Heat seal paper and package

Abstract

There is provided heat seal paper in which heat seal regions in which a portion where there is a heat seal agent and a portion where there is no heat seal agent are regularly repeated are provided on at least a part of at least one surface of a paper base material. In the heat seal region, an area ratio occupied by the portion where there is no heat seal agent is 1% or more and less than 50%. It is preferable that when the heat seal regions are overlapped and heat-sealed at 160°C and 0.2 MPa for 1 second, the peel strength measured according to JIS Z 1707 is 4.0 N / 15 mm or more.

Description

Heat-sealable paper and packaging

[0001] The present invention relates to heat-sealable paper and packaging using the same. This application claims priority to Japanese Patent Application No. 2025-066590, filed in Japan on April 15, 2025, and Japanese Patent Application No. 2025-201890, filed in Japan on November 21, 2025, the contents of which are incorporated herein by reference.

[0002] Packaging using the heat-sealing method is widely used for general industrial products, food products, and more. The packaging materials used are extremely diverse, including single-layer films, composite films, paper-and-film composite materials, and plain paper.

[0003] In recent years, the problem of plastic waste has become increasingly serious worldwide. The global packaging sector produces a very large amount of plastic, which is a major contributing factor to the plastic waste problem. Some types of plastic do not decompose almost indefinitely, leading to microplastic formation in the natural environment and serious impacts on global ecosystems. As a solution to this problem, the replacement of plastic packaging materials with paper has been proposed and recommended.

[0004] Furthermore, the e-commerce market has expanded rapidly since the COVID-19 pandemic began at the end of 2019. Major online retailers and distributors are shifting from cardboard box delivery to simpler packaging methods such as bags and envelopes. Delivering small packages in simpler packaging improves loading efficiency and reduces GHG emissions, and further technological innovation is expected in the future.

[0005] For example, Patent Document 1 describes a heat-sealable paper having at least one heat-seal layer on at least one surface of a paper substrate, which has excellent impact resistance and processability. However, using the heat-sealable paper described in Patent Document 1 resulted in air being trapped inside the packaging during packaging, causing the packaging to become unnecessarily bulky and reducing delivery efficiency.

[0006] Japanese Patent Publication No. 2021-188241

[0007] The present invention provides heat-sealable paper that allows excess trapped air to be released when a product is packaged using a heat-sealable packaging system, enabling compact packaging of the product. Furthermore, the present invention provides heat-sealable paper that, when used to package a product using a heat-sealable packaging system, can form a packaging bag that protects the packaged product from impact by the air trapped inside the bag, and prevents the packaging bag from bursting due to impact.

[0008] The present invention has the following embodiments: [1] A heat-sealable paper having a heat-sealable region on at least a part of at least one surface of a paper substrate in which a portion of the portion where a heat-sealable agent is present and a portion where a heat-sealable agent is not present are regularly repeated, wherein the area ratio of the portion where a heat-sealable agent is not present in the heat-sealable region is 1% or more and less than 50%. [2] The heat-sealable paper according to [1], wherein when the heat-sealable regions are overlapped and heat-sealed for 1 second under the conditions of 160°C and 0.2 MPa, the peel strength measured in accordance with JIS Z1707 is 4.0 N / 15 mm or more. [3] The heat-sealable paper according to [1] or [2], wherein the heat-sealable region is provided over the entire surface of at least one surface of the paper substrate. [4] The heat-sealable paper according to any one of [1] to [3], wherein the air permeability resistance measured in the heat-sealable region in accordance with JIS P8117 is 15 seconds or more and 300 seconds or less. [5] The heat-sealable paper according to any one of [1] to [4], wherein the areas where the heat-sealing agent is present and the areas where the heat-sealing agent is not present form at least one pattern selected from the group consisting of a stripe-shaped pattern, a dot-shaped pattern, and a mesh-shaped pattern arranged in one direction on the surface of the paper substrate. [6] The heat-sealable paper according to any one of [1] to [5], wherein the time required for degassing measured by method A, which includes the following steps (1) to (4), is 10 to 600 seconds. Step (1): A sample of the heat-sealable paper as a package is made to B5 size, and three sides are sealed by heat sealing at 160°C for 1 second under a width of 20 mm and a pressure of 0.2 MPa, leaving an opening for air injection. Step (2): Next, a gas inlet tube is inserted and air is filled inside, and immediately after the gas inlet tube is removed, the opening is sealed with tape.Step (3): Using a Tensilon tensile testing machine (model number: RTG-1310) manufactured by A&D Co., Ltd. (hereinafter referred to as Tensilon), a creep test is performed using a test apparatus equipped with a load cell rated at 250 N, in the following procedure: (3-i) The sample is placed on the Tensilon stand, and a 210 mm x 270 mm x 2 mm thick (weighing approximately 100 g) piece of cardboard is placed on top of the sample. While manually applying a load, the air is gradually removed and the sample is compressed to a height of 50 mm to prepare a sample for the creep test. (3-ii) A piece of cardboard or stainless steel plate larger than the test sample is placed under the sample to suppress localized stress concentration between the sample surface and the load-transmission surface and to distribute the load uniformly. (3-iii) The creep test is performed under the following conditions. (Creep test conditions) The operation mode is set to creep operation, the deformation mode to compression test, and the crosshead speed is set to 60 mm / min. After the start of the test, the crosshead is lowered at 60 mm / min, and when the load reaches the target load of 1.96 N, the system automatically switches to constant load holding mode. The endpoint of the creep test is when the relative displacement between the sample and the load transfer plate stops under constant load (when all the air has escaped), and during this time, the amount of strain over time is continuously recorded. Step (4): The creep characteristics are analyzed from the obtained elapsed time-strain data, and the time required for all the air to escape is defined as the venting time. [7] A package in which at least a portion of the heat-seal area of ​​the heat-seal paper described in any of [1] to [6] is heat-bonded.

[0009] The present invention provides a heat-sealable paper that allows for compact packaging of products by releasing excess air trapped during packaging, while also possessing sufficient adhesive strength.

[0010] This is a schematic diagram showing the heat-sealing region of heat-sealing paper according to one embodiment of the present invention. This is a schematic diagram showing the heat-sealing region of heat-sealing paper according to another embodiment of the present invention. This is a schematic diagram showing the heat-sealing region of heat-sealing paper according to another embodiment of the present invention.

