Polyester chip twin-screw melt extruder

Abstract

The invention relates to the technical field of extruders, in particular to a polyester chip double-screw melt extruder which comprises a rack, an extrusion pipe arranged on the rack, a first feeding port and a second feeding port which are respectively formed in the end part and the middle rear part of the extrusion pipe, and a discharge port formed in the other end part of the extrusion pipe, two extrusion screws are arranged in the extrusion pipe in parallel, and each extrusion screw sequentially comprises a feeding section, a pressurizing section, a pressure releasing section, a pressure building section, a coupling and mixing section and a homogenizing section from the first feeding port to the discharging port. The device has the beneficial effects that through collaborative innovation of the six-section discontinuous lead screw and the homogenizing section dynamic crushing system, the energy consumption and the maintenance cost are reduced, through stirring and crushing of a mixture by the stirring rod and the crushing part, the residual rate of non-nuggets is reduced, and isotropy of filler distribution is realized.

Description

Technical Field

[0001] This invention relates to the field of extruder technology, specifically to a twin-screw melt extruder for polyester chips. Background Technology

[0002] The twin-screw extruder for polyester chips is a core piece of equipment in the field of polymer material processing, mainly used for the melting, mixing, devolatilization, and extrusion molding of polyesters (such as PET, PBT, PLA, etc.). Its working principle involves two screws rotating in the same or opposite directions generating shear heat and conveying pressure, melting solid polyester chips into a homogeneous melt, which is then extruded through a die. This equipment is widely used in fiber spinning, packaging materials, engineering plastics, and other fields.18 Traditional designs emphasize a balance of "high torque, high speed, and high output," but the thermal sensitivity of polyester materials (e.g., PET is easily degraded above 290℃) and processing characteristics (e.g., moisture content must be ≤50ppm) impose stringent requirements on process control.

[0003] Currently, twin-screw extruders face multiple technical challenges in polyester processing, severely restricting the improvement of efficiency and quality: The conflict between high rotational speed and material degradation: While increasing rotational speed can improve yield, it can also trigger excessive shear heat, leading to a sharp rise in melt temperature, resulting in a decrease in intrinsic viscosity and molecular chain breakage. Simultaneously, in highly filled systems, fillers impede heat transfer, exacerbating the risk of localized carbonization.

[0004] Low compression ratio sacrifices melting efficiency: To protect heat-sensitive materials and brittle fillers, a low compression ratio design is often adopted. Although this design reduces shear damage, it weakens the compaction ability of the melting section, resulting in a significant increase in the solid residue rate. Incompletely melted particles will encapsulate additives (such as color masterbatch and glass fiber), forming a "core-shell" defect, causing problems such as fish eyes and white spots in the finished product.

[0005] Uneven mixing of side feed: When the second feed port is located upstream of the melting section (such as Coperon ZSK series), the heat-sensitive filler (glass fiber / flame retardant) decomposes due to high temperature and long residence time; while downstream feed results in layered distribution of filler due to the high viscosity of the melt (>250Pa·s) (the upper layer concentration is 110% higher than the lower layer, see Polymer Engineering and Science 2023). Summary of the Invention

[0006] The purpose of this invention is to provide a twin-screw melt extruder for polyester chips to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a twin-screw melt extruder for polyester chips, comprising a frame, an extrusion tube mounted on the frame, a first feed port and a second feed port respectively located at the end and rear of the extrusion tube, and a discharge port located at the other end of the extrusion tube; two extrusion screws are arranged in parallel within the extrusion tube, and the extrusion screws, from the first feed port to the discharge port, are sequentially a feeding section, a pressurizing section, a pressure releasing section, a pressure building section, a mixing section, and a homogenizing section; the homogenizing section is divided into two sections, the middle part of which is a hollow section, and a fixed rod is provided on each of the two extrusion screws in the hollow section, the fixed rod is provided with an arc-shaped baffle, the arc-shaped baffle is provided with several openings, a movable rod is provided in the openings, one end of the movable rod is fixedly connected to a pressure plate, an elastic element is provided between the pressure plate and the arc-shaped baffle, and the extrusion screw is provided with blades that cooperate with the pressure plate.

[0008] Preferably, the extrusion tube is covered with a cover, and the cover is provided with a first feeding bin and a second feeding bin corresponding to the first feeding port and the second feeding port, respectively. The frame located inside the cover is provided with a number of air outlets.

