JP2022084283A - Paper laminate and method for manufacturing the same - Google Patents

Abstract

To provide a paper laminate which is excellent in processing resistance and has high oxygen barrier property (especially, oxygen barrier property after bending).SOLUTION: A paper laminate has a clay coat layer, an undercoat layer, a vapor-deposited layer and an overcoat layer in this order on at least one surface of a paper base material, in which the vapor-deposited layer is at least any one of a layer composed of metal and a layer composed of ceramic, and has a thickness of 1 nm or more and 1,000 nm or less, and the overcoat layer contains a polyurethane-based resin.SELECTED DRAWING: None

Description

The present invention relates to a paper laminate and a method for producing the same.

Conventionally, a packaging material in which a paper substrate is provided with a steam barrier property that barriers water vapor and a gas barrier property that barriers a gas other than water vapor, and in particular, a packaging material that is provided with an oxygen barrier property that barriers oxygen to a paper substrate has been used. , Used in the packaging of foods, medical products, electronic parts, etc. to prevent deterioration of the quality of the contents.

As a method for imparting water vapor barrier property or gas barrier property to a paper base material, a method of laminating a synthetic resin film having excellent water vapor barrier property or gas barrier property on the paper base material is common. However, it is difficult to recycle paper, synthetic resin, etc. after use of a material in which a synthetic resin film or the like is laminated on a paper base material, which poses an environmental problem.

Therefore, the development of a barrier material having a water vapor barrier property and a gas barrier property has been promoted without using a synthetic resin film or the like. For example, Patent Document 1 discloses a paper packaging material having an organic substance coating layer, a metal or metal oxide layer, and an organic substance coating layer inside a paper layer and having a barrier property against moisture and oxygen.

On the other hand, metal-deposited paper is widely used for label paper with excellent design such as liquor, beer, and refreshing drinking water, wrapping paper for confectionery, etc. by taking advantage of its glossiness. Since it is necessary to form a thin film, improvements in its adhesiveness and manufacturing methods are being studied. For example, Patent Document 2 discloses an aluminum-deposited paper using a base paper in which an aluminum-deposited layer is provided on a base paper and the back surface is treated so that the natural polarization potential value of the surface of the vapor-deposited layer is within a specific range. There is.

Japanese Patent Application Laid-Open No. 2002-321307 Japanese Unexamined Patent Publication No. 4-65599

Although attempts have been made to improve the barrier properties such as water vapor barrier property and oxygen barrier property of the paper substrate by using metal as in Patent Documents 1 and 2, in consideration of recyclability, flexibility, and texture of paper. When a very thin film such as a vapor-deposited film is formed, durability during use or processing becomes a problem. That is, when three-dimensional processing such as embossing or bending processing is performed, there is a problem that the barrier performance is deteriorated probably because the metal vapor deposition film is damaged such as cracks.
Therefore, it is an object of the present invention to provide a paper laminate having excellent resistance to processing and having high oxygen barrier properties (particularly, oxygen barrier properties after bending).

As a result of diligent studies, the present inventors have a clay coat layer, an undercoat layer, a vapor deposition layer and an overcoat layer in this order on at least one surface of the paper substrate, and the vapor deposition layer includes a layer made of metal and a layer made of metal. It has been found that at least one of the layers made of ceramic, which has a specific thickness, and the overcoat layer is a paper laminate containing a polyurethane resin, which solves the above-mentioned problems.
That is, the present invention relates to the following <1> to <20>.
<1> A clay coat layer, an undercoat layer, a vapor deposition layer, and an overcoat layer are provided in this order on at least one surface of a paper substrate, and the vapor deposition layer is at least one of a layer made of metal and a layer made of ceramic. The overcoat layer is a paper laminate containing a polyurethane resin and having a thickness of 1 nm or more and 1000 nm or less.
<2> The paper laminate according to <1>, wherein the overcoat layer has a thickness of 0.1 μm or more and 10 μm or less.
<3> The paper laminate according to <1> or <2>, wherein the coating amount of the overcoat layer is 0.1 g / m ² or more and 10 g / m ² or less in terms of solid content.
<4> The polyurethane resin contained in the overcoat layer has an oxygen permeability of 100 ml / (m ² · day · atm) or less at 23 ° C. and 50% RH when converted into a sheet having a thickness of 25 μm. The paper laminate according to any one of <1> to <3>.
<5> The polyurethane resin contained in the overcoat layer contains at least one of a structural unit derived from metaxylylene diisocyanate and a structural unit derived from hydrogenated metaxylylene diisocyanate, according to the above <1> to <4>. The paper laminate according to any one.
<6> The polyurethane resin contained in the overcoat layer has a total content of the constituent units derived from metaxylylene diisocyanate and the constituent units derived from hydrogenated metaxylylene diisocyanate 50 with respect to the total amount of the constituent units derived from polyisocyanate. The paper laminate according to <5> above, which is mol% or more.
<7> The paper laminate according to any one of <1> to <6>, wherein the coating amount of the clay coat layer is 5 g / m ² or more and 30 g / m ² or less in terms of solid content.
<8> The paper laminate according to any one of <1> to <7>, wherein the coating amount of the undercoat layer is 0.1 g / m ² or more and 10 g / m ² or less in terms of solid content.
<9> The undercoat layer mainly contains a binder, and the resin contained in the binder is one or more selected from vinyl alcohol-based resin, acrylic resin, polyurethane-based resin, and polyester resin. <1> The paper laminate according to any one of <8>.
<10> The polyurethane resin contained in the undercoat layer has an oxygen permeability of 100 ml / (m ² · day · atm) or less at 23 ° C. and 50% RH when converted into a sheet having a thickness of 25 μm. The paper laminate according to <9>.
<11> In the above <9> or <10>, the polyurethane resin contained in the undercoat layer contains at least one of a structural unit derived from metaxylylene diisocyanate and a structural unit derived from hydrogenated metaxylylene diisocyanate. The paper laminate described.
<12> The polyurethane resin contained in the undercoat layer has a total content of the constituent units derived from metaxylylene diisocyanate and the constituent units derived from hydrogenated metaxylylene diisocyanate 50 with respect to the total amount of the constituent units derived from polyisocyanate. The paper laminate according to <11>, which is mol% or more.
<13> The paper laminate according to any one of <1> to <12>, wherein the basis weight of the paper base material is 20 g / m ² or more and 500 g / m ² or less.
<14> The paper laminate according to any one of <1> to <13>, wherein the vapor-deposited layer is at least one of a layer made of aluminum, a layer made of silicon oxide, and a layer made of aluminum oxide.
<15> The paper laminate according to any one of <1> to <14>, further comprising a resin layer containing a thermoplastic resin having a thickness of 1 μm or more and less than 15 μm on the surface of the overcoat layer.
<16> The paper laminate according to <15>, wherein the thermoplastic resin is a heat-sealable resin.
<17> The thermoplastic resin is at least one selected from an olefin / unsaturated carboxylic acid-based copolymer, a biodegradable resin, a polyolefin resin, an acrylic resin, and a vinyl alcohol-based resin. Alternatively, the paper laminate according to <16>.
<18> The paper laminate according to <17>, wherein the thermoplastic resin is an olefin / unsaturated carboxylic acid-based copolymer.
<19> The paper laminate according to any one of <1> to <18>, wherein the undercoat layer and the overcoat layer are formed by using an aqueous medium.
<20> An overcoat layer coating liquid is applied to a vapor-deposited paper having a clay coat layer, an undercoat layer, and a vapor-deposited layer in this order on at least one surface of a paper substrate, dried, and overcoated. A method for manufacturing a paper laminate including a step of forming a layer, wherein the vapor-deposited layer is at least one of a layer made of metal and a layer made of ceramic, and has a thickness of 1 nm or more and 1000 nm or less, and is over. The coating liquid for the coat layer is a method for manufacturing a paper laminate containing a polyurethane resin.

