Preparation method of polyacrylonitrile spinning solution, ultra-high molecular weight polyacrylonitrile precursor and preparation method of ultra-high molecular weight polyacrylonitrile precursor

Abstract

The invention relates to the technical field of carbon fibers, and provides a preparation method of a polyacrylonitrile spinning solution, an ultra-high molecular weight polyacrylonitrile precursor and a preparation method of the ultra-high molecular weight polyacrylonitrile precursor. According to the method, the polyacrylonitrile powder is dissolved and defoamed by adopting the vacuum defoaming homogenizer, so that the process of preparing the polyacrylonitrile spinning solution can be effectively simplified and shortened, and the preparation efficiency is improved. Moreover, the ultra-high molecular weight polyacrylonitrile powder is used as a raw material to prepare a spinning solution, then the ultra-high molecular weight polyacrylonitrile precursor is prepared through the steps of spinning, first solidification drafting, second solidification drafting, washing drafting, oiling, drying, steam drafting and the like, and the obtained ultra-high molecular weight polyacrylonitrile precursor is high in tensile strength and excellent in performance.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon fiber, and in particular to a method for preparing a polyacrylonitrile spinning solution and an ultra-high molecular weight polyacrylonitrile precursor and a method for preparing the same. Background Art

[0002] Polyacrylonitrile-based carbon fiber is a typical high-performance fiber that has both the inherent properties of carbon materials and the softness of fibers. Composite materials with extremely excellent performance can be obtained by compounding polyacrylonitrile-based carbon fiber with resin, metal, ceramic and other materials. It can be used as a structural material to bear loads and meet special functional requirements such as anti-corrosion and heat insulation.

[0003] The production process of carbon fiber mainly includes: first preparing polyacrylonitrile spinning solution, spinning the spinning solution to obtain polyacrylonitrile precursor, and pre-oxidizing and carbonizing the polyacrylonitrile precursor to obtain carbon fiber. It can be seen from the preparation process that the preparation of polyacrylonitrile spinning solution is the basic step in preparing carbon fiber, and it is also a key step in determining the efficiency of carbon fiber preparation. However, when preparing polyacrylonitrile spinning solution at present, polyacrylonitrile is stirred and dissolved in a solvent, and then vacuum degassing is performed. The dissolution time of polyacrylonitrile is long, resulting in low preparation efficiency of the spinning solution. In addition, the mechanical properties of the current polyacrylonitrile precursor are poor, which in turn affects the performance of the final carbon fiber. 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 and a method for preparing the same. The method for preparing the polyacrylonitrile spinning solution provided by the present invention is simple to operate, has a short dissolution time, and has high preparation efficiency; the polyacrylonitrile precursor provided by the present invention has good mechanical properties and high tensile strength.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

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

[0007] Adding polyacrylonitrile powder and solvent into a reaction kettle, and then placing the reaction kettle into a vacuum degassing homogenizer for mixing, dissolving and vacuum degassing to remove impurities, to obtain polyacrylonitrile spinning solution;

[0008] During the mixing, the revolution speed of the vacuum degassing homogenizer is 10 to 1000 rpm, and the rotation speed is 10 to 1000 rpm; the mixing time is 0.1 to 1 hour;

[0009] The revolution speed of the vacuum degassing homogenizer during dissolution is 20 to 10,000 rpm, and the rotation speed is 20 to 10,000 rpm; the dissolution time is 0.2 to 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] During the vacuum degassing and impurity removal, the revolution speed of the vacuum degassing homogenizer is 500 to 20000 rpm, and the vacuum degree is -0.1 to -200 kPa; the time of the vacuum degassing and impurity removal 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, zinc chloride aqueous solution, sodium thiocyanate aqueous solution and nitric acid aqueous solution.

[0012] Preferably, the raw material for preparing the polyacrylonitrile spinning solution also includes water, and the mass of the water is 0-5% of the total mass of the solution obtained by dissolving.

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

[0014] Using ultra-high molecular weight polyacrylonitrile powder as raw material, preparing spinning solution according to the method described in the above scheme; the viscosity average molecular weight of the ultra-high molecular weight polyacrylonitrile powder is 500,000 to 1.5 million;

[0015] The spinning solution is subjected to spinning, and the ejected filament bundle is subjected to a first coagulation and drawing to obtain a nascent fiber;

[0016] The as-spun fibers are sequentially subjected to second coagulation drawing, water washing drawing, oiling, drying and steam drawing to obtain the ultra-high molecular weight polyacrylonitrile precursor fibers.

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

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

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

[0020] The first coagulation bath used for the first coagulation and stretching is a mixture of solvent and water, and 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 the solvent to water in the first coagulation bath is 2-8:8-2; the temperature of the first coagulation bath is 20-100°C; and the stretching multiple of the first coagulation and stretching is 1-10 times.

