Barrier paper, industrial materials and packaging materials

Abstract

The present invention provides a barrier paper that can suppress the decrease in barrier properties when folded, and also has good heat seal strength, suitability for bag making, and blocking suppression properties. [Solution] A barrier paper according to one aspect of the present invention comprises a base material, a gas barrier layer laminated on one or both sides of the base material, and a water vapor barrier layer laminated on the surface of the gas barrier layer, wherein the gas barrier layer mainly consists of polyvinyl alcohol, the water vapor barrier layer contains a wax resin and a styrene-acrylic copolymer as its main component, the amount of wax resin in the water vapor barrier layer is 3 parts by mass or more and 11 parts by mass or less per 100 parts by mass of styrene-acrylic copolymer, the gas barrier layer contains an inorganic compound in an amount of 15 parts by mass or less per 100 parts by mass of polyvinyl alcohol, or does not contain an inorganic compound, and the water vapor barrier layer does not contain an inorganic compound.

Description

[Technical Field]

[0001] This invention relates to barrier paper, industrial materials, and packaging materials. [Background technology]

[0002] In packaging for food, agriculture, and other industrial sectors, packaging materials with paper as the base material and provided with water vapor barrier and gas barrier properties have traditionally been used to prevent deterioration of the quality of the contents.

[0003] As a packaging material having such water vapor barrier and gas barrier properties, a paper barrier packaging material has been proposed in which a water vapor barrier layer and a gas barrier layer are provided on a base material (see Patent Document 1). In the above conventional paper barrier packaging material, the water vapor barrier layer contains 50% to 100% by mass of kaolin with an average particle size of 5 μm or more and an aspect ratio of 10 or more relative to the total pigment, and the gas barrier layer contains polyvinyl alcohol as a binder resin. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2013 / 069788 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, in the conventional paper barrier packaging materials described above, when folded, the barrier layer at the folded portion is subjected to compressive force, which can easily damage the barrier layer and reduce its barrier properties. On the other hand, such paper barrier packaging materials are generally heat-sealed on the surface of the barrier layer during the bag-making process, and it is necessary to ensure sufficient heat-seal strength. Furthermore, the bag-making process can lead to a decrease in the quality of the packaging material due to meandering of the barrier paper, misalignment of the heat-sealed and cut portions, etc., so there is a need to improve the suitability for bag-making processes to minimize these issues. In addition, in paper barrier packaging materials, if the heat-sealed portion of the barrier layer blocks, the peelability decreases, so there is also a need to improve blocking suppression.

[0006] The present invention was made based on the above circumstances, and aims to provide a barrier paper that can suppress the decrease in barrier properties when folded, and has good heat seal strength, suitability for bag making, and blocking suppression properties. [Means for solving the problem]

[0007] A barrier paper according to one aspect of the present invention comprises a base material, a gas barrier layer laminated on one or both sides of the base material, and a water vapor barrier layer laminated on the surface of the gas barrier layer, wherein the gas barrier layer mainly consists of polyvinyl alcohol, the water vapor barrier layer contains a wax resin and a styrene-acrylic copolymer as the main component, the amount of wax resin in the water vapor barrier layer is 3 parts by mass or more and 11 parts by mass or less per 100 parts by mass of styrene-acrylic copolymer, the gas barrier layer contains an inorganic compound in an amount of 15 parts by mass or less per 100 parts by mass of polyvinyl alcohol, or does not contain an inorganic compound, and the water vapor barrier layer does not contain an inorganic compound. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a barrier paper that can suppress the decrease in barrier properties when folded, and that has good heat seal strength, suitability for bag making, and blocking suppression properties. [Modes for carrying out the invention]

[0009] [Description of Embodiments of the Invention] A barrier paper according to one aspect of the present invention comprises a base material, a gas barrier layer laminated on one or both sides of the base material, and a water vapor barrier layer laminated on the surface of the gas barrier layer, wherein the gas barrier layer mainly consists of polyvinyl alcohol, the water vapor barrier layer contains a wax resin and a styrene-acrylic copolymer as the main component, the amount of wax resin in the water vapor barrier layer is 3 parts by mass or more and 11 parts by mass or less per 100 parts by mass of styrene-acrylic copolymer, the gas barrier layer contains an inorganic compound in an amount of 15 parts by mass or less per 100 parts by mass of polyvinyl alcohol, or does not contain an inorganic compound, and the water vapor barrier layer does not contain an inorganic compound.

