JP2022149469A - paper packaging material - Google Patents

Abstract

To provide a paper packaging material which has oxygen barrier properties and water vapor barrier properties, is excellent in disaggregation properties, and has excellent sealing processability by heat sealing.SOLUTION: The problem can be solved by the paper packaging material which has a paper support, a first coating layer on one side of said paper support, a second coating layer on the outside of said first coating layer relative to the paper support, and a third coating layer on an outside of the second coating layer with respect to a paper support, and the paper support has a Parker Print Surf surface roughness of 2 μm or more and 4 μm or less in accordance with ISO8791-4:1992, and a first coating layer contains ethylene-modified polyvinyl alcohol and bentonite, the second coating layer contains an ionomer resin made of a copolymer of ethylene and an unsaturated carboxylic acid-based monomer and bentonite, and the third coating layer is a heat seal layer.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a paper packaging material that has oxygen barrier properties and water vapor barrier properties and that is excellent in sealing processability by heat sealing.

For packaging, a packaging material having oxygen barrier properties and water vapor barrier properties is used in order to prevent deterioration and deterioration of foods and industrial products due to oxidation and deterioration and deterioration due to moisture absorption or drying. Conventional packaging materials are mainly laminates made of plastic films or plastic films having a metal deposition film. On the other hand, plastic products need to be reduced due to the problem of environmental pollution in that they flow out into the natural world without proper disposal. In the field of packaging materials, paper is a promising alternative to plastic films as a support or base material. Paper packaging materials using a paper support or paper base include, for example, gas barrier composite materials having a structure in which a paper base layer, an adhesive vinylidene chloride resin layer, and an olefin resin layer are laminated in this order (see, for example, Patent Document 1). ), and a single barrier layer on a paper substrate, wherein the barrier layer is a styrene-butadiene-based polymer, a styrene-acrylic polymer, polyvinyl alcohol, polyvinylidene chloride, polyacrylonitrile, polyvinyl chloride and polyethylene vinyl alcohol Barrier laminates containing one or more polymers or copolymers selected from these are known (see, for example, Patent Document 2).

JP-A-61-11246 Japanese Patent Publication No. 2020-530409

As in Patent Documents 1 and 2, a paper packaging material has a resin layer mainly containing a resin that exhibits barrier properties to a paper substrate or a paper support (hereinafter referred to as "paper support"). often have The paper support is usually recyclable as recycled paper. Therefore, from the viewpoint of paper recycling, it is important for paper packaging materials having a resin layer that the paper support and the resin layer can be easily separated at the time of disposal, and that the paper support easily disaggregates in water. Polyvinylidene chloride, including the above adhesive vinylidene chloride resin, is one of the few resins that is superior in oxygen barrier properties and water vapor barrier properties to other general-purpose resins. However, polyvinylidene chloride has a strong adhesiveness to paper and is difficult to separate from the paper support, so that the ease of disintegrating the paper support into water is inferior.
The packaging material is also used for packaging bags. For example, the packaging material contains articles such as cosmetics, food, and pharmaceuticals, and is heat-sealed to form a bag. As for the shape of the bag, there are gusset bags such as a four-sided bag, a three-sided bag, a pillow bag, and a standing bag. For example, pillow bags and standing bags are heat-sealed by folding the packaging material during the formation process. Paper packaging materials tend to be twisted and/or wrinkled during the forming process, compared to packaging materials such as plastic film laminates or plastic films having metallized films. Therefore, it is necessary for paper packaging materials to improve sealing workability by heat-sealing without twisting and/or wrinkling during the forming process.

An object of the present invention is to have oxygen barrier properties and water vapor barrier properties, to allow easy separation of the paper support and the first coating layer, and to facilitate the disintegration of the paper support into water (hereinafter referred to as "disaggregation property"). It is to provide a paper-made packaging material which is excellent in heat sealing processability by heat sealing.

The above problems can be solved by the following.

[1] A paper support, a first coating layer on one side of the paper support, a second coating layer on the outside of the first coating layer relative to the paper support, and the paper support relative to As a third coating layer on the outside of the second coating layer, the paper support has a Parker Print Surf surface roughness of 2 μm or more and 4 μm or less in accordance with ISO8791-4:1992, and the first coating The coating layer contains ethylene-modified polyvinyl alcohol and bentonite, the second coating layer contains an ionomer resin made of a copolymer of ethylene and an unsaturated carboxylic acid monomer and bentonite, and the third coating layer contains A paper packaging material whose layer is a heat-sealable layer.

