Heat-sealing paper and packaging method

Abstract

To provide heat-sealable paper and a packaging method that prevent the heat-sealed portion from opening during packaging and prevent the surface of the paper substrate of the heat-sealable paper from blocking the surface of the adjacent resin layer when stored as a roll. [Solution] The invention comprises a paper substrate 10, an undercoat layer 11, and a heat-sealable resin layer 12, wherein the undercoat layer 11 contains a first water-dispersible resin, and the tensile energy of the undercoat layer 11 is 150 MJ / m 3 or more, and the mass is 3 g / m 2 The present invention provides a heat-sealable paper 1 in which the heat-sealable resin layer 12 comprises a second water-dispersible resin and a lubricant 13, the glass transition temperature of the second water-dispersible resin is 0°C or higher, the lubricant 13 comprises at least one selected from the group consisting of metal soaps and inorganic particles, and the content of the lubricant 13 is less than 10% by mass relative to the total amount of the first and second water-dispersible resins.

Description

[Technical Field]

[0001] The present invention relates to heat-sealable paper and packaging methods. [Background technology]

[0002] Conventionally, food packaging materials, pharmaceutical packaging materials, chemical packaging materials, etc., have been multilayered structures with heat-sealing properties. Sheets are widely used. Such multilayer sheets usually have a substrate and a heat-sealable layer, and a package can be formed by heat-sealing the heat-sealable layers together. Paper substrates, plastic substrates, etc. have been used as the substrates of multilayer sheets. However, with increasing awareness of environmental issues in recent years, environmental pollution caused by the disposal of petroleum-derived plastic substrates has become a concern. Therefore, even in applications where plastic substrates have traditionally been used, the use of paper substrates, which have a smaller environmental impact, has been considered.

[0003] As a technique relating to a multilayer sheet using a paper base material, for example, Patent Document 1 describes a multilayer sheet comprising a paper base material mainly composed of unbleached softwood kraft pulp and a heat seal layer laminated on one side of the paper base material, in which the folding endurance of the paper base material in the machine direction is 500 times or more and 1,000 times or less, the folding endurance in the width direction is 80 times or more and 200 times or less, the Beck smoothness of the surface of the heat seal layer laminated surface is 3 seconds or more and 230 seconds or less, the main component of the heat seal layer is an ionomer resin, and the coating amount of the heat seal layer is 1.5 g / m 2 More than 10.0g / m 2 The following heat-sealable paper is disclosed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-024906 Summary of the Invention [Problem to be solved by the invention]

[0005] Further applications of heat-sealable paper have been proposed, including its use as a packaging material to replace corrugated cardboard. This is because corrugated cardboard is bulky, making it difficult to secure storage space, and also presents environmental problems such as the difficulty of smoothly conserving resources. It is hoped that lightweight and compact heat-sealable paper can solve these environmental problems. From this perspective, heat-sealable paper is required to have sufficient strength to be used as a substitute for corrugated cardboard.

[0006] However, packaging made of heat-sealable paper generally has poor impact resistance, so there is a problem that, for example, when packaging a product, the heat-sealed portion is prone to opening depending on the weight and shape of the product. In this regard, for example, the packaging using heat-sealable paper described in Patent Document 1 above does not sufficiently suppress the occurrence of opening in the heat-sealed portion, so there is at least room for improvement. In addition, when heat-sealable paper is wound into a roll and stored as a roll, there is a problem that the surface of the paper substrate of the heat-sealable paper and the surface of the resin layer adjacent to the surface of the paper substrate tend to block each other.

[0007] The present invention has been made in view of the above circumstances, and aims to provide heat-sealable paper and a packaging method that prevent the heat-sealed portion from opening when packaging contents, and that prevent the surface of the paper substrate of the heat-sealable paper from blocking the surface of the resin layer adjacent to the surface of the paper substrate when the heat-sealable paper is wound into a roll for storage. [Means for solving the problem]

[0008] As a result of extensive research into achieving the above-mentioned object, the present inventors have discovered a heat-sealable paper comprising a paper substrate, an undercoat layer, and a heat-sealable resin layer in this order, wherein the undercoat layer contains a first water-dispersible resin, and the tensile energy per unit volume of the undercoat layer is 150 MJ / m 3or more, and the mass per unit area of ​​the undercoat layer is 3 g / m 2 Based on the above findings, we have found that the heat-sealable resin layer comprises a second water-dispersible resin and a lubricant, the glass transition temperature of the second water-dispersible resin is 0°C or higher, the lubricant comprises at least one selected from the group consisting of metal soaps and inorganic particles, and the lubricant content is less than 10% by mass relative to the total amount of the first water-dispersible resin and the second water-dispersible resin, thereby completing the present invention.

[0009] That is, the present invention is as follows.

[0010] (1) A heat-sealable paper comprising a paper substrate, an undercoat layer, and a heat-sealable resin layer in this order, wherein the undercoat layer contains a first water-dispersible resin, and the tensile energy per unit volume of the undercoat layer is 150 MJ / m 3 or more, and the mass per unit area of ​​the undercoat layer is 3 g / m 2 The heat-sealable resin layer comprises a second water-dispersible resin and a lubricant, the glass transition temperature of the second water-dispersible resin is 0°C or higher, the lubricant comprises at least one selected from the group consisting of metal soaps and inorganic particles, and the lubricant content is less than 10% by mass relative to the total amount of the first water-dispersible resin and the second water-dispersible resin, thus forming a heat-sealable paper. (2) The heat-sealable paper according to (1), wherein the heat-sealable resin layer is located on the outermost surface of the heat-sealable paper. (3) The heat sealable paper according to (1) or (2) contains a urethane resin as the first water-dispersible resin. (4) The heat seal paper according to (3) further contains at least one selected from the group consisting of styrene-butadiene rubber and ethylene-vinyl acetate copolymer as the first water-dispersible resin. (5) The heat sealable paper according to (1) or (2) contains styrene-butadiene rubber as the second water-dispersible resin. (6) The heat-seal paper according to (1) or (2) comprises at least one metal soap selected from the group consisting of calcium fatty acid, zinc fatty acid, barium fatty acid, magnesium fatty acid, and lithium fatty acid. (7) The heat-sealable paper according to (1) or (2) is wherein the inorganic particles include at least one selected from the group consisting of amorphous silica, spherical silica, calcium carbonate, talc, kaolin, and titanium dioxide. (8) The heat seal paper according to (1) or (2) is for pillow packaging. (9) This is a packaging method in which a package is formed by pillow packaging using the heat seal paper described in (1) or (2), and an article is packaged in the package. [Effects of the Invention]

[0011] The present invention has been made in consideration of the above-mentioned circumstances, and provides heat-sealed paper and a packaging method in which no opening occurs in the heat-sealed portion when packaging contents, and in which, when the heat-sealed paper is wound into a roll and stored, there is no blocking between the surface of the paper base material of the heat-sealed paper and the surface of the resin layer adjacent to the surface of the paper base material. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view showing an example of the heat seal paper according to the present embodiment. [Figure 2] FIG. 2 is a diagram illustrating the roll body according to this embodiment. [Figure 3] FIG. 3 is a perspective view showing an example of a state in which contents are packaged with the heat seal paper according to this embodiment. [Figure 4] FIG. 4 is a diagram illustrating a pillow packaging method according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] The following describes in detail embodiments for carrying out the present invention (hereinafter simply referred to as "this embodiment"). This embodiment is illustrative for explaining the present invention and is not intended to limit the present invention to the following content. The present invention can be implemented by modifying it as appropriate within the scope of its gist.

[0014] Furthermore, identical elements in the drawings will be given the same reference numeral, and redundant explanations will be omitted. Unless otherwise specified, positional relationships such as top, bottom, left, and right will be based on those shown in the drawings. Moreover, the dimensional ratios in the drawings are not limited to those shown.

[0015] 1.Heat seal paper

[0016] Figure 1 is a cross-sectional view showing an example of the heat-sealable paper 1 according to this embodiment. Figure 2 is a diagram illustrating the roll body 5 according to this embodiment.

[0017] The heat-sealable paper 1 according to this embodiment comprises a paper substrate 10, an undercoat layer 11, and a heat-sealable resin layer 12 in this order, wherein the undercoat layer 11 contains a first water-dispersible resin, and the tensile energy per unit volume of the undercoat layer 11 is 150 MJ / m 3 Furthermore, the mass per unit area of ​​the undercoat layer 11 is 3 g / m². 2The heat-sealable resin layer 12 contains a second water-dispersible resin and a lubricant 13, the glass transition temperature of the second water-dispersible resin being 0°C or higher, the lubricant 13 containing at least one selected from the group consisting of metal soaps and inorganic particles, and the content of the lubricant 13 being less than 10% by mass of the total amount of the first water-dispersible resin and the second water-dispersible resin. A packaging bag using this heat-sealable paper 1 does not open at the heat-sealed portion when packaging contents, and when the heat-sealable paper 1 is wound into a roll 5 and stored, there is no blocking between the surface of the paper substrate 10 of the heat-sealable paper 1 and the surface of the resin layer adjacent to the surface of the paper substrate 10.

