Liquid paper container base paper and liquid paper container

Abstract

To provide: a liquid paper container base paper that exhibits high barrier properties, excellent recyclability, reduced liquid paper container weight, excellent moldability, and excellent crack resistance; and a liquid paper container employing the same.SOLUTION: A liquid paper container base paper 10 comprises: a barrier paper 16 having a barrier coating layer 14 on one surface of a barrier paper substrate 12; a base paper substrate 18 provided on a surface of the barrier paper 16 opposite to the barrier coating layer 14; a first protective layer 20 formed on the outermost surface on the base paper substrate 18 side; and a second protective layer 22 formed on the outermost surface on the barrier coating layer 14 side of the barrier paper 16. Also disclosed is a liquid paper container 7 formed using the liquid paper container base paper 10.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a base paper for a liquid-storing paper container, and a liquid-storing paper container using the base paper for a liquid-storing paper container. [Background technology]

[0002] 2. Description of the Related Art Paper containers used for juice, alcoholic beverages, and the like include paper containers in which a polyethylene layer, an aluminum layer, and the like are laminated to a paper base material (see Patent Document 1). When paper pack containers with laminated aluminum layers become waste, it is difficult to separate and recover the constituent paper, polyethylene, and aluminum, so most are incinerated or disposed of in landfills.

[0003] From the viewpoint of recycling resources, it is required to separate and collect aluminum-laminated paper pack containers. A method for collecting paper is disclosed in, for example, Patent Document 2. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-2196 A [Patent Document 2] Japanese Patent Application Publication No. 06-220784 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method described in Patent Document 2 is capable of separating and recovering the paper, but is unable to separate and recover the aluminum layer and the polyethylene layer. In recent years, there has been a demand for further weight reduction and improved formability of paper containers, as well as an increased demand for improved crack resistance to prevent cracks from occurring in the base paper of the paper container when it is folded to form the paper container.

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide a base paper for liquid paper containers that has high barrier properties and excellent recyclability even without an aluminum layer, and further allows the liquid paper container to be made lighter, and has excellent formability and cracking resistance, and a liquid paper container using this base paper for liquid paper containers. [Means for solving the problem]

[0007] The present invention has been made to solve the above problems, and it has been found that the problems of the present invention can be solved by laminating a barrier paper consisting of a barrier coating layer and a barrier paper substrate with a base paper substrate, and thus the present invention has been completed. The gist of the present invention is as follows. [1] A base paper for liquid paper containers comprising: barrier paper having a barrier coating layer on one side of a barrier paper base material; a base paper base material provided on the side of the barrier paper opposite the barrier coating layer; a first protective layer provided on the outermost surface of the base paper base material side; and a second protective layer provided on the outermost surface of the barrier paper facing the barrier coating layer. [2] The basis weight of the paper constituting the barrier paper base is 25 to 100 g / m 2 The paper constituting the base paper substrate has a basis weight of 100 to 350 g / m 2 The base paper for liquid paper containers according to [1]. [3] The base paper for liquid paper containers according to [1] or [2], wherein the barrier paper substrate is made of acidic paper. [4] The base paper for liquid paper containers according to any one of [1] to [3], wherein the barrier paper and the base paper substrate are laminated via an adhesive layer. [5] The base paper for liquid paper containers according to [1] to [4], wherein the barrier coating layer has at least a water vapor barrier layer and a gas barrier layer, the water vapor barrier layer and the gas barrier layer being disposed in this order on the barrier paper base material. [6] The base paper for liquid paper containers described in [5], wherein at least one of the water vapor barrier layer and the gas barrier layer contains a flat pigment. [7] A liquid paper container formed using the base paper for a liquid paper container according to any one of [1] to [6], wherein the barrier coating layer side of the barrier paper is arranged on the inside. [8] A liquid paper container according to [7], which is formed into a cylindrical shape using a sealing tape. Effect of the Invention

[0008] According to the present invention, it is possible to provide a base paper for a liquid paper container that has high barrier properties, excellent recyclability, and further allows the liquid paper container to be made lighter, and has excellent formability and crack resistance, and a liquid paper container using the base paper for a liquid paper container can be provided. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a diagram showing the layer structure of the base paper for a liquid paper container of the present invention. [Diagram 2] FIG. 13 is an explanatory diagram showing a packaging tube that has been sealed vertically with a sealing tape and then sealed horizontally. [Diagram 3] 3 is a cross-sectional view taken along line XX in FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The base paper for a paper container for liquid and the paper container for liquid according to the present invention will be described below with reference to the attached drawings. Fig. 1 is a conceptual diagram showing the layer structure of the base paper for a paper container for liquid according to the present invention.

[0011] [Base paper for liquid paper containers] The base paper 10 for liquid paper containers of the present invention comprises barrier paper 16 having a barrier coating layer 14 on one side of a barrier paper substrate 12, a base paper substrate 18 provided on the side of the barrier paper 16 opposite the barrier coating layer 14, a first protective layer 20 provided on the outermost surface on the base paper substrate 18 side, and a second protective layer 22 provided on the outermost surface of the barrier paper 16 on the barrier coating layer 14 side. In the base paper 10 for a liquid-storing paper container of the present invention, the second protective layer 22 side becomes the inner surface side of the liquid-storing paper container, and the first protective layer 20 side becomes the surface side.

