Preparation process of polymerization and chip spinning filament

Abstract

The invention discloses a preparation process of polymerization and chip spinning filaments, and relates to the technical field of spinning filament preparation. The method comprises the following specific steps: 1) adding terephthalic acid powder and sufficient ethylene glycol into a mixing tank, wherein a raw material ethylene glycol solution is mixed with an antimony triacetate solution; 2) pumping ethylene glycol dissolved with terephthalic acid powder in the step 1) into a preheating tank; (3) pumping the slurry in the preheating tank into a tubular esterification reactor through a small liquid pump to carry out flow esterification reaction, wherein the liquid outlet end of the tubular esterification reactor is connected into an ethylene glycol evaporator; (4) adding an esterification solution obtained in the esterification reaction stage into a continuous pressure reduction polycondensation reaction system; the tubular esterification reactor and the tubular polycondensation reactor are used for completing the esterification reaction and the polycondensation reaction respectively, and the problems that in the existing filament spinning preparation process, energy loss is large, product quality controllability is not high after the reaction is finished, and polycondensation molecular weight is unbalanced are solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of long filament preparation, and particularly relates to a preparation process of polymeric and chip long filament. BACKGROUND

[0002] The esterification reaction of purified terephthalic acid (PTA) and ethylene glycol needs to be carried out at about 280 DEG C, needs to use biphenyl for heat preservation, and needs to be stirred without stopping. The reaction process consumes a large amount of energy, and the reaction is not complete, and the esterification rate is generally not higher than 96%. The reaction is generally carried out in an esterification reaction tube, and needs to be reacted in batches. The product after esterification needs to be transferred to a pre-polycondensation reactor and a final polycondensation reactor, and the energy loss is large in the transfer process. In the polycondensation reaction process, a plurality of polycondensation reactors are needed, and the ethylene glycol generated in the process needs to be independently evaporated by an ethylene glycol evaporator. The whole process is complex and high in cost. Moreover, the pre-polycondensation reactor and the final polycondensation reactor can only select one air pressure value for reaction for a period of time, and then be transferred to the next reactor. The energy loss will occur in the transfer process, and the energy utilization rate will be low. Moreover, the pressure in the polycondensation process is not gradually changed, the molecular weight of the product in the polycondensation process fluctuates greatly and is not balanced, the stretching performance of the melt fluctuates, and the product quality cannot be well controlled. The product quality after polymerization will affect the quality of the chip.

[0003] Therefore, the present application provides a preparation process of polymeric and chip long filament to solve the above problems. SUMMARY

[0004] The present application aims to provide a preparation process of polymeric and chip long filament, which completes the esterification reaction and the polycondensation reaction by a tubular esterification reactor and a tubular polycondensation reactor respectively, and solves the problems of large energy loss in the existing long filament preparation process, low controllability of product quality after the reaction, and unbalanced molecular weight in the polycondensation.

[0005] To solve the above technical problems, the present application is realized by the following technical scheme: The present application is a preparation process of polymeric and chip long filament, and the specific steps are as follows: I. Slurry preparation S1: The terephthalic acid powder and sufficient ethylene glycol are added from two feeding pipes of a mixing tank, the raw material ethylene glycol solution is mixed with antimony tris-acetate solution, the mixing tank is heated to a temperature of 150-155 DEG C, and the stirring is not stopped until the terephthalic acid powder is slurried in the sufficient ethylene glycol; S2: The ethylene glycol in which the terephthalic acid powder is dissolved in step S1 is pumped into a preheating tank, the preheating tank 2 is preheated to 220-250 DEG C, and a booster pump is installed at the top of the preheating tank; II. Esterification reaction stage S1: the preheating tank slurry 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 light extinction agent solution input pipe is connected to the pipe for pumping into the tubular esterification reactor, the light extinction agent solution is titanium dioxide nano powder dissolved in ethylene glycol solution, and the outlet end of the tubular esterification reactor is connected to an ethylene glycol evaporator; S2: after the ethylene glycol evaporator evaporates the ethylene glycol, the ethylene glycol 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 a second tubular esterification reactor for secondary reaction, and then discharged into a second ethylene glycol evaporator to evaporate the residual ethylene glycol; III. Polycondensation stage S1: the esterification solution after the esterification reaction stage is added to a continuous pressure reduction polycondensation reaction system, the continuous pressure reduction polycondensation reaction system comprises a plurality of negative pressure tanks and a plurality of tubular polycondensation reactors, the negative pressure tanks and the tubular polycondensation reactors are alternately and sequentially connected, the pressure in the negative pressure tanks gradually decreases from the first to the last, the structure of the tubular polycondensation reactor is the same as that of the tubular esterification reactor, and the reaction temperature in the tubular polycondensation reactor is also 280-290℃. S2: the pressure in the first negative pressure tank of the negative pressure tank is 0.3-0.5 atm, and the pressure in the last negative pressure tank of the negative pressure tank is less than 0.01 atm. IV. Melt treatment The melt formed in the last negative pressure tank is discharged into a melt filter, and then discharged into a melt treatment system for treatment. V. Slice spinning After the treatment of the melt treatment system, the melt is sent to a spinning device or a slice production filament device to produce spun filaments.

