JP2025015607A - Packaging material - Google Patents

Abstract

To provide a packaging material having adhesivity of a face to be heat sealed, heat sealability and anti-blocking property.SOLUTION: A packaging material has a paper holding body and one or two or more coating layers on one surface of the paper holding body. The paper holding body has density of 0.83 g/cm3 or more and 1.03 g/cm3 or less, and 2.3 mass% or less of ash. In the packaging material, the outermost coating layer with the paper holding body as a reference in the coating layer, contains at least ionomer resin of ethylene unsaturated carboxylic acid copolymer.SELECTED DRAWING: None

Description

The present invention relates to a packaging material made of a paper support and suitable for heat sealing, and in particular to a packaging material used for a bag-shaped secondary package.

Food products such as confectioneries displayed in retail stores are often packaged in a primary package containing the food product and a secondary package containing one or more of the primary packages.
Usually, the primary packaging exists to protect food, and the secondary packaging exists to protect the primary packaging. There are bag-type and box-type secondary packaging. The bag-type secondary packaging is generally made by covering the primary packaging with a packaging material and heat-sealing the end face of the packaging material to form a bag shape. Therefore, the packaging material used for the bag-type secondary packaging needs to be heat-sealable.

Packaging materials having heat sealability are known. For example, a packaging paper having at least one heat seal layer on at least one surface of a paper base material, the heat seal layer containing an ionomer, and the dry coating weight of the heat seal layer is 2 to 10 g/ ^m2 in total is known (see, for example, Patent Document 1).

JP 2020-117311 A

In recent years, due to environmental pollution caused by microplastics, plastic films have tended not to be used in the field of packaging materials. Paper supports are a promising alternative to plastic films. Patent Document 1 also discloses packaging paper that replaces plastic with paper to reduce the amount of plastic used. However, paper supports are less smooth than plastic films. Therefore, the packaging material needs to have good adhesion on the surface to be heat-sealed so that gaps do not occur at the heat-sealed areas or the heat-sealed areas have uniform strength. On the other hand, improving the adhesion of the surface to be heat-sealed in the packaging material can cause blocking between packaging materials.

A particular issue with secondary packaging is the heat problem that occurs during heat sealing. That is, when the packaging material is heat sealed to form a bag, the heat from the heat sealing process can damage the food in the primary package. For example, if the food is chocolate, the chocolate may melt during heat sealing. When handling food, heat sealing must be achieved at a relatively low temperature in a short time.

In view of the above, it is an object of the present invention to provide a packaging material having the following qualities:
(1) The surfaces to be heat sealed must adhere well (adhesion).
(2) The ability to perform heat sealing at a relatively low temperature in a short time (heat sealability).
(3) Ability to suppress blocking between packaging materials (blocking resistance).

As a result of intensive research, the inventors have found that the object of the present invention is achieved as follows.

[1] A packaging material having a paper support and one or more coating layers on one side of the paper support, the paper support having a density of 0.83 g/cm3 ^{or more} and 1.03 g/cm3 ^or less and an ash content of 2.3 mass% or less, and an outermost coating layer located outermost relative to the paper support in the coating layers, which contains at least an ionomer resin of an ethylene-unsaturated carboxylic acid copolymer.

[2] The packaging material described in [1] above, in which the outermost coating layer is a layer that does not substantially contain an inorganic pigment.

The present invention provides a packaging material that has adhesion, heat sealability, and blocking resistance.

