Paper laminate

Abstract

To provide a paper laminate which is excellent in resistance against processing and has high barrier performance.SOLUTION: A paper laminate has a vapor-deposited layer which has thickness of 1 to 1,000 nm and is formed of metal or ceramic on at least one surface of a paper base material, and has a resin layer which has thickness of 1 μm or more and less than 15 μm and is formed of a thermoplastic resin on the vapor-deposited layer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a paper laminate. [Background technology]

[0002] Packaging materials with water vapor barrier properties or gas barrier properties (particularly oxygen barrier properties) added to a paper base have traditionally been used in packaging foods, medical products, electronic components, and the like to prevent deterioration of the contents.

[0003] A common method for imparting water vapor barrier properties and gas barrier properties to a paper substrate is to laminate a synthetic resin film with excellent gas barrier properties onto the paper substrate. However, materials in which a synthetic resin film or the like is laminated onto a paper substrate have environmental issues, as it is difficult to recycle the paper and synthetic resin after use. Therefore, efforts are being made to develop barrier materials that do not require lamination of synthetic resin films, etc. For example, Patent Document 1 discloses a paper packaging material that has barrier properties against moisture and oxygen and that has an organic substance coating layer, a metal or metal oxide layer, and an organic substance coating layer on the inside of a paper layer.

[0004] Meanwhile, metallized paper, taking advantage of its glossiness, is widely used for label paper with excellent design for alcohol, beer, soft drinks, etc., and for wrapping paper for confectionery, etc. However, since it is necessary to form a thin metal film on a paper substrate, improvements in its adhesiveness and manufacturing methods have been studied. For example, Patent Document 2 discloses aluminum-metallized paper that has an aluminum-metallized layer on a base paper and uses a base paper that has been treated on the back side so that the spontaneous polarization potential value of the surface of the metallized layer falls within a specific range. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-321307 [Patent Document 2] Japanese Patent Application Publication No. 4-65599 Summary of the Invention

[0006] Although attempts have been made to improve the barrier properties of paper substrates by using metal foil or metal oxide foil, as in Patent Document 1, when a very thin film such as a vapor-deposited film is formed in consideration of recyclability, flexibility, and the texture of the paper, durability during use or processing becomes an issue. Specifically, when three-dimensional processing such as embossing or bending is performed, the barrier performance decreases, possibly because damage such as cracks occurs in the vapor-deposited metal or metal oxide film. Therefore, an object of the present invention is to provide a paper laminate that has excellent resistance to processing and high barrier performance.

[0007] After extensive research, the inventors discovered that a laminate having a paper base material, a metal or ceramic vapor-deposited layer of a specific thickness, and further having a resin layer made of a thermoplastic resin of a specific thickness can solve the above-mentioned problem. That is, the present invention provides the following: <1> ~ <14> Regarding. <1> A paper laminate having a vapor-deposited layer of metal or ceramic having a thickness of 1 to 1000 nm on at least one side of a paper substrate, and further having a resin layer of thermoplastic resin having a thickness of 1 μm or more and less than 15 μm on the vapor-deposited layer. <2> The paper base has a basis weight of 20 to 500 g / m 2 That is, <1> The paper laminate according to claim 1. <3> The vapor-deposited layer is made of aluminum, silicon oxide, or aluminum oxide. <1> or <2> The paper laminate according to claim 1. <4> The thermoplastic resin constituting the resin layer is a heat-sealable resin. <1> ~ <3> 10. The paper laminate according to claim 9, wherein the paper laminate is a laminate of a paper material having a thickness of 10 <5> The thermoplastic resin is at least one selected from an olefin-unsaturated carboxylic acid copolymer, a biodegradable resin, polyethylene, polypropylene, an acrylic resin, and ethylene vinyl alcohol; <1> ~ <4> 10. The paper laminate according to claim 9, wherein the paper laminate is a laminate of a paper material having a thickness of 10 <6> The biodegradable resin is at least one selected from polylactic acid, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate terephthalate, and poly(3-hydroxybutyrate-co-hydroxyhexanoate). <5> The paper laminate according to claim 1. <7> The paper substrate has one or more layers selected from a clay coating layer and an undercoat layer between the paper substrate and the vapor deposition layer. <1> ~ <6> 10. The paper laminate according to claim 9, wherein the paper laminate is a laminate of a paper material having a thickness of 10 <8> A clay coating layer and an undercoat layer are provided between the paper substrate and the vapor deposition layer, and an undercoat layer is provided between the clay coating layer and the vapor deposition layer. <1> ~ <7> 10. The paper laminate according to claim 9, wherein the paper laminate is a laminate of a paper material having a thickness of 10 <9> the undercoat layer is mainly composed of a binder, and the resin contained in the binder is at least one selected from polyvinyl alcohol, ethylene-modified polyvinyl alcohol, an acrylic resin, a polyurethane resin, and a polyester resin; <7> or <8> The paper laminate according to claim 1. <10> The resin layer is the outermost layer. <1> ~ <9> 10. The paper laminate according to claim 9, wherein the paper laminate is a laminate of a paper material having a thickness of 10 <11> The paper substrate is the outermost layer. <1> ~ <10> 10. The paper laminate according to claim 9, wherein the paper laminate is a laminate of a paper material having a thickness of 10 <12> The thickness of the resin layer is 3 to 7 μm. <1> ~ <11> 10. The paper laminate according to claim 9, wherein the paper laminate is a laminate of a paper material having a thickness of 10 <13> The thermoplastic resin is at least one selected from an olefin-unsaturated carboxylic acid copolymer and a polylactic acid. <1> ~ <12> 10. The paper laminate according to claim 9, wherein the paper laminate is a laminate of a paper material having a thickness of 10 <14> A method for producing a paper laminate, comprising the steps of applying a resin solution or resin dispersion to a metal- or ceramic-deposited paper having a metal- or ceramic-deposited layer of 1 to 1000 nm thick on at least one side of the paper substrate, and drying the coated paper to form a resin layer made of a thermoplastic resin having a thickness of 1 μm or more and less than 15 μm. DETAILED DESCRIPTION OF THE INVENTION

