CN110359114B - Polyacrylonitrile fiber, polyacrylonitrile-based carbon fiber and preparation method thereof - Google Patents
Polyacrylonitrile fiber, polyacrylonitrile-based carbon fiber and preparation method thereof Download PDFInfo
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- CN110359114B CN110359114B CN201910718254.XA CN201910718254A CN110359114B CN 110359114 B CN110359114 B CN 110359114B CN 201910718254 A CN201910718254 A CN 201910718254A CN 110359114 B CN110359114 B CN 110359114B
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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
- D01D5/04—Dry spinning methods
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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
- D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
- D01F6/28—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
- D01F6/38—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds comprising unsaturated nitriles as the major constituent
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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
- 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
- D01F9/225—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 from stabilised polyacrylonitriles
Abstract
The invention relates to polyacrylonitrile fiber, polyacrylonitrile-based carbon fiber and a preparation method thereof. The main technical scheme adopted is as follows: a preparation method of polyacrylonitrile fiber comprises the following steps: extruding the polyacrylonitrile spinning solution through a spinneret orifice to form spinning trickle; solidifying and forming the spinning trickle to obtain nascent fiber; drawing the nascent fiber in a gas medium; and (4) carrying out post-treatment on the drawn nascent fiber to obtain the polyacrylonitrile fiber. The method is mainly used for reducing the amount of wastewater generated in the preparation process of polyacrylonitrile fibers and polyacrylonitrile-based carbon fibers.
Description
Technical Field
The invention relates to the technical field of fibers, in particular to polyacrylonitrile fibers, polyacrylonitrile-based carbon fibers and preparation methods thereof.
Background
The polyacrylonitrile fiber has wide application, can be directly used in textile industry, and can also be prepared into polyacrylonitrile-based carbon fiber after heat treatment.
When the wet spinning process or the dry-jet wet spinning process is utilized to prepare the polyacrylonitrile fiber: the spinning stream is first passed through a coagulation bath to form coagulated filaments (coagulated filaments are also called as primary fibers), and then the coagulated filaments are subjected to post-treatment processes (such as washing, drawing, oiling, drying and the like) to convert the coagulated filaments into polyacrylonitrile fibers. However, the coagulated filaments from the coagulation bath contain a large amount of solvent, which must be removed in a post-treatment process to improve fiber properties and meet the requirements for subsequent processing.
In the prior art, the solvent contained in the solidified silk is directly removed by adopting a water washing mode. However, the inventors of the present invention found that: the technology of removing the solvent in the solidified silk by adopting a direct water washing mode directly has the direct consequence of generating a large amount of waste water, thereby not only increasing the production cost, but also polluting the environment.
Disclosure of Invention
In view of the above, the present invention provides polyacrylonitrile fibers, polyacrylonitrile-based carbon fibers and a preparation method thereof, and mainly aims to reduce the amount of wastewater generated in the preparation process of polyacrylonitrile fibers and polyacrylonitrile-based carbon fibers.
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 fiber, which is characterized by comprising the following steps:
preparing nascent fiber: extruding the polyacrylonitrile spinning solution through a spinneret orifice to form spinning trickle; solidifying and forming the spinning trickle to obtain nascent fiber;
drawing treatment: drawing the nascent fiber in a gas medium;
and (3) post-treatment: and (4) carrying out post-treatment on the drawn nascent fiber to obtain the polyacrylonitrile fiber.
The object of the present invention and the technical problems solved thereby can be further achieved by the following technical measures.
Preferably, in the step of the drawing treatment, the drawing treatment is a positive drawing treatment; preferably, in the step of drawing, the primary fiber is subjected to 2-3 stages of drawing; preferably, in the step of drawing, the total drawing ratio applied to the as-spun fibers is 1.05 to 3.5 times, preferably 1.2 to 3 times, and more preferably 1.5 to 2 times.
Preferably, in the step of the draft treatment: the temperature of the gaseous medium is not higher than 50 ℃, preferably not higher than 25 ℃; the temperature of the gas medium is not lower than the glass transition temperature of the primary fiber and the melting point of the solvent contained in the primary fiber.
Preferably, in the step of the draft treatment: the gas medium is one or a mixture of air, nitrogen, water vapor, inert gas and carbon dioxide.
Preferably, in the step of preparing the nascent fiber: the nascent fiber is wholly in a solidification state or a gel state; or the part of the nascent fiber is in any one of a condensed state, a gel state and a solution state.
Preferably, in the step of preparing the nascent fiber, the spinning solution is prepared into the nascent fiber by any one of a wet spinning method, a dry-jet wet spinning method and a dry spinning method;
preferably, when the polyacrylonitrile spinning solution is prepared into the nascent fiber by the wet spinning method: the temperature of the coagulating bath is 0-70 ℃, preferably 15-65 ℃; and/or the draft multiple of the spinning nozzle is 0.7-1.5 times, preferably 0.75-1.2 times, and further preferably 0.8-1.1 times;
preferably, when the polyacrylonitrile spinning solution is prepared into the nascent fiber by adopting a dry-jet wet spinning method: the temperature of the coagulating bath is-50 to 10 ℃, more preferably-25 to 4 ℃, and still more preferably-18 to 4 ℃; and/or the draft multiple of the spinneret is 2 to 12 times, preferably 3 to 8 times, and more preferably 4 to 6 times.