[0009] Preferably, the frame is provided with a first driving unit and a second driving unit. The first driving unit is used to drive the extrusion screw. An isolation cover is provided between the second driving unit and the extrusion tube. A transmission rod powered by the second driving unit is provided inside the isolation cover. A cutting blade corresponding to the discharge port is provided on the transmission rod.

[0010] Preferably, it also includes a receiving hopper corresponding to the discharge port, the receiving hopper being connected to a receiving bucket via a pipe, the pipe being connected to the air outlet of the blower.

[0011] Preferably, a limiting ring is provided at the discontinuity between the pressure building section and the mixing section, and the limiting ring is fixedly connected to the extrusion pipe.

[0012] Preferably, a stirring rod is provided at the discontinuity between the mixing section and the homogenization section.

[0013] Preferably, the other end of the movable rod is provided with a breaking part, which is initially positioned outside the opening.

[0014] Preferably, the bottom of the fan blade is provided with a connecting rod and a rotating rod at both ends, and the other end of the rotating rod is rotatably connected to the rod body of the extrusion screw.

[0015] Preferably, the extrusion screw has a sliding ring on its shaft that fits against the pressure plate, and the two ends of the connecting rod are rotatably connected to the fan blade and the sliding ring, respectively.

[0016] Preferably, the two fixing rods are of different lengths, and the two sets of fan blades, pressure plates, and arc-shaped baffles connected to the two fixing rods are arranged one in front of the other on the two extrusion screws.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. In this invention, when the increase of unmelted particles in the melt leads to an increase in pipeline pressure, the melt pushes the pressure plate to move axially against the resistance of the elastic element, causing the movable rod to slide in the extrusion direction, so that the breaking part at the end of the movable rod extends out from the opening of the arc-shaped baffle. The breaking part directly and forcibly breaks the blockage of unmelted particle clumps, significantly reducing the unmelted nucleus residue rate and avoiding defects such as fish eyes and white spots in the finished product.

[0018] 2. In this invention, when the pressure plate moves, it pushes the sliding ring to move axially, which drives the fan blade to rotate around the pivot point of the rotating rod via the connecting rod (initial pumping angle → horizontal thrust angle → reverse thrust angle; the greater the pressure, the greater the fan blade tilt angle; when the pressure reaches the threshold, the fan blade switches to the reverse thrust state; in the low-pressure state, the fan blade maintains the pumping angle to accelerate the melt output; when the amount of unmelted material increases under high pressure, the fan blade switches to horizontal or reverse thrust to prolong the residence time of plastic waste and enhance the reverse turbulence; furthermore, the staggered design of the two extrusion screws and the alternating action of the two sets of fan blades due to the difference in the length of the fixed rod eliminate the flow dead zone and achieve isotropic distribution of the filler. 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 the internal structure of the cover of the present invention; Figure 3 This is a schematic diagram of the internal structure of the extrusion tube of the present invention; Figure 4 This is a schematic diagram of the internal structure of the isolation cover of the present invention; Figure 5 For the present invention Figure 4 Enlarged view of the structure at point A in the middle; Figure 6 This is a schematic diagram of the extrusion screw structure of the present invention. Figure 1 ; Figure 7 This is a side view of the extrusion tube of the present invention; Figure 8 This is a schematic diagram of the extrusion screw structure of the present invention. Figure 2 ; Figure 9 For the present invention Figure 8 Enlarged view of the structure at point B in the middle; Figure 10 This is a schematic diagram of the arc-shaped baffle and the pressure plate of the present invention.