[0008] In this specification, the numerical range expressed as "X to Y" means X or more and Y or less. [Paper laminate] A paper laminate according to one embodiment of the present invention has a metal or ceramic vapor-deposited layer 1 to 1000 nm thick on at least one side of a paper substrate, and a resin layer made of a thermoplastic resin 1 μm or more and less than 15 μm thick on the vapor-deposited layer. The paper laminate has excellent resistance to the processing of the present invention and high barrier performance. The paper laminate according to one embodiment of the present invention has a vapor-deposited layer that provides high barrier properties, and a resin layer that protects the vapor-deposited layer and maintains barrier properties even when the paper is deformed during processing. Depending on the resin that makes up the resin layer, heat-sealing properties can also be imparted. Furthermore, damage to the glossy vapor-deposited layer can be prevented, resulting in excellent design properties.

[0009] The paper substrate may have a vapor-deposited layer on one side or both sides, but from the viewpoint of production efficiency, it is preferable to have a vapor-deposited layer on one side. In the present invention, sufficient barrier properties can be exhibited even if a vapor-deposited layer is provided on only one side. When a vapor-deposited layer is provided on one side, it is preferable to have a resin layer only on the vapor-deposited layer side. In terms of production efficiency, when a vapor-deposited layer is provided on one side, it is preferable that the paper substrate be the outermost layer in the paper laminate of the present invention. When the substrate has a vapor-deposited layer on both sides, it is preferable that a resin layer made of a thermoplastic resin be provided on one or both sides, and it is particularly preferable that a resin layer made of a thermoplastic resin be provided on one side. By providing a resin layer made of a thermoplastic resin on one side, production efficiency is excellent, and when the laminate of the present invention is heat-sealed, bags and the like can be easily produced. The resin layer is preferably formed directly on the vapor-deposited layer, which can efficiently protect the vapor-deposited layer from damage due to deformation during processing.

[0010] <Paper base material> The paper substrate used in the paper laminate of the present invention is preferably a commonly used paper whose main component is plant-derived pulp, more preferably a paper whose main component is wood pulp, and is also preferably a paper whose main component is pulp that is easily dispersible in water by mechanical disintegration. Specific examples include bleached kraft paper, unbleached kraft paper, fine paper, paperboard, liner paper, coated paper, one-side glazed paper, glassine paper, graphene paper, etc., and among these, bleached kraft paper, unbleached kraft paper, fine paper, and one-side glazed paper are preferred.

[0011] From the viewpoint of improving barrier properties, the disintegrated freeness (freeness) of the paper base material measured in accordance with JIS P8121:2012 is preferably 800 ml or less, and more preferably 500 ml or less. Here, disintegrated freeness refers to the Canadian standard freeness measured in accordance with JIS P8121:2012 on the pulp obtained by disintegrating paper after papermaking in accordance with JIS P8220-1. Known methods can be used to beat the pulp to adjust the disintegrated freeness.

[0012] The sizing degree of the paper substrate is not particularly limited, but from the viewpoint of improving barrier properties, it is preferable that the Stockigt sizing degree according to JIS P8122: 2004 is 1 second or more. The sizing degree of the paper substrate can be controlled by the type and content of the internal sizing agent, the type of pulp, smoothing treatment, etc. Examples of internal sizing agents include rosin-based, alkyl ketene dimer-based, alkenyl succinic anhydride-based, styrene-acrylic, higher fatty acid-based, petroleum resin-based, etc. The content of the internal sizing agent is preferably 3 parts by mass or less per 100 parts by mass of pulp in the paper base material.

