Continuous extrusion and granulation integrated device for polypropylene modification

Abstract

The invention relates to the technical field of polypropylene recovery and modification, in particular to a continuous extrusion and granulation integrated device for polypropylene modification, and aims at solving the problems that an existing device is poor in modification effect, low in production efficiency and the like. The device comprises a modified extrusion unit, a shaping and pelletizing unit and a supercritical fluid supply module, the modified extrusion unit is a multi-section screw extruder and comprises a feeding section, a melting section, a cross-linking section and a homogenizing section which are arranged in sequence, and the cross-linking section is provided with a cross-linking agent adding opening for adding a compound cross-linking agent; and the supercritical fluid supply module conveys mixed fluid of supercritical CO2 and nitrogen to each extrusion section in a multi-point injection mode. The device realizes full-process continuous operation, improves the dispersion uniformity and crosslinking efficiency of the supercritical fluid, reduces the defects of finished products, remarkably improves the mechanical properties of recycled polypropylene, reduces the production cost, and promotes the recycled polypropylene to be upgraded to middle and high-end applications.

Description

Technical Field

[0001] This invention relates to the field of polypropylene recycling and modification technology, and more specifically to an integrated continuous extrusion granulation apparatus for polypropylene modification. Background Technology

[0002] Polypropylene, as one of the most widely produced and used general-purpose plastics, relies heavily on waste recycling as a crucial pathway to promoting green and low-carbon development. Currently, the recycling and granulation of waste polypropylene often employs simple processes such as crushing, screening, and melt extrusion, resulting in poor mechanical properties and processing stability of the recycled polypropylene, making it difficult to meet the demands of mid-to-high-end applications such as automotive parts and appliance casings.

[0003] To improve the performance of recycled polypropylene, supercritical fluid synergistic dynamic crosslinking technology has been gradually introduced into existing technologies. This technology utilizes the high diffusivity and low viscosity of supercritical fluids to improve melt processing performance and constructs a three-dimensional network structure through dynamic crosslinking to enhance material strength. However, in existing devices, supercritical fluids are often injected at a single point, resulting in uneven fluid distribution in the melt and a tendency to generate bubble defects. At the same time, dynamic crosslinking agents are mostly single systems or simple blends, resulting in low crosslinking efficiency and difficulty in forming a uniform and stable crosslinked network.

[0004] Therefore, there is an urgent need for a highly efficient, integrated device to improve the quality and efficiency of waste polypropylene recycling and modification, and to promote the upgrading of the polypropylene recycling industry towards high-end development. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes an integrated continuous extrusion granulation device for polypropylene modification, aiming to achieve continuous operation of the entire process, including modified extrusion, shaping, and pelletizing of recycled polypropylene, thereby improving the overall performance of recycled polypropylene and reducing production costs.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: An integrated continuous extrusion granulation device for polypropylene modification includes a modified extrusion unit and a shaping and pelletizing unit. The modified extrusion unit includes a multi-stage screw extruder, and the shaping and pelletizing unit is connected to the discharge end of the screw extruder for shaping and pelletizing the extruded polypropylene melt. It also includes a supercritical fluid supply module for assisting the modified extrusion unit, wherein the modified extrusion unit includes a feed section extrusion module, a melt section extrusion module, a crosslinking section extrusion module and a homogenization section extrusion module arranged sequentially. The supercritical fluid supply module includes a supercritical CO2 generator, a nitrogen generator, a gas mixer, and a flow and pressure regulating component. The output ends of the supercritical CO2 generator and the nitrogen generator are both connected to the gas mixer. The output end of the gas mixer is connected to the feed section extrusion module, the melt section extrusion module, the crosslinking section extrusion module, and the homogenization section extrusion module for multi-point injection.

[0007] Preferably, the extrusion module of the feeding section is provided with a feeding hopper near the feeding end for adding recycled polypropylene, and the extrusion module of the homogenization section is provided with a discharge port near the discharge end for collecting the finished pellets after pelleting.

[0008] Preferably, the gas mixer includes four mixing chambers corresponding to the feeding section extrusion module, the melting section extrusion module, the crosslinking section extrusion module, and the homogenizing section extrusion module, respectively. Each mixing chamber is provided with a first gas pipe, a second gas pipe, a third gas pipe, and a fourth gas pipe that supply gas to the corresponding extrusion module.

[0009] Preferably, the modified extrusion unit includes a first drive device that provides power to the modified extrusion unit.

