JP2005097752A - Carbon fiber woven or knitted fabric, method for producing the same and gas diffusion layer substrate for fuel cell using the same woven or knitted fabric - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin and dense carbon fiber woven or knitted fabric having excellent electroconductivity, suitable as a gas diffusion layer substrate for a fuel cell and preventing the lowering of flow rate of the fuel gas and a gas such as oxygen because the woven or knitted fabric is deficient in drapeability and stiff and groove parts of a ribbed separation plate (hereinafter referred to also as a reserve plate) cannot be filled when used as the gas diffusion layer substrate for the fuel cell. <P>SOLUTION: The carbon fiber woven or knitted fabric is composed of a carbonized multifilament textured yarn having 0.1-5 dtex single filament fineness and 20-400 dtex total fineness. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a carbon fiber woven fabric, a method for producing the same, and a gas diffusion layer base material for a fuel cell comprising the carbon fiber woven fabric.

  Carbon fiber woven and knitted fabrics have been widely produced mainly as a base material for composite materials. Carbon fiber woven fabrics have also attracted attention as conductive substrates because of their good electrical conductivity and excellent mechanical strength and corrosion resistance.

  Gas diffusion layer base materials for polymer electrolyte fuel cells are required to have gas diffusibility, gas permeability, water retention, strength, flexibility, strength to withstand compression during electrode production or when electrodes are assembled, etc. . In addition, since the polymer electrolyte fuel cell is required to be smaller than the phosphoric acid fuel cell, the gas diffusion layer base material is also required to be thin. As the gas diffusion layer base material for such a polymer electrolyte fuel cell, those using carbon fiber paper or carbon fiber knitted fabric as the base material are the mainstream.

Patent Document 1 proposes a parameterization of a preferable correlation between a woven fabric form, a firing process passability, and CFRP mechanical properties when an acrylic fiber bundle is woven, oxidized, and carbonized. However, the yarn processing of the acrylic fiber bundle is intended only for improving the weaving property, and it cannot be said that the performance is sufficiently described.
Patent Document 2 proposes an activated carbon fabric obtained by carbonizing a raw material organic fiber that can be carbonized, but has a firing temperature of 1000 ° C. or less in order to suppress wrinkles. Was not obtained.

Patent Document 3 proposes a method of performing activation treatment after entanglement treatment of flameproof fibers. Although this method is effective for maintaining the workability and yarn strength to make a woven or knitted fabric, it must pass through an oxidation treatment-air entanglement-activation treatment and a firing process twice, for efficient production and cost reduction. Is not suitable.
Patent Document 4 proposes a conductive carbon fiber sheet having both air permeability and rigidity. However, in order to obtain rigidity, it was necessary to bind the fibers with a binder.
Patent Document 5 proposes a carbonized fiber woven fabric in which polyacrylonitrile-based oxidized fiber is used as a woven fabric after air entanglement, and the fiber cross-sectional shape is flattened by compression treatment. However, it is unclear to what extent the effect of air entanglement is present in the compression process.

JP-A-56-101917 JP 58-213615 A JP 59-227705 A JP 2002-327355 A JP 2003-64539 A

  The present invention overcomes the above-mentioned problems, and provides a woven or knitted fabric suitable for a gas diffusion layer substrate for fuel cells that is efficient, excellent in gas diffusibility and conductivity, and a method for producing the same, and a low humidification environment. An object of the present invention is to provide a gas diffusion layer base material for a fuel cell that can exhibit good battery performance even underneath.

The first gist of the present invention is a carbon fiber woven or knitted fabric made of carbonized multifilament processed yarn having a single fiber fineness of 0.1 to 5 dtex and a total fineness of 20 to 400 dtex.
The second gist is a method for producing the carbon fiber woven knitted fabric, in which a carbonized multifilament having a single fiber fineness of 0.2 to 6 dtex and a total fineness of 50 to 500 dtex is processed into a knitted fabric and then carbonized. .

