packaging paper

Abstract

To provide packaging paper that achieves a reduced amount of use of plastic, and is suitable for use as a bag and excellent in processing suitability such as bending.SOLUTION: This invention relates to packaging paper having at least one heat seal layer on at least one side of a paper substrate, the heat seal layer containing an ionomer, and a total amount of dry coating of the heat seal layer being 2-10 g / m2. The packaging paper has a basis weight of 10-100 g / m2, and the packaging paper has a tensile breaking elongation in a CD direction (JIS P-8113) of 3% or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a packaging paper that uses a reduced amount of plastic, and also to a packaging paper that is suitable for use as a bag and has excellent processability, particularly in folding processing. [Background technology]

[0002] In recent years, the problem of plastic waste has become more serious. Global plastic production is said to exceed 400 million tons per year, with a large amount of plastic produced in the packaging sector, causing plastic waste. Plastic does not decompose permanently, and this waste breaks down into microplastics in the natural environment, causing serious damage to the ecosystem. The most commonly used plastics for packaging are polyethylene terephthalate (PET), used in beverage bottles, and polyethylene (PE) and polypropylene (PP), used in plastic bags and container lamination. Marine pollution is particularly severe, and it is said that the plastic waste is impossible to recover. Reducing plastic use in the future is necessary for the global environment.

[0003] Meanwhile, the use of biodegradable plastics, which can be completely decomposed by microorganisms, has been proposed worldwide as a measure against plastic waste. Biodegradable plastics decompose in nature within a certain period of time, but until they are decomposed they are still considered waste, and unless their usage and disposal amounts are reduced, they cannot be considered an immediately effective measure (see Patent Documents 1 and 2).

[0004] As an immediate solution, replacing plastic with paper has been proposed, but when processing paper into bags or containers, a large amount of polyethylene or polypropylene is laminated as a heat seal agent. The amount of lamination of these plastics varies depending on the product concept, but is generally 20 to 50 g / m 2 and 300 g / m 2Therefore, even when plastic is replaced with paper for packaging, the amount of plastic used remains a problem, 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] Japanese Patent Application Laid-Open No. 2012-148444 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-141763 Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is to provide a packaging paper that can reduce the amount of plastic used, and in particular, to provide a packaging paper that is suitable for use as a bag and has excellent processability, particularly for folding. [Means for solving the problem]

[0007] In the present invention, an ionomer is used to reduce the amount of polyethylene or polypropylene used in conventional plastic-laminated paper (hereinafter sometimes abbreviated as polylaminated paper). That is, the packaging paper according to the present invention is a packaging paper having at least one heat-seal layer on at least one side of a paper base material, the heat-seal layer containing an ionomer, and the coating amount of the heat-seal layer is 2 to 10 g / m. 2 The laminated amount of polyethylene or polypropylene used in the heat seal layer of conventional polylaminated paper is 20 g / m 2Compared to the conventional method, which requires more than 1000 kJ / s, the amount of plastic used in the heat-seal layer can be reduced to about 10 to 50%. Here, ionomer is a synthetic resin that uses the cohesive force of metal ions to aggregate polymers, and is a synthetic resin that combines acrylic acid or methacrylic acid with ethylene or the like. For example, it is produced by intermolecularly bonding an acrylic polymer and ethylene with the addition of metal cations such as sodium or zinc.

[0008] In the present invention, the basis weight of the packaging paper is 10 to 100 g / m 2 The tensile elongation at break (JIS P-8113) of the packaging paper in the CD (cross direction; width direction (transverse) of the paper machine) must be 3% or more. If it is not within this range, the heat-sealed layer will break when folded, resulting in a loss of water resistance and oil resistance. This is because the heat-sealed layer containing an ionomer is thinner than the polyethylene layer, and is therefore less flexible and elongated, making it more susceptible to cracking. If the tensile elongation at break is low, force will be concentrated at the distorted apex of the fold during folding, stretching the fibers, and the heat-sealed layer will also be stretched concomitantly, causing cracks. If the tensile elongation at break is high, the elongation between the fibers will be averaged at the distorted area of ​​the fold during folding, preventing cracks in the heat-sealed area and resulting in packaging paper with excellent water resistance and oil resistance.