[0010] Preferably, the pelletizing unit includes a second drive device that provides pelletizing power and a cutting blade installed at the output end of the second drive device and cooperating with the extrusion port of the homogenization section extrusion module.

[0011] Preferably, the crosslinking segment extrusion module is provided with a crosslinking agent addition port near the feed end for adding the crosslinking agent of the compound system.

[0012] Preferably, the crosslinking agent in the compound system is a combination of terminal alkenyl hyperbranched polymer and aromatic disulfide dynamic covalent crosslinking agent, with a mass ratio of 1:1 to 3:1, and the amount added is 0.5 to 2% of the mass of polypropylene raw material.

[0013] Preferably, the total supercritical fluid injection flow rate in the supercritical fluid supply module is 1% to 5% of the mass of the polypropylene raw material, and the injection pressure adjustment range is 10 to 30 MPa.

[0014] Preferably, the temperature of the feeding section is controlled at 150~170℃, the temperature of the melting section is controlled at 170~190℃, the temperature of the crosslinking section is controlled at 180~200℃, and the temperature of the homogenization section is controlled at 175~195℃.

[0015] The present invention has at least the following beneficial effects: Compared to existing technologies that simply inject supercritical fluid at a single point, this device employs a multi-point precise injection design within the supercritical fluid supply module. This allows a mixture of supercritical CO2 and nitrogen to be injected into the feeding section, melting section, crosslinking section, and homogenization section extrusion module through four independent mixing chambers and corresponding gas pipes. This multi-point, segmented injection method enables the supercritical fluid mixture to gradually penetrate the polypropylene raw material and melt at different processing stages. Leveraging the high diffusivity and low viscosity of supercritical fluid, it not only effectively reduces melt viscosity and improves flowability but also prevents fluid aggregation and the formation of large bubbles. This fundamentally reduces bubble defects in the finished product particles, improving both the product's appearance and internal quality stability.

[0016] This invention significantly improves the overall mechanical properties of recovered polypropylene through the synergistic effect of a compound crosslinking agent and supercritical fluid. The device incorporates a crosslinking agent addition port in the crosslinking section, introducing a compound system of terminal alkenyl hyperbranched polymer and aromatic disulfide-based dynamic covalent crosslinking agent. The two work synergistically in an optimized ratio, solving the problems of low crosslinking efficiency and uneven crosslinking networks associated with single crosslinking agents or simple compound systems.

[0017] Among them, terminal alkenyl hyperbranched polymers provide abundant active sites, promote grafting reactions with polypropylene molecular chains, and provide more connection nodes for the construction of cross-linked networks; aromatic disulfide cross-linking agents can achieve reversible covalent bond recombination, forming a stable three-dimensional cross-linked network and endowing the melt with self-healing ability.

[0018] Meanwhile, supercritical mixed fluids can reduce the activation energy of crosslinking reactions and promote the uniform dispersion of crosslinking agents, further improving the crosslinking effect. Ultimately, this significantly improves the tensile strength, impact strength, and other mechanical properties of recycled polypropylene, meeting the needs of mid-to-high-end applications such as automotive parts and home appliance housings. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of a partially disassembled structure in this invention; The attached figures are labeled as follows: 100. First drive unit; 200. Feed section extrusion module; 210. Feed hopper; 300. Melt section extrusion module; 400. Crosslinking section extrusion module; 410. Crosslinking agent addition port; 500. Homogenization section extrusion module; 600. Shaping and pelletizing unit; 610. Second drive unit; 620. Cutter; 630. Discharge port; 700. Supercritical fluid supply module; 710. Supercritical CO2 generator; 720. Nitrogen generator; 730. Gas mixer; 740. Mixing chamber; 741. First gas pipe; 742. Second gas pipe; 743. Third gas pipe; 744. Fourth gas pipe. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be further described in detail below with reference to the embodiments of the present invention.

[0021] Figure 1 system Figure 2 An integrated continuous extrusion granulation device for polypropylene modification is presented, comprising a modified extrusion unit, a shaping and pelletizing unit 600, and a supercritical fluid supply module 700. The three work together to achieve continuous production from waste polypropylene raw materials to modified finished granules, eliminating the need for intermediate transfer links, effectively reducing production costs, and improving product quality stability.

