Wrapping paper and wrapped package

Abstract

To provide: a wrapping paper that reduces environmental impact, is excellent in hand tearability (openability), burst resistance and perforation retention, and also has heat sealability; and a wrapped package using the wrapping paper.SOLUTION: The wrapping paper has a heat seal layer on a paper base material, where the basis weight of the paper base material is 40 g / m2 or less, the content of the paper base material in the wrapping paper is 50 mass% or more, the tearing strength of the wrapping paper in both the longitudinal direction and the cross direction is 240 mN 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.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] In recent years, the global plastic waste problem has been worsening. For the improvement of the global environment, the reduction and elimination of plastics in packaging materials have been promoted, and there has been a strong movement to replace plastic packaging with paper-based packaging. However, paper has the problem of being weaker in strength and more prone to tearing compared to plastic materials. Patent Document 1 aims to provide a packaging base paper for a sealed container that has high strength against bending, excellent impact resistance, and maintains strength that is not easily torn even by impacts during distribution after packaging the contents. The packaging base paper for a sealed container mainly composed of pulp, wherein 70% by mass or more of the pulp is softwood pulp, contains a dry paper strength enhancer and a wet paper strength enhancer, and carboxymethyl cellulose is applied to at least one surface of the base paper, is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Although the packaging base paper described in Patent Document 1 has high strength and can firmly hold the contents, its tearability (openability) is insufficient, and it is difficult to take out the contents, so there is room for improvement. An object of the present invention is to provide a wrapping paper that reduces the environmental load, has excellent tearability (openability), excellent burst resistance and perforation retention (the perforation tie part is not easily torn), and has heat sealability, and a package using the wrapping paper.

Means for Solving the Problem

[0005] The inventors of the present invention have found that in wrapping paper having a heat-sealing layer, by setting the basis weight of the paper base material to a specific value or less, the content of the paper base material to a specific value or more, the tear strength in both the longitudinal and transverse directions to a specific value or less, the puncture strength to a specific value or more, and further the length-weighted average fiber length of the pulp constituting the paper base material to a specific value or less, the above problems can be solved. That is, the present invention relates to the following <1> to <7>. <1> Wrapping paper having a heat-sealing layer on a paper base material, wherein the basis weight of the paper base material is 40 g / m 2 or less, the content of the paper base material in the wrapping paper is 50% by mass or more, the tear strength in the longitudinal and transverse directions of the wrapping paper is both 240 mN 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. <2> The wrapping paper according to <1>, having a thickness of 70 μm or less. <3> The basis weight is 60 g / m 2 or less, the wrapping paper according to <1> or <2>. <4> The wrapping paper according to any one of <1> to <3>, having a fracture toughness in the longitudinal direction of 0.18 J / m or more. <5> The wrapping paper according to any one of <1> to <4>, wherein the raw material pulp of the paper base material contains hardwood sun-dried kraft pulp, and the content of hardwood sun-dried kraft pulp in the raw material pulp is 85% by mass or more. <6> The wrapping paper according to any one of <1> to <5>, wherein the paper base material and the heat-sealing layer are directly laminated. <7> A package having a lid material and a bottom material having a recess, and capable of accommodating and sealing an object to be accommodated in the recess by heat-sealing the lid material and the bottom material, wherein the lid material and the bottom material are made of the wrapping paper according to any one of <1> to <6>.

Advantages of the Invention

[0006] According to the present invention, there are provided a wrapping paper having a reduced environmental load, excellent tearability (openability), excellent bursting strength and perforation retention, and heat sealability, and a package using the wrapping paper.

Brief Description of Drawings

[0007]

Figure 1

Embodiments for Carrying Out the Invention

[0008] [Wrapping Paper] The wrapping paper of this embodiment is a wrapping paper having a heat seal layer on a paper base material, the basis weight of the paper base material is 40 g / m 2 or less, the content of the paper base material in the wrapping paper is 50% by mass or more, the tear strength in the longitudinal and transverse directions of the wrapping paper is both 240 mN 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. According to the wrapping paper of this embodiment, there is provided a wrapping paper having a reduced environmental load, excellent tearability (openability), excellent bursting strength and perforation retention, and heat sealability. The reason for obtaining the above effects is that since the content of the paper base material in the wrapping paper is 50% by mass or more, the content of the plastic material in the wrapping paper becomes 50% by mass or less, and the environmental load is reduced. Also, the basis weight of the paper base material is 40 g / m 2 or less, the content of the paper base material in the wrapping paper is 50% by mass or more, the tear strength in the longitudinal and transverse directions of the wrapping paper is both 240 mN 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. As a result, it is considered that the wrapping paper has appropriate flexibility and mechanical strength, and can improve tearability (openability), bursting strength, and perforation retention at the same time. Note that the reason for obtaining the above effects is not limited to this. Moreover, according to the wrapping paper of the present embodiment, since the length-weighted average fiber length of the pulp constituting the paper base material is 0.92 mm or less, unevenness of the paper base material is suppressed, and as a result of improved surface uniformity, it is considered that a heat seal layer can be formed with a basis weight less than that of the conventional heat seal layer. Hereinafter, the present invention will be described in more detail.

[0009] In this specification, the numerical range represented by "X to Y" means a numerical range including X as the lower limit value and Y as the upper limit value. When the numerical ranges are described stepwise, the upper and lower limits of each numerical range can be arbitrarily combined. Also, in this specification, unless otherwise specified, measurements of operations, physical properties, etc. are performed under the conditions of room temperature (20 to 25°C) / relative humidity 40 to 50%RH. Further, "(meth)acrylic" is a general term including both acrylic and methacrylic. Also, the longitudinal direction of the wrapping paper and the paper base material means the paper-making direction (MD) in the paper base material, and the transverse direction means the direction (CD) orthogonal to the paper-making direction.

[0010] <Paper base material> The wrapping paper of the present embodiment has a heat seal layer on the paper base material. Note that the paper base material may be formed of a single layer or multiple layers and is not particularly limited. The paper base material is a sheet mainly made of pulp, and the base paper obtained by papermaking a papermaking stock containing raw material pulp, fillers, various auxiliaries, etc. as it is, or on at least one surface of the base paper, a sizing layer, an ink receiving layer, a water-resistant layer, an oil-resistant layer, a water vapor barrier layer, a gas barrier layer, etc. One or more functional layers can be used.

