Polypropylene-based film and laminate

Abstract

To provide a polypropylene-based film which utilizes recycled materials and enables reduction of odor caused by the recycled materials, and to provide a laminate.SOLUTION: In a laminate film mainly composed of a polypropylene-based resin comprising at least three layers including a first surface layer, an intermediate layer, and a second surface layer, the intermediate layer is composed of 5 to 95 wt.% of a recycled polyolefin-based resin and 5 to 95 wt.% of either of a petroleum-derived polypropylene-based resin and a plant-derived polypropylene-based resin, or a mixture thereof. Each of the first surface layer and the second surface layer is composed of either of a petroleum-derived polyolefin-based resin and a plant-derived polyolefin-based resin, or a mixture thereof. A content of the recycled polyolefin-based resin in the laminate film is 3 wt.% or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a polypropylene-based film and a laminate, and particularly to a polypropylene-based film and a laminate using recycled raw materials.

Background Art

[0002] In recent years, efforts have been made to reduce the emission of greenhouse gases as a measure to prevent global warming. For example, since carbon dioxide generated when waste plastic materials are incinerated becomes a greenhouse gas that causes global warming, plastics are recycled from waste plastic materials as a measure to prevent global warming.

[0003] As a recycled thermoplastic resin composition using such recycled resin by recycling, a recycled thermoplastic resin composition composed of 10 to 90% by weight of a high molecular weight polyolefin resin having a weight average molecular weight of 500,000 or more and 90 to 10% by weight of a recycled polyolefin resin has been proposed (see Patent Document 1). The recycled thermoplastic resin composition of Patent Document 1 has mechanical properties equivalent to or better than those of ordinary unused thermoplastic resins, and is particularly excellent in long-term durability (creep resistance performance), so it is used for applications such as structural materials, construction members, and civil engineering and architectural members such as storage water tanks.

[0004] In the future, it is expected that the use of recycled raw materials will progress also in the field of packaging films due to the increasing awareness of environmental problems such as global warming. Therefore, the use of plastics recycled from waste plastic materials has been studied also in packaging films. However, since waste plastic materials contain foreign substances such as colorants and solvents, there is a concern that plastics recycled from the waste plastic materials may generate odors due to the foreign substances. Particularly in packaging films for foods and the like, it is required to reduce odors in order to maintain the original taste of the food and the like.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-119697 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] The present invention has been proposed in view of the above points, and provides a polypropylene-based film and a laminate in which the odor caused by recycled raw materials can be reduced in a film using recycled raw materials. [Means for Solving the Problems]

[0007] That is, a first invention is a laminated film mainly composed of a polypropylene-based resin composed of at least three layers of a first surface layer, an intermediate layer, and a second surface layer, wherein the intermediate layer is composed of 5 to 95 wt% of a recycled polyolefin-based resin and 5 to 95 wt% of either one of a petroleum-derived polypropylene-based resin or a plant-derived polypropylene-based resin or a mixture thereof, and the first surface layer and the second surface layer are composed of either one of a petroleum-derived polyolefin-based resin or a plant-derived polyolefin-based resin or a mixture thereof, and the content of the recycled polyolefin-based resin in the laminated film is 3 wt% or more.

[0008] A second invention relates to a polypropylene-based film in which a nucleating agent is added in an amount of 0.1 to 10 wt% to at least one of the first surface layer, the intermediate layer, and the second surface layer in the first invention.

[0009] A third invention relates to a polypropylene-based film in which a cyclic olefin-based resin or an alicyclic resin is added to at least one of the first surface layer, the intermediate layer, and the second surface layer in the first invention.

[0010] The fourth invention relates to a polypropylene-based film in which an odor adsorbent is added to at least one of the first surface layer, the intermediate layer, and the second surface layer in the first to third inventions.

[0011] The fifth invention relates to a polypropylene-based film in which 1 to 30 wt% of a polypropylene-based elastomer as a compatibilizer is added to the intermediate layer in the first to third inventions.

[0012] The sixth invention relates to a polypropylene-based film in which a phenolic antioxidant or a phosphorus-based antioxidant is added to the intermediate layer in the first to third inventions.

[0013] The seventh invention relates to a laminate using the polypropylene-based film of the first to third inventions, and relates to a laminate composed of a plurality of resin layers including the polypropylene-based film.

Advantages of the Invention

[0014] According to the polypropylene-based film according to the first invention, it is a laminated film mainly composed of a polypropylene-based resin composed of at least three layers of a first surface layer, an intermediate layer, and a second surface layer. The intermediate layer is composed of 5 to 95 wt% of a recycled polyolefin-based resin and 5 to 95 wt% of either a petroleum-derived polypropylene-based resin or a plant-derived polypropylene-based resin or a mixture thereof. The first surface layer and the second surface layer are composed of either a petroleum-derived polyolefin-based resin or a plant-derived polyolefin-based resin or a mixture thereof. Since the content of the recycled polyolefin-based resin in the laminated film is 3 wt% or more, the first and second surface layers function as a barrier layer that prevents the movement of odor components generated from the intermediate layer due to the recycled polyolefin-based resin, and it is possible to reduce the odor caused by the recycled polyolefin-based resin (recycled raw material).

[0015] According to the polypropylene-based film according to the second invention, in the first invention, since a nucleating agent is added in an amount of 0.1 to 10 wt% to at least one of the first surface layer, the intermediate layer, and the second surface layer, the crystallinity of at least one layer is increased, and the movement of odor components from the intermediate layer is more hindered, so that it is possible to suppress the emission of odor from the film.

