High-strength medium-mold carbon fiber densification regulation method

Abstract

The present application relates to a kind of high-strength medium modulus carbon fiber densification regulation method, belong to polyacrylonitrile carbon fiber spinning technical field, solve at least one of the problems in the prior art such as high-strength medium modulus carbon fiber (especially precursor) insufficient densification, many hole type defects, performance fluctuation etc..The present application discloses a kind of high-strength medium modulus carbon fiber densification regulation method, after polyacrylonitrile-based polymer spinning solution is obtained by coagulation and drawing, using the multi-section washing process of step-by-step heating, 1.01~1.10 times draft is applied in each section washing;The fiber after washing is hot water drawing (multi-section), and the draft ratio and hot water temperature of each sub-section gradually rise.The regulation method is designed by process flow and parameter optimization, so that the residual of precursor fiber is lower, the orientation degree is higher, and the densification is better;The orientation degree of the precursor prepared by the regulation method is ≥91.5%, the precursor strength is ≥6.8cN / dtex, the elastic modulus of the carbon fiber prepared is 320~340GPa, and the tensile strength is >6000MPa.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of polyacrylonitrile carbon fiber spinning technology, and particularly relates to a high-strength medium modulus carbon fiber densification regulation method. BACKGROUND

[0002] Polyacrylonitrile carbon fiber is an inorganic material with a carbon content of more than 90%, and the strength is largely dependent on the densification degree of the original silk. The original silk is formed by polymerization of acrylonitrile monomers into a spinning solution, and the spinning solution becomes a single filament stream through a spinneret. The single filament stream is prepared into an original silk under the synergistic action of the coagulation double diffusion and the washing hot water drawing.

[0003] Because the spinning solution of different compositions is highly sensitive to the coagulation bath and the drawing process parameters (temperature, medium, draw ratio, etc.), the original silk is prone to have poor orientation consistency, many hole defects, and insufficient densification during the preparation process, thereby affecting the densification degree and strength of the carbon fiber prepared subsequently.

[0004] Therefore, it is necessary to develop a high-strength medium modulus carbon fiber densification regulation method to obtain a carbon fiber with high densification degree, drawing strength, drawing modulus, and excellent comprehensive performance. SUMMARY

[0005] In view of the above analysis, the present application aims to provide a high-strength medium modulus carbon fiber densification regulation method to solve at least one of the problems of poor orientation consistency, many hole defects, and insufficient densification of the original silk, thereby improving the densification degree and comprehensive performance of the carbon fiber prepared subsequently.

[0006] The present application provides a high-strength medium modulus carbon fiber densification regulation method, which comprises the following steps:

[0007] S1: preparing an acrylonitrile-based polymer spinning solution, the spinning solution is spun into a coagulation liquid for coagulation bath and drawing at the same time to obtain a coagulation yarn, i.e. an as-spun fiber;

[0008] S2: washing the as-spun fiber, and using a multi-stage washing process with step-by-step temperature rise, and applying a draw ratio of 1.01-1.10 times in each washing stage;

[0009] S3: hot water drawing the washed fiber, and using a multi-stage drawing process in the hot water drawing stage, the draw ratio and hot water temperature of each sub-stage are gradually increased, and after completion of the drawing and cooling, the fiber is oiled, dried, and steam-drawn to obtain a densified original silk, which is used to prepare a high-strength medium modulus carbon fiber.

[0010] Specifically, the acrylonitrile-based polymer spinning solution in step S1 is prepared by polymerization reaction from a copolymer solution, the copolymer solution comprising a copolymerization main monomer acrylonitrile, a copolymerization monomer itaconic acid, an initiator and a solvent;

[0011] The mass ratio of acrylonitrile to itaconic acid is 50-80:20-50, the sum of the mass of acrylonitrile and itaconic acid accounts for 15-25% of the mass of the copolymer solution, the mass of the initiator accounts for 1-1.5% of the mass of the copolymer solution, and the rest is solvent.

[0012] Specifically, the specific operation of step S1 is as follows:

[0013] The spinning solution is sprayed out through a spinneret and enters a coagulation liquid, the coagulation liquid is a mixed solution of dimethyl sulfoxide and water, the mass fraction of dimethyl sulfoxide is 70-78%, and the coagulation temperature is 20-60°C.

[0014] Specifically, the coagulation bath process in step S1 is performed by drawing the coagulation yarn, and the draw ratio is 1.01-1.20 times.

[0015] Further, the spinneret is a ring spinneret, liquid is introduced into the inner ring, the flow rate of the liquid in the inner ring is controlled to be 100-1000 L / h, the liquid in the inner ring is a mixed solution of dimethyl sulfoxide and water, and the mass fraction of dimethyl sulfoxide is 65-75%;

[0016] The mass fraction of dimethyl sulfoxide in the coagulation liquid is greater than the mass fraction of dimethyl sulfoxide in the liquid in the inner ring, and the temperature of the coagulation liquid and the liquid in the inner ring is the same.

[0017] Specifically, step S2 adopts a flower roller type washing, the water flow direction and the fiber direction are countercurrent, the washing temperature is gradually increased, and the washing temperature range is controlled to be 30-80°C;

[0018] Stretching distribution is performed during the washing process, when the washing temperature is ≤45°C, 1.01-1.03 times of stretching is applied; when the washing temperature is >45°C, 1.02-1.05 times of stretching is applied;

[0019] The temperature and the draw ratio of the next segment of washing are not less than the temperature and the draw ratio of the previous segment of washing.

[0020] Preferably, the total number of washing segments in step S2 is 16, the first segment is set to 30-40 degrees, each segment of washing is increased by 2-4 degrees, and the 16th segment of washing is 60-70 degrees.

[0021] Specifically, in step S3, the hot water temperature is ≥70°C, the total draw ratio of hot water is 2-4 times; the hot water drawing is divided into 2-6 segments, and the temperature and the draw ratio of each segment of hot water are gradually increased.