[0006] The tubular esterification reactor comprises a heat preservation box, a liquid inlet collecting box, a liquid outlet collecting box and a plurality of bent reaction pipes, the liquid inlet collecting box and the liquid outlet collecting box have the same structure, a liquid inlet is arranged in the middle of one side wall of the liquid inlet collecting box, a liquid outlet is arranged on the other side wall, the side walls of the liquid outlets of the liquid inlet collecting box and the liquid outlet collecting box are oppositely arranged, and a bent reaction pipe is connected between the corresponding liquid outlets of the liquid inlet collecting box and the liquid outlet collecting box.

[0007] The bent reaction pipe comprises a straight pipe and a U-shaped end pipe, the straight pipe and the U-shaped end pipe are sequentially and spacedly connected in threads, the straight pipe is filled with turbulence pieces, the turbulence pieces are uniformly provided with liquid flow holes, and a plurality of abutting columns are uniformly arranged on one side surface of the turbulence pieces.

[0008] The glycol evaporator further comprises an overflow box and a condensing box, a plurality of overflow plates with equal intervals are arranged in the overflow box, the heights of the plurality of overflow plates gradually decrease from the liquid inlet end to the liquid outlet end, the thickness of the overflow plate is 10-20 cm, the overflow box is provided with an evaporation port on the top wall of the right half part, the condensing box is an L-shaped pipe horizontally placed, one end of the condensing box is open and the other end is closed, the open end of the condensing box is sealingly connected to the evaporation port, the condensing box is provided with a liquid leakage hole at the bottom close to the closed end, and a plurality of condensing plates inclined towards the closed end are arranged on the top wall of the horizontally placed pipe in equal intervals.

[0009] The glycol evaporator further comprises an overflow box and a condensing box, a plurality of overflow plates with equal intervals are arranged in the overflow box, the heights of the plurality of overflow plates gradually decrease from the liquid inlet end to the liquid outlet end, the thickness of the overflow plate is 10-20 cm, the overflow box is provided with an evaporation port on the top wall of the right half part, the condensing box is an L-shaped pipe horizontally placed, one end of the condensing box is open and the other end is closed, the open end of the condensing box is sealingly connected to the evaporation port, the condensing box is provided with a liquid leakage hole at the bottom close to the closed end, and a plurality of condensing plates inclined towards the closed end are arranged on the top wall of the horizontally placed pipe in equal intervals. The first negative pressure tank, the second negative pressure tank and the third negative pressure tank are all provided with a negative pressure vacuum pump at the top, a turbine pump is arranged on the liquid discharge pipe at the bottom of the fourth negative pressure tank, the air pressure in the first negative pressure tank is 0.3-0.5 atm, the air pressure in the second negative pressure tank is 0.1-0.2 atm, the air pressure in the third negative pressure tank is 0.05-0.1 atm, and the air pressure in the fourth negative pressure tank is less than 0.01 atm.