According to the present invention, it is possible to provide a paper laminate having excellent resistance to processing and having high oxygen barrier properties (particularly, oxygen barrier properties after bending).

[Paper laminate]
The paper laminate of the present embodiment has a clay coat layer, an undercoat layer, a vapor deposition layer, and an overcoat layer in this order on at least one surface of a paper substrate, and the vapor deposition layer is a layer made of metal and a ceramic. The overcoat layer is at least one of layers having a thickness of 1 nm or more and 1000 nm or less, and the overcoat layer contains a polyurethane resin. The paper laminate has excellent resistance to processing and has high barrier performance.
The paper laminate of the present embodiment has a high barrier property by having a thin-film vapor deposition layer, and can further enhance the oxygen barrier property by having an overcoat layer containing a polyurethane resin, and can be used during processing. In addition to being able to protect the vapor-filmed layer and maintain barrier properties even when the paper is deformed, it is also possible to prevent damage to the glossy-filmed layer, and thus it is also excellent in design.
Further, it is preferable that the paper laminate of the present embodiment further has a resin layer, but by further having a resin layer, the protection against the vapor-deposited layer is improved, and depending on the resin constituting the resin layer, heat sealing is performed. It is also more excellent in design because it can impart the property and can surely prevent the vapor-filmed layer having a glossy feeling from being damaged.
By having the clay coat layer, the paper laminate of the present embodiment can seal and smooth the paper base material.
By having the undercoat layer, the paper laminate of the present embodiment can protect the clay coat layer even if the paper is deformed during processing.

The paper substrate may have a thin-film deposition layer on one side or both sides, but it is preferable to have a thin-film deposition layer on one side from the viewpoint of production efficiency. In the present embodiment, even if the vapor deposition layer is provided on only one side, sufficient barrier properties can be exhibited. When the vapor deposition layer is provided on one side, the overcoat layer or the resin layer may be provided only on the vapor deposition layer side.
When the vapor deposition layer is provided on one side from the viewpoint of production efficiency, the paper substrate may be the outermost layer in the paper laminate of the present embodiment.

<Paper base material>
The paper base material in the present embodiment is preferably a generally used paper containing plant-derived pulp as a main component, and more preferably a paper containing wood pulp as a main component. Further, the paper base material used in the paper laminate of the present embodiment is preferably paper containing pulp as a main component, which is easily dispersed in water by a mechanical dissociation action.
Specific examples of the paper base material used in the paper laminate of the present embodiment include bleached kraft paper, unbleached kraft paper, high-quality paper, paperboard, liner paper, coated paper, single-gloss paper, glassin paper, and graphan. Examples include paper. Among these, bleached kraft paper, unbleached kraft paper, woodfree paper, and single glossy paper are preferable.

The dissociation freeness (drainage degree) measured according to JIS P 811-2: 2012 of the paper substrate is preferably 800 ml or less, and more preferably 500 ml or less, from the viewpoint of improving the barrier property. The lower limit is not particularly limited, but from the viewpoint of ease of papermaking, it is preferably 150 ml or more, more preferably 250 ml or more. Here, the freeness of decoupling is a Canadian standard drainage degree obtained by measuring the pulp obtained by decoupling the paper after papermaking in accordance with JIS P 820-1: 2012 in accordance with JIS P 811-2: 2012. Freeens). As a method for beating the pulp in order to adjust the disintegration freeness, a known method can be used.

The degree of size of the paper substrate is not particularly limited, but from the viewpoint of improving the barrier property, it is preferable that the degree of sizing human size according to JIS P 8122: 2004 is 1 second or more. The upper limit is not particularly limited, but is preferably 100 seconds or less, more preferably 30 seconds or less. The degree of size of the paper substrate can be controlled by the type and content of the internal sizing agent, the type of pulp, the smoothing treatment, and the like.
Examples of the internal sizing agent include rosin-based, alkylketene dimer-based, alkenyl succinic anhydride-based, styrene-unsaturated carboxylic acid-based, higher fatty acid-based, petroleum resin-based, and the like. The content of the internal sizing agent is not particularly limited, but is preferably 0 parts by mass or more and preferably 3 parts by mass or less with respect to 100 parts by mass of the pulp of the paper base material.

In addition to the internal sizing agent, other known internal additives may be added to the paper substrate. Examples of internal additives include fillers, paper strength enhancers, yield improvers, pH adjusters, drainage improvers, water resistant agents, fabric softeners, antistatic agents, defoamers, slime control agents, dyes and pigments. And so on.
Examples of fillers include titanium dioxide, kaolin, talc, calcium carbonate (heavy calcium carbonate, light calcium carbonate), calcium sulfite, gypsum, calcined kaolin, white carbon, amorphous silica, delaminated kaolin, diatomaceous soil, and carbonic acid. Examples thereof include magnesium, aluminum hydroxide, calcium hydroxide, magnesium hydroxide and zinc hydroxide.

The paper substrate is obtained by making a papermaking material containing a pulp slurry as a main component.
The pulp slurry is obtained from wood or non-wood raw material chips through steps such as cooking, washing and bleaching. The method in the cooking step, the washing step, the bleaching step and the like is not particularly limited. The pulp slurry obtained through these steps is further beaten in the presence of water. Examples of wood pulp include softwood pulp and hardwood pulp. Examples of non-wood pulp include cotton pulp, hemp pulp, kenaf pulp, bamboo pulp and the like. Materials other than pulp fibers such as synthetic fibers such as rayon fibers and nylon fibers may also be blended as auxiliary paper materials as long as the effects of the present invention are not impaired.

For paper making of a paper base material, a known wet paper machine can be appropriately selected and used.
Examples of the paper machine include a long net type paper machine, a gap former type paper machine, a circular net type paper machine, and a short net type paper machine.
The paper layer formed by the paper machine is preferably conveyed by, for example, felt and dried by a dryer. A multi-stage cylinder dryer may be used as a pre-dryer before drying the dryer.

Further, the paper substrate obtained as described above may be surface-treated with a calendar to make the paper thickness and gloss profile uniform. As the calendar processing, a known calendar processing machine can be appropriately selected and used.

