Film, laminate and packaging container

Abstract

To enhance heat deformation resistance in a film comprising a layer containing polyethylene as a principal component.SOLUTION: A multilayer film comprises at least a first surface resin layer containing high-density polyethylene (A) as a principal component, and a second surface resin layer containing polyethylene as the principal component, where the high-density polyethylene (A) has a peak whose maximum value of dW / d(LogM) is 0.80 or more and whose half-width is less than 1.1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to films, laminates and packaging containers. [Background technology]

[0002] Packaging containers are used to store contents such as liquids and powders. Packaging containers are made using, for example, packaging materials that include a base material and a heat-sealing layer (see, for example, Patent Document 1). Polyethylene film is flexible, transparent, and has excellent heat-sealing properties, so it is widely used as the heat-sealing layer that constitutes the packaging material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-55156 Summary of the Invention [Problem to be solved by the invention]

[0004] Compared with other thermoplastic resins, polyethylene is a resin that softens at a relatively low temperature. Therefore, when a polyethylene film is used as the substrate of a packaging material, the substrate may deform or, in some cases, melt when the packaging material is heat-sealed. Furthermore, polyethylene film may have insufficient strength compared to other thermoplastic resin films. For this reason, resin films with excellent heat resistance and strength, such as polyester film and nylon film, are generally used as the substrate. For example, a packaging material comprising a polyester film or nylon film as the substrate and a polyethylene film as the heat-sealing layer is used.

[0005] In recent years, with the growing demand for a recycling-oriented society, attempts have been made to recycle packaging materials. However, packaging materials that contain different types of resin films, such as a combination of polyester film or nylon film and polyethylene film, are difficult to separate by type of resin. Therefore, such packaging materials tend not to be suitable for recycling.

[0006] Stretched films and the like that have improved heat resistance and strength by stretching polyethylene films have been studied. However, the heat resistance of these films is still insufficient, and they tend to undergo significant thermal deformation, for example, when placed in a high-temperature environment. An object of the present disclosure is to improve the thermal deformation resistance of a film that includes a layer containing polyethylene as a main component. [Means for solving the problem]

[0007] The multilayer film of one embodiment of the present disclosure comprises: a first surface resin layer containing high-density polyethylene (A) as a main component; a second surface resin layer containing polyethylene as a main component; At least The high-density polyethylene (A) has a peak in a differential molecular weight distribution curve (horizontal axis: common logarithm (LogM) of molecular weight (M); vertical axis: dW / d(LogM) obtained by differentiating cumulative concentration fraction (W) with common logarithm of molecular weight (M)) obtained by high-temperature gel permeation chromatography (GPC) measurement, in which the maximum value of dW / d(LogM) is 0.80 or more and the half-width is less than 1.1.

[0008] The stretched film of one embodiment of the present disclosure comprises: a first surface resin layer containing high-density polyethylene (A) as a main component; a second surface resin layer containing polyethylene as a main component; A film comprising at least the above is stretched, The high-density polyethylene (A) has a peak in a differential molecular weight distribution curve obtained by high-temperature gel permeation chromatography (GPC) measurement, in which the maximum value of dW / d(LogM) is 0.80 or more and the half-width is less than 1.1. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a film having a layer containing polyethylene as a main component, which has excellent heat resistance and exhibits little thermal deformation when placed in a high-temperature environment, for example. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic cross-sectional view showing one embodiment of a stretched film. [Figure 2] FIG. 2 is a schematic cross-sectional view showing one embodiment of a stretched film. [Figure 3] FIG. 3 is a schematic cross-sectional view showing one embodiment of a stretched film. [Figure 4] FIG. 4 is a schematic cross-sectional view showing one embodiment of the laminate. [Figure 5] FIG. 5 is a schematic cross-sectional view showing one embodiment of the laminate. [Figure 6] FIG. 6 is a schematic cross-sectional view showing one embodiment of a laminate. [Figure 7] FIG. 7 is a schematic diagram illustrating a differential molecular weight distribution curve. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described in detail. For clarity of explanation, the drawings may show the width, thickness, shape, etc. of each layer more schematically than in the embodiments, but these are merely examples and do not limit the interpretation of the embodiments of the present disclosure. In this specification and each drawing, elements similar to those already described with reference to the previous drawings are designated by the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0012] In this specification, when multiple upper limit candidates and multiple lower limit candidates are listed for a certain parameter, the numerical range of the parameter may be constructed by combining any one upper limit candidate with any one lower limit candidate. Examples of such parameters include physical properties, component content, and layer thickness. As an example, the following statement will be explained: "Parameter B is preferably A1 or greater, more preferably A2 or greater, and even more preferably A3 or greater. Parameter B is preferably A4 or less, more preferably A5 or less, and even more preferably A6 or less." In this example, the numerical range of parameter B may be A1 or greater and A4 or less, A1 or greater and A5 or less, A1 or greater and A6 or less, A2 or greater and A4 or less, A2 or greater and A5 or less, A2 or greater and A6 or less, A3 or greater and A4 or less, A3 or greater and A5 or less, or A3 or greater and A6 or less.

[0013] In this specification, polyethylene refers to a polymer in which the content of ethylene-derived structural units exceeds 50 mol% of the total amount of structural units derived from polymerizable monomers. In this polymer, the content of ethylene-derived structural units is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and particularly preferably 95 mol% or more. The content is measured by nuclear magnetic resonance spectroscopy (NMR method).

[0014] In this specification, the polyethylene may be a homopolymer of ethylene or a copolymer of ethylene and an ethylenically unsaturated monomer other than ethylene. Examples of the ethylenically unsaturated monomer other than ethylene include α-olefins having 3 to 20 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, 3-methyl-1-butene, 4-methyl-1-pentene, and 6-methyl-1-heptene; vinyl monomers, such as vinyl acetate and vinyl propionate; and (meth)acrylic acid esters, such as methyl (meth)acrylate and ethyl (meth)acrylate.

[0015] In this specification, examples of polyethylene include high-density polyethylene, medium-density polyethylene, linear low-density polyethylene, high-pressure low-density polyethylene, ethylene-vinyl acetate copolymer, and ethylene-(meth)acrylic acid ester copolymer. From the viewpoint of reducing the environmental load, the polyethylene may be biomass-derived polyethylene (hereinafter also referred to as "biomass polyethylene") or mechanically or chemically recycled polyethylene (hereinafter also referred to as "recycled polyethylene").

[0016] In this specification, the density of polyethylene is as follows: The density of the high density polyethylene is preferably 0.945 g / cm 3 The density of the high density polyethylene is preferably greater than 0.970 g / cm 3 The density of the medium density polyethylene is preferably 0.930 g / cm or less. 3 More than 0.945g / cm 3 The density of the linear low density polyethylene is preferably 0.860 g / cm 3 More than 0.930g / cm 3 less than 0.900 g / cm 3 More than 0.930g / cm 3 The density of the high-pressure low-density polyethylene is preferably less than 0.860 g / cm 3 More than 0.930g / cm 3 less than 0.900 g / cm 3 More than 0.930g / cm 3 In this specification, the density of polyethylene is measured in accordance with JIS K7112-2:2023 (density gradient tube method, 23°C).

[0017] In this specification, high-density polyethylene (HDPE) includes, for example, ethylene homopolymers and ethylene-α-olefin copolymers. Examples of α-olefins include the above-mentioned α-olefins having from 3 to 20 carbon atoms, with α-olefins having from 3 to 8 carbon atoms being preferred, and α-olefins having from 4 to 8 carbon atoms being more preferred. Examples of ethylene-α-olefin copolymers include ethylene-1-butene copolymers (C4-HDPE) in which the comonomer is at least 1-butene, ethylene-1-hexene copolymers (C6-HDPE) in which the comonomer is at least 1-hexene, and ethylene-1-octene copolymers (C8-HDPE) in which the comonomer is at least 1-octene. In these copolymers, the comonomer is not limited to the above-mentioned comonomers, and additional comonomers may also be used.

[0018] In this specification, examples of medium-density polyethylene (MDPE) include ethylene homopolymers and ethylene-α-olefin copolymers. Examples of α-olefins include the above-mentioned α-olefins having from 3 to 20 carbon atoms, with α-olefins having from 3 to 8 carbon atoms being preferred, and α-olefins having from 4 to 8 carbon atoms being more preferred. Examples of ethylene-α-olefin copolymers include ethylene-1-butene copolymers (C4-MDPE) in which the comonomer is at least 1-butene, ethylene-1-hexene copolymers (C6-MDPE) in which the comonomer is at least 1-hexene, and ethylene-1-octene copolymers (C8-MDPE) in which the comonomer is at least 1-octene. In these copolymers, the comonomers are not limited to the above-mentioned comonomers, and additional comonomers may also be used.

[0019] Linear low-density polyethylene is polyethylene obtained by polymerizing ethylene and a small amount of α-olefins using a polymerization method with a multi-site catalyst such as a Ziegler-Natta catalyst or a single-site catalyst such as a metallocene catalyst. High-pressure low-density polyethylene is polyethylene obtained by polymerizing ethylene using a high-pressure polymerization method.

[0020] In this specification, examples of linear low-density polyethylene (LLDPE) include ethylene-α-olefin copolymers. Examples of α-olefins include the above-mentioned α-olefins having from 3 to 20 carbon atoms, with α-olefins having from 3 to 8 carbon atoms being preferred, and α-olefins having from 4 to 8 carbon atoms being more preferred. Examples of linear low-density polyethylene include ethylene-1-butene copolymers (C4-LLDPE) in which the comonomer is at least 1-butene, ethylene-1-hexene copolymers (C6-LLDPE) in which the comonomer is at least 1-hexene, and ethylene-1-octene copolymers (C8-LLDPE) in which the comonomer is at least 1-octene. In these copolymers, the comonomers are not limited to the above-mentioned comonomers, and additional comonomers may also be used.

[0021] Polyethylenes with different molecular weight distributions, molecular weights, densities, or branches, which will be described later, can be obtained by appropriately selecting the polymerization method and polymerization conditions, etc. For example, it is preferable to use a multi-site catalyst such as a Ziegler-Natta catalyst or a single-site catalyst such as a metallocene catalyst as the polymerization catalyst and carry out polymerization in one stage or in two or more stages by any of gas phase polymerization, slurry polymerization, solution polymerization, and high-pressure ionic polymerization.

[0022] From the viewpoint of film-forming and processability, the melt flow rate (MFR) of the polyethylene herein is preferably 0.01 g / 10 min or more or 0.05 g / 10 min or more, more preferably 0.1 g / 10 min or more, even more preferably 0.2 g / 10 min or more, even more preferably 0.3 g / 10 min or more, particularly preferably 0.5 g / 10 min or more, and preferably 30 g / 10 min or less, more preferably 20 g / 10 min or less, even more preferably 10 g / 10 min or less, even more preferably 5 g / 10 min or less, particularly preferably 3 g / 10 min or less, for example, 0.01 g / 10 min or more and 30 g / 10 min or less. The MFR of polyethylene herein is measured by Method A in accordance with JIS K7210-1:2014 at a temperature of 190°C under a load of 2.16 kg.

[0023] In this specification, the melting point of the high-density polyethylene and the medium-density polyethylene is, from the viewpoints of strength, heat resistance, and the like, preferably 110°C or higher, more preferably 115°C or higher, even more preferably 120°C or higher, and particularly preferably 125°C or higher, and is preferably 140°C or lower, and may be, for example, 135°C or lower, for example, 110°C or higher and 140°C or lower. In this specification, the melting point of the linear low-density polyethylene and the high-pressure low-density polyethylene is preferably 70°C or higher, more preferably 80°C or higher, even more preferably 85°C or higher, and is preferably lower than 130°C, more preferably lower than 125°C, even more preferably lower than 120°C, for example, 70°C or higher and lower than 130°C. In this specification, the melting points of various materials are melting peak temperatures obtained by differential scanning calorimetry (DSC) in accordance with JIS K7121:2012 (3.(2) (however, using test specimens conditioned at a cooling rate of 10°C / min)).

[0024] In this specification, each of the components (for example, polyolefins such as polyethylene, α-olefins, and additives) appearing in the following description may be used alone or in combination of two or more.

[0025] In this specification, "film" and "sheet" may be referred to, but "film" and "sheet" are not distinguished from each other solely on the basis of the difference in name. In this specification, "multilayer" means two or more layers.

[0026] In this specification, a stretched film that has a small dimensional change rate in the stretching direction when placed in a high-temperature environment (preferably small thermal shrinkage) is also referred to as "excellent thermal shape stability."

[0027] In this specification, the term "main component" in a layer refers to a component that accounts for 50% by mass or more in the layer, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

[0028] [Multilayer films and oriented films] The multilayer film of the present disclosure comprises: a first layer containing high-density polyethylene (A) as a main component; a second layer containing polyethylene as a main component; At least the following is provided. The stretched film of the present disclosure comprises: a first layer containing high-density polyethylene (A) as a main component; a second layer containing polyethylene as a main component; In the following description, unless otherwise specified, "the film" refers to the multilayer film having at least the first layer and the second layer before the stretching treatment. The high-density polyethylene (A) will be described in detail later.

[0029] The film has a first major surface and a second major surface opposite the first major surface. In one embodiment, the first layer of the film constitutes a first main surface of the film, and the second layer of the film constitutes a second main surface of the film, i.e., in one embodiment, the first layer of the film is a first surface resin layer that constitutes one main surface of the film, and the second layer of the film is a second surface resin layer that constitutes the other main surface of the film.

[0030] The film preferably further comprises an intermediate layer (hereinafter also referred to as a "PE intermediate layer") between the first and second layers, the intermediate layer containing polyethylene as a main component. The provision of the PE intermediate layer makes it possible to adjust the balance between the stretchability of the film and the heat resistance and puncture resistance of the stretched film obtained by stretching the film, for example. The film may include a first PE intermediate layer, a second PE intermediate layer, and a third PE intermediate layer between the first and second layers, in this order in the stacking direction. That is, the film may include a first layer, a first PE intermediate layer, a second PE intermediate layer, a third PE intermediate layer, and a second layer, in this order in the stacking direction.

[0031] The stretched film of the present disclosure comprises at least a first layer and a second layer. The stretched film has a first major surface and a second major surface opposite to the first major surface. In one embodiment, the first layer of the stretched film constitutes a first main surface of the film, and the second layer of the stretched film constitutes a second main surface of the film, i.e., in one embodiment, the first layer of the stretched film is a first surface resin layer that constitutes one main surface of the film, and the second layer of the stretched film is a second surface resin layer that constitutes the other main surface of the film.

