Tensile polypropylene film and preparation method thereof

Abstract

The invention provides a tensile polypropylene film and a preparation method thereof, and relates to the technical field of polymer films. The tensile polypropylene film is of a five-layer structure and sequentially comprises a polypropylene anti-sticking layer, a polypropylene anti-static layer, a polypropylene tensile core layer, a polypropylene anti-static layer and a polypropylene anti-sticking layer from top to bottom, and the polypropylene tensile core layer is prepared from the following raw materials in percentage by weight: 98-99% of homo-polypropylene resin, 1-3% of polypropylene anti-static layer, 1-3% of polypropylene anti-sticking layer, 1-3% of polypropylene anti-static layer and 1-3% of polypropylene anti-sticking layer. 0.5%-1% of silicate clay; and 0.5%-1% of fishbone-shaped carbon nanofibers. The preparation method comprises the steps of burdening, multi-layer co-extrusion, longitudinal stretching and transverse stretching of a casting piece, corona treatment and the like. According to the invention, a five-layer structure and a core-layer double-reinforced filler technology are adopted, resin modification is not needed, and the cable has high tensile property, antistatic property and anti-adhesion property; the multi-layer co-extrusion and two-way stretching process shortens the period and improves the product consistency, raw materials are easy to obtain, the process is controllable, and the method is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of polymer film technology, and in particular to a tensile polypropylene film and its preparation method. Background Technology

[0002] Polypropylene film has advantages such as being lightweight and transparent, having good gloss and moisture barrier properties, high mechanical strength, and good dimensional stability. It is an important polymer film material and is widely used in the field of food flexible packaging.

[0003] Chinese invention application (title: "A Method for Producing a Tensile High-Barrier Polypropylene Film", publication number: CN109233105A, publication date: 20190118) discloses a method for producing a tensile high-barrier polypropylene film. The method involves coupling isotactic polypropylene with terminal hydroxyl groups to polyethylene glycol monomethyl ether using isophorone diisocyanate as a coupling agent to prepare isotactic polypropylene-b-polyethylene glycol diblocks. This synthetic technique is convenient to implement, low in cost, and highly efficient. The raw materials used are simple, readily available, and inexpensive. The method is inexpensive, using isotactic polypropylene-b-polyethylene glycol diblock copolymer as a compatibilizer for isotactic polypropylene and polyvinyl alcohol. Polyvinyl alcohol has excellent oxygen barrier properties, and the isotactic polypropylene-b-polyethylene glycol diblock copolymer as a compatibilizer enables good compatibility between isotactic polypropylene and polyvinyl alcohol, allowing the polyvinyl alcohol phase to be uniformly dispersed in polypropylene resin, forming a subcontinuous phase or lamellar structure, thereby significantly improving the barrier properties of the blend film. The selection of clay and ceramic whiskers to blend with copolymerized polypropylene effectively improves the tensile strength of the film.

[0004] However, this production method does not specify the final tensile strength of the polypropylene film, and it requires prior modification of the hydroxyl-terminated isotactic polypropylene, making the production process lengthy. Summary of the Invention

[0005] This invention aims to provide a tensile-strength polypropylene film and its preparation method. Through a five-layer structural partitioning design and a core layer of double-reinforced fillers, the overall tensile strength of the film is significantly improved without prior resin modification. It also possesses antistatic and anti-adhesion properties, making it suitable for the needs of flexible food packaging. The integrated process of multi-layer co-extrusion and biaxial stretching avoids the lengthy modification process of existing technologies and shortens the production cycle. The process parameters are precisely matched with the product composition, ensuring the directional arrangement of fillers and tight interlayer bonding, improving product consistency and stability. Furthermore, the raw materials are readily available and the process is controllable, making it suitable for large-scale industrial production.

[0006] The technical solution adopted in this invention is: A tensile-resistant polypropylene film has a five-layer structure, consisting of, from top to bottom, a polypropylene anti-adhesive layer, a polypropylene antistatic layer, a polypropylene tensile-resistant core layer, a polypropylene antistatic layer, and a polypropylene anti-adhesive layer, with the sum of the layers representing 100% by weight. The raw materials comprising the polypropylene tensile-resistant core layer include: Homopolymer polypropylene resin, 98%~99%; Silicate clay (montmorillonite, kaolinite, illite, or chlorite), 0.5%~1%; Fishbone-shaped carbon nanofibers, 0.5%~1%.

