Stretching wrapping film and preparation method thereof

Abstract

The invention relates to the technical field of packaging materials, and particularly discloses a stretching wrapping film and a preparation method thereof. The stretching and winding film comprises an upper-layer film and a lower-layer film; the upper-layer film is prepared from the following raw materials in parts by weight: 28 to 35 parts of MLLDPE and 3 to 6 parts of LMDPE; the lower layer film is prepared from the following raw materials in parts by weight: 30 to 40 parts of LLDPE (Linear Low Density Polyethylene), 5 to 8 parts of MDPE (Methylene Diphenyl Phenylene) and 55 to 70 parts of functional master batch; the functional master batch is prepared from the following raw materials: metallocene polyethylene, an elastomer, sodium polyacrylate modified talcum powder and a maleic anhydride grafted elastomer. The mechanical property and the processing property of the stretch wrapping film are improved through the upper-layer film made of the specific raw materials according to the specific ratio, the elasticity, the toughness and the tensile strength of the stretch wrapping film are improved through the lower-layer film made of the specific raw materials according to the specific ratio, and the mechanical property of the stretch wrapping film is remarkably improved through the functional master batch; and the dispersibility of the lower-layer film raw material and the thermal stability of the lower-layer film material are also improved.

Description

Technical Field

[0001] The present invention relates to the technical field of packaging materials, and in particular to a stretch wrap film and a preparation method thereof. Background Art

[0002] Polyethylene (PE) stretch wrap film has the advantages of strong tensile strength, large elongation, good self-adhesion, puncture resistance and tear resistance. It can be used for manual wrapping film or machine wrapping film. It can wrap objects into a whole to prevent them from scattering and collapsing during transportation. It is widely used in cargo pallet packaging, such as industrial enterprises, food processing, logistics packaging and other industries. It plays a role in fixing, waterproofing, dustproofing and protecting the wrapped objects (anti-damage) for the packaged products. However, in actual use, conventional PE stretch wrap film has poor uniformity, low tensile strength, poor puncture resistance and tear resistance, and cannot meet large-scale applications. Summary of the invention

[0003] In view of the above problems, the present invention provides a stretch wrap film and a preparation method thereof, which significantly improves the mechanical properties of the stretch wrap film, especially the stretchability and puncture resistance, by limiting the raw material components and their ratios.

[0004] In order to solve the above technical problems, the technical solution provided by the present invention is: In a first aspect, the present invention provides a stretch wrap film, comprising an upper film and a lower film; The upper film 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 film 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 with the prior art, the stretch wrap film provided by the present invention comprises an upper film raw material comprising metallocene linear low-density polyethylene (MLLDPE) and linear medium-density polyethylene (LMDPE) in a specific ratio, which synergistically improve the mechanical properties and processing properties of the stretch wrap film; a lower film raw material comprising linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE) and functional masterbatch in a specific ratio, which synergistically effectively improve the elasticity, toughness and tensile strength of the stretch wrap film, and the functional masterbatch not only significantly increases the mechanical properties of the stretch wrap film, but also increases the dispersibility of the lower film raw material and the thermal stability of the lower film material, effectively solving the stiffness problem of the wrap film, and enabling the stretch wrap film to have good toughness and not be easily deformed.

[0006] Among the raw materials of stretch wrap film, LLDPE has high softening temperature and melting temperature, high strength, good toughness, high rigidity, good heat resistance and cold resistance, and also has good environmental stress cracking resistance, impact strength, tear strength and other properties. Metallocene is added to it to form MLLDPE. Since metallocene is a highly stereoregular polymer with a very narrow molecular weight distribution, the physical properties of the polymer can be accurately controlled, and the tensile strength, puncture resistance and tear resistance of the stretch wrap film can be significantly improved; LMDPE can increase the density of the upper film material, improve its orientation, increase the transparency of the wrap film, and improve the comprehensive performance of the film layer. At the same time, it can also reduce the friction coefficient of the non-sticky layer of the wrap film to avoid adhesion between packaged goods; since the molecular weight distribution of metallocene is narrow, the processing range is also narrow, and the processing conditions are difficult to control, adding a certain amount of MDPE to it can reduce the viscosity of the melt, make it easier to regulate the processing process, and increase the flatness of the stretch wrap film. Among the functional masterbatches, metallocene polyethylene (MPE) can significantly improve the tensile strength, puncture resistance and tear resistance of the stretch wrap film, the elastomer can significantly improve the elasticity and toughness of the stretch wrap film, and the sodium polyacrylate modified talc powder as a filler can significantly improve the mechanical properties of the stretch wrap film. The maleic anhydride grafted elastomer and the sodium polyacrylate modified talc powder are compounded to improve the dispersibility of the sodium polyacrylate modified talc powder through the soft-encapsulated hard core-shell structure.

