Wrapping Paper and Packaging

Abstract

To provide a wrapping paper which reduces the burden on the environment, has excellent visibility when used as a package, has excellent paper feedability (hard to tear even when the end is pulled at a desired speed) when used for packaging by a machine, and has heat sealability, and a package made using the wrapping paper. The present invention relates to a wrapping paper having a heat seal layer on a paper base material, and the paper base material has a basis weight of 60 g / m 2 a wrapping paper having a paper base material content of 50% by mass or more, an opacity of the wrapping paper of 80% or less, and a tensile strength in the longitudinal direction of the wrapping paper of 1.2 kN / m or more.

Description

[Technical field]

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

[0002] In recent years, the problem of plastic waste has become more serious worldwide, and in order to improve the global environment, efforts are being made to eliminate or reduce the use of plastic in packaging materials, with a strong movement to replace plastic packaging with paper packaging. However, paper has the problem that it is weaker in strength than plastic materials and easily tears. Patent Document 1 discloses a packaging base paper for sealed containers that is primarily composed of pulp, with the aim of providing a packaging base paper for sealed containers that has high strength against bending, excellent impact resistance, and maintains strength that makes it difficult to tear even when subjected to impacts during distribution after the contents are packaged therein, 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 side of the base paper is coated with carboxymethyl cellulose. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-67787 A Summary of the Invention [Problem to be solved by the invention]

[0004] The packaging base paper described in Patent Document 1 has high strength and can firmly hold the contents, but it is difficult to visually grasp the contents, that is, visibility is poor, and there is room for improvement. The present invention aims to provide a wrapping paper that reduces the burden on the environment, has excellent visibility when made into a package, and has excellent paper feedability (i.e., is less likely to tear even when the ends are pulled at a desired speed) when used for packaging using a machine, and has heat sealability, as well as a package made using the wrapping paper. [Means for solving the problem]

[0005] The inventors have discovered that the above problem can be solved by making the basis weight of the paper base material not exceeding a specific value, making the content of the paper base material not less than a specific value, making the opacity not exceeding a specific value, and making the longitudinal tensile strength not less than a specific value in a wrapping paper having a heat seal layer. That is, the present invention provides the following: <1> ~ <7> Regarding. <1> This is a wrapping paper with a heat seal layer on a paper base material, and the basis weight of the paper base material is 60 g / m 2 a wrapping paper having a paper base material content of 50% by mass or more, an opacity of the wrapping paper of 80% or less, and a tensile strength in the longitudinal direction of the wrapping paper of 1.2 kN / m or more. <2> The thickness is 90 μm or less. <1> The wrapping paper described in <3> Basis weight 75g / m 2 Below is the <1> or <2> The wrapping paper described in <4> 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. <1> ~ <3> A wrapping paper according to any one of the above. <5> The paper base material and the heat seal layer are directly laminated together. <1> ~ <4> The wrapping paper according to any one of the preceding claims. <6> The heat seal layer has a basis weight of 20 g / m 2 Laminate layer with a basis weight of less than 3 g / m 2 A coating layer of less than <1> ~ <5> A wrapping paper according to any one of the above. <7> A package having a lid and a base having a recess, the package being capable of housing and sealing an object in the recess by heat sealing the lid and the base, the package comprising: <1> ~ <6> A packaging material comprising the packaging paper according to any one of the preceding claims. Effect of the Invention

[0006] According to the present invention, there is provided a wrapping paper which reduces the burden on the environment, has excellent visibility when made into a package, and has excellent paper feeding properties and heat sealing properties when used for packaging using a machine, as well as a package made using said wrapping paper. [Brief description of the drawings]

