Continuous pelletizing method for PBT (Polybutylece Terephthalate) production

Abstract

The invention discloses a continuous pelletizing method for PBT production, and relates to the technical field of plastic granulation. The method comprises the steps of vacuum chain and double-screw extrusion, three-section type graded water cooling, oscillation infrared online crystallization, nitrogen positive pressure pelletizing and air knife water removal-energy recovery. The cooling tank is partitioned according to the temperature of 25-40 DEG C to 60 DEG C, and a V-shaped quartz guide rail is arranged to support the fuse strip; the infrared lamp is applied to the wave band of 2-3 m at the micro-vibration of 8 Hz and + / -2 mm, so that the crystallinity of the surface layer of the fuse strip reaches 40-45%; 0.03 MPa nitrogen and O < = 1% are maintained in a pelletizing cavity, yellowing is prevented, and the dust explosion risk is reduced; according to the method, stable melt purity, on-line rapid crystallization, low-oxygen safe pelletizing and energy closed-loop utilization are realized, the production line is shortened, the energy consumption is reduced, and the obtained pellets are bright and clean.

Description

Technical Field

[0001] The present invention relates to the technical field of plastic granulation, and specifically to a continuous pelletizing method for PBT production. Background Art

[0002] The existing continuous pelletizing production of PBT generally follows the process of "single-stage normal-temperature water tank cooling + hot air / oven offline crystallization + atmospheric air pelletizing". Its defects are mainly reflected in: Cooling defect: The cooling rate of a single normal-temperature water tank is too fast, the melt bar is cooled from the outside and heated from the inside, with large residual stress, and subsequent pelletizing is prone to crack and chip, and the metal guide rail scratches the surface. Low crystallization efficiency: Offline hot air or oven crystallization requires long strip winding and then secondary heating, with a long process, high energy consumption, large floor area, and uneven crystallization caused by secondary moisture absorption. Oxidation and safety risks: When pelletizing with atmospheric air, the fresh cut surface above 130°C is exposed to an oxygen-rich environment and is prone to yellowing; the minimum ignition energy of PBT dust is only 40 mJ, and electrostatic accumulation induces potential safety hazards of St2-level dust explosion. Summary of the Invention

[0003] To overcome the defects of the above-mentioned prior art, the present invention provides the following technical solutions: A continuous pelletizing method for PBT production, including the following steps: S1. After drying, PBT slices are melted by a twin-screw reactive extruder, vacuum devolatilized, and chain extender is injected to form a melt bar; S2. The melt bar is introduced into a cooling tank, and the cooling tank is divided into three cooling strokes by a stainless steel partition. Each stroke is provided with an independent temperature zone, namely the first temperature zone of 25°C (rapid shaping), the second temperature zone of 40°C (stress relaxation), and the third temperature zone of 60°C (preheating and crystallization matching). And an air knife is provided on the side of the cooling tank far from the heat sink to remove surface residual water; S3. The cooled melt bar enters the oscillating infrared crystallization section, the infrared lamp surface is 30 mm away from the melt bar, and the whole vibrates at 8 Hz, ±2 mm, so that the surface crystallinity of the melt bar reaches 40–45%; S4. The melt bar enters the pelletizing cavity and is sheared by pelletizing tools. There are a total of three pelletizing tools, which are fixed on the pelletizing tool mounting plate in a circular array. Among them, the pelletizing cavity is filled with nitrogen with a pressure 0.03 MPa higher than the atmospheric pressure, so that the volume fraction of O2 ≤ 1%; S5. The melt bar after pelletizing is discharged through the discharge port and enters the finished product bin.

[0004] Preferably, the distance between the air knife nozzle and the surface of the melt bar ≤ 150 mm, and the spraying speed is 300 ± 20 m / s.

[0005] Preferably, the infrared lamps in the oscillating infrared crystallization section are four 2 kW iodine tungsten lamps, which are evenly arranged along the axial direction of the melt bar.

