JP2024109897A - Food wrapping paper and food packaging method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide wrapping paper in which ink or the like is not taken away from a package outer surface even when rubbed against a surface of a table, a counter or the like while hot food is being served on the wrapping paper, during or after packaging of the hot food.

SOLUTION: There is provided food wrapping paper obtained by laminating, in this order: an oil-resistant base material; a printing layer made of an aqueous flexographic printing ink composition containing a pigment, a styrene-acrylic emulsion type film-forming resin having a glass transition temperature of -30 to 60°C, a dispersion of wax resin particles having an average particle size of 3 to 6 μm, and a solvent containing water; and a coating layer made of a heat-resistant aqueous coating composition containing an alkali-soluble resin, an emulsion-type film-forming resin, a dispersion of wax resin particles having an average particle size of 1 to 10 μm, and an aqueous medium, wherein a weight ratio of "emulsion-type film-forming resin/(emulsion-type film-forming resin/alkali-soluble resin)" is 80 mass% or more.

SELECTED DRAWING: None

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to food wrapping paper for use on heated countertops and the like, and a food wrapping method using the same.

Fast food items such as hamburgers are provided to customers wrapped in tissue paper or the like that has been printed on an oil-resistant base material. When wrapping hamburgers and the like in tissue paper, the work is done on a counter such as a cooking table made of a metal plate heated to 40-60°C so that the hamburgers and the like do not cool down while being cooked in the store. However, when using conventional tissue paper or the like that has been printed on an oil-resistant base material, problems arise in that the ink is removed by friction with the surface of the heated cooking table or the like, making the print unclear or the printed parts accumulate on the table (see, for example, Patent Document 1).

International Publication No. 2012/091022

The object of the present invention is to obtain a wrapping paper that will not remove the ink or other residue from the outer surface of the wrapping paper even when it is rubbed against the surface of a table, kitchen counter, or other surface while hot food is being served on the wrapping paper or while hot food is being wrapped or packaged. In particular, the object of the present invention is to provide a food wrapping paper that will not remove the ink even when food is served, wrapped, or the wrapped food is slid and moved on a kitchen counter or other surface that is heated to 40 to 60°C and has excellent coating film properties such as water resistance, abrasion resistance, oil resistance, and other abrasion resistance, and a food packaging method using the same.

The present inventors discovered that the above problems can be solved by adopting the following configuration, and have thus achieved the present invention.
[1] A food packaging paper comprising an oil-resistant substrate, a printed layer made of an ink composition that satisfies the following condition 1, and a coating layer made of a heat-resistant aqueous coating agent composition that satisfies the following conditions 2 and 3, laminated in this order, said food packaging paper being used on a substrate having a surface temperature of 40 to 60°C.
Condition 1: The ink composition is an aqueous flexographic printing ink composition containing a pigment, a styrene-acrylic emulsion-type film-forming resin having a glass transition temperature of −30 to 60° C., a dispersion of wax resin microparticles having an average particle size of 3 to 6 μm, and a solvent containing water.
Condition 2: The heat-resistant aqueous coating composition contains an alkali-soluble resin, an emulsion-type film-forming resin, a dispersion of wax resin microparticles having an average particle size of 1 to 10 μm, and an aqueous medium.
Condition 3: In the heat-resistant aqueous coating composition, the emulsion type film-forming resin/(emulsion type film-forming resin+alkali-soluble resin)×100=60% by mass or more.
[2] The food packaging paper according to [1], wherein the ink composition further contains a rosin-based resin having an acid value of 0 mg KOH/g and/or 350 mg KOH/g or less.
[3] The food packaging paper according to [1] or [2], wherein the ink composition contains an alkali-soluble resin and/or an ethylene oxide/propylene oxide block polymer as a pigment dispersion resin.
[4] The food packaging paper according to either [2] or [3], wherein the ink composition contains 10% by mass or more of raw material components capable of being carbon neutral, and the solids ratio of the rosin-based resin to the styrene-acrylic emulsion-type film-forming resin is in the range of 1:0.8 to 1:3.5.
[5] The food packaging paper according to any one of [1] to [4], wherein the alkali-soluble resin contained in the heat-resistant aqueous coating composition has a glass transition temperature of 110° C. or higher.
[6] The food packaging paper according to any one of [1] to [5], wherein the emulsion-type film-forming resin contained in the heat-resistant aqueous coating composition is at least one selected from the group consisting of styrene-acrylic emulsion-type resins, styrene-maleic acid emulsion-type resins, and styrene-maleic acid half ester emulsion-type resins, each having a glass transition temperature of -30 to 60°C.
[7] The food packaging paper according to any one of 1. to 6., wherein the aqueous medium contained in the heat-resistant aqueous coating composition contains a print modifier, and the print modifier is at least one selected from the group consisting of a compound represented by the following formula (1), a compound represented by the following formula (2), 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol isobutyrate, 2-ethyl-1,3-hexanediol, 1,6-hexanediol diacetate, and isoamyl acetate, and is contained in an amount of 0.1 to 5% by mass in the aqueous coating composition.
(1) R ₁ -O-(C _m H _2m O)n-R ₂
(In formula (1), R ₁ and R ₂ are each independently a hydrogen atom or an alkyl group, the sum of the number of carbon atoms in R ₁ and the number of carbon atoms in R ₂ is 4 or more, m is 2 or 3, and n is 1, 2, or 3.)
(2) R ₃ -O-(C _m H _2m O) ₂ -CO-CH ₃
(In formula (2), _R3 is an alkyl group having 1 to 4 carbon atoms, and m is 2 or 3.)
[8] The food packaging paper according to any one of [1] to [7], which is formed by sequentially laminating a printing layer having a coating amount (solid content) of 3.0 to 9.0 g/ ^m2 and a coating layer having a coating amount (solid content) of 1.5 to 6.0 g/ ^m2 on an oil-resistant substrate.
[9] On one surface of an oil-resistant substrate,
A printing layer made of an ink composition that satisfies the following condition 1 is provided,
Next, a coating layer made of a heat-resistant aqueous coating composition that satisfies the following conditions 2 and 3 is provided, and a printing layer and a coating layer are laminated in this order on the substrate. This method for producing food packaging paper to be used on a base having a surface temperature of 40 to 60°C.
Condition 1: The ink composition is an aqueous flexographic printing ink composition containing a pigment, a styrene-acrylic emulsion type film-forming resin having a glass transition temperature of −30 to 60° C., a dispersion of wax resin microparticles having an average particle size of 3 to 6 μm, and a solvent containing water.
Condition 2: The heat-resistant aqueous coating composition contains an alkali-soluble resin, an emulsion-type film-forming resin, a dispersion of wax resin microparticles having an average particle size of 1 to 10 μm, and an aqueous medium.
Condition 3: In the heat-resistant aqueous coating composition, the emulsion type film-forming resin/(emulsion type film-forming resin+alkali-soluble resin)×100=60% by mass or more.
[10] The method for producing food packaging paper according to [9], wherein the ink composition is an aqueous flexographic printing ink composition further containing a rosin-based resin having an acid value of 0 mg KOH/g and/or 350 mg KOH/g or less.
[11] A food packaging method comprising wrapping food in the food packaging paper according to any one of [1] to [8].

