Structure, method for producing structure, oil-resistant paper, gas barrier paper, odor barrier

Abstract

Provided are: a structure in which cracks in a layer having heat sealability are reduced, and which has excellent water vapor barrier properties, heat sealability and oxygen barrier properties; a method for producing the structure; and an oil-resistant paper, a gas barrier paper, an odor barrier paper and a packaging material which are obtained using the structure. A structure in which a layer A, a layer B, and a layer C are laminated in this order on at least one surface of a paper substrate, the layer A including at least one type selected from the group consisting of olefin polymers, styrene polymers, and polyester polymers, the layer B including a vinyl alcohol polymer, and the layer C including a polymer having a glass transition temperature of-100 DEG C to 5 DEG C (inclusive).

Description

Technical Field

[0001] The present invention relates to a structure, a method for manufacturing the structure, an oil-resistant paper, a gas barrier paper, an odor barrier paper, and a packaging material. Background Art

[0002] In the packaging of foods, medical supplies, electronic components, etc., packaging materials that impart water vapor barrier properties and gas barrier properties (especially oxygen barrier properties) to a paper substrate have been used. Patent Documents 1 and 2 describe packaging materials in which a water vapor barrier layer, a gas barrier layer, and a heat-sealing layer are sequentially provided on a paper substrate. In Patent Documents 1 and 2, as such a packaging material, a packaging material obtained by using an ethylene alcohol-based polymer in the gas barrier layer is also described.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2020-163675

[0006] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2021-20398 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] In the packaging materials described in Patent Documents 1 and 2, each layer is usually provided on a paper substrate by coating. However, when a heat-sealing layer is provided on the surface of a gas barrier layer containing an ethylene alcohol-based polymer, cracks or the like may occur in the formed coating film, and uniform heat-sealing properties may not be obtained. In addition, the present inventors have also found that cracks in the heat-sealing layer cause a decrease in water vapor barrier properties.

[0009] An object of the present invention is to provide a structure, a method for manufacturing such a structure, and an oil-resistant paper, a gas barrier paper, an odor barrier paper, and a packaging material obtained by using such a structure, in which the structure has few cracks in a layer having heat-sealing properties and excellent water vapor barrier properties, heat-sealing properties, and oxygen barrier properties.

[0010] Means for Solving the Problems

[0011] The above problems are solved by providing any one of the following solutions.

[0012] [1] A structure in which an A layer, a B layer, and a C layer are sequentially laminated on at least one side of a paper substrate, the A layer contains at least one selected from an olefin-based polymer, a styrene-based polymer, and a polyester-based polymer, the B layer contains an ethylene alcohol-based polymer, and the C layer contains a polymer having a glass transition temperature of -100°C or higher and 5°C or lower;

[0013] [2]The structure according to [1], wherein the C layer has a melting point of 120 °C or lower.

[0014] [3]The structure according to [1] or [2], wherein the A layer contains the above-mentioned olefin-based polymer, and the olefin-based polymer contains an olefin-unsaturated carboxylic acid-based polymer;

[0015] [4]The structure according to [1], [2] or [3], wherein the A layer further contains talc;

[0016] [5]The structure according to [4], wherein the content of the talc in the A layer is 1% by mass or more and 80% by mass or less;

[0017] [6]The structure according to any one of [1] to [5], wherein the vinyl alcohol-based polymer is a vinyl-modified vinyl alcohol-based polymer;

[0018] [7]The structure according to any one of [1] to [6], wherein the polymer having a glass transition temperature of -100 °C or higher and 5 °C or lower is a styrene-acrylic copolymer;

[0019] [8]The structure according to any one of [1] to [7], wherein the C layer further contains wax;

[0020] [9]The structure according to [8], wherein the content of the wax in the C layer is 0.1% by mass or more and 30% by mass or less;

[0021]

[10] The structure according to [8] or [9], wherein the wax contains paraffin wax;

[0022]

[11] The structure according to

[10] , wherein the content of the paraffin wax in the C layer is 1% by mass or more and 30% by mass or less;

[0023]

[12] The structure according to any one of [1] to

[11] , wherein the vinyl alcohol-based polymer contains two or more vinyl alcohol-based polymers having different degrees of polymerization;

[0024]

[13] The structure according to any one of [1] to

[12] , wherein the A layer contains at least two selected from the above-mentioned olefin-based polymer, styrene-based polymer and polyester-based polymer;

[0025]

[14] The structure according to any one of [1] to

[13] , wherein the C layer contains two or more polymers;

[0026]

[15] The manufacturing method of the structure according to any one of [1] to

[14] , which includes: a step of using a curtain coater to provide at least one layer of the above-mentioned A layer, B layer and C layer;

[0027]

[16] Grease-resistant paper, which contains the structure of any one of [1] to

[14] ;

[0028]

[17] Gas barrier paper, which contains the structure of any one of [1] to

[14] ;

[0029]

[18] Odor barrier paper, which contains the structure of any one of [1] to

[14] ;

[0030]

[19] Packaging material, which contains at least one selected from the grease-resistant paper of

[16] , the gas barrier paper of

[17] , and the odor barrier paper of

[18] .

[0031] Advantages of the Invention

[0032] According to the present invention, a structure, a method for manufacturing such a structure, and a grease-resistant paper, a gas barrier paper, an odor barrier paper, and a packaging material obtained by using such a structure can be provided. In the structure, the layer having heat sealability has few cracks, and the water vapor barrier property, heat sealability, and oxygen barrier property are excellent. Description of the Drawings

[0033] Figure 1 It is a schematic cross-sectional view showing the structure according to one embodiment of the present invention. Detailed Description

[0034] <Structure>

[0035] The structure according to one embodiment of the present invention is a structure in which an A layer, a B layer, and a C layer are sequentially laminated on at least one side of a paper substrate. The above A layer contains at least one selected from an olefin-based polymer, a styrene-based polymer, and a polyester-based polymer. The above B layer contains a vinyl alcohol-based polymer. The above C layer contains a polymer having a glass transition temperature of -100 °C or higher and 5 °C or lower.

[0036] In this structure, the layer having heat sealability has few cracks, and the water vapor barrier property, heat sealability, and oxygen barrier property are excellent. The reason for this structure to exhibit such an effect is not yet determined, but it can be speculated as the following reason. By using a vinyl alcohol-based resin having excellent oxygen barrier property in the B layer, the oxygen barrier property can be improved. However, since the vinyl alcohol-based polymer is a resin with large changes in swelling and shrinkage, when the C layer is provided on the B layer containing the vinyl alcohol-based polymer, it cannot follow the swelling and shrinkage of the B layer, and sometimes cracks may occur in the C layer. Therefore, by using a polymer having a glass transition temperature of -100 °C or higher and 5 °C or lower, that is, a polymer having a low glass transition temperature, in the C layer, the C layer can sufficiently follow the swelling and shrinkage of the B layer. As a result, in this structure, cracks in the C layer are suppressed, and the water vapor barrier property can be improved.

[0037] As Figure 1 shown, the structure 10 according to an embodiment of the present invention includes a paper substrate 11, an A layer 12, a B layer 13, and a C layer 14. The structure 10 is a laminate in which the A layer 12, the B layer 13, and the C layer 14 are sequentially laminated on one side of the paper substrate 11. In the structure 10, the paper substrate 11 is directly laminated with the A layer 12, the A layer 12 is directly laminated with the B layer 13, and the B layer 13 is directly laminated with the C layer 14. Further, in the structure 10, the C layer 14 forms the outermost layer. The structure 10 may be coated paper.

