A stretch wrap film and method of making the same

Abstract

The application relates to the technical field of packaging materials, and particularly discloses a stretch wrapping film and a preparation method thereof. The stretch wrapping film comprises an upper layer film and a lower layer film; the upper layer film comprises the following raw materials: 28-35 parts of MLLDPE and 3-6 parts of LMDPE; the lower layer film comprises the following raw materials: 30-40 parts of LLDPE, 5-8 parts of MDPE and 55-70 parts of functional master batches; the functional master batches comprise the following raw materials: metallocene polyethylene, elastomer, polyacrylic acid sodium modified talc powder and maleic anhydride grafted elastomer. The upper layer film with specific raw materials and a specific proportion improves the mechanical property and the processing performance of the stretch wrapping film, the lower layer film with specific raw materials and a specific proportion improves the elasticity, the toughness and the tensile strength of the stretch wrapping film, the functional master batches not only significantly increase the mechanical property of the stretch wrapping film, but also increase the dispersibility of the lower layer film raw materials and the thermal stability of the lower layer film materials.

Description

Technical Field

[0001] This invention relates to the field of packaging materials technology, and in particular to a stretch wrap film and its preparation method. Background Technology

[0002] Polyethylene (PE) stretch wrap film boasts advantages such as high tensile strength, high elongation, good self-adhesion, puncture resistance, and tear resistance. It can be used for both manual and machine wrapping, effectively wrapping objects into a single unit to prevent scattering and collapse during transport. It is widely used in pallet packaging for goods in industries such as industrial enterprises, food processing, and logistics packaging, providing fixation, waterproofing, dustproofing, and protection against damage. However, conventional PE stretch wrap film suffers from poor uniformity, low tensile strength, and poor puncture and tear resistance in practical applications, making it unsuitable for large-scale use. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a stretch wrap film and its preparation method. By limiting the components and proportions of each raw material, the mechanical properties of the stretch wrap film, especially its tensile strength and puncture resistance, are significantly improved.

[0004] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: In a first aspect, the present invention provides a stretch wrapping film, comprising an upper film and a lower film; The upper membrane comprises the following raw materials in parts by weight: 28 to 35 parts of metallocene linear low-density polyethylene and 3 to 6 parts of linear medium-density polyethylene; The lower membrane comprises the following raw materials in parts by weight: 30 to 40 parts of linear low-density polyethylene, 5 to 8 parts of medium-density polyethylene, and 55 to 70 parts of functional masterbatch; The functional masterbatch comprises the following raw materials: metallocene polyethylene, elastomer, sodium polyacrylate-modified talc, and maleic anhydride-grafted elastomer.

[0005] Compared to existing technologies, the stretch wrap film provided by this invention comprises an upper layer of metallocene linear low-density polyethylene (MLLDPE) and linear medium-density polyethylene (LMDPE) in a specific ratio, which synergistically improve the mechanical properties and processing performance of the stretch wrap film. The lower layer of the film comprises a lower layer of linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), and functional masterbatch in a specific ratio, which synergistically and effectively improve the elasticity, toughness, and tensile strength of the stretch wrap film. The functional masterbatch not only significantly increases the mechanical properties of the stretch wrap film but also increases the dispersibility of the lower layer of the film material and the thermal stability of the lower layer of the film material, effectively solving the stiffness problem of the wrap film and giving the stretch wrap film good toughness and making it less prone to deformation.

[0006] Among the raw materials for stretch wrap film, LLDPE has a high softening and melting temperature, high strength, good toughness, high rigidity, good heat and cold resistance, and also has good resistance to environmental stress cracking, impact strength, and tear strength. Adding metallocene to form MLLDPE, since metallocene is a highly stereoregular polymer with a very narrow molecular weight distribution, allows for precise control of the polymer's physical properties, significantly improving the tensile strength, puncture resistance, and tear resistance of the stretch wrap film. LMDPE can increase the density of the upper film material, improve its orientation, increase the transparency of the wrap film, and improve the overall performance of the film layer. At the same time, it can also reduce the friction coefficient of the non-adhesive layer of the wrap film, preventing the packaged goods from sticking together. Because metallocene has a narrow molecular weight distribution and a narrow processing range, processing conditions are difficult to control. Adding a certain amount of MDPE can reduce the viscosity of the melt, making it easier to control the processing and increase the smoothness of the stretch wrap film. In the functional masterbatch, metallocene polyethylene (MPE) can significantly improve the tensile strength, puncture resistance and tear resistance of stretch wrap film, elastomer can significantly improve the elasticity and toughness of stretch wrap film, sodium polyacrylate modified talc as filler can significantly improve the mechanical properties of stretch wrap film, and maleic anhydride grafted elastomer combined with sodium polyacrylate modified talc can improve the dispersibility of sodium polyacrylate modified talc through a soft-encapsulated hard core-shell structure.

