Polyethylene film for shipping packaging and method for preparing the same
By combining a three-layer structure with a specific ratio of polyethylene film, the problem of preparing thin polyethylene film with good mechanical properties for shipping packaging was solved, achieving stable molding with a thickness of less than 20μm and excellent mechanical properties.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHUHAI ZHENGTAI NEW MATERIAL TECH CO LTD
- Filing Date
- 2026-03-04
- Publication Date
- 2026-05-15
AI Technical Summary
Existing technologies make it difficult to produce thin polyethylene films with good mechanical properties for shipping packaging, especially polyethylene films with a thickness of less than 20 μm.
The polyethylene film adopts a three-layer structure, in which the middle layer is composed of a first low-density polyethylene and linear low-density polyethylene in a specific ratio, and the outer and inner layers are composed of POE elastomer, second low-density polyethylene, composite metallocene low-density polyethylene and opening agents and other additives in a specific ratio. Through the composite with a specific melt index, combined with additives such as silane-modified spherical silica, the dispersibility and anti-blocking effect are improved.
Stable molding of polyethylene films with a thickness of less than 20μm was achieved, reducing film bubble vibration and sagging problems, improving mechanical properties and anti-adhesion effect, and ensuring stable processing and good performance of the film.
Smart Images
Figure CN121756698B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of advanced inorganic non-metallic materials, and in particular to a polyethylene film for shipping packaging and its preparation method. Background Technology
[0002] Shipping packaging polyethylene film, also known as industrial stretch wrap film or freight film, is a polyethylene film specifically designed for bundling, securing, and protecting palletized goods. It is typically required to have good tensile strength, tear resistance, and impact resistance.
[0003] Currently, stretch wrap films in related technologies are typically three-layer or multi-layer polyethylene films made from a blend of metallocene linear low-density polyethylene and low-density polyethylene. Furthermore, the thickness of these polyethylene films is usually above 20 μm, making it difficult to produce polyethylene films with a thickness below 20 μm while maintaining good mechanical properties. Therefore, how to provide a polyethylene film with both thinness and good mechanical properties is one of the urgent problems to be solved in the development of stretch wrap films. Summary of the Invention
[0004] In order to provide a thin polyethylene film with good mechanical properties, this application provides a polyethylene film for shipping packaging and a method for preparing the same.
[0005] Firstly, the polyethylene film for shipping packaging provided in this application adopts the following technical solution:
[0006] A polyethylene film for shipping packaging includes an outer layer, a middle layer, and an inner layer, wherein the thickness ratio of the outer layer, the middle layer, and the inner layer is (3-4):(2-4):(3-4).
[0007] The middle layer is a first polyethylene material, which is composed of 20-40 wt% first low-density polyethylene and the balance of linear low-density polyethylene.
[0008] The outer and inner layers are made of a second polyethylene material, which is composed of 3-5 wt% POE elastomer, 0.8-1.2 wt% opening agent, 0.5-1 wt% slip agent, 0.1-1 wt% other processing aids, 0-5 wt% color masterbatch, 10-20 wt% second low-density polyethylene, and the balance being composite metallocene low-density polyethylene.
[0009] Wherein, the melt index of the linear low-density polyethylene is 6-8 g / 10 min; the melt index of the first low-density polyethylene is 6-8 g / 10 min; and the melt index of the second low-density polyethylene is 1.8-2.5 g / 10 min.
[0010] The melt index of the POE elastomer is 1-1.5 g / 10 min;
[0011] The composite metallocene low-density polyethylene includes metallocene linear low-density polyethylene with a melt index of 0.75-0.85 g / 10 min, metallocene linear low-density polyethylene with a melt index of 1.2-1.8 g / 10 min, and metallocene linear low-density polyethylene with a melt index of 3.2-3.8 g / 10 min.
[0012] The above melt index test conditions are 190℃ and 2.16kg.
[0013] In this application, the polyethylene film comprises an outer layer, a middle layer, and an inner layer. The middle layer is made of a first low-density polyethylene and a linear low-density polyethylene with a specific ratio and melt index, which can reduce costs while working in conjunction with the outer and inner layers to achieve stable molding of thin polyethylene films. The outer and inner layers are prepared by a specific ratio of POE elastomer, a second low-density polyethylene, a composite metallocene low-density polyethylene, and additives such as opening agents. Through the combined use of the composite metallocene low-density polyethylene with a specific melt index, POE elastomer, second low-density polyethylene, and the middle layer material, problems such as film bubble vibration and sagging are reduced, and the blow-up ratio can reach 3:1, enabling stable processing of polyethylene films with a thickness of less than 20 μm while maintaining good mechanical properties.