The packaging material has a paper support and one or more coating layers on one side of the paper support. In the coating layers, the coating layer located outermost based on the paper support is called the outermost coating layer. When there is one coating layer, the coating layer becomes the outermost coating layer. When there are two or more coating layers, the coating layer present between the base paper and the outermost coating layer is not particularly limited. In some embodiments, the coating layer present between the base paper and the outermost coating layer is provided to impart various functions to the packaging material as necessary. Examples of the coating layer include a gas barrier layer containing a gas barrier agent, a water vapor barrier layer containing a water vapor barrier agent, an oil barrier layer containing an oil-resistant agent, and a heat insulating layer containing a heat insulating material. In some embodiments, in the case of a packaging material used for a secondary package, the coating layer is one layer including the outermost coating layer. That is, the coating layer is only the outermost coating layer. The reason for this is that the manufacturing cost is advantageous as a packaging material used for a secondary package. The coating layer may be present on one or both sides of the paper support. In some embodiments, the packaging material has an outermost coating layer on only one side of the paper support. In some embodiments, a packaging material having an outermost coating layer on only one side of the paper support has a conventionally known printing coating layer or backcoat layer on the opposite side of the paper support for the purpose of improving printability or dimensional stability. As a packaging material used for secondary packaging, the side of the packaging material facing the contents is the side of the packaging material having the outermost coating layer.

The paper support is a base paper made by a conventional papermaking method under acidic, neutral or alkaline conditions using a paper stock in which various additives such as fillers, internal sizing agents, fixing agents, retention agents and paper strength agents are added as necessary to a slurry consisting of wood pulp and/or non-wood pulp; base paper obtained by subjecting the base paper to a calendaring treatment; fine paper obtained by size pressing the base paper with a size press liquid containing a surface sizing agent; or fine paper obtained by subjecting the fine paper to a calendaring treatment.

The above-mentioned paper stock may contain one or more additives selected from the group consisting of pigment dispersants, binders, thickeners, flow improvers, bulking agents, defoamers, foam inhibitors, release agents, foaming agents, penetrating agents, coloring dyes, coloring pigments, fluorescent brighteners, ultraviolet absorbers, antioxidants, preservatives, mold inhibitors, and water-resistant agents, as appropriate, within the range that does not impair the desired effects of the present invention.

Calendering is a process in which paper is passed between rolls to average out its smoothness and thickness. Examples of calendering devices include machine calenders, soft nip calenders, super calenders, multi-stage calenders, and multi-nip calenders.

Size pressing is a process that imparts water resistance to the surface of paper. Size pressing is carried out using a size pressing device that is conventionally known in the papermaking field. Examples of size pressing devices include inclined size presses, horizontal size presses, film transfers such as rod metering size presses, roll metering size presses, and blade metering size presses, rod metering size presses such as shim sizers, optisizers, and speed sizers, roll metering size presses such as gate roll coaters, bill blade coaters, twin blade coaters, Belbapa coaters, tab size presses, and calendar size presses.

Wood pulp is well known in the papermaking field, and examples of wood pulp include chemical pulp such as Leaf Bleached Kraft Pulp (LBKP) and Needle Bleached Kraft Pulp (NBKP), mechanical pulp such as Groundwood Pulp (GP), Pressure GroundWood pulp (PGW), Refiner Mechanical Pulp (RMP), ThermoMechanical Pulp (TMP), ChemiThermoMechanical Pulp (CTMP), ChemiMechanical Pulp (CMP), and ChemiGroundwood Pulp (CGP), and waste paper pulp such as DeInked Pulp (DIP).
Non-wood pulp is pulp made of non-wood fibers conventionally known in the papermaking field. Examples of raw materials for non-wood fibers include woody bast such as paper mulberry, Mitsumata, and Gampi, herbaceous bast such as flax, hemp, and kenaf, leaf fibers such as Manila hemp, abaca, and sisal, grass plants such as rice straw, wheat straw, sugarcane bagasse, bamboo, and esparto, and seed hairs such as cotton and linter.
The wood pulp and/or non-wood pulp is one or more selected from the group consisting of the above-mentioned wood pulps and non-wood pulps.

In some embodiments, the base paper for the paper support contains at least NBKP and LBKP as pulp. In some embodiments, the total content of NBKP and LBKP in the base paper for the paper support is 90% by mass or more relative to the pulp in the base paper. This is because the strength of the base paper is improved. The paper strength is important for packaging materials used for secondary packaging, as they also serve the purpose of protecting the primary packaging during transportation.

