Heat-sealable paper, rolls, packaging bags and packaging materials

Abstract

To provide heat-sealable paper that reduces environmental impact, is easy to open, and is resistant to tearing during opening, as well as rolls, packaging bags, and packaging bodies made using the heat-sealable paper. [Solution] A heat-sealable paper having a heat-seal layer on one side of a paper substrate, wherein the paper substrate content in the heat-sealable paper is 50% by mass or more, and the geometric mean of the pure bending stiffness in the longitudinal direction and the pure bending stiffness in the transverse direction of the heat-sealable paper is 0.80 g·cm 2 A heat-sealable paper having a length of 1.8 kN / m or less, a longitudinal tensile strength of 1.8 kN / m or more, and a static friction coefficient of 0.750 or less on the side of the heat-sealable layer opposite to the paper substrate.

Description

Technical Field

[0001] The present invention relates to heat-sealing paper, rolls, packaging bags, and packages.

Background Art

[0002] Packages using the heat-sealing method are widely used not only for packaging general industrial products but also for packaging food, pharmaceuticals, medical devices, etc.

[0003] In recent years, the plastic waste problem has been worsening. Among the world's plastic production volume, the plastic production volume in the packaging container sector is large, which has caused plastic waste. Plastic is not decomposed semi-permanently, and this waste is microplastics in the natural environment, having a serious adverse impact on the ecosystem. As a countermeasure, it has been proposed to replace plastic with paper.

[0004] For example, in Patent Document 1, for the purpose of providing paper for a flexible packaging material that can be formed into a bag by a bag-making machine and a flexible package using this flexible packaging material paper, a paper base material and a heat-sealing layer on at least one outermost surface are provided. The paper base material has a thickness of 25 μm or more and 100 μm or less, and the ratio of pulp to all papermaking fibers contained in the paper base material exceeds 90% by weight, and a flexible packaging material paper characterized by satisfying specific conditions is disclosed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The packaging bag using the flexible packaging material paper described in Patent Document 1 has insufficient ease of opening when opening. The present invention aims to provide heat-sealable paper that reduces environmental impact, is easy to open, and is resistant to tearing during opening, as well as rolls, packaging bags, and packaging bodies made using the heat-sealable paper. [Means for solving the problem]

[0007] The inventors have found that the above problems can be solved by providing a heat-sealable paper having a heat-seal layer on one side of a paper substrate, by setting the content of the paper substrate in the heat-sealable paper, the geometric mean of the pure bending stiffness in the longitudinal direction and the pure bending stiffness in the transverse direction of the heat-sealable paper, and the tensile strength in the longitudinal direction of the heat-sealable paper to be above a specific value, and by setting the static friction coefficient of the side of the heat-seal layer opposite to the paper substrate to be below a specific value. In other words, the present invention is as follows: <1> ~ <10> Regarding. <1> A heat-sealable paper having a heat-seal layer on one side of a paper substrate, The paper substrate content in the heat-sealing paper is 50% by mass or more. The geometric mean of the pure bending stiffness in the longitudinal and transverse directions of the heat-sealing paper is 0.80 g·cm. 2 It is less than / cm, The tensile strength of the heat-sealing paper in the longitudinal direction is 1.8 kN / m or more. A heat-sealable paper in which the static friction coefficient of the heat-sealable layer on the side opposite to the paper substrate is 0.750 or less. <2> The vertical bending stiffness of the heat-sealing paper is 1.20 g·cm. 2 It is less than / cm. <1> The heat-sealing paper described above. <3> The lateral pure bending stiffness of the heat-sealing paper is 0.60 g·cm. 2 It is less than / cm. <1> or <2> The heat-sealing paper described above. <4> The heat seal layer contains a slip agent. <1> ~ <3> Heat seal paper as described in one of the following. <5> The heat-seal layer is the laminate layer. <1> ~ <4> Heat seal paper as described in one of the following. <6> Basis weight 80g / m² 2The following is: <1> ~ <5> Heat seal paper as described in one of the following. <7> For packaging bags having a heat-seal layer on the inside, <1> ~ <6> Heat seal paper as described in one of the following. <8> <1> ~ <7> A roll made from heat-sealable paper described in any one of the following, with both ends of the overlapping heat-sealable layers heat-sealed vertically, and wound vertically. <9> <1> ~ <7> Heat seal paper or <8> A packaging bag using the roll described above. <10> <9> A package containing the contents in the packaging bag described above. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide heat-sealable paper that reduces the environmental burden, is easy to open, and is resistant to tearing during opening, as well as rolls, packaging bags, and packaging bodies made using the heat-sealable paper. [Modes for carrying out the invention]

[0009] [Heat seal paper] The heat-sealable paper of this embodiment is a heat-sealable paper having a heat-seal layer on one side of a paper substrate, wherein the paper substrate content in the heat-sealable paper is 50% by mass or more, and the geometric mean of the pure bending stiffness in the longitudinal direction and the pure bending stiffness in the transverse direction of the heat-sealable paper is 0.80 g·cm 2 The coefficient of friction is 0.750 or less on the side of the heat-sealing layer opposite the paper substrate, the tensile strength in the longitudinal direction of the heat-sealing paper is 1.80 kN / m or more, and the coefficient of static friction of the heat-sealing layer on the side opposite the paper substrate is 0.750 or less.

