Barrier paper, industrial material, packaging material and laminate

Abstract

To provide a barrier paper with good water repellency and water resistance, as well as preventing a decrease in barrier properties when it is processed by folding.SOLUTION: A barrier paper according to an embodiment of the present invention comprises a substrate, a gas barrier layer laminated to one or both surfaces of a base paper, and a water vapor barrier layer laminated to a surface of the gas barrier layer, and the gas barrier layer comprises polyvinyl alcohol as a main component, the water vapor barrier layer contains wax resin, and styrene acrylic copolymer as the main component, and the gas barrier layer contains an inorganic compound with a content of 15 pts.mass or less relative to 100 pts.mass of the polyvinyl alcohol, or does not contain an inorganic compound, and the water vapor barrier layer does not contain an inorganic compound. Preferably, the content of the wax resin in the water vapor barrier layer is 1 pt.mass or more and 15 pts.mass or less relative to 100 pts.mass of the styrene acrylic copolymer.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to barrier papers, industrial materials, packaging materials and laminates. [Background technology]

[0002] 2. Description of the Related Art In the packaging of food, agriculture and other industrial fields, etc., packaging materials based on paper and provided with water vapor barrier properties and gas barrier properties have been used in order to prevent deterioration of the quality of the contents.

[0003] As a packaging material having such water vapor barrier properties and gas barrier properties, a paper barrier packaging material in which a water vapor barrier layer and a gas barrier layer are provided on a base paper has been proposed (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 pigments, 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 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned paper barrier packaging materials of the conventional technology, when folding is performed, the barrier layer at the folded portion is subjected to compressive strength, which may easily damage the barrier layer and reduce the barrier properties. Furthermore, if the contents of the paper barrier packaging material contain moisture, it will be difficult to maintain sufficient quality as a packaging material unless the material has resistance to moisture, such as water repellency.

[0006] The present invention has been made in light of the above circumstances, and has an object to provide a barrier paper that can suppress a decrease in barrier properties when folded, and has good water repellency and water resistance. [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 paper, and a water vapor barrier layer laminated on the surface of the gas barrier layer, wherein the gas barrier layer is primarily composed of polyvinyl alcohol, the water vapor barrier layer contains a wax resin and a styrene-acrylic copolymer as a primary component, the 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 contains no inorganic compound, and the water vapor barrier layer contains no inorganic compound. Effect of the Invention

[0008] According to the present invention, it is possible to provide a barrier paper that can suppress the deterioration of barrier properties when folded and has good water repellency and water resistance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Description of the embodiment of the present 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 paper, and a water vapor barrier layer laminated on the surface of the gas barrier layer, wherein the gas barrier layer is primarily composed of polyvinyl alcohol, the water vapor barrier layer contains a wax resin and a styrene-acrylic copolymer as a primary component, the 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 contains no inorganic compound, and the water vapor barrier layer contains no 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 the polyvinyl alcohol, or does not contain any inorganic compound, and has a coating weight of 5 g / m 2 More than 10g / m 2 or less, the coating properties when laminating the water vapor barrier layer on the surface of the gas barrier layer can be improved, and the properties of the water vapor barrier layer can be improved. Furthermore, the barrier paper has a good effect of suppressing the deterioration of the barrier property when folded. Furthermore, since the water vapor barrier layer contains a wax resin and a styrene-acrylic copolymer as a main component, the barrier paper can have good water vapor barrier property and can have improved water repellency and water resistance. Furthermore, since the water vapor barrier layer does not contain an inorganic compound, damage to the water vapor barrier layer when the barrier paper is folded can be reduced without reducing flexibility, and the deterioration of the barrier property when folded can be further suppressed. Therefore, the barrier paper can suppress the deterioration of the barrier property when folded and can have improved water repellency and water resistance. The above-mentioned "main component" refers to the component with the largest content, which is 70 mass% or more.

[0011] The content of the wax resin in the water vapor barrier layer is preferably from 1 to 15 parts by mass per 100 parts by mass of styrene-acrylic copolymer. By having the content of the wax resin in the water vapor barrier layer within this range, the water resistance of the water vapor barrier layer can be improved, and the effect of suppressing the occurrence of cracks when the barrier paper is folded can be enhanced.

[0012] It is preferable that the gas barrier layer does not contain the inorganic compound. When the gas barrier layer does not contain the inorganic compound, the barrier layer is less likely to be damaged when the barrier paper is folded, and the water vapor barrier performance can be further improved.

