JP4282964B2 - Carbon fiber woven fabric - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a carbonaceous fiber woven fabric.
[0002]
[Prior art]
In recent years, great efforts have been put into the development of fuel cells.
Fuel cells are classified into alkaline type, phosphoric acid type, molten carbonate type, solid electrolyte type, solid polymer type, etc., depending on the type of electrolyte used, but among these, they can be operated at low temperatures and handled. 2. Description of the Related Art Solid polymer fuel cells that are easy and have a high output density have attracted attention for applications such as electric vehicles and household power supplies. Solid polymer fuel cells are being considered for cogeneration systems that improve overall thermal efficiency by using heat generated during power generation for heating and hot water supply.
[0003]
Main components of a single cell for a polymer electrolyte fuel cell are usually a membrane electrode body and a grooved separator. The basic structure of the membrane electrode body is obtained by sequentially joining a catalyst layer, a gas diffusion layer, and a current collector on both sides of a polymer solid electrolyte membrane (ion exchange membrane). The catalyst layer is mainly composed of a mixture of a catalyst and carbon black. The gas diffusion layer may also function as a current collector. A single cell of a polymer electrolyte fuel cell is formed by bonding a grooved separator to both surfaces of the membrane electrode body.
[0004]
In the polymer electrolyte fuel cell, fuel (hydrogen gas) is supplied to the anode side catalyst layer through the groove of the grooved separator, and oxidant (oxygen-containing gas) is supplied to the cathode side catalyst layer to cause a cell reaction. Sometimes, the flow of electrons generated through the membrane electrode body is taken out to the outside as electric energy. Therefore, the following is desired as the gas diffusion layer material.
(1) In order to operate this mechanism efficiently, the fuel and oxidant are supplied smoothly and evenly to the membrane electrode assembly.
(2) In order not to reduce the extraction efficiency of electric energy as much as possible, it has sufficient conductivity (that is, low volume resistivity),
(3) A moderate amount of water is retained so that the solid electrolyte membrane in the center of the membrane electrode body can exhibit proton conductivity (water retention),
{Circle around (4)} The water produced by the battery reaction can be discharged smoothly (drainage).
[0005]
However, water retention and drainage are contradictory, and it is generally difficult to satisfy both at the same time.
Carbon paper is mainly used as a material for the gas diffusion layer (which may also serve as a current collector), but recently we have examined the use of carbonaceous fiber woven fabrics made by weaving carbonaceous fibers. Has been.
[0006]
Carbon fiber woven fabric has greater air permeability than carbon paper, facilitates the smooth and even supply of fuel to membrane electrode assemblies, facilitates lowering of volume resistivity, and thickness depending on the material and weaving method. There are advantages that carbon paper does not have because it can be elastic in the direction, is not mechanically brittle, and is easy to control water retention and drainage.
[0007]
However, in a carbon fiber woven fabric, warp and weft of the woven fabric intersect each other, so that a slight thickness unevenness is likely to occur compared to carbon paper. Therefore, a slight difference in the contact state between the separator and the carbon cloth as the gas diffusion layer material results in unstable electrical resistance at that portion, resulting in unstable electrical resistance of the entire woven fabric. There is a problem that it is easy to become.
[0008]
Several methods for solving such problems of carbon fiber woven fabric have been proposed. For example, Japanese Patent Application Laid-Open No. 58-165254 describes filling a void portion of a carbonaceous fiber woven fabric with a mixture of a fluororesin and carbon black (see Patent Document 1). Japanese Patent Application Laid-Open No. 10-261421 describes that a layer made of a fluororesin and carbon black is formed on the surface of a carbon fiber woven fabric (see Patent Document 2). These methods are expected to reduce thickness unevenness by forming a fluororesin / carbon black mixed phase on the cloth surface.
[0009]
However, these methods are intended to adjust the water retention, drainage, gas permeability, etc. of the gas diffusion layer by filling the carbon fiber woven fabric with fluororesin, carbon black, etc. This is accompanied by the drawback that the battery characteristics are lowered due to the increased resistance, and the gas permeability, which is an advantage of the carbon fiber woven fabric, is lowered.
In addition, since the carbon fiber woven fabric is supple, when a fuel cell is formed by combining a membrane electrode body using the gas diffusion layer with a grooved separator, the carbon fiber woven fabric enters the groove of the grooved separator. There is a problem that the flow of gas in the groove is obstructed. Furthermore, since the contact point between the fibers is not fixed in the carbon fiber woven fabric, there is a problem that the electrical resistance in this portion is not stable, and as a result, the electrical resistance of the entire woven fabric tends to be unstable.
[0010]
[Patent Document 1]
JP 58-165254 A
[Patent Document 2]
JP-A-10-261421
[0011]
[Problems to be solved by the invention]
Therefore, the object of the present invention is to balance the properties desired as a gas diffusion layer material such as gas permeability, conductivity (low resistance), water retention, drainage, etc., and is uniform and has small thickness unevenness. Providing a carbonaceous fiber woven fabric that can reduce the difference in contact resistance at a minute level between the separator and the gas diffusion layer, and as a result, can stabilize battery characteristics such as output characteristics; and Due to the high rigidity of the carbon fiber woven fabric, there is almost no sag in the groove of the separator, and as a result, gas diffusion in the fuel cell is uniform and stable power generation characteristics can be expressed. The object is to provide a carbonaceous fiber woven fabric suitable as an expanding material, and particularly to provide a carbonaceous fiber woven fabric suitable as a gas diffusion layer material for a polymer electrolyte fuel cell.
[0012]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventors have obtained rigidity and thickness unevenness by combining weaving, pressing, carbonization / graphitization, and rigidity imparting treatment in a specific order. The present inventors have found that a carbon fiber woven fabric with a small amount can be obtained, and the present invention has been completed based on this.
[0013]
That is, the gist of the present invention is a woven fabric mainly composed of carbonaceous fiber yarns having a basis weight of 50 to 200 g / m. ² The thickness is 0.05 to 2 mm, the bulk density is 0.2 to 0.6 g / cc, the volume specific resistance in the plane direction is 0.2 Ωcm or less, and the warp yarn direction and the weft yarn direction are the sides. When the square is cut into two squares, the variation coefficient of the thickness of the woven fabric at a total of 20 dividing points obtained by dividing the two diagonals into 11 equal parts is 3.2% or less, and the warp and weft constituting the woven fabric Is a carbonaceous fiber woven fabric characterized in that the major axis of the cross section is twice or more the minor axis and the stiffness index value (L) based on the 45 ° cantilever method is 6 cm or more.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
The carbonaceous fiber woven fabric of the present invention is a woven fabric mainly composed of carbonaceous fiber yarns, and has a specific weight, thickness and coefficient of variation thereof, bulk density, and surface volume resistivity in a specific range. The cross-sections of the warp and weft constituting the woven fabric have a specific shape, and the stiffness index value based on the 45 ° cantilever method is in a specific range.
[0015]
The method for producing the carbonaceous fiber woven fabric of the present invention is not particularly limited as long as a material satisfying specific physical properties is obtained.For example, after pressing a woven fabric obtained by weaving carbonaceous precursor fibers, It can be produced by fusing the fibers to each other during carbonization and further graphitization. Further, more preferably, weaving the carbonaceous precursor fiber, pressing the resulting woven fabric, carbonizing treatment, and further graphitizing if desired, specifically, giving a rigidity, specifically, It can be produced by attaching a binder such as a resin and further carbonizing the attached binder component to obtain a carbonized product.
[0016]
Hereinafter, this manufacturing method will be described in detail.
(Carbonaceous precursor fiber)
As the carbonaceous precursor fiber as a starting material, any known carbonaceous precursor fiber such as polyacrylonitrile-based, pitch-based, cellulose-based, polynosic-based, phenolic resin-based, or a mixture thereof can be used. Usually, pitch system or polyacrylonitrile system is used. Among them, it is preferable to use a polyacrylonitrile-based carbonaceous precursor fiber. The polyacrylonitrile-based carbonaceous precursor fiber is made from polyacrylonitrile with 100% acrylonitrile as the raw material, or acrylonitrile-based copolymer mainly composed of acrylonitrile with 50% or more of acrylonitrile, depending on the content ratio of acrylonitrile units. In addition, there are various types such as those made from acrylonitrile-based copolymers containing 20-50% acrylonitrile as acrylonitrile, and carbonaceous precursor fibers made from any of these may be used. it can.