[0010] According to the heat-sealable paper of this embodiment, it is possible to obtain packaging bags and packaging bodies that reduce the environmental burden, are easy to open (excellent ease of opening), and are resistant to tearing during opening. The reason the above effects are achieved is that the paper base material content in the heat-sealing paper is 50% by mass or more, resulting in a plastic material content of 50% by mass or less, thus reducing the environmental impact. In addition, the geometric mean of the pure bending stiffness in the longitudinal and transverse directions of the heat-sealing paper is 0.80 g·cm. 2 The coefficient of friction is less than / cm, and the static friction coefficient of the heat-seal layer on the side opposite the paper substrate is 0.750 or less. This makes it possible for opposing heat-seal layers to slide easily against each other when used in packaging, resulting in excellent openability. Furthermore, the tensile strength of the heat-seal paper in the longitudinal direction is 1.80 kN / m or more, making it less likely to tear due to stress during opening. Furthermore, the reasons for obtaining the above effects are not limited to these. The present invention will be described in more detail below.

[0011] In this specification, a numerical range expressed as "X~Y" means a numerical range that includes X as the lower limit and Y as the upper limit. When a numerical range is described in steps, the upper and lower limits of each numerical range can be combined in any way. Furthermore, unless otherwise specified in this specification, operations and measurements of physical properties, etc., shall be performed under conditions of room temperature (20~25°C) / relative humidity (RH) 40~50%. In heat-sealable paper and paper substrates, the longitudinal direction refers to the papermaking direction (MD) in the paper substrate, and the transverse direction refers to the direction perpendicular to the papermaking direction (CD). Each component contained in the heat-sealing paper may be used individually or in combination of two or more components. The front side of heat-seal paper refers to the side that will be facing outwards when the paper is made into a packaging bag. The back side of heat-seal paper refers to the side that will be facing inwards when the paper is made into a packaging bag.

[0012] <Paper base material> The paper substrate is preferably paper that is commonly used with plant-derived pulp as its main component, and more preferably paper that is primarily composed of wood pulp. Furthermore, it is preferable that the paper is primarily composed of pulp that is easily dispersed in water due to mechanical disintegration. Specifically, examples include sun-dried or non-sun-dried kraft paper, fine paper, cardboard, liner paper, coated paper, single-sided glossy paper, glassine paper, and the like. Among these, from the perspective of obtaining a packaging body with excellent easy-opening property and a packaging bag that is not easily torn by the operation during opening, sun-dried kraft paper, glassine paper, and graphfan paper are preferred. From the perspective of obtaining a packaging body with excellent visibility of the contained items, glassine paper and graphfan paper are more preferred. Generally, glassine paper mainly contains softwood chemical pulp as the pulp raw material, is highly beaten, formed into paper at an acidic to neutral pH, and finished by compression treatment using a supercalender or the like. Specific examples of the pulp preferably include chemical pulp made from softwood materials such as spruce and hemlock. In addition, chemical pulp made from hardwood materials, mechanical pulp, waste paper, synthetic pulp, etc. may be mixed and blended.

[0013] (Grammage) From the perspective of obtaining a packaging bag that is not easily torn by the operation during opening, the grammage of the paper base material is preferably 22.0 g / m 2 or more, more preferably 24.5 g / m 2 or more, still more preferably 28.0 g / m 2 or more. And from the perspective of obtaining a packaging body with excellent easy-opening property, it is preferably 65.0 g / m 2 or less, more preferably 60.0 g / m 2 or less, still more preferably 55.0 g / m 2 or less, even more preferably 50.0 g / m 2 or less, still more preferably 45.0 g / m 2 or less, even more preferably 40.0 g / m 2 or less, still more preferably 35.0 g / m 2 or less. The grammage of the paper base material is measured in accordance with JIS P 8124:2011.

[0014] (Thickness) Furthermore, the thickness of the paper substrate is preferably 22 μm or more, more preferably 24.5 μm or more, and even more preferably 28 μm or more, from the viewpoint of obtaining a packaging bag that is difficult to tear during opening, and from the viewpoint of obtaining a packaging body with excellent ease of opening, it is preferably 60 μm or less, more preferably 55 μm or less, even more preferably 50 μm or less, even more preferably 45 μm or less, even more preferably 40 μm or less, and even more preferably 35 μm or less.

