High-performance polyester fiber production method adopting low-temperature polymerization technology

Abstract

The invention relates to the technical field of polyester fiber production, and discloses a high-performance polyester fiber production method adopting a low-temperature polymerization technology, which comprises the following steps: raw material preparation: selecting terephthalic acid, ethylene glycol and a catalyst; performing low-temperature prepolymerization, adding materials into the reaction kettle, and maintaining a low-temperature condition; carrying out low-temperature polycondensation, and adjusting the temperature and pressure to polycondensation conditions; generating high molecular weight polyester; spinning preparation: conveying a polyester melt and filtering impurities; preparing a spinning assembly; fiber spinning, wherein the melt is extruded into filaments through a spinning assembly; the filaments are cooled to be solidified and formed; performing fiber post-treatment, namely performing stretching treatment on the fibers; carrying out heat setting treatment; and detecting and optimizing the product, and detecting various performance indexes of the fiber. By controlling the dosage of the raw materials, an appropriate raw material basis is provided for the subsequent polymerization reaction, all the raw materials and auxiliaries are ensured to play a role in the reaction, the reaction system is in a relatively ideal initial state, and the problem of low polymerization reaction efficiency caused by unreasonable raw material ratio is solved.

Description

Technical Field

[0001] The invention relates to the technical field of polyester fiber production, in particular to a method for producing high-performance polyester fibers by adopting low-temperature polymerization technology. Background Art

[0002] Polyester fiber is a fiber material prepared by chemical synthesis. Due to its remarkable properties such as high strength, good wear resistance, chemical stability and easy molding through conventional textile processing technology, it has been widely used in many key fields such as textiles, industry, medical care, etc.

[0003] The core link of polyester fiber production lies in the polymerization reaction, which usually uses terephthalic acid (PTA) and ethylene glycol (EG) as the main raw materials. Under certain conditions, polyester polymers are generated through a series of chemical reactions such as esterification and polycondensation, and then the finished fiber is obtained through spinning and related post-processing processes. However, in the actual production process, the problem of low polymerization efficiency due to unreasonable raw material ratio is often faced.

[0004] If ethylene glycol (EG) is excessive, it will be more difficult to remove small molecules during polycondensation, the molecular chain will grow slowly, the molecular weight will be difficult to meet the standard, and it will also interfere with the molecular chain arrangement and subsequent processing stability; if terephthalic acid (PTA) is excessive, it will destroy the uniformity of the reaction system, reduce the esterification reaction rate, affect the polycondensation reaction, and slow down the progress of the entire polymerization reaction. The unreasonable raw material ratio is caused by factors such as differences in raw material supply and the metering accuracy and human operation of the batching link at the production site. This problem restricts production efficiency, product quality and corporate benefits and needs to be solved urgently. The present invention is intended to overcome this problem. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for producing high-performance polyester fibers using low-temperature polymerization technology, which solves the problem of low polymerization reaction efficiency caused by unreasonable raw material ratio.

[0006] To achieve the above objectives, the present invention is implemented by the following technical scheme: A method for producing high-performance polyester fibers using low-temperature polymerization technology comprises the following steps:

[0007] S1. Raw material preparation: selecting terephthalic acid, ethylene glycol, catalyst, stabilizer and modifier; pre-treating raw materials to ensure purity and dryness;

[0008] S2, low temperature prepolymerization, adding materials to the reactor, introducing inert gas and heating to a low temperature range; maintaining low temperature conditions, performing prepolymerization to generate oligomers;

[0009] S3, low temperature polycondensation, adjusting the temperature and pressure to polycondensation conditions; continuing the polycondensation reaction to generate high molecular weight polyester;

[0010] S4, spinning preparation, conveying polyester melt and filtering impurities; preparing spinning components;

[0011] S5, fiber spinning, the melt is extruded into filaments through the spinning assembly; the filaments are cooled to solidify and form;

[0012] S6, fiber post-treatment, stretching the fiber; performing heat setting treatment;

[0013] S7. Product testing and optimization: testing various fiber performance indicators; optimizing production process parameters based on test results.

[0014] Preferably, the S1 specifically comprises the following steps:

[0015] S101, Raw material selection: Select high-purity terephthalic acid, the purity must reach 99.5% or above, and the particle size is controlled at 100-200 mesh; select ethylene glycol that meets national standards, the purity is not less than 99.8%, and the water content is less than 0.1%. Weigh the corresponding amount according to the molar ratio of terephthalic acid to ethylene glycol of 1:1.1-1.5; determine the titanium series and antimony series of catalysts according to production needs, and weigh 0.01%-0.1% of titanium series and antimony series according to the appropriate proportion of the total raw material mass; at the same time, weigh an appropriate amount of phosphate stabilizer, accounting for 0.05%-0.2% of the total raw material mass, and 1%-5% of hydrophilic modifier;

[0016] S102, raw material pretreatment: Place the weighed phthalic acid, ethylene glycol and various additives in a vacuum oven and other equipment, dry at 60℃-80℃ for 12-24 hours to remove moisture and impurities, seal the pretreated raw materials and store them, waiting to be put into the polymerization reactor.

[0017] Preferably, the S2 specifically comprises the following steps:

[0018] S201. Reactor preparation and feeding: Use a reactor equipped with stirring at 50-1000r / min, temperature control fluctuation within ±1°C, and inert gas to maintain a slight positive pressure of 100-500Pa. Add the pretreated raw materials and additives into the reactor in sequence and close the feeding port.

