Paper barrier packaging materials

Abstract

The present invention addresses the problem of providing a barrier paper packaging material that has excellent bending resistance.　The present invention provides, as a means for solving the problem, a barrier paper packaging material which comprises a water vapor barrier layer and a gas barrier layer on a paper base material, wherein: the water vapor barrier layer contains a water vapor barrier resin and a pigment; the water vapor barrier resin contains a styrene resin that has a glass transition temperature of -20°C to 50°C; the gas barrier layer contains a gas barrier resin; and the content of the pigment relative to 100 parts by weight of the gas barrier resin is 90 parts by weight or less.

Description

[Technical Field]

[0001] The present invention relates to a paper barrier packaging material. [Background technology]

[0002] It is important to impart gas barrier properties (particularly oxygen barrier properties) to paper packaging materials in order to protect various packaged products from deterioration due to gases, such as oxidation due to oxygen. Conventionally, the main method of imparting gas barrier properties to paper packaging materials has been to extrusion laminate or attach to the paper base a gas barrier layer made of a metal foil or metal vapor-deposited film made of a metal such as aluminum, a resin film such as polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyvinylidene chloride, or polyacrylonitrile, or a film coated with one of these resins, or a ceramic vapor-deposited film vapor-deposited with an inorganic oxide such as silicon oxide or aluminum oxide.

[0003] Other paper packaging materials that have been given gas barrier properties include paper gas barrier materials having a gas barrier layer made of a water-soluble polymer and an inorganic layered compound (Patent Document 1 and Patent Document 2). It is also important to impart water resistance (particularly water vapor barrier properties) to paper packaging materials in order to protect the various packaged products from deterioration due to water vapor. A paper barrier packaging material with gas barrier and water vapor barrier properties has been disclosed, which has, on a paper substrate, a water vapor barrier layer containing a water vapor barrier resin and a pigment, and a gas barrier layer containing a polyvinyl alcohol resin and a pigment (Patent Document 3).

[0004] Such paper barrier packaging materials may bend during processing into packaging containers, or during product transportation or use, resulting in a significant loss of barrier properties. Therefore, there is a demand for paper barrier packaging materials with excellent bending resistance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-184138 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-094574 [Patent Document 3] Patent No. 5331265 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a paper barrier packaging material that has excellent flex resistance. [Means for solving the problem]

[0007] The means for solving the problems of the present invention are as follows. 1. A paper substrate having a water vapor barrier layer and a gas barrier layer, the water vapor barrier layer contains a water vapor barrier resin and a pigment, the water vapor barrier resin contains a styrene-based resin having a glass transition temperature of −20 to 95° C., A paper barrier packaging material characterized in that the gas barrier layer contains a gas barrier resin, and the pigment content is 90 parts by weight or less per 100 parts by weight of the gas barrier resin. 2. The paper barrier packaging material described in 1, characterized in that it has the water vapor barrier layer and the gas barrier layer in this order on the paper base material. 3. The water vapor barrier layer contains an ethylene-based resin, 3. The paper barrier packaging material according to 1. or 2., characterized in that it contains the styrene-based resin and the ethylene-based resin in a weight ratio (dry weight) of 99 / 1 to 1 / 99. 4. The paper barrier packaging material according to 3, characterized in that the glass transition temperature of the ethylene-based resin is -20 to 95°C. 5. The paper barrier packaging material according to any one of 1. to 4., characterized in that the pigment content in the gas barrier layer is, on a dry weight basis, 5 to 80 parts by weight per 100 parts by weight of the gas barrier resin. 6. The paper barrier packaging material according to any one of 1. to 5., wherein the water vapor barrier layer contains a pigment with an average particle size of 5 μm or more and an aspect ratio of 10 or more. 7. The paper barrier packaging material according to any one of 1. to 6., wherein the gas barrier resin contains a polyvinyl alcohol-based resin. 8. The paper barrier packaging material according to any one of 1. to 7., wherein the gas barrier layer contains a plasticizer. 9. The paper barrier packaging material according to any one of 1. to 8., wherein the gas barrier layer contains an adhesive aid. [Effects of the Invention]

[0008] The paper barrier packaging material of the present invention has excellent flex resistance and shows little deterioration in barrier properties when flexed. The paper barrier packaging material of the present invention can be suitably used for flexible packaging bags that are prone to bending. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention provides a paper substrate having a water vapor barrier layer and a gas barrier layer thereon, the water vapor barrier layer contains a water vapor barrier resin and a pigment, and the water vapor barrier resin contains a styrene-based resin having a glass transition temperature of -20 to 95°C; The present invention relates to a paper barrier packaging material in which the gas barrier layer contains a gas barrier resin, and the pigment content per 100 parts by weight of the gas barrier resin is 90 parts by weight or less. In this specification, the expression "A to B (A and B are numbers)" means a numerical range including the values ​​of A and B, that is, A or more and B or less.

[0010]

[0003] Paper barrier packaging materials preferably have a water vapor barrier layer and a gas barrier layer, in this order, on a paper base material. Paper barrier packaging materials having a water vapor barrier layer and a gas barrier layer, in this order, on a paper base material have excellent water vapor barrier properties and gas barrier properties. The reason for this is presumed to be as follows: When a gas barrier layer and a water vapor barrier layer are provided on a paper base material in this order, the gas barrier resin in the gas barrier layer is prone to degradation due to moisture in the paper base material and moisture in the air that permeates via the paper base material. On the other hand, by having a water vapor barrier layer and a gas barrier layer, in this order, on a paper base material, which contain a resin with good water resistance, the water vapor barrier layer can effectively suppress the impact (deterioration) of the gas barrier layer due to moisture in the paper base material and the like. For this reason, paper barrier base paper having a water vapor barrier layer and a gas barrier layer, in particular, in this order, has excellent water vapor barrier properties and gas barrier properties.

