Preparation process and device of modified polypropylene foam material

Abstract

The invention relates to the technical field of foaming materials, and particularly discloses a preparation process and device of a modified polypropylene foaming material.The preparation process comprises the steps that polypropylene resin, a performance additive and a foaming agent are sequentially injected into a double-screw extruder body through an injection port in the double-screw extruder body; the polypropylene resin is melted in a temperature interval of 140-200 DEG C, and is plasticized with the modification additive and the foaming agent to form a homogeneous system. According to the invention, polypropylene resin, a performance additive and a foaming agent are directly injected into the twin-screw extruder body, and the input end of the underwater granulator is combined for granulation, so that continuous production of the modified polypropylene foamed particles can be realized, and the production time of the modified polypropylene foamed particles is greatly shortened; and the production quality of the modified polypropylene foaming particles can be guaranteed through the continuous production mode, and the situation that the production quality of the modified polypropylene foaming particles is not uniform is prevented.

Description

Technical Field

[0001] This invention relates to the field of foaming materials technology, and in particular to a preparation process and apparatus for modified polypropylene foaming materials. Background Technology

[0002] Modified polypropylene foam material refers to lightweight, high-strength, heat-insulating, and environmentally friendly polymer foam material obtained by physically or chemically modifying ordinary polypropylene (PP) to improve its bulk strength, thermal stability, and foaming performance, and then through a foaming process.

[0003] Traditional production of modified polypropylene foam requires a reactor to maintain pressure on the raw materials. After the reaction, the raw materials need to be transferred from the reactor before further processing. This intermittent processing method not only increases production time but also leads to inconsistent product quality due to batch processing. A twin-screw extruder combined with an underwater pelletizer can be used for continuous production of modified polypropylene particles. However, when the underwater pelletizer cuts the modified polypropylene, the foam particles may adhere to the blades. This adhesion affects the cutting quality of the modified polypropylene foam. If the machine is stopped for manual cleaning, it increases the workload of the workers and also affects the production speed of the modified polypropylene foam particles. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a process and apparatus for preparing modified polypropylene foam materials.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A process for preparing modified polypropylene foam material involves sequentially adding polypropylene resin, modifying agents, and a foaming agent into the interior of a twin-screw extruder through a filling port. The polypropylene resin melts and plasticizes with the modifying agents and foaming agent within a temperature range of 140-200℃ to form a homogeneous system. The molten homogeneous polypropylene is then extruded from the output end of the twin-screw extruder to the input end of an underwater pelletizer under a pressure of 5-25 MPa. The underwater pelletizer cuts the plastic melt into spherical beads, which are then cooled and shaped in the water pipes of the underwater pelletizer to obtain modified polypropylene foam particles.

[0006] Preferably, the twin-screw extruder body has a length-to-diameter ratio of 240:1. A pentane-based physical foaming agent is injected via a metering pump in the fifth-sixth zone of the twin-screw extruder body. The amount of foaming agent injected is 2-15% of the polymer weight. The residence time of the material in the screw is controlled to be no more than 5 minutes. The modified additives consist of polypropylene resin, silicates, compatibility agents, and coupling agents. The silicates are selected from one or more of montmorillonite, kaolin, Moskva clay, and talc, with a particle size of 800 μm. ~ 4000 mesh, the compatibility additive is maleic anhydride-grafted polypropylene, the coupling agent is titanate coupling agent or silane coupling agent, the cutting speed of the underwater pelletizer is 800-1500 rpm, the particle size of the modified polypropylene foam particles is in the range of 0.8-1.5 mm, and the cooling water is controlled by a chiller circulation system to keep the temperature fluctuation range within +2℃.

[0007] Preferably, the temperatures of each zone of the twin-screw extruder body are set as follows: zone 1 120℃, zone 2 140℃, zone 3 160℃, zone 4 180℃, zone 5 190℃, zone 6 195℃, zone 7 200℃, and die head 200℃. Under the conditions of 0.2-0.35MPa water pressure and 50-70℃ water temperature, the modified polypropylene foam particles obtained by the underwater pelletizer have a moisture content of less than 0.5%.

