Melt extrusion process method for preparing polypropylene film

Abstract

According to the melt extrusion process method, melt extrusion equipment is included, the melt extrusion equipment comprises a melt extrusion bin, the inner wall of one end of the melt extrusion bin is connected with a raw material mixing mechanism through a feeding pipe, and a discharging opening is formed in the other end of the melt extrusion bin; one side of the discharging port is connected with a cleaning mechanism through a hinge seat, the other side of the discharging port and the other side of the cleaning mechanism are connected with a buckle at the same time, and an adhesion mechanism is arranged on the cleaning mechanism; the raw material mixing mechanism comprises a mixing bin, a feeding port is formed in the inner wall of the top end of the mixing bin, an inclined groove is formed in the position, located on one side of the feeding port, of the inner wall of the top end of the mixing bin, and a plurality of first protruding blocks are arranged on the inner wall of the inclined groove at equal density; the melt extrusion process method for preparing the polypropylene film, disclosed by the invention, has the effects that large particles can be synchronously treated during uniform mixing, the subsequent melting efficiency is effectively improved, and uniform distribution of raw materials is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of polypropylene film preparation, in particular to a melt extrusion process for preparing a polypropylene film. Background Art

[0002] Polypropylene film is a thermoplastic resin made by polymerization of propylene. There are three configurations: isotactic, atactic and syndiotactic. Industrial products are mainly composed of isotactic. Polypropylene also includes copolymers of propylene and a small amount of ethylene. It is usually a translucent colorless solid, odorless and non-toxic.

[0003] In the process of preparing polypropylene film, the raw materials need to be mixed first, and then transferred to the extrusion die for extrusion molding after melt extrusion. The general melt extrusion equipment will be equipped with a spiral stirring rod at the inlet, which will simultaneously transport the materials while stirring them, so that they can enter the melt extrusion chamber for subsequent heating and other processes. However, during the mixing process, due to the continuous conveying state, the mixing effect is limited, and the function is single, and large particles of materials cannot be crushed, thereby failing to better improve the subsequent melting efficiency. Summary of the invention

[0004] The invention discloses a melt extrusion process for preparing a polypropylene film, aiming to solve the technical problem that a general melt extrusion bin has a limited mixing effect and a single function during the mixing process because it is continuously in a conveying state and cannot crush large particles of material, thereby failing to better improve the subsequent melting efficiency.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A melt extrusion process for preparing a polypropylene film comprises the following specific steps:

[0007] S1: preparing raw material particles for polypropylene film, and uniformly placing them into a melt extrusion device for sequential mixing, melting, and extrusion, and then guiding the mixture into an extrusion die for the film;

[0008] S2: The mixture is extruded by a die head on the extrusion die to give it a preliminary shape to form a continuous film;

[0009] S3: pulling and squeezing by squeezing rollers, and synchronous cooling and shaping by cooling equipment;

[0010] S4: Winding according to customer needs, divided into film rolls of specific weight;

[0011] The melt extrusion equipment in S1 comprises a melt extrusion bin, and the inner wall of one end of the melt extrusion bin is connected to a raw material mixing mechanism through a feed pipe, and the other end of the melt extrusion bin is provided with a discharge port, and one side of the discharge port is connected to a cleaning mechanism through a hinge seat, and the discharge port and the other side of the cleaning mechanism are simultaneously connected with buckles, and the cleaning mechanism is provided with a bonding mechanism;

[0012] The raw material mixing mechanism includes a mixing bin, and a feed port is provided on the top inner wall of the mixing bin, an inclined groove is provided on one side of the feed port on the top inner wall of the mixing bin, and a plurality of first protrusions are provided on the inner wall of the inclined groove at equal density, a circular support plate is movably connected to the bottom inner wall of the mixing bin, and a plurality of stirring blades are fixedly connected to the outer wall of the circular support plate at equal density, a plurality of second protrusions are fixedly connected to the outer wall of one side of the plurality of stirring blades, and a first motor is fixedly connected to the bottom outer wall of the circular support plate.

[0013] A raw material mixing mechanism is provided, in which when the material falls and contacts the rapidly rotating stirring blades, it will rebound on the fan surface and enter the chute for secondary rebound, thereby achieving complete mixing of different particles during the rebound process, and simultaneously breaking up large particles of raw materials under the impact of the first protrusion and the second protrusion, and simultaneously processing large particles during uniform mixing, thereby effectively improving subsequent melting efficiency and ensuring uniform distribution of raw materials.