[0013] In addition to the internal sizing agent, other known internal additives may be added to the paper base material, such as fillers, paper strength agents, retention aids, pH adjusters, drainage aids, water-resistant agents, softeners, antistatic agents, antifoaming agents, slime control agents, dyes and pigments, etc. Examples of fillers include titanium dioxide, kaolin, talc, and calcium carbonate.

[0014] In making paper substrates, any known wet paper machine can be appropriately selected and used. Examples of the paper machine include a Fourdrinier paper machine, a gap former type paper machine, a cylinder type paper machine, and a short wire type paper machine. The paper layer formed by the paper machine is preferably conveyed on a felt and dried in a dryer. A multi-stage cylinder dryer may be used as a pre-dryer before drying in the dryer.

[0015] The paper substrate thus obtained may be subjected to a surface treatment using a calendar to make the thickness and profile uniform. A known calendaring machine can be appropriately selected and used for the calendaring treatment.

[0016] The paper base weight is 20 to 500 g / m 2 It is preferable that the density is 20 to 400 g / m 2 More preferably, 20 to 200 g / m 2 is more preferably 30 to 100 g / m 2 is even more preferred. From the viewpoint of molding processability, the density of the paper base material is 0.5 to 1.2 g / cm 3 is preferably 0.6 to 1.0 g / cm 3 is more preferred. To obtain a uniform vapor-deposited layer, the paper substrate preferably has an Oken smoothness of at least 5 seconds, more preferably 10 to 1000 seconds, on the surface on which the vapor-deposited layer is to be formed, and from the viewpoint of printability, the paper substrate preferably has a 75° gloss of 5% or more, more preferably 10 to 70%.

[0017] <Vapour-deposited layer> The vapor-deposited layer used in the paper laminate of the present invention is made of metal or ceramic and has a thickness of 1 to 1000 nm. The thickness of the vapor-deposited layer is 1 to 1000 nm, preferably 2 to 500 nm, and more preferably 3 to 100 nm. From the viewpoint of barrier properties, it is more preferably 10 to 80 nm, and even more preferably 25 to 70 nm. From the viewpoints of adhesion to other layers and cost, it is preferably 4 to 100 nm, more preferably 4 to 70 nm, even more preferably 4 to 50 nm, and even more preferably 5 to 50 nm, and may be, for example, 5 to 30 nm.

[0018] The deposited layer may be made of metal or ceramic, preferably metal. When the vapor-deposited layer is made of a metal, specific examples include aluminum and titanium, with aluminum being preferred. When the vapor-deposited layer is a ceramic, specific examples thereof include silicon oxide, titanium oxide, and aluminum oxide, with silicon oxide and aluminum oxide being preferred. That is, the vapor-deposited layer is more preferably made of aluminum, silicon oxide or aluminum oxide, and among these, aluminum is even more preferred.

[0019] <Resin layer> The paper laminate of the present invention has a resin layer made of a thermoplastic resin having a thickness of 1 μm or more and less than 15 μm. The thickness of the resin layer is 1 μm or more and less than 15 μm, preferably 2 to 10 μm, and more preferably 3 to 7 μm. When the resin layer is 1 μm or more and less than 15 μm thick, the paper can be easily disintegrated during recycling while maintaining excellent protection for the vapor-deposited layer, resulting in excellent recyclability.Furthermore, when the resin layer is 1 μm or more and less than 15 μm thick, the paper laminate also has excellent heat-sealing properties. In the paper laminate of the present invention, the resin layer is preferably the outermost layer. By having the resin layer as the outermost layer, the resin layer can be given heat-sealing properties, allowing the container to be formed. Furthermore, since it is not affected by other layers, the vapor-deposited layer can be easily protected from external forces due to deformation. Furthermore, the design of the glossy vapor-deposited layer is not impaired.

[0020] The resin constituting the resin layer is a thermoplastic resin from the viewpoints of facilitating the formation of the resin layer, providing excellent protection for the vapor-deposited layer, and imparting heat-sealing properties. The thermoplastic resin is preferably at least one selected from an olefin-unsaturated carboxylic acid copolymer, a biodegradable resin, polyethylene, polypropylene, an acrylic resin, and ethylene vinyl alcohol, more preferably at least one selected from an olefin-unsaturated carboxylic acid copolymer, a biodegradable resin, and an acrylic resin, even more preferably at least one selected from an olefin-unsaturated carboxylic acid copolymer and a biodegradable resin, and more specifically at least one selected from an olefin-unsaturated carboxylic acid copolymer and polylactic acid. From the viewpoint of protecting the vapor-deposited layer, an olefin-unsaturated carboxylic acid copolymer is even more preferable, and from the viewpoints of recyclability and reducing the environmental load, a biodegradable resin is even more preferable.

