CN111733473B - Preparation method of polyacrylonitrile-based carbon fiber precursor - Google Patents
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- 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
- D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
- D01F6/44—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from mixtures of polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds as major constituent with other polymers or low-molecular-weight compounds
- D01F6/54—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from mixtures of polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds as major constituent with other polymers or low-molecular-weight compounds of polymers of unsaturated nitriles
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
- C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
- C08F220/42—Nitriles
- C08F220/44—Acrylonitrile
- C08F220/46—Acrylonitrile with carboxylic acids, sulfonic acids or salts thereof
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- 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
- D01D1/10—Filtering or de-aerating the spinning solution or melt
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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
- D01D1/00—Treatment of filament-forming or like material
- D01D1/10—Filtering or de-aerating the spinning solution or melt
- D01D1/103—De-aerating
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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
- D01D1/00—Treatment of filament-forming or like material
- D01D1/10—Filtering or de-aerating the spinning solution or melt
- D01D1/106—Filtering
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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
- D01D4/00—Spinnerette packs; Cleaning thereof
- D01D4/02—Spinnerettes
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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
- D01D5/00—Formation of filaments, threads, or the like
- D01D5/06—Wet spinning methods
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- 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
- D01F1/00—General methods for the manufacture of artificial filaments or the like
- D01F1/02—Addition of substances to the spinning solution or to the melt
- D01F1/10—Other agents for modifying properties
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Abstract
The invention discloses a preparation method of polyacrylonitrile-based carbon fiber precursor. The method comprises the following steps: firstly, polyacrylonitrile spinning solution obtained by pretreating polyacrylonitrile solution is continuously fed from a main feeding hole of a double-screw extruder; secondly, continuously feeding the modifier from a side feeding port of the double-screw extruder according to the dosage; and finally, the polyacrylonitrile spinning solution fed from the main feed port and the modifier fed from the side feed port sequentially pass through a conveying section, a degassing section and a pressurizing section of a double-screw extruder to obtain a modified polyacrylonitrile solution, the pressurized modified polyacrylonitrile solution forms an extruded liquid flow through a spinneret plate, the extruded liquid flow enters a coagulating bath through an air drying section for coagulation forming, and the extruded liquid flow is drawn out of the coagulating bath to prepare the nascent fiber. The pretreated material is subjected to online modifier addition by adopting double screws, so that the full deaeration and precise filtration of the material are ensured, the spinnability of the polyacrylonitrile-based spinning stock solution is improved, the micropore defect of the fiber is reduced, and the process stability is improved.
Description
Technical Field
The invention belongs to the technical field of carbon fiber preparation, and particularly relates to a preparation method of polyacrylonitrile-based carbon fiber precursor.
Background
The carbon fiber is a very important structure function integrated material, has wide application in aerospace, sports and leisure, transportation and industrial production, is divided into a plurality of varieties according to different raw materials, and is the polyacrylonitrile-based carbon fiber which is most widely applied. The traditional preparation method of the polyacrylonitrile carbon fiber precursor comprises wet spinning and dry-wet spinning, and concentration changes caused by double diffusion of a solvent and a non-solvent can occur in the forming process of nascent fiber by the two spinning forming methods; the concentration variations of the solvent and non-solvent cause phase separation, resulting in the formation of larger void defects in the nascent fibers, which are then passed on to the final carbon fibers, and are one of the major causes of reduced final product performance. The dry-wet spinning can be generally carried out at a lower coagulation bath temperature for the reason that the spinning liquid flow passes through the air drying section before entering the coagulation bath, so that the defects of the surface and the interior of the fiber are reduced compared with the wet spinning, however, the lower coagulation bath temperature causes higher energy consumption, the spinning liquid flow is easy to generate broken ends due to the fluctuation of external conditions, and the suitable spinning process range is narrower.
