JP7615837B2 - Barrier Paper - Google Patents

Description

The present invention relates to a barrier paper that has excellent oxygen barrier properties, water vapor barrier properties and interlayer adhesion, and to a gas barrier paper-based laminate, a gas barrier paper-based material and a gas barrier paper-based packaging material made from the barrier paper.

In recent years, environmental issues such as microplastics have been receiving a lot of attention, and in order to reduce the environmental impact of paper-based products, there is now a demand to improve recyclability by making products out of paper as much as possible, and even to consider biodegradability.
Conventional packaging methods for preventing deterioration of the contents of foods, medical products, chemical products, cosmetics, etc. due to moisture and oxygen have included the use of packaging materials with high gas barrier properties, gas replacement of the content storage section with an inert gas such as nitrogen gas, and the inclusion of an oxygen absorber packaged with reduced iron powder or the like. However, there are problems such as insufficient performance, increased packaging costs, increased garbage as waste, only functioning in moist environments, and the risk of accidental ingestion.
When considering the recycling or incineration of used packaging materials, packaging materials using paper have begun to attract attention. However, paper alone does not have sufficient gas barrier properties. In order to improve gas barrier properties, the surface is coated with resin or a resin film having a metal foil or inorganic vapor deposition layer is laminated. This inhibits the recycling or biodegradation of the paper alone, causes damage to incinerators when burned, and generates large amounts of incineration residue due to the metal foil.

Patent Document 1 discloses a laminate in which a thin gas barrier layer formed by plasma polymerization is laminated on a substrate made of paper or pulp mold having a surface with a filler layer made of a polycondensate of polysaccharide and silicon compound. However, in this laminate, the thickness of the filler layer needs to be increased to about several tens of μm, and the method of applying the filler layer is limited. Furthermore, when the substrate made of paper or pulp mold is placed in the plasma polymerization device when forming the thin gas barrier layer, paper powder or pulp powder generated from the paper or pulp mold tends to prevent the inside of the plasma polymerization device from being reduced in pressure to a level suitable for plasma polymerization, making it difficult to form a stable thin gas barrier layer, and the adhesion between the filler layer and the thin gas barrier layer tends to be insufficient, resulting in a disadvantage in that the gas barrier property tends to be unstable.

Patent Document 2 discloses a gas barrier laminate in which a first gas barrier layer containing an ethylene-modified polyvinyl alcohol resin and an inorganic layered compound and a second gas barrier layer made of ethylene-modified polyvinyl alcohol are sequentially provided on a paper support. However, it has been difficult to meet various quality requirements due to insufficient interlayer adhesion between the paper support and the first gas barrier layer and limitations on the types of resins used in the first and second gas barrier layers.

Patent No. 4622201 Patent Publication 2009-184138

An object of the present invention is to solve the above-mentioned problems and to provide an environmentally friendly barrier paper that has excellent oxygen barrier property, water vapor barrier property, and interlayer adhesion before and after bending or before and after bag making, and that reduces the amount of organic solvent used, as well as an environmentally friendly gas barrier paper-based laminate, gas barrier paper-based material, and gas barrier paper-based packaging product made from the environmentally friendly barrier paper.

As a result of various studies, the inventors have found that the above-mentioned objective can be achieved by a barrier paper having a layer structure in which a specific fixed sealing layer and a specific gas barrier layer are laminated adjacent to each other in this order on at least both sides of a paper base layer.

The present invention is characterized in the following points.
1. A laminate structure in which at least a fixed filling layer in contact with the paper base layer and a gas barrier layer in contact with the fixed filling layer are laminated on both sides of a paper base layer,
The fixing filling layer contains one or more resins selected from the group consisting of polystyrene-based resins, polyurethane-based resins, and acrylic-based resins,
The fixed sealing layers on both sides have the same or different compositions,
the gas barrier layer contains a polyurethane resin and/or a polyvinyl alcohol resin,
The gas barrier layers on both sides have the same or different compositions;
13. A barrier paper, wherein the gas barrier layer on at least one side further contains an inorganic filler.
2. The barrier paper according to claim 1, wherein the fixed sealing layer on at least one side further contains an inorganic filler.
3. The barrier paper according to 1 or 2 above, wherein the fixed sealing layer on at least one side contains a polyurethane-based resin.
4. The barrier paper according to any one of 1 to 3 above, wherein the gas barrier layers on both sides each further contain an inorganic filler.
5. The barrier paper according to any one of 1 to 4 above, characterized in that the oxygen transmission rate at a temperature of 23° C. and a humidity of 0% according to JIS K7126 is 0.01 cc/m ² /day/atm or more and 20 cc/m ² /day/atm or less.
6. The barrier paper according to any one of 1 to 5 above, characterized in that the water vapor transmission rate according to JIS K7129 at a temperature of 40°C and a humidity of 90% is 0.01 g/m ² /day or more and 30 g/m ² /day or less.
7. The barrier paper according to any one of 1 to 6 above, characterized in that after bending treatment in which the paper is folded in half at 180 degrees and then stretched, the oxygen transmission rate according to JIS K7126 at a temperature of 23°C and a humidity of 0% is 0.1 cc/ ^m2 /day/atm or more and 100 cc/ ^m2 /day/atm or less.
8. The barrier paper according to any one of 1 to 7 above, characterized in that after bending treatment in which the paper is folded in half at 180 degrees and then stretched, the water vapor transmission rate according to JIS K7129 at a temperature of 40°C and a humidity of 90% is from 0.1 g/ ^m2 /day to 40 g/ ^m2 /day.
9. A gas barrier paper laminate having oxygen barrier properties and water vapor barrier properties, produced using the barrier paper according to any one of 1 to 8 above.
10. A gas barrier paper-based material having oxygen barrier properties and water vapor barrier properties, produced using the gas barrier paper-based laminate described in 9 above.
11. A gas barrier paper-based packaging body having oxygen barrier properties and water vapor barrier properties, produced using the gas barrier paper-based material described in 10 above.

According to the present invention, it is possible to obtain environmentally friendly barrier paper that has excellent oxygen barrier property, water vapor barrier property and interlayer adhesion before and after bending or before and after bag making, and in which the amount of organic solvent used is reduced, as well as environmentally friendly gas barrier paper-based laminates, gas barrier paper-based materials and gas barrier paper-based packaging products made from the environmentally friendly barrier paper.

FIG. 1 is a schematic cross-sectional view showing an example of the layer structure of a barrier paper of the present invention. FIG. 1 is a schematic cross-sectional view showing an example of the layer structure of a gas barrier paper material of the present invention.

The environmentally friendly barrier paper, gas barrier paper laminate, gas barrier paper material, and gas barrier paper packaging of the present invention are described in detail below with reference to the drawings.

The resin names used in the present invention are those commonly used in the industry. Furthermore, the present invention is not limited to the specific examples listed below.
In the present invention, films and sheets are collectively referred to as films.
In the present invention, the term "gas barrier property" refers to oxygen barrier property and water vapor gas barrier property.