[0010] The barrier paper has good gas barrier properties due to the inclusion of a gas barrier layer mainly composed of polyvinyl alcohol. The gas barrier layer contains an inorganic compound in an amount of 15 parts by mass or less per 100 parts by mass of polyvinyl alcohol, or it does not contain an inorganic compound, which improves the coating properties when laminating a water vapor barrier layer onto the surface of the gas barrier layer. Therefore, when the paper is folded, the reduction in barrier properties is effectively suppressed. Furthermore, the water vapor barrier layer contains a wax resin and a styrene-acrylic copolymer as its main component, which improves the water vapor barrier properties of the barrier paper, as well as its heat seal strength, suitability for bag making, and blocking suppression. The wax resin content in the water vapor barrier layer is 3 parts by mass or more and 11 parts by mass or less per 100 parts by mass of styrene-acrylic copolymer, which improves bag making suitability and heat seal strength. Furthermore, because the water vapor barrier layer does not contain inorganic compounds, damage to the water vapor barrier layer when the barrier paper is folded can be reduced without causing a decrease in flexibility, thus further suppressing the decrease in barrier properties when folded. Therefore, the barrier paper can suppress the decrease in barrier properties when folded, and can also improve heat seal strength, suitability for bag making, and blocking suppression. The "main component" above refers to the component with the highest content, preferably with a content of 70% by mass or more.

[0011] It is preferable that the oil absorption rate on the coated surface of the above substrate is 90 seconds or less. Having an oil absorption rate of 90 seconds or less on the coated surface of the above substrate allows for further improvement of ink drying performance during printing on the non-layered surface of the barrier layer. "Oil absorption rate" refers to the value measured using No. 2 light oil (10 μl) in accordance with JIS-P8130 (1994).

[0012] It is preferable that the gas barrier layer does not contain the inorganic compound. The absence of the inorganic compound in the gas barrier layer makes it less likely for damage to occur when the barrier paper is folded, thus further improving the water vapor barrier performance.

[0013] An industrial material or packaging material according to an aspect of the present invention includes the barrier paper. By including the barrier paper, the industrial material or packaging material has excellent gas barrier properties and water vapor barrier properties, can suppress a decrease in barrier properties when bent, and can obtain an industrial material or packaging material that can improve heat seal strength, bag-making process suitability, and blocking suppression properties.

[0014] [Details of Embodiments of the Present Invention] Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be based on typical embodiments or specific examples, but the present invention is not limited to such embodiments.

[0015] <Barrier Paper> The barrier paper includes a base material, a gas barrier layer laminated on one or both sides of the base material, and a water vapor barrier layer laminated on the surface of the gas barrier layer.

[0016] [Base Material] As the base material, a paper base material formed by papermaking raw pulp, glassine paper processed with a material that imparts transparency, cellophane paper or parchment paper obtained from pulp raw materials, semi-transparent paper such as paraffin paper impregnated with waxes, etc. can be used. For applications where paper quality and strength are required, a paper base material formed by papermaking raw pulp is preferably used. For applications where transparency is required, semi-transparent paper such as glassine paper, cellophane paper, parchment paper, paraffin paper, etc. is preferably used.

[0017] Examples of the material that imparts the above transparency include transparent resins such as acrylic resin, polyethylene resin, polyester resin, urethane resin, nitrocellulose, shellac, rosin, vegetable oils such as tung oil, linseed oil, castor oil, hydrophilic castor oil, coconut oil, soybean oil, commercially available salad oil, and waxes such as carnauba wax, palm wax, beeswax, whale wax, and wood wax.

[0018] The above-mentioned base material is obtained by papermaking a slurry containing raw pulp. The base material may be single-layer or multi-layer. Known base materials include fine paper, medium-grade paper, coated paper, one-sided glossy paper, kraft paper, one-sided glossy kraft paper, bleached kraft paper, glassine paper, cardboard, white cardboard, and liner. Among these, one-sided glossy paper, which has one side glossy by drying using a Yankee dryer, may be used as the base material from the viewpoint of dimensional stability, and fine paper, which is made of 100% chemical pulp and is uncoated, may be used from the viewpoint of strength and printability.

[0019] (Raw pulp) As raw material pulp for the base material, for example, virgin pulp, recycled paper pulp, or combinations of these pulps can be used.

[0020] As virgin pulp, chemical pulps such as bleached hardwood kraft pulp (LBKP), bleached softwood kraft pulp (NBKP), semi-bleached hardwood kraft pulp (LSBKP), semi-bleached softwood kraft pulp (NSBKP), unbleached softwood kraft pulp (NKP or NUKP), hardwood sulfite pulp, and softwood sulfite pulp; and mechanical pulps (MP) such as stone ground pulp (SGP), pressurized stone ground pulp (TGP), chemigland pulp (CGP), crushed wood pulp (GP), and thermomechanical pulp (TMP) can be used individually or in combination. From the viewpoint of the appearance of the printed surface and its use in food packaging, it is preferable to use only bleached kraft pulp.