[0013] An industrial material or packaging material according to one aspect of the present invention includes the barrier paper, which makes it possible to obtain an industrial material or packaging material that has excellent gas barrier properties and water vapor barrier properties, is able to suppress a decrease in barrier properties when folded, and has improved water repellency and water resistance.

[0014] The laminate comprises the barrier paper, and a vapor deposition layer, a heat seal layer, or a combination thereof, laminated on one or both sides of the barrier paper. By comprising the barrier paper, and a vapor deposition layer, a heat seal layer, or a combination thereof, laminated on one or both sides of the barrier paper, it is possible to obtain a multifunctional and easily processable laminate that has excellent gas barrier properties and water vapor barrier properties, is able to suppress a decrease in barrier properties when folded, and is able to improve water repellency and water resistance.

[0015] [Details of the embodiment of the present invention] The present invention will be described in detail below. The following description of the components may be based on representative embodiments or specific examples, but the present invention is not limited to such embodiments.

[0016] <Barrier paper> The barrier paper comprises a substrate, a gas barrier layer laminated on one or both sides of the substrate, and a water vapor barrier layer laminated on the surface of the gas barrier layer.

[0017] [Base material] The substrate may be a paper substrate made from raw pulp, glassine paper further processed with a material that imparts transparency, cellophane paper or parchment paper obtained from raw pulp, or translucent paper such as paraffin paper impregnated with wax. For applications requiring paper quality and strength, a paper substrate made from raw pulp is preferably used. For applications requiring transparency, translucent paper such as glassine paper, cellophane paper, parchment paper, or paraffin paper is preferably used.

[0018] Examples of materials that impart transparency include transparent resins such as acrylic resin, polyethylene resin, polyester resin, urethane resin, nitrocellulose, shellac, and rosin; vegetable oils such as tung oil, linseed oil, castor oil, hydrophilic castor oil, coconut oil, soybean oil, and commercially available salad oil; and waxes such as carnauba wax, palm wax, beeswax, spermaceti, and Japan wax.

[0019] The substrate is obtained by papermaking a slurry containing raw pulp. The substrate may be either single-layered or multi-layered. Examples of the substrate include well-known ones such as fine paper, medium-quality paper, coated paper, one-sided glossy paper, kraft paper, one-sided glossy kraft paper, bleached kraft paper, glassine paper, paperboard, white paperboard, and liner. Among these, one-sided glossy paper may be used as the substrate from the viewpoint of dimensional stability, and one-sided glossy paper may be used from the viewpoint of strength and printability, and a fine paper made of 100% chemical pulp and being uncoated paper may be used.

[0020] (Raw pulp) As the raw material pulp constituting the base material, for example, virgin pulp, recycled paper pulp, a combination of these pulps, etc. can be used.

[0021] Examples of virgin pulp include 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), hardwood sulfite pulp, and softwood sulfite pulp; and mechanical pulps (MP) such as stone ground pulp (SGP), pressurized stone ground pulp (TGP), chemi-ground pulp (CGP), groundwood pulp (GP), and thermomechanical pulp (TMP). These pulps may be produced chemically or mechanically, either alone or in combination. From the viewpoint of appearance of the printed surface and use in food packaging applications, it is preferable to use only bleached kraft pulp.

[0022] Examples of waste paper pulp that can be used include disintegrated waste paper pulp, disintegrated and deinked waste paper pulp (DIP), and disintegrated, deinked and bleached waste paper pulp, which are produced from, for example, brown waste paper, kraft envelope paper, magazine paper, newspaper paper, flyer paper, office paper, corrugated cardboard paper, white waste paper, Kent waste paper, imitation waste paper, and land certificate paper, and can be used alone or in combination.

[0023] The lower limit of the freeness of the raw pulp is preferably 300 ml, more preferably 310 ml. The upper limit of the freeness of the raw pulp is preferably 400 ml, more preferably 390 ml. Here, the freeness is a value obtained by disintegrating the pulp in accordance with the pulp disintegration method of JIS-P8220-1-2012 to obtain disintegrated pulp, and measuring the disintegrated pulp in accordance with the Canadian standard freeness test method of JIS-P8121-2-2012. By having a freeness of 300 ml or more, uneven formation during drying can be reduced, and unevenness in the barrier performance can be suppressed. By having a freeness of 400 ml or less, the voids in the paper layer are reduced, and the amount of penetration of the coating liquid of the gas barrier layer into the substrate can be suppressed, so that a uniform water vapor barrier layer is formed on the surface of the gas barrier layer, and the water vapor barrier performance can be further improved.