[0008] A preparation apparatus for modified polypropylene foam material is disclosed. This apparatus is suitable for the aforementioned preparation process. The apparatus includes a twin-screw extruder body. An underwater pelletizer is located at the output end of the twin-screw extruder body. An extrusion head cover is located at the output end of the twin-screw extruder body. A pelletizer head is located at the input end of the underwater pelletizer. A quick connector is located on the pelletizer head, connecting to the extrusion head cover on the side closest to it. An extrusion mechanism is located inside the extrusion head cover. A pelletizing mechanism is located inside the pelletizer head. Two movable rods are movably mounted inside the extrusion head cover. Movable rings are movably mounted on the movable rods, and auxiliary mechanisms are located on the movable rings.

[0009] Preferably, the extrusion mechanism includes an extrusion disc with multiple extrusion holes connected to the output end of the twin-screw extruder body. The pelletizing mechanism includes a drive rod, a cutter disc, and blades. The drive rod is located on the side of the pelletizer head near the extrusion head cover. A fixed threaded rod is located on the end of the drive rod away from the pelletizer head. A fixed sleeve is threaded to the outer side of the fixed threaded rod. A cutter disc is connected to the side of the fixed sleeve away from the drive rod. Multiple blades are evenly distributed on the side of the cutter disc away from the drive rod.

[0010] Preferably, the cutter head has a plurality of fixing holes evenly distributed on the side near the drive rod, and two fixing rods are installed on the outer side of the drive rod. A first slot is formed at the end of the fixing rod facing the cutter head. A first electric telescopic rod is installed at the bottom of the inner wall of the first slot. The telescopic end of the first electric telescopic rod faces the cutter head. A plug-in rod is slidably installed inside the first slot. The end of the plug-in rod near the first electric telescopic rod is connected to the telescopic end of the first electric telescopic rod. The end of the plug-in rod near the cutter head can be inserted into the inside of the fixing hole.

[0011] Preferably, the inner wall of the extrusion head cover has a movable groove near the movable rod, and a movable electric slider is slidably installed inside the movable groove. The movable electric slider is connected to the movable rod on the side near the movable rod. A piezoresistive sensor is installed on the movable rod. A third slot is opened on the side of the movable rod near the movable ring. A rotating threaded rod is rotatably installed inside the third slot. A rotating motor is installed at one end of the movable rod. The output end of the rotating motor movably passes through the end wall of the movable rod and is connected to the rotating threaded rod. A sliding block is slidably installed inside the third slot. The rotating threaded rod threaded through the sliding block. The sliding block is connected to the movable ring on the side near the movable ring.

[0012] Preferably, the auxiliary mechanism includes a scraper, and a displacement groove is provided on the inner wall of the movable ring. Multiple displacement electric sliders are uniformly slidably installed inside the displacement groove. A first electric extension rod is connected to the side of the displacement electric slider facing the center of the movable ring. The extension end of the first electric extension rod faces the center of the movable ring, and the extension end of the first electric extension rod is connected to the scraper.

[0013] Preferably, the scraper has a fourth slot and a fifth slot on the side facing the extrusion disc, a cleaning brush is movably installed inside the fourth slot, and a plug block is slidably installed inside the fifth slot.

[0014] Preferably, the inner wall of the fourth slot is provided with a first sliding groove at both the top and bottom. A first electric slider is slidably installed inside the first sliding groove. The side of the first electric slider close to the cleaning brush is connected to the cleaning brush. A second electric extension rod is installed at the bottom of the inner wall of the fifth slot. The extension end of the second electric extension rod is away from the bottom of the inner wall of the fifth slot. The extension end of the second electric extension rod is connected to the plug block.

[0015] Compared with the prior art, the beneficial effects of the present invention are: In this invention, polypropylene resin, modifying agents, and foaming agents are directly added into the twin-screw extruder body and granulated at the input end of an underwater pelletizer. This method enables continuous production of modified polypropylene foam particles, significantly shortening the production time. Furthermore, the continuous production method ensures the quality of the modified polypropylene foam particles and prevents inconsistencies in their production quality.