[0022] More preferably, the hot water drawing is 4 stages;

[0023] 1st stage 70-80 DEG C, drawing ratio 1.1-1.2; 2nd stage 75-85 DEG C, drawing ratio 1.2-1.3; 3rd stage 80-90 DEG C, drawing ratio 1.3-1.4; 4th stage 85-95 DEG C, drawing ratio 1.4-1.5.

[0024] The application further discloses a high-strength medium-modulus carbon fiber prepared from the precursor fiber prepared by the regulation method.

[0025] The precursor fiber has an orientation degree of greater than or equal to 91.5% and a strength of greater than 6.5 cN / dtex; the carbon fiber has an elastic modulus of 320-340 GPa and a drawing strength of greater than 6000 MPa.

[0026] Compared with the prior art, the application can achieve at least one of the following beneficial effects:

[0027] 1. The precursor fiber provided by the application has high orientation degree consistency, the orientation degree of the precursor fiber is greater than or equal to 91.5%, the strength of the precursor fiber is greater than 6.5 cN / dtex, the residual dimethyl sulfoxide in the precursor fiber is significantly reduced, the residual amount of dimethyl sulfoxide in the precursor fiber is less than 1000 ppm, the hole-type defects in the precursor fiber are significantly reduced, the densification degree and the strength of the precursor fiber are improved, and the comprehensive performance of the carbon fiber prepared subsequently is improved.

[0028] Since the precursor fiber is composed of a plurality of filaments, each filament has a certain diameter, and the solidification and diffusion of the filaments from the spinning hole is gradually performed from the outer surface to the core of the filament, in the double-diffusion solidification process, the skin of the filament is solidified first, gradually densifies, and hinders the double diffusion of the core of the filament, so that the dimethyl sulfoxide in the core cannot be released, and defects are formed. The application firstly adjusts the concentration of the solidification solution, the solidification temperature, the drawing ratio and other parameters to realize fine denier solidification, the fiber is finer in the solidification bath, and the dimethyl sulfoxide in the core of the filament is more likely to be precipitated, and the densification of the as-spun fiber is better (that is, the content of dimethyl sulfoxide in the as-spun fiber is reduced).

[0029] More preferably, when a ring spinneret is used, the contact between the spinning solution and the solidification liquid (strictly speaking, the inner ring liquid is also part of the solidification liquid) can be made more sufficient, the solidification process is more uniform, and the orientation and uniformity of the as-spun fiber are improved.

[0030] Further, the present application significantly increases the number of washing stages, preferably 16 stages, and gradually increases the temperature during the washing process, and strictly controls the draft ratio (slightly increases according to the temperature change), which achieves the purposes of washing the coagulant dimethyl sulfoxide and further improving the fiber densification, and the residual dimethyl sulfoxide in the original wire is less than 1000 ppm. Too few washing stages or too low temperature will cause the fiber bundle to have too high sulfoxide content, and too few washing stages or too low temperature will cause the washing time to be insufficient, and the residual sulfoxide will be high, and the fiber will have poor plasticity, and defects will occur during drafting, affecting the densification. Too many washing stages will cause resource waste and long process; the temperature during washing should not be too high, on the one hand, high temperature will cause the residual dimethyl sulfoxide to diffuse rapidly, although the residual coagulant is removed, but it will cause the internal or surface of the original wire to have a hole type defect, on the other hand, when the washing temperature is greater than 90 DEG C, the crystallinity in the original wire will be reduced, causing the internal structure to change, and then causing the strength of the original wire to decrease, in addition, it will also cause energy waste.

[0031] Further, the present application strictly controls the temperature of hot water drafting and divides it into multiple stages / sub-stages, each stage sets different draft ratio, to realize the step-by-step optimization of the internal structure of the original wire. Too few stages, and too large draft distribution of each stage, will cause broken wire and defects, the temperature of each stage is gradually increased, the draft ratio increases with the temperature, the temperature gradually increases, the fiber plasticity becomes better, the draft ratio gradually increases, the fiber is gradually fine denier, and the densification becomes better.

[0032] Particularly preferably, the hot water drafting is 4 stages; wherein, 1 stage 70-80 DEG C, the draft ratio is 1.1-1.2 times; 2 stage 75-85 DEG C, drafting 1.2-1.3 times; 3 stage 80-90 DEG C, drafting 1.3-1.4 times; 4 stage 85-95 DEG C, 1.4-1.5 times. The preferred scheme has a moderate temperature gradient and draft ratio, and has less damage to the fiber drafting, and the fiber densification is higher.

[0033] Through the linkage of the above steps (corresponding to S1, S2, S3), according to the characteristics of the acrylonitrile-based polymer spinning solution and the coagulant (dimethyl sulfoxide), the technical targets and parameter design of each process stage are closely related and cooperatively act, and finally the densification regulation of the original wire (low residual, reduce hole type defects, high orientation consistency) is realized, and then the performance of the original wire and the downstream carbon fiber product is improved.

[0034] 2, The device involved in the regulation method provided by the present application is easy to obtain, the process conditions are mild, the energy consumption is small, and the method is suitable for large-scale production and wide promotion.

[0035] The technical solutions in the present application can be combined with each other to realize more preferred combination solutions. Other features and advantages of the present application will be described in the following description, and some advantages will become apparent from the description, or will be understood by those skilled in the art through implementation of the present application. The objects and other advantages of the present application can be realized and obtained by the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0036] The accompanying drawings are included to provide a further understanding of the present application, and are incorporated in and constitute a part of this application. The drawings illustrate embodiments of the present application and, together with the description, serve to explain the principles of the present application.

[0037] Figure 1 A carbon fiber physical photograph in Example 1. DETAILED DESCRIPTION

[0038] Preferred embodiments of the present application will be described in detail below with reference to the drawings, wherein the drawings constitute a part of this application and are used to explain the principles of the embodiments of the present application, but are not used to limit the scope of the present application.

