Note: Descriptions are shown in the official language in which they were submitted.
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BAC~GROUND OF THE INVENTION:
The present invention relates to a co~posite
electrode substrate for a fuel cell of phosphoric acid
type, and more in detail, relates to a composite elec-
trode substrate wherein a porous and carbonaceous
electrode provided with flow channels of a reactant gas
is joined to both surfaces of the separator via a
flexible graphite sheet, the separator has been extended
beyond the electrode and to the thus extended par'c of
the separator, (1) a peripheral sealer on the side of the
electrode parallel to the flow channels therein, which
comprises a gas-impermeable, compact and carbonaceous
material or (2) a manifold which comprises a gas-imperme-
able, compact and carbonaceous material and is provided
with a flow passage for supplying a reactant gas
is joined via a layer of a fluorocarbon resin,
and a process for producing the composite electrode
substrate.
Generally, the electrode substrate as an elec-
trode of a fuel cell of phosphoric acid type has been
stacked so that one side thereof contacts to the phospho-
ric acid matrix and the other side thereof faces to the
separator.
In addition, in the case where the electrode
substrates are stacked for making a fuel cell, (1) a
sealer is provided at the edge (peripheral) part of the
electrode substrate so as to prevent the diffusion of
- 2 - ~? D
S' .'~ '~
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the reactant gas from the side of the electrode substrate
to outside or (2) a manifold is provided at the edge part
of the electrode substrate so as to supply the reactant
gas to the fuel cell and at the same time to prevent the
diffusion of the reactant gas from the side of the elec-
trode substrate to outside.
Hitherto, in such a fuel cell, the joining
between the composite materials has been carried out by
using a carbon cement. However, since the carbon cement
is eroded by phosphoric acid, there has been a possibility
of causing exfoliation between the jointed composite
materials and gas leakage through the jointed part.
- In addition, since the electrode substrate is
generally a thin plate type, there has been a problem in
the point of mechanical strength that the elect~ode
substrate is broken by handling, particularly in the case
where the area of the electrode substrate is large.
Further, as a method of joining the porous
electroconductive materials wherein the gas-impermeability
between the porous electroconductive materials has been
increased, a method has been proposed recently. According
to the proposed method, the porous electroconductive
material is impregnated with a fluorinated ethylene-
propylene polymer, a polysulphone resin, etc., and the
thus impregnated layer is joined as an interface to another
electroconductive material by hot-pressing while maintaining
73~
electroconductivity through the gas impervious region
(for instance, refer to U.S. Patent No. 4,505,992).
However, in the case of using the above-mentioned
methods for the peripheral sealer of the composite electrode
substrate, although the passage of the gas between the two
carbon materials is prevented by the thus resin-impregnated
carbon layer, in the case where the electroconductive
material is the porous carbon material, since such a
carbon material is weak in mechanical strength, the
usage of the thus obtained composite material is limited.
On the other hand, even in the case where an electrode in
a composite electrode substrate is produced by the above-
mentioned method, the thus obtained resin-impregnated
electrode is unsatisfactory in quality for using it in
the composite electrode substrate for a fuel cell, because
the used thermoplastic resin is substantially large in
resistance to thermal and electric conductivities.
As a result of the present inventors' studies
for obtaining a composite electrode substrate for a fuel
cell wherein the above-mentioned demerits have been solved,
it has been found by the present inventors that the com-
posite electrode substrate provided with a peripheral
sealer on the side of the electrode parallel to the flow
channels therein, wherein the separator and the electrode
are joined via a flexible graphite sheet and calcined to
be one body as carbon, and the peripheral sealer and the
separator are joined together via a fluorocarbon resin,
is particularly excellent in resistance to phosphoric
acid and at the same time, that since the peripheral
sealer are evenly disposed and joined in a crossed state
while holding the separator in both sides, there is a
reinforcemental effect and the composite electrode ,
substrate of the above-mentioned structure is also
excellent in handling. On the basis of the above-
mentioned findings, the present inventors have attained
the present invention.
