Laminate, oil-resistant paper, gas barrier paper, and packaging material

Abstract

The present invention provides: a laminate which is excellent in terms of coatability at the time when a gas barrier layer is formed, and which has excellent productivity and still exhibits excellent water vapor barrier properties after folding; and oil-resistant paper, gas barrier paper, and a packaging material, each of which uses this laminate. The present invention specifically provides a laminate which sequentially has, on a paper base material, a precoat layer (X) and a layer (Y) that contains a vinyl alcohol-based polymer (A) in this order. The content of the vinyl alcohol-based polymer (A) in the layer (Y) is 50 mass% to 100 mass% inclusive. With respect to the molecular weight of the vinyl alcohol-based polymer (A) in terms of polyethylene glycol as determined by gel permeation chromatography analysis using a differential refractometer, the weight average molecular weight (Mw) is 20,000 to 54,000 inclusive and the molecular weight distribution (Mw / Mn) is 3.2 to 4.5 inclusive. The saponification degree of the vinyl alcohol-based polymer (A) is 90 mol% to 100 mol% inclusive.

Description

Laminates, oil-resistant paper, gas barrier paper and packaging materials

[0001] The present invention relates to a laminate, greaseproof paper, gas barrier paper, and packaging material.

[0002] Paper packaging materials have traditionally been used as packaging materials for foods, medical products, electronic components, etc. As one such paper packaging material, Patent Document 1 describes grease-resistant paper obtained by applying a coating agent containing a carboxyl group-containing polyvinyl alcohol-based polymer to a paper substrate. However, the grease-resistant paper of Patent Document 1 has insufficient gas barrier properties (particularly water vapor barrier properties and oxygen gas barrier properties). As paper packaging materials for improving gas barrier properties, Patent Documents 2 and 3 describe paper packaging materials in which a water vapor barrier layer, a gas barrier layer, and a heat seal layer are laminated on a paper substrate, and the gas barrier layer contains a vinyl alcohol-based polymer (hereinafter, the vinyl alcohol-based polymer will also be referred to as "PVOH").

[0003] International Publication No. 2022 / 202997 Japanese Patent Application Laid-Open No. 2020-163675 Japanese Patent Application Laid-Open No. 2021-20398

[0004] The paper packaging materials of Patent Documents 2 and 3 have good barrier properties, such as water vapor barrier properties. However, due to their multilayer structure, the manufacturing process is complicated, leaving room for improvement in productivity. In particular, coating properties can be problematic when forming a gas barrier layer on another coating layer. Furthermore, paper packaging materials are harder than film packaging materials, and the resin layer provided on the paper packaging material is prone to cracking when folded. Therefore, the water vapor barrier properties of paper packaging materials are prone to decline when folded, making it necessary to improve the water vapor barrier properties after folding. In particular, highly hydrophobic resin layers (e.g., precoat layers) that exhibit water vapor barrier properties are more flexible than vinyl alcohol-based polymer resin layers. However, when cracks occur in the vinyl alcohol-based polymer layer, which is relatively susceptible to cracking, the highly hydrophobic resin layer may also crack following the cracks, resulting in a significant decline in water vapor barrier properties. To improve barrier properties after folding, it is possible to provide a gas barrier layer containing a vinyl alcohol-based polymer with a high degree of polymerization. However, when a vinyl alcohol polymer with a high degree of polymerization is used, the viscosity of the coating solution used to form the gas barrier layer increases, causing problems with coatability.On the other hand, when a vinyl alcohol polymer with a low viscosity is used to improve coatability, the water vapor barrier property after bending becomes insufficient.

[0005] The present invention has been made to solve the above-mentioned problems, and has an object to provide a laminate that has excellent coatability when forming a gas barrier layer, good productivity, and excellent water vapor barrier properties after folding, as well as greaseproof paper, gas barrier paper, and packaging materials that use such a laminate.

[0006] The above-mentioned problems are solved by the following: [1] a laminate having, on a paper substrate, a precoat layer (X) and a layer (Y) containing a vinyl alcohol-based polymer (A) in this order, wherein the content of the vinyl alcohol-based polymer (A) in the layer (Y) is 50% by mass or more and 100% by mass or less, and the molecular weight of the vinyl alcohol-based polymer (A) calculated as polyethylene glycol by gel permeation chromatography analysis using a differential refractometer is such that the weight average molecular weight (Mw) is 20,000 or more and 54,000 or less and the molecular weight distribution (Mw / Mn) is 3.2 or more and 4.5 or less, and the degree of saponification of the vinyl alcohol-based polymer (A) is 90 mol % or more and 100 mol % or less; [2] the laminate of [1], wherein the vinyl alcohol-based polymer (A) contains a vinyl alcohol-based polymer (B) having a weight average molecular weight (Mw) of 20,000 or more and 80,000 or less and a vinyl alcohol-based polymer (C) having a weight average molecular weight (Mw) of 10,000 or more and less than 20,000; [3] The laminate of [2], in which the content of the vinyl alcohol polymer (B) is 60 parts by mass or more and 90 parts by mass or less, and the content of the vinyl alcohol polymer (C) is 10 parts by mass or more and 40 parts by mass or less, based on the total of the vinyl alcohol polymer (B) and the vinyl alcohol polymer (C); [4] Any of the laminates of [1] to [3], in which the vinyl alcohol polymer (A) contains an ethylene-modified vinyl alcohol polymer; [5] The laminate of [4], in which the ethylene-modified vinyl alcohol polymer has an ethylene unit content of 0.1 mol % or more and 19 mol % or less; [6] Any of the laminates of [1] to [5], further comprising a heat seal layer (Z); [7] Any of the laminates of [1] to [6], in which the precoat layer (X) contains an inorganic compound (D); [8] The laminate of [7], in which the inorganic compound (D) is a layered inorganic compound having an aspect ratio of 50 or more; The problem is solved by providing any one of the following: [9] a laminate of any one of [1] to [8], further having an inorganic vapor deposition layer (W) adjacent to at least one surface of the layer (Y);

[10] greaseproof paper comprising any one of the laminates [1] to [9];

[11] gas barrier paper comprising any one of the laminates [1] to [9];

[12] a packaging material comprising the greaseproof paper of

[10] ;

[13] a packaging material comprising the gas barrier paper of

[11] .

[0007] The present invention can provide a laminate that exhibits excellent coatability when forming a gas barrier layer, has good productivity, and yet exhibits excellent water vapor barrier properties after folding, as well as greaseproof paper, gas barrier paper, and packaging materials that use such a laminate.

[0008] <Laminate> A laminate according to one embodiment of the present invention has, on a paper substrate, a precoat layer (X) and a layer (Y) containing a vinyl alcohol-based polymer (A) (PVOH (A)) in this order, wherein the content of PVOH (A) in the layer (Y) is 50% by mass or more and 100% by mass or less, and the molecular weight of the PVOH (A) calculated as polyethylene glycol, as determined by gel permeation chromatography analysis using a differential refractometer, is such that the weight average molecular weight (Mw) is 20,000 or more and 54,000 or less and the molecular weight distribution (Mw / Mn) is 3.2 or more and 4.5 or less, and the degree of saponification of the PVOH (A) is 90 mol % or more and 100 mol % or less.

[0009] A laminate according to one embodiment of the present invention exhibits excellent coatability when forming the layer (Y) that is a gas barrier layer, good productivity, and excellent water vapor barrier properties after bending. The reason why the laminate exhibits such effects is unclear, but the following reasons are presumed. The PVOH (A), a constituent component of the layer (Y), has a weight-average molecular weight (Mw) within a predetermined range, a molecular weight distribution (Mw / Mn) value, i.e., a wide range of molecular weight variation, and a state in which low molecular weight and high molecular weight molecules are mixed in an appropriate balance. The inclusion of a moderately low-molecular-weight PVOH in the PVOH (A) reduces the viscosity of the coating solution, improving coatability and improving productivity. Meanwhile, the inclusion of a moderately high-molecular-weight PVOH in the PVOH (A) makes the layer (Y) less susceptible to cracking even when bent, resulting in excellent water vapor barrier properties after bending. Furthermore, the laminate also tends to exhibit good oil resistance after bending.

[0010] The laminate according to one embodiment of the present invention may have layers other than the paper substrate, the precoat layer (X), and the layer (Y). For example, the laminate may have a heat seal layer (Z), an inorganic vapor deposition layer (W), or other layers. Each component of the laminate will be described in detail below.

[0011] (Paper substrate) The paper substrate is a paper layer that serves as the base material in the laminate. The paper substrate may be the outermost layer on one side of the laminate. In other words, no other layer may be laminated on one side of the paper substrate. Other layers may be laminated on both sides of the paper substrate. The paper substrate may have a single-layer structure or a multi-layer structure. The paper substrate may be printed or the like.