[0009] The basis weight is 10 g / m 2 ~100g / m 2 This allows for a flexible bag and a practical wrapping paper to be obtained.

[0010] In the present invention, the paper base material may contain a sizing agent, because this allows the resulting wrapping paper to have excellent water resistance and oil resistance.

[0011] In the present invention, it is preferable that the tensile elongation at break in the CD direction of the paper substrate (JIS P-8113) is 3% or more and smaller than the tensile elongation at break of the packaging paper, because this allows for the production of packaging paper with excellent water resistance and oil resistance.

[0012] In the present invention, the pulp component contained in the paper base material preferably contains 5 parts by mass or more of softwood pulp, because this allows for the production of packaging paper with excellent water resistance and oil resistance.

[0013] In the present invention, the paper substrate preferably contains a water-soluble polymer, and the water-soluble polymer preferably contains starches and / or polyacrylamides. [Effects of the Invention]

[0014] The present invention makes it possible to produce packaging paper with reduced plastic usage. Even if container products using the packaging paper of the present invention are inappropriately disposed of as waste in nature, they can reduce the negative impact of plastic waste on the natural environment, thereby helping to solve the plastic waste problem. The packaging paper of the present invention can be processed into a wide range of packaging containers, including bags, food cups for ice cream and other beverages, coffee and other beverages, food containers for hot snacks, and trays, boxes, cases, dishes, envelopes, and other products. As a packaging paper for thin items, it is particularly suitable for processing into bags and has excellent water and oil resistance. DETAILED DESCRIPTION OF THE INVENTION

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

[0016] In this embodiment, "ionomer" refers to a synthetic resin in which polymers are aggregated using the cohesive force of metal ions. This refers to a resin formed by combining acrylic acid or methacrylic acid with ethylene or the like. In other words, metal salts of ethylene-methacrylic acid copolymers, metal salts of ethylene-acrylic copolymers, metal salts of ethylene-urethane copolymers, and metal salts of ethylene-fluorine-based polymer copolymers are all referred to as ionomers. Metals that form salts include, for example, alkali metal ions and alkaline earth metal ions, specifically, sodium, potassium, calcium, magnesium, and zinc ions. In the present invention, the ionomer is preferably a self-emulsifying emulsion of a metal salt of ethylene-methacrylic acid copolymer. A heat-seal layer with sufficient heat-seal strength can be formed even with a relatively small coating weight.

[0017] In this embodiment, a heat-seal layer can be provided by applying a coating liquid for a heat-seal layer containing an ionomer emulsion to at least one side of a paper substrate and drying it. By using an ionomer emulsion, it is possible to control the coating weight to a relatively low level, and furthermore, by using an aqueous ionomer emulsion, VOC emissions are eliminated, thereby reducing the burden on the natural environment. The coating weight of the heat-seal layer is 2 to 10 g / m2 in terms of solid content per side of the paper substrate. 2 and preferably 3 to 8 g / m 2 2g / m 2 If it is less than 10g / m, sufficient heat seal strength cannot be achieved. 2 If the heat seal strength exceeds this value, the quality is excessive in terms of heat seal strength and the effect of reducing plastics is poor. In the packaging paper of the present invention, the heat seal layer is usually provided on the entire surface of the paper substrate, rather than only on a portion of the surface. In other words, it is preferable that the heat seal layer is provided so as to cover the entire surface of the paper substrate, rather than being provided only on the portion necessary for adhesion by heat sealing, such as in a net, island, or line shape.

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

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

[0020] In this embodiment, the heat seal layer may be formed of two or more layers. This is because two or more layers can increase the air permeability of the packaging paper and further impart water resistance and oil resistance, thereby obtaining properties similar to or close to those of plastic film-laminated paper. When the heat seal layer has two or more layers, it is preferable that the coating weight of the lowermost heat seal layer closest to the paper substrate be greater than the total coating weight of the other heat seal layers. This is because the air permeability of the packaging paper can be further improved, and the water resistance and oil resistance can be further enhanced.