[0016] In this invention, a scraper is provided. When it is necessary to clean the modified polypropylene foam particles attached to the blade, the end of the scraper can move against the side of the blade. In this way, the device can automatically clean the modified polypropylene foam particles attached to the blade without opening the extrusion head cover and pelletizer head, reducing the workload of the workers. The operation method of disassembling without stopping the machine ensures the production speed of modified polypropylene foam particles. By sliding the electric slider in the displacement groove, multiple scrapers can move in a circular motion along the movable ring, thereby agitating the modified polypropylene foam particles formed at the extrusion orifice. This effectively prevents the collapse of the foam cells caused by gas escape from the modified polypropylene foam particles, ensuring the stability of the internal structure of the particles. In addition, the shearing action can reduce the local viscosity of the melt, further reducing the risk of clogging and ensuring the stability of continuous production. The plug-in block is inserted into the inside of the fixing hole, and then the cutter head can be rotated by multiple scrapers rotating on the movable ring. When the fixing threaded rod is disengaged from the fixing sleeve, the cutter head is automatically disassembled. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the installation structure of the extrusion head cover, pelletizer head, and quick connector of the present invention; Figure 3 This is a schematic diagram of the drive rod, cutter head, and blade mounting structure of the present invention; Figure 4 This is a schematic diagram of the fixing hole structure of the present invention; Figure 5 This is a schematic diagram of the installation structure of the first electric telescopic pole of the present invention; Figure 6 This is a schematic diagram of the mounting structure of the fixing rod and the plug-in rod of the present invention; Figure 7 This is a schematic diagram of the installation structure of the first electric telescopic pole of the present invention; Figure 8 This is a schematic diagram of the internal structure of the extrusion head cover of the present invention; Figure 9 This is a schematic diagram of the mounting structure of the movable electric slider of the present invention; Figure 10 This is a schematic diagram of the installation structure of the movable ring and movable rod of the present invention; Figure 11 For the present invention Figure 10 Enlarged structural diagram at point B; Figure 12 This is a schematic diagram of the installation structure of the plug block and cleaning brush of the present invention; Figure 13 This is a schematic diagram of the second electric extension rod mounting structure of the present invention; Figure 14 For the present invention Figure 13 Enlarged structural diagram at point C.

[0018] In the diagram: 1. Twin-screw extruder body; 2. Underwater pelletizer; 3. Extrusion head cover; 4. Pelletizer head; 5. Quick connector; 6. Drive rod; 7. Cutter disc; 8. Blade; 9. Fixing rod; 10. Insert rod; 11. Fixing hole; 12. Fixing sleeve; 13. First slot; 14. First electric telescopic rod; 15. Fixing threaded rod; 18. Extrusion disc; 19. Movable ring; 20. Movable rod; 21. Moving chute; 22. Moving electric slider; 23. Piezoresistive sensor; 24. Rotating motor; 25. Third slot; 26. Rotating threaded rod; 27. Sliding block; 28. Displacement chute; 29. ​​Displacement electric slider; 30. First electric extension rod; 31. Scraper; 32. Insert block; 33. Fourth slot; 34. Cleaning brush; 35. Fifth slot; 36. Second electric extension rod; 37. First chute; 38. First electric slider. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] Reference Figure 1-14 A process for preparing modified polypropylene foam material involves sequentially adding polypropylene resin, modifying agents, and a foaming agent into the body of a twin-screw extruder 1 through an inlet. The polypropylene resin melts and plasticizes with the modifying agents and foaming agent within a temperature range of 140-200℃ to form a homogeneous system. The molten homogeneous polypropylene is then extruded from the output end of the twin-screw extruder 1 to the input end of an underwater pelletizer 2 under a pressure of 5-25 MPa. The underwater pelletizer 2 cuts the molten plastic into spherical beads, which are then cooled and solidified in the water pipes of the underwater pelletizer 2 to obtain modified polypropylene foam particles. This continuous production process using the twin-screw extruder and underwater pelletizer 2 significantly shortens the production time and ensures the quality of the modified polypropylene foam particles, preventing inconsistencies in production quality.

