Heat sealing paper and packaging bag

Abstract

A heat-sealing paper having one or more heat-sealing layers on at least one surface of a paper substrate, the heat-sealing layers containing a water-dispersible resin binder, the heat-sealing paper having a longitudinal and transverse geometric average of a tear index of 10 mN m < 2 > / g or more, a rupture index of 3.0 kPa m < 2 > / g or more, and a heat-sealing layer containing a water-dispersible resin binder, the heat-sealing paper being characterized in that: the heat-sealing paper has a longitudinal and transverse geometric average of a tear index of 10 mN m < 2 > / g or more; the heat-sealing peel strength when the heat-sealing layers are heat-sealed to each other under the conditions of 150 DEG C, 0.2 MPa, and 1 second is 2.0 N / 15 mm or more and 10 N / 15 mm or less.

Description

Technical Field

[0001] The invention relates to heat-sealing paper and a packaging bag obtained by using the heat-sealing paper. Background Art

[0002] In addition to being widely used in the packaging of general industrial products, packaging bodies obtained by heat sealing are also widely used in the packaging of food, medicines, medical devices, etc.

[0003] In recent years, the problem of plastic waste has become increasingly serious. Among the plastic production in the world, the production of plastic in the field of packaging containers is the largest, which has become the cause of plastic waste. Plastic does not decompose semi-permanently, and its waste is micro-plasticized in the natural environment, causing serious adverse effects on the ecosystem. As a countermeasure, a plan to replace plastic with paper has been proposed.

[0004] For example, Japanese Patent Gazette No. 2022-024664 discloses a water-resistant and oil-resistant heat-seal paper for the purpose of providing a water-resistant and oil-resistant heat-seal paper that has water resistance, oil resistance, heat-seal adaptability and can be stored for a long time. The water-resistant and oil-resistant heat-seal paper is characterized in that a coating layer containing a thermoplastic resin, wax and a pigment is provided on at least one side of a paper substrate. Summary of the invention

[0005] The heat-sealing paper described in Japanese Patent Application Laid-Open No. 2022-024664 has excellent blocking resistance, but has not been studied for bag breakage during transportation or ease of opening during opening.

[0006] An object of the present invention is to provide a heat-sealing paper capable of obtaining a packaging bag that is not easily broken and can be easily opened when opened, and a packaging bag obtained by using the heat-sealing paper.

[0007] The subject of the present invention can be solved by the following <1> ~ <17> technical solutions to solve it.

[0008] <1> A heat-sealing paper having one or more heat-sealing layers on at least one surface of a paper substrate, wherein the heat-sealing layer contains a water-dispersible resin binder, and the longitudinal and transverse geometric mean of the tear index of the heat-sealing paper is 10 mN·m 2 / g or more, the rupture index of the aforementioned heat sealing paper is 3.0 kPa·m 2 / g or more, and a heat seal peel strength of 2.0 N / 15 mm or more and 10 N / 15 mm or less when the heat seal layers are heat-sealed under the conditions of 150°C, 0.2 MPa, and 1 second.

[0009] <2> according to <1> The heat-sealing paper, wherein the heat-sealing layer further comprises a lubricant.

[0010] <3> according to <2> The heat-sealing paper, wherein the lubricant comprises at least one selected from the group consisting of paraffin wax, carnauba wax and polyolefin wax.

[0011] <4> according to <2> or <3> The heat-sealing paper, wherein the content of the lubricant in the heat-sealing layer is greater than 1 mass % and less than 5 mass %.

[0012] <5> according to <1> ~ <4> The heat-sealing paper according to any one of the preceding claims, wherein the water-dispersible resin binder has a glass transition temperature of 0°C or higher and 100°C or lower.

[0013] <6> according to <1> ~ <5> The heat-sealing paper described in any one of the preceding claims, wherein the water-dispersible resin binder comprises at least one selected from the group consisting of styrene-butadiene copolymers and olefin-unsaturated carboxylic acid copolymers.

[0014] <7> according to <2> ~ <6> The heat-sealing paper described in any one of the preceding claims, wherein the water-dispersible resin binder comprises a styrene-butadiene copolymer, and the lubricant comprises paraffin wax.

[0015] <8> according to <2> ~ <6> The heat-sealing paper described in any one of the preceding claims, wherein the water-dispersible resin binder comprises an olefin-unsaturated carboxylic acid copolymer, and the lubricant comprises carnauba wax.

[0016] <9> according to <1> ~ <8> The heat seal paper described in any one of the preceding claims, wherein the pulp constituting the paper substrate has a Canadian Standard Freeness of 500 mL or more and 750 mL or less.

[0017] <10> according to <1> ~ <9> The heat-sealing paper described in any one of the preceding claims, wherein the main component of the pulp constituting the paper substrate is coniferous tree unbleached kraft pulp.

[0018] <11> according to <1> ~ <10> The heat-sealing paper described in any one of the preceding claims, wherein the longitudinal and transverse geometric mean of the Clark stiffness is divided by the basis weight (g / m 2 ) and the value (Clark stiffness / basis weight) is 0.20m 2 / g or more and 1.20m 2 / g or less.

[0019] <12> according to <1> ~ <11> The heat sealing paper described in any one of the preceding claims, wherein the puncture strength of the heat sealing paper is greater than or equal to 10.0 N.

[0020] <13> according to <1> ~ <12> The heat-sealing paper according to any one of the preceding claims, wherein the basis weight of the paper substrate is 50 g / m 2 Above and 150g / m 2 the following.

[0021] <14> according to <1> ~ <13> The heat-sealing paper according to any one of the preceding claims, wherein the basis weight of the heat-sealing layer is 3 g / m 2 Above and 30g / m 2 the following.

[0022] <15> according to <1> ~ <14> The heat sealing paper according to any one of the preceding claims, wherein the basis weight of the heat sealing paper is 50 g / m 2 Above and 200g / m 2 the following.

[0023] <16> according to <1> ~ <15> The heat-sealing paper described in any one of the preceding claims, wherein the paper substrate is elastic paper.

[0024] <17> A packaging bag, which is used <1> ~ <16> Made of any one of the heat-sealing papers described above. DETAILED DESCRIPTION

[0025] The preferred embodiment of the present invention is described below. It should be noted that, in this specification, "X to Y" indicating a range means "above X and below Y". When the numerical range is recorded in stages, the upper limit and lower limit of each numerical range can be arbitrarily combined. In addition, in this specification, unless otherwise specified, operations and measurements of physical properties are carried out under the conditions of room temperature (20 to 25°C) / relative humidity of 40 to 50% RH. In addition, "(meth)acrylic" is a general term including both acrylic and methacrylic.

[0026] <Heat seal paper>

[0027] The heat-sealing paper of the present embodiment (hereinafter also referred to as "heat-sealing paper") is a heat-sealing paper having one or more heat-sealing layers on at least one surface of a paper substrate, wherein the heat-sealing layer contains a water-dispersible resin binder, and the longitudinal and transverse geometric mean of the tear index of the heat-sealing paper is 10 mN·m 2 / g or more, the rupture index of the aforementioned heat sealing paper is 3.0 kPa·m 2 / g or more, and the heat seal peel strength when the heat seal layers are heat-sealed at 150°C, 0.2 MPa, and 1 second is 2.0 N / 15 mm or more and 10 N / 15 mm or less. The heat seal paper of this embodiment can obtain a packaging bag that is not easily broken and can be easily opened when opened.

[0028] The heat sealability can be achieved by forming the heat seal layer using a water-dispersible resin binder. It is also believed that the longitudinal and transverse geometric mean of the tear index of the heat seal paper is 10 mN·m 2 / g or more, so that the heat-sealing paper can resist shearing caused by falling and deformation during transportation, and the heat-sealing paper is not easily damaged. In addition, it can be considered that: by making the rupture index of the heat-sealing paper 3.0 kPa·m 2 / g or more, so that the packaging bag obtained by the heat-sealing paper can suppress the bag breakage caused by falling during transportation. It can be further considered that: by making the heat seal peel strength above 2.0N / 15mm, the damage of the heat-sealed portion caused by falling during transportation, etc. can be suppressed. In addition, by being below 10N / 15mm, it is easy to open. It should be noted that the effect of the present invention is not limited to the above mechanism. In this specification, the longitudinal direction of the heat-sealing paper refers to the direction corresponding to the papermaking direction (MD direction) of the paper substrate, and the transverse direction of the heat-sealing paper refers to the direction corresponding to the width direction (CD direction) of the paper substrate.

[0029] [Paper base material]

[0030] (Raw pulp)

[0031] The pulp constituting the paper substrate is not particularly limited, and known pulps can be used. Specifically, unbleached pulps such as hardwood unbleached kraft pulp (LUKP) and conifer unbleached kraft pulp (NUKP); chemical pulps such as hardwood bleached kraft pulp (LBKP) and conifer bleached kraft pulp (NBKP); mechanical pulps such as groundwood pulp (GP), pressure stone groundwood pulp (PGW), refiner mechanical pulp (RMP), thermomechanical pulp (TMP), preheated wood chip chemimechanical pulp (CTMP), chemimechanical pulp (CMP), and chemical groundwood pulp (CGP); waste paper pulp; non-wood fiber pulps such as kenaf, bagasse, bamboo, and cotton; and synthetic pulps. These pulps can be used alone or in combination of two or more. Among these, at least one selected from the group consisting of unbleached broadleaf kraft pulp (LUKP), unbleached coniferous tree kraft pulp (NUKP), bleached broadleaf kraft pulp (LBKP), and bleached coniferous tree kraft pulp (NBKP) is preferred, at least one selected from the group consisting of unbleached broadleaf kraft pulp (LUKP) and unbleached coniferous tree kraft pulp (NUKP) is more preferred, and unbleached coniferous tree kraft pulp (NUKP) is even more preferred.