Preferably, the components of the coagulation bath include a solvent and a non-solvent; wherein the mass ratio of the non-solvent to the solvent is 1: 0-3: 7, preferably 1: 0-4: 6, more preferably 9: 1-5: 5, and even more preferably 8: 2-6: 4; preferably, the non-solvent is one or a mixture of more of formic acid, glycerol, ethylene glycol, acetic acid, ethanol, methanol, chloroform, isobutanol, isoamyl alcohol, butanediol, benzyl alcohol, carbon tetrachloride, toluene, acetone, water and dioxane.
Preferably, the post-processing step includes: carrying out water washing treatment, stretching treatment, oiling treatment and drying treatment on the drawn nascent fiber to obtain polyacrylonitrile fiber;
preferably, the total draft applied to the fiber in the process of producing the polyacrylonitrile fiber is 10 times or more and less than 350 times, and more preferably 25 times or more and less than 150 times.
Preferably, the polymer in the polyacrylonitrile spinning solution is polyacrylonitrile homopolymer; or
The polymer in the polyacrylonitrile spinning solution is a polyacrylonitrile copolymer; or
The polymer in the polyacrylonitrile spinning solution comprises a mixture of polyacrylonitrile homopolymer and polyacrylonitrile copolymer.
On the other hand, the embodiment of the invention provides a preparation method of polyacrylonitrile-based carbon fiber, which comprises the following steps:
the polyacrylonitrile fiber is prepared by adopting the preparation method of the polyacrylonitrile fiber;
and carrying out heat treatment on the polyacrylonitrile fiber to obtain the polyacrylonitrile-based carbon fiber.
On the other hand, the embodiment of the invention also provides a polyacrylonitrile-based fiber, wherein the polyacrylonitrile-based fiber is prepared by the preparation method of the polyacrylonitrile fiber;
preferably, when the diameter D of the spinneret hole in the step of preparing the nascent fiber is 0.045 ≦ D<0.1mm time: the diameter of the polyacrylonitrile fiber is 4.2-12 mu m, and the bulk density of the polyacrylonitrile fiber is 1.186-1.20 g/cm3；
When the diameter D of the spinneret orifice is not less than 0.1 in the step of preparing the nascent fiber<0.3mm time: the diameter of the polyacrylonitrile fiber is 6-13.2 mu m, and the bulk density of the polyacrylonitrile fiber is 1.184-1.19 g/cm3；
When the diameter D of the spinneret orifice is not less than 0.3 and not more than 2mm in the step of preparing the nascent fiber: the diameter of the polyacrylonitrile fiber is 7-17 mu m, and the bulk density of the polyacrylonitrile fiber is 1.184-1.195 g/cm3。
On the other hand, the embodiment of the invention also provides the polyacrylonitrile-based carbon fiber, wherein the polyacrylonitrile-based carbon fiber is prepared by the preparation method of the polyacrylonitrile-based carbon fiber;
preferably, when the diameter D of the spinneret hole in the step of preparing the nascent fiber is 0.045 ≦ D<0.1mm time: the diameter of the polyacrylonitrile-based carbon fiber is 3-7.6 μm, and the bulk density of the polyacrylonitrile-based carbon fiber is 1.84-1.96 g/cm3；
When the diameter D of the spinneret orifice is not less than 0.1 in the step of preparing the nascent fiber<0.3mm time: the diameter of the polyacrylonitrile-based carbon fiber is 4.5-8.1 mu m, and the bulk density of the polyacrylonitrile-based carbon fiber is 1.79-2.0 g/cm3；
When the diameter D of the spinneret orifice is not less than 0.3 and not more than 2mm in the step of preparing the nascent fiber: the diameter of the polyacrylonitrile-based carbon fiber is 5-10 mu m, and the bulk density of the polyacrylonitrile-based carbon fiber is 1.180-1.83 g/cm3。
Compared with the prior art, the polyacrylonitrile fiber, the polyacrylonitrile-based carbon fiber and the preparation method thereof have the following beneficial effects:
in one aspect, the preparation method of polyacrylonitrile fiber provided by the embodiment of the present invention is implemented after the step of forming the nascent fiber and before the step of performing post-treatment (including washing, stretching, oiling and drying processes) on the nascent fiber: the step of positively drafting the nascent fiber in a gas medium is added, so that tension can be applied to the nascent fiber, the solvent contained in the sliver is squeezed while the sliver in the nascent fiber shape is lengthened, the solvent contained in the sliver is forced to seep to the surface of the sliver, and the seeped solvent forms liquid drops to leave the sliver, so that the technical effect of removing part of the solvent in the sliver is achieved, and the wastewater amount of the subsequent water washing process is reduced.
