A method for producing carbon fiber precursor

Abstract

The present invention relates to the technical field of carbon fiber precursor production, and specifically discloses a carbon fiber precursor production method. The production method provided by the present invention enables each process to change gradually within a suitable time step, ensuring production efficiency while achieving smooth conversion between different production states, especially distributing the change in the amount of glue supplied within a longer time step, ensuring that its rate of change does not exceed the maximum allowable deviation of the linear density, so that the fiber linear density index meets the quality requirements. This method reduces the phenomenon of roller winding and wire breakage when switching production states, reduces waste wire loss, meets the requirements of continuous and stable production of products, reduces degradation losses, does not require active bobbin dropping, reduces operational difficulty and strength, and significantly improves the production efficiency, economic benefits and safety of the carbon fiber precursor production process.

Description

Technical Field

[0001] The invention belongs to the technical field of carbon fiber precursor production, and in particular relates to a carbon fiber precursor production method. Background Art

[0002] Carbon fiber precursor is the precursor for preparing carbon fiber. The production of high-quality carbon fiber precursor is inseparable from good process matching conditions. The state of the tow on the drive roller of the precursor production line mainly refers to the realization of the crystallinity and orientation of the fiber, which is an important process control. In this process, the fiber needs to be stretched to a certain extent at each process position to improve the intrinsic microscopic arrangement of the fiber microscopic molecular chain segments, realize the orderly rearrangement of the molecular chain, and improve the strength performance of the fiber. Drafting is achieved through the different speed differences of the drive rollers between each process. Generally, the drafting multiple is controlled between 6 and 15 times according to different process conditions, and the wet process production is generally controlled between 7 and 13 times.

[0003] In the actual production process, the production speed of the spinning line is often adjusted due to changes in the demand for customer order varieties. However, since the products in the raw silk production process adopt the winding mode, the sudden speed increase, that is, the increase in the spinning speed of the entire line, will cause the subsequent winding process to be broken or damaged. If the consistency of product quality needs to be guaranteed, the general method is to plan to drop all the existing tows, and then re-spin after the new speed runs smoothly. Although this adjustment method can maintain the consistency of product quality, it will cause material waste and reduce production efficiency. Especially under the management mode of "zero" inventory storage mode, production efficiency and product grade rate will be significantly affected. Generally, a speed adjustment process will lead to a decrease of 8% to 10% in the effective production efficiency of the day, and the product grade rate will be reduced by 40% to 50%, and a large amount of waste silk will be generated.

[0004] In the fiber production process, the single-filament fineness or linear density is an important indicator to measure the fiber performance, where the linear density is defined as the mass of the fiber per unit length, and the unit is g / m. These indicators are greatly affected by the response time of the production line speed change. When the production speed changes, the electrical appliances and equipment rotate the equipment from front to back in the entire process length after the command is issued, and the speed changes to respond to the target value state at the same time, but from the process material analysis, the material operation state cannot be followed immediately, that is, the speed state of the filament bundle on the transmission roller changes, but the increase or decrease in the amount of glue pumped out by the metering pump has not had time to travel all the transmission roller positions, resulting in a large degree of deviation in fineness or linear density, which in turn leads to unqualified indicators and downgrades. For example: the spinning speed is adjusted from 100 m / min to 105 m / min. After the instruction is issued, the metering pump speed is adjusted immediately, and the glue supply increases by 5.0%. However, this time point only occurs at the coagulation bath position. The subsequent washing tank process, oiling process, drying process, etc. have not yet reached the material increment. At the same time, each process is replenished, which will cause the fineness and linear density to become thinner. The deviation range is generally uneven within the range of 4.0%-6.0%. This kind of deviation fluctuation is unacceptable to the process.