[0021] As a technical optimization of the present invention, the twin-screw extruder body 1 has a length-to-diameter ratio of 240:1. A pentane-based physical foaming agent is injected via a metering pump in the fifth-sixth zone of the middle part of the twin-screw extruder body 1. The amount of foaming agent injected is 2-15% of the polymer weight. The residence time of the material in the screw is controlled to be no more than 5 minutes. The modified additives consist of polypropylene resin, silicate, compatibility agent, and coupling agent. The silicate is selected from one or more of montmorillonite, kaolin, Moskva clay, and talc, with a particle size of 800 μm. ~ The material has a mesh size of 4000 mesh, and the compatibility additive is maleic anhydride-grafted polypropylene. The coupling agent is either a titanate coupling agent or a silane coupling agent. The underwater pelletizer 2 has a cutting speed of 800-1500 rpm. The particle size of the modified polypropylene foam particles is in the range of 0.8-1.5 mm. The cooling water is circulated through a chiller system to control temperature fluctuations within +2℃. This design allows the polypropylene resin, modifying additive, and foaming agent to fully mix and react inside the twin-screw extruder body 1, thereby improving the production quality of the modified polypropylene foam particles.

[0022] As a technical optimization of this invention, the temperatures of each zone of the twin-screw extruder body 1 are set as follows: Zone 1 120℃, Zone 2 140℃, Zone 3 160℃, Zone 4 180℃, Zone 5 190℃, Zone 6 195℃, Zone 7 200℃, and the die head 200℃. Under the conditions of 0.2-0.35MPa water pressure and 50-70℃ water temperature, the moisture content of the resulting modified polypropylene foamed particles is less than 0.5%. By designing different temperatures in different zones of the twin-screw extruder body 1, excessive reactions between polypropylene resin, modifying agents, and foaming agents can be prevented, which would affect the production quality of polypropylene foamed particles. The design of water pressure and water temperature allows the modified polypropylene foamed particles to be cooled in situ by water through vaporization and heat absorption after cutting, preventing cell collapse and improving the uniformity of the cell structure.

[0023] A preparation apparatus for modified polypropylene foam material is disclosed. This apparatus is suitable for the aforementioned preparation process. The apparatus includes a twin-screw extruder body 1, an underwater pelletizer 2 at the output end of the twin-screw extruder body 1, an extrusion head cover 3 at the output end of the twin-screw extruder body 1, and a pelletizer head 4 at the input end of the underwater pelletizer 2. A quick connector 5 is provided on the pelletizer head 4, and the quick connector 5 is connected to the extrusion head cover 3 on the side closest to the extrusion head cover 3. An extrusion mechanism is located inside the extrusion head cover 3, and a pelletizing mechanism is located inside the pelletizer head 4. Two movable rods 20 are movably installed inside the extrusion head cover 3, and movable rings 19 are movably installed on the movable rods 20. An auxiliary mechanism is provided on the movable rings 19. The pelletizing mechanism can pelletize the polypropylene, and the auxiliary mechanism can agitate the foam particles, effectively preventing cell collapse caused by gas escape from the modified polypropylene foam particles, ensuring the stability of the internal structure of the particles. Furthermore, it can reduce the local viscosity of the melt through shearing action, further reducing the risk of clogging and ensuring the stability of continuous production.

[0024] As an optimized technical solution of the present invention, the extrusion mechanism includes an extrusion disc 18 with multiple extrusion holes connected to the output end of the twin-screw extruder body 1. The pelletizing mechanism includes a drive rod 6, a cutter disc 7, and blades 8. The drive rod 6 is located on the side of the pelletizer head 4 near the extrusion head cover 3, and a fixed threaded rod 15 is located on the end of the drive rod 6 away from the pelletizer head 4. A fixed sleeve 12 is threadedly connected to the outer side of the fixed threaded rod 15. The cutter disc 7 is connected to the side of the fixed sleeve 12 away from the drive rod 6, and multiple blades 8 are evenly distributed on the side of the cutter disc 7 away from the drive rod 6. The drive rod 6 drives the cutter disc 7 to move and rotate, so that the blades 8 can cut the molten homogeneous polypropylene. The threaded connection between the fixed threaded rod 15 and the fixed sleeve 12 allows for quick disassembly.