Furthermore, in the preparation method of the polyacrylonitrile fiber provided by the embodiment of the invention, when the nascent fiber is prepared, the temperature of the coagulation bath and the composition of the coagulation bath liquid are controlled, so that the nascent fiber is in a gel state (or partially in a gel state), and the gel-state nascent fiber is cooperated with positive drafting treatment, the effect of extruding the filament is more obvious, most of the solvent in the filament can be extruded, and the wastewater amount of the subsequent washing process is greatly reduced.
On the other hand, the embodiment of the invention also provides a preparation method of the polyacrylonitrile-based carbon fiber, wherein the preparation method of the polyacrylonitrile-based carbon fiber comprises the preparation method of the polyacrylonitrile fiber, so that the preparation method of the polyacrylonitrile-based carbon fiber provided by the embodiment of the invention also realizes the beneficial effect of reducing the amount of wastewater.
In addition, compared with the prior art, the preparation method of the polyacrylonitrile fiber and the preparation method of the polyacrylonitrile-based carbon fiber provided by the embodiment of the invention can ensure that the prepared polyacrylonitrile fiber and the polyacrylonitrile-based carbon fiber have smaller diameters and larger bulk densities, so that the polyacrylonitrile fiber and the polyacrylonitrile-based carbon fiber have more excellent structures and properties.
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 intended purpose, the following preferred embodiments describe the detailed description, structure, features and effects of the invention according to the present application. 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.
On one hand, the embodiment of the invention provides a preparation method of polyacrylonitrile fiber, which comprises the following steps:
1) extruding the polyacrylonitrile spinning solution through a spinneret orifice to form spinning trickle; and (3) obtaining the nascent fiber after solidification forming treatment of the spinning trickle.
The polyacrylonitrile spinning solution in the step is as follows: polyacrylonitrile and polyacrylonitrile solvent are used as component solution. The polyacrylonitrile here means a blend mainly composed of polyacrylonitrile homopolymer, or a copolymer mainly composed of acrylonitrile, and polyacrylonitrile obtained from acrylonitrile homopolymer or a copolymer mainly composed of acrylonitrile. The polyacrylonitrile-based spinning solution may contain other substances as long as the effects of the present invention are not impaired.
Here, the polyacrylonitrile solvent is a solvent that can dissolve polyacrylonitrile; preferably, the compound is a single substance such as dimethyl sulfoxide, dimethylformamide, dimethylacetamide, dimethyl sulfoxide/lithium chloride, an ionic liquid, a sodium thiocyanate solution, a zinc chloride solution, or the like, or a mixture thereof.
The molecular weight and distribution of polyacrylonitrile are not particularly limited, and polyacrylonitrile in a fiber form may be obtained by a spinning process. In view of the mechanical properties of the polyacrylonitrile fiber, the molecular weight of polyacrylonitrile is preferably 7 ten thousand or more, and more preferably 10 ten thousand or more. The higher the molecular weight, the better the mechanical properties of the obtained polyacrylonitrile fiber, but the higher the molecular weight, the lower the solubility of the polyacrylonitrile in the solvent, so the upper limit of the molecular weight of the polyacrylonitrile is not particularly limited as long as the polyacrylonitrile can be dissolved in the solvent, and usually the polyacrylonitrile is less than 150 ten thousand. In order to give consideration to both the mechanical property and the spinning property of the polyacrylonitrile fiber, the polyacrylonitrile with large molecular weight and the polyacrylonitrile with small molecular weight can be dissolved in the solvent together to obtain the spinning solution of the polyacrylonitrile.
Preferably, in this step, the spinning process is a process of spinning a polyacrylonitrile spinning solution to obtain a filament having a fiber form. The spinning process is preferably a wet spinning method or a dry-jet wet spinning method.
Preferably, the polyacrylonitrile fiber-shaped filament formed in the spinning process used in this step may be in a coagulated state (non-elastic) as a whole, and may be in a gel state; but may also be partially in a coagulated state (e.g., only the sheath of the fiber is coagulated and the core may be in a solution or gel state), in a solution state (e.g., the sheath of the fiber is coagulated or gel state and the core of the fiber is in a solution state), or in a gel state (e.g., the sheath of the fiber is coagulated and the core is in a gel state; e.g., the sheath of the fiber is in a gel state and the core of the fiber is in a solution state). The spinning process conditions are preferably selected so that the nascent fiber as a whole is in the gel state.
Preferably, the spinning process of this step may preferably be such that the polyacrylonitrile spinning solution may be subjected to gel-state spinning process conditions during fiber formation, such as fiber formation process conditions using a low-temperature coagulation bath. The loss modulus of the polyacrylonitrile spinning solution is greater than the storage modulus, and the gel state refers to a state that the polyacrylonitrile spinning solution is converted into a state that the loss modulus of the polyacrylonitrile spinning solution is equal to or less than the storage modulus in the spinning process, but part of the polyacrylonitrile spinning solution is still not subjected to phase separation.
In the step, the spinning process can be any one of a dry method, a wet spinning method and a dry-jet wet spinning method; wet spinning or dry-jet wet spinning is preferred.
