Carbon fiber paper based on asphalt / polyacrylonitrile-based non-woven felt as well as preparation method and application of carbon fiber paper

Abstract

The invention belongs to the technical field of carbon fiber paper, and provides carbon fiber paper based on asphalt / polyacrylonitrile-based non-woven felt as well as a preparation method and application of the carbon fiber paper. The method comprises the following steps: sequentially stirring, mixing and dissolving a soluble asphalt solution and an acrylonitrile-itaconic acid copolymer solution, defoaming, carrying out electrostatic spinning on an electrostatic spinning solution, and sequentially carrying out drying and programmed pre-oxidation on an asphalt / polyacrylonitrile-based non-woven felt to obtain a pre-oxidized felt; the pre-oxidized felt is soaked in a resin solution, and then drying, hot-pressing curing, carbonization and graphitization are conducted in sequence. The soluble asphalt component is introduced into the electrospinning stock solution, the characteristic that the polycyclic aromatic hydrocarbon easily forms carbon crystals at a high temperature is utilized, the distribution of graphite microcrystals in the carbon fibers is regulated and controlled, then the electron transfer performance of the carbon fiber paper is improved, synchronous and accurate regulation and control of conduction, ventilation and ultrathin thickness are achieved, and the carbon fiber paper has a good application effect in fuel cells.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon fiber paper, and in particular to a carbon fiber paper based on asphalt / polyacrylonitrile-based non-woven felt, and a preparation method and application thereof. Background Art

[0002] The gas diffusion layer (GDL) is a core component of the proton exchange membrane fuel cell (PEMFC). Located between the catalyst layer and the bipolar plate, it primarily performs multiple functions, including transporting fuel gas from the bipolar plate to the catalyst layer, transferring the "electrons, heat, and water" generated by the electrochemical reaction in the catalyst layer to the bipolar plate, and supporting the catalyst layer and microporous layer. It plays a key role in the overall performance of the PEMFC. Therefore, carbon fiber paper, with its excellent electrical conductivity, chemical resistance, mechanical stability, and air permeability, is widely used in the GDL.

[0003] There are two main factors that affect the conductivity of carbon fiber paper: one is the electronic conductivity of the matrix material carbon fiber itself, and the other is the electronic conductivity between the resin carbon and the fiber that acts as a bonding fiber. The former has a more important impact on conductivity. "A method for preparing carbon fiber paper" (application number: 201810741949.5) uses mesophase pitch-based carbon fiber as a functional additive, mixes it with polyacrylonitrile-based carbon fiber in a certain proportion, and then wet-makes paper to improve the conductivity of carbon fiber paper; patent application number 202110706943.6 proposes a method of using a melt-blown method to add a mesophase pitch fiber layer to the surface of carbon fiber base paper to improve the conductivity of carbon fiber paper. Mixing the two fibers for papermaking or melt-blown laying can improve the conductivity of carbon fiber paper. However, asphalt-based carbon fibers are brittle and prone to breakage during service, destroying the original conductive path and causing the resistivity of carbon fiber paper to increase, making it difficult to meet the current urgent needs of PEMFC for high energy density and fast response speed.

[0004] More than 90% of carbon fiber is composed of carbon elements, with very few surface active functional groups and high surface inertness. The wet papermaking process improves the dispersion uniformity and stability of chopped carbon fibers in the aqueous phase by introducing additives (water-soluble dispersants, surfactants, etc.). However, the formation of fiber bundles cannot be effectively avoided during the papermaking process, resulting in uneven thickness, rough surface, and poor air permeability of the paper after forming. During battery operation, the contact resistance between the carbon fiber paper and the catalyst layer is increased, thereby reducing battery performance. "A continuous production process for carbon fiber paper specifically for fuel cell gas diffusion layer" (application number: 202210520497.4) uses an air-laid carding machine to make loose carbon fiber paper with chopped carbon fibers, then uses a high-pressure jet device to inject carbon powder in a direction perpendicular to the paper surface for fixation, immerses it in a mixed slurry such as resin, controls the thickness through a rolling mill, and obtains special carbon fiber paper after carbonization and graphitization, which improves the dispersion and conductivity problems of chopped carbon fibers. However, the preparation process is complicated, the cost is high, and the carbon powder affects the air permeability of the carbon fiber paper. The patent with application number 202310262305.9 uses an electrospinning process to prepare a polyacrylonitrile-based non-woven felt, and the corresponding carbon fiber paper is obtained after procedural treatment, which avoids the problem of fiber dispersion. However, the conductivity problem of the polyacrylonitrile-based carbon fiber paper has not been improved.

[0005] The graphite crystallite size of pitch-based carbon fiber is highly controllable, and the single crystal size can be larger than 10nm. The easy graphitization property makes the electron transfer path inside the fiber rich, and the single fiber resistance can be less than 0.12mΩ·cm, but it is very brittle. The graphite crystallite size of polyacrylonitrile-based carbon fiber is difficult to control, and the single crystal size is less than 10nm. The difficult graphitization property makes it have a chaotic layer graphite structure, outstanding mechanical properties and high resistivity.

[0006] Therefore, the research has obtained a functional carbon fiber paper with good mechanical properties, low cost, high conductivity, controllable thickness and ultra-thinness, which has important application value and practical significance. Summary of the Invention

[0007] The purpose of the present invention is to provide a carbon fiber paper based on asphalt / polyacrylonitrile-based non-woven felt and its preparation method and application in order to overcome the shortcomings of the existing technology, so as to solve the problems of poor conductivity, uneven thickness and high cost of carbon fiber paper in the existing technology.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0009] The present invention provides a method for preparing carbon fiber paper based on asphalt / polyacrylonitrile-based non-woven felt, comprising the following steps:

[0010] 1) stirring and mixing the soluble asphalt solution and the acrylonitrile-itaconic acid copolymer solution in sequence, and degassing them to obtain an electrospinning stock solution;

[0011] 2) electrospinning the electrospinning solution to obtain a pitch / polyacrylonitrile-based non-woven felt; and sequentially drying and pre-oxidizing the pitch / polyacrylonitrile-based non-woven felt to obtain a pre-oxidized felt;

[0012] 3) The pre-oxidized felt is impregnated in a resin solution, and then dried, hot-pressed, carbonized, and graphitized in sequence to obtain a carbon fiber paper based on a pitch / polyacrylonitrile-based non-woven felt.

