JPS6090805A - Manufacture of impermeable molded carbon body - Google Patents

Abstract

PURPOSE:To manufacture a molded carbon body having superior gas and liq. impermeability by extrusion-molding a kneaded composition contg. a thermosetting resin into a flat plate, rolling the plate with rolls, drying and curing it, and carrying out carbonization and calcination in a nonoxidizing atmosphere. CONSTITUTION:A kneaded composition is prepd. by kneading a soln. of a thermosetting resin such as phenolic resin, xylene resin or melamine resin with 100 pts.wt. powder of a thermosetting resin such as phenolic resin having <=50mum particle size, <=50pts.wt. carbon powder such as graphite powder and 1-20pts.wt. org. thickener such as methylcellulose. The kneaded composition is extruded into a plate with a plunger extruder or the like, and the plate is rolled to a prescribed thickness with rolls. It is dried to evaporate the solvent in the thermosetting resin soln., and calcination is carried out at 1,000-1,500 deg.C in a nonoxidizing atmosphere such as He or Ar to obtain a carbon sheet having superior gas and liq. impermeability and suitable for use as a separating plate for a fuel cell contg. phosphoric acid.

Description

[Detailed description of the invention] The present invention relates to a method for producing an impermeable carbon molded body.

Impermeable carbon molded bodies, which are highly impermeable to gases and liquids, have low electrical resistance and excellent chemical resistance in addition to these properties, making them widely used in industrial fields such as electronics, nuclear power, and aerospace. Among them, because of the above-mentioned characteristics, it can be suitably used as a separator plate for phosphoric acid fuel cells, which have been attracting attention in recent years.

In a phosphoric acid fuel cell, for example, a pair of porous electrode plates carrying a required catalyst are arranged with a matrix impregnated with phosphoric acid as an electrolyte sandwiched between them, and a separating plate is arranged on the outside of each of the porous electrode plates. A unit cell is formed by stacking a large number of cells. For example, in the case of a fuel cell called a ribbed electrode type, ribs are formed on the separation plate side of each of the electrodes, and fuel gas or oxidant gas is supplied to the grooves between these ribs. That is, gaseous fuel such as hydrogen gas is supplied to the grooves of one electrode, and gaseous oxidation ThJ such as air or oxygen is supplied to the grooves of the other electrode, thereby carrying out a cell reaction. Thus, one separator plate is supplied with fuel on one side and oxidizer on the other side.
The separation plate needs to have excellent gas impermeability so that these gases do not mix, and furthermore, in order to function as a current collector for a fuel cell constructed by stacking unit cells as described above. In addition to having high conductivity, it is necessary to have a thin plate shape and high lamination compressive strength and bending strength.

However, all of the conventionally known impermeable carbon molded bodies are insufficient in the above-mentioned required characteristics. For example, in JP-A-54-20991, fine powder of a cured phenolic resin and a phenol/aldehyde initial condensate are kneaded, molded and hardened, and then carbonized and fired to make only vitreous carbon. A method for obtaining a carbon molded body comprising: However, the molded product obtained in this way lacks compactness as a molded product because the resin undergoes significant volumetric shrinkage during the firing process, and therefore does not have sufficient gas impermeability. When thinned to a thickness of about 0.4 to 5 inches, which is preferable as a plate, the strength is poor.

On the other hand, various impermeable carbon molded bodies whose carbonaceous substance is graphite are already known. For example, an impermeable carbon molded body can be obtained by impregnating the voids of a graphite molded body obtained by carbonization firing with an impregnating agent such as pitch, tar, or resin, and then firing it again to carbonize the impregnating material. Although it is known, according to this method, fine cracks often occur in the resulting carbonized and fired product due to the difference in thermal shrinkage rate between the graphite molded body and the impregnated material.

Furthermore, Japanese Patent Application Laid-open No. 57-72273 discloses a method of molding graphite powder with a phenol resin liquid as a binder and firing it at a high temperature to obtain an impermeable carbon molded body made entirely of graphite. However, when this method is used, fine cracks tend to occur frequently during firing due to the difference in thermal shrinkage rate between the graphite in the molded body and the binder, and furthermore, the fired product does not have a good gas impregnation. In order to provide permeability, it is necessary to repeatedly impregnate with a binder, which increases the number of steps and increases manufacturing costs.

