Packaging paper

Abstract

To provide a packaging paper reduced in a use amount of plastics.SOLUTION: The packaging paper includes at least one heat seal layer on at least one surface of a paper base material. The heat seal layer contains an ionomer, and a dried coating amount of the heat seal layer is 2 to 10 g / min the whole layers.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to packaging paper that reduces the amount of plastic used. [Background technology]

[0002] In recent years, the plastic waste problem has become increasingly serious. Global plastic production is said to exceed 400 million tons per year, with the packaging sector accounting for a large portion and contributing significantly to plastic waste. Plastic does not decompose semi-permanently, and its waste breaks down into microplastics in the natural environment, severely impacting ecosystems. The most commonly used plastics in packaging are polyethylene terephthalate (PET), used in beverage bottles, and polyethylene (PE) and polypropylene (PP), used in shopping bags and container laminations. Marine pollution, in particular, is severe, and the resulting plastic waste is considered impossible to recover. Reducing plastic use is essential for the global environment.

[0003] On the other hand, the application of biodegradable plastics, which can be completely decomposed by microorganisms, is being proposed worldwide as a measure against plastic waste. Although biodegradable plastics decompose in nature within a certain period of time, they are still waste until they decompose, and unless their usage and disposal amounts are reduced, it cannot be said to be an immediate solution (see Patent Documents 1 and 2).

[0004] As an immediate solution, replacing plastic with paper has been proposed. However, when processing paper into bags and containers, large amounts of polyethylene or polypropylene are laminated onto the paper as heat sealants. The amount of these plastics laminated varies depending on the product concept, but is generally around 20-50 g / m². 2 It is 300g / m 2In some cases, it may also increase significantly. Therefore, even in the packaging containers where plastic is replaced with paper, there is still a problem that the amount of plastic used is not sufficiently reduced, and there is an urgent need for a means to directly reduce the use of plastic.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide a packaging paper capable of reducing the amount of plastic used.

Means for Solving the Problems

[0007] In the present invention, ionomer is used to reduce the amount of polyethylene or polypropylene used in a conventional plastic laminate paper (hereinafter sometimes abbreviated as poly-laminated paper). That is, the packaging paper according to the present invention is a packaging paper having at least one heat-sealing layer on at least one surface of a paper substrate, the heat-sealing layer contains ionomer, and the coating amount of the heat-sealing layer is 2 to 10 g / m 2 It is characterized by this. The lamination amount of polyethylene or polypropylene used in the heat-sealing layer of the conventional poly-laminated paper is 20 g / m 2When compared with exceeding this, the amount of plastic used for the heat-sealing layer can be reduced to about 10 to 50% of the conventional amount. Here, an ionomer is a synthetic resin in which polymers are aggregated using the cohesive force of metal ions, and is a synthetic resin obtained by combining acrylic acid or methacrylic acid with ethylene or the like. For example, it is manufactured by adding metal cations such as sodium or zinc to an acrylic polymer and ethylene and causing intermolecular bonding.

[0008] In the present invention, the heat-sealing layer may be formed in two or more layers on at least one surface. By adopting such a configuration, packaging paper having high air permeability, water repellency, and oil repellency can be obtained.

[0009] In the present invention, the air permeability of the packaging paper may exceed 10,000 seconds. By adopting such a configuration, the barrier property for blocking air is enhanced, and further, packaging paper having improved water repellency and oil repellency can be obtained.

[0010] In the present invention, the ionomer may be a metal salt of an ethylene-methacrylic acid copolymer. Packaging paper having excellent heat-sealing suitability can be obtained.

[0011] Further, the method for manufacturing the packaging paper in the present invention includes a step of preparing a coating liquid for the heat-sealing layer containing an ionomer emulsion, and applying the coating liquid for the heat-sealing layer to at least one surface of a paper substrate in a range of 2 to 10 g / m 2 in terms of solid content. In particular, by using an aqueous ionomer emulsion as the ionomer emulsion, the coating amount can be controlled relatively low, and since there is no VOC emission, packaging paper with a small environmental load can be obtained.

[0012] Furthermore, in the present invention, it is preferable to apply the heat-seal coating liquid to a surface of the paper substrate that has a smoothness of 10 seconds or more. This is preferable because the heat-seal layer tends to form a uniform thin film layer without becoming island-like or mesh-like, reducing variations in heat-seal strength and consequently increasing the heat-seal strength of the packaging paper. Heat-seal strength is the most important characteristic when processing packaging containers using packaging paper.