[0007] Preferably, the functional masterbatch comprises the following raw materials in the following mass percentages: 20%~30% metallocene polyethylene, 50%~60% elastomer, 1%~2% sodium polyacrylate modified talc, 5%~10% maleic anhydride grafted elastomer, 2%~5% tackifier, 1%~3% antioxidant and 1%~3% dispersant.

[0008] This invention further enhances the synergistic effect of each raw material by limiting the raw material components and proportions of the functional masterbatch. Talc powder is a rigid particle that can significantly improve the mechanical strength of stretch wound films. However, its compatibility with the resin matrix is ​​extremely poor. Direct addition not only fails to improve its mechanical strength but also causes stratification due to poor dispersibility, thereby reducing the overall performance of the stretch wound film. This invention uses sodium polyacrylate to modify talc powder, which can improve the suspension stability of talc powder, improve the compatibility of the talc powder surface with other components, and thus improve the dispersion homogeneity of talc powder, preventing stratification and sedimentation during long-term storage. Maleic anhydride-grafted elastomer not only improves the toughness of the stretch wound film but also significantly improves the compatibility between sodium polyacrylate-modified talc powder and the resin matrix, allowing the sodium polyacrylate-modified talc powder to be better dispersed in the resin matrix and thus exert its function.

[0009] Preferably, the elastomer comprises at least one of ethylene propylene diene monomer (EPR), ethylene propylene diene monomer (EPDM), ethylene-vinyl acetate copolymer (EVA), or acrylic resin (ACR).

[0010] Preferably, the preparation method of the sodium polyacrylate modified talc powder includes the following steps: A sodium polyacrylate aqueous solution was fluidized and sprayed onto the surface of talc powder, and then dried to obtain sodium polyacrylate modified talc powder.

[0011] More preferably, the talc powder has a particle size of 600 mesh to 800 mesh.

[0012] More preferably, the mass ratio of the sodium polyacrylate aqueous solution to the talc powder is (5~10):100.

[0013] More preferably, the mass concentration of the sodium polyacrylate aqueous solution is 8% to 13%.

[0014] Preferably, the maleic anhydride-grafted elastomer comprises at least one of maleic anhydride-grafted styrene-butadiene-styrene copolymer or maleic anhydride-grafted linear low-density polyethylene.

[0015] More preferably, the thickener comprises thickening masterbatch ZH-102.

[0016] In this invention, the tackifying masterbatch ZH-102 has good lap adhesion and peel adhesion, which can improve the stretch ratio, gloss and transparency of the stretch wrap film. It can make the wrap film have a certain adhesive effect and good surface looseness, thus providing better packaging protection for goods.

[0017] More preferably, the antioxidant includes at least one of antioxidant 1010, antioxidant 168, antioxidant 1076, antioxidant 242, antioxidant 626 or antioxidant 1135.

[0018] More preferably, the dispersant includes at least one of carboxymethyl cellulose, polyacrylamide, or glucon.

[0019] More preferably, the method for preparing the functional masterbatch includes the following steps: S1. Weigh each raw material according to the design ratio, mix sodium polyacrylate modified talc powder with maleic anhydride grafted elastomer, plasticize, and pass through thin sheets to obtain fine particles. S2, the fine particles are mixed with metallocene polyethylene, elastomer, tackifier, antioxidant and dispersant, melt extruded and granulated to obtain functional masterbatch.

[0020] The method for preparing the functional masterbatch provided by this invention involves first plasticizing sodium polyacrylate-modified talc powder with maleic anhydride-grafted elastomer, which forms a soft-shell structure, thereby further improving the compatibility between sodium polyacrylate-modified talc powder and the resin matrix. The maleic anhydride-grafted elastomer can also improve the compatibility with polyethylene in the subsequent process. Then, the masterbatch is mixed with the remaining raw materials and granulated to obtain a high-performance functional masterbatch, which is beneficial to improving the overall performance of subsequent stretch wrapping films.

[0021] More preferably, in S1, the plasticizing temperature is 125℃~135℃ and the plasticizing time is 10min~15min.

[0022] More preferably, in S2, the melt extrusion is performed using a twin-screw extruder, wherein the heating temperature of the screw extruder is 180℃~205℃ and the main extruder speed is 90rpm~110rpm.

[0023] Preferably, the mass ratio of the upper membrane to the lower membrane is 1:(2.5~3.5).

[0024] Preferably, an outer membrane with the same raw material composition and ratio as the upper membrane is disposed on the side of the upper membrane away from the lower membrane, and an inner membrane with the same raw material composition and ratio as the lower membrane is disposed on the side of the lower membrane away from the upper membrane.