[0039] The present application provides a high-strength medium-modulus carbon fiber densification regulation method, and the regulation method comprises the following steps:

[0040] S1: preparing an acrylonitrile-based polymer spinning solution, the spinning solution is sprayed into a coagulation liquid for coagulation bath and stretching at the same time, to obtain a coagulation yarn, i.e. a primary fiber;

[0041] S2: washing the primary fiber, and adopting a multi-stage water washing process with step-by-step temperature rising, and applying 1.01-1.10 times of stretching in each stage of water washing;

[0042] S3: hot water stretching the fiber after water washing, and adopting a multi-stage stretching process in the hot water stretching stage, and the stretching multiple and hot water temperature in each sub-stage are gradually increased, and after completion of the stretching and cooling, the densified precursor is prepared through oiling, drying and steam stretching, and the precursor is used to prepare high-strength medium-modulus carbon fiber.

[0043] It is worth noting that the regulation method is suitable for a wet spinning process using an acrylonitrile-based polymer spinning solution, and is particularly suitable for a coagulation liquid system using dimethyl sulfoxide as a coagulant. When the acrylonitrile-based polymer spinning solution meets certain specific conditions, the regulation method has more significant effects, and the properties of the obtained precursor and carbon fiber are more excellent.

[0044] Specifically, the acrylonitrile-based polymer spinning solution in step S1 is prepared from a copolymer solution through a polymerization reaction, and the copolymer solution comprises a copolymerization main monomer acrylonitrile, a copolymerization monomer itaconic acid, an initiator and a solvent.

[0045] The mass ratio of acrylonitrile to itaconic acid is 50-80:20-50, the sum of the mass of acrylonitrile and itaconic acid accounts for 15-25% of the mass of the copolymer solution, the mass of the initiator accounts for 1-1.5% of the mass of the copolymer solution, and the rest is solvent. Within a reasonable range, the mass fraction of the copolymer main monomer is as high as possible, which helps to obtain a spinning solution with high viscosity and high solid content. The higher the content of the copolymer main monomer acrylonitrile, the higher the solid content of the polymer, but it cannot be increased unlimitedly; in a high-concentration polymerization and high-solid-content system, a slight inadaptation of polymerization conditions will cause gelation, which is PAN colloidal particles, and the gelation is easy to block the spinneret hole during spinning, causing broken filaments, affecting the quality of the filaments and the stability of the spinning process.

[0046] Preferably, the initiator accounts for 1-1.2% of the mass of the copolymer solution, and the initiator is azobisisobutyronitrile. If the content of the initiator is too low, the reaction is incomplete, and there will be a large amount of copolymer main monomer and comonomer left; if the content of the initiator is too high, the reaction is too intense, and it is difficult to control the process, and although the unreacted monomer is reduced, the produced polymer has a small molecular chain and low viscosity.

[0047] The solvent is dimethyl sulfoxide. Particularly preferably, the solvent and the coagulant of the spinning solution are both dimethyl sulfoxide, which is beneficial to the subsequent removal of dimethyl sulfoxide (if different solvents and coagulants are selected, due to the different characteristics of different substances, it is difficult to remove them at the same time or the process steps are increased), and it is also beneficial to the recycling of dimethyl sulfoxide.

[0048] Specifically, after the polymerization reaction is completed, the single and bubbles are removed, and then the spinning solution with appropriate viscosity and solid content is obtained in the storage tank of the circulating water.

[0049] Specifically, the viscosity of the spinning solution is 500-800 P, and the solid content is 19.00-21.00%.

[0050] Specifically, the specific operation of step S1 is as follows:

[0051] The spinning solution is outputted by a spinning metering pump, flows through a buffer, is sprayed out of a spinneret and enters a coagulating liquid, the coagulating liquid being a mixed solution of dimethyl sulfoxide and water, the mass fraction of dimethyl sulfoxide being 60-80%, preferably 70-78%, and the coagulating temperature being 20-60℃. The spinning solution is a mixed solution of dimethyl sulfoxide and polyacrylonitrile, the solid content of 19-21% representing the content of polyacrylonitrile, and the content of dimethyl sulfoxide being 79-81%. The coagulating process is a double diffusion process, the high concentration diffusing to the low concentration, i.e. the dimethyl sulfoxide in the spinning stream after the spinneret diffuses into the coagulating liquid, and the water in the coagulating liquid diffuses into the spinning stream after the spinneret, so the concentration of dimethyl sulfoxide in the coagulating liquid is lower than the corresponding component concentration in the spinning solution. The coagulating temperature is generally equivalent to the spinning solution temperature, and the spinning solution temperature is generally controlled below 60 degrees. If the temperature is too high, the viscosity of the spinning solution is low, and the fiber performance is reduced. If the temperature is low, the spinning solution has poor spinnability because the spinning hole is not easy to form a spinning stream. Therefore, the coagulating temperature ranges from 20 to 60℃.

[0052] Specifically, the coagulated yarn is drawn in the coagulating bath process in step S1, and the draw ratio is 1.01-1.20 times. When the double diffusion coagulation is performed, the nascent yarn is particularly "delicate" and the intermolecular force is very small, and it is easy to deform and not easy to apply a large uniaxial drawing force, otherwise the yarn will be damaged, resulting in broken yarn and irregular deformation. The tension of the drawing is controlled below 200 mg per single yarn, and the single yarn tension corresponding to the drawing ratio of 1.20 times is about 200 mg per single yarn.

[0053] Further, the spinneret is a ring spinneret, liquid is introduced into the inner ring, and the flow rate of the liquid in the inner ring is controlled to be 100-1000 L / h. The liquid in the inner ring is a mixed solution of dimethyl sulfoxide and water, and the mass fraction of dimethyl sulfoxide is 60-80%, preferably 65-75%.

