CN116334777B - Water bath drafting device and PAN-based carbon fiber precursor production system - Google Patents
Water bath drafting device and PAN-based carbon fiber precursor production system Download PDFInfo
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- CN116334777B CN116334777B CN202310604696.8A CN202310604696A CN116334777B CN 116334777 B CN116334777 B CN 116334777B CN 202310604696 A CN202310604696 A CN 202310604696A CN 116334777 B CN116334777 B CN 116334777B
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Classifications
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D5/00—Formation of filaments, threads, or the like
- D01D5/12—Stretch-spinning methods
- D01D5/14—Stretch-spinning methods with flowing liquid or gaseous stretching media, e.g. solution-blowing
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
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- B01D19/0021—Degasification of liquids by bringing the liquid in a thin layer
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D19/00—Degasification of liquids
- B01D19/0036—Flash degasification
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/10—Vacuum distillation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/14—Fractional distillation or use of a fractionation or rectification column
- B01D3/143—Fractional distillation or use of a fractionation or rectification column by two or more of a fractionation, separation or rectification step
- B01D3/146—Multiple effect distillation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/42—Regulation; Control
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D5/00—Condensation of vapours; Recovering volatile solvents by condensation
- B01D5/0003—Condensation of vapours; Recovering volatile solvents by condensation by using heat-exchange surfaces for indirect contact between gases or vapours and the cooling medium
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D5/00—Condensation of vapours; Recovering volatile solvents by condensation
- B01D5/0057—Condensation of vapours; Recovering volatile solvents by condensation in combination with other processes
- B01D5/006—Condensation of vapours; Recovering volatile solvents by condensation in combination with other processes with evaporation or distillation
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D1/00—Treatment of filament-forming or like material
- D01D1/10—Filtering or de-aerating the spinning solution or melt
- D01D1/103—De-aerating
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D5/00—Formation of filaments, threads, or the like
- D01D5/06—Wet spinning methods
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D5/00—Formation of filaments, threads, or the like
- D01D5/12—Stretch-spinning methods
- D01D5/16—Stretch-spinning methods using rollers, or like mechanical devices, e.g. snubbing pins
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
- Y02P70/62—Manufacturing or production processes characterised by the final manufactured product related technologies for production or treatment of textile or flexible materials or products thereof, including footwear
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Mechanical Engineering (AREA)
- Textile Engineering (AREA)
- Inorganic Fibers (AREA)
Abstract
The invention discloses a water bath drafting device and a production system of PAN-based carbon fiber precursors, wherein the water bath drafting device comprises: the water bath drawing tank is used for containing water bath; the water washing rollers are arranged in the water bath drafting groove, are partially immersed below the liquid level of the water bath, and are arranged at intervals along the movement direction of the nascent fibers; the drafting roller assembly is arranged above the water bath drafting tank and corresponds to a spacing area between two adjacent washing rollers; the solidified nascent fiber alternately bypasses the washing roller and the drawing roller assembly and is subjected to water bath drawing; wherein the nascent fibers are immersed below the liquid surface while bypassing the lower part of the water washing roll. In the invention, the nascent fiber is immersed in the water bath only in a short time remained at the lower part of the washing roller, so that the duration of resistance caused by countercurrent washing on the fiber is shortened, the damage of water flow to the fiber is further reduced, and the spinning speed is improved on the premise of ensuring the quality of the precursor fiber.
Description
Technical Field
The invention belongs to the technical field of carbon fiber manufacturing and application, and particularly relates to a water bath drafting device and a PAN-based carbon fiber precursor production system.
Background
Currently, industrial production of carbon fibers can be classified into three major categories, namely Polyacrylonitrile (PAN) -based carbon fibers, pitch-based carbon fibers and viscose-based carbon fibers, according to the raw material route. The production of carbon fiber is to continuously remove impurity elements (mainly H, N, O, etc.), reduce defects, purify and reform carbon chains.
The high mechanical carbon fiber prepared from viscose fiber must be graphitized by high temperature stretching, the carbonization yield is low (only 20-30%), the technical difficulty is high, the equipment is complex, the cost is high, and the product is mainly ablation-resistant material and heat insulation material.
The carbon fiber is prepared from asphalt, the raw material sources are rich, but the preparation and treatment processes of the raw materials are complex, the product performance is poor, and the large-scale development is not achieved. The asphalt precursor enters the small holes of the spinneret plate through a metering pump under high pressure, is cooled by air, and is finally coiled into fibers. In this process, the fracture stress is as high as 20%, and the fracture is easy. The carbonization yield of the pitch-based carbon fiber is 80% -90%, which is higher than that of the polyacrylonitrile-based carbon fiber (50% -60%), the raw material pitch is far cheaper than acrylonitrile, and the differences theoretically lead the cost of the pitch-based carbon fiber to be lower than that of the polyacrylonitrile-based carbon fiber.
However, to produce high performance carbon fibers, impurities in the raw pitch must be completely removed, and the pitch is converted into mesophase pitch, which greatly increases the cost of the high performance pitch-based carbon fibers. In practice, the cost of high performance pitch-based carbon fibers is rather higher than that of polyacrylonitrile-based carbon fibers. So that it is currently limited to use in very few fields, such as aerospace sector, where performance is only sought and costs are not to be considered. Compared with polyacrylonitrile-based carbon fiber, pitch-based carbon fiber has relatively retarded development, and its application is not as wide as PAN-based carbon fiber.
In the prior art, PAN-based carbon fiber is mainly adopted, DMSO is adopted as a solvent in a common production process, a one-step dry-jet wet spinning is adopted to prepare a precursor, and the productivity, the yield and the consumption of the high-performance carbon fiber produced by adopting the process are at the top in the whole world. The high-performance carbon fiber, especially the carbon fiber with high strength, has excellent mechanical properties, can be used for manufacturing structures such as blades in wind turbines, and has good application prospects.
To achieve high strength carbon fiber production, it is desirable to improve the quality of the PAN-based carbon fiber precursor. Meanwhile, in order to meet a great deal of demands on carbon fibers in the market, production efficiency needs to be improved as much as possible on the premise of ensuring the quality of PAN-based carbon fiber precursors. In the prior art, the degree of orientation of the fiber can be improved by stretching the fiber during the production of the precursor, so that the properties of the fiber, such as breaking strength, are improved. However, when the draft multiple reaches a certain level, the spinning speed of the existing production process is limited, and the yarn breakage is easily caused when the higher spinning speed is adopted, so that the production efficiency cannot be further improved.
In view of this, the present invention has been made.
Disclosure of Invention
The invention aims to solve the technical problems of overcoming the defects of the prior art, and provides a water bath drafting device and a PAN-based carbon fiber precursor production system, which can shorten the continuous residence time of fibers in a water bath drafting process without influencing the water washing effect, can ensure the precursor quality at a high spinning speed and are beneficial to improving the production efficiency.
In order to solve the technical problems, the invention adopts the basic conception of the technical scheme that:
a water bath drawing device for PAN-based carbon fiber precursor production, comprising:
the water bath drawing tank is used for containing water bath;
the water washing rollers are arranged in the water bath drafting groove, are partially immersed below the liquid level of the water bath, and are arranged at intervals along the movement direction of the nascent fibers;
the drafting roller assembly is arranged above the water bath drafting tank and corresponds to a spacing area between two adjacent washing rollers;
the nascent fiber alternately bypasses the washing roller and the drawing roller assembly to be drawn in a water bath; wherein the nascent fibers are immersed below the liquid surface while bypassing the lower part of the water washing roll.
In the scheme, the water bath drafting device is alternately provided with the water washing roller and the drafting roller assembly along the movement direction of the nascent fiber, so that the nascent fiber alternately passes by and bypasses the water washing roller and the drafting roller assembly to carry out water bath drafting. The primary fiber is immersed into the water bath only in a short time passing through the lower part of the water washing roller, so that the continuous soaking time of the fiber in the water bath can be greatly shortened, and the time for continuously bearing water resistance of the fiber in the water bath drafting process is reduced.
Through improving the structure of water bath drafting arrangement, can realize that the time that nascent fiber soaked in water shortens, and the length of continuous entering in the water bath also shortens, and the fibre can attach a certain amount of water (about 2 ~ 4 times of fibre self weight) when leaving the water bath liquid level simultaneously, and then also has the washing effect in the a period of leaving the water bath. Therefore, the excessive damage to the fibers caused by continuous countercurrent washing is avoided, the spinning speed can be improved under the condition of ensuring the quality of the precursor, and the improvement of the production efficiency is facilitated.
Further, the draft roller assembly is connected with a driving device and is used for driving the draft roller assembly to rotate so as to drive the nascent fiber to move; the washing roller is driven by the nascent fiber to rotate;
the diameter of the washing roller is 200-300 mm, and the height of the washing roller immersed in the water bath is 1/4-1/2 of the diameter of the washing roller, preferably 1/3 of the diameter of the washing roller.
It is found by test that when the size range is adopted by the water washing roller and the immersing height of the water washing roller in the water bath is matched, the continuous length of the primary fiber immersed in the water bath can be controlled to be 200-400 mm, the duration of continuous immersing in the water bath is controlled to be 0.1-0.35 s, and the ratio of the time of immersing the primary fiber in the water bath to the time passing in the air is 1 in the whole water bath drafting process: 4 to 8. At this time, the water bath drafting process can ensure the effective washing effect of the nascent fiber and ensure the fiber not to be damaged to the greatest extent.
