Carbon fiber raw paper for fuel cell and method for manufacturing the same

Abstract

The application relates to the technical field of paper for fuel cells, and particularly discloses carbon fiber raw paper for fuel cells and a preparation method thereof, which comprises the following components: 100 parts (70-95 parts of short-cut carbon fibers and 5-30 parts of water-soluble fibers) of fibers, 40-50 parts of dispersant A, 50-100 parts of dispersant B and 0.5-1 part of defoaming agent; after the short-cut carbon fibers and the water-soluble fibers are defibrated, the dispersant A is added for mixing and high-speed stirring to complete foam dispersion, water is added for dilution to first-concentration carbon fiber slurry; the defoaming agent is added for first-time stirring to obtain carbon fiber dispersion slurry; the remaining dispersant A and the dispersant B are added for second-time stirring, water is added for dilution to second-concentration carbon fiber slurry; the second-concentration carbon fiber slurry is used for papermaking to obtain the carbon fiber raw paper for fuel cells. The carbon fibers are prone to occur in the dispersion process, the phenomenon of silk and flocculation is solved, the paper uniformity is good, the tensile strength is high, the carbon fiber raw paper for fuel cells is used for fuel cells, and the important index requirements of porosity and resistance and the like are met.

Description

Technical Field

[0001] This invention relates to the field of paper technology for fuel cells, and specifically to a carbon fiber base paper for fuel cells and its preparation method. Background Technology

[0002] A fuel cell is a power generation device that efficiently and environmentally friendly converts the chemical energy stored in fuel and oxidant into electrical energy directly without combustion through an electrochemical reaction. Among various types of fuel cells, proton exchange membrane fuel cells are widely recognized as the preferred clean and efficient power generation device for the 21st century.

[0003] Carbon paper for proton exchange membrane fuel cells, as a high-performance carbon fiber paper, is produced by wet-processing to form carbon fiber paper base paper, followed by resin impregnation, hot pressing, and carbonization. Short-cut carbon fibers are formed by cutting bundles of carbon fiber filaments. During dispersion, they are prone to filament agglomeration and flocculation. The uniformity of dispersion directly affects the paper's uniformity and important performance indicators such as porosity and resistivity, especially for carbon fibers longer than 10mm. Based on the aggregation factor theory, at the same wire density, the aggregation factor N of 12mm carbon fiber is 4 times that of 6mm carbon fiber and 16 times that of 3mm carbon fiber. Therefore, how to minimize fiber agglomeration and achieve optimal dispersion of carbon fibers during the production of carbon fiber base paper is a crucial problem that needs to be solved. Summary of the Invention

[0004] To address the aforementioned problems, one objective of this invention is to provide a method for preparing carbon fiber base paper for fuel cells. The method involves adding a polymeric surfactant to an aqueous dispersion system of carbon fibers, and mechanically stirring to generate dense foam. This foam adheres to the surface of the carbon fibers, ensuring uniform dispersion. An antifoaming agent is then added to the dispersion system to eliminate most of the foam. A dispersant is added again, and the synergistic effect of the dispersant and antifoaming agent further stabilizes the carbon fiber dispersion. The paper is then wet-processed using a wire mesh paper machine to form the final carbon fiber base paper for fuel cells. This method solves the problem of carbon fibers easily agglomerating and flocculating during dispersion, directly affecting the uniformity and tensile strength of the base paper, thus impacting important performance indicators such as porosity and electrical resistance.

[0005] The second objective of this invention is to provide a carbon fiber base paper for fuel cells, which has the characteristics of good uniformity and high tensile strength, and is used in fuel cells to meet the requirements of important indicators such as porosity and electrical resistance.

[0006] The first technical solution adopted in this invention is: a method for preparing carbon fiber base paper for fuel cells, comprising the following steps:

[0007] Step 1: Weigh the raw materials, which include 100 parts of fiber, 40-50 parts of dispersant A, 50-100 parts of dispersant B and 0.5-1 parts of defoamer. The fiber includes 70-95 parts of chopped carbon fiber and 5-30 parts of water-soluble fiber.