[0012] The paper base material can be a general paper whose main component is plant-derived pulp. In this specification, the term "main component" refers to the component with the highest content by mass. In addition to pulp, the paper base material may contain sizing agents, fillers, paper strength agents, retention aids, pH adjusters, drainage aids, water-resistant agents, softeners, antistatic agents, antifoaming agents, slime control agents, dyes, pigments, etc.

[0013] Examples of paper substrates include kraft paper, bleached kraft paper, fine paper, medium-quality paper, alkaline paper, paperboard, glassine paper, semi-glassine paper, and parchment paper, with kraft paper or bleached kraft paper being preferred.

[0014] The basis weight (mass per unit area) of the paper base material is 20 g / m ２ More than 500g / m ２ Preferably, 30 g / m or less ２ More than 300g / m ２ More preferably, 40 g / m or less ２ More than 200g / m ２ More preferably, 50 g / m or less ２ More than 100g / m ２ Even more preferred are the following:

[0015] The density of the paper base material is 0.5 g / cm ３ 1.2g / cm or more ３ Preferably, 0.6 g / cm or less ３ 1.0g / cm or more ３ The following is more preferred:

[0016] The paper substrate can be produced by a known method, and commercially available paper substrates can also be used.

[0017] (Precoat layer (X)) The precoat layer (X) is a layer located between the paper substrate and the layer (Y). The precoat layer (X) may be a layer directly laminated on the paper substrate. The precoat layer (X) is usually a layer formed by coating (coating layer).

[0018] The precoat layer (X) usually contains a polymer. The polymer used in the precoat layer (X) may be at least one selected from the group consisting of olefin polymers, styrene polymers, polyester polymers, vinyl alcohol polymers, and starch. The precoat layer (X) is preferably, for example, at least one selected from the group consisting of olefin polymers, styrene polymers, and polyester polymers. When the precoat layer (X) contains such a relatively hydrophobic polymer, it can exhibit good water vapor barrier properties, etc. The polymer is preferably a water-dispersible polymer. The polymer is preferably the main component of the precoat layer (X).

[0019] The olefin polymer is a polymer containing an olefin as a monomer. The olefin polymer may be a polyolefin, which is a polymer of one or more olefins, or a copolymer of one or more olefins with one or more other monomers other than olefins.

[0020] Examples of the olefin include α-olefins such as ethylene, propylene, n-butene, and isobutylene.

[0021] Examples of the monomer other than the olefin constituting the olefin polymer include unsaturated carboxylic acid compounds, diene compounds, vinyl esters, vinyl ethers, vinyl halides, vinylidene halides, and allyl compounds. Of these, vinyl esters or unsaturated carboxylic acid compounds are preferred, and unsaturated carboxylic acid compounds are more preferred.

[0022] The unsaturated carboxylic acid compound refers to an unsaturated carboxylic acid or a compound in which the hydrogen atom of the carboxy group constituting the unsaturated carboxylic acid is substituted with another atom or another group. That is, the unsaturated carboxylic acid compound includes not only unsaturated carboxylic acid but also unsaturated carboxylic acid esters, unsaturated carboxylic acid salts, etc. The unsaturated carboxylic acid compound is preferably a monomer having a carboxy group or a salt thereof.

[0023] Examples of unsaturated carboxylic acid compounds include unsaturated carboxylic acids such as (meth)acrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and butenetricarboxylic acid; unsaturated carboxylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, itaconic acid monoethyl ester, and fumaric acid monobutyl ester; and unsaturated carboxylic acid salts such as sodium (meth)acrylate. Note that "(meth)acrylic acid" means acrylic acid and methacrylic acid.

[0024] Examples of vinyl esters include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate, etc. Of these, vinyl acetate is preferred.

[0025] As the olefin-based polymer, polyolefin, olefin-vinyl ester copolymer, and olefin-unsaturated carboxylic acid copolymer are preferred, with olefin-unsaturated carboxylic acid copolymers being more preferred. An olefin-vinyl ester copolymer refers to a copolymer of one or more olefins and one or more vinyl esters. An 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, an olefin-unsaturated carboxylic acid copolymer, which is a copolymer of one or more olefins and one or more unsaturated carboxylic acids, is preferred.

[0026] Examples of the olefin-vinyl ester copolymer include ethylene-vinyl formate copolymer, ethylene-vinyl acetate copolymer, and ethylene-vinyl propionate copolymer, among which ethylene-vinyl acetate copolymer is preferred. These copolymers may further be copolymerized with other monomers copolymerizable with the olefin and vinyl ester.

[0027] Examples of olefin-unsaturated carboxylic acid copolymers include ethylene-(meth)acrylic acid copolymer, ethylene-methyl(meth)acrylate copolymer, ethylene-ethyl(meth)acrylate copolymer, and ethylene-butyl(meth)acrylate copolymer. Among these, ethylene-(meth)acrylic acid copolymer is preferred. Copolymers of ethylene and unsaturated carboxylic acid compounds are also preferred. These copolymers may further be copolymerized with other monomers copolymerizable with the olefin and unsaturated carboxylic acid compound.

[0028] A styrene-based polymer is a polymer containing a styrene-based compound as a monomer. The styrene-based compound refers to styrene and compounds in which the hydrogen atoms of styrene are substituted with other atoms or other groups. Examples of the styrene-based compound include styrene, α-methylstyrene, vinyltoluene, and chlorostyrene, with styrene being preferred.

[0029] Examples of the styrene copolymer include polystyrene, styrene-acrylic copolymer, and styrene-butadiene copolymer.

[0030] The styrene-acrylic copolymer is a copolymer of the above-mentioned styrene compound and an acrylic compound. The acrylic compound refers to (meth)acrylic acid and a compound in which the hydrogen atom of the carboxy group constituting (meth)acrylic acid is substituted with another atom or another group. Examples of the acrylic compound include (meth)acrylic acid, (meth)acrylic acid esters, and (meth)acrylic acid salts. Examples of the (meth)acrylic acid esters include (meth)acrylic acid alkyl esters such as methyl (meth)acrylate and ethyl (meth)acrylate. Examples of the (meth)acrylic acid salts include sodium (meth)acrylate.

[0031] Examples of styrene-acrylic copolymers include styrene-(meth)acrylic acid copolymers, styrene-(meth)acrylic acid ester copolymers, styrene-(meth)acrylate copolymers, etc. The styrene-acrylic copolymers may be further copolymerized with other monomers.

[0032] The styrene-butadiene copolymer is a copolymer of the above-mentioned styrene compound and a butadiene compound. The butadiene compound refers to butadiene and compounds in which the hydrogen atoms of butadiene have been substituted with other atoms or other groups. Examples of the butadiene compound include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene, with 1,3-butadiene being preferred.

[0033] The styrene-butadiene copolymer is preferably a styrene-butadiene copolymer, which may be further copolymerized with other monomers.

[0034] As the styrene polymer, a styrene-acrylic copolymer and a styrene-butadiene copolymer are preferred.

[0035] A polyester polymer is a polymer formed by polymerizing one or more types of monomers via ester bonds. Examples of polyester polymers include polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polyglycolic acid, and aromatic liquid crystal polyester.

[0036] From the viewpoint of water vapor barrier properties and the like, the polymer used in the precoat layer (X) is preferably at least one selected from the group consisting of olefin-based polymers and styrene-based polymers, more preferably an olefin-based polymer, and even more preferably an olefin-unsaturated carboxylic acid copolymer.

[0037] The polymer used in the precoat layer (X) may be at least one selected from the group consisting of vinyl alcohol polymers and starch. When the precoat layer (X) contains such a polymer, the precoat layer (X) can function as a good sealing layer.

[0038] The vinyl alcohol polymer is a polymer having a vinyl alcohol unit (-CH ２ Vinyl alcohol polymers are generally obtained by saponifying vinyl ester polymers.

[0039] The viscosity-average degree of polymerization of the vinyl alcohol polymer is preferably 200 or more and 5,000 or less. The lower limit of the viscosity-average degree of polymerization may be 300, 400, 500, or 800. On the other hand, the upper limit of the viscosity-average degree of polymerization may be 3,000, 2,500, 2,000, 1,200, or 1,000.

[0040] The viscosity-average degree of polymerization of a vinyl alcohol polymer is measured in accordance with JIS K 6726:1994. Specifically, the intrinsic viscosity [η] (liters / g) of the vinyl alcohol polymer is measured in water at 30°C, and the viscosity-average degree of polymerization P is calculated using the value of the intrinsic viscosity [η] according to the following formula. When the saponification degree of the vinyl alcohol polymer is less than 99.5 mol%, the polymer is saponified to a saponification degree of 99.5 mol% or more, and then the intrinsic viscosity [η] is measured. P = ([η] x 10 ４ / 8.29) （１／０．６２）

[0041] The lower limit of the saponification degree of the vinyl alcohol polymer is preferably 70 mol%, more preferably 80 mol%, more preferably 90 mol%, even more preferably 95 mol%, and may be 96 mol%, 97 mol%, 98 mol%, or 99 mol%. On the other hand, the upper limit of the saponification degree may be 100 mol% or 99.9 mol%. The saponification degree of the vinyl alcohol polymer is measured in accordance with JIS K 6726:1994.