[0032] The stretched film preferably further comprises an intermediate layer (PE intermediate layer) containing polyethylene as a main component between the first layer and the second layer, which allows adjustment of the balance between the heat resistance, puncture resistance, etc. of the stretched film, for example. The stretched film may include a first PE intermediate layer, a second PE intermediate layer, and a third PE intermediate layer in this order in the stacking direction between the first layer and the second layer, i.e., the stretched film may include a first layer, a first PE intermediate layer, a second PE intermediate layer, a third PE intermediate layer, and a second layer in this order in the stacking direction.

[0033] The stretched film of the present disclosure is obtained by stretching the above-mentioned film. The laminate structure of the stretched film and the above-mentioned film is the same except for the presence or absence of stretching. Therefore, the first main surface of the stretched film corresponds to the first main surface of the above-mentioned film. The second main surface of the stretched film corresponds to the second main surface of the above-mentioned film. The first layer of the stretched film corresponds to the first layer of the above-mentioned film. The second layer of the stretched film corresponds to the second layer of the above-mentioned film. The PE interlayer of the stretched film corresponds to the PE interlayer of the above-mentioned film. The first, second, or third PE interlayer of the stretched film corresponds to the first, second, or third PE interlayer of the above-mentioned film, respectively. In the following description, unless otherwise specified, corresponding layers in both the above-mentioned film and its stretched film will be indicated using the same name.

[0034] A stretched film is a film obtained by stretching the above-mentioned film. Stretching can improve, for example, the strength, rigidity, heat resistance, transparency, and printability of the film. The stretching may be uniaxial stretching or biaxial stretching. The biaxial stretching may be sequential biaxial stretching or simultaneous biaxial stretching. The stretching method is not particularly limited, but examples include a method in which a film is uniaxially stretched by varying the rotation speed of two or more rolls, a method in which a film is biaxially stretched by a tenter method, and a method in which a film is biaxially stretched by a tubular method.

[0035] The stretching direction of the film is not particularly limited, but examples include the machine direction (flow direction, MD) of the film and the width direction (direction perpendicular to the MD, TD) of the film. When the film is stretched in the machine direction (flow direction, MD), the stretching ratio is preferably 2 or more, more preferably 3 or more, from the viewpoint of improving strength, etc.; and preferably 10 or less, more preferably 7 or less, even more preferably 5 or less, from the viewpoint of excellent thermal shape stability, for example, 2 to 10 or 3 to 5. When the film is stretched in the width direction (direction perpendicular to the MD, TD), the stretching ratio is preferably 2 or more, more preferably 3 or more, from the viewpoint of improving strength, etc.; and preferably 10 or less, more preferably 7 or less, even more preferably 5 or less, from the viewpoint of excellent thermal shape stability, for example, 2 to 10 or 3 to 5. The stretched film is preferably a film obtained by uniaxially stretching the above film, i.e., a uniaxially stretched film, specifically a film obtained by uniaxially stretching the above film in the MD.

[0036] The stretched film can be produced, for example, by forming the materials constituting each layer into a film, and then stretching the film. Examples of film-forming methods include inflation molding and T-die casting, with inflation molding being preferred. When producing the film by inflation molding, the MFR of the polyethylene is preferably 0.01 g / 10 min or more and 15 g / 10 min or less, more preferably 0.05 g / 10 min or more and 10 g / 10 min or less, from the viewpoints of film-forming ability and processability.

[0037] The stretching temperature in the stretching treatment is not particularly limited. The stretched film may be subjected to a heat setting treatment if necessary. The annealing temperature in the heat setting treatment is not particularly limited.

[0038] In one embodiment, the film is a coextruded film. In one embodiment, the stretched film is obtained by stretching a co-extruded film. In one embodiment, the stretched film is obtained by co-extrusion of the material constituting the first layer, the material constituting the PE intermediate layer, and the material constituting the second layer in this order in the lamination direction, and then stretching the resulting co-extruded film. The co-extruded film can be obtained, for example, by inflation molding or T-die casting.

[0039] The thickness of the multilayer film is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, particularly preferably 40 μm or more, and is preferably 1000 μm or less, more preferably 500 μm or less, even more preferably 250 μm or less, particularly preferably 150 μm or less, for example, 10 μm or more and 1000 μm or less.

[0040] The thickness of the stretched film is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more, particularly preferably 20 μm or more, and preferably 200 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less, particularly preferably 30 μm or less, for example, 5 μm or more and 200 μm or less. Stretched films having a thickness equal to or greater than the lower limit exhibit, for example, excellent strength, rigidity, and heat resistance. Stretched films having a thickness equal to or less than the upper limit exhibit, for example, excellent processability. In this specification, the thickness of the film and each layer is the average value of thicknesses measured at 10 points in a scanning electron microscope (SEM) image obtained by observing a cross section of the film in the lamination direction (thickness direction) perpendicular to the main surface of the film with an SEM.

[0041] The polyethylene content in the film and stretched film is preferably more than 50% by mass, more preferably at least 60% by mass, even more preferably at least 70% by mass, still more preferably at least 80% by mass, and particularly preferably at least 85%, at least 90%, or at least 95% by mass. Such stretched films and laminates including the stretched films have excellent recyclability, for example.

[0042] At least one selected from the above-mentioned film and stretched film may be subjected to a surface treatment. Such a film and stretched film have, for example, excellent adhesion to other layers. Examples of surface treatment methods include physical treatment and chemical treatment. Examples of physical treatments include corona treatment, ozone treatment, low-temperature plasma treatment using oxygen gas and / or nitrogen gas, and glow discharge treatment. Examples of chemical treatments include oxidation treatment using chemicals.

[0043] <First layer> The first layer of the film contains high-density polyethylene (A) as a main component, and therefore the stretched film of the film has excellent heat resistance, such as heat seal resistance.

[0044] The high-density polyethylene (A) has a peak in a differential molecular weight distribution curve (horizontal axis: common logarithm (LogM) of molecular weight (M); vertical axis: dW / d(LogM) obtained by differentiating cumulative concentration fraction (W) with common logarithm of molecular weight (M)) obtained by high-temperature gel permeation chromatography (GPC) measurement, in which the maximum value of dW / d(LogM) is 0.80 or more and the half-width is less than 1.1. That is, the peak has a maximum value of dW / d(LogM) of 0.80 or more and a half-width of less than 1.1. Polydispersity (Mw / Mn) is sometimes used as an index of the spread of the differential molecular weight distribution. Here, Mn is the number-average molecular weight, and Mw is the weight-average molecular weight. The combination of dW / d(LogM) and half-width is preferable to polydispersity, as it allows for a more appropriate evaluation of the shape (sharp or broad) of the differential molecular weight distribution.

[0045] W is the cumulative concentration fraction (cumulative mass fraction) of the molecular weight of the polymer to be measured, such as high-density polyethylene. Log is the common logarithm. M is the molecular weight of the polymer to be measured, such as high-density polyethylene. The half-width refers to the width of the peak when the value of dW / d(LogM) is half the height of the peak appearing in the differential molecular weight distribution curve (full width at half maximum; LogM2-LogM1) (see Figure 7A).

[0046] When two or more overlapping peaks exist in a differential molecular weight distribution curve, the half-width is calculated as follows: The peak with the smallest molecular weight at its peak top position is designated P1, and the height of P1 (maximum value of dW / d(LogM)) is designated H1. The peak with the largest molecular weight at its peak top position is designated P2, and the height of P2 (maximum value of dW / d(LogM)) is designated H2. The molecular weight value satisfying dW / d(LogM) = H1 / 2 on the differential molecular weight distribution curve on the lower molecular weight side than the peak top position of P1 is designated M1. The molecular weight value satisfying dW / d(LogM) = H2 / 2 on the differential molecular weight distribution curve on the higher molecular weight side than the peak top position of P2 is designated M2. The difference between LogM2 and LogM1 (LogM2 - LogM1) is the "half-width" (see Figure 7B). However, peaks whose height from the baseline (in the case of a shoulder peak, the height of the shoulder from the baseline) is 0.10 or less are ignored.

[0047] The differential molecular weight distribution curve for a polymer can be obtained as follows: First, an integrated molecular weight distribution curve is obtained by high-temperature GPC measurement. The integrated molecular weight distribution curve is obtained by plotting data with the common logarithm (LogM) of the polymer molecular weight on the horizontal axis and the cumulative polymer concentration fraction on the vertical axis. The vertical axis of the integrated molecular weight distribution curve shows the mass fraction of polymers below a certain molecular weight in the entire polymer. Next, the differential value of the above curve (the slope of the integrated molecular weight distribution curve) for each molecular weight is determined. The horizontal axis represents the common logarithm (LogM) of the molecular weight (M) and the vertical axis represents the above differential value (the value obtained by differentiating the integrated concentration fraction by the common logarithm of the molecular weight, dW / d(LogM)). In this way, the differential molecular weight distribution curve is obtained. Details of the conditions for high-temperature GPC measurement are described in the Examples section.

[0048] The present inventors have found that the shape of the peak in the differential molecular weight distribution curve of a high-density polyethylene is related to the heat resistance (specifically, heat distortion resistance) of a stretched film. A high-density polyethylene (A) having a peak with a maximum dW / d(LogM) value of 0.80 or more and a half-width of less than 1.1 can be said to have a sharp molecular weight distribution (narrow molecular weight distribution). Stretched films having a first layer containing high-density polyethylene (A) tend to be less susceptible to thermal deformation (e.g., thermal shrinkage) in the stretching direction, despite having been stretched. Therefore, the stretched film of the present disclosure can effectively suppress thermal deformation (e.g., thermal shrinkage) during heat sealing, for example. Although the reason for this is unclear, the inventors speculate as follows: Polyethylene with a broad molecular weight distribution contains a large amount of polyethylene with a relatively low molecular weight. Therefore, when the film is heated, molecular motion begins with the low molecular weight polyethylene, making the film prone to thermal deformation (e.g., thermal shrinkage). On the other hand, polyethylene with a sharp molecular weight distribution contains spherulites of similar size, and these spherulites contain many lamellar crystals of similar size. These lamellar crystals are neatly aligned by stretching. The increase in oriented crystals by stretching suppresses molecular motion of the polyethylene. These oriented crystals contribute to suppressing thermal deformation, such as thermal shrinkage, of the film. Note that the above explanation is merely speculation and does not in any way limit the stretched film of the present disclosure.

[0049] Stretched films having a first surface resin layer containing high-density polyethylene (A) as a main component tend to be able to suppress the generation of white powder on the film surface. This is presumably because high-density polyethylene (A) has a narrow molecular weight distribution, and therefore contains a relatively small proportion of low-molecular-weight polyethylene. Furthermore, stretched films having a first surface resin layer containing high-density polyethylene (A) as a main component tend to have low external haze and excellent transparency.

[0050] The maximum value of dW / d(LogM) at the peak of the high-density polyethylene (A) is 0.80 or more, preferably 0.85 or more, more preferably 0.90 or more, particularly preferably 0.95 or more, and preferably 1.30 or less, more preferably 1.25 or less, even more preferably 1.20 or less, particularly preferably 1.10 or less. The maximum value is, for example, 0.80 or more and 1.30 or less.

[0051] The half width of the peak of the high-density polyethylene (A) is less than 1.1, preferably 1.08 or less, more preferably 1.06 or less, particularly preferably 1.04 or less, and is preferably 0.66 or more, more preferably 0.68 or more, even more preferably 0.70 or more, particularly preferably 0.72 or more, 0.74 or more, or 0.76 or more. The half width is, for example, 0.66 or more and less than 1.1.

[0052] The first layer may contain two or more types of high-density polyethylene (A). In this case, it is preferable that the differential molecular weight distribution curve of the mixture of two or more types of high-density polyethylene (A) has a peak that satisfies the above-mentioned requirements for the maximum value and half-width of dW / d(LogM).

[0053] The high-density polyethylene (A) may have a unimodal or multimodal, such as bimodal, differential molecular weight distribution curve, and preferably has a unimodal differential molecular weight distribution curve having one peak at which the maximum value of dW / d(LogM) is 0.80 or more.

[0054] The weight average molecular weight (Mw) of the high density polyethylene (A) is preferably 0.50×10 5 or more, more preferably 1.00 x 10 5 or more preferably 1.50 × 10 5 or more, preferably 6.00 × 10 5 or less, preferably 5.00 x 10 5 or less, more preferably 4.00 × 10 5 Below, particularly preferably 3.00 × 10 5 The Mw is, for example, 0.50 × 10 5 Over 6.00 x 10 5 In this specification, the above Mw is obtained by high-temperature GPC measurement, and the detailed conditions are described in the Examples section.

[0055] The density of the high density polyethylene (A) is preferably 0.945 g / cm 3 More preferably, 0.948 g / cm 3 or more, preferably 0.970 g / cm 3 or less, more preferably 0.965 g / cm 3 or less, more preferably 0.960 g / cm 3 The density is, for example, 0.945 g / cm 3 Super 0.970g / cm 3 The high-density polyethylene (A) having such a density contributes to improving the heat resistance of the stretched film, for example.

[0056] The melting point of the high-density polyethylene (A) is preferably within the range described above for the melting point of high-density polyethylene, and particularly preferably not less than 130° C. A high-density polyethylene (A) having such a melting point contributes to improving the heat resistance of a stretched film, for example.

[0057] From the viewpoint of heat resistance, the content of the high-density polyethylene (A) in the first layer is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 98% by mass or more.

[0058] The first layer may contain a polyethylene other than the high-density polyethylene (A). The first layer may contain a resin material other than polyethylene. Examples of the resin material other than polyethylene include polyolefins other than polyethylene, polyesters, polyamides, (meth)acrylic resins, vinyl resins, cellulose resins, and ionomer resins.

[0059] The first layer may contain additives such as crosslinkers, antioxidants, UV absorbers, light stabilizers, antiblocking agents, slip agents, fillers, reinforcing agents, antistatic agents, compatibilizers, pigments, and modifying resins.

[0060] The thickness of the first layer in the stretched film is preferably 0.5 μm or more, more preferably 1 μm or more, even more preferably 2 μm or more, still more preferably 3 μm or more, particularly preferably 4 μm or more, and is preferably 25 μm or less, more preferably 20 μm or less, even more preferably 15 μm or less, still more preferably 12 μm or less, particularly preferably 9 μm or less, for example, 0.5 μm or more and 25 μm or less.