[0014] In a preferred embodiment, the cleaning mechanism includes an outer sleeve, and the hinge seat and the adhesion mechanism are respectively fixed to the outer walls of both sides of the outer sleeve, and the top inner wall and the bottom inner wall of the outer sleeve are respectively penetrated by limit slide grooves, and the two limit slide grooves are respectively movably engaged with limit sliders, and the top outer wall of the outer sleeve is fixedly connected to a support seat, and a gas rod is fixedly connected to the support seat, and the output end of the gas rod is connected to one of the limit sliders, and the two limit sliders are simultaneously fixedly connected to a first inner support plate, and the first inner support plate is attached to the inner wall of the outer sleeve, one side outer wall of the first inner support plate is fixedly connected to the second inner support plate through a connecting frame, and one side outer wall of the second inner support plate is fixedly connected to multiple heating rollers with equal density, and the outer walls of the multiple heating rollers are simultaneously attached to the inner wall of the discharge port, the outer wall of the first inner support plate is fixedly connected to a second motor, and the output end of the second motor is fixedly connected to the connecting frame.

[0015] By providing a cleaning mechanism, during the melt extrusion process, after a single extrusion is completed, there will generally be a certain amount of residual adhesion at the discharge port, which needs to be manually cleaned. Since the effect of manual cleaning is limited, it may affect the smoothness and extrusion quality of the secondary extrusion. In the cleaning mechanism, through the heating of the heating roller and the second motor driving multiple heating rollers to rotate synchronously along the inner wall of the discharge port, the waste adhered to the discharge port can be heated and melted and then smoothed synchronously, which is convenient for the waste to fall off and ensures the cleaning effect of the discharge port.

[0016] The two gears are connected to each other with a toothed wheel, and the two toothed wheels are connected along the axis of the two gears, and the two toothed wheels are connected along the axis of the two gears respectively.

[0017] By providing an adhesion mechanism, in the adhesion mechanism, after the heating roller rotates and melts for a period of time, the third motor drives the two threaded rods to move outward until they touch the inner wall of the discharge port. Based on the friction of the threaded rods, the molten material can adhere to the surface of the threaded rods. After that, the two threaded rods rotate on their own. At the same time, the second motor drives the overall rotation, so that the waste can be stably connected to the threaded rods. When the gas rod retracts and drives the overall structure to retract, all the waste can be pulled out synchronously to achieve automatic cleaning, thereby further improving the thoroughness of cleaning.

[0018] As can be seen from the above, a melt extrusion process for preparing a polypropylene film comprises the following specific steps: S1: preparing raw material particles for the polypropylene film, and uniformly placing them in a melt extrusion device for sequential mixing, melting, and extrusion, and then guiding the mixture into an extrusion die for the film; S2: extruding the mixture by a die head on the extrusion die to preliminarily shape it to form a continuous film; S3: pulling and extruding by an extrusion roller, and synchronously cooling and shaping by a cooling device; S4: winding according to customer needs, and dividing it into film rolls of specific weight; the melt extrusion device in S1 comprises a melt extrusion bin, and the inner wall of one end of the melt extrusion bin is connected to a raw material mixing bin through a feed pipe. The raw material mixing mechanism comprises a mixing bin, and the other end of the melt extrusion bin is provided with a discharge port, and one side of the discharge port is connected to a cleaning mechanism through a hinge seat, and the other side of the discharge port and the cleaning mechanism are simultaneously connected with buckles, and the cleaning mechanism is provided with an adhesion mechanism; the raw material mixing mechanism comprises a mixing bin, and the top inner wall of the mixing bin is provided with a feed port, the top inner wall of the mixing bin is provided with an inclined groove on one side of the feed port, and the inner wall of the inclined groove is provided with a plurality of first protrusions of equal density, the bottom inner wall of the mixing bin is movably connected with a circular support plate, and the outer wall of the circular support plate is fixedly connected with a plurality of stirring blades of equal density, the outer wall of one side of the plurality of stirring blades is fixedly connected with a plurality of second protrusions, and the bottom outer wall of the circular support plate is fixedly connected with a first motor. The melt extrusion process method for preparing polypropylene film provided by the present invention has the technical effect of being able to simultaneously process large particles during uniform mixing, effectively improving the subsequent melting efficiency, and ensuring the uniform distribution of raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention provides a schematic diagram of the overall structure of a melt extrusion device for a melt extrusion process method for preparing a polypropylene film.

