JP7515243B2 - Wrapping Paper - Google Patents

Description

The present invention relates to packaging paper that uses a reduced amount of plastic. It also relates to packaging paper that is suitable for use as bags and has excellent workability, particularly in terms of folding and other processes.

In recent years, the problem of plastic waste has become more serious. It is said that the world's plastic production exceeds 400 million tons per year, of which a large amount is produced in the packaging sector, which is the cause of plastic waste. Plastic does not decompose for a long time, and the waste turns into microplastics in the natural environment, causing serious damage to the ecosystem. The most commonly used plastics for packaging containers are polyethylene terephthalate (PET), which is used for beverage bottles, and polyethylene (PE) and polypropylene (PP), which are used for plastic bags and container lamination. Marine pollution is particularly severe, and it is said that the plastic waste is impossible to recover. In the future, it will be necessary for the global environment to reduce the use of plastic.

On the other hand, the use of biodegradable plastics that can be completely decomposed by microorganisms has been proposed around the world as a measure against plastic waste. Biodegradable plastics decompose in nature within a certain period of time, but until they decompose they are still waste, and unless their usage and disposal amounts are reduced, this cannot be considered an immediate solution (see Patent Documents 1 and 2).

As an immediate solution, it has been proposed to replace plastic with paper, but when processing paper into bags or containers, a large amount of polyethylene or polypropylene is laminated as a heat sealant. The amount of plastic laminate varies depending on the product concept, but is generally 20 to 50 g/ ^m2 , and can be as much as 300 g/ ^m2 . Therefore, even in packaging containers where plastic has been replaced with paper, there is still the problem that the amount of plastic used is not sufficiently reduced, and a means to directly reduce the use of plastic is urgently needed.

JP 2012-148444 A JP 2013-141763 A

The objective of the present invention is to provide a wrapping paper that can reduce the amount of plastic used. In particular, the objective is to provide a wrapping paper that is suitable for use as a bag and has excellent workability, particularly in terms of folding and other processes.

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/ ^m2 . Compared to the amount of polyethylene or polypropylene laminate used in the heat seal layer of conventional polylaminated paper exceeding ²⁰ g/m2, the amount of plastic used for the heat seal layer can be reduced to about 10 to 50% of the conventional amount. Here, an ionomer is a synthetic resin that uses the coagulation force of metal ions to make a polymer into an aggregate, and is a synthetic resin that combines acrylic acid or methacrylic acid with ethylene or the like. For example, it is produced by adding a metal cation such as sodium or zinc to an acrylic polymer and ethylene to form an intermolecular bond.

In the present invention, the basis weight of the packaging paper is 10 to 100 g/ ^m2 , and the tensile elongation at break (JIS P-8113) in the CD direction (cross direction; width direction (horizontal direction) of the papermaking machine) of the packaging paper is required to be 3% or more. If it is not within this range, the heat seal layer is destroyed when folded, and the water resistance and oil resistance are impaired. This is because the heat seal layer containing an ionomer is thin and has small flexibility and elongation, making it more likely to crack, compared to the polyethylene layer. If the tensile elongation at break is low, force is concentrated at the distorted apex of the folded part during folding processing, stretching the fibers between the fibers, and the heat seal layer is also stretched concomitantly, causing cracks. If the tensile elongation at break is high, the elongation between the fibers is averaged at the distorted part of the folded part during folding processing, so that no cracks occur in the heat seal part, and a packaging paper with excellent water resistance and oil resistance can be obtained.

Furthermore, a basis weight of 10 g/m ² to 100 g/m ² makes it possible to produce a flexible bag, and thus a practical wrapping paper.

In the present invention, the paper base material may contain a sizing agent. This is because it results in a wrapping paper with excellent water resistance and oil resistance.

In the present invention, it is preferable that the tensile elongation at break in the CD direction of the paper base material (JIS P-8113) is 3% or more and is smaller than the tensile elongation at break of the packaging paper. This is because packaging paper with excellent water resistance and oil resistance can be obtained.

In the present invention, it is preferable that the pulp component contained in the paper base material contains 5 parts by mass or more of softwood pulp. This is because it results in a wrapping paper with excellent water resistance and oil resistance.