  INDUSTRIAL APPLICABILITY According to the present invention, a woven or knitted fabric suitable for a gas diffusion layer base material for fuel cells, which is thin and dense and has excellent conductivity, can be obtained. Further, since the carbon fiber woven fabric of the present invention lacks draping properties and is rigid, when used as a gas diffusion layer base material for a fuel cell, the groove portion of a ribbed separator (also referred to as a reserve plate) is not filled. It is possible to prevent a decrease in the flow rate of gases such as gas and oxygen. Furthermore, it is possible to produce at a low cost by using a consistent firing process and equipment that has been widely used.

The carbon fiber woven or knitted fabric of the present invention may be a woven or knitted fabric after carbonizing a carbonizable multifilament, or may be carbonized after forming a woven or knitted fabric.
The carbonizable multifilament raw material may be any of polyacrylonitrile fiber, rayon fiber, pitch and the like, but polyacrylonitrile fiber having a relatively high mechanical strength of the multifilament when carbonized is preferable.

  The polyacrylonitrile fiber here is produced using a polymer containing acrylonitrile as a main component as a raw material. The polyacrylonitrile fiber is heated to 300 to 2500 ° C. in an inert atmosphere such as nitrogen, argon, helium, etc. in a flameproofing process in which the fiber is heated and fired in an air atmosphere of 200 to 400 ° C. to convert it into oxidized fibers. The carbonized multifilament is obtained through a carbonization process.

  In the present invention, the carbonized multifilament needs to have a single fiber fineness of 0.1 to 5 dtex and a total fineness of 20 to 400 dtex. When the single fiber fineness of the carbonized multifilament is less than 0.1 dtex, fluff is likely to occur and the strength is inferior, and conversely when it exceeds 5 dtex, the flexibility is lacking. Further, the lower limit of the single fiber fineness is preferably 0.5 dtex or more because of the conductive effect, and the upper limit is preferably 1.5 dtex or less in terms of handleability.

  When the fineness of the carbonized multifilament is less than 20 dtex, it is easy to form a dense and thin woven or knitted fabric, but the manufacturing cost is high. Conversely, when it exceeds 400 dtex, the fine and thin thickness suitable for the gas diffusion layer substrate is increased. It is hard to be a woven or knitted fabric. Further, the lower limit of the fineness is preferably 100 dtex or more in terms of compression resistance, and the upper limit is preferably 350 dtex or less in terms of flexibility.

In the present invention, it is necessary that the carbonized multifilament is a processed yarn. In the present invention, the processed yarn refers to a yarn having a form formed by generally performed yarn processing. Specifically, the yarn having an entanglement or loop between single fibers of a filament bundle, and having a real twist And those having a combusted flame, those having crimps, those having a core-sheath structure, and the like. The form of the processed yarn of the present invention is different from the crimp formed by the structure constraint of warp and weft due to the woven structure or formed due to the knitted structure. Generally, carbonized multifilaments are preferred to be straight, since the strength can be maintained. However, in the formed woven or knitted fabric, if the single fibers are not bundled in any way, On the contrary, it is disadvantageous to maintain strength due to the occurrence of fluff.
Moreover, when it is set as the gas diffusion layer base material for fuel cells, it is preferable that moderate bulkiness is obtained by deformation of the filament bundle or single fiber, and the compression resistance is improved.

  The carbon fiber woven or knitted fabric of the present invention has a bending resistance of 15 cm or more according to the JIS L1096 8.19.1A method. In this measurement method, since the sample length is about 15 cm, it is practically non-contact with the measurement table, which means that it is rigid. The carbon fiber woven or knitted fabric of the present invention is rigid and used as a gas diffusion layer base material for a fuel cell, and does not embed in the groove of the separator even when assembling a cell stack. Can be prevented.

In the present invention, it is desirable that the carbonized multifilament processed yarn is an entangled yarn.
In the present invention, the entangled yarn means one in which single fibers of a filament bundle are entangled or have a loop. The degree of entanglement is not particularly limited, but the number of entangled parts is preferably 20 to 250 / m as the fuel cell gas diffusion layer base material. When the number of entangled portions is less than 20 / m, good focusing cannot be maintained, and when the number is more than 250 / m, the bending of the single fiber is excessive, and fluff is likely to occur. More preferably, it is 50-100 pieces / m, and a stable entangled form can be maintained.