[0013] Preferably, the soluble asphalt solution in step 1) comprises an asphalt extract and an organic solvent; the mass fraction of the soluble asphalt solution is 5 to 35%;

[0014] The mass fraction of the acrylonitrile-itaconic acid copolymer solution is 12 to 30%;

[0015] The mass ratio of the acrylonitrile-itaconic acid copolymer solution to the soluble asphalt solution is 1:0.10-0.65. Preferably, the asphalt extract is prepared by mixing asphalt and an organic solvent, extracting, centrifuging, rotary evaporating, and drying the mixture in sequence to obtain the asphalt extract;

[0016] The asphalt comprises one or more of naphthalene asphalt, petroleum asphalt and coal asphalt;

[0017] The organic solvent comprises one or more of n-heptane, quinoline, pyridine, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide;

[0018] The mass ratio of the asphalt to the organic solvent is 1:4-8.

[0019] Preferably, the extraction method is one or more of ultrasound-assisted extraction, Soxhlet extraction and magnetic stirring;

[0020] The stirring and mixing temperature and the degassing temperature are independently 40 to 90° C., and the stirring and mixing time and the degassing time are independently 3 to 12 hours.

[0021] Preferably, the electrospinning flow rate in step 2) is 0.8 to 2.2 mL / h, the electrospinning time is 2 to 6 h, and the thickness of the asphalt / polyacrylonitrile-based non-woven felt is 0.14 to 0.30 mm.

[0022] Preferably, the drying temperature in step 2) is 60-100° C. and the drying time is 1-3 hours;

[0023] The programmed pre-oxidation includes three pre-oxidations, the first pre-oxidation temperature is 170-200°C, the time is 10-20 minutes, the second pre-oxidation temperature is 220-260°C, the time is 25-90 minutes, and the third pre-oxidation temperature is 280-320°C, the time is 30-60 minutes.

[0024] Preferably, the mass fraction of the resin solution in step 3) is 5 to 18%, the resin in the resin solution is boron phenolic resin, and the solvent is methanol and / or ethanol; the immersion time in the resin solution is 10 to 80 minutes;

[0025] Step 3) The drying temperature is 50-100° C. and the time is 20-60 min; the hot pressing curing temperature is 130-170° C., the pressure is 5-13 MPa, and the time is 10-25 min.

[0026] Preferably, in step 3), the carbonization temperature is 800-1400° C., and the time is 5-30 min; the graphitization temperature is 2000-2800° C., and the time is 5-20 min; the heating rate from room temperature to carbonization temperature and the heating rate from carbonization temperature to graphitization temperature are independently 3-10° C. / min; and carbonization and graphitization are carried out under a protective atmosphere.

[0027] The present invention also provides a carbon fiber paper based on asphalt / polyacrylonitrile non-woven felt prepared by the preparation method, wherein the carbon fiber paper has a resistivity of 3 to 8 mΩ·cm, a thickness of 0.05 to 0.12 mm, and an air permeability of 1500 to 2200 mL·mm / (cm 2 ·hr·mmAq).

[0028] The present invention also provides the use of the carbon fiber paper based on asphalt / polyacrylonitrile-based non-woven felt in a gas diffusion layer of a proton exchange membrane fuel cell.

[0029] The beneficial effects of the present invention include the following:

[0030] 1) The present invention uses soluble asphalt and polyacrylonitrile-based carbon fibers as raw materials for carbon fiber paper. The asphalt has a macromolecular structure of polycyclic aromatic hydrocarbons and alkyl side chains. It can exhibit soft carbon properties under high temperature conditions and has a high degree of graphitization. Compared with polyacrylonitrile-based carbon fibers, asphalt-based carbon fibers often have higher conductivity, but poor mechanical properties. Based on this, by introducing a soluble asphalt component into the polyacrylonitrile copolymer (acrylonitrile-itaconic acid copolymer) solution, the characteristic of polycyclic aromatic hydrocarbons that easily form carbon crystals at high temperatures is utilized to regulate the distribution of graphite microcrystals inside the fiber, thereby improving the electron transfer performance of the carbon fiber paper. This expands the preparation process of carbon fiber paper for fuel cell gas diffusion layers and reduces the preparation cost of carbon fiber paper.

[0031] 2) The present invention adopts electrospinning technology to prepare carbon fiber paper. By adjusting parameters such as the concentration of the spinning solution, the spinning flow rate, and the spinning time, non-woven felts of different thicknesses and different pore structures can be accurately prepared without the need for a dispersant, thereby solving the problems of difficult fiber dispersion and uneven thickness. Carbon fiber paper based on asphalt / polyacrylonitrile is prepared through a process of pre-oxidation-resin impregnation-hot pressing curing-carbonization-graphitization, thereby achieving simultaneous and precise control of the "conductive-breathable-ultra-thin" properties of the carbon fiber paper.