[0018] From the viewpoint of achieving the above-mentioned effects more effectively, it is preferable that the heat-sealable resin layer 12 of the heat-sealable paper 1 according to this embodiment be located on the outermost surface of the heat-sealable paper 1. Unless otherwise specified, the heat-sealable paper 1 according to this embodiment is not necessarily limited to a three-layer structure, as long as it includes the paper substrate 10, the undercoat layer 11, and the heat-sealable resin layer 12 in this order. Nor is it limited to a structure in which these three layers are in contact with each other. For example, it goes without saying that a structure of four or more layers, in which another layer is disposed between these three layers, may be used, if necessary.

[0019] According to this embodiment, the heat seal paper 1 can be made such that openings do not occur in the heat seal portion when packaging contents. In particular, one of its preferred modes is, for example, when used for pillow packaging in which contents are packaged continuously, it can effectively prevent openings from occurring in the heat seal portion even when the contents are heavy, weighing 1 kg or more. This is because the undercoat layer 11 contains a first water-dispersible resin, and the mass per unit area of ​​the undercoat layer 11 is 3 g / m or less. 2or more, and the content of the lubricant 13 contained in the heat-sealable resin layer 12 is less than 10 mass % with respect to the total amount of the first water-dispersible resin and the second water-dispersible resin, sufficient heat-seal strength can be obtained, and further, the tensile energy per unit volume of the undercoat layer 11 can be 150 MJ / m 3 It is believed that the above makes it easier for the undercoat layer 11 to stretch, thereby reducing the impact when a heavy object comes into contact with the heat-sealed portion (however, the functions and effects of this embodiment are not limited to these).

[0020] The heat seal strength of the heat-sealable paper 1 according to this embodiment is preferably 6.5 N / 15 mm or more, more preferably 7.0 N / 15 mm or more, and even more preferably 7.5 N / 15 mm or more. When the heat seal strength is above the lower limit mentioned above, heat sealing can be performed more effectively when making bags with a pillow packaging machine. The upper limit of the heat seal strength is not particularly limited, but for example, it is preferably 30.0 N / 15 mm or less, and more preferably 25.0 N / 15 mm or less. The heat seal strength can be adjusted, for example, by controlling the mass of the heat-sealable resin layer 12 per unit area, the basis weight of the paper substrate 10, etc. The heat seal strength can be measured, for example, by pressing the surfaces of the heat sealable resin layer 12 of the heat seal paper 1 together under conditions of 160°C, 0.2 MPa, and 1 second, and then using a tensile testing machine (Shimadzu Corporation, product name "Autograph AG-500NIS") in accordance with JIS Z 1707, as the maximum load when peeled off at a tensile speed of 300 mm / min.

[0021] Furthermore, according to this embodiment, a heat-sealable resin layer 12 is provided on the side of the undercoat layer 11 opposite to the side with the paper substrate 10, and the heat-sealable resin layer 12 contains a second water-dispersible resin and a lubricant 13. The glass transition temperature of the second water-dispersible resin is 0°C or higher, and the lubricant 13 contains at least one selected from the group consisting of metal soaps and inorganic particles, and the content of the lubricant 13 is less than 10% by mass relative to the total amount of the first water-dispersible resin and the second water-dispersible resin (100% by mass). As a result, even with heat-sealable paper 1 having high heat-seal strength, when stored as a roll 5 wound into a roll shape as shown in Figure 2, the lubricant 13 acts as an anti-blocking agent, and the surface of the paper substrate 10 of the heat-sealable paper 1 and the surface of the heat-sealable resin layer 12 adjacent to the surface of the paper substrate 10 do not block each other (however, the effects and benefits according to this embodiment are not limited to these).

[0022] The basis weight of the heat seal paper 1 is not particularly limited, but is preferably 30 to 120 g / m 2 The lower limit is preferably 40 g / m 2 More preferably, it is 50 g / m or more. 2 The upper limit is 110 g / m 2 More preferably, it is 100 g / m or less. 2 The following is even more preferable: If the basis weight of the heat-seal paper 1 is within the above range, the lightness and flexibility of the heat-seal paper 1 will be good, making it easier to manufacture bags. In addition, the balance with strength tends to be even better. If the basis weight of the heat-seal paper 1 is below the above upper limit, it is possible to prevent the stiffness of the heat-seal paper from becoming too high, and thus prevent poor transportability. The basis weight can be measured in accordance with JIS P 8124:2011.

[0023] The thickness of the heat seal paper 1 is not particularly limited, but is preferably 40 to 150 μm. The lower limit is more preferably 50 μm or more, and even more preferably 60 μm or more. The upper limit is more preferably 140 μm or less, and even more preferably 130 μm or less. When the thickness of the heat seal paper 1 is equal to or greater than the above-mentioned lower limit, the strength of the heat seal paper 1 tends to be improved, and unintentional tearing tends to be more effectively prevented. Furthermore, when the thickness of the paper substrate 10 is equal to or less than the above-mentioned upper limit, the lightness and flexibility tend to be improved, and bag production tends to be easier. The thickness can be measured in accordance with JIS P 8118:2014.

[0024] Each component of the heat seal paper 1 will be described below.

[0025] (Paper base material 10)

[0026] The paper substrate 10 is not particularly limited and can be appropriately selected depending on the application of the heat seal paper 1. Examples of such paper substrates 10 include fine paper, kraft paper, Clupak paper, glassine paper, parchment paper, rayon paper, gravure paper, art paper, coated paper, recycled paper, etc. Among these, fine paper, unbleached kraft paper, bleached kraft paper, glassine paper, art paper, and cast-coated paper are more preferred, and unbleached kraft paper is even more preferred. One layer of these paper substrates 10 may be used alone, or two or more layers of the same or different paper substrates 10 may be laminated together.

[0027] The basis weight of the paper substrate 10 is not particularly limited, but is preferably 20 to 200 g / m 2 The lower limit is preferably 30 g / m 2 More preferably, it is 40 g / m or more. 2 The upper limit is 150 g / m 2 More preferably, it is 100 g / m or less. 2The following is even more preferable: When the basis weight of the paper substrate 10 is within the above range, the balance between the lightness and strength of the paper substrate 10 tends to be even better. The basis weight can be measured in accordance with JIS P 8124:2011.

[0028] The thickness of the paper substrate 10 is not particularly limited, but is preferably 20 to 200 μm. The lower limit is more preferably 30 μm or more, and even more preferably 40 μm or more. The upper limit is more preferably 150 μm or less, and even more preferably 100 μm or less. When the thickness of the paper substrate 10 is above the lower limit mentioned above, the strength of the paper substrate 10 tends to be better, and unintentional tearing is further suppressed. Also, when the thickness of the paper substrate 10 is below the upper limit mentioned above, the lightness and flexibility tend to be better. Note that "thickness of the paper substrate 10" refers to the total thickness of the paper substrate 10, and if the paper substrate 10 is a substrate consisting of multiple layers, it refers to the total thickness of all layers constituting the paper substrate 10. The thickness can be measured in accordance with JIS P 8118:2014.

[0029] The paper substrate 10 is preferably subjected to a surface modification treatment to improve adhesion on the side on which the undercoat layer 11 is provided. Examples of surface modification treatments include the formation of a primer layer, ozone treatment, corona treatment, plasma treatment, and ultraviolet treatment. Among these, ozone treatment and corona treatment are more preferred. These surface treatments may be performed individually or in combination.

[0030] (Undercoat layer 11)

[0031] The heat-sealable paper 1 according to this embodiment includes at least a paper substrate 10 and an undercoat layer 11 in that order, but it is preferable that the undercoat layer 11 is present on at least one surface of the paper substrate 10. Furthermore, the undercoat layer 11 may be one layer or two or more layers. The composition of the two or more undercoat layers 11 may be the same or different.

[0032] The undercoat layer 11 contains a first water-dispersible resin. The water-dispersible resin is, for example, a resin that is not water-soluble but is finely dispersed in water, such as in an emulsion or suspension.

[0033] The first water-dispersible resin preferably contains a urethane resin. In this case, the first water-dispersible resin may be a single urethane resin, or may be used in combination with a water-dispersible resin other than the urethane resin. In this case, the content of the urethane resin relative to 100% by mass of the total amount of the first water-dispersible resin is preferably greater than 5% by mass. By setting the proportion of the urethane resin within this range, the tensile energy per unit volume of the undercoat layer 11 can be effectively controlled. As a result, the undercoat layer 11 stretches more effectively when the contents are filled, resulting in more excellent impact resistance. Even when a packaging bag formed from the heat-sealable paper 1 contains 1 kg or more of contents, the opening of the heat-sealed portion due to the weight of the contents can be effectively prevented (however, the functions and effects of this embodiment are not limited to these).

[0034] To achieve these effects more effectively, the lower limit of the content of the urethane resin relative to 100% by mass of the total amount of the first water-dispersible resin is preferably 6% by mass or more, more preferably 8% by mass or more, even more preferably 10% by mass or more, even more preferably 20% by mass or more, and even more preferably 50% by mass or more. The upper limit of the content of the urethane resin is not particularly limited, but is preferably, for example, 90% by mass or less, and more preferably 80% by mass or less. This provides more suitable extensibility to the heat-sealable resin layer 12 and effectively prevents deterioration of the undercoat layer 11 due to hydrolysis caused by moisture absorption of the urethane resin during storage.

[0035] As the urethane resin, for example, polyether-based, polyester-based, polycarbonate-based, and other urethane resins are preferred. Among these, polyether-based and polycarbonate-based resins are preferred in terms of flexibility, strength, and hydrolysis resistance. Such urethane resins may be commercially available products. Examples of commercially available products include "Hydran WLS-230" manufactured by DIC Corporation and "Superflex: Variety 470" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. These may be used alone or in combination of two or more types.