[0012] <Barrier paper> The barrier paper 16 constituting the base paper 10 for liquid paper containers of the present invention has a barrier coating layer 14 on one side of the barrier paper substrate 12 which serves as the substrate layer.

[0013] <Barrier paper base material> In the present invention, the barrier paper substrate 12 is a sheet made of pulp, filler, various auxiliary agents, and the like. The pulp may be chemical pulp such as bleached hardwood kraft pulp (LBKP), bleached softwood kraft pulp (NBKP), unbleached hardwood kraft pulp (LUKP), unbleached softwood pulp (NUKP), sulfite pulp, etc., mechanical pulp such as stone grind pulp and thermomechanical pulp, wood fibers such as deinked pulp and waste paper pulp, non-wood fibers obtained from kenaf, bamboo, hemp, etc., and may be used in appropriate combinations. Among these, it is preferable to use chemical pulp or mechanical pulp of wood fiber, and it is more preferable to use chemical pulp, for reasons such as the fact that foreign matter is unlikely to be mixed into the barrier paper substrate 12, discoloration is unlikely to occur over time when used paper containers are recycled as waste paper raw materials, and the fact that the high whiteness of the pulp makes the surface feel good when printed, and the fact that the value of the pulp is particularly high when used as a packaging material.

[0014] As the filler, 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. The filler is an optional component, and the composition may not contain any filler. In addition, aluminum sulfate and various anionic, cationic, nonionic, or amphoteric retention improvers, drainage improvers, paper strength enhancers, internal sizing agents, and other papermaking internal additives can be used as necessary. Furthermore, dyes, fluorescent whitening agents, pH adjusters, defoamers, pitch control agents, slime control agents, and the like can be added as necessary.

[0015] The manufacturing (papermaking) method for the barrier paper substrate 12 is not particularly limited, and the barrier paper substrate can be manufactured by acidic papermaking, neutral papermaking, or alkaline papermaking using a known Fourdrinier former, on-top hybrid former, gap former machine, etc. The barrier paper substrate 12 may be composed of one layer, or two or more layers. Furthermore, the surface of the barrier paper substrate 12 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, and these can be used alone or in combination of two or more. Furthermore, these various chemicals may 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, silicate salts, colloidal silica, and satin white, and organic pigments such as solid, hollow, and core-shell types, and these can be used alone or in combination of two or more.

[0016] The method for surface treatment of the barrier paper substrate 12 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 the barrier paper substrate 12 obtained in this manner include various known types of paper, such as fine paper, medium quality paper, coated paper, one-sided glossy paper, kraft paper, one-sided glossy kraft paper, bleached kraft paper, glassine paper, paperboard, white paperboard, and liner. Furthermore, although either acidic or neutral paper can be used as the barrier paper substrate 12, it is preferable to use acidic paper. When the liquid paper container base paper 10 of the present invention is used for an aseptic liquid container, it is passed through a tank of hydrogen peroxide solution when passing through a filling machine for cleaning and sterilization, but by using acidic paper, cleaning and sterilization can be performed without the barrier paper substrate 12 absorbing hydrogen peroxide.

[0017] The basis weight of the barrier paper substrate 12 can be appropriately selected depending on the various qualities and handling properties desired for the liquid paper container, but is usually 25 g / m 2 More than 100g / m 2 The following is preferred: 40 g / m 2 More than 60g / m 2 The following is more preferable. Since the base paper 10 for liquid paper containers of the present invention has the base paper substrate 18 in addition to the barrier paper substrate 12 of the barrier paper 16, the basis weight of the barrier paper substrate 12 can be reduced to the above-mentioned range, which is less than usual.

[0018] <Barrier coating layer> The barrier coating layer 14 is provided on one side of the barrier paper substrate 12 and has at least a water vapor barrier layer and a gas barrier layer, with the water vapor barrier layer and the gas barrier layer being provided on the barrier paper substrate 12 in this order.

[0019] (Water vapor barrier layer) The water vapor barrier layer contains a water vapor barrier resin and a pigment. The water vapor barrier resin preferably contains a styrene-based resin. The styrene-based resin refers to a resin obtained by copolymerizing a styrene monomer with other monomers such as acrylic acid, methacrylic acid, acrylonitrile, butadiene, etc., but may also be a resin obtained by combining and copolymerizing various comonomers for the purpose of modification. Examples of the comonomer include methyl methacrylate, acrylonitrile, acrylamide, hydroxyethyl acrylate, and unsaturated carboxylic acids such as itaconic acid and maleic acid. Examples of the styrene-based resin include styrene-acrylic resin, styrene-butadiene resin, and styrene-butadiene-acrylic resin, and styrene-acrylic resin is preferred. The glass transition temperature (Tg) of the styrene-based resin is preferably -20°C or higher, more preferably -10°C or higher, and even more preferably 0°C or higher, and is preferably 50°C or lower, more preferably 40°C or lower, and even more preferably 30°C or lower. The styrene-based resin may be used alone or in a mixture of two or more types.

[0020] 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, various copolymers such as paraffin (WAX), butadiene-methyl methacrylate, and vinyl acetate-butyl acrylate, synthetic adhesives such as maleic anhydride copolymers and acrylic acid-methyl methacrylate copolymers, or synthetic adhesives containing paraffin (WAX), etc., can be used in combination. Among these, ethylene-based resins are preferred, and ethylene-acrylic resins are 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.

