CN110685030B - Spinning method of spinning solution with narrow molecular weight distribution - Google Patents

Spinning method of spinning solution with narrow molecular weight distribution Download PDF

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CN110685030B
CN110685030B CN201810733837.5A CN201810733837A CN110685030B CN 110685030 B CN110685030 B CN 110685030B CN 201810733837 A CN201810733837 A CN 201810733837A CN 110685030 B CN110685030 B CN 110685030B
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temperature
spinning
fiber
steam
drafting
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CN110685030A (en
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王贺团
沈志刚
陈辉
赵微微
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China Petroleum and Chemical Corp
Sinopec Shanghai Research Institute of Petrochemical Technology
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China Petroleum and Chemical Corp
Sinopec Shanghai Research Institute of Petrochemical Technology
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    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D13/00—Complete machines for producing artificial threads
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D1/00—Treatment of filament-forming or like material
    • D01D1/02—Preparation of spinning solutions
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D10/00—Physical treatment of artificial filaments or the like during manufacture, i.e. during a continuous production process before the filaments have been collected
    • D01D10/02—Heat treatment
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/12—Stretch-spinning methods
    • D01D5/14—Stretch-spinning methods with flowing liquid or gaseous stretching media, e.g. solution-blowing
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
    • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
    • D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
    • D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
    • D01F9/20—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products
    • D01F9/21—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D01F9/22—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyacrylonitriles

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  • Engineering & Computer Science (AREA)
  • Textile Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
  • Artificial Filaments (AREA)

Abstract

The invention relates to a spinning method of a spinning solution with narrow molecular weight distribution, which mainly solves the problems of more broken filaments in a coagulating bath and large CV value of fiber in the prior art. The method comprises the following steps: adding polymerization raw materials acrylonitrile, a comonomer 1 and/or a comonomer 2, a solvent and an initiator into a reactor, starting constant-temperature reaction under the protection of gas inert to reaction substances, and controlling the reaction temperature to be 60-65 ℃; when the conversion rate exceeds T1Then, raising the temperature by 5-10 ℃, and continuing to react; when the conversion rate exceeds T2Then, raising the temperature by 5-10 ℃, and continuing to react; when the conversion rate reaches T3When the polymerization reaction is finished, the spinning solution is obtained through demonomerization and defoaming; then the polyacrylonitrile precursor is obtained through the technical scheme of solidification forming, drafting and water washing, oiling, drying densification, steam drafting, steam heat setting and filament collection, the problem is solved well, and the polyacrylonitrile precursor can be used in the industrial production of polyacrylonitrile-based carbon fiber precursors.

Description

Spinning method of spinning solution with narrow molecular weight distribution
Technical Field
The invention belongs to a preparation method of polyacrylonitrile protofilament for carbon fiber, and particularly relates to a spinning method of spinning solution with narrow molecular weight distribution.
Background
From the last 50 century, developed countries are in urgent need of new structural materials and corrosion-resistant materials for developing large rockets and artificial satellites and improving the performance of airplanes in a comprehensive manner, so that carbon fibers reappear on a stage made of the new materials, and three raw material systems of PAN-based carbon fibers, viscose-based carbon fibers and asphalt-based carbon fibers are gradually formed. Compared with other methods, the PAN-based carbon fiber production process is simple, and the mechanical property of the product is good, so that the PAN-based carbon fiber is rapidly developed and becomes the mainstream of the current carbon fiber production.
PAN-based carbon fiber has excellent properties of high strength, high modulus, high temperature resistance, corrosion resistance and the like, and is widely applied to the fields of aerospace, national defense, military and the like. In addition, the composite material also has wide application prospect in the fields of airplane industry, automobile industry, ship manufacturing, medical appliances, sports equipment, novel building materials and the like. The preparation of the PAN-based carbon fiber mainly comprises the following steps: polymeric spinning, thermal stabilization of the PAN filaments, and carbonization or further graphitization of the PAN stabilized fibers. The polymerization spinning process mainly comprises monomer polymerization, monomer removal and separation and spinning. The spinning process comprises a wet method, a dry-wet method and a melting method, and the wet spinning is the most widely applied process at present. The quality of the precursor is easy to control in wet spinning, the obtained precursor has small fineness dispersion and less solvent residue, and the process is relatively mature.
The high-quality PAN precursor is the first necessary condition for manufacturing the high-performance carbon fiber and is one of the most critical factors influencing the quality of the carbon fiber. The prepared protofilament is required to realize high purification, high strengthening, fine denier and densification; the division linearity between the monofilaments is good, and the surface of the protofilament cannot have obvious defects. The precondition for preparing the high-quality carbon fiber is that high-quality polyacrylonitrile precursor fiber must be used, which is the summary of experience for many years, and the high-quality polyacrylonitrile precursor fiber can be spun only by good spinning solution. The good spinning dope, besides requiring regular polyacrylonitrile molecular chain structure, no branching and no crosslinking, and uniform distribution of the comonomer on the main chain, must also have moderate viscosity, high molecular weight and proper molecular weight distribution.
The viscosity of the spinning solution is related to the solid content, the conversion, the molecular weight of the polyacrylonitrile and its distribution. The higher the molecular weight of polyacrylonitrile, the narrower the molecular weight distribution, the higher the solid content, the higher the conversion rate of the polymerization reaction, the higher the viscosity of the spinning solution. The polyacrylonitrile protofilament with good mechanical property can be obtained by spinning with the spinning solution with high viscosity and high molecular weight. The spinning solution with high viscosity and high molecular weight has poor flowability and spinning property, so that the phenomena of blockage of a spinneret orifice, overflowing of the spinning solution on the surface of a spinneret plate and the like are easily caused, the defects of broken filaments, broken filaments and fiber surfaces are caused, and the quality of polyacrylonitrile protofilaments is seriously reduced. Therefore, in order to open the channel from the spinning solution with high viscosity, high molecular weight and high viscosity to the polyacrylonitrile protofilament with good mechanical property, it is necessary to find an efficient and economical spinning method and spinning process matched with raw materials and products.
