JPH0831231A - Conductive mold - Google Patents

Abstract

PURPOSE:To raise the conductivity without marring the mold processability by specifying the cavity rate of an obtained mold using ketchen black and right globular graphite particles being burned at specified temperature for conductive fillers. CONSTITUTION:50-100 pts.wt. of ketchen black and 150 or more pts.wt. of right globular graphite particles being baked at 1500 deg.C or over are mixed to 100 pts.wt. of thermoplastic resin or thermosetting resin. This mixture is made into a molded item, where the cavity rate is 5% or under, preferably, 3% or under and the ratio of volume resistivity value in Z direction to that in X-Y direction of the itself is 2 or under, by press molding or the like. Hereby, a molded item, where the conductivity and the mechanical strength such as shock strength and flexural strength is balanced, can be obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a fuel cell separator,
Conductive material for connector, movable contact for push button switch, I
The present invention relates to a conductive molded article useful as an antistatic tray for C and the like.

[0002]

A fuel cell is an electrochemical system that uses fossil energy to generate electricity with high efficiency and low pollution. The fuel cells include phosphoric acid fuel cells (hereinafter referred to as PAFCs), solid oxide fuel cells, solid polymer electrolyte fuel cells (hereinafter referred to as PEFCs), molten carbonate fuel cells, alkaline fuel cells. There are various types of such. Current,
The above-mentioned various fuel cells have been studied and put into practical use. Among them, in PAFC and PEFC, conductive molded products such as separators (hereinafter referred to as molded products) are used. The separator is indispensable when stacking unit cells,
In this, hydrogen gas on one surface, a grooved separator system in which oxygen and water vapor channels are provided on the other surface,
There are two types, a flat plate type separator method with no groove on the surface.

By the way, the separator needs to have conductivity of 10 ^-1 Ω · cm or less, and it has to withstand chemical corrosion such as oxidation, and further, hydrolysis resistance and hot water resistance are required. A fired product called a glassy carbon plate is generally used. The glassy carbon plate is obtained by firing a plate-shaped molded product obtained by curing and reacting a phenol resin, a polyimide resin, an epoxy resin, a furan resin or the like as a raw material in an inert atmosphere. However, since the glassy carbon plate has a weak compressive stress, it has a drawback that it is easily damaged when it is tightened and fixed with bolts during assembly of the fuel cell. In addition, since it has no elasticity, hydrogen gas and oxygen gas cannot be prevented from leaking from the mating surface with the electrode, and therefore a smoothness of 10 μm level is required. In addition, the glassy carbon plate requires many forming and processing steps such as raw material blending → molding → curing → firing → machining → inspection in the manufacturing process, which makes it extremely expensive and causes the cost increase of the fuel cell. It was also accompanied.

[0004]

In order to solve these problems, a resin conductive plate in which a resin is mixed with a carbon filler has been studied.
It is required that the volume resistivity value in the Y direction and the volume resistivity value in the Z direction be as equal and low as possible. For this reason, the applicant has previously proposed a conductive composition and a molded body in which carbon black and a spherical conductive filler are added to a resin, but in this case, when it is attempted to satisfy the conductive characteristics, the conductive filler is Had to be added in a large amount, and the flowability of the compound was lowered thereby, making molding and processing difficult. In addition, due to this, there is a problem that voids are likely to occur inside the molded product, resulting in a decrease in compressive stress and being easily damaged when tightening and fixing with a bolt or the like during assembly of the fuel cell. It was In order to prevent deterioration of moldability and processability and deterioration of assemblability, it is necessary to limit the addition of conductive filler, and the conductive characteristics of 10 ^-1 Ωcm or less may not be satisfied. It wasn't enough. Therefore, an object of the present invention is to provide a conductive molded product having enhanced conductive properties without impairing the molding processability, whereby the voids inside the molded product can be reduced, and even when the fuel cell is assembled, it is damaged. It aims to provide something that is difficult to do.

[0005]

In order to solve the above-mentioned problems, the present inventors have selected the type, shape, particle size distribution of conductive particles, type of thermoplastic resin and thermosetting resin, molding method, and molded article. As a result of further studying the relationship of the porosity, etc., thermoplastic resin or thermosetting resin was used to obtain a conductive molded product with satisfactory conductivity that does not impair moldability and processability and is less likely to be damaged during fuel cell assembly. 100 parts by weight of curable resin, Ketjen Black 50-100 as conductive filler
Parts by weight and spherical graphite particles 150 calcined at 1500 ° C or higher
When the porosity is 5% or less, preferably 3% or less, the ratio of the volume specific resistance value in the Z direction to the volume specific resistance value in the X-Y direction of the molded article obtained by blending 1 part by weight or more is The present invention has been completed by finding that it is preferable to make a molded body of 2 or less. Here, the porosity means a value calculated by the following formula (I). Porosity (%) = [1- (molded product bulk specific gravity / theoretical specific gravity)] × 100 (I)