The basis weight of the paper substrate is not particularly limited, but is preferably 20 g / m ² or more, more preferably 30 g / m ² or more, further preferably 40 g / m ² or more, and. It is preferably 500 g / m ² or less, more preferably 400 g / m ² or less, further preferably 200 g / m ² or less, and even more preferably 100 g / m ² or less. The basis weight of the paper substrate is measured in accordance with JIS P 8124: 2011.
From the viewpoint of moldability, the paper substrate preferably has a density of 0.5 / cm ³ or more, more preferably 0.6 / cm ³ or more, and 1.2 g / cm ³ or less. It is preferably 1.0 g / cm ³ or less, and more preferably 1.0 g / cm 3. The density of the paper base material is calculated from the thickness of the paper base material measured in accordance with JIS P 8118: 2014 and the basis weight described above.
From the viewpoint of obtaining a uniform thin-film deposition layer, the paper substrate preferably has a Wangken-type smoothness of at least the surface on which the vapor-film deposition layer is provided, preferably 5 seconds or longer, and more preferably 10 seconds or longer. The upper limit is not particularly limited, but is preferably 1000 seconds or less, for example. Further, from the viewpoint of printability, the paper substrate preferably has a 75 ° glossiness of 5% or more, more preferably 10% or more, and preferably 80% or less. The Oken-type smoothness of the paper substrate is measured in accordance with JIS P 8155: 2010.

<Clay coat layer>
The paper laminate of the present embodiment has a clay coat layer between the paper base material and an undercoat layer described later. This makes it possible to seal and smooth the paper substrate. As a result, a uniform thin-film deposition layer can be formed, and the barrier property is improved.

The clay coat layer is mainly composed of clay and a binder. In addition, "the clay coat layer is mainly composed of clay and a binder" means that the total content of clay and a binder in the clay coat layer is, for example, 50% by mass or more, preferably 60% by mass or more, more preferably. It means that it is 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more. The upper limit is not particularly limited, but is 100% by mass or less. In addition to the clay and the binder, the clay coat layer may further contain any component.
The clay contained in the clay coat layer is not particularly limited, and examples thereof include kaolin, talc, and mica. The aspect ratio of the clay is preferably 10 or more, more preferably 20 or more, and even more preferably 30 or more. The upper limit is not particularly limited, but is preferably 10,000 or less. The aspect ratio can be measured by observation with an electron microscope or X-ray diffraction measurement. The clay content in the clay coat layer is preferably 50% by mass or more, more preferably 60% by mass or more, particularly preferably 70% by mass or more, and 98% by mass or less. It is preferably 90% by mass or less, more preferably 85% by mass or less, and particularly preferably 85% by mass or less.
The binder contained in the clay coat layer is not particularly limited, but includes styrene-butadiene resin; methyl acrylate copolymer, methyl methacrylate copolymer, styrene-acrylic copolymer, styrene-methacrylic copolymer and the like. Acrylic resins; olefin / unsaturated carboxylic acid copolymers such as ethylene-acrylic acid copolymers and ethylene-methacrylic acid copolymers; acrylic resins are preferable, and styrene-acrylic copolymers are preferable. More preferred. The content of the binder in the clay coat layer is preferably 2% by mass or more, more preferably 10% by mass or more, particularly preferably 15% by mass or more, and 50% by mass or less. It is preferably 40% by mass or less, more preferably 30% by mass or less, and particularly preferably 30% by mass or less.
The amount of the clay coat layer applied is not particularly limited, but the solid content is preferably 5 g / m ² or more, more preferably 7 g / m ² or more, and 30 g / m ² or less. It is preferably 20 g / m ² or less, and more preferably 20 g / m 2.
The method for forming the clay coat layer is not particularly limited, but a method of forming by applying a dispersion liquid containing clay and a resin binder onto a paper substrate and drying it is preferable.
As the dispersion liquid containing the clay and the resin binder, an aqueous dispersion liquid is preferable.

<Undercoat layer>
The paper laminate of the present embodiment has an undercoat layer between the clay coat layer and a thin-film deposition layer described later. By providing the undercoat layer, the adhesion between the vapor-film deposition layer and the paper substrate is improved, and the barrier property is improved.

The undercoat layer mainly contains a binder. In addition, "the undercoat layer mainly contains a binder" means that the binder content in the undercoat layer is, for example, 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 80. It means that it is by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass or more. The upper limit is not particularly limited, but is 100% by mass or less. The undercoat layer may further contain any component other than the binder.
The binder contained in the undercoat layer is not particularly limited, but is an alkyd resin; an acrylic resin such as a methyl acrylate copolymer, a methyl methacrylate copolymer, a styrene-acrylic copolymer, and a styrene-methacrylic copolymer. Olefin / unsaturated carboxylic acid-based copolymers such as ethylene-acrylic acid copolymers and ethylene-methacrylic acid copolymers; vinyl alcohol-based resins such as polyvinyl alcohol and ethylene vinyl alcohol copolymers (ethylene-modified polyvinyl alcohol). ; Cellulous resin; Polyurethane resin; Polyester resin and the like. Among these, one or more selected from vinyl alcohol-based resin, acrylic resin, polyurethane-based resin and polyester resin is preferable, and from the viewpoint of further improving the oxygen barrier property, polyvinyl alcohol-based resin and polyurethane-based resin are selected. It is more preferably one or more, and even more preferably a polyurethane resin.
The amount of the undercoat layer applied is not particularly limited, but the solid content is more preferably 0.1 g / m ² or more, more preferably 1 g / m ² or more, and 10 g / m ² or more. It is preferably less than or equal to, and more preferably 5 g / m ² or less.
The method for forming the undercoat layer is not particularly limited, but it is preferable to apply an aqueous medium such as an aqueous solution of a binder or an aqueous dispersion and dry it to form the undercoat layer.

The polyurethane resin as the binder contained in the undercoat layer is not particularly limited, and for example, it can be appropriately selected from those that can be used for the overcoat layer described later. The polyurethane resin as the binder contained in the undercoat layer may be the same type as the polyurethane resin contained in the overcoat layer, or may be of a different type, but may be of the same type. preferable.
The polyurethane resin as the binder contained in the undercoat layer is more preferably one or more selected from the group consisting of polyurethane resin dispersions or emulsions, and further preferably polyurethane resin dispersions or emulsions. It is even more preferable that the polyurethane resin dispersion is preferable.
That is, the polyurethane resin contained in the undercoat layer preferably has an oxygen permeability of 100 ml / (m ² · day · atm) or less at 23 ° C. and 50% RH when converted into a sheet having a thickness of 25 μm. , 50 ml / (m ² , day, atm) or less, more preferably. By including such a polyurethane resin in the undercoat layer, the oxygen barrier property of the paper laminate is further improved.
In the present specification, the oxygen permeability is measured using an oxygen permeability measuring device (OX-TRAN2 / 20 manufactured by MOCON) under the conditions of 23 ° C. and 50% RH.
The polyurethane resin contained in the undercoat layer preferably contains at least one of a constituent unit derived from metaxylylene diisocyanate and a constituent unit derived from hydrogenated metaxylylene diisocyanate. The total content of the constituent units derived from xylylene diisocyanate and the constituent units derived from hydrogenated metaxylylene diisocyanate is preferably 50 mol% or more. Such a polyurethane-based resin exhibits a high cohesive force due to hydrogen bonds and a stacking effect between xylylene groups, and thus has excellent gas barrier properties. The above content can be identified using a known analytical method such as ¹ H-NMR.
As the polyurethane resin, a synthetic product may be used, and examples thereof include the polyurethane resin described in International Publication No. 2015/016869.
As the polyurethane resin, a commercially available product may be used. For example, "Takelac W-based (trade name)", "Takelac WPB-based (trade name)", and "Takelac WS-based (trade name)" manufactured by Mitsui Chemicals, Inc. may be used. ) ”, And specifically, Takelac WPB-341 is exemplified.