[0016] According to the polypropylene-based film according to the third invention, in the first invention, since a cyclic olefin-based resin or an alicyclic resin is added to at least one of the first surface layer, the intermediate layer, and the second surface layer, it is possible to further suppress the emission of odor from the film.

[0017] According to the polypropylene-based film according to the fourth invention, in the first to third inventions, since an odor adsorbent is added to at least one of the first surface layer, the intermediate layer, and the second surface layer, it is possible to adsorb odor components generated from the intermediate layer and further suppress the emission of odor from the film.

[0018] According to the polypropylene-based film according to the fifth invention, in the first to third inventions, since a polypropylene-based elastomer as a compatibilizer is added to the intermediate layer in an amount of 1 to 30 wt%, it is possible to reduce the occurrence of fish eyes due to incompatible resins and suppress the occurrence of appearance defects.

[0019] According to the polypropylene-based film according to the sixth invention, in the first to third inventions, since a phenolic antioxidant or a phosphorus-based antioxidant is added to the intermediate layer, it is possible to reduce the deterioration of the recycled polyolefin-based resin due to thermal oxidation.

[0020] According to the laminate according to the seventh invention, since it is composed of a plurality of resin layers including the polypropylene-based film of the first to third inventions, by laminating resin layers having physical properties according to the application, it is possible to utilize the recycled polyolefin-based resin (recycled raw material) while having the performance required as a film.

Embodiments for Carrying Out the Invention

[0021] The polypropylene-based film according to an embodiment of the present invention is a laminated film mainly composed of a polypropylene-based resin composed of at least three layers of a first surface layer, an intermediate layer, and a second surface layer. The polypropylene-based film of the present invention can be used as a base film or a laminate film of a laminate composed of a plurality of resin layers. This laminated film is suitably used, for example, as a packaging material for various articles such as foods, daily necessities, and parts.

[0022] The intermediate layer is a layer containing a recycled polyolefin-based resin from the viewpoint of promoting the use of recycled raw materials, and is composed of a recycled polyolefin-based resin and either one of a petroleum-derived polypropylene-based resin or a plant-derived polypropylene-based resin or a mixture thereof. As the recycled polyolefin-based resin, for example, polyolefin recycled from products, polyolefin recycled from waste, etc. are suitably used. Examples of the waste include plastic materials such as container packaging materials, building materials, and fibers. Note that the waste plastic material contains foreign substances such as coloring agents and solvents, and these foreign substances may generate odors as described later.

[0023] The recycled polyolefin-based resin is recycled by methods such as material recycling and chemical recycling. Examples of the recycled polyolefin-based resin include polypropylene resin, polyethylene resin, and polystyrene. From the viewpoint of compatibility with a petroleum-derived polypropylene-based resin or a plant-derived polypropylene-based resin, a polypropylene resin is preferable as the recycled polyolefin-based resin.

[0024] The petroleum-derived polypropylene-based resin is polypropylene produced from propylene obtained from fossil fuels such as petroleum. Examples of the petroleum-derived polypropylene-based resin include propylene homopolymers, propylene-α-olefin random copolymers such as propylene-ethylene random copolymers and propylene-ethylene-butene random copolymers, or propylene-ethylene block copolymers.

[0025] Plant-derived polypropylene resins include those obtained using bioalcohol obtained by fermenting plants as raw materials, bio-naphtha obtained by distillation and separation of plant-derived oil, which is an oil derived from plants, and those obtained from bio-propane, which is a by-product of bio-diesel fuel obtained by decomposing plant-derived oil with a catalyst or the like. Examples of plant-derived oils include soybean oil, sesame oil, rice bran oil, sunflower oil, cottonseed oil, corn oil, rapeseed oil, olive oil, perilla oil, almond oil, waste oils thereof, crude tall oil, which is a by-product during kraft pulp production, and oils extracted from wood such as wood chips. Plant-derived polypropylene resins are produced using all or part of the bio-propylene produced from these plant-derived raw materials, and contribute to the reduction of petroleum-derived raw materials.

[0026] Since petroleum-derived polypropylene resins are widely spread, they are rich in types and advantageous in terms of price. On the other hand, although greenhouse gases (carbon dioxide) are generated when plant-derived polypropylene resins are incinerated, these greenhouse gases are balanced with the carbon dioxide absorbed during the growth of the plants that are the raw materials of the plant-derived polypropylene resins, so they are excellent in that the greenhouse gas emissions can be substantially reduced to zero. Therefore, using plant-derived polypropylene resins in the intermediate layer can save fossil fuels such as petroleum and reduce the environmental load. Note that petroleum-derived polypropylene resins or plant-derived polypropylene resins may be appropriately selected according to the use, purpose, etc. and contained in the intermediate layer, or a mixture of a petroleum-derived polypropylene resin and a plant-derived polypropylene resin may be contained in the intermediate layer. This mixture includes appropriate mixtures such as those obtained by mixing and polymerizing a petroleum-derived propylene monomer and a plant-derived propylene monomer, and those obtained by mixing petroleum-derived polypropylene and plant-derived polypropylene.

[0027] The content of the recycled polyolefin resin and either one of the petroleum-derived polypropylene resin or the plant-derived polypropylene resin or a mixture thereof in the intermediate layer is preferably such that the recycled polyolefin resin is 5 to 95 wt% and either one of the petroleum-derived polypropylene resin or the plant-derived polypropylene resin or a mixture thereof is 5 to 95 wt%. The content of the recycled polyolefin resin is 5 wt% or more from the viewpoint of promoting the use of recycled raw materials, and the upper limit is 95 wt% from the viewpoints such as ensuring the moldability of the film and the quality equivalent to that of a film not containing recycled raw materials. More preferably, it is 10 to 75 wt%. The content of either one of the petroleum-derived polypropylene resin or the plant-derived polypropylene resin or a mixture thereof is 5 to 95 wt%, preferably 8 to 90 wt% from the viewpoint of ensuring properties such as mechanical strength and heat resistance. In particular, when using a plant-derived polypropylene resin, it can contribute to reducing the environmental load.

