CN112142888B - Polyacrylonitrile spinning solution and preparation method thereof - Google Patents
Polyacrylonitrile spinning solution and preparation method thereof Download PDFInfo
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- CN112142888B CN112142888B CN201910563190.0A CN201910563190A CN112142888B CN 112142888 B CN112142888 B CN 112142888B CN 201910563190 A CN201910563190 A CN 201910563190A CN 112142888 B CN112142888 B CN 112142888B
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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
- C08F120/00—Homopolymers 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
- C08F120/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
- C08F120/42—Nitriles
- C08F120/44—Acrylonitrile
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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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- 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
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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
- D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
- D01F8/04—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers
- D01F8/08—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers with at least one polyacrylonitrile as constituent
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- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
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- 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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Abstract
The invention relates to a polyacrylonitrile spinning solution and a preparation method thereof. The main technical scheme adopted is as follows: a preparation method of polyacrylonitrile spinning solution comprises the following steps: polymerizing acrylonitrile monomer to form polyacrylonitrile oligomer, making acrylonitrile monomer and comonomer undergo the process of copolymerization reaction to obtain polyacrylonitrile copolymer, and making the polyacrylonitrile oligomer and polyacrylonitrile copolymer undergo the process of solution blending so as to obtain polyacrylonitrile spinning solution. A polypropylene spinning solution is prepared by the preparation method of the polyacrylonitrile spinning solution. The polyacrylonitrile-based carbon fiber spinning solution is mainly used for preparing polyacrylonitrile-based carbon fibers, and the polyacrylonitrile-based carbon fibers with less broken filaments and better strength can be prepared by using the polyacrylonitrile-based carbon fiber spinning solution.
Description
Technical Field
The invention relates to the technical field of carbon fibers, in particular to a polyacrylonitrile spinning solution and a preparation method thereof.
Background
The structure and performance of polyacrylonitrile protofilament directly influence the quality of polyacrylonitrile-based carbon fiber; the performance of the polyacrylonitrile precursor is influenced by various factors such as the polymerization process and the polymerization mode of the polyacrylonitrile spinning solution. In the production and preparation of the polyacrylonitrile-based carbon fiber, as the initial step of the whole production process, the polymerization process is the key for determining the performance of the polyacrylonitrile-based carbon fiber product.
The polymerization process is the starting point and the kerbstone of the whole polyacrylonitrile-based carbon fiber preparation process; the polymerization conditions and the polymerization method determine the basic chemical structure (such as molecular weight and distribution thereof, comonomer content and distribution thereof, and the like) of the PAN precursor, thereby influencing the solution properties of the PAN spinning solution and the thermal properties of the pre-oxidized filaments. High performance polyacrylonitrile carbon fibers require that the polyacrylonitrile polymer should have appropriate molecular weight and distribution, small branching degree, and proper comonomer composition.
The relative molecular mass and the distribution of the polyacrylonitrile spinning solution have great influence on the stability and the quality of the polyacrylonitrile protofilament production process; the processability of polyacrylonitrile filaments, fiber formation, water-wash drawing and the quality of the finished product are all related to the relative molecular mass and its distribution. The larger the relative molecular mass of the polyacrylonitrile spinning solution is, the higher the strength of the polyacrylonitrile protofilament is, but the increased proportion is gradually reduced, and finally a limit value is reached; when the relative molecular mass of the polyacrylonitrile spinning solution is too large, the spinnability of spinning is directly influenced, and the phenomenon of yarn breakage occurs, so that broken yarns are formed in the production process. The relative molecular mass of the spinning solution is too low, which greatly affects the strength and the drawability of the protofilament product and is not beneficial to preparing high-quality protofilaments. The relative molecular mass distribution of the polyacrylonitrile spinning solution has great influence on the production process and the fiber property of the precursor, the prepared fiber has low strength and poor drawability when the relative molecular mass distribution is wide, the uniformity of the precursor is poor, and the phenomenon of filament breakage and roll winding is easy to occur to form broken filaments.
In conclusion, in the prior art, the strength of polyacrylonitrile protofilament and polyacrylonitrile-based carbon fiber is improved by preparing the polyacrylonitrile copolymer with higher molecular weight as the polyacrylonitrile spinning solution. However, the viscosity of the polyacrylonitrile spinning solution is high, so that the processability, fiber forming and drafting performance of the precursor are poor, and finally, the filament quantity of the polyacrylonitrile precursor and the polyacrylonitrile-based carbon fiber is large.
Disclosure of Invention
In view of the above, the present invention provides a polyacrylonitrile spinning solution and a preparation method thereof, and mainly aims to prepare a polyacrylonitrile spinning solution, wherein the polyacrylonitrile spinning solution can be used for preparing polyacrylonitrile-based carbon fibers with less broken filament amount and good strength.
In order to achieve the purpose, the invention mainly provides the following technical scheme:
on one hand, the embodiment of the invention provides a preparation method of polyacrylonitrile spinning solution, which comprises the following steps:
the oligomer preparation step comprises: polymerizing acrylonitrile monomer to form polyacrylonitrile oligomer;
copolymer preparation step: carrying out copolymerization reaction on acrylonitrile monomer and comonomer to prepare polyacrylonitrile copolymer;
solution blending step: and (3) carrying out solution blending on the polyacrylonitrile oligomer and the polyacrylonitrile copolymer to obtain the polyacrylonitrile spinning solution.
Preferably, in the oligomer preparation step, the acrylonitrile monomer is polymerized into the polyacrylonitrile oligomer by adopting a free radical telomerization method.
Preferably, the oligomer preparation step comprises the following steps: 1) polymerizing a reaction mixture containing an acrylonitrile monomer, a chain transfer agent and an initiator at a first set temperature for a first set time to obtain a first polymerization solution; 2) removing a monomer, removing a chain transfer agent and purifying the first polymerization liquid to obtain a polyacrylonitrile oligomer; preferably, the chain transfer agent is one or more of 3-mercaptopropionic acid, 2-mercaptoethanol, isopropanol, aliphatic mercaptan and dodecyl mercaptan; preferably, the initiator is one or more of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptonitrile and dimethyl azobisisobutyrate. Preferably, the first set temperature is 40-70 ℃, preferably 55-65 ℃; the first set time is 10-30h, preferably 20-25 h; preferably, the molar ratio of the acrylonitrile monomer, the chain transfer agent and the initiator in the reaction mixture is 1: (0.05-0.1): (0.01-0.05), preferably 1: (0.08-0.1):(0.01-0.02).
Preferably, step 2) of the oligomer preparation step comprises:
21) carrying out vacuum distillation treatment on the first polymerization liquid to remove polyacrylonitrile monomers and chain transfer agents in the first polymerization liquid to obtain a liquid product;
22) mixing the liquid product with a first solvent, and filtering to obtain a filtrate; wherein the first solvent can dissolve the polyacrylonitrile oligomer; preferably, the first solvent is acetone or polyacrylonitrile wet spinning solvent;
wherein, when the first solvent is acetone: the step 2) in the oligomer preparation step further comprises: 23) rotationally evaporating the filtrate to evaporate acetone in the filtrate to obtain a viscous polyacrylonitrile oligomer;
wherein, when the first solvent is polyacrylonitrile wet spinning solvent: the filtrate obtained in the step 22) is polyacrylonitrile oligomer solution; in the solution blending step, solution blending is carried out on polyacrylonitrile oligomer solution and polyacrylonitrile copolymer to obtain polyacrylonitrile spinning solution;
preferably, the polyacrylonitrile wet spinning solvent is dimethyl sulfoxide.
Preferably, the viscosity average molecular weight of the polyacrylonitrile oligomer is 700-1500.