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

[0008] The present invention further improves the synergistic effect of each raw material by limiting the raw material components and proportions of the functional masterbatch. Talc is a rigid particle that can significantly improve the mechanical strength of the stretch wrap film. However, its compatibility with the resin matrix is ​​extremely poor. Direct addition will not only fail to improve its mechanical strength, but will cause stratification due to poor dispersibility, thereby reducing the overall performance of the stretch wrap film. The present invention uses sodium polyacrylate to modify talc, which can improve the suspension stability of talc, improve the compatibility of the talc surface with other components, and then improve the dispersion homogeneity of talc, and long-term storage will not cause stratification or sedimentation; maleic anhydride grafted elastomer can not only improve the toughness of the stretch wrap film, but also significantly improve the compatibility of sodium polyacrylate modified talc with the resin matrix, so that the sodium polyacrylate modified talc can be better dispersed in the resin matrix to play its role.

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

[0010] Preferably, the preparation method of the sodium polyacrylate modified talc comprises the following steps: The sodium polyacrylate aqueous solution is fluidized and sprayed on the surface of the talc powder, and then dried to obtain the sodium polyacrylate modified talc powder.

[0011] Further preferably, the particle size of the talc is 600 mesh to 800 mesh.

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

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

[0014] Preferably, 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.

[0015] Further preferably, the tackifier includes tackifying masterbatch ZH-102.

[0016] In the present invention, the tackifying masterbatch ZH-102 has good lap adhesion and peel adhesion, can improve the elongation, glossiness and transparency of the stretch wrap film, can make the wrap film have a certain adhesive effect, and has good surface looseness, and has a better packaging protection effect on the goods.

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

[0018] Further preferably, the dispersant comprises at least one of carboxymethyl cellulose, polyacrylamide or guar gum.

[0019] Further preferably, the preparation method of the functional masterbatch comprises the following steps: S1, weighing various raw materials according to the designed ratio, mixing sodium polyacrylate modified talc powder and maleic anhydride grafted elastomer, plasticizing, and thinning to obtain fine particles; S2, mixing the fine particles with metallocene polyethylene, elastomer, tackifier, antioxidant and dispersant, melt-extruding and granulating to obtain functional masterbatch.

[0020] The preparation method of the functional masterbatch provided by the present invention comprises the following steps: firstly plasticizing the sodium polyacrylate modified talc powder and the maleic anhydride grafted elastomer, the two of which can form a soft-encapsulated hard core-shell structure, thereby further improving the compatibility of the sodium polyacrylate modified talc powder with the resin matrix, and the maleic anhydride grafted elastomer can also improve the subsequent compatibility with polyethylene; and then mixing with the remaining raw materials for granulation, thereby obtaining a functional masterbatch with excellent performance, which is beneficial to improving the comprehensive performance of the subsequent stretch wrapping film.

[0021] More preferably, in S1, the temperature of the plasticizing is 125°C to 135°C, and the plasticizing time is 10 min to 15 min.

[0022] More preferably, in S2, the melt extrusion adopts a twin-screw extruder, the heating temperature of the screw extruder is 180° C. to 205° C., and the main engine speed is 90 rpm to 110 rpm.

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

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

[0025] In actual use, at least 2 layers of film can basically meet the use requirements. By using 4 layers of film, the structure of the upper and lower films can be strengthened, and a more optimized effect can be achieved through better adjustment of raw materials. By using the same raw material components and proportions for reinforcement, it can ensure that the stretch wrap film can avoid collateral damage as much as possible after being torn, sheared and other defects, and form a certain clamping effect between the layers, so that the product's tear resistance and puncture resistance are better.

[0026] In a second aspect, the present invention provides a method for preparing a stretch wrap film, comprising the following steps: Sa, weighing the raw materials of the upper film and the lower film according to the designed ratio, and mixing the raw materials of the upper film evenly to obtain a first mixed material; and mixing the raw materials of the lower film evenly to obtain a second mixed material; Sb, extruding the first mixed material and the second mixed material through a screw extruder at high temperature to obtain upper film plastic particles and lower film plastic particles; Sc, placing the upper film plastic particles and the lower film plastic particles into corresponding chambers of a casting machine respectively, and performing casting to form a film to obtain a stretch wrap film.