[0017]
(Flame resistance treatment)
Prior to weaving the carbonaceous precursor fiber into a woven fabric, it can be subjected to flame resistance treatment.
Flameproofing treatment (infusibilization treatment) is a chemical reaction in which oxygen atoms are introduced into the molecular structure of pitch or polyacrylonitrile, and is usually 200 to 300 ° C., at most below 400 ° C. This is done by contact for a minute. In general, the greater the amount of oxygen introduced into the molecular structure, the greater the effect of preventing fusion during the subsequent carbonization treatment. As the index, the limiting oxygen concentration necessary for burning the fiber, generally called LOI value, is used. In order not to cause fusion as in the case of production of normal carbonaceous fibers, flameproofing treatment should be performed so that the LOI value becomes 35-60. Also in the production of the carbonaceous fiber woven fabric of the present invention, it is preferable to perform a flame resistance treatment so that the LOI value of the carbonaceous precursor is 35-60.
[0018]
That is, when the carbonaceous fibers constituting the woven fabric are not fused, the flame resistance treatment may be performed so that the LOI value becomes 35-60. Conversely, when it is desired to improve the characteristics of the fuel cell by fusing the fibers into a woven fabric having rigidity, the flame resistance treatment may be performed so that the LOI value is less than 35, particularly 33 or less. . Note that if the LOI value is too small, the subsequent carbonization treatment becomes excessively fused, and the resulting carbonaceous fiber woven fabric becomes brittle, so that the LOI value is 20 or more, particularly 25 or more. Is preferably performed. The LOI value can be adjusted by changing the contact temperature and contact time with oxygen during the flameproofing treatment.
[0019]
For example, in one of the preferable methods, a flameproof fiber obtained by flameproofing a polyacrylonitrile fiber in air at 200 to 300 ° C. is used. The polyacrylonitrile fiber used for the flameproofing treatment may be either a long fiber or a short fiber spun, and the yarn may be either a single yarn or a twin yarn. Further, the fiber can be stretched during the flameproofing treatment to improve the toughness of the fiber.
[0020]
(Carbonaceous precursor fiber yarn)
The yarn to be used for weaving may be either a filament yarn or a spun yarn, but a spun yarn is preferred because a dense and uniform woven fabric structure is obtained and the productivity of the yarn is high. As a spinning method for obtaining a spun yarn, any known method can be applied, and examples thereof include spinning methods such as cotton spinning, 2-inch spinning, worsted spinning, spun spinning, and direct spinning. In the case of a polyacrylonitrile-based flameproof fiber, it is preferable to use a spun yarn obtained by spinning a sliver obtained by checking out a continuous filament tow of polyacrylonitrile by eyelash spinning.
[0021]
(Thread type)
The yarn for use in the weaving may be a single yarn, a double yarn, a triple twisted yarn, a filament yarn, or a composite yarn composed of carbonaceous precursor fibers of different raw materials.
The spun yarn may be either a double yarn or a single yarn, but in general, the double yarn has a higher tensile strength than the single yarn, so that a woven fabric with a uniform thickness can be produced. It is preferable because it is possible.
[0022]
(Fine fineness (count))
The fineness of the yarn is metric, usually 14 or more, preferably 16 or more, more preferably 18 or more, and usually 50 or less, preferably 45 or less.
In the case of a single yarn, it is metric, usually 1/14 Nm or more, preferably 1/16 Nm or more, more preferably 1/18 Nm or more, and usually 1/50 Nm or less, preferably 1/45 Nm or less. In the case of twin yarn, it is metric, usually 2/28 Nm or more, preferably 2/32 Nm or more, more preferably 2/36 Nm or more, and usually 2/100 Nm or less, preferably 2/90 Nm or less.
[0023]
When the count is thicker than 1/14 Nm or 2/28 Nm, the number of fluffs per unit length tends to increase. Moreover, when the count is finer than 1/50 Nm or 2/100 Nm, the tensile strength of the yarn tends to be low.
(Number of yarn twists)
The number of twists of the yarn is measured according to JIS L 1095 (general spun yarn test method).
[0024]
The number of twists in the case of single yarn is usually 300 times / m or more, preferably 500 times / m or more, and usually 800 times / m or less, preferably 700 times / m or less per 1 m of yarn length. . The preferred number of twists varies slightly depending on the yarn count, but when the number is less than 300, the number of fluffs of the yarn tends to increase. Moreover, when the number of twists is too large, yarn breakage is likely to occur during twisting. When the number of twists is increased, the number of fluffs is reduced, but when the number of twists is 700 times or more, the effect of fluff reduction by increasing the number of twists is almost saturated.
[0025]
In the case of twin yarns, the number of upper twists is usually 300 times / m or more, preferably 400 times / m or more, and usually 800 times / m or less, preferably 750 times / m or less per 1 m of yarn length. is there. If the number of upper twists is small, the number of fluff tends to increase. In addition, if the number of upper twists is large, the probability of occurrence of yarn breakage during twisting increases, and thickness unevenness may increase. The number of twists is usually 500 times / m or more, preferably 600 times / m or more, and usually 900 times / m or less, preferably 850 times / m or less. If the number of lower twists is small, the number of fluff tends to increase. Moreover, if the number of lower twists is large, the probability of occurrence of yarn breakage tends to increase during twisting.
[0026]
(Weaving)
The above-mentioned polyacrylonitrile-based flameproof fiber, etc., may be used to weave a flameproof carbonaceous precursor fiber to form a flameproof woven fabric, or the polyacrylonitrile-based fiber itself, etc., a carbonaceous precursor that has not been flameproofed. Body fibers may be woven to form a woven fabric, which may be subjected to a flameproofing treatment to provide a flameproofed woven fabric. In this case, the woven fabric may be brought into contact with an oxidizing gas such as air, ozone, or nitrogen oxide, sulfuric acid, nitric acid, or the like to obtain a flame resistant woven fabric having a suitable LOI value.
[0027]
(Weave)
The structure of the woven fabric may be plain weave, oblique weave, satin weave, or any other structure, but since plain weave has the largest number of crossings per unit area of warp and weft, the volume resistivity of the woven fabric is Since it becomes small, it is preferable.
(Background density)
The weft density (the number of warp and weft yarns per unit length) in the case of plain weave is generally 20 to 60 yarns per inch, but specifically, single yarn, double yarn or thick yarn It chooses suitably according to it.
[0028]
(Carbonaceous precursor fiber woven fabric)
The basis weight of the carbonaceous precursor fiber woven fabric, that is, the mass per unit area is usually 50 g / m. ² Or more, preferably 60 g / m ² Or more, more preferably 80 g / m ² In addition, it is usually 350 g / m ² Or less, preferably 250 g / m ² It is as follows. If the basis weight is too small, the rigidity and the tensile strength are reduced, and if the basis weight is too large, the eyes are clogged too much and the gas diffusibility is lowered.
[0029]
The thickness of the woven fabric is usually 0.05 mm or more, preferably 0.10 mm or more, more preferably 0.20 mm or more, and usually 5 mm or less, preferably 3 mm or less. If the thickness is too small, the tensile strength is lowered, and if it is too large, the eyes are clogged and the gas permeability is lowered.
The bulk density of the woven fabric is usually 0.2 g / cc or more, preferably 0.25 g / cc or more, and usually 0.8 g / cc or less, preferably 0.7 g / cc or less. If the bulk density is too small, the tensile strength is lowered, and if the bulk density is too large, the eyes are clogged and the gas permeability is lowered.
[0030]
The width of the woven fabric is usually 5 cm or more, preferably 10 cm or more, and is usually 250 cm or less, preferably 200 cm or less, more preferably 100 cm or less. If the width is too small, shrinkage in the width direction of the woven fabric may be increased, resulting in wrinkles and uneven thickness. In addition, if the width is too large, it is difficult to uniformly perform carbonization and graphitization, and in particular, uneven thickness tends to occur due to non-uniform shrinkage during carbonization.