[0042] The molecular weight distribution (Mw / Mn) of the vinyl alcohol polymer is not particularly limited, and may be, for example, 1 to 10, or 1.5 to 5.

[0043] Preferred embodiments of the vinyl alcohol polymer other than the viscosity-average degree of polymerization, the degree of saponification and the molecular weight distribution are the same as the preferred embodiments of the PVOH (A) described later.

[0044] The starch is not particularly limited, and examples thereof include natural starches such as corn starch, potato starch, sweet potato starch, wheat starch, rice starch, tapioca starch, and sago starch; and processed starches that have been subjected to etherification, esterification, oxidation, or the like.

[0045] The lower limit of the content of the polymer in the precoat layer (X) is preferably 50% by mass, more preferably 60% by mass, and may be 70%, 80%, or 90% by mass. On the other hand, the upper limit of this content may be 100% by mass, or may be 99%, 95%, 90%, or 80% by mass. Furthermore, when the precoat layer (X) contains at least one polymer selected from the group consisting of vinyl alcohol polymers and starch, the lower limit of the polymer may be 95% or 98% by mass, and the precoat layer (X) may consist essentially of the polymer.

[0046] The precoat layer (X) preferably contains an inorganic compound (D). By including the inorganic compound (D) in the precoat layer (X), the water vapor barrier property, filling property, and the like can be improved. The inorganic compound (D) is not particularly limited, and inorganic oxides, inorganic nitrides, inorganic salts, metals, and the like can be used, but a layered inorganic compound is preferred. Using a layered inorganic compound as the inorganic compound (D) can further improve the water vapor barrier property, and the like. On the other hand, when the precoat layer generally contains an inorganic compound, particularly a layered inorganic compound, layer cracking due to bending tends to occur, and the water vapor barrier property after bending tends to be easily reduced. Therefore, in the laminate according to one embodiment of the present invention, when the precoat layer (X) contains an inorganic compound (D), particularly a layered inorganic compound, the advantage of excellent water vapor barrier property after bending is significantly obtained. Examples of layered inorganic compounds include micas, mica, talc, montmorillonite, kaolinite, vermiculite, smectite, hectorite, taeniolite, and acid clay. The layered inorganic compound may be a natural product or a synthetic product. The inorganic compound (D) may be used alone or in combination of two or more kinds.

[0047] The average particle size of the inorganic compound (D) is preferably 1 μm or more and 50 μm or less, and more preferably 4 μm or more and 30 μm or less. When the average particle size of the inorganic compound (D) is within the above range, the water vapor barrier property, etc. can be further improved. The average particle size of the inorganic compound (D) is the average value of the particle sizes (longest diameter) of any 20 particles in a magnified image obtained by atomic force microscopy.

[0048] When the inorganic compound (D) is a layered inorganic compound, the aspect ratio of the layered inorganic compound is preferably 50 or more, more preferably 100 or more. The aspect ratio may be, for example, 10,000 or less, 7,000 or less, 3,000 or less, or 1,000 or less. The aspect ratio refers to the average major diameter relative to the average thickness of flat particles. The average thickness and average major diameter are the average values ​​of the thickness and major diameter (longest diameter) of any 20 particles in an enlarged image obtained by atomic force microscopy.

[0049] The lower limit of the content of the inorganic compound (D) in the precoat layer (X) is preferably 0.5% by mass, more preferably 1% by mass, even more preferably 2% by mass, and may be 3% by mass, 4% by mass, 5% by mass, 6% by mass, 7% by mass, or 8% by mass. On the other hand, the upper limit of this content is preferably 40% by mass, more preferably 30% by mass, and even more preferably 20% by mass. Furthermore, the lower limit of the content of the inorganic compound (D) relative to 100 parts by mass of the polymer in the precoat layer (X) is preferably 0.2 parts by mass, more preferably 1 part by mass, even more preferably 2 parts by mass, and may be 3 parts by mass, 4 parts by mass, 5 parts by mass, 6 parts by mass, 7 parts by mass, or 8 parts by mass. On the other hand, the upper limit of this content is preferably 40 parts by mass, more preferably 30 parts by mass, and even more preferably 20 parts by mass. By setting the content of the inorganic compound (D) in the precoat layer (X) within the above range, it is possible to further improve the water vapor barrier property after bending, etc.

[0050] The precoat layer (X) may further contain components other than the polymer and the inorganic compound (D), such as resins other than the polymer, dispersants, surfactants, antifoaming agents, dyes, thickeners, etc.

[0051] Examples of resins other than the polymer include cationic resins. When the precoat layer (X) contains a cationic resin together with the inorganic compound (D), the water vapor barrier properties are further improved. Examples of the cationic resin include polyamine resins, cation-modified polyamide resins (for example, amine-modified polyamide resins), polyamide epichlorohydrin resins, polyethyleneimine resins, polyalkylene polyamine resins, polyamide compounds, polyamidoamine-epihalohydrin or formaldehyde condensation reaction products, polyamine-epihalohydrin or formaldehyde condensation reaction products, polyamide polyurea-epihalohydrin or formaldehyde condensation reaction products, polyamine polyurea-epihalohydrin or formaldehyde condensation reaction products, polyamidoamine polyurea-epihalohydrin or formaldehyde condensation reaction products, polyamide polyurea compounds, polyamine polyurea compounds, polyamidoamine polyurea compounds, polyamidoamine compounds, polyvinylpyridine, amino-modified acrylamide compounds, polyvinylamine resins, and polydiallyldimethylammonium chloride. Among these, at least one selected from the group consisting of polyamine resins, cation-modified polyamide resins, polyamide epichlorohydrin resins, and polyethyleneimine resins is preferred.

[0052] The lower limit of the content of the cationic resin in the precoat layer (X) is preferably 0.1 mass%, more preferably 1 mass%, and even more preferably 2 mass%. Meanwhile, the upper limit of this content is preferably 20 mass%, more preferably 10 mass%. Furthermore, the lower limit of the content of the cationic resin in the precoat layer (X) relative to 100 mass parts of the polymer is preferably 0.1 mass parts, more preferably 1 mass part, and even more preferably 2 mass parts. Meanwhile, the upper limit of this content is preferably 20 mass parts, more preferably 10 mass parts. By setting the content of the cationic resin in the precoat layer (X) within the above range, it is possible to further improve the water vapor barrier property after bending, etc.

[0053] The total content of the polymer, inorganic compound (D), and cationic resin in the precoat layer (X) may be 90% by mass or more, 95% by mass or more, 99% by mass or more, or substantially 100% by mass.

[0054] The lower limit of the mass per unit area of ​​one precoat layer (X) is 1 g / m ２ is preferred, and 3 g / m ２ More preferably, 5 g / m ２ When the mass per unit area of ​​one precoat layer (X) is equal to or greater than the above lower limit, the water vapor barrier property and the like can be further improved. The upper limit of the mass per unit area of ​​one precoat layer (X) is 100 g / m ２ is preferred, and 40 g / m ２ More preferably, 20 g / m ２ More preferably, 15 g / m ２ When the mass per unit area of ​​one precoat layer (X) is equal to or less than the upper limit, it is possible to reduce the thickness of the laminate.

[0055] (Layer (Y)) The layer (Y) is a layer located on the side of the precoat layer (X) opposite to the paper substrate. The layer (Y) may be a layer directly laminated on the precoat layer (X). The layer (Y) is usually a layer formed by coating (coating layer).

[0056] The layer (Y) contains PVOH (A). The laminate according to one embodiment of the present invention has the layer (Y) containing PVOH (A), and thus can exhibit excellent water vapor barrier properties, oxygen barrier properties, etc. The PVOH (A) contains a vinyl alcohol unit (-CH ２ PVOH (A) is a polymer having a —CHOH— group. PVOH (A) is usually obtained by saponifying a vinyl ester polymer. PVOH (A) can be used alone or in combination of two or more types.

[0057] The lower limit of the saponification degree of PVOH (A) is 90 mol%, preferably 92 mol%, more preferably 95 mol%, even more preferably 97 mol%, and even more preferably 98 mol%. When the saponification degree is equal to or greater than the above lower limit, the water vapor barrier property, oxygen barrier property, etc. can be further improved. On the other hand, the upper limit of the saponification degree may be 100 mol% or 99.9 mol%. The saponification degree of PVOH (A) is measured in accordance with JIS K 6726:1994.

[0058] The lower limit of the weight average molecular weight (Mw) of PVOH (A) is 20,000, preferably 30,000, more preferably 35,000, even more preferably 38,000, even more preferably 40,000, and particularly preferably 42,000. When the weight average molecular weight (Mw) of PVOH (A) is at least the above lower limit, the water vapor barrier property, oxygen barrier property, water vapor barrier property after bending, etc. are improved. The upper limit of the weight average molecular weight (Mw) of PVOH (A) is 54,000, preferably 52,000, more preferably 50,000, and even more preferably 49,000. When the weight average molecular weight (Mw) of PVOH (A) is at most the above upper limit, the coatability when forming layer (Y) with a coating liquid containing PVOH (A) is improved, and productivity can be improved.