In the present invention, it is preferable that the paper base material contains a water-soluble polymer, and it is preferable that the water-soluble polymer contains starch and/or polyacrylamide.

The present invention makes it possible to manufacture packaging paper with reduced plastic usage. If a container product uses the packaging paper of the present invention, even if it is inappropriately released into the natural environment as garbage, it is possible to reduce the adverse impact of plastic garbage on the natural environment, which will help solve the plastic garbage problem. The packaging paper of the present invention can be processed into general packaging containers such as bags, food cups for ice cream, beverage cups for coffee, etc., food containers for hot snacks, etc., and trays, boxes, cases, containers, envelopes, etc. In particular, as a thin packaging paper, it is suitable for processing into bags and has excellent water resistance and oil resistance.

Next, the present invention will be described in detail with reference to an embodiment, but the present invention should not be interpreted as being limited to these descriptions. Various modifications of the embodiment may be made as long as the effects of the present invention are achieved.

In this embodiment, ionomer is a general term for synthetic resins in which polymers are aggregated by utilizing the cohesive force of metal ions, and is a resin in which acrylic acid or methacrylic acid is combined 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-fluorine polymer copolymers, etc. are all called ionomers. Examples of metals that form salts include alkali metal ions and alkaline earth metal ions, specifically, sodium, potassium, calcium, magnesium, and zinc ions. In the present invention, it is preferable that the ionomer is a self-emulsifying emulsion of a metal salt of ethylene-methacrylic acid copolymer. A heat seal layer having sufficient heat seal strength can be provided even if the coating amount of the heat seal layer is relatively small.

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 amount to a relatively low level, and further, by using an aqueous ionomer emulsion, VOC emissions are eliminated, and the burden on the natural environment can be reduced. The coating amount of the heat seal layer is 2 to 10 g/m ² , preferably 3 to 8 g/m ² , calculated as solid content per one side of the paper substrate. If it is less than 2 g/m ² , sufficient heat seal strength cannot be satisfied. On the other hand, if it exceeds 10 g/m ² , 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, not only on a part of the surface of the paper substrate. In other words, the heat seal layer is preferably provided so as to cover the entire surface of the paper base material, rather than being provided only in areas required for adhesion by heat sealing, such as in a net, island or line shape.

In addition to the ionomer emulsion, various auxiliary agents may be added to the coating liquid for the heat seal layer. For example, viscosity adjusters, defoamers, leveling agents such as surfactants and alcohols, color pigments, color dyes, etc. However, the addition of these auxiliary agents tends to reduce the heat seal strength, so 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 an ionomer emulsion.

The method for applying the coating liquid for the heat seal layer is not particularly limited, and any commonly used coating device can be used. For example, various known coating devices 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, and lip coater.

In this embodiment, the heat seal layer may be formed of two or more layers. By forming two or more layers, the air permeability of the packaging paper can be increased, and furthermore, water resistance and oil resistance can be imparted, and properties similar to or close to those of plastic film laminated paper can be obtained. When the heat seal layer has two or more layers, it is preferable that the coating amount of the lowermost 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 resistance and oil resistance can be further improved.

In the present invention, it is necessary that the basis weight of the packaging paper is 10 to 100 g/ ^m2 , and the tensile elongation at break in the CD direction (JIS P-8113) of the packaging paper is 3% or more. If the basis weight is less than 10 g/ ^m2 , the strength as a bag cannot be maintained and it cannot be used practically. If the basis weight is more than 100 g/ ^m2 , the flexibility as a bag decreases and it cannot be used practically. If the tensile elongation at break in the CD direction is less than 3%, the force is concentrated at the distorted apex of the fold during folding processing, stretching the fibers, and the heat seal layer is also stretched concomitantly, causing cracks, and the water resistance and oil resistance are reduced. If the tensile elongation at break in the CD direction is 3% or more, the elongation between the fibers is averaged at the distorted part of the fold during folding processing, so that cracks do not occur in the heat seal layer. There is no particular specification for the tensile elongation at break in the MD direction (machine direction; the direction in which the papermaking machine travels). It is presumed that cracks do not occur in the heat seal layer because the fibers are aligned in the MD direction and the gaps between the fibers are unlikely to widen.

