Rust-proof tray manufacturing method

Abstract

This invention relates to a method for manufacturing a rust-proof pallet. Specifically, the invention includes the following steps: extruding a substrate sheet; hot-laminating the extruded substrate sheet with a rust-proof film; and vacuum-forming the composite sheet to obtain a rust-proof pallet. The rust-proof pallet manufactured by the method of this invention possesses both excellent mechanical strength and long-term rust prevention.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a rust-proof pallet. Background Technology

[0002] In recent years, with the development of battery technology and the widespread use of various electronic devices, the requirements for battery performance and safety have been continuously increasing. Especially for rechargeable batteries like lithium-ion batteries, their ease of use has been constantly improving, making corrosion issues that may occur during transportation and storage a significant concern. When batteries are exposed to high temperatures and humidity during transportation, the battery's metal casing or components may corrode, which not only reduces battery performance but may also lead to safety problems.

[0003] To address these issues, the industry has developed tray systems that utilize vaporized rust inhibitors. This technology works by vaporizing the rust inhibitor at room temperature, forming a rust-preventive film on the battery surface, thereby inhibiting corrosion.

[0004] However, the aforementioned rust inhibitors will continue to vaporize during long-term use, leading to a decrease in effectiveness. If the packaging is not completely sealed, or if the rust inhibitor is lost over time, the thickness and durability of the anti-rust film formed on the battery surface will decrease, and the anti-corrosion effect will weaken accordingly. Furthermore, the aforementioned vaporizable rust inhibitors may interact with certain battery materials, potentially producing unexpected side effects. Finally, in the process of applying the aforementioned vaporizable rust inhibitors to the tray substrate, if the coating thickness cannot be guaranteed to be uniform, or if the coating is too thick, the rust inhibitor will not be able to vaporize smoothly. This will limit the effectiveness of the rust prevention and may also negatively impact the mechanical strength of the tray itself.

[0005] To address these issues, it is necessary to develop a sealed packaging technology that can maintain the effectiveness of vaporized rust inhibitors over a long period, a rust inhibitor selection scheme that is stably compatible with battery materials, and a rust-proof tray that combines excellent mechanical strength and long-lasting rust prevention performance through optimized coating processes. Summary of the Invention

[0006] [Technical Problem to be Solved] The present invention aims to provide a method for manufacturing a rust-proof pallet. The pallet manufactured by this method has excellent rust prevention effect during long-term use, and also performs well in terms of mechanical properties.

[0007] [Technical Solution to the Problem] This invention provides a method for manufacturing a rust-proof tray, comprising the following steps: S1) extruding a substrate sheet; S2) bonding the extruded substrate sheet with a rust-proof film by hot lamination or adhesive; S3) vacuum forming the bonded sheet.

[0008] According to one embodiment of the present invention, the above-mentioned substrate sheet may be obtained by extrusion of a mixture of 100 parts by weight of polypropylene resin, 10 to 100 parts by weight of high-density polyethylene resin, 5 to 20 parts by weight of low-density polyethylene resin and 10 to 100 parts by weight of inorganic particles.

[0009] According to one embodiment of the present invention, the melt index (ASTM D 1238, 190°C, 2.16 kg) of the above-mentioned high-density polyethylene resin is 0.1 to 0.5 g / 10 min, and the melt index (ASTM D 1238, 190°C, 2.16 kg) of the above-mentioned low-density polyethylene resin is 40 to 60 g / 10 min.

[0010] According to one embodiment of the present invention, the substrate sheet may contain 25 to 40 parts by weight of low-density polyethylene resin relative to 100 parts by weight of high-density polyethylene resin, and the melt index of the high-density polyethylene resin and the melt index of the low-density polyethylene resin satisfy the condition of Formula 1 below.

[0011] Formula 1

[0012] 0.5≤(HDPE MI / LDPE MI)×100≤1.0.

[0013] HDPE MI refers to the melt index of high-density polyethylene resin measured under the melt index conditions (ASTM D 1238, 190℃, 2.16kg); LDPE MI refers to the melt index of low-density polyethylene resin measured under the melt index conditions (ASTM D 1238, 190℃, 2.16kg).

[0014] According to one embodiment of the present invention, the melt index (ASTM D 1238, 190°C, 2.16 kg) of the above-mentioned polypropylene resin can be 0.1 to 0.5 g / 10 min.