Disclosure of Invention
The invention aims to solve the technical problems of more broken filaments in a coagulation bath and large CV value of fiber in the prior art, and provides a spinning method of spinning solution with narrow molecular weight distribution, which has the advantages of low dispersion coefficient of mechanical property of polyacrylonitrile protofilament, small broken filament quality of the coagulation bath and the like.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a spinning method of spinning solution with narrow molecular weight distribution adopts wet spinning, and comprises the following steps:
(1) preparing a spinning solution: 1) adding polymerization raw materials acrylonitrile, a comonomer 1 and (or) a comonomer 2, a solvent dimethyl sulfoxide and an initiator into a reactor, starting constant-temperature reaction under the protection of gas inert to reaction substances, and controlling the reaction temperature to be 60-65 ℃; 2) when the conversion exceeds T1Then, raising the temperature by 5-10 ℃, and continuing to react; 3) when the conversion exceeds T2Then, raising the temperature by 5-10 ℃, and continuing to react; 4) when the conversion rate reaches T3Then, the polymerization reaction is ended; 5) starting a demonomerization reaction, controlling the temperature to be 70-75 ℃ and the pressure to be 50-300 Pa; standing and defoaming, controlling the temperature to be 70-75 ℃ and the pressure to be 100-200 Pa, and finally obtaining the spinning solution.
Wherein, the conversion rate T160 to 70 percent. Said conversion rate T280-90%. Said conversion rate T3Not less than 90%. The molecular weight of the spinning solution is 6-12 ten thousand, the molecular weight distribution is 2-4, the viscosity of the solution (60 ℃) can be controlled to be 20-100 Pa.s, and the content of the residual monomers is 500-1700 ppm.
(2) Solidification and forming: metering the spinning stock solution by a metering pump, extruding the spinning stock solution by a spinning nozzle, and carrying out solidification forming to obtain nascent fiber;
(3) drawing and washing: drafting the nascent fiber by hot water; then washing with water to obtain fiber I;
(4) oiling and drying densification: oiling and at least 2 drying densification processes are carried out on the fiber I to obtain a fiber II;
(5) steam drafting: carrying out steam drafting on the fiber II to obtain a fiber III;
(6) steam heat setting and filament winding: performing steam heat setting on the fiber III, and then collecting the fiber to obtain a polyacrylonitrile precursor product;
in the above technical solution, the comonomer 1 and/or the comonomer 2 is preferably at least one of itaconic acid, acrylic acid, methyl acrylate, methyl methacrylate, ethyl methacrylate, isobutyl acrylic acid, β -butyl itaconate, acrylamide oxime, hydroxyethyl acrylonitrile, α -chloroacrylonitrile or diacetone acrylamide.
In the technical scheme, the molecular weight of the spinning solution is preferably 6-12 ten thousand, the molecular weight distribution is preferably 2-4, the viscosity (60 ℃) of the solution is preferably 20-100 Pa.s, and the residual monomer content is preferably 500-1700 ppm.
In the above technical scheme, the conversion rate T1Preferably 60 to 70%.
In the above technical scheme, the conversion rate T2Preferably 80 to 90 percent.
In the above technical scheme, the conversion rate T3Preferably not less than 90%.
In the technical scheme, the polymerization raw material ratio is preferably 10-35 parts by weight of acrylonitrile, 1-10 parts by weight of comonomer 1, 0.1-10 parts by weight of comonomer 2, 45-86 parts by weight of solvent and 0.2-1% by weight of the total weight of the copolymerization components of the initiator.
In the above technical solution, a further preferred scheme is that the polymerization raw materials comprise, by weight, 20-30 parts of acrylonitrile, 1-4 parts of comonomer, 0.1-2 parts of comonomer, 64-79 parts of solvent, and the amount of the initiator is 0.2-1% of the total weight of the copolymerization components.
In the above technical solution, the gas inert to the reaction substance is preferably at least one selected from nitrogen, argon, and helium.
In the above technical solution, the method for measuring the viscosity of the stock solution preferably uses a rotational rheometer, and the shear rate is preferably 0.1s-1～10s-1By 8s-1The viscosity of the dope was taken as the final viscosity of the dope, and the test conditions included both pre-shearing and non-pre-shearing.
In the above technical solution, the solidification molding preferably adopts 1 to 3 passes.
In the above technical solution, the total multiple of the hot water drafting is preferably 2 to 8 times, and the total multiple of the hot water drafting is a ratio of a speed of the driving roller after the hot water drafting process to a speed of the driving roller before the hot water drafting process; the temperature of hot water drawing is preferably not lower than 90 ℃.
In the technical scheme, the number of the washing tracks is preferably at least 3, the total draft multiple of washing is preferably-5% to 0, and the total draft multiple of washing is the percentage of the ratio of the speed of the driving roller after the washing procedure to the speed of the driving roller before the washing procedure; the temperature of each wash is preferably not higher than 80 ℃.
In the technical scheme, the oiling is preferably at least 2.
In the above technical solution, the medium used in the steam drafting step is saturated steam, the steam pressure is preferably 1 to 6kg, the draft multiple is preferably 1 to 4, and the draft multiple is a ratio of the speed of the driving roller after the saturated steam drafting step to the speed of the driving roller before the saturated steam drafting step.
In the technical scheme, the medium used in the heat setting step adopts saturated steam, the steam pressure is preferably 1 to 3 kilograms, the drafting multiple is preferably-10% to 0, and the heat setting multiple is the ratio of the speed of the driving roller after the heat setting process to the speed of the driving roller before the heat setting process.
In the technical scheme, the yarn receiving speed is preferably 10m/min to 100m/min, and the yarn receiving tension is preferably 1.0cN/dtex to 4.0 cN/dtex.
In the technical scheme, the metered spinning stock solution is subjected to pressure reduction to remove residual monomers and air bubbles in the step (2), and then is filtered and extruded through a spinneret.
In the technical scheme, the breaking strength of the polyacrylonitrile protofilament is preferably 5cN/dtex to 8cN/dtex, the CV value of the breaking strength is preferably not more than 6%, the elongation at break is preferably 8% to 16%, the CV value of the elongation at break is preferably not more than 6%, and the broken filament mass of the coagulation bath in 100 hours is preferably less than 1 g. .