Namely, the first object of the present invention
is to provide a composite electrode substrate provided
with a peripheral gas sealer on the side of the electrode
parallel to the flow channels therein, wherein the
peripheral gas-sealer is joined to the separator to form
one body.
Still more, the present inventors have found
that the composite electrode substrate provided with a
manifold for a fuel cell, wherein all the composite
materials are joined by carbon or a fluorocarbon resin,
is particularly excellent in resistance to phosphoric
acid and since the peripheral sealer material (hereinafter
referred to as a manifold) which also serves as the gas
manifold is joined to the peripheral part of the electrode
~273~
substrate, such a composite electrode substrate is
excellent in handling.
Namely, the second object of the present invention
is to provide a composite electrode substrate provided with
a manifold for a fuel cell, wherein the manifold provided
with a flow passage for supplying the reactant gas is
joined to the separator in one body.
The third object of the present invention is to
provide the above-mentioned composite electrode substrate
for a fuel cell of phosphoric acid type, which is excellent
in resistance to phosphoric acid.
The other objects of the present invention and
the merits thereof will be clearly understood from the
following description.
SUMMARY OF THE INVENTION: -
In a first aspect of the present invention, thereis provided a composite electrode substrate for a fuel
cell, comprising a porous and carbonaceous electrode
provided with f'ow channels of the reactant gas and joined
to both surfaces of a separator via a flexible graphite
sheet, and
peripheral sealer on the side of the electrode
parallel to the flow channels therein, which comprises a
gas-impermeable and compact carbon material or a manifold
which comprises a gas-impermeable and compact carbon
~3~3~
plate and provided with a flow passaye for supplying
the reactant gas, the peripheral sealer or manifold
being joined to the extended part of the separator
beyond the electrode via a fluorocarbon resin
layer.
In a second aspect of the present invention,
there is provided a process for produ~ing a composite
electrode substrate for a fuel cell which process
comprising (1) joining a porous and carbonaceous electrode
material provided with flow channels of the reactant gas
to a separator material which is larger in an surface
area than the electrode material by an adhesive while
interposing a flexible graphite sheet between the elec-
trode material and the separator material so that said
separator material is extended beyond the electrode
material, (2) calcining the thus joined materials at a
temperature of not less than about 1000C under a reduced
pressure and/or in an inert atmosphere, thereby producing
an electrode substrate part wherein the porous and
carbonaceous electrode is joined to both surfaces of the
separator via the flexible graphite sheet, and (3) joining
a peripheral sealer on the side of the electrode parallel
to the flow channels therein, which comprises a gas-
impermeable carbon material or a manifold material
comprising a gas-impermeable and compact carbon plate to
~ ~t7~
the extended part of the separator beyond -the electrode
via a sheet or a dlspersion of a fluorocarbon resin.
BRIEF EXPLANATION OF DRAWINGS:
Of the attached drawings, Fiy. 1 shows an example
of the composite electrode substrate provided with a
peripheral sealer on the side of the electrode parallel
to flow channels therein according to the present invention,
Fig. 2 is a ground plan of the composite electrode substrate
provided with a manifold for a fuel cell according to the
present invention, Figs. 3 and 4 are respectively the
sectional views of III - III and IV - IV of Fig. 2,
and Fig. 5 shows the internal construction of the
manifold of the composite electrode substrate provided
with the manifold according to the present invention,
the figures in the left side of Fig. 5 being the partial
cross-section and the figures in the right side of Fig. 5
being the partial ground plan of the manifold.
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DETAILED DESCRIPTION OF THE INVENTION:
. .
The electrode used in the composite electrode
substrate according to the present invention is porous
and carboneous, and after being calcined at a ~empera-
ture of not less than 1000C under a reduced pressureand/or in an inert atmosphere, the mean bulk density,
the gas-permeability and the electric resistivity thereof
are preferably from 0.3 to 0.9 g/cc, not less than 200
ml/cm .hour.mmAq, and not more than 200 mQ~cm,
respectively.
The mean bulk density, the gas-permeability
and the electric resistivity of the separator used ln the
composite electrode substrate according to the present
invention are preferably not less than 1.4 g/cc, not
more than 10 6 ml/cm2.hour.mn~q and not more than
10 mQ.cm, respectively. The thickness of the same
separator is preferably not more than 2 mm.