[0032] The main component of the pulp constituting the paper substrate used in the heat-sealing paper of the present embodiment is preferably conifer pulp, and more preferably conifer unbleached kraft pulp (NUKP). "The main component of the pulp constituting the paper substrate is conifer pulp" means: in the pulp constituting the paper substrate, the content of conifer pulp exceeds 50% by mass, and the content of conifer pulp is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 100% by mass. Similarly, "the main component of the pulp constituting the paper substrate is conifer unbleached kraft pulp" means: in the pulp constituting the paper substrate, the content of conifer unbleached kraft pulp exceeds 50% by mass, and the content of conifer unbleached kraft pulp is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 100% by mass. Conifer pulp has a long average fiber length, and by using a paper substrate using conifer pulp as a raw material pulp, a heat-sealing paper having a desired tear index and rupture index can be obtained, so it is preferred. Furthermore, if coniferous unbleached kraft pulp (NUKP) is used as the pulp constituting the paper base material, the strength of the pulp fiber itself is higher than that of coniferous bleached kraft pulp (NBKP), broadleaved unbleached kraft pulp (LUKP), etc., so there is an advantage that the strength and elongation of the obtained paper base material become higher.

[0033] From the viewpoint of obtaining heat seal paper having a desired tear index and burst index, the softwood pulp is preferably pulp obtained from at least one selected from the group consisting of Douglas fir and pine tree, and more preferably pulp obtained from Douglas fir.

[0034] The raw material pulp constituting the paper substrate preferably contains one or more kinds selected from the group consisting of bleached kraft pulp and unbleached kraft pulp, and more preferably contains unbleached kraft pulp.

[0035] (Canadian Standard Freeness)

[0036] The beating degree of the raw material pulp constituting the paper substrate is not particularly limited, but from the viewpoint of obtaining heat seal paper having a desired tear index and burst index, the Canadian Standard Freeness (CSF) is preferably 500 mL or more, more preferably 550 mL or more, and preferably 750 mL or less, more preferably 700 mL or less. In addition, the smoothness of the paper surface becomes good, and the printing suitability can be maintained.

[0037] CSF is measured according to JIS P 8121-2:2012 “Pulps - Test methods for freeness - Part 2: Canadian Standard Freeness Method”.

[0038] (Kappa value)

[0039] From the viewpoint of obtaining heat-sealing paper having impact resistance and processability, the carba value of the pulp constituting the paper base material measured in accordance with JIS P8211:2011 is preferably 30 or more, and preferably 60 or less, more preferably 55 or less, further preferably 50 or less, and further preferably 46 or less. The carba value of the pulp constituting the paper base material is measured in accordance with JIS P 8211:2011 using a paper base material pulp dissociated in accordance with JIS P 8220-1:2012 as a sample.

[0040] (Basis Weight)

[0041] The basis weight of the paper substrate is not particularly limited, but is preferably 50 g / m2 from the viewpoint of obtaining a heat seal paper having a desired tear index and rupture index. 2 More preferably 60 g / m 2 More preferably, 70 g / m 2 More than, and preferably 150g / m 2 Below, more preferably 120g / m 2 Below, more preferably 110g / m 2 Below, more preferably 100g / m 2 The basis weight of the paper substrate was measured in accordance with JIS P8124:2011.

[0042] (thickness)

[0043] From the viewpoint of obtaining heat-sealing paper having a desired tear index and rupture index, the thickness of the paper substrate is preferably 60 μm or more, more preferably 80 μm or more, and further preferably 100 μm or more, and is preferably 200 μm or less, more preferably 180 μm or less, and further preferably 160 μm or less. The thickness of the paper substrate is measured in accordance with JIS P 8118:2014.

[0044] (density)

[0045] From the viewpoint of obtaining heat-sealing paper having a desired tear index and rupture index and from the viewpoint of molding processability, the density of the paper substrate is preferably 0.3 g / cm 3 More preferably, 0.5 g / cm 3 More than, and preferably 1.0 g / cm 3 Below, more preferably 0.9 g / cm 3 Below, more preferably 0.75 g / cm 3 The density of the paper substrate is calculated from the basis weight and thickness of the paper substrate obtained by the above-mentioned measurement method.

[0046] (Optional Ingredients)

[0047] The paper substrate may contain optional components such as anionic, cationic or amphoteric yield improvers, filterability improvers, dry paper strength enhancers, wet paper strength enhancers, sizing agents, fixers, fillers and other internal additives, water resistance agents, dyes, fluorescent whitening agents and the like as needed.

[0048] Examples of the dry paper strengthening agent include cationized starch, polyacrylamide, carboxymethyl cellulose, etc. The content of the dry paper strengthening agent is not particularly limited, but is preferably 3.0% by mass or less based on the raw material pulp (absolute dry mass).

[0049] Examples of the wet paper strengthening agent include polyamide polyamine epichlorohydrin, urea formaldehyde resin, melamine formaldehyde resin, etc. The content of the wet paper strengthening agent is not particularly limited, but is preferably 3.0% by mass or less based on the raw material pulp (absolute dry mass).

[0050] Examples of the sizing agent include internal sizing agents such as rosin sizing agents, synthetic sizing agents, and petroleum resin sizing agents; and surface sizing agents such as styrene / acrylic acid copolymers and styrene / methacrylic acid copolymers. The content of the sizing agent is not particularly limited, but is preferably 3.0% by mass or less relative to the raw material pulp (absolute dry mass).

[0051] Examples of the fixing agent include aluminum sulfate, polyethyleneimine, etc. The content of the fixing agent is not particularly limited, but is preferably 3.0% by mass or less based on the raw material pulp (absolute dry mass).

[0052] Examples of the filler include inorganic fillers such as talc, kaolin, calcined kaolin, calcium carbonate, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, aluminum oxide, magnesium carbonate, magnesium oxide, silicon dioxide, white carbon, bentonite, zeolite, sericite, and montmorillonite; and organic fillers such as acrylic resins and vinylidene chloride resins.

[0053] As the paper substrate, for example, stretchable paper (elastic paper) obtained by performing stretching treatment to shrink the paper can be used. It should be noted that elastic paper refers to paper with a longitudinal or transverse elongation of 5% or more measured in accordance with JIS P 8113:2006, and examples thereof include kraft paper No. 1 and No. 2 of the five types described in JIS P 3401:2000. From the viewpoint of obtaining heat-sealed paper with desired Clark stiffness and puncture strength, the paper substrate is preferably stretchable paper (elastic paper).

[0054] [Heat seal layer]

[0055] The heat seal paper of the present embodiment has at least one heat seal layer on at least one surface of a paper base material. The heat seal layer is a layer that is melted and bonded by heating, ultrasonic waves, or the like.

[0056] (Water-dispersible resin binder)

[0057] The heat seal layer contains a water-dispersible resin binder. A water-dispersible resin binder refers to a resin binder that is not water-soluble (specifically, the solubility in water at 25°C is less than 10 g / L), but is in a micro-dispersed state in water like an emulsion or a suspension. By using a water-dispersible resin binder to apply an aqueous coating to the heat seal layer, a heat seal paper having excellent re-dissociability and capable of being recycled as paper can be obtained. It should be noted that when a water-dispersible resin binder also meets the following lubricant, it is classified as a lubricant.

[0058] The water-dispersible resin binder is not particularly limited as long as the effects of the present invention are exhibited, and examples thereof include polyolefin resins (polyethylene, polypropylene, etc.), vinyl chloride resins, styrene resins, styrene-butadiene copolymers, styrene-unsaturated carboxylic acid copolymers (e.g., styrene-(meth)acrylic acid copolymers), acrylic resins, acrylonitrile-styrene copolymers, acrylonitrile-butadiene copolymers, ABS resins, AAS resins, AES resins, vinylidene chloride resins, polyurethane resins, poly-4-methylpentene-1 resins, polybutene-1 resins, vinylidene fluoride resins, vinyl fluoride resins, fluorine resins, polycarbonate resins, polyamide resins, acetal resins, polyphenylene ether resins, polyester resins (polyethylene terephthalate, polybutylene terephthalate, etc.), polyphenylene sulfide resins, polyimide resins, polysulfone resins, polyethersulfone resins, polyarylate resins, olefin-unsaturated carboxylic acid copolymers, and modified products thereof. These may be used alone or in combination of two or more.

[0059] Among these, it is preferred that at least one selected from the group consisting of styrene-butadiene copolymers and olefin-unsaturated carboxylic acid copolymers is contained.

[0060] Furthermore, from the viewpoint of improving the heat seal peel strength, it is more preferable to contain an olefin-unsaturated carboxylic acid copolymer, and from the viewpoint of easy availability, cost aspect and recyclability, it is more preferable to contain a styrene-butadiene copolymer.

[0061] Examples of the olefin-unsaturated carboxylic acid copolymer include ethylene-(meth)acrylic acid copolymers, ethylene-alkyl (meth)acrylate copolymers, etc. Among them, it is preferred to include an ethylene-(meth)acrylic acid copolymer, and it is more preferred to include an ethylene-acrylic acid copolymer.