Further, it is desirable that the maximum unentangled portion length is 15 mm or less. The maximum unentangled part length is a length between continuous entangled parts in the longitudinal direction of the multifilament, and is measured as follows.
Fix one end of the entangled yarn of about 1 m in length, apply a load of total fineness (dtex) x 0.03 (mN) to the other end and hang it vertically, starting from 5 cm below where it was fixed, A needle-like portion having a diameter of 0.5 mm or less is stabbed into the center of the multifilament bundle (the number of filaments is divided into almost the same number), and the load is applied to the total fineness (dtex) × 0.3 (mN), and the speed is 2 cm / Decrease in seconds and measure the length where the speed can no longer be maintained. The length from the starting point to the point at which the needle cannot first descend due to resistance is defined as the unentangled part length. In addition, since the single fibers are well entangled, the portion where the needle cannot descend is the entangled portion.

  For the stopped needle, the length of the non-entangled portion is measured repeatedly in the same manner, starting from directly below the entangled portion. Continuously measure 50 cm or more, and the maximum length of the unentangled part is the maximum unentangled part length.

  If the maximum unentangled part length is longer than 15 mm, good convergence cannot be obtained. More preferably, a stable focusing property of 3 to 10 mm can be obtained. Moreover, it is preferable that each unentangled part length is a uniform entanglement form with little variation.

  In the present invention, it is also desirable that the carbonized multifilament processed yarn is a real twist yarn. In the present invention, the actual twisted yarn refers to additional twisted yarn, combined twisted yarn of a plurality of filament bundles, twisted yarn, wall twisted yarn and the like. The actual twist number is not particularly limited. What is necessary is just a grade which provides the focusing property suitable for the carbonized multifilament. For example, in the case of a twisted yarn, bundling can be obtained if the actual number of twists is 20 t / m or more, but more preferably, the shape of the multifilament is stable when the number is 100 t / m or more.

  The woven or knitted fabric made of the above carbonized multifilament is suitable as a gas diffusion layer base material for a fuel cell. In the present invention, the structure of the woven or knitted fabric is not limited and may be one that is generally manufactured and used. For example, the woven fabric may be a changed structure in addition to a basic structure such as plain weave, twill weave, and satin weave. Multiple weaves may be used as necessary. The knitted fabric may be a warp knitting, a flat knitting, or a circular knitting, and may be a basic organization such as a flat knitting or a rubber knitting, or a change organization.

  More preferably, the fuel cell gas diffusion layer base material has a high weaving and knitting density. It is preferable that the gaps between the woven and stitches are not visible by visual inspection, that is, those having a high apparent cover factor and good gas diffusibility.

  In particular, a basic plain weave (one where warps and wefts intersect each other), which is composed of the maximum number of multifilaments used, is preferred. The basic plain weave has many intersections of warp and weft per unit area, and the multifilament bends at that time also increase, so that the conductivity in the thickness direction after carbonization becomes good.

The woven or knitted fabric of the present invention may be fired as it is, or may be fired after impregnating the carbonizable material into the woven or knitted fabric, and a gas diffusion layer base material for a fuel cell, particularly a gas diffusion layer of a polymer electrolyte fuel cell It can be used as a substrate.
The fuel cell gas diffusion layer substrate made of the woven or knitted fabric of the present invention preferably has a thickness of 0.05 to 0.5 mm and a bulk density of 0.3 to 0.8 g / cm ³ . When the thickness is less than 0.05 mm, the strength in the thickness direction is weakened, and it becomes impossible to withstand handling when the cell stack is assembled. On the other hand, when the thickness exceeds 0.5 mm, the electric resistance increases, and the total thickness increases when the stack is stacked.

The bulk density is preferably 0.3 to 0.8 g / cm ^3, when the bulk density is less than 0.3 g / cm ^3, after which the electrical resistance increases, not even have the flexibility satisfactory. On the other hand, if it exceeds 0.8 g / cm ³ , the gas permeability is deteriorated and the performance of the fuel cell is deteriorated. 0.4 to 0.7 g / cm ³ is more preferable. The thickness of the gas diffusion layer substrate of the present invention is measured using a thickness thickness dial thickness gauge. At this time, the size of the probe is 10 mm in diameter and the measurement pressure is 1.5 kPa.

