Note: Descriptions are shown in the official language in which they were submitted.
~J ~
HOECH5T AKTIENGESELLSCHAFT HOE 91/F 064 DCh.SY/sch
Description
Porous semipermeable membrane resistant to chemicals and
heat
Since the introduction of asymmetric membranes of cellu-
lose acetate by Loeb and Sourira~an (S. Sourira~an,
Reverse Osmosis, Logos Press, London 1970) and of hydro-
phobic polymers ~US-A-3,615,024), numerous membranes have
been developed and proposed, in particular for separa-
tions of low- and high- molecular-weight constituents
dissolved in water, the structure and suitability of
which are described in the literature (Desalination, 35
(1980), 5-20) and which have also been tested success-
fully in industrial practice or for medical purposes.
Many of the membranes described have particularly advan-
tageous properties for achieving specific ob~ects. As a
result of their chemical and physical structure, the
individual membranes can in each case have the optimum
suitability only for quite specific separation problems.
This results in the fundamental re~uirement of the
constant development of new membrane~ for new tasks.
An overview of the advantages and disadvantages of
membranes which are already known is given in
EP-A-0,082,433. There are thus, for example, hydrophilic,
asymmetric membranes of cellulose acetate which have
satisfactory anti-adsorptive properties but leave a great
deal to be desired in recpect of their resistance to heat
and chemicals. Although membranes of polysulfones or
similar polymers have a ~ood resistance to heat and
chemicals, they are sensitive to the action of organic
solvents.
Hydrophilicity and a sLmultaneous resistance to solvents
are found in membranes of regenerated cellulose, however,
these can be hydrolyzed relatively easily in acid or
-- 2 --
alkaline media, and they are moreover rapidly attacked by
microorganisms.
DE-A-3,321,860 describes chemically resistant membranes
of partly sulfonated polyether ketone. Although these
me~branes are not dissolved under the action of organic
solvents~ such as acetone or tetrahydrofuran (THF), they
swell severely and thereby change their membranes proper-
ties irreversibly.
The membranes are absorbed onto woven fabrics or non-
wovens in order to achieve an increased mechanical
stabilization. The carrier materials generally used
comprise polypropylene or polyethylene terephthalate.
Nevertheless, such carrier mem~ranes have the disad-
vantage that, for example, the service temperatures are
reduced considerably because of the inadeguate heat
stability of the non-wovens or the woven fabrics. The
action of organic solvents, acids and alkalis furthermore
leads to the dissolution o. these carrier materials or to
the detachment of the membrane.
~he invention i6 therefore based on the ob~ect of provid-
ing semipermeable membranes which have a high stability,
are resistant both to hydrolyzing agents and to oxidizing
agents, have a high heat stability and are not attacked
by organic solvents, even at elevated temperatures.
The object is achieved by a semipermeable membrane
consisting of a carrier material and a layer adhering to
this, the carrier material being a woven fabric or a non-
woven based on a polyphenylene 6ulfide, a polyether
ketone or a polyaramid. ~he membranes described here are
particularly suitable for micro-, nano- and ultra-
filtration.
In the membranes according to the invention, the semi-
permeable layer on the carrier material can comprise
either a polyether ketone or a polyaramid.
L t~
-- 3 --
The semipermeable layer and if appropriate also the
carrier layer i8 derived from a polyether ketone having
the recurring units of the formula (Ia)
~ O ~ C ~ (Ia)
in particular from a polyether ketone ha~ing the recur-
ring units of the formula (Ib)
~ O ~ C ~ l~ ~ O A ~ (Ib)
in which -A- is a radical
~ or ~ z
in which
R1, RZ, R3 and R4 can be identical or different and are
hydrogen, a (Cl-C4)-alkyl, (C6-C14)-
aryl or (C6-Cl4)-hydroxyaryl group or
NO2, CN, NR52 (R5 = (Cl-C6)-alkyl) or
halogen and
-Z- is one of the groupings
CH3 CF
-O-,-S-,-CH2-,-CF2.,-C-, -C-, -SO2r or -CO-
CH3 CF3
~he preparation of polyether ketones, for example by
nucleophilic aromatic polycondensation, iR known and is
described in EP-A-0,001,879 and GB-A-1,414,421. Polyether
ketones such as are used for the membranes according to
-- 4 --
the invention are described, for example, in
DE-A-3,936,997, which is of earlier priority and i5 not
a prior publication.