The present invention will be described in detail below. The resin used in the present invention is preferably a thermoplastic resin or a thermosetting resin, and a separator for PAFC has a maximum continuous use temperature of about 220 ° C., so heat resistance satisfying this is required, and gas-free Permeability, hydrolysis resistance, hot water resistance,
Properties such as acid resistance are also required. Examples of the thermoplastic resin satisfying these required characteristics include fluororesin, polyetheretherketone resin, polyetherimide resin, polyamideimide resin, polyphenylene sulfide resin, polyethersulfone resin, polyetherketone resin and polyoxybenzoyl. Ester resins, liquid crystal polyester resins and the like, and as thermosetting resins, for example, phenol resins, bismaleimide triazine resins,
Examples thereof include unsaturated polyester resins, diallyl phthalate resins, polyamino bismaleimide resins, aromatic polyimide resins, and the like. On the other hand, since the continuous use temperature of PEFC separator is about 100 to 150 ° C. at maximum, it is necessary to adopt a resin satisfying the heat resistance condition and the same required characteristics as above. As such a resin, in addition to the above resins, aromatic polyester, polyacetal, polyamide, polyarylate, polyallyl sulfone, polybenzimidazole, polyether nitrile, polythioether sulfone, polyimide, polyamino bismaleimide, polyketone, Examples thereof include polyphenylene ether and polysulfone.

On the other hand, as the conductive filler used in the present invention, Ketjen black and true spherical graphite particles calcined at 1500 ° C. or higher are used. As long as it is within the above range, other conductive fillers may be used in combination. This conductive filler has a volume resistivity of 10 ^-1 Ω.
・ It is desirable that the size is cm or less. Even if a filler with a volume resistivity higher than this is added, the effect on lowering resistance cannot be expected so much, and in order to produce the effect, it is necessary to add a large amount of conductive filler, and the flow of the composition Of the fuel cell becomes extremely difficult to form in the worst case, or even if it can be formed, voids are likely to occur inside the molded product (porosity easily exceeds 5%). When it is assembled, it is easily damaged when it is tightened and fixed with bolts. The conductive fillers other than the above Ketjen black and true spherical graphite particles that can satisfy the required characteristics include, for example, oil furnace black made from crude oil, acetylene black made from acetylene, gold, silver, copper, nickel. Such metal-based particles are listed.

The amount of Ketjenblack to be blended is 50 to 100 with respect to 100 parts by weight of the thermoplastic resin or thermosetting resin, from the viewpoints of high filling property, conductive property, processability and moldability of the obtained molded product. Used in parts by weight. This is 50
When the amount is less than the weight part, the developed structure structure, which is the characteristic of Ketjen Black molded in the molded product, becomes insufficient, and when the conductivity required for the fuel cell separator is obtained, other conductivity A large amount of filler has to be added, and as a result, the fluidity of the compound is extremely reduced as described above, making molding impossible in the worst case, or molding even if molding is possible. Voids are likely to occur inside the product, and are easily damaged when tightened and fixed with bolts or the like during assembly of the fuel cell.
On the other hand, even if the amount exceeds 100 parts by weight, the fluidity of the compound is extremely reduced, and in the worst case, molding becomes impossible, or even if molding is possible, voids are generated inside the molded product. This is not preferable because it is easy to damage and easily damaged when tightening and fixing with a bolt or the like at the time of assembling the fuel cell.

Next, the other conductive filler used in the present invention, the true spherical graphite particles fired at 1500 ° C. or higher, will be described. Here, the meaning of "spherical" means
The shape of a particle is made to rest on a plane in the most stable state of one particle, the projected image on this plane is sandwiched by two parallel lines, and the distance when the distance between the parallel lines is the minimum, The minor axis diameter W of the particle, the distance when the particle is sandwiched by two parallel lines perpendicular to the two parallel lines, the major axis diameter L of the particle, the distance when sandwiched by the plane parallel to the maximum stable plane, When defined as the height H of a particle, the value of the ratio of any two of W, L and H is in the range of 0.67 to 1.5, preferably W = L = H and the surface area is expressed by πL ^2. It is a thing. The true spherical graphite particles used are those fired at 1500 ° C. or higher, preferably 2000 ° C. or higher. Graphitization has not proceeded sufficiently with the one that is fired at a temperature of less than 1500 ° C.
The true spherical graphite particles do not have a sufficiently low resistance value, and the conductivity required for a fuel cell separator cannot be satisfied.

