Polyethylene sealant film with excellent balance of rigidity and strength.

Abstract

To provide a polyethylene sealant film which is suitable as a polyethylene sealant film in a polyethylene mono-material packaging material, and a resin laminate using the same and a packaging material.SOLUTION: There are provided a polyethylene sealant film which contains a polyethylene resin composition P having specific ranges of (1) density, (2) a melt flow rate (MFR), (3) a fusion calorie parameter by DSC and (4) an index of the number of short-chain branches (SCB) per 1,000 pieces of carbon atoms (each numeric value range, and definition are described in the specifications), and has a value of dart drop impact of 150 g or more and elastic modulus in a machine direction (MD) of 300 MPa or more; and a polyethylene mono-material resin laminate in which the film is stacked on a polyethylene base material film.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a monomaterial sealant film with excellent rigidity-strength balance for use in resin laminates such as polyethylene monomaterial packaging materials, a polyethylene monomaterial resin laminate containing the monomaterial sealant 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 film is 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 as a result, 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, polyethylene 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] Polyethylene monomaterial packaging materials generally consist of a polyethylene base film and a polyethylene sealant film. In particular, examples of polyethylene monomaterial packaging materials include polyethylene monomaterial packaging materials that use a polyethylene sealant film made of linear low-density polyethylene, which is available on the market (Patent Document 2), and polyethylene monomaterial packaging materials that improve processability during sealing by using a polyethylene resin composition with specific resin properties in the polyethylene sealant film (Patent Document 3). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2009-202519 [Patent Document 2] Japanese Patent Publication No. 2019-166810 [Patent Document 3] Special Publication No. 2020-526412 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, the polyethylene monomaterial packaging materials described above do not use polyester substrate films, which have superior rigidity compared to polyethylene substrate films, nor polyamide substrate films, which have superior strength. As a result, they suffer from a poorer balance of rigidity and strength compared to packaging materials with a more conventional composition, and this problem remains unresolved. For these reasons, there has been a desire for the development of a monomaterial packaging material with a good balance of rigidity and strength among polyethylene monomaterial packaging materials. The object of the present invention is to provide a polyethylene sealant film suitable as a polyethylene sealant film in polyethylene monomaterial packaging materials, and a resin laminate and packaging material using the same. [Means for solving the problem]

[0008] The present inventors conducted extensive research to solve the above problems and discovered that by using a polyethylene resin composition that satisfies specific conditions as a polyethylene sealant, they were able to obtain a monomaterial sealant film or monomaterial resin laminate exhibiting properties that can solve the above problems. Based on these findings, they completed the invention.

[0009] In other words, according to the present invention [1], a polyethylene sealant film for a polyethylene monomaterial resin laminate laminated on a polyethylene substrate film is provided, which contains a polyethylene resin composition P that satisfies the following requirements (1) to (4), and is characterized in that the dirt drop impact (DDI) value is 150 g or more and the elastic modulus in the mechanical direction (MD) is 300 MPa or more. (1) Density of 0.920~0.940 g / cm³ 3 (2) Melt flow rate (MFR) at 190℃ and 2.16kg load is 0.1~10g / 10min (3) In a program that uses a differential scanning calorimeter (DSC) to raise the temperature from 20°C to 200°C at a rate of 40°C / min, hold at 200°C for 5 minutes, then lower the temperature from 200°C to 20°C at a rate of 10°C / min, hold at 20°C for 5 minutes, and then raise the temperature again from 20°C to 200°C at a rate of 10°C / min, if ΔH is the amount of heat of fusion from 40°C to 140°C during the second heating cycle, and ΔH(T) is the amount of heat of fusion from 40°C to T°C, then the temperature T at which ΔH(T) / ΔH = 0.7 is between 118°C and 128°C. (4) The number of short chain branches (SCB) per 1000 carbon atoms calculated by gel permeation chromatography (GPC) is calculated using formula (A), and the SCB index is 1.10 or higher. Equation (A) SCB exponent = (SCB at log5.2) / (SCB at log4.2)

[0010] Furthermore, according to the present invention [2], a polyethylene sealant film is provided which has a multilayer structure of two or more layers and contains the polyethylene resin composition P described in [1] in at least one layer.