[0010] The glycol evaporator further comprises an overflow box and a condensing box, a plurality of overflow plates with equal intervals are arranged in the overflow box, the heights of the plurality of overflow plates gradually decrease from the liquid inlet end to the liquid outlet end, the thickness of the overflow plate is 10-20 cm, the overflow box is provided with an evaporation port on the top wall of the right half part, the condensing box is an L-shaped pipe horizontally placed, one end of the condensing box is open and the other end is closed, the open end of the condensing box is sealingly connected to the evaporation port, the condensing box is provided with a liquid leakage hole at the bottom close to the closed end, and a plurality of condensing plates inclined towards the closed end are arranged on the top wall of the horizontally placed pipe in equal intervals. The glycol evaporator further comprises an overflow box and a condensing box, a plurality of overflow plates with equal intervals are arranged in the overflow box, the heights of the plurality of overflow plates gradually decrease from the liquid inlet end to the liquid outlet end, the thickness of the overflow plate is 10-20 cm, the overflow box is provided with an evaporation port on the top wall of the right half part, the condensing box is an L-shaped pipe horizontally placed, one end of the condensing box is open and the other end is closed, the open end of the condensing box is sealingly connected to the evaporation port, the condensing box is provided with a liquid leakage hole at the bottom close to the closed end, and a plurality of condensing plates inclined towards the closed end are arranged on the top wall of the horizontally placed pipe in equal intervals.

[0011] The glycol evaporator further comprises an overflow box and a condensing box, a plurality of overflow plates with equal intervals are arranged in the overflow box, the heights of the plurality of overflow plates gradually decrease from the liquid inlet end to the liquid outlet end, the thickness of the overflow plate is 10-20 cm, the overflow box is provided with an evaporation port on the top wall of the right half part, the condensing box is an L-shaped pipe horizontally placed, one end of the condensing box is open and the other end is closed, the open end of the condensing box is sealingly connected to the evaporation port, the condensing box is provided with a liquid leakage hole at the bottom close to the closed end, and a plurality of condensing plates inclined towards the closed end are arranged on the top wall of the horizontally placed pipe in equal intervals.

[0012] The glycol evaporator further comprises an overflow box and a condensing box, a plurality of overflow plates with equal intervals are arranged in the overflow box, the heights of the plurality of overflow plates gradually decrease from the liquid inlet end to the liquid outlet end, the thickness of the overflow plate is 10-20 cm, the overflow box is provided with an evaporation port on the top wall of the right half part, the condensing box is an L-shaped pipe horizontally placed, one end of the condensing box is open and the other end is closed, the open end of the condensing box is sealingly connected to the evaporation port, the condensing box is provided with a liquid leakage hole at the bottom close to the closed end, and a plurality of condensing plates inclined towards the closed end are arranged on the top wall of the horizontally placed pipe in equal intervals.

[0013] The application is further provided that the pipe esterification reactor and the pipe polycondensation reactor are all made of stainless steel, and the wall thickness is 2-3mm, the inner diameter of the pipe esterification reactor is 20-30mm, the inner diameter of the pipe polycondensation reactor gradually increases from the first polycondensation reactor, the second polycondensation reactor and the third polycondensation reactor to adapt to the increasing viscosity of the polycondensation reaction, and the inner diameter of the pipe polycondensation reactor is at least 30mm.

[0014] The application has the following beneficial effects: 1. The reaction slurry is dissolved at a temperature of 150℃, and the ethylene glycol is not evaporated. After dissolution, the slurry is preheated to a temperature close to the reaction temperature in the preheating tank. Since the preheating tank is sealed, the evaporation of ethylene glycol is limited. The slurry is then transferred to the pipe esterification reactor for esterification reaction. Since there is no space for ethylene glycol evaporation in the pipe, the reaction is more complete, and the conversion rate of PTA to ethylene glycol terephthalate is higher than that of traditional esterification. The heat loss is low. Moreover, the pipe reaction is a continuous reaction, and the slurry can be continuously transported for continuous esterification reaction. There is no need to clean up the reaction tank after esterification reaction for the next reaction, which results in heat loss.

[0015] 2. The ethylene glycol evaporator is specially designed for continuous reaction and evaporation of ethylene glycol. Since it is a continuous esterification reaction, the reaction product is continuously output in small amounts. The reaction liquid is continuously discharged into the overflow box, where it slowly overflows from left to right. The overflow plate is very thin, which can quickly and fully evaporate ethylene glycol. The slow evaporation of ethylene glycol inside the box can cause some ethylene glycol not to evaporate, which is then recovered for subsequent operation.