The paper packaging material of the present invention has oxygen-barrier properties and water-vapor-barrier properties, is excellent in disaggregation properties, and is excellent in sealing processability by heat sealing.

Embodiments of the present invention will be described in detail below, but the present invention is not limited to these descriptions, and can be implemented by appropriately modifying the embodiments within the scope of the purpose of the present invention.

The paper packaging material of the present invention comprises a paper support, a first coating layer on one side of the paper support, a second coating layer on the outside of the first coating layer with respect to the paper support, and a third coating layer outside the second coating layer relative to the paper support. In addition, the paper packaging material is intended to improve printability for offset printing or gravure printing on the opposite side of the paper support to the side having the first coating layer, second coating layer and third coating layer. Alternatively, it may have a printing coating layer or a backcoat layer for the purpose of improving the dimensional stability of the paper support. Printing coating layers and back coating layers are conventionally known in the coated paper art. Furthermore, the paper packaging sheet can have a first coating layer, a second coating layer and/or a third coating layer between the printing coating layer or back coating layer and the paper support. As an embodiment of the paper packaging material, the surface of the paper packaging sheet facing the contents is the side having the first coating layer, the second coating layer and the third coating layer of the packaging sheet.

Paper supports are chemical pulps such as LBKP (bleached hardwood kraft pulp), LUKP (unbleached hardwood kraft pulp), NBKP (bleached softwood kraft pulp) and NUKP (unbleached softwood kraft pulp), GP (groundwood pulp), PGW. (pressurized groundwood pulp), RMP (refiner mechanical pulp), TMP (thermomechanical pulp), CTMP (chemithermomechanical pulp) and CMP (chemimechanical pulp), and waste paper such as DIP (deinked pulp) A paper material containing at least one cellulose pulp selected from the group consisting of pulp, a filler, a sizing agent, and optionally various additives such as a fixing agent, a retention agent, and a paper strength agent, Paper made by a conventionally known method under acidic, neutral or alkaline conditions. Further, the paper support includes fine paper obtained by size-pressing the paper with a size press liquid, fine paper obtained by surface-treating the paper with a surface treatment liquid, and calendering the paper or the fine paper. Includes high-quality paper with Examples of calendering equipment include machine calenders, soft nip calenders, super calenders, multi-stage calenders, multi-nip calenders, and lab soft calenders consisting of laboratory elastic rolls and metal rolls.

Fillers are pigments conventionally known in the papermaking arts. Examples of pigments include light calcium carbonate, ground calcium carbonate, kaolin, talc, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, silica, aluminum silicate, diatomaceous earth, activated clay, alumina, alumina Inorganic pigments such as hydrates, aluminum hydroxide, lithopone, zeolite, magnesium carbonate and magnesium hydroxide can be mentioned. Furthermore, organic pigments such as styrene plastic pigments, acrylic plastic pigments, polyethylene plastic pigments, urea resins, melamine resins and microcapsules can be used. The filler is one or more selected from the group consisting of these.

The sizing agent is an internal sizing agent conventionally known in the papermaking art. Examples of internal sizing agents include rosin sizing agents for acidic paper, alkenyl succinic anhydride, alkyl ketene dimers, neutral rosin sizing agents and cationic styrene acrylic sizing agents for neutral paper. can be mentioned. The sizing agent used in the size press liquid is a surface sizing agent conventionally known in the field of papermaking. Examples of surface sizing agents include starch-based sizing agents, cellulose-based sizing agents, polyvinyl alcohol-based sizing agents, styrene acrylic-based sizing agents, olefin-based sizing agents, styrene-maleic acid-based sizing agents, and acrylamide-based sizing agents. can be done. The size press is performed using a size press apparatus conventionally known in the papermaking field. Examples of size press equipment include an incline size press, a horizontal size press, a rod metering size press, a roll metering size press and a blade metering size press as film transfer, and a shim sizer and an optimizer as the rod metering size press. and a speed sizer, a gate roll coater as the roll metering size press, a bill blade coater, a twin blade coater, a velvapa coater, a tab size press, a calendar size press, and the like.

In some embodiments, the paper packaging material has a paper support with an ash content of 3% by mass or more and 10% by mass or less. The reason for this is that the paper support can be flexible and does not lose its strength. Here, the ash content is the ratio (mass %) of the incombustible matter after the paper support is burned at 500° C. for 1 hour to the absolute dry weight of the paper support before the combustion process. The ash content can be controlled by conventionally known methods such as adjusting the filler content in the paper.