The food packaging paper and the food packaging method using the same of the present invention will be described in detail below.
The food packaging paper of the present invention is basically a food packaging paper formed by laminating in this order a base material having oil resistance, a printed layer made of an ink composition (a water-based flexographic printing ink composition containing a pigment, a styrene-acrylic emulsion-type film-forming resin having a glass transition temperature of -30 to 60°C, a dispersion of wax resin microparticles having an average particle size of 3 to 6 μm, and a solvent containing water), and a coating layer made of a heat-resistant water-based coating agent composition.More preferably, from an environmental perspective, the food packaging paper is basically a food packaging paper in which the ink composition contains a rosin-based resin having an acid value of 0 mgKOH/g and/or 350 mgKOH/g or less.

<Oil-resistant substrate>
The oil-resistant substrate must be sufficiently flexible and capable of being folded and kept in a packaged state. Conventionally used base paper can be used in which at least one side of the base paper is laminated with polyolefin resin, particularly polyethylene laminated, or coated with resin to impart oil resistance to the base paper. As the base paper, thin paper such as fine paper, pure white roll paper, bleached kraft paper, and glassine paper having a basis weight of 15 to 50 g/ ^m2 can be used. If the basis weight is less than 15 g/ ^m2 , the strength of the wrapping paper may be insufficient. If the basis weight is more than 50 g/ ^m2 , the folds of the base paper that have been formed may return to their original state after packaging the food.
The oil-resistant surface is the surface that comes into contact with food in the packaged state.

<Printed layer made of ink composition>
The printing layer made of the ink composition in the present invention is a printing layer made of an aqueous printing ink composition containing a pigment, a styrene-acrylic emulsion type film-forming resin having a glass transition temperature of -30 to 60°C, a dispersion of wax resin microparticles having an average particle size of 3 to 6 µm, and a solvent containing water.
The printed layer is a layer formed on the outer surface side of the substrate when the food packaging paper is used to package food inside (the inner surface side of the substrate). The printed layer is formed on the entire surface or a part of the substrate layer by any method such as coating or printing. When the printed layer is formed by printing, it is particularly preferably formed by flexographic printing.
In addition, when environmental considerations are required, the printing layer made of the ink composition of the present invention may contain a raw material component capable of achieving carbon neutrality, such as a rosin-based resin having an acid value of 0 mg KOH/g and/or 350 mg KOH/g or less, and it is preferable that the raw material component capable of achieving carbon neutrality is contained in an amount of 10 mass% or more in the solid content of the aqueous flexographic printing ink composition.

The ink composition for forming the printed layer of the present invention will be described below.
(Pigment)
The pigment used in the ink composition may be any pigment that has been used in water-based flexographic printing inks.Specific examples of inorganic pigments include colored pigments such as titanium oxide, red iron oxide, antimony red, cadmium yellow, cobalt blue, Prussian blue, ultramarine blue, carbon black, and graphite.In addition, examples of organic pigments include soluble azo pigments, insoluble azo pigments, azo lake pigments, condensed azo pigments, copper phthalocyanine pigments, and condensed polycyclic pigments.One or more of the above pigments may be used.
The concentration of the pigment in the aqueous flexographic printing ink composition is 5 to 60% by weight, typically 6 to 35% by weight for organic pigments and 30 to 60% by weight for inorganic pigments.