[0021] Preferably, the second coagulation and stretching is a multi-stage coagulation and stretching, and the number of stages of the multi-stage coagulation and stretching is 2 to 8; the coagulation bath used for the multi-stage coagulation and stretching is a mixture of solvent and water, and 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 for the multi-stage coagulation and stretching is 2 to 8:8 to 2; the total stretching multiple of the multi-stage coagulation and stretching is 1 to 5 times.

[0022] Preferably, the temperature of the water washing and drawing is 20 to 100° C.; the total drawing multiple of the water washing and drawing is 1 to 5 times;

[0023] The temperature of the oil used for oiling is 20-80°C; the drafting multiple of the oiling is 1-3 times.

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

[0025] The steam stretching has a stretching multiple of 2 to 5 times; the steam stretching is performed in a steam stretching box.

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

[0027] The invention provides a method for preparing a polyacrylonitrile spinning solution, comprising the following steps: adding polyacrylonitrile powder and a solvent into a reaction kettle, then placing the reaction kettle into a vacuum degassing homogenizer for mixing, dissolving and vacuum degassing and impurity removal in sequence to obtain the polyacrylonitrile spinning solution; during the mixing, the revolution speed of the vacuum degassing homogenizer is 10 to 1000 rpm, and the rotation speed is 10 to 1000 rpm; the mixing time is 0.1 to 1 hour; during the dissolving, the revolution speed of the vacuum degassing homogenizer is 20 to 10000 rpm , the rotation speed is 20~10000rpm; the dissolution time is 0.2~3h; the revolution speed of the vacuum degassing homogenizer during the dissolution is greater than the revolution speed of the vacuum degassing homogenizer during the mixing; the rotation speed of the vacuum degassing homogenizer during the dissolution is greater than the rotation speed of the vacuum degassing homogenizer during the mixing; the revolution speed of the vacuum degassing homogenizer during the vacuum degassing and impurity removal is 500~20000rpm, and the vacuum degree is -0.1~-200kPa; the vacuum degassing and impurity removal time is 0.1~2h. The present invention adopts a vacuum degassing homogenizer to dissolve and degas polyacrylonitrile powder, and stirs and dissolves the polyacrylonitrile powder and the solvent by setting different revolution and rotation speeds. On the one hand, the revolution and rotation can fully stir the solution to make the solution more uniform, and on the other hand, by increasing the rotation and revolution speeds, the friction between molecules can be increased to heat the solution and promote the dissolution. In the process of degassing and removing impurities from the polyacrylonitrile solution, on the one hand, increasing the vacuum degree can extract the bubbles in the solution, and on the other hand, centrifuging the solution at a higher revolution speed allows the bubbles to be separated from the solution, and the larger mass impurities and incompletely dissolved polyacrylonitrile sink to the bottom and wall of the reaction kettle due to gravity and centrifugation. In summary, the method provided by the present invention is simple to operate, can effectively simplify and shorten the process of preparing polyacrylonitrile spinning solution, and improve the preparation efficiency.

[0028] The present invention also provides a method for preparing ultra-high molecular weight polyacrylonitrile precursor, comprising the following steps: using ultra-high molecular weight polyacrylonitrile powder as raw material, preparing spinning solution according to the method described in the above scheme; the viscosity-average molecular weight of the ultra-high molecular weight polyacrylonitrile powder is 500,000 to 1.5 million; spinning the spinning solution, and performing the first coagulation and drawing of the ejected filament bundle to obtain nascent fibers; and sequentially performing the second coagulation and drawing, water washing and drawing, oiling, drying and steam drawing of the nascent fibers to obtain the ultra-high molecular weight polyacrylonitrile precursor. The present invention uses ultra-high molecular weight polyacrylonitrile as raw material to prepare polyacrylonitrile precursor, and the obtained polyacrylonitrile precursor has good mechanical properties and high tensile strength. In addition, the molecular chain of ultra-high molecular weight polyacrylonitrile is long, and compared with polyacrylonitrile of ordinary molecular weight, the proportion of the molecular chain end is small, and the molecular chain end is often easy to become a key site for causing defects in the process of converting polyacrylonitrile into carbon fiber. Therefore, the present invention uses ultra-high molecular weight polyacrylonitrile to prepare polyacrylonitrile precursor, which is also conducive to reducing the defects of the carbon fiber obtained by subsequent carbonization and improving the quality of the carbon fiber.

[0029] Furthermore, ultra-high molecular weight polyacrylonitrile is sensitive to process parameters such as temperature, humidity, and drawing speed, and spinning is difficult. The present invention can achieve a stable spinning process by controlling the spinning parameters of each step to obtain high-quality ultra-high molecular weight polyacrylonitrile precursor. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the vacuum degassing homogenizer used in the present invention. DETAILED DESCRIPTION

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

[0032] Adding polyacrylonitrile powder and solvent into a reaction kettle, and then placing the reaction kettle into a vacuum degassing homogenizer for mixing, dissolving and vacuum degassing to remove impurities to obtain polyacrylonitrile spinning solution;

[0033] During the mixing, the revolution speed of the vacuum degassing homogenizer is 10 to 1000 rpm, and the rotation speed is 10 to 1000 rpm; the mixing time is 0.1 to 1 hour;

[0034] The revolution speed of the vacuum degassing homogenizer during dissolution is 20 to 10,000 rpm, and the rotation speed is 20 to 10,000 rpm; the dissolution time is 0.2 to 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] During the vacuum degassing and impurity removal, the revolution speed of the vacuum degassing homogenizer is 500 to 20000 rpm, and the vacuum degree is -0.1 to -200 kPa; the time of the vacuum degassing and impurity removal is 0.1 to 2 hours.