[0011] Furthermore, according to the present invention [3], a polyethylene sealant film according to [1] or [2] is provided, characterized in that it has a thickness of 10 to 200 μm.

[0012] Furthermore, according to the present invention [4], a polyethylene sealant film is provided that satisfies EM ≥ 300 MPa and ET ≥ 300 MPa when the elastic modulus in the mechanical direction (MD) is EM and the elastic modulus in the orthogonal direction (TD) is ET.

[0013] Furthermore, according to the present invention [5], a polyethylene monomaterial resin laminate is provided, characterized by comprising at least a polyethylene base film and a polyethylene sealant film as described in any of [1] to [4] above.

[0014] Furthermore, according to the present invention [6], a polyethylene monomaterial resin laminate according to [5] is provided, characterized in that the polyethylene base film is a polyethylene stretched base film made of a polyethylene resin composition.

[0015] Furthermore, according to the present invention [7], a polyethylene monomaterial resin laminate is provided, characterized in that each layer constituting the laminate is a monomaterial resin laminate composed entirely of a polyethylene resin composition, as described in [5] or [6] above.

[0016] Furthermore, according to the present invention [8], a packaging material is provided that uses a polyethylene monomaterial resin laminate as described in any of [5] to [7] above. [Effects of the Invention]

[0017] The polyethylene sealant film of the present invention can provide a sealant film suitable for polyethylene monomer material packaging materials. Further, by using a polyethylene base film and laminating it with the polyethylene sealant film of the present invention, a highly recyclable packaging material, particularly a monomer material laminate and packaging material composed of a single material, can be provided.

Brief Description of the Drawings

[0018] [Figure 1] The results of the DSC measurement of Example 4 are shown. [Figure 2] The results of the GPC measurement of Example 1, Example 4, Example 5, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are shown.

Modes for Carrying Out the Invention

[0019] 1. Polyethylene resin composition The polyethylene resin composition in the present invention is a resin composition used as a raw material for a polyethylene sealant film, which means both a single polyethylene resin or a mixture of polyethylene resins, and additives necessary therefor may be added.

[0020] · Polymerization catalyst and polymerization method of polyethylene resin composition The polyethylene resin constituting the polyethylene resin composition is produced using a conventionally known catalyst such as a Ziegler-Natta catalyst, a Phillips catalyst, a metallocene catalyst, etc., with at least one of ethylene derived from petroleum raw materials, ethylene derived from biomass raw materials, or ethylene obtained by chemical recycling as a raw material. Preferably, it is a Ziegler-Natta catalyst or a metallocene catalyst. Generally, these catalysts are in a state where a complex composed of an organometallic compound is supported on a carrier such as silica or a Mg compound. Polymerization methods include high-pressure methods, solution methods, slurry methods, and gas-phase methods. The high-pressure method uses a radical source such as oxygen or peroxide, or a catalyst consisting of a metal complex, as an initiator. Ethylene, comonomers, and the initiator are added to a reaction vessel, and polymerization is carried out under high temperature and high pressure conditions. Depending on the shape of the reaction vessel, this method can be further divided into tubular and autoclave methods. Solution polymerization is a polymerization method in which the polymer is dissolved in a hydrocarbon solvent at a temperature above the polymer's melting point. Slurry polymerization is a polymerization method in which hydrocarbon compounds such as hexane or isobutane are used as solvents, and the resulting polyethylene exists as a slurry in the solvent. Depending on the shape of the reaction vessel, it is broadly classified into two types: autoclave polymerization and loop pipe polymerization. The gas-phase method is a polymerization method in which ethylene and α-olefin as a comonomer, along with hydrogen as a chain transfer agent, are fed in gaseous form from the bottom of a vertical reaction vessel, and a polymerization catalyst is then added (from Polyethylene Technology Reader, edited by Kazuo Matsuura and Naotaka Mikami). The gas-phase method is preferred as the method for producing the polyethylene resin composition of the present invention.

[0021] 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 P for sealant films that satisfies the requirements of the present invention.