[0028] If the content of the recycled polyolefin resin is too low or the content of the petroleum-derived polypropylene resin or the plant-derived polypropylene resin is too high, the utilization of recycled raw materials will be insufficient. If the content of the recycled polyolefin resin is too high or the content of the petroleum-derived polypropylene resin or the plant-derived polypropylene resin is too low, the quality of the polypropylene film may be deteriorated due to foreign substances or odors caused by the recycled raw material (recycled polyolefin resin).

[0029] The first surface layer and the second surface layer laminated with the intermediate layer in between are made of either a petroleum-derived polyolefin resin or a plant-derived polyolefin resin, or a mixture thereof. The petroleum-derived polyolefin resin is a polyolefin resin produced from raw materials obtained from fossil fuels such as petroleum. Examples of the petroleum-derived polyolefin resin include petroleum-derived polypropylene resin, petroleum-derived polyethylene resin, petroleum-derived polystyrene, and the like. From the viewpoint of compatibility with the petroleum-derived polypropylene resin or plant-derived polypropylene resin in the intermediate layer, the petroleum-derived polypropylene resin is preferred as the petroleum-derived polyolefin resin.

[0030] The plant-derived polyolefin resin is a polyolefin resin produced from plant-derived raw materials. Examples of the plant-derived polyolefin resin include plant-derived polypropylene resin, plant-derived polyethylene resin, plant-derived polystyrene, and the like. From the viewpoint of compatibility with the petroleum-derived polypropylene resin or plant-derived polypropylene resin in the intermediate layer, the plant-derived polypropylene resin is preferred as the plant-derived polyolefin resin.

[0031] When petroleum-derived polyolefin resins are used for the first and second surface layers, it is possible to reduce the odor caused by the recycled polyolefin contained in the intermediate layer and the appearance defects caused by foreign substances contained in the recycled polyolefin. Also, when plant-derived polyolefin resins are used for the first and second surface layers, in addition to the same effects as when petroleum-derived polyolefin resins are used for the first and second surface layers (reduction of odor and appearance defects), it is possible to further save fossil fuels such as petroleum and reduce the environmental load. The petroleum-derived polyolefin resin and the plant-derived polyolefin resin can be appropriately selected according to the use, purpose, etc. For example, the first and second surface layers can be made of the same type of polyolefin resin, or different types of polyolefin resins can be used for each surface layer, such as using a petroleum-derived polyolefin resin for the first surface layer and a plant-derived polyolefin resin for the second surface layer. In addition, it is also possible to appropriately combine them by using a mixture of a petroleum-derived polyolefin resin and a plant-derived polyolefin resin for the first layer or the second layer. This mixture also includes the same type as the mixture contained in the above intermediate layer.

[0032] In the laminated film, in order to obtain a film that effectively uses recycled materials, the content of the recycled polyolefin resin in the laminated film is preferably 3 wt% or more, more preferably 6 wt%. If the content of the recycled polyolefin resin is too small, the utilization of the recycled material in the laminated film will be insufficient. On the other hand, the upper limit of the content of the recycled polyolefin resin is not particularly limited. The content of the recycled polyolefin resin in the laminated film depends on the blending ratio of the resins in the first and second surface layers in the laminated film, but can be appropriately increased by increasing the blending ratio of the recycled polyolefin resin constituting the intermediate layer. For example, the content in the laminated film can be 70 wt% or more, more preferably 80 wt% or more at a high concentration. The higher the content of the recycled polyolefin resin in the laminated film, the more favorable it is because the contribution to environmental load reduction increases.

[0033] In the present invention, from the perspective of promoting the use of recycled raw materials in the field of packaging films, the above-mentioned intermediate layer contains a recycled polyolefin resin. This recycled polyolefin resin is obtained by recycling waste plastic materials containing foreign substances such as colorants and solvents through material recycling, chemical recycling, or the like. For this reason, when promoting the use of recycled raw materials, there has been a concern that the recycled polyolefin resin may generate odors caused by the foreign substances.

[0034] Therefore, the inventors have found that, as a polypropylene-based film using a recycled polyolefin resin, by using the recycled polyolefin resin as a constituent material of the intermediate layer and forming a laminated film in which a first surface layer and a second surface layer are laminated with the intermediate layer therebetween, the first surface layer and the second surface layer can function as barrier layers that prevent the movement of odor components generated from the intermediate layer due to the recycled polyolefin resin, and effectively suppress the release of odors from the film.

[0035] In the present invention, as a means for further suppressing the movement of odor components generated from the intermediate layer due to the recycled polyolefin resin, it is preferable to add a nucleating agent to at least one of the first surface layer, the intermediate layer, and the second surface layer. The nucleating agent is an additive that promotes the crystallization of the resin constituting the added layer. By increasing the crystallinity of the resin, it becomes difficult for odor components to move from the intermediate layer, and the release of odors to the outside of the film can be suppressed. The addition amount of the nucleating agent is preferably 0.1 to 10 wt%, more preferably about 0.1 to 2 wt% with respect to the layer to which it is added. If the addition amount of the nucleating agent is too small, the crystallinity of the layer to which the nucleating agent is added cannot be increased, so that the movement of odor components is allowed, and there is a possibility that the reduction of odors released from the film becomes insufficient.

