Note: Descriptions are shown in the official language in which they were submitted.
73~
C-7925
INTER-ELECTRODE GAP CONTROL FOR
ELECTROL~TIC CELL
_ _ _
Backgxound of the Invention
The present invention relates to spacer means
suitable for use in a filter press-type electrolytic
cell. More particularly, the invention relates to
spacer means utilized to maintain a fixed and pre-
determined gap between the adjacent electrode frames
in an electrolytic cell~
Commercial cells for the production of chlorine and
alkali metal hydroxides have been continually developed
and improved over a period of time dating back to at
least 1892. In general, chlor-alkali cells are of the
deposited asbestos diaphra~m type or the flowing mercury
cathode type. During the past few years, developments
have been made in cells employing separators having ion
e~change properties which promise advantages over
either diaphragm or mercury cells. It is desirable to
take advantage of existing technology, particularly in
diaphragm cells, but it is also necessary to provi~e
cell designs which meet the requirements o~ these newer
separator materials. Since suitable ~eparator materials,
such as those marketed by E. I. Du ~ont de Nemours and
Company under the trademark ~Nafion~ and by Asahi Glass
Company Ltd. under the trademark "Flemion~", are available
primarily in sheet form, the most generally used cell
~;~ 7~
employing such separators are of the "filter press"
type. Filter press cells may employ electrode struc-
tures which are monopolar or bipolar.
In the filter press cell, separators in sheet form
are clamped bet~een the sides of frame members~ The
sealing means employ~d, no~mally elastomeric gaskets,
must effectively provide a fluid-tiyht seal between
the frame members and the sepaxator without damaging
the separator. Part of the difficulty in obtaining
a flu~d-tight seal has been ~ound to reside in the fact
that the gaskets utilized to separate the elec~rode
frame members are available with thicknesses that widely
vary because of large manufacturing tolerances.
It has been found in the assembly of filter press
membrane cells that this difference in thickness between
the gaskets employed on adjacent electrode frames
can present problems when attempting to compress the
frames into a fluid-tight cell. Frequently, hydraulic
rams or other types of pressure-applying apparatus are
employed to compxess the electrode frames and the
separating gaskets together. Where there are differences
in the thickness of the gaskets, it has been found that
each gasket is not subjected to an equal level of
compression. The thicker gaskets are naturally subjected
to greater compression than thinner gaskets. Where the
dif~erence in thickness is too great, a predetermined
compression force applied to a cell and its component
electrode frames can leave spaces between the thinner
gaskets and adjacent frames so that fluid leakage will
occur. To correct thi~, additional pressure must be
applied to the electrode frames to achieve a level of
compression in the separating gaskets that will form a
fluid tight seal. Frequently, during this additional
compression-applying step, excessive force can be
applied which causes the frames to deform or bend.
Additionally, if the surfaces of the electrode frames are
not completely flat or are rounded, it has been found
~'73~ ~
that the gaskets will pop ou~ from between the electrode
frames because of the contour of the frames and the
pressure being applied to the gaskets. This situation
has necessitated that frames be individually assembled
and carefully aligned to prevent leakage. To correct,
for example, a O.Q10 of an inch spacing gap between a
gasket and an adjacent frame that is causing fluid
leakage, it has been fou~d necessary to tighten all of
the gaskets 0.010 of an inch to stop the leak.
Sealing means, including gaskets and other appro-
priate apparatus, for cells employing ion exchange
membranes as separators included those described in
U.S. Patent No. 4,026,782, issued May 31, 1977, to P.
Bouy et al, U.S. Patent No. 4,175,025, issued November
20, 1979, to E. D. Creamer et al, and U.S. Patent No.
4,207,165, issued June 10, 1980, to Mose et al. U.S.
Patent No. 4,026,782 teaches bipolar cells having
frames with recesses into which the sealing members
fit. In one of the recesses, a diaphragm is sealed
into the frame with a putty or caulked gasket. This
sealing arrangement requires a complex frame structure
which utilizes spacer apparatus that is a part of one
of the electrode frames. This arrangement suffers from
the disadvantage of not being able to vary the gap
between the electrode frames with simply the replacement
of the sealing means should it be necessary to have a
different gap between the electrode frames~
U.S. Patent No. 4,175,025 describes filter press
frames having at least one formed recess into which a
gasket is fit. The membrane is sized to extend beyond
the edges of the frame so that shrinkage of the membrane
during regeneration will not prevent its re-use.