Furthermore, in order to obtain an impermeable carbon molded body with a predetermined shape,
The above publication describes the use of casting or extrusion molding, but if a cast molded body or an extrusion molded body is obtained in this way, for example, the above-mentioned separator plates for fuel cells will not meet the requirements. In order to obtain a wide thin plate shaped body having a thickness of about 0.4 to 1.5 w, it is necessary to further cut the formed body larger than the predetermined dimensions, which requires processing costs, It is also uneconomical from a material standpoint, and in addition to this, precision cutting of the entire plate surface is required to obtain the required flatness. In this way, according to the conventional method,
In the production of impermeable carbon molded bodies, there are various problems including the molding method.

The present invention has been made to solve the various problems described above, and is an impermeable carbon molding that has excellent gas and liquid impermeability and is particularly suitable for obtaining a wide and thin plate-like molded product. The purpose is to provide a method for manufacturing the body.

The method for producing an impermeable carbon molded article according to the present invention involves extruding a cross-wire composition containing a thermosetting resin into a flat plate, rolling it with rolls, drying and curing it, and then placing it in a non-oxidizing atmosphere. It is characterized by being carbonized and fired.

In the present invention, the kneading composition containing a thermosetting resin is preferably at least 11% selected from both a thermosetting resin liquid, a thermosetting resin powder, and a carbon powder. It is a crosstalk composition containing, particularly preferably, 1 part by weight of thermosetting resin powder, 0 to 50 parts by weight of carbon powder, and thermosetting resin liquid. More preferably, the kneaded composition of the present invention contains an organic thickener that is soluble in the thermosetting resin liquid and that can be decomposed and volatilized during carbonization and firing of the cured molded body of the cross-wire composition, as described below. Crosstalk composition 1-2
It is a composition containing in the range of 0M amount %.

In the present invention, water-based or oil-based adhesives such as phenol resins, xylene resins, melamine resins, urea resins, epoxy resins, and furan resins are used as the thermosetting resin liquid.

Note that the thermosetting resin liquid includes not only solutions but also emulsions and suspensions. In the present invention, although not particularly limited, an aqueous resin liquid is preferably used for convenience of drying.

In addition, in the present invention, thermosetting resin powder is 800 to 2000°C in a non-oxidizing atmosphere, preferably 100°C.
It refers to thermosetting resin powder that changes into glassy carbon by carbonization firing at a temperature of 0 to 1500°C, and usually resin powders such as phenol resin, furan resin, xylene resin, melamine resin, aniline resin, etc. are used. However,
In particular, phenolic resin powder is preferably used.

In the present invention, as described above, the kneading composition consists of a thermosetting resin powder and/or carbon powder together with a thermosetting resin liquid; It can be used alone or as a mixture of two or more.

However, it is desirable that the resin components in the thermosetting resin powder and the resin liquid are the same resin. The thermosetting resin liquid makes it easy to knead and mold a composition containing thermosetting resin powder and carbon powder into a desired shape, and after heating and curing, it is baked together with the thermosetting resin powder to form an amorphous resin. Vitreous carbon is formed, and when the kneading composition contains carbon powder, a matrix of carbon powder is formed.

The carbon powder provides a high packing density to the resulting impermeable carbon molded body, and therefore provides an impermeable carbon molded body with excellent properties such as mechanical strength, electrical conductivity, and thermal conductivity. Here, carbon powder means crystalline carbon powder, such as graphite powder, and amorphous carbon powder, such as carbon black, and graphite powder is particularly preferably used. The blending amount of carbon powder is 5 parts by weight per 100 parts by weight of thermosetting resin powder.
It is 0 parts by weight or less. When blending in a large amount exceeding 50 parts by weight, fine cracks are likely to occur when the kneaded composition is molded and carbonized and fired, which is not preferable.