[0006] Preferably, the tip radius of the pelletizing tool is 0.05 mm, and the cutting edge is coated with titanium aluminum nitride TiAlN.

[0007] Preferably, the twin-screw reactive extruder includes a feeding section, a plasticizing section, a homogenizing section, a vacuum devolatilization port, and a metering and extrusion section, and finally a melt bar is formed; among them, the feeding section, the plasticizing section, and the homogenizing section are located in a vacuum environment.

[0008] Preferably, the inside of the stainless steel partition is hollow, and the lower surface of the cooling tank is in contact with and equipped with refrigeration chips at the positions of the first temperature zone of 25 °C, the second temperature zone of 40 °C, and the third temperature zone of 60 °C. The lower surface of the refrigeration chip is in contact with and equipped with a heat sink. The cooling tank is fixed overhead on the heat sink, so that the refrigeration chip is clamped between the cooling tank and the heat sink; the heat sink is fixedly installed on the support base, and a gas guide chamber is provided on one side of the support base away from the twin-screw reactive extruder. A melt bar through-hole is opened on the gas guide chamber, and melt bar through-holes are opened on both of the two stainless steel partitions, and the melt bar through-holes facilitate the passing of the melt bar.

[0009] Preferably, the oscillating infrared crystallization section is fixed overhead on the feeding table, the feeding table and the support base are both fixed on the frame, and the gas guide chamber is communicated with the bottom surface of the support base. Among them, the air flow blown by the air knife will pass through the melt bar through-hole on the gas guide chamber and enter the inside of the gas guide chamber, and flow along the guidance of the gas guide chamber to the bottom surface of the support base to dissipate heat from the heat sink, and the heat sink is in contact with the heating surface of the refrigeration chip.

[0010] Preferably, the pelletizing chamber is fixedly installed on the feeding table, the pelletizing chamber is communicated with the discharge port, and the nitrogen gas inside the pelletizing chamber is provided in real time by the nitrogen supply unit; among them, the pelletizing tool mounting disc is rotatably installed on the inner wall of the pelletizing chamber, and a pelletizing motor is fixedly installed on the outer wall of the pelletizing chamber. The output shaft of the pelletizing motor is fixedly matched with the pelletizing tool mounting disc, and the output shaft of the pelletizing motor is rotationally and sealingly matched with the pelletizing chamber.

[0011] Preferably, an extrusion roller is arranged between the oscillating infrared crystallization section and the pelletizing chamber, and a driving friction roller magnetically matched with the extrusion roller is arranged below the extrusion roller. The driving friction roller is rotatably embedded under the upper surface of the feeding table, so that the peripheral edge of the driving friction roller protrudes from the upper surface of the feeding table. Rubber is arranged on the circumferential surfaces of the extrusion roller and the driving friction roller to increase or decrease the friction force on the solidified melt bar.

[0012] Preferably, two side conveying brackets are symmetrically and fixedly installed on the feeding table. Among them, the driving friction roller is rotatably installed between the two side conveying brackets, and a side driving motor is fixedly installed on the side conveying bracket. The driving friction roller is fixedly installed on the output shaft of the side driving motor to drive the driving friction roller to rotate. A chute is also opened on each side conveying bracket, and both ends of the extrusion roller are rotatably and slidably arranged in the chute.