[0019] S202, prepolymerization operation: introduce nitrogen into the reactor with the flow rate controlled at 10-30L / min, ventilate for 10-20 minutes to replace the air, maintain a slight positive pressure of nitrogen, and then increase the temperature to 160°C-200°C at a heating rate of 1-2°C / min; after reaching the set temperature, adjust the stirring speed to 50-100r / min, react for 1.5-3 hours, monitor and adjust the temperature in real time during the reaction, and detect the change in reactant concentration every 30-60 minutes.

[0020] Preferably, the S3 specifically includes the following steps:

[0021] S301, Condition adjustment: After the prepolymerization is completed, maintain an inert gas atmosphere, increase the temperature to 200°C-240°C at a gradient of 0.5-1°C / min, and gradually reduce the pressure of the reaction system to 50-200Pa using a high-efficiency vacuum system;

[0022] S302, polycondensation reaction execution: under the adjusted temperature and pressure conditions, the stirring speed is adjusted to 100-150r / min, the polycondensation reaction is continued for 2-4 hours, and the melt viscosity change is monitored in real time by an online viscometer to judge the reaction progress.

[0023] Preferably, the S4 specifically comprises the following steps:

[0024] S401, melt delivery configuration: Use a high-precision metering pump with a flow accuracy within ±1% to deliver polyester melt, install a filter with a 200-500 mesh filter on the melt delivery pipeline to filter out tiny impurities, calibrate the metering pump flow parameters, and check the installation and sealing of the filter;

[0025] S402, spinning assembly preparation: select the spinning process according to product requirements, install the corresponding spinning assembly, where the spinneret aperture is controlled at 0.2-0.5mm, and the number of holes is determined according to the spinning scale and fiber specifications.

[0026] Preferably, the S5 specifically includes the following steps:

[0027] S501, melt extrusion: the polyester melt is filtered and then enters the spinning assembly, and is extruded through a spinneret to form filaments, and the melt temperature, pressure and spinneret temperature parameters are controlled to make the extrusion uniform and continuous to obtain primary fibers;

[0028] S502, cooling and forming: After being extruded, the primary fibers enter the cooling zone, and side blowing or ring blowing is used to control the cooling air temperature at 15-30°C and the wind speed at 0.5-1.5 m / s to rapidly cool and solidify the filaments.

[0029] Preferably, the S6 specifically comprises the following steps:

[0030] S601, stretching process: multi-stage stretching is applied to the nascent fiber, the first-stage stretching multiple is set to 2-3 times, the temperature is 60-80°C; the second-stage stretching multiple is set to 3-4 times, the temperature is 100-120°C, and the corresponding tension is applied by the equipment to orient the molecular chains;

[0031] S602, heat setting process: heat setting the stretched fiber at 150-200°C for 10-30 seconds, while applying a tension of 0.1-0.5 cN / dtex to perfect the crystal structure.

[0032] Preferably, the S7 specifically includes the following steps:

[0033] S701, Performance testing: Use a universal material testing machine to test the mechanical properties of the fiber, use TGA and DSC thermal analysis methods to measure the thermal properties, use dyeing tests combined with instruments to measure the dyeing properties, and use a microscope to observe the microstructure;

[0034] S702, Optimization and adjustment: Analyze whether the product performance meets the standards based on the test results. If there are deficiencies, trace back the raw material ratio and process parameter production process to find the reasons, and adjust the catalyst dosage and change the corresponding temperature parameters in a targeted manner.

[0035] Working principle: In the raw material preparation stage, according to the chemical composition requirements of polyester fiber, high-purity terephthalic acid and ethylene glycol are accurately weighed in a specific molar ratio, and appropriate amounts of catalysts, stabilizers, modifiers and other additives are added to lay the foundation for subsequent reactions and ensure that all components can participate in the reaction under appropriate conditions.

[0036] During the low-temperature prepolymerization stage, a reactor equipped with precise temperature control, stirring and inert gas protection is used. Nitrogen is first introduced to replace the air and maintain a slight positive pressure. The temperature is then raised to a specific low-temperature range at a suitable heating rate. With a suitable stirring speed, terephthalic acid and ethylene glycol are esterified to form oligomers under the action of the catalyst. During this period, the temperature is monitored and controlled in real time, and changes in the concentration of reactants are detected to ensure that the reaction proceeds smoothly and efficiently, and to avoid side reactions and molecular chain degradation caused by high temperature.

[0037] During low-temperature polycondensation, the temperature is gradually increased and the pressure is reduced under an inert gas atmosphere. The reaction is promoted in the forward direction by removing small molecule by-products. At the same time, the stirring speed is adjusted, and the melt viscosity is monitored with the help of an online viscometer to judge the progress and adjust the parameters in time to promote the growth of the oligomer molecular chain to form a high molecular weight polyester and achieve a stable polycondensation reaction.

[0038] In the spinning preparation stage, a high-precision metering pump is used to accurately transport the melt and filter impurities through a filter. The spinning process is selected according to product requirements and suitable spinning components are installed to ensure that the melt is pure and can be extruded into filaments as required.

[0039] During the fiber spinning process, the relevant parameters of melt extrusion are precisely controlled to ensure that the filaments are uniform and continuous, and then the nascent fibers are cooled at the set temperature and wind speed through side blowing or ring blowing to achieve rapid solidification and molding.

[0040] The stretching process of fiber post-processing is based on multi-stage stretching based on applying tension at different temperatures to orient the molecular chains; the heat setting process improves the crystal structure and eliminates internal stress at specific temperature and tension to improve the overall performance of the fiber.

[0041] Finally, we can fully understand the fiber performance through performance testing, and trace the production process based on the test results to optimize the raw material ratio and process parameters to ensure that the product continues to meet high performance requirements. All links in the whole process are closely coordinated and interrelated to achieve efficient and stable production of high-performance polyester fibers.