The mean bulk density and the gas-
permeability of a peripheral sealer on the side of
the electrode parallel to the flow channels therein and
a manifold used in the composite electrode substrate
according to the present invention are preferably not
less than 1.4 g/cc and not more than 10 4 ml/cm2.hour.mmAq,
respectively.
. . ~
~;~73~
In the composite electrode substrate provided
with the peripheral sealer according to the present
invention, the porous and carbonaceous electrode provided
with flow channels of the reactant gas is joined to the
both surfaces of the separator via a flexible yraphite
sheet, and the peripheral sealer comprising a gas-
impermeable, compact and carbonaceous material is joined
to the above~mentioned separator via a layer of a
fluorocarbon resin.
In addition, in the composite electrode
substrate provided with the peripheral sealer according
to the present invention, the both electrodes are
joined to the both surfaces of the separator so that
the flow channels of the reactant gas in one of the
electrodes are perpendicular to those of the another
electrode, and a pair of the peripheral sealers are
joined to the extended part of the separator via a
layer of a fluorocarbon resin while being adjacent to
the periphery of the electrode parallel to the flow
channels of the reactant gas in the electrode as are
seen in Fig. 1. Namely, the separator shown in Flg. 1
extends beyond the periphery of the electrode parallel
to the flow channels therein.
-- 10 --
That is, Fig. 1 is an oblique view of the
preferable composite elec-trode substrate provided with
the peripheral sealer according to the present invention.
The composite electrode substrate provided with
the peripheral sealer according to the present invention
has a structure comprising the two electrodes 1, 1' provided
with flow channels 5, 5' of the reactant gas, the separator
4 interposed between the two electrodes and the peripheral
sealer 8 adjacent to periphery of the electrode parallel to
the flow channels 5, 5' of the reactant gas in the above-
mentioned electrodes.
The separator 4 is larger in a surface area than
the electrodes _, 1' and as is shown in Fig. 1, it is extended
beyond the periphery of the electrode parallel to the flow
channel 5 or 5' of the reactant gas in one of the electrodes (the
outer edge of the extended part being coincided with the
outer edge of the another electrode), and the peripheral
sealer 8 is joined to the extended part via a fluorocarbon
resin 40. Between the separator 4 and the electrodes 1, 1'
a flexible graphite sheet _ has been inserted, and the
peripheral part (extended part) of the separator and the
peripheral sealer 8 are mutually joined via a fluorocarbon
resin 40.
As has been described, in the composite electrode
substrate provided with the peripheral sealer according
to the present invention, all the peripheral sealers and
-- 11 --
the separator are joined together via a fluorocarbon
resin and although the amount of leakaye of the reactant
gas to outside through the peripheral sealer including
the joined part is subject to gas diffusion and is not
so much influenced by the pressure of the reactant gas,
the gaseous leakage per unit time per the peripheral
length of the joined part under the differential pressure
of 500 mmAq in the present invention is preferably not
more than 10 ml/cm.hour.mmAq, when the gas leakage is
represented by [the amount of lea~ed gas/~the side
length) x (the differential pressure)].
In the composite electrode substrate provided
with a manifold, which is another enforced mode of the
present invention, the porous and carbonaceous electrode
provided with the flow channels of the reactant gas is
joined to both the surfaces of the separator via a flexible
graphite sheet, the separator has been extended beyond
the all periphery of the electrode and to the extended
part of the separator, a manifold comprising a gas-
impermeable, compact and carbonaceous plate provided with
the flow passage for supplying the reactant gas is
joined via a layer of a fluorocarbon resin.
Fig. 2 is a ground plan of the composite electrode
substrate provided with the manifold accarding to the
present invention, and Figs. 3 and 4 are respectively the
cross-sectional views of III ~ III and IV - IV of Fig. 2.
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.
:
~2~
The composite electrode substrate provided with
the manifold according to the present invention has a
construction comprising the two electrodes 1, 1' provided with
flow channels 5, 5' of the reactant gas, the separator 4
interposed between the two electrodes and the manifolds 2, 2'
adjacent to the all periphery of the electrode.
