Packaging paper and packaging body

Abstract

The purpose of the present invention is to provide: a packaging paper which has a reduced load on the environment, has excellent flexibility, has excellent breaking resistance, and also has heat sealability; and a packaging body that is formed of the packaging paper.　This packaging paper comprises a paper substrate with a heat seal layer disposed thereon. The paper substrate has a basis weight of 40 g / m2 or less; the content of the paper substrate in the packaging paper is 50 mass% or more; the Clark stiffness in the longitudinal direction of the packaging paper is 15.5 or less; the piercing strength of the packaging paper is 1.3 N or more; and the length-weighted average fiber length of pulp constituting the paper substrate is 0.92 mm or less.

Description

Wrapping paper and packaging

[0001] The present invention relates to wrapping paper and packaging.

[0002] In recent years, the problem of plastic waste has become more serious worldwide. To improve the global environment, efforts to eliminate and reduce the use of plastic in packaging materials have been promoted, and there has been a growing movement to replace plastic packaging with paper packaging. However, paper has the problem of being weaker and more easily torn than plastic materials. Patent Document 1 discloses a packaging base paper for sealed containers that has high bending strength, excellent impact resistance, and maintains strength that is resistant to tearing even when subjected to impacts during distribution after packaging contents. The packaging base paper for sealed containers is primarily composed of pulp, and is characterized in that 70% or more by mass of the pulp is softwood pulp, the pulp contains a dry strength agent and a wet strength agent, and at least one surface of the base paper is coated with carboxymethyl cellulose.

[0003] JP 2023-67787 A

[0004] The packaging base paper described in Patent Document 1 is strong and can firmly hold the contents, but is poor in flexibility, and for example, when a package is made using a mold with continuous irregularities, it tends to be poor in conformity to the mold, resulting in poor packaging properties, and there is room for improvement.The present invention aims to provide a packaging paper that has a reduced burden on the environment, is excellent in flexibility and tear resistance, and has heat-sealing properties, and a package made using said packaging paper.

[0005] The present inventors have found that the above problems can be solved by making the basis weight of the paper base material not more than a specific value, making the content of the paper base material not less than a specific value, making the Clark stiffness not more than a specific value, making the puncture strength not less than a specific value, and making the length-average fiber length of the pulp constituting the paper base material not more than a specific value in a packaging paper having a heat-seal layer. That is, the present invention relates to the following <1> to <7>. <1> A packaging paper having a heat-seal layer on a paper base material, wherein the basis weight of the paper base material is 40 g / m ２<2> The wrapping paper according to <1>, having a thickness of 70 μm or less, a paper base material content of 50% by mass or more, a Clark stiffness in the longitudinal direction of the wrapping paper of 15.5 or less, a puncture strength of the wrapping paper of 1.3 N or more, and a length-weighted average fiber length of pulp constituting the paper base material of 0.92 mm or less. <3> The wrapping paper according to <1>, having a basis weight of 60 g / m or less. ２ The wrapping paper according to <1> or <2>, which is as follows: <4> The wrapping paper according to any one of <1> to <3>, wherein the raw material pulp of the paper base contains hardwood bleached kraft pulp, and the content of hardwood bleached kraft pulp in the raw material pulp is 85% by mass or more. <5> The wrapping paper according to any one of <1> to <4>, wherein the fiber orientation ratio is 1.85 or less. <6> The wrapping paper according to any one of <1> to <5>, wherein the paper base and the heat seal layer are directly laminated together. <7> A packaging body having a lid material and a base material having a recessed portion, which can contain and seal an item in the recessed portion by heat sealing the lid material and the base material, wherein the lid material and the base material are made of the wrapping paper according to any one of <1> to <6>.

[0006] According to the present invention, there are provided a wrapping paper that reduces the burden on the environment, has excellent flexibility and resistance to tearing, and has heat-sealing properties, and a package made using the wrapping paper.

[0007] 1A to 1C are cross-sectional schematic diagrams illustrating the manufacturing process of a package suitable for an embodiment.

[0008] [Wrapping Paper] The wrapping paper of this embodiment is a wrapping paper having a heat seal layer on a paper base material, and the paper base material has a basis weight of 40 g / m ２or less, the content of the paper base material in the wrapping paper is 50% by mass or more, the Clark stiffness in the longitudinal direction of the wrapping paper is 15.5 or less, the puncture strength of the wrapping paper is 1.3 N or more, and the length-weighted average fiber length of the pulp constituting the paper base material is 0.92 mm or less. The wrapping paper of this embodiment provides wrapping paper that reduces the burden on the environment, has excellent flexibility and puncture resistance, and has heat-sealing properties. Because the wrapping paper of this embodiment has excellent flexibility, it has excellent conformability to molds, etc., when packaging using a machine. The reason for obtaining the above effects is that the content of the paper base material in the wrapping paper is 50% or more, so the content of plastic materials in the wrapping paper is 50% or less, reducing the environmental burden. In addition, the basis weight of the paper base material is 40 g / m ２ Hereinafter, it is believed that when the content of the paper base material in the wrapping paper is 50% by mass or more, the Clark stiffness in the longitudinal direction of the wrapping paper is 15.5 or less, and the length-weighted average fiber length of the pulp constituting the paper base material is 0.92 mm or less, the wrapping paper becomes flexible, resulting in excellent conformability to molds, etc. Furthermore, it is believed that when the puncture strength of the wrapping paper is 1.3 N or more, it becomes less likely to tear and has excellent resistance to puncture. However, the reason for obtaining the above effects is not limited to this. Furthermore, according to the wrapping paper of this embodiment, the length-weighted average fiber length of the pulp constituting the paper base material is 0.92 mm or less, which suppresses unevenness in the paper base material and improves surface uniformity, making it possible to form a heat-seal layer with a basis weight lower than that of conventional heat-seal layers. The present invention will be described in more detail below.

[0009] In this specification, the numerical range represented by "X to Y" means a numerical range including X as the lower limit and Y as the upper limit. When numerical ranges are described in stages, the upper and lower limits of each numerical range can be combined arbitrarily. Furthermore, in this specification, unless otherwise specified, operations and measurements of physical properties are performed under conditions of room temperature (20-25°C) and relative humidity of 40-50% RH. Furthermore, "(meth)acrylic" is a generic term that includes both acrylic and methacrylic. Furthermore, the longitudinal direction of packaging paper and paper substrate refers to the papermaking direction (MD) of the paper substrate, and the transverse direction refers to the direction perpendicular to the papermaking direction (CD).