[0008] Step 2: After the short-cut carbon fibers and water-soluble fibers are loosened, 8-10 parts of dispersant A are added and mixed. The mixture is stirred at high speed to complete the foam dispersion. Water is added to dilute the mixture to obtain the first concentration carbon fiber slurry.

[0009] Step 3: Add defoamer to the carbon fiber slurry of the first concentration and stir for the first time to obtain carbon fiber dispersion slurry;

[0010] Step 4: Add the remaining dispersant A and dispersant B to the carbon fiber dispersion slurry, stir for a second time, dilute with water, and obtain a carbon fiber slurry of the second concentration;

[0011] Step 5: The second concentration carbon fiber slurry is used for papermaking to obtain carbon fiber base paper for fuel cells.

[0012] Preferably, the chopped carbon fibers include one or more of polyacrylonitrile-based carbon fibers and pitch-based carbon fibers;

[0013] The chopped carbon fibers have a diameter of 7-17 μm and a length of 5-15 mm.

[0014] Preferably, the water-soluble fiber includes one or more of polyvinyl alcohol water-soluble fiber and carboxymethyl cellulose fiber;

[0015] The water-soluble fiber has a length of 3-5 mm.

[0016] Preferably, the dispersant A is a styrene-maleic anhydride copolymer dispersant with a mass concentration of 0.2%.

[0017] The dispersant B is one or more of polyethylene oxide and polyacrylamide, with a mass concentration of 0.2%.

[0018] Preferably, the defoamer is one or more of silicone defoamers and polyether defoamers.

[0019] Preferably, the conditions for high-speed stirring are: stirring speed 2000-3500 r / min, time 5-15 min;

[0020] The conditions for the first stirring are: stirring speed 300-1000 r / min;

[0021] The conditions for the second stirring are: stirring speed 30-50 r / min.

[0022] Preferably, the mass percentage concentration of the first concentration carbon fiber slurry is 1.2% to 1.5%;

[0023] The second concentration of carbon fiber slurry has a mass percentage concentration of 0.1% to 0.4%.

[0024] Preferably, the papermaking process includes: forming, pressing and dehydration, drying in a drying cylinder, spraying and peeling, and winding;

[0025] The drying conditions for the drying cylinder are: 80-105℃;

[0026] The spraying stripping conditions are: mineral oil descaling agent.

[0027] The second technical solution adopted in this invention is: a carbon fiber base paper for fuel cells.

[0028] Preferably, the basis weight of the carbon fiber base paper for fuel cells is 15 g / m³. 2 ~80g / m 2 .

[0029] The beneficial effects of the above technical solution are as follows:

[0030] (1) The present invention uses an amphiphilic dispersant to generate dense foam, which avoids phenomena such as filament bundling and agglomeration when dispersing carbon fibers, so that the carbon fibers are evenly dispersed in water and present as single-fiber dispersed state as much as possible. This provides the best dispersion state of carbon fiber slurry for subsequent papermaking, and solves the problem that carbon fibers are very easy to filament bundling and agglomeration during the dispersion process, which directly affects the uniformity and tensile strength of the base paper, and thus affects the porosity, electrical resistance and other important performance indicators of the paper.

[0031] (2) This invention addresses the problem that carbon fibers, which are solid phases in multiphase fluids, are prone to flocculation, dispersion, and re-flocculation during the pumping process due to the different rheological properties of foam and water. Based on the synergistic effect between SMA dispersant and defoamer, the dispersant is added in two parts (the first part is added in a high-speed stirring dispersion tank, and the second part is added in the pre-coating pool). Defoamer is used to selectively eliminate the larger foams that drive the carbon fibers to re-agglomerate, thus avoiding the phenomenon of carbon fibers re-agglomerating in unstable water-based foam systems due to pumping, and effectively improving the uniformity and tensile strength of carbon fiber base paper.