The separator 4 is larger in a surface area than
the electrodes 1, 1' and as is shown in Fig. 2, the separator
has been extended beyond the periphery of the electrodes
1, 1' and the manifolds 2, 2' are joined to the thus extended part.
Between the separator and the electrode, a
flexible graphite sheet 30 is inserted, and the peripheral
part of the separator which has been extended beyond the
periphery of the electrode, and the manifold are mutually
joined via the fluorocarbon resin 40 (refer to Fig. 5).
In addition, in the.above-mentioned manifold 2, the flow
passage 3 for supplying the reactant gas is provided while
penetrating the separator 4 and the manifold 2, The flow
passage 3 for supplying the reactant gas is (1) connected
to the flow channel 5 of the reactant gas provided in the
electrode 1 comprising the gas diffusion part 6 and rib 7,
via a flow passage 11 of the reactant gas provided in the
manifold 2 or (2) connected directly to the flow channel 5
of the reactant gas provided in the electrode 1, and the
another electrode 1' is sealed by the manifold 2' (refer
to Fig. 4).
... .
In Fig. 3, the flow passaye 3' for s~pplying the
reactant gas is (1) connected to the flow channel 5' of
the reactant gas provided in the electrode 1' ~ia a flow
passage 11' of the reactant gas provided in the manifold
2' or (2) connected directly to the fIow channel 5' of
the reactant gas provided in the electrode 1', and the
another electrode 1 is sealed by the manifold 2.
The flow direction of the reactant gas is shown by
arrows in Fig. 3 and Fig. 4.
The flow channel 5 of the reactant gas is
prescribed by the gas diffusion part 6 and the rib 7
in the electrode 1 and the separator 4 or the flexible
graphite sheet (refer to 30 of Fig. 5) which has been
joined to the separator 4.
There are various types of the internal construc-
tion of the manifold, and several instances thereof are
shown in Fig. 5. The figures in the left half of Fig. 5
are the partial cross-sectional view thereof and those in
the right half of Fig. 5 are the partial ground plans
thereof.
In (1) of Fig. 5, the manifold has a construction
of being divided into three parts 21, 22 and 23, and the
rib 7 of one of the electrodes has a construction of
entering a little under the manifold part 21 (for instance
to the position 7''). The internal edge of the manifold
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- - -
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part 22 is shown by 22'. The two parts 21 and 22 of the
manifold, 22 and the separator 4 and 23 and the separator 4
are mutually joined via a fluorocarbon resin as shown by
40 in (1) of Fig. 5, respectively.
In (2) of Fig. 5, the manifold parts 21 and 22
in the above (1) has been formed in one body and the
manlfold consists of the two parts 21 and 23. The rib 7
ends in the same plane 7''as the edge surface of the gas-
diffusion part 6. In addition, the surface corresponding
to the inner edge 22' of (1) is shown by 21'.
In (3) and (4) of Fig. 5, a structure is shown
wherein one of the electrodes joined to the separator has
been extended to either end of the flow passage 3 for
supplying the reactant gas (the end being shown by 1'') and
contacts to the inner edge of the manifold part 21.
In every case the manifold and the separator
have been joined together via the fluorocarbon resin.
In addition, each structure shown in Fig. 5 is only an
instance of the present invention, and the internal
construction of the manifold according to the present
invention can take another mode different from those shown
in Fig. 5.
As has been described above, in the composite
ele~trode substrate provided with the manifold according
to the present invention, all the manifold and the separa-
tor have been joined together via a fluorocarbon resin,
-- 15 --
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however, when the amount of leakage of the reactant gas
through the manifold per the peripheral length under a
definite diferential pressure per unit time is repre-
sented by [the amount of leaked gas/(the side length) x (the
differential pressure)]the amount is preferably less than
10 2 ml/cm.hour.mmAq which value is the same as that in
the composite electrode substrate provided with the
peripheral sealer.