[0022] The modified extrusion unit, as the core processing module, adopts a multi-segment screw extruder structure. Through segmented temperature control and segmented functional design, it realizes the gradual melting, cross-linking modification, and homogenization of polypropylene. The shaping and pelletizing unit 600 is connected to the discharge end of the screw extruder and is used to quickly shape and accurately pelletize the extruded polypropylene melt to ensure that the finished particles are uniform in size and regular in shape. The supercritical fluid supply module 700 provides uniformly dispersed supercritical mixed fluid for the modified extrusion process, which helps to improve the melt processing performance and cross-linking effect. The three form an organic whole to realize the integrated closed-loop operation of feeding, melting, modification, extrusion, shaping, and pelletizing.

[0023] Specifically, the modified extrusion unit includes a feeding section extrusion module 200, a melting section extrusion module 300, a crosslinking section extrusion module 400, and a homogenization section extrusion module 500 arranged sequentially. Each module is integrated into the corresponding section of the multi-segment screw extruder and is equipped with an independent temperature control component. Through precise temperature control, it matches the process requirements of each processing stage. At the same time, the modified extrusion unit also includes a first drive device 100 that provides power to it. The first drive device 100 adopts a variable frequency speed control motor, which can flexibly adjust the speed of the screw extruder according to the characteristics of the raw materials and processing requirements, ensuring that the processing of each segment is stable and controllable, and avoiding problems such as uneven melt mixing and unstable extrusion caused by speed fluctuations.

[0024] The extrusion module 200 in the feeding section is equipped with a feeding hopper 210 near the feed end. The feeding hopper 210 is used to add waste polypropylene granules that have undergone recycling processes such as crushing, washing, and drying. The temperature in the feeding section is controlled between 150 and 170°C. This temperature range allows the waste polypropylene granules to soften initially, facilitating rapid melting in the subsequent melting section, while also preventing premature melting and agglomeration of the raw materials, ensuring smooth feeding. In addition, the extrusion module 200 in the feeding section is also connected to a supercritical fluid supply module 700. A small amount of supercritical mixed fluid is injected at this stage, allowing it to penetrate into the gaps between the polypropylene granules in advance, laying the foundation for uniform mixing in the subsequent melting section. At the same time, the low viscosity of the supercritical fluid reduces the flow resistance of the raw materials in the feeding section, improving feeding efficiency.

[0025] The molten section extrusion module 300 is connected to the outlet end of the feed section extrusion module 200. Its temperature is controlled between 170 and 190°C, which is the optimal melting temperature for polypropylene. This temperature range allows the polypropylene particles, which have been initially softened in the feed section, to completely melt and form a uniform polypropylene melt. Simultaneously, the spiral blades in the molten section employ a special pitch design to enhance the shearing action of the melt, breaking up agglomerates in the polypropylene melt and resulting in a more uniform melt texture. The molten section extrusion module 300 is also connected to the supercritical fluid supply module 700. At this stage, an appropriate amount of supercritical mixed fluid is injected. Utilizing the high diffusivity of the supercritical fluid, it quickly penetrates into the molten polypropylene melt, effectively reducing melt viscosity, improving melt flowability and processing performance, and providing a uniform reaction environment for the subsequent crosslinking reaction in the crosslinking section, avoiding uneven dispersion of the crosslinking agent due to excessively high melt viscosity.

[0026] The crosslinking section extrusion module 400 is connected to the discharge end of the melting section extrusion module 300 and is the core section for polypropylene modification and upgrading. Its temperature is controlled at 180~200℃. This temperature range can activate the reactivity of the crosslinking agent and promote the efficient crosslinking reaction. The crosslinking section extrusion module 400 is provided with a crosslinking agent addition port 410 near the feed end for adding the crosslinking agent of the compound system. The crosslinking agent of the compound system is a combination of terminal alkenyl hyperbranched polymer and aromatic disulfide dynamic covalent crosslinking agent. The mass ratio of the two is 1:1 to 3:1, and the addition amount is 0.5~2% of the mass of polypropylene raw material. This ratio can ensure crosslinking efficiency and avoid melt embrittlement caused by excessive crosslinking.