According to the invention, the reaction temperature is adjusted in a gradient manner according to the change of the conversion rate in the polymerization reaction process, so that the mass transfer and heat transfer efficiency of reactants is improved, the half-life period of the initiator is reduced, the residue of the initiator in the spinning solution is reduced, and the polyacrylonitrile protofilament is spun by using the obtained spinning method, and has small mechanical property dispersion coefficient and less coagulation bath filament breakage.
By adopting the technical scheme of the invention, the mass of broken filaments of the coagulation bath in 100 hours is less than 1g, the breaking strength of the polyacrylonitrile fiber is 5cN/dtex to 8cN/dtex, the CV value of the breaking strength is not more than 6%, the elongation at break is 8% to 16%, and the CV value of the elongation at break is not more than 6%. And a better technical effect is achieved.
The following is a specific embodiment of the present invention and is described in detail with reference to comparative examples.
Detailed Description
[ example 1 ]
(1) Preparing a spinning solution: 99kg of distilled Acrylonitrile (AN), 0.5kg of Itaconic Acid (IA), 0.25kg of sodium methallylsulfonate, 0.5kg of Azobisisobutyronitrile (AIBN) and 390kg of dimethyl sulfoxide (DMSO) are added into a reactor, stirred uniformly, the reactor is sealed, a constant temperature reaction is started under nitrogen protection and micro-positive pressure, and the reaction temperature is controlled at 60 ℃. When the conversion rate reaches 70%, raising the temperature to 5-65 ℃, and continuing the reaction; when the conversion rate reaches 90%, raising the temperature to 5-70 ℃, and continuing the reaction; the polymerization was stopped when the conversion reached 95% and the total polymerization time was 22 hours. Removing the seed sheet for 8 hours, controlling the temperature to be 70 ℃ and the pressure to be 200 Pa; standing and defoaming for 12 hours, controlling the temperature at 75 ℃ and the pressure at 150 Pa.
Spinning dope molecular weight 7 ten thousand, molecular weight distribution 3.3, dope viscosity (@8 s)-1@60 ℃ C.) 70 pas and a residual monoacrylonitrile content of 1000ppm。
(2) Solidification and forming: the preparation method adopts a wet spinning method, the spinning solution is metered by a metering pump, after filtration, the heat preservation temperature of a spinning solution pipeline, a filter and a spinning assembly is 60 ℃, and the spinning solution is extruded by a spinning nozzle and then solidified for 2 times to obtain nascent fiber; the concentration of the first-pass solidification is 55 wt%, and the temperature is 45 ℃; the concentration of the second solidification is 35 wt%, and the temperature is 30 ℃; the concentration of the third solidification is 20 wt%, and the temperature is 25 ℃.
(3) Drawing and washing: drafting the nascent fiber by hot water with the total multiple of 4 and the temperature of 95 ℃; and then washing with water at 60 ℃ for 4 times, wherein the water washing adopts a step heating mode, and the drafting multiple of the water washing is-3%.
(4) Oiling and drying densification: oiling the fiber obtained in the step (3) for 2 times, drying and densifying for 4 times, and oiling for 2 times; the concentration of the first oiling is 1 wt%; the concentration of the oil on the second pass was 2 wt%.
(5) Steam drafting: and (4) carrying out steam drafting on the fiber obtained in the step (4), wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 3 kilograms, and the drafting multiple is 3.
(6) Steam heat setting and filament winding: and (3) performing steam heat setting on the fiber obtained in the step (5) and then collecting the fiber, wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 2 kilograms, the drafting multiple is-5 percent, the fiber collecting speed is 20m/min, and the tension of the collected fiber is 2 cN/dtex. The strength of the polyacrylonitrile protofilament of the final product is 5.86cN/dtex, and the CV value is 5.30%; elongation at break was 15.34%, CV value was 5.82%, and mass of broken filaments in coagulation bath in 100 hours was 0.9 g.
[ example 2 ]
(1) 121kg of distilled Acrylonitrile (AN), 2.75kg of methyl methacrylate, 0.2kg of sodium propylene sulfonate, 0.75kg of Azobisisobutyronitrile (AIBN) and 376kg of dimethyl sulfoxide (DMSO) are added into a reactor, stirred uniformly, the reactor is sealed, a constant temperature reaction is started under helium protective micro-positive pressure, and the reaction temperature is controlled to be 65 ℃. When the conversion rate reaches 65%, raising the temperature to 5-70 ℃, and continuing the reaction; when the conversion rate reaches 85 percent, raising the temperature to 10-80 ℃, and continuing the reaction; the polymerization was stopped when the conversion reached 90% and the total polymerization time was 20 hours. Removing the seed sheet for 8 hours, controlling the temperature to be 75 ℃ and the pressure to be 300 Pa; standing and defoaming for 12 hours, controlling the temperature at 75 ℃ and the pressure at 200 Pa.
Spinning dope molecular weight 6 ten thousand, molecular weight distribution 2.6, dope viscosity (@8 s)-1@60 ℃ C.) 80 pas and a residual monoacrylonitrile content of 1200 ppm.
(2) Solidification and forming: the preparation method adopts a wet spinning method, the spinning solution is metered by a metering pump, after filtration, the heat preservation temperature of a spinning solution pipeline, a filter and a spinning assembly is 65 ℃, and the spinning solution is extruded by a spinning nozzle and then solidified by 3 times to obtain nascent fiber; the concentration of the first-pass solidification is 79 wt%, and the temperature is 68 ℃; the concentration of the second solidification is 58 wt%, and the temperature is 59 ℃; the third solidification had a concentration of 13 wt% and a temperature of 69 ℃.
(3) Drawing and washing: drafting the nascent fiber by hot water with the total multiple of 7 and the temperature of 98 ℃; and then 9 times of washing at 78 ℃, wherein the washing adopts a step heating mode, and the drafting multiple of the washing is-3 percent-.
(4) Oiling and drying densification: oiling the fiber obtained in the step (3) for 2 times, drying and densifying for 4 times, and oiling for 2 times; the concentration of the first oiling is 1.3 wt%; the concentration of the oil on the second pass was 2.4 wt%.
(5) Steam drafting: and (5) performing steam drafting on the fiber obtained in the step (4), wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 5 kilograms, and the drafting multiple is 2.5.