<Embedded layer>
The thin-film deposition layer used in the paper laminate of the present embodiment is at least one of a layer made of metal and a layer made of ceramic. That is, the thin-film deposition layer may be any of a metal layer, a ceramic layer, and a laminate of a metal layer and a ceramic layer. When the vapor-filmed layer is a laminate of a metal layer and a ceramic layer, the metal layer may be on the undercoat layer side or the ceramic layer may be on the undercoat layer side, and is not particularly limited.
The thickness of the thin-film deposition layer is 1 nm or more, preferably 2 nm or more, more preferably 3 nm or more, and 1000 nm or less, preferably 500 nm or less, and preferably 100 nm or less. More preferred.
From the viewpoint of barrier properties, the thickness of the thin-film deposition layer is preferably 10 nm or more, more preferably 25 nm or more, and more preferably 80 nm or less, more preferably 70 nm. ..
Further, the thickness of the thin-film deposition layer is preferably 4 nm or more, more preferably 5 nm or more, and more preferably 100 nm or less, preferably 70 nm, from the viewpoint of adhesion to other layers and cost. It is more preferably less than or equal to, and particularly preferably 60 nm or less.

The thin-film deposition layer may be a layer made of metal, a layer made of ceramic, or a laminate thereof, but a layer made of metal is preferable.
When the vapor-filmed layer is a layer made of metal, specific examples of the metal include aluminum and titanium. These may be used alone or in combination of two or more. Among these, aluminum is preferable.
When the vapor-filmed layer is a layer made of ceramic, specific examples of the ceramic include silicon oxide, titanium oxide, aluminum oxide and the like. These may be used alone or in combination of two or more. Among these, silicon oxide and aluminum oxide are preferable.
That is, the vapor-deposited layer is more preferably any of a layer made of aluminum, a layer made of silicon oxide, a layer made of titanium oxide, a layer made of aluminum oxide, and a laminate thereof, and the layer made of aluminum and oxidation. Any of a layer made of silicon, a layer made of aluminum oxide, and a laminate thereof is more preferable, and a layer made of aluminum is particularly preferable.

<Overcoat layer>
The paper laminate of the present embodiment has an overcoat layer containing a polyurethane resin on the thin-film deposition layer. The paper laminate of the present embodiment has a certain barrier property by having a thin-film deposition layer, but the oxygen barrier property can be further improved by having an overcoat layer containing a polyurethane resin on the vapor-film deposition layer. Further, the vapor-filmed layer is not easily damaged by processing such as bending, and even if it is damaged, the oxygen barrier property can be ensured by the overcoat layer, and excellent oxygen barrier property can be maintained.

The polyurethane resin as the binder contained in the overcoat layer is more preferably one or more selected from the group consisting of polyurethane resin dispersions or emulsions, and further preferably polyurethane resin dispersions or emulsions. It is even more preferable that the polyurethane resin dispersion is preferable.
The polyurethane resin contained in the overcoat layer preferably has an oxygen permeability of 100 ml / (m ² · day · atm) or less at 23 ° C. and 50% RH when converted into a sheet having a thickness of 25 μm. It is more preferably 50 ml / (m ² , day, atm) or less.
The polyurethane resin contained in the overcoat layer preferably contains at least one of a constituent unit derived from metaxylylene diisocyanate and a constituent unit derived from hydrogenated metaxylylene diisocyanate, and is a meta with respect to the total amount of constituent units derived from polyisocyanate. The total content of the constituent units derived from xylylene diisocyanate and the constituent units derived from hydrogenated metaxylylene diisocyanate is preferably 50 mol% or more. Such a polyurethane-based resin exhibits a high cohesive force due to hydrogen bonds and a stacking effect between xylylene groups, and thus has excellent gas barrier properties.
As the polyurethane resin, a synthetic product may be used, and examples thereof include the polyurethane resin described in International Publication No. 2015/016869.
As the polyurethane resin, a commercially available product may be used. For example, "Takelac W-based (trade name)", "Takelac WPB-based (trade name)", and "Takelac WS-based (trade name)" manufactured by Mitsui Chemicals, Inc. may be used. ) ”, And specifically, Takelac WPB-341 is exemplified.
The glass transition temperature of the polyurethane resin contained in the overcoat layer is important to have high film forming property from the viewpoint of protecting the vapor-filmed layer, and is preferably 150 ° C. or lower, preferably 140 ° C. or lower. Is more preferable, and it is particularly preferable that the temperature is 135 ° C. or lower.

The overcoat layer constituting the paper laminate of the present embodiment may contain other resins and additives as long as the effects of the present invention are not impaired.
The content of the polyurethane resin in the overcoat layer is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, still more preferably 99% by mass or more. Is. The upper limit is not particularly limited, but is 100% by mass or less.
Examples of the additive include surfactants, pigments, antioxidants, antistatic agents, dyes, plasticizers, lubricants, mold release agents and the like. When the polyurethane resin is used as an aqueous dispersion, it is preferable to use a dispersant in order to disperse the polyurethane resin in an aqueous medium and obtain a uniform overcoat layer film.

Further, in the paper laminate of the present embodiment, the overcoat layer may be the outermost layer. Even if the overcoat layer is the outermost layer, it does not impair the design of the vapor-filmed layer having a glossy feeling.
When the vapor deposition layer is provided on both sides, an overcoat layer may be provided on one side or both sides thereof. Among these, it is preferable to have an overcoat layer on one side.
Having an overcoat layer on one side is excellent in production efficiency.

The thickness of the overcoat layer is preferably 0.1 μm or more, more preferably 0.2 μm or more, particularly preferably 0.3 μm or more, and preferably 10 μm or less. It is more preferably 7 μm or less, and particularly preferably 4 μm or less.
When the thickness of the overcoat layer is 0.1 μm or more and 10 μm or less, the protection against the vapor-filmed layer is improved, the paper is excellent in dissociation during recycling, and the recyclability is also excellent.

The coating amount of the overcoat layer is preferably 0.1 g / m ² or more, more preferably 0.2 g / m ² or more, and 0.3 g / m ² or more in terms of solid content. It is particularly preferable, and it is preferably 10 g / m ² or less, more preferably 7 g / m ² or less, and particularly preferably 4 g / m ² or less.

The method for forming the overcoat layer is not particularly limited, but it is preferably formed by applying an aqueous medium such as an aqueous solution of a polyurethane resin or an aqueous dispersion and drying it.

