CN101092761A - Method for preparing Nano carbon fiber by using phenol formaldehyde (PF) resin - Google Patents

Abstract

The invention relates to a method for preparing nanometer carbon fiber with phenolic resin (PF). The method includes step (1) preparation of nano-carbon fiber precursors: using polypropylene (PP) as a matrix and phenolic resin (PF) as a dispersed phase, blending the weight percentage PF/PP=1-50/99-50; the blend PF/PP blended fibers are prepared by melt spinning; nano-carbon fiber precursors are obtained after the blended fibers are cross-linked and solidified. (2) Carbonization of carbon nanofiber precursors: oxidation and carbonization at 600-1200° C. for 50-90 minutes in a nitrogen atmosphere. The method has the advantages of simple process, uniform size and high purity of the prepared fiber, with a diameter of 100-1000 nanometers, large specific surface area, chemical stability and long fiber structure, and is suitable for industrialized production.

Description

A kind of method that prepares nanometer carbon fiber with phenolic resin (PF)

technical field

The invention relates to the field of preparing carbon nanofibers, in particular to a method for preparing carbon nanofibers with phenolic resin (PP).

Background technique

Carbon fiber is a kind of high-strength, high-modulus, high-temperature-resistant special fiber with a carbon content greater than 90% made from polyacrylonitrile (PAN), pitch, viscose fiber, etc., after pre-oxidation and carbonization.

Carbon fiber plays an extremely important role in national defense, military fields and various pillar industries of the national economy. However, the world's carbon fiber production is mainly concentrated in developed countries such as Japan, the United States, and the United Kingdom, and South Korea and India also have a small amount of production. In addition to Taiwan Plastics Group, my country's carbon fiber production only accounts for 0.4% of the world's total output. Today, carbon fiber has developed into an independent and complete new industrial system, and has been widely used in military equipment, aerospace, sports equipment, medical equipment, textiles and other fields.

The reason why there is a big gap between my country's high-performance carbon fiber production and foreign countries is that the quality of domestic raw silk is not high and uneven. In the face of this situation, we have to find another way: prepare nano-carbon fibers, control appropriate electrical conductivity, and develop nano-carbon materials with both absorbing and enhanced properties, which are both in line with my country's national conditions and advanced.

Carbon nanofiber (Carbon nanofiber, CNF) generally refers to a fibrous carbon material with a diameter of 50-200nm and an aspect ratio of 100-500. Its size range fills the size gaps of conventional carbon fibers (7-10 μm in diameter), single-walled carbon nanotubes (about 1-10 nm in diameter) and multi-walled carbon nanotubes (10-100 nm in diameter). The performance is similar to that of conventional carbon fiber, with high strength, modulus, excellent thermal stability and electrical conductivity, and the characteristics of large aspect ratio of carbon nanotubes, high specific surface area, and good chemical activity.

The preparation methods of carbon nanofibers include traditional gas phase growth method (CVD) and electrospinning method, and there are some domestic patents in this regard.

The CVD method uses high-temperature cracking of carbon-containing compounds (carbon source: CH ₄ and benzene, etc.) to provide free carbon atoms, and then forms vapor phase deposition under the action of a catalyst. Catalysts are generally transition metals (such as iron, nickel, etc.). According to the state of the catalyst, the CVD method can be divided into the matrix method, the spray method and the flow catalytic method.

The matrix method generally uses graphite or ceramics as the matrix, disperses nano-scale catalyst particles on the matrix, and passes through carbon source gas at high temperature (700-1200°C) for cracking, and grows carbon nanotubes on the catalyst. The yield of carbon nanotubes prepared by this method is not high, and the size is greatly affected by the catalyst particles.

The spray forest method is to mix the catalyst into the organic compound liquid such as benzene, and spray the mixed liquid into the high-temperature reaction chamber under the action of external force, and react at about 1150°C to obtain carbon nanofibers with high yield, but the size distribution is wide, there are Carbon black particles are formed.

Instead of attaching the catalyst to the substrate or dispersing the catalyst precursor in the carbon source solution, the flow catalysis method directly heats the catalyst precursor and introduces it into the high-temperature reaction chamber together with the hydrocarbon gas in the form of gas. They pass through different temperature regions to complete the catalysis and decomposition of hydrocarbon gases. The decomposed catalyst atoms gradually aggregate into nanoparticles, and the carbon atoms generated by pyrolysis grow nanocarbon fibers on the nanoscale catalyst particles. Catalyst particles decomposed from organic compounds can be distributed throughout the reaction space, while the amount of catalyst volatilization is controllable. Therefore, this method has a large output per unit time and can be continuously produced.

