JP7729035B2 - Anti-rust film and anti-rust packaging - Google Patents

Description

This disclosure relates to a rust-preventive film that prevents rust from forming on packaged contents, and to a rust-preventive package that includes this rust-preventive film.

Packaging materials are being developed for the purpose of transporting or long-term storage of metal-containing articles, such as metal articles made of metal materials or parts using metal, and there is a demand for packaging materials that have higher and more stable rust prevention properties and that can be produced by a simple manufacturing process with a simple layer structure so as to maintain the functions and properties of the metal articles contained therein.
For example, Patent Documents 1 to 3 describe packaging laminates in which a highly volatile rust inhibitor that volatilizes at room temperature and exerts a rust-preventing effect is contained in a resin for the purpose of preventing rust on metal articles.
However, in the case of anti-rust films using volatile anti-rust agents, if the sealing of the package manufactured from the anti-rust film is insufficient, there is a problem that the anti-rust effect on the contents is hardly exhibited. In addition, volatile anti-rust agents may contain substances harmful to the human body (e.g., carcinogenicity), so they must be handled with care. Therefore, there is a demand for anti-rust films that do not use volatile anti-rust agents.

JP 2010-254350 A Japanese Patent Application Laid-Open No. 2007-308726 JP 2010-052751 A

This disclosure was made in light of the above-mentioned circumstances, and its primary objective is to provide a rust-preventive film that has a simple layer structure and does not require the use of volatile rust inhibitors, yet is capable of preventing rust from forming on the packaged contents.

The rust-preventive film of the present disclosure has a first layer and a second layer laminated on one side of the first layer, wherein the first layer contains a rust inhibitor and polyethylene resin, the second layer contains polyethylene resin, and the first layer contains an antioxidant as the rust inhibitor in a range of 0.3% by mass or more and 2.0% by mass or less.

The anti-corrosion film of the present disclosure may further include an intermediate layer between the first layer and the second layer.

In the anti-corrosion film of the present disclosure, the antioxidant may contain a phenolic antioxidant.

In the rust-preventive film of the present disclosure, the first layer may contain at least one of a neutralizing agent, an antiblocking agent, and a slip agent as an additive, and the content of the additive may be 50 ppm or more and 100 ppm or less.

The rust-proof packaging of the present disclosure has the above-mentioned rust-proof film.

This disclosure makes it possible to provide a rust-preventive film that has a simple layer structure and can prevent rust from occurring on packaged contents without using a volatile rust inhibitor.

1 is a schematic cross-sectional view showing an example of a layer structure of a rust-preventive film according to the present disclosure. 1 is a schematic cross-sectional view showing another example of the layer structure of the anti-corrosion film of the present disclosure.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the size and proportions of components may be changed or exaggerated for ease of understanding. Furthermore, for clarity, parts that are unnecessary for explanation or repeated reference numerals may be omitted.
Although not shown in the drawings, an adhesive layer may be provided between the layers.
Furthermore, if necessary, in order to strengthen the adhesive strength (adhesion strength) between each layer, the laminated surfaces of each layer may be subjected in advance to a physical surface treatment such as corona discharge treatment, ozone treatment, plasma treatment, glow discharge treatment, sandblasting treatment, etc., or a chemical surface treatment such as oxidation treatment using chemicals.

(Anti-rust film)
Fig. 1 is a schematic cross-sectional view showing an example of the layer structure of a rust-preventive film of the present disclosure. The rust-preventive film 1 shown in Fig. 1 has a first layer 11 and a second layer 12 laminated on one surface of the first layer 11. The first layer 11 contains a rust inhibitor and a polyethylene resin, and the second layer 12 contains a polyethylene resin.
In the rust-preventive film 1 shown in FIG. 1, the first layer 11 is a single layer, but the first layer of the rust-preventive film of the present disclosure may be composed of multiple layers.

Fig. 2 is a schematic cross-sectional view showing another example of the layer structure of the anti-rust film of the present disclosure. The anti-rust film of the present disclosure may further include an intermediate layer between the first layer and the second layer. For example, the anti-rust film 2 shown in Fig. 2 further includes an intermediate layer 13 between the first layer 11 and the second layer 12.
In the rust-preventive film 2 shown in FIG. 2, the intermediate layer 13 is a single layer, but the intermediate layer of the rust-preventive film of the present disclosure may be composed of multiple layers.

An adhesive layer may also be present between each layer of the anti-rust film 1 shown in Figure 1 and the anti-rust film 2 shown in Figure 2.

The thickness of the rust-preventive film of the present disclosure is not particularly limited, but is preferably 25 μm or more and 200 μm or less. If the thickness of the rust-preventive film is thinner than the above range, the rust-preventive film may have problems such as being too low in rigidity or being easily torn. In addition, it may be difficult for the rust-preventive film to exhibit a good balance of sufficient support, rust-preventing effect, heat-sealing properties, etc. On the other hand, if the thickness of the rust-preventive film is thicker than the above range, the rust-preventive film may be too rigid, making it difficult to use as a packaging material.

The anti-rust film is preferably transparent, and a high degree of transparency is more preferable, because an anti-rust package manufactured from a highly transparent anti-rust film allows the contents to be easily seen.
Anti-rust films are usually used in combination with other packaging materials when packaging steel materials, and it is often necessary to distinguish them from transparent general-purpose olefin films (polyethylene, polypropylene).
For this reason, colorants such as blue, orange, yellow, and green are added and the film is supplied as a light color, but it is manufactured with a transparency that allows the contents (steel) to be seen.
This type of colored film is light in color when used alone and the difference in color from films without added coloring agents is small, but when rolled up, it becomes clearly distinguishable from other packaging materials.