[0042] The present invention provides a method for producing high-performance polyester fibers using low-temperature polymerization technology. It has the following beneficial effects:

[0043] 1. The present invention can provide a suitable and stable raw material basis for subsequent polymerization reactions by controlling the purity, particle size, ratio and dosage of various additives of the raw materials, ensuring that each raw material and additive plays its due role in the reaction, so that the reaction system is in a relatively ideal initial state, which is conducive to the generation of high-quality and stable-performance polyester polymers, and solves the problem of low polymerization efficiency caused by low raw material purity and unreasonable ratio.

[0044] 2. The present invention achieves a stable and efficient esterification reaction of terephthalic acid and ethylene glycol under low temperature and stable conditions by controlling nitrogen ventilation, heating rate, reaction temperature, stirring speed and real-time monitoring of changes in reactant concentrations, thereby generating oligomers with a relatively regular molecular chain structure and a suitable molecular weight distribution range. The entire reaction process can be in a well-controlled state, thus solving the problems of excessive thermal degradation of polymer molecular chains and increased side reactions caused by excessively high reaction temperatures in traditional high-temperature polymerization processes.

[0045] 3. The present invention realizes precise control of the progress of the polycondensation reaction by reasonably adjusting the stirring speed, setting a continuous and stable reaction time, and using an online viscometer for real-time monitoring and adjusting the reaction conditions in a timely manner according to the monitoring results, thereby ensuring that the polycondensation reaction can proceed stably and efficiently, allowing the polyester molecular chain to grow steadily, and ultimately obtaining a high molecular weight polyester product with a higher molecular weight, a narrower molecular weight distribution and good thermal stability, thereby solving the problem of local reaction differences caused by uneven stirring during the polycondensation reaction.

[0046] 4. The present invention realizes the delivery of polyester melt to the spinning assembly at a stable and accurate flow rate through a high-precision metering pump, a filter and corresponding calibration and inspection operations, while effectively removing tiny impurities in the melt, ensuring that the melt entering the spinning assembly has a high degree of purity, a stable flow rate and meets the requirements of the spinning process, laying the foundation for subsequent uniform and high-quality spinning, ensuring that the spinning process can proceed stably, reducing spinning quality problems caused by unstable melt flow or impurities, and solving the problems of uneven thickness and broken wires in the spinning process caused by unstable melt flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The figure is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0048] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] Please refer to the attached Figure 1 The embodiment of the present invention provides a method for producing high-performance polyester fibers using low-temperature polymerization technology, comprising the following steps:

[0050] S1. Raw material preparation: selecting terephthalic acid, ethylene glycol, catalyst, stabilizer and modifier; pre-treating raw materials to ensure purity and dryness;

[0051] S2, low temperature prepolymerization, adding materials to the reactor, introducing inert gas and heating to a low temperature range; maintaining low temperature conditions, performing prepolymerization to generate oligomers;

[0052] S3, low temperature polycondensation, adjusting the temperature and pressure to polycondensation conditions; continuing the polycondensation reaction to generate high molecular weight polyester;

[0053] S4, spinning preparation, conveying polyester melt and filtering impurities; preparing spinning components;

[0054] S5, fiber spinning, the melt is extruded into filaments through the spinning assembly; the filaments are cooled to solidify and form;

[0055] S6, fiber post-treatment, stretching the fiber; performing heat setting treatment;

[0056] S7. Product testing and optimization: testing various fiber performance indicators; optimizing production process parameters based on test results.

[0057] The S1 specifically includes the following steps:

[0058] S101, Raw material selection: Select high-purity terephthalic acid, the purity must reach 99.5% or above, and the particle size is controlled at 100-200 mesh; select ethylene glycol that meets national standards, the purity is not less than 99.8%, and the water content is less than 0.1%. Weigh the corresponding amount according to the molar ratio of terephthalic acid to ethylene glycol of 1:1.1-1.5; determine the titanium series and antimony series of catalysts according to production needs, and weigh 0.01%-0.1% of titanium series and antimony series according to the appropriate proportion of the total raw material mass; at the same time, weigh an appropriate amount of phosphate stabilizer, accounting for 0.05%-0.2% of the total raw material mass, and 1%-5% of hydrophilic modifier;

[0059] S102, raw material pretreatment: Place the weighed phthalic acid, ethylene glycol and various additives in a vacuum oven and other equipment, dry at 60℃-80℃ for 12-24 hours to remove moisture and impurities, seal the pretreated raw materials and store them, waiting to be put into the polymerization reactor.

[0060] Specifically, for terephthalic acid (PTA), a raw material with high purity (99.5% and above) and a particle size controlled at 100-200 mesh is selected because high purity can reduce the interference of impurities on subsequent polymerization reactions, and the appropriate particle size range helps it to be better dispersed in the reaction system and fully contact with ethylene glycol to ensure reaction uniformity. Ethylene glycol (EG) is selected to meet national standards, with a purity of not less than 99.8% and a water content of less than 0.1%. Low water content can avoid the influence of excess water on reaction balance and product quality during the polymerization process. PTA and EG are weighed according to a specific molar ratio (1:1.1-1.5). This molar ratio is determined based on the stoichiometric relationship of polyester synthesis, which can ensure that the two are fully reacted in the subsequent reaction to form polyester, avoiding the waste of raw materials or the increase of side reactions due to the excess of one raw material.

