A vapor phase anti-rust cold stretch protective film and its preparation method and application

Abstract

The present invention provides a vapor phase rust-proof cold stretch protective film, which comprises an inner layer, a middle layer and an outer layer from the inside out; the outer layer, by weight, comprises 70-80 parts of metallocene linear polyethylene, 20-30 parts of linear polyethylene and 1-4 parts of processing aid masterbatch as raw materials; the middle layer, by weight, comprises 5-30 parts of ethylene propylene copolymer and 70-95 parts of metallocene linear polyethylene as raw materials; the inner layer, by weight, comprises 60-80 parts of metallocene linear polyethylene, 20-30 parts of linear polyethylene, 2-10 parts of vapor phase rust-proof masterbatch and 1-4 parts of processing aid masterbatch as raw materials. The protective film of the present invention has excellent tensile strength and tear resistance, small permanent deformation, good flexure and resilience, and the cold stretch protective film produced using the material has excellent clamping force and weather resistance, high packaging efficiency during use, is not easily damaged, and can better improve production efficiency; when used as a protective film in the field of ferrous metal products, it has an excellent and long-lasting rust-proof effect.

Description

Technical Field

[0001] The present invention relates to the technical field of packaging films, and in particular to a vapor phase rust-proof cold-stretching protective film, a preparation method thereof, and an application thereof. Background Art

[0002] Once rust forms on mechanical equipment and parts made of metal, it will affect their normal operation. Effectively preventing metal corrosion has become a critical factor in the transportation and storage of various metal-related products. Currently, the most commonly used industrial method for rust prevention is to coat the metal surface with rust-proof oil. However, this method loses its effectiveness due to oxidation, and removing the protective layer is time-consuming and labor-intensive, making it unhygienic and unsafe. Desiccant rust prevention offers low cost, simple operation, safety, environmental protection, and easy removal of protective packaging, but its effectiveness is short-lived and significantly affected by ambient temperature. As an emerging technology, vapor phase anti-rust packaging is gaining increasing attention for its simplicity, practicality, safety, and effectiveness.

[0003] Chinese patent CN204509463U discloses a VCI bag comprising a main body comprising an inner layer, arranged from the inside out, a middle layer made of a VCI VCI film, and an outer wear-resistant layer. The inner layer is provided with a plurality of through-holes. The advantage is that the multi-layer film provided within the bag prevents workpieces from puncturing the bag, thereby improving the quality of the cylinder bag. However, the bag disclosed in this patent exhibits poor resilience and tensile strength during use. Chinese patent CN109291577A discloses a VCI high-tensile heat-shrinkable film. This film is stable at room temperature, exhibits no resilience, has a certain degree of anti-counterfeiting functionality, is simple and compact, and forms a protective vapor layer when packaging metal workpieces, thereby preventing them from rusting. However, the film disclosed in this patent requires reheating to shrink and has poor resilience.

[0004] Existing vapor phase anti-rust protective films (bags) are limited by the size of the protective films (bags) during use, and cannot package products that exceed the existing size of the vapor phase anti-rust protective films (bags). The protective films lack tensile properties and resilience properties. In addition, during use, due to the sharp angles of the workpiece, the vapor phase anti-rust film (bag) will be punctured by the workpiece with sharp angles, causing the vapor phase anti-rust film (bag) to lose its anti-rust function.

[0005] Therefore, developing a protective film that has high tensile strength, high resilience, small permanent deformation, and long-lasting and excellent anti-rust effect at room temperature is still an urgent problem to be solved. Summary of the Invention

[0006] In response to the above problems, the present invention provides a vapor phase rust-proof cold-stretched protective film, which has excellent tensile strength and tear resistance, small permanent deformation, good flexure and resilience. The cold-stretched protective film produced using this material has excellent clamping force and weather resistance, high packaging efficiency during use, is not easy to be damaged, and can better improve production efficiency. When used as a protective film in the field of ferrous metal products such as steel, hardware, auto parts, and military products, it has an excellent and long-lasting anti-rust effect.