[0025] In practical use, a minimum of two layers of film is generally sufficient to meet the requirements. Using four layers of film allows for structural reinforcement of both the upper and lower layers, and better optimization can be achieved through adjustments to the raw materials. Using the same raw material components and proportions for reinforcement ensures that the stretch wrap film avoids cascading damage after being subjected to defects such as tearing or shearing, and forms a certain clamping effect between the layers, resulting in better tear and puncture resistance of the product.

[0026] Secondly, the present invention provides a method for preparing a stretch wrap film, comprising the following steps: Sa, weigh the raw materials of the upper and lower membranes according to the design ratio, mix the raw materials of the upper membrane evenly to obtain the first mixture; mix the raw materials of the lower membrane evenly to obtain the second mixture; Sb, the first mixture and the second mixture are respectively extruded at high temperature through a screw extruder to obtain upper film plastic particles and lower film plastic particles; Sc, the upper layer plastic particles and the lower layer plastic particles are respectively placed into the corresponding chambers of the casting machine to cast film, thus obtaining a stretch wound film.

[0027] This invention employs a casting process to prepare stretch wrap film, which is simple, easy to implement, and suitable for large-scale production. Furthermore, the stretch wrap film produced by this invention using the casting process achieves mechanical strength and ductility comparable to or even superior to stretch wrap films produced by existing blow molding processes.

[0028] Preferably, the method for preparing the stretch wrap film includes the following steps: Sa, weigh the raw materials of the outer membrane, upper membrane, lower membrane and inner membrane according to the design ratio, mix the raw materials of the upper membrane evenly to obtain the first mixture; mix the raw materials of the lower membrane evenly to obtain the second mixture; mix the raw materials of the outer membrane evenly to obtain the third mixture; mix the raw materials of the inner membrane evenly to obtain the fourth mixture. Sb, the first mixture, the second mixture, the third mixture and the fourth mixture are respectively extruded at high temperature through a screw extruder to obtain upper film plastic particles, lower film plastic particles, outer film plastic particles and inner film plastic particles; Sc, the outer layer plastic particles, the upper layer plastic particles, the lower layer plastic particles and the inner layer plastic particles are respectively placed into the corresponding chambers of the casting machine to cast film and obtain a stretch wound film.

[0029] Preferably, in Sb, the heating temperature of the screw extruder is 195℃~215℃, and the heating time is 22h~26h.

[0030] Preferably, in Sc, the temperature for casting the film is 250℃~280℃, and the time is 22h~26h.

[0031] This invention ensures smooth film casting and improves work efficiency by controlling the heating temperature of the screw extruder and the film casting temperature.

[0032] Preferably, in Sc, after the casting process, the process further includes cooling, slitting, winding, forming and packaging to obtain a stretch wrap film.

[0033] In the example, in Sc, cooling is performed by a casting cooling roller, the temperature of which is 20°C to 30°C.

[0034] Preferably, in Sc, the winding tension is below 8 kg.

[0035] This invention can further ensure the overall performance of stretch wrap film by limiting the temperature of the casting cooling roller; the winding tension affects the flatness and winding tightness of the stretch wrap film. If the winding tension is too high, stress will remain in the stretch wrap film, which will reduce the elongation and other properties of the stretch wrap film and easily cause film breakage. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0037] This invention does not specify the exact type of each raw material. In the examples and comparative examples, Dow Chemical's ELITE 5500G was used for MLLDPE and Dow Axelron was used for LMDPE. TM FO 8864 BK, LLDPE is DowDuPont AT 6101, MDPE is Chevron Phillips HHM TR-130, MPE is ExxonMobil 4518CB, and tackifier is Tianjin Zeheng Packaging Products Co., Ltd.'s tackifier masterbatch ZH-102. Other materials, unless otherwise specified, are commercially available products.

[0038] Example 1 This embodiment provides a stretch wrap film, composed of an outer film, an upper film, a lower film, and an inner film in a mass ratio of 1:1:2.9:2.9. Wherein, The outer membrane is composed of the following parts by weight of raw materials: 31 parts of metallocene linear low-density polyethylene and 5 parts of linear medium-density polyethylene; The upper membrane is composed of the following parts by weight of raw materials: 32 parts of metallocene linear low-density polyethylene and 4 parts of linear medium-density polyethylene; The lower membrane is composed of the following parts by weight of raw materials: 35 parts of linear low-density polyethylene, 6 parts of medium-density polyethylene, and 64 parts of functional masterbatch; The inner membrane is composed of the following parts by weight of raw materials: 35 parts of linear low-density polyethylene, 6 parts of medium-density polyethylene, and 64 parts of functional masterbatch; The functional masterbatch is composed of the following raw materials in weight percentage: 26% metallocene polyethylene, 56.5% elastomer (equal masses of EPR and EPDM), 1.5% sodium polyacrylate modified talc, 8% maleic anhydride grafted linear low-density polyethylene, 4% tackifying masterbatch ZH-102, 2% antioxidant (equal masses of 1010 and 168), and 2% dispersant (carboxymethyl cellulose).

