JP7298409B2 - Barrier laminate - Google Patents

Description

The present invention relates to a barrier laminate.

Conventionally, there has been known a barrier laminate composed of a paper base material and a water vapor barrier layer and a gas barrier layer provided in this order on the paper base material in order to impart water vapor barrier properties and gas barrier properties to the paper base material.

Patent Document 1 discloses a paper barrier material in which a water vapor barrier layer and a gas barrier layer are provided in this order on a paper substrate, wherein the water vapor barrier layer contains a water vapor barrier resin and a water repellent agent, and the gas barrier layer contains a water-soluble polymer and a surfactant.

WO2017/170462

The paper barrier material described in Patent Document 1 is inferior in water resistance because the gas barrier layer contains a water-soluble polymer such as polyvinyl alcohol as a main component. Therefore, the paper barrier material described in Patent Document 1 is provided with a laminate layer in addition to the water vapor barrier layer and the gas barrier layer in order to ensure water resistance. There was a problem.

The present invention has been made in view of the above problems, and provides a barrier laminate that is excellent in water vapor barrier properties and gas barrier properties, has water resistance, and is economically efficient even if the number of layers is small. intended to In this specification, gas barrier properties refer to barrier properties against gases other than water vapor, particularly against oxygen. In addition, water vapor barrier properties and gas barrier properties are also collectively referred to as barrier properties.

The present inventor has provided a paper substrate, and a resin layer and a protective layer in this order on at least one surface of the paper substrate, the resin layer being a water-suspendable polymer having a predetermined aspect ratio. A barrier laminate containing a plate-like inorganic compound and a cationic resin and having a protective layer with a contact angle of 50° or more with respect to water exhibits excellent water vapor barrier properties and gas barrier properties and water resistance even when the number of layers is small. found to have
That is, the present invention relates to the following <1> to <11>.
<1> A barrier laminate comprising a paper substrate and a resin layer and a protective layer in this order on at least one surface of the paper substrate, wherein the resin layer comprises a water-suspendable polymer, A barrier laminate containing a plate-like inorganic compound having an aspect ratio of 100 or more and a cationic resin, wherein the protective layer has a contact angle of 50° or more with respect to water.
<2> The water-suspendable polymer in the resin layer is selected from the group consisting of an olefin/unsaturated carboxylic acid copolymer, a styrene/butadiene copolymer, and a styrene/acrylic copolymer. The barrier laminate according to <1>, which is at least seed.
<3> The barrier laminate according to <1> or <2>, wherein the plate-like inorganic compound in the resin layer is one or more selected from the group consisting of synthetic mica, bentonite, and kaolin.
<4> The barrier laminate according to any one of <1> to <3>, wherein the resin layer contains 0.1% by mass or more and 50% by mass or less of the plate-like inorganic compound.
<5> The barrier laminate according to any one of <1> to <4>, wherein the resin layer further contains 25 parts by mass or less of a water-soluble polymer with respect to 100 parts by mass of the water-suspendable polymer. body.
<6> The barrier laminate according to <5>, wherein the water-soluble polymer in the resin layer is one or more selected from the group consisting of polyvinyl alcohol and modified polyvinyl alcohol.
<7> The barrier laminate according to any one of <1> to <6>, wherein the protective layer contains a water-suspendable polymer.
<8> The group in which the water-suspendable polymer in the protective layer comprises an olefin/unsaturated carboxylic acid copolymer, a styrene/butadiene copolymer, a styrene/acrylic copolymer, and a biodegradable resin. The barrier laminate according to <7>, which is one or more selected from:
<9> The barrier laminate according to <7> or <8>, wherein the protective layer further contains 25 parts by mass or less of a water-soluble polymer with respect to 100 parts by mass of the water-suspendable polymer.
<10> The barrier laminate according to any one of <1> to <9>, wherein the protective layer contains 0.1% by mass or more and 50% by mass or less of the plate-like inorganic compound.
<11> The barrier laminate according to <10>, wherein the plate-like inorganic compound in the protective layer is one or more selected from the group consisting of synthetic mica, bentonite, and kaolin.

According to the present invention, it is possible to provide a barrier laminate having excellent water vapor barrier properties and gas barrier properties, water resistance, and excellent economic efficiency even when the number of layers is small.

[Barrier laminate]
The barrier laminate of the present invention (hereinafter also simply referred to as "barrier laminate") comprises a paper substrate, and a barrier layer comprising a resin layer and a protective layer in this order on at least one surface of the paper substrate. wherein the resin layer contains a water-suspendable polymer, a plate-like inorganic compound having an aspect ratio of 100 or more, and a cationic resin, and the contact angle of the protective layer to water is 50° or more. be.

The barrier laminate of the present invention comprises a resin layer containing a water-suspendable polymer, a plate-like inorganic compound having a predetermined aspect ratio, and a cationic resin on at least one surface of a paper base material. It has been clarified that by providing a protective layer on a resin layer, it is possible to provide a barrier laminate having excellent water vapor barrier properties and gas barrier properties and water resistance even when the number of layers is small.
By providing a protective layer on the resin layer, it is possible to fill fine pores, cracks, etc. existing on the surface of the resin layer. It is presumed that the maze effect, in which the moving distance of water vapor or the like becomes longer, is exerted also on gases, especially oxygen.

