JP2022151410A - Sealant film, laminate, and packaging bag - Google Patents

Abstract

To provide a sealant film having an anti-static performance, as well as having excellent laminate strength against another layer.SOLUTION: A sealant film includes an inner face and an outer face. The sealant film includes a first layer and a second layer composing the inner face. The first layer contains a polyethylene and an anti-static agent. The second layer contains a polyethylene. The first layer has a crystallinity index A. The second layer has a crystallinity index B. A relation of the crystallinity index A and the crystallinity index B satisfies the crystallinity index A<the crystallinity index B.SELECTED DRAWING: Figure 1

Description

The present invention relates to sealant films, laminates and packaging bags.

Conventionally, packaging bags have been used to fill and package contents such as foodstuffs, pharmaceuticals, chemicals, and cosmetics. As a laminate constituting a packaging bag, there is a laminate comprising a base layer such as a stretched film and a sealant film having sealing properties. In the packaging bag, the sealant film contacts the contents of the packaging bag.

Contents include, for example, powdery materials such as wheat flour and powdered medicine. If the sealant film is not subjected to any treatment when packaging such a powdery substance, the powdery substance adheres to the sealant film due to the effects of static electricity, making it difficult to take out the contents. In addition, there is a possibility that the powdery substance may adhere to the opening when the powdery substance is filled. If so, it is likely to cause defective fusion of the sealed portion by heat sealing during the production of the packaging bag.

For this reason, antistatic agents have been added to sealant films. A kneading type antistatic agent is known, and this type of antistatic agent is mixed in the resin of the film, thereby imparting antistatic performance to the sealant film (for example, Cited Document 1).

Japanese Patent Application Laid-Open No. 2004-3399398

However, the antistatic agent migrates in the sealant film and appears on its surface. Lower.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a sealant film having antistatic performance and excellent lamination strength with other layers.
Another object of the present invention is to provide a laminate comprising the above sealant film. Another object of the present invention is to provide a packaging bag comprising the laminate.

The present invention is a sealant film comprising an inner surface and an outer surface, comprising:
The sealant film comprises a first layer constituting the inner surface and a second layer,
wherein the first layer comprises polyethylene and an antistatic agent;
wherein the second layer comprises polyethylene;
The first layer has a degree of crystallinity A, the second layer has a degree of crystallinity B, and the relationship between the degree of crystallinity A and the degree of crystallinity B is such that the degree of crystallinity A<the degree of crystallinity It is a sealant film that satisfies B.

In the sealant film according to the present invention, the second layer may contain, as a main component, at least one polyethylene selected from the group consisting of high-pressure low-density polyethylene and medium-density polyethylene.

The sealant film according to the invention may contain high pressure low density polyethylene as a main component.

In the sealant film according to the present invention, the first layer may contain linear low-density polyethylene as a main component.

In the sealant film according to the present invention, the inner surface may have a surface resistivity of 9.0×10 ¹² Ω/□ or less.

In the sealant film according to the present invention, the antistatic agent is at least one antistatic agent selected from the group consisting of anionic antistatic agents, cationic antistatic agents, amphoteric antistatic agents and nonionic antistatic agents. It's okay.

In the sealant film according to the present invention, the second layer may not contain an antistatic agent.

The present invention is a laminate comprising at least a substrate layer and a sealant layer,
The sealant layer is a laminate including the sealant film, and the outer surface of the sealant film is located on the substrate layer side.

The sealant film according to the invention may comprise an adhesive layer located between said substrate layer and said sealant layer.

The present invention is a packaging bag comprising the laminate.

According to the present invention, it is possible to provide a sealant film having antistatic performance and excellent lamination strength with other layers.
can.
According to another aspect of the present invention, a laminate comprising the above sealant film can be provided.
According to another aspect of the present invention, it is possible to provide a packaging bag comprising the laminate.

1 is a schematic cross-sectional view showing one embodiment of a sealant film according to the present invention; FIG. 1 is a schematic cross-sectional view showing one embodiment of a sealant film according to the present invention; FIG. 1 is a schematic cross-sectional view showing one embodiment of a sealant film according to the present invention; FIG. 1 is a schematic cross-sectional view showing one embodiment of a laminate according to the present invention; FIG. 1 is a schematic cross-sectional view showing one embodiment of a laminate according to the present invention; FIG. 1 is a schematic front view showing one embodiment of a packaging bag according to the present invention; FIG. It is the schematic which shows the measuring method of seal strength. It is the schematic which shows the measuring method of lamination strength. It is the schematic which shows the measuring method of lamination strength. It is a figure which shows the measurement result of lamination strength. FIG. 2 is a plan view showing a test piece for measuring tear strength; 1 is a plan view showing a group of test specimens for measuring tear strength; FIG.

An embodiment of the present invention will be described. In addition, in the drawings attached to this specification, for convenience of illustration and easy understanding, the scale, the ratio of length and width, etc. are appropriately changed and exaggerated from those of the real thing.

Terms such as "perpendicular", "identical", length and angle values, etc. that specify shapes and geometric conditions and their degrees used herein are not bound by a strict meaning. , to include the extent to which similar functions can be expected.

As used herein, the term “inner surface” means the surface of the packaging bag located on the side of the contents, and the term “outer surface” refers to the surface of the packaging bag located on the side opposite to the contents, i.e., another layer. and the surface to be laminated.

[Sealant film]
A sealant film according to the present invention includes an inner surface and an outer surface. The sealant film comprises a first layer forming an inner surface and a second layer, the first layer containing polyethylene and an antistatic agent, and the second layer containing polyethylene. In the sealant film, the first layer has a crystallinity A, the second layer has a crystallinity B, and the relationship between the crystallinity A and the crystallinity is such that the crystallinity A < the crystallinity B meet. Such a sealant film has antistatic performance and excellent lamination strength with other layers. The reason is considered as follows.

Lamination of the sealant film and other layers is generally performed by dry lamination using an adhesive having a polar group or sand lamination using an adhesive resin having a polar group. Since the antistatic agent has a hydrophilic group, the hydrophilic group is attracted to these polar groups, and the antistatic agent migrates to the outer surface side of the sealant film. This migrated antistatic agent affects the adhesion between the sealant film and other layers, thereby lowering the lamination strength of the sealant film and other layers. In order to improve adhesion to adjacent layers, the sealant film is sometimes subjected to surface treatment such as corona treatment and flame treatment to make the surface of the sealant film hydrophilic. The hydrophilic group of the antistatic agent is also attracted to the surface, and the antistatic agent migrates to the outer surface side of the sealant film. This reduces the lamination strength of the sealant film and other layers.
In the sealant film according to the present invention, the relationship between the crystallinity A of the first layer and the crystallinity B of the second layer is set to crystallinity A < crystallinity B, so that the crystallinity is low. The migration of the antistatic agent contained in the first layer is suppressed by the second layer having a high degree of crystallinity, and migration of the antistatic agent to the outer surface side of the sealant film is suppressed. As a result, the sealant film is considered to have excellent lamination strength with other layers.

The ratio of crystallinity B to crystallinity A is preferably 1.01 or more, more preferably 1.05 or more, and still more preferably 1.1 or more. Thereby, migration of the antistatic agent can be further suppressed, and lamination strength of the sealant film can be improved. On the other hand, the ratio of the crystallinity B to the crystallinity A is, for example, 5 or less, may be 2 or less, or may be 1.5 or less.

In the range where crystallinity A>crystallinity B is satisfied, the difference between crystallinity B and crystallinity A is preferably 1%, more preferably 3%, and still more preferably 5% or more. is. On the other hand, the difference between the crystallinity B and the crystallinity A is, for example, 30% or less, may be 20% or less, or may be 10% or less.

In this specification, the degree of crystallinity A is the analysis result of the inner surface side of the sealant film. Therefore, if there is data exceeding the crystallinity A in the n-th (n is an integer of 1 or more) analysis results from the outer surface of the sealant film, the existence of the second layer having the crystallinity B can be supported.

As used herein, "crystallinity" is a value calculated as a ratio of the heat of fusion obtained from a DSC curve drawn in accordance with JIS K7121:2012 to the heat of fusion of a perfectly crystalline material.

