Polyethylene stretched substrate film and packaging material

Abstract

To provide a polyethylene resin laminate which is suitable as a base material in a polyethylene mono-material packaging material, a polyethylene stretched base material film using the same, and a resin laminate and a packaging material using the same.SOLUTION: A polyethylene resin laminate that is used in a polyethylene stretched base material film of a polyethylene mono-material resin laminate having at least a polyethylene stretched base material film and a polyethylene sealant film has a layer structure of at least three layers, is stretched in at least one direction, in the layers of the resin laminate, a layer (1a) on the outermost surface facing polyethylene sealant and a layer (2a) on the outermost surface opposite to the layer (1a) are layers containing a high density polyethylene resin composition (A) satisfying a specific requirement, and the intermediate layer is a layer containing a straight chain low density polyethylene resin composition (B) satisfying a specific requirement.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to polyethylene monomaterial packaging materials, specifically a polyethylene stretched base film having an excellent rigidity-strength balance, a packaging material using the same, a resin laminate containing the polyethylene stretched base film, and a packaging material composed of the laminate. [Background technology]

[0002] Conventionally, one of the basic components of packaging materials is a base film and a sealant film bonded together with an adhesive. Of these, the sealant film is widely used to be a film made of a polyethylene resin composition that has moderate flexibility, transparency, and excellent heat-sealing properties. On the other hand, the base layer is used to be a film made by stretching a film made of a polyester resin composition or a polyamide resin composition from the viewpoint of rigidity, impact resistance, and heat resistance (see Patent Document 1).

[0003] In recent years, with the growing demand for a circular economy, there has been a need for packaging materials with high recyclability. However, as mentioned above, conventional packaging materials are composed of different types of resin materials, making it difficult to separate them, and therefore they are not currently recycled.

[0004] One way to achieve high recyclability is to construct packaging materials made entirely from the same resin material (monomaterial packaging materials). Since polyethylene resin compositions are widely used as raw materials for packaging materials, monomaterial packaging materials, in which both the base film and sealant film are made from polyethylene resin compositions, are expected to be highly recyclable packaging materials that contribute to a circular economy.

[0005] One configuration of polyethylene monomaterial packaging materials is a structure in which a polyethylene base film and a polyethylene sealant film are laminated. However, when using a film made of polyethylene resin composition as a base material, if the film obtained by the inflation molding method or T-die molding method is used as is, the impact strength of the packaging material will be insufficient, and the lack of rigidity will cause the film to stretch when printed, resulting in image misalignment. To compensate for this, a polyethylene stretched base film is used, which is obtained by stretching a film obtained by molding a polyethylene resin composition by the inflation molding method or T-die molding method.

[0006] Examples of stretched polyethylene films include a stretched polyethylene film obtained by producing a raw material from a resin composition blended with linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE) using inflation molding, and then hot-roll stretching (see Patent Document 2), and a stretched polyethylene film obtained by forming a sheet from a resin composition containing HDPE and LLDPE and then uniaxially stretching it (see Patent Document 3). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2009-202519 [Patent Document 2] Japanese Patent Publication No. 2005-89693 [Patent Document 3] Patent No. 5069423 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, the polyethylene stretched film described in Patent Document 2 was for shrink packaging film use, and the film described in Patent Document 3 was for twist packaging film use, neither of which were for base film use. In addition, the films described in these patent documents lacked the rigidity and strength required for polyethylene stretched base film, and there was a need to develop a film with a good balance of these two physical properties. The object of the present invention is to provide a polyethylene resin laminate suitable as a base material for polyethylene monomaterial packaging materials, a polyethylene stretched base material film using the same, and a resin laminate and packaging material using the same. [Means for solving the problem]

[0009] The present inventors conducted extensive research to solve the above problems and discovered that laminating a high-polyethylene resin composition that satisfies specific conditions exhibits properties that can solve the above problems. Based on these findings, they completed the invention.

[0010] In other words, according to the present invention [1], a polyethylene resin laminate for use in a polyethylene monomaterial resin laminate having at least a polyethylene stretched base film and a polyethylene sealant film is provided, wherein the laminate has a layer structure of at least three layers, is stretched in at least one direction, and the outermost surface layer (1a) of the resin laminate facing the polyethylene sealant and the outermost surface layer (2a) on the opposite side are layers containing a high-density polyethylene resin composition (A), and the intermediate layer is a layer containing a linear low-density polyethylene resin composition (B), wherein (A) and (B) satisfy the following requirements. (A) (a-1) Density of 0.945~0.970 g / cm³ 3 (a-2) Melt flow rate (MFR) of 0.1-20 g / 10 min at a temperature of 190°C and a load of 2.16 kg. (a-3) The molecular weight distribution (Mw / Mn), which is the ratio of the number-average molecular weight (Mn) to the weight-average molecular weight (Mw) obtained from GPC (Gel Permeation Chromatography), is between 1.5 and 10. (B) (b-1) Density of 0.870~0.915 g / cm³ 3 (b-2) MFR of 0.1~20g / 10min at a temperature of 190℃ and a load of 2.16kg (b-3) The melt tension (MT) determined from the capillary graph is 5.0 g or less. (b-4) The molecular weight distribution (Mw / Mn), which is the ratio of the number-average molecular weight (Mn) to the weight-average molecular weight (Mw) obtained from GPC, is between 1.5 and 10. (b-5) The number of short-chain branches per 1000C calculated by GPC and the SCB index calculated using formula (a) are 1.02 or higher. Equation (a) SCB exponent = (number of short chain branches at log 5.2) / (number of short chain branches at log 4.2)

[0011] Furthermore, according to the present invention [2], a polyethylene stretched substrate film as described in [1] is provided, characterized in that a polyethylene resin laminate obtained by inflation molding or T-die molding is stretched by 5 times or more in the mechanical direction (MD).