[0015] (density) From the viewpoint of ease of manufacturing heat-sealable paper, the density of the paper substrate is preferably 0.65 g / cm³. 3 More preferably 0.70 g / cm³ 3 More preferably 0.75 g / cm³ 3 More preferably, 0.85 g / cm³ 3 More preferably 0.90 g / cm³ 3 More preferably, 0.95 g / cm³ 3 The above applies, and preferably 1.25 g / cm³. 3 More preferably, 1.20 g / cm³ 3 More preferably, 1.15 g / cm³ 3 The following applies: The density of the paper substrate is calculated from the basis weight and thickness of the paper substrate, which are obtained by the measurement method described above.

[0016] (Irregular Freeness) In this embodiment, from the viewpoint of obtaining a packaging bag and packaging body with excellent visibility of the contents, it is preferable that the irregular freeness of the pulp constituting the paper substrate is 100 mL or more and 800 mL or less. Here, irregular freeness refers to the freeness (filtration rate) measured in the Canadian standard filtration rate method specified in JIS P 8121:2012, by changing the pulp sample amount from 3 g to 0.3 g and changing the JIS standard screen plate to an 80 mesh wire. It is preferable that the irregular freeness of the pulp constituting the paper substrate is above the lower limit, as this improves the dimensional stability of the paper substrate and makes it less prone to bumps, and that it is below the upper limit, as this maintains the transparency of the paper substrate. The irregular freeness of the pulp constituting the paper substrate is more preferably 300 mL to 700 mL, and even more preferably 400 mL to 600 mL. Known methods can be used to beat the pulp in order to adjust the irregular freeness. The irregular freeness of the pulp constituting the paper substrate is specifically measured by the method described in the examples. Note that "irregular freeness of the pulp constituting the paper substrate" refers to the irregular freeness of the disintegrated pulp obtained by disintegrating the paper substrate.

[0017] When bleached kraft paper is used as the paper substrate, the freeness (Canadian Standard CSF) of the disintegrated pulp obtained by disintegrating the pulp constituting the bleached kraft paper is preferably 200 mL to 700 mL, more preferably 300 mL to 600 mL, and even more preferably 350 mL to 550 mL. Specifically, the freeness of the disintegrated pulp obtained by disintegrating the pulp constituting the bleached kraft paper is measured by the method described in the examples.

[0018] The static friction coefficient of the surface of the heat-sealing paper is preferably 0.100 or higher, more preferably 0.150 or higher, even more preferably 0.200 or higher, and even more preferably 0.220 or higher, and preferably 0.500 or lower, more preferably 0.400 or lower, and even more preferably 0.300 or lower, from the viewpoint of making it easier to wind the heat-sealing paper in the vertical direction into a roll. The static friction coefficient is measured in accordance with JIS P 8147:2010. When the surface of the heat-sealable paper of this embodiment is the side opposite to the heat-seal layer of the paper substrate (i.e., the heat-sealable paper of this embodiment does not have an arbitrary layer on the side opposite to the heat-seal layer of the paper substrate), the static friction coefficient of the surface can be adjusted by the type of raw pulp, the concentration and degree of pulp slurry during beating, the presence or absence of calendering and the processing conditions, etc. Specifically, when the linear pressure is reduced during calendering, the static friction coefficient of the surface tends to increase. Also, when the pulp is beated to a high degree, the static friction coefficient of the surface tends to decrease. Furthermore, when the surface of the heat-sealable paper of this embodiment is the surface of an arbitrary layer (i.e., the heat-sealable paper of this embodiment has an arbitrary layer on the side opposite to the heat-seal layer of the paper substrate), the static friction coefficient of the surface can be adjusted by the printing method and conditions, coating method and conditions, etc. Specifically, when an arbitrary layer is formed by curtain coating, the static friction coefficient of the surface tends to increase. Furthermore, forming an arbitrary layer by blade coating tends to decrease the surface static friction coefficient.

[0019] <Heat seal layer> The heat-sealable paper of this embodiment has a heat-sealing layer on one side of the paper substrate. The heat-sealing layer is the uppermost layer. The heat seal layer is a layer that is melted and bonded by heating, ultrasound, or the like. The heat seal layer may be provided by coating, dry lamination, or extrusion lamination. Among these, from the viewpoint of ease of manufacturing heat seal paper, it is preferable to provide it by lamination. From the viewpoint of obtaining a package with excellent ease of opening, it is preferable that the heat seal layer be formed on the entire surface of one side of the paper substrate. Furthermore, from the viewpoint of ease of manufacturing the heat seal paper and obtaining a package with excellent visibility of the contents, it is preferable that the heat seal layer be laminated directly onto the paper substrate or laminated via an adhesive layer.