[0014] In some specific embodiments, the weight ratio of the metallocene linear low-density polyethylene with a melt index of 0.75-0.85 g / 10 min, the metallocene linear low-density polyethylene with a melt index of 1.2-1.8 g / 10 min, and the metallocene linear low-density polyethylene with a melt index of 3.2-3.8 g / 10 min is (2-4):(3-5):3.
[0015] In this application, the weight ratio of metallocene linear low-density polyethylene with a melt index of 0.75-0.85 g / 10 min, metallocene linear low-density polyethylene with a melt index of 1.2-1.8 g / 10 min, and metallocene linear low-density polyethylene with a melt index of 3.2-3.8 g / 10 min is further preferred to be (2-4):(3-5):3. By combining the three metallocene linear low-density polyethylenes with specific melt indices, the mechanical properties of the polyethylene film are further improved.
[0016] In some specific embodiments, the opening agent is silane-modified spherical silica.
[0017] Traditional spherical silica has hydroxyl groups on its surface, which makes it highly hydrophilic and has poor dispersibility in other raw materials. In this application, the preferred opening agent is silane-modified spherical silica with hydrophobic properties, which is beneficial to improving the dispersion effect.
[0018] In some specific embodiments, the particle size range of the silane-modified spherical silica is 1-2 μm.
[0019] In this application, the particle size range of silane-modified spherical silica is further preferred to be 1-2 μm, which is beneficial to reduce the adhesion of polyethylene film and improve the anti-adhesion effect.
[0020] In some specific embodiments, the slip agent is at least one of erucamide and oleamide.
[0021] In some specific embodiments, the other processing aids include one or more of light stabilizers, antioxidants, and EPDM rubber.
[0022] In some specific embodiments, the light stabilizer has a weight percentage of 0.3-0.5%, and the light stabilizer is one or more of hindered amine light stabilizers and ultraviolet absorbers.
[0023] In some specific embodiments, hindered amine light stabilizers include, but are not limited to, light stabilizer 770, light stabilizer 944, light stabilizer 622, and light stabilizer 3346.
[0024] In some specific embodiments, the ultraviolet absorbers include, but are not limited to, UV-0 ultraviolet absorbers, UV-9 ultraviolet absorbers, UV-531 ultraviolet absorbers, UV-P ultraviolet absorbers, UV-234 ultraviolet absorbers, UV-326 ultraviolet absorbers, and UV-327 ultraviolet absorbers.
[0025] In some specific embodiments, the antioxidant has a weight percentage of 0.3-0.5%, wherein the antioxidant includes hindered phenolic primary antioxidants and phosphite secondary antioxidants, and the weight ratio of the hindered phenolic primary antioxidants to the phosphite secondary antioxidants is (3-4):1.
[0026] In some specific embodiments, hindered phenolic primary antioxidants include, but are not limited to, antioxidant 1010 and antioxidant 1076.
[0027] In some specific implementations, phosphite co-antioxidants include, but are not limited to, antioxidant 168.
[0028] In some specific implementations, the weight percentage of EPDM rubber is 0.3-0.5%. EPDM rubber has extremely excellent ozone resistance, UV resistance and weather aging resistance, and good low-temperature flexibility. By reasonably controlling the amount of EPDM rubber, the aging resistance and low-temperature flexibility of polyethylene film can be improved without affecting the stability of the film bubble.
[0029] Secondly, the method for preparing a polyethylene film for shipping packaging provided in this application adopts the following technical solution:
[0030] A method for preparing a polyethylene film for shipping packaging includes the following steps:
[0031] The first polyethylene material is fed into the middle extruder of a three-layer co-extrusion blown film machine for melting, and the second polyethylene material is fed into the outer and inner extruders of the three-layer co-extrusion blown film machine for melting. Then, the three melted and uniformly plasticized melts are compounded and extruded to form a tubular preform.
[0032] The tubular blank is blown into a film using an upward blowing method, then cooled and shaped, flattened and wound up to obtain a polyethylene film.