[0012] Furthermore, according to the present invention [3], when the elastic modulus in the mechanical direction (MD) and the elastic modulus in the orthogonal direction (TD) of the polyethylene stretched substrate film described in [1] or [2] is EM, the EM is 1500 MPa or more and the ET is 1000 MPa or more, and a polyethylene stretched substrate film is provided.

[0013] Furthermore, according to the present invention [4], a polyethylene stretched substrate film is provided, characterized in that the dirt drop impact test of the polyethylene stretched substrate film described in any of [1] to [3] is 30 g or more.

[0014] Further, according to the present invention [5], in the heat seal strength test of the polyethylene stretched base film according to any one of [1] to [4] above, the seal strength at a seal temperature of 140 ° C is 5 N / 15 mm or less, and a polyethylene stretched base film is provided.

[0015] Further, according to the present invention [6], there is provided the polyethylene stretched base film according to [1] above, which is obtained by stretching a polyethylene resin laminate obtained by inflation molding or T-die molding 2 times or more in the MD and TD directions.

[0016] Further, according to the present invention [7], there is provided a resin laminate including a layer made of the polyethylene stretched base film according to any one of [1] to [6] above.

[0017] Further, according to the present invention [8], there is provided the resin laminate according to [7] above, which includes a layer made of the polyethylene stretched base film according to any one of [1] to [6] above as a base material and includes a sealant film.

[0018] Further, according to the present invention [9], there is provided the resin laminate according to [7] or [8] above, which includes a layer made of the polyethylene stretched base film according to any one of [1] to [6] above as a base material and includes a polyethylene sealant film.

[0019] Further, according to the present invention

[10] , there is provided the resin laminate according to any one of [7] to [9] above, wherein all the layers constituting the resin laminate are a polyethylene monomaterial resin laminate composed of a polyethylene-based resin composition.

[0020] Further, according to the present invention

[11] , there is provided a packaging material using the polyethylene stretched base film according to any one of [1] to [6] above.

[0021] Further, according to the present invention

[12] , there is provided a packaging material using the resin laminate according to any one of [7] to

[10] above.

Advantages of the Invention

[0022] The polyethylene resin laminate of the present invention provides a polyethylene stretchable base film with excellent stretchability, heat resistance, and a good balance of rigidity and strength. Since printing is possible on the surface of such a polyethylene stretchable base film, by using this stretchable base film as a base material for packaging materials and laminating it with a polyethylene sealant film, it is possible to provide a highly recyclable packaging material, in particular a monomaterial laminate and packaging material composed of a single material. [Brief explanation of the drawing]

[0023] [Figure 1] The GPC curves for Example 1-1 and Comparative Example 1-1 are shown. [Figure 2] The GPC curves for Example 1-2, Comparative Example 1-2, Comparative Example 1-3, and Comparative Example 1-4 are shown. [Figure 3] The SCB curves for Example 1-2, Comparative Example 1-2, Comparative Example 1-3, and Comparative Example 1-4 are shown. [Modes for carrying out the invention]

[0024] 1. Polyethylene resin composition In the present invention, the polyethylene resin composition refers to a resin composition used as a raw material for polyethylene stretched substrate films or polyethylene sealant films, and means both polyethylene resin alone or a mixture thereof, and may contain necessary additives.

[0025] • Polymerization catalyst and polymerization method for polyethylene resin compositions Polyethylene resins used to make up polyethylene resin compositions are produced using either ethylene derived from petroleum raw materials or ethylene derived from biomass raw materials, or both, as raw materials, and conventionally known catalysts such as Ziegler-Natta catalysts, Phillips catalysts, and metallocene catalysts. Generally, these catalysts are complexes composed of organometallic compounds supported on a carrier such as silica or Mg compounds.

[0026] Polymerization methods include high-pressure methods, solution methods, slurry methods, and gas-phase methods. The high-pressure method uses a catalyst consisting of a radical source such as oxygen or peroxide, or a metal complex, as an initiator, and polymerizes ethylene, comonomers, and the initiator by introducing them into a reaction vessel under high temperature and high pressure conditions. Depending on the shape of the reaction vessel, it can be further divided into the tubular method and the autoclave method. The solution method is a polymerization method in which the polymer is dissolved in a hydrocarbon solvent at a temperature above the melting point of the polymer. The slurry method is a polymerization method in which a hydrocarbon compound such as hexane or isobutane is used as the solvent, and the resulting polyethylene exists in the solvent as a slurry. Depending on the shape of the reaction vessel, it can be broadly divided into the autoclave method and the loop-pipe method. The gas-phase method is a polymerization method in which ethylene and α-olefin as a comonomer, and hydrogen as a chain transfer agent are fed in gaseous form from the bottom of a vertical reaction vessel, and a polymerization catalyst is introduced thereto (edited by Kazuo Matsuura and Naotaka Mikami / Polyethylene Technology Reader). The polyethylene resin composition of the present invention is preferably one polymerized using a metal catalyst.