Further, the particle size of the spherical graphite particles is
Those in the range of 0.1 to 200 μm, particularly those in the range of 1 to 70 μm are preferable. If the particle size is less than 0.1 μm, secondary agglomeration is likely to occur, processability such as kneading is reduced, and fluidity is also reduced, so voids are likely to remain inside the molded product, and during assembly of the fuel cell. It is easily damaged when tightening and fixing it with bolts. On the other hand, if the particle size exceeds 200 μm, there is no problem in workability and moldability, but since the filling rate of the molded product is difficult to increase, it may not be possible to obtain sufficient conductivity. . The particle size distribution of the true spherical graphite particles used here is such that the average particle size is 10 to 20 μm, and a continuous distribution close to a normal distribution is taken within the above-mentioned preferable particle size range, together with the conductivity. It is preferable because it is satisfactory in terms of moldability, processability, and assembling property of the fuel cell.

The amount of the spherical graphite particles to be blended should be 150 parts by weight or more, preferably 150 to 300 parts by weight, based on 100 parts by weight of the thermoplastic resin or thermosetting resin. When it is less than 150 parts by weight, in order to satisfy the required volume resistivity value (paragraph number 0007
It is also possible to add other conductive fillers (as described above), but the ratio of the true spherical graphite particles to the total conductive particles is decreased, so that the Z direction relative to the volume resistivity value in the X-Y direction of the molded body in the Z direction. The ratio of volume resistivity values of No. 1 becomes large, and it becomes impossible to maintain the preferable characteristics as a fuel cell separator, and the fluidity of the blend decreases, so that molding becomes impossible, or even if molding is possible. However, voids are likely to remain inside the molded product, and when the fuel cell is assembled and tightened with bolts or the like, it may be easily damaged. On the other hand, when the content of the spherical graphite particles exceeds 300 parts by weight, voids are likely to remain inside the molded product as well, and damage tends to occur when the fuel cell is assembled by tightening with bolts and the like. It is not preferable because it may occur.

Various methods such as extrusion molding, injection molding, press molding, and calendar molding can be adopted for molding a fuel cell separator from a mixture comprising the above components. Further, in order to reduce the porosity of the molded product, it can be molded under reduced pressure, the molding pressure can be increased, a molding aid can be added, and the particle size distribution of the conductive filler to be reduced can be adjusted. It is also possible to combine these with the above-mentioned molding methods as appropriate.

[0013]

EXAMPLES Specific embodiments of the present invention will be described below with reference to examples. Examples 1 to 4, Comparative Example 1: 100 parts by weight of acrylic rubber RV-2520 (manufactured by Nissin Chemical Industry Co., Ltd.), 75 parts by weight of Ketjen Black EC (manufactured by Lion Corp., trade name), spherical graphite Particles: Glass Bon P (Owada Carbon Co., Ltd., trade name, average particle size 30 μm, 2000 ° C. baked product) and spherical (not true spherical) conductive particles: Bell Pearl C-2000 (Kanebo Co., Ltd. trade name, average particle) 15 μm in diameter, baked at 2000 ° C) and the amount shown in Table 1 (parts by weight), lubricant: Stearic acid F-3 (Kawaken Fine Chemical Co., trade name) 1 part by weight, stabilizer: Naugard # 445 (US) Uniroyal Co., Ltd., 1 part by weight, vulcanization accelerator: Sumifine BM (Sumitomo Chemical Co., Ltd.,
Brand name) 2.4 parts by weight and vulcanizing agent C-13 (manufactured by Shin-Etsu Chemical Co., Ltd., trade name) 4.8 parts by weight are added, and each compound is kneaded with a two-roll mill, and in Examples 1 to 4, it is dispensed. The obtained sheet was pressed under the conditions of a temperature of 150 ° C., a pressure of 90 kgf / cm ² , and a time of 10 minutes to obtain a molded product having a size of 100 mm × 100 mm × 5 mm. With respect to each of the obtained molded products, the volume resistivity values in the XY direction and the Z direction and the porosity were measured by the following methods, and the results of roll workability evaluated by the following methods are also shown in Table 1. In Comparative Example 1 in which the true spherical graphite particles were blended in a small amount, the roll workability was poor and a dispensing sheet could not be obtained, so that the respective characteristic values could not be measured.

(Measurement of volume resistivity value) In the XY directions, a test piece of 80 mm × 20 mm × 5 mm size was prepared from a molded product obtained by press molding, and the standard specification SRIS-
The volume resistivity was measured based on 2301. In addition,
The electrode was prepared by applying a conductive resin material: DOTITE FA-303 (manufactured by Fujikura Kasei Co., Ltd., trade name) to a test piece and drying. 10 mm x 10 mm x from the molded product obtained by press molding in the Z direction
A test piece with a size of 5 mm was prepared, and a conductive resin material: DOTITE FA-303 (described above) was applied to both sides of 10 mm x 10 mm and dried to prepare an electrode. Was measured. (Measurement of Porosity) The porosity of the molded product by each compounding is calculated by calculating the theoretical specific gravity value of each compounding and JIS K 7112 A
From the actual bulk specific gravity value obtained by the method (substitution method in water), it was obtained by the formula (I). (Evaluation Criteria for Roll Workability) ⊚: Very good workability, a dispensing sheet can be easily obtained, and a fuel cell separator can be obtained. ◯: Good workability, a dispensing sheet is obtained, and a fuel cell separator is obtained. Δ: The workability is slightly lowered, but a dispensing sheet is obtained,
A fuel cell separator is obtained. X: The workability is poor and a dispensing sheet cannot be obtained, so that the fuel cell separator cannot be molded.

