CN114606579B - Ammoniation method and device for polyacrylonitrile spinning solution - Google Patents
Ammoniation method and device for polyacrylonitrile spinning solution Download PDFInfo
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- CN114606579B CN114606579B CN202011412180.6A CN202011412180A CN114606579B CN 114606579 B CN114606579 B CN 114606579B CN 202011412180 A CN202011412180 A CN 202011412180A CN 114606579 B CN114606579 B CN 114606579B
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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
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D1/00—Treatment of filament-forming or like material
- D01D1/10—Filtering or de-aerating the spinning solution or melt
- D01D1/103—De-aerating
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- 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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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
- Y02P70/62—Manufacturing or production processes characterised by the final manufactured product related technologies for production or treatment of textile or flexible materials or products thereof, including footwear
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Abstract
The invention discloses an ammonification method and an ammonification device for polyacrylonitrile spinning solution, wherein the ammonification method comprises the following steps: (1) Quantitatively mixing an ammoniation reagent with a solvent to obtain a mixed solution with controllable ammonia content; (2) Dispersing polyacrylonitrile powder into the mixed solution with controllable ammonia content prepared in the step (1), and uniformly stirring to obtain polyacrylonitrile slurry; (3) Heating and dissolving the polyacrylonitrile slurry prepared in the step (2) to obtain transparent and uniform polyacrylonitrile solution; (4) And (3) carrying out deaeration treatment on the product obtained in the step (3) to obtain the polyacrylonitrile spinning solution. Compared with an ammonia bubbling method and a solution polymerization method which are commonly adopted in the prior art, the ammoniation method which is used for mixing and heating the ammonia-containing solution and the polyacrylonitrile powder can flexibly adjust the polyacrylonitrile content in the spinning solution, meet the requirement of the spinning process on the pressure before spinning, and reduce the pressure of the spinning due to the increase of viscosity caused by ammoniation; the ammoniation treatment by adopting the ammonia water can ensure the full ammoniation reaction and simultaneously control the ammoniation degree, thereby being suitable for popularization and use.
Description
Technical Field
The invention belongs to the field of polyacrylonitrile spinning, and particularly relates to an ammonification method and an ammonification device for a polyacrylonitrile spinning solution.
Background
Nowadays, carbon fiber materials are widely used in military fields such as aerospace, national defense and military, and civil fields such as some sports goods and medical equipment. The Polyacrylonitrile (PAN) based carbon fiber has wide application prospect in the fields by virtue of the characteristics of high strength, high modulus, low density, high temperature resistance, friction resistance, good electric conductivity, good heat conductivity, chemical corrosion resistance and the like.
At present, the preparation process of PAN precursor can be divided into a one-step method and a two-step method, wherein the one-step method adopts homogeneous solution polymerization to prepare spinning solution for spinning, and the two-step method adopts heterogeneous precipitation polymerization to prepare PAN polymer powder, and then adopts proper solvent to dissolve the powder to prepare the spinning solution. Wherein, the spinning flexibility of the two-step method is higher.
Since the PAN filaments have a partial structure that is retained to some extent during the subsequent pre-oxidation and carbonization, the structure of the filaments determines to a large extent the properties of the final carbon fiber. To improve the performance of carbon fibers, stable continuous production of high quality PAN filaments is critical. In the production process of the PAN precursor, the structure and the performance of the PAN precursor are greatly influenced by the solidification forming process of the spinning solution in the solidification bath. The coagulation forming of the spinning solution is completed by double diffusion and precipitation of PAN molecules through a solvent and a precipitator. Because the solidification double diffusion rate in the wet spinning process is relatively high, the PAN fiber is extremely easy to form structural defects such as macropores, skin-core structures, irregular fiber structures and the like, and is transmitted to the PAN fiber and the carbon fiber, so that the performance and the application field of the carbon fiber are seriously weakened. The solidification double-diffusion process has a great relationship with the hydrophilic property of the spinning solution, and the improvement of the hydrophilic property of the spinning solution can slow down the solidification forming speed of the spinning solution and slow down the structural defects of macropores, skin-core structures, irregular fiber structures and the like. Therefore, improving the hydrophilicity of the dope is one of the key technologies for producing high quality PAN filaments.