The method has the advantages that the gelation temperature of the spinning liquid flow can be obviously increased, a bicontinuous phase homogenization structure is easily formed in the fiber solidification forming process, but the ultra-high molecular weight polymer is difficult to prepare by adopting the solution polymerization in the one-step spinning process, and new defects can be brought by adopting a low solid content spinning solution or a large-aperture spinneret plate for spinning due to the large molecular weight; in the two-step spinning process, water or alcohol is added as a modifier in the dissolving process of dry resin (Chinese patent CN102154723A), the mixture is cured after being mixed by a stirring kettle to form gel spinning solution in advance, and then gel spinning is carried out; there are problems in that: not only the process is complex, but also the common stirring condition can not fully ensure the mixing uniformity, and the viscosity of the resin system is higher after the modifier is further added in advance, so that the defoaming and the precise filtration are difficult.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a preparation method of polyacrylonitrile-based carbon fiber precursor, the materials after demonomerization and defoamation are subjected to online modifier addition by adopting double screws, so that the sufficient defoamation and precise filtration of the materials are ensured, the spinnability of polyacrylonitrile-based spinning solution is improved, the micropore defect of the fiber is reduced, and the process stability is improved.
The invention provides a preparation method of polyacrylonitrile-based carbon fiber precursor, which comprises the following steps:
step 1, continuously feeding polyacrylonitrile spinning solution obtained by pretreating polyacrylonitrile solution from a main feeding hole of a double-screw extruder;
step 2, continuously feeding the modifier from a side feeding port of the double-screw extruder according to the dosage;
and 3, sequentially passing the polyacrylonitrile spinning solution fed from the main feed inlet and the modifier fed from the side feed inlet through a conveying section, a degassing section and a pressurizing section of a double-screw extruder to obtain a modified polyacrylonitrile solution, forming an extruded liquid flow by the pressurized modified polyacrylonitrile solution through a spinneret plate, entering a coagulating bath through an air drying section for coagulation forming, and drawing out of the coagulating bath to prepare the nascent fiber.
As a further improvement of the invention:
the polyacrylonitrile solution in the step 1 is prepared by polymerizing acrylonitrile and comonomer free radical solution;
the comonomer in the step 1 is one or two of itaconic acid or derivatives thereof and acrylic acid or derivatives thereof;
the solvent of the polyacrylonitrile solution in the step 1 is one of dimethyl sulfoxide, dimethylformamide and dimethylacetamide;
the pretreatment in the step 1 is to perform demonomerization, defoaming and precise filtration treatment on the polyacrylonitrile solution;
the temperature of the polyacrylonitrile spinning solution in the step 1 is constant at 45-60 ℃;
the viscosity of the polyacrylonitrile spinning solution in the step 1 is 60-120 Pa.s at 40 ℃, and the solid content is 18-22%;
as a further improvement of the invention:
the solvent used by the polyacrylonitrile solution in the step 1, the solvent contained by the modifier in the step 2 and the solvent contained by the coagulating bath in the step 3 are the same solvent.
The modifier in the step 2 is an aqueous solution of a solvent, and the mass ratio of the solvent to water is 1: 1-0.2: 1; the temperature of the modifier is 45-60 ℃.
An ultrasonic degassing device is arranged in the storage tank of the modifier in the step 2, so that trace air dissolved in the solution can be removed; the modifier degassed by ultrasonic is pressurized by air pressure or pump pressure, accurately metered by a mass flowmeter and continuously fed into a side feed inlet of a double screw machine;
the feeding amount of the modifier in the step 2 is 0.1-1.5% of the mass of the polyacrylonitrile spinning solution fed from the main feed inlet of the double-screw extruder.
As a further improvement of the invention:
the temperature of the conveying section of the double-screw extruder in the step 3 is constant at 45-60 ℃, and the temperature of the degassing section and the pressurizing section is constant at 60-70 ℃.