[0011] (Paper base material) In the present invention, the paper substrate is a sheet made of pulp, fillers, various auxiliaries, and the like. Pulp can be selected from a variety of pulps, including chemical pulps such as bleached hardwood kraft pulp (LBKP), bleached softwood kraft pulp (NBKP), unbleached hardwood kraft pulp (LUKP), unbleached softwood pulp (NUKP), and sulfite pulp; mechanical pulps such as stone-ground pulp and thermomechanical pulp; wood fibers such as deinked pulp and recycled paper pulp; and non-wood fibers obtained from kenaf, bamboo, hemp, and the like, and can be used in appropriate combinations. Among these, chemical pulp and mechanical pulp made from wood fibers are preferred, and chemical pulp is more preferred, for reasons such as the fact that foreign matter is less likely to be mixed into the paper base material, that discoloration is less likely to occur over time when used paper containers are recycled as recycled paper materials, and that high whiteness results in a good surface appearance when printed, thereby increasing the value of the material, particularly when used as a packaging material.

[0012] Known fillers such as white carbon, talc, kaolin, clay, heavy calcium carbonate, light calcium carbonate, titanium oxide, zeolite, and synthetic resin fillers can be used. Fillers are optional components, and the paper may contain no fillers. Internal papermaking aids such as aluminum sulfate and various anionic, cationic, nonionic, or amphoteric retention aids, drainage aids, paper strength agents, and internal sizing agents can be used as needed. Furthermore, dyes, fluorescent whitening agents, pH adjusters, antifoaming agents, pitch control agents, slime control agents, and the like can also be added as needed.

[0013] The method for producing the paper base material (papermaking) is not particularly limited, and the paper base material can be produced by acidic papermaking, neutral papermaking, or alkaline papermaking using a known Fourdrinier former, on-top hybrid former, gap former machine, etc. The paper base material may be composed of one layer, or two or more layers. Furthermore, the surface of the paper substrate can be treated with various chemicals. Examples of chemicals that can be used include oxidized starch, hydroxyethyl etherified starch, enzyme-modified starch, polyacrylamide, polyvinyl alcohol, surface sizing agents, water-resistant agents, water-retention agents, thickeners, and lubricants. These can be used alone or in combination of two or more. Furthermore, these various chemicals can be used in combination with pigments. Examples of pigments include inorganic pigments such as kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light calcium carbonate, mica, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicates, colloidal silica, and satin white, as well as organic pigments such as solid, hollow, and core-shell pigments, which can be used alone or in combination of two or more.

[0014] The method for treating the surface of the paper substrate is not particularly limited, but known coating devices such as a rod metering size press, a pond type size press, a gate roll coater, a spray coater, a blade coater, and a curtain coater can be used. Examples of paper substrates obtained in this manner include various known types such as fine paper, medium-quality paper, coated paper, one-side glossy paper, kraft paper, one-side glossy kraft paper, bleached kraft paper, glassine paper, paperboard, white paperboard, and liner.

[0015] The basis weight of the paper substrate can be selected appropriately depending on the desired qualities and handling properties of the paper barrier packaging material, but is usually 20 g / m 2 More than 500g / m 2 For paper barrier packaging materials used for packaging purposes such as food packaging, containers, and cups, a minimum of 25 g / m2 is preferred. 2 More than 400g / m 2 The following is more preferable, and in particular for paper barrier packaging materials used for flexible packaging bags described below, 30 g / m 2 More than 140g / m 2 The following is more preferred:

[0016] (Water vapor barrier layer) The water vapor barrier layer contains a water vapor barrier resin and a pigment. Water vapor barrier resins include styrene-based resins with a glass transition temperature (Tg) of -20°C or higher and 95°C or lower. Styrenic resins refer to resins copolymerized with styrene monomer and other monomers such as acrylic acid, methacrylic acid, acrylonitrile, and butadiene. In addition, resins copolymerized with various comonomers for the purpose of modification may also be used. Examples of comonomers include methyl methacrylate, acrylonitrile, acrylamide, hydroxyethyl acrylate, and unsaturated carboxylic acids such as itaconic acid and maleic acid. Examples of styrene-based resins include styrene-acrylic resins, styrene-butadiene resins, and styrene-butadiene-acrylic resins, with styrene-acrylic resins being preferred. The glass transition temperature of styrene-based resins is preferably -20°C or higher, more preferably -10°C or higher, even more preferably 0°C or higher, and preferably 50°C or lower, more preferably 40°C or lower, and even more preferably 30°C or lower. Styrenic resins can be used alone or in combination.

[0017] In addition, as the water vapor barrier resin, ethylene-based resins obtained by copolymerizing ethylene monomers with other monomers, such as ethylene-acrylic resins and ethylene-vinyl acetate resins, paraffin (wax)-based resins, various copolymers such as butadiene-methyl methacrylate-based and vinyl acetate-butyl acrylate-based resins, synthetic adhesives such as maleic anhydride copolymers and acrylic acid-methyl methacrylate copolymers, or synthetic adhesives containing paraffin (wax) can be used in combination. Among these, ethylene-based resins are preferred, and ethylene-acrylic resins are more preferred. The glass transition temperature of the ethylene-based resin is preferably -20°C or higher and 95°C or lower, more preferably -15°C or higher, even more preferably -10°C or higher, and preferably 50°C or lower, and even more preferably 40°C or lower. When an ethylene-based resin is used in combination, the weight ratio of the styrene-based resin to the ethylene-based resin (dry weight, styrene / ethylene) is preferably 99 / 1 to 1 / 99, more preferably 90 / 10 to 10 / 90, more preferably 70 / 30 to 30 / 70, and even more preferably 65 / 35 to 45 / 55.

[0018]

[0043] Furthermore, provided that the water vapor barrier properties are not affected, it is also possible to use in combination with the above-mentioned water vapor barrier resins water-soluble polymers such as fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, ethylene copolymer polyvinyl alcohol, and other polyvinyl alcohols; proteins such as casein, soybean protein, and synthetic protein; starches such as oxidized starch, cationized starch, urea phosphate esterified starch, and hydroxyethyl etherified starch; cellulose derivatives such as carboxymethyl cellulose, hydroxymethyl cellulose, and hydroxyethyl cellulose; polyvinylpyrrolidone; and sodium alginate.