[0054] When the ring spinneret is used, the concentration and flow rate of the liquid in the inner ring can be controlled to make the contact between the spinning solution and the coagulating liquid (strictly speaking, the liquid in the inner ring is also part of the coagulating liquid) more sufficient, and the coagulating process is more uniform, which is beneficial to improve the orientation and uniformity of the nascent fiber.

[0055] The mass fraction of dimethyl sulfoxide in the coagulating liquid is greater than the mass fraction of dimethyl sulfoxide in the liquid in the inner ring, and the temperature of the coagulating liquid and the liquid in the inner ring is the same. The spinning solution is extruded from the spinneret under the pressure drive of the metering pump, forms a stream and enters the coagulating liquid, the stream is in a columnar state, and the concentration of the solvent in the stream is higher than that of the coagulating liquid. Under the action of the concentration difference, the solvent in the stream diffuses into the coagulating liquid, and the concentration of the solvent in the inner ring of the columnar stream is high. In order to make the coagulating liquid in the inner ring (the liquid in the inner ring) have the same concentration as the coagulating liquid in the periphery of the columnar stream, the concentration of the coagulating liquid in the inner ring (the liquid in the inner ring) is lower than that of the coagulating liquid.

[0056] Since the original wire is composed of a plurality of monofilaments, each monofilament has a certain diameter, and the solidification and diffusion of the monofilament from the spinneret is gradually from the outer surface to the core of the monofilament. In the double diffusion solidification process, the monofilament skin solidifies first, gradually densifies, and hinders the double diffusion of the monofilament core, so that the dimethyl sulfoxide in the core cannot be released, and defects are formed. The present application first realizes the solidification of fine denier by adjusting the concentration of the solidification solution, the solidification temperature, the draw ratio and other parameters. The fiber becomes finer in the solidification bath, which is more conducive to the precipitation of dimethyl sulfoxide in the core of the monofilament, and the densification of the as-spun fiber after solidification is better (that is, the content of dimethyl sulfoxide in the as-spun fiber is reduced); the densification of the as-spun fiber increases first and then decreases with the increase of the solidification bath temperature. When the temperature is low, the solidification double diffusion is slow, and the as-spun fiber is dense. With the increase of the temperature, the double diffusion is intense, and the dense surface hinders the double diffusion, so that the sulfoxide in the monofilament cannot be released, and the hole defects are formed. With the increase of the concentration of the solidification solution, the concentration difference between the solidification bath and the spinning solution body decreases, the double diffusion is slow, the fiber structure is regular, the densification is strong, and the concentration of the solidification solution decreases. The concentration difference between the two is large, the double diffusion is fast, and the yarn will be obviously lost and white. This is because the solidification is too fast, and the fine hole defects are formed. The purpose of stretching is to make the fiber fine and denier, which is conducive to the release of sulfoxide in the core of the monofilament, and conducive to the progress of double diffusion and densification.

[0057] Specifically, step S2 adopts a water washing with a flower roller, the water flow direction and the fiber direction are countercurrent, the water washing temperature is gradually increased, and the water washing temperature range is controlled to be 30-80℃;

[0058] The drawing distribution is carried out during the water washing. When the water washing temperature is ≤45℃, 1.01-1.03 times of the drawing is applied; when the water washing temperature is >45℃, 1.02-1.05 times of the drawing is applied.

[0059] The temperature and the draw ratio of the next water washing segment are not less than the temperature and the draw ratio of the previous water washing segment.

[0060] The present application significantly improves the number of washing stages, preferably 16 washing stages, and gradually increases the temperature during the washing process, and strictly controls the draft ratio (slightly increases according to the temperature change), and achieves the purposes of washing the coagulant dimethyl sulfoxide and further improving the fiber densification in the process, and the residual amount of dimethyl sulfoxide in the raw yarn is less than 1000 ppm. Too few washing stages or too low temperature will cause the fiber bundle to have too high sulfoxide content, and too few washing stages and insufficient washing time will result in high sulfoxide residue, and poor plasticity of the fiber at low washing temperature, which will become a defect during drafting and affect the densification. Too many washing stages will cause resource waste and long process; the temperature during washing should not be too high, on the one hand, high temperature will cause the residual dimethyl sulfoxide to diffuse rapidly, although the residual coagulant is removed, but it will cause the internal or surface of the raw yarn to have a hole type defect, on the other hand, when the washing temperature is greater than 90 DEG C, the crystallinity in the raw yarn will be reduced, which will cause the internal structure to change, and then cause the strength of the raw yarn to decrease, in addition, it will also cause energy waste.

[0061] Preferably, the total number of washing stages in step S2 is 16, the first stage is set to 30-40 DEG C, and each stage is increased by 2-4 DEG C, and the 16th stage is washed at 60-70 DEG C.

[0062] Specifically, in step S3, the hot water temperature in the hot water drafting link is greater than or equal to 70 DEG C, and the total draft ratio is 2-4 times; the hot water drafting is divided into 2-6 stages, and the temperature and draft ratio of each stage are gradually increased.

[0063] The present application strictly controls the temperature of hot water drafting and divides it into multiple stages / sub-stages, each stage is set to different draft ratio, to realize the step-by-step optimization of the internal structure of the raw yarn. Too few stages and too large draft ratio of each stage will cause yarn breakage and form defects, the temperature of each stage is gradually increased, the draft ratio is increased with the increase of temperature, the temperature is gradually increased, the plasticity of the fiber is better, the draft ratio is gradually increased, the fiber is gradually fine denier, and the densification is better.

[0064] More preferably, the hot water drafting is 4 stages;

[0065] Among them, 1 stage is 70-80 DEG C, and the draft ratio is 1.1-1.2 times; 2 stage is 75-85 DEG C, and the draft ratio is 1.2-1.3 times; 3 stage is 80-90 DEG C, and the draft ratio is 1.3-1.4 times; 4 stage is 85-95 DEG C, and the draft ratio is 1.4-1.5 times. The preferred scheme has a moderate temperature gradient and a moderate draft ratio, which causes less damage to the fiber drafting and higher fiber densification.