The barrier laminate of the present invention may be provided with a resin layer and a protective layer in this order on at least one surface of the paper base material, and the resin layer and the protective layer on the other surface as well. You may have them in order. Moreover, the barrier laminate of the present invention may comprise a plurality of resin layers and protective layers in this order.

When the gas-barrier laminate of the present invention is used for packaging food, for example, it is preferable that only one side of the paper substrate is provided with a resin layer and a protective layer in this order. With such a configuration, when the barrier laminate of the present invention is heat-sealed, a bag-like package can be easily produced.

<Paper substrate>
The paper base material used in the barrier laminate of the present invention is preferably a paper that is generally used with plant-derived pulp as a main component, and more preferably a paper with wood pulp as a main component. preferable. Moreover, it is preferable that the paper is mainly composed of pulp, which is easily dispersed in water by a mechanical disaggregation action.
Specific examples include bleached or unbleached kraft paper, woodfree paper, paperboard, liner paper, coated paper, one-sided glossy paper, glassine paper, graphane paper, etc. Among these, bleached or unbleached kraft paper, woodfree paper , Single gloss paper is preferred.

(Canadian Standard Freeness (CSF))
The Canadian Standard Freeness (CSF) of the pulp constituting the paper substrate, measured in accordance with JIS P 8121-2:2012, is preferably 800 mL or less, more preferably 500 mL, from the viewpoint of improving barrier properties. and the lower limit is not particularly limited.
The CSF of the pulp that constitutes the paper base is measured in accordance with JIS P 8121-2:2012 using a sample of paper base pulp that has been disaggregated in accordance with JIS P 8220-1:2012.

(Size degree by Stockigt method)
The sizing degree of the paper substrate according to the Stockigt method (hereinafter also simply referred to as "sizing degree") measured in accordance with JIS P 8122:2004 is not particularly limited, but from the viewpoint of improving barrier properties, preferably 1 second or more. The sizing degree of the paper substrate depends on the type and content of internal sizing agents such as rosin, alkylketene dimer, alkenyl succinic anhydride, styrene-acrylic, higher fatty acid, and petroleum resin, the type of pulp, It can be controlled by smoothing processing or the like. The content of the internal sizing agent is preferably 3 parts by mass or less with respect to 100 parts by mass of the paper base pulp.

In addition to the internal sizing agent, other known internal additives may be added to the paper substrate. Examples of internal additives include fillers such as titanium dioxide, kaolin, talc, and calcium carbonate, dry strength agents, wet strength agents, yield improvers, pH adjusters, drainage improvers, water resistance agents, and softeners. agents, antistatic agents, antifoaming agents, slime control agents, dyes, pigments and the like.

In the papermaking of the paper substrate, a known wet paper machine (for example, a fourdrinier paper machine, a gap former paper machine, a cylinder paper machine, a short mesh paper machine, etc.) is appropriately selected and used. be able to. A paper layer formed by a 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.

Further, the paper base material obtained as described above may be subjected to a surface treatment using a calendar to make the thickness and profile uniform. For calendering, a known calendering machine can be appropriately selected and used.

(basis weight)
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, still more preferably 40 g/m ² or more, and preferably 500 g/m ² or less. , more preferably 400 g/m ² or less, still more preferably 300 g/m ² or less, even more 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 according to JIS P 8124:2011.

(thickness)
The thickness of the paper substrate is preferably 5 μm or more, more preferably 10 μm or more, still more preferably 20 μm or more, and preferably 150 μm or less, more preferably 100 μm or less, still more preferably 75 μm or less.
The thickness of the paper substrate is measured according to JIS P 8118:2014.

(density)
From the viewpoint of molding processability, the density of the paper substrate is preferably 0.5 g/cm ³ or more, more preferably 0.6 g/cm ³ or more, and preferably 1.2 g/cm ³ or less. It is preferably 1.0 g/cm ³ or less.
The density of the paper base is calculated from the basis weight and thickness of the paper base obtained by the above-described measuring method.

<Resin layer>
The resin layer contains a water-suspendable polymer, a plate-like inorganic compound having an aspect ratio of 100 or more, and a cationic resin.

(Water-suspendable polymer)
Water-suspendable polymers are polymers that can be suspended in water, making it easy to prepare a coating solution using water as a dispersion medium when forming a resin layer on a paper substrate. to Since the water-suspendable polymer functions as a binder in the formation of the resin layer, it is possible to form the resin layer containing the plate-like inorganic compound and the like on the paper substrate.
The water-suspendable polymer is preferably one or more selected from the group consisting of olefin/unsaturated carboxylic acid copolymers, styrene/butadiene copolymers, and styrene/acrylic copolymers.