The electrospinning method is a spinning technology realized by using a high-voltage electric field. The fiber-forming polymer solution is injected into a thin stream, stretched under the action of a high-voltage electric field to form a jet, and at the same time split, the solvent evaporates rapidly, and finally on the receiving screen Fibers in the form of non-woven fabrics are obtained, with diameters ranging from several micrometers to several nanometers. Obviously, electrospinning can only be achieved with highly volatile solvents, and the recovery of solvents also increases the preparation cost.

Compared with the preparation methods of the above two types of nano-carbon fibers, the polymer blend spinning method to be adopted in this patent is a new method, which is to carry out co-production of carbon fiber precursor polymer (CPP) and pyrolysis polymer (TDP). Mix to achieve uniform dispersion of CPP in TDP, then spin the blended system into fibers, and stretch the fibers. During this process, CPP is dispersed in TDP in the form of microfibrils. The pyrolytic polymer is then removed by thermal oxidation and carbonization to obtain ultrafine carbon fibers.

There are no literature and patent reports in China to prepare carbon nanofibers by carbonization after polymer blend spinning.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for preparing carbon nanofibers with phenolic resin (PF). The method has the advantages of simple process, uniform size and high purity of the prepared fiber, with a diameter of 100-1000 nanometers, large specific surface area, chemical stability and long fiber structure. Suitable for industrial production.

A kind of method of preparing carbon nanofiber with phenolic resin (PF) of the present invention, comprises the following steps:

(1) Preparation of carbon nanofiber precursors: including two steps of blending and spinning and crosslinking and curing.

A: blend spinning

With polypropylene (PP) as the matrix and phenolic resin (PF) as the dispersed phase, the blending system with weight percent PF/PP=1-50/99-50 is fully mixed in a twin-screw extruder, extruded and granulated . After the slices are dried, use conventional melt spinning equipment to melt the blended slices prepared above and extrude through the spinneret holes, and then prepare PF/PP blended fibers through cooling and solidification, oiling, winding and drawing. ; Nano carbon fiber precursor;

B: Preparation of nano-carbon fiber precursors obtained after cross-linking and curing of PF/PP blend fibers

Measure 500-550ml of 35-40% formaldehyde, 500-600ml of 35-40% hydrochloric acid, and 20-30ml of ethanol, place them in a container equipped with a stirring paddle, a thermocouple and a reflux condenser, and stir evenly. Control the temperature of the solution at 20-40°C, add about 7-10g of fibers fixed on the splint, and keep at this temperature for 1-2hr; -1hr; then use 1-2hr to raise the temperature to 80-100°C, and keep the temperature constant for 0.5-1hr. After the reaction is finished, after the solution is cooled to room temperature, the fibers are taken out, washed with 8-10% NH ₃ .H ₂ O solution until neutral, washed with boiling water and dried.

(2) Carbonization of carbon nanofiber precursors

Fix the nano-carbon fiber precursors in the constant temperature zone of the electric heating furnace, pass _N2 to exhaust the air in the constant temperature zone of the electric heating furnace, connect the water cooling backflow device, and pass the tail gas discharge pipe into the lye. Under the protection of _N2 , heat to 600-1200°C at a rate of 2-20°C/min, keep the temperature for 50-90 minutes, turn off the power, stop the electric heating furnace, continue to feed _N2 , and lower the temperature to room temperature Then remove the sample.

The phenolic resin (PF) described in step 1 is a carbon fiber precursor (CPP), and the polypropylene is a pyrolysis polymer (TDP). PF should be thermoplastic, such as Julong brand PF produced by Shanghai Qinan Adhesive Material Factory; the melt index of PP is 20-100g/10min, such as: Sinopec Shanghai Petrochemical's Y2600, Y3700, Yangzi Petrochemical's F904, etc.

The carbon fiber precursor described in step 1 must be uniformly dispersed in the pyrolysis polymer in the form of microfibers, which is a "sea-island" structure when viewed from the fiber cross section (Figure 1).