[0036] In this embodiment, the undercoat layer 11 may further contain a water-dispersible resin other than a urethane resin as the first water-dispersible resin. Preferably, the first water-dispersible resin further contains at least one selected from the group consisting of styrene-butadiene rubber and ethylene-vinyl acetate copolymer. This reduces deterioration of the undercoat layer 11 due to the hydrolysis of the urethane resin, and more effectively ensures the storage stability of the heat-sealable paper 1.

[0037] The styrene-butadiene rubber is preferably one having a single film elongation rate of 100% or more. Such styrene-butadiene rubber may be a commercially available product. Examples of commercially available products include "Narstar SR-107" manufactured by Nippon A&L Co., Ltd., "Narstar SR-102" manufactured by Nippon A&L Co., Ltd., and "Narstar SR-107" manufactured by Nippon A&L Co., Ltd. These may be used alone or in combination of two or more types.

[0038] The ethylene-vinyl acetate copolymer preferably has a free-standing elongation of 100% or more. Commercially available ethylene-vinyl acetate copolymers may be used. Examples of commercially available products include "Sumikaflex (registered trademark) S-510HQ" and "Sumikaflex (registered trademark) S-470HQ" manufactured by Sumika Chemtex Corporation. These may be used alone or in combination of two or more.

[0039] The blending ratio of the urethane resin described above to the styrene-butadiene rubber and ethylene-vinyl acetate copolymer is not particularly limited, but when it is desired to satisfy the required level of various physical properties and to further effectively improve the elongation of the undercoat layer 11, it is preferable that the total ratio of urethane resin to styrene-butadiene rubber and ethylene-vinyl acetate copolymer be 100:0 to 10:90, more preferably 100:0 to 20:80, even more preferably 100:0 to 30:70, and even more preferably 100:0 to 50:50.

[0040] The tensile energy per unit volume of the undercoat layer 11 is 150 MJ / m 3 The lower limit is 200MJ / m 3 It is preferable that the concentration is 250MJ / m or more. 3 The upper limit is not particularly limited, but is preferably 1000 MJ / m 3 It is preferable that the concentration is less than 900MJ / m 3 The following is more preferable: If the tensile energy per unit volume is above the lower limit mentioned above, the extensibility of the undercoat layer 11 improves to a range suitable for a packaging bag when filling the contents into the packaging bag, resulting in a packaging bag with excellent impact resistance, which can suppress the opening of the heat-sealed part and tearing of the paper. Furthermore, because the undercoat layer 11 is extensible, it has excellent impact resistance when used as a packaging bag, so various types of paper base materials 10 can be applied to the heat-sealable paper 1. Note that the tensile energy per unit volume of the undercoat layer 11 is the tensile energy of the undercoat layer 11 alone, excluding other layers such as the paper base material 10 and the heat-sealable resin layer 12, and can be measured in accordance with JIS K 7161. "Tensile energy of the undercoat layer 11 alone" means the tensile energy of the entire undercoat layer 11, and if the undercoat layer 11 is composed of multiple layers, it means the tensile energy measured as a single layer of the undercoat layer 11 composed of multiple layers.

[0041] (Content of undercoat layer 11)

[0042] The mass per unit area of ​​the undercoat layer 11 included in the heat seal paper 1 according to this embodiment is 3.0 g / m 2 The lower limit is 4.0 g / m 2 It is preferable that the content is 6.0 g / m or more. 2 The upper limit is not particularly limited, but for example, it is 13.0 g / m 2 Preferably, it is 11.0 g / m or less. 2 The following conditions are more preferable: If the mass per unit area of ​​the undercoat layer 11 is above the lower limit mentioned above, sufficient heat seal strength can be ensured, and the impact resistance of the packaging bag is improved. If the mass per unit area of ​​the undercoat layer 11 is below the upper limit mentioned above, the occurrence of contamination during the bag-making process can be suppressed more effectively. In addition, the amount of resin is small, which is also preferable from an environmental perspective.

[0043] In addition, "mass per unit area of ​​the undercoat layer 11" means the weight of the layer 11 per unit area unless otherwise specified. For example, it means the amount of the layer 11 formed on the coating target (paper substrate 10 or another layer, etc.) and corresponds to the amount of solid components contained in the layer 11 per unit area. Furthermore, in this embodiment, if the layer 11 contains two or more types of solid components, unless otherwise specified, "mass per unit area" means the total amount of these components. Moreover, "mass per unit area of ​​the undercoat layer 11" refers to the mass of a single layer of the undercoat layer 11, excluding other layers such as the paper substrate 10 or the heat-sealable resin layer 12. And, "mass of a single layer of the undercoat layer 11" means the mass per unit area of ​​the entire undercoat layer 11. If the undercoat layer 11 is composed of multiple layers, it means the mass measured as a single layer of the undercoat layer 11 composed of multiple layers.

[0044] The content of the first water-dispersible resin in the undercoat layer 11 is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 100% by mass (i.e., the undercoat layer 11 is composed only of the first water-dispersible resin). This ensures even higher heat seal strength and further improves the impact resistance of the packaging bag.

[0045] The undercoat layer 11 contains a first water-dispersible resin having a mass per unit area of ​​3.0 g / m 2 The lower limit is preferably 4.0 g / m or more. 2 It is preferable that the content is 6.0 g / m or more. 2 The upper limit is not particularly limited, but for example, it is 13.0 g / m 2 Preferably, it is 11.0 g / m or less. 2 It is more preferable that the thickness is not more than 100 mm. This makes it possible to ensure higher heat seal strength and further improve the impact resistance of the packaging bag.

[0046] The undercoat layer 11 may further contain various additives in addition to the first water-dispersible resin, as necessary. However, it is preferable that the additives do not include the lubricant 13 described below. By not including the lubricant 13 in the undercoat layer 11, even higher heat seal strength can be ensured. The additives are not particularly limited, but examples thereof include antifoaming agents, thickeners, thickening polysaccharides, neutralizing agents, plasticizers, preservatives, pH adjusters, crosslinking agents, dyes, etc.

[0047] (Heat-sealable resin layer 12)

[0048] The heat-sealable paper 1 according to this embodiment comprises, in this order, a paper substrate 10, an undercoat layer 11, and a heat-sealable resin layer 12. That is, the heat-sealable resin layer 12 is preferably provided on the surface of the undercoat layer 11 opposite to the surface on which the paper substrate 10 is provided. The heat-sealable resin layer 12 may be one layer or two or more layers. The compositions of the two or more heat-sealable resin layers 12 may be the same or different.

[0049] The heat-sealable resin layer 12 contains a second water-dispersible resin and a lubricant 13, the glass transition temperature of which is 0°C or higher, and the lubricant 13 contains at least one selected from the group consisting of metal soaps and inorganic particles, and the content of the lubricant 13 is less than 10 mass% of the total amount of the first water-dispersible resin and the second water-dispersible resin. This makes it possible to maintain sufficient heat-seal strength and prevent blocking between the surface of the paper substrate 10 of the heat-sealable paper 1 and the surface of the resin layer (preferably the heat-sealable resin layer 12) adjacent to the surface of the paper substrate 10 when the heat-sealable paper 1 is wound into a roll and stored as a roll 5 (however, the functions and effects of this embodiment are not limited to these).

[0050] The glass transition temperature (Tg) of the second water-dispersible resin may be 0°C or higher, more preferably 4°C or higher, even more preferably 5°C or higher, even more preferably 6°C or higher, and even more preferably 7°C or higher. The upper limit is preferably 40°C or lower, more preferably 35°C or lower, even more preferably 30°C or lower, even more preferably 25°C or lower, and even more preferably 23°C or lower. When the glass transition temperature (Tg) is above the above-mentioned lower limit, blocking can be effectively suppressed when the heat seal paper 1 is stored as a roll 5. When the glass transition temperature (Tg) is below the above-mentioned upper limit, better heat sealability can be exhibited under low-temperature conditions.

[0051] Here, "glass transition temperature (Tg)" refers to the temperature at which a polymer transitions from a rubbery state to a solidified state, and is measured using a differential scanning calorimeter (DSC) (such as the "DSC600" manufactured by Hitachi High-Tech Corporation) in accordance with JIS K 7121:1987.

[0052] Examples of water-dispersible resins having the above-mentioned glass transition temperatures include styrene-butadiene rubber, methacrylic-butadiene rubber, acrylonitrile-butadiene rubber, ethylene-vinyl acetate, and styrene-acrylic resin. Among these water-dispersible resins, it is preferable to include styrene-butadiene rubber as the second water-dispersible resin. This more effectively prevents blocking when the heat seal paper 1 is stored as a roll 5. Such styrene-butadiene rubber may be a commercially available product. Examples of commercially available products include "Narstar SR-102" and "Narstar SR-103" manufactured by Nippon A&L Co., Ltd. These may be used alone or in combination of two or more.

[0053] The heat-sealable resin layer 12 contains a lubricant 13 for the purpose of suppressing blocking when stored as a roll 5, and the lubricant 13 contains at least one selected from the group consisting of metal soaps and inorganic particles.