[0007] On the one hand, the present invention provides a vapor phase anti-rust cold stretching protective film, which comprises an inner layer, a middle layer and an outer layer from the inside to the outside;

[0008] The outer layer comprises, by weight, 70-80 parts of metallocene linear polyethylene, 20-30 parts of linear polyethylene and 1-4 parts of processing aid masterbatch;

[0009] The middle layer comprises, by weight, 5-30 parts of ethylene propylene copolymer and 70-95 parts of metallocene linear polyethylene;

[0010] The inner layer comprises, by weight, 60-80 parts of metallocene linear polyethylene, 20-30 parts of linear polyethylene, 2-10 parts of vapor phase anti-rust masterbatch and 1-4 parts of processing aid masterbatch.

[0011] Preferably, the metallocene linear polyethylene has a melt index of 0.10 g / 10 min to 1 g / 10 min at 190°C / 2.16 kg and a density of 0.5 g / cm 3 -1.5g / cm 3 .

[0012] More preferably, the metallocene linear polyethylene has a melt index of 0.50 g / 10 min at 190°C / 2.16 kg and a density of 0.912 g / cm 3 .

[0013] More preferably, the metallocene linear polyethylene is Exxon mLLDPE 7052.

[0014] More preferably, the linear polyethylene is a low-density linear polyethylene.

[0015] Preferably, the low-density linear polyethylene has a melt index of 0.5-1.5 g / 10 min at 190°C / 2.16 kg and a density of 0.5 g / cm 3 -1.5g / cm 3 .

[0016] Further preferably, the low-density linear polyethylene has a melt index of 1.0 g / 10 min at 190°C / 2.16 kg and a density of 0.916 g / cm3 .

[0017] More preferably, the low-density linear polyethylene is a mixture of one or more of Dow Chemical 5401G and Dow Chemical 5400G.

[0018] More preferably, the low-density linear polyethylene is Dow Chemical 5400G.

[0019] In order to effectively improve the opening and heat sealing properties of the protective film, the present invention uses metallocene linear polyethylene and materials as the main raw materials, and the protective film obtained has excellent heat sealing properties, impact strength, tear strength and resistance to environmental stress cracking. The inventors found that pure metallocene linear polyethylene has poor fluidity and is not easy to process and shape. However, when linear polyethylene is mixed with metallocene linear polyethylene, especially when the melt index of metallocene linear polyethylene at 190℃ / 2.16kg is 0.10g / 10min-1g / 10min and the density is 0.5g / cm 3 -1.5g / cm 3 The linear polyethylene is a low-density linear polyethylene, and the melt index of the low-density linear polyethylene at 190°C / 2.16kg is 0.5-1.5g / 10min, and the density is 0.5g / cm 3 -1.5g / cm 3 When the material is prepared, it has excellent mechanical properties, opening properties, heat sealing properties and processability. The inventors analyzed that this may be because the molecules of metallocene linear polyethylene are linear in structure, with very few long chain branches, a narrow molecular weight distribution, and no small molecules melt and flow first, so its melt viscosity is high, its fluidity is poor, and its sensitivity to shear rate is poor, resulting in its poor processability. The low-density linear polyethylene used has a linear structure containing long chain branches, and the two are mixed to form a continuous phase, which effectively enhances its processability. However, the inventors found that if the amount of linear polyethylene used is too much, or its melt index is too high, it will lead to deterioration of the mechanical properties of the protective film, such as impact strength and tear strength.

[0020] Preferably, in the middle layer, the mass ratio of ethylene propylene copolymer to metallocene linear polyethylene is 1:8-10.

[0021] Preferably, the ethylene propylene copolymer has a melt index of 1 g / 10 min to 2 g / 10 min at 190° C. / 2.16 kg.

[0022] Further preferably, the melt index of the ethylene propylene copolymer at 190°C / 2.16kg is 1.4 g / 10 min.

[0023] More preferably, the mass ratio of ethylene in the ethylene-propylene copolymer is 10%-20%.

[0024] More preferably, the mass ratio of ethylene in the ethylene-propylene copolymer is 16%.