[0011] (Raw material pulp) The pulp constituting the paper base material is not particularly limited, and known pulp can be used. Specifically, unbleached pulp such as unbleached hardwood kraft pulp (LUKP) and unbleached softwood kraft pulp (NUKP); chemical pulp such as bleached hardwood kraft pulp (LBKP) and bleached softwood kraft pulp (NBKP); groundwood pulp (GP), pressure groundwood pulp (PGW), refiner mechanical pulp (RMP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), chemimechanical pulp (CMP), chemiground pulp (CGP), etc.; wastepaper pulp; non-wood fiber pulp such as kenaf, bagasse, bamboo, cotton, etc.; synthetic pulp, etc. 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 preferable, at least one selected from the group consisting of bleached hardwood kraft pulp (LBKP) and bleached softwood kraft pulp (NBKP) is more preferable, and bleached hardwood kraft pulp (LBKP) is even more preferable.

[0012] The main component of the pulp constituting the paper base material used for the wrapping paper of this embodiment is preferably hardwood pulp, and more preferably bleached hardwood kraft pulp (LBKP). "The main component of the pulp constituting the paper base material is hardwood pulp (or bleached hardwood kraft pulp)" means that the content of hardwood pulp (or bleached hardwood kraft pulp) in the pulp constituting the paper base material exceeds 50% by mass. The content of hardwood pulp (or bleached hardwood kraft pulp) is preferably 85% by mass or more, more preferably 90% by mass or more, still 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. By using a paper base material made of hardwood pulp as the raw material pulp, a wrapping paper having a desired tear strength can be obtained, and it is preferable because it has excellent hand tearability (openability). Also, by using hardwood pulp, preferably hardwood kraft pulp, as the raw material pulp, the average fiber length of the pulp constituting the paper base material tends to be short. As a result, paper unevenness is suppressed, and a paper base material with better surface uniformity can be obtained. To form a heat-sealing layer on a paper base material with high surface uniformity, even if a heat-sealing layer with a lower basis weight is formed, a uniform heat-sealing layer can be formed, and the formation of a heat-sealing layer with a lower basis weight also has the effect of imparting good heat-sealing properties.

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

[0014] The wrapping paper of this embodiment has a length-weighted average fiber length of the pulp constituting the paper base material of 0.92 mm or less. When the length-weighted average fiber length of the pulp constituting the paper base material is 0.92 mm or less, a wrapping paper with excellent opening properties can be obtained. From the viewpoints of opening properties and bursting strength, the length-weighted average fiber length of the pulp constituting the paper base material is preferably 0.30 mm or more and 0.90 mm or less, more preferably 0.80 mm or less, still more preferably 0.75 mm or less, even more preferably 0.70 mm or less, and more preferably 0.40 mm or more, still more preferably 0.50 mm or more, even more preferably 0.55 mm or more, and most preferably 0.60 mm or more. The length-weighted average fiber length of the pulp constituting the paper base material can be adjusted to a desired range by appropriately selecting the type of raw material pulp used, the beating degree, etc. When comparing hardwood pulp and softwood pulp as raw material pulps, hardwood pulp tends to have a shorter fiber length, and by increasing the content of hardwood pulp in the raw material pulp, the length-weighted average fiber length can be decreased. Also, when the beating degree is increased, the length-weighted average fiber length tends to become shorter. 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 wrapping paper, and specifically, it is measured by the method described in the examples. Note that the length-weighted average fiber length of the raw material pulp when preparing the paper base material and the length-weighted average fiber length of the disintegrated pulp obtained by disintegrating the wrapping paper are not significantly different, and by adjusting the length-weighted average fiber length of the raw material pulp, the length-weighted average fiber length of the pulp constituting the paper base material can be appropriately adjusted.

[0015] (Canadian Standard Freeness) The beating degree of the raw material pulp is not particularly limited, but from the viewpoint of obtaining a wrapping paper having a desired tear strength, puncture strength, and length-weighted average fiber length, as the Canadian Standard Freeness (CSF), it is preferably 300 mL or more and 700 mL or less, more preferably 350 mL or more, still more preferably 380 mL or more, and then, more preferably 600 mL or less, still more preferably 500 mL or less, and even more preferably 450 mL or less. When the CSF of the raw material pulp is within the above range, the smoothness of the paper base material surface becomes good, and even if the basis weight is small, a uniform heat-sealing layer tends to be obtained, which is preferable. CSF is measured according to JIS P 8121-2:2012 "Pulp - Freeness test method - Part 2: Canadian Standard Freeness method".

[0016] (Basis weight) In the present embodiment, the basis weight of the paper base material is 40 g / m from the viewpoint of obtaining a desired tear strength. 2 or less. Preferably 36 g / m 2Hereinafter, more preferably 32 g / m 2 or less. The lower limit is not particularly limited, but from the viewpoint of obtaining a desired puncture strength, it is preferably 10 g / m 2 or more, more preferably 15 g / m 2 or more, still more preferably 17 g / m 2 or more. When the basis weight of the paper substrate is within the above range, it is preferable because a wrapping paper excellent in peelability, bursting resistance, and perforation retention 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 thickness of the heat-sealing layer may be measured with a scanning electron microscope (SEM), and the basis weight of the paper substrate may be calculated by calculating the basis weight of the heat-sealing layer from the results of the component analysis of the heat-sealing layer.

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

[0018] (Density) The density of the paper substrate is preferably 0.3 g / cm 3 or more and 1.0 g / cm 3 or less, more preferably 0.5 g / cm 3 or more, still more preferably 0.6 g / cm 3 or more, and more preferably 0.95 g / cm 3 or less, still more preferably 0.9 g / cm3 The following is the case. When the thickness of the paper base material is within the above range, it is preferable because a wrapping paper excellent in peelability, bursting strength resistance, and perforation retention can be obtained. The density of the paper base material is calculated from the basis weight and thickness of the paper base material obtained by the above-described measuring method.