[0015] According to one embodiment of the present invention, the inorganic particles may include any one or more of the following: mica, zirconium oxide, bentonite, titanium dioxide, barium sulfate, calcium carbonate, magnesium carbonate, zinc carbonate, zinc oxide, magnesium oxide, calcium phosphate, silicon dioxide, aluminum oxide, talc, and kaolin.

[0016] According to one embodiment of the present invention, the thickness of the substrate sheet is 500 to 1000 μm, and the thickness of the anti-rust film is 20 to 120 μm.

[0017] According to one embodiment of the present invention, the thickness of the substrate sheet and the thickness of the anti-rust film can satisfy the conditions of Formula 2.

[0018] Formula 2

[0019] 0.05≤Rust-proof film thickness / substrate sheet thickness≤0.15.

[0020] According to one embodiment of the present invention, the above-mentioned substrate sheet may be a sheet produced by extrusion at 100 to 300°C.

[0021] According to one embodiment of the present invention, the above-mentioned anti-rust film may be prepared by extruding a mixture of 100 parts by weight of high-density polyethylene resin, 50 to 200 parts by weight of low-density polyethylene resin and 1 to 20 parts by weight of vaporizable rust inhibitor.

[0022] According to one embodiment of the present invention, the melt index (ASTM D 1238, 190°C, 2.16 kg) of the above-mentioned high-density polyethylene resin is 0.1 to 0.5 g / 10 min, and the melt index (ASTM D 1238, 190°C, 2.16 kg) of the above-mentioned low-density polyethylene resin is 40 to 60 g / 10 min.

[0023] According to one embodiment of the present invention, the above-mentioned anti-rust film may contain 80 to 100 parts by weight of low-density polyethylene resin and 5 to 10 parts by weight of vaporizable rust inhibitor relative to 100 parts by weight of high-density polyethylene resin, and the melt index of the high-density polyethylene resin and the melt index of the low-density polyethylene resin satisfy the conditions of Formula 1 below.

[0024] Formula 1

[0025] 0.5≤HDPE MI / LDPE MI×100≤1.0.

[0026] HDPE MI refers to the melt index of high-density polyethylene resin measured under the melt index conditions (ASTM D 1238, 190℃, 2.16kg); LDPE MI refers to the melt index of low-density polyethylene resin measured under the melt index conditions (ASTM D 1238, 190℃, 2.16kg).

[0027] According to one embodiment of the present invention, the above-mentioned anti-rust film may be a sheet material extruded at 100-300°C.

[0028] According to one embodiment of the present invention, the above-mentioned vaporizable rust inhibitor may contain any one or more of the following: nitrite metal compounds, amine nitrites, organic amines, and carboxylates.

[0029] According to one embodiment of the present invention, a rust-proof pallet can be provided by the above-described rust-proof pallet manufacturing method.

[0030] The rust-proof tray of the present invention is made by hot laminating a rust-proof film containing a vaporizing rust inhibitor with a substrate sheet, thus possessing both excellent mechanical properties and processability, while also exhibiting outstanding rust-proof effect.

[0031] Furthermore, the rust-proof tray of the present invention has excellent thermal bonding strength between its substrate sheet and rust-proof film, and is not prone to delamination, thus maintaining the rust-proof effect for a long time.

[0032] The present invention will now be described in more detail with reference to the embodiments shown in the accompanying drawings. However, the following embodiments are merely examples illustrating the present invention, and the present invention is not limited thereto and can be implemented in various forms.

[0033] Furthermore, unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of effectively describing particular embodiments only and is not intended to limit the invention.

[0034] Furthermore, the singular form used in the specification and claims may also include the plural form, unless the context clearly indicates otherwise.

[0035] Furthermore, when a part "contains" a constituent element, unless otherwise stated, it does not exclude other constituent elements, but rather means that other constituent elements may be further contained.

[0036] The traditional method for making rust-proof pallets involves impregnating the finished pallet with a solution containing rust-preventing components, or placing a rust-preventing film / impregnation solution between base material sheets to create a three-layer rust-preventing sheet before forming the pallet.

[0037] The method of immersing the pallet in rust-preventive solution not only has poor rust prevention effect, but also has a short duration of rust prevention.

[0038] Furthermore, the method of sandwiching an anti-rust film between substrate sheets or impregnating them with an anti-rust solution to create a three-layer composite sheet not only results in extremely poor anti-rust performance but also leads to deterioration of mechanical properties due to low adhesion between the sheets. Attempts have been made to improve anti-rust performance by creating micropores in the substrate sheets, but this not only fails to provide lasting anti-rust protection but also causes a decrease in mechanical properties due to the opening of the pores.