[0011] Preferred embodiments of the present invention will be described below. Unless otherwise specified in this specification, operations and measurements of physical properties, etc., will be performed under room temperature (20-25°C) / relative humidity of 40-50% RH.

[0012] <Heat-Sealable Paper> The heat-sealable paper according to an embodiment of the present invention (hereinafter also simply referred to as "heat-sealable paper") is a heat-sealable paper having a heat-sealable region on at least one surface of a paper substrate in which a portion where a heat-sealing agent is present and a portion where a heat-sealing agent is not present are regularly repeated, wherein the area ratio occupied by the portion where a heat-sealing agent is not present in the heat-sealable region is 1% or more and less than 50%.

[0013] <Paper Substrate> (Raw Pulp) The paper substrate used in the heat-sealable paper of the present invention is preferably made of raw pulp mainly composed of softwood pulp. "Raw pulp mainly composed of softwood pulp" means that the softwood pulp content in the raw pulp is 50% by mass or more, and the softwood pulp content is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass. Softwood pulp has a long average fiber length, and paper substrates using softwood pulp as raw pulp tend to have excellent impact resistance and processability.

[0014] As for the coniferous tree pulp, from the viewpoint of obtaining heat-sealable paper with excellent impact resistance and processability, it is preferably pulp obtained from one or more species selected from the group consisting of Douglas fir and pine, and more preferably pulp obtained from Douglas fir.

[0015] The raw material pulp that constitutes the paper substrate is preferably one or more selected from the group consisting of bleached kraft pulp and unbleached kraft pulp, and more preferably unbleached kraft pulp.

[0016] (Tensile Energy Absorption) When the paper substrate used in the heat-sealable paper of the present invention has a longitudinal tensile energy absorption amount of X1 and a transverse tensile energy absorption amount of Y1, measured in accordance with JIS P 8113:2006, the geometric mean of X1 and Y1 is 120 J / m ２ The above conditions are met, and it is preferable that the ratio of X1 to Y1 (X1 / Y1) is 0.5 or more and 2.0 or less. From the viewpoint of further improving the effects of the present invention, the geometric mean of X1 and Y1 (the square root of the product of X1 and Y1) is preferably 150 J / m ２ More preferably, 180 J / m ２ Furthermore, even more comfortable at 200 J / m ２ That concludes the explanation. The upper limit of the geometric mean of X1 and Y1 is not particularly limited, but is preferably 400 J / m ２ The following is preferable. From the viewpoint of further improving the effects of the present invention, the ratio of X1 to Y1 (X1 / Y1) is preferably 0.8 or more, more preferably 1.0 or more. The ratio of X1 to Y1 (X1 / Y1) is preferably 1.8 or less, more preferably 1.5 or less.

[0017] (Specific Tensile Energy Absorption) When the paper substrate used in the heat-sealable paper of the present invention has a specific tensile energy absorption amount in the MD direction (Machine Direction; longitudinal direction) measured in accordance with JIS P 8113:2006, X2 is the specific tensile energy absorption amount in the transverse direction measured in accordance with JIS P 8113:2006, and Y2 is the specific tensile energy absorption amount in the transverse direction, it is preferable that the geometric mean of X2 and Y2 is 2.0 J / g or more. From the viewpoint of further improving the effects of the present invention, the geometric mean of X2 and Y2 (square root of the product of X2 and Y2) is preferably 2.4 J / g or more. The upper limit of the geometric mean of X2 and Y2 is not particularly limited, but is preferably 5.0 J / g or less, and more preferably 4.0 J / g or less.

[0018] (Tensile Strength) The paper substrate used in the heat-sealable paper of the present invention preferably has a tensile strength in the MD direction of 3 kN / m or more, and more preferably 4 kN / m or more, as measured in accordance with JIS P8113:2006. When the tensile strength is above the lower limit, the effect of excellent mechanical durability during bag-making processing by an automatic packaging machine is obtained. The upper limit of the tensile strength is not particularly limited, but is preferably 10 kN / m or less, and more preferably 7 kN / m or less.

[0019] (Tear Strength) The paper substrate used in the heat-sealable paper of the present invention preferably has a tear strength in the MD direction of 400 mN or more, and more preferably 500 mN or more, as measured in accordance with JIS P8116:2000. If the tear strength is above the lower limit, the effect of suppressing bag breakage accidents during bag making by automatic packaging machines and during delivery can be obtained. The upper limit of the tear strength is not particularly limited, but is preferably 2000 mN or less, and more preferably 1600 mN or less.

[0020] (Burst Strength) The paper substrate used in the heat-sealable paper of the present invention preferably has a burst strength of 100 to 700 kPa, and more preferably 250 to 600 kPa, as measured in accordance with JIS P 8112:2008. If the burst strength is below the upper limit, the force required to tear the packaging in order to remove the contents from the packaging using the heat-sealable paper is not large, and even a person with little strength can do so with little burden. In addition, it is easy to adjust the amount of force applied, and the packaging can be torn without causing the contents to fly out when force is applied. Furthermore, because the force required to tear the packaging is small, deformation or cracking of the contents is less likely to occur when tearing the packaging. If the burst strength is above the lower limit, it has sufficient strength even when easy peeling is performed, and damage to the paper substrate is less likely to occur during peeling.

[0021] (Basis weight) The basis weight of the paper substrate is not particularly limited, but from the viewpoint of obtaining heat-sealable paper with impact resistance and processability, it is preferably 30 g / m². ２ More preferably, 50 g / m ２ More preferably 70 g / m² ２or more, and is preferably 150 g / m ２ or less, more preferably 140 g / m ２ or less, even more preferably 120 g / m ２ or less. The basis weight of the paper substrate is measured in accordance with JIS P 8124:2011.

[0022] (Thickness) From the viewpoint of obtaining heat-sealable paper having impact resistance and processability, the thickness of the paper substrate is preferably 20 μm or more, more preferably 30 μm or more, even more preferably 40 μm or more, still more preferably 60 μm or more, even further preferably 80 μm or more, and is preferably 200 μm or less, more preferably 180 μm or less, even more preferably 160 μm or less. The thickness of the paper substrate is measured in accordance with JIS P 8118:2014.

