JP7676907B2 - Sealant film, laminate and packaging bag - Google Patents

Description

The present invention relates to a sealant film, a laminate, and a packaging bag.

Traditionally, packaging bags have been used to fill and package contents such as food, medicines, chemicals, and cosmetics. The laminate that constitutes the packaging bag includes a base layer such as a stretched film and a sealant film that has sealing properties. In the packaging bag, the sealant film comes into contact with the contents of the packaging bag.

The contents may be powdery materials such as flour or powdered medicine. If the sealant film is not treated in any way when packaging such powdery materials, the powdery materials will adhere to the sealant film due to static electricity, making it difficult to remove the contents. In addition, when filling the bag with powdery materials, the powdery materials may adhere to the opening. This can easily cause poor fusion of the sealed area by heat sealing when the packaging bag is made.

For this reason, antistatic agents have been added to sealant films. Kneading-type antistatic agents are known, and these types of antistatic agents are mixed into the resin of the film, thereby imparting antistatic properties to the sealant film (for example, Reference 1).

JP 2004-3399398 A

However, the antistatic agent migrates through the sealant film and appears on its surface, and the antistatic agent that migrates to the base layer side of the sealant film reduces the laminate strength between the sealant film and other layers.

SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a sealant film which has antistatic properties 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 above laminate.

The present invention provides a sealant film including an inner surface and an outer surface,
The sealant film includes a first layer constituting the inner surface and a second layer,
the first layer comprises polyethylene and an antistatic agent;
the second layer comprises polyethylene;
The sealant film has a crystallinity degree A, and the second layer has a crystallinity degree B, and the relationship between the crystallinity degree A and the crystallinity degree B satisfies crystallinity degree A<crystallinity degree B.

In the sealant film according to the present invention, the second layer may contain, 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.

The sealant film according to the present 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 may be at least one antistatic agent selected from the group consisting of anionic antistatic agents, cationic antistatic agents, amphoteric antistatic agents, and nonionic antistatic agents.

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

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

The sealant film according to the present invention may include an adhesive layer located between the substrate layer and the 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 that has antistatic properties and also has excellent lamination strength with other layers.
can.
According to another aspect of the present invention, there is provided a laminate comprising the above sealant film.
According to another aspect of the present invention, a packaging bag including the above-mentioned laminate can be provided.

1 is a schematic cross-sectional view showing one embodiment of a sealant film according to the present invention. 1 is a schematic cross-sectional view showing one embodiment of a sealant film according to the present invention. 1 is a schematic cross-sectional view showing one embodiment of a sealant film according to the present invention. 1 is a schematic cross-sectional view showing one embodiment of a laminate according to the present invention. 1 is a schematic cross-sectional view showing one embodiment of a laminate according to the present invention. 1 is a schematic front view showing one embodiment of a packaging bag according to the present invention. FIG. 2 is a schematic diagram showing a method for measuring seal strength. FIG. 2 is a schematic diagram showing a method for measuring laminate strength. FIG. 2 is a schematic diagram showing a method for measuring laminate strength. FIG. 13 is a diagram showing the measurement results of laminate strength. FIG. 2 is a plan view showing a test piece for measuring tear strength. FIG. 1 is a plan view showing a group of test specimens for measuring tear strength.

The following describes an embodiment of the present invention. In the drawings accompanying this specification, the scale and aspect ratios have been appropriately altered and exaggerated from those of the actual product for the sake of ease of illustration and understanding.

Terms used in this specification that specify shapes, geometric conditions, and their degrees, such as "orthogonal" and "same," as well as values of lengths and angles, are not limited to their strict meanings and are interpreted to include the range within which similar functions can be expected.

In this specification, "inner surface" refers to the surface of the packaging bag facing the contents, and "outer surface" refers to the surface of the packaging bag facing away from the contents, i.e., the surface that is laminated with another layer.

[Sealant film]
The sealant film according to the present invention includes an inner surface and an outer surface. The sealant film includes a first layer constituting the 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 satisfies crystallinity A<crystallinity B. Such a sealant film has antistatic properties and is excellent in lamination strength with other layers. The reason for this is believed to be as follows.

The lamination of the sealant film and other layers is generally performed by dry lamination using an adhesive having a polar group or by sand lamination using an adhesive resin having a polar group. The antistatic agent has a hydrophilic group, and the hydrophilic group is attracted to the polar group, and the antistatic agent migrates to the outer surface side of the sealant film. The migrated antistatic agent affects the adhesion between the sealant film and other layers, and the laminate strength between the sealant film and other layers decreases. In addition, in order to improve the adhesion between the sealant film and adjacent layers, the surface of the sealant film may be hydrophilized by surface treatment such as corona treatment or frame treatment, but the hydrophilic group of the antistatic agent is also attracted to this hydrophilized surface, and the antistatic agent migrates to the outer surface side of the sealant film. This decreases the laminate strength between the sealant film and other layers.
In the sealant film according to the present invention, by making the relationship between the crystallinity A of the first layer and the crystallinity B of the second layer such that A<B, the migration of the antistatic agent contained in the first layer having a low crystallinity is suppressed by the second layer having a high crystallinity, and the migration of the antistatic agent to the outer surface side of the sealant film is suppressed. As a result, it is believed that the sealant film has 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 even more preferably 1.1 or more. This can further suppress migration of the antistatic agent and improve the laminate strength of the sealant film. On the other hand, the ratio of crystallinity B to crystallinity A is, for example, 5 or less, or may be 2 or less, or may be 1.5 or less.