(6) Steam heat setting and filament winding: and (3) performing steam heat setting on the fiber obtained in the step (5) and then collecting the fiber, wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 3.5kg, the drafting multiple is-5%, the fiber collecting speed is 70m/min, and the tension of the collected fiber is 3.5 cN/dtex. The strength of the polyacrylonitrile protofilament of the final product is 6.62cN/dtex, and the CV value is 5.80%; elongation at break was 12.65%, CV value was 5.62%, and mass of broken filaments in coagulation bath within 100 hours was 0.7 g.
[ example 3 ]
(1) Preparing a spinning solution: 146kg of distilled Acrylonitrile (AN), 3kg of acrylamide, 1.5kg of sodium methallylsulfonate, 0.9kg of Azobisisobutyronitrile (AIBN) and 350kg of dimethyl sulfoxide (DMSO) are added into a reactor, stirred uniformly, the reactor is sealed, a constant temperature reaction is started under the protection of argon and under the micro-positive pressure, and the reaction temperature is controlled at 62 ℃. When the conversion rate reaches 60 percent, raising the temperature to 10-72 ℃, and continuing the reaction; when the conversion rate reaches 80%, raising the temperature to 5-77 ℃, and continuing the reaction; the polymerization was stopped when the conversion reached 95% and the total polymerization time was 22 hours. Removing the seed sheet for 8 hours, controlling the temperature to be 70 ℃ and the pressure to be 100 Pa; standing and defoaming for 12 hours, controlling the temperature at 75 ℃ and the pressure at 100 Pa.
Spinning dope molecular weight 8 ten thousand, molecular weight distribution 3.7, dope viscosity (@8 s)-1@60 ℃ C.) 90 pas and a residual monoacrylonitrile content of 1700 ppm.
(2) Solidification and forming: the preparation method adopts a wet spinning method, the spinning solution is metered by a metering pump, after filtration, the heat preservation temperature of a spinning solution pipeline, a filter and a spinning assembly is 70 ℃, and the spinning solution is extruded by a spinning nozzle and then solidified by 1 path to obtain nascent fiber; the concentration of the first-pass solidification is 50 wt%, and the temperature is 43 ℃; the concentration of the second solidification is 34 wt%, and the temperature is 33 ℃; the concentration of the third solidification was 16 wt%, and the temperature was 30 ℃.
(3) Drawing and washing: drafting the nascent fiber by hot water with the total multiple of 8 and the temperature of 93 ℃; then the obtained product is washed by water at 60 ℃ for 7 times, the washing adopts a step heating mode, and the drafting multiple of the washing is-2 percent-.
(4) Oiling and drying densification: oiling the fiber obtained in the step (3) for 2 times, drying and densifying for 4 times, and oiling for 2 times; the concentration of the first oiling is 0.8 wt%; the concentration of the oil on the second pass was 1.6 wt%.
(5) Steam drafting: and (4) carrying out steam drafting on the fiber obtained in the step (4), wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 4 kilograms, and the drafting multiple is 1.8.
(6) Steam heat setting and filament winding: and (3) performing steam heat setting on the fiber obtained in the step (5) and then collecting the fiber, wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 2.5 kg, the drafting multiple is-4%, the fiber collecting speed is 35m/min, and the tension of the collected fiber is 3.5 cN/dtex. The strength of the polyacrylonitrile protofilament of the final product is 7.56cN/dtex, and the CV value is 5.69%; elongation at break 16.66%, CV value 5.36%, and mass of broken filaments in coagulation bath within 100 hours was 0.3 g.
[ example 4 ]
(1) Preparing a spinning solution: 146kg of distilled Acrylonitrile (AN), 2kg of acrylamide oxime, 0.2kg of sodium methallylsulfonate, 0.9kg of Azobisisobutyronitrile (AIBN) and 350kg of dimethyl sulfoxide (DMSO) are added into a reactor, stirred uniformly, the reactor is closed, a constant temperature reaction is started under the protection of nitrogen and micro-positive pressure, and the reaction temperature is controlled at 60 ℃. When the conversion rate reaches 70%, raising the temperature to 5-65 ℃, and continuing the reaction; when the conversion rate reaches 90%, raising the temperature to 5-70 ℃, and continuing the reaction; the polymerization was stopped when the conversion reached 95% and the total polymerization time was 20 hours. Removing the seed sheet for 8 hours, controlling the temperature to be 70 ℃ and the pressure to be 50 Pa; standing and defoaming for 12 hours, controlling the temperature at 75 ℃ and the pressure at 200 Pa.
Molecular weight of spinning dope 9 ten thousand, molecular weight distribution 4.0, dope viscosity (@8 s)-1@60 ℃ C.) 100 pas and a residual monoacrylonitrile content of 800 ppm.
(2) Solidification and forming: the preparation method adopts a wet spinning method, the spinning solution is metered by a metering pump, after filtration, the heat preservation temperature of a spinning solution pipeline, a filter and a spinning assembly is 63 ℃, and the spinning solution is extruded by a spinning nozzle and then solidified for 3 times to obtain nascent fiber; the concentration of the first-pass solidification is 73 wt%, and the temperature is 60 ℃; the concentration of the second solidification is 53 wt%, and the temperature is 50 ℃; the concentration of the third solidification was 27 wt%, and the temperature was 66 ℃.
(3) Drawing and washing: drafting the nascent fiber by hot water with the total multiple of 4 and the temperature of 91 ℃; and then 9 times of washing with water at 65 ℃, wherein the washing with water adopts a step heating mode, and the drafting multiple of the washing with water is-3%.
(4) Oiling and drying densification: oiling the fiber obtained in the step (3) for 2 times, drying and densifying for 3 times, and oiling for 2 times; the concentration of the first oiling is 0.9 wt%; the concentration of the oil on the second pass was 1.8 wt%.
(5) Steam drafting: and (4) carrying out steam drafting on the fiber obtained in the step (4), wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 2.5 kilograms, and the drafting multiple is 2.8.
(6) Steam heat setting and filament winding: and (3) performing steam heat setting on the fiber obtained in the step (5) and then collecting the fiber, wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 2 kilograms, the drafting multiple is-5 percent, the fiber collecting speed is 19m/min, and the tension of the collected fiber is 2.8 cN/dtex. The strength of the polyacrylonitrile protofilament of the final product is 6.17cN/dtex, and the CV value is 5.56%; elongation at break was 13.58%, CV value was 5.59%, and mass of broken filaments in coagulation bath in 100 hours was 0.5 g.