The bulk density is calculated by the following formula using the actually measured thickness.
Bulk density (g / cm ³ ) = Weight per unit (g / m ² ) / (1000 × Thickness (mm))

The surface resistance of the fuel cell gas diffusion layer substrate comprising the woven or knitted fabric of the present invention is preferably 15 Ω · cm or less, more preferably 10 Ω · cm or less, and the ratio of the warp direction to the weft direction is preferably 1.5 or less. resistance 15 [Omega] · cm ² or less, more is preferably 5 [Omega · cm ² or less. In addition, sheet resistance measures resistance when a copper wire is put on one side of the gas diffusion layer base material with an interval of 2 cm and a current is passed at a current density of 10 mA / cm ² .

The penetration resistance of the fuel cell gas diffusion layer substrate made of the woven or knitted fabric of the present invention was such that the gas diffusion layer substrate was sandwiched between copper plates, pressed at 1 MPa from the top and bottom of the copper plate, and a current was passed at a current density of 10 mA / cm ² . Measure the resistance value and calculate from the following formula.
Penetration resistance (Ω · cm ² ) = Measured resistance value (Ω) × Sample area (cm ² )

Next, the manufacturing method of the woven or knitted fabric of the present invention will be described.
In the production method of the present invention, in view of suitability of the resulting woven or knitted fabric as a gas diffusion layer base material, a carbonizable multifilament having a fineness of 50 to 500 dtex and a single fiber fineness of 0.2 to 6 dtex is processed into yarn and then woven. Carbonized as a knitted fabric.

  As described above, the carbonizable multifilament is a carbonized raw material such as polyacrylonitrile-based fiber, rayon fiber, or pitch, which is multifilament. Since it is not carbonized, there is no rigidity and brittleness, and thread processability and weaving are good.

  In addition, the yarn processing referred to in the present invention refers to yarn processing that is generally widely performed. Specific examples include air entanglement processing, turbulent flow processing, swirling flow processing, twisted yarn, combined twist, false twist, and core-sheath winding processing. These treatments may be performed at the final stage of spinning, or may be performed in a separate process from spinning. If possible, it is more effective to reduce costs and stabilize quality by consistently performing spinning. Further, these processes may be performed alone or in combination. The order of implementation is not specified.

  In the production method of the present invention, the multifilament capable of carbonization needs to have a single fiber fineness of 0.2 to 6 dtex and a total fineness of 50 to 500 dtex.

  When the single fiber fineness of the carbonizable multifilament is less than 0.2 dtex, fluff is likely to occur and the strength is inferior. Conversely, when it exceeds 6 dtex, the flexibility is insufficient, and there are few binding points between the fibers. A gas diffusion layer substrate produced using such a carbonizable multifilament has a large resistance. Furthermore, the lower limit of the single fiber fineness is preferably 0.5 dtex or more from the viewpoint of the production of multifilaments, and the upper limit is preferably 1.5 dtex or less in terms of handleability. By using such thin single fibers, flexibility and high conductivity can be obtained when a woven or knitted fabric is obtained.

  When the total fineness of the carbonizable multifilament is less than 50 dtex, it is easy to form a dense and thin woven or knitted fabric, but the manufacturing cost is high. Conversely, when it exceeds 500 dtex, it is difficult to form a dense woven or knitted fabric. When the gas diffusion layer substrate is used, the performance is inferior. Further, the lower limit of the fineness is preferably 100 dtex or more because of compression resistance and flexibility, and the upper limit is preferably 400 dtex or less because a suitable thickness can be easily obtained.

  In the method for producing a woven or knitted fabric of the present invention, it is preferable to carbonize a multi-filament that can be carbonized as a woven or knitted fabric after having been entangled in advance.

  Generally, it is common practice to provide spinning twist or a winding oil agent in the production of carbonizable multifilament to give the yarn as a bundle, but in the present invention, it has better bundle and better weaving. In order to obtain a yarn, it is desirable to further entangle the filament bundle of multifilaments that can be carbonized.