[0023] (Density) From the viewpoint of molding processability, the density of the paper substrate is preferably 0.3 g / cm ３ or more, more preferably 0.5 g / cm ３ or more, and is preferably 1.2 g / cm ３ or less, more preferably 1.0 g / cm ３ or less. The density of the paper substrate is calculated from the basis weight and thickness of the paper substrate obtained by the measurement methods described above.

[0024] (Optional Components) The paper substrate may contain optional components as needed, such as anionic, cationic, or amphoteric yield agents, water drainage improvers, dry strength enhancers, wet strength enhancers, sizing agents, fillers and other internal additives, water-resistant agents, dyes, and fluorescent whitening agents. Examples of dry strength enhancers include cationized starch, polyacrylamide, and carboxymethylcellulose. The content of the dry strength enhancer is not particularly limited, but is preferably 3.0% by mass or less per raw pulp (oven-dry mass). Examples of wet strength enhancers include polyamide polyamine epichlorohydrin, urea formaldehyde resin, and melamine formaldehyde resin. Examples of sizing agents include rosin sizing agents, synthetic sizing agents, petroleum resin-based sizing agents and other internal sizing agents, and surface sizing agents such as styrene / acrylic acid copolymer and styrene / methacrylic acid copolymer. The content of the sizing agent is not particularly limited, but is preferably 3.0% by mass or less per raw pulp (oven-dry mass). Examples of fixing agents include aluminum sulfate and polyethyleneimine. The content of the fixing agent is not particularly limited, but is preferably 3.0% by mass or less per raw pulp (oven-dry mass). Examples of fillers include inorganic fillers such as talc, kaolin, calcined kaolin, calcium carbonate, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, alumina, magnesium carbonate, magnesium oxide, silica, white carbon, bentonite, zeolite, sericite, and smectite, and organic fillers such as acrylic resins and vinylidene chloride resins.

[0025] As a paper substrate, for example, a type of paper that has undergone a crumpling process to shrink the paper fibers can be used.

[0026] <Heat Seal Layer> The heat seal paper according to this embodiment has a heat seal region on at least one surface of the paper substrate in which areas where a heat sealant is present (hereinafter also referred to as the "heat seal layer" or "heat sealant coated area") and areas where a heat sealant is not present (hereinafter also referred to as the "heat sealant-free area") are regularly repeated. In the heat seal region, the area ratio occupied by the heat sealant-free area is 1% or more and less than 50%.

[0027] In the heat-sealed region, the heat-sealed areas and the heat-sealed areas form a specific pattern. Examples of this specific pattern include parallel stripe patterns, dot patterns, mesh patterns, and combinations thereof. The stripe pattern is not limited to straight lines, but also includes wavy and dashed lines. In the following description, "straight line" includes the concepts of "wavy line" and "dashed line." The shape of the dots in the dot pattern is not limited to circles, but also includes polygons, stars, etc. Note that, as long as the area ratio occupied by the heat-sealed areas is within the above range, there may be parts of the heat-sealed region where the heat-sealed areas and heat-sealed areas do not form the above pattern. For example, there may be areas where the heat-sealed areas continuously occupy a certain or larger area. The specific pattern can be obtained, for example, by transferring the heat-sealed material onto the paper substrate using a gravure roll with a pattern imprinted on its surface. In this specification, "parallel stripe patterns" refers, for example, to a state where multiple parallel, linear heat-sealed areas form a striped pattern. Here, "parallel" includes being approximately parallel, and specifically means that the angle between two adjacent linear heat sealant coated portions is within ±5° of 0°. In this specification, "mesh pattern" refers to a state in which multiple linear heat sealant coated portions arranged in parallel in one direction intersect with multiple linear heat sealant coated portions arranged in parallel in another direction. The mesh pattern may be, for example, a grid pattern. The intersection angle between the one direction and the other direction is preferably 30° to 150°, more preferably 40° to 100°, and may also be 90°. In this specification, "dot pattern" refers to a state in which heat sealant coated portions or heat sealant-free portions are scattered as multiple independent island-like dots without contacting each other.In the heat-seal area, the heat-seal agent coated areas and heat-seal agent-free areas are arranged in a regularly repeating pattern. Here, "regular" can be defined, for example, as follows, in the case of areas where the heat-seal agent has the pattern exemplified above. In the case of a stripe-like or mesh-like pattern, "regular" means that the width of the heat-seal agent coated areas and the width of the heat-seal agent-free areas are uniform. Here, "uniform" width includes not only cases where it is perfectly uniform, but also cases where the width is within ±5% of the reference width W. In the case of a dot-like pattern, "regular" means that the uniformity of the dot dispersion is high. For example, if the dots are located at the intersections of the mesh pattern described above, it means that the dots are arranged at approximately constant pitches along the first and second directions, and the standard deviation of the pitch is within 30% of the average pitch. The average value and standard deviation of the pitch can be measured, for example, by the following method. Select one regular arrangement direction between each dot in the heat-seal area, measure the interval between the center points of each dot in the regular arrangement direction for 20 or more dots, and calculate the average value and standard deviation. The calculation results are taken as the mean and standard deviation of the dot pattern spacing. The center point of the dot shape can be represented by the center of a circle inscribed in the shape of the dot. If the shape of the dot is flat, it can be represented by the intersection of the major and minor axes of an ellipse inscribed in the shape of the dot. Furthermore, this definition of "regular" includes a state in which the dots are arranged at substantially equal intervals on the circumference of the gravure roll, or a state in which the position of each dot is arranged with a specific regularity along the circumference. Moreover, this definition of "regular" includes a state in which, even if the center position of the dots fluctuates slightly, the fluctuation as a whole maintains a specific periodicity or order.

