Production process of carbon paper base paper for gas diffusion layer and carbon paper base paper

Abstract

The present invention discloses a production process for carbon paper base for a gas diffusion layer, comprising the following steps: S1: preparing a suspended slurry; S2: papermaking, pressing, heating to T1, and drying to obtain a first base paper; S3: applying an aqueous resin dispersion containing conductive particles to the first base paper, heating to T2 for pre-drying, and obtaining a second base paper; S4: continuously spraying water onto the second base paper in a mist-like manner, non-contact heating the second base paper to T3, dissolving the first water-soluble fiber in the second base paper, and pressing and drying to obtain a third base paper; S5: hot pressing and carbonizing the third base paper to obtain a carbon paper base for a gas diffusion layer; T1 and T2 are lower than the water-soluble temperature of the first water-soluble fiber, and T3 is higher than the water-soluble temperature of the first water-soluble fiber and lower than the water-soluble temperature of the second water-soluble fiber. This production process for carbon paper base for a gas diffusion layer is advantageous in reducing the resistivity of the flocs and improving the porosity and air permeability of the carbon paper base paper. The present invention also discloses a carbon paper.

Description

Technical Field

[0001] The invention relates to the technical field of gas diffusion layer carbon paper production, and in particular to a production process of carbon paper base paper for a gas diffusion layer and the carbon paper base paper. Background Art

[0002] The gas diffusion layer (GDL) is a key component of fuel cells. Its functions include: transporting oxygen and hydrogen to the corresponding catalyst layers to support the reactions; transferring byproduct water to the bipolar plate's current collecting channels to prevent water accumulation in the catalyst layers, which could reduce the reaction rate; conducting electrons generated by hydrogen at the anode through the GDL to an external circuit and flow to the cathode; transferring heat to the bipolar plates; and providing strength support for the entire membrane electrode. Therefore, the GDL must possess excellent electrical conductivity, strength, porosity, and surface properties. Existing GDLs are composed of a laminated base layer and a microporous layer, with the base layer connected to the bipolar plates and the microporous layer connected to the catalyst layers.

[0003] Both CN114457620A and CN116716755A disclose methods for preparing fiber slurries using polyvinyl alcohol (PVA) fibers and carbon fibers. The PVA fibers enhance the bonding between the fibers. However, after drying, the PVA flocs cover a large area of ​​the carbon fiber surface, increasing the resistivity of the flocs. Therefore, vapor-grown carbon fibers and copper powder are added to the slurry in CN114457620A to improve the conductivity of the carbon paper. However, dense fiber accumulation also results in smaller pores and poorer air permeability in the area. Summary of the Invention

[0004] One of the purposes of the present invention is to overcome the defects existing in the prior art and provide a production process for carbon paper base paper for gas diffusion layer, using a first water-soluble fiber as a template to optimize the uniformity of dispersion of conductive particles on the surface of carbon paper fibers, reduce the resistivity at the flocs, and improve the porosity and air permeability at the dense fiber flocs by dissolving the first water-soluble fiber.

[0005] In order to achieve the above technical effects, the technical solution of the present invention is: a production process of carbon paper base paper for gas diffusion layer, comprising the following steps:

[0006] S1: preparing a suspension slurry containing chopped fibers, wherein the chopped fibers mainly include carbon fibers, first water-soluble fibers, and second water-soluble fibers;

[0007] S2: papermaking, pressing, heating to T1 and drying to obtain the first base paper;

[0008] S3: preparing a resin aqueous dispersion containing conductive particles, applying the resin aqueous dispersion to the first base paper, heating to T2 for pre-drying, and obtaining a second base paper with a predetermined liquid content;

[0009] S4: continuously spraying water onto the second base paper in an atomized manner, heating the second base paper in a non-contact manner to T3, dissolving the first water-soluble fiber in the second base paper, and squeezing and drying to obtain a third base paper;

[0010] S5: The third base paper is hot pressed and carbonized to obtain a carbon paper base for a gas diffusion layer;

[0011] T1 and T2 are lower than the water-soluble temperature of the first water-soluble fiber, and T3 is higher than the water-soluble temperature of the first water-soluble fiber and lower than the water-soluble temperature of the second water-soluble fiber. A preferred technical solution is that the mass ratio of the carbon fiber, the first water-soluble fiber, and the second water-soluble fiber in the suspended slurry is 1:(0.02-0.08):(0.06-0.13), and the surface density of the first base paper is 30-55 g / m 2 .