The degassing section of the double-screw extruder in the step 3 adopts a vacuum pump to assist in degassing;
and 3, carrying out spinning extrusion on the modified polyacrylonitrile solution in the step 3 through a spinneret plate, and then, keeping the distance from the air dry section of the liquid level of the coagulation bath to be 5-15 mm.
The temperature of the coagulating bath in the step 3 is-3-20 ℃; the concentration of the solvent contained in the coagulating bath is 30-55%;
the pore size of the spinneret plate in the step 3 is 0.10-0.15 mm;
and the drawing ratio of the primary fiber out of the coagulating bath in the step 3 is 1.5-5.
Compared with the prior art, the invention has the following beneficial effects:
(1) the viscosity of the polyacrylonitrile solution before modification is relatively low, so that demonomerization, defoaming and precise filtration treatment can be conveniently carried out;
(2) the aqueous solution of the organic solvent is used as the modifier, so that the local excessive gelation caused by adding pure water is avoided, the solvent which is volatilized in the demonomerization and defoaming processes can be properly compensated in the presence of the solvent, and the solid content of the spinning solution is kept in a reasonable range;
(3) the modifier is continuously added in the conveying process of the polyacrylonitrile spinning solution, so that the problems of overhigh viscosity and poor spinnability caused by excessive modification due to long-time storage of materials are solved;
(4) the double-screw extruder is adopted for auxiliary modification, compared with the traditional kettle type stirring, the full mixing of materials can be guaranteed, the problems of uneven materials, long stirring time or long curing time and the like are avoided, trace low-volatility gas can be further removed through the degassing function of the vacuum-assisted double-screw extruder, the broken ends in the spinning process are avoided, and the sectional temperature control mechanism is adopted, so that the viscosity of the materials is easy to regulate and control, and the proper pressure before spinning is guaranteed;
(5) the on-line continuous modification can adopt a spinneret plate with a small spinneret pore diameter (less than 0.2mm) for spinning, the final fine denier of the carbon fiber precursor can be realized within a proper range of the total draft multiplying power, and the range of proper spinneret solidification forming conditions is wide.
(6) The spinning method has simple and convenient process, easy industrial realization, stable spinning process and less micropore defects of the fiber section.
Detailed Description
The present application will be described in further detail with reference to examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.
Example 1:
preparing acrylonitrile and itaconic acid according to a mass ratio of 98:2, using azobisisobutyronitrile as an initiator and dimethyl sulfoxide as a solvent, polymerizing by adopting a free radical solution to obtain a polyacrylonitrile solution, performing demonomerization, defoaming and precise filtration to obtain a polyacrylonitrile spinning stock solution with the viscosity of 60 Pa.s (40 ℃) and the solid content of 18%, keeping the temperature at 45 ℃, and accurately metering and continuously feeding the polyacrylonitrile spinning stock solution into a main feeding hole of a double-screw extruder; the modifying agent is an aqueous solution of dimethyl sulfoxide, wherein the mass ratio of dimethyl sulfoxide to water is 0.2:1, the modified polyacrylonitrile solution is obtained by carrying out ultrasonic degassing, keeping the temperature at 45 ℃, accurately metering by using a mass flow meter by using air pressure or pump pressure according to 1.5 percent of the mass of polyacrylonitrile spinning stock solution fed from a main feed inlet, continuously feeding the polyacrylonitrile stock solution into a side feed inlet of a double screw extruder, and sequentially passing the polyacrylonitrile stock solution fed from the main feed inlet through a conveying section, a degassing section and a pressurizing section of the double screw extruder, wherein the temperatures of the conveying section, the degassing section and the pressurizing section are respectively 45 ℃, 60 ℃ and 60 ℃. The pressurized modified polyacrylonitrile solution is extruded by a spinneret plate with the aperture of 0.1mm, enters a coagulation bath through an air dry section with the distance of 5mm, the coagulation bath is a water solution of dimethyl sulfoxide, the concentration of a solvent is 30%, the temperature is-3 ℃, the solvent is led out by a return guide roller in the coagulation bath, the drawing speed of the solution out of the coagulation bath is 1.5 times of the spinning speed, and the nascent fiber is prepared, and the spinning stability is good after 24 hours of continuous operation. The nascent fiber is sliced by a Ha's slicer, and the section of the fiber is observed by an optical fiber mirror, so that no obvious skin-core light transmission difference is found, and no micropore defect larger than 0.2 micrometer is found.
