Polyolefin resin film and laminate using the same

Abstract

[Problem] The purpose of the present invention is to provide a laminate of a polyolefin-based resin film and a high-strength base material film such as a biaxially oriented polyamide-based resin film, wherein the laminate has high fracture-resistant bag characteristics and high flex-resistant pinhole properties even while exhibiting high heat seal strength. [Solution] A laminate that includes: a polyolefin-based resin film satisfying conditions 1) to 3) below, the polyolefin-based resin film being formed from a polypropylene-based resin composition containing a propylene-α-olefin random copolymer; and a biaxially stretched nylon film, wherein the laminate satisfies conditions 4) to 6) below. 1) A sealing layer, a core layer, and a laminate layer are included in the stated order. 2) The straight-chain low-density polyethylene content of a polypropylene-based resin composition constituting the seal layer is 3 wt% or less. 3) The straight-chain low-density polyethylene content of a polypropylene-based resin composition constituting the core layer and the laminate layer is 3-50 wt% (inclusive). 4) The number of pinholes after the laminate is flexed 1000 times at 1°C is 35 or less. 5) The piercing strength is 10 N or greater. 6) The heat seal strength of the laminate is 20 N / 15 mm or greater.

Description

[Technical Field]

[0001] The present invention relates to a polyolefin resin film. It also relates to a laminate of a biaxially oriented film made of at least one polymer selected from the group consisting of polyamide resin films, polyester resin films, and polypropylene resin films. [Background technology]

[0002] The packaging is mainly manufactured by heat-sealing (hereinafter referred to as "heat sealing") the periphery of a laminate consisting of a base film such as a polyamide resin film, polyester resin film, or polypropylene resin film and a sealant such as a polyolefin resin film, at a temperature near the melting point of the polyolefin resin film, with the surfaces of the polyolefin resin films in contact with each other.

[0003] These packaging materials are used to wrap and transport a variety of foods, including fresh produce, prepared foods, and confectionery. Using these packaging materials not only allows for efficient delivery of food to consumers, but also slows down spoilage, extending shelf life, and prevents contamination during transportation and storage.

[0004] Polypropylene resin films are inexpensive, and packaging materials made from them have excellent heat-sealing properties, making them widely used as heat-sealing films. Packaging materials require high heat seal strength and tear resistance, and it is also necessary to minimize pinholes caused by bending during transportation. Packaging materials using high-strength films such as biaxially oriented polyamide resin films as the base film are known to have particularly improved heat seal strength and tear resistance.

[0005] However, further performance improvements are required, and efforts are being made to improve the tear resistance properties of heat-seal films.

[0006] Furthermore, a technique is known in which block polypropylene resin is used and polyethylene resin is added (see, for example, Patent Document 1). However, block polypropylene resins had problems such as poor transparency and a high heat-sealing start temperature.

[0007] Therefore, a technique is known in which linear low-density polyethylene is added to a polypropylene resin film (see, for example, Patent Document 2). However, when laminated with a high-strength base film such as a biaxially oriented polyamide resin film, there was a problem with reduced heat seal strength. This problem did not become apparent when a low-strength polypropylene film was used as the base film. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2017-132186 [Patent Document 2] Japanese Patent Publication No. 2020-75400 [Overview of the project] [Problems that the invention aims to solve]

[0009] The present invention aims to provide a laminate of a high-strength base film, such as a biaxially oriented polyamide resin film, and a polyolefin resin film that exhibits high heat seal strength while also having high resistance to bag tearing and bending pinholes.

[0010] As a result of intensive studies to achieve such an object, the present inventors have found that in a polypropylene-based resin film composed of a polypropylene-based resin composition containing a propylene-α olefin random copolymer, by controlling the dispersion state of linear low-density polyethylene, even in a laminate with a high-strength base film such as a biaxially oriented polyamide-based resin film, high heat seal strength is exhibited while the bag breakage resistance and flexural pinhole resistance are improved, leading to the completion of the present invention. That is, the present invention has the following aspects.

[0011] [1] A polyolefin-based resin film composed of a polypropylene-based resin composition containing a propylene-α olefin random copolymer and satisfying the following 1) to 3), and a laminate containing a biaxially stretched nylon film and satisfying the following 4) to 6). 1) It includes a seal layer, a core layer, and a laminate layer in this order. 2) The content of linear low-density polyethylene in the polypropylene-based resin composition constituting the seal layer is 3% by weight or less. 3) The content of linear low-density polyethylene in the polypropylene-based resin composition constituting the core layer and the laminate layer is 3% by weight or more and 50% by weight or less. 4) The number of pinholes after 1000 flexures at 1°C is 35 or less. 5) The puncture strength is 10 N or more. 6) The heat seal strength of the laminate is 20 N / 15 mm or more.

[0012] [2] The laminate according to [1], wherein the Young's modulus in the longitudinal and width directions of the polyolefin-based resin film is 400 MPa or more and 800 MPa or less.

[0013] [3] The laminate according to [1] or [2], wherein the thickness of the polyolefin-based resin film is 15 μm or more and 80 μm or less.

[0014] [4] The density of the linear low-density polyethylene is 910 kg / m 3 or more and 935 kg / m3 A laminate according to any one of [1] to [3], wherein the following conditions are met, and the melt flow rate is 2.0 g / 10 min or more and 7.0 g / 10 min or less.

[0015] [5] The laminate according to any one of [1] to [4], wherein the linear low-density polyethylene is linear low-density polyethylene obtained by polymerizing ethylene, including plant-derived ethylene. [Effects of the Invention]

[0016] The polyolefin resin film of the present invention is suitable for providing a polyolefin resin film that exhibits high heat seal strength while also having high resistance to bag tearing. [Modes for carrying out the invention]

[0017] The present invention will now be described in detail. The polyolefin resin film in the present invention consists of a polypropylene resin composition containing a propylene-α-olefin random copolymer.

[0018] (Seal layer) (Propylene-α-olefin random copolymer) In the present invention, the polypropylene resin composition constituting the sealing layer includes a propylene-α-olefin random copolymer from the viewpoint of heat seal strength. A propylene-α-olefin random copolymer can be a copolymer of propylene and at least one α-olefin having 2 or 4 to 20 carbon atoms other than propylene. Examples of such α-olefin monomers having 2 or 4 to 20 carbon atoms include ethylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, octene-1, etc. For propylene-α-olefin random copolymers, it is preferable to use ethylene as the α-olefin other than propylene, having 2 or 4 to 20 carbon atoms. Furthermore, at least one type is sufficient, and two or more types can be mixed as needed. Particularly preferred are propylene-ethylene-butene random copolymers, where the main monomer is propylene and a certain amount of ethylene and butene are copolymerized. In this report, random copolymers are listed in descending order of their monomer composition ratio.

[0019] The lower limit of the melt flow rate (MFR) of the propylene-α-olefin random copolymer is preferably 0.6 g / 10 min, more preferably 1.0 g / 10 min, and even more preferably 1.2 g / 10 min. Below 0.6 g / 10 min, the uniformity of the film thickness may be impaired. The upper limit of the melt flow rate of the random copolymer is preferably 12.0 g / 10 min, more preferably 9.0 g / 10 min, and even more preferably 8.0 g / 10 min. Specifically, examples include propylene-ethylene random copolymer (Prime PolyPro F-724NPC, manufactured by Prime Polymer Co., Ltd., MFR 7.0g / 10min at 230℃ and a load of 2.16kg, melting point 142℃), propylene-ethylene-butene random copolymer (Sumitomo Noblen FL8115A, manufactured by Sumitomo Chemical Co., Ltd., MFR 7.0g / 10min at 230℃ and a load of 2.16kg, melting point 148℃), propylene-ethylene-butene random copolymer (Prime PolyPro F-794NV, manufactured by Prime Polymer Co., Ltd., MFR 5.7g / 10min at 230℃ and a load of 2.16kg, melting point 134℃), and propylene-ethylene-butene random copolymer (Sumitomo Noblen FL6745A, manufactured by Sumitomo Chemical Co., Ltd., MFR 6.0g / 10min at 230℃ and a load of 2.16kg, melting point 130℃). In terms of heat seal strength, the content of propylene-α-olefin random copolymer in the polypropylene resin composition constituting the seal layer is preferably 94% by weight or more, more preferably 97% by weight or more, even more preferably 99% by weight or more, and particularly preferably 100% by weight.