[0013] Furthermore, in the present invention, the ionomer emulsion may be a self-emulsifying emulsion. Packaging paper having a heat-sealable layer with a uniform film thickness can be obtained even as a thin film. [Effects of the Invention]

[0014] The present invention makes it possible to manufacture packaging paper with reduced plastic usage. Even if container products using the packaging paper of the present invention are improperly released into the natural environment as plastic waste, the negative impact on the natural environment will be minimized, thus contributing to the solution of the plastic waste problem. The packaging paper of the present invention can be processed into various types of packaging containers, such as bags, food cups for ice cream, beverage cups for coffee, food containers for hot snacks, trays, boxes, cases, bowls, and envelopes. [Modes for carrying out the invention]

[0015] Next, the present invention will be described in detail with reference to embodiments, but the present invention is not to be construed as being limited to these descriptions. Various modifications of the embodiments are possible as long as the effects of the present invention are achieved.

[0016] In this embodiment, an ionomer is a general term for synthetic resins in which polymers are aggregated by the cohesive force of metal ions, and is a resin obtained by combining acrylic acid or methacrylic acid with ethylene or the like. That is, metal salts of ethylene-methacrylic acid copolymers, metal salts of ethylene-acrylic copolymers, metal salts of ethylene-urethane copolymers, metal salts of ethylene-fluoropolymer copolymers, etc. are all called ionomers. Examples of the metal forming the salt include alkali metal ions and alkaline earth metal ions, specifically, ions of sodium, potassium, calcium, magnesium, zinc, etc. In the present invention, it is preferable that the ionomer is a self-emulsifying emulsion which is a metal salt of an ethylene-methacrylic acid copolymer. A heat-sealing layer having sufficient heat-sealing strength can be provided with a relatively small coating amount of the heat-sealing layer.

[0017] In this embodiment, a heat-sealing layer can be provided by applying a coating liquid for a heat-sealing layer containing an ionomer emulsion to at least one surface of a paper substrate and drying it. By using an ionomer emulsion, it is possible to control the coating amount to be relatively low, and further, by using an aqueous ionomer emulsion, VOC emissions can be eliminated and the load on the natural environment can be reduced. The coating amount of the heat-sealing layer is 2 to 10 g / m 2 in terms of solid content per side of the paper substrate, preferably 3 to 8 g / m 2 . If it is less than 2 g / m 2 , sufficient heat-sealing strength cannot be satisfied. Conversely, if it exceeds 10 g / m 2 , it is of excessive quality in terms of heat-sealing strength and the plastic reduction effect becomes poor. In the packaging paper of the present invention, the heat-sealing layer is usually provided not only on a part of the surface of the paper substrate but on the entire surface. That is, the heat-sealing layer is preferably provided so as to cover the entire surface of the paper substrate, rather than being provided only on the parts necessary for adhesion by heat-sealing, such as in a net shape, island shape, linear shape, etc.

[0018] In addition to the ionomer emulsion, various additives may be added to the coating liquid for the heat seal layer. Examples include viscosity modifiers, defoamers, leveling agents such as surfactants and alcohols, coloring pigments, and coloring dyes. However, the addition of these additives tends to reduce the heat seal strength, so it is preferable to add them in small amounts. In this embodiment, it is preferable that the coating liquid for the heat seal layer consists only of the ionomer emulsion.

[0019] The method for applying the coating liquid for the heat seal layer is not particularly limited, and commonly used coating equipment can be used. For example, various known coating equipment such as air knife coaters, blade coaters, gravure coaters, rod blade coaters, roll coaters, reverse roll coaters, bar coaters, curtain coaters, die slot coaters, champlex coaters, metering blade type size press coaters, short dwell coaters, spray coaters, gate roll coaters, and lip coaters can be used.

[0020] In this embodiment, it is preferable that the heat-seal layer is formed of two or more layers. By forming two or more layers, the air permeability of the packaging paper can be increased, and water and oil repellency can be imparted, making it possible to obtain properties similar to or close to those of plastic film laminated paper. When there are two or more heat-seal layers, it is preferable that the coating amount of the bottom heat-seal layer closest to the paper substrate is greater than the total coating amount of the other heat-seal layers. This is because the air permeability of the packaging paper can be further improved, and the water and oil repellency can be further enhanced.

[0021] In this embodiment, it is preferable that the air permeability of the packaging paper exceeds 10,000 seconds. More preferably, it is 12,000 seconds or more, and even more preferably 15,000 seconds or more. By making the air permeability of the packaging paper 10,000 seconds or more, the barrier properties in the sense of blocking air are further enhanced, and the water repellency and oil repellency are further improved. There are no particular limitations on how to make the air permeability of the packaging paper 10,000 seconds or more, but for example, it can be achieved by using a paper substrate with high air permeability. Furthermore, the air permeability of the packaging paper can also be increased by increasing the smoothness of the surface to which the heat seal coating liquid is applied. This is because it is possible to further reduce pinholes and cracks in the heat seal layer that is formed thereafter. For example, the smoothness of the surface to which the heat seal coating liquid is applied can be increased by providing a pigment coating layer and then performing calendering treatment or the like. In addition, applying two or more heat seal layers also has the effect of increasing air permeability. The two-layer heat-seal coating is thought to improve air permeability because the second coating layer (upper layer), applied on top of the first coating layer, covers any minute pinholes or cracks present in the first coating layer (lower layer). Increasing the amount of heat-seal coating also improves air permeability. In terms of film formation of the heat-seal layer, air permeability tends to improve if the drying temperature of the heat-seal coating liquid after application is set to a temperature above the melting point of the ionomer.