<Barrier paper>
The barrier paper of the present invention has oxygen barrier properties and water vapor barrier properties before and after bending or before and after bag making, and is an environmentally friendly barrier paper in which the amount of organic solvents used during production is reduced.
Here, the bending treatment refers to an alternative treatment that imparts a bending load to the packaging material during bag production. For quantitative evaluation, for example, the bending treatment can be a process in which the barrier paper is folded in half at 180 degrees (mountain fold) so that the paper layer is on the outside, and then stretched and returned to its original state.
The barrier paper of the present invention has a layer structure in which at least a fixed filling layer and a gas barrier layer are laminated adjacent to each other in this order on both sides of a paper base layer.
The gas barrier layer is a layer that imparts oxygen barrier property and water vapor barrier property, and the fixing filling layer is a layer that fills the paper base layer, fixes the gas barrier layer between the gas barrier layer and the paper base layer, improves adhesion, and supports the oxygen barrier property and water vapor barrier property. The high adhesion can prevent deterioration of the oxygen barrier property and water vapor barrier property due to internal peeling.

In the barrier paper, the fixed sealing layer and the gas barrier layer are laminated on both sides of the paper base layer. By laminating them on both sides, the functional load of the fixed sealing layer and the gas barrier layer on each side can be reduced, and a wider range of composition and thickness can be provided than when they are laminated only on one side, making it possible to achieve a wide range of balance such as a reduced number of constituent layers, a reduced thickness, high productivity, and suppression of high rigidity of the barrier paper, thereby improving usability in packaging material applications.
The fixing filling layers on both sides may have the same composition or different compositions, and the gas barrier layers on both sides may have the same composition or different compositions.

The thickness of the barrier paper of the present invention is not particularly limited, but is preferably 20 μm or more and 250 μm or less, and more preferably 30 μm or more and 120 μm or less. If it is thinner than the above range, it is likely to be difficult to form a fixing sealing layer and a gas barrier layer of sufficient thickness, and there is a risk that the rigidity of the packaging material will be insufficient when used in packaging materials. If it is thicker than the above range, there is a risk that the rigidity of the packaging material will be too strong when used in packaging materials.

The thickness or basis weight of the paper base layer is not particularly limited, but the thickness is preferably 20 μm or more and 200 μm or less, and more preferably 30 μm or more and 100 μm or less. The basis weight is preferably 25 g/m2 or ^more and 600 g/m2 or ^less , and more preferably 50 g/ ^m2 or more and 450 g/ ^m2 or less. If the basis weight and/or thickness is smaller than the above range, it is likely to be difficult to achieve sufficient rigidity, and curling and waviness are likely to occur during production of the barrier paper, and if it is larger than the above range, the rigidity will be too strong, resulting in poor workability, and the winding diameter of the barrier paper will increase, which is likely to reduce work efficiency, and there is a risk of it being less suitable as a barrier paper.
The thickness ratio of the paper base layer in the barrier paper of the present invention is not particularly limited, but is preferably from 80% to 99%, and more preferably from 90% to 98%. If it is lower than the above range, the recyclability and biodegradability efficiency of the barrier paper are likely to decrease, and even if it is higher than the above range, the recyclability and biodegradability efficiency are unlikely to change any further, and sufficient oxygen barrier property and water vapor barrier property may not be exhibited.

The thickness or coating amount of the fixing filler layer is not particularly limited, but the thickness is preferably 0.2 μm or more and 25 μm or less, and more preferably 0.5 μm or more and 20 μm or less. The coating amount is preferably 0.5 g/m2 ^or more and 30 ^m2 or less, and more preferably 1 g/m2 ^or more and 20 ^m2 or less. If the thickness is thinner than the above range, it is likely to be difficult to fix the gas barrier layer with sufficient filling properties, and even if the thickness is thicker than the above range, the filling properties and the effect of fixing the gas barrier layer are not significantly improved.
The thicknesses of the fixed filling layers on both sides of the paper base layer may be the same or different.

The thickness or coating amount of the gas barrier layer is not particularly limited, but the thickness is preferably 0.1 μm or more and 10 μm or less, and more preferably 0.2 μm or more and 5 μm or less. The coating amount is preferably 0.3 g/m2 ^{or more} and 10 ^m2 or less, and more preferably 0.5 g/ ^m2 or more and 5 ^m2 or less. If the layer is thinner than the above range, it is likely to be difficult to have sufficient oxygen barrier property and water vapor barrier property, and even if the layer is thicker than the above range, the oxygen barrier property and water vapor barrier property are not significantly improved.
The thickness of the gas barrier layers on both sides of the paper base layer may be the same or different.

The barrier paper of the present invention exhibits excellent oxygen barrier properties and water vapor barrier properties due to the synergistic effect of the fixing filling layer and the gas barrier layer.
It is also preferred that the barrier paper of the present invention maintains excellent oxygen barrier properties and water vapor barrier properties even after bending treatment.
Furthermore, when the fixed filling layer and the gas barrier layer are present on both sides, the film is likely to exhibit better oxygen barrier property and water vapor barrier property than when they are present on only one side, and in particular, the oxygen barrier property and water vapor barrier property after bending treatment are likely to be better.

The oxygen barrier property and water vapor barrier property can be represented by the oxygen permeability and water vapor permeability measured by methods in accordance with JIS K7126 and K7129, respectively.
The oxygen permeability of the barrier paper before bending treatment at a temperature of 23°C and a humidity of 0% is preferably 0.01 cc/ ^m2 /day/atm or more and 20 cc/ ^m2 /day/atm or less, and more preferably 0.05 cc/ ^m2 /day/atm or more and 10 cc/ ^m2 /day/atm or less. Paper with a permeability lower than the above range is difficult to produce, and paper with a permeability higher than the above range is likely to have insufficient oxygen barrier properties.

For example, after folding in half at 180 degrees and undergoing bending treatment, the oxygen permeability at a temperature of 23°C and a humidity of 0% is preferably 0.1 cc/ ^m2 /day/atm or more and 100 cc/ ^m2 /day/atm or less, and more preferably 0.5 cc/ ^m2 /day/atm or more and 50 cc/ ^m2 /day/atm or less. Those with a permeability lower than the above range are difficult to produce, and those with a permeability higher than the above range are likely to have insufficient oxygen barrier properties.

The barrier paper before bending has a water vapor permeability of 0.01 at a temperature of 40°C and a humidity of 90%.
It is preferable that the coating density is from 0.05 g/ ^m2 /day to 30 g/ ^m2 /day, and more preferably from 0.05 g/ ^m2 /day to 20 g/ ^m2 /day. Coatings with a coating density lower than the above range are difficult to manufacture, while coatings with a coating density higher than the above range tend to have insufficient water vapor barrier properties.

For example, after bending treatment in which the sheet is folded in half at 180 degrees and then stretched, the water vapor permeability at a temperature of 40° C. and a humidity of 90% is preferably 0.1 g/ ^m2 /day to 40 g/ ^m2 /day, and more preferably 0.5 g/ ^m2 /day to 30 g/ ^m2 /day. Those with a permeability lower than the above range are difficult to produce, and those with a permeability higher than the above range tend to have insufficient water vapor barrier properties.

The barrier paper of the present invention can be subjected to secondary processing for the purpose of imparting surface functions such as chemical functions, electrical functions, magnetic functions, mechanical functions, friction/wear/lubrication functions, optical functions, thermal functions, biocompatibility, etc.
Examples of secondary processing include embossing, painting, adhesion, printing, metallizing (plating, etc.), mechanical processing, surface treatment (antistatic treatment, corona discharge treatment, plasma treatment, photochromism treatment, physical vapor deposition, chemical vapor deposition, coating, etc.), etc. The laminate of the present invention can also be subjected to lamination (dry lamination or extrusion lamination), bag making, and other post-processing.