[0019] Examples of pigments include inorganic pigments such as kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light calcium carbonate, mica, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicates, colloidal silica, and satin white, as well as solid, hollow, and core-shell organic pigments, which can be used alone or in combination of two or more. Among these pigments, flat inorganic pigments such as kaolin, mica, and talc are preferred, with kaolin or mica being more preferred, from the standpoint of improving water vapor barrier properties and improving adhesion with adjacent layers. Furthermore, it is preferred to use inorganic pigments, either alone or in combination of two or more types, with a 50% volume average particle size (D50) (hereinafter also referred to as "average particle size") of 5 μm or greater and an aspect ratio of 10 or greater. If the average particle size or aspect ratio of the inorganic pigment used is smaller than the above range, the number of detours that water vapor takes within the water vapor barrier layer decreases, shortening the distance it travels, which may result in a reduced effect on improving water vapor barrier properties.

[0020] In the present invention, from the perspective of improving water vapor barrier properties and improving adhesion with adjacent layers, it is preferable for a water vapor barrier layer containing an inorganic pigment with an average particle size of 5 μm or more and an aspect ratio of 10 or more to further contain a pigment with an average particle size of 5 μm or less. By using a pigment with an average particle size of 5 μm or less in combination, it is possible to reduce the voids in the water vapor barrier layer formed by the inorganic pigment with an average particle size of 5 μm or more and an aspect ratio of 10 or more, thereby achieving even better water vapor barrier properties. In other words, when pigments with different average particle sizes are contained in the water vapor barrier layer, the pigment with the smaller average particle size fills the voids formed by the inorganic pigment with the larger average particle size in the water vapor barrier layer, allowing water vapor to bypass the pigment and pass through, and it is presumed that this will result in higher water vapor barrier properties than a water vapor barrier layer that does not contain a pigment with a different average particle size.

[0021] In the present invention, examples of pigments having an average particle size of 5 μm or less that can be used in combination with inorganic pigments having an average particle size of 5 μm or more and an aspect ratio of 10 or more include inorganic pigments such as kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light calcium carbonate, mica, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicates, colloidal silica, and satin white, as well as solid, hollow, and core-shell organic pigments, which can be used alone or in combination of two or more. Of these pigments, heavy calcium carbonate is preferred.

[0022] The blending amount of the pigment in the water vapor barrier layer, in dry weight, is preferably from 50 to 1,000 parts by weight, more preferably from 120 to 1,000 parts by weight, and particularly preferably from 150 to 300 parts by weight, per 100 parts by weight of the water vapor barrier resin. In the present invention, when an inorganic pigment having an average particle size of 5 μm or more and an aspect ratio of 10 or more is used in combination with a pigment having an average particle size of 5 μm or less, the blending ratio of the inorganic pigment having an average particle size of 5 μm or more and an aspect ratio of 10 or more to the pigment having an average particle size of 5 μm or less is preferably 50 / 50 to 99 / 1 by dry weight. If the blending ratio of the inorganic pigment having an average particle size of 5 μm or more and an aspect ratio of 10 or more is less than the above range, the number of detours that water vapor takes in the water vapor barrier layer decreases, shortening the distance it travels, which may reduce the effect of improving the water vapor barrier property. On the other hand, if the blending ratio is more than the above range, the pigment having an average particle size of 5 μm or less cannot sufficiently fill the voids formed by the inorganic pigment with a large average particle size in the water vapor barrier layer, and no further improvement in the water vapor barrier property is observed.

[0023]

[0043] Furthermore, in addition to the water vapor barrier resin, water-soluble polymer, and pigment described above, the water vapor barrier layer may contain various commonly used auxiliary agents such as plasticizers, crosslinking agents, water repellents, dispersants, thickeners, water retention agents, antifoaming agents, water-resistant agents, dyes, and fluorescent dyes.

[0024] In the present invention, a plasticizer can be added to the water vapor barrier layer. The addition of a plasticizer improves the flexibility of the water vapor barrier layer, making it less likely to crack when bent, resulting in improved flex resistance. Glycol-based plasticizers such as glycerin and ethylene glycol are preferably used as the plasticizer. The amount of plasticizer blended is not particularly limited, but the amount of plasticizer blended is preferably 0.1 to 50 parts by weight, more preferably 1 part by weight or more, and even more preferably 20 parts by weight or less, per 100 parts by weight of the water vapor barrier resin on a dry weight basis. If the amount of plasticizer blended is less than 0.1 part by weight, there is a possibility that the effects of improving flexibility and bendability of the water vapor barrier property will not be fully achieved. On the other hand, if it exceeds 50 parts by weight, there is a possibility that sufficient water vapor barrier property will not be achieved.

[0025] In the present invention, a crosslinking agent, such as a polyvalent metal salt, can be added to the water vapor barrier layer. The crosslinking agent undergoes a crosslinking reaction with the water vapor barrier resin and water-soluble polymer contained in the water vapor barrier layer, thereby increasing the number of bonds (crosslinking points) in the water vapor barrier layer. In other words, the water vapor barrier layer has a dense structure, allowing it to exhibit good water vapor barrier properties.

[0033] In the present invention, the type of crosslinking agent is not particularly limited, and can be appropriately selected and used according to the type of water vapor barrier resin and water-soluble polymer contained in the water vapor barrier layer, including polyvalent metal salts (compounds in which a polyvalent metal such as copper, zinc, silver, iron, potassium, sodium, zirconium, aluminum, calcium, barium, magnesium, or titanium is bonded to an ionic substance such as carbonate ion, sulfate ion, nitrate ion, phosphate ion, silicate ion, nitrogen oxide, or boron oxide), amine compounds, amide compounds, aldehyde compounds, and hydroxy acids. Of these, from the perspective of achieving a crosslinking effect in the styrene-based resin contained in the water vapor barrier resin, it is preferable to use a polyvalent metal salt, and it is more preferable to use potassium alum. The amount of crosslinking agent blended is not particularly limited as long as it is within the range of coatable coating concentration and coating viscosity, but preferably the amount of crosslinking agent is 1 part by weight to 10 parts by weight, and more preferably 3 parts by weight to 5 parts by weight, per 100 parts by weight of the water vapor barrier resin. If the amount is less than 1 part by weight, the effect of adding the crosslinking agent may not be fully obtained. Furthermore, if the amount is more than 10 parts by weight, the viscosity of the coating may increase significantly, making coating difficult.