[0039] Therefore, the present invention provides a rust-proof tray manufacturing method comprising the following steps: extruding a substrate sheet; bonding the extruded substrate sheet to a rust-proof film by hot lamination or adhesive; and vacuum forming the bonded sheet, thereby providing a rust-proof tray that can maintain its anti-corrosion performance for a long time while also possessing high mechanical strength and impact resistance.

[0040] The manufacturing method of the above-mentioned rust-proof pallet will be described in detail below.

[0041] The above-mentioned hot lamination process improves the adhesion between the substrate sheet and the anti-rust film by heating to physically bond and melt the two films, thereby achieving excellent mechanical strength and anti-rust effect.

[0042] The upper limit of the surface temperature of the substrate sheet and the anti-rust film can be above 50℃, above 70℃, above 90℃, above 100℃, above 110℃, above 130℃, above 150℃, above 170℃, above 190℃, above 200℃, above 230℃, and above 250℃ respectively; the upper limit can be below 400℃, below 350℃, below 300℃, and below 280℃ respectively, but is not limited to these.

[0043] Heating to the aforementioned temperature allows the film surface to reach a softenable and molten state. In particular, the heat lamination temperature can be adjusted according to the Vicat softening temperature or melting point of the material used.

[0044] The heated films can be tightly bonded together for thermal lamination. To maximize the adhesion between the film surfaces, an exemplary pressure of 1 to 10 MPa can be applied, but this is not limited to. The above pressure conditions can be adjusted according to the characteristics of the film material.

[0045] In this invention, an adhesive can also be used instead of heat lamination to bond the substrate sheet to the anti-rust film. In this case, the adhesive can form a highly adhesive layer between the two films, providing uniform anti-rust performance even in heat-sensitive film materials.

[0046] A 5-20 μm thick adhesive can be uniformly coated onto the surface of the substrate sheet or rust-proof film to form a high-adhesion layer. Then, the adhesive-coated films are laminated or pressurized, and cured at room temperature (25℃) or low temperature (below 50℃) to stabilize the bond between the two films.

[0047] The adhesives mentioned above can be thermosetting adhesives, thermocuring adhesives, etc. For example, any one or more of ethylene-vinyl acetate (EVA) adhesives, polyurethane (PU) adhesives, acrylic adhesives, silicone adhesives, epoxy adhesives and nitrile adhesives can be selected, but are not limited to these.

[0048] According to one embodiment of the present invention, the substrate sheet may be obtained by extrusion of a mixture of 100 parts by weight of polypropylene resin, 10-100 parts by weight of high-density polyethylene resin, 5-20 parts by weight of low-density polyethylene resin, and 10-100 parts by weight of inorganic particles; preferably, it may contain 100 parts by weight of polypropylene resin, 10-50 parts by weight of high-density polyethylene resin, 5-15 parts by weight of low-density polyethylene resin, and 10-50 parts by weight of inorganic particles; more preferably, it may contain 100 parts by weight of polypropylene resin, 20-30 parts by weight of high-density polyethylene resin, 5-10 parts by weight of low-density polyethylene resin, and 20-40 parts by weight of inorganic particles, but is not limited thereto.

[0049] The above mixing ratio can provide the strength and thermal stability of the substrate sheet, while enhancing its rust-proof properties.

[0050] According to one embodiment of the present invention, the melt index (ASTM D 1238, 190°C, 2.16 kg) of the high-density polyethylene resin is 0.1 to 0.5 g / 10 min, and the melt index (ASTM D 1238, 190°C, 2.16 kg) of the low-density polyethylene resin is 40 to 60 g / 10 min; preferably, the melt index of the high-density polyethylene resin is 0.2 to 0.4 g / 10 min, and the melt index of the low-density polyethylene resin is 50 to 60 g / 10 min; more preferably, the melt index of the high-density polyethylene resin is 0.2 to 0.4 g / 10 min, and the melt index of the low-density polyethylene resin is 53 to 57 g / 10 min, but not limited thereto.

[0051] By incorporating polypropylene and polyethylene resins with melt flow indexes within the aforementioned range into the substrate sheet or rust-resistant film, the processability of the sheet can be optimized, while mechanical strength and impact resistance can be improved.

[0052] According to one embodiment of the present invention, the above-mentioned substrate sheet may contain 25 to 40 parts by weight of low-density polyethylene resin relative to 100 parts by weight of high-density polyethylene resin.