[0059] The lower limit of the molecular weight distribution (Mw / Mn) of the PVOH (A) is 3.2, preferably 3.3, more preferably 3.4, and even more preferably 3.5. The upper limit of the molecular weight distribution (Mw / Mn) of the PVOH (A) is 4.5, preferably 4.3, more preferably 4.2, even more preferably 4.1, and even more preferably 4.0. When the weight-average molecular weight (Mw) of the PVOH (A) is within a predetermined range and the molecular weight distribution (Mw / Mn) is within the above range, the PVOH (A) contains a mixture of low-molecular-weight and high-molecular-weight PVOH in an appropriate balance. This makes it possible to achieve both the effect of improving coatability due to the low-molecular-weight PVOH and the effect of improving water vapor barrier properties after bending due to the high-molecular-weight PVOH. The molecular weight distribution (Mw / Mn) is the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) and is an index showing the degree of molecular weight variation.

[0060] The weight-average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of PVOH (A) are based on the molecular weight (molecular weight distribution curve) of PVOH (A) converted into polyethylene glycol by gel permeation chromatography analysis using a differential refractometer. Specifically, the weight-average molecular weight (Mw), number-average molecular weight (Mn) of PVOH (A) and the ratio thereof, the molecular weight distribution (Mw / Mn), are values ​​determined under the conditions described in the Examples.

[0061] PVOH (A) having a relatively large molecular weight distribution (Mw / Mn) can be obtained relatively easily by blending two or more types of PVOH having different weight-average molecular weights (Mw). For example, PVOH (A) preferably contains PVOH (B) having a weight-average molecular weight (Mw) of 20,000 or more and 80,000 or less and PVOH (C) having a weight-average molecular weight (Mw) of 10,000 or more and less than 20,000, and more preferably consists of PVOH (B) and PVOH (C). PVOH (A) may be a mixture of PVOH (B) and PVOH (C). PVOH (A) may have two or more peaks in a molecular weight distribution curve obtained by gel permeation chromatography analysis.

[0062] The lower limit of the weight average molecular weight (Mw) of PVOH (B) is preferably 30,000, more preferably 40,000, and even more preferably 50,000. The upper limit of the weight average molecular weight (Mw) of PVOH (B) is preferably 70,000, more preferably 65,000, and even more preferably 60,000. The weight average molecular weight (Mw) of PVOH (C) is preferably 10,000 or more and 19,000 or less.

[0063] The mixing ratio of PVOH (B) to PVOH (C) is preferably such that the content of PVOH (B) relative to the total of PVOH (B) and PVOH (C) is 60 to 90 parts by mass and the content of PVOH (C) is 10 to 40 parts by mass. It is more preferable that the content of PVOH (B) relative to the total of PVOH (B) and PVOH (C) is 70 to 85 parts by mass and the content of PVOH (C) is 15 to 30 parts by mass. The contents of PVOH (B) and PVOH (C) can sometimes be determined from PVOH (A) by, for example, peak-separating the molecular weight distribution curve of PVOH (A) and identifying the PVOH corresponding to each peak as PVOH (B) or PVOH (C). Furthermore, the weight-average molecular weights (Mw) of PVOH (B) and PVOH (C) can sometimes be determined from the molecular weight distribution curves obtained by peak separation.

[0064] PVOH (A) may have monomer units derived from other monomers than vinyl alcohol units and vinyl ester units. PVOH having monomer units derived from other monomers than vinyl alcohol units and vinyl ester units is also called modified PVOH, and PVOH not having monomer units derived from other monomers than vinyl alcohol units and vinyl ester units is also called unmodified PVOH. Examples of other monomers include α-olefins such as ethylene, propylene, n-butene, and isobutylene; (meth)acrylic acid and its salts; (meth)acrylic acid esters; (meth)acrylamide; (meth)acrylamide derivatives such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, diacetone(meth)acrylamide, (meth)acrylamidopropanesulfonic acid and its salts, (meth)acrylamidopropyldimethylamine and its salts or quaternary salts, and N-methylol(meth)acrylamide and its derivatives; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, and i-propyl vinyl ether. vinyl ethers such as butyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-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; vinyl halides such as vinylidene chloride and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and fumaric acid, and salts or esters thereof; vinyl silyl compounds such as vinyltrimethoxysilane; isopropenyl acetate; 1,4-diacetoxybutene; 3,4-diacetoxy-1-butene; vinylformamide; and vinylpyrrolidone.

[0065] The other monomer is preferably an α-olefin, and more preferably ethylene. That is, PVOH (A) preferably contains an α-olefin-modified PVOH, and more preferably contains an ethylene-modified PVOH. Furthermore, PVOH (A) is also preferably an α-olefin-modified PVOH, and more preferably an ethylene-modified PVOH. Use of such a modified PVOH can further improve coatability, water vapor barrier properties after bending, and the like. For example, when PVOH (A) contains PVOH (B) and PVOH (C), one of PVOH (B) and PVOH (C) may be a modified PVOH and the other may be an unmodified PVOH, or both may be modified PVOH. The lower limit of the content of α-olefin-modified PVOH or ethylene-modified PVOH in PVOH (A) is preferably 5% by mass, more preferably 10% by mass, and even more preferably 20% by mass, and may be 30%, 50%, 70%, or 90% by mass. The upper limit of the content of the α-olefin-modified PVOH or ethylene-modified PVOH in the PVOH (A) may be 100% by mass.

[0066] The lower limit of the content of α-olefin units relative to all monomer units in α-olefin-modified PVOH is preferably 0.1 mol%, more preferably 0.5 mol%, even more preferably 1 mol%, and may be 2 mol% or 3 mol%. On the other hand, the upper limit of this content is preferably 19 mol%, more preferably 15 mol%, even more preferably 13 mol%, and may be 10 mol% or 8 mol%. The lower limit of the content of ethylene units relative to all monomer units in ethylene-modified PVOH is preferably 0.1 mol%, more preferably 0.5 mol%, even more preferably 1 mol%, and may be 2 mol% or 3 mol%. On the other hand, the upper limit of this content is preferably 19 mol%, more preferably 15 mol%, even more preferably 13 mol%, and may be 10 mol% or 8 mol%. The content of α-olefin units relative to all monomer units is also referred to as the α-olefin modification amount. For example, the content of ethylene units relative to all monomer units is also referred to as the ethylene modification amount. By ensuring that the amount of α-olefin modification or the amount of ethylene modification is within the above range, it is possible to further improve the water vapor barrier property after bending.

[0067] The total content of vinyl alcohol units, vinyl ester units, and any α-olefin units relative to all monomer units in PVOH (A) is preferably 95 mol % or more, more preferably 99 mol % or more, and may be 100 mol %.

[0068] The lower limit of the content of PVOH (A) in layer (Y) is 50% by mass, preferably 60% by mass, more preferably 70% by mass, even more preferably 80% by mass, even more preferably 90% by mass, and may be 95% by mass or 97% by mass. By setting the content of PVOH (A) in layer (Y) to the above-mentioned lower limit or more, the water vapor barrier property after bending can be further improved. On the other hand, the upper limit of this content is 100% by mass, and may be 99% by mass or 97% by mass.

[0069] The layer (Y) may contain an inorganic compound (E). The inorganic compound (E) is preferably a layered inorganic compound. When the layer (Y) contains the inorganic compound (E), the water vapor barrier properties of the laminate after bending can be further improved. For example, the inorganic compound may be contained in only one of the precoat layer (X) and the layer (Y), or in both.

[0070] Examples of the inorganic compound (E) include the same compounds as those exemplified as the inorganic compound (D) in the description of the precoat layer (X). The inorganic compound (E) can be used alone or in combination of two or more.

[0071] When the layer (Y) contains the inorganic compound (E), the lower limit of the content of the inorganic compound (E) in the layer (Y) is preferably 1% by mass, more preferably 3% by mass. On the other hand, the upper limit of this content is preferably 20% by mass, more preferably 10% by mass. By setting the content of the inorganic compound (E) in the layer (Y) within the above range, it is possible to further improve the water vapor barrier property after bending. The content of the inorganic compound (E) in the layer (Y) may be 5% by mass or less, 1% by mass or less, or 0.1% by mass or less.

[0072] The layer (Y) may further contain components other than the PVOH (A) and the inorganic compound (E). Examples of such components include resins other than the PVOH (A), dispersants, surfactants, antifoaming agents, dyes, preservatives, fillers, interlayer adhesives, and thickeners. However, the total content of the PVOH (A) and the optional inorganic compound (E) in the layer (Y) is preferably 90% by mass or more, more preferably 95% by mass or more, or more preferably 99% by mass or more.