[0019] (Optional component) The paper base material may contain, if necessary, for example, internal additives such as anionic, cationic or amphoteric retention aids, drainage improvers, dry paper strength enhancers, wet paper strength enhancers, sizing agents, fixing agents, fillers, etc., and optional components such as water resistance agents, dyes, fluorescent brightening agents, etc.

[0020] Examples of the dry paper strength enhancer include cationized starch, polyacrylamide, carboxymethyl cellulose, etc. The content of the dry paper strength enhancer is not particularly limited, but is preferably 3.0 parts by mass or less with respect to 100 parts by mass of the raw material pulp (dry mass).

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

[0022] Examples of the sizing agent include internal sizing agents such as rosin sizing agent, synthetic sizing agent (for example, alkyl ketene dimer), petroleum resin-based sizing agent, and surface sizing agents such as styrene / acrylic acid copolymer, styrene / methacrylic acid copolymer, etc. 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 material pulp (dry mass).

[0023] Examples of the fixing agent include sulfuric acid band, polyethyleneimine, etc. The content of the fixing agent is not particularly limited, but is preferably 3.0% by mass or less per raw material pulp (dry mass).

[0024] Examples of the filler 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 substrate> The method for manufacturing the paper substrate preferably includes a step of papermaking a slurry containing the above raw material pulp. The papermaking method is not particularly limited, and examples thereof include an acid papermaking method in which papermaking is performed at a pH of around 4.5, a neutral papermaking method in which papermaking is performed at a pH of about 6 to about 9, and the like. In the papermaking step, if necessary, papermaking chemicals such as a pH adjuster, an antifoaming agent, a pitch control agent, and a slime control agent can be appropriately added. The paper machine is not particularly limited, and examples thereof include continuous paper machines such as a fourdrinier type, a cylinder type, and an inclined type, or a multi-layer combined paper machine in which these are combined.

[0026] In addition, in the present embodiment, surface treatment for treating the surface of the paper substrate with a chemical may be performed. Examples of the chemical used for the surface treatment include a sizing agent, a water resistance agent, a water retention agent, a thickening agent, and a lubricant. As the apparatus used in the surface treatment step, a known apparatus can be used.

[0027] <Heat seal layer> The packaging paper of the present 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, by dry lamination, or by extrusion lamination. Among these, from the viewpoint of obtaining a packaging paper having excellent peelability, excellent burst resistance and perforation retention, and reduced environmental load, it is preferable to provide it by coating or by extrusion lamination. The heat-sealing layer is preferably directly laminated on the paper substrate. By not passing through other layers, it is possible to reduce the basis weight of the entire wrapping paper, and it is preferable because a wrapping paper with excellent peelability can be obtained.

[0028] (Coating layer) When provided by coating, the heat-sealing layer preferably contains a water-dispersible resin binder. A water-dispersible resin binder is a resin binder that is not water-soluble (specifically, the solubility in water at 25 ° C is 10 g / L or less), but is in a state of being finely dispersed in water like an emulsion or a suspension. In addition, when the water-dispersible resin binder also falls under the following lubricants, it shall be classified as a lubricant.

[0029] The water-dispersible resin binder is not particularly limited as long as it exhibits the effects of the present invention. Examples include polyolefin resins (such as polyethylene and polypropylene), vinyl chloride resins, styrene resins, styrene-butadiene copolymers, styrene-unsaturated carboxylic acid copolymers (for example, styrene-(meth)acrylic acid copolymer), 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 oxide resins, polyester resins (such as polyethylene terephthalate and polybutylene terephthalate), 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. Among these, at least one selected from the group consisting of a styrene-butadiene copolymer and an olefin-unsaturated carboxylic acid copolymer is preferable. Furthermore, from the viewpoint of increasing the heat seal peel strength, an olefin-unsaturated carboxylic acid copolymer is more preferable, and from the viewpoints of availability, cost, and recyclability, a styrene-butadiene copolymer is more preferable.

[0030] Examples of the olefin-unsaturated carboxylic acid copolymer include ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid alkyl ester copolymer, etc. Among them, ethylene-(meth)acrylic acid copolymer is preferable, and ethylene-acrylic acid copolymer is more preferable. 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. Note that the olefin-unsaturated carboxylic acid copolymer may be an ionomer.

[0031] As the styrene-butadiene copolymer, either a synthetic product or a commercially available product may be used. Commercially available products include Nipol latex LX407G51, LX407S10, LX407S12, LX410, LX415M, LX416, LX430, LX433C, 2507H manufactured by Zeon Corporation, Nalster SR-101, SR-102, SR-103, SR-115, SR-153 manufactured by A&L Japan Co., Ltd., styrene butadiene latex 0602, 0597C manufactured by JSR Corporation, etc.

[0032] As the ethylene-(meth)acrylic acid copolymer, either a synthetic product or a commercially available product may be used. Commercially available products include MP498345N, MP4983R, MP4990R, MFHS1279 manufactured by Michaelman Japan Co., Ltd., Zicen (registered trademark) A, Zicen (registered trademark) AC manufactured by Sumitomo Seika Chemical Co., Ltd., Chemparl S series manufactured by Mitsui Chemicals, Inc., etc.

[0033] 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 having a glass transition temperature equal to or higher than the above lower limit value, the occurrence of blocking can also be suppressed. And from the viewpoint of heat sealability, it is preferably 100 °C or lower, more preferably 80 °C or lower, even more preferably 60 °C or lower, and still more preferably 50 °C or lower. The glass transition temperature of the water-dispersible resin binder shall be the value measured by a differential scanning calorimeter.

[0034] 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 still 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-seal paper having high heat-seal peel strength can be obtained.

[0035] 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 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.

[0036] - Lubricant - From the viewpoints of imparting slipperiness to the heat-seal paper and suppressing blocking, the heat-seal layer may contain a lubricant in addition to the above water-dispersible resin binder. A lubricant is a substance that can reduce the friction coefficient of the surface of the heat-seal layer when blended into the heat-seal layer.