<Resin layer>
It is preferable that the paper laminate of the present embodiment further has a resin layer containing a thermoplastic resin.
The thickness of the resin layer is preferably 1 μm or more, more preferably 2 μm or more, particularly preferably 3 μm or more, and preferably less than 15 μm, more preferably 10 μm or less. It is preferably 7 μm or less, and particularly preferably 7 μm or less.
When the thickness of the resin layer is 1 μm or more and less than 15 μm, the protection against the vapor-filmed layer is improved, the paper is excellent in dissociation during recycling, and the recyclability is also excellent. Further, when the thickness of the present resin layer is 1 μm or more and less than 15 μm, the paper laminate also has excellent heat-sealing properties.
Further, when the paper laminate of the present embodiment has a resin layer, the resin layer is preferably the outermost layer. Since the resin layer is the outermost layer, the resin layer can be imparted with heat-sealing properties to form a container. Furthermore, since it is not affected by other layers, it is easy to protect the vapor-filmed layer from external forces due to deformation. Moreover, it does not impair the design of the thin-film deposition layer having a glossy feeling.
When the vapor deposition layer is provided on both sides, a resin layer containing a thermoplastic resin may be provided on one side or both sides thereof. Among these, it is preferable to have a resin layer containing a thermoplastic resin on one side.
By having a resin layer containing a thermoplastic resin on one side, the production efficiency is excellent, and when the paper laminate of the present embodiment is heat-sealed, a bag-shaped material or the like can be easily produced.

The resin constituting the resin layer is preferably a thermoplastic resin from the viewpoint of facilitating the formation of the resin layer, providing excellent protection of the vapor-deposited layer, and imparting heat-sealing property.
The thermoplastic resin is preferably a heat-sealable resin, and is an olefin / unsaturated carboxylic acid-based copolymer such as an ethylene-acrylic acid copolymer and an ethylene-methacrylic acid copolymer; a biodegradable resin. Polyolefin resins such as polyethylene and polypropylene; acrylic resins such as methyl acrylate copolymers, methyl methacrylate copolymers, styrene-acrylic copolymers and styrene-methacrylic copolymers; and polyvinyl alcohols and ethylene vinyl alcohols It is more preferable that the amount is one or more selected from vinyl alcohol-based resins such as polymers.
Among these, one or more selected from olefin / unsaturated carboxylic acid-based copolymers, biodegradable resins, and polyolefin resins is more preferable, and olefin / unsaturated carboxylic acid-based copolymers and biodegradable. It is even more preferably one or more selected from the resin, and particularly preferably one or more selected from the ethylene-acrylic acid-based copolymer and polylactic acid. From the viewpoint of protecting the vapor-deposited layer, an olefin / unsaturated carboxylic acid-based copolymer is further preferable, and from the viewpoint of recyclability and reduction of environmental load, a biodegradable resin is further preferable.
In the present specification, it is assumed that the acrylic resin does not contain an olefin / unsaturated carboxylic acid-based copolymer.

When an olefin / unsaturated carboxylic acid-based copolymer is used as an aqueous dispersion, the carboxyl group derived from the unsaturated carboxylic acid-based monomer is an alkali metal hydroxide, ammonia, an alkylamine, an alkanolamine, or the like. It is preferable that the salt is partially or completely neutralized.

When an olefin / unsaturated carboxylic acid-based copolymer is used, the content of the olefin / unsaturated carboxylic acid-based copolymer in the resin layer is preferably 20% by mass or more, preferably 50% by mass or more, based on the total solid content of the resin layer. It is more preferably 0% by mass or more, further preferably 60% by mass or more, further preferably 70% by mass or more, further preferably 80% by mass or more, and 90% by mass or more. It is particularly preferable to have it, and it is most preferable that it is 95% by mass or more. The upper limit is not particularly limited, but is 100% by mass or less.

Examples of the olefin-based monomer of the olefin / unsaturated carboxylic acid-based copolymer include ethylene, propylene, and butadiene. These may be one kind alone or two or more kinds. Of these, ethylene is preferable.
Examples of the unsaturated carboxylic acid-based monomer of the olefin / unsaturated carboxylic acid-based copolymer include acrylic acid, methacrylic acid, crotonic acid, silicic acid, itaconic acid, fumaric acid, maleic acid, butentricarboxylic acid and the like. Saturated carboxylic acid; unsaturated polycarboxylic acid alkyl ester having at least one carboxyl group such as itaconic acid monoethyl ester, fumaric acid monobutyl ester, maleic acid monobutyl ester; acrylamide propanesulfonic acid, acrylate sodium acrylate Examples thereof include an unsaturated sulfonic acid monomer such as a salt and a sulfopropyl sodium methacrylate salt or a salt thereof. These may be one kind, or two or more kinds may be used in combination.
Among these, unsaturated carboxylic acid is preferable, acrylic acid and methacrylic acid are more preferable, and acrylic acid is particularly preferable.
That is, as the olefin / unsaturated carboxylic acid-based copolymer, an ethylene / acrylic acid-based copolymer such as an ethylene / acrylic acid copolymer and an ethylene / methacrylic acid copolymer is preferable. Among these, the ethylene / acrylic acid copolymer has excellent availability and can be synthesized as an aqueous dispersion, so that a resin layer can be easily formed on the overcoat layer by coating and drying. It is possible and preferable.

The ethylene / unsaturated carboxylic acid-based copolymer is preferably obtained by emulsion polymerization of ethylene and the unsaturated carboxylic acid-based monomer. As the ethylene / unsaturated carboxylic acid-based copolymer, an ethylene / acrylic acid copolymer and an ethylene / methacrylic acid copolymer are preferable. As long as the effect of the present invention is not impaired, the copolymer may be copolymerized with a monomer composed of ethylene and other compounds copolymerizable with the unsaturated carboxylic acid-based monomer.

The content of the unsaturated carboxylic acid-based monomer unit (copolymerization ratio of the unsaturated carboxylic acid-based monomer) in the ethylene / unsaturated carboxylic acid-based copolymer is preferably 1 mol% or more. It is more preferably mol% or more, more preferably 50 mol% or less, and even more preferably 30 mol% or less. When the ethylene / unsaturated carboxylic acid-based copolymer contains an acrylic acid unit as an unsaturated carboxylic acid-based monomer unit, the content of the acrylic acid unit (copolymerization ratio of acrylic acid) is 1 mol% or more. It is preferably 10 mol% or more, more preferably 50 mol% or less, and even more preferably 30 mol% or less. When the content of the unsaturated carboxylic acid-based monomer unit is 1 mol% or more and 50 mol% or less, the melting temperature is 60 ° C. or more and 120 ° C. or less, and excellent ethylene / non-polyform exhibiting good heat-sealing property. It becomes a saturated carboxylic acid-based copolymer.

The weight average molecular weight of the ethylene / unsaturated carboxylic acid-based copolymer is preferably 10,000 or more, more preferably 100,000 or more, and more preferably 100,000 or more, from the viewpoint of the viscosity of the coating liquid and the strength of the coating film. , 10 million or less, more preferably 5 million or less.