[0020] (Propylene homopolymer) In the present invention, the slipperiness can be improved by including a propylene homopolymer in the polypropylene resin composition constituting the sealing layer. While there are no particular limitations on the propylene homopolymer used, isotactic polypropylene is preferred from the viewpoint of blocking resistance.

[0021] The melt flow rate (MFR) (measured at 230°C and a load of 2.16 kg) of the above propylene homopolymer is not particularly limited, but is preferably between 1.0 g / 10 min and 10.0 g / 10 min, and more preferably between 2.0 g / min and 8.0 g / min. Below 1 g / 10 min, the viscosity is too high, making extrusion with a T-die difficult. Conversely, above 10 g / 10 min, problems arise such as stickiness of the film and poor impact strength of the film. Specifically, for example, there is the propylene homopolymer FLX80E4 manufactured by Sumitomo Chemical (MFR 7.5 g / 10 min, melting point 164°C). In the polypropylene resin composition constituting the seal layer, the content of propylene homopolymer is preferably 3% by weight or less, more preferably 2% by weight, even more preferably 1% by weight or less, and particularly preferably 0% by weight, from the viewpoint of heat seal strength. If the heat seal layer contains a large amount of polyethylene resin such as linear low-density polyethylene, the heat seal strength may decrease due to poor compatibility between the two.

[0022] (Linear low-density polyethylene) The polypropylene resin composition constituting the seal layer can be improved in terms of its resistance to flexural pinholes by including linear low-density polyethylene. Linear low-density polyethylene can be produced by methods such as the high-pressure method, the solution method, or the gas phase method. Linear low-density polyethylene can be a copolymer of ethylene and at least one α-olefin having 3 or more carbon atoms. The α-olefin can be any α-olefin generally referred to as such, and is preferably an α-olefin having 3 to 12 carbon atoms, such as propylene, butene-1, hexene-1, octen-1, or 4-methyl-1-pentene. Examples of copolymers of ethylene and α-olefins include ethylene-hexene-1 copolymer, ethylene-butene-1 copolymer, and ethylene-octen-1 copolymer, with ethylene-hexene copolymer being preferred from the viewpoint of resistance to flexural pinholes.

[0023] (Plant-derived linear low-density polyethylene) Linear low-density polyethylene may contain plant-derived linear low-density polyethylene, which is obtained by polymerizing ethylene derived from plants such as sugarcane with α-olefins such as ethylene derived from fossil fuels such as petroleum or plants. Plant-derived linear low-density polyethylene has almost the same physical properties as fossil fuel-derived linear low-density polyethylene, but from the standpoint of carbon neutrality, it has the effect of reducing carbon dioxide emissions and can suppress global warming. The lower limit of the plant-derived ethylene content in plant-derived linear low-density polyethylene is preferably 50%, and more preferably 80%. A content of 50% or more provides a good carbon dioxide reduction effect. The upper limit is preferably 98%, and more preferably 96%. If it exceeds 98%, the ratio of α-olefin copolymerized decreases, and the resistance to flexural pinholes decreases.

[0024] The lower limit of the MFR (measured at 190 °C and 2.18 kg) of linear low-density polyethylene is preferably 1.0 g / 10 min, more preferably 2.0 g / 10 min. The upper limit is preferably 7.0 g / min, more preferably 5.0. By setting it within the above range, the compatibility with polypropylene-based resins is good and high seal strength can be obtained.

[0025] The lower limit of the density of linear low-density polyethylene is preferably 910 kg / m 3 and more preferably 913 kg / m 3 . By setting it to 910 kg / m 3 or more, good antiblocking properties can be obtained. The upper limit is 935 kg / m 3 and more preferably 930 kg / m 3 . By setting it to 930 kg / m 3 or more and less than this value, good bag breakage resistance can be obtained. Specifically, for example, Braskem's ethylene-hexene copolymer (plant-derived linear low-density polyethylene) SLH218 (MFR 2.3 g / min, density 916 kg / m 3 , melting point 126 °C) and Sumitomo Chemical's ethylene-hexene copolymer (fossil fuel-derived linear low-density polyethylene) FV405 (MFR 4.0 g / min, density 923 kg / m 3 , melting point 118 °C), etc. In terms of heat seal strength, the content of linear low-density polyethylene in the polypropylene-based resin composition constituting the seal layer is preferably 3% by weight or less, more preferably 2% by weight, still more preferably 1% by weight or less, and particularly preferably 0% by weight. Since the slipperiness depends greatly on the addition amount of additives such as antiblocking agents and organic lubricants, adding linear low-density polyethylene to the seal layer does not change much.

[0026] (Additive) The polyolefin resin composition constituting the sealing layer of the present invention may contain an antiblocking agent. While one type of antiblocking agent may be used, incorporating two or more inorganic particles with different particle sizes and shapes allows for the formation of complex protrusions even on the uneven surface of the film, resulting in a more advanced antiblocking effect. The antiblocking agent to be added is not particularly limited, but inorganic particles such as spherical silica, amorphous silica, zeolite, talc, mica, alumina, hydrotalcite, and aluminum borate, as well as organic particles such as polymethyl methacrylate and ultra-high molecular weight polyethylene, can be added. The antiblocking agent contained in the polypropylene resin composition constituting the sealing layer is preferably 3000 ppm or less, and more preferably 2500 ppm or less, relative to the polyolefin resin of the layer to which it is added. By setting it to 3000 ppm or less, the shedding of the antiblocking agent can be reduced. Furthermore, it is preferably 500 ppm or more, and more preferably 1000 ppm or more. By setting it to 500 ppm or more, good antiblocking properties can be obtained.

[0027] The polyolefin resin composition may contain an organic lubricant. This improves the lubricity and anti-blocking effect of the laminated film, and improves the handling of the film. This is thought to be because the organic lubricant bleeds out and remains on the film surface, resulting in the lubricating and release effects. Organic lubricants are preferably those with a melting point above room temperature. Examples of organic lubricants include fatty acid amides and fatty acid esters. Specifically, these include oleamide, erucamide, behenamide, ethylenebisoleamide, hexamethylenebisoleamide, and ethylenebisoleamide. While these can be used individually, using two or more in combination is preferable because it maintains lubricity and anti-blocking effects even in harsh environments. The organic lubricant in the polypropylene resin composition is preferably 1500 ppm or less, and more preferably 1000 ppm or less, relative to the polyolefin resin. A concentration of 1500 ppm or less makes blocking less likely to occur even when stored in high-temperature environments such as warehouses in the summer. Furthermore, a concentration of 200 ppm or more is preferable, and more preferably 250 ppm or more. A concentration of 200 ppm or more provides good lubricity.

[0028] The polyolefin resin composition constituting the sealing layer of the present invention may, as necessary and without impairing the purpose of the present invention, contain appropriate amounts of antioxidants, antistatic agents, antifogging agents, neutralizing agents, nucleating agents, colorants, other additives, and inorganic fillers in any layer. Antioxidants can be used in combination with phenolic and phosphite-based antioxidants, or individually with a molecule containing both phenolic and phosphite-based skeletons. Calcium stearate can be used as a neutralizing agent.

[0029] (Core layer) (Propylene-α-olefin random copolymer) In the present invention, the polypropylene resin composition constituting the core layer includes a propylene-α-olefin random copolymer from the viewpoint of heat seal strength. A propylene-α-olefin random copolymer can be a copolymer of propylene and at least one α-olefin having 2 or 4 to 20 carbon atoms other than propylene. Examples of such α-olefin monomers having 2 or 4 to 20 carbon atoms include ethylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, octene-1, etc. For propylene-α-olefin random copolymers, ethylene is used as the α-olefin other than propylene, due to its heat-sealability, and the carbon atoms number are 2 or 4-20. It is preferable to do so. Furthermore, at least one type is sufficient, and two or more types can be mixed and used as needed. Particularly preferred is a propylene-ethylene-butene random copolymer in which the main monomer is propylene and a certain amount of ethylene and butene are copolymerized. In this report, the monomers constituting the random copolymer are named and described in order of decreasing monomer composition ratio.