[0061] In terms of catalysts, titanium or antimony catalysts are selected according to production needs and weighed at 0.01%-0.1% of the total raw material mass. This is because the catalyst within this ratio range can provide appropriate catalytic activity in the polymerization reaction, promote the smooth esterification and polycondensation reaction between PTA and EG, and will not cause problems such as residues that affect product quality due to excessive catalysts. Phosphate stabilizers are weighed at 0.05%-0.2% of the total raw material mass. They can capture active substances such as free radicals generated in the reaction system during the polymerization reaction, inhibit side reactions such as oxidative degradation caused by factors such as heat and oxygen, and ensure the stability of the polyester molecular chain. The hydrophilic modifier is weighed at a mass percentage of 1%-5% in order to introduce hydrophilic functional groups into the polyester molecular chain, change the surface properties of the polyester fiber, and improve its hydrophilicity.

[0062] The weighed terephthalic acid, ethylene glycol and various additives are placed in a vacuum oven and other equipment, and dried at 60℃-80℃ for 12-24 hours. The combined effect of temperature and vacuum environment allows the moisture in the raw materials and additives to be vaporized and extracted at a lower temperature, and some volatile impurities can also be removed at the same time. Within this temperature range, it can ensure that moisture and impurities are effectively removed, and will not cause adverse effects on the chemical properties of the raw materials themselves due to excessive temperature, such as avoiding decomposition, oxidation and other reactions of the raw materials. The pre-treated raw materials are sealed and stored to prevent moisture, oxygen, etc. from entering the external environment again, and to ensure that the raw materials are always in a dry and pure state before being put into the polymerization reactor.

[0063] By controlling the purity, particle size, ratio of raw materials and the dosage of various additives, it is possible to provide a suitable and stable raw material basis for subsequent polymerization reactions, ensuring that each raw material and additive plays its due role in the reaction, and putting the reaction system in a relatively ideal initial state, which is conducive to the production of high-quality, stable-performance polyester polymers, and solves the problem of low polymerization reaction efficiency caused by low raw material purity and unreasonable ratio.

[0064] The S2 specifically includes the following steps:

[0065] S201. Reactor preparation and feeding: Use a reactor equipped with stirring at 50-1000r / min, temperature control fluctuation within ±1°C, and inert gas to maintain a slight positive pressure of 100-500Pa. Add the pretreated raw materials and additives into the reactor in sequence and close the feeding port.

[0066] S202, prepolymerization operation: introduce nitrogen into the reactor with the flow rate controlled at 10-30L / min, ventilate for 10-20 minutes to replace the air, maintain a slight positive pressure of nitrogen, and then increase the temperature to 160°C-200°C at a heating rate of 1-2°C / min; after reaching the set temperature, adjust the stirring speed to 50-100r / min, react for 1.5-3 hours, monitor and adjust the temperature in real time during the reaction, and detect the change in reactant concentration every 30-60 minutes.

[0067] Specifically, a polymerization reactor equipped with specific functions is selected, and its stirring device can be adjusted within the speed range of 50-1000r / min, so that the pretreated raw materials and additives added to the reactor can be fully mixed and evenly mixed, ensuring that each reactant molecule has sufficient contact opportunities during the subsequent reaction process, which is conducive to the full development of the reaction. The temperature control device can accurately control the temperature fluctuation within ±1°C, which allows the reaction to be carried out in an extremely stable temperature environment that meets the preset requirements, avoiding side reactions or affecting the reaction rate due to large temperature fluctuations. The inert gas protection system can maintain the reactor in a slightly positive pressure state with a pressure range of 100-500Pa. It isolates the outside air by introducing inert gas (such as nitrogen) to prevent oxygen and other components in the air from entering the reaction system, because oxygen may participate in some unnecessary oxidation reactions and interfere with the normal polymerization process. The raw materials (terephthalic acid, ethylene glycol, etc.) and various additives (catalysts, stabilizers, modifiers, etc.) that are accurately weighed and pretreated as required are added to the reactor in sequence, and then the feed port is closed to ensure the sealing of the reaction system, creating conditions for the subsequent prepolymerization reaction in a stable environment isolated from external interference.

[0068] First, nitrogen is introduced into the reactor at a flow rate of 10-30L / min for ventilation for 10-20 minutes. The air originally present in the reactor is fully replaced and discharged by the introduction of nitrogen, so that the reaction system is in a nitrogen protective atmosphere. Then, the nitrogen is continuously maintained at a slightly positive pressure to prevent the outside air from entering again. Subsequently, with the help of the temperature control device of the reactor, the temperature of the reaction system is slowly raised to a low temperature range of 160℃-200℃ at a heating rate of 1-2℃ / min. In this temperature range, terephthalic acid and ethylene glycol begin to undergo esterification reaction under the action of catalysts and other additives to generate oligomers. When the set temperature is reached, the speed of the stirring device is adjusted to 50-100r / min. The appropriate stirring speed can ensure that the reactants continue to fully contact with each other, and will not destroy the molecular chain structure of the oligomer being generated due to excessive stirring. During the entire reaction period of 1.5-3 hours, the temperature of the reaction system is monitored in real time through a temperature sensor, and the temperature is adjusted in time according to the set temperature fluctuation range (within ±1°C) to ensure that the temperature is always in the appropriate range to ensure the smooth progress of the reaction. At the same time, the concentration of the reactants is detected every 30-60 minutes, and the progress of the reaction is judged based on the concentration changes, so as to promptly detect whether there are any abnormalities in the reaction, such as the reactants being consumed too slowly or too quickly, so that corresponding adjustment measures can be taken.

[0069] By controlling nitrogen ventilation, heating rate, reaction temperature, stirring speed and real-time monitoring of changes in reactant concentrations, it is possible to achieve a smooth and efficient esterification reaction of terephthalic acid and ethylene glycol under low-temperature and stable conditions to generate oligomers with a relatively regular molecular chain structure and a suitable molecular weight distribution range. The entire reaction process can be in a well-controlled state, ensuring the quality stability of the prepolymerization product and solving the problems of excessive thermal degradation of polymer molecular chains and increased side reactions caused by excessively high reaction temperatures in traditional high-temperature polymerization processes.