[0062] Therefore, the water-dispersible resin binder contained in the heat seal layer preferably contains at least one selected from the group consisting of styrene-butadiene copolymers and ethylene-(meth)acrylic acid copolymers. The olefin-unsaturated carboxylic acid copolymer may be an ionomer.

[0063] As the styrene-butadiene copolymer, any of synthetic products and commercial products can be used. Commercial products include Nipol Latex LX407G51, LX407S10, LX407S12, LX410, LX415M, LX416, LX430, LX433C, and 2507H manufactured by Japan ZEON Co., Ltd.; NALSTAR SR-101, SR-102, SR-103, SR-115, and SR-153 manufactured by Japan A&L Co., Ltd.; and Styrene Butadiene Latex 0602 and 0597C manufactured by JSR Co., Ltd.

[0064] As the ethylene-(meth)acrylic acid copolymer, any of a synthetic product and a commercially available product can be used. Examples of commercially available products include MP498345N, MP4983R, MP4990R, and MFHS1279 manufactured by Michelman Japan Co., Ltd.; ZAIKTHENE (registered trademark) A and ZAIKTHENE (registered trademark) AC manufactured by Sumitomo Seika Chemicals Co., Ltd.; and CHEMIPEARL S series manufactured by Mitsui Chemicals, Inc.

[0065] The glass transition temperature of the water-dispersible resin binder is preferably 0°C or higher, more preferably 10°C or higher, and further preferably 15°C or higher. By using a water-dispersible resin binder having a glass transition temperature of at least the above lower limit, the blocking resistance of the heat-sealing paper can also be improved. From the viewpoint of heat sealability, the glass transition temperature is preferably 100°C or lower, more preferably 80°C or lower, further preferably 60°C or lower, and further preferably 50°C or lower.

[0066] The glass transition temperature of the water-dispersible resin binder is a value measured by a differential scanning calorimeter.

[0067] The content of the water-dispersible resin binder in the heat seal layer is preferably 30% by mass or more, more preferably 50% by mass or more, further preferably 70% by mass or more, and further preferably 80% by mass or more, and is 100% by mass or less, preferably 99% by mass or less, and more preferably 98% by mass or less. If it is within the above range, a heat seal paper having a high heat seal peel strength can be obtained.

[0068] That is, according to one embodiment of the present invention, the content of styrene-butadiene copolymer and / or olefin-unsaturated carboxylic acid copolymer (preferably ethylene-(meth)acrylic acid copolymer) in the heat seal layer is preferably 30% by mass or more, more preferably 50% by mass or more, further preferably 70% by mass or more, and further preferably 90% by mass or more, and is 100% by mass or less, preferably 99% by mass or less, and more preferably 98% by mass or less. Here, the "content of A and / or B" refers to the content thereof when only A or B is contained, and refers to their total content when both A and B are contained.

[0069] (Lubricant)

[0070] From the viewpoint of imparting smoothness and anti-blocking properties to the heat seal paper, the heat seal layer preferably contains a lubricant in addition to the water-dispersible resin binder. The lubricant is a substance that can reduce the friction coefficient of the heat seal layer surface by being added to the heat seal layer.

[0071] As lubricants, there are no particular limitations, and for example, waxes, metal soaps, fatty acid esters, etc. can be used. One lubricant can be used alone, or two or more lubricants can be used in combination. As waxes, natural waxes such as animal or plant-derived waxes (such as beeswax, carnauba wax, etc.), mineral waxes (such as microcrystalline wax, etc.), petroleum waxes, etc.; synthetic waxes such as polyolefin waxes, paraffin waxes, polyester waxes, etc. can be cited. As metal soaps, for example, calcium stearate, sodium stearate, zinc stearate, aluminum stearate, magnesium stearate, fatty acid sodium soaps, potassium oleate soaps, castor oil potassium soaps, and their complexes can be cited. Among the above lubricants, paraffin wax, carnauba wax, and polyolefin wax are preferred from the perspective of having a low melting point, a wax component that is easily formed on the surface of the coating layer, and an excellent effect of improving adhesion resistance. That is, the lubricant preferably includes at least one selected from the group consisting of paraffin wax, carnauba wax, and polyolefin wax. From the viewpoint of imparting smoothness and improving moisture resistance, paraffin wax is preferably included.

[0072] As carnauba wax, any of synthetic products and commercial products can be used, and commercial products include Serozol 524 manufactured by Chukyo Oil & Fats Co., Ltd. and Michem Lube 160RPH manufactured by Michelman Co., Ltd. As paraffin wax, any of synthetic products and commercial products can be used, and commercial products include Hidorin L-700 manufactured by Chukyo Oil & Fats Co., Ltd. As polyethylene wax, any of synthetic products and commercial products can be used, and commercial products include Aquacer 531 manufactured by BYK Co., Ltd.

[0073] When the water-dispersible resin binder comprises a styrene-butadiene copolymer, the lubricant preferably comprises paraffin wax. Alternatively, when the water-dispersible resin binder comprises an olefin-unsaturated carboxylic acid copolymer (preferably an ethylene-(meth)acrylic acid copolymer), the lubricant preferably comprises carnauba wax.

[0074] When the heat seal layer contains a lubricant, the content of the lubricant is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, and further preferably 1 part by mass or more, and is preferably 30 parts by mass or less, more preferably 10 parts by mass or less, and further preferably 5 parts by mass or less, based on 100 parts by mass of the water-dispersible resin binder.

[0075] When the heat seal layer contains a lubricant, the content of the lubricant in the heat seal layer is preferably 0.1 mass % or more, more preferably 0.3 mass % or more, further preferably 1 mass % or more, and is preferably 30 mass % or less, more preferably 10 mass % or less, further preferably 5 mass % or less.

[0076] In this embodiment, the heat seal layer contains a water-dispersible resin binder, and preferably contains a lubricant in addition to the water-dispersible resin binder. In addition, a pigment may be contained in addition to the water-dispersible resin binder and the lubricant as needed.

[0077] (pigment)

[0078] In this embodiment, the heat seal layer may contain a pigment in addition to the water-dispersible resin binder and a lubricant as required. By containing the pigment, the problem of the coated surface of the heat seal layer adhering to the back of the heat seal paper and peeling (blocking) is suppressed when the heat seal paper is manufactured, and a heat seal paper with excellent blocking resistance can be obtained.

[0079] The pigment is not particularly limited, and various pigments used in the pigment coating layer in the past can be exemplified. One pigment can be used alone, or two or more pigments can be used in combination. As the pigment, from the viewpoint of heat seal peel strength and blocking resistance, it is preferred to include a pigment having an aspect ratio of 20 or more. The aspect ratio of the pigment is more preferably 25 or more, further preferably 30 or more, and particularly preferably 60 or more, and from the viewpoint of ease of acquisition and smoothness of the surface of the heat seal layer, it is preferably 10,000 or less, more preferably 1,000 or less, and further preferably 300 or less. The aspect ratio of the pigment refers to the major diameter / minor diameter, and can be measured by the following method.

[0080] The pigment preferably comprises a layered inorganic compound having an aspect ratio of greater than 20. The layered inorganic compound is in the form of a plate. If the pigment is in the form of a plate, the pigment can be prevented from protruding from the surface of the heat seal layer, and a heat seal layer having excellent anti-blocking properties can be obtained while maintaining heat sealability.

[0081] The length (average particle size) of the pigment is preferably 0.1 μm or more and 100 μm or less. If the length is 0.1 μm or more, the pigment is easily arranged in parallel with respect to the paper substrate. In addition, if the length is 100 μm or less, there is little possibility that a part of the pigment protrudes from the heat seal layer. The length of the pigment is more preferably 0.3 μm or more, further preferably 0.5 μm or more, particularly preferably 1.0 μm or more, and more preferably 30 μm or less, further preferably 20 μm or less, particularly preferably 15 μm or less.

[0082] Here, the length of the pigment contained in the heat seal layer is calculated as follows. An electron microscope is used to take an enlarged photograph of the cross section of the heat seal layer. At this time, the magnification is set to include about 20 to 30 pigments in the picture. The length of each pigment in the picture is measured. And the average value of the obtained length is calculated as the length of the pigment. It should be noted that the length of the pigment is sometimes recorded as the particle size.

[0083] The thickness of the pigment is preferably 200 nm or less. The thickness of the pigment is more preferably 100 nm or less, further preferably 80 nm or less, further preferably 50 nm or less, and particularly preferably 30 nm or less. In addition, it is preferably 5 nm or more, more preferably 10 nm or more. When the average thickness of the pigment is small, a high heat seal peel strength can be obtained. Here, the thickness of the pigment in the state contained in the heat seal layer is calculated as follows. An enlarged photograph is taken of the cross section of the heat seal layer using an electron microscope. At this time, the magnification is set to include about 20 to 30 pigments in the picture. The thickness of each pigment in the picture is measured. And the average value of the obtained thickness is calculated as the thickness of the pigment.

[0084] Specific examples of pigments include mica, bentonite, kaolin, pyrophyllite, talc, montmorillonite, vermiculite, chlorite, brittle chlorite, serpentine, black hard chlorite, montmorillonite, heavy calcium carbonate (crushed calcium carbonate), light calcium carbonate (synthetic calcium carbonate), composite synthetic pigments of calcium carbonate and other hydrophilic organic compounds, satin white, lithopone, titanium dioxide, silicon dioxide, barium sulfate, calcium sulfate, aluminum oxide, aluminum hydroxide, zinc oxide, magnesium carbonate, silicates, colloidal silica, hollow or dense organic pigments, plastic pigments, binder pigments, plastic beads, microcapsules, etc., and it is preferred to contain at least one selected from the group consisting of these.