[0061] From the viewpoint of heat resistance, the thickness of the first layer in the stretched film may be, for example, 5% to 90% or 5% to 85% or 5% to 80% of the thickness of the stretched film, preferably 5% to 75% or 8% to 72% or 8% to 70% or 10% to 50%. Similarly, from the viewpoint of heat resistance, the thickness of the first layer in the film may be, for example, 5% to 90% or 5% to 85% or 5% to 80% of the thickness of the stretched film, preferably 5% to 75% or 8% to 72% or 8% to 70% or 10% to 50%.

[0062] <Second layer> The second layer of the film contains polyethylene as a major component. Examples of polyethylene contained in the second layer include high-density polyethylene, medium-density polyethylene, linear low-density polyethylene, high-pressure low-density polyethylene, ethylene-vinyl acetate copolymer, and ethylene-(meth)acrylic acid ester copolymer. Among these, at least one selected from high-density polyethylene, medium-density polyethylene, linear low-density polyethylene, and high-pressure low-density polyethylene is preferred.

[0063] The polyethylene contained in the second layer may be the same as or different from the high-density polyethylene (A) contained in the first layer. The compositions of the first and second layers may be the same as or different from each other. The thicknesses of the first and second layers may be the same as or different from each other.

[0064] The weight average molecular weight (Mw) of the polyethylene contained in the second layer is preferably 0.50×10 5 or more, more preferably 1.00 x 10 5 or more preferably 1.50 × 10 5 or more, preferably 6.00 × 10 5 or less, preferably 5.00 x 10 5 or less, more preferably 4.00 × 10 5 Particularly preferably 3.50 × 10 5 or less or 3.00 x 10 5 The Mw is, for example, 0.50 × 10 5 Over 6.00 x 10 5 The following is the result.

[0065] The content of polyethylene in the second layer is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 98% by mass or more.

[0066] The second layer may be, for example, a layer containing high-density polyethylene (B) as a main component; a layer containing, as a main component, at least one polyethylene selected from linear low-density polyethylene and high-pressure low-density polyethylene (hereinafter also referred to as "low-density polyethylene (C1)"); and a layer containing medium density polyethylene as a main component; Examples include:

[0067] The second layer may be a layer containing high-density polyethylene (B) as a main component, which is preferred from the viewpoint of suppressing curling of the stretched film. The high-density polyethylene (B) is a high-density polyethylene having a broader molecular weight distribution than the high-density polyethylene (A) in the differential molecular weight distribution curve obtained by high-temperature GPC measurement. In other words, the high-density polyethylene (A) is a high-density polyethylene having a molecular weight distribution with a sharper shape (narrower molecular weight distribution) than the high-density polyethylene (B) in the differential molecular weight distribution curve obtained by high-temperature GPC measurement. A polyethylene having a peak with a larger maximum value of dW / d(LogM) and a smaller half-width than the target polyethylene in the differential molecular weight distribution curve obtained by high-temperature GPC measurement can be said to have a molecular weight distribution with a sharper shape (narrower molecular weight distribution) than the target polyethylene.

[0068] The high-density polyethylene (B) preferably has a peak in a differential molecular weight distribution curve obtained by high-temperature GPC measurement, in which the maximum value of dW / d(LogM) is less than 0.80 and the half-value width is 1.1 or more. That is, the peak preferably has a maximum value of dW / d(LogM) of less than 0.80 and a half-value width of 1.1 or more.

[0069] High-density polyethylene (B) having a peak with a maximum dW / d(LogM) value of less than 0.80 and a half-width of 1.1 or more can be said to have a broad molecular weight distribution (wide molecular weight distribution). The above film in which the second layer contains high-density polyethylene (B) not only can suppress thermal deformation such as heat shrinkage after stretching, but also has excellent stretchability. This is presumably because polyethylene with a wide molecular weight distribution has better stretchability than polyethylene with a narrow molecular weight distribution.

[0070] The maximum value of dW / d(LogM) at the peak of the high-density polyethylene (B) is, for example, less than 0.80, preferably 0.75 or less, more preferably 0.70 or less, particularly preferably 0.65 or less, and preferably 0.20 or more, more preferably 0.25 or more, even more preferably 0.30 or more, particularly preferably 0.35 or more. The maximum value is, for example, 0.20 or more and less than 0.80.

[0071] The half width of the peak of the high-density polyethylene (B) is, for example, 1.1 or more, preferably 1.2 or more, more preferably 1.3 or more, even more preferably 1.4 or more, particularly preferably 1.5 or more, and is preferably 3.0 or less, more preferably 2.9 or less, even more preferably 2.8 or less, particularly preferably 2.7 or less, 2.6 or less, 2.55 or less, 2.50 or less, or 2.45 or less. The half width is, for example, 1.1 or more and 3.0 or less.

[0072] The second layer may contain two or more types of high-density polyethylene (B). In this case, it is preferable that the differential molecular weight distribution curve of the mixture of two or more types of high-density polyethylene (B) has a peak that satisfies the above-mentioned requirements for the maximum value and half-width of dW / d(LogM).

[0073] The high-density polyethylene (B) may have a unimodal differential molecular weight distribution curve, or may have a multimodal, such as bimodal, differential molecular weight distribution curve.

[0074] The weight average molecular weight (Mw) of the high-density polyethylene (B) is preferably 0.50×10 5 or more, more preferably 1.00 x 10 5 or more preferably 1.50 × 10 5 or more, preferably 6.00 × 10 5 or less, preferably 5.00 x 10 5 or less, more preferably 4.00 × 10 5 Particularly preferably 3.50 × 10 5 The Mw is, for example, 0.50 × 10 5 Over 6.00 x 10 5 The following is the result.

[0075] The density of the high density polyethylene (B) is preferably 0.945 g / cm 3 More preferably, 0.950 g / cm 3 More preferably, 0.953 g / cm 3 or more, preferably 0.970 g / cm 3 The density is, for example, 0.945 g / cm 3 Super 0.970g / cm 3 The high-density polyethylene (B) having such a density contributes to improving the heat resistance of the stretched film, for example.

[0076] The melting point of the high-density polyethylene (B) is preferably within the range described above for the melting point of high-density polyethylene, and particularly preferably not less than 130° C. A high-density polyethylene (B) having such a melting point contributes to improving the heat resistance of a stretched film, for example.

[0077] The second layer may be a layer containing low-density polyethylene (C1) as a main component. The film in which the second layer contains low-density polyethylene (C1) can not only suppress thermal deformation such as thermal shrinkage after stretching treatment, but also has excellent stretchability itself and excellent puncture resistance after stretching treatment. This is presumably due to the fact that linear low-density polyethylene and high-pressure process low-density polyethylene usually contain more amorphous components than high-density polyethylene, and thus are more excellent in stretchability and more excellent in puncture resistance. Low-density polyethylene (C1) is preferably linear low-density polyethylene.

[0078] The second layer may be a layer containing medium-density polyethylene as a main component.

[0079] The second layer may contain the above-mentioned resin materials other than polyethylene. The second layer may contain the above-mentioned additives.

[0080] The thickness of the second layer in the stretched film is preferably 0.5 μm or more, more preferably 1 μm or more, still more preferably 2 μm or more, even more preferably 3 μm or more, particularly preferably 4 μm or more, and preferably 25 μm or less, more preferably 20 μm or less, still more preferably 15 μm or less, even more preferably 12 μm or less, particularly preferably 9 μm or less, and is, for example, 0.5 μm or more and 25 μm or less.

[0081] The ratio of the thickness of the second layer to the thickness of the first layer is preferably 0.6 or more and 1.4 or less, more preferably 0.7 or more and 1.3 or less, still more preferably 0.8 or more and 1.2 or less, particularly preferably 0.9 or more and 1.1 or less, from the viewpoints of film symmetry and suppression of curl generation.

[0082] <PE intermediate layer> The film preferably further comprises a PE intermediate layer between the first and second layers, the PE intermediate layer containing polyethylene as a main component. The film may comprise one PE intermediate layer, or two or more PE intermediate layers. The number of PE intermediate layers may be, for example, one to seven, or three to five. The number of PE intermediate layers may be, for example, one or three.

[0083] When the film has two or more PE intermediate layers, the compositions of the PE intermediate layers may be the same or different, and the thicknesses of the PE intermediate layers may be the same or different. The compositions of the first layer and the PE intermediate layer may be the same or different. The thicknesses of the first layer and the PE intermediate layer may be the same or different. The compositions of the second layer and the PE intermediate layer may be the same or different. The thicknesses of the second layer and the PE intermediate layer may be the same or different. When the film has first to third PE intermediate layers, the compositions of the first to third PE intermediate layers may be the same or different, and the thicknesses of the first to third PE intermediate layers may be the same or different.

[0084] Examples of polyethylene contained in the PE intermediate layer include high-density polyethylene, medium-density polyethylene, linear low-density polyethylene, high-pressure low-density polyethylene, ethylene-vinyl acetate copolymer, and ethylene-(meth)acrylic acid ester copolymer. Among these, at least one selected from high-density polyethylene, medium-density polyethylene, linear low-density polyethylene, and high-pressure low-density polyethylene is preferred.

[0085] The weight average molecular weight (Mw) of the polyethylene contained in the PE intermediate layer is preferably 0.50×10 5 or more, more preferably 1.00 x 10 5 or more preferably 1.50 × 10 5 or more, preferably 6.00 × 10 5 or less, preferably 5.00 x 10 5 or less, more preferably 4.00 × 10 5Particularly preferably 3.50 × 10 5 or less or 3.00 x 10 5 The Mw is, for example, 0.50 × 10 5 Over 6.00 x 10 5 The following is the result.

[0086] The polyethylene content in the PE intermediate layer is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 98% by mass or more.

[0087] The PE intermediate layer can be, for example: an intermediate layer containing high-density polyethylene (A) as a main component; an intermediate layer containing high-density polyethylene (B) as a main component; an intermediate layer containing, as a main component, at least one polyethylene selected from linear low-density polyethylene and high-pressure low-density polyethylene (hereinafter also referred to as "low-density polyethylene (C2)"); and an intermediate layer containing medium density polyethylene as a main component; Examples include:

[0088] The film may have an intermediate layer containing high-density polyethylene (A) as a main component. Details of the high-density polyethylene (A) are as described above. A stretched film of such a film has even better heat resistance, specifically, even better thermal shape stability.

[0089] The film may also include an intermediate layer containing high-density polyethylene (B) as a main component. Details of the high-density polyethylene (B) are as described above. The film, which includes a first layer containing high-density polyethylene (A) as a main component and an intermediate layer containing high-density polyethylene (B) as a main component, not only can suppress thermal deformation such as heat shrinkage after stretching, but also has excellent stretchability. This is presumably because polyethylene with a wide molecular weight distribution has better stretchability than polyethylene with a narrow molecular weight distribution.

[0090] The film may also include an intermediate layer containing low-density polyethylene (C2) as a primary component. The film, which includes a first layer containing high-density polyethylene (A) as a primary component and an intermediate layer containing low-density polyethylene (C2) as a primary component, can not only suppress thermal deformation such as heat shrinkage after stretching, but also has excellent stretchability and puncture resistance after stretching. This is presumably because linear low-density polyethylene and high-pressure low-density polyethylene typically contain a larger amount of amorphous components than high-density polyethylene, resulting in superior stretchability and puncture resistance.

[0091] The low-density polyethylene (C2) is preferably a linear low-density polyethylene.

[0092] Low-density polyethylene (C2) generally contains a larger amount of amorphous components than high-density polyethylene, and therefore tends to have excellent stretchability. Furthermore, low-density polyethylene (C2) is a polymer that is less likely to be oriented by stretching than high-density polyethylene, and therefore tends to have less of an effect on thermal shape stability. Therefore, the molecular weight distribution of the low-density polyethylene (C2) is not particularly limited. However, from the viewpoint of further improving the thermal shape stability of the stretched film, low-density polyethylene (C2) having a narrow molecular weight distribution may be used.

[0093] From the viewpoint of further improving thermal shape stability, the low-density polyethylene (C2) may have a molecular weight distribution in a differential molecular weight distribution curve obtained by high-temperature GPC measurement that is as narrow as that of the high-density polyethylene (A). From the viewpoint of further improving thermal shape stability, the low-density polyethylene (C2) may have a peak in a differential molecular weight distribution curve obtained by high-temperature GPC measurement, in which the maximum value of dW / d(LogM) is 0.80 or more and the half-width is less than 1.1.

[0094] The maximum value of dW / d(LogM) at the peak of the low-density polyethylene (C2) is preferably 0.80 or more, more preferably 0.85 or more, even more preferably 0.90 or more, particularly preferably 0.95 or more, and is preferably 1.30 or less, more preferably 1.25 or less, even more preferably 1.20 or less, particularly preferably 1.10 or less. The maximum value is, for example, 0.80 or more and 1.30 or less.

[0095] The half width of the peak of the low-density polyethylene (C2) is preferably less than 1.1, more preferably 1.08 or less, even more preferably 1.06 or less, and particularly preferably 1.04 or less, and is preferably 0.66 or more, more preferably 0.68 or more, even more preferably 0.70 or more, and particularly preferably 0.72 or more, 0.74 or more, or 0.76 or more. The half width is, for example, 0.66 or more and less than 1.1.

[0096] The intermediate layer may contain two or more low-density polyethylenes (C2). In this case, it is preferable that the differential molecular weight distribution curve of the mixture of two or more low-density polyethylenes (C2) has a peak that satisfies the above-mentioned requirements for the maximum value and half-width of dW / d(LogM).

[0097] The low-density polyethylene (C2) may have a unimodal differential molecular weight distribution curve, or may have a multimodal, such as bimodal, differential molecular weight distribution curve.

[0098] The weight average molecular weight (Mw) of the low-density polyethylene (C2) is preferably 0.50×10 5 or more, more preferably 1.00 x 10 5 or more preferably 1.50 × 10 5 or more, preferably 6.00 × 10 5 or less, preferably 5.00 x 10 5 or less, more preferably 4.00 × 10 5 Below, particularly preferably 3.00 × 10 5 The Mw is, for example, 0.50 × 10 5 Over 6.00 x 10 5The following is the result.