[0036] In the present 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 1.5 million.

[0037] In the present invention, 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; the present invention has no special requirements for the specific concentrations of the zinc chloride aqueous solution, sodium thiocyanate aqueous solution and nitric acid aqueous solution, as long as the polyacrylonitrile powder can be completely dissolved. In a specific embodiment of the present invention, the concentrations of the zinc chloride aqueous solution, sodium thiocyanate aqueous solution and nitric acid aqueous solution can be 45-60wt%, specifically 50wt%; the mass ratio of the polyacrylonitrile powder to the solvent is preferably (5-50): (95-50), specifically 5:95, 7:93, 10:90, 12:88, 14:86 or 16:84. In a specific embodiment of the present invention, the polyacrylonitrile powder and the solvent can be directly added to the reactor without stirring; the present invention has no special requirements for the specific specifications of the reactor, as long as it can be placed in a vacuum degassing homogenizer.

[0038] In the present invention, the raw material for preparing the polyacrylonitrile spinning solution also includes water, and 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%. The present invention can adjust the properties of the spinning solution and adjust the phase separation process by adding a trace amount of water.

[0039] In the present invention, after adding polyacrylonitrile powder and solvent into a reaction kettle, the present invention puts the reaction kettle into a vacuum degassing homogenizer and fixes it. The rotation speed and revolution speed of the vacuum degassing homogenizer used in the present invention can be freely adjusted, and different degrees of vacuum can be provided. Figure 1 It is a schematic diagram of the vacuum degassing homogenizer used in the present invention.

[0040] In the present invention, the revolution speed of the vacuum degassing homogenizer during the mixing is 10 to 1000 rpm, preferably 100 to 400 rpm, specifically 200 rpm, 250 rpm or 350 rpm; the rotation speed of the vacuum degassing homogenizer during the mixing is 10 to 1000 rpm, preferably 100 to 400, specifically 200 rpm, 250 rpm or 350 rpm; the mixing time is 0.1 to 1 h, preferably 0.15 to 0.3 h; in a specific embodiment of the present invention, after the reactor is fixed in the vacuum degassing homogenizer, the revolution speed and the rotation speed of the vacuum degassing homogenizer are adjusted within the above range, and the polyacrylonitrile powder and the solvent are mixed. The present invention controls the revolution speed and the rotation speed of the vacuum degassing homogenizer within the above range, and can achieve full mixing of the polyacrylonitrile powder and the solvent.

[0041] In the present invention, the revolution speed of the vacuum degassing homogenizer during the dissolution is 20 to 10000 rpm, preferably 600 to 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 the dissolution is 20 to 10000 rpm, preferably 600 to 5000 rpm, specifically 700 rpm, 800 rpm, 1000 rpm, 2000 rpm, 3000 rpm or 4000 rpm; the dissolution time is 0.2 to 3 h, preferably 0.5 h to 2 h; in the present invention, by increasing the rotation and revolution speeds of the vacuum degassing homogenizer, the friction between molecules can be increased, thereby heating the solution, thereby promoting the dissolution of polyacrylonitrile powder. In the present invention, the revolution speed of the vacuum degassing homogenizer during dissolution is greater than the revolution speed of the vacuum degassing homogenizer during mixing. Specifically, the revolution speed of the vacuum degassing homogenizer during dissolution is preferably 5 to 10 times 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. Specifically, the rotation speed of the vacuum degassing homogenizer during dissolution is preferably 5 to 10 times the rotation speed of the vacuum degassing homogenizer during mixing; in a specific embodiment of the present 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 the present invention, the revolution speed of the vacuum degassing homogenizer during the vacuum degassing and impurity removal is 500-20000rpm, preferably 1000-10000rpm, specifically 2000rpm, 3000rpm, 4000rpm, 5000rpm, 6000rpm, 7000rpm, 8000rpm or 9000rpm; in a specific embodiment of the present invention, the revolution speed of the vacuum degassing homogenizer during the vacuum degassing and impurity removal is preferably 500-20000rpm, preferably 1000-10000rpm, specifically 2000rpm, 3000rpm, 4000rpm, 5000rpm, 6000rpm, 7000rpm, 8000rpm or 9000rpm. 1 to 10 times the revolution speed of the vacuum degassing homogenizer; the vacuum degassing homogenizer has no self-rotation during the vacuum degassing and impurity removal, that is, the self-rotation speed is 0; the vacuum degree of the vacuum degassing homogenizer during the vacuum degassing and impurity removal is -0.1 to -200kPa, preferably -0.1 to -101kPa, specifically -0.2kPa, -0.5kPa, -30kPa, -50kPa or -80kPa; the time of the vacuum degassing and impurity removal is 0.1 to 2h, preferably 0.3 to 1h. The present invention can extract bubbles in the polyacrylonitrile solution by increasing the vacuum degree, and at the same time centrifuge the solution by a larger revolution speed, so that the bubbles can be separated from the polyacrylonitrile solution, and the larger mass impurities and incompletely dissolved polyacrylonitrile sink to the bottom and wall of the reactor due to gravity and centrifugation.