[0012] Taking the mass of carbon fiber as a reference, the mass ratio of carbon fiber to the first water-soluble fiber can be selected as 1:0.02, 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.07, 1:0.08 point values ​​or an interval range with the above two point values ​​as the maximum and minimum values. At the same time, the mass ratio of carbon fiber to the second water-soluble fiber can be selected as 1:0.06, 1:0.07, 1:0.08, 1:0.09, 1:0.10, 1:0.11, 1:0.12, 1:0.13 point values ​​or an interval range with the above two point values ​​as the maximum and minimum values.

[0013] The surface density of the first base paper can be selected from 30, 33, 36, 40, 43, 46, 50, 52, 55 g / m 2 Furthermore, the surface density of the first base paper will affect the distribution of the conductive particles in the resin aqueous dispersion.

[0014] A preferred technical solution is that the mass ratio of the chopped fibers, electrolytic inorganic salt dispersant, and thickener in the main components of the suspension slurry is 1:(0.05-0.13):(1.5-5). Taking the chopped fibers as a reference, the mass ratio of the chopped fibers to the electrolytic inorganic salt dispersant can be selected from 1:0.05, 1:0.07, 1:0.09, 1:0.11, 1:0.13, or an interval with the above two points as the maximum and minimum values. The mass ratio of the chopped fibers to the thickener is 1:1.5, 1:2.0, 1:2.5, 1:3.0, 1:3.5, 1:4.0, 1:4.5, and 1:5.0.

[0015] Furthermore, the suspension slurry consists of chopped fibers, an electrolytic inorganic salt dispersant, a thickener and water.

[0016] The preferred technical solution is that the average diameter of the carbon fiber is 5 to 15 μm, and the average length is 1 to 6 mm; the average diameter of the first water-soluble fiber is 0.5 to 3 μm, the average diameter of the second water-soluble fiber is 5 to 15 μm, and the average length of the first water-soluble fiber and the second water-soluble fiber is 1 to 4 mm.

[0017] The average diameter of the carbon fiber can be selected as 5, 7, 9, 11, 13, 15 μm or a range with the above two point values ​​as the maximum and minimum values; the average length of the carbon fiber can be selected as 1, 2, 3, 4, 5, 6 mm or a range with the above two point values ​​as the maximum and minimum values; the average diameter of the first water-soluble fiber can be selected as 0.5, 1, 2, 3 μm or a range with the above two point values ​​as the maximum and minimum values; the average diameter of the second water-soluble fiber can be selected as 5, 7, 9, 11, 13, 15 μm or a range with the above two point values ​​as the maximum and minimum values; the average length of the first water-soluble fiber and the second water-soluble fiber can be selected as 1, 2, 3, 4 mm or a range with the above two point values ​​as the maximum and minimum values.

[0018] A preferred technical solution is that the resin aqueous dispersion comprises, by weight, 0.5-1 part of nano-conductive graphite powder, 0.15-1 part of a wetting and dispersing agent, 8-15 parts of an aqueous dispersion resin, 5-12 parts of a lower alcohol, and 80 parts of water. Furthermore, the resin dispersion comprises nano-conductive graphite powder, a wetting and dispersing agent, an aqueous dispersion resin, a lower alcohol, and water.

[0019] Furthermore, the lower alcohol is a C1-C4 alcohol. Furthermore, the number of nano-scale conductive graphite powder in 80 parts of water is 0.5, 0.7, 1, or a range with the above two points as the maximum and minimum values; the number of wetting and dispersing agents in 80 parts of water is 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or a range with the above two points as the maximum and minimum values; the number of aqueous dispersion resins in 80 parts of water is 8, 9, 10, 11, 12, 13, 14, 15, or a range with the above two points as the maximum and minimum values; and the number of lower alcohols in 80 parts of water is 5, 7, 9, 10, 12, or a range with the above two points as the maximum and minimum values.