Further, the water bath drawing tank comprises a primary water bath drawing tank, a secondary water bath drawing tank and a tertiary water bath drawing tank, and the drawing roller assembly comprises a low-power drawing roller assembly and a high-power drawing roller assembly;
the low-power drafting roller assembly is arranged corresponding to the first water bath drafting groove and the third water bath drafting groove, and the high-power drafting roller assembly is arranged corresponding to the second water bath drafting groove.
Further, the low-power drafting roller assembly is a single drafting roller, and the nascent fiber bypasses above the drafting roller;
the high-power drafting roller assembly comprises two first drafting rollers and a second drafting roller, the two first drafting rollers are arranged at the same height at intervals along the horizontal direction, and the second drafting roller is arranged below the interval between the two first drafting rollers; the primary fiber passes alternately over the first and second draft rollers, wherein the primary fiber is bypassed by the top of the first draft roller and the bottom of the second draft roller.
In the above scheme, when the nascent fiber passes through the water bath drafting device, low-power drafting can be performed first, then high-power drafting is performed, and finally low-power drafting is performed. By utilizing the characteristic of good ductility of the middle section fiber in the water bath drawing process, higher total drawing multiple can be realized. The high-power drafting roller assembly adopts a triplet drafting roller, so that drafting tension can be enhanced.
A production system of PAN-based carbon fiber precursor comprises a solidification device and the water bath drafting device;
the solidifying device is used for solidifying and forming the yarn formed by spinning the spinning solution to obtain nascent fibers; and (3) the nascent fiber obtained by the coagulation device enters a water bath drafting device for water bath drafting.
Further, the coagulation device contains a coagulation bath liquid with the temperature of 0-20 ℃, and the temperature of the coagulation bath liquid is preferably 0-10 ℃; the production system further comprises a recovery unit for recovering coagulant from the coagulation bath;
the recovery unit includes:
the coagulating bath liquid enters the rectifying tower, the purified solution is discharged from the bottom of the tower, and the steam is discharged from the top of the tower;
the condenser is connected with the top of the rectifying tower, and steam discharged from the top of the rectifying tower enters the condenser for condensation;
the coagulating bath liquid enters between the rectifying towers, passes through the condenser first and exchanges heat with the steam discharged from the tower top to realize the condensation of the steam.
In the scheme, the condenser is respectively used for exchanging heat with the coagulating bath liquid with lower temperature and high-temperature steam discharged from the top of the rectifying tower. On the one hand, the low temperature of the coagulation bath is used for condensing the steam, and no additional cold water is needed to be fed. On the other hand, when the coagulating bath passes through the condenser, the heat can be obtained by the steam to realize preheating, which is favorable for obtaining higher purification efficiency in the rectifying tower.
Further, the rectifying tower comprises a primary rectifying tower and a secondary rectifying tower, and the purified solution discharged from the primary rectifying tower enters the secondary rectifying tower for further purification;
the condenser comprises a first condenser, a second condenser and a third condenser, wherein the first condenser is connected with the top of the primary rectifying tower;
the coagulating bath liquid inlet of the recovery unit is respectively connected with the first condenser and the second condenser through two branches, one part of coagulating bath liquid passes through the first condenser, and the other part passes through the second condenser; the coagulating bath liquid flowing out of the first condenser and the second condenser are collected and then enter the first-stage rectifying tower together;
preferably, the first-stage rectifying tower comprises a first-effect rectifying tower, a second-effect rectifying tower and a third-effect rectifying tower which are arranged in parallel, the coagulating bath liquid is shunted into the first-effect rectifying tower, the second-effect rectifying tower and the third-effect rectifying tower, and purified solutions discharged from the bottoms of the first-effect rectifying tower, the second-effect rectifying tower and the third-effect rectifying tower are collected into a middle storage tank and then conveyed to the second-stage rectifying tower for purification again by the middle storage tank.
In the scheme, the low-temperature coagulating bath is split, so that the coagulating bath flows through the two condensers in the recovery unit simultaneously, the coagulating bath entering the first condenser and the second condenser is ensured to be in a low-temperature state without preheating, higher heat exchange efficiency can be realized, and the condensing efficiency of steam discharged from the top of the tower is further improved.
Further, the spinning device also comprises a stock solution preparation unit, wherein the stock solution preparation unit comprises a single-removing and deaerating tower, and is used for performing single-removing and deaerating treatment on the crude stock solution obtained through the polymerization reaction to obtain spinning stock solution for spinning;
a feed inlet is arranged at the top of the single-removal deaeration tower, and a packing layer is arranged below the feed inlet and used for dispersing the crude stock solution; the liquid dropping assembly is arranged in the single-removing and deaerating tower, the upper surface of the liquid dropping assembly is a dispersing surface, the dispersing surface gradually decreases from the center to the periphery, and the highest position of the dispersing surface is positioned below the packing layer;
the liquid dropping component is also provided with a guide surface, and the guide surface extends downwards obliquely from the periphery of the dispersing surface and gradually approaches to the middle part; the included angle between the dispersing surface and the horizontal direction is smaller than the included angle between the guide surface and the horizontal direction.
Further, an included angle between the dispersing surface and the horizontal direction is smaller than 45 degrees, and an included angle between the guiding-out surface and the horizontal direction is larger than 45 degrees and smaller than 90 degrees;
more preferably, the angle between the dispersion surface and the guide-out surface is greater than 90 °;
more preferably, the included angle between the dispersing surface and the horizontal direction is 40-45 degrees, and the included angle between the guiding-out surface and the horizontal direction is 60-65 degrees.
In the scheme, the crude stock solution is dispersed by the filler layer and falls onto the dispersion surface of the liquid dropping assembly, a liquid layer with a certain thickness is formed along the dispersion surface in a flowing mode, a certain vacuum degree is formed in the single-removing and defoaming tower, and the single-removing and defoaming effects can be achieved by dispersing the crude stock solution into a thin liquid layer. The dispersed crude stock solution flows onto the guide surface from the periphery of the dispersion surface, the guide surface is inclined relative to the vertical direction, and the stock solution can be controlled to slowly flow and fall along the guide surface without rapidly dripping from the liquid dropping component, so that the efficiency of single removal and defoaming is further improved in the process of flowing along the guide surface.
According to the invention, the flow speed of the crude stock solution and the thickness of the liquid layer can be controlled through the included angle between the dispersing surface and the horizontal direction, so that higher single removal and defoaming efficiency can be realized. The inclination of the dispersing surface and the guide surface are matched, so that the stock solution can flow from the periphery of the dispersing surface to the guide surface without direct dripping from the periphery of the dispersing surface, and the single removal and defoaming efficiency is further ensured. The process of removing the single unit and defoaming the crude stock solution can be completed in one step in the single unit and defoaming tower, and the single unit removing and defoaming effects are good, thereby being beneficial to shortening the production period and improving the production efficiency.
Further, the bottom of the single-removal and deaeration tower is connected with a delivery pump, and is used for extracting the raw liquid after single removal and deaeration from the bottom of the tower;
the single-removal deaeration tower is also provided with a circulating inlet which is communicated with the liquid outlet end of the conveying pump; the circulating inlet is arranged on the side peripheral wall of the single-removal deaeration tower, and the setting height of the circulating inlet is lower than the highest position of the dispersing surface and higher than the peripheral height of the dispersing surface; the stock solution after the removal of the monomer and the defoaming is pumped from the bottom of the tower and is sprayed onto the dispersion surface through a circulation inlet by using the conveying pressure of a conveying pump, and the removal of the monomer and the defoaming are performed again.
In the scheme, the stock solution extracted from the bottom of the tower can be conveyed by a conveying pump and enters the single-removing and deaerating tower again through the circulating inlet, so that the stock solution with poor single-removing and deaerating effects is treated again, and the quality of the finally obtained spinning stock solution is ensured. The circulating inlet is arranged on the side peripheral wall of the single-removing and deaerating tower, and the raw liquid is sprayed to the dispersing surface to be dispersed by utilizing the conveying pressure of the conveying pump, so that the single-removing and deaerating efficiency is ensured.
By adopting the technical scheme, compared with the prior art, the invention has the following beneficial effects.
1. According to the invention, through arrangement of the water washing rollers and the arrangement of the primary fiber bypass paths in the water bath drafting device, the water washing effect is ensured, and meanwhile, the time for immersing the primary fiber in the water bath is shortened, so that the duration of resistance caused by countercurrent water washing on the fiber is shortened, the damage of water flow to the fiber is reduced, the spinning speed is improved, and the production efficiency is improved while the quality of the precursor fiber is ensured.
2. In the invention, the recovery unit can utilize the low-temperature characteristic of the coagulating bath to condense the steam discharged from the top of the rectifying tower, thereby saving the trouble of additionally feeding cold water, and the coagulating bath can realize the preheating effect when exchanging heat with the steam, so as to improve the purification efficiency in the rectifying tower.
3. According to the invention, the crude stock solution obtained by polymerization is subjected to single-removal and defoaming treatment in the single-removal and defoaming tower, so that the process flow is saved, and the thickness and the flow speed of a liquid layer after the crude stock solution is dispersed can be controlled by structural design of a liquid-reduction component in the single-removal and defoaming tower, thereby being beneficial to realizing higher single-removal and defoaming efficiency.
