A method for preparing a polyacrylonitrile spinning solution and a method for preparing an ultra-high molecular weight polyacrylonitrile filament

Abstract

The present application relates to the technical field of carbon fibers, and provides a preparation method of polyacrylonitrile spinning solution and a preparation method of ultra-high molecular weight polyacrylonitrile filaments.The present application adopts a vacuum defoaming homogenizer to dissolve and defoam polyacrylonitrile powder, which can effectively simplify and shorten the process of preparing polyacrylonitrile spinning solution and improve the preparation efficiency.Moreover, the present application uses ultra-high molecular weight polyacrylonitrile powder as raw material to prepare the spinning solution, and then prepares ultra-high molecular weight polyacrylonitrile filaments through the steps of spinning, first coagulation drafting, second coagulation drafting, water washing drafting, oiling, drying and steam drafting, and the obtained ultra-high molecular weight polyacrylonitrile filaments have high tensile strength and excellent performance.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber technology, and in particular to a method for preparing a polyacrylonitrile spinning solution and ultra-high molecular weight polyacrylonitrile precursor fiber and its preparation method. Background Technology

[0002] Polyacrylonitrile-based carbon fiber is a typical high-performance fiber that possesses both the inherent properties of carbon materials and the flexibility of fibers. Combining polyacrylonitrile-based carbon fiber with materials such as resins, metals, and ceramics yields composite materials with extremely excellent properties, capable of serving as structural materials to bear loads and also meeting special functional requirements such as corrosion resistance and thermal insulation.

[0003] The production process of carbon fiber mainly includes: first, preparing a polyacrylonitrile (PA) spinning solution; then, solution spinning of the spinning solution to obtain PA precursor fibers; and finally, pre-oxidation and carbonization of the PA precursor fibers to obtain carbon fibers. As can be seen from the preparation process, the preparation of the PA spinning solution is the fundamental step in carbon fiber production and a key step determining the efficiency of carbon fiber production. However, currently, the preparation of PA spinning solutions involves dissolving the PA in a solvent by stirring, followed by vacuum degassing. This dissolution time for PA is relatively long, resulting in low spinning solution preparation efficiency. Furthermore, the current PA precursor fibers have poor mechanical properties, which in turn affects the performance of the final carbon fibers. Summary of the Invention

[0004] In view of this, the present invention provides a method for preparing a polyacrylonitrile spinning solution and an ultra-high molecular weight polyacrylonitrile precursor fiber and the same method. The method for preparing the polyacrylonitrile spinning solution provided by the present invention is simple to operate, has a short dissolution time, and high preparation efficiency; the polyacrylonitrile precursor fiber provided by the present invention has good mechanical properties and high tensile strength.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] A method for preparing a polyacrylonitrile spinning solution includes the following steps:

[0007] Polyacrylonitrile powder and solvent are added to a reaction vessel, and then the reaction vessel is placed in a vacuum degassing homogenizer for mixing, dissolving and vacuum degassing to remove impurities, thereby obtaining a polyacrylonitrile spinning solution.

[0008] The revolution speed of the vacuum degassing homogenizer during mixing is 10–1000 rpm, and the rotation speed is 10–1000 rpm; the mixing time is 0.1–1 h.

[0009] The revolution speed of the vacuum degassing homogenizer during dissolution is 20–10000 rpm, and its rotation speed is 20–10000 rpm; the dissolution time is 0.2–3 hours; the revolution speed of the vacuum degassing homogenizer during dissolution is greater than the revolution speed of the vacuum degassing homogenizer during mixing; the rotation speed of the vacuum degassing homogenizer during dissolution is greater than the rotation speed of the vacuum degassing homogenizer during mixing.

[0010] The revolution speed of the vacuum degassing homogenizer during the vacuum degassing and impurity removal process is 500 to 20000 rpm, and the vacuum degree is -0.1 to -200 kPa; the vacuum degassing and impurity removal time is 0.1 to 2 hours.

[0011] Preferably, the polyacrylonitrile powder includes one or more of polyacrylonitrile homopolymer powder and polyacrylonitrile copolymer powder; the solvent includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, dimethyl tetrasulfide, aqueous zinc chloride solution, aqueous sodium thiocyanate solution, and aqueous nitric acid solution.

[0012] Preferably, the raw materials for preparing the polyacrylonitrile spinning solution further include water, wherein the mass of the water is 0 to 5% of the total mass of the solution obtained by dissolving.

[0013] This invention also provides a method for preparing ultra-high molecular weight polyacrylonitrile precursor fibers, comprising the following steps:

[0014] Using ultra-high molecular weight polyacrylonitrile powder as raw material, a spinning solution is prepared according to the method described above; the viscosity-average molecular weight of the ultra-high molecular weight polyacrylonitrile powder is 500,000 to 1,500,000.

[0015] The spinning solution is spun into filaments, and the spun filaments are subjected to a first coagulation and stretching process to obtain nascent fibers.

[0016] The nascent fibers are subjected to a second coagulation stretching, water washing stretching, oiling, drying and steam stretching in sequence to obtain the ultra-high molecular weight polyacrylonitrile precursor fiber.

[0017] Preferably, the solid content of the spinning solution is 4-25%.

[0018] Preferably, spinning the spinning solution includes: storing the spinning solution under heat preservation conditions and conveying it to a spinning assembly for spinning; the heat preservation temperature is 40-100°C; the spinning assembly includes a conveying channel and a spinneret, and the temperature of the spinning assembly is 40-150°C.

[0019] Preferably, the spinning is carried out in air, and the air layer height of the spinning is 1-20 mm;

[0020] The first coagulation bath used for the first coagulation stretching is a mixture of solvent and water. The solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, dimethyl tetrasulfide, zinc chloride aqueous solution, sodium thiocyanate aqueous solution, and nitric acid aqueous solution. The mass ratio of solvent to water in the first coagulation bath is 2-8:8-2. The temperature of the first coagulation bath is 20-100°C. The stretching ratio of the first coagulation stretching is 1-10 times.