[0027] The polyethylene resin compositions obtained by these manufacturing methods have a wide range of combinations of densities, melt flow rates (MFRs), and other resin properties to meet various conventionally known applications. However, the present invention is characterized by selecting and using a polyethylene resin composition that satisfies the requirements of the present invention.

[0028] • Comonomer composition of polyethylene resin composition The polyethylene resin composition may be an ethylene homopolymer, or a copolymer of ethylene and one or more α-olefins selected from α-olefins having 3 to 18 carbon atoms. Preferably, the α-olefins have 3 to 12 carbon atoms, and examples include propylene, 1-butene, 1-hexene, 1-octene, and 4-methyl-1-pentene. Furthermore, the total content of these α-olefins is usually selected to be 30 mol% or less, preferably 20 mol% or less. Within this range, the flexibility and heat resistance of films and the like are good. Here, the α-olefin content is determined under the following conditions 13 This value is measured by the 1C-NMR method. Device: JEOL-GSX270 (manufactured by JEOL Corporation) Concentration: 300mg / 2mL Solvent: Orthodichlorobenzene

[0029] 2. Polyethylene stretched substrate film The polyethylene stretched substrate film according to the requirements of the present invention refers to a stretched film obtained by stretching a film obtained from a polyethylene resin composition by inflation molding or T-die molding, and which is used as a substrate for a resin laminate.

[0030] • Raw material manufacturing method and manufacturing conditions Polyethylene stretched substrate film is obtained by stretching a raw material. Methods for manufacturing the raw material include inflation molding, T-die molding, and calendering, but inflation molding or T-die molding are preferred from the viewpoint of production speed and ease of manufacture. The manufacturing conditions for the raw material are not particularly limited, but the thickness of the raw material film is preferably 20 μm to 200 μm. More preferably 30 μm to 200 μm, and even more preferably 50 μm to 200 μm.

[0031] ·Layer composition The polyethylene stretched substrate film according to the requirements of the present invention must be a multilayer structure of three or more layers using multiple polyethylene resin compositions having predetermined resin properties. In the case of a three-layer structure, when the high-density polyethylene resin composition according to the requirements of the present invention is (A) and the linear low-density polyethylene resin composition is (B), it is essential that the structure is (A) / (B) / (A). In this case, one of the layers (A) will be the outermost layer (or sometimes called the "outer layer") facing the polyethylene sealant. The other layer (A) will be the outermost layer (or sometimes called the "inner layer") on the opposite side, and layer (B) will constitute the intermediate layer. In the case of a multilayer structure with more than three layers, there are no particular restrictions, but high-density polyethylene (HDPE), medium-density polyethylene (MDPE), linear low-density polyethylene (LLDPE), and ultra-low-density polyethylene (ULDPE) can be combined. In the case of a 5-layer structure, examples include (A) / MDPE / (B) / MDPE / (A), (A) / LLDPE / (B) / LLDPE / (A), (A) / ULDPE / (B) / ULDPE / (A), (A) / (B) / (A) / (B) / (A), (A) / (B) / HDPE / (B) / (A), (A) / (B) / MDPE / (B) / (A), (A) / (B) / LLDPE / (B) / (A), and (A) / (B) / ULDPE / (B) / (A). As is clear from these examples, layer (A) may be included as part of the intermediate layer, and layer (B) may be separated from other resin layers in the intermediate layer to form multiple layers.

[0032] • High-density polyethylene resin composition The high-density polyethylene resin composition (A) used in the polyethylene stretched substrate film according to the requirements of the present invention has a density of 0.945 to 0.970 g / cm³. 3The melt flow rate (MFR) at 190°C and a 2.16 kg load must be between 0.1 and 20 g / 10 min, and the molecular weight distribution (Mw / Mn), which is the ratio of number-average molecular weight (Mn) to weight-average molecular weight (Mw) determined from GPC (Gel Permeation Chromatography), must be within the range of 1.5 to 10. Films outside this range are unsuitable because they will have insufficient rigidity and heat resistance, and high-magnification stretching will not be possible, resulting in insufficient rigidity. A more preferable range is a density of 0.950 to 0.965 g / cm³. 3 The MFR is 0.5-10g / 10min, and the Mw / Mn ratio is 3-9.

[0033] • Linear low-density polyethylene resin composition The linear low-density polyethylene resin composition (B) used in the polyethylene stretched substrate film according to the requirements of the present invention must have a density of 0.870 to 0.915 g / cm³, an MFR of 0.1 to 20 g / 10 min at 190°C and a 2.16 kg load, a melt tension (MT) of 5.0 g or less determined by capillary spectroscopy at 190°C, a molecular weight distribution (Mw / Mn), which is the ratio of number-average molecular weight (Mn) to weight-average molecular weight (Mw) determined from GPC, of ​​1.5 to 10, and an SCB index of 1.02 or more calculated using the short-chain branching formula (a) per 1000°C calculated by GPC. Failure to meet these requirements is undesirable because the strength of the polyethylene stretched substrate film will be insufficient. A more preferable range is a density of 0.875 to 0.913 g / cm³. 3 The MFR is 0.5-10g / 10min, Mw / Mn is 3-9, MT is 4.0g or less, and SCB index is 1.03 or higher. Equation (a) SCB exponent = (number of short chain branches at log 5.2) / (number of short chain branches at log 4.2)

[0034] • Resin blend The high-density polyethylene resin composition or linear low-density polyethylene resin composition used in the polyethylene stretched substrate film according to the requirements of the present invention may be blended with other polyethylene resin compositions to satisfy the requirements of the present invention. Examples of polyethylene resin compositions to be blended include HDPE, MDPE, LLDPE, LDPE, and ULDPE.