[0021] As recycled paper pulp, for example, disintegrated recycled paper pulp, disintegrated and deinked recycled paper pulp (DIP), disintegrated, deinked and bleached recycled paper pulp, etc., manufactured from brown recycled paper, kraft envelope recycled paper, magazine recycled paper, newspaper recycled paper, flyer recycled paper, office recycled paper, corrugated cardboard recycled paper, white recycled paper recycled paper, Kent recycled paper recycled paper, imitation recycled paper recycled paper, land destiny recycled paper recycled paper, etc., can be used individually or in combination of multiple types.

[0022] The lower limit of the freeness of the raw pulp is preferably 400 ml, and more preferably 410 ml. A freeness of 400 ml or more reduces the voids in the paper layer, allowing the oil absorption of the substrate to be within a good range. On the other hand, the upper limit of the freeness of the raw pulp is preferably 600 ml, and more preferably 580 ml. A freeness of 600 ml or less reduces unevenness in the formation, allowing the oil absorption of the substrate to be within a good range. By setting the freeness of the raw pulp within the above ranges, the oil absorption of the substrate is adjusted to a good range, and the amount of coating liquid of the gas barrier layer that penetrates into the substrate can be suppressed. As a result, a uniform water vapor barrier layer is formed on the surface of the gas barrier layer, further improving the water vapor barrier performance. The above freeness is a value obtained by disintegrating pulp in accordance with the pulp disintegration method of JIS-P8220-1 (2012), and then measuring this disintegrated pulp in accordance with the Canadian standard filtration rate test method of JIS-P8121-2 (2012).

[0023] (Other additives) Other additives may be added to the base material as needed. Examples of additives include fillers, pigments, sizing agents, coagulants, oil resistant agents, fluorescent whitening agents, aluminum sulfate, yield enhancers, water drainage enhancers, dry strength enhancers, wet strength enhancers, coloring dyes, coloring pigments, water-resistant agents, etc., which can be used individually or in combination.

[0024] (Average thickness of the base material) The average thickness of the substrate is preferably between 30 μm and 150 μm. Maintaining an average thickness within this range allows for low basis weight and weight reduction while maintaining strength. The "average thickness" is measured in accordance with JIS-P8118:2014.

[0025] (Basis weight of the base material) Basis weight (g / m 2 The basis weight shall be measured in accordance with JIS-P-8124:2011 "Paper and cardboard - Method for measuring basis weight". The lower limit of the basis weight of the base material shall be 30.0 g / m². 2 Preferably, 35.0 g / m 2 More preferably, 40.0 g / m 2is more preferable. When the basis weight of the base material is 30.0 g / m 2 or more, it is possible to suppress the decrease in barrier properties due to the generation of pinholes during papermaking. On the other hand, as the upper limit of the basis weight of the base material, 80.0 g / m 2 is preferable, 75.0 g / m 2 is more preferable, and 70.0 g / m 2 is even more preferable. When the basis weight of the base material is 80.0 g / m 2 or less, it is possible to reduce the load on the barrier layer when the base material is bent due to its increased thickness.

[0026] (Oil absorption of the coated surface of the base material) As the lower limit of the oil absorption of the coated surface of the above base material, 25 seconds is preferable, and 30 seconds is more preferable. When the oil absorption of the coated surface of the above base material is 25 seconds or more, excessive penetration of the barrier layer coating liquid can be suppressed. On the other hand, the upper limit of the oil absorption of the coated surface of the base material is not particularly limited, and it may be, for example, 1200 seconds, 300 seconds is preferable, 120 seconds is more preferable, 100 seconds is even more preferable, and 90 seconds is particularly preferable. When the oil absorption of the coated surface of the base material is 300 seconds or less, the drying property of the ink during printing on the non-laminated surface of the barrier layer can be improved. Also, when the oil absorption of the coated surface of the base material is 300 seconds or less, the permeability of the coating liquid to the base material is in a good range, so the heat seal strength can be further improved. The above oil absorption can be adjusted by the freeness of the raw material pulp in the base material, the Bekk smoothness, the content of the sizing agent and the paper strength enhancer contained, etc.

[0027] (Bekk smoothness of the coated surface of the base material) The lower limit of the Beck smoothness of the surface on which the gas barrier layer of the above-mentioned substrate is provided is preferably 50 seconds, and more preferably 60 seconds. When the Beck smoothness of the coated surface of the above-mentioned substrate is 50 seconds or more, the flatness of the surface of the barrier paper is improved, the contact area is increased, and the heat seal strength can be maintained well. On the other hand, the upper limit of the Beck smoothness is preferably 450 seconds, more preferably 400 seconds, and more preferably 350 seconds. When the Beck smoothness of the coated surface of the above-mentioned substrate is 450 seconds or less, pinholes are less likely to occur in the gas barrier layer, and the properties of the water vapor barrier layer above it are improved, so the heat seal strength can be maintained well. The Beck smoothness is a value in accordance with the "Paper and cardboard - Smoothness test method using a Beck smoothness tester" described in JIS-P8119 (1998). The above-mentioned Beck smoothness is evaluated from the amount of air flow (air leak). The Beck smoothness measurement described above involves sandwiching the sheet being measured between an optically flattened glass sample stage and a rubber clamping plate under a pressure of 100 kPa, with 10 ml of air in a relatively wide 10 cm space. 2 Beck smoothness is expressed as the time required for a substance to pass between a glass standard surface and into a container held under reduced pressure at approximately 370 ml of mercury column, and indicates the so-called smoothness of the surface of the object being measured. Beck smoothness evaluates macroscopic smoothness over a relatively large surface. In the case of this barrier paper, the waviness of the surface of the substrate can be evaluated by Beck smoothness. Therefore, the surface of the substrate can be evaluated more appropriately using Beck smoothness.