[0032] (3) Compared with the traditional wet forming method, the preparation method provided by the present invention can greatly reduce the phenomena that affect paper uniformity and other key indicators, such as filament bundling and agglomeration.

[0033] (4) The carbon fiber base paper for fuel cells provided by the present invention has the characteristics of good uniformity and high tensile strength. When further used in the field of fuel cells, it meets the requirements of important indicators such as uniformity, porosity and resistance. It is a carbon fiber base paper that meets the standards for use in the field of fuel cells. Attached Figure Description

[0034] Figure 1 A process flow diagram of the preparation method of carbon fiber base paper for fuel cells provided by the present invention;

[0035] Figure 2 This is a process flow diagram of the preparation method of carbon fiber base paper for fuel cells provided in Embodiment 1 of the present invention. Detailed Implementation

[0036] The embodiments of this application will be described in further detail below. Obviously, the described embodiments are only a part of the embodiments of this application, and not an exhaustive list of all embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0037] The terms “first,” “second,” etc. (if applicable) in the specification and claims are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data used in this way can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion, such as a process, method, system, product, or apparatus that comprises a series of steps or units, not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0038] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0039] This invention provides a method for preparing carbon fiber base paper for fuel cells, comprising the following steps:

[0040] Step 1: Weigh the raw materials, including 100 parts of fiber, which comprises 70-95 parts of chopped carbon fiber and 5-30 parts of water-soluble fiber; also including components by total fiber weight: 40-50 parts of dispersant A, 50-100 parts of dispersant B, and 0.5-1 part of defoamer; preferably, the chopped carbon fiber comprises one or more of polyacrylonitrile-based carbon fiber and pitch-based carbon fiber, with a diameter of 7-17 μm and a length of 5-15 mm. The water-soluble fiber comprises one or more of polyvinyl alcohol water-soluble fiber and carboxymethyl cellulose fiber; the length of the water-soluble fiber is 3-5 mm. Dispersant A is a styrene-maleic anhydride copolymer dispersant (SMA dispersant) with a mass concentration of 0.2%; dispersant B is one or more of polyethylene oxide and polyacrylamide with a mass concentration of 0.2%. The defoamer is one or more of organosilicon defoamer and polyether defoamer.

[0041] Step 2: After dispersing the chopped carbon fibers and water-soluble fibers, add 8-10 parts of dispersant A and mix. Stir at high speed (2000-3000 r / min, 5-15 min) to complete foam dispersion. Dilute with water to obtain a first-concentration carbon fiber slurry (mass percentage concentration of 1.2%-1.5%). The purpose of the first high-speed stirring is to generate dense foam in the dispersion system. Because the dispersant used is amphiphilic and has a high viscosity, it can effectively reduce the surface tension of the liquid phase in the dispersion system. After high-speed stirring, dense and stable foam is formed. During this process, the foam acts as a carrier to support the fibers. Because the foam shape is close to spherical, the large surface area of ​​the foam allows the filamentous carbon fiber raw material to be dispersed evenly. Furthermore, the presence of foam reduces fiber collisions, overlaps, and flocculation, allowing the carbon fibers to remain as dispersed as possible even at higher concentrations.

[0042] Step 3: Add defoamer to the carbon fiber slurry of the first concentration and perform the first stirring (stirring speed 300-1000 r / min) to obtain carbon fiber dispersion slurry. Since the large amount of dense foam in the slurry after the first stirring is very easy to break during the pumping process, the fibers will accumulate in the pipeline and pump, causing blockage and unstable flow control. At the same time, as time goes by, the dense foam will generate bubble aggregation under the mutual collision. The large bubbles formed will cause the single dispersed carbon fibers to flocculate again. Therefore, after uniform dispersion, an appropriate amount of defoamer is added. The SMA dispersant changes the half-life of the bubbles in the slurry, causing the larger bubbles in the slurry to break, retaining the small bubbles that are beneficial to fiber dispersion, increasing the fluidity of the slurry and maintaining the good dispersion of carbon fibers.

