments, and the like. Both non-acid-treated pigments and acid-treated pigments can be used.

Inorganic pigments include white inorganic pigments such as titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, litbon, antimony white, and gypsum. Among inorganic pigments, the use of titanium oxide is particularly preferred. Titanium oxide exhibits a white color and is preferable from the viewpoints of coloring power, hiding power, chemical resistance and weather resistance. From the viewpoint of printing performance, the titanium oxide is preferably treated with silica and/or alumina.
Examples of non-white inorganic pigments include aluminum particles, mica (mica), bronze powder, chrome vermilion, yellow lead, cadmium yellow, cadmium red, ultramarine blue, Prussian blue, red iron oxide, yellow iron oxide, iron black, and zircon. Although the aluminum is in the form of powder or paste, it is preferable to use it in the form of paste from the viewpoints of handling and safety, and whether to use leafing or non-leafing is appropriately selected from the viewpoint of brightness and density.
The average particle size of the pigment is preferably in the range of 10 to 200 nm, more preferably about 50 to 150 nm.

The amount of the pigment is sufficient to ensure the concentration and coloring strength of the aqueous liquid printing ink, that is, 1 to 60% by mass of the total mass of the ink, and 10 to 90% by mass of the solid content in the ink. It is preferably contained in proportion. Moreover, these pigments can be used individually or in combination of 2 or more types.

<Water-based liquid printing ink>
A water-based liquid printing ink is obtained by dispersing a mixture containing a colorant, a binder resin, an aqueous medium, a dispersant, an antifoaming agent, etc. described below with a disperser to obtain a pigment dispersion. It can be obtained by adding a resin, an aqueous medium, and, if necessary, an additive such as a leveling agent to the obtained pigment dispersion, and stirring and mixing. As a dispersing machine, bead mill, eiger mill, sand mill, gamma mill, attritor, etc., which are commonly used for the production of gravure and flexographic printing inks, are used. The viscosity is preferably 7 to 25 seconds at 25° C. using Zahn Cup #4 manufactured by Rigosha, more preferably 10 to 20 seconds. The surface tension of the obtained flexographic ink at 25° C. is preferably 25-50 mN/m, more preferably 33-43 mN/m. The lower the surface tension of the ink, the better the wettability of the ink to the substrate such as a film. tends to be easily connected, and tends to cause stains on the printing surface called dot bridges. On the other hand, if the surface tension exceeds 50 mN/m, the wettability of the ink to the base material such as a film is lowered, which tends to cause repelling.

On the other hand, when a water-based liquid printing ink is used as a gravure ink, the viscosity may be 7 to 25 seconds at 25° C. using Zahn Cup #3 manufactured by Rigosha, more preferably 10 to 20 seconds. . The surface tension of the obtained gravure ink at 25° C. is preferably 25 to 50 mN/m, more preferably 33 to 43 mN/m, like the flexo ink. The lower the surface tension of the ink, the better the wettability of the ink to the substrate such as a film. tends to be easily connected, and tends to cause stains on the printing surface called dot bridges. On the other hand, if the surface tension exceeds 50 mN/m, the wettability of the ink to the base material such as a film is lowered, which tends to cause repelling.

Water-based liquid printing ink has excellent adhesion to substrates such as paper and synthetic paper, and is suitable for gravure printing using gravure printing plates such as electronic engraving intaglio, or flexographic printing using flexographic printing plates such as resin plates. Useful as an ink.
The film thickness of printing ink formed by gravure printing or flexographic printing using water-based liquid ink is, for example, 10 μm or less, preferably 5 μm or less.

<<binder resin>>
Binder resins for water-based liquid printing inks are not particularly limited, and include urethane resins, polyvinyl alcohols, polyvinylpyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymers, and acrylic acid that are commonly used for water-based liquid printing inks. Acrylic copolymers such as potassium-acrylonitrile copolymer, acrylic acid ester polymer emulsion, polyester urethane dispersion, vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid alkyl ester copolymer; Acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid- Styrene-acrylic acid resin such as acrylic acid alkyl ester copolymer; styrene-maleic acid; styrene-maleic anhydride; vinylnaphthalene-acrylic acid copolymer; vinylnaphthalene-maleic acid copolymer; vinyl acetate-ethylene copolymer vinyl acetate-based copolymers such as vinyl acetate-fatty acid vinyl ethylene copolymers, vinyl acetate-maleic acid ester copolymers, vinyl acetate-crotonic acid copolymers, vinyl acetate-acrylic acid copolymers, and these Salt can be used. These binder resins can be used alone or in combination of two or more.
Among them, it is preferable to use an acrylic resin or a urethane resin as the binder resin because they are readily available, and acrylic acid ester polymer emulsions and polyester urethane dispersions are particularly preferable.
The binder resin preferably accounts for 5 to 50% by mass in terms of solid content of the water-based liquid printing ink. If it is 5% by mass or more, the strength of the ink coating film does not decrease, and good adhesion to substrates, resistance to water rubbing, etc. can be maintained. Conversely, when the amount is 50% by mass or less, it is possible to suppress a decrease in coloring power, avoid high viscosity, and prevent a decrease in workability. Among them, 5 to 40% by mass is more preferable, and 5 to 20% by mass is most preferable.

<<aqueous medium>>
Aqueous media for aqueous liquid printing inks include, for example, water, water-miscible organic solvents, and mixtures thereof. Examples of water-miscible organic solvents include alcohol solvents such as methanol, ethanol, n-propanol and isopropanol; ketone solvents such as acetone and methyl ethyl ketone; polyalkylene glycols such as ethylene glycol, diethylene glycol and propylene glycol; alkyl ethers of; and lactam solvents such as N-methyl-2-pyrrolidone. The aqueous medium may be water alone, a mixture of water and a water-miscible organic solvent, or a water-miscible organic solvent alone. As the aqueous medium, water alone or a mixture of water and an organic solvent miscible with water is preferable, and water alone is particularly preferable, from the viewpoint of safety and environmental load.

The water-based liquid printing ink may also contain the aforementioned colorants, extenders, pigment dispersants, leveling agents, defoamers, plasticizers, infrared absorbers, ultraviolet absorbers, fragrances, flame retardants, and the like. Fatty acid amides such as oleic acid amide, stearic acid amide, and erucic acid amide for imparting friction resistance and slipperiness, among others, and silicon-based, non-silicon-based defoaming agents and pigments for suppressing foaming during printing Various dispersing agents that improve the wettability of the polymer are useful.

(Overcoating coating layer)
The coated paper of the present invention is laminated with an overcoating coating layer, and the overcoating coating layer contains a styrene-acrylic copolymer comprising a copolymer of styrenes and (meth)acrylate. .
In the present invention, an embodiment in which at least one overcoating layer is the outermost layer is preferred.

The overcoating layer preferably contains a styrene-acrylic copolymer (A) of styrene, α-methylstyrene and (meth)acrylate.
The overcoating coating layer in the first embodiment, which is an example of a preferred embodiment excellent in oil resistance and water resistance, is, for example, a styrene-acrylic copolymer of styrene, α-methylstyrene, and (meth)acrylate ( It is formed by a coating composition (CS) containing an emulsion containing A) and an aqueous medium.
The overcoating coating layer in the second embodiment, which is an example of a preferred embodiment particularly excellent in water resistance, is, for example, an overcoating coating containing at least an aqueous solvent, a styrene-acrylic copolymer, and wax. It is formed by a waterproof coating composition for layer formation.