[0020] The components represented by each number in the attached diagram are listed below: 1. Frame; 2. First drive unit; 3. Second drive unit; 4. Cover; 5. First feeding bin; 6. Second feeding bin; 7. Isolation cover; 8. Receiving hopper; 9. Collecting bin; 10. Blower; 11. First heating unit; 12. Second heating unit; 13. Extrusion pipe; 14. Air outlet; 15. Extrusion screw; 1501. Feeding section; 1502. Pressurization section; 1503. Depressurization section; 1504. 04. Pressure building section; 1505. Coupling section; 1506. Homogenization section; 16. Discharge port; 17. Transmission rod; 18. Cutting blade; 19. First feeding port; 20. Second feeding port; 21. Stirring rod; 22. Restricting ring; 23. Fixing rod; 24. Arc-shaped baffle; 25. Fan blade; 26. Sliding ring; 27. Pressure plate; 28. Rotating rod; 29. ​​Elastic element; 30. Movable rod; 31. Opening; 32. Crushing section; 33. Connecting rod. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1: The present invention provides a technical solution: such as Figures 1-9 The illustrated polyester chip twin-screw melt extruder includes a frame 1, an extrusion tube 13 mounted on the frame 1, a first feed port 19 and a second feed port 20 located at the end and rear middle of the extrusion tube 13, respectively, and a discharge port 16 located at the other end of the extrusion tube 13. Two extrusion screws 15 are arranged in parallel within the extrusion tube 13. From the first feed port 19 to the discharge port 16, the extrusion screws 15 sequentially comprise a feeding section 1501, a pressurizing section 1502, a pressure-relieving section 1503, and a pressure-building section. 1504, mixing section 1505, homogenization section 1506; the homogenization section 1506 is divided into two sections, with the middle part being a hollow section. Each of the two extrusion screws 15 in the hollow section is provided with a fixed rod 23. The fixed rod 23 is provided with an arc-shaped baffle 24. The arc-shaped baffle 24 is provided with several openings 31. A movable rod 30 is provided in the openings 31. One end of the movable rod 30 is fixedly connected to a pressure plate 27. An elastic element 29 is provided between the pressure plate 27 and the arc-shaped baffle 24. The extrusion screw 15 is provided with a fan blade 25 that cooperates with the pressure plate 27.

[0023] Working principle: Plastic waste enters the feeding section 1501 through the first feeding port 19. Two extrusion screws 15 rotate in opposite directions, conveying polyester chips forward. The large lead of the screw thread in the feeding section 1501 achieves high throughput conveying. Next, the plastic waste enters the pressurization section 1502. Due to the reduced screw pitch and shallower thread depth, the plastic waste is compressed and heated, initially melting. During this process, the sudden reduction in lead compresses the plastic waste, facilitating rapid melting in conjunction with the heating module. It then reaches the depressurization section 1503, where the screw pitch suddenly increases, creating a negative pressure zone that promotes the discharge of volatiles from the melt. The moderate lead here ensures stable conveying. The melt undergoes its first depressurization between the pressurization section 1502 and the depressurization section 1503, with volatile gases venting from the exhaust port. The melt continues into the pressure-building section 1504, where it is repressurized through a contraction channel, and then enters the pressure-building section 1504 from the depressurization section 1503. During the process, the reduced lead generates high shear force, further breaking up unmelted grains. The pressurized melt flows to the mixing section 1505, where the meshing elements of the twin screws perform high-intensity shearing on the plastic waste. At this time, additives such as color masterbatch added from the second feed port 20 are forcibly mixed. The pre-mixed plastic waste enters the homogenization section 1506, where it is reheated by the heating module, ensuring that the plastic waste is fully melted in both stages. If unmelted plastic waste appears, the pressure inside the pipe increases, and the pressure plate 27 moves in the extrusion direction along with the movable rod 30. The movable rod 30 opens the hole 31, breaking up unmelted particles and accelerating the melting of unmelted particle clumps. Subsequently, the plastic waste enters the discharge port 16 and gradually cools, completing the extrusion process.

[0024] In this embodiment, when the unmelted plastic waste in the mixing section 1505 and the homogenization section 1506 further increases and the opening 31 is blocked, the pressure plate 27 moves further in the direction of plastic waste extrusion. The pressure plate 27 pushes the fan blade 25, causing the fan blade 25 to enter the horizontal and reverse pushing state. As the extrusion screw 15 rotates, it stirs and pushes the plastic waste back, further extending the residence time of the plastic waste. At the same time, the returned plastic waste collides with the forward plastic waste, accelerating the melting of the unmelted plastic waste.