Specific examples of the ethylene / unsaturated carboxylic acid-based copolymer include Zyxene (registered trademark) AC (aqueous dispersion of ethylene / acrylic acid copolymer ammonium salt, melting point: 95 ° C., copolymerization ratio of acrylic acid 20 mol). %, Made by Sumitomo Seika Co., Ltd.), etc.

Biodegradable resins include polylactic acid (PLA), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polybutylene adipate terephthalate (PBAT), and poly (3-hydroxybutyrate-co-hydroxy). It is preferably one or more selected from (hexanoate) (PHBH), more preferably one or more selected from polylactic acid and polybutylene succinate, and particularly preferably polylactic acid. A packaging material or the like using a paper base material has an advantage of reducing an environmental load as compared with a packaging material or the like made of a resin film. However, by using a biodegradable resin as the resin layer in the present embodiment, The environmental load can be further reduced.

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

As described above, the thermoplastic resin used for the resin layer in the present embodiment is preferably heat-sealable. Therefore, when the resin constituting the resin layer has a melting point, the melting point is preferably 60 ° C. or higher, more preferably 70 ° C. or higher, particularly preferably 80 ° C. or higher, and 200 ° C. or higher. The temperature is preferably ° C or lower, more preferably 190 ° C or lower, and particularly preferably 180 ° C or lower.
Since the resin layer can be heat-sealed, it is possible to easily obtain a packaging bag or the like made of only the paper laminate of the present embodiment. Further, by fusing to another sheet, film, container or the like, the paper laminate can be used as the main body of the packaging container, the lid of the packaging container or the like. The packaging bag and packaging container thus obtained have excellent barrier properties.

The tensile strength of the thermoplastic resin is preferably 5 MPa or more, more preferably 10 MPa or more, preferably 30 MPa or less, and even more preferably 20 MPa or less. Tensile strength is measured according to JIS K7161.
The elongation at break point of the thermoplastic resin is preferably 200% or more, more preferably 300% or more, preferably 600% or less, and more preferably 500% or less. Break point elongation is measured according to JIS K7161.

The resin layer constituting the paper laminate of the present embodiment may contain other resins and additives as long as the effects of the present invention are not impaired.
The content of the thermoplastic resin in the resin layer is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, still more preferably 99% by mass or more. be. The upper limit is not particularly limited, but is 100% by mass or less.
Examples of the additive include surfactants, pigments, antioxidants, antistatic agents, dyes, plasticizers, lubricants, mold release agents and the like. When the thermoplastic resin is used as an aqueous dispersion, it is preferable to use a dispersant in order to disperse the thermoplastic resin in an aqueous medium and obtain a uniform resin layer film.

[Manufacturing method of paper laminate]
The method for producing the paper laminate of the present embodiment is not limited, but a vapor-deposited paper having a clay coat layer, an undercoat layer, and a vapor-deposited layer on at least one surface of a paper substrate in this order is used for an overcoat layer. It is preferable to include a step of applying a coating liquid and drying it to form an overcoat layer.

The vapor-deposited paper used in the method for producing a paper laminate of the present embodiment is obtained by forming a clay coat layer and an undercoat layer on the surface of the paper substrate in order, and further depositing at least one of metal and ceramic. Is preferable.
The clay coat layer is preferably formed by applying a dispersion liquid containing clay and a binder onto a paper substrate and drying it.
The undercoat layer is preferably formed by applying an aqueous medium such as an aqueous solution of a binder or an aqueous dispersion onto the clay coat layer and drying it.

As a method for depositing a metal or ceramic, a method of vacuum-depositing the metal or ceramic directly on the surface of the undercoat layer is preferable.

Next, an overcoat layer is formed on the vapor-filmed paper.
It is preferable to form the overcoat layer directly on the vapor-filmed layer of the thin-film-deposited paper from the viewpoint of efficiently protecting the vapor-filmed layer and enhancing the barrier property.
As a method for forming the overcoat layer, it is preferable to apply the coating liquid for the overcoat layer and dry the overcoat layer.
By applying a coating liquid for an overcoat layer to form an overcoat layer, an overcoat layer having a relatively thin film of 10 μm or less can be formed. By forming such a relatively thin overcoat layer, it is possible to impart excellent dissociation property to the obtained paper laminate, and it is possible to obtain a laminate having excellent recyclability.

Examples of the coating liquid for the overcoat layer used here include a solution using an organic solvent that dissolves the polyurethane resin, a dispersion liquid that uses an organic solvent that disperses the polyurethane resin, and a dispersion liquid that uses an aqueous medium. Therefore, a dispersion liquid using an aqueous medium is preferable from the viewpoint of coatability and environmental load.

Examples of the method for applying the coating liquid for the overcoat layer include a bar coat method, a blade coat method, a squeeze coat method, an air knife coat method, a roll coat method, a gravure coat method, a transfer coat method, and the like. Or a coating machine such as a slit die coater may be used.
The coated vapor-deposited paper coated with the coating liquid for the overcoat layer can be dried to remove the organic solvent or the aqueous medium, and a paper laminate having the overcoat layer on the vapor-deposited layer can be obtained.

Further, a resin layer made of a thermoplastic resin having a thickness of 1 μm or more and less than 15 μm may be formed on the overcoat layer.
Examples of the method for forming the resin layer include coating a resin solution or a resin dispersion and drying the resin layer to obtain the resin layer, extruding and laminating the resin layer. Among these, it is preferable to apply a resin solution or a resin dispersion and dry the mixture.
By applying a resin solution or a resin dispersion to form a resin layer, a resin layer having a relatively thin film of less than 15 μm can be formed. By forming such a relatively thin resin layer, it is possible to impart excellent dissociation property to the obtained paper laminate, and it is possible to obtain a laminate having excellent recyclability.

Examples of the resin solution or resin dispersion used here include a solution using an organic solvent that dissolves the resin, a dispersion liquid that uses an organic solvent that disperses the resin, and a dispersion liquid that uses an aqueous medium. In terms of environmental load and environmental load, a dispersion using an aqueous medium is preferable.

Examples of the method for applying the resin solution or the resin dispersion include a bar coat method, a blade coat method, a squeeze coat method, an air knife coat method, a roll coat method, a gravure coat method, a transfer coat method, and the like. A coating machine such as a slit die coater may be used.
The paper laminate coated with the resin solution or the resin dispersion can be dried to remove the organic solvent or the aqueous medium, and a paper laminate having a resin layer made of a thermoplastic resin on the overcoat layer can be obtained. ..

[Physical characteristics of paper laminate]
The thickness of the paper laminate of the present embodiment is preferably 20 μm or more, more preferably 50 μm or more, preferably 200 μm or less, and more preferably 150 μm or less.

The oxygen permeability of the paper laminate of the present embodiment before bending is preferably 1.0 ml / (m ² · day · atm) or less, and is preferably 0.5 ml / (m ² · day · atm) or less. It is more preferable (lower limit: 0 ml / ( ^m2 · day · atm)). The oxygen permeability of the paper laminate before bending is measured by the method described in Examples.