Within the range where crystallinity A is greater than crystallinity B, the difference between crystallinity B and crystallinity A is preferably 1%, more preferably 3%, and even more preferably 5% or more. On the other hand, the difference between crystallinity B and crystallinity A is, for example, 30% or less, may be 20% or less, or may be 10% or less.

In this specification, crystallinity A is the analysis result on the inner surface of the sealant film. Therefore, if the analysis result of the nth time (n is an integer of 1 or more) from the outer surface of the sealant film shows data that exceeds crystallinity A, the presence of a second layer with crystallinity B can be confirmed.

In this specification, "crystallinity" is a value calculated as the ratio of the heat of fusion obtained from a DSC curve plotted in accordance with JIS K7121:2012 to the heat of fusion of a completely crystalline material.

The DSC curve is plotted in accordance with JIS K7121:2012 from differential scanning calorimeter (DSC) data obtained during the second heating under the following conditions: As the differential scanning calorimeter, a DSC200F3Maia manufactured by NETZSCH can be used.
(conditions)
Sample weight: Approximately 10 mg was weighed out 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 from the heat of fusion obtained from the above DSC curve and the heat of fusion of the complete crystal according to the following formula (1). The unit of heat of fusion is "J/g".
Crystallinity [%] = (heat of fusion obtained from DSC curve / heat of fusion of perfect crystal) x 100 (1)
The heat of fusion of a completely crystalline substance may be a value found in a literature, such as "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 completely crystalline substance in polyethylene is 293 J/g.

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

Examples of the homopolymer of ethylene include high density polyethylene (HDPE), medium density polyethylene (MDPE), and high pressure low density polyethylene (LDPE).
In this specification, high density polyethylene means polyethylene having a density of 0.942 g/ ^cm3 or more, and medium density polyethylene means polyethylene having a density of 0.930 g/ ^cm3 or more and less than 0.942 g/ ^cm3 . High pressure low density polyethylene means polyethylene having a density of 0.910 g/ ^cm3 or more and less than 0.930 g/ ^cm3 . High pressure low density polyethylene can be obtained, for example, by polymerizing ethylene under high pressure of 1000 atmospheres or more and less than 2000 atmospheres.
In this specification, the density of the resin, layer, film, etc. is measured in accordance with Method B (pycnometer method) or Method D (density gradient tube method) of JIS K7112:1999. Method B or Method D is selected appropriately depending on 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 may also be called linear polyethylene. Linear polyethylene will now be described.
Linear polyethylene is a copolymer of ethylene and an α-olefin polymerized using a multi-site catalyst such as a Ziegler-Natta catalyst or a single-site catalyst such as a metallocene catalyst. It is therefore distinguished from a homopolymer of ethylene. The α-olefins that serve as monomers for linear polyethylene have 3 or more carbon atoms, and examples of such α-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-nonene, 4-methylpentene, 3,3-dimethylbutene, and mixtures thereof.
Linear polyethylene having a density less than 0.930 g/ ^cm3 may be referred to as linear low density polyethylene (LLDPE).

The single-site catalyst is a catalyst capable of forming a uniform active species, and is usually prepared by contacting a metallocene transition metal compound or a nonmetallocene transition metal compound with an activation cocatalyst. Compared to multi-site catalysts, single-site catalysts have a uniform active site structure, and therefore can polymerize polymers with high molecular weight and highly uniform structures. Particularly preferred examples of single-site catalysts include metallocene catalysts. Metallocene catalysts are catalysts that contain a transition metal compound of Group IV of the periodic table that contains a ligand having a cyclopentadienyl skeleton, a cocatalyst, and if necessary, an organometallic compound and each of the catalyst components of the carrier.

In the above-mentioned 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. Examples of the substituted cyclopentadienyl group include those having at least one substituent selected from a hydrocarbon group having 1 to 30 carbon atoms, a silyl group, a silyl-substituted alkyl group, a silyl-substituted aryl group, a cyano group, a cyanoalkyl group, a cyanoaryl group, a halogen group, a haloalkyl group, a halosilyl group, and the like. The substituted cyclopentadienyl group may have two or more substituents, and the substituents may be bonded to each other to form a ring, such as an indenyl ring, a fluorenyl ring, an azulenyl ring, or a hydrogenated product thereof. The rings formed by bonding the substituents to each other may further have substituents.

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

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

The above-mentioned transition metal compounds of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton can be used as a catalyst component, either alone or in a mixture of two or more kinds.

The co-catalyst refers to a catalyst that can effectively use the above-mentioned transition metal compound of Group IV of the periodic table as a polymerization catalyst, or can balance the ionic charge in a catalytically activated state. Examples of the co-catalyst include benzene-soluble aluminoxanes of organoaluminum oxy compounds and benzene-insoluble organoaluminum oxy compounds, ion-exchangeable layered silicates, boron compounds, ionic compounds consisting of cations with or without active hydrogen groups and non-coordinating anions, lanthanoid salts such as lanthanum oxide, tin oxide, and phenoxy compounds containing fluoro groups.

The transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton may be used by being supported on an inorganic or organic carrier, preferably an inorganic or organic porous oxide, specifically, _ion -exchangeable layered silicate such as _{montmorillonite} , _SiO2 , _Al2O3 , MgO, _ZrO2 , _TiO2 , _B2O3 , CaO, ZnO, BaO, _ThO2 , or mixtures thereof.

Examples of organometallic compounds that may be used as needed include organoaluminum compounds, organomagnesium compounds, and organozinc compounds. Of these, organoaluminum compounds are 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 entirely of monomers derived from fossil fuels.
Biomass polyethylene is polyethylene produced from a raw material containing a monomer derived from biomass. The raw material for biomass polyethylene may contain a monomer derived from a fossil fuel. The raw material for biomass polyethylene is, for example, a raw material containing ethylene derived from biomass and ethylene derived from a fossil fuel and/or an α-olefin derived from a fossil fuel, or a raw material containing an α-olefin derived from biomass and ethylene derived from a fossil fuel.