[0010] <Paper base material> The wrapping paper of this embodiment has a heat seal layer on the paper base material. The paper base material may be formed of a single layer or may be formed of multiple layers, and is not particularly limited. The paper base material is a sheet mainly made of pulp, and may be a base paper obtained by papermaking a paper stock containing raw pulp, fillers, various auxiliaries, etc., as is, or a base paper with one or more functional layers, such as a sealing layer, ink-receiving layer, water-resistant layer, oil-resistant layer, water vapor barrier layer, or gas barrier layer, formed on at least one side thereof.

[0011] (Raw material pulp) The pulp constituting the paper base material is not particularly limited, and known pulps can be used.Specific examples include unbleached pulp such as hardwood unbleached kraft pulp (LUKP) and softwood unbleached kraft pulp (NUKP); chemical pulp such as hardwood bleached kraft pulp (LBKP) and softwood bleached kraft pulp (NBKP); mechanical pulp such as groundwood pulp (GP), pressure groundwood pulp (PGW), refiner mechanical pulp (RMP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), chemi-mechanical pulp (CMP), and chemi-ground pulp (CGP); recycled paper pulp; non-wood fiber pulp such as kenaf, bagasse, bamboo, and cotton; and synthetic pulp.These pulps may be used alone or in combination of two or more. Among these, at least one selected from the group consisting of unbleached hardwood kraft pulp (LUKP), unbleached softwood kraft pulp (NUKP), bleached hardwood kraft pulp (LBKP), and bleached softwood kraft pulp (NBKP) is preferred, at least one selected from the group consisting of bleached hardwood kraft pulp (LBKP) and bleached softwood kraft pulp (NBKP) is more preferred, and bleached hardwood kraft pulp (LBKP) is even more preferred.

[0012] The main component of the pulp constituting the paper base material used in the wrapping paper of this embodiment is preferably hardwood pulp, and more preferably hardwood bleached kraft pulp (LBKP). "The main component of the pulp constituting the paper base material is hardwood pulp (or hardwood bleached kraft pulp)" means that the content of hardwood pulp (or hardwood bleached kraft pulp) in the pulp constituting the paper base material is more than 50% by mass, and the content of hardwood pulp (or hardwood bleached kraft pulp) is preferably 85% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 100% by mass. Hardwood pulp has a shorter average fiber length than softwood pulp, and using a paper base material using hardwood pulp as the raw material pulp is preferred because it allows for the production of wrapping paper with the desired Clark stiffness and excellent flexibility. Furthermore, by using hardwood pulp, preferably hardwood bleached pulp, as the raw material pulp, the average fiber length of the pulp constituting the paper base material tends to be shorter, resulting in suppressed paper unevenness and a paper base material with better surface uniformity. Since the heat-seal layer is formed on a paper base material with high surface uniformity, it is possible to form a uniform heat-seal layer even if a heat-seal layer with a lower basis weight is formed, and there is also the effect that good heat-sealability is imparted even by forming a heat-seal layer with a low basis weight.

[0013] That is, the raw material pulp preferably contains bleached hardwood kraft pulp (LBKP) and, if necessary, bleached softwood kraft pulp (NBKP). The total content of the hardwood kraft pulp and bleached softwood kraft pulp in the raw material pulp is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass. The mass ratio of the bleached softwood kraft pulp (NBKP) to the bleached hardwood kraft pulp (LBKP) in the raw material pulp (NBKP / LBKP) is preferably 0 / 100 or more and 15 / 85 or less, more preferably 10 / 90 or less, and even more preferably 5 / 95 or less.

[0014] In the wrapping paper of this embodiment, the length-weighted average fiber length of the pulp constituting the paper base is 0.92 mm or less. When the length-weighted average fiber length of the pulp constituting the paper base is 0.92 mm or less, wrapping paper with excellent flexibility can be obtained. From the viewpoints of flexibility and puncture resistance, the length-weighted average fiber length of the pulp constituting the paper base is preferably 0.30 mm or more and 0.90 mm or less, more preferably 0.80 mm or less, even more preferably 0.75 mm or less, still more preferably 0.70 mm or less, more preferably 0.40 mm or more, even more preferably 0.50 mm or more, still more preferably 0.55 mm or more, and even more preferably 0.60 mm or more. The length-weighted average fiber length of the pulp constituting the paper base can be adjusted to a desired range by appropriately selecting the type of raw pulp used, the degree of beating, etc. Comparing hardwood pulp and softwood pulp as raw material pulps, hardwood pulp tends to have shorter fiber lengths, and increasing the content of hardwood pulp in the raw material pulp can reduce the length-weighted average fiber length. Furthermore, increasing the degree of beating tends to shorten the length-weighted average fiber length. The length-weighted average fiber length of the pulp constituting the paper base material is the length-weighted average fiber length of the disintegrated pulp obtained by disintegrating the packaging paper, and is measured specifically by the method described in the Examples. The length-weighted average fiber length of the raw material pulp used to prepare the paper base material is not significantly different from the length-weighted average fiber length of the disintegrated pulp obtained by disintegrating the packaging paper. Therefore, adjusting the length-weighted average fiber length of the raw material pulp allows the length-weighted average fiber length of the pulp constituting the paper base material to be appropriately adjusted.

[0015] (Canadian Standard Freeness) The beating degree of the raw pulp is not particularly limited, but from the viewpoint of obtaining a wrapping paper having the desired Clark stiffness, puncture strength, and length-weighted average fiber length, the Canadian Standard Freeness (CSF) is preferably 300 mL or more and 700 mL or less, more preferably 350 mL or more, even more preferably 380 mL or more, and more preferably 600 mL or less, even more preferably 500 mL or less, and even more preferably 450 mL or less. When the CSF of the raw pulp is within the above range, the smoothness of the paper substrate surface is improved, and a uniform heat-sealable layer tends to be obtained even with a low basis weight, which is preferable. The CSF is measured in accordance with JIS P 8121-2:2012, "Pulp - Freeness Testing Method - Part 2: Canadian Standard Freeness Method."

[0016] (Basis Weight) In this embodiment, the basis weight of the paper substrate is 40 g / m2 from the viewpoint of obtaining a desired Clark stiffness. ２ Preferably, the thickness is 36 g / m or less. ２ or less, more preferably 32 g / m ２ The lower limit is not particularly limited, but from the viewpoint of obtaining a desired puncture strength, it is preferably 10 g / m ２ More preferably, 15 g / m ２ More preferably, 17 g / m ２ That's all. When the basis weight of the paper substrate is within the above range, it is preferable because a wrapping paper that is excellent in flexibility and resistance to puncture can be obtained. The basis weight of the paper substrate is measured in accordance with JIS P 8124:2011. When measuring the basis weight of the paper substrate from the wrapping paper, the basis weight of the paper substrate may be calculated by measuring the thickness of the heat seal layer with a scanning electron microscope (SEM) and calculating the basis weight of the heat seal layer from the results of component analysis of the heat seal layer.