[0021] In the present invention, the basis weight of the packaging paper is 10 to 100 g / m 2 The tensile elongation at break in the CD direction (JIS P-8113) of the packaging paper must be 3% or more. 2 If the weight is less than 100g / m, the bag will not be strong enough to be used practically. 2If it exceeds this, the flexibility of the bag will decrease and it will not be practically usable. If the tensile elongation at break in the CD direction is below 3%, force will be concentrated at the distorted apex of the fold during folding, stretching the fibers, and the heat-sealed layer will also be stretched, causing cracks and reducing water and oil resistance. If the tensile elongation at break in the CD direction is 3% or more, the elongation between the fibers will be averaged at the distorted part of the fold during folding, so cracks will not occur in the heat-sealed layer. There are no specific specifications for the tensile elongation at break in the MD direction (machine direction; the direction in which the paper machine travels). It is assumed that cracks will not occur in the heat-sealed layer because the fibers are aligned in the MD direction and the gaps between the fibers are less likely to widen.

[0022] In this embodiment, the tensile elongation at break in the CD direction of the paper substrate (JIS P-8113) is preferably 3% or more and less than the tensile elongation at break in the CD direction of the packaging paper. Outside this range, water resistance and oil resistance may be reduced. The tensile elongation at break in the CD direction of the paper substrate can be adjusted by the type of pulp, pulp freeness, the addition of chemicals such as paper strength agents, density, etc. Below, we describe the phenomenon and effects that occur when the tensile elongation at break in the CD direction of the paper substrate is smaller than the tensile elongation at break in the CD direction of the packaging paper. When a heat-seal layer coating liquid is applied to a paper substrate, moisture in the coating liquid is absorbed by the fibers. As the moisture evaporates during drying, the fibers shrink, and the tensile elongation at break tends to be higher than before coating. It is believed that the tensile elongation at break of the fibers near the heat-seal layer that has absorbed moisture is particularly high. This leads to more uniform elongation between fibers in the curved area of ​​the fold during folding, particularly near the heat-seal layer, making the heat-seal layer less likely to crack. The tensile elongation at break in the CD direction of the packaging paper (JIS P-8113) is preferably at least 0.1% greater than the tensile elongation at break in the CD direction of the paper substrate. On the other hand, if the tensile elongation at break in the CD direction of the paper substrate is not smaller than the tensile elongation at break in the CD direction of the packaging paper, the effect is lost, and there is a risk of cracks in the heat-seal layer during folding. For example, if the fibers of the paper substrate are in a state where they do not absorb moisture when the heat-seal layer coating liquid is applied (for example, if they are covered with a non-absorbent resin or a water-resistant material), the tensile elongation at break in the CD direction of the paper substrate may not be smaller than the tensile elongation at break in the CD direction of the packaging paper.

[0023] When a separate coating layer (underlayer) is provided between the paper substrate and the heat seal layer, the tensile elongation at break in the CD direction of the paper substrate is preferably smaller than the tensile elongation at break in the CD direction of the packaging paper. When a separate layer is provided, the tensile elongation may be larger for the above-mentioned reasons.