[0013] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention adopts a three-stage cooling water tank of "25°C rapid shaping - 40°C slow stress release - 60°C pre-heating", supplemented by a V-shaped quartz guide rail with a top angle of 60° and a groove depth of 2mm to support the melting rod, which not only reduces the internal stress locking caused by the drastic cooling of the traditional single-stage normal temperature water tank, but also avoids secondary contamination of the metal guide rail; the melting rod slides on the inert quartz surface with the minimum contact area, without adhesion or scratches along the way, and the cooling stress is released in stages , uniform size shrinkage, almost no warping or cracking in subsequent pelletizing, and significantly improved convergence of particle size distribution; (2) The oscillating infrared crystallization section of the present invention precisely couples the 2-3µm band of the 2kW iodine tungsten lamp to the C-H frequency doubling and carbonyl combined vibration absorption peaks of the PBT molecule, and realizes axial frequency sweep of the light spot through 8Hz, ±2mm micro-vibration. The surface layer rises from 60℃ to 100℃ within hundreds of milliseconds, and the crystallinity rises to 40-45%; compared with the traditional two-stage oven, which takes 3-5 minutes to reach the same temperature The crystallinity is the same as that of the conventional design. The crystallization is completed online, the production line is shortened by ≥2m, the energy consumption is reduced by more than 35%, and the gradient diffusion eliminates the temperature difference between water cooling and hot drying. There is no cracking or chipping during pelletizing, and the dust volume is reduced by half. (3) The pelletizing chamber of the present invention maintains a slightly positive pressure of nitrogen at 0.03MPa, so that the O2 volume fraction is ≤1%. The fresh cut surface is still in a low oxygen state under the friction heating environment of 130℃, blocking the yellowing and white fog caused by surface oxidation. Nitrogen has low thermal conductivity and carries static electricity, which makes the powder The minimum ignition energy of dust is increased, the Dust-Ex level is reduced from St2 to St1, and the safety factor is increased by two levels; at the same time, positive pressure prevents the backflow of air and water vapor, eliminates wire drawing and secondary hydrolysis, and the gloss and color of the particles are stable for a long time. The life of the tool is also extended by 30% due to anaerobic corrosion; (4) The 300m / s air knife of the present invention scrapes off the residual water on the surface with a spray distance of ≤150mm, and the purge air flow reversely cools the heat sink through the air guide chamber, so that the hot surface of the refrigeration plate obtains secondary heat exchange, and the utilization rate of the cold source is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is the overall flow chart of the present invention.

[0015] Figure 2 It is a structural schematic diagram of the support base of the present invention.

[0016] Figure 3 It is a structural schematic diagram of the air guide chamber of the present invention.

[0017] Figure 4 For the present invention Figure 3 Schematic diagram of the structure at point A in the middle.

[0018] Figure 5 It is a schematic diagram of the cooling tank structure of the present invention.

[0019] In the figure: 101 - support base; 102 - heat sink; 103 - thermoelectric cooler; 104 - cooling tank; 105 - stainless steel partition; 106 - through hole for welding rod; 107 - air guide chamber; 108 - air knife; 109 - feeding table; 110 - oscillating infrared crystallization section; 111 - pelletizing chamber; 112 - discharge port; 113 - side conveyor support; 114 - side drive motor; 115 - chute; 116 - extrusion roller; 117 - pelletizing motor; 118 - pelletizing cutter; 119 - pelletizing cutter mounting disc; 120 - twin-screw reactive extruder; 121 - protective housing; 122 - driving friction roller. Detailed implementation manners

[0020] The following combines with the attached Figures 1-5 drawings, and further illustrates the technical solution of the present invention through specific implementation manners.