In this embodiment, 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 is smaller than the tensile elongation at break in the CD direction of the packaging paper. If it is not within this range, there is a risk of a decrease in water resistance and oil resistance. The tensile elongation at break in the CD direction of the paper substrate can be adjusted by the type of pulp, the freeness of the pulp, the addition of chemicals such as paper strength agents, density, etc. Below, the phenomenon and effect 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 will be described. When the heat seal layer coating liquid is applied to the paper substrate, the moisture in the coating liquid is absorbed by the fibers, and when the moisture evaporates during drying, the fibers shrink, and the tensile elongation at break tends to be larger than before coating. It is thought that the tensile elongation at break of the fibers near the heat seal layer that has absorbed moisture is particularly large, and the elongation between the fibers in the curved part of the fold during folding processing, especially near the heat seal layer, is more averaged, making it difficult for the heat seal layer to crack. It is preferable that the tensile elongation at break in the CD direction of the packaging paper (JIS P-8113) is 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 not obtained, and there is a risk of the heat seal layer cracking during folding processing. 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 (e.g., 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.

When a separate coating layer (underlayer) is provided between the paper substrate and the heat seal layer, it is preferable that 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 providing a separate layer, the tensile elongation may be larger for the reasons described above.

The paper base material used in this embodiment is not particularly limited, and any known paper base material containing pulp as the main component can be used. As the pulp that is the main component of the paper base material, chemical pulps such as LBKP (hardwood bleached kraft pulp), NBKP (softwood bleached kraft pulp), LUKP (hardwood unbleached kraft pulp), and NUKP (softwood unbleached kraft pulp), mechanical pulps such as GP (groundwood pulp), PGW (pressurized groundwood pulp), RMP (refiner mechanical pulp), TMP (thermo mechanical pulp), CTMP (chemi-thermo mechanical 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 can be used. These can be used alone or mixed in any ratio. Hardwood pulp is a relatively short fiber, which tends to be disadvantageous in terms of tensile elongation at break. On the other hand, softwood pulp and non-wood pulp are longer fibers than hardwood pulp, have higher strength, 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) as the pulp. The strength is sufficient for practical use when used as a bag, and the water resistance and oil resistance are excellent. 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 resistance and oil resistance. It is preferable to use a pulp containing 5 to 20% by mass of NBKP (softwood bleached kraft pulp) and 95 to 80% by mass of LBKP (hardwood bleached kraft pulp). Furthermore, when the tensile breaking elongation is further strengthened, it is preferable to use pulp containing 80 to 95 mass% NBKP (softwood bleached kraft pulp) and 5 to 20 mass% LBKP (hardwood bleached kraft pulp). In addition, synthetic fibers can be further blended within a range that does not impair the intended effect of the present invention. From the viewpoint of environmental conservation, ECF (elemental chlorine free) pulp, TCF (total chlorine free) pulp, unbleached pulp, waste paper pulp, and pulp obtained from plantation trees are preferable. In addition, for example, the appropriate beating degree of pulp is 200 to 700 ml CSF, for example, 320 to 6600 ml CSF in Canadian standard freeness (JIS P 8121: 1995 "Test method for freeness of pulp"). Beating the 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 is beaten excessively, and the bonds between the pulp fibers become too dense, so the tensile elongation at break tends to decrease. If the freeness is above 700 ml, the bonds between the pulp fibers are weak, and the tensile elongation at break tends to decrease. By adjusting the freeness to an appropriate range, it is possible to adjust the tensile elongation at break.

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 the pulp. For example, light calcium carbonate may be contained in an amount of 1 to 15 parts by mass, preferably 2 to 10 parts by mass, per 100 parts by mass of the dry mass of the pulp.

In addition, the inclusion of a water-soluble polymer in the paper base material 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. More preferably, it is 0.1 parts by mass or more. For example, it is preferable to include 0.1 to 10 parts by mass, preferably 0.1 to 7.0 parts by mass, of the water-soluble polymer per 100 parts by mass of pulp. Furthermore, it is preferable to contain 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 cationic starch, per 100 parts by mass of pulp. Known methods such as internal addition and coating (size press, air knife coater, etc.) can be used to contain them.