[0054] The metal soap preferably contains at least one selected from the group consisting of fatty acid calcium, fatty acid zinc, fatty acid barium, fatty acid magnesium, and fatty acid lithium, and more preferably contains at least one selected from the group consisting of fatty acid calcium. This more effectively prevents blocking during storage as roll body 5. Furthermore, by imparting slipperiness to heat-sealable resin layer 12 with the metal soap, it is possible to effectively prevent contamination of parts of the bag-making device that come into contact with heat-sealable resin layer 12 during the bag-making process, as well as transportation problems due to friction.

[0055] The inorganic particles preferably contain at least one selected from the group consisting of amorphous silica, spherical silica, calcium carbonate, talc, kaolin, and titanium oxide, and more preferably amorphous silica. This more effectively prevents blocking during storage in roll body 5. Furthermore, during the bag-making process, the contact area between the parts of the bag-making device and heat-sealable resin layer 12 can be reduced, effectively preventing contamination of the parts of the bag-making device and transport problems due to friction.

[0056] The content of lubricant 13 in the heat-sealable resin layer 12 is less than 10% by mass relative to the total amount of the first water-dispersible resin and the second water-dispersible resin. This makes it possible to both suppress the opening of the heat-sealed portion or tearing of the paper due to the weight of the contents when packaging with the heat-sealable paper 1, and to suppress blocking when the heat-sealable paper 1 is stored. From the viewpoint of further improving these effects, the upper limit is preferably 9% by mass or less, more preferably 8% by mass or less, even more preferably 7% by mass or less, and even more preferably 5% by mass or less. The lower limit is preferably 2% by mass or more, and more preferably 3% by mass or more.

[0057] The content of the lubricant 13 in the heat-sealable resin layer 12 is preferably 5 to 40% by mass relative to the total amount of the heat-sealable resin layer 12. The lower limit of this content is more preferably 10% by mass or more, and even more preferably 15% by mass or more. The upper limit of this content is more preferably 37% by mass or less, and even more preferably 30% by mass or less. This ensures even higher heat seal strength.

[0058] Furthermore, the blending ratio (mass ratio) of the second water-dispersible resin to the lubricant 13 in the heat-sealable resin layer 12 is not particularly limited, but when it is desired to satisfy the required levels of various physical properties and more effectively suppress blocking during storage, the second water-dispersible resin:lubricant 13 ratio is preferably 95:5 to 55:45, more preferably 90:10 to 60:40, and even more preferably 85:15 to 63:37.

[0059] (Content of heat-sealable resin layer)

[0060] The mass per unit area of ​​the heat-sealable resin layer 12 contained in the heat-sealable paper 1 according to this embodiment is 0.5 to 8.0 g / m². 2 It is preferable that this be the case. The lower limit is 1.0 g / m 2 It is more preferable that the amount be greater than or equal to 1.5 g / m 2 It is even more preferable that it be greater than or equal to 7.0 g / m². The upper limit is 7.0 g / m². 2 It is more preferable that the following conditions apply: 6.0 g / m 2 When the mass per unit area of ​​the heat-sealable resin layer 12 is equal to or greater than the above-mentioned lower limit, blocking can be more effectively suppressed when the heat-sealable paper 1 is stored in the form of a roll 5, and when the mass per unit area of ​​the heat-sealable resin layer 12 is equal to or less than the above-mentioned upper limit, even higher heat-seal strength can be ensured.

[0061] Unless otherwise specified, the "mass per unit area of ​​the heat-sealable resin layer 12" refers to the weight of the layer 12 per unit area. For example, it refers to the amount of the layer 12 formed on the object to be coated (such as the undercoat layer 11 or another layer), and corresponds to the amount of solid components contained in the layer 12 per unit area. In this embodiment, if the layer 12 contains two or more solid components, the "mass per unit area" refers to the total amount of these components unless otherwise specified. Furthermore, the "mass per unit area of ​​the heat-sealable resin layer 12" refers to the mass of the single layer of the heat-sealable resin layer 12, excluding other layers such as the paper substrate 10 and the undercoat layer 11. The "mass of the single layer of the heat-sealable resin layer 12" refers to the mass per unit area of ​​the entire heat-sealable resin layer 12. When the heat-sealable resin layer 12 is composed of multiple layers, it refers to the mass of the heat-sealable resin layer 12, measured as a single layer. Furthermore, "heat-sealable resin layer 12" refers to a layer containing at least a second water-dispersible resin and a lubricant 13.

[0062] The content of the second water-dispersible resin in the heat-sealable resin layer 12 is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, thereby ensuring even higher heat-seal strength.

[0063] The heat-sealable resin layer 12 has a second water-dispersible resin with a mass per unit area (solid component content) of 0.3 to 7.0 g / m². 2 It is preferable that this be the case. The lower limit is 0.6 g / m 2 It is more preferable that the value be greater than or equal to 0.9 g / m 2 It is even more preferable that it be greater than or equal to 6.0 g / m². The upper limit is 6.0 g / m². 2 It is more preferable that the following is the case: 5.0 g / m 2 It is more preferable that the mass per unit area of ​​the second water-dispersible resin is equal to or greater than the above-mentioned lower limit. When the mass per unit area of ​​the second water-dispersible resin is equal to or greater than the above-mentioned upper limit, it is possible to effectively prevent the lubricant 13 from falling off. When the mass per unit area of ​​the second water-dispersible resin is equal to or less than the above-mentioned upper limit, it is possible to ensure even higher heat seal strength.

[0064] The heat-sealable resin layer 12 may further contain various additives, if necessary, in addition to the second water-dispersible resin and the lubricant 13. The additives are not particularly limited, but examples thereof include antifoaming agents, thickeners, thickening polysaccharides, neutralizing agents, plasticizers, preservatives, pH adjusters, crosslinking agents, fillers, dyes, etc.

[0065] 2. Heat seal paper manufacturing method

[0066] The heat seal paper 1 can be produced, for example, by producing the above-mentioned paper substrate 10 and forming the above-mentioned undercoat layer 11 and heat sealable resin layer 12 in this order on at least one surface of the paper substrate 10.

[0067] The method for manufacturing the paper substrate 10 is not particularly limited, and can be manufactured, for example, by conventionally known methods.

[0068] The method for forming the undercoat layer 11 is not particularly limited, but an example is a method in which an undercoat layer-forming coating liquid, in which a first water-dispersible resin is dissolved in a dispersion medium, is applied to one surface of the paper substrate 10 and dried. The dispersion medium can be selected appropriately depending on the form of the first water-dispersible resin, and examples include water, alcohols such as isopropanol and ethanol, polyhydric alcohols such as diethylene glycol and glycerin, and water-soluble organic solvents such as dimethylformamide, but water is preferred from an environmental perspective. It is preferable that the above-mentioned additives be mixed into the undercoat layer-forming coating liquid as necessary.

[0069] The method for forming the heat-sealable resin layer 12 is not particularly limited, but examples include a method in which a second water-dispersible resin is dissolved in a dispersion medium, and a lubricant 13 is further mixed therein to form a coating liquid for forming a heat-sealable resin layer, which is then applied to the surface of the undercoat layer 11 and dried. The dispersion medium may be selected appropriately depending on the form of the second water-dispersible resin, and examples include water, alcohols such as isopropanol and ethanol, polyhydric alcohols such as diethylene glycol and glycerin, and water-soluble organic solvents such as dimethylformamide, but water is preferred from an environmental perspective. The method for mixing the lubricant 13 is not particularly limited, and it can be mixed, for example, using a disperser. It is preferable that the above-mentioned additives be further mixed into the coating liquid for forming the heat-sealable resin layer as necessary.

[0070] The method for applying these coating solutions is not particularly limited, and examples of methods that can be used include coating by appropriately selecting various coating devices such as a blade coater, an air knife coater, a rod blade coater, a bar blade coater, a gravure coater, a bar coater, a multistage roll coater, a roll coater, a reverse roll coater, a curtain coater, a spray coater, a gate roll coater, a size press coater, and a shim sizer.

[0071] The method for drying the applied coating liquid is not particularly limited, and any conventionally known method can be used. The drying temperature and drying time are also not particularly limited, and may be set appropriately, but for example, drying at 100 to 150°C for 30 seconds to 1 minute is preferred.

[0072] The surface to be coated with the heat-sealable resin layer 12 may be smoothed by, for example, super calendering, gloss calendering, soft calendering, etc. Alternatively, the surface may be roughened by embossing.

[0073] The obtained heat seal paper 1 is preferably wound into a roll and stored as a roll body 5. Before or after storage, both ends of the roll body 5 may be removed with a slitter, if necessary, to adjust the width of the heat seal paper 1 to the width of a processing machine in a subsequent process.

[0074] The uses of the heat seal paper 1 described above are not particularly limited, but it can be used, for example, as a packaging material for pillow packaging, gusset packaging, three-sided seal packaging, four-sided seal packaging, etc. Among these, the heat seal paper 1 according to this embodiment does not open or tear at the heat-sealed portion when packaging contents, and therefore can be suitably used, for example, as a packaging material for pillow packaging, which continuously packages contents in a vertical pillow packaging machine that is susceptible to impacts from the contents when filling.

[0075] Figure 3 is a perspective view showing an example of a state in which the contents 4 are packaged with the heat-sealable paper 2 according to this embodiment.