[0039] The above-mentioned method for preparing stretch wrap film includes the following steps: S1, Preparation of sodium polyacrylate modified talc: A 10wt% sodium polyacrylate aqueous solution was fluidized and sprayed onto the surface of 800-mesh talc powder. The mass ratio of sodium polyacrylate aqueous solution to talc powder was 8:100. After drying, sodium polyacrylate modified talc powder was obtained.

[0040] S2, Preparation of functional masterbatch: S2-1, Weigh each raw material according to the design ratio, mix sodium polyacrylate modified talc powder with maleic anhydride grafted linear low-density polyethylene, plasticize at 130℃ for 13 minutes, and pass through thin sheets to obtain fine granules. S2-2 involves mixing fine particles with metallocene polyethylene, elastomer, tackifying masterbatch ZH-102, antioxidant, and dispersant, then feeding the mixture into a twin-screw extruder with a main extrusion speed of 100 rpm. The mixture is then melt-extruded and granulated at 180℃~205℃ to obtain the functional masterbatch.

[0041] S3, Preparation of the mixture: Weigh out the raw materials for the outer membrane, upper membrane, lower membrane, and inner membrane according to the design ratio. Mix the raw materials for the upper membrane evenly to obtain the first mixture; mix the raw materials for the lower membrane evenly to obtain the second mixture; mix the raw materials for the outer membrane evenly to obtain the third mixture; and mix the raw materials for the inner membrane evenly to obtain the fourth mixture.

[0042] S4, Preparation of plastic particles: The first mixture, the second mixture, the third mixture, and the fourth mixture are extruded at high temperature through a screw extruder (heating temperature of 195℃~215℃). After 24 hours, upper film plastic particles, lower film plastic particles, outer film plastic particles, and inner film plastic particles are obtained.

[0043] Sc, Preparation of stretch wrap film: The outer layer plastic particles, upper layer plastic particles, lower layer plastic particles and inner layer plastic particles are placed into the corresponding chambers of the casting machine, and the film is formed after casting at 270℃ for 23 hours. The film is then cooled by casting cooling rollers at 25℃, slit, wound (tension below 5kg), formed and boxed to obtain stretch wrap film.

[0044] Example 2 This embodiment provides a stretch wrap film, composed of an outer film, an upper film, a lower film, and an inner film in a mass ratio of 1:1:3.3:3.3. The outer membrane is composed of the following parts by weight of raw materials: 29 parts of metallocene linear low-density polyethylene and 4 parts of linear medium-density polyethylene; The upper membrane is composed of the following parts by weight of raw materials: 29 parts of metallocene linear low-density polyethylene and 4 parts of linear medium-density polyethylene; The lower membrane is composed of the following parts by weight of raw materials: 38 parts of linear low-density polyethylene, 7 parts of medium-density polyethylene, and 65 parts of functional masterbatch; The inner membrane is composed of the following parts by weight of raw materials: 37 parts of linear low-density polyethylene, 7 parts of medium-density polyethylene, and 66 parts of functional masterbatch; The functional masterbatch is composed of the following raw materials in the following weight percentages: 28% metallocene polyethylene, 50% elastomer (EVA), 2% sodium polyacrylate modified talc, 10% maleic anhydride grafted ethylene-butadiene-styrene copolymer, 2% tackifying masterbatch ZH-10, 3% antioxidant (equal weights of 1076 and 242) and 3% dispersant (polyacrylamide).

[0045] The above-mentioned method for preparing stretch wrap film includes the following steps: S1, Preparation of sodium polyacrylate modified talc: An 11 wt% sodium polyacrylate aqueous solution was fluidized and sprayed onto the surface of 700 mesh talc powder. The mass ratio of sodium polyacrylate aqueous solution to talc powder was 7:100. After drying, sodium polyacrylate modified talc powder was obtained.

[0046] S2, Preparation of functional masterbatch: S2-1, Weigh each raw material according to the design ratio, mix sodium polyacrylate modified talc powder with maleic anhydride grafted ethylene-butadiene-styrene copolymer, plasticize at 130℃ for 13min, and pass through thin sheets to obtain fine particles. S2-2 involves mixing fine particles with metallocene polyethylene, elastomer, tackifying masterbatch ZH-102, antioxidant, and dispersant, then feeding the mixture into a twin-screw extruder with a main extrusion speed of 100 rpm. The mixture is then melt-extruded and granulated at 180℃~205℃ to obtain the functional masterbatch.