[0033] In some specific embodiments, the temperature parameters of the middle extruder, outer extruder, and inner extruder are set as follows: Zone 1: 185-205℃, Zone 2: 185-205℃, Zone 3: 190-210℃, Zone 4: 195-215℃, Zone 5: 195-215℃.
[0034] In this application, the middle extruder, outer extruder, and inner extruder are set with specific temperature parameters, which can ensure that the polyethylene material is fully melted and uniformly plasticized during the extrusion process, which is conducive to forming a tubular preform with stable quality.
[0035] In summary, this application includes at least the following beneficial technical effects:
[0036] (1) In this application, the polyethylene film includes an outer layer, a middle layer and an inner layer. The middle layer is made of a first low-density polyethylene and a linear low-density polyethylene with a specific ratio and melt index. It can reduce costs while working together with the outer and inner layers to achieve stable molding of thin polyethylene films. The outer and inner layers are prepared by a specific ratio of POE elastomer, a second low-density polyethylene, a composite metallocene low-density polyethylene and additives such as opening agents. Through the combined use of the composite metallocene low-density polyethylene with a specific melt index, POE elastomer, second low-density polyethylene and middle layer materials, problems such as film bubble vibration and sagging are reduced, and the blow-up ratio can reach 3:1. It can stably process polyethylene films with a thickness of less than 20 μm, while taking into account good mechanical properties.
[0037] (2) In this application, the weight ratio of metallocene linear low-density polyethylene with a melt index of 0.75-0.85 g / 10 min, metallocene linear low-density polyethylene with a melt index of 1.2-1.8 g / 10 min and metallocene linear low-density polyethylene with a melt index of 3.2-3.8 g / 10 min is (2-4): (3-5): 3. By combining the three metallocene linear low-density polyethylenes with specific melt indices, the mechanical properties of the polyethylene film are further improved.
[0038] (3) In this application, the particle size range of silane-modified spherical silica is further preferred to be 1-2 μm, which is beneficial to reduce the adhesion of polyethylene film and improve the anti-adhesion effect. Attached Figure Description
[0039] Figure 1 This is a schematic diagram of the structure of a polyethylene film for shipping packaging according to this application.
[0040] Explanation of reference numerals in the attached figures:
[0041] 1. Outer layer; 2. Middle layer; 3. Inner layer. Detailed Implementation
[0042] The following section provides further explanation of this application in conjunction with specific experiments.
[0043] Preparation Example
[0044]
Preparation Example 1
[0045] A silane-modified spherical silica is obtained by reacting hexamethyldisilazane with spherical silica at 80°C with stirring, followed by vacuum purification at 150°C. The particle size of the spherical silica ranges from 1 to 2 μm, and the weight ratio of hexamethyldisilazane to spherical silica is 10:100.
[0046]
Preparation Example 2
[0047] A silane-modified spherical silica is obtained by reacting hexamethyldisilazane with spherical silica at 80°C with stirring, followed by vacuum purification at 150°C. The particle size of the spherical silica ranges from 500 to 600 nm, and the weight ratio of hexamethyldisilazane to spherical silica is 10:100. Example
[0048]
Example 1
[0049] A polyethylene film for shipping packaging, referenced Figure 1 It includes an outer layer 1, a middle layer 2 and an inner layer 3. The thickness ratio of the outer layer 1, the middle layer 2 and the inner layer 3 is 3:4:3. The middle layer 2 is a first polyethylene material, and the outer layer 1 and the inner layer 3 are second polyethylene materials.
[0050] Specifically, the raw materials for the first polyethylene material consist of 30 wt% first low-density polyethylene and 70 wt% linear low-density polyethylene. The raw materials for the second polyethylene material consist of 3 wt% POE elastomer, 1.2 wt% silane-modified spherical silica prepared in [Preparation Example 1], 0.5 wt% erucamide, 0.3 wt% light stabilizer 770, 0.24 wt% antioxidant 1010, 0.06 wt% antioxidant 168, 20 wt% second low-density polyethylene, 29.88 wt% metallocene linear low-density polyethylene a, 22.41 wt% metallocene linear low-density polyethylene b, and 22.41 wt% metallocene linear low-density polyethylene c.