[0036] The crystal nucleating agent is not particularly limited as long as it is a substance that promotes the crystallization of the resin, and it may be either an organic crystal nucleating agent or an inorganic crystal nucleating agent. Examples of the organic crystal nucleating agent include high-density polyethylene, carboxylic acid metal salt-based crystal nucleating agents, sorbitol-based crystal nucleating agents, phosphate ester metal salt-based crystal nucleating agents, β-crystal nucleating agents, etc. Examples of the inorganic crystal nucleating agent include talc, etc. Among these crystal nucleating agents, it is preferable to use high-density polyethylene, which is inexpensive, as the crystal nucleating agent.

[0037] In the present invention, as another means for further suppressing the movement of odor components generated from the intermediate layer, a cyclic olefin-based resin or an alicyclic resin may be added to at least one of the first surface layer, the intermediate layer, and the second surface layer. The cyclic olefin-based resin and the alicyclic resin have the property of suppressing the movement of odor components. Examples of the cyclic olefin-based resin include polymers of cyclic olefin monomers, copolymers of cyclic olefin monomers and other monomers such as ethylene, etc. The alicyclic resin includes those obtained by hydrogenating aromatic resins, etc. Examples of the alicyclic resin include aliphatic-based, aromatic-based, polymerization resins using dicyclopentadiene (DCPD)-based monomers as raw materials, terpene resins, etc. Due to the properties of the cyclic olefin-based resin or the alicyclic resin added to the at least one layer, the movement of odor components from the intermediate layer is suppressed, so that the emission of odor from the film can be suppressed.

[0038] In the present invention, as a means for suppressing the emission of odor from the film, an odor adsorbent may be added to at least one of the first surface layer, the intermediate layer, and the second surface layer. The odor adsorbent has the function of absorbing odor components. Examples of the odor adsorbent include activated carbon, zeolite, silicon dioxide, alumina, aluminum hydroxide, and mixtures thereof, etc. The odor adsorbent added to the at least one layer can adsorb the odor components generated from the intermediate layer due to the recycled polyolefin-based resin. Therefore, the emission of odor from the film can be further suppressed. The odor adsorbent can also be used in combination with the crystal nucleating agent, the cyclic olefin-based resin or the alicyclic resin. In addition, in order to more effectively adsorb the odor components, it is preferable to add the odor adsorbent to the intermediate layer.

[0039] In the present invention, it is preferable that a polypropylene-based elastomer as a compatibilizer is added to the intermediate layer for the purpose of reducing appearance defects caused by mixing a resin having low compatibility with the film. Examples of the polypropylene-based elastomer include copolymers of propylene and ethylene or 1-butene.

[0040] Since the recycled polyolefin-based resin contained in the intermediate layer contains a large amount of a resin incompatible with polypropylene, fish eyes due to the incompatible resin may occur in the film. When fish eyes occur in the film, appearance defects may occur and the commercial value of the film may decrease. The above compatibilizer is used to improve the compatibility between resins. The addition amount of the compatibilizer is 1 to 30 wt%, preferably about 20 wt% from the viewpoint of improving the compatibility between the recycled polyolefin-based resin and either one of the petroleum-derived polypropylene-based resin or the plant-derived polypropylene-based resin or a mixture thereof. If the addition amount of the compatibilizer is too small, the compatibility between the recycled polyolefin-based resin and either one of the petroleum-derived polypropylene-based resin or the plant-derived polypropylene-based resin or a mixture thereof may be insufficient. If the addition amount of the compatibilizer is too large, the rigidity, breaking strength, etc. of the film may decrease and the mechanical properties may become insufficient. By improving the compatibility with an appropriate amount of the compatibilizer, the occurrence of fish eyes due to the incompatible resin can be reduced, and the occurrence of appearance defects of the film can be suppressed.

[0041] In addition, when the number of fish eyes occurring in the film increases, appearance defects occur in the form of the film surface becoming rough. Therefore, regarding the appearance defects due to fish eyes, the quality can be evaluated based on the ten-point average roughness (R Z ) measured on the film surface. If the ten-point average roughness (R Z ) is too large, the number of fish eyes tends to increase, which is not preferable. If the ten-point average roughness (R Z ) does not exceed 2 μm, a good appearance can be obtained.

[0042] In the present invention, a phenolic antioxidant or a phosphorus-based antioxidant may be added to the intermediate layer. For example, resin products are heated during the molding process, and the resin as a constituent material is thermally damaged. When such a resin product is used as a recycling raw material, since it is reheated during the film molding process, the recycling raw material may be further thermally damaged and the resin is likely to deteriorate. Therefore, by adding a phenolic antioxidant or a phosphorus-based antioxidant to the intermediate layer containing a recycled polyolefin resin (recycling raw material), it is possible to reduce the deterioration of the recycled polyolefin resin due to thermal oxidation.

[0043] Examples of the phenolic antioxidant include tetrakis[methylene-3-(3’,5’-di-t-butyl-4’-hydroxyphenyl)propionate]methane, 2,6-di-t-butyl-4-methylphenol, n-octadecyl-3-(3’,5’-di-t-butyl-4’-hydroxyphenyl)propionate, tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, and the like. Examples of the phosphorus-based antioxidant include tris(2,4-di-t-butylphenyl)phosphite, tris(nonylphenyl)phosphite, distearyl pentaerythritol diphosphite, tetrakis(2,4-di-t-butylphenyl)-4,4’-biphenylene-diphosphonite, and the like.