(Pigment dispersion resin)
The pigment dispersing resin used in the ink composition may contain an alkali-soluble resin and/or an (ethylene oxide/propylene oxide) block polymer.

(Alkali-soluble water-soluble resin)
The alkali-soluble resin can be any resin obtained by polymerizing a monomer having an unsaturated double bond, which is used in a typical aqueous flexographic printing ink composition, or a resin obtained by a reaction between functional groups, without any particular limitation.
Specifically, suitable examples of binder resins include acrylic resins obtained by copolymerizing acrylic acid or methacrylic acid with its alkyl esters, or styrene or the like as a main monomer component, styrene-acrylic resins, styrene-maleic acid resins, styrene-acrylic-maleic acid resins, polyurethane resins, polyester resins, and the like.
These alkali-soluble resins are usually dissolved in water in the presence of a basic compound and used as water-soluble resin varnish. Examples of the basic compound used to dissolve the alkali-soluble resin in water include ammonia, organic amines, and alkali metal hydroxides. Specifically, the organic amines include alkylamines such as diethylamine, triethylamine, and ethylenediamine, and alkanolamines such as monoethanolamine, ethylethanolamine, diethylethanolamine, diethanolamine, and triethanolamine. Examples of the alkali metal hydroxides include sodium hydroxide and potassium hydroxide. Among them, it is preferable to use volatile and non-volatile basic compounds from the viewpoint of coating film properties and resolubility.
When an alkali-soluble resin is blended in the ink composition, the concentration thereof is preferably from 1.0 to 10.0% by mass, and more preferably from 3.0 to 6.0% by mass.

((Ethylene oxide/propylene oxide) block polymer)
The (ethylene oxide/propylene oxide) block polymer that can be contained as the pigment dispersing resin contains two or more blocks, and each block is composed of polyethylene oxide or polypropylene oxide.
The (ethylene oxide/propylene oxide) block polymer may be one synthesized by a known method, for example, one in which a polyethylene oxide polymer is reacted with propylene oxide to form a poly(propylene oxide/ethylene oxide/propylene oxide) block polymer, or, as another method, one in which a polypropylene oxide polymer is reacted with ethylene oxide to form a poly(ethylene oxide/propylene oxide/ethylene oxide) block polymer may be used.
The (ethylene oxide/propylene oxide) block polymer that can be used in the present invention has a weight average molecular weight in the range of 5,000 to 100,000.

Series etc.
From the viewpoint of stability in a solvent containing water, the HLB value of the (ethylene oxide/propylene oxide) block polymer is preferably 8-20.
Here, the HLB value indicates the balance between the hydrophilic and lipophilic parts of a molecule (hydrophile-lipophile balance) used in the field of surfactants, and the HLB value can be calculated by applying the Griffin formula shown below (a formula based on an experimental value calculated from the measurement of the emulsification efficiency for a certain oil and the weight fraction of the hydrophilic part).
[Griffin's formula] HLB = (100/5) x hydrophilic group weight / (hydrophilic group weight + hydrophobic group weight)
The total amount of the alkali-soluble resin and the (ethylene oxide/propylene oxide) block polymer used is preferably 10 to 30 parts by mass per 100 parts by mass of the pigment.

(Styrene-acrylic emulsion type film-forming resin)
The styrene-acrylic emulsion type film-forming resin used in the ink composition is preferably a styrene-acrylic emulsion type resin having a glass transition temperature of -30 to 60°C and having film-forming properties.
The glass transition temperature is preferably from -15 to 55°C, and more preferably from -10 to 50°C.
Such styrene-acrylic emulsion type film-forming resins are produced by known methods and preferably have an acid value of 30 to 80 mgKOH/g, more preferably 35 to 65 mgKOH/g.
Among such styrene-acrylic emulsion type film-forming resins, in order to improve the printability of rosin-based resins, those which form films at room temperature and are obtained by copolymerizing a styrene-based monomer and, if necessary, an alkyl ester of (meth)acrylic acid, using as a polymer emulsifier a water-soluble acrylic resin obtained by neutralizing an acrylic resin having an acid value of 150 to 250 mgKOH/g with a basic compound can be preferably used.
From an environmental perspective, when the aqueous flexographic printing ink composition contains 10 mass % or more of a carbon-neutral raw material component in its solid content, the aqueous flexographic printing ink composition contains the following rosin-based resin, and preferably the solid content ratio of the rosin-based resin to the styrene-acrylic emulsion type film-forming resin is in the range of 1:0.8 to 1:3.5.