[0022] • Comonomer composition of polyethylene resin composition P The polyethylene resin composition P used in the present invention is an ethylene homopolymer, or a copolymer of ethylene and one or more α-olefins selected from α-olefins having 3 to 18 carbon atoms. The α-olefins having 3 to 18 carbon atoms are preferably those having 3 to 12 carbon atoms, specifically including 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

[0023] ·density The polyethylene resin composition P used in this invention has a density of 0.920 to 0.940 g / cm³. 3 It is essential that the density is within this range. The preferred density is 0.922 to 0.938 g / cm³. 3 It falls within this range. Here, the density is a value measured in accordance with JIS K6922-1 and 2. Density is 0.920 g / cm³ 3 If the density is less than 0.940 g / cm³, the sealant film will have sufficient strength but insufficient rigidity, which is undesirable. On the other hand, a density of 0.940 g / cm³ is undesirable. 3 If it exceeds this value, the sealant film will have sufficient rigidity but insufficient strength, which is undesirable.

[0024] Meltflow Rate (MFR) The polyethylene resin composition P used in this invention must have an MFR in the range of 0.1 to 10 g / 10 min. A preferred MFR is in the range of 0.5 to 8 g / 10 min. If the MFR is less than 0.1 g / 10 min, there is a risk of gel formation, while if the MFR exceeds 10 g / 10 min, the moldability of the sealant film deteriorates, which is undesirable. The MFR is the amount of extrusion measured by extruding molten polymer from a die (length 8 mm, outer diameter 9.5 mm, inner diameter 2.095 mm) at 190°C and a load of 2.16 kg in accordance with JIS K6922-2.

[0025] • Heat of fusion In the present invention, the polyethylene resin composition P is subjected to a program using a differential scanning calorimeter (DSC) in which the temperature is increased from 20°C to 200°C at a rate of 40°C / min, held at 200°C for 5 minutes, then cooled from 200°C to 20°C at a rate of 10°C / min, held at 20°C for 5 minutes, and then increased again from 20°C to 200°C at a rate of 10°C / min. In this program, if ΔH is the amount of heat of fusion from 40°C to 140°C during the second heating cycle, and ΔH(T) is the amount of heat of fusion from 40°C to T°C, then the temperature T at which ΔH(T) / ΔH = 0.7 must be between 118°C and 128°C. If the temperature is below 118°C or above 128°C, the rigidity-strength balance of the polyethylene sealant film deteriorates, which is undesirable.

[0026] ·SCB index The polyethylene resin composition P used in the present invention must have an SCB index of 1.10 or higher. Preferably, it is 1.15 or higher. The SCB index is the value calculated using the following formula (A) for the number of short-chain branches (SCB) per 1000 carbon atoms, which is determined by gel permeation chromatography (GPC). That is, it is the quotient of 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 log5.2) / (number of short chain branches at log4.2)

[0027] • Resin blend The polyethylene resin composition P used in the present invention may be a single resin, or it may be produced by mixing two or more resins to create a polyethylene resin composition P that satisfies the requirements of the present invention, and then used. The polyethylene resin to be mixed may be a virgin resin obtained by homopolymerizing ethylene or copolymerizing ethylene and α-olefin, or a recycled resin obtained by mechanically recycling a product mainly composed of used polyethylene. Examples include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE), but from the viewpoint of film rigidity and strength balance, MDPE, a mixture of HDPE and LLDPE, or a mixture of MDPE and LLDPE are preferred.

[0028] • Additives The polyethylene resin composition P used in 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.

[0029] 2. Polyethylene base film The polyethylene monomaterial resin laminate of the present invention comprises at least a polyethylene base film and a polyethylene sealant film. As the polyethylene base film, a stretched base film or an electron beam crosslinked film can be used, but a stretched base film is preferably used. A stretched substrate film refers to a film obtained by stretching a film made from a polyethylene resin composition using inflation molding or T-die molding, and is used as a substrate for a resin laminate.