When laminating the layers constituting the barrier paper of the present invention, if necessary, the surface of each layer can be pretreated, for example, by corona treatment or ozone treatment. In addition, anchor coating agents such as isocyanate-based (urethane-based), polyethyleneimine-based, polybutadiene-based, and organotitanium-based, or anchor coating agents such as polyurethane-based, polyacrylic-based, polyester-based, epoxy-based, polyvinyl acetate-based, cellulose-based, and other laminating adhesives can be used as desired.

[Paper base layer]
The paper base layer is a layer made of a paper base material, and may be a single layer structure or a multi-layer structure of two or more layers. In the case of a multi-layer structure, each layer may be made of the same or different paper base material, may have the same or different thickness, and may be bonded to each other with an adhesive.

(Paper base material)
There are no particular limitations on the paper base material used in the paper base layer, and any commonly known and commonly used paper base material can be used as long as it has sufficient strength, toughness, heat resistance, and other mechanical, physical, and chemical properties to withstand typical lamination processes and adhesive layer formation processes.
The paper base material can be a bleached or unbleached paper base material with strong sizing properties. Specifically, pure white roll paper, kraft paper, paperboard, coated paper, cast coated paper, milk base paper, processed base paper, wood-free paper, lightly coated printing paper, coated printing paper, resin coated paper, release base paper, double-sided coated release base paper, coated greaseproof paper, impregnated paper, etc. can be used. Among these, coated paper, bleached kraft paper, etc. are particularly preferred.
The paper substrate layer may be composed of one layer, or may be composed of two or more layers of the same or different paper substrates. The paper substrates may be laminated by any lamination means via an adhesive layer.

As the raw material pulp for the paper base material, softwood pulp (N wood) or hardwood pulp (L wood) can be used, and these can also be used in combination. By changing the content of each, it is possible to adjust the balance of strength, flexibility, smoothness, and barrier properties that can withstand the release paper manufacturing process and the transfer product manufacturing process, and a paper base material with performance suited to the application can be produced.
For example, by increasing the content of softwood pulp (N wood), it is possible to increase bending resistance and make the sheet less susceptible to cracking, whereas by increasing the content of hardwood pulp (L wood), it is possible to increase smoothness and/or gas barrier properties.
In order to ensure that the paper base material has sufficient heat resistance, it is preferably neutral paper, and more preferably neutral paper sized using an alkyl ketene dimer as a sizing agent.

When the paper substrate layer and/or the paper substrate has a multi-layer structure, the paper substrate and/or the base paper to be laminated are preferably laminated via an adhesive layer by extrusion lamination or wet lamination.
The adhesive for forming the adhesive layer may be the same as that used for the adhesive layer when producing barrier paper or a gas barrier paper-based laminate, but it is preferable to use a lamination adhesive or a wet lamination adhesive.

In addition, if necessary, plastic compounding agents and additives such as lubricants, crosslinking agents, antioxidants, UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, and pigments can be added to the paper base material in order to improve or modify its processability, heat resistance, weather resistance, mechanical properties, dimensional stability, oxidation resistance, slipperiness, release properties, flame retardancy, mold resistance, electrical properties, strength, etc. The amount of these additives can be freely selected depending on the purpose, as long as it does not adversely affect other properties.

To improve the adhesion between the paper substrate and/or substrate layer and other layers, if necessary, a paper substrate having a coating layer containing a resin or the like on its surface may be used, or the surface of the paper substrate and/or substrate layer that comes into contact with the adhesive may be subjected to a physical surface treatment such as corona discharge treatment, ozone treatment, plasma treatment, glow discharge treatment, sandblasting treatment, or a chemical surface treatment such as oxidation treatment using chemicals.

[Fixed sealing layer]
The fixing filling layer is a layer made of a fixing filling resin composition.
The fixing filling layer contains at least a fixing filling resin, and may further contain an inorganic filler, an additive, and the like, as necessary.
Since the surface of the paper base material is porous and uneven, it is sealed with a fixed sealing layer.
The fixed filling layer may have a single layer structure or a multi-layer structure of two or more layers. In the case of a multi-layer structure, each layer may have the same or different composition, the same or different thickness or basis weight, and each layer may be bonded to each other with an adhesive.

The fixed filling layer can be formed by melt (co)extrusion laminating or coating the fixed filling resin composition on the substrate layer.
In the case of forming the layer by application, the fixed filling resin composition, which is a liquid, is applied to the base material layer using a two-roll size press, a gate roll size press, a rod metering size press, an air knife coater, a curtain coater, a direct gravure coater, a reverse gravure coater, an offset gravure coater, a gravure kiss coater, a die coater, a blade coater, a knife coater, an impregnation coater, or the like, and then dried by heating using a dryer.

(Fixing and sealing resin composition)
The filling resin composition is a resin composition for forming a filling layer, contains components for constituting the filling layer, contains at least a filling resin, and may further contain inorganic fillers, additives, etc., as necessary.
The fixed filling resin composition may be one that melts at high temperatures, and may further contain an aqueous solvent and be an aqueous solution in which an aqueous resin is dissolved in an aqueous solvent, or an aqueous emulsion in which an aqueous resin is dispersed.
In this case, by using no solvent or an aqueous solvent, the generation of organic solvent vapor during the drying step is suppressed, which is environmentally friendly.
In order to suppress the penetration of the solvent into the paper substrate, it is preferable that the solid content in the fixing filling resin composition is high.

(Fixed sealing resin)
The fixed filling resin is preferably one that can fill (fill) minute holes in the surface of the paper base material and further exhibits strong adhesion to the gas barrier layer. When the fixed filling resin composition contains an aqueous solvent, the fixed filling resin is preferably a resin that can be emulsified and dispersed in the aqueous solvent, or a resin that dissolves in the aqueous solvent.

The fixed filling resin preferably has high water resistance and low solubility in the solvent contained in the gas barrier resin composition so that the fixed filling layer can be easily formed and maintained.
Specific examples of the fixing and filling resin include thermoplastic resins, such as polystyrene-based resins, polyurethane-based resins, and acrylic-based resins. One of these resins may be used, or two or more of them may be mixed and used.

The polystyrene resin refers to a homopolymer of a styrene monomer or a copolymer of a styrene monomer and another copolymerizable monomer.
Specific examples of styrene-based monomers include styrene and styrene-based compounds having a substituent such as methylstyrene, paravinylphenol, t-butoxystyrene, and chlorostyrene.
Specific examples of the copolymerizable monomer include monomers copolymerizable with styrene-based monomers, such as (meth)acrylic acid, (meth)acrylic acid esters, and acrylonitrile.

The polystyrene resin preferably has good water resistance.
Specific examples of polystyrene-based resins include polystyrene, (methyl)styrene-(meth)acrylic acid copolymers, (methyl)styrene-(meth)acrylic acid ester copolymers, (methyl)styrene-acrylonitrile copolymers, styrene-acrylonitrile-butadiene copolymers, etc. Among these, styrene-acrylic acid copolymers are preferred.