Example 2:
polymerizing acrylonitrile and itaconic acid by using a radical solution with a mass ratio of 98:2, azodiisobutyronitrile as an initiator and dimethyl sulfoxide as a solvent to obtain a polyacrylonitrile solution, performing demonomerization, defoaming and precise filtration to obtain a polyacrylonitrile spinning stock solution with the viscosity of 70 Pa.s (40 ℃) and the solid content of 19%, keeping the temperature at 50 ℃, and accurately metering and continuously feeding the polyacrylonitrile spinning stock solution into a main feed inlet of a double-screw extruder; the mass ratio of dimethyl sulfoxide to water in the modifier is 1:1, after ultrasonic degassing, the constant temperature is 50 ℃, the mass of polyacrylonitrile-based spinning stock solution fed through a main feed inlet is 1.0 percent of that of the polyacrylonitrile-based spinning stock solution fed through a main feed inlet, the polyacrylonitrile-based spinning stock solution is accurately metered and continuously fed into a side feed inlet of a double screw extruder, and the polyacrylonitrile-based spinning stock solution fed through the main feed inlet sequentially passes through a conveying section, a degassing section and a pressurizing section of the double screw extruder to obtain modified polyacrylonitrile solution, wherein the temperatures of the conveying section, the degassing section and the pressurizing section are respectively 50; the pressurized modified polyacrylonitrile solution is extruded by a spinneret plate with the aperture of 0.1mm, enters a coagulation bath through an air dry section with the distance of 10mm, the coagulation bath is a water solution of dimethyl sulfoxide, the concentration of a solvent is 35%, the temperature is 0 ℃, the solution is led out by a coagulation bath turning guide roller, the drawing speed of the solution is 2.5 times of the spinning speed, the nascent fiber is prepared, the nascent fiber continuously runs for more than 24 hours, the spinning stability is good, the nascent fiber is sliced by a Ha's slicer, and the fiber section is observed by an optical fiber mirror, so that the micropore defect larger than 0.2 micrometer is not found.
Example 3:
preparing acrylonitrile, itaconic acid and methyl methacrylate in a mass ratio of 98:1:1 in a dimethyl sulfoxide solvent, using azobisisobutyronitrile as an initiator, polymerizing by adopting a free radical solution to obtain a polyacrylonitrile solution, performing demonomerization, defoaming and precise filtration to obtain a polyacrylonitrile spinning stock solution with the viscosity of 80 Pa.s (40 ℃), the solid content of 20 percent, keeping the temperature at 55 ℃, and accurately metering and continuously feeding the polyacrylonitrile spinning stock solution into a main feed inlet of a double-screw extruder; the mass ratio of dimethyl sulfoxide to water in the modifier is 0.5:1, after ultrasonic degassing, the constant temperature is 55 ℃, the mass of polyacrylonitrile-based spinning stock solution fed through a main feed inlet is 1.0 percent, the polyacrylonitrile-based spinning stock solution is accurately metered and continuously fed into a side feed inlet of a double screw extruder, and the polyacrylonitrile-based spinning stock solution fed through the main feed inlet sequentially passes through a conveying section, a degassing section and a pressurizing section of the double screw extruder to obtain modified polyacrylonitrile solution, wherein the temperatures of the conveying section, the degassing section and the pressurizing section are respectively 55 ℃, 65 ℃ and 65 ℃; the pressurized modified polyacrylonitrile solution is extruded by a spinneret plate with the aperture of 0.12mm, enters a coagulation bath through an air section with the distance of 12mm, the coagulation bath is a water solution of dimethyl sulfoxide, the concentration of a solvent is 35%, the temperature is 5 ℃, the solvent is led out by a coagulation bath turning-back guide roller, the drawing speed of the solution is 3 times of the spinning speed, the nascent fiber is prepared, the spinning stability is good after the nascent fiber continuously runs for more than 24 hours, the nascent fiber is sliced by a Ha's slicer, and the fiber section is observed by an optical fiber mirror, so that the defect of micropores larger than 0.2 micrometer is not found.
