Heat-seal paper, rolls, packaging bags and packages

Abstract

To provide a heat seal paper from which a packaging bag and a package can be obtained that have a reduced load on the environment, are easy to open, and are not easily torn by the opening operation, and a roll, a packaging bag, and a package made using the heat seal paper. The heat seal paper has a heat seal layer on one side of a paper substrate, and the content of the paper substrate in the heat seal paper is 50% by mass or more. The geometric mean of the pure bending stiffness in the longitudinal direction and the pure bending stiffness in the transverse direction of the heat seal paper is 0.80 g cm. 2 / cm or less, the tensile strength of the heat seal paper in the machine direction is 1.8kN / m or more, and the static friction coefficient of the heat seal layer on the surface opposite to the paper substrate is 0.750 or less.

Description

[Technical Field]

[0001] The present invention relates to heat seal paper, rolls, packaging bags and packages. [Background technology]

[0002] Packages using the heat seal method are widely used for packaging general industrial products as well as for packaging food, medicines, medical equipment, and the like.

[0003] The problem of plastic waste has become more serious in recent years. Of the total amount of plastic produced worldwide, a large amount is produced in the packaging sector, which is the cause of plastic waste. Plastic does not decompose for a long time, and this waste breaks down into microplastics in the natural environment, causing serious damage to the ecosystem. As a countermeasure, it has been proposed to replace plastic with paper.

[0004] For example, Patent Document 1 discloses flexible packaging paper that can be used to make bags using a folding bag machine, and a flexible package using this flexible packaging paper, which has a paper base and a heat seal layer on at least one outermost surface, the paper base having a thickness of 25 μm or more and 100 μm or less, and the proportion of pulp to all papermaking fibers contained in the paper base exceeds 90% by weight, and which satisfies certain conditions. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2023-182608 Summary of the Invention [Problem to be solved by the invention]

[0006] The packaging bag made of the flexible packaging paper described in Patent Document 1 is not easy to open. The present invention aims to provide heat-sealable paper that reduces the burden on the environment, is easy to open, and can be used to obtain packaging bags and packaging bodies that are not easily torn during opening, as well as a roll, packaging bags, and packaging bodies made from the heat-sealable paper. [Means for solving the problem]

[0007] The inventors have discovered that the above problem can be solved by setting the content of paper substrate in the heat-seal paper, the geometric mean of the pure bending stiffness in the longitudinal direction and the pure bending stiffness in the lateral direction of the heat-seal paper, and the tensile strength in the longitudinal direction of the heat-seal paper to specific values ​​or more in a heat-seal paper having a heat-seal layer on one side of the paper substrate, and by setting the static friction coefficient of the heat-seal layer on the side opposite the paper substrate to a specific value or less. That is, the present invention provides the following: <1> ~ <10> Regarding. <1> A heat-sealable paper having a heat-sealable layer on one side of a paper substrate, The content of the paper substrate in the heat seal paper is 50% by mass or more, The geometric mean of the pure bending stiffness in the longitudinal direction and the pure bending stiffness in the transverse direction of the heat seal paper is 0.80 g cm 2 / cm or less, The tensile strength of the heat seal paper in the longitudinal direction is 1.8 kN / m or more, A heat-sealable paper in which the coefficient of static friction of the heat-sealable layer on the surface opposite to the paper substrate is 0.750 or less. <2> The pure bending stiffness of the heat seal paper in the longitudinal direction is 1.20 g cm 2 / cm or less, <1> The heat seal paper according to claim 1. <3> The pure bending stiffness of the heat seal paper in the horizontal direction is 0.60 g cm 2 / cm or less, <1> or <2> The heat seal paper according to claim 1. <4> the heat seal layer contains a slip agent; <1> ~ <3> 10. The heat seal paper according to any one of the preceding items. <5> The heat seal layer is a laminate layer; <1> ~ <4> 10. The heat seal paper according to any one of the preceding items. <6> Basis weight: 80g / m 2Below is the <1> ~ <5> 10. The heat seal paper according to any one of the preceding items. <7> It is for a packaging bag having a heat seal layer on the inside, <1> ~ <6> 10. The heat seal paper according to any one of the preceding items. <8> <1> ~ <7> 1. A roll of the heat-sealable paper according to any one of the above items 1 to 5, wherein both ends of the overlapping heat-sealable layers are heat-sealed in the longitudinal direction and the heat-sealable paper is wound up in the longitudinal direction. <9> <1> ~ <7> or <8> A packaging bag using the roll described in . <10> <9> A package comprising the packaging bag according to claim 1, containing an item to be contained. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide heat-sealable paper that reduces the burden on the environment, is easy to open, and can be used to obtain packaging bags and packages that are not easily torn during opening operations, as well as rolls, packaging bags, and packages made using the heat-sealable paper. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Heat seal paper] The heat seal paper of this embodiment is a heat seal paper having a heat seal layer on one side of a paper substrate, the content of the paper substrate in the heat seal 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 seal paper is 0.80 g cm 2 / cm or less, the tensile strength in the machine direction of the heat seal paper is 1.80 kN / m or more, and the static friction coefficient of the surface of the heat seal layer opposite to the paper substrate is 0.750 or less.