Here, for the dry spinning process: the fibre leaving the shaft also contains a large amount of solvent, i.e. when the fibre has not yet solidified completely, part of the solvent can be removed by this method and then be subjected to subsequent treatment. The dry spinning mode is adopted, namely the spinning solution enters a channel, but the temperature in the channel is low, at the moment, the spinning solution trickles form a gel state, and the solvent can be removed by air drafting in the subsequent process.
Preferably, when the wet spinning method or the dry-jet wet spinning method is used in the spinning process of the step, the coagulation bath components mainly comprise a polyacrylonitrile solvent (a solvent for dissolving polyacrylonitrile, referred to as a solvent for short) and a polyacrylonitrile non-solvent (a solvent for not dissolving polyacrylonitrile, referred to as a non-solvent for short); wherein the mass ratio of the non-solvent to the solvent is 1: 0-3: and 7, forming the spinning solution of the polyacrylonitrile into a fiber shape by using the coagulating bath. Preferably, the mass ratio of the non-solvent to the solvent is 1: 0-4: 6, more preferably 9: 1-5: 5, more preferably 8: 2-6: 4. here, the non-solvent may be a single substance or a mixture of different substances; for example, the solvent may be one or more of formic acid, glycerol, ethylene glycol, acetic acid, ethanol, methanol, chloroform, isobutanol, isoamyl alcohol, butanediol, benzyl alcohol, carbon tetrachloride, toluene, acetone, water and dioxane. The components of the coagulation bath other than the solvent and the non-solvent may contain other components which do not impair the effect of the present invention, that is, other components may be present in the coagulation bath other than the listed solvents and non-solvents.
Preferably, for the spinning process using the wet spinning method or the dry-jet wet spinning method, the coagulation bath temperature is preferably-50 to 70 ℃ and higher than the melting point of the coagulation bath composition. Wherein, when the spinning process is wet spinning, the temperature of the coagulation bath is preferably 0-70 ℃, and more preferably 15-65 ℃. When the spinning process is dry-jet wet spinning, the temperature of the coagulation bath is preferably set to be low, and the specific temperature of the coagulation bath is preferably-50-10 ℃, more preferably-25-4 ℃, and even more preferably-18-4 ℃. When the temperature of the coagulation bath is lower than minus 50 ℃, the spinning solution of polyacrylonitrile is slow in coagulation and formation and high in energy consumption; when the temperature of the coagulation bath is higher than 70 ℃, the coagulation speed of the polyacrylonitrile spinning solution is too high, which is not favorable for forming fiber strands with uniform structures. When the temperature of the coagulation bath is-18-10 ℃, the polyacrylonitrile spinning solution is favorable for forming a gel state, so that the fiber strand is uniform in structure and strong in drawability, and high-quality coagulated yarns are favorably obtained.
The composition of the coagulating bath and the temperature of the coagulating bath are set, so that the fibers can be prevented from being separated in the forming process as much as possible, the nascent fibers are in a gel state (or can be partially in the gel state) as much as possible, the gel-state nascent fibers and positive drafting treatment are matched in a synergistic manner, the effect of extruding the silk slivers is more obvious, most of solvent in the silk slivers can be extruded, and the wastewater amount of the subsequent washing process is greatly reduced.
Preferably, if wet spinning is adopted in the step, the draft ratio of the spinneret may be 0.7 to 1.5 times, preferably 0.75 to 1.2 times, and more preferably 0.8 to 1.1 times. If the dry jet wet spinning is adopted in the step, the draft multiple of the spinning nozzle can be 2-12 times, preferably 3-8 times, and more preferably 4-6 times (when the draft multiple of the spinning nozzle is too small, fibers are accumulated in a coagulating bath, the fiber performance is not good, no draft is obtained, the diameter and CV value of the fibers are not controlled, and when the draft multiple of the spinning nozzle is too large, broken filaments are easily generated, continuous generation is influenced, and in addition, the fibers are difficult to be drafted again in post-treatment).
In the present application, the term "spinneret draft" refers to, for a person skilled in the art: after spinning, the ratio of the speed of the first driving transmission roller to the speed of the spinning solution trickles flowing out of the spinning holes.
2) And (3) drawing the nascent fiber in a gas medium.
Preferably, in this step, the drawing process is a positive drawing process.
Preferably, in this step, the draft ratio applied to the as-spun fibers is 1.05 to 3.5 times, preferably 1.2 to 3 times, and more preferably 1.5 to 2 times.
Preferably, in this step, the nascent fiber may be subjected to a multi-stage drawing process; the main benefit of fractionation is to reduce the amount of filaments produced by the high draw and to increase the extrusion efficiency.
Preferably, in this step, the temperature of said gaseous medium is not higher than 25 ℃; the temperature of the gas medium is not lower than the glass transition temperature of the primary fiber and the freezing temperature of the solvent contained in the primary fiber.
Preferably, in this step: the gas medium is any one of air, nitrogen, water vapor, inert gas and carbon dioxide.
