A process for the production of polymeric and cut-pile spun yarn

Abstract

The application discloses a preparation process of polymeric and sliced long spinning filaments and relates to the technical field of long spinning filament preparation. The specific steps are as follows: 1) terephthalic acid powder and sufficient ethylene glycol are added into a mixing tank, and the raw material ethylene glycol solution is mixed with antimony tris-acetate solution; 2) the ethylene glycol in which terephthalic acid powder is dissolved in step 1) is pumped into a preheating tank; 3) the slurry in the preheating tank is pumped into a tubular esterification reactor by a small liquid pump to perform a flow esterification reaction, and the liquid outlet end of the tubular esterification reactor is connected to an ethylene glycol evaporator; 4) the esterification solution after the completion of the esterification reaction stage is added into a continuous pressure-reducing polycondensation reaction system; 5) melt treatment; and 6) slicing and spinning long filaments. The esterification reaction and the polycondensation reaction are respectively completed through the tubular esterification reactor and the tubular polycondensation reactor, so that the problems in the prior long spinning filament preparation process, such as great energy loss, low controllability of product quality after the completion of the reaction, and uneven polycondensation molecular weight, are solved.

Description

Technical Field

[0001] This invention belongs to the field of filament preparation technology, and in particular relates to a preparation process for polymer and chip spinning filaments. Background Technology

[0002] The esterification reaction of purified terephthalic acid (PTA) with ethylene glycol requires a temperature of approximately 280°C, necessitating the use of biphenyl for heat preservation and continuous stirring. The reaction process is energy-intensive and incomplete, with the esterification rate typically not exceeding 96%. The reaction usually takes place in esterification reactors, requiring batch-by-batch reactions. After esterification, the products must be transferred to pre-polymerization and final polymerization reactors, resulting in significant energy losses during the transfer process. Multiple polymerization reactors are needed for the polymerization process, and the produced ethylene glycol requires a separate evaporator, making the entire process complex and costly. Furthermore, the pre-polymerization and final polymerization reactors can only operate at one pressure for a specific period before transferring to the next reactor, leading to energy losses and low energy utilization. Moreover, the pressure during polymerization is not gradual, resulting in large and uneven fluctuations in the molecular weight of the polymerized product, leading to variations in the melt's tensile properties and making it difficult to effectively control product quality. The quality of the polymerized product ultimately affects the quality of the subsequent fiber cutting.

[0003] Therefore, a process for preparing polymerized and chipped filaments is provided to solve the problems mentioned above. Summary of the Invention

[0004] The purpose of this invention is to provide a process for preparing polymerized and spun filaments, which uses a tubular esterification reactor and a tubular polycondensation reactor to complete the esterification and polycondensation reactions respectively, thus solving the problems of high energy loss, low product quality control after the reaction, and uneven molecular weight of polycondensation in the existing filament preparation process.

[0005] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0006] This invention relates to a process for preparing polymerized and chipped filaments, the specific steps of which are as follows:

[0007] I. Slurry Preparation

[0008] S1: Add terephthalic acid powder and sufficient ethylene glycol through the two feed pipes of the mixing tank. The raw material ethylene glycol solution is mixed with antimony triacetate solution. Heat the mixture in the mixing tank to 150-155℃ and stir continuously until the terephthalic acid powder slurry is dissolved in sufficient ethylene glycol.

[0009] S2: The ethylene glycol containing the dissolved terephthalic acid powder from step S1 is pumped into a preheating tank 2, which is preheated to 220-250°C. A booster pump is installed on the top of the preheating tank.

[0010] II. Esterification Reaction Stage

[0011] S1: The slurry in the preheating tank is pumped into the tubular esterification reactor by a small liquid pump for flow esterification reaction. The reaction temperature in the tubular esterification reactor is 280-290℃. A matting agent solution input pipe is connected to the pipe pumped into the tubular esterification reactor. The matting agent solution is titanium dioxide nanopowder dissolved in ethylene glycol solution. The liquid outlet of the tubular esterification reactor is connected to the ethylene glycol evaporator.

[0012] S2: After the ethylene glycol evaporator evaporates the ethylene glycol, it is discharged into the input end of the polycondensation reaction stage. If one ethylene glycol evaporator cannot completely evaporate the ethylene glycol, the liquid in the ethylene glycol evaporator is discharged again into the second tubular esterification reactor for secondary reaction through a liquid pump, and then discharged into the second ethylene glycol evaporator to evaporate the residual ethylene glycol.

