Polyethylene-based resin film, laminate, and package

Abstract

Provided is a polyethylene-based resin film that has excellent scratch resistance, heat sealability, blocking resistance, and slipperiness, and is unlikely to wrinkle even when being transported by rolling a film roll. The polyethylene-based resin film has, on a surface layer thereof, a heat seal layer comprising a polyethylene-based resin composition, and has on the other surface layer thereof, a laminate layer comprising a polyethylene-based resin composition. The surface layers satisfy conditions 1) to 4). 1) Containing 1,900-16,000 ppm of particles formed from a spherical polyethylene-based resin having an average particle diameter of 9 μm or greater. 2) Containing 3,100-15,000 ppm of spherical particles having an average particle diameter of less than 9 μm. 3) The total content of spherical inorganic particles having an average particle diameter of 9 μm or greater and spherical crosslinked organic particles having an average particle diameter of 9 μm or greater is 1,000 ppm or less. 4) The content of non-spherical particles is 2,500 ppm or less.

Description

Polyethylene resin film, laminate, and packaging material

[0001] The present disclosure relates to a polyethylene-based resin film, a polyethylene-based resin film, a laminate, and a package.

[0002] Packaging materials are used to package and transport a variety of foods, including fresh produce, prepared foods, and confectionery. Using packaging materials not only efficiently delivers food to consumers, but also delays food spoilage, extending its shelf life, and preventing the introduction of debris during transportation and storage. Packaging materials are manufactured by laminating multiple films. Sealant films are typically laminated with a base film. When stored in roll form after lamination with these base films, blocking can occur between the sealant film and the base film, making it difficult to unwind the laminate film before bag-making. Blocking can also occur between the sealant films that form the inner surface of the bag during bag-making, making it difficult to fill the food. To address this issue, a polyethylene-based resin film incorporating inorganic fine powders or inorganic particles, such as silica, has been reported (Patent Document 1). However, this technology suffers from insufficient scratch resistance, resulting in scratches on the film when processing the film roll using an automatic packaging machine, reducing the visibility of the contents.

[0003] Also known is a polyethylene resin film containing particles made of polyethylene resin as an antiblocking agent added to the polyethylene resin film (Patent Documents 2 and 3).

[0004] Patent No. 6467825 International Publication No. 2020 / 217931 International Publication No. 2020 / 217932

[0005] When transporting film rolls from a manufacturing plant to a use plant, they are packaged to prevent damage during transportation. While this packaging process is sometimes performed manually, it is increasingly being performed partially or entirely automatically using automatic packaging machines and the like to reduce costs. The inventors' research has revealed that wrinkles occur when film rolls are rolled and transported using automatic packaging machines and the like. Furthermore, the inventors' research has revealed that when a film roll wound up in a slitting process is transported horizontally to a packaging process, the roll is sometimes rolled because it moves back and forth and side to side. However, when pushing or stopping the roll, external forces are applied to parts of the roll body, which reduces the slipperiness of the film in the areas where the force is applied.

[0006] Therefore, an object of the present invention is to provide a polyethylene resin film that is excellent in scratch resistance, heat sealing property, blocking resistance and slipperiness, and that is less likely to wrinkle even when transported by rolling a film roll.

[0007] As a result of extensive research to achieve this object, the inventors have found that by controlling the particle size and content of the spherical particles made of polyethylene-based resin and the spherical inorganic particles, a special surface structure can be formed on at least one surface, resulting in improved slipperiness and suppressing wrinkles when the film roll is rolled and transported, while also improving scratch resistance and suppressing scratches caused by rubbing between the inner surfaces of the bag when used as a package. This makes it possible to suppress fine scratches on, for example, the contents of food, and to prevent the food from losing its flavor. In one or more embodiments, the polyethylene-based resin film, laminate, or package has any of the following configurations.

[0008] [1] A polyethylene-based resin film having a heat-sealable layer made of a polyethylene-based resin composition as one surface layer and a laminate layer made of a polyethylene-based resin composition as the other surface layer, wherein at least one surface layer satisfies the following 1) to 4): 1) It contains 1,900 ppm to 16,000 ppm of spherical particles made of a polyethylene-based resin having an average particle size of 9 μm or more. 2) It contains 3,100 ppm to 15,000 ppm of spherical particles having an average particle size of less than 9 μm. 3) The total content of spherical inorganic particles having an average particle size of 9 μm or more and spherical crosslinked organic particles having an average particle size of 9 μm or more is 1,000 ppm or less. 4) The content of non-spherical particles is 2,500 ppm or less. [2] The polyethylene-based resin film according to [1], wherein the weighted average density of the polyethylene-based resin composition constituting the heat-sealable layer is lower than the weighted average density of the polyethylene-based resin composition constituting the laminate layer. [3] The polyethylene resin film according to [1] or [2], wherein the spherical particles made of polyethylene resin having an average particle size of 9 μm or more have a viscosity-average molecular weight of 1.5 million to 2.5 million. [4] The polyethylene resin composition constituting the laminate layer has a weighted average density of 910 kg / m ３ More than 945kg / m ３ or less, and the weighted average density of the polyethylene resin composition constituting the heat seal layer is 900 kg / m ３ More than 930kg / m ３ [5] The polyethylene-based resin film according to any one of [1] to [3], wherein one or more core layers are present between the heat seal layer and the laminate layer, and the weighted average density of the polyethylene-based resin composition constituting the core layer is 910 kg / m or less. ３ More than 930kg / m ３[6] The polyethylene-based resin film according to any one of [1] to [5], wherein the polyethylene-based resin contained in the polyethylene-based resin composition constituting the laminate layer and the polyethylene-based resin contained in the polyethylene-based resin composition constituting the heat-sealable layer are linear low-density polyethylenes. [7] The polyethylene-based resin film according to any one of [1] to [6], wherein the arithmetic mean roughness SRa of at least one surface of the laminate layer and the heat-sealable layer is 60 nm or more and 200 nm or less, and the maximum height SRmax of at least one surface of the laminate layer and the heat-sealable layer is 2 μm or more and 9 μm or less. [8] The polyethylene-based resin film according to any one of [1] to [7], wherein 1) the average particle size of the spherical particles made of polyethylene-based resin is 20 μm or less, and 2) the average particle size of the spherical particles is 3 μm or more. [9] The polyethylene-based resin film according to any one of [1] to [8], wherein 3) the total content of spherical particles having an average particle size of 9 μm or more is 1000 ppm or less.

[10] 2) The polyethylene-based resin film according to any one of [1] to [9], wherein the spherical particles are inorganic particles.

[11] The polyethylene-based resin film according to any one of [1] to

[10] , wherein the heat-sealable layer satisfies the above 1) to 4).

[12] A laminate comprising at least one film selected from the group consisting of a uniaxially oriented polyolefin-based resin film, a biaxially oriented polyolefin-based resin film, a uniaxially oriented polyamide-based resin film, a biaxially oriented polyamide-based resin film, a uniaxially oriented polyester-based resin film, and a biaxially oriented polyester-based resin film, and the polyolefin-based resin film according to any one of [1] to

[11] .

[13] A packaging product comprising the laminate according to

[12] .

[0009] The above-described constitution provides a polyethylene-based resin film that is excellent in scratch resistance, heat sealing property, blocking resistance, and slip property. Such a polyethylene-based resin film is suitable for use as a non-stretched polyethylene-based resin film that is resistant to wrinkles even when transported by rolling a film roll.

[0010] In one or more embodiments, the polyethylene-based resin film has a heat-sealable layer made of a polyethylene-based resin composition on one surface layer and a laminate layer made of a polyethylene-based resin composition on the other surface layer, and at least one of the surface layers satisfies the following 1) to 4). At least one of the surface layers satisfies the following 1) to 4). "At least one of the surface layers satisfies the following 1) to 4)" means that one surface layer, the other surface layer, or one surface layer and the other surface layer satisfy the following 1), 2), 3), and 4). It is preferable that the heat-sealable layer on one surface layer satisfies the following 1) to 4). 1) It contains 1900 ppm to 16000 ppm of spherical particles made of a polyethylene-based resin and having an average particle size of 9 μm or more. 2) It contains 3100 ppm to 15000 ppm of spherical particles having an average particle size of less than 9 μm. 3) The total content of spherical inorganic particles having an average particle size of 9 μm or more and spherical crosslinked organic particles having an average particle size of 9 μm or more is 1000 ppm or less. 4) The content of non-spherical particles is 2500 ppm or less.

[0011] The polyethylene resin film according to one or more embodiments will be described in detail below.

[0012] (Polyethylene Resin Film) The polyolefin resin film has a laminate layer on one surface layer and a heat-seal layer on the other surface layer. The heat-seal layer and the laminate layer are layers located on the surface side of the film, and the polyolefin resin film may have one or more core layers between them. The laminate layer is a layer suitable for bonding a substrate film such as a uniaxially oriented or biaxially oriented polyamide film, and is preferably laminated to the substrate film via an adhesive resin. The laminate layer can also be printed. The heat-seal layer is a layer suitable for producing a package by overlapping two of the above-mentioned laminates and heat-sealing them so that the polyolefin resin film of the resulting laminate is on the inside.

[0013] (Thickness of polyethylene-based resin multilayer film) The lower limit of the thickness of the polyethylene-based resin film is preferably 15 μm, more preferably 20 μm, and even more preferably 25 μm. When it is 15 μm or more, heat seal strength is easily obtained. The upper limit of the thickness of the polyethylene-based resin film is preferably 100 μm, more preferably 80 μm, even more preferably 60 μm, and even more preferably 50 μm. When it is 100 μm or less, the film does not have too much stiffness and is easy to process, and it is easy to produce a suitable package, which is also preferable in terms of cost.

[0014] The weighted average density of the polyethylene resin composition constituting the heat seal layer of the polyethylene resin film is preferably smaller than the weighted average density of the polyethylene resin composition constituting the laminate layer. The organic lubricant contained therein is less likely to migrate to the layer with higher density, and is therefore effective in maintaining the slipperiness of the heat seal layer after lamination and in maintaining the laminate strength over time.

[0015] (Multilayer structure) The polyethylene resin film has a multilayer structure of two or more layers including a heat seal layer and a laminate layer. In the case of three or more layers, the polyolefin resin film may have one or more other layers such as a core layer in addition to the laminate layer and the heat seal layer.

[0016] (Heat Seal Layer) The heat seal layer is made of a polyethylene resin composition. The polyethylene resin composition mainly contains a polyethylene resin, and preferably also contains particles made of a polyethylene resin. The polyethylene resin composition preferably contains 50% by weight or more of a polyethylene resin, more preferably 70% by weight or more, and even more preferably 90% by weight or more. On the other hand, the polyethylene resin composition preferably contains 99.5% by weight or less of a polyethylene resin, more preferably 99.0% by weight or less. This allows the polyethylene resin composition to contain various particles, additives, etc. The lower limit of the thickness ratio of the heat seal layer of the polyethylene resin film is preferably 12%, more preferably 18%. By setting it to 12% or more, good heat seal strength can be achieved. The upper limit of the thickness ratio of the heat seal layer of the polyethylene resin film is preferably 50%, more preferably 40%, and even more preferably 30%. By setting it to 50% or less, good blocking resistance can be achieved.

[0017] (Polyethylene Resin of Heat Seal Layer) The polyethylene resin contained in the polyethylene resin composition constituting the heat seal layer preferably contains a homopolymer of an ethylene monomer, a copolymer of an ethylene monomer and an α-olefin, or a mixture thereof, and more preferably contains a copolymer of an ethylene monomer and an α-olefin. The α-olefin preferably contains propylene, butene-1, hexene-1, 4-methylpentene-1, octene-1, decene-1, or a combination thereof, and more preferably contains hexene-1. The polyethylene resin is preferably a linear low-density polyethylene. Examples of linear low-density polyethylene include linear short-chain branched polyethylene. The linear low-density polyethylene preferably has a density of 900 to 930 kg / m ３ is.

[0018] The lower limit of the melt flow rate (hereinafter sometimes referred to as MFR) of the polyethylene resin contained in the polyethylene resin composition constituting the heat seal layer is preferably 1.5 g / 10 min, more preferably 2.0 g / 10 min, and even more preferably 2.3 g / 10 min. When it is 1.5 g / 10 min or more, it is easy to extrude and process it into a film, and the viscosity average molecular weight of the particles made of the polyethylene resin is less likely to decrease. The upper limit of the MFR of the polyethylene resin contained in the polyethylene resin composition constituting the heat seal layer is preferably 7.0 g / 10 min, more preferably 6.0 g / 10 min, even more preferably 5.4 g / 10 min, and particularly preferably 4.5 g / 10 min. When it is 7.0 g / 10 min or less, the thickness uniformity is good.

[0019] The lower limit of the melting point of the polyethylene resin contained in the polyethylene resin composition constituting the heat seal layer is preferably 85°C, more preferably 90°C, even more preferably 100°C, and particularly preferably 110°C. When the melting point is 85°C or higher, the surface protrusions do not sink and the anti-blocking function can be properly exhibited, resulting in good blocking resistance and slippage. In addition, the particles made of polyethylene resin support the contact between films, resulting in excellent scratch resistance. The upper limit of the melting point of the polyethylene resin contained in the polyethylene resin composition constituting the heat seal layer is preferably 125°C, more preferably 120°C, and even more preferably 117°C. When the melting point is 125°C or lower, good low-temperature sealability is achieved.

[0020] The polyethylene resin may be a single system, but two or more polyethylene resins with different densities may be blended as long as they are within the density range described below. When two or more polyethylene resins with different densities are blended, the average density and blending ratio can be estimated by GPC measurement or density measurement.

[0021] The lower limit of the density range of the polyethylene resin contained in the polyethylene resin composition constituting the heat seal layer is preferably 900 kg / m ３and more preferably 904 kg / m ３ and more preferably 910 kg / m ３ and particularly preferably 915 kg / m ３ 900 kg / m ３ When the density is 930 kg / m or more, the polyethylene resin contained in the polyethylene resin composition constituting the heat seal layer has excellent stiffness and is easy to process into bags. ３ and more preferably 927 kg / m ３ and more preferably 923 kg / m ３ and particularly preferably 920 kg / m ３ 930 kg / m ３ When the density is less than 1 / 2, the heat-sealing initiation temperature is not high and transparency is also excellent. The density of the polyethylene resin contained in the polyethylene resin composition constituting the heat-sealing layer is preferably smaller than the density of the polyethylene resin contained in the polyethylene resin composition constituting the laminate layer described below. This makes it easier to achieve both transparency and stiffness of the polyethylene resin film.