[0031]
The length of the woven fabric is usually 50 cm or more, preferably 100 cm or more, and is usually 300 m or less, preferably 200 m or less. If the length is too short, shrinkage in the length direction (long direction) may increase, wrinkles occur, and thickness unevenness tends to occur. In addition, when the longer length is used for the gas diffusion layer material (when the sealing process is continuously performed by applying a paste containing carbon black as a main component to the woven fabric), the woven fabrics have a longer length. This is preferable because the number of connections (the number of times the ends of the woven fabric are connected) is reduced. However, in actuality, in order to prevent the occurrence of thickness unevenness, it is necessary to reduce the winding tension of a long length of 300 m or more. There is virtually no winding equipment that can be controlled and wound stably from the beginning to the end of winding.
[0032]
(Press working)
Pressing is performed in order to reduce thickness unevenness of the carbonaceous precursor fiber woven fabric. Normally, it is easy to imagine that if the woven fabric after carbonization (graphitization) is pressed as pressing, the unevenness in thickness can be suppressed, but when pressing under mild pressing conditions to maintain the fiber shape Unevenness in thickness increases. On the other hand, if the press conditions are set so as to eliminate unevenness in thickness, the fiber itself cannot maintain its original shape.
[0033]
Therefore, before the carbonization / graphitization treatment is completed (until the completion of the graphitization treatment or until the completion of the carbonization treatment), the press work must be performed. That is, by performing the press working before the heat treatment at a temperature higher than the thermal history of the fibers constituting the woven fabric and higher than the temperature necessary for the carbonization treatment of the fibers, A woven fabric having the following physical properties can be obtained.
[0034]
(Type of press)
Examples of the press for performing the press working include a flat plate press having a flat press surface, a roll press that performs press working with a roll, and the like. A roll type press is preferred because the fabric can be continuously pressed. Moreover, examples of the pressurizing method of the press device include a hydraulic type, a pneumatic type, a spring pressure type, and the like. Any of them may be used, but a hydraulic type capable of high-pressure pressing is generally preferable.
[0035]
(Roll type press)
In a roll type press, generally, a woven fabric is sandwiched between rotating upper and lower rolls made of metal, and the pressing is continuously performed. The diameter of the roll of the roll type press is usually about 10 to 80 cm, and the width of the contact portion between the roll and the woven fabric is about 2 to 10 mm although it varies depending on the roll diameter. Further, the effective length of the roll is preferably about 50 to 200 cm in order to perform press working with uniform pressure. The pressure per roll unit length obtained by applying pressure by hydraulic pressure or the like and dividing the total load by the effective roll length is 50 to 500 kg / cm, preferably 100 to 400 kg / cm. If the thickness is less than 50 kg / cm, the thickness unevenness is reduced, but the reduction amount is small. On the other hand, when it exceeds 500 kg / cm, the fiber of the woven fabric is partially compressed and broken, although it varies slightly depending on the thickness of the woven fabric before pressing, thickness unevenness, yarn thickness, weft density, etc. The strength of the fabric may be significantly reduced. The passing speed of the woven fabric between the pressing rolls varies depending on the pressing pressure, but is usually preferably about 2 to 20 m / min. Outside this range, uniform pressing may not be performed.
[0036]
The number of press processings may be repeated not only once but 2-10 times.
(Flat plate press)
In the case of a flat plate type press, the pressing pressure during pressing is a surface pressure of 20 to 2000 kg / cm. ² Is preferred. 20kg / cm ² Even if the thickness is less than the thickness unevenness, the amount of reduction is small. 2000kg / cm ² Exceeds the thickness of the woven fabric before pressing, thickness unevenness, thread thickness, weft density of the woven fabric, etc. It may be significantly reduced.
[0037]
The time for pressurization at a predetermined pressure is usually preferably 10 seconds to 10 minutes. If it is less than 10 seconds, the effect of reducing thickness unevenness is small. On the other hand, even if it is pressed for a long time exceeding 10 minutes, the effect is small.
In any case, the number of woven fabrics to be pressed with a press is usually one by one, but in order to increase productivity, about 2 to 20 sheets may be stacked and pressed. However, with 20 sheets or more, there are cases where the effect of reducing thickness unevenness is not seen in the woven fabric after press working.
[0038]
In addition, in order to increase the effect of reducing thickness unevenness, the woven fabric before press processing is glued with polyvinyl alcohol, starch paste or the like, or phenol resin, furan resin, polyimide resin, polyethylene resin, polypropylene resin, polyimide resin, A thermosetting resin such as polyamide resin or a thermoplastic resin dissolved in an organic solvent or a finely pulverized product of these resins may be added.
[0039]
Further, at the time of pressing, the temperature of the pressing surface may be raised to a temperature higher than room temperature (for example, about 50 to 500 ° C., preferably about 100 to 300 ° C.) for pressing. In this case, the above-described resin is melted and cured, and moisture contained in the woven fabric is removed, so that more uniform pressing can be performed.
By pressing as described above, not only the thickness unevenness is reduced, but also a fluff having a length of about several millimeters existing on the surface of the carbon fiber woven fabric, which can be one of the causes of the voltage drop of the fuel cell. The effect of reducing the fluff of can be expected.
[0040]
(Carbonization treatment)
Subsequent to the press processing, carbonization treatment of the carbonaceous precursor fiber woven fabric is performed.
The carbonization treatment may be performed in an inert gas at 400 ° C. or higher, preferably 600 ° C. or higher and 1400 ° C. or lower, preferably 1300 ° C. or lower. From the viewpoint of the conductivity of the woven fabric, it is preferably heated to 700 ° C. or higher, more preferably 800 ° C. or higher, and more preferably 900 ° C. or higher.
[0041]
In the carbonization treatment, carbonization is performed at 800 to 1400 ° C via a thermal decomposition temperature of about 300 to 750 ° C. The heating rate during the pyrolysis process is preferably 5 to 300 ° C./min, and the temperature holding time during the carbonization process is preferably 1 minute or more and 4 hours or less. Also, depending on the heat capacity of the heat treatment furnace and the conveying speed of the raw material woven fabric into the furnace, the woven fabric is introduced into the carbonization zone at a constant temperature from the beginning without providing a thermal decomposition zone of 750 ° C. or less, and The temperature that the fabric receives from the carbonization zone may increase the temperature of the woven fabric and cause thermal decomposition, and then carbonization may proceed. The gas atmosphere in the furnace is preferably an inert atmosphere having an oxygen concentration of 100 ppm or less in any case.
[0042]
The carbonization furnace for performing the carbonization treatment may be either a batch heat treatment furnace or a continuous heat treatment furnace. However, a continuous furnace is used because of the advantage that a long woven fabric can be carbonized continuously and uniformly. preferable.
The continuous heat treatment furnace is a horizontal continuous heating furnace or a vertical continuous heating furnace provided with heating means in multiple stages. The horizontal type is more deformed and non-uniformized by the weight of the woven fabric than the vertical type. It is preferable because it is difficult. In-furnace transportation of workpieces is usually carried directly on a metal (steel, stainless steel, etc.) mesh or non-mesh belt and transported at a constant speed by external control of the belt. preferable.
[0043]
(Graphitization treatment)
Subsequent to the carbonization treatment, further graphitization treatment can be performed.
The graphitization temperature is usually 1400 ° C. or higher, preferably 1600 ° C. or higher, and usually 3000 ° C. or lower, preferably 2500 ° C. or lower. If the temperature is 1400 ° C. or higher, the volume resistivity of the woven fabric is further reduced, which is more preferable as a gas diffusion layer material. In addition, the volume resistivity after the heat treatment in the treatment up to about 3000 ° C. is not problematic for use as a gas diffusion layer material.
[0044]
The time for the graphitization treatment is usually 10 minutes or longer, preferably 20 minutes or longer, and is usually 4 hours or shorter, preferably 2 hours or shorter. If the treatment time is less than 10 minutes, graphitization may not be completed uniformly. On the other hand, when the treatment time is long, the productivity and thermal efficiency are low, and the woven fabric may be contaminated with impurities generated from the heat insulating material of the graphitization furnace, the heating element, or the like.