[0024] (Other additives) Other additives may be added to the base material as necessary, such as fillers, pigments, sizing agents, coagulants, oil-resistant agents, fluorescent whitening agents, aluminum sulfate, retention aids, drainage aids, dry strength agents, wet strength agents, coloring dyes, coloring pigments, and water-resistant agents, which may be used alone or in combination.

[0025] (Basis weight of substrate) Basis weight (g / m 2 ) is measured in accordance with JIS-P-8124:2011 "Paper and paperboard - Method of measurement of basis weight". The lower limit of the basis weight of the substrate is 30.0 g / m 2 is preferred, and 32.0 g / m 2 More preferably, 35.0 g / m 2 The upper limit of the basis weight of the substrate is 80.0 g / m 2is preferred, and 75.0 g / m 2 More preferably, 70.0 g / m 2 The basis weight of the substrate is more preferably 30.0 g / m 2 By setting the basis weight at 80.0 g / m or more, it is possible to suppress the deterioration of the barrier properties due to the occurrence of pinholes during papermaking. 2 By making the thickness of the substrate smaller than or equal to 100 mm, it is possible to reduce the load on the barrier layer when the substrate is folded, which would otherwise be caused by an increase in thickness of the substrate.

[0026] (average thickness of substrate) The average thickness of the substrate is preferably 30 μm or more and 150 μm or less. By having the average thickness of the substrate in the above range, it is possible to maintain strength while enabling low basis weight and weight reduction. The "average thickness" is measured in accordance with JIS-P8118:2014.

[0027] (Bekk smoothness of the coated surface of the substrate) The lower limit of the Beck smoothness of the surface of the substrate on which the gas barrier layer is to be provided is 50 seconds, preferably 60 seconds. On the other hand, the upper limit of the Beck smoothness is 1150 seconds, preferably 1100 seconds. When the Beck smoothness of the coated surface of the substrate is equal to or greater than the lower limit, the sealing property of the coating liquid of the gas barrier layer is improved, and the properties of the gas barrier layer can be improved. On the other hand, when the Beck smoothness of the coated surface of the substrate exceeds the upper limit, pinholes are generated in the gas barrier layer, and when a water vapor barrier layer is formed thereon, the properties of the water vapor barrier layer may be deteriorated. The Beck smoothness is a value according to "Paper and cardboard - Smoothness test method using a Beck smoothness tester" described in JIS-P8119 (1998). The Beck smoothness is evaluated based on the amount of air flow (air leak). The Beck smoothness is measured by sandwiching the sheet to be measured between an optically flat glass sample stage and a rubber pressure plate at a pressure of 100 kPa, and then 10 ml of air is placed over a relatively wide area of ​​10 cm. 2It is expressed as the time required for the liquid to pass between the glass standard surface and the sample and flow into a vessel held at a reduced pressure of about 370 mml of mercury, and indicates the smoothness of the surface of the object being measured. Beck smoothness evaluates the macroscopic smoothness of a relatively large surface. In the case of the barrier paper, the waviness of the surface of the substrate can be evaluated by Beck smoothness. Therefore, the surface of the substrate can be more appropriately evaluated by Beck smoothness.

[0028] [Gas barrier layer] The barrier paper includes 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 including the gas barrier layer, the barrier paper can have good gas barrier properties. The gas barrier layer contains polyvinyl alcohol as a main component.

[0029] (Polyvinyl alcohol) The gas barrier layer is mainly composed of polyvinyl alcohol, which can form a film closely attached to the substrate and at the same time improve the gas barrier properties. As the polyvinyl alcohol, for example, unmodified polyvinyl alcohol in which the OH group is not substituted, ethylene-modified polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, phosphoric acid-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 mole percent of ethylene units relative to the total monomer units (ethylene units + vinyl alcohol units). However, the vinyl alcohol units also include unsaponified vinyl acetate units. The degree of ethylene modification is preferably 2 mole % or more and 12 mole % or less.

[0031] The average polymerization degree of polyvinyl alcohol is preferably 800 or more and 1,500 or less from the viewpoint of film-forming property and coating property.