[0021] The present invention provides a continuous pelletizing method for PBT production, including the following steps: S1. After drying, the PBT chips are melted, vacuum devolatilized, and chain extender is injected through a twin-screw reactive extruder 120 to form a melt strip; S2. The melt strip is introduced into a cooling tank 104. The cooling tank 104 is divided into three cooling strokes by a stainless steel partition 105. Each stroke is provided with an independent temperature zone, namely the first temperature zone at 25°C (rapid shaping), the second temperature zone at 40°C (stress relaxation), and the third temperature zone at 60°C (preheating and crystallization matching). And an air knife 108 is arranged on the side of the cooling tank 104 away from the heat sink 102 to remove surface residual water; the total effective cooling stroke of the cooling tank 104 is ten meters, and a V-shaped quartz guide rail is arranged inside to support the melt strip. The apex angle of the V-shaped quartz guide rail is 60°, and the depth of the guide rail groove is 2 mm; S3. The cooled melt strip enters an oscillating infrared crystallization section 110. The infrared lamp surface is 30 mm away from the melt strip, and the whole vibrates at 8 Hz and ±2 mm, so that the surface crystallinity of the melt strip reaches 40–45%; the selected 2–3 µm infrared band highly coincides with the absorption peak of the C–H overtone and carbonyl (C=O) combined vibration in the PBT molecule. Therefore, the surface layer of the melt strip can quickly absorb radiation energy and be raised from about 60°C to about 100°C within hundreds of milliseconds to achieve rapid directional crystallization; the micro-vibration (±2 mm, 8 Hz) makes the light spot sweep evenly in the axial direction to avoid local overheating. The surface crystallinity is increased to 40-45%, the surface hardness rises, and the toughness remains, which is convenient for subsequent neat shearing; the infrared heating diffuses in a gradient from the outside to the inside, and the micro-vibration increases the convective heat transfer coefficient, the gradient is gentle, and the temperature difference and residual stress generated by the cooling water tank are eliminated, so that there are no explosion marks or chip dropping during pelletizing, and the dust amount is reduced. Crystallization is completed online without a secondary oven, shortening the production line length by ≥2 m; S4. The melt strip enters a pelletizing chamber 111 and is sheared by pelletizing cutters 118. There are three pelletizing cutters 118 in total, and the three pelletizing cutters 118 are fixedly arranged on a pelletizing cutter mounting disc 119 in a circular array. Among them, the pelletizing chamber 111 is filled with nitrogen with a pressure 0.03 MPa higher than the atmospheric pressure, so that the volume fraction of O2 ≤ 1%; the linear speed of the cutter disc is 65 m / s, and the local frictional heat generation > 130°C; O2 will cause surface oxidation, yellowing or white fog on the fresh cut surface. The slightly positive pressure nitrogen reduces the O2 concentration to ≤ 1%, which can improve the glossiness of the pellet surface, keep it unchanged in color during long-term storage, and inhibit oxidation and white spots; the positive pressure is formed from the inside of the pelletizing chamber 111 to the outside, and air and water vapor cannot backflow into the inside of the pelletizing chamber 111, effectively preventing air back suction from generating drawing; at the same time, the minimum ignition energy of PBT dust is 40 mJ; the low-oxygen environment + nitrogen removes static charges, and the Dust-Ex rating of the pelletizing area is changed from St2→St1, improving the safety rating and reducing the risks of dust explosion and static electricity; nitrogen has a low thermal coefficient and no oxygen corrosion, extending the tool life; S5. The melt strip after pelletizing is discharged through a discharge port 112 and enters a finished product bin.

[0022] The distance between the air knife 108 nozzle and the surface of the melt strip is ≤ 150 mm, and the spraying speed is 300 ± 20 m / s. The infrared lamps in the oscillating infrared crystallization section 110 are four 2-kW iodine-tungsten lamps, which are evenly arranged along the axial direction of the melt strip; they are integrally installed on a spring frame and driven by an eccentric wheel to vibrate slightly at 8 Hz and ± 2 mm; this raises the surface temperature of the melt strip to 100 °C and increases the crystallinity to 40–45%. The tip radius of the granulation cutter 118 is 0.05 mm, and the cutting edge is coated with TiAlN (titanium aluminum nitride).

[0023] The twin-screw reactive extruder 120 includes a feeding section, a plasticizing section, a homogenizing section, a vacuum devolatilization port, and a metering and extrusion section, and finally forms a melt strip; among them, the feeding section, the plasticizing section, and the homogenizing section are in a vacuum environment. In an environment below atmospheric pressure, the volatile small molecules (such as water, residual monomers, solvents, residual oligomers, degradation by-products, etc.) in the polymer melt vaporize rapidly due to a significant reduction in boiling point and are continuously extracted, thereby improving the resin purity, stabilizing the melt viscosity, and suppressing defects.