[0020] The heat seal layer preferably contains a slip agent from the viewpoint of reducing the static friction coefficient on the back surface of the heat seal paper.

[0021] (Laminate layer) When the heat seal layer is provided by lamination, it can be manufactured by appropriately selecting from conventionally known manufacturing methods, such as dry lamination, melt extrusion, melt casting, and calendering. Among these, dry lamination is preferred from the viewpoint of ease of manufacturing the heat seal paper of this embodiment.

[0022] Any thermoplastic resin, whether crystalline or amorphous, can be used as the resin constituting the heat seal layer. Examples of thermoplastic resins include polyethylene (low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), etc.), polyolefin resins such as polypropylene and polymethylpentene, polyester resins such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), polyamide resins, biodegradable resins such as polylactic acid (PLA), polyhydroxybutyrate (PHB), polybutylene succinate (PBS), poly(butylene adipate-co-butylene terephthalate) (PBAT), polycaprolactone (PCL), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), as well as polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene (ABS) resin, acrylic resin, and modified polyphenylene ether (PPE). Among these, it is preferable to use polyethylene (LDPE, MDPE, HDPE, LLDPE, etc.), polyolefin resins such as polypropylene and polymethylpentene, or polylactic acid (PLA) as the thermoplastic resin, and it is more preferable to use polyethylene.

[0023] A resin film containing a slip agent can also be used as the laminate layer. Specific examples of resin films containing a slip agent include LL-XMTN (PE film, manufactured by Futamura Chemical Co., Ltd.) and LL-MT NR (PE film, manufactured by Futamura Chemical Co., Ltd.).

[0024] The heat seal layer may be formed as a single layer of a single resin, as a single layer formed by mixing multiple resins, or as a multilayer of these (for example, single resin layer / single resin layer, single resin layer / mixed resin layer, mixed resin layer / mixed resin layer).

[0025] (Basic weight) The basis weight of the heat-seal layer should be appropriately selected within a range where the paper substrate content in the heat-seal paper is 50% by mass or more. When a heat seal layer is provided by coating, the basis weight of the heat seal layer is preferably 1 g / m² from the viewpoint of reducing environmental impact and ensuring heat sealability. 2 More than 2g / m 2 The above, and preferably 20 g / m² 2 More preferably 10 g / m 2 More preferably 5 g / m 2 More preferably, 3 g / m 2 The following applies: Furthermore, when the heat seal layer is provided by lamination, the basis weight of the heat seal layer is preferably 5 g / m² from the viewpoint of reducing environmental impact and heat sealability. 2 In addition, a comfortable 7g / m 2 More preferably 10 g / m 2 Therefore, from the viewpoint of obtaining a package with excellent ease of opening, 25 g / m² is preferred. 2 More preferably 20 g / m 2 The following applies: Furthermore, when the heat seal layer is provided by lamination, the thickness of the heat seal layer is preferably 5 μm or more, more preferably 9 μm or more, even more preferably 12 μm or more, and preferably 24 μm or less, more preferably 21 μm or less, from the same viewpoint.

[0026] <Any layer> The heat-sealable paper of this embodiment may have an arbitrary layer on the side of the paper substrate opposite to the heat-sealable layer, but it is preferable that it does not have an arbitrary layer from the viewpoint of making it easier to wind the heat-sealable paper in the vertical direction into a roll. Specific examples of arbitrary layers include a printing layer, a coating layer, a laminating layer, and a barrier layer.

[0027] <Characteristics of heat-sealable paper> (Paper base material content) In the heat-sealable paper of this embodiment, from the viewpoint of reducing environmental impact, the content of paper substrate in the heat-sealable paper is 50% by mass or more, preferably 53% by mass or more, more preferably 55% by mass or more, and from the viewpoint of heat-sealability, it is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less.

[0028] (Basic weight) From the viewpoint of obtaining a packaging bag that is resistant to tearing during opening, the basis weight of the heat-sealing paper in this embodiment is preferably 22 g / m². 2 Above, a comfortable 30g / m 2 More preferably 35 g / m² 2 More preferably 40 g / m² 2 More preferably 45 g / m² 2 Therefore, from the viewpoint of obtaining a package that is easy to open and a package that is easy to see the contents of, it is preferably 80 g / m². 2 More preferably, 75 g / m 2 More preferably, 70 g / m 2 More preferably 65 g / m 2 More preferably, 60 g / m 2 The following applies: The basis weight of the heat-sealable paper can be adjusted to a desired range by appropriately adjusting the basis weight of the paper substrate and the heat-sealable layer. The basis weight of the heat-sealable paper is measured by the method described in the examples.