[0021] The olefin-unsaturated carboxylic acid copolymer is preferably an ethylene-acrylic copolymer, which is readily available and can be synthesized as an aqueous dispersion, making it easy to form a resin layer on the vapor-deposited layer by coating and drying. When the olefin-unsaturated carboxylic acid copolymer is used as an aqueous dispersion, it is preferable that the unsaturated carboxylic acid or acrylic monomer component is a salt that has been partially or completely neutralized with an alkali metal hydroxide, ammonia, alkylamine, alkanolamine, etc.

[0022] When an olefin-unsaturated carboxylic acid copolymer is used, the content of the olefin-unsaturated carboxylic acid copolymer in the resin layer is preferably 20% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and most preferably 95% by mass or more, based on the total solid content of the resin layer. The upper limit is not particularly limited, but is preferably 100% by mass or less.

[0023] Examples of the acrylic monomer constituting the ethylene-acrylic copolymer include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and butenetricarboxylic acid; unsaturated polycarboxylic acid alkyl esters having at least one carboxyl group such as itaconic acid monoethyl ester, fumaric acid monobutyl ester, and maleic acid monobutyl ester; and unsaturated sulfonic acid monomers or salts thereof such as acrylamidopropanesulfonic acid, acrylate sulfoethyl sodium salt, and methacrylate sulfopropyl sodium salt. Unsaturated carboxylic acids are preferred, with acrylic acid and methacrylic acid being more preferred, and acrylic acid being even more preferred. The acrylic monomer constituting the ethylene-acrylic copolymer may be one type or two or more types in combination.

[0024] The ethylene-acrylic copolymer is preferably obtained by emulsion polymerization of ethylene and the acrylic monomer. The ethylene-acrylic copolymer is preferably an ethylene-acrylic acid copolymer or an ethylene-methacrylic acid copolymer. The copolymer may contain a monomer composed of another compound copolymerizable with ethylene and the acrylic monomer, provided that the effect of the present invention is not impaired.

[0025] The content of acrylic monomer units in the ethylene-acrylic copolymer (copolymerization ratio of acrylic monomers) is preferably 1 to 50 mol%, more preferably 10 to 30 mol%. When the ethylene-acrylic copolymer contains acrylic acid units as the acrylic monomer units, the content of acrylic acid units (copolymerization ratio of acrylic acid) is preferably 1 to 50 mol%, more preferably 10 to 30 mol%. When the content of acrylic monomer units is 1 to 50 mol%, the melting temperature is 60 to 120°C, resulting in an excellent ethylene-acrylic copolymer that exhibits good heat-sealing properties.

[0026] The weight average molecular weight of the ethylene-acrylic copolymer is preferably from 10,000 to 10,000,000, and more preferably from 100,000 to 5,000,000, from the viewpoint of the viscosity of the coating liquid and the strength of the coating film.

[0027] Specific examples of ethylene-acrylic copolymers include ZAIXXEN (registered trademark) AC (aqueous dispersion of ethylene-acrylic acid copolymer ammonium salt, copolymerization ratio of acrylic acid: 20 mol %, manufactured by Sumitomo Seika Chemicals Co., Ltd.).

[0028] The biodegradable resin is preferably one or more selected from polylactic acid (PLA), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polybutylene adipate terephthalate (PBAT), and poly(3-hydroxybutyrate-co-hydroxyhexanoate) (PHBH), more preferably one or more selected from polylactic acid and polybutylene succinate, and even more preferably polylactic acid. Packaging materials using a paper substrate have the advantage of reducing the environmental impact compared to packaging materials made of resin films, but using a biodegradable resin as the resin layer of the present invention can further reduce the environmental impact.

[0029] From the viewpoint of facilitating coating and reducing the burden on the environment, it is preferable to use an aqueous dispersion of the biodegradable resin, and from the viewpoint of availability, it is more preferable to use an aqueous dispersion of polylactic acid. Specific examples of polylactic acid include Randy PL-1000 and Randy PL-3000 (aqueous dispersion of polylactic acid, manufactured by Miyoshi Oil & Fats Co., Ltd.).

[0030] The thermoplastic resin used in the resin layer constituting the paper laminate of the present invention is preferably heat-sealable. Therefore, when the resin constituting the resin layer has a melting point, the melting point is preferably 60 to 120°C, more preferably 70 to 110°C, and even more preferably 80 to 100°C. Because the resin layer is heat-sealable, packaging bags and the like made solely of the paper laminate of the present invention can be easily obtained. Furthermore, by fusing the paper laminate to other sheets, films, containers, etc., the paper laminate can be used as a packaging container body, a packaging container lid, etc. The packaging bags and packaging containers obtained in this manner have excellent barrier properties.