[0024] The paper base material used in this embodiment is not particularly limited, and any known paper base material containing pulp as a primary component can be used. Examples of pulp that can be used as a primary component of the paper base material include chemical pulps such as LBKP (bleached hardwood kraft pulp), NBKP (bleached softwood kraft pulp), LUKP (unbleached hardwood kraft pulp), and NUKP (unbleached softwood kraft pulp), mechanical pulps such as GP (groundwood pulp), PGW (pressure groundwood pulp), RMP (refiner mechanical pulp), TMP (thermomechanical pulp), CTMP (chemithermomechanical pulp), CMP (chemi-mechanical pulp), and CGP (chemi-ground pulp), wood pulps such as DIP (deinked pulp), and non-wood pulps such as kenaf, bagasse, bamboo, cotton, and Manila hemp. These pulps can be used alone or in any combination. Hardwood pulp has relatively short fibers, which tends to be detrimental to tensile elongation at break. On the other hand, softwood pulp and non-wood pulp have longer fibers than hardwood pulp, which are stronger and tend to increase tensile elongation at break. For example, it is preferable to use 5 parts by mass or more of softwood pulp, such as NBKP (softwood bleached kraft pulp) or NUKP (softwood unbleached kraft pulp), in the pulp. This provides sufficient strength for practical use when used as a bag, and also provides excellent water and oil resistance. If the amount is less than 5 parts by mass, the strength may be insufficient for practical use when used as a bag, and the tensile elongation at break may decrease, resulting in reduced water and oil resistance. Preferably, pulp containing 5 to 20 mass% of NBKP (softwood bleached kraft pulp) and 95 to 80 mass% of LBKP (hardwood bleached kraft pulp) is used. Furthermore, when the tensile elongation at break is further increased, it is preferable to use pulp containing 80 to 95 mass% of NBKP (softwood bleached kraft pulp) and 5 to 20 mass% of LBKP (hardwood bleached kraft pulp). Furthermore, synthetic fibers can be further blended within a range that does not impair the intended effects of the present invention. From the viewpoint of environmental conservation, ECF (elemental chlorine free) pulp, TCF (total chlorine free) pulp, unbleached pulp, recycled paper pulp, and pulp obtained from planted trees are preferred.For example, the appropriate beating degree of pulp is 200 to 700 ml CSF, for example, 320 to 700 ml CSF in terms of Canadian standard freeness (JIS P 8121:1995 "Testing method for freeness of pulp"). 660 mlCSF. Beating pulp causes minute branches and fuzzing in the pulp fibers, which has the effect of strengthening the bonds between the pulp fibers. If the freeness is below 200 ml, the pulp will be beaten excessively, and the bonds between the pulp fibers will become too dense, which tends to reduce the tensile elongation at break. If the freeness is above 700 ml, the bonds between the pulp fibers will be weak, which tends to reduce the tensile elongation at break. By adjusting the freeness to an appropriate range, it is possible to adjust the tensile elongation at break.

[0025] The paper base material may contain a filler. 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 base material is, for example, 1 to 30 parts by mass per 100 parts by mass of the dry mass of pulp. For example, the paper base material may contain 1 to 15 parts by mass, preferably 2 to 10 parts by mass, of light calcium carbonate per 100 parts by mass of the dry mass of pulp.

[0026] Furthermore, the inclusion of a water-soluble polymer in the paper substrate can improve the tensile elongation at break. Examples of water-soluble polymers that can be used include corn starch, potato starch, tapioca starch, and starches such as crosslinker-modified starch, oxidized starch, enzyme-modified starch, esterified starch, etherified starch, cationic starch, and amphoteric starch, as well as polyvinyl alcohol and polyacrylamide. Starches and polyacrylamides are particularly preferred. The amount of water-soluble polymer added is 0.05 parts by mass or more per 100 parts by mass of pulp, and more preferably 0.1 parts by mass or more. For example, the water-soluble polymer is preferably added in an amount of 0.1 to 10 parts by mass, preferably 0.1 to 7.0 parts by mass, per 100 parts by mass of pulp. Furthermore, it is preferable to add 0.1 to 7.0 parts by mass, preferably 0.1 to 5.0 parts by mass of polyacrylamide and / or 0.1 to 3.0 parts by mass, preferably 0.1 to 2.0 parts by mass of starch, preferably cationized starch, relative to 100 parts by mass of pulp. As a method for adding them, known methods such as internal addition and coating (size press, air knife coater, etc.) can be used.