[0007] [Figure 1] 1A to 1C are schematic cross-sectional views showing the manufacturing process of a package suitable for an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [Wrapping paper] The wrapping paper of the present 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 60 g / m 2 the content of the paper base material in the wrapping paper is 50% by mass or more, the opacity of the wrapping paper is 80% or less, and the tensile strength in the longitudinal direction of the wrapping paper is 1.2 kN / m or more. The wrapping paper of this embodiment reduces the burden on the environment, has excellent visibility when made into a package, and provides wrapping paper with excellent paper feeding properties and heat sealing properties when used for packaging using a machine. The reason for the above effect 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 impact. In addition, the basis weight of the paper base material is 60 g / m 2 In the following, it is considered that the wrapping paper has a suitable strength and excellent paper feedability by having a paper base material content of 50% by mass or more and a longitudinal tensile strength of 1.2 kN / m or more. Furthermore, it is considered that the visibility is excellent by having an opacity of 80% or less. However, the reason why the above effect is obtained is not limited to this. In addition, according to the wrapping paper of the present embodiment, the raw pulp constituting the paper base material is beaten so that the opacity is 80% or less, and the basis weight of the paper base material is 60 g / m 2By doing so, it is believed that unevenness in the paper base material is suppressed and the entire paper base material can be heated uniformly during heat sealing, making it possible to form a heat seal layer with a smaller basis weight than conventional heat seal layers. The present invention will now be described in further detail.

[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 the numerical range is described in stages, the upper and lower limits of each numerical range can be arbitrarily combined. In this specification, unless otherwise specified, operations and measurements of physical properties are performed under the conditions of room temperature (20 to 25°C) and relative humidity 40 to 50% RH. In addition, "(meth)acrylic" is a generic term including both acrylic and methacrylic. In addition, the machine direction of the wrapping paper and the paper base material means the papermaking direction (MD) of the paper base material, and the cross direction means the direction perpendicular to the papermaking direction (CD).

[0010] <Paper base material> The wrapping paper of the present embodiment has a heat seal layer on a 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 material containing raw pulp, fillers, various auxiliaries, etc., as is, or a base paper with one or more functional layers formed on at least one side thereof, such as a sealing layer, ink-receiving layer, water-resistant layer, oil-resistant layer, water vapor barrier layer, gas barrier layer, etc.

[0011] (Raw 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), pressurized groundwood pulp (PGW), refiner mechanical pulp (RMP), thermomechanical pulp (TMP), chemi-thermomechanical pulp (CTMP), chemi-mechanical pulp (CMP), and chemi-ground pulp (CGP); waste 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 mass%, and the content of hardwood pulp (or hardwood bleached kraft pulp) is preferably 85 mass% or more, more preferably 90 mass% or more, even more preferably 95 mass% or more, and even more preferably 100 mass%. Hardwood pulp has a shorter average fiber length than softwood pulp, and by using a paper base material using hardwood pulp as the raw material pulp, wrapping paper having the desired tensile strength can be obtained, and it is preferable because it has excellent paper feedability. In addition, by using hardwood pulp, preferably bleached hardwood pulp, as the raw material pulp, the average fiber length of the pulp constituting the paper base material tends to be shorter, and as a result, unevenness in the paper is suppressed, and a paper base material with excellent surface uniformity is obtained. 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 an 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 (NBKP / LBKP) of softwood bleached kraft pulp (NBKP) to hardwood bleached 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, and even more preferably 5 / 95 or less.

[0014] (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 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 material pulp is within the above range, the smoothness of the paper base surface is good, and even if the basis weight is small, a uniform heat seal layer tends to be obtained, which is preferable. CSF is measured in accordance with JIS P 8121-2:2012 "Pulp - Test method for freeness - Part 2: Canadian standard freeness method".

[0015] (Basic weight) In this embodiment, the basis weight of the paper base material is 60 g / m 2 Preferably, the thickness is 55 g / m 2 Less than 45g / m 2 Less than 36 g / m, more preferably 36 g / m 2 Less than 32 g / m 2 The lower limit is not particularly limited, but from the viewpoint of obtaining a desired tensile 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 base material is within the above range, it is preferable since a wrapping paper having excellent visibility and excellent paper feedability can be obtained. The basis weight of the paper base material is measured in accordance with JIS P 8124:2011. When measuring the basis weight of the paper base material from the wrapping paper, the basis weight of the paper base material 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.