[0015]

[Table 1]

Comparative Examples 2 to 6: As the true spherical graphite particles in the composition of Example 1, Unibex GCP-30 (manufactured by Unitika Ltd., trade name, average particle size 30 μm) was used in place of the glass bon P.
, 1200 ° C fired product) was used and the test was conducted in exactly the same manner. Table 2 shows the results. From this, the firing temperature is 1500
It was found that the use of the true spherical graphite particles having a temperature of less than 0 ° C. does not allow the volume resistivity value of 10 ⁻¹ Ω · cm or less required for a fuel cell separator to be obtained. In Comparative Example 6, the compounding amount of the true spherical graphite particles was further small, and the roll workability was poor, so that a dispensing sheet was not obtained and each characteristic value could not be measured.

[0017]

[Table 2]

Example 5: Polyphenylene sulfide:
Fortron 0220A9 (manufactured by Polyplastics, trade name)
In 100 parts by weight, 75 parts by weight of Ketjen Black EC (explained above), spherical conductive filler: Glass Bon P (explained above) 200
Parts by weight and spherical conductive filler: Belpearl C-2000
(Above) 100 parts by weight was added, and this was kneaded with a pressure kneader and then pressed under the conditions of a temperature of 290 ° C and a pressure of 90 kgf / cm ^2.
A molded product of 100 mm × 100 mm × 0.6 mm was obtained. When this molded product was tested for phosphoric acid resistance, heat resistance, gas impermeability and the like required as a PAFC separator, there was no problem at all.

Example 6 The composition shown in Example 3 above was kneaded with a pressure kneader, then at a temperature of 290 ° C. and a pressure of 90 kg.
It was pressed under the condition of f / cm ² to obtain a molded product of 100 mm × 100 mm × 5 mm. The volume resistivity was measured in the same manner as in Example 1. As a result, the XY direction was 0.045 Ω · cm, the Z direction was 0.081 Ω · cm, the ratio (Z direction / XY direction) was 1.8, and the porosity was 3.0. %Met.

Examples 7 to 8 and Comparative Example 7: Acrylic rubber R
V-2520 (above), Ketjen Black EC (above), true spherical graphite particles: glass bon P (above) with an average particle size of 10 μm and 30 μm, spherical conductive particles: Belpearl C-2000
A test was conducted in the same manner as in Example 1 except that the amounts (parts by weight) shown above in Table 3 were changed to those shown in Table 3, and the results are also shown in Table 3. From this, the average particle size of spherical graphite particles

[0021]

[Table 3] It should be noted that 100 mm × 100 mm molded using the formulation of each example
When the fuel cell was assembled with the molded product of × 5, no damage occurred. On the other hand, when a similar fuel cell was assembled with a molded product of 100 mm × 100 mm × 5 molded using the formulation of Comparative Example 7, breakage sometimes occurred.

Reference Example: 100 mm × 1 as in Example 1.
After obtaining a 00 mm × 0.5 mm sheet-shaped molded product, die pressing was performed to produce an IC tray. 10 ICs on the obtained IC tray
Place individually, and 10 times on a stainless steel plate at a humidity of 30% RH
A sieve vibration of min × 20 gf was applied, but there was no IC leak.

[0023]

The electrically conductive molded article of the present invention is produced by press molding,
Injection molding, extrusion molding, calendar molding and the like are possible, and at the time of molding, it can also be molded as a separator including passages for cooling water, hydrogen gas and oxygen gas. Also, the porosity is 5%
By the following, it is possible to obtain a fuel cell separator having well-balanced conductivity and mechanical properties such as impact strength and bending strength. In the above description, the fuel cell separator was described, but the molded product of the present invention is a connector conductive material, a push button switch movable contact,
It can be widely applied to various members such as IC antistatic trays and the like, which require conductivity or antistatic function, containers, and the like.

Claims (1)

[Claims] 1. Ketjenblack 50-1 as a conductive filler in 100 parts by weight of a thermoplastic resin or a thermosetting resin.
00 parts by weight and spherical graphite particles fired at 1500 ° C or higher 1
The porosity obtained by blending 50 parts by weight or more is 5% or less, and the ratio of the volume specific resistance value in the Z direction to the volume specific resistance value in the XY direction of the molded product is 2 or less. A conductive molded product characterized by.