[0035] • Additives The polyethylene resin composition used in the polyethylene stretched substrate film according to the requirements of the present invention may contain additives commonly used in resin compositions, such as antioxidants, heat stabilizers, neutralizing agents, antiblocking agents, tackifiers, antistatic agents, slip agents, nucleating agents, foaming agents, crosslinking agents, biomass resources, biodegradation accelerators, etc., to the extent that the objectives of the present invention are not impaired.

[0036] ·Stretching method The polyethylene stretched substrate film according to the requirements of the present invention is not particularly limited, but may be a uniaxially oriented film or a biaxially oriented film. Any stretching method can be longitudinal uniaxial stretching, transverse uniaxial stretching, sequential biaxial stretching, or simultaneous biaxial stretching, with longitudinal uniaxial stretching being preferred.

[0037] • Vertical extension ratio The stretching ratio in the mechanical direction (MD) of the polyethylene stretched substrate film according to the requirements of the present invention is preferably 2 times or more and 15 times or less, and preferably 5 times or more and 10 times or less. It is even more preferable to have a stretching ratio of 6 times or more. By increasing the stretching ratio in the MD of the polyethylene stretched substrate film, the strength and heat resistance of the laminate of the present invention can be improved. In addition, the transparency of the substrate can be improved, thereby improving the printability of the substrate. As a result, when an image is formed on the surface of the polyethylene stretched substrate film that is in contact with the polyethylene sealant film, its visibility can be improved. On the other hand, there is no particular upper limit to the stretching ratio in the MD of the polyethylene stretched substrate film, but from the viewpoint of the breaking limit of the stretched film, it is preferable to have a stretching ratio of 15 times or less, and more preferably 10 times or less.

[0038] ·Horizontal stretch ratio The stretching ratio of the polyethylene stretched substrate film according to the requirements of the present invention is preferably 1.5 times or more, and more preferably 2 times or more. By setting the stretching ratio of the TD of the polyethylene stretched substrate film to 1.5 times or more, the strength and heat resistance of the laminate of the present invention can be improved. Furthermore, the transparency of the substrate can be improved, thereby improving the printability of the substrate. This improves the visibility of the image when it is formed on the surface of the polyethylene stretched substrate film that is in contact with the polyethylene sealant film. On the other hand, there is no particular upper limit to the stretching ratio of the TD of the polyethylene stretched substrate film, but from the viewpoint of the breaking limit of the stretched film, it is preferable to set it to 10 times or less.

[0039] ·Biaxial stretching ratio When the polyethylene stretched substrate film according to the requirements of the present invention is biaxially stretched, the MD and TD ratios are preferably 1.5 times or more, and more preferably 2 times or more. By increasing the stretching ratios of the MD and TD of the polyethylene stretched base film, the strength and heat resistance of the laminate of the present invention can be improved. This improves the visibility of the image when it is formed on the surface of the polyethylene stretched base film that is in contact with the polyethylene sealant film. On the other hand, there is no particular upper limit to the stretching ratios of the MD and TD of the polyethylene stretched base film, but from the viewpoint of the breaking point limit of the stretched film, it is preferable to set the lower limit of the stretching ratios of MD and TD to 1.5 times, preferably 2 times, and the product of the MD stretching ratio and the TD stretching ratio to be 50 or less.

[0040] ·rigidity In a film obtained by stretching a film obtained by inflation molding or T-die molding using a polyethylene resin composition used in a polyethylene stretched substrate film according to the requirements of the present invention, the film must be stretched five times or more in the mechanical direction (MD), where EM is the modulus of elasticity in the MD direction and ET is the modulus of elasticity in the direction perpendicular to MD (TD), and EM is 1500 MPa or more and ET is 1000 MPa or more. Preferably, EM is 1600 MPa or more and ET is 1100 MPa or more. If EM and MT are less than the values ​​shown above, the polyethylene stretched film will stretch during printing or lamination with a polyethylene sealant film, causing the printed image to shift and worsening the processability of the lamination, which is undesirable.

[0041] ·Strength In the present invention, a film obtained by stretching a film obtained by inflation molding or T-die molding using a polyethylene resin composition used in the polyethylene stretched base film according to the requirements of the present invention, by more than 5 times in the mechanical direction (MD), must have a dart drop impact (DDI) value of 30 g or more. Preferably, it is 35 g or more. If the DDI is less than the value shown in the preceding paragraph, the strength of the polyethylene stretched base film will be insufficient, it will tear vertically during processing, and it will not be strong enough to be used as a packaging material, which is undesirable. DDI is a measurement that determines the fracture mass / strength at which 50% of the test piece is destroyed when a weight (dart) of an arbitrary load is dropped from a predetermined height.