[0024] The inside of the stainless-steel partition 105 is hollow. Refrigeration chips 103 are arranged in contact at the positions where the lower surface of the cooling tank 104 is located in the first temperature zone of 25 °C, the second temperature zone of 40 °C, and the third temperature zone of 60 °C. A heat sink 102 is arranged in contact with the lower surface of the refrigeration chip 103. The cooling tank 104 is fixed above the heat sink 102 in a suspended manner, so that the refrigeration chip 103 is clamped between the cooling tank 104 and the heat sink 102; Water faucets with electric valves are arranged at the corresponding positions of the first temperature zone of 25 °C, the second temperature zone of 40 °C, and the third temperature zone of 60 °C for supplementing water into their respective temperature zones. Water level sensors are arranged in the first temperature zone of 25 °C, the second temperature zone of 40 °C, and the third temperature zone of 60 °C. The water level sensors are used to control the opening degree of the electric valves, so that the water levels inside the first temperature zone of 25 °C, the second temperature zone of 40 °C, and the third temperature zone of 60 °C remain constant. Temperature sensors are arranged inside the first temperature zone of 25 °C, the second temperature zone of 40 °C, and the third temperature zone of 60 °C for detecting the real-time temperature inside their respective temperature zones. When the temperature rises, the input current of the corresponding refrigeration chip 103 is controlled, thereby controlling the temperature of the cooling surface of the refrigeration chip 103 to achieve temperature control inside the corresponding temperature zone (since the melt strip has a temperature, the temperature will only rise, and only heat dissipation and cooling are required. At the same time, heating wires are arranged in the three temperature zones for preheating the cooling water inside the cooling tank 104).

[0025] The heat sink 102 is fixedly installed on the support base 101. On one side of the support base 101 away from the twin-screw reactive extruder 120, there is a gas guide chamber 107. A melt bar through-hole 106 is provided on the gas guide chamber 107. The melt bar through-hole 106 is also provided on each of the two stainless steel partitions 105. The melt bar through-hole 106 facilitates the passing of the melt bar. The oscillating infrared crystallization section 110 is fixedly installed overhead on the feeding table 109. The feeding table 109 and the support base 101 are both fixed on the frame. The gas guide chamber 107 communicates with the bottom surface of the support base 101. The air flow blown out by the air knife 108 will pass through the melt bar through-hole 106 on the gas guide chamber 107 and enter the interior of the gas guide chamber 107, and flow along the guidance of the gas guide chamber 107 to the bottom surface of the support base 101 to dissipate heat from the heat sink 102. The heat sink 102 is in contact with the heating surface of the refrigeration sheet 103. The pelletizing chamber 111 is fixedly installed on the feeding table 109. The pelletizing chamber 111 is communicated with the discharge port 112. The nitrogen gas inside the pelletizing chamber 111 is provided in real time by the nitrogen gas supply unit. The pelletizing tool mounting disc 119 is rotatably installed on the inner wall of the pelletizing chamber 111. A pelletizing motor 117 is fixedly installed on the outer wall of the pelletizing chamber 111. The output shaft of the pelletizing motor 117 is fixedly fitted with the pelletizing tool mounting disc 119. The output shaft of the pelletizing motor 117 is rotationally and sealingly fitted with the pelletizing chamber 111.

[0026] An extrusion roller 116 is provided between the oscillating infrared crystallization section 110 and the pelletizing chamber 111. A driving friction roller 122 magnetically engaged with the extrusion roller 116 is provided below the extrusion roller 116. The driving friction roller 122 is rotatably embedded under the upper surface of the feeding table 109, so that the peripheral edge of the driving friction roller 122 protrudes from the upper surface of the feeding table 109. Rubber is provided on the circumferential surfaces of the extrusion roller 116 and the driving friction roller 122 to increase or decrease the friction force on the solidified melt bar. Two side conveying brackets 113 are symmetrically and fixedly installed on the feeding table 109. The driving friction roller 122 is rotatably installed between the two side conveying brackets 113. A side driving motor 114 is fixedly installed on the side conveying bracket 113. The driving friction roller 122 is fixedly installed on the output shaft of the side driving motor 114 to drive the driving friction roller 122 to rotate. A chute 115 is also provided on each side conveying bracket 113. The two ends of the extrusion roller 116 are rotatably and slidably arranged in the chute 115.