[0022] Density is 900 kg / m ３ When the above polyethylene resin is used, the particles made of polyethylene resin make it easy to control the arithmetic mean roughness SRa of the surface of the heat seal layer to 200 nm or less and the maximum peak height SRmax to 9 μm or less, and it is easy to improve transparency and stiffness. ３ When the following polyethylene resin is used, the particles made of polyethylene resin make it easy to make the arithmetic mean roughness SRa of the surface of the heat seal layer 60 nm or more and the maximum peak height SRmax 2 μm or more, and the polyethylene resin film is easy to obtain slipperiness, blocking resistance, and scratch resistance, so that wrinkles and lumps are less likely to occur during coating processing, printing processing, and bag making processing, and transparency is also easily maintained. In particular, the blocking resistance is less likely to fluctuate between the measured values ​​measured three times and is stable. This is because the density is 930 kg / m ３It is presumed that when particles made of the following polyethylene and polyethylene-based resin are melt-mixed, particle size changes due to a decrease in the viscosity average molecular weight of the particles made of polyethylene-based resin or entanglement of molecular chains with polyethylene-based resins other than the particles made of polyethylene-based resin are unlikely to occur, and as a result, protrusions on the surface are likely to be formed.

[0023] The density as described above is 900 to 930 kg / m ３ Examples of polyethylene resins that can be selected depending on the application include high-pressure low-density polyethylene (LDPE), which is transparent, flexible, and has excellent average tear and tensile strength; linear short-chain branched polyethylene (LLDPE), which is copolymerized with small amounts of butene-1, hexene-1, and / or octene-1 and has many short molecular chains in the molecular chain, resulting in excellent sealing performance and physical strength; and metallocene-catalyzed linear short-chain branched polyethylene (LLDPE), which exhibits a very sharp molecular weight distribution, a uniform comonomer distribution, and excellent tear, tensile, and puncture strengths and pinhole resistance. Linear low-density polyethylene is preferred from the perspective of heat seal strength and sealability as a packaging material. Furthermore, the use of plant-derived high-pressure low-density polyethylene or plant-derived linear low-density polyethylene can reduce environmental impact. As the polyethylene-based resin used in the sealing layer, commercially available products can also be used, and examples thereof include Yumerit 2040FC, 0540FA, and 3540FC manufactured by Ube Maruzen Polyethylene Co., Ltd., Sumikathene E FV402 and FV405 manufactured by Sumitomo Chemical Co., Ltd., NC564A manufactured by Japan Polyethylene Corporation, and SLH218 manufactured by Braskem.

[0024] The lower limit of the weighted average density of the polyethylene resin composition constituting the heat seal layer is preferably 900 kg / m ３ and more preferably 904 kg / m ３ and more preferably 910 kg / m ３ and particularly preferably 915 kg / m ３ 900 kg / m ３ When the density is 100% or more, the polyethylene resin constituting the heat seal layer has excellent stiffness and is easy to process into bags. The upper limit of the weighted average density of the polyethylene resin constituting the heat seal layer is preferably 930 kg / m ３and more preferably 927 kg / m ３ and more preferably 923 kg / m ３ and particularly preferably 920 kg / m ３ 930 kg / m ３ When the temperature is not higher than this, the heat seal initiation temperature is not high and transparency is also excellent.

[0025] (Spherical polyethylene resin particles having an average particle size of 9 μm or more) The polyethylene resin composition constituting the heat seal layer preferably contains spherical polyethylene resin particles having an average particle size of 9 μm or more. This makes it easy to form large protrusions on the surface of the heat seal layer. Indicators of large protrusions include the ten-point average roughness SRz and the maximum height SRmax. When the three-dimensional surface roughness SRa and the maximum protrusion height SRmax are large, it is easy to obtain sufficient slip properties and blocking resistance for film processing.

[0026] The lower limit of the content of spherical polyethylene resin particles having an average particle size of 9 μm or more in the polyethylene resin composition constituting the heat seal layer is preferably 1900 ppm by weight, more preferably 3000 ppm, even more preferably 4000 ppm, and even more preferably 5000 ppm. At 1900 ppm or more, blocking resistance of the heat seal surface is easily obtained. The upper limit of the content of spherical polyethylene resin particles having an average particle size of 9 μm or more in the polyethylene resin composition constituting the heat seal layer is preferably 16000 ppm by weight, more preferably 15000 ppm, even more preferably 11000 ppm, and even more preferably 7000 ppm. At 16000 ppm or less, the heat seal surface does not have too many protrusions, and transparency and low-temperature sealability are also likely to be improved.

[0027] The upper limit of the average particle size of spherical polyethylene resin particles having an average particle size of 9 μm or more contained in the polyethylene resin composition constituting the heat seal layer is preferably 20 μm, more preferably 17 μm, and even more preferably 15 μm. If the particle size is 20 μm or less, the three-dimensional surface roughness SRa and maximum protrusion height SRmax of the heat seal layer will not be too large, and the number of protrusions will increase compared to when the same weight of polyethylene resin particles is added, making it easier to obtain sufficient slip properties and blocking resistance for film processing. In addition, it is preferable that the composition does not contain particles having an average particle size of 30 μm or more. Even if the average particle size of spherical polyethylene resin particles is 20 μm or less, if a predetermined amount of 10% or more particles having an average particle size of 30 μm or more are contained, the maximum peak height of the film surface will likely exceed 15 μm, which will cause the flickering described below when the film surface is visually observed. Furthermore, particles having an average particle size of 30 μm or more will have an appearance similar to that of gel-like defects.

[0028] Spherical polyethylene resin particles with an average particle size of 9 μm or more are less likely to be scratched by friction between films due to their spherical shape. Here, when the average value of the minor axis / major axis values ​​of 10 polyethylene resin particles, i.e., the sphericity of the polyethylene resin particles, is 0.90 or more, the polyethylene resin particles are considered spherical. The sphericity is preferably 1.00 or less.

[0029] The use of spherical polyethylene resin particles with an average particle size of 9 μm or more reduces the risk of scratches caused by friction between films. Furthermore, because polyethylene resin particles have a lower specific gravity than inorganic particles, they can form more large protrusions even when added by the same weight. Although spherical inorganic particles and crosslinked organic particles with an average particle size of 9 μm or more are less likely to cause scratches caused by friction between films than non-spherical inorganic particles, their large particle size results in a very large particle surface area in contact with the film surface when the film surfaces are rubbed together, making them prone to scratches. Furthermore, there is a concern that they are prone to falling off the film surface, which can easily cause smearing in the die.

[0030] The spherical particles made of polyethylene resin and having an average particle size of 9 μm or more contained in the polyethylene resin composition constituting the heat seal layer preferably have a viscosity-average molecular weight of 1.5 million or more, more preferably 1.6 million or more, and even more preferably 1.7 million or more. Also, it is preferably 2.5 million or less, more preferably 2.4 million or less, and even more preferably 2.3 million or less. A viscosity-average molecular weight within this range makes it possible to control the average particle size of the spherical particles made of polyethylene resin. By using the polyethylene resin in combination with a polyethylene resin of a specific density, for example, it is possible to set the three-dimensional surface roughness SRa of at least one surface of the heat seal layer to 60 nm or more and 200 nm or less, and the maximum peak height SRmax to 2 μm or more and 9 μm or less. The reason for this is presumably that if there is a very large difference in molecular weight between the spherical particles made of polyethylene-based resin and the polyethylene-based resin other than the particles made of polyethylene-based resin, the molecules do not mix sufficiently, and the spherical particles made of polyethylene-based resin easily maintain a shape close to spherical even in the film obtained by melt-mixing and extrusion, and aggregation due to fusion or adhesion between particles is unlikely to occur, making it possible to form protrusions with controlled shapes on the film surface.

[0031] The viscosity average molecular weight of spherical particles made of polyethylene resin can be measured by the following method. First, 10 mg of particles are placed in 20 ml of decalin (decahydronaphthalene) and stirred at 150°C for 2 hours to dissolve the particles. The solution is placed in a thermostatic bath at 135°C and the falling time between the marked lines (t ｓ ) is measured. Similarly, measurements are made for 5 mg of particles. As a blank, the falling time (t ｂ Then, the specific viscosity (η) of the particles was calculated according to the following formula: ｓｐ / C) are plotted to determine the relationship between the concentration (C) and the specific viscosity (η ｓｐ / C) and extrapolate it to a concentration of 0 to determine the intrinsic viscosity (η). ｓｐ / C = (t ｓ / t ｂ−1) / 0.1 Furthermore, the viscosity average molecular weight (Mv) is calculated from this intrinsic viscosity (η) according to the following formula: Mv = 5.34 × 10 ４ η １．４９

[0032] When the viscosity-average molecular weight of the polyethylene resin spherical particles having an average particle size of 9 μm or more is 1.5 million or more, even under film-forming conditions with high shear and draft ratios using a large extruder, if the temperature during melt mixing with polyethylene resins other than the polyethylene resin spherical particles is higher than the melting point peak of the polyethylene resin spherical particles, the polyethylene resin particles are less likely to undergo decomposition due to heat or shear, fusion and aggregation between polyethylene resin particles, or changes in particle size and shape due to partial compatibility with polyethylene resins other than the polyethylene resin spherical particles. As a result, controlled protrusion formation, similar to that of inorganic particles or organic crosslinked resin particles, is more likely to occur, providing sufficient antiblocking agent functionality and less adverse effects on the appearance (e.g., transparency), mechanical strength, or heat-sealability of the film. Furthermore, it has been found that despite their resistance to aggregation in polyethylene resins, spherical particles made of polyethylene resins having a viscosity-average molecular weight of 1.5 million or more are less likely to fall off from the polyethylene resin near the film surface, a feature not found in inorganic particles or organic crosslinked resin particles. When the viscosity average molecular weight is 1,500,000 or more and 2,500,000 or less, it becomes easy to set the average particle size to 5 μm or more and 20 μm or less, and when the sealing layer raw material is melt-mixed and extruded to form a film, it tends to be easy to form suitable film surface protrusions. Furthermore, when the viscosity average molecular weight of the particles made of polyethylene resin is 1,500,000 or more, the particles themselves have lubricity, contributing to improving blocking resistance and slippage, and since the particles made of polyethylene resin are soft, it is thought that scratch resistance also improves.

[0033] The resin hardness of spherical particles made of polyethylene resin with an average particle size of 9 μm or more is preferably D70 or less. When the hardness is D70 or less, defects are less likely to occur in the laminated layers of the film, for example, the vapor deposition layer, and the barrier properties are less likely to deteriorate. The hardness is more preferably D68 or less. Furthermore, when the hardness of particles made of polyethylene resin is D60 or more, the slipperiness is also improved, and the slipperiness is less likely to deteriorate even when exposed to heat during film processing. The resin hardness is preferably Shore D hardness, and Shore D hardness can be measured using a Shore D hardness tester in accordance with ASTM D2240.

[0034] The spherical particles made of a polyethylene resin having an average particle size of 9 μm or more are preferably a homopolymer of an ethylene monomer, a copolymer of an ethylene monomer and an α-olefin, or a mixture thereof. The α-olefin preferably includes propylene, butene-1, hexene-1, 4-methylpentene-1, octene-1, decene-1, or a combination thereof.

[0035] The lower limit of the density of the polyethylene resin constituting the spherical particles made of polyethylene resin having an average particle size of 9 μm or more is preferably 930 kg / m ３ and more preferably 935 kg / m ３ and more preferably 937 kg / m ３ 930 kg / m ３ In this case, the particles are not too soft and the shape of the particles is not easily maintained during melt extrusion, so that the blocking resistance is not easily reduced. The upper limit of the density of the polyethylene resin constituting the spherical particles made of polyethylene resin is preferably 950 kg / m ３ and more preferably 945 kg / m ３ and more preferably 942 kg / m ３ The density is 950 kg / m ３ If the particle size exceeds this value, not only will the particles become hard and scratch resistance will be reduced, but the affinity with the base polyethylene resin will decrease, which may result in reduced resistance to falling off.

[0036] As an example of spherical particles made of polyethylene resin with an average particle size of 9 μm or more, there is Mipelon PM200 (average particle size 10 μm, melting point 136° C., viscosity average molecular weight 1.8 million, proportion of particles with a particle size exceeding 30 μm 0%, resin hardness D65, density 940 kg / m) manufactured by Mitsui Chemicals, Inc. ３ , ultra-high molecular weight polyethylene particles).

[0037] (Spherical inorganic particles having an average particle size of 9 μm or more, and spherical crosslinked organic particles having an average particle size of 9 μm or more) In the polyethylene resin composition constituting the heat seal layer, the upper limit of the total content of spherical inorganic particles having an average particle size of 9 μm or more and spherical crosslinked organic particles having an average particle size of 9 μm or more is preferably 1000 ppm, more preferably 700 ppm, even more preferably 500 ppm, still more preferably 200 ppm, particularly preferably 100 ppm or less, and most preferably 0 ppm. If it exceeds 1000 ppm, scratch resistance may be impaired. Furthermore, in the polyethylene resin composition constituting the heat seal layer, the upper limit of the total content of spherical particles having an average particle size of 9 μm or more other than spherical particles made of polyethylene resin is preferably 1000 ppm, more preferably 700 ppm, even more preferably 500 ppm, still more preferably 200 ppm, particularly preferably 100 ppm or less, and most preferably 0 ppm.

[0038] Examples of spherical inorganic particles having an average particle size of 9 μm or more include silica, calcium carbonate, zeolite, and mixtures thereof. Examples of spherical inorganic particles having an average particle size of 9 μm or more include KMP-130-10 (spherical silica particles, average particle size 10 μm) manufactured by Shin-Etsu Silicon Co., Ltd.