[0085] Specific examples of mica include synthetic mica (e.g., swelling synthetic mica), muscovite, sericite, phlogopite, biotite, fluorphlogopite (artificial mica), red mica, sodium mica, vanadium mica, illite, zinc mica, orange glass, brittle mica, etc. Specific examples of bentonite include montmorillonite.

[0086] Specific examples of kaolin include various kaolins such as kaolin, calcined kaolin, structured kaolin, and delaminated kaolin.

[0087] Among these, from the viewpoint of heat seal peel strength, blocking resistance and economic efficiency, it is preferred to contain a pigment having an aspect ratio of 20 or more, more preferred to contain at least one of mica, bentonite, kaolin and talc, and even more preferred to contain kaolin.

[0088] When the heat seal layer contains a pigment, from the viewpoint of blocking resistance, the content of the pigment is preferably 1 part by mass or more, more preferably 3 parts by mass or more, further preferably 5 parts by mass or more, and further preferably 8 parts by mass or more relative to 100 parts by mass of the water-dispersible resin binder, and on the other hand, from the viewpoint of heat sealability, it is preferably 200 parts by mass or less, more preferably 100 parts by mass or less, and further preferably 30 parts by mass or less.

[0089] When the heat seal layer contains a pigment, the content of the pigment in the heat seal layer is preferably 1 mass % or more, more preferably 3 mass % or more, further preferably 5 mass % or more, further preferably 8 mass % or more, from the viewpoint of blocking resistance and recyclability, and is preferably 70 mass % or less, more preferably 30 mass % or less, further preferably 20 mass % or less, from the viewpoint of heat sealability.

[0090] (Other ingredients)

[0091] The heat seal layer may contain other components in addition to the water-dispersible resin binder and, if necessary, a lubricant and / or a pigment. Examples of other components include silane coupling agents, defoamers, viscosity modifiers, leveling agents such as surfactants and alcohols, and colorants such as coloring dyes.

[0092] The coating amount (basis weight) of the heat seal layer is not particularly limited, but is preferably 3 g / m2 from the viewpoint of obtaining sufficient heat sealability and obtaining a packaging bag that is not easily broken and can be easily opened when opened. 2 More preferably 5g / m 2 More preferably, 8 g / m 2From the viewpoint of economy and recyclability, 30 g / m 2 Below, more preferably 20g / m 2 Below, more preferably 15g / m 2 the following.

[0093] <Physical properties of heat seal paper>

[0094] (Tear Index)

[0095] From the perspective of obtaining a packaging bag that is not easily broken and can be easily opened when opened, the vertical and horizontal geometric mean of the tear index of the heat-sealed paper is 10 mN·m 2 / g or more, preferably 12mN·m 2 / g or more, and the upper limit is not particularly limited, but is preferably 30 mN·m 2 / g or less, more preferably 25mN·m 2 / g or less, more preferably 20mN·m 2 / g or less.

[0096] The tear index of heat-sealing paper is a value obtained by dividing the tear strength measured in accordance with JIS P 8116:2000 by the basis weight.

[0097] The method for adjusting the longitudinal and transverse geometric mean of the tear index of the heat-sealed paper to the above range is not particularly limited, and can be adjusted by selecting the type of pulp constituting the paper substrate, beating conditions (beating degree, pulp concentration during beating, etc.), for example, by using conifer pulp, preferably conifer unbleached kraft pulp, the tear index can be improved. In addition, by setting the appropriate beating degree, the tear index can be adjusted. If the beating degree is high (CSF is small), there is a tendency for the tear index to decrease. In addition, by performing high-concentration beating, the pulp is further branched or microfibrous, and the tear strength can also be improved. Furthermore, by using elastic paper that has been subjected to stretching treatment as the paper substrate, the energy during tearing can be absorbed due to extension, and a high tear index can be obtained.

[0098] From the viewpoint of obtaining a packaging bag that is not easily broken and can be easily opened when opened, the longitudinal tear index of the heat-sealed paper is preferably 8 mN·m 2 / g or more, more preferably 10 mN·m 2 / g or more, and the upper limit is not particularly limited, but is preferably 30 mN·m 2 / g or less, more preferably 24mN·m 2 / g or less, more preferably 18mN·m 2 / g or less.

[0099] From the viewpoint of obtaining a packaging bag that is not easily broken and can be easily opened when opened, the transverse tear index of the heat-sealing paper is preferably 10 mN·m 2 / g or more, more preferably 12mN·m 2 / g or more, more preferably 14mN·m 2 / g or more, and the upper limit is not particularly limited, but is preferably 32 mN·m 2 / g or less, more preferably 28mN·m 2 / g or less, more preferably 24mN·m 2 / g or less.

[0100] (Rupture Index)

[0101] From the perspective of obtaining a packaging bag that is not easily broken and can be easily opened when opened, the bursting index of heat-sealed paper is 3.0 kPa·m 2 / g or more, preferably 3.5 kPa·m 2 / g or more, and the upper limit is not particularly limited, but is preferably 10.0 kPa·m 2 / g or less, more preferably 8.5 kPa·m 2 / g or less, more preferably 7.0 kPa·m 2 / g or less.

[0102] The bursting index of heat seal paper is a value obtained by dividing the bursting strength measured in accordance with JIS P 8112:2008 by the basis weight.

[0103] The method for adjusting the bursting index of the heat seal paper to the above range is not particularly limited, and can be adjusted by selecting the type and beating degree of the pulp constituting the paper substrate. For example, the bursting index can be improved by using conifer pulp, preferably conifer unbleached kraft pulp. In addition, the bursting index can be adjusted by setting an appropriate beating degree. If the beating degree is high (CSF is small), there is a tendency for the bursting index to decrease. In addition, by beating at a high concentration, the pulp is further branched or microfibrous, and the bursting strength can also be improved.

[0104] Furthermore, a high bursting index can be obtained by using elastic paper treated with stretching as the paper base material. In addition, the bursting index can be increased by adding an internal paper strengthening agent to the paper base material.

[0105] (Heat seal peel strength)

[0106] Regarding the heat-sealing paper of the present embodiment, from the viewpoint of obtaining a packaging bag that is not easy to break and can be easily opened when unsealed, the heat seal peel strength is 2.0N / 15mm or more, preferably 3.0N / 15mm or more, more preferably 4.0N / 15mm or more, and more preferably 4.5N / 15mm or more, and 10.0N / 15mm or less, more preferably 9.0N / 15mm or less, more preferably 8.0N / 15mm or less, more preferably 6.5N / 15mm or less, and more preferably 7.0N / 15mm or less. Furthermore, from the viewpoint of automatic packaging formability, it is preferably 4.8N / 15mm or more. The peel strength of the heat-sealing layer is the peel strength when the heat-sealing layers are heat-sealed to each other under the conditions of 150°C, 0.2MPa, and 1 second, specifically, it is the value measured by the method described in the embodiments described later.

[0107] The peel strength can be adjusted by selecting the glass transition temperature and type of the water-dispersible resin binder, as well as the coating amount. For example, by setting the glass transition temperature of the water-dispersible resin binder to 100° C. or less, the resin melts under the prescribed heat-sealing conditions, and the heat-sealing layers are well bonded to each other, thereby ensuring the desired peel strength.

[0108] (Surface smoothness)

[0109] From the viewpoint of improving the heat seal peel strength, the Wang Yan type smoothness of the heat seal layer surface of the heat seal paper of the present embodiment is preferably 30 seconds or more, more preferably 40 seconds or more, and further preferably 50 seconds or more. The upper limit is not particularly limited, but is preferably 500 seconds or less, more preferably 300 seconds or less, and further preferably 100 seconds or less.

[0110] It should be noted that the heat seal layer can be provided on the W side (wire side) or the F side (felt side) of the paper substrate, without particular limitation. Here, the W side (wire side) refers to the side in contact with the wire when forming the paper, and the opposite side is the F side (felt side).

[0111] In addition, from the viewpoint of improving printability, the Wang Yan type smoothness of the side opposite to the heat seal layer (for example, when the heat seal layer is provided on only one side of the paper substrate and the other side is exposed to the paper substrate, it is the surface of the paper substrate) is preferably 3 seconds or more, more preferably 5 seconds or more, and the upper limit is not particularly limited, but is preferably 1000 seconds or less, more preferably 300 seconds or less, and further preferably 100 seconds or less.

[0112] Wangyan smoothness is measured according to JIS P8155:2010.

[0113] The surface of the heat-sealing layer of the heat-sealing paper and the surface opposite thereto can be adjusted to the above range by, for example, a high-calendering treatment described later.

[0114] (Basis Weight)

[0115] From the viewpoint of obtaining a packaging bag that is not easily broken and can be easily opened when opened, the basis weight of the heat-sealing paper of this embodiment is preferably 50 g / m 2 More preferably 70 g / m 2 More preferably, 80 g / m 2 More preferably, 85 g / m 2 More than, and preferably 200g / m 2 Less than, more preferably 150g / m 2 Below, more preferably 120g / m 2 Below, more preferably 100g / m 2 the following.

[0116] The basis weight of the heat seal paper is measured in accordance with JIS P 8124:2011.

[0117] (thickness)

[0118] From the viewpoint of obtaining a packaging bag that is not easily broken and can be easily opened when opened, the thickness of the heat-sealing paper of the present embodiment is preferably 60 μm or more, more preferably 80 μm or more, further preferably 90 μm or more, further preferably 100 μm or more, and is preferably 300 μm or less, more preferably 200 μm or less, further preferably 150 μm or less.