4. The PAN-based carbon fiber precursor produced by the water bath drafting device and the production system has the advantages of light specific gravity and low density, has high strength and high modulus, is thin and soft, can be used for preparing high-performance carbon fiber, has excellent mechanical property and wide application, and can be used for preparing high-strength carbon fiber, and particularly can be used for preparing blades in wind engines or other structures requiring high strength.
The following describes the embodiments of the present invention in further detail with reference to the accompanying drawings.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. It is evident that the drawings in the following description are only examples, from which other drawings can be obtained by a person skilled in the art without the inventive effort. In the drawings:
FIG. 1 is a schematic flow chart of the preparation of the spinning dope in the present invention;
FIG. 2 is a schematic diagram of the structure of the de-singulation and de-bubbling tower according to the present invention;
FIG. 3 is a process flow diagram of a spinning unit in accordance with the present invention;
FIG. 4 is a schematic view of the construction of the solidifying means of the present invention;
FIG. 5 is a schematic view of the structure of the water bath drafting device in the invention;
FIG. 6 is a schematic diagram of a recovery unit in the present invention;
FIG. 7 is a schematic view of a water bath draft apparatus used in comparative example 4 of the present invention.
In the figure: 1. a washing tank; 2. a washing roller; 3. a draft roller;
101. a feed inlet; 102. a circulation inlet; 103. a vacuum suction port; 104. a bottom outlet; 110. a filler layer; 120. a liquid dropping component; 121. a dispersion surface; 122. a lead-out surface; 130. a transfer pump;
210. Primary coagulation bath; 211. a first-stage draft roller; 212. a primary circulation pump; 213. a primary coagulation bath storage tank; 220. a secondary coagulation bath; 221. a second-stage draft roller; 222. a secondary circulation pump; 223. a secondary coagulation bath storage tank; 230. a spinneret;
310. a primary water bath drafting tank; 320. a second-stage water bath drafting tank; 330. a three-stage water bath drafting tank; 340. a washing roller; 350. a low power draft roller assembly; 351. a draft roller; 360. a high draft roller assembly; 361. a first draft roller; 362. a second draft roller; 370. a water washing circulation pump; 380. a heat exchanger;
401. DMSO feed tank; 402. DMSO intermediate storage tank; 403. a wastewater recovery tank; 410. a rectifying tower; 411. a first-effect rectifying tower; 412. a double-effect rectifying tower; 413. a three-effect rectifying tower; 414. a second-stage rectifying tower; 415. a first-stage rectifying tower; 421. a one-effect reboiler; 422. a double-effect reboiler; 423. a triple effect reboiler; 424. a secondary rectifying tower reboiler; 431. a first gas-liquid separator; 432. a second gas-liquid separator; 433. a third gas-liquid separator; 440. a condenser; 441. a first condenser; 442. a second condenser; 450. and a vacuum pump.
It should be noted that these drawings and the written description are not intended to limit the scope of the inventive concept in any way, but to illustrate the inventive concept to those skilled in the art by referring to the specific embodiments.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions in the embodiments will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention, and the following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.
The invention provides a water bath drafting device for producing high-performance PAN-based carbon fiber precursor and a production system comprising the water bath drafting device.
The production system is used for realizing the preparation process of obtaining spinning stock solution from production raw materials and then preparing PAN-based carbon fiber precursor from the spinning stock solution. Specifically, the preparation process comprises the following steps: the azodiisobutyronitrile is used as an initiator to initiate the polymerization reaction of acrylonitrile, comonomer methyl acrylate and itaconic acid in dimethyl sulfoxide solution, so that the spinning dope can be prepared in one step without preparing a polymer and then dissolving the polymer, and the obtained spinning dope can be further prepared into PAN-based carbon fiber precursor by adopting a dry-jet wet spinning method. The water bath drafting device is used for the water bath drafting process in the PAN-based carbon fiber precursor prepared from the spinning solution.
In the invention, the production system at least comprises a stock solution preparation unit and a spinning unit. Wherein, the production raw materials are mixed in the stock solution preparation unit to initiate polymerization reaction, and finally the spinning stock solution is prepared. And conveying the obtained spinning solution to a spinning unit, and preparing the PAN-based carbon fiber precursor through a dry-jet wet spinning process. The spinning unit comprises the water bath drafting device.
In the dope preparation unit of the invention, the preparation of the spinning dope is performed according to the following steps:
(1) Mixing acrylonitrile, methyl acrylate, itaconic acid and dimethyl sulfoxide and heating to 60-70 ℃;
(2) Adding azodiisobutyronitrile, and stirring at 60-70 ℃ for 10-20 hours;
(3) Heating to 72-77 ℃, and continuing stirring for 10-20 hours to obtain crude stock solution;
(4) And (3) performing single removal and defoaming treatment and filtering treatment on the crude stock solution to obtain the spinning stock solution.
Wherein the mixing and polymerization reaction processes of the steps (1) to (3) are batch processes, and the removal and defoaming and filtering of the step (4) are continuous processes. The batch polymerization mode is convenient for the actual production process, and the technological parameters can be flexibly adjusted. The process parameters of the single-removal defoaming treatment and the filtering treatment are not required to be adjusted, and the subsequent treatment process is continuously carried out after the crude stock solution is prepared, so that higher production efficiency is realized.
As shown in FIG. 1, in the present invention, the stock solution preparing unit comprises a stainless steel reactor for mixing and polymerizing the raw materials for the production in the steps (1) to (3). The reactor is provided with a stirrer and a cooling jacket, the stirrer is used for stirring the production raw materials, the cooling jacket can be filled with circulating cold water, and the low-temperature circulating cold water is used for absorbing reaction heat to keep the reaction temperature inside the reactor stable. The stock solution preparation unit also comprises a crude stock solution storage tank, and the crude stock solution obtained by the reaction in the reactor is discharged into the crude stock solution storage tank for storage.
In detail, the process for preparing the crude stock solution comprises the following steps:
adding 116-120 parts by weight of acrylonitrile, 0.3-1 part by weight of methyl acrylate, 1.4-1.8 parts by weight of itaconic acid and 375-400 parts by weight of DMSO into a reactor to obtain a mixed solution;
heating the obtained mixed solution to 60-70 ℃ and adding 0.2-0.5 part by weight of AIBN;
removing the heat of reaction by circulating cold water in the cooling jacket, and stirring the solution at 60-70 ℃ for 10-20 hours to perform a chain growth reaction;
and then the reaction temperature is increased to 72-77 ℃ for polymerization, and stirring is continued for 10-20 hours, so that crude stock solution is obtained, and the crude stock solution is discharged into a crude stock solution storage tank which is kept at 35 ℃ for storage.
Under the reaction conditions, the conversion rate of the acrylonitrile in the obtained crude stock solution is 90-95%.
In the invention, the preparation process of the spinning solution mainly generates polymerization reaction, and comprises ternary polymerization of acrylonitrile, methyl acrylate and itaconic acid. The polymerization of acrylonitrile is a free radical addition polymerization, and the polyaddition reaction of small molecular monomers is an exothermic process, so that the reaction temperature is strictly controlled during the reaction. In the invention, each addition polymerization needs to open one pi bond of olefin, two sigma single bonds are generated at the same time, energy is required to be absorbed when the pi bond is opened, energy can be released when the two sigma single bonds are generated, and the heat can be released by about 73.3kJ/mol in the whole reaction process.
Specifically, in the invention, the itaconic acid in the form of solid powder can be dissolved more sufficiently and uniformly by heating and mixing in the step (1), so that the itaconic acid is sufficiently mixed with other reaction raw materials. In the step (2), azobisisobutyronitrile (AIBN) is added as an initiator to initiate polymerization. The polymerization reaction can be divided into two stages with different temperatures, wherein in the step (2), each reaction monomer is polymerized to form chains at 60-70 ℃. In the step (3), the temperature is further raised after the chain forming reaction, the chain growth reaction is carried out, and finally the polymer with the molecular weight of 25-35 ten thousand g/mol is obtained.
In detail, in the step (2), since exothermic reaction occurs, heat exchange is performed by circulating cold water in the cooling jacket, thereby timely removing exothermic reaction, so that the reaction temperature in the reactor is maintained at 60-70 ℃. In the step (3), the exothermic heat of reaction is continuously removed by circulating cold water, so that the reaction temperature in the reactor is kept at 72-77 ℃.
Further, the stock solution preparation unit further comprises a single-removing and defoaming tower shown in fig. 2, and the crude stock solution obtained in the step (3) enters the single-removing and defoaming tower to realize single-removing and defoaming treatment in one step. Specifically, in the step (4), the obtained crude stock solution is heated to 70-80 ℃ by a heat exchanger, and then enters a single-removing and defoaming tower which is kept at 70-80 ℃ and has the pressure of minus 90-minus 99kPa for single-removing and defoaming treatment. After the single removal and defoaming treatment, the temperature of the stock solution is about 50 ℃, the dynamic viscosity is 650-730 poise, and the residual acrylonitrile is not higher than 0.03wt%.
Specifically, the top of the single-removing and deaerating tower is provided with a feed inlet 101, and a packing layer 110 is arranged below the feed inlet 101 and used for dispersing the crude stock solution. The inside of the single-removing and deaerating tower is provided with a liquid-reducing component 120, the bottom of the single-removing and deaerating tower is provided with a tower bottom outlet 104, the crude stock solution is dispersed by a filler layer 110 and falls onto the liquid-reducing component 120, flows downwards along the surface of the liquid-reducing component 120, realizes single-removing and deaerating treatment in a negative pressure environment, and is finally discharged from the tower bottom outlet 104. The top of the single-removal deaeration tower is also provided with a vacuum suction port 103 which is used for being connected with a vacuum system, so that the negative pressure environment of-90 to-99 kPa is maintained inside.