[0073] The layer (Y) may be a single layer or may have a laminate structure of multiple layers. When the layer (Y) has a laminate structure of multiple layers, the compositions of the layers may be the same or different. The layer (Y) may have a two-layer structure, for example, a layer containing PVOH (B) and a layer containing PVOH (C). In one embodiment of the present invention, the layer (Y) is preferably a single layer.

[0074] The mass per unit area of ​​the layer (Y) is 0.3 g / m ２ 15g / m or more ２ Preferably, 0.5 g / m or less ２ 10g / m or more ２ More preferably, 1 g / m or less ２ 6g / m or more ２ More preferably, 1.5 g / m or less ２ 4.0g / m or more ２ The following is even more preferable. When the mass per unit area of ​​one layer (Y) is not less than the above lower limit, the water vapor barrier property after folding can be further improved. On the other hand, when the mass per unit area of ​​one layer (Y) is not more than the above upper limit, the thickness of the laminate can be reduced.

[0075] (Heat seal layer (Z)) The heat seal layer (Z) is usually the outermost layer of the laminate. The outermost layers on both sides of the laminate may both be heat seal layers (Z). The heat seal layer (Z) may be a layer formed by coating (coating layer).

[0076] The heat seal layer (Z) usually contains a polymer. The polymer is preferably the main component of the heat seal layer (Z). The polymer used in the heat seal layer (Z) is preferably a thermoplastic resin. The melting point of the polymer used in the heat seal layer is preferably 50°C or higher and 140°C or lower, more preferably 70°C or higher and 110°C or lower. One or more types of polymers can be used.

[0077] Examples of polymers used in the heat seal layer (Z) include those exemplified as polymers used in the precoat layer (X). That is, the polymer used in the heat seal layer (Z) is preferably at least one selected from the group consisting of olefin polymers, styrene polymers, and polyester polymers. Among these, at least one selected from the group consisting of olefin polymers and styrene polymers is preferred, with olefin polymers being more preferred, olefin-vinyl ester copolymers and olefin-unsaturated carboxylic acid copolymers being even more preferred, and olefin-unsaturated carboxylic acid copolymers being particularly preferred.

[0078] The lower limit of the polymer content in the heat seal layer (Z) is preferably 50% by mass, more preferably 60% by mass, even more preferably 70% by mass, and even more preferably 80%, 85% by mass, or 90% by mass, while the upper limit of this content is preferably 100% by mass, and may be 99% by mass or 95% by mass.

[0079] The heat seal layer (Z) may further contain components other than the above-mentioned polymers, such as wax (e.g., paraffin wax), dispersants, surfactants, antifoaming agents, dyes, thickeners, etc.

[0080] The mass per unit area of ​​one heat seal layer (Z) is 1 g / m ２ 50g / m or more ２ Preferably, 2 g / m or less ２ 30g / m or more ２ More preferably, 3 g / m or less ２ 20g / m or more ２ More preferably, 4 g / m or less ２ 15g / m or more ２ Even more preferably, ２ 10g / m or more ２ The following is particularly preferred. When the mass per unit area of ​​one heat seal layer (Z) is not less than the above lower limit, sufficient heat sealability can be exhibited and the water vapor barrier property after folding can be further improved. On the other hand, when the mass per unit area of ​​one heat seal layer (Z) is not more than the above upper limit, the laminate can be made thinner, etc.

[0081] (Inorganic vapor deposition layer (W)) The inorganic vapor deposition layer (W) is a layer formed by vapor deposition of an inorganic substance. When the laminate has the inorganic vapor deposition layer (W), the water vapor barrier property, gas barrier property, etc. are further improved. The inorganic vapor deposition layer (W) is preferably provided adjacent to at least one surface of the layer (Y).

[0082] Examples of inorganic substances constituting the inorganic vapor deposition layer (W) include metals (e.g., aluminum), metal oxides (e.g., silicon oxide, aluminum oxide, magnesium oxide), metal nitrides (e.g., silicon nitride), metal nitride oxides (e.g., silicon oxynitride), and metal carbonitrides (e.g., silicon carbonitride). Among the above examples of inorganic substances, silicon is considered to be included in the metals. Among these, aluminum, aluminum oxide, silicon oxide, magnesium oxide, or silicon nitride is preferred from the viewpoints of barrier properties, industrial productivity, and the like, with aluminum or aluminum oxide being more preferred, and aluminum being even more preferred.

[0083] The average thickness of one inorganic vapor deposition layer (W) is preferably 5 nm to 200 nm, more preferably 10 nm to 150 nm, even more preferably 20 nm to 100 nm, even more preferably 30 nm to 100 nm, and may be 30 nm to 80 nm or 30 nm to 60 nm. By setting the average thickness of the inorganic vapor deposition layer (W) to the above-mentioned lower limit or more, it is possible to improve the barrier properties. On the other hand, by setting the average thickness of the inorganic vapor deposition layer (W) to the above-mentioned upper limit or less, cracking of the inorganic vapor deposition layer (W) during bending is suppressed, and deterioration of the water vapor barrier properties after bending can be particularly sufficiently reduced. The average thickness of the inorganic vapor deposition layer (W) is the average value of thicknesses at any 10 points on the cross section of the inorganic vapor deposition layer (W) measured using an electron microscope.

[0084] (Other Layers, Layer Structure, etc.) The laminate according to one embodiment of the present invention may further include layers other than the paper substrate, precoat layer (X), layer (Y), heat seal layer (Z), and inorganic vapor deposition layer (W). Examples of other layers include other resin layers, metal foil layers, etc. In one embodiment of the present invention, the laminate does not necessarily have layers other than the paper substrate, precoat layer (X), layer (Y), heat seal layer (Z), and inorganic vapor deposition layer (W).

[0085] In the laminate according to one embodiment of the present invention, the number of paper substrates may be only one or may be multiple. In the laminate according to one embodiment of the present invention, the number of paper substrates is preferably only one.

[0086] In a laminate according to one embodiment of the present invention, the precoat layer (X) and the layer (Y) may each be a single layer or two or more layers. In a laminate according to one embodiment of the present invention, the precoat layer (X) is preferably a single layer. In a laminate according to one embodiment of the present invention, the layer (Y) is preferably a single layer. When there are two or more precoat layers (X) and two or more layers (Y), the compositions, thicknesses, etc. of the precoat layers (X) and the layer (Y) may be the same or different.

[0087] When the laminate according to one embodiment of the present invention has a heat seal layer (Z), the heat seal layer (Z) may be a single layer or two or more layers. In the laminate according to one embodiment of the present invention, the heat seal layer (Z) is preferably a single layer. When the laminate according to one embodiment of the present invention has an inorganic vapor deposition layer (W), the inorganic vapor deposition layer (W) may be a single layer or two or more layers. In the laminate according to one embodiment of the present invention, the inorganic vapor deposition layer (W) is preferably a single layer. When there are two or more layers of either the heat seal layer (Z) or the inorganic vapor deposition layer (W), the compositions, thicknesses, etc. of the layers may be the same or different.

[0088] Examples of the layer structure of the laminate according to one embodiment of the present invention are as follows: X represents the precoat layer (X), Y represents the layer (Y), Z represents the heat seal layer (Z), W represents the inorganic vapor deposition layer (W), and V represents other layers. Paper substrate / X / Y Paper substrate / X / Y / Z Paper substrate / X / Y / W Paper substrate / X / Y / W / Z Paper substrate / X / W / Y / Z V / Paper substrate / X / Y V / Paper substrate / X / Y / Z V / Paper substrate / X / Y / W V / Paper substrate / X / Y / W / Z V / Paper substrate / X / W / Y / Z Y / X / Paper substrate / X / Y V / Y / X / Paper substrate / X / Y / Z

[0089] The laminate according to one embodiment of the present invention can be suitably used as greaseproof paper, gas barrier paper, flavor barrier paper, packaging material, etc. When the laminate has a heat seal layer (Z), it can also be used in a state where it has been formed into a predetermined shape (for example, a bag shape) by heat sealing the heat seal layers (Z) together. The heat sealing method is not particularly limited, and known methods can be used, and heat sealing can be performed using, for example, a hot plate heat sealer, an impulse sealer, an ultrasonic sealer, a frictional heat sealer, a dielectric heating sealer, etc.

[0090] <Method for Producing Laminate> The method for producing a laminate according to one embodiment of the present invention is not particularly limited, but it can typically be produced by providing a precoat layer (X) and a layer (Y) in this order on a paper substrate by coating. Even when produced through multiple coating processes, the laminate has excellent coatability when forming the layer (Y), resulting in good productivity. The laminate according to one embodiment of the present invention may be coated paper. The method for producing a laminate according to one embodiment of the present invention may include the steps of preparing a coating liquid (coating liquid for forming layer (Y)) containing PVOH (A) and a solvent, and applying the coating liquid onto the precoat layer (X). The step of preparing the coating liquid may include the step of mixing PVOH (B) and PVOH (C).