[0027] The present invention adopts a casting process to prepare the stretch wrap film, the preparation process is simple and easy, and can be mass-produced. In addition, the stretch wrap film prepared by the casting process can achieve mechanical strength and ductility comparable to or even better than the stretch wrap film prepared by the existing blow molding process.

[0028] Preferably, the method for preparing the stretch wrap film comprises the following steps: Sa, weigh the raw materials of the outer film, the upper film, the lower film and the inner film according to the designed ratio, mix the raw materials of the upper film evenly to obtain a first mixture; mix the raw materials of the lower film evenly to obtain a second mixture; mix the raw materials of the outer film evenly to obtain a third mixture; mix the raw materials of the inner film evenly to obtain a fourth mixture; Sb, extruding the first mixed material, the second mixed material, the third mixed material and the fourth mixed material through a screw extruder at high temperature to obtain upper film plastic particles, lower film plastic particles, outer film plastic particles and inner film plastic particles; Sc, the outer film plastic particles, the upper film plastic particles, the lower film plastic particles and the inner film plastic particles are respectively placed in corresponding chambers of a casting machine to perform casting to form a film, thereby obtaining a stretch wrap film.

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

[0030] Preferably, in Sc, the temperature of the film casting is 250° C. to 280° C., and the time is 22 h to 26 h.

[0031] The invention can ensure smooth film casting and improve work efficiency by controlling the heating temperature of the screw extruder and the temperature of the film casting.

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

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

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

[0035] The present invention can further ensure the comprehensive performance of the stretch wrap film by limiting the temperature of the cast cooling roller; the winding tension will affect the flatness and winding tightness of the stretch wrap film, and if the winding tension is too large, stress will remain in the stretch wrap film, causing the elongation and other properties of the stretch wrap film to decrease, which is likely to cause film breakage. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution 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 understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] The present invention does not require the specific types of the raw materials. In the embodiments and comparative examples, MLLDPE uses Dow Chemical ELITE5500G, and LMDPE uses Dow AXELERON TM FO 8864 BK, LLDPE uses DowDuPont AT 6101, MDPE uses Chevron Phillips HHM TR-130, MPE uses ExxonMobil 4518CB, and the tackifier uses the tackifier masterbatch ZH-102 from Tianjin Zeheng Packaging Products Co., Ltd. Other materials are commercially available unless otherwise specified.

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

[0039] The preparation method of the stretch wrap film comprises the following steps: S1, preparation of sodium polyacrylate modified talc: A 10 wt % sodium polyacrylate aqueous solution was fluidized and sprayed on the surface of 800 mesh talc powder, the mass ratio of the sodium polyacrylate aqueous solution to the talc powder was 8:100, and the mixture was dried to obtain sodium polyacrylate modified talc powder.

[0040] S2, preparation of functional masterbatch: S2-1, weigh all raw materials according to the designed ratio, mix sodium polyacrylate modified talc and maleic anhydride grafted linear low-density polyethylene, plasticize at 130°C for 13 minutes, and thinly slice to obtain fine particles; S2-2, mix the fine particles with metallocene polyethylene, elastomer, thickening masterbatch ZH-102, antioxidant and dispersant, put into a twin-screw extruder with a main engine speed of 100 rpm, melt-extrude and granulate at 180°C~205°C to obtain functional masterbatch.

[0041] S3, preparing a mixture: Weigh the raw materials of the outer film, upper film, lower film and inner film according to the designed ratio, mix the raw materials of the upper film evenly to obtain the first mixture; mix the raw materials of the lower film evenly to obtain the second mixture; mix the raw materials of the outer film evenly to obtain the third mixture; mix the raw materials of the inner film evenly to obtain the fourth mixture.

[0042] S4, preparing plastic particles: The first mixture, the second mixture, the third mixture and the fourth mixture are respectively extruded at high temperature through a screw extruder (heating temperature is 195°C~215°C), and 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 film plastic particles, upper film plastic particles, lower film plastic particles and inner film plastic particles are respectively placed in the corresponding chambers of the casting machine, cast at 270°C for 23 hours to form a film, cooled by a 25°C casting cooling roller, slit, wound (tension is less than 5kg), formed and packed to obtain the stretch wrapping film.

