Continuous preparation method and device of carbon fiber paper

Abstract

The invention relates to the field of manufacturing of carbon fiber paper, in particular to a continuous preparation method and device suitable for continuous carbon fiber paper. The method comprises the following steps: preliminarily dispersing different types of carbon fibers in a device, further mixing and dissociating under the action of a dispersing agent, diluting, dispersing and homogenizing to obtain stable carbon fiber slurry. Then, in a designed continuous production device, a resin net is adopted as a receiving carrier, a carbon fiber paper wet green body is formed from the slurry under the vacuum adsorption effect, and continuous carbon fiber raw paper is obtained through specific step treatment and drying. And finally, performing carbonization treatment under different conditions to obtain a final carbon fiber paper product.

Description

Technical Field

[0001] The invention relates to the technical field of carbon fiber paper, and in particular to a continuous preparation method of carbon fiber paper and a corresponding device thereof, which are particularly suitable for continuous preparation of carbon fiber paper. Background Art

[0002] GDL (gas diffusion layer for fuel cells) is a functional material that supplies hydrogen and air as fuel to the electrodes, collects electrons generated by chemical reactions on the electrodes, retains moisture in the electrolyte membrane, and discharges the generated moisture. In addition to air permeability and conductivity, it also needs to meet requirements such as acid resistance.

[0003] Carbon fiber paper is a gas diffusion layer material widely used in electrodes. It is required to have excellent conductivity, gas diffusion, drainage and mechanical properties. At the same time, in order to meet the use requirements of electrode materials, especially when used as a supporting material for gas diffusion layer electrodes in fuel cells, the current density should be uniform and no local current should be generated. Carbon fiber is required to have uniform dispersion and appropriate pore size.

[0004] Traditional papermaking processes mostly use intermittent wet papermaking processes to make carbon fiber paper wet embryos. Due to the inertness of the carbon fiber surface, high static electricity, and serious friction and entanglement problems between fibers, the uniformity of fiber dispersion is difficult to guarantee, and the efficiency is low in the actual industrialization process, and the thickness is uneven. In order to make the carbon fiber dispersed evenly, when the raw materials are pulped and dispersed, long-term high-speed shearing and stirring are required to overcome the entanglement between the fibers, especially for long fibers. However, since carbon fiber is a brittle material, long-term high-speed shearing and dispersion will cause fiber breakage and crushing, which will seriously damage the conductivity and mechanical properties of the final carbon paper product. There is also a method that discloses a process for papermaking by mixing adhesive fibers and carbon fibers at the same time, but in the actual mixing process, due to the different densities of the adhesive and organic fibers and carbon fibers, in the papermaking process, due to gravity and density reasons, the sedimentation and dispersion of organic resin fibers and carbon fibers are different, and then face the problem of uneven conductivity during carbonization and graphitization. In addition, in the current domestic intermittent preparation method of carbon fiber paper, the uniformity and permeability of resin impregnation are difficult to guarantee and the processing time is long, which affects production efficiency and product rate. There is a method of mixing resin particles and carbon fibers for compression molding, but this method will hinder the contact between the fibers, thereby affecting the mechanical properties and electrical and thermal conductivity of the carbon fiber paper. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects in the prior art, thereby providing a continuous preparation method and device for carbon fiber paper.

[0006] The present invention aims at the problems of uneven carbon fiber dispersion, insufficient resin penetration, and the inability to discontinue the production process in the existing carbon fiber paper preparation technology, and provides a method for preparing continuous carbon fiber paper. Short-cut carbon fibers are pre-dispersed, and corresponding high-efficiency dispersants are introduced. At the same time, the preparation process of carbon fiber paper wet embryos is optimized to ensure sufficient resin penetration. After carbonization and graphitization treatment, continuous preparation of carbon fiber paper with high air permeability, water permeability, high conductivity and high strength is achieved.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] A continuous preparation method of carbon fiber paper comprises the following steps:

[0009] 1. Fiber dispersion:

[0010] In the preparation process of carbon fiber paper, the dispersion of the fibers directly affects the performance of the final carbon paper cost. In the present invention, the chopped carbon fibers are initially loosened in a commercial loosening machine, and air is blown at a certain speed to destroy the friction, entanglement and bundling between the fibers. Afterwards, the carbon fibers obtained in the above steps are mixed with a solvent to obtain a slurry, which is then transferred to a high-frequency oscillating mixer for the next step of dispersion to form a stable carbon fiber slurry.

