Method of manufacturing packaging paper

Abstract

The present invention aims to provide packaging paper that can reduce plastic waste and a method for manufacturing the same. [Solution] The present invention relates to a method for manufacturing packaging paper having at least one barrier layer on at least one surface of a paper substrate, characterized in that the barrier layer is provided by gravure printing and the coating roll plate is a honeycomb plate.

Description

[Technical Field]

[0001] This invention relates to packaging paper that reduces plastic waste and a method for producing the same. [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 becoming the main source of 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. Ocean pollution caused by plastic waste is particularly severe, and this 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 still have adverse effects on ecosystems until they decompose, and unless their use and disposal amounts are reduced, they cannot be considered an immediate solution (see Patent Documents 1 and 2).

[0004] As an immediate solution, replacing plastic with paper has been proposed. However, when paper is processed into bags and containers, a large amount of plastic such as polyethylene or polypropylene is laminated as a barrier layer. 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, the amount of plastic used can be quite large. Therefore, even with packaging containers that replace paper with plastic, the amount of plastic used is still not sufficiently reduced, and there is an urgent need for direct measures to reduce the use of plastic.

[0005] Various methods have been proposed to solve these problems, including applying a barrier agent to a paper substrate using a coater. However, this method is more expensive than laminated products, and a manufacturing method that reduces costs is needed. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2012-148444 [Patent Document 2] Japanese Patent Publication No. 2013-141763 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The object of the present invention is to provide packaging paper that can reduce plastic waste and a method for manufacturing the same. [Means for solving the problem]

[0008] The present invention relates to a method for manufacturing packaging paper, characterized in that a barrier layer is provided by gravure printing using a gravure printing machine, and the coating roll plate is a honeycomb plate. By using a honeycomb plate, the leveling properties of the coating liquid for the barrier agent are increased, making it possible to obtain packaging paper with a barrier layer with fewer pinholes compared to conventional grid-type plates and diagonal-type plates. Furthermore, since the coating device is a gravure printing machine, it is possible to provide packaging paper with multiple barrier layers in a single pass. Moreover, by using a gravure printing machine as the coating device, it is also possible to coat the barrier layer and print a design on the opposite side of the barrier layer in a single pass. Therefore, it is possible to achieve higher efficiency and lower product costs compared to conventional packaging paper manufacturing methods. In another embodiment of the present invention, when printing is not particularly necessary, the method for manufacturing packaging paper of the present invention can also be carried out by simply performing gravure coating using a gravure coater instead of the gravure printing method using a gravure printing machine.

[0009] In the present invention, it is preferable to add alcohol to the coating liquid for the barrier layer. By adding alcohol, the leveling properties and barrier properties of the coating liquid can be further improved. Furthermore, in the present invention, it is preferable to prepare the paper substrate by adding 0.05 to 1.0 parts by mass of a sizing agent per 100 parts by mass of pulp.

[0010] Furthermore, it is preferable to form two or more barrier layers on at least one surface. This makes it possible to maintain a higher level of barrier properties. In addition, in the present invention, it is preferable to use an aqueous barrier agent. This reduces VOC emissions and further reduces the environmental burden. Moreover, the present invention relates to packaging paper having at least one barrier layer on at least one surface of a paper substrate, wherein the barrier layer is made of an ionomer resin or a polyvinylidene chloride resin (PVDC), and the coating amount of the barrier layer is 15 g / m². 2 The following conditions apply, and the Cobb water absorption (120 seconds) of the surface with the barrier layer, according to JIS P8140, is 10 g / m². 2Relates to wrapping paper as follows.

Effects of the Invention

[0011] According to the present invention, it is possible to efficiently manufacture wrapping paper that can reduce plastic waste. The wrapping paper manufactured by the present invention can be used for all packaging containers such as bags, cartons, cups, trays, boxes, cases, utensils, etc.

Brief Description of the Drawings

[0012] [Figure 1] Figure 1 is a diagram showing a schematic view of a honeycomb version.