[0027] From a mechanistic perspective, terminal alkenyl hyperbranched polymers possess abundant terminal alkenyl active sites, which can undergo grafting reactions with polypropylene molecular chains, providing more connection nodes for the formation of crosslinked networks. Meanwhile, aromatic disulfide dynamic covalent crosslinking agents can undergo reversible covalent bond breaking and recombination at certain temperatures, forming a stable three-dimensional crosslinked network, improving the mechanical properties of polypropylene, and endowing the polypropylene melt with a certain self-healing ability, thus improving melt stability during processing. When the two work synergistically, the active sites of terminal alkenyl hyperbranched polymers can promote the dispersion and reaction of aromatic disulfide crosslinking agents in the melt, avoiding the problems of low crosslinking efficiency and uneven crosslinked networks that exist with single crosslinking agents. Ultimately, a uniform and stable three-dimensional crosslinked network is formed, significantly improving the tensile strength, impact strength, and other mechanical properties of recycled polypropylene.

[0028] Meanwhile, the crosslinking section extrusion module 400 is connected to the supercritical fluid supply module 700. The supercritical mixed fluid injected at this stage can further promote the uniform dispersion of the crosslinking agent in the melt, reduce the activation energy of the crosslinking reaction, accelerate the crosslinking reaction rate, and suppress the generation of bubbles during the crosslinking process to avoid bubble defects in the finished particles.

[0029] The homogenization section extrusion module 500 is connected to the discharge end of the crosslinking section extrusion module 400. A discharge port 630 is located near the discharge end to transport the homogenized polypropylene melt to the shaping and pelletizing unit 600. The discharge port 630 is also equipped with a filter assembly to filter impurities and unreacted crosslinking agent particles from the melt, ensuring the purity of the melt and guaranteeing its quality for subsequent shaping and pelletizing. The homogenization section temperature is controlled between 175 and 195°C. This temperature range is slightly lower than that of the crosslinking section, allowing the crosslinking reaction to stabilize while maintaining good melt flowability. The spiral blades in the homogenization section employ a dense design to fully stir and shear the melt after the crosslinking reaction, ensuring complete and uniform mixing of the polypropylene molecular chains, crosslinking agent, and supercritical fluid. This ensures uniform composition and properties of the melt and avoids fluctuations in the performance of the finished pellets due to uneven mixing.

[0030] In addition, the homogenization section extrusion module 500 is connected to the supercritical fluid supply module 700. A small amount of supercritical mixed fluid is injected at this stage, which can further adjust the viscosity of the melt, ensure smooth extrusion of the melt, and reduce the retention of the melt at the outlet 630, thus avoiding material degradation caused by local overheating.

[0031] The injection volume of supercritical mixed fluid in each extrusion module is as follows: The feed section extrusion module 200 injects 10% to 20% of the total injection volume. A small amount of fluid forms diffusion channels between particles, which improves the mixing efficiency of supercritical fluid and melt in the subsequent melting section. Combined with the low temperature section temperature control of 150 to 170°C, it promotes the initial softening of particles and lays the foundation for rapid and complete melting in the subsequent melting section.

[0032] The injection volume of the 300-stage extrusion module accounts for 40% to 50% of the total injection flow of the supercritical fluid. By utilizing the low viscosity and high diffusivity of the supercritical fluid, the viscosity of the polypropylene melt is significantly reduced, the fluidity of the melt is improved, and the agglomerate structure of the polypropylene melt is broken. Combined with the specially designed helical blades, the shearing effect of the melt is enhanced, making the melt texture more uniform and providing a better premise for the uniform reaction of the crosslinking stage.

[0033] The injection volume of the crosslinking section extrusion module 400 accounts for 20% to 30% of the total injection flow of the supercritical fluid. The injection volume is between the feeding section and the melting section, and is used to promote the crosslinking reaction and suppress bubble defects.

[0034] The homogenization section extrusion module 500 injects 10% to 20% of the total supercritical fluid injection flow rate, and is used to fine-tune the melt state and ensure extrusion stability.

[0035] The supercritical fluid supply module 700 is a key component in assisting the modified extrusion unit to achieve quality improvement and efficiency enhancement. It includes a supercritical CO2 generator 710, a nitrogen generator 720, a gas mixer 730, and a flow and pressure regulating component. The supercritical CO2 generator 710 is used to prepare supercritical CO2. Supercritical CO2 has the characteristics of high diffusivity, low viscosity, and chemical inertness, and is the core medium for improving the processing performance of polypropylene melt. The nitrogen generator 720 is used to prepare high-purity nitrogen. As an auxiliary gas, nitrogen can be mixed with supercritical CO2 to form a mixed fluid, which can reduce the critical pressure and temperature of supercritical CO2, reduce the preparation cost, and inhibit the aggregation of supercritical CO2 in the melt to form large-sized bubbles, thereby improving the uniformity of fluid dispersion.