The filler is an inorganic pigment conventionally known in the papermaking field. Examples of inorganic pigments include light calcium carbonate, heavy 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 hydrate, aluminum hydroxide, lithopone, zeolite, magnesium carbonate, and magnesium hydroxide. The filler is one or more selected from the group consisting of the inorganic pigments.
In some embodiments, the base paper for the paper support is substantially free of filler. The reason for this is that the strength of the base paper is improved. This "substantially free" means that if the filler content is such that the strength of the base paper is not deteriorated, then this corresponds to "free of filler." In at least one embodiment, the filler content in the base paper is 3% by mass or less relative to the pulp in the base paper. The reason for this is that if the filler content is 3% by mass or less relative to the pulp, then the strength of the base paper is not deteriorated.

The sizing agent is a sizing agent conventionally known in the papermaking field.
Examples of internal sizing agents added to the paper stock include rosin-based sizing agents for acidic paper, and alkenyl succinic anhydride, alkyl ketene dimer, neutral rosin-based sizing agents, and cationic styrene acrylic-based sizing agents for neutral paper.
The surface sizing agent used in the size press liquid is a known one in the papermaking field, and examples of the surface sizing agent include starch-based sizing agents, cellulose-based sizing agents, polyvinyl alcohol-based sizing agents, styrene-acrylic sizing agents, olefin-based sizing agents, styrene-maleic acid-based sizing agents, and acrylamide-based sizing agents.
In some embodiments, the paper support is a wood-free paper obtained by size pressing a base paper with a size press liquid containing a surface sizing agent, because this improves adhesion and heat sealability.

The fixing agent is a fixing agent conventionally known in the papermaking field. The fixing agent improves the adhesion of the sizing agent. Examples of fixing agents include inorganic salts such as aluminum sulfate.

The retention agent is a retention agent that is conventionally known in the papermaking field. The retention agent improves the retention of various additives added to the paper stock. Examples of retention agents include organic polymer electrolytes such as polyacrylamide, polyamide, and polyethyleneimine, as well as polyethylene oxide.

The paper strength agent is a paper strength agent that is conventionally known in the papermaking field. The paper strength agent improves the strength of the base paper. Examples of the paper strength agent include cationic starch, dialdehyde starch, vegetable gum, urea formaldehyde resin, polyamide polyamine epichlorohydrin polycondensate, and glyoxal modified polyacrylamide.

The density of the paper support is 0.83 g/cm ³ or more and 1.03 g/cm ³ or less. The density of the paper support is related to the smoothness of the paper support, and therefore affects the formation of a coating layer by applying a coating layer coating liquid to the paper support. If the density is high, the smoothness increases, and if the density is low, the smoothness decreases. On the other hand, if the density of the paper support is too high, it adversely affects the blocking resistance. The density is a value measured in accordance with ISO534:2011 "Paper and board-Determination of thickness, density and specific volume". The density of the paper support is a parameter conventionally known in the papermaking field, and can be adjusted by, for example, papermaking conditions such as press part conditions, the type and beating degree of pulp, the type and content of filler, and the presence or absence and conditions of calendaring. Generally, the density of the paper support is increased by increasing the nip pressure of the press part, strengthening the beating of the pulp, blending a filler, performing a size press, performing a calendar treatment, etc. In some embodiments, the density of the paper support is adjusted by a size press and a calendar treatment. The reason for this is that the smoothness of the paper support is improved, which has a positive effect on adhesion and heat sealability.

The paper support has an ash content of 2.3% by mass or less. The ash content of the paper support indicates the content of metal components derived from fillers and inorganic salts contained in the paper support. The ash content of the paper support is related to the permeability of the paper support, and therefore affects the formation of a coating layer in which a coating layer coating liquid is applied to the paper support. High ash content increases permeability, and low ash content decreases permeability. The ash content is a value measured in accordance with ISO1762:2019 "Paper, board, pulps and cellulose nanomaterials - Determination of residue (ash content) on ignition at 525 degrees C". The ash content of the paper support is a parameter conventionally known in the papermaking field, and can be adjusted by, for example, the type and content of fillers and/or inorganic salts as fixing agents. In some embodiments, the base paper for the paper support contains substantially no fillers. This is because the ash content is easily adjusted to 2.3% by mass or less.