[0021] Preferably, the second solidification drawing is a multi-stage solidification drawing, wherein the number of stages in the multi-stage solidification drawing is 2 to 8; the coagulation bath used in the multi-stage solidification drawing is a mixture of solvent and water, wherein the solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, dimethyl tetrasulfide, zinc chloride aqueous solution, sodium thiocyanate aqueous solution, and nitric acid aqueous solution; the mass ratio of solvent to water in the coagulation bath used in the multi-stage solidification drawing is 2 to 8:8 to 2; and the total draw ratio of the multi-stage solidification drawing is 1 to 5 times.

[0022] Preferably, the temperature of the water washing and stretching is 20–100°C; the total stretching ratio of the water washing and stretching is 1–5 times.

[0023] The temperature of the oiling agent used for oiling is 20-80℃; the draw ratio of the oiling agent is 1-3 times.

[0024] Preferably, the drying temperature is 100-150°C and the draw ratio is 0-3 times;

[0025] The steam drawing ratio is 2 to 5 times; the steam drawing is carried out in a steam drawing chamber.

[0026] The present invention also provides ultra-high molecular weight polyacrylonitrile precursor fibers prepared by the preparation method described above.

[0027] This invention provides a method for preparing a polyacrylonitrile spinning solution, comprising the following steps: adding polyacrylonitrile powder and solvent into a reaction vessel, then placing the reaction vessel into a vacuum degassing homogenizer for sequential mixing, dissolution, and vacuum degassing to remove impurities, thereby obtaining a polyacrylonitrile spinning solution; during mixing, the revolution speed of the vacuum degassing homogenizer is 10–1000 rpm, and its rotation speed is 10–1000 rpm; the mixing time is 0.1–1 h; during dissolution, the revolution speed of the vacuum degassing homogenizer is 20–10000 rpm. The rotation speed of the vacuum degassing homogenizer is 20–10000 rpm; the dissolution time is 0.2–3 h; the revolution speed of the vacuum degassing homogenizer during dissolution is greater than that during mixing; the rotation speed of the vacuum degassing homogenizer during dissolution is greater than that during mixing; the revolution speed of the vacuum degassing homogenizer during vacuum degassing and impurity removal is 500–20000 rpm, and the vacuum degree is -0.1–-200 kPa; the vacuum degassing and impurity removal time is 0.1–2 h. This invention uses a vacuum degassing homogenizer to dissolve and degas polyacrylonitrile powder. By setting different revolution and rotation speeds, the polyacrylonitrile powder and solvent are stirred and dissolved. Revolution and rotation, on the one hand, can fully stir the solution to make it more uniform; on the other hand, increasing the rotation and revolution speeds can increase the intermolecular friction, thereby heating the solution and promoting dissolution. In the process of degassing and removing impurities from the polyacrylonitrile solution, increasing the vacuum level can extract air bubbles from the solution, while centrifugation at a higher revolution speed causes the air bubbles to detach from the solution. Larger impurities and incompletely dissolved polyacrylonitrile settle to the bottom and walls of the reaction vessel due to gravity and centrifugation. In summary, the method provided by this invention is simple to operate, effectively simplifies and shortens the process of preparing polyacrylonitrile spinning solution, and improves preparation efficiency.

[0028] This invention also provides a method for preparing ultra-high molecular weight polyacrylonitrile (UHMWPA) precursor fibers, comprising the following steps: using UHMWPA powder as raw material, preparing a spinning solution according to the method described above; the viscosity-average molecular weight of the UHMWPA powder is 500,000 to 1,500,000; spinning the spinning solution into fibers, subjecting the spun fibers to a first solidification and drawing process to obtain nascent fibers; subjecting the nascent fibers to a second solidification and drawing process, water washing and drawing process, oiling process, drying process, and steam drawing process to obtain the UHMWPA precursor fibers. This invention uses UHMWPA as raw material to prepare UHMWPA precursor fibers, resulting in UHMWPA precursor fibers with good mechanical properties and high tensile strength. Furthermore, UHMWPA has a longer molecular chain, and compared to ordinary molecular weight polyacrylonitrile, the proportion of its molecular chain ends is smaller. Since the molecular chain ends often become key defect sites during the conversion of polyacrylonitrile into carbon fibers, this invention's use of UHMWPA to prepare UHMWPA precursor fibers also helps reduce defects in the subsequent carbonization of the resulting carbon fibers, improving the quality of the carbon fibers.

[0029] Furthermore, ultra-high molecular weight polyacrylonitrile is sensitive to process parameters such as temperature, humidity, and drawing speed, making spinning difficult. This invention, by controlling the spinning parameters at each step, can achieve stable spinning process and obtain high-quality ultra-high molecular weight polyacrylonitrile precursor fibers. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the vacuum degassing homogenizer used in this invention. Detailed Implementation

[0031] This invention provides a method for preparing a polyacrylonitrile spinning solution, comprising the following steps:

[0032] Polyacrylonitrile powder and solvent are added to a reaction vessel, and then the reaction vessel is placed in a vacuum degassing homogenizer for mixing, dissolving and vacuum degassing to remove impurities to obtain polyacrylonitrile spinning solution.

[0033] The revolution speed of the vacuum degassing homogenizer during mixing is 10–1000 rpm, and the rotation speed is 10–1000 rpm; the mixing time is 0.1–1 h.

[0034] The revolution speed of the vacuum degassing homogenizer during dissolution is 20–10000 rpm, and its rotation speed is 20–10000 rpm; the dissolution time is 0.2–3 hours; the revolution speed of the vacuum degassing homogenizer during dissolution is greater than the revolution speed of the vacuum degassing homogenizer during mixing; the rotation speed of the vacuum degassing homogenizer during dissolution is greater than the rotation speed of the vacuum degassing homogenizer during mixing.