[0042] ·Heat resistance The polyethylene stretched substrate film according to the requirements of the present invention must have a seal strength of 5 N / 15 mm or less in a heat seal strength test at 140°C. If the seal strength does not meet the requirement, the substrate may fuse to the heat seal bar when making packaging materials using the polyethylene stretched substrate film, which is undesirable. A more preferable value for the seal strength is 4 N / 15 mm or less.

[0043] 3. Polyethylene sealant film • Polyethylene resin composition to be used A polyethylene sealant film is a film characterized by containing layers made of at least one polyethylene resin composition, which can be sealed by fusion. There are no particular restrictions on the polyethylene resin compositions that can be used, but examples include ultra-low density polyethylene (ULDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), and high density polyethylene (HDPE).

[0044] • Additives The polyethylene resin composition used in polyethylene sealant films may contain additives commonly used in resin compositions, such as antioxidants, heat stabilizers, neutralizing agents, antiblocking agents, tackifiers, antistatic agents, slip agents, nucleating agents, foaming agents, crosslinking agents, biomass resources, and biodegradation accelerators, to the extent that they do not impair the function of the sealant film.

[0045] • Method and manufacturing conditions for polyethylene sealant film Known techniques can be used for manufacturing polyethylene sealant films. Specifically, these include inflation molding, T-die molding, and calendering, with inflation molding and T-die molding being preferred. The thickness of the sealant film is not particularly limited, but is preferably 10 to 200 μm, and more preferably 30 to 180 μm.

[0046] • Polyethylene sealant film structure The polyethylene sealant film may have a single-layer or multi-layer structure. In the case of a single-layer structure, the polyethylene resin composition may be used alone or mixed with other polyethylene resin compositions. In the case of a multi-layer structure, it is preferable to use the above-mentioned known techniques and to form it by co-extrusion molding, and it is preferable to have at least three layers.

[0047] 4. Others The resin laminate may be a resin laminate in which all layers constituting the resin laminate are composed of polyethylene-based resin. This resin laminate can be treated as a monomaterial resin laminate. There are no particular restrictions on the proportion of the main component in the monomaterial resin laminate, but it is preferably 80% by weight, more preferably 90% by weight.

[0048] • Surface treatment It is preferable that the polyethylene stretched substrate film and the polyethylene sealant film are surface-treated. This improves adhesion with adjacent layers. The surface treatment method is not particularly limited and includes physical treatments such as corona discharge treatment, ozone treatment, low-temperature plasma treatment using oxygen gas and / or nitrogen gas, glow discharge treatment, and chemical treatments such as oxidation treatment using chemicals. Alternatively, an anchor coat layer may be formed on the substrate surface using a conventionally known anchor coat agent.

[0049] ·printing Images such as characters, patterns, or symbols may be formed on at least one surface of the polyethylene stretched substrate film or the polyethylene sealant film. It is preferable that the images be formed on the surfaces of the polyethylene stretched substrate film and the polyethylene sealant film facing each other, in order to prevent deterioration of the images over time. The method of image formation is not particularly limited and can include conventionally known printing methods such as gravure printing, offset printing, and flexographic printing. Among these, flexographic printing is preferred from the viewpoint of environmental impact.

[0050] • Vapor-deposited film A vapor-deposited film may be provided on at least one surface of the polyethylene stretched substrate film or polyethylene sealant film. Examples of vapor-deposited films include those composed of metals such as aluminum, and inorganic oxides such as aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, zirconium oxide, titanium oxide, boron oxide, hafnium oxide, and barium oxide.

[0051] Also, the thickness of the vapor deposition film is preferably 1 nm or more and 150 nm or less, more preferably 5 nm or more and 60 nm or less, and even more preferably 10 nm or more and 40 nm or less. By setting the thickness of the vapor deposition film to 1 nm or more, the oxygen barrier property and water vapor barrier property of the laminate of the present invention can be further improved. Further, by setting the thickness of the vapor deposition film to 150 nm or less, generation of cracks in the vapor deposition film can be prevented, and the recyclability of the laminate of the present invention can be improved.

[0052] When the vapor deposition film is an aluminum vapor deposition film, its OD value is preferably 2 or more and 3.5 or less. Thereby, while maintaining the productivity of the laminate of the present invention, the oxygen barrier property and water vapor barrier property can be improved. In the present invention, the OD value can be measured in accordance with JIS-K-7361.

[0053] The vapor deposition film can be formed using a conventionally known method. For example, physical vapor deposition methods (Physical Vapor Deposition method, PVD method) such as vacuum evaporation method, sputtering method, and ion plating method, and chemical vapor deposition methods (Chemical Vapor Deposition method, CVD method) such as plasma chemical vapor deposition method, thermal chemical vapor deposition method, and photo chemical vapor deposition method can be mentioned.

[0054] Also, for example, a composite film composed of two or more layers of vapor deposition films of different inorganic oxides can be formed and used by using both a physical vapor deposition method and a chemical vapor deposition method in combination. The degree of vacuum in the vapor deposition chamber is preferably about 10 -2 ~10 -8 mbar before oxygen introduction, and preferably 10 -1 ~10 -6A pressure of approximately mbar is preferred. The amount of oxygen introduced will vary depending on the size of the deposition machine. Inert gases such as argon, helium, or nitrogen may be used as carrier gases for the oxygen introduced, within reasonable limits. The film transport speed can be approximately 10 to 800 m / min.

[0055] It is preferable that the surface of the deposited film is subjected to the above-mentioned surface treatment. This improves adhesion with adjacent layers.