[0011] In the present invention, the diameter of the above-mentioned carbon fiber is moderately selected to be 3-10um, the number of fiber roots is 1000-600000, and the length of the carbon fiber is more appropriately between 2mm-20mm, preferably between 3-10mm. The longer the fiber length, the more contact points between the fibers, which will be more conducive to conductivity and mechanical properties.

[0012] In the present invention, the gas flow rate is 0.01L-10L / min.

[0013] In the present invention, the fiber content accounts for 0.1%-20% of the solvent content.

[0014] In the present invention, the oscillation direction may be up and down, rotational and circular motion, and preferably oscillates in a circular direction to achieve sufficient relief.

[0015] In the present invention, the loosening time is selected between 5min-180min, preferably between 10min-45min, and more preferably between 15min-30min, so as to ensure sufficient loosening while reducing damage to fibers, improving production efficiency and reducing energy consumption.

[0016] In the present invention, the preparation of the carbon fiber dispersion usually adopts a high molecular polymer or a surfactant as a dispersing aid, a defoaming agent and a binder. Polyvinyl alcohol, polyacrylamide, polyethylene oxide, modified polyacrylamide, starch, Tween 80, cellulose, nanocellulose, cyclodextrin, chitosan, etc. can be selected, or two or more of them are compounded and used, and the amount is controlled at 0.01%-20% of the mass of the dispersion to adjust the viscosity of the slurry, preferably controlled at 0.01%-10% of the mass of the dispersion.

[0017] In the present invention, the solvent can be deionized water, methanol, ethanol, etc. to ensure that the fiber dispersing aid is fully dissolved, or it can be a combination of several solvents. Deionized water is more preferred, and water-soluble polymers are selected as dispersing aids to effectively promote fiber dispersion while reducing costs. In this process, the aid can be heated and dissolved according to actual conditions.

[0018] 2. Carbon fiber green paper forming:

[0019] In the present invention, the slurry preliminarily dispersed in step 1 is transferred to a stirring barrel for further dispersion and stirring. The stirring time is 10-200 min and the stirring rate is 200-3000 r. In order to prevent the fiber from being damaged, the preferred stirring time is 20 min-60 min and the stirring rate is 1800-2500 r. The room temperature is controlled at 25-30 degrees Celsius.

[0020] The present invention also provides a device for forming carbon fiber green paper from slurry.

[0021] The stirred slurry is pumped into the device for flow spreading and forming. The output is controlled according to the thickness of the paper. This process requires a forming net to support the carbon fiber slurry. At the same time, since vacuum assistance is required to remove excess solvents and adhesives through vacuum suction, it is necessary to select a suitable forming net.

[0022] In the present invention, polyester fiber filter screen, polytetrafluoroethylene screen, nylon screen and other high temperature resistant screens, or stainless steel screen or filter paper coated with hydrophobic coating are used, and the mesh size is 100-2000 mesh. The thickness of the filter screen is selected according to the needs of the device. In the present invention, polytetrafluoroethylene screen, nylon screen and filter paper are preferably used, and the mesh size is preferably 200-1000 mesh. The line speed is 0.01-5M / min.

[0023] In the present invention, the vacuum-formed carbon fiber wet embryo needs to be further dried, and the drying temperature in the drying zone of the device is controlled at 70-100 degrees Celsius according to the solvent selection, the drying time is 5-100 minutes, and the line speed is 0.01-5M / min.

[0024] 3. Resin impregnation and curing molding

[0025] In the present invention, in order to improve the carbon yield and thus improve the electrical conductivity and thermal conductivity of the final product, phenolic resin, modified phenolic resin, melamine resin, condensed polynuclear aromatic resin, polyester resin, etc. are used; or a suitable solvent is selected as needed for compounding. In the present invention, phenolic resin, or phenolic resin and aromatic resin are preferably used in compound. In addition, in order to further improve the electrical conductivity and thermal conductivity of carbon fiber paper, as well as the bonding compactness between the resin and the carbon fiber green embryo, according to the method proposed in patent CN118702907A, a carbon nanotube auxiliary agent can be added to the resin dispersion to assist in improving the electrical conductivity and thermal conductivity of the carbon fiber paper.