The preparation method of the copolymer comprises the following steps: 1) copolymerizing a reaction system comprising a polymerization monomer, a solvent and an initiator at a second set temperature for a second set time to obtain a second polymerization solution; 2) and carrying out monomer removal treatment on the second polymerization liquid to obtain the polyacrylonitrile copolymer. Preferably, the second set temperature is 55-75 ℃, preferably 65-70 ℃; the second set time is 5-20h, preferably 12-18 h; preferably, the polymerized monomers include acrylonitrile monomers and comonomers; preferably, in the reaction system, the mass fraction of the polymerized monomer is 15-25 wt%, preferably 19-21 wt%; preferably, the comonomers include methyl acrylate and itaconic acid; preferably, the mass fraction of the methyl acrylate in the polymerized monomers is 1-5 wt%, preferably 2-3 wt%; preferably, in the polymerized monomers, the mass fraction of the itaconic acid is 0.5-2 wt%, preferably 0.5-1 wt%; preferably, the solvent is dimethyl sulfoxide; preferably, the initiator is azobisisobutyronitrile; preferably, the amount of the initiator is 0.3 to 0.8 wt% of the amount of the polymerization monomer; preferably, the reaction system also comprises a chain transfer agent; wherein the amount of the chain transfer agent is 0.5-2 wt% of the amount of the polymerization monomer; preferably, in the copolymerization reaction, when the conversion rate of the polymerization monomer reaches 85 to 95%, the reaction is stopped to obtain a second polymerization liquid.
Preferably, the viscosity average molecular weight of the polyacrylonitrile copolymer is 10 to 20 ten thousand; and/or; the falling ball viscosity of the polyacrylonitrile copolymer is 60-150Pa.s at 40 ℃.
Preferably, the solution blending step comprises: mixing polyacrylonitrile oligomer and polyacrylonitrile copolymer to obtain a mixed solution; and (4) defoaming the mixed solution to obtain the polyacrylonitrile spinning solution. Preferably, in the mixed solution, the mass fraction of the polyacrylonitrile oligomer is 0.05-0.2%, and preferably 0.05-0.1%; preferably, the pressure of the defoaming treatment is 5-20KPa, preferably 5-10 KPa; the temperature of the defoaming treatment is 20-80 ℃, preferably 50-70 ℃; the time for the defoaming treatment is 1 to 6 days, preferably 4 to 6 days.
In another aspect, embodiments of the present invention provide a polyacrylonitrile spinning solution; wherein the polyacrylonitrile spinning solution comprises polyacrylonitrile oligomer and polyacrylonitrile copolymer;
preferably, the viscosity-average molecular weight of the polyacrylonitrile oligomer is between 700 and 1500;
preferably, the viscosity average molecular weight of the polyacrylonitrile copolymer is 10 to 20 ten thousand;
preferably, in the polyacrylonitrile spinning solution, the mass fraction of the polyacrylonitrile oligomer is 0.05-0.2%, and preferably 0.05-0.1%;
preferably, the solid content of the polyacrylonitrile spinning solution is 18-25 wt%;
preferably, the falling ball viscosity of the polyacrylonitrile spinning solution is 60-120Pa.s at 40 ℃;
preferably, the polyacrylonitrile spinning solution is prepared by the preparation method of the polyacrylonitrile spinning solution.
Compared with the prior art, the polyacrylonitrile spinning solution and the preparation method thereof have the following beneficial effects:
the invention provides a preparation method of polyacrylonitrile spinning solution, which is prepared by firstly preparing low-molecular-weight polyacrylonitrile oligomer and high-molecular-weight polyacrylonitrile copolymer and then carrying out solution blending on the polyacrylonitrile oligomer and the polyacrylonitrile copolymer. The high molecular weight polyacrylonitrile copolymer in the polyacrylonitrile spinning solution can ensure the strength of the polyacrylonitrile precursor and the carbon fiber. And the polyacrylonitrile oligomer with low molecular weight enters the macromolecular chains to form hydrogen bonds, so that the interaction force between the macromolecular chains is enhanced, the orientation degree of the macromolecular chains is improved, the mechanical property of the fiber is improved, and the contradiction between high performance and good spinnability of the material is solved. Therefore, the polyacrylonitrile-based carbon fiber with less broken filament and better strength can be prepared by the synergistic effect of the polyacrylonitrile oligomer with low molecular weight and the polyacrylonitrile copolymer with high molecular weight in the polyacrylonitrile spinning solution prepared by the invention.
The invention also provides polyacrylonitrile spinning solution, wherein the polyacrylonitrile spinning solution comprises polyacrylonitrile oligomer with molecular weight and polyacrylonitrile copolymer with high molecular weight. The polyacrylonitrile copolymer with high molecular weight in the polyacrylonitrile spinning solution can ensure the strength of polyacrylonitrile protofilament and carbon fiber. And the polyacrylonitrile oligomer with low molecular weight enters the macromolecular chains to form hydrogen bonds, so that the interaction force between the macromolecular chains is enhanced, the orientation degree of the macromolecular chains is improved, the mechanical property of the fiber is improved, and the contradiction between high performance and good spinnability of the carbon fiber is solved. Therefore, the polyacrylonitrile-based carbon fiber with less broken filament and better strength can be prepared by adopting the polyacrylonitrile spinning solution provided by the invention.
The foregoing is a summary of the present invention, and in order to provide a clear understanding of the technical means of the present invention and to be implemented in accordance with the present specification, the following is a detailed description of the preferred embodiments of the present invention.
Detailed Description
To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, the following detailed description of the embodiments, structures, features and effects according to the present application will be provided in conjunction with the preferred embodiments. In the following description, different "one embodiment" or "an embodiment" refers to not necessarily the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
From the structure of polyacrylonitrile protofilament, high compactness and high orientation are the main ways to improve the mechanical properties of polyacrylonitrile-based carbon fiber. The higher the viscosity of the polymer in the polyacrylonitrile spinning solution (the higher the solid content and the molecular weight of the solution), the more compact the structure of the precursor; however, the larger the molecular weight and the higher the viscosity of the polymer, the lower the processability, fiber formation and drawing properties of the precursor, and finally the larger the amount of the filaments of the polyacrylonitrile precursor and the polyacrylonitrile-based carbon fiber.
In order to overcome the above-mentioned drawback, i.e., the contradiction between the high performance and good spinnability of carbon fibers. The inventor of the invention carries out a great deal of research on polyacrylonitrile spinning solution, a polymerization process thereof and a process of polyacrylonitrile-based carbon fiber, and discovers for the first time that:
the polyacrylonitrile oligomer (the oligomer refers to a polymer with low molecular weight and an oligomer) not only contains cyano-group in the structure, but also has small molecular weight, can enter into polyacrylonitrile macromolecular chains to form hydrogen bonds, enhances the interaction force among the macromolecular chains, improves the orientation degree of the macromolecular chains, improves the mechanical property of fibers, does not influence the heat resistance of the fibers, and solves the contradiction between high performance and good spinnability of materials. Meanwhile, polyacrylonitrile oligomer can repair micropore defects in Polyacrylonitrile (PAN) base carbon fibers to improve tensile property, and because the molecular weight of the polyacrylonitrile oligomer is small, the polyacrylonitrile oligomer can enter the micropore defects of the fibers in the spinning process and can generate cyclization crosslinking reaction in the subsequent heat treatment process, so that the carbon fibers can effectively repair the defects in the carbon fibers, and the tensile property of the carbon fibers is improved.
Based on the above innovative findings of the inventor of the present invention, the present invention provides a polyacrylonitrile spinning solution and a preparation method thereof, specifically comprising:
on one hand, the embodiment of the invention provides a preparation method of polyacrylonitrile spinning solution, which comprises the following steps:
1. the oligomer preparation step comprises: the acrylonitrile monomer is polymerized into polyacrylonitrile oligomer.