[0099] The density of the low density polyethylene (C2) is preferably 0.920 g / cm 3 or less, more preferably 0.915 g / cm 3 or less, more preferably 0.910 g / cm 3 The low-density polyethylene (C2) having such a density contributes to, for example, improving the stretchability of the film and the impact resistance and puncture resistance of the stretched film. The density of the low-density polyethylene (C2) is preferably 0.860 g / cm or less. 3 More preferably, 0.900 g / cm 3 The density is, for example, 0.860 g / cm 3 More than 0.920g / cm 3 The following is the result.

[0100] The melting point of the low-density polyethylene (C2) is preferably less than 130°C, more preferably less than 125°C, and even more preferably less than 120°C, and in one embodiment, it may be particularly preferably less than 115°C, or less than 110°C, or 105°C or less, or 100°C or less. The melting point of the low-density polyethylene (C2) is preferably 70°C or higher, more preferably 80°C or higher, and even more preferably 85°C or higher. The melting point is, for example, 70°C or higher and less than 130°C.

[0101] The film may include an intermediate layer containing a primary component of medium density polyethylene. The weight average molecular weight (Mw) of the medium density polyethylene is preferably 0.50×10 5 or more, more preferably 1.00 x 10 5 or more preferably 1.50 × 10 5 or more, preferably 6.00 × 10 5 or less, preferably 5.00 x 10 5 or less, more preferably 4.00 × 10 5 Below, particularly preferably 3.00 × 10 5 The Mw is, for example, 0.50 × 10 5 Over 6.00 x 10 5The following is the result.

[0102] The PE intermediate layer may contain the above-mentioned resin materials other than polyethylene. The PE interlayer may contain the additives mentioned above.

[0103] The thickness of the PE intermediate layer in the stretched film is preferably 4 μm or more, more preferably 8 μm or more, even more preferably 10 μm or more, particularly preferably 12 μm or more, and preferably 150 μm or less, more preferably 80 μm or less, even more preferably 40 μm or less, particularly preferably 25 μm or less, for example, 4 μm or more and 150 μm or less. A stretched film having a PE intermediate layer whose thickness is equal to or greater than the lower limit exhibits, for example, excellent strength, rigidity, heat resistance, and recyclability. A stretched film having a PE intermediate layer whose thickness is equal to or less than the upper limit exhibits, for example, excellent processability. When a stretched film has two or more PE intermediate layers, the above "thickness of the PE intermediate layer" means the sum of the thicknesses of the individual PE intermediate layers.

[0104] From the viewpoint of heat resistance, the total thickness of the second layer and the PE intermediate layer in the stretched film may be, for example, 10% to 95% or 15% to 95% or 20% to 95% of the thickness of the stretched film, preferably 25% to 95% or more, more preferably 28% to 92% or more, even more preferably 30% to 92% or less, and particularly preferably 50% to 90%. When the stretched film has two or more PE intermediate layers, the thickness of the PE intermediate layer refers to the sum of the thicknesses of the PE intermediate layers. Similarly, from the viewpoint of heat resistance, the total thickness of the second layer and the PE intermediate layer in the film may be, for example, 10% to 95% or 15% to 95% or 20% to 95% of the thickness of the film, preferably 25% to 95% or more, more preferably 28% to 92% or more, even more preferably 30% to 92% or less, and particularly preferably 50% to 90%.

[0105] In one embodiment, the film comprises at least a first layer; PE intermediate layer, a second layer; and are provided in this order in the stacking direction. In one embodiment, the film is a three-layer coextruded film.

[0106] In one embodiment, the film comprises: a first layer containing high-density polyethylene (A) as a main component; the intermediate layer containing low-density polyethylene (C2) as a main component; a second layer containing high-density polyethylene (B) as a main component; In one embodiment, the film α1 is a three-layer co-extruded film. The film α1 has excellent stretchability because the intermediate layer and the second layer provide stretchability. The stretched film of the film α1 has excellent heat resistance because the first layer suppresses thermal deformation such as thermal shrinkage.

[0107] In one embodiment, the film comprises: a first layer containing high-density polyethylene (A) as a main component; the intermediate layer containing medium-density polyethylene as a main component; a second layer containing high-density polyethylene (B) as a main component; In one embodiment, the film α2 is a three-layer co-extruded film. The film α2 has excellent stretchability because the second layer provides stretchability. The stretched film of the film α2 has excellent heat resistance because the first layer suppresses thermal deformation such as thermal shrinkage.

[0108] In one embodiment, the film comprises: a first layer containing high-density polyethylene (A) as a main component; the intermediate layer containing low-density polyethylene (C2) as a main component; a second layer containing medium density polyethylene as a primary component; In one embodiment, the film α3 is a three-layer co-extruded film. The film α3 has excellent stretchability because the second layer provides stretchability. The stretched film of the film α3 has excellent heat resistance because the first layer suppresses thermal deformation such as thermal shrinkage.

[0109] In one embodiment, the film comprises: a first layer containing high-density polyethylene (A) as a main component; the intermediate layer containing medium-density polyethylene as a main component; a second layer containing medium density polyethylene as a primary component; In one embodiment, the film α4 is a three-layer co-extruded film. The stretched film of the film α4 has excellent heat resistance because the first layer suppresses thermal deformation such as thermal shrinkage.

[0110] In one embodiment, the film comprises: a first layer containing high-density polyethylene (A) as a main component; the intermediate layer containing low-density polyethylene (C2) as a main component; a second layer containing low-density polyethylene (C1) as a main component; In one embodiment, the film α5 is a three-layer co-extruded film. The film α5 has excellent stretchability because the second layer and the intermediate layer provide stretchability. The stretched film of the film α5 has excellent heat resistance because the first layer suppresses thermal deformation such as thermal shrinkage.

[0111] In one embodiment, the film comprises at least a first layer; a first PE intermediate layer; a second PE intermediate layer; a third PE intermediate layer; a second layer; and are provided in this order in the stacking direction. In one embodiment, the film is a five-layer coextruded film.

[0112] As described above, in one embodiment, the content of the main component in each layer of the above films, such as films α1 to α5, is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 98% by mass or more.

[0113] In the above description, when adjacent layers constituting a multilayer film or a stretched film have the same resin composition and are indistinguishable from one another, the adjacent layers may be integrated to form a single layer.

[0114] <Layer structure of stretched film> Hereinafter, several examples of the layer structure of the stretched film of the present disclosure will be given with reference to the drawings. The stretched film 1 shown in Fig. 1 includes a first layer 10 and a second layer 20, in this order in the stacking direction. The stretched film 1 shown in Fig. 2 includes a first layer 10, a PE intermediate layer 30, and a second layer 20, in this order in the stacking direction. The stretched film 1 shown in Fig. 3 includes a first layer 10, a first PE intermediate layer 31, a second PE intermediate layer 32, a third PE intermediate layer 33, and the second layer 20, in this order in the stacking direction.

[0115] <Raman spectroscopy measurement> The stretched film of the present disclosure preferably has a scattering intensity obtained by Raman spectroscopy of the cross section of the film that satisfies the requirements described below. The cross section of the stretched film is a plane parallel to a plane including the thickness direction (stacking direction) perpendicular to the main surface of the film and the stretching direction of the film (e.g., MD direction or TD direction). The method for obtaining the cross section and details of the Raman spectroscopy are described in the Examples section.

[0116] In Raman spectroscopy, the vertical axis represents the scattering intensity of the Raman scattered light (Intensity), and the horizontal axis represents the Raman shift (cm -1) is obtained. In the Raman spectrum, -1 More than 1150cm -1 The maximum scattering intensity of the peak (peak 1) observed in the following region is designated as "I1", especially at 1130 cm -1 The maximum scattering intensity of the peak near 1130 " Also, 1050cm -1 More than 1100cm -1 The maximum scattering intensity of the peak (peak 2) observed in the region below 1063 cm is indicated as "I2", and -1 The maximum scattering intensity of the peak near 1063 The maximum scattering intensity (peak intensity) means the height of each peak from the baseline.

[0117] In one embodiment, Peak 1 is attributed to CC symmetric stretching vibration in the trans chain of the polyethylene crystalline phase. The scattering intensity of Peak 1 is likely to change depending on the molecular orientation state of the polyethylene. When the stretching direction and the vibration direction of the excitation light (polarized laser) are parallel, the scattering intensity of Peak 1 becomes strong. A strong scattering intensity of Peak 1 indicates that the orientation of the polyethylene in the stretching direction has progressed.

[0118] In one embodiment, Peak 2 is attributed to the CC antisymmetric stretching vibration of the trans chain of the polyethylene crystalline phase. The scattering intensity of Peak 2 does not show a significant change depending on the molecular orientation state of the polyethylene, and therefore is not significantly affected by the stretching treatment.

[0119] Thus, Peak 1 and Peak 2 differ in the influence of the molecular orientation state. By comparing the scattering intensity I1 and the scattering intensity I2, the molecular orientation of polyethylene due to the stretching treatment can be evaluated. In other words, the molecular orientation of polyethylene can be evaluated using the value of I1 / I2. Polyethylene in a state of high molecular orientation tends to have an I1 / I2 of 1.1 or more. Polyethylene in a state of low molecular orientation tends to have an I1 / I2 of less than 1.1. In one embodiment, I1 / I2 is 1130 / I 1063 is.

[0120] Examples of polyethylenes that are likely to become highly oriented by stretching include high-density polyethylene and medium-density polyethylene. In one embodiment, a layer containing high-density polyethylene and / or medium-density polyethylene as a main component has an I1 / I2 ratio of 1.1 or greater, preferably 1.2 or greater and 4.0 or less, more preferably 1.4 or greater and 3.0 or less, and even more preferably 1.5 or greater and 2.0 or less, after stretching. In such a layer, oriented crystals are aligned, and it can be said that molecular motion is less likely to occur after stretching compared to before stretching.

[0121] Examples of polyethylenes whose orientation changes little upon stretching include linear low-density polyethylene and high-pressure low-density polyethylene. In one embodiment, a layer containing linear low-density polyethylene and / or high-pressure low-density polyethylene as a primary component has an I1 / I2 ratio of less than 1.1 after stretching, preferably 0.5 or more and less than 1.1, more preferably 0.6 or more and less than 1.1, and even more preferably 0.7 or more and less than 1.1. This indicates that despite the polyethylene being stretched, the orientation of the polyethylene is low or not oriented at all. In the case of a film in which the first layer contains high-density polyethylene (A) as a primary component and the second layer contains high-density polyethylene and / or medium-density polyethylene as a primary component, the stress in the intermediate layer containing linear low-density polyethylene and / or high-pressure low-density polyethylene as a primary component is thought to be small, and it is presumed that this layer does not significantly contribute to shrinkage.

[0122] The I1 / I2 ratios obtained by Raman spectroscopy of the cross sections of the first layer, the layer corresponding to the intermediate layer containing high-density polyethylene (A) as a main component, the layer corresponding to the (intermediate) layer containing high-density polyethylene (B) as a main component, and the layer corresponding to the (intermediate) layer containing medium-density polyethylene as a main component of the stretched film are each independently preferably 1.1 or more, more preferably 1.2 or more and 4.0 or less, even more preferably 1.4 or more and 3.0 or less, and particularly preferably 1.5 or more and 2.0 or less.

[0123] The I1 / I2 ratio obtained by Raman spectroscopy of the cross section of the layer of the stretched film corresponding to the (intermediate) layer containing low-density polyethylene (C1) or (C2) as the main component is preferably less than 1.1, more preferably 0.5 or more and less than 1.1, even more preferably 0.6 or more and less than 1.1, and particularly preferably 0.7 or more and less than 1.1.

[0124] In the case of a uniaxially stretched film stretched in the MD direction, the cross section is a cross section parallel to the MD direction. In the case of a uniaxially stretched film stretched in the TD direction, the cross section is a cross section parallel to the TD direction. In the case of a biaxially stretched film stretched in both the MD and TD directions, the cross sections are a cross section parallel to the MD direction and a cross section parallel to the TD direction, and it is preferable that the stretched film satisfies the above requirements for the scattering intensity ratio for each cross section.

[0125] <Dimensional change rate> In the stretched film of the present disclosure, the dimensional change rate in the stretching direction, measured after leaving it to stand in an environment of 120°C for 5 minutes, is preferably −7% or more and 0% or less, more preferably −6% or more and 0% or less, even more preferably −5% or more and 0% or less, still more preferably −4% or more and 0% or less, and particularly preferably −3% or more and 0% or less. When the stretched film of the present disclosure is a uniaxially stretched film, the dimensional change rate in the stretching direction (e.g., MD direction or TD direction) is preferably −7% or more and 0% or less, more preferably −6% or more and 0% or less, even more preferably −5% or more and 0% or less, still more preferably −4% or more and 0% or less, and particularly preferably −3% or more and 0% or less. When the stretched film of the present disclosure is a biaxially stretched film, the dimensional change rate in the stretching direction (e.g., MD direction and TD direction) is preferably −7% or more and 0% or less, more preferably −6% or more and 0% or less, even more preferably −5% or more and 0% or less, still more preferably −4% or more and 0% or less, and particularly preferably −3% or more and 0% or less. The definition of the dimensional change rate and the conditions for measuring it are described in the Examples section.

[0126] <Puncture strength> The puncture strength of the stretched film of the present disclosure is not particularly limited, but is preferably 2.5 N / mmφ or more, more preferably 3.0 N / mmφ or more, even more preferably 3.5 N / mmφ or more, and particularly preferably 4.0 N / mmφ or more. The puncture strength of the stretched film of the present disclosure may be, for example, 10.0 N / mmφ or less, 8.0 N / mmφ or less, or even 6.0 N / mmφ or less. The puncture strength is measured from the first layer side in accordance with JIS Z1707:2019, and details of the measurement conditions are described in the Examples section. The puncture strength can be increased, for example, by using a high-density polyethylene with a high melt tension or a medium-density polyethylene with a high melt tension, or by using the low-density polyethylene (C1) or (C2) described above.

[0127] <Half width> In one embodiment, the entire polyethylene contained in the multilayer film or stretched film of the present disclosure preferably has a peak with a half-width of less than 1.3 in a differential molecular weight distribution curve obtained by high-temperature GPC measurement. The half-width may be, for example, less than 1.1. The half-width is preferably 0.75 or greater. The differential molecular weight distribution curve is measured for the entire polyethylene contained in the multilayer film or stretched film.