The fluorocarbon resin used for producing the
composite electrode substrate according to the present
invention is generally a fluorocarbon resin of not less
than 200C in the melting point, and although it is not
restricted, for instance, polytetrafluoroethylene resin
(abbreviated to PTEE, a melting point of 327C and a
thermally deforming temperature of 121C under 4.6
kgf/cm2G), a copolymer resin of ketrafluoroethylene and
hexafluoropropylene (abbreviated to FEP, a melting point
of 250 to 280C and a thermally deforming temperature of
72C under 4.6 kgf/cm2G), polyfluoroalkoxyethylene resin
(abbreviated to PFA, a melting point of 300 to 310C, and
a thermally deforming temperature of 75C under 4.6
kgf/cm2G), fluorinated copolymer resin of ethylene and
propylene (abbreviated to TFP, a melting point of 290 -
300C), etc. may be mentioned. These fluorocarbon resins
are commerciallized. In the above fluorocarbon resins,
- 16 -
polytetrafluoroethylene resin is most preferable for
producing the product according to the present invention.
According to the present invention, the above-
mentioned fluorocarbon resin is,for instance, used as a
sheet of about 50 micrometers in thickness or a dispersion
of about 60 % by weight. A small amount of a surfactant
may be added to the above-mentioned dispersion.
For producing the composite electrode substrate
for a fuel cell according to the present invention, the
electrode material and the separator are joined together
by inserting a flexible graphite sheet between the elec-
trode material and the separator material and applying
an adhesive on both sides of the flexible graphite sheet
and after calcining the thus joined materials at a temper-
ature of not less than 1000C under a reduced pressure
and/or in an inert atmosphere, the extended part of the
separator which has been extended beyond the periphery
of the electrode and the peripheral sealer,or manifold
material are joined together via a sheet of a fluorocarbon
resin or a dispersion of a fluorocarbon resin.
In addition, the hole 3 which is used as the flow
passage of the reactant gas in the manifold of the composite
electrode substrate provided with the manifold may be made
in any optional stage of the process for producing the
composite electrode substrate according to the present
invention, for instance, before or after joining each
manifold material to the separator by a suitable means.
Of course, it is preferable to make a passage connecting
the hole 3 to the flow channel 5 of the reactant gas in
the electrode before joining the rnanifold material thereto.
As the electrode material of the composite elec-
trode substrate according to the present invention, the
following substances are used:
(1) A material made by thermally molding a
mixture of short carbon fibers, a binder and an organic
granular substance under a pressure (refer to ~apanese
Patent Application Laid-Open No. 59-68170 (1984)).
Particularly, the material prepared by molding a mixture
consisting of 20 to 60 % by weight of short carbon fibers
of not more than 2 mm in length, 20 to 50 % by weight of a
, . .
phenol resin and 20 to 50 % by weight of an organic
granular substance ~a micro-pore regulator) at a molding
temperature of 100 to 180C, under a molding pressure of
2 to 100 kgf/cm2G for one to 60 min.
(2) A material made by calcining the molded
material of the above-mentioned (1) at a temperature of
not less than 1000C under a reduced pressure and/or in an
inert atmosphere.
(3) A molded body comprising (a) gas diffusion
part made of the resin-impregnated paper sheet obtained
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by impregnating a paper sheet obtained from a mixture of
carbon fibers of not more than 20 mm in length, at least
one kind of organic fibers selected from the yroup con-
sisting of pulp, regenerated cellulose fibers, polyacry-
lonitrile fibers, etc. and a paper-making binder (poly-
vinyl alcohol fibers, etc.) by paper-manufacturing method
with a solution of a phenol resin (for instance, refer to
~apanese Patent Publication No. 53-18603 (1978)) and (b)
the rib prepared by using the raw material of the above-
mentioned (1).
(4) A material obtained by calcining the molded
body of the above-mentioned (3) at a temperature of not
less than 1000C under a reduced pressure and/or in an
inert atmosphere.
As the separator material used in producing the
composite electrode substrate according to the present
invention, a compact carbon plate of a calcining
shrinkage of not more than 0.2 % in the case of calcining
it at 2000C under a reduced pressure and/or in an inert
atmosphere is preférable.