The DSC curve is drawn according to JIS K7121:2012 from differential scanning calorimeter (DSC) data obtained during the second heating under the following conditions. DSC200F3Maia manufactured by NETZSCH can be used as a differential scanning calorimeter.
(conditions)
Sample amount: Accurately weigh about 10 mg Measurement atmosphere: Nitrogen Pan material: Al
Flow rate: 100 mL/min Measurement range: 30°C to 150°C Heating rate: 10°C/min

The degree of crystallinity is a value calculated by the following formula (1) from the heat of fusion obtained from the above DSC curve and the heat of fusion of the perfect crystal. The unit of heat of fusion is "J/g".
Crystallinity [%] = (heat of fusion obtained from DSC curve / heat of fusion of perfect crystal) × 100 (1)
As the heat of fusion of the perfect crystal, the literature value may be adopted. References include "THERMAL APPLICATIONS NOTE Polymer Heats of Fusion, Roger L. Blaine TA Instruments, 109 Lukens Drive, New Castle DE 19720, USA". For example, the heat of fusion of a perfect crystal in polyethylene is 293 J/g.

As used herein, polyethylene includes homopolymers of ethylene and copolymers of ethylene and α-olefin (hereinafter also referred to as ethylene-α-olefin copolymers). The content of α-olefin units in the ethylene-α-olefin copolymer is, for example, 15 mol % or less, may be 10 mol % or less, or may be 5 mol % or less.

Examples of homopolymers of ethylene include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), high-pressure low-density polyethylene (LDPE), and the like.
As used herein, high-density polyethylene means polyethylene having a density of 0.942 g/cm ³ or more, and medium-density polyethylene means polyethylene having a density of 0.930 g/cm ^{3 or more and less than 0.942 g/cm 3 .} means polyethylene with High-pressure low-density polyethylene means polyethylene having a density of 0.910 g/cm ³ or more and less than 0.930 g/cm ³ . High-pressure low-density polyethylene is obtained, for example, by polymerizing ethylene under a high pressure of 1,000 to less than 2,000 atmospheres.
In this specification, the densities of resins, layers, films and the like are measured according to Method B (pycnometer method) or Method D (density gradient tube method) of JIS K7112:1999. B method and D method are appropriately selected according to the shape and mass of the test piece to be measured. In method D, the measurement temperature (liquid temperature) is 23°C.

The ethylene-α-olefin copolymer can also be referred to as linear polyethylene. Here, linear polyethylene will be explained.
Linear polyethylene is a copolymer of ethylene and α-olefin polymerized using a multi-site catalyst typified by a Ziegler-Natta catalyst or a single-site catalyst typified by a metallocene catalyst. Therefore, it is distinguished from homopolymers of ethylene. α-Olefin, which is a monomer for linear polyethylene, has 3 or more carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-nonene, 4-methylpentene. , 3,3-dimethylbutene, etc., and mixtures thereof.
Linear polyethylene having a density of less than 0.930 g/cm ³ may be referred to as linear low density polyethylene (LLDPE).

The above single-site catalyst is a catalyst capable of forming uniform active species, and is usually prepared by contacting a metallocene-based transition metal compound or non-metallocene-based transition metal compound with an activating co-catalyst. be. A single-site catalyst has a more uniform active site structure than a multi-site catalyst, and therefore can polymerize a polymer having a high molecular weight and a highly uniform structure. As single site catalysts, metallocene catalysts are particularly preferred. The metallocene-based catalyst is a catalyst containing a transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, a cocatalyst, an organometallic compound if necessary, and each catalyst component of a carrier. is.

In the transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, the cyclopentadienyl skeleton is a cyclopentadienyl group, a substituted cyclopentadienyl group, or the like. . Substituted cyclopentadienyl groups include hydrocarbon groups having 1 to 30 carbon atoms, silyl groups, silyl-substituted alkyl groups, silyl-substituted aryl groups, cyano groups, cyanoalkyl groups, cyanoaryl groups, halogen groups, haloalkyl groups and halosilyl groups. and those having at least one substituent selected from groups and the like. The substituted cyclopentadienyl group may have two or more substituents, and the substituents are bonded to each other to form a ring to form an indenyl ring, a fluorenyl ring, an azulenyl ring, hydrogenated forms thereof, and the like. You may A ring formed by combining substituents with each other may further have a substituent with each other.

In the transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, examples of the transition metal include zirconium, titanium, hafnium, and the like, and particularly preferably zirconium and/or hafnium. be. The transition metal compound preferably has usually two ligands having a cyclopentadienyl skeleton, and each ligand having a cyclopentadienyl skeleton is bonded to each other by a bridging group. is. The bridging group includes an alkylene group having 1 to 4 carbon atoms, a silylene group, a dialkylsilylene group, a substituted silylene group such as a diarylsilylene group, and a substituted germylene group such as a dialkylgermylene group and a diarylgermylene group. The bridging groups are preferably substituted silylene groups.

In the transition metal compounds of Group IV of the periodic table, ligands other than ligands having a cyclopentadienyl skeleton include hydrogen, hydrocarbon groups having 1 to 20 carbon atoms (alkyl groups, alkenyl groups, aryl groups , an alkylaryl group, an aralkyl group, a polyenyl group, etc.), a halogen, a metaalkyl group, a metaaryl group, and the like.

One or a mixture of two or more of the transition metal compounds of Group IV of the periodic table containing the ligand having a cyclopentadienyl skeleton can be used as a catalyst component.

The co-catalyst is one that can make the above Group IV transition metal compound of the periodic table effective as a polymerization catalyst or can balance the ionic charges in a catalytically activated state. Examples of co-catalysts include benzene-soluble aluminoxanes of organoaluminumoxy compounds, benzene-insoluble organoaluminumoxy compounds, ion-exchange layered silicates, boron compounds, cations containing or not containing active hydrogen groups, and non-coordinating anions. ionic compounds, lanthanide salts such as lanthanum oxide, tin oxide, and phenoxy compounds containing a fluoro group.

The transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton may be supported on an inorganic or organic compound carrier before use. As the carrier, porous oxides of inorganic or organic compounds are preferable, and specifically, ion-exchange layered silicates such as montmorillonite, SiO ₂ , Al ₂ O ₃ , MgO, ZrO ₂ , TiO ₂ and B ₂ O. ₃ , CaO, ZnO, BaO, _ThO2 , etc. or mixtures thereof.

Examples of organometallic compounds that are used as necessary include organoaluminum compounds, organomagnesium compounds, and organozinc compounds. Of these, organic aluminum is preferably used.

As the polyethylene, fossil fuel polyethylene, biomass polyethylene, or both of them may be used.
Fossil fuel polyethylene is polyethylene produced from raw materials consisting only of monomers derived from fossil fuels.
Biomass polyethylene is polyethylene produced from raw materials containing biomass-derived monomers. Biomass polyethylene may contain monomers derived from fossil fuels as raw materials for biomass polyethylene. Raw materials for biomass polyethylene include, for example, raw materials containing biomass-derived ethylene, fossil fuel-derived ethylene and/or fossil fuel-derived α-olefins, and raw materials containing biomass-derived α-olefins and fossil fuel-derived ethylene. is.

Whether the sealant film contains biomass polyethylene can be determined by measuring the degree of biomass of the sealant film. If the sealant film contains biomass polyethylene, the degree of biomass of the sealant film will be greater than 0%.

Here, the degree of biomass will be explained.
Since carbon dioxide in the atmosphere contains a certain amount of C14 (105.5 pMC), plants that grow by taking in carbon dioxide in the atmosphere, such as corn, also contain about 105.5 pMC of C14. It is known that It is also known that fossil fuels contain almost no C14. Therefore, by measuring the ratio of C14 contained in all carbon atoms, the ratio of biomass-derived carbon can be calculated.
"Biomass degree" indicates the weight ratio of biomass-derived components. Taking polyethylene terephthalate as an example, polyethylene terephthalate is obtained by polymerizing ethylene glycol containing two carbon atoms and terephthalic acid containing eight carbon atoms at a molar ratio of 1:1. In the case of using only those derived from biomass, the weight ratio of biomass-derived components in the polyester is 31.25%, so the theoretical value of biomass degree is 31.25%. Specifically, the mass of polyethylene terephthalate is 192, of which the mass derived from biomass-derived ethylene glycol is 60, so 60÷192×100=31.25. In addition, the weight ratio of the biomass-derived component in the fossil fuel polyester produced using fossil fuel-derived ethylene glycol and fossil fuel-derived dicarboxylic acid is 0%, and the biomass degree of the fossil fuel polyester is 0%. Become. Hereinafter, unless otherwise specified, the “biomass degree” indicates the weight ratio of biomass-derived components.