[0028] [Gas barrier layer] The barrier paper comprises a gas barrier layer laminated on one or both sides of the substrate. That is, the water vapor barrier layer is laminated on the surface of the gas barrier layer. By comprising the gas barrier layer, the barrier paper can achieve good gas barrier properties. The gas barrier layer mainly consists of polyvinyl alcohol.

[0029] (Polyvinyl alcohol) The above-mentioned gas barrier layer, by primarily being composed of polyvinyl alcohol, can form a film that adheres closely to the substrate while simultaneously providing good gas barrier properties. As the polyvinyl alcohol, for example, unmodified polyvinyl alcohol in which the OH groups are not substituted, ethylene-modified polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, phosphate-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, etc., can be used. Among these, ethylene-modified polyvinyl alcohol is preferred from the viewpoint of good film strength and odor suppression.

[0030] The degree of ethylene modification of ethylene-modified polyvinyl alcohol is expressed as the molar percentage of ethylene units relative to the total monomer units (ethylene units + vinyl alcohol units). However, vinyl alcohol units also include unsaponified vinyl acetate units. The degree of ethylene modification is preferably between 2 mol% and 12 mol%.

[0031] From the viewpoint of film-forming properties and coating properties, the average degree of polymerization of polyvinyl alcohol is preferably 800 to 1500.

[0032] The lower limit of the polyvinyl alcohol content in the gas barrier layer described above is preferably 70% by mass, more preferably 80% by mass, and even more preferably 85% by mass. A polyvinyl alcohol content of 70% by mass further improves the gas barrier properties of the gas barrier layer.

[0033] (Inorganic compound) The above-mentioned gas barrier layer may contain inorganic compounds to balance the penetration and suppression of the gas barrier coating liquid. Examples of inorganic compounds include kaolin such as fine kaolin, primary kaolin, secondary kaolin, and delaminated kaolin, as well as layered compounds (flat compounds) such as bentonite, mica, and talc. Among these, kaolin is preferred from the viewpoint of achieving both barrier performance and coating properties.

[0034] The lower limit of the aspect ratio of the inorganic compound is preferably 15, and more preferably 18. If the aspect ratio of the inorganic compound is less than 15, the gas barrier properties may not be sufficient. On the other hand, the upper limit of the aspect ratio of the inorganic compound is preferably 120, and more preferably 100. By having an aspect ratio of 120 or less of the inorganic compound, the coating liquid of the gas barrier layer can be applied uniformly, and penetration into the substrate is also suppressed, so that high gas barrier properties can be achieved with a low coating amount. Here, "aspect ratio" refers to the shape of inorganic particles, specifically the ratio of their major axis (longest diameter) to their thickness (shortest diameter). The above aspect ratio can be obtained, for example, by particle image analysis using a laser diffraction / scattering particle distribution analyzer (Horiba LA 950, manufactured by Horiba, Ltd.) or by photographing powder particles with an electron microscope, randomly selecting 500 particles, and calculating the average value by dividing the diameter by the thickness.

[0035] The lower limit of the average particle diameter of the above inorganic compound is preferably 0.1 μm, and more preferably 0.5 μm. On the other hand, the upper limit of the average particle diameter of the above inorganic compound is preferably 10.0 μm, and more preferably 5.0 μm. By having the average particle diameter of the above inorganic compound within the above range, surface irregularities of the gas barrier layer are reduced, improving the coatability of the coating liquid for the water vapor barrier layer and improving the properties of the water vapor barrier layer. The above average particle diameter is the median diameter (D), which is the 50% volume particle diameter of the particle size distribution curve measured by laser diffraction scattering. 50 )

[0036] The above gas barrier layer contains an inorganic compound in an amount of 15 parts by mass or less per 100 parts by mass of polyvinyl alcohol, or does not contain an inorganic compound. The gas barrier layer contains an inorganic compound in an amount of 15 parts by mass or less per 100 parts by mass of polyvinyl alcohol, or does not contain an inorganic compound. This improves the coating properties when laminating a water vapor barrier layer onto the surface of the above gas barrier layer, thereby improving the properties of the water vapor barrier layer. Furthermore, when the barrier paper is folded, it effectively suppresses the deterioration of barrier properties. It is preferable that the gas barrier layer does not contain an inorganic compound. By the gas barrier layer not containing an inorganic compound, damage to the barrier layer when the barrier paper is folded becomes less likely.

