Wet spinning method and carbon fiber

Abstract

The invention provides a wet spinning method and a preparation method of carbon fiber, the wet spinning method comprises the following steps: 1) preparing a polyacrylonitrile spinning solution, the polyacrylonitrile spinning solution comprises a copolymer obtained by polymerizing a carboxyl-containing monomer and acrylonitrile, the number-average molecular weight of the copolymer is 20000-500000, and the molecular weight distribution Mw / Mn is 1.0-1.9; the solid content of the polyacrylonitrile spinning solution is 20%-33%, the solidification value is 20-80 g, and the intrinsic viscosity is 1.0-1.6 dL / g; (2) spraying the polyacrylonitrile spinning solution from a spinneret plate at the speed of 10-40m / min, and coagulating through a first coagulating bath to obtain nascent fibers; and 3) the nascent fiber is subjected to N-stage coagulating bath drafting, water washing, oiling, densification, steam drafting and shaping, and then is wound to obtain the protofilament. The wet spinning method provided by the invention can realize the effects that the protofilament take-up rate is not less than 180m / min and the filament output stability is kept good.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wet spinning, in particular to a wet spinning method and a carbon fiber. BACKGROUND

[0002] Currently, there are two kinds of PAN-based carbon fiber precursor spinning processes, namely wet spinning and dry-jet wet spinning. In the dry-jet wet spinning process, the quality stability of the spinneret and the spinning solution is required to be very high. A slight hole blockage or gelation or air bubble in the spinning solution will cause the spinning solution to flow over the surface of the spinneret, resulting in termination of production. Compared with the dry-jet wet spinning process, the wet spinning process has relatively low requirements for the spinning solution, and occasional broken filaments have little effect on the production of the precursor.

[0003] In the wet spinning process, the spinning solution is directly introduced into the coagulation bath after being extruded through the spinneret hole, and the surface layer is rapidly coagulated, while the core layer is coagulated slowly. Therefore, the wet spinning coagulation bath is difficult to withstand a large amount of draft, and in order to prevent coagulation breakage, a wet spinning process usually uses a spinneret with a smaller hole diameter to increase the yarn speed. Whether the hole diameter of the spinneret is reduced or the flow of the spinning solution is increased (the yarn speed is increased), the extrusion swelling effect will be intensified, resulting in unstable flow of the spinning solution and increased surface defects, which is not conducive to the improvement of the orientation of the nascent fiber.

[0004] Based on the above reasons, the yarn speed of the wet spinning process is usually much lower than that of the dry-jet wet spinning process. Currently, the dry-jet wet spinning speed of PAN precursor can reach more than 500 m / min, while the wet spinning speed of PAN precursor is difficult to exceed 150 m / min, and is usually below 100 m / min. In order to solve the problem of low wet spinning speed of PAN precursor, patent CN201410259184.3 proposes a combined coagulation process, which is essentially to solve the problem of spinnability of the wet spinning process. However, this process also causes the weakening or even disappearance of the fiber grooves. Patent JP2010-229577 proposes a method of mixing two PAN solutions with different molecular weights to obtain a special molecular weight distribution, which can improve the spinnability of the spinning solution. However, this method has the disadvantage of complex spinning solution preparation process. Patent JP2001-329426A proposes a method of increasing the concentration of the coagulation bath to the vicinity of the critical concentration to improve the spinnability. However, in actual production, the concentration of the coagulation bath near the yarn outlet of the spinneret is quite different from that of other positions of the coagulation bath. If the coagulation bath is controlled at the critical concentration, it is easy to cause incomplete coagulation or large pore defects. SUMMARY

[0005] The present application provides a wet spinning method, which can realize a yarn speed of not less than 180 m / min, significantly improve the spinning efficiency of the conventional wet spinning process, and maintain good yarn stability.

[0006] The present application also provides a carbon fiber, since the precursor fiber used in the carbon fiber is prepared by the above method, the strength and modulus of the carbon fiber are better.

[0007] In detail, in a first aspect, the present application provides a wet spinning method, comprising the following steps:

[0008] 1) preparing a polyacrylonitrile spinning solution, wherein the polyacrylonitrile spinning solution comprises a copolymer of a carboxyl-containing monomer and acrylonitrile, the number average molecular weight of the copolymer is 20000-500000, and the molecular weight distribution Mw / Mn is 1.0-1.9; the solid content of the polyacrylonitrile spinning solution is 20%-33%, the coagulation value is 20-80 g, and the intrinsic viscosity is 1.0-1.6 dL / g;

[0009] 2) the polyacrylonitrile spinning solution is sprayed from a spinneret at a speed of 10-40 m / min, and the nascent fiber is obtained by coagulation in a first coagulation bath;

[0010] 3) the nascent fiber is drawn in an N-stage coagulation bath, washed, oiled, densified, steam-drawn, and shaped, and then wound to obtain a precursor fiber, wherein the winding speed is not less than 180 m / min;

[0011] In step 3), N is greater than or equal to 1; the swelling degree of the nascent fiber is 180-250%, and the draw ratio of the nascent fiber in the first coagulation bath is 0.4-4.

[0012] Further, the rotational viscosity of the polyacrylonitrile spinning solution is 20-150 Pa.s;

[0013] and / or, the intrinsic viscosity of the polyacrylonitrile spinning solution is 1.1-1.5 dL / g;

[0014] and / or, the solid content of the polyacrylonitrile spinning solution is 22%-30%.

[0015] Further, the carboxyl-containing monomer is one or more of acrylic acid, methacrylic acid, itaconic acid, itaconic acid monomethyl ester, itaconic acid monoethyl ester, itaconic acid mono-n-propyl ester, itaconic acid mono-isopropyl ester, itaconic acid mono-n-butyl ester, itaconic acid mono-isobutyl ester, itaconic acid mono-tert-butyl ester, maleic acid, methyl maleic acid, maleic anhydride, fumaric acid, and methyl fumaric acid.