[0076] An example of the form of the packaging material after packaging is a packaging bag, and the packaging bag 3 has a bag-shaped bag body including heat seal paper 2, and the bag body preferably has a heat sealable resin layer located on its inner surface. That is, the packaging bag 3 according to this embodiment is more preferably manufactured in a state where the heat sealable resin layer of the heat seal paper 2 is located on the inner surface of the bag. Furthermore, the heat sealable resin layer may be provided at least in the heat seal portion of the packaging bag 3 (seal portion 34 and center seal portion (not shown)) of the inner surface of the bag body, but it is preferable that the heat sealable resin layer be provided on the entire inner surface.

[0077] 3 shows the product packaged in pillow packaging, the packaging form is not necessarily limited to this, and may be, for example, gusset packaging, three-side sealed packaging, four-side sealed packaging, etc.

[0078] 3. Packaging method

[0079] FIG. 4 is a diagram illustrating a pillow packaging method according to this embodiment.

[0080] The heat-sealable resin layer of the heat-sealable paper 2 according to this embodiment can be heat-sealed, for example, by applying pressure and heat, making it easier to make and seal bags. The bag-making and sealing methods are not particularly limited and can be carried out by conventionally known methods, but as described above, the heat-sealable paper 2 according to this embodiment is preferably used in a packaging method in which a package is formed using the heat-sealable paper 2 by pillow packaging, and an article is packaged in the package.

[0081] Pillow packaging is a type of packaging in which, as shown in Figure 4, for example, a packaged item (contents 4) is placed on or below a sheet of heat-sealable paper 2, and the heat-sealable paper 2 is overlapped at both ends in the width direction with their inner surfaces facing each other to form a cylindrical shape. The overlapped portion is then sealed with a center seal portion 36, and the bottom portion or opening portion (insertion opening 38) is sealed horizontally with a seal portion 34 according to the length (height) of the bag, and each bag is cut at this sealed portion. This pillow packaging can be performed using conventionally known equipment.

[0082] In addition, pillow packaging includes, for example, vertical pillow packaging in which the heat-seal paper 2 is fed vertically and the contents 4 are filled and wrapped from above, and horizontal pillow packaging in which the heat-seal paper 2 is fed horizontally and the contents 4 are wrapped. However, the heat-seal paper 2 according to this embodiment is suitable for packaging heavy objects, and the packaging bag 3 can effectively withstand the impact of heavy objects being dropped on its heat-sealed portion, so it can be suitably used in both vertical and horizontal pillow packaging.

[0083] Furthermore, while there are no particular limitations on the method of heat sealing the seal portion 34 and the center seal portion 36 in this case, it is preferable to heat seal the heat-sealable resin layers together at 120 to 220°C and 0.1 to 0.5 MPa for 0.1 to 1.0 seconds. [Example]

[0084] The present invention will be described in more detail by the following examples and comparative examples, but the present invention is not limited in any way by the following examples. Unless otherwise specified, percentages, etc., are based on mass.

[0085] Example 1

[0086] (Preparation of heat-sealable paper 1)

[0087] As the paper base material 10, unbleached kraft paper (manufactured by Chuetsu Pulp Industry Co., Ltd., product name "Unbleached Kraft Paper for Light Bags", basis weight 60g / m²)2 ) was used, and as the first water-dispersible resin, a water-based urethane resin (abbreviation "PU", manufactured by DIC Corporation, product name "Hydran WLS-230", glass transition temperature -75℃) was used. As the second water-dispersible resin, styrene-butadiene rubber (abbreviation "SBR(2)", manufactured by Nippon A&L Co., Ltd., product name "Nalstar SR-102", glass transition temperature Tg=21℃) was used, and as lubricant 13, calcium fatty acid (abbreviation "fatty acid Ca", manufactured by Toho Chemical Industry Co., Ltd., product name "LB Coat LB-2700S") was used.

[0088] A coating liquid for forming an undercoat layer containing 20% ​​by mass of the first water-dispersible resin and water as a dispersion medium was prepared, and the dry adhesion amount of the solid component (the first water-dispersible resin) was 6 g / m. 2 The coating liquid was applied to one surface (felt side) of the paper substrate 10 with a Mayer bar so that the coating liquid was applied to one surface (felt side) of the paper substrate 10, and dried at 150°C for 30 seconds to form an undercoat layer 11 on the surface of the paper substrate 10.

[0089] Next, a coating solution for forming a heat-sealable resin layer was prepared by mixing a lubricant 13 in an amount equal to 5% by mass of the total amount (solid component amount) of the first and second water-dispersible resins (100% by mass) with water, which contained 15% by mass of the second water-dispersible resin and water as a dispersion medium. The dry adhesion amount of the solid components (the second water-dispersible resin and lubricant 13) of this coating solution was 2 g / m². 2 The mixture was applied to the surface of the undercoat layer 11 with a Mayer bar so that the composition satisfies the following formula: and dried at 150° C. for 30 seconds to form a heat-sealable resin layer 12 on the surface of the paper substrate 10.

[0090] As a result, the heat seal paper 1 shown in Fig. 1 was obtained. With respect to the heat seal paper 1 of this example, the mass per unit area of ​​the single undercoat layer 11 was 6 g / m 2 In the case of this example, the content of the first water-dispersible resin in the undercoat layer 11 was 100% by mass, and the mass per unit area of ​​the first water-dispersible resin in the undercoat layer 11 (dry adhesion amount) was 6 g / m 2The mass per unit area of ​​the single layer of the heat-sealable resin layer 12 was 2 g / m 2 In this example, the content of the second water-dispersible resin in the heat-sealable resin layer 12 was 80% by mass, and the content of the lubricant 13 was 20% by mass (second water-dispersible resin:lubricant=80:20 (mass ratio)). Therefore, the total mass per unit area (dry adhesion weight) of the second water-dispersible resin in the heat-sealable resin layer 12 and the mass per unit area (dry adhesion weight) of the lubricant 13 was 2 g / m 2 It was.

[0091] <Example 2>

[0092] Heat-sealable paper 1 was obtained in the same manner as in Example 1, except that the first water-dispersible resin in Example 1 was a combination of 90 mass% styrene-butadiene rubber (abbreviated as "SBR(1)", manufactured by Nippon A&L Co., Ltd., trade name "Nalstar SR-107", glass transition temperature Tg = -15°C) and 10 mass% water-based urethane resin (abbreviated as "PU", manufactured by DIC Corporation, trade name "Hydran WLS-230", glass transition temperature -75°C). The mass per unit area of ​​the single undercoat layer 11 of the heat-sealable paper 1 in this example was 6 g / m. 2 In the case of this example, the content of the first water-dispersible resin in the undercoat layer 11 was 100 mass %, and the dry adhesion amount of the first water-dispersible resin in the undercoat layer 11 was 6 g / m 2 The mass per unit area of ​​the single layer of the heat-sealable resin layer 12 was 2 g / m 2 In this example, the content of the second water-dispersible resin in the heat-sealable resin layer 12 was 80% by mass, and the content of the lubricant 13 was 20% (second water-dispersible resin:lubricant 13=80:20 (mass ratio)). Therefore, the total mass per unit area (dry adhesion weight) of the second water-dispersible resin in the heat-sealable resin layer 12 and the mass per unit area (dry adhesion weight) of the lubricant 13 was 2 g / m 2 It was.

[0093] Example 3

[0094] Except for using 80% by mass of styrene-butadiene rubber (abbreviation "SBR(1)", manufactured by Nippon A&L Co., Ltd., trade name "Nalstar SR-107", glass transition temperature Tg=-15℃) and 20% by mass of water-based urethane resin (abbreviation "PU", manufactured by DIC Corporation, trade name "Hydran WLS-230", glass transition temperature -75℃) as the first water-dispersible resin in Example 1, heat seal paper 1 was obtained in the same manner as in Example 1. For the heat seal paper 1 of this example, the mass per unit area of ​​a single layer of undercoat layer 11 was 6 g / m². 2 In the case of this example, the content of the first water-dispersible resin in the undercoat layer 11 was 100% by mass, and the mass per unit area of ​​the first water-dispersible resin in the undercoat layer 11 (dry adhesion amount) was 6 g / m 2 The mass per unit area of ​​the single layer of the heat-sealable resin layer 12 was 2 g / m 2 In this embodiment, the content of the second water-dispersible resin in the heat-sealable resin layer 12 was 80% by mass, and the content of the lubricant 13 was 20% by mass (second water-dispersible resin: lubricant 13 = 80:20 (mass ratio)). Therefore, the sum of the mass per unit area (dry adhesion amount) of the second water-dispersible resin and the mass per unit area (dry adhesion amount) of the lubricant 13 in the heat-sealable resin layer 12 was 2 g / m². 2 It was.

[0095] Example 4

[0096] A coating solution for forming an undercoat layer containing a first water-dispersible resin was prepared, and the dry adhesion amount of the first water-dispersible resin was 8 g / m 2 Heat-sealable paper 1 was obtained in the same manner as in Example 3, except that a coating liquid was applied. For the heat-sealable paper 1 of this example, the mass per unit area of ​​a single undercoat layer 11 was 8 g / m². 2In this example, the content of the first water-dispersible resin in the undercoat layer 11 was 100% by mass, and the mass per unit area (dry adhesion amount) of the first water-dispersible resin in the undercoat layer 11 was 8 g / m². 2 The mass per unit area of ​​the single layer of the heat-sealable resin layer 12 was 2 g / m 2 In this embodiment, the content of the second water-dispersible resin in the heat-sealable resin layer 12 was 80% by mass, and the content of the lubricant 13 was 20% by mass (second water-dispersible resin: lubricant 13 = 80:20 (mass ratio)). Therefore, the sum of the mass per unit area (dry adhesion amount) of the second water-dispersible resin and the mass per unit area (dry adhesion amount) of the lubricant 13 in the heat-sealable resin layer 12 was 2 g / m². 2 It was.