Adjacent frames may contain recesses which are opposite
each other, but of different sizes. Gaskets having
different hardnesses are used to seal the membrane
between them. The gap between the electrode frames in
this type of sealing arrangement is entirely dependent
upon the gasket height and the amount of compression
applied to the frames. Thus, the gap can vary between each
pair of adjacent frames as the thickness of the gaskets
employed varies or the recesses machined into the frames
vary.
7~36
To provide recesses in the frame members of the
type disclosed in U.S. PatentNos. 4,026,782 and
4,175,025, operations such as machining must be employed.
These operations add undesired increases to the cost
of producing the frames.
The arranyement disclosed in U.S. Patent 4,207,165
employs a fixed spacer member between the adjacent
electrodes to establish a desired gapO However, the
method of securing the membrane between the gasket
members requires massive, expensive electrode frames
and could promote tearing of the membrane or separator.
Additionally, this technique could permit the membrane
to slip completely from between the retaining
electrodes.
The aforementioned problems are solved in the
design of the apparatus comprising the present invention
by providing in a filter press membrane electrolytic cell
improved spacer means of a predetermined thickness
positioned between the adjacent electrode frames~
to define and maintain a uniform gap between the frames
when the frames are pressed together in fluid-tiyht
fashion by clamping means and which are employed in
combination with improved sealing means to prevent the
undesired slipping of the separator means during
assembly.
~ ~ 737~6
Summary Of The Invention
It is an object of the present invention to pro-
vide sealing means in filter press cells using frames
which are simple and in which dixect contact between
the separator and ~he frame member is avoided.
Another object of the present invention is to
provide sealing means which prevent undesired slippage
between the sealing means and the slippery surfaces of
the separator which is wet with electrolytes such as
caustic solutions.
A further object of the present invention i5 to
provide sealing means which contribute to the control
of the compression pressures employed.
It is a further object of the present invention to
provide spacer means that can be placed between adjacent
electrode frames having sealing means separating the
frames and a separator positioned between each frame
to provide a positive fixed gap which is established
independently of sealing means pressures or sealing
means compression and independently of any bolt
; torquing or hydraulic or other similar closure system
forces utiliæed to compress the frames together during
assembly of the cell.
It is yet another object of the present invention to
provide non-compressible and insulating spacer means
between adjacent electrodes which ensure a uniform gap
between the electrodes and which facilitate the forming
of a fluid-tight seal among the sealing means and
alectrode frames during assembly and operation of the
electrolytic cell.
It is a feature of the present invention that
improved sealing means are installed with spacer means
to provide a more positive and secure gripping of the
sepax~tor between each pair of electrode frames as
well as maintaining a fixed and generally uniform gap
between the electrode frames.
'`
:
~73
--6--
It is another ~eature of the present invention that
spacer means can be installed directly between outrigger
blocks attached to each electrode frame.
It is a further feature of the present invention
that the spacer means ~re substantially non-compressible
and insulating.
It is yet another feature of the present invention
that the spacer means do not take the full closure force
applied to the cell during assembly, but bear only those
excess forces that result from varying deformation of
the sealing means and cell dimension variations.
~t i5 an advantage of the present invention that
the improved sealing means and spacer means of the
present invention avoid unequal distribution of the
compression among the sealing means when the electrolytic
cell is assembled.
It is a further advantage of the present invention
that the impxoved sealing means and spacer means provide
an easy method of correcting any fluid leakage from
between the electrode frames during operation.
It is yet another advantage of the present invention
that the improved sealing means and spacer means maintain
a uniform gap between all of the electrode frames
independently of the sealing means pressures, sealing
means compression or closure system force which is
applied to compress the cell.