[0045]
(Rigidity imparting process)
By attaching a binder, preferably an organic binder such as resin or pitch, to these carbonaceous fiber woven fabrics, and binding the carbonaceous fibers constituting the woven fabric to each other, the carbonaceous fiber woven fabric according to the present invention. A cloth can be obtained. The organic binder can be attached by, for example, immersing the woven fabric in a solution of the organic binder or applying the solution to the woven fabric.
[0046]
For example, a woven fabric is immersed in a solution in which an organic binder is dissolved in water, methanol, acetone, toluene, xylene, quinoline, N, N-dimethylformamide or the like in an appropriate solvent to adhere the organic binder to the woven fabric, and then dried. After that, it is possible to use a method of curing the organic binder by heating with a hot press, calendar roll, oven or the like. As the organic binder solution used for dipping the woven fabric, a solution having a concentration of usually 0.1 to 10% by weight, preferably about 0.5 to 5% by weight may be used. In addition to simply curing the organic binder, the woven fabric with the organic binder attached may be further heated in an inert atmosphere such as nitrogen or argon to carbonize and further graphitize the organic binder.
[0047]
Examples of the organic binder include phenol resin, furan resin, polyphenylene resin, polyethylene, polystyrene, polyimide, polyamide, polyacrylonitrile, polyvinyl alcohol, polyethylene glycol, polyamide imide, polyether imide, polyether ether ketone, polycarbonate, acetal resin, Polyphenylene oxide, polyphenylene sulfide, polybutylene terephthalate, polyethylene terephthalate, bismaleimide resin, thermoplastic polyurethane, ABS resin, AAS resin, poly-4-methyl-1-pentene, poly-1-butene, acrylonitrile-styrene resin, polyvinyl Butyral, silicone resin, unsaturated polyester resin, diallyl phthalate resin, melamine resin, urea resin , Cellulose, epoxy resins, polyesters, coal tar pitch, petroleum pitch, or the like may be used mesophase pitches.
[0048]
Further, rubber-like materials such as ethylene-propylene copolymer rubber, polydiene, polyurethane rubber, natural rubber, polyvinylidene chloride, polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-hexafluoro Fluorine rubber such as propylene fluorine rubber, fluoroethylene-vinyl ether copolymer (for example, “Lumiflon” manufactured by Asahi Glass Co., Ltd.), amorphous perfluoro resin (for example, “Cytop” manufactured by Asahi Glass Co., Ltd.) In addition, fluorine-containing resins such as thermoplastic fluororubber (for example, “Dai-L Thermoplastic” manufactured by Daikin Industries, Ltd.) and soft fluororesin (for example, “Cefral Soft” manufactured by Central Glass Co., Ltd.) can also be used. Among these, it is preferable to use a thermosetting material. In particular, when carbonizing after adhering to a woven fabric, a thermosetting material should be used so that the shape can be maintained during the carbonization treatment, and when using a thermoplastic material, the carbonization treatment is performed. Prior to this, pretreatment such as flameproofing should be performed.
[0049]
In the present invention, when the carbonaceous fibers constituting the woven fabric are bound to each other with the binder or the carbonized product thereof, the binder or the carbonized product does not block the gap of the woven fabric and does not deteriorate the gas diffusibility of the woven fabric. It is important to do so.
For this purpose, the following two methods are suitable.
That is, (1) the surface of the carbonaceous fiber is coated with a relatively small amount of binder or its carbonized product by dipping the woven fabric in a low-concentration binder solution or by applying this solution to the entire surface of the woven fabric. Or (2) a high-concentration binder solution is sprayed on the woven fabric and the binder is adhered to the woven fabric in the form of dots, so that a relatively large amount of the binder or its carbonized carbon fiber is used. May be bound discontinuously.
[0050]
The state of binding of the carbonaceous fiber surface with the binder or carbonized product thereof can be easily confirmed by observing the woven fabric with a transmission electron micrograph.
First, as the above (1), the organic binder is usually immersed in the woven fabric by immersing the woven fabric in a relatively low concentration binder solution of about 0.1 to 20% by weight, preferably about 0.5 to 10% by weight. After adhering and then drying, the organic binder can be cured by heating with a hot press, a calender roll, an oven or the like. Therefore, when a large amount of organic binder is deposited, the organic binder should be carbonized after deposition. In addition, when carbonizing the organic binder adhered to the woven fabric, it is preferable to use an organic binder having a residual ratio after carbonization of 20% or more, particularly 40 to 65%. Further, powdered activated carbon, activated carbon fiber, porous carbon black such as ketjen black, etc. may be mixed in the binder and adhered to the woven fabric. These are preferably mixed in an amount of about 10 to 90% by weight, particularly about 30 to 80% by weight, based on the binder, and this can generally increase the rigidity of the carbon fiber woven fabric finally obtained. In this case, the content of the binder or carbonized product thereof in the obtained carbonaceous fiber woven fabric is usually 0.01% by weight or more, preferably 0.05% by weight or more. Further, it is usually 30% by weight or less, preferably 25% by weight or less, more preferably 20% by weight or less, and further preferably 10% by weight or less.
[0051]
If the content of the binder or the carbonized product is large, the gas permeability of the woven fabric tends to be impaired. Therefore, it can be said that it is preferable that the content is small as long as rigidity and the like are satisfied. From this viewpoint, the content of the binder or its carbonized product is preferably 16% by weight or less, more preferably 10% by weight or less, and particularly preferably 5% by weight or less.
[0052]
Next, as a method of discontinuously binding carbonaceous fibers with the binder or the carbonized product thereof in the above (2), the following can be mentioned. First, it is preferable to select a thermosetting resin such as a phenol resin, a furan resin, an unsaturated polyester resin, a urea resin, an epoxy resin, a melamine resin, a diallyl phthalate resin, or a silicone resin as the kind of binder or carbonized product thereof. This thermosetting resin is usually an average particle size of 3 μm or more, preferably an average particle size of 10 μm or more, and usually an average particle size of 50 μm or less, preferably an average particle size of 30 μm or less (the maximum particle size is usually 200 μm or less). , Preferably 150 μm or less, and minimum particle size is usually 0.1 μm or more, preferably 0.5 μm or more) as a dispersion of semi-cured resin fine particles, sprayed or applied to a woven fabric, suitably dried and pressed, It can be produced by heating and complete curing.
[0053]
The semi-cured resin refers to a resin having a dissolution amount of 30 to 97% by weight, especially 70 to 95% by weight when the resin is boiled with a large excess of methanol. If the thermosetting resin is completely cured, it does not substantially dissolve even in a large excess of methanol, but if it does not reach complete curing, it partially dissolves, so the degree of cure can be expressed by the amount dissolved.
[0054]
Drying is usually performed at 50 to 170 ° C., preferably 90 to 160 ° C., and complete curing is not less than the curing temperature of the thermosetting resin to be used, and is usually 120 to 400 ° C., preferably 180 to 330 ° C. Just do it.
The thermosetting resin is particularly preferably a semi-cured product of a phenol resin and a modified phenol resin, considering heat resistance, chemical stability, conductivity, and the like.
[0055]
When a large amount of organic binder is deposited, the organic binder should be carbonized after deposition. In addition, when carbonizing the organic binder adhered to the woven fabric, it is preferable to use an organic binder having a residual ratio after carbonization of 20% or more, particularly 40 to 65%. Further, powdered activated carbon, activated carbon fiber, porous carbon black such as ketjen black, etc. may be mixed in the binder and adhered to the woven fabric. These are preferably mixed in an amount of about 10 to 90% by weight, particularly about 30 to 80% by weight, based on the binder, and this can generally increase the rigidity of the carbon fiber woven fabric finally obtained. In this case, the content of the binder or the carbonized product thereof in the obtained carbon fiber woven fabric is usually 10% by weight or more, preferably 20% by weight or more, and usually 40% by weight or less, preferably 35% by weight. Hereinafter, it is more preferably 30% by weight or less.
[0056]
A woven fabric with increased rigidity using a semi-cured product of such a thermosetting resin as a binder can bind carbon-fibres in a point contact with the semi-cured product. As in the case where it is used, not only the adhesion between the carbonaceous fibers but also the increase in electric resistance generated because the resin covers the surface of the fibers is preferable.