[0027] To protect the safety of construction workers, protective housings 121 are sleeved outside the material feeding table 109, the oscillating infrared crystallization section 110, the pelletizing cavity 111 (the overlapping section with the pelletizing tool mounting disc 119 and the pelletizing tool 118), and the air knife 108. Start the side driving motor 114, and the output shaft of the side driving motor 114 drives the driving friction roller 122 to rotate. The driving friction roller 122 drives the solidified melt strip to move through friction (the extrusion roller 116 and the driving friction roller 122 attract each other to provide driving friction). Before use, it is necessary to wait for the twin-screw reactive extruder 120 to extrude the melt strip, and then after solidification and cooling, manually conduct traction and operate slowly, passing through the melt strip through holes 106 on the two stainless steel partitions 105, the melt strip through holes 106 on the air guiding chamber 107, between the air knife 108 and the material feeding table 109, below the oscillating infrared crystallization section 110, and between the extrusion roller 116 and the driving friction roller 122 in sequence, and finally enter the pelletizing cavity 111 to be cut by the pelletizing tool 118. Start the pelletizing motor 117, and the output shaft of the pelletizing motor 117 drives the pelletizing tool 118 on the pelletizing tool mounting disc 119 to rotate, and then quickly conduct pelletizing work on the solidified melt strip entering the pelletizing cavity 111.

Claims

1. A continuous pelletizing method for PBT production, characterized in that, It includes the following steps: S1. After drying, the PBT chips are melted by a twin-screw reactive extruder (120), degassed under vacuum, and a chain extender is injected to form a melt strip; S2. The melt strip is introduced into the cooling tank (104). The cooling tank (104) is divided into three cooling strokes by a stainless-steel partition (105). Each stroke is provided with an independent temperature zone, namely the first temperature zone at 25 °C, the second temperature zone at 40 °C, and the third temperature zone at 60 °C. And an air knife (108) is arranged on the side of the cooling tank (104) away from the heat sink (102) to remove residual water on the surface; S3. The cooled melt strip enters the oscillating infrared crystallization section (110). The distance between the infrared lamp surface and the melt strip is 30 mm, and the whole vibrates at 8 Hz and ±2 mm, so that the surface crystallinity of the melt strip reaches 40–45%; S4. The melt strip enters the pelletizing chamber (111) and is sheared by the pelletizing cutter (118). There are three pelletizing cutters (118) in total, and the three pelletizing cutters (118) are fixedly arranged in a circular array on the pelletizing cutter mounting disk (119). Among them, the pelletizing chamber (111) is filled with nitrogen at 0.03 MPa higher than atmospheric pressure, so that the volume fraction of O2 ≤ 1%; S5. The melt strip after pelletizing is discharged through the discharge port (112) and enters the finished product bin.

2. The continuous pelletizing method for PBT production according to claim 1, characterized in that: The distance between the nozzle of the air knife (108) and the surface of the melt strip ≤ 150 mm, and the spraying speed is 300 ± 20 m / s.

3. A continuous pelletizing method for PBT production according to claim 2, characterized in that: The infrared lamps in the oscillating infrared crystallization section (110) are four 2-kW iodine-tungsten lamps, which are evenly arranged along the axial direction of the melt strip.

4. A continuous pelletizing method for PBT production according to claim 3, characterized in that: The tip radius of the pelletizing cutter (118) is 0.05 mm, and the cutting edge is coated with titanium aluminum nitride TiAlN.