[0047] S3, Preparation of the mixture: Weigh out the raw materials for the outer membrane, upper membrane, lower membrane, and inner membrane according to the design ratio. Mix the raw materials for the upper membrane evenly to obtain the first mixture; mix the raw materials for the lower membrane evenly to obtain the second mixture; mix the raw materials for the outer membrane evenly to obtain the third mixture; and mix the raw materials for the inner membrane evenly to obtain the fourth mixture.

[0048] S4, Preparation of plastic particles: The first mixture, the second mixture, the third mixture, and the fourth mixture are extruded at high temperature through a screw extruder (heating temperature of 195℃~215℃). After 25 hours, upper film plastic particles, lower film plastic particles, outer film plastic particles, and inner film plastic particles are obtained.

[0049] Sc, Preparation of stretch wrap film: The outer layer plastic particles, upper layer plastic particles, lower layer plastic particles and inner layer plastic particles are placed into the corresponding chambers of the casting machine, and the film is cast at 260℃ for 24 hours. The film is then cooled by the casting cooling roller at 24℃, cut, and wound (tension below 5kg), and then formed and boxed to obtain the stretch wrap film.

[0050] Example 3 This embodiment provides a stretch wrap film, composed of an outer film, an upper film, a lower film, and an inner film in a mass ratio of 1:1:2.8:2.8. Wherein, The outer membrane is composed of the following parts by weight of raw materials: 35 parts of metallocene linear low-density polyethylene and 3 parts of linear medium-density polyethylene; The upper membrane is composed of the following parts by weight of raw materials: 35 parts of metallocene linear low-density polyethylene and 3 parts of linear medium-density polyethylene; The lower membrane is composed of the following parts by weight of raw materials: 30 parts of linear low-density polyethylene, 5 parts of medium-density polyethylene, and 70 parts of functional masterbatch; The inner membrane is composed of the following parts by weight of raw materials: 30 parts of linear low-density polyethylene, 5 parts of medium-density polyethylene, and 70 parts of functional masterbatch; The functional masterbatch is composed of the following raw materials in the following weight percentages: 20% metallocene polyethylene, 57% elastomer (ACR), 2% sodium polyacrylate modified talc, 10% maleic anhydride grafted ethylene-butadiene-styrene copolymer, 25% tackifying masterbatch ZH-10, 3% antioxidant (equal masses of 626 and 1135) and 3% dispersant (guar gum).

[0051] The above-mentioned method for preparing stretch wrap film includes the following steps: S1, Preparation of sodium polyacrylate modified talc: An 8 wt% sodium polyacrylate aqueous solution was fluidized and sprayed onto the surface of 700 mesh talc powder. The mass ratio of sodium polyacrylate aqueous solution to talc powder was 10:100. After drying, sodium polyacrylate modified talc powder was obtained.

[0052] S2, Preparation of functional masterbatch: S2-1, Weigh each raw material according to the design ratio, mix sodium polyacrylate modified talc powder with maleic anhydride grafted ethylene-butadiene-styrene copolymer, plasticize at 125℃ for 15min, and pass through thin sheets to obtain fine particles. S2-2 involves mixing fine particles with metallocene polyethylene, elastomer, tackifying masterbatch ZH-102, antioxidant, and dispersant, then feeding the mixture into a twin-screw extruder with a main engine speed of 90 rpm. The mixture is then melt-extruded and granulated at 180℃~205℃ to obtain the functional masterbatch.

[0053] S3, Preparation of the mixture: Weigh out the raw materials for the outer membrane, upper membrane, lower membrane, and inner membrane according to the design ratio. Mix the raw materials for the upper membrane evenly to obtain the first mixture; mix the raw materials for the lower membrane evenly to obtain the second mixture; mix the raw materials for the outer membrane evenly to obtain the third mixture; and mix the raw materials for the inner membrane evenly to obtain the fourth mixture.

[0054] S4, Preparation of plastic particles: The first mixture, the second mixture, the third mixture, and the fourth mixture are extruded at high temperature through a screw extruder (heating temperature of 195℃~215℃). After 26 hours, upper film plastic particles, lower film plastic particles, outer film plastic particles, and inner film plastic particles are obtained.

[0055] Sc, Preparation of stretch wrap film: The outer layer plastic particles, upper layer plastic particles, lower layer plastic particles and inner layer plastic particles are placed into the corresponding chambers of the casting machine, and the film is formed after casting at 250℃ for 26 hours. The film is then cooled by casting cooling rollers at 20℃, slit, wound (tension below 5kg), formed and boxed to obtain stretch wrap film.

