Rust-proof film

Abstract

We provide a rust-preventive film that offers excellent rust prevention while using recycled resin. [Solution] A rust-preventive film comprising at least a first layer containing virgin polyethylene and a volatile rust inhibitor, and a second layer containing recycled polyethylene and an antioxidant, wherein the first layer and the second layer are co-extruded.

Description

[Technical Field]

[0001] This disclosure relates to a rust-preventive film, and more particularly to a rust-preventive film for packaging metal components such as machine parts to suppress oxidation and rust formation on the metal surface during storage, transport, and transportation. [Background technology]

[0002] Traditionally, when storing metal components for extended periods, it was common practice to apply rust-preventive oil before packaging and storing them to prevent rust formation. For machine parts where rust prevention by applying rust-preventive oil is not possible, alternative methods include packaging and storing them with volatile rust inhibitors or rust-preventive films made by kneading volatile rust inhibitors into resin films.

[0003] In rust-preventive films using the volatile rust inhibitors described above, it is necessary to have breathability so that the volatile rust inhibitors can vaporize. In single-layer films, the volatile rust inhibitors volatilize not only inside but also outside the packaging, so a multi-layer film structure is adopted. For example, a multi-layer film has been proposed in which a resin film containing a volatile rust inhibitor is laminated with a base film such as nylon. It is said that such a multi-layer rust-preventive film can suppress the diffusion or volatilization of the volatile rust inhibitor to the outer layer (atmospheric side), and maintain a high rust-inhibiting effect over a long period of time (for example, Patent Document 1).

[0004] Furthermore, a multilayer film has been proposed that contains a volatile corrosion inhibitor in the innermost layer, a gas barrier resin layer as an intermediate layer, and a base material layer as the outermost layer. It is known that with this multilayer film, the barrier properties of the corrosion inhibitor against vaporized gas, oxygen, or water vapor are improved by providing the intermediate layer (for example, Patent Document 2, etc.).

[0005] Furthermore, to improve barrier properties, a multilayer anti-corrosion film is disclosed in which a barrier film having a vapor-deposited film and an organic coating layer on the substrate is laminated to a sealant layer (for example, Patent Document 3). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2013-059864 [Patent Document 2] Japanese Patent Publication No. 2019-155611 [Patent Document 3] Japanese Patent Publication No. 2020-189689 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Incidentally, in recent years, the use of recycled products has been recommended from the perspective of reducing environmental impact. In fields such as packaging films, efforts are being made to actively use recycled resin products. However, while recycled resins such as polyester and polyethylene are available on the market, recycled products for special gas barrier resins and the like are not currently available.

[0008] Furthermore, for example, recycled polyethylene may have antioxidants added to prevent thermal decomposition and gelation during the re-melting process of recycling. Phenolic antioxidants and phosphate-based antioxidants are used as such antioxidants to prevent thermal degradation of polyethylene.

[0009] In rust-preventive films containing volatile corrosion inhibitors as described above, if the recycled polyethylene constituting the resin film contains an antioxidant, the antioxidant may deactivate the volatile corrosion inhibitor, reducing the rust-preventive effect of the rust-preventive film.

[0010] Therefore, the purpose of this disclosure is to provide a rust-preventive film that has excellent rust-preventive properties while using recycled resin. [Means for solving the problem]

[0011] The inventor has found that by incorporating a vaporizable rust inhibitor into a layer composed of virgin polyethylene not containing an antioxidant and making it a separate layer from a layer composed of recycled polyethylene containing an antioxidant, the inactivation of the vaporizable rust inhibitor by the antioxidant can be suppressed, and a rust-preventive film excellent in rust-preventive effect can be realized while using recycled resin. The present invention is based on such findings.

[0012] [1] At least comprising a first layer containing virgin polyethylene and a vaporizable rust inhibitor, and a second layer containing recycled polyethylene and an antioxidant, A rust-preventive film obtained by co-extrusion molding of the first layer and the second layer. [2] The rust-preventive film according to [1], wherein the antioxidant is a phenolic antioxidant. [3] The rust-preventive film according to [1], wherein the vaporizable rust inhibitor is at least one selected from carboxylic acid ester-based rust inhibitors, alkanolamine-based vaporizable rust inhibitors, and heterocyclic aromatic compounds. [4] The rust-preventive film according to [1], wherein the second layer further contains virgin polyethylene. [5] The rust-preventive film according to [1], wherein the vaporizable rust inhibitor is contained in a proportion of 2 to 10% by mass based on the virgin polyethylene in the first layer. [6] The rust-preventive film according to [4], wherein the antioxidant is contained in a proportion of 500 to 5000 ppm based on the polyethylene constituting the second layer. [7] The polyethylene constituting the first layer has a density of 0.860 g / cm or more and 0.932 g / cm 3 or less. The rust-preventive film according to [1]. [8] The polyethylene having a density of 0.860 g / cm 3 or more and 0.932 g / cm 3 or less is at least one selected from low-density polyethylene and linear low-density polyethylene. The rust-preventive film according to [7]. [9] Further comprising a third layer composed of polyethylene, The rust-preventive film according to [1], wherein the first layer, the second layer, and the third layer are co-extruded. [Effects of the Invention]