[0029] (thickness) The thickness of the heat-sealing paper in this embodiment is preferably 30 μm or more, more preferably 35 μm or more, and even more preferably 40 μm or more, from the viewpoint of obtaining a packaging bag that is difficult to tear during opening, and from the viewpoint of obtaining a packaging body that is easy to open and has excellent visibility of the contents, it is preferably 80 μm or less, more preferably 75 μm or less, even more preferably 70 μm or less, even more preferably 66 μm or less, even more preferably 62 μm or less, even more preferably 58 μm or less, and even more preferably 54 μm or less. The thickness of the heat-sealable paper can be adjusted to a desired range by appropriately adjusting the thickness of the paper substrate and the heat-sealable layer. The thickness of the heat-sealing paper is measured by the method described in the examples.

[0030] (density) From the viewpoint of ease of manufacturing the heat-sealable paper, the density of the heat-sealable paper in this embodiment is preferably 0.70 g / cm³. 3 More preferably 0.75 g / cm³ 3 More preferably 0.80 g / cm³ 3 More preferably, 0.85 g / cm³ 3 More preferably 0.90 g / cm³ 3 More preferably, 0.95 g / cm³ 3 The above is true, and preferably 1.20 g / cm³. 3 More preferably, 1.15 g / cm³ 3 More preferably, 1.10 g / cm³ 3 The following applies: The density of the heat-sealable paper can be set to a desired range by appropriately adjusting the density of the paper substrate and the type of resin used in the heat-sealing layer. The density of heat-sealable paper is calculated from its basis weight and thickness.

[0031] (Pure bending stiffness) The synergistic mean of the pure bending stiffness in the longitudinal direction and the pure bending stiffness in the transverse direction of the heat-sealable paper according to this embodiment is 0.80 g·cm², from the viewpoint of obtaining a package with excellent ease of opening.2 It is less than or equal to / cm, preferably 0.60g·cm 2 Less than / cm, more preferably 0.40g·cm 2 Less than or equal to / cm, more preferably 0.20g·cm 2 Less than or equal to / cm, more preferably 0.16g·cm 2 The density should be less than or equal to / cm, and from the viewpoint of ease of manufacturing the heat-sealable paper, preferably 0.01 g·cm 2 / cm or more, more preferably 0.02g·cm 2 / cm or more, more preferably 0.03g·cm 2 It is greater than / cm.

[0032] In this embodiment, the longitudinal pure bending stiffness of the heat-sealable paper is preferably 1.20 g·cm², from the viewpoint of obtaining a package with excellent ease of opening. 2 Less than or equal to / cm, more preferably 0.80g·cm 2 Less than or equal to / cm, more preferably 0.40g·cm 2 Less than or equal to / cm, more preferably 0.20g·cm 2 The density should be less than or equal to / cm, and from the viewpoint of ease of manufacturing the heat-sealable paper, preferably 0.01 g·cm 2 / cm or more, more preferably 0.03g·cm 2 / cm or more, more preferably 0.05g·cm 2 It is greater than / cm.

[0033] From the viewpoint of obtaining a package with excellent ease of opening, the synergistic mean of the transverse pure bending stiffness of the heat-sealable paper according to this embodiment is preferably 0.60 g·cm. 2 Less than / cm, more preferably 0.40g·cm 2 Less than or equal to / cm, more preferably 0.20g·cm 2 Less than or equal to / cm, more preferably 0.15g·cm 2 Less than or equal to / cm, more preferably 0.12g·cm 2 The density should be less than or equal to / cm, and from the viewpoint of ease of manufacturing the heat-sealable paper, preferably 0.01 g·cm 2 / cm or more, more preferably 0.02g·cm 2 It is greater than / cm.

[0034] The pure bending stiffness in the longitudinal and transverse directions of heat-sealable paper can be adjusted by the type of raw pulp, the type and amount of paper strength enhancer, the concentration and degree of pulp slurry during beating, the drying conditions during papermaking (e.g., the position of the drying device in the paper machine), whether or not calendering is performed and the conditions of the calendering, and the basis weight. For example, increasing the basis weight or thickness of the paper substrate tends to increase the pure bending stiffness in both the longitudinal and transverse directions. The longitudinal and transverse pure bending stiffness of the heat-sealable paper is measured by the method described in the examples.

[0035] (Tensile strength) The longitudinal tensile strength of the heat-seal paper in this embodiment is 1.80 kN / m or more, preferably 1.90 kN / m or more, more preferably 2.00 kN / m or more, even more preferably 2.10 kN / m or more, and even more preferably 2.20 kN / m or more, and from the viewpoint of obtaining a packaging body with excellent ease of opening, it is preferably 5.00 kN / m or less, more preferably 4.50 kN / m or less, even more preferably 4.00 kN / m or less, even more preferably 3.50 kN / m or less, and even more preferably 3.00 kN / m or less. Tensile strength is measured in accordance with JIS P 8113:2006. Tensile strength is adjusted by appropriately selecting the degree of beating of the raw pulp, the basis weight, thickness, and density of the paper substrate, the papermaking conditions for the paper substrate, and the type and thickness of the heat seal layer. For example, increasing the basis weight of the paper substrate or the heat seal layer tends to increase tensile strength.