The paper support has a density of 0.83 g/ ^cm3 to 1.03 g/ ^cm3 and an ash content of 2.3 mass% or less. A paper support having a density and ash content within the above ranges has appropriate smoothness and permeability. The packaging material exhibits adhesion, heat sealability and blocking resistance due to the synergistic effect of the paper support having the above physical properties and the outermost coating layer described below. If the density or ash content of the packaging material is outside the above ranges, it will not be able to satisfy at least one of the effects of the present invention.

In some embodiments, the paper support has an opacity of 70% or more and 85% or less. This is because the adhesion, heat sealability and/or blocking resistance are improved. The opacity is a value measured in accordance with ISO2471:2008 "Paper and board-Determination of opacity (paper backing)-Diffuse reflectance method".
The opacity of the paper support is a parameter conventionally known in the papermaking field, and can be adjusted by, for example, the type and degree of beating of the pulp, the type and content of the filler, and the presence or absence and conditions of calendaring. In general, weakening the beating of the pulp, blending a filler, and performing a size press increase the opacity of the paper support, while performing a calendaring process decreases the opacity of the paper support. The opacity of the paper support indirectly represents the void state of the paper support. If voids that cause light scattering are present in the paper support, the opacity of the paper support increases. On the other hand, if the voids in the paper support that cause light scattering are crushed or filled, the opacity of the paper support decreases. Also, if the thickness of the paper support decreases, the opacity of the paper support decreases.

The outermost coating layer contains an ionomer resin of an ethylene-unsaturated carboxylic acid copolymer. The ionomer resin of an ethylene-unsaturated carboxylic acid copolymer is a compound represented by the following general formula:

x, y, and z represent the composition ratio of each monomer in the resin. R1 and R2 represent a hydrogen atom or an alkyl group. In some embodiments, the alkyl group is an alkyl group having 1 to 4 carbon atoms. M represents a metal that forms a salt with a carboxyl group. The M is, for example, sodium, potassium, calcium, magnesium, zinc, etc. In some embodiments, the M is one or more selected from the group consisting of alkali metals and alkaline earth metals. Ionomer resins of ethylene unsaturated carboxylic acid copolymers are commercially available from, for example, Mitsui Chemicals, Inc., Dow Mitsui Polychemicals, Maruyoshi Chemical Co., Ltd., etc.

The ionomer resin of ethylene-unsaturated carboxylic acid copolymer has adhesiveness due to diffusion of cross-linked bonds of metal ions by heat, and as a result, has excellent heat sealability. Moreover, the inventors presume that the ionomer resin of ethylene-unsaturated carboxylic acid copolymer forms a microcrystalline structure with M as a nucleus in the outermost coating layer formed by coating and drying, and that the microcrystalline structure contributes to blocking resistance. The inventors believe that the microcrystalline structure is well formed and blocking resistance can be expressed when the paper support has a density of 0.83 g/cm3 or ^more and 1.03 g/cm3 ^or less and an ash content of 2.3 mass% or less.