[0016] (Thickness) The thickness of the paper base material is preferably 20 μm or more and 85 μm or less, more preferably 22 μm or more, even more preferably 25 μm or more, and more preferably 75 μm or less, even 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 base material is within the above range, the desired tensile strength is obtained, and a wrapping paper having excellent visibility and paper feed properties is obtained, which is preferable. The thickness of the paper base material is measured in accordance with JIS P 8118:2014, and more specifically, by the method described in the examples.

[0017] (density) The density of the paper substrate is preferably 0.3 g / cm 3 More than 1.0g / cm 3 More preferably, it is 0.5 g / cm 3More preferably, 0.6 g / cm 3 More preferably, it is 0.9 g / cm 3 Less than 0.8 g / cm, more preferably 0.8 g / cm 3 The following is the result. When the density of the paper base material is within the above range, the desired tensile strength is obtained, and a wrapping paper having excellent visibility and paper feed properties is obtained, which is preferable. The density of the paper substrate is calculated from the basis weight and thickness of the paper substrate obtained by the above-mentioned measuring method.

[0018] (optional ingredient) The paper base material may contain optional components as necessary, such as anionic, cationic or amphoteric retention agents, drainage improvers, dry strength agents, wet strength agents, sizing agents, fixing agents, internal additives such as fillers, water-resistant agents, dyes, and fluorescent whitening agents.

[0019] Examples of the dry strength agent include cationic 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 the raw pulp (bone dry mass).

[0020] 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).

[0021] Examples of the sizing agent 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).

[0022] 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 pulp (bone dry mass).

[0023] 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.

[0024] <Manufacturing method of paper base material> The method for producing the paper base material preferably includes a step of making 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 about 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 appropriately added as necessary. The papermaking machine is not particularly limited, and examples thereof include continuous papermaking machines of the Fourdrinier type, cylinder type, and tilt type, and multi-layer papermaking machines that combine these.

[0025] In the present embodiment, the surface of the paper substrate may be treated with a chemical. Examples of the chemicals used in the surface treatment include sizing agents, water-resistant agents, water retention agents, thickeners, lubricants, etc. Any known device may be used in the surface treatment step.

[0026] <Heat seal layer> The wrapping 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, etc. The heat seal layer may be provided by coating, dry lamination, or extrusion lamination. Among these, from the viewpoint of providing a wrapping paper with excellent visibility and paper feedability, and with reduced environmental impact, it is preferable to apply the protective layer by coating or extrusion lamination. The heat seal layer is preferably laminated directly onto the paper substrate, since not using any other layers makes it possible to reduce the basis weight of the entire wrapping paper and also provides wrapping paper with excellent visibility, which is preferable.

[0027] (Coating layer) When the heat seal layer is formed by coating, it is preferable that the heat seal layer contains a water-dispersible resin binder. The water-dispersible resin binder is a resin binder that is not water-soluble (specifically, has a solubility of 10 g / L or less in water at 25°C) but is finely dispersed in water, such as an emulsion or suspension. If the water-dispersible resin binder also falls under the category of a lubricant, it is classified as a lubricant.

[0028] The water-dispersible resin binder is not particularly limited as long as it exhibits the effects of the present invention. Examples of the water-dispersible resin binder 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 the resin include 4-methylpentene-1 resin, polybutene-1 resin, vinylidene fluoride resin, vinyl fluoride resin, fluorine 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 copolymers and olefin-unsaturated carboxylic acid copolymers is preferred. 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.

[0029] Examples of the olefin-unsaturated carboxylic acid copolymer include an ethylene-(meth)acrylic acid copolymer, an ethylene-(meth)acrylic acid alkyl ester copolymer, etc. Among them, 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.

[0030] 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 Zeon Corporation; Nalstar 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.

[0031] 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 Michaelman 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.

[0032] 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 lower limit, the occurrence of blocking can 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.

[0033] 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 seal paper having high heat seal peel strength can be obtained.

[0034] 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 even 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.

[0035] - Lubricant - From the viewpoint of imparting slipperiness to the heat seal paper and suppressing blocking, the heat seal layer may contain a lubricant in addition to the water-dispersible resin binder. A lubricant is a substance that can reduce the friction coefficient of the heat seal layer surface by being blended in the heat seal layer.