[0005] In the prior art, the electrical inverter of the transmission equipment will switch to the target speed instantly, usually within a few seconds. This rapid switching can cause the drafting of the tow to break or fluctuate, and even cause problems such as roller entanglement and a large amount of waste yarn. The linear density of the unwound product is uneven, and the linear density deviation rate increases significantly, which seriously affects the uniformity of the fiber. The linear density deviation rate reflects the uniformity of the fiber. The lower the deviation rate, the better the product quality. The traditional rapid switching method will significantly increase the linear density deviation rate and reduce product quality. In order to deal with the risks when switching production status, some companies design a reference platform in the software of the engineering station to transition the production status. The reference platform is a production status. Its design is based on production experience and safety needs. It is generally set at a low speed state with a spinning speed of 50-60 meters / minute. By switching at a low speed, operators can handle the roller entanglement problem more safely and easily at low speed, reducing accidental injuries. However, even when running at a low speed, the risk of roller entanglement still exists, especially when the speed is increased from the reference platform to a high speed again. In actual production, simply reducing the speed cannot completely avoid the roller entanglement phenomenon, nor can it completely eliminate quality fluctuations, so there will still be problems such as product unevenness or index fluctuations. Therefore, in the carbon fiber production process, how to achieve frequent and stable state switching according to production needs is a key technical issue.

[0006] To solve the above problems, it is necessary to develop a production method that can smoothly switch between different production states to ensure that the quality indicators of the fiber are not affected when the production speed changes, thereby achieving a controllable and stable production process.

[0007] In view of this, the present invention is proposed. Summary of the invention

[0008] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for producing carbon fiber precursor. The production method provided by the present invention can achieve seamless conversion between different production states, avoid roller entanglement and wire breakage when switching production states, reduce waste wire loss, meet the requirements of continuous and stable production of products, avoid degradation losses, and at the same time reduce the operating difficulty and intensity, so that the production efficiency, economic benefits and safety of the carbon fiber precursor production process are significantly improved.

[0009] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0010] The present invention provides a method for producing carbon fiber precursor, characterized in that it comprises the following steps:

[0011] (1) determining a first production state and a second production state;

[0012] (2) taking the amount of glue supplied in the first production state as the initial amount of glue supplied and the spinning speed as the initial spinning speed;

[0013] (3) taking the glue supply amount in the second production state as the target glue supply amount and the spinning speed as the target spinning speed;

[0014] (4) Calculating the change rate of the glue supply amount by using the initial glue supply amount and the target glue supply amount;

[0015] (5) Determine the maximum allowable deviation of line density;

[0016] (6) Calculate the time step required for the change in the amount of glue supplied by the metering pump based on the rate of change of the amount of glue supplied and the maximum allowable deviation of the linear density;

[0017] (7) Determine the length of the production line;

[0018] (8) calculating the initial stroke time and the target stroke time by the production line length, the initial spinning speed, and the target spinning speed;

[0019] (9) Calculate the average of the initial travel time and the target travel time as the necessary time step;

[0020] (10) Compare the necessary time step and the time step required for the change in the amount of glue supplied, and select the larger value as the theoretical time step;

[0021] (11) Determine the actual time step based on the theoretical time step;

[0022] (12) calculating the speed change rate by the spinning speed and the actual time step;

[0023] (13) The spinning speed is changed according to the calculated speed change rate, and the initial production state is converted to the target production state within the actual time step.

[0024] The present invention provides a production method that enables different production states to be smoothly switched within a suitable time step, and this time step allows for smooth production state switching while taking into account economic rationality. Traditional methods for switching production states are usually completed within a few seconds to 10 seconds. For example, the spinning speed changes suddenly in a short period of time. This drastic change can easily lead to unstable product quality and increased deviation. The production method provided by the present invention extends the process of switching these production states to a suitable time period, and while achieving a smoother state switching, there will be no problem of reducing production efficiency due to excessive conversion time, thereby affecting economic benefits.

[0025] The present invention changes the spinning speed by a gradual change, i.e., by a reasonable speed change rate, so that the spinning speed gradually changes to the target value within a suitable time step, rather than in one step. This gradual adjustment can effectively reduce the impact of sudden speed changes on fiber quality, thereby ensuring the stability and uniformity of the fiber throughout the production process. During the production state conversion process, the parameters of multiple processes such as the glue supply pump, water washing tank, oiling tank, and drying tank will be adjusted synchronously. Among them, the roller speed of each process in the production line changes synchronously according to the fixed ratio of the draft ratio, ensuring that the draft ratio remains stable under different speed conditions to avoid fiber breakage or quality fluctuations.