[0028] When the aforementioned specific pattern is a striped or mesh-like pattern arranged in parallel in one direction, the width of the heat sealant-coated area is preferably 3 mm to 50 mm, and more preferably 5 mm to 40 mm. This range allows for the packaging of products of various sizes and shapes. Regarding mesh-like patterns such as grids, if the rectangles constituting the grid (heat sealant-coated areas) are square or rhombic, the length of either side of the rectangle may be considered as the width of the heat sealant-coated area. If the rectangles constituting the grid (heat sealant-coated areas) have a long side and a short side, the length of the short side shall be considered as the width of the heat sealant-coated area. Furthermore, in the case of the striped or mesh-like pattern, the width of the heat sealant-free area is preferably 0.5 mm to 10 mm, and more preferably 1.0 mm to 7.0 mm. If the width of the heat sealant-free area is above the lower limit, degassing can be performed in a short time even on a high-speed automated packaging line. If the width of the heat sealant-free area is below the upper limit, sufficient heat seal strength can be obtained. Furthermore, in the case of the stripe-like or mesh-like pattern, the ratio of the width W2 of the heat sealant-free area to the width W1 of the heat sealant-coated area (W2 / W1) is preferably 0.01 or more and 0.50 or less, and more preferably 0.02 or more and 0.40 or less.

[0029] If the aforementioned specific pattern is a dot pattern, the heat seal area is 100 cm. ２ The number of dots per unit area, for example, when the heat sealant-free area is a circle with a diameter of 1.0 mm, is preferably 100 to 6500, more preferably 300 to 5000, and even more preferably 1000 to 4000. Conversely, for example, when the heat seal covering area is a circle with a diameter of 1.0 mm, the number of dots per unit area is preferably 100 cm². ２ The number of dots per unit area is preferably 5,000 to 13,000, more preferably 8,000 to 12,500, and even more preferably 8,500 to 12,000.

[0030] In the heat-sealed area of ​​the heat-sealed paper, the area ratio occupied by the heat-sealing agent-free portion is preferably 1% or more and less than 50%, preferably 3% or more and less than 30%, and more preferably 9% or more and less than 18%. In one embodiment of this product, the area ratio is more preferably 5% or more and less than 25%. By setting the area ratio occupied by the heat-sealing agent-free portion in the heat-sealed area to be above the lower limit, it is possible to easily degas through the paper substrate of the heat-sealing agent-free portion during heat-sealed packaging, preventing the package from trapping air. Furthermore, by setting it below the upper limit, sufficient adhesive strength can be obtained after heat sealing.

[0031] In actual packaging processes, a portion of the heat-seal area of ​​the heat-seal paper is heat-sealed to either the rest of the heat-seal area, the non-heat-seal area of ​​the heat-seal paper, or other packaging materials. When handling a package that has been inflated with trapped air during packaging, if sudden external pressure is applied to the package, the heat-seal-free areas and the areas that are not heat-sealed or are not heat-sealed during the heat-sealing process become air passages. Degassing through the paper substrate alone is insufficient, and there is a risk of the package bursting. However, the configuration with the aforementioned air passages is preferable because it can prevent the package from bursting in response to sudden external pressure.

[0032] To more reliably obtain the above effects, the heat-sealing paper according to this embodiment preferably has an air permeability resistance measured in the heat-sealing region in accordance with JIS P8117 of 15 seconds to 300 seconds, more preferably of 20 seconds to 150 seconds, and even more preferably of 25 seconds to 100 seconds.

[0033] Furthermore, in order to more reliably obtain the above effects, the heat-sealing paper according to this embodiment preferably has a degassing time of 10 to 600 seconds, more preferably 20 to 400 seconds, and more preferably 30 to 200 seconds, as measured by the following method A. When the degassing time is less than or equal to the upper limit, excess air trapped in the packaging can be released quickly, making it possible to package the product compactly. This reduces the space occupied by the packaging when loading it into a container, thereby improving delivery efficiency. When the degassing time is greater than or equal to the lower limit, sufficient shock absorption performance can be provided to the packaging.

[0034] <Measurement Method A for Required Degassing Time> The required degassing time is measured by a method including the following steps (1) to (4). Step (1): A sample of the heat-sealable paper formed into a package is set to B5 size, and with an opening for air injection left, three sides are sealed by heat sealing for 1 second at 160°C under a pressure of 0.2 MPa with a width of 20 mm. Step (2): Next, a gas inflow tube (such as a straw) is inserted to fill the interior with air, the gas inflow tube is immediately pulled out, then the opening is sealed with tape to prepare an empty package sample. Step (3): Using a tensile tester Tensilon (model number: RTG-1310) manufactured by A&D Company, Limited (hereinafter referred to as Tensilon), and using a test apparatus equipped with a load cell with a rated capacity of 250 N, a creep test is carried out according to the following procedure: (3-i) Place the package sample on the stage of Tensilon, place a paperboard of 210 mm × 270 mm × 2 mm thick (weighing about 100 g) on the package sample, then gradually extract air while manually applying a load, and compress until the height reaches 50 mm to prepare a test specimen for the creep test. (3-ii) Under the specimen, place a paperboard or stainless steel plate of a size larger than the test specimen, so as to suppress local stress concentration occurring between the specimen surface and the load transmission surface and distribute the load uniformly. (3-iii) Perform the creep test under the following conditions. (Creep Test Conditions) The operation mode is set to creep operation, the deformation mode to compression test, and the crosshead speed to 60 mm / min. After the test starts, the crosshead is lowered at 60 mm / min, and when the load reaches the target load of 0.2 kgf (about 1.96 N), the mode automatically shifts to constant load holding mode. The end point of the creep test is defined as the point when the relative displacement between the specimen and the load transmission plate under constant load stops (the point when air is completely evacuated), and during this period, the strain amount over time is continuously recorded. Step (4): The creep characteristics are analyzed from the obtained elapsed time-strain data, and the time required for air to be completely evacuated is evaluated as the "required degassing time".

[0035] In embodiments that facilitate the formation of channels for degassing, it is preferable that the heat-seal-free areas in the heat-seal region are arranged in a striped or mesh-like pattern, or that the areas where the heat-seal agent is present are arranged in an island-like (dot-like) pattern. In these embodiments, continuous uncoated areas (heat-seal-free areas) form channels for degassing, thereby improving the ability to release trapped excess air when a product is packaged using a heat-seal packaging system. On the other hand, embodiments in which the heat-seal-free areas are arranged in an island-like (dot-like) pattern are also included in the present invention. In this embodiment, degassing is performed evenly from the entire heat-seal region through the paper substrate, making it less likely for tearing to occur during degassing. Furthermore, since the heat-seal-coated areas (heat-seal-covered areas) are connected to the entire heat-seal region, the heat-sealed areas are less likely to peel off when the heat-seal region is heat-bonded, thereby improving the reliability of the packaging. In the island-like arrangement embodiment, each island is conveniently referred to as a dot in this specification. The shape of the dots is not limited to circles, but also includes polygons, stars, sectors, and combinations thereof. The size D of the dot is the diameter of the dot if the dot is circular. If the dot is not circular, the size D is the diameter of the circle inscribed in the dot. If the dot is flat, the size D is the average of the major and minor axes of the ellipse inscribed in the dot. If the sizes of the dots are not uniform, the size D is the average value. If the heat sealant-free area is dot-shaped, the size D of the dot is preferably 0.5 to 50 mm, more preferably 0.7 to 30 mm, and even more preferably 1.0 to 10 mm.

