JPH0248466A - Production of thin sheetlike carbon material - Google Patents

Abstract

PURPOSE:To obtain a thin sheetlike carbon material especially useful as phosphoric acid type fuel cell separators by impregnating a cellulosic substrate with a specific electrically conductive varnish to form sheets of prepreg, laminating and molding the resultant sheets of prepreg and calcining the molded prepreg. CONSTITUTION:Sheets of cellulosic paper or cellulose film as a substrate are impregnated with a varnish containing a thermosetting resin as a matrix and carbon black having high electric conductivity as a filler mixed and kneaded therewith to form sheets of prepreg having a homogeneous composition even to the interior thereof. The resultant sheets of prepreg are then laminated, molded and calcined. Carbon black prepared by graphitizing at >=2000 deg.C temperature is preferably used to further improve characteristics. The carbon black is preferably blended in an amount of 2-50wt.% based on the thermosetting resin.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for manufacturing a thin plate-like carbon material, and particularly to a method for manufacturing a carbon material for a phosphoric acid fuel cell separator.

<Prior Art> In general, a phosphoric acid fuel cell includes an electrolyte layer holding, for example, phosphoric acid, a porous electrode substrate disposed on both sides of the electrolyte layer and supporting a platinum catalyst, and an electrolyte layer formed on each outer surface of the electrode substrate. A separator is provided to cover a flow groove, and unit cells are stacked with the separator interposed therebetween.

Since fuel gas and oxygen gas flow through the upper and lower surfaces of such a separator, the separator needs to function as a boundary for separating fuel gas and oxygen gas and as a connector between unit cells. Therefore, the material is required to have excellent properties such as gas impermeability, electrical conductivity, mechanical strength, and resistance to phosphoric acid at operating temperatures, and carbon materials are usually used.

Conventionally, methods for producing the carbon material include forming a paste by adding and kneading a thermosetting resin to fine graphite powder by roll forming, curing it, and then subjecting it to heating carbonization treatment.
For example, it is disclosed in Japanese Unexamined Patent Publication No. 59-26907.

Further, as a method for manufacturing the carbon material, a method of laminating and pressing cellulose paper impregnated with a thermosetting resin and containing graphite powder or carbon fiber, hardening and firing is disclosed, for example, in JP-A No. 60-161144. Disclosed in the official gazette.

<Problems to be Solved by the Invention> According to the method disclosed in JP-A-59-28907, a carbon material with excellent electrical properties can be obtained, but it is difficult to produce a thin plate. There was a problem.

In the method disclosed in JP-A-60-161144, carbon fillers such as carbon fibers and graphite powder adhere to the surface of the base material without being completely impregnated, and the composition differs from the inside of the base material, resulting in The result is a carbon material in which glassy carbon-rich layers made of thermosetting resin and cellulose paper and carbon filler-rich layers are interposed alternately in the thickness direction, resulting in a decrease in electrical conductivity in the thickness direction. There is a problem.

An object of the present invention is to provide a method for producing a thin plate-like carbon material, in which a thin-plate carbon material with excellent electrical properties can be obtained by impregnating the material with a varnish containing highly conductive carbon black.

<Means for Solving the Problems> In order to achieve the above object, according to the present invention, a cellulose paper or a cellulose film is used as a base material, and a thermosetting resin and a highly conductive filler are added to the base material by applying a matrix thereto. Provided is a method for producing a thin plate-like carbon material obtained by impregnating a varnish mixed and kneaded with carbon black containing carbon black to obtain a prepreg having a uniform composition throughout the interior, layer-molding the prepreg, and subjecting the prepreg to a firing treatment. .

Although it is possible to use carbon black that is not graphitized, it is preferable to use carbon black that has been graphitized at a temperature of 2000° C. or higher because the properties are further improved.

Moreover, it is preferable that the mixing ratio of carbon black to the thermosetting resin is 2 to 50 wt% with respect to the thermosetting resin.

The present invention will be explained in more detail below.

In the present invention, first, a fiber aggregate or a film-like base material,
It is impregnated with conductive varnish made by mixing and kneading liquid resin and filler to make conductive prepreg. As the fiber aggregate and film used for the base material, materials such as cellulose paper and cellulose film that remain in the base material in a carbonized form during firing treatment at 800° C. or higher are used.

As the cellulose paper, general papers such as industrial filter paper and kraft paper can be used, and papers with excellent impregnation properties, such as those used for phenol laminates, are more preferable.

Moreover, the cellulose film is preferably a porous film with a pore diameter of 30 to 100 μm obtained by hydrolyzing acetyl cellulose. Furthermore, in order to improve impregnation properties, a porous cellulose film is prepared by mixing acetyl cellulose with a porous material such as polyvinyl alcohol in advance, and after film forming, the porous material is eluted and the pore diameter is adjusted to 100 to 500 μm. It is even more preferable to use

The thickness of the base material is preferably 10 to 1000 μm.