[0070] The S3 specifically includes the following steps:

[0071] S301, Condition adjustment: After the prepolymerization is completed, maintain an inert gas atmosphere, increase the temperature to 200°C-240°C at a gradient of 0.5-1°C / min, and gradually reduce the pressure of the reaction system to 50-200Pa using a high-efficiency vacuum system;

[0072] S302, polycondensation reaction execution: under the adjusted temperature and pressure conditions, the stirring speed is adjusted to 100-150r / min, the polycondensation reaction is continued for 2-4 hours, and the melt viscosity change is monitored in real time by an online viscometer to judge the reaction progress.

[0073] Specifically, after the prepolymerization reaction is completed, the inert gas (such as nitrogen) atmosphere is still maintained. This is because the inert gas can effectively isolate the outside air, prevent oxygen and other components in the air from mixing into the reaction system, avoid oxygen participating in the reaction to cause unnecessary oxidation and other side reactions, and ensure that the entire polycondensation reaction can be carried out in a pure and stable chemical environment. Then, the temperature of the reaction system is gradually increased to the range of 200°C-240°C at a heating rate of 0.5-1°C / min by using a gradient heating method. This slow and stable heating process is based on the chemical kinetics principle of polyester polycondensation reaction. In this temperature range, as the temperature rises, the oligomer molecules have more suitable energy, the activity of the molecular chain increases, and it is more conducive to the subsequent polycondensation reaction. At the same time, a high-efficiency vacuum system is connected to the reaction system, and small molecular byproducts (such as water, ethylene glycol, etc.) in the reaction system are gradually extracted through vacuum pumps and other equipment, and the pressure of the reaction system is gradually reduced to 50-200Pa. According to the principle of chemical equilibrium, reducing the pressure of the reaction system will prompt the reaction to proceed in the direction of producing high molecular weight polyester, which is conducive to the continuous condensation reaction between oligomers. Because the timely removal of small molecular by-products breaks the original chemical equilibrium, it drives the reaction to continue to move in the positive direction, thereby promoting the continuous growth of the polyester molecular chain.

[0074] Under the specific conditions of the temperature being adjusted to 200-240°C and the pressure being maintained at 50-200Pa, the stirring speed of the stirring device is adjusted to 100-150r / min. The appropriate stirring speed can ensure that the materials in the reaction system remain evenly mixed, so that each oligomer molecule can fully contact in the system, and ensure that the polycondensation reaction proceeds evenly in the entire reaction system, avoiding the situation of inconsistent local reaction degree. Then, the polycondensation reaction is continued for 2-4 hours, during which time, the melt viscosity change is monitored in real time with the help of an online viscometer. Since there is a positive correlation between the molecular weight and melt viscosity of polyester, as the condensation reaction proceeds, the polyester molecular chain continues to grow, the molecular weight gradually increases, and the melt viscosity will continue to increase accordingly. Therefore, by real-time monitoring of the change in melt viscosity, the progress of the condensation reaction can be judged based on the viscosity change trend, the growth rate of the molecular chain and whether the reaction is proceeding as expected can be understood, and then the reaction conditions such as temperature, pressure and stirring speed can be fine-tuned in time according to the monitored data. For example, when it is found that the viscosity increases too slowly, the temperature can be appropriately increased or the pressure can be further reduced to speed up the reaction rate, ensuring that the condensation reaction continues smoothly and efficiently.

[0075] By reasonably adjusting the stirring speed, setting a continuous and stable reaction time, and using an online viscometer for real-time monitoring and adjusting the reaction conditions in a timely manner based on the monitoring results, the process of the polycondensation reaction is precisely controlled to ensure that the polycondensation reaction can proceed stably and efficiently, allowing the polyester molecular chain to grow steadily, and ultimately obtaining a high molecular weight polyester product with a higher molecular weight, a narrower molecular weight distribution and good thermal stability, ensuring that the quality and performance of the polyester product meet the requirements of subsequent spinning and fiber forming processes, and solving the problem of local reaction differences caused by uneven stirring during the polycondensation reaction.

[0076] The S4 specifically comprises the following steps:

[0077] S401, melt delivery configuration: Use a high-precision metering pump with a flow accuracy within ±1% to deliver polyester melt, install a filter with a 200-500 mesh filter on the melt delivery pipeline to filter out tiny impurities, calibrate the metering pump flow parameters, and check the installation and sealing of the filter;

[0078] S402, spinning assembly preparation: select the spinning process according to product requirements, install the corresponding spinning assembly, where the spinneret aperture is controlled at 0.2-0.5mm, and the number of holes is determined according to the spinning scale and fiber specifications.

[0079] Specifically, the use of a high-precision metering pump with a flow accuracy control within ±1% to transport polyester melt is based on the principle of precise flow control. The metering pump can output the polyester melt stably and accurately according to the set flow value through a precise mechanical structure and a precise transmission device, so that the melt enters the subsequent spinning assembly at a constant and uniform flow rate. Installing a filter with a 200-500 mesh filter in the melt delivery pipeline is to utilize the physical barrier effect of the filter. The mesh size allows the polyester melt to pass smoothly, and for the tiny impurities that may exist in the melt, such as unreacted raw material particles, catalyst residual particles or other mixed solid impurities, the size of these impurities is larger than the mesh of the filter, and they will be intercepted on one side of the filter, thereby filtering the melt. At the same time, calibrating the flow parameters of the metering pump is to use professional calibration equipment and methods, according to the standard specifications of flow measurement, to accurately adjust the flow output of the metering pump to ensure that its actual output flow is highly consistent with the set flow. Checking the installation and sealing of the filter is to ensure that the filter can work stably during the entire melt conveying process, to avoid looseness and gaps due to insecure installation, to prevent unfiltered melt from bypassing the filter and directly entering the subsequent links, and to prevent melt leakage during the conveying process.