Furthermore, the overcoating coating layer comprises a styrene-acrylic copolymer (A) of styrene, α-methylstyrene, and (meth)acrylate, and an acrylic copolymer (B) of (meth)acrylic acid and (meth)acrylate. It may contain a styrene-acrylic copolymer consisting of.
Moreover, the styrene-acrylic copolymer is preferably a styrene-acrylic copolymer having a core-shell structure.

The overcoating layer of the first embodiment, which has excellent oil resistance and water resistance, will be described below, and then the overcoating layer of the second embodiment, which has particularly excellent water resistance, will be described.

[Overcoating layer in the first embodiment]
As described above, the overcoating coating layer in the first embodiment includes, for example, an emulsion containing a styrene-acrylic copolymer (A) of styrene, α-methylstyrene, and (meth)acrylate, and an aqueous medium. It is formed by the containing coating composition (CS). The overcoating coating layer according to the embodiment is a coating layer having excellent oil resistance and water resistance.

<Coating composition (CS) containing styrene acrylic copolymer (A)>
<<Emulsion containing styrene-acrylic copolymer (A)>>
First, an emulsion containing a styrene-acrylic copolymer (A) of styrene, α-methylstyrene and (meth)acrylate will be described. In this embodiment, (meth)acrylate is a generic term for acrylate and methacrylate, and (meth)acrylic acid is a generic term for acrylic acid and methacrylic acid.

In this embodiment, α-methylstyrene in the styrene-acrylic copolymer (A) represents either o-methylstyrene, m-methylstyrene or p-methylstyrene or a mixture thereof.

In addition, the styrene-acrylic copolymer (A) includes the above styrene and styrene derivatives other than the above α-methylstyrene (p-dimethylsilylstyxystyrene, p-tert-butyldimethylsiloxystyrene, p-tert-butylstyrene), vinyl Naphthalene, vinylanthracene, 1,1-diphenylethylene, etc. may be partially used as long as they do not impair the scope of the present embodiment.

The (meth)acrylate is not particularly limited, and examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, iso-propyl (meth)acrylate, allyl (meth)acrylate, n-(meth)acrylate, Butyl, iso-butyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-amyl (meth)acrylate, iso-amyl (meth)acrylate, (meth)acrylate n-hexyl acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-lauryl (meth)acrylate, n-tridecyl (meth)acrylate, n-stearyl (meth)acrylate , phenyl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, 4-tert-butylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, tricyclodecanyl (meth)acrylate , dicyclopentadienyl (meth)acrylate, adamantyl (meth)acrylate, glycidyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 2-methoxyethyl (meth)acrylate, (meth)acrylic acid 2-ethoxyethyl, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, trifluoroethyl methacrylate, tetrafluoropropyl methacrylate, pentafluoropropyl methacrylate, octafluoropentyl methacrylate, pentadeca methacrylate Fluorooctyl, heptadecafluorodecyl methacrylate, N,N-dimethyl(meth)acrylamide, acryloylmorpholine, (meth)acrylonitrile, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, polyethylene glycol-polypropylene glycol (meth)acrylate Acrylate, polyethylene glycol-polybutylene glycol (meth)acrylate, polypropylene glycol-polybutylene glycol (meth)acrylate, methoxypolyethyleneglycol (meth)acrylate, ethoxypolyethyleneglycol (meth)acrylate, butoxypolyethyleneglycol (meth)acrylate, octoxy polyethylene glycol (meth)acrylate, lauroxypolyethyleneglycol (meth)acrylate, stearoxypolyethyleneglycol (meth)acrylate, phenoxypolyethyleneglycol (meth)acrylate, methoxypolypropyleneglycol (meth)acrylate, octoxypolyethyleneglycol-polypropyleneglycol (meth)acrylate ) General-purpose (meth)acrylates such as polyalkylene oxide group-containing (meth)acrylic monomers such as acrylates can be used. Among them, a homopolymer having an acrylate is preferable because it exhibits a lower glass transition temperature, and it is preferable that the main component is an acrylate having an alkyl group having 1 to 20 carbon atoms, and an alkyl group having 1 to 12 carbon atoms. It is preferable that the main component is an acrylate having a Examples of such acrylates having an alkyl group having 1 to 12 carbon atoms include methyl acrylate, ethyl acrylate, iso-propyl acrylate, allyl acrylate, n-butyl acrylate, iso-butyl acrylate, ( meth)sec-butyl acrylate, tert-butyl acrylate, n-amyl acrylate, iso-amyl acrylate, n-hexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, (meth)acrylic acid n - includes lauryl and the like.

The (meth)acrylate used as a constituent component of the styrene-acrylic copolymer (A) of the present embodiment may be one type or two or more types, and two or more types of (meth)acrylates are used. Among them, it is preferable to use two or more acrylates having an alkyl group of 1 to 12 carbon atoms as main components.

The emulsion containing the styrene acrylic copolymer (A) preferably further contains a copolymer of (meth)acrylic acid and (meth)acrylate. A copolymer of (meth)acrylic acid and (meth)acrylate is a copolymer of (meth)acrylic acid and the above (meth)acrylate (also referred to as acrylic copolymer (B)). The (meth)acrylate is not particularly limited, but is preferably an acrylate having an alkyl group having 1 to 20 carbon atoms. The main component is preferably an acrylate having an alkyl group of 1 to 20 atoms, and preferably an acrylate having an alkyl group of 1 to 12 carbon atoms. Examples of such acrylates having an alkyl group having 1 to 12 carbon atoms include methyl acrylate, ethyl acrylate, iso-propyl acrylate, allyl acrylate, n-butyl acrylate, iso-butyl acrylate, ( meth)sec-butyl acrylate, tert-butyl acrylate, n-amyl acrylate, iso-amyl acrylate, n-hexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, (meth)acrylic acid n - includes lauryl and the like.

The emulsion containing the styrene-acrylic copolymer (A) preferably contains the styrene-acrylic copolymer (A) and the acrylic copolymer (B). The emulsion of the styrene-acrylic copolymer (A) polymerized by a known polymerization method using an aqueous medium, and the acrylic copolymer polymerized by a known polymerization method using an aqueous medium such as emulsion polymerization or transfer emulsification. It may be an emulsion obtained by appropriately mixing the emulsion (B), or an emulsion of a resin in which the styrene-acrylic copolymer (A) and the acrylic copolymer (B) form a core-shell structure. good. The "resin containing the styrene-acrylic copolymer (A)" may be, for example, a resin that forms a core-shell structure composed of the styrene-acrylic copolymer (A), or the styrene-acrylic copolymer (A ) and the acrylic copolymer (B) may be a resin forming a core-shell structure.

The core-shell structure is formed by having a region in which the "styrene-acrylic copolymer (A)" is abundant and a region in which the "acrylic copolymer (B)" is abundant. be. In the core-shell structure, for example, "acrylic copolymer (B)" may be present in a region where "styrene-acrylic copolymer (A)" is abundant, or these copolymers may It may be polymerized.

The emulsion containing the styrene-acrylic copolymer (A) preferably contains a resin containing at least the styrene-acrylic copolymer (A) and has a minimum film-forming temperature in the range of -30°C to 30°C. The range of 10 to 25°C is more preferred, and the range of -5 to 20°C is even more preferred. In the present embodiment, the minimum film-forming temperature is the minimum temperature required to form a continuous film when the synthetic rubber latex evaporates and dries, and is obtained by the temperature gradient plate method. .

The glass transition temperature (hereinafter sometimes referred to as Tg) of the emulsion containing the styrene-acrylic copolymer (A) is preferably in the range of -40°C to 30°C, especially in the range of -35°C to 25°C. It is preferably in the range of -30 to 23°C. In this embodiment, the glass transition temperature is obtained by measurement with a differential scanning calorimeter.

