film

Abstract

To provide a film which can achieve reduction in environmental loads, and can keep a haze value to be a low range over a long period.SOLUTION: A film has at least one polyethylene resin layer which is composed of a polyethylene resin composition containing linear low-density polyethylene and low-density polyethylene, wherein the linear low-density polyethylene is composed of a polymer of plant-derived ethylene, the low-density polyethylene is composed of a polymer of plant-derived ethylene, a content ratio of the low-density polyethylene in the polyethylene resin composition is 25 mass% or more, and a melt flow rate of the low-density polyethylene is 1.0 g / 10 min or more and 40.0 g / 10 min or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a film comprising a polyethylene resin layer using a plant-derived synthetic resin material. Background Art

[0002] Polyethylene films can be used in a wide range of fields, for example, as the agricultural covering material (agricultural film) for so-called greenhouse cultivation and tunnel cultivation, in which useful plants are cultivated under covering with an agricultural covering material, and as sealant films that constitute the inner surface layer of laminated films for pouches for forming pouch packaging bags. In recent years, in response to the demand for reducing environmental load through the construction of a recycling-oriented society, it has been desired to shift from fossil fuel-derived materials to plant-derived materials for synthetic resin materials. Conventionally, polyethylene films made of linear low-density polyethylene, low-density polyethylene, or mixtures thereof are known. As resin films using plant-derived materials, bio-polyethylene films using plant-derived linear low-density polyethylene or low-density polyethylene have been proposed (see Patent Document 1 and Patent Document 2).

[0003] On the other hand, it has been found that when such a film is stored at room temperature for a long period of time, the haze value increases due to the influence of water-insoluble bleed-out products, and the desired transparency may not be maintained. The haze value is the ratio of diffuse transmittance to total light transmittance, and a higher haze value indicates a more cloudy state. Prior Art Documents Patent Documents

[0004] Patent Document 1 Japanese Patent No. 6197820 Patent Document 2 Japanese Unexamined Patent Publication No. 2017-114495 Summary of the Invention [Problems that the invention aims to solve]

[0005] The present invention was made based on the circumstances described above, and its purpose is to provide a film that can reduce environmental impact and maintain a low haze value over a long period of time. [Means for solving the problem]

[0006] The film of the present invention is a film having at least one polyethylene resin layer made of a polyethylene resin composition containing linear low-density polyethylene and low-density polyethylene, The aforementioned linear low-density polyethylene consists of a polymer of plant-derived ethylene and has a bio-concentration of 85% or more. The aforementioned low-density polyethylene consists of a polymer of plant-derived ethylene and has a bio-concentration of 90% or more. The content of the low-density polyethylene in the polyethylene resin composition is 25 to 50% by mass. The melt flow rate of the low-density polyethylene is 2.7g / 10min or more and 3.8g / 10min or less And, The melt flow rate of the linear low-density polyethylene is 0.8 g / 10 min or more and 1.0 g / 10 min or less. The aforementioned polyethylene The resin composition has a bio-concentration of 89% or more. The polyethylene resin composition teeth , not containing low-density polyethylene other than the aforementioned low-density polyethylene, and containing linear low-density polyethylene other than the aforementioned linear low-density polyethylene. Furthermore, it contains high-density polyethylene. It is characterized by not doing so.

[0007] In the film of the present invention, it is preferable that the haze value of the polyethylene resin layer is 5.0 to 11.0%.

[0009] Furthermore, the film of the present invention is preferably used as an agricultural film. [Effects of the Invention]

[0010] According to the film of the present invention, the polyethylene resin layer, in which both linear low-density polyethylene and low-density polyethylene contained in the polyethylene resin composition are made of polymers of plant-derived ethylene, reduces the reliance on raw materials derived from fossil fuels, thereby reducing the environmental burden. Furthermore, because the content of low-density polyethylene in the polyethylene resin composition is 25% by mass or more, and the melt flow rate of said low-density polyethylene is 1.0 g / 10 min or more and 40.0 g / 10 min or less, the haze value can be maintained in a low range over a long period of time, and as a result, the film can maintain the desired transparency even after long-term storage. [Modes for carrying out the invention]

[0011] The embodiments of the present invention will be described in detail below. [film] The film of the present invention has at least one polyethylene resin layer made of a polyethylene resin composition containing specific low-density polyethylene and specific linear low-density polyethylene, i.e., a film having a bio-polyethylene layer.