[0020] Figure 2 The present invention provides a schematic structural diagram of a raw material mixing mechanism of a melt extrusion device for a melt extrusion process method for preparing a polypropylene film.

[0021] Figure 3 The present invention provides a schematic diagram of the connection structure of a cleaning mechanism of a melt extrusion device in a melt extrusion process for preparing a polypropylene film.

[0022] Figure 4 The present invention provides a schematic diagram of the internal structure of a cleaning mechanism of a melt extrusion device in a melt extrusion process for preparing a polypropylene film.

[0023] Figure 5 The present invention provides a schematic diagram of the disassembled structure of the adhesion mechanism of the melt extrusion equipment in the melt extrusion process method for preparing a polypropylene film.

[0024] Figure 6The present invention provides a specific flow chart of a melt extrusion process for preparing a polypropylene film.

[0025] In the figure: 1, raw material mixing mechanism; 2, feed pipe; 3, melt extrusion chamber; 4, cleaning mechanism; 5, discharge port; 6, hinge seat; 7, adhesion mechanism; 8, buckle; 101, feed port; 102, chute; 103, first protrusion; 104, stirring fan blade; 105, second protrusion; 106, circular support plate; 107, first motor; 108, mixing chamber; 401, outer sleeve; 402, limit slider; 403, limit slide; 40 4. Gas rod; 405. Support seat; 406. Second motor; 407. First inner support plate; 408. Second inner support plate; 409. Heating roller; 410. Connecting frame; 701. Threaded rod; 702. Rack; 703. Connecting seat; 704. Limiting rod; 705. Face gear; 706. First gear; 707. Double-headed motor; 708. First bearing seat; 709. Third motor; 710. Second bearing seat; 711. Second gear. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0027] The invention discloses a melt extrusion process method for preparing a polypropylene film, which is mainly used in the scenario of preparing a polypropylene film.

[0028] Reference Figure 1-Figure 6A melt extrusion process for preparing a polypropylene film comprises the following specific steps: S1: preparing raw material particles for the polypropylene film, and uniformly placing them into a melt extrusion device for sequential mixing, melting, and extrusion, and then guiding the mixture into an extrusion die for the film; S2: extruding the mixture by a die head on the extrusion die to preliminarily shape it to form a continuous film; S3: pulling and extruding it through an extrusion roller, and synchronously cooling and shaping it through a cooling device; S4: winding it according to customer needs and dividing it into film rolls of specific weights; the melt extrusion device in S1 comprises a melt extruder The press bin 3 is provided with a raw material mixing mechanism 1, and the inner wall of one end of the melt extrusion bin 3 is connected to the raw material mixing mechanism 1 through the feed pipe 2, the other end of the melt extrusion bin 3 is provided with a discharge port 5, and one side of the discharge port 5 is connected to the cleaning mechanism 4 through the hinge seat 6, the discharge port 5 and the other side of the cleaning mechanism 4 are simultaneously connected with a buckle 8, and the cleaning mechanism 4 is provided with a bonding mechanism 7; the raw material mixing mechanism 1 includes a mixing bin 108, and the top inner wall of the mixing bin 108 is provided with a feed port 101, the top inner wall of the mixing bin 108 is located on one side of the feed port 101 and is provided with an inclined groove 102, and the inner wall of the inclined groove 102 is provided with multiple equal density. A first protrusion 103 is provided, and a circular support plate 106 is movably connected to the inner wall of the bottom end of the mixing bin 108, and a plurality of stirring blades 104 are fixedly connected to the outer wall of the circular support plate 106 with equal density, and a plurality of second protrusions 105 are fixedly connected to the outer wall of one side of the plurality of stirring blades 104, and a first motor 107 is fixedly connected to the outer wall of the bottom end of the circular support plate 106. In the raw material mixing mechanism 1, the granular material is placed into the mixing bin 108 through the feed port 101. Since the mixing bin 108 and the stirring blades 104 are both in an inclined state, when the material falls and contacts the rapidly rotating stirring blades 104, It rebounds on the fan surface and enters the chute 102 for secondary rebound, thereby achieving complete mixing of different particles in the rebound process, and synchronously breaking up large particles of raw materials under the impact of the first protrusion 103 and the second protrusion 105. By adjusting the rotation frequency of the first motor 107, low-speed rotation is interspersed with high-speed rotation at a fixed frequency. During the low-speed rotation, part of the raw materials can fall from the gaps in the stirring blades 104 into the melt extrusion chamber 3 for melt extrusion. Therefore, large particles can be processed synchronously during uniform mixing, effectively improving subsequent melting efficiency and ensuring uniform distribution of raw materials.