Furthermore, the smaller the particle size of the thermosetting resin powder and carbon powder, the better the impermeability of the resulting molded product to gases and liquids. Therefore, in the present invention, the thermosetting resin powder must have an average particle size of 50 μm or less, and the carbon powder must have an average particle size of 1/2 or less of the average particle size of the thermosetting resin powder. is preferred. When the average particle diameter of the thermosetting resin powder exceeds 50 μm, it is difficult to obtain a compact and strong molded body. If the average particle size of the carbon powder is larger than 1/2 of the average particle size of the thermosetting resin powder used, internal stress will occur when the cured thermosetting resin and resin liquid are carbonized and fired, resulting in a similar problem. This will reduce the strength of the molded product.

In the method of the present invention, the moldability of the mixed material containing preferably thermosetting resin powder and carbon powder together with the thermosetting resin liquid, particularly the slipperiness and shape retention during extrusion molding, and the roll In order to obtain a thin plate-like impermeable carbon molded product that has good elongation during rolling, prevents the occurrence of minute cracks, and has excellent gas impermeability, it is soluble in the thermosetting resin liquid. In addition, it is preferable to mix into the kneaded composition an organic thickener that can be decomposed and volatilized during carbonization and firing of the molded product of the kneaded composition. This organic thickener needs to be water-soluble when the above-mentioned aqueous resin liquid is used as the thermosetting resin liquid. Therefore, as a preferable thickener, for example, methyl cellulose , carboxymethyl cellulose, carboxymethyl starch, hydroxyethyl cellulose, hydroxypropyl cellulose,
Examples include sodium ligninsulfonate, calcium ligninsulfonate, polyvinyl alcohol, polyacrylic acid ester, polymethacrylic acid ester, guar gum, and alginate.

In order for the thickener to have the above-mentioned effect, it is desirable that the thickener be contained in the crosstalk composition at least 1% by weight; on the other hand, when it is contained in a large amount exceeding 20% by weight. This is not preferable because the impermeability of the resulting molded product is reduced and its strength is also reduced.

In the method of the present invention, the above-mentioned cross-wire composition is extruded and rolled to form a molded product of the required shape A) S, and then dried to volatilize the solvent of the resin liquid, and then heated to release the resin. Let it harden.

A thermosetting resin liquid, preferably a thermosetting resin powder and/or
Alternatively, the method of kneading the mixture consisting of carbon powder and an organic thickener is not particularly limited, and any conventional mixing device known in the art may be used. The kneaded composition is then extruded into a predetermined plate shape using an extruder. For this extrusion molding, a conventional extrusion molding machine, such as a screw extrusion machine or a plunger extrusion machine, can be used. In addition, when using a one-screw extrusion molding machine, the preparation of the kneaded product can be performed at the same time.

The extruded product is then rolled by roll rolling,
Here, according to the method of the present invention, the rolling rate of - times is 115
As mentioned above, it is preferable to perform rolling at least twice or more times.

If rolled to a predetermined thickness at once, air may be drawn into the molded product, or the resin powder or carbon powder may have directionality, resulting in an uneven layer that tends to cause microscopic cracks with directionality. It is.

Furthermore, in the method of the present invention, when roll rolling is performed multiple times, it is preferable to perform roll rolling at least once in a direction perpendicular to the extrusion direction in order to eliminate the above-mentioned directionality in the molded product. .

Furthermore, during roll rolling, the thermosetting resin liquid tends to adhere to the roll surface, making it difficult for the rolled plate to release from the roll after rolling. Therefore, interposing a release sheet between the extrusion plate to be rolled and the roll and/or subjecting the roll surface to a release treatment in advance is a preferred method in order to smoothly obtain the rolled plate. In particular, by forming the release sheet from polytetrafluoroethylene and performing the roll release treatment using this polymer, it is possible not only to obtain a rolled plate extremely smoothly, but also to obtain an impermeable carbon material. This is preferable because the molded article has excellent flatness.

FIG. 1 shows a preferred example of roll rolling according to the method of the present invention. A feed belt 3 and a feed belt 4 made of polytetrafluoroethylene are disposed adjacent to the opposing rolling rolls 1 and 2, and a workpiece 5 to be rolled is fed between the rolling rolls by the feeding heald and rolled to a predetermined thickness. The rolled plate 6 is transported out by a delivery roll. In order to prevent the rolling plate from adhering to the upper and lower sides of the rolling roll, release sheets 7 and 8 made of polytetrafluoroethylene sheets are appropriately supported, and while being in contact with the rolling roll, the release sheets 7 and 8 are appropriately supported. They are forced to travel at the same speed.