[0020] The preferred technical solution is that the aqueous dispersion resin is a phenolic resin;

[0021] The resin aqueous dispersion further comprises 0.08 to 1 part of glutaraldehyde and 0.05 to 0.5 part of glycerol, wherein the proportions of glutaraldehyde and glycerol are based on 80 parts of water.

[0022] A preferred technical solution is that the liquid content of the second base paper after pre-drying in S3 is 5% to 10%. The optional liquid content of the second base paper after pre-drying in S3 is 5%, 6%, 7%, 8%, 9%, 10%, or an interval with the above two points as the maximum and minimum values.

[0023] The preferred technical solution is that the pressing pressure of S2 is 0.2-0.3 MPa; the water-soluble temperature of the first water-soluble fiber is 85-90°C; the water-soluble temperature of the second water-soluble fiber is 95-100°C; the drying temperature of the second base paper in S4 is 100-105°C, and the pressing pressure in S4 is 0.5-1.2 MPa.

[0024] The pressing pressure of S2 can be selected as 0.2, 0.23, 0.25, 0.27, 0.3 MPa or a range with the above two points as the maximum and minimum values; the water-soluble temperature of the first water-soluble fiber can be selected as 85, 87, 90°C or a range with the above two points as the maximum and minimum values; the water-soluble temperature of the first water-soluble fiber can be selected as 95, 97, 99, 100 or a range with the above two points as the maximum and minimum values. The pressing pressure of S4 can be selected as 0.5, 0.7, 0.9, 1, 1.2 MPa or a range with the above two points as the maximum and minimum values; the drying temperature of the second base paper in S4 can be selected as 100°C, 102°C, 104°C, 105°C or a range with the above two points as the maximum and minimum values.

[0025] The preferred technical solution is that in S5, the hot pressing temperature is 150-170°C, the hot pressing time is 20-30 minutes, and the pressure is 3-7 MPa; the carbonization furnace temperature is 800-1400°C, and the carbonization time is 40-120 minutes.

[0026] The hot pressing temperature in S5 can be selected as 150, 155, 160, 165, 170℃ or an interval range with the above two point values ​​as the maximum and minimum values; the carbonization furnace temperature can be selected as 800, 900, 1000, 1100, 1200, 1300℃, 1400℃ or an interval range with the above two point values ​​as the maximum and minimum values.

[0027] A second object of the present invention is to provide a carbon paper base, which is produced by the above-mentioned production process of carbon paper base for gas diffusion layer.

[0028] The advantages and beneficial effects of the present invention are:

[0029] The production process of carbon paper base paper for a gas diffusion layer comprises: a first base paper made of chopped carbon fibers, a first water-soluble fiber, and a second water-soluble fiber; a resin aqueous dispersion is applied to the first base paper and adheres to the chopped fibers; the resin dispersion wets the chopped fibers and / or penetrates between the fibers due to a capillary effect; the pre-dried second base paper is subjected to a dissolving treatment of the first water-soluble fibers; the first water-soluble fibers in the second base paper are dissolved or partially dissolved, and more pores are introduced between the water-soluble fibers and the carbon fibers, resulting in a lower fiber density where the chopped fibers are evenly stacked, which helps optimize the porosity and air permeability of the base paper;

[0030] The production steps of pre-drying and then dissolving the first water-soluble fiber have little effect on the number of contact points between fibers, and the conductive particles stacked deep between the fibers can effectively reduce the resistivity of this area;

[0031] The carbon paper base has high uniformity, and its porosity and air permeability are improved due to the dissolution of the first water-soluble fiber, and is suitable for stacking to prepare gradient pore carbon paper. DETAILED DESCRIPTION

[0032] The following examples are only used to illustrate the technical solution of the present invention more clearly, and are not intended to limit the scope of protection of the present invention.

[0033] Soluble fiber

[0034] The water-soluble fiber can be selected from polyvinyl acetal fiber (vinylon), seaweed fiber and carboxymethyl cellulose fiber, preferably polyvinyl alcohol fiber.

[0035] The resin aqueous dispersion may be applied to the first base paper by known methods such as spraying and dipping.