[0053] The melt index of the above-mentioned high-density polyethylene resin and the melt index of low-density polyethylene resin satisfy the conditions of Equation 1 below.

[0054] Formula 1

[0055] 0.5≤(HDPE MI / LDPE MI)×100≤1.0.

[0056] HDPE MI refers to the melt index of high-density polyethylene resin measured under the melt index conditions (ASTM D 1238, 190℃, 2.16kg); LDPE MI refers to the melt index of low-density polyethylene resin measured under the melt index conditions (ASTM D 1238, 190℃, 2.16kg).

[0057] When the substrate sheet contains high-density polyethylene resin and low-density polyethylene resin that meet the above conditions, it has excellent vacuum forming and processability, while also possessing excellent mechanical properties and durability.

[0058] According to one embodiment of the present invention, the melt index (ASTM D 1238, 190°C, 2.16 kg) of the polypropylene resin can be 0.1 to 1.0 g / 10 min; preferably, it is 0.2 to 0.8 g / 10 min; more preferably, it is 0.4 to 0.6 g / 10 min, but is not limited thereto.

[0059] When the melt flow index of polypropylene resin meets the above range, its compatibility with high-density polyethylene and low-density polyethylene resins can be improved.

[0060] According to one embodiment of the present invention, the inorganic particles may comprise any one or more of mica, zirconium oxide, bentonite, titanium dioxide, barium sulfate, calcium carbonate, magnesium carbonate, zinc carbonate, zinc oxide, magnesium oxide, calcium phosphate, silicon dioxide, aluminum oxide, talc, and kaolin; preferably, any one or more of talc, kaolin, calcium carbonate, magnesium carbonate, and magnesium oxide; more preferably, any one or more of talc, kaolin, and calcium carbonate, but not limited thereto.

[0061] According to one embodiment of the present invention, the average particle size of the inorganic particles can be 1 to 100 μm; preferably, it is 5 to 60 μm, but not limited thereto.

[0062] By including the aforementioned inorganic particles in the substrate sheet, the mechanical properties of the substrate sheet can be enhanced, the rust prevention effect can be improved, and the physical properties can be maintained stably at high temperatures.

[0063] According to one embodiment of the present invention, the thickness of the substrate sheet can be 500–1000 μm; preferably, it is 600–900 μm. The thickness of the anti-rust film can be 20–120 μm; preferably, it is 60–100 μm, but is not limited thereto.

[0064] Within the aforementioned thickness range, hot lamination of the substrate sheet and the anti-rust film into an anti-rust pallet ensures the durability of the anti-rust pallet while achieving optimal anti-rust performance through the appropriate combination of the anti-rust film and the substrate sheet.

[0065] According to one embodiment of the present invention, the thickness of the substrate sheet and the thickness of the anti-rust film satisfy the condition of Formula 2.

[0066] Formula 2

[0067] 0.05≤Rust-proof film thickness / substrate sheet thickness≤0.15.

[0068] When the thickness of the substrate sheet and the rust-proof film of the rust-proof tray meets the requirements of Formula 2 above, the physical uniformity of the sheet composite can be guaranteed, achieving appropriate strength and flexibility during hot lamination. It also possesses excellent rust-proof effect, processability, and mechanical properties.

[0069] According to one embodiment of the present invention, the above-mentioned substrate sheet may be a sheet extruded at 100 to 300°C; preferably, it may be extruded at 150 to 250°C, but is not limited thereto.

[0070] Extruding substrate sheets within the above temperature range can optimize polymer flowability, strengthen the internal structural bonding of the sheet, and produce sheets with minimal deformation at high temperatures.

[0071] According to one embodiment of the present invention, the aforementioned rust-preventive film may be obtained by extruding a mixture of 100 parts by weight of high-density polyethylene resin, 50-200 parts by weight of low-density polyethylene resin, and 1-20 parts by weight of a vaporizable rust inhibitor; preferably, it may contain 100 parts by weight of high-density polyethylene resin, 80-150 parts by weight of low-density polyethylene resin, and 2-15 parts by weight of a vaporizable rust inhibitor; more preferably, it may contain 100 parts by weight of high-density polyethylene resin, 80-100 parts by weight of low-density polyethylene resin, and 5-10 parts by weight of a vaporizable rust inhibitor; even more preferably, it may contain 100 parts by weight of high-density polyethylene resin, 90-100 parts by weight of low-density polyethylene resin, and 5-10 parts by weight of a vaporizable rust inhibitor, but is not limited thereto.