At present, two main methods for improving the hydrophilicity of PAN spinning solution exist in patent reports: firstly, carrying out homogeneous solution polymerization reaction on a comonomer containing a hydrophilic group and acrylonitrile to prepare a PAN spinning solution with high hydrophilicity, and carrying out relevant reports on Chinese patents CN201310514441.9, CN201210239630.5 and the like; secondly, PAN spinning solution is prepared by homogeneous solution polymerization, and then ammoniated by ammonia, and Chinese patent CN201310132151.8, CN201110180192.5 and the like are reported. The above methods can improve the hydrophilicity of the spinning solution, but have some disadvantages, mainly as follows: firstly, the solid content adjustability of the spinning solution prepared by adopting homogeneous solution polymerization is poor, and the viscosity after ammoniation is not easy to regulate and control; secondly, the ammoniation degree of the spinning solution is not easy to control, the difference between batches is large, and the quality stability of the product is affected; thirdly, ammonia gas is not easy to be uniformly mixed and react with the high-viscosity spinning solution; fourthly, ammoniation can have an obstacle effect on solution polymerization reaction and simultaneously have adverse effects on mass transfer and heat transfer in the polymerization process.
In view of this, the present invention has been made.
Disclosure of Invention
The invention aims to solve the technical problems of overcoming the defects of the prior art and providing a polyacrylonitrile spinning liquid ammonia gasification technology adopting a two-step method for spinning, wherein the prepared ammonia-containing mixed solution is mixed with polyacrylonitrile powder, an ammoniation process is completed in the process of forming slurry, and the spinning solution is prepared by heating, so that the hydrophilicity of the PAN spinning solution is improved, and the stable production of PAN precursor with a round section and compactness is realized.
In order to solve the technical problems, the invention adopts the basic conception of the technical scheme that:
the invention provides an ammonification method of polyacrylonitrile spinning solution, which comprises the following steps:
(1) Quantitatively mixing an ammoniation reagent with a solvent to obtain a mixed solution with controllable ammonia content;
(2) Dispersing polyacrylonitrile powder into the mixed solution with controllable ammonia content prepared in the step (1), and uniformly stirring to obtain polyacrylonitrile slurry;
(3) Heating and dissolving the polyacrylonitrile slurry prepared in the step (2) to obtain transparent and uniform polyacrylonitrile solution;
(4) And (3) defoaming the polyacrylonitrile solution prepared in the step (3) to prepare the polyacrylonitrile spinning solution.
In the scheme, the ammoniation method for the two-step spinning provided by the invention can flexibly select the types of solvents and the preparation concentration of the spinning solution according to the requirements of the spinning process, and avoid the defects of unstable ammoniation process and poor process adjustability in the one-step solution polymerization spinning. Specifically, the scheme adopted by the invention disperses the polymerized polyacrylonitrile powder in the mixed solution with controllable ammonia content to form slurry, so that on one hand, the content of an ammoniation reagent can be ensured to be stable, the condition of loss of ammonia content in the one-step polymerization process is avoided, and on the other hand, the mixed solution with controllable ammonia content is adopted instead of directly adding ammonia water, so that the mixed effect of the ammonia water and the polyacrylonitrile powder is prevented from being influenced by a viscous system formed by the ammonia water and the polyacrylonitrile powder, and a better ammoniation effect is obtained.
According to the ammoniation method, the ammoniation reagent in the step (1) is selected from ammonia water with the mass concentration of 25-28%.
According to the above ammoniation method, the mass concentration of ammonia in the mixed solution with controllable ammonia content in the step (1) is 0.01-1%, preferably 0.02-0.4%.
In the scheme, as the ammoniation process of the scheme provided by the invention is stable, a solution with the mass concentration of ammonia lower than that of an ammoniation reagent used in one-step spinning can be generally adopted, and a better ammoniation effect can be realized. In addition, the finally formed polyacrylonitrile spinning solution can not generate gel, color deepening and other phenomena in a short time, and the usable time of the polyacrylonitrile spinning solution is prolonged.