In a further preferred embodiment, the semipermeable
layer and if appropriate the carrier material comprises
an aromatic homo- or copolyamide having at least one of
the recurring structural unit~ of the formula (II)
O O
-(C-E'-C-NH-E2-NH)- (II)
in which -E1- and -E2- are identical or different and are
selected from one or more of the grouping6
H3C CH3
CH3
~NH CO~
-Arl- or
--A~ l--X--Ar2
in which -Arl- and -Ar2- are identical or different
1,2-phenylene, 1,3-phenylene, 1,4-phenylene radicals or
(C6-C~4)-arylene radicals, which can be substituted by one
or more (cl-c6)-alkyl~ (C~-C6)-alkoxy or CF3 groups or
halogen, in particular fluorine, chlorine or bromine
atoms, or are a heteroaromatic radical, for example a
~2,5]- or [3,4]-furano radical,
and the radical -X-
a) is a direct bond or i8 one of the following divalent
radicals
-O-, -C(CF3) 2- ~ -S2- ~ -CO- or -C(R6) 2- ~ in which R6
is hydrogen or a (Cl-C6)-alkyl or (C~-C4)-fluoroalkyl
group, or
b) is -Y-Arl-Y-, in which -Y- is the radical -O- or
-- 5 --
-C(CH3)2-
~or
c) is -O-Arl-Q-ArZ-0-, in which -Q- has the meaning
given under Xa).
The pxeparation of the polyaramids which are suitable as
carrier materials and as layer materials for ~he mem-
branes according to the invention is described in
DE-A-3,903,098 and DE-A-3,802,030.
Examples of suitable starting materials for their prepa-
ration are
a) dicarboxylic acid dichlorides of the formula (IV)
Cl-C0-E2-C0-Cl (IV)
in which El has the abovementioned meaning.
Examples of ~ompounds of the formula (IV~ are 4,4'-di-
phenyl sulfone-dicarboxylic acid dichloride, 4,4'-
diphenyl ether-dicarboxylic acid dichloride, 4,4'-di-
phenyldicarboxylic acid dichloride, 2,6-naphthalene-
dicarboxylic acid dichlGride, isophthalic acid dichloride
and 2,5-furandicarboxylic acid dichloride, but in par-
ticular terephthalic acid dichloride and substitutedt.erephthalic acid dichloride, for example 2-chlorotere-
phthalic acid dichloride;
b) aromatized diamines of the formula (V)
H2I~-E2--NH2 ~V)
for example m-phenylenediamine or substituted phenylene-
diamines, for example 2-chloro-, 2,5-dichloro- or 2-meth-
oxy-p-phenylenediamine, in particular p-phenylenediamine,
and
substituted benzidine derivatives, for example 4,4'-di-
aminobenzophenone, bis-[4-aminophenyl] sulfone, bis-[4-
(4'-aminophenoxy)phenyl3 sulfone, 1,2-bis-[4'-aminophen-
oxy]benzene, 1,4-bis-~(4~-aminophenyl)isopropyl]benzene
and 2,2'-bis-t4-(4'-aminophenoxy~phenyl]propane, in par-
ticular 1,4-bis-(4'-aminophenoxy)benzene, and mixtures
,J ~
-- 6 --
of the diamines mentioned.
In the semipermeable membranes according to the inven-
tion, both the carrier material and the semipermeable
layer can comprise the same polyether ketone or different
polyether ketones of the ~ormula (Ia) and tIb), or the
same polyaramid or different polyaramids of the formula
(II), or the carrier material and layer material can al~o
comprise different materials.
It i~ particularly advantageous if the carrier material
is derived from a polyphenylene sulfide having recurring
structural units of the formula (III).
~ S ~ (III)
The abovementioned polyaramids, polyether ketones and
polyphenylene sulfides are employed in the form of non-
woven~ or woven fabrics, preferably as non-wovens, for
the membranes according to the invention.
To produce the membranes according to the invention, the
polymer i6 first dissolved, filtered and degassed.