[0026] In the switching between different production states, the change in the amount of glue supplied is one of the key factors. The present invention distributes the adjustment of the amount of glue supplied in a longer time step to ensure that the change rate of the amount of glue supplied does not exceed the maximum allowable deviation of the linear density index. This control method effectively maintains the uniformity of the fiber and avoids linear density fluctuations caused by sudden increases or decreases in the amount of glue supplied.

[0027] During the production state switching process, the time step determines the speed of change of the process parameters. If the time step is too short, the parameters will change too quickly, which may cause product quality problems, especially the uniformity and consistency of the fiber. If the time step is too long, it may lead to reduced production efficiency. In order to balance quality and efficiency, the time step of the production state switching needs to match the production line speed. The carbon fiber precursor production method provided by the present invention controls the change rate of the glue supply and the change rate of the spinning speed by extending the time step of the production state switching, thereby ensuring the uniformity of the fiber while ensuring production efficiency.

[0028] In the above technical solution, the calculation formula of step (4) is:

[0029]

[0030] Where: Q 增 is the rate of change of glue supply;

[0031] Q1 is the initial glue supply, unit is mL / min;

[0032] Q2 is the target glue supply amount, unit is mL / min.

[0033] In the above technical solution, the calculation formula of step (6) is:

[0034]

[0035] Where: T a The time step required for the change of the glue supply amount, in min;

[0036] Q 增 is the rate of change of glue supply;

[0037] m is the maximum allowable deviation of line density;

[0038] a is the first redundant time coefficient;

[0039] In the above technical solution, the value range of the first redundant time coefficient a is 1.1-2.0.

[0040] The maximum allowable deviation of linear density refers to the maximum allowable fluctuation boundary of the raw yarn linear density index, that is, the maximum deviation of the center value. The smaller the maximum allowable deviation of linear density, the higher the uniformity of the linear density of the fiber. Therefore, in the production process, the rate of change of the process must be controlled under the premise of ensuring this deviation requirement. Therefore, the changes in each process between different production states in the production process, especially the change rate of the amount of glue supplied, do not exceed the maximum allowable deviation of linear density, in order to maintain the uniformity of the fiber. The maximum allowable deviation of linear density of the current raw yarn production line engineering capacity is generally around 2.0%.

[0041] In order to maintain the uniformity of the fiber, it is necessary to ensure that the rate of change of the amount of glue supplied does not exceed the range of the maximum allowable deviation of the linear density. The present invention uses calculus to disperse the rate of change of the amount of glue supplied in time, assuming that the cumulative effect of the rate of change of the amount of glue supplied within a unit time (1 minute) will not exceed the maximum allowable deviation. Then, the rate of change of the amount of glue supplied divided by the maximum allowable deviation of the linear density gives the required time step to ensure that the change in the amount of glue supplied does not exceed the maximum allowable deviation. At the same time, in order to further improve the reliability of control, the necessary redundant time coefficient, i.e., the first redundant time coefficient a, is assigned. The value range of the first redundant time coefficient a is generally between 1.1 and 2.0. This coefficient is determined according to the characteristics of the fiber and the nonlinear degree of the elastic state of the primary fiber. Generally, the better the elasticity of the fiber, the larger the redundant time coefficient is usually required, which is beneficial to the control of fiber stability changes. At this time, the time step T required for the change in the amount of glue supplied can be obtained. a .

[0042] In the above technical solution, the calculation formula of step (8) is:

[0043]

[0044] Where: t1 is the initial travel time, unit min;

[0045] t2 is the target travel time, in min;

[0046] L is the length of the production line, in m;

[0047] V1 is the initial spinning speed, in m / min;

[0048] V2 is the target spinning speed, in m / min.

[0049] In the above technical solution, the calculation formula of step (9) is:

[0050]

[0051] Where: T b is the necessary time step, in min;

[0052] t1 is the initial travel time, in min;

[0053] t2 is the target travel time, in min;

[0054] b is the second redundant time coefficient.

[0055] In the above technical solution, the value range of the second redundant time coefficient b is 1.3-2.5.