The oxygen permeability of the paper laminate of the present embodiment after bending is preferably 5.0 ml / (m ² · day · atm) or less, and preferably 1.0 ml / (m ² · day · atm) or less. It is more preferable (lower limit: 0 ml / ( ^m2 · day · atm)). The oxygen permeability of the paper laminate after bending is measured by the method described in Examples.

The water vapor transmission rate of the paper laminate of the present embodiment before bending is preferably 1.0 g / (m ² · day) or less, and more preferably 0.7 g / (m ² · day) or less. (Lower limit: 0 g / (m ² · day)). The water vapor transmission rate of the paper laminate before bending is measured by the method described in Examples.

The water vapor transmission rate of the paper laminate of the present embodiment after bending is preferably 10.0 g / (m ² · day) or less, and more preferably 5.0 g / (m ² · day) or less. (Lower limit: 0 g / (m ² · day)). The water vapor transmission rate after bending of the paper laminate is measured by the method described in Examples.

[Use of paper laminate]
The paper laminate of the present embodiment can be suitably used as a packaging material for foods such as coffee, confectionery, milk, pharmaceuticals, medical products, electronic parts, etc. by taking advantage of the above-mentioned excellent water vapor barrier property and gas barrier property. can. Among these, since it has resistance to processing, it can be suitably used for flexible packaging materials, paper containers for heavy bags, packaging containers such as milk cartons, and the like.

Hereinafter, the features of the present invention will be described in more detail with reference to Examples and Comparative Examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed as limiting by the specific examples shown below.

[Example 1]
[Manufacturing of paper laminate (1)]
80 parts by mass of kaolin (Contour Xtreme, manufactured by Imerys, aspect ratio 33) and 20 parts by mass (solid content) of a styrene-acrylic copolymer binder (JONCRYL HSL-9012, manufactured by BASF) are mixed and clay coated. A coating solution for layers was prepared. Single gloss paper (manufactured by Oji Materia Co., Ltd., basis weight 65 g / m ² , thickness 62 μm, density 0.76 g / m ³ , dissolution freeness (water drainage degree) 370 ml measured according to JIS P 811-2: 2012, JIS P 8122: 2004-like Sutekihito size degree 9 seconds, 75 ° gloss 70%, Oken type smoothness on one side 427 seconds, Oken type smoothness on the other side 17 seconds) The above-mentioned coating liquid for clay coat layer was coated on a surface having a degree of 17 seconds with Mayer bar and dried at 120 ° C. for 1 minute to form a clay coat layer (10 g / m ² ). Next, on the clay coat layer, an aqueous dispersion of a polyurethane resin binder having a thickness of 25 μm and an oxygen permeability (23 ° C., 50% RH) of 2.0 ml / ( ^m2・ day ・ atm) (Mitsui Chemicals). Takelac WPB-341, manufactured by Takelac Co., Ltd .: glass transition temperature 130 ° C.) was coated with Mayer bar and dried at 120 ° C. for 1 minute to form an undercoat layer (2 g / m ² ). Next, an aluminum-deposited layer (thickness 50 nm) was formed on the undercoat layer to obtain an aluminum-deposited paper.
An aqueous dispersion of a polyurethane resin binder having an oxygen permeability (23 ° C., 50% RH) of 2.0 ml / (m ²・ day ・ atm) on the above aluminum vapor-deposited paper of a 25 μm thick sheet (manufactured by Mitsui Chemicals, Inc.). Takelac WPB-341) was coated with Mayer bar and dried at 120 ° C. for 1 minute to form an overcoat layer (0.5 g / m ² , thickness: 0.5 μm). Further, on the overcoat layer, an aqueous dispersion of an ethylene / acrylic acid copolymer ammonium salt (effective content 29.2% by mass, Zyxen AC, acrylic acid copolymerization ratio 20 mol%, melting point: 95 ° C., Sumitomo Seika (Manufactured by Co., Ltd.) was diluted with water so that the effective content was 20% by mass, coated with Mayer bar, and then dried at 120 ° C. for 1 minute to form a resin layer to obtain a paper laminate (1). The thickness of the resin layer was 5 μm. When ¹ H-NMR measurement was performed on the polyurethane resin used for the undercoat layer and the overcoat layer, the content of the constituent units derived from metaxylylene diisocyanate was 50 mol with respect to the total amount of the constituent units derived from polyisocyanate. It was more than%.
Table 1 shows the evaluation results of the obtained paper laminate (1).

[Example 2]
[Manufacturing of paper laminate (2)]
A paper laminate (2) was obtained in the same manner as in Example 1 except that the resin layer was not applied on the overcoat layer.
Table 1 shows the evaluation results of the obtained paper laminate (2).

[Example 3]
[Manufacturing of paper laminate (3)]
The same as in Example 2 except that the coating amount of the overcoat layer was changed from 0.5 g / m ² (thickness: 0.5 μm) to 3.0 g / m ² (thickness: 3.0 μm). A paper laminate (3) was obtained.
Table 1 shows the evaluation results of the obtained paper laminate (3).

[Example 4]
[Manufacturing of paper laminate (4)]
Instead of forming a resin layer using an aqueous dispersion of an ethylene / acrylic acid copolymer ammonium salt (Zyxen AC, manufactured by Sumitomo Seika Co., Ltd.), an aqueous dispersion of polylactic acid (melting point: 170 ° C.) (Randy PL) A paper laminate (4) was obtained in the same manner as in Example 1 except that the resin layer was formed using -3000 (manufactured by Miyoshi Oil & Fat Co., Ltd.).
Table 1 shows the evaluation results of the obtained paper laminate (4).

[Example 5]
[Manufacturing of paper laminate (5)]
Instead of forming a resin layer using an aqueous dispersion of an ethylene / acrylic acid copolymer ammonium salt (Zyxen AC, manufactured by Sumitomo Seika Co., Ltd.), low-density polyethylene (melting point: 130 ° C.) (manufactured by Nippon Polyethylene Co., Ltd.) ) Was extruded to a basis weight of 13 g / m ² (thickness 14 μm) to form a resin layer, and a paper laminate (5) was obtained in the same manner as in Example 1.
Table 1 shows the evaluation results of the obtained paper laminate (5).

[Comparative Example 1]
[Manufacturing of paper laminate (6)]
Instead of forming an overcoat layer using an aqueous dispersion of a polyurethane resin binder (Mitsui Chemicals, Inc., Takelac WPB-341), an aqueous dispersion of an ethylene / acrylic acid copolymer ammonium salt (Zyxen AC, Sumitomo) A paper laminate (6) was obtained in the same manner as in Example 2 except that the overcoat layer was formed using (manufactured by Seika Co., Ltd.).
Table 1 shows the evaluation results of the obtained paper laminate (6).

[Comparative Example 2]
[Manufacturing of paper laminate (7)]
A paper laminate (7) was obtained in the same manner as in Example 2 except that the overcoat layer was not provided.
Table 1 shows the evaluation results of the obtained paper laminate (7).