The outermost coating layer may contain a conventionally known resin other than the ionomer resin of an ethylene unsaturated carboxylic acid copolymer. Examples of the resin include conjugated diene resins such as styrene butadiene copolymer resins and acrylonitrile butadiene copolymer resins, acrylic resins such as acrylic acid ester or methacrylic acid ester polymer resins or methacrylic acid ester butadiene copolymer resins, vinyl resins such as vinyl chloride resins, vinylidene chloride resins, ethylene vinyl acetate copolymer resins and vinyl chloride vinyl acetate copolymer resins, thermosetting synthetic resins such as polyurethane resins, alkyd resins, polyester resins, melamine resins and urea resins, starches such as natural rubber, starch, various processed starches and various modified starches, celluloses such as carboxymethyl cellulose and hydroxyethyl cellulose, natural polymer resins such as casein, gelatin and soybean protein or derivatives thereof, polyvinylpyrrolidone, polyvinyl alcohol and modified polyvinyl alcohol, polypropylene glycol, and polyethylene glycol. In some embodiments, the outermost coating layer may contain various conventionally known auxiliaries in addition to the ionomer resin of an ethylene-unsaturated carboxylic acid copolymer, such as a viscosity modifier, a defoamer, a surfactant, a leveling agent, and a colorant.
In some embodiments, the outermost coating layer contains 90% by weight or more of an ionomer resin of an ethylene-unsaturated carboxylic acid copolymer based on the dry solid content of the outermost coating layer, because this improves adhesion, heat sealability, and/or blocking resistance.

In some embodiments, the outermost coating layer is substantially free of inorganic pigments. This is because the heat sealability is improved. "Substantially free" here refers to the inorganic pigment content being 2% by mass or less based on the dry solid content of the outermost coating layer. The inorganic pigments are those conventionally known in the papermaking field, and are similar to the inorganic pigments exemplified above as fillers.

The coating layers, including the outermost coating layer, can be provided by applying and drying a coating layer coating liquid to a paper support. Examples of the coating and drying method include a method of applying and drying a coating layer coating liquid using a coating device and a drying device conventionally known in the field of coated paper. Examples of the coating device include a film press coater, an air knife coater, a rod blade coater, a bar coater, a blade coater, a gravure coater, a curtain coater, an E-bar coater, and a film transfer coater. Examples of the drying device include various drying devices such as a straight tunnel dryer, an arch dryer, an air loop dryer, a sine curve air float dryer, and other hot air dryers, an infrared heating dryer, and a dryer using microwaves.

In some embodiments, the coating amount of the ionomer resin of ethylene unsaturated carboxylic acid copolymer in the outermost coating layer is 3 g/ ^m2 or more per one side of the paper support in terms of dry solid content. This is because adhesion and heat sealability are improved. There is no particular upper limit to the coating amount. In some embodiments, the upper limit of the coating amount is 8 g/ ^m2 or less in view of the relationship between adhesion and heat sealability and material costs.

The present invention will be described in more detail below with reference to examples. Note that the present invention is not limited to these examples. Here, "parts by mass" and "% by mass" represent the amount of dry solids or the amount of substantial components, respectively. The coating amount of each layer represents the amount of dry solids.

<Paper support>
The following paper materials were prepared.
LBKP (freeness 630 mlcsf) 500 parts by weight NBKP (freeness 470 mlcsf) 500 parts by weight Aluminum sulfate (number of parts is shown in Table 1) Light calcium carbonate (number of parts is shown in Table 1) Cationic starch 12 parts by weight Rosin sizing agent 5 parts by weight Polyacrylamide retention agent 0.1 parts by weight The above-mentioned paper stock was made on a Fourdrinier papermaking machine, and base paper with a basis weight of 54 g/ ^m2 was obtained by adjusting the press part conditions of the papermaking machine. This was subjected to size pressing using oxidized starch as a surface sizing agent. The coating amount of oxidized starch was adjusted in the range of 0.8 g/ ^m2 to 1.8 g/ ^m2 . Next, a supercalendering treatment was performed while adjusting the conditions to obtain a paper support. The density, ash content, and opacity of the obtained paper support are shown in Table 1.

<Coating solution for outermost coating layer>
A coating solution for the outermost coating layer was prepared using water as a medium and containing the following:
Resin 100 parts by mass Calcium carbonate The number of parts is shown in Table 1. The solid content of the coating liquid for the coating layer was adjusted to 28% by mass. The resin is shown in Table 1.