The polyurethane resin is a (co)polymer having a urethane bond (-NHCOO-) in the main skeleton, and may have various functional groups as required.
The polyurethane resin preferably has good water resistance.

The acrylic resin is a (co)polymer using (meth)acrylic acid or a (meth)acrylic acid ester, and may have various functional groups as required.
The acrylic resin preferably has good water resistance.

(Inorganic filler contained in fixed sealing layer)
The inorganic filler contained in the fixed filling layer can enhance the filling effect of the fixed filling layer on the paper base material.
The type of inorganic filler contained in the fixed sealing layer is not particularly limited, and examples thereof include alumina (aluminum oxide), titanium oxide, zirconia (zirconium oxide), ceria, lithium silicate, diamond, silicon nitride, silicon carbide, iron oxide, mica, kaolin, chromium oxide, silica (silicon oxide), antimony oxide, calcium carbonate, etc. These inorganic fillers may be used alone or in combination of two or more. Among these, it is preferable to use silica, mica, alumina, and kaolin.

The average particle size of the inorganic filler particles contained in the fixed filling layer is not particularly limited, but in order to stably obtain an excellent filling effect, it is preferably 0.1 μm or more and 10 μm or less, and more preferably 0.5 μm or more and 5 μm or less, depending on the thickness and coarseness of the paper base material. If it is smaller or larger than the above range, the filling effect is likely to decrease.

There are no particular limitations on the shape of the inorganic filler contained in the fixed sealing layer, and a wide variety of shapes, such as spherical, elliptical, crushed, and scaly, can be used. One type of inorganic filler of these shapes may be used, or two or more types may be mixed and used. Among these, crushed ones are preferred.

The surface of the inorganic filler contained in the fixed filling layer may be organically modified. The organic modification improves the affinity with the fixed filling resin and the solvent, reduces aggregation, and facilitates uniform dispersion in the fixed filling resin composition or the fixed filling layer.

The content of the inorganic filler in the fixed sealing layer is preferably 1 part by mass or more and 50 parts by mass or less, and more preferably 10 parts by mass or more and 40 parts by mass or less, relative to 100 parts by mass of the fixed sealing resin. Within the above range, the fixed sealing resin composition exhibits an appropriate melt viscosity for easy melt extrusion or appropriate viscosity for easy application, and the fixed sealing layer can exhibit a sufficient and stable sealing effect.

(Solvent for liquid sealing resin composition)
The main component of the solvent of the liquid filling resin composition is water, and the composition may further contain a water-soluble lower alcohol in order to adjust the solubility and dispersibility of the resin component.
In order to suppress the penetration of the solvent into the paper substrate, it is preferable that the aqueous solvent has low permeability into the paper substrate.

[Gas barrier layer]
The gas barrier layer is a layer made of a gas barrier resin composition. The gas barrier layer contains at least a gas barrier resin, and may further contain an inorganic filler, an additive, and the like, as necessary.
The gas barrier layer may be a single layer structure or a multi-layer structure of two or more layers. In the case of a multi-layer structure, each layer may have the same or different composition, the same or different thickness or coating amount, and each layer may be bonded to each other with an adhesive.
The gas barrier layer contains at least a gas barrier resin. Of the gas barrier layers on both sides, at least one of the gas barrier layers on at least one side preferably further contains an inorganic filler.

The gas barrier layer can be formed by melt (co)extrusion laminating or coating the gas barrier resin composition on the fixed filling layer.
When forming the gas barrier resin composition by coating, the gas barrier resin composition, which is a liquid, is coated onto the fixed filling layer using a two-roll size press, a gate roll size press, a rod metering size press, an air knife coater, a curtain coater, a direct gravure coater, a reverse gravure coater, an offset gravure coater, a gravure kiss coater, a die coater, a blade coater, a knife coater, an impregnation coater or the like, and then dried by heating using a dryer.

(Gas barrier resin composition)
The gas barrier resin composition is a resin composition for forming a gas barrier layer, and contains components for constituting the gas barrier layer, including at least a gas barrier resin, and may further contain additives, etc., as necessary.
The gas barrier resin composition may be one that melts at high temperatures, and may further contain an aqueous solvent and be in the form of an aqueous solution in which an aqueous resin is dissolved in an aqueous solvent, or an aqueous emulsion in which an aqueous resin is dispersed.
In this case, by using no solvent or an aqueous solvent, the generation of organic solvent vapor during the drying step is suppressed, which is environmentally friendly.

(Gas barrier resin)
The gas barrier resin is a resin having oxygen barrier properties and/or water vapor barrier properties, and is preferably a thermoplastic resin, and is preferably one that exhibits strong adhesion to the fixing and filling resin. When the gas barrier resin composition contains an aqueous solvent, it is further preferably a resin that can be dissolved in the aqueous solvent to be turned into a solution, or a resin that can be emulsified and dispersed in the aqueous solvent.
As the barrier resin, a resin having both oxygen barrier properties and water vapor barrier properties may be used alone, or a resin having oxygen barrier properties and a resin having water vapor barrier properties may be used in combination.
The barrier resin preferably has an oxygen permeability of 1.0×10 ^-4 cc/m ² /day/atm or more and 20 cc/m ² /day/atm or less at a temperature of 23° C. and a humidity of 0%, as measured by a method conforming to JIS K 7126, for a 20 μm-thick resin film consisting of the barrier resin alone. It is difficult to procure a resin with a permeability lower than the above range, and a resin with a permeability higher than the above range is likely to have insufficient oxygen barrier properties.
The barrier resin preferably has a water vapor permeability of 0.1 g/ ^m2 /day to 30 g/m2/day at a temperature of 40°C and a humidity of 90%, measured by a method conforming to JIS K 7129, for a 25 ^µm -thick resin film made solely of the barrier resin. It is difficult to procure a resin with a permeability lower than the above range, and a resin with a permeability higher than the above range is likely to have insufficient water vapor barrier properties.
Furthermore, a resin with a high cohesive energy density is suitable as a barrier resin.
For example, polyethylene is not suitable as a barrier resin because of its low cohesive energy density.

In barrier paper having a layer structure in which at least a fixed filling layer and a gas barrier layer are laminated adjacent to each other in this order on both sides of a paper base layer, specific barrier resins include polyvinyl alcohol-based resins, polyurethane-based resins, ethylene-vinyl alcohol copolymers, polyvinylidene chloride, cycloolefin polymers, etc., and one of these resins may be used, or two or more may be mixed and used.
Among these resins, it is particularly preferable to contain a polyvinyl alcohol-based resin or a polyurethane-based resin. The polyvinyl alcohol-based resin is a resin that can be dissolved in an aqueous solvent to form a solution, and the polyurethane-based resin is a resin that can be dispersed in an aqueous solvent to form an emulsion.
However, although polyvinyl alcohol-based resins have high oxygen barrier properties and water vapor barrier properties in a low-humidity atmosphere, as the humidity increases, the oxygen barrier properties and water vapor barrier properties, in particular the water vapor barrier property, tend to be easily degraded, and the water vapor barrier property is particularly likely to be degraded in an atmosphere with a humidity of 70% or more.
For this reason, it is preferable that at least one of the gas barrier layers on both sides contains an inorganic filler, and it is more preferable that the gas barrier layers on both sides contain an inorganic filler.
When the barrier paper has a layer structure in which a fixed filling layer and a gas barrier layer are laminated adjacent to each other in this order on at least both sides of a paper base layer, the gas barrier layer can exhibit sufficient gas barrier properties even if it contains only a polyvinyl alcohol-based resin as the barrier resin, but it is preferable to use another barrier resin or an inorganic filler in the gas barrier layer on at least one side.