[0036] A case where a mesh shape is adopted as the specific pattern will be described with reference to Figure 1. Figure 1 is a schematic diagram showing the heat seal region 1 of the heat seal paper according to an embodiment of the present invention. In the heat seal region 1, the heat seal layer (heat seal agent coated portion) 2 and the heat seal agent-free portion 3 form a grid-like pattern. In Figure 1, the quadrilaterals (heat seal agent coated portions 2) constituting the grid are squares, but the present invention is not limited thereto, and they may be rhombuses or rectangles.

[0037] Examples of the method for forming the heat seal layer 2 on the paper base material in the specific pattern include a partial coating method, a transfer method using a roll engraved with the pattern, and the like.

[0038] When forming a stripe pattern, the stripe pattern may be formed along the flow direction of the production line, or an oblique stripe pattern may be formed so as to have an angle of more than 0° and 90° or less with respect to the flow direction of the production line. Also when forming a mesh pattern, the direction of the mesh pattern relative to the flow direction of the production line is not particularly limited. For example, in the case of a grid-like pattern, the grid-like pattern may be formed such that any side of the quadrilaterals constituting the grid extends along the flow direction of the production line, or the grid-like pattern may be formed such that any side of the quadrilaterals constituting the grid has an angle of more than 0° and less than 90° with respect to the flow direction of the production line.

[0039] A roll of heat seal paper in which the heat seal layer constituting a stripe pattern is provided on a paper base material, the roll having the stripe pattern so as to have an angle of 30° to 60° with respect to the flow direction of the roll, is a preferred embodiment because it easily forms a flow path for deaeration whether heat sealing is performed in the flow direction or in the width direction on an automatic packaging line. Similarly, when forming a grid-like pattern, a roll having the grid-like pattern such that any side of the quadrilaterals constituting the grid has an angle of 30° to 60° with respect to the flow direction of the roll is a preferred embodiment because it easily forms a flow path for deaeration whether heat sealing is performed in the flow direction or in the width direction on an automatic packaging line.

[0040] Furthermore, in another embodiment of the present invention, as shown in Figure 2, the heat sealant-free areas 3 may be arranged in an island-like (dot-like) pattern in the heat seal region 1. In this embodiment, the heat seal layer (heat sealant-coated area) 2 constitutes the sea area, and the entire heat seal region 1 has a sea-island structure. As described above, in this embodiment, degassing is performed evenly from the entire heat seal region 1 through the paper substrate, making it difficult for tears to occur during degassing. Also, since the heat sealant-coated area 2 is connected to the entire heat seal region 1 as a continuous sea area, the heat-sealed parts are less likely to peel off when the heat seal region 1 is heat-bonded, thereby increasing the reliability of the packaging. Furthermore, in another embodiment of the present invention, as shown in Figure 3, in the heat seal region 1, there are areas where the heat sealant-coated area continuously occupies a certain large area or more, but the area ratio occupied by the heat sealant-free areas is within the range of the present invention.

[0041] The heat-seal area may be provided on only a portion of at least one surface of the paper substrate, or it may be provided over the entire surface of at least one surface of the paper substrate. When the heat-seal area is provided over the entire surface of at least one surface of the paper substrate, heat sealing can be performed at all positions, resulting in a highly versatile heat-sealable paper that can accommodate the packaging of articles of various sizes and shapes.

[0042] When the heat-sealed regions are overlapped and heat-sealed for 1 second at 160°C and 0.2 MPa, it is preferable that the peel strength measured in accordance with JIS Z1707 is 4.0 N / 15 mm or more. A peel strength of 4.0 N / 15 mm or more makes it difficult for the heat-sealed portion to peel off due to the internal pressure generated when degassing occurs from the heat-sealant-free areas when the article is packaged.

[0043] (Water-dispersible resin binder) The heat-seal layer preferably contains a water-dispersible resin binder. A water-dispersible resin binder is a resin binder that is not water-soluble but becomes finely dispersed in water, like an emulsion or suspension. By coating the heat-seal layer with a water-based coating using a water-dispersible resin binder, heat-seal paper with excellent redispersibility and recyclability as paper can be obtained. If the water-dispersible resin binder also falls under the category of lubricant as described below, it shall be classified as a lubricant.

[0044] The polymer forming the backbone of the water-dispersible resin binder is not particularly limited, but includes polyolefin resins (polyethylene, polypropylene, etc.), ethylene-vinyl acetate copolymers, vinyl chloride resins, styrene resins, styrene / butadiene copolymers, styrene / unsaturated carboxylic acid copolymers (e.g., styrene / (meth)acrylic acid copolymers), styrene / acrylic copolymers (e.g., styrene / (meth)acrylic acid ester copolymers), acrylic resins, acrylonitrile / styrene copolymers, acrylonitrile / butadiene copolymers, ABS resins, AAS resins, and AES. Examples include polyvinyl acetate resins, vinylidene chloride resins, polyurethane resins, poly-4-methylpentene-1 resins, polybutene-1 resins, vinylidene fluoride resins, vinyl fluoride resins, fluorine resins, polycarbonate resins, polyamide resins, acetal resins, polyphenylene oxide resins, polyester resins (polyethylene terephthalate, polybutylene terephthalate, etc.), polyphenylene sulfide resins, polyimide resins, polysulfone resins, polyethersulfone resins, polyarylate resins, olefin / unsaturated carboxylic acid copolymers, and modified versions thereof. These may be used individually or in combination of two or more. Among these, ethylene-vinyl acetate copolymers and olefin / unsaturated carboxylic acid copolymers are preferred due to their high heat seal strength.