[0027] It is also preferable for the paper substrate to contain a sizing agent. By incorporating a sizing agent, penetration of the coating solution into the substrate during application of the heat seal layer or underlayer is moderately suppressed, resulting in excellent water and oil resistance. Furthermore, moderately suppressed penetration is thought to allow the fibers near the coating layer to absorb moisture, which is particularly beneficial for improving the tensile elongation at break. The content is, for example, 0.05 parts by mass or more per 100 parts by mass of pulp. Examples of sizing agents include neutral rosin sizing agents, fortified rosin sizing agents, acidic rosin sizing agents, weakly acidic rosin sizing agents, AKD (alkyl ketene dimer), and ASA (alkenyl succinic anhydride). Fluorine-based water and oil repellents are not preferred as sizing agents due to their high cost, poor economic efficiency, and high environmental impact. In the present invention, it is preferable for the paper substrate to contain 0.05 to 1.0 parts by mass, or even 0.1 to 0.5 parts by mass, of a neutral rosin sizing agent per 100 parts by mass of pulp.

[0028] In addition to pulp and filler, the paper base material may contain various known papermaking additives, such as sizing agents, internal paper strength agents such as wet strength agents, bulking agents, retention aids, drainage aids, coloring dyes, coloring pigments, fluorescent brighteners, fluorescent decolorizers, and pitch control agents. The paper base material may also be coated with water-soluble polymers such as starch, polyvinyl alcohol, and polyacrylamide.

[0029] The method for making the paper base material is not particularly limited, and the paper base material can be produced using various paper machines such as a Fourdrinier paper machine, a multi-layer Fourdrinier paper machine, a cylinder paper machine, a multi-layer cylinder paper machine, a multi-layer Fourdrinier cylinder combination paper machine, a twin-wire paper machine, etc. In the present invention, the paper base material may be a single-layer paper machine, a multi-layer paper machine, or a laminate of multiple layers.

[0030] The paper substrate may have one or more coating layers (underlayers) other than the heat seal layer, such as a pigment coating layer containing a pigment and an adhesive. The pigment in the pigment coating layer may be any of the well-known pigments used in coating layers of typical coated printing papers, including 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, and magnesium hydroxide. Examples of suitable pigments include inorganic pigments such as acrylic, styrene, vinyl chloride, and nylon, as well as organic pigments obtained by copolymerizing these pigments (so-called plastic pigments). For example, a combination of 20 to 40 parts by weight of kaolin and 60 to 80 parts by weight of heavy calcium carbonate may be used. The adhesive can be any known adhesive used in coating layers of general coated printing papers, including starches such as butadiene copolymer latex, crosslinker-modified starch, oxidized starch, enzyme-modified starch, esterified 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 blending ratio of pigment and adhesive in the pigment coating layer is not particularly limited, but a ratio of 5 to 50 parts by weight of adhesive per 100 parts by weight of pigment is preferred. For example, a combination of 1 to 5 parts by weight of phosphated starch and 5 to 15 parts by weight of styrene-butadiene latex per 100 parts by weight of pigment can be used as the adhesive. The pigment coating layer may contain various auxiliaries within the range that does not impair the intended effects of the present invention, such as viscosity adjusters, softeners, gloss-imparting agents, water-resistant agents, dispersants, flow modifiers, UV absorbers, stabilizers, antistatic agents, crosslinking agents, sizing agents, fluorescent whitening agents, colorants, pH adjusters, antifoaming agents, plasticizers, and preservatives. The coating weight of such a pigment coating layer is, 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 base having a pigment coating layer on only one side, where the pigment coating layer is not provided. [Example]

[0031] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Furthermore, "parts" and "%" in the examples represent "parts by mass" and "% by mass", respectively, unless otherwise specified. The number of added parts is a value calculated on a solid content basis.

[0032] Example 1 (Preparation of paper substrate) 90 parts of softwood bleached kraft pulp and 10 parts of hardwood bleached kraft pulp were mixed and beaten to a Canadian Standard Freeness of 400 mlcsf. Next, 3.5 parts of light calcium carbonate (product name: TP-123, manufactured by Okutama Kogyo Co., Ltd.), 3 parts of polyacrylamide (product name: DS4429, manufactured by Seiko PMC Co., Ltd.), 1 part of cationized starch (product name: Neotack 30T, manufactured by Nippon Shokuhin Kako Co., Ltd.), and 0.3 parts of a neutral rosin sizing agent (product name: CC1401, manufactured by Seiko PMC Co., Ltd.) were added to the beaten pulp to prepare a paper stock. The paper stock was then spun using a fourdrinier multi-cylinder paper machine to a basis weight of 38 g / m. 2 Oxidized starch (product name: MS3800, manufactured by Nippon Shokuhin Kako Co., Ltd.) was applied to this base paper by a size press in a dry coating amount of 2 g / m on both sides. 2 Apply the coating so that it becomes 40g / m2 and dry it. 2 The tensile elongation at break in the CD direction was 7.0%.