The term "transparent" means that the anticorrosive film has a transparency sufficient to allow viewing from one side to the other side through the anticorrosive film, and it is desirable that the anticorrosive film has a visible light transmittance of, for example, 90% or more. The visible light transmittance is specified as the average value of the transmittance at each wavelength measured using a spectrophotometer (Shimadzu Corporation's "UV-3100PC," compliant with JIS K 0115) within the measurement wavelength range of 380 nm to 780 nm.
Therefore, the haze of the anti-corrosion film is set to be less than 20%. The haze value is measured in accordance with JIS K7136 using, for example, a haze meter HM-150 manufactured by Murakami Color Research Laboratory Co., Ltd.
In the anti-rust film of the present disclosure, in order to avoid the influence of the anti-rust agent contained in the first layer on the anti-rust effect, a colorant is added to the second layer or intermediate layer formed on the first layer.
In particular, by adding a colorant only to the middle layer, even if the second layer comes into contact with the first layer when the rust-preventive film of the present disclosure is wound up, more specifically, even if the outer surface of the second layer comes into contact with the inner surface of the first layer (i.e., the surface of the first layer that comes into contact with the contents as a package), since no colorant is added to the second layer, it is possible to avoid the colorant affecting the rust-preventive properties of the first layer.

(1st layer)
The first layer of the rust-preventive film of the present disclosure (the layer designated by reference numeral 11 in FIGS. 1 and 2 ) contains a rust inhibitor and a polyethylene resin and has heat-sealability. The first layer of the rust-preventive film of the present disclosure may be a single layer containing two or more rust inhibitors, or may be composed of multiple layers containing different types or contents of rust inhibitors.

The first layer of the rust-preventive film of the present disclosure has a second layer on one side thereof, and at least a portion of the side opposite to the side having the second layer comes into contact with the contents packaged by the rust-preventive film of the present disclosure. For example, when the rust-preventive film of the present disclosure is used as a package, the side with the first layer becomes the inner layer (i.e., inner layer) of the package, and the side with the second layer becomes the outer layer (i.e., outer layer) of the package.
The predetermined rust inhibitor contained in the first layer of the rust-preventive film of the present disclosure exerts a rust-preventive effect on the packaged contents.

The thickness of the first layer of the rust-preventive film of the present disclosure can be set appropriately within the range of rust-preventive film thicknesses, but is preferably from 5 μm to 150 μm, more preferably from 10 μm to 100 μm, and even more preferably from 10 μm to 50 μm. If the thickness of the first layer is thinner than the above range, it may not be possible to achieve sufficient rust-preventive effect. On the other hand, if the thickness of the first layer is thicker than the above range, the rust-preventive effect will not be significantly improved, and the overall rigidity of the rust-preventive film may become too strong, reducing its usability as a packaging material.

<Rust inhibitor>
The rust inhibitor contained in the first layer of the rust-preventive film of the present disclosure is a compound that inhibits rust from occurring in the contents packaged by the rust-preventive film of the present disclosure.
The rust inhibitor contained in the first layer of the rust-preventive film of the present disclosure is preferably uniformly dispersed on the surface of the first layer (more specifically, on the surface opposite to the surface having the second layer). This is because the surface of the first layer is the surface that comes into contact with the contents packaged by the rust-preventive film of the present disclosure, and uniform dispersion of the rust inhibitor on this surface allows the contents to be uniformly protected from rust.
The rust inhibitor contained in the first layer of the rust-preventive film of the present disclosure may be dispersed uniformly on the surface of the first layer as described above, and may be dispersed with a concentration gradient in the thickness direction of the first layer. In other words, the rust inhibitor contained in the first layer of the rust-preventive film of the present disclosure may be dispersed with a concentration gradient in the thickness direction of the first layer, but is preferably dispersed uniformly in the plane direction of the first layer.
The rust inhibitor contained in the first layer adheres to the surface of the contents by contact transfer, for example, in a package manufactured from the rust-preventive film of the present disclosure, and inhibits oxidation on the surface of the contents, thereby inhibiting the occurrence of rust.

The first layer of the rust-preventive film of the present disclosure contains a predetermined amount of a predetermined antioxidant as a rust inhibitor. Known antioxidants used in packaging materials can be used as the antioxidant. It is preferable to use a primary antioxidant that captures generated radicals in combination with a secondary antioxidant that decomposes hydroperoxides generated from the radicals. An antioxidant that functions as both a primary antioxidant and a secondary antioxidant may also be used.
Examples of primary antioxidants include phenol-based antioxidants, amine-based antioxidants, and hindered amine-based antioxidants. Examples of secondary antioxidants include phosphorus-based antioxidants and sulfur-based antioxidants. Examples of antioxidants that function as both primary and secondary antioxidants include hydroxylamine-based antioxidants.
The antioxidant contained in the first layer of the rust-preventive film of the present disclosure is preferably a phenolic antioxidant, one containing a phenolic antioxidant and a phosphorus-based antioxidant, or a hydroxylamine-based antioxidant, and among these, one having a hydrophilic group and a hydrophobic group is more preferred.
Furthermore, the phosphorus-based antioxidant and the hydroxylamine-based antioxidant also function to prevent discoloration of the polyethylene film.

Examples of phenolic antioxidants include the following:
Examples of monophenol-based antioxidants include 2,6-di-tert-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-tert-butyl-4-ethylphenol, and octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.
Examples of bisphenol-based antioxidants include 2,2'-methylene-bis-(4-methyl-6-tert-butylphenol), 2,2'-methylene-bis-(4-ethyl-6-tert-butylphenol), 4,4'-thiobis-(3-methyl-6-tert-butylphenol), 4,4'-butylidene-bis-(3-methyl-6-tert-butylphenol), and 3,9-bis[{1,1-dimethyl-2-{β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}ethyl}2,4,9,10-tetraoxaspiro]5,5-undecane.
Examples of polymeric phenolic antioxidants include 1,1,3-tris-(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, tetrakis-{methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate}methane, bis{(3,3'-bis-4'-hydroxy-3'-tert-butylphenyl)butyric acid}glycol ester, 1,3,5-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)-s-triazine-2,4,6-(1H,3H,5H)trione, and tocopherol (vitamin E).
Among the above, tetrakis-{methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate}methane is particularly preferred as the phenolic antioxidant.