[0017] (Thickness) From the viewpoint of obtaining a wrapping paper having the desired Clark stiffness and puncture strength, the thickness of the paper substrate is preferably 20 μm or more and 65 μm or less, more preferably 22 μm or more, even more preferably 25 μm or more, and more preferably 60 μm or less, even more preferably 50 μm or less, and even more preferably 45 μm or less. When the thickness of the paper substrate is within the above range, it is preferable because a wrapping paper having excellent flexibility and excellent puncture resistance can be obtained. The thickness of the paper substrate is measured in accordance with JIS P 8118:2014, and in detail, measured by the method described in the examples.

[0018] (Density) The density of the paper substrate is preferably 0.3 g / cm3 from the viewpoint of obtaining a wrapping paper having the desired Clark stiffness and puncture strength. ３ 1.0g / cm or more ３ or less, more preferably 0.5 g / cm ３ More preferably, 0.6 g / cm ３ More preferably, it is 0.9 g / cm or more. ３ More preferably, 0.8 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.

[0019] (Optional Components) The paper base material may contain optional components as needed, such as anionic, cationic or amphoteric retention aids, drainage improvers, dry strength agents, wet strength agents, sizing agents, fixing agents, internal additives such as fillers, water-resistant agents, dyes, and fluorescent brighteners.

[0020] Examples of dry strength agents include cationized starch, polyacrylamide, carboxymethyl cellulose, etc. The content of the dry strength agent is not particularly limited, but is preferably 3.0 parts by mass or less per 100 parts by mass of raw pulp (bone dry mass).

[0021] Examples of the wet strength agent include polyamide polyamine epichlorohydrin, urea formaldehyde resin, melamine formaldehyde resin, etc. The content of the wet strength agent is not particularly limited, but is preferably 3.0 parts by mass or less per 100 parts by mass of the raw pulp (bone dry mass).

[0022] Examples of sizing agents include internal sizing agents such as rosin sizing agents, synthetic sizing agents (e.g., alkyl ketene dimers), and petroleum resin-based 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 parts by mass or less per 100 parts by mass of the raw pulp (bone dry mass).

[0023] 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 (bone dry mass).

[0024] Examples of fillers include inorganic fillers such as talc, kaolin, calcined kaolin, calcium carbonate, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, alumina, magnesium carbonate, magnesium oxide, silica, white carbon, bentonite, zeolite, sericite, and smectite, and organic fillers such as acrylic resins and vinylidene chloride resins.

[0025] <Method for manufacturing paper base material> The method for manufacturing a paper base material preferably includes a step of making a paper from a slurry containing the above-mentioned raw material pulp. The papermaking method is not particularly limited, and examples thereof include an acidic papermaking method in which papermaking is carried out at a pH of around 4.5, and a neutral papermaking method in which papermaking is carried out at a pH of about 6 to about 9. In the papermaking process, chemicals for the papermaking process such as a pH adjuster, an antifoaming agent, a pitch control agent, and a slime control agent can be added as needed. The papermaking machine is also not particularly limited, and examples thereof include a continuous papermaking machine such as a Fourdrinier type, a cylinder type, or an inclined type, or a multi-layer papermaking machine that combines these.

[0026] In this embodiment, in the papermaking process, the jet / wire ratio (J / W ratio), which is the ratio of the flow velocity (J) of the paper stock jetted onto the wire to the running speed (W) of the papermaking wire, may be appropriately adjusted from the viewpoint of maintaining the fiber orientation ratio in the desired range. From the viewpoint of maintaining the Clark stiffness in the longitudinal direction in the desired range, the fiber orientation ratio (longitudinal / transverse) is preferably 1.85 or less, more preferably 1.80 or less, even more preferably 1.60 or less, even more preferably 1.40 or less, and even more preferably 1.30 or less. The lower limit is not particularly limited, but is 1.0 or more, and from the viewpoint of ease of papermaking, it is preferably 1.03 or more. The fiber orientation ratio of the wrapping paper is measured by the method described in the Examples.

[0027] In this embodiment, the surface of the paper substrate may be treated with a chemical. Examples of chemicals used in the surface treatment include sizing agents, water-resistant agents, water-retention agents, thickeners, lubricants, etc. Known devices can be used in the surface treatment process.

[0028] <Heat Seal Layer> The wrapping paper of this embodiment has a heat seal layer. The heat seal layer is a layer that melts and adheres by heating, ultrasonic waves, or the like. The heat seal layer may be provided by coating, dry lamination, or extrusion lamination. Among these, from the viewpoint of providing wrapping paper that is excellent in flexibility and puncture resistance and has a reduced environmental impact, it is preferable to provide it by coating or extrusion lamination. The heat seal layer is preferably laminated directly on the paper substrate. By not using another layer, it is possible to reduce the basis weight of the entire wrapping paper, and it is also preferable because a wrapping paper with excellent flexibility can be obtained.

[0029] (Coating layer) When provided by coating, the heat seal layer preferably contains a water-dispersible resin binder. The water-dispersible resin binder is a resin binder that is not water-soluble (specifically, has a solubility in water at 25°C of 10 g / L or less) but is finely dispersed in water, such as an emulsion or suspension. Note that if the water-dispersible resin binder also falls under the category of a lubricant, it is classified as a lubricant.

[0030] The water-dispersible resin binder is not particularly limited as long as it exhibits the effects of the present invention, and examples thereof include polyolefin resins (polyethylene, polypropylene, etc.), vinyl chloride resins, styrene resins, styrene-butadiene copolymers, styrene-unsaturated carboxylic acid copolymers (for example, 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 Examples of suitable resins include 4-methylpentene-1 resin, polybutene-1 resin, vinylidene fluoride resin, vinyl fluoride resin, fluorine-based resin, polycarbonate resin, polyamide resin, acetal resin, polyphenylene oxide resin, polyester resin (polyethylene terephthalate, polybutylene terephthalate, etc.), polyphenylene sulfide resin, polyimide resin, polysulfone resin, polyethersulfone resin, polyarylate resin, olefin-unsaturated carboxylic acid copolymer, and modified products thereof. These may be used alone or in combination of two or more. Among these, at least one selected from the group consisting of styrene-butadiene copolymer and olefin-unsaturated carboxylic acid copolymer is preferred. Furthermore, from the viewpoint of increasing heat seal peel strength, olefin-unsaturated carboxylic acid copolymer is more preferred, and styrene-butadiene copolymer is more preferred from the viewpoints of availability, cost, and recyclability.