[0037] In addition to polyvinyl alcohol and inorganic compounds, the above-mentioned gas barrier layer may appropriately incorporate conventional additives as needed, such as thickeners, fluidity improvers, defoamers, antifoaming agents, lubricants, release agents, foaming agents, penetrating agents, coloring dyes, coloring pigments, fluorescent whitening agents, ultraviolet absorbers, antioxidants, preservatives, fungicides, water-resistant agents, dyes, and fixing agents.

[0038] The lower limit for the amount of gas barrier layer coating is 5 g / m². 2 Preferably, 6 g / m 2 This is more preferable. On the other hand, the upper limit for the above coating amount (in terms of solid content) is 10 g / m 2 Preferably, 8 g / m 2 This is more preferable. The amount of gas barrier layer coating is 5 g / m². 2 As a result, the gas barrier layer can be uniformly coated onto the surface of the substrate. On the other hand, the coating amount of the gas barrier layer is 10 g / m². 2 The following conditions allow for good drying properties of the coating liquid in the gas barrier layer.

[0039] [Water vapor barrier layer] The water vapor barrier layer is laminated on the surface of the gas barrier layer. The water vapor barrier layer contains a wax resin and a styrene-acrylic copolymer as its main component. By including a wax resin together with the styrene-acrylic copolymer in the water vapor barrier layer, the barrier paper can have good water vapor barrier properties, as well as improved heat seal strength, suitability for bag making, and blocking suppression.

[0040] The styrene-acrylic copolymer is not particularly limited as long as it is obtained by copolymerizing various styrene monomers with various (meth)acrylic monomers.

[0041] The lower limit of the content of the styrene-acrylic copolymer in the above-mentioned water vapor barrier layer is preferably 87% by mass and more preferably 89% by mass on a solid content basis. The upper limit of the content of the styrene-acrylic copolymer is preferably 99% by mass and more preferably 95% by mass on a solid content basis. By having the content of the styrene-acrylic copolymer within the above range, the water vapor barrier properties of the water vapor barrier layer can be further improved.

[0042] The wax resin is not particularly limited, and can be paraffinic wax resins mainly composed of alkane compounds, natural oil-based wax resins derived from plants and animals such as carnauba and lanolin, silicone-based wax resins containing silicone or silicone compounds, or fluorine-containing wax resins containing fluorine compounds. The wax resin can be used individually or in mixtures of two or more types.

[0043] The lower limit of the wax resin content is 3 parts by mass, preferably 4 parts by mass, and more preferably 5 parts by mass, per 100 parts by mass of styrene-acrylic copolymer. If the wax resin content is less than 3 parts by mass, the blocking suppression effect tends to decrease. The upper limit of the wax resin content is 11 parts by mass, preferably 9 parts by mass, and more preferably 8 parts by mass, per 100 parts by mass of styrene-acrylic copolymer. If the wax resin content exceeds 11 parts by mass, the surface of the substrate may become slippery after the water vapor barrier coating liquid is applied to the substrate, which may reduce the suitability for bag making. In addition, if the wax resin content exceeds 11 parts by mass, the heat seal strength may decrease.

[0044] The above-mentioned water vapor barrier layer does not contain inorganic compounds. Because the above-mentioned water vapor barrier layer does not contain inorganic compounds, damage to the water vapor barrier layer during bending of the barrier paper is eliminated, thereby further suppressing the decrease in barrier performance when the paper is folded. The above-mentioned inorganic compounds refer to those similar to those exemplified in the gas barrier layer.

[0045] In addition to the styrene-acrylic copolymer and wax resin, the above-mentioned water vapor barrier layer may contain, as needed, conventional additives such as thickeners, fluidity improvers, defoamers, antifoaming agents, lubricants, release agents, foaming agents, penetrating agents, coloring dyes, coloring pigments, fluorescent whitening agents, ultraviolet absorbers, antioxidants, preservatives, fungicides, water-resistant agents, dyes, and fixing agents.

[0046] The lower limit for the amount of water vapor barrier layer coating is 2.0 g / m². 2 Preferably, 3.0 g / m 2 This is more preferable. On the other hand, the upper limit of the above coating amount is 10.0 g / m² from the viewpoint of improving sealing properties. 2 Preferably, 9.0 g / m 2 This is more preferable. If the amount of water vapor barrier layer coating is less than the above lower limit, the water vapor barrier properties may decrease. On the other hand, if the amount of water vapor barrier layer coating exceeds the above upper limit, blocking may occur during product winding, making it unusable as packaging material.