Furthermore, examples of phosphorus-based antioxidants (also called phosphite-based antioxidants) include the following:
For example, triphenyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite, 4,4'-butylidene-bis(3-methyl-6-tert-butylphenyl-di-tridecyl)phosphite, cyclic neopentanetetraylbis(octadecyl phosphite), tris(mono- and/or dinonylphenyl)phosphite, tris(2,4-di-tert-butylphenyl)phosphite, diisodecyl pentaerythritol diphosphite, 9,10-dihydro-9-oxa-10-phosphaphenathren-10-oxide, 10-(3,5-di-tert-butyl-4-hydroxybenzyl)-9,10-dihydro-9-oxa-10-phosphaphenathren-10-oxide, oxa-10-phosphaphenanthrene-10-oxide, 10-decyloxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene, cyclic neopentanetetraylbis(2,4-di-tert-butylphenyl)phosphite, cyclic neopentanetetraylbis(2,6-di-tert-butylphenyl)phosphite, 2,2-methylenebis(4,6-tert-butylphenyl)octylphosphite, 2,4,8,10-tetratert-butyl-6-(3-(3-methyl-4-hydroxy-5-tert-butylphenyl)propoxy)dibenzo(d,f)(1,3,2)dioxaphosphepine, and the like.
Among the above, tris(2,4-di-tert-butylphenyl)phosphite is particularly preferred.

In the rust-preventive film of the present disclosure, phenolic and phosphorus-based antioxidants are preferably used due to their antioxidant effect, thermal stability, and economy, and using a combination of the two is even more preferable, as this increases the antioxidant effect relative to the amount added.

The content of the antioxidant in the first layer of the rust-preventive film of the present disclosure is preferably in the range of 0.3 mass % or more and 2.0 mass % or less.
If the content of the antioxidant is less than 0.3% by mass, it is difficult to achieve a sufficient rust-preventing effect, which is undesirable.If the content of the antioxidant is more than 2.0% by mass, the rust-preventing effect is not significantly improved, and film-forming properties and heat-sealing properties tend to deteriorate, which is also undesirable.

The rust inhibitor contained in the first layer of the rust-preventive film of the present disclosure is preferably contained in a masterbatch in which the rust inhibitor is melt-blended at a high concentration with a polyethylene resin, because this makes it easier to incorporate the predetermined rust inhibitor in a uniformly dispersed state into the first layer of the rust-preventive film of the present disclosure.
The rust inhibitor and polyethylene resin to be melt-blended into the masterbatch may each be one type or two or more types, and one masterbatch may contain one or two or more types of rust inhibitor.
The polyethylene resin used in the masterbatch may be the same as or different from the main polyethylene resin constituting the first layer of the rust-preventive film of the present disclosure.

The first layer of the rust-preventive film of the present disclosure may contain, in addition to the antioxidant described above, another rust inhibitor in an amount that does not inhibit the effect of the antioxidant. Here, an amount that does not inhibit the effect of the antioxidant described above is, for example, 100 ppm or less. Examples of other rust inhibitors include phosphates (polyphosphates, phosphonates, orthophosphates), silicates, metasilicates, chromates, benzotriazole, tolyltriazole, mercatobenzothiazole, nitrates, molybdates, tungstates, chromates, hydrazine, sulfites, and other rust inhibitors that are not volatile rust inhibitors.

<Additives other than antioxidants>
When additives other than an antioxidant are contained in the first layer of the rust-preventive film of the present disclosure, it is desirable that the amount of additives added be as small as possible, because the antioxidant contained in the first layer of the rust-preventive film of the present disclosure is affected by the presence of a large amount of other additives, making it difficult to uniformly disperse the antioxidant, and reducing the rust-preventive effect.
Examples of additives other than antioxidants include neutralizing agents, antiblocking agents, slipping agents, etc. For example, when the first layer of the rust-preventive film of the present disclosure contains at least one of a neutralizing agent, an antiblocking agent, and a slipping agent as an additive, the content of the additive (when there are multiple types of additives, the total content) is preferably 50 ppm or more and 100 ppm or less in order to prevent a decrease in the rust-preventive effect while maintaining film-forming properties, etc.

<Neutralizing agent>
The neutralizing agent is added particularly for the purpose of capturing chlorine ions contained in polyethylene polymerized with a Ziegler catalyst, and is selected from hydrotalcites, silicates, metal oxides, metal hydroxides, fatty acid metal salts, and the like.
Hydrotalcites include those that do not contain hydrated basic carbonates or crystal water of magnesium, calcium, zinc, aluminum, _{bismuth ,} etc. Natural and synthetic products can be used. Natural products include those with _the structure _Mg6Al2 (OH) _16CO3.4H2O . Examples of synthetic products include _Mg0.7Al0.3 (OH) ₂ ( _{CO3 ) 0.15.0.54H2O , Mg4.5Al2} (OH) _13CO3.3.5H2O , _{Mg4.2Al2 ( OH ) 12.4CO3 , Zn6Al2 ( OH} ) _{16CO3.4H2O , Ca6Al2} ( _{OH)16CO3.4H2O , and Mg14Bi2 ( OH ) 29.6.4.2H2O .}
Examples of silicates include aluminum silicate and calcium silicate. Examples of metals in metal oxides and metal hydroxides include metals in Group II of the periodic table, zinc, aluminum, tin, lead, etc. Among these metal oxides and metal hydroxides, magnesium oxide, calcium oxide, zinc oxide, calcium hydroxide, aluminum hydroxide, magnesium hydroxide, etc. are commonly used.

<Anti-blocking agent>
Antiblocking agents are added to prevent adhesion between films. Antiblocking agents have the effect of roughening the surface of the film by adding inorganic fine particles, and various natural or artificial inorganic minerals such as silica, talc, and zeolite are used. When two or more antiblocking agents are added, the total amount of the antiblocking agents is defined as the amount of antiblocking agent added.