As the peripheral sealer and the manifold material,
a compact carbon material of a calcining shrinkage
of not more than 0.2 % in the case of calcining each of
them at 2000C under a reduced pressure and/or in an inert
atmosphere is preferable.
-- 19 --
~7~
he flexible graphite sheet used for producing
the composite electrode substrate according to the present
invention has been prepared by compressing the expanded
graphite particles obtained by subjecting graphite particles
of not more than 5 mm in diameter to acid-treatment and
further heating the thus treated particles, and it is
preferable that the flexible graphite sheet is not more
than 1 mm in thickness, has a bulk density of 1.0 to
1.5 g/cc, shows a compression strain ratio (i.e. a strain
ratio to the compression load of 1 kgf/cm2) of not more
than 0.35 x 10 2 cm2/kgf and has a flexibility of not
breaking in the case of bending the sheet to the radius
of curvature of 20 mm. Of the commerciallized flexible
graphite sheet, GRAFOIL~ (made by U.C.C.) is a suitable
example. -
As the adhesive used on each joining surface
in joining the above-mentioned electrode material with the
separator material via a flexible graphite sheet, an
adhesive generally used in joining carbon materials may
be used, however, particularly, a thermosetting resln
selected from the group consisting of phenol resins, epoxy
resins, furan resins, etc. is preferable.
Although the thickness of the layer of the adhe-
sive is not particularly restricted, it is generally
preferable to apply uniformly the adhesive in thickness
of not more than 0.5 mm thereon.
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In addition, the joininy by the above-mentioned
adhesive can be carried out at a temperature of 100 to
180C, under a pressure of 1.5 to 50 kgf/cm2G for a
pressing time of one to 120 min.
After joining the electrode material with the
separator material via the flexible graphite sheet as
mentioned above, the thus joined materials are calcined
at a temperature of not less than about 1000C under a
reduced pressure and/or in an inert atmosphere.
Thereafter, a sheet of a fluorocarbon resin is
inserted or a dispersion of the fluorocarbon resin is
applied between the extended part of the separator and
the surface of the peripheral sealer or the manifold
material which is to be joined to the extended part, and
the thus composite materials are joined by melt-adhesion
of the resin at a temperature of not lower than the
temperature of lower by 50C than the melting point of
the fluorocar~on resin under a pressure of not less than
2 kgf/cm G while holding the pressure for not less than
10 sec.
Since the peripheral sealer of the thus obtained
composite electrode substrate provided with the peripheral
sealer for a fuel cell according to the present invention
is formed and joined to the substrate in one body, it is
not necessary, as a matter of course, to provide a special
peripheral sealer for preventing the leakage of the
'3~
reactant gas to the fuel cell side (such a peripheral sealer
is regarded necessary in a conventional fuel cell), and at
the same time, such a construction according to -the present
invention has the following effect.
Namely, since the electrode and the separator are
joined together in one body via the flexible graphite
sheet/and the peripheral sealer and the separator are
joined together in one body via the fluorocarbon resin,
the thus joined material is excellent in resistance to
phosphoric acid and is particularly useful as -the composite
electrode substrate for a fuel cell of phosphoric acid
type. In addition, since the peripheral sealers are
evenly disposed and joined around the thin pl.ate-like
electrode substrate while holding the separator alternate-
ly in both sides, such a structure has a reinforcing effect,
and as a result, the composite electrode substrate is
excellent in handling in the case of producing the fuel
cell.
Since the manifold of the composite electrode
substrate provided with the manifold for a fuel cell
according tothe present invention has been joined to the
substrate in one body, the supply and the discharge of the
necessary gas is made possible as a whole fuel cell
through the each manifold sections of the stacked fuel
cell when the reactant gas is simply introduced into the
manifold, and accordingly, it is not necessary, of course,
- 22 -
~2~3~3~
to provide an outer manifold for supply and discharye of
the reaetant gas, etc. whieh is regarded neeessary in a
eonventional fuel cell, and at the same time, such a
construction has the following effect:
Namely, the electrode and the separator are
joined together in one body via the flexible graphite
sheet, and the manifold and the separator are joined
together via the fluorocarbon resin, and accordingly, the
thus joined materials are excellent in resistance to
phosphoric acid, and such a construction is useful as a
eomposite electrode substrate for a fuel cell of phospho-
ric aeid type. In addition, since the manifold are
uniformly disposed and joined around the thin-plate like
electrode substrate, sueh a construetion has a reinforeing
effeet. As a result, sueh a eonstruction is excellent in
handling in the case of producing the fuel cell.