[0013] III. Condensation Stage

[0014] S1: The esterification solution completed in the esterification reaction stage is added to a continuous depressurization polycondensation reaction system. The continuous depressurization polycondensation reaction system includes multiple negative pressure tanks and multiple tubular polycondensation reactors. The negative pressure tanks and tubular polycondensation reactors are connected alternately and sequentially. The pressure in the negative pressure tanks decreases step by step from the first to the last. The structure of the tubular polycondensation reactor is the same as that of the tubular esterification reactor. The reaction temperature in both the tubular polycondensation reactor and the tubular esterification reactor is between 280-290℃.

[0015] S2: The pressure inside the first negative pressure tank of the negative pressure tank is 0.3-0.5 atmospheres, and the pressure inside the last negative pressure tank of the negative pressure tank is less than 0.01 atmospheres;

[0016] IV. Melt Treatment

[0017] The melt formed by the reaction in the last negative pressure tank is discharged into the melt filter for filtration, and then discharged into the melt processing system for processing.

[0018] V. Spinning of chips into filaments

[0019] After being processed by the melt treatment system, the melt is fed into the filament spinning device or the filament slicing equipment to produce filaments.

[0020] The present invention is further configured such that the tubular esterification reactor includes an insulated box, an inlet collection box, an outlet collection box, and multiple bent reaction tubes. The inlet collection box and the outlet collection box have the same structure. The inlet collection box has an inlet at the middle of one side wall and an outlet on the other side wall. The outlet side walls of the inlet collection box and the outlet collection box are arranged opposite to each other. A bent reaction tube is connected between the corresponding outlets of the inlet collection box and the outlet collection box. The bent reaction tubes are connected and bent in multiple U-shaped tubes from bottom to top.

[0021] The present invention is further configured such that the bent reaction tube includes a straight tube and a U-shaped end tube, the straight tube and the U-shaped end tube are sequentially threaded together at intervals, the straight tube is filled with a baffle plate, the baffle plate has flow holes evenly distributed on it, and multiple abutment posts are evenly provided on one side of the baffle plate.

[0022] The present invention is further configured such that the ethylene glycol evaporator includes an overflow box and a condenser box. The overflow box contains multiple equally spaced overflow plates, the height of which gradually decreases from the liquid inlet end to the liquid outlet end. The thickness of the overflow plates is 10-20 cm. The overflow box has an evaporation port on the top wall of the right half. The condenser box is a horizontally placed L-shaped tube with one end open and the other end closed. The open end of the condenser box is sealed and connected to the evaporation port. The condenser box has a leakage hole at the bottom near the closed end. The condenser box has multiple condenser plates that are equally spaced on the top wall of the horizontally placed tube and tilt downward toward the closed end.

[0023] The present invention is further configured such that the negative pressure tank includes a first negative pressure tank, a second negative pressure tank, a third negative pressure tank and a fourth negative pressure tank arranged from left to right, and the tubular polycondensation reactor includes a first polycondensation reactor, a second polycondensation reactor and a third polycondensation reactor, and a flow control valve is provided on the connecting pipe between the negative pressure tank on the left and the adjacent tubular polycondensation reactor on the right.

[0024] The first, second, and third negative pressure tanks are all equipped with negative pressure vacuum pumps at their tops, and the fourth negative pressure tank is equipped with a turbine pump on its drain pipe at the bottom. The air pressure inside the first negative pressure tank is 0.3-0.5 atmospheres, the air pressure inside the second negative pressure tank is 0.1-0.2 atmospheres, the air pressure inside the third negative pressure tank is 0.05-0.1 atmospheres, and the air pressure inside the fourth negative pressure tank is less than 0.01 atmospheres.

[0025] The present invention is further configured such that the outlet of the negative pressure vacuum pump at the top of the first negative pressure tank, the second negative pressure tank and the third negative pressure tank is connected to the inlet of the condensing equipment by a pipe;

[0026] The ethylene glycol recovered by the ethylene glycol evaporator and the ethylene glycol recovered by the condensation equipment are reused and discharged into the mixing tank for further use.