[0038] In an embodiment different from the Figure 1 structure 10, the A layer, the B layer, and the C layer may be sequentially laminated on both sides of the paper substrate. The A layer, the B layer, and the C layer are sequentially laminated on one side of the paper substrate, and one or more of the A layer, the B layer, the C layer, or other layers may be laminated on the other side of the paper substrate. One or more of the interfaces between the paper substrate and the A layer, between the A layer and the B layer, between the B layer and the C layer, and the surface of the C layer may have other layers. Hereinafter, each constituent member of the structure will be described in detail.

[0039] (Paper Substrate)

[0040] As the paper substrate, ordinary paper mainly composed of plant-derived pulp can be used. It should be noted that in this specification, "main component" means the component with the highest content based on mass. In addition to pulp, the paper substrate may contain sizing agents, fillers, paper strength enhancers, yield improvers, pH regulators, drainage improvers, water resistance agents, softeners, antistatic agents, defoamers, slime control agents, dyes, pigments, etc.

[0041] Examples of the paper substrate include kraft paper, fine paper, medium paper, alkaline paper, paperboard, cellophane, semi-cellophane, parchment paper, etc., and fine paper is preferred.

[0042] As the basis weight (mass per unit area) of the paper substrate, it is preferably 20 g / m 2 or more and 500 g / m 2 or less, more preferably 30 g / m 2 or more and 300 g / m 2 or less, further preferably 40 g / m 2 or more and 200 g / m 2 or less, still more preferably 50 g / m 2 or more and 100 g / m 2 or less.

[0043] As the density of the paper substrate, it is preferably 0.5 g / cm 3 or more and 1.2 g / cm 3 or less, more preferably 0.6 g / cm3 1.0 g / cm³ or more 3 and below.

[0044] The paper substrate can be manufactured by known methods. Additionally, commercially available products can be used as the paper substrate.

[0045] (Layer A)

[0046] Layer A is a layer present between the paper substrate and Layer B. Layer A can be directly laminated on the paper substrate.

[0047] (Polymer (a))

[0048] Layer A contains at least one selected from olefin polymers, styrene polymers, and polyester polymers (hereinafter also referred to as "polymer (a)"). By making Layer A contain such a polymer (a) with relatively high hydrophobicity, Layer A can exhibit good water vapor barrier properties, etc. Polymer (a) is preferably the main component of Layer A. One kind or two or more kinds of polymer (a) can be used.

[0049] (Olefin polymer)

[0050] An olefin polymer is a polymer containing olefins as monomers. As the olefin polymer, it can be a polymer of one kind or two or more kinds of olefins, that is, a polyolefin, or a copolymer of one kind or two or more kinds of olefins and one kind or two or more kinds of other monomers other than olefins.

[0051] Examples of the olefin include α-olefins such as ethylene, propylene, n-butene, and isobutene.

[0052] Examples of the other monomers other than the olefins constituting the olefin polymer include unsaturated carboxylic acid compounds, diene compounds, vinyl ethers, vinyl halides, vinylidene halides, allyl compounds, etc., and unsaturated carboxylic acid compounds are preferred.

[0053] An unsaturated carboxylic acid compound refers to a compound in which a hydrogen atom of the carboxyl group of an unsaturated carboxylic acid is replaced by another atom or another group. That is, the unsaturated carboxylic acid compound includes not only unsaturated carboxylic acids but also unsaturated carboxylic acid esters, unsaturated carboxylates, etc. The unsaturated carboxylic acid compound is preferably a monomer having a carboxyl group or its salt.

[0054] Examples of the unsaturated carboxylic acid compound include unsaturated carboxylic acids such as (meth)acrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and butene tricarboxylic acid; unsaturated carboxylic acid esters such as (meth)acrylic acid methyl ester, (meth)acrylic acid ethyl ester, itaconic acid monoethyl ester, and fumaric acid monobutyl ester; unsaturated carboxylates such as (meth)acrylic acid sodium salt, etc. Note that "(meth)acrylic acid" refers to acrylic acid and methacrylic acid.

[0055] As an olefin-based polymer, a polyolefin and an olefin-unsaturated carboxylic acid copolymer are preferred, and an olefin-unsaturated carboxylic acid copolymer is more preferred. The olefin-unsaturated carboxylic acid copolymer refers to a copolymer of one or more olefins and one or more unsaturated carboxylic acid compounds. Among the olefin-unsaturated carboxylic acid copolymers, a copolymer of one or more olefins and one or more unsaturated carboxylic acids, that is, an olefin-unsaturated carboxylic acid copolymer, is preferred.

[0056] Examples of the olefin-unsaturated carboxylic acid copolymer include ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid methyl ester copolymer, ethylene-(meth)acrylic acid ethyl ester copolymer, ethylene-(meth)acrylic acid butyl ester copolymer, etc. Among these, ethylene-(meth)acrylic acid copolymer is preferred. In addition, a copolymer of ethylene and an unsaturated carboxylic acid compound is also preferred. These copolymers can be further copolymerized with other monomers that can copolymerize with olefins and unsaturated carboxylic acid compounds.

[0057] (Styrene-based polymer)

[0058] A styrene-based polymer is a polymer containing a styrene-based compound as a monomer. The styrene-based compound refers to styrene and a compound in which a hydrogen atom of styrene is replaced by another atom or another group. Examples of the styrene-based compound include styrene, α-methylstyrene, vinyltoluene, chlorostyrene, etc., and styrene is preferred.

[0059] Examples of the styrene-based copolymer include polystyrene, styrene-acrylic acid copolymer, styrene-butadiene copolymer, etc.

[0060] The styrene-acrylic acid copolymer is a copolymer of the above-mentioned styrene-based compound and an acrylic acid-based compound. The acrylic acid-based compound refers to (meth)acrylic acid and a compound in which a hydrogen atom of the carboxyl group constituting (meth)acrylic acid is replaced by another atom or another group. Examples of the acrylic acid-based compound include (meth)acrylic acid, (meth)acrylic acid ester, (meth)acrylate, etc. Examples of the (meth)acrylic acid ester include (meth)acrylic acid alkyl esters such as (meth)acrylic acid methyl ester and (meth)acrylic acid ethyl ester. Examples of the (meth)acrylate include (meth)sodium acrylate, etc.

[0061] Examples of the styrene-acrylic acid copolymer include styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid ester copolymer, styrene-(meth)acrylate copolymer, etc. The styrene-acrylic acid copolymer can be further copolymerized with other monomers.

[0062] Styrene-butadiene copolymer is a copolymer of the above styrene compounds and butadiene compounds. Butadiene compounds refer to butadiene and compounds formed by substituting hydrogen atoms of butadiene with other atoms or other groups. Examples of butadiene compounds include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, etc., and 1,3-butadiene is preferred.

[0063] As the styrene-butadiene copolymer, styrene-butadiene copolymer is preferred. The styrene-butadiene copolymer may be further copolymerized with other monomers.

[0064] As the styrene polymer, styrene-acrylic copolymer and styrene-butadiene copolymer are preferred.

[0065] (Polyester polymer)

[0066] Polyester polymer is a polymer formed by polymerizing one or more monomers through ester bonds. Examples of polyester polymers include polyethylene terephthalate, polybutylene terephthalate, poly(1,3-propanediol terephthalate), polyethylene naphthalate, polyglycolic acid, aromatic liquid crystal polyester, etc.