(rosin resin)
The rosin-based resin that may be used in the ink composition is a rosin-based resin having an acid value of 0 mg KOH/g and/or 350 mg KOH/g or less.
The rosin-based resin may be either an emulsion or a water-soluble type.
The acid value of the solid content of the rosin resin emulsion is preferably 0 mgKOH/g and/or 0 to 150 mgKOH/g, more preferably 10 to 110 mgKOH/g, and the acid value of the water-soluble rosin resin, such as an alkali-soluble type, is preferably 100 to 350 mgKOH/g, more preferably 120 to 200 mgKOH/g.
The range of acid value of 0 mgKOH/g and/or 350 mgKOH/g certainly includes the embodiment of 0 mgKOH/g.
The rosin-based resin emulsion may be one obtained by dispersing rosin or a rosin derivative such as rosin ester, which is made of a material obtained by extraction from a plant, in the form of fine particles in water in the presence of a low molecular weight emulsifier.Specific examples include Hariestar SK218NS, SK370N, SK385NS, and SK501NS manufactured by Harima Chemical Industries, Ltd., Snowpack XW-2442, XW-2551, XW-2561, XW-2582, SE780G, and 100G manufactured by Lawter, and Superester NS-121, NS-100H, and E-865NT manufactured by Arakawa Chemical Industries, Ltd.
The water-soluble rosin resin is a rosin resin having an acid value of 100 to 350 mgKOH/g, the acid value of which is partially or entirely neutralized with a basic compound and dissolved in water.Specific examples include Tespol 150, 154, and 158 manufactured by Hitachi Chemical Co., Ltd., Harima Chemical Co., Ltd.'s Harimac T-80, Hariestar MSR-4, and AS-5, and Arakawa Chemical Co., Ltd.'s Marquid 31, 32, and 33.
Examples of the basic compound include ammonia, organic amines, and alkali metal hydroxides. Specifically, the organic amines include alkylamines such as diethylamine, triethylamine, and ethylenediamine, and alkanolamines such as monoethanolamine, ethylethanolamine, diethylethanolamine, diethanolamine, and triethanolamine. Examples of the alkali metal hydroxides include sodium hydroxide and potassium hydroxide. Among them, it is desirable to use volatile and non-volatile basic compounds from the viewpoint of coating film properties and resolubility.
Among rosin-based resins with different acid values, those with an acid value of 0 to 200 mgKOH/g are preferred, and when water resistance and abrasion resistance are required, rosin-based resin emulsions with an acid value of 0 to 100 mgKOH/g are preferred.
In cases where environmental considerations are required, the rosin-based resin in the aqueous flexographic printing ink composition of the present invention preferably contains a carbon-neutral raw material component in an amount of 10 mass % or more based on the solid content of the aqueous flexographic printing ink composition. Note that the carbon-neutral raw material component refers to a raw material component derived from a plant material.
Such a rosin resin can be blended in the ink composition in an amount of 0 to 20.0% by mass, preferably 3.0 to 20.0% by mass, and more preferably 4.0 to 10.0% by mass.

(Wax resin fine particles)
The wax resin particles used in the ink composition have an average particle size of 3 to 6 μm as measured by the Coulter Counter method in order to improve the abrasion resistance of the coating film. The wax is blended in a state of being dispersed in a solvent. The obtained wax resin fine particles are preferably polyethylene waxes, specifically, for example, Chemipearl W100, W200, W300, W308, W400, and W500 (all of which have a solid content concentration of 40%) manufactured by Mitsui Chemicals, Inc. The amount of the wax resin fine particle dispersion to be added is preferably about 1 to 7 mass % in terms of solid content in 100 wt % of the aqueous flexographic printing ink composition as the dispersion, taking into consideration the balance between the improvement in abrasion resistance in the coating film properties and the adverse effect on the hue.

(Water-containing solvent)
As the solvent used in the ink composition, in addition to water, a water-soluble organic solvent is used within a range that does not cause a decrease in the performance of the ink composition used in the present invention.
The water-soluble organic solvent is an alcohol or polyhydric alcohol solvent, specifically, methanol, ethanol, propanol, butanol, hexanol, octanol, decanol, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monooctyl ether, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol mono Propyl ether, triethylene glycol monobutyl ether, propylene glycol, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monobutyl ether, dibutyl glycol, glycerin, and the like can be added.

(Additives)
Various additives can be used in the ink composition as necessary. Specific examples of the additives include extender pigments such as calcium carbonate, kaolin, barium sulfate, aluminum hydroxide, clay, and talc for improving drying properties, inorganic fine particles and adhesive resins (acrylic resins, vinyl acetate resins) for imparting anti-slip properties, leveling agents for improving leveling properties, antifoaming agents for imparting antifoaming properties, basic compounds such as caustic soda for imparting resolubility, and film-forming emulsions.

(Production method)
In a method for producing an ink composition by a conventional method, a pigment, a pigment dispersion resin, and a solvent containing water are mixed, and then the mixture is milled using various milling machines, for example, a bead mill, a pearl mill, a sand mill, a ball mill, an attritor, a roll mill, or the like, and further, a styrene-acrylic emulsion type film-forming resin, a rosin resin when environmental considerations are required, or other predetermined materials and additives as necessary are mixed.
Next, if dilution is required during printing, a solvent containing water may be further added to form an aqueous flexographic printing ink composition. An example of a method for producing a printed matter using this aqueous flexographic printing ink composition is printing on the surface of paper or resin, particularly on thin paper for food packaging, using the aqueous flexographic printing ink composition with a flexographic printer.