[0097] <Example 5>

[0098] A coating solution for forming an undercoat layer containing a first water-dispersible resin was prepared, and the dry adhesion amount of the first water-dispersible resin was 4 g / m 2 Heat-sealable paper 1 was obtained in the same manner as in Example 3, except that a coating liquid was applied. For the heat-sealable paper 1 of this example, the mass per unit area of ​​a single undercoat layer 11 was 4 g / m². 2 In this example, the content of the first water-dispersible resin in the undercoat layer 11 was 100% by mass, and the mass per unit area (dry adhesion amount) of the first water-dispersible resin in the undercoat layer 11 was 4 g / m². 2 The mass per unit area of ​​the single layer of the heat-sealable resin layer 12 was 2 g / m 2 In this example, the content of the second water-dispersible resin in the heat-sealable resin layer 12 was 80% by mass, and the content of the lubricant 13 was 20% by mass (second water-dispersible resin:lubricant=80:20 (mass ratio)). Therefore, the total mass per unit area (dry adhesion weight) of the second water-dispersible resin in the heat-sealable resin layer 12 and the mass per unit area (dry adhesion weight) of the lubricant 13 was 2 g / m 2 It was.

[0099] Example 6

[0100] As the paper base material 10, unbleached Kurupack paper (manufactured by Tokushu Tokai Paper Co., Ltd., product name "Kraft Tokai TKK", basis weight 73 g / m²) 2 A heat-sealable paper 1 was obtained in the same manner as in Example 3, except that the following was used. For the heat-sealable paper 1 of this example, the mass per unit area of ​​a single undercoat layer 11 is 6 g / m². 2 In the case of this example, the content of the first water-dispersible resin in the undercoat layer 11 was 100% by mass, and the mass per unit area of ​​the first water-dispersible resin in the undercoat layer 11 (dry adhesion amount) was 6 g / m 2 The mass per unit area of ​​the single layer of the heat-sealable resin layer 12 was 2 g / m 2 In this embodiment, the content of the second water-dispersible resin in the heat-sealable resin layer 12 was 80% by mass, and the content of the lubricant 13 was 20% by mass (second water-dispersible resin: lubricant 13 = 80:20 (mass ratio)). Therefore, the sum of the mass per unit area (dry adhesion amount) of the second water-dispersible resin and the mass per unit area (dry adhesion amount) of the lubricant 13 in the heat-sealable resin layer 12 was 2 g / m². 2 It was.

[0101] Example 7

[0102] As the paper base material 10, unbleached kraft paper (manufactured by Shin Tokai Paper Co., Ltd., product name "Tokai Kraft CF", basis weight 50 g / m²) 2 A heat-sealable paper 1 was obtained in the same manner as in Example 3, except that the following was used. For the heat-sealable paper 1 of this example, the mass per unit area of ​​a single undercoat layer 11 is 6 g / m². 2 In the case of this example, the content of the first water-dispersible resin in the undercoat layer 11 was 100% by mass, and the mass per unit area of ​​the first water-dispersible resin in the undercoat layer 11 (dry adhesion amount) was 6 g / m 2The mass per unit area of ​​the single layer of the heat-sealable resin layer 12 was 2 g / m 2 In this embodiment, the content of the second water-dispersible resin in the heat-sealable resin layer 12 was 80% by mass, and the content of the lubricant 13 was 20% by mass (second water-dispersible resin: lubricant 13 = 80:20 (mass ratio)). Therefore, the sum of the mass per unit area (dry adhesion amount) of the second water-dispersible resin and the mass per unit area (dry adhesion amount) of the lubricant 13 in the heat-sealable resin layer 12 was 2 g / m². 2 It was.

[0103] Example 8

[0104] As the paper substrate 10, bleached glassine paper (manufactured by Lintec Corporation, product name "White Glassine", basis weight 50 g / m 2 A heat-sealable paper 1 was obtained in the same manner as in Example 3, except that the following was used. For the heat-sealable paper 1 of this example, the mass per unit area of ​​a single undercoat layer 11 is 6 g / m². 2 In the case of this example, the content of the first water-dispersible resin in the undercoat layer 11 was 100% by mass, and the mass per unit area of ​​the first water-dispersible resin in the undercoat layer 11 (dry adhesion amount) was 6 g / m 2 The mass per unit area of ​​the single layer of the heat-sealable resin layer 12 was 2 g / m 2 In this embodiment, the content of the second water-dispersible resin in the heat-sealable resin layer 12 was 80% by mass, and the content of the lubricant 13 was 20% by mass (second water-dispersible resin: lubricant 13 = 80:20 (mass ratio)). Therefore, the sum of the mass per unit area (dry adhesion amount) of the second water-dispersible resin and the mass per unit area (dry adhesion amount) of the lubricant 13 in the heat-sealable resin layer 12 was 2 g / m². 2 It was.

[0105] Example 9

[0106] A heat-sealable paper 1 was obtained in the same manner as in Example 3, except that amorphous silica (manufactured by Fuji Silysia Chemical Co., Ltd., trade name "SYLYSIA® 380") was used as the lubricant 13. For the heat-sealable paper 1 of this example, the mass per unit area of ​​a single layer of the undercoat layer 11 was 6 g / m². 2 In the case of this example, the content of the first water-dispersible resin in the undercoat layer 11 was 100% by mass, and the mass per unit area of ​​the first water-dispersible resin in the undercoat layer 11 (dry adhesion amount) was 6 g / m 2 The mass per unit area of ​​the single layer of the heat-sealable resin layer 12 was 2 g / m 2 In this embodiment, the content of the second water-dispersible resin in the heat-sealable resin layer 12 was 80% by mass, and the content of the lubricant 13 was 20% by mass (second water-dispersible resin: lubricant 13 = 80:20 (mass ratio)). Therefore, the sum of the mass per unit area (dry adhesion amount) of the second water-dispersible resin and the mass per unit area (dry adhesion amount) of the lubricant 13 in the heat-sealable resin layer 12 was 2 g / m². 2 It was.

[0107] Example 10

[0108] Heat-sealable paper 1 was obtained in the same manner as in Example 3, except that the lubricant 13 in Example 3 was a mixture of fatty acid calcium salts in an amount of 2% by mass and amorphous silica (manufactured by Fuji Silysia Chemical Ltd., trade name "SYLYSIA (registered trademark) 380") in an amount of 3% by mass, based on 100% by mass of the total (solid content) of the first water-dispersible resin and the second water-dispersible resin. The mass per unit area of ​​the single undercoat layer 11 of the heat-sealable paper 1 in this example was 6 g / m. 2 In the case of this example, the content of the first water-dispersible resin in the undercoat layer 11 was 100% by mass, and the mass per unit area of ​​the first water-dispersible resin in the undercoat layer 11 (dry adhesion amount) was 6 g / m 2 The mass per unit area of ​​the single layer of the heat-sealable resin layer 12 was 2 g / m 2In this example, the content of the second water-dispersible resin in the heat-sealable resin layer 12 was 80% by mass, and the content of the lubricant 13 (total of calcium fatty acid and amorphous silica) was 20% by mass (second water-dispersible resin: lubricant 13 = 80:20 (mass ratio)). Therefore, the sum of the mass per unit area (dry adhesion amount) of the second water-dispersible resin and the mass per unit area (dry adhesion amount) of the lubricant 13 in the heat-sealable resin layer 12 was 2 g / m². 2 It was.

[0109] Example 11

[0110] Heat seal paper 1 was obtained in the same manner as in Example 3, except that the lubricant 13 of Example 3 was a mixture of calcium fatty acid in an amount of 5% by mass and amorphous silica (manufactured by Fuji Silysia Chemical Co., Ltd., trade name "SYLYSIA® 380") in an amount of 4% by mass, based on 100% by mass of the total amount (solid component amount) of the first and second water-dispersible resins. For the heat seal paper 1 of this example, the mass per unit area of ​​a single layer of the undercoat layer 11 was 6 g / m². 2 In the case of this example, the content of the first water-dispersible resin in the undercoat layer 11 was 100% by mass, and the mass per unit area of ​​the first water-dispersible resin in the undercoat layer 11 (dry adhesion amount) was 6 g / m 2 The mass per unit area of ​​the single layer of the heat-sealable resin layer 12 was 2 g / m 2 In this example, the content of the second water-dispersible resin in the heat-sealable resin layer 12 was 64% by mass, and the content of the lubricant 13 (total of calcium fatty acid and amorphous silica) was 36% by mass (second water-dispersible resin: lubricant = 64:36 (mass ratio)). Therefore, the sum of the mass per unit area (dry adhesion amount) of the second water-dispersible resin and the mass per unit area (dry adhesion amount) of the lubricant 13 in the heat-sealable resin layer 12 was 2 g / m². 2 It was.