[0010] The heat seal paper of this embodiment can provide a packaging bag and package that reduces the burden on the environment, is easy to open (excellent in ease of opening), and is not easily torn during opening. The reason for the above effects is that the content of the paper base material in the heat-seal paper is 50% by mass or more, so the content of plastic materials in the heat-seal paper is 50% by mass or less, reducing the environmental impact. In addition, the geometric mean of the pure bending stiffness in the longitudinal direction and the pure bending stiffness in the transverse direction of the heat-seal paper is 0.80 g cm 2 / cm or less, and the coefficient of static friction of the heat-seal layer on the side opposite the paper substrate is 0.750 or less, it is believed that when made into a package, the opposing heat-seal layers slide easily against each other, resulting in excellent opening properties. Furthermore, since the heat-seal paper has a longitudinal tensile strength of 1.80 kN / m or more, it is believed that it will not easily tear due to stress when opening the package. However, the reason why the above effect is obtained is not limited to this. The present invention will be described in further detail below.

[0011] In this specification, a numerical range represented by "X to Y" means a numerical range including X as the lower limit and Y as the upper limit. When a numerical range is described in stages, the upper and lower limits of each numerical range can be combined arbitrarily. Furthermore, in this specification, unless otherwise specified, operations and measurements of physical properties, etc. are performed under conditions of room temperature (20 to 25°C) and relative humidity (RH) of 40 to 50%. The machine direction of the heat seal paper and paper substrate means the machine direction (MD) of the paper substrate, and the cross direction means the direction perpendicular to the machine direction (CD). The components contained in the heat seal paper may be used alone or in combination of two or more. The front side of heat seal paper refers to the side that will be on the outside when it is made into a packaging bag. The back side of heat seal paper refers to the side that will be on the inside when it is made into a packaging bag.

[0012] <Paper base material> The paper substrate is preferably a commonly used paper whose main component is plant-derived pulp, more preferably a paper whose main component is wood pulp, and more preferably a paper whose main component is pulp that is easily dispersible in water by mechanical disintegration. Specific examples include bleached or unbleached kraft paper, fine paper, paperboard, liner paper, coated paper, one-side glazed paper, glassine paper, etc. Among these, bleached kraft paper, glassine paper, and graphene paper are preferred from the viewpoint of obtaining a package that is easy to open and a package bag that is not easily torn when opened, and glassine paper and graphene paper are more preferred from the viewpoint of obtaining a package that provides excellent visibility of the contents contained therein. Generally, glassine paper is mainly made of softwood chemical pulp, which is beaten at a high temperature and made into paper at an acidic or neutral pH, and then compressed using a supercalender, etc. Specific examples of pulp include chemical pulp made from softwoods such as spruce and hemlock, and may also be mixed with chemical pulp made from hardwoods, mechanical pulp, recycled paper, synthetic pulp, etc.

[0013] (Basic weight) The basis weight of the paper substrate is preferably 22.0 g / m from the viewpoint of obtaining a packaging bag that is difficult to tear when opened. 2 More preferably, 24.5 g / m 2 More preferably, 28.0 g / m 2 From the viewpoint of obtaining a package that is easy to open, it is preferably 65.0 g / m 2 or less, more preferably 60.0 g / m 2 or less, more preferably 55.0 g / m 2 or less, even more preferably 50.0 g / m 2 More preferably 45.0 g / m or less 2 More preferably, 40.0 g / m or less 2 or less, and even more preferably 35.0 g / m 2 The following is the result. The basis weight of the paper substrate is measured in accordance with JIS P 8124:2011.