[ example 5 ]
(1) Preparing a spinning solution: adding 120kg of distilled Acrylonitrile (AN), 1kg of itaconic acid, 0.5kg of sodium methallylsulfonate, 0.5kg of Azobisisobutyronitrile (AIBN) and 375kg of dimethyl sulfoxide (DMSO) into a reactor, uniformly stirring, sealing the reactor, starting a constant-temperature reaction under helium protective micro-positive pressure, and controlling the reaction temperature to be 60 ℃. When the conversion rate reaches 70%, raising the temperature to 5-65 ℃, and continuing the reaction; when the conversion rate reaches 90%, raising the temperature to 5-70 ℃, and continuing the reaction; the polymerization was stopped when the conversion reached 95% and the total polymerization time was 22 hours. Removing the seed sheet for 8 hours, controlling the temperature to be 75 ℃ and the pressure to be 300 Pa; standing and defoaming for 12 hours, controlling the temperature at 75 ℃ and the pressure at 200 Pa.
Spinning dope molecular weight 8 ten thousand, molecular weight distribution 2.9, dope viscosity (@8 s)-1@60 ℃ C., 70 pas, and a residual monoacrylonitrile content of 1200 ppm.
(2) Solidification and forming: the preparation method adopts a wet spinning method, the spinning solution is metered by a metering pump, after filtration, the heat preservation temperature of a spinning solution pipeline, a filter and a spinning assembly is 60 ℃, and the spinning solution is extruded by a spinning nozzle and then solidified by 3 times to obtain nascent fiber; the concentration of the first solidification is 66 wt%, and the temperature is 58 ℃; the concentration of the second solidification is 37 wt%, and the temperature is 60 ℃; the third solidification had a concentration of 24 wt.% and a temperature of 70 ℃.
(3) Drawing and washing: drafting the nascent fiber by hot water with the total multiple of 5 and the temperature of 93 ℃; and then 9 times of washing with water at 66 ℃, wherein the washing with water adopts a step heating mode, and the draft multiple of the washing with water is-2%.
(4) Oiling and drying densification: oiling the fiber obtained in the step (3) for 2 times, drying and densifying for 4 times, and oiling for 2 times; the concentration of the first oiling is 0.7 wt%; the concentration of the oil on the second pass was 1.4 wt%.
(5) Steam drafting: and (4) carrying out steam drafting on the fiber obtained in the step (4), wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 3.6 kilograms, and the drafting multiple is 2.0.
(6) Steam heat setting and filament winding: and (3) performing steam heat setting on the fiber obtained in the step (5) and then collecting the fiber, wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 2 kilograms, the drafting multiple is-4 percent, the fiber collecting speed is 30m/min, and the tension of the collected fiber is 3.5 cN/dtex. The strength of the polyacrylonitrile protofilament of the final product is 7.86cN/dtex, and the CV value is 4.64%; elongation at break was 13.98%, CV value was 4.67%, and mass of broken filaments in coagulation bath in 100 hours was 0.6 g.
[ example 6 ]
(1) Preparing a spinning solution: 120kg of distilled Acrylonitrile (AN), 3.5kg of hydroxyethyl acrylonitrile, 1.5kg of sodium methallylsulfonate, 0.5kg of Azobisisobutyronitrile (AIBN) and 375kg of dimethyl sulfoxide (DMSO) are added into a reactor, stirred uniformly, the reactor is sealed, a constant temperature reaction is started under the protection of argon and micro-positive pressure, and the reaction temperature is controlled at 60 ℃. When the conversion rate reaches 70%, raising the temperature to 5-65 ℃, and continuing the reaction; when the conversion rate reaches 80%, raising the temperature to 5-70 ℃, and continuing the reaction; the polymerization was stopped when the conversion reached 95% and the total polymerization time was 22 hours. The demould is started for 6 hours, the temperature is controlled to be 72 ℃, and the pressure is controlled to be 300 Pa; standing for defoaming for 10 hours, controlling the temperature at 74 ℃ and the pressure at 100 Pa.
Spinning dope molecular weight 6.5 ten thousand, molecular weight distribution 3.6, dope viscosity (@8 s)-1@60 ℃ C.) 68 pas and a residual acrylonitrile content of 1500 ppm.
(2) Solidification and forming: the preparation method adopts a wet spinning method, the spinning solution is metered by a metering pump, after filtration, the heat preservation temperature of a spinning solution pipeline, a filter and a spinning assembly is 60 ℃, and the spinning solution is extruded by a spinning nozzle and then solidified by 3 times to obtain nascent fiber; the concentration of the first-pass solidification is 77 wt%, and the temperature is 42 ℃; the concentration of the second solidification is 55 wt%, and the temperature is 65 ℃; the concentration of the third solidification was 15 wt%, and the temperature was 60 ℃.
(3) Drawing and washing: drafting the nascent fiber by hot water with the total multiple of 6 and the temperature of 97 ℃; and then washing with water at 70 ℃ for 9 times, wherein the water washing adopts a step heating mode, and the drafting multiple of the water washing is-5%.
(4) Oiling and drying densification: oiling the fiber obtained in the step (3) for 2 times, drying and densifying for 4 times, and oiling for 2 times; the concentration of the first oiling is 1.0 wt%; the concentration of the oil on the second pass was 2.0 wt%.
(5) Steam drafting: and (5) performing steam drafting on the fiber obtained in the step (4), wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 3 kilograms, and the drafting multiple is 1.8.
(6) Steam heat setting and filament winding: and (3) performing steam heat setting on the fiber obtained in the step (5) and then collecting the fiber, wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 2kg, the drafting multiple is-4%, the fiber collecting speed is 32m/min, and the tension of the collected fiber is 3.5 cN/dtex. The strength of the polyacrylonitrile protofilament of the final product is 6.35cN/dtex, and the CV value is 5.88%; elongation at break was 15.67%, CV value was 5.83%, and mass of filament broken in coagulation bath within 100 hours was 0.8 g.