[0128] [Printed film] The printed film of the present disclosure comprises the above-described multilayer film or stretched film and a printed layer, specifically, the above-described multilayer film or stretched film and a printed layer provided on at least one main surface selected from the first and second main surfaces of the multilayer film or stretched film. From the viewpoints of suppressing thermal deformation of the stretched film, printability, etc., the printed layer is preferably provided on the first surface resin layer.

[0129] The print layer includes an image. Examples of the image include letters, figures, patterns, symbols, and combinations thereof. The image may include text information such as the product name, the name of the item in the packaging container, the manufacturer, and the names of ingredients. The image may be a single, solid color (a so-called solid image).

[0130] The printed layer can be formed, for example, using an ink composition. Methods for forming the printed layer include, for example, gravure printing, offset printing, flexographic printing, screen printing, letterpress printing, and transfer printing. From the viewpoint of reducing the environmental load, the printed layer may be formed by flexographic printing. From the viewpoint of reducing the environmental load, the printed layer may be formed using ink derived from biomass.

[0131] The thickness of the printed layer is preferably 0.1 μm or more, more preferably 0.2 μm or more, even more preferably 0.3 μm or more, and preferably 10 μm or less, more preferably 5 μm or less, even more preferably 3 μm or less, for example, 0.1 μm or more and 10 μm or less.

[0132] [Barrier film] The barrier film of the present disclosure comprises the above-described multilayer film or stretched film and a vapor-deposited film, specifically, the above-described multilayer film or stretched film and a vapor-deposited film provided on at least one main surface selected from the first and second main surfaces of the multilayer film or stretched film. The vapor-deposited film is preferably provided on the first surface resin layer from the viewpoint of suppressing thermal deformation of the stretched film or cracking of the vapor-deposited film. The barrier film has, for example, excellent gas barrier properties, specifically, oxygen barrier properties and water vapor barrier properties, and, when the vapor-deposited film is a metal vapor-deposited film, excellent brightness. Packaging containers made using such a barrier film have excellent gas barrier properties.

[0133] The barrier film may be subjected to the above-mentioned surface treatment, and such a barrier film has, for example, excellent adhesion to other layers.

[0134] <Vapor deposition film> The vapor-deposited film may be composed of, for example, a metal and / or an inorganic oxide. The vapor-deposited film may be a metal vapor-deposited film composed of one or more metals, or an inorganic oxide vapor-deposited film composed of one or more inorganic oxides. The inorganic oxide vapor-deposited film may be a transparent vapor-deposited film. Examples of metals include aluminum, chromium, tin, nickel, copper, silver, gold, and platinum. Examples of inorganic oxides include aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, zirconium oxide, titanium oxide, boron oxide, hafnium oxide, barium oxide, and silicon carbide oxide (carbon-containing silicon oxide). Among vapor-deposited films, aluminum vapor-deposited films, aluminum oxide (alumina) vapor-deposited films, silicon oxide (silica) vapor-deposited films, and silicon carbide vapor-deposited films are preferred.

[0135] The barrier film may be a multilayer film or a stretched film having two or more vapor-deposited layers thereon.

[0136] From the viewpoint of gas barrier properties, the thickness of the vapor-deposited film is preferably 1 nm or more, more preferably 5 nm or more, and even more preferably 10 nm or more. From the viewpoint of suppressing cracking in the vapor-deposited film and the recyclability of the packaging container, the thickness of the vapor-deposited film is preferably 150 nm or less, more preferably 100 nm or less, and even more preferably 80 nm or less. The thickness of the vapor-deposited film is, for example, 1 nm or more and 150 nm or less.

[0137] The surface of the vapor-deposited film may be subjected to the above-mentioned surface treatment, which may provide, for example, excellent adhesion to other layers.

[0138] Examples of methods for forming vapor-deposited films include physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, and ion plating, as well as chemical vapor deposition (CVD) methods such as plasma-enhanced chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition. The vapor-deposited film may be a composite film containing two or more different vapor-deposited film layers formed by combining both physical vapor deposition and chemical vapor deposition.

[0139] The vacuum level in the deposition chamber was 10 -2 ~10 -8 After oxygen is introduced, the pressure is preferably about 10 -1 ~10 -6 A pressure of about mbar is preferable. The amount of oxygen introduced varies depending on the size of the deposition machine. The oxygen introduced may be mixed with an inert gas such as argon gas, helium gas, or nitrogen gas as a carrier gas, provided that this does not cause any problems. The transport speed of the target film on which the deposition film is formed is, for example, 10 m / min to 800 m / min.

[0140] The vapor-deposited film may be a single layer formed by a single vapor deposition process, or may be a multilayer formed by multiple vapor deposition processes. When the vapor-deposited film is a multilayer film, each layer may be composed of the same or different components. Each layer may be formed by the same method or by different methods.

[0141] <Barrier coat layer> The barrier film of the present disclosure may further include a barrier coat layer on the vapor-deposited film. That is, the barrier film may further include a barrier coat layer on the surface of the vapor-deposited film opposite to the surface facing the multilayer film or stretched film. Such a barrier film has excellent scratch resistance and gas barrier properties, and when the vapor-deposited film is composed of an inorganic oxide such as aluminum oxide or silicon oxide, for example, it can effectively prevent cracks from occurring in the vapor-deposited film and prevent a decrease in gas barrier properties.

[0142] In one embodiment, the barrier coat layer contains a gas barrier resin. A barrier film including such a layer has even better gas barrier properties. The barrier coat layer can be formed, for example, by applying a coating liquid obtained by dissolving or dispersing a material such as a gas barrier resin in water or an appropriate organic solvent to a vapor-deposited film and drying the resulting coating liquid.

[0143] Examples of gas barrier resins include ethylene-vinyl alcohol copolymers, polyvinyl alcohol, polyamides, polyvinylidene chloride, polyesters, polyether polyols, polyester polyols, polyurethanes, polyacrylonitrile, and (meth)acrylic resins.

[0144] In one embodiment, the content of the gas barrier resin in the barrier coat layer is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, still more preferably 80% by mass or more, and particularly preferably 90% by mass or more. Such a layer has, for example, excellent gas barrier properties.

[0145] The barrier coat layer may contain the above-mentioned additives.

[0146] The thickness of the barrier coat layer containing the gas barrier resin is preferably 0.01 μm or more, more preferably 0.1 μm or more, from the viewpoint of gas barrier properties. The thickness of the barrier coat layer containing the gas barrier resin is preferably 10 μm or less, more preferably 5 μm or less, from the viewpoint of processability of the barrier film and recyclability of the packaging container. The thickness is, for example, 0.01 μm or more and 10 μm or less.

[0147] In another embodiment, the barrier coat layer is a gas barrier coating film formed by applying a gas barrier composition to a vapor-deposited film and drying it. The gas barrier composition is obtained by mixing a metal alkoxide, a water-soluble polymer, and optionally a silane coupling agent, and adding, optionally, water, optionally an organic solvent, and optionally a sol-gel catalyst. The gas barrier coating film contains a hydrolysis polycondensate obtained by hydrolyzing and polycondensing the metal alkoxide or the like by a sol-gel method. By providing such a film on a vapor-deposited film, when the vapor-deposited film is composed of an inorganic oxide, the gas barrier properties can be improved and the occurrence of cracks in the vapor-deposited film can be effectively suppressed.

[0148] Examples of metal alkoxides include alkoxysilanes, specifically tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane.

[0149] Examples of water-soluble polymers include hydroxyl group-containing polymers such as polyvinyl alcohol and ethylene-vinyl alcohol copolymers. These water-soluble polymers can also contribute to improving gas barrier properties, for example. Depending on the desired physical properties, such as oxygen barrier properties, water vapor barrier properties, water resistance, and weather resistance, either polyvinyl alcohol or ethylene-vinyl alcohol copolymers may be used, or both may be used in combination. Furthermore, a gas barrier coating film obtained using polyvinyl alcohol and a gas barrier coating film obtained using an ethylene-vinyl alcohol copolymer may be laminated. The amount of water-soluble polymer used is preferably 5 to 500 parts by mass per 100 parts by mass of the metal alkoxide.

[0150] As the silane coupling agent, a known organoalkoxysilane containing an organic reactive group can be used, and an organoalkoxysilane having an epoxy group is preferred, such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. The amount of the silane coupling agent used is preferably 1 part by mass or more and 20 parts by mass or less per 100 parts by mass of the metal alkoxide.

[0151] The gas barrier composition may contain water in an amount of preferably 0.1 mol or more, more preferably 0.5 mol or more, per mol of metal alkoxide, and preferably 100 mol or less, more preferably 60 mol or less. By setting the water content at or above the lower limit, for example, the oxygen barrier property and water vapor barrier property of the barrier film can be improved. By setting the water content at or below the upper limit, for example, the hydrolysis reaction can be carried out quickly.

[0152] The gas barrier composition may contain an organic solvent, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, or n-butyl alcohol.

[0153] The sol-gel catalyst is preferably an acid or an amine compound.

[0154] Examples of methods for applying the gas barrier composition include roll coating using a gravure roll coater or the like, spray coating, spin coating, dipping, brush coating, bar coating, and applicator coating.

[0155] Hereinafter, one embodiment of the method for forming a gas barrier coating film will be described. A gas barrier composition is prepared by mixing a metal alkoxide, a water-soluble polymer, a sol-gel catalyst, water, an organic solvent, and, if necessary, a silane coupling agent. A polycondensation reaction gradually progresses within the composition. The composition is then coated onto the vapor-deposited film by a conventional method and dried. This drying process further promotes polycondensation of the metal alkoxide and the water-soluble polymer (and the silane coupling agent, if the composition contains one) to form a composite polymer layer. Multiple composite polymer layers may be laminated by repeating the above process. For example, the coated composition is heated at a temperature of preferably 20°C or higher, more preferably 50°C or higher, and even more preferably 70°C or higher, and preferably 150°C or lower, more preferably 120°C or lower, and even more preferably 100°C or lower, for 1 second to 10 minutes. In this manner, a gas barrier coating film can be formed.

[0156] The thickness of the gas barrier coating film is preferably 0.01 μm or more, more preferably 0.05 μm or more, even more preferably 0.1 μm or more, and is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 5 μm or less, still more preferably 2 μm or less, and particularly preferably 1 μm or less, for example, 0.01 μm or more and 100 μm or less. A barrier film having such a gas barrier coating film has, for example, excellent gas barrier properties, can suppress the occurrence of cracks in a vapor-deposited film made of an inorganic oxide, and also provides excellent recyclability and processability of the packaging container.

[0157] <Print layer> The barrier film of the present disclosure may further include the above-described printed layer. The printed layer may be provided, for example, on at least one of the first and second main surfaces of the multilayer film or stretched film, on the surface of the vapor-deposited film, or on the surface of the barrier coat layer.

[0158] [Application] At least one film selected from the multilayer film, stretched film, printed film, and barrier film of the present disclosure described above is also referred to as the "film of the present disclosure." The film of the present disclosure can be suitably used as a substrate constituting a packaging material. Because the film of the present disclosure has high heat resistance, it can be suitably used as a printing substrate.

[0159] [Laminate] The laminate of the present disclosure comprises at least a film of the present disclosure; and a heat seal layer; are provided in this order in the stacking direction. In one embodiment, the laminate of the present disclosure comprises at least a first heat seal layer; a film of the present disclosure; and a second heat seal layer; and are provided in this order in the stacking direction.

[0160] The laminate of the present disclosure can be suitably used as a packaging material. The laminate of the present disclosure, which includes the first and second heat-sealing layers, can be suitably used, for example, as a packaging material for forming the body of a tube container. In this case, for example, the second heat-sealing layer is a sealant layer on the outer surface of the body, and the first heat-sealing layer is a sealant layer on the inner surface of the body. That is, the body includes, from the outside to the inside of the body, the second heat-sealing layer, the film of the present disclosure, and the first heat-sealing layer, in this order.

[0161] In one embodiment, the laminate of the present disclosure does not include aluminum foil. In one embodiment, the laminate of the present disclosure does not include either a polyethylene terephthalate film or aluminum foil. Such a laminate and a packaging container including the laminate have excellent recyclability.

[0162] In one embodiment, the total thickness of the laminate of the present disclosure may be 40 μm or more, 60 μm or more, 80 μm or more, 100 μm or more, 120 μm or more, 140 μm or more, 400 μm or less, 350 μm or less, or 300 μm or less, for example, 40 μm or more and 400 μm or less. The total thickness of the laminate can be changed as appropriate depending on, for example, the use or shape of the packaging container.

[0163] <Base material> The laminate of the present disclosure includes the film of the present disclosure as a substrate. The laminate of the present disclosure may include two or more films of the present disclosure. Details of these films are as described above, and detailed description will be omitted here.

[0164] The laminate of the present disclosure may further include a polyolefin oriented substrate other than the above-described stretched film. The polyolefin oriented substrate is a polyolefin substrate that has been subjected to a stretching treatment. The polyolefin oriented substrate contains polyolefin as a main component. Examples of polyolefins include polyethylene, polypropylene, polybutene, and polymethylpentene. Among these, polyethylene and polypropylene are preferred, with polyethylene being more preferred. Examples of the polyolefin oriented substrate include a polyethylene oriented substrate containing polyethylene as a main component and a polypropylene oriented substrate containing polypropylene as a main component, with a polyethylene oriented substrate being more preferred. The stretching treatment may be uniaxial or biaxial. Details of the stretching treatment are as described above, and will not be described here. The polyolefin oriented substrate may be, for example, a uniaxial or biaxially stretched substrate.

[0165] The oriented polyolefin substrate may contain a biomass polyolefin. The oriented polyolefin substrate may contain recycled polyolefin. The oriented polyolefin substrate may contain the above-mentioned additives.

[0166] The polyolefin content in the oriented polyolefin substrate is 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

[0167] The oriented polyolefin substrate may have a single layer structure or a multilayer structure. The thickness of the oriented polyolefin substrate is preferably 5 μm or more, more preferably 8 μm or more, and even more preferably 10 μm or more, from the viewpoint of the strength and heat resistance of the laminate, and is preferably 300 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less, for example, 5 μm or more and 300 μm or less, from the viewpoint of the processability of the laminate.

[0168] The oriented polyolefin substrate may be subjected to the above-mentioned surface treatment. Such an oriented polyolefin substrate has, for example, excellent adhesion to a layer adjacent to the substrate. An anchor coating layer may be formed on the surface of the oriented polyolefin substrate using a conventionally known anchor coating agent.