[0039] Examples of spherical crosslinked organic particles having an average particle size of 9 μm or more include those produced by crosslinking polymethyl acrylate resins, those produced by crosslinking styrene-based resins, etc. Note that spherical crosslinked organic particles having an average particle size of 9 μm or more do not include spherical particles made of polyethylene-based resins having an average particle size of 9 μm or more.

[0040] (Spherical particles with an average particle size of less than 9 μm) The polyethylene resin composition constituting the heat seal layer preferably contains spherical particles with an average particle size of less than 9 μm. This makes it easier to form small protrusions on the surface of the heat seal layer. An index of small protrusions is the protrusion density in a region with a small slice level, such as a height of 250 nm from the reference plane. A high protrusion density can improve slipperiness. Improved slipperiness can prevent wrinkling even when a rolled film product is rolled and transported in an automatic packaging machine or the like.

[0041] The lower limit of the content of spherical particles having an average particle size of less than 9 μm contained in the polyethylene resin composition constituting the heat seal layer is preferably 3100 ppm by weight, more preferably 4000 ppm, even more preferably 4500 ppm, and even more preferably 6000 ppm. At 3100 ppm or more, the slipperiness of the heat seal surface is improved, and conveyance wrinkles are less likely to occur. The spherical particles having an average particle size of less than 9 μm may be inorganic particles, particles made of a polyethylene resin, or crosslinked organic particles, but crosslinked organic particles and / or inorganic particles are preferred, and inorganic particles are more preferred. The lower limit of the content of spherical particles having an average particle size of less than 9 μm contained in the polyethylene resin composition constituting the heat seal layer is preferably 15000 ppm by weight, more preferably 10000 ppm, and even more preferably 8000 ppm. At 15000 ppm or less, scratch resistance is improved.

[0042] Inorganic particles include those with shapes such as spheres, cubes, and irregular shapes, but particles with regular shapes such as spherical particles and cubic particles are artificially produced synthetic particles. Spherical inorganic particles such as synthetic silica have a relatively narrow particle size distribution and are nearly spherical in shape, and therefore are characterized by good dispersibility in films, especially when the average particle size is less than 9 μm. Furthermore, since they have no corners, they are suitable for providing good scratch resistance. Examples of spherical inorganic particles with an average particle size less than 9 μm include silica, calcium carbonate, zeolite, and mixtures thereof. Examples of spherical inorganic particles with an average particle size less than 9 μm include Shilton JC-50 (spherical zeolite particles, average particle size 5.0 μm) manufactured by Mizusawa Industrial Chemicals, Ltd.

[0043] Examples of spherical crosslinked organic particles having an average particle size of less than 9 μm include those produced by crosslinking polymethyl acrylate resins and those produced by crosslinking styrene-based resins. Examples of spherical crosslinked organic particles include MBX-8 (spherical polymethyl methacrylate particles, average particle size 8 μm) manufactured by Sekisui Chemical Co., Ltd. and SX-500H (spherical styrene-based particles, average particle size 5 μm) manufactured by Soken Chemical & Engineering Co., Ltd. Note that spherical crosslinked organic particles having an average particle size of less than 9 μm do not include spherical particles made of polyethylene-based resins having an average particle size of less than 9 μm.

[0044] The lower limit of the average particle size of spherical particles having an average particle size of less than 9 μm contained in the polyethylene resin composition constituting the heat seal layer is preferably 3 μm, more preferably 4 μm, and even more preferably 5 μm. When the average particle size of the spherical particles is 3 μm or more, the particles are less likely to sink to the film surface, and the slipperiness is more likely to cause protrusions, making it less likely for wrinkles to occur when the roll is transported. When the particles have an average particle size or are spherical, scratches due to friction between films are less likely to occur. Here, spherical means that the sphericity is 0.9 or more, and sphericity can be defined as the average value of the minor axis / major axis values ​​of 10 particles.

[0045] (Non-spherical particles) Since non-spherical particles are prone to scratches due to friction between films, it is preferable to reduce their content. Here, "non-spherical" means that the sphericity is less than 0.90, and the sphericity can be defined as the average value of the minor axis / major axis values ​​of 10 particles.

[0046] In the polyethylene resin composition constituting the heat seal layer, the upper limit of the content of non-spherical particles is preferably 2500 ppm, more preferably 1000 ppm, even more preferably 500 ppm, still more preferably 200 ppm, and particularly preferably 0 ppm. If it exceeds 2500 ppm, transparency and scratch resistance are likely to be impaired. In the polyethylene resin composition constituting the heat seal layer, the upper limit of the content of non-spherical particles having an average particle size of 9 μm or more is preferably 500 ppm, more preferably 300 ppm, even more preferably 200 ppm, still more preferably 100 ppm, and particularly preferably 100 ppm. If it exceeds 500 ppm, transparency and scratch resistance are likely to be impaired. In the polyethylene resin composition constituting the heat seal layer, the upper limit of the content of non-spherical particles having an average particle size of less than 9 μm is preferably 2500 ppm, more preferably 1500 ppm, even more preferably 1000 ppm, still more preferably 500 ppm, particularly preferably 200 ppm, and particularly preferably 0 ppm. If it exceeds 2500 ppm, transparency and scratch resistance are likely to be impaired.

[0047] Examples of non-spherical particles include non-spherical inorganic particles. Preferably, the non-spherical inorganic particles include, for example, silica, talc, calcium carbonate, diatomaceous earth, zeolite, or a mixture thereof. Non-spherical inorganic particles are mainly produced by pulverizing naturally collected particles. These particles have a high hardness relative to polyethylene resin films and, due to their many corners, tend to deteriorate scratch resistance. Examples of non-spherical inorganic particles include calcium carbonate particles (CUBE-50KAS (Mohs hardness 3, average particle size 5 μm) manufactured by Maruo Calcium Co., Ltd.), zeolite particles obtained by pulverizing natural zeolite with a pin mill, and diatomaceous earth particles obtained by pulverizing diatomaceous earth with a pin mill.

[0048] In terms of suppressing die buildup and cost, it is preferable that the content of crosslinked organic particles in the polyethylene resin composition constituting the heat seal layer be equal to or less than the amount of particles made of polyethylene resin. As with inorganic particles, in order to maximize the effects of adding particles made of polyethylene resin, such as scratch resistance and particle shedding, it is most preferable that the polyethylene resin composition constituting the heat seal layer does not contain crosslinked organic particles. The crosslinked organic particles referred to here are organic crosslinked particles typified by polymethyl acrylate resins, etc.

[0049] The polyethylene resin composition constituting the heat seal layer preferably contains an organic lubricant (organic slip agent). This improves the film's slipperiness and anti-blocking properties, improving film handling. The reason for this is believed to be that the organic lubricant bleeds out and is present on the film surface, thereby exerting its lubricating and release effects. Furthermore, it is preferable to add an organic lubricant with a melting point above room temperature. Examples of organic lubricants include fatty acid amides and fatty acid esters. Specific examples include oleic acid amide, erucic acid amide, behenic acid amide, ethylene bisoleic acid amide, hexamethylene bisoleic acid amide, and ethylene bisstearic acid amide. While these may be used alone, using two or more of them in combination is preferred, as this allows for maintaining slipperiness and anti-blocking effects even in harsh environments.

[0050] The lower limit of the total content of the organic lubricant in the polyethylene resin composition constituting the heat seal layer is preferably 500 ppm by weight, more preferably 1000 ppm, even more preferably 1200 ppm, and particularly preferably 1500 ppm. If it is 500 ppm or more, the slipperiness tends to be stable immediately after film formation. The upper limit of the total content of the organic lubricant in the polyethylene resin composition constituting the heat seal layer is preferably 3000 ppm, more preferably 2500 ppm. If it is 3000 ppm or less, it is not too slippery and is less likely to whiten over time.

[0051] The polyethylene resin composition constituting the heat seal layer may contain a heat stabilizer. This can suppress defects such as gelation that occur when the resin deteriorates due to heat or oxidation during melt extrusion. Commercially available heat stabilizers and antioxidants can be used as the heat stabilizer. Specific examples include a hindered phenol-based antioxidant (Irganox 1010) manufactured by BASF, a phosphite-treated stabilizer (Irgafos 168) manufactured by BASF, and a phenol-phosphorus-based antioxidant (Sumilizer GP) manufactured by Sumitomo Chemical Co., Ltd. A single heat stabilizer may be used, or two or more types may be combined. While commercially available polyolefin resins are often supplemented with a heat stabilizer during production, they may also be added as a masterbatch or the like.

[0052] The lower limit of the concentration of the heat stabilizer in the polyethylene resin composition is preferably 1600 ppm or more, more preferably 1800 ppm or more, and even more preferably 2000 ppm or more, in total, relative to the heat seal layer. If the concentration is less than this, defects such as gelation are likely to occur. The upper limit is preferably 5000 ppm, more preferably 4000 ppm, and even more preferably 3500 ppm, in total, relative to the heat seal layer. If the concentration exceeds this limit, the edge of the film roll may turn red, impairing the appearance.

[0053] The polyethylene resin composition constituting the heat seal layer may contain, as needed, appropriate amounts of an antistatic agent, an antifogging agent, a neutralizing agent, a nucleating agent, a colorant, other additives, an inorganic filler, etc., within the scope of the present disclosure. Examples of neutralizing agents include calcium stearate.

[0054] These polyethylene resin particles, inorganic particles, organic lubricants, etc. can be added by known methods such as addition as a masterbatch or direct addition during melt extrusion.

[0055] (Laminate Layer) The laminate layer is made of a polyethylene-based resin composition. The polyethylene-based resin composition mainly contains a polyethylene-based resin and may also contain particles made of a polyethylene-based resin. The polyethylene-based resin composition preferably contains 50% by weight or more of a polyethylene-based resin, more preferably 70% by weight or more, and even more preferably 90% by weight or more. On the other hand, the polyethylene-based resin composition preferably contains 100% by weight or less of a polyethylene-based resin. The polyethylene-based resin composition may contain various particles, additives, etc. The lower limit of the thickness ratio of the laminate layer of the polyethylene-based resin film is preferably 12%, more preferably 18%. By setting it to 12% or more, good laminate strength can be achieved. The upper limit of the thickness ratio of the laminate layer of the polyethylene-based resin film is preferably 50%, more preferably 40%, and even more preferably 30%. By setting it to 50% or less, good heat seal strength can be achieved.

[0056] (Polyethylene Resin of Laminate Layer) The polyethylene resin contained in the polyethylene resin composition constituting the laminate layer preferably contains a homopolymer of an ethylene monomer, a copolymer of an ethylene monomer and an α-olefin, or a mixture thereof, and more preferably contains a copolymer of an ethylene monomer and an α-olefin. The α-olefin preferably contains propylene, butene-1, hexene-1, 4-methylpentene-1, octene-1, decene-1, or a combination thereof, and more preferably contains butene-1, hexene-1, or a combination thereof. The polyethylene resin is preferably linear low-density polyethylene. Examples of linear low-density polyethylene include linear short-chain branched polyethylene. The linear low-density polyethylene has a density of 900 to 945 kg / m ３ and the density is preferably 910 to 945 kg / m ３ is.

[0057] The lower limit of the melt flow rate (hereinafter sometimes referred to as MFR) of the polyethylene resin contained in the polyethylene resin composition constituting the laminate layer is preferably 1.5 g / 10 min, more preferably 2.0 g / 10 min, and even more preferably 2.3 g / 10 min. When it is 1.5 g / 10 min or more, it is easy to extrude and process it into a film, and the viscosity average molecular weight of the particles made of the polyethylene resin is less likely to decrease. The upper limit of the MFR of the polyethylene resin contained in the polyethylene resin composition constituting the laminate layer is preferably 7.0 g / 10 min, more preferably 6.0 g / 10 min, even more preferably 5.4 g / 10 min, and particularly preferably 4.5 g / 10 min. When it is 7.0 g / 10 min or less, the thickness uniformity is good.

[0058] The lower limit of the melting point of the polyethylene resin contained in the polyethylene resin composition constituting the laminate layer is preferably 100°C, more preferably 110°C, even more preferably 115°C, and particularly preferably 122°C. When it is 100°C or higher, the polyethylene resin has excellent stiffness and is easy to process into bags. The upper limit of the melting point of the polyethylene resin contained in the polyethylene resin composition constituting the laminate layer is preferably 135°C, more preferably 130°C, and even more preferably 127°C. When it is 135°C or lower, curling is small and transparency is excellent.

[0059] The polyethylene resin may be a single system, but two or more polyethylene resins with different densities may be blended as long as they are within the density range described below. When two or more polyethylene resins with different densities are blended, the average density and blending ratio can be estimated by GPC measurement or density measurement. The lower limit of the weighted average density of the polyethylene resin composition constituting the laminate layer is preferably 910 kg / m ３ and more preferably 915 kg / m ３ and more preferably 920 kg / m ３ 910 kg / m ３ When the density is 100% or more, the polyethylene resin composition constituting the laminate layer has excellent stiffness and is easy to process into bags. The upper limit of the weighted average density of the polyethylene resin composition constituting the laminate layer is preferably 945 kg / m ３ and more preferably 935 kg / m ３ and more preferably 930 kg / m ３ 945 kg / m ３ When the thickness is less than 100 μm, curling is small and transparency is excellent.

[0060] The density of the polyethylene resin contained in the polyethylene resin composition constituting the laminate layer is preferably 910 kg / m ３ and more preferably 915 kg / m ３ and more preferably 920 kg / m ３ The upper limit of the density of the polyethylene resin contained in the polyethylene resin composition constituting the laminate layer is preferably 945 kg / m ３ and more preferably 935 kg / m３ and more preferably 930 kg / m ３ Such a density is 910 to 945 kg / m ３ Examples of polyethylene resins that can be selected depending on the application include high-pressure low-density polyethylene (LDPE), which is transparent, flexible, and has excellent average tear and tensile strength; linear short-chain branched polyethylene (LLDPE), which is copolymerized with small amounts of butene-1, hexene-1, and / or octene-1 and has many short molecular chains in the molecular chain, resulting in excellent sealing performance and physical strength; and metallocene-catalyzed linear short-chain branched polyethylene (LLDPE), which exhibits a very sharp molecular weight distribution, a uniform comonomer distribution, and excellent tear, tensile, and puncture strengths and pinhole resistance. Linear low-density polyethylene is preferred from the perspective of heat seal strength and sealability as a packaging material. Furthermore, the use of plant-derived high-pressure low-density polyethylene or plant-derived linear low-density polyethylene can reduce environmental impact. As the polyethylene resin used in the laminate layer, commercially available products can also be used, and examples thereof include Umerit 2040FA, 825CA, 4040FC, and 846CC manufactured by Ube Maruzen Polyethylene Co., Ltd., Sumikathene FV402, FV405, and FV407 manufactured by Sumitomo Chemical Co., Ltd., and SLH218 manufactured by Braskem.