The method comprises the following steps: the polyacrylonitrile oligomer (B) is synthesized by adopting a free radical telomerization method. Specifically, in a three-neck flask with a spherical condenser, the reaction temperature was measured according to the following 1: (0.05-0.1) acrylonitrile, a chain transfer agent (preferably 3-mercaptopropionic acid) and an initiator (preferably azobisisobutyronitrile) are added in a molar ratio of (0.01-0.05), and nitrogen is introduced for 5-20min under magnetic stirring. Placing the flask in an oil bath kettle for reaction for 10-30h (preferably 20-25h) under the protection of nitrogen at 40-70 ℃ (preferably 55-65 ℃), transferring the reactant to a single-neck flask, installing a distillation device, carrying out vacuum distillation at 80-85 ℃ to remove the unreacted acrylonitrile, and continuously heating to 120-130 ℃ to distill out the 3-mercaptopropionic acid. The distilled 3-mercaptopropionic acid was collected for the next use. Uniformly mixing the product liquid with acetone with the same volume, filtering with filter paper, and evaporating the acetone from the filtrate by using a rotary evaporator to obtain a viscous liquid acrylonitrile oligomer; or mixing the product liquid with wet spinning solvent (such as dimethyl sulfoxide) of polyacrylonitrile, and filtering with filter paper to obtain dimethyl sulfoxide solution of polyacrylonitrile oligomer. The polyacrylonitrile wet spinning solvent herein refers to a solvent commonly used for polyacrylonitrile wet spinning (specifically, a solvent commonly used in the preparation of a spinning dope), such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, and the like.
The addition of chain transfer agent does not have a large effect on the reaction rate, but only shortens the chain length. Chain transfer agents may be used to control the chain length of the polymer, i.e., to control the degree of polymerization of the polymer, or the viscosity of the polymer. Generally, the more chain transfer agent is added, the shorter the polymer chain and the smaller the viscosity. The chain transfer agent can be 3-mercaptopropionic acid, 2-mercaptoethanol, isopropanol, aliphatic mercaptan, dodecyl mercaptan and the like. The preferred reason for the chain transfer agent of 3-mercaptopropionic acid in the present invention is as follows: (1) the chain transfer agent is a common chain transfer agent, has low price and is suitable for mass synthesis; (2) the 3-mercaptopropionic acid has a moderate chain transfer constant, and the reaction molecular weight is convenient to control; (3) the telomer end group obtained by using 3-mercaptopropionic acid as a chain transfer agent is carboxyl, so that the cyclization reaction of polyacrylonitrile under heat treatment can be promoted, a trapezoidal structure can be formed more easily, and the thermal stability and the thermal yield of the polyacrylonitrile are improved; (4) the carboxyl end group of the polymer can also improve the solubility of the telomer in common polar solvents.
The initiator can be one or a mixture of azodiisobutyronitrile, azodiisovaleronitrile, azodiisoheptonitrile and dimethyl azodiisobutyrate. The invention selects the azobisisobutyronitrile as the initiator, belongs to the first-order reaction, has no side reaction, is better controlled, and is widely applied to the research and production of macromolecules.
The viscosity-average molecular weight distribution of the polyacrylonitrile oligomer is 700-1500.
2. Copolymer preparation step: the acrylonitrile monomer and the comonomer are subjected to copolymerization reaction to prepare the polyacrylonitrile copolymer.
The method comprises the following steps: dimethyl sulfoxide is used as a solvent, azobisisobutyronitrile is used as an initiator, acrylonitrile, methyl acrylate and itaconic acid are used as polymerization monomers, and free radical polymerization is adopted to obtain a polymerization stock solution. Wherein, in the reaction system, the total amount of the polymerized monomers is 15-25 wt% (preferably 19-21 wt%), the feeding amount of methyl acrylate accounts for 1-5 wt% (preferably 2-3 wt%) of the total amount of all the polymerized monomers, the feeding amount of itaconic acid accounts for 0.5-2 wt% (preferably 0.5-1 wt%) of the total amount of all the polymerized monomers, and the feeding amount of azobisisobutyronitrile accounts for 0.3-0.8 wt% of the total amount of all the polymerized monomers. The polymerization temperature is 55-75 deg.C (65-70 deg.C), and the reaction time is 5-20h (preferably 12-18 h).
Under the protection of inert gas, dimethyl sulfoxide, acrylonitrile, methyl acrylate, itaconic acid, azodiisobutyronitrile and isopropanol (chain transfer agent) are added into a polymerization kettle for copolymerization reaction, demonomerization can be carried out when the monomer conversion rate reaches 85-95%, and unreacted monomers are removed from a polymerization solution by a rotary thin film evaporation method until the mass concentration of residual acrylonitrile is less than 0.1%.
The viscosity average molecular weight of the polyacrylonitrile copolymer is 10-20 ten thousand; the falling ball viscosity of the polyacrylonitrile copolymer is 60-150 Pa.s.
3. Solution blending step: and (3) carrying out solution blending on the polyacrylonitrile oligomer and the polyacrylonitrile copolymer to obtain the polyacrylonitrile spinning solution.
The method comprises the following steps: the polyacrylonitrile oligomer and the polyacrylonitrile copolymer are mixed in solution in a certain weight ratio (the polyacrylonitrile oligomer accounts for 0.05-0.2% of the total weight) in a mixing kettle with a stirrer. The mixing kettle can not only distill and concentrate the concentration of the demonomerization liquid under negative pressure, but also dilute the demonomerization liquid by adding dimethyl sulfoxide, thereby adjusting the solid content and viscosity of the spinning solution, and simultaneously fully and uniformly stirring the mixed demonomerization liquid.
And finally, pumping the obtained mixed demonomerization liquid into a defoaming kettle, regulating the pressure (absolute pressure is 5-20KPa) and the temperature (20-80 ℃), defoaming for a period of time (1-6 days), and filtering to obtain the spinning solution meeting the spinning requirement.
Wherein the solid content of the spinning solution is 18-25 wt%, and the falling ball viscosity at 40 ℃ is 60-120 Pa.s.
On the other hand, the embodiment of the invention also provides a polyacrylonitrile spinning solution, wherein the polyacrylonitrile spinning solution comprises polyacrylonitrile oligomer and polyacrylonitrile copolymer. Wherein, in the polyacrylonitrile spinning solution, the mass fraction of the polyacrylonitrile oligomer is 0.05-0.2%, preferably 0.05-0.1%. Preferably, the viscosity average molecular weight of the polyacrylonitrile oligomer is distributed in the range of 700-1500. Preferably, the viscosity average molecular weight of the polyacrylonitrile copolymer is 10 to 20 ten thousand; preferably, the solid content of the polyacrylonitrile spinning solution is 18-25 wt%; preferably, the falling ball viscosity of the polyacrylonitrile spinning solution is 60-120Pa.s at 40 ℃; preferably, the polyacrylonitrile spinning solution is prepared by the preparation method of the polyacrylonitrile spinning solution.
In conclusion, aiming at the defects in the prior art, the polyacrylonitrile spinning solution is formed by blending polyacrylonitrile oligomer with low molecular weight and polyacrylonitrile copolymer solution with high molecular weight; therefore, the viscosity of the polyacrylonitrile spinning solution is reduced, the amount of the broken filaments of the polyacrylonitrile protofilament and the polyacrylonitrile-based carbon fiber prepared from the polyacrylonitrile spinning solution is small, and other properties such as strength of the polyacrylonitrile protofilament and the polyacrylonitrile-based carbon fiber are not influenced.
The following is further illustrated by the specific examples:
example 1
The preparation method of the polyacrylonitrile spinning solution comprises the following steps:
1) polymerizing acrylonitrile monomer into oligomer with low molecular weight by adopting a free radical telomerization method;
in a three-necked flask with a spherical condenser, the reaction was carried out in a ratio of 1: adding acrylonitrile, 3-mercaptopropionic acid and azobisisobutyronitrile according to the molar ratio of 0.08:0.01, and introducing nitrogen for 15min under magnetic stirring. The flask is placed in an oil bath kettle at 55 ℃ for reaction for 25 hours under the protection of nitrogen, the reactant is transferred to a single-neck flask, a distillation device is arranged, the unreacted acrylonitrile is removed by vacuum distillation at 85 ℃, and the temperature is continuously increased to 125 ℃ to distill the 3-mercaptopropionic acid. And uniformly mixing the product liquid with acetone with the same volume, filtering with filter paper, and evaporating the acetone from the filtrate by using a rotary evaporator to obtain a viscous liquid polyacrylonitrile oligomer (wherein the viscosity-average molecular weight of the polyacrylonitrile oligomer is 1200).