When the woven fabric obtained by weaving the flame resistant fiber is carbonized and further graphitized, the fibers can be fused together to produce the carbonaceous fiber woven fabric according to the present invention without using a binder. However, in the same manner as described above, a binder may be added to the woven fabric obtained in this manner to bind the carbonaceous fibers constituting the woven fabric to each other. In addition, the carbonization of the woven fabric and the carbonization of the organic binder can be performed simultaneously by attaching an organic binder to the flameproof fiber woven fabric before carbonization treatment. The organic binder may be appropriately selected from those described above.
[0057]
In addition, the carbonization conditions of the above-mentioned resin binder are normally 400-2200 degreeC, Preferably it is 700-1600 degreeC, More preferably, it is 800-1200 degreeC, Usually 1 minute-5 hours, Preferably it is 10-30 minutes It is.
(Other processing)
The carbonaceous fiber woven fabric obtained above consists essentially of carbonaceous fibers, but contains the binder or carbonized product thereof, and further includes powdered activated carbon, conductive carbon black, Conductive substances such as carbonized products of various pitches can also be included. For example, pitch is dissolved in an organic solvent to form a pitch solution, and powdered activated carbon or conductive carbon black suspended therein is applied to the woven fabric obtained above, and then heated in an inert gas. The pitch is carbonized. Even in that case, the proportion of carbonaceous fibers in the woven fabric is usually 60% by weight or more, and preferably 80% by weight or more.
[0058]
The carbon fiber woven fabric obtained as described above can be used as it is as a material for a gas diffusion layer of a fuel cell, but it can be further processed and used as a material for a gas diffusion layer. For example, in order to prevent the deterioration of battery characteristics by holding moderate moisture in the membrane electrode body constituting the battery or by adsorbing and removing impurities contained in the fuel and oxidant supplied to the battery, The carbonaceous fiber woven fabric is brought into contact with water vapor or carbon dioxide of about 800 to 1200 ° C. or air of about 300 to 500 ° C., and a part of the carbonaceous material is gasified to generate fine pores in the carbonaceous fiber, It can be set as the woven fabric which consists of a porous carbonaceous fiber.
[0059]
(Physical properties of carbon fiber woven fabric)
The basis weight of the obtained carbon fiber woven fabric is 50 g / m. ² Or more, preferably 60 g / m ² Or more and 200 g / m ² Or less, preferably 180 g / m ² It is as follows. If the weight per unit area is too small, the tensile strength becomes small and the gas diffusion layer material cannot be used. If the basis weight is too large, the gas permeability is too small.
[0060]
The bulk density (g / cc) of the carbon fiber woven fabric is obtained by dividing the basis weight of the woven fabric by the thickness of the woven fabric. The bulk density of the woven fabric is 0.2 g / cc or more, preferably 0.25 g / cc or more, and 0.6 g / cc or less, preferably 0.55 g / cc or less. If the bulk density is less than 0.2 g / cc, the tensile strength of the woven fabric is weak and impractical. On the other hand, if the bulk density is too large, gas diffusibility is lowered.
[0061]
The volume specific resistance in the plane direction of the carbon fiber woven fabric is 0.2 Ωcm or less, preferably 0.15 Ωcm or less, more preferably 0.10 Ωcm or less. This value is preferably as low as possible, but if it is about 0.05 Ωcm or less, the volume resistivity is sufficiently low as a gas diffusion layer material.
The fineness of the yarn constituting the woven fabric is metric, usually 16 or more, preferably 18 or more, more preferably 20 or more, and usually 60 or less, preferably 55 or less.
[0062]
In the case of a single yarn, it is metric, usually 1/16 Nm or more, preferably 1/18 Nm or more, more preferably 1/20 Nm or more, and usually 1/60 Nm or less, preferably 1/55 Nm or less. In the case of twin yarn, it is metric, usually 2/32 Nm or more, preferably 2/36 Nm or more, more preferably 2/40 Nm or more, and usually 2/120 Nm or less, preferably 2/110 Nm or less.
[0063]
When the count is thicker than 1/16 Nm or 2/32 Nm, the number of fluffs per unit length tends to increase. Further, when the count is smaller than 1/60 Nm or 2/120 Nm, the tensile strength of the yarn tends to be low.
The carbonaceous fiber is obtained through a process of spinning, flame resistance, carbonization (graphitization), and the fineness is about 10 to 20% in the process of carbonizing and further graphitizing the flame resistant thread. Decrease. In the present invention, the fineness of the yarn constituting the woven fabric is about the yarn of the finally obtained woven fabric, and can be measured by extracting the yarn from the woven fabric and measuring it.
[0064]
The weft density (number of warp and weft per unit length) of plain weave carbon fiber is about 10 in the process of carbonizing and graphitizing the yarn (flame-resistant yarn) constituting the woven fabric. In general, the number is 30 to 70 per inch. Specifically, the number is appropriately selected according to whether single yarn or double yarn or the thickness of the yarn. For example, the weft density when 2/40 Nm spun yarn is used for the warp and weft is usually 100 to 300/10 cm for both the warp and weft per 10 cm length of the woven fabric, preferably 180 ˜250 / 10 cm. Further, when the gap between the warp yarn and the weft yarn is observed with a scanning electron microscope, the hole diameter corresponding to the gap between the yarns is 10 to 150 μm when used for the gas diffusion layer of the fuel cell. It is preferable for ensuring water retention and drainage.
[0065]
One example of a preferred woven fabric is obtained by plain weaving 40-60 count yarns composed of single fibers having a diameter of 7-10 μm at a density of 30-70 warps and wefts per inch. .
The thickness (average value) and thickness unevenness (coefficient of variation) of the carbonaceous fiber woven fabric are obtained as follows. A square with sides in the warp and weft directions is cut out from the woven fabric so as not to include a portion up to 5 mm from the end, preferably up to 10 mm, and divided into 20 equal parts, each of which is divided into two equal parts. Measure the thickness of the point woven fabric. An average value and a coefficient of variation in thickness (standard deviation of woven fabric thickness / average value of woven fabric thickness x 100%) are determined from the measured values. The size of the woven fabric to be cut out varies depending on the width of the woven fabric, but it is standard to cut into a square with a fabric width of 40 to 98% excluding the end portion, with a fabric width of about 70 to 90%. Although not limited, a 10-40 cm square is preferable.
[0066]
Thickness measurement is about 10 g / cm for a disk-shaped terminal with a diameter of 5 mm. ² The thickness is measured by contacting the surface of the woven fabric with a load of. The above measurement is performed every 5 to 50 m so as not to include a portion up to 5 mm from the end, preferably 10 mm in the length direction of the woven fabric, but when the woven fabric length is less than 5 m, The thickness of the carbon fiber woven fabric and the coefficient of variation of the thickness are obtained from the value measured by cutting one arbitrary point into a square. If the length is 5 m or more, divide into 5 equal parts in the length direction, and calculate the thickness and coefficient of variation of the thickness for a total of 5 points obtained by cutting one arbitrary point from each of them into squares. The thickness of the long carbon fiber woven fabric and the coefficient of variation of the thickness.
[0067]
The thickness of the carbon fiber woven fabric is 0.05 mm or more, preferably 0.1 mm or more, and 2 mm or less, preferably 1 mm or less, more preferably 0.35 mm or less. If the thickness is less than 0.05 mm, the tensile strength is small and the gas diffusion layer material is insufficient. On the other hand, if the thickness exceeds 2 mm, the gas permeability is lowered and the gas diffusion layer material is insufficient.
[0068]
The variation coefficient of the thickness of the carbon fiber woven fabric is 3.2% or less, preferably 3% or less, more preferably 2.8% or less. Since the binder adhering to the rigidity imparting treatment or the carbonized material thereof enters the portion where the thickness unevenness occurs and the coefficient of variation is improved, it is usually 2.5% or less, preferably 2.3% or less, more Preferably it is 2% or less. A smaller coefficient of variation is better, but about 1% is sufficient.
[0069]
(Cross-sectional shape of warp and weft constituting the woven fabric)
In a normal woven fabric that is not pressed, the overall cross-sectional shape of the yarn after weaving can be approximated by a substantially circular shape or an ellipse having a major axis / minor axis ratio close to 1. On the other hand, the cross-sectional shape of the yarn of the woven fabric after press working can be approximated by an ellipse having a major axis in the surface direction, a minor axis in the thickness direction, and a major axis / minor axis ratio of 2 or more.