It is also preferable that the paper base material contains a sizing agent. When the heat seal layer or under layer is applied, the penetration of the coating liquid into the base material is moderately suppressed by the inclusion of a sizing agent, resulting in excellent water resistance and oil resistance. In addition, it is considered that when the penetration is moderately suppressed, the fibers near the coating layer in particular absorb moisture and have an advantageous effect on 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 types of sizing agents include neutral rosin sizing agents, reinforced 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 preferable as sizing agents because they are expensive, have poor economic efficiency, and have a high environmental impact. In the present invention, it is preferable that the paper base material contains 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.

In addition to the pulp and the 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. Water-soluble polymers such as starch, polyvinyl alcohol, and polyacrylamide may also be applied to the paper base material.

The method for making the paper base material is not particularly limited, and the paper base material can be made using various papermaking machines such as a Fourdrinier papermaking machine, a multi-layer Fourdrinier papermaking machine, a cylinder papermaking machine, a multi-layer cylinder papermaking machine, a multi-layer Fourdrinier cylinder papermaking machine, and a twin-wire papermaking machine. In addition, in the present invention, the paper base material may be a single layer or multi-layer papermaking machine, or a laminated product of multiple layers.

The paper substrate may have one or more coating layers (underlayers) other than the heat seal layer, for example, a pigment coating layer containing a pigment and an adhesive. The pigment in the pigment coating layer may be a known pigment used in the coating layer of a general printing coated paper, for example, 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 other inorganic pigments, or acrylic, styrene, vinyl chloride, nylon itself, or organic pigments obtained by copolymerizing these (so-called plastic pigments). For example, a combination of 20 to 40 parts by mass of kaolin and 60 to 80 parts by mass of heavy calcium carbonate may be used as the pigment. The adhesive may be a known adhesive used in the coating layer of a general coated printing paper, and examples of such adhesives include starches such as butadiene-based copolymer latex, crosslinker-modified starch, oxidized starch, enzyme-modified starch, esterified starch, cationic starch, and amphoteric starch, water-soluble polymers such as gelatin, casein, soybean 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 the pigment and 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, the adhesive may be a combination of 1 to 5 parts by mass of phosphated starch and 5 to 15 parts by mass of styrene butadiene latex per 100 parts by mass of pigment. The pigment coating layer may contain various auxiliaries within the range that does not impair the intended effect of the present invention, such as a viscosity regulator, a softener, a gloss imparting agent, a water resistant agent, a dispersant, a flow modifier, an ultraviolet absorbing agent, a stabilizer, an antistatic agent, a crosslinking agent, a sizing agent, a fluorescent brightening agent, a colorant, a pH adjusting agent, an antifoaming agent, a plasticizer, and a preservative. The coating amount of such a pigment coating layer is, for example, 2 to 40 g/ ^m2 in terms of solid content per one side of the base paper. In 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 material having a pigment coating layer on only one side, on which the pigment coating layer is not provided.

Next, the present invention will be described in more detail 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. The number of parts added is a value calculated as the solid content.

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 (trade name: TP-123, manufactured by Okutama Kogyo Co., Ltd.), 3 parts of polyacrylamide (trade name: DS4429, manufactured by Seiko PMC Co., Ltd.), 1 part of cationic starch (trade name: Neotac 30T, manufactured by Nihon Shokuhin Kako Co., Ltd.), and 0.3 parts of neutral rosin sizing agent (trade name: CC1401, manufactured by Seiko PMC Co., Ltd.) were added to the beaten pulp to prepare a paper stock, and a base paper with a basis weight of 38 g/m ² was produced using a fourdrinier multi-cylinder papermaking machine. Oxidized starch (trade name: MS3800, manufactured by Nihon Shokuhin Kako Co., Ltd.) was applied to this base paper by a size press so that the dry coating amount on both sides was 2 g/m ² , and then dried to obtain a base paper with a weight of 40 g/m ² . The tensile elongation at break in the CD direction was 7.0%.

(Making wrapping paper)
One side of the paper base material obtained above was coated with 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 Microtrack method: 0.5 μm) using an air knife coater so that the dry coating amount was 5 g/ ^m2 , and then dried to provide a heat seal layer, thereby producing packaging paper. The tensile elongation at break in the CD direction was 9.5%.