[0067] Among the polymers (a), from the viewpoints of water vapor barrier property, etc., olefin polymers and styrene polymers are preferred, and olefin polymers are more preferred.

[0068] As the lower limit of the content of the polymer (a) in the A layer, 20% by mass is preferred, 40% by mass is more preferred, and it may be 60% by mass, 70% by mass, 80% by mass or 90% by mass. On the other hand, as the upper limit of its content, it may be 100% by mass, and it may be 99% by mass, 90% by mass, 80% by mass or 60% by mass.

[0069] (Other components in the A layer, etc.)

[0070] The A layer preferably contains a layered inorganic compound. By making the A layer contain a layered inorganic compound, the water vapor barrier property of the structure can be further improved, etc.

[0071] Examples of the layered inorganic compound include mica, mica, talc, montmorillonite, kaolinite, vermiculite, montmorillonite, lithium montmorillonite, sericite, acid clay, etc. From the viewpoints of water vapor barrier property, etc., talc is preferred as the layered inorganic compound used in the A layer. One or more kinds of layered inorganic compounds can be used.

[0072] When the A layer contains a layered inorganic compound such as talc, the lower limit of the content of the layered inorganic compound in the A layer is preferably 1% by mass, more preferably 5% by mass, and still more preferably 10% by mass, 20% by mass, or 30% by mass. On the other hand, as the upper limit of its content, it is preferably 80% by mass, more preferably 70% by mass, and still more preferably 60% by mass, 50% by mass, or 40% by mass. By setting the content of the layered inorganic compound in the A layer within the above range, the water vapor barrier property and the like can be further improved.

[0073] The A layer may further contain other components in addition to the polymer (a) and the layered inorganic compound. Examples of other components include resins other than the polymer (a), dispersants, surfactants, defoamers, dyes, thickeners, and the like. Among them, the total content of the polymer (a) and any layered inorganic compound in the A layer is preferably 90% by mass or more, more preferably 95% by mass or more, or 99% by mass or more. In addition, in the A layer, the content of the cationic resin is sometimes preferably 10% by mass or less, and sometimes more preferably 5% by mass or less, 1% by mass or less, or 0.5% by mass or less.

[0074] As the mass per unit area of one layer of the A layer, it is preferably 1 g / m 2 or more and 100 g / m 2 or less, more preferably 3 g / m 2 or more and 50 g / m 2 or less, still more preferably 5 g / m 2 or more and 30 g / m 2 or less, even more preferably 7 g / m 2 or more and 20 g / m 2 or less, particularly preferably 9 g / m 2 or more and 15 g / m 2 or less. By making the mass per unit area of one layer of the A layer above the above lower limit, the water vapor barrier property and the like can be further improved. On the other hand, by making the mass per unit area of one layer of the A layer below the above upper limit, the thinning of the structure body and the like can be achieved.

[0075] (B layer)

[0076] The B layer is a layer present between the A layer and the C layer. The B layer may be a layer directly laminated on the A layer.

[0077] (Polymer (b))

[0078] The B layer contains a vinyl alcohol-based polymer (hereinafter also referred to as "polymer (b)"). By making the structure body have a B layer containing the polymer (b), excellent oxygen barrier properties can be exhibited. The polymer (b) is preferably the main component of the B layer. The polymer (b) is a polymer having a vinyl alcohol unit (-CH2 Polymers of (-CHOH-). Polymer (b) is usually obtained by saponification of a vinyl ester polymer. One or more than two kinds of polymer (b) can be used.

[0079] As the lower limit of the saponification degree of polymer (b), it is sometimes preferably 80 mol%, more preferably 90 mol%, and further preferably 95 mol%, 97 mol%, 98 mol% or 99 mol%. By making the saponification degree above the above lower limit, the oxygen barrier property etc. can be further improved. On the other hand, the upper limit of the saponification degree can be 100 mol%, and can be 99.9 mol%. The saponification degree of polymer (b) is measured according to JIS K 6726:1994.

[0080] The viscosity-average degree of polymerization of polymer (b) is preferably 200 or more and 3,000 or less. The lower limit of the viscosity-average degree of polymerization can be 300, can be 500, can be 800. On the other hand, the upper limit of the viscosity-average degree of polymerization can be 2,500, can be 2,000, can be 1,200, can be 800. By making the viscosity-average degree of polymerization of polymer (b) within the above range, the oxygen barrier property etc. can be further improved, and the coatability when setting the B layer by coating, the strength of the B layer etc. are also optimized.

[0081] The viscosity-average degree of polymerization of polymer (b) is measured according to JIS K 6726:1994. Specifically, the intrinsic viscosity [η] (l / g) of polymer (b) is measured in water at 30 °C, and using the value of this intrinsic viscosity [η], the viscosity-average degree of polymerization P is calculated by the following formula. It should be noted that when the saponification degree of polymer (b) is less than 99.5 mol%, after saponifying until the saponification degree reaches 99.5 mol% or more, the intrinsic viscosity [η] is measured.

[0082] P = ([η] × 10 4 / 8.29) (1 / 0.62)

[0083] Polymer (b) may have monomer units derived from other monomers in addition to vinyl alcohol units and vinyl ester units. Examples of other monomers include α-olefins such as ethylene, propylene, 1-butene, and isobutene; (meth)acrylic acid and its salts; (meth)acrylates; (meth)acrylamides; (meth)acrylamide derivatives such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, diacetone(meth)acrylamide, (meth)acrylamidopropylsulfonic acid and its salts, (meth)acrylamidopropyldimethylamine and its salts or quaternary salts, and N-hydroxymethyl(meth)acrylamide and its derivatives; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether, dodecyl vinyl ether, and stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; vinylidene dihalides such as vinylidene dichloride and vinylidene difluoride; allyl compounds such as allyl acetate and allyl chloride; unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and fumaric acid and their salts or esters; vinylsilyl compounds such as vinyltrimethoxysilane; and isopropyl acetate, etc.

[0084] As other monomers, α-olefins are preferred, and ethylene is more preferred. That is, polymer (b) is preferably an α-olefin-modified vinyl alcohol-based polymer, and more preferably an ethylene-modified vinyl alcohol-based polymer. By using such a modified vinyl alcohol-based polymer, the oxygen barrier property and the like can be further improved.

[0085] As the lower limit of the content ratio of the α-olefin unit in the α-olefin-modified vinyl alcohol-based polymer relative to all monomer units, it is preferably 0.1 mol%, more preferably 1 mol%, and may be 2 mol%, 5 mol%, or 7 mol%. On the other hand, as the upper limit of this content ratio, it may be 30 mol%, and may be 20 mol%, 15 mol%, or 12 mol%. It should be noted that the content ratio of the α-olefin unit relative to all monomer units is also referred to as the α-olefin modification amount. For example, the content ratio of the ethylene unit relative to all monomer units is also referred to as the ethylene modification amount.

[0086] The total content ratio of the vinyl alcohol unit, vinyl ester unit, and any α-olefin unit in polymer (b) relative to all monomer units is preferably 95 mol% or more, more preferably 99 mol% or more, and may be 100 mol%.