[0037] The lubricant is not particularly limited, and for example, wax, metallic soap, fatty acid ester, etc. can be used. The lubricant may be used alone or in combination of two or more. Examples of wax include natural waxes such as waxes derived from animals or plants (e.g., beeswax, carnauba wax, etc.), mineral waxes (e.g., microcrystalline wax, etc.), petroleum waxes; synthetic waxes such as polyolefin wax, paraffin wax, polyester wax, etc. Examples of metallic soap include calcium stearate, sodium stearate, zinc stearate, aluminum stearate, magnesium stearate, sodium fatty acid soap, potassium oleate soap, potassium castor oil soap, and their composites, etc. Among the above lubricants, paraffin wax, carnauba wax, and polyolefin wax are preferred because they have a relatively low melting point and the wax component is easily formed on the surface of the coating layer, and they have an excellent blocking suppression effect. That is, the lubricant is preferably at least one selected from the group consisting of paraffin wax, carnauba wax, and polyolefin wax. From the viewpoints of imparting slipperiness and improving moisture resistance, paraffin wax is preferred. As for carnauba wax, either a synthetic product or a commercially available product can be used. Examples of commercially available products include Cerol 524 manufactured by Chukyo Yushi Co., Ltd., ML160RPH manufactured by Michaelman Co., etc. As for paraffin wax, either a synthetic product or a commercially available product can be used. Examples of commercially available products include Hydrin L-700 manufactured by Chukyo Yushi Co., Ltd., etc. As for polyethylene wax, either a synthetic product or a commercially available product can be used. Examples of commercially available products include Aquacer 531 manufactured by BYK Co., etc.

[0038] When the heat-sealing layer contains a lubricant, the content of the lubricant is preferably 0.2 parts by mass or more and 30 parts by mass or less, more preferably 0.5 parts by mass or more, still more preferably 1 part by mass or more, and more preferably 10 parts by mass or less, still more preferably 5 parts by mass or less, based on 100 parts by mass of the water-dispersible resin binder.

[0039] When the heat-sealing layer contains a lubricant, the content of the lubricant in the heat-sealing layer is preferably 0.1% by mass or more and 30% by mass or less, more preferably 0.3% by mass or more, still more preferably 1% by mass or more, and more preferably 10% by mass or less, still more preferably 5% by mass or less.

[0040] In the present embodiment, the heat-sealing layer contains a water-dispersible resin binder, and in addition to the water-dispersible resin binder, it preferably contains a lubricant. Further, in addition to the water-dispersible resin binder and, if necessary, the lubricant, a pigment may be contained.

[0041] - Pigment - In the present embodiment, the heat-sealing layer may contain a pigment in addition to the above water-dispersible resin binder. By containing a pigment, when manufacturing the heat-sealing paper, the problem that the coated surface of the heat-sealing layer adheres to the back surface of the heat-sealing paper and peeling (blocking) occurs is suppressed, and a heat-sealing paper excellent in blocking resistance can be obtained.

[0042] The pigment is not particularly limited, and various pigments used in conventional pigment coating layers are exemplified. The pigment may be used alone or in combination of two or more. As the pigment, a pigment having an aspect ratio of 20 or more and 10,000 or less is preferable. When the aspect ratio of the pigment is 20 or more, it is preferable because it is excellent in terms of heat-sealing peel strength and blocking resistance. Also, when it is 10,000 or less, it is preferable because it is easily available and excellent in the smoothness of the surface of the heat-sealing layer. The aspect ratio of the pigment is more preferably 25 or more, still more preferably 30 or more, particularly preferably 60 or more, and more preferably 1,000 or less, still more preferably 300 or less. The aspect ratio of the pigment means the major axis / minor axis and may be measured by the following method.

[0043] The pigment is preferably a layered inorganic compound having an aspect ratio of 20 or more. The form of the layered inorganic compound is plate-like. When the pigment is plate-like, the protrusion of the pigment from the surface of the heat-sealing layer is suppressed, and a heat-sealing layer excellent in blocking resistance can be obtained while maintaining the heat-sealing property.

[0044] The length (average particle diameter) of the pigment is preferably 0.1 μm or more and 100 μm or less. When the length is 0.1 μm or more, the pigment is likely to be arranged in parallel to the paper substrate. Also, when the length is 100 μm or less, there is little concern that a part of the pigment protrudes from the heat-sealing layer. The length of the pigment is more preferably 0.3 μm or more, still more preferably 0.5 μm or more, particularly preferably 1.0 μm or more, and more preferably 30 μm or less, still more preferably 20 μm or less, particularly preferably 15 μm or less.

[0045] Here, the length of the pigment in the state of being contained in the heat-sealing layer is determined as follows. For the cross-section of the heat-sealing layer, a magnified photograph is taken using an electron microscope. At this time, the magnification is such that about 20 to 30 pigments are included in the screen. The individual lengths of the pigments in the screen are measured. Then, the average value of the obtained lengths is calculated and taken as the length of the pigment. Note that the length of the pigment may also be described in terms of particle diameter.

[0046] The thickness of the pigment is preferably 5 nm or more and 200 nm or less. The thickness of the pigment is more preferably 100 nm or less, still more preferably 80 nm or less, even more preferably 50 nm or less, particularly preferably 30 nm or less. Also, it is more preferably 10 nm or more. A smaller average thickness of the pigment results in a higher heat-sealing peel strength. Here, the thickness of the pigment in the state of being contained in the heat-sealing layer is determined as follows. For the cross-section of the heat-sealing layer, a magnified photograph is taken using an electron microscope. At this time, the magnification is such that about 20 to 30 pigments are included in the screen. The individual thicknesses of the pigments in the screen are measured. Then, the average value of the obtained thicknesses is calculated and taken as the thickness of the pigment.

[0047] Specific examples of the pigment include mica, bentonite, kaolin, pyrophyllite, talc, smectite, vermiculite, chlorite, septarian chlorite, serpentine, stilpnomelane, montmorillonite, heavy calcium carbonate (ground calcium carbonate), light calcium carbonate (synthetic calcium carbonate), composite synthetic pigment 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, silicate, colloidal silica, plastic pigments of organic pigments that are hollow or dense, binder pigments, plastic beads, microcapsules, and the like.