The present invention will be explained more in
detail while referring to the non-limitative examples as
follows:
EXAMPLE 1:
1-1: Electrode material:
After mixing 35 % by weight of short carbon fibers
(made by KUREHA KAGAKU KOGYO Co., Ltd., under the trade name
of M-204S, of a mean diameter of 14 ~m and a mean length
of 400 ~m), 30 % by weight of a phenol resin (ASAHI-Y~KIZAI
Co., Ltd., under the trade name of RM-210) and 35 % by
~27;~
weight of granules of polyvinyl alcohol (made by NIPPON GOSEI
KAGAKU KOGYO Co., Ltd. of a mean diameter of 180 ~m), the
mixture was supplied to a prescribed metal mold and molded
under the conditions of the molding temperature of 135C, the
molding pressure of 35 kgf/cm2G and the pressure holding
time of 20 min to obtain a ribbed electrode material of
600 mm in width, 720 mm in length and 1.5 mm in thickness.
The thickness of the rib and the thickness of the gas-
diffusion part thereof were 1.0 mm and 0.5 mm, respectively.
1-2: Separator materialc
A compact carbon plate of 0.8 mm in thickness
(made by SHOWA DENKO Co., Ltd.) was cut into a piece of
720 mm in length and 720 mm in width to obtain the separa-
tor material.
1-3: Peripheral sealers:
.,
. A compact'carbon plate of a bulk density of
1.85 g/cc and of a thickness of 1.5 mm (made by TOKAI
Carbon Co., Ltd.) was cut into four pieces of 60 mm in
width and 720 mm in length to obtain the peripheral
sealers.
1-4: Fluorocarbon resin:
A TEFLON~ sheet ~made by NICHIAS Co., Ltd. of
0.05 mm in thickness) was used as the sheet of a fluoro-
carbon resin.
1-5: Flexible graphite sheet:
A GRAFOIL~ sheet (made by U.C.C., of a bulk
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~ ~27~
density of 1.10 g/cc and of a thickness of 0.13 mm) was
cut into pieces according to the dimension of the joining
surface suitably.
After applying the adhesive of phenol resin series
onto the both surface of the separator material and onto
one of the sides of the GRAFOIL sheet, the thus applied
adhesive was dried and the two materials were joined
together at a temperature of 135C under a pressure of
10 kgf/cm G for 20 min.
Thereafter, the same adhesive was applied onto
the GRAFOIL surface of the thus joined separator material
and dried, and in the same manner, the same adhesive was
applied onto the rib surface of the electrode material
and dried. Thereafter the thus treated joined separator
material and the electrode material were joined together
at 135C under a pressure of 10 kgf/cm G for 20 min, and
the thus joined materials were calcined at 2000C under
a reduced pressure of 1 Torr and in an inert gaseous
atmosphere.
Thereafter, the TEFLON sheet was inserted between
the peripheral sealer and the separator, and the thus
combined materials were press-joined by melt-adhesion of
the TEFLON at 360C under a pressure of 20 kgf/cm G.
In order to determine the adhesive strength of the
press-joined surface by the melt-adhesion, the test piece
was adhered to a measure jig with an adhesive of epoxy
~z~
resin series and a tensile test was carried out. Since
the exfoliation did not occur at the joining part of the
TEFLON sheet and occurred at the joining part of the
adhesive of epoxy resin series, it was presumed that the
adhesive strength was not less than 90 kgf/cm2. Such a
large adhesive strength of not less than 90 kgf/crn2 is
30 times as large as 3 kgf/cm2 of the peeling strength in
the case where carbon materials are adhered with a solution
type adhesive of a conventional thermosetting resin
together.