[0016] 3. The application requires continuous pressure reduction to improve the degree of polycondensation reaction. Multiple pre-polycondensation reactors and a final polycondensation reactor are required. Since the pressure does not change slowly, energy is lost during the transfer of the reaction liquid. The connection between multiple continuous pressure reduction negative pressure tanks and the pipe polycondensation reactor can ensure the transfer process, and the reaction liquid is still in a low pressure state for low pressure reaction. Moreover, the reaction liquid is always in a low pressure and slow change process, and the reaction does not have sudden pressure changes that can cause uneven polymerization of the reaction product, making the product performance controllable. When the pressure in the bent reaction tube is not enough to transfer the viscous product, a viscous liquid pump can be installed on the pipe to increase the pressure for transfer.

[0017] Of course, implementing any product of the application does not necessarily require all the advantages described above. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the description of the embodiments will be briefly introduced. Obviously, the drawings described in the following are only some of the embodiments of the present application, and all other drawings obtained by those skilled in the art without creative effort based on the embodiments of the present application are within the scope of protection of the present application.

[0019] Figure 1 It is a schematic diagram of the process flow structure of the device for the preparation process of polymeric and sliced long filament.

[0020] Figure 2 It is a schematic diagram of the cross-sectional structure. Figure 1

[0021] Figure 3 It is a schematic diagram of the structure of the bent reaction tube.

[0022] Figure 4 It is a schematic diagram of the structure of the bent reaction tube.

[0023] Figure 5 It is a schematic diagram of the structure of the bent reaction tube.

[0024] Figure 6 It is a process flow chart of the reaction stage of the preparation process of polymeric and sliced long filament.

[0025] In the drawings, the component list represented by each reference numeral is as follows: 1, mixing tank; 2, preheating tank; 3, tubular esterification reactor; 31, bent reaction tube; 311, turbulence sheet; 312, liquid flow hole; 32, liquid inlet liquid collection box; 33, liquid outlet liquid collection box; 4, ethylene glycol evaporator; 40, condensation box; 401, condensation plate; 402, liquid 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 DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present application.

[0027] Please refer to Figures 1-6 The present application is a preparation process of polymeric and sliced long filament, and the specific steps are as follows: I. Slurry preparation ​S1: terephthalic acid powder and sufficient amount of ethylene glycol are added from two feeding pipes of mixing tank 1, the raw material ethylene glycol solution is mixed with antimony tris-acetate solution, the mixing tank 1 is heated to a temperature of 150-155°C, and the stirring is not stopped until the terephthalic acid powder is slurried in sufficient amount of ethylene glycol; the mixing tank 1 is a raw material stirring and dissolving tank, antimony tris-acetate is used as a catalyst for polycondensation reaction, and is continuously metered from a feeding tank to a slurry preparation tank in an interval arrangement mode, because the raw material is also continuously added and dissolved. The two feeding pipes can ensure that the terephthalic acid powder and the ethylene glycol are added separately and mixed in the tank.

[0028] S2: the ethylene glycol in which the terephthalic acid powder is dissolved in step S1 is pumped into a preheating tank 2, the preheating tank 2 is preheated to 220-250°C, and a booster pump is installed at the top of the preheating tank 2; The purpose of preheating is to quickly reach the reaction temperature when the reaction liquid enters the tubular esterification reactor 3, and the preheating temperature makes the evaporation of ethylene glycol not very fast, and after entering the pipeline, the evaporation of ethylene glycol can be inhibited again. Titanium dioxide is a commonly used matting agent for fiber grade polyester chips. The titanium dioxide is prepared into a high-concentration matting agent suspension, and after grinding by a grinder to break up large particles, it is diluted to the required concentration in ethylene glycol, and then large particles are separated by a centrifugal machine, and filtered by a filter, and then sent into.

[0029] II. Esterification reaction 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°C, an input pipe 20 for matting agent solution is connected to the pipeline for pumping into the tubular esterification reactor 3, the matting agent solution is titanium dioxide nano-powder dissolved in ethylene glycol solution, and the outlet of the tubular esterification reactor is connected to an ethylene glycol evaporator 4; The small liquid pump is slowly pumped in, which can ensure that the reaction liquid slowly flows in the tubular esterification reactor 3 for reaction, and stirring is not needed, and better flow reaction can be performed.