[0031] Examples of the olefin-unsaturated carboxylic acid copolymer include an ethylene-(meth)acrylic acid copolymer and an ethylene-(meth)acrylic acid alkyl ester copolymer. Among these, an ethylene-(meth)acrylic acid copolymer is preferred, and an ethylene-acrylic acid copolymer is more preferred. Therefore, the water-dispersible resin binder contained in the heat seal layer is preferably at least one selected from the group consisting of a styrene-butadiene copolymer and an ethylene-(meth)acrylic acid copolymer. The olefin-unsaturated carboxylic acid copolymer may be an ionomer.

[0032] The styrene-butadiene copolymer may be either a synthetic product or a commercially available product. Examples of commercially available products include Nipol Latex LX407G51, LX407S10, LX407S12, LX410, LX415M, LX416, LX430, LX433C, and 2507H manufactured by Nippon Zeon Co., Ltd., Nalustar SR-101, SR-102, SR-103, SR-115, and SR-153 manufactured by Nippon A&L Inc., and Styrene-Butadiene Latex 0602 and 0597C manufactured by JSR Corporation.

[0033] The ethylene-(meth)acrylic acid copolymer may be either a synthetic product or a commercially available product. Examples of commercially available products include MP498345N, MP4983R, MP4990R, and MFHS1279 manufactured by Michelman Japan LLC, ZAIXXEN (registered trademark) A and ZAIXXEN (registered trademark) AC manufactured by Sumitomo Seika Chemicals Co., Ltd., and the Chemipearl S series manufactured by Mitsui Chemicals, Inc.

[0034] The glass transition temperature of the water-dispersible resin binder is preferably 0°C or higher, more preferably 10°C or higher, and even more preferably 15°C or higher. By using a water-dispersible resin binder whose glass transition temperature is equal to or higher than the above lower limit, the occurrence of blocking can also be suppressed. From the viewpoint of heat sealability, the glass transition temperature is preferably 100°C or lower, more preferably 80°C or lower, even more preferably 60°C or lower, and even more preferably 50°C or lower. The glass transition temperature of the water-dispersible resin binder is a value measured by a differential scanning calorimeter.

[0035] 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, even more preferably 70% by mass or more, and even more 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. Within the above range, a heat-sealable paper having high heat-seal peel strength can be obtained.

[0036] That is, according to one embodiment of the present invention, the content of the styrene-butadiene copolymer and the olefin-unsaturated carboxylic acid copolymer (preferably an ethylene-(meth)acrylic acid copolymer) in the heat seal layer is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 70% by mass or more, and still more 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.

[0037] Lubricant: In order to provide the heat seal paper with slipperiness and prevent blocking, the heat seal layer may contain a lubricant in addition to the water-dispersible resin binder. A lubricant is a substance that, when incorporated into the heat seal layer, can reduce the coefficient of friction of the heat seal layer surface.

[0038] The lubricant is not particularly limited, and examples thereof include waxes, metal soaps, and fatty acid esters. Lubricants may be used alone or in combination. Examples of waxes include natural waxes such as animal- or plant-derived waxes (e.g., beeswax, carnauba wax, etc.), mineral waxes (e.g., microcrystalline wax, etc.), and petroleum wax; and synthetic waxes such as polyolefin wax, paraffin wax, and polyester wax. Examples of metal soaps include calcium stearate, sodium stearate, zinc stearate, aluminum stearate, magnesium stearate, fatty acid sodium soap, potassium oleate soap, castor oil potassium soap, and complexes thereof. Among the above lubricants, paraffin wax, carnauba wax, and polyolefin wax are preferred because they have a relatively low melting point, facilitate the formation of wax components on the coating layer surface, and provide excellent blocking suppression. That is, the lubricant is preferably at least one selected from the group consisting of paraffin wax, carnauba wax, and polyolefin wax. From the perspectives of providing slipperiness and improving moisture resistance, paraffin wax is preferred. As the carnauba wax, either a synthetic product or a commercially available product may be used, and examples of commercially available products include Cellosol 524 manufactured by Chukyo Yushi Co., Ltd. and ML160RPH manufactured by Michelman Co., Ltd. As the paraffin wax, either a synthetic product or a commercially available product may be used, and examples of commercially available products include Hydrin L-700 manufactured by Chukyo Yushi Co., Ltd. As the polyethylene wax, either a synthetic product or a commercially available product may be used, and examples of commercially available products include Aquacer 531 manufactured by BYK.

[0039] 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, even more preferably 1 part by mass or more, and preferably 30 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, per 100 parts by mass of the water-dispersible resin binder.

[0040] When the heat seal layer contains a lubricant, the content of the lubricant in the heat seal layer is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 1% by mass or more, and preferably 30% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less.

[0041] 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 to the water-dispersible resin binder and, if necessary, the lubricant, the heat seal layer may also contain a pigment.

[0042] Pigment In the present embodiment, the heat seal layer may contain a pigment in addition to the water-dispersible resin binder. By containing a pigment, the problem of the coated surface of the heat seal layer sticking to the back surface of the heat seal paper and causing peeling (blocking) during production of the heat seal paper is suppressed, and heat seal paper with excellent blocking resistance can be obtained.

[0043] The pigment is not particularly limited, and examples include various pigments used in conventional pigment coating layers. A single pigment may be used, or two or more pigments may be used in combination. From the viewpoints of heat seal peel strength and blocking resistance, a pigment having an aspect ratio of 20 or more is preferred. The aspect ratio of the pigment is more preferably 25 or more, even more preferably 30 or more, and particularly preferably 60 or more. Furthermore, from the viewpoints of availability and the smoothness of the heat seal layer surface, the aspect ratio is preferably 10,000 or less, more preferably 1,000 or less, and even more preferably 300 or less. The aspect ratio of the pigment means the major axis / minor axis ratio, and may be measured by the following method.

[0044] The pigment is preferably a layered inorganic compound having an aspect ratio of 20 or more. The layered inorganic compound has a tabular form. When the pigment is tabular, protrusion of the pigment from the surface of the heat seal layer is suppressed, and a heat seal layer having excellent blocking resistance while maintaining heat sealability can be obtained.