<Slip agent>
Slip agents (also called lubricants) are added to thermoplastic resins during heat molding to maintain the physical stability of the material during processing, such as preventing adhesion to the metal surfaces of processing equipment, reducing friction with metal surfaces, and improving the flowability of the material.
As the slip agent, fatty acids are used, including fatty acids, metallic fatty acids, and fatty acid esters. Specific fatty acids include caproic acid, heptanoic acid, nonanoic acid, octanoic acid, decanoic acid, undecylic acid, lauric acid, stearic acid, nonadecylic acid, and arachidic acid.
Examples of metallic fatty acids include alkali metal salts and alkaline earth metal salts of the above-mentioned fatty acids, and specific examples include calcium stearate, zinc stearate, magnesium stearate, etc. These are known to also function as the neutralizing agents described above.
Examples of fatty acid esters include alcohol esters of the above-mentioned fatty acids and glycerin fatty acid esters. As the glycerin fatty acid esters, glycerin trifatty acid esters are preferred, glycerin fatty acid esters are more preferred, and glycerin tricaprylic acid ester is more preferred.
When two or more slip agents are added, the total amount of the slip agents is the total amount of the slip agents added.

<Other additives>
The rust-preventive film of the present disclosure may contain trace amounts of various plastic compounding agents and additives other than the above-mentioned neutralizing agents, antiblocking agents, and slip agents, for the purpose of improving or modifying, for example, processability, heat resistance, weather resistance, mechanical properties, dimensional stability, antioxidant properties, release properties, flame retardancy, mildew resistance, electrical properties, strength, etc. However, the content is limited to a range that does not reduce the rust-preventive effect of the antioxidant contained in the first layer of the rust-preventive film of the present disclosure.
In the above, examples of common compounding agents that may be included include crosslinking agents, ultraviolet absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, modifying resins, and the like.

<Polyethylene resin>
The polyethylene resin contained in the first layer of the rust-preventive film of the present disclosure is preferably a resin that has an affinity suitable for dispersing the rust inhibitor and has excellent film-forming properties, and more preferably a resin that has heat-sealing properties.

Specific examples of polyethylene resins contained in the first layer of the rust-preventive film of the present disclosure include low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE), with linear low-density polyethylene (LLDPE) being more preferred. One type of polyethylene resin may be used, or two or more types may be mixed together.

(middle class)
The intermediate layer (the layer designated by reference numeral 13 in FIG. 2 ) can be a layer that can impart various mechanical, physical, and chemical functions to the rust-preventive film of the present disclosure, such as support, rigidity, flexibility, pinhole resistance, etc. For example, when a water vapor barrier layer is provided as the intermediate layer, a package produced from the rust-preventive film of the present disclosure can effectively prevent moisture from penetrating into the package.
Furthermore, as described above, by adding a colorant only to the middle layer, even if the second layer comes into contact with the first layer when the rust-preventive film of the present disclosure is wound up, more specifically, even if the outer surface of the second layer comes into contact with the inner surface of the first layer (i.e., the surface of the first layer that comes into contact with the contents as a package), since no colorant is added to the second layer, it is possible to avoid the colorant affecting the rust-preventive properties of the first layer.
The thickness of the intermediate layer can be set appropriately within the range of the thickness of the anti-rust film, but if the purpose is to impart appropriate strength and stiffness to the anti-rust film, it is preferably 5 μm or more and 100 μm or less, and more preferably 10 μm or more and 50 μm or less.

(Second layer)
The second layer of the rust-preventive film of the present disclosure (the layer designated by reference numeral 12 in FIGS. 1 and 2) is a layer containing a polyethylene resin. When the rust-preventive film of the present disclosure is used as a package, the first layer side becomes the inner layer (i.e., inner layer) of the package, and the second layer side becomes the outer layer (i.e., outer layer) of the package. The second layer of the rust-preventive film of the present disclosure may be a single layer or may be composed of multiple layers.
The rust-preventive film of the present disclosure has a second outer layer in addition to a first layer containing a predetermined amount of a predetermined rust inhibitor. This second layer does not contain as much rust inhibitor as the first layer. Therefore, the rust-preventive film of the present disclosure can prevent the rust inhibitor from adhering to other objects on the surface of the outer layer or from scattering outside the package.
Furthermore, by not adding as much rust inhibitor to the second layer as to the first layer, the film formation process can be stabilized. Therefore, the occurrence of poor appearance in the rust-preventive film of the present disclosure can be further prevented. Furthermore, by not adding as much rust inhibitor to the second layer as to the first layer, the amount added to the entire film can be reduced, which is also beneficial in terms of cost.

Specific examples of the polyethylene resin contained in the second layer of the rust-preventive film of the present disclosure include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE).
Among these, low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE) are preferred, and linear low-density polyethylene (LLDPE) is more preferred, because of their processability, sealability, strength, etc. The polyethylene resin may be used alone or in combination of two or more.
In this disclosure, polyethylene with a density of 0.87 g/ ^cm3 or more and 0.91 g/cm3 or ^less is referred to as low-density polyethylene, polyethylene with a density of 0.92 g/ ^cm3 or more and 0.96 g/ ^cm3 or less is referred to as medium-density polyethylene, and polyethylene with a density greater than 0.96 g/ ^cm3 is referred to as high-density polyethylene.

The polyethylenes having different densities and branches as described above 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 a polymerization catalyst, and to carry out the polymerization in one stage or in two or more stages by any of gas phase polymerization, slurry polymerization, solution polymerization, and high pressure ionic polymerization.
The single-site catalyst is a catalyst capable of forming a uniform active species, and is usually prepared by contacting a metallocene transition metal compound or a non-metallocene transition metal compound with an activating co-catalyst. Single-site catalysts are preferred because they have a more uniform active site structure than multi-site catalysts, making it possible to polymerize polymers with high molecular weights and highly uniform structures. Metallocene catalysts are particularly preferred as single-site catalysts. Metallocene catalysts are catalysts containing the following catalytic components: a transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, a co-catalyst, and optionally an organometallic compound and a carrier.