[0035] The revolution speed of the vacuum degassing homogenizer during the vacuum degassing and impurity removal process is 500 to 20000 rpm, and the vacuum degree is -0.1 to -200 kPa; the vacuum degassing and impurity removal time is 0.1 to 2 hours.

[0036] In this invention, the polyacrylonitrile powder preferably includes one or more of polyacrylonitrile homopolymer powder and polyacrylonitrile copolymer powder; the viscosity-average molecular weight of the polyacrylonitrile powder is preferably 50,000 to 1,500,000.

[0037] In this invention, the solvent preferably includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, dimethyltetrasulfide, zinc chloride aqueous solution, sodium thiocyanate aqueous solution, and nitric acid aqueous solution. This invention does not have specific requirements for the concentrations of the zinc chloride aqueous solution, sodium thiocyanate aqueous solution, and nitric acid aqueous solution, as long as they are sufficient to completely dissolve the polyacrylonitrile powder. In specific embodiments of this invention, the concentrations of the zinc chloride aqueous solution, sodium thiocyanate aqueous solution, and nitric acid aqueous solution can be 45–60 wt%, specifically 50 wt%. The preferred mass ratio of the polyacrylonitrile powder to the solvent is (5–50):(95–50), specifically 5:95, 7:93, 10:90, 12:88, 14:86, or 16:84. In specific embodiments of this invention, the polyacrylonitrile powder and solvent can be directly added to the reaction vessel without stirring. This invention does not have specific requirements for the specific specifications of the reaction vessel, as long as it can be placed in a vacuum degassing homogenizer.

[0038] In this invention, the raw materials for preparing the polyacrylonitrile spinning solution also include water, wherein the mass of the water is 0-5% of the total mass of the solution obtained by dissolving, preferably 0-4%, and specifically can be 3.5%, 2%, 1.5%, 1%, or 0.5%. This invention, by adding a trace amount of water, can control the properties of the spinning solution and simultaneously regulate the phase separation process.

[0039] In this invention, after adding polyacrylonitrile powder and solvent to a reaction vessel, the reaction vessel is placed in a vacuum degassing homogenizer and fixed therein. The vacuum degassing homogenizer used in this invention has freely adjustable rotation and revolution speeds and can provide different degrees of vacuum. Figure 1 This is a schematic diagram of the vacuum degassing homogenizer used in this invention.

[0040] In this invention, the revolution speed of the vacuum degassing homogenizer during mixing is 10–1000 rpm, preferably 100–400 rpm, specifically 200 rpm, 250 rpm, or 350 rpm; the rotation speed of the vacuum degassing homogenizer during mixing is 10–1000 rpm, preferably 100–400 rpm, specifically 200 rpm, 250 rpm, or 350 rpm; the mixing time is 0.1–1 h, preferably 0.15–0.3 h. In a specific embodiment of this invention, after fixing the reaction vessel in the vacuum degassing homogenizer, the revolution speed and rotation speed of the vacuum degassing homogenizer are adjusted within the above ranges to mix the polyacrylonitrile powder and the solvent. This invention controls the revolution speed and rotation speed of the vacuum degassing homogenizer within the above ranges, enabling thorough mixing of the polyacrylonitrile powder and the solvent.

[0041] In this invention, the revolution speed of the vacuum degassing homogenizer during dissolution is 20–10000 rpm, preferably 600–5000 rpm, specifically 700 rpm, 800 rpm, 1000 rpm, 2000 rpm, 3000 rpm, or 4000 rpm; the rotation speed of the vacuum degassing homogenizer during dissolution is 20–10000 rpm, preferably 600–5000 rpm, specifically 700 rpm, 800 rpm, 1000 rpm, 2000 rpm, 3000 rpm, or 4000 rpm; the dissolution time is 0.2–3 h, preferably 0.5 h–2 h. In this invention, increasing the rotation and revolution speeds of the vacuum degassing homogenizer increases intermolecular friction, thereby heating the solution and promoting the dissolution of polyacrylonitrile powder. In this invention, the revolution speed of the vacuum degassing homogenizer during dissolution is greater than that during mixing. Specifically, the revolution speed of the vacuum degassing homogenizer during dissolution is preferably 5 to 10 times that during mixing. The rotation speed of the vacuum degassing homogenizer during dissolution is greater than that during mixing. Specifically, the rotation speed of the vacuum degassing homogenizer during dissolution is preferably 5 to 10 times that during mixing. In a specific embodiment of this invention, after mixing is completed, the revolution speed and rotation speed of the vacuum degassing homogenizer are increased to dissolve the polyacrylonitrile powder.

[0042] In this invention, the revolution speed of the vacuum degassing homogenizer during vacuum degassing and impurity removal is 500–20000 rpm, preferably 1000–10000 rpm, specifically 2000 rpm, 3000 rpm, 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm, 8000 rpm, or 9000 rpm; in a specific embodiment of this invention, the revolution speed of the vacuum degassing homogenizer during vacuum degassing and impurity removal is preferably the same as that used during dissolution. The rotational speed of the vacuum degassing homogenizer is 1 to 10 times that of the homogenizer. During vacuum degassing and impurity removal, the vacuum degassing homogenizer does not rotate, i.e., its rotational speed is 0. The vacuum degree of the vacuum degassing homogenizer during vacuum degassing and impurity removal is -0.1 to -200 kPa, preferably -0.1 to -101 kPa, specifically -0.2 kPa, -0.5 kPa, -30 kPa, -50 kPa, or -80 kPa. The vacuum degassing and impurity removal time is 0.1 to 2 hours, preferably 0.3 to 1 hour. This invention, by increasing the vacuum degree, can extract bubbles from the polyacrylonitrile solution. Simultaneously, centrifugation of the solution at a higher rotational speed allows bubbles to detach from the polyacrylonitrile solution. Larger impurities and incompletely dissolved polyacrylonitrile settle to the bottom and walls of the reaction vessel due to gravity and centrifugation.