[0044] Example 2 This embodiment provides a stretch wrap film, which is 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 film is composed of the following raw materials in parts by weight: 29 parts of metallocene linear low-density polyethylene and 4 parts of linear medium-density polyethylene; The upper film is composed of the following raw materials in parts by weight: 29 parts of metallocene linear low-density polyethylene and 4 parts of linear medium-density polyethylene; The lower film is composed of the following raw materials in parts by weight: 38 parts of linear low-density polyethylene, 7 parts of medium-density polyethylene and 65 parts of functional masterbatch; The inner layer film is composed of the following raw materials in parts by weight: 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 percentage by weight: 28% metallocene polyethylene, 50% elastomer (EVA), 2% sodium polyacrylate modified talc, 10% maleic anhydride grafted ethylene-butadiene-styrene copolymer, 24% tackifier masterbatch ZH-10, 3% antioxidant (equal weight of 1076 and 242) and 3% dispersant (polyacrylamide).

[0045] The preparation method of the stretch wrap film comprises the following steps: S1, preparation of sodium polyacrylate modified talc: A 11 wt % sodium polyacrylate aqueous solution was fluidized and sprayed on the surface of 700 mesh talc powder, the mass ratio of the sodium polyacrylate aqueous solution to the talc powder was 7:100, and the mixture was dried to obtain sodium polyacrylate modified talc powder.

[0046] S2, preparation of functional masterbatch: S2-1, weigh all raw materials according to the designed ratio, mix the sodium polyacrylate modified talc and the maleic anhydride grafted ethylene-butadiene-styrene copolymer, plasticize at 130°C for 13 minutes, and thinly slice to obtain fine particles; S2-2, mix the fine particles with metallocene polyethylene, elastomer, thickening masterbatch ZH-102, antioxidant and dispersant, put into a twin-screw extruder with a main engine speed of 100 rpm, melt-extrude and granulate at 180°C~205°C to obtain functional masterbatch.

[0047] S3, preparing a mixture: Weigh the raw materials of the outer film, upper film, lower film and inner film according to the designed ratio, mix the raw materials of the upper film evenly to obtain the first mixture; mix the raw materials of the lower film evenly to obtain the second mixture; mix the raw materials of the outer film evenly to obtain the third mixture; mix the raw materials of the inner film evenly to obtain the fourth mixture.

[0048] S4, preparing plastic particles: The first mixture, the second mixture, the third mixture and the fourth mixture are respectively extruded at high temperature through a screw extruder (heating temperature is 195°C~215°C), and 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 film plastic particles, upper film plastic particles, lower film plastic particles and inner film plastic particles are respectively placed in the corresponding chambers of the casting machine, cast at 260°C for 24 hours to form a film, cooled by a 24°C casting cooling roller, slit, wound (tension is less than 5kg), formed and packed to obtain the stretch wrapping film.

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

[0051] The preparation method of the stretch wrap film comprises the following steps: S1, preparation of sodium polyacrylate modified talc: 8 wt % sodium polyacrylate aqueous solution was fluidized and sprayed on the surface of 700 mesh talc powder, the mass ratio of the sodium polyacrylate aqueous solution to the talc powder was 10:100, and dried to obtain sodium polyacrylate modified talc powder.

[0052] S2, preparation of functional masterbatch: S2-1, weigh all raw materials according to the designed ratio, mix the sodium polyacrylate modified talc and the maleic anhydride grafted ethylene-butadiene-styrene copolymer, plasticize at 125°C for 15 minutes, and thinly slice to obtain fine particles; S2-2, mix the fine particles with metallocene polyethylene, elastomer, thickening masterbatch ZH-102, antioxidant and dispersant, put into a twin-screw extruder with a main engine speed of 90 rpm, melt extrude and granulate at 180°C~205°C to obtain functional masterbatch.

[0053] S3, preparing a mixture: Weigh the raw materials of the outer film, upper film, lower film and inner film according to the designed ratio, mix the raw materials of the upper film evenly to obtain the first mixture; mix the raw materials of the lower film evenly to obtain the second mixture; mix the raw materials of the outer film evenly to obtain the third mixture; mix the raw materials of the inner film evenly to obtain the fourth mixture.

[0054] S4, preparing plastic particles: The first mixture, the second mixture, the third mixture and the fourth mixture are respectively extruded at high temperature through a screw extruder (heating temperature is 195°C~215°C), and 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 film plastic particles, upper film plastic particles, lower film plastic particles and inner film plastic particles are respectively placed in the corresponding chambers of the casting machine, cast at 250°C for 26 hours to form a film, cooled by a 20°C casting cooling roller, slit, wound (tension is less than 5kg), formed and packed to obtain the stretch wrapping film.