[0061] When the heat seal layer satisfies the following 1) to 4), it is preferable that the laminate layer does not satisfy the following 1) to 4). Furthermore, when the heat seal layer satisfies the following 1) to 4), it is preferable that the laminate layer does not contain particles, but it may contain particles within a range that does not impair the effects of the present disclosure. 1) It contains 1900 ppm to 16000 ppm of spherical particles made of a polyethylene resin having an average particle size of 9 μm or more. 2) It contains 3100 ppm to 15000 ppm of spherical particles having an average particle size of less than 9 μm. 3) The total content of spherical inorganic particles having an average particle size of 9 μm or more and spherical crosslinked organic particles having an average particle size of 9 μm or more is 1000 ppm or less. 4) The content of non-spherical particles is 2500 ppm or less.

[0062] However, if the heat seal layer does not satisfy any of the above requirements 1) to 4), it is preferable that the laminate layer satisfy the following requirements 1) to 4). Below, we will mainly explain the case where the laminate layer satisfies the following requirements 1) to 4). 1) It contains 1,900 ppm to 16,000 ppm of spherical polyethylene resin particles with an average particle size of 9 μm or more. 2) It contains 3,100 ppm to 15,000 ppm of spherical particles with an average particle size of less than 9 μm. 3) The total content of spherical inorganic particles with an average particle size of 9 μm or more and spherical crosslinked organic particles with an average particle size of 9 μm or more is 1,000 ppm or less. 4) The content of non-spherical particles is 2,500 ppm or less.

[0063] (Spherical polyethylene resin particles having an average particle size of 9 μm or more) The polyethylene resin composition constituting the laminate layer preferably contains spherical polyethylene resin particles having an average particle size of 9 μm or more. This average particle size makes it easy to form large protrusions on the surface of the laminate layer. Indicators of large protrusions include the ten-point average roughness SRz and the maximum height SRmax. When the three-dimensional surface roughness SRa and the maximum protrusion height SRmax are large, it is easy to obtain sufficient slip properties and blocking resistance for film processing.

[0064] The lower limit of the content of spherical polyethylene resin particles having an average particle size of 9 μm or more in the polyethylene resin composition constituting the laminate layer is preferably 1900 ppm by weight, more preferably 3000 ppm, even more preferably 4000 ppm, and even more preferably 5000 ppm. At 1900 ppm or more, blocking resistance of the heat-sealed surface is easily obtained. The upper limit of the content of polyethylene resin particles in the polyethylene resin composition constituting the laminate layer is preferably 16000 ppm by weight, more preferably 15000 ppm, even more preferably 11000 ppm, and even more preferably 7000 ppm. At 16000 ppm or less, the heat-sealed surface does not have too many protrusions, and transparency and low-temperature sealability are easily improved.

[0065] The upper limit of the average particle size of the spherical polyethylene resin particles having an average particle size of 9 μm or more contained in the polyethylene resin composition constituting the laminate layer is preferably 20 μm, more preferably 17 μm, and even more preferably 15 μm. If the particle size is 20 μm or less, the three-dimensional surface roughness SRa and maximum protrusion height SRmax of the laminate layer do not become too large, and the number of protrusions increases compared to when the same weight of polyethylene resin particles is added, making it easier to obtain sufficient slip properties and blocking resistance for film processing. In addition, it is preferable that the composition does not contain particles having an average particle size of 30 μm or more. Even if the average particle size of the spherical polyethylene resin particles is 20 μm or less, if a predetermined amount of 10% or more particles having an average particle size of 30 μm or more are contained, the maximum peak height of the film surface is likely to exceed 15 μm, which will cause the flickering described below when the film surface is visually observed. Furthermore, particles having an average particle size of 30 μm or more will have an appearance similar to gel-like defects, resulting in reduced quality.

[0066] Spherical polyethylene resin particles with an average particle size of 9 μm or more are less likely to be scratched by friction between films due to their spherical shape. When the average value of the minor axis / major axis values ​​of 10 polyethylene resin particles, i.e., the sphericity of the polyethylene resin particles, is 0.90 or more, the polyethylene resin particles are spherical. The sphericity is preferably 1.00 or less.

[0067] The use of spherical polyethylene resin particles with an average particle size of 9 μm or more reduces the risk of scratches caused by friction between films. Furthermore, because polyethylene resin particles have a lower specific gravity than inorganic particles, they can form more large protrusions even when added by the same weight. Although spherical inorganic particles and crosslinked organic particles with an average particle size of 9 μm or more are less likely to cause scratches caused by friction between films than non-spherical inorganic particles, their large particle size results in a very large particle surface area in contact with the film surface when the film surfaces are rubbed together, making them prone to scratches. Furthermore, there is a concern that they are prone to falling off the film surface, which can easily cause smearing in the die.

[0068] The polyethylene resin spherical particles having an average particle size of 9 μm or more contained in the polyethylene resin composition constituting the laminate layer preferably have a viscosity-average molecular weight of 1.5 million or more, more preferably 1.6 million or more, and even more preferably 1.7 million or more. Also, the viscosity-average molecular weight is preferably 2.5 million or less, more preferably 2.4 million or less, and even more preferably 2.3 million or less. A viscosity-average molecular weight within this range makes it possible to control the average particle size of the polyethylene resin spherical particles. By using the polyethylene resin in combination with a polyethylene resin of a specific density, for example, the three-dimensional surface roughness SRa of at least one surface of the laminate layer can be adjusted to 60 nm or more and 200 nm or less, and the maximum peak height SRmax can be adjusted to 2 μm or more and 9 μm or less. The reason for this is presumably that if there is a very large difference in molecular weight between the spherical particles made of polyethylene-based resin and the polyethylene-based resin other than the particles made of polyethylene-based resin, the molecules do not mix sufficiently, and the spherical particles made of polyethylene-based resin easily maintain a shape close to spherical even in the film obtained by melt-mixing and extrusion, and aggregation due to fusion or adhesion between particles is unlikely to occur, making it possible to form protrusions with controlled shapes on the film surface.

[0069] When the viscosity-average molecular weight of the polyethylene resin spherical particles having an average particle size of 9 μm or more is 1.5 million or more, even under film-forming conditions with high shear and draft ratios using a large extruder, if the temperature during melt mixing with polyethylene resins other than the polyethylene resin spherical particles is higher than the melting point peak of the polyethylene resin spherical particles, the polyethylene resin particles are less likely to undergo decomposition due to heat or shear, fusion and aggregation between polyethylene resin particles, or changes in particle size and shape due to partial compatibility with polyethylene resins other than the polyethylene resin spherical particles. As a result, controlled protrusion formation, similar to that of inorganic particles or organic crosslinked resin particles, is more likely to occur, providing sufficient antiblocking agent functionality and less adverse effects on the appearance (e.g., transparency), mechanical strength, or heat-sealability of the film. Furthermore, it has been found that despite their resistance to aggregation in polyethylene resins, spherical particles made of polyethylene resins having a viscosity-average molecular weight of 1.5 million or more are less likely to fall off from the polyethylene resin near the film surface, a feature not found in inorganic particles or organic crosslinked resin particles. When the viscosity average molecular weight is 1,500,000 or more and 2,500,000 or less, it becomes easy to set the average particle size to 5 μm or more and 20 μm or less, and when the sealing layer raw material is melt-mixed and extruded to form a film, it tends to be easy to form suitable film surface protrusions. Furthermore, when the viscosity average molecular weight of the particles made of polyethylene resin is 1,500,000 or more, the particles themselves have lubricity, contributing to improving blocking resistance and slippage, and since the particles made of polyethylene resin are soft, it is thought that scratch resistance also improves.

[0070] The resin hardness of spherical particles made of polyethylene resin with an average particle size of 9 μm or more is preferably D70 or less. When the hardness is D70 or less, defects are less likely to occur in the laminated layers of the film, for example, the vapor deposition layer, and the barrier properties are less likely to deteriorate. The hardness is more preferably D68 or less. Furthermore, when the hardness of particles made of polyethylene resin is D60 or more, the slipperiness is also improved, and the slipperiness is less likely to deteriorate even when exposed to heat during film processing. The resin hardness is preferably Shore D hardness, and Shore D hardness can be measured using a Shore D hardness tester in accordance with ASTM D2240.

[0071] The spherical particles made of a polyethylene resin having an average particle size of 9 μm or more are preferably a homopolymer of an ethylene monomer, a copolymer of an ethylene monomer and an α-olefin, or a mixture thereof. The α-olefin preferably includes propylene, butene-1, hexene-1, 4-methylpentene-1, octene-1, decene-1, or a combination thereof.

[0072] The lower limit of the density of the polyethylene resin constituting the spherical particles made of polyethylene resin having an average particle size of 9 μm or more is preferably 930 kg / m ３ and more preferably 935 kg / m ３ and more preferably 937 kg / m ３ 930 kg / m ３ In this case, the particles are not too soft and the shape of the particles is not easily maintained during melt extrusion, so that the blocking resistance is not easily reduced. The upper limit of the density of the polyethylene resin constituting the spherical particles made of polyethylene resin is preferably 950 kg / m ３ and more preferably 945 kg / m ３ and more preferably 942 kg / m ３ The density is 950 kg / m ３ If the particle size exceeds this value, not only will the particles become hard and scratch resistance will be reduced, but the affinity with the base polyethylene resin will decrease, which may result in reduced resistance to falling off.

[0073] As an example of spherical particles made of polyethylene resin with an average particle size of 9 μm or more, there is Mipelon PM200 (average particle size 10 μm, melting point 136° C., viscosity average molecular weight 1.8 million, proportion of particles with a particle size exceeding 30 μm 0%, resin hardness D65, density 940 kg / m) manufactured by Mitsui Chemicals, Inc. ３ , ultra-high molecular weight polyethylene particles).

[0074] (Spherical inorganic particles having an average particle size of 9 μm or more, and spherical crosslinked organic particles having an average particle size of 9 μm or more) In the polyethylene resin composition constituting the laminate layer, the upper limit of the total content of spherical inorganic particles having an average particle size of 9 μm or more and spherical crosslinked organic particles having an average particle size of 9 μm or more is preferably 1000 ppm, more preferably 700 ppm, even more preferably 500 ppm, still more preferably 200 ppm, particularly preferably 100 ppm or less, and most preferably 0 ppm. If it exceeds 1000 ppm, scratch resistance may be impaired. Furthermore, the upper limit of the total content of spherical particles having an average particle size of 9 μm or more other than spherical particles made of polyethylene resin in the polyethylene resin composition constituting the laminate layer is preferably 1000 ppm, more preferably 700 ppm, even more preferably 500 ppm, still more preferably 200 ppm, particularly preferably 100 ppm or less, and most preferably 0 ppm.

[0075] Examples of spherical inorganic particles having an average particle size of 9 μm or more include silica, calcium carbonate, zeolite, and mixtures thereof. Examples of spherical inorganic particles having an average particle size of 9 μm or more include KMP-130-10 (spherical silica particles, average particle size 10 μm) manufactured by Shin-Etsu Silicon Co., Ltd.

[0076] Examples of spherical crosslinked organic particles having an average particle size of 9 μm or more include those produced by crosslinking polymethyl acrylate resins, those produced by crosslinking styrene-based resins, etc. Note that spherical crosslinked organic particles having an average particle size of 9 μm or more do not include spherical particles made of polyethylene-based resins having an average particle size of 9 μm or more.

[0077] (Spherical particles with an average particle size of less than 9 μm) The polyethylene resin composition constituting the laminate layer preferably contains spherical particles with an average particle size of less than 9 μm. This makes it easier to form small protrusions on the surface of the laminate layer due to the average particle size. An index of small protrusions is the protrusion density in a region with a small slice level, such as a height of 250 nm from the reference plane. A high protrusion density can improve slipperiness. Improved slipperiness can prevent wrinkling even when a rolled film product is rolled and transported in an automatic packaging machine or the like.

[0078] The lower limit of the content of spherical particles having an average particle size of less than 9 μm contained in the polyethylene resin composition constituting the laminate layer is preferably 3100 ppm by weight, more preferably 4000 ppm, even more preferably 4500 ppm, and even more preferably 6000 ppm. A content of 3100 ppm or more improves the slipperiness of the heat-sealed surface, making it less likely for wrinkles to form during transport. The spherical particles having an average particle size of less than 9 μm may be inorganic particles, particles made of a polyethylene resin, or crosslinked organic particles. However, crosslinked organic particles and / or inorganic particles are preferred, and inorganic particles are more preferred. For details of these crosslinked organic particles and inorganic particles, please refer to the description of the spherical particles having an average particle size of less than 9 μm contained in the polyethylene resin composition constituting the heat-sealed layer. The lower limit of the content of spherical particles having an average particle size of less than 9 μm contained in the polyethylene resin composition constituting the laminate layer is preferably 15000 ppm by weight, more preferably 10000 ppm, and even more preferably 8000 ppm. If the content is 15,000 ppm or less, scratch resistance is good.

[0079] The lower limit of the average particle size of spherical particles having an average particle size of less than 9 μm contained in the polyethylene resin composition constituting the laminate layer is preferably 3 μm, more preferably 4 μm, and even more preferably 5 μm. When the average particle size of spherical particles is 3 μm or more, the particles are less likely to sink to the film surface, and the slipperiness is more likely to cause protrusions, making wrinkles less likely to occur when the roll is transported. Furthermore, when the particles are spherical, scratches due to friction between films are less likely to occur. Here, spherical means that the sphericity is 0.90 or more, and sphericity can be defined as the average value of the minor axis / major axis values ​​of 10 particles. The sphericity is preferably 1.00 or less.