[0026] In the present invention, when a crosslinking agent is added to the coating material for the water vapor barrier layer, it is preferable to dissolve the crosslinking agent in a polar solvent such as ammonia and then add it to the coating material. When the crosslinking agent is dissolved in a polar solvent, the crosslinking agent and the polar solvent form a bond, so that when the crosslinking agent is added to the coating material, a crosslinking reaction with the water vapor barrier resin or water-soluble polymer does not immediately occur, thereby suppressing an increase in the viscosity of the coating material. In this case, it is presumed that the polar solvent components volatilize upon drying after coating on the paper substrate, causing a crosslinking reaction with the water vapor barrier resin or water-soluble polymer, resulting in the formation of a dense water vapor barrier layer.

[0027] In the present invention, a water repellent can be incorporated into the water vapor barrier layer from the viewpoint of improving the water vapor barrier property. Examples of water repellents include paraffin-based water repellents mainly composed of alkane compounds, natural oil-based water repellents derived from plants and animals such as carnauba and lanolin, silicone-containing water repellents containing silicone or silicone compounds, and fluorine-containing water repellents containing fluorine compounds. Of these, paraffin-based water repellents are preferred from the viewpoint of achieving water vapor barrier performance. These water repellents can be used alone or in combination of two or more.

[0028] In the present invention, the amount of water repellent blended is not particularly limited, but the amount of water repellent blended is preferably 1 part by weight to 100 parts by weight per 100 parts by weight of the total of the water vapor barrier resin and the water-soluble polymer, in dry weight. If the amount of water repellent blended is less than 1 part by weight, there is a possibility that the effect of improving the water vapor barrier property will not be sufficiently obtained. On the other hand, if the amount exceeds 100 parts by weight, it will be difficult to form a uniform gas barrier layer when providing it on the water vapor barrier layer, and there is a possibility that the gas barrier property will be reduced.

[0029] Furthermore, in the present invention, in order to improve the water vapor barrier property and the adhesion to the adjacent layer, the wetting tension of the water vapor barrier layer surface is preferably 10 mN / m or more and 60 mN / m or less, and more preferably 15 mN / m or more and 50 mN / m or less. When a gas barrier layer is provided on top of a water vapor barrier layer, from the viewpoint of adhesion to the water vapor barrier layer, the surface tension of the paint for the gas barrier layer is preferably adjusted to between 10 mN / m and 60 mN / m, and more preferably between 15 mN / m and 50 mN / m. Furthermore, from the viewpoint of adhesion between the water vapor barrier layer and the gas barrier layer, it is preferable to adjust the surface tension of the paint for the gas barrier layer to between ±20 mN / m and the wetting tension of the surface of the water vapor barrier layer.

[0030] (gas barrier layer) The gas barrier layer contains a gas barrier resin. Examples of gas barrier resins that can be used include water-soluble polymers or water-dispersible polymers, such as polyvinyl alcohol resins such as fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, and ethylene copolymer polyvinyl alcohol; proteins such as casein, soy protein, and synthetic protein; starches such as oxidized starch, cationized starch, urea phosphate esterified starch, and hydroxyethyl etherified starch; cellulose derivatives such as carboxymethyl cellulose, hydroxymethyl cellulose, and hydroxyethyl cellulose; polyvinylpyrrolidone; and sodium alginate. Among these, from the viewpoint of gas barrier properties, polyvinyl alcohol resins and cellulose derivatives are preferred, polyvinyl alcohol resins are more preferred, polyvinyl alcohol resins having a degree of polymerization of 400 to 1700 are even more preferred, and polyvinyl alcohol resins having a degree of polymerization of 800 to 1400 are even more preferred.

[0031] The gas barrier layer contains 90 parts by weight or less of a pigment per 100 parts by weight of the gas barrier resin, on a dry weight basis. The pigment is an optional component in the gas barrier layer, and it is possible for it to be absent (0 part by weight). By ensuring that the pigment content of the gas barrier layer is within this range, the paper barrier packaging material of the present invention can exhibit excellent flex resistance. Furthermore, by including a pigment in the gas barrier layer, adhesion between the gas barrier layer and the layer in contact with it is improved. The lower the pigment content, the better the flex resistance, but the lower the gas barrier properties. Therefore, the pigment content can be adjusted depending on the flex resistance and gas barrier properties required for the paper barrier packaging material; for example, it can be set to between 5 and 80 parts by weight per 100 parts by weight of the gas barrier resin.

[0032] Pigments that can be incorporated into the gas barrier layer include inorganic pigments such as kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light calcium carbonate, mica, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicates, colloidal silica, and satin white, as well as solid, hollow, and core-shell organic pigments, which can be used alone or in combination of two or more. The pigment is preferably a flat pigment with an average particle size of 3 μm or more and an aspect ratio of 10 or more, and more preferably a flat pigment with an average particle size of 5 μm or more and an aspect ratio of 30 or more. When a gas barrier layer contains a pigment, particularly a flat pigment, gases such as oxygen bypass the pigment, resulting in superior gas barrier properties, particularly in high-humidity environments, compared to gas barrier layers that do not contain a pigment.

[0033]

[0044] In the present invention, in addition to the gas barrier resin and pigment described above, the gas barrier layer may contain various commonly used auxiliaries such as crosslinking agents, surfactants, adhesion aids, plasticizers, dispersants, thickeners, water retention agents, antifoaming agents, water-resistant agents, dyes, and fluorescent dyes.