[0032] 3) The method of inducing fiber graphitization by large-sized graphite microcrystals of asphalt during the high-temperature carbonization stage of the present invention has simple process operation, low energy consumption, and low cost. On the basis of good mechanical properties, it realizes the preparation of low-cost, highly conductive, thickness-controllable, ultra-thin functional carbon fiber paper. It is easy to prepare high-performance carbon fiber paper in large quantities, has good application effect in fuel cells, and provides a new path for further industrial production of carbon fiber paper. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a surface scanning electron microscope image of the pre-oxidized felt impregnated with resin in Example 1;

[0034] Figure 2 This is a surface scanning electron microscope image of the carbon fiber paper of Example 2;

[0035] Figure 3 This is a scanning electron micrograph of a cross section of the resin-impregnated pre-oxidized felt of Example 3;

[0036] Figure 4 This is a scanning electron microscope image of the cross section of the carbon fiber paper of Example 4;

[0037] Figure 5 These are the in-situ X-ray diffraction patterns of the carbon fiber paper carbonized in Example 5 and the carbon fiber paper carbonized in Comparative Example 1. DETAILED DESCRIPTION

[0038] The present invention provides a method for preparing carbon fiber paper based on asphalt / polyacrylonitrile-based non-woven felt, comprising the following steps:

[0039] 1) stirring and mixing the soluble asphalt solution and the acrylonitrile-itaconic acid copolymer solution in sequence, and degassing them to obtain an electrospinning stock solution;

[0040] 2) electrospinning the electrospinning solution to obtain a pitch / polyacrylonitrile-based non-woven felt; and sequentially drying and pre-oxidizing the pitch / polyacrylonitrile-based non-woven felt to obtain a pre-oxidized felt;

[0041] 3) The pre-oxidized felt is impregnated in a resin solution, and then dried, hot-pressed, carbonized, and graphitized in sequence to obtain a carbon fiber paper based on a pitch / polyacrylonitrile-based non-woven felt.

[0042] In the present invention, the soluble asphalt solution in step 1) comprises an asphalt extract and an organic solvent; the mass fraction of the soluble asphalt solution is preferably 5 to 35%, more preferably 10 to 30%, and more preferably 15 to 25%;

[0043] The mass fraction of the acrylonitrile-itaconic acid copolymer solution is preferably 12 to 30%, more preferably 15 to 25%, and more preferably 18 to 22%;

[0044] The mass ratio of the acrylonitrile-itaconic acid copolymer solution to the soluble asphalt solution is preferably 1:0.10 to 0.65, more preferably 1:0.15 to 0.55, and even more preferably 1:0.20 to 0.40.

[0045] In the present invention, the preparation method of the asphalt extract is as follows: asphalt and an organic solvent are mixed, and the mixture is extracted, centrifuged, rotary evaporated, and dried in sequence to obtain the asphalt extract;

[0046] The asphalt preferably comprises one or more of naphthalene asphalt, petroleum asphalt and coal asphalt;

[0047] The organic solvent preferably comprises one or more of n-heptane, quinoline, pyridine, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide;

[0048] The mass ratio of the asphalt to the organic solvent is preferably 1:4-8, more preferably 1:5-7, and even more preferably 1:6.

[0049] In the present invention, the asphalt is preferably obtained by grinding and sieving an asphalt block, and the mesh number of the sieving is 100 mesh.

[0050] In the present invention, the extraction method is preferably one or more of ultrasound-assisted extraction, Soxhlet extraction and magnetic stirring;

[0051] The stirring and mixing temperature and the degassing temperature are independently preferably 40 to 90° C., more preferably 50 to 80° C., and more preferably 60 to 70° C., and the stirring and mixing time and the degassing time are independently preferably 3 to 12 h, more preferably 4 to 10 h, and more preferably 5 to 8 h.

[0052] In the present invention, the extraction temperature is preferably 30-40°C, more preferably 32-38°C, more preferably 35-36°C, the extraction time is preferably 10-14h, more preferably 11-13h, more preferably 12h; the centrifugal speed is preferably 5000-7000rpm, more preferably 5500-6500rpm, more preferably 6000rpm, the centrifugal time is preferably 8-12min, more preferably 9-11min, more preferably 10min, the rotary evaporation temperature is preferably 50-100°C, more preferably 70-90°C, more preferably 80°C, the rotary evaporation speed is preferably 130-140rpm, more preferably 135rpm; the drying temperature is preferably 50-70°C, more preferably 55-65°C, more preferably 60°C, and the drying time is preferably 22-26h, more preferably 23-25h, more preferably 24h.

[0053] In the present invention, the electrospinning flow rate of step 2) is preferably 0.8 to 2.2 mL / h, more preferably 1 to 2 mL / h, more preferably 1.2 to 1.8 mL / h, and the electrospinning time is preferably 2 to 6 h, more preferably 3 to 5 h, more preferably 4 h; the positive voltage of electrospinning is preferably 12 to 20 kV, more preferably 14 to 18 kV, more preferably 15 to 16 kV; the thickness of the asphalt / polyacrylonitrile-based non-woven felt is preferably 0.14 to 0.30 mm, more preferably 0.15 to 0.28 mm, more preferably 0.18 to 0.25 mm.

[0054] In the present invention, the preparation process of the electrospinning solution is as follows: after mixing a soluble asphalt solution and N,N-dimethylformamide, slowly adding an acrylonitrile-itaconic acid copolymer solution multiple times, stirring and vacuum degassing are carried out in sequence to obtain the electrospinning solution.

[0055] In the present invention, by regulating the content of asphalt in the acrylonitrile-itaconic acid copolymer solution, an electrospinning solution with different sensitivities to the electric field can be obtained. The difference in the number and distribution of graphite microcrystals inside the fiber in subsequent processing can achieve differentiated and precise control of the conductivity of the carbon fiber paper. The process flow is simple and the cost is low.