The paper support is compliant with ISO8791-4:1992 "Paper and board - Determination of roughness/smoothness (air leak methods) - Part 4: Print-surf method" and is clamped at a clamping pressure of 1 MPa using a soft rubber backing disk. The Parker Print Surf surface roughness measured under the conditions is 2 μm or more and 4 μm or less. In at least one embodiment, the paper support has the Parker Print Surf surface roughness of 3.1 μm or more and 3.5 μm or less. The reason for this is that sealing workability is improved. The Parker Print Surf surface roughness of a paper support can be measured, for example, using a Messmer Parker Print Surf Roughness Tester (eg Model 58-06-00) according to ISO 8791-4:1992. The Parker Print Surf surface roughness of the paper support depends on the type of pulp and the degree of beating of the pulp, the type, size and amount of filler added, the presence or absence of size press treatment and its conditions, the composition of the size press liquid, and the calender treatment. It can be adjusted depending on the presence or absence of calendering conditions and the like. Calendering is suitable for setting the surface roughness of the paper support to 2 μm or more and 4 μm or less.

Calendering to make the surface roughness of Parker Print Surf in the range of 2 μm or more and 4 μm or less is a condition that does not excessively smooth the surface of the paper support. Methods such as calendering with a reduced number of paper passes (number of nips) and calendering with a roll having a rough surface can be mentioned. The Parker Print Surf surface roughness measures the unevenness (flatness) of the surface of the paper support in areas separated by narrow intervals of several tens of microns. Unevenness can be evaluated. By setting the Parker Print Surf surface roughness of the paper support to 2 μm or more and 4 μm or less, the paper packaging material can obtain detachability and sealing processability. If the Parker Print Surf surface roughness is less than 2 μm, it is difficult to obtain disaggregation properties. If the Parker Print Surf surface roughness exceeds 4 μm, it is difficult to obtain disaggregation and encapsulation processability.

The first coating layer contains ethylene-modified polyvinyl alcohol and bentonite. The first coating layer mainly functions as an oxygen barrier layer that suppresses permeation of oxygen gas. The first coating layer also functions as a release layer when the paper support is disintegrated in water.
In some embodiments, in the first coating layer, the total content of ethylene-modified polyvinyl alcohol and bentonite in the first coating layer is 80% by mass or more relative to the dry solid content forming the first coating layer. is. The reason for this is that the oxygen barrier properties of the paper packaging material are improved. In some embodiments, the content of ethylene-modified polyvinyl alcohol in the first coating layer is 20 parts by mass or more and 500 parts by mass or less with respect to 100 parts by mass of bentonite. In at least one embodiment, the content of ethylene-modified polyvinyl alcohol in the first coating layer is 50 parts by mass or more and 200 parts by mass or less per 100 parts by mass of bentonite. The reason for these is that the oxygen barrier properties of the paper packaging material are particularly improved. In some embodiments, the first coating layer has a dry solid content of 2 g/m ² or more and 10 g/m ² or less. The reason for this is that the oxygen barrier properties of the paper packaging material are improved.
In at least one embodiment, in the first coating layer, the total content of ethylene-modified polyvinyl alcohol and bentonite in the first coating layer is 80% by mass or more relative to the dry solid content forming the first coating layer. , the content of ethylene-modified polyvinyl alcohol in the first coating layer is 50 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of bentonite in the first coating layer, and the coating amount is 2 g / m ² or more and 10 g/m ² or less.

The first coating layer can contain various additives conventionally known in the field of coated paper within limits that do not impair the effects of the present invention. Examples of additives include antifoaming agents, dispersants, wetting agents, pigments other than bentonite, resins other than ethylene-modified polyvinyl alcohol, and colorants.

Bentonite contains clay mineral montmorillonite as a main component, silicate minerals such as quartz, α-cristobalite and opal as secondary components, silicate minerals such as feldspar, mica and zeolite, carbonate minerals such as calcite, dolomite and gypsum. It is a weakly alkaline claystone associated with sulfate minerals and sulfide minerals such as pyrite.
Montmorillonite, which is the main component, has a structure in which a plurality of thin plate-like unit crystals are laminated.
A unit crystal of montmorillonite has a sandwich structure in which a tetrahedral sheet in which tetrahedrons composed of silicon atoms and oxygen atoms are linked in a sheet form sandwiches an octahedral sheet in which octahedrons composed of aluminum atoms and hydroxyl groups are linked in a sheet form. have. Montmorillonite contains cations between the layers of unit crystals. Cations can include, for example, Na ⁺ , Ca ²⁺ , K ⁺ and Mg ²⁺ . In general, bentonites can be classified according to the interlamellar cations that montmorillonite contains. Examples of bentonite include Na-type bentonite and Ca-type bentonite.
In some embodiments, the bentonite has a montmorillonite content of 90% by mass or more and 99.5% by mass or less. In at least one embodiment, the bentonite has a montmorillonite content of 90% by mass or more and 99.5% by mass or less and is of Na type. The reason for this is that the swelling property is high, and thin plate-like crystals form a layered structure in water-based coating to prevent permeation of oxygen and water vapor, and as a result, high barrier properties can be obtained.
Bentonite is commercially available from, for example, Hojun Corporation, Mizusawa Chemical Industry Co., Ltd., Kunimine Industry Co., Ltd., and the like.