[0034] In the present invention, a crosslinking agent, such as a polyvalent metal salt, can be added to the gas barrier layer. The crosslinking agent undergoes a crosslinking reaction with the polymer contained in the gas barrier layer, thereby increasing the number of bonds (crosslinking points) in the gas barrier layer. In other words, the gas barrier layer has a dense structure, allowing it to exhibit good gas barrier properties. In the present invention, the type of crosslinking agent is not particularly limited, and can be appropriately selected and used depending on the type of water-soluble polymer contained in the gas barrier layer, such as polyvalent metal salts (compounds in which a polyvalent metal such as copper, zinc, silver, iron, potassium, sodium, zirconium, aluminum, calcium, barium, magnesium, or titanium is bonded to an ionic substance such as carbonate ion, sulfate ion, nitrate ion, phosphate ion, silicate ion, nitrogen oxide, or boron oxide), amine compounds, amide compounds, aldehyde compounds, or hydroxy acids. From the viewpoint of exerting a crosslinking effect, it is preferable to use polyvalent metal salts, and it is more preferable to use potassium alum. The amount of crosslinking agent to be added is not particularly limited as long as it is within the range of coatable coating concentration and viscosity, but preferably the amount of crosslinking agent is 1 part by weight to 10 parts by weight, more preferably 3 parts by weight to 5 parts by weight, per 100 parts by weight of the gas barrier resin. If the amount is less than 1 part by weight, the effect of adding the crosslinking agent may not be fully obtained. On the other hand, if the amount is more than 10 parts by weight, the viscosity of the coating may increase significantly, making coating difficult.

[0035] When a gas barrier layer is provided on a coating layer, it is preferable to include a surfactant in the gas barrier layer from the viewpoint of adhesion to the coating layer. The ionicity of the surfactant is not limited, and any of anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants may be used alone or in combination of two or more. Specific surfactants include silicone-based surfactants, fluorine-based surfactants, alcohol-based surfactants, acetylene-based surfactants having an acetylene group, acetylene diol-based surfactants having an acetylene group and two hydroxyl groups, alkylsulfonic acid-based surfactants having an alkyl group and sulfonic acid, ester-based surfactants, amide-based surfactants, amine-based surfactants, alkyl ether-based surfactants, phenyl ether-based surfactants, sulfate ester-based surfactants, and phenol-based surfactants. Among these, acetylene diol-based surfactants are preferred because they have a significant effect of improving the leveling properties of the coating. Improved leveling properties of the coating improve the uniformity of the gas barrier layer, thereby improving the gas barrier properties.

[0036] In the present invention, an adhesion promoter can be added to the gas barrier layer. The addition of an adhesion promoter improves adhesion to adjacent layers and can suppress the occurrence of interlayer delamination during bending or processing, thereby improving flex resistance. Examples of adhesion promoters that can be used include polyethyleneimine, organic titanium compounds, and polybutadiene compounds, with polyethyleneimine being particularly preferred. The amount of the adhesive aid to be blended is not particularly limited, but the amount of the adhesive aid to be blended is preferably 0.1 parts by weight or more and 50 parts by weight or less, and more preferably 1 part by weight or more and 20 parts by weight or less, per 100 parts by weight of the gas barrier resin on a dry weight basis.

[0037] In the present invention, a plasticizer can be added to the gas barrier layer. The addition of a plasticizer improves the flexibility of the gas barrier layer, making it less likely to crack when bent, resulting in improved flex resistance. Glycol-based plasticizers such as glycerin, ethylene glycol, diglycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and trimethylolpropane are preferably used as plasticizers. These can be used alone or in combination of two or more. Of these, glycerin, ethylene glycol, and diglycerin are preferred. The amount of plasticizer to be blended is not particularly limited, but the amount of plasticizer blended is preferably 0.1 to 50 parts by weight, and more preferably 1 to 20 parts by weight, per 100 parts by weight of the gas barrier resin on a dry basis. If the amount of plasticizer blended is less than 0.1 part by weight, the effects of improving the flexibility and flexibility of the gas barrier properties may not be sufficiently obtained. On the other hand, if the amount exceeds 50 parts by weight, sufficient gas barrier properties may not be obtained.

[0038] (Water vapor barrier layer, gas barrier layer coating) In the present invention, the coating method for the water vapor barrier layer and the gas barrier layer is not particularly limited, and coating can be performed using known coating devices and coating systems. Examples of coating devices include blade coaters, bar coaters, roll coaters, air knife coaters, reverse roll coaters, curtain coaters, spray coaters, size press coaters, and gate roll coaters. Furthermore, examples of coating systems include aqueous coating using a solvent such as water, and solvent-based coating using a solvent such as an organic solvent. The water vapor barrier layer and the gas barrier layer can be dried using a conventional method such as a steam heater, gas heater, infrared heater, electric heater, hot air heater, microwave, or cylinder dryer.

[0039] In the present invention, the coating amount of the water vapor barrier layer is 3 g / m2 in dry weight. 2 More than 50g / m 2It is preferable that the density is 5 g / m or less. 2 More than 40g / m 2 It is more preferable that the density is 7 g / m or less. 2 More than 30g / m 2 It is more preferable that the coating weight of the water vapor barrier layer is 3 g / m or less. 2 If the coating weight is less than 50 g / m, it may be difficult to completely cover the paper substrate with the coating liquid, resulting in insufficient water vapor barrier properties, or the gas barrier layer may penetrate into the paper substrate, resulting in insufficient gas barrier properties. 2 If the amount is larger, the drying load during coating increases. In the present invention, the water vapor barrier layer may be a single layer, or may be configured as two or more layers. When the water vapor barrier layer is configured as two or more layers, it is preferable that the total coating weight of all the water vapor barrier layers is within the above range.

[0040] In the present invention, the coating amount of the gas barrier layer is 0.2 g / m2 in terms of dry weight. 2 More than 20g / m 2 The coating weight of the gas barrier layer is preferably 0.2 g / m or less. 2 If the density is less than 20 g / m, it is difficult to form a uniform gas barrier layer, and sufficient gas barrier properties may not be obtained. 2 If the amount is larger, the drying load during coating increases. In the present invention, the gas barrier layer may be a single layer or may be configured as two or more layers. When the gas barrier layer is configured as two or more layers, it is preferable that the total coating weight of all the gas barrier layers is within the above range.