The rolled plate rolled in this way is then
After drying to volatilize the solvent in the thermosetting resin liquid, the thermosetting resin is cured by heating.

The temperature for curing this thermosetting resin is appropriately selected depending on the resin used, the shape of the molded product, etc., but is usually 100°C.
~180°C. Incidentally, after the thermosetting resin is heat-cured to obtain a molded body, the molded body may be further impregnated with a resin liquid, dried, and heat-cured, if necessary.

- The molded body thus formed is then carbonized and fired in a non-oxidizing atmosphere. The atmosphere is usually
Helium, argon, nitrogen, etc. are used. Heating for carbonization and firing to obtain a fugitive carbon molded body is performed at temperatures ranging from about 200°C to about 500°C to about 700°C, for example, as described in the above-mentioned Japanese Patent Application Laid-open No. 72273/1983.
It is desirable to heat at a slow temperature increase rate of about several tens of degrees Celsius/hour. Thereafter, the impermeable carbon molded body of the present invention is obtained by heating to a predetermined carbonization firing temperature at a heating rate within the above range or higher and firing for a certain period of time. The carbonization firing temperature is required to be at least 800°C, preferably in the range of 1000 to 1500°C. The required firing time depends on the shape and dimensions of the molded product, and it is sufficient to perform the firing for a time long enough to carbonize substantially all of the thermosetting resin and transform it into vitreous carbon, but it is usually several hours to a few hours. It's several dozen hours. During this carbonization firing, the organic thickener is decomposed and volatilized.

In addition, in the present invention, in order to further increase the strength of the obtained molded product, a substance having good bonding properties to the carbon matrix of the molded product, for example, a metal carbide such as silicon carbide, titanium carbide, or tungsten carbide, is used. , carbon fiber, etc. can be added in appropriate amounts to a molding raw material consisting of thermosetting resin powder, carbon powder, and thermosetting resin liquid, and this can be molded, dried, and fired as described above.

As described above, according to the present invention, a cross-wire composition is extruded,
Furthermore, since roll rolling is performed, a thin plate-like impermeable carbon molded body can be easily obtained, and in particular, by adding an organic thickener to the kneaded composition, moldability in extrusion molding and roll rolling is improved. Therefore, a thin plate-like impermeable carbon molded body can be obtained without the occurrence of minute cracks or the like. In this case, further according to the present invention, the occurrence of fine cracks can be more effectively prevented by performing roll rolling a plurality of times, preferably at least once in a direction perpendicular to the extrusion direction. Thus, according to the method of the present invention, unlike conventional methods, it is not necessary to cut the molded product again to the required thickness after firing, or to cut the entire surface to obtain the required flatness. A plate-shaped impermeable carbon molded body having high strength, uniformity, and excellent plate thickness accuracy and flatness can be obtained.

Further, according to the method of the present invention, a kneaded composition containing a predetermined amount of an organic thickener and carbon powder is molded into a thermosetting resin powder, and carbonized and fired, whereby the carbon powder becomes a thermosetting resin. It is uniformly dispersed in the vitreous carbon matrix formed by carbonization firing, giving a dense carbon molded body without cracking, and the impermeable carbon molded body thus obtained is impermeable to gases and liquids. Not only is it excellent, but it also has excellent strength such as laminated compressive strength and bending strength, and conductivity.

The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way. In addition, in the following, parts mean parts by weight.

Example 1 100 parts of phenol formaldehyde resin powder with an average particle size of 39 μm, an average particle size of 12 with 99% or more of fixed carbon
10 parts of µm graphite powder, 9 parts of carboxymethyl cellulose and 3 parts of hydroxypropyl cellulose as water-soluble organic thickeners, and 23 parts of aqueous phenol resin liquid (concentration 50% by weight) were kneaded using an extruder with a plunger. It was extruded into a plate shape having a cross section of 500 mm width and 20 m thickness.

Next, using a 400w diameter 20-mill rolling mill, the first stage rolled it to a thickness of 7°Q++m in the direction perpendicular to the extrusion direction, and the second stage rolled it to a thickness of 3.2vm in the extrusion direction. As the third stage, the thickness is reduced to 1.5 mm in the direction perpendicular to the extrusion direction.
Rolled on.