[0044] Further, the polypropylene-based film of the present invention may have a laminated structure including layers other than the first surface layer, the intermediate layer, and the second surface layer, if necessary. For example, as a polypropylene-based film having a laminated structure, an arbitrary layer may be laminated between the first surface layer and the intermediate layer or between the second surface layer and the intermediate layer, if necessary. The polypropylene-based film of the present invention preferably has a laminated structure of 3 to 5 layers.

[0045] In the polypropylene-based film of the present invention, the thickness is not particularly limited and is appropriately determined according to demand, use, etc. For example, it is preferably 5 to 150 μm, more preferably 10 to 100 μm. Among these, the thickness of the first surface layer and the second surface layer of the polypropylene-based film is preferably 0.3 to 50 μm, more preferably 0.5 to 35 μm, and even more preferably 0.6 to 20 μm. The thickness of the intermediate layer is preferably 2 to 135 μm, more preferably 3 to 90 μm, and even more preferably 4 to 54 μm. If the surface layer is too thin, the function as a barrier layer that prevents the movement of odor components may be insufficient. If the surface layer is too thick, the intermediate layer becomes relatively thin, and the amount of recycled polyolefin resin added to the intermediate layer decreases, which is unsuitable from the viewpoint of promoting the use of recycled raw materials.

[0046] The polypropylene-based film of the present invention can be obtained by a known film forming method, whether it is stretched or unstretched. The unstretched film is obtained by cooling and solidifying the molten resin extruded from a T-die, a circular die, etc. to a predetermined thickness using a cooling roll or air. The stretched film is obtained by uniaxially or biaxially stretching by a known tenter method, tubular method, roll stretching, etc.

[0047] In the present invention, the above polypropylene-based film can be used as a base film, and a laminate composed of a plurality of resin layers including the polypropylene-based film can be provided. When it is a multilayer body, the resin constituting the polypropylene-based film can be co-extruded and molded together with the resins constituting each layer of the multilayer body, or the films constituting each layer can be adhered to form a laminate having an arbitrary layer structure. For such a laminate, by laminating a resin layer having physical properties according to the use, it is possible to utilize a recycled polyolefin resin (recycled raw material) while having the performance required as a film.

[0048] In the present invention, it is also possible to provide a laminated film in which a polypropylene-based film used as a base film is appropriately laminated with printing, a gas barrier layer, etc. The printing process is performed on the film surface of the polypropylene-based film, and known methods such as screen printing, flexographic printing, offset printing, and gravure printing are used. Further, when printing is performed on the polypropylene-based film of the present invention, the film surface is surface-treated by corona discharge treatment or the like prior to printing to improve the ink affinity and adhesion.

[0049] The gas barrier layer is disposed directly on the surface layer or via an anchor coat layer for the purpose of imparting barrier properties against water vapor, oxygen, etc. The gas barrier layer can be formed using known vapor deposition methods such as vacuum vapor deposition, sputtering, and ion plating. When a gas barrier layer is disposed on the polypropylene-based film of the present invention, the film surface is surface-treated in advance by corona discharge treatment or the like to improve the wettability and adhesion to the anchor coat layer and the gas barrier layer.

[0050] The anchor coat layer is not particularly limited, and examples include polyurethane-based resins and polyester-based resins. The gas barrier layer is also not particularly limited, and examples include metal thin film layers and inorganic oxide layers. The metal thin film layer is a thin film layer made of a known metal such as aluminum, gold, silver, copper, and chromium, and may be a thin film layer of oxides, sulfides, or nitrides of these metals. Further, the metal thin film layer may be a single layer or a plurality of layers of two or more different or the same kinds. The inorganic oxide layer is made of a known inorganic oxide such as aluminum oxide, silicon oxide, magnesium fluoride, and magnesium oxide, and is a thin film layer using one or more inorganic oxides.

[0051] Further, in the laminated film, when another resin film is laminated on the polypropylene-based film of the present invention, by using another resin film made of the same material or substantially the same material as the polypropylene-based film, it is possible to realize a single materialization of the obtained laminate, packaging materials, packaging bags, etc. using the laminate.

Examples

[0052] [Production of non-stretched polypyromellitic film] The following materials were compounded, melted, and kneaded, and then extruded by the T-die method so as to be laminated in the order of the first surface layer, the intermediate layer, and the second surface layer, and cooled by a cooling roll to form non-stretched films of Prototype Examples 1 to 12. In each prototype example, the compounding ratio of each material was adjusted so that it was 100 wt% for each of the first surface layer, the intermediate layer, and the second surface layer. The materials used in each layer of Prototype Examples 1 to 12 are shown in Tables 1 and 2 described later. Incidentally, for the non-stretched films of Prototype Examples 1 to 12, films were formed such that the thickness was 30 μm, the thicknesses of the first surface layer and the second surface layer were 6 μm, and the thickness of the intermediate layer was 18 μm.

[0053] [Production of stretched polypyromellitic film] The following materials were compounded, melted, and kneaded, and then extruded by the T-die method so as to be laminated in the order of the first surface layer, the intermediate layer, and the second surface layer, and cooled by a cooling roll to form a 1.2-mm sheet. After stretching the sheet 5 times in the longitudinal direction in an atmosphere of 160°C using a batch-type stretching machine, it was stretched 8 times in the transverse direction to form the stretched film of Prototype Example 13. The compounding ratio of each material was adjusted so that it was 100 wt% for each of the first surface layer, the intermediate layer, and the second surface layer. The materials used in each layer of Prototype Example 13 are shown in Table 2 described later. Incidentally, for the stretched film of Prototype Example 13, a film was formed such that the thickness was 30 μm, the thicknesses of the first surface layer and the second surface layer were 1.5 μm, and the thickness of the intermediate layer was 27 μm.