[0025] More preferably, the ethylene propylene copolymer is Vistamaxx 6012FL.

[0026] In order to ensure the tensile properties and elasticity of the protective film material and enable it to have excellent rebound performance, the middle layer of the protective film of the present invention is made of metallocene linear polyethylene and ethylene propylene copolymer. In particular, when the mass ratio of metallocene linear polyethylene and ethylene propylene copolymer used is 1:8-10, and the melt index of ethylene propylene copolymer at 190℃ / 2.16kg is 1g / 10min-2g / 10min, the obtained film material also has excellent tensile resilience and puncture resistance. The inventors found that pure metallocene linear polyethylene has excellent tensile strength and puncture resistance, but its elasticity and processability are poor. By using ethylene propylene copolymer in combination, its tensile strength and puncture resistance can be effectively maintained, while its elasticity and processability are greatly improved. The inventors analyzed that this may be due to the presence of a specific amount of ethylene propylene copolymer as a dispersed phase, in which the low content of ethylene destroys the regularity of the material, reduces its crystallinity, and becomes a high-toughness elastomeric material with greatly enhanced elongation at break. However, if the content of ethylene propylene copolymer is too high, forming larger dispersed particles, it will destroy the crystalline structure of the metallocene linear polyethylene, resulting in a sharp drop in its tensile strength.

[0027] The inventors unexpectedly discovered that using a metallocene linear polyethylene and ethylene-propylene copolymer in a mass ratio of 1:8-10 further enhances the stability and heat-sealing properties of the protective film. The inventors analyzed that this may be due to the ethylene-propylene copolymer's ability to enhance the interfacial adhesion between the different mixed phases, resulting in a stronger, more stable, and more balanced blend's mechanical properties. This effectively strengthens the bond between the different layers, resulting in improved stability and mechanical properties, and further enhances the toughness of the blend. The significant toughening effect significantly increases the protective film's elongation at break, tensile strength, and resilience.

[0028] Preferably, in the inner layer, the vapor phase rust-proof masterbatch accounts for 1%-8% of the total mass of the inner layer.

[0029] Further preferably, in the inner layer, the vapor phase rust-proof masterbatch accounts for 5% of the total mass of the inner layer.

[0030] Preferably, in the inner layer, the vapor phase rust-proof masterbatch is WD-40.

[0031] The inventors discovered that the best rust prevention effect is achieved when the VCI masterbatch accounts for 1%-8% of the total mass of the inner layer. The inventors analyzed that this may be because under these conditions, the masterbatch can be evenly dispersed in the system, forming a stable phase interface with other components, and having strong interfacial adhesion, which enables the slow release of the gaseous rust-inhibiting ingredients, achieving a long-lasting and stable rust prevention effect. However, if the masterbatch content is too low, the total amount of VCI gas released is insufficient to meet the rust prevention function under extreme conditions, and an effective rust prevention effect cannot be achieved. However, if too much is used, the rust prevention effect is not significantly enhanced and the cost is too high.

[0032] Preferably, the processing aid is Aksu oleamide.

[0033] Preferably, the mass ratio of the inner layer, the middle layer and the outer layer is 1:1-3:1.

[0034] In the present invention, especially when the mass ratio of the inner layer, the middle layer and the outer layer is 1:1-3:1, the protective film material obtained has the best comprehensive performance. The inventor analyzed that it may be due to the cooperation of the outer layer and the inner layer, which makes the material have good opening, heat sealing and rust resistance, while the middle layer provides good resilience and puncture resistance. Through the joint action of the three layers of materials, a strong interfacial bonding force is generated between each other, with excellent bonding strength and stability. The protective film obtained also has excellent resilience, puncture resistance, tensile strength and opening performance, heat sealing, and when used as a protective film in the fields of ferrous metal products such as steel, hardware, auto parts, and military products, it has excellent and long-lasting rust prevention effect.