[0087] Two or more kinds of polymer (b) can be used in combination. For example, polymer (b) may include two or more kinds of vinyl alcohol polymers having different degrees of polymerization. The vinyl alcohol polymer having a low degree of polymerization has a low viscosity and excellent coatability. On the other hand, the vinyl alcohol polymer having a high degree of polymerization is excellent in strength and the like. Therefore, by using in combination two or more kinds of vinyl alcohol polymers having different degrees of polymerization, their balance can be achieved. It should be noted that the vinyl alcohol polymer composed of two or more kinds having different degrees of polymerization may have two or more peaks in the molecular weight distribution curve obtained by GPC (gel permeation chromatography) analysis.

[0088] As the lower limit of the content of polymer (b) in the B layer, it is preferably 70% by mass, more preferably 80% by mass, and still more preferably 90% by mass. By setting the content of polymer (b) in the B layer to be above the above lower limit, the oxygen barrier property and the like can be further improved. On the other hand, as the upper limit of its content, it may be 100% by mass, may be 99% by mass, or may be 97% by mass.

[0089] (Other components in the B layer, etc.)

[0090] The B layer preferably contains a layered inorganic compound. By making the B layer contain a layered inorganic compound, the oxygen barrier property of the structure can be further improved.

[0091] Examples of the layered inorganic compound include the same substances as those exemplified in the description of the A layer. From the viewpoint of oxygen barrier property and the like, mica is preferably used as the layered inorganic compound in the B layer. One kind or two or more kinds of layered inorganic compounds can be used.

[0092] When the B layer contains a layered inorganic compound such as mica, the lower limit of the content of the layered inorganic compound in the B layer is preferably 1% by mass, more preferably 3% by mass. On the other hand, as the upper limit of its content, it is preferably 30% by mass, more preferably 20% by mass, and still more preferably 10% by mass. By setting the content of the layered inorganic compound in the B layer within the above range, the oxygen barrier property and the like can be further improved.

[0093] The B layer may further contain other components in addition to polymer (b) and the layered inorganic compound. Examples of the other components include resins other than polymer (b), dispersants, surfactants, defoamers, dyes, thickeners, and the like. Among them, the total content of polymer (b) and any layered inorganic compound in the B layer is preferably 90% by mass or more, more preferably 95% by mass or more or 99% by mass or more.

[0094] As the mass per unit area of one layer of the B layer, it is preferably 0.3 g / m 2 or more and 20 g / m 2Hereinafter, it is more preferably 0.5 g / m 2 or more and 10 g / m 2 or less, and further preferably 1 g / m 2 or more and 7 g / m 2 or less, and even more preferably 2 g / m 2 or more and 5 g / m 2 or less. By making the mass per unit area of one layer of the B layer above the above lower limit, the oxygen barrier property and the like can be further improved. On the other hand, by making the mass per unit area of one layer of the B layer below the above upper limit, the thinning of the structure body and the like can be achieved.

[0095] (C layer)

[0096] The C layer is a layer existing on the side of the B layer opposite to the A layer. The C layer may be a layer directly laminated on the B layer. In addition, the C layer may be the outermost layer.

[0097] (Polymer (c))

[0098] The C layer contains a polymer (hereinafter also referred to as "polymer (c)") having a glass transition temperature of -100°C or more and 5°C or less. Polymer (c) is preferably the main component of the C layer. One kind or two or more kinds of polymer (c) can be used.

[0099] The upper limit of the glass transition temperature of polymer (c) is 5°C, preferably 3°C, more preferably 2°C, further preferably 1°C, 0°C, -1°C, -3°C, -5°C or -10°C. By making the glass transition temperature of polymer (c) below the above upper limit, the cracks in the C layer are suppressed, and the water vapor barrier property can be improved. On the other hand, the lower limit of this glass transition temperature is -100°C, and it can be -80°C, and it can be -60°C, -50°C or -40°C.

[0100] The upper limit of the melting point of polymer (c) can be 120°C, preferably 100°C, more preferably 85°C, further preferably 80°C, even more preferably 75°C, 70°C or 65°C. By making the melting point of polymer (c) below the above upper limit, the heat sealability can be improved. The melting point of polymer (c) can be lower than 80°C. On the other hand, the lower limit of this melting point is preferably 30°C, more preferably 40°C, further preferably 50°C.

[0101] The glass transition temperature and melting point of polymer (c) are measured by differential scanning calorimetry (DSC). Specifically, it can be measured by the method described in the examples.

[0102] As the polymer (c), there is no particular limitation as long as it is a polymer having a glass transition temperature of -100°C or higher and 5°C or lower. As the polymer (c), for example, polymers among the olefin-based polymers, styrene-based polymers, and polyester-based polymers described as the polymer (a) and having a glass transition temperature of -100°C or higher and 5°C or lower can be used.

[0103] As the polymer (c), an olefin-based polymer and a styrene-based polymer are preferred, a styrene-based polymer is more preferred, a styrene-acrylic copolymer and a styrene-butadiene copolymer are further preferred, a styrene-acrylic copolymer is still further preferred, and a styrene-(meth)acrylate copolymer is particularly preferred. Among the olefin-based polymers, an olefin-unsaturated carboxylic acid copolymer is preferred, an olefin-unsaturated carboxylic acid copolymer is more preferred, and an ethylene-(meth)acrylic acid copolymer is further preferred. As the polymer (c), a copolymer of a hydrocarbon monomer and an acrylic compound is also preferred. Examples of the hydrocarbon monomer include the above-mentioned olefins and styrene-based compounds. By using such a polymer as the polymer (c), the water vapor barrier property, heat sealability, etc. can be further improved. The specific forms of the olefin-based polymer and the styrene-based polymer as these polymers (c) are the same as those described above for the olefin-based polymer and the styrene-based polymer in the polymer (a).

[0104] In one embodiment of the present invention, the polymer (a) and the polymer (c) may be the same type of polymer or different types of polymers. For example, in order to optimize the functions of the A layer and the C layer, different types of polymers can be used for the polymer (a) and the polymer (c).

[0105] As the lower limit of the content of the polymer (c) in the C layer, 50% by mass is preferred, 60% by mass is more preferred, 70% by mass is further preferred, 80% by mass, 85% by mass, or 90% by mass is still further preferred. On the other hand, as the upper limit of its content, 100% by mass is preferred, 99% by mass is more preferred, and 95% by mass is further preferred.

[0106] (Other components in the C layer, etc.)

[0107] The C layer preferably contains wax. By making the C layer contain wax, the water vapor barrier property, etc. can be further improved. In addition, by making the C layer contain wax, the oil resistance, etc. tend to be improved.

[0108] The wax preferably contains paraffin wax. As the paraffin wax, for example, paraffin wax having a normal-chain alkane with 20 or more and 40 or less carbon atoms and a molecular weight of 300 or more and 500 or less as the main component can be used. The paraffin wax can be a commercially available product.

[0109] When the C layer contains wax, as the lower limit of the content of the wax in the C layer, it can be, for example, 0.1% by mass, preferably 1% by mass, more preferably 3% by mass, and still more preferably 5% by mass. On the other hand, as the upper limit of its content, it can be, for example, 30% by mass, preferably 20% by mass, more preferably 15% by mass, and still more preferably 12% by mass. By setting the content of the wax in the C layer within the above range, the water vapor barrier property and the like can be further improved. In addition, when the C layer contains paraffin wax, as the lower limit of the content of the paraffin wax in the C layer, it can be, for example, 0.1% by mass, preferably 1% by mass, more preferably 3% by mass, and still more preferably 5% by mass. On the other hand, as the upper limit of its content, it can be, for example, 30% by mass, preferably 20% by mass, more preferably 15% by mass, and still more preferably 12% by mass. By setting the content of the paraffin wax in the C layer within the above range, the water vapor barrier property and the like can be further improved.