[0030] S2: after the ethylene glycol evaporator 4 evaporates the ethylene glycol, it is discharged into the input end of the polycondensation reaction stage, if one of the ethylene glycol evaporators 4 cannot completely evaporate the ethylene glycol, the liquid in the ethylene glycol evaporator 4 is discharged again into the second tubular esterification reactor 3 for secondary reaction, and then discharged into the second ethylene glycol evaporator 4 to evaporate the residual ethylene glycol; the ethylene glycol evaporator 4 is a special evaporator, which can evaporate and recover ethylene glycol under the flow reaction liquid. The outer wall of the ethylene glycol evaporator 4 is wrapped with a heating and heat preservation device (a heating plate, a heating wire, or a heat preservation biphenyl can be used, and the internal heat preservation is at 220-250°C).

[0031] III. Polycondensation stage S1: the esterification solution of the esterification reaction stage is added to a continuous decompression polycondensation reaction system, the system includes a plurality of negative pressure tanks and a plurality of tubular polycondensation reactors, the negative pressure tanks are connected to the tubular polycondensation reactors alternately and sequentially, the pressure in the negative pressure tanks gradually decreases from the first to the last, the tubular polycondensation reactors have the same structure as the tubular esterification reactor 3, and the reaction temperature in the tubular polycondensation reactors and the tubular esterification reactor 3 is between 280-290℃; S2: the pressure in the first negative pressure tank 5 of the negative pressure tank (each negative pressure tank is provided with a stirring device, conventional stirring, and the structure is not drawn out, and a vacuum pump installed at the negative pressure can be installed at a top side edge point, and a stirring motor is installed at the top center) is between 0.3-0.5 atm, and the pressure in the last negative pressure tank of the negative pressure tank is less than 0.01 atm. Since the negative pressure tank gradually decreases from left to right, there is a pressure difference between two adjacent negative pressure tanks, and the reaction liquid flows from the negative pressure tank with high pressure to the negative pressure tank with low pressure. During the flow process, the pressure in the pipeline gradually changes, which not only enables the reaction to continue during the transfer process, but also achieves a better uniform balance of the polycondensation degree, that is, the polycondensation molecular weight is more concentrated and does not deviate greatly.

[0032] Four, melt treatment The melt formed in the last negative pressure tank is discharged into a melt filter for filtration, and then discharged into a melt treatment system for treatment.

[0033] Five, chip spinning After the melt treatment system, the melt is sent to a spinning device or a chip production filament equipment to produce spun filaments.

[0034] The melt treatment and chip spinning are existing treatment methods, and the specific detailed steps are not described here.

[0035] The tubular esterification reactor 3 includes a heat preservation box, a liquid inlet collection box 32, a liquid outlet collection box 33, and a plurality of bent reaction pipes 31, the liquid inlet collection box 32 and the liquid outlet collection box 33 have the same structure, one side wall of the liquid inlet collection box 32 is provided with a liquid inlet in the middle position, and the other side wall is provided with a row of liquid outlets, the liquid inlet collection box 32 and the liquid outlet collection box 33 are oppositely provided on the side wall of the liquid outlet, and each of the liquid inlet collection box 32 and the liquid outlet collection box 33 is connected with a bent reaction pipe 31 corresponding to the liquid outlet, and the bent reaction pipe 31 is connected in a plurality of U-shaped tubular bends from bottom to top.

[0036] Reaction liquid flows from the bottom of the bent reaction tube 31 to the top, smooth flow, using the pipeline design, can ensure uniform heating, more thorough reaction, the reaction process without evaporation of ethylene glycol. Make the reaction effect better. Liquid inlet collection box 32 is to realize the uniform reaction liquid into each bent reaction tube 31, and then from the multiple bent reaction tube 31 gathered in the liquid outlet collection box 33, to the ethylene glycol evaporator 4.

[0037] The bent reaction tube 31 comprises a straight pipe and a U-shaped end pipe, the straight pipe and the U-shaped end pipe are sequentially connected by spacing and screwing, the straight pipe is filled with turbulence pieces 311, the turbulence pieces 311 are uniformly distributed with liquid flow holes 312, and a plurality of abutting columns 313 are uniformly arranged on one side of the turbulence pieces 311.