[0045] Examples of olefin / unsaturated carboxylic acid copolymers include ethylene-(meth)acrylic acid copolymers and ethylene-(meth)acrylic acid alkyl ester copolymers. Among these, ethylene-(meth)acrylic acid copolymers are preferred, and ethylene-acrylic acid copolymers are more preferred. Therefore, in a preferred embodiment of the present invention, the water-dispersible resin binder contained in the heat seal layer is at least one selected from the group consisting of ethylene-vinyl acetate copolymers and ethylene-(meth)acrylic acid copolymers. Furthermore, from the viewpoint of suppressing contamination of the equipment during coating and improving operability, ethylene-(meth)acrylic acid copolymers are more preferred. Note that the olefin / unsaturated carboxylic acid copolymer may also be an ionomer.

[0046] As the ethylene-(meth)acrylic acid copolymer, either a synthetic product or a commercially available product may be used. Examples of commercially available products include MP498345N, MP4983R, and MP4990R from Michaelman Japan LLC, Zaychsen® A and Zaychsen® AC from Sumitomo Seika Co., Ltd., and ChemiPearl S series from Mitsui Chemicals, Inc.

[0047] As the ethylene-vinyl acetate copolymer, either a synthetic product or a commercially available product may be used. Examples of commercially available products include Sumikaflex S-201HQ, S-305, S-305HQ, S-400HQ, S-401HQ, S-408HQE, S-450HQ, S-455HQ, S-456HQ, S-460HQ, S-467HQ, S-470HQ, and S-4, manufactured by Sumika Chemtex Co., Ltd. Examples include 80HQ, S-510HQ, S-520HQ, S-752, S-755, Polysol AD-2, AD-5, AD-6, AD-10, AD-11, AD-14, AD-56, AD-70, AD-92 from Showa Denko Corporation, and Aquatex EC1200, EC1400, EC1700, EC1800, MC3800 from Japan Coating Resin Co., Ltd.

[0048] The content of the water-dispersible resin binder in the heat-seal layer is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 45% by mass or more, even more preferably 50% by mass or more, and preferably 100% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less. Within the above range, heat-seal paper with high heat-seal strength can be obtained.

[0049] In other words, according to one embodiment of the present invention, the content of ethylene-vinyl acetate copolymer and ethylene-(meth)acrylic acid copolymer in the heat seal layer is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 45% by mass or more, even more preferably 50% by mass or more, and preferably 100% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less.

[0050] When the water-dispersible resin binder is an ethylene-vinyl acetate copolymer, the content of the ethylene-vinyl acetate copolymer in the heat seal layer is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 65% ​​by mass or more, particularly preferably 70% by mass or more, and preferably 100% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less.

[0051] Furthermore, when the water-dispersible resin binder is an ethylene-(meth)acrylic acid copolymer, the content of the ethylene-(meth)acrylic acid copolymer in the heat seal layer is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 45% by mass or more, particularly preferably 50% by mass or more, and preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less.

[0052] (Pigments) From the viewpoint of suppressing blocking of heat-seal paper, it is preferable that the heat-seal layer contains pigments in addition to the water-dispersible resin binder mentioned above.

[0053] The average particle size of the pigment is not particularly limited, but from the viewpoint of blocking resistance and heat sealability, it is preferably 0.1 μm or more, more preferably 0.3 μm or more, even more preferably 0.5 μm or more, and preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less. The average particle size of the pigment shall be the value measured by a laser diffraction / scattering particle size distribution analyzer.

[0054] If the heat seal layer contains a pigment, the pigment content is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 5 parts by mass or more, and preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 60 parts by mass or less, per 100 parts by mass of the water-dispersible resin binder.

[0055] If the heat seal layer contains a pigment, the pigment content in the heat seal layer is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less.

[0056] (Lubricant) From the viewpoint of imparting slipperiness to the heat-seal paper and suppressing blocking, it is preferable that the heat-seal layer contains a lubricant in addition to the water-dispersible resin binder mentioned above. A lubricant is a substance that, when incorporated into the heat-seal layer, can reduce the coefficient of friction of the surface of the heat-seal layer.

[0057] The lubricant is not particularly limited, and for example, waxes, metal soaps, fatty acid esters, etc., can be used. The lubricant may be used alone or in combination of two or more types. 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 polyethylene wax, paraffin wax, and polyester wax.

[0058] Examples of metal soaps include calcium stearate, sodium stearate, zinc stearate, aluminum stearate, magnesium stearate, sodium fatty acid soap, potassium oleate soap, potassium castor oil soap, and complexes thereof.

[0059] Among the lubricants mentioned above, polyethylene wax is preferred because it has a high melting point, the coating layer is less likely to soften even in relatively high-temperature environments, and it exhibits excellent blocking suppression effects. Carnauba wax is also preferred because it has a relatively low melting point, the wax component is easily formed on the surface of the coating layer, and it exhibits excellent blocking suppression effects. For polyethylene wax, either synthetic or commercially available products may be used, and examples of commercially available products include Chemipearl W-310 manufactured by Mitsui Chemicals, Inc. For carnauba wax, either synthetic or commercially available products may be used, and examples of commercially available products include Cellosol 524 manufactured by Chukyo Oil & Fat Co., Ltd.

[0060] If the heat seal layer contains a lubricant, the lubricant content is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 50 parts by mass or less, and more preferably 40 parts by mass or less, per 100 parts by mass of the water-dispersible resin binder.

[0061] If the heat seal layer contains a lubricant, the lubricant content in the heat seal layer is preferably 0.2% by mass or more, more preferably 0.5% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less.

[0062] In the present invention, the heat seal layer preferably contains a water-dispersible resin binder, more preferably contains a pigment in addition to the water-dispersible resin binder, and even more preferably contains a lubricant in addition to the water-dispersible resin binder and pigment.

[0063] <Heat-Sealable Paper> The heat-sealable paper of the present invention requires the above-mentioned paper substrate and heat-sealing agent, but a printed layer, a water-repellent layer, a lubricant layer, etc. may be provided as needed, or other substrates may be laminated. However, the air permeability resistance measured in the heat-sealed area according to JIS P8117 is preferably 15 seconds or more and 300 seconds or less, more preferably 20 seconds or more and 150 seconds or less, and even more preferably 25 seconds or more and 100 seconds or less.