[0043] Step 4: Add the remaining dispersant A and dispersant B to the carbon fiber dispersion slurry, and stir for the second time (stirring speed 30-50 r / min). Dilute with water to obtain a second concentration carbon fiber slurry (mass percentage concentration of 0.1% to 0.4%). The second stirring further reduces the concentration of the slurry. At the same time, dispersant A and dispersant B are added. The amphiphilic dispersant A uniformly coats the surface of the carbon fibers that have been dispersed in the first step. The slurry is uniformly dispersed through intermolecular repulsion and hydrophilic properties. Meanwhile, dispersant B increases the viscosity of the slurry and increases the resistance to free flow of the fibers, so that the entire dispersion system remains in a stable suspension state.

[0044] Step 5: The second concentration of carbon fiber slurry is formed on an inclined wire paper machine to obtain carbon fiber base paper for fuel cells.

[0045] The papermaking process includes: forming, pressing and dehydration, drying in a drying cylinder at 80-105℃, spraying and peeling with a mineral oil desiccant, and winding to obtain a weight of 15g / m³. 2 ~80g / m 2 This is a carbon fiber base paper for fuel cells. Since there is no bonding force between carbon fibers, a certain proportion of water-soluble fiber is added to solidify the carbon fibers and ensure the paper's strength. The water-soluble fiber dissolves in water under certain temperature and humidity conditions and disperses evenly in the wet paper web. When the temperature is further increased to dry the moisture, the water-soluble fiber can precipitate and solidify, providing bonding strength to the carbon fibers. However, due to its strong adhesive force, a mineral oil release agent needs to be sprayed during peeling to completely peel the paper. Without adding a release agent to the drying cylinder, the paper will stick to the cylinder and cannot be formed.

[0046] Example 1

[0047] Step 1: Weigh the raw materials: 95 parts short-cut carbon fiber (polyacrylonitrile-based carbon fiber) and 5 parts water-soluble fiber (polyvinyl alcohol water-soluble fiber);

[0048] It also includes components based on the total weight of the fibers: 50 parts dispersant A (SMA dispersant, mass concentration of 0.2%), 100 parts dispersant B (polyoxyethylene, mass concentration of 0.2%), and 0.5 parts defoamer (commercially available silicone defoamer).

[0049] Step 2: After disintegrating the short-cut carbon fibers and water-soluble fibers, add 10% dispersant A and mix. Stir at high speed (stirring speed 2800 r / min, time 15 min) to complete foam dispersion. Add water to dilute and obtain carbon fiber slurry of the first concentration (concentration is 1.2%).

[0050] Step 3: Add defoamer to the carbon fiber slurry of the first concentration and stir for the first time (stirring speed 850 r / min) to obtain carbon fiber dispersion slurry;

[0051] Step 4: Add the remaining dispersant A and dispersant B to the carbon fiber dispersion slurry, stir for the second time (stirring speed 30 r / min), dilute with water to obtain a second concentration carbon fiber slurry (concentration of 0.1%).

[0052] Step 5: The second concentration of carbon fiber slurry is formed on an inclined wire paper machine to obtain carbon fiber base paper for fuel cells.

[0053] The papermaking process includes: forming, pressing and dehydration, drying in a drying cylinder at 105℃, spraying and peeling with a mineral oil desiccant, and winding to obtain a weight of 30g / m³. 2 Carbon fiber base paper for fuel cells.

[0054] Example 2

[0055] Step 1: Weigh the raw materials: 75 parts short-cut carbon fiber (pitch-based carbon fiber) and 25 parts water-soluble fiber (a combination of polyvinyl alcohol water-soluble fiber and carboxymethyl cellulose fiber in a ratio of 3:2).

[0056] It also includes components by total fiber weight: 42 parts dispersant A (SMA dispersant, mass concentration of 0.2%), 50 parts dispersant B (polyacrylamide, mass concentration of 0.2%), and 1 part defoamer (commercially available polyether defoamer).