Theoretically, if only biomass-derived raw materials are used as raw materials for polyethylene, the concentration of biomass-derived ethylene is 100%, so the biomass degree of biomass polyethylene is 100%.
The concentration of biomass-derived ethylene in fossil fuel polyethylene produced only from fossil fuel-derived raw materials is 0%. Therefore, the biomass degree of polyethylene derived from fossil fuel is 0%.

The degree of biomass of the sealant film is preferably 20% or more, more preferably 25% or more, and more preferably 50% or more, from the viewpoint of environmental load reduction. On the other hand, the degree of biomass of the sealant film is, for example, 90% or less, and may be 80% or less.

The sealant film preferably contains high pressure low density polyethylene as a main component. Thereby, the tearability of the sealant film can be improved.
In addition, in this specification, a "main component" means a component exceeding 50 mass %.

The content of the high-pressure low-density polyethylene in the sealant film is preferably 70% by mass or more, more preferably 80% by mass or more. On the other hand, the content of the high-pressure low-density polyethylene in the sealant film is, for example, 99% by mass or less, and may be 90% by mass or less.

In the sealant film, the relationship between the density of the first layer (hereinafter also referred to as "density A") and the density of the second layer (hereinafter also referred to as density B) preferably satisfies density A≦density B. When the relationship between density A and density B satisfies density A≦density B, migration of the antistatic agent to the outer surface of the sealant film can be further suppressed, and lamination strength of the sealant film can be improved.

The ratio of density B to density A is preferably 1.001 or more, more preferably 1.01 or more. On the other hand, the ratio of density B to density A is, for example, 1.5 or less, may be 1.3 or less, or may be 1.1 or less.

The thickness of the sealant film is preferably 15 μm or more and 200 μm or less, more preferably 30 μm or more and 100 μm or less.

The inner surface of the sealant film may be surface-treated. This can improve adhesion with adjacent layers.
The surface treatment method is not particularly limited. For example, corona treatment, flame treatment, ozone treatment, low temperature plasma treatment using oxygen gas and / or nitrogen gas, physical treatment such as glow discharge treatment, and chemical chemical treatment such as oxidation treatment.

In one embodiment, the sealant film may further comprise a third layer.

An embodiment of the sealant film according to the present invention will be described below with reference to FIGS. 1 to 3. FIG.

In one embodiment, the sealant film 10 comprises a first layer 11 and a second layer 12, as shown in FIG. As shown in FIG. 1 , the first layer 11 is located on the inner surface X side of the sealant film 10 , and the second layer 12 is located on the outer surface Y side of the sealant film 10 .

In one embodiment, the sealant film 10 comprises a first layer 11, a second layer 12 and a third layer 13, as shown in FIG. As shown in FIG. 2 , the first layer 11 is positioned on the inner surface X side of the sealant film 10 , and the third layer 13 is positioned on the outer surface Y side of the sealant film 10 . The second layer 12 is located between the first layer 11 and the third layer 13 .

In one embodiment, the sealant film 10 comprises a first layer 11, a second layer 12 and a third layer 13, as shown in FIG. As shown in FIG. 3 , the first layer 11 is located on the inner surface X side of the sealant film 10 , and the second layer 12 is located on the outer surface Y side of the sealant film 10 . A third layer 13 is located between the first layer 11 and the second layer 12 .

The layer structure of the sealant film 10 described above can be combined as appropriate.

The first, second and third layers that the sealant film can have are described below.

<First layer>
The first layer contains polyethylene and an antistatic agent. Thereby, antistatic performance can be imparted to the sealant film.
In the sealant film, the first layer is the sealing layer. As used herein, the term “seal layer” refers to a layer that constitutes one surface layer of the laminate or both surface layers of the laminate when the sealant film is used in the laminate. layer.

In the first layer, polyethylene may be the main component. The content of polyethylene in the first layer is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more with respect to the entire first layer.

Examples of antistatic agents contained in the first layer include anionic antistatic agents such as adipic acid, glutamic acid, sulfonates, sulfate ester salts, phosphate ester salts, and phosphonates; amines, imidazolines, amine oxide ethylene; Cationic antistatic agents such as adducts, quaternary ammonium salts and pyridinium salts; guanidine salts having both cationic and anionic groups, e.g., alkylamines reacted with maleic anhydride, sulfonic acids derived from polyethyleneimine, etc. amphoteric antistatic agents; nonionic antistatic agents such as polyols, ester compounds of polyols and aliphatic carboxylic acids, ether compounds, higher alcohol ethylene oxide adducts, alkylphenol ethylene oxide adducts, fatty acid amides and their ethylene oxide adducts agents and the like. The first layer may contain one or more of these antistatic agents.
The antistatic agent contained in the first layer is preferably at least one antistatic agent selected from the group consisting of anionic antistatic agents, cationic antistatic agents, amphoteric antistatic agents and nonionic antistatic agents. is an agent.
In one embodiment, the first layer comprises an anionic antistatic agent and an amphoteric antistatic agent. The first layer is particularly preferably composed of an organic sulfonate such as alkylsulfonic acid as an anionic antistatic agent and an ester compound, ether compound, or alkyldialcoholamide of a polyol and a carboxylic acid as an amphoteric antistatic agent. ,including. As an antistatic agent, ELECUT MASTER LM530 manufactured by Takemoto Oil & Fat Co., Ltd. can be used.
The antistatic agent can be added to the first layer in the form of a masterbatch containing polyethylene as the base material.
In addition, in this specification, the content of the antistatic agent and the additive described later is determined by the GC/MS method. As a measuring instrument, Shimadzu GCMS-TQ8050 can be used.

The content of the antistatic agent in the first layer is preferably 0.05% by mass or more and 3% by mass, more preferably 0.1% by mass or more and 2% by mass or less, relative to the entire first layer, More preferably, it is 0.5% by mass or more and 1.5% by mass or less.
By setting the content of the antistatic agent in the first layer within the above range, it is possible to obtain a sealant film that is excellent in both sealing properties and antistatic properties.

The first layer preferably contains linear low density polyethylene as a main component. Thereby, the sealing strength of the sealant film can be improved.
The content of the linear low-density polyethylene in the first layer is preferably 70% by mass or more, more preferably 80% by mass or more, relative to the entire first layer. On the other hand, the content of linear low-density polyethylene in the first layer is, for example, 98% by mass or less, and may be 97% by mass or less.

The first layer may contain at least one polyethylene selected from the group consisting of high pressure low density polyethylene and medium density polyethylene.
The content of the polyethylene in the first layer is preferably 25% by mass or less, more preferably 20% by mass or less, and still more preferably 15% by mass with respect to the entire first layer. On the other hand, the polyethylene content is, for example, 1% by mass or more, and may be 2% by mass or more.

The first layer may comprise biomass polyethylene.

In addition to the antistatic agent, the first layer may contain one or more additives as long as the properties of the present invention are not impaired. Additives contained in the first layer include, for example, antiblocking agents, plasticizers, UV stabilizers, anti-coloring agents, matting agents, deodorants, flame retardants, weathering agents, yarn friction reducing agents, and slip agents. , antioxidants, ion exchange agents, and color pigments.

The first layer may contain high-density polyethylene as long as the characteristics of the present invention are not impaired.

The density of the first layer is, for example, 0.900 g/cm ³ or more, may be 0.910 g/cm ^{3 or more, or may be 0.920 g/cm 3 or} more. On the other hand, the density of the first layer is, for example, 0.940 g/cm ³ or less, may be 0.935 g/cm ³ or less, or may be 0.930 g/cm ³ or less.

The thickness of the first layer is preferably 5 μm or more, more preferably 7 μm or more. On the other hand, the thickness of the first layer is preferably 50 μm or less, more preferably 20 μm or less.

<Second layer>
The second layer comprises polyethylene. In the second layer, polyethylene may be the main component. The content of polyethylene in the second layer is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more with respect to the entire second layer.
In one embodiment, the second layer preferably consists of polyethylene only.

The second layer preferably contains at least one polyethylene selected from the group consisting of high pressure low density polyethylene and medium density polyethylene as a main component. Thereby, the tearing strength of the sealant film can be reduced, and the tearability can be improved.
The content of the polyethylene in the second layer is preferably 80% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass or more with respect to the entire second layer. On the other hand, the content of the polyethylene in the second layer is, for example, 98% by mass or less, and may be 97% by mass or less with respect to the entire second layer.