[0016] Further, the polyacrylonitrile spinning solution is prepared by a method comprising the following steps:

[0017] The monomer containing carboxyl, acrylonitrile, initiator and solvent are continuously pumped into a tubular reactor with an inner diameter of 1-10 mm, and the polymerization reaction is carried out under the conditions of a pressure of 0.1-1 MPa and a temperature of 60-120 DEG C, and then the reaction system after cooling and monomer removal is subjected to defoaming treatment; the defoamed reaction system is mixed with ammonia gas to obtain the polyacrylonitrile spinning solution.

[0018] Further, the diameter of the orifice of the spinneret is 0.04-0.2 mm.

[0019] Further, the N is greater than 1, the draw ratio of the fiber in the N-1th coagulation bath is R n-1 , and the draw ratio of the fiber in the Nth coagulation bath is R n , wherein R n-1 / R n is 1.05-12.

[0020] Further, the medium of the first coagulation bath and the Nth coagulation bath is dimethyl sulfoxide aqueous solution.

[0021] Further, in the first coagulation bath, the concentration of the dimethyl sulfoxide aqueous solution is 40-80%; and / or, the N is greater than 1, the concentration of the dimethyl sulfoxide aqueous solution in the N-1th coagulation bath is C N-1 , and the concentration of the dimethyl sulfoxide aqueous solution in the Nth coagulation bath is C N , wherein C N-1 / C N is 1-4.

[0022] Further, the coagulation temperature of the first coagulation bath is 20-70 DEG C, and / or the coagulation temperature of the N-1th coagulation bath is T n-1 , and the coagulation temperature of the Nth coagulation bath is T n , wherein T n / T n-1 is 1-3.

[0023] Further, the draw ratio of the fiber in the steam drawing is 2-5 times.

[0024] In the second aspect, the present application provides a carbon fiber prepared from the precursor filament obtained by the wet spinning method of the first aspect.

[0025] The wet spinning method provided by the present application can greatly improve the spinning efficiency by controlling the parameters of the polyacrylonitrile spinning solution, reasonable coagulation process and drawing process, and specifically, the precursor filament collection rate is not less than 180 m / min, and the filament stability is maintained well. DETAILED DESCRIPTION

[0026] In order to make the objects, technical solutions and advantages of the present application clearer, the following will combine the embodiments of the present application to clearly and completely describe the technical solutions in the described embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0027] In a first aspect, the present application provides a wet spinning method, comprising the following steps:

[0028] 1) preparing a polyacrylonitrile spinning solution, wherein the polyacrylonitrile spinning solution comprises a copolymer obtained by polymerization of a monomer containing a carboxyl group and acrylonitrile, the number average molecular weight of the copolymer is 20000-500000, and the molecular weight distribution Mw / Mn is 1.0-1.9; the solid content of the polyacrylonitrile spinning solution is 20%-33%, the coagulation value is 20-80 g, and the intrinsic viscosity is 1.0-1.6 dL / g;

[0029] 2) the polyacrylonitrile spinning solution is sprayed from a spinneret at a speed of 10-40 m / min, and the nascent fiber is obtained by coagulation in a first coagulation bath;

[0030] 3) the nascent fiber is drawn in an N-stage coagulation bath, washed, oiled, densified, steam-drawn, and shaped, and then wound to obtain a raw yarn, wherein the winding speed is not less than 180 m / min;

[0031] In step 3), N is greater than or equal to 1; the swelling degree of the nascent fiber is 180-250%, and the draw ratio of the nascent fiber in the first coagulation bath is 0.4-4.

[0032] The wet spinning method of the present application can greatly improve the spinning efficiency by controlling the parameters of the polyacrylonitrile spinning solution, reasonable coagulation process and drawing process, etc. The main reasons include: 1. The copolymer with specific molecular weight and narrow distribution has the advantages of longer relaxation time and lower gel temperature, which can reduce the coagulation speed of the polyacrylonitrile spinning solution and enhance the spinnability of the polyacrylonitrile spinning solution; 2. The intrinsic viscosity of the polyacrylonitrile spinning solution in the range of 1.0-1.6 dL / g can further enhance the spinnability of the spinning solution, if it is higher than 1.6 dL / g, the spinnability of the spinning solution under high shear will be poor, and if it is lower than 1.0 dL / g, the fiber adhesion probability will be increased; 3. The coagulation value of the polyacrylonitrile spinning solution in the above range can obtain the primary fiber with reasonable swelling degree; 4. The solid content of the polyacrylonitrile spinning solution in the range of the present application can further improve the spinnability of the polyacrylonitrile spinning solution, if the solid content is lower than 20%, the fiber filament obtained by coagulation in the coagulation bath will be too poor in density, and the orientation degree will be difficult to improve, and the heat resistance will be insufficient during the spinning process; if the solid content is higher than 30%, the spinnability of the spinning solution will be poor, and the spinning solution will be easy to gel during storage; 5. The speed of the spinning solution ejected from the spinneret hole is 10-40 m / min, which can balance the relationship between the spinning efficiency and the original wire quality, if the spinning line speed is lower than 10 m / min, not only the spinning efficiency will be reduced, but also the linear density will be uneven, and even the wire will be broken; in addition, since the shear received by the spinning solution in the spinneret hole is reduced, the inhibition of the entanglement of macromolecular chains by shear will be inhibited, when the spinning line speed exceeds 40 m / min, the drawability of the fiber will be poor, and during the high multiple orientation process, the hairiness will be easily generated, and even the drawability during the carbonization process will be affected; 6. The reasonable drawing ratio of the primary fiber in the coagulation bath can reduce the amount of hairiness and ensure the quality of the wire, if it is not in the above range, the wire will be broken or the fineness will be too large; 7. If the swelling degree of the primary fiber is lower than 180%, the fiber will be easy to lose transparency and form a serious skin-core structure, and if the swelling degree is higher than 250%, the coagulation rate will be too slow, the coagulation will be insufficient, the fiber will be easy to adhere, and the spinning speed will be affected.