[0047] When a gas barrier layer and a water vapor barrier layer are laminated on both sides of the above-mentioned substrate, the composition of the gas barrier layer and the water vapor barrier layer, the amount of coating, etc., can be configured as described above.

[0048] When a gas barrier layer and a water vapor barrier layer are laminated on one side of the above-mentioned substrate, a print-enhancing coating layer, such as a pigment layer, can be provided on the non-laminated side (back side) of the substrate for the purpose of improving printability for gravure printing machines, digital printing machines, inkjet printing, laser printing, etc. As the print-enhancing coating layer, conventionally known materials in the fields of coated paper for printing, inkjet paper, and laser printer paper can be used.

[0049] [Physical properties of barrier paper] (Basis weight of barrier paper) The basis weight of the barrier paper is 37.0 g / m². 2 More than 100.0g / m 2 The following is preferable: The basis weight of the barrier paper is within the above range, which allows for weight reduction while maintaining strength.

[0050] (Average thickness of barrier paper) The lower limit of the average thickness of the barrier paper is preferably 40 μm, and more preferably 45 μm. The upper limit of the average thickness is preferably 150 μm, and more preferably 100 μm. By having the average thickness of the barrier paper within the above range, it is possible to improve processability while enabling low basis weight and weight reduction.

[0051] (Oxygen permeability and moisture permeability of the flat surface of barrier paper) The oxygen permeability of the flat surface of the barrier paper is 15 g / m². 2 • Preferably 24 hours or less, 10 g / m² 2 • 24 hours or less is more preferable. The moisture permeability of the flat surface of the barrier paper is 30 g / m². 2 • Preferably 24 hours or less, 20 g / m² 2 • 24 hours or less is even more preferable. The barrier paper has good barrier properties when the oxygen permeability and moisture permeability of the surface of the barrier paper are within the above range.

[0052] [Manufacturing method for barrier paper] The method for manufacturing the barrier paper is not particularly limited and may include steps such as: producing a base material by papermaking a raw pulp slurry and subjecting it to a press part and a dryer part; applying a gas barrier layer coating liquid to the surface of the base material in an undercoater part, followed by a drying treatment to laminate the gas barrier layer; and applying a water vapor barrier layer coating liquid to the surface of the gas barrier layer. Both the base material and the gas barrier layer, or one of the base material and the gas barrier layer, may be subjected to smoothing treatment by calendering.

[0053] Coating equipment used when applying a coating liquid for a gas barrier layer or a water vapor barrier layer includes, for example, a size press, a blade metering size press, a rod metering size press, a blade coater, a bar coater, a gate roll coater, a rod coater, and an air knife coater.

[0054] Furthermore, for smoothing processes using calenders, various calenders, such as supercalenders, gloss calenders, and soft compact calenders, which combine metal or drums with elastic rolls, are used as appropriate in on-machine or off-machine configurations.

[0055] <Industrial materials or packaging materials> The industrial material or packaging material comprises the barrier paper. By comprising the barrier paper, the industrial material or packaging material can be made which has excellent gas barrier properties and water vapor barrier properties, can suppress the decrease in barrier properties when folded, and can improve heat seal strength, suitability for bag making, and blocking suppression.

[0056] Examples of applications for this industrial material include replacing plastic materials used in agricultural sheets, interleaving paper, sheets used in acoustics, clothing, and building materials, and sheets used in electrical and electronic equipment. Furthermore, because this industrial material can suppress the intrusion of oxygen and moisture, it can suppress the decay and deterioration of the contents, as well as suppress the leakage of odors from the contents.

[0057] Examples of applications for this packaging material include paper barrier packaging materials used for packaging food, containers, cups, etc., as well as replacements for plastic materials such as packs, pouches, boxes, shrink wrap, cans, and laminated packaging. This packaging material can suppress deterioration of the contents due to oxidation by oxygen and moisture, thereby extending the shelf life.

[0058] <Other Embodiments> The present invention is not limited to the embodiments described above, and can be implemented in various modified and improved forms in addition to those described above. [Examples]

[0059] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. Note that the content and coating amount of each agent refer to values ​​on a solid content basis.

[0060] [Examples 1-4, 6-8, and Comparative Examples 1-4] First, pulp slurries with the raw pulp compositions listed in Table 1 were prepared. To these pulp slurries, 10 kg / t of aluminum sulfate, 0.1 kg / t of yield agent, and 5 kg / t of sizing agent were added as additives. The obtained pulp slurries were then made into paper using a wire screen paper machine and dried in a Yankee dryer to obtain the substrates for Examples 1 to 4, Examples 6 to 8, and Comparative Examples 1 to 4.