[0031] The tensile strength of the thermoplastic resin is preferably 5 to 30 MPa, more preferably 10 to 20 MPa. The tensile strength is measured in accordance with JIS K7161. The elongation at break of the thermoplastic resin is preferably 200 to 600%, more preferably 300 to 500%. The elongation at break is measured in accordance with JIS K7161.

[0032] The resin layer constituting the paper laminate of the present invention is made of a thermoplastic resin, but may contain other resins and additives within a range that does not impair the effects of the present invention. In other words, when the resin layer is "made of a thermoplastic resin," it means that the main component of the resin layer is a thermoplastic resin, and the content of the thermoplastic resin in the resin layer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 99% by mass or more. The additives may include surfactants, pigments, antioxidants, antistatic agents, dyes, plasticizers, lubricants, release agents, etc. When the resin is used as an aqueous dispersion, it is preferable to use a dispersant to disperse the resin in an aqueous medium and obtain a uniform resin layer film.

[0033] <any layer> The paper laminate of the present invention may include an optional layer in addition to the paper substrate, vapor-deposited layer, and resin layer. Optional layers include a clay coating layer and an undercoat layer. The paper laminate of the present invention preferably has one or more layers selected from a clay coating layer and an undercoat layer between the paper substrate and the vapor-deposited layer. In other words, it is preferable that the paper laminate of the present invention has layers laminated on at least one surface of a paper base material in the order of clay coat layer, vapor deposition layer, and resin layer, or that the layers laminated on at least one surface of a paper base material in the order of undercoat layer, vapor deposition layer, and resin layer. Furthermore, it is more preferable that the paper laminate of the present invention has both a clay coating layer and an undercoat layer between the paper base material and the vapor deposition layer, and in that case, it is even more preferable that an undercoat layer be present between the clay coating layer and the vapor deposition layer. That is, it is more preferable that the paper laminate of the present invention has layers laminated on at least one surface of the paper base material in the following order: clay coat layer, undercoat layer, vapor deposition layer, and resin layer.

[0034] (clay court layer) The clay coating layer is preferably provided in the paper laminate from the viewpoint of sealing and smoothing the paper substrate, and as described above, the paper laminate of the present invention preferably has a clay coating layer between the paper substrate and the vapor deposition layer, and more preferably has a clay coating layer between the paper substrate and the undercoat layer.

[0035] The clay coat layer is mainly composed of clay and a binder. The phrase "the clay coat layer is mainly composed of clay and a binder" means that the total content of clay and binder in the undercoat layer is, for example, 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. There is no particular upper limit, but 100% by mass or less is preferred. The clay coat layer may further contain any optional components in addition to the clay and binder. The clay contained in the clay coat layer is not particularly limited, but examples thereof include kaolin, talc, and mica. The aspect ratio of the clay is preferably 10 or more, more preferably 20 or more, and even more preferably 30 or more. The upper limit is not particularly limited, but is preferably 10,000 or less. The aspect ratio can be measured by observation with an electron microscope or X-ray diffraction measurement. The clay content in the clay coat layer is preferably 50 to 98% by mass, more preferably 60 to 90% by mass, and even more preferably 70 to 85% by mass. The binder contained in the clay coating layer is not particularly limited, but examples thereof include acrylic resins, styrene-butadiene resins, styrene-acrylic copolymers, ethylene-acrylic copolymers, etc., with acrylic resins and styrene-acrylic copolymers being preferred. The content of the binder in the clay coating layer is preferably 2 to 50% by mass, more preferably 10 to 40% by mass, and even more preferably 15 to 30% by mass. The coating amount of the clay coating layer is not particularly limited, but is preferably 5 to 30 g / m2 in terms of solid content. 2 and more preferably 7 to 20 g / m 2 is. The method for forming the clay coating layer is not particularly limited, but a method in which a dispersion containing clay and a resin binder is applied to a paper substrate and then dried is preferred. The dispersion containing clay and a resin binder is preferably an aqueous dispersion.

[0036] (undercoat layer) The undercoat layer is preferably provided in the paper laminate from the viewpoint of increasing the adhesion between the paper substrate and the vapor deposition layer, and as described above, the paper laminate of the present invention preferably has an undercoat layer between the paper substrate and the vapor deposition layer, and more preferably has an undercoat layer between the clay coat layer and the vapor deposition layer.