[0025] As a technical optimization of the present invention, a plurality of fixing holes 11 are evenly provided on the side of the cutter head 7 near the drive rod 6. Two fixing rods 9 are installed on the outer side of the drive rod 6. A first slot 13 is provided on the end of the fixing rod 9 facing the cutter head 7. A first electric telescopic rod 14 is installed at the bottom of the inner wall of the first slot 13. The telescopic end of the first electric telescopic rod 14 faces the cutter head 7. A plug-in rod 10 is slidably installed inside the first slot 13. The end of the plug-in rod 10 near the first electric telescopic rod 14 is connected to the telescopic end of the first electric telescopic rod 14. The end of the plug-in rod 10 near the cutter head 7 can be inserted into the interior of the fixing hole 11. The first electric telescopic rod 14 drives the plug-in rod 10 to extend, so that the plug-in rod 10 can extend into the interior of the fixing hole 11, thereby increasing the connection stability between the cutter head 7 and the drive rod 6.

[0026] As a technical optimization of the present invention, the inner wall of the extrusion head cover 3 is provided with a movable groove 21 near the movable rod 20. A movable electric slider 22 is slidably installed inside the movable groove 21. The movable electric slider 22 is connected to the movable rod 20 on the side near the movable rod 20. A piezoresistive sensor 23 is provided on the movable rod 20. A third slot 25 is provided on the side of the movable rod 20 near the movable ring 19. A rotating threaded rod 26 is rotatably installed inside the third slot 25. A rotating motor 24 is installed at one end of the movable rod 20. The output end of the rotating motor 24 movably passes through the end wall of the movable rod 20 and is connected to the rotating threaded rod 26. A sliding block 27 is slidably installed inside the third slot 25. The rotating threaded rod 26 is threaded through the sliding block 27. The sliding block 27 is connected to the movable ring 19 on the side near the movable ring 19. By moving the electric slider 22 in the movable chute 21, the movable rod 20 and the movable ring 19 can move out of the interior of the extrusion head cover 3. The pressure value inside the connection between the extrusion head cover 3 and the pelletizer head 4 is monitored by the piezoresistive sensor 23. If the pressure value changes beyond the standard change range, it indicates that the sealing at the connection between the extrusion head cover 3 and the pelletizer head 4 is unqualified. The rotating motor 24 drives the rotating threaded rod 26 to rotate, which can drive the sliding block 27 to slide inside the third slot 25 according to different usage requirements.

[0027] As a technical optimization of the present invention, the auxiliary mechanism includes a scraper 31. A displacement groove 28 is formed on the inner wall of the movable ring 19. Multiple displacement electric sliders 29 are uniformly slidably installed inside the displacement groove 28. A first electric extension rod 30 is connected to the side of the displacement electric slider 29 facing the center of the movable ring 19. The extension end of the first electric extension rod 30 faces the center of the movable ring 19 and is connected to the scraper 31. By sliding the displacement electric slider 29 in the displacement groove 28, the first electric extension rod 30 can be moved on the movable ring 19, and the first electric extension rod 30 can drive the scraper 31 to extend.

[0028] As a technical optimization of the present invention, the scraper 31 has a fourth slot 33 and a fifth slot 35 on the side facing the extrusion disc 18. A cleaning brush 34 is movably installed inside the fourth slot 33, and a plug-in block 32 is slidably installed inside the fifth slot 35. The plug-in block 32 can be inserted into the inside of the fixing hole 11. Combined with the rotation of the scraper 31, the blade disc 7 can be rotated and disassembled. The cleaning brush 34, combined with the rotation of the scraper 31, can clean the extrusion disc 18.

[0029] As a technical optimization of the present invention, the top and bottom of the inner wall of the fourth slot 33 are provided with first sliding grooves 37. A first electric slider 38 is slidably installed inside the first sliding groove 37. The side of the first electric slider 38 near the cleaning brush 34 is connected to the cleaning brush 34. A second electric extension rod 36 is installed at the bottom of the inner wall of the fifth slot 35. The extension end of the second electric extension rod 36 is away from the bottom of the inner wall of the fifth slot 35 and is connected to the insertion block 32. By sliding the first electric slider 38 in the first sliding groove 37, the cleaning brush 34 moves out of the interior of the fourth slot 33. The second electric extension rod 36 drives the insertion block 32 to extend, causing the insertion block 32 to move out of the interior of the fifth slot 35.