<<Olefin/unsaturated carboxylic acid copolymer>>
The olefin/unsaturated carboxylic acid-based copolymer is a copolymer obtained by emulsion polymerization of an olefin monomer and an unsaturated carboxylic acid-based monomer.
The olefin monomers of the olefin/unsaturated carboxylic acid copolymer include ethylene and α-olefins such as propylene and butylene. Among these, ethylene is preferred.
The unsaturated carboxylic acid-based monomer of the olefin/unsaturated carboxylic acid-based copolymer includes an unsaturated carboxylic acid monomer and an unsaturated carboxylic acid ester monomer that forms a carboxylic acid upon hydrolysis. Examples of unsaturated carboxylic acid monomers for olefin/unsaturated carboxylic acid copolymers include acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and butenetricarboxylic acid. Unsaturated carboxylic acids and their esters; unsaturated polycarboxylic acid alkyl esters having at least one carboxy group, such as itaconic acid monoethyl ester, fumaric acid monobutyl ester, maleic acid monobutyl ester.
The unsaturated carboxylic acid-based monomers constituting the olefin/unsaturated carboxylic acid-based copolymer may be used alone or in combination of two or more. The olefin/unsaturated carboxylic acid-based copolymer may be copolymerized with a small amount of other monomers copolymerizable with the olefin and the unsaturated carboxylic acid-based monomer.
Among these, the olefin/unsaturated carboxylic acid copolymer is preferably one or more selected from the group consisting of ethylene/acrylic acid copolymers and ethylene/methacrylic acid copolymers. /acrylic acid copolymer, ethylene/methacrylic acid copolymer, ethylene/methyl acrylate copolymer, ethylene/methyl methacrylate copolymer, ethylene/ethyl acrylate copolymer, ethylene/ethyl methacrylate copolymer , an ethylene/butyl acrylate copolymer, and an ethylene/butyl methacrylate copolymer, and more preferably an ethylene/acrylic acid copolymer.

In the olefin/unsaturated carboxylic acid copolymer, the content of unsaturated carboxylic acid monomer units is preferably 1 mol% or more, more preferably 10 mol% or more, and preferably 50 mol% or less, and more It is preferably 30 mol % or less. When the content of the unsaturated carboxylic acid-based monomer is within the above range, the dispersibility of the plate-like inorganic compound is excellent.

The weight-average molecular weight of the olefin/unsaturated carboxylic acid copolymer is preferably 10,000 or more, more preferably 20,000 or more, and preferably It is 10 million or less, more preferably 5 million or less.

A commercially available product may be used as the olefin/unsaturated carboxylic acid copolymer, and examples thereof include "Zaixen (trade name)" manufactured by Sumitomo Seika Co., Ltd., and the like.

<<Styrene/butadiene copolymer>>
Examples of the styrene/butadiene copolymer include styrene/butadiene rubber (SBR) and modified styrene/butadiene rubber (modified SBR).
Modified styrene/butadiene rubbers include acid-modified styrene/butadiene rubbers (acid-modified SBR).
A commercial product may be used as the styrene/butadiene copolymer, and examples thereof include "Nipol LX407S series (trade name)" and "Nipol LX407BP series (trade name)" manufactured by Zeon Corporation.

<<Styrene/acrylic copolymer>>
A styrene/acrylic copolymer is a copolymer obtained by emulsion polymerization of a styrene monomer, an acrylic monomer, and, if necessary, other monomers copolymerizable therewith. is. Styrenic monomers include aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, pt-butylstyrene and chlorostyrene. Examples of acrylic monomers include unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and butentricarboxylic acid; Unsaturated polycarboxylic acid alkyl esters having at least one carboxy group such as acid monobutyl ester, maleic acid monobutyl ester, acrylamidopropanesulfonic acid, sulfoethyl acrylate sodium salt, or sulfopropyl methacrylate sodium salt ( meth)acrylic sulfonic acid monomers or salts thereof. Other monomers include alkyl (meth)acrylates (having 1 to 24 carbon atoms).
Styrene is suitable as the styrene-based monomer. As acrylic monomers, acrylic acid, methacrylic acid, itaconic acid, and fumaric acid are suitable.
Commercially available products may be used as the styrene/acrylic copolymer, such as "Hervil Series C-3 (trade name)" manufactured by Daiichi Paint Co., Ltd., "ACRONAL4160" manufactured by BASF, and the like. be done.

(Plate-like inorganic compound)
The plate-like inorganic compound has an aspect ratio of 100 or more, preferably 200 or more, more preferably 300 or more, and still more preferably 500 or more. The higher the aspect ratio, the longer the distance that water vapor and gas move, resulting in a labyrinthine effect that improves the water vapor barrier properties and gas barrier properties. Moreover, the addition amount of a plate-like inorganic compound can be reduced, so that an aspect-ratio is large. Although the upper limit of the aspect ratio is not particularly limited, it is preferably 10,000 or less from the viewpoint of availability, viscosity when forming a resin layer on a paper substrate, and the like.
The aspect ratio of the plate-like inorganic compound is obtained by taking an enlarged photograph of a cross section in the thickness direction parallel to the direction in which the resin layer is applied using an electron microscope, and measuring the length and length of at least 30 plate-like inorganic compounds. The thickness is measured and arithmetically averaged to determine the average length and thickness. A value obtained by dividing the average length of the plate-like inorganic compound by the average thickness is defined as the aspect ratio of the plate-like inorganic compound.

The plate-like inorganic compound is not particularly limited as long as it has the above aspect ratio, but it is preferably one or more selected from the group consisting of synthetic mica, bentonite, and kaolin, more preferably synthetic mica, and one or more selected from the group consisting of kaolin.