[0029] Reference Figure 3-Figure 5 In a preferred embodiment, the cleaning mechanism 4 includes an outer sleeve 401, and the hinge seat 6 and the adhesion mechanism 7 are respectively fixed to the outer walls on both sides of the outer sleeve 401, and the top inner wall and the bottom inner wall of the outer sleeve 401 are respectively penetrated by limiting slide grooves 403.

[0030] Reference Figure 3-Figure 5In a preferred embodiment, the two limiting slide grooves 403 are respectively movably connected to the limiting sliders 402, and the top outer wall of the outer sleeve 401 is fixedly connected to the support seat 405, and the support seat 405 is fixedly connected to the gas rod 404, and the output end of the gas rod 404 is connected to one of the limiting sliders 402, and the two limiting sliders 402 are also fixedly connected to the first inner support plate 407, and the first inner support plate 407 is attached to the inner wall of the outer sleeve 401.

[0031] Reference Figure 3-Figure 5 In a preferred embodiment, the outer wall of one side of the first inner support plate 407 is fixedly connected to the second inner support plate 408 through a connecting frame 410, and the outer wall of one side of the second inner support plate 408 is fixedly connected to multiple heating rollers 409 with equal density, and the outer walls of the multiple heating rollers 409 are simultaneously attached to the inner wall of the discharge port 5, and the outer wall of the first inner support plate 407 is fixedly connected to the second motor 406, and the output end of the second motor 406 is fixedly connected to the connecting frame 410. During the melt extrusion process, after a single extrusion is completed, there will generally be a certain amount of residual adhesion at the position of the discharge port 5, which needs to be manually cleaned. Since the effect of manual cleaning is limited, it may affect the smoothness of the secondary extrusion. In order to improve the degree and extrusion quality, in the cleaning mechanism 4, the discharge port 5 is combined with the outer sleeve 401 through the hinge seat 6 and the buckle 8, and the limit slider 402 is moved in the limit slide groove 403 through the extension of the gas rod 404, driving the first inner support plate 407, the connecting frame 410 and the second inner support plate 408 to move along the inner wall of the outer sleeve 401, driving multiple heating rollers 409 to fit the inner wall of the discharge port 5, and the multiple heating rollers 409 are driven by the heating of the heating rollers 409 and the second motor 406 to rotate synchronously along the inner wall of the discharge port 5, so that the waste adhered to the discharge port 5 can be heated and melted and then smoothed synchronously, which is convenient for the waste to fall off and ensures the cleaning effect of the discharge port 5.

[0032] Reference Figure 4 and Figure 5 In a preferred embodiment, the adhesion mechanism 7 includes two connecting seats 703, and the two connecting seats 703 are movably connected to the second inner support plate 408, and the inner walls on the opposite sides of the two connecting seats 703 are respectively fixedly connected with racks 702, and the two racks 702 are simultaneously meshed with the second gear 711.

[0033] Reference Figure 4 and Figure 5 In a preferred embodiment, the outer walls on opposite sides of the two connecting seats 703 are respectively fixedly connected with limiting rods 704, and the two limiting rods 704 are movably inserted into the corresponding racks 702, and the outer wall on one side of the second gear 711 is fixedly connected with the third motor 709.

[0034] Reference Figure 4 and Figure 5In a preferred embodiment, the third motor 709 is arranged on the second bearing seat 710, and the second bearing seat 710 is fixed to the outer wall of one side of the second inner support plate 408, and the inner walls of the same side of the two connecting seats 703 are respectively movably connected with the threaded rod 701, and one end of the threaded rod 701 is respectively fixedly connected with the face gear 705.