[0032] (Inorganic compound) The gas barrier layer may contain an inorganic compound from the viewpoint of balancing the penetration and inhibition of the gas barrier layer coating solution. Examples of inorganic compounds include layered compounds (flat compounds) such as kaolin, such as fine kaolin, primary kaolin, secondary kaolin, delaminated kaolin, and calcined kaolin, bentonite, mica, and colloidal silica. Among these, kaolin is preferred from the viewpoint of achieving both barrier performance and coatability.

[0033] The lower limit of the aspect ratio of the inorganic compound is preferably 15, more preferably 18. If the aspect ratio of the inorganic compound is less than 15, the gas barrier property may be insufficient. On the other hand, the upper limit of the aspect ratio of the inorganic compound is preferably 120, more preferably 100. When the aspect ratio of the inorganic compound is 120 or less, the coating liquid of the gas barrier layer can be uniformly applied and the penetration into the substrate can be suppressed, so that high gas barrier property can be obtained with a low coating amount. Here, the "aspect ratio" refers to the shape of the inorganic particle, and refers to the ratio of its major diameter (longest diameter) to its thickness (shortest diameter). The above aspect ratio can be obtained, for example, by particle image analysis using a laser diffraction / scattering type particle distribution measuring device (Horiba LA 950, manufactured by Horiba, Ltd.) or by photographing powder particles with an electron microscope and dividing the diameter by the thickness for 500 randomly selected particles to obtain an average value.

[0034] The lower limit of the average particle size of the inorganic compound is preferably 0.1 μm, and more preferably 0.5 μm. Meanwhile, the upper limit of the average particle size of the inorganic compound is preferably 10.0 μm, and more preferably 5.0 μm. When the average particle size of the inorganic compound is within the above range, unevenness on the surface of the gas barrier layer is 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 size is the median diameter (D 50 ).

[0035] 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 any inorganic compound. This allows for good coating properties when laminating a water vapor barrier layer on the surface of the gas barrier layer, thereby improving the properties of the water vapor barrier layer. Furthermore, the barrier paper has a good effect of suppressing deterioration of barrier properties when folded. It is preferable that the gas barrier layer does not contain an inorganic compound. When the gas barrier layer does not contain an inorganic compound, damage to the barrier layer is less likely to occur when the barrier paper is folded.

[0036] The lower limit of the polyvinyl alcohol content in the gas barrier layer is preferably 70% by mass, more preferably 80% by mass, and even more preferably 85% by mass. By keeping the polyvinyl alcohol content within the above range, the gas barrier property of the gas barrier layer can be further improved.

[0037]

[0113] In addition to polyvinyl alcohol and inorganic compounds, the gas barrier layer may contain, as necessary, suitable conventional additives such as thickeners, flow improvers, defoamers, foam inhibitors, lubricants, release agents, foaming agents, penetrating agents, coloring dyes, coloring pigments, fluorescent brightening agents, ultraviolet absorbing agents, antioxidants, preservatives, antifungal agents, water resistant agents, dyes, and fixing agents.

[0038] The lower limit of the coating weight of the gas barrier layer is 5 g / m 2 is preferred, and 6 g / m 2 On the other hand, the upper limit of the coating amount (converted into solid content) is 10 g / m 2 is preferred, and 8 g / m 2 The coating weight of the gas barrier layer is more preferably 5 g / m. 2 By setting the coating weight of the gas barrier layer at 10 g / m or more, the surface of the substrate can be uniformly coated with the gas barrier layer. 2 By ensuring that the above ratio is not more than 1, the drying properties of the coating solution for the gas barrier layer can be improved.

[0039] (Bekk smoothness of the gas barrier layer surface) The lower limit of the Beck smoothness of the surface of the gas barrier layer is 50 seconds, preferably 60 seconds. Meanwhile, the upper limit of the Beck smoothness is 1150 seconds, preferably 1100 seconds. When the Beck smoothness of the surface of the gas barrier layer is equal to or greater than the lower limit, the coatability of the coating liquid of the water vapor barrier layer laminated on the surface of the gas barrier layer is improved, and the properties of the water vapor barrier layer can be improved. Meanwhile, when the Beck smoothness of the surface of the gas barrier layer exceeds the upper limit, the gas barrier layer exhibits high flatness (improved slipperiness) even when the water vapor barrier layer is formed on the surface of the gas barrier layer, so that there is a risk of a decrease in the suitability for bag making.

[0040] [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 a main component. By containing the wax resin together with the styrene-acrylic copolymer in the water vapor barrier layer, the barrier paper can have good water vapor barrier properties and can have improved water repellency and water resistance.