[0030] The lower limit of the melt flow rate (MFR) of the propylene-α-olefin random copolymer in the core layer is preferably 0.6 g / 10 min, more preferably 1.0 g / 10 min, and even more preferably 1.2 g / 10 min. At 0.6 g / 10 min, the uniformity of the film thickness may be impaired. The upper limit of the melt flow rate of the random copolymer is preferably 12.0 g / 10 min, more preferably 9.0 g / 10 min, and even more preferably 8.0 g / 10 min. Specifically, examples include propylene-ethylene random copolymer (Prime PolyPro F-724NPC, manufactured by Prime Polymer Co., Ltd., MFR 7.0g / 10min at 230℃ and a load of 2.16kg, melting point 142℃), propylene-ethylene-butene random copolymer (Sumitomo Noblen FL8115A, manufactured by Sumitomo Chemical Co., Ltd., MFR 7.0g / 10min at 230℃ and a load of 2.16kg, melting point 148℃), propylene-ethylene-butene random copolymer (Prime PolyPro F-794NV, manufactured by Prime Polymer Co., Ltd., MFR 5.7g / 10min at 230℃ and a load of 2.16kg, melting point 134℃), and propylene-ethylene-butene random copolymer (Sumitomo Noblen FL6745A, manufactured by Sumitomo Chemical Co., Ltd., MFR 6.0g / 10min at 230℃ and a load of 2.16kg, melting point 130℃). The content of propylene-α-olefin random copolymer in the polypropylene resin composition constituting the core layer is preferably 25% by weight or more, more preferably 40% by weight or more, even more preferably 60% by weight or more, particularly preferably 75% by weight or more, and particularly preferably 80% by weight or more, from the viewpoint of heat seal strength. From the viewpoint of resistance to flexural pinholes, it is preferably 97% by weight or less, more preferably 90% by weight or less, and even more preferably 85% by weight or less.

[0031] (Propylene homopolymer) In the present invention, the heat resistance can be improved by including a propylene homopolymer in the polypropylene resin composition that constitutes the core layer. As the propylene homopolymer used, isotactic polypropylene, which has high crystallinity and suppresses deterioration of the thermal shrinkage rate, is preferred.

[0032] The melt flow rate (MFR) (measured at 230°C and a load of 2.16 kg) of the above propylene homopolymer is not particularly limited, but is preferably between 1.0 g / 10 min and 10.0 g / 10 min, and more preferably between 2.0 g / min and 8.0 g / min. Below 1 g / 10 min, the viscosity is too high, making extrusion with a T-die difficult. Conversely, above 10 g / 10 min, problems arise such as stickiness of the film and poor impact strength of the film. Specifically, for example, there is the propylene homopolymer FLX80E4 manufactured by Sumitomo Chemical (MFR 7.5 g / 10 min, melting point 164°C). The content of propylene homopolymer in the polypropylene resin composition constituting the core layer is preferably 30% by weight or more, and more preferably 40% by weight or more, from the viewpoint of heat resistance. From the viewpoint of heat seal strength and tear resistance, it is preferably 50% by weight or less, more preferably 30% by weight or less, even more preferably 10% by weight or less, and particularly preferably 0% by weight. Since the lubricity largely depends on the amount of additives such as antiblocking agents and organic lubricants added, adding linear low-density polyethylene to the core layer does not significantly change its properties.

[0033] (Linear low-density polyethylene) The polypropylene resin composition constituting the core layer can be improved in terms of resistance to flexural pinholes by including linear low-density polyethylene. Linear low-density polyethylene can be produced by manufacturing methods such as the high-pressure method, solution method, or gas-phase method. Linear low-density polyethylene can be a copolymer of ethylene and at least one α-olefin having 3 or more carbon atoms. The α-olefin can be any α-olefin generally referred to as such, and is preferably an α-olefin having 3 to 12 carbon atoms, such as propylene, butene-1, hexene-1, octene-1, or 4-methyl-1-pentene. Examples of copolymers of ethylene and α-olefins include ethylene-hexene-1 copolymer, ethylene-butene-1 copolymer, and ethylene-octene-1 copolymer, with ethylene-hexene copolymer being preferred from the viewpoint of resistance to flexural pinholes.

[0034] (Plant-derived linear low-density polyethylene) Linear low-density polyethylene may contain plant-derived linear low-density polyethylene, which is obtained by polymerizing ethylene derived from plants such as sugarcane with α-olefins such as ethylene derived from fossil fuels such as petroleum or plants. Plant-derived linear low-density polyethylene has almost the same physical properties as fossil fuel-derived linear low-density polyethylene, but from the standpoint of carbon neutrality, it has the effect of reducing carbon dioxide emissions and can suppress global warming. The lower limit of the plant-derived ethylene content in plant-derived linear low-density polyethylene is preferably 50%, more preferably 80%. A content of 50% or more provides a good carbon dioxide reduction effect. The upper limit is preferably 98%, more preferably 96%. If it exceeds 98%, the ratio of α-olefin copolymerized decreases, and the resistance to flexural pinholes decreases.

[0035] The lower limit of the MFR (measured at 190°C, 2.18 kg) of linear low-density polyethylene is preferably 1.0 g / 10 min, more preferably 2.0 g / 10 min. The upper limit is preferably 7.0 g / min, more preferably 5.0 g / min. By keeping it within the above range, good compatibility with polypropylene resins and high seal strength can be obtained.

[0036] The lower limit of the density of linear low-density polyethylene is preferably 910 kg / m³. 3 More preferably, 913 kg / m 3 It is 910 kg / m 3 By doing so, good resistance to blocking can be obtained. The upper limit is 935 kg / m 3 More preferably, 930 kg / m 3 It is 930 kg / m 3 Good tear resistance can be obtained by meeting the above and below conditions. Specifically, for example, Braschem's ethylene-hexene copolymer (plant-derived linear low-density polyethylene) SLH218 (MFR 2.3 g / min, density 916 kg / m³) 3 (melting point 126℃) and Sumitomo Chemical's ethylene-hexene copolymer (fossil fuel-derived linear low-density polyethylene) FV405 (MFR 4.0g / min, density 923kg / m³) 3 Examples include, , with a melting point of 118°C. In the polypropylene resin composition constituting the core layer, the content of linear low-density polyethylene is preferably 3% by weight or more, more preferably 8% by weight or more, even more preferably 12% by weight or more, and particularly preferably 15% by weight or more, in terms of flexural pinhole resistance. In terms of heat resistance, it is preferably 50% by weight or less, more preferably 40% by weight or less, even more preferably 30% by weight or less, and particularly preferably 25% by weight or less.

[0037] (Additives) The polyolefin resin composition constituting the core layer of the present invention may contain an antiblocking agent. The antiblocking agent to be added is not particularly limited, but inorganic particles such as spherical silica, amorphous silica, zeolite, talc, mica, alumina, hydrotalcite, and aluminum borate, as well as organic particles such as polymethyl methacrylate and ultra-high molecular weight polyethylene, can be added. The antiblocking agent contained in the polypropylene resin composition constituting the core layer is preferably 3000 ppm or less, more preferably 2500 ppm or less, even more preferably 1000 ppm or less, and particularly preferably 500 ppm or less, relative to the polyolefin resin of the layer to which it is added.

[0038] The polyolefin resin composition may contain an organic lubricant. This improves the lubricity and anti-blocking effect of the laminated film, and improves the handling of the film. This is thought to be because the organic lubricant bleeds out and remains on the film surface, resulting in the lubricating and release effects. Organic lubricants are preferably those with a melting point above room temperature. Examples of organic lubricants include fatty acid amides and fatty acid esters. Specifically, these include oleamide, erucamide, behenamide, ethylenebisoleamide, hexamethylenebisoleamide, and ethylenebisoleamide. While these can be used individually, using two or more in combination is preferable because it maintains lubricity and anti-blocking effects even in harsh environments. The organic lubricant in the polypropylene resin composition is preferably 1500 ppm or less, and more preferably 1000 ppm or less, relative to the polyolefin resin. A concentration of 1500 ppm or less makes blocking less likely to occur even when stored in high-temperature environments such as warehouses in the summer. Furthermore, a concentration of 200 ppm or more is preferable, and more preferably 250 ppm or more. A concentration of 200 ppm or more provides good lubricity.

[0039] The polyolefin resin composition constituting the core layer of the present invention may optionally contain appropriate amounts of antioxidants, antistatic agents, antifogging agents, neutralizing agents, nucleating agents, colorants, other additives, and inorganic fillers in any layer, as long as the objectives of the present invention are not impaired. Antioxidants can be used in combination with phenolic and phosphite-based antioxidants, or individually with a molecule containing both phenolic and phosphite-based skeletons. Calcium stearate can be used as a neutralizing agent.