The second layer may comprise linear polyethylene. The linear polyethylene contained in the second layer may be linear low-density polyethylene.

The second layer may comprise biomass polyethylene.

The second layer may contain an antistatic agent as long as the properties of the present invention are not impaired, but the second layer preferably does not contain an antistatic agent.
As used herein, the term "does not contain" means that the content measured by the pyrolysis GC method is 100 ppm or less, or that the target component is not detected.

The second layer may contain one or more additives as long as the properties of the present invention are not impaired, but the second layer preferably contains no additives. Additives contained in the second layer include, for example, antiblocking agents, plasticizers, UV stabilizers, anti-coloring agents, matting agents, deodorants, flame retardants, weathering agents, thread friction reducing agents, and slip agents. , antioxidants, ion exchange agents, and coloring pigments. The content of the additive in the second layer is preferably less than 0.05% by mass, more preferably 0.01% by mass or less. The second layer is particularly preferably additive-free.

The second layer may contain high-density polyethylene as long as the properties of the present invention are not impaired.

The density of the second layer is, for example, 0.900 g/cm ³ or more, may be 0.910 g/cm ^{3 or more, or may be 0.920 g/cm 3 or} more. On the other hand, the density of the second layer is, for example, 0.940 g/cm ³ or less, may be 0.935 g/cm ³ or less, or may be 0.930 g/cm ³ or less.

In one embodiment, when the sealant film is composed of two layers, the second layer is a laminate layer. A laminate layer is a layer that constitutes the outer surface of the sealant film.
In one embodiment, when the sealant film is composed of three or more layers, the second layer is a laminate layer or interlayer. An intermediate layer is a layer located between the sealing layer and the laminate layer. If the sealant film consists of three or more layers, the second layer is preferably a laminate layer.
The second layer may be multiple layers present in the sealant film. That is, both the laminate layer and the intermediate layer may be the second layer.
The intermediate layer may be a single layer or multiple layers. When the intermediate layer is multi-layered, the composition of each intermediate layer may be the same or different.

When the sealant film is composed of a seal layer and a laminate layer, the thickness of the laminate layer is preferably 10 μm or more, more preferably 23 μm or more. On the other hand, the thickness of the laminate layer is preferably 150 μm or less, more preferably 80 μm or less.
When the sealant film is composed of a seal layer, an intermediate layer and a laminate layer, the thickness of the laminate layer is preferably 5 μm or more, more preferably 7 μm or more. The thickness of the laminate layer is preferably 50 μm or less, more preferably 20 μm or less.
When the sealant film is composed of a seal layer, an intermediate layer and a laminate layer, the thickness of the intermediate layer is preferably 5 μm or more, more preferably 16 μm or more. On the other hand, the thickness of the intermediate layer is preferably 100 μm or less, more preferably 60 μm or less.
When the laminate layer and the intermediate layer are multiple layers, the above thickness means the total thickness of the multiple layers.

<Third layer>
A third layer comprises polyethylene. In the third layer, polyethylene may be the main component. The content of polyethylene in the third layer is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more with respect to the entire third layer.
In one embodiment, the third layer preferably consists of polyethylene only.

In one embodiment, the third layer has a degree of crystallinity C, and in the sealant film, the relationship between the degree of crystallinity A, the degree of crystallinity B, and the degree of crystallinity C is such that the degree of crystallinity C ≤ crystallization degree A<crystallinity degree B is satisfied.

A third layer may comprise biomass polyethylene.

In one embodiment, the third layer is a laminate layer or interlayer. The third layer is preferably an intermediate layer. The third layer may be multiple layers present in the sealant film.

The third layer is preferably free of antistatic agents.

The third layer may contain one or more additives as long as the properties of the present invention are not impaired, but the third layer preferably does not contain an antistatic agent. Additives contained in the third layer include, for example, antiblocking agents, plasticizers, UV stabilizers, anti-coloring agents, matting agents, deodorants, flame retardants, weathering agents, yarn friction reducing agents, and slip agents. , antioxidants, ion exchange agents, and coloring pigments.

When the third layer is a laminate layer, the thickness of the third layer is preferably 5 μm or more, more preferably 7 μm or more. On the other hand, the thickness of the third layer is preferably 50 μm or less, more preferably 20 μm or less.
When the third layer is an intermediate layer, the thickness of the third layer is preferably 5 μm or more, more preferably 16 μm or more. On the other hand, the thickness of the third layer is preferably 100 μm or less, more preferably 60 μm or less.
When the laminate layer and the intermediate layer are multiple layers, the above thickness means the total thickness of the multiple layers.

In the sealant film, the thickness of the intermediate layer is preferably greater than the thickness of the laminate layer. Thereby, the curling phenomenon of the sealant film can be suppressed. The thickness of the intermediate layer with respect to the thickness of the laminate layer is preferably 1 or more and 10 or less, more preferably 2 or more and 5 or less.
In the sealant film, the thickness of the intermediate layer is preferably greater than the thickness of the sealing layer. Thereby, the curling phenomenon of the sealant film can be suppressed. The thickness of the intermediate layer with respect to the thickness of the sealing layer is preferably 1 or more and 10 or less, more preferably 2 or more and 5 or less.

The thickness of the sealing layer with respect to the thickness of the sealant film is, for example, 1/2 or less, may be 1/3 or less, or may be 1/4 or less. The thickness of the sealing layer with respect to the thickness of the sealant film is, for example, 1/20 or more, and may be 1/10 or more.

The thicknesses of the seal layer, laminate layer, and intermediate layer are calculated from observation results of the cross section of the sealant film. As a device for observing the cross section of the sealant film, for example, a polarizing microscope is used.

<Characteristics of sealant film>
In the sealant film, the surface resistivity of the inner surface is preferably 9.0×10 ¹² Ω/□ or less, more preferably 9.0×10 ¹¹ Ω/□ or less. The surface specific resistivity of the inner surface is, for example, 1.0×10 ¹⁰ or more.
The surface specific resistivity of the inner surface can be measured according to JIS K6911:1995. As a measuring instrument, a high resistivity diameter Hiresta UX MCP-HT800 (manufactured by Mitsui Chemicals Analytech Co., Ltd.) can be used. In the present application, unless otherwise specified, the environment during the measurement of surface specific resistivity is 20° C. temperature and 65% relative humidity.

The breaking strength of the sealant film is, for example, 10 MPa or more, may be 15 MPa or more, or may be 25 MPa or more in at least one direction. On the other hand, the breaking strength of the sealant film is, for example, 50 MPa or less, and may be 30 MPa or less, in at least one direction.
In one embodiment, the breaking strength of the sealant film is, for example, 10 MPa or higher, or 15 MPa or higher, or 25 MPa or higher in the machine direction (MD) of the sealant film. On the other hand, the breaking strength of the sealant film is, for example, 50 MPa or less in MD, and may be 30 MPa or less.
In one embodiment, the breaking strength of the sealant film is, for example, 10 MPa or more, or even 15 MPa or more, or 25 MPa or more in the machine direction (TD) of the sealant film. On the other hand, the breaking strength of the sealant film in TD is, for example, 50 MPa or less, and may be 30 MPa or less.

The breaking elongation of the sealant film in at least one direction is, for example, 150% or more, may be 200% or more, may be 500% or more, or may be 600% or more. On the other hand, the elongation at break of the sealant film is, for example, 1500% or less, and may be 1000% or less, in at least one direction.
In one embodiment, the elongation at break of the sealant film in MD is, for example, 150% or more, may be 200% or more, may be 500% or more, or may be 600% or more. On the other hand, the elongation at break of the sealant film in MD is, for example, 1500% or less, and may be 1000% or less.
In one embodiment, the elongation at break of the sealant film in TD is, for example, 150% or more, may be 200% or more, may be 500% or more, or may be 600% or more. On the other hand, the elongation at break of the sealant film in TD is, for example, 1500% or less, and may be 1000% or less.

Breaking strength and breaking elongation can be measured according to JIS Z1702:1994. As a measuring instrument, Tensilon universal material testing machine RTC-1530 (manufactured by Orientec) can be used. As the test piece, a dumbbell-shaped piece cut out of the sealant film can be used. The measurement width of the test piece is 10 mm, the distance between the pair of chucks holding the test piece at the start of measurement is 50 mm, and the tensile speed is 200 mm/min. The length of the test piece can be adjusted as long as the test piece can be gripped by the pair of chucks. In the present application, unless otherwise specified, the environment for measuring the breaking strength and breaking elongation is 25° C. temperature and 50% relative humidity.