2) Preparing a polyacrylonitrile copolymer with high molecular weight;
dimethyl sulfoxide is used as a solvent, azobisisobutyronitrile is used as an initiator, acrylonitrile, methyl acrylate and itaconic acid are used as polymerization monomers, and free radical polymerization is adopted to obtain a polymerization stock solution. In the reaction system, the total amount of the polymerized monomers is 21 wt%, the feeding amount of methyl acrylate accounts for 2 wt% of the total amount of all the polymerized monomers, the feeding amount of itaconic acid accounts for 0.5 wt% of the total amount of all the polymerized monomers, and the feeding amount of azobisisobutyronitrile accounts for 0.3 wt% of the total amount of all the polymerized monomers. The polymerization temperature was 65 ℃ and the reaction time was 14 h.
Under the protection of inert gas, adding dimethyl sulfoxide, acrylonitrile, methyl acrylate, itaconic acid, azodiisobutyronitrile and isopropanol (isopropanol is used as a chain transfer agent, the dosage of the isopropanol accounts for 0.5 wt% of the total amount of all the polymerization monomers) into a polymerization kettle for copolymerization reaction, removing monomers when the monomer conversion rate reaches 90%, removing unreacted monomers from the polymerization solution by a rotary film evaporation method until the mass concentration of the residual acrylonitrile is less than 0.1%, and obtaining a polyacrylonitrile copolymer, wherein the viscosity average molecular weight of the polyacrylonitrile copolymer is 16 ten thousand, and the falling ball viscosity at 40 ℃ is 100 Pa.s.
3) And (2) carrying out solution blending on the polyacrylonitrile oligomer prepared in the step 1) and the polyacrylonitrile copolymer prepared in the step 2) in a mixing kettle with stirring (the polyacrylonitrile oligomer accounts for 0.05 percent of the total weight). Finally, the obtained mixed demonomerization liquid is injected into a defoaming kettle, pressure regulation (absolute pressure 15KPa) and temperature regulation (50 ℃) are carried out, defoaming is carried out for a period of time (5 days), and then filtration is carried out, so as to obtain polyacrylonitrile spinning solution; wherein the solid content of the polyacrylonitrile spinning solution is 19.5%, and the falling ball viscosity at 40 ℃ is 98 Pa.s.
Example 2
The preparation method of the polyacrylonitrile spinning solution comprises the following steps:
1) polymerizing acrylonitrile monomer into oligomer with low molecular weight by adopting a free radical telomerization method;
in a three-necked flask with a spherical condenser, the reaction was carried out in a ratio of 1: adding acrylonitrile, 3-mercaptopropionic acid and azobisisobutyronitrile according to the molar ratio of 0.08:0.01, and introducing nitrogen for 15min under magnetic stirring. Placing the flask in an oil bath kettle for reaction for 20 hours under the protection of nitrogen at 65 ℃, transferring the reactant to a single-neck flask, installing a distillation device, carrying out vacuum distillation at 85 ℃ to remove the unreacted acrylonitrile, and continuously heating to 125 ℃ to distill the 3-mercaptopropionic acid. And uniformly mixing the product liquid with acetone with the same volume, filtering by using filter paper, and evaporating the acetone from the filtrate by using a rotary evaporator to obtain viscous liquid polyacrylonitrile oligomer (wherein the viscosity-average molecular weight of the polyacrylonitrile oligomer is 1200).
2) Preparing a polyacrylonitrile copolymer with high molecular weight;
dimethyl sulfoxide is used as a solvent, azobisisobutyronitrile is used as an initiator, acrylonitrile, methyl acrylate and itaconic acid are used as polymerization monomers, and free radical polymerization is adopted to obtain a polymerization stock solution. In the reaction system, the total amount of the polymerized monomers is 21 wt%, the feeding amount of methyl acrylate accounts for 2 wt% of the total amount of all the polymerized monomers, the feeding amount of itaconic acid accounts for 0.5 wt% of the total amount of all the polymerized monomers, and the feeding amount of azobisisobutyronitrile accounts for 0.3 wt% of the total amount of all the polymerized monomers; the polymerization temperature was 65 ℃ and the reaction time was 14 h.
Under the protection of inert gas, adding dimethyl sulfoxide, acrylonitrile, methyl acrylate, itaconic acid, azodiisobutyronitrile and isopropanol (isopropanol is used as a chain transfer agent, the dosage of the isopropanol accounts for 0.5 wt% of the total amount of all the polymerization monomers) into a polymerization kettle for copolymerization reaction, removing monomers when the monomer conversion rate reaches 90%, removing unreacted monomers from the polymerization solution by a rotary film evaporation method until the mass concentration of the residual acrylonitrile is less than 0.1%, and obtaining a polyacrylonitrile copolymer, wherein the viscosity average molecular weight of the polyacrylonitrile copolymer is 16 ten thousand, and the falling ball viscosity at 40 ℃ is 100 Pa.s.
3) And (2) carrying out solution blending on the polyacrylonitrile oligomer prepared in the step 1) and the polyacrylonitrile copolymer prepared in the step 2) in a mixing kettle with stirring (the polyacrylonitrile oligomer accounts for 0.05 percent of the total weight). Finally, the obtained mixed demonomerization liquid is injected into a defoaming kettle, pressure regulation (absolute pressure 15KPa) and temperature regulation (50 ℃) are carried out, defoaming is carried out for a period of time (5 days), and then filtration is carried out, so as to obtain polyacrylonitrile spinning solution; the solid content of the polyacrylonitrile spinning solution is 19.5%, and the falling ball viscosity at 40 ℃ is 98 Pa.s.
Example 3
The preparation method of the polyacrylonitrile spinning solution comprises the following steps:
1) polymerizing acrylonitrile monomer into oligomer with low molecular weight by adopting a free radical telomerization method;
in a three-necked flask with a spherical condenser, the reaction was carried out in a ratio of 1: adding acrylonitrile, 3-mercaptopropionic acid and azobisisobutyronitrile in a molar ratio of 0.1:0.015, and introducing nitrogen for 15min under magnetic stirring. Placing the flask in an oil bath kettle for reaction for 20 hours under the protection of nitrogen at 65 ℃, transferring the reactant to a single-neck flask, installing a distillation device, carrying out vacuum distillation at 85 ℃ to remove the unreacted acrylonitrile, and continuously heating to 125 ℃ to distill the 3-mercaptopropionic acid. And uniformly mixing the product liquid with acetone with the same volume, filtering by using filter paper, and evaporating the acetone from the filtrate by using a rotary evaporator to obtain a viscous liquid acrylonitrile oligomer (wherein the viscosity-average molecular weight of the polyacrylonitrile oligomer is 1000).
2) Preparing a polyacrylonitrile copolymer with high molecular weight;
dimethyl sulfoxide is used as a solvent, azobisisobutyronitrile is used as an initiator, acrylonitrile, methyl acrylate and itaconic acid are used as polymerization monomers, and free radical polymerization is adopted to obtain a polymerization stock solution. In the reaction system, the total amount of the polymerized monomers is 21 wt%, the feeding amount of methyl acrylate accounts for 2 wt% of the total amount of all the polymerized monomers, the feeding amount of itaconic acid accounts for 0.5 wt% of the total amount of all the polymerized monomers, and the feeding amount of azobisisobutyronitrile accounts for 0.3 wt% of the total amount of all the polymerized monomers. The polymerization temperature was 65 ℃ and the reaction time was 14 h.
Under the protection of inert gas, adding dimethyl sulfoxide, acrylonitrile, methyl acrylate, itaconic acid, azodiisobutyronitrile and isopropanol (isopropanol is used as a chain transfer agent, the dosage of the isopropanol accounts for 0.5 wt% of the total amount of all the polymerization monomers) into a polymerization kettle for copolymerization reaction, removing monomers when the monomer conversion rate reaches 90%, removing unreacted monomers from the polymerization solution by a rotary film evaporation method until the mass concentration of the residual acrylonitrile is less than 0.1%, and obtaining a polyacrylonitrile copolymer, wherein the viscosity average molecular weight of the polyacrylonitrile copolymer is 16 ten thousand, and the falling ball viscosity at 40 ℃ is 100 Pa.s.