[0022] In this embodiment, it is preferable that the surface of the paper substrate to which the heat-seal coating liquid is applied has a smoothness of 10 seconds or more. More preferably, it has a smoothness of 20 seconds or more. A higher smoothness of the paper substrate makes it easier to achieve a uniform film thickness of the applied heat-seal layer (less likelihood of fine irregularities), and as a result, variations in heat-seal strength can be reduced, and uniform heat-seal strength can be provided on a flat surface. The method for increasing the smoothness of the paper substrate is not particularly limited, and examples include calendering using known calendering devices such as supercalenders, gloss calenders, shoenip calenders, and soft calenders. Paper with a mirrored surface transferred from a Yankee dryer, such as single-sided gloss kraft paper, is also suitable as a paper substrate with high smoothness. Note that pinholes and cracks invisible to the naked eye may exist in the heat-seal layer, but if they are of a certain degree, they do not adversely affect the heat-sealability. In addition, a leveling agent for the purpose of preventing pinholes can be added to the heat-seal layer coating liquid as long as it does not impair the effects of the present invention.

[0023] The paper substrate used in this embodiment is not particularly limited, and known paper substrates mainly composed of pulp can be used. As the pulp that forms the main component of the paper substrate, chemical pulps such as LBKP (bleached hardwood kraft pulp) and NBKP (bleached softwood kraft pulp), mechanical pulps such as GP (wood pulp), PGW (pressure-processed wood pulp), RMP (refiner mechanical pulp), TMP (thermomechanical pulp), CTMP (chemothermomechanical pulp), CMP (chemimechanical pulp), and CGP (chemigland pulp) can be used, as well as wood pulps such as DIP (deinking pulp) and non-wood pulps such as kenaf, bagasse, bamboo, and cotton. These can be used individually or mixed in any proportion. For example, 90 to 100 parts by mass of LBKP (bleached hardwood kraft pulp) can be used as the pulp. Furthermore, synthetic fibers can be further blended, as long as it does not impair the effects intended by the present invention. From an environmental perspective, ECF (Elemental Chlorine Free) pulp, TCF (Total Chlorine Free) pulp, recycled paper pulp, and pulp obtained from plantation trees are preferred. For example, an appropriate degree of pulp beating is 200-700 mlCSF, or for example, 450-620 mlCSF, in terms of Canadian standard freeness (JIS P 8121:1995 "Test Method for Freeness of Pulp").

[0024] Paper substrates containing fillers can also be used. Examples of fillers include light calcium carbonate, heavy calcium carbonate, talc, clay, kaolin, calcined clay, titanium dioxide, and aluminum hydroxide. The filler content in the paper substrate is, for example, 1 to 30 parts by mass per 100 parts by mass of dry pulp. For example, it is preferable to include 1 to 10 parts by mass of light calcium carbonate per 100 parts by mass of dry pulp.

[0025] Furthermore, the paper substrate may contain various known papermaking additives in addition to pulp and fillers. Examples of papermaking additives include sizing agents, internally added paper strength enhancers such as wet paper strength enhancers, bulk enhancers, yield enhancers, water drainage enhancers, coloring dyes, coloring pigments, fluorescent whitening agents, fluorescent decolorizing agents, and pitch control agents. In addition, water-soluble polymers such as starch, polyvinyl alcohol, and polyacrylamide may be coated onto the paper.

[0026] The papermaking method for paper substrates is not particularly limited and can be used with various papermaking machines such as screenwound paper machines, screenwound multilayer paper machines, cylinder screen paper machines, cylinder screen multilayer paper machines, screenwound and cylinder combination multilayer paper machines, and twin-wire paper machines. Furthermore, in the present invention, the paper substrate may be single-layer, multilayer, or a laminated product of multiple layers.