[0056] Coat A polyethylene stretched substrate film or polyethylene sealant film may be provided with a heat-resistant coating layer or a barrier coating layer as a coating layer on at least one surface, and may contain at least one type of resin material. Examples of resin materials for the coating layer include polyester, polyolefin, cellulose resin, (meth)acrylic resin, urethane resin, and vinyl resin.

[0057] The proportion of the resin material contained in the coating layer to the total weight of the laminate is preferably 3% by mass or less, and more preferably 1% by mass or less. This makes it possible to improve the heat resistance and barrier properties of the laminate of the present invention while maintaining its recyclability.

[0058] The thickness of the coating layer is preferably 0.1 μm or more and 5 μm or less, and more preferably 0.5 μm or more and 3 μm or less. This makes it possible to improve the heat resistance and barrier properties of the laminate obtained using the stretched base film of the present invention while maintaining its recyclability.

[0059] ·glue Adhesives can be used to laminate the above-mentioned resin laminates. The adhesive used contains at least one resin composition, but is not particularly limited. Examples of adhesives that can be used include epoxy, acrylic, and urethane types. Furthermore, adhesives containing any of the above resin compositions are not particularly limited, but one-component, two-component, or hot-melt types may be used as needed. Furthermore, using barrier adhesives such as PASLIM (manufactured by DIC Corporation) or Maxive (manufactured by Mitsubishi Gas Chemical Company, Inc.) is preferable because it reduces the amount of other barrier materials used and increases the polyethylene ratio in the resin laminate.

[0060] 4. Packaging materials The laminate of the present invention can be used particularly suitably for packaging material applications. The shape of the packaging material is not particularly limited and may be a packaging bag or a stand-up pouch. In the case of a stand-up pouch, only the body may be formed from the resin laminate, only the bottom may be formed from the resin laminate, or both the body and the bottom may be formed from the resin laminate.

[0061] ·Packaging bag The bag-shaped packaging material can be manufactured by folding the laminated material in half and overlapping the two halves so that the polyethylene sealant film (heat-seal layer) is on the inside, and then heat-sealing the edges. Furthermore, bag-shaped packaging materials can also be manufactured by overlapping two laminated materials so that the heat-sealed layers face each other, and then heat-sealing the edges.

[0062] • Stand-up pouch The stand-up pouch packaging material can be manufactured by first forming the body by heat-sealing the laminated material in a cylindrical shape with the heat-seal layer facing inward, and then folding the laminated material in a V-shape with the heat-seal layer facing inward, sandwiching it from one end of the body, and heat-sealing it to form the bottom.

[0063] The heat sealing method is not particularly limited and can be carried out by known methods such as bar seals, rotary roll seals, belt seals, impulse seals, high-frequency seals, and ultrasonic seals.

[0064] The contents to be filled into the packaging material are not particularly limited and may be liquids, powders, or gels. They may also be food products or non-food products. After filling with contents, the opening can be heat-sealed to create a package. [Examples]

[0065] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The evaluations and resins used in the examples and comparative examples are as follows.

[0066] <Evaluation Method> (1) Density Measurements were taken in accordance with JIS K6922-1 and 2.

[0067] (2) MFR Measurements were taken in accordance with JIS K6922-2, under conditions of 190°C and a 2.16 kg load.

[0068] (3) Melt tension (MT) Using a capillary graph manufactured by Toyo Seiki Seisakusho, resin heated and stabilized at 190°C in a furnace was extruded through an orifice with an inner diameter of 2.095 mm and a length of 8 mm at a piston speed of 1 cm / min. The extruded molten resin was then pulled at a speed of 4 m / min, and the resistance force generated at that time was measured and defined as the molten tension value.

[0069] (4)Molecular weight distribution Measurements were taken using GPC (Gel Permeation Chromatography) under the following conditions. [Measurement conditions] Equipment used: Polymer Char HT GPC-IR System Detector: IR-6 Measurement temperature: 145℃ Solvent: Orthodichlorobenzene (ODCB) (trimethylphenol 3.6g / 18L added as antioxidant) Columns: Showa Denko Shodex HT-806M x 2 Flow rate: 1.0mL / min Injection volume: 20μL

[0070] • Sample preparation The sample was placed in vials at a dose of 5-8 mg and set up in an autosampler. The autosampler was programmed to inject 8 mL of solvent (room temperature) and dissolve the sample at 150°C for 2 hours. Heptane was used as a flow marker for pump flow rate correction.

[0071] • Creation of a calibration curve Calibration curves were created using standard polystyrene and converted to polyethylene equivalents. The standard polystyrene samples used were the Showdex Standard SM-105 sample set, as well as n-eicosane and n-tetracontane.

[0072] • Calculation of molecular weight Measurements were performed under the aforementioned conditions, and chromatograms were recorded with a sampling interval of 1 s. Chromatogram recording (data acquisition) and average molecular weight calculation were performed using dedicated software (GPC One, manufactured by Polymer Char) on a PC with Microsoft Windows® 10 installed.