[0056] In the above technical solution, the second redundant time coefficient b is 1.5.

[0057] The travel time refers to the time required for a certain cross-section of the fiber to gradually travel from the starting end of the production line to the end end. The starting end usually starts from the change in the speed of the glue pump, and the end end is the position where the product is completed at the winding and forming station. The total length L of the production line is the distance from the starting end to the end end. Depending on the specific process route, the travel time of the fiber at all stations usually takes 5 to 10 minutes to complete. This means the length of time required for the fiber to go through all processes on the production line.

[0058] According to the travel time formula, the initial travel time and the target travel time can be calculated. In the process of converting the production state, if the time step of the change in the amount of glue supplied is less than the travel time required for the fiber to travel from the starting end to the end, the uniformity of the fiber will be negatively affected. Therefore, it is necessary to ensure that the time step of the change in the amount of glue supplied is at least equal to or greater than the average travel time in order to basically meet the production requirements. Considering the non-completely linear characteristics of the change in the elastic modulus during the stretching process of the elastic fiber, a necessary redundant time coefficient, namely the second redundant time coefficient b, is generally given. This coefficient is used to provide a certain degree of redundant protection for potential errors in the production process and ensure the stability of product quality. In general, the value of the second redundant time coefficient is about 1.5 times, but it can be adjusted according to the verification results in actual operation, the accuracy requirements of product quality deviations, and economic factors. A larger redundant time coefficient can improve the stability of the production process, but it will also reduce economic benefits. Therefore, the selection of the redundant time coefficient requires a balance between quality and efficiency. Finally, according to the travel time and the second redundant time coefficient b, the necessary time step T of the entire production process can be determined b .

[0059] The necessary time step represents the time required for the fiber to pass through the entire process, which is determined based on the dual attributes of the production line length and spinning speed of the entire process. When adjusting the spinning speed, the speeds of the drafting, winding and other links are adjusted synchronously to keep the fiber's draft ratio, tension and other parameters within a reasonable range. The glue supply of the glue pump, the parameters of the washing tank, the oiling tank, the drying tank and other processes should also be adjusted synchronously. The necessary time step is an important indicator to ensure the uniformity and consistency of the fiber throughout the production process. If the time step of the change in the glue supply is lower than the necessary time step, the fiber may not be able to fully adapt to the changes in the glue supply and roller speed, and the glue supply of the glue pump cannot be synchronized with the transmission speed of the fiber on the entire production line, resulting in fluctuations in the fiber's linear density, strength and other indicators, and a decrease in the fiber quality grade.

[0060] In the above technical solution, the formula of step (10) is:

[0061] T0=max(T a , T b )

[0062] Where: T0 is the theoretical time step, unit min;

[0063] T a The time step required for the change of the glue supply amount, in min;

[0064] T b is the necessary time step, in min.

[0065] T is the actual time step, in min.

[0066] In the above technical solution, the calculation formula of the speed change rate in step (12) is:

[0067]

[0068] Where: G is the velocity change rate, unit is m / s 2 ;

[0069] V1 is the initial spinning speed, in m / min;

[0070] V2 is the target spinning speed, in m / min;

[0071] T is the actual time step, in min.

[0072] In the above technical solution, the actual time step ≥ the theoretical time step.

[0073] The theoretical time step is the larger value of the time step required for the change of the glue supply amount and the necessary time step, so as to meet the requirements of both fiber performance and process operation efficiency.

[0074] The production method provided by the present invention is also applicable to the transition switching process with a reference platform. In this case, the present invention calculates the time step and speed change rate required for switching through the following steps:

[0075] According to the first production state and the glue supply and spinning speed of the reference platform, the theoretical time step for switching from the first production state to the reference platform is calculated. The actual time step is determined, and the speed change rate is calculated by the speed difference of the spinning speed and the actual time step. The spinning speed is gradually adjusted according to the speed change rate, so that the production process is converted from the first production state to the reference platform; after the reference platform is stably operated, the theoretical time step from the reference platform to the second production state is calculated again according to the glue supply and spinning speed of the second production state. The speed change rate is obtained by determining the actual time step, and the spinning speed is gradually adjusted according to the speed change rate, so that the production process smoothly transitions to the second production state. Similarly, when adjusting the spinning speed, the speed of the drawing, winding and other links, the glue supply of the glue pump, the parameters of multiple processes such as the washing tank, the oiling tank, and the drying tank are also adjusted synchronously. Optionally, the fiber production process is allowed to run stably on the reference platform for 30s-60s.