[0056] In the present invention, the electrospinning solution is electrospun on a roller collector through electrospinning technology, and the spinning flow, voltage and time are adjusted to obtain a non-woven felt; this process does not require the introduction of external additives, the fibers are evenly dispersed, the thickness and pore structure of the non-woven felt can be precisely controlled, the energy consumption is low, the cost is low, and the non-woven felt can be easily prepared on a large scale.

[0057] In the present invention, the drying temperature in step 2) is preferably 60-100° C., more preferably 70-90° C., more preferably 80° C., and the drying time is preferably 1-3 h, more preferably 1.5-2.5 h, more preferably 2 h;

[0058] The programmed pre-oxidation preferably includes three pre-oxidations, the temperature of the first pre-oxidation is preferably 170-200°C, more preferably 175-190°C, more preferably 180-185°C, the time of the first pre-oxidation is preferably 10-20 min, more preferably 12-18 min, more preferably 14-16 min, the temperature of the second pre-oxidation is preferably 220-260°C, more preferably 230-255°C, more preferably 240-250°C, the time of the second pre-oxidation is preferably 25-90 min, more preferably 35-85 min, more preferably 50-80 min, the temperature of the third pre-oxidation is preferably 280-320°C, more preferably 290-315°C, more preferably 300-310°C, and the time of the third pre-oxidation is preferably 30-60 min, more preferably 35-55 min, more preferably 40-50 min.

[0059] In the present invention, the heating rate from room temperature to 170-200°C is preferably 3-8°C / min, more preferably 4-7°C / min, more preferably 5-6°C / min; the heating rate from 170-200°C to 220-260°C is preferably 0.5-2°C / min, more preferably 1.1-1.8°C / min, more preferably 1.3-1.7°C / min; the heating rate from 220-260°C to 280-320°C is preferably 4-8°C / min, more preferably 4.5-6.5°C / min, more preferably 5-6°C / min.

[0060] In the present invention, the pre-oxidation atmosphere of the non-woven felt is air.

[0061] In the present invention, the mass fraction of the resin solution in step 3) is preferably 5-18%, more preferably 8-12%, and more preferably 10%; in the resin solution, the resin is preferably a boron phenolic resin, and the solvent is preferably methanol and / or ethanol; the immersion time in the resin solution is preferably 10-80 min, more preferably 20-70 min, and more preferably 30-60 min; the boron phenolic resin solution is impregnated by vacuum impregnation or atmospheric pressure impregnation, and the vacuum degree of vacuum impregnation is preferably 100-150 Pa, more preferably 110-130 Pa, and more preferably 115-125 Pa.

[0062] In the present invention, the preparation method of the boron phenolic resin adopts a method well known in the art. The boron phenolic resin is a resin with a high residual carbon rate; the boron phenolic resin can improve the bonding condition at the intersections between monofilament fibers, which can not only stabilize the mechanical properties of carbon fiber paper, but also ensure good electron transport properties.

[0063] In the present invention, the drying temperature in step 3) is preferably 50-100°C, more preferably 60-90°C, more preferably 70-80°C, and the drying time is preferably 20-60 min, more preferably 30-50 min, more preferably 40 min; the temperature of the hot pressing curing is preferably 130-170°C, more preferably 140-160°C, more preferably 150°C, the pressure of the hot pressing curing is preferably 5-13 MPa, more preferably 7-11 MPa, more preferably 8-10 MPa, and the hot pressing curing time is preferably 10-25 min, more preferably 15-20 min, more preferably 16-18 min.

[0064] In the present invention, the carbonization temperature in step 3) is preferably 800-1400°C, more preferably 900-1300°C, more preferably 1000-1200°C, and the carbonization time is preferably 5-30 min, more preferably 10-25 min, more preferably 15-20 min; the graphitization temperature is preferably 2000-2800°C, more preferably 2200-2600°C, more preferably 2300-2500°C, and the graphitization time is preferably 5-20 min, more preferably 8-18 min, more preferably 10-15 min; the heating rate from room temperature to carbonization temperature and the heating rate from carbonization temperature to graphitization temperature are independently preferably 3-10°C / min, more preferably 5-8°C / min, more preferably 6-7°C / min; carbonization and graphitization are preferably carried out under a protective atmosphere, and the protective atmosphere is preferably high-purity nitrogen or high-purity argon.

[0065] In the present invention, the carbonization and graphitization process is preferably carried out in a multi-stage distributed program-controlled temperature tubular furnace to perform one-step carbonization and graphitization.

[0066] The present invention also provides a carbon fiber paper based on asphalt / polyacrylonitrile non-woven felt prepared by the preparation method, wherein the carbon fiber paper has a resistivity of 3 to 8 mΩ·cm, a thickness of 0.05 to 0.12 mm, and an air permeability of 1500 to 2200 mL·mm / (cm 2 ·hr·mmAq).

[0067] In the present invention, the resistivity of the carbon fiber paper based on the pitch / polyacrylonitrile nonwoven felt is preferably 3.2 to 6 mΩ·cm, more preferably 4 to 5 mΩ·cm, the thickness is preferably 0.06 to 0.10 mm, more preferably 0.07 to 0.09 mm, and the air permeability is preferably 1700 to 2100 mL·mm / (cm 2 ·hr·mmAq), more preferably 1800 to 2000 mL·mm / (cm 2 ·hr·mmAq).

[0068] The present invention also provides the use of the carbon fiber paper based on asphalt / polyacrylonitrile-based non-woven felt in a gas diffusion layer of a proton exchange membrane fuel cell.

[0069] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0070] The model of the multi-stage step-by-step program temperature-controlled tube furnace used in the examples and comparative examples is KSL-1700X-GS.