[0027] The paper substrate may have one or more coating layers other than the heat-seal layer, for example, a pigment coating layer containing a pigment and an adhesive. As the pigment in the pigment coating layer, known pigments used in the coating layers of general printing coated paper can be used, for example, inorganic pigments such as calcium carbonate (heavy calcium carbonate, light calcium carbonate, etc.), kaolin (including clay), calcined clay, talc, magnesium carbonate, barium sulfate, calcium sulfate, titanium dioxide, zinc oxide, zinc sulfate, zinc carbonate, calcium silicate, aluminum silicate, magnesium silicate, diatomaceous earth, aluminum hydroxide, magnesium hydroxide, or organic pigments (so-called plastic pigments) obtained by copolymerizing acrylic, styrene, vinyl chloride, nylon itself, or these. For example, as the pigment, a combination of 20 to 40 parts by mass of kaolin and 60 to 80 parts by mass of heavy calcium carbonate can be used. Furthermore, known adhesives used in the coating layers of general printing coated paper can be used as adhesives. Examples include starches such as butadiene copolymer latex, crosslinking agent-modified starch, oxidized starch, enzyme-modified starch, esterified starch, etherified starch, cationic starch, and amphoteric starch; water-soluble polymers such as gelatin, casein, soy protein, and polyvinyl alcohol; and synthetic resins such as vinyl acetate, ethylene vinyl acetate, polyurethane resins, acrylic resins, polyester resins, and polyamide resins. The mixing ratio of pigment to adhesive in the pigment coating layer is not particularly limited, but it is preferable to use 5 to 50 parts by mass of adhesive per 100 parts by mass of pigment. For example, as an adhesive, a combination of 1 to 5 parts by mass of phosphate-esterified starch and 5 to 15 parts by mass of styrene-butadiene latex can be used per 100 parts by mass of pigment. The pigment coating layer may contain various auxiliary agents to the extent that they do not impair the effects intended by the present invention. For example, it may contain viscosity modifiers, softeners, gloss enhancers, water-resistant agents, dispersants, flow modifiers, UV absorbers, stabilizers, antistatic agents, crosslinking agents, sizing agents, fluorescent whitening agents, colorants, pH adjusters, defoamers, plasticizers, and preservatives. The amount of such a pigment coating layer applied may be, for example, 2 to 40 g / m² in terms of solid content per side of the base paper. 2In one embodiment of the packaging paper of the present invention, the heat seal layer may be provided on such a pigment coating layer, and in another embodiment, the heat seal layer may be provided on the side of a paper substrate on which the pigment coating layer is not provided, with the pigment coating layer provided on only one side.

[0028] In this embodiment, the basis weight of the packaging paper is not particularly limited, but for example, 10 to 1000 g / m² 2 The basis weight of the packaging paper, which possesses high levels of barrier, water-repellent, and oil-repellent properties and can be used for flexible packaging, is 30-500 g / m². 2 Preferably, 50-300 g / m 2 This is preferable. [Examples]

[0029] Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In the examples, "parts" and "%" refer to "parts by mass" and "% by mass," respectively, unless otherwise specified. Note that the number of added parts is the value on a solid content basis.

[0030] (Example 1) (Preparation of the base paper) A pulp was prepared by adding water to 100 parts Canadian Standard Freeness 520ml csf hardwood bleached kraft pulp, 5 parts light calcium carbonate (product name: TP-121, manufactured by Okutama Kogyo Co., Ltd.), 0.2 parts cationized starch (product name: Neotack 30T, manufactured by Nippon Shokuhin Kako Co., Ltd.), and 0.2 parts neutral rosin sizing (product name: CC167, manufactured by Seikou PMC Co., Ltd.). The resulting paper was then processed using a multi-cylinder, long-wire paper machine to produce a basis weight of 58 g / m². 2 A base paper was prepared. Oxidized starch (product name: MS3800, manufactured by Nippon Shokuhin Kako Co., Ltd.) was applied to this base paper using a gate roll coater at a dry coating rate of 2 g / m² per side. 2 Apply so that it becomes 60g / m² and dry. 2 We obtained the base paper.

[0031] (Preparation of coating solution for pigment coating layer) A pigment slurry was prepared by adding 30 parts of kaolin (product name: Contour 1500, manufactured by Imerys) and 70 parts of heavy calcium carbonate (product name: Carvilax, manufactured by Imerys) to 0.2 parts of a dispersant (product name: Aron T-50, manufactured by Toagosei Co., Ltd.), adding water, and dispersing the mixture using a Koles disperser. To this pigment slurry, 2 parts of phosphated starch (product name: MS4600, manufactured by Nippon Shokuhin Kako Co., Ltd.) and 8 parts of styrene-butadiene latex (product name: PA0372, manufactured by Nippon A&L Co., Ltd.) as binders, and further dispersing the mixture with water to prepare a coating solution for a pigment coating layer with a solid content of 50%.

[0032] (Preparation of paper substrate) Apply the pigment coating solution to both sides of the base paper obtained above, with a dry coating amount of 10 g / m² per side. 2 The coating was applied using a blade coater and dried to achieve the desired result. Afterwards, calendering was performed, resulting in a basis weight of 80 g / m². 2 A paper substrate (coated paper) was prepared. The smoothness of the coated surface (the surface to which the heat-seal layer will be applied in a later process) was 400 seconds.