From the viewpoint of improving water vapor barrier properties and gas barrier properties, the resin layer preferably contains 0.1% by mass or more of a plate-like inorganic compound, more preferably 1.0% by mass or more, and even more preferably 2.0% by mass. From the viewpoint of production, the content is preferably 50% by mass or less, more preferably 40% by mass, even more preferably 30% by mass or less, and even more preferably 20% by mass or less.

The content of the plate-like inorganic compound in the resin layer is preferably 5 parts by mass or more, more preferably 10 parts by mass, with respect to 100 parts by mass of the water-suspendable polymer, from the viewpoint of improving water vapor barrier properties and gas barrier properties. or more, and preferably 30 parts by mass or less, more preferably 25 parts by mass or less.

(cationic resin)
By containing the cationic resin in the resin layer, the dispersibility of the plate-like inorganic compound is improved, and the water vapor barrier property is greatly improved. The plate-like inorganic compound is likely to be anionically charged at the plate-like plane portion and cationic at the edge portion. It has been known. Due to this card house structure, the aqueous dispersion of the plate-like inorganic compound has a very high viscosity. On the other hand, the house-of-cards structure is easily destroyed by applying force such as stirring, so aqueous dispersions of plate-like inorganic compounds exhibit thixotropic properties. It is thought that when an appropriate cationic resin is added to an aqueous dispersion of a plate-like inorganic compound, the card house structure is destroyed by the adsorption of the cationic resin on the anionically charged planar portion of the plate-like inorganic compound. be done. As a result, it is presumed that the plate-like inorganic compound is suppressed from being sterically linked, and the plate-like inorganic compound is more likely to be laminated in parallel with the plane of the paper substrate, leading to an improvement in water vapor barrier properties. Furthermore, it is presumed that gas barrier properties are also improved.

Cationic resins include polyamine resins, cation-modified polyamide resins (e.g., amine-modified polyamide resins), polyamide epichlorohydrin resins, polyethyleneimine resins, polyalkylenepolyamine resins, polyamide compounds, polyamidoamine-epihalohydrin, or formaldehyde condensation reaction. polyamine-epihalohydrin or formaldehyde condensation reaction product, polyamidepolyurea-epihalohydrin or formaldehyde condensation reaction product, polyaminepolyurea-epihalohydrin or formaldehyde condensation reaction product, polyamidoaminepolyurea-epihalohydrin or formaldehyde condensation reaction product, Polyamide polyurea compounds, polyamine polyurea compounds, polyamidoamine polyurea compounds and polyamidoamine compounds, polyvinylpyridine, amino-modified acrylamide compounds, polyvinylamine resins, polydiallyldimethylammonium chloride and the like can be mentioned.
Among these, the cationic resin is preferably at least one selected from polyamine resins, cation-modified polyamide resins, and polyethyleneimine resins, and more preferably cation-modified polyamide resins.

From the viewpoint of improving water vapor barrier properties, the content of the cationic resin in the resin layer is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, relative to 100 parts by mass of the water-suspendable polymer. It is more preferably 3 parts by mass or more, and preferably 20 parts by mass or less, more preferably 15 parts by mass, and still more preferably 10 parts by mass.

(water-soluble polymer)
The resin layer may contain a water-soluble polymer from the viewpoint of improving gas barrier properties. In this case, the resin layer preferably further contains 25 parts by mass or less of a water-soluble polymer with respect to 100 parts by mass of the water-suspendable polymer, from the viewpoint of improving both the water vapor barrier property and the gas barrier property. More preferably, it is contained in an amount of 20 parts by mass or less.

Examples of the water-soluble polymer in the resin layer include polyvinyl alcohol, modified polyvinyl alcohol, starch and its derivatives, cellulose derivatives, polyvinylpyrrolidone, urethane resins, polyacrylic acid and its salts, casein, polyethyleneimine and the like. Among these, from the viewpoint of gas barrier properties, the water-soluble polymer is preferably one or more selected from the group consisting of polyvinyl alcohol and modified polyvinyl alcohol, more preferably modified polyvinyl alcohol.
Examples of modified polyvinyl alcohol include ethylene-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, and the like. Among these, the modified polyvinyl alcohol is preferably one or more selected from the group consisting of ethylene-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, and acetoacetyl-modified polyvinyl alcohol. and carboxy-modified polyvinyl alcohol, more preferably at least one selected from the group consisting of ethylene-modified polyvinyl alcohol.
Polyvinyl alcohol and modified polyvinyl alcohol are preferably completely saponified or partially saponified. Full saponification means a degree of saponification greater than 96%.

A commercially available product may be used as the water-soluble polymer, and examples thereof include modified polyvinyl alcohol such as "Exeval (trade name)" manufactured by Kuraray Co., Ltd.

In the resin layer, in addition to the water-suspendable polymer, plate-like inorganic compound, cationic resin, and water-soluble polymer, dispersants other than the above-described cationic resins, surfactants, and dispersants may be added as necessary. Foaming agents, wetting agents, dyes, tinting agents, thickening agents, etc. can be added.

<Protective layer>
The protective layer is not particularly limited as long as it has film formability and a contact angle with water of 50° or more.

(Contact angle with water)
The contact angle of the protective layer with water is 50° or more, preferably 55° or more, and more preferably 60° or more from the viewpoint of water resistance, etc., and the upper limit is not particularly limited, but is preferably 150°. It is below.
The contact angle of the protective layer to water is measured according to JIS R 3257:1999.
The contact angle of the protective layer to water can be adjusted by adjusting the type and content of the resin in the protective layer.