The upper surface of the dropping unit 120 is a dispersing surface 121, the dispersing surface 121 gradually decreases from the center to the periphery, and the highest position of the dispersing surface 121 is located under the filler layer 110. The downcomer assembly 120 further has a leading face 122, the leading face 122 extending obliquely downward from the outer periphery of the dispersing face 121 and gradually approaching the middle. The angle between the dispersing surface 121 and the horizontal direction is smaller than the angle between the guiding surface 122 and the horizontal direction.
In the present invention, preferably, the angle between the dispersion surface 121 and the horizontal direction is smaller than 45 °, and the angle between the guiding-out surface 122 and the horizontal direction is larger than 45 ° and smaller than 90 °. More preferably, the angle between the dispersing surface 121 and the guiding surface 122 is greater than 90 °.
The single-removing and deaerating tower with the structure is adopted, the crude stock solution is dispersed by the filler layer 110 and falls on the dispersing surface 121, flows along the dispersing surface 121 to the periphery and spreads out to form a liquid layer with a certain thickness, and the single-removing and deaerating effects are realized in a negative pressure environment. In the outer peripheral region of the dispersing surface 121, the raw liquid flows from the dispersing surface 121 to the adhering discharge surface 122, flows down along the discharge surface 122, finally drops to the bottom of the column at or near the lowest region of the discharge surface 122, and can be discharged from the bottom outlet 104. The coarse stock solution completes the single removal and the defoaming treatment in one step in the single removal and defoaming tower, has good single removal and defoaming effects, is beneficial to shortening the production period and improving the production efficiency.
In one embodiment, the included angle between the dispersing surface 121 and the horizontal direction is 40 ° to 45 °, and the included angle between the guiding surface 122 and the horizontal direction is 60 ° to 65 °. The included angle between the dispersing surface 121 and the horizontal direction can control the flow rate of the crude raw liquid and the thickness of the liquid layer, so that higher single-removing and defoaming efficiency can be realized. The inclination of the dispersing surface 121 and the guiding surface 122 are matched, so that the stock solution can flow onto the guiding surface 122 from the periphery of the dispersing surface 121, and can not directly drop from the periphery of the dispersing surface 121, and the single removal and defoaming efficiency is further ensured.
Further, the bottom outlet 104 of the de-singulation and deaeration tower is connected to a transfer pump 130, and is used for pumping out the stock solution after de-singulation and deaeration from the bottom outlet 104. The single-removal deaeration tower is also provided with a circulating inlet 102, and the circulating inlet 102 is communicated with a liquid outlet end of the conveying pump 130. The circulation inlet 102 is provided in a side peripheral wall of the single-removal and deaeration tower, and is provided at a height lower than the highest position of the dispersion surface 121 and higher than the outer peripheral height of the dispersion surface 121, and the raw liquid after the single-removal and deaeration, which is drawn out from the bottom outlet 104 of the tower, is sprayed onto the dispersion surface 121 by the conveyance pressure of the conveyance pump 130 from the circulation inlet 102, and the single-removal and deaeration process is performed again.
Specifically, two circulation inlets 102 are symmetrically arranged relative to the feed inlet 101, and the conveying pump 130 conveys the stock solution from bottom to top, so that the circulated stock solution enters the tower through the circulation inlets 102 at a certain speed, and can impinge on the dispersing surface 121 at a higher speed, thereby realizing the full dispersion of the stock solution on the dispersing surface 121. Meanwhile, the height of the de-singulation and de-bubbling tower needs to meet the pre-pump working pressure requirement of the transfer pump 130. In the present invention, the working pressure before the pump of the transfer pump 130 is 0.03-0.05 MPa, the height of the leading-out surface 122 of the liquid dropping component 120 along the vertical direction is H2, the height difference from the bottom end of the leading-out surface 122 to the bottom of the tower is H1, wherein H2 is 5-10 m, and H1 is 10-15 m.
In the present invention, the transfer pump 130 may transfer the extracted stock solution to the filtration step. Specifically, the liquid outlet end of the delivery pump 130 may be connected to a three-way control structure, where one outlet of the three-way control structure is connected to the circulation inlet 102, and the other outlet is connected to the filtering process. When the stock solution pumped from the bottom outlet 104 has a dynamic viscosity of 650-730 poise, wherein the residual acrylonitrile amount is not higher than 0.03wt%, the liquid outlet end of the delivery pump 130 can be communicated with the filtering process through the three-way control structure, so that the stock solution is delivered to the filtering process for subsequent filtering treatment. If the dynamic viscosity or the acrylonitrile residual quantity of the stock solution does not meet the above conditions, the liquid outlet end of the delivery pump 130 and the circulation inlet 102 are conducted through the three-way control structure, and the stock solution is circulated into the single-removal and deaeration tower for further treatment.
Preferably, in the process of removing the single unit and defoaming, the discharged acrylonitrile and the bubbles are collected from the top of the removing and defoaming tower and can be sent into a reactor for polymerization reaction, so that the purpose of recycling the recovered acrylonitrile is realized, and the consumption of reaction raw materials can be saved. Specifically, acrylonitrile, methyl acrylate, itaconic acid and DMSO are mixed and then added to the reactor, and acrylonitrile and bubbles collected in the process of removing monomers and defoaming may be incorporated into the mixture fed to the reactor so as to be fed to the reactor together with each production raw material.
Further, the stock solution preparation unit also comprises a filtering device, and the filtering device is used for filtering the stock solution subjected to the single removal and deaeration. Wherein, the filter device is provided with a filter material with a mesh of 0.5 mu m, thereby realizing the filter precision of 0.5 mu m. The filtering material is PP material. The spinning solution is obtained after filtering treatment and can be sent to a spinning solution storage tank for storage or directly sent to a spinning unit for spinning.
Further, in the present invention, the spinning unit of the production system specifically includes:
the spinning device is used for spinning the spinning solution;
the solidification device is used for solidifying and forming the yarn sprayed by the spinning device in the solidification device so as to obtain nascent fibers;
the primary fiber passes through the water bath drafting device to be subjected to water bath drafting;
the oiling device is used for oiling the fiber after the water bath drafting;
the drying device is used for heating and drying the fibers after oiling;
and the steam drafting device is used for carrying out steam drafting on the dried fiber.
The production system also comprises a winding device, and the PAN-based carbon fiber precursor obtained after steam drafting is collected and wound on a spool by using the winding device.
Accordingly, as shown in fig. 3, the dope from the dope preparation unit was produced into PAN-based carbon fiber filaments in the spinning unit according to the following procedure:
spinning the spinning solution in air;
the sprayed yarn is put into a solidification device for solidification and molding, so as to obtain primary fibers;
and drawing the nascent fiber by water bath, oiling, drying and steam drawing to obtain the PAN-based carbon fiber precursor.
Specifically, the spinning solution from the stock solution preparation unit is conveyed to the spinning unit, the solid content of the spinning solution is 21% -23%, the spinning solution is cooled to 20-35 ℃ by a spinning cooler, and is measured by a metering pump, filtered by a filter, and then spun into the air.
As shown in fig. 4, the spinning device includes a spinneret 230, and the spinning dope is extruded from the spinneret orifices of the spinneret 230 to form filaments. The coagulation device is arranged below the spinneret 230, the coagulation bath liquid surface is arranged at intervals from the spinneret 230, and an air section is formed between the liquid surface and the spinneret 230. In the invention, the distance of the air section is 3-10 mm, the temperature is 5-20 ℃, and the relative humidity is 20% -50%.
Further, the coagulation device includes a primary coagulation bath 210 and a secondary coagulation bath 220, and the filament yarn discharged from the spinneret 230 sequentially passes through the primary coagulation bath 210 and the secondary coagulation bath 220. Wherein the temperature of the primary coagulation bath 210 is lower than the temperature of the secondary coagulation bath 220, and the concentration of the coagulant in the primary coagulation bath 210 is higher than the concentration of the coagulant in the secondary coagulation bath 220.
Specifically, the coagulants in both primary coagulation bath 210 and secondary coagulation bath 220 are DMSO. The temperature of the primary coagulation bath 210 is 0-10 ℃, wherein the mass concentration of the dimethyl sulfoxide is 35-40%; the temperature of the secondary coagulation bath 220 is 0 to 20 ℃, wherein the mass concentration of dimethyl sulfoxide is not more than 35%, but not 0.
Preferably, the temperature of the primary coagulation bath 210 is 0-5 ℃, wherein the mass concentration of dimethyl sulfoxide is 35% -38%; the temperature of the secondary coagulation bath 220 is 5-10 ℃, wherein the mass concentration of the dimethyl sulfoxide is 30-35%.
Further, a primary drawing roll 211 is provided between the primary coagulation bath 210 and the secondary coagulation bath 220, a secondary drawing roll 221 is provided after the secondary coagulation bath 220, and the primary fiber guided by the secondary drawing roll 221 is fed to the water bath drawing device. The linear velocity of rotation of the primary drawing roller 211 is smaller than the linear velocity of rotation of the secondary drawing roller 221, and the yarn is pre-drawn 1.1 to 2 times, preferably 1.8 to 2 times, in the secondary coagulation bath 220.