Modes for Carrying Out the Invention

[0013] Next, embodiments of the present invention will be shown and described in detail, but the present invention is not construed as being limited to these descriptions. As long as the effects of the present invention are achieved, the embodiments may be variously modified. The barrier property in this embodiment refers to, for example, gas barrier properties such as water vapor barrier and oxygen barrier, odor barrier, heat barrier, water repellency, and oil repellency. Examples of the barrier agent include water-soluble polymers such as butadiene-based copolymer latex (SBR), starch, gelatin, casein, soy protein, polyvinyl alcohol (PVA), butenediol vinyl alcohol copolymer (BVOH), synthetic resins such as vinyl acetate, ethylene vinyl acetate (EVA), polyurethane-based resin, acrylic resin, styrene acrylic resin, ionomer-based resin, polyvinylidene chloride-based resin (PVDC), polyester-based resin (PET), polyamide-based resin, ethylene copolymer-based resin, polylactic acid (PLA), polybutylene succinate (PBS), etc. As the barrier agent, ionomer-based resin and polyvinylidene chloride-based resin (PVDC) are preferable. As long as the barrier property is not inhibited, pigments (for example, light calcium carbonate, heavy calcium carbonate, talc, clay, kaolin clay, calcined clay, titanium dioxide, aluminum hydroxide) may be added to the barrier layer.

[0014] In this embodiment, the coating amount of the barrier layer is preferably 15 g / m in terms of solid content per one side of the paper substrate. 2 More preferably, it is 2 to 13 g / m. 2 Whether the barrier layer is one layer or two or more layers, the coating amount of the barrier layer is preferably 2 to 15 g / m in terms of solid content, 2、 more preferably 2 to 13 g / m. 2 If it is less than 2 g / m, the coating liquid for the barrier layer is absorbed by the paper layer, the density of the coating layer decreases, and sufficient barrier properties cannot be obtained. On the contrary, if it exceeds 15 g / m, 2 the plastic reduction effect becomes poor. 2 Also, it is preferable to coat at least one side with two or more layers of the coating liquid for the barrier layer. The barrier properties are more excellent.

[0015]

[0016] The present invention is characterized in that a barrier layer is provided by gravure printing using a gravure printing machine having a coating roll, and the plate of the coating roll is a honeycomb plate. The plate used in gravure printing is made of a metal roll (base cylinder) made of iron or aluminum as the base material, and its surface is plated to create small concave indentations called "cells" that will become the pattern to be printed. A schematic diagram of a honeycomb plate is shown in Figure 1. A honeycomb plate is a plate in which hexagonal cells are arranged in two dimensions as shown in Figure 1 (a series of hexagonal concave indentations). A coating liquid for the barrier layer is placed in these cells and transferred to a paper substrate. By using a honeycomb plate, the leveling properties of the coating liquid for the barrier agent are increased, making it possible to obtain a barrier layer with fewer pinholes compared to conventional grid-type plates and diagonal-type plates. The pitch of the honeycomb plate cells is preferably 80 lines / inch to 200 lines / inch. Furthermore, since the coating device is a gravure printing machine, it is possible to provide multiple barrier layers in a single pass. Furthermore, for the same reason, it is possible to perform the coating of the barrier layer and the design printing on the opposite side of the barrier layer in a single pass. This allows for more efficient manufacturing than conventional manufacturing methods and reduces the cost of product manufacturing. Moreover, in another embodiment of the present invention, when printing is not particularly necessary, the method for manufacturing packaging paper of the present invention can be carried out more simply and economically by performing gravure coating using a gravure coater with a coating roll, instead of a gravure printing method using a gravure printing machine.

[0017] In this invention, the Cobb water absorption (120 seconds) of the barrier layer conforming to JIS P8140 is 10 g / m². 2 The following is preferable: Good water repellency and excellent barrier properties. Preferably 5 g / m² 2 More preferably 2 g / m 2The following applies. However, there is no absolute standard for water repellency, and it varies depending on the product concept; it is sufficient to control the Cobb water absorption to the required level. Also, in the case of paper substrates, unlike film substrates, the barrier layer coating is absorbed into the paper substrate, so by optimizing the pitch of the honeycomb board, pinholes are reduced, the barrier properties are improved, and water repellency is enhanced. Furthermore, it is possible to lower the Cobb water absorption value and improve water repellency by incorporating a sizing agent into the paper substrate. The amount of sizing agent added is preferably 0.05 parts by mass or more per 100 parts by mass of pulp. More preferably 0.1 parts by mass or more. For example, the amount of sizing agent added is preferably 0.05 to 1.0 parts by mass per 100 parts by mass of pulp. Examples of sizing agents include rosin-based, alkyl ketene dimer (AKD)-based, alkenyl succinic anhydride (ASA)-based, polyvinyl alcohol (PVA)-based, styrene-acrylic copolymer (copolymer)-based, and styrene-methacrylic copolymer-based sizing agents. For example, it is preferable to prepare a paper substrate by adding 0.01 to 1 part by mass, for example, 0.05 to 1 part by mass, or 0.1 to 0.6 parts by mass, of a neutral rosin sizing agent to 100 parts by mass of pulp.

