JP2023096150A - Packaging paper - Google Patents

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 The present invention relates to packaging paper that uses less plastic. The present invention also relates to a packaging paper suitable for use as a bag, particularly excellent in workability such as folding.

In recent years, the problem of plastic waste has become more serious. The world's plastic production is said to exceed 400 million tons/year, and among them, plastic production in the packaging and container sector is large, causing plastic waste. Plastic does not decompose semi-permanently, and its garbage turns into microplastics in the natural environment, which has a serious adverse effect on the ecosystem. The most commonly used plastics for packaging containers are polyethylene terephthalate (PET), which is used for beverage bottles, etc., and polyethylene (PE) and polypropylene (PP), which are used for laminating plastic bags and containers. . In particular, the pollution of the ocean is remarkable, and it is said that the plastic garbage cannot be collected. In the future, it is necessary for the global environment to reduce the use of plastics.

On the other hand, the application of biodegradable plastics that can be completely decomposed by microorganisms has been proposed all over the world as a countermeasure against plastic waste. Biodegradable plastics decompose in the natural world within a certain period of time, but they are still garbage until they are decomposed. See Patent Documents 1 and 2).

Substituting paper for plastic has been proposed as an immediate countermeasure, but when processing paper into bags and containers, a large amount of polyethylene or polypropylene is laminated and used as a heat sealing agent. be. The amount of these plastics to be laminated varies depending on the product concept, but is generally 20 to 50 g/m ² , and may be as large as 300 g/m ² . Therefore, even in packaging containers in which paper is substituted for plastic, there is still the problem that the amount of plastic used is not sufficiently reduced, and means for directly reducing the use of plastic is urgently needed.

JP 2012-148444 A JP 2013-141763 A

SUMMARY OF THE INVENTION An object of the present invention is to provide a packaging paper that can reduce the amount of plastic used. In particular, it is an object of the present invention to provide a packaging paper which is suitable for use as a bag and which is particularly excellent in workability such as folding.

In the present invention, an ionomer is used in order to reduce the amount of polyethylene or polypropylene used in conventional plastic-laminated paper (hereinafter sometimes abbreviated as poly-laminated paper). That is, the packaging paper according to the present invention is a packaging paper having at least one heat-seal layer on at least one surface of a paper substrate, wherein the heat-seal layer contains an ionomer, and the coating amount of the heat-seal layer is It is characterized by being 2 to 10 g/m ² . Compared to the amount of polyethylene or polypropylene used in the heat seal layer of conventional polylaminated paper, which exceeds 20 g/m ² , the amount of plastic used for the heat seal layer can be reduced to about 10 to 50% of the conventional amount. can be reduced. Here, the ionomer is a synthetic resin in which macromolecules are aggregated by utilizing the cohesive force of metal ions, and is a synthetic resin in which acrylic acid or methacrylic acid is combined with ethylene or the like. For example, it is produced by intermolecular bonding of an acrylic polymer and ethylene by adding a metal cation such as sodium or zinc.

In the present invention, the basis weight of the packaging paper is 10 to 100 g/m ² , and the tensile elongation at break (JIS P- 8113) must be 3% or more. If the thickness is not within this range, the heat-seal layer will be destroyed during folding, resulting in loss of water resistance and oil resistance. This is because the heat-sealing layer containing the ionomer is thinner than the polyethylene layer, and has less flexibility and elongation, and is more likely to break. When the tensile elongation at break is low, the force concentrates on the distorted apex of the folded portion during bending, stretching the space between the fibers, which in turn stretches the heat-seal layer, resulting in cracking. When the tensile elongation at break is high, the elongation between the fibers is evened out in the distorted parts of the folded part during the folding process, so cracks do not occur in the heat-sealed part, and the package has excellent water and oil resistance. This is because paper is available.

Also, when the basis weight is 10 g/m ² to 100 g/m ² , the bag can be flexible and a practical wrapping paper can be obtained.

In the present invention, the paper substrate may contain a sizing agent. This is because a packaging paper having excellent water resistance and oil resistance can be obtained.

In the present invention, the tensile elongation at break (JIS P-8113) of the paper substrate in the CD direction is preferably 3% or more and smaller than the tensile elongation at break of the packaging paper. This is because a packaging paper having excellent water resistance and oil resistance can be obtained.

In the present invention, among the pulp components contained in the paper substrate, it is preferable that 5 parts by mass or more of softwood pulp is contained. This is because a packaging paper having excellent water resistance and oil resistance can be obtained.