[0013] According to this disclosure, it is possible to provide a rust-preventive film that has excellent rust-preventive properties while using recycled resin. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a schematic cross-sectional view showing one embodiment of the anti-corrosion film of the present disclosure. [Figure 2] Figure 2 is a schematic cross-sectional view showing one embodiment of the anti-corrosion film of the present disclosure. [Figure 3] Figure 3 shows the GC-MS measurement results for the resin compositions of Example 1 and Comparative Example 1. [Figure 4] Figure 4 shows the GC-MS measurement results for the resin compositions of Example 2 and Comparative Example 2. [Modes for carrying out the invention]

[0015] In this specification, when multiple candidate upper limits and multiple candidate lower limits are given for a certain parameter, the numerical range of that parameter may be constructed by combining any one candidate upper limit and any one candidate lower limit. As an example, consider the statement, "Parameter B is preferably A1 or greater, more preferably A2 or greater, even more preferably A3 or greater. Parameter B is preferably A4 or less, more preferably A5 or less, even more preferably A6 or less." In this example, the numerical range of parameter B may be A1 or greater and A4 or less, A1 or greater and A5 or less, A1 or greater and A6 or less, A2 or greater and A4 or less, A2 or greater and A5 or less, A2 or greater and A6 or less, A3 or greater and A4 or less, A3 or greater and A5 or less, or A3 or greater and A6 or less.

[0016] In this specification, polyethylene refers to a polymer in which the content ratio of ethylene-derived structural units exceeds 50 mol% in the total amount of structural units derived from polymerizable monomers. In this polymer, the content ratio of ethylene-derived structural units is preferably 70 mol% or more, more preferably 80 mol% or more, still more preferably 90 mol% or more, and particularly preferably 95 mol% or more. The above content ratio is measured by nuclear magnetic resonance spectroscopy (NMR method).

[0017] In this specification, polyethylene may be a homopolymer of ethylene or a copolymer of ethylene and an ethylenically unsaturated monomer other than ethylene. Examples of the ethylenically unsaturated monomer other than ethylene include α-olefins having 3 to 20 carbon atoms such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, 3-methyl-1-butene, 4-methyl-1-pentene, and 6-methyl-1-heptene, vinyl monomers such as vinyl acetate and vinyl propionate, and (meth)acrylate esters such as methyl (meth)acrylate and ethyl (meth)acrylate.

[0018] In this specification, examples of polyethylene include high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, and ethylene-(meth)acrylate copolymer.

[0019] In this specification, the density of polyethylene is as follows. The density of low-density polyethylene is 0.860 g / cm 3 or more and 0.932 g / cm 3 or less, more preferably 0.900 g / cm 3 or more and 0.932 g / cm 3 or less. The density of linear low-density polyethylene is 0.860 g / cm 3 or more and 0.932 g / cm 3The following, and more preferably 0.900 g / cm³ 3 More than 0.932g / cm 3 The following applies: The density of medium-density polyethylene is 0.932 g / cm³. 3 Exceeding 0.945 g / cm³ 3 The following applies: The density of high-density polyethylene is 0.945 g / cm³. 3 It exceeds, preferably 0.965 g / cm³ 3 The following applies: The density of polyethylene is measured in accordance with JIS K7112-2:2023 (density gradient pipe method, 23°C).

[0020] Low-density polyethylene is, for example, polyethylene obtained by polymerizing ethylene by high-pressure polymerization (high-pressure low-density polyethylene). Linear low-density polyethylene is, for example, polyethylene obtained by polymerizing ethylene and a small amount of α-olefin by polymerization using a multi-site catalyst such as a Ziegler-Natta catalyst or a single-site catalyst such as a metallocene catalyst.