[0072] By including a vaporizable rust inhibitor within the above-mentioned content range in the rust-proof film, the corrosion resistance of the rust-proof tray can be improved, and the rust-proof components are evenly distributed within the rust-proof film, maximizing the rust-proof effect.

[0073] According to one embodiment of the present invention, the melt index (ASTM D 1238, 190°C, 2.16 kg) of the high-density polyethylene resin is 0.1 to 0.5 g / 10 min, and the melt index (ASTM D 1238, 190°C, 2.16 kg) of the low-density polyethylene resin is 40 to 60 g / 10 min; preferably, the melt index of the high-density polyethylene resin is 0.2 to 0.4 g / 10 min, and the melt index of the low-density polyethylene resin is 50 to 60 g / 10 min; more preferably, the melt index of the high-density polyethylene resin is 0.2 to 0.4 g / 10 min, and the melt index of the low-density polyethylene resin is 53 to 57 g / 10 min, but not limited thereto.

[0074] According to one embodiment of the present invention, the above-mentioned anti-rust film may contain 100 parts by weight of high-density polyethylene resin, 80 to 100 parts by weight of low-density polyethylene resin, and 5 to 10 parts by weight of vaporizable rust inhibitor.

[0075] The melt index of the above-mentioned high-density polyethylene resin and the melt index of low-density polyethylene resin satisfy the conditions of Equation 1 below.

[0076] Formula 1

[0077] 0.5≤(HDPE MI / LDPE MI)×100≤1.0.

[0078] HDPE MI refers to the melt index of high-density polyethylene resin measured under the melt index conditions (ASTM D 1238, 190℃, 2.16kg); LDPE MI refers to the melt index of low-density polyethylene resin measured under the melt index conditions (ASTM D 1238, 190℃, 2.16kg).

[0079] When the anti-rust film is manufactured according to the above conditions and then laminated with a substrate sheet to form an anti-rust tray, it can achieve the best anti-rust effect.

[0080] According to one embodiment of the present invention, the above-mentioned anti-rust film can be a sheet material extruded at 100 to 300°C; preferably, it can be extruded at 150 to 250°C, but is not limited thereto.

[0081] According to one embodiment of the present invention, the above-mentioned vaporizable rust inhibitor may be any one or more selected from nitrite metal compounds, amine nitrites, organic amines, and carboxylates; preferably, it may contain nitrite metal compounds.

[0082] Specifically, nitrite metal compounds can be any one or more of sodium nitrite, potassium nitrite, and calcium nitrite.

[0083] The aforementioned amine nitrites may be any one or more selected from dimethylamine nitrite, trimethylamine nitrite, and ethylamine nitrite.

[0084] The aforementioned organic amines may include aniline.

[0085] The aforementioned carboxylates may be any one or more selected from sodium acetate, calcium formate, and potassium oxalate.

[0086] The substrate sheet and the rust-proof film are heat-pressed to form a rust-proof tray, which has excellent rust prevention effect, while also exhibiting excellent mechanical properties and processability.

[0087] Rust-proof pallets manufactured using this method have excellent rust-proof effects, especially compared to single-layer sheets that directly mix vaporizable rust inhibitors into ordinary resin, where the rust-proof effect is more outstanding.

[0088] Therefore, using the rust-proof tray of the present invention to package secondary battery cells can significantly reduce the risk of cell corrosion, and has excellent processability, high mechanical strength, and can flexibly adapt to the shape of the battery cells.

[0089] The rust-proof pallet manufactured using this invention has both excellent mechanical properties and rust-proof effect.

[0090] The rust-proof tray of the present invention can achieve a rust-proof effect level of Level 2 (good) or above, preferably Level 3 (excellent), according to the DIN EN TL8135-0043 standard.

[0091] Furthermore, the rust-proof pallet of the present invention has a lower limit of tensile strength measured according to ASTM D638 standard of 15 MPa or more, 16 MPa or more, 17 MPa or more, 18 MPa or more, 19 MPa or more, or 20 MPa or more; and an upper limit of 30 MPa or less, 29 MPa or less, 28 MPa or less, 27 MPa or less, 26 MPa or less, 25 MPa or less, 24 MPa or less, 23 MPa or less, 22 MPa or less, or 21 MPa or less; preferably 14 to 25 MPa, more preferably 16 to 25 MPa, even more preferably 19 to 23 MPa, and most preferably 20 to 21 MPa, but is not limited thereto.