3) And (2) carrying out solution blending on the polyacrylonitrile oligomer prepared in the step 1) and the polyacrylonitrile copolymer prepared in the step 2) in a mixing kettle with stirring (the polyacrylonitrile oligomer accounts for 0.05 percent of the total weight). And finally, pumping the obtained mixed demonomerization liquid into a defoaming kettle, regulating the pressure (absolute pressure is 15KPa), regulating the temperature (50 ℃), defoaming for a period of time (5 days), and filtering to obtain the polyacrylonitrile spinning solution, wherein the solid content of the polyacrylonitrile spinning solution is 19.6%, and the falling ball viscosity at 40 ℃ is 98 Pa.s.
Example 4
The preparation method of the polyacrylonitrile spinning solution comprises the following steps:
1) polymerizing acrylonitrile monomer into oligomer with low molecular weight by adopting a free radical telomerization method;
in a three-necked flask with a spherical condenser, the reaction was carried out in a ratio of 1: adding acrylonitrile, 3-mercaptopropionic acid and azobisisobutyronitrile in a molar ratio of 0.1:0.015, and introducing nitrogen for 15min under magnetic stirring. Placing the flask in an oil bath kettle for reaction for 20 hours under the protection of nitrogen at 65 ℃, transferring the reactant to a single-neck flask, installing a distillation device, carrying out vacuum distillation at 85 ℃ to remove the unreacted acrylonitrile, and continuously heating to 125 ℃ to distill the 3-mercaptopropionic acid. And uniformly mixing the product liquid with acetone with the same volume, filtering by using filter paper, and evaporating the acetone from the filtrate by using a rotary evaporator to obtain a viscous liquid acrylonitrile oligomer (wherein the viscosity-average molecular weight of the polyacrylonitrile oligomer is 1000).
2) Preparing a polyacrylonitrile copolymer with high molecular weight;
dimethyl sulfoxide is used as a solvent, azobisisobutyronitrile is used as an initiator, acrylonitrile, methyl acrylate and itaconic acid are used as polymerization monomers, and free radical polymerization is adopted to obtain a polymerization stock solution. In the reaction system, the total amount of the polymerized monomers is 21 wt%, the feeding amount of methyl acrylate accounts for 2 wt% of the total amount of all the polymerized monomers, the feeding amount of itaconic acid accounts for 0.5 wt% of the total amount of all the polymerized monomers, and the feeding amount of azobisisobutyronitrile accounts for 0.3 wt% of the total amount of all the polymerized monomers. The polymerization temperature was 65 ℃ and the reaction time was 14 h.
Under the protection of inert gas, adding dimethyl sulfoxide, acrylonitrile, methyl acrylate, itaconic acid, azodiisobutyronitrile and isopropanol (isopropanol is used as a chain transfer agent, the dosage of the isopropanol accounts for 0.5 wt% of the total amount of all the polymerization monomers) into a polymerization kettle for copolymerization reaction, removing monomers when the monomer conversion rate reaches 90%, removing unreacted monomers from the polymerization solution by a rotary film evaporation method until the mass concentration of the residual acrylonitrile is less than 0.1%, and obtaining a polyacrylonitrile copolymer, wherein the viscosity average molecular weight of the polyacrylonitrile copolymer is 16 ten thousand, and the falling ball viscosity at 40 ℃ is 100 Pa.s.
3) And (2) carrying out solution blending on the polyacrylonitrile oligomer prepared in the step 1) and the polyacrylonitrile copolymer prepared in the step 2) in a mixing kettle with stirring (the polyacrylonitrile oligomer accounts for 0.1 percent of the total weight). And finally, pumping the obtained mixed demonomerization liquid into a defoaming kettle, regulating the pressure (absolute pressure is 15KPa), regulating the temperature (50 ℃), defoaming for a period of time (5 days), and filtering to obtain the polyacrylonitrile spinning solution, wherein the solid content of the polyacrylonitrile spinning solution is 19.5%, and the falling ball viscosity at 40 ℃ is 98 Pa.s.
Example 5
The preparation method of the polyacrylonitrile spinning solution comprises the following steps:
1) polymerizing acrylonitrile monomer into oligomer with low molecular weight by adopting a free radical telomerization method;
in a three-necked flask with a spherical condenser, the reaction was carried out in a ratio of 1: adding acrylonitrile, 3-mercaptopropionic acid and azobisisobutyronitrile in a molar ratio of 0.1:0.015, and introducing nitrogen for 15min under magnetic stirring. Placing the flask in an oil bath kettle for reaction for 20 hours under the protection of nitrogen at 65 ℃, transferring the reactant to a single-neck flask, installing a distillation device, carrying out vacuum distillation at 85 ℃ to remove the unreacted acrylonitrile, and continuously heating to 125 ℃ to distill the 3-mercaptopropionic acid. And uniformly mixing the product liquid with acetone with the same volume, filtering by using filter paper, and evaporating the acetone from the filtrate by using a rotary evaporator to obtain a viscous liquid acrylonitrile oligomer (wherein the viscosity-average molecular weight of the polyacrylonitrile oligomer is 900).
2) Preparing a polyacrylonitrile copolymer with high molecular weight;
dimethyl sulfoxide is used as a solvent, azobisisobutyronitrile is used as an initiator, acrylonitrile, methyl acrylate and itaconic acid are used as polymerization monomers, and free radical polymerization is adopted to obtain a polymerization stock solution. In the reaction system, the total amount of the polymerized monomers is 21 wt%, the feeding amount of methyl acrylate accounts for 2 wt% of the total amount of all the polymerized monomers, the feeding amount of itaconic acid accounts for 0.5 wt% of the total amount of all the polymerized monomers, and the feeding amount of azobisisobutyronitrile accounts for 0.3 wt% of the total amount of all the polymerized monomers. The polymerization temperature was 65 ℃ and the reaction time was 14 h.
Under the protection of inert gas, adding dimethyl sulfoxide, acrylonitrile, methyl acrylate, itaconic acid, azodiisobutyronitrile and isopropanol (isopropanol is used as a chain transfer agent, the dosage of the isopropanol accounts for 0.5 wt% of the total amount of all the polymerization monomers) into a polymerization kettle for copolymerization reaction, removing monomers when the monomer conversion rate reaches 90%, removing unreacted monomers from the polymerization solution by a rotary film evaporation method until the mass concentration of the residual acrylonitrile is less than 0.1%, and obtaining a polyacrylonitrile copolymer, wherein the viscosity average molecular weight of the polyacrylonitrile copolymer is 16 ten thousand, and the falling ball viscosity at 40 ℃ is 100 Pa.s.
3) And (2) carrying out solution blending on the polyacrylonitrile oligomer prepared in the step 1) and the polyacrylonitrile copolymer prepared in the step 2) in a mixing kettle with stirring (the polyacrylonitrile oligomer accounts for 0.2 percent of the total weight). And finally, pumping the mixed demonomerization liquid into a defoaming kettle, regulating the pressure (absolute pressure is 15KPa), regulating the temperature (50 ℃), defoaming for a period of time (5 days), and filtering to obtain the polyacrylonitrile spinning solution, wherein the solid content of the polyacrylonitrile spinning solution is 19.5%, and the falling ball viscosity at 40 ℃ is 97.9 Pa.s.
Example 6
The preparation method of the polyacrylonitrile spinning solution comprises the following steps:
1) polymerizing acrylonitrile monomer into oligomer with low molecular weight by adopting a free radical telomerization method;
in a three-necked flask with a spherical condenser, the reaction was carried out in a ratio of 1: adding acrylonitrile, 3-mercaptopropionic acid and azobisisobutyronitrile in a molar ratio of 0.1:0.02, and introducing nitrogen for 15min under magnetic stirring. The flask is placed in an oil bath kettle at 55 ℃ for reaction for 25 hours under the protection of nitrogen, the reactant is transferred to a single-neck flask, a distillation device is arranged, the unreacted acrylonitrile is removed by vacuum distillation at 85 ℃, and the temperature is continuously increased to 125 ℃ to distill the 3-mercaptopropionic acid. And uniformly mixing the product liquid with acetone with the same volume, filtering by using filter paper, and evaporating the acetone from the filtrate by using a rotary evaporator to obtain a viscous liquid acrylonitrile oligomer (wherein the viscosity-average molecular weight of the polyacrylonitrile oligomer is 850).