[0057] Step 2: After disintegrating the short-cut carbon fibers and water-soluble fibers, add Dispersant A and mix. Stir at high speed (stirring speed 2200 r / min, time 10 min) to complete foam dispersion. Add water to dilute and obtain carbon fiber slurry of the first concentration (concentration is 1.5%).

[0058] Step 3: Add defoamer to the carbon fiber slurry of the first concentration and stir for the first time (stirring speed 500 r / min) to obtain carbon fiber dispersion slurry;

[0059] Step 4: Add the remaining dispersant A and dispersant B to the carbon fiber dispersion slurry, stir for the second time (stirring speed 35 r / min), dilute with water to obtain a second concentration carbon fiber slurry (concentration of 0.1%).

[0060] Step 5: The second concentration of carbon fiber slurry is formed on an inclined wire paper machine to obtain carbon fiber base paper for fuel cells.

[0061] The papermaking process includes: forming, pressing and dehydration, drying in an 85℃ drying cylinder, spraying and peeling with a mineral oil desiccant, and winding to obtain a weight of 45g / m³. 2 Carbon fiber base paper for fuel cells.

[0062] Example 3

[0063] Step 1: Weigh the raw materials: 85 parts short-cut carbon fiber (a combination of polyacrylonitrile-based carbon fiber and pitch-based carbon fiber in a ratio of 8:2) and 15 parts water-soluble fiber (carboxymethyl cellulose fiber).

[0064] It also includes components by total fiber weight: 45 parts dispersant A (SMA dispersant, mass concentration of 0.2%), 85 parts dispersant B (a combination of polyethylene oxide and polyacrylamide in a 5:5 ratio, mass concentration of 0.2%), and 1 part defoamer (a combination of commercially available silicone defoamer and polyether defoamer in a 5:5 ratio).

[0065] Step 2: After disintegrating the short-cut carbon fibers and water-soluble fibers, add 10% dispersant A and mix. Stir at high speed (stirring speed 2600 r / min, time 5 min) to complete foam dispersion. Add water to dilute and obtain carbon fiber slurry of the first concentration (concentration is 1.3%).

[0066] Step 3: Add defoamer (a combination of commercially available silicone defoamer and polyether defoamer in a 5:5 ratio) to the carbon fiber slurry of the first concentration, and stir for the first time (stirring speed 300 r / min) to obtain carbon fiber dispersion slurry;

[0067] Step 4: Add the remaining dispersant A and dispersant B to the carbon fiber dispersion slurry, stir for the second time (stirring speed 40 r / min), dilute with water to obtain a second concentration carbon fiber slurry (concentration of 0.4%).

[0068] Step 5: The second concentration of carbon fiber slurry is formed on an inclined wire paper machine to obtain carbon fiber base paper for fuel cells.

[0069] The papermaking process includes: forming, pressing and dehydration, drying in a 98℃ drying cylinder, spraying and peeling with a mineral oil desiccant, and winding to obtain a weight of 80g / m³. 2 Carbon fiber base paper for fuel cells.

[0070] Example 4

[0071] Step 1: Weigh the raw materials: 88 parts of short-cut carbon fiber (a combination of polyacrylonitrile-based carbon fiber and pitch-based carbon fiber in a ratio of 7:3) and 12 parts of water-soluble fiber (polyvinyl alcohol water-soluble fiber).

[0072] It also includes components by total fiber weight: 45 parts dispersant A (SMA dispersant, mass concentration of 0.2%), 85 parts dispersant B (a combination of polyethylene oxide and polyacrylamide in a 5:5 ratio, mass concentration of 0.2%), and 1 part defoamer (a combination of commercially available silicone defoamer and polyether defoamer in a 5:5 ratio).

[0073] Step 2: After disintegrating the short-cut carbon fibers and water-soluble fibers, add 10% dispersant A and mix. Stir at high speed (stirring speed 2600 r / min, time 5 min) to complete foam dispersion. Add water to dilute and obtain carbon fiber slurry of the first concentration (concentration is 1.3%).