[0041] (protective layer) The paper barrier packaging material of the present invention can have a protective layer on at least one surface. The protective layer prevents deterioration of the water vapor barrier layer and gas barrier layer due to moisture in the air, etc., and can also impart additional water vapor barrier properties and gas barrier properties to the paper barrier packaging material, or can impart oil resistance, solvent resistance, heat resistance, abrasion resistance, impact resistance, light resistance, etc. Furthermore, if the protective layer is a resin layer, it can also impart heat sealability. The protective layer can be provided on both sides of the paper barrier packaging material, but it is preferable to have a protective layer on at least the surface having the gas barrier layer. Examples of the protective layer include a resin layer, a paper layer, and a metal foil, and among these, a resin layer is preferred.

[0042] (resin layer) Resins for the resin layer may include fossil resource-derived resins such as polyester, polyvinyl alcohol, polypropylene, polyethylene, polystyrene, polyethylene terephthalate, polybutylene terephthalate, polymethylpentene, polyvinyl chloride, acrylonitrile-butadiene-styrene, acrylonitrile-styrene, polymethyl methacrylic, polyvinylidene chloride, polyamide (nylon), polyacetal, and polycarbonate, as well as biologically derived resins such as polylactic acid (PLA), esterified starch, cellulose acetate, polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), biopolyethylene, biopolyethylene terephthalate, and biopolyurethane. Bio-based resins are polymeric materials with a number average molecular weight (Mn) of 1,000 or more that contain substances derived from renewable organic resources as raw materials and are obtained by chemical or biological synthesis. In addition, resins derived from fossil resources and bio-derived resins that can be used include biodegradable resins such as polylactic acid (PLA), esterified starch, cellulose acetate, polybutylene succinate (PBS), and polybutylene succinate adipate (PBSA), as well as non-biodegradable resins such as polyethylene, polypropylene, polyester, polyethylene terephthalate, polyamide (nylon), and biopolyethylene.Biodegradable resins are resins that can be broken down to the molecular level by the action of microorganisms, ultimately becoming carbon dioxide and water that are circulated back into nature.

[0043] In the present invention, the resin layer is preferably a resin laminate layer, and examples of the resin laminate layer include an extrusion laminate layer and a film attachment layer such as a barrier film or a vapor-deposited film. When the resin laminate layer is an extrusion laminate layer, the various resins mentioned above are laminated as a resin laminate layer by extrusion lamination on at least one side of the paper barrier base paper. When the resin laminate layer is a film attachment layer, a film made from the various resins mentioned above is attached as a resin laminate layer on at least one side of the paper barrier base paper by dry lamination, sand lamination or the like. The resin layer can be provided on both sides of the paper barrier base paper, but it is preferable that it is provided at least on the side that has the gas barrier layer. Furthermore, it is preferable that a resin layer be provided on the gas barrier layer of the paper barrier base paper.

[0044] In the present invention, examples of films used for the film attachment layer include films made of the various resins described above. Among these films, preferred are barrier films such as films whose main component is a resin such as polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyvinylidene chloride, or polyacrylonitrile; films made of the various resins described above coated with a resin such as polyvinyl alcohol; films made of the various resins described above attached with a metal foil made of various metals such as aluminum; and vapor-deposited films made of the various resins described above vapor-deposited with various metals such as aluminum or inorganic oxides such as silicon oxide or aluminum oxide, with vapor-deposited films being more preferred. Depending on the purpose, these films can be used by attaching one or more layers.

[0045] The paper barrier packaging material of the present invention can be used as is, or laminated with various resins, etc., or attached with various general-purpose films, barrier films, aluminum foil, etc., to form paper barrier packaging materials used for packaging applications such as food packaging, containers, cups, etc., or laminates used for industrial materials, etc. Among these, the paper barrier packaging material of the present invention can be suitably used as a paper barrier packaging material used for packaging applications such as food packaging, containers, cups, etc., and can be particularly suitably used as a flexible packaging bag for food, etc. Note that a flexible packaging bag is a packaging material made of a highly flexible material, and generally refers to a packaging material made of thin, flexible materials such as paper, film, aluminum foil, etc., either alone or bonded together. The shape of the flexible packaging bag is not particularly limited, and examples include vertical pillow packaging bags, horizontal pillow packaging bags, side seal bags, two-side seal bags, three-side seal bags, gusset bags, bottom gusset bags, and stand-up bags.

[0046] When the paper barrier packaging material of the present invention is used as a packaging material for food and the like, in particular as a flexible packaging bag, laminating it with a resin having heat-sealing properties can improve the airtightness of the packaging material, protect the contents from oxidation by oxygen and deterioration due to moisture, etc., and enable an extension of the storage period. Furthermore, because flexible packaging materials are thin and flexible, they are prone to bending during production, transportation, storage, sales, etc., but the paper barrier packaging material of the present invention has excellent bending resistance and reduces the decline in barrier properties even when bending occurs, so it is possible to prevent the quality of the contents from being damaged by unexpected bending. Furthermore, when used as a laminate for industrial materials, etc., it is possible to prevent decay and deterioration by suppressing the intrusion of oxygen and moisture, and it is also expected to have effects such as flavor barrier properties that prevent the leakage of solvent odors. [Example]

[0047] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, parts and % in the examples represent parts by weight and % by weight, respectively. The obtained metallized paper substrate and metallized paper were subjected to tests based on the evaluation methods shown below.

[0048] (Evaluation method) Oxygen permeability Measurements were taken using a MOCON OX-TRAN2 / 21 under conditions of 23°C and 0% RH (dry conditions). Measurements were taken on the sheet sample as is (no creases) and on a sheet sample that had been folded with the barrier layer side facing outward, with a rubber roller weighing approximately 400g rolling it back and forth five times to create a cross crease (creased).The folded sample was measured so that the cross was positioned in the center of the jig.The measured values ​​are shown in Table 1.