[Method for producing sealant film]
The sealant film according to the present invention can be produced by a conventionally known method, and the first and second layers included in the sealant film can be formed by appropriately selecting the type, density and amount of polyethylene used as raw materials.

The method for producing the sealant film according to the present invention is not particularly limited, and it can be produced by a conventionally known method. The sealant film is preferably co-extruded, more preferably co-extruded by the T-die method or the inflation method. An example of a method for producing a sealant film by the T-die method and the inflation method will be described below.

In the T-die method, first, after drying the material constituting each layer, it is supplied to a melt extruder heated to a temperature above the melting point (Tm) to Tm + 100 ° C. to melt them, A sealant film can be formed by extruding a sheet from a die of a T-die and rapidly cooling and solidifying the extruded sheet with a rotating cooling drum or the like.
As the melt extruder, a single-screw extruder, a twin-screw extruder, a vent extruder, a tandem extruder, or the like can be used depending on the purpose.

In the inflation method, first, after drying the material constituting each layer, it is supplied to a melt extruder heated to a temperature above the melting point (Tm) to Tm + 100 ° C. to melt these and form a ring. It is extruded into a cylindrical shape through the die of the die. At this time, air is sent from below into the cylindrical molten resin to expand the diameter of the cylinder to a predetermined size, and cooling air is sent outside the cylinder from below. This expanded cylindrical body is called a bubble. Subsequently, the bubble is folded into a film by means of guide plates and pinch rolls and wound up in a winding section. The folded film may be wound as it is in a cylindrical shape, or both ends of the cylinder may be removed by a slitter or the like, cut into two films, and then each film may be wound. Thereby, a sealant film can be formed.
As the melt extruder, a single-screw extruder, a twin-screw extruder, a vent extruder, a tandem extruder, or the like can be used depending on the purpose.

[Laminate]
A laminate according to the present invention comprises at least a substrate layer and a sealant layer. In the laminate according to the invention, the sealant layer comprises the sealant film according to the invention, the outer surface of the sealant film being located on the substrate layer side. The laminate according to the invention has excellent lamination strength since it comprises the sealant film according to the invention.
A laminate having excellent lamination strength tends to have excellent tearability.

In one embodiment, the laminate may comprise an adhesive layer.

Hereinafter, the layer structure of the laminate according to the present invention will be described with reference to the drawings.

FIG. 4 is a schematic cross-sectional view showing one embodiment of the laminate according to the invention. The laminate 20 includes a base material layer 21 and a sealant layer 22, as shown in FIG. In laminate 20 , sealant layer 22 comprises sealant film 10 . As shown in FIG. 4 , the outer surface Y of the sealant film 10 is located on the base layer 21 . Also, as shown in FIG. 4, the inner surface X of the sealant film is located on the opposite side to the outer surface Y. As shown in FIG.
In one embodiment, laminate 20 may include barrier and/or support layers (not shown) between substrate layer 21 and sealant layer 22 .

FIG. 5 is a schematic cross-sectional view showing one embodiment of the laminate according to the invention. The laminate 20 includes a substrate layer 21, an adhesive layer 23, and a sealant layer 22 in this order, as shown in FIG. That is, the adhesive layer 23 is positioned between the base layer 21 and the sealant layer 22 . In laminate 20 , sealant layer 22 comprises sealant film 10 . As shown in FIG. 5, the outer surface Y of the sealant film 10 is positioned on the base layer 21 side. Also, as shown in FIG. 5, the inner surface X of the sealant film is located on the opposite side to the outer surface Y. As shown in FIG.
In one embodiment, the laminate 20 may comprise a barrier layer and/or a support layer between the base layer 21 and the adhesive layer 23 and/or between the adhesive layer 23 and the sealant layer 22 ( not shown).

In one embodiment, the laminate 20 may comprise a printed layer provided on at least one surface of the substrate layer 21 and/or the support layer (not shown).

The layer configurations of the laminate 20 described above can be combined as appropriate.

Each layer that can be included in the laminate according to the present invention will be described below. The sealant layer is a layer provided with the sealant film of the present invention, and the sealant film is described above. Therefore, description of the sealant layer is omitted.

<Base material layer>
A base material layer is a layer which has a function to support a laminated body. For the substrate layer, for example, a paper substrate, a resin film, or a laminate thereof can be appropriately used.

As the paper substrate, those having printability, bending resistance, rigidity, stiffness, strength, etc. can be used, and various types of paper such as kraft paper, roll paper, paperboard and processed paper can be used.

The resin film contains at least one resin material. Examples of the resin material contained in the resin film include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), 1,4-polycyclohexylene dimethylene terephthalate, terephthalic acid-cyclohexanedimethanol- Polyesters such as ethylene glycol copolymers, polyamides such as nylon 6, nylon 6,6 and polymetaxylylene adipamide (MXD6), polyolefins such as polyethylene (PE), polypropylene (PP) and polymethylpentene, polyvinyl chloride , polyvinyl alcohol (PVA), polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, vinyl resins such as polyvinyl butyral and polyvinylpyrrolidone (PVP), (meth) acrylics such as polyacrylate, polymethacrylate and polymethyl methacrylate Examples include resins, cellophane, cellulose acetate, nitrocellulose, cellulose resins such as cellulose acetate propionate (CAP) and cellulose acetate butyrate (CAB), styrene resins such as polystyrene (PS), and chlorinated resins thereof. Among these, the resin material contained in the resin film is preferably at least one selected from the group consisting of polyolefin, polyester and polyamide, more preferably polypropylene, polyethylene terephthalate, nylon 6 and nylon 6,6. At least one selected from the group consisting of

The resin film may be a stretched film or an unstretched film. From the viewpoint of strength, the resin film is preferably a uniaxially or biaxially stretched film.

The surface of the resin film may be surface-treated. The surface treatment method is not particularly limited. For example, corona treatment, flame treatment, ozone treatment, low temperature plasma treatment using oxygen gas and / or nitrogen gas, physical treatment such as glow discharge treatment, and chemical chemical treatment such as oxidation treatment.

The thickness of the base material layer is, for example, 5 μm or more, and may be 10 μm. On the other hand, the thickness of the base material layer is, for example, 200 μm or less, may be 100 μm or less, may be 50 μm or less, or may be 20 μm or less.

<Adhesive layer>
The adhesive layer is an adhesive layer or adhesive resin layer formed to bond two layers by lamination. The adhesive layer is preferably an adhesive layer because it has good adhesion to various layers, especially to the sealant layer.

The adhesive layer is a layer formed using at least one one-part or two-part curable or non-curable laminating adhesive. As such, the adhesive layer includes a laminating adhesive. Examples of laminating adhesives include vinyl-based, (meth)acrylic-based, polyamide-based, polyester-based, polyether-based, polyurethane-based, epoxy-based and rubber-based, solvent-based, water-based or emulsion-based laminating adhesives. Adhesives are included.
Examples of adhesive coating methods include a direct gravure roll coating method, a gravure roll coating method, a kiss coating method, a reverse roll coating method, a fonten method and a transfer roll coating method.
The coating amount in a dry state is, for example, 0.1 g/m ² or more, and may be 1 g/m ² or more. On the other hand, the coating amount is, for example, 10 g/m ² or less in a dry state, and may be about 5 g/m ² or less.

The adhesive resin layer contains at least one thermoplastic resin. Examples of the thermoplastic resin contained in the adhesive resin layer include high-pressure low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, and ethylene-acrylic acid copolymer. , ethylene-ethyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, ethylene-maleic acid copolymer and ionomer resin. Further, as the thermoplastic resin contained in the adhesive resin layer, for example, a resin obtained by graft polymerization or copolymerization of an unsaturated carboxylic acid, an unsaturated carboxylic acid, an unsaturated carboxylic acid anhydride, or an ester monomer to a polyolefin, A resin obtained by graft-modifying maleic anhydride to polyolefin may also be used.
The thermoplastic resin may be a fossil fuel-derived material, a biomass-derived material, or both.

<Support layer>
The support layer is a layer for supporting the laminate together with the base material layer and improving the strength characteristics, durability, etc. of the laminate.