The acid value of the emulsion is preferably in the range of 30 to 80 mgKOH/g, more preferably in the range of 40 to 75 mgKOH/g, more preferably in the range of 50 to 70 mgKOH/g. In this embodiment, the acid value is obtained by a measuring method based on JIS test method K0070-1992.

The coating composition (CS) containing the emulsion of the styrene-acrylic copolymer (A) has fine film-forming properties without defects such as pinholes, and is therefore excellent in water resistance and oil resistance. Therefore, the water resistance and oil resistance of the laminate can be improved. In addition, since the coating composition (CS) also has adhesiveness, it is excellent in adhesiveness to the heat-sealable coat layer and/or the paper substrate, and does not impair the function of the heat-sealable coat layer. Excellent compatibility when used in combination with a heat-sealable coating layer.

Moreover, since the composition of the present embodiment contains the styrene-acrylic copolymer (A), the heat resistance is improved. Therefore, it is applicable even when the contents are at high temperature such as heated food.

<<Method for Producing Emulsion Containing Styrene-Acrylic Copolymer (A)>>
In the present embodiment, the emulsion can be obtained by polymerization using a known aqueous medium, such as known emulsion polymerization or transfer emulsification, without any particular limitation. In addition, there are various expressions such as emulsion, dispersion, suspension, etc. for a form in which a polymer is dispersed in an aqueous medium.

For example, a monomer mixture is supplied in an aqueous medium and polymerized in the presence of an initiator to polymerize the emulsion.

In the case of an emulsion obtained by appropriately mixing the emulsion of the styrene-acrylic copolymer (A) and the emulsion of the acrylic copolymer (B), it is obtained by mixing emulsions obtained by polymerizing the respective monomer mixtures.

In the case of an emulsion forming a core-shell structure, a step (1) of supplying a monomer mixture forming a core polymer and polymerizing the monomer mixture in the presence of an initiator to form a core polymer; to the core polymer of step (1) and polymerizing the monomer mixture in the presence of an initiator to form a shell on the core polymer (step (2)). In addition, step (i) of supplying a monomer mixture that forms a shell polymer and polymerizing the monomer mixture in the presence of an initiator to form a shell polymer; and polymerizing this monomer mixture in the presence of an initiator to form a shell on the core polymer (ii).

There are no particular limitations on the initiator, and peroxides, persulfates, azo compounds, redox compounds, or mixtures thereof used in emulsion polymerization may be used. Peroxides include, for example, hydrogen peroxide, ammonium peroxide, sodium or potassium peroxide, t-butyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, and benzene peroxide. Persulfates include, for example, ammonium persulfate, sodium persulfate, and potassium persulfate. Examples of azo compounds include 2,2-azobisisobutyronitrile and 4,4'-(4-cyanovaleric acid). The redox system also consists of an oxidizing agent and a reducing agent, the oxidizing agent being, for example, one of the peroxides, persulfates or azo compounds listed above, or sodium chloride or potassium chloride, or bromide Sodium or potassium bromide may be mentioned. Reducing agents include, for example, ascorbic acid, glucose, ammonium, sodium or potassium hydrogensulfate, sodium or potassium hydrogensulfite, sodium thiosulfate or potassium thiosulfate, sodium sulfide or potassium sulfide, or iron (II) ammonium sulfate. Among them, persulfates, more preferably ammonium persulfate, are preferred.

Polymerization of the monomer mixture can be carried out in the presence of additives such as surfactants, chain transfer agents, chelating agents, for example, in the presence of surfactants and chain transfer agents. These additives may be added in advance to the aqueous medium used in step (1), or may be mixed with the monomer mixture supplied in step (1) or step (2).

The surfactant is not particularly limited, but examples thereof include disodium dodecyldiphenyl oxide, disulfonate and the like. The chain transfer agent is also not particularly limited, but examples thereof include α-methylstyrene dimer, thioglycolic acid, sodium hydrogen phosphite, 2-mercaptoethanol, N-dodecylmercaptan, and t-dodecylmercaptan. . The chelating agent is not particularly limited, but includes, for example, ethylenediaminetetraacetic acid.

When forming a core-shell structure, in order to increase the stability in an aqueous medium, it is preferable that the acrylic copolymer (B) having an acidic group serves as the shell. There is no problem even if the emulsion has a structure in which (B) does not form a shell and part of the styrene-acrylic copolymer (A) forms a shell.

Further, when neutralization is required, bases such as ammonia, triethylamine, aminomethylpropanol, monoethanolamine, diethylaminoethanol, sodium hydroxide and potassium hydroxide can be used as neutralizing agents.

<<Other Resins>>
The coating composition (CS) according to this embodiment may contain resins other than the styrene-acrylic copolymer (A) and the acrylic copolymer (B). The material of the other resin is not particularly limited, but in order not to impair the properties such as oil resistance and heat resistance of the coating composition (CS) according to the present embodiment, a styrene-acrylic copolymer is preferred. More preferably, it is the same material as the resin containing the styrene-acrylic copolymer (A). In addition, the content of other resins can be appropriately adjusted within a range that does not impair the effects of the present embodiment. The coalescence (A)/other resin) is preferably 100/0 to 50/50, preferably 100/0 to 60/40.

<<Aqueous solvent>>
The coating composition (CS) contains water. As water, pure water such as ion-exchanged water, ultrafiltrated water, reverse osmosis water, distilled water, or ultrapure water can be used. As the water, it is preferable to use water sterilized by ultraviolet irradiation, addition of hydrogen peroxide, or the like, because the generation of mold or bacteria can be prevented when the composition is stored for a long period of time. Among them, it is most preferable to use water.

A water-soluble organic solvent such as an alcohol that dissolves in water may be mixed and used. Examples of alcohols include methanol, ethanol, isopropyl alcohol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, butyl alcohol and pentyl alcohol. These alcohols can be used alone or in combination of two or more.

<<Other Additives>>
The coating composition (CS) may also contain silica, alumina, polyethylene wax, antifoaming agents, leveling agents, tackifiers, preservatives, antibacterial agents, antirust agents, and the like.

The coating composition (CS) may contain wax. Waxes include waxes such as fatty acid amide wax, carnauba wax, polyolefin wax, paraffin wax, Fischer-Tropsch wax, beeswax, microcrystalline wax, polyethylene oxide-wax, amide wax, and the like. These may be used alone or in combination.

Among them, fatty acid amide wax, carnauba wax, Fischer-Tropsch wax, polyolefin wax and paraffin wax are preferably used, and carnauba wax, polyolefin wax and paraffin wax are particularly preferably used.

Specific examples of fatty acid amide waxes include pelargonic acid amide, capric acid amide, undecylic acid amide, lauric acid amide, tridecylic acid amide, myristic acid amide, pentadecylic acid amide, palmitic acid amide, heptadecylic acid amide, and stearic acid amide. , nonadecanic acid amide, arachidic acid amide, behenic acid amide, lignoceric acid amide, oleic acid amide, cetreic acid amide, linoleic acid amide, linoleic acid amide, mixtures thereof and animal and vegetable oil fatty acid amides.

Specific examples of the carnauba wax include MICROK LEAR 418 (manufactured by Micro Powders, Inc.) and purified carnauba wax No. 1 powder (Nippon Wax Co., Ltd.).

Specific examples of the olefin wax include polyethylene wax and polypropylene wax, such as MPP-635VF (Micro Powders, Inc.) and MP-620VF XF (Micro Powders, Inc.).

Specific examples of the paraffin wax include MP-28C, MP-22XF and MP-28C (Micro Powders, Inc.).