[0066] The present application also discloses a high-strength medium-modulus carbon fiber prepared from the raw yarn prepared by the regulation method.

[0067] The original silk orientation is greater than or equal to 91.5%, and the original silk strength is greater than or equal to 6.8 cN / dtex; the carbon fiber elastic modulus is 320-340 GPa, and the tensile strength is greater than 6000 MPa.

[0068] Exemplarily, the original silk is made into carbon fiber through the processes of (constant tension fiber withdrawal, pre-oxidation, low-temperature carbonization, high-temperature carbonization, electrolysis, sizing, drying, and fiber collection.

[0069] All the examples and comparative examples use dimethyl sulfoxide as the solvent and coagulant.

[0070] Example 1

[0071] The mass fraction of the copolymerization main monomer acrylonitrile accounts for 52% of the mass of the copolymer, the mass fraction of the copolymerization monomer itaconic acid accounts for 48% of the mass of the copolymer, and the initiator azobisisobutyronitrile accounts for 1.2% of the total mass of the copolymer solution. After polymerization, single removal and defoaming, the spinning solution with a viscosity of 700P and a solid content of 20.00% is obtained in a circulating water storage tank at 80°C.

[0072] The flow rate of the liquid introduced into the inner ring of the spinneret is 200 L / h, and the mass fraction of the liquid dimethyl sulfoxide in the inner ring is 70%; the concentration of the coagulant dimethyl sulfoxide is controlled at 75%, and the temperature of the coagulant is controlled at 35°C.

[0073] The draw ratio in the coagulant is 1.10 times, the water washing mode adopts a flower roller type water washing, the water flow direction and the fiber direction are countercurrent, when the water washing temperature is less than or equal to 45°C, the draw ratio is 1.02 times, and when the water washing temperature is greater than 45°C, the draw ratio is 1.04 times.

[0074] The number of water washing sections is 16, the first section is set to 30 degrees, and each section is increased by 2 degrees, and the 16th section is 60 degrees.

[0075] The hot drawing adopts 4 sections, the first section is 70 degrees, the draw ratio is 1.1 times; the second section is 80 degrees, the draw ratio is 1.3 times; the third section is 90 degrees, the draw ratio is 1.4 times; and the fourth section is 95 degrees, the draw ratio is 1.5 times.

[0076] Then, the finished original silk 1 is obtained through oiling, drying, and steam drawing.

[0077] Example 2

[0078] The mass fraction of the main monomer acrylonitrile accounts for 55% of the mass of the copolymer, the mass fraction of the copolymerization monomer itaconic acid accounts for 45% of the mass of the copolymer, and the initiator azobisisobutyronitrile accounts for 1.5% of the total mass of the copolymer solution. After polymerization, single removal and defoaming, the spinning solution with a viscosity of 750P and a solid content of 21.00% is obtained in a circulating water storage tank at 80°C.

[0079] The flow rate of liquid in the inner ring of the spinneret is 500 L / h, and the mass fraction of dimethyl sulfoxide in the inner ring liquid is 75%; the concentration of dimethyl sulfoxide in the coagulating liquid is controlled at 78%, and the temperature of the coagulating liquid is controlled at 40℃;

[0080] The draw ratio in the coagulating liquid is 1.15 times, the water washing mode is flower roller type water washing, the water flow direction and the fiber direction are countercurrent, when the water washing temperature is ≤45℃, the applied draw ratio is 1.02 times, and when the water washing temperature is >45℃, the applied draw ratio is 1.04 times.

[0081] The number of water washing sections is 16, the first section is set to 40 degrees, and each section is increased by 2 degrees, and the 16th section is 70 degrees.

[0082] The hot drawing is 4 sections, 1 section is 75 degrees, the draw ratio is 1.1 times; 2 sections are 80 degrees, the draw ratio is 1.3 times; 3 sections are 90 degrees, the draw ratio is 1.4 times; and 4 sections are 95 degrees, the draw ratio is 1.5 times.

[0083] Then, the finished raw silk 2 is obtained through oiling, drying, and steam drawing.

[0084] Example 3

[0085] The mass fraction of the main monomer acrylonitrile accounts for 60% of the mass of the copolymer, the mass fraction of the comonomer itaconic acid accounts for 40% of the mass of the copolymer, and the initiator azobis isobutyronitrile accounts for 1.0% of the total mass of the copolymer solution. After polymerization, single removal and degassing, in a 80℃ circulating water storage tank, a spinning solution with a viscosity of 750P and a solid content of 21.00% is obtained.

[0086] The flow rate of liquid in the inner ring of the spinneret is 500 L / h, and the mass fraction of dimethyl sulfoxide in the inner ring liquid is 75%; the concentration of dimethyl sulfoxide in the coagulating liquid is controlled at 78%, and the temperature of the coagulating liquid is controlled at 40℃;

[0087] The draw ratio in the coagulating liquid is 1.20 times, the water washing mode is flower roller type water washing, the water flow direction and the fiber direction are countercurrent, when the water washing temperature is ≤45℃, the applied draw ratio is 1.03 times, and when the water washing temperature is >45℃, the applied draw ratio is 1.05 times.

[0088] The number of water washing sections is 16, the first section is set to 45 degrees, and each section is increased by 2 degrees, and the 16th section is 75 degrees.

[0089] The hot drawing is 4 sections, 1 section is 75 degrees, the draw ratio is 1.1 times; 2 sections are 80 degrees, the draw ratio is 1.3 times; 3 sections are 85 degrees, the draw ratio is 1.4 times; and 4 sections are 90 degrees, the draw ratio is 1.5 times.

[0090] Then, the finished raw silk 3 is obtained through oiling, drying, and steam drawing.