[0033] (Preparation of packaging paper) On one side of the paper substrate obtained above, a water-based ionomer emulsion (product name: Chemipearl S-300, manufactured by Mitsui Chemicals, composition: metal salt of ethylene-methacrylic acid copolymer, self-emulsifying emulsion, average particle size 0.5 μm by microtrac method) was applied with a dry coating amount of 5 g / m². 2 The packaging paper was prepared by coating it using an air knife coater, drying it, and creating a heat-seal layer.

[0034] (Example 2) In Example 1, the coating amount of the heat seal layer was 10 g / m². 2 Except for the change made, the packaging paper was prepared in the same manner as in Example 1.

[0035] (Example 3) In Example 1, the coating amount of the heat seal layer was 9 g / m². 2 Except for the change made, the packaging paper was prepared in the same manner as in Example 1.

[0036] (Example 4) In Example 1, the amount of heat seal layer applied was 2 g / m². 2 Except for the change made, the packaging paper was prepared in the same manner as in Example 1.

[0037] (Example 5) In Example 1, the amount of heat seal layer applied was 3 g / m². 2 Except for the change made, the packaging paper was prepared in the same manner as in Example 1.

[0038] (Example 6) A base paper was prepared in the same manner as in Example 1. Next, the same pigment coating solution as in Example 1 was applied to both sides of the base paper using a gate roll coater, with a dry coating rate of 10 g / m² per side. 2 The coating was applied. Next, the same coating liquid for the coating layer as in Example 1 was applied as the upper layer to both sides using a blade coater, with a dry coating rate of 10 g / m² per side. 2 After coating and supercalendering, the basis weight is 100g / m². 2 A paper substrate (coated paper) was prepared. The smoothness of the coated surface (the surface to which the heat-seal layer will be applied in a later process) was 2500 seconds. Next, a heat-seal layer was applied to one side of the paper substrate obtained above in the same manner as in Example 1 to prepare packaging paper.

[0039] (Example 7) (Preparation of paper substrate) 100 parts Canadian Standard Freeness 580mlcsf bleached hardwood kraft pulp, 5 parts light calcium carbonate (product name: TP-121, manufactured by Okutama Kogyo Co., Ltd.), 0.2 parts cationized starch (product name: Neotack 30T, manufactured by Nippon Shokuhin Kako Co., Ltd.), and 0.2 parts neutral rosin sizing (Sizing Pine NT-78, manufactured by Arakawa Chemical Industries Co., Ltd.) were mixed with water to prepare the pulp, and the resulting paper was processed using a multi-cylinder, long-screen paper machine to produce a basis weight of 188 g / m². 2 A base paper was prepared. Oxidized starch (product name: MS3800, manufactured by Nippon Shokuhin Kako Co., Ltd.) was applied to this base paper using a size press, with a dry coating amount of 2g / m² per side. 2 Apply so that it becomes 190g / m² and dry. 2A paper substrate was obtained. The smoothness of the surface of this paper substrate (the surface on which the heat-seal layer will be applied in a later process) was 10 seconds.

[0040] (Preparation of packaging paper) On one side of the paper substrate obtained above, a water-based ionomer emulsion (product name: Chemipearl S-100, manufactured by Mitsui Chemicals, composition: metal salt of ethylene-methacrylic acid copolymer, self-emulsifying emulsion, average particle size 0.1 μm by microtrac method) was applied at a dry coating rate of 6 g / m². 2 The packaging paper was prepared by coating it using an air knife coater, drying it, and creating a heat-seal layer.

[0041] (Example 8) Packaging paper was prepared in the same manner as in Example 7, except that the base paper was calendered after being coated with oxidized starch. The smoothness of the base paper surface (the surface on which the heat-seal layer will be applied in a later step) was 20 seconds.

[0042] (Example 9) (Preparation of paper substrate) A pulp was prepared by adding water to 100 parts Canadian Standard Freeness 580mlcsf hardwood bleached kraft pulp, 5 parts light calcium carbonate (product name: TP-121, manufactured by Okutama Kogyo Co., Ltd.), 0.2 parts cationized starch (product name: Neotack 30T, manufactured by Nippon Shokuhin Kako Co., Ltd.), and 0.2 parts neutral rosin sizing (Sizing Pine NT-78, manufactured by Arakawa Chemical Industries Co., Ltd.). The resulting paper was then processed using a three-layer, long-wire, multi-cylinder paper machine to produce a basis weight of 298 g / m². 2 A base paper (three-layered) was prepared. Oxidized starch (product name: MS3800, manufactured by Nippon Shokuhin Kako Co., Ltd.) was applied to this base paper using a size press, with a dry coating amount of 2g / m² per side. 2 Apply the coating in this manner, allow it to dry, and then treat it with soft calender to achieve a basis weight of 300 g / m². 2 A paper substrate was obtained. The smoothness of the surface of the paper substrate (the surface on which the heat-seal layer will be applied in a later process) was 100 seconds.