[0054] As materials for each layer, a plant-derived polyolefin resin (plant-derived polypropylene resin), a recycled polyolefin resin, a crystal nucleating agent, an alicyclic resin, an odor adsorbent, and a compatibilizer were used. The melt flow rate (MFR) of each of the plant-derived polyolefin resin (plant-derived polypropylene resin), recycled polyolefin resin, and crystal nucleating agent (high-density polyethylene) conforms to JIS K 7210 (2014) and is the value measured at a test temperature of 230°C unless specific numerical values are described. Also, the weight average molecular weight (Mw) of each of the plant-derived polyolefin resin (plant-derived polypropylene resin) and recycled polyolefin resin was measured based on the following measurement conditions using a high-temperature GPC system (manufactured by Tosoh Corporation) equipped with the following equipment, etc. High-temperature GPC device HLC-8321GPC / HT Dissolution filtration device DF-8321 Column TSKgel guardcolumnHHR(S)HT + TSKgel GMHHR-H(S)HT × 3 pieces Eluent ODCB Dissolution / measurement temperature 145°C Sample concentration 0.1 wt / vol% Injection volume 0.3 ml Flow rate 1.0 ml / min Detector Differential refractometer

[0055] [Plant-derived polyolefin resin (plant-derived polypropylene resin)] ·PP1: Plant-derived polypropylene (manufactured by LyondellBasell; C14 HP456J), MFR: 3.2 g / 10 min, Mw: 486000

[0056] [Recycled polyolefin resin] ·R-PP1: Material recycled polypropylene (manufactured by Toyama Environmental Improvement Co., Ltd.; RBP-PP(K)), MFR: 3.2 g / 10 min, Mw: 450000 ·R-PP2: Material recycled polypropylene (manufactured by GUOLONG; GL-0540F), MFR: 14.2 g / 10 min, Mw: 250000 ·R-PP3: Chemical Recycled Polypropylene (manufactured by Lotte Chemical Corporation; FO-135), MFR: 3.0 g / 10 min, Mw: 491000 ·R-PE1: Material Recycled Polyethylene (manufactured by Martogg LCM; marLENE (registered trademark)), MFR: 0.6 g / 10 min, Mw: 410000

[0057] [Nucleating Agent] ·CN1: High-Density Polyethylene (manufactured by Japan Polyethylene Corporation; HF562), MFR: 7.5 g / 10 min (190 °C) ·CN2: Phosphate Metal Salt-Based Nucleating Agent (manufactured by ADEKA Corporation; Adeka Stab NA-11)

[0058] [Alicyclic Resin] ·PR: Alicyclic Hydrocarbon-Based Petroleum Resin (manufactured by ENEOS Corporation; OP501)

[0059] [Odor Adsorbent] ·OR: Activated Carbon (manufactured by Futamura Chemical Co., Ltd.; SA1000)

[0060] [Compatibilizer] ·CP: Polypropylene Elastomer (manufactured by ExxonMobil; Vistamaxx 6102FL)

[0061] [Prototype Example 1] Prototype Example 1 is an unstretched polypropylene film that uses 100 wt% of PP1 in the first surface layer, 90 wt% of PP1 and 10 wt% of R-PP1 in the intermediate layer, and 100 wt% of PP1 in the second surface layer.

[0062] [Prototype Example 2] Prototype Example 2 is an unstretched polypropylene film that uses 100 wt% of PP1 in the first surface layer, 88 wt% of PP1, 10 wt% of R-PP1, and 2 wt% of CN1 in the intermediate layer, and 100 wt% of PP1 in the second surface layer.

[0063] [Prototype Example 3] Prototype Example 3 is an unstretched polypropylene film using 100 wt% of PP1 in the first surface layer, 89.9 wt% of PP1, 10 wt% of R-PP1, and 0.1 wt% of CN2 in the intermediate layer, and 100 wt% of PP1 in the second surface layer.

[0064] [Prototype Example 4] Prototype Example 4 is an unstretched polypropylene film using 100 wt% of PP1 in the first surface layer, 77.5 wt% of PP1, 10 wt% of R-PP1, and 12.5 wt% of PR in the intermediate layer, and 100 wt% of PP1 in the second surface layer.

[0065] [Prototype Example 5] Prototype Example 5 is an unstretched polypropylene film using 100 wt% of PP1 in the first surface layer, 85 wt% of PP1, 10 wt% of R-PP1, and 5 wt% of OR in the intermediate layer, and 100 wt% of PP1 in the second surface layer.

[0066] [Prototype Example 6] Prototype Example 6 is an unstretched polypropylene film using 100 wt% of PP1 in the first surface layer, 28 wt% of PP1, and 72 wt% of R-PP2 in the intermediate layer, and 100 wt% of PP1 in the second surface layer.

[0067] [Prototype Example 7] Prototype Example 7 is an unstretched polypropylene film using 100 wt% of PP1 in the first surface layer, 8 wt% of PP1, 72 wt% of R-PP2, and 20 wt% of CP in the intermediate layer, and 100 wt% of PP1 in the second surface layer.

[0068] [Prototype Example 8] Prototype Example 8 is an unstretched polypropylene film using 100 wt% of PP1 in the first surface layer, 8 wt% of PP1, 72 wt% of R-PP3, and 20 wt% of CP in the intermediate layer, and 100 wt% of PP1 in the second surface layer.

[0069] [Prototype Example 9] Prototype Example 9 is an unstretched polypropylene film using 100 wt% of PP1 in the first surface layer, 100 wt% of PP1 in the intermediate layer, and 100 wt% of PP1 in the second surface layer.