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

Here, the biomass degree will be described.
Carbon dioxide in the atmosphere contains a certain percentage of C14 (105.5 pMC), so it is known that the C14 content in plants that grow by absorbing carbon dioxide from the atmosphere, such as corn, is also about 105.5 pMC. It is also known that fossil fuels contain very little C14. Therefore, by measuring the percentage of C14 in the total carbon atoms, the percentage of carbon derived from biomass can be calculated.
The term "biomass degree" refers to the weight ratio of biomass-derived components. For example, in the case of polyethylene terephthalate, polyethylene terephthalate is a polymer of ethylene glycol containing two carbon atoms and terephthalic acid containing eight carbon atoms in a molar ratio of 1:1. Therefore, when only biomass-derived ethylene glycol is used, the weight ratio of biomass-derived components in the polyester is 31.25%, so the theoretical value of the 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 biomass-derived components in the fossil fuel polyester produced using ethylene glycol derived from fossil fuel and dicarboxylic acid derived from fossil fuel is 0%, and the biomass degree of the fossil fuel polyester is 0%. Hereinafter, unless otherwise specified, "biomass degree" refers to 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 will be 100%, and therefore the biomass content of biomass polyethylene will be 100%.
The concentration of biomass-derived ethylene in fossil fuel polyethylene produced only from raw materials derived from fossil fuels is 0%, so the biomass content of fossil fuel-derived polyethylene is 0%.

From the viewpoint of reducing the environmental load, the biomass degree of the sealant film is preferably 20% or more, more preferably 25% or more, and even more preferably 50% or more. On the other hand, the biomass degree 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, which can improve the tearability of the sealant film.
In this specification, the term "main component" means a component that accounts for more than 50% by mass.

The content of high-pressure low-density polyethylene in the sealant film is preferably 70% by mass or more, and more preferably 80% by mass or more. On the other hand, the content of 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 the laminate strength of the sealant film can be improved.

The ratio of density B to density A is preferably 1.001 or more, and 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, and more preferably 30 μm or more and 100 μm or less.

The inner surface of the sealant film may be subjected to a surface treatment, which can improve adhesion to the adjacent layers.
The method of the surface treatment is not particularly limited, and examples thereof include physical treatments such as corona treatment, flame treatment, ozone treatment, low-temperature plasma treatment using oxygen gas and/or nitrogen gas, and glow discharge treatment, as well as chemical treatments such as oxidation treatment using chemicals.

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

Below, one embodiment of the sealant film according to the present invention will be described with reference to Figures 1 to 3.

In one embodiment, the sealant film 10 includes a first layer 11 and a second layer 12, as shown in FIG. 1. 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 includes a first layer 11, a second layer 12, and a third layer 13, as shown in FIG. 2. As shown in FIG. 2, the first layer 11 is located on the inner surface X side of the sealant film 10, and the third layer 13 is located 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 includes a first layer 11, a second layer 12, and a third layer 13, as shown in FIG. 3. 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. The 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 following describes the first, second, and third layers that the sealant film may have.

<First layer>
The first layer contains polyethylene and an antistatic agent, which can impart antistatic properties to the sealant film.
In the sealant film, the first layer is a sealing layer. In this specification, the term "sealing layer" refers to a layer that constitutes one surface layer or both surface layers of a laminate when the sealant film is used in the laminate, and that is fused by heat.

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 even more preferably 90% by mass or more, based on the entire first layer.

Examples of the antistatic agent contained in the first layer include anionic antistatic agents such as adipic acid, glutamic acid, sulfonates, sulfates, phosphates, and phosphonates; cationic antistatic agents such as amines, imidazolines, amine ethylene oxide adducts, quaternary ammonium salts, and pyridinium salts; amphoteric antistatic agents having both cationic and anionic groups, such as guanidine salts obtained by reacting maleic anhydride with an alkylamine, and sulfonic acids derived from polyethyleneimine; and 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 ethylene oxide adducts thereof. 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.
In one embodiment, the first layer contains an anionic antistatic agent and an amphoteric antistatic agent. The first layer particularly preferably contains an organic sulfonate such as an alkylsulfonic acid as the anionic antistatic agent, and an ester compound, an ether compound, or an alkyl dialcohol amide of a polyol and a carboxylic acid as the amphoteric antistatic agent. As the antistatic agent, Elecut Master LM530 manufactured by Takemoto Oil Co., Ltd. can be used.
The antistatic agent may be added to the first layer in the form of a masterbatch that includes polyethylene as the base material.
In this specification, the content of the antistatic agent and the additives described below is measured by GC/MS. A Shimadzu GCMS-TQ8050 can be used as a measuring device.

The content of the antistatic agent in the first layer is preferably 0.05% by mass or more and 3% by mass or less, more preferably 0.1% by mass or more and 2% by mass or less, and even more preferably 0.5% by mass or more and 1.5% by mass or less, based on the entire first layer.
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 property and antistatic property.

The first layer preferably contains linear low-density polyethylene as a main component, which can improve the seal strength of the sealant film.
The content of the linear low density polyethylene in the first layer is preferably 70% by mass or more, and more preferably 80% by mass or more, based on the total mass of the first layer, while the content of the 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 comprise 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 even more preferably 15% by mass, based on the total mass of the first layer, while the content of the polyethylene is, for example, 1% by mass or more, and may be 2% by mass or more.

The first layer may include biomass polyethylene.

