CN100387762C - A kind of polyacrylonitrile-based mesoporous-macroporous ultrafine carbon fiber and preparation method thereof - Google Patents

Abstract

The polyacrylonitrile-based mesoporous-macroporous ultrafine carbon fiber disclosed by the invention is a solid carbon fiber or hollow carbon fiber with a diameter of 10 nanometers to 5 microns, and the carbon fiber has mesopores or macropores with a diameter of 20 to 100 nanometers. Its preparation method: dissolve a polymer that can be fully thermally decomposed under a non-oxidizing atmosphere and polyacrylonitrile or polyacrylonitrile copolymer in a co-solvent, and prepare superfine fibers by high-voltage electrospinning; then The fiber is dried, pre-oxidized at 100-300°C, and then carbonized at a temperature of 300-1800°C in nitrogen or other inert gas atmosphere. The pyrolyzable polymer decomposes completely, leaving pores with a diameter of 20-100 nanometers in the fiber. The ultra-fine carbon fiber fiber of the present invention has small diameter, large specific surface area, and easy adjustment of pore size and pore shape. Because the pore size is in the range of mesopore and macropore, the fiber is particularly suitable for the adsorption and absorption of certain large particle size particles (such as bacteria and viruses). separate.

Description

A kind of polyacrylonitrile-based mesoporous-macroporous ultrafine carbon fiber and preparation method thereof

technical field

The invention relates to ultrafine carbon fibers with mesoporous or macroporous structures and a preparation method thereof, in particular to a polyacrylonitrile-based mesoporous or macroporous ultrafine carbon fiber and a preparation method thereof,

Background technique

Porous carbon fiber has important application value in material adsorption, separation, catalyst carrier, hydrogen storage material, special activated carbon for supercapacitor, etc. Pore size and distribution have a decisive influence on the properties of porous carbon fibers. At present, the method of preparing porous carbon fiber is mainly to carbonize the organic polymer fiber obtained by solution spinning or melt spinning at high temperature, then activate it with water vapor, carbon monoxide, carbon dioxide and other atmospheres at high temperature, and various small molecule additives Such as metal ions, phosphoric acid (CN00117577.7), boric acid (CN99116239.0), etc. help to increase the porosity and specific surface area of carbon fibers. Another method is to make natural fibers, such as coconut fiber, etc. through high-temperature carbonization, activation and other processes. However, the diameter of the pores in the porous activated carbon fibers and hollow fiber membranes usually obtained by the above method is less than 2 nanometers, which belongs to the range of micropores. For the adsorption and filtration of microorganisms such as bacteria and viruses, the role of micropores is not obvious. At the same time, for activated carbon dedicated to supercapacitors, when the pore size is less than 2 nanometers, the electrolyte solution can no longer infiltrate, which is not conducive to improving its capacitance. Therefore, carbon fibers with mesoporous (2nm-50nm) and macroporous structures (>50nm) will play a very important role in some specific fields. Chinese patent CN02103749.3 discloses a method for preparing a hollow carbon fiber membrane from a mixed solution of 70-80% polyacrylonitrile, 5-15% polymethylmethacrylate and 5-15% polyvinylpyrrolidone. The molecular weight cut-off of the membrane is 50,000-150,000, which belongs to the range of ultrafiltration membranes. However, its spinning method adopts a solution spinning method, and the fiber diameter obtained by the solution spinning method is generally about 10 microns, which does not belong to the scope of superfine fibers.

On the other hand, high-voltage electrospinning is an effective means to prepare polymer ultrafine fibers, fiber mats and non-woven fabrics. The fiber non-woven fabric prepared by this method has the advantages of small fiber diameter, good uniformity, high porosity, large specific surface area and the like. Different from traditional solution spinning and melt spinning, the diameter of fibers obtained by high-voltage electrospinning is generally tens of nanometers to several microns, which is much smaller than that obtained by traditional spinning methods, so it has broad application prospects . Korean patent KR2002008227 provides a method for manufacturing carbon nanofibers for supercapacitors by high-voltage electrospinning, but the fibers do not have a porous structure. So far, there are no patents and reports on the preparation of mesoporous-macroporous carbon fibers by high-voltage electrospinning.

Contents of the invention

The object of the present invention is to provide a polyacrylonitrile-based mesoporous-macroporous ultrafine carbon fiber and a preparation method thereof.

The polyacrylonitrile-based mesoporous-macroporous ultrafine carbon fiber of the present invention is a solid carbon fiber or hollow carbon fiber with a diameter of 10 nanometers to 5 microns, and the carbon fiber has mesopores or macropores with a diameter of 20 to 100 nanometers.