[0036] The gas mixer 730 includes four mixing chambers 740 corresponding to the feeding section extrusion module 200, the melting section extrusion module 300, the crosslinking section extrusion module 400, and the homogenization section extrusion module 500, respectively. Each mixing chamber 740 can precisely adjust the mixing ratio of supercritical CO2 and nitrogen according to the process requirements of the corresponding extrusion module. The mixing chamber 740 is equipped with a first gas supply pipe, a second gas supply pipe, a third gas supply pipe, and a fourth gas supply pipe, respectively supplying gas to the corresponding extrusion module, so as to realize multi-point precise injection of supercritical mixed fluid and solve the problem of uneven fluid distribution caused by single-point injection in the prior art. The flow and pressure regulating component includes a flow controller and a pressure regulating valve, which can control the total injection flow of supercritical fluid to 1%~5% of the mass of polypropylene raw material, and the injection pressure can be controlled within the range of 10~30MPa. This parameter range has been optimized through experiments. If the flow rate is too low, the supercritical fluid cannot play its role. If the flow rate is too high, there will be too many bubbles in the melt. If the pressure is too low, the supercritical fluid will have difficulty penetrating into the melt. If the pressure is too high, it will increase the equipment load and may even lead to melt leakage. Through precise adjustment of flow and pressure, it can be ensured that the supercritical mixed fluid can be evenly dispersed in each extrusion section, forming a good synergistic effect with the melt and crosslinking agent.

[0037] The shaping and pelletizing unit 600 is connected to the discharge port 630 of the homogenization section extrusion module 500 and is used to quickly shape and pelletize the extruded polypropylene melt. It includes a second drive device 610 that provides pelletizing power and a cutting blade 620 installed at the output end of the second drive device 610 and corresponding to the extrusion port of the homogenization section extrusion module 500. The second drive device 610 also adopts a variable frequency speed control motor, which can flexibly adjust the rotation speed of the cutting blade 620 according to the melt extrusion speed to ensure that the finished pellets are uniform in size. The cutting blade 620 is made of wear-resistant alloy material, which can effectively extend its service life, reduce the replacement frequency, and reduce production costs.

[0038] The pelletizing unit 600 can also be equipped with a cooling and shaping component. When the homogenized polypropylene melt is extruded from the outlet 630, the cooling and shaping component can quickly cool the melt, causing the melt to solidify and form quickly. Then, the cutting blade 620, driven by the second driving device 610, precisely pelletizes the solidified melt. The finished pellets are collected by the collecting mechanism below the outlet 630, completing the entire modified pelletizing process.

[0039] The overall working process of this device is as follows: First, the recycled waste polypropylene granules are fed into the extrusion module 200 of the feeding section at a constant speed through the quantitative feeding mechanism of the feeding hopper 210. The feeding section softens the polypropylene granules at a temperature of 150~170℃. At the same time, the supercritical fluid supply module 700 injects a small amount of supercritical mixed fluid into the feeding section through the first air supply pipe. The fluid penetrates into the gaps between the granules and reduces the feeding resistance. Subsequently, the pre-softened particles enter the extrusion module 300 of the melting section and are completely melted at a temperature of 170~190℃ to form a uniform melt. The second gas supply pipe injects an appropriate amount of supercritical mixed fluid into the melting section to reduce the viscosity of the melt, improve its fluidity, and enhance the shear mixing effect of the melt. Next, the molten melt enters the crosslinking section extrusion module 400, and the crosslinking agent of the compound system is added through the crosslinking agent addition port 410. At a temperature of 180~200℃, the terminal alkenyl hyperbranched polymer and the aromatic disulfide crosslinking agent work together to undergo a crosslinking reaction to form a three-dimensional network structure. The supercritical mixed fluid injected by the third gas supply pipe promotes the uniform dispersion of the crosslinking agent, accelerates the crosslinking reaction rate, and inhibits the generation of bubbles. Then, the cross-linked modified melt enters the homogenization section extrusion module 500. At a temperature of 175~195℃, the melt, cross-linking agent, and supercritical fluid are completely homogenized by the stirring and shearing of dense spiral blades. A small amount of supercritical mixed fluid is injected into the fourth gas supply pipe to adjust the melt viscosity. The homogenized melt is filtered through the discharge port 630 and then transported to the shaping and pelletizing unit 600. Finally, the cooling and solidification component rapidly cools and solidifies the melt, and the second drive device 610 drives the cutting blade 620 to cut the solidified melt into pellets, and the finished pellets are collected to complete the operation.