The first layer may contain one or more additives in addition to the antistatic agent, as long as the properties of the present invention are not impaired. Examples of additives contained in the first layer include antiblocking agents, plasticizers, UV stabilizers, color inhibitors, matting agents, deodorants, flame retardants, weather resistance agents, thread friction reducers, slip agents, antioxidants, ion exchange agents, and color pigments.

The first layer may contain high density polyethylene as long as it does not impair the properties of the present invention.

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

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

<Second layer>
The second layer contains polyethylene. In the second layer, polyethylene may be a 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 even more preferably 90% by mass or more, based on the entire second layer.
In one embodiment, the second layer preferably consists solely of polyethylene.

The second layer preferably contains, as a main component, at least one polyethylene selected from the group consisting of high-pressure low-density polyethylene and medium-density polyethylene, which can reduce the tear strength of the sealant film and improve the tearability.
The content of the polyethylene in the second layer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, based on the entirety of the 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, based on the entirety of the second layer.

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

The second layer may include 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.
In this specification, the term "free" means that the content is 100 ppm or less as measured by pyrolysis GC, or 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 does not contain any additives. Examples of additives contained in the second layer include antiblocking agents, plasticizers, UV stabilizers, color inhibitors, matting agents, deodorants, flame retardants, weather resistance agents, thread friction reducers, slip agents, antioxidants, ion exchange agents, and color pigments. The content of additives in the second layer is preferably less than 0.05% by mass, and more preferably 0.01% by mass or less. It is particularly preferable that the second layer does not contain any additives.

The second layer may contain high density polyethylene as long as it does not impair the properties of the present invention.

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

In one embodiment, when the sealant film is composed of two layers, the second layer is a laminate layer, which is the 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 an intermediate layer. An intermediate layer is a layer located between the seal layer and the laminate layer. When the sealant film is composed of three or more layers, the second layer is preferably a laminate layer.
The second layer may be a layer present in a plurality of layers within the sealant film, i.e., 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 a multiple layer, 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, while 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, and 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, while the thickness of the intermediate layer is preferably 100 μm or less, more preferably 60 μm or less.
In addition, when the laminate layer and the intermediate layer are multiple layers, the above thickness means the total thickness of the multiple layers.

<3rd layer>
The third layer contains polyethylene. In the third layer, polyethylene may be a 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 even more preferably 90% by mass or more, based on the entire third layer.
In one embodiment, the third layer preferably consists solely of polyethylene.

In one embodiment, the third layer has a crystallinity C, and in the sealant film, the relationship between crystallinity A, crystallinity B, and crystallinity C satisfies crystallinity C≦crystallinity A<crystallinity B.

The third layer may include biomass polyethylene.

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

The third layer preferably does not contain an antistatic agent.

The third layer may contain one or more additives as long as they do not impair the properties of the present invention, but preferably does not contain an antistatic agent. Examples of additives contained in the third layer include antiblocking agents, plasticizers, UV stabilizers, color inhibitors, matting agents, deodorants, flame retardants, weather resistance agents, thread friction reducers, slip agents, antioxidants, ion exchange agents, and color 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, whereas 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, whereas the thickness of the third layer is preferably 100 μm or less, more preferably 60 μm or less.
In addition, 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 thicker than the thickness of the laminate layer. This can suppress curling of the sealant film. The ratio of the thickness of the intermediate layer to the thickness of the laminate layer is preferably 1 to 10, more preferably 2 to 5.
In the sealant film, the thickness of the intermediate layer is preferably thicker than the thickness of the seal layer. This can suppress curling of the sealant film. The ratio of the thickness of the intermediate layer to the thickness of the seal layer is preferably 1 to 10, more preferably 2 to 5.

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

The thicknesses of the sealing layer, laminate layer, and intermediate layer are calculated from the results of observing the cross section of the sealant film. For example, a polarizing microscope is used as an instrument for observing the cross section of the sealant film.

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

The breaking strength of the sealant film in at least one direction is, for example, 10 MPa or more, or may be 15 MPa or more, or may be 25 MPa or more, whereas the breaking strength of the sealant film in at least one direction is, for example, 50 MPa or less, or may be 30 MPa or less.
In one embodiment, the breaking strength of the sealant film in the machine direction (MD) of the sealant film is, for example, 10 MPa or more, or may be 15 MPa or more, or may be 25 MPa or more, whereas the breaking strength of the sealant film in the MD is, for example, 50 MPa or less, or may be 30 MPa or less.
In one embodiment, the breaking strength of the sealant film in the direction perpendicular to the machine direction (TD) of the sealant film is, for example, 10 MPa or more, or may be 15 MPa or more, or may be 25 MPa or more, whereas the breaking strength of the sealant film in the TD is, for example, 50 MPa or less, or may be 30 MPa or less.

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

The breaking strength and breaking elongation can be measured in accordance with JIS Z1702:1994. As a measuring instrument, a Tensilon universal material testing machine RTC-1530 (manufactured by Orientec Co., Ltd.) can be used. As a test piece, a sealant film cut into a dumbbell shape 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 the 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 held by the pair of chucks. In this application, unless otherwise specified, the environment during measurement of the breaking strength and breaking elongation is a temperature of 25°C and a relative humidity of 50%.

[Method of manufacturing sealant film]
The sealant film of the present invention can be produced by a conventionally known method, and the first and second layers of the sealant film can be formed by appropriately selecting the type, density and amount of polyethylene used as the raw material.

The method for producing the sealant film according to the present invention is not particularly limited, and the film can be produced by a conventionally known method. The sealant film is preferably co-extruded, and more preferably, the co-extrusion is performed 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 is described below.

