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Патент USA US3022197

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Feb. 20, 1962
c. EYR AUD ET AL
POROUS MEMBRANES 0F VERY FINE POROSITY, AND
PROCESSES FOR PRODUCTION THEREOF
Filed Feb. 18, 1959
Q
4
3,022,187
"h
3,022,187
PatentedFeb. 20, 1962
2
v
'
'
dation causing migration of the metals in the form of
3,022,187
POROUS MEMBRANES 0F VERY FINE PORGSITY
lOIlS.
' AND PROCESSES FOR PRODUCTION THEREOF ’
Charles Eyraud, Marcel Prettre, Yves Tramhouze, Jean
a
-
larly suited for-ultra?ltration and for separation by gas
1 nine Lenoir, and Germaine Thomas, Lyon, and Pierre
Plnrien, 'Paris,-:.France, . assignors to Commissariat va
eous diifusion of the constituents of a mixture. Suit
able choice of the different components of the mem
l’Ener-gie Atomique, Paris, France
branes. of. the present invention provides resistance to
- . Claims priority, application France Feb. 24, 1958
'
Filed Feb. 18, 1%59, Ser. No. 793,968
the various types of corrosion.
-
-
> .
The accompanying, drawing is a cross-sectional view
12 ‘?laims? (Cl. 117-,-16)
10 through a representative embodiment ofa porous mem
It is known that the permeability of a barrier increases,
at constant pore radius, in inverse ratio to its thickness.
brane prepared in accordancewith the processesdescribed
herein. This drawing shows a thin metallic ?lm depos=
ited on the‘supp'ort penetrating. super?cial: surface zones
depending upon the presence :of the grainsof metallic
To obtain porous membranes of very small pore radii
and possessing a high permeability requires as thin 21
membrane as possible. Limitations are imposed on thin-'
ness by conditions of mechanical strength, resistance to
oxide deposited in the support.
by a gas stream, and the like..
of the support; C is a submicronic particle'of metallic
'
oxide; andD is theJthin metallic ?lm.
Porous membranes made by known processes have no
-
v
The present invention relates to novel processes for the
In this ‘drawing ‘A >
is the sintered metallic support; B arethe large pores
deterioration by vibration, by destruction of the surface
external protection or support.
:
The membranes of the presentinvention are particu
‘
. ‘
The submicronic grains of metallic oxide C completely
20 ?ll at least the surface pores B ot‘the support, this being
a critical feature of the invention; and the pores of the
support beneaththe surface are ?lled completely as at
122 or partially ?lled as at b1 and b3.-. The depth of pene
tration of the grains of metallic oxide'iston the order
production of membranes of very ?ne porosity and to
the novel membranes obtained'by' these processes.- -
These processes are characterized in that, in the in}
terior of a rigid support having relatively large pores, 25 of one ,u to seventy p.- .The. porous structure of .the
a membrane is ‘constructed of very- ?ne‘ porosity by ?lling
present concept mustbe vunderstood-as tri-dimens'ional
the relatively large pores. with submicronic grains having‘
so that the pores. which appear to be closed in them‘.
very ?nechannels between them. Deposit of the grains‘ 'companying drawing are actually connectedto neighbor-'
may be obtained by suction of va solid-gas or solid-liquid
ing pores. This is true tor-the large ‘pores ,of-the sup
suspension through the support. If desired, the assembly 30 port
and for thepores provided byvthe spaces between
thus formed may be covered with a. thin metallic ?lm
having a thickness of from 500 to 5000 A. which pro
the vsubmicronic grains of metal oxide.
a sintered metal such as steel, nickel or bronze.
without departing from the'scope thereof. 1
. . -.
Speci?c embodiments of the present invention will now
tects the ?ne grains without impairing porosity. This
be described toillustrateuthe ‘invention without thereby
?lmmay be obtained by any knownmetallization process.
the scope-of the inventive concept. The proc-‘
The‘required external mechanical strength (rigidity) 35 limiting
esses described in connection‘ with'these embodiments are“
of the membrane is provided by a very permeable strong
to be considered astorming part .of the invention, it
" support, having pores of a large radius,‘ for example
being understood that equivalentproce's'ses may be ‘used,
With
in the poresof thesintered metal, which may have diam
eters of from ten to severalltens-of microns, a membrane
'
of very ?ne,‘ porosity is constructed by passing through
Egtampleyl
.