[0035] Reference Figure 4 and Figure 5 In a preferred embodiment, the outer walls of the same side of the two face gears 705 are respectively meshed with the first gear 706, and the two first gears 706 are fixedly connected to the two output ends of the double-headed motor 707 at the same time, and the two face gears 705 are movably connected to the first bearing seat 708 at the same time, and the first bearing seat 708 is fixed on the first inner support plate 407. In the bonding mechanism 7, after the heating roller 409 rotates and melts for a period of time, the second gear 711 is driven to rotate by the third motor 709, and the two threaded rods 701 are moved to the opposite direction by the movement of the rack 702. The threaded rod 701 moves outward until it contacts the inner wall of the discharge port 5. Based on the friction of the threaded rod 701, the molten material can adhere to the surface of the threaded rod 701. At the same time, as the double-headed motor 707 drives the two first gears 706 to rotate, the two threaded rods 701 are driven to rotate synchronously through the engagement with the face gear 705. At the same time, under the action of the second motor 406 driving the overall rotation, the waste can be stably connected to the threaded rod 701. When the air rod 404 retracts and drives the overall structure to retract, all the waste can be pulled out synchronously to achieve automatic cleaning, thereby further improving the thoroughness of cleaning.

[0036] Working principle: During the preparation process, when the raw materials are mixed by the raw material mixing mechanism 1, the granular materials are placed into the mixing bin 108 through the feed port 101. Since the mixing bin 108 and the stirring blades 104 are both in an inclined state, when the material falls and contacts the rapidly rotating stirring blades 104, it will rebound on the fan surface and enter the chute 102 for a second rebound, thereby achieving complete mixing of different particles during the rebound process, and synchronously breaking up the large granular raw materials under the impact of the first protrusion 103 and the second protrusion 105. By adjusting the rotation frequency of the first motor 107, the low-speed rotation is interspersed with the high-speed rotation at a fixed frequency. During the low-speed rotation, part of the raw materials can fall from the gap between the stirring blades 104 into the melt extrusion chamber 3 for melt extrusion. Thus, large particles can be processed simultaneously during uniform mixing, effectively improving the subsequent melting efficiency and ensuring the uniform distribution of the raw materials. During the melt extrusion process, after a single extrusion is completed, there will generally be a certain amount of residual adhesion at the discharge port 5, which requires manual cleaning. Since the effect of manual cleaning is limited, it may affect the smoothness and extrusion quality of the secondary extrusion. In the cleaning mechanism 4, the discharge port 5 is combined with the outer sleeve 401 through the hinge seat 6 and the buckle 8, and the limit is made by extending the gas rod 404. The slider 402 moves in the limiting slide groove 403, driving the first inner support plate 407, the connecting frame 410 and the second inner support plate 408 to move along the inner wall of the outer sleeve 401, driving multiple heating rollers 409 to fit the inner wall of the discharge port 5. The heating of the heating rollers 409 and the second motor 406 drive the multiple heating rollers 409 to rotate synchronously along the inner wall of the discharge port 5, so that the waste adhered to the discharge port 5 can be heated and melted and then smoothed synchronously, which is convenient for the waste to fall off and ensures the cleaning effect of the discharge port 5. In the adhesion mechanism 7, after the heating rollers 409 rotate and melt for a period of time, the third motor 709 drives the second gear 711 to rotate , the two threaded rods 701 are moved outward by the movement of the rack 702 until they touch the inner wall of the discharge port 5. Based on the friction of the threaded rod 701, the molten material can adhere to the surface of the threaded rod 701. At the same time, as the double-headed motor 707 drives the two first gears 706 to rotate, the two threaded rods 701 are driven to rotate synchronously through the engagement with the face gear 705. At the same time, under the action of the second motor 406 driving the overall rotation, the waste can be stably connected to the threaded rod 701. When the air rod 404 retracts and drives the overall structure to retract, all the waste can be pulled out synchronously to achieve automatic cleaning, thereby further improving the thoroughness of cleaning.