The resins listed in Table 1 are as follows.
Resin 1: Ionomer resin of ethylene unsaturated carboxylic acid copolymer (Mitsui Chemicals, Inc., Chemipearl (registered trademark) S100, Microtrack method average particle size 0.1 μm)
Resin 2: Ionomer resin of ethylene unsaturated carboxylic acid copolymer (Maruyoshi Chemical Industry, MYE-30MAZ, Microtrack method average particle size 0.3 μm)
Resin 3: Ionomer resin of ethylene unsaturated carboxylic acid copolymer (Mitsui Chemicals, Chemipearl S300, Microtrack average particle size 0.5 μm)
Resin 4: Ionomer resin of ethylene unsaturated carboxylic acid copolymer (Mitsui Chemicals, Chemipearl S500, Microtrack average particle size 0.7 μm)
Resin 5: Polyethylene resin (San Nopco, SN Coat 287)
Resin 6: Ethylene methyl methacrylate copolymer resin (Sumitomo Chemical Co., Ltd., Acryft (registered trademark) WK307)

<Packaging materials>
The coating solution for the outermost coating layer was applied to one side of the paper support using an air knife coater and dried using a hot air dryer to obtain a packaging material provided with an outermost coating layer. The coating amount is shown in Table 1.

The resulting packaging material was evaluated as follows:

<Adhesion>
The packaging materials were placed with the surfaces having the outermost coating layers facing each other, and heat sealed using a heat sealer under conditions of a pressure of 2.0 kg/cm ² , 130° C., and 1 second.
The heat-sealed packaging material was cut into 10 pieces with a width of 15 mm, and left to stand at 20°C and 65% RH for 24 hours, after which the edges of the packaging material were lightly pulled by hand several times to release the heat-sealed areas, and the heat-sealed areas were observed. From the observation results, the adhesion was evaluated according to the following criteria. In the present invention, a packaging material that is rated A, B, or C is deemed to have adhesion on the surface to be heat-sealed.
A: There are no gaps in the heat sealed areas.
And the strength is uniform at all 10 heat-sealed points.
B: There are no gaps in the heat sealed areas.
and there is very slight unevenness in strength at 10 heat seal points.
C: There are no gaps in the heat sealed areas.
and slight unevenness in strength at 10 heat seal points.
D: There is a gap at the heat sealed portion.
And/or the strength is uneven at 10 heat-sealed points.

<Heat sealability>
The packaging materials were placed with the surfaces having the outermost coating layers facing each other, and heat sealed using a heat sealer under conditions of a pressure of 2.0 kg/cm ² , a relatively low temperature of 90° C., and a time of 1 second.
The heat-sealed packaging material was cut into a width of 15 mm, and allowed to stand at 20°C and 65% RH for 24 hours. The heat-sealability was then evaluated by measuring the peel strength of the heat-sealed portion using a tensile tester at a pulling speed of 200 mm/min and a pulling angle of 180°. The measurement was performed on 5 samples, and the average value of the 5 samples was recorded. From the measured values, the heat-sealability was evaluated according to the following criteria. In the present invention, a packaging material is deemed to have heat-sealability if it is rated A or B.
A: Value is 16N/15mm or more.
B: The value is 10N/15mm or more and less than 16N/15mm.
C: The value is 4 N/15 mm or more and less than 10 N/15 mm.
D: The value is less than 4N/15mm.

<Blocking resistance>
The packaging material was wound in a roll (length 500 m) on a paper tube with a diameter of 150 mm, with the outermost coating layer on the outside. The roll was left to stand for 24 hours at 20°C and 65% RH in two ways, directly on the surface and suspended in the air. After standing, the packaging material was unwound from the winder. At this time, the state of blocking of the packaging material was visually observed. From the observation results, the blocking resistance was evaluated according to the following criteria. In the present invention, a packaging material is considered to have blocking resistance if it is rated A or B.
A: No blocking was observed in either the upright or suspended method.
B: Very weak blocking was observed when the sample was placed upright.
Blocking by hanging is not permitted.
C: Weak blocking was observed when the sample was placed upright.
Blocking by hanging is not permitted.
D: Blocking was observed using the hanging method.