Y ‘The support consists, of adisk of sintered' stainlessv steel;
the‘relatively large pores of the support a solid-gas or
having a pore diameter of about 30 microns. Through
solid liquid suspension containing submicronic grains
this diskpla suspension in water of _1 g; perliter of TiO-,,
of a metal oxide which are ,monodispersed vas much ‘as
is drawn under vacuum. , The grains ofthe suspension.
possible. The order ofmagnitude of these grains is from’ 45 have an average size of 100 to 150 A.
one micron to several hundredths of a micron. ,Better
surface cohesion is provided to obtain more e?‘icient pro
, Ifya surface-active agent is‘ added as, for example a
drop of a commercial solution of “Teelpol” per 10 liters
tection against the external agents which might tear
away the ?ne grains. This may be done by metallizing
of suspension the surface layer is then formed by ag
glomerates comprising only a few elementary grains.
the active surface of the membrane. Experience has
shown that when the metal is suitably ?xed, the pores
are not obturated and the material is deposited substan
tially normal to the ?ne grains of thesurface.
After this treatment, the active portion of the mem
brane is formed by the deposit of the ?ne grains and by
the addition of the metal ?lm. The thickness of this
“Teepol” is a'mixture of the sodium salts of sulfated
fatty alcohols made by reducing the mixed fatty acids of
coconut oil or of cottonseed oil or ?sh oils.
The membrane is then dried under vacuum, in the
_- cold and the radius of the pores is 0.06 micron and the
active portion may be on the order of one to several tens
permeability §=3 15 X10“7 mole air/sq. cm./ minute/ cm.
of Hg.
Example 11
'
The main advantage of the membranes of the present
On the membrane prepared as in Example I, there is
invention is that they have excellent mechanical strength, 6 O deposited by evaporation under a vacuum of 10"4 mm.
of microns.
are very thin and have great permeability. The radius
of the pores may be determined as desired by choice
of the radius of the grains in the suspension.
Metallization, as described above, can be obtainedv
by any known metallization process, for example by 65
evaporation of metal under. vacuum, or by deposition by
of Hg a layer of copper having a thickness of 2,000 A.
The radius of the pores F measured by a permeameter
is 0.06 micron and the permeability is 200x104. mole
air/sq. cm./minute/cm. of Hg.
‘ 1
Example 111
chemical reduction of a metal salt. By evaporation un
der vacuum of various metals such as Al, Ni, Cu, and
The support consists of a disk of sintered stainless
of the stopping surface. The dry membranes are kept
away from atmospheric moisture in order to avoid oxi
surface-active agent (one drop of commercial solution
per 10 liters of suspension) and dispersion is then 0b
steel having a mean diameter of the pores of about 30
the like, it is possible to produce porous metallic ?lms
‘ microns. Through this disk is drawn ?rst a suspension of
whose distribution and channels correspond to the relief 70 l g. per liter of Ti02r in water with “Teepol” as the
3,029,187
mixture, the steps of permanently depositing submicronic
The membrane is then dried under vacuum in the cold
grains of a metallic oxide having dimensions on the or
and ¥='0.055 ‘micron, and €=260><10'7 mole air/sq.
cmJminute/cm. of Hg.
der of 100 to 10,000 A. within a rigid support of rela
tively large pore size of from ten to several tens of
microns selected from the group consisting of sintered
‘
Example IV
4
7. In a process of making a porous membrane for
separation by gaseous diffusion of the constituents of a
tained by centrifuging of the support and contained sus
pension at 6,000 r.p.m. for 3 hours.
,
steel, sintered nickel, sintered bronze and sintered stain
less steel by drawing by suction a suspension of the grains
, On the membrane prepared as in Example III, there
is deposited‘ by evaporation under‘ a vacuum, of 10‘4 mm.
of Hg a layer of nickel having a thickness of 1600 A.