The shape of the carbon fiber cross section can be circular, circular, elliptical, polygonal or any other non-circular shape.

The preparation method of polyacrylonitrile-based mesoporous-macroporous ultrafine carbon fiber of the present invention comprises the following steps:

1) Dissolve the polymer homopolymer or copolymer and polyacrylonitrile or polyacrylonitrile copolymer in an organic solvent in a weight ratio of 1:10 to 10:1 to form a uniform solution, wherein acrylonitrile is fully polymerized The weight content in the product is 1% to 99%, and the weight concentration of the polymer in the solution is 0.5% to 60%;

2) The above solution is prepared into superfine fibers by high-voltage electrospinning method, the spinning voltage is 1000-200,000 volts, the spinning speed is 0.01-100 ml/hour, and the distance between the spinneret and the receiver is 5-50 cm between;

3) Dry the prepared ultrafine fibers at 50-150°C, then pre-oxidize at 200-300°C, then slowly raise the temperature to 600-1800°C under the protection of nitrogen or argon inert gas, and keep warm for 0.1- For 10 hours, wherein the flow rate of the inert gas was between 0.1 ml/min and 100 ml/min, polyacrylonitrile-based mesoporous-macroporous ultrafine carbon fibers were obtained.

In order to further increase the specific surface area of the carbon fiber, the obtained polyacrylonitrile-based mesoporous-macroporous ultrafine carbon fiber can be further activated with water vapor, carbon monoxide or carbon dioxide at 700-900°C.

In the present invention, the selection of polymer homopolymers or copolymers needs to meet three conditions: one, be able to dissolve together with polyacrylonitrile or polyacrylonitrile copolymers in a certain solvent; two, after the solvent volatilizes, the Phase separation occurs between the polymer and polyacrylonitrile or polyacrylonitrile copolymer; third, it can be fully thermally decomposed in a non-oxidizing atmosphere. The above-mentioned polymer homopolymer or copolymer can be selected from a homopolymer formed by a monomer containing an active unsaturated double bond or a monomer formed by two or more monomers containing an active unsaturated double bond in various ratios. copolymer. The above monomers containing active unsaturated double bonds can be acrylate monomers, acrylonitrile, styrene and its derivatives, α-methylstyrene and its derivatives, vinyl acetate and its derivatives, butadiene , isoprene, vinyl chloride, vinylpyrrolidone, acrylamide monomer or vinylpyridine, etc. Among them, preferred are acrylate monomers, including methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, hydroxyethyl methacrylate, methyl acrylate, ethyl acrylate, Butyl acrylate, hexyl acrylate, hydroxyethyl acrylate or glycidyl methacrylate, etc.

In the present invention, said polyacrylonitrile copolymer is polyacrylonitrile and acrylate monomer containing active unsaturated double bonds, styrene and its derivatives, α-methylstyrene and its derivatives, vinyl acetate Copolymers formed from esters and their derivatives, butadiene, isoprene, vinyl chloride, vinylpyrrolidone, acrylamide monomers or vinylpyridine.

In the present invention, said organic solvent is dimethylformamide, dimethylacetamide or dimethylsulfoxide.

The beneficial effects of the present invention are: the fiber diameter is small, the specific surface area is large, and the pore size and pore shape are easy to adjust. Since the pore size is in the range of mesopores and macropores, the fibers are especially suitable for the adsorption of certain large-diameter particles (such as bacteria and viruses) and separation.

Description of drawings

Fig. 1 is the scanning electron micrograph of the electrospun fiber that is obtained by the polyacrylonitrile/acrylonitrile-methyl methacrylate blend of 40:60 by composition ratio;

Fig. 2 is the scanning electron micrograph of the mesoporous-macroporous ultrafine carbon fiber that the polyacrylonitrile/acrylonitrile-methyl methacrylate blend that composition ratio obtains of 40:60;

Figure 3 is a scanning electron micrograph of polyacrylonitrile-based mesoporous-macroporous ultrafine carbon fibers.

The structure of mesoporous-macroporous carbon fibers was observed by scanning electron microscopy and transmission electron microscopy. The specific surface area of the fibers was measured by a nitrogen gas adsorption method.