[0036] (Static friction coefficient) The static friction coefficient on the back surface of the heat-sealing paper in this embodiment is 0.750 or less, preferably 0.600 or less, more preferably 0.450 or less, even more preferably 0.300 or less, and even more preferably 0.250 or less, from the viewpoint of obtaining a package with excellent ease of opening, and preferably 0.100 or more, and more preferably 0.150 or more, from the viewpoint of ease of handling when used as a packaging bag. The static friction coefficient on the back surface of the heat-sealing paper in this embodiment is considered to be isotropic. The static friction coefficient is measured in accordance with JIS P 8147:2010. The static friction coefficient on the back surface of the heat-seal paper in this embodiment is adjusted according to the method of forming the heat-seal layer. When the heat-seal layer is formed by a dry lamination method, it is adjusted, for example, by the content of the slip agent in the heat-seal layer. A higher content of the slip agent tends to decrease the static friction coefficient on the back surface. When the heat-seal layer is formed by a melt-extrusion lamination method, the static friction coefficient on the back surface is adjusted, for example, by the surface roughness of the cooling roll. Reducing the surface roughness of the cooling roll tends to decrease the static friction coefficient on the back surface. When the heat-seal layer is formed by coating, the static friction coefficient on the back surface is adjusted, for example, by the content of the slip agent. A higher content of the slip agent tends to decrease the static friction coefficient on the back surface.

[0037] (Opacity) The opacity of the heat-seal paper in this embodiment is preferably 60% or less, more preferably 55% or less, even more preferably 50% or less, even more preferably 45% or less, even more preferably 40% or less, and even more preferably 35% or less, from the viewpoint of obtaining a package with excellent visibility of the contents, and preferably 5% or more, more preferably 10% or more, and even more preferably 15% or more, from the viewpoint of ease of manufacturing the heat-seal paper. The opacity of the heat-sealable paper can be set to a desired range by appropriately adjusting the type of paper substrate, the basis weight of the paper substrate and the heat-sealable layer, and their respective thicknesses. The opacity of the heat-sealable paper is measured by the method described in the examples.

[0038] 〔roll〕 The roll of this embodiment is formed by overlapping the heat-sealing layers of the heat-sealing paper of this embodiment, with both ends heat-sealed in the vertical direction, and then winding it up in the vertical direction. Using the roll of this embodiment, the packaging bags of this embodiment can be manufactured efficiently.

[0039] [Packaging bag] The packaging bag of this embodiment is manufactured by heat-sealing the heat-seal layers of the heat-seal paper of this embodiment, with the heat-seal layers on the inside. Preferably, the packaging bag of this embodiment is made only of the heat-seal paper of this embodiment. Examples of the packaging bags in this embodiment include three-side sealed packaging bags, four-side sealed packaging bags, and pillow packaging bags, with three-side sealed packaging bags and four-side sealed packaging bags being preferred.

[0040] [Packaging] The packaging of this embodiment is formed by placing the contents to be contained in the packaging bag of this embodiment. Examples of the contents to be contained include metal fittings, food, stationery, daily necessities, and miscellaneous goods. The contents may be one item or two or more items. [Examples]

[0041] Examples are given below to illustrate the present invention in detail, but the present invention is not limited to these examples. Unless otherwise specified, the following operations were carried out under conditions of 23°C and 50% relative humidity. In the examples and comparative examples, "parts" and "%" refer to "parts by mass" and "mass%", respectively, unless otherwise specified.

[0042] [Example 1] Paper base material with a basis weight of 23.0 g / m² 2Glassine paper (manufactured by Oji F-Tex Co., Ltd., 100% by mass of bleached coniferous kraft pulp, irregular freeness of disintegrated pulp 500 mL) was used. On one side of the PE film (manufactured by Futamura Chemical Co., Ltd., LL-XMTN), an adhesive mixture of 10 parts DIC Dry LX-500 (manufactured by DIC Corporation) and 1 part DIC Dry KW-75 (manufactured by DIC Corporation) was applied at a rate of 5 g / m². 2 The coating was applied to a thickness of 5 μm. A PE film coated with adhesive was dry-laminated to one side of the glassine paper to obtain heat-sealable paper.

[0043] [Example 2] Glassine paper with a basis weight of 30.5 g / m² 2 Heat-sealable paper was obtained in the same manner as in Example 1, except that (100% by mass of bleached softwood kraft pulp manufactured by Oji F-Tex Co., Ltd., with an irregular freeness of disintegrated pulp of 500 mL) was used.