The amount of the above wax is preferably 1.5 to 20% by mass based on 100% by mass of solid content in the coating composition (CS). If the total amount of wax is 3% by mass or more with respect to the total solid content of 100% in the coating composition (CS), the blocking resistance tends to be maintained, and the total amount of wax is the total amount of 100% solid content of the coating composition (CS). If it is 15% by mass or less, the heat-sealing property tends to be maintained.

Also, the melting point of the wax is preferably in the range of 80° C. to 130° C. from the viewpoint of oil resistance and heat resistance. The wax may be directly added to the resin emulsion containing the styrene-acrylic copolymer (A) and mixed and dispersed, or a wax dispersion may be prepared and then mixed with the emulsion. As a dispersion method, a known method such as a dispersion device using media such as a paint shaker, a ball mill, an attritor, a basket mill, a sand mill, a sand grinder, a Dyno mill, a Dispermat, an SC mill, a spike mill, and an agitator mill is used. Dispersion can be carried out by an ultrasonic homogenizer, a high-pressure homogenizer, a nanomizer, a dissolver, a disper, a high-speed impeller disperser, or the like, which does not use media.

When a powdery wax is used, it is preferable to perform kneading using a medium or blend after preparing a dispersion of the wax in order to uniformly disperse the wax.
The kneading method can be performed by a known method.

Moreover, when multiple types of waxes are used together, the multiple types of waxes may be added at the same time, or may be added in multiple steps.

In addition, the coating composition (CS) preferably uses a polymer antifoaming agent, a silicon antifoaming agent, or a fluorine antifoaming agent in order to prevent foaming of the composition when coating with various coaters. be done. As these antifoaming agents, both emulsifying and dispersing types and solubilizing types can be used. Among them, polymer antifoaming agents are preferred.

The amount of the antifoaming agent added is preferably 0.005% by weight to 0.1% by weight based on the total amount of the coating composition (CS).

[Overcoating layer in the second embodiment]
As described above, the overcoating coating layer in the second embodiment is formed from, for example, a water-resistant coating composition for forming an overcoating coating layer containing at least an aqueous solvent, a styrene-acrylic copolymer, and wax. be done. The overcoating coating layer according to the present embodiment is a coating layer particularly excellent in water resistance.

<Aqueous solvent>
As the aqueous solvent, the same aqueous solvent as described in the above <<aqueous solvent>> in the above <coating composition (CS) containing styrene-acrylic copolymer (A)> can be used.

<Styrene acrylic copolymer>
Styrene-acrylic copolymers are copolymers of styrenes and (meth)acrylates, or copolymers of styrenes and (meth)acrylates, and styrenes and (meth)acrylates. and (meth)acrylic acid are preferably copolymers.
Moreover, the styrene-acrylic copolymer is more preferably a styrene-acrylic copolymer having a core-shell structure.

The styrenes and (meth)acrylates used as constituent components of the styrene-acrylic copolymer may be the same as those used for the styrene-acrylic copolymer (A) in the overcoating layer described above.

As a constituent component of the styrene acrylic copolymer, other known polymerizable compounds other than styrenes, (meth)acrylates and (meth)acrylic acid may be contained.

The styrene-acrylic copolymer (A) contained in the waterproof coating composition preferably contains a wax, which will be described later. Water resistance can be further improved by containing wax in the styrene-acrylic copolymer (A). Wax may be present in the core portion or in the shell portion. It may exist on the surface of the styrene-acrylic copolymer.

In the styrene-acrylic copolymer (A) contained in the waterproof coating composition, "a copolymer of styrenes and (meth)acrylate" and "a copolymer of styrenes, (meth)acrylate and (meth)acrylic acid" The mass ratio of the "copolymer" is preferably in the range of 20:80 to 95:5, more preferably in the range of 30:70 to 92:8, and most preferably in the range of 40:60 to 90:10.

In the copolymer of styrenes and (meth)acrylate, the ratio of styrenes and (meth)acrylate is preferably in the range of 20:80 to 80:20, more preferably in the range of 30:70 to 70:30. More preferably, the range of 40:60 to 60:40 is most preferred.

In the copolymer of styrenes, (meth)acrylate and (meth)acrylic acid, the proportion of styrenes is preferably 10 to 90% by mass, more preferably 20 to 80% by mass, and 30 to 70% by weight is most preferred. Further, in the copolymer of styrenes, (meth)acrylate and (meth)acrylic acid, the proportion of (meth)acrylate is preferably 10 to 80% by mass, more preferably 15 to 70% by mass. Preferably, 20 to 60% by mass is most preferred. Further, in the copolymer of styrenes, (meth)acrylate and (meth)acrylic acid, the proportion of (meth)acrylic acid is preferably 10 to 70% by mass, more preferably 15 to 60% by mass. More preferably, it is most preferably 20 to 50% by mass.

When the styrene-acrylic copolymer (A) contains other known polymerizable compounds other than styrenes, (meth)acrylates, and (meth)acrylic acid, other polymerization in the styrene-acrylic copolymer (A) The ratio of the organic compound is preferably 10% by mass or less, more preferably 5% by mass or less.

The glass transition temperature (hereinafter sometimes referred to as Tg) of the styrene-acrylic copolymer (A) is in the range of -30°C to 10°C, preferably -25°C to 5°C, more preferably It ranges from -20°C to 0°C. In this embodiment, the glass transition temperature is obtained by measurement with a differential scanning calorimeter.

A styrene-acrylic copolymer can be produced by a known method. Among them, it is preferable to polymerize the monomer mixture in the presence of wax for the styrene-acrylic copolymer. That is, by adding the wax to the aqueous medium in advance or mixing it with the monomer mixture, a core-shell structure in which the wax is incorporated in the styrene-acrylic copolymer can be formed.

<Wax>
The waterproof coating composition can further improve the water resistance by further containing a wax. The wax is preferably at least one wax selected from paraffin wax, microcrystalline wax, polyethylene oxide wax, and amide wax, more preferably paraffin wax or microcrystalline wax. These may be used alone or in combination.

The melting point of the wax is preferably in the range of 30°C to 130°C, more preferably in the range of 50°C to 100°C. The blending amount of the wax is preferably 0.5 to 20% by mass, preferably 1 to 15% by mass, based on 100% by mass of the styrene-acrylic copolymer.

The wax may be dispersed in the waterproof coating composition, but as described above, the presence of the wax in the core portion and/or the shell portion of the styrene-acrylic copolymer allows the wax to separate from the styrene-acrylic copolymer. It is preferable to exist integrally. In the water-resistant coating composition, the wax may be present in the form of being contained in the styrene-acrylic copolymer and may be present without being contained in the styrene-acrylic copolymer.

<Other additives>
In addition to the above components, the waterproof coating composition further contains silica, alumina, wax, antifoaming agent, leveling agent, tackifier, preservative, antibacterial agent, Additives such as rust preventives may be added. Moreover, other resins than the styrene-acrylic copolymer may be blended. Among them, it is preferable that a leveling agent and/or wax are further blended.

(Paper substrate)
The paper substrate laminated on the coated paper of the present invention is produced by a known paper machine using natural fibers for papermaking such as wood pulp, but the papermaking conditions are not particularly defined. .
Examples of natural fibers for papermaking include wood pulp such as softwood pulp and hardwood pulp, non-wood pulp such as Manila hemp pulp, sisal pulp and flax pulp, and pulp obtained by chemically modifying these pulps. The types of pulp that can be used include chemical pulp, ground pulp, chemi-grand pulp, thermomechanical pulp, and the like prepared by sulfate cooking, acidic/neutral/alkaline sulfite cooking, soda salt cooking, and the like. Moreover, various types of commercially available fine paper, coated paper, lined paper, impregnated paper, cardboard, paperboard, etc. can also be used.