[0092] Furthermore, the rust-proof pallet of the present invention has an elongation / strain of more than 300%, more than 340%, more than 380%, more than 400%, more than 410%, more than 420%, or more than 430% as measured according to ASTM D638 standard; and an upper limit of less than 600%, less than 550%, less than 500%, less than 480%, or less than 450%; preferably 340~550%, more preferably 410~500%, and most preferably 430~450%, but is not limited thereto.

[0093] Furthermore, the rust-proof pallet of the present invention has an impact strength of at least 250 J / m, at least 260 J / m, at least 280 J / m, at least 290 J / m, at least 300 J / m, at least 340 J / m, or at least 360 J / m, as measured according to ASTM D1709 standard (23°C). The upper limit of the impact strength can be less than 500 J / m, less than 480 J / m, less than 450 J / m, less than 430 J / m, less than 400 J / m, less than 380 J / m, or less than 370 J / m. Preferably, it is 250~500 J / m, more preferably 290~400 J / m, more preferably 340~380 J / m, and most preferably 360~370 J / m, but it is not limited thereto.

[0094] Furthermore, the manufactured rust-proof pallets can be stacked and stored or transported in general-purpose boxes made of paper materials, or they can be stacked and stored or transported in general-purpose boxes made of plastic materials, but the present invention is not limited thereto.

[0095] The present invention will be described in more detail below with reference to embodiments and comparative examples. However, the embodiments and comparative examples described below are merely illustrative examples of the present invention, and the present invention is not limited thereto.

[0096] [Physical properties].

[0097] Tensile strength and elongation (strain) were determined according to ASTM D638, and impact strength was determined according to ASTM D1709 (23°C).

[0098] [Rust prevention test].

[0099] Rust prevention testing was conducted according to DIN EN TL8135-0043 standard. Specifically, a rust-resistant tray sample with a height of 2.5 cm × dimensions of 10 × 10 cm² was placed in a sealed container along with 1 L of air. The sealed container was then placed in an incubator at 24°C for 20 hours. Afterward, 10 ml of potassium chloride aqueous solution was added to the sealed container, and the incubator temperature was raised to 40°C, and the container was incubated for another 2 hours. Subsequently, the sample was removed from the container for rust prevention testing, and the results are shown in Table 1. Figure 1 Rust-proof pallets manufactured using rust-resistant materials. Figure 2 Pallets are manufactured using standard materials. Figure 3 The effect of using a rust-proof tray to hold battery casings.

[0100]

Example 1

[0101] Based on 100 parts by weight of polypropylene resin (B-310, Lotte Chemical) with a melt index (ASTM D1238, 190℃, 2.16kg) of 0.5g / 10min, 25 parts by weight of high-density polyethylene resin (BL6200, Lotte Chemical) with a melt index (ASTM D1238, 190℃, 2.16kg) of 0.35g / 10min, 8.4 parts by weight of low-density polyethylene resin (XJ800, Lotte Chemical) with a melt index (ASTM D1238, 190℃, 2.16kg) of 55g / 10min, and 33.3 parts by weight of talc powder with an average particle size of 20μm, the first base material resin particles were prepared by mixing them in a twin-screw mixer and then heating and melting them at 200℃ through a heated extruder.

[0102] Based on 100 parts by weight of high-density polyethylene resin with a melt index (ASTM D1238, 190℃, 2.16kg) of 0.35g / 10min, 94 parts by weight of low-density polyethylene resin with a melt index (ASTM D1238, 190℃, 2.16kg) of 55g / 10min and 6 parts by weight of sodium nitrite were mixed using a twin-screw mixer and then melted at 200℃ through a heated extruder to prepare the second rust-preventive resin granules.

[0103] The first substrate resin particles were fed into a blower extruder and extruded at approximately 180°C to obtain a substrate sheet with a thickness of 800 μm. Subsequently, the second rust-preventive resin particles were also fed into a blower extruder and extruded at approximately 180°C to obtain a rust-preventive film with a thickness of 80 μm. The substrate sheet and the rust-preventive film were then laminated together and hot-laminated at approximately 150°C to obtain a composite sheet, which was then vacuum-formed into a rust-preventive tray.

[0104] The rust prevention grades of the aforementioned rust-proof trays are shown in Table 1; meanwhile, the physical properties of the composite sheet before vacuum forming were measured, and the results are shown in Table 2.