[0007] Furthermore, when the silicate clay is used, it is first heated to 300~400℃ and kept at that temperature for 1~2 hours. Then, it is ball-milled in a vacuum environment while still hot (before ball milling, the zirconia ceramic grinding balls are simultaneously heated to 300℃~400℃ and kept at that temperature for 1~2 hours to prevent the temperature from dropping sharply when the hot silicate clay comes into contact with the low-temperature zirconia ceramic grinding balls, which would affect the hot grinding effect). The temperature drops until the D50 particle size is less than 1nm. Then, it is heated to 300℃~400℃ again and kept at that temperature for 1~2 hours before being cooled and stored for later use. In the prior art, when silicate clay is used as a filler, it is generally used after only simple grinding or drying. However, the present application has the following advantages through two heat treatments and hot grinding: (1) Two heat treatments at 300℃~400℃ can completely remove the moisture, organic impurities and volatile components in the clay, avoiding the generation of bubbles and pinholes due to impurities or water vapor volatilization during subsequent film processing, thus ensuring the density of the film structure. (2) Hot vacuum ball milling combined with precise control of "D50 particle size less than 1nm" can reduce clay brittleness and improve grinding efficiency by utilizing high temperature, and can also prevent clay particles from oxidizing or agglomerating through vacuum environment, achieving uniform dispersion at the nanoscale, laying the foundation for tensile reinforcement of the core layer. (3) Secondary heating and heat preservation can further activate the active sites on the clay surface, improve its interfacial bonding force with homopolymer polypropylene resin and compatibilizer, reduce interfacial defects between filler and resin, and allow the reinforcing filler to play a more efficient role in tensile synergy. (4) The entire process does not require complex modifying reagents, and only achieves performance optimization through temperature, vacuum degree and particle size control. The process is simple and controllable, with low cost, and the treated clay is suitable for multilayer co-extrusion and biaxial stretching processes, which can stably improve the overall mechanical strength and dimensional stability of the film.

[0008] Furthermore, the fishbone-shaped carbon nanofibers are obtained through the following method: using acetylene as the carbon source, nitrogen as the carrier gas, hydrogen as the reducing gas, and nickel foam with a thickness of 0.1 mm to 2 mm as the catalyst, a chemical vapor deposition method is employed, reacting at a temperature of 500℃ to 700℃. Nitrogen and hydrogen are first introduced and held at this temperature for 5 to 8 hours, followed by the introduction of the carbon source and holding at this temperature for 1.5 to 3 hours. The flow rate ratio of carbon source to nitrogen is 1:3 to 1:6, and the flow rate ratio of carbon source to hydrogen is 1:1 to 2:1. This invention, through the above method, can obtain carbon nanofibers with a special microstructure. Their bridging effect with polypropylene directly enhances tensile strength, and their combination with silicate clay significantly optimizes the microporous structure. The two work synergistically to amplify the core layer reinforcement effect and improve interfacial bonding.

[0009] Furthermore, based on a total weight percentage of 100%, the constituent raw materials of the polypropylene antistatic layer include: Homopolymer polypropylene resin, 96%~97%; Antistatic agent, 1%~2%; Compatibilizer, 1%~3%; The amount of homopolymer polypropylene resin used in the polypropylene antistatic layer is less than the amount of homopolymer polypropylene resin used in the polypropylene tensile core layer.

[0010] Furthermore, the antistatic agent is one or more of the following: quaternary ammonium salt antistatic agents, polyetheramine antistatic agents, and polyethylene glycol ester antistatic agents.

[0011] Furthermore, based on a total weight percentage of 100%, the constituent raw materials of the polypropylene anti-adhesive layer include: Homopolymer polypropylene resin, 97.5%~98%; Anti-blocking agent, 0.8%~1.2%; Compatibilizer, 0.8%~1.7%; Wherein, the amount of homopolymer polypropylene resin in the raw materials of the polypropylene anti-adhesive layer is less than or equal to the amount of homopolymer polypropylene resin in the polypropylene tensile core layer, and greater than the amount of homopolymer polypropylene resin in the polypropylene antistatic layer.