Ethylene-modified polyvinyl alcohol is polyvinyl alcohol modified by introducing an ethylene group into the main chain of polyvinyl alcohol. In some embodiments, the content of ethylene groups in the ethylene-modified polyvinyl alcohol molecule is 1 mol % or more and 10 mol % or less. In some embodiments, the ethylene-modified polyvinyl alcohol has a number average degree of polymerization of 200 or more and 4000 or less. In some embodiments, the degree of saponification of the ethylene-modified polyvinyl alcohol is 90 mol% or more and 99.5 mol% or less. The reason for these is that the oxygen barrier property of the paper packaging material is improved and water resistance can be obtained. In at least one embodiment, the ethylene-modified polyvinyl alcohol has an ethylene group content of 1 mol% or more and 10 mol% or less, a number average degree of polymerization of 200 or more and 4000 or less, and a saponification degree of 90 mol% or more and 99.5 mol%. It is below.
Ethylene-modified polyvinyl alcohol is commercially available from Kuraray Co., Ltd., for example.

The second coating layer contains an ionomer resin composed of a copolymer of ethylene and an unsaturated carboxylic acid-based monomer, and bentonite. The second coating layer mainly functions as a water vapor barrier layer. In some embodiments, the second coating layer has a total content of an ionomer resin comprising a copolymer of ethylene and an unsaturated carboxylic acid-based monomer and bentonite in the second coating layer. It is 80% by mass or more relative to the dry solid content forming the layer. The reason for this is that the water vapor barrier property of the paper packaging material is improved. In some embodiments, the content of the ionomer resin in the second coating layer is 20 parts by mass or more and 500 parts by mass or less with respect to 100 parts by mass of bentonite. In at least one embodiment, the content of the ionomer resin in the second coating layer is 50 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of bentonite. The reason for these is that the water vapor barrier properties of the paper packaging material are particularly improved. In some embodiments, the second coating layer has a dry solid content of 3 g/m ² or more and 15 g/m ² or less. The reason for this is that the water vapor barrier property of the paper packaging material is improved.
In at least one embodiment, the second coating layer has a total content of an ionomer resin comprising a copolymer of ethylene and an unsaturated carboxylic acid-based monomer in the second coating layer and bentonite 80% by mass or more of the dry solid content forming the layer, and the content of the ionomer resin in the second coating layer is 50 parts by mass or more and 200 parts by mass with respect to 100 parts by mass of bentonite in the second coating layer and the coating amount of the second coating layer is 3 g/m ² or more and 15 g/m ² or less in dry solid content.

The second coating layer may contain various additives conventionally known in the field of coated paper within limits that do not impair the effects of the present invention. Examples of additives include antifoaming agents, dispersants, wetting agents, pigments other than bentonite, resins other than ionomer resins composed of copolymers of ethylene and unsaturated carboxylic acid monomers, and colorants. be able to.

The bentonite contained in the second coating layer is the same as the bentonite contained in the first coating layer, and the description is omitted here.

An ionomer resin comprising a copolymer of ethylene and an unsaturated carboxylic acid-based monomer has at least It is a resin partially neutralized with metal ions. Examples of the metal ions include monovalent cations such as sodium ions, potassium ions and silver ions, divalent cations such as copper ions, calcium ions, barium ions, zinc ions and magnesium ions, and aluminum ions. Mention may be made of trivalent cations. In some embodiments, the metal ions are one or two selected from the group consisting of sodium ions and potassium ions. In some embodiments, the ionomer resin contains 30 mol % or more of the metal ion-neutralized monomer relative to the unsaturated carboxylic acid-based monomer. The reason for these is that the water vapor barrier property of the paper packaging material is improved.

The unsaturated carboxylic acid-based monomer is a monomer having at least one carboxyl group in ethylene series hydrocarbons, and includes carboxylic acid, carboxylate and carboxylate based on the state of the carboxyl group. Unsaturated carboxylic acid-based monomers include, for example, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid and butentricarboxylic acid, and unsaturated carboxylic acid salts thereof. , as well as the unsaturated carboxylic acid esters of these esters.