[0071] The preparation process of the acrylonitrile-itaconic acid copolymer solution is as follows: acrylonitrile and itaconic acid are added to N,N-dimethylformamide solvent in a mass ratio of 98:2, and stirred for 60 minutes in a 35°C water bath under a nitrogen atmosphere; an initiator azobisisoheptanenitrile (the mass of the initiator is 0.8% of the total mass of the acrylonitrile and itaconic acid monomers) is added and fully dissolved in the solvent, and the reaction is carried out at a water bath temperature of 50°C and a rotation speed of 130 rpm for 20 hours. Unreacted monomers are removed (the equipment automatically removes unreacted monomers) and degassing is performed to obtain an acrylonitrile-itaconic acid copolymer solution with a certain mass fraction;

[0072] The ultrasonic frequency of the ultrasonic-assisted solvent extraction was 45 kHz, the vacuum degree of the vacuum rotary evaporation was 0.08 MPa, and the vacuum degree of the vacuum degassing was -0.7 bar.

[0073] Example 1

[0074] Naphthalene asphalt is fully ground in a grinder and sieved through a 100-mesh sieve. The obtained powder is mixed with quinoline in a mass ratio of 1:5. The mixture is subjected to ultrasonic-assisted solvent extraction at 35°C for 12 hours, then transferred to a centrifuge tube and centrifuged at 6000 rpm for 10 minutes. After filtration and separation, the extract is vacuum rotary evaporated at a speed of 135 rpm and a water bath temperature of 90°C. The precipitated soluble asphalt is dried in a 60°C forced air drying oven for 24 hours to obtain an asphalt extract; the asphalt extract is placed in quinoline and mixed evenly to obtain a soluble asphalt solution with a mass fraction of 15%.

[0075] N,N-dimethylformamide was added to the soluble asphalt solution (0.4 mL of N,N-dimethylformamide was added to each mL of soluble asphalt solution), and the mixture was stirred at a rate of 500 rpm for 60 min. Acrylonitrile-itaconic acid copolymer solution was slowly added to the system in three portions (the mass fraction of the acrylonitrile-itaconic acid copolymer solution was 20%, and the mass ratio of the acrylonitrile-itaconic acid copolymer solution to the soluble asphalt solution was 1:0.15). The mixture was stirred at 60°C and 300 rpm for 6 h, and then vacuum degassed at 60°C for 5 h to obtain asphalt / polyacrylonitrile spinning solution.

[0076] Electrospinning technology was used with a positive voltage of 13kV, a negative voltage of -1.5kV, a receiving distance of 15cm, and a flow rate of 1.5mL / h. The spinning solution beam was evenly sprayed onto the roller collector by relying on the Taylor cone formed after the polarization of the spinning solution at the needle tip. The spinning time was 4h, and a non-woven felt with a thickness of 0.22mm was obtained. It was then placed in a 65℃ forced air drying oven and dried for 2h.

[0077] The non-woven felt was placed in a multi-stage step-by-step temperature-controlled tubular furnace with an air flow rate of 0.4 L / min. The temperature was raised from room temperature to 180°C at a rate of 5°C / min and held for 15 minutes; then raised from 180°C to 250°C at a rate of 1.2°C / min and held for 50 minutes; and finally raised from 250°C to 300°C at a rate of 5°C / min and held for 45 minutes to obtain a pre-oxidized felt. The pre-oxidized felt was then slowly placed in a methanol solution of boron phenolic resin (the mass fraction of boron phenolic resin in the methanol solution was 12%) and vacuum impregnated at 120 Pa for 60 minutes. After impregnation, the felt was transferred to a 70°C forced air drying oven for drying for 45 minutes. The felt was then hot-pressed for 18 minutes with the upper and lower plates of the flat vulcanizer at a temperature of 150°C and a pressure of 8 MPa to obtain the resin-impregnated pre-oxidized felt.

[0078] The resin-impregnated pre-oxidized felt was transferred into a multi-stage step-by-step programmed temperature-controlled tubular furnace. Under a high-purity nitrogen atmosphere, the temperature was raised from room temperature to 1000°C at a rate of 5°C / min and kept warm for 20 minutes. Then, under a high-purity argon atmosphere, the temperature was raised from 1000°C to 2300°C at a rate of 7°C / min and kept warm for 15 minutes to obtain asphalt / polyacrylonitrile-based carbon fiber paper.

[0079] The carbon fiber paper of this embodiment has a resistivity of 4.3 mΩ·cm, a thickness of 0.11 mm, and an air permeability of 1800 mL·mm / (cm 2 ·hr·mmAq).

[0080] The surface scanning electron microscope image of the pre-oxidized felt impregnated with resin in this embodiment is as follows: Figure 1 As shown by Figure 1From the morphology and microstructure of the pre-oxidized felt, it can be seen that the fibers inside the pre-oxidized felt are staggered and overlapped, especially at the overlap, the resin tightly bonds the two fibers together, and at the same time the original pore structure of the pre-oxidized felt is retained.

[0081] Example 2

[0082] The mass ratio of the acrylonitrile-itaconic acid copolymer solution to the soluble asphalt solution in Example 1 was changed to 1:0.30, and the other conditions were the same as in Example 1.

[0083] The resistivity of the carbon fiber paper in this embodiment is 3.9 mΩ·cm, the thickness is 0.12 mm, and the air permeability is 1730 mL·mm / (cm 2 ·hr·mmAq).

[0084] The surface scanning electron microscope image of the carbon fiber paper of this embodiment is as follows Figure 2 As shown by Figure 2 From the surface morphology, it can be seen that after the one-step carbonization and graphitization treatment, the resin carbon is tightly bonded to the fiber overlap, and there is no blockage of the pore structure due to the breakage of the resin carbon, which effectively connects the overlap of the monofilament fibers.

[0085] Example 3

[0086] The solvent for extracting asphalt in Example 1 was changed from quinoline to dimethyl sulfoxide, and other conditions were the same as in Example 1.