[0048] Specific examples of mica include synthetic mica (for example, swelling synthetic mica), muscovite (mascovite), sericite (sericite), phlogopite (fluorophlogopite), biotite (biotite), fluorophlogopite (synthetic mica), red mica, soda mica, vanadium mica, illite, tin mica, paragonite, brittle mica, and the like. Specific examples of bentonite include montmorillonite.

[0049] Specific examples of kaolin include various kaolins such as kaolin, calcined kaolin, structured kaolin, and delaminated kaolin.

[0050] Among these, from the viewpoints of heat seal peel strength, blocking resistance, and economy, pigments with an aspect ratio of 20 or more are preferred, and it is more preferred to contain one or more of mica, bentonite, kaolin, and talc, and kaolin is even more preferred.

[0051] When the heat-sealing 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, still more preferably 5 parts by mass or more, and even more preferably 8 parts by mass or more with respect to 100 parts by mass of the water-dispersible resin binder from the viewpoints of blocking resistance and recyclability. On the other hand, from the viewpoint of heat-sealing property, it is preferably 200 parts by mass or less, more preferably 100 parts by mass or less, and still more preferably 30 parts by mass or less.

[0052] When the heat-sealing layer contains a pigment, the content of the pigment in the heat-sealing layer is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, and even 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 still more preferably 20% by mass or less from the viewpoint of heat-sealing property.

[0053] -Other components- The heat-sealing layer may contain other components in addition to the above water-dispersible resin binder, lubricant and / or pigment as required. Examples of other components include silane coupling agents; defoaming agents; viscosity modifiers; leveling agents such as surfactants and alcohols; colorants such as coloring dyes.

[0054] The method of coating the heat-sealing layer on the paper substrate is not particularly limited, and known coating equipment may be used. Examples of the coating equipment include blade coaters, bar coaters, air knife coaters, slit die coaters, gravure coaters, microgravure coaters, roll coaters, size presses, gate roll coaters, simsizers, etc.

[0055] After coating, it is preferable to dry the coating liquid, and the drying equipment for drying is not particularly limited, and known equipment can be used. Examples of the drying equipment include hot air dryers, infrared dryers, gas burners, hot plates, etc. Also, the drying temperature may be appropriately set in consideration of the drying time and the like. Further, after drying the coating liquid, supercalendering treatment may be performed. Supercalendering treatment is installed independently of papermaking. Generally, paper or the like to be treated is passed between metal rolls or between a metal roll and an elastic roll, and heating, pressurization, etc. are performed. The supercalendering treatment may be performed in one stage or in multiple stages, and is not particularly limited.

[0056] The solvent of the heat-sealing layer coating liquid is not particularly limited, and water or organic solvents such as ethanol, isopropyl alcohol, methyl ethyl ketone, and toluene can be used. Among these, from the viewpoint of not causing problems with volatile organic solvents, water is preferable as the dispersion medium of the heat-sealing layer coating liquid. That is, the heat-sealing layer coating liquid is preferably an aqueous composition for the heat-sealing layer.

[0057] The solid content (solid content concentration) of the heat-sealing layer coating liquid is not particularly limited and may be appropriately selected from the viewpoints of coatability and ease of drying. Preferably, it is 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more, and preferably 80% by mass or less, more preferably 60% by mass or less, still more preferably 50% by mass or less, and even more preferably 40% by mass or less.

[0058] (Laminated layer) When the heat-sealing layer is provided by lamination, it may be appropriately selected and manufactured from conventionally known manufacturing methods. For example, it may be appropriately selected from the dry lamination method, the melt extrusion method, the melt casting method, the calendar method, etc. Among these, laminating with the paper substrate without an adhesive layer is preferable from the viewpoint of reducing the environmental load, the melt extrusion method and the melt casting method are preferable, and the melt extrusion method is more preferable.

[0059] As the resin constituting the heat-sealing layer, any thermoplastic resin, either a crystalline resin or an amorphous resin, can be used according to the application. Examples of thermoplastic resins 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; polylactic acid (PLA); polyhydroxybutyric acid (PHB); polybutylene succinate (PBS); poly(butylene adipate-co-butylene terephthalate) (PBAT); polycaprolactone (PCL); biodegradable resins such as 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 thermoplastic resins, it is preferable to use polyolefin resins such as polyethylene (LDPE, MDPE, HDPE, LLDPE, etc.), polypropylene, and polymethylpentene, and polylactic acid (PLA), and it is more preferable to use polyethylene and polypropylene. These thermoplastic resins may be used alone or in combination of two or more.

[0060] The heat-sealing 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 these multi-layers (for example, single resin layer / single resin layer, single resin layer / mixed resin layer, mixed resin layer / mixed resin layer).

[0061] (Grammage) The grammage of the heat-sealing layer may be appropriately selected within the range where the content of the paper base material 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 peelability, it is preferable that the grammage is small. When the heat-sealing layer is provided by coating, the grammage of the heat-sealing layer is preferably 1 g / m from the viewpoints of reducing environmental load, heat-sealing property, and peelability. 2More than 20g / m 2 More preferably, it is 2 g / m or less. 2 More preferably, it is 10 g / m or more. 2 Less than 5 g / m, more preferably 2 Less than 3 g / m 2 is less than.

[0062] In addition, 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 openability. 2 More than 40g / m 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 Less than 25 g / m, more preferably 2 More preferably, 20 g / m or less 2 less than 19 g / m 2 The following is the result. Furthermore, when the heat seal layer is provided by lamination, from the same viewpoint, the thickness of the heat seal layer is 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, even more preferably less than 20 μm, and even more preferably 19 μm or less.

[0063] <Characteristics of wrapping paper> (Paper base material content) In the wrapping paper of this embodiment, the content of the paper base material in the wrapping paper is 50% by mass or more from the viewpoint of reducing the environmental load. The content of the paper base material is preferably 55% by mass or more, more preferably 60% by mass or more. In addition, 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.