[0080] The appropriate spinning process is selected based on the different final requirements of the product, such as the purpose of the fiber (whether it is used in the textile and clothing field with high requirements for softness and fineness, or used in the industrial filter material field with special requirements for strength and corrosion resistance, etc.) and the required fiber specifications (such as fiber thickness, length, etc.). For example, the melt spinning process is suitable for large-scale production of conventional polyester fibers, while the dry and wet spinning processes are more conducive to the preparation of fibers with special properties or structures. Then, the corresponding spinning assembly is installed according to the selected spinning process. The spinneret in the spinning assembly is a key component, and its aperture is controlled in the range of 0.2-0.5mm. Different aperture sizes determine the thickness of the extruded filaments. Finer apertures can spin finer fibers to meet some application scenarios that require fiber fineness; and the number of holes is determined according to the spinning scale (for example, large-scale production requires more spinneret holes to increase output) and fiber specifications (for example, the number of holes can be appropriately reduced for the production of thicker fibers, and the number of holes can be increased for the production of fine fibers to ensure output and quality). By reasonably setting the aperture and number of holes of the spinneret, the polyester melt can form filaments that meet the requirements during extrusion. The shape and quantity.

[0081] Through high-precision metering pumps, filters, and corresponding calibration and inspection operations, the polyester melt is delivered to the spinning assembly at a stable and precise flow rate. At the same time, tiny impurities in the melt are effectively removed, ensuring that the melt entering the spinning assembly has a high degree of purity, a stable flow rate and meets the requirements of the spinning process, laying the foundation for subsequent uniform and high-quality spinning, ensuring that the spinning process can proceed stably, reducing spinning quality problems caused by unstable melt flow or impurities, and solving the problems of uneven thickness and broken wires in the spinning process caused by unstable melt flow.

[0082] The S5 specifically includes the following steps:

[0083] S501, melt extrusion: the polyester melt is filtered and then enters the spinning assembly, and is extruded through a spinneret to form filaments, and the melt temperature, pressure and spinneret temperature parameters are controlled to make the extrusion uniform and continuous to obtain primary fibers;

[0084] S502, cooling and forming: After being extruded, the primary fibers enter the cooling zone, and side blowing or ring blowing is used to control the cooling air temperature at 15-30°C and the wind speed at 0.5-1.5 m / s to rapidly cool and solidify the filaments.

[0085] Specifically, the polyester melt enters the spinning assembly after being filtered to remove tiny impurities in the early stage. The spinning assembly has a specific structural design inside, in which the spinneret plays a key role, and it contains many spinnerets with a pore size of 0.2-0.5mm. When the polyester melt reaches the spinneret under a certain pressure drive, based on the principle of fluid mechanics, the melt is extruded through these spinnerets under the action of the pressure difference to form filaments. In this process, the parameters such as melt temperature, pressure and spinneret temperature are strictly controlled because the physical properties of the melt such as fluidity and viscosity are closely related to temperature. The appropriate melt temperature can ensure that it has good fluidity, so that it can be smoothly extruded through the spinneret, avoiding the situation where the melt viscosity is too high due to low temperature and it is difficult to extrude or the spinneret is blocked; and the appropriate pressure provides sufficient power for the melt, so that it can pass through the spinneret in a stable and uniform state, ensuring that the extruded filaments are uniform in thickness and continuous. The control of spinneret temperature is equally important, as it affects the state of the melt at the spinneret and the stability of the filament extrusion. The appropriate temperature can keep the melt in a good shape at the moment of extrusion, which helps to form high-quality filaments. Through the coordinated control of these parameters, the entire extrusion process can be carried out stably and orderly, thus obtaining primary fibers.

[0086] After the nascent fiber is extruded from the spinning assembly, it immediately enters the cooling zone, and the cooling method of side blowing or ring blowing is based on the principle of heat exchange. When the cooling air blows to the high-temperature filament at a certain temperature (15-30℃) and wind speed (0.5-1.5m / s), there is a temperature difference between the filament and the cooling air, and the heat will be transferred from the high-temperature filament to the low-temperature cooling air, so that the temperature of the filament will drop rapidly. The appropriate cooling air temperature can ensure that the filament is cooled quickly, and the internal structure of the fiber will not be adversely affected by the low temperature, such as excessive internal stress, too fast crystallization, etc.; and the appropriate wind speed ensures the efficiency of heat exchange, so that the filament can be fully in contact with the cooling air in a short time, realize the rapid transfer of heat, and promote the rapid cooling and solidification of the filament. In this way, the physical state of the nascent fiber is changed, so that it is transformed from a high-temperature flowable melt state to a solid fiber, and in this process, by reasonably controlling the cooling parameters, it helps the fiber to form a relatively stable and regular internal structure, laying the foundation for the subsequent improvement of fiber performance.

[0087] By selecting a suitable cooling method and accurately controlling the cooling air temperature and wind speed, the nascent fibers can be cooled and solidified rapidly and stably to form solid fibers with relatively stable structure and good physical properties, ensuring the smooth transition of the fibers from melt to solid state. At the same time, the internal structure of the fibers can be optimized during the cooling process, which is beneficial to the subsequent post-processing steps such as fiber stretching and heat setting, improving the overall quality of fiber products and solving the problems of poor fiber molding quality and unstable internal structure caused by improper cooling of nascent fibers.