In the T-die method, first, the materials constituting each layer are dried, and then supplied to a melt extruder heated to a temperature above the melting point (Tm) to a temperature of Tm+100°C, where they are melted and extruded into a sheet from the T-die. The extruded sheet is then quenched and solidified on a rotating cooling drum or the like to form a sealant film.
As the melt extruder, a single screw extruder, a twin screw extruder, a vent extruder, a tandem extruder, etc. can be used depending on the purpose.

In the inflation method, the materials constituting each layer are first dried, and then fed into a melt extruder heated to a temperature above the melting point (Tm) to Tm+100°C, where they are melted and extruded into a cylindrical shape through an annular die. At this time, air is fed into the cylindrical molten resin from below to expand the diameter of the cylinder to a predetermined size, and cooling air is fed from below to the outside of the cylinder. This expanded cylindrical body is called a bubble. Next, the bubble is folded into a film shape by a guide plate and a pinch roll, and wound up in a winding section. The folded film can be wound up as it is in a cylindrical shape, or both ends of the cylinder can be removed with a slitter or the like, cut into two films, and then each can be wound up. This allows the sealant film to be formed.
As the melt extruder, a single screw extruder, a twin screw extruder, a vent extruder, a tandem extruder, etc. can be used depending on the purpose.

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

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

The layer structure of the laminate according to the present invention will be explained below with reference to the drawings.

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

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

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

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

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

<Base material layer>
The substrate layer is a layer having a function of supporting the laminate. For example, a paper substrate, a resin film, or a laminate thereof can be appropriately used as the substrate layer.

The paper base material can be one that has printability, flex resistance, rigidity, stiffness, strength, etc., 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 type of resin material. Examples of resin materials contained in the resin film include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), 1,4-polycyclohexylene dimethylene terephthalate, and terephthalic acid-cyclohexane dimethanol-ethylene glycol copolymers; polyamides such as nylon 6, nylon 6,6, and polymetaxylylene adipamide (MXD6); polyolefins such as polyethylene (PE), polypropylene (PP), and polymethylpentene; vinyl resins such as polyvinyl chloride, polyvinyl alcohol (PVA), polyvinyl acetate, vinyl chloride-vinyl acetate copolymers, polyvinyl butyral, and polyvinylpyrrolidone (PVP); (meth)acrylic resins such as polyacrylate, polymethacrylate, and polymethyl methacrylate; cellulose resins such as cellophane, cellulose acetate, nitrocellulose, 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, and more preferably at least one selected from the group consisting of polypropylene, polyethylene terephthalate, nylon 6, and nylon 6,6.

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

The surface of the resin film may be subjected to a surface treatment. The method of the surface treatment is not particularly limited, and examples include physical treatments such as corona treatment, flame treatment, ozone treatment, low-temperature plasma treatment using oxygen gas and/or nitrogen gas, and glow discharge treatment, as well as chemical treatments such as oxidation treatment using chemicals.

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

<Adhesive layer>
The adhesive layer is an adhesive layer or an adhesive resin layer formed for bonding two layers by lamination. The adhesive layer is preferably an adhesive layer because it has good adhesion to various layers, particularly to a sealant layer.

The adhesive layer is a layer formed using at least one type of one-part or two-part curable or non-curable laminating adhesive. Therefore, 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.
Examples of methods for coating the adhesive include a direct gravure roll coating method, a gravure roll coating method, a kiss coating method, a reverse roll coating method, a Fontaine method, and a transfer roll coating method.
The coating amount in a dry state is, for example, 0.1 g/ ^m2 or more, and may be 1 g/ ^m2 or more. On the other hand, the coating amount in a dry state is, for example, 10 g/m2 or ^less , and may be about 5 g/ ^m2 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, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, ethylene-maleic acid copolymer, and ionomer resin. Examples of the thermoplastic resin contained in the adhesive resin layer include resins obtained by graft-polymerizing or copolymerizing unsaturated carboxylic acid, unsaturated carboxylic acid anhydride, or ester monomer to polyolefin, and resins obtained by graft-modifying maleic anhydride to polyolefin.
The thermoplastic resin may be made of a material derived from a fossil fuel, a material derived from biomass, or a combination of both.

<Support layer>
The support layer is a layer that supports the laminate together with the base layer and improves the strength characteristics, durability, and the like of the laminate.

The support layer contains one or more resin materials. Examples of resin materials contained in the support layer include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), 1,4-polycyclohexylene dimethylene terephthalate, and terephthalic acid-cyclohexanedimethanol-ethylene glycol copolymers; polyamides such as nylon 6, nylon 6,6, and polymetaxylylene adipamide (MXD6); polyolefins such as polyethylene (PE), polypropylene (PP), and polymethylpentene; vinyl resins such as polyvinyl chloride, polyvinyl alcohol (PVA), polyvinyl acetate, vinyl chloride-vinyl acetate copolymers, polyvinyl butyral, and polyvinylpyrrolidone (PVP); (meth)acrylic resins such as polyacrylate, polymethacrylate, and polymethyl methacrylate; cellulose resins such as 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 the above-mentioned resin material. From the viewpoint of strength, the resin film is preferably a film stretched in a uniaxial or biaxial direction.

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, and may be 100 μm or less, 50 μm or less, or 20 μm or less.

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

In one embodiment, the barrier layer may include a vapor-deposited film of an inorganic substance or an inorganic oxide, such as one or more inorganic substances such as silicon (Si), aluminum (Al), magnesium (Mg), calcium (Ca), potassium (K), tin (Sn), sodium (Na), boron (B), titanium (Ti), lead (Pb), zirconium (Zr), and yttrium (Y), or a vapor-deposited film of an inorganic oxide thereof.
The vapor-deposited film can be formed on the surface of the base layer and/or support layer, etc. Examples of methods for forming the vapor-deposited film include known methods such as vacuum 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 film located on the surface of the vapor deposition film. By providing the barrier layer with a gas barrier coating film, the gas barrier properties can be further improved.