An ionomer resin composed of a copolymer of ethylene and an unsaturated carboxylic acid-based monomer has an unsaturated carboxylic acid-based monomer in the copolymer in order to neutralize the carboxyl groups of the copolymer with metal ions. It has at least an unsaturated carboxylic acid in the mer.

In some embodiments, the ionomer resin comprising a copolymer of ethylene and an unsaturated carboxylic acid monomer is a compound represented by the following general formula.

x, y and z represent the composition ratio of each monomer in the copolymer. R1 and R2 represent a hydrogen atom, an unsubstituted alkyl group or a substituted alkyl group. R1 and R2 may be different. M represents the metal of the metal ion that neutralizes the carboxy group. In some embodiments, R1 and R2 are hydrogen atoms or unsubstituted alkyl groups having 1 to 4 carbon atoms. Also, in some embodiments, M is one or two selected from sodium and potassium. In at least one embodiment, R1 and R2 are hydrogen atoms or unsubstituted alkyl groups having 1 to 4 carbon atoms, and M is one or two selected from sodium and potassium. The reason for these is that the water vapor barrier properties are improved.
In some embodiments, ionomer resins comprising copolymers of ethylene and unsaturated carboxylic acid-based monomers include acrylic acid or methacrylic acid as the unsaturated carboxylic acid-based monomers. The reason for this is that it is readily available as an ionomer resin.
Ionomer resins comprising copolymers of ethylene and unsaturated carboxylic acid monomers are commercially available from Mitsui Chemicals, Inc., for example.

A paper packaging material having a first coating layer and a second coating layer on a paper support can have oxygen barrier properties and water vapor barrier properties comparable to a resin layer containing polyvinylidene chloride. can. Moreover, the paper packaging material is excellent in disaggregation properties due to the synergistic effect of the paper support and the first coating layer.

The third coating layer is a heat seal layer. The heat-sealing layer has a sealing function capable of sealing the paper packaging material into a bag by heat-sealing. The third coating layer, which is a heat-sealing layer, contains a thermoplastic resin having heat-sealing properties. In some embodiments, the third coating layer is 70% by weight or more of the dry solid content of the heat-sealable thermoplastic resin forming the third coating layer. In at least one embodiment, the third coating layer is 85% by mass or more of the dry solid content of the heat-sealable thermoplastic resin forming the third coating layer. The reason for these is that the seal strength is improved.

The third coating layer may contain various additives conventionally known in the field of coated paper within limits that do not impair the heat-sealing property. Examples of additives include starch, various modified starches, polysaccharides such as hydroxyethyl cellulose, methyl cellulose and carboxymethyl cellulose, resins other than thermoplastic resins having heat-sealing properties, release agents, antifoaming agents, dispersants, and wetting agents. , pigments, and coloring agents.

The coating amount of the third coating layer is not particularly limited as long as the heat-sealing property is exhibited. In some embodiments, the coating amount of the third coating layer is 15% by mass or more and 35% by mass or less as a dry solid content relative to the basis weight (g/m ² ) of the paper support. The reason for this is that the process of heat sealing is facilitated.

By providing the first coating layer, the second coating layer and the third coating layer on the paper support, the paper packaging material has oxygen barrier properties and water vapor barrier properties, It has excellent disaggregation properties and good sealing workability by heat sealing.

Thermoplastic resins having heat-sealing properties are conventionally known resins in the field of packaging materials. Examples of heat-sealable thermoplastic resins include polyolefins such as polyethylene and polypropylene, acid-modified polyolefins such as acid-modified polyethylene and acid-modified polypropylene, chlorinated polyolefins such as chlorinated polyethylene and chlorinated polypropylene, and unsaturated carboxylic acids. Polymers of acid-based monomers, copolymers of ethylene and unsaturated carboxylic acid-based monomers, ionomer resins composed of copolymers of ethylene and unsaturated carboxylic acid-based monomers, styrene and unsaturated carboxylic acid-based monomers Copolymers with acid monomers, copolymers of acrylonitrile and unsaturated carboxylic acid monomers, copolymers of methacrylonitrile and unsaturated carboxylic acid monomers, ethylene and acrylonitrile Copolymers, copolymers of ethylene and methacrylonitrile, ionomer resins composed of copolymers of ethylene and urethane monomers, copolymers of ethylene and vinyl acetate, copolymers of styrene and butadiene , polyamides, polylactic acid and its salts, and biodegradable resins such as polybutylene succinate and polybutylene succinate adipate.