[0043] (Preparation of packaging paper) On one side of the paper substrate obtained above, a water-based ionomer emulsion (product name: Chemipearl S-500, manufactured by Mitsui Chemicals, composition: metal salt of ethylene-methacrylic acid copolymer, self-emulsifying emulsion, average particle size 0.7 μm by microtrac method) was applied at a dry coating rate of 4 g / m². 2 The packaging paper was prepared by coating it using an air knife coater, drying it, and creating a heat-seal layer.

[0044] (Example 10) On one side of the paper substrate obtained in Example 9, the same pigment coating solution as in Example 1 was applied using an air knife coater, with a drying amount of 20 g / m². 2 The surface is coated in this manner and treated with a soft calender to achieve a density of 320g / m². 2 A paper substrate was prepared. The smoothness of the uncoated surface of this paper substrate (the surface of the paper substrate that does not have a pigment coating layer) was 150 seconds. Next, a heat seal layer was applied to the uncoated surface of the paper substrate obtained above in the same manner as in Example 1 to prepare packaging paper.

[0045] (Example 11) On one side of the paper substrate obtained in Example 9, a water-based ionomer emulsion (product name: Chemipearl S-300, manufactured by Mitsui Chemicals, composition: metal salt of ethylene-methacrylic acid copolymer, self-emulsifying emulsion, average particle size 0.5 μm by microtrac method) was applied with a dry coating amount of 5 g / m². 2 The surface was coated using an air knife coater and dried to form a heat-seal layer (lower layer). Next, the same aqueous ionomer emulsion was applied to the surface of the heat-seal layer (lower layer) at a dry coating rate of 2 g / m². 2 The packaging paper was prepared by coating it using an air knife coater, drying it, and then creating a heat-sealed layer (upper layer).

[0046] (Example 12) In Example 10, an aqueous ionomer emulsion (product name: MYE-30ER, manufactured by Maruyoshi Chemical Co., Ltd., composition: metal salt of ethylene-methacrylic acid copolymer, self-emulsifying emulsion, average particle size by microtrac method: 0.2 μm) was applied to the uncoated surface (the surface of the paper substrate without a pigment coating layer) of the paper substrate prepared in Example 10, with a dry coating amount of 3 g / m². 2 The surface was coated using an air knife coater and dried to form a heat-seal layer (lower layer). Next, a water-based ionomer emulsion (product name: MYE-30MAZ, manufactured by Maruyoshi Chemical Co., Ltd., composition: metal salt of ethylene-methacrylic acid copolymer, self-emulsifying emulsion, average particle size 0.3 μm by microtrac method) was applied to the surface of the heat-seal layer (lower layer) at a drying rate of 1 g / m². 2 The packaging paper was prepared by coating it using an air knife coater, drying it, and then creating a heat-sealed layer (upper layer).

[0047] (Example 13) In Example 10, an aqueous ionomer emulsion (product name: Chemipearl S-300, manufactured by Mitsui Chemicals, composition: metal salt of ethylene-methacrylic acid copolymer, self-emulsifying emulsion, average particle size by microtrac method: 0.5 μm) was applied to the uncoated surface (the surface of the paper substrate without a pigment coating layer) of the paper substrate prepared in Example 10, with a dry coating amount of 5 g / m². 2 The surface was coated using an air knife coater and dried to form a heat-seal layer (lower layer). Next, the same aqueous ionomer emulsion was applied to the surface of the heat-seal layer (lower layer) at a dry coating rate of 1 g / m². 2 The packaging paper was prepared by coating it using an air knife coater, drying it, and then creating a heat-sealed layer (upper layer).

[0048] (Example 14) In Example 10, an aqueous ionomer emulsion (product name: Chemipearl S-300, manufactured by Mitsui Chemicals, composition: metal salt of ethylene-methacrylic acid copolymer, self-emulsifying emulsion, average particle size by microtrac method: 0.5 μm) was applied to the uncoated surface (the surface of the paper substrate without a pigment coating layer) of the paper substrate prepared in Example 10, with a dry coating amount of 1 g / m². 2The surface was coated using an air knife coater and dried to form a heat-seal layer (lower layer). Next, the same aqueous ionomer emulsion was applied to the surface of the heat-seal layer (lower layer) at a dry coating rate of 9 g / m². 2 The packaging paper was prepared by coating it using an air knife coater, drying it, and then creating a heat-sealed layer (upper layer).

[0049] (Example 15) In Example 10, an aqueous ionomer emulsion (product name: Chemipearl S-300, manufactured by Mitsui Chemicals, composition: metal salt of ethylene-methacrylic acid copolymer, self-emulsifying emulsion, average particle size by microtrac method: 0.5 μm) was applied to the uncoated surface (the surface of the paper substrate without a pigment coating layer) of the paper substrate prepared in Example 10, with a dry coating amount of 9 g / m². 2 The surface was coated using an air knife coater and dried to form a heat-seal layer (lower layer). Next, the same aqueous ionomer emulsion was applied to the surface of the heat-seal layer (lower layer) at a dry coating rate of 1 g / m². 2 The packaging paper was prepared by coating it using an air knife coater, drying it, and then creating a heat-sealed layer (upper layer).