In the above-mentioned transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, the cyclopentadienyl skeleton is a cyclopentadienyl group, a substituted cyclopentadienyl group, or the like. The substituted cyclopentadienyl group has at least one substituent selected from a hydrocarbon group having from 1 to 30 carbon atoms, a silyl group, a silyl-substituted alkyl group, a silyl-substituted aryl group, a cyano group, a cyanoalkyl group, a cyanoaryl group, a halogen group, a haloalkyl group, a halosilyl group, and the like. The substituted cyclopentadienyl group may have two or more substituents, and the substituents may be bonded to each other to form a ring, such as an indenyl ring, a fluorenyl ring, an azulenyl ring, or a hydrogenated product thereof. The rings formed by bonding the substituents to each other may further have substituents.
In the transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, the transition metal can be zirconium, titanium, hafnium, etc., with zirconium and hafnium being particularly preferred. The transition metal compound typically contains two ligands having a cyclopentadienyl skeleton, and the cyclopentadienyl ligands are preferably bonded to each other via a bridging group. Examples of the bridging group include alkylene groups having 1 to 4 carbon atoms, silylene groups, substituted silylene groups such as dialkylsilylene groups and diarylsilylene groups, and substituted germylene groups such as dialkylgermylene groups and diarylgermylene groups. Substituted silylene groups are preferred. The above-mentioned transition metal compounds of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton can be used as a catalyst component, either singly or in combination.

The co-catalyst refers to a catalyst that can effectively use the above-mentioned transition metal compounds of Group IV of the periodic table as a polymerization catalyst, or that can balance the ionic charge in a catalytically activated state. Examples of co-catalysts include benzene-soluble aluminoxanes of organoaluminum oxy compounds and benzene-insoluble organoaluminum oxy compounds, ion-exchangeable layered silicates, boron compounds, ionic compounds consisting of a cation with or without an active hydrogen group and a non-coordinating anion, lanthanoid salts such as lanthanum oxide, tin oxide, and phenoxy compounds containing a fluoro group.

The transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton may be used by being supported on an inorganic or organic support. The support is preferably an inorganic or organic porous oxide, specifically, ion-exchange layered silicate such as montmorillonite, SiO ₂ , Al ₂ O ₃ , MgO, ZrO ₂ , TiO ₂ , B ₂ O ₃ , CaO, ZnO, BaO, ThO ₂ , or a mixture thereof. Furthermore, examples of organometallic compounds that may be used if necessary include organoaluminum compounds, organomagnesium compounds, and organozinc compounds. Of these, organoaluminum compounds are preferred.

In addition, in the present invention, polyethylene includes copolymers of ethylene and other monomers in addition to the above-mentioned high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE). Examples of ethylene copolymers include copolymers of ethylene and an α-olefin having from 3 to 20 carbon atoms. Examples of α-olefins having from 3 to 20 carbon atoms include 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. Furthermore, copolymers with vinyl acetate, acrylic esters, and the like may also be used, provided that the objectives of the present disclosure are not impaired.

The thickness of the second layer of the rust-preventive film of the present disclosure can be set appropriately within the range of the thickness of the rust-preventive film, but is preferably 10 μm or more and 100 μm or less. If the thickness of the second layer is within the above range, there is little risk of it having a significant adverse effect on the heat-sealing properties and film-forming properties of the entire rust-preventive film.

(Method for producing anti-rust film)
A method for producing the rust-preventive film of the present disclosure will be described below. Note that the production method described below is an example and does not limit the present disclosure.
Each layer constituting the rust-preventive film of the present disclosure can be produced by any method such as a T-die extrusion method, an extrusion inflation method, or the like.
The lamination of each layer of the rust-preventive film having a multilayer structure can be carried out by any method such as T-die coextrusion, coextrusion inflation, wet lamination, dry lamination, solventless dry lamination, extrusion lamination, coextrusion lamination, etc. Among the above, the T-die coextrusion and coextrusion inflation are preferred in terms of cost because they can reduce the number of steps compared to lamination methods.

For example, the case where the rust-preventive film of the present disclosure is produced by a coextrusion inflation method will be described. Note that, although the method for producing a rust-preventive film having a three-layer structure of a first layer, an intermediate layer, and a second layer will be described here, a rust-preventive film having a two-layer structure of a first layer and a second layer can also be produced in the same way.
First, resin compositions for forming the first layer, intermediate layer, and second layer are prepared. Then, the first layer, intermediate layer, and second layer are co-extruded and laminated by inflation film formation to produce a three-layer anticorrosive film. An aging treatment may be performed as needed. The resulting anticorrosive film may also be stretched uniaxially or biaxially as needed.

The anticorrosive film can be subjected to secondary processing for the purpose of imparting surface functions such as chemical functions, electrical functions, magnetic functions, mechanical functions, friction/wear/lubrication functions, optical functions, thermal functions, and biocompatibility.
Examples of secondary processing include embossing, painting, adhesive, printing, metallizing (plating, etc.), machining, surface treatment (antistatic treatment, corona discharge treatment, plasma treatment, photochromic treatment, physical vapor deposition, chemical vapor deposition, coating, etc.), etc. The anti-corrosion film can also be subjected to lamination (dry lamination or extrusion lamination), bag making, and other post-processing.

(Rust-proof packaging)
The rust-proof packaging of the present disclosure includes the rust-proof film of the present disclosure. In other words, the rust-proof packaging of the present disclosure is a packaging produced from the rust-proof film of the present disclosure.
There are no particular limitations on the shape of the rust-proof packaging of the present disclosure, and the rust-proof film of the present disclosure can be folded, layered to encase the contents, or heat-sealed to form a variety of shapes, and added value can also be added by printing decorations.