The polyvinyl alcohol resin is a (co)polymer having a repeating unit of --CH ₂ CH(OH)-- in the main skeleton, and can have various functional groups as required.
In particular, polyvinyl alcohol resins having a high degree of saponification and many hydroxyl groups in one molecule are preferred because they have a high cohesive energy density.

The polyurethane resin is a (co)polymer having a repeating unit of --NHCOO-- in the main skeleton, and may have various functional groups as required.
In particular, polyurethane resins having many hydroxyl groups are preferred because they have a high cohesive energy density.

(Inorganic filler contained in gas barrier layer)
The inorganic filler contained in the gas barrier layer can enhance the gas barrier properties of the gas barrier layer.
The type of inorganic filler contained in the gas barrier layer is not particularly limited, and examples thereof include alumina (aluminum oxide), titanium oxide, zirconia (zirconium oxide), ceria, lithium silicate, diamond, silicon nitride, silicon carbide, iron oxide, calcium carbonate, kaolin, chromium oxide, mica, silica (silicon oxide), and antimony oxide. These inorganic fillers may be used alone or in combination of two or more. Among these, mica, silica, alumina, and the like are preferred, and mica is particularly preferred.

There are no particular restrictions on the average particle size of the inorganic filler particles contained in the gas barrier layer, but to stably obtain a balance between excellent gas barrier properties, appropriate rigidity, and flexibility, the average particle size is preferably 0.1 μm or more and 20 μm or less, and more preferably 1 μm or more and 15 μm or less, depending on the coarseness of the paper base material. If the average particle size is smaller or larger than the above range, the balance is likely to decrease.

There are no particular limitations on the shape of the inorganic filler contained in the gas barrier layer, and a wide variety of shapes, such as spherical, elliptical, crushed, and scaly, can be used. One type of inorganic filler having these shapes may be used, or two or more types may be mixed and used. Among these, scaly ones are preferred.

The surface of the inorganic filler contained in the gas barrier layer may be organically modified. Organic modification improves affinity with the gas barrier resin and solvent, reduces aggregation, and facilitates uniform dispersion in the gas barrier resin composition or gas barrier layer.

The content of the inorganic filler in the gas barrier layer is preferably 5 parts by mass or more and 70 parts by mass or less, and more preferably 10 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the barrier resin. Within the above range, the gas barrier resin composition exhibits an appropriate viscosity for easy application, and the gas barrier layer can exhibit sufficient and stable oxygen barrier effect and water vapor barrier effect.

(Solvent for liquid gas barrier resin composition)
The main component of the solvent for the liquid gas barrier resin composition is water, and the solvent may further contain a water-soluble lower alcohol in order to adjust the solubility and dispersibility of the resin component.

<Adhesive layer>
The adhesive layer can be formed using a general-purpose adhesive that is known and in public use, and the adhesive layer may be formed after the anchor coat layer is formed in advance.
The anchor coating agent is not particularly limited, and any of the following anchor coating agents can be used: isocyanate-based (urethane-based), polyethyleneimine-based, polybutadiene-based, organotitanium-based, etc. anchor coating agents; or polyurethane-based, polyacrylic-based, polyester-based, epoxy-based, polyvinyl acetate-based, cellulose-based, and other laminating adhesives.

The adhesive layer may be, for example, a layer formed by a non-solvent lamination method (non-solvent lamination layer), a layer formed by coating (coating layer), a layer formed by extrusion resin (extrusion resin layer), a layer formed using a wet lamination adhesive (wet lamination layer), or a layer formed by dry lamination using a dry lamination adhesive (dry lamination layer).

The adhesive may be of any type, such as an organic solvent type, a water-based type, or a solventless type, but the amount of residual organic solvent in the adhesive layer is preferably small, and is preferably 6 mg/ ^m2 or less. The amount of residual organic solvent is most preferably 0 mg/ ^m2 , and is preferably substantially 6 mg/m2 or ^less .
Setting the amount of residual organic solvent in the adhesive layer within the above range is advantageous in that it prevents a decrease in adhesive strength due to the residual organic solvent, prevents distortion at the adhesive interface due to volume shrinkage during drying and the occurrence of minute peeling defects, and prevents deterioration of the gas barrier properties. It is also advantageous in that it prevents the emission of an organic solvent odor from the barrier paper of the present invention.
In order to reduce the amount of the residual organic solvent, it is advantageous and preferable to form the adhesive layer using a solventless or water-based adhesive.

However, if there is sufficient interlayer adhesion, the adhesive layer formed can be sufficiently usable even if the amount of residual organic solvent in the adhesive layer is more than 6 mg/ ^m2 , and depending on the conditions of use, the organic solvent odor can be solved by other means, so the above does not necessarily have to be met.
Here, when the barrier paper of the present invention does not include a configuration containing an organic solvent other than in the adhesive layer, the organic solvent content in the adhesive layer can be detected by measuring the organic solvent content of the entire barrier paper.
In the present invention, "solvent-free" means that no solvent is actively contained, and the adhesive may contain a trace amount of organic solvent derived from organic solvent remaining in the raw materials, within a range that allows the amount of residual organic solvent in the formed adhesive layer to be 6 mg/ ^m2 or less.

Examples of resins that can be used in the adhesive include two-component curing urethane adhesives, polyester polyurethane adhesives, polyether polyurethane adhesives, acrylic adhesives, polyester adhesives, polyamide adhesives, polyvinyl acetate adhesives, epoxy adhesives, rubber adhesives, polyolefin resins, and acid-modified polyolefin resins obtained by graft polymerization or copolymerization of polyolefin resins with unsaturated carboxylic acids or their anhydrides, such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, etc., polyvinyl acetate resins, poly(meth)acrylic resins, polyvinyl chloride resins, and other resins. These resins can be used alone or in combination.

The adhesive layer may contain additives such as antioxidants, ultraviolet absorbers, light stabilizers, antistatic agents, antiblocking agents, flame retardants, crosslinking agents, and colorants, provided the additives do not impair the properties of the present invention.
The thickness of the adhesive layer is not particularly limited, but is preferably 1 g/m2 or ^more and 20 g/m2 ^or less, more preferably 2 g/m2 or ^more and 10 g/m2 or ^less , or preferably 1 μm or more and 20 μm or less, more preferably 2 μm or more and 10 μm or less. If the thickness is thinner than the above numerical range, it is difficult to exhibit sufficiently high and stable adhesiveness, and even if the thickness is thicker than the above numerical range, the adhesiveness does not change much and the formation method is easily limited, which is not preferable.

The organic solvent contained in the organic solvent-based adhesive is preferably one that can dissolve the resin raw materials that make up the organic solvent-based adhesive, has a boiling point and volatility appropriate for the manufacturing process of the barrier paper of the present invention, and can reduce the organic solvent content of the formed adhesive layer to 6 mg/ ^m2 or less.
When a highly polar solvent is used, workability is likely to be poor. For example, when a highly soluble solvent such as acetone is used, the boiling point is low and water from the outside air is likely to be taken in, so that a problem may occur in that the viscosity of the crack-resistant adhesive is likely to increase due to a reaction between water and isocyanate.
The main component of the aqueous solvent contained in the aqueous adhesive is water, and the aqueous solvent may further contain a water-soluble lower alcohol in order to adjust the solubility and dispersibility of the resin component.