[0110] The C layer may further contain other components in addition to the polymer (c) and the wax. Examples of the other components include resins other than the polymer (c), dispersants, surfactants, defoamers, dyes, thickeners, and the like. The C layer may contain two or more polymers. The two or more polymers that the C layer may contain may be a combination of the polymer (c) and other polymers, or may be two or more polymers (c). Among them, the total content of the polymer (c) and any wax in the C layer is preferably 90% by mass or more, more preferably 95% by mass or more or 99% by mass or more.

[0111] In particular, the C layer preferably substantially does not contain a vinyl alcohol-based polymer. The content of the vinyl alcohol-based polymer in the C layer is preferably 10% by mass or less, more preferably 3% by mass or less, still more preferably 1% by mass or less, and even more preferably 0.1% by mass or less. In this way, by reducing the content of the vinyl alcohol-based polymer in the C layer, when the C layer is formed by coating, an increase in the viscosity of the coating liquid for forming the C layer can be suppressed, and the C layer can be effectively formed.

[0112] The C layer preferably has a melting point of 120°C or lower. The upper limit of the melting point of the C layer is preferably 100°C, more preferably 85°C, still more preferably 80°C, and even more preferably 75°C, 70°C, or 65°C. By setting the melting point of the C layer below the above upper limit, the heat sealability can be improved. The melting point of the C layer may be lower than 80°C. On the other hand, the lower limit of this melting point is preferably 30°C, more preferably 40°C, and still more preferably 50°C. The melting point of the C layer is measured by differential scanning calorimetry (DSC). It should be noted that when one of the components (the polymer (c) and other optional components) contained in the C layer has a specified melting point T, generally the C layer also has the specified melting point T.

[0113] The mass per unit area of the first layer of the C layer is preferably 1 g / m 2 or more and 100 g / m 2 or less, more preferably 3 g / m 2 or more and 50 g / m 2 or less, still more preferably 5 g / m 2 or more and 30 g / m 2 or less, even more preferably 7 g / m 2 or more and 20 g / m 2 or less, particularly preferably 9 g / m 2 or more and 15 g / m 2 or less. By making the mass per unit area of the first layer of the C layer above the above-mentioned lower limit, the water vapor barrier property and the like can be further improved. On the other hand, by making the mass per unit area of the first layer of the C layer below the above-mentioned upper limit, the thinning of the structure body and the like can be achieved.

[0114] This structure can be suitably used as greaseproof paper, gas barrier paper, odor barrier paper, packaging materials, etc. This structure can also be used in a state where it is formed into a predetermined shape (for example, a bag shape) by heat-sealing the C layers to each other. As the heat-sealing method, there is no particular limitation, and known methods can be used. Heat-sealing can be performed, for example, by a hot plate heat-sealing machine, a pulse sealer, an ultrasonic sealer, a friction heat sealer, a dielectric heating sealer, etc.

[0115] <Manufacturing method of the structure>

[0116] The method for manufacturing the structure according to one embodiment of the present invention is not particularly limited. Typically, it can be manufactured by sequentially providing the A layer, the B layer, and the C layer on a paper substrate by coating. Specifically, for example, the A layer is provided by coating a coating liquid for forming the A layer on the surface of the paper substrate and drying it. Next, the B layer is provided by coating a coating liquid for forming the B layer on the surface of the A layer and drying it. Next, the C layer is provided by coating a coating liquid for forming the C layer on the surface of the B layer and drying it, whereby the structure can be obtained. Each time the coating liquid is coated, drying may not be performed, and a simultaneous multi-layer coating method can be adopted.

[0117] The coating of each coating liquid can be performed by existing known methods. Coating can be performed using, for example, a doctor blade coater, a rod coater, an air knife coater, a slot die coater, an intaglio coater, a micro intaglio coater, a gravure coater, a curtain coater, etc. Among these, it is preferably performed using a curtain coater.

[0118] That is, the manufacturing method of the structure according to one embodiment of the present invention includes: a step of using a curtain coater to provide at least one of the A layer, the B layer, and the C layer. In this manufacturing method, it is preferable to use a curtain coater to provide all of the A layer, the B layer, and the C layer.

[0119] As a method for drying the applied coating liquid, there is no particular limitation, and for example, a hot air dryer, an infrared dryer, a gas spray gun, a hot plate, etc. can be used for drying.

[0120] As the solvent or dispersion medium of the coating liquid for forming each layer, there is no particular limitation, and water, organic solvents (ethanol, isopropyl alcohol, methyl ethyl ketone, toluene, etc.) can be used, and water is preferably used.

[0121] The solid content amount (solid content concentration) of the coating liquid for forming each layer is not particularly limited. For example, it can be set to 3% by mass or more and 70% by mass or less, or it can be set to 5% by mass or more and 60% by mass or less, or it can be set to 10% by mass or more and 50% by mass or less.

[0122] <Greaseproof paper>

[0123] The greaseproof paper according to one embodiment of the present invention includes the structure according to one embodiment of the present invention. The greaseproof paper according to one embodiment of the present invention may be composed of the structure according to one embodiment of the present invention.

[0124] This greaseproof paper has excellent water vapor barrier properties and oxygen barrier properties, and also has good adhesion in the case of the presence of a heat-sealed portion. This greaseproof paper is suitably used as, for example, a packaging material used when providing foods high in oil content such as French fries and fried foods; a packaging material for wrapping butter, etc.; cooking paper used when baking bread, cakes, etc.

[0125] The oil resistance degree (KIT value) of this greaseproof paper is preferably 5 or more, more preferably 6 or 7 or more. The oil resistance degree is set to the value when measuring the surface of layer C by the TAPPI UM-557 method (kit method).

[0126] <Gas barrier paper>

[0127] The gas barrier paper according to one embodiment of the present invention includes the structure according to one embodiment of the present invention. The gas barrier paper according to one embodiment of the present invention may be composed of the structure according to one embodiment of the present invention.

[0128] This gas barrier paper has excellent oxygen barrier properties and water vapor barrier properties, and also has good adhesion in the case of the presence of a heat-sealed portion. This gas barrier paper can be suitably used as, for example, a packaging material for foods, pesticides, pharmaceuticals, cosmetics, medical products, electronic components, clothing, etc.

[0129] As the oxygen permeability of this gas barrier paper, it is preferably 10 cc / m 2 ·24 h or less, more preferably 5 cc / m 2 ·24 h or less, still more preferably 3 cc / m2 ·Below 24 h. The oxygen permeability is set to the value measured under the conditions of 23 °C and 65% RH.

[0130] <Odor barrier paper>

[0131] The odor barrier paper according to one embodiment of the present invention includes the structure according to one embodiment of the present invention. The odor barrier paper according to one embodiment of the present invention may be composed of the structure according to one embodiment of the present invention.

[0132] The odor barrier paper has excellent oxygen barrier properties and water vapor barrier properties, and also has good sealing properties in the presence of a heat-sealed portion. The odor barrier paper can be suitably used as a packaging material for scented items such as snacks, tea, coffee, spices, tobacco, cosmetics, and fragrances. The odor barrier paper is also useful as a packaging material for other foods, pesticides, pharmaceuticals, clothing, etc.