[0040] In summary, this embodiment achieves continuous operation of the entire process of waste polypropylene modification and granulation through the segmented design of the multi-segment screw extruder, the multi-point precise injection of supercritical fluid, and the synergistic effect of the compound crosslinking agent. The synergistic cooperation between various structures and components effectively solves the problems of uneven melt mixing, low crosslinking efficiency, bubble defects in finished products, and poor mechanical properties in the existing technology. It significantly improves the comprehensive performance of recycled polypropylene, reduces production costs, and enables recycled polypropylene to meet the needs of mid-to-high-end applications such as automotive parts and home appliance casings, thus promoting the upgrading of the polypropylene recycling industry towards high-end and green development.

[0041] The terms "upper," "lower," "outer," "inner," etc., used in the specification, claims, and accompanying drawings of this invention are used to distinguish relative positional relationships and are not necessarily qualitative. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0042] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A continuous extrusion granulation integrated device for polypropylene modification, comprising a modified extrusion unit and a shaping and pelletizing unit, wherein the modified extrusion unit includes a multi-stage screw extruder, and the shaping and pelletizing unit is connected to the discharge end of the screw extruder for shaping and pelletizing the extruded polypropylene melt; characterized in that: It also includes a supercritical fluid supply module for assisting the modified extrusion unit, wherein the modified extrusion unit includes a feed section extrusion module, a melt section extrusion module, a crosslinking section extrusion module and a homogenization section extrusion module arranged sequentially. The supercritical fluid supply module includes a supercritical CO2 generator, a nitrogen generator, a gas mixer, and a flow and pressure regulating component. The output ends of the supercritical CO2 generator and the nitrogen generator are both connected to the gas mixer. The output end of the gas mixer is connected to the feed section extrusion module, the melt section extrusion module, the crosslinking section extrusion module, and the homogenization section extrusion module for multi-point injection.

2. The integrated continuous extrusion granulation apparatus for polypropylene modification as described in claim 1, characterized in that: The extrusion module in the feeding section is provided with a feeding hopper near the feeding end for adding recycled polypropylene, and the extrusion module in the homogenization section is provided with a discharge port near the discharge end for collecting the finished pellets after pelleting.

3. The integrated continuous extrusion granulation apparatus for polypropylene modification as described in claim 1, characterized in that: The gas mixer includes four mixing chambers corresponding to the feeding section extrusion module, the melting section extrusion module, the crosslinking section extrusion module, and the homogenizing section extrusion module, respectively. Each mixing chamber is provided with a first gas pipe, a second gas pipe, a third gas pipe, and a fourth gas pipe that supply gas to the corresponding extrusion module.

4. The integrated continuous extrusion granulation apparatus for polypropylene modification as described in claim 1, characterized in that: The modified extrusion unit includes a first drive device that provides power to the modified extrusion unit.

5. The integrated continuous extrusion granulation apparatus for polypropylene modification as described in claim 1, characterized in that: The pelletizing unit includes a second drive device that provides pelletizing power and a cutting blade installed at the output end of the second drive device and cooperating with the extrusion port of the homogenization section extrusion module.

6. The integrated continuous extrusion granulation apparatus for polypropylene modification as described in claim 1, characterized in that: The crosslinking section extrusion module is provided with a crosslinking agent addition port near the feed end for adding the crosslinking agent of the compound system.

7. The integrated continuous extrusion granulation apparatus for polypropylene modification as described in claim 5, characterized in that: The crosslinking agent in the compound system is a combination of terminal alkenyl hyperbranched polymer and aromatic disulfide dynamic covalent crosslinking agent, with a mass ratio of 1:1 to 3:1, and the amount added is 0.5 to 2% of the mass of polypropylene raw material.

8. The continuous extrusion granulation integrated apparatus for polypropylene modification as described in claim 5, characterized in that: The total supercritical fluid injection flow rate in the supercritical fluid supply module is 1% to 5% of the mass of polypropylene raw material, and the injection pressure adjustment range is 10 to 30 MPa.

9. The continuous extrusion granulation integrated apparatus for polypropylene modification as described in any one of claims 1 to 8, characterized in that: The temperature of the feeding section is controlled at 150~170℃, the temperature of the melting section is controlled at 170~190℃, the temperature of the crosslinking section is controlled at 180~200℃, and the temperature of the homogenization section is controlled at 175~195℃.

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