Detailed ways

Example 1

4 grams of polyacrylonitrile and 6 grams of acrylonitrile-methyl methacrylate copolymer with a composition ratio of 1:9 were dissolved in 250 grams of dimethylformamide solution and obtained by high-voltage electrospinning to obtain superfine fibers, fiber mats or non-woven fabrics. spinning. The spinning voltage was 30,000 volts and the spinning speed was 0.5 ml/hour. The distance between the spinneret and receiver was 15 cm. The obtained electrospun fibers are shown in Fig. 1, and the diameter of the fibers is about 100 to 500 nm. The fiber mat obtained by electrospinning was vacuum-dried at 80°C, then pre-oxidized at 280°C for 2 hours, then slowly heated to 800°C under the protection of nitrogen, and kept for 1 hour, and the flow rate of nitrogen was 10 ml/min. Wherein the pyrolyzable polymer is completely decomposed to obtain mesoporous-macroporous ultrafine carbon fibers, as shown in Figure 2, the diameter of the carbon fibers is below 500 nanometers. A large number of micropores are distributed inside and on the surface of the fiber, and the diameter of the pores is about 20 nanometers. Its specific surface area was measured by the nitrogen adsorption method to be 50 m2/g.

Example 2

2 grams of polyacrylonitrile and 8 grams of acrylonitrile-methyl methacrylate-polystyrene copolymer with a composition ratio of 1:8.5:0.5 were dissolved in 250 grams of dimethyl sulfoxide solution, and high-voltage electrospinning was used to obtain fibers felt. The spinning voltage was 30,000 volts and the spinning speed was 2 ml/hour. The distance between the spinneret and receiver was 15 cm. Drying and pre-oxidation are the same as in Example 1, the carbonization temperature is 700° C., and the time is 2 hours. After carbonization, the fibers are obviously porous and adhere to each other (see Figure 3). Its specific surface area was 92 m2/g as measured by the nitrogen adsorption method. The obtained mesoporous-macroporous ultrafine carbon fiber was activated with carbon dioxide at 800° C., and the specific surface area was measured as 245 square meters per gram by nitrogen adsorption method.

Example 3

5 grams of polyacrylonitrile and 5 grams of acrylonitrile-methyl methacrylate-butyl methacrylate terpolymer with a composition ratio of 1:8:1 were dissolved in 250 grams of dimethylacetamide solution, Fiber mats are obtained by spinning. The spinning voltage was 20,000 volts and the spinning speed was 5 ml/hour. The distance between the spinneret and receiver was 15 cm. Drying and pre-oxidation are the same as in Example 1, the carbonization temperature is 1000° C., and the time is 2 hours. The diameter of the fibers is 5 microns. The fiber contains a large number of micropores, and the diameter of the pores is about 100 nanometers. Its specific surface area was measured by the nitrogen adsorption method to be 54 m2/g.

Example 4

5 grams of polyacrylonitrile and 5 grams of acrylonitrile-ethyl acrylate copolymer with a composition ratio of 1:9 were dissolved in 250 grams of dimethylacetamide solution, and high-voltage electrospinning was used to obtain a fiber mat. The spinning voltage was 30,000 volts and the spinning speed was 0.5 ml/hour. The distance between the spinneret and receiver was 15 cm. Drying and pre-oxidation are the same as in Example 1, the carbonization temperature is 1800° C., and the time is 0.5 hour. The diameter of the fibers is 0.4 microns. The fiber contains a large number of micropores, and the diameter of the pores is about 20 nanometers. Its specific surface area was 356 m2/g as measured by the nitrogen gas adsorption method.

Example 5

7 grams of polyacrylic acid-polyacrylonitrile binary copolymer with a composition ratio of 0.5:9.5 and 3 grams of acrylonitrile-methyl methacrylate-butyl methacrylate terpolymer with a composition ratio of 1:7:2 were dissolved Fiber mats were obtained by high-voltage electrospinning in 250 g of dimethylformamide solution. The spinning voltage was 20,000 volts, and the spinning speed was 1 ml/hour. The distance between the spinneret and receiver was 15 cm. Drying and pre-oxidation are the same as in Example 1, the carbonization temperature is 800° C., and the time is 9 hours. The diameter of the fibers is 2 microns. The diameter of the micropores in the fiber is about 20 nanometers. Its specific surface area was 132 m2/g as measured by the nitrogen gas adsorption method.