The evaluation results are shown in Table 1.

From Table 1, it can be seen that Examples 1 to 15, which correspond to the present invention, are packaging materials having adhesion, heat sealability, and blocking resistance, while Comparative Examples 1 to 6, which do not satisfy the constitution of the present invention, are packaging materials that do not satisfy at least one of adhesion, heat sealability, and blocking resistance.
Mainly from the comparison between Examples 3, 14 and 15, it can be seen that when the outermost coating layer is substantially free of inorganic pigments, the packaging material has improved heat sealability.
Mainly by comparing Examples 3, 5, 6, 7, and 8 with Examples 9 and 10, it can be seen that when the opacity of the paper support is 70% or more and 85% or less, the packaging material has improved adhesion, heat sealability, and/or blocking resistance.

The following notes are further provided with respect to the embodiment of the present invention described above.

＜1＞
A packaging material having a paper support and one or more coating layers on one side of the paper support, the paper support having a density of 0.83 g/cm3 or ^more and 1.03 g/cm3 ^or less and an ash content of 2.3 mass% or less, an outermost coating layer located outermost with respect to the paper support among the coating layers contains at least an ionomer resin of an ethylene-unsaturated carboxylic acid copolymer, the opacity of the paper support is 70% or more and 85% or less, and the coating amount of the ionomer resin of an ethylene-unsaturated carboxylic acid copolymer in the outermost coating layer is 3 g/m2 ^or more per one side of the paper support in terms of dry solid content.

＜2＞
The packaging material according to the above-mentioned <1>, wherein the content of the inorganic pigment is 2 mass% or less based on the dry solid content of the outermost coating layer.

＜3＞
The packaging material according to the above item <1> or <2>, wherein the coating layer is one layer including the outermost coating layer.

＜4＞
The packaging material according to any one of <1> to <3> above, wherein the ionomer resin of an ethylene-unsaturated carboxylic acid copolymer accounts for 90 mass% or more of the dry solid content of the outermost coating layer.

＜5＞
The packaging material according to any one of the above items <1> to <4>, wherein the content of the filler in the base paper for the paper support is 3% by mass or less based on the pulp in the base paper.
＜6＞
The packaging material according to any one of <1> to <5> above, wherein the aluminum sulfate content in the base paper for the paper support is 6 parts by mass or more and 10 parts by mass or less per 1,000 parts by mass of pulp in the base paper.
＜７＞
The packaging material according to any one of <1> to <6> above, wherein the base paper for the paper support contains at least NBKP and LBKP as pulp.

Claims (6)

A packaging material having a paper support and one or more coating layers on one side of the paper support, the paper support having a density of 0.83 g/cm3 or ^more and 1.03 g/cm3 ^or less and an ash content of 2.3 mass% or less, an outermost coating layer located outermost with respect to the paper support among the coating layers contains at least an ionomer resin of an ethylene-unsaturated carboxylic acid copolymer, the opacity of the paper support is 70% or more and 85% or less, and the coating amount of the ionomer resin of an ethylene-unsaturated carboxylic acid copolymer in the outermost coating layer is 3 g/m2 ^or more per one side of the paper support in terms of dry solid content. The packaging material according to claim 1, in which the inorganic pigment content is 2% by mass or less based on the dry solid content of the outermost coating layer. The packaging material according to claim 1 or 2, wherein the coating layer, including the outermost coating layer, is one layer. The packaging material according to claim 1 or 2, wherein the ionomer resin of an ethylene-unsaturated carboxylic acid copolymer is 90% by mass or more of the dry solid content of the outermost coating layer. The packaging material according to claim 1 or 2, wherein the content of the filler in the base paper relating to the paper support is 3% by mass or less relative to the pulp in the base paper. The packaging material according to claim 1 or 2, wherein the aluminum sulfate content in the base paper for the paper support is 6 parts by mass or more and 10 parts by mass or less per 1000 parts by mass of pulp in the base paper.