[0091] In the case of a laminate having a heat seal layer (Z), the heat seal layer (Z) can also be provided by coating. The heat seal layer (Z) may be provided by a method other than coating. In addition, in the case of a laminate having an inorganic vapor deposition layer (W), the inorganic vapor deposition layer (W) can be provided by vapor deposition.

[0092] For example, the precoat layer (X), layer (Y), and heat seal layer (Z) can be formed by applying and drying a coating liquid for forming each layer. Drying does not need to be performed after each coating liquid, and a simultaneous multi-layer coating method may be employed. The coating of each coating liquid can be carried out by a conventionally known method. Coating can be carried out using, for example, a blade coater, a flexo coater, a comma coater, a metering rod size press, a two-roll size press, a shim sizer, a bar coater, an air knife coater, a slit die coater, a gravure coater, a reverse gravure coater, a microgravure coater, a gate roll coater, a curtain coater, or the like.

[0093] The method for drying the applied coating liquid is not particularly limited, and can be carried out using, for example, a hot air dryer, an infrared dryer, a gas burner, a hot plate, or the like.

[0094] The solvent or dispersion medium for the coating liquid for forming each layer is not particularly limited, and water or an organic solvent (ethanol, isopropyl alcohol, methyl ethyl ketone, toluene, etc.) can be used, with water being preferred.

[0095] The solid content (solid content concentration) of the coating liquid for forming each layer is not particularly limited, but can be, for example, 3% by mass or more and 70% by mass or less, 5% by mass or more and 50% by mass or less, or 10% by mass or more and 30% by mass or less.

[0096] The viscosity of the coating liquid for forming layer (Y) at 20° C. is preferably 20 mPa·s or more and less than 2,000 mPa·s, and more preferably 100 mPa·s or more and less than 1,500 mPa·s. When the viscosity of the coating liquid for forming layer (Y) is within the above range, particularly good coatability can be exhibited.

[0097] When a coating liquid with high viscosity is applied using a wire bar, streaks from the wire bar may remain as irregularities on the surface of the layer, resulting in surface defects. In contrast, by using a coating liquid having a viscosity within the above range in forming the layer (Y), the occurrence of surface defects in the layer (Y) can be suppressed.

[0098] The inorganic vapor deposition layer (W) can be formed by a known vapor deposition method such as vacuum deposition, sputtering, ion plating, or chemical vapor deposition (CVD).

[0099] <Grease-resistant paper> The grease-resistant paper according to one embodiment of the present invention includes the laminate according to one embodiment of the present invention. The grease-resistant paper according to one embodiment of the present invention may be made of the laminate according to one embodiment of the present invention.

[0100] The greaseproof paper has good productivity and excellent water vapor barrier properties after folding. The greaseproof paper is suitable for use as packaging for oily foods such as French fries and fried chicken, packaging for wrapping butter, and cooking paper for baking bread and cakes.

[0101] The oil resistance (KIT value) of the greaseproof paper is preferably at least grade 5, and more preferably at least grade 6 or at least grade 7. This oil resistance is a value measured on the surface by a kit test based on TAPPI No. T559cm-02.

[0102] <Gas barrier paper> The gas barrier paper according to one embodiment of the present invention includes the laminate according to one embodiment of the present invention. The gas barrier paper according to one embodiment of the present invention may be made of the laminate according to one embodiment of the present invention.

[0103] The gas barrier paper has good productivity and excellent water vapor barrier properties even after folding. The gas barrier paper is suitable for use as packaging material for, for example, food, agricultural chemicals, pharmaceuticals, cosmetics, medical products, electronic components, clothing, etc.

[0104] The oxygen permeability of the gas barrier paper is 50 cc / m ２ ・24 hours or less is preferable, 30cc / m ２ 24 hours or less is more preferable, 10 cc / m ２ The oxygen permeability is a value measured under conditions of 23°C and 65% RH.

[0105] <Packaging Material> A packaging material according to one embodiment of the present invention includes the grease-resistant paper according to one embodiment of the present invention or the gas barrier paper according to one embodiment of the present invention. A packaging material according to one embodiment of the present invention may include the laminate according to one embodiment of the present invention. A packaging material according to one embodiment of the present invention may be made of the laminate according to one embodiment of the present invention, the grease-resistant paper according to one embodiment of the present invention, or the gas barrier paper according to one embodiment of the present invention.

[0106] The packaging material has good productivity and excellent water vapor barrier properties after folding. The packaging material is suitable for use as packaging for, for example, food, agricultural chemicals, pharmaceuticals, cosmetics, medical products, electronic components, clothing, etc.

[0107] The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples in any way.

[0108] (Method for Measuring Molecular Weight) The molecular weight of PVOH was measured by the following procedure. First, PVOH was dissolved in a 0.1 M aqueous sodium nitrate solution, and then acetonitrile was added to prepare a 0.1 mass % PVOH aqueous solution with a 0.1 M aqueous sodium nitrate solution / acetonitrile ratio of 8 / 2 (volume ratio). 0.1 mL of the prepared PVOH aqueous solution was injected into a GPC and analyzed. The detailed conditions were: a GPC101 apparatus (manufactured by Shodex Corporation), two α-M columns (manufactured by Tosoh Corporation), a temperature of 40°C, an injection amount of 0.1 mL, a detector RI (differential refractometer), and a standard polyethylene glycol. The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were determined for the measured molecular weight.

[0109] (Evaluation of Coatability) A 12% by mass aqueous solution of PVOH was prepared, and the viscosity was measured at 20°C using a Brookfield viscometer. The coatability was evaluated according to the following criteria: A: Viscosity less than 1,500 mPa·s B: Viscosity 1,500 mPa·s or more but less than 2,000 mPa·s C: Viscosity 2,000 mPa·s or more

[0110] (Evaluation of water vapor barrier property after folding) The laminate was folded in half with the coated surface facing outward, pressed to create a complete crease, then unfolded, and further folded with the coated surface facing inward so that the crease was perpendicular to the original crease, and pressed to create a complete crease. Thereafter, the water vapor transmission rate (WVTR) of the laminate was measured at a temperature of 40°C and a relative humidity of 90% using the cup method in accordance with JIS Z 2080, with the coated surface facing inward.

[0111] (Evaluation of oil resistance after folding) The oil resistance of the laminate after folding was evaluated by a KIT test. Specifically, a KIT test of the folded portion was carried out based on TAPPI No. T559cm-02. In the KIT test of the folded portion, the laminate was folded in half with the coated surface facing outward, pressed to create a complete crease, and then unfolded, and the oil resistance of the crease portion was measured based on TAPPI No. T559cm-02. The measurement was carried out visually.

[0112] [Production Example] Production of Polymer (PVOH (A)) and Evaluation of Coatability

[0113] The PVOH (B) and PVOH (C) used to obtain the following polymers (PVOH (A)) were both produced by conventionally known methods.

[0113] [PVOH1] PVOH1 was obtained by mixing 75 parts by mass of PVOH (B) having a weight average molecular weight (Mw) of 54,600, a degree of saponification of 98.4 mol%, and an ethylene modification content of 5.2 mol% with 25 parts by mass of unmodified PVOH (C) having a weight average molecular weight (Mw) of 15,600 and a degree of saponification of 98.7 mol%. PVOH1 had a weight average molecular weight (Mw) of 46,500, a degree of saponification of 98.5 mol%, and a molecular weight distribution (Mw / Mn) of 3.5. A 12% by mass aqueous solution of PVOH1 was prepared and its coatability was evaluated. The viscosity was 1,242 mPa·s, and the coatability was rated A.

[0114] [PVOH2] PVOH2 was obtained by mixing 75 parts by mass of PVOH (B) having a weight average molecular weight (Mw) of 57,900, a degree of saponification of 95.7 mol%, and an ethylene modification content of 5.0 mol% with 25 parts by mass of unmodified PVOH (C) having a weight average molecular weight (Mw) of 15,300 and a degree of saponification of 96.2 mol%. PVOH2 had a weight average molecular weight (Mw) of 46,300, a degree of saponification of 95.8 mol%, and a molecular weight distribution (Mw / Mn) of 3.9. A 12% by mass aqueous solution of PVOH2 was prepared and its coatability was evaluated. The viscosity was 1,280 mPa·s, and the coatability was rated A.

[0115] [PVOH3] PVOH3 was obtained by mixing 80 parts by mass of unmodified PVOH (B) having a weight average molecular weight (Mw) of 63,300 and a degree of saponification of 98.2 mol% with 20 parts by mass of unmodified PVOH (C) having a weight average molecular weight (Mw) of 15,600 and a degree of saponification of 98.7 mol%. PVOH3 had a weight average molecular weight (Mw) of 52,700, a degree of saponification of 98.3 mol%, and a molecular weight distribution (Mw / Mn) of 4.0. A 12% by mass aqueous solution of PVOH3 was prepared and its coatability was evaluated. The viscosity was 1,620 mPa s, and the coatability was rated B.