A pouch-shaped anti-rust package can be produced in various shapes by, for example, folding an anti-rust film in half, or by preparing two sheets of anti-rust film, overlapping them with the first layer surfaces facing each other, and heat-sealing the peripheral edges.
For example, rust-proof packages of various shapes can be produced by heat sealing using a heat sealing method such as a side seal type, a two-sided seal type, a three-sided seal type, a four-sided seal type, an envelope seal type, a palm seal type (pillow seal type), a pleated seal type, a flat bottom seal type, a square bottom seal type, or a gusset type.
In the above, examples of the heat sealing method that can be used include bar sealing, rotary roll sealing, belt sealing, impulse sealing, high frequency sealing, and ultrasonic sealing.

In the rust-preventive packaging body of the present disclosure, the first layer of the rust-preventive film of the present disclosure is located on the inner layer side of the rust-preventive packaging body, and the second layer is located on the outer layer side.
By adopting such a positional relationship, the rust-preventive packaging body of the present disclosure can adhere the rust inhibitor contained in the first layer of the rust-preventive film of the present disclosure to the surface of the packaged contents, thereby suppressing the occurrence of rust on the contents. Furthermore, in the rust-preventive film of the present disclosure, since the rust inhibitor is not added to the second layer, which is the outer layer side, it is possible to prevent the rust inhibitor from adhering to other objects on the surface of the outer layer side or from scattering outside the package.
When producing the rust-proof package, the package may be sealed while the air inside the package is being sucked out or while the space inside the package is being replaced with a gas having a low oxygen concentration or low humidity.

The present disclosure will be described in more detail with reference to the following examples and comparative examples, but the present disclosure is not limited to these examples. Details of the raw materials used in the examples and comparative examples are as follows.
In the following examples and comparative examples, when one or more of a neutralizing agent, an antiblocking agent, and a slip agent were added as additives other than antioxidants, the content of these additives (the total content if multiple additives were used) was adjusted to 50 ppm to 100 ppm. Here, the content of the above additives (additives other than antioxidants) was 100 ppm or less (0.01 mass % or less), which is 1/30 or less of the content of the antioxidant added as a rust inhibitor (0.3 mass % or more) and can be approximated to 0. Therefore, in the following examples and comparative examples, they are not included in the parts by mass of each resin composition.

[Antioxidants]
Antioxidant A: A060, a phenolic antioxidant manufactured by Adeka Corporation.
Antioxidant B: SUMILIZER GP, a phenolic and phosphorus-based synthetic antioxidant manufactured by Sumitomo Chemical Co., Ltd.
Antioxidant C: Tokyo Chemical Industry Co., Ltd. amine-based antioxidant, P0197.

[Polyethylene resin]
LDPE1: LDPE manufactured by Japan Polyethylene Co., Ltd., Novatec LC520. Density: 0.923 g/cm ³ , MFR: 3.6 g/10 min.
LLDPE1: Evolue SP2020 LLDPE manufactured by Prime Polymer Co., Ltd. Density: 0.916 g/cm ³ , MFR: 2.0 g/10 min.

<Preparation of Masterbatch>
[Preparation of Masterbatch 1]
Antioxidant A and LDPE 1 were melt-blended in the following ratio to obtain Masterbatch 1 (MB1).
LDPE1 95 parts by mass Antioxidant A 5 parts by mass

[Preparation of Masterbatches 2 to 4]
Masterbatches 2 to 4 (MB2 to MB4) were obtained by melt blending in the same manner as for Masterbatch 1 according to the following formulation.
MB2: LDPE1 95 parts by mass / antioxidant B 5 parts by mass MB3: LDPE1 99 parts by mass / antioxidant B 1 part by mass MB4: LDPE1 89 parts by mass / antioxidant B 11 parts by mass

[Preparation of Masterbatch 5]
Masterbatch 5 (MB5) was obtained by melt blending in the same manner as Masterbatch 1 according to the following formulation.
MB5: LDPE1 95 parts by mass/Antioxidant C 5 parts by mass

[Example 1]
MB1 and LLDPE1 were dry blended in the following proportions to obtain a resin composition for the first layer of the rust-preventive film of Example 1.
The resin composition for the first layer obtained above and LLDPE1 constituting the second layer were formed into a film and laminated at 160°C using a co-extrusion inflation method to obtain the following two-layer rust-proofing film (60 μm thick).
Layer structure: 1st layer / 2nd layer = 30 μm thickness / 30 μm thickness

[Example 2]
MB1 and LLDPE1 were dry-blended in the following proportions to obtain a resin composition for the first layer of the rust-preventive film of Example 2.
MB1 20 parts by mass LLDPE1 80 parts by mass The resin composition for the first layer obtained above and LLDPE1 constituting the second layer were formed into a film and laminated at 160°C using a co-extrusion inflation method to obtain the following two-layer rust-proof film (60 μm thick).
Layer structure: 1st layer / 2nd layer = 30 μm thickness / 30 μm thickness

[Example 3]
MB1 and LLDPE1 were dry blended in the following proportions to obtain a resin composition for the first layer of the rust-preventive film of Example 3.
The resin composition for the first layer obtained above and LLDPE1 constituting the second layer were formed into a film and laminated at 160°C using a co-extrusion inflation method to obtain the following two-layer rust-proofing film (60 μm thick).
Layer structure: 1st layer / 2nd layer = 30 μm thickness / 30 μm thickness

[Example 4]
MB1 and LLDPE1 were dry blended in the following proportions to obtain a resin composition for the first layer of the rust-preventive film of Example 4.
The resin composition for the first layer obtained above, LLDPE1 constituting the intermediate layer, and LLDPE1 constituting the second layer were formed into a film and laminated at 160°C using a co-extrusion inflation method to obtain the following three-layer rust-proofing film (60 μm thick).
Layer configuration: 1st layer/intermediate layer/2nd layer = 15 μm thickness/30 μm thickness/15 μm thickness