[0038] Due to the low viscosity of esterification reaction, combined with high temperature reaction, it is basically liquid, and a large amount of ethylene glycol solution is mixed in the bent reaction tube 31, and the fluidity is good, so the turbulence of the turbulence piece 311 can replace stirring. Continuous esterification reaction can be realized.

[0039] The ethylene glycol evaporator 4 comprises an overflow box 41 and a condensation box 40, a plurality of overflow plates 411 are arranged in the overflow box 41, the heights of the plurality of overflow plates 411 gradually decrease from the liquid inlet end to the liquid outlet end, the thickness of the overflow plate 411 is 10-20 cm, the overflow box 41 is provided with an evaporation port on the top wall of the right half, the condensation box 40 is an L-shaped pipe placed horizontally, one end of the condensation box 40 is open and the other end is closed, the open end of the condensation box 40 is sealingly connected to the evaporation port, the condensation box 40 is provided with a liquid leakage hole 402 at the bottom close to the closed end, and a plurality of condensation plates 401 inclined toward the closed end are arranged on the top wall of the horizontally placed pipe in the condensation box 40.

[0040] The reaction liquid discharged into the overflow box 41 at the beginning has space for evaporation of ethylene glycol, and a large amount of steam and splashing liquid will be generated instantaneously, therefore, the top of the front half of the overflow box 41 is closed, the splashing liquid is sprayed to the top and will drop down, and the evaporated ethylene glycol in the back half will rise, flow in the L-shaped pipe to the condensation plate 401, condense into liquid drops when meeting the condensation plate 401, drop to the lower side, and then be discharged from the liquid leakage hole 402 for recycling.

[0041] The negative pressure tank comprises 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 reactor comprises a first polycondensation reactor 6, a second polycondensation reactor 70 and a third polycondensation reactor 80, and a flow control valve 50 is arranged on the connecting pipeline between the left negative pressure tank and the adjacent tubular polycondensation reactor on the right side.

[0042] The flow control valve 50 can control the flow rate of the reaction liquid. If the discharge of the reaction liquid is affected (when the viscosity is large, the valve can be fully opened, and the flow rate is not controlled), the polycondensation reactor is used to smoothly discharge the reaction liquid to the next negative pressure tank (also called a tank type polycondensation reactor with stirring function).

[0043] The first negative pressure tank 5, the second negative pressure tank 7, and the third negative pressure tank 8 are each provided with a negative pressure vacuum pump at the top. A turbine pump is arranged on the discharge pipe at the bottom of the fourth negative pressure tank 9. The gas pressure in the first negative pressure tank 5 is 0.3-0.5 atm, the gas pressure in the second negative pressure tank 7 is 0.1-0.2 atm, the gas pressure in the third negative pressure tank 8 is 0.05-0.1 atm, and the gas pressure in the fourth negative pressure tank 9 is less than 0.01 atm.

[0044] The pressure value is set according to the need. The third negative pressure tank 8 and the fourth negative pressure tank 9 are basically close to the existing ultimate polycondensation reactor pressure. When the reaction liquid is difficult to discharge due to the pressure difference between the negative pressure tank 5 and the polycondensation reactor, a viscous liquid pump can be arranged to increase the pressure discharge capacity.

[0045] The outlet of the negative pressure vacuum pump at the top of the first negative pressure tank 5, the second negative pressure tank 7, and the third negative pressure tank 8 is connected to the inlet of the condensing equipment by a pipeline. The negative pressure vacuum pump is used to reduce the pressure of each negative pressure tank. Ethylene glycol is generated during the reaction process and is pumped out by the negative pressure vacuum pump for condensation and recovery.

[0046] The ethylene glycol recovered by the ethylene glycol evaporator 4 and the ethylene glycol recovered by the condensing equipment are reused and discharged into the mixing tank 1 for reuse.

[0047] The recovered ethylene glycol can be reused. The condensing equipment is the existing recovery equipment.