[0012] In a polyethylene resin composition constituting a polyethylene resin layer, a specific low-density polyethylene is made of a polymer of plant-derived ethylene. This polymer is obtained, for example, by radical polymerization of plant-derived ethylene under high pressure using a radical polymerization initiator. The ethylene used to obtain the specific low-density polyethylene may be entirely plant-derived, or partly derived from fossil fuels. Alternatively, the specific low-density polyethylene may be a copolymer obtained by copolymerizing ethylene with a small amount of other monomers.

[0013] Furthermore, the specific low-density polyethylene preferably has a bio-content of 90% or more, and more preferably 95% or more. Having a bio-content of 90% or more in the specific low-density polyethylene reduces the amount of fossil fuel-derived raw materials used, thereby reducing the environmental impact.

[0014] The bio-concentration represents the concentration of plant-derived ethylene in polyethylene. It can be measured by utilizing the property that plants, which grow by taking in carbon dioxide from the atmosphere, contain a certain percentage (105.5 pMC) of radioactive carbon (C14), while fossil fuels contain almost no C14. Specifically, the bio-concentration can be calculated by measuring the amount of C14 contained in the total carbon atoms of polyethylene and dividing it by (C14 content in polyethylene) / 105.5 × 100.

[0015] Furthermore, the specific low-density polyethylene has a melt flow rate (MFR) measured in accordance with JIS K7210 (temperature 190°C, load 2.16 kg) of 1.0 g / 10 min or more and 40.0 g / 10 min or less, preferably 2.0 to 8.3 g / 10 min, and more preferably 2.7 to 3.8 g / 10 min. If low-density polyethylene with a melt flow rate (MFR) exceeding 40.0 g / 10 min is used, film formation stability may not be obtained, and even if film formation stability is obtained, the resulting film may have low rigidity. In addition, if the melt flow rate (MFR) of the specific low-density polyethylene is less than 1.0 g / 10 min, it may be difficult to uniformly knead the specific low-density polyethylene and the specific linear low-density polyethylene.

[0016] Furthermore, certain low-density polyethylenes have a density of 0.916 to 0.928 g / cm³. 3 It is preferable to use one that has the following density: 0.916 g / cm³ of a specific low-density polyethylene. 3When the density is less than the above value, the film may have low rigidity, and may also become sticky, making handling difficult. On the other hand, when the density of the specific low-density polyethylene is 0.928 g / cm 3 If the density exceeds the above value, the film may have low impact resistance.

[0017] In the polyethylene resin composition constituting the polyethylene resin layer, the content ratio of the specific low-density polyethylene is 25% by mass or more, and preferably 25 to 50% by mass. When the content ratio of the specific low-density polyethylene is less than 25% by mass, the film may have low rigidity. On the other hand, when the content ratio of the specific low-density polyethylene is excessive, the film may have low impact resistance.

[0018] In the polyethylene resin composition constituting the polyethylene resin layer, the specific linear low-density polyethylene is a polymer of plant-derived ethylene. A copolymer formed of ethylene and an α-olefin having 4 to 10 carbon atoms can be used. As the specific linear low-density polyethylene, a copolymer polymerized using a single-site catalyst such as a metallocene catalyst, a multi-site catalyst such as a Ziegler catalyst, or the like can be used. All ethylene for obtaining the specific linear low-density polyethylene may be derived from plants, or a part thereof may be derived from fossil fuels. Further, the specific linear low-density polyethylene may be a copolymer obtained by copolymerizing ethylene with a small amount of another monomer.