[0169] The laminate further comprising an oriented polyolefin substrate may, for example, comprise a heat seal layer, a film of the present disclosure, and an oriented polyolefin substrate in this order, or may comprise a heat seal layer, an oriented polyolefin substrate, and a film of the present disclosure in this order.

[0170] <Print layer> The laminate of the present disclosure may have a printed layer on one or both sides of the substrate, such as the film of the present disclosure and a polyolefin stretched substrate. The laminate of the present disclosure may have a printed layer on the second heat-sealable layer described below. Details of the printed layer are as described above, and will not be described here.

[0171] <Heat seal layer> The laminate of the present disclosure comprises a heat seal layer. The heat-seal layer contains, as its main component, a heat-sealable resin that can melt and fuse together when heated. Examples of heat-sealable resins include polyolefins such as polyethylene, polypropylene, and polymethylpentene, cyclic polyolefins, cyclic olefin copolymers, ionomer resins, acid-modified polyolefins, and ethylene-(meth)acrylic acid ester-unsaturated carboxylic acid terpolymers. Examples of polyethylene include linear low-density polyethylene, high-pressure low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, and ethylene-(meth)acrylic acid ester copolymer. Examples of acid-modified polyolefins include resins obtained by modifying polyolefins such as polyethylene and polypropylene with unsaturated carboxylic acid compounds such as (meth)acrylic acid and maleic anhydride. The heat-sealable resin may be derived from fossil fuels, biomass, or both.

[0172] In recent years, there has been a demand for recycling packaging containers in order to reduce environmental impact. From the viewpoint of recyclability, it is preferable that the substrate and the heat seal layer are each made of the same type of resin material (mono-material). In one embodiment, the heat seal layer contains polyethylene as a main component. This configuration enables the packaging container to be made mono-material. Such packaging containers have excellent recyclability, and for example, after collecting used packaging containers, there is no need to separate the substrate and the heat seal layer.

[0173] From the viewpoint of heat-sealability, the heat-seal layer preferably contains high-pressure low-density polyethylene and / or linear low-density polyethylene. When the heat-seal layer contains high-pressure low-density polyethylene and linear low-density polyethylene, the content (mass%) of the linear low-density polyethylene may be greater than the content (mass%) of the high-pressure low-density polyethylene.

[0174] From the viewpoint of a balance between heat resistance and heat sealability, the melting point of the polyethylene contained in the heat seal layer is preferably 90°C or higher, more preferably 95°C or higher, and preferably 140°C or lower, more preferably 130°C or lower, for example, 90°C or higher and 140°C or lower.

[0175] In one embodiment, the polyethylene content in the heat seal layer is 50% by mass or more. The content is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more. A laminate including such a heat seal layer has excellent recyclability, for example.

[0176] The heat seal layer may contain the above-mentioned additives.

[0177] In one embodiment, the polyethylene content in the entire laminate of the present disclosure is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. Such a laminate has excellent recyclability, for example. For example, the laminate can be used to produce a mono-material packaging container, thereby improving the recyclability of the packaging container.

[0178] The laminate of the present disclosure may include a first heat-sealing layer as the heat-sealing layer, a film of the present disclosure, and a second heat-sealing layer as the heat-sealing layer, in this order in the lamination direction. The first heat-sealing layer and the second heat-sealing layer can be melted and fused to each other by heating. Such a laminate can be suitably used, for example, as a packaging material for forming the body of a tube container.

[0179] In one embodiment, the first and second heat-seal layers contain polyethylene as a main component, and the polyethylene contained in the first heat-seal layer and the polyethylene contained in the second heat-seal layer may be the same or different.

[0180] The heat seal layer may have a single-layer structure or a multi-layer structure. The first and second heat seal layers may have a single-layer structure or a multi-layer structure.

[0181] The thickness of the heat seal layer may be 10 μm or more, 20 μm or more, 30 μm or more, 50 μm or more, 60 μm or more, 70 μm or more, or 80 μm or more from the viewpoint of heat sealing properties and recyclability of the packaging container. The thickness of the heat seal layer may be 300 μm or less, 200 μm or less, or 150 μm or less from the viewpoint of processability of the laminate. The thickness of the heat seal layer is, for example, 10 μm or more and 300 μm or less. The thicknesses of the first and second heat seal layers are also preferably independently within the above ranges. The thickness of the heat seal layer can be appropriately changed depending on, for example, the use or shape of the packaging container. In the case of a small bag, the thickness of the heat seal layer may be, for example, 20 μm or more and 60 μm or less, but is not particularly limited. In the case of a standing pouch, the thickness of the heat seal layer may be, for example, 60 μm or more and 150 μm or less, but is not particularly limited. In the case of a tube container, the thickness of each heat seal layer may be, for example, 50 μm or more, 60 μm or more, 70 μm or more, or 80 μm or more, but is not particularly limited.

[0182] From the viewpoint of heat sealing property, the heat seal layer is preferably an unstretched resin film, more preferably an unstretched co-extruded resin film, and each layer constituting the heat seal layer is a co-extruded resin layer. The above resin film can be produced, for example, by using a T-die casting method or an inflation molding method. The concept of "unstretched film" includes not only a film that is not stretched at all, but also a film that is slightly stretched due to the tension applied during film formation.

[0183] For example, an unstretched resin film corresponding to the heat seal layer may be laminated on the film of the present disclosure via an adhesive layer as needed, or a heat-sealable resin or a resin composition thereof may be melt-extruded onto the film of the present disclosure to form the heat seal layer. In the latter case, an adhesive layer may not be provided. Examples of adhesive layers include the following adhesive layers.

[0184] <Adhesive layer> The laminate of the present disclosure may include an adhesive layer between any layers, such as between a substrate such as a film of the present disclosure and a heat seal layer. Such a laminate has, for example, excellent adhesion between the substrate and the heat seal layer.

[0185] The laminate of the present disclosure may, for example, comprise a heat-sealing layer, an adhesive layer, and a film of the present disclosure in this order in the lamination direction, or a heat-sealing layer, a first adhesive layer, a film of the present disclosure, a second adhesive layer, and a stretched polyolefin substrate in this order in the lamination direction, or a heat-sealing layer, a first adhesive layer, a stretched polyolefin substrate, a second adhesive layer, and a film of the present disclosure in this order in the lamination direction.The laminate of the present disclosure may, for example, comprise a first heat-sealing layer, a first adhesive layer, a film of the present disclosure, a second adhesive layer, and a second heat-sealing layer in this order in the lamination direction.

[0186] In one embodiment, the adhesive layer may be an adhesive layer made of an adhesive. The adhesive may be any of a one-component curing adhesive, a two-component curing adhesive, and a non-curing adhesive. The adhesive may be a solventless adhesive or a solvent-based adhesive. Among these, a solvent-based adhesive is preferred because it has better resistance to contents.

[0187] Examples of solvent-free adhesives, i.e., non-solvent laminate adhesives, include polyether adhesives, polyester adhesives, silicone adhesives, epoxy adhesives, and urethane adhesives. Among these, urethane adhesives are preferred, and two-component curing urethane adhesives are more preferred.

[0188] Examples of solvent-based adhesives include rubber-based adhesives, vinyl-based adhesives, olefin-based adhesives, silicone-based adhesives, epoxy-based adhesives, phenol-based adhesives, and urethane-based adhesives. Among these, urethane-based adhesives are preferred, and two-component curing urethane-based adhesives are more preferred.

[0189] In one embodiment, the laminate of the present disclosure may be produced by laminating the film of the present disclosure, an optionally stretched polyolefin substrate, and a resin film corresponding to the heat seal layer by a non-solvent lamination method using a solvent-free adhesive, or by a dry lamination method using a solvent-based adhesive. The adhesive layer can be formed by applying an adhesive to the film of the present disclosure or the like by a method such as direct gravure roll coating, gravure roll coating, kiss coating, reverse roll coating, Fontaine coating, or transfer roll coating, and then drying the adhesive.

[0190] The thickness of the adhesive layer may be 0.1 μm or more, 0.2 μm or more, 0.5 μm or more, 10 μm or less, 8 μm or less, or 6 μm or less, for example, 0.1 μm or more and 10 μm or less. The thickness of the adhesive layer may be 2 μm or less.

[0191] In one embodiment, the adhesive layer may be an adhesive resin layer containing a thermoplastic resin, or an extruded resin layer containing a thermoplastic resin. Examples of the thermoplastic resin include the above-mentioned heat-sealable resins. The thermoplastic resin may be a material derived from fossil fuels, a material derived from biomass, or both.

[0192] The thickness of the extruded resin layer is preferably 5 μm or more, more preferably 10 μm or more, from the viewpoint of interlayer adhesion. The thickness of the extruded resin layer is preferably 30 μm or less, more preferably 25 μm or less, from the viewpoint of reducing the production cost of the laminate and improving its productivity. The thickness of the extruded resin layer is, for example, 5 μm or more and 30 μm or less.

[0193] <Layer structure of laminate> Hereinafter, several examples of the layer configuration of the laminate of the present disclosure will be given with reference to the drawings. 4 includes, in this order in the stacking direction, a heat seal layer 80, an adhesive layer 60, and a stretched film 1. The laminate 2 may further include a printed layer (not shown), for example, a printed layer may further be provided on the stretched film 1.

[0194] 5 includes, in this order in the stacking direction, a heat seal layer 80, a first adhesive layer 61, a stretched film 1, a second adhesive layer 62, and a stretched polyolefin substrate 70. The laminate 2 may further include a printed layer (not shown), for example, a printed layer may further be provided on the stretched polyolefin substrate 70.

[0195] 6 includes a first heat-seal layer 81, a first adhesive layer 61, a stretched film 1, a second adhesive layer 62, and a second heat-seal layer 82, in this order in the stacking direction. The laminate 2 may further include a printed layer (not shown), for example, a printed layer on the second heat-seal layer 82. A laminate having such a configuration is suitable, for example, as a packaging material for forming the barrel of a tube container body.

[0196] In the laminate 2 of Figures 4 to 6, the orientation of the stretched film 1 may be reversed. In the laminate 2 of Figures 4 to 6, a multilayer film, a printed film, or a barrier film may be provided instead of the stretched film 1. In Figures 4 to 6, the adhesive layers 60, 61, and 62 may be, for example, adhesive layers or extruded resin layers.

[0197] [Packaging container] The laminate of the present disclosure can be suitably used for packaging material applications. The packaging material is used to produce packaging containers. Examples of packaging containers include packaging bags, tube containers, and containers with lids.

[0198] Examples of packaging bags include various types of packaging bags, such as stand-up pouch type, side seal type, two-sided seal type, three-sided seal type, four-sided seal type, envelope seal type, grommed seal type (pillow seal type), pleated seal type, flat bottom seal type, square bottom seal type, and gusset type.The packaging bag may be, for example, a small pouch or a zipper bag.The packaging bag may also be a refill pouch, particularly a stand-up pouch, that contains contents such as liquids and powders and is refilled into containers such as bottles.The packaging bag may also be, for example, a flexible packaging bag.

[0199] The packaging container of the present disclosure comprises the laminate of the present disclosure. The packaging container of the present disclosure may be, for example: one or more laminates of the present disclosure; a seal portion where the heat seal layers of the laminate are joined together; a storage section for storing contents; It has. The seal portion includes an inner edge that defines the receptacle portion.

[0200] Examples of methods for forming the sealed portion include heat sealing, which involves melting the heat-sealed layers of the laminate by heating or the like to fuse the heat-sealed layers together, and specific examples include bar sealing, rotary roll sealing, belt sealing, impulse sealing, high-frequency sealing, and ultrasonic sealing. For example, after placing the contents in a packaging bag, the opening of the packaging bag can be heat-sealed to seal the packaging bag.

[0201] The packaging bag may have an easy-to-open portion. Examples of the easy-to-open portion include a notch portion that serves as a starting point for tearing the packaging bag, and a half-cut line formed by laser processing or a cutter as a path for tearing the packaging bag.

[0202] In one embodiment, the laminate of the present disclosure is used as a lid material in a lidded container. The lidded container comprises a container body having a storage compartment and a lid material joined (heat sealed) to the container body so as to seal the storage compartment. Here, the lid material, i.e., the heat seal layer of the laminate, and the container body are heat sealed. Examples of the shape of the container body include a cup shape and a cylindrical shape with a bottom. The container body is made of, for example, polystyrene, polypropylene, polyethylene, or paper.

[0203] Examples of contents housed in packaging containers include liquids, solids, powders, and gels. The contents may be food or beverages, or non-food or beverages such as chemicals, cosmetics, pharmaceuticals, metal parts, and electronic components. Examples of contents include shampoo, rinse, conditioner, hand soap, body soap, air fresheners, deodorants, insect repellents, fabric softeners, detergents; sauces, soy sauce, dressings, cooking oils, mayonnaise, ketchup, syrups, cooking alcohol, and other liquid or viscous condiments; fruit juices; spices; liquid beverages, jelly-like beverages, liquid soups, powdered soups, instant foods, other food and beverages; creams; toothpaste; toothpaste; metal parts, and electronic components. For example, toothpaste and toothpaste are preferred contents for tube containers.

[0204] In one embodiment, a packaging bag can be produced by folding the laminate of the present disclosure in half and overlapping it so that the film of the present disclosure is on the outside and the heat seal layer is on the inside, and then heat sealing the edges, etc. In another embodiment, a packaging bag can be produced by overlapping multiple laminates of the present disclosure so that the heat seal layers face each other and heat sealing the edges, etc. The entire packaging bag may be composed of the above-mentioned laminate, or only a portion of the packaging bag may be composed of the above-mentioned laminate.

[0205] In one embodiment, the stand-up pouch comprises a body portion composed of side sheets and a bottom portion composed of a bottom sheet. The bottom sheet maintains the shape of the side sheets, thereby imparting self-supporting properties to the pouch and enabling it to be a stand-up pouch. A storage compartment for storing contents is formed within the area surrounded by the side sheets and the bottom sheet. In the stand-up pouch, only the side sheets may be the laminate of the present disclosure, only the bottom sheet may be the laminate of the present disclosure, or both the side sheets and the bottom sheet may be the laminate of the present disclosure.

[0206] In one embodiment, the side sheet can be formed by preparing two laminates of the present disclosure, overlapping them with their heat-sealable layers facing each other, and heat-sealing both side edges to form a bag.