Next, this rolled plate was placed in a heat insulating tank at 40° C. for 8 o'clock, and then heated at a temperature of 110° C. for 12 hours to harden the thermosetting resin. After this, it was charged into a calcining furnace and heated under an argon atmosphere at a heating rate of 40°C/hour to a temperature of 700"C, and then heated at a rate of 100°C/hour to a temperature of 1300"C. , keep it at this temperature for 2 hours and reduce the thickness to 0.
．． A thin plate-like impermeable carbon molded body having a length of 6 m, a width of 5°Ol, and a length of 500fl was obtained.

The molded body thus obtained had a flatness within ±0.02. Also, the nitrogen permeability is 1kg/c++! When there is a differential pressure of 4X10cc/min・d, electrical resistivity is 3
．． 5×10 Ω country, three-point bending strength was 721 kg/era.

Example 2 An impermeable carbon molded body with the same dimensions was obtained in the same manner as in Example 1, except that a furan resin liquid (48% by weight) was used instead of the phenol resin liquid as the resin liquid. Ta.

This molded body also had a flatness within ±0.02. In addition, the nitrogen permeability is 6 x 10-4 cc/min・d, the electrical resistivity is 3.8 x 10-3 Ω, and the three-point bending strength is 70.
4 kg/a (was.

Example 3 The same procedure as in Example 1 was carried out except that the amount of the mixture of carboxymethyl cellulose and hydroxypropyl cellulose as a water-soluble organic thickener was varied in the crosstalk composition. A transparent carbon molded body was obtained. The gas permeability of the molded body thus obtained was examined. The results are shown in Figure 2. When the amount of thickener blended is less than 2% by weight of the kneaded composition, not only the gas permeability is poor, but also many fine cracks are observed on the surface of the molded product; It has been confirmed that when the amount exceeds 20% by weight of the crosstalk composition, the density of the obtained molded product is low, porous defects are observed, and the gas permeability is also poor.

Example 4 100 parts of the same ferrite/formaldehyde resin powder as in Example 1, 23 parts of carbon black, the same aqueous phenol resin liquid as in Example and 8 parts of methylcellulose were kneaded in the same manner as in Example 1, and this kneaded composition was prepared. An impermeable carbon molded body was obtained by processing in the same manner as in Example 1.

The nitrogen permeability of this molded body is 1O-4cc/min・-1 electrical resistivity 7×10-3Ω country, three-point bending strength 724mm/c
It was i.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a rolling apparatus suitable for carrying out the method of the present invention, and FIG. 2 is a graph showing the relationship between an organic thickener and the gas permeability of the impermeable carbon compact obtained. . 1.2... Rolling roll, 3... Feed belt, 4
...Feeding belt, 5... Rolled object, 6... Rolled plate, 7... Release sheet. Procedural amendment (voluntary) June 28, 1980 Commissioner of the Japan Patent Office 1. Method for producing display-impermeable carbon molded bodies in the case 3. Person making the amendment Relationship to the case Patent applicant address Chuo-ku, Kobe City Wakihamacho 1-3-18 Name
Kobe Steel Co., Ltd. Representative: Fuyuhiko Maki 4, Agent address: 1-8-3-5 Shinmachi, Nishi-ku, Osaka Date of amendment order: Showa Year, month, day Contents of amendment + 11 Ferrite, page 19, line 4, 1 of the specification ' is corrected to 'phenol'. that's all

Claims (1)

[Claims] (11) The cross-wire composition containing the thermosetting resin is extruded into a flat plate shape, rolled, then dried and hardened, and then carbonized and fired in a non-oxidizing atmosphere. A method for manufacturing an impermeable carbon molded article. (2) When rolling the mixed wire composition, roll rolling is performed twice on the roof, and the rolling rate per roll is 115.
A method for manufacturing an impermeable carbon molded body according to claim 1, characterized in that the above is performed. (3) The method for producing an impermeable carbon molded body according to claim 2, wherein the kneaded composition is rolled at least once in a direction perpendicular to the extrusion direction.