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

[0057] The preparation method of the stretch wrap film comprises the following steps: S1, preparation of sodium polyacrylate modified talc: A 13 wt % sodium polyacrylate aqueous solution was fluidized and sprayed on the surface of 600 mesh talc powder, the mass ratio of the sodium polyacrylate aqueous solution to the talc powder was 5:100, and the mixture was dried to obtain sodium polyacrylate modified talc powder.

[0058] S2, preparation of functional masterbatch: S2-1, weigh all raw materials according to the designed ratio, mix sodium polyacrylate modified talc and maleic anhydride grafted linear low-density polyethylene, plasticize at 135°C for 10min~15min, and thinly slice to obtain fine particles; S2-2, the fine particles are mixed with metallocene polyethylene, elastomer, thickening masterbatch ZH-102, antioxidant and dispersant, and put into a twin-screw extruder with a main engine speed of 110 rpm, and melt-extruded and granulated at 180°C~205°C to obtain functional masterbatch.

[0059] S3, preparing a mixture: Weigh the raw materials of the outer film, upper film, lower film and inner film according to the designed ratio, mix the raw materials of the upper film evenly to obtain the first mixture; mix the raw materials of the lower film evenly to obtain the second mixture; mix the raw materials of the outer film evenly to obtain the third mixture; mix the raw materials of the inner film evenly to obtain the fourth mixture.

[0060] S4, preparing plastic particles: The first mixture, the second mixture, the third mixture and the fourth mixture are respectively extruded at high temperature through a screw extruder (heating temperature is 195°C~215°C), and 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 film plastic particles, upper film plastic particles, lower film plastic particles and inner film plastic particles are respectively placed in the corresponding chambers of the casting machine, cast at 280°C for 22 hours to form a film, cooled by a 30°C casting cooling roller, slit, wound (tension is less than 5kg), formed and packed to obtain the stretch wrapping film.

[0062] Example 5 This embodiment provides a stretch wrap film, which is 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 film and the lower film are the same as those in Example 1 and will not be described in detail.

[0063] The preparation method of the stretch wrap film comprises the following steps: S1, preparing sodium polyacrylate modified talc: the same as Example 1, no further details are given.

[0064] S2, preparing functional masterbatch: the same as Example 1, no further details are given.

[0065] S3, preparing a mixture: Weigh the raw materials of the upper film and the lower film according to the designed ratio, mix the raw materials of the upper film evenly to obtain a first mixed material; mix the raw materials of the lower film evenly to obtain a second mixed material.

[0066] S4, preparing plastic particles: The first mixed material and the second mixed material are respectively extruded through a screw extruder (heating temperature is 195°C~215°C) at high temperature, and upper film plastic particles and lower film plastic particles are obtained after 24 hours.

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

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

[0069] The preparation method of the stretch wrap film is the same as that of Example 5 and will not be described in detail.

[0070] Comparative Example 1 This comparative example provides a stretch wrap film, which is 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, the upper film, the lower film and the inner film are similar to those of Example 1, except that in the functional masterbatch, the raw material sodium polyacrylate modified talc is replaced with talc of equal mass.

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

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

[0073] The preparation method of the stretch wrap film is similar to that of Example 1, except that: in S2, each raw material is weighed according to the designed ratio, sodium polyacrylate modified talc, metallocene polyethylene, elastomer, tackifier masterbatch ZH-102, antioxidant and dispersant are mixed, and put into a twin-screw extruder with a main engine speed of 100 rpm, melt-extruded and granulated at 180° C. to obtain a 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, which is composed of an upper film and a lower film in a mass ratio of 1:2.9. The raw material components and proportions of the upper film are the same as those in Example 5 and are not repeated here. The lower film is composed of the following raw materials in mass parts: 35 parts of linear low-density polyethylene, 6 parts of medium-density polyethylene, and 264 parts of ExxonMobil VM 610.

[0075] The preparation method of the stretch wrap film comprises the following steps: S1, weighing various raw materials according to the designed ratio, mixing the metallocene linear low-density polyethylene and the linear medium-density polyethylene to obtain a first mixed material; mixing the linear low-density polyethylene, the medium-density polyethylene and ExxonMobil VM 6102 to obtain a second mixed material.