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

[0044] Using ultra-high molecular weight polyacrylonitrile powder as raw material, preparing spinning solution according to the method described in the above scheme; the viscosity average molecular weight of the ultra-high molecular weight polyacrylonitrile powder is 500,000 to 1.5 million;

[0045] The spinning solution is subjected to spinning, and the ejected filament bundle is subjected to a first coagulation and drawing to obtain a nascent fiber;

[0046] The as-spun fibers are sequentially subjected to second coagulation drawing, water washing drawing, oiling, drying and steam drawing to obtain the ultra-high molecular weight polyacrylonitrile precursor fibers.

[0047] The present invention uses ultra-high molecular weight polyacrylonitrile powder as raw material and prepares a spinning solution according to the method described in the above scheme; the preparation method of the spinning solution is not repeated here; the viscosity-average molecular weight of the ultra-high molecular weight polyacrylonitrile powder is 500,000 to 1.5 million, preferably 500,000 to 1.3 million, and more preferably 600,000 to 1 million.

[0048] In the present 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 performs spinning on the spinning solution, and performs the first coagulation and drawing of the ejected filament bundle to obtain the nascent fiber. In the present invention, the spinning solution is preferably subjected to spinning, which includes: storing the spinning solution under heat preservation conditions and conveying it to the spinning assembly for spinning; the heat preservation temperature is preferably 40 to 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 to 150°C, specifically 40°C, 65°C, 70°C, 80°C, 100°C, 120°C or 130°C.

[0050] In the present invention, the spinning is preferably carried out in air, and the air layer height 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 the present invention, the first coagulation bath used for the first coagulation and drawing is preferably a mixture of solvent and water, and 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 the 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 drawing multiple of the first coagulation and drawing is preferably 1-10 times, specifically 1 time, 2 times, 3 times, 6 times, 8 times or 9 times.

[0052] After obtaining the spun fibers, the present invention sequentially performs second coagulation and drawing, water washing and drawing, oiling, drying and steam drawing on the spun fibers to obtain the ultra-high molecular weight polyacrylonitrile precursor. In the present invention, the second coagulation and drawing is preferably multi-stage coagulation and drawing, and the number of stages of the multi-stage coagulation and drawing is preferably 2 to 8. In a specific embodiment of the present invention, the number of stages of the multi-stage coagulation and drawing is preferably determined according to actual needs; the coagulation bath used for the multi-stage coagulation and drawing is preferably a mixture of solvent and water, and 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 used for the multi-stage coagulation and drawing is the same as the solvent used to prepare the spinning solution.

[0053] In the present invention, the mass ratio of the solvent and water in the coagulation bath used for the multi-stage coagulation and stretching is preferably 2-8:8-2. Specifically, in the multi-stage coagulation and stretching process, the proportion of the solvent in the coagulation bath used for each stage of coagulation and stretching is preferably gradually reduced, and the proportion of water is gradually increased. Specifically, when the number of the multi-stage coagulation and stretching is 4, the mass ratio of the solvent and water in the coagulation bath used for coagulation and stretching from level 1 to level 4 is preferably 5.5:4.5, 5:5, 4.5:5.5 and 4:6, respectively; the total stretching multiple of the multi-stage coagulation and stretching is preferably 1-5 times, specifically 1 times, 2 times, 3 times, 4 times or 5 times. In a specific embodiment of the present invention, when the number of the multi-stage coagulation and stretching is 4, the stretching multiples from level 1 to level 4 are preferably 1.5 times, 1 times, 1 times and 0.5 times, respectively.

[0054] In the present invention, the temperature of the water-washing and stretching is preferably 20-100°C, specifically 25°C, 30°C, 50°C, 70°C, 80°C or 90°C; the total stretching multiple of the water-washing and stretching is preferably 1-5 times, specifically 1 time, 2 times, 3 times, 4 times or 5 times; the number of levels of the water-washing and stretching is preferably 2-8 levels, specifically 2 levels, 4 levels, 5 levels or 7 levels; in a specific embodiment of the present invention, when the number of levels of water-washing and stretching is 4 levels, the stretching multiples of water-washing and stretching from level 1 to level 4 are preferably 0.5 times, 0.5 times, 0.5 times and 0.5 times, respectively.