As for the above-mentioned paper substrate, the kind of paper, thickness, etc. can be successively selected according to the purpose. For example, burger wraps correspond to a basis weight of about 20 g/m ² , paper cups correspond to a basis weight of 200 to 300 g/m ² , paper plates, paper spoons, paper stirrers, etc. correspond to a basis weight of 50 to 500 grams. /m ² base paper for food such as base paper for cups is preferred. From the viewpoint of recycling efficiency and cost reduction, these papers are preferably not laminated with a polyethylene film, aluminum, or the like.

The coated paper of the present invention may be further laminated with a primer layer (anchor layer) and a heat seal layer described below, in addition to the above-described paper substrate, printed layer, and overcoating layer.

(Heat seal layer)
A heat seal layer may be laminated on the coated paper of the present invention.
A heat-sealing layer refers to a coat layer containing a heat-sealing agent. The heat seal layer can be formed using a known heat seal coating agent (also referred to as a heat seal agent (HS)).
Composition examples of the heat sealing agent are described below.

<Heat sealing agent (HS)>
In order to improve water resistance, heat sealing agents (HS) are vinyl chloride vinyl acetate copolymer resins, (meth)acrylate resins, olefin-α,β unsaturated carboxylic acid copolymer resins, and polyolefin resins. Alternatively, it preferably contains at least one selected from polyester resins, and at least one selected from vinyl chloride vinyl acetate copolymer resins, (meth)acrylate resins, and olefin-α,β unsaturated carboxylic acid copolymer resins. more preferably.

The vinyl chloride-vinyl acetate copolymer resin is not particularly limited as long as it is a copolymer of vinyl chloride and vinyl acetate. From the viewpoint of improving the heat-sealing property, it is preferably a vinyl chloride-vinyl acetate copolymer containing an acid group, and more preferably an acid-modified vinyl chloride-vinyl acetate copolymer-based resin. As the acid group, those using maleic acid or fumaric acid are preferred.

The (meth)acrylate resin is not particularly limited as long as it is a homopolymer or copolymer of (meth)acrylate. and copolymers. Further, when an aqueous solvent is used, it is preferably a copolymer having an acid value for the purpose of imparting water dispersibility and water solubility.

The (meth)acrylate used as a constituent component of the (meth)acrylate homopolymer or copolymer is not particularly limited, and is similar to the (meth)acrylate used in the styrene-acrylic copolymer (A) described above. is used.

Examples of (meth)acrylates and vinyl monomers copolymerizable with (meth)acrylates include aromatic (meth)acrylates such as benzyl (meth)acrylate; 2-hydroxyethyl (meth)acrylate, 2- hydroxyl group-containing monomers such as hydroxypropyl (meth)acrylate; alkylpolyalkylene glycol mono(meth)acrylates such as methoxypolyethylene glycol mono(meth)acrylate and methoxypolypropylene glycol mono(meth)acrylate; perfluoroalkylethyl (meth)acrylate, etc. fluorine-based (meth)acrylate; styrene, styrene derivatives (p-dimethylsilylstyrene, (p-vinylphenyl) methylsulfide, p-hexynylstyrene, p-methoxystyrene, p-tert-butyldimethylsiloxystyrene, o- methylstyrene, p-methylstyrene, p-tert-butylstyrene, α-methylstyrene, etc.), aromatic vinyl compounds such as vinylnaphthalene, vinylanthracene, 1,1-diphenylethylene; glycidyl (meth)acrylate, epoxy (meth ) acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylene glycol tetra(meth)acrylate, 2-hydroxy-1,3-diacryloxypropane, 2 , 2-bis[4-(acryloxymethoxy)phenyl]propane, 2,2-bis[4-(acryloxyethoxy)phenyl]propane, dicyclopentenyl (meth)acrylate tricyclodecanyl (meth)acrylate, tris (Acryloxyethyl)isocyanurate, (meth)acrylate compounds such as urethane (meth)acrylate; having alkylamino groups such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, etc. (Meth)acrylates; vinylpyridine compounds such as 2-vinylpyridine, 4-vinylpyridine and naphthylvinylpyridine; 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3- conjugated dienes such as butadiene, 1,3-pentadiene, 1,3-hexadiene and 1,3-cyclohexadiene; These monomers can be used singly or in combination of two or more.

In addition, for the purpose of introducing one or more acidic groups selected from the group consisting of carboxyl groups and carboxylate groups in which the carboxyl groups are neutralized with a basic compound, (meth)acrylic acid, crotonic acid, itaconic acid, , Maleic acid, fumaric acid, β-(meth)acryloyloxyethyl hydrogen succinate, β-(meth)acryloyloxyethyl hydrogen phthalate, etc.) It is possible to obtain a copolymer having

When introducing an acidic group, it is preferable to appropriately adjust the amount of the monomer so that the acid value falls within the desired range.

The (meth)acrylate homopolymer or copolymer can be produced, for example, by polymerizing one or more monomers in the presence of a polymerization initiator in a temperature range of 50°C to 180°C. , 80° C. to 150° C. is more preferable. Polymerization methods include, for example, bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Moreover, the polymerization mode includes, for example, random copolymers, block copolymers, graft copolymers, and the like. The copolymer may also be of the core-shell type.

The olefin-α,β-unsaturated carboxylic acid copolymer resin includes an olefin, an α,β-unsaturated carboxylic acid, a metal salt of an α,β-unsaturated carboxylic acid, and an α,β-unsaturated carboxylic acid. Examples thereof include copolymers with at least one monomer selected from the group consisting of esters. Specifically, it is a copolymer of an α,β-unsaturated carboxylic acid, a metal salt of an α,β-unsaturated carboxylic acid or an α,β-unsaturated carboxylic acid ester and an olefin, and an olefin-α,β Unsaturated carboxylic acid copolymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, ethylene-acrylic acid-maleic anhydride copolymer, ethylene-acrylic acid Ester-maleic anhydride copolymers, ethylene-methacrylic acid-maleic anhydride copolymers, ethylene-methacrylic acid ester-maleic anhydride copolymers, metal salts thereof and the like can be mentioned. These copolymers may be used alone or as a mixture of two or more.

Among them, an olefin-α,β unsaturated carboxylic acid copolymer is preferred. Olefin-α,β-unsaturated carboxylic acid copolymers include random copolymers or block copolymers of ethylene and α,β-unsaturated carboxylic acid.

Examples of the olefins include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 4-methyl-1-pentene, butadiene, dicyclopentadiene, 5-ethylidene-2- and norbornene. Among them, ethylene is preferred.
Examples of the α,β-unsaturated carboxylic acid include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid. Among these, acrylic acid and methacrylic acid are preferably used. These α,β-unsaturated carboxylic acids may be used alone or in combination of two or more.

As the α,β-unsaturated carboxylic acid ester, known acrylic acid or methacrylic acid alkyl esters, hydroxyalkyl esters, alkoxyalkyl esters and the like can be used without particular limitation. For example, specifically, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, n-octyl acrylate, acrylate- acrylic esters such as 2-hydroxyethyl and 2-methoxyethyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, Methacrylic acid esters such as 2-ethylhexyl methacrylate, n-lauryl methacrylate, 2-hydroxyethyl methacrylate, and 2-ethoxyethyl methacrylate can be exemplified. These can be used singly or in combination of two or more.