Theseand other objects, features and advantages are
provided in an electrolytic cell having a plurality of
adjacently positioned electrodes held together by
clamping means by providing spacer means of predetermined
thickness removably connected to at least a first frame
and a second frame, each frame having opposing sides
with electrode faces connected thereto, separator
means positioned between sealing means so that at least
one of the opposing sides bf the first frame
and tne adjacent opposing side of the second frame
~73~ ~
define a first p-lane and a generally parallel
second plane such that the spacer means define and
maintain a uniform gap between the planes when the
frames are pressed together in fluid-tight fashion.
-8-
Brief Descri~tion Of The_Drawings
The advantages o~ thls in~ention will become
apparent upon consideration of the following detailed
disclosure of the invention, especially when it is
taken in conju~ction with the accompanying drawings
wherein:
FIGURE 1 is a side perspective view of a monopolar
filter press membrane electrolytic cell with appropriate
portions ~roken away to illustrate the anodes, cathodes,
anolyte disengager, the catholyte disengager, and the
positioning of the spacer means between each pair of
electrode frames;
FIGURE 2 is an enlarged diagramatic illustration of
the spacer means positioned in a partially inserted
manner between two adjacent electrode frames, but not
showing the sealing means;
FIGURE 3 illustrates a front elevation in perspec-
tive view of a pair of adjacent electrode frames
: employing the novel sealing means and spacer means of
~ the-present invention;
FIGURE 4 is an enlarged partial sectional view of
: the electrode frame of FIGURE 3 taken along the line
4-4 showing one embodiment of the sealing means in
cooperative association with the spacer means of the
present invention;
FIGURE 5 depicts a partlal sectional view of
another embodiment of the sealing means in cooperative
association with the spacer means of the present invention;
FIGURE 6 illustrates a partial sectional view of
an additional embodiment of the sealing means in
: cooperative association with the spacer means of the
present invention; and
FIGURE 7 shows a partial sectional view of a further
embodiment of the sealin~ means in cooperative association
with the spacer means of the present invention used with
bar-shaped frames.
-
.~ ~7~i36
Detailed Description O~ The Preferred Embodiment
Referring to FIGURE 1, a filter press membrane
cell, indicated generally by the numberal 10, is shown
in a side perspective view, It can be seen that cathode
S frames 11 and anode frames 12 alternate and are oriented
generally vertically. ~he cathode ~rames 11 and anode
frames 12 are supported by vertical side frame members
14, horizontal side frame members 15, and intermediate
vertical side frame members 16 ~only one of which is
shown~. The cathode frames 11 and anode frame~ 12 are
pressed together and secured by a series of tie bolts 18
which are inserted thxough appropriate mounting means
affixed to the vertical side frame membexs 14 and
horizontal side frame members 15. To prevent short
circuiting between the electrodes during the electrolytic
process, the tie bolts 18 have tie bolt insulators 17
~hrough which the tie bolts 18 are passed in the area of
the cathode frames 11 and anode frames 12.
Electrical current is passed, for example, from
an external power source through the anode bus and then
via anode bus nuts, both not shown, into the anode
conductor rods I9 of FIGURE 3. From that point, the
anode conductor rods 19 carry the current into the
opposing anode faces 13, see briefly FIGURES 4-7. The
current continues flowing through the membrane 20,
through the opposing cat~ode faces 21, see briefly
FIGURES 4-7, the cathode conductor rods 22 and the
cathode bus nuts 24 to the cathode bus 25 where it con-
tinues its path out of the cell. The cathode bus nuts
24 are only partially shown in FIGURE 1 since there is
a corresponding cathode bus nut for each cathode frame
11 and cathode conductor rod 22. Ion-selective permeable
membranes 20 are diagramatically shown in FIGURE 1 to
illustrate how each anode frame 12 and cathode frame 11
are separated by the membrane.
Projecting from the top of anode frames 12 and
cathode frames 11 are a series of fluid flow conduits.
FIGURES 1 and 3 show anode risers 26 and anode downcomers
.
:~ ~ '73713~
--10--
or anolyte return lines 28 projecting from the top of
each anode ~rame 12~ $imilarly, cathode risers 29 and
cathode downcomers or catholyte return lines 30 are
shown projecting ~rom the top of each cathode frame 11.