[0036] Non-contact heating, such as infrared heating, does not directly contact the first base paper, unlike contact heating methods such as roller heating. This prevents the distribution of fibers within the first base paper from being affected by changes in position or drafting. While the front side of the first base paper is being non-contact heated, water containing the first water-soluble fibers can be removed from the back side of the first base paper while water is continuously sprayed to accelerate water flow and dissolution of the first water-soluble fibers.

[0037] The diameter and length of the water-soluble fibers determine their distribution in the first base paper, and also affect the distribution of the resin aqueous dispersion and the conductive particles therein in the base paper.

[0038] Electrolytic inorganic salt dispersant

[0039] Electrolytic inorganic salt dispersants are further polyacrylamide dispersants. Taking carbon fiber as an example, polyacrylamide forms colloidal particles in water. The colloidal particles are adsorbed on the surface of carbon fiber. The electrostatic repulsion between carbon fibers with the same charge increases, which promotes the dispersion of carbon fiber.

[0040] The thickener increases the viscosity of the slurry, which is beneficial for the stable suspension of the fibers. Preferably, the thickener is sodium carboxymethyl cellulose.

[0041] Conductive particles can be metal powders (such as silver powder, copper powder, and nickel powder), carbon-based conductive powders, and composite metal oxide-based conductive powders (nano-antimony-doped tin dioxide). Carbon-based conductive powders have a low density and are more easily absorbed into the stacked fibers with the resin aqueous dispersion. Pre-drying increases the number of fiber contact points.

[0042] The aqueous dispersion resin may be selected from polyurethane resin, phenolic resin, or epoxy resin, preferably phenolic resin. Glutaraldehyde is further added to the resin aqueous dispersion as a crosslinking agent, and glycerin is a small molecule polyhydroxy compound, which helps to increase the crosslinking density of the second water-soluble fiber and the electrolytic inorganic salt dispersant and reduces the effect of the dissolution treatment of the water-soluble fiber on the pre-dried phenolic resin on the surface of the chopped fiber.

[0043] The average diameter of the carbon fibers is 10 μm and the average length is 5 mm;

[0044] The first water-soluble fiber, vinylon, has an average diameter of 2 μm and an average length of 4 mm;

[0045] The second water-soluble fiber, vinylon, has an average diameter of 8 μm and an average length of 4 mm.

[0046] Example 1

[0047] S1: preparing chopped fibers, a polyacrylamide dispersant, and sodium carboxymethyl cellulose in a mass ratio; the chopped fibers are composed of 1 part of carbon fiber, 0.06 parts of a first water-soluble fiber, and 0.11 parts of a second water-soluble fiber;

[0048] Prepare the suspension slurry in the following proportions: 1.17 parts of chopped fiber, 0.0936 parts of polyacrylamide dispersant, and 2.925 parts of sodium carboxymethyl cellulose by weight;

[0049] Take 100 parts of water, dissolve sodium carboxymethyl cellulose in water to prepare a sodium carboxymethyl cellulose solution, dissolve a polyacrylamide dispersant in the sodium carboxymethyl cellulose solution, add the carbon fiber, the first water-soluble fiber and the second water-soluble fiber to the solution in sequence, and finally disperse at high speed using a fiber decompressor for 15 minutes, add water to dilute and disperse, until the mass percentage of short-cut fibers in the suspended slurry is 0.015%;

[0050] S2: The suspended slurry is introduced into the paper sample making machine, and the short-cut fibers are freely settled on the copper mesh. The wet paper web on the copper mesh is transferred to the flat vulcanizing machine, pressed and shaped at 0.25MPa, heated to 81±2℃ under normal pressure or reduced pressure, and dried for 4 hours to obtain the dried first base paper. The surface density of the first base paper is controlled at 50±1g / m 2 within the scope;

[0051] S3: Prepare a resin aqueous dispersion according to 0.8 parts of nano-conductive graphite powder, 0.3 parts of sodium dodecylbenzenesulfonate, 10 parts of phenolic resin (added as phenolic resin aqueous dispersion, 10 parts based on the solid content of the phenolic resin aqueous dispersion), 9 parts of ethanol and 80 parts of water;