Suitable solvents for polyether ketones are, for e~ample,
H2S04, CF3-S03H, HF, Cl2HC-COOH and in particular mixtures
of Cl2HC-COOH and H2S04, and suitable solvents for poly-
aramids are, in particular, N-methylpyrrolidone, N,N-
dimethylacetamide, dimethylsulfoxide and dimethylform-
amide. A semipermeable membrane is produced from these
solutions in a known manner by the phase inversion
process (Robert E. Kesting, "Synthetic Polymeric
Membranes", 2nd Edition, 1985, page 237 et se~.). For
this purpo~e, the polymer solution is spread as a liquid
layer on the carrier material. Precipitating liquid which
is miscible with the solvent but in which the polymer~
dissolved in the polymer solution are insoluble and are
precipitated as a semipermeable membrane i~ then allowed
2~ J
-- 7 --
to act on the liquid layer. The precipitating liquid used
is, for example, water.
When carrying out the process, the precipitating liquid
is advantageously allowed to act on the membrane precipi-
tated by this until practically the entire solvent fromthis has been replaced by precipitating liquid. The
membrane formed i8 then freed from precipitating liquid,
for example by drying the membrane directly in a stream
of air or firæt treating it with a softening agent, such
as glycerol, and then drying it.
~he thickness of the membranes according to the invention
together with the carrier layer is in the range from
150 to 350 ~m, in particular from 200 to 300 ~m. The
thickness of the semipermeable layer here is 20 to 150
~m, preferably 50 to 100 ~m.
The membranes according to the invention can be produced
in the form of flat or tubular membranes, in particular
in the form of flat membranes. Processes for the produc-
tion of these membranes are known from the prior art.
The membranes according to the invention consist of a
carrier material of polyether ketone, polyphenylene
sulfide or polyaramid, preferably of polyphenylene
sulfide, and of a semipermeable layer of a polyether
ketone or a polyaramid, and are distinguished by their
high resistance to chemicals, mechanical stresses and
heat. Membranes with polyphenylene sulfide as the carrier
material and polyether ketones as the semipermeable layer
are thus resistant up to above 200C. Membranes with
polyaramids as the semipermeable layer and as the carrier
material or with polyphenylene sulfide as the carrier
layer can preferably be employed in those areas where a
particularly high resistance to aggressive media is
required. Such membranes are thus not attacked by acids,
alkalis or organic solvents, 8uch as chlorobenzene and
methanol, or oxidizing agents, such as, for example,
~ 3
-- 8 --
sodium hypochlorite, even at elevated temperatures. The
separation efficiency of the membrane, its selectivity
and also its mechanical stability are retained even after
these extreme stresses. They are furthermore distin-
guished by a high resistance to enzymatic and microbialattack, which means they are especially suitable for
processing media from biotechnology. Another very promis-
ing use of the membranes according to the invention is to
be found in the removal of rhodium catalysts in Oxo syn-
thesis (hydroformylation of olefins to give aldehydes).
The advantages of the membranes according to the inven-
tion are illustrated further with the aid of the
following embodiment examples.
Examples
Polyaramid membranes
Examples 1 to 7
For the membranes investigated in the Examples, the
polyaramid IIA was prepared from:
>95 mol~ of terephthalic acid dichloride (TPC),
25 mol% of para-phenylenediamine (PPD),
50 mol% of 3,3'-dimethylbenzidine (DMB) and
25 mol% of 1,4-bis-(4-aminophenoxy)benzene (BAPOB)
by a polycondensation reaction at 50C in N-methyl-
pyrrolidone (NMP) as the solvent.
The polyaramid IIB is prepared from:
~95 mol% of TPC and
100 mol% of 2,2'-bis-[4-(4'-aminophenoxy)phenyl]propane
in the same manner.
After neutralization with 100 mol% of CaO, the viscous
solutions are filtered and degassed directly, or solid
poly-N-vinylpyrrolidone is added, while stirring, and a
polymer blend is thus prepared. The resulting clear
solutions having various Staudinger indices and various
/ y~
- 9 -
concentrations are then applied to a carrier (a non-woven
or a woven fabric) with a casting device. The membranes
are precipitated in water at 5 to 20C. The membranes are
then impregnated with a 40 to 50 % strength glycerol
solution and dried at 50C. The membranes have a thick-
ness of between 150 and 350 ~m, depending on the
thickness of the carrier.