[0133] Generally, when the oxygen permeability is low, there is a tendency for the property of masking the fragrance to become higher. As the oxygen permeability of the odor barrier paper, it is preferably 10 cc / m 2 ·Below 24 h, more preferably 5 cc / m 2 ·Below 24 h, further preferably 3 cc / m 2 ·Below 24 h.

[0134] <Packaging material>

[0135] The packaging material according to one embodiment of the present invention includes at least one selected from the greaseproof paper according to one embodiment of the present invention, the gas barrier paper according to one embodiment of the present invention, and the odor barrier paper according to one embodiment of the present invention. The packaging material according to one embodiment of the present invention may include the structure according to one embodiment of the present invention.

[0136] The packaging material has excellent water vapor barrier properties and oxygen barrier properties, and also has good sealing properties in the presence of a heat-sealed portion. The packaging material can be suitably used as a packaging material for foods, pesticides, pharmaceuticals, cosmetics, medical products, electronic components, clothing, etc.

[0137] Examples

[0138] Hereinafter, the present invention will be described more specifically using examples, but the present invention is not limited to these examples at all.

[0139] [Production Example 1] Production of PVA-1

[0140] 1,050 g of vinyl acetate and 1,950 g of methanol were charged into a reaction vessel equipped with a stirrer, a nitrogen inlet, and an initiator addition port. After heating to 60 °C, nitrogen replacement of the system was carried out by nitrogen bubbling for 30 minutes. After adjusting the temperature inside the reaction vessel to 60 °C, 1.6 g of azobisisobutyronitrile (AIBN) as a polymerization initiator was added, and polymerization was started. When the polymerization rate reached 50% after 3 hours, cooling was carried out to stop the polymerization. Unreacted vinyl acetate monomer was removed, and methanol was added to obtain a methanol solution of polyvinyl acetate (PVAc) (concentration: 30% by mass). To 400 g of this methanol solution of PVAc (120 g of PVAc in the solution), 55.8 g of a 10% methanol solution of NaOH (molar ratio [MR] of the amount of NaOH to the vinyl acetate unit in PVAc was 0.10) was added, and saponification was carried out at 40 °C. After adding the NaOH methanol solution, the gelled product was crushed with a crusher, and the saponification reaction was carried out for a total of 1 hour. Thereafter, 1,000 g of methyl acetate was added to neutralize the remaining base. After confirming the end of neutralization using a phenolphthalein indicator, filtration was carried out, 1,000 g of methanol was added to the obtained white solid, and it was left to wash at room temperature for 3 hours. After repeating the above washing operation 3 times, centrifugal dewatering was carried out, and the obtained solid was placed in a dryer at 70 °C for 2 days for drying, whereby a vinyl alcohol-based polymer (PVA-1) was obtained.

[0141] [Production Example 2] Production of PVA-2

[0142] 1,440 g of vinyl acetate and 1,560 g of methanol were charged into a 5 L pressurized reaction vessel equipped with a stirrer, a nitrogen inlet, an ethylene inlet, and an initiator addition port. After heating to 60 °C, nitrogen replacement of the system was carried out by nitrogen bubbling for 30 minutes. Then, ethylene was introduced in such a way that the reaction vessel pressure became 7.8 kg / cm 2 . After adjusting the temperature inside the reaction vessel to 60 °C, 2.0 g of AIBN as a polymerization initiator was added, and polymerization was started. During the polymerization, ethylene was introduced, and the reaction vessel pressure was maintained at 7.8 kg / cm 2, the polymerization temperature was maintained at 60 °C. When the polymerization rate reached 50% after 3 hours, cooling was carried out to stop the polymerization. The reaction tank was opened and ethylene was removed, and then nitrogen was further bubbled in. Next, the unreacted vinyl acetate monomer was removed under reduced pressure, and methanol was added to obtain a methanol solution (concentration: 30% by mass) of ethylene-vinyl acetate copolymer. To 400 g of this methanol solution of ethylene-vinyl acetate copolymer (ethylene-vinyl acetate copolymer in the solution: 120 g), 55.8 g of a 10% methanol solution of NaOH (molar ratio [MR] of the amount of NaOH to the vinyl acetate units in the ethylene-vinyl acetate copolymer was 0.10) was added, and saponification was carried out at 40 °C. After adding the NaOH methanol solution, the gel was crushed with a crusher, and the saponification reaction was carried out for a total of 1 hour. Thereafter, 1,000 g of methyl acetate was added to neutralize the remaining alkali. After confirming the end of neutralization using a phenolphthalein indicator, filtration was carried out, 1,000 g of methanol was added to the obtained white solid, and it was left to wash at room temperature for 3 hours. After repeating the above washing operation 3 times, centrifugal dewatering was carried out, and the obtained solid was placed in a dryer at 70 °C for 2 days to obtain an ethylene-modified vinyl alcohol-based polymer (PVA-2).

[0143] [Production Example 3-5] Production of PVA-3 to PVA-5

[0144] Regarding the polymerization conditions and saponification conditions described in Table 1, as shown in Table 1, except for this, each ethylene-modified vinyl alcohol-based polymer (PVA-3 to PVA-5) was produced by the same method as in Production Example 2.

[0145] The viscosity-average degree of polymerization, saponification degree, and ethylene modification amount (ethylene unit content) of the obtained PVA-1 to PVA-5 were measured. The measurement results are shown in Table 1.

[0146] Each polymer other than PVA-1 to PVA-5 used in the examples and comparative examples is as follows.

[0147] (Polymer (a))

[0148] Polymer a1: "MFP1883" (manufactured by Michelman, Inc.), olefin-acrylic copolymer emulsion, solid content: 27% by mass

[0149] Polymer a2: "OP-671" (manufactured by Lion Corporation), styrene-acrylate copolymer emulsion, solid content: 48% by mass

[0150] Polymer a3: "CHEMIPEARL S-100" (manufactured by Mitsui Chemicals, Inc.), ethylene-methacrylic acid copolymer emulsion, solid content: 27% by mass

[0151] Polymer a4: "Tykote1004" (manufactured by Mallard Creek Polymers, Inc.), styrene-butadiene copolymer emulsion

[0152] (Polymer (b))

[0153] PU-1: "TAKELAC WPB-341" (manufactured by Mitsui Chemicals, Inc.), polyurethane emulsion, solid content 30 mass%

[0154] (Polymer (c))

[0155] Polymer c1: "VAPCT2200" (manufactured by Michelman, Inc.), styrene-acrylate copolymer emulsion, solid content 48 mass%, glass transition temperature -32.3 °C, melting point 60.4 °C

[0156] Polymer c2: "498340R" (manufactured by Michelman, Inc.), ethylene-acrylic acid copolymer emulsion, solid content 40 mass%, glass transition temperature -0.5 °C, melting point 78.7 °C Polymer c3: "OP-671" (manufactured by Lion Corporation), styrene-butadiene copolymer emulsion, solid content 48 mass%, glass transition temperature 2.8 °C, melting point 47.0 °C

[0157] Polymer c4: "CHEMIPEARL S-100" (manufactured by Mitsui Chemicals, Inc.), ethylene-methacrylic acid copolymer emulsion, solid content 27 mass%, glass transition temperature 23.9 °C, melting point 86.9 °C

[0158] (Method for measuring glass transition temperature and melting point)

[0159] The glass transition temperature and melting point of Polymer (C) are measured by the following method.