[0043] This invention also provides a method for preparing ultra-high molecular weight polyacrylonitrile precursor fibers, comprising the following steps:

[0044] Using ultra-high molecular weight polyacrylonitrile powder as raw material, a spinning solution is prepared according to the method described above; the viscosity-average molecular weight of the ultra-high molecular weight polyacrylonitrile powder is 500,000 to 1,500,000.

[0045] The spinning solution is spun into filaments, and the spun filaments are subjected to a first coagulation and stretching process to obtain nascent fibers.

[0046] The nascent fibers are subjected to a second coagulation stretching, water washing stretching, oiling, drying and steam stretching in sequence to obtain the ultra-high molecular weight polyacrylonitrile precursor fiber.

[0047] This invention uses ultra-high molecular weight polyacrylonitrile powder as raw material and prepares spinning solution according to the method described above; the preparation method of the spinning solution will not be repeated here; the viscosity-average molecular weight of the ultra-high molecular weight polyacrylonitrile powder is 500,000 to 1,500,000, preferably 500,000 to 1,300,000, and more preferably 600,000 to 1,000,000.

[0048] In this invention, the solid content of the spinning solution is preferably 4-25%, specifically 4.5%, 6%, 10%, 15% or 20%.

[0049] After obtaining the spinning solution, the present invention spins the spinning solution into fibers, and the spun fibers undergo a first solidification and stretching process to obtain nascent fibers. In the present invention, spinning the spinning solution preferably includes: storing the spinning solution under a heat-preserving condition and conveying it to a spinning assembly for spinning; the heat-preserving temperature is preferably 40–100°C, specifically 50°C, 60°C, 70°C, 80°C, or 90°C; the spinning assembly includes a conveying channel and a spinneret, and the temperature of the spinning assembly is preferably 40–150°C, specifically 40°C, 65°C, 70°C, 80°C, 100°C, 120°C, or 130°C.

[0050] In this invention, the spinning is preferably carried out in air, and the height of the air layer of the spinning is preferably 1 to 20 mm, specifically 1 mm, 3 mm, 5 mm, 10 mm, 15 mm or 18 mm.

[0051] In this invention, the first coagulation bath used for the first coagulation drawing is preferably a mixture of solvent and water. The solvent preferably includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, dimethyl tetrasulfide, zinc chloride aqueous solution, sodium thiocyanate aqueous solution, and nitric acid aqueous solution. Specifically, the solvent used in the first coagulation bath is the same as the solvent used to prepare the spinning solution. The mass ratio of solvent to water in the first coagulation bath is preferably 2-8:8-2, specifically 3:7, 4:6, 5:5, or 7:3. The temperature of the first coagulation bath is preferably 20-100°C, specifically 20°C, 25°C, 30°C, 50°C, 60°C, or 80°C. The draw ratio of the first coagulation drawing is preferably 1-10 times, specifically 1, 2, 3, 6, 8, or 9 times.

[0052] After obtaining the nascent fiber, the present invention sequentially performs a second coagulation drawing, water washing drawing, oiling, drying, and steam drawing on the nascent fiber to obtain the ultra-high molecular weight polyacrylonitrile precursor fiber. In the present invention, the second coagulation drawing is preferably multi-stage coagulation drawing, and the number of stages of the multi-stage coagulation drawing is preferably 2 to 8. In a specific embodiment of the present invention, the number of stages of the multi-stage coagulation drawing is preferably determined according to actual needs. The coagulation bath used for the multi-stage coagulation drawing is preferably a mixture of solvent and water. The solvent preferably includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, dimethyl tetrasulfide, zinc chloride aqueous solution, sodium thiocyanate aqueous solution, and nitric acid aqueous solution. Specifically, the solvent used in the coagulation bath for the multi-stage coagulation drawing is the same as the solvent used to prepare the spinning solution.

[0053] In this invention, the preferred mass ratio of solvent to water in the coagulation bath used for multi-stage coagulation drawing is 2-8:8-2. Specifically, during the multi-stage coagulation drawing process, the proportion of solvent in the coagulation bath used for each stage of coagulation drawing preferably gradually decreases, while the proportion of water gradually increases. Specifically, when the number of stages of multi-stage coagulation drawing is 4, the preferred mass ratio of solvent to water in the coagulation bath used for stages 1 to 4 is 5.5:4.5, 5:5, 4.5:5.5, and 4:6, respectively. The preferred total draw ratio of the multi-stage coagulation drawing is 1 to 5 times, specifically 1, 2, 3, 4, or 5 times. In a specific embodiment of this invention, when the number of stages of multi-stage coagulation drawing is 4, the preferred draw ratios for stages 1 to 4 are 1.5, 1, 1, and 0.5 times, respectively.

[0054] In this invention, the preferred temperature for the water washing and stretching is 20–100°C, specifically 25°C, 30°C, 50°C, 70°C, 80°C, or 90°C; the preferred total stretching ratio for the water washing and stretching is 1–5 times, specifically 1, 2, 3, 4, or 5 times; the preferred number of stages for the water washing and stretching is 2–8 stages, specifically 2, 4, 5, or 7 stages; in a specific embodiment of this invention, when the number of stages for the water washing and stretching is 4, the stretching ratios from stage 1 to stage 4 are preferably 0.5 times, 0.5 times, 0.5 times, and 0.5 times respectively.

[0055] In this invention, the temperature of the oiling agent used for oiling is preferably 20 to 80°C, specifically 25°C, 30°C, 60°C, 75°C or 80°C; the draw ratio of the oiling is preferably 1 to 3 times, specifically 1.5 times, 2 times or 3 times.