[0051] In this embodiment, the first low-density polyethylene used is Saudi Aramco LDPE E1970 (melt index of 7 g / 10 min at 190℃ and 2.16 kg), the second low-density polyethylene is CNOOC Shell LDPE 2426H (melt index of 1.9 g / 10 min at 190℃ and 2.16 kg), the linear low-density polyethylene is DowDuPont LLDPE 2035 (melt index of 6 g / 10 min at 190℃ and 2.16 kg), the metallocene linear low-density polyethylene a is DowDuPont mLLDPE AT6101 (melt index of 0.8 g / 10 min at 190℃ and 2.16 kg), the metallocene linear low-density polyethylene b is DowDuPont mLLDPE 5500G (melt index of 1.5 g / 10 min at 190℃ and 2.16 kg), and the metallocene linear low-density polyethylene c is DowDuPont mLLDPE 5220G (melt index of 3.5g / 10min at 190℃ and 2.16kg), the POE elastomer is Dow POE polyolefin elastomer 8842 (melt index of 1g / 10min at 190℃ and 2.16kg, elongation at break of 1200% as measured by ASTM D638).
[0052] In this embodiment, the method for preparing polyethylene film for shipping packaging includes the following steps:
[0053] Each raw material of the first polyethylene material is fed into the middle extruder of the three-layer co-extrusion blown film machine, and each raw material of the second polyethylene material is fed into the outer and inner extruders of the three-layer co-extrusion blown film machine. The temperatures of the middle extruder, the outer extruder, and the inner extruder are controlled at 185°C in zone one, 185°C in zone two, 190°C in zone three, 195°C in zone four, and 195°C in zone five. Then, the three melted and uniformly plasticized melts are compositely extruded to form a tubular preform.
[0054] The tubular preform was blown into film using the top-blowing method at a temperature of 200℃, a blow-up ratio of 3:1, and a stretch ratio of 8:1. The film was then cooled, shaped, flattened, and wound up to obtain a polyethylene film.
[0055]
Example 2
[0056] A polyethylene film for shipping packaging, referenced Figure 1 It includes an outer layer 1, a middle layer 2 and an inner layer 3. The thickness ratio of the outer layer 1, the middle layer 2 and the inner layer 3 is 3.5:3:3.5. The middle layer 2 is made of a first polyethylene material, and the outer layer 1 and the inner layer 3 are made of a second polyethylene material.
[0057] Specifically, the raw materials for the first polyethylene material consist of 35 wt% first low-density polyethylene and 65 wt% linear low-density polyethylene. The raw materials for the second polyethylene material consist of 4 wt% POE elastomer, 1 wt% silane-modified spherical silica prepared in [Preparation Example 1], 0.75 wt% erucamide, 0.4 wt% UV-P ultraviolet absorber, 0.3 wt% antioxidant 1010, 0.1 wt% antioxidant 168, 15 wt% second low-density polyethylene, 23.535 wt% metallocene linear low-density polyethylene a, 31.38 wt% metallocene linear low-density polyethylene b, and 23.535 wt% metallocene linear low-density polyethylene c.
[0058] In this embodiment, the first low-density polyethylene used is Saudi Aramco LDPE E1970 (melt index of 7 g / 10 min at 190℃ and 2.16 kg), the second low-density polyethylene is CNOOC Shell LDPE 2426H (melt index of 1.9 g / 10 min at 190℃ and 2.16 kg), the linear low-density polyethylene is DowDuPont LLDPE 2035 (melt index of 6 g / 10 min at 190℃ and 2.16 kg), the metallocene linear low-density polyethylene a is DowDuPont mLLDPE AT6101 (melt index of 0.8 g / 10 min at 190℃ and 2.16 kg), the metallocene linear low-density polyethylene b is DowDuPont mLLDPE 5500G (melt index of 1.5 g / 10 min at 190℃ and 2.16 kg), and the metallocene linear low-density polyethylene c is DowDuPont mLLDPE 5220G (melt index of 3.5g / 10min at 190℃ and 2.16kg), the POE elastomer is Dow POE polyolefin elastomer 8842 (melt index of 1g / 10min at 190℃ and 2.16kg, elongation at break of 1200% as measured by ASTM D638).