[Example 5]
MB1 and LLDPE1 were dry blended in the following proportions to obtain a resin composition for the first layer of the rust-preventive film of Example 5.
The resin composition for the first layer obtained above, LLDPE1 constituting the intermediate layer, and LLDPE1 constituting the second layer were formed into a film and laminated at 160°C using a co-extrusion inflation method to obtain the following three-layer rust-proofing film (60 μm thick).
Layer configuration: 1st layer/intermediate layer/2nd layer = 15 μm thickness/30 μm thickness/15 μm thickness

[Example 6]
MB2 and LLDPE1 were dry blended in the following proportions to obtain a resin composition for the first layer of the rust-preventive film of Example 6.
The resin composition for the first layer obtained above and LLDPE1 constituting the second layer were formed into a film and laminated at 160°C using a co-extrusion inflation method to obtain the following two-layer rust-proofing film (60 μm thick).
Layer structure: 1st layer / 2nd layer = 30 μm thickness / 30 μm thickness

[Example 7]
MB2 and LLDPE1 were dry blended in the following proportions to obtain a resin composition for the first layer of the rust-preventive film of Example 7.
The resin composition for the first layer obtained above and LLDPE1 constituting the second layer were formed into a film and laminated at 160°C using a co-extrusion inflation method to obtain the following two-layer rust-proofing film (60 μm thick).
Layer structure: 1st layer/2nd layer = 30μm thickness/30μm thickness

[Example 8]
MB2 and LLDPE1 were dry blended in the following proportions to obtain a resin composition for the first layer of the rust-preventive film of Example 8.
The resin composition for the first layer obtained above and LLDPE1 constituting the second layer were formed into a film and laminated at 160°C using a co-extrusion inflation method to obtain the following two-layer rust-proofing film (60 μm thick).
Layer structure: 1st layer / 2nd layer = 30 μm thickness / 30 μm thickness

[Example 9]
MB2 and LLDPE1 were dry blended in the following proportions to obtain a resin composition for the first layer of the rust-preventive film of Example 9.
The resin composition for the first layer obtained above, LLDPE1 constituting the intermediate layer, and LLDPE1 constituting the second layer were formed into a film and laminated at 160°C using a co-extrusion inflation method to obtain the following three-layer rust-proofing film (60 μm thick).
Layer configuration: 1st layer/middle layer/2nd layer = 15 μm thickness/30 μm thickness/15 μm thickness

[Example 10]
MB2 and LLDPE1 were dry blended in the following ratio to obtain a resin composition for the first layer of the rust-preventive film of Example 10.
The resin composition for the first layer obtained above, LLDPE1 constituting the intermediate layer, and LLDPE1 constituting the second layer were formed into a film and laminated at 160°C using a co-extrusion inflation method to obtain the following three-layer rust-proofing film (60 μm thick).
Layer configuration: 1st layer/middle layer/2nd layer = 15 μm thickness/30 μm thickness/15 μm thickness

[Example 11]
MB5 and LLDPE1 were dry-blended in the following proportions to obtain a resin composition for the first layer of the rust-preventive film of Example 11.
The resin composition for the first layer obtained above and LLDPE1 constituting the second layer were formed into a film and laminated at 160°C using a co-extrusion inflation method to obtain the following two-layer rust-proofing film (60 μm thick).
Layer structure: 1st layer / 2nd layer = 30 μm thickness / 30 μm thickness

[Example 12]
MB5 and LLDPE1 were dry-blended in the following proportions to obtain a resin composition for the first layer of the rust-preventive film of Example 12.
The resin composition for the first layer obtained above and LLDPE1 constituting the second layer were formed into a film and laminated at 160°C using a co-extrusion inflation method to obtain the following two-layer rust-proofing film (60 μm thick).
Layer structure: 1st layer/2nd layer = 30μm thickness/30μm thickness

[Example 13]
MB5 and LLDPE1 were dry blended in the following ratio to obtain a resin composition for the first layer of the rust-preventive film of Example 13.
The resin composition for the first layer obtained above and LLDPE1 constituting the second layer were formed into a film and laminated at 160°C using a co-extrusion inflation method to obtain the following two-layer rust-proofing film (60 μm thick).
Layer structure: 1st layer / 2nd layer = 30 μm thickness / 30 μm thickness

[Example 14]
MB5 and LLDPE1 were dry blended in the following ratio to obtain a resin composition for the first layer of the rust-preventive film of Example 14.
The resin composition for the first layer obtained above, LLDPE1 constituting the intermediate layer, and LLDPE1 constituting the second layer were formed into a film and laminated at 160°C using a co-extrusion inflation method to obtain the following three-layer rust-proofing film (60 μm thick).
Layer configuration: 1st layer/intermediate layer/2nd layer = 15 μm thickness/30 μm thickness/15 μm thickness

[Example 15]
MB5 and LLDPE1 were dry blended in the following ratio to obtain a resin composition for the first layer of the rust-preventive film of Example 15.
The resin composition for the first layer obtained above, LLDPE1 constituting the intermediate layer, and LLDPE1 constituting the second layer were formed into a film and laminated at 160°C using a co-extrusion inflation method to obtain the following three-layer rust-proofing film (60 μm thick).
Layer configuration: 1st layer/intermediate layer/2nd layer = 15 μm thickness/30 μm thickness/15 μm thickness

[Comparative Example 1]
A two-layer laminated film was produced in the same manner as in Example 1, except that the first layer was formed using 100 parts by mass of LLDPE1 without adding any rust inhibitor.
Layer structure: 1st layer (LLDPE1) / 2nd layer = 30 μm thickness / 30 μm thickness