The risers are genexally utilized to carry the appro-
priate electrolyte fiuid with the accompanying gas,
either anolyte with chlorine gas or catholyte with
hydrogen gas, to the appropriate disengager mounted
atop the filter press membrane cell 10. The anolyte
disengager is ind~cated generally by the numeral 31,
while the catholyte disengager is indicated generally
by the numeral 32. Each disengager is supported atop
of the cell 10 by disengager supports 33, seen in FIGURE
1. It is in each of these disengagers that the entrained
gas is enabled to separate from the liquid of the anolyte
or catholyte fluid, as appropriate, and is relased from
the appropriate disengager via either a cathode gas
release pipe 34 or an anode gas release pipe 35 affixed
to the appxopriate catholyte disengager cover 36 or
anolyte disengager cover 37.
Also partially illustrated in FIGURE 1 is the ~.
catholyte replenisher conduit 38 which carries deionized
water into the catholyte disengager 32. The deionized
water is appropriately fed through the catholyte dis-
engager 32 to each cathode frame 11 in cell 10. A
catholyte outlet pipe 3g is also partially illustrated
and serves to control the level of liquid fluid in the
catholyte disengager 32 by removing caustic to its
appropriate processing apparatus.
An anoly~e replenisher conduit 40 carries fresh
brine into the anolyte disengager 31 and is best seen
in FIGURE 1. The fresh brine is then appropriately fed
into each anode frame 12 with the existing anolyte fluid
which is recirculated from the anolyte disengager 31
into each anode frame 12 ~ia the downcomers 28, An
anolyte outlet pipe 41 is also shown and ser~es to control
the level of liquid in the anolyte fluid within the
anolyte disengager 31 by removing the spent brine from the
disengager 31 for reyeneratiOn.
:., . . . . ~
~73~
--1].--
Also shown in FIGURE 1 are a cathodic bottom
manifold 42 and an anodic bottom manifold 44, which are
utilized to drain the appropriate electrodes.
The filter press membrane cell 10 has been des~
cribed only generally s~nce the structure and the
function of its central components are well known to one
of skill in the art~ ~ ~
:
~ -
Still referring to FIGURE 1, spacer means,
indicated generally by the numeral 45, are shown
appropriately fastened to the exterior of the cathode
frames 11 and anode frames 12. The spacer means 45
are positioned about the cell 10 so that there are
generally three along the longitudinal or bottom to
top side members of each cathode frame 11 and anode
frame 12, while two a,re generally spaced along the
top and bottom portions of the electrodes. The enlarged
diagramatic illustration in FIGURE 2 shows the spacer
means 45 comprising outrigger blocks 46 which are
appropriately fixedly fastened to the side members of
the adjacent cathode frames 11 and anode frames 12.
Outrigger blocks 46 are normally welded to the
electrode frames. A spacer block 48, as shown in
FIGURE 2, is partially removed and is positioned
between the outrigger blocks 46. Because FIGURE 2 is
a diagramatic illustration~ it does not show the
membrane or separator 20, nor the sealing means or
gaskets, which are positioned between the adjacent
cathode frames 11 and anode frames 12 and are best
seen in FIGURES 3 through 7. FIGURES 4-7 show how the
spacer blocks 4g are positioned and retained by the
outrigger blocks 46 along planes that pass through
the adjacent opposing sides of the adjacent electrode
frames.
:~f~ '
~:,`'7
737~6
-12-
FIGURE 3 shows that the cathode frames ll and
anode frames 12 comprise anode vertical members 49,
only one of which is shown, and cathode vertical members
50. Interconnecting the cathode vertical frame members
50 are the generally horizontal cathode frame members
51. SLmilarly, interconnecting the anode vertical
frclme member~ 49 are anode generally horizontal frame
members 52, only one of which is shown. When assembled
the appropriate cathode and anoae frame members
comprise cathode and anode frames ll and 12 respectively,
which have generally planar opposing first and second
sides.