Example 4:
preparing acrylonitrile, itaconic acid and methyl methacrylate in a dimethyl sulfoxide solvent according to a mass ratio of 98:1:1, using azobisisobutyronitrile as an initiator, polymerizing by adopting a free radical solution to obtain a polyacrylonitrile solution, performing demonomerization, defoaming and precise filtration to obtain a polyacrylonitrile spinning stock solution with the viscosity of 100Pa & s (40 ℃), the solid content of 21%, keeping the temperature at 60 ℃, and accurately metering and continuously feeding the polyacrylonitrile spinning stock solution into a main feed inlet of a double-screw extruder; the mass ratio of dimethyl sulfoxide to water in the modifier is 0.4:1, the modified polyacrylonitrile solution is obtained by performing ultrasonic degassing at a constant temperature of 60 ℃ and accurately metering 0.7 percent of the mass of polyacrylonitrile-based spinning stock solution fed from a main feed inlet, feeding the polyacrylonitrile-based spinning stock solution into a side feed inlet of a double screw extruder, and sequentially passing the polyacrylonitrile-based spinning stock solution fed from the main feed inlet through a conveying section, a degassing section and a pressurizing section of the double screw extruder, wherein the temperatures of the conveying section, the degassing section and the pressurizing section are respectively 60 ℃, 65 ℃ and 65 ℃; the pressurized modified polyacrylonitrile solution is extruded by a spinneret plate with the aperture of 0.12mm, enters a coagulation bath through an air section with the distance of 12mm, the coagulation bath is a water solution of dimethyl sulfoxide, the concentration of a solvent is 40%, the temperature is 10 ℃, the solvent is led out by a coagulation bath turning-back guide roller, the drawing speed of the solution is 3.5 times of the spinning speed, the nascent fiber is prepared, the spinning stability is good after the fiber continuously runs for more than 24 hours, the nascent fiber is sliced by a Ha's slicer, and the fiber section is observed by an optical fiber mirror, so that the micropore defect larger than 0.2 micrometer is not found.
Example 5:
preparing acrylonitrile and itaconic acid in a dimethyl sulfoxide solvent according to a mass ratio of 98.5:1.5, polymerizing a free radical solution by using azodiisobutyronitrile as an initiator to obtain a polyacrylonitrile solution, performing demonomerization, defoaming and precise filtration to obtain a polyacrylonitrile spinning stock solution with the viscosity of 100 pas (40 ℃), the copolymer content of 20%, and continuously feeding the polyacrylonitrile spinning stock solution into a main feed inlet of a double-screw extruder after precise metering at a constant temperature of 60 ℃; the mass ratio of dimethyl sulfoxide to water in the modifier is 0.4:1, the modified polyacrylonitrile solution is obtained by accurately measuring a side feed inlet of a double-screw machine at a constant temperature of 60 ℃ after ultrasonic degassing according to 0.8 percent of the mass of polyacrylonitrile-based spinning stock solution fed from a main feed inlet, and sequentially passing the polyacrylonitrile-based spinning stock solution fed from the main feed inlet through a conveying section, a degassing section and a pressurizing section of the double-screw extruder, wherein the temperatures of the conveying section, the degassing section and the pressurizing section are respectively 60 ℃, 67 ℃ and 67 ℃; the pressurized modified polyacrylonitrile solution is extruded by a spinneret plate with the aperture of 0.15mm, enters a coagulation bath through an air section with the distance of 12mm, the coagulation bath is a water solution of dimethyl sulfoxide, the concentration of a solvent is 45%, the temperature is 15 ℃, the solvent is led out by a coagulation bath turning-back guide roller, the drawing speed of the solution is 4 times of the spinning speed, the nascent fiber is prepared, the spinning stability is good after the nascent fiber continuously runs for more than 24 hours, the nascent fiber is sliced by a Ha's slicer, and the fiber section is observed by an optical fiber microscope, so that the defect of micropores larger than 0.2 micrometer is not found.