[0012] Further, the compatibilizer is one or more of the following: isotactic polypropylene-ethylene copolymer, maleic anhydride-grafted polypropylene, ethylene-vinyl acetate copolymer, polypropylene-grafted glycidyl methacrylate, ethylene-methyl acrylate copolymer, propylene-styrene-maleic anhydride terpolymer, and polyolefin elastomer-grafted maleic anhydride.

[0013] Furthermore, the anti-blocking agent is one or more of silica, talc, calcium carbonate, and synthetic silicates.

[0014] Furthermore, the thicknesses of the polypropylene anti-adhesive layer, the polypropylene antistatic layer, and the polypropylene tensile core layer are 1μm~1.5μm, 1μm~1.5μm, and 10μm~50μm, respectively.

[0015] Based on the same inventive concept, the present invention also provides a method for preparing a tensile polypropylene film to obtain the tensile polypropylene film as described above, comprising the following steps: Step S1: Prepare the raw materials for each layer, and then use a multi-layer co-extrusion equipment to extrude and cool to form a cast sheet; wherein, the extruder temperature corresponding to the polypropylene anti-stick layer is 180℃~230℃, the extruder temperature corresponding to the polypropylene antistatic layer is 210℃~250℃, and the extruder temperature corresponding to the polypropylene tensile core layer is 210℃~250℃. Step S2: Preheat the casting sheet and stretch it longitudinally on a casting machine; wherein the preheating temperature is 100℃~125℃, the stretching temperature is 100℃~125℃, and the longitudinal stretching ratio is 4~6 times. Step S3: Continue to stretch laterally on the casting machine; wherein the preheating temperature is 160℃~180℃, the stretching temperature is 140℃~165℃, the annealing temperature is 165℃~175℃, and the maximum stretching magnification is 8~11 times. Step S4: Corona treatment is performed on both sides of the film product obtained in step S3, and then the film is wound up to obtain a tensile polypropylene film.

[0016] The beneficial effects of this invention are: 1. This invention provides a tensile-strength polypropylene film, which, through optimized five-layer structural design and the composition of raw materials for each layer, has significant advantages over existing technologies (CN109233105A): Firstly, it explicitly uses silicate clay and fishbone-shaped carbon nanofibers as the core layer dual-reinforcing fillers, synergistically combining the high proportion (96%~99%) of homopolymer polypropylene resin and the core layer thickness advantage (5μm~50μm), significantly improving the overall tensile strength of the film and solving the defect of existing technologies that do not clearly define tensile strength; Secondly, it eliminates the need for pre-modification of the polypropylene resin, directly integrating it with the fillers in each layer. The gradient design (core layer homopolymer PP content > anti-stick layer > antistatic layer) optimizes strength, simplifies raw material pretreatment, and shortens the production cycle. Thirdly, the five-layer structure has clear functional zones, with the anti-stick layer, antistatic layer, and tensile core layer each performing their respective functions. While ensuring high tensile strength, it also possesses excellent anti-blocking and antistatic effects, meeting the dual requirements of mechanical strength and ease of use for food flexible packaging. Fourthly, compatibilizers are added to each layer to ensure tight bonding between different components and layers, improving film dimensional stability and reliability. Furthermore, the raw materials are simple, readily available, and cost-effective, making it suitable for large-scale applications.

[0017] 2. This invention provides a method for preparing tensile polypropylene film, which has significant advantages over the prior art (CN109233105A): Firstly, it adopts a multi-layer co-extrusion integrated process, eliminating the need for pre-modification of the polypropylene resin, and directly co-extrudes each layer of raw materials, avoiding the lengthy raw material modification process in the prior art, significantly shortening the production cycle and improving production efficiency; secondly, the biaxial stretching process parameters (temperature, stretch ratio) are precisely matched with the composition of each layer, and the stretch ratio of 4-6 times in the longitudinal direction and 8-11 times in the transverse direction can promote the directional arrangement of the core layer reinforcing filler, further... First, the tensile strength advantage is amplified to ensure stable and controllable overall film strength. Second, by precisely controlling the extrusion temperature, stretching preheating, and annealing temperature of each layer, the raw materials of each layer are fully melted and bonded, avoiding interlayer delamination, while controlling the thickness tolerance within a reasonable range to improve product consistency. Third, the end-of-life corona treatment optimizes the film surface properties, adapting to the subsequent processing requirements of food flexible packaging. Moreover, the entire process is simple and controllable, the equipment is highly versatile, the production cost is low, and it is easy to carry out large-scale industrial production, which can stably produce polypropylene films with high tensile strength, antistatic properties, and anti-adhesion properties. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the five-layer structure of the tensile polypropylene film in Example 1. Detailed Implementation

[0020] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0021] The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. To simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Of course, these are merely examples and are not intended to limit the present invention.