[0035] The second aspect of the present invention provides a method for preparing a vapor phase anti-rust cold stretch protective film, comprising the following steps: respectively conveying the raw materials for the inner layer, middle layer and outer layer to three extruders, plasticizing them in the three extruders and then conveying them to the same three-layer film blowing die head, and sequentially hot-bonding the inner layer, middle layer and outer layer together to obtain the vapor phase anti-rust cold stretch protective film.

[0036] The third aspect of the present invention provides an application of a vapor phase rust-proof cold-stretched protective film, which is used as a protective film in the field of ferrous metal products such as steel, hardware, and auto parts.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The vapor phase anti-rust cold-stretch protective film of the present invention has excellent tensile strength and tear resistance, small permanent deformation, good flexure and resilience due to the combined effect of specific components in each layer. The cold-stretch protective film produced using this material has excellent clamping force and weather resistance, high packaging efficiency during use, is not easy to be damaged, and can better improve production efficiency. At the same time, the ethylene propylene copolymer has good compatibility with the polyethylene material. The material can be recycled repeatedly after use and is environmentally friendly.

[0039] The vapor phase rust-inhibiting cold-stretch protective film of the present invention incorporates elastic materials into each layer of the film, allowing the film to be stretched within room temperature. The desired product is then placed within the film tube, where it is wrapped by the film's inherent resilience. Heat-sealing the product as needed also provides waterproofing, resulting in an excellent protective film product. When used as a protective film for ferrous metal products such as steel, hardware, auto parts, and military products, the inner layer emits VCI rust-inhibiting gas, which continuously and slowly vaporizes within a confined space and condenses on exposed metal surfaces, including hard-to-reach areas such as holes and crevices, forming a stable gas protective film. This protects metal workpieces from rust, providing excellent, long-lasting rust prevention. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is the round iron rod of Sample 1 after the anti-rust effect test of Example 1 of the present invention. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be noted that the following embodiments are for further explanation of the present invention, rather than for limitation thereof.

[0042] Example

[0043] Example 1

[0044] This embodiment provides a vapor phase anti-rust cold-stretching protective film, which includes an inner layer, a middle layer and an outer layer from the inside to the outside;

[0045] The outer layer, by weight, comprises 76.5 parts of metallocene linear polyethylene, 22 parts of linear polyethylene and 1.5 parts of processing aid masterbatch as raw materials; the middle layer, by weight, comprises 10 parts of ethylene propylene copolymer and 90 parts of metallocene linear polyethylene as raw materials; the inner layer, by weight, comprises 71.5 parts of metallocene linear polyethylene, 22 parts of linear polyethylene, 5 parts of vapor phase anti-rust masterbatch and 1.5 parts of processing aid masterbatch as raw materials.

[0046] The mass ratio of the inner layer, the middle layer and the outer layer is 1:2:1.

[0047] The metallocene linear polyethylene is Exxon mLLDPE 7052, purchased from ExxonMobil; the linear polyethylene is Dow Chemical 5400G, purchased from Dow Chemical; the ethylene propylene copolymer is Vistamaxx 6012FL, purchased from ExxonMobil; the vapor phase anti-rust masterbatch is WD-40, purchased from Guangzhou Duobao Anti-Rust Trading Co., Ltd.; the processing aid masterbatch is Aksu oleamide, purchased from Dongguan Caihe Masterbatch Co., Ltd., model QC-066.

[0048] On the other hand, this embodiment provides a method for preparing a vapor phase rust-inhibiting cold-stretching protective film, and the specific steps are as follows:

[0049] The raw materials for the inner layer, middle layer, and outer layer were fed into three extruders, where they were mixed and plasticized in screws at 170°C before being fed into a single three-layer blown film die. The inner layer, middle layer, and outer layer were then thermally bonded together at 185°C to produce the vapor phase rust-inhibiting cold-stretch protective film.