[0088] The S6 specifically comprises the following steps:

[0089] S601, stretching process: multi-stage stretching is applied to the nascent fiber, the first-stage stretching multiple is set to 2-3 times, the temperature is 60-80°C; the second-stage stretching multiple is set to 3-4 times, the temperature is 100-120°C, and the corresponding tension is applied by the equipment to orient the molecular chains;

[0090] S602, heat setting process: heat setting the stretched fiber at 150-200°C for 10-30 seconds, while applying a tension of 0.1-0.5 cN / dtex to perfect the crystal structure.

[0091] Specifically, the multi-stage stretching method for the primary fiber is based on the deformation characteristics of polymer materials and the principle of molecular chain orientation. When the fiber is in the primary state, the polymer chain inside it presents a relatively disordered arrangement state. During the primary stretching process, the corresponding tension is applied by the equipment to stretch the fiber in a specific temperature range (60-80°C), and the multiple is set to 2-3 times. This temperature range gives the fiber a certain flexibility and deformability. Under the action of tension, the fiber molecular chain will gradually begin to orient and arrange along the stretching direction. The originally disordered molecular chains are straightened and arranged in the same direction. The length of the fiber increases and the diameter becomes thinner. With the completion of the primary stretching, the secondary stretching stage is entered. At this time, the temperature is raised to 100-120°C, and the stretching multiple is further increased to 3-4 times. The higher temperature makes the fiber molecular chain more active and can better respond to the tension. Further, the molecular chain is more fully oriented to make its arrangement more regular and orderly, thereby improving the crystallization performance and orientation degree of the fiber, and then enhancing the mechanical properties and other performance indicators of the fiber. Different levels of stretching and the corresponding temperature and stretching ratio settings are determined based on the deformability and orientation effect of the fiber molecular chain under different conditions, and the transformation of the molecular chain from disorder to high order is achieved in a step-by-step manner.

[0092] When the stretched fiber is heat-set, the fiber is placed in a temperature environment of 150-200℃ for 10-30 seconds, and a tension of 0.1-0.5cN / dtex is applied at the same time. This is based on the principle of thermal relaxation and crystallization perfection of polymer materials. After the stretching process, although the fiber molecular chain has a good orientation arrangement, there is still a certain internal stress, and the crystal structure can be further optimized. Under the temperature conditions of heat setting, the fiber molecular chain obtains enough energy and begins to relax thermally. With the assistance of tension, the molecular chain will adjust to a more stable position, further eliminate internal stress, and make the fiber size more stable. At the same time, within this temperature range, the fiber molecular chain will continue to crystallize and grow in a relatively stable and orderly state, improve the crystal structure, make the crystallization more regular and perfect, and improve the crystallinity, thereby enhancing the fiber's heat resistance, chemical stability and other properties, and making the fiber's appearance, shape, size, etc. more stable and less prone to deformation and other changes.

[0093] Through multi-stage stretching and precise control of the stretching temperature and stretching ratio at each stage, and with the help of equipment to apply appropriate tension, it is possible to transform the fiber molecular chain from a disordered initial state to a highly oriented state. The crystallization performance of the fiber is significantly improved, and its internal structure is more regular and orderly, thereby effectively improving the fiber's strength, modulus and other mechanical properties. At the same time, it also improves the fiber's dimensional stability, etc., so that the fiber has better comprehensive performance and meets the needs of subsequent higher quality applications, solving the problem of insufficient mechanical properties of primary fibers due to disordered molecular chains.

[0094] The S7 specifically comprises the following steps:

[0095] S701, Performance testing: Use a universal material testing machine to test the mechanical properties of the fiber, use TGA and DSC thermal analysis methods to measure the thermal properties, use dyeing tests combined with instruments to measure the dyeing properties, and use a microscope to observe the microstructure;

[0096] S702, Optimization and adjustment: Analyze whether the product performance meets the standards based on the test results. If there are deficiencies, trace back the raw material ratio and process parameter production process to find the reasons, and adjust the catalyst dosage and change the corresponding temperature parameters in a targeted manner.

[0097] Specifically, we use universal material testing machines, TGA, DSC thermal analysis methods, dyeing tests combined with relevant instruments and microscopes and other testing methods, and according to their respective professional principles, we respectively test the mechanical properties, thermal properties, dyeing properties and microstructure of the fibers, so as to achieve the effect of comprehensively and accurately obtaining multi-faceted performance data of the fibers, solving the problems of being unable to accurately judge whether the product quality meets the standards and incomplete understanding of product performance, and providing a reliable basis for subsequent optimization.

[0098] Based on the performance test results, the production process is traced back to investigate the reasons for the raw material ratio and process parameters. For insufficient product performance, such as insufficient strength and poor thermal stability, parameters such as catalyst dosage and heat setting temperature are adjusted accordingly. Through multiple rounds of testing and adjustment cycles, the production is optimized and the product performance is improved to the standard level. The problems of substandard product performance, unstable quality and difficulty in improving quality due to blind production are solved, thus ensuring product quality and stable development of the enterprise.

[0099] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for producing high-performance polyester fibers using low-temperature polymerization technology, characterized in that: The following steps are involved: S1. Raw material preparation: selecting terephthalic acid, ethylene glycol, catalyst, stabilizer and modifier; Pre-treat raw materials to ensure purity and dryness; S2, low temperature prepolymerization, adding materials to the reactor, introducing inert gas and heating to a low temperature range; maintaining low temperature conditions, performing prepolymerization to generate oligomers; S3, low temperature polycondensation, adjusting the temperature and pressure to polycondensation conditions; continuing the polycondensation reaction to generate high molecular weight polyester; S4, spinning preparation, conveying polyester melt and filtering impurities; preparing spinning components; S5, fiber spinning, the melt is extruded into filaments through the spinning assembly; the filaments are cooled to solidify and form; S6, fiber post-treatment, stretching the fiber; performing heat setting treatment; S7. Product testing and optimization: testing various fiber performance indicators; optimizing production process parameters based on test results.