[0021]

[0043] As long as there are no problems with the water vapor barrier properties, 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, synthetic protein, and other starches such as oxidized starch, cationized starch, urea phosphate esterified starch, hydroxyethyl etherified starch, and other cellulose derivatives such as carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, and other cellulose derivatives; polyvinylpyrrolidone, sodium alginate, and other water-soluble polymers.

[0022] The 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, and organic pigments such as solid, hollow, and core-shell types, which can be used alone or in combination of two or more types. Among these pigments, from the viewpoint of improving the water vapor barrier property and improving the adhesion with the adjacent layer, flat inorganic pigments such as kaolin, mica, and talc are preferred, and kaolin or mica is more preferred. In addition, it is preferred to use a single inorganic pigment or a mixture of two or more inorganic pigments with a volume 50% average particle size (D50) (hereinafter also referred to as "average particle size") of 5 μm or more and an aspect ratio of 10 or more. 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 in the water vapor barrier layer decreases, and the distance traveled is shortened, which may result in a smaller improvement in the water vapor barrier property.

[0023] In the present invention, from the viewpoint of improving the water vapor barrier property and improving the adhesion with the adjacent layer, it is preferable that the water vapor barrier layer containing an inorganic pigment having an average particle size of 5 μm or more and an aspect ratio of 10 or more further contains a pigment having an average particle size of 5 μm or less. By using a pigment having 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 having an average particle size of 5 μm or more and an aspect ratio of 10 or more, and thus even better water vapor barrier property is expressed. In other words, when pigments with different average particle sizes are contained in the water vapor barrier layer, the voids formed by the inorganic pigment having a large average particle size in the water vapor barrier layer are filled with the pigment having a small average particle size, and water vapor passes through by bypassing the pigment, so it is presumed that the water vapor barrier layer has higher water vapor barrier property than a water vapor barrier layer that does not contain a pigment with a different average particle size.

[0024] 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, and organic pigments such as solid, hollow, and core-shell types, which can be used alone or in combination of two or more. Of these pigments, it is preferable to use heavy calcium carbonate.

[0025] The blending amount of the pigment in the water vapor barrier layer, in dry weight, is preferably from 50 parts by weight to 1,000 parts by weight, more preferably from 120 parts by weight to 1,000 parts by weight, and particularly preferably from 150 parts by weight to 300 parts by weight, per 100 parts by weight of the water vapor barrier resin.

[0026] 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 times that water vapor takes a detour in the water vapor barrier layer decreases, and the distance traveled is shortened, which may reduce the effect of improving the water vapor barrier property. On the other hand, if it 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 having a large average particle size in the water vapor barrier layer, and therefore no further improvement in the water vapor barrier property is observed.

[0027]

[0043] In addition to the above-mentioned water vapor barrier resins, water-soluble polymers, and pigments, the water vapor barrier layer can contain various commonly used auxiliaries such as plasticizers, crosslinking agents, water repellents, dispersants, thickeners, water retention agents, defoamers, water resistance agents, dyes, and fluorescent dyes.

[0028] 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. As the plasticizer, a glycol-based plasticizer such as glycerin or ethylene glycol is preferably used. The amount of the plasticizer is not particularly limited, but the amount of the plasticizer is preferably 0.1 parts by weight or more and 50 parts by weight or less, more preferably 1 part by weight or more, and more preferably 20 parts by weight or less, relative to 100 parts by weight of the water vapor barrier resin in dry weight. If the amount of the plasticizer is less than 0.1 parts by weight, the effect of improving the flexibility and flexibility of the water vapor barrier property may not be sufficiently obtained. On the other hand, if it exceeds 50 parts by weight, sufficient water vapor barrier property may not be obtained.

[0029] In the present invention, a crosslinking agent, typically 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 or 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.

[0030] In the present invention, the type of crosslinking agent is not particularly limited, and it is possible to appropriately select and use, depending on the type of water vapor barrier resin or water-soluble polymer contained in the water vapor barrier layer, polyvalent metal salts (compounds in which a polyvalent metal such as copper, zinc, silver, iron, potassium, sodium, zirconium, aluminum, calcium, barium, magnesium, titanium, or the like is bonded to an ionic substance such as carbonate ion, sulfate ion, nitrate ion, phosphate ion, silicate ion, nitrogen oxide, boron oxide, or the like), amine compounds, amide compounds, aldehyde compounds, hydroxy acids, etc. Among these, from the viewpoint of the expression of the crosslinking effect in the styrene-based resin contained in the water vapor barrier resin, it is preferable to use polyvalent metal salts, and it is more preferable to use potassium alum.

[0031] The amount of crosslinking agent to be added is not particularly limited as long as it is within the range of the paint concentration and viscosity that can be applied, but the amount of crosslinking agent is preferably 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 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. If the amount is more than 10 parts by weight, the viscosity of the paint may increase significantly, making application difficult.

[0032] 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 even if the crosslinking agent is added to the coating material, a crosslinking reaction with the water vapor barrier resin or the water-soluble polymer does not immediately occur, and thickening of the coating material can be suppressed. In that case, it is presumed that the polar solvent components volatilize by drying after coating on the barrier paper substrate, and a crosslinking reaction with the water vapor barrier resin or the water-soluble polymer occurs, forming a dense water vapor barrier layer.