[0027] The present invention is further configured such that the total length of the bent reaction tubes in the tubular esterification reactor and the tubular polycondensation reactor is 10-15m, the flow time of the reaction liquid from the inlet end to the outlet end of the bent reaction tube in the tubular esterification reactor is 1.5-2.5h, and the flow time of the reaction liquid from the inlet end to the outlet end of the bent reaction tube in the tubular polycondensation reactor is 10-30min.

[0028] The present invention is further configured such that the space inside the tubular esterification reactor and the tubular polycondensation reactor, outside the bent reaction tube, the inlet collection box and the outlet collection box, is filled with heat transfer oil. The heat transfer oil is biphenyl-biphenyl ether, triacetin, or silicone oil. The boiling point of the heat transfer oil used must be above 300°C. The outer walls of the tubular esterification reactor 3 and the tubular polycondensation reactor are wrapped with a heat-insulating ceramic layer.

[0029] The present invention is further configured such that the bent reaction tubes, inlet collection box, and outlet collection box in the tubular esterification reactor and the tubular polycondensation reactor are all made of stainless steel with a wall thickness of 2-3 mm. The inner diameter of the bent reaction tube in the tubular esterification reactor is 20-30 mm. The inner diameter of the bent reaction tube in the tubular polycondensation reactor gradually increases from the first polycondensation reactor, the second polycondensation reactor, and the third polycondensation reactor to adapt to the increase in viscosity of the polycondensation reaction. The inner diameter of the bent reaction tube in the first polycondensation reactor is at least 30 mm. As the inner diameter of the bent reaction tube 31 in the tubular polycondensation reactor increases, the number of bent reaction tubes in it decreases accordingly.

[0030] The present invention has the following beneficial effects:

[0031] 1. In this invention, the reaction slurry is first dissolved at a temperature of 150°C, preventing ethylene glycol evaporation. After dissolution, it is discharged into a preheating tank and preheated to near the reaction temperature. Due to the sealed nature of the preheating tank, ethylene glycol evaporation is limited. The slurry is then discharged into a tubular esterification reactor for esterification. Because there is no space for ethylene glycol evaporation within the pipeline, the reaction is more complete, maximizing the formation of ethylene glycol terephthalate from PTA. The conversion rate is higher than that of traditional esterification reactions, with lower heat loss. Furthermore, the pipeline reaction is a continuous reaction, allowing for continuous slurry delivery and continuous esterification. This eliminates the need for cleaning and reprocessing after each esterification reaction, thus preventing heat loss.

[0032] 2. The ethylene glycol evaporator of this invention is specially designed for continuous reaction evaporation and recovery of ethylene glycol. Because it is a continuous esterification reaction, the reaction products are continuously output in small amounts. The reaction liquid will gradually and continuously flow into the overflow box, where it will slowly overflow from left to right. The overflowing reaction liquid will be very thin on the overflow plate, which can quickly and fully evaporate the ethylene glycol. It will not cause problems such as slow evaporation of ethylene glycol inside, resulting in some ethylene glycol not evaporating. The reaction liquid can be recovered for subsequent operations.

[0033] 3. This invention requires continuous pressure reduction to increase the degree of polycondensation reaction, necessitating multiple pre-polycondensation reactors and one final polycondensation reactor. Since the pressure change is not gradual, there will be energy loss during the transfer of the reaction liquid. By connecting multiple continuously depressurized negative pressure tanks with tubular polycondensation reactors to transfer the reaction liquid, it can be ensured that the reaction liquid remains under low pressure during the transfer process, allowing for a low-pressure reaction. Moreover, the reaction liquid is always in a low-pressure, slowly changing process, preventing sudden pressure changes that could lead to uneven polymerization of the reaction products. This improves the controllability of product performance. If the pressure inside the bent reaction tube is insufficient to transfer viscous products during the transfer process, a viscous liquid pump can be installed on the pipeline to increase the pressure for transfer.

[0034] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the equipment flow structure for a process of preparing polymerized and spun filaments.

[0037] Figure 2 for Figure 1 A schematic diagram of the cross-sectional structure.

[0038] Figure 3 This is a schematic diagram of the structure below the insulated box at the tubular esterification reactor.

[0039] Figure 4 This is a schematic diagram of the bent reaction tube structure.

[0040] Figure 5 This is a schematic diagram of the spoiler structure.

[0041] Figure 6 This is a process flow diagram of the reaction stages in a polymerization and chip spinning process for preparing filaments.