The above olefin-α,β unsaturated carboxylic acid copolymer can be produced by a known method such as radical copolymerization at high temperature and high pressure.

The content of α,β-unsaturated carboxylic acid in the olefin-α,β-unsaturated carboxylic acid copolymer is desirably 8 to 24% by weight, preferably 18 to 23% by weight. When the content of the α,β-unsaturated carboxylic acid is less than 8% by weight, the dispersibility in the aqueous dispersion medium is inferior due to the non-polar nature derived from the ethylene unit, and the olefin-α,β-unsaturation is excellent. It may become difficult to obtain a carboxylic acid copolymer resin aqueous dispersion. On the other hand, if the content of the α,β-unsaturated carboxylic acid exceeds 24% by weight, the anti-blocking property of the resulting film may deteriorate.

The olefin-α,β unsaturated carboxylic acid copolymer used in the heat sealing agent is preferably used as an aqueous dispersion in an aqueous solvent. The method for dispersing in the aqueous solvent is not particularly limited, and any known method may be used. Examples include a method of emulsifying with a surfactant and dispersing it in an aqueous solvent, and a method of neutralizing an olefin-α,β unsaturated carboxylic acid copolymer with a basic compound and then dispersing it in an aqueous solvent.

As the surfactant used for emulsification, various known anionic, cationic, nonionic surfactants, or various water-soluble polymers can be appropriately used in combination.

Examples of basic compounds used for neutralization include ammonia, organic amines such as methylamine, ethylamine, diethylamine, dimethylethanolamine, diethanolamine and triethanolamine, sodium hydroxide, potassium hydroxide and lithium hydroxide. and other alkali metal hydroxides. These basic compounds may be used alone or in combination of two or more.

The degree of neutralization with a basic compound may be a degree of neutralization that allows the olefin-α,β unsaturated carboxylic acid copolymer to exist stably in an aqueous solvent. For example, it may be 30 to 100 mol %, more preferably 40 to 90 mol %, of the carboxyl groups in the copolymer.

Examples of the dispersing method include known methods such as a dispersing device using media such as a paint shaker, a ball mill, an attritor, a basket mill, a sand mill, a sand grinder, a dyno mill, a dispermat, an SC mill, a spike mill, and an agitator mill. Dispersion can be carried out using an ultrasonic homogenizer, a high-pressure homogenizer, a nanomizer, a dissolver, a disper, a high-speed impeller disperser, or the like, which does not use media.

The solid content of the aqueous dispersion of the olefin-α,β unsaturated carboxylic acid copolymer used in the present invention is not particularly limited. It may be appropriately determined depending on the drying conditions, the film thickness of the film, and the like. In general, the solid content concentration is often applied in the range of 10 to 40% by mass.

<Solvent>
The heat sealing agent (HS) is preferably used by dissolving the above-described resin in various organic solvents or aqueous solvents in order to improve coating performance. For example, when vinyl chloride-vinyl acetate copolymer system resin, (meth)acrylate system resin, polyolefin system resin or polyester system resin is used, it is preferable to use an organic solvent.

The organic solvent is not particularly limited, and examples include aromatic hydrocarbons such as toluene, xylene, Solvesso #100 and Solvesso #150, aliphatic hydrocarbons such as hexane, heptane, octane, and decane, methyl acetate, and acetic acid. Various ester-based organic solvents such as ethyl, isopropyl acetate, butyl acetate, amyl acetate, ethyl formate, and butyl propionate can be used. In addition, alcohols such as methanol, ethanol, propanol and butanol, ketones such as acetone, methyl ethyl ketone and cyclohaxanone, ethylene glycol (mono, di)methyl ether, ethylene glycol (mono, di)ethyl ether, ethylene glycol monopropyl ether, Ethylene glycol monoisopropyl ether, monobutyl ether, diethylene glycol (mono, di)methyl ether, diethylene glycol (mono, di)ethyl ether, diethylene glycol monoisopropyl ether, diethin glycol monobutyl ether, triethylene glycol (mono, di)methyl ether, propylene Glycol ethers such as glycol (mono, di)methyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol (mono, di) methyl ether, and N,N-dimethyl as organic solvents with good solubility. Examples include various organic solvents such as formamide, N,N-diethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone and other amide solvents. Of these, it is preferable to use toluene, methyl ethyl ketone, ethyl acetate, and mixtures thereof, which usually have a high drying speed.

When using a (meth)acrylate-based resin or a polyolefin-based resin, it is preferable to use an aqueous solvent. As the aqueous solvent, the same aqueous solvent as used in the coating composition (CS) can be used. Among them, it is preferable to use water.

<Wax>
The heat sealing agent (HS) preferably contains wax. Blocking resistance can be maintained by containing wax. Examples of the wax include waxes such as fatty acid amide wax, carnauba wax, polyolefin wax, paraffin wax, Fischer-Tropsch wax, beeswax, microcrystalline wax, polyethylene oxide wax, amide wax, coconut oil fatty acid and soybean oil fatty acid. be able to. These may be used alone or in combination.

Among them, fatty acid amide wax, carnauba wax, Fischer-Tropsch wax, polyolefin wax and paraffin wax are preferably used, and fatty acid amide wax and carnauba wax are particularly preferably used.

Specific examples of fatty acid amide waxes include pelargonic acid amide, capric acid amide, undecylic acid amide, lauric acid amide, tridecylic acid amide, myristic acid amide, pentadecylic acid amide, palmitic acid amide, heptadecylic acid amide, and stearic acid amide. , nonadecanic acid amide, arachidic acid amide, behenic acid amide, lignoceric acid amide, oleic acid amide, cetreic acid amide, linoleic acid amide, linoleic acid amide, mixtures thereof and animal and vegetable oil fatty acid amides.
Specific examples of the carnauba wax include MICROKLEAR 418 (manufactured by Micro Powders, Inc.) and purified carnauba wax No. 1 powder (Nippon Wax Co., Ltd.).

It is preferable that the total amount of the wax is 1.5 to 20% by mass based on the solid content of 100% by mass of the heat sealing agent (HS). If the total amount of wax is 3% by mass or more with respect to the solid content of 100% of the heat sealing agent (HS), the blocking resistance tends to be maintained, and the total amount of wax is 100% of the solid content of the heat sealing agent (HS). If it is 15% by mass or less with respect to the total amount, there is a tendency that the heat-sealing property can be maintained.

Among the above waxes, the combination of the above fatty acid amide wax and the above carnauba wax is more preferable because the anti-blocking property is further improved. When used in combination, the ratio is not particularly limited, but fatty acid amide wax:carbana wax is preferably in the range of 1:1 to 1:10, more preferably in the range of 1:1 to 1:5.

Among the above waxes, a combination of polyolefin wax and paraffin wax is more preferable because the anti-blocking property is further improved. When used in combination, the ratio is not particularly limited, but the polyolefin wax:paraffin wax ratio is preferably in the range of 1:1 to 10:1, more preferably in the range of 1:1 to 5:1.

When using an aqueous solvent, it is preferable to further use a wax, and it is particularly preferable to use it in combination with the above olefin-α,β unsaturated carboxylic acid copolymer or (meth)acrylic resin. In this case, the wax may be added directly to the aqueous dispersion of the olefin-α,β unsaturated carboxylic acid copolymer or (meth)acrylic resin and mixed and dispersed, or the above olefin-α,β unsaturated carboxylic acid copolymer It may be added and mixed and dispersed at the same time as the polymer or (meth)acrylic resin is dispersed in the aqueous solvent. As a dispersing method, the method used for dispersing the above olefin-α,β unsaturated carboxylic acid copolymer in an aqueous solvent can be appropriately used.