(Water-suspendable polymer)
The protective layer preferably contains a water-suspendable polymer. A water-suspendable polymer facilitates preparation of a coating solution using water as a dispersion medium when forming a protective layer on a resin layer.
The water-suspendable polymer in the protective layer is selected from the group consisting of olefin/unsaturated carboxylic acid copolymers, styrene/butadiene copolymers, styrene/acrylic copolymers, and biodegradable resins. One or more is preferable.

<<Olefin/unsaturated carboxylic acid copolymer>>
The olefin monomers of the olefin/unsaturated carboxylic acid copolymer include ethylene and α-olefins such as propylene and butylene. Among these, ethylene is preferred.
The unsaturated carboxylic acid-based monomer of the olefin/unsaturated carboxylic acid-based copolymer includes an unsaturated carboxylic acid monomer and an unsaturated carboxylic acid ester monomer that forms a carboxylic acid upon hydrolysis. Examples of unsaturated carboxylic acid monomers for olefin/unsaturated carboxylic acid copolymers include acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and butenetricarboxylic acid. Unsaturated carboxylic acids and their esters; unsaturated polycarboxylic acid alkyl esters having at least one carboxy group, such as itaconic acid monoethyl ester, fumaric acid monobutyl ester, maleic acid monobutyl ester.
The unsaturated carboxylic acid-based monomers constituting the olefin/unsaturated carboxylic acid-based copolymer may be used alone or in combination of two or more. The olefin/unsaturated carboxylic acid-based copolymer may be copolymerized with a small amount of other monomers copolymerizable with the olefin and the unsaturated carboxylic acid-based monomer.

Among these, the olefin/unsaturated carboxylic acid copolymer in the protective layer is at least one selected from the group consisting of ethylene/acrylic acid copolymers and ethylene/methacrylic acid copolymers. are preferred, ethylene/acrylic acid copolymer, ethylene/methacrylic acid copolymer, ethylene/methyl acrylate copolymer, ethylene/methyl methacrylate copolymer, ethylene/ethyl acrylate copolymer, ethylene/methacrylic acid It is more preferably one or more selected from the group consisting of an ethyl copolymer, an ethylene/butyl acrylate copolymer, and an ethylene/butyl methacrylate copolymer, and an ethylene/acrylic acid copolymer. More preferred.

<<Styrene/butadiene copolymer>>
Examples of the styrene/butadiene copolymer in the protective layer include styrene/butadiene rubber (SBR) and modified styrene/butadiene rubber (modified SBR).
Modified styrene/butadiene rubbers include acid-modified styrene/butadiene rubbers (acid-modified SBR).

<<Styrene/acrylic copolymer>>
A styrene/acrylic copolymer is a copolymer obtained by emulsion polymerization of a styrene monomer, an acrylic monomer, and, if necessary, other monomers copolymerizable therewith. is. Styrenic monomers include aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, pt-butylstyrene and chlorostyrene. Examples of acrylic monomers include unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and butentricarboxylic acid; Unsaturated polycarboxylic acid alkyl esters having at least one carboxy group such as acid monobutyl ester, maleic acid monobutyl ester, acrylamidopropanesulfonic acid, sulfoethyl acrylate sodium salt, or sulfopropyl methacrylate sodium salt ( meth)acrylic sulfonic acid monomers or salts thereof. Other monomers include alkyl (meth)acrylates (having 1 to 24 carbon atoms).
Styrene is suitable as the styrene-based monomer. As acrylic monomers, acrylic acid, methacrylic acid, itaconic acid, and fumaric acid are suitable.
Commercially available products may be used as the styrene/acrylic copolymer, such as "Hervil Series C-3 (trade name)" manufactured by Daiichi Paint Co., Ltd., "ACRONAL4160" manufactured by BASF, and the like. be done.

≪Biodegradable Resin≫
Examples of biodegradable resins include, but are not limited to, polylactic acid, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate terephthalate, 3-hydroxybutanoic acid/3-hydroxyhexanoic acid copolymer, and the like. A barrier laminate using a paper substrate can reduce the environmental load compared to a barrier laminate using a thermoplastic resin. By using , the environmental load can be further reduced.
A commercially available product may be used as the biodegradable resin, and examples of polylactic acid include "Randy PL Series (trade name)" manufactured by Miyoshi Oil Co., Ltd., and the like.

(water-soluble polymer)
The protective layer may contain a water-soluble polymer from the viewpoint of improving gas barrier properties. In this case, the protective layer preferably contains 25 parts by mass or less, more preferably 20 parts by mass or less of the water-soluble polymer per 100 parts by mass of the water-suspendable polymer. When the content of the water-soluble polymer is within the above range, a barrier laminate having excellent water vapor barrier properties and gas barrier properties while preventing a decrease in water resistance can be obtained.