[0050] Example 2

[0051] This embodiment provides a vapor phase anti-rust cold-stretching protective film, which includes an inner layer, a middle layer and an outer layer from the inside to the outside;

[0052] The outer layer, by weight, comprises 76.5 parts of metallocene linear polyethylene, 22 parts of linear polyethylene and 1.5 parts of processing aid masterbatch as raw materials; the middle layer, by weight, comprises 10 parts of ethylene propylene copolymer and 90 parts of metallocene linear polyethylene as raw materials; the inner layer, by weight, comprises 71.5 parts of metallocene linear polyethylene, 26 parts of linear polyethylene, 1 part of vapor phase anti-rust masterbatch and 1.5 parts of processing aid masterbatch as raw materials.

[0053] The mass ratio of the inner layer, the middle layer and the outer layer is 1:2:1.

[0054] The specific sources of raw materials in this example are the same as those in Example 1.

[0055] On the other hand, this embodiment provides a method for preparing a vapor phase rust-proof cold-stretching protective film, and its specific implementation method is the same as that of Example 1.

[0056] Example 3

[0057] This embodiment provides a vapor phase anti-rust cold-stretching protective film, which includes an inner layer, a middle layer and an outer layer from the inside to the outside;

[0058] The outer layer, by weight, comprises 76.5 parts of metallocene linear polyethylene, 22 parts of linear polyethylene and 1.5 parts of processing aid masterbatch as raw materials; the middle layer, by weight, comprises 10 parts of ethylene propylene copolymer and 90 parts of metallocene linear polyethylene as raw materials; the inner layer, by weight, comprises 68.5 parts of metallocene linear polyethylene, 22 parts of linear polyethylene, 8 parts of vapor phase anti-rust masterbatch and 1.5 parts of processing aid masterbatch as raw materials.

[0059] The mass ratio of the inner layer, the middle layer and the outer layer is 1:2:1.

[0060] The specific sources of raw materials in this example are the same as those in Example 1.

[0061] On the other hand, this embodiment provides a method for preparing a vapor phase rust-proof cold-stretching protective film, and its specific implementation method is the same as that of Example 1.

[0062] Example 4

[0063] This embodiment provides a vapor phase anti-rust cold-stretching protective film, and the specific implementation method is the same as that of Example 1. The difference from Example 1 is that the mass ratio of the inner layer, the middle layer and the outer layer is 1:3:1.

[0064] Comparative Example 1

[0065] This embodiment provides a vapor phase anti-rust cold-stretching protective film, and the specific implementation method is the same as that of Example 1. The difference from Example 1 is that the mass ratio of the inner layer, the middle layer and the outer layer is 1:4:1.

[0066] Comparative Example 2

[0067] This embodiment provides a vapor phase anti-rust cold stretch protective film, and the specific implementation method is the same as that of Example 1. The difference from Example 1 is that in the middle layer, the metallocene linear polyethylene accounts for 110 parts.

[0068] Comparative Example 3

[0069] This embodiment provides a vapor phase anti-rust cold stretch protective film, and the specific implementation method is the same as that of Example 1. The difference from Example 1 is that there is no vapor phase anti-rust masterbatch in the inner layer.

[0070] Comparative Example 4

[0071] This embodiment provides a vapor phase rust-proof cold-stretching protective film. The specific implementation method is the same as that of Example 1. The difference from Example 1 is that the melt index of the metallocene linear polyethylene at 190°C / 2.16kg is 2g / 10min.

[0072] Performance Testing

[0073] 1. Tensile strength and nominal strain at break: Tested in accordance with GB / T 1040.3-2006 "Plastics - Determination of tensile properties, Part 3: Test conditions for film and sheeting".

[0074] 2. Right-angle tear strength: Tested according to QB / T 1130-1991 "Test method for right-angle tear properties of plastics".

[0075] 3. Impact damage quality: Tested in accordance with GB / T 9639.1-2008 "Plastic film and sheeting - Test method for impact resistance - Free-fall dart method - Part 1: Ladder method".

[0076] 4. Heat seal strength: Tested according to QB / T 2358-1998 "Test method for heat seal strength of plastic film packaging bags".