[0033] In the present invention, from the viewpoint of improving the water vapor barrier property, a water repellent can be contained in the water vapor barrier layer. Examples of water repellents include paraffin-based water repellents mainly composed of alkane compounds, natural oil-based water repellents derived from animals and plants such as carnauba and lanolin, silicone-containing water repellents containing silicone or silicone compounds, and fluorine-containing water repellents containing fluorine compounds. Among these, it is preferable to use a paraffin-based water repellent from the viewpoint of expressing water vapor barrier performance. Moreover, these water repellents can be used alone or in a mixture of two or more kinds.

[0034] In the present invention, the amount of the water repellent is not particularly limited, but the amount of the water repellent is preferably 1 part by weight or more and 100 parts by weight or less per 100 parts by weight of the total of the water vapor barrier resin and the water-soluble polymer, in terms of dry weight. If the amount of the water repellent is less than 1 part by weight, the effect of improving the water vapor barrier property may not be sufficiently obtained. On the other hand, if it exceeds 100 parts by weight, it becomes difficult to form a gas barrier layer uniformly when providing the gas barrier layer on the water vapor barrier layer, and the gas barrier property may be deteriorated.

[0035] In the present invention, in order to improve the water vapor barrier property and the adhesion to a contacting layer, the wetting tension of the surface of the water vapor barrier layer 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 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 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. In addition, 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 ±20 mN / m with respect to the wetting tension of the water vapor barrier layer surface.

[0036] (Gas barrier layer) The gas barrier layer contains a gas barrier resin. As the gas barrier resin, a water-soluble polymer or a water-suspendable polymer can be used, and examples thereof include polyvinyl alcohol-based resins such as fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, and ethylene copolymerized polyvinyl alcohol, proteins such as casein, soybean protein, and synthetic protein, starches such as oxidized starch, cationic starch, urea phosphate esterified starch, and hydroxyethyl etherified starch, cellulose derivatives such as carboxymethyl cellulose, hydroxymethyl cellulose, and hydroxyethyl cellulose, polyvinylpyrrolidone, and sodium alginate, etc. Among these, from the viewpoint of gas barrier properties, polyvinyl alcohol-based resins and cellulose derivatives are preferred, polyvinyl alcohol-based resins are more preferred, polyvinyl alcohol-based resins having a degree of polymerization of 400 to 1700 are even more preferred, and polyvinyl alcohol-based resins having a degree of polymerization of 800 to 1400 are even more preferred.

[0037] The gas barrier layer contains 90 parts by weight or less of pigment per 100 parts by weight of gas barrier resin, in terms of dry weight. Note that the pigment is an optional component in the gas barrier layer, and it is also possible to not contain it (0 parts by weight). By setting the pigment blending amount in the gas barrier layer within this range, the paper barrier packaging material of the present invention can exhibit excellent flex resistance. Furthermore, by the gas barrier layer containing a pigment, the adhesion between the gas barrier layer and the layer in contact with it is improved. The smaller the blending amount of pigment, the more improved the flex resistance is, while the gas barrier property is reduced. Therefore, the blending amount of pigment can be adjusted according to the flex resistance and gas barrier property required for the paper barrier packaging material, and can be, for example, 5 parts by weight or more and 80 parts by weight or less per 100 parts by weight of the gas barrier resin.

[0038] 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, and organic pigments such as solid, hollow, and core-shell types, 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 pass through it by bypassing the pigment, and therefore the gas barrier layer has superior gas barrier properties, particularly in high humidity environments, compared to gas barrier layers that do not contain a pigment.

[0039]

[0113] In the present invention, in addition to the above-mentioned gas barrier resin and pigment, the gas barrier layer may contain various commonly used auxiliary agents such as crosslinking agents, surfactants, adhesion aids, plasticizers, dispersants, thickeners, water retention agents, defoamers, water resistance agents, dyes, and fluorescent dyes.

[0040] In the present invention, a crosslinking agent, such as a polyvalent metal salt, can be added to the gas barrier layer. The crosslinking agent causes a crosslinking reaction with the polymer contained in the gas barrier layer, increasing the number of bonds (crosslinking points) in the gas barrier layer. In other words, the gas barrier layer has a dense structure and can exhibit good gas barrier properties. In the present invention, the type of crosslinking agent is not particularly limited, and it is possible to appropriately select and use polyvalent metal salts (compounds in which polyvalent metals such as copper, zinc, silver, iron, potassium, sodium, zirconium, aluminum, calcium, barium, magnesium, titanium, etc. are bonded to ionic substances such as carbonate ions, sulfate ions, nitrate ions, phosphate ions, silicate ions, nitrogen oxides, boron oxides, etc.), amine compounds, amide compounds, aldehyde compounds, hydroxy acids, etc., depending on the type of water-soluble polymer contained in the gas barrier layer. From the viewpoint of the expression of the crosslinking effect, it is preferable to use polyvalent metal salts, and it is more preferable to use potassium alum.

[0041] The amount of crosslinking agent is not particularly limited as long as it is within the range of paint concentration and paint viscosity that can be applied, but preferably the amount of crosslinking agent is 1 part by weight or more and 10 parts by weight or less, more preferably 3 parts by weight or more and 5 parts by weight or less, 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 sufficient. If the amount is more than 10 parts by weight, the viscosity of the paint may increase significantly, making coating difficult.