[0052] S4: spraying the resin aqueous dispersion onto the first base paper until the resin aqueous dispersion soaks the first base paper, with the spraying amount of the resin dispersion per unit area being 100% of the mass of the first base paper; heating to 81±2°C under normal pressure or reduced pressure to pre-dry until the liquid pick-up rate of the second base paper reaches 6%;

[0053] Liquid carryover rate = (mass of the second base paper after pre-drying - mass of the first base paper) / mass of the first base paper * 100%

[0054] S5: Continuously spray water on the second base paper in a mist-like manner above the second base paper, heat the second base paper to 91±2°C in a non-contact manner, vacuum-suck the water from the second base paper below the second base paper, and continue this operation for 1 hour. Then, introduce the second base paper into a flat-plate vulcanizer, press the second base paper at 0.8 MPa, heat to 100°C, and maintain for 20 minutes to obtain a dried third base paper;

[0055] S6: hot pressing the third base paper at 160° C. for 30 min at a pressure of 5 MPa; the hot pressed base paper is introduced into a carbonization furnace and carbonized at 1300° C. for 60 min under nitrogen protection.

[0056] After weighing, the mass of the sample paper of Example 1 is 51.4g / m 2 ;

[0057] According to GB / T 22819 Determination of air permeability of highly breathable paper, the air permeability of the sample paper of Example 1 was measured to be 320 L / m 2 ;

[0058] The tensile strength of the sample paper of Example 1 was measured to be 1.03 kN / m by the constant rate tensile method of GB / T 12914 Paper and paperboard - Determination of tensile strength.

[0059] The resistivity of the sample paper of Example 1 was measured using a four-probe method and was found to be 14.84 mΩ·cm.

[0060] Example 2

[0061] S1: preparing chopped fibers, a polyacrylamide dispersant, and sodium carboxymethyl cellulose in a mass ratio; the chopped fibers are composed of 1 part of carbon fiber, 0.06 parts of a first water-soluble fiber, and 0.11 parts of a second water-soluble fiber;

[0062] Prepare the suspension slurry in the following proportions: 1.17 parts of chopped fiber, 0.0936 parts of polyacrylamide dispersant, and 2.925 parts of sodium carboxymethyl cellulose by weight;

[0063] Take 100 parts of water, dissolve sodium carboxymethyl cellulose in water to prepare a sodium carboxymethyl cellulose solution, dissolve a polyacrylamide dispersant in the sodium carboxymethyl cellulose solution, add the carbon fiber, the first water-soluble fiber and the second water-soluble fiber to the solution in sequence, and finally disperse at high speed using a fiber decompressor for 15 minutes, add water to dilute and disperse, until the mass percentage of short-cut fibers in the suspended slurry is 0.015%;

[0064] S2: Pour the suspended slurry into a paper sample making machine, and the short-cut fibers are freely settled on the copper mesh. The wet paper web on the copper mesh is transferred to a flat vulcanizing press, pressed and shaped at 0.25 MPa, heated to 81±2°C under normal pressure or reduced pressure, and dried for 4 hours to obtain the first dry base paper. The surface density of the first base paper is 50 g / m 2 ;

[0065] S3: Prepare a resin aqueous dispersion according to 0.8 parts of nano-conductive graphite powder, 0.3 parts of sodium dodecylbenzenesulfonate, 10 parts of phenolic resin (added as phenolic resin aqueous dispersion, 10 parts based on the solid content of the phenolic resin aqueous dispersion), 9 parts of ethanol, 0.85 parts of glutaraldehyde, and 80 parts of water;

[0066] S4: spraying the resin aqueous dispersion onto the first base paper until the resin aqueous dispersion soaks the first base paper, with the spraying amount of the resin dispersion being 100% of the mass of the first base paper per unit area; heating to 81±2°C under normal pressure or reduced pressure to pre-dry until the liquid content of the second base paper reaches 6%;

[0067] Liquid carryover rate = (mass of the second base paper after pre-drying - mass of the first base paper) / mass of the first base paper * 100%

[0068] S5: Continuously spray water on the second base paper in a mist-like manner above the second base paper, heat the second base paper to 91±2°C in a non-contact manner, vacuum-suck the water from the second base paper below the second base paper, and continue this operation for 1 hour. Then, introduce the second base paper into a flat-plate vulcanizer, press the second base paper at 0.8 MPa, heat to 100°C, and maintain for 20 minutes to obtain a dried third base paper;

[0069] S6: hot pressing the third base paper at 150-170° C. for 20-30 min at a pressure of 5 MPa; introducing the hot-pressed base paper into a carbonization furnace and carbonizing it at 1300° C. for 60 min under nitrogen protection.