More specific heat-sealable thermoplastic resins include polyacrylic acid, polymethacrylic acid, polymethyl acrylate, polyethyl acrylate, polybutyl acrylate, polymethyl methacrylate, polyethyl methacrylate, and polymethacrylic acid. Butyl, ethylene acrylic acid copolymer, ethylene methacrylic acid copolymer, ethylene methyl acrylate copolymer, ethylene ethyl acrylate copolymer, ethylene butyl acrylate copolymer, ethylene methyl methacrylate copolymer, ethylene methacryl Ethyl acid copolymer, ethylene butyl methacrylate copolymer, ethylene acrylate methyl acrylate copolymer, ethylene acrylate ethyl acrylate copolymer, ethylene acrylate butyl acrylate copolymer, ethylene methacrylate methyl methacrylate Copolymer, ethylene methacrylate ethyl methacrylate copolymer, ethylene methacrylate butyl methacrylate copolymer, styrene acrylic acid copolymer, styrene methacrylate copolymer, styrene methyl acrylate copolymer, styrene ethyl acrylate Copolymer, styrene butyl acrylate copolymer, styrene methyl methacrylate copolymer, styrene ethyl methacrylate copolymer, styrene butyl methacrylate copolymer, styrene acrylate methyl acrylate copolymer, styrene acrylate acrylic acid Ethyl acid copolymer, styrene butyl acrylate copolymer, styrene methyl methacrylate methacrylate copolymer, styrene ethyl methacrylate methacrylate copolymer, styrene methacrylate butyl methacrylate copolymer, polyacrylonitrile, poly Methacrylonitrile, ethylene acrylonitrile copolymer, ethylene methacrylonitrile copolymer, styrene acrylonitrile copolymer, styrene methacrylonitrile copolymer, ionomer resin of ethylene acrylic acid copolymer, ionomer of ethylene methacrylic acid copolymer Resin, ionomer resin of ethylene acrylate methyl acrylate copolymer, ionomer resin of ethylene methacrylate methyl methacrylate copolymer, ethylene vinyl acetate copolymer, styrene-butadiene copolymer, nylon, polylactic acid and salts thereof, and Biodegradable resins such as polybutylene succinate and polybutylene succinate adipate can be mentioned.

Each layer of the first coating layer, the second coating layer and the third coating layer is formed by coating a coating solution forming each layer on a paper support or layer using a conventionally known coating device and drying device. It can be obtained by processing and drying. Examples of coating equipment include film press coaters, air knife coaters, rod coaters, rod blade coaters, bar coaters, blade coaters, gravure coaters, curtain coaters, E bar coaters, and film transfer coaters. Examples of the drying device include hot air dryers such as straight tunnel dryers, arch dryers, air loop dryers, sine curve air float dryers, infrared heating dryers, microwave dryers and the like.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples. Here, "mass parts" and "mass %" represent respective values of dry solid content or substantial component. Coating weights represent dry solids values.

(Example 1)
<Production of paper support>
50 parts by mass of LBKP prepared to have a freeness of 450 mlcsf by beating and 50 parts by weight of NBKP prepared to have a freeness of 480 mlcsf were dispersed in water using a pulper to obtain a dispersion. 1 part by mass of aluminum sulfate, 7 parts by mass of light calcium carbonate, 0.8 parts by mass of cationized starch, 0.2 parts by mass of rosin-based sizing agent, and 0.2 parts by mass of a yield improver for the dispersion containing 100 parts by mass of KP. 01 parts by mass was added and further dispersed using a pulper. Thereafter, the mixture was stirred with an agitator (registered trademark) in a chest tank to obtain a stock for papermaking. The stock was made into paper by a Fourdrinier paper machine to obtain a base paper having a basis weight of 60 g/m ² . The base paper was calendered at a temperature of 30° C., a processing speed of 3 m/min, and a linear pressure of 23 kg/cm using a laboratory soft calender to obtain a paper support. The resulting paper support had a Parkerprint Surf surface roughness of 3.1 μm as measured using a Messmer Parkerprint Surf Roughness Tester, Model 58-06-00.

<Coating solution for forming the first coating layer>
A dispersion liquid was obtained by pulverizing and dispersing bentonite (Bengel (registered trademark) HVP, Hojun Co., Ltd.) in water with a high-speed mixer. An aqueous solution of ethylene-modified polyvinyl alcohol is mixed so that 100 parts by mass of ethylene-modified polyvinyl alcohol (Exeval (registered trademark) AQ-4104, Kuraray Co., Ltd.) is added to the dispersion liquid containing 100 parts by mass of bentonite, and then defoaming is performed. 0.2 parts by mass of the agent was added to obtain a coating liquid for forming the first coating layer.