[0021] Polyethylenes with different densities or branching can be obtained by appropriately selecting a polymerization method. For example, it is preferable to use a multi-site catalyst such as a Ziegler-Natta catalyst or a single-site catalyst such as a metallocene catalyst as the polymerization catalyst, and to carry out polymerization in one or more stages using one of the following methods: gas-phase polymerization, slurry polymerization, solution polymerization, or high-pressure ionic polymerization.

[0022] The melt flow rate (MFR) of polyolefins such as polyethylene as used herein is described below. From the viewpoint of film-forming properties and processability, the above MFR is preferably 0.1 g / 10 min or more, more preferably 0.3 g / 10 min or more, even more preferably 0.5 g / 10 min or more, preferably 30 g / 10 min or less, more preferably 20 g / 10 min or less, even more preferably 10 g / 10 min or less, and particularly preferably 5 g / 10 min or less. The above MFR is, for example, 0.1 g / 10 min or more and 30 g / 10 min or less. The MFR of polyolefins is measured by Method A under a load of 2.16 kg in accordance with JIS K7210-1:2014. The measurement temperature of the MFR is set according to the melting point of the polyolefin, etc., and is 190°C in the case of polyethylene.

[0023] In this specification, a biomass-derived resin material (hereinafter also referred to as "biomass polyethylene") may be used as polyethylene. A biomass material is, for example, a resin material obtained using biomass-derived raw materials (specifically, plant-derived raw materials) as at least a part of the raw materials. Since biomass materials are carbon-neutral materials, they can reduce the environmental burden of laminates or packaging bags.

[0024] In this specification, recycled polyethylene means polyethylene recycled from used polyethylene products by mechanical recycling or chemical recycling. Mechanical recycling generally involves crushing collected polyethylene film, washing it with alkali to remove dirt and foreign matter from the film surface, drying it at high temperature and under reduced pressure for a certain period of time to disperse contaminants remaining inside the film, decontamination, removing dirt from the film, and returning it to polyethylene. Chemical recycling generally involves decomposing collected polyethylene film down to the monomer level and then repolymerizing the monomers to obtain polyethylene. In this specification, virgin polyethylene means polyethylene that is not recycled polyethylene, but obtained using raw materials derived from fossil fuels or biomass.

[0025] The embodiments of this disclosure will be described in detail below. This disclosure can be implemented in many different forms and is not construed as being limited to the embodiments described below. The drawings may schematically represent the width, thickness, and shape of each layer, etc., compared to the embodiments, in order to clarify the explanation, but these are merely examples and do not limit the interpretation of this disclosure. In this specification and in each figure, elements similar to those already described in the previously shown figures are denoted by the same reference numerals, and detailed explanations may be omitted as appropriate.

[0026] The embodiments of the rust-preventive film of this disclosure will be described below with reference to the drawings as appropriate.

[0027] Figure 1 is a schematic cross-sectional view showing one embodiment of the rust-preventive film of the present disclosure. The rust-preventive film 1 according to one embodiment of the present disclosure has a multilayer structure comprising at least a first layer 10 containing virgin polyethylene and a volatile rust inhibitor, and a second layer 20 containing recycled polyethylene and an antioxidant. Figure 2 is a schematic cross-sectional view showing another embodiment of the rust-preventive film of the present disclosure. The rust-preventive film 1 according to another embodiment of the present disclosure has a multilayer structure comprising a first layer 10 containing virgin polyethylene and a volatile rust inhibitor, a second layer 20 containing recycled polyethylene and an antioxidant, and a third layer 30 made of polyethylene. The first layer containing the volatile rust inhibitor is the innermost layer when the rust-preventive film is used as packaging for metal parts, etc. In the rust-preventive film 1 of the present disclosure shown in Figure 1, the second layer 20 is the outermost layer when used as packaging. Furthermore, in the rust-preventive film 1 of this disclosure shown in Figure 2, the third layer 30 is the innermost layer when the rust-preventive film is used as packaging for metal parts, etc., and the second layer 20 is an intermediate layer provided between the first layer 10, which is the innermost layer, and the third layer 30, which is the outermost layer. The following describes each layer constituting the rust-preventive film 1 of this disclosure.