[0030] In use, all electrical devices in this device are powered by an external power source connected via wires. The device is controlled by a pre-set control system. The twin-screw extruder body 1, underwater pelletizer 2, extrusion head cover 3, pelletizer head 4, and quick connector 5 used in this device are all existing mature technologies, and therefore will not be described in detail. The piezoresistive sensor 23 used in this device is also existing mature technology, and therefore will not be described in detail. Figure 1 The underwater pelletizer 2 shown is only a part of the equipment. The cooling water pipe system and other mechanisms of the underwater pelletizer 2 are not shown in the pictures. The underwater pelletizer 2 is a mature existing technology, so it will not be described in detail. In this device, the movement of the internal components is supported by a laser displacement sensor.

[0031] When the device is in use, the homogeneous polypropylene molten in the twin-screw extruder body 1 is extruded through the extrusion holes on the extrusion disc 18. The drive rod 6 drives the cutter disc 7 and the blades 8 to a preset position outside the extrusion disc 18. Then, the drive rod 6 drives the cutter disc 7 to rotate, and the blades 8 can granulate the polypropylene extruded from the extrusion holes. At this time, the polypropylene granules are cooled and transported through the circulating water pipeline system of the underwater pelletizer 2, which can form the required modified polypropylene foamed particles.

[0032] When the blade 8 cuts the polypropylene, the displacement electric slider 29 slides in the displacement groove 28, allowing multiple scrapers 31 to move circumferentially along the movable ring 19. This agitates the modified polypropylene foam particles formed at the extrusion orifice, effectively preventing the collapse of the foam cells caused by gas escape from the modified polypropylene foam particles, ensuring the stability of the internal structure of the particles. Furthermore, the shearing action reduces the local viscosity of the melt, further reducing the risk of clogging and ensuring the stability of continuous production.

[0033] When the device is assembled and put into trial operation, it is necessary to test the sealing performance of the connection between the extrusion head cover 3 and the pelletizer head 4. At this time, the internal passage of the equipment is closed, and then gas is injected into the connection between the extrusion head cover 3 and the pelletizer head 4 through the pressurization device so that the internal pressure reaches the preset value. Then, within a preset time, the pressure value inside the connection between the extrusion head cover 3 and the pelletizer head 4 is monitored by the piezoresistive sensor 23. If the pressure value changes beyond the standard change range, it indicates that the sealing performance of the connection between the extrusion head cover 3 and the pelletizer head 4 is unqualified.

[0034] When it is necessary to clean the modified polypropylene foam particles attached to the blade 8, the rotating motor 24 drives the rotating threaded rod 26 to rotate, causing the sliding block 27 to slide in the third slot 25. This allows the movable ring 19 to move on the movable rod 20. Combined with the displacement electric slider 29 sliding in the displacement groove 28, the scraper 31 can move to the preset use position outside the blade 8. Then, the first electric extension rod 30 drives the scraper 31 to extend, so that the end of the scraper 31 can abut against the side of the blade 8 and move. In this way, the device can automatically clean the modified polypropylene foam particles attached to the blade 8 without opening the extrusion head cover 3 and the pelletizer head 4, increasing the ease of use of the device.

[0035] When auxiliary cleaning of the extrusion holes at the extrusion disc 18 is required, the first electric slider 38 slides in the first groove 37, causing the cleaning brush 34 to move out of the fourth slot 33. Then, the movable ring 19 moves closer to the extrusion disc 18, so that the cleaning brush 34 can come into contact with the extrusion holes on the extrusion disc 18. Then, the scraper 31 rotates on the movable ring 19 to clean the extrusion holes on the extrusion disc 18.