[0070] [Prototype Example 10] Prototype Example 10 is an unstretched polypropylene film using 100 wt% of PP1 in the first surface layer, 90 wt% of PP1 and 10 wt% of R-PP1 in the intermediate layer, 90 wt% of PP1 and 10 wt% of R-PP1 in the second surface layer.

[0071] [Prototype Example 11] Prototype Example 11 is an unstretched polypropylene film using 100 wt% of PP1 in the first surface layer, 28 wt% of PP1 and 72 wt% of R-PP2 in the intermediate layer, 28 wt% of PP1 and 72 wt% of R-PP2 in the second surface layer.

[0072] [Prototype Example 12] Prototype Example 12 is an unstretched polypropylene film using 100 wt% of PP1 in the first surface layer, 95 wt% of PP1 and 5 wt% of R-PE1 in the intermediate layer, and 100 wt% of PP1 in the second surface layer.

[0073] [Prototype Example 13] Prototype Example 13 is a biaxially stretched polypropylene film using 100 wt% of PP1 in the first surface layer, 90 wt% of PP1 and 10 wt% of R-PE1 in the intermediate layer, and 100 wt% of PP1 in the second surface layer.

[0074] For Prototype Examples 1 to 13, evaluations were conducted on environmental performance, odor, and film appearance. The evaluations are shown in Tables 1 and 2 below.

[0075] [Evaluation of Environmental Performance] Environmental performance is an index for determining whether the recyclability is good by using a recycled polyolefin resin (recycled material) in the film. The evaluation of environmental performance was conducted based on the following criteria. 〇: The content of the recycled polyolefin resin (recycled material) in the film is 3 wt% or more and the recyclability is good. ×: The content of the recycled polyolefin resin (recycled material) in the film is less than 3 wt% and the recyclability is not good.

[0076] [Odor Evaluation] Odor means an offensive odor such as a raw smell or a putrid smell that people find unpleasant. When evaluating the odor, a 5 cm × 10 cm sample was cut out from the films of Prototype Examples 1 to 13, sealed in a 300 ml flask, and held in an oven at 40°C for 72 hours. After holding, the sample was left at room temperature for 24 hours. The odor of the sample after the above-mentioned leaving was subjected to sensory evaluation. The sensory evaluation was taken as the average score of 5 panelists based on the 6-level odor intensity display method shown below. The odor evaluation was considered good when the average score of the odor intensity did not exceed 4. Odor intensity 0: Odorless Odor intensity 1: Barely perceptible odor Odor intensity 2: Weak odor whose source can be identified Odor intensity 3: Readily perceptible odor Odor intensity 4: Strong odor Odor intensity 5: Intense odor

[0077] [Appearance Evaluation of Film] The appearance of the film is an index for judging the quality (commercial value of the film) of the film surface based on the presence or absence of the occurrence of fish eyes. Since the roughness of the film surface increases as the number of fish eyes increases, for the appearance of the film, a laser microscope (Keyence Corporation: VK-X3000) was used, and the quality was evaluated based on the ten-point average roughness (R Z ) in accordance with JIS B 0601 (1994). In this appearance evaluation, the measurement of the ten-point average roughness (R Z ) of the surface of the second surface layer by the laser microscope was carried out 5 times, and the average value was taken as the measured value. The appearance of the film was considered good when the ten-point average roughness (R Z ) did not exceed 2 μm.

[0078] [Table 1]

[0079] [Table 2]

[0080] [Results and Discussion] Prototype Example 9 is a film that does not contain recycled raw materials. As shown in Table 2, Prototype Example 9 has extremely good film properties such as odor and appearance. However, since Prototype Example 9 does not contain recycled raw materials, it is not suitable for films that meet the recent social requirements considering the environment. Therefore, the films of Prototype Examples 1 to 8, 10 to 13 that contain recycled raw materials and satisfy environmental performance are examined based on the film properties of odor and appearance. Note that the recycled polyolefin resin (R-PP1) used as the recycled raw material emits a strong odor, and the other recycled polyolefin resins (R-PP2, R-PP3, R-PE1) emit a weak odor.

[0081] Prototype Examples 1 to 8, 12, and 13 all had the desired film properties (odor, film appearance). Prototype Example 10 did not have the desired properties in terms of odor and film appearance, and Prototype Example 11 did not have the desired property in terms of odor.

[0082] Prototype Example 1 is a film in which the intermediate layer contains a recycled raw material (R-PP1) with a strong odor, and neither the first surface layer nor the second surface layer contains recycled raw materials. In contrast, Prototype Example 10 uses the same resin containing the recycled raw material (R-PP1) as the intermediate layer for the second surface layer, and the other parts are the same as Prototype Example 1. Also, for Prototype Examples 6 and 11, except that the recycled raw material used is a recycled raw material (R-PP2) with a weak odor, the comparison relationship is the same as that between Prototype Example 1 and Prototype Example 10.

[0083] As understood from the odor tests of Tables 1 and 2, good results were not obtained in the odor tests of Prototypes 10 and 11 containing recycled resin in the second surface layer, whereas good results were obtained in the odor tests of Prototypes 1 and 6 in which surface layers not containing recycled raw materials (the first surface layer and the second surface layer) were disposed on both sides of the intermediate layer containing recycled resin. By sandwiching the intermediate layer containing recycled raw materials with surface layers not containing recycled raw materials, it is considered that both surface layers (the first and the second surface layers) functioned as barrier layers that prevent the transfer of odor components caused by recycled raw materials, suppressing the release of odor from the film.