[0033] In a specific embodiment, the rotational viscosity of the polyacrylonitrile spinning solution is 20-150 Pa.s;

[0034] And / or, the intrinsic viscosity of the polyacrylonitrile spinning solution is 1.1-1.5 dL / g;

[0035] And / or, the solid content of the polyacrylonitrile spinning solution is 22%-30%.

[0036] Wherein, if the rotational viscosity of the polyacrylonitrile spinning solution is higher than 150 Pa.s, the spinnability of the spinning solution will be affected, and if the rotational viscosity is lower than 20 Pa.s, it will have adverse effects on the fiber forming and strength.

[0037] For example, the swelling degree of the nascent fiber is 190% to 240%, the draw ratio of the nascent fiber in the coagulation bath is 0.8 to 3, the polyacrylonitrile spinning solution is ejected from the spinneret at a speed of 15 to 30 m / min, and the coagulation value of the polyacrylonitrile spinning solution is 25 to 75 g.

[0038] In one specific embodiment, the carboxyl-containing monomer is one or more of acrylic acid, methacrylic acid, itaconic acid, monomethyl itaconic acid, monoethyl itaconic acid, monopropyl itaconic acid, monoisopropyl itaconic acid, monobutyl itaconic acid, monoisobutyl itaconic acid, monotert-butyl itaconic acid, maleic acid, methylmaleic acid, maleic anhydride, fumaric acid, and methylfumaric acid.

[0039] In one specific embodiment, the copolymer is formed by polymerizing a carboxyl-containing monomer and acrylonitrile under the action of an initiator.

[0040] For example, the carboxyl-containing comonomer accounts for 0.1-10% of the mass of acrylonitrile during polymerization, preferably 0.2-5%; the polymerization is carried out in solution.

[0041] In one specific embodiment, the solvent used in the polymerization is dimethyl sulfoxide.

[0042] For example, the copolymer is obtained by free radical polymerization, controlled radical polymerization, and conventional free radical polymerization. Conventional free radical polymerization can be divided into continuous, semi-continuous, and batch polymerization. It is difficult to obtain polymers with a molecular weight distribution (Mw / Mn) below 2.0 by batch polymerization with full backmixing and semi-continuous methods (multiple reactors in series).

[0043] This invention discovers that in continuous polymerization in a tubular reactor, due to the plug flow of material inside the tube and the low degree of backmixing, narrow-distribution PAN polymers can be obtained even when using conventional free radical polymerization.

[0044] In one specific embodiment, the polyacrylonitrile spinning solution is prepared by a method comprising the following steps:

[0045] A monomer containing a carboxyl group, acrylonitrile, an initiator, and a solvent are continuously pumped into a tubular reactor with an inner diameter of 1–10 mm. The polymerization reaction is carried out under conditions of 0.1–1 MPa pressure and 60–120 °C temperature. After cooling and monomer removal, the reaction system is degassed. The degassed reaction system is then mixed with ammonia gas to obtain the polyacrylonitrile spinning solution.

[0046] In an embodiment, the diameter of the orifices of the spinneret is 0.04-0.2 mm; further 0.05-0.15 mm.

[0047] wherein a smaller orifice diameter means a higher extrusion speed, and under the condition that the extrusion speed of the primary fiber in the primary coagulation bath is constant, the use of a spinneret with a smaller orifice diameter will reduce the draw ratio of the primary fiber, which is beneficial to reduce the damage of fiber drawing, but as mentioned above, too low draw ratio of the primary fiber will easily lead to an increase in the amount of hair; from the perspective of cleaning the spinneret, the spinneret with a small diameter is difficult to clean, and it is easy to produce hair due to incomplete cleaning of the spinneret.

[0048] In an embodiment, N is greater than 1, the draw ratio of the fiber in the N-1th coagulation bath is R n-1 , and the draw ratio of the fiber in the Nth coagulation bath is R n , wherein R n-1 / R n is 1.05-12.

[0049] In an embodiment, the medium of the first coagulation bath and the Nth coagulation bath is dimethyl sulfoxide aqueous solution.

[0050] In an embodiment, the concentration of dimethyl sulfoxide aqueous solution in the first coagulation bath is 40-80%; and / or, N is greater than 1, the concentration of dimethyl sulfoxide aqueous solution in the N-1th coagulation bath is C N-1 , and the concentration of dimethyl sulfoxide aqueous solution in the Nth coagulation bath is C N , wherein C N-1 / C N is 1-4. In the above embodiment, by limiting the stepwise change of the concentration of dimethyl sulfoxide aqueous solution in the N coagulation baths, the fiber can gradually improve the crystallinity and orientation degree while reducing defects such as broken yarn and fusion.

[0051] In an embodiment, the coagulation temperature of the first coagulation bath is 20-70℃, and / or the coagulation temperature of the N-1th coagulation bath is T n-1 , and the coagulation temperature of the Nth coagulation bath is T n , wherein T n / T n-1 is 1-3. In the above embodiment, by limiting the stepwise change of the coagulation temperature of the N coagulation baths, the crystallinity and orientation degree of the fiber can be further improved, the grain size can be controlled, and defects such as broken yarn and fusion can be reduced.

[0052] Illustratively, N satisfies: 1≤N≤3.

[0053] In an embodiment, the primary fiber stays in the coagulation bath for 3-24 s.