[0045] The length (average particle diameter) 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 likely to be aligned parallel to the paper substrate. Furthermore, if the length is 100 μm or less, there is little concern that part of the pigment will protrude from the heat seal layer. The length of the pigment is more preferably 0.3 μm or more, even more preferably 0.5 μm or more, particularly preferably 1.0 μm or more, and more preferably 30 μm or less, even more preferably 20 μm or less, particularly preferably 15 μm or less.

[0046] Here, the length of the pigment contained in the heat seal layer is determined as follows: A magnified photograph of the cross section of the heat seal layer is taken using an electron microscope. At this time, the magnification is set so that approximately 20 to 30 pigment particles are contained within the image. The length of each pigment within the image is measured. The average value of the obtained lengths is then calculated and used as the length of the pigment. The length of the pigment is sometimes expressed as particle diameter.

[0047] The thickness of the pigment is preferably 200 nm or less. The thickness of the pigment is more preferably 100 nm or less, even more preferably 80 nm or less, even more preferably 50 nm or less, and particularly preferably 30 nm or less. It is also preferably 5 nm or more, more preferably 10 nm or more. The smaller the average thickness of the pigment, the higher the heat seal peel strength that can be obtained. Here, the thickness of the pigment contained in the heat seal layer is determined as follows: A magnified photograph of the cross section of the heat seal layer is taken using an electron microscope. The magnification should be such that approximately 20 to 30 pigment particles are included within the image. The thickness of each pigment within the image is measured. The average of the obtained thicknesses is then calculated to determine the thickness of the pigment.

[0048] Specific examples of pigments include mica, bentonite, kaolin, pyrophyllite, talc, smectite, vermiculite, chlorite, septe chlorite, serpentine, stilpnomelane, montmorillonite, heavy calcium carbonate (ground calcium carbonate), light calcium carbonate (synthetic calcium carbonate), composite synthetic pigments of calcium carbonate and other hydrophilic organic compounds, satin white, lithopone, titanium dioxide, silica, barium sulfate, calcium sulfate, alumina, aluminum hydroxide, zinc oxide, magnesium carbonate, silicates, colloidal silica, hollow or solid organic pigment plastic pigments, binder pigments, plastic beads, and microcapsules.

[0049] Specific examples of mica include synthetic mica (e.g., swellable synthetic mica), white mica (muscovite), sericite (sericite), phloxopite, biotite (biotite), fluorphlogopite (artificial mica), red mica, soda mica, vanadium mica, illite, zinc mica, paragonite, brittle mica, etc. Specific examples of bentonite include montmorillonite.

[0050] Specific examples of kaolin include various types of kaolin such as kaolin, calcined kaolin, structured kaolin, and delaminated kaolin.

[0051] Among these, pigments having an aspect ratio of 20 or more are preferred from the viewpoints of heat seal peel strength, blocking resistance, and economy, and the pigments containing one or more of mica, bentonite, kaolin, and talc are more preferred, with kaolin being even more preferred.

[0052] When the heat seal layer contains a pigment, the content of the pigment is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and still more preferably 8 parts by mass or more, relative to 100 parts by mass of the water-dispersible resin binder, from the viewpoints of blocking resistance and recyclability, while from the viewpoint of heat sealability, the content is preferably 200 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 30 parts by mass or less.

[0053] When the heat seal layer contains a pigment, the content of the pigment in the heat seal layer is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and still more preferably 8% by mass or more from the viewpoints of blocking resistance and recyclability, and is preferably 70% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less from the viewpoint of heat sealability.

[0054] Other Components 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 a silane coupling agent, an antifoaming agent, a viscosity modifier, a leveling agent such as a surfactant or alcohol, and a colorant such as a coloring dye.

[0055] The method for applying the heat seal layer to the paper substrate is not particularly limited, and known coating equipment may be used, such as a blade coater, a bar coater, an air knife coater, a slit die coater, a gravure coater, a microgravure coater, a roll coater, a size press, a gate roll coater, or a shim sizer.

[0056] After coating, it is preferable to dry the coating liquid. The drying equipment for drying is not particularly limited, and known equipment can be used. Examples of drying equipment include a hot air dryer, an infrared dryer, a gas burner, and a hot plate. The drying temperature may be set appropriately taking into account the drying time, etc. After drying the coating liquid, a supercalendering treatment may be performed. The supercalendering treatment is performed by passing the paper or the like to be treated between metal rolls or between a metal roll and an elastic roll, and then heating, pressurizing, etc., while being installed independently of the papermaking process. The supercalendering treatment may be performed in one stage or multiple stages, and is not particularly limited.

[0057] The solvent for the heat-seal layer coating liquid is not particularly limited, and water or an organic solvent such as ethanol, isopropyl alcohol, methyl ethyl ketone, or toluene can be used. Among these, water is preferred as the dispersion medium for the heat-seal layer coating liquid, from the viewpoint of avoiding the problems of volatile organic solvents. In other words, the heat-seal layer coating liquid is preferably an aqueous composition for a heat-seal layer.

[0058] The solid content (solid content concentration) of the heat seal layer coating liquid is not particularly limited and may be appropriately selected from the viewpoints of coatability and ease of drying, but is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and is preferably 80% by mass or less, more preferably 60% by mass or less, even more preferably 50% by mass or less, and even more preferably 40% by mass or less.

[0059] (Laminate Layer) When the heat seal layer is provided by lamination, it may be produced by an appropriate selection from conventionally known production methods, for example, a dry lamination method, a melt extrusion method, a melt casting method, a calendar method, etc. Among these, lamination with a paper substrate without an adhesive layer is preferred from the viewpoint of reducing environmental load, and the melt extrusion method and the melt casting method are preferred, with the melt extrusion method being more preferred.

[0060] The resin constituting the heat seal layer may be either a crystalline or amorphous thermoplastic resin, depending on the application. Examples of the thermoplastic resin include polyolefin resins such as polyethylene (low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), etc.), polypropylene, and polymethylpentene, polyester resins such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), polyamide resins, biodegradable resins such as polylactic acid (PLA), polyhydroxybutyric acid (PHB), polybutylene succinate (PBS), poly(butylene adipate-co-butylene terephthalate) (PBAT), polycaprolactone (PCL), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene (ABS) resin, acrylic resin, and modified polyphenylene ether (PPE). Among these, as the thermoplastic resin, it is preferable to use polyolefin resins such as polyethylene (LDPE, MDPE, HDPE, LLDPE, etc.), polypropylene, polymethylpentene, etc., or polylactic acid (PLA), and it is more preferable to use polyethylene or polypropylene. These thermoplastic resins may be used alone or in combination of two or more.