[0080] (Non-spherical particles) Non-spherical particles are prone to scratches due to friction between films, so it is preferable to reduce their content. Here, "non-spherical" means that the sphericity is less than 0.90, and the sphericity can be defined as the average value of the minor axis / major axis values ​​of 10 particles. In the polyethylene resin composition constituting the laminate layer, the upper limit of the content of non-spherical particles is preferably 2500 ppm, more preferably 1000 ppm, even more preferably 500 ppm, even more preferably 200 ppm, and particularly preferably 0 ppm. If the content exceeds 2500 ppm, transparency and scratch resistance are likely to be impaired. In the polyethylene resin composition constituting the laminate layer, the upper limit of the content of non-spherical particles having an average particle size of 9 μm or more is preferably 500 ppm, more preferably 300 ppm, even more preferably 200 ppm, even more preferably 100 ppm, and particularly preferably 100 ppm. If it exceeds 500 ppm, transparency and scratch resistance are likely to be impaired. In the polyethylene resin composition constituting the laminate layer, the upper limit of the content of non-spherical particles having an average particle size of less than 9 μm is preferably 2500 ppm, more preferably 1500 ppm, even more preferably 1000 ppm, still more preferably 500 ppm, particularly preferably 200 ppm, and most preferably 0 ppm. If it exceeds 2500 ppm, transparency and scratch resistance are likely to be impaired.

[0081] Examples of non-spherical particles include non-spherical inorganic particles. Non-spherical inorganic particles preferably include, for example, silica, talc, calcium carbonate, diatomaceous earth, zeolite, or a mixture thereof. Non-spherical inorganic particles are mainly produced by pulverizing naturally collected particles. These particles have a high hardness relative to polyethylene resin films and, due to their many corners, tend to deteriorate scratch resistance. Examples of non-spherical inorganic particles include calcium carbonate particles (CUBE-50KAS (Mohs hardness 3, average particle size 5 μm) manufactured by Maruo Calcium Co., Ltd.), zeolite particles obtained by pulverizing natural zeolite with a pin mill, and diatomaceous earth particles obtained by pulverizing diatomaceous earth with a pin mill.

[0082] The polyethylene resin composition constituting the laminate layer may or may not contain an organic lubricant, but it is preferable not to add an organic lubricant because the organic lubricant may bleed out onto the laminate surface and impair the adhesive strength of the laminate.

[0083] The polyethylene resin composition constituting the laminate layer may contain a heat stabilizer. This can suppress defects such as gels that occur when the resin deteriorates due to heat or oxidation during melt extrusion. Commercially available heat stabilizers and antioxidants can be used. Specific examples include BASF's hindered phenol-based antioxidant (Irganox 1010), BASF's phosphite-treated stabilizer (Irgafos 168), and Sumitomo Chemical's phenol-phosphorus-based antioxidant (Sumilizer GP). Heat stabilizers may be used alone or in combination of two or more. While commercially available polyolefin resins are often added during production, they may also be added as masterbatches or the like. The lower limit of the heat stabilizer concentration in the polyethylene resin composition is preferably 1600 ppm or more, more preferably 1800 ppm or more, and even more preferably 2000 ppm or more, in total, relative to the laminate layer. If the concentration is below this level, defects such as gels are likely to occur. The upper limit is preferably 5000 ppm, more preferably 4000 ppm, and even more preferably 3500 ppm in total relative to the laminate layer. If the upper limit is exceeded, the end surface of the film roll may turn red, impairing the appearance.

[0084] The polyethylene resin composition constituting the laminate layer may contain, as needed, appropriate amounts of an antistatic agent, an antifogging agent, a neutralizing agent, a nucleating agent, a colorant, other additives, etc., within the scope of the present disclosure. Examples of neutralizing agents include calcium stearate.

[0085] These polyethylene resin particles, inorganic particles, organic lubricants, etc. can be added by known methods such as addition as a masterbatch or direct addition during melt extrusion.

[0086] It is preferable that the surface of the laminate layer of the polyethylene resin film is activated by corona treatment or the like, as this improves the lamination strength with the base film.

[0087] (Core Layer) The polyethylene-based resin film preferably has a core layer between the laminate layer and the heat-seal layer. The core layer is suitable for increasing the thickness of the film and improving firmness while reducing costs. The core layer is preferably made of a polyethylene-based resin composition. The polyethylene-based resin composition mainly contains a polyethylene-based resin and may contain particles made of a polyethylene-based resin. The polyethylene-based resin composition preferably contains 50% by weight or more of a polyethylene-based resin, more preferably 70% by weight or more, and even more preferably 90% by weight or more. On the other hand, the polyethylene-based resin composition preferably contains 100% by weight or less of a polyethylene-based resin. The polyethylene-based resin composition may contain additives, etc. The lower limit of the thickness ratio of the core layer of the polyethylene-based resin film is not particularly limited, but is preferably 30% and more preferably 40%. A thickness ratio of 30% or more can achieve good heat-seal strength. The upper limit of the thickness ratio of the core layer of the polyethylene-based resin film is preferably 80%, more preferably 70%, and even more preferably 65%. A thickness ratio of 80% or less can improve firmness.

[0088] (Polyethylene Resin of Core Layer) The polyethylene resin constituting the core layer preferably contains a homopolymer of an ethylene monomer, a copolymer of an ethylene monomer and an α-olefin, or a mixture thereof, and more preferably contains a copolymer of an ethylene monomer and an α-olefin. The α-olefin preferably contains propylene, butene-1, hexene-1, 4-methylpentene-1, octene-1, decene-1, or a combination thereof, and more preferably contains butene-1, hexene-1, or a combination thereof. The polyethylene resin is preferably linear low-density polyethylene. Examples of linear low-density polyethylene include linear short-chain branched polyethylene. The linear low-density polyethylene has a density of 900 to 945 kg / m ３ and the density is preferably 910 to 930 kg / m ３ is.

[0089] The lower limit of the melt flow rate (hereinafter sometimes referred to as MFR) of the polyethylene resin contained in the polyethylene resin composition constituting the core layer is preferably 1.5 g / 10 min, more preferably 2.0 g / 10 min, and even more preferably 2.3 g / 10 min. When it is 1.5 g / 10 min or more, it is easy to process it into a film by extrusion molding, and the viscosity average molecular weight of the particles made of the polyethylene resin is less likely to decrease. The upper limit of the MFR of the polyethylene resin contained in the polyethylene resin composition constituting the core layer is preferably 7.0 g / 10 min, more preferably 6.0 g / 10 min, even more preferably 5.4 g / 10 min, and particularly preferably 4.5 g / 10 min. When it is 7.0 g / 10 min or less, good thickness uniformity is achieved.

[0090] The lower limit of the melting point of the polyethylene resin contained in the polyethylene resin composition constituting the core layer is 100°C, more preferably 104°C, even more preferably 110°C, and particularly preferably 114°C. When it is 100°C or higher, the polyethylene resin has excellent firmness and is easy to process into bags. The upper limit of the melting point of the polyethylene resin contained in the polyethylene resin composition constituting the core layer is preferably 130°C, more preferably 127°C, and even more preferably 124°C. When it is 130°C or lower, the low-temperature sealability is good.

[0091] The polyethylene resin may be a single system, but two or more polyethylene resins with different densities may be blended as long as they are within the density range described below. When two or more polyethylene resins with different densities are blended, the average density and blending ratio can be estimated by GPC measurement or density measurement. The lower limit of the weighted average density of the polyethylene resin composition constituting the core layer is preferably 910 kg / m ３ and more preferably 912 kg / m ３ and more preferably 915 kg / m ３ 910 kg / m ３ When the density is 100% or more, the polyethylene resin composition constituting the core layer has excellent stiffness and is easy to process into bags. The upper limit of the weighted average density of the polyethylene resin composition constituting the core layer is preferably 930 kg / m ３and more preferably 927 kg / m ３ and more preferably 925 kg / m ３ 930 kg / m ３ When the temperature is not higher than this, the heat seal initiation temperature is not high and transparency is also excellent.

[0092] The lower limit of the density of the polyethylene resin contained in the polyethylene resin composition constituting the core layer is preferably 910 kg / m ３ and more preferably 912 kg / m ３ and more preferably 915 kg / m ３ 910 kg / m ３ When the density is 930 kg / m or more, the polyethylene resin contained in the polyethylene resin composition constituting the core layer has excellent stiffness and is easy to process into bags. ３ and more preferably 927 kg / m ３ and more preferably 925 kg / m ３ Such a density is 910 to 930 kg / m ３ Examples of polyethylene resins that can be selected depending on the application include high-pressure low-density polyethylene (LDPE), which is transparent, flexible, and has excellent average tear and tensile strength; linear, short-chain branched polyethylene (LLDPE), which is copolymerized with small amounts of butene-1, hexene-1, and / or octene-1 and has many short molecular chains in the molecular chain, resulting in excellent sealing performance and physical strength; and metallocene-catalyzed linear, short-chain branched polyethylene (LLDPE), which exhibits a very sharp molecular weight distribution, a uniform comonomer distribution, and excellent tear, tensile, and puncture strengths and pinhole resistance. However, linear low-density polyethylene is preferred from the perspective of heat seal strength and sealability as a packaging material. Furthermore, the use of plant-derived high-pressure low-density polyethylene or plant-derived linear low-density polyethylene can reduce environmental impact.

[0093] Plant-derived polyethylene resins can be produced using ethanol derived from sugarcane, corn, or other raw materials, using methods such as high-pressure methods, solution methods, and gas-phase methods. Examples of plant-derived polyethylene resins include copolymers of plant-derived ethylene and at least one α-olefin having 3 or more carbon atoms. The α-olefin may be derived from a fossil fuel, as long as it is generally referred to as an α-olefin. Preferred α-olefins are α-olefins having 3 to 12 carbon atoms, such as propylene, butene-1, hexene-1, octene-1, and 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. From the viewpoint of flex pinhole resistance, ethylene-hexene copolymer is preferred. The lower limit of the plant-derived carbon content in plant-derived polyethylene resins is preferably 50% by weight, more preferably 80% by weight. A content of 50% by weight or more provides a favorable carbon dioxide reduction effect. The upper limit is preferably 100% by weight. The polyethylene resin used in the core layer may be a commercially available product, and examples thereof include Umerit 2040FA and 825CA manufactured by Ube Maruzen Polyethylene Co., Ltd., Sumikathene E FV402 and FV405 manufactured by Sumitomo Chemical Co., Ltd., NC564A manufactured by Japan Polyethylene Corporation, and SLH218 manufactured by Braskem.

[0094] In this case, particles made of the polyethylene resin, inorganic particles, or crosslinked organic particles may or may not be added to the core layer. However, since the presence of large particles such as coarse particles is likely to cause lamination separation, it is preferable not to intentionally add such particles, except for particles contained in the raw materials of recycled products.

[0095] The polyethylene resin composition constituting the core layer may or may not contain an organic lubricant. Examples of organic lubricants include fatty acid amides and fatty acid esters. Specific examples include oleic acid amide, erucic acid amide, behenic acid amide, ethylene bisoleic acid amide, hexamethylene bisoleic acid amide, and ethylene bisstearic acid amide. These may be used alone, but it is preferable to use two or more of them in combination, as this allows the lubrication and anti-blocking effects to be maintained even under harsh environments.

[0096] The lower limit of the total content of the organic lubricant in the polyethylene resin composition constituting the core layer is not particularly limited, but is preferably 100 ppm or more.The upper limit of the total content of the organic lubricant in the polyethylene resin composition constituting the core layer is preferably 3000 ppm, more preferably 2500 ppm.When it is 3000 ppm or less, it is not too slippery and is less likely to whiten over time.

[0097] By adding pellets made from recycled semi-finished products generated during the manufacturing process and finished film to the core layer, resin can be reused without compromising heat seal strength, reducing the environmental impact. In addition, the organic lubricant contained in the core layer can be supplemented by the organic lubricant in the core layer.

[0098] The polyethylene resin composition constituting the core layer may contain a heat stabilizer. This can suppress defects such as gels that occur when the resin deteriorates due to heat or oxidation during melt extrusion. Commercially available heat stabilizers and antioxidants can be used. Specific examples include BASF's hindered phenol-based antioxidant (Irganox 1010), BASF's phosphite-treated stabilizer (Irgafos 168), and Sumitomo Chemical's phenol-phosphorus-based antioxidant (Sumilizer GP). Heat stabilizers may be used alone or in combination of two or more. While commercially available polyolefin resins are often added during production, they may also be added additionally using a masterbatch or the like. The lower limit of the heat stabilizer concentration in the polyethylene resin composition, in total relative to the core layer, is preferably 1600 ppm or more, more preferably 1800 ppm or more, and even more preferably 2000 ppm or more. If the concentration is below this level, defects such as gels are likely to occur. The upper limit is preferably 5000 ppm, more preferably 4000 ppm, and even more preferably 3500 ppm in total relative to the core layer. If the upper limit is exceeded, the end surface of the film roll may turn red, impairing the appearance.

[0099] The polyethylene resin composition constituting the core layer may contain, in any layer as needed, an appropriate amount of an antistatic agent, an antifogging agent, a neutralizing agent, a nucleating agent, a colorant, other additives, an inorganic filler, etc., within the scope of the present disclosure. Examples of neutralizing agents include calcium stearate.

[0100] These polyethylene resin particles, inorganic particles, organic lubricants, etc. can be added by known methods such as addition as a masterbatch or direct addition during melt extrusion.

[0101] (Method for producing polyethylene-based resin film) As a specific method for forming a multilayer film in this manner, a general multilayering device (such as a multilayer feed block, a static mixer, or a multilayer multi-manifold) can be used. For example, a method can be used in which thermoplastic resins fed from different flow paths using two or more extruders are laminated into multiple layers using a field block, a static mixer, a multi-manifold die, or the like. It is also possible to use only one extruder and install the above-mentioned multilayering device in the melt line from the extruder to the T-die.