[0033] (Wrapping paper production) A water-based ionomer emulsion (product name: Chemipearl S-300, manufactured by Mitsui Chemicals, Inc., composition: metal salt of ethylene-methacrylic acid copolymer, self-emulsifying emulsion, average particle size measured by Microtrac method: 0.5 μm) was applied to one side of the paper substrate obtained above at a dry coating weight of 5 g / m 2The coating was then dried to form a heat seal layer, producing a packaging paper. The tensile elongation at break in the CD was 9.5%.

[0034] Example 2 Packaging paper was produced in the same manner as in Example 1, except that the pulp was changed to 10 parts softwood bleached kraft pulp and 90 parts hardwood bleached kraft pulp. The tensile elongation at break in the CD direction of the paper base material was 4.0%. The tensile elongation at break in the CD direction of the packaging paper was 5.1%.

[0035] Example 3 Packaging paper was produced in the same manner as in Example 2, except that the amount of neutral rosin sizing agent (product name: CC1401, manufactured by Seiko PMC Corporation) was changed to 0 parts. The tensile elongation at break in the CD direction of the paper base material was 4.0%. The tensile elongation at break in the CD direction of the packaging paper was 4.8%.

[0036] Example 4 Packaging paper was produced in the same manner as in Example 2, except that the amount of polyacrylamide (product name: DS4429, manufactured by Seiko PMC) was changed to 0 parts, and the amount of cationized starch (product name: Neotack 30T, manufactured by Nippon Shokuhin Kako Co., Ltd.) was changed to 0 parts. The tensile elongation at break in the CD direction of the paper base material was 3.2%. The tensile elongation at break in the CD direction of the packaging paper was 4.0%.

[0037] Example 5 Packaging paper was produced in the same manner as in Example 1, except that the pulp was changed to 0 parts softwood bleached kraft pulp and 100 parts hardwood bleached kraft pulp. The tensile elongation at break in the CD direction of the paper base material was 3.3%. The tensile elongation at break in the CD direction of the packaging paper was 4.2%.

[0038] Example 6 Packaging paper was produced in the same manner as in Example 2, except that the Canadian Standard Freeness was changed to 650 mlcsf. The tensile elongation at break in the CD direction of the paper base material was 3.4%. The tensile elongation at break in the CD direction of the packaging paper was 4.3%.

[0039] Example 7 Packaging paper was produced in the same manner as in Example 1, except that the pulp was changed to 90 parts unbleached softwood kraft pulp and 10 parts bleached hardwood kraft pulp. The tensile elongation at break in the CD direction of the paper base material was 7.2%. The tensile elongation at break in the CD direction of the packaging paper was 9.6%.

[0040] Example 8 Packaging paper was produced in the same manner as in Example 2, except that the amount of precipitated calcium carbonate (product name: TP-123, manufactured by Okutama Kogyo Co., Ltd.) was changed to 10 parts. The tensile elongation at break in the CD direction of the paper base material was 3.1%. The tensile elongation at break in the CD direction of the packaging paper was 3.9%.

[0041] Example 9 Packaging paper was produced in the same manner as in Example 2, except that the amount of cationic starch (product name: Neotack 30T, manufactured by Nippon Shokuhin Kako Co., Ltd.) was changed to 0 parts. The tensile elongation at break in the CD direction of the paper base material was 3.5%. The tensile elongation at break in the CD direction of the packaging paper was 4.5%.

[0042] Example 10 Packaging paper was produced in the same manner as in Example 2, except that the amount of polyacrylamide (product name: DS4429, manufactured by Seiko PMC Corporation) was changed to 0 parts. The tensile elongation at break in the CD direction of the paper base material was 3.4%. The tensile elongation at break in the CD direction of the packaging paper was 4.4%.