[0084] As understood from the appearance tests of Tables 1 and 2, in Prototypes 1 and 10, good results were not obtained in the appearance test of Prototype 10, whereas good results were obtained in the appearance test of Prototype 1. On the other hand, in Prototypes 6 and 11, good results were obtained in both appearance tests. From this, it is considered that in films containing recycled raw material (R-PP1) with a stronger odor than recycled raw material (R-PP2) with a weaker odor, appearance defects such as fish eyes are likely to occur. This is presumably because recycled raw material with a stronger odor contains more foreign substances than recycled raw material with a weaker odor, and these foreign substances have an adverse effect on the appearance of the film.

[0085] Prototypes 2 to 5 are examples in which a nucleating agent (Prototypes 2 and 3), an alicyclic resin (Prototype 4), and an odor adsorbent (Prototype 5) were added as additives to the intermediate layer. In Prototypes 2 to 5, the results were improved in comparison with the odor test of Prototype 1. Therefore, it is considered that the addition of these additives can more effectively reduce odor.

[0086] Prototype 7 is an example in which a compatibilizer was added to the intermediate layer. In Prototype 7, the result of the appearance test was improved in comparison with Prototype 6. Therefore, it is considered that the addition of a compatibilizer can more effectively reduce appearance defects.

[0087] Prototype Example 8 is an example in which a different recycled raw material (R-PP3) is used from Prototype Examples 1 and 6. In Prototype Example 8, since the intermediate layer is sandwiched between the first surface layer and the second surface layer as in Prototype Examples 1 and 6, good results were obtained in both odor and appearance.

[0088] Prototype Example 12 is an example in which a polyethylene-based recycled raw material (R-PE1) is used, while Prototype Examples 1, 6, 8, etc. used polypropylene-based recycled raw materials (R-PP1, R-PP2, R-PP3). Also in Prototype Example 12, since the intermediate layer is sandwiched between the first surface layer and the second surface layer and good results were obtained in both odor and appearance, it was found that even when a polyethylene-based recycled raw material is included, problems with odor and appearance can be improved.

[0089] Prototype Example 13 is an example of a laminated film in which the intermediate layer contains a recycled raw material (R-PP2) and neither the first surface layer nor the second surface layer contains a recycled raw material, and is a stretched film (biaxially stretched). Also in Prototype Example 13, since the intermediate layer is sandwiched between the first surface layer and the second surface layer and good results were obtained in both odor and appearance, it was found that even in the case of a stretched film as in the case of an unstretched film, problems with odor and appearance can be improved.

[0090] As described above, the polypropylene-based film of the present invention is a laminated film mainly composed of a polypropylene-based resin having at least three layers of a first surface layer, an intermediate layer, and a second surface layer. The intermediate layer is composed of a recycled polyolefin-based resin and either a petroleum-derived polypropylene-based resin or a plant-derived polypropylene-based resin or a mixture thereof. The first surface layer and the second surface layer are composed of either a petroleum-derived polyolefin-based resin or a plant-derived polyolefin-based resin or a mixture thereof, so that the first and second surface layers function as a barrier layer that prevents the movement of odor components generated from the intermediate layer due to the recycled polyolefin-based resin, and it is possible to suppress the release of odor from the film. Thereby, it is possible to reduce the odor caused by the recycled polyolefin-based resin (recycled raw material).

Industrial Applicability

[0091] The polypropylene-based film of the present invention has a laminated structure in which an intermediate layer containing a recycled raw material is sandwiched between a first surface layer and a second surface layer that do not contain the recycled raw material in a film using a recycled raw material, thereby enabling reduction of odor caused by the recycled raw material. Further, for a laminate composed of a plurality of resin layers including the polypropylene-based film of the present invention, by laminating resin layers having physical properties according to the intended use, it is possible to use a recycled raw material while having the performance required as a film. Furthermore, it can also be made into a package using the laminate. Thus, it is promising as an alternative to existing laminates and packages as films and packages using recycled raw materials.

Claims

1. A laminated film mainly composed of a polypropylene-based resin composed of at least three layers of a first surface layer, an intermediate layer, and a second surface layer, wherein the intermediate layer is composed of 5 to 95 wt% of a recycled polyolefin-based resin and 5 to 95 wt% of either a petroleum-derived polypropylene-based resin or a plant-derived polypropylene-based resin or a mixture thereof, the first surface layer and the second surface layer are each composed of either a petroleum-derived polyolefin-based resin or a plant-derived polyolefin-based resin or a mixture thereof, and the content of the recycled polyolefin-based resin in the laminated film is 3 wt% or more. A polypropylene-based film characterized by the above.

2. The polypropylene-based film according to claim 1, wherein a nucleating agent is added in an amount of 0.1 to 10 wt% to at least one of the first surface layer, the intermediate layer, and the second surface layer.

3. The polypropylene-based film according to claim 1, wherein a cyclic olefin-based resin or an alicyclic resin is added to at least one of the first surface layer, the intermediate layer, and the second surface layer.

4. The polypropylene-based film according to any one of claims 1 to 3, wherein an odor adsorbent is added to at least one of the first surface layer, the intermediate layer, and the second surface layer.

5. The polypropylene-based film according to any one of claims 1 to 3, wherein a polypropylene-based elastomer as a compatibilizer is added to the intermediate layer in an amount of 1 to 30 wt%.

6. The polypropylene-based film according to any one of claims 1 to 3, wherein a phenolic antioxidant or a phosphorus-based antioxidant is added to the intermediate layer.

7. A laminate composed of a plurality of resin layers including the polypropylene-based film according to any one of claims 1 to 3.

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