[0116] [PVOH4] PVOH4 was obtained by mixing 80 parts by mass of PVOH (B) having a weight average molecular weight (Mw) of 54,600, a degree of saponification of 98.4 mol%, and an ethylene modification content of 5.2 mol% with 20 parts by mass of PVOH (C) having a weight average molecular weight (Mw) of 12,200, a degree of saponification of 98.6 mol%, and an ethylene modification content of 9.0 mol%. PVOH4 had a weight average molecular weight (Mw) of 46,600, a degree of saponification of 98.4 mol%, and a molecular weight distribution (Mw / Mn) of 3.9. A 12% by mass aqueous solution of PVOH4 was prepared and its coatability was evaluated. The viscosity was 1,210 mPa·s, and the coatability was rated A.

[0117] [PVOH5] PVOH (B) having a weight average molecular weight (Mw) of 54,600, a degree of saponification of 98.4 mol%, and an ethylene modification amount of 5.2 mol% was designated PVOH5. The molecular weight distribution (Mw / Mn) of PVOH5 was 3.0. A 12% by mass aqueous solution of PVOH5 was prepared and its coatability was evaluated. The viscosity was 2,950 mPa s, and the coatability was rated C.

[0118] [PVOH6] PVOH (C) having a weight average molecular weight (Mw) of 12,200, a degree of saponification of 98.6 mol%, and an ethylene modification amount of 9.0 mol% was designated PVOH6. The molecular weight distribution (Mw / Mn) of PVOH6 was 2.0. A 12% by mass aqueous solution of PVOH6 was prepared and its coatability was evaluated. The viscosity was 54 mPa s, and the coatability was rated A.

[0119] [PVOH7] PVOH7 was obtained by mixing 50 parts by mass of unmodified PVOH (B) having a weight average molecular weight (Mw) of 94,900 and a degree of saponification of 98.8 mol% with 50 parts by mass of unmodified PVOH (C) having a weight average molecular weight (Mw) of 15,600 and a degree of saponification of 98.5 mol%. PVOH7 had a weight average molecular weight (Mw) of 48,000, a degree of saponification of 98.6 mol%, and a molecular weight distribution (Mw / Mn) of 4.7. A 12% by mass aqueous solution of PVOH7 was prepared and its coatability was evaluated. The viscosity was 1,120 mPa s, and the coatability was rated A.

[0120] [PVOH8] Unmodified PVOH (B) having a weight average molecular weight (Mw) of 63,300 and a degree of saponification of 98.2 mol% was designated PVOH8. The molecular weight distribution (Mw / Mn) of PVOH8 was 3.6. A 12% by mass aqueous solution of PVOH8 was prepared and its coatability was evaluated. The viscosity was 3,094 mPa s, and the coatability was rated C.

[0121] [Example 1] A dispersion was prepared as a coating liquid (X) for forming a precoat layer (X) by blending 5 parts by mass of a cation-modified amide resin ("SPI-203" manufactured by Taoka Chemical Co., Ltd.) and 15 parts by mass of a layered inorganic compound having an aspect ratio of approximately 300 ("ME300B-4T" manufactured by Katakura Co-op Agri Co., Ltd.) with 100 parts by mass of a solid content of an ethylene-acrylic acid copolymer ("Zaixen AC" manufactured by Mitsui Chemicals, Inc.). As a coating liquid (Y) for forming a layer (Y), a 12% by mass aqueous solution of PVOH1 was prepared. ２ The coating weight after drying was 6 g / m on bleached kraft paper. ２ The coating solution (X) was applied using a wire bar so that the coating amount after drying was 2 g / m. ２ The coating solution (Y) was applied using a wire bar so that the thickness of the laminated sheet became 1 / 2 mm, and the coated sheet was dried at 100° C. for 5 minutes to provide a layer (Y). The water vapor transmission rate (WVTR) of the resulting laminated sheet after bending was 11 cc / day, and the water vapor barrier property was good.

[0122] Example 2 A dispersion was prepared as a coating solution (X) for forming a precoat layer (X) by blending 5 parts by mass of a cation-modified amide resin ("SPI-203" manufactured by Taoka Chemical Co., Ltd.) and 10 parts by mass of a layered inorganic compound ("ME300B-4T" manufactured by Katakura Co-op Agri Co., Ltd.) with 100 parts by mass of a solid content of an ethylene-acrylic acid copolymer ("Zaixen AC" manufactured by Mitsui Chemicals, Inc.). A dispersion was prepared as a coating solution (Y) for forming a layer (Y) by blending 5 parts by mass of a layered inorganic compound ("ME300B-4T" manufactured by Katakura Co-op Agri Co., Ltd.) with 12% by mass of an aqueous solution of PVOH 1 in terms of solid content ratio to 100 parts by mass of PVOH 1. A dispersion of an ethylene-acrylic acid copolymer ("Zaixen AC" manufactured by Mitsui Chemicals, Inc.) was prepared as a coating solution (Z) for forming a heat seal layer (Z). A paper substrate with a basis weight of 80 g / m2 was used. ２ The coating weight after drying was 10 g / m on bleached kraft paper. ２ The coating solution (X) was applied using a wire bar so that the coating amount after drying was 3 g / m.２ The coating solution (Y) was applied using a wire bar so that the coating amount after drying was 6 g / m. ２ The coating liquid (Z) was applied onto the laminate so that the thickness of the laminate was 1 / 3 of the thickness of the heat seal layer (Z), and the laminate was dried at 100°C for 5 minutes to provide a heat seal layer (Z). The water vapor transmission rate (WVTR) of the resulting laminate after bending was 16 cc / day, and the water vapor barrier property was good. The oil resistance after bending was also good, being KIT7 or higher.

[0123] [Example 3] As a coating liquid (X) for forming a precoat layer (X), a dispersion was prepared by blending 5 parts by mass of a cation-modified amide resin ("SPI-203" manufactured by Taoka Chemical Co., Ltd.) and 10 parts by mass of a layered inorganic compound ("ME300B-4T" manufactured by Katakura Co-op Agri Co., Ltd.) with 100 parts by mass of a solid content of an ethylene-acrylic acid copolymer ("Zaixen AC" manufactured by Mitsui Chemicals, Inc.). As a coating liquid (Y) for forming a layer (Y), a 12% by mass aqueous solution of PVOH2 was prepared. ２ The coating weight after drying was 6 g / m on bleached kraft paper. ２ The coating solution (X) was applied using a wire bar so that the coating amount after drying was 2 g / m. ２ The coating solution (Y) was applied using a wire bar so that the thickness of the laminate became 1 / 3 of the thickness of the laminate, and the laminate was dried at 100° C. for 5 minutes to provide a layer (Y). The water vapor transmission rate (WVTR) of the resulting laminate after bending was 21 cc / day, and the water vapor barrier property was good.

[0124] [Example 4] As a coating liquid (X) for forming a precoat layer (X), a dispersion was prepared by blending 5 parts by mass of a cation-modified amide resin ("SPI-203" manufactured by Taoka Chemical Co., Ltd.) and 10 parts by mass of a layered inorganic compound ("ME300B-4T" manufactured by Katakura Co-op Agri Co., Ltd.) with 100 parts by mass of a solid content of an ethylene-acrylic acid copolymer ("Zaixen AC" manufactured by Mitsui Chemicals, Inc.). As a coating liquid (Y) for forming a layer (Y), a 12% by mass aqueous solution of PVOH3 was prepared. ２The coating weight after drying was 6 g / m on bleached kraft paper. ２ The coating solution (X) was applied using a wire bar so that the coating amount after drying was 2 g / m. ２ The coating solution (Y) was applied using a wire bar so that the thickness of the laminated sheet became 100° C. and the applied coating solution (Y) was dried at 100° C. for 5 minutes to provide a layer (Y). The water vapor transmission rate (WVTR) of the resulting laminated sheet after bending was 19 cc / day, and the water vapor barrier property was good.

[0125] [Example 5] As a coating liquid (X) for forming a precoat layer (X), a dispersion was prepared by blending 5 parts by mass of a cation-modified amide resin ("SPI-203" manufactured by Taoka Chemical Co., Ltd.) and 10 parts by mass of a layered inorganic compound ("ME300B-4T" manufactured by Katakura Co-op Agri Co., Ltd.) with 100 parts by mass of a solid content of an ethylene-acrylic acid copolymer ("Zaixen AC" manufactured by Mitsui Chemicals, Inc.). As a coating liquid (Y) for forming a layer (Y), a 12% by mass aqueous solution of PVOH4 was prepared. ２ The coating weight after drying was 6 g / m on bleached kraft paper. ２ The coating solution (X) was applied using a wire bar so that the coating amount after drying was 2 g / m. ２ The coating solution (Y) was applied using a wire bar so that the thickness of the laminate became 1 / 3 of the thickness of the laminate, and the laminate was dried at 100° C. for 5 minutes to provide a layer (Y). The water vapor transmission rate (WVTR) of the resulting laminate after bending was 17 cc / day, and the water vapor barrier property was good.