FIGURE 4 shows the cooperation between the cathode
frames ll, anode frames 12, spacer means 45, the sealing
means or gaskets, indicated generally by the numeral .54,
and the opposing surfaces of the separator or membrane
20. As seen in FIGURE 4, separator or membrane 20 is
............ positioned between gaskets 55 and 56, which are placed
between the adjacent legs of the cathode vertical
frame member 50 and the anode vertical frame member 49O
Although not shown in their entireties in FIGURE 4,
the first and second generally planar cathode electrode
faces 21 are shown fastened to one of the two cathode
vertical frame members 50. The cathode vertical
frame members combine with the horizontal-frame members .
52 to form the generally planar opposing firs~ and
second sides. The anode frame 12 also has generally
planar electrode faces 13 fastened thereto. As seen
in FIGURE 4, a third generally planar electrode face 13
is fastened to the anode vertical:frame member 49 o~
_ __ the first_~e.nerall~_pianar..side of.the..~node.fr.ame l
formed by the anode vertical frame members 49 and the
anode generally horizontal frame members 52. Gasket 55
is comprised of a base portion which_contacts the second
side 58 of the cathode frame 11 at frame membex 50 and
a raised portion 59 which contacts the first surface of
the separator or membrane 20. Gasket 56 contacts the
first side 60 of the adjacent anode frame 12.at~he
vertical frame member 49 and the opposing second -
surface of separator or membrane 20. The area of
~l 73~
-13-
contact for gasket 56 with the membrane 20 is greater
than that of the raised portion 59 of gasket 55.
~elded to the cathode vertical frame member 50
and the partially illustrated anode vertical frame
member 49 are outrigger blocks 46. Outrigger blocks 46
are shown generally as being rectangular with the
same thickness as the frame of the appropriate electrode.
Positioned between the outrigger blocks 46 is a
removable spacer block 48. Spacer block 48 is selected
with a predetermined thickness to ensure a uniform
gap between the adjacent electrode frames. 5pacer
block 48 must be of a good insulating quality and
essentially non-compressible. Spacer block 48 may
be of any substance possessing these characteristics;
however, micarta has been the preferred substance.
Impregnated wood or un-impregnated suitable hardwood
can also be employed as spacers. It is even possible
that plexi-glass of sufficient strength could be
employed.
In the embodiment shown in FIGURE 5, the sealing
means employed utilizes one end of gaskets 61 and 62
~o rest against shoulders 64 of edges 65 and 66 of
cathode vertical frame member 50 and anode vertical
frame member 49, respectively. Separator or membrane
20 is sealed during compression between the raised
portion 68 of gasket 61 and the inset portion 69 of
gasket 62. Fixedly fastened to cathode vertical frame
member 50 and the adjacent anode vertical frame
member 49 are outrigger blocks 46. Positioned between
outrigge- blocks 46 is the spacer block 48, again
selected to a suitable predetermined thickness to
maintain a uniform gap between the adjacent electrode
frames after the cell 10 is compressed.
.:i , .
~ .~7;~7~36
-14-
FIGURE 6 illustrates an additional embodiment of
the sealing means 54 of the present invention in which
the separator or membrane 20 is sealed between the
gaskets 70 and 71. The gaskets 70 and 71 extend beyond
the edges 72 and 74 of the cathode vertical frame
member 50 and the anode vertical frame member 49,
respectively. ~nder compression, the membrane or
separator 20 is effectively sealed between the raised
portion 75 of gasket 70 and gasket 71. Again, outrigger
blocks 46 are fixedly fastened to the cathode vertical
frame member 50 and anode vertical frame member 49.
Placed therebetween is spacer block 48, selected according
to a suitable predetermined thickness to establish the
desired gap between the adjacent electrode frames.
FIGURE 7 illustrates a further alternate embodiment
of the sealing means 54 in cooperative association with
the spacer means 45 of the present invention. In this
embodiment, separator or membrane 20 is cealed between
inserts 76 which prevent undesired friction between
the membrane 20 and narrow gasket 79 and wider gasket
78. Gaskets 78 and 79 are positioned between the
adjacent sides 80 and 81 of cathode frame 11 and anode
frame 12, respectively. ~ixedly fastened to the sides
80 and 81 are outrigger blocks 46. Spacer block 48
; 25 is positioned between the outrigger blocks 46 to
;~ establish the desired gap between the aforementioned
planes which pass through the adjacent opposing sides
of the adjacent electrode frames after the cell 10
,,,
is compressed.