[0018] In the present invention, it is preferable to add alcohol to the barrier layer coating solution from the viewpoint of barrier properties. Commercially available alcohols such as methanol, ethanol, isopropyl alcohol (IPA), and propanol can be used as the alcohol, but isopropyl alcohol (IPA) is preferred from the viewpoint of barrier properties. The amount added is preferably 1 to 15% by mass relative to the barrier layer coating solution. Furthermore, the drying temperature after coating with the barrier layer coating solution is preferably 100 to 200°C. If the drying temperature is below 100°C, the barrier properties of the coating layer will decrease, and if the drying temperature exceeds 200°C, the moisture content of the paper will decrease, making the barrier layer coating layer prone to cracking.

[0019] 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 serves as 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 (groundwood pulp), PGW (pressure-processed groundwood pulp), RMP (refiner mechanical pulp), TMP (thermomechanical pulp), CTMP (chemothermetic 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. Furthermore, unbleached pulp that has not been bleached can also be used. For example, LBKP (bleached hardwood kraft pulp) can be used as the pulp in an amount of 90 to 100 parts by mass, preferably 95 to 100 parts by mass, for example, 100 parts by mass. Furthermore, synthetic fibers can be further blended in a range that does not impair the effects intended for this invention. From the viewpoint of environmental protection, ECF (Elemental Chlorine Free) pulp, TCF (Total Chlorine Free) pulp, recycled paper pulp, and pulp obtained from plantation trees are preferred. Also, for example, an appropriate degree of pulp beating is 200 to 700 mlCSF, for example, 450 to 620 mlCSF, in terms of Canadian standard freeness (JIS P 8121:1995 "Test method for freeness of pulp").

[0020] 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.

[0021] 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. For example, oxidized starch may be applied in a dry coating amount of 1 to 5 g / m² per side. 2 It can be applied in such a manner. The papermaking method for the paper substrate is not particularly limited and can be manufactured using various papermaking machines such as a long screen papermaking machine, a long screen multilayer papermaking machine, a cylinder screen papermaking machine, a cylinder screen multilayer papermaking machine, a long screen and cylinder screen combination multilayer papermaking machine, and a twin wire papermaking machine. Furthermore, in the present invention, the paper substrate may be single-layer, multilayer, or a laminated product of multiple layers.

[0022] The paper substrate may have one or more pigment coating layers other than the barrier layer, for example, a pigment coating layer containing a pigment and an adhesive may be provided. 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 these, such as acrylic, styrene, vinyl chloride, nylon itself, or copolymers thereof. 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 it does not impair the effects intended by the present invention. For example, it may contain colorants, viscosity modifiers, softeners, gloss enhancers, water-resistant agents, dispersants, flow modifiers, UV absorbers, stabilizers, antistatic agents, crosslinking agents, sizing agents, pH adjusters, defoamers, plasticizers, and preservatives. The amount of such a pigment coating layer applied is, for example, 2 to 40 g / m² in terms of solid content per side of a paper substrate. 2In one embodiment of the packaging paper of the present invention, the barrier layer may be provided on such a pigment coating layer, that is, it is preferable that the pigment coating layer is provided on the inside of the barrier layer, i.e., between the outer barrier layer and the inner paper substrate. In another embodiment, the barrier layer may be provided on the side of the paper substrate that does not have a pigment coating layer, where the pigment coating layer is provided on only one side.

[0023] In this embodiment, the basis weight of the packaging paper is not particularly limited, but for example, 10 to 500 g / m² 2 Therefore, considering the coating and processing suitability of the barrier layer, it is preferably 20 to 400 g / m². 2 It is preferable.