In the present invention, the paper substrate preferably contains a water-soluble polymer, and the water-soluble polymer preferably contains starches and/or polyacrylamide.

With the present invention, it is possible to produce packaging paper with reduced plastic usage. If the container product uses the packaging paper of the present invention, even if it is inappropriately discharged into the natural world as garbage, it is possible to reduce the adverse effect of plastic garbage on the natural environment. It will help solve the garbage problem. In addition, the wrapping paper in the present invention is processed into general packaging containers such as bags, food cups such as ice cream, beverage cups such as coffee, food containers such as hot snacks, and trays, boxes, cases, vessels, envelopes, etc. It is possible. In particular, it is suitable for processing into bags as a thin wrapping paper, and is excellent in water resistance and oil resistance.

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

In the present embodiment, the ionomer is a general term for synthetic resins in which macromolecules are aggregated by utilizing the cohesive force of metal ions, and is a resin obtained by combining acrylic acid or methacrylic acid with ethylene or the like. That is, metal salts of ethylene/methacrylic acid copolymers, metal salts of ethylene/acrylic copolymers, metal salts of ethylene/urethane copolymers, metal salts of ethylene/fluoropolymer copolymers, etc. All are called ionomers. Salt-forming metals 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 that is a metal salt of an ethylene/methacrylic acid copolymer. A heat-sealing layer having a sufficient heat-sealing strength can be provided with a relatively small coating amount of the heat-sealing layer.

In the present embodiment, a heat seal layer can be provided by applying a heat seal layer coating liquid containing an ionomer emulsion to at least one surface of a paper substrate and drying the coating liquid. By using an ionomer emulsion, it is possible to control the amount of coating to a relatively low level, and by using a water-based ionomer emulsion, VOC emissions are eliminated and the load 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 in terms of solid content, per one side of the paper substrate. If it is less than 2 g/m ² , sufficient heat seal strength cannot be achieved. Conversely, if it exceeds 10 g/m ² , the quality is excessive in terms of heat seal strength, and the plastic reduction effect is poor. In addition, in the packaging paper of the present invention, the heat seal layer is usually provided not only on a part of the surface of the paper substrate but also on the entire surface. That is, the heat-seal layer is provided not only in a portion necessary for adhesion by heat-sealing, such as in a network shape, an island shape, or a linear shape, but is provided so as to cover the entire surface of the paper base material. and good.

In addition to the ionomer emulsion, various auxiliary agents may be added to the heat seal layer coating solution. Examples thereof include viscosity modifiers, antifoaming agents, leveling agents such as surfactants and alcohols, coloring pigments, and coloring dyes. However, the addition of these auxiliaries tends to cause a decrease in the heat seal strength, so when they are added, they are preferably added in small amounts. In the present embodiment, it is preferable that the heat-sealing layer coating liquid consists only of the ionomer emulsion.

The method of applying the heat-sealing layer coating liquid is not particularly limited, and a generally used coating apparatus can be used. 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 Various known coating devices such as a coater, gate roll coater and lip coater can be used.

In this embodiment, the heat seal layer may be formed of two or more layers. By using two or more layers, the air permeability of the packaging paper can be increased, and further, water resistance and oil resistance can be imparted, and properties similar to or close to those of plastic film laminated paper can be obtained. It is from. When the number of heat-seal layers is two or more, it is preferable that the coating amount of the lowest heat-sealing layer closest to the paper substrate is larger than the total coating amount of the other heat-sealing layers. This is because the air permeability of the packaging paper can be further improved, and the water resistance and oil resistance are further improved.

In the present invention, it is necessary that the basis weight of the wrapping paper is 10 to 100 g/m ² and the tensile elongation at break (JIS P-8113) of the wrapping paper in the CD direction is 3% or more. If the basis weight is less than 10 g/m ² , the bag cannot maintain its strength and cannot be used practically. On the other hand, if the basis weight exceeds 100 g/m ² , it cannot be used practically because the flexibility of the bag is lowered. If the tensile elongation at break in the CD direction is less than 3%, the force is concentrated on the distorted apex of the folded portion during bending, stretching the interfibers, and the heat seal layer is also stretched along with it, resulting in cracking. and the water resistance and oil resistance decrease. When the tensile elongation at break in the CD direction is 3% or more, the elongation between the fibers is averaged in the distorted portion of the folded portion during the folding process, so cracking of the heat seal layer does not occur. The tensile elongation at break in the machine direction (MD) is not specified. Since the fibers are arranged in the MD direction and the gaps between the fibers are difficult to widen, it is presumed that cracks do not occur in the heat seal layer.