Further, in the primary coagulation bath 210, the yarn is jet-drawn, and the draft ratio of the jet-drawn yarn is 1.1 to 1.5 times, preferably 1.1 to 1.3 times.
In the above coagulation device, the filament extruded from the spinneret 230 enters the primary coagulation bath 210 through the air section, is primarily molded in the primary coagulation bath 210, and obtains a certain strength, and then enters the secondary coagulation bath 220, so that the fiber is pre-drawn in a state of slow double diffusion degree, and further, the total drawing multiple can be further improved by matching with the subsequent water bath drawing and steam drawing, thereby improving the breaking strength of the obtained precursor. The lower concentration of coagulant in secondary coagulation bath 220 may also provide a certain water wash effect.
The temperature of the coagulation bath and the concentration of the coagulant therein need to be kept constant, and for this purpose, the primary coagulation bath 210 is connected to a primary circulation pump 212 and a primary coagulation bath storage tank 213, and the coagulation bath is circulated by the primary circulation pump 212. Similarly, the secondary coagulation bath 220 is connected to a secondary circulation pump 222 and a secondary coagulation bath storage tank 223, thereby realizing circulation of the coagulation bath liquid in the secondary coagulation bath 220.
In a further scheme of the invention, the spun fibers are led out by a yarn guiding machine and sent to a water bath drafting device for water bath drafting, and the coagulator attached to the fibers is washed off and a certain drafting multiple is realized.
Specifically, as shown in fig. 5, the water bath drawing device comprises a water bath drawing tank for holding a water bath, a water washing roller 340 arranged in the water bath drawing tank and partially immersed below the water bath liquid level, and a drawing roller assembly arranged above the water bath drawing tank. The washing rollers 340 are disposed at intervals along the movement direction of the nascent fiber, and the draft roller assembly is disposed corresponding to an interval region between two adjacent washing rollers 340.
The nascent fibers alternately bypass the water wash roll 340 and the draw roll assembly for water bath drawing. The nascent fibers are immersed below the water bath level only when bypassing the lower portion of the water wash roll 340.
The water bath drafting device with the structure is used for carrying out water bath drafting on the nascent fibers, and the fibers are only immersed into the water bath in a short time when staying at the lower part of the water washing roller 340, so that the continuous soaking time of the fibers in the water bath is greatly shortened, the accumulated soaking time is also shortened to a certain extent, and the time of bearing water resistance of the fibers in the water bath drafting process is reduced. Thus, the excessive damage to the fiber caused by continuous countercurrent washing can be avoided, and the spinning speed can be improved without the phenomenon of yarn breakage.
Further, in the invention, the water bath drawing comprises a primary water bath drawing, a secondary water bath drawing and a tertiary water bath drawing which are sequentially carried out. The water bath temperature of the primary water bath drafting is lower than the water bath temperatures of the secondary water bath drafting and the tertiary water bath drafting; the draft multiple of the primary water bath draft is smaller than that of the secondary water bath draft, and the draft multiple of the secondary water bath draft is larger than that of the tertiary water bath draft.
Specifically, the water bath temperature of the primary water bath drafting is 40-60 ℃, the water bath temperature of the secondary water bath drafting is not lower than 95 ℃, and the water bath temperature of the tertiary water bath drafting is not lower than 95 ℃. The draft multiple of the primary water bath draft is 1-1.5 times, the draft multiple of the secondary water bath draft is 1.5-6 times, and the draft multiple of the tertiary water bath draft is 1-1.5 times.
Preferably, the water bath temperature of the primary water bath draft is 30-50 ℃, the water bath temperature of the secondary water bath draft is 90-99 ℃, and the water bath temperature of the tertiary water bath draft is 90-99 ℃. The draft multiple of the primary water bath draft is 1.1-1.5 times, the draft multiple of the secondary water bath draft is 2-3 times, and the draft multiple of the tertiary water bath draft is 1.1-1.5 times.
In the above-mentioned scheme, the coagulated and formed nascent fiber is washed off the coagulant attached to the fiber by the water bath drawing process, and a certain drawing multiple is realized. By adopting the water bath drafting mode, three-stage water bath drafting is mutually matched, so that the total drafting multiple is ensured, each independent drafting multiple can be reduced, and the problem of yarn breakage caused by excessively high drafting multiple applied in one water washing is avoided. In particular, in a two-stage water bath draft, the fibers have good ductility, and a larger draft multiple is easier to apply to the fibers; in three-stage water bath drafting, the fiber is basically shaped, and the small-amplitude drafting can avoid the fiber from being broken by high-multiple drafting. Therefore, not only can the higher total draft multiple be achieved, but also the phenomenon of yarn breakage caused by the increase of the draft multiple can be avoided to the greatest extent.
The water bath temperature of each level of water bath drafting is gradually increased, but the mode of applying the maximum drafting multiple in the second level of water bath drafting is adopted to wash and draft the nascent fiber. Thus, the stable passing of the fiber can be ensured in the primary water bath drafting; then, the fiber has good ductility in the secondary water bath drafting process, so that high-power drafting is easier to realize and cannot be easily broken; finally, in the three-stage water bath drafting, the fiber is shaped to a certain extent, and the problems of broken filaments and broken filaments can be reduced by adopting relatively low drafting multiple.
In order to realize the water washing drafting process, the water bath drafting device specifically comprises a primary water bath drafting tank 310, a secondary water bath drafting tank 320 and a tertiary water bath drafting tank 330, and the primary fiber sequentially passes through the primary water bath drafting tank 310, the secondary water bath drafting tank 320 and the tertiary water bath drafting tank 330, so that total tertiary water bath drafting is realized. And each water bath drafting groove is provided with a water washing roller 340, and the water washing rollers 340 are partially immersed under the water bath liquid level, and the nascent fibers bypass the lower part of the water washing rollers 340, so that water washing is realized in the water bath.
Each water bath drawing tank is respectively connected with an independent circulating pipeline, a water washing circulating pump 370 and a heat exchanger 380 are arranged on the circulating pipeline, the water washing circulating pump 370 is started, the water bath in the water bath drawing tank is driven to circulate through the heat exchanger 380, on one hand, water flow in the water bath drawing tank is driven to reversely flow relative to nascent fibers for washing, and on the other hand, the temperature of the water bath is ensured to be kept stable.
Further, the number of the primary water bath drawing tank 310, the secondary water bath drawing tank 320 and the tertiary water bath drawing tank 330 is 3-6, and each water bath drawing tank is provided with a water washing roller 340, so that a plurality of water washing rollers 340 are arranged at intervals along the movement direction of the nascent fiber.
Specifically, along the direction of motion of the nascent fibers, a water washing roller 340 is disposed in the middle of each water bath draft tank, and a draft roller assembly is disposed above the junction of two adjacent water bath draft tanks. The primary fibers alternately bypass the water wash roller 340 and the draft roller assembly, and only after passing the water wash roller 340 are the primary fibers immersed below the liquid level while bypassing the lower portion of the water wash roller 340, the primary fibers extend obliquely upward out of the water bath until the draft roller assembly is extended. Wherein the time elapsed from below the liquid surface of the primary fiber on one of the water-washing rolls 340 is controlled to be less than 0.4s, preferably to be 0.1 to 0.35s, more preferably to be 0.2 to 0.3s.
In detail, the primary fiber is applied with a certain draft multiple in the water bath draft process, and thus the speed of the primary fiber is not uniform while passing through each of the washing rolls 340. The speed of the nascent fibers is gradually increased when the nascent fibers sequentially pass through each water bath drawing tank, and then when the diameters of the water washing rollers 340 are consistent, the residence time of the nascent fibers on the single water washing roller 340 is gradually shortened. In one embodiment, the residence time of the nascent fiber on the single water wash roll 340 is reduced from 0.35s to 0.1s throughout the water bath drawing process.
The water bath drafting device with the structure can realize the three-stage water bath drafting process, and simultaneously greatly shortens the duration of immersing the nascent fiber in the water bath drafting process, namely shortens the duration of bearing water resistance of the nascent fiber, can improve the spinning speed without worrying about excessive damage to the fiber caused by countercurrent water washing, and leads to the problem of yarn breakage. Meanwhile, after the nascent fiber leaves the water bath liquid level, water with the weight of about 3 times of the nascent fiber can be taken away, and the attached water can continue to play a water washing role when the fiber moves above the water bath liquid level, so that a certain water washing effect is achieved. Therefore, through improving the structure of the water bath drafting device, on the premise of not influencing the washing effect, the excessive damage to the fiber caused by continuous countercurrent washing is avoided, the spinning speed can be improved under the condition of ensuring the quality of the precursor, and the improvement of the production efficiency is facilitated.
Furthermore, the invention adds a low-concentration secondary coagulating bath in the coagulating device, and has a certain water washing effect. The length of time for immersing the fiber in the water bath is shortened in the water bath drafting process, and the fiber is matched with the process for adding the low-concentration secondary coagulating bath, so that the spinning speed can be improved without influencing the overall washing effect, the quality of the precursor is not influenced, and the production efficiency is improved.
In a further aspect of the invention, the water-washed roller 340 is a passive roller. Specifically, the draft roller assembly is connected with a driving device and is used for driving the draft roller assembly to rotate. The primary fiber moves under the drive of the drawing roller assembly, and then the primary fiber drives the water washing roller 340 to rotate.