The gas barrier coating film is obtained from a gas barrier composition which contains at least one alkoxide represented by 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 atomic valence of M) and the above-mentioned polyvinyl alcohol resin and/or ethylene-vinyl alcohol copolymer, and which is further polycondensed by a sol-gel process in the presence of a sol-gel process catalyst, an acid, water, and an organic solvent.

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

In the alkoxide represented by the above general formula R ¹ _n M(OR ² ) _m , the metal atom represented by M may be silicon, zirconium, titanium, aluminum, etc. Preferred metals include, for example, silicon, titanium, etc. The alkoxide may be used alone or in the form of a mixture of two or more different metal atoms in the same solution.

In the alkoxides represented by the above general formula R ¹ _n M(OR ² ) _m , specific examples of the organic group represented by R ¹ include alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, t-butyl, n-hexyl, n-octyl, etc. In the alkoxides represented by the above general formula R ¹ _n M(OR ² ) _m , specific examples of the organic group represented by R ² include methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, etc. These alkyl groups may be the same or different in the same molecule.

When preparing the gas barrier composition, for example, a silane coupling agent may be added. As the silane coupling agent, a known organoalkoxysilane containing an organic reactive group can be used. In particular, an organoalkoxysilane having an epoxy group can be preferably used. As the organoalkoxysilane having an epoxy group, for example, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, or β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane can be mentioned. The silane coupling agent may be used alone or in a mixture of two or more kinds.

In one embodiment, the barrier layer may include a metal foil. The metal foil is a foil containing one or more metal materials. Examples of the metal materials contained in the metal foil include aluminum, gold, silver, copper, stainless steel, titanium, and nickel.
The metal foil can be laminated to the base layer and/or support layer via an adhesive layer.

<Printing layer>
The print layer is an image formed using a conventionally known pigment or dye. Examples of the image include characters, patterns, symbols, and combinations thereof. The print layer can be formed by a conventionally known method.

[Method for producing laminate]
The method for producing the laminate according to the present invention is not particularly limited, and the laminate can be produced by a conventionally known method such as melt extrusion lamination, dry lamination, sand lamination, etc. The laminate can be produced, for example, by a method in which a sealant film is extruded onto a base layer by melt extrusion lamination, or a method in which a base layer and a sealant film are bonded together via an adhesive layer by dry lamination or sand lamination.

[Packaging bag]
The packaging bag according to the present invention includes the laminate according to the present invention. Fig. 6 is a front view showing one embodiment of the packaging bag according to the present invention. Hereinafter, one example of the packaging bag according to the present invention will be described with reference to Fig. 6.

The packaging bag shown in FIG. 6 is packaging bag 30. Packaging bag 30 has a storage section 30a that stores the contents.

The packaging bag 30 includes an upper portion 31, a lower portion 32, and a side portion 33, and has a generally rectangular outline in a front view. The names "upper portion," "lower portion," and "side portion," as well as terms such as "above" and "below," merely indicate the relative positions and directions of the packaging bag 30 and its components. The position, etc., of the packaging bag 30 during transportation or use is not limited by the names and terms used in this specification.

As shown in FIG. 6, the packaging bag 30 includes a top sheet 34 that forms the top surface and a back sheet 35 that forms the back surface. In the packaging bag 30 shown in FIG. 6, the top sheet 34 and the back sheet 35 are formed from a single 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 seal. In the front view of the packaging bag 30 shown in Figure 6, the seal is hatched.

6, the packaging bag 30 has a seal portion extending along three edges 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 a pair of side portions 33. Note that, in the packaging bag 30 in a state before the contents are filled (a state in which the contents are not filled), an opening (not shown) is formed in the upper portion 31 of the packaging bag 30. Then, after the contents are placed in the packaging bag 30, the inner surface of the top sheet 34 and the inner surface of the back sheet 35 are joined at the upper portion 31 to form the upper seal portion 31a and seal the packaging bag 30.
The upper seal portion 31 a and the side seal portion 33 a are seal portions formed by joining the inner surface of the top sheet 44 and the inner surface of the back sheet 35 .

As long as the opposing sheets can be joined together to seal the packaging bag 30, there is no particular limitation on the method for forming the seal. For example, the seal can be formed by melting the inner surfaces of the sheets by heating or the like and fusing the inner surfaces together, i.e., by heat sealing.

Although not shown, in the packaging bag 30, the top sheet 34 and the back sheet 35 may each be formed from a single laminate 20. In this case, the packaging bag 30 has a seal portion that extends along the edges of the packaging bag 30 in four directions.

The contents of the packaging bag are not particularly limited, but because the packaging bag has antistatic properties, it is particularly suitable for packaging powdered materials such as powdered foods (rice toppings, fried chicken powder), powdered medicines, and powdered drinks (coffee, tea).

Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the description of the following examples as long as it does not deviate from the gist of the invention.