o- 2
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tn ~? + h oo t51
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U~ ~ ~ ~: ~1 P ~ O ~ S.l ,1
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u ,1 ~ O ~ ~
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a) ~ ~ .,, a~ tO .c ~ ~ ~
U ~ ~ ~ rl ~ ~ ~n
O ~ ~ ~ _l ~ la
O ~ _I t7' R ~ O O
tJl ~:: R 1-1 :1 ~ h t~ E~
o ~1 o _I ~n ~: a) u
P1 L~ ~ o .r~ P1 O
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11 C L .3 C _ ~ S
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al a
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O O O O O O O O O _I N
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o _ ~ O o
O ~ t`~ CO ~O ~ Cl~ t` U~ O o _I O~ '
~ O~ ~ l ~~0~ CO _I O~CD O j~O .~
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o~ ta 5!2
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h N tlr) O O~ O ~I O~ ~ O S-l--I ta
~ _~ _l ~_ o _l 1~
_l ~ Z ~ U ~ -
a) 3~ _ _ _
R , . . _ _ _
S l 1 1 _ ~
O ~: O ~ ~q 0 ~ O
~3 a) ,~ P1 ~ u~
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1 r~ ~ t~ o u~ ~U~ U0--I
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P1 U ~ - ~ ~ ~
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_ o~0~
~ o o o o o ~ X~'
- - - - -- - ~ ~ p ~ w o
~ .C ~ O F
~ _ _ ~ w a~ w
_1 ~ ~ 3 w~
~ E~ u~ q) o ~.q ~.q u~ ~-a w ~ 1:
h 0 ,1 1~3 Pl _~ _I ~ ~ Pl ~ ~ ~`C 0 0
1 P~ P~ ~ e~ P~ Pl P~ ~: 0 ~ ~ ~
o ~ In ~ m m ~ ~ h g~ 0 .4 R
0 0 0 H H 0 X 0 X H H H J-~ ~ O W ~ ~
U E3 H H _ ~ ~--~3 H H H 0 al 3 Ul la
_ _ _ . . _ ~ W I
w h 1: ~ to
~--1 0 0 ~Q ~
h .~ h G~ w
~3 _i ~ ~ ~r n ~D t- O~
oo
,~
.. _ _ __ . __ _ _-- ~ + a ~ E~ K
J
- 12 -
Staudinger index t~] (limiting vi8c08ity, intrinsic
viscosity) is understood as meaning the expression
17.p
lim ---= [~1]
C2 ~ C2
in which
~8p = specific viscosity = ~
c2 = concentration of the dissolved substance
= viscosity of the solution
~, = viscosity of the pure solvent
Examples 8 to 10
Membranes of polyaramid IIA, polyether ketone ~Ia, b) or
polyphenylene sulfide (III) as carrier materials can also
be used in organic media. Thus, for example, noble metal
catalysts can be removed from solutions which are pre-
cipitated during the Oxo synthesis using the membranes
according to the invention. The separations in this case
are carried out in overflow cells of stainless steel.
_
Ex- Poly- Operating Permeate Cataly~t
ample aramid/ tempera- flow retention
~ carrier ture (l/m2h) (%)
8 IIA/PET 40 14 70
__
9 IIA~PPS 40 12 68
IIA/PPS ~ 110 32 ~ 55
* the polyaramid membrane on PET can be used up to 40C
~ the polyaramid membrane on PPS is stable far beyond
100C
- 13 -
Polyether ketone membranes
Examples 11 to 15
To produce a polyether ketone membrane (PER as the semi-
permeable layer), 120 g of a polyether ketone (Ib) are
dissolved in 880 g of 96 ~ strength H2SO4 at about 30C
while stirring. After about 12 hours, the solution i~
filtered and degassed. Membranes are produced as des-
cribed for polyaramid membranes in Examples 1 to 7.
10 ~ Ex- PEK (Ib)/ Water I Reten- Permeat~ ¦Thick ;
ample carrier flow tion flow nes 8
_ jmaterial (l/m2h) (%) (l/m2h) (~m)
11 PEK 200 97 (R 30) 36 360
12 PER 175 96 (R 30) 34 350
~ (Ib)/PET _
13 PER 120 97 (R 30) 38 230
(Ib)/PPS
14+~ ~as Ex- _ _ _ _
ample 11)
.
15L (as Ex- 80 99 (R 30) 20 240
. ample 12)
~ PET non-woven dissolves, the membranes can no longer be
employed
A alkaline treatment: 24 hours in 2 % strength NaOH at
70C