[0042] When a gas barrier layer is provided on the water vapor barrier layer, it is preferable to contain a surfactant in the gas barrier layer from the viewpoint of adhesion to the water vapor barrier layer. There is no limitation on the ionicity of the surfactant, and any type of anionic surfactant, cationic surfactant, amphoteric surfactant, or nonionic surfactant may be used alone or in combination of two or more types. Specific types include silicone surfactants, fluorine surfactants, alcohol surfactants, acetylene surfactants having an acetylene group, acetylene diol surfactants having an acetylene group and two hydroxyl groups, alkylsulfonic acid surfactants having an alkyl group and sulfonic acid, ester surfactants, amide surfactants, amine surfactants, alkyl ether surfactants, phenyl ether surfactants, sulfate ester surfactants, and phenol surfactants. Among these, it is preferable to use an acetylene diol surfactant, which has a large effect of improving the leveling property of the paint. Note that when the leveling property of the paint is improved, the uniformity of the gas barrier layer is improved, and therefore the gas barrier property is improved.

[0043] In the present invention, an adhesive aid can be added to the gas barrier layer. The addition of the adhesive aid improves adhesion to the adjacent layer, and can suppress the occurrence of interlayer peeling during bending or processing, thereby improving flex resistance. As the adhesive aid, polyethyleneimine, an organic titanium compound, a polybutadiene compound, etc. can be used, and polyethyleneimine is particularly preferably used. 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 part 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.

[0044] 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. As the plasticizer, glycol-based plasticizers such as glycerin, ethylene glycol, diglycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and trimethylolpropane are preferably used. These can be used alone or in combination of two or more. Among these, glycerin, ethylene glycol, and diglycerin are preferred.

[0045] The amount of the plasticizer is not particularly limited, but the amount of the plasticizer is preferably 0.1 to 50 parts by weight, more preferably 1 to 20 parts by weight, per 100 parts by weight of the gas barrier resin in dry weight. If the amount of the plasticizer is less than 0.1 parts by weight, the effect 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.

[0046] (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 a known coating device and coating system. Examples of coating devices include a blade coater, a bar coater, a roll coater, an air knife coater, a reverse roll coater, a curtain coater, a spray coater, a size press coater, and a gate roll coater. Examples of coating systems include water-based coating using a solvent such as water, and solvent-based coating using a solvent such as an organic solvent. As a method for drying the water vapor barrier layer and the gas barrier layer, for example, a usual method such as using a steam heater, a gas heater, an infrared heater, an electric heater, a hot air heater, a microwave, or a cylinder dryer is used.

[0047] In the present invention, the coating amount of the water vapor barrier layer is 3 g / m2 in terms of dry weight.2 More than 50g / m 2 It is preferable that the density is 5 g / m or less. 2 More than 40g / m 2 More preferably, it should be 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 thickness is less than 50 g / m, it may be difficult to completely cover the barrier paper substrate with the coating liquid, resulting in insufficient water vapor barrier properties, or the gas barrier layer may penetrate into the barrier paper substrate, resulting in insufficient gas barrier properties. 2 If it is more than this amount, the drying load during coating increases. In the present invention, the water vapor barrier layer may be one 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 amount of all the water vapor barrier layers is within the above range.

[0048] 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 thickness 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 it is more than this amount, the drying load during coating increases. In the present invention, the gas barrier layer may be one 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 amount of all the gas barrier layers is within the above range.

[0049] <Base paper base material> The base paper 10 for a liquid paper container of the present invention has a base paper substrate 18 on the side of the barrier paper 16 opposite the barrier coating layer 14 . The base paper substrate 18 may be the same as the barrier paper substrate 12 described above. The basis weight of the base paper substrate 18 can be appropriately selected depending on the various qualities and handling properties desired for the liquid paper container, but is usually 100 g / m 2 More than 350g / m 2 The following is preferred: 120 g / m 2 More than 220g / m 2 The following is more preferred: Since the base paper 10 for liquid paper containers of the present invention has the barrier paper substrate 12 in the barrier paper 16, the basis weight of the base paper substrate 18 can be reduced to within the above range. Furthermore, the basis weight of the entire base paper 10 for liquid paper containers can be reduced even when the basis weights of the barrier paper substrate 12 and the base paper substrate 18 are combined. By reducing the basis weight of the entire base paper 10 for liquid paper containers, the liquid paper container formed using the base paper 10 for liquid paper containers of the present invention can be made lighter, and formability and crack resistance can be improved.

[0050] <First protective layer> The base paper 10 for a liquid-storing paper container of the present invention has a first protective layer 20 on the outermost surface on the base paper substrate 18 side. Polyethylene can be used as the resin used for the first protective layer 20. The polyethylene used may be polyethylene derived from fossil fuels, polyethylene derived from biomass, or a mixture of these.

[0051] In the production of biomass-derived ethylene, it is preferable to use biomass-derived fermented ethanol obtained from a plant raw material as a raw material. Examples of plant raw materials include, but are not limited to, corn, sugarcane, and beet. In addition, the method for polymerizing a monomer containing biomass-derived ethylene is not particularly limited, and can be carried out by a known method.

[0052] The polyethylene constituting the first protective layer 20 preferably contains low density polyethylene (LDPE) with a biomass ratio of 70% or more. If the biomass ratio is 70% or more, the amount of fossil fuel used can be significantly reduced, and the environmental load can be reduced to fully meet the needs of global warming countermeasures and the creation of a recycling-oriented society. From the above perspective, the biomass ratio is more preferably 80% or more, even more preferably 90% or more, and may be 100%.