3) And (4) carrying out post-treatment on the drawn nascent fiber to obtain the polyacrylonitrile fiber.
The post-processing step comprises: and (3) carrying out water washing treatment, stretching treatment, oiling treatment and drying treatment on the drawn nascent fiber to obtain the polyacrylonitrile fiber.
Preferably, the stretching treatment may be a bath stretching treatment, or a steam stretching treatment or a dry heat stretching treatment.
Preferably, the oiling treatment is to endow a protective layer on the surface layer of the fiber, prevent fiber adhesion, reduce static electricity, increase the convergence and fiber distribution of the fiber bundle, and preferably perform oiling treatment after stretching the fiber strand in a bath.
When the stretching ratio is increased, molecules are easy to align along the axial direction of the fiber, and the performance of the fiber is increased. In the production of the polyacrylonitrile fiber, the total draft applied to the fiber is 10 times or more and less than 350 times, more preferably 25 times or more and less than 150 times (i.e., the draft in all steps from the start of spinning to the final winding of the yarn).
In summary, compared with the prior art, the preparation method of the polyacrylonitrile fiber provided by the embodiment of the present invention includes, after the step of forming the nascent fiber, before the step of performing post-treatment (including washing, stretching, oiling, and drying processes) on the nascent fiber: the step of positively drafting the nascent fiber in a gas medium is added, so that tension can be applied to the nascent fiber, the solvent contained in the sliver is squeezed while the sliver in the nascent fiber shape is lengthened, the solvent contained in the sliver is forced to seep to the surface of the sliver, and the seeped solvent forms liquid drops to leave the sliver, so that the technical effect of removing part of the solvent in the sliver is achieved, and the wastewater amount of the subsequent water washing process is reduced.
On the other hand, the embodiment of the invention also provides a polyacrylonitrile-based carbon fiber, which comprises the following steps:
preparing polyacrylonitrile fiber: the polyacrylonitrile fiber is prepared by adopting the preparation method of the polyacrylonitrile fiber;
and (3) heat treatment: and carrying out heat treatment on polyacrylonitrile to obtain the polyacrylonitrile-based carbon fiber.
The heat treatment process is not particularly limited as long as the polyacrylonitrile fiber can be converted into a carbon fiber by heating, and examples thereof include a pre-oxidation process, a low-temperature carbonization process, and a high-temperature carbonization process.
Preferably, the polyacrylonitrile fiber is subjected to the following processes in sequence to obtain the carbon fiber:
a pre-oxidation process, namely pre-oxidizing the obtained carbon fiber precursor fiber in the air at the temperature of 185-350 ℃;
a low-temperature carbonization process, wherein the fibers obtained in the pre-oxidation process are carbonized at low temperature in an inert atmosphere at the temperature of 400-850 ℃;
and (3) a high-temperature carbonization process, namely carbonizing the fibers obtained in the low-temperature carbonization process at the temperature of 1200-3000 ℃ in an inert atmosphere.
In order to increase the bonding strength of the carbon fibers to the matrix in the fiber-reinforced composite material, the surface of the carbon fibers may be treated by electrolysis. After the electrolytic treatment, in order to increase the bundling property and subsequent use performance of the carbon fiber, sizing treatment can be carried out on the carbon fiber. The sizing agent used in the sizing treatment is selected according to the type of the matrix in the composite material.
The following is described in further detail by way of specific experimental examples.
Example 1
The embodiment provides a preparation method of polyacrylonitrile fiber and polyacrylonitrile-based carbon fiber, which specifically comprises the following steps:
1) preparing polyacrylonitrile spinning solution: a polyacrylonitrile solution obtained by solution polymerization using dimethyl sulfoxide as a solvent and acrylonitrile and itaconic acid as comonomers is a polyacrylonitrile spinning solution, which has a viscosity-average molecular weight of 14 ten thousand and a viscosity of 80pa.s (here, this example and the following examples mainly use a polyacrylonitrile spinning solution having a viscosity-average molecular weight of 14 ten thousand and a viscosity of 80pa.s as an example, but are not limited thereto, and any one of the polyacrylonitrile spinning solutions is suitable for the present invention).
2) Preparing nascent fiber: preparing nascent fiber by adopting a dry jet wet spinning method (wherein the drafting multiple of a spinning head is 6.0, and the diameter of a spinning hole is 0.12 mm); in this step: the temperature of the coagulating bath is controlled to be-15 ℃, and the coagulating bath comprises the following components in percentage by mass of 7: 3 and water.
3) Drawing treatment: drafting the nascent fiber in a gas medium; wherein the gas medium is air, and the drafting multiple applied to the nascent fiber is 3.5 times.
4) And (3) post-treatment: washing and stretching the drafted nascent fiber by using a water bath to obtain water bath fiber; and oiling the water bath fiber, drying and densifying the fiber by using a drying roller, and drafting in high-temperature steam to obtain the polyacrylonitrile fiber.
The polyacrylonitrile fiber with the fiber fineness of 0.90dtex is obtained in the preparation process of the polyacrylonitrile fiber.