In this embodiment, it is preferable that the tensile elongation at break (JIS P-8113) of the paper substrate in the CD direction is 3% or more and smaller than the tensile elongation at break in the CD direction of the packaging paper. If it is out of this range, the water resistance and oil resistance may deteriorate. 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, the density, and the like. Hereinafter, phenomena and effects 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 fibers absorb the moisture in the coating liquid, and when the moisture evaporates during drying, the fibers shrink, and the tensile elongation at break becomes lower than before coating. tend to be larger. It is thought that the tensile breaking elongation rate of the fibers near the heat seal layer that has absorbed moisture is particularly large, and the stretch between the fibers in the curved portion of the folded portion during the bending process, especially near the heat seal layer, is more evened out. , cracking of the heat seal layer is less likely to occur. It is preferable that the tensile elongation at break (JIS P-8113) in the CD direction of the packaging paper is 0.1% or more higher 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 in the CD direction of the packaging paper, the above effect is not obtained, and cracks occur in the heat seal layer during bending. There is fear. For example, when the heat-seal layer coating solution is applied, if the fibers of the paper substrate do not absorb moisture (such as being covered with a non-absorbent resin or water-resistant material), the CD of the paper substrate The tensile elongation at break in the direction may not be less than the tensile elongation at break in the CD direction of the wrapping paper.

In the case where another coating layer (under layer) 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 equal to the tensile elongation at break in the CD direction of the packaging paper. is preferably smaller than When another layer is provided, the tensile elongation may be increased for the reasons mentioned above.

The paper substrate used in the present embodiment is not particularly limited, and known paper substrates containing pulp as a main component can be used. The pulp that is the main component of the paper base material includes chemical pulps such as LBKP (bleached hardwood kraft pulp), NBKP (bleached softwood kraft pulp), LUKP (unbleached hardwood kraft pulp), NUKP (unbleached softwood kraft pulp), GP (ground wood pulp), PGW (pressurized ground wood pulp), RMP (refiner mechanical pulp), TMP (thermomechanical pulp), CTMP (chemi-thermomechanical pulp), CMP (chemi-mechanical pulp), CGP (chemi-grand pulp), etc. mechanical pulp, DIP (deinked pulp) and other wood pulps 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 relatively short fiber, which tends to work against tensile elongation at break. On the other hand, softwood pulp and non-wood pulp have longer fibers than hardwood pulp, have higher strength, and tend to increase tensile elongation at break. For example, it is preferable to use softwood pulp such as NBKP (softwood bleached kraft pulp) or NUKP (softwood unbleached kraft pulp) in an amount of 5 parts by mass or more in the pulp. Practically sufficient strength when used as a bag, and excellent water resistance and oil resistance. If the amount is less than 5 parts by mass, the strength of the bag may be insufficient for practical use, and the tensile elongation at break may decrease, resulting in a decrease in water resistance and oil resistance. Preferably, a pulp containing 5-20% by weight of NBKP (bleached softwood kraft pulp) and 95-80% by weight of LBKP (bleached hardwood kraft pulp) is used. Furthermore, when the tensile elongation at break is to be further enhanced, it is preferable to use a pulp containing 80 to 95% by mass of NBKP (bleached softwood kraft pulp) and 5 to 20% by mass of LBKP (bleached broadleaf kraft pulp). In addition, 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, waste paper pulp, and pulp obtained from planted trees are preferred. In addition, for example, an appropriate freeness of pulp is 200 to 700 ml CSF, for example, 320 to 6600 ml CSF in Canadian standard freeness (JIS P 8121: 1995 "Pulp freeness test method"). . By beating the pulp, fine branching and fluffing occur in the pulp fibers, which has the effect of strengthening the bonds between the pulp fibers. When the freeness is less than 200 ml, the pulp fibers are beaten excessively, and the bonds between the pulp fibers become too dense, so the tensile elongation at break tends to decrease. If the freeness exceeds 700 ml, the bonding between pulp fibers is 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.

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 weight with respect to 100 parts by weight of dry pulp. For example, 1 to 15 parts by mass, preferably 2 to 10 parts by mass of light calcium carbonate may be included with respect to 100 parts by mass of dry pulp.