[0056] Example 4 This embodiment provides a stretch wrap film, composed of an outer film, an upper film, a lower film, and an inner film in a mass ratio of 1:1:3.0:3.0. Wherein, The outer membrane is composed of the following parts by weight of raw materials: 28 parts of metallocene linear low-density polyethylene and 6 parts of linear medium-density polyethylene; The upper membrane is composed of the following parts by weight of raw materials: 28 parts of metallocene linear low-density polyethylene and 6 parts of linear medium-density polyethylene; The lower membrane is composed of the following parts by weight of raw materials: 40 parts of linear low-density polyethylene, 8 parts of medium-density polyethylene, and 55 parts of functional masterbatch; The inner membrane is composed of the following parts by weight of raw materials: 40 parts of linear low-density polyethylene, 8 parts of medium-density polyethylene, and 55 parts of functional masterbatch; The functional masterbatch is composed of the following raw materials in the following mass percentages: 30% metallocene polyethylene, 60% elastomer (equal mass of EPDM and ACR), 1% sodium polyacrylate modified talc, 5% maleic anhydride grafted linear low-density polyethylene, 2% tackifying masterbatch ZH-102, 1% antioxidant (1010) and 1% dispersant (equal mass of carboxymethyl cellulose and glucon).

[0057] The above-mentioned method for preparing stretch wrap film includes the following steps: S1, Preparation of sodium polyacrylate modified talc: A 13wt% sodium polyacrylate aqueous solution was fluidized and sprayed onto the surface of 600-mesh talc powder. The mass ratio of sodium polyacrylate aqueous solution to talc powder was 5:100. After drying, sodium polyacrylate modified talc powder was obtained.

[0058] S2, Preparation of functional masterbatch: S2-1, Weigh each raw material according to the design ratio, mix sodium polyacrylate modified talc powder with maleic anhydride grafted linear low-density polyethylene, plasticize at 135℃ for 10min~15min, and pass through thin sheets to obtain fine granules. S2-2 involves mixing fine particles with metallocene polyethylene, elastomer, tackifying masterbatch ZH-102, antioxidant, and dispersant, then feeding the mixture into a twin-screw extruder with a main extrusion speed of 110 rpm. The mixture is then melt-extruded and granulated at 180℃~205℃ to obtain the functional masterbatch.

[0059] S3, Preparation of the mixture: Weigh out the raw materials for the outer membrane, upper membrane, lower membrane, and inner membrane according to the design ratio. Mix the raw materials for the upper membrane evenly to obtain the first mixture; mix the raw materials for the lower membrane evenly to obtain the second mixture; mix the raw materials for the outer membrane evenly to obtain the third mixture; and mix the raw materials for the inner membrane evenly to obtain the fourth mixture.

[0060] S4, Preparation of plastic particles: The first mixture, the second mixture, the third mixture, and the fourth mixture are extruded at high temperature through a screw extruder (heating temperature of 195℃~215℃). After 22 hours, upper film plastic particles, lower film plastic particles, outer film plastic particles, and inner film plastic particles are obtained.

[0061] Sc, Preparation of stretch wrap film: The outer layer plastic particles, upper layer plastic particles, lower layer plastic particles and inner layer plastic particles are placed into the corresponding chambers of the casting machine, and the film is formed after casting at 280℃ for 22 hours. The film is then cooled by casting cooling rollers at 30℃, slit, wound (tension below 5kg), formed and boxed to obtain stretch wrap film.

[0062] Example 5 This embodiment provides a stretch wrap film, composed of an upper film and a lower film with a mass ratio of 1:2.9. The raw material composition and ratio of the upper and lower membranes are the same as in Example 1, and will not be repeated here.

[0063] The above-mentioned method for preparing stretch wrap film includes the following steps: S1, Preparation of sodium polyacrylate modified talc: Same as in Example 1, and will not be repeated.

[0064] S2, Preparation of functional masterbatch: Same as in Example 1, and will not be repeated.

[0065] S3, Preparation of the mixture: Weigh the raw materials for the upper and lower membranes according to the design ratio, mix the raw materials for the upper membrane evenly to obtain the first mixture, and mix the raw materials for the lower membrane evenly to obtain the second mixture.

[0066] S4, Preparation of plastic particles: The first mixture and the second mixture are extruded at high temperature through a screw extruder (heating temperature is 195℃~215℃), and after 24 hours, the upper film plastic particles and the lower film plastic particles are obtained.

[0067] Sc, Preparation of stretch wrap film: The upper and lower layer plastic particles are placed into the corresponding chambers of the casting machine and cast at 270°C for 24 hours to form a film. The film is then cooled by a casting cooling roller at 25°C, slit, and wound (tension below 5 kg), and then formed and boxed to obtain a stretch wrap film.