[0111] Example 12

[0112] A heat-sealable paper 1 was obtained in the same manner as in Example 10, except that styrene-butadiene rubber (abbreviated as "SBR(3)", manufactured by Nippon A&L Co., Ltd., trade name "Nalstar SR-103", glass transition temperature Tg = 7°C) was used as the second water-dispersible resin in Example 10. The mass per unit area of ​​the single undercoat layer 11 of the heat-sealable paper 1 in this example was 6 g / m 2 In the case of this example, the content of the first water-dispersible resin in the undercoat layer 11 was 100% by mass, and the mass per unit area of ​​the first water-dispersible resin in the undercoat layer 11 (dry adhesion amount) was 6 g / m 2 The mass per unit area of ​​the single layer of the heat-sealable resin layer 12 was 2 g / m 2 In this embodiment, the content of the second water-dispersible resin in the heat-sealable resin layer 12 was 80% by mass, and the content of the lubricant 13 was 20% by mass (second water-dispersible resin: lubricant 13 = 80:20 (mass ratio)). Therefore, the sum of the mass per unit area (dry adhesion amount) of the second water-dispersible resin and the mass per unit area (dry adhesion amount) of the lubricant 13 in the heat-sealable resin layer 12 was 2 g / m². 2 It was.

[0113] Example 13

[0114] Heat-sealable paper 1 was obtained in the same manner as in Example 1, except that the first water-dispersible resin in Example 1 was a combination of 70 mass% styrene-butadiene rubber (abbreviated as "SBR(1)", manufactured by Nippon A&L Co., Ltd., trade name "Nalstar SR-107", glass transition temperature Tg = -15°C) and 30 mass% water-based urethane resin (abbreviated as "PU", manufactured by DIC Corporation, trade name "Hydran WLS-230", glass transition temperature -75°C). The mass per unit area of ​​the single undercoat layer 11 of the heat-sealable paper 1 in this example was 6 g / m. 2 In the case of this example, the content of the first water-dispersible resin in the undercoat layer 11 was 100% by mass, and the mass per unit area of ​​the first water-dispersible resin in the undercoat layer 11 (dry adhesion amount) was 6 g / m2 The mass per unit area of ​​the single layer of the heat-sealable resin layer 12 was 2 g / m 2 In this embodiment, the content of the second water-dispersible resin in the heat-sealable resin layer 12 was 80% by mass, and the content of the lubricant 13 was 20% by mass (second water-dispersible resin: lubricant 13 = 80:20 (mass ratio)). Therefore, the sum of the mass per unit area (dry adhesion amount) of the second water-dispersible resin and the mass per unit area (dry adhesion amount) of the lubricant 13 in the heat-sealable resin layer 12 was 2 g / m². 2 It was.

[0115] Example 14

[0116] Except for using 50% by mass of styrene-butadiene rubber (abbreviation "SBR(1)", manufactured by Nippon A&L Co., Ltd., trade name "Nalstar SR-107", glass transition temperature Tg=-15℃) and 50% by mass of water-based urethane resin (abbreviation "PU", manufactured by DIC Corporation, trade name "Hydran WLS-230", glass transition temperature -75℃) as the first water-dispersible resin in Example 1, heat seal paper 1 was obtained in the same manner as in Example 1. For the heat seal paper 1 of this example, the mass per unit area of ​​a single layer of undercoat layer 11 is 6 g / m². 2 In the case of this example, the content of the first water-dispersible resin in the undercoat layer 11 was 100% by mass, and the mass per unit area of ​​the first water-dispersible resin in the undercoat layer 11 (dry adhesion amount) was 6 g / m 2 The mass per unit area of ​​the single layer of the heat-sealable resin layer 12 was 2 g / m 2 In this embodiment, the content of the second water-dispersible resin in the heat-sealable resin layer 12 was 80% by mass, and the content of the lubricant 13 was 20% by mass (second water-dispersible resin: lubricant 13 = 80:20 (mass ratio)). Therefore, the sum of the mass per unit area (dry adhesion amount) of the second water-dispersible resin and the mass per unit area (dry adhesion amount) of the lubricant 13 in the heat-sealable resin layer 12 was 2 g / m². 2 It was.

[0117] Example 15

[0118] A coating liquid for forming a heat-sealable resin layer is prepared by mixing a lubricant 13 in an amount equal to 5% by mass of the total amount (solid component amount) of the first water-dispersible resin and the second water-dispersible resin (100% by mass), and the dry adhesion amount of the solid components (second water-dispersible resin and lubricant 13) is 6 g / m². 2 A heat-sealable paper 1 was obtained in the same manner as in Example 3, except that the coating liquid was applied to the surface of the undercoat layer 11. For the heat-sealable paper 1 of this example, the mass per unit area of ​​a single layer of the undercoat layer 11 was 6 g / m². 2 In the case of this example, the content of the first water-dispersible resin in the undercoat layer 11 was 100% by mass, and the mass per unit area of ​​the first water-dispersible resin in the undercoat layer 11 (dry adhesion amount) was 6 g / m 2 The mass per unit area of ​​the single layer of the heat-sealable resin layer 12 was 6 g / m 2 In this embodiment, the content of the second water-dispersible resin in the heat-sealable resin layer 12 was 90% by mass, and the content of the lubricant 13 was 10% by mass (second water-dispersible resin: lubricant 13 = 90:10 (mass ratio)). Therefore, the sum of the mass per unit area (dry adhesion amount) of the second water-dispersible resin and the mass per unit area (dry adhesion amount) of the lubricant 13 in the heat-sealable resin layer 12 was 6 g / m². 2 It was.

[0119] <Comparative Example 1>

[0120] As the paper base material, unbleached kraft paper (manufactured by Chuetsu Pulp Industries Co., Ltd., product name "Unbleached Kraft Paper for Light Bags", basis weight 60 g / m 2 Using a water-dispersible resin, an ionomer-based resin (abbreviated as "ionomer-based," manufactured by Mitsui Chemicals, trade name "Chemipearl S-100") was used. A coating solution containing 20% ​​by mass of the water-dispersible resin and water as the dispersion medium was prepared, and the dry adhesion amount of the solid component (the water-dispersible resin) was 8 g / m². 2The coating solution was applied to one surface (felt side) of the paper substrate with a Mayer bar so that the coating solution was applied to one surface (felt side) of the paper substrate and dried at 150°C for 30 seconds to form an undercoat layer on the surface of the paper substrate. For the heat seal paper of this comparative example, the mass per unit area of ​​the undercoat layer was 8g / m 2 In the case of this comparative example, the content of the first water-dispersible resin in the undercoat layer was 100% by mass, and the mass per unit area of ​​the first water-dispersible resin in the undercoat layer (dry adhesion amount) was 8 g / m 2 Furthermore, no heat-sealable resin layer was formed.

[0121] <Comparative Example 2>

[0122] A heat-sealable paper was obtained in the same manner as in Example 1, except that the first water-dispersible resin used was 95% by mass of styrene-butadiene rubber (abbreviation "SBR(1)", manufactured by Nippon A&L Co., Ltd., trade name "Nalstar SR-107", glass transition temperature Tg=-15℃) and 5% by mass of water-based urethane resin (abbreviation "PU", manufactured by DIC Corporation, trade name "Hydran WLS-230", glass transition temperature Tg=-75℃), in combination with the first water-dispersible resin of Example 1. For the heat-sealable paper of this comparative example, the mass per unit area of ​​the undercoat layer single layer was 6 g / m². 2 In the case of this comparative example, the content of the first water-dispersible resin in the undercoat layer was 100% by mass, and the mass per unit area of ​​the first water-dispersible resin in the undercoat layer (dry adhesion amount) was 6 g / m 2 Furthermore, the mass per unit area of ​​a single heat-sealable resin layer was 2 g / m². 2 In the comparative example, the content of the second water-dispersible resin in the heat-sealable resin layer was 80% by mass, and the content of the lubricant was 20% by mass (second water-dispersible resin: lubricant = 80:20 (mass ratio)). Therefore, the sum of the mass per unit area (dry adhesion amount) of the second water-dispersible resin and the mass per unit area (dry adhesion amount) of the lubricant in the heat-sealable resin layer was 2 g / m². 2 It was.

[0123] <Comparative Example 3>

[0124] The dry adhesion amount of the coating liquid containing the first water-dispersible resin is 2 g / m 2 A heat-sealable paper was obtained in the same manner as in Example 3, except that the coating liquid was applied in the same manner as in Example 3. For the heat-sealable paper of this comparative example, the mass per unit area of ​​the undercoat layer was 2 g / m². 2 In the comparative example, the content of the first water-dispersible resin in the undercoat layer was 100% by mass, and the mass per unit area (dry adhesion amount) of the first water-dispersible resin in the undercoat layer was 2 g / m². 2 Furthermore, the mass per unit area of ​​a single heat-sealable resin layer was 2 g / m². 2 In the case of this comparative example, the content of the second water-dispersible resin in the heat-sealable resin layer was 90% by mass, and the content of the lubricant was 10% by mass (second water-dispersible resin:lubricant=90:10 (mass ratio)). Therefore, the total mass per unit area of ​​the second water-dispersible resin (dry adhesion weight) and the mass per unit area of ​​the lubricant (dry adhesion weight) in the heat-sealable resin layer was 2 g / m 2 It was.