[0076] The method of the present invention is directly applied to the existing reference platform transition switching process, and there is no need to upgrade the existing engineering station logic operation software, which greatly reduces the implementation cost.

[0077] The reference platform has a safety attribute, that is, there is a certain maximum time limit, which is generally no more than 5 minutes, so that once the fiber breaks and the production line is entangled, the spinning speed can be adjusted to a lower state in a short time, thereby maintaining the safety of manual processing. At this time, the products produced need to be downgraded and isolated. When the production method provided by the present invention is adopted, the probability of broken wires or roller entanglement can be greatly reduced. When entanglement inevitably occurs, an emergency braking method can be adopted to deal with it. Although it will also cause certain economic losses, from the statistical analysis of the probability of occurrence, the production method provided by the present invention still has certain economic rationality.

[0078] After adopting the above technical scheme, the present invention has the following beneficial effects compared with the prior art.

[0079] The technical solution provided by the present invention calculates a reasonable time step when switching between different production states, thereby accurately controlling the production process, so that the fiber line density index meets the quality requirements and eliminates the problem of degradation of physical and chemical indicators.

[0080] The technical solution provided by the present invention can achieve seamless transition between different production states, so that hundreds or thousands of control point parameters can be adjusted in a coordinated manner, thereby improving the matching between fiber production conditions and fiber quality, and achieving the goal of stable production of high-quality products.

[0081] The technical solution provided by the present invention can meet the requirements of continuous and stable production of products, will not produce differences in product quality due to speed changes, reduce degradation losses, and meet the economic model of continuous production operation.

[0082] The technical solution provided by the present invention can be switched at any time, avoiding excessive deviation of fiber index properties and reducing the loss caused by active bobbin dropping, thereby greatly saving production costs, especially when applied to a production scale of 10,000 tons, the benefits are even more considerable.

[0083] The technical solution provided by the present invention can also greatly reduce the phenomenon of roller entanglement and wire breakage when switching production states, reduce waste wire loss, and do not require active bobbin drop, effectively reducing the operating difficulty and labor intensity of front-line employees, thereby improving the production efficiency of the carbon fiber precursor production process and making the production process safer. DETAILED DESCRIPTION

[0084] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in combination with the embodiments 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.

[0085] Example 1

[0086] Take a 25K product with a linear density of 3.0 g / m as an example:

[0087] (1) The production line length L is 300m;

[0088] (2) determining a first production state and a second production state;

[0089] The first production state: the spinning speed V1 is 85m / min, and the glue supply Q1 is 1300mL / min;

[0090] The second production state: the spinning speed V2 is 90 m / min, and the rubber supply amount Q2 is 1376 mL / min.

[0091] (3) Determine that the maximum allowable deviation m of the fiber linear density is 2.0%; the first redundant time coefficient a is 2.0; and the second redundant time coefficient b is 1.5;

[0092] (4) The time period during which the amount of glue supplied increases from the initial state to the target speed. Therefore, the theoretical time step is calculated by the formula:

[0093]

[0094] T0=max(T a , T b )=max(5.5,5.1)=5.5min

[0095] T=T0=5.5min

[0096]

[0097] (5) 2.5×10 -4 m / s 2 The spinning speed is gradually increased from 85 m / min to 95 m / min by the speed change rate, completing the switch from the first production state to the second production state. During the switching process, the deviation of the fiber linear density per unit time is (5.5% ÷ 5.5min =) 1.0%, which is less than the maximum allowable deviation of the linear density of 2.0%, meeting the requirements of both fiber performance and process operation.

[0098] (6) The production process is tracked in real time. The changes in the spinning speed and the probability of broken wires and roller entanglement in this embodiment are shown in Table 1.