[0025] Example 2: Please refer to the appendix. Figures 1-9This embodiment further explains the first embodiment. The extrusion tube 13 is covered by a cover 4. The cover 4 is provided with a first feeding bin 5 and a second feeding bin 6 corresponding to the first feeding port 19 and the second feeding port 20, respectively. The frame 1 located inside the cover 4 is provided with a plurality of air outlets 14. The frame 1 is provided with a first drive unit 2 and a second drive unit 3. The first drive unit 2 is used to drive the extrusion screw 15. An isolation cover 7 is provided between the second drive unit 3 and the extrusion tube 13. The isolation cover 7 is provided with a transmission rod 17 powered by the second drive unit 3. The transmission rod 17 is provided with a cutting blade 18 corresponding to the discharge port 16. It also includes a receiving hopper 8 corresponding to the discharge port 16. The receiving hopper 8 is connected to a receiving bucket 9 through a pipe. The pipe is connected to the air outlet of the blower 10.

[0026] In this embodiment, the cover 4 completely covers the extrusion tube 13 and integrates the first feeding bin 5 and the second feeding bin 6 for heat preservation and oxidation prevention, which can maintain the temperature stability of the melting zone and isolate external contaminants; The two separate compartments (first feeding compartment 5 and second feeding compartment 6) control the feeding ratio and feeding time of main and auxiliary materials respectively. The first drive unit 2 is directly connected to the extrusion screw 15, and the second drive unit 3 drives the cutting blade 18 through the isolation cover 7. The independent power supply can avoid lubricating oil contamination of plastic waste (compliant with FDA standards) and can also achieve independent control of pelletizing frequency and extrusion speed. The isolation cover 7 is equipped with a transmission rod 17, and the end of the transmission rod 17 is equipped with a cutting knife 18 facing the discharge port 16 to realize online granulation (the rotating blade of the cutting knife 18 cuts the extruded strip melt). The material particles cut by the cutting blade 18 directly enter the receiving hopper 8. The receiving hopper 8 → pipe → blower 10 → collection bucket 9 achieves heat-free conveying. The advantages of this design are: airflow cooling prevents the particles from sticking together, and negative pressure adsorption avoids mechanical crushing.

[0027] Example 3: Please refer to the appendix. Figures 1-9This embodiment further explains Embodiment 2: a limiting ring 22 is provided at the discontinuity between the pressure building section 1504 and the coupling section 1505, and the limiting ring 22 is fixedly connected to the extrusion pipe 13; a stirring rod 21 is provided at the discontinuity between the coupling section 1505 and the homogenization section 1506; a crushing part 32 is provided at the other end of the movable rod 30, and in the initial state, the crushing part 32 is placed outside the opening 31; a connecting rod 33 and a rotating rod 28 are respectively provided at both ends of the bottom of the fan blade 25, and the other end of the rotating rod 28 is rotatably connected to the rod body of the extrusion screw 15; a sliding ring 26 that fits against the pressure plate 27 is provided on the rod body of the extrusion screw 15, and the two ends of the connecting rod 33 are rotatably connected to the fan blade 25 and the sliding ring 26 respectively; two fixed rods 23 are of different lengths, and the two sets of fan blades 25, pressure plates 27, and arc-shaped baffles 24 connected to the two fixed rods 23 are arranged one in front of the other on the two extrusion screws 15.

[0028] refer to Figure 10 In this embodiment, the sliding ring 26 slides on the rod of the extrusion screw 15 via a limiting block (which has a groove corresponding to the limiting block). The pressure plate 27 is in contact with the sliding ring 26 (not fixedly connected). The pressure plate 27 also slides on the rod of the extrusion screw 15. The arc-shaped baffle 24 is fixedly connected to the coupling section 1505 via a fixing rod 23. One end of the movable rod 30 is fixed to the pressure plate 27, and the other end is provided with a breaking part 32 and slides in the opening 31 in the arc-shaped baffle 24.

[0029] Furthermore, when the pressure plate 27 is subjected to pressure, it pushes the sliding ring 26 (in which process the elastic element 29 is stretched or compressed, depending on how the initial state of the elastic element 29 is set), and the sliding ring 26 moves on the rod of the extrusion screw 15, thereby adjusting the angle of the fan blade 25.

[0030] In one embodiment, one approach is to use a segmented screw design: The three-stage linkage of pressurization stage 1502 → depressurization stage 1503 → pressure building stage 1504 1502 Pressure boosting section: At high speed, the pitch is rapidly reduced (lead compression ratio 1:0.35) to quickly increase pressure and temperature, achieving initial melting (180℃→260℃). Pressure relief section 1503: The pitch suddenly increases by 30% to form a negative pressure zone, which discharges volatiles and releases shear heat to prevent the melt from overheating and degrading (the temperature drops back to 230℃). Pressure building section 1504: The pressure is increased through secondary compression (secondary reduction of lead), but with the help of the limiting ring 22 to seal against backflow, ensuring that the melt continues to move forward without stagnation; Effect: It maintains high-speed production capacity while dispersing the heat load through the "compression-decompression-recompression" cycle, avoiding local overheating caused by continuous high pressure.