[0068] Example 6 This embodiment provides a stretch wrap film, composed of an upper film and a lower film with a mass ratio of 1:2.9. The upper membrane is composed of the following parts by weight of raw materials: 30 parts of metallocene linear low-density polyethylene and 4 parts of linear medium-density polyethylene; The lower membrane is composed of the following parts by weight of raw materials: 33 parts of linear low-density polyethylene, 7 parts of medium-density polyethylene, and 60 parts of functional masterbatch; The functional masterbatch is composed of the following raw materials in the following mass percentages: 24% metallocene polyethylene, 59.5% elastomer (equal mass of EVA and ACR), 1.5% sodium polyacrylate modified talc, 7% maleic anhydride grafted linear low-density polyethylene, 4% tackifying masterbatch ZH-102, 2% antioxidant (168) and 2% dispersant (equal mass of carboxymethyl cellulose and polyacrylamide).

[0069] The preparation method of the above-mentioned stretch wrapping film is the same as that in Example 5, and will not be repeated here.

[0070] Comparative Example 1 This comparative example provides a stretch wound film composed of an outer film, an upper film, a lower film, and an inner film in a mass ratio of 1:1:2.9:2.9. The raw material components and proportions of the outer film, upper film, lower film, and inner film are similar to those in Example 1, except that in the functional masterbatch, the raw material sodium polyacrylate modified talc is replaced with an equal mass of talc.

[0071] The preparation method of the above-described stretch wrap film is similar to that of Example 1, except that step S1 is omitted and the sodium polyacrylate-modified talc powder in S2 is replaced with an equal mass of talc powder. The remaining operations are the same as in Example 1 and will not be repeated here.

[0072] Comparative Example 2 This comparative example provides a stretch wound film composed of an outer film, an upper film, a lower film, and an inner film in a mass ratio of 1:1:2.9:2.9. The raw material composition and proportions of the outer film, upper film, lower film, and inner film are similar to those in Example 1, except that in the functional masterbatch, maleic anhydride-grafted linear low-density polyethylene is replaced with an equal mass of elastomer. That is, in this comparative example, the functional masterbatch is composed of the following raw materials in the following mass percentages: metallocene polyethylene 26%, elastomer (equal masses of EPR and EPDM) 64.5%, sodium polyacrylate modified talc 1.5%, tackifying masterbatch ZH-102 4%, antioxidant (equal masses of 1010 and 168) 2%, and dispersant (carboxymethyl cellulose) 2%.

[0073] The preparation method of the above-mentioned stretch wrap film is similar to that of Example 1, except that in S2, each raw material is weighed according to the designed ratio, and the sodium polyacrylate modified talc powder, metallocene polyethylene, elastomer, tackifying masterbatch ZH-102, antioxidant and dispersant are mixed and put into a twin-screw extruder with a main engine speed of 100 rpm. The mixture is then melt-extruded and granulated at 180℃~205℃ to obtain the functional masterbatch. The remaining operations are the same as in Example 1 and will not be repeated.

[0074] Comparative Example 3 This comparative example provides a stretch wrap film composed of an upper film and a lower film in a mass ratio of 1:2.9. The raw material composition and proportions of the upper film are the same as in Example 5, and will not be repeated here. The lower film is composed of the following raw materials in parts by mass: 35 parts of linear low-density polyethylene, 6 parts of medium-density polyethylene, and 64 parts of ExxonMobil VM 6102.

[0075] The above-mentioned method for preparing stretch wrap film includes the following steps: S1. Weigh each raw material according to the design ratio, mix metallocene linear low-density polyethylene and linear medium-density polyethylene to obtain the first mixture; mix linear low-density polyethylene, medium-density polyethylene and ExxonMobil VM 6102 to obtain the second mixture.

[0076] S2~S3 are the same as S4~S5 in Example 5, and will not be described again.

[0077] Comparative Example 4 This comparative example provides a stretch wound film composed of an upper film and a lower film in a mass ratio of 1:2.9. The raw material composition and proportions of the upper film are the same as in Example 5, and will not be repeated here. The lower film is composed of the following raw materials in parts by mass: 35 parts of linear low-density polyethylene, 6 parts of medium-density polyethylene, 230 parts of ExxonMobil VM 610, and 34 parts of functional masterbatch.

[0078] The preparation method of the above-described stretch wrap film is similar to that of Example 5, except that in S3, the raw material composition and ratio of the lower layer film are prepared and mixed according to the comparative proportion. The remaining operations are the same as in Example 5 and will not be repeated here.

[0079] Performance testing Referring to the standards GB / T 6672-2001 and BB / T 0024-2018, the thickness, tensile strength, puncture resistance and adhesion of the stretch wrap films of Examples 1-6 and Comparative Examples 1-4 were tested respectively. The test results are shown in Table 1.