[0091] Example 4

[0092] The main monomer acrylonitrile accounts for 75% of the mass of the copolymer, the comonomer itaconic acid accounts for 25% of the mass of the copolymer, the initiator azobisisobutyronitrile accounts for 1.2% of the total mass of the copolymer solution, after polymerization, single removal and defoaming, the spinning solution with a viscosity of 750P and a solid content of 21.00% is obtained in a circulating water storage tank at 80°C.

[0093] The flow rate of the liquid introduced into the inner ring of the spinneret is 500L / h, and the mass fraction of the liquid dimethyl sulfoxide in the inner ring is 75%; the concentration of the coagulation liquid dimethyl sulfoxide is controlled at 78%, and the temperature of the coagulation liquid is controlled at 40°C.

[0094] The draw ratio in the coagulation liquid is 1.10 times, the water washing mode adopts a flower roller type water washing, the water flow direction and the fiber direction are countercurrent, when the water washing temperature is ≤45°C, the draw ratio is 1.03 times, and when the water washing temperature is >45°C, the draw ratio is 1.05 times.

[0095] The number of water washing sections is 16, the first section is set to 45 degrees, each section is increased by 2 degrees, and the 16 sections are set to 75 degrees.

[0096] The hot drawing adopts 4 sections, the first section is 75 degrees, the draw ratio is 1.15 times; the second section is 85 degrees, the draw ratio is 1.2 times; the third section is 90 degrees, the draw ratio is 1.3 times; and the fourth section is 95 degrees, the draw ratio is 1.4 times.

[0097] Then, the finished yarn 4 is obtained through oiling, drying and steam drawing.

[0098] Example 5

[0099] The main monomer acrylonitrile accounts for 60% of the mass of the copolymer, the comonomer itaconic acid accounts for 40% of the mass of the copolymer, the initiator azobisisobutyronitrile accounts for 1.2% of the total mass of the copolymer solution, after polymerization, single removal and defoaming, the spinning solution with a viscosity of 750P and a solid content of 21.00% is obtained in a circulating water storage tank at 80°C.

[0100] The flow rate of the liquid introduced into the inner ring of the spinneret is 500L / h, and the mass fraction of the liquid dimethyl sulfoxide in the inner ring is 75%; the concentration of the coagulation liquid dimethyl sulfoxide is controlled at 78%, and the temperature of the coagulation liquid is controlled at 40°C.

[0101] The draw ratio in the coagulation liquid is 1.10 times, the water washing mode adopts a flower roller type water washing, the water flow direction and the fiber direction are countercurrent, when the water washing temperature is ≤45°C, the draw ratio is 1.03 times, and when the water washing temperature is >45°C, the draw ratio is 1.05 times.

[0102] The number of water washing sections is 16, the first section is set to 40 degrees, each section is increased by 2 degrees, and the 16 sections are set to 70 degrees.

[0103] Hot drawing is adopted for 4 stages, 1st stage 80 degrees, drawing 1.20 times; 2nd stage 85 degrees, drawing 1.3 times; 3rd stage 90 degrees, drawing 1.35 times; 4th stage 95 degrees, drawing 1.4 times.

[0104] Then the finished product 5 is obtained through oiling, drying and steam drawing.

[0105] Example 6

[0106] The acrylonitrile spinning solution disclosed in patent CN 103145915 A (corresponding to the spinning solution in Example 1 of patent CN 103145915 A) is adopted.

[0107] The flow rate of the liquid passing through the inner ring of the spinneret is 500 L / h, and the mass fraction of dimethyl sulfoxide in the inner ring liquid is 75%; the concentration of dimethyl sulfoxide in the coagulation liquid is controlled at 78%, and the temperature of the coagulation liquid is controlled at 40℃;

[0108] The drawing multiple in the coagulation liquid is 1.15 times, the water washing mode adopts flower roller type water washing, the water flow direction and the fiber direction are countercurrent, when the water washing temperature is ≤45℃, 1.02 times of drawing is applied, when the water washing temperature is >45℃, 1.04 times of drawing is applied.

[0109] The number of water washing stages is 16, the 1st stage is set to 40 degrees, and each 1st stage is increased by 2 degrees, and the 16th stage is 70 degrees.

[0110] Hot drawing is adopted for 4 stages, 1st stage 75 degrees, drawing 1.1 times; 2nd stage 80 degrees, drawing 1.3 times; 3rd stage 85 degrees, drawing 1.4 times; 4th stage 90 degrees, drawing 1.5 times.

[0111] Then the finished product 6 is obtained through oiling, drying and steam drawing.

[0112] Example 7

[0113] The acrylonitrile spinning solution disclosed in patent CN 103145915 A (corresponding to the spinning solution in Example 2 of patent CN 103145915 A) is adopted.

[0114] The drawing multiple in the coagulation liquid is 1.20 times, the water washing mode adopts flower roller type water washing, the water flow direction and the fiber direction are countercurrent, when the water washing temperature is ≤45℃, 1.03 times of drawing is applied, when the water washing temperature is >45℃, 1.05 times of drawing is applied.

[0115] The number of water washing stages is 16, the 1st stage is set to 45 degrees, and each 1st stage is increased by 2 degrees, and the 16th stage is 75 degrees.

[0116] Hot drawing is adopted for 4 stages, 1st stage 75 degrees, drawing 1.1 times; 2nd stage 80 degrees, drawing 1.3 times; 3rd stage 85 degrees, drawing 1.4 times; 4th stage 90 degrees, drawing 1.5 times.

[0117] The finished yarn 7 is obtained by oiling, drying and steam drawing.

[0118] Example 8

[0119] The mass fraction of the main monomer acrylonitrile accounts for 52% of the mass of the copolymer, the mass fraction of the comonomer itaconic acid accounts for 48% of the mass of the copolymer, and the initiator azobisisobutyronitrile accounts for 1.2% of the total mass of the copolymer. After polymerization, single removal and defoaming, the spinning solution with a viscosity of 700P and a solid content of 20.00% is obtained in a circulating water storage tank at 80°C.