[0087] The carbon fiber paper of this embodiment has a resistivity of 5.1 mΩ·cm, a thickness of 0.10 mm, and an air permeability of 2000 mL·mm / (cm 2 ·hr·mmAq).

[0088] The cross-sectional scanning electron microscope image of the pre-oxidized felt impregnated with resin in this embodiment is as follows: Figure 3 As shown by Figure 3 From the cross-sectional morphology, it can be seen that the resin penetrates well into the interior of the pre-oxidized felt along the thickness direction of the pre-oxidized felt, especially at the overlap, where the overlap intersections of the monofilament fibers are tightly bonded together by the resin, and the original pore structure is well retained.

[0089] Example 4

[0090] The spinning time in Example 1 was changed from 4 h to 2 h, and the other conditions were the same as in Example 1.

[0091] The carbon fiber paper of this embodiment has a resistivity of 4.0 mΩ·cm, a thickness of 0.06 mm, and an air permeability of 2100 mL·mm / (cm 2 ·hr·mmAq).

[0092] The cross-sectional scanning electron microscope image of the carbon fiber paper of this embodiment is as follows: Figure 4 As shown by Figure 4 From the cross-sectional morphology, it can be seen that along the thickness direction of the carbon fiber paper, the overlapped intersections of the single fibers are tightly bonded by the resin carbon, and there is no phenomenon of resin carbon falling off and causing pore structure blockage; along the horizontal direction of the carbon fiber paper, the fibers are well dispersed and the thickness is uniform.

[0093] Example 5

[0094] The petroleum asphalt was fully ground in a grinder and sieved through a 100-mesh sieve. The obtained powder was mixed with tetrahydrofuran at a mass ratio of 1:6. The mixture was subjected to ultrasonic-assisted solvent extraction at 35°C for 12 hours. The mixture was then transferred to a centrifuge tube and centrifuged at 6000 rpm for 10 minutes. After filtration and separation, the extract was vacuum rotary evaporated at a speed of 135 rpm and a water bath temperature of 50°C. The precipitated soluble asphalt was dried in a 60°C forced air drying oven for 24 hours to obtain an asphalt extract. The asphalt extract was placed in tetrahydrofuran and mixed evenly to obtain a soluble asphalt solution with a mass fraction of 15%.

[0095] N,N-dimethylformamide was added to the soluble asphalt solution (0.5 mL of N,N-dimethylformamide was added to each mL of soluble asphalt solution), and the mixture was stirred at a rate of 500 rpm for 60 min. Acrylonitrile-itaconic acid copolymer solution was slowly added to the system in three portions (the mass fraction of the acrylonitrile-itaconic acid copolymer solution was 22%, and the mass ratio of the acrylonitrile-itaconic acid copolymer solution to the soluble asphalt solution was 1:0.20). The mixture was stirred at 60°C and 300 rpm for 6 h, and then vacuum degassed at 60°C for 5 h to obtain asphalt / polyacrylonitrile spinning solution.

[0096] Electrospinning technology was used with a positive voltage of 13kV, a negative voltage of -1.5kV, a receiving distance of 15cm, and a flow rate of 1.8mL / h. The spinning solution beam was evenly sprayed onto the roller collector by relying on the Taylor cone formed after the polarization of the spinning solution at the needle tip. The spinning time was 2.5h, and a non-woven felt with a thickness of 0.17mm was obtained. The felt was placed in a 65℃ forced air drying oven and dried for 2h.

[0097] The non-woven felt was placed in a multi-stage step-by-step temperature-controlled tubular furnace with an air flow rate of 0.4 L / min. The temperature was raised from room temperature to 185°C at a rate of 5°C / min and held for 15 minutes; then raised from 185°C to 240°C at a rate of 1.2°C / min and held for 50 minutes; and finally raised from 240°C to 300°C at a rate of 5°C / min and held for 50 minutes to obtain a pre-oxidized felt. The pre-oxidized felt was then slowly placed in a methanol solution of boron phenolic resin (the mass fraction of boron phenolic resin in the methanol solution was 10%) and vacuum impregnated at 120 Pa for 50 minutes. After impregnation, the felt was transferred to a 70°C forced air drying oven for drying for 45 minutes. The felt was then hot-pressed for 15 minutes with the upper and lower plates of the flat vulcanizer at a temperature of 150°C and a pressure of 10 MPa to obtain a resin-impregnated pre-oxidized felt.

[0098] The resin-impregnated pre-oxidized felt was transferred into a multi-stage step-by-step programmed temperature-controlled tubular furnace. Under a high-purity nitrogen atmosphere, the temperature was raised from room temperature to 1000°C at a rate of 5°C / min and kept warm for 20 minutes. Then, under a high-purity argon atmosphere, the temperature was raised from 1000°C to 2200°C at a rate of 7°C / min and kept warm for 15 minutes to obtain asphalt / polyacrylonitrile-based carbon fiber paper.

[0099] The carbon fiber paper of this embodiment has a resistivity of 3.9 mΩ·cm, a thickness of 0.09 mm, and an air permeability of 1900 mL·mm / (cm 2 ·hr·mmAq).

[0100] Example 6

[0101] The coal tar pitch was fully ground in a grinder and sieved through a 100-mesh sieve. The obtained powder was mixed with pyridine in a mass ratio of 1:5. The mixture was subjected to ultrasonic-assisted solvent extraction at 35°C for 12 hours, then transferred to a centrifuge tube and centrifuged at 6000 rpm for 10 minutes. After filtration and separation, the extract was vacuum rotary evaporated at a speed of 135 rpm and a water bath temperature of 90°C. The precipitated soluble asphalt was dried in a 60°C forced air drying oven for 24 hours to obtain an asphalt extract. The asphalt extract was placed in pyridine and mixed evenly to obtain a soluble asphalt solution with a mass fraction of 25%.