Example 2
A wrapping paper was produced in the same manner as in Example 1, except that the pulp was changed to 10 parts of softwood bleached kraft pulp and 90 parts of hardwood bleached kraft pulp. The tensile breaking elongation in the CD direction of the paper base material was 4.0%. The tensile breaking elongation in the CD direction of the wrapping paper was 5.1%.

( Reference Example 3)
A wrapping paper was prepared in the same manner as in Example 2, except that the neutral rosin sizing agent (product name: CC1401, manufactured by Seiko PMC Corporation) was changed to 0 parts. The tensile breaking elongation in the CD direction of the paper base material was 4.0%. The tensile breaking elongation in the CD direction of the wrapping paper was 4.8%.

Example 4
A wrapping paper was prepared 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 cationic starch (product name: Neotac 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 wrapping paper was 4.0%.

Example 5
A wrapping paper was produced in the same manner as in Example 1, except that the pulp was changed to 0 parts of softwood bleached kraft pulp and 100 parts of hardwood bleached kraft pulp. The tensile breaking elongation in the CD direction of the paper base material was 3.3%. The tensile breaking elongation in the CD direction of the wrapping paper was 4.2%.

Example 6
A wrapping paper was produced in the same manner as in Example 2, except that the Canadian Standard Freeness was changed to 650 mlcsf. The tensile breaking elongation in the CD direction of the paper base material was 3.4%. The tensile breaking elongation in the CD direction of the wrapping paper was 4.3%.

(Example 7)
A wrapping paper was produced in the same manner as in Example 1, except that the pulp was changed to 90 parts of unbleached softwood kraft pulp and 10 parts of 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 wrapping paper was 9.6%.

(Example 8)
A wrapping 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 breaking elongation in the CD direction of the paper base material was 3.1%. The tensile breaking elongation in the CD direction of the wrapping paper was 3.9%.

Example 9
A wrapping paper was prepared in the same manner as in Example 2, except that the amount of cationic starch (product name: Neotac 30T, manufactured by Nippon Shokuhin Kako Co., Ltd.) was changed to 0 part. The tensile breaking elongation in the CD direction of the paper base material was 3.5%. The tensile breaking elongation in the CD direction of the wrapping paper was 4.5%.

Example 10
A wrapping paper was prepared 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 breaking elongation in the CD direction of the paper base material was 3.4%. The tensile breaking elongation in the CD direction of the wrapping paper was 4.4%.

(Comparative Example 1)
The pulp was changed to 0 parts of softwood bleached kraft pulp and 100 parts of hardwood bleached kraft pulp, the Canadian Standard Freeness was changed to 650 mlcsf, the polyacrylamide (product name: DS4429, manufactured by Seiko PMC) was changed to 0 parts, the cationic 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 Co., Ltd.) was changed to 0 parts, and the light calcium carbonate (product name: TP-123, manufactured by Okutama Kogyo Co., Ltd.) was changed to 25 parts. The wrapping paper was produced in the same manner as in Example 1. The tensile elongation at break in the CD direction of the paper base material was 2.5%. The tensile elongation at break in the CD direction of the wrapping paper was 2.8%.

The wrapping papers obtained in each of the examples and comparative examples were evaluated using the methods described below. The results are shown in Tables 1 to 3.

(1) Tensile elongation at break in CD direction: Measured in accordance with JIS P-8113.

(2) Heat seal strength The obtained wrapping paper was cut into two pieces with a width of 8 mm and a length of 15 cm, and the front and back sides of the wrapping paper were overlapped and heat sealed under fixed conditions (adhesion width: 4 mm, temperature: 180°C, pressure: 0.4 MPa, pressing time: 0.5 seconds, pitch: 4 mm) using a heat sealer (manufactured by Palmec, model number: PTS-100). The heat sealed sample was then peeled under fixed conditions (peel speed: 100 mm/min, peel length: 10 cm) using a peel strength tester (manufactured by Shimadzu Corporation, model number: Autograph AGS-X) 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 preferable that the breakage occurs inside the paper substrate and peeling (commonly called material breakage).
◎: The paper base material is broken, and it is at a practical level.
◯: The paper base material is torn, and some peeling has occurred from the heat seal layer. Practical level.
Δ: The heat seal layer is broken and peeled off. Not practical.
×: Peeling occurred at the heat seal layer-to-heat seal layer interface. Unsuitable for practical use.