[0056] In this invention, the drying temperature is preferably 100-150℃, more preferably 100-120℃, and the drying draw ratio is preferably 0-3 times, specifically 0.5 times, 2 times, or 2.5 times. In embodiments of this invention, gradient drying is preferably performed using guide rollers with different temperatures. Specifically, the number of guide rollers is preferably 20, grouped into sets of 5, and sequentially labeled as the first group, second group, third group, and fourth group according to the order in which the yarn passes through. The temperature of the first group is 100℃, the temperature of the second group is 110℃, the temperature of the third group is 115℃, and the temperature of the fourth group is 120℃.

[0057] In this invention, the steam drawing ratio is preferably 2 to 5 times, specifically 2.5 times, 3 times, 4 times or 5 times; the steam drawing is preferably carried out in a steam drawing chamber, specifically a high-pressure steam drawing chamber.

[0058] This invention also provides ultra-high molecular weight polyacrylonitrile precursor fibers prepared by the method described above. The ultra-high molecular weight polyacrylonitrile precursor fibers provided by this invention exhibit high tensile strength and excellent performance.

[0059] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0060] Example 1

[0061] Weigh 0.5 kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5 kg of dimethyl sulfoxide into a reaction vessel. Without stirring, place the reaction vessel in a vacuum degassing homogenizer. Set the revolution and rotation speeds of the vacuum degassing homogenizer to 200 rpm and 200 rpm, respectively, and mix the polyacrylonitrile powder and dimethyl sulfoxide thoroughly for 5 minutes. Then, set the revolution and rotation speeds of the vacuum degassing homogenizer to 1000 rpm and 1000 rpm, respectively, and allow the mixed solution to fully dissolve for 60 minutes. Subsequently, set the revolution speed of the vacuum degassing homogenizer to 5000 rpm and the vacuum degree to -90 kPa to degas and remove impurities from the solution for 5 minutes, obtaining a polyacrylonitrile / dimethyl sulfoxide spinning solution with a solid content of 5%.

[0062] Example 2

[0063] Weigh 0.5 kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5 kg of dimethylformamide and pour them into a reaction vessel without stirring. Place the reaction vessel in a vacuum degassing homogenizer and set the revolution and rotation speeds of the vacuum degassing homogenizer to 200 rpm and 200 rpm, respectively. Mix the polyacrylonitrile powder and dimethyl sulfoxide thoroughly for 5 minutes. Then set the revolution and rotation speeds of the vacuum degassing homogenizer to 1000 rpm and 1000 rpm, respectively, and allow the mixed solution to dissolve completely for 60 minutes. Subsequently, set the revolution speed of the vacuum degassing homogenizer to 5000 rpm and the vacuum degree to -90 kPa to degas and remove impurities from the solution for 5 minutes, obtaining a polyacrylonitrile / dimethyl sulfoxide spinning solution with a solid content of 5%.

[0064] Example 3

[0065] Weigh 0.5 kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5 kg of dimethylacetamide into a reaction vessel. Without stirring, place the reaction vessel in a vacuum degassing homogenizer. Set the revolution and rotation speeds of the vacuum degassing homogenizer to 200 rpm and 200 rpm, respectively, and thoroughly mix the polyacrylonitrile powder and dimethyl sulfoxide for 5 minutes. Then, set the revolution and rotation speeds of the vacuum degassing homogenizer to 1000 rpm and 1000 rpm, respectively, and thoroughly dissolve the mixture for 60 minutes. Subsequently, set the revolution speed of the vacuum degassing homogenizer to 5000 rpm and the vacuum degree to -90 kPa to degas and remove impurities from the solution for 5 minutes, obtaining a polyacrylonitrile / dimethylacetamide spinning solution with a solid content of 5%.

[0066] Example 4

[0067] Weigh 0.5 kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5 kg of zinc chloride aqueous solution (concentration of 50 wt%) into a reaction vessel. Without stirring, place the reaction vessel in a vacuum degassing homogenizer. Set the revolution and rotation speeds of the vacuum degassing homogenizer to 200 rpm and 200 rpm, respectively. Mix the polyacrylonitrile powder and dimethyl sulfoxide thoroughly for 5 minutes. Then, set the revolution and rotation speeds of the vacuum degassing homogenizer to 1000 rpm and 1000 rpm, respectively, and allow the mixed solution to fully dissolve for 60 minutes. Subsequently, set the revolution speed of the vacuum degassing homogenizer to 5000 rpm and the vacuum degree to -90 kPa to degas and remove impurities from the solution for 5 minutes, obtaining a polyacrylonitrile / zinc chloride aqueous solution spinning solution with a solid content of 5%.

[0068] Example 5

[0069] Weigh 0.5 kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5 kg of sodium thiocyanate aqueous solution (concentration of 50 wt%) into a reaction vessel. Without stirring, place the reaction vessel in a vacuum degassing homogenizer. Set the revolution and rotation speeds of the vacuum degassing homogenizer to 200 rpm and 200 rpm, respectively. Mix the polyacrylonitrile powder and dimethyl sulfoxide thoroughly for 5 minutes. Then, set the revolution and rotation speeds of the vacuum degassing homogenizer to 1000 rpm and 1000 rpm, respectively, and allow the mixed solution to dissolve completely for 60 minutes. Subsequently, set the revolution speed of the vacuum degassing homogenizer to 5000 rpm and the vacuum degree to -90 kPa to degas and remove impurities from the solution for 5 minutes, obtaining a polyacrylonitrile / sodium thiocyanate aqueous solution spinning solution with a solid content of 5%.