[0059] In this embodiment, the method for preparing polyethylene film for shipping packaging includes the following steps:
[0060] Each raw material of the first polyethylene material is fed into the middle extruder of the three-layer co-extrusion blown film machine, and each raw material of the second polyethylene material is fed into the outer and inner extruders of the three-layer co-extrusion blown film machine. The temperatures of the middle extruder, the outer extruder, and the inner extruder are controlled as follows: zone 1: 190°C, zone 2: 190°C, zone 3: 200°C, zone 4: 205°C, and zone 5: 205°C. Then, the three melted and uniformly plasticized melts are compositely extruded to form a tubular preform.
[0061] The tubular preform was blown into film using the top-blowing method at a temperature of 205℃, a blow-up ratio of 3:1, and a stretch ratio of 8:1. The film was then cooled, shaped, flattened, and wound up to obtain a polyethylene film.
[0062]
Example 3
[0063] A polyethylene film for shipping packaging, referenced Figure 1 It includes an outer layer 1, a middle layer 2, and an inner layer 3. In this embodiment, the thickness ratio of the outer layer 1, the middle layer 2, and the inner layer 3 is 4:2:4, the middle layer 2 is a first polyethylene material, and the outer layer 1 and the inner layer 3 are second polyethylene materials.
[0064] Specifically, the raw materials for the first polyethylene material consist of 40 wt% first low-density polyethylene and 60 wt% linear low-density polyethylene. The raw materials for the second polyethylene material consist of 5 wt% POE elastomer, 0.8 wt% silane-modified spherical silica prepared in [Preparation Example 1], 1 wt% erucamide, 0.5 wt% UV-327 ultraviolet absorber, 0.4 wt% antioxidant 1010, 0.1 wt% antioxidant 168, 10 wt% second low-density polyethylene, 16.44 wt% metallocene linear low-density polyethylene a, 41.1 wt% metallocene linear low-density polyethylene b, and 24.66 wt% metallocene linear low-density polyethylene c.
[0065] In this embodiment, the first low-density polyethylene used is Saudi Aramco LDPE E1970 (melt index of 7 g / 10 min at 190℃ and 2.16 kg), the second low-density polyethylene is CNOOC Shell LDPE 2426H (melt index of 1.9 g / 10 min at 190℃ and 2.16 kg), the linear low-density polyethylene is DowDuPont LLDPE 2035 (melt index of 6 g / 10 min at 190℃ and 2.16 kg), the metallocene linear low-density polyethylene a is DowDuPont mLLDPE AT6101 (melt index of 0.8 g / 10 min at 190℃ and 2.16 kg), the metallocene linear low-density polyethylene b is DowDuPont mLLDPE 5500G (melt index of 1.5 g / 10 min at 190℃ and 2.16 kg), and the metallocene linear low-density polyethylene c is DowDuPont mLLDPE 5220G (melt index of 3.5g / 10min at 190℃ and 2.16kg), the POE elastomer is Dow POE polyolefin elastomer 8842 (melt index of 1g / 10min at 190℃ and 2.16kg, elongation at break of 1200% as measured by ASTM D638).
[0066] In this embodiment, the method for preparing polyethylene film for shipping packaging includes the following steps:
[0067] Each raw material in the first polyethylene material is fed into the middle extruder of a three-layer co-extrusion blown film machine, and each raw material in the second polyethylene material is fed into the outer and inner extruders of the three-layer co-extrusion blown film machine. The temperatures of the middle extruder, outer extruder, and inner extruder are controlled as follows: zone 1: 205°C; zone 2: 205°C; zone 3: 210°C; zone 4: 215°C; zone 5: 215°C. Then, the three melted and uniformly plasticized melts are compositely extruded to form a tubular preform.
[0068] The tubular preform was blown into film using the top-blowing method at a temperature of 215℃, a blow-up ratio of 3:1, and a stretch ratio of 8:1. The film was then cooled, shaped, flattened, and wound up to obtain a polyethylene film.
[0069]
Example 4
[0070] A polyethylene film for shipping packaging differs from [Example 2] in that the silane-modified spherical silica is replaced by an equal mass of the silane-modified spherical silica prepared in [Preparation Example 2].
[0071]
Example 5
[0072] A polyethylene film for shipping packaging differs from that in [Example 2] in that the weight percentages of metallocene linear low-density polyethylene a, metallocene linear low-density polyethylene b, and metallocene linear low-density polyethylene c are different. In this example, the weight percentage of metallocene linear low-density polyethylene a is 7.845 wt%, the weight percentage of metallocene linear low-density polyethylene b is 39.225 wt%, and the weight percentage of metallocene linear low-density polyethylene c is 31.38 wt%.