5) And (3) heat treatment: and pre-oxidizing the obtained polyacrylonitrile fiber in air with a temperature gradient in a temperature range of 185-350 ℃ to obtain the pre-oxidized fiber. And carbonizing the obtained pre-oxidized fiber at a low temperature in a nitrogen atmosphere at the temperature of 400-850 ℃ to obtain the low-temperature carbonized fiber. And carbonizing the low-temperature carbonized fiber at high temperature in a nitrogen atmosphere with the highest temperature of 1600 ℃, performing electrolytic treatment by using an ammonium bisulfate solution as an electrolyte, washing with water, drying, and then performing sizing treatment to obtain the polyacrylonitrile-based carbon fiber.
Example 2
The embodiment provides a preparation method of polyacrylonitrile fiber and polyacrylonitrile-based carbon fiber; this example differs from example 1 in that:
in the step of preparing the nascent fiber: the drafting multiple of the spinning jet is 2 times; the diameter of the spinneret orifice is 0.5 mm; the temperature of the coagulation bath was 10 ℃; the coagulating bath comprises the following components in percentage by mass: 4 dimethylacetamide and water;
in the drawing treatment step: the gas medium is air, and the drafting multiple applied to the nascent fiber in the gas medium is 2 times;
the other steps were identical to those of example 1.
Example 3
The embodiment provides a preparation method of polyacrylonitrile fiber and polyacrylonitrile-based carbon fiber; this example differs from example 1 in that:
in the step of preparing the nascent fiber: the drafting multiple of the spinneret is 12 times, and the diameter of the spinneret orifice is 0.15 mm; the temperature of the coagulating bath is-25 ℃, and the components of the coagulating bath are ethanol;
in the drawing treatment step: the gas medium is air, and the drafting multiple applied to the nascent fiber in the gas medium is 3 times;
the other steps were identical to those of example 1.
Example 4
The embodiment provides a preparation method of polyacrylonitrile fiber and polyacrylonitrile-based carbon fiber; this example differs from example 1 in that:
in the step of preparing the nascent fiber: the drawing multiple of the spinning jet is 1.2 times, the diameter of a spinning hole is 0.1mm, the temperature of the coagulating bath is 3 ℃, and the component of the coagulating bath is water;
in the drawing treatment step: the gaseous medium is air, and the drafting multiple applied to the nascent fiber in the gaseous medium is 1.5 times.
The other steps were identical to those of example 1.
Example 5
The embodiment provides a preparation method of polyacrylonitrile fiber and polyacrylonitrile-based carbon fiber; this example differs from example 1 in that:
in the step of preparing the nascent fiber: the drafting multiple of the spinning jet is 8 times, and the diameter of a spinning hole is 0.2 mm; the temperature of the coagulating bath is-18 ℃, and the components of the coagulating bath in mass ratio are 9:1 ethanol and water;
in the drawing treatment step: the gaseous medium was air and the draft applied to the as-spun fibers in the gaseous medium was 2.5 times.
The other steps were identical to those of example 1.
Example 6
The embodiment provides a preparation method of polyacrylonitrile fiber and polyacrylonitrile-based carbon fiber; this example differs from example 1 in that:
in the step of preparing the nascent fiber: the drafting multiple of the spinning jet is 4 times, and the diameter of a spinning hole is 0.3 mm; the temperature of the coagulation bath is 1 ℃, and the composition of the coagulation bath is as follows by mass ratio of 5:5 isopropyl alcohol and dimethyl formamide;
in the drawing treatment step: the gaseous medium was air, and the draft applied to the as-spun fibers in the gaseous medium was 1.05 times.
The other steps were identical to those of example 1.
Example 7
The embodiment provides a preparation method of polyacrylonitrile fiber and polyacrylonitrile-based carbon fiber; this example differs from example 1 in that:
in the step of preparing the nascent fiber: adopting a wet spinning process, wherein the drawing multiple of a spinning nozzle is 1.1 times, and the diameter of a spinning hole is 0.045 mm; the temperature of the coagulation bath is 15 ℃, and the composition of the coagulation bath is as follows by mass ratio of 4:6 dimethyl sulfoxide and water;
in the drawing treatment step: the gaseous medium was nitrogen and the draft applied to the as-spun fibers in the gaseous medium was 1.4 times.
The other steps were identical to those of example 1.
Example 8
The embodiment provides a preparation method of polyacrylonitrile fiber and polyacrylonitrile-based carbon fiber; this example differs from example 1 in that:
in the step of preparing the nascent fiber: adopting a wet spinning process, wherein the drafting multiple of a spinning nozzle is 0.8 times, and the diameter of a spinning hole is 0.06 mm; the temperature of the coagulating bath is 65 ℃, and the components of the coagulating bath in mass ratio are 6:4 dimethyl sulfoxide and water;
in the drawing treatment step, the gaseous medium is nitrogen, and the drawing factor applied to the as-spun fibers in the gaseous medium is 1.2 times.
The other steps were identical to those of example 1.