[0070] Example 6

[0071] Weigh 0.5 kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5 kg of nitric acid aqueous solution (concentration of 50 wt%) into a reaction vessel. Without stirring, place the reaction vessel in a vacuum degassing homogenizer. Set the revolution and rotation speeds of the vacuum degassing homogenizer to 200 rpm and 200 rpm, respectively. Mix the polyacrylonitrile powder and dimethyl sulfoxide thoroughly for 5 minutes. Then, set the revolution and rotation speeds of the vacuum degassing homogenizer to 1000 rpm and 1000 rpm, respectively, and allow the mixed solution to dissolve completely for 60 minutes. Subsequently, set the revolution speed of the vacuum degassing homogenizer to 5000 rpm and the vacuum degree to -90 kPa to degas and remove impurities from the solution for 5 minutes, obtaining a polyacrylonitrile / nitric acid aqueous solution spinning solution with a solid content of 5%.

[0072] Example 7

[0073] Weigh 0.5 kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000, 9.45 kg of dimethylacetamide, and 0.05 kg of water into a reaction vessel. Without stirring, place the reaction vessel in a vacuum degassing homogenizer. Set the revolution and rotation speeds of the vacuum degassing homogenizer to 200 rpm and 200 rpm, respectively, and thoroughly mix the polyacrylonitrile powder and dimethyl sulfoxide for 5 minutes. Then, set the revolution and rotation speeds of the vacuum degassing homogenizer to 1000 rpm and 1000 rpm, respectively, and thoroughly dissolve the mixture for 60 minutes. Finally, set the revolution speed of the vacuum degassing homogenizer to 5000 rpm and the vacuum degree to -90 kPa to degas and remove impurities from the solution for 5 minutes, obtaining a polyacrylonitrile / dimethylacetamide spinning solution with a solid content of 5%.

[0074] Comparative Example 1

[0075] 0.5 kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5 kg of dimethyl sulfoxide were weighed and poured into a reactor equipped with a stirrer and a temperature control system. The reactor temperature and stirring speed were initially set to 40℃ and 200 rpm, respectively, and the mixture was thoroughly mixed for 20 minutes. Then, the temperature and stirring speed were set to 80℃ and 40 rpm, respectively, and the mixture was allowed to dissolve completely over 10 hours. After dissolution, the reactor temperature was set to 50℃, and the reactor was evacuated to degas the spinning solution, yielding a polyacrylonitrile / dimethyl sulfoxide spinning solution with a solid content of 5%.

[0076] Comparative Example 2

[0077] 0.5 kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5 kg of dimethylformamide were weighed and poured into a reactor equipped with a stirrer and a temperature control system. The reactor temperature and stirring speed were initially set to 40℃ and 200 rpm, respectively, and the mixture was thoroughly mixed for 20 minutes. Then, the temperature and stirring speed were set to 80℃ and 40 rpm, respectively, and the mixture was allowed to dissolve completely over 10 hours. After dissolution, the reactor temperature was set to 50℃, and the reactor was evacuated to degas the spinning solution, yielding a polyacrylonitrile / dimethylformamide spinning solution with a solid content of 5%.

[0078] Comparative Example 3

[0079] 0.5 kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5 kg of dimethylacetamide were weighed and poured into a reactor equipped with a stirrer and a temperature control system. The reactor temperature and stirring speed were initially set to 40℃ and 200 rpm, respectively, and the mixture was thoroughly mixed for 20 minutes. Then, the temperature and stirring speed were set to 80℃ and 40 rpm, respectively, and the mixture was allowed to dissolve completely over 9.5 hours. After dissolution, the reactor temperature was set to 50℃, and the reactor was evacuated to degas the spinning solution, yielding a polyacrylonitrile / dimethylacetamide spinning solution with a solid content of 5%.

[0080] Comparative Example 4

[0081] Weigh 0.5 kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5 kg of zinc chloride aqueous solution (concentration of 50 wt%) and pour them into a reactor equipped with a stirrer and a temperature control system. First, set the temperature and stirring speed of the reactor to 40℃ and 200 rpm, respectively, and mix thoroughly for 20 min. Then, set the temperature and stirring speed to 80℃ and 40 rpm, respectively, and allow it to dissolve completely for 8 h. After dissolution, set the temperature of the reactor to 50℃ and apply a vacuum to the reactor to degas the spinning solution, obtaining a polyacrylonitrile / zinc chloride aqueous solution spinning solution with a solid content of 5%.

[0082] Comparative Example 5

[0083] Weigh 0.5 kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5 kg of sodium thiocyanate aqueous solution (concentration of 50 wt%) and pour them into a reactor equipped with a stirrer and a temperature control system. First, set the temperature and stirring speed of the reactor to 40℃ and 200 rpm, respectively, and mix thoroughly for 20 min. Then, set the temperature and stirring speed to 80℃ and 40 rpm, respectively, and allow it to dissolve completely for 8.5 h. After dissolution, set the temperature of the reactor to 50℃ and apply a vacuum to the reactor to degas the spinning solution, obtaining a polyacrylonitrile / dimethyl sulfoxide spinning solution with a solid content of 5%.

[0084] Comparative Example 6

[0085] Weigh 0.5 kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5 kg of nitric acid aqueous solution (concentration of 50 wt%) and pour them into a reactor equipped with a stirrer and a temperature control system. First, set the temperature and stirring speed of the reactor to 40℃ and 200 rpm, respectively, and mix thoroughly for 20 min. Then, set the temperature and stirring speed to 80℃ and 40 rpm, respectively, and allow it to dissolve completely for 10 h. After dissolution, set the temperature of the reactor to 50℃ and evacuate the reactor to degas the spinning solution, obtaining a polyacrylonitrile / nitric acid aqueous solution spinning solution with a solid content of 5%.