[0119] The thickness of the heat sealing paper is measured in accordance with JIS P 8118:2014.

[0120] (density)

[0121] From the viewpoint of obtaining a packaging bag that is not easily broken and can be easily opened when opened, the density of the heat-sealing paper is preferably 0.50 g / cm 3 More preferably, 0.60 g / cm 3 More preferably, 0.65 g / cm 3 More than, and preferably 1.0 g / cm 3 Below, more preferably 0.90 g / cm 3 Below, more preferably 0.80 g / cm 3 The density of the heat-sealing paper is calculated based on the basis weight and thickness of the heat-sealing paper obtained by the above-mentioned measuring method.

[0122] (Clark Stiffness)

[0123] From the viewpoint of obtaining a packaging bag that is not easily broken and can be easily opened when opened, the longitudinal and transverse geometric mean of the Clark stiffness of the heat-sealing paper is preferably 20 or more, more preferably 30 or more, further preferably 35 or more, and further preferably 40 or more, and from the viewpoint of automatic packaging formability, it is preferably 150 or less, more preferably 100 or less, further preferably 85 or less, further preferably 70 or less, can be 60 or less, and can be 50 or less.

[0124] The longitudinal and transverse geometric mean of the Clark stiffness of the heat-sealing paper is obtained by calculating the geometric mean of the Clark stiffness in the longitudinal and transverse directions measured by the method of Examples in accordance with JIS P 8143:2009.

[0125] The method for adjusting the longitudinal and transverse geometric mean of the Clarke stiffness of the heat-sealed paper to the above range is not particularly limited, and can be adjusted by selecting various conditions such as the type of pulp constituting the paper substrate, the beating degree, the basis weight, the calendering treatment, the stretching treatment, etc. For example, when using coniferous pulp and broadleaf pulp as the pulp constituting the paper substrate, if the blending amount of broadleaf pulp is increased, there is a tendency for the Clarke stiffness to decrease. In addition, when using pulp constituting the paper substrate with an increased beating degree and a low CSF, there is a tendency for the Clarke stiffness to decrease. Furthermore, if the basis weight is reduced, there is a tendency for the Clarke stiffness to decrease, and if the paper substrate is subjected to stretching treatment and calendering treatment, there is a tendency for the Clarke stiffness to decrease.

[0126] From the viewpoint of obtaining a packaging bag that is not easily broken and can be easily opened when opened, the longitudinal Clark stiffness of the heat-sealing paper is preferably 20 or more, more preferably 30 or more, and further preferably 40 or more, and from the viewpoint of automatic packaging formability, it is preferably 250 or less, more preferably 200 or less, further preferably 150 or less, further preferably 100 or less, further preferably 85 or less, further preferably 80 or less, particularly preferably 75 or less, and can be 70 or less, 65 or less, or 55 or less.

[0127] From the viewpoint of obtaining a packaging bag that is not easily broken and can be easily opened when opened, the transverse Clark stiffness of the heat-sealing paper is preferably 20 or more, more preferably 30 or more, and further preferably 35 or more. From the viewpoint of automatic packaging formability, it is preferably 250 or less, more preferably 200 or less, further preferably 150 or less, further preferably 100 or less, further preferably 85 or less, further preferably 80 or less, particularly preferably 70 or less, and can be 60 or less, and can be 50 or less.

[0128] (Clark Stiffness / Basis Weight)

[0129] From the perspective of obtaining a packaging bag that is not easily broken and can be easily opened when opened, as well as from the perspective of formability (for example, the appearance of the bag), the longitudinal and transverse geometric mean of the Clark stiffness of the heat-sealing paper is divided by the basis weight (g / m 2 ) and the value obtained (Clark stiffness / basis weight) (unit: m 2 / g) is preferably 0.20m 2 / g or more, more preferably 0.30m 2 / g or more, more preferably 0.40m 2 / g or more, and preferably 1.20 m / g from the viewpoint of automatic packaging moldability. 2 / g or less, more preferably 1.00m 2 / g or less, more preferably 0.90m 2 / g or less, and more preferably 0.80m 2 / g or less, particularly preferably 0.65m 2 / g or less, can be 0.60m 2 / g or less, can be 0.55m 2 / g or less.

[0130] In addition, it can be considered that: by making the "vertical and horizontal geometric mean of Clark stiffness / basis weight (unit: m 2 / g)” is 1.00m 2 / g or less, so that the heat-sealing paper has moderate softness. When forming in the bag-making machine, the heat-sealing paper can follow the deformation, thus suppressing wrinkles and poor appearance, and excellent automatic packaging formability. In addition, it can be considered that if the "vertical and horizontal geometric mean of Clark stiffness / basis weight" (unit: m 2 / g)” is 0.20m 2 / g or more, the shape retention and durability of the packaging bag are improved, and the breakage of the packaging bag is suppressed.

[0131] In this specification, "excellent automatic packaging formability" means: the bag can be continuously made using an automatic packaging machine, and the appearance of the obtained bag is good. Here, "can be continuously made into bags" means: when the packaging bag is formed using an automatic packaging machine, the packaging material does not wrinkle, meander, break, stick to the packaging machine, etc., or even if it occurs, it is not an obstacle to continuous bag making. In addition, "good appearance of the bag" means: no wrinkles, poor sealing (deviated sealing part), deformation and other poor appearance of the bag are observed, or even if observed, they are within the acceptable range.

[0132] From the perspective of obtaining a packaging bag that is not easily broken and can be easily opened when opened, the Clark stiffness of the heat-sealing paper in the longitudinal direction is divided by the basis weight (g / m 2 ) and the value obtained (Clark stiffness / basis weight) (unit: m2 / g) is preferably 0.20m 2 / g or more, more preferably 0.30m 2 / g or more, more preferably 0.40m 2 / g or more, and preferably 2.40 m / g from the viewpoint of automatic packaging moldability. 2 / g or less, more preferably 2.00m 2 / g or less, more preferably 1.50m 2 / g or less, more preferably 1.00m 2 / g or less, more preferably 0.90m 2 / g or less, more preferably 0.80m 2 / g or less, and more preferably 0.70m 2 / g or less, can be 0.60m 2 / g or less, can be 0.55m 2 / g or less.

[0133] From the perspective of obtaining a packaging bag that is not easily broken and can be easily opened when opened, the Clark stiffness in the transverse direction of the heat-sealing paper is divided by the basis weight (g / m 2 ) and the value obtained (Clark stiffness / basis weight) (unit: m 2 / g) is preferably 0.20m 2 / g or more, more preferably 0.30m 2 / g or more, more preferably 0.40m 2 / g or more, and preferably 1.20 m / g from the viewpoint of automatic packaging moldability. 2 / g or less, more preferably 1.00m 2 / g or less, more preferably 0.90m 2 / g or less, particularly preferably 0.80m 2 / g or less, can be 0.60m 2 / g or less.

[0134] (Puncture Strength)

[0135] From the viewpoint of obtaining a packaging bag that is not easily broken, the puncture strength of the heat-sealing paper is preferably 10.0N or more, more preferably 11.0N or more, further preferably 12.0N or more, and further preferably 12.5N or more, and the upper limit is not particularly limited. From the viewpoint of obtaining a heat-sealing paper having a desired Clark stiffness and the viewpoint of ease of manufacturing, it is preferably 30.0N or less, more preferably 25.0N or less, further preferably 20.0N or less, further preferably 18.0N or less, and further preferably 17.0N or less.

[0136] The puncture strength of heat-sealing paper was measured in accordance with JIS Z 1717:2019.

[0137] The method for adjusting the puncture strength of the heat-sealed paper to the above range is not particularly limited, and can be adjusted by selecting various conditions such as the type of pulp constituting the paper substrate, the beating degree, the basis weight, and the ductility treatment. For example, when at least one kind selected from conifer pulp and broadleaf pulp is used as the pulp constituting the paper substrate, if the blending amount of conifer pulp is increased, there is a tendency for the puncture strength to increase. In addition, when the pulp constituting the paper substrate has an increased beating degree and a low CSF, there is a tendency for the puncture strength to decrease. Furthermore, if the basis weight is increased, there is a tendency for the puncture strength to increase. In addition, if the paper substrate is subjected to ductility treatment, the elongation of the paper is increased, and the impact caused by puncture can be absorbed, so there is a tendency for the puncture strength to increase.

[0138] [Method for producing heat-sealing paper]

[0139] The manufacturing method of the heat-sealing paper of the present embodiment is not particularly limited. For example, a manufacturing method including a coating step of coating at least one heat-sealing layer on at least one surface of a paper substrate can be cited, wherein the paper substrate is obtained by a method including the following steps: a cooking step of performing a cooking treatment on raw pulp; a beating step of beating a dispersion containing 20% ​​to 45% by mass of the raw pulp that has been cooked; and a papermaking step of making paper from the raw pulp that has been beaten. Each step of the manufacturing method is described below.

[0140] (Steaming process)

[0141] The cooking step is a step of performing a cooking treatment on the raw material pulp. The kappa number of the raw material pulp is preferably set to 30 or more and 60 or less by the cooking step. Although not particularly limited, it is preferred that the raw material pieces used as the material of the raw material pulp are treated with a chemical solution containing sodium hydroxide, and as a treatment method using a chemical solution containing sodium hydroxide, a known treatment method using a known chemical solution can be adopted.