[0042] The attached diagram lists the components represented by each number as follows:

[0043] 1. Mixing tank; 2. Preheating tank; 3. Tubular esterification reactor; 31. Bending reaction tube; 311. Baffle plate; 312. Flow hole; 32. Inlet collection box; 33. Outlet collection box; 4. Ethylene glycol evaporator; 40. Condensation box; 401. Condensation plate; 402. Leakage hole; 41. Overflow box; 411. Overflow plate; 5. First negative pressure tank; 6. First polycondensation reactor; 7. Second negative pressure tank; 70. Second polycondensation reactor; 8. Third negative pressure tank; 80. Third polycondensation reactor; 9. Fourth negative pressure tank. Detailed Implementation

[0044] 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.

[0045] Please see Figure 1-6 This invention relates to a process for preparing polymerized and chipped filaments, the specific steps of which are as follows:

[0046] I. Slurry Preparation

[0047] S1: Terephthalic acid powder and sufficient ethylene glycol are added through two feed pipes in mixing tank 1. The raw material ethylene glycol solution is mixed with antimony triacetate solution. The temperature in mixing tank 1 is heated to 150-155℃, and the mixture is stirred continuously until the terephthalic acid powder slurry is dissolved in sufficient ethylene glycol. Mixing tank 1 is also the raw material stirring and dissolving tank. Antimony triacetate, as a catalyst for the polycondensation reaction, is continuously metered and added to the slurry preparation tank from the feed tank using an intermittent feeding method, because the raw materials are also continuously added and dissolved. The two feed pipes ensure that the terephthalic acid powder and ethylene glycol are added separately and mixed in the tank.

[0048] S2: The ethylene glycol containing the dissolved terephthalic acid powder in step S1 is pumped into the preheating tank 2, which is preheated to 220-250°C. A booster pump is installed on the top of the preheating tank 2.

[0049] The purpose of preheating is to ensure that the reaction liquid reaches the reaction temperature quickly upon entering the tubular esterification reactor 3. Preheating also slows down the evaporation of ethylene glycol, further inhibiting its evaporation after it enters the pipeline. Titanium dioxide is a commonly used matting agent for fiber-grade polyester chips. A high-concentration matting agent suspension of titanium dioxide is prepared, ground to break up large aggregates, diluted with ethylene glycol to the required concentration, and then separated by centrifugation and filtration before being fed into the reactor.

[0050] II. Esterification Reaction Stage

[0051] S1: The slurry in the preheating tank 2 is pumped into the tubular esterification reactor 3 by a small liquid pump for flow esterification reaction. The reaction temperature in the tubular esterification reactor 3 is 280-290℃. A matting agent solution inlet pipe 20 is connected to the pipe that is pumped into the tubular esterification reactor 3. The matting agent solution is titanium dioxide nanopowder dissolved in ethylene glycol solution. The outlet end of the tubular esterification reactor is connected to the ethylene glycol evaporator 4.

[0052] A small liquid pump slowly pumps in the solution, ensuring that the reaction liquid flows slowly in the tubular esterification reactor 3, allowing for optimal flow reaction without the need for stirring.

[0053] S2: After the ethylene glycol evaporator 4 evaporates the ethylene glycol, the liquid is discharged into the input end of the polycondensation reaction stage. If one ethylene glycol evaporator 4 cannot completely evaporate the ethylene glycol, the liquid in the ethylene glycol evaporator 4 is pumped back into the second tubular esterification reactor 3 for a secondary reaction, and then discharged into the second ethylene glycol evaporator 4 to evaporate the remaining ethylene glycol. The ethylene glycol evaporator 4 is a specially designed evaporator that can evaporate and recover ethylene glycol under flowing reaction liquid. The outer wall of the ethylene glycol evaporator 4 is wrapped with a heating and insulation device (heating plate, heating wire, or insulation biphenyl are all acceptable, and the internal temperature is maintained at 220-250℃).

[0054] III. Condensation Stage

[0055] S1: The esterification solution completed in the esterification reaction stage is added to the continuous depressurization polycondensation reaction system, which includes multiple negative pressure tanks and multiple tubular polycondensation reactors. The negative pressure tanks and tubular polycondensation reactors are connected alternately and sequentially. The pressure in the negative pressure tanks decreases step by step from the first to the last. The structure of the tubular polycondensation reactor is the same as that of the tubular esterification reactor 3. The reaction temperature in both the tubular polycondensation reactor and the tubular esterification reactor 3 is between 280-290℃.