[0080] Table 1 Performance test results of stretch wrap film

[0081] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A stretch wrap film, characterized in that, Includes the upper membrane and the lower membrane; The upper membrane comprises the following raw materials in parts by weight: 28 to 35 parts of metallocene linear low-density polyethylene and 3 to 6 parts of linear medium-density polyethylene; The lower membrane comprises the following raw materials in parts by weight: 30 to 40 parts of linear low-density polyethylene, 5 to 8 parts of medium-density polyethylene, and 55 to 70 parts of functional masterbatch; The functional masterbatch comprises the following raw materials: metallocene polyethylene, elastomer, sodium polyacrylate modified talc, maleic anhydride grafted elastomer, tackifier, antioxidant and dispersant. The preparation method of the functional masterbatch includes the following steps: S1, sodium polyacrylate modified talc powder is mixed with maleic anhydride grafted elastomer, plasticized, and sheeted to obtain fine particles; S2, the fine particles are mixed with metallocene polyethylene, elastomer, tackifier, antioxidant and dispersant, melt extruded and granulated to obtain functional masterbatch.

2. The stretch wrap film as described in claim 1, characterized in that, The functional masterbatch comprises the following raw materials in the following weight percentages: 20%~30% metallocene polyethylene, 50%~60% elastomer, 1%~2% sodium polyacrylate modified talc, 5%~10% maleic anhydride grafted elastomer, 2%~5% tackifier, 1%~3% antioxidant and 1%~3% dispersant.

3. The stretch wrap film as described in claim 1 or 2, characterized in that, The elastomer includes at least one of ethylene propylene diene monomer (EPDM), ethylene propylene diene monomer (EPDM), ethylene-vinyl acetate copolymer, or acrylic resin. The maleic anhydride-grafted elastomer includes at least one of maleic anhydride-grafted styrene-butadiene-styrene copolymer or maleic anhydride-grafted linear low-density polyethylene.

4. The stretch wrap film as described in claim 1 or 2, characterized in that, The preparation method of the sodium polyacrylate modified talc powder includes the following steps: A sodium polyacrylate aqueous solution was fluidized and sprayed onto the surface of talc powder, and then dried to obtain sodium polyacrylate modified talc powder. The mass ratio of the sodium polyacrylate aqueous solution to the talc is (5~10):100; the mass concentration of the sodium polyacrylate aqueous solution is 8%~13%.

5. The stretch wrapping film as described in claim 1 or 2, characterized in that, The mass ratio of the upper membrane to the lower membrane is 1:(2.5~3.5); An outer membrane with the same raw material composition and ratio as the upper membrane is disposed on the side of the upper membrane away from the lower membrane, and an inner membrane with the same raw material composition and ratio as the lower membrane is disposed on the side of the lower membrane away from the upper membrane.

6. The stretch wrap film as described in claim 1, characterized in that, In S1, the plasticizing temperature is 125℃~135℃, and the plasticizing time is 10min~15min; In S2, the melt extrusion is performed using a twin-screw extruder, the heating temperature of which is 180℃~205℃ and the main extruder speed is 90rpm~110rpm.

7. The method for preparing the stretch wrap film according to any one of claims 1 to 6, characterized in that, Includes the following steps: Sa, weigh the raw materials of the upper and lower membranes according to the design ratio, mix the raw materials of the upper membrane evenly to obtain the first mixture; mix the raw materials of the lower membrane evenly to obtain the second mixture; Sb, the first mixture and the second mixture are respectively extruded at high temperature through a screw extruder to obtain upper film plastic particles and lower film plastic particles; the heating temperature of the screw extruder is 195℃~215℃; Sc, the upper layer plastic particles and the lower layer plastic particles are respectively placed into the corresponding chambers of the casting machine to cast film and obtain stretch wound film.

8. The method for preparing the stretch-wound film as described in claim 7, characterized in that, Includes the following steps: Sa, weigh the raw materials of the outer membrane, upper membrane, lower membrane and inner membrane according to the design ratio, mix the raw materials of the upper membrane evenly to obtain the first mixture; mix the raw materials of the lower membrane evenly to obtain the second mixture; mix the raw materials of the outer membrane evenly to obtain the third mixture; mix the raw materials of the inner membrane evenly to obtain the fourth mixture. Sb, the first mixture, the second mixture, the third mixture and the fourth mixture are respectively extruded at high temperature through a screw extruder to obtain upper film plastic particles, lower film plastic particles, outer film plastic particles and inner film plastic particles; Sc, the outer layer plastic particles, the upper layer plastic particles, the lower layer plastic particles and the inner layer plastic particles are respectively placed into the corresponding chambers of the casting machine to cast film and obtain a stretch wound film.

Images