[0061] The heat seal layer may be formed as a single layer of a single resin, or may be formed as a single layer by mixing a plurality of resins, or may be formed as a multilayer thereof (for example, single resin layer / single resin layer, single resin layer / mixed resin layer, mixed resin layer / mixed resin layer).

[0062] (Basis Weight) The basis weight of the heat seal layer may be appropriately selected within a range in which the content of the paper substrate in the wrapping paper is 50% by mass or more, and is not particularly limited. However, from the viewpoint of obtaining wrapping paper with excellent flexibility, a small basis weight is preferable. When the heat seal layer is provided by coating, the basis weight of the heat seal layer is preferably 1 g / m from the viewpoint of reducing the environmental load, heat sealability, and flexibility. ２ 20g / m or more ２ More preferably, it is 2 g / m or less.２ More preferably, it is 10 g / m or more. ２ More preferably, 5 g / m or less ２ More preferably, 3 g / m or less ２ is less than.

[0063] When the heat seal layer is provided by lamination, the basis weight of the heat seal layer is preferably 5 g / m from the viewpoints of reducing the environmental load, heat sealability, and flexibility. ２ 40g / m or more ２ More preferably, it is 10 g / m or less. ２ More preferably, 15 g / m ２ More preferably, it is 30 g / m or more. ２ More preferably 25 g / m or less ２ More preferably, 20 g / m or less ２ less than 19 g / m ２ When the heat seal layer is provided by lamination, the thickness of the heat seal layer is, from the same viewpoint, preferably 5 μm or more and 40 μm or less, more preferably 9 μm or more, even more preferably 12 μm or more, and more preferably 30 μm or less, even more preferably 25 μm or less, still more preferably less than 20 μm, and even more preferably 19 μm or less.

[0064] <Characteristics of wrapping paper> (Paper base material content) In the wrapping paper of this embodiment, from the viewpoint of reducing the environmental load, the content of the paper base material in the wrapping paper is 50% by mass or more. The content of the paper base material is preferably 55% by mass or more, more preferably 60% by mass or more. Furthermore, although there is no particular upper limit, from the viewpoint of heat sealability, it is preferably 98% by mass or less, more preferably 96% by mass or less, and even more preferably 94% by mass or less.

[0065] (Basis Weight) From the viewpoint of flexibility and resistance to package breakage, the basis weight of the wrapping paper of this embodiment is preferably 20 g / m ２ 65g / m or more ２ More preferably, 25 g / m or less. ２ More preferably, 30 g / m ２ More preferably, it is 60 g / m or more.２ More preferably 55 g / m or less ２ More preferably 50 g / m or less ２ The basis weight of the wrapping paper can be adjusted to a desired range by appropriately adjusting the basis weight of the paper substrate and the heat seal layer. The basis weight of the wrapping paper is measured by the method described in the examples.

[0066] (Thickness) From the viewpoint of flexibility and resistance to puncture, the thickness of the wrapping paper of this embodiment is preferably 20 μm or more and 80 μm or less, more preferably 25 μm or more, even more preferably 30 μm or more, even more preferably 34 μm or more, even more preferably 38 μm or more, and more preferably 70 μm or less, even more preferably 65 μm or less. The thickness of the wrapping paper can be adjusted to the desired range by appropriately adjusting the thickness of the paper base material and the heat seal layer. The thickness of the wrapping paper is measured by the method described in the examples.

[0067] (Density) From the viewpoint of flexibility and resistance to package breakage, the density of the wrapping paper of the present embodiment is preferably 0.5 g / cm ３ 1.0g / cm or more ３ More preferably, it is 0.65 g / cm or less. ３ More preferably, 0.70 g / cm ３ More preferably, it is 0.95 g / cm or more. ３ More preferably, 0.90 g / cm ３ More preferably, 0.85 g / cm or less ３ The density of the wrapping paper can be adjusted to a desired range by appropriately adjusting the density of the paper substrate and the type of resin used in the heat seal layer. The density of the wrapping paper is measured by the method described in the examples.

[0068] (Clark Stiffness) The packaging material of this embodiment has a Clark Stiffness of 15.5 or less in the longitudinal direction. By setting the Clark Stiffness in the longitudinal direction to 15.5 or less, a packaging paper with excellent flexibility can be obtained. The Clark Stiffness in the longitudinal direction is preferably 15.0 or less, more preferably 13.0 or less, and even more preferably 12.0 or less. From the viewpoint of resistance to puncture, the lower limit of the Clark Stiffness in the longitudinal direction is preferably 3.0 or more, more preferably 3.5 or more, even more preferably 4.0 or more, still more preferably 4.5 or more, even more preferably 4.8 or more, and even more preferably 5.0 or more. Clark Stiffness is measured in accordance with JIS P 8143:2009.

[0069] From the viewpoint of flexibility and rupture resistance, the Clark stiffness in the transverse direction is preferably 3.0 or more and 15.5 or less, more preferably 3.5 or more, even more preferably 4.0 or more, even more preferably 4.5 or more, even more preferably 5.0 or more, and more preferably 15.0 or less, more preferably 12.0 or less, and even more preferably 9.0 or less. The Clark stiffness can be adjusted by appropriately selecting the type of raw pulp, the degree of beating, the basis weight, thickness, and density of the paper base material, the papermaking conditions of the paper base material, the type and thickness of the heat-seal layer, etc. The Clark stiffness tends to decrease when a large amount of hardwood-derived raw pulp is used as the raw pulp, and the Clark stiffness tends to decrease when the degree of beating is increased. Furthermore, the Clark stiffness tends to increase when the basis weight, thickness, and density of the paper base material and the thickness of the heat-seal layer are large. Furthermore, increasing the J / W of the paper base material tends to increase the Clark stiffness in the longitudinal direction and decrease the Clark stiffness in the transverse direction.

[0070] The wrapping paper of this embodiment has a puncture strength of 1.3 N or more. When the wrapping paper has a puncture strength of 1.3 N or more, tearing of the package during transportation and storage is suppressed when the wrapping paper is used as a package, resulting in a wrapping paper with excellent puncture resistance. From the viewpoints of puncture resistance, flexibility, and ease of manufacture, the puncture strength is preferably 1.4 N or more and 7.0 N or less, more preferably 1.5 N or more, even more preferably 1.6 N or more, and more preferably 5.0 N or less, even more preferably 4.0 N or less, and even more preferably 3.0 N or less. The puncture strength tends to increase by increasing the basis weight of the paper base material and the heat seal layer. Furthermore, when at least one selected from hardwood pulp and softwood pulp is used as the raw material pulp, the puncture strength tends to increase as the softwood pulp content increases. The puncture strength is measured in accordance with JIS Z 1707:2019.