[0049] Adhesion evaluation Adhesive tape (Nichiban Cellotape (registered trademark), 12 mm wide) was applied to the surface of the sheet sample (the side on which the water vapor barrier layer and gas barrier layer were present), and a rubber roller weighing approximately 2,300 g was rolled over the tape five times. The Cellotape (registered trademark) was then forcefully peeled off in a direction perpendicular to the surface of the sheet sample, and the peeling behavior of each barrier layer was observed and evaluated as follows. The results are shown in Table 1. ○: The coating film on the adhesive tape peels off along with part (or all) of the paper substrate (suitable for practical use) ×: Only the coating film peeled off from the area where the adhesive tape was attached (not suitable for practical use)

[0050] [Example 1] (Preparation of paper substrate) The raw material pulp was prepared by blending hardwood bleached kraft pulp (LBKP) with a Canadian standard freeness (CSF) of 500 ml and softwood bleached kraft pulp (NBKP) with a CSF of 530 ml in a weight ratio of 80 / 20. The raw pulp was mixed with 0.1% of polyacrylamide (PAM) with a molecular weight of 2.5 million as a dry strength agent, 0.35% of alkyl ketene dimer (AKD) as a sizing agent, 0.15% of polyamide epichlorohydrin (PAEH) resin as a wet strength agent, and 0.08% of polyacrylamide (PAM) with a molecular weight of 10 million as a retention agent, based on the weight of the absolute dry pulp. The mixture was then made into paper at a speed of 300 m / min on a Duoformer FM paper machine, with a basis weight of 59 g / m. 2 I got the paper. Next, polyvinyl alcohol (PVA117, manufactured by Kuraray Co., Ltd.) adjusted to a solids concentration of 2% was applied to the obtained paper using a rod metering size press to a total of 1.0 g / m on both sides. 2 Coated and dried, basis weight 60g / m 2 The obtained base paper was smoothed using a chilled calender at a speed of 300 m / min, a linear pressure of 50 kgf / cm, and one pass to obtain a paper substrate.

[0051] (Preparation of Coating Solution 1 for Water Vapor Barrier Layer) Sodium polyacrylate was added as a dispersant to engineered kaolin (Imerys, Barrisurf HX, average particle size 90 μm, aspect ratio 80-100) (0.2% relative to the pigment), and the mixture was dispersed in a Serie mixer to prepare a kaolin slurry with a solids concentration of 55%. To the resulting kaolin slurry, 25 parts (solids) of a styrene-acrylic copolymer emulsion (Tg 23°C) and 20 parts (solids) of an ethylene-acrylic copolymer emulsion (Tg 25°C) were blended as water vapor barrier resins per 100 parts (solids) of pigment, yielding Coating Solution 1 for the water vapor barrier layer with a solids concentration of 48.5%.

[0052] (Preparation of Coating Solution 1 for Gas Barrier Layer) An aqueous solution of polyvinyl alcohol (VC-10, manufactured by Nippon Vinyl Acetate & Poval Co., Ltd.) with a solids concentration of 12% was prepared and used as coating solution 1 for gas barrier layer.

[0053] (Production of paper barrier packaging materials) Onto the obtained paper substrate, Coating Solution 1 for water vapor barrier layer was applied in a coating amount of 12.0 g / m2 (dry weight). 2 After drying, the coating solution 1 for the gas barrier layer was applied on top of it in an amount of 3.0 g / m2 in dry weight. 2 The paper barrier packaging material 1 was obtained by coating on one side so that the coating amount was as follows:

[0054] "Example 2" (Preparation of Coating Solution 2 for Gas Barrier Layer) Sodium polyacrylate was added as a dispersant to engineered kaolin (Imerys, Barisurf HX, average particle size 90 μm, aspect ratio 80-100) (0.2% relative to the pigment), and the mixture was dispersed in a Serie mixer to prepare a kaolin slurry with a solids concentration of 55%. Coating Solution 1 for gas barrier layer and kaolin slurry were mixed so that the solid content ratio of PVA:pigment was 100:10, to obtain Coating Solution 2 for gas barrier layer with a solid content concentration of 12.9%. (Production of paper barrier packaging materials) This gas barrier layer coating solution 2 was applied in a dry weight of 3.5 g / m 2A paper barrier packaging material 2 was obtained in the same manner as in Example 1, except that one side was coated so that the thickness was 1 / 4 of the paper barrier packaging material 2.

[0055] "Example 3" (Preparation of Coating Solution 3 for Gas Barrier Layer) Coating Solution 3 for gas barrier layer with a solids concentration of 14.6% was prepared in the same manner as Coating Solution 2 for gas barrier layer, except that the solids ratio was PVA:pigment=100:30. (Production of paper barrier packaging materials) This gas barrier layer coating solution 3 was applied in a dry weight of 3.5 g / m 2 Paper barrier packaging material 3 was obtained in the same manner as in Example 1, except that one side was coated so that the thickness was 1 / 4 of the paper barrier packaging material 3. Example 4 (Preparation of Coating Solution 4 for Gas Barrier Layer) Coating Solution 4 for gas barrier layer with a solids concentration of 17.0% was prepared in the same manner as Coating Solution 2 for gas barrier layer, except that the solids ratio was PVA:pigment=100:60. (Production of paper barrier packaging materials) This gas barrier layer coating solution 4 was applied in a dry weight of 3.5 g / m 2 Paper barrier packaging material 4 was obtained in the same manner as in Example 1, except that one side was coated so that the thickness was 1 / 4 of the paper barrier packaging material 4.

[0056] "Example 5" (Preparation of Coating Solution 5 for Gas Barrier Layer) An aqueous solution of ethylene copolymerized polyvinyl alcohol (RS-4104, manufactured by Kuraray Co., Ltd.) with a solids concentration of 13% was prepared and used as Coating Solution 5 for gas barrier layer. (Production of paper barrier packaging materials) This gas barrier layer coating solution 5 was applied in a dry weight of 3.0 g / m 2 A paper barrier packaging material 5 was obtained in the same manner as in Example 1, except that one side was coated so that the thickness was 1 / 4 of the paper barrier packaging material 5.

[0057] "Example 6" (Preparation of Coating Solution 6 for Gas Barrier Layer) A polyethyleneimine-based adhesive aid was blended into Coating Solution 1 for gas barrier layer so that the amount was 10 parts (solid content) per 100 parts of polyvinyl alcohol to prepare Coating Solution 6 for gas barrier layer with a solid content concentration of 12%. (Production of paper barrier packaging materials) This gas barrier layer coating solution 6 was applied in a dry weight of 3.3 g / m 2 A paper barrier packaging material 6 was obtained in the same manner as in Example 1, except that one side was coated so that the thickness was 1 / 4 of the paper barrier packaging material 6.