<Gas barrier paper laminate>
The gas barrier paper-based laminate of the present invention is produced using the environmentally friendly barrier paper of the present invention, and is an environmentally friendly laminate in which the amount of organic solvents used during production is reduced, and the gas barrier paper-based laminate has excellent oxygen barrier properties and water vapor barrier properties.

<Gas barrier paper-based materials>
The gas barrier paper material of the present invention is produced using the environmentally friendly gas barrier paper laminate of the present invention, and is an environmentally friendly paper material in which the amount of organic solvents used during production is reduced. The gas barrier paper material has excellent oxygen barrier properties and water vapor barrier properties, and can be used as a packaging material.
The layer structure of the gas barrier paper-based material may be the same as that of the gas barrier paper-based laminate, or may be a layer structure in which a sealant layer (heat seal layer) or a layer for protecting the gas barrier layer is further laminated as necessary.

The sealant layer may be laminated on the paper base layer or on the gas barrier layer, and may be provided on either one or both surfaces of the gas barrier paper material.
For example, by using a gas barrier paper-based laminate having a layer structure of paper base layer/fixed filling layer/gas barrier layer, gas barrier layer, paper base layer/fixed filling layer/gas barrier layer, sealant layer/paper base layer/fixed filling layer/gas barrier layer/sealant layer, sealant layer/paper base layer/fixed filling layer/gas barrier layer/sealant layer, etc. can be used.

The thickness of the sealant layer is preferably 5 to 500 μm, more preferably 10 to 250 μm, and even more preferably 15 to 100 μm. Alternatively, in the case of a heat seal layer formed by coating, the thickness is preferably 1 to 30 g/ ^m2 , and more preferably 5 to 20 g/ ^m2 . If the thickness is thinner than the above range, it is difficult to obtain sufficient heat sealability and heat seal strength, and if the thickness is thicker than the above range, costs will increase and the rigidity of the gas barrier paper-based material will become too strong, which is likely to deteriorate workability.

The oxygen barrier property and water vapor barrier property can be represented by the oxygen permeability and water vapor permeability measured by methods in accordance with JIS K7126 and K7129, respectively.
The gas barrier paper material before bending treatment preferably has an oxygen permeability of 0.01 cc/ ^m2 /day/atm or more and 20 cc/m2/day/atm or less, and more preferably 0.05 cc/ ^m2 / ^day /atm or more and 10 cc/ ^m2 /day/atm or less, at a temperature of 23°C and a humidity of 0%. It is difficult to produce a material with a permeability lower than the above range, and it is easy for the oxygen barrier property to be insufficient if the permeability is higher than the above range.

For example, after folding in half at 180 degrees and undergoing bending treatment, the oxygen permeability at a temperature of 23°C and a humidity of 0% is preferably 0.1 cc/ ^m2 /day/atm or more and 100 cc/ ^m2 /day/atm or less, and more preferably 0.5 cc/ ^m2 /day/atm or more and 50 cc/ ^m2 /day/atm or less. Those with a permeability lower than the above range are difficult to produce, and those with a permeability higher than the above range are likely to have insufficient oxygen barrier properties.

The gas barrier paper material before bending treatment preferably has a water vapor transmission rate of 0.01 g/m ² /day or more and 30 g/m ² /day or less at a temperature of 40° C. and a humidity of 90%.
It is more preferable that the coating density is 0.05 g/m ² /day or more and 20 g/m ² /day or less. Coatings lower than the above range are difficult to manufacture, while coatings higher than the above range tend to have insufficient water vapor barrier properties.

For example, after folding in half at 180 degrees and undergoing bending treatment, the water vapor permeability at a temperature of 40°C and a humidity of 90% is preferably 0.1 g/ ^m2 /day to 40 g/ ^m2 /day, and more preferably 0.5 g/ ^m2 /day to 30 g/ ^m2 /day. Those with a permeability lower than the above range are difficult to produce, and those with a permeability higher than the above range are likely to have insufficient water vapor barrier properties.

Specific examples of gas barrier paper-based materials include gas barrier paper-based packaging materials for packaging food, cosmetics, medicines, etc., gas barrier paper-based container materials for making containers such as cups and plates, and gas barrier paper-based lid materials.

[Sealant layer]
The sealant layer is a layer that imparts heat-sealing properties to the gas barrier paper-based material, and contains a heat-sealable resin that can melt and fuse when heated. In the present invention, when the sealant layer is formed by applying a heat-sealing agent, it is also referred to as a heat-sealing layer.
The sealant layer may be a single layer or a multi-layer structure of two or more layers. In the case of a multi-layer structure, the compositions of the layers may be the same or different, and the sealant layer may include a layer consisting of only a heat-sealable resin or a layer not containing a heat-sealable resin. Furthermore, the sealant layer may include a functional layer having various functions or an adhesive layer. However, it is preferable that the layer constituting the outermost layer on one side of the gas barrier paper-based material contains a heat-sealable resin.

Examples of heat-sealable resins include polyolefin resins, ionomer resins, polyethylene terephthalate (PET), polyacrylonitrile (PAN), and the like.
Examples of polyolefin resins include polyethylene resins, polypropylene resins, methylpentene polymers, ethylene-propylene copolymers, cyclic polyolefin resins, cyclic olefin copolymers, and unsaturated carboxylic acid modified polyolefin resins.
Specific examples of polyethylene resins include low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, metallocene polyethylene, and the like.
Specific examples of the unsaturated carboxylic acid modified polyolefin resin include ethylene-unsaturated carboxylic acid copolymers, ethylene-unsaturated carboxylic acid ester copolymers, etc. More specific examples include ethylene-(meth)acrylic acid copolymers, ethylene-(meth)acrylic acid ester copolymers, ethylene-vinyl acetate copolymers, ethylene-(meth)acrylic acid ester-unsaturated carboxylic acid terpolymer resins, etc. Specific examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, etc.
The heat-sealable resin may be one of these resins or a combination of two or more of them.

The sealant layer can be formed by applying a heat-sealable resin, melt (co)extrusion lamination, bonding a film or sheet made of a heat-sealable resin with heat or by bonding with an adhesive, etc. Alternatively, the heat-sealable layer can be formed by applying an emulsion prepared by dispersing a heat-sealable resin in an aqueous solvent, followed by drying.
As the above-mentioned film or sheet, any of unstretched film or sheet, and uniaxially or biaxially stretched film or sheet can be used.

<Gas barrier paper packaging>
The gas barrier paper packaging of the present invention is an environmentally friendly packaging produced using the environmentally friendly gas barrier paper material of the present invention, and also includes gas barrier paper containers, and has excellent oxygen barrier properties and water vapor barrier properties.
The gas barrier paper-based packaging material of the present invention has excellent oxygen barrier properties and water vapor barrier properties due to the synergistic effect of the fixed sealing layer and the gas barrier layer, and by having the fixed sealing layer and the gas barrier layer on both sides of the paper base layer, it exhibits better oxygen barrier properties and water vapor barrier properties than if they were present on only one side.
[0043] Examples of the gas barrier paper-based packaging body of the present invention include packaging forms such as lids, paper cups, pillow packaging bags, three-sided sealed bags, four-sided sealed bags, standing pouches, and gusset bags, which can be produced by a heat sealing process that heat-seals the sealant layer of the gas barrier paper-based material.