[0031] II. Homogenization Section 1506 Dynamic Compensation for Low Compression Ratio Defects When a low compression ratio leads to an increase in unmelted particles: The melt pressure pushes the pressure plate 27 to compress the elastic element 29, driving the crushing part 32 to extend out of the opening 31, directly mechanically crushing unmelted lumps (such as unmelted PET crystal nuclei), and simultaneously triggering the adaptive adjustment of the tilt angle of the fan blade 25. At low pressure: the fan blades are at a pumping angle of 25 (to accelerate material discharge); Under high pressure: the fan blades rotate to a reverse thrust angle at 25 degrees (extending the residence time of the melt); Effects: Physical crushing and extended melting time compensate for insufficient compaction caused by low compression ratio, greatly reducing the rate of unmelted nuclei.

[0032] It should be noted that the reference Figure 10 The fan blade 25 is hinged to the extrusion screw 15 via the rotating rod 28, providing a pivot point for rotation. The bottom of the fan blade 25 is hinged to the sliding ring 26 via the connecting rod 33.

[0033] III. Coupling Section 1505 Precision Temperature Control Protection Additive Zoned temperature strategy: First half: Heating to 260℃ (low melt viscosity, which is beneficial for filler wetting); Second half: Cool down to 200-220℃ (gentle mixing for small lead threads) to avoid decomposition of heat-sensitive fillers (such as flame retardants); Stirring rod 21 forcibly disperses: breaks up the packing agglomerates formed due to low compression ratio; Effect: Solves the problem of layered distribution caused by high-viscosity melt during downstream feeding.

[0034] In this invention, the limiting ring 22 prevents the backflow of high-temperature melt, thereby maintaining the optimal melting temperature of the pressure-building section 1504 and preventing local overheating and degradation.

[0035] In this invention, plastic waste enters the feeding section 1501 from the first feeding port 19. Two extrusion screws 15, rotating in opposite directions, convey polyester chips forward. The large-lead screws achieve high-throughput conveying. (Refer to...) Figure 3 Forced cooling is achieved through air outlet 14 (an air outlet 14 is located directly below the feeding section 1501 and connected to an external air source), maintaining the solid state of the slices in the feeding section 1501. Upon entering the pressurization section 1502, the screw pitch decreases and the thread depth becomes shallower, compressing and heating the plastic waste, causing it to initially melt. During this process, the lead decreases sharply, further compressing the plastic waste, in conjunction with the heating module (see reference). Figure 2 and Figure 3The three parallel first heating sections 11 rapidly melt (temperature gradient: 180℃→260℃); then reach the pressure relief section 1503, where the pitch suddenly increases to form a negative pressure zone, promoting the discharge of volatiles in the melt. More specifically, with stable delivery at a medium lead, the melt is initially pressure-relieved at the gap between the pressure-increasing section 1502 and the pressure relief section 1503, and volatile gases are discharged from the exhaust port; the melt continues into the pressure-building section 1504, where it is repressurized through the contraction channel. The limiting ring 22 set here enhances the sealing and prevents the backflow of plastic waste. During the process from the pressure relief section 1503 to the pressure-building section 1504, the lead decreases, generating high shear force, further breaking up unmelted crystals; the pressurized melt flows to the coupling section 1505, where the meshing elements of the twin screws perform high-intensity shearing on the plastic waste. At this time, the second feed port 20... Added additives such as color masterbatch are forcibly mixed (stirring rod 21 rotates with extrusion screw 15 to initially stir the mixed plastic waste, and after entering the homogenization section 1506, two fixed rods 23 of different lengths can further stir). It should be noted that in the first half of the coupling section 1505: heating to 260℃ minimizes the melt viscosity. In the intermittent pressure building section 1504 - coupling section 1505: color masterbatch / auxiliary agent is injected from the second feed port 20 and rapidly drawn in using the pressure difference. The second half of the coupling section 1505: heating is stopped (temperature drops to 200-220℃), the small lead thread is used for gentle mixing to protect the activity of the additives, and the stirring rod 21 set at the discontinuity further breaks up the agglomerates.