[0019] Further, the specific linear low-density polyethylene preferably has a biobased content of 85% or more, more preferably 87% or more. When the biobased content of the specific linear low-density polyethylene is 85% or more, the usage amount of raw materials derived from fossil fuels can be reduced, thereby achieving a reduction in environmental load.

[0020] Further, the specific linear low-density polyethylene has a density of 0.910 to 0.929 g / cm 3Preferably 0.915~0.926 g / cm³ 3 The density of a specific linear low-density polyethylene is 0.910 g / cm³. 3 If the density is less than 0.929 g / cm³, the film may have low rigidity and may become sticky, making it difficult to handle. On the other hand, if the density of a specific linear low-density polyethylene is 0.929 g / cm³, 3 If the value exceeds this, the film may have low impact resistance.

[0021] Furthermore, the specific linear low-density polyethylene preferably has a melt flow rate (MFR) of 2.5 g / 10 min or less, measured in accordance with JIS K7210 (temperature 190°C, load 2.16 kg), and more preferably 0.8 to 2.2 g / 10 min. If the melt flow rate of the specific linear low-density polyethylene exceeds 2.5 g / 10 min, the film may have low impact resistance.

[0022] In the polyethylene resin composition constituting the polyethylene resin layer, the content of specific linear low-density polyethylene is not particularly limited as long as it is present, but it is preferably 50% by mass or more. Excellent film-forming stability and transparency can be obtained by having the content ratios of the specific low-density polyethylene and the specific linear low-density polyethylene within the above range.

[0023] The polyethylene resin composition constituting the polyethylene resin layer may contain resins other than specific low-density polyethylene and linear low-density polyethylene, as long as it does not hinder the objectives of the present invention. Furthermore, the polyethylene resin composition constituting the polyethylene resin layer may contain various additives such as lubricants, antioxidants, and antiblocking agents.

[0024] The film of the present invention preferably has a haze value of 5.0 to 11.0% immediately after the manufacture of the polyethylene resin layer, more preferably 8.5 to 9.5%. Furthermore, the haze value after long-term storage at room temperature is preferably 6.2 to 20.0%, more preferably 10.5 to 15.5%. In addition, it is preferable that the increase rate of the haze value after long-term storage from the haze value immediately after manufacture is within 75%. Here, the haze value of the polyethylene resin layer was measured in accordance with JIS K7361 (2000).

[0025] In the film of the present invention, the thickness of the polyethylene resin layer varies depending on the application, but when used as an agricultural film, it is preferably 10 to 1000 μm, more preferably 50 to 500 μm, and even more preferably 50 to 200 μm. If the thickness of the agricultural film is within this range, sufficient strength and workability for stretching can be obtained. When the polyethylene resin layer of the present invention is used as a sealant layer, the thickness of the polyethylene resin layer is preferably 70 to 190 μm, more preferably 100 to 170 μm, and particularly preferably 110 to 150 μm. If the thickness of the polyethylene resin layer is less than 70 μm, for example, when constructing a standing pouch (made by laminating a 15 μm biaxially oriented nylon film and a sealant layer and then forming a bag), it becomes difficult to impart pouch rigidity. On the other hand, if the thickness of the polyethylene resin layer exceeds 190 μm, it is satisfactory in terms of performance such as drop resistance and pouch rigidity, but it is undesirable in terms of environmental aspects such as effective use of resources and economic aspects such as cost-effectiveness.

[0026] Furthermore, the film of the present invention may be a single-layer structure consisting only of the polyethylene resin layer described above, or it may be a laminated film having a laminated structure of the polyethylene resin layer described above and other resin layers. Examples of materials constituting the other resin layers include linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, and mixtures thereof.

[0027] The applications of the film described above are not particularly limited and can generally be used as a substitute for polyethylene film. However, it is particularly suitable for films that require a certain level of transparency. For example, it can be used as a single layer or laminated with a substrate as a sealant film that constitutes the inner layer of agricultural films or laminated films for pouches that require transparency.