[0043] (Comparative Example 1) Packaging paper was produced in the same manner as in Example 1, except that the pulp was changed to 0 parts softwood bleached kraft pulp and 100 parts hardwood bleached kraft pulp, the Canadian Standard Freeness was changed to 650 ml csf, the polyacrylamide (product name: DS4429, manufactured by Seiko PMC) was changed to 0 parts, the cationized starch (product name: Neotack 30T, manufactured by Nippon Shokuhin Kako Co., Ltd.) was changed to 0 parts, the neutral rosin size (product name: CC1401, manufactured by Seiko PMC) was changed to 0 parts, and the precipitated calcium carbonate (product name: TP-123, manufactured by Okutama Kogyo Co., Ltd.) was changed to 25 parts. The tensile elongation at break in the CD direction of the paper substrate was 2.5%. The tensile elongation at break in the CD direction of the packaging paper was 2.8%.

[0044] The wrapping papers obtained in each of the Examples and Comparative Examples were evaluated by the methods described below. The results are shown in Tables 1 to 3.

[0045] (1) Tensile elongation at break in the CD direction Measurement was carried out in accordance with JIS P-8113.

[0046] (2) Heat seal strength The resulting wrapping paper was cut into two pieces measuring 8 mm wide and 15 cm long, and the front and back sides of the wrapping paper were overlapped and heat-sealed using a heat-sealing device (Palmec, model number: PTS-100) under set conditions (adhesion width: 4 mm, temperature: 180°C, pressure: 0.4 MPa, pressing time: 0.5 seconds, pitch: 4 mm). The heat-sealed sample was then peeled using a peel strength tester (Shimadzu, model number: Autograph AGS-X) under set conditions (peel speed: 100 mm / min, peel length: 10 cm) to evaluate whether peeling occurred on the paper substrate, within the heat-seal layer, or at the heat-seal layer-heat-seal layer interface. It is desirable for fracture to occur within the paper substrate, resulting in peeling (commonly referred to as material breakage). ◎: The paper base material is broken down and is at a practical level. Good: The paper base material is torn, and some peeling has occurred from the heat seal layer. Practical level. △: The heat seal layer is broken and peeled off. Unsuitable for practical use. ×: Peeling occurred at the heat seal layer-heat seal layer interface, to a level not suitable for practical use.

[0047] (3) Water resistance of the folded part The resulting packaging paper was cut to a size of 5 cm wide and 10 cm long, folded in half with the heat seal layer side facing inward, and a 5 kg metal roll was passed back and forth over the fold. The folded portion was aligned so that the fold was in the machine direction (MD; the direction in which the paper machine travels). The folded portion was opened, and a test liquid with a surface tension of 38 mN / m in accordance with JIS K 6768:1999 (Plastics - Films and Sheets - Wetting Tension Test Method) was dropped onto the fold on the heat seal layer side. After 15 seconds, the test liquid was wiped off, and the penetration of the test liquid into the paper substrate was evaluated. ◎: No penetration, practical level. 〇: Slight penetration, but practical level. △: Penetrated to the point where it is not practical. ×: The penetrating liquid has leaked to the back side, making it unusable.

[0048] (4) Oil resistance of bent parts The resulting packaging paper was cut to a size of 5 cm wide and 10 cm long, folded in half with the heat seal layer side facing inward, and a 5 kg metal roll was passed back and forth over the fold. The folded portion was aligned so that the fold was in the machine direction (MD; the direction in which the paper machine travels). The folded portion was then opened, and a test liquid with a kit value of 8 in accordance with TAPPI T-559cm-02 (kit method) was dropped onto the fold on the heat seal layer side. After 15 seconds of application, the test liquid was wiped off, and the penetration of the test liquid into the paper substrate was evaluated. ◎: No penetration, practical level. 〇: Slight penetration, but practical level. △: Penetrated to the point where it is not practical. ×: The penetrating liquid has leaked to the back side, making it unusable.