[0099] Table 1:

[0100]

[0101] Example 2

[0102] Convert the first production state to the second production state

[0103] (1) The production line length L is 300m;

[0104] (2) Determine the first production state: the spinning speed V1 is 100 m / min, and the glue supply amount Q1 is 1529.4 mL / min;

[0105] (3) Determine the second production state: the spinning speed V2 is 120 m / min, and the glue supply amount Q2 is 1835 mL / min.

[0106] (4) Determine that the maximum allowable deviation m of the fiber linear density is 2.0%; the first redundant time coefficient a is 1.2; and the second redundant time coefficient b is 1.5;

[0107] (5) The calculation process is the same as in Example 1, and the theoretical time step for converting from the first production state to the second production state is 10.02 min.

[0108] The calculation process is as follows:

[0109]

[0110] T0=max(T a , T b )=max(10.02,4.125)=10.02min

[0111] (6) Determine the actual time step T to be 10.1 min.

[0112] (7) The production process is tracked in real time. The changes in the spinning speed and the probability of broken wires and roller entanglement in this embodiment are shown in Table 2.

[0113] Table 2:

[0114]

[0115] Example 3

[0116] In the process designed with a reference platform, the speed of the reference platform is a safe speed, generally designed to be 60 m / min. In the production process with a reference platform, the production method provided by the present invention is used to switch the first production state to the second production state after the transition of the reference platform, wherein the first production state and the second production state and the production line length L are exactly the same as those in Example 2.

[0117] (1) Benchmark platform: spinning speed V is 60 m / min, rubber supply Q is 917.4 mL / min;

[0118] (2) The maximum allowable deviation m of the fiber linear density is 2.0%; the first redundant time coefficient a is 1.2; the second redundant time coefficient b is 1.5;

[0119] (3) The calculation process and principle are the same as those in Example 1, and the theoretical time step for converting from the first production state to the reference platform is 24 minutes; the theoretical time step for converting from the reference platform to the second production state is 30 minutes;

[0120] (4) Determine that the actual time step from the first production state to the reference platform is 24 minutes, and the actual time step from the reference platform to the second production state is 30 minutes;

[0121] (5) The production process is tracked in real time. The changes in the spinning speed and the probability of broken wires and roller entanglement in this embodiment are shown in Table 3.

[0122] Table 3:

[0123]

[0124] Therefore, when the process logic module design of an enterprise adopts this benchmark platform design solution, the present invention can also be used to achieve speed conversion and achieve the goal of speed increase and output balance. Although the time step required for Example 3 is longer than that of Example 2, it still has certain economic rationality and feasibility compared to the traditional method of cutting the tow and rewinding it.

[0125] Comparative Example 1

[0126] Under traditional production conditions, the response time of the electrical equipment is the actual time step, that is, when the inherent response time of the motor is 5 seconds, the spinning speed is directly increased from 100m / min to 120m / min, and the production process is tracked in real time. The changes in spinning speed and the probability of broken wire and roller when the production state is converted using the traditional switching method are shown in Table 4.

[0127] Table 4:

[0128]

[0129] By comparing Example 2 with Comparative Example 1, it is found that when the first production state and the second production state and the production line length L are exactly the same, the change rate of the spinning speed in Example 2 is 5.5×10 -4 m / s 2 The change rate of spinning speed in Comparative Example 1 is about 0.067 m / s 2 , which indicates that the rate of change of the spinning speed when the production state is switched by the traditional switching method is much higher than the rate of change of the spinning speed when the production state is switched by the carbon fiber precursor production method provided by the present invention.

[0130] Compared with Comparative Example 1, Examples 1-3 all significantly reduce the probability of broken wires and roller entanglement during the production process, indicating that the carbon fiber precursor production method provided by the present invention makes the change rate of the spinning speed very small, and the impact on the product is negligible, which greatly improves the stability of the product, enhances the ability of flexible production, reduces active bobbin loss and waste wire loss, improves production efficiency, and saves production costs.