Example 6:
preparing acrylonitrile and acrylic acid in a dimethyl sulfoxide solvent according to a mass ratio of 98:2, taking azobisisobutyronitrile as an initiator, polymerizing a free radical solution to obtain a polyacrylonitrile solution, performing demonomerization, defoaming and precise filtration to obtain a polyacrylonitrile spinning stock solution with the viscosity of 110 Pa.s (40 ℃) and the copolymer content of 20%, keeping the temperature at 46 ℃, and feeding the polyacrylonitrile spinning stock solution into a main feed inlet of a double-screw extruder after precise metering; the mass ratio of dimethyl sulfoxide to water in the modifier is 0.5:1, the constant temperature is 46 ℃ after ultrasonic degassing, and the mass of the polyacrylonitrile-based spinning solution fed into a main feed inlet is 0.5 percent of that of the polyacrylonitrile-based spinning solution fed into a double-screw machine side feed inlet in an accurate metering manner; the polyacrylonitrile solution is fed with a main feed inlet and sequentially passes through a book conveying section, a degassing section and a pressurizing section of a double-screw extruder, so that a modified polyacrylonitrile solution is obtained, the temperatures of the conveying section, the degassing section and the pressurizing section are 47 ℃, 62 ℃ and 62 ℃, respectively, the pressurized modified polyacrylonitrile solution is extruded by a spinneret plate with the aperture of 0.15mm, the modified polyacrylonitrile solution enters a coagulation bath through an air section with the distance of 12mm, the coagulation bath is a dimethyl sulfoxide aqueous solution, the concentration of a solvent is 45 percent, the temperature is 15 ℃, after being led out by a coagulation bath return guide roller, the drawing speed of the coagulation bath is 4 times of the spinning speed, so that a nascent fiber is prepared, the spinning stability is good after continuous operation for more than 24 hours, the nascent fiber is sliced by a Ha slicer, and the section of the fiber is not found to have the micropore defect more than 0.
Example 7:
preparing acrylonitrile, itaconic acid and methyl methacrylate in a dimethyl sulfoxide solvent according to a mass ratio of 98:1:1, using azodiisobutyronitrile as an initiator, polymerizing a free radical solution to obtain a polyacrylonitrile solution, performing demonomerization, defoaming and precise filtration to obtain a polyacrylonitrile spinning stock solution with the viscosity of 120 Pa.s (40 ℃), the copolymer content of 22%, keeping the temperature at 60 ℃, and feeding the polyacrylonitrile spinning stock solution into a main feed inlet of a double-screw extruder after precise metering; the mass ratio of dimethyl sulfoxide to water in the modifier is 0.6:1, after ultrasonic degassing, the mass of the modified polyacrylonitrile solution is constant at 60 ℃, 0.1 percent of the mass of polyacrylonitrile-based spinning solution fed from a main feed inlet is accurately metered and continuously fed into a side feed inlet of a double screw extruder, and the polyacrylonitrile solution fed from the main feed inlet sequentially passes through a conveying section, a degassing section and a pressurizing section of the double screw extruder to obtain a modified polyacrylonitrile solution, wherein the temperatures of the conveying section, the degassing section and the pressurizing section are respectively 60 ℃, 70 ℃ and 70 ℃; the pressurized modified polyacrylonitrile solution is extruded by a spinneret plate with the aperture of 0.12mm, enters a coagulation bath through an air section with the distance of 15mm, the coagulation bath is a water solution of dimethyl sulfoxide, the concentration of a solvent is 55%, the temperature is 20 ℃, the solvent is led out by a coagulation bath return guide roller, the drawing speed of the solution is 5 times of the spinning speed, the nascent fiber is prepared, the spinning stability is good after the nascent fiber continuously runs for more than 24 hours, the nascent fiber is sliced by a Ha's slicer, and the fiber section is observed by an optical fiber microscope, so that the defect of micropores larger than 0.2 micrometer is not found.