Moreover, when multiple types of waxes are used together, the multiple types of waxes may be added at the same time, or may be added in multiple steps. For example, after the first wax is added when dispersing the olefin-α,β unsaturated carboxylic acid copolymer or (meth)acrylic resin in an aqueous solvent, the second wax is added to the obtained first wax. and the above olefin-α,β unsaturated carboxylic acid copolymer or (meth)acrylic resin are further added to an aqueous dispersion to obtain a heat sealing agent (HS).

The heat sealing agent (HS) contains silica, alumina, antifoaming agent, viscosity modifier, leveling agent, tackifier, antiseptic agent, antibacterial agent, antiseptic agent, in addition to the above components as long as the object of the present invention is not impaired. Additives such as rust agents, antioxidants and silicone oils may be added.

In the heat sealing agent (HS), polymer antifoaming agents, silicon antifoaming agents, and fluorine antifoaming agents are preferably used in order to prevent foaming during coating using various coaters. As these antifoaming agents, both emulsifying and dispersing types and solubilizing types can be used. Among them, polymer antifoaming agents are preferred. The amount of the antifoaming agent to be added is preferably 0.005% by weight to 0.1% by weight based on the total amount of the water-based heat sealing agent.

The heat sealing agent (HS) can be used as a heat sealing agent when manufacturing paper packaging materials such as bags and boxes, and paper containers. Lamination with an overcoating layer containing a polymer can further improve the water resistance of the laminate. By laminating the heat-sealed portion, various packaging materials such as bags, boxes, containers, etc. can be produced according to the application, and the workability is excellent.

(Characteristics of coated paper)
In the coated paper of the present invention, the coating amount of the overcoating layer is 0.5 to 10.0 g/m ² , more preferably 1.0 to 5.0 g/m ² .
In the coated paper of the present invention, the coating amount of the overcoating layer is 1 to 10 g/m ² , more preferably 1 to 5 g/m ² .
In the coated paper of the present invention, the coating amount of the heat seal layer is preferably 0.5 to 12 g/m ² , more preferably 2.0 to 8.0 g/m ² .

(Method for producing coated paper)
In the method for producing coatability of the present invention, the step of forming the printed layer and the step of forming the overcoating coating layer can be printed in a continuous in-line manner. Thereby, a coated paper in which migration is controlled can be obtained.
In the method for producing coatability of the present invention, the step of forming the printed layer and the step of forming the overcoating coating layer may be printed off-line.
The coated paper of the present invention is, for example, printed on one side of the paper substrate (when the primer layer is laminated, the printed layer is formed after applying the primer layer), and the printed It can be formed by applying an overcoat layer on the layer in an in-line manner.

Moreover, when the coated paper of the present invention has a heat-seal layer, it can be formed, for example, by applying the heat-seal layer to the other surface of the paper substrate.

Examples of methods for applying the coating composition onto the paper substrate and other layers include comma coaters, roll coaters, reverse roll coaters, direct gravure coaters, reverse gravure coaters, offset gravure coaters, roll kiss coaters, Reverse Kiss Coater, Kiss Gravure Coater, Reverse Kiss Gravure Coater, Air Doctor Coater, Knife Coater, Bar Coater, Wire Bar Coater, Die Coater, Lip Coater, Dip Coater, Blade Coater, Brush Coater, Curtain Coater, Die Slot Coater, Flexo Any one of a coater, an impregnation coater, a cast coater, a spray coater, an offset printer, a screen printer, etc. or a combination of two or more coating methods can be used.

Alternatively, a coating layer to be laminated on the paper base material or the laminate containing the paper base material is provided by impregnating the paper base material or the laminate containing the paper base material and other layers with the composition. may A drying step may be provided in an oven or the like after coating.

[Package or container]
The coated paper of the present invention can be processed into boxes, bags, containers, etc., and can be used as packages or containers.

Examples of packaging include packaging bags, paper bags, paper boxes, corrugated cardboard, wrapping paper, envelopes, cup sleeves, lids, and the like. Examples of containers include paper containers, paper plates, trays, cup holders, and paper cups. Since the coated paper of the present invention is excellent in water resistance and oil resistance, it is preferably used for packaging materials such as food and fertilizer that require water resistance and oil resistance. Moreover, since the coated paper of the present invention is excellent in water vapor barrier properties and gas barrier properties, it is preferably used for packaging materials such as foods and fertilizers that require water vapor barrier properties and gas barrier properties.
For example, cups or lids for desserts such as cup noodles, ice cream, pudding, jelly, etc., bags or boxes for confectionery, grains, beans, powders, pet food, fertilizers, etc. Wrapping paper for hamburgers and hot dogs , pizza and other take-out containers, containers for hot snacks such as fried chicken and potatoes, food paper containers and packaging materials such as cups for side dishes such as natto, and hygiene products such as detergents and sanitary products and a bag or box.

For example, when producing a paper cup using the coated paper of the present invention, it is preferable to provide a heat-sealing layer on the inner surface of the container and on the bonding portion when assembling the container to bond them together. That is, the paper cup consists of a body member (1) having the coated paper of the present invention rolled up and superimposed so that the bonded surfaces of both ends are adhered to each other, and a plate-like bottom member adhered to the lower end of the body member (1). (2), the heat seal layer provided in the adhesive part is adhered by the heat seal function, and the heat seal layer and overcoating coating layer provided in the part other than the adhesive part are water resistant and oil resistant can function. Since the heat-sealing layer and the overcoating layer provided on the portion other than the adhesive portion are highly safe to the human body and the environment, they can be stored in direct contact with food. Furthermore, by providing a coating layer with excellent water resistance as an overcoating coating layer on the outside of the paper cup, excellent water resistance can be obtained even when used for a long time.

Similarly, paper boxes, paper bags, etc. can be produced by heat sealing using the coated paper of the present invention.

As a specific method of heat sealing, a heat seal layer is placed on at least one of the two parts of the coated paper (may be both parts), and the two parts are superimposed and heated. A method of softening by is preferred. Heat sealing agents can be easily softened by heating with a burner or hot air, and can bond paper to paper or paper to other materials, and then cool to solidify the bonded portion, thereby bonding paper to paper or paper to other materials. It can be tightly sealed.
As for the lamination order of various layers in the coated paper of the present invention, there are several preferable patterns as described above. In addition to heat-sealing by overlapping layers, heat-sealing by overlapping a paper substrate and an overcoating coating layer, and heat-sealing by overlapping an overcoating coating layer and an overcoating coating layer. You may When these layers are heat-sealed without providing a heat-sealing layer, the sealability is slightly inferior compared to the case of heat-sealing with a heat-sealing layer, but the overcoating layer having the composition of the present invention is heat-sealed. Since it seals, good sealing performance can be secured.

As the heating method, conventionally known means such as a heat source such as a burner, hot air, electric heat, infrared rays, and electron beams can be used. A heat welding sealing method, an ultrasonic sealing method, or a high frequency sealing method is preferable. The heating temperature at this time is preferably 200 to 500° C., and the heating time is preferably 0.1 to 3 seconds.

In addition, the heat sealing agent (HS) can be easily heated and softened even by non-contact heating, and can be softened to some extent even if it is separated from the heat source, in addition to the method of melting by contacting it directly with a heat source such as a heat sealing bar. The heat seal function lasts for hours. Since the coated paper of the present invention uses a paper substrate, the paper may scorch if it is brought into direct contact with a heat source. It is particularly useful as a heat-sealing agent for industrial production of paper containers, which require high line speeds, because its function lasts.