2. The method for producing high-performance polyester fiber using low-temperature polymerization technology according to claim 1, characterized in that: The S1 specifically includes the following steps: S101, Raw material selection: Select high-purity terephthalic acid, the purity must reach 99.5% or above, and the particle size is controlled at 100-200 mesh; select ethylene glycol that meets national standards, the purity is not less than 99.8%, and the water content is less than 0.1%. Weigh the corresponding amount according to the molar ratio of terephthalic acid to ethylene glycol of 1:1.1-1.5; determine the titanium series and antimony series of catalysts according to production needs, and weigh 0.01%-0.1% of titanium series and antimony series according to the appropriate proportion of the total raw material mass; at the same time, weigh an appropriate amount of phosphate stabilizer, accounting for 0.05%-0.2% of the total raw material mass, and 1%-5% of hydrophilic modifier; S102, raw material pretreatment: Place the weighed phthalic acid, ethylene glycol and various additives in a vacuum oven and other equipment, dry at 60℃-80℃ for 12-24 hours to remove moisture and impurities, seal the pretreated raw materials and store them, waiting to be put into the polymerization reactor.

3. The method for producing high-performance polyester fiber using low-temperature polymerization technology according to claim 1, characterized in that: The S2 specifically includes the following steps: S201. Reactor preparation and feeding: Use a reactor equipped with stirring at 50-1000r / min, temperature control fluctuation within ±1°C, and inert gas to maintain a slight positive pressure of 100-500Pa. Add the pretreated raw materials and additives into the reactor in sequence and close the feeding port. S202, prepolymerization operation: introduce nitrogen into the reactor with the flow rate controlled at 10-30L / min, ventilate for 10-20 minutes to replace the air, maintain a slight positive pressure of nitrogen, and then increase the temperature to 160°C-200°C at a heating rate of 1-2°C / min; after reaching the set temperature, adjust the stirring speed to 50-100r / min, react for 1.5-3 hours, monitor and adjust the temperature in real time during the reaction, and detect the change in reactant concentration every 30-60 minutes.

4. The method for producing high-performance polyester fiber using low-temperature polymerization technology according to claim 1, characterized in that: The S3 specifically includes the following steps: S301, Condition adjustment: After the prepolymerization is completed, maintain an inert gas atmosphere, increase the temperature to 200°C-240°C at a gradient of 0.5-1°C / min, and gradually reduce the pressure of the reaction system to 50-200Pa using a high-efficiency vacuum system; S302, polycondensation reaction execution: under the adjusted temperature and pressure conditions, the stirring speed is adjusted to 100-150r / min, the polycondensation reaction is continued for 2-4 hours, and the melt viscosity change is monitored in real time by an online viscometer to judge the reaction progress.

5. The method for producing high-performance polyester fiber using low-temperature polymerization technology according to claim 1, characterized in that: The S4 specifically comprises the following steps: S401, melt delivery configuration: Use a high-precision metering pump with a flow accuracy within ±1% to deliver polyester melt, install a filter with a 200-500 mesh filter on the melt delivery pipeline to filter out tiny impurities, calibrate the metering pump flow parameters, and check the installation and sealing of the filter; S402, spinning assembly preparation: select the spinning process according to product requirements, install the corresponding spinning assembly, where the spinneret aperture is controlled at 0.2-0.5mm, and the number of holes is determined according to the spinning scale and fiber specifications.

6. The method for producing high-performance polyester fiber using low-temperature polymerization technology according to claim 1, characterized in that: The S5 specifically includes the following steps: S501, melt extrusion: the polyester melt is filtered and then enters the spinning assembly, and is extruded through a spinneret to form filaments, and the melt temperature, pressure and spinneret temperature parameters are controlled to make the extrusion uniform and continuous to obtain primary fibers; S502, cooling and forming: After being extruded, the primary fibers enter the cooling zone, and side blowing or ring blowing is used to control the cooling air temperature at 15-30°C and the wind speed at 0.5-1.5 m / s to rapidly cool and solidify the filaments.

7. The method for producing high-performance polyester fiber using low-temperature polymerization technology according to claim 1, characterized in that: The S6 specifically comprises the following steps: S601, stretching process: multi-stage stretching is applied to the nascent fiber, the first-stage stretching multiple is set to 2-3 times, the temperature is 60-80°C; the second-stage stretching multiple is set to 3-4 times, the temperature is 100-120°C, and the corresponding tension is applied by the equipment to orient the molecular chains; S602, heat setting process: heat setting the stretched fiber at 150-200°C for 10-30 seconds, while applying a tension of 0.1-0.5 cN / dtex to perfect the crystal structure.

8. The method for producing high-performance polyester fiber using low-temperature polymerization technology according to claim 1, characterized in that: The S7 specifically comprises the following steps: S701. Performance testing: Use a universal material testing machine to test the mechanical properties of the fiber, use TGA and DSC thermal analysis methods to measure thermal properties, use dyeing tests combined with instruments to measure dyeing properties, and use a microscope to observe the microstructure. S702, Optimization and adjustment: Analyze whether the product performance meets the standards based on the test results. If there are deficiencies, trace back the raw material ratio and process parameter production process to find the reasons, and adjust the catalyst dosage and change the corresponding temperature parameters in a targeted manner.

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