[0048] The total length of the bent reaction tube 31 in the tubular esterification reactor 3 and the tubular polycondensation reactor is 10-15 m. The flow time of the reaction liquid in the bent reaction tube of the tubular esterification reactor 3 from the inlet end to the outlet end is 1.5-2.5 h. The flow time of the reaction liquid in the bent reaction tube 31 of the tubular polycondensation reactor from the inlet end to the outlet end is 10-30 min.

[0049] The higher the viscosity of the subsequent polycondensation reaction, the shorter and thicker the bent reaction tube 31 in the tubular polycondensation reactor will be to increase the discharge effect.

[0050] The space outside the bent reaction tube 31, the inlet liquid collection box 32, and the outlet liquid collection box 33 in the tubular esterification reactor 3 and the tubular polycondensation reactor is filled with heat conducting oil. The heat conducting oil is biphenyl-biphenyl ether, triacetin, or silicone oil. The boiling point of the heat conducting oil used should be above 300°C. The outer wall of the tubular esterification reactor 3 and the tubular polycondensation reactor is wrapped with a heat preservation ceramic layer.

[0051] Each insulation box is sealed and left with about 10% air to prevent the insulation box from expanding when heated. Heating is achieved by laying heating pipes at the bottom of the insulation box or along the inner side wall without touching the bent reaction tube 31.

[0052] The bent reaction tubes 31, liquid inlet collecting boxes 32 and liquid outlet collecting boxes 33 in 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 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 adapt to the increasing 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, and as the inner diameter of the bent reaction tubes 31 in the tubular polycondensation reactor increases, the number of the bent reaction tubes 31 therein decreases accordingly.

[0053] Because the esterification reaction product has a low viscosity, a thinner curved reaction tube 31 can be used, and a baffle 311 can be installed inside it to improve the reaction efficiency. The subsequent tubular polycondensation reactor primarily operates under uninterrupted negative pressure (i.e., the reaction liquid is not removed and transferred to another low-pressure tank, but instead is transported through a pipeline with a gradual pressure reduction effect). This allows for direct transfer. Each negative pressure tank serves as a polycondensation reactor (similar to a conventional tank reaction). The inner diameter of the curved reaction tube 31 within the subsequent polycondensation reactor may be greater than 10 cm. However, the curved reaction tube 31 within the polycondensation reactor is intermittently opened for drainage (drainage can be performed through the polycondensation reactor after a period of reaction in the negative pressure tank, 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, essentially allowing for the final reaction of the small amount of subsequent product that has not yet reached the polycondensation effect. However, this is not limited to four negative pressure tanks; 5-8 can be provided as needed.

[0054] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these 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 any one or more embodiments or examples.

[0055] The preferred embodiments of the application disclosed above are only to facilitate the elucidation of the application. The preferred embodiments do not describe all the details of the application and limit the application to the specific embodiments described. Obviously, many modifications and variations can be made in light of the teachings above. The description is chosen and described in order to best explain the principles of the application and its practical application to thereby enable others skilled in the art to best utilize the application and get the best results from the application. The application is only limited by the claims and their full scope and equivalents.

Claims

1. A process for preparing filaments by polymerization and chip spinning, characterized in that: The specific steps are as follows:

1. Slurry preparation S1: Add terephthalic acid powder and ethylene glycol from two feeding pipes of a mixing tank (1). The raw material ethylene glycol solution is mixed with antimony triacetate solution. The mixing tank (1) is heated to 150-155°C and stirred to dissolve. S2: Pump the solution in step S1 into the preheating tank (2), preheat the preheating tank (2) to 220-250°C, and install a booster pump on the top of the preheating tank (2); 2. 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°C. 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: Ethylene glycol evaporator (4) evaporates the ethylene glycol and discharges it into the input end of the polycondensation reaction stage; 3. Polycondensation stage S1: adding the esterification solution completed in the esterification reaction stage to a continuous decompression polycondensation reaction system, which includes multiple negative pressure tanks and multiple tubular polycondensation reactors. The negative pressure tanks and the tubular polycondensation reactors are alternately connected in sequence, and 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) of the negative pressure tank is 0.3-0.5 atmospheres, and the pressure inside the last negative pressure tank is less than 0.01 atmospheres; 4. 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 treatment; 5. Slice spinning filament After melt treatment, it is fed into a filament spinning device or a slicing and filament production device to produce spun filaments.