Moreover, the tensile elongation at break can be improved by including a water-soluble polymer in the paper substrate. Examples of water-soluble polymers include starches such as corn starch, potato starch, tapioca starch, cross-linking agent-modified starch, oxidized starch, enzyme-modified starch, esterified starch, etherified starch, cationic starch, and amphoteric starch. , polyvinyl alcohol, polyacrylamide, and the like can be used. Starch and polyacrylamide are particularly preferred. The amount of the water-soluble polymer added is 0.05 parts by mass or more with respect to 100 parts by mass of pulp. More preferably, it is 0.1 parts by mass or more. For example, 0.1 to 10 parts by mass, preferably 0.1 to 7.0 parts by mass of the water-soluble polymer is contained with respect to 100 parts by mass of pulp. Furthermore, 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, with respect to 100 parts by mass of pulp, Preferably, 0.1 to 2.0 parts by mass of starch, preferably cationized starch, is contained. Known methods such as internal addition and coating (size press, air knife coater, etc.) can be used as the method of containing.

Moreover, it is preferable to contain a sizing agent in a paper base material. By containing a sizing agent, when the heat-sealing layer or the under layer is coated, the penetration of the coating liquid into the base material is moderately suppressed, resulting in excellent water resistance and oil resistance. Also, it is thought that if the permeation is moderately suppressed, the fibers in the vicinity of the coating layer will particularly absorb moisture, which will have a dominant effect on the tensile elongation at break. The content is, for example, 0.05 parts by mass or more with respect to 100 parts by mass of pulp. Types of sizing agents include neutral rosin sizing agents, strong rosin sizing agents, acidic rosin sizing agents, weakly acidic rosin sizing agents, AKD (alkylketene dimer), ASA (alkenyl succinic anhydride), and the like. Fluorine-based water and oil repellents are not preferable as sizing agents because they are costly, economically inferior, and have a high environmental load. In the present invention, the paper substrate preferably contains 0.05 to 1.0 parts by mass, more preferably 0.1 to 0.5 parts by mass of a neutral rosin sizing agent per 100 parts by mass of pulp.

The paper substrate may also contain various known papermaking additives in addition to the pulp and filler. Examples of papermaking additives include sizing agents, internal strength agents such as wet strength agents, bulking agents, retention aids, drainage improvers, coloring dyes, coloring pigments, fluorescent whitening agents, fluorescent Decoloring agents, pitch control agents, etc. Also, a water-soluble polymer such as starch, polyvinyl alcohol or polyacrylamide may be applied.

The paper-making method for the paper substrate is not particularly limited, and includes a fourdrinier paper machine, a fourdrinier multi-layer paper machine, a cylinder paper machine, a fourdrinier multi-layer paper machine, a fourdrinier cylinder combi multi-layer paper machine, and a twin wire paper machine. It can be manufactured by various paper machines such as Further, in the present invention, the paper base material may be a single-layer paper, a multi-layer paper, or a laminate of multiple layers.

The paper substrate may be provided with one or more coating layers (under layer) other than the heat seal layer, for example, a pigment coating layer containing a pigment and an adhesive. good too. As the pigment in the pigment coating layer, known pigments used in the coating layer of general coated printing paper can be used. Examples include 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, hydroxide Examples include inorganic pigments such as magnesium, acryl, styrene, vinyl chloride, nylon itself, and organic pigments obtained by copolymerizing these (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 ground calcium carbonate can be used as the pigment. As the adhesive, known adhesives used for the coating layer of general coated printing paper can be used. Starches such as esterified starch, etherified starch, cationic starch and amphoteric starch, water-soluble polymers such as gelatin, casein, soybean protein, polyvinyl alcohol, vinyl acetate, ethylene vinyl acetate, polyurethane resin, acrylic resin, Synthetic resins such as polyester-based resins and polyamide-based resins can be exemplified. The mixing ratio of the pigment and the adhesive in the pigment coating layer is not particularly limited, but it is preferable to use 5 to 50 parts by weight of the adhesive per 100 parts by weight of the pigment. For example, as the adhesive, a combination of 1 to 5 parts by weight of phosphate esterified starch and 5 to 15 parts by weight of styrene-butadiene latex can be used with respect to 100 parts by weight of the pigment. The pigment coating layer may contain various auxiliary agents within a range that does not impair the intended effects of the present invention, such as viscosity modifiers, softening agents, gloss imparting agents, waterproofing agents, dispersants, and flow modifiers. , ultraviolet absorbers, stabilizers, antistatic agents, cross-linking agents, sizing agents, fluorescent whitening agents, colorants, pH adjusters, antifoaming agents, plasticizers, and preservatives. The coating amount of such a pigment coating layer is, for example, 2 to 40 g/m ² in terms of solid content per side of the base paper. As one embodiment of the wrapping paper of the present invention, the heat seal layer may be provided on such a pigment coating layer, and as another embodiment, only one side has a pigment coating layer. A heat seal layer may be provided on the side of the paper substrate provided with the non-pigment coating layer.