[0064] By setting the air permeability in the heat-sealed region of the heat-sealing paper of the present invention to 300 seconds or less according to JIS P8117, air is removed from the surface of the heat-sealing paper during the packaging process, thus preventing the packaged item from becoming bulky due to trapped air.

[0065] (Packaging) The heat-sealable paper of the present invention can be used for packaging various products and closing them using a heat-sealing (heat-bonding) method. It can be used in pillow packaging made of one sheet of heat-sealable paper, packaging in which a product is placed between two folded sheets of heat-sealable paper and the three ends are heat-sealed to create a bag, packaging in which a product is sandwiched between two sheets of heat-sealable paper, and packaging in which the heat-sealable paper of the present invention is combined with other non-breathable packaging materials.

[0066] <Example 1> [Preparation of Heat Seal Layer Coating] 182 parts of ethylene-vinyl acetate copolymer (Sumika Chemtex Co., Ltd., Sumikaflex S-470HQ, solid content 55%), 52 parts of low molecular weight polyethylene wax dispersion (Mitsui Chemicals, Inc., Chemipearl W-310, solid content 38.5%), and 20 parts of a 50% aqueous dispersion of kaolin A (average particle size 8 μm) were mixed, and water was added and stirred to obtain a heat seal layer coating (concentration 40%).

[0067] [Manufacturing of paper substrate] A pulp slurry (solid content concentration 3.7% by mass) was obtained by mixing 100 parts by mass of unbleached softwood kraft pulp with 0.8 parts by mass of polyacrylamide, 0.7% by mass of cationized starch, 0.2 parts by mass of irrigating agent, and 1.0 part by mass of aluminum sulfate. Paper was made using the pulp slurry on a wire screen paper machine to a basis weight of 100 g / m². ２ A paper substrate was obtained.

[0068] [Manufacturing of Heat-Seal Paper] The obtained heat-seal layer coating was applied in stripes along the flow direction of the manufacturing line to one side of the paper substrate using a gravure coater, so that the area ratio of discontinuous portions (heat-seal agent-free areas) was 10%, thereby forming a heat-seal layer. The coating amount of the heat-seal layer after drying was 8 g / m². ２ The width of the striped area where the heat sealant was present was 27 mm, and the width of the striped area where the heat sealant was not present was 3.5 mm.

[0069] In the above paper substrate, X1 is the longitudinal tensile energy absorption amount measured in accordance with JIS P 8113:2006, Y1 is the transverse tensile energy absorption amount measured in accordance with JIS P 8113:2006, X2 is the longitudinal specific tensile energy absorption amount measured in accordance with JIS P 8113:2006, and Y2 is the transverse specific tensile energy absorption amount measured in accordance with JIS P 8113:2006. The same applies to the following examples and comparative examples.

[0070] <Example 2> Heat-seal paper was obtained in the same manner as in Example 1, except that the heat-seal coating pattern was changed to a mesh pattern during the heat-seal layer coating. The area ratio of the heat-seal agent-free area was 10%. The width of the heat-seal agent-coated area was 26.0 mm and the width of the heat-seal agent-free area was 1.5 mm.

[0071] <Example 3> Heat-sealable paper was obtained in the same manner as in Example 1, except that the area ratio of the discontinuous portion during the heat-seal layer coating was changed to 20%. The width of the striped portion where the heat-sealing agent was present was 24 mm, and the width of the striped portion where the heat-sealing agent was not present (heat-sealing agent-free portion) was 6.5 mm.

[0072] <Example 4> Heat-seal paper was obtained in the same manner as in Example 1, except that the heat-seal coating pattern was changed to a diagonal stripe pattern (angle with respect to the flow direction of the manufacturing line: 45°) during the heat-seal layer coating process.

[0073] <Example 5> Heat-seal paper was obtained in the same manner as in Example 1, except that the heat-seal coating pattern was changed to a dot pattern (heat-seal agent-free areas were dots (islands)) during the heat-seal layer coating process. The area ratio occupied by the heat-seal agent-free areas was 10%. The dots (heat-seal agent-free areas) were approximately squares of 2 mm x 2 mm.

[0074] <Example 6> Paper substrate with a basis weight of 80 g / m² ２ Except for the above, heat-sealable paper was obtained in the same manner as in Example 2.

[0075] <Example 7> Heat-sealable paper was obtained in the same manner as in Example 5, except that the dots were made into circles with a diameter of 1 mm.

[0076] <Example 8> Heat-sealable paper was obtained in the same manner as in Example 7, except that the area ratio of the heat-seal agent-free portion was set to 20%.

[0077] <Example 9> Heat-sealable paper was obtained in the same manner as in Example 7, except that the area ratio of the heat-seal agent-free portion was set to 1%.

[0078] <Example 10> Heat sealable paper was obtained in the same manner as in Example 7, except that the area ratio of the heat sealant-free portion was set to 49%.

[0079] <Example 11> When applying the heat seal layer, the heat seal coating pattern was changed to a mesh pattern, and heat seal paper was obtained in the same manner as in Example 2. The area ratio of the heat sealant-free area was 1%. The width of the heat sealant-coated area was 198.0 mm, and the width of the heat sealant-free area was 1.0 mm.

[0080] <Example 12> When applying the heat seal layer, the heat seal coating pattern was changed to a mesh pattern, and heat seal paper was obtained in the same manner as in Example 2. The area ratio occupied by the heat sealant-free area was 49%. The width of the heat sealant-coated area was 2.5 mm, and the width of the heat sealant-free area was 1.0 mm.

[0081] <Comparative Example 1> Heat-sealable paper was obtained in the same manner as in Example 1, except that the heat-sealable layer was applied to the entire surface of one side of the paper substrate.

[0082] <Comparative Example 2> Heat-seal paper was obtained in the same manner as in Example 1, except that the area ratio of the discontinuous portion during the heat-seal layer coating was changed to 0.5%.

[0083] <Comparative Example 3> Heat-seal paper was obtained in the same manner as in Example 1, except that the area ratio of the discontinuous portion during the heat-seal layer coating was changed to 55%.