[0056] S2: The pressure inside the first negative pressure tank 5 of the negative pressure tank (each negative pressure tank is equipped with a stirring device, which is a conventional stirring device and its structure is not shown) is 0.3-0.5 atmospheres, and the pressure inside the last negative pressure tank is less than 0.01 atmospheres.

[0057] Because the pressure in the negative pressure tanks gradually decreases from left to right, there is a pressure difference between two adjacent negative pressure tanks. The reaction liquid flows from the high-pressure negative pressure tank to the low-pressure negative pressure tank. During the flow, the pressure of the reaction liquid in the pipeline changes gradually, achieving both uninterrupted reaction during the transfer process and optimal consistency and uniformity in the degree of polycondensation. That is, the molecular weight of the polycondensation is relatively concentrated and does not deviate significantly.

[0058] IV. Melt Treatment

[0059] The melt formed by the reaction in the last negative pressure tank is discharged into the melt filter for filtration, and then discharged into the melt processing system for further processing.

[0060] V. Spinning of chips into filaments

[0061] After being processed by the melt treatment system, the melt is fed into the filament spinning device or the filament slicing equipment to produce filaments.

[0062] Melt treatment and chip spinning are existing processing methods, and the specific detailed steps will not be described here.

[0063] The tubular esterification reactor 3 includes an insulated box, an inlet collection box 32, an outlet collection box 33, and multiple bent reaction tubes 31. The inlet collection box 32 and the outlet collection box 33 have the same structure. The inlet collection box 32 has an inlet in the middle of one side wall and an outlet on the other side wall. The outlet side walls of the inlet collection box 32 and the outlet collection box 33 are arranged opposite to each other. A bent reaction tube 31 is connected between the corresponding outlets of the inlet collection box 32 and the outlet collection box 33. The bent reaction tubes 31 are connected and bent in multiple U-shaped tubes from bottom to top.

[0064] The reaction liquid flows smoothly upwards from the bottom of the bent reaction tube 31. The pipeline design ensures uniform heating and a more thorough reaction, with no ethylene glycol evaporating during the process, resulting in better reaction performance. The inlet collection box 32 ensures the reaction liquid enters each bent reaction tube 31 evenly, and then collects from multiple bent reaction tubes 31 into the outlet collection box 33 before being discharged into the ethylene glycol evaporator 4.

[0065] The bent reaction tube 31 includes a straight tube and a U-shaped end tube. The straight tube and the U-shaped end tube are connected by threads at intervals. The straight tube is filled with baffles 311. The baffles 311 have flow holes 312 evenly distributed on them. Multiple abutment posts 313 are evenly provided on one side of the baffles 311.

[0066] Because the esterification reaction has low viscosity and is carried out at high temperatures, it is essentially a liquid. Furthermore, the bent reaction tube 31 contains a large amount of ethylene glycol solution, resulting in good flowability. Therefore, the flow-deflecting plate 311 can be used instead of stirring to swerve the flow, enabling continuous esterification.

[0067] The ethylene glycol evaporator 4 includes an overflow box 41 and a condenser box 40. The overflow box 41 contains multiple equally spaced overflow plates 411, the height of which gradually decreases from the liquid inlet end to the liquid outlet end. The thickness of the overflow plates 411 is 10-20 cm. The overflow box 41 has an evaporation port on the top wall of the right half. The condenser box 40 is a horizontally placed L-shaped tube with one end open and the other end closed. The open end of the condenser box 40 is sealed and connected to the evaporation port. The condenser box 40 has a leakage hole 402 at the bottom near the closed end. The condenser box 40 has multiple condenser plates 401 that are inclined downward toward the closed end and are equally spaced on the top wall of the horizontally placed tube.

[0068] The reaction liquid initially discharged into the overflow box 41 has space to evaporate ethylene glycol. When the reaction liquid is discharged, a large amount of steam and splashed liquid will be generated. Therefore, the top of the first half of the overflow box 41 is closed. The splashed liquid will drip down after hitting the top. The ethylene glycol evaporated in the second half will rise and flow from the L-shaped tube to the condenser plate 401. When it encounters the condenser plate 401, it will condense into droplets and drip down. Then it will be discharged and recycled through the drain hole 402.