Suitable as sealing means 54 are gaskets comprised
of elastomer such as Neoprene r Hypalon* ethylenepropylene
dimonomer (EPDM) or gum rubber. The hardness of the
sealing means is not critical and any suitable hardness
may be selected independently for either gasket.
Preferably, gaskets have a low degree of hardness which
:~ allows the gaskets to fill in irregularities on the
~ frame members and thus permit reduced tolerances which
- minimizes, for example, machining of metal frames and
reduces production costs.
* Trademark
~l73~
During assembly tie bolts 18 are individually
tightened around the perimeter of the cell 10. This
tightening of the tie bolts 18 holds the individual
electrode frames together. Between any two adjacent
electrodes, the cathode frame 11 and the anode frame 12
are pressed together so that the sealing means 54 is
compressed. Since each cathode frame 11 and anode frame
12 have individual gaske~s which extend about the
entire periphery of the electrode frames, the electrodes
are separated by the individual gaskets and the membrane
or separator 20 which is i~serted therebetween. The
opposing faces of the electrodes are separated by a
uniform gap that is established by the thickness of
the spacer block 48. Since tha electrodes are compressed
together by the application of a suitable closure force,
the gaskets deform in a manner which effects a fluid-tight
seal between the adjacent electrode frames, as well as
securing the membrane 20 along both surfaces to avoid
any undesired slippage. The amount of compression
between the adjacent cathode frames 11 and anode frames
12 is determined by the thickness of the spacer block
, 48 which is pressed between the adjacent outrigger
blocks 46 fixedly fastened to each electrode frame.
Once the desired compression has been achieved, the
tie bolts 18 are secured in a manner to retain this
compression and the fluid-tight seal effected by the
improved sealing ~eans 54. A uniform inter-electrode
gap is obtained because the spacer blocks 48 are
distributed about the periphery of the electrode frames.
Once a fluid-tight seal has been effected be~ween any
~ two adjacent cathode frames 11 and anode frames 12
; so that the spacer blocks 48 are subject to compressive
forces conducted through the adjacent outrigger blocks 46,
any additional compressive force will be borne by the
spacer blocks positioned between the adjacent cathode
frame 11 and anode frame 12.
'
,~ 378~
-16-
The width of the raised portion of the second
gasket is selected to provide less area of contact
with the separator than that of the first gasket.
Further, the wid~h of the raised portion is selected to
provide ~he desired control of the gasket compression
pressures and the gasket frame surface structural
forces. Control of these pressures minimize compression
set for gasket materials and bending or twisting of
frame members. The embodiment of the novel sealing
means shown in FIGURE 5 is particularly suitable where
the electrolytic cell employs higher compression
pressures.
The width of the raised portion of the gasket
is especially selected to provide the desired control
lS of the gasket compression and of the frame surface
structural forces. The width of the raised portion is
kept narrow enough not to exceed the structural strength
of the frame member. The force on the frame member per
lineal inch of frame member is Fi = P X W where P is
the gasket pressure of the raised portion and W is
the expanded width of the raised portion in compression.
The e~panded width W = w- (1 c) where w is the
initial width o~ the raised portion and c is the
fractional compression expressed as a decimal. The
compression factor c is selected high enough to assure
sealing, depending upon the gasket material and may
be from O~OS to 0.55 and preferably from 0.2 to 0.4.
A preferred embodiment of the sealing means of the
present invention is that of the type illustrated in
FIGURE 6. The gaskets extend beyond the width of the
frame so that the uncompressed gasket material outside
of the frame will not slip into the higher pressure
zone within the frame. The narrow raised portion of the
one gasket mates with a narrow area on the second gasket
to effectively seal the separator and take up the
greatest amount of compression at the design force load.