[0102] N,N-dimethylformamide was added to the soluble asphalt solution (0.7 mL of N,N-dimethylformamide was added to each mL of soluble asphalt solution), and the mixture was stirred at a rate of 500 rpm for 60 min. Acrylonitrile-itaconic acid copolymer solution was slowly added to the system in three portions (the mass fraction of the acrylonitrile-itaconic acid copolymer solution was 22%, and the mass ratio of the acrylonitrile-itaconic acid copolymer solution to the soluble asphalt solution was 1:0.40). The mixture was stirred at 60°C and 300 rpm for 6 h, and then vacuum degassed at 60°C for 5 h to obtain asphalt / polyacrylonitrile spinning solution.

[0103] Electrospinning technology was used with a positive voltage of 13kV, a negative voltage of -1.5kV, a receiving distance of 15cm, and a flow rate of 1.6mL / h. The spinning solution beam was evenly sprayed onto the roller collector by relying on the Taylor cone formed after the polarization of the spinning solution at the needle tip. The spinning time was 3h, and a non-woven felt with a thickness of 0.17mm was obtained. It was then placed in a 65℃ forced air drying oven and dried for 2h.

[0104] The non-woven felt was placed in a multi-stage step-by-step temperature-controlled tubular furnace with an air flow rate of 0.4 L / min. The temperature was raised from room temperature to 180°C at a rate of 5.5°C / min and held for 15 minutes; then raised from 180°C to 260°C at a rate of 1.5°C / min and held for 80 minutes; and finally raised from 260°C to 320°C at a rate of 4.5°C / min and held for 50 minutes to obtain a pre-oxidized felt. The pre-oxidized felt was then slowly placed in a methanol solution of boron phenolic resin (the mass fraction of boron phenolic resin in the methanol solution was 9%) and vacuum impregnated at 120 Pa for 60 minutes. After impregnation, the felt was transferred to a 70°C forced air drying oven for 45 minutes. It was then hot-pressed and cured for 20 minutes. The upper and lower plate temperatures of the flat-plate vulcanizer were 140°C and the pressure was 9 MPa to obtain the resin-impregnated pre-oxidized felt.

[0105] The resin-impregnated pre-oxidized felt was transferred into a multi-stage step-by-step programmed temperature-controlled tubular furnace. Under a high-purity nitrogen atmosphere, the temperature was raised from room temperature to 1200°C at a rate of 7°C / min and kept warm for 20 minutes. Then, under a high-purity argon atmosphere, the temperature was raised from 1200°C to 2200°C at a rate of 7°C / min and kept warm for 20 minutes to obtain asphalt / polyacrylonitrile-based carbon fiber paper.

[0106] The resistivity of the carbon fiber paper in this embodiment is 3.5 mΩ·cm, the thickness is 0.10 mm, and the air permeability is 1730 mL·mm / (cm 2 ·hr·mmAq).

[0107] Comparative Example 1

[0108] The soluble asphalt solution in Example 1 was replaced with the same mass of solvent quinoline, N,N-dimethylformamide was added to quinoline (0.4 mL of N,N-dimethylformamide was added to each mL of quinoline), and the mixture was stirred at a rate of 500 rpm for 60 min. The acrylonitrile-itaconic acid copolymer solution was slowly added to the system in three portions (the mass fraction of the acrylonitrile-itaconic acid copolymer solution was 20%, and the mass ratio of the acrylonitrile-itaconic acid copolymer solution to quinoline was 1:0.15). The other process conditions were the same as in Example 1.

[0109] The carbon fiber paper of this comparative example has a resistivity of 10.3 mΩ·cm, a thickness of 0.09 mm, and an air permeability of 1500 mL·mm / (cm 2·hr·mmAq).

[0110] The in-situ X-ray diffraction patterns of the carbonized carbon fiber paper of Example 5 and the carbonized carbon fiber paper of Comparative Example 1 are as follows: Figure 5 As shown by Figure 5 It can be seen that under the same preparation and processing conditions, the introduction of soluble pitch in Example 5 is beneficial to reducing the inter-layer spacing of the carbon fibers and increasing the crystallite size. The polyacrylonitrile-based carbon fibers in Comparative Example 1 have larger inter-layer spacing and smaller crystallite size.

[0111] Comparative Example 2

[0112] Carbon fiber paper was prepared using a traditional wet papermaking process. Commercially available short-cut polyacrylonitrile-based carbon fibers (T700, 8 mm) were placed in a fiber disintegrator and slowly added to an aqueous solution of a surfactant (hydroxymethyl cellulose with a viscosity of 100,000 and polyethylene oxide with a viscosity-average molecular weight of 5,000,000, with the mass fraction of both hydroxymethyl cellulose and polyethylene oxide at 0.1%). The mixture was stirred at 500 rpm for 3 minutes to obtain a chopped carbon fiber dispersion.

[0113] The dispersion was transferred to a paper sheet former and dehydrated under a vacuum condition of 0.05 MPa for 80 seconds. The chopped carbon fiber dispersion was passed through a stainless steel filter to form a 20 cm × 20 cm, 0.16 mm thick carbon fiber base paper on the filter surface; it was slowly placed in a methanol solution of boron phenolic resin (the mass fraction of boron phenolic resin in the methanol solution was 12%), vacuum impregnated at 120 Pa for 60 minutes, and transferred to a 70°C forced air drying oven for drying for 45 minutes; then hot pressed for 18 minutes, with the upper and lower plate temperatures of the flat vulcanizer at 150°C and the pressure at 8 MPa to obtain the resin-impregnated carbon fiber base paper; it was transferred to a multi-stage step-by-step program temperature-controlled tubular furnace, and under a high-purity nitrogen atmosphere, the temperature was increased from room temperature to 1000°C at a rate of 5°C / min and kept warm for 20 minutes; then under a high-purity argon atmosphere, the temperature was increased from 1000°C to 2300°C at a rate of 7°C / min and kept warm for 15 minutes to obtain the carbon fiber paper.