[0054] In one embodiment, the drawing ratio of the fiber in the steam drawing is 2-5. The drawing of the fiber can make the fiber reach higher crystallinity and orientation by the plasticizing effect of the high-pressure steam water molecules.

[0055] In a second aspect, the present application provides a carbon fiber prepared from the precursor fiber obtained by the wet spinning method of the first aspect.

[0056] Further, the precursor fiber is subjected to oxidation treatment at 200-280℃, primary carbonization treatment at 300-800℃, and secondary carbonization treatment at 1000-1500℃ in sequence to obtain the carbon fiber.

[0057] The present application is described in detail below in combination with specific examples:

[0058] The following experiments relate to the testing methods of the parameters:

[0059] <Intrinsic viscosity>

[0060] The polymer powder / film is dried at 120℃ for 2h to constant weight, 40-50mg sample is dissolved in 50mL dimethylformamide solution, and the intrinsic viscosity is measured at 50℃ by using an Ubbelohde viscometer.

[0061]

[0062] Wherein η sp = (t / t0)-1; η r = t / t0.

[0063] <Rotational viscosity>

[0064] The rotational viscosity of the spinning solution is tested by using a Kinexus Jl009 rheometer, the shear rate is 10S -1 , and the testing temperature is 60℃.

[0065] <Swelling degree>

[0066] 10-20cm tow is put into a centrifuge for centrifugation at 3000rpm for 10min to remove the coagulation bath or water adsorbed on the surface of the tow, and the mass is weighed as A. The centrifuged fiber is put into a Soxhlet extractor and refluxed with deionized water for 4h. The tow is taken out and dried in an oven at 120℃ for 2h to obtain the dry tow mass B, and the swelling degree is obtained by (A-B) / B·100%.

[0067] <Setting value>

[0068] The PAN solution was diluted with dimethyl sulfoxide (DMSO) to form a 1% (mass) solution. 50 g of the solution was gradually added dropwise into 70% dimethyl sulfoxide aqueous solution at 25°C under constant stirring until the solution became turbid. The mass of the dimethyl sulfoxide aqueous solution added dropwise was recorded as the coagulation value.

[0069] <Stretching strength and tensile modulus>

[0070] The GB3362-2017 "Carbon Fiber Filament Tensile Property Test Method" was used.

[0071] Example 1

[0072] This example provides a wet spinning method, which includes the following steps:

[0073] 1) 30 parts of acrylonitrile, 0.5 parts of itaconic acid, 70 parts of dimethyl sulfoxide, and 0.18 parts of azobisisobutyronitrile were mixed uniformly at 25°C or below, and were continuously pumped into a tubular reactor with an inner diameter of 8 mm. The reactor tube had a fluorinated coating on the inside, and the outer wall was connected to a circulating heat conduction oil. The reaction pressure was set to 0.6 MPa, the heat conduction oil temperature was 105°C, the material residence time in the reaction tube was 15 min, and the solution was then entered into a cooling tube at 60°C for 1 min. A copolymer solution with a solid content of 18% and a intrinsic viscosity of 1.46 dl / g was obtained. The above copolymer solution was subjected to removal of unreacted acrylonitrile monomers at 65°C and 1 kPa pressure. The polymer solution had a solid content of 20.5%, an intrinsic viscosity of 1.41 dl / g, and an acrylonitrile monomer content of 1200 ppm. After the removal of the monomers, the solution was input into a defoaming kettle and was defoamed at 65°C and 1 kPa pressure for 5 h. The polymer solution had a solid content of 21%, a rotational viscosity of 38 Pa.s, an intrinsic viscosity of 1.40 dl / g, a number average molecular weight Mn of 62000, a weight average molecular weight Mw of 80600, a Mw / Mn of 1.3, and a Mz / Mw of 1.22.

[0074] 2) The defoamed polymer solution was mixed with ammonia gas to react with the carboxyl groups on the PAN chain to improve its hydrophilicity. The ammonia gas and itaconic acid unit had a molar ratio of 1.4:1. After the amination, a polyacrylonitrile spinning solution was obtained, which had a coagulation value of 33 g, a solid content of 21%, a rotational viscosity of 38 Pa.s, and an intrinsic viscosity of 1.40 dl / g. The spinning solution was filtered through a 5 μm precision filter, the temperature of the spinning solution was adjusted to 45°C through a static mixer, and was then sent to a pre-spinning jet unit.

[0075] 3) using 1 k spinneret with a hole diameter of 0.1 mm, the polyacrylonitrile spinning solution is ejected from the spinneret at a speed of 14 m / min, and the nascent fiber is obtained by being coagulated in a first coagulation bath, wherein the temperature of the first coagulation bath is 45°C, the coagulation liquid is a dimethyl sulfoxide aqueous solution with a concentration of 68%, and the nascent fiber stays in the coagulation bath for 12 s; the nascent fiber is taken out of the bath at a speed of 20 m / min, is drawn by 1.43 times, and has a swelling degree of 230%; the nascent fiber enters a second coagulation bath, the coagulation liquid is a dimethyl sulfoxide aqueous solution with a concentration of 30%, the temperature is 60°C, the nascent fiber is drawn by 2 times, enters a third coagulation bath, the coagulation liquid is a dimethyl sulfoxide aqueous solution with a concentration of 10%, the temperature is 80°C, and the nascent fiber is drawn by 1.5 times.

[0076] 4) the fiber drawn through the coagulation bath is sequentially subjected to water washing, oiling, and densification, is drawn by 3.33 times under a saturated water vapor pressure of 0.5 Mpa, is shaped at 150°C, and is wound after being shaped, the winding speed is 197 m / min, and the original yarn linear density is 1.2 dtex.