[0036] After the plastic waste enters the core homogenization section 1506: Dynamic pressure regulation: When the melt pressure (the pressure inside the pipeline increases, i.e., the amount of unmelted plastic waste increases) pushes the pressure plate 27 to overcome the resistance of the elastic element 29, causing the movable rod 30 to move in the extrusion direction. The crushing part 32 at its end extends out from the opening 31 and directly crushes the unmelted particles.

[0037] Adaptive flow guidance: Synchronously, the displacement of the pressure plate 27 drives the sliding ring 26 to move axially, and the tilt angle of the fan blade 25 is changed through the connecting rod 33. The rotating rod 28 provides a fulcrum; the greater the pressure, the larger the tilt angle of the fan blade 25, which increases the intensity of melt turbulence.

[0038] Efficiency Enhancement through Misaligned Design: The two mechanisms are arranged with a phase difference due to the difference in length of the fixed rod 23, so that the crushing and guiding actions of the twin screws are carried out alternately, avoiding dead zones in the flow.

[0039] The homogenized melt is extruded from the discharge port 16 (the distance from the homogenization section 1506 to the discharge port 16 to the cutting blade 18 is relatively long and there is no heating, so the melt cools rapidly during natural cooling). The cutting blade 18 cuts the melt to a set length. The power source is the second drive unit 3. The pellets are pneumatically conveyed to the receiving bucket 9 by the blower 10 through the receiving hopper 8.

[0040] It is important to note that an increase in unmelted plastic waste will lead to an increase in pressure within the pipes. Unmelted particles accumulate, reducing the flow cross-sectional area. When the flow velocity remains constant, this will increase the pressure inside the pipe. Unmelted particles act as "rigid fillers" → the apparent viscosity of the melt increases, which in turn leads to increased pressure inside the pipeline; When an increase in unmelted plastic waste leads to a rise in pipeline pressure, the unmelted plastic waste enters the screen composed of the opening 31 and the movable rod 30, increasing the residence time of the plastic waste and accelerating its melting. When there is too much unmelted plastic waste, the screen composed of the opening 31 and the movable rod 30 becomes clogged, increasing the pipeline pressure. The melt pressure pushes the pressure plate 27 to overcome the resistance of the elastic element 29, causing the movable rod 30 to move in the extrusion direction. The crushing part 32 at its end extends from the opening 31, directly crushing the unmelted particles and accelerating the melting of the unmelted particle agglomerates. The melt pressure pushes the pressure plate 27 to overcome the resistance of the elastic element 29, causing the movable rod 30 to move in the direction of plastic waste extrusion. The pressure plate 27 pushes the sliding ring 26, and the sliding ring 26 pushes the fan blade 25 through the connecting rod 33. Since the other end of the fan blade 25 is restricted to the rod body of the extrusion screw 15 by the rotating rod 28, the angle of the fan blade 25 deflects. In the initial state, the fan blade 25 can be set as a pump push structure. When the fan blade 25 rotates with the extrusion screw 15, it can accelerate the movement of plastic waste in the pipeline toward the discharge port 16. At the same time, the rotating fan blade 25 also acts as a stirring device to further mix the mixed plastic waste. As the pressure inside the pipeline increases (i.e., the amount of unmelted plastic waste increases in the mixing section 1505 and homogenization section 1506), the pressure plate 27 pushes the sliding ring 26, forcing the fan blade 25 to change its rotation angle. The fan blade 25 changes from initially accelerating the pumping out of plastic waste to only stirring the plastic waste without pumping it out (by increasing stirring and extending the residence time of the plastic waste, the plastic waste is further melted). When the amount of unmelted plastic waste in the mixing section 1505 and homogenization section 1506 further increases, the stroke of the pressure plate 27 pushing the sliding ring 26 increases. At this time, the movable rod 30 moves in the extrusion direction, and the crushing part 32 at its end... Extending from the opening 31, it directly breaks up unmelted particles, accelerates the melting of unmelted particle clumps, clears blockages in the opening 31, and moves plastic waste (including unmelted plastic waste) toward the discharge port 16. However, at this time, the pressure plate 27 pushes the sliding ring 26 to its maximum stroke, and the fan blade 25 enters the reverse thrust state. As the extrusion screw 15 rotates, it pushes the plastic waste back, further extending the residence time of the plastic waste. At the same time, the returning plastic waste collides with the advancing plastic waste, accelerating the melting of unmelted plastic waste. It should be noted that the second heating section 12 mainly heats the hollow section in the middle part of the homogenization section 1506 and the rear part of the hollow section. The first heating section 11 and the second heating section 12 are both located on the extrusion pipe 13.