[0028] [First layer] The first layer constituting the rust-preventive film of this disclosure is a layer containing virgin polyethylene as the main component of the resin component. In this disclosure, "a layer containing polyethylene as the main component" means a layer in which the content of virgin polyethylene in 100% by mass of the layer is 50% by mass or more. The above content is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

[0029] From the perspective of reducing environmental impact, it is preferable to use recycled polyethylene rather than virgin polyethylene. However, recycled polyethylene, especially mechanically recycled polyethylene, is manufactured by remelting used polyethylene as described above, and antioxidants are sometimes added to prevent thermal degradation of the polyethylene during this process. Antioxidants suppress the severing and crosslinking of polyethylene molecular chains by capturing radicals produced when polyethylene is thermally decomposed during remelting. On the other hand, such antioxidants may deactivate volatile corrosion inhibitors. As a result, the corrosion-preventive effect of the resulting corrosion-preventive film is reduced. In this disclosure, a layer made of recycled polyethylene containing antioxidants is used as the second layer, and virgin polyethylene with a low antioxidant content is used as the resin component constituting the first layer containing volatile corrosion inhibitors. This makes it possible to achieve a corrosion-preventive film with excellent corrosion-preventive effect while reducing environmental impact.

[0030] The virgin polyethylene used for the first layer has a density of 0.860 g / cm³. 3 More than 0.932g / cm 3 Preferably, the following conditions apply, and as described above, low-density polyethylene or linear low-density polyethylene can be suitably used, and more preferably linear low-density polyethylene can be used. The resin component constituting the rust inhibitor-containing layer has a density of 0.900 g / cm³. 3 More than 0.932g / cm 3 It is more preferable to use the following linear low-density polyethylene.

[0031] The rust inhibitor-containing layer constituting the rust-preventive film of this disclosure contains a volatile rust inhibitor. The rust inhibitor-containing layer can be formed by kneading the volatile rust inhibitor into polyethylene of a predetermined density, which is the resin component described above, and forming a film.

[0032] As volatile rust inhibitors, conventionally known volatile rust inhibitors that volatilize at 40°C to 60°C and exhibit rust-preventive effects can be used without particular limitation. Examples include various ammonium salts of aliphatic or aromatic acids, nitrites of amines, carboxylates of amines, chromates of amines, esters of carboxylic acids, heterocyclic compounds and thioureas, mercapto groups, triazole rings, pyrrole rings, pyrazole rings, thiazole rings, imidazole rings, and other heterocyclic compounds. Among these, carboxylic acid esters, alkanolamines, and heterocyclic aromatic compounds can be preferably used from the viewpoint of environmental adaptability.

[0033] As a carboxylic acid ester-based rust inhibitor, fatty acid esters can be preferably used. Fatty acid esters with 6 to 20 carbon atoms in the fatty acid portion are preferred. If the number of carbon atoms is less than the above range, the boiling point may be too close to the film formation temperature, which may cause bubbles to form or prevent film formation. Specific fatty acid esters include alcohol esters of the above-mentioned fatty acids and glycerin fatty acid esters. Glycerin fatty acid esters are preferably glycerin tri-fatty acid esters, glycerin fatty acid esters, and more preferably glycerin tricaprylic acid esters. Among the above-mentioned fatty acids, it is preferable to use one or more selected from the group consisting of heptanoic acid, octanoic acid, decanoic acid, lauric acid, stearic acid, caprylic acid, capric acid, calcium stearate, and glycerin tricaprylic acid ester.

[0034] Amine-based volatile rust inhibitors include dicyclohexylamine, monoethanolamine, diethanolamine, diisopropylamine, cyclohexylamine, nitronaphthaleneamine, ammonium benzoate (ammonium benzoate), cyclohexylammonium benzoate, cyclohexylammonium carbamate, cyclohexylammonium nitrite, cyclohexylammonium caprylate, cyclohexylammonium laurate, dicyclohexylammonium benzoate, dicyclohexylammonium carbamate, isopropylammonium nitrite, isopropylammonium caprylate, isopropylammonium laurate, and isopropylammonium Examples include benzoate, isopropylammonium carbamate, diisopropylammonium nitrite, diisopropylammonium caprylate, diisopropylammonium laurate, diisopropylammonium benzoate, diisopropylammonium carbamate, benzylammonium nitrite, benzylammonium caprylate, benzylammonium laurate, benzylammonium benzoate, benzylammonium carbamate, dibenzylammonium nitrite, dibenzylammonium caprylate, dibenzylammonium laurate, dibenzylammonium benzoate, and dibenzylammonium carbamate.

[0035] Examples of heterocyclic aromatic compounds include compounds having a triazole ring, pyrrole ring, pyrazole ring, thiazole ring, or imidazole ring, with particular preference for compounds having a triazole ring or being benzoate compounds. More specifically, examples of rust inhibitors having a triazole ring include benzotriazole (BTA) and tolyltriazole (TTA). Examples of benzoate compounds include monoethanolamine benzoate (MEA·BA), dicyclohexylammonium benzoate (DICHA·BA), and diisopropylammonium benzoate (DIPA·BA).