[0058] "Example 7" (Preparation of Coating Solution 7 for Gas Barrier Layer) Sodium polyacrylate was added as a dispersant to engineered kaolin (Imerys, Barisurf HX, average particle size 90 μm, aspect ratio 80-100) (0.2% relative to the pigment), and the mixture was dispersed in a Serie mixer to prepare a kaolin slurry with a solids concentration of 55%. Coating Solution 6 for gas barrier layer and kaolin slurry were mixed so that the solid content was 12.9% (PVA:pigment=100:30 in solid content), to obtain Coating Solution 7 for gas barrier layer. (Production of paper barrier packaging materials) This gas barrier layer coating solution 7 was applied in a dry weight of 3.5 g / m 2 Paper barrier packaging material 7 was obtained in the same manner as in Example 1, except that one side was coated so that the thickness was 1 / 4 of the original thickness.

[0059] "Example 8" (Preparation of Coating Solution 8 for Gas Barrier Layer) A plasticizer (glycerin) was blended into Coating Solution 1 for gas barrier layer so that the ratio was 10 parts (solid content) per 100 parts of polyvinyl alcohol to prepare a PVA solution. Sodium polyacrylate was added as a dispersant to engineered kaolin (Imerys, Barisurf HX, average particle size 90 μm, aspect ratio 80-100) (0.2% relative to the pigment), and the mixture was dispersed in a Serie mixer to prepare a kaolin slurry with a solids concentration of 55%. The PVA solution and kaolin slurry were mixed so that the solid content was PVA:pigment=100:60, to obtain Coating Solution 8 for gas barrier layer with a solid content concentration of 17.1%. (Production of paper barrier packaging materials) This gas barrier layer coating solution 8 was applied in a dry weight of 3.5 g / m 2 A paper barrier packaging material 8 was obtained in the same manner as in Example 1, except that one side was coated so that the thickness was 1 / 4 of the paper barrier packaging material 8.

[0060] "Comparative Example 1" (Preparation of Coating Solution 9 for Gas Barrier Layer) Sodium polyacrylate was added as a dispersant to engineered kaolin (Imerys, Barisurf HX, average particle size 90 μm, aspect ratio 80-100) (0.2% relative to the pigment), and the mixture was dispersed in a Serie mixer to prepare a kaolin slurry with a solids concentration of 55%. Coating Solution 1 for gas barrier layer and kaolin slurry were mixed so that the solid content ratio of PVA:pigment was 100:125, to obtain Coating Solution 9 for gas barrier layer with a solid content concentration of 21.2%. (Production of paper barrier packaging materials) This gas barrier layer coating solution 9 was applied in a dry weight of 4.0 g / m 2 Paper barrier packaging material 9 was obtained in the same manner as in Example 1, except that one side was coated so that the thickness was 1 / 4 of the paper barrier packaging material 9.

[0061] "Comparative Example 2" (Preparation of Coating Solution 10 for Water Vapor Barrier Layer) Sodium polyacrylate was added as a dispersant (0.2% relative to the pigment) to engineered kaolin (Imerys Corporation, Barrisurf HX, average particle size 90μm, aspect ratio 80-100), and the mixture was dispersed in a Serie mixer to prepare a kaolin slurry with a solids concentration of 55%. To the resulting kaolin slurry, 30 parts (solids) of an acrylic copolymer emulsion (Tg -9°C) and 10 parts (solids) of a wax emulsion (Seiko PMC Corporation, WR3932) were blended as water vapor barrier resins per 100 parts (solids) of pigment, yielding Coating Solution 10 for the water vapor barrier layer with a solids concentration of 48.0%. (Production of paper barrier packaging materials) This water vapor barrier layer coating solution 10 was applied to a substrate at a dry weight of 13.0 g / m 2 After drying, the coating solution 1 for the gas barrier layer was applied on top of it in an amount of 4.0 g / m2 in dry weight. 2The paper barrier packaging material 10 was obtained by coating on one side so that the paper barrier packaging material 10 was obtained.

[0062] "Example 9" A paper barrier packaging material 11 was obtained in the same manner as in Example 1, except that a styrene-acrylic copolymer emulsion with a Tg of 9°C was used instead of the styrene-acrylic copolymer emulsion with a Tg of 23°C.

[0063] [Table 1]

[0064] The paper barrier packaging materials obtained in Examples 1 to 9 of the present invention were able to maintain high gas barrier properties even after being folded. As the blending amount of pigment increased, there was a tendency for flex resistance to decrease and adhesion to improve, but it was confirmed that flex resistance could be maintained by blending an adhesion aid and a plasticizer.

Claims

1. A paper substrate having a water vapor barrier layer and a gas barrier layer, the water vapor barrier layer contains a water vapor barrier resin and a pigment, the water vapor barrier resin contains a styrene-based resin having a glass transition temperature of −20 to 95° C. and an ethylene-based resin having a glass transition temperature of −20 to 95° C. in a weight ratio (dry weight) of 99 / 1 to 1 / 99; 1. A paper barrier packaging material characterized in that the gas barrier layer contains a gas barrier resin, and the pigment content per 100 parts by weight of the gas barrier resin is 0 parts by weight or more and 90 parts by weight or less.

2. The paper barrier packaging material according to claim 1, characterized in that it has the water vapor barrier layer and the gas barrier layer in this order on the paper base material.

3. The paper barrier packaging material according to claim 1 or 2, characterized in that the pigment content in the gas barrier layer is 5 to 80 parts by weight per 100 parts by weight of the gas barrier resin, on a dry weight basis.

4. The paper barrier packaging material according to any one of claims 1 to 3, characterized in that the water vapor barrier layer contains a pigment with an average particle size of 5 μm or more and an aspect ratio of 10 or more.

5. The paper barrier packaging material according to any one of claims 1 to 4, characterized in that the gas barrier resin contains a polyvinyl alcohol-based resin.

6. The paper barrier packaging material according to any one of claims 1 to 5, characterized in that the gas barrier layer contains a plasticizer.

7. The paper barrier packaging material according to any one of claims 1 to 6, characterized in that the gas barrier layer contains an adhesive aid.

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