[0070]
The method for observing the cross-sectional shape of the yarn in the woven fabric is not particularly limited. For example, a photograph in which the fractured surface of the woven fabric is cut parallel to the warp or weft, and the cut cross-section is photographed with a microscope such as a scanning electron microscope. Can be obtained from It is possible to use scissors with sharp blades for cutting the woven fabric, but in addition, the woven fabric is embedded in a thermosetting resin with small dimensional change after curing, completely cured, and then the fracture surface May be cut out with a cutting tool and used as an observation target sample.
[0071]
The ratio of the major axis / minor axis ratio of the warp and weft yarns that make up the woven fabric may vary slightly depending on the thickness of the yarn (yarn count), the number of twisted yarns, twin or single yarn, or the weft density of the woven fabric. Although different, it must be 2 or more, preferably 2.5 or more, more preferably 3 or more. When the ratio of major axis / minor axis is less than 2, the effect of reducing thickness unevenness is small. The ratio of major axis / minor axis is usually 10 or less, preferably 8 or less. When the ratio exceeds 10, a portion where the thickness of the woven fabric becomes extremely thin occurs, and the thickness unevenness may increase.
[0072]
The measured values of the major axis and minor axis are slightly different depending on the thickness of the yarn (yarn count), the number of twisted yarns, twin yarn or single yarn, or the weft density of the woven fabric, but the major axis is usually 200 to 800 μm. The minor axis is usually 80 to 200 μm.
(Gas permeability)
The gas permeability was measured by an air permeability test (Fragile type method) of JIS L 1096 (General Textile Test Method). The measured value of gas permeability obtained by this evaluation method reflects the degree of gas permeability and water retention when carbonaceous fibers are used as the gas diffusion layer material for fuel cells.
[0073]
The gas permeability of woven fabric is usually 200cm ^Three / Cm ² -Sec or less, preferably 150cm ^Three / Cm ² -Sec or less. The lower the gas permeability, the better the water retention, but for use as a gas diffusion layer material, 30 cm ^Three / Cm ² -50 cm or more when used in high output applications that require generation of a large current instantly, such as solid polymer fuel cells for automobiles, over a sec. ^Three / Cm ² -More than sec is preferable.
[0074]
(Size of carbon fiber monofilament)
The diameter of the single fiber of the carbonaceous fiber is usually 6 to 50 μm, preferably 6 to 30 μm. In particular, a woven fabric obtained from a spun yarn composed of a single fiber having a diameter of 7 to 15 μm is preferable because thickness unevenness is hardly generated by the above carbonization treatment and graphitization treatment.
(Flexibility index value)
In the carbon fiber woven fabric of the present invention, the stiffness index value (L) based on the 45 ° cantilever method needs to be 6 cm or more. The stiffness index value (L) according to the 45 ° cantilever method is an index of the flexibility (flexibility) of the woven fabric defined in JIS L 1096.
[0075]
In the measurement of the stiffness index value by the 45 ° cantilever method, a test piece sampled at a size of 2 cm × about 15 cm is placed on a smooth horizontal table with a 45-degree inclined surface at one end and the short side of the test piece. To the scale baseline. Next, the test piece is gently slid in the direction of the slope, and when the center point of one end of the test piece is in contact with the inclined surface, the position of the other end is read with a scale. The bending resistance is indicated by the length of the test piece thus obtained.
[0076]
A normal carbon fiber woven fabric is flexible, and an index value (L) of a woven fabric having a thickness of 0.05 to 1 mm is usually 5 cm or less. The carbonaceous fiber woven fabric according to the present invention has an index value (L) of 6 or more by fusing or binding the fibers forming the woven fabric. The index value (L) is preferably 8 cm or more.
In addition, the bending resistance index value (L) by the 45 ° cantilever method has a maximum value of about 15 cm in the JIS standard, but by increasing the length of the test piece to be longer than 15 cm, the index value of the one with higher rigidity is obtained. Therefore, if the stiffness index value (L) is 30 cm or less, it is generally allowed as an index of rigidity in accordance with JIS standards. The carbonaceous fiber woven fabric according to the present invention preferably has a bending resistance index value (L) of 25 cm or less based on the 45 ° cantilever method.
[0077]
JIS L 1096 describes the Clark method for evaluating the rigidity of a sample having a higher rigidity than the 45 ° cantilever method.
In the Clark method, a test piece sampled in a size of 2 cm x 15 cm to 25 cm is sandwiched between two rollers of a Clark type tester, the handle is turned left and right, and the angle scale plate indicates when the test piece falls to the left or right. Adjust the length overhanging the roller so that the sum of the left and right angles is 90 ° ± 2 °, and measure the length at that time.
[0078]
As for the Clark method, as in the 45 ° cantilever method, the maximum value of the stiffness index value (L) is about 25 cm, but if it is 40 cm or less, it is generally accepted as an index of rigidity in accordance with JIS standards. Yes. When the preferred upper limit of 25 cm of the bending resistance index value of the carbon fiber woven fabric of the present invention is represented by the bending resistance index value (L) based on the Clark method, it is about 35 cm.
[0079]
When a carbon fiber woven fabric is used as a gas diffusion layer material for a fuel cell, if the stiffness is too strong, the woven fabric is difficult to be wound and difficult to handle. As an index for evaluating the rigidity of a sample having a higher rigidity (hardness) than the Clark method, it is possible to make a numerical value based on a bending elastic modulus by a bending stiffness test using an Olsen-type testing machine. Although there is a slight difference depending on the thickness, this flexural modulus is 1 × 10 ^Four kgf / cm ² If it exceeds the upper limit, although it depends on the roll diameter, it is not suitable for use in a fuel cell because it is broken by winding. For example, a woven fabric that cracks or cracks when wound on a roll having an outer diameter of 10 cm cannot be used as a gas diffusion layer material for a fuel cell. However, if the stiffness index value (L) conforming to the 45 ° cantilever method is 25 cm, and the stiffness index value (L) conforming to the Clark method is approximately 35 cm, the diameter is 3 inches (76 mm). Since it has a winding property that can be wound on a winding core, it is suitable for practical use.
[0080]
(Degree of fluff of carbon fiber woven fabric)
A carbonaceous fiber woven fabric having less fuzz is preferable in terms of electrical characteristics. The degree of fluffing can be measured by the fuzz adhesion test method (QTEC cello tape (R) method) described below.
That is, a cellophane tape with a width of 18 mm is applied to a plastic plate with a smooth surface at 40 gf / cm. ² Cellophane tape having a peel strength of 350 ± 25 gf according to the JIS L 1089 test method (for example, cello tape (R) of Nichiban Co., Ltd. having a width of 18 mm, product number CT-18 or LP-18) Is applied to a fiber woven fabric which is a sample to be measured, and 40 gf / cm. ² The operation of applying the load of No. 5 and leaving it for 5 seconds and peeling it off is repeated with the same tape at five points in the same direction in the vertical or horizontal direction of the woven fabric. The amount of fluff adhering to the cellophane tape is judged by comparing with the fluff adhesion test judgment scale (1-5 grade) established by Japan Textile Products Quality Technology Center (abbreviation QTEC).
[0081]
In this evaluation method, the first class has the largest fluff amount of the fiber woven fabric, and the higher the series, the smaller the fluff amount. Grade 5 has the least fluff. The evaluation series is expressed as a 2-3 class (2.5 class) between integer series, for example, between the 2nd class and the 3rd class.
The carbonaceous fiber woven fabric according to the present invention preferably has a fuzziness of 2nd grade or higher in this fluff adhesion test method. Particularly preferred are those of grade 3 or higher, particularly those of grade 3-4 (3.5 grade) or higher. When the fuzziness is not achieved to the second grade, a large amount of carbonaceous fibers protrudes from the surface of the carbonaceous fiber woven fabric, and therefore, when used for a gas diffusion layer of a fuel cell, a short circuit is likely to occur.