[0131] Comparative Example 2

[0132] At present, the production of raw silk generally adopts the method of product winding storage or storage and transportation. The length of each winding is generally in the range of tens of thousands of meters, and the conventional range is generally 36,000-150,000 meters. Generally, each specification of winding time has a fixed time to form a full barrel product. For example, one shaft product is produced in 25 hours. However, in actual production, due to the spinnability breakage factor, the barrel drop time of the entire line is often randomly staggered and distributed, and it is difficult to achieve a unified centralized time. The traditional practice is often to drop all the silk once, and there are about 50% of small yarn products of unequal length, or downgraded products, and re-spinning after the new formula transition is complete. This method will produce a certain amount of economic losses each time the spinning speed is adjusted, generally about 80,000 to 120,000 yuan of downgraded product losses each time. The output of each batch of products when the raw silk line is in stable production and the output of each batch of products when the traditional method of barrel drop is used to switch the production state are shown in Table 5.

[0133] Table 5:

[0134]

[0135] Among them, the quality of the unequal length small yarn products or downgraded products produced by the traditional method of doffing is 50% of the quality of the full bobbin original yarn during stable production;

[0136] Full barrel nominal weight = linear density × full barrel nominal length;

[0137] The nominal weight of the whole batch of the whole line = the nominal weight of the full barrel × the number of spindles;

[0138] The weight of the non-full drum by the traditional method = the nominal weight of the whole batch × 50%;

[0139] Loss of partial and full barrels = price difference between partial and full barrels × (nominal weight of the entire batch of the entire line - weight of partial barrels using traditional methods);

[0140] As shown in Table 5, when the traditional method is used to switch the production state, the speed is adjusted once a quarter and four times a year due to the adjustment of product variety and output or customer requirements for spinning speed, which will cause a degradation loss of about 4 million yuan throughout the year. However, when the production state is switched by the carbon fiber precursor production method provided by the present invention, it can be switched at any time without the need for doffing, thus avoiding degradation losses, greatly saving production costs and improving production efficiency.

[0141] Comparative Example 3

[0142] When the traditional method is used to convert the production status, the weight loss of waste silk generated by the centralized replacement of the core of each batch of raw silk thread is shown in Table 6.

[0143] Hourly output = linear density × spinning speed × 60 × number of spindles;

[0144] The weight of waste silk generated by the whole line = hourly output × the time of changing the core of the whole line;

[0145] Loss of incomplete bobbin and full bobbin = price difference between full bobbin and waste silk × weight of waste silk generated by the whole line;

[0146] Table 6:

[0147]

[0148] Therefore, when switching the production status by the traditional method, a waste silk loss of about 20,000 to 30,000 yuan will be generated each time. However, when switching the production status by the carbon fiber precursor production method provided by the present invention, it can be achieved at any time without the need for bobbin dropping, thus avoiding the loss of waste silk, saving production costs, and improving production efficiency.

[0149] Experimental Example 1

[0150] (1) 10 groups of fibers were selected from a production line running at a steady spinning speed of 100 m / min. Ten samples were taken from each group of fibers at equal time intervals for linear density testing. The linear density of the fibers at this time was obtained as shown in Table 7.

[0151] Table 7:

[0152]

[0153] Among them, the calculation formula of the maximum deviation of line density is:

[0154]

[0155] It can be seen from Table 7 that when the spinning speed is 100 m / min and the fiber linear density deviation is not more than 1.72% during stable operation, which is at a relatively low fineness deviation rate level.

[0156] (2) Using the traditional switching method: When the time step is set from the safety condition requirement to the maximum value of 5 minutes, the spinning speed is directly increased from 100 m / min to 120 m / min to complete the switching of the production state. 10 groups of fibers are selected on this production line. During the process of switching the production state, each group of fibers is sampled 10 times at equal time intervals for linear density detection. The deviation of the obtained fiber linear density is shown in Table 8.

[0157] Table 8:

[0158]

[0159] It can be seen from Table 8 that when the traditional switching method is adopted and the spinning speed is directly increased from 100 m / min to 120 m / min while taking into account the safety requirements, the fiber linear density deviation is large when the production state is switched. In this example, the linear density deviation rate is between 3.24% and 5.87%, and it is uneven, which cannot meet the customer's linear density stability index requirements.