[0036] The lubricant is not particularly limited, and for example, wax, metal soap, fatty acid ester, etc. can be used. The lubricant may be used alone or in combination of two or more. 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, the wax component is easily formed on the coating layer surface, and 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 viewpoint 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 Michaelman 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 Co., Ltd.

[0037] When the heat seal 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, even more preferably 1 part by mass or more, and more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, relative to 100 parts by mass of the water-dispersible resin binder.

[0038] 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 and 30% by mass or less, more preferably 0.3% by mass or more, even more preferably 1% by mass or more, and more preferably 10% by mass or less, even more preferably 5% by mass or less.

[0039] In the present 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 contain a pigment.

[0040] -Pigments- In this embodiment, the heat seal layer may contain a pigment in addition to the water-dispersible resin binder. By containing the pigment, the problem of the heat seal layer coating surface sticking to the back surface of the heat seal paper and causing peeling (blocking) during production of the heat seal paper is suppressed, and a heat seal paper with excellent blocking resistance can be obtained.

[0041] The pigment preferably has an aspect ratio of 20 or more and 10,000 or less. When the aspect ratio of the pigment is 20 or more, it is preferable from the viewpoint of heat seal peel strength and blocking resistance. When the aspect ratio is 10,000 or less, it is easy to obtain and has excellent smoothness of the heat seal layer surface. The aspect ratio of the pigment is more preferably 25 or more, even more preferably 30 or more, particularly preferably 60 or more, and more preferably 1,000 or less, even 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.

[0042] 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, the pigment is prevented from protruding from the surface of the heat seal layer, and a heat seal layer having excellent blocking resistance can be obtained while maintaining heat sealability.

[0043] The length (average particle size) of the pigment is preferably 0.1 μm or more and 100 μm or less. If the length is 0.1 μm or more, the pigment is likely to be aligned parallel to the paper substrate. Also, if the length is 100 μm or less, there is little concern that a 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.

[0044] 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 about 20 to 30 pigment particles are contained within the image. The length of each pigment within the image is measured. Then, the average value of the obtained lengths is calculated and used as the length of the pigment. The length of the pigment is sometimes expressed as particle diameter.

[0045] 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, even more preferably 80 nm or less, even more preferably 50 nm or less, and particularly preferably 30 nm or less. Also, it is 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 in the state that it is contained in the heat seal layer is obtained as follows. A magnified photograph is taken of the cross section of the heat seal layer using an electron microscope. At this time, the magnification is set so that about 20 to 30 pigments are contained in the screen. The thickness of each pigment in the screen is measured. Then, the average value of the obtained thicknesses is calculated to be the thickness of the pigment.

[0046] 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 pigments, plastic pigments, binder pigments, plastic beads, and microcapsules.

[0047] Specific examples of mica include synthetic mica (e.g., swellable synthetic mica), white mica (muscovite), sericite (sericite), phlocopite, biotite (biotite), fluorine phlogopite (artificial mica), red mica, soda mica, vanadium mica, illite, chin mica, paragonite, brittle mica, etc. Specific examples of bentonite include montmorillonite.

[0048] Specific examples of kaolin include various types of kaolin such as kaolin, calcined kaolin, structured kaolin, and delaminated kaolin.

[0049] Among these, from the viewpoints of heat seal peel strength, blocking resistance, and economy, pigments having 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, with kaolin being even more preferred.

[0050] When the heat seal layer contains a pigment, the content of the pigment is, relative to 100 parts by mass of the water-dispersible resin binder, 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 even more preferably 8 parts by mass or more 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.

[0051] When the heat seal layer contains a pigment, the content of the pigment in the heat seal layer is preferably 1 mass % or more, more preferably 3 mass % or more, even more preferably 5 mass % or more, and even more preferably 8 mass % or more from the viewpoint of blocking resistance and recyclability, and is preferably 70 mass % or less, more preferably 30 mass % or less, and even more preferably 20 mass % or less from the viewpoint of heat sealability.

[0052] -Other Ingredients- The heat seal layer may contain other components in addition to the above-mentioned water-dispersible resin binder and, if necessary, a lubricant and / or a pigment, such as a silane coupling agent, a defoaming agent, a viscosity modifier, a leveling agent such as a surfactant or alcohol, and a colorant such as a coloring dye.