[0142] Heat-sealing paper that can form a packaging bag that is not easily broken and can be easily opened when opened can be obtained by setting the carba number of the raw pulp to 30 or more and 60 or less. From this viewpoint, the carba number of the raw pulp is preferably 50 or less, and more preferably 45 or less.

[0143] The raw material flakes used as the raw material pulp preferably contain conifer pulp as the main component. "Raw material flakes containing conifer pulp as the main component" means that the conifer content in the raw material flakes exceeds 50% by mass, and the conifer content is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 100% by mass.

[0144] The raw material pulp may or may not be subjected to a bleaching treatment. The raw material pulp is preferably at least one selected from the group consisting of bleached kraft pulp and unbleached kraft pulp, and more preferably unbleached kraft pulp.

[0145] (Beating process)

[0146] The beating step is a step of beating a dispersion liquid containing preferably 20% by mass or more and 45% by mass or less of the raw material pulp subjected to the cooking treatment. The beating method is not particularly limited, but it is preferred that the raw material pulp subjected to the cooking treatment is dispersed in water to prepare a dispersion liquid having the above raw material pulp concentration, and then beating is performed. The beating method is not particularly limited, and the beating can be performed using a beating machine such as a double-acting disc refiner, a single mill, or a conical refiner.

[0147] By beating a dispersion containing 20% ​​by mass or more and 45% by mass or less of a raw material pulp subjected to a steaming treatment, a paper base having impact resistance and processability and a heat seal paper obtained using the paper base can be obtained with excellent productivity.

[0148] (Papermaking process)

[0149] The papermaking process is a process of making paper from the raw material pulp that has been subjected to a pulping treatment. There is no particular limitation on the papermaking method, and examples thereof include an acidic papermaking method in which papermaking is performed at a pH of about 4.5, and a neutral papermaking method in which papermaking is performed at a pH of about 6 to about 9. In the papermaking process, chemical reagents for the papermaking process such as a pH adjuster, a defoamer, a resin control agent, and a slime control agent may be appropriately added as needed. There is no particular limitation on the papermaking machine, and examples thereof include continuous papermaking machines such as a long-net type, a cylinder type, and an inclined type, and a multi-layer papermaking machine obtained by combining them.

[0150] The paper substrate used in the heat-sealing paper of the present embodiment can be obtained by a method including the above-mentioned steaming step, beating step and papermaking step. After the papermaking step, a stretching step of shrinking the paper using a stretching device can be performed as needed. As the stretching device, a known device can be used. It should be noted that the method for manufacturing the paper substrate used in the heat-sealing paper of the embodiment is not limited to the above-mentioned method.

[0151] In addition, in the present embodiment, the method for manufacturing heat-sealed paper may include a surface treatment step of treating the surface of the paper substrate with a chemical solvent. As the chemical solvent used in the surface treatment step, sizing agents, water-resistant agents, water-retaining agents, tackifiers, lubricants, etc. may be cited. As the device used in the surface treatment step, a known device may be used.

[0152] The method for producing heat seal paper of the present embodiment includes a coating step of coating a heat seal layer on at least one surface of the paper substrate obtained as described above. It should be noted that the heat seal layer coating liquid (heat seal layer coating material) may be coated twice or more.

[0153] When forming multiple heat seal layers on a paper substrate, the above method of forming the heat seal layers one by one is preferred, but it is not limited thereto, and a simultaneous multi-layer coating method may be used. The simultaneous multi-layer coating method refers to a method of simultaneously forming multiple heat seal layers by spraying multiple coating liquids from respective slit-shaped nozzles to form a liquid laminate, and coating the laminate on a paper substrate.

[0154] The coating equipment for coating the heat seal layer coating liquid on the paper substrate is not particularly limited, and any known equipment may be used. Examples of the coating equipment include a blade coater, a rod coater, an air knife coater, a slot die coater, a gravure coater, a micro gravure coater, a roll coater, a size press, a gate roll coater, and a SYM-SIZER.

[0155] The drying device for drying the heat seal layer is not particularly limited, and known devices can be used. As the drying device, for example, hot air dryer, infrared dryer, gas burner, heating plate, etc. can be listed. In addition, the drying temperature can be appropriately set as long as the drying time, etc. are taken into consideration.

[0156] The solvent of the heat seal layer coating liquid is not particularly limited, and water or an organic solvent such as ethanol, isopropanol, methyl ethyl ketone, toluene, etc. can be used. Among these, water is preferably used as the dispersion medium of the heat seal layer coating liquid from the viewpoint of not causing the problem of volatile organic solvents. That is, the heat seal layer coating liquid is preferably an aqueous composition for heat seal layer.

[0157] The solid content (solid content concentration) of the heat seal layer coating liquid is not particularly limited and can be appropriately selected from the viewpoints of coatability and ease of drying. It is preferably 10% by mass or more, more preferably 20% by mass or more, and further preferably 30% by mass or more, and is preferably 80% by mass or less, more preferably 60% by mass or less, further preferably 50% by mass or less, and further preferably 40% by mass or less.

[0158] The preferred range of the coating amount of the heat seal layer (after drying) is as described above. The heat seal layer may be one layer or two or more layers. When the heat seal layer is two or more layers, the above coating amount represents the total coating amount.

[0159] After the heat seal layer is applied and dried, it is also preferred to perform a high calendering treatment. Here, the high calendering treatment means: a treatment is performed independently of papermaking, usually by passing the paper or the like to be treated between metal rolls or between a metal roll and an elastic roll, and heating, pressurizing, etc. The high calendering treatment may be performed in one stage or in multiple stages, and is not particularly limited.

[0160] High-calendering treatment is preferred because it improves the smoothness of the heat seal layer surface, and as a result, improves the heat seal peel strength (lowers the minimum substrate failure temperature) and reduces the Clark stiffness.

[0161] In addition, the smoothness of the side opposite to the heat seal layer (for example, when the heat seal layer is provided on only one side of the paper substrate and the other side is exposed to the paper substrate, the surface of the paper substrate) is improved, and as a result, the printability is improved, which is preferred.

[0162] Furthermore, by performing a high calendering treatment, there is a tendency for the density of the heat-sealing paper to increase. In addition, as described above, the surface smoothness is improved. Therefore, when making bags, the heat-sealing paper in the packaging machine is fed well and the processing adaptability is improved, which is preferred.

[0163] The linear pressure in the supercalendering treatment is preferably 10 kg / cm or more, more preferably 30 kg / cm or more, and even more preferably 50 kg / cm or more, and is preferably 1000 kg / cm or less, more preferably 500 kg / cm or less, and even more preferably 200 kg / cm or less. The linear pressure can be appropriately changed according to the desired smoothness and density.

[0164] In addition, when heating is performed during the high calendering treatment, the heating temperature is not particularly limited. From the viewpoint of improving the treatment effect and preventing thermal degradation of the paper substrate and the heat sealing layer and adhesion of the heat sealing layer, the heating temperature is preferably 20°C or more, more preferably 30°C or more, and further preferably 35°C or more, and is preferably 80°C or less, more preferably 70°C or less, and further preferably 60°C or less.

[0165] <Purpose>

[0166] The heat-sealed paper described in this embodiment can be suitably used as a packaging bag for food, daily necessities, books, daily necessities (soap, lotion, paper diapers), etc. Therefore, the present invention also provides a packaging bag obtained by using the above-mentioned heat-sealed paper.

[0167] Example

[0168] Hereinafter, examples are given to specifically illustrate the present invention, but the present invention is not limited to these examples. It should be noted that, unless otherwise specified, the following operations are performed at 23° C. and a relative humidity of 50% RH. In addition, “parts” and “%” in the examples and comparative examples represent “parts by mass” and “% by mass”, respectively, unless otherwise specified.

[0169] [Example 1]

[0170] <Preparation of heat seal coating>

[0171] 98 parts (in terms of solid content) of a water dispersion of a styrene / butadiene copolymer (Nipol Latex LX407S12 manufactured by ZEON Japan, with a solid content of 46% and a glass transition temperature of 18°C ​​(product catalog value)) and 2 parts (in terms of solid content) of a paraffin emulsion (Hidorin L-700 manufactured by Chukyo Oil Co., Ltd., with a solid content of 30%) were mixed, and water was added and stirred in such a way that the solid content concentration became 33%, thereby preparing a heat seal layer coating (concentration of 33%). The solubility of the styrene / butadiene copolymer in water at 25°C was less than 10 g / L.

[0172] <Manufacturing of heat-sealing paper>

[0173] Basis weight 82.9g / m 2 , thickness 123μm, density 0.67g / cm 3 On the W side of the elastic paper (manufactured by Oji Materia Co., Ltd., 100% by mass of unbleached coniferous kraft pulp, Canadian standard freeness of 677 mL, stretch treatment, smoothness: F side 4 seconds, W side 7 seconds), the coating amount of the heat seal layer after drying is 10 g / m 2 The heat seal layer coating is formed into a heat seal layer by an air knife coater, and dried by a dryer at 130-160°C. Finally, the line pressure is set to 90kg / cm, the coated surface is in contact with a cooling roller, the non-coated surface is in contact with a cotton roller, the roller is heated to 40°C, and a high calendering treatment is performed in one stage to obtain heat seal paper (smoothness: 8 seconds for the F side and 64 seconds for the W side). Compared with the paper before coating, the high calendering treatment increases the smoothness and improves the printing adaptability.