[0120] The flow rate of the liquid in the inner ring of the spinneret is 200L / h, and the mass fraction of the liquid dimethyl sulfoxide in the inner ring is 70%; the concentration of the coagulation liquid dimethyl sulfoxide is controlled at 75%, and the temperature of the coagulation liquid is controlled at 35°C.

[0121] The drawing ratio in the coagulation liquid is 1.00 times, the water washing mode is flower roller washing, the water flow direction and the fiber direction are countercurrent, when the water washing temperature is ≤45°C, the drawing is 1.02 times, and when the water washing temperature is >45°C, the drawing is 1.04 times.

[0122] The number of water washing sections is 16, the first section is set to 35 degrees, each section is increased by 2 degrees, and the 16th section is 75 degrees.

[0123] The hot drawing is 2 sections, 1 section is 90 degrees, and the drawing is 1.5 times; 2 section is 95 degrees, and the drawing is 1.8 times. The finished yarn 8 is obtained by oiling, drying and steam drawing.

[0124] Example 9

[0125] The mass fraction of the main monomer acrylonitrile accounts for 52% of the mass of the copolymer, the mass fraction of the comonomer itaconic acid accounts for 48% of the mass of the copolymer, and the initiator azobisisobutyronitrile accounts for 1.2% of the total mass of the copolymer. After polymerization, single removal and defoaming, the spinning solution with a viscosity of 700P and a solid content of 20.00% is obtained in a circulating water storage tank at 80°C.

[0126] The flow rate of the liquid in the inner ring of the spinneret is 200L / h, and the mass fraction of the liquid dimethyl sulfoxide in the inner ring is 70%; the concentration of the coagulation liquid dimethyl sulfoxide is controlled at 75%, and the temperature of the coagulation liquid is controlled at 35°C.

[0127] The drawing ratio in the coagulation liquid is 1.10 times, the water washing mode is flower roller washing, the water flow direction and the fiber direction are countercurrent, when the water washing temperature is ≤45°C, the drawing is 1.02 times, and when the water washing temperature is >45°C, the drawing is 1.04 times.

[0128] The number of water washing sections is 16, the first section is set to 35 degrees, each section is increased by 2 degrees, and the 16th section is 75 degrees.

[0129] The hot drawing is performed in 6 stages, 1st stage 75 degrees, drawing 1.1 times; 2nd stage 80 degrees, drawing 1.15 times, 3rd stage 85 degrees, drawing 1.15 times, 4th stage 90 degrees, drawing 1.25 times, 5th stage 95 degrees, drawing 1.25 times, 6th stage 98 degrees, drawing 1.3 times, and then the finished raw yarn 9 is obtained through oiling, drying and steam drawing.

[0130] Comparative Example 1

[0131] The same spinning solution as in Example 6 is used.

[0132] The flow rate of the liquid in the inner ring of the spinneret is 500 L / h, and the mass fraction of the liquid dimethyl sulfoxide in the inner ring is 75%; the concentration of the coagulating liquid dimethyl sulfoxide is controlled at 78%, and the temperature of the coagulating liquid is controlled at 40°C.

[0133] The drawing ratio in the coagulating liquid is 1.10 times, and the water washing mode is the flower roller type water washing, the water flow direction and the fiber direction are countercurrent, when the water washing temperature is ≤45°C, the drawing is 1.03 times, and when the water washing temperature is >45°C, the drawing is 1.05 times.

[0134] The number of water washing stages is 10, and each stage is 65 degrees, and the drawing of each stage is 1.03 times.

[0135] The hot drawing is performed in 4 stages, 1st stage 75 degrees, drawing 1.15 times; 2nd stage 85 degrees, drawing 1.4 times; 3rd stage 90 degrees, drawing 1.3 times; 4th stage 95 degrees, drawing 1.4 times.

[0136] The finished raw yarn 10 is obtained through oiling, drying and steam drawing.

[0137] Comparative Example 2

[0138] The mass fraction of the main monomer acrylonitrile accounts for 60% of the mass of the copolymer, the mass fraction of the comonomer itaconic acid accounts for 40% of the mass of the copolymer, and the initiator azobis isobutyronitrile accounts for 1.2% of the total mass of the copolymer solution. After polymerization, single removal and defoaming, the spinning solution with a viscosity of 750P and a solid content of 21.00 is obtained in a 80°C circulating water storage tank.

[0139] The flow rate of the liquid in the inner ring of the spinneret is 500 L / h, and the mass fraction of the liquid dimethyl sulfoxide in the inner ring is 75%; the concentration of the coagulating liquid dimethyl sulfoxide is controlled at 78%, and the temperature of the coagulating liquid is controlled at 40°C.

[0140] The drawing ratio in the coagulating liquid is 1.10 times, and the water washing mode is the flower roller type water washing, the water flow direction and the fiber direction are countercurrent, when the water washing temperature is ≤45°C, the drawing is 1.03 times, and when the water washing temperature is >45°C, the drawing is 1.05 times.

[0141] The water washing section number is 10 sections, and each section is washed at 65 degrees. The draft of each section is 1.03 times

[0142] The hot draft is 4 sections, 1 section at 75 degrees with a draft of 1.4 times; 2 sections at 85 degrees with a draft of 1.4 times; 3 sections at 90 degrees with a draft of 1.2 times; and 4 sections at 95 degrees with a draft of 1.1 times. The hot water draft stage is not operated according to the gradual increase in temperature and draft ratio, and after the first two sections of draft, there are hair filaments and winding roll phenomena.

[0143] Then, the finished product raw silk 11 is prepared through oiling, drying, and steam draft.

[0144] The above raw silk (1-11) is subjected to constant tension unwinding, pre-oxidation, low-temperature carbonization, high-temperature carbonization, electrolysis, sizing, drying, and silk collection processes to produce carbon fibers.

[0145] Table 1: Performance table corresponding to the examples and comparative examples

[0146]

[0147]

[0148] The hole type defects are evaluated by observing the results of the electric microscope at 2000 times.