[0040] (Laminate layer) (Propylene-α-olefin random copolymer) In the present invention, the polypropylene resin composition constituting the laminate layer includes a propylene-α-olefin random copolymer from the viewpoint of heat seal strength. A propylene-α-olefin random copolymer can be a copolymer of propylene and at least one α-olefin having 2 or 4 to 20 carbon atoms other than propylene. Examples of such α-olefin monomers having 2 or 4 to 20 carbon atoms include ethylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, octene-1, etc. For propylene-α-olefin random copolymers, it is preferable to use ethylene as the α-olefin other than propylene, having 2 or 4 to 20 carbon atoms. Furthermore, at least one type is sufficient, and two or more types can be mixed as needed. Particularly preferred are propylene-ethylene-butene random copolymers, where the main monomer is propylene and a certain amount of ethylene and butene are copolymerized. In this report, random copolymers are listed in descending order of their monomer composition ratio.

[0041] The lower limit of the melt flow rate (MFR) of the propylene-α-olefin random copolymer is preferably 0.6 g / 10 min, more preferably 1.0 g / 10 min, and even more preferably 1.2 g / 10 min. At 0.6 g / 10 min, the uniformity of the film thickness may be impaired. The upper limit of the melt flow rate of the random copolymer is preferably 12.0 g / 10 min, more preferably 9.0 g / 10 min, and even more preferably 8.0 g / 10 min. Specifically, examples include propylene-ethylene random copolymer (Prime PolyPro F-724NPC, manufactured by Prime Polymer Co., Ltd., MFR 7.0g / 10min at 230℃ and a load of 2.16kg, melting point 142℃), propylene-ethylene-butene random copolymer (Sumitomo Noblen FL8115A, manufactured by Sumitomo Chemical Co., Ltd., MFR 7.0g / 10min at 230℃ and a load of 2.16kg, melting point 148℃), propylene-ethylene-butene random copolymer (Prime PolyPro F-794NV, manufactured by Prime Polymer Co., Ltd., MFR 5.7g / 10min at 230℃ and a load of 2.16kg, melting point 134℃), and propylene-ethylene-butene random copolymer (Sumitomo Noblen FL6745A, manufactured by Sumitomo Chemical Co., Ltd., MFR 6.0g / 10min at 230℃ and a load of 2.16kg, melting point 130℃). The content of propylene-α-olefin random copolymer in the polypropylene resin composition constituting the laminate layer is preferably 25% by weight or more, more preferably 40% by weight or more, even more preferably 60% by weight or more, particularly preferably 75% by weight or more, and particularly preferably 80% by weight or more, from the viewpoint of heat seal strength. From the viewpoint of resistance to bending pinholes, it is preferably 90% by weight or less, more preferably 85% by weight or less, even more preferably 80% by weight or less, particularly preferably 75% by weight or less, and particularly preferably 70% by weight or less.

[0042] (Propylene homopolymer) In the present invention, the heat resistance can be improved by including a propylene homopolymer in the polypropylene resin composition that constitutes the seal laminate layer. As the propylene homopolymer to be used, isotactic polypropylene, which has high crystallinity and suppresses deterioration of the thermal shrinkage rate, is preferred.

[0043] The melt flow rate (MFR) (measured at 230°C and a load of 2.16 kg) of the above propylene homopolymer is not particularly limited, but is preferably between 1.0 g / 10 min and 10.0 g / 10 min, and more preferably between 2.0 g / min and 8.0 g / min. Below 1 g / 10 min, the viscosity is too high, making extrusion with a T-die difficult. Conversely, above 10 g / 10 min, problems arise such as stickiness of the film and poor impact strength of the film. Specifically, for example, there is the propylene homopolymer FLX80E4 manufactured by Sumitomo Chemical (MFR 7.5 g / 10 min, melting point 164°C). The content of propylene homopolymer in the polypropylene resin composition constituting the laminate layer is preferably 30% by weight or more, more preferably 40% by weight or more, and particularly preferably 50% by weight or more, from the viewpoint of heat resistance. From the viewpoint of heat seal strength and resistance to bending pinholes, it is preferably 70% by weight or less, more preferably 65% ​​by weight or less, even more preferably 30% by weight or less, and particularly preferably 0% by weight.

[0044] (Linear low-density polyethylene) By including linear low-density polyethylene in the polypropylene resin composition that constitutes the laminate layer, the resistance to flexural pinholes can be improved. The resistance to flexural pinholes is dramatically improved when linear low-density polyethylene is also included in the film surface layer compared to when it is only included in the core layer. Linear low-density polyethylene can be produced by manufacturing methods such as the high-pressure method, solution method, and gas-phase method. Linear low-density polyethylene can be a copolymer of ethylene and at least one α-olefin having 3 or more carbon atoms. The α-olefin can be any α-olefin generally referred to as such, and is preferably an α-olefin having 3 to 12 carbon atoms, such as propylene, butene-1, hexene-1, octene-1, or 4-methyl-1-pentene. Examples of copolymers of ethylene and α-olefins include ethylene-hexene-1 copolymer, ethylene-butene-1 copolymer, and ethylene-octene-1 copolymer, with ethylene-hexene copolymer being preferred from the viewpoint of resistance to flexural pinholes.

[0045] (Plant-derived linear low-density polyethylene) Linear low-density polyethylene may contain plant-derived linear low-density polyethylene, which is obtained by polymerizing ethylene derived from plants such as sugarcane with α-olefins such as ethylene derived from fossil fuels such as petroleum or plants. Plant-derived linear low-density polyethylene has almost the same physical properties as fossil fuel-derived linear low-density polyethylene, but from the standpoint of carbon neutrality, it has the effect of reducing carbon dioxide emissions and can suppress global warming. The lower limit of the plant-derived ethylene content in plant-derived linear low-density polyethylene is preferably 50%, more preferably 80%. A content of 50% or more provides a good carbon dioxide reduction effect. The upper limit is preferably 98%, more preferably 96%. If it exceeds 98%, the ratio of α-olefin copolymerized decreases, and the resistance to flexural pinholes decreases.

[0046] The lower limit of the MFR (measured at 190°C, 2.18 kg) of linear low-density polyethylene is preferably 1.0 g / 10 min, more preferably 2.0 g / 10 min. The upper limit is preferably 7.0 g / min, more preferably 5.0 g / min. By keeping it within the above range, good compatibility with polypropylene resins and high seal strength can be obtained.

[0047] The lower limit of the density of linear low-density polyethylene is preferably 910 kg / m³. 3 More preferably, 913 kg / m 3 It is 910 kg / m 3 By doing so, good resistance to blocking can be obtained. The upper limit is 935 kg / m 3 More preferably, 930 kg / m 3 It is 930 kg / m 3 The above conditions result in good tear resistance. Specifically, for example, Braschem's ethylene-hexene copolymer (plant-derived linear low-density polyethylene) SLH218 (MFR 2.3 g / min, density 916 kg / m³) 3 (melting point 126℃) and Sumitomo Chemical's ethylene-hexene copolymer (fossil fuel-derived linear low-density polyethylene) FV405 (MFR 4.0g / min, density 923kg / m³) 3 Examples include, , with a melting point of 118°C. In the polypropylene resin composition constituting the laminate layer, the linear low-density polyethylene content is preferably 3% by weight or more, more preferably 8% by weight or more, even more preferably 15% by weight or more, particularly preferably 20% by weight or more, and most preferably 25% by weight or more, in terms of flexural pinhole resistance. In terms of heat resistance and heat seal strength, it is preferably 50% by weight or less, more preferably 40% by weight or less, and even more preferably 30% by weight or less. Since the slipperiness largely depends on the amount of additives such as antiblocking agents and organic lubricants added, adding linear low-density polyethylene to the laminate layer does not change it much.