[0069] The negative pressure tanks include a first negative pressure tank 5, a second negative pressure tank 7, a third negative pressure tank 8, and a fourth negative pressure tank 9 arranged from left to right. The tubular polycondensation reactors include a first polycondensation reactor 6, a second polycondensation reactor 70, and a third polycondensation reactor 80. A flow control valve 50 is provided on the connecting pipe between the negative pressure tank on the left and the adjacent tubular polycondensation reactor on the right.

[0070] The flow control valve 50 can control the flow rate of the reaction liquid. If it affects the discharge (when the viscosity is high, it can be fully opened without controlling the speed), the polycondensation reactor is used to smoothly discharge the reaction liquid to the next negative pressure tank (also called a tank-type polycondensation reactor, which has a stirring function).

[0071] The first negative pressure tank 5, the second negative pressure tank 7, and the third negative pressure tank 8 are all equipped with negative pressure vacuum pumps at their tops, and the fourth negative pressure tank 9 is equipped with a turbine pump on its drain pipe at the bottom. The air pressure inside the first negative pressure tank 5 is 0.3-0.5 atmospheres, the air pressure inside the second negative pressure tank 7 is 0.1-0.2 atmospheres, the air pressure inside the third negative pressure tank 8 is 0.05-0.1 atmospheres, and the air pressure inside the fourth negative pressure tank 9 is less than 0.01 atmospheres.

[0072] The pressure values ​​are set as needed, and the pressure of the third negative pressure tank 8 and the fourth negative pressure tank 9 is basically close to that of the existing final polycondensation reactor. When it is difficult to drain the reaction liquid from the negative pressure tank 5 into the polycondensation reactor by pressure difference, a viscous liquid pump can be installed to increase the pressure drainage capacity.

[0073] The negative pressure vacuum pump outlets at the top of the first negative pressure tank 5, the second negative pressure tank 7, and the third negative pressure tank 8 are connected to the air inlet of the condensing equipment via pipes; the negative pressure vacuum pump is used to depressurize each negative pressure tank, and ethylene glycol is produced during the reaction process, which is pumped out by the negative pressure vacuum pump for condensation and recovery.

[0074] The ethylene glycol recovered by the ethylene glycol evaporator 4 and the ethylene glycol recovered by the condenser are reused and discharged into the mixing tank 1 for reuse.

[0075] Ethylene glycol can be recycled and reused; the condensation equipment is simply an existing recycling device.

[0076] The total length of the bent reaction tubes 31 in both the tubular esterification reactor 3 and the tubular polycondensation reactor is 10-15m. The flow time of the reaction liquid from the inlet end to the outlet end in the bent reaction tube of the tubular esterification reactor 3 is 1.5-2.5h, and the flow time of the reaction liquid from the inlet end to the outlet end in the bent reaction tube 31 of the tubular polycondensation reactor is 10-30min.

[0077] As the viscosity of the subsequent polycondensation reaction increases, the bent reaction tube 31 inside the tubular polycondensation reactor will become shorter and thicker to increase the drainage effect.

[0078] The tubular esterification reactor 3 and the tubular polycondensation reactor are filled with heat-conducting oil in the space outside the bent reaction tube 31, the inlet collection box 32 and the outlet collection box 33. The heat-conducting oil is biphenyl-diphenyl ether, triacetin, or silicone oil. The boiling point of the heat-conducting oil used must be above 300°C. The outer wall of the tubular esterification reactor 3 and the tubular polycondensation reactor is wrapped with a heat-insulating ceramic layer.

[0079] The insulated boxes are sealed and each box will have about 10% air to prevent them from bursting open when heated. Heating is achieved by laying heating pipes at the bottom of the insulated box or along the inner side wall, but without contacting the bent reaction tube 31.

[0080] The bent reaction tubes 31, inlet collection box 32, and outlet collection box 33 in the tubular esterification reactor 3 and tubular polycondensation reactor are all made of stainless steel with a wall thickness of 2-3 mm. The inner diameter of the bent reaction tubes 31 in the tubular esterification reactor 3 is 20-30 mm. The inner diameter of the bent reaction tubes 31 in the tubular polycondensation reactor gradually increases from the first polycondensation reactor 6, the second polycondensation reactor 70, and the third polycondensation reactor 80 to accommodate the increase in viscosity of the polycondensation reaction. The inner diameter of the bent reaction tubes 31 in the first polycondensation reactor 6 is at least 30 mm. As the inner diameter of the bent reaction tubes 31 in the tubular polycondensation reactor increases, the number of bent reaction tubes 31 in the tubular polycondensation reactor decreases accordingly.