[0055] In the present invention, the temperature of the oil used for oiling is preferably 20-80°C, specifically 25°C, 30°C, 60°C, 75°C or 80°C; the stretching multiple of the oiling is preferably 1-3 times, specifically 1.5 times, 2 times or 3 times.

[0056] In the present invention, the drying temperature is preferably 100-150°C, preferably 100-120°C, and the drying stretching multiple is preferably 0-3 times, specifically 0.5 times, 2 times or 2.5 times; in an embodiment of the present invention, guide rollers with different temperatures are preferably used for gradient drying. Specifically, the number of guide rollers is preferably 20, with 5 as a group, and they are recorded as the first group, the second group, the third group and the fourth group in the order of the passing of the silk thread, wherein the temperature of the first group is 100°C, the temperature of the second group is 110°C, the temperature of the third group is 115°C, and the temperature of the fourth group is 120°C.

[0057] In the present invention, the steam stretching multiple is preferably 2 to 5 times, specifically 2.5 times, 3 times, 4 times or 5 times; the steam stretching is preferably carried out in a steam stretching box, specifically a high-pressure steam stretching box.

[0058] The present invention also provides an ultra-high molecular weight polyacrylonitrile precursor prepared by the preparation method described in the above scheme. The ultra-high molecular weight polyacrylonitrile precursor provided by the present invention has high tensile strength and excellent performance.

[0059] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[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 reactor without stirring. Put the reactor into a vacuum degassing homogenizer, set the revolution and rotation speeds of the vacuum degassing homogenizer to 200 rpm and 200 rpm respectively, fully 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 fully dissolve the mixed solution for 60 minutes. Then set the revolution speed of the vacuum degassing homogenizer to 5000 rpm, and the vacuum degree is -90 kPa to degas and remove impurities from the solution for 5 minutes to obtain 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 into a reactor without stirring. Put the reactor into a vacuum degassing homogenizer, set the revolution and rotation speeds of the vacuum degassing homogenizer to 200 rpm and 200 rpm respectively, fully 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 fully dissolve the mixed solution for 60 minutes. Subsequently, set the revolution speed of the vacuum degassing homogenizer to 5000 rpm, and the vacuum degree is -90 kPa to degas and remove impurities from the solution for 5 minutes to obtain 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 and pour them into a reactor. Without stirring, put the reactor into a vacuum degassing homogenizer, set the revolution and rotation speeds of the vacuum degassing homogenizer to 200 rpm and 200 rpm respectively, fully 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 fully dissolve the mixed solution for 60 minutes. Subsequently, set the revolution speed of the vacuum degassing homogenizer to 5000 rpm, and the vacuum degree is -90 kPa to degas and remove impurities from the solution for 5 minutes to obtain a polyacrylonitrile / dimethylacetamide spinning solution with a solid content of 5%.

[0066] Example 4

[0067] Weigh 0.5kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5kg of zinc chloride aqueous solution (concentration of 50wt%) and pour them into a reactor without stirring. Put the reactor into a vacuum degassing homogenizer, set the revolution and rotation speeds of the vacuum degassing homogenizer to 200rpm and 200rpm respectively, fully mix the polyacrylonitrile powder and dimethyl sulfoxide for 5 minutes, then set the revolution and rotation speeds of the vacuum degassing homogenizer to 1000rpm and 1000rpm respectively, and fully dissolve the mixed solution for 60 minutes. Then set the revolution speed of the vacuum degassing homogenizer to 5000rpm, and the vacuum degree is -90kPa to degas and remove impurities from the solution for 5 minutes to obtain a polyacrylonitrile / zinc chloride aqueous solution spinning solution with a solid content of 5%.

[0068] Example 5

[0069] Weigh 0.5kg of polyacrylonitrile powder with a viscosity average molecular weight of 800,000 and 9.5kg of sodium thiocyanate aqueous solution (concentration of 50wt%) and pour them into a reactor without stirring. Put the reactor into a vacuum degassing homogenizer, set the revolution and rotation speeds of the vacuum degassing homogenizer to 200rpm and 200rpm respectively, fully mix the polyacrylonitrile powder and dimethyl sulfoxide for 5 minutes, then set the revolution and rotation speeds of the vacuum degassing homogenizer to 1000rpm and 1000rpm respectively, and fully dissolve the mixed solution for 60 minutes. Then set the revolution speed of the vacuum degassing homogenizer to 5000rpm, and the vacuum degree is -90kPa to degas and remove impurities from the solution for 5 minutes to obtain 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%) and pour them into a reactor. Without stirring, put the reactor into a vacuum degassing homogenizer, set the revolution and rotation speeds of the vacuum degassing homogenizer to 200 rpm and 200 rpm respectively, fully 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 fully dissolve the mixed solution for 60 minutes. Subsequently, set the revolution speed of the vacuum degassing homogenizer to 5000 rpm, and the vacuum degree is -90 kPa to degas and remove impurities from the solution for 5 minutes to obtain a polyacrylonitrile / nitric acid aqueous solution spinning solution with a solid content of 5%.