[0050] (Example 16) On one side of the paper substrate prepared in Example 7, an aqueous ionomer emulsion (product name: Chemipearl S-300, manufactured by Mitsui Chemicals, composition: metal salt of ethylene-methacrylic acid copolymer, self-emulsifying emulsion, average particle size 0.5 μm by microtrac method) was applied, with a dry coating amount of 5 g / m². 2 The surface was coated using an air knife coater and dried to form a heat-seal layer (lower layer). Next, the same aqueous ionomer emulsion was applied to the surface of the heat-seal layer (lower layer) at a dry coating rate of 1 g / m². 2 The packaging paper was prepared by coating it using an air knife coater, drying it, and then creating a heat-sealed layer (upper layer).

[0051] (Example 17) In Example 7, a water-based ionomer emulsion (product name: Chemipearl S-300, manufactured by Mitsui Chemicals, composition: metal salt of ethylene-methacrylic acid copolymer, self-emulsifying emulsion, average particle size 0.5 μm by microtrac method) was applied to both sides of the paper substrate, with a dry coating amount of 5 g / m² per side. 2 The surface was coated using an air knife coater and dried to form a heat-seal layer (lower layer). Next, the same aqueous ionomer emulsion was applied to the surface of the heat-seal layer (lower layer) with a dry coating amount of 1 g / m² per side. 2 The packaging paper was prepared by coating both sides of the upper substrate using an air knife coater, drying it to create a heat-seal layer (upper layer), and then applying the coating to both sides of the upper substrate.

[0052] (Comparative Example 1) On one side of the paper substrate prepared in Example 1, low-density polyethylene (Petrocene DLZ19A, manufactured by Tosoh Corporation) was coated using an extrusion coater (melt extruder) at a rate of 30 g / m². 2 The packaging paper was created by laminating it and adding a heat-seal layer to achieve the desired result.

[0053] (Comparative Example 2) On one side of the paper substrate prepared in Example 1, polypropylene (Novatec FL03H, manufactured by Nippon Polypropylene Co., Ltd.) was coated using an extrusion coater (melt extruder) at a rate of 30 g / m². 2 The packaging paper was created by laminating it and adding a heat-seal layer to achieve the desired result.

[0054] (Comparative Example 3) In Example 1, packaging paper was prepared in the same manner as in Example 1, except that the aqueous ionomer emulsion was replaced with an aqueous polyethylene emulsion (Sunopco, SN Coat 287).

[0055] (Comparative Example 4) Packaging paper was prepared in the same manner as in Example 1, except that the aqueous ionomer emulsion was replaced with an aqueous polypropylene emulsion (Hi-Tec P-5300, manufactured by Toho Chemical Industry Co., Ltd.).

[0056] The packaging paper obtained in each example and comparative example was evaluated using the method described below. The results are shown in Tables 1 to 3. For convenience, if there was only one heat-seal layer, the coating amount is indicated in the "Coating Amount for the Upper Heat-Seal Layer" column.

[0057] (1) Smoothness In accordance with JIS P 8155:2010, the smoothness (seconds) of the surface of the paper substrate adjacent to the heat seal layer (heat seal layer formation surface) before the heat seal layer was applied was measured using a digital Ogane-type air permeability and smoothness tester (manufactured by Asahi Seiko Co., Ltd., model number: EYDO-6-2M). A higher value indicates a smoother surface of the paper substrate.

[0058] (2) Air permeability In accordance with JIS P 8117:2009, the air permeability (seconds) of the packaging paper was measured using a digital Ogane-type air permeability and smoothness tester (manufactured by Asahi Seiko Co., Ltd., model number: EYDO-6-2M). A higher value indicates lower air permeability (higher barrier properties).

[0059] (2) Heat seal strength Two pieces of the obtained packaging paper were cut to a size of 8 mm wide and 15 cm long. The front and back sides of the packaging paper were overlapped and heat-sealed using a heat sealing device (Palmec, model number: PTS-100) under specific conditions (adhesion width: 4 mm, temperature: 180°C, pressure: 0.4 MPa, pressing time: 0.5 seconds, pitch: 4 mm). Next, the peel strength of the heat-sealed sample was measured using a peel strength tester (Shimadzu Corporation, model number: Autograph AGS-X) under specific conditions (peel speed: 100 mm / min, peel length: 10 cm) and defined as the heat seal strength (gf / 4 mm). A higher value indicates better performance. Note that if both sides are heat-sealed layers, this represents the adhesive strength between the heat-sealed layers.