[0036] From the viewpoint of the volatilization properties of the rust inhibitor and the extrusion film-forming properties of the resin, the amount of volatile rust inhibitor to be added is preferably 0.1% by mass or more and 30% by mass or less relative to the virgin polyethylene constituting the first layer, preferably 0.5% by mass or more and 20% by mass or less, and more preferably 2% by mass or more and 10% by mass or less.

[0037] The thickness of the first layer constituting the rust-preventive film is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more, from the viewpoint of the diffusion of the volatile rust inhibitor. From the viewpoint of film-forming properties and processability, it is preferably 60 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less. The thickness of the rust inhibitor-containing layer is, for example, 10 to 30 μm.

[0038] [Second layer] The second layer constituting the rust-preventive film of this disclosure is the outer layer of the first layer (the outer layer when the rust-preventive film is used as packaging for metal parts, etc.), and contains recycled polyethylene as the main component of the resin. By using recycled polyethylene, the environmental burden can be reduced. Recycled polyethylene, in particular mechanical recycled polyethylene, can suppress thermal degradation by containing antioxidants as described above, but it may deactivate volatile corrosion inhibitors. However, the rust-preventive film of this disclosure has a second layer made of recycled polyethylene, separate from the first layer which contains a volatile corrosion inhibitor, thereby reducing the environmental burden while providing excellent rust prevention effects. Furthermore, recycled polyethylene contains impurities and various grades compared to virgin polyethylene resin, and if recycled polyethylene is used as the main component in the outermost layer or the rust inhibitor-containing layer, a higher film-forming temperature is required. In addition, recycled polyethylene is known to produce fisheyes and wrinkles when the film is formed, compared to virgin polyethylene. In this disclosure, the rust-preventive film is constructed in a two-layer structure, and recycled polyethylene is used as the second layer, thereby reducing the environmental impact while resolving the above-mentioned problems.

[0039] Recycled polyethylene (especially mechanically recycled polyethylene) is a mixture of various types of used polyethylene (low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, and other polyethylenes) that are mixed together during the recycling process. However, considering film-forming properties and processability, it is preferable to use recycled polyethylene with an MFR of 0.1 g / 10 min to 30 g / 10 min.

[0040] The rust-preventive film of this disclosure may contain virgin polyethylene in addition to recycled polyethylene as a second layer. By appropriately adding virgin polyethylene, film-forming properties and processability can be improved. When the intermediate layer contains recycled polyethylene and virgin polyethylene, the virgin polyethylene content is preferably between 0% and 50% by mass, and preferably between 15% and 35% by mass, relative to the entire intermediate layer.

[0041] If the second layer contains virgin polyethylene, the amount of virgin polyethylene is preferably 0.860 g / cm³. 3 More than 0.932g / cm 3 The following low-density polyethylene, more preferably 0.900 g / cm³ 3 More than 0.932g / cm 3 The following low-density polyethylene, or preferably 0.860 g / cm³ 3 More than 0.932g / cm 3The following linear low-density polyethylene, more preferably 0.900 g / cm³ 3 More than 0.932g / cm 3 The following is linear low-density polyethylene.

[0042] The second layer, which mainly consists of recycled polyethylene, contains an antioxidant to prevent thermal degradation of the polyethylene. While conventionally known antioxidants such as phenol-based, phosphoric acid-based, sulfur-based, and amine-based antioxidants can be used, it is preferable to use a dicyclohexylamine antioxidant from the viewpoint of rust prevention.

[0043] Examples of phenolic antioxidants include octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and pentaerythritol tetrakis[3-(3,5-ditter-butyl-4-hydroxyphenyl)propionate]. Commercially available phenolic antioxidants may also be used, such as 3,3',3”,5,5',5”-Hexa-tert-butyl-.alpha,.alpha',.alpha”-(mesitylene-2,4,6-triyl)tri-p-cresol (BASF IRGANOX 1330) and 3,9-Bis{2-“3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy”-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro“5.5”undecane (ADEKA ADEKA Stab AO-80).

[0044] Phenolic antioxidants can be incorporated into recycled polyethylene to form a rust-preventive film, or they can be added to used polyester during mechanical recycling when it is remelted. In other words, the phenolic antioxidant may already be contained in the recycled polyester.

[0045] The phenolic antioxidant is preferably present in a ratio of 500 to 5000 ppm relative to the recycled polyethylene, and more preferably in a ratio of 1000 to 4000 ppm. It should be noted that this does not exclude the presence of phenolic antioxidants used in the production of recycled polyethylene; recycled polyethylene may contain conventionally used antioxidants (phosphoric acid-based, sulfur-based, amine-based, etc.).