Examples of the water-soluble polymer in the protective layer include polyvinyl alcohol, modified polyvinyl alcohol, starch and its derivatives, cellulose derivatives, polyvinylpyrrolidone, urethane resins, polyacrylic acid and its salts, casein, polyethyleneimine and the like. Among these, from the viewpoint of gas barrier properties, the water-soluble polymer is preferably one or more selected from the group consisting of polyvinyl alcohol and modified polyvinyl alcohol, more preferably modified polyvinyl alcohol.
Examples of modified polyvinyl alcohol include ethylene-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, and the like. Among these, the modified polyvinyl alcohol is preferably one or more selected from the group consisting of ethylene-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, and acetoacetyl-modified polyvinyl alcohol. and carboxy-modified polyvinyl alcohol, more preferably at least one selected from the group consisting of ethylene-modified polyvinyl alcohol.
Polyvinyl alcohol and modified polyvinyl alcohol are preferably completely saponified or partially saponified. Full saponification means a degree of saponification greater than 96%.

(Plate-like inorganic compound)
The protective layer may contain a plate-like inorganic compound from the viewpoint of water vapor barrier properties and gas barrier properties. In this case, the protective layer preferably contains 0.1% by mass or more and 50% by mass or less of the plate-like inorganic compound, more preferably 1.0% by mass or more, and still more preferably 2.0% by mass or more, The content is more preferably 40% by mass or less, still more preferably 30% by mass or less, and even more preferably 20% by mass or less. By also containing the plate-like inorganic compound in the protective layer, it is possible to obtain a barrier laminate having excellent water vapor barrier properties and gas barrier properties.

The plate-like inorganic compound in the protective layer is preferably one or more selected from the group consisting of synthetic mica, bentonite and kaolin, more preferably one or more selected from the group consisting of synthetic mica and kaolin. be.

The plate-like inorganic compound in the protective layer preferably has an aspect ratio of 100 or more, more preferably 200 or more, even more preferably 300 or more, and still more preferably 500 or more. As the aspect ratio increases, the movement of water vapor and gas is inhibited more, so the water vapor barrier properties and gas barrier properties can be improved. Although the upper limit of the aspect ratio is not particularly limited, it is preferably 10,000 or less from the viewpoint of availability, viscosity when applied onto the resin layer, and the like.

The protective layer may have the same composition as the resin layer, or may have a different composition from the resin layer. When the protective layer has the same composition as the resin layer, there is no need to separately prepare a protective layer-imparting liquid for forming the protective layer, and two resin layer-imparting liquids for forming the resin layer are placed on the paper substrate. It is easy to manufacture because it is only necessary to impart a degree of hardness (coating). By applying (coating) the resin layer applying liquid twice on the paper substrate, as described above, it is possible to fill fine pores, cracks, etc. existing on the surface of the resin layer, and as a result, the resin Due to the high aspect ratio plate-like inorganic compound layer, the labyrinth effect that the movement of water vapor, etc. is long is also exhibited for gas. A laminate can be provided.

In addition to the water-suspendable polymer, water-soluble polymer, and plate-like inorganic compound, the protective layer may contain dispersants, surfactants, antifoaming agents, wetting agents, dyes, and tint modifiers as needed. , a thickening agent, etc. can be added.

[Method for producing barrier laminate]
In the barrier laminate of the present invention, a resin layer and a protective layer are formed in this order on at least one surface of a paper substrate. Although the method for forming each layer is not particularly limited, it is preferably formed by a coating method. Specifically, a resin layer coating liquid (resin layer paint) is applied onto a paper substrate, dried to form a resin layer, and then a protective layer coating liquid (protective layer paint) is applied. and dried to form a protective layer.

In the case of forming a plurality of coating layers on a paper substrate, the above method of sequentially forming coating layers is preferable, but the method is not limited to this, and a simultaneous multi-layer coating method may be employed. . Simultaneous multi-layer coating method involves ejecting multiple types of coating liquids separately from slit-shaped nozzles to form a liquid laminate, which is then applied to a paper substrate to achieve multiple layers of coating. It is a method of forming a working film at the same time.

The coating equipment for applying the coating liquid is not particularly limited, and known equipment may be used. Examples of coating equipment include blade coaters, bar coaters, air knife coaters, slit die coaters, gravure coaters, micro gravure coaters, and gate roll coaters. In particular, for forming the resin layer, a coater that scrapes the coating surface, such as a blade coater, a bar coater, an air knife coater, a slit die coater, etc., is preferable in terms of promoting the orientation of the plate-like inorganic compound.

The drying equipment for drying the coating layer is not particularly limited, and known equipment can be used. Examples of drying equipment include hot air dryers, infrared dryers, gas burners, hot plates, and the like. Moreover, the drying temperature may be appropriately set in consideration of the drying time and the like.

The solvent of the coating liquid for each layer is not particularly limited, and water or an organic solvent such as ethanol, isopropyl alcohol, methyl ethyl ketone or toluene can be used.
Among these, in the present invention, water is preferable as the dispersion medium of the coating liquid for each layer from the viewpoint of not causing the problem of the volatile organic solvent. That is, it is preferable that the resin layer coating liquid is a resin layer water-based composition, and the protective layer coating liquid is a protective layer water-based composition.

The solid content of the coating solution for each layer is not particularly limited, and may be appropriately selected from the viewpoint of coatability and drying easiness. It is 10% by mass or more, and preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less.