[0053] The method for coating the paper substrate with the heat seal layer is not particularly limited, and any 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, a shim sizer, etc.

[0054] 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 the drying equipment include a hot air dryer, an infrared dryer, a gas burner, and a hot plate. The drying temperature may be appropriately set in consideration of the drying time, etc. After drying the coating liquid, a supercalendering process may be performed. The supercalendering process is performed by passing the paper or the like to be treated between metal rolls or between a metal roll and an elastic roll, which are installed independently of the papermaking process, and applying heat, pressure, etc. The supercalendering process may be performed in one stage or multiple stages, and is not particularly limited.

[0055] The solvent of the heat seal layer coating liquid is not particularly limited, and water or an organic solvent such as ethanol, isopropyl alcohol, methyl ethyl ketone, toluene, etc. can be used. Among these, water is preferred as the dispersion medium of the heat seal layer coating liquid from the viewpoint of not causing the problem of volatile organic solvents. That is, the heat seal layer coating liquid is preferably an aqueous composition for heat seal layers.

[0056] 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.

[0057] (Laminate layer) When the heat seal layer is provided by lamination, it may be produced by appropriately selecting from conventionally known production methods, for example, dry lamination method, melt extrusion method, melt casting method, calendar method, etc. Among these, lamination with the paper base material without an adhesive layer is preferred from the viewpoint of reducing the environmental load, and the melt extrusion method and melt casting method are preferred, with the melt extrusion method being more preferred.

[0058] The resin constituting the heat seal layer may be either a crystalline or non-crystalline 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, it is preferable to use polyolefin resins such as polyethylene (LDPE, MDPE, HDPE, LLDPE, etc.), polypropylene, polymethylpentene, etc., and polylactic acid (PLA) as the thermoplastic resin, and it is more preferable to use polyethylene and polypropylene. These thermoplastic resins may be used alone or in combination of two or more kinds.

[0059] 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 multiple resins, or may be formed as a multilayer of these (e.g., single resin layer / single resin layer, single resin layer / mixed resin layer, mixed resin layer / mixed resin layer).

[0060] (Basic weight) The basis weight of the heat seal layer may be appropriately selected within a range in which 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 visibility, 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 viewpoints of reducing the environmental load, heat sealability and visibility. 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.

[0061] 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 visibility. 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.

[0062] <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.

[0063] (Basic weight) The basis weight of the wrapping paper of the present embodiment is preferably 20 g / m from the viewpoints of visibility and paper feedability. 2 More than 85g / m 2 More preferably, it is 25 g / m 2 More preferably, 30 g / m 2 More preferably, it is 75 g / m 2 Less than 60 g / m, more preferably 2 or less, even more preferably 55 g / m 2 More preferably 50 g / m 2 The following is the result. 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.

[0064] (Thickness) The thickness of the wrapping paper of this embodiment is preferably 20 μm or more and 100 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 90 μm or less, even more preferably 70 μm or less, and even more preferably 65 μm or less. When the thickness of the wrapping paper is within the above range, the desired tensile strength is obtained, and the wrapping paper has excellent visibility and excellent paper feed properties, which is preferable. The thickness of the wrapping paper can be adjusted to a 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.

[0065] (density) The density of the wrapping paper of this embodiment is preferably 0.5 g / cm 3 More than 1.0g / cm 3 More preferably, it is 0.65 g / cm 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 3More preferably, 0.85 g / cm 3 The following is the result. When the density of the wrapping paper is within the above range, the desired tensile strength is obtained, and the wrapping paper has excellent visibility and excellent paper feedability, which is preferable. The density of the wrapping paper can be adjusted to a desired range by appropriately adjusting the density of the paper base material 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.

[0066] (Opacity) From the viewpoint of visibility, the opacity of the wrapping paper of this embodiment is 80% or less. The opacity of the wrapping paper is preferably 15% or more and 70% or less, more preferably 60% or less, even more preferably 55% or less, and more preferably 25% or more, even more preferably 35% or more. When the opacity of the wrapping paper is within the above range, it is preferable because it has excellent visibility and ease of production. The opacity of the wrapping paper can be adjusted to a desired range by appropriately adjusting the basis weight and thickness of the paper base material and the heat seal layer. The opacity of the wrapping paper is measured by the method described in the Examples.