[0174] [Example 2]

[0175] Change the elastic paper to a basis weight of 78.3g / m 2 , thickness 126μm, density 0.62g / cm 3The elastic paper (manufactured by Oji Materia Co., Ltd., 100% by mass of unbleached coniferous kraft pulp, Canadian standard freeness of 563 mL, smoothness: F side 12 seconds, W side 29 seconds) was used so that the coating amount of the heat seal layer after drying was 12 g / m 2 , except that the same operation as in Example 1 was performed to form a heat seal layer and perform a high calendering treatment to obtain a heat seal paper (smoothness: 15 seconds for the F side and 61 seconds for the W side).

[0176] [Example 3]

[0177] Change the elastic paper to a basis weight of 79.2g / m 2 , thickness 132μm, density 0.60g / cm 3 Heavy packaging paper (manufactured by Oji Materia Co., Ltd., 100% by mass of unbleached coniferous kraft pulp, Canadian standard freeness of 578 mL, smoothness: F side 3 seconds, W side 2 seconds, no stretch treatment) was prepared so that the coating amount of the heat seal layer after drying was 10 g / m 2 , except that the same operation as in Example 1 was performed to form a heat seal layer and perform a high calendering treatment to obtain a heat seal paper (smoothness: 25 seconds for the F side and 65 seconds for the W side).

[0178] [Example 4]

[0179] 98 parts (solid content conversion) of a commercially available aqueous dispersion of ethylene-acrylic acid copolymer (glass transition temperature of 45°C) and 2 parts (solid content conversion) of a commercially available aqueous dispersion of carnauba wax (MichemLube 160RPH, manufactured by Michelman, with a solid content concentration of 25% by mass) were mixed, and water was added and stirred in such a way that the solid content concentration became 35% to prepare a heat seal layer coating (concentration of 35%). The heat seal layer coating obtained was used, and except for this, the heat seal layer was formed and highly calendered in the same manner as in Example 2 to obtain heat seal paper (smoothness: 8 seconds for the F side and 82 seconds for the W side). The solubility of the above-mentioned ethylene-acrylic acid copolymer in water at 25°C was less than 10 g / L.

[0180] [Example 5]

[0181] The heat seal layer was formed and supercalendered in the same manner as in Example 1, to obtain heat seal paper (smoothness: 8 seconds for the F side and 42 seconds for the W side).

[0182] [Example 6]

[0183] Heat seal paper (smoothness: 12 seconds for the F side and 40 seconds for the W side) was obtained in the same manner as in Example 2 except that the high-calendering treatment was not performed.

[0184] [Example 7]

[0185] The heat seal layer was formed and the supercalendering treatment was performed in the same manner as in Example 1 except that the paraffin emulsion was not added, thereby obtaining a heat seal paper (smoothness: 8 seconds for the F side and 60 seconds for the W side).

[0186] [Example 8]

[0187] Heat seal paper (smoothness: 8 seconds for the F side and 12 seconds for the W side) was obtained in the same manner as in Example 1 except that 10 parts (solid content conversion) of a 50% solid content aqueous dispersion of kaolin (average particle size 8 μm, aspect ratio 80-100), 88 parts (solid content conversion) of an aqueous dispersion of a styrene / butadiene copolymer (Nipol Latex LX407S12 manufactured by ZEON Co., Ltd., solid content concentration 46%, glass transition temperature 18° C. (catalog value)), and 2 parts (solid content conversion) of a paraffin emulsion (Hidorin L-700 manufactured by Chukyo Oil & Fats Co., Ltd., solid content concentration 30%) were used to prepare a heat seal layer coating.

[0188] [Example 9]

[0189] The heat seal layer was formed and the super calendering treatment was performed in the same manner as in Example 1, to obtain heat seal paper (smoothness: 8 seconds for the F side and 64 seconds for the W side).

[0190] [Example 10]

[0191] The heat seal layer was formed and supercalendered in the same manner as in Example 2, except that 2 parts (solid content conversion) of polyethylene wax emulsion (Aquacer 531, manufactured by BYK, solid content concentration of 45 mass %) was added instead of 2 parts (solid content conversion) of paraffin wax emulsion to prepare a heat seal layer coating. Heat seal layer formation and supercalendering treatment were performed to obtain heat seal paper (smoothness: 15 seconds for the F side and 42 seconds for the W side).

[0192] [Example 11]

[0193] Change the elastic paper to a basis weight of 100.0 g / m 2 , thickness 149μm, density 0.67g / cm 3The elastic paper (manufactured by OjiMateria Co., Ltd., 100% by mass of coniferous unbleached kraft pulp, Canadian standard freeness of 677 mL, stretch treatment, smoothness: F side is 7 seconds, W side is 18 seconds), except that the heat sealing layer is formed and the high calendering treatment is performed in the same manner as in Example 1, to obtain heat sealing paper (smoothness: F side is 8 seconds, W side is 57 seconds).

[0194] [Example 12]

[0195] Heat seal paper (smoothness: 15 seconds for the F side and 24 seconds for the W side) was obtained in the same manner as in Example 2 except that 10 parts (solid content conversion) of a 50% solid content aqueous dispersion of kaolin (average particle size 8 μm, aspect ratio 80-100), 88 parts (solid content conversion) of an aqueous dispersion of a styrene / butadiene copolymer (Nipol Latex LX407S12 manufactured by ZEON Co., Ltd., solid content concentration 46%, glass transition temperature 18° C. (catalog value)), and 2 parts (solid content conversion) of a paraffin emulsion (Hidorin L-700 manufactured by Chukyo Oil & Fats Co., Ltd., solid content concentration 30%) were used to prepare a heat seal layer coating.

[0196] [Example 13]

[0197] The heat seal layer was formed and the supercalendering treatment was performed in the same manner as in Example 2, to obtain heat seal paper (smoothness: 15 seconds for the F side and 62 seconds for the W side).

[0198] [Comparative Example 1]

[0199] Change the elastic paper to a basis weight of 80.5g / m 2 , thickness 114μm, density 0.71g / cm 3 An unbleached lightweight packaging paper (manufactured by Oji Materia Co., Ltd., coniferous unbleached kraft pulp / broadleaved bleached kraft pulp=80 / 20 (mass ratio), Canadian standard freeness of 478 mL, smoothness: F side is 17 seconds, W side is 16 seconds), except that the operation was carried out in the same manner as in Example 1, the heat sealing layer was formed and the high calendering treatment was performed to obtain heat sealing paper (smoothness: F side is 89 seconds, W side is 219 seconds).

[0200] [Comparative Example 2]

[0201] At basis weight 70.0g / m 2 , thickness 100μm, density 0.70g / cm3 Polyethylene was melt-extruded and laminated on unbleached lightweight packaging paper (manufactured by Oji Materia Co., Ltd., coniferous unbleached kraft pulp / broadleaf bleached kraft pulp = 80 / 20 (mass ratio), Canadian standard freeness 478 mL, smoothness: F side 16 seconds, W side 14 seconds) to a thickness of 20 μm, and a basis weight of 89.2 g / m 2 Polyethylene laminated paper (smoothness: F side is 16 seconds, W side is 140 seconds).

[0202] [Comparative Example 3]

[0203] The heat seal layer was formed and supercalendered in the same manner as in Example 3, except that an aqueous dispersion of ethylene / vinyl acetate copolymer (SUMIKAFLEX 470HQ manufactured by SUMIKA CHEMTEX Co., Ltd., solid content: 55%, glass transition temperature: 0° C. (catalog value)) was used instead of an aqueous dispersion of styrene / butadiene copolymer as the heat seal layer coating, and no paraffin emulsion was used, to obtain heat seal paper (smoothness: 25 seconds for the F side and 56 seconds for the W side).

[0204] [Comparative Example 4]

[0205] Change the elastic paper to a basis weight of 78.2g / m 2 , thickness 100μm, density 0.78g / cm 3 A single-sided glossy kraft paper (manufactured by OjiMateria Co., Ltd., coniferous tree bleached kraft pulp / broadleaf tree bleached kraft pulp=35 / 65 (mass ratio), Canadian standard freeness of 578 mL, smoothness: F side is 120 seconds, W side is 18 seconds), except that the same operations as in Example 1 were performed to form a heat seal layer and perform high calendering treatment to obtain heat seal paper (smoothness: F side is 300 seconds, W side is 291 seconds).

[0206] [Comparative Example 5]

[0207] Change the elastic paper to a basis weight of 50.7g / m 2 , thickness 61μm, density 0.83g / cm 3 A single-sided glossy bleached kraft paper (manufactured by Oji F-Tex Co., Ltd., 100% by mass of bleached kraft pulp from broadleaf trees, Canadian standard freeness of 420 mL, smoothness: 430 seconds for the F side, 16 seconds for the W side, and no stretch treatment) was prepared. Except for this, the heat sealing layer was formed and the high calendering treatment was performed in the same manner as in Example 1 to obtain heat sealing paper (smoothness: 963 seconds for the F side, 219 seconds for the W side).

[0208] [Comparative Example 6]

[0209] Change the elastic paper to a basis weight of 30.6g / m 2 , thickness 30μm, density 1.01g / cm 3 A heat seal layer was formed and a high calendering treatment was performed in the same manner as in Example 1, except that a thick glassine paper (manufactured by Oji F-Tex Co., Ltd., 100% by mass of bleached conifer kraft pulp, smoothness: 1300 seconds for the F side, 1350 seconds for the W side) was prepared to obtain heat seal paper (smoothness: 1700 seconds for the F side, 1500 seconds for the W side).

[0210] [Measurement method]

[0211] The following measurements were performed on the obtained heat-sealed paper.