If it is less than 10 μm, the strength as a base material cannot be maintained, and if it exceeds 1000 μm, impregnation, lamination molding,
A problem arises in that the thickness of the carbon material obtained by firing becomes non-uniform.

In addition, the thermosetting resin used as the matrix has
Liquid resins such as phenol resin, furan resin, polyimide resin, and epoxy resin are used.

Furthermore, the filler that is mixed and kneaded with this liquid resin has excellent dispersibility when made into a varnish, and can safely and uniformly penetrate into the fiber aggregate or film material that is the base material.
And have conductivity, especially those with improved conductivity and an average particle diameter of 10 to 1000 m1 and a specific resistance of JIS -14.
It is preferable to use carbon black with a resistance of 0.1 to 1.0 Ω-cm as determined by the fi9 resistivity measurement method.

Furthermore, it is preferable to use carbon black that has been graphitized at 2000° C. or higher because it further improves the conductivity of the final carbon material.

As a method of mixing and kneading the liquid resin and filler,
General kneading devices such as an oven roll kneader, intensive mixer ball mill, and Miki roll kneader can be mentioned. Further, the mixing ratio of the liquid resin and the filler is preferably 2 to 50 wt% of the filler to the resin. When the filler mixing ratio is 2wt% without grooves, there is a problem that the conductivity is low;
In the case of super, the conductivity improves, but when used as a varnish, the viscosity becomes high and a problem arises in impregnation into the base material.

Methods for impregnating the base material with conductive varnish include dipping the base material in varnish in a vat-shaped container, dipping it into the base material,
A general impregnation method of applying varnish by spraying or the like, a method using an impregnation device having a roll, etc. are used.

By this impregnation treatment, a conductive prepreg having a uniform composition from the surface of the base material to the inside thereof can be obtained.

After drying the obtained prepreg at 100-150℃, several sheets were laminated and heated at 100-150℃ for 50-150k.
Heat compression molding is performed at g/cm2 to obtain a conductive laminate. The number of layers of prepreg to be laminated is adjusted according to the final thickness of the desired carbon material.In addition, methods used for molding include hot press molding, hot roll molding, etc.
- A simple molding method is used.

Next, the obtained conductive laminate is set in a firing furnace, and fired and carbonized to obtain the desired thin plate-like carbon material. As the furnace used for firing, commercially available Matsufuru furnaces, tunnel furnaces, etc. that can create a non-oxidizing atmosphere inside the furnace can be used.
Firing while passing an inert gas such as N2 or Ar,
It is preferable to perform firing while filling the periphery of the sample with coke fine powder. There are no particular restrictions on the firing temperature, but the maximum temperature is usually 900 to 1500°C.

<Example> The present invention will be specifically explained below based on Examples.

(Example 1) Commercially available phenol resin solution (Regitop PL manufactured by Gunsong Chemical
-2211, non-volatile content 56wt%) and conductive carbon black (Toka Black manufactured by Tokai Carbon@),
After mixing and kneading 20 wt% (average particle size 50 nm) in a ball mill to make a conductive varnish, it was milled in a stainless steel vat, and commercially available cellulose trade paper for laminates (manufactured by Daicel Chemical Co., Ltd.) was passed through it. Impregnation treatment was performed.

The resulting prepreg was heated in an oven for 10 hours at room temperature.
After drying at 00° C. for 30 minutes, it was cut into a size of 200×200 mm. 15 sheets of prepreg having the specified dimensions were stacked, set in a hot press, and then molded at a molding temperature of 150°C and a molding pressure of 150 kg/cm' to a thickness of 2.
A conductive laminate with a thickness of 0 mm was used.

Next, this laminated plate was set in a stainless steel baking box, the top and bottom were held with graphite plates, and the surrounding area was backed with fine coke powder.
Carbonization was performed by firing at a heating rate of 10"C/hr and a maximum temperature of 1000°C to obtain a thin plate-like carbon material. The properties of this carbon material are shown in Table 1.

(Example 2) 80 wt% of the same phenolic resin solution as in Example 1, and 2
A conductive varnish was prepared by mixing and kneading 20 wt % of carbon black (Toka Black manufactured by Tokai Carbon ■, average particle size 50 nm) which had been graphitized at 500°C to improve conductivity. This varnish was transferred to a stainless steel vat, and cellulose paper for laminates was passed through it in the same manner as in Example 1 to perform impregnation treatment.

The obtained prepreg was dried in the same manner as in Example 1 at room temperature for 10 hours and in an oven at 100°C for 30 minutes, and then dried at 200×
Cut into 200 mm dimensions, stack 15 sheets, and heat press at a temperature of 150°C and a molding pressure of 150 kg/cm2.
It was molded under the following conditions to obtain a conductive laminate with a thickness of 2.0 mm.