Example 9
The embodiment provides a preparation method of polyacrylonitrile fiber and polyacrylonitrile-based carbon fiber; this example differs from example 1 in that:
in the step of preparing the nascent fiber: adopting a wet spinning process, wherein the drafting multiple of a spinning nozzle is 0.75 times, and the diameter of a spinning hole is 0.07 mm; the temperature of the coagulating bath is 70 ℃, and the components of the coagulating bath in mass ratio of 7: 3 dimethyl sulfoxide and water;
in the drawing treatment step: the gaseous medium was carbon dioxide and the draft applied to the as-spun fibers in the gaseous medium was 1.1 times.
The other steps were identical to those of example 1.
Example 10
The embodiment provides a preparation method of polyacrylonitrile fiber and polyacrylonitrile-based carbon fiber; this example differs from example 1 in that:
in the step of preparing the nascent fiber: the drafting multiple of the spinning jet is 3 times, and the diameter of a spinning hole is 1 mm; the temperature of the coagulating bath is-50 ℃, and the composition of the coagulating bath is methanol;
in the drawing treatment step: the gaseous medium is water vapor, and the draft multiple applied to the nascent fiber in the gaseous medium is 1.6 times.
The other steps were identical to those of example 1.
Example 11
The embodiment provides a preparation method of polyacrylonitrile fiber and polyacrylonitrile-based carbon fiber; this example differs from example 1 in that:
in the step of preparing the nascent fiber: the drafting multiple of the spinning jet is 1.5 times, and the diameter of a spinning hole is 2 mm; the temperature of the coagulation bath is-10 ℃, and the composition of the coagulation bath is 4: 5: 1 dimethyl sulfoxide, water, methanol;
in the drawing treatment step: the gaseous medium was nitrogen and the draft applied to the as-spun fibers in the gaseous medium was 1.8 times.
The other steps were identical to those of example 1.
Example 12
The embodiment provides a preparation method of polyacrylonitrile fiber and polyacrylonitrile-based carbon fiber; this example differs from example 1 in that:
in the step of preparing the nascent fiber: adopting a wet spinning process, wherein the drafting multiple of a spinning nozzle is 0.7 times, and the diameter of a spinning hole is 0.25 mm; the temperature of the coagulating bath is 60 ℃, and the components of the coagulating bath in a mass ratio of 3:7 dimethyl sulfoxide and water;
in the drawing treatment step: the gaseous medium was nitrogen and the draft applied to the as-spun fibers in the gaseous medium was 1.3 times.
The other steps were identical to those of example 1.
Comparative example 1
In the preparation process of polyacrylonitrile fiber and polyacrylonitrile-based carbon fiber, the primary fiber is not drawn in a gas medium, and the other steps are the same as those in example 1 to obtain the polyacrylonitrile-based carbon fiber.
Comparative example 2
In the preparation process of polyacrylonitrile fiber and polyacrylonitrile-based carbon fiber, the primary fiber is not drawn in a gas medium, and the other steps are the same as those in example 2 to obtain the polyacrylonitrile-based carbon fiber.
Comparative example 3
In the preparation process of polyacrylonitrile fiber and polyacrylonitrile-based carbon fiber, the primary fiber is not drawn in a gas medium, and the other steps are the same as those in example 3 to obtain the polyacrylonitrile-based carbon fiber.
Comparative example 4
In the preparation process of the polyacrylonitrile-based fiber and the polyacrylonitrile-based carbon fiber, the primary fiber is not drawn in a gas medium, and the polyacrylonitrile-based carbon fiber is obtained by the same operation as that in the example 4.
Comparative example 5
In the preparation process of polyacrylonitrile fiber and polyacrylonitrile-based carbon fiber, the primary fiber is not drawn in a gas medium, and the other steps are the same as those in example 5 to obtain the polyacrylonitrile-based carbon fiber.
Comparative example 6
In the preparation process of polyacrylonitrile fiber and polyacrylonitrile-based carbon fiber, the primary fiber is not drawn in a gas medium, and the other steps are the same as those in example 8 to obtain the polyacrylonitrile-based carbon fiber.
Comparative example 7
In the preparation process of polyacrylonitrile fiber and polyacrylonitrile-based carbon fiber, the primary fiber was not drawn in a gas medium, and the other steps were performed in the same manner as in example 9 to obtain polyacrylonitrile-based carbon fiber.
The preparation process parameters and the amount of wastewater generated in the preparation process of examples 1 to 12 and comparative examples 1 to 7 are shown in Table 1.
Table 1 shows the preparation process parameters and the amounts of wastewater produced in the preparation processes of examples 1 to 12 and comparative examples 1 to 7
As can be seen from table 1:
(1) the preparation method of polyacrylonitrile fiber and polyacrylonitrile-based carbon fiber provided by the embodiment of the invention can reduce the amount of wastewater by more than 10%.
(2) The temperature of the coagulating bath and the composition of the coagulating bath liquid are controlled to enable the nascent fiber to be in a gel state, so that the gel-state nascent fiber is cooperated with positive drafting treatment, the effect of extruding the silk strips is more obvious, most of solvent in the silk strips can be extruded, and the wastewater amount of the subsequent washing process is greatly reduced.