[0024] In another embodiment of the present invention, there is a packaging paper having at least one barrier layer on at least one surface of a paper substrate, wherein the barrier layer is made of an ionomer resin or a polyvinylidene chloride resin (PVDC), and the coating amount of the barrier layer is 15 g / m². 2 The following conditions apply, and the Cobb water absorption (120 seconds) of the surface with the barrier layer, according to JIS P8140, is 10 g / m². 2 The following relates to packaging paper. Preferably, this packaging paper is manufactured by the packaging paper manufacturing method of the present invention. [Examples]

[0025] 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.

[0026] (Example 1) (Preparation of paper substrate) A pulp was prepared by adding water to 100 parts Canadian Standard Freeness 525ml csf bleached hardwood kraft pulp, 5 parts light calcium carbonate (product name: TP-121, manufactured by Okutama Kogyo Co., Ltd.), 0.3 parts cationized starch (product name: Neotack 30T, manufactured by Nippon Shokuhin Kako Co., Ltd.), and 0.4 parts neutral rosin sizing agent (product name: CC167, manufactured by Seikou PMC Co., Ltd.). The resulting pulp was then processed using a multi-cylinder, long-screen paper machine to produce a paper with a basis weight of 248 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 250g / m² and let it dry. 2 A paper substrate was obtained.

[0027] (Preparation of coating solution for pigment coating layer) Fifteen parts of kaolin (product name: Contour 1500, manufactured by Imerys) and eighty-five parts of heavy calcium carbonate (product name: Carvilax, manufactured by Imerys) were mixed with 0.15 parts of a dispersant (product name: Aron T-50, manufactured by Toagosei Co., Ltd.), water was added, and the mixture was dispersed in a Koles disperser to prepare a pigment slurry. To this pigment slurry, one part of phosphated starch (product name: MS4600, manufactured by Nippon Shokuhin Kako Co., Ltd.) and ten parts of styrene-butadiene latex (product name: PA0372, manufactured by Nippon A&L Co., Ltd.) were added as binders, and water was further added and dispersed to prepare a coating solution for a pigment coating layer with a solid content of 50%.

[0028] (Preparation of coated 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 surface was coated using a blade coater and dried to achieve the desired finish. Afterwards, it underwent calendering treatment, resulting in a basis weight of 270 g / m². 2 A coated paper substrate (coated paper) was manufactured.

[0029] (Preparation of packaging paper) On one side of the coated paper substrate obtained above, a water-based ionomer polymer emulsion (product name: Chemipearl S300, manufactured by Mitsui Chemicals, Inc.) was diluted with isopropyl alcohol (IPA) to a solid content concentration of 33% (IPA addition rate 5.7%), resulting in a total dry coating weight of 8 g / m². 2 To achieve this, the gravure printing press honeycomb plate (175 lines / inch) was used to apply two coats of coating (total coating amount after two coats: 8 g / m²). 2 The material was dried at 120°C to create a barrier layer, and packaging paper was produced.

[0030] (Example 2) In Example 1, the coating amount of the barrier layer was 15 g / m². 2 Packaging paper was prepared in the same manner as in Example 1, except for the following:

[0031] (Example 3) In Example 1, the coating amount of the barrier layer was 3 g / m². 2 Except for the change made, the packaging paper was prepared in the same manner as in Example 1.

[0032] (Example 4) Similar to Example 1, after applying the barrier layer, UV 4-color printing was performed on the side opposite the barrier layer in a single pass to produce packaging paper.

[0033] (Example 5) Packaging paper was prepared in the same manner as in Example 1, except that the amount of neutral rosin sizing added to the paper substrate was changed to 0.05 parts. (The sizing agent content of this paper substrate was quantified by gas chromatography-mass spectrometry (GC-MS) and was found to be 0.02% by mass.)

[0034] (Example 6) Packaging paper was prepared in the same manner as in Example 1, except that the amount of neutral rosin sizing added to the paper substrate was changed to 0 parts.