[0072] Example 7

[0073] Weigh 0.5kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000, 9.45kg of dimethylacetamide and 0.05kg of water into a reactor without stirring. Put the reactor into a vacuum degassing homogenizer, set the revolution and rotation speeds of the vacuum degassing homogenizer to 200rpm and 200rpm respectively, fully mix the polyacrylonitrile powder and dimethyl sulfoxide for 5 minutes, then set the revolution and rotation speeds of the vacuum degassing homogenizer to 1000rpm and 1000rpm respectively, and fully dissolve the mixed solution for 60 minutes. Then set the revolution speed of the vacuum degassing homogenizer to 5000rpm, and the vacuum degree is -90kPa to degas and remove impurities from the solution for 5 minutes to obtain a polyacrylonitrile / dimethylacetamide spinning solution with a solid content of 5%.

[0074] Comparative Example 1

[0075] Weigh 0.5kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5kg of dimethyl sulfoxide into a reactor equipped with a stirring paddle and a temperature control system. First, set the temperature and stirring speed of the reactor to 40°C and 200rpm, mix them thoroughly for 20 minutes, and then set the temperature and stirring speed to 80°C and 40rpm respectively. Dissolve them thoroughly for 10 hours. After the dissolution is completed, set the temperature of the reactor to 50°C, and vacuum the reactor to degas the spinning solution to obtain a polyacrylonitrile / dimethyl sulfoxide spinning solution with a solid content of 5%.

[0076] Comparative Example 2

[0077] Weigh 0.5kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5kg of dimethylformamide and pour them into a reactor with a stirring paddle and a temperature control system. First, set the temperature and stirring speed of the reactor to 40°C and 200rpm, mix them thoroughly for 20 minutes, and then set the temperature and stirring speed to 80°C and 40rpm respectively. Dissolve them thoroughly for 10 hours. After the dissolution is completed, set the temperature of the reactor to 50°C, and vacuum the reactor to degas the spinning solution to obtain a polyacrylonitrile / dimethylformamide spinning solution with a solid content of 5%.

[0078] Comparative Example 3

[0079] Weigh 0.5kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5kg of dimethylacetamide and pour them into a reactor with a stirring paddle and a temperature control system. First, set the temperature and stirring speed of the reactor to 40°C and 200rpm, mix them thoroughly for 20 minutes, and then set the temperature and stirring speed to 80°C and 40rpm respectively. Dissolve them thoroughly for 9.5 hours. After the dissolution is completed, set the temperature of the reactor to 50°C, and vacuum the reactor to degas the spinning solution to obtain a polyacrylonitrile / dimethylacetamide spinning solution with a solid content of 5%.

[0080] Comparative Example 4

[0081] Weigh 0.5kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5kg of zinc chloride aqueous solution (concentration of 50wt%) and pour them into a reactor with a stirring paddle and a temperature control system. First, set the temperature and stirring speed of the reactor to 40°C and 200rpm, mix them thoroughly for 20min, and then set the temperature and stirring speed to 80°C and 40rpm respectively. Dissolve them thoroughly for 8h. After the dissolution is completed, set the temperature of the reactor to 50°C, and vacuum the reactor to degas the spinning solution to obtain a polyacrylonitrile / zinc chloride aqueous solution spinning solution with a solid content of 5%.

[0082] Comparative Example 5

[0083] Weigh 0.5kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5kg of sodium thiocyanate aqueous solution (concentration of 50wt%) and pour them into a reactor with a stirring paddle and a temperature control system. First, set the temperature and stirring speed of the reactor to 40°C and 200rpm, fully mix them for 20min, and then set the temperature and stirring speed to 80°C and 40rpm respectively. Fully dissolve them, and the dissolution time is 8.5h. After the dissolution is completed, set the temperature of the reactor to 50°C, and vacuum the reactor to degas the spinning solution to obtain a polyacrylonitrile / dimethyl sulfoxide spinning solution with a solid content of 5%.

[0084] Comparative Example 6

[0085] Weigh 0.5kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5kg of nitric acid aqueous solution (concentration of 50wt%) and pour them into a reactor with a stirring paddle and a temperature control system. First, set the temperature and stirring speed of the reactor to 40°C and 200rpm, mix them thoroughly for 20 minutes, and then set the temperature and stirring speed to 80°C and 40rpm respectively. Dissolve them thoroughly for 10 hours. After the dissolution is completed, set the temperature of the reactor to 50°C, and evacuate the reactor to degas the spinning solution to obtain 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 reactor. First, set the stirring speed and temperature to 500 rpm and 40°C respectively to fully mix the powder and the solvent, and then set the stirring speed and temperature to 40 rpm and 80°C respectively to fully dissolve them for 6 hours. The obtained solution is filtered through 600 and 2000 mesh filter screens in turn, and then degassed at -80 kPa at a degassed temperature of 60°C to obtain a spinning solution.

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

[0089] Example 8

[0090] 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 reaction kettle, and a spinning solution was prepared in the manner of Example 1.