[0086] Comparative Example 7

[0087] Weigh 0.5 kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5 kg of N,N-dimethylformamide and pour them into a reaction vessel. First, set the stirring speed and temperature to 500 rpm and 40℃ respectively to mix the powder and solvent thoroughly. Then, set the stirring speed and temperature to 40 rpm and 80℃ respectively to dissolve them thoroughly for 6 hours. Filter the resulting solution through 600 and 2000 mesh filters in sequence, and then degas it at -80 kPa and 60℃ to obtain the spinning solution.

[0088] As can be seen from Examples 1-7 and Comparative Examples 1-7, the present invention uses a vacuum degassing homogenizer to prepare spinning solution, which can significantly shorten the dissolution time of polyacrylonitrile powder and improve the preparation efficiency of spinning solution.

[0089] Example 8

[0090] Weigh 0.5 kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5 kg of dimethyl sulfoxide into a reaction vessel, and prepare the spinning solution according to the method in Example 1.

[0091] The spinning solution is stored at 70℃. After passing through a conveying assembly at 70℃, the spinning solution enters a first coagulation bath with a water:dimethyl sulfoxide ratio of 4:6 (mass ratio) after passing through a 5mm air layer. The temperature of the first coagulation bath is 40℃. The speed of the guide roller is then adjusted to achieve a draw ratio of 4 in the first coagulation bath. The fiber bundle is then subjected to coagulation and drawing at 40℃ in multi-stage coagulation baths with dimethyl sulfoxide to water mass ratios of 5.5:4.5, 5:5, 4.5:5.5, and 4:6, with draw ratios of 1.5, 1, 1, and 0.5 times, respectively. The filament bundle was then subjected to four stages of water washing and stretching at 40°C, with stretching ratios of 0.5, 0.5, 0.5, and 0.5 times respectively. After stretching, the filament bundle was oiled with an oiling agent at 40°C, with a stretching ratio of 2 times. The oiled filament bundle was then dried at a gradient temperature of 100–120°C, with a stretching ratio of 0.5 times during drying. Finally, it underwent four times high-pressure steam stretching to obtain the precursor fiber. The tensile strength of the obtained polyacrylonitrile precursor fiber was 9.08 cN / dtex.

[0092] Example 9

[0093] Weigh 0.5 kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5 kg of N,N-dimethylacetamide and pour them into a reaction vessel to prepare a spinning solution according to the method in Example 1.

[0094] The spinning solution is stored at 70℃. After passing through a conveying assembly at 70℃, the spinning solution enters a first coagulation bath with a water:N,N-dimethylacetamide ratio of 4:6 (mass ratio) after passing through a 5mm air layer. The temperature of the first coagulation bath is 40℃. The speed of the guide roller is then adjusted to achieve a draw ratio of 4 in the first coagulation bath. The fiber bundle is then subjected to coagulation and drawing at 40℃ in multi-stage coagulation baths with N,N-dimethylacetamide:water mass ratios of 5.5:4.5, 5:5, 4.5:5.5, and 4:6, with draw ratios of 1.5, 1, 1, and 0.5 times, respectively. The filament bundle was then subjected to a four-stage water wash at 40°C, with draw ratios of 0.5x, 0.5x, 0.5x, and 0.5x respectively. After drawing, the filament bundle was oiled with an oiling agent at 40°C, with a draw ratio of 2x. The oiled filament bundle then underwent gradient drying via 20 heated guide rollers, arranged in groups of five. These rollers were designated as Group 1, Group 2, Group 3, and Group 4 according to the order in which the filaments passed through. The temperatures for each group were 100°C, 110°C, 115°C, and 120°C, respectively, with a draw ratio of 0.5x during drying. Finally, it underwent high-pressure steam drawing at a ratio of 4x to obtain the precursor filament. The tensile strength of the obtained polyacrylonitrile precursor filament was 9.07 cN / dtex.

[0095] Example 10

[0096] Weigh 0.5 kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5 kg of N,N-dimethylformamide and pour them into a reaction vessel to prepare a spinning solution according to the method in Example 1.

[0097] The spinning solution is stored at 70℃. After passing through a conveying assembly at 70℃, the spinning solution enters a first coagulation bath with a water:N,N-dimethylformamide ratio of 4:6 (mass ratio) after passing through a 5mm air layer. The temperature of the first coagulation bath is 40℃. The speed of the guide roller is then adjusted to achieve a draw ratio of 4 in the first coagulation bath. The fiber bundle is then subjected to coagulation and drawing at 40℃ in multi-stage coagulation baths with N,N-dimethylformamide:water mass ratios of 5.5:4.5, 5:5, 4.5:5.5, and 4:6, with draw ratios of 1.5, 1, 1, and 0.5 times, respectively. The filament bundle was then subjected to a four-stage water wash at 40°C, with draw ratios of 0.5x, 0.5x, 0.5x, and 0.5x respectively. After drawing, the filament bundle was oiled with an oiling agent at 40°C, with a draw ratio of 2x. The oiled filament bundle then underwent gradient drying via 20 heated guide rollers, arranged in groups of five, designated as Group 1, Group 2, Group 3, and Group 4 according to the order in which the filaments passed. The temperatures for each group were 100°C, 110°C, 115°C, and 120°C respectively, with a draw ratio of 0.5x during drying. Finally, it underwent high-pressure steam drawing at 4x to obtain the precursor filament. The tensile strength of the obtained polyacrylonitrile precursor filament was 9.06 cN / dtex.

[0098] Comparative Example 8

[0099] 2.2 kg of polyacrylonitrile powder with a viscosity-average molecular weight of 200,000 and 7.8 kg of N,N-dimethylacetamide were weighed and poured into a reaction vessel to prepare a spinning solution according to the method in Example 1.