[0067] (Tensile strength) The wrapping paper of this embodiment has a tensile strength in the machine direction of 1.2 kN / m or more. Since the wrapping paper of this embodiment has a tensile strength in the machine direction of 1.2 kN / m or more, the wrapping paper of this embodiment has excellent paper feeding properties and is prevented from breaking during feeding. The longitudinal tear strength is preferably 1.3 kN / m or more and 10.0 kN / m or less, and from the viewpoint of ease of production, more preferably 8.0 kN / m or less, even more preferably 6.5 kN / m or less, and even more preferably 5.0 kN / m or less.

[0068] From the viewpoint of paper feedability, the tensile strength in the transverse direction is preferably 1.1 kN / m or more and 9.0 kN / m or less, more preferably 1.2 kN / m or more, and from the viewpoint of ease of manufacture, it is more preferably 7.0 kN / m or less, even more preferably 5.5 kN / m or less, and even more preferably 4.0 kN / m or less. The tensile strength is measured in accordance with JIS P 8116:2000. The tensile strength is adjusted by appropriately selecting the degree of beating of the raw pulp, the basis weight, thickness, density of the paper base material, the papermaking conditions of the paper base material, the type and thickness of the heat seal layer, etc. Increasing the degree of beating of the raw pulp tends to increase the tensile strength. Also, increasing the basis weight, thickness, density of the paper base material and the thickness of the heat seal layer tends to increase the tensile strength.

[0069] [Packaging] The packaging body of the present embodiment is a packaging body produced using the wrapping paper of the present embodiment, and is preferably a packaging body consisting only of the wrapping paper of the present embodiment. The packaging body of this embodiment may be a packaging body produced by any method, and may be used, for example, for three-sided sealed packaging bags, four-sided sealed packaging bags, pillow packaging bags, etc., but is preferably used for a packaging body that has a lid material and a base material with a recess, and can contain an item to be contained in the recess and seal by heat sealing the lid material and the base material. An example of a suitable package for this embodiment is shown in Fig. 1. Fig. 1 shows a schematic cross-sectional view of the package in the manufacturing process. It is preferable to place wrapping paper 2 as a base material on a mold 1 in which a recess is formed, conforming it to the shape of the recess, placing an item 4 to be contained on wrapping paper 2 as a base material, placing wrapping paper 3 as a lid material, and heat-sealing wrapping paper 2 as a base material and wrapping paper 3 as a lid material to obtain package 10. In Fig. 1, the arrow indicates the vertical direction of the wrapping paper. When forming the package shown in Figure 1, the wrapping paper needs to have the longitudinal conformability to conform to the recesses in the substrate, and conformability is particularly important for use in this application. Moreover, it is preferable that the contained object 4 has a rod-like shape. Thus, the wrapping paper of this embodiment is preferably used for wrapping when the contents are rod-shaped substances. EXAMPLES

[0070] The features of the present invention will be described in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, processing contents, 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. In addition, "parts" and "%" mean "parts by mass" and "% by mass" unless otherwise specified.

[0071] [Evaluation and Analysis] The raw pulp, wrapping paper, and wrapping bodies of the examples and comparative examples were evaluated and analyzed as follows.

[0072] [Raw pulp] <Measurement of Canadian Standard Freeness (CSF)> The Canadian Standard Freeness (CSF) of the raw pulp was measured in accordance with JIS P 8121-2:2012.

[0073] [Paper base material and wrapping paper] <Basic weight> The basis weights of the paper base material and the wrapping paper were measured in accordance with JIS P 8124: 2011. The basis weight of the heat seal layer was calculated from the values ​​of the paper base material and the wrapping paper.

[0074] <Thickness> The thickness of the paper base material and the wrapping paper are measured in accordance with JIS P 8118:2014, and a pressure of 100 kPa ± 10 kPa is applied to the circular area (200 mm 2 ) was added to the mixture and the thickness was measured. The thickness of the heat seal layer was calculated from the values ​​of the paper base material and the wrapping paper.