[0037] The undercoat layer is mainly composed of a binder. The phrase "the undercoat layer is mainly composed of a binder" means that the binder content in the undercoat layer is, for example, 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more (upper limit 100% by mass). The undercoat layer may further contain any optional components other than the binder. The binder contained in the undercoat layer is not particularly limited, and examples thereof include alkyd resins, acrylic resins, vinyl resins, cellulose resins, urethane resins, polyester resins, etc. Among these, it is more preferable to use one or more types selected from polyvinyl alcohol resins, ethylene-modified polyvinyl alcohol, acrylic resins, urethane resins, and polyester resins, even more preferable to use one or more types selected from polyvinyl alcohol resins and urethane resins, and even more preferable to use polyvinyl alcohol resins from the viewpoint of oxygen barrier properties. The coating amount of the undercoat layer is not particularly limited, but is preferably 1 to 10 g / m in terms of solid content. 2 and more preferably 1 to 5 g / m 2 is. The method for forming the undercoat layer is not particularly limited, but it is preferable to form the undercoat layer by applying an aqueous solution or aqueous dispersion of a binder and drying it.

[0038] [Manufacturing method of paper laminate] There are no limitations on the method for producing the paper laminate of the present invention, but it is preferable to include a step of applying a resin solution or resin dispersion to a vapor-deposited paper having a vapor-deposited layer of metal or ceramic 1 to 1000 nm thick on at least one side of the paper base material, and drying the paper to form a resin layer made of a thermoplastic resin having a thickness of 1 μm or more and less than 15 μm.

[0039] The metal-deposited paper used in the manufacturing method of the present invention is preferably obtained by depositing a metal or ceramic on the paper substrate. As described above, a clay coating layer may be provided on the surface of the paper substrate. Examples of clays used in the clay coating layer include, but are not limited to, kaolin. Examples of binders include, but are not limited to, acrylic resins, styrene-butadiene polymers, and styrene-acrylic copolymers. When providing a clay coating layer, it is preferable to form it by coating a dispersion containing clay and a binder onto the paper substrate and drying it, as described above.

[0040] Furthermore, an undercoat layer may be provided on the surface of the paper substrate as described above. The undercoat layer is preferably made of a binder such as an alkyd resin, an acrylic resin, a vinyl resin, a cellulose resin, a urethane resin, or a polyester resin, and among these, polyvinyl alcohol, ethylene-modified polyvinyl alcohol, an acrylic resin, a urethane resin, or a polyester resin is more preferred. When providing an undercoat layer, it is preferably formed by applying an aqueous solution or aqueous dispersion of the binder and drying it.

[0041] As a method for depositing a metal or ceramic on a paper substrate, a method in which the metal or ceramic is directly deposited by vacuum deposition on the surface of the paper substrate or the undercoat layer is preferred. The metal or ceramic used here includes aluminum, silicon oxide, and aluminum oxide, with aluminum being preferred from the standpoint of cost and appearance.

[0042] Next, a resin layer made of a thermoplastic resin and having a thickness of 1 μm or more and less than 15 μm is formed on the metallized paper. It is preferable to form the resin layer directly on the vapor-deposited layer of the metallized paper, from the viewpoint of efficiently protecting the vapor-deposited layer and enhancing the barrier properties. The resin layer is preferably formed by applying a resin solution or a resin dispersion and drying it. By using a method of forming a resin layer by applying a resin solution or resin dispersion, it is possible to form a relatively thin resin layer of less than 15 μm. By forming such a relatively thin resin layer, it is possible to impart excellent disintegration properties to the resulting paper laminate, thereby obtaining a laminate with excellent recyclability.

[0043] The resin used here is preferably a resin that is suitable for use in the resin layer described above, and is preferably one or more selected from an olefin-unsaturated carboxylic acid copolymer, a biodegradable resin, polyethylene, polypropylene, an acrylic resin, and ethylene vinyl alcohol, more preferably one or more selected from an olefin-unsaturated carboxylic acid copolymer, a biodegradable resin, and an acrylic resin, and even more preferably one or more selected from an olefin-unsaturated carboxylic acid copolymer and a biodegradable resin.

[0044] These resins are applied to the metallized paper as a resin solution or resin dispersion. The resin solution or dispersion used here may be a solution using an organic solvent to dissolve the resin, a dispersion using an organic solvent to disperse the resin, or a dispersion using an aqueous medium. From the viewpoints of coatability and environmental impact, a dispersion using an aqueous medium is preferred. Among these, aqueous dispersions of olefin-unsaturated carboxylic acid copolymers, biodegradable resins, and acrylic resins are more preferred.