[0091] The storage temperature of the spinning solution is 70°C. The spinning solution is transported to the spinneret through a transport component, wherein the temperature of the transport component is 70°C. The spinning solution passes through a 5mm air layer from the spinneret and enters a first coagulation bath of water: dimethyl sulfoxide = 4:6 (mass ratio), wherein the temperature of the first coagulation bath is 40°C, and then the speed of the guide roller is adjusted so that the drafting multiple of the tow in the first coagulation bath is 4. Then, the tow is coagulated and drafted at 40°C in a multi-stage coagulation bath with a mass ratio of dimethyl sulfoxide to water of 5.5:4.5, 5:5, 4.5:5.5, and 4:6, respectively, and the drafting multiples are 1.5 times, 1 times, 1 times, and 0.5 times, respectively. Then the tow was subjected to four-stage water washing and drawing at 40°C, with the drawing multiples being 0.5, 0.5, 0.5, and 0.5 respectively. The tow after drawing was oiled with a 40°C oil agent, with the drawing multiple being 2 times. The oiled tow was dried at a gradient temperature of 100 to 120°C, with the drawing multiple being 0.5 times, and then drawn with 4 times high-pressure steam to obtain the raw yarn. The tensile strength of the obtained polyacrylonitrile raw yarn was 9.08 cN / dtex.

[0092] Example 9

[0093] 0.5 kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5 kg of N,N-dimethylacetamide were weighed and poured into a reaction kettle, and a spinning solution was prepared according to the method in Example 1.

[0094] The storage temperature of the spinning solution is 70°C. The spinning solution is transported to the spinneret through a transport component, wherein the temperature of the transport component is 70°C. The spinning solution passes through a 5mm air layer from the spinneret and enters a first coagulation bath of water: N,N-dimethylacetamide = 4:6 (mass ratio), wherein the temperature of the first coagulation bath is 40°C, and then the speed of the guide roller is adjusted so that the drafting multiple of the tow in the first coagulation bath is 4. Then, the tow is coagulated and drafted at 40°C in a multi-stage coagulation bath with a mass ratio of N,N-dimethylacetamide to water of 5.5:4.5, 5:5, 4.5:5.5, and 4:6, respectively, and the drafting multiples are 1.5 times, 1 times, 1 times, and 0.5 times, respectively. Then the tow was washed with water at 40℃ for four stages, and the drafting ratios were 0.5 times, 0.5 times, 0.5 times, and 0.5 times, respectively. The tow after drafting was oiled with a 40℃ oil agent, and the drafting ratio of oiling was 2 times. The tow after oiling was gradient dried by 20 heating guide rollers in sequence. The heating guide rollers were grouped into 5 groups, and were recorded as the first group, the second group, the third group, and the fourth group in the order of passing the silk threads. The temperatures of each group were 100℃, 110℃, 115℃, and 120℃, respectively. The drafting ratio during drying was 0.5 times, and then the raw silk was drawn by 4 times high-pressure steam. The tensile strength of the obtained polyacrylonitrile raw silk was 9.07cN / dtex.

[0095] Example 10

[0096] 0.5 kg of polyacrylonitrile powder with a viscosity-average molecular weight of 800,000 and 9.5 kg of N,N-dimethylformamide were weighed and poured into a reaction kettle, and a spinning solution was prepared according to the method in Example 1.

[0097] The storage temperature of the spinning solution is 70°C. The spinning solution is transported to the spinneret through a transport component, wherein the temperature of the transport component is 70°C. The spinning solution passes through a 5mm air layer from the spinneret and enters a first coagulation bath of water: N,N-dimethylformamide = 4:6 (mass ratio), wherein the temperature of the first coagulation bath is 40°C, and then the speed of the guide roller is adjusted so that the drafting multiple of the tow in the first coagulation bath is 4. Then, the tow is coagulated and drafted at 40°C in a multi-stage coagulation bath with a mass ratio of N,N-dimethylformamide to water of 5.5:4.5, 5:5, 4.5:5.5, and 4:6, respectively, and the drafting multiples are 1.5 times, 1 times, 1 times, and 0.5 times, respectively. Then the tow was washed with water at 40℃ for four times, and the drafting ratio was 0.5 times, 0.5 times, 0.5 times, and 0.5 times respectively. The tow after drafting was oiled with oil at 40℃, and the drafting ratio was 2 times. The tow after oiling was gradient dried by 20 heating guide rollers in turn. The heating guide rollers were grouped into 5 groups, and were recorded as the first group, the second group, the third group, and the fourth group in the order of passing the silk thread. The temperature of each group was 100℃, 110℃, 115℃, and 120℃ respectively. The drafting ratio during drying was 0.5 times, and then the raw silk was drawn by 4 times high-pressure steam. The tensile strength of the obtained polyacrylonitrile raw silk was 9.06cN / 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 kettle, and a spinning solution was prepared according to the method of Example 1.