[0046] Furthermore, if virgin polyethylene is included in addition to recycled polyethylene, a phenolic antioxidant may be used during the manufacture of the virgin polyethylene. In this case, the amount of phenolic antioxidant shall be the total amount of phenolic antioxidants contained in the recycled polyethylene and virgin polyethylene, as well as the phenolic antioxidants added during the manufacture of the rust-preventive film.

[0047] The thickness of the second layer is preferably 80 μm or less, more preferably 70 μm or less, and even more preferably 60 μm or less, from the viewpoint of film-forming properties and processability. The thickness of the intermediate layer is, for example, 40 to 60 μm.

[0048] Furthermore, it is preferable that the second layer has a thickness of 2 to 4 times that of the first layer containing the volatile corrosion inhibitor. When using recycled polyethylene, the melting temperature during film formation needs to be slightly higher (around 200 to 210°C) than that of virgin polyethylene. As will be described later, when the first and second layers are formed using, for example, an inflation co-extrusion film formation method, the thickness of the second layer can be set to 2 to 4 times that of the first layer. This allows for sufficient heat to melt the recycled polyethylene during extrusion film formation while simultaneously allowing the surface of the innermost layer, the first layer, to be air-cooled. This suppresses thermal degradation and volatilization of the volatile corrosion inhibitor in the first layer. It is even more preferable that the second layer has a thickness of 2 to 3 times that of the first layer.

[0049] [Third layer] The rust-preventive film of this disclosure may further comprise a third layer in addition to the second layer. If a third layer is present, the third layer constitutes the outermost layer when the rust-preventive film is used as packaging for metal parts or the like. By comprising the third layer, the volatile rust inhibitor contained in the rust inhibitor-containing layer can be prevented from diffusing into the atmosphere outside the rust-preventive film. The third layer mainly consists of polyethylene as a resin component, having the same density as or greater than the polyethylene constituting the rust inhibitor-containing layer described above. For example, if the polyethylene constituting the rust inhibitor-containing layer is low-density polyethylene or linear low-density polyethylene, the outermost layer can be made of low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, or high-density polyethylene.

[0050] From the viewpoint of suppressing the diffusion of volatile corrosion inhibitors, it is preferable to use polyethylene with a high density for the third layer. However, from the viewpoint of film formation properties when forming the corrosion-preventive film and suppression of curling of the resulting film, polyethylene should be selected so that the density difference between the recycled polyethylene that makes up the innermost first layer and the polyethylene that makes up the outermost third layer is not large. From the viewpoint of suppressing the diffusion of volatile corrosion inhibitors and suppressing curling, it is preferable to use low-density polyethylene or linear low-density polyethylene that has the same density as or greater than the recycled polyethylene that makes up the first layer.

[0051] Furthermore, either virgin polyethylene or recycled polyethylene may be used as the polyethylene constituting the third layer. From the viewpoint of reducing environmental impact, it is preferable to use recycled polyethylene for the third layer as well. However, as mentioned above, from the viewpoint of suppressing the diffusion of volatile corrosion inhibitors and suppressing curling, it is preferable to use virgin polyethylene (low-density polyethylene or linear low-density polyethylene) that has the same density as or greater than the recycled polyethylene constituting the first layer.

[0052] Whether the polyethylene constituting the third layer is virgin polyethylene or recycled polyethylene, the above-mentioned phenolic antioxidant may be included. When a phenolic antioxidant is included, the content is preferably 500 to 5000 ppm relative to the polyethylene constituting the third layer, and more preferably 1000 to 4000 ppm. This does not exclude the inclusion of phenolic antioxidants used in the production of recycled polyethylene, and recycled polyethylene may contain conventionally used antioxidants (phosphoric acid-based, sulfur-based, amine-based, etc.).

[0053] The thickness of the third layer constituting the anti-corrosion film is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more, from the viewpoint of suppressing the diffusion of volatile rust inhibitors. From the viewpoint of film-forming properties and processability, it is preferably 60 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less.

[0054] The total thickness of the rust-preventive film disclosed herein is adjusted as appropriate depending on the application, but is generally 50 μm or more, more preferably 60 μm or more, even more preferably 80 μm or more, and generally 150 μm or less, more preferably 120 μm or less, and even more preferably 100 μm or less.