[0212] <Smoothness>

[0213] The smoothness value was determined by the Oken smoothness measurement according to JIS P8155: 2010. The smoothness of the paper substrate was also measured in the same manner as above.

[0214] <Clark Stiffness>

[0215] According to JIS P 8143:2009, the Clark stiffness in the longitudinal direction and the transverse direction of the paper were measured respectively, and the geometric mean of the two was taken as the Clark stiffness geometric mean value.

[0216] <Tear Index of Heat Sealing Paper>

[0217] The tear strength of heat-sealed paper was measured according to JIS P 8116:2000. The tear strength was measured in the longitudinal direction and the transverse direction, and the obtained value was divided by the basis weight to obtain the tear index. The longitudinal and transverse geometric mean was calculated based on the obtained longitudinal and transverse tear indices.

[0218] <Heat sealing paper burst index>

[0219] The bursting strength of the heat seal paper was measured according to JIS P 8112: 2008. The obtained value was divided by the basis weight to obtain a bursting index.

[0220] <Piercing Strength>

[0221] The test was performed in accordance with JIS Z1717:2019.

[0222] <Determination of Heat Seal Peel Strength>

[0223] Two sets of heat-sealed paper were overlapped in a way that the heat-sealed layers were opposite to each other, and heat-sealed using a heat-seal tester (manufactured by TESTERSANGYO, TP-701-B) at 150°C, 0.2MPa, and 1 second. The heat-sealed test piece was left to stand for more than 4 hours in a room at a temperature of 23°C ± 1°C and a humidity of 50% ± 2%. Next, the heat-sealed test piece was cut into 15 mm wide pieces, and a tensile tester was used to perform T-peeling at a tensile speed of 300 mm / min, and the maximum load recorded was taken as the heat-seal peel strength.

[0224] <Drop test with sand>

[0225] Two 400 mm square heat-sealed papers were heat-sealed on three sides with the heat-sealed layers facing each other. After about 2 kg of sand was sealed, the last side was heat-sealed to make a packaging bag containing the contents. A drop test was performed according to JIS Z 0202:2017. In the drop test, 5 bags were made as above, and the number of damages, bag breaks, and heat-sealed part openings of all bags was counted, and the judgment was made according to the following criteria (only A was qualified).

[0226] A: In the drop test, there was no damage to the paper, bag breakage, or opening of the heat seal.

[0227] B: In the drop test, the total number of locations where the paper is damaged or the heat-sealed portion is opened is 1 or more and 4 or less

[0228] C: In the drop test, the paper is damaged or the heat seal is opened at a total of 5 or more locations

[0229] <Drop test with gravel>

[0230] Two 400 mm square heat-sealed papers are heat-sealed on three sides with the heat-sealed layers facing each other. After about 2 kg of gravel (sharper than sand) is sealed, the last side is heat-sealed to make a packaging bag containing the contents. A drop test is performed on it according to JISZ 0202:2017. In the drop test, 5 bags are made as above, and the number of damage, bag breakage, and heat-sealed opening of all bags is counted, and the judgment is made according to the following criteria (only A is qualified).

[0231] A: In the drop test, there was no damage to the paper or bag.

[0232] B: In the drop test, the total number of locations where the paper is broken or the bag is broken is 1 or more and 4 or less

[0233] C: In the drop test, the paper is damaged or the bag is broken in 5 or more places in total

[0234] <Easy to open test>

[0235] The heat-sealed portion of the packaging bag identical to that used in the aforementioned drop test was not torn, but stretched in two directions perpendicular to the heat-sealed surface (in order to peel the heat-sealed layers from each other, the two heat-sealed papers were pulled in opposite directions), and the ease of opening was evaluated as follows.

[0236] A: Can be opened easily

[0237] B: Very strong and difficult to open

[0238] <Blocking resistance>

[0239] Ten sheets of heat-sealing paper were stacked so that the coated surface and the non-coated surface of the heat-sealing paper were in contact with each other, and heated to 40°C from top to bottom using a heat press at 20 kgf / cm 2 The paper was then released and the results of manual peeling were evaluated.

[0240] A: No damage or paper peeling

[0241] B: Damage or paper peeling occurs

[0242] <Automatic packaging formability test>

[0243] Use a high-speed horizontal pillow packaging machine (αWrapper FW3410, manufactured by Fujikikai) to continuously make bags with heat-sealed paper. At this time, the contents are not loaded, and the bags are formed in the form of empty bags. The appearance and operability are observed and the following judgments are made. Here, "unable to continuously make bags" means that wrinkles or meandering occur and the bags are not formed or the paper is broken. In addition, "poor appearance" refers to the mixing of wrinkles, the deviation of the sealing part, or the deformation of the bag (A and B are qualified).

[0244] A: Can continuously make bags with good appearance

[0245] B: Bags can be made continuously, but the appearance of the bags is slightly defective

[0246] C: Unable to make bags continuously

[0247] [Table 1]

[0248]

[0249] [Table 2]

[0250] Table 2

[0251]

[0252] According to Table 1, the packaging bags obtained from the heat-sealed papers of Examples 1 to 13 were excellent in drop resistance and were less likely to break. In addition, the bags could be easily opened when opened.

[0253] On the other hand, according to Table 2, the rupture index is less than 3.0 kPa·m 2 The packaging bag obtained by the heat-sealed paper of Comparative Example 1, which has a heat-seal peel strength of more than 10N / 15mm and a PE layer is provided on the unbleached light packaging paper by lamination, has poor resistance to falling and poor ease of opening. Furthermore, the packaging bag obtained by the heat-sealed paper of Comparative Example 3, which has a heat-seal peel strength of more than 10N / 15mm, has poor ease of opening. In addition, the longitudinal and transverse geometric mean of the tear index is less than 10mN·m 2 The packaging bags obtained by using the heat-sealed papers of Comparative Examples 4 to 6 with a drop resistance of 0.1 / g were inferior and the bags were broken.

[0254] It should be noted that the heat seal papers of Examples 1 to 6 and 8 to 13 containing a lubricant are excellent in blocking resistance. In addition, from the comparison between Examples 2 and 6, it can be seen that the Clark stiffness is reduced and the heat seal peel strength is improved by performing the high calendering treatment.

[0255] Based on the above results, it can be said that the heat-sealing paper of the present embodiment can provide a packaging bag that is not easily broken and can be easily opened when opened.

Claims

1. A heat-sealing paper having one or more heat-sealing layers on at least one surface of a paper substrate, The heat seal layer contains a water-dispersible resin binder, The longitudinal and transverse geometric mean of the tear index of the heat-sealing paper is 10 mN·m 2 / g or above, The rupture index of the heat sealing paper is 3.0 kPa·m 2 / g or above, The heat seal peel strength when the heat seal layers are heat-sealed under the conditions of 150° C., 0.2 MPa, and 1 second is 2.0 N / 15 mm or more and 10 N / 15 mm or less.

2. The heat-sealing paper according to claim 1, wherein: The heat seal layer also contains a lubricant.

3. The heat-sealing paper according to claim 2, wherein: The lubricant includes at least one selected from the group consisting of paraffin wax, carnauba wax, and polyolefin wax.

4. The heat sealing paper according to claim 2 or 3, wherein: The content of the lubricant in the heat seal layer is 1 mass % or more and 5 mass % or less.

5. The heat-sealing paper according to any one of claims 1 to 4, wherein: The water-dispersible resin binder has a glass transition temperature of 0° C. or higher and 100° C. or lower.

6. The heat-sealing paper according to any one of claims 1 to 5, wherein: The water-dispersible resin binder includes at least one selected from the group consisting of styrene-butadiene copolymers and olefin-unsaturated carboxylic acid copolymers.

7. The heat-sealing paper according to any one of claims 2 to 6, wherein: The water-dispersible resin binder includes a styrene-butadiene copolymer, and the lubricant includes a paraffin wax.

8. The heat-sealing paper according to any one of claims 2 to 6, wherein: The water-dispersible resin binder includes an olefin-unsaturated carboxylic acid copolymer, and the lubricant includes carnauba wax.

9. The heat-sealing paper according to any one of claims 1 to 8, wherein The Canadian Standard Freeness of the pulp constituting the paper substrate is 500 mL or more and 750 mL or less.

10. The heat-sealing paper according to any one of claims 1 to 9, wherein: The main component of the pulp constituting the paper base material is coniferous unbleached kraft pulp.

11. The heat-sealing paper according to any one of claims 1 to 10, wherein: Clark stiffness is the geometric mean of the longitudinal and transverse directions divided by the basis weight (g / m 2 ) and the value (Clark stiffness / basis weight) is 0.20m 2 / g or more and 1.20m 2 / g or less.

12. The heat-sealing paper according to any one of claims 1 to 11, wherein The puncture strength of the heat sealing paper is above 10.0N.

13. The heat-sealing paper according to any one of claims 1 to 12, wherein: The basis weight of the paper substrate is 50g / m 2 Above and 150g / m 2 the following.

14. The heat-sealing paper according to any one of claims 1 to 13, wherein: The basis weight of the heat seal layer is 3g / m 2 Above and 30g / m 2 the following.

15. The heat-sealing paper according to any one of claims 1 to 14, wherein: The basis weight of heat sealing paper is 50g / m 2 Above and 200g / m 2 the following.

16. The heat-sealing paper according to any one of claims 1 to 15, wherein: The paper substrate is elastic paper.

17. A packaging bag, which is made of the heat-sealing paper according to any one of claims 1 to 16.

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