[0160] Approximately 3 mg of the measurement sample is filled into a sample pan, and the glass transition temperature and melting point are measured using a DSC Q2000 (manufactured by TA Instruments, Inc.) device. The sample is heated from 30 °C to 200 °C, then cooled to -90 °C and held for 5 minutes, and then heated to 200 °C. Both heating and cooling are carried out at 10 °C / minute.

[0161] [Example 1] Fabrication of the structure

[0162] As the paper substrate, high-quality paper with a basis weight of 70.5 g / m 2 is prepared. On one side of this paper substrate, with a dry mass of 10.0 g / m 2The coating amount of "MFP1883", which is an emulsion of polymer a1, is applied as a coating liquid for forming the A layer, and dried to set the A layer. Then, on the surface of the A layer, an aqueous solution of PVA-1 (solid content: 10% by mass) is applied at a coating amount of 3.0 g / m 2 as a coating liquid for forming the B layer, and dried to set the B layer. Then, on the surface of the B layer, "VAPCT2200", which is an emulsion of polymer c1, is applied at a coating amount of 10.0 g / m 2 as a coating liquid for forming the C layer, and dried to set the C layer. Through the above operations, the structure of Example 1 is obtained. The coating of any layer among the A layer, B layer, and C layer is performed using a wire bar. For the obtained structure and the coating liquid for forming the C layer used, the following evaluations are carried out. The evaluation results are shown in Table 3.

[0163] [Evaluation]

[0164] (1) Viscosity of the coating liquid for forming the C layer

[0165] After adjusting the temperature of the coating liquid for forming the C layer in a room at 20°C, the viscosity of the coating liquid for forming the C layer is measured using a B-type viscometer under the condition of 60 rpm.

[0166] (2) Viscosity stability of the coating liquid for forming the C layer

[0167] The solid content of the coating liquid for forming the C layer is adjusted to 22% by mass, and the fluidity when stirring this coating liquid is evaluated according to the following criteria.

[0168] A: Flows without thickening.

[0169] B: Thickens but still flows.

[0170] C: The fluidity is impaired (shows a paste-like state).

[0171] (3) Oxygen permeability (gas barrier property)

[0172] For the oxygen permeability of the structure, it is measured using "OX-TRAN2 / 21" manufactured by MOCON under the conditions of 23°C and 65% RH.

[0173] (4) Water vapor transmission rate (water vapor barrier property)

[0174] For the water vapor transmission rate of the structure, according to JIS Z 2080, it is measured using the cup method under the conditions of a temperature of 40 ± 0.5°C and a relative humidity difference of 90 ± 2%.

[0175] (5) Cracks in the C layer

[0176] Regarding the presence and degree of cracks in the C layer of the structure, visual inspection is carried out according to the following criteria for evaluation.

[0177] A + : No cracks are observed.

[0178] A: Cracks are locally observed.

[0179] B: Continuous cracks are locally observed.

[0180] C: Continuous cracks are observed overall.

[0181] (6) Heat sealability

[0182] The C layers of the structures are overlapped with each other, and heat sealing is carried out using a heat tilt testing machine under the conditions of 160 °C, 0.3 MPa, and 1 second. Thereafter, a 180° peel test is carried out using an Autograph, and the fracture site is evaluated according to the following criteria.

[0183] A: The material of the paper substrate is damaged (the strength between the C layers is higher than that of the paper substrate and is strong enough).

[0184] B: Interlayer peeling (although sealed, the strength is lower than that of the paper substrate).

[0185] C: Natural peeling (unsealed state).

[0186] [Example 2]

[0187] In the coating liquid for forming the B layer, PVA-2 is used instead of PVA-1. As the coating liquid for forming the C layer, "498340R", which is an emulsion of polymer c2, is used. Except for this, the same operations as in Example 1 are carried out to obtain the structure of Example 2. Evaluation is carried out by the same method as in Example 1. The evaluation results are shown in Table 3.

[0188] [Example 3]

[0189] As the coating liquid for forming the C layer, "OP-671", which is an emulsion of polymer c3, is used. Except for this, the same operations as in Example 2 are carried out to obtain the structure of Example 3. Evaluation is carried out by the same method as in Example 1. The evaluation results are shown in Table 3.

[0190] [Example 4]

[0191] "Haricoat RT" (manufactured by Harima Chemicals Group, Inc.), which is a paraffin emulsion, was added to "VAPACT 2200", which is an emulsion of polymer c1, to prepare a mixed solution in which the content of "Haricoat RT" in terms of solid components is 0.5 parts by mass relative to polymer c1 (100 parts by mass). This mixed solution was used as a coating solution for forming the C layer. Except for this, the same operations as in Example 2 were carried out to obtain the structure of Example 4. Evaluation was carried out by the same method as in Example 1. The evaluation results are shown in Table 3.

[0192] [Example 5]

[0193] The content of "Haricoat RT" in terms of solid components in the coating solution for forming the C layer was set to 10 parts by mass relative to polymer c1 (100 parts by mass). Except for this, the same operations as in Example 4 were carried out to obtain the structure of Example 5. Evaluation was carried out by the same method as in Example 1. The evaluation results are shown in Table 3.

[0194] [Example 6]

[0195] The content of "Haricoat RT" in terms of solid components in the coating solution for forming the C layer was set to 22 parts by mass relative to polymer c1 (100 parts by mass). Except for this, the same operations as in Example 4 were carried out to obtain the structure of Example 6. Evaluation was carried out by the same method as in Example 1. The evaluation results are shown in Table 3.

[0196] [Example 7]

[0197] As the coating solution for forming the A layer, "OP-671", which is an emulsion of polymer a2, was used. Except for this, the same operations as in Example 5 were carried out to obtain the structure of Example 7. Evaluation was carried out by the same method as in Example 1. The evaluation results are shown in Table 3.

[0198] [Example 8]

[0199] As the coating solution for forming the A layer, "CHEMIPEARL S-100", which is an emulsion of polymer a3, was used. Except for this, the same operations as in Example 5 were carried out to obtain the structure of Example 8. Evaluation was carried out by the same method as in Example 1. The evaluation results are shown in Table 3.

[0200] [Example 9]

[0201] As the coating liquid for forming the A layer, "Tykote 1004", which is an emulsion of polymer a4, was used. Except for this, the same operations as in Example 5 were carried out to obtain the structure of Example 9. Evaluation was carried out by the same method as in Example 1. The evaluation results are shown in Table 3.

[0202] [Example 10]

[0203] "Finntalc C10B" (manufactured by Elementis), which is a talc dispersion liquid, was added to "MFP1883", which is an emulsion of polymer a1, to prepare a mixed liquid in which the content of talc is 50 parts by mass relative to polymer a1 (100 parts by mass). This mixed liquid was used as the coating liquid for forming the A layer. Except for this, the same operations as in Example 5 were carried out to obtain the structure of Example 10. Evaluation was carried out by the same method as in Example 1. The evaluation results are shown in Table 3.

[0204] [Example 11]

[0205] "ME-100" (manufactured by Katakura&Co-op Agri Corporation), which is a mica dispersion liquid, was added to an aqueous solution of PVA-2 (solid content: 10 mass%) to prepare a mixed liquid in which the content of mica is 5 parts by mass relative to PVA-2 (100 parts by mass). This mixed liquid was used as the coating liquid for forming the B layer. Except for this, the same operations as in Example 5 were carried out to obtain the structure of Example 11. Evaluation was carried out by the same method as in Example 1. The evaluation results are shown in Table 3.