[0070] After weighing and testing, the mass of the sample paper of Example 2 is 51.9g / m 2 , air permeability is 315L / m 2 ; Tensile strength is 1.11kN / m; Resistivity is 14.51mΩ.cm.

[0071] Example 3

[0072] Example 3 is based on Example 2, but differs in the composition of the resin aqueous dispersion.

[0073] S3: Prepare a resin aqueous dispersion according to 0.8 parts of nano-conductive graphite powder, 0.3 parts of sodium dodecylbenzenesulfonate, 10 parts of phenolic resin (added as phenolic resin aqueous dispersion, 10 parts based on the solid content of the phenolic resin aqueous dispersion), 9 parts of ethanol, 0.85 parts of glutaraldehyde, 0.4 parts of glycerol, and 80 parts of water.

[0074] After weighing and testing, the mass of the sample paper of Example 3 is 52.4g / m 2 , air permeability is 312L / m 2 ; Tensile strength is 1.27kN / m; Resistivity is 12.77mΩ.cm.

[0075] Example 4 is based on Example 1, except that the average diameter of the first water-soluble fiber in Example 3 is 5 μm;

[0076] S4: Continuously spray water in a mist on the second base paper above the second base paper, heat the second base paper to 91±2°C in a non-contact manner, and vacuum-suck the water from the second base paper below the second base paper. After continuing this operation for 1.5 hours, the second base paper is introduced into a flat-plate vulcanizer, pressed at 0.8 MPa, heated to 100°C, and maintained for 20 minutes to obtain a dry third base paper.

[0077] After weighing and testing, the mass of the sample paper of Example 4 is 50.8g / m 2 , air permeability is 331L / m 2 ; Tensile strength is 0.97kN / m; Resistivity is 15.05mΩ.cm.

[0078] Comparative Example 1

[0079] The method is based on Example 1, except that the second base paper is pre-dried by heating to 81±2°C under normal pressure or reduced pressure until the liquid content of the second base paper is 6%; the second base paper is pressed on a flat vulcanizer at 0.8 MPa, heated to 100°C, and maintained for 20 minutes to obtain a dried third base paper; and the third base paper is subjected to hot pressing and carbonization treatment as in Example 1, with the same hot pressing and carbonization process parameters as in Example 1.

[0080] After weighing and testing, the mass of the base paper of Comparative Example 1 is 54.3 g / m 2 , air permeability is 293L / m 2 ; Tensile strength is 1.25kN / m; Resistivity is 14.79mΩ.cm.

[0081] Example 1 and Comparative Example 1 form a comparison of whether the first water-soluble fiber is dissolved or not. Compared with Example 1, Comparative Example 1 still retains the first water-soluble fiber, and the carbonization of the first water-soluble fiber causes the resistivity to decrease slightly; however, since the first water-soluble fiber has a small diameter and a large surface area, the phenolic resin covers the surface of the water-soluble fiber and fills between the fibers. There are few pores at the fiber stacking, especially at the agglomeration, so the air permeability is significantly lower than that of Example 1, but the tensile strength is higher than that of Example 1.

[0082] A comparison of the resin aqueous dispersions of Example 1 and Example 2 was performed. The resin aqueous dispersion of Example 2 further contained glutaraldehyde, which served as a crosslinking agent to increase the reaction probability between the vinylon and the surface groups of the phenolic resin, thereby increasing the crosslinking density between the phenolic resin, the water-soluble fiber, and the thickener in the pre-dried second base paper, and reducing the loss of the phenolic resin caused by the dissolution of the first water-soluble fiber. As a result, the air permeability was slightly reduced, the tensile strength was increased, and the resistivity was lower than that of Example 1.