It can be used as a heat sealing agent by applying a heat sealing agent (HS), softening the coated portion by heating, and then press-bonding the coated portion and another portion while overlapping each other. The crimping method is not particularly limited, and a hot plate method, ultrasonic sealing, or high-frequency sealing can be used.

EXAMPLES The contents and effects of the present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these.
"Parts" in the following examples represent "parts by mass" and "%" represents "% by mass".

(Preparation of coating composition (CS) containing styrene acrylic copolymer (A))
100 parts of isopropyl alcohol was charged into a four-necked flask purged with nitrogen gas, the temperature was raised to 80 to 82° C., and then 1 part of myristyl acrylate, 30 parts of styrene, 10 parts of acrylic acid, and 5 parts of methyl methacrylate were charged to the dropping funnel. A mixture of 1 part of benzoyl peroxide and 1 part of benzoyl peroxide was added dropwise over 2 hours. After the dropwise addition, 0.5 part of benzoyl peroxide was added, and the reaction was further continued for 2 hours. The temperature was lowered to 40° C., and dimethylethanolamine and ion-exchanged water were added. Thereafter, the temperature of the reaction flask was raised to 80-82° C. and stripping was carried out to finally obtain a water-soluble resin with a solid content of 30%.

To the water-soluble resin obtained above, 10 parts of ion-exchanged water was charged in a reaction flask, the temperature was raised to 80 ° C. to 82 ° C., 2 parts of potassium persulfate were added, 15 parts of styrene and 5 parts of α-methylstyrene were added. , 24 parts of 2-ethylhexyl acrylate and 10 parts of butyl acrylate were added dropwise over 2 hours. After completion of dropping, 0.2 part of potassium persulfate was added and reacted for 2 hours. The acrylic emulsion (resin 1) thus obtained had a solid content of 40%, a minimum film-forming temperature of 1°C, a glass transition point of -27°C, and an acid value of the solid content of 64 mgKOH/g. .

A total of 100 parts of 85 parts of the above acrylic emulsion (resin 1), 0.03 parts of a polymer-based antifoaming agent, and 14.97 parts of ion-exchanged water were thoroughly stirred at 25° C. for 15 minutes with a disper to form a coating composition. (CS1) was produced.

(Adjustment of styrene acrylic copolymer (B))
<Production Example 1>
100 parts of isopropyl alcohol was charged in a four-necked flask purged with nitrogen gas, the temperature was raised to 80 to 82 ° C., and then 30 parts of styrene, 15 parts of 2-ethylhexyl acrylate, and 20 parts of (meth)acrylic acid were charged to the dropping funnel. A mixture of 1 part of methyl methacrylate and 1 part of benzoyl peroxide was added dropwise over 2 hours. After the dropwise addition, 0.5 part of benzoyl peroxide was added, and the reaction was further continued for 2 hours. The temperature was lowered to 40° C., and dimethylethanolamine and ion-exchanged water were added. Thereafter, the temperature of the reaction flask was raised to 80-82° C. and stripping was carried out to finally obtain a water-soluble resin with a solid content of 30%.
To the water-soluble resin obtained above, 2 parts by mass of paraffin wax (Paraffin Wax 155, manufactured by Nippon Seiro Co., Ltd.) as a wax (W2) was added and stirred to prepare a wax dispersion. Subsequently, 10 parts of ion-exchanged water was added to the wax dispersion in a reaction flask, the temperature was raised to 80° C. to 82° C., 2 parts of potassium persulfate were added, and 30 parts of styrene and 24 parts of 2-ethylhexyl acrylate were added. was added dropwise over 2 hours. After completion of dropping, 0.2 part of potassium persulfate was added and reacted for 2 hours. The aqueous dispersion (B-1) of the styrene-acrylic copolymer thus obtained had a solid content of 35% and a glass transition point of -10°C.

<Production Example 2>
In the synthesis of the styrene acrylic copolymer (B-1), the styrene acrylic copolymer (B Aqueous dispersion (B-2) of a styrene-acrylic copolymer was obtained in the same manner as in the synthesis of -1). The aqueous dispersion (B-2) had a solid content of 35% and a glass transition point of -10°C.

<Production Example 3>
As the styrene-acrylic copolymer (B), a copolymer of styrenes and (meth)acrylate and a copolymer of styrenes, (meth)acrylate and (meth)acrylic acid form a core-shell structure, A commercially available aqueous dispersion of a styrene-acrylic copolymer (B-3) having a glass transition temperature in the range of -30°C to 10°C was used. The aqueous dispersion (B-3) had a solid content of 40% and a glass transition point of -21°C.

(Production of coated paper (laminate))
<Example 1>
A paper substrate (Pearl Card, Mitsubishi Paper Mills, 260 g) was prepared, and a printing layer was applied to one side of the paper substrate using an offset printing machine. SunPak DirectFood Plus manufactured by Sun Chemical was used as the printing ink for the printing layer.
After that, an overcoating coating layer was applied on the printed layer as follows. Using the above aqueous dispersion (B-1), a composition mixed according to the composition shown in Table 1 was sufficiently stirred with a disper to prepare a composition for an overcoating layer. The overcoating coating layer composition was applied to a film thickness of 5 g/m ² and dried at 60° C. using a dryer.
Thus, the coated paper of Example 1 was produced.

<Examples 2 to 4>
Coated papers of Examples 2 to 4 were prepared in the same manner as in Example 1, except that the water dispersion (B-1) was changed as shown in Table 1.

<Example 5>
A coated paper of Example 5 was prepared in the same manner as in Example 1, except that the above coating composition (CS1) was used instead of the above aqueous dispersion (B-1). bottom.

表中のワックス（Ｗ３）は、ケミパールＷ－４００（三井化学（株）製）を使用した。
また、表中のレベリング剤は、サーフィノール４２０（日信化学工業（株）製）を使用した。

Chemipearl W-400 (manufactured by Mitsui Chemicals, Inc.) was used as the wax (W3) in the table.
Surfynol 420 (manufactured by Nissin Chemical Industry Co., Ltd.) was used as the leveling agent in the table.

The coated papers of Examples 1 to 5 of the present invention were excellent in all of oil resistance, water resistance and safety.

Claims (9)

A printed layer and an overcoating layer are laminated in this order on one side of the paper substrate,
The printed layer is formed of ink that can come into contact with food,
Coated paper, wherein the overcoating layer contains a styrene-acrylic copolymer comprising a copolymer of styrenes and (meth)acrylate. The coated paper according to claim 1, wherein the styrene-acrylic copolymer contained in the overcoating coating layer is a styrene-acrylic copolymer of styrene, α-methylstyrene and (meth)acrylate. The styrene-acrylic copolymer contained in the overcoating coating layer is a styrene-acrylic copolymer of styrene, α-methylstyrene, and (meth)acrylate, and a copolymer of (meth)acrylic acid and (meth)acrylate. The coated paper according to claim 2, which is a styrene-acrylic copolymer consisting of The coated paper according to any one of claims 1 to 3, wherein the styrene-acrylic copolymer contained in the overcoating layer is a styrene-acrylic copolymer having a core-shell structure. The coated paper according to any one of claims 1 to 4, wherein the overcoating layer further contains wax. 6. The coated paper of claim 5, wherein the wax is present within the core-shell structure of the styrene-acrylic copolymer. The coated paper according to any one of claims 1 to 6, wherein the food-contactable ink is an ink composed of a raw material approved as a food component or a food-contact component. The coated paper according to any one of claims 1 to 7, wherein the printed layer and the overcoating layer are printed and coated inline. A package or container using the coated paper according to any one of claims 1 to 8.