[0073] Comparative Example
[0074] Comparative Example 1
[0075] A polyethylene film for shipping packaging differs from [Example 2] in that: the first low-density polyethylene is CNOOC Shell LDPE 2426H (melt index of 1.9 g / 10 min at 190°C and 2.16 kg); the linear low-density polyethylene is DowDuPont LLDPE 2047G (melt index of 2.3 g / 10 min at 190°C and 2.16 kg), and the rest is the same as [Example 2].
[0076] Comparative Example 2
[0077] A polyethylene film for shipping packaging differs from [Example 2] in that the POE elastomer is DowDuPont POE 8411 (melt index of 18g / 10min at 190°C and 2.16 kg, and elongation at break of 1000% as measured by ASTM D638), while the rest is the same as [Example 2].
[0078] Performance testing
[0079] (1) Polyethylene films with a thickness of 15 μm were produced according to the processes of Examples 1-5 and Comparative Examples 1-2. The stability of the film bubble was observed and the results were recorded in Table 1 below. Among them, film bubble instability refers to the occurrence of the following phenomena at least once within two hours during the production process: unstable film bubble spiral, oscillation of condensation line, film bubble sagging, film bubble trembling and film bubble contraction, which leads to production difficulties.
[0080] (2) Film adhesion: The test was conducted in accordance with GB / T 16276-2016. The sample size was 100mm*100mm, and the pressure applied after two samples were stacked was 0.5N / cm. 2 The samples were kept at 40℃ for 24 hours, then transferred to a standard laboratory environment (23℃, 50%RH) for 4 hours. A tensile testing machine was then used to peel the samples at a constant speed of 250 mm / min at a 90° angle, and the maximum force during the separation process was recorded. Five groups of samples were taken from each example and comparative example for testing, and the test results are recorded in Table 1 below.
[0081] (3) Elongation at break: GB / T 1040.3-2006, 5A type specimen, tensile speed of 200 mm / min, 5 groups of specimens were taken for each example and comparative example for testing, and the average test results were recorded in Table 2 below.
[0082] (4) Tear resistance: GB / T 11999-2021 was used for testing. Five groups of samples were taken for each example and comparative example, and the average test results were recorded in Table 2 below.
[0083] (5) Drop impact strength: The test was conducted in accordance with GB / T 9639.1-2022. Five groups of samples were taken for each example and comparative example, and the average test results were recorded in Table 2 below.
[0084] Table 1
[0085]
[0086] Table 2
[0087]
[0088] The difference between Comparative Example 1 and Example 2 lies in the first polyethylene material used in the interlayer. In Comparative Example 1, the melt index of the first low-density polyethylene used in the interlayer is 1.9 g / 10 min, and the melt index of the linear low-density polyethylene is 2.3 g / 10 min. In Example 2, the melt index of the first low-density polyethylene used in the interlayer is 7 g / 10 min, and the melt index of the linear low-density polyethylene is 6 g / 10 min. Compared to Comparative Example 1, the interlayer of Example 2 has better flowability and extensibility, and can better absorb and balance external pressure fluctuations, reducing the risk of membrane bubble vibration, sagging, local thinning, or membrane rupture. However, the melt index of the first low-density polyethylene and the linear low-density polyethylene should not be too high, as this can easily cause the interlayer to be too soft, the membrane bubble to be unstable, and defects such as wavy lines or membrane rupture to easily appear on the film surface.
[0089] Compared with Example 2, Comparative Example 2 differs in the melt index and elongation at break of the POE elastomer. The melt index of the POE elastomer is significantly different from that of metallocene low-density polyethylene, which can easily damage the stability of the film bubble and reduce the mechanical properties of the film.
[0090] Compared with Example 2, Example 4 differs in the particle size range of the silane-modified spherical silica. Specifically, the particle size range of the silane-modified spherical silica is 1-2 μm, which is more conducive to reducing the adhesion of the film.