[0207] In another embodiment, the side sheets can be formed by preparing two laminates of the present disclosure, overlapping them with their heat-sealable layers facing each other, inserting two V-folded laminates with their heat-sealable layers facing outward between the laminates at the side edges of both sides of the overlapped laminates, and heat-sealing the two laminates. This production method produces a stand-up pouch having a body with side gussets.

[0208] In one embodiment, the bottom sheet can be formed by inserting the laminate of the present disclosure between the lower portions of the side sheets of a bag and heat-sealing the laminate. More specifically, the bottom sheet can be formed by inserting the laminate folded in a V-shape with the heat-seal layer facing outward between the lower portions of the side sheets of a bag and heat-sealing the laminate.

[0209] In one embodiment, two laminates of the present disclosure are prepared and stacked together with their heat-sealable layers facing each other. Then, another laminate of the present disclosure is folded in a V-shape with its heat-sealable layer facing outward, and this is sandwiched between the two laminates and heat-sealed to form a bottom. Next, two sides adjacent to the bottom are heat-sealed to form a body. In this manner, a stand-up pouch according to one embodiment can be formed.

[0210] The tube container comprises a tube container body and a cap attached to the top. Hereinafter, a case where the laminate of the present disclosure is applied to a tube container body constituting a tube container will be described. The tube container body includes the laminate of the present disclosure. The tube container body includes a head and a body, and for example, the body is formed from the laminate of the present disclosure.

[0211] The head portion has a shoulder portion connected to one end of the body portion, and a spout portion connected to the shoulder portion. In one embodiment, the spout portion has threads for threading a cap thereon.

[0212] In one embodiment, the head portion is formed from a resin composition containing a thermoplastic resin. Examples of thermoplastic resins include polyolefins such as polyethylene and polypropylene, polyesters, cellulose resins, and vinyl resins. The resin composition may contain the additives described above. In one embodiment, the head portion is formed from a resin composition containing polyethylene. This configuration improves the recyclability of the tube container body. Examples of polyethylene include high-density polyethylene, medium-density polyethylene, high-pressure low-density polyethylene, and linear low-density polyethylene. Among these, high-density polyethylene is preferred from the viewpoints of shape retention and moldability. The resin composition may contain at least one selected from biomass polyethylene and recycled polyethylene.

[0213] The head portion can be produced by a conventionally known method, for example, by compression molding or injection molding, and can be joined to the body portion.

[0214] In the tube container body, the body is connected to the shoulder of the head. The body has a fused portion formed, for example, by overlapping the laminate of the present disclosure so that the surface of the first heat-seal layer at one end and the surface of the second heat-seal layer at the other end are in contact, rolling the laminate into a cylindrical shape, and heat-sealing the overlapped portion. The body has a bottom seal portion formed, for example, by heat-sealing the opening of the laminate rolled into a cylindrical shape.

[0215] Examples of heat sealing methods include conventionally known methods such as bar sealing, rotary roll sealing, belt sealing, impulse sealing, high frequency sealing, ultrasonic sealing, and flame sealing.

[0216] For example, a cylindrical body portion may be produced by overlapping one end of the laminate of the present disclosure so that the surface of the first heat-seal layer at one end is in contact with the surface of the second heat-seal layer at the other end, rolling the laminate into a cylindrical shape, and heat-sealing the overlapped portion. From the viewpoint of heat-sealability, it is preferable that one overlapping end is the first heat-seal layer and the other end is the second heat-seal layer. In this case, the first heat-seal layer and the second heat-seal layer are melted and joined to form a fused portion.

[0217] In the above embodiment, the fused portion is formed by overlapping. Alternatively, the same surfaces of both ends of the laminate may be butted together and the first heat-seal layers may be heat-sealed to join them. In this case, a joining tape may be applied to the outer surface of the body portion so as to cover the joining portion.

[0218] [Example of situation] The present disclosure relates to, for example, the following [1] to

[26] . [1] A first surface resin layer containing high-density polyethylene (A) as a main component; a second surface resin layer containing polyethylene as a main component; A multilayer film comprising at least The high-density polyethylene (A) has a peak in a differential molecular weight distribution curve (horizontal axis: common logarithm (LogM) of molecular weight (M); vertical axis: dW / d(LogM) obtained by differentiating cumulative concentration fraction (W) with common logarithm of molecular weight (M)) obtained by high-temperature gel permeation chromatography (GPC) measurement, in which the maximum value of dW / d(LogM) is 0.80 or more and the half-width is less than 1.1. Multilayer film. [2] The high-density polyethylene (A) has a density of 0.945 g / cm 3 Super 0.970g / cm 3 The multilayer film according to [1] above, having a density of 125°C or more and / or a melting point of 125°C or more and 140°C or less. [3] The multilayer film according to [1] or [2], wherein the polyethylene contained in the second surface resin layer is at least one selected from linear low-density polyethylene, high-pressure low-density polyethylene, medium-density polyethylene, and high-density polyethylene. [4] The second surface resin layer is a layer containing high-density polyethylene (B) as a main component; a layer containing, as a main component, at least one low-density polyethylene (C1) selected from linear low-density polyethylene and high-pressure low-density polyethylene; or a layer containing medium density polyethylene as a main component; and the high-density polyethylene (B) has a broader molecular weight distribution than the high-density polyethylene (A) in a differential molecular weight distribution curve obtained by high-temperature GPC measurement; The multilayer film according to any one of [1] to [3] above. [5] The multilayer film according to [4], wherein the high-density polyethylene (B) has a peak in a differential molecular weight distribution curve obtained by high-temperature GPC measurement, in which the maximum value of dW / d(LogM) is less than 0.80 and the half-value width is 1.1 or more. [6] The multilayer film according to any one of [1] to [5], further comprising an intermediate layer containing polyethylene as a main component between the first surface resin layer and the second surface resin layer. [7] With respect to the thickness of the multilayer film, the thickness of the first surface resin layer is 5% or more and 90% or less, The total thickness of the intermediate layer and the second surface resin layer is 10% or more and 95% or less. The multilayer film according to [6] above. [8] The multilayer film according to [6] or [7], wherein the polyethylene contained in the intermediate layer is at least one selected from linear low-density polyethylene, high-pressure low-density polyethylene, medium-density polyethylene, and high-density polyethylene. [9] The multilayer film has, between the first surface resin layer and the second surface resin layer, an intermediate layer containing the high-density polyethylene (A) as a main component; an intermediate layer containing high-density polyethylene (B) as a main component; An intermediate layer containing, as a main component, at least one low-density polyethylene (C2) selected from linear low-density polyethylene and high-pressure low-density polyethylene; and an intermediate layer containing medium density polyethylene as a main component; Further comprising at least one layer selected from the high-density polyethylene (B) has a broader molecular weight distribution than the high-density polyethylene (A) in a differential molecular weight distribution curve obtained by high-temperature GPC measurement; The multilayer film according to any one of [6] to [8] above.

[10] The multilayer film according to [9], wherein the high-density polyethylene (B) has a peak in a differential molecular weight distribution curve obtained by high-temperature GPC measurement, in which the maximum value of dW / d(LogM) is less than 0.80 and the half-value width is 1.1 or more.

[11] The high-density polyethylene (B) has a density of 0.945 g / cm 3 Super 0.970g / cm 3 and / or a melting point of 125°C or higher and 140°C or lower, The low-density polyethylene (C2) has a density of 0.920 g / cm 3 and / or a melting point below 120°C, The medium density polyethylene has a density of 0.930 g / cm 3 More than 0.945g / cm 3 and / or a melting point of 120°C or higher and 135°C or lower, The multilayer film according to [9] or

[10] above.

[12] The multilayer film according to any one of [1] to

[11] above, which is a coextruded film.

[13] The multilayer film according to any one of [1] to

[12] above, which is a substrate.

[14] The multilayer film according to any one of [1] to

[13] above, which is a printing substrate.

[15] A stretched film obtained by stretching the multilayer film according to any one of [1] to

[14] above.

[16] The stretched film according to

[15] , wherein the stretched film is a uniaxially stretched film.

[17] The scattering intensity ratio I1 / I2 obtained by Raman spectroscopy measurement in a cross section of a layer of the stretched film corresponding to the first surface resin layer is 1.1 or more; a scattering intensity ratio I1 / I2 obtained by Raman spectroscopy measurement in each cross section of the stretched film, the layer corresponding to the intermediate layer containing high-density polyethylene (A) as a main component, the layer corresponding to the intermediate layer containing high-density polyethylene (B) as a main component, and the layer corresponding to the intermediate layer containing medium-density polyethylene as a main component, are each independently 1.1 or more; the scattering intensity ratio I1 / I2 obtained by Raman spectroscopy measurement in a cross section of the layer of the stretched film corresponding to the intermediate layer containing low-density polyethylene (C2) as a main component is less than 1.1; the cross section is a plane parallel to a plane including a lamination direction perpendicular to a main surface of the stretched film and a stretching direction of the stretched film, The I1 is detected by Raman spectroscopy at 1100 cm -1 More than 1150cm -1 The maximum scattering intensity of the peak observed in the following region is 1050 cm in Raman spectroscopy. -1 More than 1100cm -1 is the maximum scattering intensity of the peak observed in the region less than The stretched film according to

[15] or

[16] above.

[18] The stretched film according to any one of

[15] to

[17] , wherein the stretched film has a dimensional change rate in the stretching direction of -7% or more and 0% or less, measured after being left standing in an environment of 120°C for 5 minutes.

[19] The stretched film according to any one of

[15] to

[18] , wherein the stretched film has a polyethylene content of 80% by mass or more.

[20] The stretched film according to any one of

[15] to

[19] , wherein the entire polyethylene contained in the stretched film has a peak with a half-value width of less than 1.3 in a differential molecular weight distribution curve obtained by high-temperature GPC measurement.

[21] The stretched film according to any one of the above

[15] to

[20] , which is a substrate.

[22] The stretched film according to any one of

[15] to

[21] above, which is a printing substrate.

[23] A laminate comprising at least one film selected from the multilayer film according to any one of [1] to

[14] and the stretched film according to any one of

[15] to

[22] , and a heat seal layer.

[24] The laminate according to

[23] , wherein the heat seal layer contains polyethylene as a main component, and the content of polyethylene in the entire laminate is 80% by mass or more.

[25] A packaging container comprising the laminate according to

[23] or

[24] .

[26] The packaging container according to

[25] above, which is a packaging bag. [Example]

[0219] The multilayer film and stretched film of the present disclosure will be described in more detail below using examples, but the multilayer film and stretched film are not limited to the following examples in any way.

[0220] [Differential molecular weight distribution curve] The differential molecular weight distribution curve of polyethylene was obtained by high-temperature gel permeation chromatography (GPC) measurement as follows. Polyethylene was dissolved in o-dichlorobenzene (containing 0.025 wt% BHT) at 145°C under the conditions of standing for 1 hour and stirring for 1 hour. The resulting solution was pressure-filtered using a membrane filter with a pore size of 1.0 μm and a membrane filter with a pore size of 0.5 μm. High-temperature GPC measurement was performed using the pressure-filtered solution under the following conditions. The cumulative concentration fraction (the mass proportion of polyethylene below a certain molecular weight in total polyethylene) was calculated from the obtained data, and an integrated molecular weight distribution curve was obtained with the horizontal axis representing the common logarithm of the molecular weight in terms of polystyrene and the vertical axis representing the cumulative concentration fraction. Next, a differential molecular weight distribution curve was obtained with the horizontal axis representing the common logarithm of the molecular weight in terms of polystyrene and the vertical axis representing the value (dW / d(LogM)) obtained by differentiating the cumulative concentration fraction by the common logarithm of the molecular weight in terms of polystyrene. (conditions) Equipment: Senshu Scientific SSC-7120 HT-GPC System Sample amount: Approximately 3 mg of sample pieces per 3 mL of solvent ·Injection volume: 300μL Guard column: guard column HHR-H(S)HT2 Separation column: GMHHR-H(S)HT2 (2 columns, inner diameter: 7.8 mm) Column temperature: 145℃ Mobile phase: o-dichlorobenzene (containing 0.025 wt% BHT) ·Flow rate: 0.95mL / min Detector: Differential refractometer Molecular weight calibration: Polystyrene equivalent

[0221] We investigated the peaks that appear in the differential molecular weight distribution curve of polyethylene. Regarding the maximum value of dW / d(LogM), if the peak top value is not explicitly indicated on the data representing the differential molecular weight distribution curve, the peak top value can be determined from an approximate equation. In this case, the peak top value can be determined from an approximate equation of a sixth-order polynomial that passes through the maximum dW / d(LogM) data and four points before and after it (a total of nine points). Polyethylene having a peak with a maximum value (peak top value) of dW / d(LogM) of 0.80 or more and a half-width of less than 1.1 was judged to have a "narrow molecular weight distribution" (sharp shape). Polyethylenes having a peak with a maximum value (peak top value) of dW / d(LogM) of less than 0.80 and a half-width of 1.1 or more were judged to have a "broad molecular weight distribution" (broad shape). The weight average molecular weight (Mw) of the polyethylene was obtained by the above-mentioned high-temperature GPC measurement.