[0053] In addition, when there is an odor originating from the biomass, it is also preferable to incorporate a deodorant into the biomass polyethylene layer. Examples of the deodorant include porous substances, metal oxides, and chemically adsorbent substances having acidic or basic groups. The biomass level can be determined by measuring 14C, which is only found in substances of biological origin.

[0054] The thickness of the first protective layer 20 is preferably in the range of 1 to 30 μm. When the thickness of the first protective layer 20 is 1 μm or more, the heat sealability is sufficient, and when it is 30 μm or less, the repulsion is not strong and molding is easy. From the above viewpoints, the thickness of the first protective layer 20 is more preferably in the range of 5 to 20 μm, and further preferably in the range of 10 to 15 μm.

[0055] The method for forming the first protective layer 20 is not particularly limited, but for example, a polyethylene resin composition for forming the first protective layer 20 is prepared, and this polyethylene resin composition is extruded onto the base paper substrate 18 or onto the printing layer 24 described below, and formed by an extrusion lamination method.

[0056] <Print layer, smooth layer> The base paper 10 for a liquid-carrying paper container of the present invention has a printed layer 24 and a smooth layer 26. The printed layer 24 and the smooth layer 26 are not essential components of the base paper 10 for a liquid-carrying paper container of the present invention, but the printed layer 24 is a layer on which the product name and product information are printed when the paper is used as a liquid-carrying paper container, and is normally used in the base paper 10 for a liquid-carrying paper container. The smooth layer 26 is provided on the surface of the base paper substrate 18, and is a layer that smoothes the surface of the base paper substrate 18 and makes it easier to form the printing layer 24. The smooth layer 26 can be manufactured by extrusion lamination using low-density polyethylene that can be used in the first protective layer 20. Alternatively, the smooth layer 26 is formed by mixing a white pigment such as clay or calcium carbonate with an adhesive (binder) such as starch to create a paint, and applying it using a coater. When a coater is used, the coater and the papermaking machine can be directly connected in the paper manufacturing process to perform papermaking and coating in one process.

[0057] <First adhesive layer> In the base paper 10 for liquid paper containers of the present invention, the barrier paper substrate 12 and the base paper substrate 18 of the barrier paper 16 are preferably laminated via a first adhesive layer 28. By using the first adhesive layer 28, the adhesion (adhesion) between the barrier paper substrate 12 and the base paper substrate 18 can be improved. For the first adhesive layer 28, from the viewpoint of improving adhesion between the barrier paper substrate 12 and the base paper substrate 18, it is preferable to use low-density polyethylene resin or linear low-density polyethylene resin (LLDPE: Linear Low Density Polyethylene), and linear low-density polyethylene resin is particularly preferable.

[0058] The thickness of the first adhesive layer 28 is preferably in the range of 1 to 30 μm. If the thickness of the first adhesive layer 28 is 1 μm or more, sufficient adhesion between the barrier paper substrate 12 and the base paper substrate 18 is achieved. On the other hand, if the thickness is 30 μm or less, repulsion is not strong and molding is easy. From the above viewpoints, the thickness of the first adhesive layer 28 is more preferably in the range of 3 to 25 μm, and even more preferably in the range of 10 to 20 μm.

[0059] <Second protective layer> The base paper for liquid paper containers of the present invention has a second protective layer 22 on the outermost surface of the barrier paper 16 on the barrier coating layer 14 side. The resin used for the second protective layer 22 can be polyethylene, similar to the resin used for the first protective layer 20. The polyethylene used may be polyethylene derived from fossil fuels, polyethylene derived from biomass, or a mixture of these. In particular, it is preferable that the resin used for the second protective layer 22 contains linear low-density polyethylene. By using linear low-density polyethylene, high heat sealability can be ensured when producing a liquid paper container.

[0060] The thickness of the second protective layer 22 is preferably in the range of 10 to 100 μm. If the thickness of the second protective layer 22 is 10 μm or more, the heat sealability is sufficient, and if it is 100 μm or less, the repulsion is not strong and molding is easy. From the above viewpoints, the thickness of the second protective layer 22 is more preferably in the range of 15 to 70 μm, and further preferably in the range of 20 to 50 μm.

[0061] The method for forming the second protective layer 22 is not particularly limited. For example, a film that will become the second protective layer 22 can be formed, and then this film can be bonded to the barrier paper 16 using the second adhesive layer 30 described below.

[0062] <Second adhesive layer> In the base paper 10 for liquid paper containers of the present invention, the barrier coating layer 14 of the barrier paper 16 and the second protective layer 22 are preferably laminated via the second adhesive layer 30. By using the second adhesive layer 30, the adhesion (adhesion) between the barrier coating layer 14 and the second protective layer 22 can be improved. As the second adhesive layer 30, it is preferable to use a low-density polyethylene resin and a linear low-density polyethylene resin from the viewpoint of improving the adhesion between the barrier coating layer 14 and the second protective layer 22. In particular, as shown in FIG. 1, it is preferable to laminate a linear low-density polyethylene resin layer 32 and a low-density polyethylene resin layer 34 as the second adhesive layer 30, and to arrange the linear low-density polyethylene resin layer 32 on the barrier coating layer 14 side and the low-density polyethylene resin layer 34 on the second protective layer 22 side. Since the linear low-density polyethylene resin is easy to ensure adhesiveness, it can be preferably used for parts where it is difficult to ensure adhesiveness. In addition, the low-density polyethylene resin has good processability and can be made cheaper than the linear low-density polyethylene resin. It is preferable to determine the amount of the low-density polyethylene resin and the linear low-density polyethylene resin in consideration of the above points. Furthermore, when forming a laminate of the linear low-density polyethylene resin layer 32 and the low-density polyethylene resin layer 34 by co-extrusion, necking-in can be suppressed by co-extruding the low-density polyethylene resin together with the linear low-density polyethylene resin, thereby preventing the processing width from becoming narrow and the resin at both ends from becoming thick.