(3) Water resistance of folded parts The obtained packaging paper was cut to a size of 5 cm wide and 10 cm long, folded in half with the heat seal layer side inward, and a 5 kg metal roll was passed over the fold once. The folded part was made so that the fold was in the MD direction (machine direction; the direction in which the papermaking machine runs) of the paper. The folded part was opened, and a test liquid with a surface tension of 38 mN/m according to JIS K 6768:1999 (Plastics - Films and Sheets - Wetting Tension Test Method) was dropped on the folded part on the heat seal layer side. After 15 seconds had passed, the test liquid was wiped off, and the penetration of the test liquid into the paper substrate was evaluated.
◎: No penetration, practical level.
◯: Slight penetration, but still practical.
△: Penetrated to a level not practical for use.
×: The liquid has leaked to the back side, making it unusable.

(4) Oil resistance of folded parts The obtained packaging paper was cut to a size of 5 cm wide and 10 cm long, folded in half with the heat seal layer side inward, and a 5 kg metal roll was passed over the fold once. The folded part was made so that the fold was in the MD direction (machine direction; the direction in which the papermaking machine travels) of the paper. The folded part was opened, and a test liquid with a kit value of 8 according to TAPPI T-559cm-02 (kit method) was dropped on the folded part on the heat seal layer side. The test liquid was wiped off 15 seconds after the drop, and the penetration of the test liquid into the paper substrate was evaluated.
◎: No penetration, practical level.
◯: Slight penetration, but still practical.
△: Penetrated to a level not practical for use.
×: The liquid has leaked to the back side, making it unusable.

As is clear from Table 1, the packaging papers of Examples 1, 2, 4 to 10 and Reference Example 3 have a tensile breaking elongation in the CD direction 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 provide packaging paper that is excellent in barrier property, water repellency, and oil repellency while significantly reducing the amount of heat seal layer used compared to the amount of conventional polyethylene laminate, and contributing to reducing plastic waste.

Claims (12)

A packaging paper having at least one heat seal layer on at least one surface of a paper base material, the heat seal layer containing an ionomer, the heat seal layer having a total dry coating weight of 2 to 10 g/ ^m2 , the packaging paper having a basis weight of 10 to 100 g/ ^m2 , the packaging paper having a tensile elongation at break in the CD direction (JIS P-8113) of 3% to 9.6% , and the paper base material containing at least a sizing agent . 2. The packaging paper according to claim 1, characterized in that 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). The wrapping paper according to claim 1 or 2, characterized in that the tensile elongation at break in the CD direction of the paper base material (JIS P-8113) is 3% or more and is smaller than the tensile elongation at break of the wrapping paper. The wrapping paper according to any one of claims 1 to 3, characterized in that the pulp component contained in the paper base material contains 5 parts by mass or more of softwood pulp. The wrapping paper according to any one of claims 1 to 4, characterized in that the paper base material contains a water-soluble polymer. The wrapping paper according to claim 5, characterized in that the paper base material contains starches and/or polyacrylamides as water-soluble polymers. 7. The packaging paper according to claim 1, wherein the paper base material does not contain a fluorine-based water- and oil-repellent agent. 8. The wrapping paper according to claim 1, wherein the paper base material contains 0.05 to 1.0 part by mass of a neutral rosin sizing agent per 100 parts by mass of pulp. A method for producing a packaging paper having at least one heat seal layer on at least one side of a paper base, the heat seal layer containing an ionomer, and a 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 tensile elongation at break in the CD direction of the packaging paper (JIS P-8113) is 3% to 9.6%,
The method is characterized in that the paper base material is produced from a stock mainly composed of pulp containing a sizing agent. The method for producing packaging paper according to claim 9 , characterized in that 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). The method for producing packaging paper according to claim 9 or 10, characterized in that the paper base material does not contain a fluorine-based water- and oil-repellent agent. The method for producing packaging paper according to any one of claims 9 to 11, characterized in that the paper base material contains 0.05 to 1.0 part by mass of a neutral rosin sizing agent per 100 parts by mass of pulp.