[0074] Step 3: Add defoamer (a combination of commercially available silicone defoamer and polyether defoamer in a 5:5 ratio) to the carbon fiber slurry of the first concentration, and stir for the first time (stirring speed 300 r / min) to obtain carbon fiber dispersion slurry;

[0075] Step 4: Add the remaining dispersant A and dispersant B to the carbon fiber dispersion slurry, stir for the second time (stirring speed 40 r / min), dilute with water to obtain a second concentration carbon fiber slurry (concentration of 0.4%).

[0076] Step 5: The second concentration of carbon fiber slurry is formed on an inclined wire paper machine to obtain carbon fiber base paper for fuel cells.

[0077] The papermaking process includes: forming, pressing and dehydration, drying in a 98℃ drying cylinder, spraying and peeling with a mineral oil desiccant, and winding to obtain a weight of 15g / m³. 2 Carbon fiber base paper for fuel cells.

[0078] Example 5

[0079] Step 1: Weigh the raw materials: 90 parts of short-cut carbon fiber (polyacrylonitrile-based carbon fiber) and 10 parts of water-soluble fiber (polyvinyl alcohol water-soluble fiber);

[0080] It also includes components by total fiber weight: 48 parts dispersant A (SMA dispersant, mass concentration 0.2%), 95 parts dispersant B (polyoxyethylene, mass concentration 0.2%), and 1 part defoamer (commercially available silicone defoamer).

[0081] Step 2: After disintegrating the short-cut carbon fibers and water-soluble fibers, add 10% dispersant A and mix. Stir at high speed (stirring speed 3000 r / min, time 12 min) to complete foam dispersion. Dilute with water to obtain carbon fiber slurry of the first concentration (concentration is 1.4%).

[0082] Step 3: Add defoamer (commercially available silicone defoamer) to the carbon fiber slurry of the first concentration, and perform the first stirring (stirring speed 600 r / min) to obtain carbon fiber dispersion slurry;

[0083] Step 4: Add the remaining dispersant A and dispersant B to the carbon fiber dispersion slurry, stir for the second time (stirring speed 50 r / min), dilute with water to obtain a second concentration carbon fiber slurry (concentration of 0.18%).

[0084] Step 5: The second concentration of carbon fiber slurry is formed on an inclined wire paper machine to obtain carbon fiber base paper for fuel cells.

[0085] The papermaking process includes: forming, pressing and dehydration, drying in a drying cylinder at 102℃, spraying and peeling with a mineral oil desiccant, and winding to obtain a weight of 75g / m³. 2 Carbon fiber base paper for fuel cells.

[0086] Comparative Example 1

[0087] Step 1: Weigh the raw materials: 95 parts short-cut carbon fiber (polyacrylonitrile-based carbon fiber) and 5 parts water-soluble fiber (polyvinyl alcohol water-soluble fiber);

[0088] It also includes components based on the total weight of the fibers: 90 parts dispersant (polyoxyethylene, mass concentration 0.2%), 1 part defoamer (commercially available silicone defoamer).

[0089] Step 2: After disintegrating the short-cut carbon fibers and water-soluble fibers, dilute them with water to obtain the first concentration carbon fiber slurry (concentration of 1.2%).

[0090] Step 3: Add the dispersant and defoamer to the carbon fiber dispersion slurry, stir for the second time (stirring speed 30 r / min), dilute with water to obtain a second concentration carbon fiber slurry (concentration of 0.2%);

[0091] Step 5: The second concentration of carbon fiber slurry is formed on an inclined wire paper machine to obtain carbon fiber base paper for fuel cells.

[0092] The papermaking process includes: forming, pressing and dehydration, drying in a drying cylinder at 105℃, spraying and peeling with a mineral oil desiccant, and winding to obtain a weight of 30g / m³. 2 Carbon fiber base paper for fuel cells.