The 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 min, melting point: 111° C., biomass ratio: 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 ratio: 0%
High-pressure low-density polyethylene C (LDPE_C)...density: 0.923 g/cm ³ , MFR: 2.7 g/10 min, biomass ratio: 95%
High-pressure low-density polyethylene D (LDPE_D)...density: 0.919 g/cm ³ , melt flow rate (MFR): 2 g/10 min, melting point: 107° C., biomass content: 0%
Linear low-density polyethylene A (copolymer A): a copolymer of ethylene and 1-hexene, density: 0.916 g/cm ³ , MFR: 2.3 g/10 min, melting point: 116° C., biomass ratio: 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 min, biomass degree: 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 min, biomass degree: 87% Linear low-density polyethylene D (copolymer D)...copolymer of ethylene and 1-hexene, density: 0.918 g/cm ³ , MFR: 4 g/10 min, 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 min, melting point: 126° C., biomass content: 0%
Antistatic agent master batch A (AS agent A)...base material: high pressure low density polyethylene, antistatic agent A: Elecut Master LM530 (manufactured by Takemoto Oil Co., Ltd.), content of antistatic agent A: 18.0 mass%, density: 0.94 g/cm ³ , MFR: 4.9 g/10 min, biomass degree: 0%
Antistatic agent master batch B (AS agent B)...base material: high-pressure low-density polyethylene, content of antistatic agent A: 12.0 mass %, density: 0.95 g/cm ³ , MFR: 6.8 g/10 min, biomass ratio: 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 mass %, density: 0.961 g/cm ³ , MFR: 4.0 g/10 min, biomass degree: 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 were melted and co-extruded into a film to obtain a sealant film having a thickness of 40 μm 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 sealant layer relative to the thickness of the sealant film was 1/5.

[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 the seal layer, LDPE_B as the intermediate layer, and LDPE_A as the laminate layer were melted and extruded into a film to obtain a sealant film having a thickness of 40 μm composed of three layers. In the sealant film, the thickness of the seal 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 sealant layer relative to the thickness of the sealant film was 1/5.

[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]
Except for using only LDPE_C as the intermediate layer, a sealant film was obtained in the same manner as in Example 2. The biomass content of the sealant film was 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 content of the sealant film was 29.6%.

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

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

[Comparative Example 1]
A mixture of 97.5 parts by mass of LDPE_A and 2.5 parts by mass of AS agent B was melted and extruded into a film to obtain a single-layer sealant film having a thickness of 40 μm.

[Comparative Example 2]
A single-layer sealant film was obtained 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.

Details of the sealant films obtained in the examples and comparative examples are shown in Table 1.

<<Calculation of crystallinity>>
The heat of fusion of the laminate surface and the heat seal surface of the sealant films produced in the examples and comparative examples was obtained from a DSC curve plotted in accordance with JIS K7121:2012.
The DSC curve was plotted in accordance with JIS K7121:2012 from differential scanning calorimeter (DSC) data obtained during the first heating under the following conditions.
(conditions)
Sample weight: Approximately 10 mg was weighed out Measurement atmosphere: Nitrogen Pan material: Al
Flow rate: 100 mL/min Measurement range: 30°C to 150°C Heating rate: 10°C/min

The crystallinity was calculated by the following formula (1). The heat of fusion of a perfect crystal was that of a perfect crystal of polyethylene. 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) x 100 (1)

The heat of fusion obtained from the DSC curve and the crystallinity calculated from the formula (1) are shown in Table 2.
In the sealant films prepared in the examples, the crystallinity of the laminate surface is higher than that of the heat seal surface. This means that the sealant film has a second layer having a crystallinity B higher than the crystallinity A.

<<Break test measurement>>
The breaking strength and breaking elongation of the sealant films produced in the Examples and Comparative Examples were measured in accordance with JIS Z1702: 1994. The measuring device used was a Tensilon universal material testing machine RTC-1530 (manufactured by Orientec Co., Ltd.).
Specifically, a sealant film was cut into a dumbbell shape to prepare a test piece. The measurement width of the test piece was 10 mm, the distance between a pair of chucks holding the test piece at the start of the measurement was 50 mm, and the tensile speed was 200 mm/min.
The breaking strength and breaking elongation were measured in an environment of a temperature of 25° C. and a relative humidity of 50%. The measurement results are shown in Table 3.

<<Seal strength measurement>>
Two sheets of each sealant film prepared in the examples and comparative examples were used, and the seal layers of the sealant films were heat-sealed to each other at 90° C. to form a seal portion. Then, 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 was 15 mm.

The seal strength was measured in accordance with JIS K 7127: 1999. The measuring device used was a tensile tester SA-1150 manufactured by Orientec Co., Ltd.
Specifically, as shown in Fig. 7, two sheets of sealant film in the unsealed portion of the test piece 40 were each gripped by a gripper 41 of the measuring device. The grippers 41 were pulled in opposite directions perpendicular to the surface direction of the sealed portion 42 of the test piece 40 at a speed of 300 mm/min to measure the maximum value of the tensile stress. The average of the maximum values was taken as the seal strength. The distance S1 between the grippers 41 at the start of pulling was 50 mm.
The heat fusion temperature was changed to 100°C, 110°C, 120°C, 130°C, 140°C and 150°C, and the seal strength was measured in the same manner as above.
The environment during the measurement of the seal strength was a temperature of 25° C. and a relative humidity of 50%. The measurement results are shown in Table 3. The measurement results are shown in Table 3.

<<Measurement of surface resistivity of sealant film>>
The surface resistivity of the laminate surface and the heat seal surface of the sealant films prepared in the Examples and Comparative Examples was measured in accordance with JIS K6911: 1995. A high resistivity diameter Hirester UX MCP-HT800 (manufactured by Mitsui Chemicals Analytech Co., Ltd.) was used as the measuring device.
The surface resistivity was measured using the sealant film immediately after preparation and the sealant film after storage at a temperature of 40° C. for one week.
The surface resistivity was measured in an environment with a temperature of 20° C. and a relative humidity of 65%. The measurement results are shown in Table 3.

[Preparation of Laminate]
A laminate was produced using each of the sealant films of the examples and comparative examples.