[0105]

Example 2

[0106] Except for replacing the high-density polyethylene resin with a melt index (ASTM D1238, 190°C, 2.16 kg) of 0.6 g / 10 min in the substrate sheet and anti-rust film of Example 1, the other steps are the same as in Example 1.

[0107]

Example 3

[0108] Except that in the substrate sheet and rust-proof film of Example 1, the high-density polyethylene resin was replaced with high-density polyethylene resin with a melt index (ASTM D1238, 190°C, 2.16 kg) of 0.2 g / 10 min, and the low-density polyethylene resin was replaced with low-density polyethylene resin with a melt index (ASTM D1238, 190°C, 2.16 kg) of 55 g / 10 min, the remaining steps were the same as in Example 1.

[0109]

Example 4

[0110] Except for the fact that in Example 1, the thickness of the substrate sheet was extruded to 700 μm and the thickness of the anti-rust film was extruded to 180 μm, and then the two were hot-laminated into a composite sheet and vacuum-formed into an anti-rust tray, the remaining steps were the same as in Example 1.

[0111] [Comparative Example 1]

[0112] Based on 100 parts by weight of polypropylene resin with a melt index (ASTM D1238, 190℃, 2.16kg) of 0.5g / 10min, 5 parts by weight of NaNO3 were mixed in, extruded into polypropylene sheets with a thickness of 900μm, and then vacuum-formed into rust-proof trays.

[0113] [Comparative Example 2]

[0114] The above-mentioned rust-preventive solution was coated onto the substrate sheet prepared in Example 1 and dried to form a coating film with a thickness of 15 μm. The rust-preventive film was then vacuum-formed into a rust-preventive tray.

[0115] [Comparative Example 3]

[0116] Polypropylene resin sheets with a melt index (ASTM D 1238) of 1 g / 10 min are directly extruded and vacuum-formed into trays without a rust-proof film.

[0117] [Comparative Example 4]

[0118] The substrate sheet / rust-proof film / substrate sheet from Example 1 were sequentially heat-laminated in three layers, and then vacuum-formed to create a rust-proof tray. The thickness of each layer was: 600 μm for the rust-proof film and 140 μm for the substrate sheet.

[0119] Table 1 Example 1 No rust Level 3 (Excellent) Example 2 No rust Level 3 (Excellent) Example 3 Minor pitting and discoloration Level 2 (Good) Example 4 No rust Level 3 (Excellent) Comparative Example 1 Extensive pitting and discoloration Level 1 (Normal) Comparative Example 2 Extensive pitting and discoloration Level 1 (Normal) Comparative Example 3 Extensive pitting corrosion and complete discoloration and blackening of the surface Level 0 (No rust prevention) Comparative Example 4 Extensive pitting and discoloration Level 1 (Normal)

[0120] Table 2 Example 1 20.81 434.5 366.2 Example 2 16.65 347.2 293.96 Example 3 19.77 412.3 347.89 Example 4 18.21 379.7 320.43 Comparative Example 1 15.61 325 274.65 Comparative Example 2 15.49 322.9 272.45 Comparative Example 3 15.82 329.84 278.31

[0121] The samples in Examples 1 to 3 all exhibited excellent mechanical properties and rust prevention effects. In contrast, Comparative Example 1 not only had inferior mechanical properties compared to the Examples, but also had poor rust prevention effects. Furthermore, Comparative Example 2 had poor mechanical properties and very poor rust prevention effects; subsequent experiments revealed that its rust prevention effect decreased sharply within a short period of time. Finally, Comparative Example 3's poor rust prevention effect actually led to a decrease in mechanical properties.

[0122] As described above, although the present invention has been described with reference to specific embodiments and accompanying drawings, these are merely examples provided to facilitate a more comprehensive understanding of the invention, and the invention is not limited thereto. Those skilled in the art to which this invention pertains can make various modifications and variations within the scope of the technical concept of the invention.

[0123] Therefore, the scope of protection of this invention includes not only the embodiments described, but also all modifications and variations thereof that are equivalent to or the same as the claims of this invention.

Claims

1. A method for manufacturing a rust-proof pallet, comprising the following steps: S1) The step of extruding the substrate sheet; S2) The step of bonding the extruded substrate sheet with the anti-rust film by hot lamination or adhesive; S3) The step of vacuum forming the composite sheet after bonding.