[ example 7 ]
(1) Preparing a spinning solution: 113kg of distilled Acrylonitrile (AN), 0.2kg of itaconic acid, 0.3kg of sodium propylene sulfonate, 0.5kg of Azobisisobutyronitrile (AIBN) and 385kg of dimethyl sulfoxide (DMSO) are added into a reactor, stirred uniformly, the reactor is sealed, a constant temperature reaction is started under nitrogen protection and micro-positive pressure, and the reaction temperature is controlled at 63 ℃. When the conversion rate reaches 70%, raising the temperature to 5-68 ℃, and continuing the reaction; when the conversion rate reaches 90%, raising the temperature to 5-73 ℃, and continuing the reaction; the polymerization was stopped when the conversion reached 95% and the total polymerization time was 18 hours. The demould is started for 6 hours, the temperature is controlled to be 73 ℃, and the pressure is controlled to be 300 Pa; standing and defoaming for 12 hours, controlling the temperature at 75 ℃ and the pressure at 200 Pa.
The molecular weight of the spinning solution is 8 ten thousand, the molecular weight distribution is 3.5, the originalLiquid viscosity (@8 s)-1@60 ℃ C., 65 pas, residual monoacrylonitrile content 600 ppm.
(2) Solidification and forming: the preparation method adopts a wet spinning method, the spinning solution is metered by a metering pump, after filtration, the heat preservation temperature of a spinning solution pipeline, a filter and a spinning assembly is 61 ℃, and the spinning solution is extruded by a spinning nozzle and then solidified for 3 times to obtain nascent fiber; the concentration of the first solidification is 63 wt%, and the temperature is 58 ℃; the concentration of the second solidification is 34 wt%, and the temperature is 63 ℃; the third solidification had a concentration of 22 wt% and a temperature of 68 ℃.
(3) Drawing and washing: drafting the nascent fiber by hot water with the total multiple of 3 and the temperature of 96 ℃; and then washing with water at 68 ℃ for 9 times, wherein the water washing adopts a step heating mode, and the drafting multiple of the water washing is-3%.
(4) Oiling and drying densification: oiling the fiber obtained in the step (3) for 2 times, drying and densifying for 4 times, and oiling for 2 times; the concentration of the first oiling is 1.0 wt%; the concentration of the oil on the second pass was 2.2 wt%.
(5) Steam drafting: and (4) carrying out steam drafting on the fiber obtained in the step (4), wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 2.5 kilograms, and the drafting multiple is 3.5.
(6) Steam heat setting and filament winding: and (3) performing steam heat setting on the fiber obtained in the step (5) and then collecting the fiber, wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 2.5 kg, the drafting multiple is-5%, the fiber collecting speed is 48m/min, and the tension of the collected fiber is 3.5 cN/dtex. The strength of the polyacrylonitrile protofilament of the final product is 6.95cN/dtex, and the CV value is 5.30%; elongation at break 16.35%, CV value 5.08%, and mass of broken filaments in coagulation bath within 100 hours was 0.7 g.
[ example 8 ]
(1) Preparing a spinning solution: 113kg of distilled Acrylonitrile (AN), 0.3kg of itaconic acid, 0.1kg of sodium methallylsulfonate, 0.8kg of Azobisisobutyronitrile (AIBN) and 385kg of dimethyl sulfoxide (DMSO) are added into a reactor, stirred uniformly, the reactor is sealed, a constant temperature reaction is started under helium protective micro-positive pressure, and the reaction temperature is controlled at 60 ℃. When the conversion rate reaches 70%, raising the temperature to 5-65 ℃, and continuing the reaction; when the conversion rate reaches 90%, raising the temperature to 5-70 ℃, and continuing the reaction; the polymerization was stopped when the conversion reached 95% and the total polymerization time was 20 hours. Removing the seed sheet for 8 hours, controlling the temperature at 70 ℃ and the pressure at 300 Pa; standing and defoaming for 12 hours, controlling the temperature at 75 ℃ and the pressure at 200 Pa.
Spinning dope molecular weight 8 ten thousand, molecular weight distribution 3.5, dope viscosity (@8 s)-1@60 ℃ C.) 70 pas and a residual monoacrylonitrile content of 1700 ppm.
(2) Solidification and forming: the preparation method adopts a wet spinning method, the spinning solution is metered by a metering pump, after filtration, the heat preservation temperature of a spinning solution pipeline, a filter and a spinning assembly is 65 ℃, and the spinning solution is extruded by a spinning nozzle and then solidified by 3 times to obtain nascent fiber; the concentration of the first-pass solidification is 78 wt%, and the temperature is 64 ℃; the concentration of the second solidification is 39 wt%, and the temperature is 57 ℃; the concentration of the third solidification was 15 wt%, and the temperature was 69 ℃.
(3) Drawing and washing: drafting the nascent fiber by hot water with the total multiple of 7 and the temperature of 98 ℃; and then 9 times of washing with water at 79 ℃, wherein the washing with water adopts a step heating mode, and the draft multiple of the washing with water is-3%.
(4) Oiling and drying densification: oiling the fiber obtained in the step (3) for 2 times, drying and densifying for 4 times, and oiling for 2 times; the concentration of the first oiling is 0.9 wt%; the concentration of the oil on the second pass was 1.6 wt%.
(5) Steam drafting: and (5) performing steam drafting on the fiber obtained in the step (4), wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 2.5 kilograms, and the drafting multiple is 1.8.
(6) Steam heat setting and filament winding: and (3) performing steam heat setting on the fiber obtained in the step (5) and then collecting the fiber, wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 2 kilograms, the drafting multiple is-4 percent, the fiber collecting speed is 66m/min, and the tension of the collected fiber is 3.0 cN/dtex. The strength of the polyacrylonitrile protofilament of the final product is 7.02cN/dtex, and the CV value is 5.08%; elongation at break was 9.54%, CV value was 4.39%, and mass of broken filaments in coagulation bath in 100 hours was 0.5 g.