[0041] The styrene-acrylic copolymer is not particularly limited as long as it is a copolymer of various styrene monomers and various (meth)acrylic monomers.

[0042] The lower limit of the content of the styrene-acrylic copolymer in the water vapor barrier layer is preferably 87% by mass, more preferably 89% by mass, calculated as solid content. The upper limit of the content of the styrene-acrylic copolymer is preferably 99% by mass, more preferably 95% by mass, calculated as solid content. By having the content of the styrene-acrylic copolymer in the above range, the water vapor barrier property of the water vapor barrier layer can be further improved.

[0043] The wax resin is not particularly limited, and examples of the wax resin that can be used include paraffin wax resins mainly composed of alkane compounds, natural oil-based wax resins derived from animals and plants such as carnauba and lanolin, silicone wax resins containing silicone or silicone compounds, fluorine-containing wax resins containing fluorine compounds, etc. The wax resins can be used alone or in combination of two or more kinds.

[0044] The content of the wax resin is preferably 1 part by mass or more and 15 parts by mass or less, more preferably 5 parts by mass or more and 12 parts by mass or less, relative to 100 parts by mass of the styrene-acrylic copolymer. If the content of the wax resin is less than 1 part by mass, water resistance tends to decrease. If the content of the wax resin exceeds 15 parts by mass, the surface of the substrate becomes slippery after the coating liquid of the water vapor barrier layer is applied to the substrate, and workability may decrease. In addition, if the content of the wax resin exceeds 15 parts by mass, the water vapor barrier layer becomes brittle, and cracks are likely to occur when the barrier paper is folded.

[0045] The water vapor barrier layer does not contain an inorganic compound. Since the water vapor barrier layer does not contain an inorganic compound, the water vapor barrier layer is not damaged when the barrier paper is folded, and therefore the deterioration of the barrier properties when the barrier paper is folded can be further suppressed. The inorganic compound means the same as those exemplified for the gas barrier layer.

[0046]

[0043] In addition to the styrene-acrylic copolymer and wax resin, the water vapor barrier layer may contain, as necessary, appropriate blends of conventional additives such as thickeners, flow improvers, defoamers, foam inhibitors, lubricants, release agents, foaming agents, penetrating agents, coloring dyes, coloring pigments, fluorescent brightening agents, ultraviolet absorbing agents, antioxidants, preservatives, antifungal agents, water resistant agents, dyes, and fixing agents.

[0047] The lower limit of the coating amount of the water vapor barrier layer is 2.0 g / m 2 is preferred, and 3.0 g / m 2 On the other hand, the upper limit of the coating amount is preferably 10.0 g / m from the viewpoint of improving the sealing property.2 is preferred, and 9.0 g / m 2 If the coating weight of the water vapor barrier layer is less than the above lower limit, the water vapor barrier property may be deteriorated. On the other hand, if the coating weight of the water vapor barrier layer is more than the above upper limit, blocking may occur when the product is wound up, making it impossible to use the product as a packaging material.

[0048] When a gas barrier layer and a water vapor barrier layer are laminated on both sides of the above-mentioned base material, the components, coating amount, etc. of the gas barrier layer and the water vapor barrier layer can be configured as described above.

[0049] When a gas barrier layer and a water vapor barrier layer are laminated on one side of the above-mentioned substrate, a print-improving coating layer such as a pigment layer can be provided on the side (back side) of the above-mentioned substrate opposite to the side on which the gas barrier layer and the water vapor barrier layer are laminated, for the purpose of improving printability in gravure printing machines, digital printing machines, inkjet printing, laser printing, etc. As the print-improving coating layer, those conventionally known in the fields of coated printing paper, inkjet paper, and laser printer paper can be used.

[0050] [Barrier paper physical properties] (Basis weight of barrier paper) The barrier paper has a basis weight of 37.0 g / m 2 More than 100.0g / m 2 The following is preferable. By having the basis weight of the barrier paper in the above range, it is possible to reduce the weight while maintaining strength.

[0051] (Average thickness of barrier paper) The lower limit of the average thickness of the barrier paper is preferably 40 μm, more preferably 45 μm. The upper limit of the average thickness is preferably 150 μm, more preferably 100 μm. By keeping the average thickness of the barrier paper within the above range, it is possible to achieve a low basis weight and a lighter weight while improving processability.