[0026] In the present invention, the concentration of the resin dispersion is controlled at 1%-30%. In order to achieve a suitable pore size distribution, reduce water flooding, and improve gas permeability, the resin concentration should not be too high, and is preferably selected at a concentration of 5%-10%. The amount of carbon nanotube dispersion is preferably 0.05%-2% / resin amount.

[0027] The present invention also provides a continuous resin spray device, which is used to be connected to the tail end of the continuous carbon fiber raw paper preparation device. This device can be adjusted according to the needs and the forming width of the carbon fiber paper. At the same time, the flow rate and flow rate at the nozzle can be adjusted to achieve sufficient infiltration and meet the gas permeability requirements of the carbon paper finished product.

[0028] In the device provided by the present invention, in order to better demold and peel the carbon fiber paper, the carbon fiber raw paper obtained in step 2 needs to be covered with a release film on the upper and lower surfaces by traction rollers after being sprayed with resin. The release film can be a high temperature resistant polyester film, or a polyurethane film or a film coated with a surface modifier such as polytetrafluoroethylene. In order to ensure that the resin fully penetrates into the interior of the carbon fiber, the resin is fully infiltrated under the pressure of the pressure roller, and the excess resin and solvent are removed at the same time.

[0029] In the present invention, the pressure of the pressing roller is set to 0.1-5MPa, and the temperature of the pressing roller is set to 40-90 degrees Celsius, preferably 0.2-5MPa and the temperature is 50-70 degrees Celsius.

[0030] After passing through the spray device, the formed carbon fiber paper is cured and formed. The appropriate curing temperature and parameters are selected according to the properties of the resin. In the present invention, phenolic resin is preferably selected as the high carbon yield resin, and the curing temperature is between 120-150 degrees Celsius. The curing time is 10-180 minutes according to the line speed, and the pressure is adjusted to 0.3-2MPa.

[0031] 4. Carbonization and graphitization:

[0032] In the present invention, the carbon fiber paper obtained in step 3 needs to be further carbonized under an inert gas and graphitized at a corresponding temperature to form a graphite structure, so as to improve the electrical conductivity and heat resistance to adapt to the use temperature and place of use.

[0033] The present invention provides a carbonization and graphitization device for continuously preparing carbon paper, so as to achieve the purpose of stably and continuously producing high-quality carbon fiber paper. In this device, two upper and lower waste film collection devices are provided to recycle the release film in the peeling step 3. The carbon fiber paper enters different heating temperature zones at a certain transmission speed. This device is provided with four temperature zones for processing carbon paper, which can be closed or started according to performance requirements. A winding device is provided at the rear section for subsequent storage and cutting.

[0034] In the present invention, the temperature of temperature zone 1 is selected at 150-300 degrees Celsius, the residence time is 5-120 minutes, preferably set at 200-250 degrees Celsius, and the residence time is 1-60 minutes according to the wiring speed. The temperature of temperature zone 2 is set at 350-800 degrees Celsius, the residence time is selected at 5-60 minutes, preferably, set at 550-650 degrees Celsius. The temperature of temperature zone 3 is set at 900-1800 degrees Celsius, preferably, 1200-1500 degrees Celsius is selected, and the residence time is 1-60 minutes. The temperature of temperature zone 4 is selected at 2000-3000 degrees Celsius, preferably, the temperature range is 2200-2800 degrees Celsius, and the residence time is 1-100 minutes according to the wiring speed.