[0222] [Stretched film materials] The following materials were used in producing the stretched film. High-density polyethylene (B) (HDPE(B)) Made by Prime Polymer, Hz5000SF Density: 0.954g / cm 3 Melting point: 132°C, MFR: 0.66g / 10min Maximum value of dW / d(LogM): 0.60, half width: 1.536 Mw: 3.16 x 10 5 Determination of molecular weight distribution: Wide molecular weight distribution High-density polyethylene (B) (HDPE(B)) Dow Chemical Company, ELITE AT6900 Density: 0.969g / cm 3 Melting point: 134°C, MFR: 1.2g / 10min Maximum value of dW / d(LogM): 0.73, half width: 1.981 Mw: 2.07 x 10 5 Determination of molecular weight distribution: Wide molecular weight distribution High-density polyethylene (B) (HDPE(B)) Made by Japan Polyethylene, HY540 Density: 0.960g / cm 3 Melting point: 135°C, MFR: 1.0g / 10min Maximum value of dW / d(LogM): 0.70, half width: 1.278 Mw: 2.74×10 5 Determination of molecular weight distribution: Wide molecular weight distribution High-density polyethylene (A) (HDPE(A)) Tosoh, Nipolon-P FY13 Density: 0.950g / cm 3 Melting point: 133°C, MFR: 1.0g / 10min Maximum value of dW / d(LogM): 0.98, half width: 0.928 Mw: 2.21 x 10 5 Molecular weight distribution: Narrow molecular weight distribution Medium Density Polyethylene (MDPE) Dow Chemical Company, ELITE 5538G Density: 0.941g / cm 3 Melting point: 129°C, MFR: 1.3g / 10min Mw: 2.02 x 10 5 Linear low-density polyethylene (LLDPE) Prime Polymer, SP0820, C6-LLDPE Density: 0.910g / cm 3 Melting point: 98°C, MFR: 1.7g / 10min Maximum value of dW / d(LogM): 1.06, half width: 0.822 Mw: 2.10 x 10 5 Molecular weight distribution: Narrow molecular weight distribution Linear low-density polyethylene (LLDPE) ExxonMobil, XP8656ML, C6-LLDPE Density: 0.916g / cm 3 Melting point: 121°C, MFR: 0.5g / 10min Maximum value of dW / d(LogM): 0.77, half width: 1.252 Mw: 2.77×10 5 Determination of molecular weight distribution: Wide molecular weight distribution

[0223] [Example 1] HDPE (A) (FY13), LLDPE (SP0820), and HDPE (B) (Hz5000SF) were co-extruded into a tubular film with a layer thickness ratio of HDPE (A) layer (15.0 μm), LLDPE layer (45.0 μm), and HDPE (B) layer (15.0 μm) at a die temperature of 200°C. This resulted in a polyethylene film with a total thickness of 75 μm. The tubular polyethylene film was folded at the nip to form two layers. The values in parentheses indicate the layer thicknesses. The polyethylene film prepared above was stretched in the machine direction (MD) at a stretching temperature of 125°C to a stretch ratio of 3x and then heat-set at an annealing temperature of 125°C. The end was then slit to separate the film into two, resulting in a stretched film with a thickness of 25 μm. The stretched film comprises a 5.0 μm thick HDPE (A) layer, a 15.0 μm thick LLDPE layer, and a 5.0 μm thick HDPE (B) layer.

[0224] [Examples 2 to 11, Comparative Examples 1 to 5] Stretched films were produced in the same manner as in Example 1, except that at least one selected from the type of resin constituting each layer, the thickness of each layer, and the stretching ratio was changed as shown in Table 1 or Table 2. However, in Example 11, the stretching temperature and annealing temperature were changed to 120°C. In this specification, "←" in a table means that the composition of the layer in question is the same as the composition in the column to the left.

[0225] [Heat resistance evaluation (appearance)] The stretched films obtained in the Examples and Comparative Examples were cut into 10 cm × 10 cm pieces to obtain test pieces. Using a heat seal tester TP-701 (manufactured by Tester Sangyo Co., Ltd.), pressure was applied to a 1 cm (MD) × 10 cm (TD) area of the test piece under the following heat sealer conditions: temperature: 120°C or 130°C, pressure: 0.1 MPa, pressure time: 1 second, and single-sided heating (for the first layer). The presence or absence of shrinkage in this area was visually evaluated according to the following criteria. <Verdict> A: The stretched film is not shrinking. B: The stretched film has shrunk slightly. C: The stretched film has shrunk significantly.

[0226] [Heat resistance evaluation (dimensional change rate in the stretching direction)] The stretched films obtained in the Examples or Comparative Examples were cut to a size of 10 cm x 10 cm to obtain test specimens. A line of approximately 10 cm was drawn on the surface of the first layer of the test specimen along the stretching direction of the stretched film (MD direction in the above Examples or Comparative Examples), and the dimensions of the line were measured using a precision measuring glass scale (manufactured by Oyama Optical Co., Ltd.). Hereinafter, these dimensions will also be referred to as "dimensions before heat treatment." A clean oven DE611 (manufactured by Yamato Scientific Co., Ltd.) was used as the heat treatment device, and the test specimen was left standing in an environment of 120°C for 5 minutes for heat treatment. The test specimen was positioned so that the first layer was on top and the second layer was on the bottom. The dimensions of the line on the test specimen after heat treatment were measured using the glass scale. Hereinafter, these dimensions will also be referred to as "dimensions after heat treatment." The dimensional change rate in the stretching direction was calculated from the obtained dimensions before and after heat treatment. Dimensional change rate (%) = ((dimension after heat treatment - dimension before heat treatment) / dimension before heat treatment)) x 100 Elongation: The dimensional change rate is a positive value. Shrinkage: The dimensional change rate shows a negative value.

[0227] [Molecular orientation evaluation] A Raman spectrum was obtained for a cross section of each polyethylene layer of the stretched film obtained in the Examples or Comparative Examples using a Raman spectrometer (LabRAM HR800, manufactured by Horiba, Ltd.) as follows.

[0228] (Pretreatment) The stretched film was embedded in an embedding resin to prepare a block. Using a commercially available ultramicrotome capable of preparing frozen sections, the block was cut parallel to a plane including the thickness direction (stacking direction) perpendicular to the main surface of the stretched film and the stretching direction of the stretched film (MD direction in the above Examples and Comparative Examples) in a low-temperature environment of -100°C. In this way, a cross section of the stretched film was obtained. Finishing was performed using a diamond knife.

[0229] (Raman measurement) The cut block was fixed on the stage of a Raman spectrometer so that the polarization direction of the laser was parallel to the stretching direction of the stretched film. A He-Ne laser with a wavelength of 633 nm was used as the excitation light source, and measurements were performed by irradiating a sample area of approximately 1 μm diameter with the laser through a 100x objective lens. The laser output, irradiation time, and number of integrations were 1000 to 1600 cm. -1 The recommended conditions for the instrument were used so that the peaks could be sufficiently separated in the region and the peak intensities could be obtained stably. The measurements were performed in line mapping mode, in which the stage was moved in 1 μm steps in the direction perpendicular to the stretching direction, so that at least one spectrum could be obtained for each layer of the stretched film. The stretching direction of the stretched film is defined as the X direction, the thickness direction (stacking direction) as the Y direction, and the normal direction of the cross section as the Z direction. The incident direction of the laser is the Z direction. The polarization direction of the laser is the X direction. The mapping direction is the Y direction. In the Raman spectrum obtained by the above measurement, -1 The maximum scattering intensity of the peak near I 1130 value, and 1063 cm -1 The maximum scattering intensity of the peak near I 1063 From the value of the ratio I1130 / I 1063 When two or more spectra were obtained in the same layer, the arithmetic mean value of the above ratios obtained for each spectrum was calculated as the ratio I 1130 / I 1063 It was decided.

[0230] [Puncture strength] The puncture strength of the stretched films obtained in the examples and comparative examples was measured in accordance with JIS Z1707:2019. The stretched films obtained in the examples and comparative examples were cut to obtain test pieces measuring 5 cm in width and 5 cm in length. A Tensilon universal material testing machine RCT-1250A (manufactured by AND Co.) was used as the measuring instrument. A semicircular needle with a diameter of 1.0 mm and a tip radius of 0.5 mm was pierced into the first layer of the test piece at a test speed of 50 mm / min, and the maximum strength (N) until the needle penetrated the test piece was measured.

[0231] [Table 1]

[0232] [Table 2] [Explanation of symbols]

[0233] 1. Stretched film 2. Laminate 10 First Layer 20 Second Layer 30 PE middle layer 31 First PE middle layer 32 Second PE Intermediate Layer 33 Third PE Intermediate Layer 60 Adhesive layer 61 First adhesive layer 62 Second adhesive layer 70 Polyolefin oriented substrate 80 Heat seal layer 81 First heat seal layer 82 Second heat seal layer

Claims

1. a first surface resin layer containing high-density polyethylene (A) as a main component; a second surface resin layer containing polyethylene as a main component; A multilayer film comprising at least The high-density polyethylene (A) has a peak in a differential molecular weight distribution curve obtained by high-temperature gel permeation chromatography (GPC) measurement (horizontal axis: common logarithm (Log M) of molecular weight (M); vertical axis: dW / d(Log M) obtained by differentiating cumulative concentration fraction (W) with common logarithm of molecular weight (M)), in which the maximum value of dW / d(Log M) is 0.80 or more and the half-width is less than 1.

1. Multilayer film.

2. The high-density polyethylene (A) has a density of 0.945 g / cm 3 Super 0.970g / cm 3 2. The multilayer film of claim 1, having a density of at least 100% by mass and / or a melting point of at least 125°C and at most 140°C.

3. 2. The multilayer film according to claim 1, wherein the polyethylene contained in the second surface resin layer is at least one selected from linear low-density polyethylene, high-pressure low-density polyethylene, medium-density polyethylene, and high-density polyethylene.

4. The second surface resin layer is a layer containing high-density polyethylene (B) as a main component; a layer containing, as a main component, at least one low-density polyethylene (C1) selected from linear low-density polyethylene and high-pressure low-density polyethylene; or a layer containing medium density polyethylene as a main component; and the high-density polyethylene (B) has a broader molecular weight distribution than the high-density polyethylene (A) in a differential molecular weight distribution curve obtained by high-temperature GPC measurement; The multilayer film of claim 1.

5. 5. The multilayer film according to claim 4, wherein the high-density polyethylene (B) has a peak in a differential molecular weight distribution curve obtained by high-temperature GPC measurement, in which the maximum value of dW / d(LogM) is less than 0.80 and the half-value width is 1.1 or more.

6. The multilayer film according to claim 1 , further comprising an intermediate layer between the first surface resin layer and the second surface resin layer, the intermediate layer containing polyethylene as a main component.

7. With respect to the thickness of the multilayer film, the thickness of the first surface resin layer is 5% or more and 90% or less; the total thickness of the intermediate layer and the second surface resin layer is 10% or more and 95% or less; The multilayer film of claim 6.

8. 7. The multilayer film according to claim 6, wherein the polyethylene contained in the intermediate layer is at least one selected from linear low-density polyethylene, high-pressure low-density polyethylene, medium-density polyethylene, and high-density polyethylene.

9. The multilayer film has, between the first surface resin layer and the second surface resin layer, an intermediate layer containing the high-density polyethylene (A) as a main component; an intermediate layer containing high-density polyethylene (B) as a main component; an intermediate layer containing, as a main component, at least one low-density polyethylene (C2) selected from linear low-density polyethylene and high-pressure low-density polyethylene; and an intermediate layer containing medium density polyethylene as a main component; Further comprising at least one layer selected from the high-density polyethylene (B) has a broader molecular weight distribution than the high-density polyethylene (A) in a differential molecular weight distribution curve obtained by high-temperature GPC measurement; The multilayer film of claim 6.

10. 10. The multilayer film according to claim 9, wherein the high-density polyethylene (B) has a peak in a differential molecular weight distribution curve obtained by high-temperature GPC measurement, in which the maximum value of dW / d(LogM) is less than 0.80 and the half-value width is 1.1 or more.

11. The high-density polyethylene (B) has a density of 0.945 g / cm 3 Super 0.970g / cm 3 and / or a melting point of 125°C or higher and 140°C or lower, The low-density polyethylene (C2) has a density of 0.920 g / cm 3 and / or a melting point below 120°C, The medium density polyethylene has a density of 0.930 g / cm 3 0.945g / cm or more 3 and / or a melting point of 120°C or higher and 135°C or lower, The multilayer film of claim 9.

12. The multilayer film of claim 1 , wherein the multilayer film is a coextruded film.

13. The multilayer film of claim 1 which is a substrate.

14. The multilayer film of claim 1 which is a printing substrate.

15. A stretched film obtained by stretching the multilayer film according to claim 1.

16. 16. The stretched film of claim 15, wherein the stretched film is a uniaxially stretched film.

17. The multilayer film has, between the first surface resin layer and the second surface resin layer, an intermediate layer containing the high-density polyethylene (A) as a main component; an intermediate layer containing high-density polyethylene (B) as a main component; an intermediate layer containing, as a main component, at least one low-density polyethylene (C2) selected from linear low-density polyethylene and high-pressure low-density polyethylene; and an intermediate layer containing medium density polyethylene as a main component; Further comprising at least one layer selected from the high-density polyethylene (B) has a broader molecular weight distribution than the high-density polyethylene (A) in a differential molecular weight distribution curve obtained by high-temperature GPC measurement, The scattering intensity ratio I obtained by Raman spectroscopy measurement in a cross section of the layer corresponding to the first surface resin layer of the stretched film 1 / I 2 is 1.1 or more, a scattering intensity ratio I obtained by Raman spectroscopy measurement in each cross section of the layer corresponding to the intermediate layer containing high-density polyethylene (A) as a main component, the layer corresponding to the intermediate layer containing high-density polyethylene (B) as a main component, and the layer corresponding to the intermediate layer containing medium-density polyethylene as a main component of the stretched film; 1 / I 2 are each independently 1.1 or greater; The scattering intensity ratio I obtained by Raman spectroscopy measurement in a cross section of the layer of the stretched film corresponding to the intermediate layer containing low-density polyethylene (C2) as a main component 1 / I 2 is less than 1.1, the cross section is a plane parallel to a plane including a lamination direction perpendicular to a main surface of the stretched film and a stretching direction of the stretched film, I 1 is measured at 1100 cm in Raman spectroscopy. -1 1150cm or more -1 The maximum scattering intensity of the peak observed in the following region is I 2 is measured by Raman spectroscopy at 1050 cm -1 More than 1100cm -1 is the maximum scattering intensity of the peak observed in the region less than The stretched film according to claim 15.

18. 16. The stretched film according to claim 15, wherein the stretched film has a dimensional change rate in the stretching direction of −7% or more and 0% or less, measured after being left to stand in an environment of 120° C. for 5 minutes.

19. The stretched film according to claim 15, wherein the stretched film has a polyethylene content of 80% by mass or more.

20. 16. The stretched film according to claim 15, wherein the entire polyethylene contained in the stretched film has a peak having a half-value width of less than 1.3 in a differential molecular weight distribution curve obtained by high-temperature GPC measurement.

21. The stretched film of claim 15 which is a substrate.

22. The stretched film according to claim 15, which is a printing substrate.

23. At least one film selected from the multilayer film according to any one of claims 1 to 14 and the stretched film according to any one of claims 15 to 22; a heat seal layer; A laminate comprising at least

24. The laminate according to claim 23, wherein the heat seal layer contains polyethylene as a main component, and the content of polyethylene in the entire laminate is 80 mass % or more.

25. A packaging container comprising the laminate of claim 23.

26. 26. The packaging container according to claim 25, which is a packaging bag.

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