Specifically, first, the laminate side of the sealant film was corona treated.

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

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

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

Then, the resin film surface of the aluminum-deposited polyester film and the corona-treated surface of the sealant film were dry laminated using a two-component curing urethane adhesive (manufactured by Rock Paint Co., Ltd., base agent: RU-77T, curing agent: H-7).

As a result, a laminate was obtained that had, in this order, a biaxially oriented polypropylene film (base layer), a two-component curing urethane adhesive (adhesive layer), an aluminum vapor deposition film (barrier layer), a polyester film (support layer), a two-component curing urethane adhesive (adhesive layer), and a sealant film (sealant layer).

<<Measurement of surface resistivity of laminate>>
The surface resistivity of the surface of the sealant layer of the laminate was measured in accordance with JIS K6911: 1995. A high resistivity diameter Hirester UX MCP-HT800 (manufactured by Mitsui Chemicals Analytech Co., Ltd.) was used as the measuring device.
The surface resistivity was measured using the laminate immediately after production and the laminate after storage at a temperature of 40° C. for two months.
The surface resistivity was measured in an environment with a temperature of 20° C. and a relative humidity of 65%. The measurement results are shown in Table 4.

<<Measurement of Laminate Strength>>
The laminate was cut into a 15 mm wide strip of test piece, and the laminate strength (N/15 mm) was measured using a tensile tester (Tensilon universal material testing machine, manufactured by Orientec Co., Ltd.) in accordance with JIS Z1707:2019, at a peel speed of 50 mm/min and 180° peel (T-peel method).
Specifically, first, a laminate was cut out, and a strip-shaped test piece 50 was prepared by peeling the sealant film side 51 and the base layer side 52 by 15 mm in the long side direction as shown in FIG. 8. Then, as shown in FIG. 9, the already peeled parts of the sealant film side 51 and the base layer side 52 were each held by a gripper 53 of a measuring device. The grippers 53 were pulled at a speed of 50 mm/min in opposite directions perpendicular to the surface direction of the part where the sealant film side 51 and the base layer side 52 are still laminated, and the average value of the tensile stress F in the stable region (see FIG. 10) was measured. The interval S2 between the grippers 53 when the pulling started was 30 mm, and the interval S2 between the grippers 53 when the pulling ended was 60 mm. FIG. 10 is a diagram showing the change in the tensile stress F with respect to the interval S2 between the grippers 53. 10, the change in the tensile stress F with respect to the distance S2 passes through a first region R1 and enters a second region R2 in which the rate of change is smaller than that of the first region R1. The second region R2 is also called a stable region.
The average value of the tensile stress F in the stable region R2 was measured for the five test pieces 50, and the average value was determined as the laminate strength. The environment during the measurement of the laminate strength was a temperature of 25° C. and a relative humidity of 50%. The measurement results are shown in Table 4.

<<Measurement of tear strength>>
Using a test piece 60 cut out from the laminate, the tear strength in the machine direction (MD) was measured in accordance with JIS K7128-2:1998. FIG. 11 is a plan view showing the test piece 60. The test piece 60 includes a slit 61 extending in the measurement direction. When 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. The 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 test specimen group 65 shown in FIG. 12 including a plurality of stacked test specimens 60 was attached to a grip of a measuring device. One test specimen group 65 includes eight test specimens 60. Then, a force was applied to the test specimen group 65 along the slits 61, and the force required to tear the test specimen group 65 was recorded. An Elmendorf tear tester (manufactured by Toyo Seiki Seisakusho) was used as the measuring device. The environment during the measurement was a temperature of 25° C. and a relative humidity of 50%.
The force required to tear the five test specimen groups 65 was recorded and the average value was calculated. The average value was divided by the number of test specimens 60 included in one test specimen group 65, i.e., 8, to determine the tear strength of the laminate. The measurement results are shown in Table 4.

<<Evaluation of Laminate Strength>>
The laminate 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 had a laminate strength of 2N or more after storage at a temperature of 40°C for 2 months.
No Good: In a laminate obtained using the sealant film, the lamination strength after storing at a temperature of 40° C. for 2 months is less than 2 N.

The sealant film of the present invention has antistatic properties and excellent lamination strength with other layers.

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

Claims (10)

A sealant film including an inner surface and an outer surface,
The sealant film includes a first layer constituting the inner surface and a second layer,
the first layer comprises polyethylene and an antistatic agent;
the second layer comprises polyethylene;
the first layer has a crystallinity A, the second layer has a crystallinity B, and the relationship between the crystallinity A and the crystallinity B satisfies crystallinity A<crystallinity B;
The second layer comprises, as a main component, at least one polyethylene selected from the group consisting of high-pressure low-density polyethylene and medium -density polyethylene. 2. The sealant film according to claim 1 , which comprises a high-pressure low-density polyethylene as a main component. A sealant film including an inner surface and an outer surface,
The sealant film includes a first layer constituting the inner surface and a second layer,
the first layer comprises polyethylene and an antistatic agent;
the second layer comprises polyethylene;
the first layer has a crystallinity A, the second layer has a crystallinity B, and the relationship between the crystallinity A and the crystallinity B satisfies crystallinity A<crystallinity B;
A sealant film containing high-pressure low-density polyethylene as its 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 x 10 ¹² Ω/□ or less. The sealant film according to any one of claims 1 to 5, 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. 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 base layer and a sealant layer,
A laminate comprising the sealant film according to any one of claims 1 to 7, wherein the sealant layer is provided with an outer surface of the sealant film on the base layer side. The laminate according to claim 8, comprising an adhesive layer located between the base layer and the sealant layer. A packaging bag comprising the laminate according to claim 8 or 9.

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