[0064] (Basic weight) The basis weight of the wrapping paper of this embodiment is preferably 20 g / m 2 or more and 65 g / m 2 or less, more preferably 25 g / m 2 or more, even more preferably 30 g / m 2 or more, and more preferably 60 g / m 2 or less, even more preferably 55 g / m 2 or less, even more preferably 50 g / m 2 or less, from the viewpoints of peelability, bursting strength resistance, and perforation retention property. The basis weight of the wrapping paper can be adjusted to a desired range by appropriately adjusting the basis weights of the paper base material and the heat seal layer. The basis weight of the wrapping paper is measured by the method described in the examples.

[0065] (Thickness) 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, still more preferably 38 μm or more, and more preferably 70 μm or less, even more preferably 65 μm or less, from the viewpoints of peelability, bursting strength resistance, and perforation retention property. The thickness of the wrapping paper can be adjusted to a desired range by appropriately adjusting the thicknesses 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.

[0066] (Density) The density of the wrapping paper of this embodiment is preferably 0.5 g / cm 3 or more and 1.0 g / cm 3 or less, more preferably 0.65 g / cm 3 or more, even more preferably 0.70 g / cm 3 or more, and more preferably 0.95 g / cm 3 or less, even more preferably 0.90 g / cm 3 or less, even more preferably 0.85 g / cm 3 or less, from the viewpoints of peelability, bursting strength resistance, and perforation retention property. The density of the wrapping paper can be set within a desired range by appropriately adjusting the density of the paper base material and the type of resin used for the heat-sealing layer. The density of the wrapping paper is measured by the method described in the examples.

[0067] (Tear strength) For the wrapping paper of this embodiment, the tear strength in both the longitudinal and transverse directions is 240 mN or less. By having the tear strength in both the longitudinal and transverse directions be 240 mN or less, a package with excellent opening properties can be obtained using the wrapping paper of this embodiment. The tear strength in the longitudinal direction is preferably 30 mN or more and 230 mN or less, more preferably 210 mN or less, and from the viewpoint of burst resistance, more preferably 40 mN or more, still more preferably 50 mN or more, and even more preferably 60 mN or more.

[0068] The tear strength in the transverse direction is preferably 40 mN or more and 230 mN or less, more preferably 220 mN or less, and from the viewpoint of burst resistance, more preferably 50 mN or more, still more preferably 60 mN or more, and even more preferably 70 mN or more, from the viewpoints of opening properties and burst resistance. The tear strength is measured in accordance with JIS P 8116:2000. The tear strength is adjusted by appropriately selecting the type of raw pulp, beating degree, basis weight, thickness, density of the paper base material, papermaking conditions of the paper base material, type and thickness of the heat-sealing layer, etc. When a large amount of hardwood-derived raw pulp is used as the raw pulp, the tear strength tends to decrease, and when the beating degree is increased, the tear strength tends to increase. Also, when the basis weight, thickness, density of the paper base material, and thickness of the heat-sealing layer are large, the tear strength tends to increase.

[0069] (Puncture strength) For the wrapping paper of this embodiment, the puncture strength is 1.3 N or more. When the puncture strength is 1.3 N or more, when made into a package, breakage of the package during transportation and storage is suppressed, and a wrapping paper with excellent burst resistance can be obtained. The puncture strength is preferably 1.4 N or more and 7.0 N or less, more preferably 1.5 N or more, still more preferably 1.6 N or more, and from the viewpoint of peelability and ease of manufacture, more preferably 5.0 N or less, still more preferably 4.0 N or less, and still more preferably 3.0 N or less, from the viewpoints of burst resistance and ease of manufacture. The puncture strength tends to increase by increasing the basis weights of the paper base material and the heat-sealing layer. Further, 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 content of softwood pulp increases. The puncture strength is measured in accordance with JIS Z 1707:2019.

[0070] (Fracture toughness) The wrapping paper of this embodiment has a fracture toughness in the longitudinal direction of 0.18 J / m or more. Fracture toughness means the strength property of paper that can suppress paper pieces generated by the progress of a tear when there is a tear in the wrapping paper or the package. By having a fracture toughness in the longitudinal direction of 0.18 J / m or more, the progress of a tear due to tensile force in the longitudinal direction is suppressed, and a package excellent in perforation retention can be obtained using the wrapping paper of this embodiment. The fracture toughness in the longitudinal direction is preferably 0.18 J / m or more and 0.90 J / m or less, and from the viewpoint of peelability, more preferably 0.75 J / m or less, still more preferably 0.60 J / m or less, and even more preferably 0.45 J / m or less.

[0071] The fracture toughness in the transverse direction is preferably 0.10 J / m or more and 0.85 J / m or less from the viewpoint of obtaining a package excellent in perforation retention and peelability, and from the viewpoint of peelability, more preferably 0.70 J / m or less, still more preferably 0.55 J / m or less, and even more preferably 0.40 J / m or less. The fracture toughness is measured in accordance with SCAN-test standard P77:95. Fracture toughness is adjusted by appropriately selecting the type of raw pulp, beating degree, basis weight, thickness, density of the paper substrate, papermaking conditions of the paper substrate, type and thickness of the heat-sealing layer, etc. When a large amount of raw pulp derived from hardwood is used as the raw pulp, the fracture toughness tends to decrease. When the beating degree is increased, the fracture toughness tends to increase. Also, when the basis weight, thickness, density of the paper substrate, and thickness of the heat-sealing layer are large, the fracture toughness tends to increase.

[0072] 〔Package〕 The package of this embodiment is a package produced using the wrapping paper of this embodiment, and preferably, it is a package consisting only of the wrapping paper of this embodiment. The package of this embodiment may be a package produced by any method. For example, it may be used for a three-side sealed packaging bag, a four-side sealed packaging bag, a pillow packaging bag, etc. However, it preferably has a lid material and a bottom material having a recess, and is used for a package that can accommodate and seal the object to be contained in the recess by heat-sealing the lid material and the bottom material. Fig. 1 shows an example of a package suitable for this embodiment. Fig. 1 shows a schematic cross-sectional view in the production of the package. It is preferable that the package 10 is obtained by placing the wrapping paper 2 serving as the bottom material on the mold 1 in which the recess is formed, making it follow the shape of the recess, placing the object 4 to be contained on the wrapping paper 2 serving as the bottom material, then placing the wrapping paper 3 serving as the lid material, and heat-sealing the wrapping paper 2 serving as the bottom material and the wrapping paper 3 serving as the lid material. In Fig. 1, the arrow indicates the longitudinal direction of the wrapping paper. Also, 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 when the object to be contained is a rod-shaped substance.