According to the ammoniation method, the polyacrylonitrile slurry in the step (2) contains 18-22% by mass of polyacrylonitrile.
According to the ammoniation method, the heating temperature in the step (3) is 90-130 ℃ and the heating time is 0.3-5 min; preferably, the heating temperature is 100-120 ℃, and the heating time is 1-3 min; more preferably, the heating process is performed in a tubular heat exchanger, and the heating time is a residence time of the polyacrylonitrile slurry in the tubular heat exchanger.
According to the above-mentioned ammonification method, the temperature of the defoaming treatment in the step (4) is 65 to 80 ℃, preferably 70 to 75 ℃.
According to the above ammonification method, the pH of the polyacrylonitrile spinning solution after the defoaming treatment in the step (4) is 7 to 10, preferably 8 to 9.
According to the ammoniation method, the solvent in the step (1) is one or more selected from N, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide and sodium thiocyanate aqueous solution; n, N-dimethylacetamide is preferred.
Specifically, the ammonification method of the polyacrylonitrile spinning solution provided by the invention comprises the following steps:
(1) Quantitatively mixing ammonia water with the mass concentration of 25-28% with a solvent to obtain a mixed solution with controllable ammonia content, wherein the mass concentration of ammonia in the mixed solution is 0.01-1%, and the storage temperature of the mixed solution is-15-5 ℃;
(2) Dispersing polyacrylonitrile powder into the mixed solution with controllable ammonia content prepared in the step (1), and uniformly stirring to obtain polyacrylonitrile slurry, wherein the mass fraction of polyacrylonitrile in the slurry is 18-22%;
(3) Heating the polyacrylonitrile slurry prepared in the step (2) in a tubular heat exchanger at the temperature of 90-130 ℃ for 0.3-5 min, and dissolving to prepare transparent uniform polyacrylonitrile solution;
(4) And (3) defoaming the polyacrylonitrile solution prepared in the step (3) at 65-80 ℃ to prepare the polyacrylonitrile spinning solution, wherein the pH value of the polyacrylonitrile spinning solution is 7-10.
The invention also provides a device for realizing the polyacrylonitrile spinning liquid ammonia method, which comprises a plurality of storage tanks which are layered from top to bottom according to the gravity direction, wherein the ammonia water storage tank and the solvent storage tank are arranged on the top layer and are connected with a mixed liquid storage tank arranged on the middle layer through a weightlessness weighing system, the mixed liquid storage tank and the polyacrylonitrile powder storage tank which are arranged on the middle layer are connected with a slurry kettle arranged on the bottom layer through a weightlessness weighing system, and the slurry kettle is sequentially connected with a shell and tube heat exchanger and a defoaming kettle which are arranged on the bottom layer.
The further scheme of the device is that; the mixed liquid storage tank is internally provided with a stirring device and refrigerating equipment, and the storage temperature of the mixed liquid with controllable ammonia content in the mixed liquid storage tank is-15-5 ℃, preferably-10-5 ℃.
In the scheme, the weightless weighing system controls the discharging screw machine or the electric vibrator according to the reduction rate of the weight of the materials in the weighing hopper so as to achieve the purpose of quantitative feeding. In combination with the ammonification method, the operation flow of the device is as follows: accurately feeding the solvent from the volume storage tank and the ammonia water from the ammonia water storage tank into the mixed liquid storage tank through a weightless weighing system, fully mixing the solvent and the ammonia water under the condition of stirring, and storing at the temperature of-15 to 5 ℃; accurately feeding ammonia-containing solution from a mixed solution storage tank and PAN powder from a polyacrylonitrile storage tank into a slurry kettle through a weightlessness weighing system, and fully stirring to prepare uniformly dispersed slurry; then, the slurry is stably sent into a shell and tube heat exchanger through a gear metering pump 1, so that the slurry is fully dissolved at the temperature of 90-130 ℃ to obtain a polyacrylonitrile solution; finally, the polyacrylonitrile solution is input into a defoaming kettle for defoaming through a gear metering pump 2, so that the uniform ammoniated PAN spinning solution is prepared.