[0030] • Polyethylene resin composition to be used The polyethylene resin composition used in the stretched substrate film is not particularly limited, but may be a virgin resin obtained by homopolymerizing ethylene or copolymerizing ethylene and α-olefin, or a recycled resin obtained by mechanically recycling a product mainly composed of used polyethylene. Examples include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE), and may also be a polyethylene resin composition obtained by mixing these. Other polyethylene resin compositions other than polyethylene resin composition P that satisfy the requirements of (1) to (4) above can also be used.

[0031] • Raw material manufacturing method and manufacturing conditions The stretched base 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. Furthermore, it may be a single-layer film using a single polyethylene resin composition, or a multilayer film using multiple polyethylene resin compositions. Furthermore, while the manufacturing conditions for the raw material are not particularly limited, 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.

[0032] ·Stretching method The stretched base film may be either a uniaxially oriented film or a biaxially oriented film. The stretching method can be any of the following: longitudinal uniaxial stretching, transverse uniaxial stretching, sequential biaxial stretching, or simultaneous biaxial stretching.

[0033] • Vertical extension ratio The stretching ratio in the longitudinal direction, i.e., the mechanical direction (MD), of the stretched base film 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 7 times or more. By increasing the stretching ratio in the mechanical direction (MD) of the stretched base film, the strength and heat resistance of the laminate of the present invention can be improved. Furthermore, the printability of the base material can be improved. In addition, the transparency of the base material can be improved, so when an image is formed on the polyethylene sealant film side surface of the base material, its visibility can be improved. On the other hand, there is no particular upper limit to the stretching ratio in the mechanical direction (MD) of the stretched base film, but from the viewpoint of the breaking limit, it is preferable to have a stretching ratio of 15 times or less, and more preferably 10 times or less.

[0034] ·Horizontal stretch ratio The stretching ratio in the transverse direction, i.e., TD, of the stretched substrate film is preferably 1.5 times or more, and more preferably 2 times or more. By setting the stretching ratio of the TD of the 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 printability of the substrate can be improved. In addition, the transparency of the substrate can be improved, so when an image is formed on the polyethylene sealant side surface of the substrate, its visibility can be improved. 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, it is preferable to set it to 10 times or less.

[0035] ·Biaxial stretching ratio When stretching the stretched substrate film to MD and TD, a stretch of 1.5 times or more is preferable for each, and more preferably 2 times or more. By increasing the stretching ratios of the MD and TD of the stretched substrate film, the strength and heat resistance of the laminate of the present invention can be improved. Furthermore, the printability of the substrate can be improved. In addition, the transparency of the substrate can be improved, so when an image is formed on the polyethylene sealant film side surface of the substrate, its visibility can be improved. On the other hand, there is no particular upper limit to the stretching ratios of the MD and TD of the stretched substrate film, but from the viewpoint of the breaking point limit of the stretched substrate 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.

[0036] • Multilayer stretched film The stretched substrate film, which is made of a polyethylene resin composition, may be a multilayer stretched film formed by laminating multiple films together. Suitable resins include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and ultra-low-density polyethylene (ULDPE). Furthermore, the lamination method may involve further stretching of the co-extruded film obtained by co-extrusion molding, or by bonding the films together using an adhesive.

[0037] 3. Polyethylene sealant film • Polyethylene resin composition to be used A polyethylene sealant film is a film characterized by containing a layer (heat-seal layer) made of at least one polyethylene resin composition, which can be sealed by fusion. The polyethylene resin composition that can be used is polyethylene resin composition P, of which at least one satisfies the requirements of the present invention, and may be a virgin resin obtained by homopolymerizing ethylene or copolymerizing ethylene and α-olefin, or a recycled resin obtained by mechanically recycling a product mainly composed of used polyethylene. Examples include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE), and may be a single resin or a mixture of two or more resins.

[0038] • 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, but inflation molding and T-die molding are preferred. The thickness of the polyethylene sealant film is not particularly limited, but it is preferably 10 to 200 μm for the entire film, and more preferably 30 to 180 μm.