[0077] Example 2

[0078] This example provides a wet spinning method, which comprises the following steps:

[0079] 1) 30 parts of acrylonitrile, 0.5 parts of itaconic acid, 70 parts of dimethyl sulfoxide (DMSO), and 0.2 parts of azobisisobutyronitrile are uniformly mixed at below 25°C, are continuously pumped into a tubular reactor with an inner diameter of 8 mm, the inside of the reactor tube is coated with fluorination, the outer wall of the tube is connected with circulating heat conduction oil, the reaction pressure is set to 0.6 Mpa, the temperature of the heat conduction oil is 110°C, the material stays in the reaction tube for 12.5 min, enters a cooling tube at 60°C, and stays for 1 min, to obtain a copolymer solution with a solid content of 20.4% and a characteristic viscosity of 1.32 dl / g. The above copolymer solution is subjected to removal of unreacted acrylonitrile monomers at 65°C and 1 kPa, the solid content of the polymer solution is 21.9%, the characteristic viscosity is 1.3 dl / g, the acrylonitrile monomer content is 1100 ppm, the solution after monomer removal is input into a defoaming kettle, is defoamed at 65°C and 1 kPa for 5 h, to obtain a polymer solution with a characteristic viscosity of 1.28 dl / g and a rotary viscosity of 40 Pa.s, Mn = 56000, Mw = 75600, Mw / Mn = 1.35, and Mz / Mw = 1.28.

[0080] 2) the defoamed polymer solution is mixed with ammonia gas, the molar ratio of ammonia gas to itaconic acid unit is 1.5:1, and the polyacrylonitrile spinning solution is obtained after ammoniation, the coagulation value of which is 36 g, the solid content is 22%, the characteristic viscosity is 1.28 dl / g, and the rotary viscosity is 40 Pa.s; the spinning solution is filtered through a 5 μm precision filter, the temperature of the spinning solution is adjusted to 45°C through a static mixer, and is sent to a pre-spinning jet unit.

[0081] 3) using 1 k spinneret with a 0.1 mm aperture, the polyacrylonitrile spinning solution is ejected from the spinneret at a speed of 21.4 m / min, and the nascent fiber is obtained by being coagulated in a first coagulation bath, wherein the first coagulation bath has a temperature of 45°C, the coagulation liquid is a dimethyl sulfoxide aqueous solution with a concentration of 68%, and the nascent fiber stays in the coagulation bath for 8 s; the nascent fiber has an out-of-bath speed of 30 m / min, is drawn by 1.4 times, and has a swelling degree of 220%; the nascent fiber enters a second coagulation bath, the coagulation liquid is a dimethyl sulfoxide aqueous solution with a concentration of 30%, and the temperature is 60°C; the nascent fiber is drawn by 2 times, enters a third coagulation bath, the coagulation liquid is a dimethyl sulfoxide aqueous solution with a concentration of 10%, and the temperature is 80°C; and the nascent fiber is drawn by 1.5 times.

[0082] 4) the fiber drawn through the coagulation bath is sequentially subjected to water washing, oiling, and densification, is drawn by 3.33 times under a saturated water vapor pressure of 0.5 MPa, is shaped at 150°C, and is wound after being shaped, the winding speed is 300 m / min, and the original yarn linear density is 1.2 dtex.

[0083] Example 3

[0084] This example provides a wet spinning method, including the following steps:

[0085] 1) 30 parts of acrylonitrile, 0.5 parts of itaconic acid, 1 part of methyl acrylate, 70 parts of dimethyl sulfoxide (DMSO), and 0.2 parts of azobisisobutyronitrile are uniformly mixed below 25°C, continuously pumped into a tubular reactor with an inner diameter of 8 mm, the inside of the reactor tube is coated with fluorination, the outer wall of the tube is connected with circulating heat conduction oil, the reaction pressure is set to 0.6 MPa, the heat conduction oil temperature is 110°C, the material stays in the reaction tube for 15 min, enters a cooling tube at 60°C, and stays for 1 min, to obtain a copolymer solution with a solid content of 21.5% and a characteristic viscosity of 1.26 dl / g. The above copolymer solution is subjected to removal of unreacted acrylonitrile monomers at 65°C and 1 kPa pressure, the polymer solution has a solid content of 24.2%, a characteristic viscosity of 1.25 dl / g, and an acrylonitrile monomer content of 900 ppm. After the monomer removal, the solution is input into a defoaming kettle, and is defoamed at 65°C and 1 kPa pressure for 5 h to obtain a polymer solution with a rotational viscosity of 50 Pa.s, a characteristic viscosity of 1.23 dl / g, Mn = 48400, Mw = 68700, Mw / Mn = 1.42, and Mz / Mw = 1.26.

[0086] 2) the defoamed polymer solution is mixed with ammonia gas, the molar ratio of ammonia gas to itaconic acid unit is 1.3:1, and the ammoniated polyacrylonitrile spinning solution obtained after ammoniation has a coagulation value of 28 g, a solid content of 24.5%, a rotational viscosity of 50 Pa.s, and a characteristic viscosity of 1.23 dl / g, is filtered through a 5 μm precision filter, the temperature of the spinning solution is adjusted to 50°C through a static mixer, and is sent to a pre-spinning spinning unit.

[0087] 3) using 1 k spinneret with a 0.1 mm aperture, the polyacrylonitrile spinning solution is ejected from the spinneret at a speed of 15 m / min, and the nascent fiber is obtained by being coagulated in a first coagulation bath, wherein the first coagulation bath temperature is 50°C, the coagulation liquid is a dimethyl sulfoxide aqueous solution with a concentration of 68%, and the nascent fiber stays in the coagulation bath for 13.4 s; the nascent fiber exits the bath at a speed of 18 m / min, is drawn 1.2 times, and has a swelling degree of 198%; the nascent fiber enters a second coagulation bath, the coagulation liquid is a dimethyl sulfoxide aqueous solution with a concentration of 30%, the temperature is 60°C, and the nascent fiber is drawn 2 times; the nascent fiber enters a third coagulation bath, the coagulation liquid is a dimethyl sulfoxide aqueous solution with a concentration of 10%, the temperature is 80°C, and the nascent fiber is drawn 1.5 times.