[0093] Comparative Example 2

[0094] Step 1: Weigh the raw materials: 88 parts of short-cut carbon fiber (a combination of polyacrylonitrile-based carbon fiber and pitch-based carbon fiber in a ratio of 7:3) and 12 parts of water-soluble fiber (polyvinyl alcohol water-soluble fiber).

[0095] It also includes components by total fiber weight: 45 parts dispersant A (SMA dispersant, mass concentration of 0.2%) and 85 parts dispersant B (a combination of polyethylene oxide and polyacrylamide in a 5:5 ratio, mass concentration of 0.2%).

[0096] Step 2: After disintegrating the short-cut carbon fibers and water-soluble fibers, add 10% dispersant A and mix. Stir at high speed (stirring speed 2600 r / min, time 5 min) to complete foam dispersion. Add water to dilute and obtain carbon fiber slurry of the first concentration (concentration is 1.3%).

[0097] Step 3: Reduce the stirring speed and perform the first stirring (stirring speed 300r / min) to obtain carbon fiber dispersion slurry;

[0098] Step 4: Add the remaining dispersant A and dispersant B to the carbon fiber dispersion slurry, stir for the second time (stirring speed 40 r / min), dilute with water to obtain a second concentration carbon fiber slurry (concentration of 0.4%).

[0099] Step 5: The second concentration of carbon fiber slurry is formed on an inclined wire paper machine to obtain carbon fiber base paper for fuel cells.

[0100] The papermaking process includes: forming, pressing and dehydration, drying in a 98℃ drying cylinder, spraying and peeling with a mineral oil desiccant, and winding to obtain 15g / m³. 2 Carbon fiber base paper for fuel cells.

[0101] Performance testing of carbon fiber base paper for fuel cells

[0102] The tensile strength of the carbon fiber base paper for fuel cells in Examples 1-4 and Comparative Example 1 was tested according to GB / T12914-2018, and the uniformity index of Examples 1-4 and Comparative Example 1 was tested using an Optest micro-scanner (uniformity and dust analyzer). The test results are shown in Table 1 below.

[0103] Table 1 Performance of carbon fiber base paper for fuel cells

[0104]

[0105] According to Table 1, the carbon fiber base paper for fuel cells prepared using the method provided by this invention exhibits good uniformity and strength that meets the requirements of subsequent impregnation and other processing techniques. Performance analysis of Example 1 and Comparative Example 1 shows that the addition of SMA dispersant and the generation of dense foam significantly improve the dispersion effect of carbon fibers. Performance analysis of Example 4 and Comparative Example 2 shows that there is a unique synergistic effect between SMA dispersant and defoamer; the foam generated by SMA dispersant, after modification by defoamer, positively promotes the uniform dispersion of carbon fibers.

[0106] The above data demonstrates that this invention uses an amphiphilic dispersant to generate dense foam, avoiding phenomena such as fiber agglomeration and filament twisting during carbon fiber dispersion. This ensures uniform dispersion of carbon fibers in water, maintaining a single-fiber dispersion state as much as possible. This provides the optimal dispersion state for subsequent papermaking, solving the problem of carbon fiber agglomeration and flocculation during dispersion, which directly affects the uniformity and tensile strength of the base paper, thus impacting important performance indicators such as porosity and resistivity. This invention addresses the problem of carbon fibers, as a solid phase, easily undergoing flocculation-dispersion-re-flocculation in multiphase fluids during pumping due to the different rheological properties of foam and water. Based on the synergistic effect between SMA dispersant and defoamer, the dispersant is added in two stages (first in a high-speed stirring dispersion tank, then in the pre-papermaking tank), and a defoamer is used to selectively eliminate larger foams that drive carbon fiber re-agglomeration. This prevents carbon fibers from re-agglomerating in an unstable water-based foam system due to pumping, effectively improving the uniformity and tensile strength of the carbon fiber base paper. Compared with traditional wet forming methods, the preparation method provided by this invention can greatly reduce phenomena such as fiber agglomeration and filament twisting that affect paper uniformity and other key indicators. The carbon fiber base paper for fuel cells provided by this invention has the characteristics of good uniformity and high tensile strength. When further used in the fuel cell field, it meets the requirements of important indicators such as uniformity, porosity, and electrical resistance, and is a carbon fiber base paper that meets the standards for use in the fuel cell field.