[0048] (Additives) The polyolefin resin composition constituting the laminate layer of the present invention may contain an antiblocking agent. While one type of antiblocking agent may be used, incorporating two or more inorganic particles with different particle sizes and shapes allows for the formation of complex protrusions even on the uneven surface of the film, resulting in a more advanced antiblocking effect. The antiblocking agent to be added is not particularly limited, but inorganic particles such as spherical silica, amorphous silica, zeolite, talc, mica, alumina, hydrotalcite, and aluminum borate, as well as organic particles such as polymethyl methacrylate and ultra-high molecular weight polyethylene, can be added. The antiblocking agent contained in the polypropylene resin composition constituting the laminate layer is preferably 3000 ppm or less, more preferably 2500 ppm or less, even more preferably 1000 ppm or less, particularly preferably 500 ppm or less, and most preferably 200 ppm or less, relative to the polyolefin resin of the layer to which it is added. Setting it to 3000 ppm or less can reduce the shedding of the antiblocking agent from the surface of the laminate layer. The polyolefin resin composition may contain an organic lubricant. This improves the lubricity and anti-blocking effect of the laminated film, and improves the handling of the film. This is thought to be because the organic lubricant bleeds out and remains on the film surface, resulting in the lubricating and release effects.

[0049] Organic lubricants are preferably those with a melting point above room temperature. Examples of organic lubricants include fatty acid amides and fatty acid esters. Specifically, these include oleamide, erucamide, behenamide, ethylenebisoleamide, hexamethylenebisoleamide, and ethylenebisoleamide. While these can be used individually, using two or more in combination is preferable because it maintains lubricity and anti-blocking effects even in harsh environments. The organic lubricant in the polypropylene resin composition is preferably 1500 ppm or less, more preferably 1000 ppm or less, particularly preferably 500 ppm or less, and particularly preferably 200 ppm or less, relative to the polyolefin resin. By setting it to 1500 ppm or less, blocking is less likely to occur even when stored in places exposed to high temperatures, such as warehouses in the summer.

[0050] The polyolefin resin composition constituting the laminate layer of the present invention may, as necessary and without impairing the objectives of the present invention, contain appropriate amounts of antioxidants, antistatic agents, antifogging agents, neutralizing agents, nucleating agents, colorants, other additives, and inorganic fillers in any layer. Antioxidants can be used in combination with phenolic and phosphite-based antioxidants, or individually with a molecule containing both phenolic and phosphite-based skeletons. Calcium stearate can be used as a neutralizing agent.

[0051] (Polyolefin resin film) The polyolefin resin film of the present invention has a laminated structure, comprising a seal layer, a core layer, and a laminate layer in that order. The sealing layer and laminating layer are located on the surface side of the film, while the core layer is located between them. The laminate layer is a layer suitable for bonding a base film such as a biaxially oriented polyamide film, and in practice, it is preferable to laminate it with the base film via an adhesive resin. The sealing layer is a layer suitable for manufacturing a package by overlapping two of the laminates so that the polyolefin resin film of the resulting laminate is on the inside and then heat-sealing them.

[0052] In the polyolefin resin film of the present invention, it is preferable that the difference in the content of linear low-density polyethylene in the polypropylene resin composition constituting the seal layer and the core layer is 1% by weight or more and 18% by weight or less. More preferably, the difference in concentration of linear low-density polyethylene between the seal layer and the core layer is 15 parts by weight or less, even more preferably 10% by weight or less, and particularly preferably 8% by weight or less. By keeping the difference in content at 18% by weight or less, high interlayer strength at the interface between the seal layer and the core layer can be maintained, and high heat seal strength can be obtained.

[0053] In the polyolefin resin film of the present invention, it is preferable that the difference in the content of linear low-density polyethylene in the polypropylene resin composition constituting the core layer and the laminate layer is 1% by weight or more and 18% by weight or less. More preferably, the difference in concentration of linear low-density polyethylene between the seal layer and the core layer is 15 parts by weight or less, even more preferably 10% by weight or less, and particularly preferably 8% by weight or less. By keeping the difference in content at 18% by weight or less, high interlayer strength at the interface between the seal layer and the core layer can be maintained, and high heat seal strength can be obtained.

[0054] In the polyolefin resin film of the present invention, it is preferable that the content of linear low-density polyethylene in the polypropylene resin composition constituting the core layer is greater than the content of linear low-density polyethylene in the polypropylene resin composition constituting the seal layer, and that the content of linear low-density polyethylene in the polypropylene resin composition constituting the laminate layer is greater than the content of linear low-density polyethylene in the polypropylene resin composition constituting the core layer. This makes it easier for the linear low-density polyethylene to be uniformly dispersed in the film, which is advantageous in terms of resistance to bending pinholes. In addition, a high proportion of polypropylene resin near the heat-seal surface allows for high heat-seal strength.

[0055] Furthermore, by using a low-melting-point propylene-α-olefin random copolymer for the sealing layer and a high-melting-point propylene-α-olefin random copolymer for the layers and laminate layers, it is possible to improve heat seal strength while also enhancing heat resistance and resistance to bending pinholes.

[0056] It is preferable that the surface of the laminate layer of the polyolefin resin film of the present invention be activated by corona treatment or the like. This improves the lamination strength with the base film.

[0057] The lower limit of the thickness of the polyolefin resin film of the present invention is preferably 15 μm, more preferably 20 μm, and even more preferably 25 μm. When the thickness is 15 μm or more, heat seal strength and tear resistance are easily obtained. The upper limit of the film thickness is preferably 80 μm, more preferably 70 μm, even more preferably 65 μm, even more preferably 60 μm, and particularly preferably 50 μm. A thickness of 80 μm or less makes the film less stiff and easier to process, as well as facilitates the production of suitable packaging.

[0058] (Method for manufacturing polyolefin resin film) The present invention allows for the molding of polyolefin resin films using methods such as the inflation method and the T-die method, but the T-die method is preferred for enhancing transparency. While the inflation method uses air as a cooling medium, the T-die method uses a cooling roll, making it an advantageous manufacturing method for increasing the cooling rate. By increasing the cooling rate, crystallization of the unstretched sheet can be suppressed, resulting in improved transparency. For these reasons, the T-die method produces unoriented sheets.

[0059] The raw materials for the polypropylene resin compositions for the seal layer, core layer, and laminate layer were mixed separately and melt-mixed and extruded in separate extruders. The molten laminated sheets of the seal layer, core layer, and laminate layer were cast from a T-die onto a cooling roll to obtain an unoriented sheet. The lower limit of the cooling roll temperature is preferably 15°C, more preferably 20°C. If it is below this temperature, condensation may occur on the cooling roll, resulting in insufficient adhesion. The upper limit of the cooling roll temperature is preferably 60°C, more preferably 50°C. If it exceeds this temperature, transparency may deteriorate.

[0060] By adding pellets made from recycled semi-finished products and finished product films generated during the manufacturing process to the core layer, the resin can be reused without compromising heat seal strength, bending pinhole resistance, or tear resistance.

[0061] (Properties of polyolefin resin films) (Hayes) The lower limit of the haze of the polyolefin resin film of the present invention is preferably 1.0%, more preferably 2.0%, even more preferably 2.5%, and particularly preferably 3.0%. If it is 1.0% or higher, the unevenness of the film surface is not extremely low, so internal blocking of the package is less likely to occur. The upper limit of haze is preferably 20.0%, more preferably 15.0%, even more preferably 10.0%, even more preferably 8% or less, and particularly preferably 6% or less. A haze level of 20.0% or less makes it easier to obtain visibility of the packaging. Linear low-density polyethylene has high crystallinity and tends to increase haze, but the increase in haze can be suppressed if the addition is within the above preferred range.

[0062] (Static friction coefficient) The upper limit of the static friction coefficient of the polyolefin resin film of the present invention is preferably 0.70, more preferably 0.50, and even more preferably 0.40. When it is 0.70 or less, the non-slip surfaces slide easily when filling the packaging with food or when opening it, resulting in a smooth opening of the packaging. The lower limit of the static friction coefficient of the individual film is preferably 0.10, more preferably 0.15, even more preferably 0.20, even more preferably 0.25, and particularly preferably 0.30. A coefficient of 0.10 or higher makes it less likely for the rolled film to unravel when transported.