2) Preparing a polyacrylonitrile copolymer with high molecular weight;
dimethyl sulfoxide is used as a solvent, azobisisobutyronitrile is used as an initiator, acrylonitrile, methyl acrylate and itaconic acid are used as polymerization monomers, and free radical polymerization is adopted to obtain a polymerization stock solution. In the reaction system, the total amount of the polymerized monomers is 19 wt%, the feeding amount of methyl acrylate accounts for 3 wt% of the total amount of all the polymerized monomers, the feeding amount of itaconic acid accounts for 1 wt% of the total amount of all the polymerized monomers, and the feeding amount of azobisisobutyronitrile accounts for 0.5 wt% of the total amount of all the polymerized monomers. The polymerization temperature was 65 ℃ and the reaction time was 14 h.
Under the protection of inert gas, adding dimethyl sulfoxide, acrylonitrile, methyl acrylate, itaconic acid, azodiisobutyronitrile and isopropanol (isopropanol is used as a chain transfer agent, the dosage of the isopropanol accounts for 0.5 wt% of the total amount of all the polymerized monomers) into a polymerization kettle for copolymerization reaction, removing monomers when the monomer conversion rate reaches 90%, removing unreacted monomers from the polymerization solution by a rotary film evaporation method until the mass concentration of the residual acrylonitrile is less than 0.1%, and obtaining a polyacrylonitrile copolymer, wherein the viscosity average molecular weight of the polyacrylonitrile copolymer is 13 ten thousand, and the falling ball viscosity at 40 ℃ is 65 Pa.s.
3) And (2) carrying out solution blending on the polyacrylonitrile oligomer prepared in the step 1) and the polyacrylonitrile copolymer prepared in the step 2) in a mixing kettle with stirring (the polyacrylonitrile oligomer accounts for 0.05 percent of the total weight). And finally, pumping the obtained mixed demonomerization liquid into a defoaming kettle, regulating the pressure (absolute pressure is 15KPa), regulating the temperature (50 ℃), defoaming for a period of time (6 days), and filtering to obtain the polyacrylonitrile spinning solution, wherein the solid content of the polyacrylonitrile spinning solution is 18.5%, and the falling ball viscosity at 40 ℃ is 63 Pa.s.
Example 7
The preparation method of the polyacrylonitrile spinning solution comprises the following steps:
1) polymerizing acrylonitrile monomer into oligomer with low molecular weight by adopting a free radical telomerization method;
in a three-necked flask with a spherical condenser, the reaction was carried out in a ratio of 1: adding acrylonitrile, 3-mercaptopropionic acid and azobisisobutyronitrile according to the molar ratio of 0.05:0.05, and introducing nitrogen for 15min under magnetic stirring. Placing the flask in an oil bath kettle for reaction for 25 hours under the protection of nitrogen at 65 ℃, transferring the reactant to a single-neck flask, installing a distillation device, carrying out vacuum distillation at 85 ℃ to remove the unreacted acrylonitrile, and continuously heating to 125 ℃ to distill the 3-mercaptopropionic acid. And uniformly mixing the product liquid with acetone with the same volume, filtering by using filter paper, and evaporating the acetone from the filtrate by using a rotary evaporator to obtain a viscous liquid acrylonitrile oligomer (wherein the molecular weight of the polyacrylonitrile oligomer is 1400).
2) Preparing a polyacrylonitrile copolymer with high molecular weight;
dimethyl sulfoxide is used as a solvent, azobisisobutyronitrile is used as an initiator, acrylonitrile, methyl acrylate and itaconic acid are used as polymerization monomers, and free radical polymerization is adopted to obtain a polymerization stock solution. In the reaction system, the total amount of the polymerized monomers is 25 wt%, the feeding amount of methyl acrylate accounts for 5 wt% of the total amount of all the polymerized monomers, the feeding amount of itaconic acid accounts for 2 wt% of the total amount of all the polymerized monomers, and the feeding amount of azobisisobutyronitrile accounts for 0.8 wt% of the total amount of all the polymerized monomers. The polymerization temperature was 65 ℃ and the reaction time was 10 h.
Under the protection of inert gas, adding dimethyl sulfoxide, acrylonitrile, methyl acrylate, itaconic acid, azodiisobutyronitrile and isopropanol (isopropanol is used as a chain transfer agent, the dosage of the isopropanol accounts for 0.5 wt% of the total amount of all the polymerization monomers) into a polymerization kettle for copolymerization reaction, removing monomers when the monomer conversion rate reaches 90%, removing unreacted monomers from the polymerization solution by a rotary thin film evaporation method until the mass concentration of the residual acrylonitrile is less than 0.1%, and obtaining a polyacrylonitrile copolymer, wherein the viscosity average molecular weight of the polyacrylonitrile copolymer is 11 ten thousand, and the falling ball viscosity at 40 ℃ is 120 Pa.s.
3) And (2) carrying out solution blending on the polyacrylonitrile oligomer prepared in the step 1) and the polyacrylonitrile copolymer prepared in the step 2) in a mixing kettle with stirring (the polyacrylonitrile oligomer accounts for 0.1 percent of the total weight). And finally, pumping the obtained mixed demonomerization liquid into a defoaming kettle, regulating the pressure (absolute pressure is 15KPa), regulating the temperature (50 ℃), defoaming for a period of time (5 days), and filtering to obtain the polyacrylonitrile spinning solution, wherein the solid content of the polyacrylonitrile spinning solution is 23.8%, and the falling ball viscosity at 40 ℃ is 115 Pa.s.
Example 8
The preparation method of the polyacrylonitrile spinning solution comprises the following steps:
1) polymerizing acrylonitrile monomer into oligomer with low molecular weight by adopting a free radical telomerization method;
in a three-necked flask with a spherical condenser, the reaction was carried out in a ratio of 1: adding acrylonitrile, 3-mercaptopropionic acid and azobisisobutyronitrile according to the molar ratio of 0.08:0.05, and introducing nitrogen for 20min under magnetic stirring. Placing the flask in an oil bath kettle at 55 ℃ for reaction for 15h under the protection of nitrogen, transferring the reactant to a single-neck flask, installing a distillation device, carrying out vacuum distillation at 85 ℃ to remove the unreacted acrylonitrile, and continuously heating to 125 ℃ to distill the 3-mercaptopropionic acid. And uniformly mixing the product liquid with acetone with the same volume, filtering by using filter paper, and evaporating the acetone from the filtrate by using a rotary evaporator to obtain a viscous liquid acrylonitrile oligomer (wherein the viscosity-average molecular weight of the polyacrylonitrile oligomer is 700).
2) Preparing a polyacrylonitrile copolymer with high molecular weight;
dimethyl sulfoxide is used as a solvent, azobisisobutyronitrile is used as an initiator, acrylonitrile, methyl acrylate and itaconic acid are used as polymerization monomers, and free radical polymerization is adopted to obtain a polymerization stock solution. In the reaction system, the total amount of the polymerized monomers is 20 wt%, the feeding amount of methyl acrylate accounts for 2 wt% of the total amount of all the polymerized monomers, the feeding amount of itaconic acid accounts for 0.5 wt% of the total amount of all the polymerized monomers, and the feeding amount of azobisisobutyronitrile accounts for 0.3 wt% of the total amount of all the polymerized monomers. The polymerization temperature was 65 ℃ and the reaction time was 14 h.
Under the protection of inert gas, adding dimethyl sulfoxide, acrylonitrile, methyl acrylate, itaconic acid and azodiisobutyronitrile into a polymerization kettle for copolymerization reaction, removing monomers when the monomer conversion rate reaches 90%, removing unreacted monomers from a polymerization solution by using a rotary thin film evaporation method until the mass concentration of residual acrylonitrile is less than 0.1%, and obtaining a polyacrylonitrile copolymer, wherein the viscosity average molecular weight of the polyacrylonitrile copolymer is 16 ten thousand, and the falling sphere viscosity at 40 ℃ is 90 Pa.s.