[0100] The spinning solution is stored at 70℃. After passing through a conveying assembly at 70℃, the spinning solution enters a first coagulation bath with a water:N,N-dimethylacetamide ratio of 4:6 (mass ratio) after passing through a 5mm air layer. The temperature of the first coagulation bath is 40℃. The speed of the guide roller is then adjusted to achieve a draw ratio of 4 in the first coagulation bath. The fiber bundle is then subjected to coagulation and drawing at 40℃ in multi-stage coagulation baths with N,N-dimethylacetamide:water mass ratios of 5.5:4.5, 5:5, 4.5:5.5, and 4:6, with draw ratios of 1.5, 1, 1, and 0.5 times, respectively. The filament bundle was then subjected to a four-stage water wash at 40°C, with draw ratios of 0.5x, 0.5x, 0.5x, and 0.5x respectively. After drawing, the filament bundle was oiled with an oiling agent at 40°C, with a draw ratio of 2x. The oiled filament bundle then underwent gradient drying via 20 heated guide rollers, arranged in groups of five. These rollers were designated as Group 1, Group 2, Group 3, and Group 4 according to the order in which the filaments passed through. The temperatures for each group were 100°C, 110°C, 115°C, and 120°C, respectively, with a draw ratio of 0.5x during drying. Finally, it underwent high-pressure steam drawing at 4x to obtain the precursor filament. The tensile strength of the obtained polyacrylonitrile precursor filament was 8.6 cN / dtex. As can be seen from Comparative Example 8, using polyacrylonitrile powder with a lower molecular weight results in a precursor filament with poorer mechanical properties.

[0101] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing ultra-high molecular weight polyacrylonitrile precursor fibers, characterized in that, Includes the following steps: A spinning solution is prepared using ultra-high molecular weight polyacrylonitrile powder as raw material; the viscosity-average molecular weight of the ultra-high molecular weight polyacrylonitrile powder is 500,000 to 1,500,000. The spinning solution is spun into fibers, and the spun fibers are subjected to a first coagulation and stretching to obtain nascent fibers; the stretching ratio of the first coagulation and stretching is 1 to 10 times. The nascent fibers are subjected to a second coagulation stretching, water washing stretching, oiling, drying and steam stretching in sequence to obtain the ultra-high molecular weight polyacrylonitrile precursor fiber; the second coagulation stretching is a multi-stage coagulation stretching, the number of stages of the multi-stage coagulation stretching is 2 to 8; the total stretching ratio of the multi-stage coagulation stretching is 1 to 5 times. The method for preparing the spinning solution includes the following steps: Polyacrylonitrile powder and solvent are added to a reaction vessel, and then the reaction vessel is placed in a vacuum degassing homogenizer for mixing, dissolving and vacuum degassing to remove impurities in sequence to obtain spinning solution; The revolution speed of the vacuum degassing homogenizer during mixing is 10~1000 rpm, and the rotation speed is 10~1000 rpm; the mixing time is 0.1~1 h. The revolution speed of the vacuum degassing homogenizer during the dissolution process is 20~10000 rpm, and the rotation speed is 20~10000 rpm. The dissolution time is 0.2~3h; the revolution speed of the vacuum degassing homogenizer during dissolution is greater than the revolution speed of the vacuum degassing homogenizer during mixing; the rotation speed of the vacuum degassing homogenizer during dissolution is greater than the rotation speed of the vacuum degassing homogenizer during mixing. The revolution speed of the vacuum degassing homogenizer during the vacuum degassing and impurity removal process is 500~20000rpm, and the vacuum degree is -0.1~-200kPa; the vacuum degassing and impurity removal time is 0.1~2h.

2. The preparation method according to claim 1, characterized in that, The polyacrylonitrile powder includes one or more of polyacrylonitrile homopolymer powder and polyacrylonitrile copolymer powder; the solvent includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, dimethyl tetrasulfide, zinc chloride aqueous solution, sodium thiocyanate aqueous solution, and nitric acid aqueous solution.

3. The preparation method according to claim 1, characterized in that, The raw materials for preparing the spinning solution also include water, wherein the mass of the water is 0-5% of the total mass of the solution obtained by dissolving.

4. The preparation method according to claim 1, characterized in that, The solid content of the spinning solution is 4-25%.

5. The preparation method according to claim 1, characterized in that, Spinning the spinning solution includes: storing the spinning solution under heat preservation conditions and conveying it to a spinning assembly for spinning; the heat preservation temperature is 40~100℃; the spinning assembly includes a conveying channel and a spinneret, and the temperature of the spinning assembly is 40~150℃.

6. The preparation method according to claim 1, characterized in that, The spinning process takes place in air, and the air layer height of the spinning process is 1~20mm; The first coagulation bath used for the first coagulation stretching is a mixture of solvent and water. The solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, dimethyl tetrasulfide, zinc chloride aqueous solution, sodium thiocyanate aqueous solution, and nitric acid aqueous solution. The mass ratio of solvent to water in the first coagulation bath is 2~8:8~2. The temperature of the first coagulation bath is 20~100℃.

7. The preparation method according to claim 1, characterized in that, The coagulation bath used in the multi-stage coagulation stretching is a mixture of solvent and water. The solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, dimethyl tetrasulfide, zinc chloride aqueous solution, sodium thiocyanate aqueous solution, and nitric acid aqueous solution. The mass ratio of solvent to water in the coagulation bath used in the multi-stage coagulation stretching is 2~8:8~2.

8. The preparation method according to claim 1, characterized in that, The temperature of the water washing and stretching is 20~100℃; the total stretching ratio of the water washing and stretching is 1~5 times. The temperature of the oiling agent used for oiling is 20~80℃; the draw ratio of the oiling agent is 1~3 times; The drying temperature is 100~150℃, and the stretching ratio is 0~3 times; The steam drawing ratio is 2 to 5 times; the steam drawing is carried out in a steam drawing chamber.

9. Ultra-high molecular weight polyacrylonitrile precursor fiber prepared by the preparation method according to any one of claims 1 to 8.

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