[0091] Compared with Example 2, Example 5 differs in the proportion of the three metallocene linear low-density polyethylenes. Specifically, the weight ratio of metallocene linear low-density polyethylene with a melt index of 0.75-0.85 g / 10 min, metallocene linear low-density polyethylene with a melt index of 1.2-1.8 g / 10 min, and metallocene linear low-density polyethylene with a melt index of 3.2-3.8 g / 10 min is in the range of (2-4):(3-5):3, which is more conducive to improving the mechanical properties of the film.
[0092] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this specific embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.
Claims
1. A polyethylene film for shipping packaging, characterized in that: It includes an outer layer, a middle layer and an inner layer, wherein the thickness ratio of the outer layer, the middle layer and the inner layer is (3-4):(2-4):(3-4); The middle layer is a first polyethylene material, which is made of 30-40 wt% first low-density polyethylene and the balance linear low-density polyethylene. The outer and inner layers are made of a second polyethylene material, which is composed of 3-5 wt% POE elastomer, 0.8-1.2 wt% opening agent, 0.5-1 wt% slip agent, 0.1-1 wt% other processing aids, 0-5 wt% color masterbatch, 10-20 wt% second low-density polyethylene, and the balance being composite metallocene low-density polyethylene. Wherein, the melt index of the linear low-density polyethylene is 6-8 g / 10 min; the melt index of the first low-density polyethylene is 6-8 g / 10 min; and the melt index of the second low-density polyethylene is 1.8-2.5 g / 10 min. The melt index of the POE elastomer is 1-1.5 g / 10 min; The composite metallocene low-density polyethylene includes metallocene linear low-density polyethylene with a melt index of 0.75-0.85 g / 10 min, metallocene linear low-density polyethylene with a melt index of 1.2-1.8 g / 10 min, and metallocene linear low-density polyethylene with a melt index of 3.2-3.8 g / 10 min; the weight ratio of the metallocene linear low-density polyethylene with a melt index of 0.75-0.85 g / 10 min, the metallocene linear low-density polyethylene with a melt index of 1.2-1.8 g / 10 min, and the metallocene linear low-density polyethylene with a melt index of 3.2-3.8 g / 10 min is (2-4):(3-5):3; The above melt index test conditions are 190℃ and 2.16kg; The polyethylene film for shipping packaging is formed by extruding an outer layer, a middle layer, and an inner layer to form a tubular preform, then blowing the tubular preform using an up-blowing method, followed by cooling, shaping, flattening, and winding. The resulting polyethylene film for shipping packaging has a thickness of less than 20 μm.
2. The polyethylene film for shipping packaging according to claim 1, characterized in that: The opening agent is silane-modified spherical silica.
3. A polyethylene film for shipping packaging according to claim 2, characterized in that: The particle size range of the silane-modified spherical silica is 1-2 μm.
4. A polyethylene film for shipping packaging according to claim 1, characterized in that: The slip agent is at least one of erucamide and oleamide.
5. A polyethylene film for shipping packaging according to claim 1, characterized in that: The other processing aids include one or more of light stabilizers, antioxidants, and EPDM rubber.
6. A polyethylene film for shipping packaging according to claim 5, characterized in that: The light stabilizer has a weight percentage of 0.3-0.5%, and the light stabilizer is one or more of hindered amine light stabilizers and ultraviolet absorbers.
7. A polyethylene film for shipping packaging according to claim 5, characterized in that: The antioxidant has a weight percentage of 0.3-0.5%, wherein the antioxidant includes hindered phenolic primary antioxidants and phosphite secondary antioxidants, and the weight ratio of the hindered phenolic primary antioxidants to the phosphite secondary antioxidants is (3-4):
1.
8. A method for preparing a polyethylene film for shipping packaging as described in any one of claims 1-7, characterized in that, The process includes the following steps: The first polyethylene material is melted in the middle extruder of a three-layer co-extrusion blown film machine; the second polyethylene material is melted in the outer and inner extruders of the same machine; the three melted and uniformly plasticized melts are then compounded and extruded to form a tubular preform; the tubular preform is blown into film using an upward blowing method, then cooled, shaped, flattened, and wound to obtain a polyethylene film for shipping packaging.
9. A method for preparing a polyethylene film for shipping packaging according to claim 8, characterized in that: The temperature parameters of the middle extruder, outer extruder, and inner extruder are set as follows: Zone 1: 185-205℃, Zone 2: 185-205℃, Zone 3: 190-210℃, Zone 4: 195-215℃, Zone 5: 195-215℃.