Examples

[0073] The features of the present invention will be further specifically described below by way of examples and comparative examples. The materials, amounts used, ratios, treatment details, treatment procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed in a limited manner by the specific examples shown below. Note that "parts" and "%" mean "parts by mass" and "% by mass" unless otherwise specified.

[0074] [Evaluation and Analysis] The following evaluations and analyses were performed on the raw material pulp, wrapping paper, and package of the examples and comparative examples.

[0075] [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.

[0076] [Paper Substrate and Wrapping Paper] [Grammage] The grammage of the paper substrate and the wrapping paper was measured in accordance with JIS P 8124:2011. The grammage of the heat-sealing layer was calculated from the values of the paper substrate and the wrapping paper.

[0077] [Thickness] The thickness of the paper substrate and the wrapping paper was measured in accordance with JIS P 8118:2014 under a pressure of 100 kPa ± 10 kPa applied to the circular area (200 mm 2 ) of the test piece. Note that the thickness of the heat-sealing layer was calculated from the values of the paper substrate and the wrapping paper.

[0078] [Density] The density of the paper substrate and the wrapping paper was measured in accordance with JIS P 8118:2014. Note that the density of the heat-sealing layer was calculated from the values of the paper substrate and the wrapping paper.

[0079] [Tear Strength] The tear strength of the wrapping paper was measured in accordance with JIS P 8116:2000.

[0080] <Puncture strength> The puncture strength of the wrapping paper was measured in accordance with JIS Z 1707:2019. Although it may be measured from any surface of the wrapping paper, in this example, it was measured from the heat seal layer side.

[0081] <Fracture toughness> The fracture toughness of the wrapping paper was measured in accordance with SCAN-test standard P77:95 using a Tensile Tester with Fracture Toughness manufactured by Lorentzen & Wettre.

[0082] <Length-weighted average fiber length of the pulp constituting the paper substrate> The length-weighted average fiber length of the pulp constituting the paper substrate was measured for the obtained wrapping paper after disintegrating it by a method compliant with JIS P 8220-1:2012, and for the obtained disintegrated pulp in accordance with ISO 16065-2:2007.

[0083] <Opening property> Using the wrapping paper obtained in each example, a rod-shaped product with dimensions (LWH) 14 cm × 1.2 cm × 0.8 cm and a weight of 13.4 g was packaged by four-side sealing to obtain a package. The ease of opening of the obtained package was evaluated. The test was conducted with 10 people. First, the package of Example 2 was opened. Next, based on the force required to open the package of Example 2, the packages of Examples 1 and 3 and Comparative Examples 1 to 3 were sequentially opened, and for each example, the total score (for 10 people) was obtained and evaluated in the following two levels (「A」 and 「B」). 3: Less force is required to open than the reference 2: Can be opened with the same force as the reference 1: More force is required to open than the reference A: Total score is 15 points or more B: Total score is less than 15 points (The total score of the package of Example 2 is 10 × 2 = 20, and it is evaluated as A.)

[0084] <Resistance to tearing (burst resistance of packaging)> Using the wrapping paper obtained in each example, a rod-shaped product with dimensions (LWH) 14 cm × 1.2 cm × 0.8 cm and a weight of 13.4 g was wrapped by a four-sided seal to obtain a package. One end of the short side of the obtained package was held with both hands and hung vertically, and the presence or absence of tearing of the wrapping paper was observed when it was shaken up and down (about 10 cm) 20 times at a speed of 2 times per second. For each example, 10 packages were tested by one tester and evaluated in three grades. A: No tearing after shaking 20 times B: No tearing occurred when shaken 10 times, but there was one or more packages that tore when shaken 20 times. C: One or more packages tore when shaken 10 times.

[0085] <Stitch retention> In each example, 10 rod-shaped products with dimensions (LWH) 14 cm × 1.2 cm × 0.8 cm and a weight of 13.4 g were arranged in parallel, and two sheets of wrapping paper were used to heat-seal them so that the 10 individually wrapped rod-shaped products were connected in a row to obtain a package. That is, 10 rod-shaped products were placed between two sheets of wrapping paper, and the top, bottom, left, and right of the wrapping paper and 9 locations between the rod-shaped products were heat-sealed to obtain a package. A sewing machine cutter was used to make stitches horizontally at the 9 heat-sealed locations between the rod-shaped products to produce a package in which the rod-shaped products were individually wrapped through the stitches. With the stitches parallel to the floor, one end of the package was held with both hands and hung vertically, and it was repeatedly shaken up and down (about 10 cm) at a speed of 2 times per second. For each example, 10 packages were tested by one tester, and the following scores were assigned to each package, and the value obtained by rounding the first digit after the decimal point of the average value was taken as the score for each example. 3: No tearing occurred at the stitches in all packages after shaking 20 times 2: No tearing occurred at the stitches in all packages during shaking from 1 to 10 times, but there was one or more packages that tore at the stitches during shaking from 11 to 20 times. 1. There was one or more packages with perforations during 1 to 10 shakes.

[0086] <Heat sealability> The wrapping paper obtained in each example was cut into a size of 10 cm × 10 cm. Two pieces of each were overlapped so that the heat-sealing layers were in contact, and a heat-sealing tester (manufactured by Tester Sangyo Co., Ltd., TP-701-B) was used to perform heat-sealing on four sides under certain conditions (temperature: 130 °C, pressure: 1.0 kgf / cm 2 , time: 0.5 seconds, adhesion width: 1 cm). One tester pulled and peeled five samples for each example by hand from the edge of the heat-sealed substrate and evaluated them in three grades based on the state after peeling. A: Paper layer peeling occurred over almost the entire surface (80% or more of the area). B: Paper layer peeling occurred in part (more than 20% and less than 80% of the area). C: Almost no paper layer peeling occurred (less than 20% of the area).