[0014] (Thickness) Furthermore, from the viewpoint of obtaining a packaging bag that is difficult to tear when opened, the thickness of the paper base material is preferably 22 μm or more, more preferably 24.5 μm or more, and even more preferably 28 μm or more, and from the viewpoint of obtaining a package that is easy to open, the thickness 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) The density of the paper substrate is preferably 0.65 g / cm from the viewpoint of ease of manufacturing the heat seal paper. 3 More preferably, 0.70 g / cm 3 More preferably, 0.75 g / cm 3 More preferably, 0.85 g / cm 3 More preferably, 0.90 g / cm 3 More preferably, 0.95 g / cm 3 and preferably 1.25 g / cm 3 or less, more preferably 1.20 g / cm 3 or less, more preferably 1.15 g / cm 3 The following is the result. The density of the paper substrate is calculated from the basis weight and thickness of the paper substrate obtained by the above-mentioned measurement method.

[0016] (irregular freeness) In order to obtain a packaging bag and package that provide excellent visibility of the contents, the paper base material of this embodiment preferably has an irregular freeness of 100 mL or more and 800 mL or less. Here, the irregular freeness refers to the freeness (freeness) measured using the Canadian Standard Freeness Method specified in JIS P 8121:2012, with the pulp sample amount changed from 3 g to 0.3 g and the JIS standard screen plate changed to an 80-mesh wire. When the irregular freeness of the pulp constituting the paper base material is equal to or greater than the lower limit, the dimensional stability of the paper base material is improved and the paper base material is less likely to become lumpy. When the irregular freeness is equal to or less than the upper limit, the transparency of the paper base material is maintained, which is preferable. The irregular freeness of the pulp constituting the paper base material is more preferably 300 mL or more and 700 mL or less, and even more preferably 400 mL or more and 600 mL or less. Known methods can be used to beat the pulp to adjust the irregular freeness. The anomalous freeness of the pulp constituting the paper base material is specifically measured by the method described in the Examples. The "anomalous freeness of the pulp constituting the paper base material" refers to the anomalous freeness of the disintegrated pulp obtained by disintegrating the paper base material.

[0017] When bleached kraft paper is used as the paper base material, the freeness (Canadian Standard Freeness (CSF)) of the disintegrated pulp obtained by disintegrating the pulp that constitutes the bleached kraft paper is preferably 200 mL or more and 700 mL or less, more preferably 300 mL or more and 600 mL or less, and even more preferably 350 mL or more and 550 mL or less. The freeness of the disintegrated pulp obtained by disintegrating the pulp that constitutes the bleached kraft paper is specifically measured by the method described in the Examples.

[0018] The coefficient of static friction of the surface that will become the front surface of the heat-sealable paper is preferably 0.100 or more, more preferably 0.150 or more, even more preferably 0.200 or more, and even more preferably 0.220 or more, from the viewpoint of making it easier to wind the heat-sealable paper vertically into a roll, and is preferably 0.500 or less, more preferably 0.400 or less, and even more preferably 0.300 or less. 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 surface opposite the heat-sealable layer of the paper substrate (when the heat-sealable paper of this embodiment does not have any layer on the surface opposite the heat-sealable layer of the paper substrate), the static friction coefficient of the surface can be adjusted by the type of raw pulp, the pulp slurry concentration and degree of beating during beating, whether or not calendering is performed, and the treatment conditions. Specifically, when the linear pressure is reduced during calendering, the static friction coefficient of the surface tends to increase. Furthermore, when the pulp is beaten 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 optional layer (when the heat-sealable paper of this embodiment has an optional layer on the surface opposite the heat-sealable layer of the paper substrate), the static friction coefficient of the surface can be adjusted by the printing method and conditions, the coating method and conditions, etc. Specifically, when an optional layer is formed by curtain coating, the static friction coefficient of the surface tends to increase. Furthermore, when any layer is formed by blade coating, the surface static friction coefficient tends to decrease.