[Comparative Example 3]
[Manufacturing of paper laminate (8)]
Instead of forming an undercoat layer using an aqueous dispersion of a polyurethane resin binder (Mitsui Chemicals, Inc., Takelac WPB-341), an aqueous dispersion of an ethylene / acrylic acid copolymer ammonium salt (Zyxen AC, Sumitomo) A paper laminate (8) was obtained in the same manner as in Comparative Example 1 except that the undercoat layer was formed using (manufactured by Seika Co., Ltd.).
Table 1 shows the evaluation results of the obtained paper laminate (8).

[evaluation]
[Oxygen permeability]
Using an oxygen permeability measuring device (OX-TRAN2 / 20 manufactured by MOCON), the oxygen permeability of the paper laminate was measured under the conditions of a temperature of 23 ° C. and a relative humidity of 50%. The lower the oxygen permeability value, the better the oxygen barrier property.
In addition, as an evaluation of processing resistance, oxygen permeability after bending was also measured. The folding method is as follows: the paper laminate is folded once and then opened (crease angle 180 °), folded again along a line perpendicular to the fold line (crease angle 180 °), and then opened. The oxygen permeability was measured so that the intersection of the broken lines came to the center of the measuring section.

[Water vapor transmission rate]
In accordance with JIS Z 0208: 1976 (cup method) B method (temperature 40 ° C ± 0.5 ° C, relative humidity 90% ± 2%), the overcoat layer of the paper laminate or the vapor-deposited layer of the vapor-deposited paper is inside ( It was placed so as to come to the low humidity side), and the water vapor permeability was measured. The lower the value of water vapor transmission rate, the better the water vapor barrier property.
In addition, as an evaluation of processing resistance, the water vapor transmission rate after bending was also measured. The folding method is as follows: once the paper laminate or vapor-deposited paper is folded (fold angle 180 °), then opened again, and then re-folded along a line perpendicular to the line (fold angle 180 °), and then opened in the center of the measuring section. The water vapor permeability was measured so that the intersection of the polygonal lines came.

[Heat sealability]
In each of Examples 1, 4 and 5, two paper laminates are stacked so that the resin layers face each other, and a heat seal tester (TP-701-B, manufactured by Tester Sangyo Co., Ltd.) is used at 130 ° C. and 0.5 MPa. , Heat-sealed under the condition of 30 seconds, and the heat-sealing property was evaluated. As a result, in any of Examples 1, 4 and 5, fusion was performed and heat-sealed, and good heat-sealing property was obtained.

In the paper laminates of Examples 1 to 5, both the oxygen permeability and the water vapor transmission rate are maintained lower even after bending as compared with the paper laminates of Comparative Examples 1 and 3 and the vapor-deposited paper of Comparative Example 2, and the packaging is performed. It can be seen that high barrier properties can be maintained even when bent when used for bags and packaging containers.

Claims (20)

A clay coat layer, an undercoat layer, a vapor deposition layer and an overcoat layer are provided on at least one surface of the paper substrate in this order.
The thin-film deposition layer is at least one of a layer made of metal and a layer made of ceramic, and has a thickness of 1 nm or more and 1000 nm or less.
The overcoat layer is a paper laminate containing a polyurethane resin. The paper laminate according to claim 1, wherein the overcoat layer has a thickness of 0.1 μm or more and 10 μm or less. The paper laminate according to claim 1 or 2, wherein the coating amount of the overcoat layer is 0.1 g / m ² or more and 10 g / m ² or less in terms of solid content. Claim 1 that the polyurethane resin contained in the overcoat layer has an oxygen permeability of 100 ml / (m ² · day · atm) or less at 23 ° C. and 50% RH when converted into a sheet having a thickness of 25 μm. The paper laminate according to any one of 3 to 3. The paper according to any one of claims 1 to 4, wherein the polyurethane resin contained in the overcoat layer contains at least one of a structural unit derived from metaxylylene diisocyanate and a structural unit derived from hydrogenated metaxylylene diisocyanate. Laminate. The polyurethane resin contained in the overcoat layer has a total content of 50 mol% or more of the constituent units derived from metaxylylene diisocyanate and the constituent units derived from hydrogenated metaxylylene diisocyanate with respect to the total amount of the constituent units derived from polyisocyanate. The paper laminate according to claim 5. The paper laminate according to any one of claims 1 to 6, wherein the amount of the clay coat layer coated is 5 g / m ² or more and 30 g / m ² or less in terms of solid content. The paper laminate according to any one of claims 1 to 7, wherein the coating amount of the undercoat layer is 0.1 g / m ² or more and 10 g / m ² or less in terms of solid content. Any of claims 1 to 8, wherein the undercoat layer mainly contains a binder, and the resin contained in the binder is one or more selected from vinyl alcohol-based resin, acrylic resin, polyurethane-based resin, and polyester resin. The paper laminate described in Crab. 9. The polyurethane resin contained in the undercoat layer has an oxygen permeability of 100 ml / (m ² · day · atm) or less at 23 ° C. and 50% RH when converted into a sheet having a thickness of 25 μm. The paper laminate described in. The paper laminate according to claim 9 or 10, wherein the polyurethane resin contained in the undercoat layer contains at least one of a structural unit derived from metaxylylene diisocyanate and a structural unit derived from hydrogenated metaxylylene diisocyanate. The polyurethane resin contained in the undercoat layer has a total content of 50 mol% or more of the constituent units derived from metaxylylene diisocyanate and the constituent units derived from hydrogenated metaxylylene diisocyanate with respect to the total amount of the constituent units derived from polyisocyanate. The paper laminate according to claim 11. The paper laminate according to any one of claims 1 to 12, wherein the basis weight of the paper base material is 20 g / m ² or more and 500 g / m ² or less. The paper laminate according to any one of claims 1 to 13, wherein the vapor-deposited layer is at least one of a layer made of aluminum, a layer made of silicon oxide, and a layer made of aluminum oxide. The paper laminate according to any one of claims 1 to 14, further comprising a resin layer containing a thermoplastic resin having a thickness of 1 μm or more and less than 15 μm on the surface of the overcoat layer. The paper laminate according to claim 15, wherein the thermoplastic resin is a heat-sealable resin. The 15th or 16th claim, wherein the thermoplastic resin is at least one selected from an olefin / unsaturated carboxylic acid-based copolymer, a biodegradable resin, a polyolefin resin, an acrylic resin, and a vinyl alcohol-based resin. Paper laminate. The paper laminate according to claim 17, wherein the thermoplastic resin is an olefin / unsaturated carboxylic acid-based copolymer. The paper laminate according to any one of claims 1 to 18, wherein the undercoat layer and the overcoat layer are formed by using an aqueous medium. An overcoat layer coating liquid is applied to a vapor-deposited paper having a clay coat layer, an undercoat layer, and a vapor-deposited layer in this order on at least one surface of a paper substrate, and dried to form an overcoat layer. It is a method of manufacturing a paper laminate including a step of making a paper laminate.
The thin-film deposition layer is at least one of a layer made of metal and a layer made of ceramic, and has a thickness of 1 nm or more and 1000 nm or less.
The coating liquid for the overcoat layer is a method for producing a paper laminate containing a polyurethane resin.