3) And (2) carrying out solution blending on the polyacrylonitrile oligomer prepared in the step 1) and the polyacrylonitrile copolymer prepared in the step 2) in a mixing kettle with stirring (the polyacrylonitrile oligomer accounts for 0.05 percent of the total weight). And finally, pumping the obtained mixed demonomerization liquid into a defoaming kettle, regulating the pressure (absolute pressure is 15KPa), regulating the temperature (50 ℃), defoaming for a period of time (5 days), and filtering to obtain the polyacrylonitrile spinning solution, wherein the solid content of the polyacrylonitrile spinning solution is 19.1%, and the falling ball viscosity at 40 ℃ is 86 Pa.s.
Example 9
The preparation method of the polyacrylonitrile spinning solution comprises the following steps:
1) polymerizing acrylonitrile monomer into oligomer with low molecular weight by adopting a free radical telomerization method;
in a three-necked flask with a spherical condenser, the reaction was carried out in a ratio of 1: adding acrylonitrile, 3-mercaptopropionic acid and azobisisobutyronitrile according to the molar ratio of 0.08:0.01, and introducing nitrogen for 15min under magnetic stirring. The flask is placed in an oil bath kettle at 55 ℃ for reaction for 25 hours under the protection of nitrogen, the reactant is transferred to a single-neck flask, a distillation device is arranged, the unreacted acrylonitrile is removed by vacuum distillation at 85 ℃, and the temperature is continuously increased to 125 ℃ to distill the 3-mercaptopropionic acid. And (3) uniformly mixing the product liquid with dimethyl sulfoxide with the same volume, and filtering by using filter paper to obtain a dimethyl sulfoxide solution of the polyacrylonitrile oligomer (wherein the viscosity-average molecular weight of the polyacrylonitrile oligomer is 1200).
2) Preparing a polyacrylonitrile copolymer with high molecular weight;
dimethyl sulfoxide is used as a solvent, azobisisobutyronitrile is used as an initiator, acrylonitrile, methyl acrylate and itaconic acid are used as polymerization monomers, and free radical polymerization is adopted to obtain a polymerization stock solution. In the reaction system, the total amount of the polymerized monomers is 21 wt%, the feeding amount of methyl acrylate accounts for 2 wt% of the total amount of all the polymerized monomers, the feeding amount of itaconic acid accounts for 0.5 wt% of the total amount of all the polymerized monomers, and the feeding amount of azobisisobutyronitrile accounts for 0.3 wt% of the total amount of all the polymerized monomers. The polymerization temperature was 65 ℃ and the reaction time was 14 h.
Under the protection of inert gas, adding dimethyl sulfoxide, acrylonitrile, methyl acrylate, itaconic acid, azodiisobutyronitrile and isopropanol (isopropanol is used as a chain transfer agent, the dosage of the isopropanol accounts for 0.5 wt% of the total amount of all the polymerization monomers) into a polymerization kettle for copolymerization reaction, removing monomers when the monomer conversion rate reaches 90%, removing unreacted monomers from the polymerization solution by a rotary film evaporation method until the mass concentration of the residual acrylonitrile is less than 0.1%, and obtaining a polyacrylonitrile copolymer, wherein the viscosity average molecular weight of the polyacrylonitrile copolymer is 16 ten thousand, and the falling ball viscosity at 40 ℃ is 100 Pa.s.
3) And (2) carrying out solution blending on the dimethyl sulfoxide solution of the polyacrylonitrile oligomer prepared in the step 1) and the polyacrylonitrile copolymer prepared in the step 2) in a mixing kettle with stirring (the polyacrylonitrile oligomer accounts for 0.05 percent of the total weight). Finally, the obtained mixed demonomerization liquid is injected into a defoaming kettle, pressure regulation (absolute pressure 15KPa) and temperature regulation (50 ℃) are carried out, defoaming is carried out for a period of time (5 days), and then filtration is carried out, so as to obtain polyacrylonitrile spinning solution; wherein the solid content of the polyacrylonitrile spinning solution is 19.5%, and the falling ball viscosity at 40 ℃ is 98 Pa.s.
Comparative example 1
Dimethyl sulfoxide is used as a solvent, azobisisobutyronitrile is used as an initiator, acrylonitrile, methyl acrylate and itaconic acid are used as polymerization monomers, and free radical polymerization is adopted to obtain a polymerization stock solution. In the reaction system, the total amount of the polymerized monomers is 21 wt%, the feeding amount of methyl acrylate accounts for 2 wt% of the total amount of all the polymerized monomers, the feeding amount of itaconic acid accounts for 0.5 wt% of the total amount of all the polymerized monomers, the feeding amount of azobisisobutyronitrile accounts for 0.3 wt% of the total amount of all the polymerized monomers, the polymerization temperature is 65 ℃, and the reaction time is 14 h.
Under the protection of inert gas, adding dimethyl sulfoxide, acrylonitrile, methyl acrylate, itaconic acid, azodiisobutyronitrile and isopropanol (isopropanol is used as a chain transfer agent, the dosage of the isopropanol accounts for 0.5 wt% of the total amount of all the polymerized monomers) into a polymerization kettle for copolymerization reaction, removing monomers when the monomer conversion rate reaches 90%, removing unreacted monomers from the polymerization solution by a rotary film evaporation method until the mass concentration of the residual acrylonitrile is less than 0.1%, and obtaining the polyacrylonitrile spinning solution, wherein the viscosity average molecular weight of the polyacrylonitrile spinning solution is 16 ten thousand, and the falling ball viscosity at 40 ℃ is 100 Pa.s.
The spinning stock solutions prepared in examples 1 to 9 and comparative example 1 were subjected to spinning, solidification, molding, washing, hot drawing, oiling, dry densification, and steam drafting to prepare polyacrylonitrile precursor, and the obtained polyacrylonitrile precursor was subjected to pre-oxidation, low-temperature carbonization, and high-temperature carbonization to obtain high-strength polyacrylonitrile-based carbon fiber.
The polyacrylonitrile-based carbon fiber was tested for tensile strength, and the test results are shown in table 1.
The method for testing the amount of the polyacrylonitrile-based carbon fiber filaments is disclosed in patent CN108169052A, and the specific test results are shown in table 1.
Table 1 shows the results of the tests of the strength and the amount of the polyacrylonitrile-based carbon fiber prepared using the spinning dopes prepared in examples 1 to 9 and comparative example 1
| Amount of wool yarn (mg) | Tensile Strength (GPa) | |
| Example 1 | 2.1 | 6.02 |
| Example 2 | 1.9 | 5.87 |
| Example 3 | 1.7 | 5.94 |
| Example 4 | 1.1 | 6.12 |
| Example 5 | 0.8 | 5.62 |
| Example 6 | 1.8 | 5.20 |
| Example 7 | 1.4 | 5.78 |
| Example 8 | 2.1 | 5.54 |
| Example 9 | 2.0 | 6.02 |
| Comparative example 1 | 5.3 | 5.87 |
As can be seen from table 1: compared with the existing polyacrylonitrile spinning solution (only containing high molecular weight polyacrylonitrile polymer, such as comparative example 1), the polyacrylonitrile-based carbon fiber prepared by the polyacrylonitrile spinning solution prepared by the embodiment of the invention not only can greatly reduce the broken filament amount of the polyacrylonitrile-based carbon fiber, but also has better strength of the polyacrylonitrile-based carbon fiber.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and any simple modification, equivalent change and modification made to the above embodiment according to the technical spirit of the present invention are still within the scope of the technical solution of the present invention.