[0102] Polyethylene resin films can be formed using methods such as inflation and T-die, with the T-die being preferred for its enhanced transparency and thickness variation. While inflation uses air as a cooling medium, the T-die method uses a cooling roll, making it an advantageous production method for increasing the cooling rate of unstretched sheets. Increasing the cooling rate suppresses crystallization of the unstretched sheet, resulting in high transparency. Furthermore, stable molding results in favorable thickness variation in the flow and width directions. For these reasons, T-die molding is more preferred. As a lamination method using T-die coextrusion, conventional multi-layering devices (such as multi-layer feed blocks, static mixers, and multi-manifolds) can be used. For example, methods can be used in which thermoplastic resins delivered from different flow paths using two or more extruders are laminated into multiple layers using a field block, static mixer, multi-manifold die, etc. Alternatively, it is possible to use only one extruder and incorporate the above-mentioned multi-layering device into the melt line from the extruder to the T-die. The extruder screw may be single-screw or twin-screw, but single-screw is preferred from the viewpoint of production speed. The upper limit of the outlet temperature of the metering section, melt line, and die of the extruder is preferably 280°C, more preferably 270°C. If the temperature exceeds 280°C, the resin will deteriorate more rapidly and foreign matter such as gel will likely increase. The lower limit of the outlet temperature of the metering section, melt line, and die of the extruder is preferably 160°C, more preferably 180°C. If the temperature is below 160°C, unmelted resin may be discharged or the filter in the melt line may become clogged.

[0103] The lower limit of the temperature of the chill roll when the molten raw resin is cast to obtain a sheet is preferably 15°C, more preferably 20°C. If the temperature is lower than the above, condensation occurs on the chill roll, resulting in insufficient adhesion between the unstretched sheet and the chill roll, which may cause thickness defects. The upper limit of the chill roll is preferably 80°C, more preferably 60°C, and even more preferably 50°C. If the temperature is 80°C or lower, the transparency of the polyethylene resin film is less likely to deteriorate.

[0104] Since the thickness of both ends of the polyethylene resin sheet increases due to necking, it is preferable to trim them using a cutter, etc. This allows for uniform corona treatment and stabilizes the winding process.

[0105] The lower limit of the power density of the corona treatment applied to the laminate surface is preferably 15 W·min / m ２ and more preferably 17 W·min / m ２ 15W・min / m ２ If the power is less than this, the lamination strength and printability may be reduced. ２ and more preferably 25 W·min / m ２ 30W・min / m ２ If the thickness is more than this, strike-through may occur, resulting in roll blocking.

[0106] The lower limit of the film-forming speed is preferably 8 m / min, more preferably 15 m / min. If it is less than 8 m / min, the rotation speed of the cooling roll or the like becomes unstable, and thickness fluctuations tend to become large. The upper limit of the film-forming speed is preferably 300 m / min, more preferably 250 m / min. If it exceeds 300 m / min, sheet transport becomes unstable and wrinkles tend to occur.

[0107] The wound sheet can be cut by a slitting machine. This allows efficient production of product rolls of any width. The lower limit of the winding speed of the slitting machine is preferably 30 m / min, more preferably 50 m / min. If it is less than 30 m / min, cutting may not be able to keep up with the film-forming speed. The upper limit of the film-forming speed is preferably 300 m / min, more preferably 250 m / min. If it exceeds 300 m / min, the sheet transport becomes unstable and wrinkles are likely to occur.

[0108] (Characteristics of Polyethylene Resin Film) The "longitudinal direction" of a polyethylene resin film is the direction corresponding to the flow direction in the film production process, and the "width direction" is the direction perpendicular to the flow direction in the film production process. For polyethylene films whose flow direction in the film production process is unknown, wide-angle X-rays are incident perpendicular to the film surface, and scattering peaks derived from the (110) plane of the α-crystals are scanned in the circumferential direction. The direction with the largest diffraction intensity in the obtained diffraction intensity distribution is defined as the "longitudinal direction," and the direction perpendicular to that is defined as the "width direction."

[0109] (Protrusion density at a height of 250 nm from the reference plane of surface roughness) The protrusion density at a height of 250 nm from the reference plane of the surface roughness of a polyethylene resin film is the protrusion density at a height of 250 nm from the reference plane of a 1 mm roughness curve obtained by measuring the three-dimensional roughness using a three-dimensional surface roughness meter, where slice levels are set at intervals of 250 nm from the reference plane. ２ Number of protrusions per mm ２ ) The reference plane is a reference position (height 0 nm) determined when the entire measurement area is leveled after three-dimensional surface roughness measurement, and then cutoff is performed using a specified filter to remove components such as noise, waviness, and shape. The reference plane preferably corresponds to the center position of the movable range of the stylus in the thickness direction of the polyethylene resin film. The protrusion density at each slice level is a parameter derived from particle analysis (multiple levels) described in the measurement method described below. The protrusion density is a value calculated from the number of cut edges of protrusions when the film surface is cut horizontally on the convex side at a slice level of a predetermined height. The measurement method is performed using the method described in the Examples. The lower limit of the protrusion density at a height of 250 nm from the reference plane of the surface roughness of at least one side of the polyethylene resin film is preferably 160 / mm ２ More preferably, 200 pieces / mm ２ and more preferably 250 pieces / mm ２ 160 pieces / mm ２If the thickness is less than 1 / 2 mm, the slipperiness between the laminate surface and the heat-sealed surface of the film is poor, and wrinkles are likely to occur when the rolled film is rolled and transported. The upper limit of the protrusion density at a height of 250 nm from the reference plane of the surface roughness of at least one surface of the polyethylene-based resin film is not particularly limited, but is preferably 1000 protrusions / mm ２ and more preferably 700 pieces / mm ２ and more preferably 600 pieces / mm ２ 1000 pieces / mm ２ By setting the height to the range below, transparency and scratch resistance are improved. The height of 250 nm from the reference plane refers to a position 250 nm away from the reference plane toward the outside in the thickness direction. It is preferable that one surface of the heat seal layer has a protrusion density within the above-mentioned numerical range.

[0110] (Arithmetic Mean Roughness SRa) The arithmetic mean roughness SRa of a polyethylene-based resin film is determined by dividing the volume of the area enclosed by the roughness curved surface and the center plane by the measurement range, with the X-axis and Y-axis being orthogonal coordinate axes on the center plane of the roughness curved surface and the Z-axis being the axis perpendicular to the center plane, to express the unevenness of that section as an average value. The lower limit of the arithmetic mean roughness SRa of at least one surface of the polyethylene-based resin film is 60 nm, preferably 65 nm, and more preferably 70 nm. A value of 60 nm or more provides excellent slip properties and blocking resistance. The upper limit of the arithmetic mean roughness SRa of at least one surface of the polyethylene-based resin film is preferably 200 nm, more preferably 180 nm, and even more preferably 150 nm. A value of 200 nm or less provides excellent transparency and scratch resistance. The measurement method is the same as that described in the Examples. It is preferred that one surface of the heat-sealable layer has an arithmetic mean roughness SRa within the above-mentioned numerical range.

[0111] (Maximum height SRmax) The maximum height SRmax of a polyethylene resin film is the distance between two planes parallel to the average plane of the curved surface. The lower limit of the maximum height SRmax of at least one surface of the polyethylene resin film is preferably 2.0 μm, more preferably 4.0 μm, and even more preferably 5.0 μm. A height of 2.0 μm or more provides excellent slip properties and blocking resistance. The upper limit of the maximum height SRmax of at least one surface of the polyethylene resin film is preferably 9.0 μm, more preferably 8.0 μm. A height exceeding 9.0 μm or less is not preferred because it causes poor appearance. The measurement method is the same as that described in the examples. It is preferable that one surface of the heat seal layer has a maximum height SRmax in the above-mentioned numerical range.

[0112] (Ten-point average roughness SRz) The ten-point average roughness SRz is the distance between the average height of the fifth highest peak and the average depth of the fifth deepest peak relative to the average surface of the curved surface. The lower limit of the ten-point average roughness SRz of at least one surface of the polyethylene resin film is preferably 3,000 nm, more preferably 3,900 nm, and even more preferably 4,500 nm. A thickness of 3,000 nm or more provides excellent slip properties and blocking resistance. The upper limit of the ten-point average roughness SRz of at least one surface of the polyethylene resin film is preferably 15,000 nm, more preferably 10,000 nm, and even more preferably 7,000 nm. A thickness of 15,000 nm or less provides excellent transparency and scratch resistance. The measurement method is the same as that described in the examples. It is preferable that one surface of the heat seal layer has a ten-point average roughness SRz within the above-mentioned numerical range.

[0113] (Static Friction Coefficient) The lower limit of the static friction coefficient between the heat-sealed surfaces of the polyethylene resin film is preferably 0.05, more preferably 0.08, and even more preferably 0.13. If it is 0.05 or higher, the film roll is less likely to meander when processed. The upper limit of the static friction coefficient between the heat-sealed surfaces of the polyethylene resin film is preferably 0.70, more preferably 0.50, even more preferably 0.40, and particularly preferably 0.30. If it is 0.70 or lower, the surfaces that are not facing each other easily slide against each other when filling the package with food or when opening it, and the opening is easy. The lower limit of the static friction coefficient between the heat-sealed surface and the laminated surface of the polyethylene resin film is preferably 0.10, more preferably 0.20, and even more preferably 0.30. If it is 0.10 or higher, the film roll is less likely to unwind when transported. The upper limit of the coefficient of static friction between the heat-sealed surface and the laminated surface of the polyethylene resin film is preferably 0.70, more preferably 0.60, and even more preferably 0.50. If the coefficient is 0.70 or less, the rolled product film is less likely to wrinkle even when rolled and transported.

[0114] (Accelerated Blocking Strength) The smaller the accelerated blocking strength between the heat-sealed surfaces of the polyethylene resin film, the better. The upper limit of the accelerated blocking strength between the heat-sealed surfaces of the polyethylene resin film is preferably 300 mN / 70 mm, more preferably 200 mN / 70 mm or less, and even more preferably 150 mN / 70 mm. If it exceeds 300 mN / 70 mm, the powder-free properties and the opening properties of the bag may not be sufficiently obtained.

[0115] (Scratch Resistance) Scratch resistance refers to the change in haze after rubbing the polyethylene resin film surfaces together in a laminate obtained by laminating a biaxially oriented nylon film (15 μm) and a polyethylene resin film. The increase in haze of the polyethylene resin film before and after scratching is preferably 3.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, and particularly preferably 0.5% or less. The increase in haze before and after scratching is ideally 0%, but may be 0.01% or more, 0.05% or more, 0.1% or more, etc.

[0116] (Haze) The lower limit of the haze of the polyethylene resin film is preferably 1.0%, more preferably 2.0%, even more preferably 3.0%, and particularly preferably 4.0%. If it is 1.0% or more, the film surface is not extremely uneven, so blocking on the inner surface of the package is unlikely to occur. The upper limit of the haze of the polyethylene resin film is preferably 15.0%, more preferably 13.0%, even more preferably 10.0%, and even more preferably 8.0%. If it is 15.0% or less, visibility of the package is easily obtained.

[0117] (Transportation Wrinkles) Manufactured films are generally wound into rolls for transport, storage, and use. The rolled-up product rolls may be transported by machine or by hand. In particular, when packaging is performed using an automatic packaging machine, the film is rotated or rolled for transport more frequently. During such processes, if localized force is applied to the body of the roll by the machine, this force can cause wrinkles in the film roll (transportation wrinkles). If transport wrinkles occur, wrinkle marks will appear in the laminate or package, deteriorating its appearance. Therefore, it is preferable to prevent transport wrinkles. After extensive research into this phenomenon, we surprisingly found that the occurrence of transport wrinkles can be reduced by having fine protrusions on at least one side of the film. We believe that the presence of fine protrusions on the film improves the slipperiness of the front and back surfaces of the film, thereby dispersing the force applied by the machine during transport. The fine protrusions can be expressed, for example, by the protrusion density at a height of 250 nm from the reference plane, as mentioned above, and can be achieved by appropriately selecting the particle shape and amount of antiblocking agent added.

[0118] (Young's Modulus) The lower limit of the Young's modulus (longitudinal direction) of the polyethylene resin film is preferably 60 MPa, more preferably 70 MPa. If it is less than the above, the stiffness may be too weak and the film may be difficult to process. The upper limit of the Young's modulus (longitudinal direction) of the polyethylene resin film is preferably 600 MPa, more preferably 500 MPa, and even more preferably 400 MPa. The lower limit of the Young's modulus (width direction) of the polyethylene resin film is preferably 60 MPa, more preferably 70 MPa. If it is less than the above, the stiffness may be too weak and the film may be difficult to process. The upper limit of the Young's modulus (width direction) of the polyethylene resin film is preferably 600 MPa, more preferably 500 MPa, and even more preferably 400 MPa. The longitudinal direction refers to the flow direction (MD direction) of the equipment used to produce the film, and the width direction refers to the direction perpendicular to the longitudinal direction (TD direction).

[0119] (Heat shrinkage rate) The lower limit of the heat shrinkage rate in the longitudinal direction of the polyethylene-based resin film is preferably 0.2%, more preferably 0.3%, and even more preferably 0.5%. If it is 0.2% or higher, heat resistance is sufficient. The upper limit of the heat shrinkage rate in the longitudinal direction of the polyethylene-based resin is preferably 2.5%, more preferably 1.5%. If it is 2.5% or lower, pitch misalignment during printing is unlikely to occur. The lower limit of the heat shrinkage rate in the width direction of the polyethylene-based resin film is preferably 0.0%, more preferably 0.1%, and even more preferably 0.2%. If it is 0.0% or higher, film elongation during heating is unlikely to occur. The upper limit of the heat shrinkage rate in the width direction of the polyethylene-based resin film is preferably 1.5%, more preferably 1.0%. If it is 1.5% or lower, pitch misalignment during printing is unlikely to occur.

[0120] (Tear strength) The lower limit of the tear strength (longitudinal direction) of the polyethylene resin film is preferably 1.0 N, more preferably 2.0 N. If it is less than the above, the package may be easily torn. The upper limit of the tear strength (longitudinal direction) of the polyethylene resin film is preferably 8.0 N, more preferably 6.0 N, and even more preferably 5.0 N. If it is 8.0 N or less, the package is easy to open. The lower limit of the tear strength (width direction) of the polyethylene resin film is preferably 1.0 N, more preferably 2.0 N. If it is less than the above, the package may be easily torn. The upper limit of the tear strength (width direction) of the polyethylene resin film is preferably 8.0 N, more preferably 6.0 N, and even more preferably 5.0 N. If it is 8.0 N or less, the package is easy to open.