<Coat layer>
The coating layer made of the heat-resistant aqueous coating composition in the present invention is a coating layer made of a heat-resistant aqueous coating composition containing an alkali-soluble resin, an emulsion-type film-forming resin, a dispersion of wax resin microparticles having an average particle size of 1 to 10 μm, and an aqueous medium.
When the wrapping paper is used to package food inside (on the inner surface of the substrate), the coating layer is formed on the printed layer on the outer surface of the substrate by any method such as coating or printing. When the printed layer is formed on only a part of the substrate surface rather than on the entire substrate surface, the coating layer is formed directly on the substrate surface in the unprinted areas.

The heat-resistant aqueous coating agent composition for forming the coating layer will be described below.
(Alkali-soluble resin)
The alkali-soluble resin used in the heat-resistant aqueous coating agent composition is not particularly limited as long as it has a glass transition temperature of 110° C. or higher, preferably 120° C. or higher and 170° C. or lower, from the viewpoints of heat resistance and blocking resistance, and is obtained by polymerizing a monomer having an unsaturated double bond used in a normal ink composition, or a resin obtained by a reaction between functional groups.
Specifically, suitable examples of binder resins include water-soluble acrylic resins copolymerized with acrylic acid or methacrylic acid and their alkyl esters, or styrene or the like as the main monomer component, water-soluble styrene-acrylic resins, water-soluble styrene-maleic acid resins, water-soluble styrene-acrylic-maleic acid resins, water-soluble polyurethane resins, and water-soluble polyester resins.
These alkali-soluble resins are usually dissolved in water in the presence of a basic compound and used as water-soluble resin varnish. Examples of the basic compound used to dissolve the alkali-soluble resin in water include ammonia, organic amines, and alkali metal hydroxides. Specifically, the organic amines include alkylamines such as diethylamine, triethylamine, and ethylenediamine, and alkanolamines such as monoethanolamine, ethylethanolamine, diethylethanolamine, diethanolamine, and triethanolamine. Examples of the alkali metal hydroxides include sodium hydroxide and potassium hydroxide. Among them, it is preferable to use volatile and non-volatile basic compounds from the viewpoint of coating film properties and resolubility.

(Emulsion-type film-forming resin)
The emulsion type film-forming resin used in the heat-resistant aqueous coating composition is at least one type having film-forming properties selected from the group consisting of styrene-acrylic emulsion type resins, styrene-maleic acid emulsion type resins, and styrene-maleic acid half ester emulsion type resins, each having a glass transition temperature of -30 to 60°C. Among these, the glass transition temperature is preferably -10 to 55°C, and more preferably 0 to 50°C.
Of the emulsion type film-forming resins, styrene-acrylic emulsion type resins are preferred.
Details are omitted since they are similar to those of the above-mentioned aqueous printing ink composition.
From the viewpoint of friction resistance in a warm environment, the ratio of the styrene-acrylic emulsion type film-forming resin and the alkali-soluble resin is set to be 60% by mass or more (styrene-acrylic emulsion type film-forming resin/(styrene-acrylic emulsion type film-forming resin+alkali-soluble resin)×100) calculated as solid content, preferably 70% by mass or more, more preferably 80% by mass or more, and more preferably 95% by mass or less.

(Wax Microparticle Dispersion)
The wax resin microparticle dispersion used in the heat-resistant aqueous coating composition has an average particle size of 1 to 10 μm, preferably 2 to 9 μm, as measured by the Coulter Counter method, in order to improve the abrasion resistance of the coating film. The wax resin microparticle dispersion is preferably a polyethylene wax, specifically, for example, Chemipearl W100, W200, W300, W310, W306, W400, W410, W500, W800, etc., manufactured by Mitsui Chemicals, Inc. The amount of the wax resin microparticle dispersion added is preferably about 1 to 7 mass% in terms of solid content in 100 wt% of the heat-resistant aqueous coating composition, taking into consideration the balance between the improvement in abrasion resistance in the coating film properties and the adverse effect on the hue.

(Water-containing solvent)
As the solvent used in the heat-resistant aqueous coating composition, a solvent containing water can be used. Specific examples of the solvent that can be used include the above-mentioned various solvents.

(Additives)
The heat-resistant aqueous coating composition may contain any of the above-mentioned additives within the scope of achieving the object of the present invention.
The print improving agent may contain at least one selected from the group consisting of a compound represented by the following formula (1), a compound represented by the following formula (2), 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol isobutyrate, 2-ethyl-1,3-hexanediol, 1,6-hexanediol diacetate, and isoamyl acetate.
(1) R ₁ -O-(C _m H _2m O)n-R ₂
(In formula (1), R ₁ and R ₂ are each independently a hydrogen atom or an alkyl group, the sum of the number of carbon atoms in R ₁ and the number of carbon atoms in R ₂ is 4 or more, m is 2 or 3, and n is 1, 2, or 3.)
(2) R ₃ -O-(C _m H _2m O) ₂ -CO-CH ₃
(In formula (2), _R3 is an alkyl group having 1 to 4 carbon atoms, and m is 2 or 3.)
The print improver is contained in the aqueous coating composition in an amount of 0.1 to 5% by mass.