EX~PLE 2:
Instead of the TEFLON sheet of Example 1, a TEFLON
dispersion (made by MITSUI Fluorochemical Co., Ltd., with
an abbreviated name of PTFE, an aqueous solution containing
60 % by weight of the TEFLON) is used and applied on the
joining surface of the peripheral seaIer and the separator
evenly and dried in air. Thereafter, the materials were
press-joined by melt-adhesion of the TEFLON under a
pressure of 20 kgf/cm G at 360C. The adhesive strength
of the product was the same as that in Example 1.
EXAMPLE 3:
3-1: Electrode material:
A ribbed electrode materlal of 600 mm in width,
600 mm in length and 1.5 mm in thickness was produced by
using the same materials under the same conditi.ons as in
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~273~
Example 1. The thickness of the rib was 1.0 mm and the
thickness of the gas-diffusion part was 0.05 mm.
3-2: Separator material:
As the separator material, the same material with
the same dimensions as in Example 1 was used.
3-3: Manifold material:
A compact carbon plate (made by TOKAI Carbon Co.,
Ltd., of a bulk density of 1.85 g/cc and 1.5 mm in
thickness) was cut into two pieces of 60 mm in width and
720 mm in length and two pieces of 60 mm in width and
600 mm in length, and the each parts in the thus obtained
four pieces of the plates corresponding to the each flow
passages for supplying the reactant gas were cut to provide
the flow passages(holes)for supplying the reactant gas therein.
Then, a pair of the plates in the four pieces of the obtained
plates with the holes were respectively provided with flow
passages of the reactant gas for connecting the flow
passage for supplying the reactant gas in the manifold
to the flow channels of the reactant gas in the electrode,
by cutting the parts corresponding thereto. Thus, the four
pieces of manifold materials for joining to one surface of
the separator were obtained. Also, by using the above-
mentioned method and the same materials in quality and size
as the above-mentioned manifold materials the four pieces
of manifold materials for joining to the anot~er surface of
the separator were obtained.
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~;~7~9~
3-4: Fluorocarbon resin:
The same TEFLO ~ sheet as in Example 1 was used
as the fluorocarbon resin.
3-5: Flexible graphite sheet:
The same GRAFOI ~ sheet as in Example 1 was cut
into pieces according to the dimensions of the joining
surface suitably.
After applying an adhesive of phenol resin series
onto the both surfaces of the separator material and onto
one of the surfaces of the GRAFOIL sheet, the thus applied
adhesive was dried and the two materials were joined under
the conditions of 135C, 10 kgf/cm2G and 20 min.
In the next step, the above-mentioned adhesive
was applied onto the surface of the above-mentioned
GRAFOIL sheet and dried.
In the same manner, the above-mentioned adhesive
was applied onto the rib surface of the above-mentioned
electrode substrate and dried. Thereafter, the two
materials were joined under the conditions of 135C,
10 kgf/cm2G and 20 min., and the thus joined materials were
calcined at 2000C under a reduced pressure of 1 Torr and
in an inert gaseous atmosphere.
In the next step, between the joining surfaces of
the manifold material and the separator, the TEFLO ~ sheet
was inserted and was joined by melt-adhesion under a
pressure of 20 kgf/cm G at 360C.
- 28 -
~;~73~3~
In order to determine the adhesive str~nyth of press-
joined surface by the melt-adhesion, the same test as in
Example 1 was carried out. Since the same results as in
Example 1 was obtained,the adhesive strength was presumed
to be not less than 90 kgf/cm2. Such a large adhesive
strength of not less than 90 kgf/cm2 is 30 times as large
as 3 kgf/cm of theadhesive strength in the case where
the carbon materials are adhered with a solution type
adhesive of a conventional thermosetting resin.
EXAMPLE 4:
Instead of the TEFLO ~ sheet of Example 3, a
TEFLO ~ dispersion (the same as in Example 2) was used,
and it was applied on the joining surfaces of the
manifold material and the separator evenly an~ dried in
air. Thereafter, the two materials were joined together
by melt-adhesion at 360C under a pressure of 20 kgf/cm G.
The adhesivestrength was the same as in Exmaple 3.
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