2. The process for preparing filaments by polymerization and chip spinning according to claim 1, characterized in that: The tubular esterification reactor (3) comprises an insulation box, a liquid inlet collecting box (32), a liquid outlet collecting box (33) and a plurality of bent reaction tubes (31). The liquid inlet collecting box (32) and the liquid outlet collecting box (33) have the same structure. A liquid inlet is provided in the middle of one side wall of the liquid inlet collecting box (32), and a liquid outlet is provided on the other side wall. The liquid outlet side walls of the liquid inlet collecting box (32) and the liquid outlet collecting box (33) are arranged opposite to each other. A bent reaction tube (31) is connected between the corresponding liquid outlets on the liquid inlet collecting box (32) and the liquid outlet collecting box (33). The bent reaction tubes (31) are bent from bottom to top into a plurality of U-shaped tubular connections.

3. The process for preparing polymerization and chip spinning filaments according to claim 2, characterized in that: The bent reaction tube (31) comprises a straight tube and a U-shaped end tube, the straight tube and the U-shaped end tube being threadedly connected in sequence at intervals, the straight tube being filled with a spoiler (311), the spoiler (311) being evenly distributed with liquid flow holes (312), and a plurality of abutment columns (313) being evenly provided on one side of the spoiler (311).

4. The process for preparing filaments by polymerization and chip spinning according to claim 1, characterized in that: The ethylene glycol evaporator (4) comprises an overflow box (41) and a condensation box (40). The overflow box (41) is provided with a plurality of overflow plates (411) at equal intervals. The heights of the plurality of overflow plates (411) gradually decrease 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) is provided with an evaporation port on the top wall of the right half. The condensation box (40) is a horizontally placed L-shaped tube. The condensation box (40) is open at one end and closed at the other end. The open end of the condensation box (40) is sealed and docked with the evaporation port. The condensation box (40) is provided with a leakage hole (402) at the bottom near the closed end. The condensation box (40) is provided with a plurality of condensation plates (401) inclined downward toward the closed end at equal intervals on the top wall of the horizontally placed pipe.

5. The process for preparing polymerization and chip spinning filaments according to claim 2, characterized in that: The negative pressure tank comprises 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 reactor comprises a first polycondensation reactor (6), a second polycondensation reactor (70) and a third polycondensation reactor (80), and 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; A negative pressure vacuum pump is installed on the top of each of the first negative pressure tank (5), the second negative pressure tank (7) and the third negative pressure tank (8); a turbine pump is provided on the discharge pipe at the bottom of the fourth negative pressure tank (9); the air pressure in the first negative pressure tank (5) is 0.3-0.5 atmospheres, the air pressure in the second negative pressure tank (7) is 0.1-0.2 atmospheres, the air pressure in the third negative pressure tank (8) is 0.05-0.1 atmospheres, and the air pressure in the fourth negative pressure tank (9) is less than 0.01 atmospheres.

6. The process for preparing polymerization and chip spinning filaments according to claim 5, characterized in that: The negative pressure vacuum pump air outlets on the tops 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 condensing device are reused and discharged into the mixing tank (1) for reuse.

7. The process for preparing polymerization and chip spinning filaments according to claim 2, characterized in that: The total length of the bent reaction tube (31) in the tubular esterification reactor (3) and the tubular polycondensation reactor is 10-15 m, the reaction liquid flows from the liquid inlet end to the liquid outlet end of the bent reaction tube in the tubular esterification reactor (3) for 1.5-2.5 h, and the reaction liquid flows from the liquid inlet end to the liquid outlet end of the bent reaction tube (31) in the tubular polycondensation reactor for 10-30 min.

8. The process for preparing polymerization and chip spinning filaments according to claim 1, characterized in that: The tubular esterification reactor (3) and the tubular polycondensation reactor are filled with heat transfer oil in the space outside the bent reaction tube (31), the liquid inlet collecting box (32) and the liquid outlet collecting box (33). 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 thermal insulation ceramic layer.

9. The process for preparing polymerization and chip spinning filaments according to claim 2, characterized in that: The bent reaction tube (31), the liquid inlet collecting box (32) and the liquid outlet collecting box (33) in 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 the bent reaction tubes (31) therein decreases accordingly.

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