Example 6

5 grams of polyvinylpyrrolidone-polyacrylonitrile binary copolymer with a composition ratio of 9:1 and 5 grams of acrylonitrile-ethyl methacrylate copolymer with a composition ratio of 9:1 were dissolved in 200 grams of dimethylformamide In the solution, a fiber mat is obtained by high-voltage electrospinning. The spinning voltage is slightly 30000 volts, and the spinning speed is 0.5 ml/hour. The distance between the spinneret and receiver was 12 cm. Drying, pre-oxidation carbonization conditions are the same as in Example 1. The average diameter of the fibers is 1.5 microns. The diameter of the micropores in the fiber is about 30 nanometers. Its specific surface area was 254 m2/g as measured by the nitrogen adsorption method.

Example 7

5 grams of polyacrylamide-polyacrylonitrile binary copolymer with a composition ratio of 9:1 and 5 grams of acrylonitrile-methyl methacrylate copolymer with a composition ratio of 9:1 are dissolved in 200 grams of dimethylformamide solution In this process, high-voltage electrospinning was used to obtain fiber mats. The spinning voltage is micro 30000 volts, and the spinning speed is 0.8 ml/hour. The distance between the spinneret and receiver was 12 cm. Drying, pre-oxidation carbonization conditions are the same as in Example 1. The average diameter of the fibers is 2 microns. The diameter of the micropores in the fiber is about 30 nanometers. Its specific surface area was 203 m2/g as measured by the nitrogen gas adsorption method.

Claims (7)

1. polyacrylonitrile mesopore-macropore ultrafine carbon fiber, it is that diameter is the solid carbon fiber or the hollow carbon fiber of 10 nanometers～5 micron, it is characterized in that having on the carbon fiber the mesoporous or macropore of aperture in 20～100 nanometers.

2. the preparation method of polyacrylonitrile mesopore-macropore ultrafine carbon fiber according to claim 1 is characterized in that may further comprise the steps:

1) macromolecule homopolymers or copolymer and polyacrylonitrile or polyacrylonitrile copolymer were dissolved in the organic solvent by weight 1: 10～10: 1, be made into uniform solution, wherein, the weight content of acrylonitrile in whole polymer is 1% to 99%, and the weight concentration of polymer is 0.5% to 60% in the solution;

2) adopt the high-voltage electrostatic spinning method to be prepared into superfine fibre above-mentioned solution, spinning voltage is at 1000-200, and 000 volt, spray silk speed is at 0.01 to 100 milliliter/hour, and the distance of spinning head and receiver is between 5 to 50 centimetres;

3) superfine fibre that makes is carried out drying under 50-150 ℃; then 200-300 ℃ of following pre-oxidation; under nitrogen or argon gas inert gas shielding, slowly be warming up to 600-1800 ℃ subsequently; and be incubated 0.1-10 hour; wherein the flow velocity of inert gas obtains polyacrylonitrile mesopore-macropore ultrafine carbon fiber between 0.1 ml/min to 100 ml/min.

3. the preparation method of polyacrylonitrile mesopore-macropore ultrafine carbon fiber according to claim 2 is characterized in that the polyacrylonitrile mesopore-macropore ultrafine carbon fiber that will obtain activates with steam, carbon monoxide or carbon dioxide at 700～900 ℃.

4. the preparation method of polyacrylonitrile mesopore-macropore ultrafine carbon fiber according to claim 2 is characterized in that said macromolecule homopolymers or copolymer are the homopolymers that formed by the monomer that contains active unsaturated double-bond or the copolymer that forms with two kinds or the two or more monomers that contains active unsaturated double-bond.

5. the preparation method of polyacrylonitrile mesopore-macropore ultrafine carbon fiber according to claim 4 is characterized in that the said monomer that contains active unsaturated double-bond is acrylic ester monomer, acrylonitrile, styrene and derivative thereof, α-Jia Jibenyixi and derivative thereof, vinylacetate and derivative thereof, butadiene, isoprene, vinyl chloride, vinyl pyrrolidone, acrylamide monomers or vinylpyridine.

6. the preparation method of polyacrylonitrile mesopore-macropore ultrafine carbon fiber according to claim 2 is characterized in that said polyacrylonitrile copolymer is the copolymer that polyacrylonitrile and acrylic ester monomer, styrene and derivative thereof, α-Jia Jibenyixi and derivative thereof, vinylacetate and the derivative thereof that contains active unsaturated double-bond, butadiene, isoprene, vinyl chloride, vinyl pyrrolidone, acrylamide monomers or vinylpyridine form.

7. the preparation method of polyacrylonitrile mesopore-macropore ultrafine carbon fiber according to claim 2 is characterized in that said organic solvent is a dimethyl formamide, dimethylacetylamide or dimethyl sulfoxide (DMSO).

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