[0052] (Oxygen permeability and moisture permeability of flat barrier paper) The oxygen permeability of the barrier paper is 20g / m 224hr or less is preferable, 10g / m 2 The moisture permeability of the barrier paper on its flat surface is 50 g / m 2 24hr or less is preferable, 20g / m 2 When the plane oxygen permeability and moisture permeability of the barrier paper are within the above ranges, the barrier paper has good barrier properties.

[0053] [Barrier paper manufacturing method] The method for producing the barrier paper is not particularly limited and may, for example, include the steps of making a raw pulp slurry and subjecting it to a press part and a dryer part to produce a substrate, applying a gas barrier layer coating liquid to the surface of the substrate in an undercoater part and then drying the coated substrate to laminate the gas barrier layer, and applying a water vapor barrier layer coating liquid to the surface of the gas barrier layer. After coating of the substrate and / or the gas barrier layer, a smoothing treatment using a calendar may be performed.

[0054]

[0113] Examples of coating devices used when applying the coating liquid for the gas barrier layer or the coating liquid for the water vapor barrier layer include 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.

[0055] As a calendering device for the calendering process, various calenders such as a super calender, a gross calender, a soft compact calender, etc., which are a combination of a metal or drum and an elastic roll, are appropriately used in an on-machine or off-machine specification.

[0056] <Industrial materials or packaging materials> The industrial material or packaging material includes the barrier paper. By including the barrier paper, it is possible to obtain an industrial material or packaging material that has excellent gas barrier properties and water vapor barrier properties, is able to suppress a decrease in barrier properties when folded, and is able to improve water repellency and water resistance.

[0057] Examples of such industrial materials include agricultural sheets, interleaving paper, sheets used in audio, clothing, building materials, etc., and sheets used in electrical and electronic equipment, and can be used to replace plastic materials. In addition, since the industrial materials can prevent the intrusion of oxygen and moisture, they can prevent the contents from spoiling and deteriorating, and also prevent the odor of the contents from escaping.

[0058] Examples of the packaging material include packaging materials for food, etc., paper barrier packaging materials used for packaging applications such as containers and cups, and applications as an alternative to plastic materials such as packs, pouches, boxes, shrink packaging, cans, laminate packaging, etc. The packaging material can suppress deterioration of the contents due to oxidation caused by oxygen and moisture, and can extend the storage period.

[0059] <Laminate> The laminate comprises the barrier paper, and a vapor deposition layer, a heat seal layer, or a combination thereof, laminated on one or both sides of the barrier paper. By comprising the barrier paper, and a vapor deposition layer, a heat seal layer, or a combination thereof, laminate having excellent gas barrier properties and water vapor barrier properties, capable of suppressing a decrease in barrier properties when folded, capable of improving water repellency and water resistance, and capable of providing a multifunctional laminate with good processability.

[0060] (vapor deposited layer) The laminate can have improved barrier properties by including a vapor deposition layer. The vapor deposition layer is laminated on one or both sides of the barrier paper. The vapor deposition layer is mainly composed of a metal, an inorganic oxide, or an inorganic nitride. The metal may be aluminum, tin, nickel, copper, gold, platinum, silver, cobalt, or chromium. The inorganic oxide may be an oxide of silicon, aluminum, titanium, zirconium, tin, magnesium, lead, boron, sodium, or the like. The inorganic nitride may be a nitride of silicon, aluminum, titanium, zirconium, tin, magnesium, lead, boron, sodium, or the like. The method for forming the vapor deposition layer is not particularly limited, and may be any known method such as vacuum deposition, ion plating, sputtering, or plasma vapor deposition (CVD).

[0061] (Heat seal layer) The laminate has a heat seal layer, which improves processability in a bag making process. The heat seal layer is laminated on one or both sides of the barrier paper. When the laminate has a vapor deposition layer and a heat seal layer, the heat seal layer is preferably the outermost layer. The heat seal layer is a film layer or a coating layer mainly composed of a thermoplastic resin.

[0062] (Film layer) The film layer is mainly composed of a thermoplastic resin. Examples of the thermoplastic resin that is the material of the film layer include low density polyethylene (LDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), polypropylene (PP), polyvinyl acetate (PVAc), polyester resin (PET), ethylene methacrylic acid copolymer resin (EMAA), ethylene methyl acrylate copolymer resin (EMA), ethylene acrylic acid copolymer resin (EAA), ethylene vinyl acetate copolymer resin (EVA), styrene acrylic acid ester copolymer resin, and polylactic acid resin. There is no particular limitation on the lamination method of the film layer, and known methods such as the conventional melt extrusion lamination method, the dry lamination method using a film, and the direct melt coating method can be used.