'
.~
~'7371
--17~
Hydraulically permeable or impermeable separators
may be employed in the electrolytic cell o~ the present
invention. Preferably, inert flexible separators having
ion exchange properties and which are impervious to
the hydrodynamic flow of the electrolyte and the
pasQage of gas products produced in the cell are
employed. Suitably used are cation exchange membranes
such as those composed of fluorocarbon polymers having
a plurality of pendant sulfonic acid groups or
carboxylic acid groups or mixtures of sulfonic acid
groups and carboxylic acid groups. The terms "sulfonic
acid groups" and "carboxylic acid groups" are meant
to include salts of sulfonic acid or salts o~ carboxylic
acid which are suitably converted to or from the acid
groups by processes such as hydrolysis. One example
of a suitable membrane material having cation exchange
properties is a perfluorosulfonic acid resin membrane
composed of a copolymer of a polyfluoroolefin with a
sulfonated perfluorovinyl ether. The e~uivalent weight
of the perfluorosulfonic acid resin is from about 900
to about 1600 and preferably from about 1100 to about
1500. The perfluorosulfonic acid resin may be supported
by, a polyfluoroolefin fabric. A composite membrane
sold commercially by E. I. Du Pont de Nemours and
Company under the trademark "Nafion~" is a suitable
example of this membrane.
A second example of a suitable membrane is a
cation exchange membrane using a carboxylic acid
group as the ion exchange group. These membranes have,
or example, an ion exchange capacity of 0.5-4.0 mEq/g
of dry resin. Such a membrane can be produced by
copolymerizing a fluorinated olefin ~ith a fluorovinyl
carboxylic acid compound as described, for example,
in U.S. Patent No. 4,138,373, issued February 6, 1979,
to H. Ukihashi et al. A second method of producing the
above-described cation exchange membrane having a
carboxyl group as its ion exchange group is that
described in Japanese Patent Publication No. 1976-126398
3~
-18-
by Asahi Glass Kabushiki Gaisha issued November 4, 1976.
This method includes direct copolymerization of fluorinated
olefin monomers and monomers containing a carboxyl group
or other polymerizable group which can be converted
to carboxyl groups. Carboxylic acid type cation
exchange membranes are available commercially from the
Asahi Glass Company under the trademark "Flemion~".
Frame members may be in the shape of rectangular
bars, C or U channels, cylindrical tubes, elliptical
tubes as well as being I-shaped or H-shaped. Preferably,
the frame members are in the shape of a C channel as
shown in FIGURES 4 and 6.
The materials of construction for frame members may
be any which are resistant to corrosion by the electro-
lytes and the products of electrolysis. For example,
metals such as iron, steel, stainless steel, nickel,
titanium, or alloys of these metals may be used.
Similarly, plastic materials such as polypropylene,
polybutylene, polytetrafluoroethylene, FEP, and
chlorendic acid based polyesters can be employed.
However, the electrode rame members must be of a
suitable material to permit the outrigger blocks 46
to be fixedly fastened thereto. For example, if the
anode vertical and generally horizontal frame members
49 and 52 are made of titanium, outrigger blocks 46
made of titanium are then also used. If the cathode
vertical and generally horizontal frame members 50 and
51 are made of nickel, the outrigger blocks 46
may be made of nickel or steel. It should also he
noted that it is generally desired to have the outrigger
blocks attached to the appropriate electrode near the
tie bolts 18.
Electrolytic cells of the present invention provide
the advantages of simultaneously:
a) controlling gasket compression pressures;
b) controlling gasket frame surface structural
forces;
c) efficiently forming a seal; and
d) preventing gasket slippaye.
~'7~
--19--
In addition, cell assembly tolerances are improved and
construction costs reduced. Lower compression pressures
can be employed permi~ting the use of smaller compression
means to furtheL reduce cell cos~s.
While the preferred structure in which the
principles of the present invention have been incorporated
as shown and described above, it is to be understood
that the invention is not to be limited to the
particular details thus presented, but in fact, widely
different means may be employed in the practice of
the broader aspects of this invention. The scope of the
appended claims is intended to encompass all obvious
changes in the details, materials, and arrangements
of parts which will occur to one of skill in the art
upon a reading of the disclosure.