The diameter of the water washing roller 340 is set to 200 to 300nm, and the height of the water washing roller 340 immersed in the water bath is 1/4 to 1/2, preferably 1/3, of the diameter of the water washing roller 340. The water washing roller 340 can control the length of the nascent fiber continuously immersed below the liquid surface to be shortened to 240-400 mm by adopting the size and the installation position, and avoid the impact resistance to the fiber in a longer length range caused by countercurrent water washing.
Further, the continuous soaking time of the nascent fiber in the water bath is 0.1 to 0.35s by matching with the spinning speed of 200 to 500 m/min. By reasonably designing the distance between the drawing roller assembly and the washing roller 340, the ratio of the time of immersing the nascent fiber below the liquid level to the time of passing in the air in the process of passing through the water bath drawing device can be controlled to be 1:4 to 8. At this time, the water bath drafting process can ensure the effective washing effect of the nascent fiber and ensure the fiber not to be damaged to the greatest extent.
In addition, the duration of the primary fiber immersed under the liquid level for a single time is controlled to be 0.1-0.35 s, the duration is not too short, otherwise, the problem that the primary fiber cannot be sufficiently heated by a water bath is possibly caused, and the temperature deviation of the primary fiber is further caused, so that yarn breakage occurs under the action force of drawing.
On the other hand, since the water bath drafting of each stage is provided with a plurality of washing rollers 340, and the drafting roller assemblies are arranged between two adjacent washing rollers 340, the drafting force for enabling the fiber to reach the specified drafting multiple can be distributed to a plurality of groups of drafting roller assemblies, and the drafting force applied to the fiber by a single group of drafting roller assemblies is obviously reduced. In the water bath drafting work, the drafting roller assembly is used for driving the fiber to move, the drafting force applied by the single-group drafting roller assembly is reduced, the friction between the fiber and the drafting roller assembly can be reduced, and the fiber breakage caused by the damage of the fiber in the water bath drafting work is further avoided.
Further, to achieve different draft factors in the primary, secondary and tertiary water bath draft, the draft roller assembly includes a low draft roller assembly 350 and a high draft roller assembly 360. Wherein, the low power drawing roller assembly 350 is correspondingly arranged above the primary water bath drawing tank 310 and the tertiary water bath drawing tank 330, and the high power drawing roller assembly 360 is correspondingly arranged above the secondary water bath drawing tank 320.
Specifically, the low power draw roll assembly 350 includes a single draw roll 351 around which the nascent fiber passes over the draw roll 351.
The high power draft roller assembly 360 includes two first draft rollers 361 and one second draft roller 362, the two first draft rollers 361 are disposed at the same height at intervals along the horizontal direction, and the second draft roller 362 is disposed below the interval between the two first draft rollers 361. The primary fiber passes through the first drawing roller 361 and the second drawing roller 362 alternately, wherein the primary fiber passes through the upper part of one first drawing roller 361, passes through the lower part of the second drawing roller 362, passes through the upper part of the other first drawing roller 361, and then extends obliquely downwards to below the water bath surface, and passes through the lower part of the washing roller 340.
In the primary water bath drafting and the tertiary water bath drafting processes, lower drafting multiple is applied, and the drafting is performed by adopting a single drafting roller 351 mode, so that the operation is simple and the control is easy. In the second-stage water bath drawing process, the first drawing roller 361 and the second drawing roller 362 are combined to strengthen the drawing tension, thereby realizing higher drawing multiple.
In a further scheme of the invention, the fiber after the water bath drafting process moves to the oiling device for oiling. Specifically, the oiling device at least comprises an oiling roller, and the fiber passes through the oiling roller to be oiled at normal temperature so as to improve the bundling property of the precursor in the subsequent treatment process.
After finishing oiling, the fibers enter a drying device for drying treatment. Specifically, the drying device comprises a dryer in which the fibers are dry densified at a temperature of 150 to 160 ℃.
Thereafter, the fibers are immersed in a steam drawing device to effect a steam drawing process. Specifically, the steam drafting device comprises a high-pressure steam drafting box, the dried fiber enters the high-pressure steam drafting box, and is drafted in saturated steam with the pressure of 0.4-0.5 MPa at a draft multiple of 1.8-3 times. And after the steam drafting process is finished, the PAN-based carbon fiber precursor is obtained.
Further, in the invention, the spinning device of the production system is provided with a plurality of spinning nozzles, the silk yarns sprayed by each spinning nozzle form an independent silk bundle, and the silk bundles formed by different spinning nozzles are mutually independent to carry out the following processes of solidification molding, water bath drafting, oiling, drying and steam drafting. And after the steam drafting process is finished, combining the obtained tows, and collecting the tows on a spool at the speed of 200-500 m/min by using a winding device to obtain a PAN-based carbon fiber precursor finished product.
In a further aspect of the invention, the production system further comprises a recovery unit for recovering the coagulant, i.e. DMSO, from the coagulation bath of the coagulation device.
As shown in fig. 6, the recovery unit includes a rectifying column 410 and a condenser 440. Wherein, the coagulating bath (i.e. DMSO aqueous solution) from the coagulating device is heated and enters the rectifying tower 410, part of water in the solution is separated, the purified solution is discharged from the bottom of the rectifying tower 410, and the steam is discharged from the top of the rectifying tower. The condenser 440 is connected to the top of the rectifying column 410, and the vapor discharged from the top of the column enters the condenser 440 to be condensed.
The cooling medium for heat exchange and cooling in the condenser 440 adopts the coagulation bath. Specifically, the coagulation bath from the coagulation device passes through the condenser 440, exchanges heat with the vapor discharged from the top of the rectifying tower 410 passing through the condenser 440, and condenses the vapor.
By utilizing the low-temperature characteristic of the coagulating bath in the dry-jet wet spinning process, the coagulating bath and the steam at the bottom of the rectifying tower 410 are subjected to heat exchange in the condenser 440, and cooling and condensing of the steam can be realized without additionally introducing cooling water. At the same time, the coagulation bath is preheated as it passes through the condenser 440, which is advantageous for a higher purification efficiency in the rectifying column 410.
Further, the rectifying tower 410 includes a primary rectifying tower 415 and a secondary rectifying tower 414, and the purified solution discharged from the primary rectifying tower 415 enters the secondary rectifying tower 414 for further purification. The condenser 440 includes a first condenser 441 and a second condenser 442, wherein the first condenser 441 is connected to the top of the primary rectifying column 415, and the second condenser 442 is connected to the top of the secondary rectifying column 414.
The coagulating bath inlet of the recovery unit is respectively connected with the first condenser 441 and the second condenser 442 through two branches, one part of the coagulating bath passes through the first condenser 441, and the other part passes through the second condenser 442 to cool and condense the top discharge steam of the primary rectifying tower 415 and the secondary rectifying tower 414 respectively. The coagulation baths flowing out of the first condenser 441 and the second condenser 442 are collected and then enter the first-stage rectifying tower 415 together.
The recovery unit adopts the above-mentioned structure to shunt the coagulating bath of low temperature to two condensers 440 in the simultaneous flow recovery unit ensure that the coagulating bath that gets into first condenser 441 and second condenser 442 is not preheated low temperature state, can realize higher heat exchange efficiency, and then improves the condensing efficiency to the overhead emission steam.
Still further, the first-stage rectifying tower 415 includes a first-effect rectifying tower 411, a second-effect rectifying tower 412 and a third-effect rectifying tower 413 which are arranged in parallel, and only the top of the third-effect rectifying tower 413 is directly communicated with the first condenser 441, that is, only the top discharge steam of the third-effect rectifying tower 413 directly enters the first condenser 441 to be condensed.
The coagulation bath liquid flowing out of the first condenser 441 and the second condenser 442 is collected into the DMSO feed tank 401, and is split into the first effect rectifying column 411, the second effect rectifying column 412 and the third effect rectifying column 413 after being output from the DMSO feed tank 401. The second-stage rectifying tower 414 is provided with one, and the purified solutions discharged from the bottoms of the first-effect rectifying tower 411, the second-effect rectifying tower 412 and the third-effect rectifying tower 413 are collected into the DMSO intermediate storage tank 402, and are conveyed to the second-stage rectifying tower 414 for further purification by the DMSO intermediate storage tank 402 after meeting the feeding standard of the second-stage rectifying tower 414. The DMSO solution after rectification is discharged from the bottom of the secondary rectifying tower 414, the concentration of which can reach 99.5 percent, and the recycling of DMSO can be realized.
The first purification of the coagulation bath is performed synchronously by adopting the first-effect rectifying tower 411, the second-effect rectifying tower 412 and the third-effect rectifying tower 413, so that the recovery efficiency of DMSO can be improved.
In the invention, an effective reboiler 421 is connected with the bottom of the effective rectifying tower 411, and the coagulating bath in the DMSO feed tank 401 is heated by steam in the effective reboiler 421 and then enters the effective rectifying tower 411. Similarly, the second-effect rectifying tower 412 is connected with a second-effect reboiler 422, the third-effect rectifying tower 413 is connected with a third-effect reboiler 423, and the second-stage rectifying tower 414 is connected with a second-stage rectifying tower reboiler 424. The coagulation bath in DMSO feed tank 401 also enters a double-effect reboiler 422 and a triple-effect reboiler 423, which enter a double-effect rectifying column 412 and a triple-effect rectifying column 413, respectively. DMSO solution in DMSO intermediate tank 402 first enters secondary rectifying column reboiler 424 for heating, and then enters secondary rectifying column 414.