  The entanglement process here refers to an entanglement process method widely implemented in general yarn processing. In particular, typical examples include those in which single fibers are mixed by compressed air flow using a nozzle, and those in which a micro loop is formed. In this case, the selection of the nozzle and the setting of the air pressure and the yarn supply rate may be any as long as the multifilament can be maintained in a good form without being damaged. More preferably, when conditions are set so that the number of entangled portions is 20 to 250 pieces / m and the length of unentangled portions is 15 mm or less, the yarn suitable for forming a carbon fiber woven fabric suitable for a gas diffusion layer substrate for a fuel cell. Can be obtained.

  In the present invention, it is preferable to carbonize a multi-filament that can be carbonized as a post-woven knitted fabric that has been previously twisted. As used herein, the term “twisting” refers to a twisting method widely used in general yarn processing. Not only simple additional twisting, but also multiple twisting, multiple twisting, and wall twisting of a plurality of yarns may be used. The number of twisted yarns and the twisting direction are not particularly limited, but it is preferably set in a range in which the multifilament is not damaged and the processability is not adversely affected by the torque of the yarn itself. More preferably, when the actual number of twists is 100 t / m or more, suitable convergence can be maintained. The apparatus used for twisting is also not limited. For example, the down twister, the up twister, the double twister, and the design twisting machine which are generally used widely are mentioned.

Other examples of yarn processing include false twisting, which refers to false twisting methods widely used in general yarn processing. For example, a method of imparting crimp by twisting, heat fixing, and untwisting, a method of imparting crimp by pushing a yarn into a heated box, and pressurizing with an object having irregularities such as a gear Examples include a method of imparting shrinkage.
In any case, it is preferable to set the conditions such that the multifilament is not fluffed. If there is fluff, it will affect the knitting and knitting manufacturing process passability, and when the woven or knitted fabric is impregnated with a carbonizable substance or when firing, fluff may come off, which is not preferable in terms of strength and appearance. .

By preliminarily imparting a favorable bundling property to the multifilament, the process passability during the production of the woven or knitted fabric is improved, and the quality of the woven or knitted fabric is also stabilized. Furthermore, when using the carbon fiber woven or knitted fabric of the present invention as a gas diffusion layer substrate for a fuel cell, in addition to multifilament and woven / knitted fabric design, various types of gas diffusion layer substrates required by selecting yarn processing conditions Special characteristics can be realized.
The polymer electrolyte fuel cell using the gas diffusion layer substrate of the present invention has almost no difference in power generation characteristics depending on the type of cathode gas under the same fuel cell operating environment. In other words, the oxygen supply usually provides better performance, but in the present invention, the same battery performance can be obtained regardless of whether the supply gas is oxygen or air. This is due to excellent gas and product water diffusion performance.

  Further, in the polymer electrolyte fuel cell using the gas diffusion layer base material of the present invention, the internal resistance during operation of the fuel cell does not change much depending on the cell temperature, and the internal resistance during operation of the fuel cell at a cell temperature of 80 ° C. And the internal resistance when the fuel cell is operated at a cell temperature of 60 ° C. is 15 mΩ or less. Normally, the internal resistance is good because the electrolyte membrane is sufficiently moisturized in a highly humidified environment, but the internal resistance becomes high due to drying of the electrolyte membrane in a low humidified environment. However, since the gas diffusion layer substrate of the present invention is excellent in water retention of the electrolyte membrane, an increase in internal resistance can be suppressed even in a low humidified environment.

  In the present invention, the structure of the woven or knitted fabric made of carbonizable multifilaments is not limited and may be generally manufactured and used. For example, the woven fabric may be a changed structure in addition to a basic structure such as plain weave, twill weave, and satin weave. Multiple weaves may be used as necessary. The knitted fabric may be a warp knitting, a flat knitting, or a circular knitting, and may be a basic organization such as a flat knitting or a rubber knitting, or a change organization.

The woven or knitted fabric made of carbonizable multifilament is preferably designed on the assumption that it shrinks due to carbonization.
The carbon fiber woven or knitted fabric of the present invention lacks drapability and is rigid due to its structure, and therefore, when used as a gas diffusion layer base material for a fuel cell, the groove portion of a ribbed separator (also referred to as a reserve plate) is not filled. Therefore, it is possible to prevent a decrease in the flow rate of gas such as fuel gas and oxygen.