The support layer contains one or more resin materials. Examples of the resin material contained in the support layer include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), 1,4-polycyclohexylene dimethylene terephthalate, and terephthalic acid-cyclohexanedimethanol. - polyesters such as ethylene glycol copolymers, polyamides such as nylon 6, nylon 6,6 and polymetaxylylene adipamide (MXD6), polyolefins such as polyethylene (PE), polypropylene (PP) and polymethylpentene, polychlorides vinyl, polyvinyl alcohol (PVA), polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, vinyl resins such as polyvinyl butyral and polyvinylpyrrolidone (PVP); cellulose resins such as acrylic resins, cellophane, cellulose acetate, nitrocellulose, cellulose acetate propionate (CAP) and cellulose acetate butyrate (CAB); styrene resins such as polystyrene (PS); and chlorinated resins thereof. .
The support layer may be a resin film made of a resin material as described above. The resin film is preferably a uniaxially or biaxially stretched film from the viewpoint of strength and the like.

The thickness of the support layer is, for example, 5 μm or more, and may be 10 μm. On the other hand, the thickness of the support layer is, for example, 200 μm or less, may be 100 μm or less, may be 50 μm or less, or may be 20 μm or less.

<Barrier layer>
The barrier layer is a layer for imparting excellent gas barrier performance to the laminate. A laminate having a barrier layer has excellent barrier properties against gases such as oxygen and water vapor.

In one embodiment, the barrier layer may comprise an inorganic or inorganic oxide vapor deposited film. Examples of deposited films include silicon (Si), aluminum (Al), magnesium (Mg), calcium (Ca), potassium (K), tin (Sn), sodium (Na), boron (B), titanium (Ti ), lead (Pb), zirconium (Zr), yttrium (Y), and the like, or vapor-deposited films of inorganic oxides thereof.
A vapor deposition film can be formed on the surface of a substrate layer and/or a support layer. Examples of the method for forming the vapor deposition film include known methods such as vacuum vapor deposition, sputtering, and chemical vapor deposition.

The thickness of the deposited film is, for example, 10 nm or more, and may be 20 nm or more. On the other hand, the thickness of the deposited film is, for example, 200 nm or less, and may be 100 nm or less.

In one embodiment, the barrier layer may comprise a gas barrier coating located on the surface of the deposited film. By providing the barrier layer with the gas barrier coating film, the gas barrier properties can be further improved.

The gas barrier coating film has the general formula R ¹ _n M (OR ² ) _m (wherein R ¹ and R ² represent an organic group having 1 to 8 carbon atoms, M represents a metal atom, n represents an integer of 0 or more, m represents an integer of 1 or more, and n+m represents the valence of M.) and at least one alkoxide represented by the above polyvinyl alcohol-based A gas barrier composition containing a resin and/or an ethylene-vinyl alcohol copolymer and further polycondensed by the sol-gel method in the presence of a sol-gel catalyst, acid, water and an organic solvent.

As the alkoxide represented by the general formula R ¹ _n M(OR ² ) _m , at least one of partial hydrolyzate of alkoxide and condensate of hydrolysis of alkoxide can be used. The partial hydrolyzate of the above alkoxide does not need to have all of the alkoxy groups hydrolyzed, and may have one or more hydrolyzed alkoxides or a mixture thereof. As the condensate obtained by hydrolysis of the alkoxide, a partially hydrolyzed alkoxide that is a dimer or more, preferably a dimer or more and a hexamer or less is used.

In the alkoxide represented by the general formula R ¹ _n M(OR ² ) _m , the metal atom represented by M can be silicon, zirconium, titanium, aluminum, or the like. Preferred metals include, for example, silicon and titanium. Alkoxides may be used singly or as a mixture of alkoxides of two or more different metal atoms in the same solution.

Specific examples of the organic group represented by R ¹ in the alkoxide represented by the above general formula R ¹ _n M(OR ² ) _m include, for example, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl group, t-butyl group, n-hexyl group, n-octyl group, and the like. Specific examples of the organic group represented by R ² in the alkoxide represented by the above general formula R ¹ _n M(OR ² ) _m include, for example, methyl group, ethyl group, n-propyl group, i-propyl groups, n-butyl groups, sec-butyl groups, and the like. These alkyl groups in the same molecule may be the same or different.

For example, a silane coupling agent may be added when preparing the gas barrier composition. A known organic reactive group-containing organoalkoxysilane can be used as the silane coupling agent. In particular, organoalkoxysilanes having an epoxy group can be preferably used. Examples of organoalkoxysilanes having a poxy group include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and the like. is mentioned. Silane coupling agents may be used singly or in combination of two or more.

In one embodiment, the barrier layer may comprise metal foil. A metal foil is a foil containing one or more metal materials. Metal materials contained in the metal foil include, for example, aluminum, gold, silver, copper, stainless steel, titanium and nickel.
The metal foil can be laminated on the substrate layer and/or the support layer or the like via an adhesive layer.

<Print layer>
The print layer is an image formed using conventionally known pigments and dyes. Examples of images include characters, patterns, symbols, combinations thereof, and the like. The printed layer can be formed by a conventionally known method.

[Method for manufacturing laminate]
The method for manufacturing the laminate according to the present invention is not particularly limited, and it can be manufactured using a conventionally known method such as a melt extrusion lamination method, a dry lamination method, a sand lamination method, or the like. The laminate is formed by, for example, a melt extrusion lamination method in which a sealant film is extruded onto the base layer, and a dry lamination method or a sand lamination method in which the base layer and the sealant film are attached via an adhesive layer. It can be manufactured by a method of combining.

[Packaging bag]
A packaging bag according to the invention comprises a laminate according to the invention. FIG. 6 is a front view showing one embodiment of the packaging bag according to the present invention. An example of the packaging bag according to the present invention will be described below with reference to FIG.

The packaging bag shown in FIG. 6 is the packaging bag 30 . The packaging bag 30 includes an accommodating portion 30a that accommodates contents.

The packaging bag 30 includes an upper portion 31, a lower portion 32 and side portions 33 and has a substantially rectangular profile in front view. Names such as “upper”, “lower” and “side” and terms such as “upper” and “lower” refer to relative positions and directions of the packaging bag 30 and its components. It's nothing more than The orientation and the like of the packaging bag 30 during transportation and use are not limited by the names and terms in this specification.

As shown in FIG. 6, the packaging bag 30 includes a top sheet 34 forming the front side and a back sheet 35 forming the back side. In the packaging bag 30 shown in FIG. 6 , the top sheet 34 and the back sheet 35 are formed from one laminate 20 . At this time, the laminate 20 is folded back at the lower portion 32 so that the sealant layer 22 is positioned inside the packaging bag 30 .

The inner surfaces of the top sheet 34 and the back sheet 35 are joined together by a sealing portion. In the front view of the packaging bag 30 shown in FIG. 6, the sealing portion is hatched.

As shown in FIG. 6 , the packaging bag 30 has seal portions extending along edges in three directions of the packaging bag 30 . The seal portion includes an upper seal portion 31a extending along the upper portion 31 and a pair of side seal portions 33a extending along the pair of side portions 33. As shown in FIG. An opening (not shown) is formed in the upper portion 31 of the packaging bag 30 in the state before the content is filled (the state in which the content is not filled). After the contents are contained in the packaging bag 30, the inner surface of the top sheet 34 and the inner surface of the back sheet 35 are joined together at the upper portion 31 to form the upper sealing portion 31a and the packaging bag 30 is sealed. .
The upper seal portion 31a and the side seal portion 33a are seal portions formed by joining the inner surface of the top sheet 44 and the inner surface of the back sheet 35 together.

As long as the facing sheets can be joined together to seal the packaging bag 30, the method for forming the seal portion is not particularly limited. For example, the inner surface of the sheet is melted by heating or the like, and the inner surfaces are welded to each other, that is, by heat sealing to form the sealed portion.

Although not shown, in the packaging bag 30 , each of the topsheet 34 and the backsheet 35 may be formed by one layered body 20 . In this case, the packaging bag 30 has seal portions extending along the four edges of the packaging bag 30 .

The contents of the packaging bag are not particularly limited, but since the packaging bag has antistatic performance, it can be used for powdered foods such as powdered food (furikake, fried chicken powder), powdered medicine, powdered beverages (coffee, tea), etc. It is particularly suitable for packaging of

EXAMPLES Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the description of the Examples below as long as it does not exceed the gist thereof.