[0035] (Example 7) (Preparation of paper substrate) 100 parts Canadian Standard Freeness 520ml csf 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 0.15 parts neutral rosin sizing agent (Sizing Pine NT-78, manufactured by Arakawa Chemical Industries Co., Ltd.) were mixed with water to prepare a pulp, and the resulting paper was processed using a multi-cylinder, long-screen paper machine to produce a basis weight of 28 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 30g / m² and let it dry. 2 A paper substrate was obtained.

[0036] (Preparation of packaging paper) On one side of the paper substrate obtained above, a water-based polyvinylidene chloride polymer emulsion (product name: L536B, manufactured by Asahi Kasei Corporation) was diluted with water to a solid content concentration of 45%, and the total dry coating amount was 8 g / m². 2 To achieve this, the gravure printing press honeycomb plate (120 lines / inch) was used to apply two coats of coating (total coating amount after two coats: 8 g / m²). 2 The packaging paper was then prepared by drying it at 125°C to create a barrier layer.

[0037] (Example 8) In Example 7, the coating amount of the barrier layer was 15 g / m². 2 Packaging paper was prepared in the same manner as in Example 5, except for the following:

[0038] (Example 9) In Example 7, the coating amount of the barrier layer was 3 g / m². 2 Except for the change made, the packaging paper was prepared in the same manner as in Example 5.

[0039] (Example 10) Similar to Example 7, after applying the barrier layer, UV 4-color printing was performed on the side opposite the barrier layer in a single pass to produce packaging paper.

[0040] (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 25 g / m². 2 The packaging paper was created by laminating it to create a barrier layer.

[0041] (Comparative Example 2) In Example 1, packaging paper was prepared in the same manner as in Example 1, except that the gravure printing plate was changed to a grid-type plate.

[0042] (Comparative Example 3) In Example 1, the packaging paper was prepared in the same manner as in Example 1, except that the gravure printing plate was changed to a diagonal line printing plate.

[0043] (Comparative Example 4) In Example 1, the packaging paper was prepared in the same manner as in Example 1, except that the gravure printing plate was changed to a pyramidal plate.

[0044] The packaging paper obtained in each example and comparative example was evaluated using the method described below. The results are shown in Table 1.

[0045] (1) Cobb water absorption rate (120 seconds) In accordance with JIS P8140, the water repellency of the barrier layer surface was evaluated with a measurement time of 120 seconds. A smaller value (Cobb water absorption) indicates higher barrier properties and higher water repellency.

[0046] [Table 1]

[0047] As is clear from Table 1, the packaging papers of Examples 1 to 8 have barrier properties equivalent to Comparative Example 1 while reducing the amount of poly-lamination. Furthermore, they exhibited superior barrier properties compared to Comparative Examples 2 to 4. In particular, Examples 4 and 8 can help suppress cost increases in the production of printed products.

Claims

1. A method for manufacturing packaging paper having at least one barrier layer on at least one surface of a paper substrate, characterized in that the barrier layer is provided by gravure printing and the coating roll plate is a honeycomb plate.

2. A method for manufacturing packaging paper having at least one barrier layer on at least one surface of a paper substrate, characterized in that the barrier layer is provided by gravure coating and the coating roll plate is a honeycomb plate.

3. The coating amount of the barrier layer of the aforementioned packaging paper is 15 g / m². ２ The following applies to surfaces having a barrier layer, and the Cobb water absorption (120 seconds) according to JIS P8140 is 10 g / m². ２ A method for manufacturing packaging paper according to claim 1 or 2, characterized in that it is as follows.

4. A method for producing packaging paper according to any one of claims 1 to 3, characterized in that the paper substrate is prepared by adding 0.05 to 1.0 part by mass of a sizing agent to 100 parts by mass of pulp.

5. A method for producing packaging paper according to any one of claims 1 to 4, characterized by adding alcohol to the coating liquid for the barrier layer.

6. A method for manufacturing packaging paper according to any one of claims 1 to 5, characterized in that two or more barrier layers are formed on at least one surface.

7. A packaging paper having at least one barrier layer on at least one surface of a paper substrate, wherein the barrier layer is made of an ionomer resin or a polyvinylidene chloride resin (PVDC), The coating amount of the barrier layer is 15 g / m². ２ The following, and, The Cobb water absorption (120 seconds) of the surface with the barrier layer, according to JIS P8140, is 10 g / m². ２ The packaging paper is characterized by the following:

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