[0055] [Method for manufacturing rust-proof film] The rust-preventive film of this disclosure can be obtained by co-extruding the first and second layers (or the first, second, and third layers if a third layer is also provided) as described above. Co-extruding can be performed using an inflation co-extrusion method with a circular die or a co-extrusion method with a T die to obtain the rust-preventive film. In particular, the inflation co-extrusion method allows for melt co-extrusion at a lower temperature of 200°C or less, thus suppressing the thermal decomposition and volatilization (vaporization) of volatile rust inhibitors during film formation. Especially when recycled polyethylene is used as the resin component of the second layer, the melting temperature during film formation needs to be slightly higher (around 200-210°C) than that of virgin polyethylene. However, with the inflation co-extrusion method, the melting temperature of the virgin polyethylene of the first layer can be set to 200°C or less, and furthermore, air cooling during film formation can reduce the thermal effect on the rust inhibitor-containing layer. As a result, a rust-preventive film with excellent rust-preventive properties can be obtained while using recycled resin. Furthermore, by using a two- or three-layer co-extruded film made of polyethylene, as in the present invention, the resistance to punctures is improved compared to a single-layer film. Therefore, even when packaging metal machine components with protruding parts, the rust-preventive film of the present invention can prevent tearing by machine parts.

[0056] When forming the first layer, in order to improve the dispersibility of the volatile corrosion inhibitor, a masterbatch containing the volatile corrosion inhibitor may be used, and the film may be co-extruded using a blend of the masterbatch and polyethylene of a predetermined density. The proportion of the volatile corrosion inhibitor in the masterbatch is not particularly limited, but the masterbatch and polyethylene of a predetermined density should be blended so that the proportion of the volatile corrosion inhibitor in the corrosion inhibitor-containing layer falls within the range described above.

[0057] Furthermore, the rust-preventive film disclosed herein may have various additives added to one or more layers, to the extent that it does not impair its properties. Examples of additives include antioxidants, slip agents, plasticizers, ultraviolet stabilizers, color inhibitors, matting agents, deodorants, flame retardants, weather-resistant agents, antistatic agents, thread friction reducers, mold release agents, ion exchange agents, antiblocking agents, and coloring pigments.

[0058] The rust-preventive film disclosed herein can be used as a packaging material for packaging metal components such as machine parts. There are no particular restrictions on the shape or form of the packaging material; it can be in the form of a film to wrap the contents, or the rust-preventive film can be folded or overlapped and heat-sealed to form a bag. [Examples]

[0059] The laminates of the present disclosure will be described in more detail below with reference to examples, but the laminates of the present disclosure are not limited to the following examples.

[0060] [Example 1] A co-extruded film having a three-layer structure consisting of a first layer, a second layer, and a third layer was fabricated using a co-extrusion inflation film manufacturing machine. The first layer is composed of linear low-density polyethylene (density 0.916 g / cm³). 3 A dry blend of (MFR 2.3g / 10 min, manufactured by Nippon Polyethylene, NF444N) and a masterbatch of volatile corrosion inhibitor was used in a ratio of 90:10 by mass. The masterbatch of the volatile corrosion inhibitor was prepared by kneading ester compounds of pentanoic acid, hexanoic acid, heptanoic acid, and octanoic acid into the above linear low-density polyethylene at a concentration of 10% by mass. The second layer is composed of recycled polyethylene (density 0.920 g / cm³). 3 The following was used: MFR 1.0g / 10min (Dow Chemical Company, XUS60922.01) and a phenolic antioxidant (BASF Japan, Irganox1010) in an amount equivalent to 1500 ppm relative to recycled polyethylene. The third layer is composed of linear low-density polyethylene (density 0.931 g / cm³). 3 The MFR was 2.1g / 10min, using UZ3520 manufactured by Prime Polymer Co., Ltd. The thickness of each layer of the anti-corrosion film obtained as described above was 20 μm for the first layer, 50 μm for the second layer, and 10 μm for the third layer.

[0061] [Example 2] A rust-preventive film was obtained in the same manner as in Example 1, except that ethanolamine, an amine-based volatile rust inhibitor, was used instead of a carboxylic acid ester compound as the masterbatch containing the volatile rust inhibitor.

[0062] [Example 3] A rust-preventive film was obtained in the same manner as in Example 1, except that a phenolic antioxidant (Irgafos168, manufactured by BASF Japan) was used instead of a carboxylic acid ester compound as a volatile rust inhibitor.

[0063] [Example 4] As the third layer, recycled polyethylene (density 0.920 g / cm³) 3 A rust-preventive film was obtained in the same manner as in Example 1, except that MFR 1.0g / 10min (Dow Chemical Company, XUS60922.01) was used.