Materials used in the examples are listed below.
・High-pressure low-density polyethylene A (LDPE_A): density: 0.924 g/cm ³ , melt flow rate (MFR): 2 g/10 minutes, melting point: 111°C, biomass content: 0%
・High-pressure low-density polyethylene B (LDPE_B): Density: 0.923 g/cm ³ , MFR: 2.7 g/10 min, Melting point: 110°C, Biomass degree: 0%
・High-pressure low-density polyethylene C (LDPE_C): Density: 0.923 g/cm ³ , MFR: 2.7 g/10 min, Biomass degree: 95%
・High-pressure low-density polyethylene D (LDPE_D): density: 0.919 g/cm ³ , melt flow rate (MFR): 2 g/10 minutes, melting point: 107°C, biomass content: 0%
Linear low-density polyethylene A (copolymer A): copolymer of ethylene and 1-hexene, density: 0.916 g/cm ³ , MFR: 2.3 g/10 minutes, melting point: 116°C , Biomass degree: 0%
Linear low-density polyethylene B (copolymer B): copolymer of ethylene and 1-butene, density: 0.916 g/cm ³ , MFR: 1.0 g/10 minutes, degree of biomass: 0 % Linear low-density polyethylene C (copolymer C): copolymer of ethylene and 1-butene, density: 0.916 g/cm ³ , MFR: 1.0 g/10 minutes, degree of biomass: 87% Linear low-density polyethylene D (copolymer D): copolymer of ethylene and 1-hexene, density: 0.918 g/cm ³ , MFR: 4 g/10 minutes, melting point: 116°C , Biomass degree: 0%
Linear low-density polyethylene E (copolymer E): copolymer of ethylene and 1-hexene, density: 0.938 g/cm ³ , MFR: 3.5 g/10 minutes, melting point: 126°C , Biomass degree: 0%
・Antistatic agent masterbatch A (AS agent A) ... Base material: high-pressure low-density polyethylene, antistatic agent A: ELECUT MASTER LM530 (manufactured by Takemoto Yushi Co., Ltd.), content of antistatic agent A: 18.0% by mass, density: 0.94 g/cm ³ , MFR: 4.9 g/10 min, biomass degree: 0%
Antistatic agent masterbatch B (AS agent B): Base material: high-pressure low-density polyethylene, content of antistatic agent A: 12.0% by mass, density: 0.95 g/cm ³ , MFR: 6 .8 g/10 minutes, biomass degree: 0%
・Antistatic agent C (AS agent C): cationic surfactant ・Antiblocking agent masterbatch (AB agent): base material: polyethylene, antiblocking agent: synthetic zeolite, antiblocking agent content: 10 % by mass, density: 0.961 g/cm ³ , MFR: 4.0 g/10 min, degree of biomass: 0%

[Example 1]
A mixture of 80 parts by mass of copolymer A, 5 parts by mass of AS agent A, and 15 parts by mass of AB agent as a seal layer, and LDPE_A as a laminate layer are melted and co-extruded into a film. yielded a 40 μm thick sealant film composed of two layers. In the sealant film, the thickness of the seal layer was adjusted to 8 μm, and the thickness of the laminate layer was adjusted to 32 μm. Therefore, the thickness of the sealing layer was 1/5 of the thickness of the sealant film.

[Example 2]
A mixture of 80 parts by mass of copolymer A, 5 parts by mass of AS agent A, and 15 parts by mass of AB agent as a sealing layer, LDPE_B as an intermediate layer, and LDPE_A as a laminate layer were melted and formed into a film. to obtain a 40 μm thick sealant film composed of three layers. In the sealant film, the thickness of the sealing layer was adjusted to 8 μm, the thickness of the intermediate layer was adjusted to 24 μm, and the thickness of the laminate layer was adjusted to 8 μm. Therefore, the thickness of the sealing layer was 1/5 of the thickness of the sealant film.

[Example 3]
A sealant film was obtained in the same manner as in Example 2, except that only copolymer B was used as the intermediate layer.

[Example 4]
A sealant film was obtained in the same manner as in Example 2, except that only LDPE_C was used as the intermediate layer. The degree of biomass of the sealant film is 57.0%.

[Example 5]
A sealant film was obtained in the same manner as in Example 2, except that a mixture of 48 parts by mass of LDPE_A and 52 parts by mass of LDPE_C was used as the intermediate layer. The biomass degree of the sealant film is 29.6%.

[Example 6]
A sealant film was obtained in the same manner as in Example 2, except that only the copolymer C was used as the intermediate layer. The degree of biomass of the sealant film is 52.2%.

[Example 7]
A mixture of 96.5 parts by mass of copolymer D, 2 parts by mass of AS agent C, and 1.5 parts by mass of AB agent as a sealing layer, 99.7 parts by mass of LDPE_D as an intermediate layer, A sealant film was obtained in the same manner as in Example 2, except that a mixture with 0.3 parts by mass of AB agent was used, and only Copolymer E was used as the laminate layer.

[Comparative Example 1]
A single-layer sealant film with a thickness of 40 μm was obtained by melting a mixture of 97.5 parts by mass of LDPE_A and 2.5 parts by mass of AS agent B and extruding it into a film.

[Comparative Example 2]
A single-layer sealant film was prepared in the same manner as in Comparative Example 1 except that a mixture of 97.4 parts by mass of copolymer_A, 2 parts by mass of AS agent B, and 0.6 parts by mass of AB agent was used. got

Table 1 shows the details of the sealant films obtained in Examples and Comparative Examples.

<<Calculation of crystallinity>>
The heat of fusion of the laminated surface and the heat-sealed surface of the sealant films produced in Examples and Comparative Examples was obtained from DSC curves drawn according to JIS K7121:2012.
The DSC curve was drawn according to JIS K7121:2012 from differential scanning calorimeter (DSC) data obtained during the first heating under the following conditions.
(conditions)
Sample amount: Accurately weigh about 10 mg Measurement atmosphere: Nitrogen Pan material: Al
Flow rate: 100 mL/min Measurement range: 30°C to 150°C Heating rate: 10°C/min

The degree of crystallinity was calculated by the following formula (1). As the heat of fusion of the perfect crystal, the heat of fusion of the perfect crystal of polyethylene was used. The heat of fusion of a perfect crystal of polyethylene is 293 J/g.
Crystallinity [%] = (heat of fusion obtained from DSC curve / heat of fusion of perfect crystal) × 100 (1)

Table 2 shows the heat of fusion obtained from the DSC curve and the degree of crystallinity calculated from the formula (1).
In the sealant films produced in Examples, the degree of crystallinity of the laminated surface is higher than the degree of crystallinity of the heat-sealed surface. This means that the sealant film comprises a second layer with a crystallinity B that exceeds the crystallinity A.

<<Measurement of breaking test>>
The breaking strength and breaking elongation of the sealant films produced in Examples and Comparative Examples were measured according to JIS Z1702:1994. As a measuring instrument, a Tensilon universal material testing machine RTC-1530 (manufactured by Orientec) was used.
Specifically, first, as a test piece, a dumbbell-shaped cut out of the sealant film was prepared. The measurement width of the test piece was 10 mm, the distance between the pair of chucks holding the test piece at the start of measurement was 50 mm, and the tensile speed was 200 mm/min.
The environment during the measurement of breaking strength and breaking elongation was temperature of 25° C. and relative humidity of 50%. Table 3 shows the measurement results.

<<Measurement of seal strength>>
Using two sheets of each of the sealant films produced in Examples and Comparative Examples, the sealing layers of the sealant films were heat-sealed at 90° C. to form a sealed portion. Subsequently, a portion including the seal portion was cut out to prepare a test piece having a width of 15 mm and a length of 100 mm for measuring the seal strength. The length of the seal portion is 15 mm.

The seal strength was measured according to JIS K 7127:1999. As a measuring instrument, a tensile tester SA-1150 manufactured by Orientec Co., Ltd. was used.
Specifically, as shown in FIG. 7, the two sealant films at the unsealed portion of the test piece 40 were respectively gripped by grips 41 of the measuring instrument. The grips 41 were pulled at a rate of 300 mm/min in opposite directions in the direction orthogonal to the surface direction of the seal portion 42 of the test piece 40, and the maximum value of the tensile stress was measured. Then, the average value of the maximum values was taken as the seal strength. The interval S1 between the grips 41 when starting to pull was set to 50 mm.
The seal strength was measured in the same manner as above while changing the heat-sealing temperature to 100°C, 110°C, 120°C, 130°C, 140°C and 150°C.
The environment during the measurement of the seal strength was set at a temperature of 25° C. and a relative humidity of 50%. Table 3 shows the measurement results. Table 3 shows the above measurement results.