[0035] In the present invention, the inert gas may be argon or nitrogen, the inlet pressure may be 1-10 bar, and the gas flow rate may be 2-300 L / min. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Description of reference numerals:

[0038] Figure 1 Schematic diagram of the initial loose dispersion process of carbon fibers;

[0039] Figure 2 Continuous carbon paper raw paper preparation device;

[0040] Figure 3 Continuous resin spraying device;

[0041] Figure 4Carbonization and graphitization device for continuous preparation of carbon paper. DETAILED DESCRIPTION

[0042] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0044] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0046] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A continuous preparation method of carbon fiber paper, characterized in that: The following steps are involved: S1: fiber dispersion; The carbon fiber is chopped, and the chopped carbon fiber is loosened initially by a commercial loosening machine, and air at a certain speed is applied for blowing treatment, and then the treated carbon fiber is mixed with a solvent to obtain a slurry, and the slurry is transferred to a high-frequency oscillation mixer for dispersion to obtain a stable carbon fiber slurry; S2: Carbon fiber green paper forming; The stabilized carbon fiber slurry in step S1 is moved to a stirring barrel for further dispersion and stirring, and then the stirred carbon fiber slurry is sent to a carbon fiber green paper forming device for flow spreading and forming. During the flow spreading and forming, the carbon fiber slurry is supported by a forming net, and then vacuum filtered to form a carbon fiber wet embryo, and the carbon fiber wet embryo is transported to a drying area of ​​the device for drying to form a carbon fiber green paper; S3: resin impregnation and curing molding; spraying the carbon fiber green paper obtained in step S2 with resin, connecting the resin spraying device to the tail end of the carbon fiber green paper forming device, pulling the release film through the traction roller to fully infiltrate the dissolved resin under the pressure of the pressure roller, removing excess resin and solvent, and then selecting appropriate curing temperature and parameters for curing; S4: carbonization and graphitization; the release film of the carbon fiber paper in the peeling step S3 is recovered by the carbonization graphitization device, and then the carbon fiber paper is conveyed to different temperature zones in the carbonization graphitization device at a certain speed, and finally rolled up and stored by the winding device of the carbonization graphitization device.

2. The method according to claim 1, characterized in that In step S1, the diameter of the carbon fiber is 3-10 um, the number of fibers is 1000-600000, and the length of the carbon fiber is 2 mm-20 mm; The moving speed of the air is 0.01L-10L / min; The fiber content accounts for 0.1%-20% of the solvent content; The initial loosening time is 5-180min; The solvent is deionized water, methanol or ethanol.

3. The method according to claim 1, characterized in that In step S2, the dispersion stirring is further performed for 10-200 min, and the stirring rate is 200-3000 r; The forming mesh is a high temperature resistant mesh such as polyester fiber filter mesh, polytetrafluoroethylene mesh, nylon mesh, or a stainless steel mesh or filter paper coated with a hydrophobic coating, with a mesh size of 100-2000 meshes and a line speed of 0.01-5m / min; The drying temperature is 70-100 degrees Celsius, the drying time is 5-100 minutes, and the line speed is 0.01-5m / min.

4. The method according to claim 1, characterized in that: In step S3, the release film is a high temperature resistant polyester film, a polyurethane film or a film coated with a surface modifier such as polytetrafluoroethylene; The pressure of the roller is set to 0.1-5MPa, and the temperature of the roller is set to 40-90 degrees Celsius; The curing temperature is 120-150 degrees Celsius, the curing time is 10-180 minutes, and the pressure is 0.3-2MPa.

5. The method according to claim 1, characterized in that In step S4, the carbonization and graphitization device is provided with 4 temperature zones, temperature zone 1 is filled with inert gas, the temperature of temperature zone 1 is 150-300 degrees Celsius, and the residence time of the carbon fiber paper is 5-120 minutes; The temperature in temperature zone 2 is 350-800 degrees Celsius, and the residence time of the carbon fiber paper is 5-60 minutes; The temperature in temperature zone 3 is 900-1800 degrees Celsius, and the residence time of the carbon fiber paper is 1-60 minutes; The temperature in temperature zone 4 is 2000-3000 degrees Celsius, and the residence time of the carbon fiber paper is 1-100 minutes; The inert gas is argon or nitrogen, the inlet pressure is 1-10 bar, and the gas flow rate is 2-300 L / min.

6. A continuous preparation device for carbon fiber paper, characterized in that: The device is used to implement the method described in claims 1-5, and includes a carbon fiber green paper forming device, a resin spraying device and a graphitization device. The carbon fiber green paper forming device is used to process the slurry into carbon fiber green paper, the resin spraying device is used to spray the carbon fiber green paper with resin and discharge the excess resin and solvent inside the carbon fiber, and the graphitization device is used to recover the release film and carbonize and graphitize the carbon fiber paper.

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