Specifically, the primary reboiler 421 and the secondary rectifying tower reboiler 424 are respectively connected to an external steam source, and heat the coagulation bath or the concentrated DMSO solution.
The top discharge steam of the first-effect rectifying tower 411 enters the second-effect reboiler 422 under the action of the vacuum pump 450, and the heat of the top discharge steam is utilized to heat the coagulation bath liquid entering the second-effect reboiler 422. Similarly, the overhead vapor from the second-effect rectification column 412 is passed into a third-effect reboiler 423 for heating the coagulation bath passing therethrough.
Further, after the steam exchanges heat in the double-effect reboiler 422, the steam is introduced into the first gas-liquid separator 431, condensed water is conveyed to the waste water recovery tank 403 for storage, and the residual steam is combined with the overhead steam discharged from the double-effect rectifying tower 412 and enters the triple-effect reboiler 423 together. After the steam entering the triple-effect reboiler 423 exchanges heat, the steam is introduced into the second gas-liquid separator 432, the residual steam is combined with the steam discharged from the bottom of the triple-effect rectifying tower 413, the steam enters the first condenser 441, and the condensed water also enters the waste water recovery tank 403 for storage.
The recovery unit further comprises a third gas-liquid separator 433, after the steam is condensed by the first condenser 441 and the second condenser 442, the gas-liquid mixture is introduced into the third gas-liquid separator 433 to be separated, the residual steam is discharged by the vacuum pump 450, and the condensed water enters the waste water recovery tank 403 to be stored.
Further, the condensed water collected in the waste water recovery tank 403 can be respectively conveyed to the first-effect rectifying tower 411, the second-effect rectifying tower 412 and the third-effect rectifying tower 413, and is leached downwards from the top of the tower, so that the waste water discharge generated by the first-effect rectifying tower 411, the second-effect rectifying tower 412 and the third-effect rectifying tower 413 is controlled to reach the standard. In the gas-liquid mixture obtained by condensing the steam in the second condenser 442, part of condensed water can be directly introduced from the second rectifying tower 414, and the remaining gas-liquid mixture is conveyed to the third gas-liquid separator 433 for separation.
The DMSO is recovered by adopting the recovery unit, so that the heat exchange between the steam discharged from the top of the tower and the coagulating bath is fully utilized, and the steam consumption in the recovery process can be reduced.
Example 1
The embodiment provides a method for producing PAN-based carbon fiber precursors by adopting the production system.
Specifically, the spinning dope is prepared by the following steps:
(1) 118kg of acrylonitrile, 380kg of DMSO, 0.5kg of methyl acrylate and 1.5kg of itaconic acid were charged into a stainless steel reactor equipped with a stirrer and a cooling jacket at room temperature, and the obtained mixed solution was heated to 65 ℃;
(2) 0.3kg of AIBN was added to the mixed solution, the heat of reaction was removed by circulating cold water in the cooling jacket of the reactor, and the solution was stirred at 65℃for 12 hours;
(3) Heating the solution to 75 ℃, and continuing stirring for 12 hours to obtain a crude stock solution with the acrylonitrile conversion rate of 92.1%;
(4) Heating the crude stock solution to 80 ℃, feeding the crude stock solution into a single-removing and defoaming tower which is kept at 80 ℃ and the pressure of-95 kPa for single-removing and defoaming treatment, and collecting stock solution with the dynamic viscosity of 700 poise at 50 ℃ from the bottom of the tower, wherein the residual acrylonitrile amount is equal to 0.03 weight percent; the collected dope was filtered through a filter material (PP) having a mesh size of 0.5 μm to obtain a spinning dope.
The obtained spinning dope is prepared into PAN-based carbon fiber precursor according to the following steps:
A. the spinning stock solution with the solid content of 22 percent is filtered by a filter through a spinning cooler to 30 ℃ and metered by a metering pump, extruded through a spinning hole on a spinning head and spun in air; wherein, 3000 spinneret holes are arranged on a single spinneret, and the sprayed silk forms 3K silk bundles; the distance of the air section is 4mm, the temperature is 8 ℃, and the relative humidity is 40%;
B. the strand silk enters a primary coagulating bath for preliminary molding, the temperature of the primary coagulating bath is 5 ℃, the mass concentration of dimethyl sulfoxide is 30%, and jet drafting of 1.1 times is carried out in the primary coagulating bath; then, the fiber enters a secondary coagulating bath for pre-drawing to obtain primary fiber, wherein the temperature of the secondary coagulating bath is 25 ℃, the mass concentration of dimethyl sulfoxide is 20%, and the drawing multiple of the pre-drawing is 2 times;
C. the nascent fiber enters a primary water bath drafting tank with the water bath temperature of 50 ℃ through a guide roller, and the drafting multiple is 1.5 times; then the mixture enters a secondary water bath drafting tank with the water bath temperature of 98 ℃ and the drafting multiple is 2.5 times; then the mixture enters a three-stage water bath drafting tank with the water bath temperature of 98 ℃ and the drafting multiple is 1.0 time; in the water bath drawing step, the ratio of the time for immersing the nascent fiber below the liquid surface to the time elapsed in the air is 1:5, the residence time of the primary fiber on the single washing roller (corresponding to the time of immersing the primary fiber on the single washing roller below the liquid level) is 0.1-0.35 s;
D. The fiber passes through an oiling roller and is oiled at normal temperature;
E. drying the fibers after oiling at 140 ℃;
F. carrying out steam drafting on the dried fiber under saturated steam with the pressure of 0.4MPa, wherein the drafting multiple is 2 times;
G. and (3) superposing the 3K tows from the four spinnerets to obtain 12K tows, and collecting the 12K tows on a spool at a speed of 300m/min (namely, the spinning speed is 300m/min in the embodiment), thus obtaining the PAN-based carbon fiber precursor finished product.
In this example, the total draft multiple in the preparation of the precursor was 16.5 times, the single fiber fineness of the obtained PAN-based carbon fiber precursor was 1.1dtex, the single fiber strength was 8.9CN/dtex, and the elongation at break was 12%. The single fiber has a regular circular cross section, and the precursor is compact and has no cracks.
Example 2
The difference between this example and example 1 above is that in step C of the PAN-based carbon fiber precursor preparation process, each process parameter is replaced by:
the water bath temperature of the primary water bath drafting is 50 ℃, and the drafting multiple is 1.2 times;
the water bath temperature of the second-stage water bath drafting is 98 ℃, and the drafting multiple is 2.5 times;
the water bath temperature of three-stage water bath drafting is 98 ℃, and the drafting multiple is 1.2 times.
In this example, the total draft ratio in the preparation of the precursor was 15.84 times, the fineness of the single fibers of the obtained PAN-based carbon fiber precursor was 1.12dtex, the strength of the single fibers was 9.5CN/dtex, the elongation at break was 12.3%, and the cross section of the fiber bundles was in a regular circular arrangement.
Example 3
The difference between this example and example 1 above is that in step C of the PAN-based carbon fiber precursor preparation process, each process parameter is replaced by:
the water bath temperature of the primary water bath drafting is 50 ℃, and the drafting multiple is 1.05 times;
the water bath temperature of the second-stage water bath drafting is 98 ℃, and the drafting multiple is 2.5 times;
the water bath temperature of three-stage water bath drafting is 98 ℃, and the drafting multiple is 1.4 times.
In this example, the total draft ratio in the preparation of the precursor was 16.17 times, the fineness of the single fibers of the obtained PAN-based carbon fiber precursor was 1.13dtex, the strength of the single fibers was 8.3CN/dtex, the elongation at break was 11.7%, and the cross sections of the fiber bundles were in a regular circular arrangement.
Example 4
This example differs from example 1 above in that in step C of the PAN-based carbon fiber precursor preparation process, the ratio of the time for which the primary fiber is immersed below the liquid surface to the time elapsed in air is 1:4.
the total draft multiple in the preparation process of the precursor is 16.5 times, the single fiber fineness of the obtained PAN-based carbon fiber precursor is 1.1dtex, the single fiber strength is 9.0CN/dtex, and the elongation at break is 11.8%. The single fiber has a regular circular cross section, and the precursor is compact and has no cracks.
Example 5
This example differs from example 1 above in that in step C of the PAN-based carbon fiber precursor preparation process, the ratio of the time for which the primary fiber is immersed below the liquid surface to the time elapsed in air is 1:6.
The total draft multiple in the preparation process of the precursor is 16.5 times, the single fiber fineness of the obtained PAN-based carbon fiber precursor is 1.11dtex, the single fiber strength is 8.8CN/dtex, and the elongation at break is 12.2%. The single fiber has a regular circular cross section, and the precursor is compact and has no cracks.
Comparative example 1
The difference between this comparative example and example 2 above is that in step C of the PAN-based carbon fiber precursor preparation process, the draft ratio of the second-stage and third-stage water bath draft is reversed, i.e., the draft ratio of the first-stage water bath draft is kept at 1.2 times, the draft ratio of the second-stage water bath draft is 1.2 times, and the draft ratio of the third-stage water bath draft is 2.5 times.
In the actual production process, when spinning is carried out at a high spinning speed of more than 100m/min, the yarn breakage rate is greatly increased, and the fiber is almost completely formed in three-stage water bath drawing and cannot adapt to high drawing times.