<<Measurement of surface resistivity of sealant film>>
The surface resistivity of the laminate surface and the heat-sealed surface of the sealant films produced in Examples and Comparative Examples was measured according to JIS K6911:1995. As a measuring instrument, a high resistivity diameter Hiresta UX MCP-HT800 (manufactured by Mitsui Chemicals Analytic Tech) was used.
The surface specific resistivity was measured using the sealant film immediately after production and the sealant film after storage at a temperature of 40°C for one week.
The environment during the measurement of the surface specific resistivity was a temperature of 20° C. and a relative humidity of 65%. Table 3 shows the measurement results.

[Preparation of laminate]
A laminate was produced using each of the sealant films of Examples and Comparative Examples.

Specifically, first, the laminate surface side of the sealant film was subjected to corona treatment.

Next, a 30 μm biaxially oriented polypropylene film (manufactured by Toyobo Co., Ltd., P2171) having one side treated with corona was prepared as a substrate layer.

Next, as a support layer having a barrier layer on its surface, a 12 μm aluminum vapor-deposited polyester film (manufactured by Toray Advanced Film Co., Ltd., 1310) was prepared.

Next, the corona-treated surface of the biaxially oriented polypropylene film and the aluminum vapor-deposited film surface of the aluminum vapor-deposited polyester film were bonded together with a two-component curable urethane adhesive (manufactured by Rock Paint Co., Ltd., main agent: RU-77T, curing agent). : H-7).

Next, the resin film surface of the aluminum vapor-deposited polyester film and the corona-treated surface of the sealant film were bonded together with a two-component curable urethane adhesive (manufactured by Rock Paint Co., Ltd., main agent: RU-77T, curing agent: H-7). It was dry laminated through

As described above, a biaxially oriented polypropylene film (base layer), a two-component curable urethane adhesive (adhesive layer), an aluminum deposition film (barrier layer), a polyester film (support layer), and a two-component curing A laminate comprising a type urethane-based adhesive (adhesive layer) and a sealant film (sealant layer) in this order was obtained.

<<Measurement of surface specific resistivity of laminate>>
The surface resistivity of the surface of the sealant layer of the laminate was measured according to JIS K6911:1995. As a measuring instrument, a high resistivity diameter Hiresta UX MCP-HT800 (manufactured by Mitsui Chemicals Analytic Tech) was used.
The surface specific resistivity was measured using a layered product immediately after production and a layered product after being stored at a temperature of 40° C. for two months.
The environment during the measurement of the surface specific resistivity was a temperature of 20° C. and a relative humidity of 65%. Table 4 shows the measurement results.

<<Measurement of laminate strength>>
A test piece obtained by cutting the laminate into a strip with a width of 15 mm is measured using a tensile tester (manufactured by Orientec Co., Ltd., Tensilon Universal Material Testing Machine) in accordance with JIS Z1707: 2019, and the laminate strength (N / 15 mm) was measured using a 180° peel (T-peel method) at a peel speed of 50 mm/min.
Specifically, first, the laminate was cut out, and as shown in FIG. 8, a strip-shaped test piece 50 was prepared by separating the sealant film side 51 and the base layer side 52 by 15 mm in the long side direction. . After that, as shown in FIG. 9, the already peeled portions of the sealant film side 51 and the substrate layer side 52 were each gripped by grips 53 of the measuring instrument. Each of the grippers 53 is pulled at a speed of 50 mm/min in opposite directions to the surface direction of the portion where the sealant film side 51 and the base layer side 52 are still laminated, and the stable area ( 10) was measured. The interval S2 between the grips 53 at the start of pulling was set to 30 mm, and the interval S2 between the grips 53 at the end of pulling was set to 60 mm. FIG. 10 is a diagram showing changes in the tensile stress F with respect to the distance S2 between the grips 53. As shown in FIG. As shown in FIG. 10, the change in tensile stress F with respect to the interval S2 passes through the first region R1 and enters the second region R2 with a smaller rate of change than the first region R1. The second region R2 is also called a stability region.
The average value of the tensile stress F in the stable region R2 was measured for five test pieces 50, and the average value was defined as the laminate strength. The environment for measuring the lamination strength was a temperature of 25° C. and a relative humidity of 50%. Table 4 shows the measurement results.

<<Measurement of tear strength>>
Using a test piece 60 cut from the laminate, the tear strength in the machine direction (MD) was measured according to JIS K7128-2:1998. FIG. 11 is a plan view showing the test piece 60. FIG. A test piece 60 includes a slit 61 extending in the measurement direction. For measuring the tear strength in the machine direction (MD), the slit 61 extends in the machine direction (MD). The length L3 of the slit 61 is 20±0.5 mm. A dimension L1 of the test piece 60 in the direction in which the slit 61 extends is 63±0.5 mm. The dimension L2 of the test piece 60 in the direction perpendicular to the direction in which the slit 61 extends is 75±0.5 mm.
A strip group 65 shown in FIG. 12 containing a plurality of stacked strips 60 was attached to the gauge jaws. One test strip group 65 includes eight test strips 60 . A force was then applied to the strip group 65 along the slit 61 and the force required to tear the strip group 65 was recorded. As a measuring instrument, an Elmendorf tearing tester (manufactured by Toyo Seiki Seisakusho) was used. The environment during the measurement was a temperature of 25° C. and a relative humidity of 50%.
The force required to tear the test strip group 65 was recorded for the five test strip groups 65 and the average value was calculated. The tear strength of the laminate was obtained by dividing the average value by the number of test pieces 60 included in one test piece group 65, that is, by eight. Table 4 shows the measurement results.

<<Evaluation of lamination strength>>
The lamination strength of the sealant film was evaluated based on the following evaluation criteria. The evaluation results are shown in Table 5. Good: The laminate obtained using the sealant film has a laminate strength of 2 N or more after being stored at a temperature of 40° C. for 2 months.
- No Good: The laminate obtained using the sealant film has a laminate strength of less than 2N after being stored at a temperature of 40°C for 2 months.

The sealant film according to the present invention has antistatic performance and excellent lamination strength with other layers.

10: Sealant film 11: First layer 12: Second layer 13: Third layer 20: Laminate 21: Base material layer 22: Sealant layer 23: Adhesive layer 30: Packaging bag 30a: Storage part 31: Upper part 31a: Upper part Seal portion 32: Lower portion 33: Side portion 33a: Side seal portion 34: Surface film 35: Back film 40: Test piece 41: Grip 42: Seal portion 50: Test piece 51: Sealant film side 52: Base layer side 53: Grip X: Inner surface Y: Outer surface

Claims (10)

A sealant film comprising an inner surface and an outer surface,
The sealant film comprises a first layer constituting the inner surface and a second layer,
wherein the first layer comprises polyethylene and an antistatic agent;
wherein the second layer comprises polyethylene;
The first layer has a degree of crystallinity A, the second layer has a degree of crystallinity B, and the relationship between the degree of crystallinity A and the degree of crystallinity B is such that the degree of crystallinity A<the degree of crystallinity A sealant film that satisfies B. 2. The sealant film according to claim 1, wherein the second layer contains, as a main component, at least one type of polyethylene selected from the group consisting of high-pressure low-density polyethylene and medium-density polyethylene. 3. The sealant film according to claim 1 or 2, comprising high-pressure low-density polyethylene as a main component. The sealant film according to any one of claims 1 to 3, wherein the first layer contains linear low density polyethylene as a main component. The sealant film according to any one of claims 1 to 4, wherein the inner surface has a surface resistivity of 9.0 × 10 ¹² Ω/□ or less. Claims 1 to 1, wherein the antistatic agent is at least one antistatic agent selected from the group consisting of anionic antistatic agents, cationic antistatic agents, amphoteric antistatic agents and nonionic antistatic agents. 6. The sealant film according to any one of 5. The sealant film according to any one of claims 1 to 6, wherein the second layer does not contain an antistatic agent. A laminate comprising at least a substrate layer and a sealant layer,
A laminate, wherein the sealant layer comprises the sealant film according to any one of claims 1 to 7, and the outer surface of the sealant film is located on the base layer side. 9. The laminate of Claim 8, comprising an adhesive layer located between the substrate layer and the sealant layer. A packaging bag comprising the laminate according to claim 8 or 9.

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