Next, this laminated plate was set in a stainless steel baking box, the top and bottom were held with graphite plates, and the surrounding area was backed with fine coke powder. Using the same Matsufuru furnace as in Example 1, the temperature was raised under an N2 atmosphere. Carbonization was performed by firing at a rate of 10°C/hr and a maximum temperature of 1000°C to obtain a thin plate-like carbon material. The properties of this carbon material are shown in Table 1.

(Comparative Example 1) 80 wt % of the same phenol resin solution as in Example 1 was mixed and kneaded with 20 wt % of artificial graphite powder (average particle size 30 μm) using a ball mill to obtain a conductive varnish.゛ This varnish was poured into a stainless steel vat, and a cellulose paper for laminated board was passed through the vat in the same manner as in Example 1 to perform the impregnation treatment.

The surface of the obtained prepreg had a pattern due to poor filler impregnation. As in Example 1, this prepreg was dried at room temperature for 10 hours and in an oven at 100°C for 30 minutes, then cut into a size of 200 x 200 mm.
The sheets were laminated and molded using a hot press at a molding temperature of 150°C and a molding pressure of 150 kg/cm2 to a thickness of 2.0 m.
It was made into a conductive laminate of m.

Next, this laminated plate was set in a stainless steel baking box, the top and bottom were held with graphite plates, and the surrounding area was backed with fine coke powder. Using the same Matsufuru furnace as in Example 1, N2j
Carbonization was performed by firing at a heating rate of 10° C. and a maximum temperature of 1000° C. under a J atmosphere to obtain a thin plate-like carbon material. The properties of this carbon material are shown in Table 1.

(Example 3) 80 wt % of the same phenol resin solution as in Example 1 and 20 wt % of conductive carbon black (Toka Black manufactured by Tokai Carbon ■, average particle size 50 nm) were mixed and kneaded in a ball mill to obtain a conductive varnish. This varnish was evenly applied to a cellulose film prepared by hydrolyzing acetylcellulose using a commercially available spatula to perform an impregnation treatment.

The obtained prepreg was dried in the same manner as in Example 1 at room temperature for 10 hours and in an oven at 100°C for 30 minutes, and then dried at 200×
Cut into 200 mm dimensions, stack 15 sheets, and heat press at a temperature of 150°C and a molding pressure of 100 kg/cm2.
It was molded under the following conditions to obtain a conductive laminate with a thickness of 2.5 mm.

Next, this laminated plate was set in a stainless steel firing box, the upper and lower sides were held with graphite plates, and the surrounding area was backed with fine coke powder. Carbonization was performed by firing at a temperature rate of 10°C/hr and a maximum temperature of 1000°C to obtain a thin plate-like carbon material. The properties of this carbon material are shown in Table 1.

(Comparative Example 2) 80 wt % of the same phenolic resin solution as in Example 1 was mixed and kneaded with 20 wt % of artificial graphite powder (average particle size 100 μm) using a ball mill to obtain a conductive varnish. As in Example 3, this varnish was evenly applied to a cellulose film prepared by hydrolyzing acetylcellulose using a commercially available spatula, and impregnated.

A large amount of graphite powder that was not impregnated into the base material adhered to the surface of the obtained prepreg, and the surface quality was poor.

As in Example 1, this prepreg was dried at room temperature for 10 hours and in an oven at 100°C for 30 minutes.
It was cut to a size of 0 mm, and 15 sheets were laminated and molded by hot press at a molding temperature of 150° C. and a molding pressure of 100 kg/cm'' to obtain a conductive laminate with a thickness of 2.5 mm.

Next, this laminated plate was set in a stainless steel baking box, the top and bottom were held with graphite plates, and the surrounding area was backed with fine coke powder. Using the same Matsufuru furnace as in Example 1, the temperature was raised under an N2 atmosphere. Carbonization was performed by firing at a rate of 10°C/hr and a maximum temperature of 1000°C to obtain a thin plate-like carbon material. The properties of this carbon material are shown in Table 1.

<Effects of the Invention> Since the present invention is configured as described above, by using carbon black having high conductivity, it is possible to uniformly impregnate the inside of the base material with the conductive varnish.

As a result, a thin plate-like carbon material having excellent not only electrical properties but also mechanical properties can be obtained.

-3゜

Claims (3)

[Claims] (1) Prepreg that has a uniform composition throughout the interior by using cellulose paper or cellulose film as a base material and impregnating it with a varnish made by mixing and kneading a thermosetting resin as a matrix and highly conductive carbon black as a filler. A method for producing a thin plate-like carbon material obtained by laminating and molding this prepreg and subjecting it to a firing treatment. (2) The method for producing a thin plate-like carbon material according to claim 1, wherein the carbon black is graphitized at a temperature of 2000° C. or higher. (3) The method for producing a thin plate-like carbon material according to claim 1 or 2, wherein the mixing ratio of carbon black to the thermosetting resin is 2 to 50 wt% with respect to the thermosetting resin.