[0149] In the comparative example 1 (raw silk 10), the water washing temperature is relatively low, and the gradient temperature rise and draft ratio increase are not used, resulting in a high residual amount of dimethyl sulfoxide, a small amount of hole defects in the elements, and a decrease in the strength of the raw silk and carbon fibers.

[0150] In the comparative example 2 (raw silk 11), on the one hand, the water washing parameters are not good, and on the other hand, the hot water draft step is not operated according to the gradual increase in temperature and draft ratio, and after the first two sections of draft, there are hair filaments and winding roll phenomena. The performance of the raw silk and carbon fibers is decreased.

[0151] In summary, the raw silk / carbon fibers prepared in the examples 1-9 all have good comprehensive performance. The raw silk provided by the present application has an orientation degree of ≥91.5% and a strength of ≥6.8 cN / dtex. The carbon fibers have an elastic modulus of 320-340 GPa and a draft strength of >6000 MPa.

[0152] The above description is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or replacements within the technical range disclosed by the present application can be easily thought of by those skilled in the art, and should be covered within the protection scope of the present application.

Claims

1. A high-strength medium-mold carbon fiber densification regulation method, characterized in that, The control method comprises the following steps: S1: preparing an acrylonitrile-based polymer spinning solution, the spinning solution is extruded through a spinneret and enters a coagulation liquid for coagulation and stretching at the same time to obtain a coagulation yarn, i.e. a nascent fiber; The specific operation of step S1 is as follows: In the wet spinning process, the spinning solution is extruded through a spinneret and enters a coagulation liquid, the coagulation liquid is a mixed solution of dimethyl sulfoxide and water, the mass fraction of dimethyl sulfoxide is 75-78%, and the coagulation temperature is 20-40℃; In the coagulation bath process in step S1, the coagulation yarn is stretched, and the stretching multiple is 1.10-1.20, and the tension of stretching is controlled to be below 200 mg per filament; The spinneret is a ring spinneret, liquid is introduced into the inner ring, the flow rate of the liquid in the inner ring is controlled to be 100-1000 L / h, and the liquid in the inner ring is a mixed solution of dimethyl sulfoxide and water, the mass fraction of dimethyl sulfoxide is 65-75%; In the coagulation liquid, the mass fraction of dimethyl sulfoxide is greater than that in the liquid in the inner ring, and the temperature of the coagulation liquid and the liquid in the inner ring is the same; the spinning solution is extruded from the spinneret under the pressure driving of a metering pump, forms a fine stream, enters the coagulation liquid, and is in a columnar state, the concentration of the solvent in the fine stream is greater than that in the coagulation liquid, and the solvent in the fine stream diffuses into the coagulation liquid under the action of the concentration difference; S2: washing the nascent fiber, a multi-stage water washing process with step-by-step temperature rising is adopted in the water washing stage, the total number of water washing stages is 16, the first stage is set to 30-40℃, each stage is increased by 2-4℃, the 16th stage is 60-70℃, and stretching distribution is carried out during the water washing process; when the water washing temperature is ≤45℃, 1.01-1.03 times of stretching is applied; when the water washing temperature is >45℃, 1.02-1.05 times of stretching is applied; In the next stage of water washing, the temperature and the stretching multiple are not less than those in the previous stage of water washing; S3: hot water stretching of the fiber after water washing, a multi-stage stretching process is adopted in the hot water stretching stage, the hot water stretching is 4 stages; in the first stage, the temperature is 70-75℃, and the stretching multiple is 1.1-1.2 times; in the second stage, the temperature is 75-80℃, and the stretching is 1.2-1.3 times; in the third stage, the temperature is 80-85℃, and the stretching is 1.3-1.4 times; in the fourth stage, the temperature is 85-90℃, and the stretching is 1.4-1.5 times; the stretching multiple and the hot water temperature of each sub-stage are increased step by step, after completion of the stretching and cooling, the compacted precursor is obtained through oiling, drying and steam stretching, the precursor is used to prepare high-strength medium modulus carbon fiber; the orientation degree of the precursor is ≥91.5%, and the strength of the precursor is ≥6.8 cN / dtex; the elastic modulus of the carbon fiber is 320-340 GPa, and the tensile strength is >6000 MPa.

2. The method of claim 1, wherein, In step S1, the acrylonitrile-based polymer spinning solution is prepared from a copolymer solution through polymerization, the copolymer solution comprises a copolymerization main monomer acrylonitrile, a copolymerization monomer itaconic acid, an initiator and a solvent; In the copolymer solution, the mass ratio of acrylonitrile to itaconic acid is 50-80:20-50, the sum of the mass of acrylonitrile and itaconic acid accounts for 15-25% of the mass of the copolymer solution, the mass of the initiator accounts for 1-1.5% of the mass of the copolymer solution, and the rest is the solvent.

3. The method of claim 1, wherein the step of modulating comprises: The coagulation temperature is 35-40 DEG C.

4. The method of claim 1, wherein the step of modulating comprises: In step S1, the draft ratio is 1.15-1.20 times.

5. The method of claim 3, wherein the step of regulating is performed by a processor. The flow rate of the liquid in the inner ring is controlled to be 200-500 L / h, the liquid in the inner ring is a mixed solution of dimethyl sulfoxide and water, and the mass fraction of dimethyl sulfoxide is 70-75%.

6. The method of claim 1, wherein the step of modulating comprises: In step S2, the water washing is performed by using a flower roller, and the water flow direction and the fiber direction are countercurrent.

7. A high-strength intermediate modulus carbon fiber, characterized in that, The carbon fiber is prepared from the precursor prepared by the regulation method in any one of claims 1-6. The orientation degree of the precursor is greater than or equal to 91.5%, and the strength of the precursor is greater than or equal to 6.8 cN / dtex; the elastic modulus of the carbon fiber is 320-340 GPa, and the tensile strength is greater than 6000 MPa.

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