[0071] [Package] The package of this embodiment is a package made using the wrapping paper of this embodiment, and is preferably a package made solely of the wrapping paper of this embodiment. The package of this embodiment may be made by any method, and may be used, for example, for three-sided sealed packaging bags, four-sided sealed packaging bags, pillow packaging bags, etc. However, it is preferably used for a package having a lid material and a base material with a recess, in which an item to be contained can be placed and sealed in the recess by heat sealing the lid material and the base material. Figure 1 shows an example of a package suitable for this embodiment. Figure 1 shows a cross-sectional schematic diagram of the manufacturing process of the package. Preferably, the package 10 is obtained by placing wrapping paper 2, which serves as the base material, on a mold 1 having a recess formed therein, conforming it to the shape of the recess, placing an item to be contained 4 on the wrapping paper 2, and then placing wrapping paper 3, which serves as the lid material, and heat-sealing the wrapping paper 2, which serves as the base material, and the wrapping paper 3, which serves as the lid material. Note that the arrow in Figure 1 indicates the vertical direction of the wrapping paper. 1, excellent flexibility and conformability are required, allowing the wrapping paper to conform longitudinally to the recesses in the substrate. Flexibility (conformability) is particularly important for this application. Furthermore, the object 4 to be contained preferably has a rod-like shape. Thus, the wrapping paper of this embodiment is preferably used for a package in which the object to be contained is a rod-shaped substance.

[0072] The features of the present invention will be explained in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below. Note that "parts" and "%" mean "parts by mass" and "% by mass" unless otherwise specified.

[0073] [Evaluation and Analysis] The raw pulp, wrapping paper, and wrapping bodies of the examples and comparative examples were evaluated and analyzed as follows.

[0074] [Raw material pulp] <Measurement of Canadian standard freeness (CSF)> The Canadian standard freeness (CSF) of the raw material pulp was measured in accordance with JIS P 8121-2:2012.

[0075] [Paper substrate and wrapping paper] <Basis weight> The basis weight of the paper substrate and wrapping paper was measured in accordance with JIS P 8124: 2011. The basis weight of the heat seal layer was calculated from the values ​​of the paper substrate and wrapping paper.

[0076] <Thickness> The thickness of the paper substrate and the wrapping paper was measured in accordance with JIS P 8118:2014 by applying a pressure of 100 kPa ± 10 kPa to a circular area (200 mm ２ The thickness of the heat seal layer was calculated from the values ​​of the paper substrate and the wrapping paper.

[0077] <Density> The densities of the paper substrate and the wrapping paper were measured in accordance with JIS P 8118: 2014. The density of the heat seal layer was calculated from the values ​​of the paper substrate and the wrapping paper.

[0078] <Puncture Strength> The puncture strength of the wrapping paper was measured in accordance with JIS Z 1707: 2019. Note that the measurement may be performed from either side of the wrapping paper, but in this example, the measurement was performed from the heat seal layer side.

[0079] <Clark Stiffness> The Clark Stiffness of the wrapping paper was measured in accordance with JIS P 8143: 2009. The Clark Stiffness was measured in both the machine direction (papermaking direction) and the cross direction (direction perpendicular to the papermaking direction).

[0080] <Fiber Orientation Ratio> The fiber orientation of the wrapping paper was determined by measuring the ultrasonic wave propagation velocities in the machine direction and the cross direction using an ultrasonic wave propagation velocity meter (SST-3200, manufactured by Nomura Shoji Co., Ltd.) and calculating the ratio between these (machine direction / cross direction ratio).

[0081] <Length-weighted average fiber length of pulp constituting paper base> The obtained wrapping paper was defibrated in accordance with JIS P 8220-1:2012, and the length-weighted average fiber length of the pulp constituting the paper base was measured in accordance with ISO 16065-2:2007 for the obtained defibrated pulp.

[0082] <Flexibility (conformability)> The wrapping paper obtained in each example was cut into a size of 19 cm long (longitudinal direction of the wrapping paper) x 3 cm wide (lateral direction of the wrapping paper), and placed on a concave mold 12 cm wide and 3.5 cm high so that the length of the wrapping paper (longitudinal direction of the wrapping paper) was parallel to the width direction of the mold. The ease with which the wrapping paper bends under its own weight was evaluated into three levels based on the length of the bent wrapping paper in contact with the bottom of the mold recess. A: 6 cm or more of the wrapping paper is in contact with the bottom of the mold. B: 4 cm or more but less than 6 cm of the wrapping paper is in contact with the bottom of the mold. C: Less than 4 cm of the wrapping paper is in contact with the bottom of the mold.

[0083] <Tear resistance (package breakage resistance)> Using the wrapping paper obtained in each example, a rod-shaped product measuring (LWH) 14 cm x 1.2 cm x 0.8 cm and weighing 13.4 g was packaged with a four-sided seal to obtain a package. The obtained package was held by holding one end of the short side with both hands, hanging vertically, and shaken up and down (approximately 10 cm) 20 times at a speed of twice per second, and the presence or absence of tearing in the wrapping paper was observed. For each example, one tester tested 10 packages and evaluated them on a three-point scale. A: No tear after 20 shakes B: No tear after 10 shakes, but one or more packages were torn after 20 shakes C: One or more packages were torn after 10 shakes

[0084] <Heat sealability> The wrapping paper obtained in each example was torn into a size of 10 cm x 10 cm, and two pieces of each were stacked together so that the heat seal layers were in contact with each other. The pieces were then tested under certain conditions (temperature: 130°C, pressure: 1.0 kgf / cm) using a heat seal tester (manufactured by Tester Sangyo Co., Ltd., TP-701-B). ２ The four sides were heat-sealed with a heat seal of 0.5 seconds for 0.5 seconds and a bonding width of 1 cm. One tester manually pulled five samples for each example from the edge of the heat-sealed substrate to peel them off, and evaluated the state after peeling on a three-level scale. A: Paper layer peeled over almost the entire surface (80% or more of the area). B: Paper layer peeled over a portion (20% or more of the area but less than 80%). C: Paper layer hardly peeled off (less than 20% of the area).