[ example 9 ]
(1) Preparing a spinning solution: 113kg of distilled Acrylonitrile (AN), 1.3kg of itaconic acid, 0.8kg of sodium methallylsulfonate, 0.92kg of Azobisisobutyronitrile (AIBN) and 385kg of dimethyl sulfoxide (DMSO) are added into a reactor, stirred uniformly, the reactor is sealed, a constant temperature reaction is started under the protection of argon and under the micro-positive pressure, and the reaction temperature is controlled to be 60 ℃. When the conversion rate reaches 70%, raising the temperature to 5-65 ℃, and continuing the reaction; when the conversion rate reaches 90%, raising the temperature to 5-70 ℃, and continuing the reaction; the polymerization was stopped when the conversion reached 95% and the total polymerization time was 18 hours. Removing the seed sheet for 8 hours, controlling the temperature at 70 ℃ and the pressure at 300 Pa; standing and defoaming for 12 hours, controlling the temperature at 75 ℃ and the pressure at 200 Pa.
Spinning dope molecular weight 6.5 ten thousand, molecular weight distribution 3.2, dope viscosity (@8 s)-1@60 ℃ C.) 75 pas and a residual monoacrylonitrile content of 1600 ppm.
(2) Solidification and forming: the preparation method adopts a wet spinning method, the spinning solution is metered by a metering pump, after filtration, the heat preservation temperature of a spinning solution pipeline, a filter and a spinning assembly is 60 ℃, and the spinning solution is extruded by a spinning nozzle and then solidified by 3 times to obtain nascent fiber; the concentration of the first-pass solidification is 68 wt%, and the temperature is 60 ℃; the concentration of the second solidification is 35 wt%, and the temperature is 63 ℃; the third solidification had a concentration of 22 wt% and a temperature of 68 ℃.
(3) Drawing and washing: drafting the nascent fiber by hot water with the total multiple of 6 and the temperature of 95 ℃; and then washing with water at 80 ℃ for 9 times, wherein the water washing adopts a step heating mode, and the drafting multiple of the water washing is-5%.
(4) Oiling and drying densification: oiling the fiber obtained in the step (3) for 2 times, drying and densifying for 4 times, and oiling for 2 times; the concentration of the first oiling is 1.1 wt%; the concentration of the oil on the second pass was 2.3 wt%.
(5) Steam drafting: and (4) carrying out steam drafting on the fiber obtained in the step (4), wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 2.5 kilograms, and the drafting multiple is 2.2.
(6) Steam heat setting and filament winding: and (3) performing steam heat setting on the fiber obtained in the step (5) and then collecting the fiber, wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 2kg, the drafting multiple is-3%, the fiber collecting speed is 55m/min, and the tension of the collected fiber is 3.0 cN/dtex. The strength of the polyacrylonitrile protofilament of the final product is 5.75cN/dtex, and the CV value is 5.28%; elongation at break of 14.25%, CV value of 5.36%, and mass of broken filaments in coagulation bath within 100 hours of 0.8 g.
[ COMPARATIVE EXAMPLE 1 ]
(1) Preparing a spinning solution: 99kg of distilled Acrylonitrile (AN), 0.5kg of Itaconic Acid (IA), 0.25kg of sodium methallylsulfonate, 0.5kg of Azobisisobutyronitrile (AIBN) and 390kg of dimethyl sulfoxide (DMSO) are added into a reactor, stirred uniformly, the reactor is sealed, a constant temperature reaction is started under nitrogen protection and micro-positive pressure, and the reaction temperature is controlled at 60 ℃. The polymerization was stopped when the conversion reached 95% and the total polymerization time was 28 hours. Removing the seed sheet for 8 hours, controlling the temperature to be 70 ℃ and the pressure to be 200 Pa; standing and defoaming for 12 hours, controlling the temperature at 75 ℃ and the pressure at 150 Pa.
Spinning dope molecular weight 5.7 ten thousand, molecular weight distribution 6.0, dope viscosity (@8 s)-1@60 ℃ C.) 85 pas and a residual monoacrylonitrile content of 8000 ppm.
(2) Solidification and forming: the preparation method adopts a wet spinning method, the spinning solution is metered by a metering pump, after filtration, the heat preservation temperature of a spinning solution pipeline, a filter and a spinning assembly is 60 ℃, and the spinning solution is extruded by a spinning nozzle and then solidified for 2 times to obtain nascent fiber; the concentration of the first-pass solidification is 55 wt%, and the temperature is 45 ℃; the concentration of the second solidification is 35 wt%, and the temperature is 30 ℃; the concentration of the third solidification is 20 wt%, and the temperature is 25 ℃.
(3) Drawing and washing: drafting the nascent fiber by hot water with the total multiple of 4 and the temperature of 95 ℃; and then washing with water at 60 ℃ for 4 times, wherein the water washing adopts a step heating mode, and the drafting multiple of the water washing is-3%.
(4) Oiling and drying densification: oiling the fiber obtained in the step (3) for 2 times, drying and densifying for 4 times, and oiling for 2 times; the concentration of the first oiling is 1 wt%; the concentration of the oil on the second pass was 2 wt%.
(5) Steam drafting: and (4) carrying out steam drafting on the fiber obtained in the step (4), wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 3 kilograms, and the drafting multiple is 3.
(6) Steam heat setting and filament winding: and (3) performing steam heat setting on the fiber obtained in the step (5) and then collecting the fiber, wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 2 kilograms, the drafting multiple is-5 percent, the fiber collecting speed is 20m/min, and the tension of the collected fiber is 2 cN/dtex. The strength of the polyacrylonitrile protofilament of the final product is 5.25cN/dtex, and the CV value is 16.60%; elongation at break was 12.65%, CV value was 16.32%, and mass of filament broken in coagulation bath within 100 hours was 5.5 g.
[ COMPARATIVE EXAMPLE 2 ]
(1) Preparing a spinning solution: 99kg of distilled Acrylonitrile (AN), 0.5kg of Itaconic Acid (IA), 0.25kg of sodium methallylsulfonate, 0.5kg of Azobisisobutyronitrile (AIBN) and 390kg of dimethyl sulfoxide (DMSO) are added into a reactor, stirred uniformly, the reactor is sealed, a constant temperature reaction is started under nitrogen protection and micro-positive pressure, and the reaction temperature is controlled at 60 ℃. When the conversion rate reaches 70%, the temperature is raised to 5 ℃ to 65 ℃, the reaction is continued, and when the conversion rate reaches 95%, the polymerization is stopped, and the total polymerization time is 24 hours. Removing the seed sheet for 8 hours, controlling the temperature to be 70 ℃ and the pressure to be 200 Pa; standing and defoaming for 12 hours, controlling the temperature at 75 ℃ and the pressure at 150 Pa.