[0019] <Heat seal layer> The heat seal paper of this embodiment has a heat seal layer on one side of a paper substrate, and the heat seal layer is the uppermost 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 ease of production of the heat seal paper, it is preferable to provide the heat seal layer by lamination. The heat seal layer is preferably formed on the entire surface of one side of the paper substrate from the viewpoint of obtaining a package that is easy to open. Also, from the viewpoint of easy manufacturing of the heat seal paper and obtaining a package that is easy to see the contents of the package, the heat seal layer is preferably laminated directly to 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 may be produced by an appropriate selection from conventionally known production methods, such as dry lamination, melt extrusion, melt casting, calendering, etc. Among these, the dry lamination method is preferred from the viewpoint of ease of production of the heat seal paper of the present embodiment.

[0022] The resin constituting the heat seal layer can be either a crystalline or amorphous thermoplastic resin. Examples of thermoplastic resins include polyethylene (low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), etc.), polypropylene, polymethylpentene, etc., polyolefin resins, 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, and polymethylpentene, and 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 laminating 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, or as a single layer of a mixture of multiple resins, or as a multi-layer structure of these (e.g., 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 may be appropriately selected within a range in which the content of the paper substrate in the heat seal paper is 50% by mass or more. When the heat seal layer is provided by coating, the basis weight of the heat seal layer is preferably 1 g / m from the viewpoint of reducing the environmental load and heat sealability. 2 More preferably, 2 g / m 2 and preferably 20 g / m 2 Less than 10 g / m, more preferably 2 or less, more preferably 5 g / m 2 Even more preferably 3 g / m or less 2 The following is the result. When the heat seal layer is provided by lamination, the basis weight of the heat seal layer is preferably 5 g / m from the viewpoint of reducing the environmental load and heat sealability. 2 More preferably, 7 g / m 2 More preferably, 10 g / m 2 From the viewpoint of obtaining a package that is easy to open, it is preferably 25 g / m 2 Less than 20 g / m, more preferably 2 The following is the result. Furthermore, when the heat seal layer is provided by lamination, the thickness of the heat seal layer is, from the same viewpoint, preferably 5 μm or more, 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.

[0026] <any layer> The heat seal paper of this embodiment may have an optional layer on the surface of the paper substrate opposite to the heat seal layer, but from the viewpoint of making it easier to wind the heat seal paper vertically into a roll, it is preferable that no optional layer is included. Specific examples of the optional layer include a printing layer, a coating layer, a laminate layer, and a barrier layer.

[0027] <Characteristics of heat seal paper> (Paper base material content) In the heat seal paper of this embodiment, from the viewpoint of reducing the environmental impact, the content of the paper base material in the heat seal 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) The basis weight of the heat seal paper of this embodiment is preferably 22 g / m from the viewpoint of obtaining a packaging bag that is not easily torn when opened. 2 More preferably, 30 g / m 2 More preferably, 35 g / m 2 More preferably, 40 g / m 2 More preferably, 45 g / m 2 From the viewpoint of obtaining a package that is easy to open and a package that is excellent in visibility of the contents, it is preferably 80 g / m 2 Less than 75 g / m 2 or less, even more preferably 70 g / m 2 More preferably 65 g / m or less 2 More preferably, 60 g / m or less 2 The following is the result. The basis weight of the heat seal paper can be adjusted to a desired range by appropriately adjusting the basis weights of the paper substrate and the heat seal layer. The basis weight of the heat seal paper is measured by the method described in the examples.

[0029] (Thickness) The thickness of the heat seal paper of 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 when opened, and is preferably 80 μm or less, more preferably 75 μm or less, even more preferably 70 μm or less, still more preferably 66 μm or less, even more preferably 62 μm or less, still more preferably 58 μm or less, and even more preferably 54 μm or less, from the viewpoint of obtaining a packaging bag that is easy to open and that has excellent visibility of the contents contained therein. The thickness of the heat seal paper can be adjusted to a desired range by appropriately adjusting the thickness of the paper substrate and the heat seal layer. The thickness of the heat seal paper is measured by the method described in the Examples.

[0030] (density) The density of the heat seal paper of this embodiment is preferably 0.70 g / cm from the viewpoint of ease of manufacturing the heat seal paper. 3 More preferably, 0.75 g / cm 3 More preferably, 0.80 g / cm 3 More preferably, 0.85 g / cm 3 More preferably, 0.90 g / cm 3 More preferably, 0.95 g / cm 3 and preferably 1.20 g / cm 3 or less, more preferably 1.15 g / cm 3 or less, more preferably 1.10 g / cm 3 The following is the result. The density of the heat seal paper can be adjusted to a desired range by appropriately adjusting the density of the paper substrate and the type of resin used in the heat seal layer. The density of the heat seal paper is calculated from the basis weight and thickness of the heat seal paper.