[0077] The protective films of Examples 1-4 and Comparative Examples 1-3 were subjected to the above performance tests. The test results are shown in Table 1 below:

[0078] Table 1

[0079]

[0080] 5. Rust Prevention Test: Tested according to German test method TL 8135-002, "Corrosion Resistance Test of VCI Auxiliary Packaging Materials." Four sets of samples were set up. Three sets consisted of seven 150mm long, 25mm wide film samples placed in a flask with a cleaned round iron rod. A control set consisted of a cleaned round iron rod placed in the flask without the anti-rust strips. All four sets of samples were placed in a 20°C oven for 20 hours. After 20 hours, 10ml of a mixture (water:glycerol = 2:1) was added and kept at 20°C for 2 hours. The temperature was then raised to 40°C and kept there for 2 hours. The rubber stoppers were removed and the round iron rods were observed for rust.

[0081] The protective films of Example 1 and Comparative Example 3 were tested for their rust resistance. The test results are shown in Table 2 below:

[0082] Example 1 Rust condition of iron rods Comparative Example 3 Rust condition of iron rods Sample 1 No rust spots Sample 1 There are rust spots Sample 2 No rust spots Sample 2 There are rust spots Sample 3 No rust spots Sample 3 There are rust spots Comparison sample There are rust spots Comparison sample There are rust spots

Claims

1. A vapor phase anti-rust cold stretch protective film, characterized in that: The protective film comprises an inner layer, a middle layer and an outer layer from the inside to the outside; the raw materials of the outer layer include 70-80 parts of metallocene linear polyethylene, 20-30 parts of linear polyethylene and 1-4 parts of processing aid masterbatch, calculated by weight; the raw materials of the middle layer include 5-30 parts of ethylene propylene copolymer and 70-95 parts of metallocene linear polyethylene, calculated by weight; the raw materials of the inner layer include 60-80 parts of metallocene linear polyethylene, 20-30 parts of linear polyethylene, 2-10 parts of vapor phase anti-rust masterbatch and 1-4 parts of processing aid masterbatch, calculated by weight; the mass ratio of the inner layer, the middle layer and the outer layer is 1:1-3:1; in the middle layer, the mass ratio of ethylene propylene copolymer and metallocene linear polyethylene is 1:8-10; the melt index of the ethylene propylene copolymer at 190°C / 2.16kg is 1g / 10min-2g / 10min.

2. The vapor phase anti-rust cold stretch protective film according to claim 1, characterized in that: The metallocene linear polyethylene has a melt index of 0.10 g / 10 min to 1 g / 10 min at 190°C / 2.16 kg and a density of 0.5 g / cm 3 -1.5g / cm 3 .

3. The vapor phase anti-rust cold stretch protective film according to claim 1, characterized in that: The linear polyethylene is a low-density linear polyethylene.

4. The vapor phase anti-rust cold stretch protective film according to claim 3, characterized in that: The low-density linear polyethylene has a melt index of 0.5-1.5 g / 10 min at 190°C / 2.16 kg and a density of 0.5 g / cm 3 -1.5g / cm 3 .

5. The vapor phase anti-rust cold stretch protective film according to claim 1, characterized in that: The ethylene-propylene copolymer has a melt index of 1 g / 10 min to 2 g / 10 min at 190° C. / 2.16 kg.

6. The vapor phase anti-rust cold stretch protective film according to claim 1, characterized in that: The mass ratio of ethylene in the ethylene-propylene copolymer is 10%-20%.

7. The vapor phase anti-rust cold stretch protective film according to claim 1, characterized in that: In the inner layer, the vapor phase rust-proof masterbatch accounts for 1%-8% of the total mass of the inner layer.

8. The method for preparing a vapor phase anti-rust cold-stretching protective film according to any one of claims 1 to 7, characterized in that: The steps include: The raw materials for the inner layer, middle layer and outer layer are respectively conveyed to three extruders, plasticized in the three extruders and then conveyed to the same three-layer film blowing die head, and the inner layer, middle layer and outer layer are hot-bonded together in turn to obtain the vapor phase rust-proof cold-stretch protective film.

9. An application of the vapor phase anti-rust cold stretching protective film according to any one of claims 1 to 7, characterized in that: Used as protective film in the field of ferrous metal products.

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