After the technical scheme is adopted, compared with the prior art, the invention has the following beneficial effects:
1. the PAN spinning solution is prepared by adopting a two-step method, wherein the PAN content is flexible and adjustable, the requirement of a spinning process on the pressure before spinning is met, and particularly the pressure of viscosity increase to spinning caused by ammoniation is reduced;
2. according to the invention, the prepared ammonia-containing mixed solution is adopted to disperse polyacrylonitrile powder, so that PAN is ammoniated, the defects of difficult metering, difficult mixing and the like of ammonia gas when an ammonia gas bubbling method is used in the prior art are overcome, and the difficulty of defoaming is further reduced;
3. according to the invention, ammonia water is adopted to carry out ammoniation treatment on PAN spinning solution, so that the contact of ammonia and acidic groups in PAN can be effectively ensured, the ammoniation reaction is facilitated, the ammoniation quality is ensured, and the ammoniation degree is controllable;
4. the ammoniated spinning solution provided by the invention has certain storage performance due to the adoption of relatively stable ammoniation treatment.
The following describes the embodiments of the present invention in further detail with reference to the accompanying drawings.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. It is evident that the drawings in the following description are only examples, from which other drawings can be obtained by a person skilled in the art without the inventive effort. In the drawings:
FIG. 1 is a device for realizing the method for liquefying polyacrylonitrile spinning liquid;
FIG. 2 is a cross-sectional SEM image of a PAN precursor obtained in example 1 of the present invention;
FIG. 3 is a cross-sectional SEM image of a PAN precursor prepared according to example 2 of the present invention;
FIG. 4 is a cross-sectional SEM image of a PAN precursor obtained in example 3 of the present invention;
FIG. 5 is a cross-sectional SEM image of a PAN precursor obtained in example 4 of the present invention;
FIG. 6 is a cross-sectional SEM image of a PAN precursor obtained in comparative example 1 of the present invention.
It should be noted that these drawings and the written description are not intended to limit the scope of the inventive concept in any way, but to illustrate the inventive concept to those skilled in the art by referring to the specific embodiments.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions in the embodiments will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention, and the following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.
In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention.
In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
Example 1
In this example, the polyacrylonitrile spinning solution was aminated by the following method:
(1) Quantitatively mixing ammonia water with the mass concentration of 25% with solvent DMAc to obtain mixed solution with controllable ammonia content, wherein the mass concentration of ammonia in the mixed solution is 0.02%, and the storage temperature of the mixed solution is-10 ℃;
(2) Dispersing polyacrylonitrile powder into the mixed solution with controllable ammonia content prepared in the step (1), and uniformly stirring to obtain a polyacrylonitrile slurry, wherein the mass fraction of polyacrylonitrile in the slurry is 20%;
(3) Heating the polyacrylonitrile slurry prepared in the step (2) in a tubular heat exchanger with low-pressure steam at 130 ℃ for 0.3min, and dissolving to prepare transparent uniform polyacrylonitrile solution;
(4) And (3) defoaming the polyacrylonitrile solution prepared in the step (3) at the temperature of 75 ℃ to prepare the polyacrylonitrile spinning solution, wherein the pH value of the polyacrylonitrile spinning solution is 7.
The uniformly ammoniated PAN spinning solution prepared in this example was prepared into 25K filaments having a fineness of 1.15dtex by wet spinning. The cross section of the filament is shown in figure 2. The high-performance carbon fiber with the tensile strength of 5.4GPa and the tensile modulus of 240GPa is prepared through preoxidation and carbonization treatment.