[0061] Next, a gas barrier layer was formed by coating one side of the substrate with a coating solution having the composition described in Table 1. The materials of the gas barrier layer coating solution are as follows. The amount of each raw material added is indicated as the amount converted to solid content relative to the amount of oven-dry pulp. Furthermore, the gas barrier layer was coated on only one side of the substrate, and the amount of coating was as shown in Table 2. Ethylene-modified polyvinyl alcohol: Kuraray Co., Ltd.'s "Exceval AQ-4104" Kaolin used in Examples 8-9 and Comparative Example 1: Imerys "VariSurf HX" (aspect ratio 100)

[0062] (Water vapor barrier layer) A water vapor barrier layer was formed by coating the surface of the gas barrier layer with a water vapor barrier coating solution with the composition described in Table 2. The amount of each raw material added is indicated as the amount equivalent to the solid content relative to the amount of oven-dry pulp. Furthermore, the water vapor barrier layer was coated on only one side of the substrate, and the coating amount was as shown in Table 2. A styrene-acrylic copolymer and paraffin wax were used as materials for the coating solution of the water vapor barrier layer.

[0063] [Example 5] In the manufacturing process of the base material, the barrier paper of Example 5 was obtained in the same manner as in Example 1, except that after papermaking, the Yankee dryer was changed to a multi-cylinder dryer and the paper was dried to obtain high-quality paper.

[0064] [Example 9] The barrier paper of Example 9 was obtained in the same manner as in Example 8, except that commercially available glassine paper was used as the base material.

[0065] In this way, barrier papers for Examples 1 to 9 and Comparative Examples 1 to 4 were obtained.

[0066] [Physical properties of the substrate and gas barrier layer] The physical properties of the substrate were measured using the following method. The measurement results are shown in Table 1.

[0067] (Basic weight) Basis weight of the base material (g / m²) 2The basis weight was measured in accordance with JIS-P-8124 (2011) "Paper and cardboard - Method for measuring basis weight".

[0068] (Oil absorption on coated surfaces) The oil absorption rate of the coated surface of the substrate was measured using light oil (5 μl) in accordance with JIS-P8130 (1994).

[0069] (Freeness of the raw pulp material of the base material) The freeness of the raw pulp used as the base material was determined by disintegrating it into disintegrated pulp in accordance with the pulp disintegration method specified in JIS-P8220-1:2012, and this disintegrated pulp was measured in accordance with the Canadian standard filtration rate test method specified in JIS-P8121-2:2012.

[0070] (Beck smoothness of the coated surface of the substrate) The Beck smoothness of the coated surface of the substrate was measured in accordance with the "Smoothness Test Method using a Beck Smoothness Tester" described in JIS-P8119 (1998) for paper and cardboard.

[0071] [Table 1]

[0072] [Table 2]

[0073] [evaluation] The obtained barrier papers were evaluated using the following method.

[0074] (Oxygen permeability after cross-folding) The measurement was performed using the following procedure. First, the obtained barrier paper was folded in a cross shape with the laminated surfaces of the gas barrier layer and water vapor barrier layer facing inward. The cross-folding method involved passing the barrier paper over a 2kg roller twice to fold it so that the fold angle was 180°, then unfolding it, and then passing the 2kg roller over it twice along a line perpendicular to the fold line to fold it again so that the fold angle was 180°, and then unfolding it. Then, with the intersection of the two fold lines in the center of the measurement area, the oxygen permeability was measured as described below. Oxygen permeability was measured in accordance with JIS-K-7126-1:2006 "Plastics - Films and Sheets - Gas Permeability Test Methods - Part 1: Differential Pressure Method" using GTR-11AET from GTR Tech Co., Ltd., under an atmosphere of 23°C.

[0075] (Moisture permeability after cross-folding) Next, the obtained barrier paper was folded in the same way as the oxygen permeability after the cross-fold described above. Then, with the intersection of the two fold lines in the center of the measurement area, the moisture permeability was measured as described below. The moisture permeability was measured according to JIS-Z0208

[1976] Test method for moisture permeability of moisture-proof packaging materials [cup method], based on condition B.

[0076] (Heat seal strength) Using a thermal gradient testing machine (manufactured by Toyo Seiki Seisakusho Co., Ltd.), the sealant pressure was 2 kgf / cm². 2 The outermost surfaces of the coating layers of barrier paper were bonded together under the conditions of a 2-second sealing time and a sealing temperature of 140°C. After bonding a 10mm x 25mm area, the peel strength of the bonded portion was measured using a load cell type tensile testing machine (Strograph ES, manufactured by Toyo Seiki Seisakusho Co., Ltd.) with a peel speed of 500mm / min and a T-shaped peel, with a width of 25mm. The obtained measured strength was converted to a width of 15mm. The test environment was set up based on the standard conditions of JIS-P8111 (1998) "Standard conditions for conditioning and testing of paper, cardboard and pulp".