<Coating liquid for forming the second coating layer>
A dispersion liquid was obtained by pulverizing and dispersing bentonite (Bengel HVP, Hojun Co., Ltd.) in water with a high-speed mixer. Ionomer resin (Chemipearl (registered trademark) S-300, Mitsui Chemicals, Inc., unsaturated carboxylic acid 100 parts by mass containing methacrylic acid as a system monomer) was mixed, and 0.2 parts by mass of an antifoaming agent was further added to obtain a coating liquid for forming a second coating layer.

<Coating liquid for forming the third coating layer>
A copolymer of ethylene and an unsaturated carboxylic acid-based monomer (Zaixen (registered trademark) A, Sumitomo Seika Co., Ltd., containing acrylic acid as an unsaturated carboxylic acid-based monomer) is used as a thermoplastic resin having heat-sealing properties. ) and 0.5 parts by mass of an antifoaming agent were dispersed in water to obtain a coating solution for forming a third coating layer.

<Paper packaging materials>
A coating solution for forming a first coating layer was applied to one side of the paper support with a rod coater and dried with a hot air dryer. The concentration of the coating solution and/or the conditions of the coater were adjusted so that the coating amount was 4 g/m ² . Next, a coating liquid for forming a second coating layer was applied to the first coating layer with an air knife coater and dried with a hot air dryer. The concentration of the coating liquid and/or the conditions of the coater were adjusted so that the coating amount was 5 g/m ² . Subsequently, a coating liquid for forming a third coating layer was applied to the second coating layer with an air knife coater and dried with a hot air dryer. The concentration of the coating liquid and/or the conditions of the coater were adjusted so that the coating amount was 15 g/m ² .
As described above, a paper packaging material having a first coating layer, a second coating layer and a third coating layer on the paper support was obtained.

(Example 2)
A paper packaging material was obtained in the same manner as in Example 1, except that the linear pressure was changed to 20 kg/cm. The paper support had a Parkerprint Surf surface roughness of 3.5 μm measured using a Messmer Parkerprint Surf Roughness Tester, Model 58-06-00.

(Comparative example 1)
A paper packaging material was obtained in the same manner as in Example 1, except that the linear pressure was changed to 33 kg/cm. The paper support had a Parkerprint Surf surface roughness of 1.5 μm measured using a Messmer Parkerprint Surf Roughness Tester, Model 58-06-00.

(Comparative example 2)
A paper packaging material was obtained in the same manner as in Example 1, except that the linear pressure was changed to 8.3 kg/cm. The paper support had a Parkerprint Surf surface roughness of 4.6 μm measured using a Messmer Parkerprint Surf roughness tester, model 58-06-00.

(Comparative Example 3)
A paper packaging material was obtained in the same manner as in Example 1, except that the linear pressure was changed to 5 kg/cm. The paper support had a Parkerprint Surf surface roughness of 6.2 μm measured using a Messmer Parkerprint Surf Roughness Tester, Model 58-06-00.

(Comparative Example 4)
A paper packaging material was obtained in the same manner as in Example 1, except that the bentonite in the coating liquid forming the first coating layer was changed to kaolin (ASP (registered trademark) 200, BASF). .

(Comparative Example 5)
Paper packaging in the same manner as in Example 1 except that in Example 1, the bentonite in the coating liquid forming the second coating layer was changed to light calcium carbonate (Callite (registered trademark) SA, Taiyo Kagaku Kogyo Co., Ltd.) got the material.

(Comparative Example 6)
In Example 1, the same as Example 1 except that the ethylene-modified polyvinyl alcohol in the coating solution forming the first coating layer was changed to unmodified polyvinyl alcohol (Gosenol (registered trademark) N-300, Mitsubishi Chemical Co.). A paper packaging material was obtained.

(Comparative Example 7)
In Example 1, paper was prepared in the same manner as in Example 1, except that the ionomer resin in the coating liquid forming the second coating layer was changed to a styrene-butadiene copolymer (Nipol (registered trademark) LX430, Nippon Zeon Co., Ltd.). A packaging material was obtained.

(Comparative Example 8)
A paper packaging material was obtained in the same manner as in Example 1, except that the coating solution for forming the third coating layer was not applied.

(Comparative Example 9)
A coating liquid for forming the first coating layer described below was applied to one side of the paper support with a rod coater and dried with a hot air dryer. The concentration of the coating liquid and/or the conditions of the coater were adjusted so that the coating amount was 9 g/m ² . Next, a coating liquid for forming the third coating layer of Example 1 as the second coating layer was applied to the first coating layer with an air knife coater and dried with a hot air dryer. The concentration of the coating liquid and/or the conditions of the coater were adjusted so that the coating amount was 15 g/m ² .
As described above, a paper packaging material having two layers on the paper support was obtained.