[0064] [Comparative Example 1] The first layer is made of recycled polyethylene (density 0.920 g / cm³). 3 A dry blend was used of recycled polyethylene and a masterbatch of the above recycled polyethylene and the volatile corrosion inhibitor in a ratio of 96:4 by mass, containing 1.0 g / 10 min of MFR (XUS60922.01) and a phenolic antioxidant (BASF Japan, Irgafos168) in an amount equivalent to 1500 ppm relative to the recycled polyethylene. A corrosion-preventive film was obtained in the same manner as in Example 1, except that the masterbatch of the volatile corrosion inhibitor was prepared by kneading ester compounds of pentanoic acid, hexanoic acid, heptanoic acid, and octanoic acid into the above recycled polyethylene at a mass of 10%.

[0065] [Comparative Example 2] A rust-preventive film was obtained in the same manner as in Comparative Example 1, except that ethanolamine, an amine-based volatile rust inhibitor, was used as the masterbatch containing the volatile rust inhibitor instead of the carboxylic acid ester compound.

[0066] [Rust prevention evaluation] Each anti-corrosion film obtained as described above was cut to a size of 150 mm x 200 mm and used as an evaluation sample. A degreased iron plate (gray cast iron, FC200, degreased, shape: 40 mm x 60 mm x 10 mm) was covered with the film and stored in a constant temperature bath adjusted to 40°C and 90% RH for 20 days. After that, the appearance of the iron plate was evaluated according to the evaluation criteria below. For Comparative Example 1, one side of the bag was cut to a size of 150 mm x 200 mm and used as an evaluation sample. ◎: No rust or discoloration, or only spot rust and slight discoloration. ○: Rust occurs in less than 10% of the surface area of ​​the iron plate. △: Rust occurs in areas of the iron plate surface that cover 10% to less than 50% of the total surface area. ×: Rust has occurred in more than 50% of the surface area of ​​the iron plate. The evaluation results are shown in Table 1 below.

[0067] Furthermore, the amount of reduction in each resin composition (recycled polyethylene, antioxidant, and volatile corrosion inhibitor) constituting the first layer of Example 1 and Comparative Example 1 was measured using a mass spectrometer (GCMS-QP2010, Shimadzu Corporation) to evaluate the amount of volatile corrosion inhibitor lost. Only the volatile corrosion inhibitor was measured and used as a blank. The measurement results are shown in Figure 3.

[0068] Furthermore, the amount of volatile corrosion inhibitor lost from each resin composition constituting the first layer of Example 2 and Comparative Example 2 was evaluated in the same manner as described above. The measurement results are shown in Figure 4.

[0069] [Table 1]

[0070] As is clear from the evaluation results in Table 1 and Figures 3-4, the rust-preventive film of the present invention has excellent rust-preventive performance despite using recycled resin. [Explanation of Symbols]

[0071] 1. Rust-proof film 10. The first layer 20. Second layer 30 The third layer

Claims

1. It comprises at least a first layer containing virgin polyethylene and a volatile corrosion inhibitor, and a second layer containing recycled polyethylene and an antioxidant. A rust-preventive film comprising the first layer and the second layer, formed by co-extrusion.

2. The rust-preventive film according to claim 1, wherein the antioxidant is a phenolic antioxidant.

3. The rust-preventive film according to claim 1, wherein the volatile rust inhibitor is at least one selected from carboxylic acid ester-based rust inhibitors, alkanolamine-based volatile rust inhibitors, and heterocyclic aromatic compounds.

4. The rust-preventive film according to claim 1, wherein the second layer further comprises virgin polyethylene.

5. The rust-preventive film according to claim 1, wherein the volatile rust inhibitor is contained in a proportion of 2 to 10% by mass relative to the virgin polyethylene of the first layer.

6. The rust-preventive film according to claim 4, wherein the antioxidant is contained in a ratio of 500 to 5000 ppm with respect to the polyethylene constituting the second layer.

7. The polyethylene constituting the first component has a density of 0.860 g / cm³. 3 0.932g / cm or more 3 The rust-preventive film according to claim 1, wherein the polyethylene is as follows.

8. Density is 0.860 g / cm³ 3 0.932g / cm or more 3 The rust-preventive film according to claim 7, wherein the following polyethylene is at least one selected from low-density polyethylene and linear low-density polyethylene.

9. It further comprises a third layer made of polyethylene, The rust-preventive film according to claim 1, wherein the first layer, the second layer, and the third layer are co-extruded into a film.

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