Example 2
In this example, the polyacrylonitrile spinning solution was aminated by the following method:
(1) Quantitatively mixing 28% ammonia water with a solvent DMAc to obtain a mixed solution with controllable ammonia content, wherein the mass concentration of ammonia in the mixed solution is 0.03%, and the storage temperature of the mixed solution is-10 ℃;
(2) Dispersing polyacrylonitrile powder into the mixed solution with controllable ammonia content prepared in the step (1), and uniformly stirring to obtain a polyacrylonitrile slurry, wherein the mass fraction of polyacrylonitrile in the slurry is 20%;
(3) Heating the polyacrylonitrile slurry prepared in the step (2) in a tubular heat exchanger with low-pressure steam at 130 ℃ for 5min, and dissolving to prepare transparent uniform polyacrylonitrile solution;
(4) And (3) defoaming the polyacrylonitrile solution prepared in the step (3) at the temperature of 75 ℃ to prepare the polyacrylonitrile spinning solution, wherein the pH value of the polyacrylonitrile spinning solution is 8.
The uniformly ammoniated PAN spinning solution prepared in this example was prepared into 25K filaments having a fineness of 1.15dtex by wet spinning. The cross section of the filament is shown in figure 3. The high-performance carbon fiber with the tensile strength of 5.5GPa and the tensile modulus of 240GPa is prepared through pre-oxidation and carbonization treatment.
Example 3
In this example, the polyacrylonitrile spinning solution was aminated by the following method:
(1) Quantitatively mixing ammonia water with the mass concentration of 26% with solvent DMAc to obtain mixed solution with controllable ammonia content, wherein the mass concentration of ammonia in the mixed solution is 0.05%, and the storage temperature of the mixed solution is-10 ℃;
(2) Dispersing polyacrylonitrile powder into the mixed solution with controllable ammonia content prepared in the step (1), and uniformly stirring to obtain a polyacrylonitrile slurry, wherein the mass fraction of polyacrylonitrile in the slurry is 20%;
(3) Heating the polyacrylonitrile slurry prepared in the step (2) in a tubular heat exchanger with low-pressure steam at 130 ℃ for 0.3min, and dissolving to prepare transparent uniform polyacrylonitrile solution;
(4) And (3) defoaming the polyacrylonitrile solution prepared in the step (3) at the temperature of 75 ℃ to prepare the polyacrylonitrile spinning solution, wherein the pH value of the polyacrylonitrile spinning solution is 8.
The uniformly ammoniated PAN spinning solution prepared in this example was prepared into 25K filaments having a fineness of 1.15dtex by wet spinning. The cross section of the filament is shown in fig. 4. The high-performance carbon fiber with the tensile strength of 5.4GPa and the tensile modulus of 240GPa is prepared through pre-oxidation and carbonization treatment.
Example 4
In this example, the polyacrylonitrile spinning solution was aminated by the following method:
(1) Quantitatively mixing ammonia water with the mass concentration of 27% with solvent DMAc to obtain mixed solution with controllable ammonia content, wherein the mass concentration of ammonia in the mixed solution is 0.075%, and the storage temperature of the mixed solution is-10 ℃;
(2) Dispersing polyacrylonitrile powder into the mixed solution with controllable ammonia content prepared in the step (1), and uniformly stirring to obtain a polyacrylonitrile slurry, wherein the mass fraction of polyacrylonitrile in the slurry is 20%;
(3) Heating the polyacrylonitrile slurry prepared in the step (2) in a tubular heat exchanger with low-pressure steam at 130 ℃ for 0.3min, and dissolving to prepare transparent uniform polyacrylonitrile solution;
(4) And (3) defoaming the polyacrylonitrile solution prepared in the step (3) at the temperature of 75 ℃ to prepare the polyacrylonitrile spinning solution, wherein the pH value of the polyacrylonitrile spinning solution is 8.5.
The uniformly ammoniated PAN spinning solution prepared in this example was prepared into 25K filaments having a fineness of 1.15dtex by wet spinning. The cross section of the filament is shown in fig. 5. The high-performance carbon fiber with the tensile strength of 5.4GPa and the tensile modulus of 240GPa is prepared through pre-oxidation and carbonization treatment.