[0063] The thickness of the second adhesive layer 30 is preferably in the range of 1 to 30 μm, either as the thickness of one layer in the case of a single layer or as the total thickness in the case of a laminate. If the thickness of the second adhesive layer 30 is 1 μm or more, the adhesion between the barrier coating layer 14 and the second protective layer 22 is sufficient. On the other hand, if the thickness is 30 μm or less, the repulsion is not strong and molding is easy. From the above viewpoints, the thickness of the second adhesive layer 30 is more preferably in the range of 3 to 25 μm, and even more preferably in the range of 10 to 25 μm.

[0064] [Liquid paper container] Next, the paper container for liquid will be described. As shown in Fig. 2, the paper container for liquid 7 of the present invention is formed through a process of overlapping both ends 10a, 10b in the longitudinal direction (vertical direction) of a strip-shaped base paper 10 for a paper container for liquid of the present invention to form a packaging tube 6. Then, a sealing tape 8 is provided to cover and seal the longitudinal seam formed on the inner surface of the formed packaging tube 6.

[0065] The first protective layer 20 and the second protective layer 22 of the base paper 10 for a liquid-storing paper container of the present invention can be made of polyethylene as described above and have heat-sealing properties. The first protective layer 20 and the second protective layer 22 having heat-sealing properties can easily produce the liquid-storing paper container 7 of the present invention and can prevent liquid leakage from the liquid-storing paper container 7.

[0066] In addition, the sealing tape 8 preferably has an outermost layer made of a resin having heat sealing properties. When sealing the sealing tape 8 vertically, the sealing tape 8 can be heat-sealed to the inside of the packaging tube 6 (the second protective layer 22 of the base paper 10 for liquid-containing paper containers), thereby preventing liquid leakage from the liquid-containing paper container 7.

[0067] Furthermore, the liquid paper container manufactured using the liquid paper container base paper 10 of the present invention is manufactured so that the barrier coating layer 14 side of the barrier paper 16 is on the inside and the barrier paper base paper 12 side is on the outside, as shown in Figure 3. By having the barrier coating layer 14 on the inside, even if water vapor and gas penetrate through the barrier paper base paper 12 and base paper base paper 18 of the liquid paper container base paper 10, the barrier coating layer 14 can prevent the water vapor and gas from penetrating into the liquid paper container 7.

[0068] Next, a method for forming the liquid-filled paper container 7 of the present invention will be described. First, the longitudinal end 10b of the strip-shaped liquid-filled paper container base paper 10 configured as above and the end of the seal tape 8 are overlapped and heat-sealed, then both longitudinal ends 10a and 10b of the liquid-filled paper container base paper 10 (and the seal tape 8 previously heat-sealed to the longitudinal end 10b) are overlapped and heat-sealed, and the longitudinal seam on the inner side formed in the heat-sealed portion is vertically sealed B using the seal tape 8 configured as above to create a packaging tube 6 of the liquid-filled paper container base paper 10. The resulting packaging tube 6 is then filled with the liquid while horizontally sealing A at a constant width at a distance equivalent to one liquid-filled paper container, and the middle part of the horizontally sealed area is cut to form the final shape, such as a brick shape. EXAMPLES

[0069] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. The obtained base paper for liquid paper containers was tested based on the evaluation methods shown below.

[0070] (Evaluation method) <Oxygen permeability> The measurement was performed according to the method specified in JIS K 7126-2 (constant pressure method). Specifically, oxygen was supplied to one side of the base paper for liquid paper containers, and nitrogen carrier gas was passed through the other side at constant pressure, and the permeated oxygen was measured using an oxygen detector. ≪Weight≫ The weight of each container was measured excluding the liquid content. ≪Moldability≫ After filling, 72 liquid paper containers were visually inspected and the number of defectively molded products was counted. <Crack resistance> A paper container for liquid was molded from the base paper for the liquid container, and an adapter was attached to the liquid container from which the liquid contents had been removed. The oxygen permeability of the container was measured using the measurement method specified in JIS K 7126-2 (constant pressure method). <Recyclability> Liquid paper containers that can be recycled are marked with an "O" and those that cannot be recycled are marked with an "X."

[0071] <Example 1> The base paper for a liquid paper container in Example 1 has the following configuration. (1) First protective layer: a 15 μm-thick low-density polyethylene layer (MFR: 8.2 g / 10 min, density: 0.919 g / cm 3 ) (2) Smooth layer: 15 μm thick low-density polyethylene layer (MFR: 8.2 g / 10 min, density: 0.919 g / cm 3 ) (3) Base paper base material; acidic paper (basis weight: 135g / m 2 ) (4) First adhesive layer: a linear low-density polyethylene layer having a thickness of 18 μm (MFR: 8.0 g / 10 min, density: 0.913 g / cm 3) (5) Barrier paper; manufactured by the method described below (6) Second adhesive layer; a 10 μm thick linear low-density polyethylene layer (MFR: 8.0 g / 10 min, density: 0.913 g / cm 3 ) and a 10 μm-thick low-density polyethylene layer (MFR: 8.2 g / 10 min, density: 0.919 g / cm 3 ) laminate (with the linear low density polyethylene layer placed on the barrier paper side) (7) Second protective layer: 30 μm thick linear low density polyethylene layer The first protective layer, smooth layer, first adhesive layer, and second adhesive layer were formed by extrusion lamination, and the second protective layer was formed as a film and bonded with the second adhesive layer. The barrier paper was constructed so that a barrier coating layer was provided on the opposite side of the base paper substrate.