[0031] (pure bending stiffness) The geometric mean of the pure bending stiffness in the longitudinal direction and the pure bending stiffness in the lateral direction of the heat seal paper according to this embodiment is 0.80 g cm from the viewpoint of obtaining a package that is excellent in ease of opening.2 / cm or less, preferably 0.60 g cm 2 / cm or less, preferably 0.40 g·cm 2 / cm or less, and more preferably 0.20 g cm 2 / cm or less, and even more preferably 0.16 g cm 2 / cm or less, and from the viewpoint of ease of manufacturing the heat seal paper, it is preferably 0.01 g cm 2 / cm or more, preferably 0.02g·cm 2 / cm or more, and more preferably 0.03g cm 2 / cm or more.

[0032] The pure bending stiffness in the longitudinal direction of the heat seal paper according to this embodiment is preferably 1.20 g cm from the viewpoint of obtaining a package that is easy to open. 2 / cm or less, preferably 0.80g·cm 2 / cm or less, and more preferably 0.40 g cm 2 / cm or less, and even more preferably 0.20 g cm 2 / cm or less, and from the viewpoint of ease of manufacturing the heat seal paper, it is preferably 0.01 g cm 2 / cm or more, preferably 0.03g·cm 2 / cm or more, and more preferably 0.05g·cm 2 / cm or more.

[0033] The geometric mean of the pure bending stiffness in the lateral direction of the heat seal paper according to this embodiment is preferably 0.60 g cm from the viewpoint of obtaining a package that is easy to open. 2 / cm or less, preferably 0.40 g·cm 2 / cm or less, and more preferably 0.20 g cm 2 / cm or less, and even more preferably 0.15 g cm 2 / cm or less, more preferably 0.12 g cm 2 / cm or less, and from the viewpoint of ease of manufacturing the heat seal paper, it is preferably 0.01 g cm 2 / cm or more, preferably 0.02g·cm 2 / cm or more.

[0034] The pure bending stiffness in the longitudinal direction and the pure bending stiffness in the transverse direction of heat seal paper can be adjusted by the type of raw pulp, the type and amount of paper strength agent, the pulp slurry concentration and degree of beating during beating, the drying conditions during papermaking (for example, the position of the dryer in the papermaking machine), whether or not calendering is performed and the treatment conditions, basis weight, etc. For example, increasing the basis weight or thickness of the paper base material tends to increase the pure bending stiffness in the longitudinal direction and the pure bending stiffness in the transverse direction. The pure bending stiffness in the machine direction and the pure bending stiffness in the cross direction of the heat seal paper are measured by the method described in the examples.

[0035] (tensile strength) The longitudinal tensile strength of the heat seal paper of 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, from the viewpoint of obtaining a packaging bag that is less likely to tear when opened, and 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, from the viewpoint of obtaining a packaging body that is excellent in ease of opening. The tensile strength is measured in accordance with JIS P 8113:2006. The tensile strength can be adjusted by appropriately selecting the degree of beating of the raw pulp, the basis weight, thickness, and density of the paper base material, the papermaking conditions of the paper base material, the type and thickness of the heat-seal layer, etc. For example, increasing the basis weight of the paper base material or the heat-seal layer tends to increase the tensile strength.

[0036] (static friction coefficient) The coefficient of static friction of the back surface of the heat seal paper of 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 that is easy to open, and is preferably 0.100 or more, more preferably 0.150 or more, from the viewpoint of ease of handling when made into a packaging bag. The static friction coefficient of the back surface of the heat seal paper of this embodiment is considered to be isotropic. The static friction coefficient is measured in accordance with JIS P 8147:2010. The static friction coefficient of the back surface of the heat seal paper of this embodiment is adjusted according to the method for forming the heat seal layer. When the heat seal layer is formed by dry lamination, it is adjusted, for example, by the content of slip agent in the heat seal layer. A high content of slip agent tends to reduce the static friction coefficient of the back surface. When the heat seal layer is formed by melt extrusion lamination, the static friction coefficient of 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 reduce the static friction coefficient of the back surface. When the heat seal layer is formed by coating, the static friction coefficient of the back surface is adjusted, for example, by the content of slip agent. A high content of slip agent tends to reduce the static friction coefficient of the back surface.