<Coating solution for forming the first coating layer>
100 parts by mass of polyvinylidene chloride (Saran Latex (registered trademark) L411A, Asahi Kasei Co., Ltd.) and 0.2 parts by mass of an antifoaming agent were dispersed in water to obtain a coating solution for forming a first coating layer.

The paper packaging materials of each example and each comparative example were evaluated for oxygen barrier property, water vapor barrier property, disaggregation property, and sealing processability. Results are listed in Table 1.

<Evaluation of oxygen barrier properties>
Evaluation of oxygen barrier property is performed according to ISO15105-2:2003 "Plastics-Film and sheeting-Determination of gas-transmission rate-Part2: Equal-pressure method" Test Method-Part 2: Isobaric Method”), the results were obtained using an oxygen permeability measuring device (OX-TRAN-2/22L, MOCON). The measurement was performed using the side without the first coating layer and the second coating layer as the gas supply surface. Oxygen gas was used as the gas for the gas permeability test. The temperature and humidity conditions were 23±0.5° C. and 85±2% relative humidity. In the present invention, the paper packaging material is considered to have oxygen barrier properties if it has an oxygen permeability of 5 cc/m ² ·24 h·atm or less. It should be noted that the smaller the value of the oxygen permeability, the better the oxygen barrier properties.

<Evaluation of water vapor barrier property>
The water vapor barrier properties were evaluated from the results of measurements carried out according to JIS Z0208:1976 "Moisture Permeability Test Method for Moisture-Proof Packaging Materials (Cup Method)". The measurement was carried out with the side having the first coating layer and the second coating layer facing outward with respect to the paper support. The temperature and humidity conditions were 40±0.5° C. and 90±2% relative humidity. In the present invention, the paper packaging material is assumed to have a water vapor barrier property if it has a moisture permeability of 10 g/m ² ·24 h or less. Incidentally, the smaller the moisture permeability value, the better the water vapor barrier property.

<Disaggregation>
Using a standard pulp disintegrator (capacity 2 L, Kumagai Riki Kogyo Co., Ltd.), 15 g of paper packaging material cut into 2 cm squares was added to 1.5 L of water and stirred at 3000 rpm for 20 minutes. The disaggregation property was evaluated by visually observing the state of separation of the resin from the paper support in the disaggregation material according to the following criteria. In the present invention, if the paper packaging material is evaluated as A, it is considered to be excellent in disaggregation.
A: The resin is separated from the disaggregated material of the paper support.
B: The resin cannot be separated from the disaggregated material of the paper support.

<Encapsulation workability by heat sealing>
In Comparative Example 8, in which the coating liquid for forming the third coating layer, which is a heat seal layer, was not applied, sealing workability by heat sealing was not evaluated.
For evaluation of sealing processability, 10 pillow bags were prepared so that the third coating layer of the paper packaging material was on the inside, and the occurrence of twists and wrinkles in the heat-sealed portion of the pillow bag was visually observed. It was performed according to the following criteria. A heat seal tester (TP-701-B, Tester Sangyo Co., Ltd.) was used for heat sealing. In the present invention, if the paper packaging material is evaluated as A, the sealing workability is good.
A: No kinks or wrinkles were observed in 10 parts of the pillow bag.
B: Occurrence of kinks and/or wrinkles is observed in at least part of the pillow bag.

It can be seen that Examples 1 and 2, which correspond to the present invention, are paper packaging materials having oxygen barrier properties and water vapor barrier properties, excellent disaggregation properties, and excellent sealing processability by heat sealing. On the other hand, it can be seen that Comparative Examples 1 to 9, which do not satisfy the constitution of the present invention, are paper packaging materials that cannot satisfy at least one of the effects of the present invention.

Claims (1)

a paper support, a first coating layer on one side of said paper support, a second coating layer outside said first coating layer relative to the paper support, and said second coating layer relative to said paper support It has a third coating layer on the outside of the second coating layer, the paper support has a Parker Print Surf surface roughness of 2 μm or more and 4 μm or less in accordance with ISO8791-4:1992, and the first coating layer is It contains ethylene-modified polyvinyl alcohol and bentonite, the second coating layer contains an ionomer resin and bentonite composed of a copolymer of ethylene and an unsaturated carboxylic acid-based monomer, and the third coating layer is heated A paper packaging material that is a sealing layer.