[0085] [Example 1] (Preparation of Paper Base Material) Hardwood bleached kraft pulp (LBKP) was beaten to 400 mL of CSF, and then a pulp slurry with a concentration of 3.8% by mass was obtained. This pulp slurry was mixed with 0.9 parts by mass of an anionic dry strength agent (trade name: PS-NH20B, manufactured by Arakawa Chemical Industries, Ltd.) primarily composed of polyacrylamide, 0.9 parts by mass of a cationic wet strength agent (trade name: WS4024, manufactured by Seiko PMC Co., Ltd.) primarily composed of polyamide polyamine epichlorohydrin, and 0.3 parts by mass of an alkyl ketene dimer (trade name: AD1612, manufactured by Seiko PMC Co., Ltd.) as a neutral sizing agent, per 100 parts by mass of pulp solids, and stirred to obtain a paper stock. This paper stock was adjusted to a concentration of 0.5% by mass and made into paper on an inclined wire paper machine, with a basis weight of 18 g / m ２ A paper substrate of 100g was obtained.

[0086] (Formation of Heat-Seal Layer) LDPE (LC522, manufactured by Japan Polyethylene Co., Ltd.) was laminated on one side of the obtained paper substrate as a heat-seal layer. The heat-seal layer was laminated on one side of the paper substrate by melt extrusion under the conditions of a lamination temperature of 330°C and a lamination speed of 120 m / min. The basis weight of the heat-seal layer was 17 g / m ２ As a result, a wrapping paper with the above properties was obtained.

[0087] [Example 2] A paper substrate was made on an inclined wire paper machine and had a basis weight of 30 g / m ２ A wrapping paper was obtained under the same conditions as in Example 1, except that the J / W ratio was adjusted so that the fiber orientation ratio was 1.25.

[0088] [Example 3] A paper substrate was made on an inclined wire paper machine and had a basis weight of 30 g / m ２ A heat seal layer was formed by the following method, and a wrapping paper was obtained under the same conditions as in Example 1, except that the J / W ratio was adjusted so that the fiber orientation ratio was 1.24. (Formation of Heat Seal Layer) On one side of the obtained paper substrate, the coating amount of the heat seal layer after drying was 2.5 g / m ２The following heat seal layer paint was applied using a gravure coater (using a smoothing bar) to form a heat seal layer. - Preparation of Heat Seal Layer Paint - 98 parts (solids content equivalent) of an aqueous dispersion of a styrene / butadiene copolymer (Nipol Latex LX407S12, manufactured by Nippon Zeon Co., Ltd., solids concentration 46% by mass, glass transition temperature 18°C ​​(catalog value)) and 2 parts (solids content equivalent) of a paraffin wax emulsion (Hydrin L-700, manufactured by Chukyo Yushi Co., Ltd., solids concentration 30% by mass), and water was added to adjust the solids concentration to 33% by mass, followed by stirring to prepare a heat seal layer paint (solids concentration 33% by mass). The styrene / butadiene copolymer had a solubility in water at 25°C of 10 g / L or less.

[0089] [Example 4] A paper substrate was made on an inclined wire paper machine and had a basis weight of 30 g / m ２ A wrapping paper was obtained under the same conditions as in Example 1, except that the J / W ratio was adjusted so that the fiber orientation ratio was 1.80.

[0090] [Comparative Example 1] A paper substrate was made using an inclined wire paper machine, and the basis weight was 50 g / m ２ A wrapping paper was obtained under the same conditions as in Example 1, except that the J / W ratio was adjusted so that the fiber orientation ratio was 1.24.

[0091] [Comparative Example 2] A paper substrate was made using an inclined wire paper machine, and the basis weight was 15 g / m ２ A wrapping paper was obtained under the same conditions as in Example 1, except that the J / W ratio was adjusted so that the fiber orientation ratio was 1.20.

[0092] [Comparative Example 3] A paper substrate was made using an inclined wire paper machine, and the basis weight was 30 g / m ２ A wrapping paper was obtained under the same conditions as in Example 1, except that the J / W ratio was adjusted so that the fiber orientation ratio was 1.91.

[0093] [Comparative Example 4] The pulp raw material for the paper base material was a mixture of hardwood bleached kraft pulp (LBKP) and softwood bleached kraft pulp (NBKP) in a ratio of 80:20, and the basis weight was 30 g / m ２ A wrapping paper was obtained under the same conditions as in Example 1, except that the J / W ratio was adjusted so that the fiber orientation ratio was 1.27.

[0094] The resulting wrapping paper was evaluated as described above, and the results are shown in the table below.

[0095]

[0096] From the results of the Examples and Comparative Examples, it was found that the wrapping paper of the present embodiment had excellent flexibility, excellent resistance to tearing, and heat sealability. ２ The wrapping paper of Comparative Example 1, which had a Clark stiffness greater than 1.3 N and a longitudinal Clark stiffness greater than 15.5, was poor in flexibility. The wrapping paper of Comparative Example 2, which had a puncture strength of less than 1.3 N, was easily torn and had poor resistance to puncture. The wrapping paper of Comparative Example 3, which had a Clark stiffness greater than 15.5 in the longitudinal direction, was poor in flexibility. Furthermore, the wrapping paper of Comparative Example 4, which had a length-weighted average fiber length greater than 0.92 mm, was poor in flexibility.

[0097] The wrapping paper of the present invention is suitable as a flexible packaging material, and has excellent flexibility, resistance to tearing, and heat-sealing properties, and is therefore suitable for use in forming packaging.

[0098] 1 Mold 2 Wrapping paper as base material 3 Wrapping paper as lid material 4 Item to be contained 10 Package

Claims

1. A wrapping paper having a heat seal layer on a paper base material, the basis weight of the paper base material being 40 g / m ２ a Clark stiffness in the longitudinal direction of the wrapping paper is 15.5 or less, a content of a paper base material in the wrapping paper is 50% by mass or more, the wrapping paper has a puncture strength of 1.3 N or more, and the length-weighted average fiber length of pulp constituting the paper base material is 0.92 mm or less.

2. The wrapping paper according to claim 1, having a thickness of 70 μm or less.

3. Basis weight: 60g / m ２ 2. The wrapping paper of claim 1, wherein:

4. The wrapping paper according to claim 1, wherein the raw pulp of the paper base material contains hardwood bleached kraft pulp, and the content of hardwood bleached kraft pulp in the raw pulp is 85 mass% or more.

5. The wrapping paper according to claim 1, having a fiber orientation ratio of 1.85 or less.

6. The wrapping paper according to claim 1, wherein the paper base material and the heat seal layer are directly laminated together.

7. A packaging body having a lid material and a base material having a recess, capable of containing and sealing an item in the recess by heat sealing the lid material and the base material, wherein the lid material and the base material are made of the packaging paper according to any one of claims 1 to 6.

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