[0036] When the cutter head 7 needs to be disassembled, the second electric extension rod 36 drives the insertion block 32 to extend, so that the insertion block 32 moves out of the interior of the fifth slot 35. Then the movable ring 19 moves to the side of the cutter head 7 with the fixing hole 11. Then the first electric telescopic rod 14 drives the insertion rod 10 to retract into the interior of the first slot 13. Then the first electric extension rod 30 drives the scraper 31 to extend. Combined with the movable ring 19 moving on the movable rod 20, the insertion block 32 can be inserted into the interior of the fixing hole 11. Then, by the rotation of multiple scrapers 31 on the movable ring 19, the cutter head 7 can be rotated. When the fixing thread rod 15 is disengaged from the fixing sleeve 12, the automatic disassembly of the cutter head 7 is completed. Then the extrusion head cover 3 is separated from the pelletizer head 4. Then, by the sliding of the movable electric slider 22 in the movable slide groove 21, the movable rod 20 and the movable ring 19 can move out of the interior of the extrusion head cover 3, so that the operator can remove the disassembled cutter head 7. The new cutter head 7 is fixed in the manner described above by operating the scraper 31. Then, the cutter head 7 can be automatically installed by operating in the opposite manner. After the new cutter head 7 is installed, the insertion rod 10 is extended by the first electric telescopic rod 14, so that the insertion rod 10 can extend into the interior of the fixing hole 11, thereby increasing the connection stability between the cutter head 7 and the drive rod 6.

[0037] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A preparation process for a modified polypropylene foam material, characterized in that, Polypropylene resin, modifying agent and foaming agent are sequentially added into the interior of the twin-screw extruder body (1) through the filling port on the twin-screw extruder body (1). The polypropylene resin melts and plasticizes with the modifying agent and foaming agent in the temperature range of 140-200℃ to form a homogeneous system. The molten homogeneous polypropylene is extruded through the output end of the twin-screw extruder (1) to the input end of the underwater pelletizer (2) under a pressure of 5-25MPa. The plastic melt is cut into spherical beads by the underwater pelletizer (2). The spherical beads are cooled and shaped in the water pipe of the underwater pelletizer (2) to obtain modified polypropylene foam particles.

2. The preparation process of the modified polypropylene foam material according to claim 1, characterized in that, The twin-screw extruder body (1) has a length-to-diameter ratio of 240:

1. A pentane-based physical foaming agent is injected via a metering pump in the fifth-sixth zone of the twin-screw extruder body (1). The amount of foaming agent injected is 2-15% of the polymer weight. The residence time of the material in the screw is controlled to be no more than 5 minutes. The modified additives consist of polypropylene resin, silicates, compatibility agents, and coupling agents. The silicates are selected from one or more of montmorillonite, kaolin, Moskva clay, and talc, with a particle size of 800 μm. ~ 4000 mesh, the compatibility additive is maleic anhydride grafted polypropylene, the coupling agent is titanate coupling agent or silane coupling agent, the cutting speed of the underwater pelletizer (2) is 800-1500 rpm, the particle size of the modified polypropylene foam particles is in the range of 0.8-1.5 mm, and the cooling water is controlled by the chiller circulation system to keep the temperature fluctuation range within +2℃.

3. The preparation process of a modified polypropylene foam material according to claim 2, characterized in that, The temperature of each zone of the twin-screw extruder body (1) is set as follows: zone 1 120℃, zone 2 140℃, zone 3 160℃, zone 4 180℃, zone 5 190℃, zone 6 195℃, zone 7 200℃, and die head 200℃. Under the conditions of 0.2-0.35MPa water pressure and 50-70℃ water temperature, the modified polypropylene foam particles obtained by the underwater pelletizer (2) have a moisture content of less than 0.5%.

4. An apparatus for preparing modified polypropylene foam material, characterized in that, The preparation apparatus is applicable to the preparation process in claim 3. The preparation apparatus includes a twin-screw extruder body (1), an underwater pelletizer (2) is provided at the output end of the twin-screw extruder body (1), an extrusion head cover (3) is provided at the output end of the twin-screw extruder body (1), a pelletizer head (4) is provided at the input end of the underwater pelletizer (2), a quick connector (5) is provided on the pelletizer head (4), the quick connector (5) is connected to the extrusion head cover (3) on the side close to the extrusion head cover (3), an extrusion mechanism is provided inside the extrusion head cover (3), a pelletizing mechanism is provided inside the pelletizer head (4), two movable rods (20) are movably installed inside the extrusion head cover (3), a movable ring (19) is movably installed on the movable rods (20), and an auxiliary mechanism is provided on the movable ring (19).