Normally, when a package is made from a packaging material, the packaging material is subjected to a bending load, and therefore the oxygen barrier property and water vapor barrier property of the packaging material after the package is formed are lower than those of the original packaging material, resulting in a lower oxygen barrier property and water vapor barrier property of the package. However, the gas barrier paper-based packaging material of the present invention maintains excellent oxygen barrier property and water vapor barrier property because the gas barrier paper-based material of the present invention has excellent oxygen barrier property and water vapor barrier property even after being subjected to a bending load.

The oxygen permeability of the gas barrier paper-based material constituting the gas barrier paper-based packaging body after bag formation at a temperature of 23°C and a humidity of 0% is preferably 0.01 cc/ ^m2 /day/atm or more and 100 cc/ ^m2 /day/atm or less, and more preferably 0.05 cc/ ^m2 /day/atm or more and 50 cc/ ^m2 /day/atm or less. It is difficult to produce a gas barrier paper-based packaging body with a lower oxygen permeability than the above range, and it is easy for the oxygen barrier property to be insufficient if the gas barrier paper-based material has a higher oxygen permeability than the above range.
In addition, depending on the sealing method of the gas barrier paper-based packaging material, it is possible to reduce the bending load and further reduce the oxygen permeability. For example, when a gas barrier paper-based packaging material is produced by sealing on all four sides, the oxygen permeability can be made 0.01 cc/ ^m2 /day/atm or more and 20 cc/ ^m2 /day/atm or less.

The water vapor permeability of the gas barrier paper-based material constituting the gas barrier paper-based packaging body after bag formation at a temperature of 40°C and a humidity of 90% is preferably 0.01 g/ ^m2 /day or more and 40 g/ ^m2 /day or less, and more preferably 0.05 g/ ^m2 /day or more and 30 g/ ^m2 /day or less. It is difficult to produce a gas barrier paper-based packaging body with a water vapor permeability lower than the above range, and it is easy for the water vapor barrier property to be insufficient if the water vapor permeability is higher than the above range.
In addition, depending on the sealing method of the gas barrier paper-based packaging material, it is possible to reduce the bending load and further reduce the water vapor permeability. For example, when a gas barrier paper-based packaging material is produced by sealing on all four sides, the water vapor permeability can be reduced to 0.01 g/ ^m2 /day or more and 20 g/ ^m2 /day or less.

Details of the raw materials used in the examples are as follows:

[Gas barrier resin composition]
Gas barrier resin composition 1: a urethane-based hybrid gas barrier resin composition prepared by mixing the following:
Urethane emulsion 1 (Mitsui Chemicals, Inc., WPB-341) 27 parts by weight Synthetic mica 1 (Topy Industries, Ltd., NTS-5 (NV6)) 67 parts by weight

Gas barrier resin composition 2: a polyvinyl alcohol-based gas barrier resin composition prepared by the following procedure.
The following raw materials were used, and the polyvinyl alcohol powder 1 was first added to warm water and homogenized, and then isopropyl alcohol was added and homogenized to prepare the mixture.
Warm water (95°C) 96 parts by weight Polyvinyl alcohol powder 1 (Kuraray Poval PVA124) 4 parts by weight Isopropyl alcohol 4 parts by weight

Gas barrier resin composition 3: a filler-containing polyvinyl alcohol-based gas barrier resin composition prepared by the following procedure.
The following raw materials were used. First, polyvinyl alcohol powder 1 was added to warm water and homogenized, and then synthetic mica 1 and isopropyl alcohol were added and homogenized to prepare the mixture.
Warm water (95°C) 96 parts by weight Polyvinyl alcohol powder 1 (Kuraray Poval PVA124) 4 parts by weight Synthetic mica 1 (NTS-5 (NV6) manufactured by Topy Industries) 20 parts by weight Isopropyl alcohol 4 parts by weight

[Fixing and sealing resin composition]
Fixed sealing resin composition 1: Acrylic resin water-based emulsion, AC-1, manufactured by Sakata Inx Corporation.
Fixed sealing resin composition 2: Polyurethane resin water-based emulsion, F-2235D, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

[Paper base material]
Paper base material 1: Ryuo Coat, manufactured by Daio Paper Corporation. With a coating layer on one side. Basis weight 55 g/m ² , thickness 49 μm. A (first) sealing coating agent was applied to the coated surface before use.
Paper base material 2: Grease-resistant paper S, manufactured by Daio Paper Co., Ltd. Basis weight: 40 g/m ² , thickness: 54 μm.
Paper base material 3: Bleached kraft paper (S) manufactured by Nippon Paper Industries Co., Ltd. Basis weight 50 g/m ² , thickness 60 μm.

[Heat sealant]
Heat sealant 1: MP4983R, a heat sealant manufactured by Michelman Co. Aqueous solvent dispersion of a polyethylene resin.

Example A: Barrier paper [Example A-1]
A fixed filling resin composition 2 was applied to both sides of a paper base material 1 using a bar coater and then dried at 100°C (coating amount after drying: 3.6 g/ ^m2 ) to form first and second fixed filling layers, and a gas barrier resin composition 1 was applied to both sides using a bar coater and then dried at 100°C (coating amount after drying: 2.5 g/ ^m2 ) to form first and second gas barrier layers, thereby obtaining a barrier paper with the following layer structure. Various evaluations were then performed.
Layer structure: first gas barrier layer/first fixed filling layer/paper base layer/second fixed filling layer/first gas barrier layer=gas barrier resin composition 2 (2.5 g/ ^m2 )/fixed filling resin composition 1 (3.6 g/ ^m2 )/paper base 1 (49 m thick)/fixed filling resin composition 1 (3.6 g/ ^m2 )/gas barrier resin composition 2 (2.5 g/ ^m2 )

[Examples A-2 to A-6]
Barrier paper was produced in the same manner as in Example A-1 using the combinations of paper base material, fixing filling resin composition, and gas barrier resin composition shown in Table 1, and was evaluated in the same manner.

[Comparative Examples A-1 to A-3]
Using the combinations of paper substrates, fixed filling resin compositions, and gas barrier resin compositions shown in Table 1, paper laminates were obtained in the same manner as in Example A-1, and were similarly evaluated.