[0121] (Wet tension) The lower limit of the wet tension of the corona-treated surface (laminate surface) of the polyethylene resin film is preferably 30 mN / m, more preferably 35 mN / m. If it is 30 mN / m or more, the laminate strength is less likely to decrease. The upper limit of the wet tension of the polyethylene resin film is preferably 55 mN / m, more preferably 50 mN / m. If it is 55 mN / m or less, blocking between films is less likely to occur when the polyolefin resin film is wound around a roll.

[0122] (Heat seal initiation temperature of film alone) The lower limit of the heat seal initiation temperature of the polyethylene resin film alone is preferably 80°C, more preferably 90°C. If it is 80°C or higher, it has a high stiffness and is easy to handle. The upper limit of the heat seal initiation temperature of the polyethylene resin film is preferably 140°C, more preferably 130°C, and even more preferably 120°C. If it is 140°C or lower, packages can be produced at high speed, which is economically advantageous. The heat seal initiation temperature is greatly affected by the melting point of the heat seal layer.

[0123] (Biomass Degree) The biomass degree indicates the proportion of plant-derived carbon atoms out of all carbon atoms in the film. The higher the proportion of plant-derived carbon atoms, the greater the carbon dioxide reduction effect based on the carbon neutral concept. The lower limit of the biomass degree of the polyethylene resin film may be 0%, but is preferably 10%, more preferably 15%, and even more preferably 30%. When it is 10% or higher, the carbon dioxide reduction effect is greater. The upper limit of the biomass degree of the polyethylene resin film is not particularly limited, but is preferably 70%, more preferably 55% or less, and even more preferably 40%. When it is 70% or less, foreign matter due to plant-derived materials is less likely to increase, the appearance is good, and the filter pressure during the extrusion process is less likely to increase.

[0124] (Configuration and Manufacturing Method of Laminate) In one or more embodiments, the laminate includes at least one film selected from the group consisting of a uniaxially oriented polyolefin resin film, a biaxially oriented polyolefin resin film, a uniaxially oriented polyamide resin film, a biaxially oriented polyamide resin film, a uniaxially oriented polyester resin film, and a biaxially oriented polyester resin film, and a polyethylene resin film according to the embodiment. Furthermore, in one or more embodiments, the laminate preferably includes the polyethylene resin film according to the embodiment as a sealant and at least one film selected from the group consisting of a polyamide resin film, a polyester resin film, and a polyolefin resin film as a substrate film. Furthermore, as a known technique, these substrate films or sealants may be coated or vapor-deposited, or aluminum foil may be further laminated, for the purpose of imparting adhesiveness or barrier properties. The substrate film is preferably selected from biaxially oriented films such as a biaxially oriented polyolefin resin film, a biaxially oriented polyamide resin film, and a biaxially oriented polyester resin film, but may also be a uniaxially oriented film. Specific examples include biaxially oriented PET (polyethylene terephthalate) film / aluminum foil / sealant, biaxially oriented PET (polyethylene terephthalate) film / sealant, biaxially oriented nylon film / sealant, biaxially oriented polypropylene film / sealant, biaxially oriented polyethylene terephthalate (PET) film / biaxially oriented nylon film / sealant, uniaxially oriented polyethylene film / sealant, etc. As a lamination method, known methods such as dry lamination and extrusion lamination can be used, and any lamination method may be used.

[0125] The properties of the laminate of the embodiment are described below. (Heat seal strength) The lower limit of the heat seal strength of a laminate containing a polyethylene resin film at 160°C, 0.2 MPa, and 1 second is preferably 40 N / 15 mm, more preferably 50 N / 15 mm, and even more preferably 55 N / 15 mm. If it is 40 N / 15 mm or more, bag rupture resistance is likely to be obtained. If the heat seal strength is 60 N / 15 mm, it is very excellent, and if it is 70 N / 15 mm, it is sufficient.

[0126] (Packaging) In one or more embodiments, the packaging is made of the laminate described above. A structure formed by arranging the polyethylene-based resin film or laminate of the embodiment so as to wrap around the contents, such as food, for the purpose of protecting the contents from natural dust, gas, and the like, is called a packaging. The packaging is produced by cutting out the polyethylene-based resin film or laminate of the embodiment, bonding the inner surfaces together using a heated heat seal bar or ultrasonic waves, or by forming a bag. For example, the packaging may be a four-sided sealed bag or a back-sealed packaging bag in which two rectangular sheets are stacked with the heat seal layer side facing inward and the four sides are heat-sealed. The contents of the packaging may be food, but may also be other products such as daily necessities, and the shape of the packaging may be a shape other than a rectangle, such as a stand-up pouch or pillow packaging.

[0127] This application claims the benefit of priority based on Japanese Patent Application No. 2023-135023, filed on August 22, 2023. The entire contents of the specification of Japanese Patent Application No. 2023-135023, filed on August 22, 2023, are incorporated herein by reference.

[0128] The present disclosure will be described in detail below using examples, but is not limited to these. The properties obtained in each example were measured and evaluated by the following methods. In the evaluation, the flow direction of the film in the film production process was defined as the longitudinal direction (MD direction), and the direction perpendicular to the flow direction was defined as the width direction (TD direction).

[0129] (1) Resin Density, Weighted Average Density Density was evaluated in accordance with JIS K7112:1999 D Method (density gradient pipe). N=3 measurements were made, and the average value was calculated. The weighted average density of the resin composition in each layer was determined by averaging the densities of the resins constituting the resin composition, with the weight of each resin as the weight.

[0130] (2) Melt flow rate (MFR) Measurement was carried out in accordance with JIS K-7210-1 at 190°C under a load of 2.16 kg. N=3 measurements were made, and the average value was calculated.

[0131] (3) Melting Point The melting point was determined 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 end temperature was 180°C. N=3 measurements were made, and the average value was calculated.

[0132] (4) Sphericity of particles The surface of the film was observed using a 3D laser microscope (LEXT OLS4100) manufactured by OLYMPAS Corporation, and the minor axis and major axis of the particles were measured. A 50x objective lens was selected. The ratio of minor axis to major axis was calculated. The same measurement was performed on 10 particles of the same type, and the average of the ratios for the 10 particles was calculated, which was taken as the sphericity. The average of the major axes for the 10 particles of the same type was also calculated, which was taken as the average particle size.

[0133] (5) Particle Hardness The hardness of particles made of polyethylene resin was measured using a Shore hardness tester type D in accordance with ASTM D2240 for a resin sheet prepared by melting particles made of polyethylene resin. The Mohs hardness of the inorganic particles before crushing was determined from the Mohs hardness table. Specifically, the samples were rubbed against the uncrushed mineral in order of hardness, starting with the lowest standard material, and the hardness of the sample was determined by visually checking whether the sample was scratched.

[0134] (6) Protrusion density at a height of 250 nm from the reference plane of surface roughness For the measurement data under the conditions of the three-dimensional high-precision micro-shape measuring instrument in (7) described below, a three-dimensional surface roughness analysis system (type iFace model TDA-31) was used, and "Particle analysis (multiple levels)" was selected in the analysis tab of the menu bar. The "Output content setting" was set to "Particles: numerical output," the "Hysteresis width" item was set to 0.005 μm, and the "Slice level interval" item was set to 0.25 μm (250 nm), and the protrusion number density (pieces / mm) for each protrusion height (level increments of 0.25 μm (250 nm)) was calculated. ２ That is, the protrusion number density (pieces / mm) at each of the protrusion heights of 0 nm, 250 nm, 500 nm, 750 nm, and so on was determined. ２ ) was sought.

[0135] (7) Arithmetic mean roughness SRa, maximum height SRmax, ten-point mean roughness SR The three-dimensional roughness of the heat-sealing surface of a polyethylene resin film was measured using the following measurement conditions based on JIS-B0601 (1994). After processing using the following analysis conditions, the arithmetic mean roughness SRa, maximum height SRmax, and ten-point mean roughness SRz were selected from the "3D roughness parameters" in the analysis tab of the menu bar, and the values ​​were output in list format to determine these values.

[0136] (Measurement conditions) Measuring device: Three-dimensional high-precision microprofile measuring instrument (Model ET-4000A) manufactured by Kosaka Laboratory Co., Ltd. Stylus: Tip radius 0.5 μmR, diameter 2 μm, made of diamond Stylus pressure: 100 μN Measurement direction: Longitudinal direction of film X-axis (Longitudinal direction of film) measurement length: 1.0 mm Y-axis (Width direction of film) measurement length: 0.20 mm X-axis feed speed: 0.1 mm / s (measurement speed) Y-axis feed pitch: 2 μm (measurement interval) Number of Y-axis lines: 101 (number of measurements) Z-axis measurement magnification: 20,000 times (longitudinal magnification) (Analysis conditions) Analysis software: Three-dimensional surface roughness analysis system (Model TDA-31) Leveling: Yes, entire area Low-frequency cutoff: 0.200 mm (Waviness cutoff value) Low-frequency reserve length: λc x 0 High frequency cutoff: 0.000 mm High frequency reserve length: None

[0137] (8) Static friction coefficient A sample measuring 200 mm in the longitudinal direction and 80 mm in the width direction was cut out from the polyethylene resin film and fixed to the table of the testing machine with the measurement surface facing up. Next, a sample measuring 90 mm in the longitudinal direction and 70 mm in the width direction was similarly cut out from the polyethylene resin film and fixed to a sliding piece weighing 1.0 kg and having a bottom surface measuring 70 mm in length and 50 mm in width so that the measurement surface was facing outward. Next, the measurement surfaces of the two samples were placed face to face and overlapped, and measurements were performed. A universal tensile tester STM-T-50BP (manufactured by Toyo Baldwin) was used to measure in accordance with JIS K7125. Evaluations were performed on the heat-sealed surfaces or the overlapping of the heat-sealed surface and the laminated surface.

[0138] (9) Accelerated Blocking Strength Two samples measuring 148 mm in the longitudinal direction and 105 mm in the width direction were cut from a polyethylene resin film. The heat-sealed surface and the laminated surface were placed face-to-face and overlapped. After preheating for 30 minutes in a 50°C environment, the samples were sandwiched between 7.0 cm square aluminum plates maintained at 50°C. Using a Mini Test Press MP-SCH manufactured by Toyo Seiki Seisakusho Co., Ltd., the aluminum plate and the sample were pressed at 50°C and 100 kN and held for 15 minutes. The two removed samples were cut to a width of 70 mm. The two overlapping samples were opened 30 mm, and a 3 mm diameter metal rod was inserted parallel to the width direction. The sample was mounted on an Autograph AG-I manufactured by Shimadzu Corporation, and the load applied when the metal rod was moved in the longitudinal direction at 200 mm / min was measured. Measurements were performed with N=3, and the average value was calculated.

[0139] (10) Scratch resistance Two samples measuring 180 mm in the longitudinal direction and 50 mm in the transverse direction were cut out from each laminate obtained in Examples and Comparative Examples, and were stacked with the heat seal layer surfaces facing each other, and were set in a Gakushin abrasion tester manufactured by Yasuda Seiki Seisakusho, and were judged by the amount of change in haze after 100 abrasions at a load of 200 g. The haze was measured at the center of the film (a point was marked at the edge and a point was marked at both ends from the side opposite the abrasion surface that did not affect the haze measurement) before setting on the abrasion table, and the haze was measured at the same position after abrasion to determine the difference.

[0140] (11) Haze Haze was measured using NDH8000 manufactured by Nippon Denshoku Co., Ltd. in accordance with JIS K7136. Measurement was made for the polyolefin resin film before lamination, N=3, and the average value was calculated.

[0141] (12) Wrinkles During Transport A polyethylene resin film was wound into a length of 1000 mm wide and 4000 m long, and the end of the film at the unwound portion of the roll was taped in three places. A K-liner paper was wrapped around the surface of the resulting film roll. The film roll was rolled and transported onto a roller conveyor where rolls were arranged at 20 cm intervals, and the film roll was rotated once on the roller conveyor. The K-liner paper was removed, and the surface of the film roll was visually inspected. Ten film rolls were evaluated. Those marked ○ were deemed to have passed based on the following criteria: ○: None of the 10 film rolls had wrinkles, and the film was not deformed. △: Some film rolls had wrinkles, but the deformation marks disappeared when 10 m of the surface film was unwound. ×: Some film rolls had wrinkles, and deformation occurred beyond 10 m from the surface, leaving marks.

[0142] (13) Young's modulus The tensile strength in the longitudinal direction and the width direction was measured at 23°C in accordance with JIS-K7127. The test piece had a length of 150 mm and a width of 15 mm, and the test speed was 200 mm / min. N=3 measurements were made, and the average value was calculated.

[0143] (14) Heat Shrinkage Ratio This was measured in accordance with JIS Z1712 by the following method. The film was cut into two samples measuring 20 mm x 200 mm along the longitudinal direction or the transverse direction of the film, and these were hung in a hot air oven at 90°C and heated for 30 minutes. The length after heating was measured, and the heat shrinkage ratio was calculated as the ratio of the shrunken length to the original length.

[0144] (15) Tear Strength Tear strength was measured in accordance with JIS K7128-1:1998. The tear strength of the polyethylene resin film was evaluated. The test speed was 200 mm / min. Measurements were made in the longitudinal direction and the width direction with N=3, and the average value was calculated.

[0145] (16) Wet Tension The wet tension of the laminate layer surface was measured in accordance with JIS-K6768 Plastics - Films and Sheets - Wet Tension Test Method.