[0073] (5) SCB index The number of short-chain branches was calculated using Polymer Char's IR-6. Specifically, the concentrations of CH2 (methylene) and CH3 (methyl) were measured using IR, and the number of short-chain branches was determined from a calibration curve of standard samples with known short-chain branching numbers. The obtained number of short-chain branches was calculated using the following formula (a) to obtain the SCB index. The SCB index is the quotient between the number of short-chain branches with logM=5.2 (Mw=158000) and the number of short-chain branches with logM=4.2 (Mw=15800). Equation (a) SCB exponent = (number of short chain branches at log 5.2) / (number of short chain branches at log 4.2)

[0074] (6) Elastic modulus Measurements were taken in reference to JIS K7127. Test pieces measuring 200 mm in length and 10 mm in width were cut in the direction perpendicular to the machine direction (MD direction) and the direction perpendicular to the machine direction (TD direction) of the film. The tensile modulus was measured at a tensile speed of 2 mm / min and a chuck distance of 100 mm, resulting in an elongation of 1%.

[0075] (7) Dirt Drop Impact (DDI) Measurements were taken in reference to JIS K7124-1. The test equipment used was a Tester Sangyo Co., Ltd. IM-302 dart impact tester. A sample film was clamped, and a weight holder was installed on a support column 66 cm above the film surface. A weight (dart) consisting of a Φ38 mm aluminum hemisphere and a 150 mm long shaft was set to an arbitrary weight and placed in the weight holder. The weight was then allowed to free-fall, and the rupture of the film surface was visually judged. Five measurements were taken for each dart weight. If the film did not rupture in all five measurements, the weight of the dart was increased by a certain percentage, and the measurement was repeated. If the film ruptured in all five measurements, the weight of the dart was decreased by a certain percentage, and the measurement was repeated. The measurement was continued in this manner, changing the weight, until the weight of the dart that did not rupture in all five measurements and the weight of the dart that ruptured in all five measurements were determined. Finally, the 50% fracture mass (M50) and 50% fracture energy (E50) of the film sample were calculated using the following formulas [1][2]. [1] M50 = WS(T / 100 - 1 / 2) [2] E50 = M50 × g × H W: Minimum mass at fracture of all test samples (g) S: Mass interval (g) during repeated testing T: Sum of the destruction rates of the five film samples in each test mass (%) H: Distance from the film sample surface to the tip of the dirt (m) g:Gravity acceleration (9.81m / s 2 )

[0076] (8) Heat seal strength • Creation of heat seal samples Measurements were taken in reference to JIS Z1713. A sample with dimensions MD × TD = 200 × 150 (mm) was prepared. This sample was folded in half along the TD line, covered with a 12 μm PET film, and heat-sealed along the TD line. The sealing conditions were a pressure of 0.2 MPa, a sealing time of 1.0 s, and a sealing temperature of 140°C.

[0077] • Heat seal strength measurement Using an Orientech Tensilon universal tester, the heat-sealed samples prepared above were cut into 15mm wide MD (medium-density) strips and measured as test specimens. The measurement conditions were a chuck distance of 50mm and a tensile speed of 500mm / min. Five measurement points were used, and the weighted average of these five points was defined as the heat-seal strength.

[0078] [Example 1-1] P1 (manufactured by Nippon Polyethylene Co., Ltd., Novatec HD®, grade name HY540) was prepared as the high-density polyethylene resin composition. The density, MFR, and Mw / Mn of P1 are shown in Table 1.

[0079] [Examples 1-2] Q1 (manufactured by Nippon Polyethylene Co., Ltd., Harmolex® registered trademark, grade name NF324A) was prepared as a linear low-density polyethylene resin composition. The density, MFR, MT, Mw / Mn, and SCB index of Q1 are shown in Table 2.

[0080] [Comparative Example 1-1] P2 (manufactured by Nippon Polyethylene Co., Ltd., Harmolex® registered trademark, grade name NF396A) was prepared as the high-density polyethylene resin composition. The density, MFR, and Mw / Mn of P2 are shown in Table 1.

[0081] [Comparative Example 1-2] Q2 (manufactured by Nippon Polyethylene Co., Ltd., Harmolex® registered trademark, grade name NF464A) was prepared as a linear low-density polyethylene resin composition. The density, MFR, MT, Mw / Mn, and SCB index of Q2 are shown in Table 2.

[0082] [Comparative Examples 1-3] Q3 (manufactured by Nippon Polyethylene Co., Ltd., Novatec LL®, grade name UF230) was prepared as a linear low-density polyethylene resin composition. The density, MFR, MT, Mw / Mn, and SCB index of Q3 are shown in Table 2.

[0083] [Comparative Examples 1-4] Q4 (manufactured by Nippon Polyethylene Co., Ltd., Novatec LD®, grade name LF240) was prepared as a linear low-density polyethylene resin composition. The density, MFR, MT, Mw / Mn, and SCB index of Q4 are shown in Table 2.

[0084] [Example 2-1] The raw film was formed using a 5-layer inflation molding machine with the film composition and molding conditions shown in Table 3. This raw film was stretched using an MD 1-axial stretcher at a stretching temperature of 120°C and a stretching ratio of 7 times to obtain a polyethylene stretched base film. The elastic modulus, DDI, and heat seal strength of the polyethylene stretched base film are shown in Table 4.

[0085] [Comparative Example 2-1] The procedure was the same as in Example 2-1, except that the film composition and molding conditions shown in Table 3 were changed and the raw film was molded. The elastic modulus, DDI, and heat seal strength of the polyethylene stretched base film are shown in Table 4.