[0037] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A melt extrusion process for preparing a polypropylene film, characterized in that: The specific steps include: S1: preparing raw material particles for polypropylene film, and uniformly placing them into a melt extrusion device for sequential mixing, melting, and extrusion, and then guiding the mixture into an extrusion die for the film; S2: The mixture is extruded by a die head on the extrusion die to give it a preliminary shape to form a continuous film; S3: pulling and squeezing by squeezing rollers, and synchronous cooling and shaping by cooling equipment; S4: Winding according to customer needs, divided into film rolls of specific weight; The melt extrusion equipment in S1 comprises a melt extrusion bin (3), wherein the inner wall of one end of the melt extrusion bin (3) is connected to a raw material mixing mechanism (1) via a feed pipe (2), a discharge port (5) is provided at the other end of the melt extrusion bin (3), and one side of the discharge port (5) is connected to a cleaning mechanism (4) via a hinge seat (6), a buckle (8) is connected to the other side of the discharge port (5) and the cleaning mechanism (4), and a bonding mechanism (7) is provided on the cleaning mechanism (4); The raw material mixing mechanism (1) comprises a mixing bin (108), wherein the top inner wall of the mixing bin (108) is provided with a material inlet (101), the top inner wall of the mixing bin (108) is provided with an inclined groove (102) on one side of the material inlet (101), and the inner wall of the inclined groove (102) is provided with a plurality of first protrusions (103) at equal density, the bottom inner wall of the mixing bin (108) is movably connected with a circular support plate (106), and the outer wall of the circular support plate (106) is fixedly connected with a plurality of stirring blades (104) at equal density, the outer wall of one side of the plurality of stirring blades (104) is fixedly connected with a plurality of second protrusions (105), and the bottom outer wall of the circular support plate (106) is fixedly connected with a first motor (107).

2. The melt extrusion process for preparing a polypropylene film according to claim 1, characterized in that: The cleaning mechanism (4) comprises an outer sleeve (401), and the hinge seat (6) and the bonding mechanism (7) are respectively fixed to the outer walls on both sides of the outer sleeve (401), and the top inner wall and the bottom inner wall of the outer sleeve (401) are respectively penetrated by limited sliding grooves (403).

3. The melt extrusion process for preparing a polypropylene film according to claim 2, characterized in that: The two limiting slide grooves (403) are respectively movably connected to the limiting sliders (402), and the top outer wall of the outer sleeve (401) is fixedly connected to a support seat (405), and the support seat (405) is fixedly connected to a gas rod (404), and the output end of the gas rod (404) is connected to one of the limiting sliders (402), and the two limiting sliders (402) are simultaneously fixedly connected to a first inner support plate (407), and the first inner support plate (407) is in contact with the inner wall of the outer sleeve (401).

4. The melt extrusion process for preparing a polypropylene film according to claim 3, characterized in that: An outer wall on one side of the first inner support plate (407) is fixedly connected to a second inner support plate (408) via a connecting frame (410), and an outer wall on one side of the second inner support plate (408) is fixedly connected to a plurality of heating rollers (409) at equal density, and the outer walls of the plurality of heating rollers (409) are simultaneously attached to the inner wall of the discharge port (5), and a second motor (406) is fixedly connected to the outer wall of the first inner support plate (407), and an output end of the second motor (406) is fixedly connected to the connecting frame (410).

5. The melt extrusion process for preparing a polypropylene film according to claim 4, characterized in that: The bonding mechanism (7) comprises two connecting seats (703), and the two connecting seats (703) are movably engaged in the second inner support plate (408), and the inner walls on opposite sides of the two connecting seats (703) are respectively fixedly connected with racks (702), and the two racks (702) are simultaneously meshed with a second gear (711).

6. The melt extrusion process for preparing a polypropylene film according to claim 5, characterized in that: The outer walls on opposite sides of the two connecting seats (703) are respectively fixedly connected with limiting rods (704), and the two limiting rods (704) are movably inserted into the corresponding racks (702), and the outer wall on one side of the second gear (711) is fixedly connected with a third motor (709).

7. A melt extrusion process for preparing a polypropylene film according to claim 6, characterized in that: The third motor (709) is arranged on the second bearing seat (710), and the second bearing seat (710) is fixed to the outer wall of one side of the second inner support plate (408), and the inner walls of the same side of the two connecting seats (703) are respectively movably connected with a threaded rod (701), and one end of the threaded rod (701) is respectively fixedly connected with a face gear (705).

8. The melt extrusion process for preparing a polypropylene film according to claim 7, characterized in that: The outer walls of the same side of the two face gears (705) are respectively meshed with first gears (706), and the two first gears (706) are simultaneously fixedly connected to the two output ends of the double-headed motor (707), and the two face gears (705) are simultaneously movably connected to the first bearing seat (708), and the first bearing seat (708) is fixed to the first inner support plate (407).

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