[0044] [Example 3] Glassine paper with a basis weight of 50.0 g / m² 2 Heat-sealable paper was obtained in the same manner as in Example 1, except that (100% by mass of bleached softwood kraft pulp manufactured by Oji F-Tex Co., Ltd., with an irregular freeness of disintegrated pulp of 500 mL) was used.

[0045] [Example 4] A heat-sealable paper was obtained in the same manner as in Example 2, except that the heat-seal layer was made of a low-slip PE film (manufactured by Futamura Chemical Co., Ltd., LL-MTNR).

[0046] [Example 5] Glassine paper with a basis weight of 30.0 g / m² 2 Heat-sealable paper was obtained in the same manner as in Example 1, except that bleached kraft paper (manufactured by Oji F-Tex Co., Ltd., 100% by mass of bleached hardwood kraft pulp, with a freeness of 420 mL of disintegrated pulp) was used.

[0047] [Comparative Example 1] Glassine paper with a basis weight of 20.0 g / m² 2Heat-sealable paper was obtained in the same manner as in Example 1, except that it was manufactured using the following method. Bleached softwood kraft pulp (NBKP) was beaten to an irregular freeness of 250 mL of disintegrated pulp to obtain a 3.8% concentration pulp slurry. To this pulp slurry, 0.9 parts of an anionic dry strength enhancer mainly composed of polyacrylamide (product name: PS-NH20B, manufactured by Arakawa Chemical Industries, Ltd.), 0.9 parts of a cationic wet strength enhancer mainly composed of polyamide polyamine epichlorohydrin (product name: WS4024, manufactured by Seikoh PMC Co., Ltd.), and 0.1 parts of alkyl ketene dimer as a neutral sizing agent (product name: AD1612, manufactured by Seikoh PMC Co., Ltd.) were mixed per 100 parts of pulp solids, and the mixture was stirred to obtain a paper stock. The pulp was adjusted to a concentration of 0.5%, paper was made using a standard papermaking machine, and the resulting sheets were dried using a cylinder dryer to achieve a moisture content of 15%. Immediately after drying, the sheets were passed through a thermal calender consisting of metal and elastic rolls to obtain a basis weight of 20.0 g / m². 2 I obtained glassine paper.

[0048] [Comparative Example 2] Glassine paper with a basis weight of 75.0 g / m² 2 Heat-sealable paper was obtained in the same manner as in Example 1, except that (100% by mass of bleached softwood kraft pulp manufactured by Oji F-Tex Co., Ltd., with an irregular freeness of disintegrated pulp of 500 mL) was used.

[0049] [Comparative Example 3] Heat-sealable paper was obtained in the same manner as in Example 2, except that the heat-seal layer was changed to a PE film (LF440B, manufactured by Nippon Polyethylene Co., Ltd.) that does not contain a slip agent.

[0050] [Measurement and evaluation methods] The following measurements and evaluations were performed on the paper substrate and the resulting heat-sealable paper. <Basic weight> The basis weight of the paper substrate and heat-sealing paper was measured in accordance with JIS P 8124:2011. The basis weight of the heat-sealing layer was calculated from the values ​​of the paper substrate and heat-sealing paper.

[0051] <thickness> The thickness of the paper substrate and heat-sealing paper was measured in accordance with JIS P 8118:2014. The thickness of the heat-sealing layer was calculated from the values ​​for the paper substrate and packaging substrate.

[0052] <Irregular Freeness> The irregular freeness of the pulp constituting the paper substrate was measured using pulp that had been disintegrated in accordance with JIS P 8220-1:2012 as a sample, using the Canadian standard filtration method specified in JIS P 8121:2012, but with the pulp sample amount changed from 3g to 0.3g and the JIS standard screen plate changed to an 80-mesh wire.

[0053] <Freeness> The freeness (Canadian Standard CSF) of the pulp constituting the paper substrate was measured in accordance with JIS P 8121-2:2012, using pulp that had been disintegrated in accordance with JIS P 8220-1:2012 as a sample.

[0054] <density> The density of the paper substrate and heat-sealable paper was calculated from the basis weight and thickness.

[0055] <Static friction coefficient> The static friction coefficients of the front and back surfaces of the heat-sealing paper were measured in accordance with JIS P 8147:2010.

[0056] <Tensile strength> The tensile strength of the heat-sealable paper was measured in accordance with JIS P 8113:2006.

[0057] <Pure bending stiffness> After conditioning the heat-sealing paper to 23°C and 50% RH, test specimens were cut to a width of 80 x 80 mm and bent into MD and CD (folded perpendicular and parallel to the flow direction) sections. These specimens were then subjected to a pure bending stiffness tester (manufactured by Kato Tech Co., Ltd.) at a deformation speed of 0.5 cm / second. The change in bending moment (per unit specimen width) for two curvature changes in the ranges of 0.5 to 1.5 (front bending) and -0.5 to -1.5 (back bending) was determined, and the average value of each was defined as the pure bending stiffness.