[0125] <Comparative Example 4>

[0126] No undercoat layer is formed, and the dry adhesion amount of the solid components (the second water-dispersible resin and lubricant) of the coating liquid for forming the heat-sealable resin layer is 8 g / m 2 To achieve this, a heat-sealable paper was obtained in the same manner as in Example 1, except that the coating solution was applied to one surface (felt side) of the paper substrate using a Meyer bar. Regarding the heat-sealable paper of this comparative example, the mass per unit area of ​​a single heat-sealable resin layer was 8 g / m². 2 In the case of this comparative example, the content of the second water-dispersible resin in the single heat-sealable resin layer was 80% by mass, and the content of the lubricant was 20% (second water-dispersible resin:lubricant=80:20 (mass ratio)). Therefore, the total mass per unit area of ​​the second water-dispersible resin (dry adhesion weight) and the mass per unit area of ​​the lubricant (dry adhesion weight) in the heat-sealable resin layer was 8 g / m2 It was.

[0127] <Comparative Example 5>

[0128] A heat-sealable paper was obtained in the same manner as in Example 3, except that amorphous silica (manufactured by Fuji Silysia Chemical Ltd., trade name "SYLYSIA (registered trademark) 380") was mixed in an amount of 15% by mass relative to 100% by mass of the total (solid content) of the first water-dispersible resin and the second water-dispersible resin to prepare a coating liquid for forming a heat-sealable resin layer. For the heat-sealable paper of this comparative example, the mass per unit area of ​​the undercoat layer was 6 g / m. 2 In the case of this comparative example, the content of the first water-dispersible resin in the undercoat layer was 100% by mass, and the mass per unit area of ​​the first water-dispersible resin in the undercoat layer (dry adhesion amount) was 6 g / m 2 Furthermore, the mass per unit area of ​​a single heat-sealable resin layer was 2 g / m². 2 In the case of this comparative example, the content of the second water-dispersible resin in the heat-sealable resin layer was 40% by mass, and the content of the lubricant was 60% by mass (second water-dispersible resin:lubricant=40:60 (mass ratio)). Therefore, the total mass per unit area of ​​the second water-dispersible resin (dry adhesion weight) and the mass per unit area of ​​the lubricant (dry adhesion weight) in the heat-sealable resin layer was 2 g / m 2 It was.

[0129] <Comparative Example 6>

[0130] A heat-sealable paper was obtained in the same manner as in Example 3, except that the second water-dispersible resin was changed to styrene-butadiene rubber (abbreviated as "SBR(1)", manufactured by Nippon A&L Co., Ltd., trade name "Nalstar SR-107", glass transition temperature Tg = -15°C). For the heat-sealable paper of this comparative example, the mass per unit area of ​​the undercoat layer was 6 g / m 2In the case of this comparative example, the content of the first water-dispersible resin in the undercoat layer was 100% by mass, and the mass per unit area of ​​the first water-dispersible resin in the undercoat layer (dry adhesion amount) was 6 g / m 2 Furthermore, the mass per unit area of ​​a single heat-sealable resin layer was 2 g / m². 2 In the comparative example, the content of the second water-dispersible resin in the heat-sealable resin layer was 80% by mass, and the content of the lubricant was 20% by mass (second water-dispersible resin: lubricant = 80:20 (mass ratio)). Therefore, the sum of the mass per unit area (dry adhesion amount) of the second water-dispersible resin and the mass per unit area (dry adhesion amount) of the lubricant in the heat-sealable resin layer was 2 g / m². 2 It was.

[0131] <Comparative Example 7>

[0132] Except for not forming a heat-sealable resin layer, a heat-sealable paper was obtained in the same manner as in Example 3. For the heat-sealable paper of this comparative example, the mass per unit area of ​​the single undercoat layer was 6 g / m 2 In the case of this comparative example, the content of the first water-dispersible resin in the undercoat layer was 100% by mass, and the mass per unit area of ​​the first water-dispersible resin in the undercoat layer (dry adhesion amount) was 6 g / m 2 It was.

[0133] <Measurement> The following measurements were carried out for each of the above Examples and Comparative Examples. The measurement results are shown in Table 1.

[0134] (Tensile energy of undercoat layer)

[0135] First, a coating solution containing 35% by mass of the first water-dispersible resin and water as a dispersion medium was applied to the surface of the release agent layer of a release film (Lintec Corporation, product name "AL-5") using a 250 μm applicator, and a resin film with a thickness of 30-50 μm was prepared by heating at 120°C for 5 minutes. Then, the release film was removed from the resin film prepared above to obtain a single-layer test specimen (10 mm x 30 mm) of the undercoat layer. Next, in accordance with JIS K 7161, the work done on the test specimen (J) was calculated from the area of ​​the stress-strain curve when measured with a chuck distance of 10 mm and a tensile speed of 20 mm / min, and this value was divided by the volume of the test specimen to obtain the tensile energy (J / m²). 3 ) was calculated.

[0136] <Rating> The following evaluations were carried out for each of the above Examples and Comparative Examples. The evaluation results are shown in Table 1.

[0137] (Heat seal strength)

[0138] Two test pieces were prepared by cutting the obtained heat-sealable paper to 15 mm x 150 mm. These test pieces were stacked so that the heat-sealable resin layers faced each other, and pressed together under conditions of 160°C, 0.2 MPa, and 1 second. Then, in accordance with JIS Z 1707, the heat-seal strength was defined as the maximum load at which the pressed test pieces were peeled in a T-shape at a tensile speed of 300 mm / min using a tensile testing machine (Shimadzu Corporation, product name "Autograph AG-500NIS").

[0139] (Test against heavy objects)

[0140] The resulting heat-sealable paper was cut into two 200 mm x 200 mm test sheets. These two test sheets were overlapped with their heat-sealable resin layers (undercoat layers in Comparative Examples 1 and 7) facing each other, and three sides of the two test sheets were heat-sealed at 160°C, 0.2 MPa, and 1 second to create a three-sided bag with a single opening. Next, a 1 kg weight (M2 class) was vertically and freely dropped from a height of 30 cm from the bottom seal toward the bottom seal, which is the bottom of the three-sided bag, through the opening. The bottom seal was then evaluated for peeling (opening) after the free fall. ○: No peeling (opening) occurred in the bottom seal. ×: The bottom seal has peeled off (opening).

[0141] (Blocking decision)

[0142] The obtained heat-seal paper was cut into 10 mm x 10 mm pieces to prepare two test sheets. These two test sheets were overlapped so that the surface of the paper substrate of one test sheet was in contact with the surface of the heat-sealable resin layer (undercoat layer in the case of Comparative Examples 1 and 7) of the other test sheet, and pressed at 0.5 MPa for 8 hours using a press heated to 40 ° C. The two overlapping test sheets were then removed from the press, and the two test sheets were manually peeled apart to evaluate whether sticking or zipping occurred. ○: No zipping occurred. ×: Resistance occurred due to the two test sheets sticking together, and the paper surface became ruffled and zippy.

[0143] The composition and evaluation results of each example and comparative example are shown in Table 1. Note that the "solid content ratio" in the table is a mass ratio.

[0144] [Table 1]

[0145] From the above, it has been confirmed that, according to this embodiment, when contents are packaged in a packaging bag formed from heat-seal paper 1, no opening occurs in the heat-sealed portion, and when a roll of heat-seal paper 1 is wound up and stored, there is at least no blocking between the surface of the paper base material 10 of the heat-seal paper 1 and the surface of the resin layer adjacent to the surface of the paper base material. [Explanation of symbols]

[0146] 1, 2... Heat sealing paper 10…Paper base material 11…Undercoat layer 12…Heat-sealable resin layer 13… Lubricant 3...Packaging bag 4…Contents 5... Rolled form 34...Seal part 36... Center seal section 38... Insertion opening

Claims

1. A heat-sealable paper comprising, in this order, a paper substrate, an undercoat layer, and a heat-sealable resin layer, the undercoat layer comprises a first water-dispersible resin, The tensile energy per unit volume of the undercoat layer is 150 MJ / m ３ or more, and the mass per unit area of ​​the undercoat layer is 3 g / m ２ That's all, the heat-sealable resin layer contains a second water-dispersible resin and a lubricant, the second water-dispersible resin has a glass transition temperature of 0°C or higher; the lubricant contains at least one selected from the group consisting of metal soaps and inorganic particles, The content of the lubricant is less than 10% by mass based on the total amount of the first water-dispersible resin and the second water-dispersible resin. Heat seal paper.

2. The heat-sealable resin layer is located on the outermost surface of the heat-sealable paper. The heat seal paper according to claim 1.

3. The first water-dispersible resin contains a urethane resin. The heat seal paper according to claim 1 or 2.

4. The first water-dispersible resin further contains at least one selected from the group consisting of styrene-butadiene rubber and ethylene-vinyl acetate copolymer. The heat seal paper according to claim 3.

5. The second water-dispersible resin contains styrene-butadiene rubber. The heat seal paper according to claim 1 or 2.

6. The metal soap contains at least one selected from the group consisting of fatty acid calcium, fatty acid zinc, fatty acid barium, fatty acid magnesium, and fatty acid lithium. The heat seal paper according to claim 1 or 2.

7. The inorganic particles include at least one selected from the group consisting of amorphous silica, spherical silica, calcium carbonate, talc, kaolin, and titanium oxide. The heat seal paper according to claim 1 or 2.

8. For pillow packaging, The heat seal paper according to claim 1 or 2.

9. A packaging method, comprising forming a package using the heat seal paper according to claim 1 or 2 by pillow packaging, and packaging an article.

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