[0039] • Elastic modulus The polyethylene sealant film according to the present invention must have an elastic modulus of 300 MPa or higher when EM is the elastic modulus in the mechanical direction (MD). If it is less than 300 MPa, the rigidity of the polyethylene sealant film is low and undesirable. Furthermore, when ET is the elastic modulus in the orthogonal direction (TD), it is preferable that EM ≥ 300 MPa and ET ≥ 300 MPa.

[0040] • Dirt Drop Impact (DDI) The polyethylene sealant film according to the present invention must have a DDI value of 150g or more. Preferably, it is 175g or more, and more preferably 200g or more. If it is 150g or less, the film strength is insufficient and therefore undesirable.

[0041] • Polyethylene sealant film structure The polyethylene sealant film may have a single-layer structure or a multi-layer structure. In the case of a single-layer structure, the polyethylene resin composition P that satisfies the requirements of the present invention may be used alone, or it may be used in combination with other polyethylene resin compositions as long as the effects of the present invention are not impaired. In the case of a multi-layer structure, it is sufficient that the polyethylene resin composition P that satisfies the requirements of the present invention is included in at least one layer. Preferably, in the case of a two-layer structure, the polyethylene resin composition P is included in the inner layer of the heat-seal layer, and in the intermediate layer of a three-layer or more structure. Furthermore, in the case of a multi-layer structure, it is preferable to use the above-mentioned known techniques as long as the requirements of the present invention are not impaired, and to form the film by co-extrusion molding.

[0042] 4. Others The polyethylene monomaterial resin laminate of the present invention refers to a resin laminate in which all or the main component of the layers constituting the resin laminate is composed of polyethylene-based resin. Here, when "polyethylene-based resin" is used herein, it refers to a resin substantially composed of carbon and hydrogen, including ethylene homopolymers and copolymers of ethylene with hydrocarbon monomers such as α-olefins. This resin laminate can be treated as a monomaterial resin laminate composed of a single resin. The proportion of polyethylene-based resin, which is the main component in the resin components of the monomaterial resin laminate is not particularly limited, but is preferably 80% by weight or more, more preferably 90% by weight or more, and even more preferably 100% by weight.

[0043] • Surface treatment It is preferable that the stretched substrate film and 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.

[0044] ·printing Images such as characters, patterns, or symbols may be formed on at least one surface of the stretched substrate film or sealant. It is preferable that the image be formed on the surfaces of the stretched substrate film and the sealant film facing each other, in order to prevent deterioration of the image 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.

[0045] • Vapor-deposited film A vapor-deposited film may be provided on at least one surface of the stretched substrate film or 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.

[0046] Furthermore, the thickness of the deposited film is preferably 1 nm to 150 nm, more preferably 5 nm to 60 nm, and even more preferably 10 nm to 40 nm. By setting the thickness of the vapor-deposited film to 1 nm or more, the oxygen barrier and water vapor barrier properties of the laminate of the present invention can be further improved. Furthermore, by setting the thickness of the vapor-deposited film to 150 nm or less, the occurrence of cracks in the vapor-deposited film can be prevented, and the recyclability of the laminate of the present invention can be improved.

[0047] 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 the water vapor barrier property can be improved. In the present invention, the OD value can be measured in accordance with JIS-K-7361.

[0048] The vapor deposition film can be formed by using a conventionally known method. For example, physical vapor deposition methods (Physical Vapor Deposition method, PVD method) such as vacuum vapor deposition 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.

[0049] 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. As the degree of vacuum in the vapor deposition chamber, before oxygen introduction, about 10 -2 ~10 -8 mbar is preferable, and after oxygen introduction, about 10 -1 ~10 -6 mbar is preferable. The amount of oxygen introduced etc. varies depending on the size of the vapor deposition machine. For the oxygen to be introduced, inert gases such as argon gas, helium gas, and nitrogen gas can be used as carrier gases within a non-obstructive range. The film conveyance speed can be about 10 to 800 m / min.

[0050] The surface of the vapor deposition film is preferably subjected to the above surface treatment. Thereby, the adhesion with an adjacent layer can be improved.

[0051] ·Coat A heat-resistant coating layer or a barrier coating layer may be provided as a coating layer on at least one surface of the stretched substrate film or sealant film, and may include 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.

[0052] 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.

[0053] 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.