[0045] Examples of methods for applying the resin solution or resin dispersion include bar coating, blade coating, squeeze coating, air knife coating, roll coating, gravure coating, and transfer coating, and a coating machine such as a fountain coater or a slit die coater may be used. The coated metallized paper can be dried to remove the organic solvent or aqueous medium, to obtain a paper laminate having a resin layer made of a thermoplastic resin on the metallized layer. [Example]

[0046] The features of the present invention will be explained in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0047] [Example 1] [Production of paper laminate (1)] An aqueous dispersion of ethylene-acrylic acid copolymer ammonium salt (active component 29.2 mass%, Zaixen AC, copolymerization ratio of acrylic acid 20 mol%, manufactured by Sumitomo Seika Chemicals Co., Ltd.) was diluted with water to an active component of 20 mass%, to prepare a coating material for the resin layer. Using a Mayer bar (No. 16), aluminum-metallized paper (base paper (paper base material) basis weight 60 g / m 2 The resin layer coating was applied to a 20 nm aluminum vapor deposition layer (Oji F-Tex Co., Ltd.) and dried at 120°C for 1 minute to obtain a paper laminate (1). The resin layer had a thickness of 5 μm. The aluminum vapor deposition paper was constructed by laminating a clay coat layer, an undercoat layer, and a vapor deposition layer in this order on a base paper (paper substrate). The evaluation results of the obtained paper laminate (1) are shown in Table 1.

[0048] [Example 2] [Production of paper laminate (2)] An aqueous dispersion of polylactic acid resin (active ingredient 40% by mass, Randy PL-3000, manufactured by Miyoshi Oil & Fats Co., Ltd.) was diluted with water to an active ingredient content of 20% by mass to prepare a coating material for the resin layer. Using a Mayer bar (No. 16), aluminum-metallized paper (base paper (paper base material) basis weight 60 g / m 2 The resin layer coating was applied to a 20 nm aluminum vapor deposition layer (Oji F-Tex Co., Ltd.) and dried at 120°C for 1 minute to obtain a paper laminate (2). The resin layer had a thickness of 6 µm. The evaluation results of the obtained paper laminate (2) are shown in Table 1.

[0049] [Comparative Example 1] The aluminum-deposited paper used in Examples 1 and 2 (base paper (paper substrate) basis weight 60 g / m 2 The substrate (aluminum vapor deposition layer 20 nm, manufactured by Oji F-Tex Co., Ltd.) was used as it was and evaluated in the same manner as in Examples 1 and 2. The evaluation results are shown in Table 1.

[0050] [Example 3] [Production of paper laminate (3)] A coating solution for the clay coating layer was prepared by mixing 80 parts by mass of kaolin (Contour Xtreme, manufactured by Imerys, aspect ratio 33) and 20 parts by mass (solids) of a styrene-acrylic copolymer binder (JONCRYL HSL-9012, manufactured by BASF). 2 , thickness 62μm, density 0.76g / m 3 The clay coating layer coating solution was applied to the surface with an Oken smoothness of 17 seconds using a Mayer bar, and dried at 120°C for 1 minute to form a clay coating layer (10 g / m 2 Next, a urethane resin binder (Takelac WPB-341 manufactured by Mitsui Chemicals) was applied onto the clay coating layer with a Mayer bar and dried at 120°C for 1 minute to form an undercoat layer (2 g / m 2 Next, an aluminum vapor-deposited layer (thickness: 50 nm) was formed on the undercoat layer to obtain aluminum vapor-deposited paper. The resin layer coating material produced in Example 1 was applied to the aluminum-deposited paper using a Mayer bar (No. 16) and dried at 120°C for 1 minute to obtain a paper laminate (3). The thickness of the resin layer was 5 µm. The evaluation results of the obtained paper laminate (3) are shown in Table 2.

[0051] [Example 4] [Production of paper laminate (4)] A coating solution for the clay coating layer was prepared by mixing 80 parts by mass of kaolin (Contour Xtreme, manufactured by Imerys, aspect ratio 33) and 20 parts by mass (solids) of a styrene-acrylic copolymer binder (JONCRYL HSL-9012, manufactured by BASF). 2 , thickness 62μm, density 0.76g / m 3 The clay coating layer coating solution was applied to the surface with an Oken smoothness of 17 seconds using a Mayer bar, and dried at 120°C for 1 minute to form a clay coating layer (12 g / m 2 Next, a polyvinyl alcohol resin binder (EXCEVAL AQ-4104 manufactured by Kuraray) was applied onto the clay coating layer with a Mayer bar and dried at 120°C for 1 minute to form an undercoat layer (3 g / m 2 Next, an aluminum vapor-deposited layer (thickness: 50 nm) was formed on the undercoat layer to obtain aluminum vapor-deposited paper. The resin layer coating material produced in Example 1 was applied to the aluminum-deposited paper using a Mayer bar (No. 16) and dried at 120°C for 1 minute to obtain a paper laminate (4). The thickness of the resin layer was 5 µm. The evaluation results of the obtained paper laminate (4) are shown in Table 2.