[0088] 4) the drawn fiber is subjected to water washing, oiling, and densification in sequence, is drawn 3.33 times under a saturated water vapor pressure of 0.5 Mpa, is set at 150°C, and is wound after spinning at a speed of 180 m / min, and the original yarn linear density is 1.2 dtex.

[0089] Example 4

[0090] This example provides a wet spinning method, including the following steps:

[0091] 1) 30 parts of acrylonitrile, 0.5 parts of itaconic acid, 70 parts of dimethyl sulfoxide (DMSO), and 0.12 parts of azobisisobutyronitrile are uniformly mixed at 25°C or below, continuously pumped into a tubular reactor with an inner diameter of 8 mm, the inside of the reactor tube is coated with fluorination, the outer wall of the tube is circulated with heat conduction oil, the reaction pressure is set to 0.6 Mpa, the heat conduction oil temperature is 110°C, the material stays in the reaction tube for 15 min, enters a cooling tube at 60°C, and stays for 1 min, to obtain a copolymer solution with a solid content of 18.1% and a characteristic viscosity of 1.57 dl / g. The above copolymer solution is subjected to removal of unreacted acrylonitrile monomer at 65°C and 1 kPa pressure, the polymer solution has a solid content of 20.9%, a characteristic viscosity of 1.56 dl / g, and an acrylonitrile monomer content of 1500 ppm. After the monomer removal, the solution is input into a defoaming kettle, defoamed at 65°C and 1 kPa pressure for 5 h, to obtain a polymer solution with a rotational viscosity of 76 Pa.s, a characteristic viscosity of 1.55 dl / g, Mn = 88000, Mw = 108200, Mw / Mn = 1.23, and Mz / Mw = 1.28.

[0092] 2) the defoamed polymer solution is mixed with ammonia gas, the ammonia gas reacts with the carboxyl groups on the PAN chain to improve the hydrophilicity, the ammonia gas and itaconic acid unit molar ratio is 1.4:1, and the ammoniated polyacrylonitrile spinning solution obtained has a coagulation value of 30 g, a solid content of 21%, a rotational viscosity of 76 Pa.s, and a characteristic viscosity of 1.55 dl / g, is filtered through a 5 μm precision filter, the temperature of the spinning solution is adjusted to 50°C through a static mixer, and is sent to a pre-spinning jet unit.

[0093] 3) using 1 k spinneret with a 0.1 mm aperture, the polyacrylonitrile spinning solution is ejected from the spinneret at a speed of 15.4 m / min, and the nascent fiber is obtained by being coagulated in a first coagulation bath, wherein the first coagulation bath temperature is 50°C, the coagulation liquid is a dimethyl sulfoxide aqueous solution with a concentration of 68%, and the nascent fiber stays in the coagulation bath for 10.5 s; the nascent fiber has an out-of-bath speed of 22.9 m / min, is drawn by 1.31 times, and has a swelling degree of 217%; the nascent fiber enters a second coagulation bath, the coagulation liquid is a dimethyl sulfoxide aqueous solution with a concentration of 30%, the temperature is 60°C, the nascent fiber is drawn by 2 times, enters a third coagulation bath, the coagulation liquid is a dimethyl sulfoxide aqueous solution with a concentration of 10%, the temperature is 80°C, and the nascent fiber is drawn by 1.5 times.

[0094] 4) the fiber drawn through the coagulation bath is sequentially subjected to water washing, oiling, and densification, is drawn by 3.2 times under a saturated water vapor pressure of 0.5 Mpa, is shaped at 150°C, and is wound after the shaping to collect the yarn, the yarn collection speed is 220 m / min, and the original yarn linear density is 1.1 dtex.

[0095] Example 5

[0096] This example provides a wet spinning method, including the following steps:

[0097] 1) 30 parts of acrylonitrile, 0.5 parts of itaconic acid, 70 parts of dimethyl sulfoxide (DMSO), and 0.12 parts of azobisdimethyl isobutyronitrile are uniformly mixed at 25°C or below, and are continuously pumped into a tubular reactor with an inner diameter of 8 mm by using a plunger pump, the inside of the reactor tube is coated with fluorination, the outer wall of the tube is connected with circulating heat conduction oil, the reaction pressure is set to 0.6 Mpa, the heat conduction oil temperature is 110°C, the material stays in the reaction tube for 15 min, enters a cooling tube at 60°C, and stays for 1 min, to obtain a copolymer solution with a solid content of 18.1% and a specific viscosity of 1.57 dl / g. The above copolymer solution is subjected to removal of unreacted acrylonitrile monomers at 65°C and 1 kPa pressure, the polymer solution has a solid content of 20.9%, a specific viscosity of 1.56 dl / g, and an acrylonitrile monomer content of 1500 ppm. After the monomer removal, the solution is input into a defoaming kettle, is defoamed at 65°C and 1 kPa pressure for 5 h, to obtain a polymer solution with a rotational viscosity of 76 Pa.s, a specific viscosity of 1.55 dl / g, Mn = 88000, Mw = 108200, Mw / Mn = 1.23, and Mz / Mw = 1.28.

[0098] 2) the defoamed polymer solution is mixed with ammonia gas, the ammonia gas reacts with the carboxyl groups on the PAN chain to improve the hydrophilicity, the ammonia gas and itaconic acid units have a molar ratio of 1.4:1, and the ammoniation obtains a polyacrylonitrile spinning solution with a coagulation value of 30 g, a solid content of 21%, a rotational viscosity of 76 Pa.s, and a specific viscosity of 1.55 dl / g, which is filtered through a 5 μm precision filter, the temperature of the spinning solution is adjusted to 50°C by using a static mixer, and the spinning solution is sent to a pre-spinning spinning unit.