In the melt spinning described in step 1, the melt spinning temperature in the first zone is 190°C; in the second zone, 215-220°C; in the third zone, 230-240°C, and in the fourth zone, 240-250°C. Spinning speed 100-1000m/min, draft ratio 2-5 times;

The spinning speed described in step 1 is 500m/min, the draft ratio is 4 times, and the diameter of carbon nanofibers prepared after carbonization is less than 200nm.

The diameter of the carbon nanofiber prepared in step 3 is controllable within 100-1000 nanometers, has a large specific surface area, excellent chemical stability, and a long fibrous structure.

Phenolic resin (PF) structure of the present invention is as follows:

where n is 10-50.

Polypropylene (PP) is used as the pyrolysis polymer. Among them: phenolic resin (PF) is a thermoplastic product, such as Julong brand PF-5, etc. (Shanghai Qinan Adhesive Material Factory); polypropylene (PP) has a melt index of 20-100g/10mim, such as Y2600, Y3700 ( Shanghai Petrochemical), F904 (Yangzi Petrochemical), etc.

After heating at high temperature in an inert atmosphere, the high polymer with carbon residue is called carbon precursor polymer (CPP), and the high polymer without carbon residue is called pyrolytic polymer (TDP).

The invention adopts a blending melt spinning method to prepare nanometer carbon fiber precursors. Firstly, comparison and screening are carried out in various matrices. After comparison, it is found that when PF is used as the carbon precursor polymer (CPP), polypropylene (PP) is used as the pyrolysis polymer (TDP), which has advantages in manufacturing and cost.

The present invention controls the dispersion size of CPP in TDP by controlling the spinning speed and the draw ratio. For example, if the spinning speed is 500m/min, after 3 times stretching, the diameter of carbonized carbon nanofibers is less than 200nm (Fig. 2).

The present invention adopts acetalization treatment to crosslink and cure PF. For example: measure 500ml of 37% formaldehyde, 500ml of 37% hydrochloric acid, and 20ml of ethanol, put them in a container equipped with a stirring paddle, a thermocouple and a reflux condenser, and stir evenly. Control the temperature of the solution at 20°C, add about 7g of fibers fixed on the splint, and keep at this temperature for 2hr; then use 0.5hr to raise the temperature to 40°C, and keep the temperature at this temperature for 0.5hr; then use 2hr to raise the temperature to 100°C , Constant temperature 0.5hr. After the reaction is finished, after the solution is cooled to room temperature, the fibers are taken out, washed with 8% NH ₃ ·H ₂ O solution until neutral, washed with boiling water and dried.

Uncrosslinked phenolic resin (PF) phenolic resin after crosslinking and curing

The third technology adopted in the present invention is the high temperature carbonization method. Place the nano-carbon fiber precursors prepared by the techniques 1 and 2 adopted in the present invention in the constant temperature zone of the electric heating furnace, and under the protection of _N2 , heat at a rate of 2-20°C/min at a rate of 600-1200°C. After 50-90min the temperature was lowered to room temperature.

The beneficial effects of the present invention are:

The polymer blend spinning method is a new method for preparing nano-carbon fibers. It has the advantages of simple process, uniform fiber size and high purity. Chemical production provides an economical and convenient process route. The diameter of the carbon nanofiber prepared by using the above material and method is controllable within 100-1000 nanometers, has a large specific surface area, excellent chemical stability, and a long fibrous structure.

Description of drawings

Figure 1 shows the "sea-island" structure of the polypropylene/phenolic resin blend system.

Figure 2 shows the carbon nanofibers prepared after carbonization of the blended fibers.

Figure 3 3a: Schematic diagram of the preparation process of carbon nanofibers, 3b preparation of carbon nanofibers by polymer blending.

Detailed ways

Below in conjunction with specific embodiment, further illustrate the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Example 1

Select PP with a melt index of 16g/10min as the matrix, Julong brand price 123 PF as the dispersed phase, and the blend of PF/PP=20/80 is fully mixed in a twin-screw extruder, extruded and granulated. The conventional melt spinning equipment was used for melt spinning, the spinning speed was 400m/min, and the draft ratio was 3.6. The obtained carbon nanofiber precursors were cross-linked and solidified, and then carbonized at 900°C. This carbon nanofiber has a diameter of 100-200nm.