[0063] (Coating layer) The coating layer is mainly composed of a thermoplastic resin. Examples of the thermoplastic resin that is the material of the coating layer include olefin-unsaturated carboxylic acid copolymers such as styrene-butadiene copolymer, ethylene-acrylic acid copolymer, and ethylene-methacrylic acid copolymer, biodegradable resins, polyolefin resins such as polyethylene and polypropylene, and acrylic resins such as methyl acrylate copolymer, methyl methacrylate copolymer, styrene-acrylic copolymer, and styrene-methacrylic copolymer. The coating method is not particularly limited, and known coating devices such as conventional rod metering size press, pond type size press, gate roll coater, spray coater, blade coater, and curtain coater can be used.

[0064] <Other embodiments> The present invention is not limited to the above-described embodiment, and can be embodied in various other forms in addition to the above-described forms with various modifications and improvements. EXAMPLES

[0065] 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 drug refer to values ​​calculated as solid content.

[0066] [Examples 1, 2, 4 to 7, 9, 10, and Comparative Examples 1 to 5] First, a pulp slurry was prepared having the raw pulp composition shown in Table 1. To this pulp slurry, 10 kg / t of aluminum sulfate, 0.1 kg / t of retention aid, and 5 kg / t of sizing agent were added as additives. The obtained pulp slurry was made into paper using a Fourdrinier papermaking machine and dried using a Yankee dryer to obtain the base materials of Example 1, Example 2, Examples 4 to 7, Example 9, Example 10, and Comparative Examples 1 to 5.

[0067] Next, a gas barrier layer was formed by coating the surface of the substrate with higher Beck smoothness with a coating liquid having the composition shown in Table 1. The materials of the coating liquid for the gas barrier layer are as follows. Ethylene-modified polyvinyl alcohol: Kuraray "Exeval AQ-4104" Unmodified polyvinyl alcohol: Kuraray "Kuraray Poval 5-98" Kaolin used in Example 2 and Comparative Examples 4-5: "Varisurf HX" (aspect ratio 100) manufactured by Imerys

[0068] (Water vapor barrier layer) A coating solution for the water vapor barrier layer having the composition shown in Table 2 was applied to the surface of the gas barrier layer to form a water vapor barrier layer. The coating fluid for the water vapor barrier layer was made of styrene-acrylic copolymer and paraffin wax. As the coating liquid for the water vapor barrier layer, coating liquids having the following three compositions were used. (1) Examples 1 to 3 A coating liquid containing paraffin wax and a styrene-acrylic copolymer, in which the content of the paraffin wax was 10 parts by mass per 100 parts by mass of the styrene-acrylic copolymer, was used. (2) Examples 4 to 10, Comparative Examples 4 and 5 A coating liquid containing paraffin wax and a styrene-acrylic copolymer, in which the content of the paraffin wax was 5 parts by mass per 100 parts by mass of the styrene-acrylic copolymer, was used. (3) Comparative Example 1 A coating solution made of a styrene-acrylic copolymer was used.

[0069] The amount of each raw material added is shown as the amount converted into solid content relative to the bone dry pulp amount. The gas barrier layer and water vapor barrier layer were coated only on one side of the substrate, with the coating amount being as shown in Table 2. In this manner, the barrier papers of Examples 1 to 4, 6, and 7 and Comparative Examples 1 to 7 were obtained.

[0070] [Example 3] Barrier paper of Example 3 was obtained in the same manner as in Example 1, except that commercially available glassine paper was used as the substrate.

[0071] [Example 8] The barrier paper of Example 8 was obtained in the same manner as in Example 1, except that in the manufacturing process of the base material, the Yankee dryer was changed to a multi-cylinder dryer after papermaking and drying was performed to produce fine paper.

[0072] [Table 1]

[0073] [Table 2]

[0074] [evaluation] The obtained barrier paper was evaluated by the following methods.

[0075] <Basic weight> Basis weight of substrate (g / m 2 ) was measured in accordance with JIS-P-8124 (2011) "Paper and paperboard -- Determination of basis weight."

[0076] <Freeness of base pulp material> The freeness of the raw pulp of the base material was measured in accordance with the Canadian standard freeness test method of JIS-P8121-2:2012, which was performed by disintegrating the pulp in accordance with the pulp disintegration method of JIS-P8220-1:2012 to obtain disintegrated pulp.