[0072] (Barrier paper manufacturing method) The barrier paper used in Example 1 was produced by the following method. [Preparation of Coating Solution 1 for Water Vapor Barrier Layer] Sodium polyacrylate was added as a dispersant to engineered kaolin (Imerys, Barisurf HX, average particle size 90μm, aspect ratio 80-100) (0.2% relative to pigment), and dispersed in a Serie mixer to prepare a kaolin slurry with a solids concentration of 55%. 25 parts (solids) of styrene-acrylic copolymer emulsion (Tg23℃) and 20 parts (solids) of ethylene-acrylic copolymer emulsion (Tg25℃) were mixed as water vapor barrier resins to 100 parts (solids) of pigment in the obtained kaolin slurry, to obtain coating solution 1 for water vapor barrier layer with a solids concentration of 48.5%.

[0073] [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. [Manufacturing of barrier paper] As a barrier paper base material, acidic paper (basis weight: 50g / m 2On this barrier paper substrate, the coating solution 1 for the 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 the single-sided coating solution so that the dry weight was 3.0 g / m. 2 Thus, a barrier coating layer was formed, and barrier paper was obtained.

[0074] <Comparative Example 1> A base paper for liquid paper containers was obtained in the same configuration as in Example 1, except that the barrier coating layer of the barrier paper was placed on the base paper substrate side.

[0075] <Comparative Example 2> The base paper for a liquid paper container of Comparative Example 2 has the following configuration. (1) First protective layer: a 15 μm-thick low-density polyethylene layer (MFR: 8.2 g / 10 min, density: 0.919 g / cm 3 ) (2) Smooth layer: clay coat (3) Base paper base material; acidic paper (basis weight: 226g / m 2 ) (4) First adhesive layer: A 25 μm thick linear low-density polyethylene layer (MFR: 8.0 g / 10 min, density: 0.913 g / cm 3 ) (5) Barrier layer: 7 μm thick aluminum foil (6) Second adhesive layer; 20 μm thick ethylene-methacrylic acid copolymer (MFR: 8.0 g / 10 min, density: 0.930 g / cm 3 ) (7) Second protective layer: 35 μm thick low-density polyethylene layer (MFR: 8.2 g / 10 min, density: 0.919 g / cm 3 )

[0076] The base papers for liquid-storing paper containers produced in the Examples and Comparative Examples were evaluated by the above-mentioned evaluation methods. The results are shown in Table 1.

[0077] [Table 1] [Industrial Applicability]

[0078] INDUSTRIAL APPLICABILITY The base paper for liquid paper containers of the present invention has high barrier properties, is lightweight, and has excellent formability and crack resistance, and can therefore be suitably used for liquid paper containers for juice, alcoholic beverages, etc. [Explanation of symbols]

[0079] 6 Packaging tube 7 Liquid paper containers 8 Sealing tape 10 Base paper for liquid paper containers 10a, 10b end 12 Barrier paper base 14 Barrier coating layer 16 Barrier Paper 18 Base paper base material 20 First protective layer 22 Second layer of protection 24 Printing layer 26 Smooth layer 28 First adhesive layer 30 Second adhesive layer 32 Linear low density polyethylene resin layer 34 Low density polyethylene resin layer

Claims

1. A barrier paper having a barrier coating layer on one side of a barrier paper substrate; a base paper substrate provided on the opposite side of the barrier paper to the barrier coating layer; A base paper for a liquid paper container, comprising: a first protective layer provided on an outermost surface of the base paper substrate side; and a second protective layer provided on an outermost surface of the barrier paper on the barrier coating layer side.

2. The basis weight of the paper constituting the barrier paper substrate is 25 to 100 g / m ２ The paper constituting the base paper substrate has a basis weight of 100 to 350 g / m ２ The base paper for liquid paper containers according to claim 1 ,

3. The base paper for liquid paper containers according to claim 1 or 2, wherein the barrier paper substrate is made of acidic paper.

4. The base paper for a liquid paper container according to claim 1 or 2, wherein the barrier paper and the base paper substrate are laminated via an adhesive layer.

5. the barrier coating layer has at least a water vapor barrier layer and a gas barrier layer, The base paper for liquid paper containers according to claim 1 or 2, comprising the water vapor barrier layer and the gas barrier layer, in this order, on the barrier paper base material.

6. The base paper for liquid paper containers according to claim 5 , wherein at least one of the water vapor barrier layer and the gas barrier layer contains a flat pigment.

7. A liquid paper container formed using the base paper for liquid paper containers according to claim 1 or 2, A liquid paper container, wherein the barrier coating layer side of the barrier paper is placed on the inside.

8. The liquid paper container according to claim 7, which is formed into a cylindrical shape using a sealing tape.

Images