[0028] The substrate to be laminated with the polyethylene resin layer according to the present invention is not particularly limited and may be any film suitable for its application. Specific examples of substrates include polyolefins such as crystalline polypropylene, crystalline propylene-ethylene copolymer, crystalline polybutene-1, crystalline poly-methylpentene-1, low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), and ion-crosslinked olefin copolymers (ionomers); aromatic vinyl copolymers such as polystyrene and styrene-butadiene copolymer; halogenated vinyl polymers such as polyvinyl chloride and vinylidene chloride resin; nitrile polymers such as acrylonitrile-styrene copolymer and acrylonitrile-styrene-butadiene copolymer; polyamides such as nylon 6, nylon 66, and para- or metaxylylene adipamide; polyesters such as polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), and polybutylene terephthalate (PBT); various polycarbonates; and thermoplastic resins such as polyoxymethylene, which can be used to create resin films. Furthermore, films in which metal oxides or the like are vapor-deposited onto the resin film, or films in which organic compounds are coated, or films having a layer made of ethylene vinyl alcohol copolymer (EVOH) resin can also be used. Films made from these materials can be used unstretched, uniaxially oriented, or biaxially oriented.

[0029] As a base material, the above-mentioned resin film can be used as a single layer or by laminating two or more types. Alternatively, one or more of these resin films can be laminated with metal foil such as aluminum, paper, cellophane, etc. Preferred substrates include, for example, single-layer films made of stretched nylon film or stretched polyester film, two-layer films made by laminating polyolefin films such as low-density polyethylene or polypropylene with PET, and three-layer films made by laminating PET / nylon / polyethylene. More preferably, environmentally friendly materials are used as the materials constituting the base material. Environmentally friendly materials include, for example, resins that achieve both functionality equivalent to fossil fuel-derived resins and environmental considerations in a carbon-neutral manner by using monomers obtained from plant-derived raw materials (e.g., PET, nylon 6), resins that use monomers obtained from plant-derived raw materials (e.g., polylactic acid, polybutylene succinate (PBS), polyethylene furanoate (PEF)), and resins obtained by recycling resins that use monomers derived from fossil fuels. The recycled resin may also include resins that use monomers obtained from plant-derived raw materials. During the manufacturing of laminated films, adhesives and anchoring agents may be interposed between each layer as needed. Furthermore, the substrate may have an ink layer to express the design.

[0030] The method for producing the laminated film is not particularly limited, and examples include a method of directly laminating a substrate onto the polyethylene resin layer according to the present invention by extrusion lamination, a method of laminating a substrate onto the polyethylene resin layer according to the present invention via an adhesive by dry lamination, and a co-extrusion method in which the materials of each layer are co-extruded and laminated. These methods may also be combined. As adhesives for dry lamination, urethane adhesives, acid-modified polyolefin adhesives, polyester adhesives, polyether adhesives, polyamide adhesives, etc., can be used.

[0031] Furthermore, the overall thickness of the laminated film is preferably 110 to 240 μm, more preferably 120 to 210 μm, and particularly preferably 130 to 190 μm. [Examples]

[0032] The present invention will be described below in the form of specific embodiments, but the present invention is not limited to these embodiments. Furthermore, the specific low-density polyethylenes (LDPE(1) and LDPE(2)) and specific linear low-density polyethylenes (LLDPE(3) and LLDPE(4)) used in the following examples and comparative examples have the characteristics shown in Table 1 below.

[0033] [Table 1]

[0034] <Example 1> 25% by mass of LDPE(1) and 75% by mass of LLDPE(3) were mixed, and the resulting mixture was fed into a single-screw extruder for melt-kneading and extruded from a T-die film molding apparatus connected to the single-screw extruder. Furthermore, the extruded molten resin was cast onto a cooling roll and cooled to produce a film consisting solely of a polyethylene resin layer with a thickness of 100 μm. In the above configuration, the cylinder temperature of the single-screw extruder was 200°C, the T-die head temperature was 210°C, and the cooling roll temperature was 60°C. Furthermore, when the resin temperature was measured at the connection point between the single-screw extruder and the T-die, it was found to be between 204 and 210°C.