[0077] <Bekk smoothness of the coated surface of the substrate> The Beck smoothness of the coated surface of the substrate was measured in accordance with "Paper and paperboard - Smoothness test method using a Beck smoothness tester" described in JIS-P8119 (1998).

[0078] <Oxygen permeability after folding> The measurement was carried out according to the following procedure. First, the obtained barrier paper was folded crosswise with the laminated surfaces of the gas barrier layer and water vapor barrier layer facing inward. The method of folding crosswise was to fold the barrier paper by running a 2 kg roller back and forth twice so that the fold angle was 180°, then unfold it, and then run a 2 kg roller back and forth twice along a line perpendicular to the fold line so that the fold angle was 180°, then unfold it. The oxygen permeability was then measured as described below, with the intersection of the two fold lines positioned at the centre of the measurement area. The oxygen permeability of the barrier paper was measured in an atmosphere of 23°C using GTR Tech's "GTR-11AET" in accordance with JIS-K-7126-1:2006 "Plastics - Films and sheets - Gas permeability test methods - Part 1: Differential pressure method."

[0079] <Moisture permeability after folding crosswise> Next, in the same manner as for the oxygen transmission rate after the cross fold, the obtained barrier paper was folded crosswise so that the intersection of the two fold lines was located at the center of the measurement area, and the moisture transmission rate was measured as described below. The moisture permeability was measured under condition B in accordance with JIS-Z0208

[1976] Moisture permeability test method for moisture-proof packaging materials [cup method].

[0080] (Water repellency evaluation) The water vapor barrier layer side was measured in accordance with JAPAN TAPPI Paper and Pulp Test Method No. 68 "Paper and Paperboard - Water Repellency Test Method." In the above test method, the higher the R value, the better the water repellency, with the maximum value being R10.

[0081] (Water resistance rating) Water resistance was evaluated by dropping about 2 ml of water onto the coated surface of the barrier paper. The degree to which the water permeated the paper was visually observed and rated according to the following four-level evaluation criteria. A and B are acceptable. A: No penetration or bleeding is observed. B: Slight penetration is observed, but still within the range of usability. C: Penetration is observed. D: There is obvious soaking and it is not suitable for use.

[0082] The above measurement results and evaluation results are shown in Table 2.

[0083] As shown in Table 2, the barrier papers of Examples 1 to 10, in which the gas barrier layer was composed primarily of polyvinyl alcohol, the water vapor barrier layer contained a wax resin and a styrene-acrylic copolymer as the main component, and the gas barrier layer contained either an inorganic compound in an amount of 15 parts by mass or less per 100 parts by mass of polyvinyl alcohol or contained no inorganic compound, and the water vapor barrier layer contained no inorganic compound, had excellent gas barrier property and water vapor barrier property after being folded crosswise, and were good in water repellency and water resistance. Moreover, a comparison between Example 1 and Example 5 shows that the water vapor barrier performance can be further improved by not including the inorganic compound in the gas barrier layer.

[0084] On the other hand, the barrier papers of Comparative Examples 2 and 3, which did not have a water vapor barrier layer, and Comparative Examples 4 and 5, in which the gas barrier layer contained more than 15 parts by mass of an inorganic compound per 100 parts by mass of polyvinyl alcohol, had poor gas barrier property or water vapor barrier property or both after cross folding. Furthermore, Comparative Example 1, in which the water vapor barrier layer did not contain a wax resin, and Comparative Examples 2 and 3, which did not have a water vapor barrier layer, had poor water resistance and water repellency.

[0085] The above results show that the barrier paper can suppress the deterioration of barrier properties when folded and can improve water repellency and water resistance, demonstrating that the barrier paper is suitable for use as a thin, multifunctional industrial 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 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 content of the wax resin in the water vapor barrier layer is 1 part by mass or more and 15 parts by mass or less per 100 parts by mass of styrene-acrylic copolymer.

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.

5. A barrier paper according to claim 1 or claim 2, A vapor-deposited layer, a heat-sealed layer, or a combination thereof laminated on one or both sides of the above barrier paper and Equipped with, The above-mentioned vapor-deposited layer mainly consists of metal, inorganic oxide, or inorganic nitride. A laminate in which the heat-seal layer is a film layer or coating layer mainly composed of a thermoplastic resin.