EXAMPLES 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 addition, "parts" and "%" in the examples indicate "mass parts" and "mass%", respectively, unless otherwise specified. The number of parts to be added is a value in terms of solid content.

(Example 1)
(Preparation of paper substrate)
90 parts of bleached softwood kraft pulp and 10 parts of bleached hardwood kraft pulp were mixed and beaten to a Canadian standard freeness of 400 mlcsf. Next, to the beaten pulp, 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), cationized starch (trade name : Neotac 30T, manufactured by Nihon Shokuhin Kako Co., Ltd.) and 0.3 parts of a neutral rosin sizing agent (trade name: CC1401, manufactured by Seiko PMC Co., Ltd.) were added to prepare a paper material, and fourdrinier multi-tube paper was made. A base paper having a basis weight of 38 g/m ² was produced using a machine. This base paper was coated with oxidized starch (trade name: MS3800, manufactured by Nihon Shokuhin Kako Co., Ltd.) by a size press so that the dry coating amount per both sides was 2 g/m ² , and dried to a base paper of 40 g/m ² . got The tensile elongation at break in the CD direction was 7.0%.

(Preparation of wrapping paper)
On one side of the paper substrate obtained above, an aqueous ionomer emulsion (trade name: Chemipearl S-300, manufactured by Mitsui Chemicals, composition: metal salt of ethylene/methacrylic acid copolymer, self-emulsifying emulsion, microtrack method An average particle size of 0.5 μm) was applied using an air knife coater so that the dry coating amount was 5 g/m ² , and dried to provide a heat seal layer to prepare a 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 elongation at break in the CD direction of the paper substrate was 4.0%. The tensile elongation at break in the CD direction of the wrapping paper was 5.1%.

(Example 3)
A packaging paper was prepared in the same manner as in Example 2, except that the neutral rosin sizing agent (trade name: CC1401, manufactured by Seiko PMC) was changed to 0 parts. The tensile elongation at break in the CD direction of the paper substrate was 4.0%. The tensile elongation at break in the CD direction of the wrapping paper was 4.8%.

(Example 4)
The procedure was the same as in Example 2, except that polyacrylamide (trade name: DS4429, manufactured by Seiko PMC) was changed to 0 parts, and cationic starch (trade name: Neotac 30T, manufactured by Nihon Shokuhin Kako Co., Ltd.) was changed to 0 parts. A wrapping paper was made by The tensile elongation at break in the CD direction of the paper substrate 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 elongation at break in the CD direction of the paper substrate was 3.3%. The tensile elongation at break in the CD direction of the wrapping paper was 4.2%.

(Example 6)
A 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 substrate was 3.4%. The tensile elongation at break 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 softwood unbleached kraft pulp and 10 parts of hardwood bleached kraft pulp. The tensile elongation at break in the CD direction of the paper substrate 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 prepared in the same manner as in Example 2, except that the amount of light calcium carbonate (trade 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 substrate was 3.1%. The tensile elongation at break in the CD direction of the wrapping paper was 3.9%.

(Example 9)
A packaging paper was prepared in the same manner as in Example 2, except that the amount of cationized starch (trade name: Neotac 30T, manufactured by Nihon Shokuhin Kako Co., Ltd.) was changed to 0 parts. The tensile elongation at break in the CD direction of the paper substrate was 3.5%. The tensile elongation at break 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 (trade name: DS4429, manufactured by Seiko PMC) was changed to 0 parts. The tensile elongation at break in the CD direction of the paper substrate was 3.4%. The tensile elongation at break in the CD direction of the wrapping paper was 4.4%.

(Comparative example 1)
The pulp was changed to 0 parts of bleached softwood kraft pulp and 100 parts of bleached hardwood kraft pulp, changed to Canadian Standard Freeness 650 mlcsf, changed polyacrylamide (trade name: DS4429, manufactured by Seiko PMC) to 0 parts, and cationized starch. (product name: Neotac 30T, manufactured by Nihon Shokuhin Kako Co., Ltd.) was changed to 0 parts, neutral rosin size (product name: CC1401, manufactured by Seiko PMC) was changed to 0 parts, and light calcium carbonate (product name: TP) was changed to 0 parts. -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 wrapping paper was 2.8%.