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

[0077] Comparative Example 4 This comparative example provides a stretch wrap film, which is composed of an upper film and a lower film in a mass ratio of 1:2.9. The raw material components and proportions of the upper film are the same as those in Example 5 and are not repeated here. The lower film is composed of the following raw materials in mass parts: 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 stretch wrap film is similar to that of Example 5, except that in S3, the raw material composition and proportion of the lower film are prepared and mixed according to this comparative ratio. The remaining operations are the same as those of Example 5 and will not be described in detail.

[0079] Performance Testing With reference to standards GB / T 6672-2001 and BB / T 0024-2018, the thickness, stretchability, puncture resistance and adhesion of the stretch wrap films of Examples 1 to 6 and Comparative Examples 1 to 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 modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A stretch wrap film, characterized in that: It includes an upper membrane and a lower membrane; The upper film 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 film 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.

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

3. The stretch wrap film according to claim 1 or 2, characterized in that: The elastomer includes at least one of EPDM rubber, EPDM rubber, 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 according to claim 1 or 2, characterized in that: The preparation method of the sodium polyacrylate modified talcum powder comprises the following steps: Fluidizing and spraying the sodium polyacrylate aqueous solution on the surface of talc powder, and drying to obtain sodium polyacrylate modified talc powder; Wherein, the mass ratio of the sodium polyacrylate aqueous solution to the talc powder is (5-10):100; and the mass concentration of the sodium polyacrylate aqueous solution is 8%-13%.

5. The stretch wrap film according to claim 1 or 2, characterized in that: The mass ratio of the upper film to the lower film is 1:(2.5-3.5); An outer film having the same raw material composition and ratio as the upper film is arranged on the side of the upper film away from the lower film, and an inner film having the same raw material composition and ratio as the lower film is arranged on the side of the lower film away from the upper film.

6. The stretch wrap film according to claim 2, characterized in that: The preparation method of the functional masterbatch comprises the following steps: S1, weighing various raw materials according to the designed ratio, mixing sodium polyacrylate modified talc powder and maleic anhydride grafted elastomer, plasticizing, and thinning to obtain fine particles; S2, mixing the fine particles with metallocene polyethylene, elastomer, tackifier, antioxidant and dispersant, melt-extruding and granulating to obtain functional masterbatch.

7. The stretch wrap film according to claim 6, characterized in that: In S1, the plasticizing temperature is 125°C to 135°C, and the plasticizing time is 10min to 15min; In S2, the melt extrusion adopts a twin-screw extruder, the heating temperature of the screw extruder is 180° C. to 205° C., and the main engine speed is 90 rpm to 110 rpm.

8. The method for preparing a stretch wrap film according to any one of claims 1 to 7, characterized in that: The following steps are involved: Sa, weighing the raw materials of the upper film and the lower film according to the designed ratio, and mixing the raw materials of the upper film evenly to obtain a first mixed material; and mixing the raw materials of the lower film evenly to obtain a second mixed material; Sb, extruding the first mixed material and the second mixed material through a screw extruder at high temperature to obtain upper film plastic particles and lower film plastic particles; Sc, placing the upper film plastic particles and the lower film plastic particles into corresponding chambers of a casting machine respectively, and performing casting to form a film to obtain a stretch wrap film.

9. The method for preparing a stretch wrap film according to claim 8, characterized in that: The following steps are involved: Sa, weigh the raw materials of the outer film, the upper film, the lower film and the inner film according to the designed ratio, mix the raw materials of the upper film evenly to obtain a first mixture; mix the raw materials of the lower film evenly to obtain a second mixture; mix the raw materials of the outer film evenly to obtain a third mixture; mix the raw materials of the inner film evenly to obtain a fourth mixture; Sb, extruding the first mixed material, the second mixed material, the third mixed material and the fourth mixed material through a screw extruder at high temperature to obtain upper film plastic particles, lower film plastic particles, outer film plastic particles and inner film plastic particles; Sc, the outer film plastic particles, the upper film plastic particles, the lower film plastic particles and the inner film plastic particles are respectively placed in corresponding chambers of a casting machine to perform casting to form a film, thereby obtaining a stretch wrap film.

10. The method for preparing a stretch wrap film according to claim 8 or 9, characterized in that: In Sb, the heating temperature of the screw extruder is 195°C to 215°C, and the heating time is 22h to 26h; In Sc, the temperature of the film casting is 250°C to 280°C, and the time is 22h to 26h; In Sc, after the cast film forming, the steps of cooling, slitting, winding, forming and packaging are also performed to obtain a stretch wrapping film; the winding tension is less than 8kg.

Images