[0063] (Young's modulus) The lower limit of the Young's modulus (longitudinal direction) of the polyolefin resin film of the present invention is preferably 200 MPa, more preferably 300 MPa, even more preferably 400 MPa, even more preferably 500 MPa, and particularly preferably 600 MPa. If it is less than 200 MPa, it may be too weak and difficult to process. The upper limit of the Young's modulus (longitudinal direction) is preferably 1000 MPa, more preferably 800 MPa, and even more preferably 750 MPa. Films with a Young's modulus exceeding 1000 MPa are brittle, which may result in poor tear resistance. The lower limit of the Young's modulus (width direction) of the polyolefin resin film of the present invention is preferably 200 MPa, more preferably 300 MPa, even more preferably 400 MPa, even more preferably 500 MPa, and particularly preferably 600 MPa. Below 200 MPa, the film may be too weak and difficult to process. The upper limit of the Young's modulus (width direction) is preferably 1000 MPa, more preferably 800 MPa, and even more preferably 750 MPa. Films exceeding 1000 MPa are brittle, which may worsen their tear resistance. Adding a small amount of linear low-density polyethylene to a polypropylene resin film increases the Young's modulus.

[0064] (Impact strength) The lower limit of the impact strength of the polyolefin resin film of the present invention is preferably 0.20 J, more preferably 0.25 J, even more preferably 0.30 J, and more preferably 0.55 J. Setting the impact strength to 0.20 J or higher improves the drop-tear resistance of the packaging. An impact strength of 1.0 J is sufficient. Impact strength largely depends on the thickness and molecular orientation of the film. Furthermore, impact strength and drop-tear resistance do not necessarily correlate.

[0065] (Accelerated blocking strength) The lower limit of the accelerated blocking strength of the polyolefin resin film of the present invention is preferably 20 mN / 70 mm, more preferably 30 mN / 70 mm, and even more preferably 36 mN / 70 mm. A strength of 20 mN / 70 mm or higher makes it easier to obtain a firm film. The upper limit of the accelerated blocking strength is preferably 100 mN / 70 mm, more preferably 80 mN / 70 mm, even more preferably 70 mN / 70 mm, and particularly preferably 60 mN / 70 mm. A strength of 100 mN / 70 mm or lower makes it less likely for blocking to occur on the inner surface of the packaging. Adding linear low-density polyethylene to the core layer and laminate layer suppresses deterioration of the accelerated blocking strength.

[0066] (Piercing strength) The lower limit of the puncture strength of the polyolefin resin film of the present invention is preferably 1.0 N, more preferably 1.2 N, even more preferably 1.5 N, and even more preferably 1.7 N. A thickness of 1.0 μm or more results in good puncture pinhole resistance of the laminate. A puncture strength of 5.0 N / μm is excellent, and 3.0 N / μm is good. Puncture strength depends greatly on the orientation of the film, so it does not change much by changing the resin alone.

[0067] (Film surface orientation coefficient) The lower limit of the surface orientation coefficient of the film is preferably 0.000, more preferably 0.001. It is difficult to manufacture a film with a coefficient lower than the above. The upper limit of the surface orientation of the film is 0.010, more preferably 0.008, and even more preferably 0.006 or less. If it is higher than the above, the film may be stretched unevenly, and the uniformity of its thickness may deteriorate.

[0068] (Heat seal start temperature) The lower limit of the heat seal initiation temperature for the polyolefin resin film of the present invention is preferably 110°C, more preferably 120°C. A temperature of 110°C or higher results in a firmer texture and easier handling. The upper limit of the heat seal initiation temperature is 150°C, more preferably 10°C, and even more preferably 130°C. A temperature of 150°C or lower allows for high-speed production of the packaging, offering economic advantages. The heat seal initiation temperature is greatly influenced by the melting point of the seal layer. Therefore, if linear low-density polyethylene is used for the core layer and laminate layer, changes in the heat seal temperature can be suppressed.

[0069] (Wetting tension) The lower limit of the wet tensile strength of the surface of the polyolefin resin film of the present invention that is laminated with at least one film selected from the group consisting of polyamide resin film, polyester resin film, and polypropylene resin film is preferably 30 mN / m, and more preferably 35 mN / m. If it is 30 mN / m or higher, the lamination strength is less likely to decrease. The upper limit of the wet tensile strength is preferably 55 mN / m, and more preferably 50 mN / m. If it is 55 mN / m or lower, blocking between films is less likely to occur when the polyolefin resin film is wound onto a roll.

[0070] (Laminate structure and manufacturing method) The laminate using the polyolefin resin film of the present invention is a laminate in which the polyolefin resin film is used as a sealant and laminated with at least one film selected from the group consisting of polyamide resin film, polyester resin film, and polypropylene resin film. Furthermore, as a known technique, these base films may be coated or vapor-deposited to impart adhesiveness or barrier properties, or aluminum foil may be further laminated. Specifically, examples include biaxially oriented (polyethylene terephthalate) PET film / aluminum foil / sealant, biaxially oriented (polyethylene terephthalate) PET film / biaxially oriented nylon film / sealant, biaxially oriented nylon film / sealant, biaxially oriented polypropylene film / sealant, and biaxially oriented (polyethylene terephthalate) PET film / biaxially oriented nylon film / aluminum foil / sealant. Biaxially oriented nylon film has higher strength compared to other base films, resulting in higher sealing strength for laminates. The biaxially oriented nylon film to be used is preferably a biaxially oriented film made of nylon 6 and nylon 66, and the thickness is preferably in the range of 15 to 30 μm. By using the polyolefin resin film of the present invention as a sealant, the heat sealability, tear resistance, and pinhole resistance of the laminate can be improved. Known lamination methods such as dry lamination and extrusion lamination can be used, and any lamination method is acceptable.

[0071] This section describes the properties of laminates. (Resistance to bending and pinholes) The bending resistance can be measured by gelbopinhole evaluation. The upper limit of the number of pinholes after the laminate of the present invention is subjected to 1000 bending cycles at 1°C is preferably 35, more preferably 30, even more preferably 25, and particularly preferably 20. If the number is 35 or less, pinholes are less likely to occur due to bending impact during the transportation of the package. A pinhole count of around 10 is considered excellent.

[0072] (Piercing strength) The lower limit of the puncture strength of the laminate of the present invention is preferably 10N, more preferably 12N, and even more preferably 14N. If it is 10N or higher, pinholes are less likely to occur when a protrusion comes into contact with the packaging. The upper limit of the puncture strength is preferably 45N, more preferably 30N, and even more preferably 25N. If it is 45N or lower, the laminate is not too stiff and is easy to handle. The puncture strength depends largely on the orientation of the film, so it does not change much by changing the resin alone.

[0073] (Heat seal strength) The lower limit of the heat seal strength of the laminate of the present invention is preferably 20 N / 15 mm, more preferably 25 N / 15 mm, and even more preferably 30 N / 15 mm. A heat seal strength of 20 N / 15 mm or higher is likely to provide good tear resistance. A heat seal strength of 60 N / 15 mm is excellent, and 35 N / 15 mm is sufficient.

[0074] (packaging) The laminated material, arranged to surround the contents of food products and other items for the purpose of protecting them from dust, gases, and other elements in the natural environment, is called packaging. Packaging is manufactured by cutting out the laminated material, bonding the inner surfaces together using a heated heat sealing bar or ultrasonic waves, and forming a bag. For example, a four-sided sealed bag made by stacking two rectangular laminated materials with the sealant side facing inward and heat-sealing all four sides is widely used. The contents may be food products, but may also be other products such as daily necessities, and the shape of the packaging may also be other than rectangular, such as a standing pouch or pillow packaging.

[0075] This section describes the characteristics of the packaging material. (drop resistance) The lower limit of the drop-tear resistance of a laminated packaging body using the present invention is preferably 12 times or more, more preferably 15 times or more, even more preferably 20 times or more, even more preferably 22 times or more, and particularly preferably 24 times or more. If it is 12 times or more, even if the packaging body containing food is accidentally dropped, tear is unlikely to occur. Drop-tear resistance of about 30 times is sufficient. The drop-tear resistance of the packaging is influenced by the bending pinhole resistance, puncture strength, and heat seal strength of the laminate, and it is desirable to keep these properties within a favorable range. [Examples]

[0076] The present invention will be described in detail below with reference to examples, but is not limited to these. The characteristics obtained in each example were measured and evaluated by the following methods. During evaluation, the film flow direction in the film manufacturing process was defined as the longitudinal direction, and the direction perpendicular to the flow direction was defined as the width direction.

[0077] (1) Resin density The density was evaluated according to Method D (density gradient tube) of JIS K7112:1999. Measurements were taken with N=3, and the average value was calculated.

[0078] (2) Melt Flow Rate (MFR) Based on JIS K-7210-1, measurements were performed at 230°C and a load of 2.16 kg for propylene-α-olefin random copolymers and propylene homopolymers, and at 190°C and a load of 2.16 kg for linear low-density polyethylene. Measurements were performed with N=3, and the average value was calculated.