<Method of manufacturing food packaging paper>
The food packaging paper of the present invention is prepared by printing the above-mentioned printing ink composition on at least a portion of one side of the above-mentioned substrate (the side not facing the food to be packaged, i.e., the side that will be the outer surface when packaged) by any means such as flexographic printing.
After the layer of the printing ink composition has dried, the heat-resistant aqueous coating composition is applied to the entire surface by a known coating or printing means for paper to obtain a coating layer.
The resulting coating layer is dried to produce the food packaging paper of the present invention.

<Applications of food wrapping paper>
The wrapping paper of the present invention is a wrapping paper that does not remove ink or the like on the outer surface of the packaging even if it is rubbed against the surface of a table or cooking counter that is oily or wet while serving hot food on the wrapping paper, during packaging hot food, or after packaging. It is particularly used for applications in which the wrapping paper is in direct contact with a counter or the like when serving food, wrapping food, or moving wrapped food on the surface of a cooking counter that has been heated and kept warm at 40 to 60°C or a counter that has been heated to about 40 to 60°C by heat transfer from a cooking appliance or the like. The act of serving food on the wrapping paper is also considered to be cooking. For example, the process of making a hamburger or the like by spreading the wrapping paper of the present invention on a heated counter or the like so that the coating layer is in contact with the surface of the counter, and then placing heated bread or buns, ingredients such as vegetables and meat, and then bread or buns on top of the paper in that order corresponds to serving or cooking food.
To provide a food wrapping paper which, even when used for such purposes, does not remove the ink on the wrapping paper and has excellent coating film properties such as water resistance, abrasion resistance, oil resistance, etc., and a food wrapping method using the same.
The foods to be packaged are not particularly limited, and include hamburgers, taiyaki, pizza, meat buns, yakitori, croquettes, baked sweet potatoes, sweet chestnuts, etc. that can be packaged in a warm state immediately after cooking or keeping warm.
The food packaging paper of the present invention is formed by laminating, in order, a printed layer having a coating amount (solid content) of 3.0 to 9.0 g/ ^m2 and a coating layer having a coating amount (solid content) of 1.5 to 6.0 g/ ^m2 on an oil-resistant substrate.
The printing layer is preferably 4.0 to 8.0 g/ ^m2 , and the coating layer is preferably 2.0 to 5.0 g/ ^m2 .

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "%" means "% by mass" and "parts" means "parts by mass." The figures for the amounts of each material in the tables are also "parts by mass." The unit of acid value is mgKOH/g.

<Substrate>
As far as the test was concerned, the results of printing on base paper (K liner) were the same as those of printing on thin paper, so the evaluation was carried out using base paper (K liner).

<Printed layer made of ink composition>
(Water-based flexographic printing ink composition)
A mixture of pigments (phthalocyanine blue, C.I. Pigment Blue 15:3), the following resin varnish, EO/PO block polymer (ADEKA Corporation's "ADEKA Pluronic F-108"), dibutyl glycol and water was kneaded and dispersed in a bead mill, and then the following rosin resin, the following styrene-acrylic emulsion type film-forming resin, the following wax resin fine particle dispersion and an antifoaming agent (SN Defoamer 777#C San Nopco Corporation) were added and mixed in the proportions shown in Table 1 to obtain an aqueous flexographic printing ink composition.

(Resin varnish)
An alkali-soluble resin (Joncryl HPD-671, manufactured by BASF Corporation, glass transition temperature 120 to 128° C., acid value 214 to 218 mgKOH/g), water, and aqueous ammonia were mixed, neutralized and made aqueous at 70 to 90° C., and aqueous ammonia was further added to adjust the pH to 8.5, thereby obtaining a resin varnish (solid content 25%).

(rosin resin)
1. Emulsion, acid value 25 mg KOH/g or less (emulsifier), solid content 50%, emulsifier 2. Emulsion, acid value 100 mg KOH/g, solid content 50%, emulsifier 3. Alkali-soluble type, acid value 130 mg KOH/g, ammonia/diethanolamine, solid content 50%,
4. Alkali-soluble type Acid value 170 mg KOH/g Ammonia/diethanolamine Solid content 50%

(Styrene-acrylic emulsion type film-forming resin)
1. Acid value 51 mg KOH/g, glass transition temperature -10°C, solid content 48%
2. Acid value 38 mg KOH/g, glass transition temperature 9°C, solid content 38.5%
3. Acid value 62 mg KOH/g, glass transition temperature 43° C., solid content 45.5%

(Wax resin fine particle dispersion)
1. Chemipearl W400, particle size 4.0 μm (coal counter method), Mitsui Chemicals 2. Chemipearl W100, particle size 3.0 μm (coal counter method), Mitsui Chemicals 3. Chemipearl W500, particle size 2.5 μm (coal counter method), Mitsui Chemicals 4. Chemipearl W200, particle size 6.0 μm (coal counter method), Mitsui Chemicals 5. Chemipearl W800, particle size 8.0 μm (coal counter method), Mitsui Chemicals

<Coating layer made of heat-resistant aqueous coating composition>
(Heat-resistant aqueous coating composition)
An alkali-soluble water-soluble resin, a styrene-acrylic emulsion type film-forming resin, polyethylene wax, an antifoaming agent, a surfactant, a print modifier, and water were mixed in the proportions shown in Table 2 to obtain a heat-resistant aqueous coating composition.