[0107] The carbon fiber base paper for fuel cells provided by this invention, after being processed through resin impregnation, graphitization, and carbonization, is applied to the gas diffusion layer of a fuel cell. The air permeability of the base paper reaches 120846 ml·mm / (cm). 2 The excellent uniformity resulted in a final product with an air permeability of 4000 ml·mm / (cm·h·mmhg). 2 The carbon fiber base paper for fuel cells provided by this invention has a tensile strength of 20 MPa or higher (1500-2500 in the prior art), a planar resistivity of less than 3 mΩ·cm (10-20 in the prior art), and a tensile strength of more than 20 MPa. It can be seen that the performance of the carbon fiber base paper for fuel cells provided by this invention is significantly better than that of the carbon fiber base paper for fuel cells prepared using the prior art.

[0108] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for producing a carbon fiber raw paper for fuel cells, characterized by, It comprises the following steps: Step one: weigh the raw materials, the raw materials include 100 parts of fiber, 40-50 parts of dispersant A, 50-100 parts of dispersant B and 0.5-1 parts of defoaming agent, the fiber includes 70-95 parts of chopped carbon fiber and 5-30 parts of water-soluble fiber; the defoaming agent is one or more of silicone defoaming agent and polyether defoaming agent; Step two: after the chopped carbon fiber and water-soluble fiber are defibrated, 8-10 parts of dispersant A are added for mixing, high-speed stirring is carried out to complete the foam dispersion, water is added for dilution, and a first concentration carbon fiber slurry is obtained; the mass percentage concentration of the first concentration carbon fiber slurry is 1.2%~1.5%; Step three: defoaming agent is added to the first concentration carbon fiber slurry for the first stirring, and a carbon fiber dispersion slurry is obtained; Step four: the remaining part of dispersant A and the dispersant B are added to the carbon fiber dispersion slurry for the second stirring, water is added for dilution, and a second concentration carbon fiber slurry is obtained; the dispersant A is a styrene maleic anhydride copolymer dispersant with a mass concentration of 0.2%; the dispersant B is one or more of polyethylene oxide and polyacrylamide with a mass concentration of 0.2%; the mass percentage concentration of the second concentration carbon fiber slurry is 0.1%~0.4%; Step five: the second concentration carbon fiber slurry is papermaking to obtain a carbon fiber base paper for fuel cell.

2. The production method of carbon fiber raw paper for fuel cells according to claim 1, characterized by, The chopped carbon fiber includes one or more of polyacrylonitrile-based carbon fiber and pitch-based carbon fiber; The diameter of the chopped carbon fiber is 7-17μm, and the length is 5-15mm.

3. The production method of carbon fiber raw paper for fuel cells according to claim 1, characterized by, The water-soluble fiber includes one or more of polyvinyl alcohol water-soluble fiber and carboxymethyl cellulose fiber; The length of the water-soluble fiber is 3-5mm.

4. The production method of carbon fiber raw paper for fuel cells according to claim 1, characterized by, The high-speed stirring condition is: stirring speed 2000-3500r / min, time 5-15min; The first stirring condition is: stirring speed 300-1000r / min; The second stirring condition is: stirring speed 30-50r / min.

5. The production method of carbon fiber raw paper for fuel cells according to claim 1, characterized by, The papermaking process includes: forming, pressing dewatering, drying on the drying cylinder, spraying stripping, and winding; The drying cylinder drying condition is: 80-105℃; The spraying stripping condition is: mineral oil cylinder stripping agent.

6. A carbon fiber base paper for fuel cell prepared by the method according to any one of claims 1~5.

7. The carbon fiber raw paper for fuel cells according to claim 6, characterized by, The basis weight of the carbon fiber raw paper for fuel cells is 15 g / m 2 80 g / m 2 .

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