[0099] 3) using 1 k spinneret with a hole diameter of 0.065 mm, the polyacrylonitrile spinning solution is ejected from the spinneret at a speed of 36.5 m / min, and the as-spun fiber is obtained by coagulating in a first coagulation bath, wherein the first coagulation bath temperature is 50°C, the coagulation liquid is a dimethyl sulfoxide aqueous solution with a concentration of 68%, and the as-spun fiber stays in the coagulation bath for 7.8 s; the as-spun fiber has an out-of-bath speed of 30.5 m / min, is drawn by 0.63 times, and has a swelling degree of 205%; the as-spun fiber enters a second coagulation bath, the coagulation liquid is a dimethyl sulfoxide aqueous solution with a concentration of 30%, the temperature is 60°C, and the as-spun fiber is drawn by 2 times; the as-spun fiber enters a third coagulation bath, the coagulation liquid is a dimethyl sulfoxide aqueous solution with a concentration of 10%, the temperature is 80°C, and the as-spun fiber is drawn by 1.5 times.

[0100] 4) the drawn fiber after the coagulation bath is subjected to water washing, oiling, and densification in sequence, is drawn by 3.33 times under a saturated water vapor pressure of 0.5 MPa, is set at 150°C, and is wound after being collected at a speed of 305 m / min, and the original yarn linear density is 1.15 dtex.

[0101] Comparative Example 1

[0102] This example provides a wet spinning method, comprising the following steps:

[0103] 1) 20 parts of acrylonitrile, 0.5 parts of itaconic acid, and 80 parts of water are mixed uniformly in a batch reactor at 25°C or below, and the temperature is raised to 50°C; 0.2 parts of ammonium persulfate and 0.2 parts of ammonium bisulfite are added, and the reaction is carried out for 2 hours; the polymer slurry is filtered, washed, and dried to obtain a polymer with a molecular weight Mn = 73,000, Mw = 175,200, Mw / Mn = 2.4, and Mz / Mw = 1.69.

[0104] 2) the polymer powder is dissolved in DMSO to prepare a solution with a solid content of 20.9%, the solution is degassed at 65°C and 1 kPa for 5 hours, ammonia gas is introduced for hydrophilic modification of the spinning solution, the molar ratio of ammonia gas to itaconic acid units is 1.5:1, and the ammoniated polyacrylonitrile spinning solution is obtained, which has a 45°C rotational viscosity of 98 Pa.s, a specific viscosity of 2.1 dl / g, and a coagulation value of 24 g; the spinning solution is filtered through a 5 μm precision filter, the temperature of the spinning solution is adjusted to 60°C through a static mixer, and the spinning solution is sent to a pre-spinning jet unit.

[0105] 3) using 1 k spinneret with a hole diameter of 0.065 mm, the polyacrylonitrile spinning solution is ejected from the spinneret at a speed of 14.9 m / min, and the primary fiber is obtained through 1 coagulation bath, wherein the first coagulation bath temperature is 60°C, the coagulation liquid is a dimethyl sulfoxide aqueous solution with a concentration of 55%, the primary fiber out-of-bath speed is 8.85 m / min, the drawing is 0.6 times, and the primary fiber swelling degree is 187%; the primary fiber enters the second coagulation bath, the coagulation liquid is a dimethyl sulfoxide aqueous solution with a concentration of 30%, the temperature is 60°C, the drawing is 2 times, and the secondary fiber obtained enters the third coagulation bath, the coagulation liquid is a dimethyl sulfoxide aqueous solution with a concentration of 10%, the temperature is 80°C, the drawing is 1.5 times, and the tertiary fiber is obtained.

[0106] 3) The tertiary fiber drawn through the coagulation bath is sequentially subjected to water washing, oiling, and densification, is drawn 3.2 times under a saturated water vapor pressure of 0.5 MPa, is shaped at 150°C, and is wound after being shaped, and the original yarn linear density is 1.16 dtex.

[0107] Comparative Example 2

[0108] This example provides a wet spinning method, comprising the following steps:

[0109] 1) 20 parts of acrylonitrile, 0.5 parts of itaconic acid, 80 parts of dimethyl sulfoxide (DMSO), and 0.12 parts of azobisisobutyronitrile are mixed uniformly in a batch reaction kettle below 25°C, and are heated to 65°C for reaction for 22 hours, to obtain a copolymer solution with a solid content of 18.6% and a characteristic viscosity of 1.95 dl / g. The copolymer solution is subjected to removal of unreacted acrylonitrile monomers at 65°C and a pressure of 1 kPa, the polymer solution has a solid content of 19.2%, a characteristic viscosity of 1.9 dl / g, and an acrylonitrile monomer content of 650 ppm. After the monomer removal, the solution is input into a defoaming kettle and is defoamed at 65°C and a pressure of 1 kPa for 5 hours, to obtain a polymer solution with a characteristic viscosity of 1.91 dl / g, Mn = 73,000, Mw = 189,800, Mw / Mn = 2.6, and Mz / Mw = 1.54.

[0110] 2) The defoamed polymer solution is mixed with ammonia gas, the ammonia gas reacts with the carboxyl groups on the PAN chain to improve the hydrophilicity, the ammonia gas and the itaconic acid unit have a molar ratio of 1.5:1, the spinning solution after the amination has a coagulation value of 28 g, is filtered through a 5 μm precision filter, the temperature of the spinning solution is adjusted to 60°C through a static mixer, and is sent to a pre-spinning jet unit.