[0086] [Comparative Example 2-2] The procedure was the same as in Example 2-1, except that the film composition and molding conditions shown in Table 3 were changed and the raw film was molded. The elastic modulus, DDI, and heat seal strength of the polyethylene stretched base film are shown in Table 4.

[0087] [Comparative Example 2-3] The procedure was the same as in Example 2-1, except that the film composition and molding conditions shown in Table 3 were changed and the raw film was molded. The elastic modulus, DDI, and heat seal strength of the polyethylene stretched base film are shown in Table 4.

[0088] [Comparative Example 2-4] The raw film was formed using a single-layer inflation molding machine with the film composition and molding conditions shown in Table 3. This raw film was stretched using an MD1-axial stretcher at a stretching temperature of 120°C and a stretching ratio of 7 times to obtain a polyethylene stretched base film. The elastic modulus, DDI, and heat seal strength of the polyethylene stretched base film are shown in Table 4.

[0089] [Table 1]

[0090] [Table 2]

[0091] [Table 3]

[0092] [Table 4] [Industrial applicability]

[0093] According to the present invention, it is possible to provide a polyethylene stretched substrate film that is excellent in rigidity-strength balance, transparency, and heat resistance. Therefore, the polyethylene stretched substrate film of the present invention can be suitably used as a base material for packaging materials, in particular for polyethylene monomaterial packaging materials in which both the base material and sealant are composed of polyethylene resin compositions.

Claims

1. A polyethylene stretched substrate film for a polyethylene monomaterial resin laminate having at least a polyethylene stretched substrate film and a polyethylene sealant film, wherein the polyethylene stretched substrate film has a layer structure of at least three layers and is a polyethylene resin laminate stretched in at least one direction, and the outermost surface layer (1a) of the polyethylene resin laminate facing the polyethylene sealant and the outermost surface layer (2a) on the opposite side are layers containing a high-density polyethylene resin composition (A), and the intermediate layer is a layer containing a linear low-density polyethylene resin composition (B), wherein (A) and (B) satisfy the following requirements. (A) (a-1) Density of 0.945 to 0.970 g / cm³ ３ (a-2) Melt flow rate (MFR) at a temperature of 190°C and a load of 2.16 kg is 0.1 to 20 g / 10 min (a-3) The molecular weight distribution (Mw / Mn), which is the ratio of the number-average molecular weight (Mn) to the weight-average molecular weight (Mw) obtained from GPC (Gel Permeation Chromatography), is between 1.5 and 10. (B) (b-1) Density of 0.870–0.915 g / cm³ ３ (b-2) MFR at a temperature of 190°C and a load of 2.16 kg is 0.1 to 20 g / 10 min (b-3) The melt tension (MT) determined from the capillary graph is 5.0 g or less. (b-4) The molecular weight distribution (Mw / Mn), which is the ratio of the number-average molecular weight (Mn) to the weight-average molecular weight (Mw) obtained from GPC, is between 1.5 and 10. (b-5) The number of short-chain branches per 1000C calculated by GPC and the SCB index calculated using formula (a) are 1.02 or higher. Formula (a) SCB index = (number of short-chain branches at log 5.2) / (number of short-chain branches at log 4.2)

2. The polyethylene stretched substrate film according to claim 1, characterized in that a polyethylene resin laminate obtained by inflation molding or T-die molding is stretched by five times or more in the mechanical direction (MD).

3. A polyethylene stretched substrate film according to claim 2, characterized in that when the elastic modulus in the mechanical direction (MD) is EM and the elastic modulus in the orthogonal direction (TD) is ET, EM is 1500 MPa or more and ET is 1000 MPa or more.

4. A polyethylene stretched substrate film characterized in that the dirt drop impact test of the polyethylene stretched substrate film according to any one of claims 1 to 3 is 30 g or more.

5. A polyethylene stretched substrate film characterized in that, in a heat seal strength test of the polyethylene stretched substrate film according to any one of claims 1 to 4, the seal strength at a sealing temperature of 140°C is 5 N / 15 mm or less.

6. A polyethylene stretched substrate film according to claim 1, obtained by stretching a polyethylene resin laminate obtained by inflation molding or T-die molding by more than twice its original length in the medium and medium diameters.

7. A resin laminate comprising a layer made of a polyethylene stretched substrate film according to any one of claims 1 to 6.

8. The resin laminate according to claim 7, comprising a layer made of a polyethylene stretched substrate film as described in any one of claims 1 to 6 as a substrate, and a polyethylene sealant film provided on the outermost surface layer (1a) of the polyethylene stretched substrate film.

9. The resin laminate according to claim 7 or 8, characterized in that the layers constituting the resin laminate are all composed of polyethylene-based resin compositions, forming a polyethylene monomaterial resin laminate.

10. A packaging material using a polyethylene stretched base film according to any one of claims 1 to 6.

11. A packaging material using a resin laminate according to any one of claims 7 to 9.

12. A method for producing a polyethylene stretched substrate film according to claim 1, characterized by comprising the steps of obtaining a polyethylene resin laminate by inflation molding or T-die molding, and stretching the obtained polyethylene resin laminate by five times or more in the mechanical direction (MD).

13. A method for producing a polyethylene stretched substrate film according to claim 1, comprising the steps of obtaining a polyethylene resin laminate by inflation molding or T-die molding, and stretching the obtained polyethylene resin laminate by more than twice its original length in the medium diameter and medium diameter.

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