The packaging paper obtained in each example and comparative example was evaluated by the methods shown below. The results obtained are shown in Tables 1-3.

(1) Tensile elongation at break in the CD direction Measured according to JIS P-8113.

(2) Heat sealing strength The obtained packaging paper is cut into two pieces with a width of 8 mm and a length of 15 cm. 100) under certain conditions (adhesion width: 4 mm, temperature: 180°C, pressure: 0.4 MPa, pressing time: 0.5 seconds, pitch: 4 mm). Next, the heat-sealed sample is peeled off under certain conditions (peeling speed: 100 mm / min, peeling length: 10 cm) using a peel strength tester (manufactured by Shimadzu Corporation, model number: Autograph AGS-X). Evaluation was made on which side of the base material, the inside of the heat seal layer, or the interface between the heat seal layer and the heat seal layer was delaminated. It is preferable that the breakage occurs inside the paper substrate and peeling off (generally called material breakage).
⊚: Practical level due to material damage from the paper base material.
◯: The paper base material is broken, but some peeling occurs from the heat seal layer. practical level.
Δ: Destroyed and peeled in the heat seal layer. Impractical level.
x: Peeling occurred at the interface between the heat seal layer and the heat seal layer. Impractical level.

(3) Water resistance of the folded portion Cut the obtained wrapping paper into a size of 5 cm in width and 10 cm in length, fold the heat seal layer side inward, and roll a 5 kg metal roll on the fold. made it pass back and forth. The folding part was made so that the MD direction (Machine Direction; advancing direction of the paper machine) of the paper was the crease. The folded portion is opened, and a test liquid having a surface tension of 38 mN/m according to JIS K 6768:1999 (Plastics-Films and Sheets-Wet Tension Test Method) is dripped onto the folded portion on the heat seal layer side. After 15 seconds of dropping, the test liquid was wiped off, and the penetration of the test liquid into the paper substrate was evaluated.
A: Practical level without permeation.
O: Slightly permeated, but at a practical level.
Δ: Permeated, impracticable level.
x: The penetrating liquid has escaped to the back surface, and is at a practically unusable level.

(4) Oil resistance of folded part Cut the obtained wrapping paper into a size of 5 cm in width and 10 cm in length, fold the heat seal layer side inward, and roll a 5 kg metal roll on the fold. made it pass back and forth. The folding part was made so that the MD direction (Machine Direction; advancing direction of the paper machine) of the paper was the crease. The folded part is opened, and a test solution with a kit value of 8 according to TAPPI T-559cm-02 (kit method) is dropped on the folded part on the heat seal layer side. After 15 seconds of dropping, the test liquid was wiped off, and the penetration of the test liquid into the paper substrate was evaluated.
A: Practical level without permeation.
O: Slightly permeated, but at a practical level.
Δ: Permeated, impracticable level.
x: The penetrating liquid has escaped to the back surface, and is at a practically unusable level.

As is clear from Table 1, the packaging papers according to Examples 1 to 10 have a tensile elongation at break of 3.0% or more in the CD direction compared to Comparative Example 1. Excellent water resistance and oil resistance at the bent part. As shown by the experimental results, the present invention significantly reduces the amount of heat seal layer used compared to the conventional polyethylene laminate amount, contributing to the reduction of plastic waste while improving barrier properties, water repellency and repellency. It is possible to provide wrapping paper with excellent oil resistance.

Claims (6)

A packaging paper having at least one heat-seal layer on at least one surface of a paper substrate, wherein the heat-seal layer contains an ionomer, and the heat-seal layer has a dry coating weight of 2 to 10 g/ m ² , the basis weight of the packaging paper is 10 to 100 g/m ² , and the tensile elongation at break (JIS P-8113) of the packaging paper in the CD direction is 3% or more. wrapping paper. 2. The wrapping paper according to claim 1, wherein the paper substrate contains at least a sizing agent. 3. 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. wrapping paper. 4. The packaging paper according to any one of claims 1 to 3, wherein 5 parts by mass or more of softwood pulp is included among the pulp components contained in the paper base material. The packaging paper according to any one of claims 1 to 4, wherein the paper base material contains a water-soluble polymer. 6. The packaging paper according to claim 5, wherein the paper base material contains starches and/or polyacrylamide as the water-soluble polymer.