Comparative example 2
The difference between this comparative example and example 2 above is that in step C of the PAN-based carbon fiber precursor preparation process, the draft multiple of each stage of water bath draft is replaced with: the draft multiple of the primary water bath draft is 1.5 times, the draft multiple of the secondary water bath draft is 1.5 times, and the draft multiple of the tertiary water bath draft is 1.6 times.
In this comparative example, the respective draft multiples in the primary, secondary and tertiary water bath drafts were close, and in actual production, it was found that the fiber was completely formed during the tertiary water bath draft, and when the spinning speed reached 100m/min or more, a 1.6-fold draft resulted in a large area of broken filaments.
Comparative example 3
The difference between this comparative example and example 2 above is that in step C of the PAN-based carbon fiber precursor preparation process, the draft multiple of each stage of water bath draft is replaced with: the draft multiple of the primary water bath draft is 2.5 times, the draft multiple of the secondary water bath draft is 1.2 times, and the draft multiple of the tertiary water bath draft is 1.2 times.
The preparation method of the comparative example can prepare PAN-based carbon fiber precursor at a spinning speed of 300m/min, the single fiber titer of the obtained PAN-based carbon fiber precursor is 1.15dtex, the single fiber strength is 7.8CN/dtex, the elongation at break is 12%, and the fiber bundle sections are in regular circular arrangement. The elongation at break was lower and the monofilament strength was significantly lower than in example 2 above.
The degree of fiber formation during primary water bath drawing was low, and in this comparative example, the primary water bath drawing was too high, and at this time the fiber was subjected to a large drawing when not completely formed, and the increase in the degree of orientation was limited, and further the effect of improving the fiber strength was not obvious as compared with the manner of applying high-power drawing during the secondary water bath drawing in example 2.
Comparative example 4
This comparative example differs from example 1 above in that in step C, the nascent fiber is immersed in a water bath drawing apparatus as shown in FIG. 7 for water bath drawing. Wherein, the washing rollers 2 are respectively arranged at the positions close to the two ends in each washing tank 1, and in one washing tank 1, the nascent fiber is bypassed by the lower parts of the two washing rollers 2, so that the nascent fiber is completely immersed below the liquid level in the area between the two washing rollers 2. A draft roller 3 is arranged above the space between two adjacent washing tanks 1, and the nascent fiber bypasses above the draft roller 3 to realize draft.
In this comparative example, in the water bath drawing step, the ratio of the time taken for the primary fiber to be immersed below the liquid surface to the time taken for the primary fiber to be in air was 1:1, the time for the primary fiber to continuously immerse under the liquid surface is 1.2-3 s.
In practical production, it is found that when the spinning speed reaches 150m/min or more, the yarn breakage rate is greatly increased, and a qualified precursor product cannot be obtained at a high spinning speed. Therefore, the high spinning speed spinning effect cannot be achieved by adopting a water bath drawing mode that the nascent fiber is continuously immersed in a water bath for a long time.
According to the scheme of the embodiments of the invention, the PAN-based carbon fiber precursor can be produced at a high spinning speed by adopting the production system, and the obtained PAN-based carbon fiber precursor has light specific gravity, low density and high strength, and can be further carbonized to prepare a high-performance carbon fiber product, in particular a high-strength carbon fiber product. The carbon fiber has the characteristic of high strength, is particularly suitable for manufacturing blades in wind turbines or other structures requiring high strength, and has good application prospect.
The foregoing description is only illustrative of the preferred embodiment of the present invention, and is not to be construed as limiting the invention, but is to be construed as limiting the invention to any and all simple modifications, equivalent variations and adaptations of the embodiments described above, which are within the scope of the invention, may be made by those skilled in the art without departing from the scope of the invention.
Claims (8)
1. A water bath drawing device for PAN-based carbon fiber precursor production, comprising:
the water bath drawing tank is used for containing water bath;
the water washing rollers are arranged in the water bath drafting groove, are partially immersed below the liquid level of the water bath, and are arranged at intervals along the movement direction of the nascent fibers;
the drafting roller assembly is arranged above the water bath drafting tank and corresponds to a spacing area between two adjacent washing rollers;
the solidified nascent fiber alternately bypasses the washing roller and the drawing roller assembly and is subjected to water bath drawing; wherein the nascent fiber is immersed below the liquid surface when bypassing the lower part of the washing roller;
The water bath drawing tank comprises a primary water bath drawing tank, a secondary water bath drawing tank and a tertiary water bath drawing tank, and the drawing roller assembly comprises a low-power drawing roller assembly and a high-power drawing roller assembly; when the nascent fiber passes through the water bath drafting device, firstly carrying out low-power drafting, then carrying out high-power drafting, and finally carrying out low-power drafting;
the low-power drawing roller assembly is arranged corresponding to the primary water bath drawing tank and the tertiary water bath drawing tank, and the high-power drawing roller assembly is arranged corresponding to the secondary water bath drawing tank;
the low-power drafting roller assembly is a single drafting roller, and the nascent fiber bypasses above the drafting roller;
the high-power drafting roller assembly comprises two first drafting rollers and a second drafting roller, the two first drafting rollers are arranged at the same height at intervals along the horizontal direction, and the second drafting roller is arranged below the interval between the two first drafting rollers; the primary fiber passes alternately over the first and second draft rollers, wherein the primary fiber is bypassed by the top of the first draft roller and the bottom of the second draft roller.
2. The water bath drafting device for producing PAN-based carbon fiber precursor according to claim 1, wherein the drafting roller assembly is connected with a driving device and is used for driving the drafting roller assembly to rotate so as to drive the nascent fiber to move; the washing roller is driven by the nascent fiber to rotate;
The diameter of the washing roller is 200-300 mm, and the height of the washing roller immersed in the water bath is 1/4-1/2 of the diameter of the washing roller.
3. A PAN-based carbon fiber precursor production system comprising a coagulation device, and the water bath drawing device for PAN-based carbon fiber precursor production according to claim 1 or 2;
the solidifying device is used for solidifying and forming the yarn formed by spinning the spinning solution to obtain nascent fibers; and (3) the nascent fiber obtained by the coagulation device enters a water bath drafting device for water bath drafting.
4. The PAN-based carbon fiber precursor production system according to claim 3, wherein the coagulation device contains a coagulation bath at 0 to 20 ℃; the production system further comprises a recovery unit for recovering coagulant from the coagulation bath;
the recovery unit includes:
the coagulating bath liquid enters the rectifying tower, the purified solution is discharged from the bottom of the tower, and the steam is discharged from the top of the tower;
the condenser is connected with the top of the rectifying tower, and steam discharged from the top of the rectifying tower enters the condenser for condensation;
the coagulating bath liquid enters between the rectifying towers, passes through the condenser first and exchanges heat with the steam discharged from the tower top to realize the condensation of the steam.
5. The PAN-based carbon fiber precursor production system according to claim 4, wherein the rectifying tower comprises a primary rectifying tower and a secondary rectifying tower, and the purified solution discharged from the primary rectifying tower enters the secondary rectifying tower for further purification;
the condenser comprises a first condenser, a second condenser and a third condenser, wherein the first condenser is connected with the top of the primary rectifying tower;
the coagulating bath liquid inlet of the recovery unit is respectively connected with the first condenser and the second condenser through two branches, one part of coagulating bath liquid passes through the first condenser, and the other part passes through the second condenser; the coagulating bath liquid flowing out of the first condenser and the second condenser are collected and then enter the first-stage rectifying tower together.
6. The PAN-based carbon fiber precursor production system according to any one of claims 3 to 5, further comprising a precursor preparation unit, wherein the precursor preparation unit comprises a single-removal and deaeration tower for performing single-removal and deaeration treatment on the crude precursor obtained by the polymerization reaction to obtain a spinning precursor for spinning;
a feed inlet is arranged at the top of the single-removal deaeration tower, and a packing layer is arranged below the feed inlet and used for dispersing the crude stock solution; the liquid dropping assembly is arranged in the single-removing and deaerating tower, the upper surface of the liquid dropping assembly is a dispersing surface, the dispersing surface gradually decreases from the center to the periphery, and the highest position of the dispersing surface is positioned below the packing layer;
The liquid dropping component is also provided with a guide surface, and the guide surface extends downwards obliquely from the periphery of the dispersing surface and gradually approaches to the middle part; the included angle between the dispersing surface and the horizontal direction is smaller than the included angle between the guide surface and the horizontal direction.
7. The PAN-based carbon fiber precursor production system according to claim 6, wherein an angle between the dispersion surface and the horizontal direction is less than 45 °, and an angle between the derivation surface and the horizontal direction is greater than 45 ° and less than 90 °; the included angle between the dispersing surface and the leading-out surface is larger than 90 degrees.
8. The PAN-based carbon fiber precursor production system according to claim 6, wherein the bottom of the de-singulation and deaeration tower is connected with a delivery pump for extracting the de-singulated and deaerated precursor solution from the bottom of the de-singulation and deaeration tower;
the single-removal deaeration tower is also provided with a circulating inlet which is communicated with the liquid outlet end of the conveying pump; the circulating inlet is arranged on the side peripheral wall of the single-removal deaeration tower, and the setting height of the circulating inlet is lower than the highest position of the dispersing surface and higher than the peripheral height of the dispersing surface; the stock solution after the removal of the monomer and the defoaming is pumped from the bottom of the tower and is sprayed onto the dispersion surface through a circulation inlet by using the conveying pressure of a conveying pump, and the removal of the monomer and the defoaming are performed again.
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