2. The method for manufacturing a rust-proof pallet according to claim 1, wherein, The substrate sheet is prepared by extrusion of a mixture of 100 parts by weight of polypropylene resin, 10-100 parts by weight of high-density polyethylene resin, 5-20 parts by weight of low-density polyethylene resin, and 10-100 parts by weight of inorganic particles.

3. The method for manufacturing a rust-proof pallet according to claim 2, wherein, The melt index (ASTM D 1238, 190℃, 2.16kg) of the high-density polyethylene resin is 0.1 to 0.5 g / 10min, and the melt index (ASTM D 1238, 190℃, 2.16kg) of the low-density polyethylene resin is 40 to 60 g / 10min.

4. The method for manufacturing a rust-proof pallet according to claim 3, wherein, The substrate sheet comprises 25-40 parts by weight of low-density polyethylene resin relative to 100 parts by weight of high-density polyethylene resin; and the melt index of the high-density polyethylene resin and the melt index of the low-density polyethylene resin satisfy the condition of Formula 1 below: 0.5≤(HDPE MI / LDPE MI)×100≤1.

0. Wherein, HDPE MI refers to the melt index of high-density polyethylene resin measured under melt index conditions (ASTM D 1238, 190℃, 2.16kg); LDPE MI refers to the melt index of low-density polyethylene resin measured under melt index conditions (ASTM D 1238, 190℃, 2.16kg).

5. The method for manufacturing a rust-proof pallet according to claim 2, wherein, The melt index (ASTM D 1238, 190℃, 2.16kg) of the polypropylene resin is 0.1 to 0.5 g / 10min.

6. The method for manufacturing a rust-proof pallet according to claim 2, wherein, The inorganic particles are selected from any one or a mixture of two or more of the following: mica, zirconium oxide, bentonite, titanium dioxide, barium sulfate, calcium carbonate, magnesium carbonate, zinc carbonate, zinc oxide, magnesium oxide, calcium phosphate, silicon dioxide, aluminum oxide, talc, and kaolin.

7. The method for manufacturing a rust-proof pallet according to claim 2, wherein, The thickness of the substrate sheet is 500–1000 μm, and the thickness of the anti-rust film is 20–120 μm.

8. The method for manufacturing a rust-proof pallet according to claim 7, wherein, The thickness of the substrate sheet and the rust-proof film satisfy the condition of Equation 2 (thickness ratio).

9. The method for manufacturing a rust-proof pallet according to claim 2, wherein, The substrate sheet is a sheet produced by extrusion at 100–300°C.

10. The method for manufacturing a rust-proof pallet according to claim 1, wherein, The rust-proof film is prepared by extruding a mixture of 100 parts by weight of high-density polyethylene resin, 50-200 parts by weight of low-density polyethylene resin, and 1-20 parts by weight of vaporizable rust inhibitor.

11. The method for manufacturing a rust-proof pallet according to claim 10, wherein, The melt index (ASTM D 1238, 190℃, 2.16kg) of the high-density polyethylene resin is 0.1 to 0.5 g / 10min, and the melt index (ASTM D 1238, 190℃, 2.16kg) of the low-density polyethylene resin is 40 to 60 g / 10min.

12. The method for manufacturing a rust-proof pallet according to claim 11, wherein, The rust-preventive film, relative to 100 parts by weight of high-density polyethylene resin, comprises 80-100 parts by weight of low-density polyethylene resin and 5-10 parts by weight of vaporizable rust inhibitor; and the melt flow index of the high-density polyethylene resin and the melt flow index of the low-density polyethylene resin satisfy the following condition (Formula 1): 0.5 ≤ (HDPE MI / LDPE MI) × 100 ≤ 1.

0. Wherein, HDPE MI refers to the melt flow index of high-density polyethylene resin measured under melt flow index (ASTM D 1238, 190℃, 2.16kg) conditions; LDPE MI refers to the melt flow index of low-density polyethylene resin measured under melt flow index (ASTM D 1238, 190℃, 2.16kg) conditions.

13. The method for manufacturing a rust-proof pallet according to claim 10, wherein, The rust-proof film is a sheet material produced by extrusion at 100-300°C.

14. The method for manufacturing a rust-proof pallet according to claim 10, wherein, The vaporizable rust inhibitor is a mixture of one or more selected from nitrite metal compounds, amine nitrites, organic amines, and carboxylates.

15. A rust-proof pallet, manufactured by the rust-proof pallet manufacturing method according to any one of claims 1 to 14.

Images