[0060] (3) Water repellency The water repellency of the heat-sealed layer surface was evaluated in accordance with JIS K 6768:1999 (Plastics - Films and Sheets - Wet Tension Test Methods). A lower number indicates higher water repellency (less wetting). If heat-sealed layers were present on both sides, the average value of both sides was used.

[0061] (4)Oil repellency The oil repellency of the heat-sealed layer surface was evaluated according to the TAPPI T-559cm-02 (kit method). A higher value (kit value) indicates higher oil repellency. If heat-sealed layers were present on both sides, the average value of both sides was used.

[0062] [Table 1]

[0063] [Table 2]

[0064] [Table 3]

[0065] As is clear from Tables 1-3, the packaging papers of Examples 1-17 had heat seal strength equivalent to or better than Comparative Examples 1-2, despite a significant reduction in the amount of heat seal layer. Furthermore, they were clearly superior in heat seal strength compared to Comparative Examples 3-4. As the experimental results show, the present invention makes it possible to significantly reduce the amount of heat seal layer used compared to conventional polyethylene laminates, contributing to the reduction of plastic waste, while providing packaging paper with excellent barrier properties, water repellency, and oil repellency.

Claims

1. A packaging paper having at least one heat-seal layer on at least one surface of a paper substrate, wherein the heat-seal layer consists solely of an ionomer which is a metal salt of ethylene methacrylic acid copolymer, the heat-seal layer is provided on one or more pigment coating layers, and the dry coating amount of the heat-seal layer is 2 to 10 g / m² for the entire layer. ２ Packaging paper characterized by the following:

2. A packaging paper having a pigment coating layer on only one side of the paper substrate, and a heat-seal layer in contact with the paper substrate on the side without the pigment coating layer, wherein the heat-seal layer contains an ionomer which is a metal salt of ethylene methacrylic acid copolymer, and furthermore, the heat-seal layer does not contain phyllosilicate, and two or more heat-seal layers are formed on one side, and the dry coating amount of the heat-seal layer is 2 to 10 g / m² for the entire layer. ２ Packaging paper characterized by the following:

3. The packaging paper according to claim 1, characterized in that two or more heat-seal layers are formed on at least one surface.

4. A packaging paper according to any one of claims 1 to 3, characterized in that its air permeability exceeds 10,000 seconds.

5. The packaging paper according to any one of claims 1 to 4, wherein the pigment coating layer contains a pigment and an adhesive, and the adhesive contains phosphate-esterified starch and styrene-butadiene latex.

6. The packaging paper according to claim 2, characterized in that the heat-seal layer consists solely of an ionomer.

7. A pigment coating layer is applied to at least one surface of the paper substrate, and then, A step of preparing a coating liquid for a heat seal layer, consisting only of an ionomer emulsion in which the ionomer is a metal salt of an ethylene-methacrylic acid copolymer, Apply the heat-seal coating liquid to at least one surface of the paper substrate at a rate of 2 to 10 g / m² in terms of solid content. ２ A method for manufacturing packaging paper, comprising a step of coating within a certain range.

8. A pigment coating layer is applied to one side of the paper substrate, and then, A step to prepare a heat seal coating liquid containing an ionomer emulsion in which the ionomer is a metal salt of ethylene methacrylic acid copolymer, and which is phyllosilicate-free, Apply the heat-seal coating liquid directly to the surface of the paper substrate that does not have a pigment coating layer, in a solid content equivalent of 2 to 10 g / m². ２ A method for manufacturing packaging paper, comprising performing a coating process within a certain range twice.

9. The method for manufacturing packaging paper according to claim 7 or 8, characterized in that the heat-seal coating liquid is applied to a surface of the paper substrate having a smoothness of 10 seconds or more.

10. A method for producing packaging paper according to any one of claims 7 to 9, characterized in that the ionomer emulsion is a self-emulsifying emulsion.

11. The method for manufacturing packaging paper according to claim 8, characterized in that the heat-seal layer consists solely of an ionomer.

12. The method for producing packaging paper according to any one of claims 7 to 11, characterized in that the pigment coating layer contains a pigment and an adhesive, and the adhesive contains phosphate-esterified starch and styrene-butadiene latex.

13. A method for manufacturing packaging paper according to any one of claims 7 to 12, characterized in that the packaging paper consists only of a paper base material, a heat-seal layer, and a pigment coating layer.

14. The method for producing packaging paper according to any one of claims 7 to 13, characterized in that the pigment coating layer contains, as an adhesive, 1 to 5 parts by mass of phosphate-esterified starch and 5 to 15 parts by mass of styrene-butadiene latex per 100 parts by mass of pigment.

15. The packaging paper according to any one of claims 1 to 6, characterized in that the pigment coating layer contains, as an adhesive, 1 to 5 parts by mass of phosphate-esterified starch and 5 to 15 parts by mass of styrene-butadiene latex per 100 parts by mass of pigment.

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