[0037] (Opacity) The opacity of the heat seal paper of 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 that provides excellent visibility of the contents inside, and is 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 seal paper can be adjusted to a desired range by appropriately adjusting the type of paper substrate, and the basis weight and thickness of the paper substrate and the heat seal layer. The opacity of the heat seal paper is measured by the method described in the Examples.

[0038] 〔roll〕 The roll of the present embodiment is formed by longitudinally heat-sealing both ends of the overlapping heat-seal layers of the heat-seal paper of the present embodiment and winding the roll in the longitudinal direction. The packaging bag of the present embodiment can be efficiently produced by using the roll of the present embodiment.

[0039] [Packaging bag] The packaging bag of this embodiment is a packaging bag produced by heat-sealing the heat-seal layers of the heat-seal paper of this embodiment so that the heat-seal layers are facing each other, and the packaging bag of this embodiment has the heat-seal layer on the inside. The packaging bag of this embodiment is preferably a packaging bag made only of the heat-seal paper of this embodiment. Examples of the packaging bag of this embodiment include three-sided sealed packaging bags, four-sided sealed packaging bags, and pillow packaging bags, with three-sided sealed packaging bags and four-sided sealed packaging bags being preferred.

[0040] [Packaging] The package of this embodiment is formed by placing an object in the packaging bag of this embodiment. Examples of the object include metal fittings, food, stationery, daily necessities, miscellaneous goods, etc. The object may be one or two or more. [Example]

[0041] The following examples are provided to specifically explain the present invention, but the present invention is not limited to these examples. Unless otherwise specified, the following operations were carried out at 23°C and a relative humidity of 50%. In the examples and comparative examples, "parts" and "%" refer to "parts by mass" and "% by mass," respectively, unless otherwise specified.

[0042] [Example 1] Paper base material: basis weight 23.0 g / m 2Glassine paper (Oji F-Tex Co., Ltd., 100% softwood bleached kraft pulp, 500 mL of disintegrated pulp with variable freeness) was used. One side of a PE film (Futamura Chemical Co., Ltd., LL-XMTN) was coated with an adhesive consisting of 10 parts DIC Dry LX-500 (DIC Corporation) and 1 part DIC Dry KW-75 (DIC Corporation) at a rate of 5 g / m. 2 The adhesive was applied to one side of the glassine paper and the PE film coated with the adhesive was dry laminated to obtain a heat seal paper.

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

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

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

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

[0047] [Comparative Example 1] Glassine paper with a basis weight of 20.0 g / m 2A heat seal paper was obtained in the same manner as in Example 1, except that it was produced in the following manner so as to obtain the following. Bleached softwood kraft pulp (NBKP) was beaten to 250 mL of disintegrated pulp with an irregular freeness to obtain a 3.8% pulp slurry. This pulp slurry was mixed with 0.9 parts of an anionic polyacrylamide-based dry strength agent (trade name: PS-NH20B, manufactured by Arakawa Chemical Industries, Ltd.), 0.9 parts of a cationic polyamidepolyamine epichlorohydrin-based wet strength agent (trade name: WS4024, manufactured by Seiko PMC Co., Ltd.), and 0.1 parts of a neutral sizing agent, alkyl ketene dimer (trade name: AD1612, manufactured by Seiko PMC Co., Ltd.), per 100 parts of pulp solids, and stirred to obtain a paper stock. The stock was adjusted to a consistency of 0.5%, and made into paper using a standard handsheet machine. The resulting sheet was dried using a cylinder dryer so that the moisture content in the sheet was 15%. Immediately after drying, the paper was passed through a heat calender consisting of a metal roll and an elastic roll to a basis weight of 20.0 g / m 2 of glassine paper was obtained.

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

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

[0050] [Measurement and evaluation methods] The paper substrate and the obtained heat seal paper were subjected to the following measurements and evaluations. <Basic weight> The basis weights of the paper substrate and the heat-seal 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 substrate and the heat-seal paper.

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

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

[0053] <Freeness> The freeness (Canadian Standard Freeness (CSF)) of the pulp constituting the paper base material was measured in accordance with JIS P 8121-2:2012 using pulp samples disintegrated in accordance with JIS P 8220-1:2012.