[0022] The embodiments of the invention will now be described in detail with reference to the accompanying drawings.

[0023] Example 1

[0024] Pretreatment of silicate clay: Heat to 300℃, hold for 2 hours, and ball mill in a vacuum environment (vacuum degree ≤10Pa) until the D50 particle size is 0.8nm (zirconia ceramic grinding balls are preheated to 300℃ and held for 2 hours), then heat to 300℃ again and hold for 2 hours, and then cool for later use.

[0025] Preparation of fishbone-shaped carbon nanofibers: Acetylene was used as the carbon source, nitrogen as the carrier gas, hydrogen as the reducing gas, and 1.0 mm thick nickel foam as the catalyst, and chemical vapor deposition was used for preparation. The reaction temperature was 600℃. Nitrogen and hydrogen were first introduced and kept at the temperature for 6.5 h, and then the carbon source was introduced and kept at the temperature for 2.2 h. The flow ratio of carbon source to nitrogen was 1:3, and the flow ratio of carbon source to hydrogen was 1:1.

[0026] Ingredients: (1) Polypropylene tensile core layer: 99% homopolymer polypropylene resin, 0.5% silicate clay (montmorillonite), 0.5% fishbone-shaped carbon nanofibers; (2) Polypropylene antistatic layer: 96% homopolymer polypropylene resin, 1% polyethylene glycol stearate, 3% maleic anhydride grafted polypropylene; (3) Polypropylene anti-adhesive layer: 97.5% homopolymer polypropylene resin, 0.8% silica, 1.7% ethylene-vinyl acetate copolymer.

[0027] Preparation: A multi-layer extrusion machine was used to extrude and cool the polypropylene anti-adhesion layer (180℃), the polypropylene antistatic layer (210℃), and the polypropylene tensile core layer (210℃) to form a cast sheet. The cast sheet was preheated to 100℃ and longitudinally stretched four times at 100℃ on a casting machine. It was then preheated to 160℃, transversely stretched eight times at 140℃, annealed at 165℃, and then corona-treated on both sides before being wound up. The film structure is as follows: Figure 1 As shown in the image.

[0028] Finished product testing: longitudinal tensile strength 460MPa, transverse tensile strength 240MPa, longitudinal elongation at break 230%, transverse elongation at break 70%, surface resistivity 1×10⁻⁶. 8 Ω, dynamic friction coefficient (with steel) 0.4, thickness of each layer: polypropylene anti-adhesion layer 1μm, polypropylene antistatic layer 1μm, polypropylene tensile core layer 10μm, total thickness 12μm, thickness tolerance ±0.2μm.

[0029] Example 2

[0030] Silicate clay pretreatment: Heat to 350℃, hold for 1.5h, and ball mill in a vacuum environment (vacuum degree ≤10Pa) until the D50 particle size is 0.5nm (zirconia ceramic grinding balls are preheated to 350℃ and held for 2h). Reheat to 350℃, hold for 1.5h, and cool for later use. Preparation of fishbone-shaped carbon nanofibers: Acetylene was used as the carbon source, nitrogen as the carrier gas, hydrogen as the reducing gas, and 1.0 mm thick nickel foam as the catalyst, and chemical vapor deposition was used for preparation. The reaction temperature was 600℃. Nitrogen and hydrogen were first introduced and kept at the temperature for 6.5 h, and then the carbon source was introduced and kept at the temperature for 2.2 h. The flow ratio of carbon source to nitrogen was 1:4.5, and the flow ratio of carbon source to hydrogen was 1.5:1.

[0031] Ingredients: (1) Polypropylene tensile core layer: 98.5% homopolymer polypropylene resin, 0.75% silicate clay (montmorillonite), 0.75% fishbone-shaped carbon nanofibers; (2) Polypropylene antistatic layer: 96.5% homopolymer polypropylene resin, 1.5% polyethylene glycol stearate, 2% maleic anhydride grafted polypropylene; (3) Polypropylene anti-adhesive layer: 97.75% homopolymer polypropylene resin, 1% silica, 1.25% ethylene-vinyl acetate copolymer.