[0083] Example 2 and Example 3 form a comparison of the resin aqueous dispersion. Example 3 further adds glycerol on the basis of Example 2. Small molecular glycerol and glutaraldehyde can more easily penetrate into the pores, further improving the crosslinking density between the phenolic resin and the water-soluble fiber, thickener, etc. The addition of glycerol has a more obvious effect on the tensile strength and resistivity, but less effect on the air permeability.

[0084] Example 4 forms a comparison of the first water-soluble fiber with Example 1. Based on the same mass of the first water-soluble fiber, the larger the fiber diameter of Example 4, the smaller the surface area of ​​the first water-soluble fiber, and the fewer fiber contact points with the carbon fiber and the second water-soluble fiber. The dissolution of the first water-soluble fiber forms more and larger pores in the base paper, and the contact points between fibers are reduced, which is manifested as increased permeability and resistivity, and further reduced tensile strength.

[0085] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A process for producing carbon paper base for gas diffusion layer, characterized in that: The following steps are involved: S1: preparing a suspension slurry comprising chopped fibers, a polyacrylamide dispersant, and a thickener, wherein the chopped fibers are carbon fibers, a first water-soluble fiber, and a second water-soluble fiber; S2: papermaking, pressing, heating to T1 and drying to obtain the first base paper; S3: preparing a resin aqueous dispersion containing conductive particles, applying the resin aqueous dispersion to the first base paper, heating to T2 for pre-drying, and obtaining a second base paper with a liquid carrying rate of 5% to 10%; S4: continuously spraying water onto the second base paper in an atomized manner, heating the second base paper in a non-contact manner to T3, dissolving the first water-soluble fiber in the second base paper, and squeezing and drying to obtain a third base paper; S5: The third base paper is hot pressed and carbonized to obtain a carbon paper base for a gas diffusion layer; T1 and T2 are lower than the water-soluble temperature of the first water-soluble fiber, and T3 is higher than the water-soluble temperature of the first water-soluble fiber and lower than the water-soluble temperature of the second water-soluble fiber; The first water-soluble fiber and the second water-soluble fiber are both vinylon; the resin aqueous dispersion is composed of, by mass, 0.5-1 part of nano-conductive graphite powder, 0.15-1 part of sodium dodecylbenzenesulfonate, 8-15 parts of aqueous dispersion resin, 5-12 parts of lower alcohol, 80 parts of water, 0.08-1 part of glutaraldehyde, and 0.05-0.5 part of glycerol; the aqueous dispersion resin is a phenolic resin; The mass ratio of the carbon fiber, the first water-soluble fiber and the second water-soluble fiber in the suspension slurry is 1:(0.02-0.08):(0.06-0.13), and the surface density of the first base paper is 30-55 g / m 2 ; The average diameter of the carbon fibers is 5 to 15 μm, and the average length is 1 to 6 mm; the average diameter of the first water-soluble fibers is 0.5 to 3 μm, the average diameter of the second water-soluble fibers is 5 to 15 μm, and the average lengths of the first and second water-soluble fibers are 1 to 4 mm; Liquid pick-up rate = [(mass of the second base paper after pre-drying - mass of the first base paper) / mass of the first base paper] × 100%.

2. The process for producing carbon paper base for gas diffusion layer according to claim 1, characterized in that: The mass ratio of the chopped fibers, the polyacrylamide dispersant and the thickener in the components of the suspension slurry is 1:(0.05-0.13):(1.5-5).

3. The process for producing carbon paper base for gas diffusion layer according to claim 1, characterized in that: The pressing pressure of S2 is 0.2-0.3 MPa; the water-soluble temperature of the first water-soluble fiber is 85-90°C; the water-soluble temperature of the second water-soluble fiber is 95-100°C; the drying temperature of the second base paper in S4 is 100-105°C, and the pressing pressure in S4 is 0.5-1.2 MPa.

4. The process for producing carbon paper base for gas diffusion layer according to claim 1, characterized in that: In S5, the hot pressing temperature is 150-170° C., the hot pressing time is 20-30 min, and the pressure is 3-7 MPa; the carbonization furnace temperature is 800-1400° C., and the carbonization time is 40-120 min.

5. A carbon paper base, characterized in that: The carbon paper for gas diffusion layer is produced by the production process of carbon paper base paper for gas diffusion layer according to any one of claims 1 to 4.