[0035] <Example 2> A film consisting solely of a polyethylene resin layer with a thickness of 110 μm was produced by mixing 50% by mass of LDPE(1) and 50% by mass of LLDPE(3), and extruding the resulting mixture in the same manner as in Example 1.

[0036] <Comparative Example 1> A film consisting solely of a polyethylene resin layer with a thickness of 95 μm was produced by extruding LLDPE(4) in the same manner as in Example 1.

[0037] <Comparative Example 2> A film consisting solely of a polyethylene resin layer with a thickness of 110 μm was produced by extruding LLDPE(3) in the same manner as in Example 1.

[0038] <Comparative Example 3> A film consisting solely of a polyethylene resin layer with a thickness of 120 μm was produced by mixing 25% by mass of LDPE(2) and 75% by mass of LLDPE(3), and extruding the resulting mixture in the same manner as in Example 1.

[0039] <Comparative Example 4> A film consisting solely of a polyethylene resin layer with a thickness of 110 μm was produced by mixing 75% by mass of LDPE(2) and 25% by mass of LLDPE(3), and extruding the resulting mixture in the same manner as in Example 1.

[0040] [Film Evaluation] The films obtained in Examples 1-2 and Comparative Examples 1-4 were evaluated for their long-term storage resistance by measuring the haze value immediately after manufacturing and after 2 years of long-term storage at room temperature using the method described below. The results are shown in Table 2 below.

[0041] The haze value was measured using a 5cm x 5cm test piece cut from a film roll with a haze meter "NDH4000" (manufactured by Nippon Denshoku Industries Co., Ltd., measuring light source D65) in accordance with JIS K7136 (2000). A haze value closer to 0% indicates greater transparency. Five test pieces were prepared for each film in Examples 1-2 and Comparative Examples 1-4, and the average of the three measured values ​​(excluding the minimum and maximum values) was used as the haze value.

[0042] [Table 2]

[0043] As is clear from the results in Table 2, the films according to Example 1 and Example 2 exhibited low haze values ​​immediately after manufacturing and also showed low haze values ​​after long-term storage, confirming that they have excellent long-term storage resistance. In contrast, in the films relating to Comparative Examples 1 to 4, even if the haze value is sufficiently low immediately after manufacturing, the haze value after long-term storage is high, or the haze value is high from immediately after manufacturing and cannot maintain the desired haze value after long-term storage.

Claims

1. A film having at least one polyethylene resin layer made of a polyethylene resin composition containing linear low-density polyethylene and low-density polyethylene, The aforementioned linear low-density polyethylene consists of a polymer of plant-derived ethylene and has a bio-concentration of 85% or more. The aforementioned low-density polyethylene consists of a polymer of plant-derived ethylene and has a bio-concentration of 90% or more. The content of the low-density polyethylene in the polyethylene resin composition is 25 to 50% by mass. The melt flow rate of the low-density polyethylene is 2.7 g / 10 min or more and 3.8 g / 10 min or less. The melt flow rate of the linear low-density polyethylene is 0.8 g / 10 min or more and 1.0 g / 10 min or less. The polyethylene resin composition has a bio-concentration of 89% or more. The polyethylene resin composition is characterized by not containing low-density polyethylene other than the low-density polyethylene, not containing linear low-density polyethylene other than the linear low-density polyethylene, and not containing high-density polyethylene.

2. The film according to claim 1, characterized in that the haze value of the polyethylene resin layer is 5.0 to 11.0%.

3. The film according to claim 1 or 2, characterized in that the film includes a co-extruded film portion in which the polyethylene resin layer is laminated on both sides or one side of a substrate by co-extrusion.

4. A film according to any one of claims 1 to 3, characterized in that it is used as an agricultural film.

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