[Comparative Example 2]
MB3 and LLDPE1 were dry blended in the following proportions to obtain a resin composition for the first layer of Comparative Example 2.
The resin composition for the first layer obtained above and LLDPE1 constituting the second layer were formed into a film and laminated at 160°C using a co-extrusion inflation method to obtain the following two-layer laminate film (thickness: 60 μm).
Layer structure: 1st layer/2nd layer = 30μm thickness/30μm thickness

[Comparative Example 3]
MB4 and LLDPE1 were dry blended in the following proportions to obtain a resin composition for the first layer of Comparative Example 3.
The resin composition for the first layer obtained above and LLDPE1 constituting the second layer were formed into a film and laminated at 160°C using a co-extrusion inflation method to obtain the following two-layer laminate film (thickness: 60 μm).
Layer structure: 1st layer / 2nd layer = 30 μm thickness / 30 μm thickness

[Comparative Example 4]
A three-layer laminated film was produced in the same manner as in Example 4, except that the first layer was formed using 100 parts by mass of LLDPE1 without adding any rust inhibitor.
Layer configuration: 1st layer/intermediate layer/2nd layer = 15 μm thickness/30 μm thickness/15 μm thickness

[Comparative Example 5]
MB3 and LLDPE1 were dry blended in the following proportions to obtain a resin composition for the first layer of Comparative Example 5.
The resin composition for the first layer obtained above, LLDPE1 constituting the intermediate layer, and LLDPE1 constituting the second layer were formed into a film and laminated at 160°C using a co-extrusion inflation method to obtain a laminate film (60 μm thick) having the following three-layer structure.
Layer configuration: 1st layer/intermediate layer/2nd layer = 15 μm thickness/30 μm thickness/15 μm thickness

[Comparative Example 6]
MB4 and LLDPE1 were dry blended in the following proportions to obtain a resin composition for the first layer of Comparative Example 6.
The resin composition for the first layer obtained above, LLDPE1 constituting the intermediate layer, and LLDPE1 constituting the second layer were formed into a film and laminated at 160°C using a co-extrusion inflation method to obtain a laminate film (60 μm thick) having the following three-layer structure.
Layer configuration: 1st layer/intermediate layer/2nd layer = 15 μm thickness/30 μm thickness/15 μm thickness

The following evaluations were performed on each of the films in Examples 1 to 15 and Comparative Examples 1 to 6. The results are shown in Tables 1 to 5.

<Evaluation method>
[Film forming property]
The appearance of each film was visually observed, and the presence or absence of defects was evaluated according to the following evaluation criteria.
◯: The rust-preventive film was free from wrinkles, bumps, peeling, etc.
x: The rust-preventive film had wrinkles, bumps, peeling, etc.

[Heat sealability]
Each film was cut into a 100 mm x 100 mm piece, and the first layers were placed face to face and overlapped. Using a heat seal tester (TP-701-A manufactured by Tester Sangyo Co., Ltd.), a 1 cm x 10 cm area was heat-sealed so that the edges were bifurcated without being heat-sealed, and the pieces were further cut into 15 mm wide strips to prepare test pieces for measuring heat seal strength.
Each bifurcated end of this test piece was attached to a tensile tester, and the heat-sealed portion was pulled to peel off, and the heat-seal strength (N/15 mm width) was measured, and the test piece was judged to be pass or fail according to the pass/fail criteria below.
(Heat sealing conditions)
Temperature: 160℃
Pressure: 1 kgf/ ^cm2
Time: 1 second (tensile strength test conditions)
Test speed: 300 mm/min Load range: 50 N
(Pass/Fail criteria)
○: 30N/15mm or more, passed.
×: Less than 30N/15mm, unacceptable.

[Rust prevention (appearance)]
Each film was cut into 100 mm x 100 mm pieces, and the first layers were placed facing each other and overlapped. After that, three sides except for one side were sealed using an impulse sealer to produce a 100 mm x 100 mm pouch with one side open.
Next, the following metal pieces were placed in the pouch as contents, and the open side was sealed while the air inside the pouch was sucked out. The pouch was then stored in a thermostatic chamber adjusted to 60°C and 90% RH for 14 days, and the change in appearance was evaluated according to the following evaluation criteria.
(metal piece)
Steel plate: Cold-rolled steel plate (SPCC), 50mm x 50mm x 1mm, degreased.
Copper plate: Tough pitch copper plate (C1100P-1/4H), 50mm x 50mm x 1mm, degreased.
(Evaluation criteria)
◎: No rust or discoloration, or only rust spots and slight discoloration.
◯: Rust or poor appearance occurred in less than 10% of the area of the test piece.
△: Rust or poor appearance occurred over 10% or more but less than 50% of the area of the test piece.
×: Rust or poor appearance occurred on 50% or more of the area of the test piece.

(※1): Some appearance defects due to the coloring of the amine-based antioxidant.

(※2): There was a lot of bleeding of the antioxidant and the appearance of the white part was poor.

(※3): There was a lot of bleeding of the antioxidant and the appearance of the white part was poor.

1, 2 Anti-rust film 11 First layer 12 Second layer 13 Intermediate layer

Claims (5)

a first layer and a second layer laminated on one surface of the first layer;
the first layer contains a rust inhibitor and a linear low-density polyethylene resin,
the second layer contains a linear low-density polyethylene resin,
A rust-preventive film for packaging steel materials, wherein the first layer contains, as the rust inhibitor, an antioxidant having a phenolic antioxidant moiety and a phosphorus-based antioxidant moiety in the molecule in an amount ranging from 0.3 mass % to 2.0 mass %. The anti-corrosion film according to claim 1, further comprising an intermediate layer between the first layer and the second layer. The anticorrosive film according to claim 1 or 2, wherein the antioxidant contains 2-tert-butyl-6-methyl-4-{3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl}phenol. The anti-corrosion film according to any one of claims 1 to 3, wherein the first layer contains at least one of a neutralizing agent, an antiblocking agent, and a slip agent as an additive, and the content of the additive is 50 ppm or more and 100 ppm or less. An anti-rust packaging body having the anti-rust film described in any one of claims 1 to 4.