[0087] [Example 1] (Preparation of paper substrate) Hardwood bleached kraft pulp (LBKP) was beaten to CSF 400 mL, and then a pulp slurry with a concentration of 3.8 mass% was obtained. To this pulp slurry, 0.9 parts by mass of an anionic dry paper strength enhancer mainly composed of polyacrylamide (trade name: PS-NH20B, manufactured by Arakawa Chemical Industries, Ltd.), 0.9 parts by mass of a cationic wet paper strength enhancer mainly composed of polyamide polyamine epichlorohydrin (trade name: WS4024, manufactured by Starlight PMC Co., Ltd.), and 0.3 parts by mass of an alkyl ketene dimer (trade name: AD1612, manufactured by Starlight PMC Co., Ltd.) as a neutral sizing agent were added per 100 parts by mass of pulp solids, and the mixture was stirred to obtain a papermaking stock. This papermaking stock was adjusted to a concentration of 0.5 mass%, and paper was made using an inclined wire paper machine to obtain a paper substrate with a basis weight of 18 g / m 2 .

[0088] (Formation of heat-sealing layer) On one side of the obtained paper substrate, LDPE (manufactured by Nippon Polyethylene Co., Ltd., LC522) was laminated as a heat-sealing layer. The lamination of the heat-sealing layer on one side of the paper substrate was carried out by the melt extrusion method under the conditions of a lamination temperature of 330 °C and a lamination speed of 120 m / min. The basis weight of the heat-sealing layer was 17 g / m 2 to obtain wrapping paper.

[0089] [Example 2] The paper substrate was made by a inclined wire paper machine, and wrapping paper was obtained under the same conditions as in Example 1 except that the basis weight was 30 g / m 2

[0090] [Example 3] The paper substrate was made by a inclined wire paper machine, and wrapping paper was obtained under the same conditions as in Example 1 except that the basis weight was 30 g / m 2 and the heat-sealing layer was formed by the following method. (Formation of heat-sealing layer) On one side of the obtained paper substrate, the coating amount after drying of the heat-sealing layer was 2.5 g / m 2 and the following heat-sealing layer paint was applied with a gravure coater (using a smoothing bar) to form a heat-sealing layer. -Preparation of heat-sealing layer paint- 98 parts (in terms of solid content) of an aqueous dispersion of a styrene / butadiene copolymer (manufactured by Nippon Zeon Co., Ltd., Nipol latex LX407S12, solid content concentration 46% by mass, glass transition temperature 18 °C (catalog value)) and 2 parts (in terms of solid content) of a paraffin wax emulsion (manufactured by Chukyo Yushi Co., Ltd., Hydrin L-700, solid content concentration 30% by mass) were mixed, water was added and stirred so that the solid content concentration became 33% by mass, and a heat-sealing layer paint (solid content concentration 33% by mass) was prepared. The above styrene / butadiene copolymer had a solubility in water at 25 °C of 10 g / L or less.

[0091] [Comparative Example 1] The paper substrate was made by a inclined wire paper machine, and wrapping paper was obtained under the same conditions as in Example 1 except that the basis weight was 50 g / m 2

[0092] ​​ [Comparative Example 2] A packaging paper was obtained under the same conditions as in Example 1, except that the paper base material was formed on an inclined wire paper machine with a basis weight of 15 g / m 2

[0093] [Comparative Example 3] As the pulp raw material of the paper base material, hardwood bleached kraft pulp (LBKP) and softwood bleached kraft pulp (NBKP) were used in a ratio of 80:20, and the basis weight was 30 g / m 2 A packaging paper was obtained under the same conditions as in Example 1, except that

[0094] The above-mentioned evaluations were performed on the obtained packaging paper. The results are shown in the following table.

[0095]

Table 1

[0096] From the results of the examples and comparative examples, the package obtained using the packaging paper of this embodiment is excellent in peelability, burst resistance, and perforation retention, and further, the packaging paper of this embodiment has excellent heat sealability. On the other hand, the package obtained using the packaging paper of Comparative Example 1, in which the basis weight of the paper base material exceeded 40 g / m 2 and the tear strengths in both the longitudinal and transverse directions exceeded 240 N, was inferior in peelability. Also, the package obtained using the packaging paper of Comparative Example 2, in which the piercing strength was 1.3 N or less, was inferior in burst resistance and perforation retention. Furthermore, the package obtained using the packaging paper of Comparative Example 3, in which the tear strengths in both the longitudinal and transverse directions exceeded 240 N and the length-weighted average fiber length exceeded 0.92 mm, was inferior in peelability.

Industrial Applicability

[0097] ​The wrapping paper of the present invention is suitable as a flexible packaging material. The package obtained by using the wrapping paper of the present invention is excellent in peelability, and also excellent in burst resistance and perforation retention. Further, the wrapping paper of the present invention is excellent in heat sealability. The wrapping paper of the present invention is suitably used for forming a package.

Explanation of Signs

[0098] 1 Mold 2 Wrapping paper serving as a bottom material 3 Wrapping paper serving as a lid material 4 Object to be contained 10 Package

Claims

1. A wrapping paper having a heat-sealing layer on a paper base material, The basis weight of the paper substrate is 40 g / m ２ or less, wherein the content of the paper base material in the wrapping paper is 50% by mass or more, the tearing strength in both the longitudinal and transverse directions of the wrapping paper is 240 mN 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.

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

3. The basis weight is 60 g / m ２ The wrapping paper according to claim 1 or 2, wherein the basis weight is 60 g / m or less.

4. The wrapping paper according to claim 1 or 2, having a fracture toughness in the longitudinal direction of 0.18 J / m or more.

5. The wrapping paper according to claim 1 or 2, wherein the raw material pulp of the paper base material contains hardwood sun-dried kraft pulp, and the content of the hardwood sun-dried kraft pulp in the raw material pulp is 85% by mass or more.

6. The wrapping paper according to claim 1 or 2, wherein the paper base material and the heat-sealing layer are directly laminated.

7. A package having a lid material and a bottom material having a recess, wherein the lid material and the bottom material can seal and accommodate an object to be accommodated in the recess by heat-sealing, and the lid material and the bottom material are made of the wrapping paper according to claim 1 or 2, the package.

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