5. A continuous pelletizing method for PBT production according to claim 4, characterized in that: The twin-screw reactive extruder (120) includes a feeding section, a plasticizing section, a homogenizing section, a vacuum degassing port, and a metering extrusion section, and finally forms a melt strip; among them, the feeding section, the plasticizing section, and the homogenizing section are in a vacuum environment.

6. A continuous pelletizing method for PBT production according to claim 5, characterized in that: The inside of the stainless-steel partition (105) is hollow. Refrigerating sheets (103) are arranged in contact with the lower surface of the cooling tank (104) at the positions of the first temperature zone at 25 °C, the second temperature zone at 40 °C, and the third temperature zone at 60 °C. The lower surface of the refrigerating sheet (103) is in contact with a heat sink (102). The cooling tank (104) is fixed above the heat sink (102) so that the refrigerating sheet (103) is clamped between the cooling tank (104) and the heat sink (102); The heat sink (102) is fixedly installed on the support base (101). A gas guide chamber (107) is arranged on the side of the support base (101) away from the twin-screw reactive extruder (120). A melt strip through hole (106) is opened on the gas guide chamber (107). Melt strip through holes (106) are opened on both of the two stainless-steel partitions (105), and the melt strip through holes (106) facilitate the passing of the melt strip.

7. A continuous pelletizing method for PBT production according to claim 6, characterized in that: The oscillating infrared crystallization section (110) is fixed above the feeding table (109) in a suspended manner. The feeding table (109) and the support base (101) are both fixed on the frame. The air guide chamber (107) communicates with the bottom surface of the support base (101). Among them, the air flow blown by the air knife (108) will pass through the fuse through-hole (106) on the air guide chamber (107) and enter the interior of the air guide chamber (107), and flow along the guidance of the air guide chamber (107) to the bottom surface of the support base (101) to dissipate heat from the heat sink (102). The heat sink (102) is in contact with the heating surface of the thermoelectric cooler (103).

8. A continuous pelletizing method for PBT production according to claim 7, characterized in that: Among them, the pelletizing chamber (111) is fixedly installed on the feeding table (109). The pelletizing chamber (111) is communicated with the discharge port (112). The nitrogen gas inside the pelletizing chamber (111) is provided in real time by the nitrogen supply unit. Among them, the pelletizing tool mounting disk (119) is rotatably installed on the inner wall of the pelletizing chamber (111). A pelletizing motor (117) is fixedly installed on the outer wall of the pelletizing chamber (111). The output shaft of the pelletizing motor (117) is fixedly fitted with the pelletizing tool mounting disk (119), and the output shaft of the pelletizing motor (117) is rotatably and sealedly fitted with the pelletizing chamber (111).

9. A continuous pelletizing method for PBT production according to claim 8, characterized in that: An extrusion roller (116) is arranged between the oscillating infrared crystallization section (110) and the pelletizing chamber (111). A driving friction roller (122) magnetically matched with the extrusion roller (116) is arranged below the extrusion roller (116). The driving friction roller (122) is rotatably embedded under the upper surface of the feeding table (109) so that the peripheral edge of the driving friction roller (122) protrudes from the upper surface of the feeding table (109). Rubbers are arranged on the circumferential surfaces of the extrusion roller (116) and the driving friction roller (122) to increase or decrease the friction force on the solidified fuse.

10. A continuous pelletizing method for PBT production according to claim 9, characterized in that: Two side conveying brackets (113) are symmetrically and fixedly installed on the feeding table (109). Among them, the driving friction roller (122) is rotatably installed between the two side conveying brackets (113). A side driving motor (114) is fixedly installed on the side conveying bracket (113). The driving friction roller (122) is fixedly installed on the output shaft of the side driving motor (114) to drive the driving friction roller (122) to rotate. A chute (115) is also opened on each side conveying bracket (113). The two ends of the extrusion roller (116) are rotatably and slidably arranged in the chute (115).

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