Example 5
In this example, the polyacrylonitrile spinning solution was aminated by the following method:
(1) Quantitatively mixing ammonia water with the mass concentration of 25% with solvent DMAc to obtain mixed solution with controllable ammonia content, wherein the mass concentration of ammonia in the mixed solution is 1%, and the storage temperature of the mixed solution is 5 ℃;
(2) Dispersing polyacrylonitrile powder into the mixed solution with controllable ammonia content prepared in the step (1), and uniformly stirring to obtain polyacrylonitrile slurry, wherein the mass fraction of polyacrylonitrile in the slurry is 18%;
(3) Heating the polyacrylonitrile slurry prepared in the step (2) in a tubular heat exchanger with low-pressure steam at 90 ℃ for 2.2min, and dissolving to prepare transparent uniform polyacrylonitrile solution;
(4) And (3) defoaming the polyacrylonitrile solution prepared in the step (3) at 65 ℃ to prepare the polyacrylonitrile spinning solution, wherein the pH value of the polyacrylonitrile spinning solution is 10.
The uniformly ammoniated PAN spinning solution prepared in this example was prepared into 25K filaments having a fineness of 1.15dtex by wet spinning. The high-performance carbon fiber with the tensile strength of 5.0GPa and the tensile modulus of 240GPa is prepared through preoxidation and carbonization treatment.
Example 6
In this example, the mass concentration of ammonia in the mixed solution in the step (1) was adjusted to 0.5% based on the example 5, and the pH of the finally produced polyacrylonitrile spinning solution was 9.5. Other embodiments of this example are the same as example 5, and the uniformly ammoniated PAN dope prepared in this example is made into 25K filaments having a fineness of 1.15dtex by using a wet spinning technique. The high-performance carbon fiber with the tensile strength of 5.1GPa and the tensile modulus of 240GPa is prepared through preoxidation and carbonization treatment.
Example 7
In this example, the polyacrylonitrile spinning solution was aminated by the following method:
(1) Quantitatively mixing ammonia water with the mass concentration of 26% with solvent DMAc to obtain mixed solution with controllable ammonia content, wherein the mass concentration of ammonia in the mixed solution is 0.4%, and the storage temperature of the mixed solution is-15 ℃;
(2) Dispersing polyacrylonitrile powder into the mixed solution with controllable ammonia content prepared in the step (1), and uniformly stirring to obtain polyacrylonitrile slurry, wherein the mass fraction of polyacrylonitrile in the slurry is 22%;
(3) Heating the polyacrylonitrile slurry prepared in the step (2) in a tubular heat exchanger by low-pressure steam at 110 ℃ for 1.5min, and dissolving to prepare transparent uniform polyacrylonitrile solution;
(4) And (3) defoaming the polyacrylonitrile solution prepared in the step (3) at the temperature of 80 ℃ to prepare the polyacrylonitrile spinning solution, wherein the pH value of the polyacrylonitrile spinning solution is 9.5.
The uniformly ammoniated PAN spinning solution prepared in this example was prepared into 25K filaments having a fineness of 1.15dtex by wet spinning. The high-performance carbon fiber with the tensile strength of 5.3GPa and the tensile modulus of 240GPa is prepared through preoxidation and carbonization treatment.
Example 8
In this example, the mass concentration of ammonia in the mixed solution in the step (1) was adjusted to 0.2% based on the example 7, and the pH of the finally produced polyacrylonitrile spinning solution was 9. Other embodiments of this example are the same as in example 7, and the uniformly ammoniated PAN dope prepared in this example was prepared into 25K filaments having a fineness of 1.15dtex using a wet spinning technique. The high-performance carbon fiber with the tensile strength of 5.4GPa and the tensile modulus of 240GPa is prepared through preoxidation and carbonization treatment.
Example 9
In this example, the mass concentration of ammonia in the mixed solution in the step (1) was adjusted to 0.1% based on the example 7, and the pH of the finally produced polyacrylonitrile spinning solution was 9. Other embodiments of this example are the same as in example 7, and the uniformly ammoniated PAN dope prepared in this example was prepared into 25K filaments having a fineness of 1.15dtex using a wet spinning technique. The high-performance carbon fiber with the tensile strength of 5.5GPa and the tensile modulus of 240GPa is prepared through preoxidation and carbonization treatment.