[0058] <Opacity> The opacity of the heat-sealable paper was measured in accordance with JIS P 8149:2000. Lower opacity indicates better visibility of the packaging using heat-sealable paper.

[0059] <Easy opening> Two sheets of heat-sealable paper were placed on top of each other with the heat-sealed layers facing inward, and the sides and bottom were heat-sealed to create a packaging bag measuring 10 cm wide x 12 cm long with three sides sealed. Ten people evaluated how easy it was to open the heat-sealed packaging by pinching the opening (near the edge that is not heat-sealed) with their fingers and sliding one side of the heat-sealed paper approximately 3 cm in the vertical direction of the paper. First, the packaging bag with three sides sealed using the heat-sealed paper of Example 2 was evaluated and used as a baseline. The following scores were assigned, and the total scores of the ten people were applied to the evaluation rank below. (Score) 2 points: Easier to open than standard. 1 point: Ease of opening equivalent to the standard. 0 points: Difficult to open below the standard. (Rating Rank) A: 10 points or more B: 7 points or more and 9 points or less C: 4 points or more and 6 points or less D: 3 points or less

[0060] <Tear resistance> A packaging bag with three sides sealed was created in the same manner as the <easy-opening> method. For five packaging bags, the opening (near the edge not heat-sealed) was held between fingers, and one side of the heat-seal paper was slid approximately 3 cm in the vertical direction of the paper 200 times. The number of tears that occurred in the paper substrate was evaluated according to the evaluation rank below. The test was conducted by one person. A: Out of 5 bags, 0 had tears in the packaging. B: Out of 5 items, 1 packaging bag was torn. C: Out of 5 items, 2 or more packaging bags were torn.

[0061] [Table 1]

[0062] Table 1 shows that the packaging bags obtained using the heat-sealable paper of this embodiment were easy to open and resistant to tearing during opening (Examples 1-5). In contrast, packaging bags obtained using heat-sealable paper with a longitudinal tensile strength of less than 1.8 kN / m (1.71 kN / m) were easily torn during opening (Comparative Example 1). Furthermore, the geometric mean of the pure bending stiffness in the longitudinal and transverse directions was 0.80 g·cm. 2 / cm (1.005 g cm 2 The packaging bag obtained using heat-seal paper with a thickness of / cm (Comparative Example 2), and the packaging bag obtained using heat-seal paper with a static friction coefficient of more than 0.750 (0.795) on the surface of the heat-seal layer opposite the paper substrate (Comparative Example 3), exhibited poor ease of opening. [Industrial applicability]

[0063] The heat-sealable paper of the present invention is suitable as a packaging material, as it provides excellent visibility of the contents when used as a package, is easy to open, and is resistant to tearing when the contents are removed, making it suitable for use in forming packaged goods.

Claims

1. A heat-sealable paper having a heat-seal layer on one side of a paper substrate, The paper base material content in the heat-sealing paper is 50% by mass or more. The geometric mean of the pure bending stiffness in the longitudinal and transverse directions of the heat-sealing paper is 0.80 g·cm. ２ / cm or less, The tensile strength of the heat-sealing paper in the longitudinal direction is 1.80 kN / m or more. A heat-sealable paper in which the static friction coefficient of the heat-sealable layer on the side opposite to the paper substrate is 0.750 or less.

2. The pure bending stiffness in the longitudinal direction of the heat-sealing paper is 1.20 g·cm. ２ The heat-sealable paper according to claim 1, wherein the thickness is less than or equal to / cm.

3. The lateral pure bending stiffness of the heat-sealing paper is 0.60 g·cm. ２ The heat-sealable paper according to claim 1, wherein the thickness is less than or equal to / cm.

4. The heat-seal paper according to claim 1, wherein the heat-seal layer contains a slip agent.

5. The heat-sealable paper according to claim 1, wherein the heat-sealable layer is a laminate layer.

6. Basis weight: 80.0 g / m² ２ The heat-sealable paper according to claim 1, which is as follows:

7. The heat-sealable paper according to claim 1, for use in packaging bags having a heat-sealable layer on the inside.

8. A roll of heat-sealable paper according to claim 1, wherein both ends of the heat-sealable paper, where the heat-sealable layers are overlapped, are heat-sealed in the vertical direction, and the roll is wound in the vertical direction.

9. A packaging bag using heat-sealable paper according to any one of claims 1 to 7 or a roll according to claim 8.

10. A package comprising a packaging bag according to claim 9, with an object to be contained contained within it.

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