[0111] 3) using 1k spinneret with 0.065mm aperture, the polyacrylonitrile spinning solution is ejected from the spinneret at a speed of 16.5m / min, and the primary fiber is obtained by 1-time coagulation bath, wherein the first coagulation bath temperature is 60℃, the coagulation liquid is dimethyl sulfoxide aqueous solution with a concentration of 65%, the primary fiber out-bath speed is 9.9m / min, the drawing is 0.6 times, and the primary fiber swellability is 219%; the primary fiber enters the second coagulation bath, the coagulation liquid is dimethyl sulfoxide aqueous solution with a concentration of 30%, the temperature is 60℃, the drawing is 2 times, the obtained secondary fiber enters the third coagulation bath, the coagulation liquid is dimethyl sulfoxide aqueous solution with a concentration of 10%, the temperature is 80℃, and the drawing is 1.5 times, thereby obtaining the tertiary fiber.

[0112] 4) the fiber drawn through the coagulation bath is sequentially subjected to water washing, oiling, and densification, and is drawn by 3.2 times under 0.5Mpa saturated water vapor pressure, and is wound after setting at 150℃, thereby obtaining the original fiber with a linear density of 1.15dtex.

[0113] Test Example 1

[0114] The original fiber of the above examples and comparative examples is oxidized at 220-260℃, low-temperature carbonized at 320-690℃, and high-temperature carbonized at 1100-1250℃, thereby obtaining carbon fiber; the tensile strength, tensile modulus, and elongation at break of the prepared carbon fiber are tested, and the test results are shown in Table 1.

[0115] Table 1:

[0116]

[0117] As shown in Table 1, the wet spinning method of the examples has a higher original fiber winding speed than the comparative examples, and the fiber stability is maintained well.

[0118] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A wet spinning method characterized by, The method comprises the following steps: 1) preparing a polyacrylonitrile spinning solution, wherein the polyacrylonitrile spinning solution comprises a copolymer of a carboxyl-containing monomer and acrylonitrile, the copolymer has a number average molecular weight of 20,000-500,000 and a molecular weight distribution Mw / Mn of 1.0-1.9; the polyacrylonitrile spinning solution has a solid content of 20%-33%, a coagulation value of 20-80 g and an intrinsic viscosity of 1.0-1.6 dL / g; 2) the polyacrylonitrile spinning solution is jetted from a spinneret at a speed of 10-40 m / min and coagulated in a first coagulation bath to obtain a nascent fiber; 3) the nascent fiber is drawn in an N-stage coagulation bath, washed, oiled, densified, steam-drawn and set, and then wound to obtain a precursor, wherein the winding speed is not less than 180 m / min; In step 3), N is not less than 1; the nascent fiber has a swelling degree of 180-250%, and the nascent fiber has a draw ratio of 0.4-4 in the first coagulation bath.

2. The wet spinning method according to claim 1, characterized by, The polyacrylonitrile spinning solution has a rotational viscosity of 20-150 Pa·s; And / or, the polyacrylonitrile spinning solution has an intrinsic viscosity of 1.1-1.5 dL / g; And / or, the polyacrylonitrile spinning solution has a solid content of 22%-30%.

3. The wet spinning method according to claim 1, characterized by, The carboxyl-containing monomer is one or more of acrylic acid, methacrylic acid, itaconic acid, itaconic acid monomethyl ester, itaconic acid monoethyl ester, itaconic acid mono-n-propyl ester, itaconic acid mono-i-propyl ester, itaconic acid mono-n-butyl ester, itaconic acid mono-i-butyl ester, itaconic acid mono-t-butyl ester, maleic acid, methyl maleic acid, maleic anhydride, fumaric acid and methyl fumaric acid.

4. The wet spinning method according to any one of claims 1 to 3, characterized in that, The polyacrylonitrile spinning solution is prepared by a method comprising the following steps: The carboxyl-containing monomer, acrylonitrile, an initiator and a solvent are continuously pumped into a tubular reactor with an inner diameter of 1-10 mm, and the polymerization reaction is carried out under the conditions of a pressure of 0.1-1 MPa and a temperature of 60-120 ℃, and then the reaction system after cooling and monomer removal is subjected to defoaming treatment; the defoamed reaction system is mixed with ammonia gas to obtain the polyacrylonitrile spinning solution.

5. The wet spinning method according to any one of claims 1 to 3, characterized in that, The spinneret has a pore diameter of 0.04-0.2 mm.

6. The wet spinning method according to any one of claims 1 to 3, characterized in that, N is greater than 1, the draw ratio of the fiber in the (N-1)th coagulating bath is R n-1 , the draw ratio of the fiber in the Nth coagulating bath is R n , wherein R n-1 / R n is 1.05 to 12.

7. The wet spinning method according to any one of claims 1 to 3, characterized by, The media of the first coagulation bath and the N-stage coagulation bath are dimethyl sulfoxide aqueous solutions.

8. The wet spinning process according to claim 7, characterized in that, The concentration of the aqueous dimethyl sulfoxide solution in the first coagulating bath is 40-80%; and / or, N is greater than 1, the concentration of the aqueous dimethyl sulfoxide solution in the (N-1)th coagulating bath is C N-1 , the concentration of the aqueous dimethyl sulfoxide solution in the Nth coagulating bath is C N , wherein C N-1 / C N is 1-4.

9. The wet spinning process according to claim 8, characterized in that, The coagulation temperature of the first coagulation bath is 20-70°C, and / or the coagulation temperature of the (N-1)th coagulation bath is T n-1 , the coagulation temperature of the Nth coagulation bath is T n , T n / T n-1 is 1-3.

10. The wet spinning method according to any one of claims 1 to 3, characterized in that, In the steam drawing, the fiber has a draw ratio of 2-5 times.

11. A carbon fiber, characterized by, The precursor is prepared by the wet spinning method according to any one of claims 1-10.

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