[0054] ·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.

[0055] 4. Packaging material 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.

[0056] ·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 heat-sealed layer faces inward, and then heat-sealing the edges. Alternatively, 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.

[0057] • 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.

[0058] 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.

[0059] 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 form the packaging. [Examples]

[0060] 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.

[0061] <Evaluation Method> (1) Density Based on JIS K6922-1 and 2, the molded film was processed into a press sheet, which was then used as the sample for measurement.

[0062] (2) MFR Based on JIS K6922-2, the molded film was measured using a pressed sheet as the sample under conditions of 190°C and a 2.16 kg load.

[0063] (3) Measurement of heat of fusion Measurements were taken using a differential scanning calorimeter (DSC) under the following conditions. [Measurement conditions] Equipment used: Hitachi High-Tech Science EXTAR7000 series high-sensitivity differential scanning calorimeter DSC7020 Measurement method: heat flux type Measurement program: Table 1

[0064] [Table 1]

[0065] • Sample preparation The molded film was used as the sample. Approximately 5 mg of the sample was placed in an aluminum pan, and an aluminum lid was placed over it to seal it. An empty aluminum pan was prepared as a reference sample. • Calculation of heat of fusion For the second scan portion of the DSC curve obtained according to the program in Table 1, straight lines were drawn at two points, 40°C and 140°C, and the heat of fusion ΔH was calculated from the area enclosed by the straight lines and the DSC curve. Next, the heat of fusion ΔH(T) was calculated from the area enclosed by the straight lines and the DSC curve between 40°C and T°C. When the temperature T was varied, the temperature T at which ΔH(T) / ΔH = 0.7 was calculated.

[0066] (4) SCB index 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

[0067] • Sample preparation The molded film was placed in a vial 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 film at 150°C for 2 hours. Heptane was used as a flow marker for pump flow rate correction.

[0068] • 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.

[0069] • 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.

[0070] • Calculation of the 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), and the SCB index was determined. 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 log5.2) / (number of short chain branches at log4.2)

[0071] (5) Measurement of 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%.

[0072] (6) Measurement of 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 it was visually determined whether the film surface ruptured. Five measurements were taken for each dart weight. If the film did not rupture in all five measurements, the dart weight was increased by a certain percentage, and the measurement was repeated. If the film ruptured in all five measurements, the dart weight 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 5 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 / s2)

[0073] [Example 1] We used Harmolex® (registered trademark), grade NF396A, manufactured by Nippon Polyethylene Co., Ltd. A 50 μm film was blown at 190°C with a blow ratio of 2.0. The resin properties, modulus of elasticity, and DDI are shown in Table 2. [Example 2] We prepared two grades, NF396A and NF324A, manufactured by Nippon Polyethylene Co., Ltd., under the product name Harmolex (registered trademark). The procedure was the same as in Example 1, except that NF396A:NF324A was dry-blended in a ratio of 90:10 (by weight). The resin properties, elastic modulus, and DDI are shown in Table 2. [Example 3] The procedure was the same as in Example 2, except that the weight ratio of NF396A:NF324A was set to 80:20. The resin properties, elastic modulus, and DDI are shown in Table 2. [Example 4] The procedure was the same as in Example 2, except that the weight ratio of NF396A:NF324A was set to 70:30. The resin properties, elastic modulus, and DDI are shown in Table 2. [Example 5] We prepared two types of polyethylene products: Novatec® LL, grade UF943, manufactured by Nippon Polyethylene Co., Ltd., and Harmolex®, grade NF324A, also manufactured by Nippon Polyethylene Co., Ltd. UF943 and NF324A were dry-blended in a ratio of 70:30 (by weight), and a 50 μm film was blow-molded at 190°C with a blow ratio of 2.0. The resin properties, modulus of elasticity, and DDI are shown in Table 2.