[0075] <density> The density of the paper base material and the wrapping paper was measured in accordance with JIS P 8118:2014. The density of the heat seal layer was calculated from the values ​​of the paper base material and the wrapping paper.

[0076] <Opacity> The opacity of the wrapping paper was measured in accordance with JIS P 8149:2000.

[0077] <Visibility> Using the wrapping paper obtained in each example, a packaged article (Frixion Ball 3 Slim manufactured by Pilot Corporation) was wrapped with a four-sided seal to obtain a package. The ease of checking the presence or absence of the packaged article from the outside of the obtained package was evaluated. The test was conducted by 10 people, and the total of the scores below (for the 10 people) was obtained and evaluated on a three-level scale ("A" to "C") as follows. 4: Ability to distinguish color and shape of packaged items 3: The shape of the packaged item can be identified 2: The presence or absence of packaged items can be confirmed 1: Unable to check whether package is present or not A: Total score is 30 or more. B: Total score is between 20 and 30 points C: Total score is less than 20 points

[0078] <Paper feeding properties> The wrapping paper obtained in each example was wound into a roll (paper width 300 mm, weight 10 kg) to prepare two test specimens for each example. One test specimen was placed on a free roller conveyor, and the end of the wrapping paper was gripped with a machine (Lamyman IKO-650EM manufactured by Ubon Co., Ltd.) and pulled at a speed of 2.5 m / min to observe whether it broke or not. Similarly, the other test specimen was pulled at a speed of 3.0 m / min to observe whether it broke or not, and was evaluated on the following three-point scale. A: No tear at either speed B: No tear at 2.5m / min, but tear at 3.0m / min C: Breaking at both speeds

[0079] <Heat sealability> The wrapping paper obtained in each example was cut into pieces measuring 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 subjected to a heat seal test under a set condition (temperature: 130°C, pressure: 1.0 kgf / cm2) using a heat seal tester (TP-701-B, manufactured by Tester Sangyo Co., Ltd.). 2 The four sides were heat sealed with a bonding width of 1 cm for 0.5 seconds. One tester peeled five samples for each example by pulling them by hand from the edge of the heat-sealed substrate, and rated the condition after peeling on a three-level scale. A: Paper layer peeled off almost entirely (80% or more of the surface area) B: Partial peeling of paper layer (20% to less than 80% of area) C: Almost no peeling of the paper layer (less than 20% by area)

[0080] [Example 1] (Preparation of paper substrate) Hardwood bleached kraft pulp (LBKP) was beaten to 400 mL of CSF, and a pulp slurry with a concentration of 3.8% by mass was obtained. 0.9 parts by mass of an anionic dry strength agent mainly composed of polyacrylamide (product name: PS-NH20B, manufactured by Arakawa Chemical Industries Co., Ltd.), 0.9 parts by mass of a cationic wet strength agent mainly composed of polyamide polyamine epichlorohydrin (product name: WS4024, manufactured by Seiko PMC Co., Ltd.), and 0.3 parts by mass of an alkyl ketene dimer (product name: AD1612, manufactured by Seiko PMC Co., Ltd.) as a neutral sizing agent were mixed with this pulp slurry and stirred to obtain a paper stock. The paper stock was adjusted to a concentration of 0.5% by mass, and made into paper on an inclined wire papermaking machine with a basis weight of 18 g / m. 2 Thus, a paper substrate of 100 g was obtained.

[0081] (Formation of heat seal layer) On one side of the obtained paper substrate, LDPE (LC522, manufactured by Japan Polyethylene Co., Ltd.) was laminated 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.

[0082] [Example 2] The paper base material is made on an inclined wire paper machine, with a basis weight of 30 g / m 2 A wrapping paper was obtained under the same conditions as in Example 1, except that the above-mentioned conditions were changed.