[0146] (17) Heat-sealing initiation temperature The heat-sealing initiation temperature of a polyethylene 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 direction x length direction of the film). The heat-sealed layers of two test pieces were overlapped, and a thermal gradient tester (heat-sealing tester) manufactured by Toyo Seiki Seisakusho Co., Ltd. was used. The heat-sealing pressure was 0.2 MPa and the heat-sealing time was 1.0 sec. For measurements using the film alone, the film was protected with a biaxially oriented polyester resin film to prevent the resin from adhering to the heat-sealing bar, and then heat-sealed. The heat-sealing temperature was gradually increased from 80°C to obtain multiple test pieces. After heat-sealing, a 15 mm wide sample was cut out from each test piece. Each sample fused by heat sealing was opened 180°, the unsealed portion was clamped with a zipper, and the sealed portion was peeled off, and the peel load was measured. The test machine used was a universal material testing machine 5965 manufactured by Instron Instruments. The test speed was 200 mm / min. The values ​​were plotted on graph paper with the heat sealing temperature on the horizontal axis and the peel load on the vertical axis, and the plots were connected by straight lines. The temperature at which the peel load reached 4.9 N on the straight line was taken as the heat sealing initiation temperature. Five measurements were taken, and the average value (N=5) was calculated.

[0147] (18) Heat-sealing strength The heat-sealing conditions and strength measurement conditions were as follows. Two samples were cut from each laminate obtained in the Examples and Comparative Examples, overlapped with the polyethylene resin film sides facing each other, and heat-sealed for 1 second at a pressure of 0.2 MPa with a seal bar width of 10 mm and a heat-sealing temperature of 160°C, followed by cooling. A test piece measuring 80 mm in the longitudinal direction and 15 mm in the transverse direction was cut from the heat-sealed film, and the peel strength of the test piece was measured when the heat-sealed portion was peeled off at a crosshead speed of 200 mm / min. The test machine used was a Universal Testing Machine 5965 manufactured by Instron Instruments. Measurements were performed three times for each, and the average value was calculated.

[0148] (19) Biomass Degree Based on the ASTM D6866 Biobased Test, the biomass degree was calculated from the C14 (carbon atom with a mass number of 14) concentration in the film.

[0149] (Example 1) (Raw material resins used) LL-1: Umerit (registered trademark) 0540F (metallocene-based 1-hexene copolymer linear low-density polyethylene, density 904 kg / m) manufactured by Ube Maruzen Polyethylene Co., Ltd. ３ , MFR 4.0 g / 10 min, melting point 111°C) LL-2: Sumikathene (registered trademark) E FV402 manufactured by Sumitomo Chemical Co., Ltd. (metallocene catalyst-based 1-hexene copolymerized LLDPE, density: 913 kg / m ３ , MFR: 3.8 g / 10 min, melting point: 115°C) LL-3: Ube Maruzen Polyethylene Co., Ltd.'s Yumerit (registered trademark) 2040FA (metallocene-based 1-hexene copolymer linear low-density polyethylene, density 918 kg / m ３ , MFR 4.0 g / 10 min, melting point 116°C) LL-4: Sumikathene (registered trademark) E FV405 manufactured by Sumitomo Chemical Co., Ltd. (metallocene catalyst-based 1-hexene copolymer LLDPE, density: 923 kg / m ３ , MFR: 3.8 g / 10 min, melting point: 118°C) LL-5: Braskem SLH218 (plant-derived linear low-density polyethylene, 1-hexene / 1-butene copolymer, density 916 kg / m ３, melting point 126°C, biomass content 90%) LL-6: Ube Maruzen Polyethylene Co., Ltd.'s Yumerit (registered trademark) 846CC (metallocene-based 1-hexene copolymer linear low-density polyethylene, density 937 kg / m ３ , MFR 4.5 g / 10 min, melting point 126°C) LL-7: Ube Maruzen Polyethylene Co., Ltd.'s Yumerit (registered trademark) 4040FC (metallocene-based 1-hexene copolymer linear low-density polyethylene, density 938 kg / m ３ , MFR 3.5 g / 10 min, melting point 126°C) (Particle masterbatch) MB-1: Sumikathene (registered trademark) E FV402 manufactured by Sumitomo Chemical Co., Ltd., mixed with Mipelon PM200 (average particle size 10 μm, sphericity 0.91, melting point 136°C, density 940 kg / m ３A masterbatch containing 15% by weight of PM200 was prepared by mixing two ultra-high molecular weight polyethylene particles (viscosity average molecular weight 1.8 million, 0% of particles with a particle size greater than 30 μm, resin hardness D65, ultra-high molecular weight polyethylene particles). MB-2: Sumitomo Chemical's Sumikathene (registered trademark) E FV402 was mixed with Mizusawa Industrial Chemicals' Silton JC-50 (spherical zeolite particles, average particle size 5.0 μm, sphericity 0.96) to prepare a masterbatch containing 15% by weight of JC-50. MB-3: Sumitomo Chemical's Sumikathene (registered trademark) E FV402 was mixed with Shin-Etsu Silicone's KMP-130-10 (spherical silica particles, average particle size 10 μm, sphericity 0.98) to prepare a masterbatch containing 15% by weight of KMP-130-10. MB-4: Sumitomo Chemical's Sumikathene (registered trademark) E FV402 was mixed with Grefco Inc.'s Dicalite WF (irregular diatomaceous earth, processed to an average particle size of 5 μm using a pin mill, and used with a sphericity of 0.75) to prepare a masterbatch containing 15 wt% Dicalite WF. (Organic Lubricant Masterbatch) MB-5: Sumitomo Chemical's Sumikathene (registered trademark) E FV402 was mixed with erucic acid amide to prepare a masterbatch containing 4 wt% erucic acid amide. MB-6: Sumitomo Chemical's Sumikathene (registered trademark) E FV402 was mixed with ethylene bisoleic acid amide to prepare a masterbatch containing 2 wt% ethylene bisoleic acid amide. MB-7: Sumikathen (registered trademark) E FV402 manufactured by Sumitomo Chemical was mixed with CUBE-50KAS manufactured by Maruo Calcium Co., Ltd. (cubic calcium carbonate particles, Mohs hardness 3, average particle size 5 μm, sphericity 0.71) to prepare a master batch containing 15% by weight of cubic calcium carbonate.

[0150] (Unstretched Polyethylene Resin Film) (Example 1) For a polyethylene resin film, raw materials were prepared based on the resin composition and proportions of each layer shown in Table 1 below. For the preparation, each raw material was transported in a fixed amount using a screw feeder and weighed. One weighing batch was 14 kg for the laminate layer, 40 kg for the core layer, and 14 kg for the heat seal layer. Table 1 shows the evaluation results.

[0151] (Melt extrusion) The mixed raw materials for the core layer were introduced into a three-stage single-screw extruder with a screw diameter of 90 mm, and the mixed raw materials for the heat-seal layer and the laminate layer were introduced into a three-stage single-screw extruder with a screw diameter of 65 mm and a three-stage single-screw extruder with a screw diameter of 45 mm, respectively, in the order of heat-seal layer / core layer / laminate layer. Specifically, each was introduced into a T-slot die with a width of 1400 mm, a two-stage preland, and a curved step shape to ensure uniform flow of the molten resin within the die, and extruded at an outlet temperature of 230 ° C. The thickness ratio of the heat-seal layer / core layer / laminate layer was 20% / 60% / 20%, respectively.

[0152] (Cooling) The molten resin sheet emerging from the die was cooled on a cooling roll at 40°C to obtain an unstretched polyethylene resin film with a thickness of 50 μm. When 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. At the same time, a vacuum chamber was activated to prevent air from being drawn in between the molten resin sheet and the cooling roll. The air nozzles on both ends were installed in series in the direction of film travel. The die was surrounded by a sheet to prevent wind from blowing on the molten resin sheet. In addition, the suction port of the vacuum chamber was aligned with the direction of travel of the extruded sheet. (Trimming) The edge portions on both ends of the cooled and solidified polyolefin resin film were cut with a slit blade and introduced to a separate line. (Corona Treatment) The surface of the laminate layer of the film was corona treated (power density 20 W min / m ２ ) was applied.

[0153] (Winding) The film was produced at a speed of 40 m / min. The film was wound up while being pressed with a contact roll under tension to prevent wrinkles. After aging at 40°C for 24 hours, both ends were cut again using a slitting machine, and the film was wound up to a width of 1000 mm, resulting in a film roll of 4000 m.

[0154] (Preparation of Laminate) Each polyethylene resin film obtained in the Examples and Comparative Examples and a biaxially oriented nylon film (N1102, manufactured by Toyobo Co., Ltd., thickness 15 μm) as a substrate film were laminated with an ester adhesive obtained by mixing 33.6 parts by mass of a base agent (TM569, manufactured by Toyo-Morton Co., Ltd.), 4.0 parts by mass of a curing agent (CAT10L, manufactured by Toyo-Morton Co., Ltd.), and 62.4 parts by mass of ethyl acetate, at a coating amount of 3.0 g / m. ２ The resulting film was wound up and kept at 40° C. for 3 days to undergo aging, thereby obtaining a laminate.

[0155] (Examples 2 to 10) In Example 1, the raw materials used for the heat seal layer, core layer, and laminate layer were changed to the ratios shown in Table 1, and a 50 μm polyethylene resin film was obtained in the same manner as in Example 1. A laminate was obtained in the same manner as in Example 1. Table 1 shows the evaluation results.

[0156] (Example 11) A 30 μm polyethylene resin film was obtained in the same manner as in Example 2, except that the total film thickness was 30 μm. The thickness ratios of the heat seal layer / core layer / laminate layer were 20% / 60% / 20%, respectively. A laminate was obtained in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0157] (Comparative Examples 1 to 8) In Example 1, the raw materials used for the heat seal layer, core layer, and laminate layer were changed to the ratios shown in Table 2, and a 30 μm polyethylene resin film was obtained in the same manner as in Example 1. A laminate was obtained in the same manner as in Example 1. Table 2 shows the evaluation results.

[0158] In Comparative Example 1 and Comparative Example 2, wrinkles during transport were likely to occur due to the small number of fine protrusions. In Comparative Example 3, the amount of spherical inorganic particles with an average particle size of less than 9 μm was large, resulting in poor scratch resistance. In Comparative Example 4, wrinkles during transport were likely to occur due to the small amount of spherical polyethylene-based resin particles with an average particle size of 9 μm or more. In Comparative Example 5, the amount of spherical polyethylene-based resin particles with an average particle size of 9 μm or more was too large, resulting in poor scratch resistance. In Comparative Example 6, the amount of spherical inorganic particles with an average particle size of 9 μm or more was too large, resulting in poor scratch resistance. In Comparative Example 7, the content of non-spherical inorganic particles exceeded 2500 ppm, resulting in poor scratch resistance. In Comparative Example 8, the content of non-spherical inorganic particles exceeded 2500 ppm, resulting in poor scratch resistance.

[0159] The results are shown in Tables 1 and 2. In Tables 1 and 2, "spherical inorganic and crosslinked organic particles less than 9 μm" indicates the total amount of spherical inorganic particles less than 9 μm and spherical crosslinked organic particles less than 9 μm. In Tables 1 and 2, "spherical inorganic and crosslinked organic particles 9 μm or more" indicates the total amount of spherical inorganic particles 9 μm or more and spherical crosslinked organic particles 9 μm or more.

[0160]

[0161]

[0162] The present disclosure provides a polyethylene-based resin film that is excellent in scratch resistance, heat sealability, blocking resistance, and slipperiness. Such a polyethylene-based resin film can be used as a non-stretched polyethylene-based resin film that is resistant to wrinkles even when transported by rolling a film roll, and can make a significant contribution to industry.

Claims

1. A polyethylene-based resin film having a heat seal layer made of a polyethylene-based resin composition on one surface layer and a laminate layer made of a polyethylene-based resin composition on the other surface layer, wherein at least one of the surface layers satisfies the following 1) to 4). 1) Contains 1900 ppm to 16000 ppm of spherical polyethylene resin particles having an average particle size of 9 μm or more. 2) Contains 3100 ppm to 15000 ppm of spherical particles having an average particle size of less than 9 μm. 3) The total content of spherical inorganic particles having an average particle size of 9 μm or more and spherical crosslinked organic particles having an average particle size of 9 μm or more is 1000 ppm or less. 4) The content of non-spherical particles is 2500 ppm or less.

2. The polyethylene resin film according to claim 1, wherein the weighted average density of the polyethylene resin composition constituting the heat seal layer is lower than the weighted average density of the polyethylene resin composition constituting the laminate layer.

3. The polyethylene resin film according to claim 1, wherein the spherical particles made of polyethylene resin and having an average particle size of 9 μm or more have a viscosity average molecular weight of 1.5 million or more and 2.5 million or less.

4. The weighted average density of the polyethylene resin composition constituting the laminate layer is 910 kg / m ３ More than 945kg / m ３ The weighted average density of the polyethylene resin composition constituting the heat seal layer is 900 kg / m or less. ３ More than 930kg / m ３ The polyethylene resin film according to claim 1, wherein:

5. One or more core layers are present between the heat seal layer and the laminate layer, and the weighted average density of the polyethylene resin composition constituting the core layer is 910 kg / m ３ More than 930kg / m ３ The polyethylene resin film according to claim 1, wherein:

6. The polyethylene resin film according to claim 1, wherein the polyethylene resin contained in the polyethylene resin composition constituting the laminate layer and the polyethylene resin contained in the polyethylene resin composition constituting the heat seal layer are linear low-density polyethylene.

7. The polyethylene resin film according to claim 1, wherein the arithmetic mean roughness SRa of at least one of the surfaces of the laminate layer and the heat seal layer is 60 nm or more and 200 nm or less, and the maximum height SRmax is 2 μm or more and 9 μm or less.

8. A polyethylene-based resin film as described in claim 1, wherein 1) the spherical particles of polyethylene-based resin have an average particle size of 20 μm or less, and 2) the spherical particles have an average particle size of 3 μm or more.

9. 3) A polyethylene resin film as described in claim 1, in which the total content of spherical particles having an average particle size of 9 μm or more is 1,000 ppm or less.

10. 2) A polyethylene resin film as described in claim 1, wherein the spherical particles are inorganic particles.

11. The polyethylene resin film according to claim 1, wherein the heat seal layer satisfies the above 1) to 4).

12. A laminate comprising at least one film selected from the group consisting of uniaxially oriented polyolefin resin films, biaxially oriented polyolefin resin films, uniaxially oriented polyamide resin films, biaxially oriented polyamide resin films, uniaxially oriented polyester resin films, and biaxially oriented polyester resin films, and the polyethylene resin film according to any one of claims 1 to 11.

13. A package comprising the laminate according to claim 12.