The production process parameters and the product production parameters of examples 1 to 12 and comparative examples 1 to 7 are shown in Table 2.
Table 2 shows the preparation process parameters and the parameter lists of the prepared products of examples 1 to 12 and comparative examples 1 to 7
As can be seen from table 2:
(1) compared with the prior art, the preparation method of the polyacrylonitrile fiber provided by the embodiment of the invention can be used for realizing fine denier of the polyacrylonitrile fiber, reducing the diameter of the polyacrylonitrile fiber and increasing the bulk density of the polyacrylonitrile fiber.
(2) Compared with the prior art, the preparation method of the polyacrylonitrile-based carbon fiber provided by the embodiment of the invention can be used for fine denier of the polyacrylonitrile-based carbon fiber, reducing the diameter of the polyacrylonitrile-based carbon fiber and increasing the bulk density 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 (10)
1. A preparation method of polyacrylonitrile fiber is characterized by comprising the following steps:
preparing nascent fiber: extruding the polyacrylonitrile spinning solution through a spinneret orifice to form spinning trickle; solidifying and forming the spinning trickle to obtain nascent fiber; wherein the nascent fiber as a whole is in a gel state or a part of the nascent fiber is in a gel state;
drawing treatment: in a gas medium, carrying out positive drafting treatment on the nascent fiber; the total draft multiple applied to the nascent fiber is 1.05-2.5 times;
and (3) post-treatment: post-treating the drafted nascent fiber to obtain polyacrylonitrile fiber;
in the step of preparing the nascent fiber, preparing the polyacrylonitrile spinning solution into the nascent fiber by adopting a dry-jet wet spinning method: the temperature of the coagulating bath is-50-10 ℃, and the drafting multiple of a spinning nozzle is 2-12 times; the components of the coagulating bath comprise a solvent and a non-solvent; wherein the mass ratio of the non-solvent to the solvent is 1: 0-6: 4.
2. The method for producing polyacrylonitrile fiber according to claim 1, characterized in that, in the step of drawing treatment, 2-3 stages of drawing treatment are performed on the nascent fiber.
3. The method for producing polyacrylonitrile fiber according to claim 1, characterized in that, in the step of the drawing treatment:
the temperature of the gaseous medium is not higher than 50 ℃;
the temperature of the gas medium is not lower than the glass transition temperature of the primary fiber and the melting point of the solvent contained in the primary fiber.
4. The method for producing polyacrylonitrile fiber according to claim 1, characterized in that, in the step of the drawing treatment:
the gas medium is one or a mixture of air, nitrogen, water vapor, inert gas and carbon dioxide; and/or
The temperature of the gaseous medium is not higher than 25 ℃.
5. The method for producing polyacrylonitrile fiber according to claim 1,
the temperature of the coagulating bath is-25-4 ℃, and the drafting multiple of the spinning nozzle is 3-8 times.
6. The method for producing polyacrylonitrile fiber according to claim 1,
the non-solvent is one or a mixture of more of formic acid, glycerol, ethylene glycol, acetic acid, ethanol, methanol, chloroform, isobutanol, isoamylol, butanediol, benzyl alcohol, carbon tetrachloride, toluene, acetone, water and dioxane; and/or
The solvent is a solvent capable of dissolving polyacrylonitrile; wherein the solvent is one or a mixture of more of dimethyl sulfoxide, dimethylformamide, dimethylacetamide, a lithium chloride solution, an ionic liquid, a sodium thiocyanate solution and a zinc chloride solution.
7. The method for preparing polyacrylonitrile fibers according to any one of claims 1 to 6, characterized in that the step of post-treatment comprises: carrying out water washing treatment, stretching treatment, oiling treatment and drying treatment on the drawn nascent fiber to obtain polyacrylonitrile fiber;
wherein, in the preparation process of the polyacrylonitrile fiber: the total draft applied to the fiber is 10 times or more and less than 350 times.
8. The method for preparing polyacrylonitrile fiber according to claim 7, characterized in that, in the process of preparing polyacrylonitrile fiber: the total draft applied to the fiber is 25 times or more and less than 150 times.
9. The method for producing polyacrylonitrile fiber according to any one of claims 1 to 6, 8, characterized in that,
the polymer in the polyacrylonitrile spinning solution is polyacrylonitrile homopolymer; or
The polymer in the polyacrylonitrile spinning solution is a polyacrylonitrile copolymer; or
The polymer in the polyacrylonitrile spinning solution comprises a mixture of polyacrylonitrile homopolymer and polyacrylonitrile copolymer.
10. A preparation method of polyacrylonitrile-based carbon fibers is characterized by comprising the following steps:
preparing polyacrylonitrile fibers by using the preparation method of the polyacrylonitrile fibers according to any one of claims 1 to 9;
and carrying out heat treatment on the polyacrylonitrile fiber to obtain the polyacrylonitrile-based carbon fiber.
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