[0079] (3) Melting point The melting point was defined as the temperature of the maximum melting peak in the DSC curve of the resin, obtained using a Shimadzu Differential Scanning Calorimeter DSC-60 manufactured by Shimadzu Corporation. The starting temperature was 30°C, the heating rate was 5°C / min, and the ending temperature was 180°C. Measurements were taken with N=3, and the average value was calculated.

[0080] (4) Hayes Haze was measured according to JIS K7136. Measurements were taken for N=3 on polyolefin resin films before lamination, and the average value was calculated.

[0081] (5) Static friction coefficient The sealing layers of the films were overlapped, and measurements were taken using a universal tensile testing machine STM-T-50BP (manufactured by Toyo Baldwin) in accordance with JIS K7125. Samples were cut to a size of 200 mm in the longitudinal direction and 80 mm in the width direction using the following three methods, and measurements were taken.

[0082] (6) Young's modulus The tensile strength in the longitudinal and widthwise directions was measured at 23°C in accordance with JIS-K7127. The Young's modulus (initial tensile modulus) was calculated at that time. Measurements were taken with N=3, and the average value was calculated.

[0083] (7) Surface orientation coefficient The density was evaluated in accordance with the refractive index measurement method for chemical products, JIS K0062:1999. Measurements were taken with N=3, and the average value was calculated. The surface orientation coefficient was calculated using Equation 1. Surface orientation coefficient = (Nx + Ny) / 2 - Nz (Equation 1) Nx: Refractive index in the longitudinal direction Ny: Refractive index in the width direction Nz: Refractive index in the thickness direction

[0084] (8) Wetting tension The wet tensile strength of the laminate layer surface was measured in accordance with JIS-K6768 Plastics - Films and Sheets - Wet Tension Test Method.

[0085] (9) Impact resistance (J) The measurement was performed at 23°C using a Toyo Seiki film impact tester.

[0086] (10) Accelerated blocking strength A polyolefin resin film was cut to a length of 148 mm and a width of 105 mm. The sealed sides were placed facing each other and stacked. After preheating at 50°C for 30 minutes, the samples were sandwiched between 7.0 cm square aluminum plates maintained at 50°C. Using a Toyo Seiki Mfg. Co., Ltd. mini test press MP-SCH, the aluminum plates and samples were pressed at 50°C and 100 kN and held for 15 minutes. The removed samples were cut to a width of 70 mm. The stacked samples were opened by 30 mm and a 3 mm diameter metal rod was inserted parallel to the width. The samples were mounted on a Shimadzu Corporation Autograph AG-I and the load applied when the metal rod was moved at a speed of 200 mm / min in the longitudinal direction was measured. Measurements were taken with N=3 and the average value was calculated.

[0087] (11)Piercing strength The puncture strength of polyolefin resin films and laminates was measured at 23°C in accordance with "2. Strength Test Methods" of "Standards and Specifications for Foods, Additives, etc., Article 3: Utensils and Containers and Packaging" (Ministry of Health and Welfare Notification No. 20 of 1982) under the Food Sanitation Act. A needle with a tip diameter of 0.7 mm was pierced into the film at a piercing speed of 50 mm / min, and the strength at which the needle penetrated the film was measured. Measurements were taken with N=3, and the average value was calculated.

[0088] (12) Heat seal start temperature The heat-sealing start temperature of polyolefin resin film was measured in accordance with JIS Z 1713 (2009). The film was cut into rectangular test pieces (for heat sealing) measuring 50 mm x 250 mm (width x length). Two test pieces were placed side-by-side at the sealing layers, and a thermal gradient tester (heat seal tester) manufactured by Toyo Seiki Seisakusho Co., Ltd. was used. The heat sealing pressure was set to 0.2 MPa, and the heat sealing time to 1.0 sec. The heat sealing was then performed under conditions where the temperature was increased in 5°C increments. After heat sealing, the test pieces were cut to a width of 15 mm. The heat-sealed test pieces were opened to 180°, and the unsealed portion was clamped in a chuck to peel off the sealed portion. The temperature at which the heat seal strength reached 4.9 N was then determined. An Instron Instruments 5965 universal material tester was used. The test speed was 200 mm / min. Measurements were taken with N=5, and the average value was calculated.

[0089] (13) Resistance to bending pinholes A laminate of polyolefin resin film was cut to a length of 280 mm and a width of 260 mm. It was then shaped into a cylinder with a diameter of 89 mm and a height of 260 mm, with the polyolefin resin film facing inward, and secured with cellophane tape. The sample was mounted on a Gelboflex tester with a constant temperature chamber, manufactured by Tester Sangyo Co., Ltd., and subjected to 1000 bending cycles at 1°C. The sample was removed, and the number of pinholes was measured. Measurements were taken with N=3, and the average value was calculated.

[0090] (14) Heat seal strength The heat sealing and strength measurement conditions were as follows: The polyolefin resin film sides of the laminates obtained in the examples and comparative examples were overlapped, and heat-sealed at a pressure of 0.2 MPa for 1 second with a sealing bar width of 10 mm and a heat sealing temperature of 160°C, and then allowed to cool. Test pieces measuring 80 mm in the longitudinal direction and 15 mm in the width direction were cut from the heat-sealed films at each temperature, and the peel strength was measured when the heat-sealed portion was peeled off at a crosshead speed of 200 mm / min for each test piece. The testing machine used was an Instron Instruments 5965 universal material tester. Measurements were performed N=3 times for each case, and the average value was calculated.

[0091] (15) Drop and tear resistance A laminate was cut out, and a four-sided sealed bag with internal dimensions of 170 mm (length) x 120 mm (width) was prepared by sealing it with 200 ml of saturated saline solution. The heat sealing conditions were 0.2 MPa pressure for 1 second, a seal bar width of 10 mm, and a heat sealing temperature of 160°C. After bag making, the ends of the four-sided sealed bag were trimmed to a seal width of 5 mm. Next, the bag was left in an environment of +5°C for 8 hours, and under these conditions, the four-sided sealed bag was dropped from a height of 1.2 m onto a flat concrete floor with the surface horizontal. The dropping was repeated until the bag ruptured, and the number of repeated drops was measured. This was repeated for 20 samples, and the average value was calculated.

[0092] (Example 1) (Polyolefin resin film) For the polypropylene resin film of Example 1, the raw materials were prepared based on the resin composition and proportions of each layer shown in Tables 1 and 2 below. Using 100 parts by weight of the prepared materials for each layer listed in Tables 1 and 2, 360 ppm of behenamide was added to the seal layer as an organic lubricant, and 2000 ppm of silica with an average particle size of 4 μm was added as an inorganic antiblocking agent in a masterbatch. 2700 ppm of behenamide was added to the core layer as an organic lubricant in a masterbatch.

[0093] (Materials used in the sealing layer) PP-1: Sumitomo Chemical's propylene-ethylene-butene random copolymer FL6745A (MFR 6.0g / 10min, melting point 130℃) LL-1: Braschem ethylene-hexene copolymer (plant-derived linear low-density polyethylene) SLH218 (MFR 2.3 g / min, density 916 kg / m³) 3 (Melting point 126℃) Silica particles: Amorphous silica KMP130-4 manufactured by Shin-Etsu Chemical Co., Ltd. (average particle size 4μm) Organic lubricant: Behenin amide BNT-22H manufactured by Nippon Seika Co., Ltd.

[0094] (Materials used in the core layer) PP-2: Sumitomo Chemical's propylene-ethylene-butene random copolymer FL8115A (MFR 7.0g / 10min, melting point 148℃) PP-3: Sumitomo Chemical's propylene homopolymer FLX80E4 (MFR 7.5g / 10min, melting point 164℃) LL-1: Braschem ethylene-hexene copolymer (plant-derived linear low-density polyethylene) SLH218 (MFR 2.3 g / min, density 916 kg / m³) 3 (Melting point 126℃) LL-2: Sumitomo Chemical's ethylene-hexene copolymer (fossil fuel-derived linear low-density polyethylene) FV405 (MFR 4.0 g / min, density 923 kg / m³) 3 (Melting point 118℃) LDPE-1: Braschem-made ethylene-hexene copolymer (plant-derived low-density polyethylene) SLH818 (MFR 8.1 g / min, density 918 kg / m³) 3 ) Organic lubricant: Behenin amide BNT-22H manufactured by Nippon Seika Co., Ltd.