[0052] [evaluation] [Oxygen permeability] The oxygen permeability of the paper laminate and metallized paper was measured using an oxygen permeability measuring device (MOCON, OX-TRAN2 / 20) at a temperature of 23°C and a relative humidity of 50% (low humidity conditions). The lower the oxygen permeability value, the better the oxygen barrier property. To evaluate processing resistance, oxygen permeability after folding was also measured. The folding method involved folding the paper laminate or metallized paper once (at a fold angle of 180°), unfolding it, folding it again perpendicular to the fold line (at a fold angle of 180°), and unfolding it again. The oxygen permeability was measured by aligning the intersection of the fold line with the center of the measuring section of the oxygen permeability measuring device.

[0053] [Water vapor permeability] Water vapor permeability was measured in accordance with JIS Z0208 (cup method) Method B (temperature 40°C ± 0.5°C, relative humidity 90% ± 2%), with the paper laminate and the resin layer of the metallized paper positioned on the inner side (low humidity side). The lower the water vapor permeability value, the better the water vapor barrier property. To evaluate processing resistance, the water vapor permeability after folding was also measured. The folding method involved folding the paper laminate or metallized paper once (at a fold angle of 180°), unfolding it, folding it again perpendicular to the fold line (at a fold angle of 180°), and unfolding it again. The water vapor permeability was measured with the intersection of the fold lines at the center of the measurement area.

[0054] [Heat sealability] Two sheets of the laminate of each Example or two sheets of the metallized paper of the Comparative Example were stacked with the resin layers or metallized layers facing each other, and heat-sealed using a heat seal tester (TP-701-B, manufactured by Tester Sangyo) at 130°C, 0.5 MPa, and for 30 seconds to evaluate the heat-sealability. Samples that were fused and heat-sealed were marked with a circle, and samples that were not heat-sealed were marked with an x.

[0055] [Table 1]

[0056] [Table 2]

[0057] The paper laminates of the Examples maintained low oxygen permeability and water vapor permeability even after folding compared to the vapor-deposited paper of the Comparative Example, demonstrating that high barrier properties can be maintained even when subjected to folding processes such as those required for use in packaging bags and containers.

Claims

1. A paper laminate comprising a paper substrate having, on at least one side thereof, a clay coating layer, an undercoat layer, and a vapor-deposited layer made of a metal or ceramic and having a thickness of 1 nm or more and 1000 nm or less, in that order, and further having, on the vapor-deposited layer, a resin layer having a thickness of 1 μm or more and less than 15 μm, the resin layer containing a heat-sealable thermoplastic resin as its main component, the clay coating layer comprising at least one clay selected from the group consisting of kaolin, talc, and mica, the aspect ratio of the clay being 10 or more, and the clay content in the clay coating layer being 70% by mass or more and 85% by mass or less, the undercoat layer being mainly composed of a binder, the binder comprising at least one selected from polyvinyl alcohol and a urethane-based resin.

2. The paper base has a basis weight of 20 to 500 g / m ２ The paper laminate according to claim 1,

3. 3. The paper laminate according to claim 1, wherein the vapor-deposited layer is made of aluminum, silicon oxide, or aluminum oxide.

4. The paper laminate according to any one of claims 1 to 3, wherein the resin layer is the outermost layer.

5. The paper laminate according to any one of claims 1 to 4, wherein the paper substrate is the outermost layer.

6. The paper laminate according to any one of claims 1 to 5, wherein the resin layer has a thickness of 3 to 7 µm.

7. 7. The paper laminate according to claim 1, wherein the heat-sealable thermoplastic resin comprises an olefin-unsaturated carboxylic acid copolymer.

8. The paper laminate according to claim 7, wherein the olefin-unsaturated carboxylic acid copolymer is an ethylene-acrylic acid copolymer, and the content of acrylic acid units in the ethylene-acrylic acid copolymer (copolymerization ratio of acrylic acid) is 1 to 50 mol%.

9. A method for producing a paper laminate, comprising the steps of: applying a dispersion containing a resin binder and at least one clay selected from the group consisting of kaolin, talc, and mica to at least one surface of a paper substrate, and drying the coating to form a clay coat layer; applying an aqueous solution or aqueous dispersion of a binder containing one or more selected from polyvinyl alcohol and a urethane resin onto the clay coat layer, and drying the coating to form an undercoat layer; forming a vapor-deposited layer made of metal or ceramic and having a thickness of 1 nm to 1,000 nm on the undercoat layer; and applying a resin solution or resin dispersion onto the vapor-deposited layer, and drying the coating to form a resin layer containing a heat-sealable thermoplastic resin as a main component and having a thickness of 1 μm to less than 15 μm; wherein the aspect ratio of the clay is 10 or more, and the clay content in the clay coat layer is 70% by mass to 85% by mass.

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