  Known looms and knitting machines can be used for the production of the woven or knitted fabric of the present invention, and are not particularly limited. Since non-conductive multifilaments that can be carbonized can be used, there is no need for special electrical safety measures, and rapier looms, air jet looms, flat knitting machines, circular knitting machines, etc. that are widely used in general Since it can be used and no special equipment is required, there is a merit in terms of cost.

  Carbonized multifilament knitted or knitted fabric is a flameproofing process in which it is heated and fired in an air atmosphere at 200 to 400 ° C. to convert it into oxidized fibers, and further 300 to 2500 ° C. in an inert atmosphere such as nitrogen, argon or helium. A carbon fiber woven or knitted fabric is obtained through a carbonization step in which it is heated and carbonized. These processes can be continuously processed, and are effective for workability and cost reduction.

The fuel cell gas diffusion layer base material comprising the woven or knitted fabric of the present invention is impregnated with a thermosetting resin in a woven or knitted fabric before carbonization or a carbonized woven or knitted fabric, cured by heating and pressing, and then carbonized. Thus, a fuel cell gas diffusion layer substrate may be used.
The carbonization of the woven or knitted fabric of the present invention is preferably performed continuously over the entire length. If the gas diffusion layer substrate is long, not only the productivity of the gas diffusion layer substrate is increased, but also MEA (Membrane Electrode Assembly) production in the subsequent process can be continuously performed. This can greatly contribute to cost reduction of the fuel cell.

  The gas diffusion layer base material finally obtained from the above is preferably wound around a roll having an outer diameter of 50 cm or less, more preferably 40 cm or less. If it can be wound on a roll having an outer diameter of 50 cm or less, the product form as the gas diffusion layer substrate can be made compact, which is advantageous in terms of packaging and transportation costs.

Examples Hereinafter, the present invention will be described by way of examples.
Table 1 shows the properties of carbonized multifilaments used in each example and comparative example, the properties and woven density of the processed yarn, and the property evaluation results of the obtained carbon fiber knitted fabric.
In addition, the bending resistance of the carbon fiber woven fabric was in accordance with JIS L 1096 8.19.1 A method.
Hereinafter, the present invention will be described with reference to examples.

  Acrylonitrile-based multifilament 360dtex / 300f with a real twist of 15t / m (S direction) before winding and spinning is intermittently provided with an entangled portion with an air entanglement nozzle to obtain a processed yarn with good convergence. It was. In addition, after the air entanglement treatment, the actual twist imparted at the time of winding the spinning became unclear. A plain fabric was woven with this processed yarn using a rapier loom. Next, it was heated to 300 ° C. in an air atmosphere and further heated to 2000 ° C. in a nitrogen atmosphere to obtain a carbon fiber fabric. This fabric was low in both penetration resistance and surface resistance, and was suitable for a gas diffusion layer substrate.

  A satin fabric was woven using a rapier loom with the processed yarn 360 dtex / 300f obtained in the same manner as in Example 1. Next, when fired in the same manner, a carbon fiber fabric suitable for the gas diffusion layer base material, thicker than that obtained in Example 1, was obtained.

  The actual twist of 100 t / m (S direction) was applied to 360 dtex / 300f obtained in the same manner as in Example 1 with a down twister. When this real twisted yarn was made into a woven fabric in the same manner as in Example 1, and then baked, a carbon fiber woven fabric suitable for a gas diffusion layer substrate was obtained, although the penetration resistance and surface resistance were inferior to those of the woven fabric obtained in Example 1. .