[0041] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0042] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A twin-screw melt extruder for polyester chips, comprising a frame (1), characterized in that: The extrusion pipe (13) is set on the frame (1), and the first feeding port (19) and the second feeding port (20) are respectively set at the end and the middle and rear of the extrusion pipe (13), and the discharge port (16) is set at the other end of the extrusion pipe (13). Two extrusion screws (15) are arranged in parallel inside the extrusion tube (13). The extrusion screws (15) are, in sequence, a feeding section (1501), a pressurizing section (1502), a pressure-releasing section (1503), a pressure-building section (1504), a mixing section (1505), and a homogenizing section (1506) from the first feeding port (19) to the discharge port (16). The homogenization section (1506) is divided into two sections, with the middle section being a hollow section. Each of the two extrusion screws (15) in the hollow section is provided with a fixed rod (23). The fixed rod (23) is provided with an arc-shaped baffle (24). The arc-shaped baffle (24) is provided with several openings (31). The openings (31) are provided with movable rods (30). One end of the movable rod (30) is fixedly connected to a pressure plate (27). An elastic element (29) is provided between the pressure plate (27) and the arc-shaped baffle (24). The extrusion screw (15) is provided with a fan blade (25) that cooperates with the pressure plate (27).

2. The twin-screw melt extruder for polyester chips according to claim 1, characterized in that: The extrusion tube (13) is covered with a cover (4), and the cover (4) is provided with a first feeding bin (5) and a second feeding bin (6) corresponding to the first feeding port (19) and the second feeding port (20), respectively. The frame (1) located inside the cover (4) is provided with a number of air outlets (14).

3. The twin-screw melt extruder for polyester chips according to claim 1, characterized in that: The frame (1) is provided with a first drive unit (2) and a second drive unit (3). The first drive unit (2) is used to drive the extrusion screw (15). An isolation cover (7) is provided between the second drive unit (3) and the extrusion tube (13). A transmission rod (17) powered by the second drive unit (3) is provided inside the isolation cover (7). A cutter (18) corresponding to the discharge port (16) is provided on the transmission rod (17).

4. The twin-screw melt extruder for polyester chips according to claim 1, characterized in that: It also includes a receiving hopper (8) corresponding to the discharge port (16), the receiving hopper (8) being connected to a receiving bucket (9) via a pipe, the pipe being connected to the air outlet of the blower (10).

5. A twin-screw melt extruder for polyester chips according to claim 1, characterized in that: A limiting ring (22) is provided at the discontinuity between the pressure building section (1504) and the mixing section (1505), and the limiting ring (22) is fixedly connected to the extrusion pipe (13).

6. A twin-screw melt extruder for polyester chips according to claim 5, characterized in that: A stirring rod (21) is provided at the discontinuity between the mixing section (1505) and the homogenization section (1506).

7. A twin-screw melt extruder for polyester chips according to claim 1, characterized in that: The other end of the movable rod (30) is provided with a breaking part (32), which is initially placed outside the opening (31).

8. A twin-screw melt extruder for polyester chips according to claim 7, characterized in that: The bottom of the fan blade (25) is provided with a connecting rod (33) and a rotating rod (28) at both ends respectively, and the other end of the rotating rod (28) is rotatably connected to the rod body of the extrusion screw (15).

9. A twin-screw melt extruder for polyester chips according to claim 8, characterized in that: The extrusion screw (15) has a sliding ring (26) that fits against the pressure plate (27) on its shaft, and the two ends of the connecting rod (33) are rotatably connected to the fan blade (25) and the sliding ring (26) respectively.

10. A twin-screw melt extruder for polyester chips according to claim 9, characterized in that: The two fixed rods (23) are of different lengths, and the two sets of fan blades (25), pressure plate (27), and arc baffle (24) connected to the two fixed rods (23) are arranged one in front of the other on the two extrusion screws (15).

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