[0114] The resistivity of the carbon fiber paper of this comparative example is 12.6 mΩ·cm, the thickness is 0.19 mm, and the air permeability is 1380 mL·mm / (cm 2 ·hr·mmAq).

[0115] It can be seen from the embodiments and comparative examples that the carbon fiber paper based on asphalt / polyacrylonitrile-based non-woven felt prepared by the present invention has significantly reduced resistivity, uniform thickness, easy ultra-thin preparation, and excellent air permeability, and realizes simultaneous and precise regulation of conductivity, controllable thickness, and ultra-thinness, providing a new design idea for the preparation of functional carbon fiber paper materials for PEMFC. At the same time, the preparation process is simple, energy consumption is low, and cost is low, which has a good foundation for industrial promotion.

[0116] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing carbon fiber paper based on asphalt / polyacrylonitrile-based non-woven felt, characterized in that: The following steps are included: 1) stirring and mixing the soluble asphalt solution and the acrylonitrile-itaconic acid copolymer solution in sequence, and degassing them to obtain an electrospinning stock solution; 2) electrospinning the electrospinning solution to obtain a pitch / polyacrylonitrile-based non-woven felt; and sequentially drying and pre-oxidizing the pitch / polyacrylonitrile-based non-woven felt to obtain a pre-oxidized felt; 3) The pre-oxidized felt is impregnated in a resin solution, and then dried, hot-pressed, carbonized, and graphitized in sequence to obtain a carbon fiber paper based on a pitch / polyacrylonitrile-based non-woven felt.

2. The method for preparing carbon fiber paper based on asphalt / polyacrylonitrile-based non-woven felt according to claim 1, characterized in that: Step 1) The soluble asphalt solution comprises an asphalt extract and an organic solvent; the mass fraction of the soluble asphalt solution is 5 to 35%; The mass fraction of the acrylonitrile-itaconic acid copolymer solution is 12 to 30%; The mass ratio of the acrylonitrile-itaconic acid copolymer solution to the soluble asphalt solution is 1:0.10-0.

65.

3. The method for preparing carbon fiber paper based on asphalt / polyacrylonitrile-based non-woven felt according to claim 2, characterized in that: The asphalt extract is prepared by mixing asphalt and an organic solvent, extracting the mixture, centrifuging, rotary evaporating, and drying the mixture in sequence to obtain the asphalt extract; The asphalt comprises one or more of naphthalene asphalt, petroleum asphalt and coal asphalt; The organic solvent comprises one or more of n-heptane, quinoline, pyridine, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide; The mass ratio of the asphalt to the organic solvent is 1:4-8.

4. The method for preparing carbon fiber paper based on asphalt / polyacrylonitrile-based non-woven felt according to claim 3, characterized in that: The extraction method is one or more of ultrasound-assisted extraction, Soxhlet extraction and magnetic stirring; The stirring and mixing temperature and the degassing temperature are independently 40 to 90° C., and the stirring and mixing time and the degassing time are independently 3 to 12 hours.

5. The method for preparing carbon fiber paper based on asphalt / polyacrylonitrile-based non-woven felt according to claim 1 or 2, characterized in that: Step 2) The electrospinning flow rate is 0.8 to 2.2 mL / h, and the electrospinning time is 2 to 6 hours; the thickness of the asphalt / polyacrylonitrile-based non-woven felt is 0.14 to 0.30 mm.

6. The method for preparing carbon fiber paper based on asphalt / polyacrylonitrile-based non-woven felt according to claim 5, characterized in that: Step 2) the drying temperature is 60-100° C. and the drying time is 1-3 hours; The programmed pre-oxidation includes three pre-oxidations, the first pre-oxidation temperature is 170-200°C, the time is 10-20 minutes, the second pre-oxidation temperature is 220-260°C, the time is 25-90 minutes, and the third pre-oxidation temperature is 280-320°C, the time is 30-60 minutes.

7. The method for preparing carbon fiber paper based on asphalt / polyacrylonitrile-based non-woven felt according to claim 6, characterized in that: Step 3) The mass fraction of the resin solution is 5 to 18%, the resin in the resin solution is boron phenolic resin, and the solvent is methanol and / or ethanol; the immersion time in the resin solution is 10 to 80 minutes; Step 3) The drying temperature is 50-100° C. and the time is 20-60 min; the hot pressing curing temperature is 130-170° C., the pressure is 5-13 MPa, and the time is 10-25 min.

8. The method for preparing carbon fiber paper based on asphalt / polyacrylonitrile-based non-woven felt according to claim 6 or 7, characterized in that: Step 3) The carbonization temperature is 800-1400° C., and the time is 5-30 min; the graphitization temperature is 2000-2800° C., and the time is 5-20 min; the heating rate from room temperature to carbonization temperature and the heating rate from carbonization temperature to graphitization temperature are independently 3-10° C. / min; carbonization and graphitization are carried out under a protective atmosphere.

9. The carbon fiber paper based on asphalt / polyacrylonitrile nonwoven felt prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The carbon fiber paper has a resistivity of 3 to 8 mΩ·cm, a thickness of 0.05 to 0.12 mm, and an air permeability of 1500 to 2200 mL·mm / (cm 2 ·hr·mmAq).

10. Use of the carbon fiber paper based on asphalt / polyacrylonitrile-based non-woven felt according to claim 9 in a gas diffusion layer of a proton exchange membrane fuel cell.

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