[0081] Because the esterification product has low viscosity, a thinner, bent reaction tube 31 can be used, and it should also have internal baffles 311 to improve the reaction effect. The subsequent tubular polycondensation reactors mainly involve a continuous negative pressure reaction process (i.e., the reaction liquid is not transferred to another low-pressure tank, but is transported through pipelines with a gradual pressure reduction effect), and can be directly transferred. Each negative pressure tank is a polycondensation reactor (similar to traditional tank reactions). The inner diameter of the bent reaction tube 31 in the subsequent polycondensation reactors may reach over 10cm. However, the bent reaction tube 31 in the polycondensation reactors will be opened intermittently for drainage (drainage can be performed through the polycondensation reactor after a period of reaction in the negative pressure tanks, and the same applies to subsequent polycondensation reactors) to ensure that the subsequent negative pressure tanks also have reaction time. The reaction time in the fourth negative pressure tank is short, basically for the final reaction of the small amount of liquid that has not yet achieved polycondensation. However, it is not limited to four negative pressure tanks; 5-8 can be set up as needed.

[0082] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0083] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A process for preparing polymerized and chipped filaments, characterized in that: The specific steps are as follows: I. Slurry Preparation S1: Add terephthalic acid powder and ethylene glycol through the two feed pipes of the mixing tank (1). The raw material ethylene glycol solution is mixed with antimony triacetate solution. The mixing tank (1) is heated to 150-155℃ and stirred to dissolve. S2: Pump the solution from step S1 into the preheating tank (2), preheat the preheating tank (2) to 220-250℃, and install a booster pump on the top of the preheating tank (2); II. Esterification Stage S1: The slurry in the preheating tank (2) is pumped into the tubular esterification reactor (3) by a small liquid pump for flow esterification reaction. The reaction temperature in the tubular esterification reactor (3) is 280-290℃. A matting agent solution input pipe (20) is connected to the pipe pumped into the tubular esterification reactor (3). The liquid outlet of the tubular esterification reactor (3) is connected to the ethylene glycol evaporator (4). S2: After the ethylene glycol evaporator (4) evaporates the ethylene glycol, it is discharged into the input end of the polycondensation reaction stage; III. Condensation Stage S1: The esterification solution completed in the esterification reaction stage is added to the continuous depressurization polycondensation reaction system. The continuous depressurization polycondensation reaction system includes multiple negative pressure tanks and multiple tubular polycondensation reactors. The negative pressure tanks and tubular polycondensation reactors are connected alternately and sequentially. The pressure in the negative pressure tanks decreases step by step from the first to the last. S2: The pressure inside the first negative pressure tank (5) is 0.3-0.5 atmospheres, and the pressure inside the last negative pressure tank is less than 0.01 atmospheres; IV. Melt Treatment The melt formed by the reaction in the last negative pressure tank is discharged into the melt filter for filtration, and then discharged into the melt processing system for processing. V. Spinning of chips into filaments After melt treatment, the filament is fed into a filament spinning device or a chip-based filament production equipment to produce filaments. The tubular esterification reactor (3) includes an insulated box, an inlet collection box (32), an outlet collection box (33), and multiple bent reaction tubes (31). The inlet collection box (32) and the outlet collection box (33) have the same structure. The inlet collection box (32) has an inlet in the middle of one side wall and an outlet on the other side wall. The outlet side walls of the inlet collection box (32) and the outlet collection box (33) are arranged opposite to each other. A bent reaction tube (31) is connected between the corresponding outlets of the inlet collection box (32) and the outlet collection box (33). The bent reaction tubes (31) are connected and bent in multiple U-shaped tubes from bottom to top. The bent reaction tube (31) includes a straight tube and a U-shaped end tube. The straight tube and the U-shaped end tube are connected by threads at intervals. The straight tube is filled with a baffle plate (311). The baffle plate (311) has flow holes (312) evenly distributed on it. Multiple abutment posts (313) are evenly provided on one side of the baffle plate (311).