(Styrene-acrylic emulsion type film-forming resin)
1. Acid value 60 mg KOH/g, glass transition temperature 50°C, solid content 46%
2. Acid value 52 mg KOH/g, glass transition temperature 14°C, solid content 49%
3. Acid value 38 mg KOH/g, glass transition temperature 9°C, solid content 38.5%

(Alkali-soluble resin)
1. Acid value 240 mg KOH/g, glass transition temperature 155°C, solid content 27%
2. Acid value 216 mg KOH/g, glass transition temperature 124°C, solid content 25%

(Wax resin fine particles (polyethylene wax))
1. Chemipearl W400, particle size 4.0 μm (coal counter method), Mitsui Chemicals 2. Chemipearl W800, particle size 8.0 μm (coal counter method), Mitsui Chemicals

(Antifoaming agent)
・SN DEFORMER 777#C SAN NOPCO (Surfactant)
・EO/PO surfactants (printing modifiers)
2-Ethyl-1,3-hexanediol

(Water and abrasion resistance)
The aqueous flexographic printing ink composition and the heat-resistant aqueous coating composition were applied to a base paper (K liner) using a 200-line hand proofer, and the applied product was evaluated using a Gakushin type rub fastness tester.
Evaluation conditions: 200 g x 2 times, paper: 5 drops of water dropped onto Kanakin cloth. ⊚: No coating film was removed.
○: A small amount of ink has adhered to the paper. A small amount of ink has come off from the applied material.
○△: The ink is thinly adhered to the entire surface of the paper. The ink has come off slightly from the applied color.
△: The paper has a thin layer of ink on the entire surface. The ink on the applied layer has come off, and some of the original paper is visible.
×: The ink is thickly adhered to the entire surface of the paper. The ink has come off on the painted surface, and most of the base paper is visible.

(Abrasion resistance)
The aqueous flexographic printing ink composition and the heat-resistant aqueous coating composition were applied to a base paper (K liner) using a 200-line hand proofer, and the applied product was evaluated using a Gakushin type rub fastness tester.
Evaluation conditions: 200 g x 100 times, paper: Kanakin cloth. ⊚: No coating was removed.
◎○: A very small amount of ink has adhered to the paper. A very small amount of ink has come off of the applied material.
○: A small amount of ink has adhered to the paper. A small amount of ink has come off from the applied material.
◯△: The ink is thinly adhered to the entire surface of the paper. A small amount of ink has come off from the applied material.
△: Ink is attached to the entire surface of the paper. The ink has come off from the applied material, and some of the original paper is visible.
×: The ink is thickly adhered to the entire surface of the paper. The ink has been removed from the applied product, and most of the base paper is visible.

(Oil and abrasion resistance)
The aqueous flexographic printing ink composition and the heat-resistant aqueous coating composition were applied to a base paper (K liner) using a 200-line hand proofer, and the applied product was evaluated using a Gakushin type rub fastness tester.
Evaluation conditions: 200 g x 2 times, paper: 5 drops of salad oil applied to Kanakin cloth. ⊚: No coating was removed.
◎○: A very small amount of ink has adhered to the paper. A very small amount of ink has come off of the applied material.
○: A small amount of ink has adhered to the paper. A small amount of ink has come off from the applied material.
◯△: The ink is thinly adhered to the entire surface of the paper. A small amount of ink has come off from the applied material.
△: Ink is attached to the entire surface of the paper. The ink has come off from the applied material, and some of the original paper is visible.
×: The ink is thickly adhered to the entire surface of the paper. The ink has been removed from the applied product, and most of the base paper is visible.
In addition, as far as the test is conducted, the results of printing on the above base paper (K liner) are the same as those of printing on thin paper.

(Abrasion resistance (50°C)
The aqueous flexographic printing ink composition and the heat-resistant aqueous coating composition were applied to a base paper (K liner) using a 200-line hand proofer, and the applied product was left in a 50°C environment for 1 hour, and then evaluated for rub fastness to wear using a Gakushin type rub fastness tester in a 50°C environment.
Evaluation conditions: 200 g x 100 times, paper: Kanakin cloth. ⊚: No coating was removed.
◎○: A very small amount of ink has adhered to the paper. A very small amount of ink has come off of the applied material.
○: A small amount of ink has adhered to the paper. A small amount of ink has come off from the applied material.
◯△: The ink is thinly adhered to the entire surface of the paper. A small amount of ink has come off from the applied material.
△: Ink is attached to the entire surface of the paper. The ink has come off from the applied material, and some of the original paper is visible.
×: The ink is thickly adhered to the entire surface of the paper. The ink has been removed from the applied product, and most of the base paper is visible.