[0083] [Example 3] The paper base material is made on an inclined wire paper machine, with a basis weight of 30 g / m 2 A wrapping paper was obtained under the same conditions as in Example 1, except that the heat seal layer was formed by the following method. (Formation of heat seal layer) The coating amount of the heat seal layer after drying was 2.5 g / m on one side of the obtained paper base material. 2 The following heat seal layer coating material was applied using a gravure coater (using a smoothing bar) so as to form a heat seal layer. -Preparation of heat seal layer paint- A water dispersion of a styrene / butadiene copolymer (Nipol Latex LX407S12, solids concentration 46% by mass, glass transition temperature 18°C ​​(catalog value)) of 98 parts (solids equivalent) and a paraffin wax emulsion (Hydrin L-700, solids concentration 30% by mass, manufactured by Chukyo Yushi Co., Ltd.) of 2 parts (solids equivalent) were mixed, water was added to the mixture so that the solids concentration was 33% by mass, and the mixture was stirred to prepare a heat seal layer coating material (solids concentration 33% by mass). The solubility of the styrene / butadiene copolymer in water at 25°C was 10g / L or less.

[0084] [Example 4] The paper base material is made on an inclined wire paper machine with a basis weight of 50 g / m 2 A packaging base material was obtained under the same conditions as in Example 1, except that the above-mentioned conditions were changed.

[0085] [Comparative Example 1] The paper base material is made on an inclined wire paper machine, with a basis weight of 70 g / m 2 A wrapping paper was obtained under the same conditions as in Example 1, except that the above-mentioned conditions were changed.

[0086] [Comparative Example 2] The paper base material is made on an inclined wire paper machine, with a basis weight of 15 g / m 2 A wrapping paper was obtained under the same conditions as in Example 1, except that the above-mentioned conditions were changed.

[0087] The obtained wrapping paper was subjected to the above-mentioned evaluations. The results are shown in the table below.

[0088] [Table 1]

[0089] From the results of the Examples and Comparative Examples, it was found that the packages obtained using the wrapping paper of this embodiment had excellent visibility, and furthermore, the wrapping paper of this embodiment had excellent paper feeding properties and heat sealing properties. On the other hand, the basis weight of the paper base material is 60 g / m 2 The package obtained using the wrapping paper of Comparative Example 1, in which the opacity of the wrapping paper exceeded 80%, had poor visibility and the wrapping paper had poor heat sealability. The wrapping paper of Comparative Example 2, in which the tensile strength in the longitudinal direction was less than 1.2 kN / m, had poor paper feedability. [Industrial Applicability]

[0090] The wrapping paper of the present invention is suitable as a flexible packaging material, has excellent visibility, excellent paper feedability, and excellent heat sealability, and is suitably used for forming packaging bodies. [Explanation of symbols]

[0091] 1. Mold 2. Wrapping paper as base material 3. Wrapping paper for the lid 4. Items Detained 10 Packaging

Claims

1. A wrapping paper having a heat seal layer on a paper base material, The Canadian standard freeness of the raw pulp of the paper base material is 300 mL or more and 700 mL or less, The paper base material has a basis weight of 60 g / m ２ is as follows: The density of the paper base material is 0.8 g / cm 3 or less; The content of the paper base material in the wrapping paper is 50% by mass or more, The opacity of the wrapping paper is 80% or less; The wrapping paper has a longitudinal tensile strength of 1.2 kN / m or more and 5.0 kN / m or less, The tensile strength of the wrapping paper in the lateral direction is 1.2 kN / m or more and 4.0 kN / m or less. wrapping paper.

2. The wrapping paper of claim 1 having a thickness of 90 μm or less.

3. Basis weight 75g / m ２ The wrapping paper according to claim 1 or 2, wherein:

4. 3. 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. 3. The wrapping paper according to claim 1, wherein the paper base material and the heat seal layer are directly laminated together.

6. The heat seal layer has a basis weight of 20 g / m ２ or a laminate layer having a basis weight of 3 g / m ２ The wrapping paper according to claim 1 or 2, wherein the coating layer is less than 100 μm.

7. A cover material and a base material having a recess, A package capable of housing an object to be housed in the recess and sealing the recess by heat sealing the lid material and the base material, The lid material and the base material are made of the wrapping paper according to claim 1 or 2. packaging.

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