2. The preparation process of polymerization and chip spinning filament according to claim 1, characterized in that, The ethylene glycol evaporator (4) includes an overflow box (41) and a condenser box (40). The overflow box (41) is provided with multiple equally spaced overflow plates (411). The height of the multiple overflow plates (411) gradually decreases from the liquid inlet end to the liquid outlet end. The thickness of the overflow plates (411) is 10-20cm. The overflow box (41) has an evaporation port on the top wall of the right half. The condenser box (40) is a horizontally placed L-shaped tube. The condenser box (40) is open at one end and closed at the other end. The open end of the condenser box (40) is sealed and connected to the evaporation port. The condenser box (40) has a leakage hole (402) at the bottom near the closed end. The condenser box (40) has multiple condenser plates (401) that are inclined downward toward the closed end at equal intervals on the top wall of the horizontally placed tube.

3. The preparation process of polymerization and chip spinning filament according to claim 1, characterized in that, The negative pressure tanks include a first negative pressure tank (5), a second negative pressure tank (7), a third negative pressure tank (8), and a fourth negative pressure tank (9) arranged from left to right. The tubular polycondensation reactors include a first polycondensation reactor (6), a second polycondensation reactor (70), and a third polycondensation reactor (80). A flow control valve (50) is provided on the connecting pipe between the negative pressure tank on the left and the adjacent tubular polycondensation reactor on the right. The first negative pressure tank (5), the second negative pressure tank (7) and the third negative pressure tank (8) are all equipped with negative pressure vacuum pumps at the top. The fourth negative pressure tank (9) is equipped with a turbine pump on the drain pipe at the bottom. The air pressure inside the first negative pressure tank (5) is 0.3-0.5 atmospheres, the air pressure inside the second negative pressure tank (7) is 0.1-0.2 atmospheres, the air pressure inside the third negative pressure tank (8) is 0.05-0.1 atmospheres, and the air pressure inside the fourth negative pressure tank (9) is less than 0.01 atmospheres.

4. The preparation process of polymerization and chip spinning filament according to claim 3, characterized in that, The negative pressure vacuum pump outlets at the top of the first negative pressure tank (5), the second negative pressure tank (7), and the third negative pressure tank (8) are connected to the air inlet of the condensing equipment via pipes; The ethylene glycol recovered by the ethylene glycol evaporator (4) and the ethylene glycol recovered by the condenser are reused and discharged into the mixing tank (1) for reuse.

5. The preparation process of polymerized and spun filaments according to claim 1, characterized in that, The total length of the bent reaction tubes (31) in the tubular esterification reactor (3) and the tubular polycondensation reactor is 10-15m. The flow time of the reaction liquid from the inlet end to the outlet end in the bent reaction tube of the tubular esterification reactor (3) is 1.5-2.5h, and the flow time of the reaction liquid from the inlet end to the outlet end in the bent reaction tube (31) of the tubular polycondensation reactor is 10-30min.

6. The preparation process of polymerized and chipped filaments according to claim 1, characterized in that, The tubular esterification reactor (3) and the tubular polycondensation reactor are filled with heat-conducting oil in the space outside the bent reaction tube (31), the inlet collection box (32) and the outlet collection box (33). The heat-conducting oil is biphenyl-biphenyl ether, triacetin, or silicone oil. The boiling point of the heat-conducting oil used must be above 300°C. The outer wall of the tubular esterification reactor (3) and the tubular polycondensation reactor is wrapped with a heat-insulating ceramic layer.

7. The preparation process of polymerized and chipped filaments according to claim 1, characterized in that, The tubular esterification reactor (3) and the tubular polycondensation reactor are all made of stainless steel, with a wall thickness of 2-3 mm. The inner diameter of the bent reaction tube (31) in the tubular esterification reactor (3) is 20-30 mm. The inner diameter of the bent reaction tube (31) in the tubular polycondensation reactor gradually increases from the first polycondensation reactor (6), the second polycondensation reactor (70) and the third polycondensation reactor (80) to adapt to the increase in viscosity of the polycondensation reaction. The inner diameter of the bent reaction tube (31) in the first polycondensation reactor (6) is at least 30 mm. As the inner diameter of the bent reaction tube (31) in the tubular polycondensation reactor increases, the number of bent reaction tubes (31) in the tubular polycondensation reactor decreases accordingly.

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