Each of the examples according to the present invention had excellent water abrasion resistance, abrasion resistance, oil abrasion resistance, and abrasion resistance at 50°C. In contrast, Comparative Example 1, which used an ink composition that did not contain wax resin particles, Comparative Example 2, which had a small particle size of the wax resin particle dispersion, and Comparative Example 3, which had a large particle size of the wax resin particle dispersion, all had poor abrasion resistance at 50°C. In addition, Comparative Example 4, in which the coating composition did not satisfy condition 3, and Comparative Example 5, in which the coating composition did not contain wax resin particles, all had poor abrasion resistance at 50°C.

Claims (11)

An oil-resistant substrate;
a printing layer made of an aqueous flexographic printing ink composition containing a pigment, a styrene-acrylic emulsion type film-forming resin having a glass transition temperature of −30 to 60° C., a dispersion of wax resin microparticles having an average particle size of 3 to 6 μm, and a solvent containing water;
and a coating layer made of a heat-resistant aqueous coating composition containing an alkali-soluble resin, an emulsion-type film-forming resin, a dispersion of wax resin microparticles having an average particle size of 1 to 10 μm, and an aqueous medium, the weight ratio of which "emulsion-type film-forming resin/(emulsion-type film-forming resin/alkali-soluble resin)" is 80 mass% or more, the coating layer being laminated in this order. The food packaging paper according to claim 1, wherein the aqueous flexographic printing ink composition contains a rosin-based resin having an acid value of 0 gKOH/g or more and 350 mgKOH/g or less. The food packaging paper according to claim 1 or 2, wherein the aqueous flexographic printing ink composition contains an alkali-soluble resin and/or an (ethylene oxide/propylene oxide) block polymer as a pigment dispersion resin. The food packaging paper according to claim 2, wherein the water-based flexographic ink composition contains 10% by mass or more of carbon-neutral raw material components in the ink composition, and the solids ratio of the rosin-based resin to the styrene-acrylic emulsion-type film-forming resin is in the range of 1:0.8 to 1:3.5. The food packaging paper according to any one of claims 1 to 4, wherein the glass transition temperature of the alkali-soluble resin contained in the heat-resistant aqueous coating composition is 110°C or higher. The food packaging paper according to any one of claims 1 to 5, wherein the emulsion-type film-forming resin contained in the heat-resistant aqueous coating composition is at least one selected from the group consisting of styrene-acrylic emulsion-type resins, styrene-maleic acid emulsion-type resins, and styrene-maleic acid half ester emulsion-type resins, each having a glass transition temperature of -30 to 60°C. The aqueous medium contained in the heat-resistant aqueous coating composition contains a print modifier,
The print modifier is at least one selected from the group consisting of a compound represented by the following formula (1), a compound represented by the following formula (2), 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol isobutyrate, 2-ethyl-1,3-hexanediol, 1,6-hexanediol diacetate, and isoamyl acetate.
The print modifier is contained in the heat-resistant aqueous coating composition in an amount of 0.1 to 5% by mass.
The food packaging paper according to any one of claims 1 to 6:
(1) R ¹ -O-(C _m H _2m O)n-R ²
(In formula (1), R ¹ and R ² are each independently a hydrogen atom or an alkyl group, the sum of the number of carbon atoms in R ¹ and the number of carbon atoms in R ² is 4 or more, m is 2 or 3, and n is 1, 2, or 3.)
(2) R ³ -O-(C _m H _2m O) ₂ -CO-CH ₃
(In formula (2), ^R3 is an alkyl group having 1 to 4 carbon atoms, and m is 2 or 3.) The coating amount (solid content) of the printing layer is 3.0 to 9.0 g/ ^m2 , and the coating amount (solid content) of the coating layer is 1.5 to 6.0 g/ ^m2 ,
The food packaging paper according to any one of claims 1 to 7. On one side of an oil-resistant substrate,
providing a printing layer made of an aqueous flexographic printing ink composition containing a pigment, a styrene-acrylic emulsion type film-forming resin having a glass transition temperature of −30 to 60° C., a dispersion of wax resin microparticles having an average particle size of 3 to 6 μm, and a solvent containing water;
next, providing a coating layer made of a heat-resistant aqueous coating composition containing an alkali-soluble resin, an emulsion-type film-forming resin, a dispersion of wax resin microparticles having an average particle size of 1 to 10 μm, and an aqueous medium, and having a weight ratio of "emulsion-type film-forming resin/(emulsion-type film-forming resin/alkali-soluble resin)" of 80 mass% or more, and laminating a printing layer and a coating layer in this order on the substrate. The method for producing food packaging paper according to claim 9, wherein the aqueous flexographic printing ink composition further contains a rosin-based resin having an acid value of 0 mg KOH/g or more and 350 mg KOH/g or less. A food packaging method for wrapping food with the food packaging paper according to any one of claims 1 to 8, comprising the steps of:
The food packaging method includes a step of placing food on the food wrapping paper that has been spread on a base made of a metal plate heated to a surface temperature of 40 to 60°C so that the coating layer is in contact with the surface of the base.