Claims (8)
1. A preparation method of polyacrylonitrile-based carbon fiber precursor is characterized by comprising the following steps:
step 1, continuously feeding polyacrylonitrile spinning solution obtained by pretreating polyacrylonitrile solution from a main feeding hole of a double-screw extruder, wherein the pretreatment is to perform demonomerization, defoaming and precise filtration treatment on the polyacrylonitrile solution; (ii) a
Step 2, continuously feeding a modifier from a side feeding port of the double-screw extruder according to the dosage, wherein the modifier is an aqueous solution of a solvent, the mass ratio of the solvent to water is 1: 1-0.2: 1, and the feeding amount of the modifier is 0.1-1.5% of the mass of polyacrylonitrile spinning solution fed from a main feeding port of the double-screw extruder;
3, sequentially passing polyacrylonitrile spinning solution fed from a main feeding hole and a modifier fed from a side feeding hole through a conveying section, a degassing section and a pressurizing section of a double-screw extruder to obtain modified polyacrylonitrile solution, forming extrusion liquid flow of the pressurized modified polyacrylonitrile solution through a spinneret plate, entering a coagulating bath through an air drying section for coagulation forming, and drawing the extruded solution out of the coagulating bath to prepare nascent fiber;
the solvent used by the polyacrylonitrile solution in the step 1, the solvent contained by the modifier in the step 2 and the solvent contained by the coagulating bath in the step 3 are the same solvent.
2. The preparation method of the polyacrylonitrile-based carbon fiber precursor according to claim 1, wherein the temperature of the polyacrylonitrile spinning solution in the step 1 is constant at 45-60 ℃.
3. The preparation method of polyacrylonitrile-based carbon fiber precursor according to claim 1, wherein the temperature of the modifier in the step 2 is 45-60 ℃.
4. The method for preparing the polyacrylonitrile-based carbon fiber precursor as claimed in claim 1, wherein the temperature of the conveying section of the twin-screw extruder is 45-60 ℃, and the temperature of the degassing section and the pressurizing section are 60-70 ℃.
5. The preparation method of the polyacrylonitrile-based carbon fiber precursor as claimed in claim 1, wherein the distance of the modified polyacrylonitrile solution in the step 3 from the air dry section of the coagulation bath liquid surface after being extruded by spinning through a spinneret plate is 5-15 mm.
6. The method for preparing the polyacrylonitrile-based carbon fiber precursor according to claim 1, wherein the temperature of the coagulation bath in the step 3 is-3 to 20 ℃, and the concentration of the solvent contained in the coagulation bath is 30 to 55%.
7. The preparation method of polyacrylonitrile-based carbon fiber precursor as claimed in claim 1, wherein the size of the spinneret hole in step 3 is 0.10-0.15 mm.
8. The preparation method of the polyacrylonitrile-based carbon fiber precursor as claimed in claim 1, wherein the drawing ratio of the nascent fiber in step 3 out of the coagulation bath is 1.5-5.
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| CN202010595546.1A CN111733473B (en) | 2020-06-24 | 2020-06-24 | Preparation method of polyacrylonitrile-based carbon fiber precursor |
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