[0095] (Materials used in the laminate layer) PP-2: Sumitomo Chemical's propylene-ethylene-butene random copolymer FL8115A (MFR 7.0g / 10min, melting point 148℃) PP-3: Sumitomo Chemical's propylene homopolymer FLX80E4 (MFR 7.5g / 10min, melting point 164℃) LL-1: Braschem ethylene-hexene copolymer (plant-derived linear low-density polyethylene) SLH218 (MFR 2.3 g / min, density 916 kg / m³) 3 (Melting point 126℃) LL-2: Sumitomo Chemical's ethylene-hexene copolymer (fossil fuel-derived linear low-density polyethylene) FV405 (MFR 4.0 g / min, density 923 kg / m³) 3 (Melting point 118℃) LDPE-1: Braschem-made ethylene-hexene copolymer (plant-derived low-density polyethylene) SLH818 (MFR 8.1 g / min, density 918 kg / m³) 3 ) These raw materials are mixed uniformly in the proportions shown in Tables 1 and 2, and polyolefin resin is used. A mixed raw material for manufacturing a lipid film was obtained.

[0096] (Melting extrusion) The mixed raw materials for the intermediate layer were introduced using a 3-stage single-screw extruder with a screw diameter of 90 mm, while the mixed raw materials for the heat seal layer and the laminate layer were introduced using 3-stage single-screw extruders with diameters of 65 mm and 45 mm, respectively. The materials were introduced in the order of heat seal layer / intermediate layer / laminate layer, and introduced into a T-slot type die with a width of 800 mm and two stages of pre-landing, and the shape of the stepped section was curved to ensure uniform flow of molten resin within the die. The die outlet temperature was 230°C for extrusion. The thickness ratios of the laminate layer / intermediate layer / heat seal layer were 25% / 50% / 25%, respectively.

[0097] (cooling) The molten resin sheet emerging from the die was cooled on a cooling roll at 35°C to obtain an unstretched polyolefin resin film with a thickness of 30 μm or more. During cooling on the cooling roll, both ends of the film on the cooling roll were fixed with air nozzles, and the entire width of the molten resin sheet was pressed against the cooling roll with an air knife. Simultaneously, a vacuum chamber was applied to prevent air from being trapped between the molten resin sheet and the cooling roll. The air nozzles were installed in series at both ends in the direction of film travel. The die was surrounded with a sheet to prevent air from hitting the molten resin sheet. In addition, the direction of the vacuum chamber's suction port was aligned with the direction of travel of the extruded sheet. Furthermore, the die was surrounded with a sheet to prevent air from hitting the molten resin sheet.

[0098] (Corona treatment) Corona treatment applied to the surface of the laminate layer of the film (power density 20W·min / m²) 2 ) was applied.

[0099] (winding up) The film deposition was carried out at a rate of 20 m / min. The edges of the deposited film were trimmed, and the film was rolled up and wound.

[0100] (Creation of a laminate) The polyolefin resin film obtained in the examples and comparative examples, along with a biaxially oriented nylon film (manufactured by Toyobo Co., Ltd., N1102, 15 μm thick) as a base film, were mixed with 33.6 parts by mass of a main agent (manufactured by Toyo Morton Co., Ltd., TM569), 4.0 parts by mass of a curing agent (manufactured by Toyo Morton Co., Ltd., CAT10L), and 62.4 parts by mass of ethyl acetate to obtain an ester-based adhesive, which was applied at a rate of 3.0 g / m². 2 The material was applied to a base film and dry-laminated. This was then wound up and aged at 40°C for 3 days to obtain a laminate.

[0101] (Example 2) In Example 1, a polyolefin resin film was obtained using the same method as in Example 1, except that the raw materials shown in Tables 1 and 2 were used and the thickness of the unstretched polyolefin resin film was 60 μm. A laminate was obtained in the same manner as in Example 1.

[0102] (Examples 3 to 7) In Example 1, a 30 μm polyolefin resin film was obtained using the raw materials shown in Tables 1 and 2, in the same manner. A laminate was obtained in the same manner as in Example 1.

[0103] (Comparative Examples 1-4, 6-7) In Example 1, a 30 μm polyolefin resin film was obtained using the raw materials shown in Tables 1 and 2, in the same manner. A laminate was obtained in the same manner as in Example 1.

[0104] (Comparative Example 5) In Example 1, a single-layer 30 μm polyolefin resin film was obtained using the same method as in Example 1, using the raw materials shown in Tables 1 and 2 and an extruder with only a core layer. A laminate was obtained in the same manner as in Example 1.

[0105] In Comparative Example 1, because linear low-density polyethylene was not added to the core layer or laminate layer, the bag exhibited inferior resistance to drop-induced rupture and resistance to bending-induced pinholes.

[0106] In Comparative Examples 2 and 3, the difference in linear low-density polyethylene content between the seal layer and the core layer was large, resulting in inferior heat seal strength.

[0107] In Comparative Example 4, the heat seal strength was inferior due to the high content of linear low-density polyethylene in the seal layer.

[0108] In Comparative Example 5, because a large amount of linear low-density polyethylene was contained throughout the entire film, a large amount of linear low-density polyethylene was contained near the film surface, resulting in inferior heat seal strength.

[0109] In Comparative Example 6, although the core layer contained linear low-density polyethylene, the laminate layer did not contain linear low-density polyethylene, resulting in inferior resistance to flexural pinholes.

[0110] In Comparative Example 7, the heat seal strength was inferior because high-pressure low-density polyethylene (LDPE) was added as polyethylene.

[0111] The results are shown in Tables 1 and 2.

[0112] [Table 1]

[0113] [Table 2] [Industrial applicability]

[0114] The present invention provides a polyolefin resin film that exhibits excellent low-temperature sealing properties and high heat-seal strength, while also possessing high resistance to bag breakage and bending pinholes, even when laminated with a high-strength substrate such as a biaxially oriented polyamide resin film, thereby making a significant contribution to industry.

Claims

1. A laminate comprising a polyolefin resin film made of a polypropylene resin composition containing a propylene-α-olefin random copolymer that satisfies the following 1) to 4), and a biaxially oriented nylon film, wherein the laminate satisfies the following 5) to 7). 1) It includes a seal layer, a core layer, and a laminate layer in that order. 2) The content of linear low-density polyethylene in the polypropylene resin composition constituting the sealing layer is 3% by weight or less. 3) The polypropylene resin composition constituting the core layer and the laminate layer contains 3% by weight or more and 50% by weight or less linear low-density polyethylene. 4) The linear low-density polyethylene content in the polypropylene resin composition constituting the core layer is greater than the linear low-density polyethylene content in the polypropylene resin composition constituting the seal layer. 5) The number of pinholes after 1000 bends at 1°C is 35 or less. 6) The puncture strength is 10N or higher. 7) The heat seal strength of the laminate is 20 N / 15 mm or more.

2. The laminate according to claim 1, wherein the Young's modulus of the polyolefin resin film in the longitudinal and width directions is 400 MPa or more and 800 MPa or less.

3. The laminate according to claim 1 or 2, wherein the thickness of the polyolefin resin film is 15 μm or more and 80 μm or less.

4. The density of the aforementioned linear low-density polyethylene is 910 g / m³. ３ Above, 935g / m ３ The laminate according to any one of claims 1 to 3, wherein the melt flow rate is 2.0 g / 10 min or more and 7.0 g / 10 min or less.

5. The laminate according to any one of claims 1 to 4, wherein the linear low-density polyethylene is linear low-density polyethylene obtained by polymerizing ethylene containing plant-derived ethylene.

6. The laminate according to any one of claims 1 to 5, wherein the polypropylene resin composition constituting the sealing layer contains 94% by weight or more of a propylene-α-olefin random copolymer.

7. The laminate according to any one of claims 1 to 6, wherein the content of linear low-density polyethylene in the polypropylene resin composition constituting the laminate layer is greater than the content of linear low-density polyethylene in the polypropylene resin composition constituting the core layer.

8. The laminate according to any one of claims 1 to 7, wherein the content of linear low-density polyethylene in the polypropylene resin composition constituting the laminate layer is 12% by weight or more and 50% by weight or less.

9. A packaging body using the laminate according to any one of claims 1 to 8.

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