[0100] The storage temperature of the spinning solution is 70°C. The spinning solution is transported to the spinneret through a transport component, wherein the temperature of the transport component is 70°C. The spinning solution passes through a 5mm air layer from the spinneret and enters a first coagulation bath of water: N,N-dimethylacetamide = 4:6 (mass ratio), wherein the temperature of the first coagulation bath is 40°C, and then the speed of the guide roller is adjusted so that the drafting multiple of the tow in the first coagulation bath is 4. Then, the tow is coagulated and drafted at 40°C in a multi-stage coagulation bath with a mass ratio of N,N-dimethylacetamide to water of 5.5:4.5, 5:5, 4.5:5.5, and 4:6, respectively, and the drafting multiples are 1.5 times, 1 times, 1 times, and 0.5 times, respectively. Then the tow was washed with water at 40°C for four stages, and the drafting ratios were 0.5 times, 0.5 times, 0.5 times, and 0.5 times, respectively. The tow after drafting was oiled with a 40°C oil agent, and the drafting ratio of oiling was 2 times. The tow after oiling was gradient dried by 20 heating guide rollers in turn. The heating guide rollers were grouped into 5 groups, and were recorded as the first group, the second group, the third group, and the fourth group in the order of passing the silk thread. The temperatures of each group were 100°C, 110°C, 115°C, and 120°C, respectively. The drafting ratio during drying was 0.5 times, and then the raw silk was obtained by 4 times high-pressure steam drawing. The tensile strength of the obtained polyacrylonitrile raw silk was 8.6cN / dtex. According to Comparative Example 8, it can be seen that the mechanical properties of the obtained polyacrylonitrile raw silk are poor when spinning with polyacrylonitrile powder with a lower molecular weight.

[0101] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing polyacrylonitrile spinning solution, characterized in that: The following steps are involved: Adding polyacrylonitrile powder and solvent into a reaction kettle, and then placing the reaction kettle into a vacuum degassing homogenizer for mixing, dissolving and vacuum degassing to remove impurities, to obtain polyacrylonitrile spinning solution; During the mixing, the revolution speed of the vacuum degassing homogenizer is 10 to 1000 rpm, and the rotation speed is 10 to 1000 rpm; the mixing time is 0.1 to 1 hour; The revolution speed of the vacuum degassing homogenizer during dissolution is 20 to 10,000 rpm, and the rotation speed is 20 to 10,000 rpm; the dissolution time is 0.2 to 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; During the vacuum degassing and impurity removal, the revolution speed of the vacuum degassing homogenizer is 500 to 20000 rpm, and the vacuum degree is -0.1 to -200 kPa; the time of the vacuum degassing and impurity removal is 0.1 to 2 hours.

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 polyacrylonitrile spinning solution also include water, and the mass of the water is 0-5% of the total mass of the solution obtained by dissolving.

4. A method for preparing ultra-high molecular weight polyacrylonitrile precursor, characterized in that: The following steps are involved: Using ultra-high molecular weight polyacrylonitrile powder as raw material, preparing spinning solution according to the method of claim 1 or 2; the viscosity average molecular weight of the ultra-high molecular weight polyacrylonitrile powder is 500,000 to 1.5 million; The spinning solution is subjected to spinning, and the ejected filament bundle is subjected to a first coagulation and drawing to obtain a nascent fiber; The as-spun fibers are sequentially subjected to second coagulation drawing, water washing drawing, oiling, drying and steam drawing to obtain the ultra-high molecular weight polyacrylonitrile precursor fibers.

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

6. The preparation method according to claim 4, 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°C; the spinning assembly includes a conveying channel and a spinneret, and the temperature of the spinning assembly is 40-150°C.

7. The preparation method according to claim 4, characterized in that: The spinning is carried out in air, and the air layer height of the spinning is 1 to 20 mm; The first coagulation bath used for the first coagulation and stretching is a mixture of solvent and water, and 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 the solvent to water in the first coagulation bath is 2-8:8-2; the temperature of the first coagulation bath is 20-100°C; and the stretching multiple of the first coagulation and stretching is 1-10 times.

8. The preparation method according to claim 4, characterized in that: The second coagulation and stretching is a multi-stage coagulation and stretching, and the number of stages of the multi-stage coagulation and stretching is 2 to 8; the coagulation bath used for the multi-stage coagulation and stretching is a mixture of solvent and water, and 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 for the multi-stage coagulation and stretching is 2 to 8:8 to 2; the total stretching multiple of the multi-stage coagulation and stretching is 1 to 5 times.

9. The preparation method according to claim 4, characterized in that: The temperature of the water washing and drawing is 20 to 100° C.; the total drawing multiple of the water washing and drawing is 1 to 5 times; The temperature of the oil used for oiling is 20-80°C; the drafting multiple of the oiling is 1-3 times; The drying temperature is 100-150°C, and the drafting ratio is 0-3 times; The steam stretching has a stretching multiple of 2 to 5 times; the steam stretching is performed in a steam stretching box.

10. Ultra-high molecular weight polyacrylonitrile precursor prepared by the preparation method according to any one of claims 4 to 9.

Images