Comparative example 1
In this comparative example, based on example 1, the same amount of polyacrylonitrile powder as in example 1 was dissolved in a solvent DMAc to obtain a 20% PAN mass fraction spinning solution, which was not subjected to ammoniation treatment, and the pH of the spinning solution was measured to be 4.0.
The uniformly ammoniated PAN spinning solution prepared in this comparative example was prepared into 25K filaments having a fineness of 1.15dtex by wet spinning. The cross section of the filament is shown in fig. 6. The high-performance carbon fiber with the tensile strength of 4.7GPa and the tensile modulus of 230GPa is prepared through preoxidation and carbonization treatment.
Comparative example 2
In the comparative example, on the basis of example 1, polyacrylonitrile powder with the same quantity as that of example 1 is dissolved in a solvent DMAc to prepare a spinning solution with the PAN mass fraction of 20%, and then ammonia gas with the same ammonia content as that in the mixed solution of example 1 is introduced, so that the pH of the obtained ammoniated spinning solution is 7.0 after measurement.
The uniformly ammoniated PAN spinning solution prepared in this comparative example was prepared into 25K filaments having a fineness of 1.15dtex by wet spinning. The high-performance carbon fiber with the tensile strength of 4.8GPa and the tensile modulus of 230GPa is prepared through preoxidation and carbonization treatment.
Comparative example 3
The comparative example adopts a two-step method in the prior art, firstly, a polyacrylonitrile solution is obtained by reacting acrylonitrile, a comonomer and an initiator, a polyacrylonitrile spinning solution is obtained after single removal and deaeration (wherein the content of the polyacrylonitrile is the same as that of the embodiment 5 of the invention), then an ammonia reagent with the ammonia content being the same as that of the mixed solution of the embodiment 5 is added, and the pH value of the obtained ammoniated spinning solution is 7.0 after measurement. The high-performance carbon fiber with the tensile strength of 4.9GPa and the tensile modulus of 240GPa is prepared through pre-oxidation and carbonization treatment.
Experimental example 1
The polyacrylonitrile fibers prepared in examples 1 to 9 and comparative examples 1 to 3 were subjected to hydrophilic performance and dope stability tests to calculate saturated moisture absorption (%) to characterize hydrophilic performance, and specific test methods: taking a sample, drying at 105 ℃ for 16 hours, and measuring the weight m1; then placing the dried sample in a constant temperature and humidity machine with the temperature of 20 ℃ and the relative humidity of 65% for 24 hours, measuring the weight m2 of the sample, and then calculating the saturated moisture absorption rate (%) = (m 2-m 1)/m 1 by 100%, wherein the stability of the spinning solution is characterized by the property change of the spinning solution after being placed for a period of time at normal temperature and normal pressure, and the result is shown in the following table:
as can be seen from the above table, the polyacrylonitrile fibers prepared in examples 1 to 9 provided by the invention have the advantages of good hydrophilic property and storage for a certain time at normal temperature and pressure. Comparative example 1 did not have an ammoniation treatment of polyacrylonitrile, and although the cross section of the obtained fiber was relatively round, its hydrophilic properties were poor and the application range was small. While comparative example 2 is a polyacrylonitrile fiber which is commonly used in the prior art and is prepared by ammonifying with ammonia gas, comparative document 3 is prepared by a two-step method, and the spinning solution formed by polymerization is ammonified by a solution with a certain ammonia content, both have the defect of unstable ammonification process, and although the hydrophilicity of the prepared polyacrylonitrile fiber is improved compared with that of comparative example 1 which is not ammonified, the prepared polyacrylonitrile fiber is not the same as that of the embodiment of the application. In addition, the polyacrylonitrile prepared in the comparative examples 2 and 3 has unsatisfactory ammoniation effect, so that the spinning solution starts to be subjected to phenomena of deepening of color, increase of viscosity and the like successively after being placed for about 6 hours, and further deepening of color and further increase of viscosity occur in the subsequent 18-48 hours.