[0054] <density> The density of the paper substrate and the heat seal 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 seal paper were measured in accordance with JIS P 8147:2010.

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

[0057] <Pure bending stiffness> After conditioning the heat seal paper at 23°C and 50% RH, test pieces were cut into 80 x 80 mm widths and bent in the MD and CD (bending perpendicular and parallel to the machine direction) at a deformation rate of 0.5 cm / sec using a pure bending stiffness tester (manufactured by Kato Tech Co., Ltd.). The change in bending moment (per unit test piece width) per change in curvature was determined at two points within the curvature range of 0.5 to 1.5 (front bending) and -0.5 to -1.5 (back bending), and the average of these values ​​was taken as the pure bending stiffness.

[0058] <Opacity> The opacity of the heat seal paper was measured in accordance with JIS P 8149: 2000. The lower the opacity, the better the visibility of the package using the heat seal paper.

[0059] <Easy opening> Two sheets of heat-sealable paper were placed on top of each other with the heat-sealable layer facing inward, and both sides and the bottom were heat-sealed to create a packaging bag 10 cm wide x 12 cm long with three sides sealed. Ten people evaluated the ease of opening when the opening (near the edge not attached by heat seal) was pinched with fingers and one side of the heat seal paper was slid about 3 cm in the vertical direction of the paper. First, a packaging bag sealed on three sides made using the heat seal paper of Example 2 was evaluated as a standard, and the following scores were assigned. The total scores of the 10 people were then assigned to the following evaluation ranks. (Points) 2 points: Easier to open than standard 1 point: Ease of opening equal to the standard 0 points: harder to open than 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> In the same manner as in <Easy Opening Property>, a packaging bag sealed on three sides was prepared. Five packaging bags were pinched between the fingers at the opening (near the edge not heat-sealed) and one side of the heat-seal paper was slid vertically about 3 cm along the paper 200 times. The number of bags that broke the paper base material was evaluated according to the following ranking. The test was carried out by one person. A: 0 out of 5 bags were torn B: One of the five bags had a tear. C: Two or more of the five bags were torn.

[0061] [Table 1]

[0062] As can be seen from Table 1, the packaging bags obtained using the heat seal paper of this embodiment were easy to open and were not easily torn by the opening operation (Examples 1 to 5). In contrast, the packaging bag obtained using heat seal paper with a longitudinal tensile strength of less than 1.8 kN / m (1.71 kN / m) was easily torn by the opening operation (Comparative Example 1). In addition, the geometric mean of the pure bending stiffness in the longitudinal direction and the pure bending stiffness in the transverse direction was 0.80 g cm 2 / cm (1.005 g cm 2 The packaging bag obtained using heat-seal paper with a coefficient of static friction of 0.795 (0.795 / cm) on the surface of the heat-seal layer opposite the paper substrate (Comparative Example 2) and the packaging bag obtained using heat-seal paper with a coefficient of static friction of 0.795 (0.750) on the surface of the heat-seal layer opposite the paper substrate (Comparative Example 3) were inferior in ease of opening. [Industrial Applicability]

[0063] The heat-sealable paper of the present invention is suitable as a packaging material, and when made into a package, it provides excellent visibility of the contents contained therein, is easy to open, and can produce a packaging bag that is not easily torn when the contents are removed, making it suitable for use in forming packages.

Claims

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

2. The pure bending stiffness of the heat seal paper in the longitudinal direction is 1.20 g cm ２ 2. The heat seal paper according to claim 1, wherein the thickness is 1 / cm or less.

3. The pure bending stiffness of the heat seal paper in the horizontal direction is 0.60 g cm ２ 2. The heat seal paper according to claim 1, wherein the thickness is 1 / cm or less.

4. 10. The heat seal paper of claim 1, wherein the heat seal layer contains a slip agent.

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

6. Basis weight: 80.0 g / m ２ 2. The heat seal paper of claim 1, wherein:

7. 2. The heat sealable paper according to claim 1, which is for use in a packaging bag having a heat seal layer on the inside.

8. 2. A roll of the heat-sealable paper according to claim 1, wherein both ends of the overlapping heat-sealable layers are heat-sealed in the longitudinal direction and the roll is wound up in the longitudinal direction.

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

10. A package comprising the packaging bag according to claim 9 and an article housed therein.

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