[0126] [Example 6] A dispersion of ethylene-acrylic acid copolymer ("Zaixen AC" manufactured by Mitsui Chemicals, Inc.) was prepared as the coating liquid (X) for forming the precoat layer (X) and the coating liquid (Z) for forming the heat seal layer (Z). A 12% by mass aqueous solution of PVOH1 was prepared as the coating liquid (Y) for forming the layer (Y). ２ The coating weight after drying was 9 g / m on bleached kraft paper. ２The coating solution (X) was applied using a reverse gravure coater so that the coating amount after drying was 1.8 g / m. ２ The coating solution (Y) was applied using a reverse gravure coater so that the coating amount after drying was 6 g / m. Then, an aluminum vapor deposition layer having an average thickness of about 40 nm was formed on the layer (Y) as the inorganic vapor deposition layer (W). ２ The coating liquid (Z) was applied onto the laminate so that the thickness of the laminate was 100°C and the laminate was dried at 100°C for 5 minutes to provide a heat seal layer (Z). The water vapor transmission rate (WVTR) of the resulting laminate after bending was 7 cc / day, and the water vapor barrier property was good. The oil resistance after bending was also good, being KIT7 or higher.

[0127] Comparative Example 1 A dispersion was prepared as a coating solution (X) for forming a precoat layer (X) by blending 5 parts by mass of a cation-modified amide resin ("SPI-203" manufactured by Taoka Chemical Co., Ltd.) and 15 parts by mass of a layered inorganic compound ("ME300B-4T" manufactured by Katakura Co-op Agri Co., Ltd.) with 100 parts by mass of a solid content of an ethylene-acrylic acid copolymer ("Zaixen AC" manufactured by Mitsui Chemicals, Inc.). A 12% by mass aqueous solution of PVOH5 was prepared as a coating solution (Y) for forming a layer (Y). ２ The coating weight after drying was 6 g / m on bleached kraft paper. ２ The coating solution (X) was applied using a wire bar so that the coating amount after drying was 2 g / m. ２ The coating solution (Y) was applied using a wire bar so that the thickness of the coated surface was 100° C. and dried for 5 minutes at 100° C. The coated surface of the layer (Y) in the obtained laminate had unevenness due to the high viscosity of the coating solution (Y), and the streaks of the wire bar remained, resulting in a poor surface.

[0128] Comparative Example 2 A dispersion was prepared as a coating solution (X) for forming a precoat layer (X) by blending 5 parts by mass of a cation-modified amide resin ("SPI-203" manufactured by Taoka Chemical Co., Ltd.) and 15 parts by mass of a layered inorganic compound ("ME300B-4T" manufactured by Katakura Co-op Agri Co., Ltd.) with 100 parts by mass of a solid content of an ethylene-acrylic acid copolymer ("Zaixen AC" manufactured by Mitsui Chemicals, Inc.). A 12% by mass aqueous solution of PVOH6 was prepared as a coating solution (Y) for forming a layer (Y). ２ The coating weight after drying was 6 g / m on bleached kraft paper. ２ The coating solution (X) was applied using a wire bar so that the coating amount after drying was 2 g / m. ２ The coating solution (Y) was applied using a wire bar so that the thickness of the laminated sheet became 1 / 3 mm, and the coated sheet was dried at 100° C. for 5 minutes to provide a layer (Y). The water vapor transmission rate (WVTR) of the resulting laminated sheet after bending was 36 cc / day, and the water vapor barrier property was poor.

[0129] Comparative Example 3 A dispersion was prepared as a coating solution (X) for forming a precoat layer (X) by blending 5 parts by mass of a cation-modified amide resin ("SPI-203" manufactured by Taoka Chemical Co., Ltd.) and 15 parts by mass of a layered inorganic compound ("ME300B-4T" manufactured by Katakura Co-op Agri Co., Ltd.) with 100 parts by mass of a solid content of an ethylene-acrylic acid copolymer ("Zaixen AC" manufactured by Mitsui Chemicals, Inc.). A 12% by mass aqueous solution of PVOH7 was prepared as a coating solution (Y) for forming a layer (Y). ２ The coating weight after drying was 6 g / m on bleached kraft paper. ２ The coating solution (X) was applied using a wire bar so that the coating amount after drying was 2 g / m. ２ The coating solution (Y) was applied using a wire bar so that the thickness of the laminate became 1 / 3 mm, and the laminate was dried at 100° C. for 5 minutes to provide a layer (Y). The water vapor transmission rate (WVTR) of the resulting laminate after bending was 73 cc / day, and the water vapor barrier property was poor.

[0130] Comparative Example 4 A dispersion was prepared as a coating solution (X) for forming a precoat layer (X) by blending 5 parts by mass of a cation-modified amide resin ("SPI-203" manufactured by Taoka Chemical Co., Ltd.) and 15 parts by mass of a layered inorganic compound ("ME300B-4T" manufactured by Katakura Co-op Agri Co., Ltd.) with 100 parts by mass of a solid content of an ethylene-acrylic acid copolymer ("Zaixen AC" manufactured by Mitsui Chemicals, Inc.). A 12% by mass aqueous solution of PVOH8 was prepared as a coating solution (Y) for forming a layer (Y). A paper substrate having a basis weight of 80 g / m2 was used. ２ The coating weight after drying was 6 g / m on bleached kraft paper. ２ The coating solution (X) was applied using a wire bar so that the coating amount after drying was 2 g / m. ２ The coating solution (Y) was applied using a wire bar so that the thickness of the coated surface was 100° C. and dried for 5 minutes at 100° C. The coated surface of the layer (Y) in the obtained laminate had unevenness due to the high viscosity of the coating solution (Y), and the streaks of the wire bar remained, resulting in a poor surface.

[0131] The results of the above-mentioned Examples and Comparative Examples are shown in Tables 1 and 2.

[0132]

[0133]

[0134] Each of the laminates of Examples 1 to 6 had excellent water vapor barrier properties after bending. Furthermore, each of the coating solutions used to form layer (Y) of each of the laminates of Examples 1 to 6 had low viscosity and excellent coatability. Therefore, each of the laminates of Examples 1 to 6 also had good productivity. Furthermore, no wire bar streaks remained on the surface of layer (Y) of each of the laminates of Examples 1 to 6, and the laminates had good surface properties.

[0135] The laminate of the present invention can be suitably used as a packaging material such as greaseproof paper, gas barrier paper, and flavor barrier paper.

Claims

1. A laminate having a precoat layer (X) and a layer (Y) containing a vinyl alcohol-based polymer (A) on a paper substrate in this order, wherein the content of the vinyl alcohol-based polymer (A) in the layer (Y) is 50% by mass or more and 100% by mass or less, the molecular weight of the vinyl alcohol-based polymer (A) converted into polyethylene glycol by gel permeation chromatography analysis using a differential refractometer is a weight average molecular weight (Mw) of 20,000 or more and 54,000 or less and a molecular weight distribution (Mw / Mn) of 3.2 or more and 4.5 or less, and the degree of saponification of the vinyl alcohol-based polymer (A) is 90 mol % or more and 100 mol % or less.

2. The laminate according to claim 1, wherein the vinyl alcohol polymer (A) comprises a vinyl alcohol polymer (B) having a weight average molecular weight (Mw) of 20,000 or more and 80,000 or less, and a vinyl alcohol polymer (C) having a weight average molecular weight (Mw) of 10,000 or more and less than 20,000.

3. The laminate described in claim 2, wherein the content of the vinyl alcohol polymer (B) is 60 parts by mass or more and 90 parts by mass or less, and the content of the vinyl alcohol polymer (C) is 10 parts by mass or more and 40 parts by mass or less, based on the total of the vinyl alcohol polymer (B) and the vinyl alcohol polymer (C).

4. A laminate according to any one of claims 1 to 3, wherein the vinyl alcohol polymer (A) comprises an ethylene-modified vinyl alcohol polymer.

5. The laminate according to claim 4, wherein the ethylene unit content of the ethylene-modified vinyl alcohol polymer is from 0.1 mol % to 19 mol %.

6. The laminate according to claim 1 or 2, further comprising a heat seal layer (Z).

7. The laminate according to claim 1 or 2, wherein the precoat layer (X) contains an inorganic compound (D).

8. The laminate according to claim 7, wherein the inorganic compound (D) is a layered inorganic compound having an aspect ratio of 50 or more.

9. The laminate according to claim 1 or 2, further comprising an inorganic vapor deposition layer (W) adjacent to at least one surface of the layer (Y).

10. Greaseproof paper comprising the laminate of claim 1 or claim 2.

11. A gas barrier paper comprising the laminate according to claim 1 or 2.

12. A packaging material comprising the greaseproof paper according to claim 10.

13. A packaging material comprising the gas barrier paper according to claim 11.

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