An entangled portion was intermittently imparted with an air entangled nozzle to acrylonitrile-based multifilament 190 dtex / 160f to which an actual twist of 15 t / m (S direction) was added before winding of the spinning to obtain a processed yarn with good convergence. In addition, after the air entanglement treatment, the actual twist imparted at the time of winding the spinning became unclear. A plain fabric was woven with this processed yarn using a rapier loom. Subsequently, the carbon fiber woven fabric was obtained by heating and baking at 300 ° C. in an air atmosphere and further at 2000 ° C. in a nitrogen atmosphere. This woven fabric was thinner than Examples 1 to 3, and had low penetration resistance and surface resistance, and was suitable for a gas diffusion layer substrate.
When 10% of polytetrafluoroethylene was adhered to the carbon fiber fabric and subjected to water repellent treatment, an MEA was prepared and the battery performance was evaluated. As a result, the power generation performance was as shown in FIG. Under the same fuel cell operating environment (cell temperature 80 ° C., 60 ° C.), the same performance was obtained whether the cathode gas was oxygen or air.
In addition, oxygen was supplied to the cathode gas, and the internal resistance was measured at cell temperatures of 80 ° C. and 60 ° C., respectively. As shown in FIG. 2, the change in internal resistance due to the change in cell temperature was small (5 mΩ at the maximum), and good performance was obtained even under low humidification.
(Comparative Example 1)

  When we tried to weave a plain woven fabric of the same standard as in Example 1 without carrying out any yarn processing as it was, the generation of fluff due to rubbing between warps and its transmission were remarkable. It was difficult to weave.

  Overcoming the above problems, efficient, gas diffusivity, excellent conductivity and thin knitted fabric suitable for a gas diffusion layer base material for fuel cells and a method for producing the same, and good in a low humidified environment A gas diffusion layer base material for a fuel cell capable of exhibiting battery performance can be provided.

It is the graph which showed the current density [Current Density (mA / cm < ² >)] dependence of the voltage [Cell voltage (V)] at the time of the fuel cell driving | operation of Example 4. FIG. The legend in the graph has the following meanings. O2 (80): Supplying oxygen to cathode gas, voltage when operating at a cell temperature of 80 ° C. O2 (60): Supplying oxygen to cathode gas, voltage when operating at a cell temperature of 60 ° C. air (80)・ Air supply to cathode gas, voltage when operating at cell temperature of 80 ° C. air (60)... Air supply to cathode gas, voltage when operating at cell temperature of 60 ° C. It is the graph which showed the current density [Current Density (mA / cm < ² >)] dependence of the internal resistance [Internal resistance (m (omega | ohm))] at the time of the fuel cell driving | operation of Example 4. FIG. The legend in the graph has the following meanings. O2 (80): Supplying oxygen to the cathode gas, internal resistance when operating at a cell temperature of 80 ° C. O2 (60): Supplying oxygen to the cathode gas, internal resistance when operating at a cell temperature of 60 ° C.

Claims (10)

  A carbon fiber woven or knitted fabric made of carbonized multifilament processed yarn having a single fiber fineness of 0.1 to 5 dtex and a total fineness of 20 to 400 dtex.   The carbon fiber woven or knitted fabric according to claim 1, which has a bending resistance of 15 cm or more according to JIS L 1096 8.19.1 A method.   The carbon fiber woven or knitted fabric according to claim 1 or 2, wherein the carbonized multifilament processed yarn is an entangled yarn.   The carbon fiber woven or knitted fabric according to claim 1 or 2, wherein the carbonized multifilament processed yarn is a real twisted yarn.   A gas diffusion layer base material for a fuel cell comprising the carbon fiber woven or knitted fabric according to any one of claims 1 to 4.   The carbon fiber woven or knitted fabric according to any one of claims 1 to 4, wherein the carbonized multifilament having a single fiber fineness of 0.2 to 6 dtex and a total fineness of 50 to 500 dtex is processed into a knitted fabric and then carbonized. Production method.   The method for producing a carbon fiber woven or knitted fabric according to claim 6, wherein the carbonized multifilament is carbonized as a post-woven knitted fabric obtained by subjecting the multifilament to an entanglement treatment.   The method for producing a carbon fiber woven or knitted fabric according to claim 6, wherein the carbonized multifilament is carbonized as a post-woven knitted fabric obtained by twisting a multifilament.   A fuel cell gas diffusion layer base material that has no difference in power generation characteristics depending on the type of cathode gas under the same fuel cell operating environment.   A gas diffusion layer base material for a fuel cell, wherein a difference between an internal resistance during operation of the fuel cell having a cell temperature of 80 ° C. and an internal resistance during operation of the fuel cell having a cell temperature of 60 ° C. is 15 mΩ or less.

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