[0077] (Suitability for bag making) The barrier paper obtained in each example and comparative example was passed through a bag-making machine to form bags. The meandering behavior and the likelihood of misalignment at the heat-sealed or cut sections were evaluated on a four-point scale. A rating of A or B indicates good suitability for bag-making. A: There is no meandering of the barrier paper within the bag-making machine, nor any misalignment of the heat-sealed or cut sections, resulting in excellent processability. B: There is virtually no meandering of the barrier paper within the bag-making machine, and no misalignment of the heat-sealed or cut sections, resulting in good processability. C: There is slight meandering of the barrier paper and misalignment of the heat-sealed or cut sections within the bag-making machine, making processing difficult. D: There is a lot of meandering of the barrier paper and misalignment of the heat-sealed and cut sections within the bag-making machine, making processing difficult.

[0078] (Blocking suppression) For each example and comparative example, the outermost surfaces coated with the barrier layer of the barrier paper were brought into close contact, and a 1 kg pressure roller was applied with one back-and-forth pressure. Next, after being stored for one day under conditions of 40°C, the results of peeling them off by hand were evaluated according to the following three criteria. An evaluation of A or B indicates good blocking suppression. A: There is no blocking, and it peels off easily. B: Slightly blocked, but peels off smoothly. C: Blocking is occurring, making it difficult to peel off.

[0079] (Ink drying properties during printing on non-layered surfaces of the barrier layer) The drying properties of the ink during printing were evaluated using the ink used in the GP-2 gravure printing and coating test machine (Kurabo Industries Ltd.). The evaluation ink (PCNT391T Blue, manufactured by Toyo Ink Co., Ltd.) was used to print on a substrate surface without a barrier layer. After 1 minute, 3 minutes, and 5 minutes, high-quality paper (white paper) was brought into contact with the printed surface, and the drying properties of the ink were evaluated according to the following two criteria. An evaluation of A indicates good ink drying properties during printing. A: No transfer was observed one minute after printing, indicating good ink drying properties. B: There are no issues with use, but slight transfer may be visible 1 minute after printing.

[0080] The measurement and evaluation results are shown in Table 3.

[0081] [Table 3]

[0082] As shown in Table 3, the barrier papers of Examples 1 to 9 exhibited good heat seal strength, suitability for bag making, booking suppression, and ink drying performance during printing on the non-laminated surface of the barrier layer. In particular, among the examples, Examples 1 to 3 and Examples 6 to 8, in which the oil absorption of the substrate was less than 90 seconds, showed better ink drying performance during printing on the non-laminated surface of the barrier layer compared to Examples 4, 5, and 9, in which the oil absorption was more than 90 seconds. This is presumed to be because the amount of ink held by the substrate was reduced due to the oil absorption of less than 90 seconds, thereby promoting ink drying and release.

[0083] On the other hand, in Comparative Example 1, the barrier paper in which the inorganic compound content in the gas barrier layer exceeded 15 parts by mass per 100 parts by mass of polyvinyl alcohol may have cracked during cross-folding, and its gas barrier and water vapor barrier properties after cross-folding were very poor. Comparative Example 2, in which the wax resin content in the water vapor barrier layer significantly exceeded 11 parts by mass per 100 parts by mass of styrene-acrylic copolymer, exhibited very poor heat seal strength and suitability for bag making. Comparative Example 3, in which the wax resin content in the water vapor barrier layer was less than 3 parts by mass per 100 parts by mass of styrene-acrylic copolymer, exhibited inferior blocking suppression. Comparative Example 4, in which the wax resin content in the water vapor barrier layer exceeded 11 parts by mass per 100 parts by mass of styrene-acrylic copolymer, exhibited inferior heat seal strength and suitability for bag making.

[0084] The results show that the barrier paper can suppress the decrease in barrier properties when folded, and can also improve heat seal strength, suitability for bag making, and blocking suppression. Therefore, it has been shown that the barrier paper is suitable as a multi-functional industrial material or packaging material.

Claims

1. Substrate and A gas barrier layer laminated on one or both sides of the above substrate, A water vapor barrier layer is laminated on the surface of the above gas barrier layer and Equipped with, The above gas barrier layer is mainly composed of polyvinyl alcohol, The above water vapor barrier layer contains a wax resin and a styrene-acrylic copolymer as the main component. The amount of the wax resin in the water vapor barrier layer is 3 parts by mass or more and 11 parts by mass or less per 100 parts by mass of the styrene-acrylic copolymer. The above gas barrier layer contains an inorganic compound in an amount of 15 parts by mass or less per 100 parts by mass of the polyvinyl alcohol, or does not contain an inorganic compound. Barrier paper in which the above-mentioned water vapor barrier layer does not contain inorganic compounds.

2. The barrier paper according to claim 1, wherein the oil absorption rate on the coated surface of the above-mentioned substrate is 90 seconds or less.

3. The barrier paper according to claim 1 or claim 2, wherein the gas barrier layer does not contain the inorganic compound.

4. An industrial material or packaging material comprising the barrier paper described in claim 1 or claim 2.

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