The coating amount (after drying) of each layer is not particularly limited, but from the viewpoint of obtaining a barrier laminate having excellent water vapor barrier properties and gas barrier properties, water resistance, and excellent economic efficiency, it is preferably 1 g/m ² . Above, it is more preferably 2 g/m ² or more, still more preferably 3 g/m ² or more, and the upper limit is preferably 7 g/m ² or less.

[Physical Properties of Barrier Laminate]
(oxygen permeability)
The oxygen permeability of ^the barrier layered product ^is preferably as low as possible so that oxygen does not permeate. It is preferably 75 cc/m ² ·day·atm or less.
The oxygen permeability of the barrier laminate is measured at 23° C. and 50% RH using an oxygen permeability measuring device (OX-TRAN2/20 manufactured by MOCON).

(water vapor permeability)
The lower the water vapor transmission ^rate of the barrier laminate ^, the less water vapor is permeable. /m ² ·day or less.
The water vapor transmission rate of the barrier laminate is measured according to JIS Z 0208: 1976 by preparing a moisture permeable cup so that the protective layer of the barrier laminate is on the inside (condition B: temperature 40 ± 0.5°C, relative humidity 90±2%).

(Size degree by Stockigt method)
The sizing degree of the barrier laminate is preferably 300 seconds or more, more preferably 350 seconds or more, as measured according to JIS P 8122:2004.

INDUSTRIAL APPLICABILITY The barrier laminate of the present invention is excellent in water vapor barrier properties and gas barrier properties, and has water resistance.

The characteristics of the present invention will be described more specifically below with reference to examples and comparative examples. The materials, amounts used, proportions, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed to be limited by the specific examples shown below. "Parts" and "%" in Examples and Comparative Examples indicate "parts by mass" and "% by mass", respectively, unless otherwise specified.

[Evaluation and analysis]
The barrier laminates of Examples and Comparative Examples were evaluated and analyzed as follows.

(Contact angle with water)
In accordance with JIS R 3257:1999, using a dynamic water contact angle tester (manufactured by Fibro, 1100DAT), 1 to 4 μL of distilled water was dropped on the protective layer of the barrier laminate, and 0.1 second after dropping. was measured.

(oxygen permeability)
The oxygen permeability of the barrier laminate was measured at 23° C. and 50% RH using an oxygen permeability measuring device (OX-TRAN2/20 manufactured by MOCON).

(water vapor permeability)
The water vapor transmission rate of the barrier laminate was measured in accordance with JIS Z 0208:1976 by preparing a moisture permeable cup so that the protective layer of the barrier laminate was on the inside (condition B: temperature 40 ± 0 .5° C., 90±2% relative humidity).

(Size degree by Stockigt method)
The sizing degree of the barrier laminate was measured according to JIS P 8122:2004.

[Example 1]
<Preparation of resin layer paint>
Aqueous dispersion of plate-like inorganic compound (synthetic mica, “NTO-05 (trade name)” manufactured by Topy Industries, aspect ratio: about 1000, thickness: about 5 nm, solid content: 6%) 30.0 parts Then, while stirring, an ethylene/acrylic acid copolymer ("Zaixen AC (trade name)" manufactured by Sumitomo Seika Co., Ltd., solid content: 29.2%, copolymerization ratio of acrylic acid: 20 mol%, melting point: 80 to 95°C) 34.3 parts were added and further stirred. To this, 1.7 parts of a cation-modified polyamide resin ("Sumirez Resin SPI-203(50)H (trade name)" manufactured by Taoka Chemical Co., Ltd., solid content 53%) was added and stirred. Further, 0.1 part of a 25% aqueous ammonia solution was added and stirred. Further, water was added and stirred so that the solid content concentration became 18%, to prepare a resin layer coating material.
<Preparation of protective layer paint>
Ethylene/acrylic acid copolymer (Sumitomo Seika Co., Ltd. “Zaixen AC (trade name)”, solid content 29.2%, copolymerization ratio of acrylic acid: 20 mol%, melting point: 80 to 95 ° C.), Water was added and stirred to adjust the solid content concentration to 18% to prepare a protective layer paint.
<Production of barrier laminate>
The obtained resin layer paint was applied to bleached kraft paper (basis weight: 50 g/m ² , thickness: 60 μm) using a Meyer bar so that the coating amount of the resin layer after drying was 6 g/m ² . After coating, it was dried in a hot air dryer at 120°C for 3 minutes. Furthermore, on the resin layer, the protective layer paint is applied using a Meyer bar so that the coating amount after drying is 5 g/m ² , and then dried in a hot air dryer at 120 ° C. for 3 minutes to form a barrier. A flexible laminate was obtained. Table 1 shows the evaluation and analysis results.

[Example 2]
A barrier laminate was obtained in the same manner as in Example 1, except that the resin layer coating of Example 1 was used as the protective layer coating. Table 1 shows the evaluation and analysis results.

[Example 3]
In the preparation of the resin layer coating material and the protective layer coating material, the resin layer coating material and the protective layer coating material of Example 2 were each added with ethylene-modified polyvinyl alcohol (PVA, "Exceval AQ-4104 (trade name)" manufactured by Kuraray Co., Ltd.). 20 parts of saponified type, solid content: 10%) is added, water is added and stirred so that the solid content concentration is 15%, and the resin layer coating material and the protective layer coating material are respectively obtained. A barrier laminate was obtained in the same manner as in Example 2, except that the coating amount after drying was 3 g/m ² . Table 1 shows the evaluation and analysis results.