[0032] Preparation: The polypropylene anti-adhesive layer was extruded and cooled at 205℃, the polypropylene antistatic layer was 230℃, and the polypropylene tensile core layer was 230℃ using a multi-layer extrusion equipment to form a cast sheet; the cast sheet was preheated at 112.5℃ and stretched longitudinally by 5 times at 112.5℃ on a casting machine, then preheated at 170℃, stretched transversely by 9.5 times at 152.5℃, annealed at 170℃, and then corona treated on both sides of the film and wound up.

[0033] Finished product testing: longitudinal tensile strength 480MPa, transverse tensile strength 300MPa, longitudinal elongation at break 220%, transverse elongation at break 75%, surface resistivity 5×10⁻⁶. 7 Ω, dynamic friction coefficient (with steel) 0.45, thickness of each layer: polypropylene anti-adhesion layer 1μm, polypropylene antistatic layer 1μm, polypropylene tensile core layer 27.5μm, total thickness 29.5μm, thickness tolerance ±0.88μm.

[0034] Example 3

[0035] Silicate clay pretreatment: Heat to 400℃, hold for 1 hour, ball mill in a vacuum environment (vacuum degree ≤10Pa) to a D50 particle size of 0.3nm (zirconia ceramic grinding balls are preheated to 400℃ and held for 2 hours), reheat to 400℃, hold for 1 hour, and cool for later use.

[0036] Preparation of fishbone-shaped carbon nanofibers: Acetylene was used as the carbon source, nitrogen as the carrier gas, hydrogen as the reducing gas, and 1.0 mm thick nickel foam as the catalyst, and chemical vapor deposition was used for preparation. The reaction temperature was 700℃. Nitrogen and hydrogen were first introduced and kept at the temperature for 8 h, and then the carbon source was introduced and kept at the temperature for 3 h. The flow ratio of carbon source to nitrogen was 1:6, and the flow ratio of carbon source to hydrogen was 2:1.

[0037] Ingredients: (1) Polypropylene tensile core layer: 98% homopolymer polypropylene resin, 1% silicate clay (montmorillonite), 1% fishbone-shaped carbon nanofibers; (2) Polypropylene antistatic layer: 97% homopolymer polypropylene resin, 5% polyethylene glycol stearate, 5% maleic anhydride grafted polypropylene; (3) Polypropylene anti-adhesive layer: 98% homopolymer polypropylene resin, 1.2% silica, 0.8% ethylene-vinyl acetate copolymer.

[0038] Preparation: The polypropylene anti-adhesive layer was extruded and cooled at 230°C, the polypropylene antistatic layer was extruded at 250°C, and the polypropylene tensile core layer was extruded at 250°C to form a cast sheet. The cast sheet was preheated at 125°C and stretched longitudinally by 6 times at 125°C on a casting machine. It was then preheated at 180°C, stretched transversely by 11 times at 165°C, annealed at 175°C, and then corona treated on both sides of the film before being wound up.

[0039] Finished product testing: longitudinal tensile strength 580MPa, transverse tensile strength 290MPa, longitudinal elongation at break 250%, transverse elongation at break 60%, surface resistivity 8×10⁻⁶. 6 Ω, dynamic friction coefficient (with steel) 0.4, thickness of each layer: polypropylene anti-adhesion layer 1.5μm, polypropylene antistatic layer 1.5μm, polypropylene tensile core layer 50μm, total thickness 53μm, thickness tolerance ±1.59μm.

Claims

1. A tensile polypropylene film, which is a five-layer structure, from top to bottom, polypropylene anti-sticking layer, polypropylene anti-static layer, polypropylene tensile core layer, polypropylene anti-static layer and polypropylene anti-sticking layer, characterized in that, The composition raw materials of the polypropylene tensile core layer include, measured in the sum of weight percentages being 100%: Homopolymer polypropylene resin, 98%-99%; Silicate clay, 0.5%-1%; Fishbone-shaped nanocarbon fiber, 0.5%-1%.

2. The tensile resistant polypropylene film according to claim 1, characterized in that, The silicate clay is heated to 300-400℃ in use, and is treated for 1-2h, then is ball-milled in a vacuum environment while hot until the D50 particle size is less than 1nm, and then is heated to 300-400℃ again, treated for 1-2h, and cooled for standby.