[0049] [Table 1]

[0050] As is clear from Table 1, the packaging papers of Examples 1 to 10 have a tensile elongation at break in the CD of 3.0% or more, and therefore are excellent in heat sealability, water resistance at the folded portion, and oil resistance at the folded portion, compared to Comparative Example 1. As the experimental results show, the present invention can significantly reduce the amount of heat seal layer used compared to the amount of conventional polyethylene laminate, contributing to a reduction in 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 in contact with the paper substrate on at least one side of the paper substrate, wherein the heat seal layer contains an ionomer, and the dry coating weight of the heat seal layer is 2 to 10 g / m2 in total. ２ and the basis weight of the packaging paper is 10 to 100 g / m ２ The wrapping paper is characterized in that the tensile breaking elongation in the CD direction (JIS P-8113) of the wrapping paper is 3% to 9.6%.

2. A packaging paper consisting of a paper substrate and at least one heat seal layer on at least one side of the paper substrate, wherein the heat seal layer contains an ionomer, and the dry coating weight of the heat seal layer is 2 to 10 g / m2 in total. ２ and the basis weight of the packaging paper is 10 to 100 g / m ２ The wrapping paper is characterized in that the tensile breaking elongation in the CD direction (JIS P-8113) of the wrapping paper is 3% to 9.6%.

3. 3. The packaging paper according to claim 1, wherein the paper base material contains at least a sizing agent.

4. The wrapping paper according to any one of claims 1 to 3, characterized in that the tensile breaking elongation (JIS P-8113) of the paper base material in the CD direction is 3% or more and is smaller than the tensile breaking elongation of the wrapping paper.

5. 5. The packaging paper according to claim 1, wherein the pulp component contained in the paper base material is 5 parts by mass or more of softwood pulp.

6. 6. The wrapping paper according to claim 1, wherein the paper substrate contains a water-soluble polymer.

7. 7. The wrapping paper according to claim 6, wherein the paper substrate contains starches and / or polyacrylamides as the water-soluble polymer.

8. 4. The packaging paper according to claim 3, wherein the sizing agent is a neutral rosin sizing agent, a fortified rosin sizing agent, an acidic rosin sizing agent, a weakly acidic rosin sizing agent, AKD (alkyl ketene dimer), or ASA (alkenyl succinic anhydride).

9. A method for producing a packaging paper having at least one heat seal layer on at least one side of a paper substrate, the packaging paper having a basis weight of 10 to 100 g / m ２ The packaging paper has a tensile breaking elongation in the CD direction (JIS P-8113) of 3% to 9.6%; After preparing a paper substrate from a paper stock whose main component is pulp, a heat seal layer containing an ionomer is applied to the paper substrate with a dry coating amount of 2 to 10 g / m2 for the entire layer. ２ The method for producing the composition is characterized in that the composition is directly coated on the paper substrate so as to form the composition.

10. The method for manufacturing packaging paper according to claim 9, wherein the paper base material contains at least a sizing agent.

11. 9. The packaging paper according to claim 1, wherein the paper base material does not contain any oil-resistant and water-resistant agent.

12. The method for producing packaging paper according to claim 9 or 10, wherein the paper base material does not contain any oil-resistant and water-resistant agent.

13. 12. The wrapping paper according to claim 1, wherein the heat seal layer does not contain styrene-butadiene copolymer latex.

14. 14. The wrapping paper according to any one of claims 1 to 8, 11 and 13, wherein the heat seal layer is made of an ionomer alone.

15. 13. The method for producing a packaging paper according to claim 9, wherein the heat seal layer does not contain styrene-butadiene copolymer latex.

16. 16. The method for producing a wrapping paper according to any one of claims 9, 10, 12 and 15, wherein the heat seal layer is made of an ionomer alone.

17. A wrapping paper according to any one of claims 1 to 8, 11 and 13, characterized in that the heat seal layer does not contain inorganic pigments.

18. A method for producing a packaging paper as described in any one of claims 9, 10, 12 and 15, characterized in that the heat seal layer does not contain inorganic pigments.

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