[Example 4]
In the preparation of the resin layer coating, an aqueous dispersion of a plate-like inorganic compound (synthetic mica, "NTO-05 (trade name)" manufactured by Topy Industries, Ltd., aspect ratio: about 1000, thickness: about 5 nm, solid content: 6%), while stirring, acid-modified SBR ("Nipol LX407S12 (trade name)" manufactured by Nippon Zeon Co., Ltd., solid content: 47.3%) 90 parts, and acid-modified SBR (Nippon Zeon Co., Ltd. 10 parts of "Nipol LX407BP-6 (trade name)", solid content: 53%) was added and further stirred. To this, 5 parts of a cation-modified polyamide resin ("Sumirez Resin SPI-203(50)H (trade name)" manufactured by Taoka Chemical Co., Ltd., solid content 53%) was added and stirred. Further, 0.3 part of 25% aqueous ammonia solution was added and stirred. Furthermore, a barrier laminate was obtained in the same manner as in Example 1, except that water was added and stirred so that the solid content concentration was 20% to prepare a resin layer paint. Table 1 shows the evaluation and analysis results.

[Example 5]
In the preparation of the protective layer paint, except that the ethylene / acrylic acid copolymer was changed to polylactic acid ("Randy PL-3000 (trade name)" manufactured by Miyoshi Oil Co., Ltd., solid content: 40%). A barrier laminate was obtained in the same manner as in Example 1. Table 1 shows the evaluation and analysis results.

[Comparative Example 1]
A barrier laminate was obtained in the same manner as in Example 1, except that no protective layer paint was applied. Table 1 shows the evaluation and analysis results.

[Comparative Example 2]
A barrier laminate was obtained in the same manner as in Example 1, except that the resin layer paint was not applied. Table 1 shows the evaluation and analysis results.

[Comparative Example 3]
In the preparation of the protective layer paint, ethylene/acrylic acid copolymer was added to ethylene-modified polyvinyl alcohol (PVA, "Exeval AQ-4104 (trade name)" manufactured by Kuraray Co., Ltd., fully saponified type, solid content: 10%). , the solid content concentration was changed to 10%, and the coating amount of the protective layer after drying was 0.5 g/m ² . got a body Table 1 shows the evaluation and analysis results.

[Comparative Example 4]
In the preparation of the resin layer paint, a plate-like inorganic compound was prepared from synthetic mica to sericite (“KF1325 (trade name)” manufactured by Chuo Kaolin Co., Ltd., aspect ratio: 20 to 30 (catalog value), average particle size: 13 μm ( A barrier laminate was obtained in the same manner as in Example 1, except that the catalog value)) was changed. Table 1 shows the evaluation and analysis results.

As can be seen from Table 1, according to the barrier laminate of this example, even if the number of layers is small, the barrier laminate has excellent water vapor barrier properties and gas barrier properties, has water resistance, and is economical. provided.

Claims (8)

A barrier laminate comprising a paper substrate and a resin layer and a protective layer in this order on at least one surface of the paper substrate,
The resin layer contains a water-suspendable polymer, a plate-like inorganic compound having an aspect ratio of 500 or more, and a cationic resin,
The resin layer contains 2.0% by mass or more and 20% by mass or less of a plate-like inorganic compound,
The content of the plate-like inorganic compound in the resin layer is 5 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the water-suspendable polymer,
the protective layer contains a water-suspendable polymer,
The protective layer does not contain a water-soluble polymer, or contains 20 parts by mass or less of a water-soluble polymer with respect to 100 parts by mass of the water-suspendable polymer,
Each coating amount of the resin layer and the protective layer is 1 g/m ² or more,
A barrier laminate, wherein the protective layer has a contact angle of 50° or more with respect to water. The water-suspendable polymer in the resin layer is at least one selected from the group consisting of olefin/unsaturated carboxylic acid copolymers, styrene/butadiene copolymers, and styrene/acrylic copolymers. The barrier laminate according to claim 1, wherein 3. The barrier laminate according to claim 1, wherein the plate-like inorganic compound in the resin layer is one or more selected from the group consisting of synthetic mica, bentonite and kaolin. The barrier laminate according to any one of claims 1 to 3 , wherein the resin layer further contains 25 parts by mass or less of a water-soluble polymer with respect to 100 parts by mass of the water-suspendable polymer. 5. The barrier laminate according to claim 4 , wherein the water-soluble polymer in the resin layer is one or more selected from the group consisting of polyvinyl alcohol and modified polyvinyl alcohol. The water-suspendable polymer in the protective layer is selected from the group consisting of olefin/unsaturated carboxylic acid copolymers, styrene/butadiene copolymers, styrene/acrylic copolymers, and biodegradable resins. The barrier laminate according to any one of Claims 1 to 5, which is one or more of the The barrier laminate according to any one of claims 1 to 6 , wherein the protective layer contains 0.1% by mass or more and 50% by mass or less of the plate-like inorganic compound. 8. The barrier laminate according to claim 7 , wherein the plate-like inorganic compound in the protective layer is one or more selected from the group consisting of synthetic mica, bentonite and kaolin.