3. The tensile resistant polypropylene film according to claim 1, wherein, The fishbone-shaped nanocarbon fiber is obtained by using chemical vapor deposition method at a temperature of 500-700℃, with acetylene as carbon source, nitrogen as carrier gas, hydrogen as reducing gas, and foam nickel with a thickness of 0.1mm-2mm as catalyst, first introducing nitrogen and hydrogen, and treating for 5-8h, then introducing carbon source and treating for 1.5-3h; wherein, the flow ratio of carbon source to nitrogen is 1:3-1:6, and the flow ratio of carbon source to hydrogen is 1:1-2:

1.

4. The tensile resistant polypropylene film according to any one of claims 1 to 3, wherein The composition raw materials of the polypropylene antistatic layer include, measured in the sum of weight percentages being 100%: Homopolymer polypropylene resin, 96%-97%; Antistatic agent, 1%-2%; Compatibilizer, 1%-3%; The amount of homopolymer polypropylene resin in the polypropylene antistatic layer is less than that in the polypropylene tensile core layer.

5. The tensile resistant polypropylene film according to claim 4, wherein The antistatic agent is one or more of quaternary ammonium salt antistatic agent, polyether amine antistatic agent, and polyethylene glycol ester antistatic agent.

6. The tensile resistant polypropylene film according to claim 4, wherein The composition raw materials of the polypropylene antistatic layer include, measured in the sum of weight percentages being 100%: Homopolymer polypropylene resin, 96%-97%; Antistatic agent, 1%-2%; Compatibilizer, 1%-3%; The amount of homopolymer polypropylene resin in the polypropylene antistatic layer is less than that in the polypropylene tensile core layer.

7. The tensile resistant polypropylene film according to claim 4 or 6, characterized in that, The antistatic agent is one or more of quaternary ammonium salt antistatic agent, polyether amine antistatic agent, and polyethylene glycol ester antistatic agent.

8. The tensile resistant polypropylene film according to claim 6, wherein The composition raw materials of the polypropylene antistatic layer include, measured in the sum of weight percentages being 100%:

9. The tensile resistant polypropylene film according to claim 6, wherein, Homopolymer polypropylene resin, 96%-97%; 10. A process for the production of a tensile resistant polypropylene film to obtain a tensile resistant polypropylene film according to any one of claims 1 to 9, characterized in that Antistatic agent, 1%-2%; Compatibilizer, 1%-3%; The amount of homopolymer polypropylene resin in the polypropylene antistatic layer is less than that in the polypropylene tensile core layer. The antistatic agent is one or more of quaternary ammonium salt antistatic agent, polyether amine antistatic agent, and polyethylene glycol ester antistatic agent. The composition raw materials of the polypropylene antistatic layer include, measured in the sum of weight percentages being 100%: Homopolymer polypropylene resin, 96%-97%; Antistatic agent, 1%-2%; Compatibilizer, 1%-3%; The amount of homopolymer polypropylene resin in the polypropylene antistatic layer is less than that in the polypropylene tensile core layer. The antistatic agent is one or more of quaternary ammonium salt antistatic agent, polyether amine antistatic agent, and polyethylene glycol ester antistatic agent. The thicknesses of the polypropylene anti-adhesion layer, the polypropylene antistatic layer, and the polypropylene tensile core layer are 1-1.5μm, 1-1.5μm, and 10-50μm, respectively. The method comprises the following steps: Step S1, configuring the raw materials of each layer, and then extruding and cooling to form a cast sheet by using a multi-layer co-extrusion device; wherein, the extruder temperature corresponding to the polypropylene anti-adhesion layer is 180-230℃, the extruder temperature corresponding to the polypropylene antistatic layer is 210-250℃, and the extruder temperature corresponding to the polypropylene tensile core layer is 210-250℃. Step S2, preheating the cast sheet and longitudinally stretching on a casting machine; wherein the preheating temperature is 100-125°C, the stretching temperature is 100-125°C, and the longitudinal stretching ratio is 4-6 times; Step S3, continuing to transversely stretch on the casting machine; wherein the preheating temperature is 160-180°C, the stretching temperature is 140-165°C, the annealing temperature is 165-175°C, and the stretching amplification ratio is maximally 8-11 times; Step S4, performing corona treatment on both sides of the film product obtained in Step S3, and then winding to obtain the tensile polypropylene film.

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