10
In this membrane F==0.‘05O micron and 'G'=240><10""
mole air/sq. cmJminute/cm. .of‘Hg.
in a ?uid through the support.-
7‘
8.v In a process of making a porous membrane for
separation‘by gaseous diffusion of the constituents of a
mixture, the steps of permanently depositing submicronic
‘ Changes in or modi?cations to the above ‘described
grains of a metallic oxide having dimensions on the or
illustrative‘ embodiments of \the present invention may
der of 1001 to 10,000 A. within a rigid support of rela
now be suggested ‘to those skilled in the art without 15 tively large, pore ‘size ‘of from ten to ‘several tens of
departing from the inventive concept. Reference should
microns selected from the group consisting of sintered
steel, sintered nickel, sintered bronze and sintered stain
less steel by drawing by suction a suspension of the grains
What is claimed is:
l
in a ?uid through the support and then of covering the
1. In a process for making a porous membrane for 20 rigid support containing the‘submicronic grains with a
separation by gaseous diffusion of the constituents of a
metallic ?lm having a thickness of from 500 to 5000 A.
therefore be had to the appended claims to determine
the scope of the invention.
mixture, the step of permanently depositing submicronic
9. A process as described in claim 8 in which the metal
grains of a metallic oxide having dimensions on the order
lic ?lm is obtained by evaporation of metal under vac
of 100 to 10,000 A, within a rigid sintered metallic sup
port of relatively large pore size of from ten to several 25 uum.
10. A process as described in claim 8 in which the
tens of ‘microns by drawing by suction a suspension of
metallic ?lm is obtained by deposition by chemical re
the grains in a fluid through the support.
i
duction of a metal salt.
' 2. A process as described iniclaim l in which the
‘
.
11. A porous membrane, comprising a rigid support
grains have diameters on the order of 100 to 150 A.
selected from the group consisting of sintered steel, sin
3.‘ A process as described in claim 1 in which the 30 tered nickel, sintered, bronze and sintered stainless steel
grains are TiOg.
the pores of which are from tento several tens of mi
4. Ini'agprocess for making a porous membrane for ,
crons and permanently contain submicronic grains of a
separation by gaseous di?usion’ of vthe constituents of a‘
metal oxide having dimensions on the order of 100 ‘to
mixture, the steps of permanently depositing submicronic
A.
grains of a metallic oxide having dimensions on thefor 35 10,000
12. A‘porous membrane as described in claim 11 in
cler of 100 to 10,000 A. within a rigid sintered metallic
cluding a thin metallic ?lm having a thickness of from
support of relatively large pore size of from ten to sev
500 to 5000 A. covering the rigid support.
eral tens of microns by drawing by suction a suspension
of the grains in a fluidthrough the support and then
covering the rigid support containing the submicronic
40
grains with a metallic ?lm ‘havingia thickness of from
500 to 5000 A.
2,157,596
2,618,565
2,824,620
‘
5. A process as described in claim 4 in which the
metallic ?lm is obtained by evaporation of metal under
vacuum.
6. A process as described in claim 4 in which the metal
lic ?lm is obtained by deposition by chemical reduction‘
of a metal salt.
References Cited in the tile of this patent
UNITED STATES PATENTS ,
45
Davis ~..‘_ ____________ _._ May 9, 1939
Nicholson‘ ___________ __ Nov. 18, 1952
De Rosset ____________ __ Feb. 25, 1958
OTHER REFERENCES
Lawlor: Diatomite Filtration, Water and Sewage
Works, ‘Reference Number, June 15', 1956, R~1 89, R—l90.
UNITED STATES PATENT OFFICE
CERTIFICATE OF CORRECTION
Patent N0° 3,0222.‘I 187
February 2O‘7 1962
Charles Eyraud
It is hereby certified that error appears in the above numbered pat
ent requiring correction and that the said Letters Patent should read as
corrected below.
C01umn.2v line 47,, for ""Teelpolm read —- “'Teepol" -—;
column 3, 11ne 249 for "Ag" read —— A, —-; column 4, line 3H
for "steps" read —— step ——°
Signed and sealed this 12th day of June 19-62‘,
(SEAL)
Attest:
ERNEST w. SWIDER
DAVID L- LADD
Attesting Officer
Commissioner of Patents
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