[0084] [Evaluation] <Measurement of Heat Seal Peel Strength> The measurement was performed using the method described in JIS Z1707. Specifically, one set of heat seal paper was stacked so that the heat seal areas faced each other, and heat sealed using a heat seal tester (Tester Industries Co., Ltd., TP-701-B) at 160°C, 0.2 MPa, and 1 second. Subsequently, the heat-sealed test piece was cut to a width of 15 mm, and a tensile testing machine was used to perform a T-shaped peel at a tensile speed of 300 mm / min, and the maximum load recorded was taken as the heat seal peel strength. The results are shown in Tables 1 and 2 above. If the peel strength is 4.0 N / 15 mm or higher, it can be said that it is an excellent packaging material. If the peel strength is less than 4.0 N / 15 mm, there is a possibility that the heat-sealed portion may peel off during transportation when used as packaging material.

[0085] <Evaluation of Degassing Ability> Five three-sided sealed bags were made by cutting heat-sealing paper to 200 mm (length) x 250 mm (width), folding it in half with the heat-sealing layers facing each other, inserting a sponge measuring 60 mm (length) x 110 mm (width) x 30 mm (height) inside, and sealing it with an impulse sealer (VG-400, manufactured by Fuji Impulse Co., Ltd.) with a seal width of 10 mm. The three-sided sealed bags were placed on a table and pressed from above by hand, and the degree to which air could be released from the three-sided sealed bags was evaluated sensorily according to the following criteria. A: Air can be easily released from inside the bag, making it an excellent product packaging material that can be quickly compacted. B: There is resistance when pressed by hand, but if pressed continuously, air can be released from inside the bag, making it usable as a product packaging material that can be compacted relatively quickly. C: There is strong resistance when pressed by hand, making it difficult to release air from inside the bag, and it takes time for the air to be released, which is a problem as a product packaging material as it requires a lot of work time. Almost no air was released, making it a problem as a product packaging material. D: There is strong resistance when pressed by hand, and almost no air is removed from inside the bag, making it impossible to achieve compact product packaging. There is strong resistance when pressed by hand, and if pressed continuously, the heat-sealed part peels off, which is problematic as a product packaging material. The results are shown in Tables 1 and 2 above.

[0086] <Measurement of Air Removal Time> The time was measured using Method A described above. The results are shown in Tables 1 and 2 above.

[0087]

[0088]

[0089] The heat-sealable papers of Examples 1 to 12 possessed sufficient heat-seal strength to be used as packaging materials and exhibited excellent degassing properties, releasing excess air trapped when products were packaged. On the other hand, the heat-sealable papers of Comparative Examples 1 and 2 had poor degassing properties, reducing efficiency in product storage and transportation. Furthermore, the heat-sealable paper of Comparative Example 3 had problems with heat-seal strength.

[0090] The heat-sealable paper of the present invention is a packaging material that possesses sufficient heat-sealing and degassing properties, and offers excellent packing workability.

[0091] 1. Heat seal area 2. Heat seal layer (heat sealant coated area) 3. Heat sealant-free area

Claims

1. Heat-sealable paper having a heat-seal region on at least a portion of at least one surface of a paper substrate, in which areas where a heat-seal agent is present and areas where a heat-seal agent is absent are regularly repeated, wherein the area ratio of the areas where a heat-seal agent is absent in the heat-seal region is 1% or more and less than 50%.

2. The heat-sealable paper according to claim 1, wherein when the heat-sealable regions are overlapped and heat-sealed for 1 second at 160°C and 0.2 MPa, the peel strength measured in accordance with JIS Z1707 is 4.0 N / 15 mm or more.

3. The heat-sealable paper according to claim 1 or 2, wherein the heat-sealable area is provided over the entire surface of at least one surface of the paper substrate.

4. The heat-sealable paper according to claim 1 or 2, wherein the air permeability resistance measured in the heat-sealed region is 15 seconds or more and 300 seconds or less, in accordance with JIS P8117.

5. The heat-sealable paper according to claim 1 or 2, wherein the areas where the heat-sealing agent is present and the areas where the heat-sealing agent is absent form at least one pattern selected from the group consisting of stripe-like patterns, dot-like patterns, and mesh-like patterns arranged in one direction on the surface of the paper substrate.

6. The heat-sealable paper according to claim 1 or 2, wherein the required time for degassing, as measured by method A, which includes the following steps (1) to (4), is 10 to 600 seconds. Step (1): A sample of the heat-sealable paper as a package is made to B5 size, and three sides are sealed by heat sealing at 160°C for 1 second under a pressure of 0.2 MPa with a width of 20 mm, leaving an opening for air injection. Step (2): Next, a gas inlet tube is inserted and air is filled inside, and immediately after the gas inlet tube is removed, the opening is sealed with tape. Step (3): Using a Tensilon tensile testing machine (model number: RTG-1310) manufactured by A&D Co., Ltd. (hereinafter referred to as Tensilon), a creep test is performed using a test apparatus equipped with a load cell rated at 250 N, in the following procedure: (3-i) The sample is placed on the Tensilon stand, and a 210 mm x 270 mm x 2 mm thick (weighing approximately 100 g) piece of cardboard is placed on top of the sample. While manually applying a load, the air is gradually removed and the sample is compressed to a height of 50 mm to prepare a sample for the creep test. (3-ii) A piece of cardboard or stainless steel plate larger than the test sample is placed under the sample to suppress localized stress concentration between the sample surface and the load-transmission surface and to distribute the load uniformly. (3-iii) The creep test is performed under the following conditions. (Creep test conditions) The operation mode is set to creep operation, the deformation mode to compression test, and the crosshead speed is set to 60 mm / min. After the start of the test, the crosshead is lowered at 60 mm / min, and the system automatically switches to constant load holding mode when the load reaches the target load of 1.96 N. The endpoint of the creep test is defined as the point when the relative displacement between the sample and the load transfer plate stops under constant load (when all the air has escaped), and the amount of strain over time is continuously recorded during this period. Step (4): The creep characteristics are analyzed from the obtained elapsed time-strain data, and the time required for all the air to escape is defined as the venting time.

7. A packaging body in which at least a portion of the heat-seal area of ​​the heat-seal paper according to claim 1 or 2 is heat-bonded.

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