[0082]
(Metallic impurities in carbon fiber woven fabric)
The metal impurities in the woven fabric are preferably reduced as much as possible because they cause a decrease in battery characteristics due to an electrolysis reaction of generated water during the operation of the fuel cell. For example, it is preferable that iron is 50 μg / g or less, nickel is 50 μg / g or less, and sodium is 100 μg / g or less. The content of the metal impurities in the woven fabric can be reduced by washing the woven fabric or the carbonaceous fiber of the raw material, and further the raw material yarn with an acid such as hydrochloric acid or acetic acid.
[0083]
(Gas diffusion layer material for polymer electrolyte fuel cells)
The carbonaceous fiber woven fabric of the present invention can be suitably used as a gas diffusion layer of a fuel cell. For example, a paste obtained by mixing a dispersion of polytetrafluoroethylene, a catalyst, and carbon black is applied to a polymer solid electrolyte membrane to form a joined body of the polymer solid electrolyte membrane and the catalyst layer. A membrane electrode body can be formed by bonding the carbon fiber woven fabric of the present invention as a gas diffusion layer. Formation of a joined body of a solid polymer electrolyte membrane and a catalyst layer is performed by applying a paste of polytetrafluoroethylene dispersion, catalyst and carbon black on a release sheet to form a catalyst layer. It can also be formed by joining the molecular solid electrolyte membrane by hot pressing. Conversely, a catalyst paste is applied to the carbon fiber woven fabric of the present invention to form a joined body of the gas diffusion layer and the catalyst layer, and this is joined to the polymer solid electrolyte membrane by hot pressing to form a membrane electrode A body can also be formed. Regardless of which method is used, the carbonaceous fiber woven fabric of the present invention has moderate rigidity and is easy to handle.
[0084]
The polymer electrolyte fuel cell using the carbon fiber woven fabric of the present invention is suitably used as a power source for automobiles or a power source for cogeneration power generation systems.
[0085]
【Example】
Next, specific embodiments of the present invention will be described in more detail based on examples, but the present invention is not limited to the following examples unless it exceeds the gist.
[Comparative Example 1]
(Carbonaceous precursor fiber woven fabric)
A polyacrylonitrile flame-resistant spun yarn having a LOI value of 50 of metric count 40 count double yarn (2/40 Nm) was made into a plain weave. The woven fabric has a width of 100 cm and a length of 150 m, a thickness of 0.318 mm (average value), and a basis weight of 171 g / m. ² (Average value) and bulk density were 0.538 g / cc.
[0086]
(Press processing)
The carbonaceous precursor fiber woven fabric is brought into contact with the gap between the upper roll and the lower roll of the roll type press at a contact pressure of 300 kg / cm, and the woven fabric is passed once at a conveying speed of 10 m / min and pressed. Processing was performed.
The thickness of the woven fabric after press working is 0.299 mm (average value), and the basis weight is 171 g / m. ² (Average value) and bulk density were 0.572 g / cc.
[0087]
(Carbonization treatment)
The carbonaceous precursor fiber woven fabric after press working was cut out with a width of 50 cm, and carbonized at 950 ° C. in a horizontal continuous carbonization furnace under a nitrogen atmosphere.
(Physical properties of carbon fiber woven fabric after carbonization)
The physical properties of the carbonaceous fiber woven fabric after carbonization were measured according to the method described above. However, in order to measure the thickness of the woven fabric, the square size cut out with the warp and weft directions of the woven fabric as sides was 40 cm square.
[0088]
The carbonized fiber woven fabric after carbonization has a thickness of 0.234 mm, a thickness variation coefficient of 2.6%, and a basis weight of 112 g / m. ² The bulk density is 0.479 g / cc, the volume resistivity is 0.12 Ωcm, and the gas permeability is 98 cm. ^Three / Cm ² -Sec, the ratio of the major axis / minor axis of the yarn was 5.5 warp and 5.7 weft.
(Graphitization treatment)
The carbonized carbon fiber woven fabric after carbonization was graphitized in a vacuum graphitization furnace at 2000 ° C. or higher to obtain a graphitized woven fabric.
[0089]
(Physical properties of carbon fiber woven fabric after graphitization)
The physical properties of the carbonized fiber woven fabric after graphitization were measured according to the method described above. However, in order to measure the thickness of the woven fabric, the square size cut out with the warp and weft directions of the woven fabric as sides was 40 cm square.
The thickness of the carbonized fiber woven fabric after graphitization is 0.208 mm, the coefficient of variation in thickness is 2.6%, and the basis weight is 96 g / m. ² The bulk density is 0.462 g / cc, the volume resistivity is 0.02 Ωcm, and the gas permeability is 92 cm. ^Three / Cm ² -The ratio of sec, the major axis / minor axis of the yarn was warp 5.0 and weft 5.2, the stiffness index (L) was 4 cm, and the fluffiness was grade 2.
[0090]
[Example 1]
A graphitized carbonaceous fiber woven fabric was obtained in the same manner as in Comparative Example 1 until the graphitization treatment.
(Rigidity imparting process)
The obtained carbonized fiber woven fabric after graphitization was immersed in an ethanol solution of a phenol resin (resole type) having a concentration of 8% by weight. After drying at 130 ° C., hot pressing was performed at 330 ° C., and the resin was cured to obtain a carbonaceous fiber woven fabric.
[0091]
(Physical properties of carbon fiber woven fabric after applying rigidity)
The thickness of the carbon fiber woven fabric after the rigidity imparting treatment is 0.226 mm, the variation coefficient of the thickness is 2%, and the basis weight is 110 g / m. ² The bulk density is 0.487 g / cc, the volume resistivity is 0.07 Ωcm, and the gas permeability is 80 cm. ^Three / Cm ² -Sec, the ratio of the major axis / minor axis of the yarn is 5.0 for both the warp and the weft, the stiffness index (L) is 10 cm, the fluffiness is 3-4 grade, and the amount of binder attached is 15% by weight. It was. In addition, since carbon fiber woven fabric shrinks slightly when impregnated with phenol resin and then dried and cured, the phenol resin adhesion amount per unit area of the product is larger than the adhesion amount before hot pressing.
[0092]
[Example 2]
(Rigidity imparting process)
Carbonization treatment was performed at 980 ° C. in a horizontal continuous furnace under a nitrogen gas atmosphere using the resin-cured carbonaceous fiber woven fabric obtained in Example 1 to obtain a carbonaceous fiber woven fabric.
(Physical properties of carbon fiber woven fabric with added rigidity)
The thickness of the carbon fiber woven fabric after the rigidity imparting treatment is 0.221 mm, the variation coefficient of thickness is 1.9%, and the basis weight is 104 g / m. ² The bulk density is 0.471 g / cc, the volume resistivity is 0.03 Ωcm, and the gas permeability is 85 cm. ^Three / Cm ² -Sec, the ratio of the major axis / minor axis of the yarn is 4.9 warp, 5.1 weft, 9 cm stiffness index, 3-4 fluffiness, and 8% by weight of binder carbonized product. It was.
[0093]
[Example 3]
A graphitized carbonaceous fiber woven fabric was obtained in the same manner as in Example 1 until the graphitization treatment.
(Rigidity imparting process)
After curing the resin, which was subjected to rigidity treatment in the same manner as in Example 1 except that the obtained graphitized carbon fiber woven fabric was immersed in an ethanol solution of a phenol resin (resole type) having a concentration of 15% by weight. Carbon fiber woven fabric was obtained. Further, the obtained cured carbonaceous woven fabric was carbonized at 980 ° C. in the same manner as in Example 2 to obtain a carbonaceous woven fabric.
[0094]
(Physical properties of carbon fiber woven fabric with added rigidity)
The thickness of the carbon fiber woven fabric after the rigidity imparting treatment is 0.225 mm, the variation coefficient of the thickness is 1.4%, and the basis weight is 115 g / m. ² The bulk density is 0.511 g / cc, the volume resistivity is 0.02 Ωcm, and the gas permeability is 85 cm. ^Three / Cm ² -Sec, the ratio of the major axis / minor axis of the yarn was 5.1 for both the warp and weft, the stiffness index value was 12 cm, the fuzziness was 3-4 grade, and the adhesion amount of the binder carbonized product was 19% by weight.
[0095]
[Example 4]
A graphitized carbonaceous fiber woven fabric was obtained in the same manner as in Example 1 until the graphitization treatment.