Example 2

Using PP with a melt index of 38g/10min as the matrix, Julong brand price 123 PF as the dispersed phase, the blend of PF/PP=40/60 is fully mixed in a twin-screw extruder, extruded and granulated. The conventional melt spinning equipment was used for melt spinning, the spinning speed was 600m/min, and the draft ratio was 2.5. After cross-linking and solidifying the obtained nano-carbon fiber precursors, they are carbonized at 1000°C. The carbon nanofibers have a diameter of 300-500nm.

Example 3

Using PP with a melt index of 86g/10min as the matrix, Julong brand price 123 PF as the dispersed phase, the blend of PF/PP=50/50 is fully mixed in a twin-screw extruder, extruded and granulated. The conventional melt spinning equipment was used for melt spinning, the spinning speed was 800m/min, and the draft ratio was 1.8. The obtained carbon nanofiber precursors were cross-linked and solidified, and then carbonized at 900°C. This carbon nanofiber has a diameter of 400-700nm.

Claims (6)

1. one kind prepares the method for carbon nano-fiber with phenolic resins (PF), comprises the following steps:

(1) preparation of carbon nano-fiber precursor

With polypropylene (PP) is matrix, phenolic resins (PF) is decentralized photo, the co-mixing system of percentage by weight PF/PP=1-50/99-50 is fully mixed in double screw extruder, extruding pelletization, chip drying, blended slice is extruded through fusion and by spinneret orifice, cooling curing, oils, reels, and undrawn yarn obtains the PF/PP blended fiber through drawing-off again; Blended fiber is wanted just can become the carbon nano-fiber precursor behind the crosslinking curing: measure 35-40% formaldehyde 500-550ml, and 35-40% hydrochloric acid 500-600ml, ethanol 20-30ml stirs, and temperature 20-40 ℃, add PF/PP blended fiber 7-10g, keep 1-2hr; Be warming up to 40-50 ℃ with 0.5-1hr, constant temperature 0.5-1hr; Be warming up to 80-100 ℃ with 1-2hr, constant temperature 0.5-1hr, reaction finishes, treat that solution is cooled to room temperature after, fiber is taken out, use 8-10%NH ₃.H ₂The O solution washing is after be neutrality, and the boiling water washing is dry, makes the carbon nano-fiber precursor;

(2) carbonization of carbon nano-fiber precursor

The carbon nano-fiber precursor is fixedly placed in the electric furnace flat-temperature zone, feed N ₂Drain the air of electric furnace flat-temperature zone, connect the water cooling reflux, tail gas discharging pipe is fed to alkali lye.At N ₂Protection down is heated to 600-1200 ℃ with the speed of 2-20 ℃/min, behind the constant temperature 50-90min, stops electric furnace work, continues to feed N ₂, sample is taken out after dropping to room temperature.

2. according to the described a kind of method of using phenolic resins (PF) to prepare carbon nano-fiber of claim, it is characterized in that: the phenolic resins described in the step 1 (PF) is carbon fiber precursor (CPP), and PF is a thermoplasticity; Polypropylene is pyrolyzed-polymer (TDP).

3. according to the described a kind of method for preparing carbon nano-fiber with phenolic resins (PF) of claim, it is characterized in that: the carbon fiber precursor PF described in the step 1 is dispersed among the pyrolyzed-polymer PP with the fento form, sees it is " sea-island " structure from the fibre section.

4. according to the described a kind of method of using phenolic resins (PF) to prepare carbon nano-fiber of claim, it is characterized in that: spinning temperature one district is 190 ℃ in the melt spinning described in the step 1; Two districts are 215-220 ℃; Three districts are 230-240 ℃, four district 240-250 ℃.Spinning speed 100-1000m/min, draw ratio 2-5 are doubly.

5. according to the described a kind of method of using phenolic resins (PF) to prepare carbon nano-fiber of claim, it is characterized in that: the speed of spinning described in the step 1 is 500m/min, 4 times of draw ratios, and the carbon nano-fiber diameter that makes after the carbonization is less than 200nm.

6. according to the described a kind of method of using phenolic resins (PF) to prepare carbon nano-fiber of claim, it is characterized in that: the carbon nano-fiber diameter of preparation is in the 100-1000 nanometer, and it is big to have specific area, chemical stability, long fiber shape structure.

Images