Example B: Gas barrier paper-based material and gas barrier paper-based packaging body [Example B-1]
Heat seal agent 1 was applied using a bar coater to the second gas barrier layer side surface of the barrier paper prepared in Example A-1, and then dried at 100°C (coating amount after drying: 10 g/ ^m2 ) to form a heat seal layer, thereby producing a gas barrier paper material with the layer structure described below.
Two sheets of the obtained gas barrier paper material were then stacked with the heat seal layers facing each other, and the four sides were heat sealed to produce a gas barrier paper packaging body in the form of a four-sided sealed bag (internal size 15 cm x 15 cm).
The gas barrier properties of the gas barrier paper material before the gas barrier paper packaging body was produced and the gas barrier properties of the gas barrier paper material after the bag that constitutes the gas barrier paper packaging body was made were measured.
Layer structure: first gas barrier layer/first fixed filling layer/paper base layer/second fixed filling layer/second gas barrier layer=gas barrier resin composition 1 (2.5 g/ ^m2 )/fixed filling resin composition 1 (2 g/ ^m2 )/paper base layer 1 (49 m thick)/fixed filling resin composition 1 (2 g/ ^m2 )/gas barrier resin composition 1 (2.5 g/ ^m2 )/heat seal layer (10 g/ ^m2 )

[Examples B-2 to B-6]
Using the barrier papers produced in each of Examples A-2 to A-6, gas barrier paper materials and gas barrier paper packages were produced in the same manner as in Example B-1, and were similarly evaluated.

[Comparative Examples B-1 to 3]
Using the barrier papers prepared in each of Comparative Examples A-1 to A-3, gas barrier paper-based materials were prepared in the same manner as in Example B-1, and were similarly evaluated.

<Evaluation method>
[Oxygen permeability]
The oxygen transmission rate was measured at a temperature of 23° C. and a humidity of 0% in accordance with JIS K7126 using an oxygen transmission rate measuring device (MOCON manufactured by Hitachi High-Technologies Corporation). The measurement limit of the device is 200 cc/m ² /day/atm.
The oxygen permeability of the test piece was measured in the direction from the first gas barrier layer to the second gas barrier layer.
The bending treatment was performed by folding the barrier paper in half (mountain fold) at 180 degrees once so that the paper layer was on the outside, and then returning it to its original state.

[Water vapor permeability]
The water vapor transmission rate was measured at a temperature of 40° C. and a humidity of 90% in accordance with JIS K7129 using a Mocon water vapor transmission rate measuring device (MOCON manufactured by Hitachi High-Technologies Corporation). The measurement limit of the device is 50 g/m ² /day.
The oxygen permeability of the test piece was measured in the direction from the first gas barrier layer to the second gas barrier layer.
The bending treatment was performed by folding the barrier paper in half (mountain fold) at 180 degrees once so that the paper layer was on the outside, and then returning it to its original state.

[Interlayer adhesion]
The presence or absence of peeling between any of the layers of the barrier paper was detected by the following procedure.
The gas barrier layers and the fixed filling layers on both sides were similarly evaluated.
1) Cellophane tape (width 15 mm × length 50 mm) was attached to the gas barrier layer of the barrier paper with a load of 1,000 g, leaving 10 mm on one end.
2) The above cellophane tape was gripped at a 10 mm portion of one end that was not pressed, and peeled off at a speed of 100 mm/min using a Tensilon measuring device. The peeling state of the barrier paper was visually observed and classified as follows.
Class A: No delamination occurred at all.
Class B: Only cohesive peeling occurs within the paper base layer. There is no problem with the adhesion between the gas barrier layer and the fixed filling layer.
Class C: Peeling occurs between the fixed filling layer and the paper base layer, or cohesive peeling occurs within the fixed filling layer, and the adhesion or breaking strength of the fixed filling layer is insufficient.
Category D: Peeling occurred between the gas barrier layer and the fixed filling layer, or cohesive peeling occurred within the gas barrier layer, and the adhesion or fracture strength of the gas barrier layer was insufficient.

<Summary of results>
The double-sided barrier paper of the invention in all Examples A showed good oxygen barrier properties, water vapor barrier properties and interlayer adhesion before and after bending.
Furthermore, the gas barrier paper materials of all Examples B, which were produced by forming a sealant layer (heat seal layer) on the barrier papers of all Examples A with a double-sided configuration, exhibited good oxygen barrier property, water vapor barrier property and interlayer adhesion before and after bag formation for the gas barrier paper-based packaging material.
On the other hand, the laminates of Comparative Examples A-1 to A-3, in which neither the first nor the second gas barrier layer contained an inorganic filler, showed poor water vapor barrier properties both before and after bending.
Furthermore, the paper-based materials of Comparative Examples B-1 to B-3, which were prepared by forming a sealant layer (heat seal layer) on the laminate of Comparative Example A, showed poor water vapor barrier properties both before and after bag formation for the packaging body.

1 Barrier paper, gas barrier paper laminate 2 Gas barrier layer 2a First gas barrier layer 2b Second gas barrier layer 3 Fixed filling layer 3a First fixed filling layer 3b Second fixed filling layer 4 Paper base layer 5 Gas barrier paper material 6 Sealant layer (heat seal layer)

Claims (11)

At least the laminate has a layer structure in which a fixed filling layer in contact with the paper base layer and a gas barrier layer in contact with the fixed filling layer are laminated on both sides of the paper base layer,
The fixing sealing layer contains a styrene-acrylic acid copolymer ,
The thickness or coating amount of the fixed filling layer is 0.2 μm or more and 25 μm or less, and the coating amount is 0.5 g/m2 ^or more and 30 g/m2 ^or less,
The thickness or coating amount of the gas barrier layer is 0.1 μm or more and 10 μm or less, and the coating amount is 0.3 g/m2 ^or more and 10 g/m2 or ^less ,
The fixed sealing layers on both sides have the same or different compositions,
the gas barrier layer contains a polyurethane resin and/or a polyvinyl alcohol resin,
The gas barrier layers on both sides have the same or different compositions;
13. A barrier paper, wherein the gas barrier layer on at least one side further contains an inorganic filler. The barrier paper according to claim 1, characterized in that the fixed sealing layer on at least one side further contains an inorganic filler. 3. The barrier paper according to claim 1, wherein the fixed sealing layer on at least one side further contains a polyurethane resin. The barrier paper according to any one of claims 1 to 3, characterized in that the gas barrier layers on both sides further contain an inorganic filler. 5. The barrier paper according to claim 1, wherein the oxygen transmission rate at a temperature of 23° C. and a humidity of 0% in accordance with JIS K7126 is 0.01 cc/m ² /day/atm or more and 20 cc/m ² /day/atm or less. 6. The barrier paper according to claim 1, wherein the water vapor transmission rate according to JIS K7129 at a temperature of 40° C. and a humidity of 90% is 0.01 g/m ² /day or more and 30 g/m ² /day or less. 7. The barrier paper according to claim 1, wherein the barrier paper has an oxygen permeability of 0.1 cc/ ^m2 /day/atm or more and 100 cc/ ^m2 /day/atm or less at a temperature of 23°C and a humidity of 0%, in accordance with JIS K7126, after bending treatment in which the paper is folded in half at 180 degrees and then stretched. 8. The barrier paper according to claim 1, wherein the barrier paper has a water vapor transmission rate of from 0.1 g/ ^m2 /day to 40 g/ ^m2 /day at a temperature of 40°C and a humidity of 90%, in accordance with JIS K7129, after bending treatment in which the paper is folded in half at 180 degrees and then stretched. A gas barrier paper laminate having oxygen barrier properties and water vapor barrier properties, produced using the barrier paper described in any one of claims 1 to 8. A gas barrier paper-based material having oxygen barrier properties and water vapor barrier properties, produced using the gas barrier paper-based laminate described in claim 9. A gas barrier paper-based packaging body having oxygen barrier properties and water vapor barrier properties, produced using the gas barrier paper-based material according to claim 10.

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