[0074] [Comparative Example 1] The procedure was the same as in Example 1, except that a product manufactured by Nippon Polyethylene Co., Ltd., trade name Novatec® LL, grade name UF420, was used. The resin properties, elastic modulus, and DDI are shown in Table 2. [Comparative Example 2] The procedure was the same as in Example 1, except that we used Harmolex® (registered trademark), grade NF366A, manufactured by Nippon Polyethylene Co., Ltd. The resin properties, elastic modulus, and DDI are shown in Table 2. [Comparative Example 3] The procedure was the same as in Example 1, except that a product manufactured by Nippon Polyethylene Co., Ltd., trade name Novatec® LL, grade name UF943, was used. The resin properties, elastic modulus, and DDI are shown in Table 2. [Comparative Example 4] The procedure was the same as in Example 5, except that UF943:NF324A = 90:10 (weight ratio). The resin properties, elastic modulus, and DDI are shown in Table 2. [Comparative Example 5] The procedure was the same as in Example 5, except that the weight ratio of UF943:NF324A was set to 80:20. The resin properties, elastic modulus, and DDI are shown in Table 2.

[0075] <Rating> The polyethylene sealant film using the polyethylene resin composition P having the characteristic physical properties of the present invention has an excellent balance of rigidity and strength, as shown in Table 2. Therefore, it is extremely useful as a sealant film for use in monomaterial resin laminates in which both the substrate and the sealant film are composed of the polyethylene resin composition.

[0076] [Table 2] [Industrial applicability]

[0077] According to the present invention, a polyethylene sealant film with an excellent balance of rigidity and strength can be provided. Therefore, the polyethylene sealant film of the present invention is suitable for applications in packaging materials requiring rigidity and strength, and is particularly suitable for applications such as polyethylene monomaterial packaging materials in which both the base material and the sealant are composed of a polyethylene resin composition.

Claims

1. A polyethylene sealant film for a polyethylene monomaterial resin laminate laminated on a polyethylene substrate film, comprising a polyethylene resin composition P that satisfies the following requirements (1) to (4), characterized in that the dirt drop impact (DDI) value is 150 g or more and the elastic modulus in the mechanical direction (MD) is 300 MPa or more. (1) Density of 0.920–0.940 g / cm³ ３ (2) Melt flow rate (MFR) at 190°C and a 2.16 kg load is 0.1 to 10 g / 10 min (3) In a program that uses a differential scanning calorimeter (DSC) to raise the temperature from 20°C to 200°C at a rate of 40°C / min, hold at 200°C for 5 minutes, then lower the temperature from 200°C to 20°C at a rate of 10°C / min, hold at 20°C for 5 minutes, and then raise the temperature again from 20°C to 200°C at a rate of 10°C / min, if ΔH is the amount of heat of fusion from 40°C to 140°C during the second heating cycle, and ΔH(T) is the amount of heat of fusion from 40°C to T°C, then the temperature T at which ΔH(T) / ΔH = 0.7 is between 118°C and 128°C. (4) The number of short chain branches (SCB) per 1000 carbon atoms calculated by gel permeation chromatography (GPC) has an SCB index of 1.10 or higher, calculated using formula (A). Formula (A) SCB index = (SCB at log 5.2) / (SCB at log 4.2)

2. A polyethylene sealant film having a multilayer structure of two or more layers, wherein at least one layer contains the polyethylene resin composition P described in claim 1.

3. A polyethylene sealant film according to claim 1 or 2, characterized in that the overall thickness of the film is 10 to 200 μm.

4. A polyethylene sealant film according to any one of claims 1 to 3, characterized in that when the modulus of elasticity in the mechanical direction (MD) is EM and the modulus of elasticity in the orthogonal direction (TD) is ET, EM ≥ 300 MPa and ET ≥ 300 MPa.

5. A polyethylene monomaterial resin laminate characterized by comprising at least a polyethylene base film and a polyethylene sealant film according to any one of claims 1 to 4.

6. The polyethylene monomaterial resin laminate according to claim 5, characterized in that the polyethylene base film is a polyethylene stretched base film made of a polyethylene resin composition.

7. The polyethylene monomaterial resin laminate according to claim 5 or 6, characterized in that each layer constituting the laminate is a monomaterial resin laminate composed entirely of a polyethylene resin composition.

8. A packaging material using a polyethylene monomaterial resin laminate according to any one of claims 5 to 7.

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