(Rigidity imparting process)
The obtained carbonized fiber woven fabric after graphitization is added to an aqueous dispersion of a phenol resin semi-cured product having a concentration of 10% by weight and an average particle diameter of 20 μm (the solubility of the phenol resin semi-cured product when boiling in methanol is 95%) Soaked. After drying at 100 ° C. for 60 minutes, hot pressing was performed at 300 ° C. to cure the resin and obtain a carbonaceous fiber woven fabric.
[0096]
(Physical properties of carbon fiber woven fabric with added rigidity)
The thickness of the carbon fiber woven fabric after the rigidity imparting treatment is 0.220 mm, the variation coefficient of the thickness is 1.4%, and the basis weight is 105 g / m. ² The bulk density is 0.477 g / cc, the volume resistivity is 0.05 Ωcm, and the gas permeability is 85 cm. ^Three / Cm ² -Sec, the ratio of the major axis / minor axis of the yarn was warp 5.0, weft 5.2, stiffness index 12 cm, fluff 3-4 grade, and the amount of binder carbonized material deposited was 10 wt%. It was.
[0097]
When the obtained carbonaceous fiber woven fabric was cut out with a size of 5 mm × 5 mm square, taken with a scanning electron micrograph and observed, most of the resin component had a spherical shape of about 1 to 10 μm. Most of these were present in a form of point contact between carbonaceous fibers. In addition, it was not observed that the surface of the carbonaceous fiber was coated with the resin.
[0098]
[Example 5]
(Rigidity imparting process)
The carbonized fiber woven fabric after resin curing obtained in Example 4 was subjected to carbonization treatment at 980 ° C. in a horizontal continuous furnace under a nitrogen gas atmosphere to obtain a carbonaceous fiber woven fabric.
(Physical properties of carbon fiber woven fabric with added rigidity)
The thickness of the carbon fiber woven fabric after the rigidity imparting treatment is 0.215 mm, the variation coefficient of the thickness is 1.5%, and the basis weight is 101 g / m. ² The bulk density is 0.470 g / cc, the volume resistivity is 0.02 Ωcm, and the gas permeability is 90 cm. ^Three / Cm ² -Sec, the ratio of major axis / minor axis of the yarn was warp 4.8, weft 4.9, stiffness index value 10 cm, fuzziness degree 3 and the amount of binder carbonized material deposited was 5% by weight.
[0099]
[Comparative Example 2]
A graphitized carbonaceous fiber woven fabric was obtained in the same manner as in Example 1 until the graphitization treatment.
(Rigidity imparting process)
The carbonaceous fiber subjected to the stiffness treatment in the same manner as in Example 1 except that the obtained graphitized carbon fiber woven fabric was immersed in an ethanol solution of a phenol resin (resole type) having a concentration of 40% by weight. A woven fabric was obtained.
[0100]
(Physical properties of carbon fiber woven fabric with added rigidity)
The thickness of the carbon fiber woven fabric after the rigidity imparting treatment is 0.265 mm, the variation coefficient of the thickness is 3.1%, and the basis weight is 170 g / m. ² The bulk density is 0.641 g / cc, the volume resistivity is 0.21 Ωcm, and the gas permeability is 25 cm. ^Three / Cm ² -The ratio of sec, the major axis / minor axis of the yarn was 4.2 for both the warp and weft, the stiffness index value was 15 cm, the fluffiness was 3-4 grade, and the amount of the binder carbonized product was 78% by weight.
[0101]
[Comparative Example 3]
A graphitized carbonaceous fiber woven fabric was obtained in the same manner as in Example 1 except that the pressing process and the rigidity imparting process were not performed.
(Physical properties of carbon fiber woven fabric after graphitization)
The thickness of the carbonized fiber woven fabric after graphitization is 0.246 mm, the coefficient of variation in thickness is 3.5%, and the basis weight is 101 g / m. ² The bulk density is 0.411 g / cc, the volume resistivity is 0.02 Ωcm, and the gas permeability is 105 cm. ^Three / Cm ² -Sec, the volume resistivity was 0.02 Ωcm, the ratio of the major axis / minor axis of the yarn was warp 1.8, weft 1.9, the bending resistance index was 4 cm, and the fluffiness was grade 1-2.
[0102]
【The invention's effect】
According to the present invention, properties such as gas permeability, conductivity, water retention, drainage, etc. are balanced, thickness unevenness is small, and it has an appropriate rigidity, and is suitable as a gas diffusion layer material for a polymer electrolyte fuel cell. Carbon fiber woven fabric is provided.

Claims (12)

A woven fabric mainly composed of carbonaceous fiber threads,
The woven fabric is prepared by pressing a carbonaceous precursor fiber woven fabric, then carbonizing the carbonaceous precursor fiber woven fabric, and then attaching a binder or a carbonized product thereof, and The basis weight is 50 to 200 g / m ² , the thickness is 0.05 to ² mm, the bulk density is 0.47 to 0.6 g / cc, and the volume resistivity in the surface direction is 0.2 Ωcm or less. When the warp yarn direction and the weft yarn direction are cut into squares with sides, the variation coefficient of the thickness of the woven fabric at a total of 20 division points obtained by dividing the two diagonal lines into 11 equal parts is 3.2% or less. The warp and weft yarns that make up the woven fabric have a cross-section whose major axis is at least twice that of the minor axis, and the stiffness index value (L) in accordance with the 45 ° cantilever method is 6 cm or more . that but a 30~200cm ³ / cm ² Carbonaceous fiber woven fabric and butterflies. 2. The carbonaceous fiber woven fabric according to claim 1, wherein the carbon fine fiber woven fabric is composed of 16 to 60 yarns having a meter fineness. Claim 1 or, characterized in that are mutually bound is surface-coated carbonaceous fibers by the binder or a carbonized material, and the content of the binder or the carbonized product is 0.01 to 30 wt% 2. The carbonaceous fiber woven fabric according to 2. 4. The binder according to claim 1, wherein the carbonaceous fibers are bound to each other by a dotted binder or a carbonized product thereof, and the content of the binder or the carbonized product thereof is 10 to 40% by weight. carbonaceous fiber woven fabric according to item 1 or. The degree of fuzz, carbonaceous fiber woven fabric according to any one of claims 1 to 4, characterized in that a secondary 5 grade in determination index by fluff adhesion test method. Woven tissue is plain weave, and, carbonaceous according to any one of claims 1 to 5, wherein the history density of the warp and weft are from 30 to 70 lines per inch long Textile woven fabric. Carbonaceous fiber woven fabric according to any one of claims 1 to 6, wherein the diameter of a single fiber of carbonaceous fibers is 6～50Myuemu. Carbonaceous fiber woven fabric according to any one of claims 1 to 7, the yarn constituting the woven fabric is characterized in that it is a spun yarn. 9. The carbonaceous fiber woven fabric according to claim 8 , wherein the warp and / or the weft constituting the woven fabric is a twin yarn. The carbonaceous fiber according to claim 8 , wherein the yarn constituting the woven fabric is a twin yarn having a metric count of 2/32 to 2/120 Nm, or a single yarn having a metric count of 1/16 to 1/60 Nm. Woven cloth. Carbonaceous fiber, carbonaceous fiber woven fabric according to any one of claims 1 to 10, characterized in that a carbonized product of acrylic fiber obtained by spinning a polymer of a monomer containing acrylonitrile. Carbonaceous precursor which is woven using a single yarn of ply yarns or metric count 1 / 16~1 / 60Nm of metric count 2/32 to 2/120 Nm spun carbonaceous precursor fibers made of polymer of a monomer containing acrylonitrile We press body fiber woven fabric,
A carbonaceous fiber woven fabric is prepared by performing a carbonization treatment on the pressed carbonaceous precursor fiber woven fabric at a temperature of 900 ° C. or higher.
The binder or its carbonized product is added so that the carbonaceous fiber constituting the carbonaceous fiber woven fabric obtained by the carbonization treatment has a binder or its carbonized content of 0.01 to 30% by weight. By attaching and bonding the carbonaceous fibers to each other, a carbonaceous material having a bulk density of 0.47 to 0.6 g / cm and a bending resistance index value (L) of 6 cm or more based on the 45 ° cantilever method Prepare fiber woven fabric
A method for producing a carbonaceous fiber woven fabric characterized by the above .