5. The apparatus for preparing modified polypropylene foam material according to claim 4, characterized in that, The extrusion mechanism includes an extrusion disc (18) with multiple extrusion holes connected to the output end of the twin-screw extruder body (1). The pelletizing mechanism includes a drive rod (6), a cutter head (7), and blades (8). The pelletizer head (4) is provided with a drive rod (6) on the side near the extrusion head cover (3). The end of the drive rod (6) away from the pelletizer head (4) is provided with a fixed threaded rod (15). A fixed sleeve (12) is threadedly connected to the outer side of the fixed threaded rod (15). The side of the fixed sleeve (12) away from the drive rod (6) is connected to the cutter head (7). Multiple blades (8) are evenly provided on the side of the cutter head (7) away from the drive rod (6).

6. The apparatus for preparing modified polypropylene foam material according to claim 5, characterized in that, The cutter head (7) has a plurality of fixing holes (11) evenly distributed on the side near the drive rod (6). Two fixing rods (9) are installed on the outside of the drive rod (6). The fixing rod (9) has a first slot (13) at the end facing the cutter head (7). A first electric telescopic rod (14) is installed at the bottom of the inner wall of the first slot (13). The telescopic end of the first electric telescopic rod (14) faces the cutter head (7). A plug-in rod (10) is slidably installed inside the first slot (13). The end of the plug-in rod (10) near the first electric telescopic rod (14) is connected to the telescopic end of the first electric telescopic rod (14). The end of the plug-in rod (10) near the cutter head (7) can be inserted into the inside of the fixing hole (11).

7. The apparatus for preparing modified polypropylene foam material according to claim 6, characterized in that, The inner wall of the extrusion head cover (3) has a movable groove (21) near the movable rod (20). A movable electric slider (22) is slidably installed inside the movable groove (21). The movable electric slider (22) is connected to the movable rod (20) on the side near the movable rod (20). A piezoresistive sensor (23) is provided on the movable rod (20). A third slot (25) is provided on the side of the movable rod (20) near the movable ring (19). A rotating threaded rod (26) is rotatably installed inside the third slot (25). A rotating motor (24) is installed at one end of the movable rod (20). The output end of the rotating motor (24) movably passes through the end wall of the movable rod (20) and is connected to the rotating threaded rod (26). A sliding block (27) is slidably installed inside the third slot (25). The rotating threaded rod (26) threadedly passes through the sliding block (27). The sliding block (27) is connected to the movable ring (19) on the side near the movable ring (19).

8. The apparatus for preparing modified polypropylene foam material according to claim 7, characterized in that, The auxiliary mechanism includes a scraper (31), and a displacement groove (28) is provided on the inner wall of the movable ring (19). Multiple displacement electric sliders (29) are uniformly slidably installed inside the displacement groove (28). A first electric extension rod (30) is connected to the side of the displacement electric slider (29) facing the center of the movable ring (19). The extension end of the first electric extension rod (30) faces the center of the movable ring (19), and the extension end of the first electric extension rod (30) is connected to the scraper (31).

9. The apparatus for preparing modified polypropylene foam material according to claim 8, characterized in that, The scraper (31) has a fourth slot (33) and a fifth slot (35) on the side facing the extrusion disc (18). A cleaning brush (34) is movably installed inside the fourth slot (33), and a plug block (32) is slidably installed inside the fifth slot (35).

10. The apparatus for preparing modified polypropylene foam material according to claim 9, characterized in that, The inner wall of the fourth slot (33) is provided with a first sliding groove (37) at the top and bottom. A first electric slider (38) is slidably installed inside the first sliding groove (37). The side of the first electric slider (38) close to the cleaning brush (34) is connected to the cleaning brush (34). A second electric extension rod (36) is installed at the bottom of the inner wall of the fifth slot (35). The extension end of the second electric extension rod (36) is away from the bottom of the inner wall of the fifth slot (35). The extension end of the second electric extension rod (36) is connected to the plug block (32).

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