Spinning dope molecular weight 6.4 ten thousand, molecular weight distribution 5.2, dope viscosity (@8 s)-1@60 ℃ C.) at 78 pas and a residual monoacrylonitrile content of 5600 ppm.
(2) Solidification and forming: the preparation method adopts a wet spinning method, the spinning solution is metered by a metering pump, after filtration, the heat preservation temperature of a spinning solution pipeline, a filter and a spinning assembly is 60 ℃, and the spinning solution is extruded by a spinning nozzle and then solidified for 2 times to obtain nascent fiber; the concentration of the first-pass solidification is 55 wt%, and the temperature is 45 ℃; the concentration of the second solidification is 35 wt%, and the temperature is 30 ℃; the concentration of the third solidification is 20 wt%, and the temperature is 25 ℃.
(3) Drawing and washing: drafting the nascent fiber by hot water with the total multiple of 4 and the temperature of 95 ℃; and then washing with water at 60 ℃ for 4 times, wherein the water washing adopts a step heating mode, and the drafting multiple of the water washing is-3%.
(4) Oiling and drying densification: oiling the fiber obtained in the step (3) for 2 times, drying and densifying for 4 times, and oiling for 2 times; the concentration of the first oiling is 1 wt%; the concentration of the oil on the second pass was 2 wt%.
(5) Steam drafting: and (4) carrying out steam drafting on the fiber obtained in the step (4), wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 3 kilograms, and the drafting multiple is 3.
(6) Steam heat setting and filament winding: and (3) performing steam heat setting on the fiber obtained in the step (5) and then collecting the fiber, wherein the medium used in a steam drafting section is saturated steam, the steam pressure is 2 kilograms, the drafting multiple is-5 percent, the fiber collecting speed is 20m/min, and the tension of the collected fiber is 2 cN/dtex. The strength of the polyacrylonitrile protofilament of the final product is 4.48cN/dtex, and the CV value is 15.10%; elongation at break was 13.5%, CV value was 15.25%, and mass of filament broken in coagulation bath within 100 hours was 4.5 g.
As can be seen from comparative examples 1, 2 and 1, the spinning solution prepared by the polymerization method with gradient temperature rise is used for spinning, so that the polymerization reaction time can be shortened, and the molecular weight distribution and the residual monomer content of the spinning solution can be reduced; the broken filaments in the coagulating bath are reduced, and the dispersion coefficient of the mechanical property of the polyacrylonitrile protofilament is reduced.

Claims (9)

1. A spinning method of a spinning solution with narrow molecular weight distribution adopts wet spinning and comprises the following steps:
(1) preparing a spinning solution:
1) adding polymerization raw materials acrylonitrile, a comonomer 1 and/or a comonomer 2, a solvent and an initiator into a reactor, starting constant-temperature reaction under the protection of gas inert to reaction substances, and controlling the reaction temperature to be 60-65 ℃;
2) when the conversion exceeds T1Then, raising the temperature by 5-10 ℃, and continuing to react;
3) when the conversion exceeds T2Then, raising the temperature by 5-10 ℃, and continuing to react;
4) when the conversion rate reaches T3Then, the polymerization reaction is ended;
5) obtaining the spinning solution through demonomerization and defoaming;
wherein, the conversion rate T160-70%; said conversion rate T280-90%; said conversion rate T3Is greater than 90%;
(2) solidification and forming: extruding the metered spinning stock solution through a spinning nozzle, and carrying out solidification forming to obtain nascent fiber;
(3) drawing and washing: drafting the nascent fiber by hot water; then washing with water to obtain fiber I;
(4) oiling and drying densification: oiling and at least 2 drying densification processes are carried out on the fiber I to obtain a fiber II;
(5) steam drafting: carrying out steam drafting on the fiber II to obtain a fiber III;
(6) steam heat setting and filament winding: and (3) performing steam heat setting on the fiber III, and then collecting the fiber to obtain a polyacrylonitrile protofilament product.
2. The method of claim 1, wherein the comonomer is at least one of itaconic acid, acrylic acid, methyl acrylate, methyl methacrylate, ethyl methacrylate, isobutyl acrylic acid, beta-butyl itaconate, acrylamide oxime, hydroxyethylacrylonitrile, alpha-chloroacrylonitrile, or diacetone acrylamide.
3. The method of spinning a narrow molecular weight distribution spinning solution as recited in claim 1, wherein the dope has a molecular weight of 6 to 12 ten thousand, a molecular weight distribution of 2 to 4, a dope viscosity of 20 to 100 Pa-s at 60 ℃, and a residual monomer content of 500 to 1700 ppm.
4. The spinning method of a narrow molecular weight distribution spinning solution as claimed in claim 1, wherein the polymerization raw material ratio is 10-35 parts by weight of acrylonitrile, 1-10 parts by weight of comonomer 1, 0.1-10 parts by weight of comonomer 2, 45-86 parts by weight of solvent, and the amount of initiator is 0.2-1% of the total weight of the copolymerization components.
5. The method of claim 1, wherein the gas inert to the reaction material is selected from at least one of nitrogen, argon, or helium.
6. The method of claim 1, wherein the total number of hot water drafts is from 2 to 8; the hot water drafting temperature is not lower than 90 ℃; the number of washing tracks is at least 3, the total draft multiple of washing is-5% to 0, and the washing temperature of each washing track is not higher than 80 ℃.
7. The method of claim 1, wherein the coagulation forming is performed by using 1 to 3 passes; the oiling is carried out for at least 2 times.
8. The method of claim 1, wherein the medium used in step (5) is saturated steam, the steam pressure is 1 to 6kg, and the draft is 1 to 4 times.
9. The method of claim 1, wherein the medium used in the step (6) of steam heat-setting is saturated steam, the steam pressure is 1 to 3kg, and the draft ratio is-10% to 0; the yarn receiving speed is 10m/min to 100m/min, and the tension of the received yarn is 1.0cN/dtex to 4.0 cN/dtex.
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