[0160] (3) The carbon fiber precursor production method provided by the present invention was adopted to increase the spinning speed from 100 m / min to 120 m / min. Ten groups of fibers were selected on this production line. During the process of switching the production state, each group of fibers was sampled 10 times at equal time intervals for linear density detection. The obtained fiber linear density CV values ​​are shown in Table 9.

[0161] Table 9:

[0162]

[0163] Table 9 (continued):

[0164]

[0165] It can be seen from Table 9 that by adopting the carbon fiber precursor production method provided by the present invention, the spinning speed is increased from 100 m / min to 120 m / min, and the fiber line density deviation is small. In this example, the line density deviation rate is between 1.02% and 1.96%. Compared with the traditional switching method, the fiber line density deviation rate is obviously controlled and stabilized, meeting the customer's requirement that the maximum allowable deviation of the fiber line density is ≤2.0%.

[0166] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with the present invention can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A method for producing carbon fiber precursor, characterized in that: The steps include: (1) determining a first production state and a second production state; (2) taking the amount of glue supplied in the first production state as the initial amount of glue supplied and the spinning speed as the initial spinning speed; (3) taking the glue supply amount in the second production state as the target glue supply amount and the spinning speed as the target spinning speed; (4) Calculating the change rate of the glue supply amount by using the initial glue supply amount and the target glue supply amount; (5) Determine the maximum allowable deviation of line density; (6) Calculate the time step required for the change of the glue supply amount by the change rate of the glue supply amount and the maximum allowable deviation of the linear density; (7) Determine the length of the production line; (8) calculating the initial stroke time and the target stroke time by the production line length, the initial spinning speed, and the target spinning speed; (9) Calculate the average of the initial travel time and the target travel time as the necessary time step; (10) Compare the necessary time step and the time step required for the change in the amount of glue supplied, and select the larger value as the theoretical time step; (11) Determine the actual time step based on the theoretical time step; (12) calculating the speed change rate by the spinning speed and the actual time step; (13) The spinning speed is changed according to the calculated speed change rate, and the initial production state is converted to the target production state within the actual time step.

2. The method for producing carbon fiber precursor according to claim 1, characterized in that: The calculation formula of step (4) is: Where: Q 增 is the rate of change of glue supply; Q1 is the initial glue supply, unit is mL / min; Q2 is the target glue supply amount, unit is mL / min.

3. The method for producing carbon fiber precursor according to claim 1, characterized in that: The calculation formula of step (6) is: Where: T a The time step required for the change of the glue supply amount, in min; Q 增 is the rate of change of glue supply; m is the maximum allowable deviation of line density; a is the first redundant time coefficient.

4. A method for producing carbon fiber precursor according to claim 3, characterized in that: The value range of the first redundant time coefficient a is 1.1-2.

0.

5. The method for producing carbon fiber precursor according to claim 1, characterized in that: The calculation formula of step (8) is: Where: t1 is the initial travel time, unit min; t2 is the target travel time, in min; L is the length of the production line, in m; V1 is the initial spinning speed, in m / min; V2 is the target spinning speed, in m / min.

6. The method for producing carbon fiber precursor according to claim 1, characterized in that: The calculation formula of step (9) is: Where: T b is the necessary time step, in min; t1 is the initial travel time, in min; t2 is the target travel time, in min; b is the second redundant time coefficient.

7. A method for producing carbon fiber precursor according to claim 6, characterized in that: The value range of the second redundant time coefficient b is 1.3-2.5; Preferably, the second redundant time coefficient b is 1.

5.

8. The method for producing carbon fiber precursor according to claim 1, characterized in that: The formula for step (10) is: T0=max(T a ,T b ) Where: T0 is the theoretical time step, unit min; T a The time step required for the change of the glue supply amount, in min; T b is the necessary time step, in min.

9. The method for producing carbon fiber precursor according to claim 1, characterized in that: The calculation formula of the speed change rate in step (12) is: Where: G is the velocity change rate, unit is m / s 2 ; V1 is the initial spinning speed, in m / min; V2 is the target spinning speed, in m / min; T is the actual time step, in min.

10. The method for producing carbon fiber precursor according to claim 1, characterized in that: The actual time step ≥ the theoretical time step.

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