[0206] [Example 12]

[0207] In the coating liquid for forming the B layer, PVA-3 was used instead of PVA-2. Except for this, the same operations as in Example 5 were carried out to obtain the structure of Example 12. Evaluation was carried out by the same method as in Example 1. The evaluation results are shown in Table 3.

[0208] [Example 13]

[0209] In the coating liquid for forming the B layer, PVA-4 was used instead of PVA-2. Except for this, the same operations as in Example 5 were carried out to obtain the structure of Example 13. Evaluation was carried out by the same method as in Example 1. The evaluation results are shown in Table 3.

[0210] [Example 14]

[0211] To an aqueous solution of PVA-2 (solid content: 10% by mass), “ME-100” (manufactured by Katakura&Co-op Agri Corporation), which is a mica dispersion liquid, was added to prepare a mixed liquid in which the content of mica was 5 parts by mass relative to PVA-2 (100 parts by mass). This mixed liquid was used as the coating liquid for forming the B layer. Except for this, the same operations as in Example 10 were carried out to obtain the structure of Example 14. Evaluation was carried out by the same method as in Example 1. The evaluation results are shown in Table 3.

[0212] [Comparative Example 1]

[0213] As the coating liquid for forming the C layer, “CHEMIPEARL S-100”, which is an emulsion of polymer c4, was used. Except for this, the same operations as in Example 5 were carried out to obtain the structure of Comparative Example 1. Evaluation was carried out by the same method as in Example 1. The evaluation results are shown in Table 3.

[0214] [Comparative Example 2]

[0215] As the coating liquid for forming the C layer, “CHEMIPEARL S-100”, which is an emulsion of polymer c4, was used. Except for this, the same operations as in Example 2 were carried out to obtain the structure of Comparative Example 2. Evaluation was carried out by the same method as in Example 1. The evaluation results are shown in Table 3.

[0216] [Comparative Example 3]

[0217] PVA-5 was added to “CHEMIPEARL S-100”, which is an emulsion of polymer c4, to prepare a mixed liquid in which the content of PVA-5 was 5 parts by mass relative to polymer c4 (100 parts by mass). This mixed liquid was used as the coating liquid for forming the C layer. Except for this, the same operations as in Comparative Example 2 were carried out to obtain the structure of Comparative Example 3. Evaluation was carried out by the same method as in Example 1. The evaluation results are shown in Table 3.

[0218] [Comparative Example 4]

[0219] As the coating liquid for forming the B layer, “TAKELAC WPB-341”, which is an emulsion of PU-1, was used. Except for this, the same operations as in Comparative Example 2 were carried out to obtain the structure of Comparative Example 4. Evaluation was carried out by the same method as in Example 1. The evaluation results are shown in Table 3.

[0220] [Table 1]

[0221]

[0222] [Table 2]

[0223]

[0224] [Table 3]

[0225]

[0226] In Examples 1 to 14, the structure in which the B layer contains a vinyl alcohol-based polymer (PVA-1 to PVA-4) and the C layer contains a polymer having a glass transition temperature of -100°C or higher and 5°C or lower (Polymer c1 to Polymer c3) showed excellent results in terms of few cracks in the C layer, water vapor barrier property, heat sealability, and oxygen barrier property. In particular, from the comparison between Examples 2 and 3, which differ only in the type of polymer (c), and Comparative Example 2, it was confirmed that the glass transition temperature of the polymer (c) constituting the C layer significantly affects the generation of cracks in the C layer and the water vapor barrier property.

[0227] It should be noted that, as in Comparative Example 4, when the B layer does not contain a vinyl alcohol-based polymer, the oxygen barrier property is low. On the other hand, even if the glass transition temperature of the polymer contained in the C layer is high, cracks are less likely to occur in the C layer. In contrast, as in Comparative Examples 1 and 2, when the B layer contains a vinyl alcohol-based polymer, cracks occur in the C layer according to the glass transition temperature of the polymer contained in the C layer, and the water vapor barrier property decreases. Thus, it was confirmed that the generation of cracks in the C layer is a phenomenon that occurs significantly when the B layer contains a vinyl alcohol-based polymer. In other words, in the structures of Examples 1 to 14, by using a vinyl alcohol-based polymer with particularly high oxygen barrier property in the B layer and a polymer that is less likely to generate cracks in the C layer, it is possible to achieve both excellent oxygen barrier property and water vapor barrier property.

[0228] In addition, as in Comparative Example 3, it was found that when the coating liquid for forming the C layer contains a vinyl alcohol-based polymer, the viscosity becomes high, the viscosity stability becomes low, and the coatability decreases.

[0229] Industrial Applicability

[0230] The structure of the present invention can be suitably used as packaging materials such as greaseproof paper, gas barrier paper, and odor barrier paper.

[0231] Explanation of Reference Numerals

[0232] 10 Structure

[0233] 11 Paper Substrate

[0234] 12 A Layer

[0235] 13 B Layer

[0236] 14 C Layer

Claims

1. A structure which is a structure in which an A layer, a B layer, and a C layer are sequentially laminated on at least one side of a paper substrate. The A layer contains at least one selected from an olefin-based polymer, a styrene-based polymer, and a polyester-based polymer. The B layer contains a vinyl alcohol-based polymer. The C layer contains a polymer having a glass transition temperature of -100 °C or higher and 5 °C or lower.

2. The structure according to claim 1, wherein, The C layer has a melting point of 120 °C or lower.

3. The structure according to claim 1 or 2, wherein, The A layer contains the olefin-based polymer. The olefin-based polymer contains an olefin-unsaturated carboxylic acid copolymer.

4. The structure according to claim 1, 2, or 3, wherein, The A layer further contains talc.

5. The structure according to claim 4, wherein, The content of the talc in the A layer is 1% by mass or more and 80% by mass or less.

6. The structure according to any one of claims 1 to 5, wherein, The vinyl alcohol-based polymer is an ethylene-modified vinyl alcohol-based polymer.

7. The structure according to any one of claims 1 to 6, wherein, The polymer having a glass transition temperature of -100 °C or higher and 5 °C or lower is a styrene-acrylic copolymer.

8. The structure according to any one of claims 1 to 7, wherein, The C layer further contains wax.

9. The structure according to claim 8, wherein, The content of the wax in the C layer is 0.1% by mass or more and 30% by mass or less.

10. The structure according to claim 8 or claim 9, wherein, The wax is paraffin wax.

11. The structure according to claim 10, wherein, The content of the paraffin wax in the C layer is 1% by mass or more and 30% by mass or less.

12. The structure according to any one of claims 1 to 11, wherein, The vinyl alcohol-based polymer contains two or more vinyl alcohol-based polymers having different degrees of polymerization.

13. The structure according to any one of claims 1 to 12, wherein, The A layer contains at least two selected from the olefin-based polymer, the styrene-based polymer, and the polyester-based polymer.

14. The structure according to any one of claims 1 to 13, wherein, The C layer contains two or more polymers.

15. A method for manufacturing the structure according to any one of claims 1 to 14, which includes: a step of using a curtain coater to apply at least one of the A layer, the B layer, and the C layer.

16. An oil-resistant paper which contains the structure according to any one of claims 1 to 14.

17. A gas barrier paper which contains the structure according to any one of claims 1 to 14.

18. An odor barrier paper which contains the structure according to any one of claims 1 to 14.

19. A packaging material which contains at least one selected from the oil-resistant paper according to claim 16, the gas barrier paper according to claim 17, and the odor barrier paper according to claim 18.

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