The foregoing description is only illustrative of the preferred embodiment of the present invention, and is not to be construed as limiting the invention, but is to be construed as limiting the invention to any and all simple modifications, equivalent variations and adaptations of the embodiments described above, which are within the scope of the invention, may be made by those skilled in the art without departing from the scope of the invention.
Claims (14)
1. An ammonification method of polyacrylonitrile spinning solution is characterized by comprising the following steps:
(1) Quantitatively mixing an ammoniation reagent with a solvent to obtain a mixed solution with controllable ammonia content; the ammoniation reagent is selected from ammonia water with the mass concentration of 25-28%; the mass concentration of ammonia in the mixed solution is 0.02-0.4%;
(2) Dispersing polyacrylonitrile powder into the mixed solution with controllable ammonia content prepared in the step (1), and uniformly stirring to obtain polyacrylonitrile slurry;
(3) Heating and dissolving the polyacrylonitrile slurry prepared in the step (2) to obtain transparent and uniform polyacrylonitrile solution;
(4) And (3) defoaming the polyacrylonitrile solution prepared in the step (3) to prepare the polyacrylonitrile spinning solution.
2. The ammonification method of a polyacrylonitrile spinning solution according to claim 1, wherein the polyacrylonitrile slurry in the step (2) contains 18-22% by mass of polyacrylonitrile.
3. The ammonification method of polyacrylonitrile spinning solution according to claim 1, wherein the heating temperature in the step (3) is 90-130 ℃, and the heating time is 0.3-5 min.
4. The ammonification method of polyacrylonitrile spinning solution according to claim 3, wherein the heating temperature in the step (3) is 100-120 ℃, and the heating time is 1-3 min.
5. The method for ammonifying a polyacrylonitrile spinning solution according to claim 4, wherein said heating process of step (3) is performed in a tubular heat exchanger, and said heating time is a residence time of the polyacrylonitrile slurry in the tubular heat exchanger.
6. The ammonification method of a polyacrylonitrile spinning solution according to claim 1, wherein the temperature of the defoaming treatment in the step (4) is 65 to 80 ℃.
7. The method for ammonifying a polyacrylonitrile spinning solution according to claim 6, wherein the temperature of said defoaming treatment in step (4) is 70 to 75 ℃.
8. The ammonification method of a polyacrylonitrile spinning solution according to claim 1, wherein the pH of the polyacrylonitrile spinning solution after the defoaming treatment in the step (4) is 7 to 10.
9. The ammonification method of a polyacrylonitrile spinning solution according to claim 8, wherein the pH of the polyacrylonitrile spinning solution after the defoaming treatment in the step (4) is 8 to 9.
10. The ammonification method of polyacrylonitrile spinning solution according to claim 1, wherein the solvent in the step (1) is one or more selected from the group consisting of N, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide, and sodium thiocyanate aqueous solution.
11. The ammonification method of a polyacrylonitrile spinning solution according to claim 10, wherein the solvent in the step (1) is N, N-dimethylacetamide.
12. A device for realizing the method for the liquid ammonia of the polyacrylonitrile spinning beam according to any one of claims 1 to 11, which is characterized by comprising a plurality of storage tanks which are layered from top to bottom according to the gravity direction, wherein the ammonia water storage tank and the solvent storage tank are arranged on the top layer and are connected with a mixed liquid storage tank arranged on the middle layer through a weightless weighing system, the mixed liquid storage tank is connected with a slurry kettle arranged on the bottom layer through a weightless weighing system together with a polyacrylonitrile powder storage tank arranged on the middle layer, and the slurry kettle is sequentially connected with a tubular heat exchanger and a defoaming kettle which are arranged on the bottom layer.
13. The device according to claim 12, wherein the mixed liquor storage tank is provided with a stirring device and a refrigerating device, and the storage temperature of the mixed liquor with controllable ammonia content in the mixed liquor storage tank is-15-5 ℃.
14. The device according to claim 13, wherein the storage temperature of the mixed liquor with controllable ammonia content in the mixed liquor storage tank is-10-5 ℃.
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