Claims (27)
1. The preparation method of the polyacrylonitrile spinning solution is characterized by comprising the following steps:
the oligomer preparation step comprises: polymerizing acrylonitrile monomer to form polyacrylonitrile oligomer; wherein the viscosity-average molecular weight of the polyacrylonitrile oligomer is 700-1500;
copolymer preparation step: carrying out copolymerization reaction on acrylonitrile monomer and comonomer to prepare polyacrylonitrile copolymer; wherein the viscosity average molecular weight of the polyacrylonitrile copolymer is 10-20 ten thousand;
solution blending step: carrying out solution blending on polyacrylonitrile oligomer and polyacrylonitrile copolymer to obtain polyacrylonitrile spinning solution; wherein the solution blending step comprises: carrying out solution blending on polyacrylonitrile oligomer and polyacrylonitrile copolymer to obtain a mixed solution; defoaming the mixed solution to obtain polyacrylonitrile spinning solution; wherein in the mixed solution, the mass fraction of the polyacrylonitrile oligomer is 0.05-0.2%.
2. The method for preparing polyacrylonitrile spinning solution according to claim 1, wherein in the oligomer preparation step, acrylonitrile monomer is polymerized into polyacrylonitrile oligomer by adopting a free radical telomerization method.
3. The method for preparing polyacrylonitrile spinning solution according to claim 2, wherein the oligomer preparation step comprises the following steps:
1) polymerizing a reaction mixture containing an acrylonitrile monomer, a chain transfer agent and an initiator at a first set temperature for a first set time to obtain a first polymerization solution;
2) and removing the monomer, removing the chain transfer agent and purifying the first polymerization liquid to obtain the polyacrylonitrile oligomer.
4. The method for preparing polyacrylonitrile spinning solution according to claim 3,
the chain transfer agent is one or more of 3-mercaptopropionic acid, 2-mercaptoethanol, isopropanol and aliphatic mercaptan and dodecyl mercaptan; and/or
The initiator is one or more of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptonitrile and dimethyl azobisisobutyrate.
5. The method for preparing polyacrylonitrile spinning solution according to claim 3, wherein the first set temperature is 40-70 ℃.
6. The method for preparing polyacrylonitrile spinning solution according to claim 5, wherein the first set temperature is 55-65 ℃.
7. The method for preparing polyacrylonitrile spinning solution according to claim 3, characterized in that the first set time is 10-30 h.
8. The method of claim 7, wherein the first set time is 20 to 25.
9. The method for preparing polyacrylonitrile spinning solution according to claim 3,
the molar ratio of acrylonitrile monomer, chain transfer agent and initiator in the reaction mixture is 1: (0.05-0.1):(0.01-0.05).
10. The method for preparing polyacrylonitrile spinning solution according to claim 9, wherein the molar ratio of acrylonitrile monomer, chain transfer agent and initiator in the reaction mixture is 1: (0.08-0.1):(0.01-0.02).
11. The method for preparing polyacrylonitrile spinning solution according to claim 3, characterized in that, the step 2) in the oligomer preparation step includes:
21) carrying out vacuum distillation treatment on the first polymerization liquid to remove polyacrylonitrile monomers and chain transfer agents in the first polymerization liquid to obtain a liquid product;
22) mixing the liquid product with a first solvent, and filtering to obtain a filtrate; wherein the first solvent can dissolve the polyacrylonitrile oligomer.
12. The method for preparing polyacrylonitrile spinning solution according to claim 11, wherein the first solvent is acetone or polyacrylonitrile wet spinning solvent;
wherein, when the first solvent is acetone: the step 2) in the oligomer preparation step further comprises: 23) rotationally evaporating the filtrate to evaporate acetone in the filtrate to obtain a viscous polyacrylonitrile oligomer;
wherein, when the first solvent is polyacrylonitrile wet spinning solvent: the filtrate obtained in the step 22) is polyacrylonitrile oligomer solution; and in the solution blending step, solution blending is carried out on the polyacrylonitrile oligomer solution and the polyacrylonitrile copolymer to obtain the polyacrylonitrile spinning solution.
13. The method for preparing polyacrylonitrile spinning solution according to claim 12, wherein the polyacrylonitrile wet spinning solvent is dimethyl sulfoxide.
14. The method for preparing polyacrylonitrile spinning solution according to claim 1, wherein the copolymer preparation step comprises the following steps:
1) copolymerizing a reaction system comprising a polymerization monomer, a solvent and an initiator at a second set temperature for a second set time to obtain a second polymerization solution;
2) and carrying out monomer removal treatment on the second polymerization liquid to obtain the polyacrylonitrile copolymer.
15. The method for preparing polyacrylonitrile spinning solution according to claim 14, wherein the second set temperature is 55-75 ℃ and the second set time is 5-20 h.
16. The method for preparing polyacrylonitrile spinning solution according to claim 14, wherein the second set temperature is 65-70 ℃ and the second set time is 12-18 h.
17. The method for preparing polyacrylonitrile spinning solution according to claim 14,
the polymerized monomers include acrylonitrile monomers and comonomers; in the reaction system, the mass fraction of the polymerization monomer is 15-25 wt%; wherein the comonomers comprise methyl acrylate and itaconic acid; wherein in the polymerized monomer, the mass fraction of the methyl acrylate is 1-5 wt%, and the mass fraction of the itaconic acid is 0.5-2 wt%.
18. The method for preparing polyacrylonitrile spinning solution according to claim 17, wherein in the reaction system, the mass fraction of the polymerized monomer is 19-21 wt%; and/or
In the polymerized monomer, the mass fraction of the methyl acrylate is 2-3 wt%, and the mass fraction of the itaconic acid is 0.5-1 wt%.
19. The method for preparing polyacrylonitrile spinning solution according to claim 14,
the solvent is dimethyl sulfoxide; and/or
The initiator is azodiisobutyronitrile; and/or
The using amount of the initiator is 0.3 to 0.8 weight percent of the using amount of the polymerization monomer; and/or
The reaction system also comprises a chain transfer agent; wherein the amount of the chain transfer agent is 0.5-2 wt% of the amount of the polymerization monomer; and/or
In the copolymerization reaction, when the conversion rate of the polymerization monomer reaches 85-95%, the reaction is stopped to obtain a second polymerization solution.
20. The method for preparing polyacrylonitrile spinning solution according to any one of claims 1 to 19, wherein the falling ball viscosity of the polyacrylonitrile copolymer is 60 to 150pa.s at 40 ℃.
21. The method for preparing polyacrylonitrile spinning solution according to any one of claims 1 to 19, characterized in that, in the mixed solution, the mass fraction of the polyacrylonitrile oligomer is 0.05-0.1%.
22. The method for preparing polyacrylonitrile spinning solution according to any one of claims 1 to 19, characterized in that, the pressure of the defoaming treatment is 5 to 20KPa, the temperature of the defoaming treatment is 20 to 80 ℃, and the time of the defoaming treatment is 1 to 6 days.
23. The method for preparing polyacrylonitrile spinning solution according to claim 22, characterized in that, the defoaming pressure is 5-10KPa, the temperature of the defoaming treatment is 50-70 ℃, and the time of the defoaming treatment is 4-6 days.
24. The method of preparing polyacrylonitrile spinning solution according to any one of claims 1 to 19, characterized in that the solid content of polyacrylonitrile spinning solution is 18-25 wt%; and/or
And at the temperature of 40 ℃, the falling ball viscosity of the polyacrylonitrile spinning solution is 60-120 Pa.s.
25. The polyacrylonitrile spinning solution is characterized by comprising polyacrylonitrile oligomer and polyacrylonitrile copolymer;
wherein in the polyacrylonitrile spinning solution, the mass fraction of the polyacrylonitrile oligomer is 0.05-0.2%; the viscosity-average molecular weight of the polyacrylonitrile oligomer is 700-1500; the viscosity average molecular weight of the polyacrylonitrile copolymer is 10-20 ten thousand.
26. The polyacrylonitrile spinning solution of claim 25, characterized in that,
in the polyacrylonitrile spinning solution, the mass fraction of the polyacrylonitrile oligomer is 0.05-0.1%; and/or
The solid content of the polyacrylonitrile spinning solution is 18-25 wt%; and/or
And at the temperature of 40 ℃, the falling ball viscosity of the polyacrylonitrile spinning solution is 60-120 Pa.s.
27. The polyacrylonitrile spinning solution according to the claim 25 or 26, which is prepared by the preparation method of the polyacrylonitrile spinning solution according to any one of the claims 1 to 24.
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