CA2061990A1

CA2061990A1 - Porous semipermeable membrane resistant to chemicals and heat

Info

Publication number: CA2061990A1
Application number: CA002061990A
Authority: CA
Inventors: Harald Cherdron; Claus-Peter Krieg; Juergen Schneider; Juergen Wildhardt
Original assignee: Harald Cherdron; Claus-Peter Krieg; Juergen Schneider; Juergen Wildhardt; Hoechst Aktiengesellschaft
Current assignee: Hoechst AG
Priority date: 1991-02-28
Filing date: 1992-02-27
Publication date: 1992-08-29
Also published as: TW205513B; JPH04317733A; MX9200822A; EP0501425A1; KR920016135A

Abstract

Abstract of the disclosure: HOE 91/F 064 Porous semipermeable membrane resistant to chemicals and heat A semipermeable membrane for micro-, nano- and ultra-filtration, comprising a carrier material and a semi-permeable layer adhering to this. The carrier material is a woven fabric or a non-woven based on a polyphenylene sulfide, a polyether ketone or a polyaramid. To produce the semipermeable membrane, the polymers are first dissolved in a solvent and the solution is filtered and degassed. In a subsequent step, a membrane is produced by the phase inversion process, H2SO4, CF3-SO3H, HF, Cl2HC-COOH or a mixture of Cl2HC-COOH and H2SO4 being employed as the solvent for polyether ketones and N-methylpyrrolidone, dimethylacetamide or dimethyl-formamide being employed as the solvent for polyaramids.

Description

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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 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~

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 -O-,-S-,-CH2-,-CF2.,-C-, -C-, -SO2r or -CO-~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 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 ~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 -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 ~

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

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 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~

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.

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Staudinger index t~] (limiting vi8c08ity, intrinsic viscosity) is understood as meaning the expression 17.p lim ---= [~1]
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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) (%) __ 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 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
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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

Claims

1. A semipermeable membrane for micro-, nano- and ultrafiltration, comprising a carrier material and a semipermeable layer adhering to this, wherein the carrier material is a woven fabric or a non-woven based on a polyphenylene sulfide, a polyether ketone or a polyaramid.

2. A semipermeable membrane as claimed in claim 1, wherein the semipermeable layer comprises a poly-ether ketone having the following recurring units of the formula (Ia) (Ia)

3. A semipermeable membrane as claimed in claim 1, wherein the semipermeable layer comprises a poly-ether ketone having the following recurring units of the formula (Ib):

(Ib) in which -A- is or R1, R2, R3 and R4 can be identical or different and are hydrogen, a (C1-C4)-alkyl, (C6-C14)-aryl or (C6-C14)-hydroxyaryl group or _ 15 -NO2, CN, NR52 (R5 = (C1-C6)-alkyl) or halogen and -Z- is one of the groupings or -CO-

4. A semipermeable membrane as claimed in claim 1, wherein the semipermeable layer comprises an aro-matic homo- or copolyamide having at least one of the recurring structural units of the formula (II) (II) in which -E1- and -E2- are identical or different and are selected from one or more of the groupings -Ar1-or -Ar1-X-Ar2-, in which -Ar1- and -Ar2- are identical or different 1,2-phenylene, 1,3-phenylene, 1,4-phenylene radicals or (C6-C14)-arylene radicals, which can be substitu-ted by one or more (C1-C6)-alkyl, (C1-C6)-alkoxy or CF3 groups or halogen, in particular fluorine, chlorine or bromine, or are a heteroaromatic radical, and the radical X

a) is a direct bond or is one of the following divalent radicals -O-, -C(CF3)2-, -SO2-, -CO- or -C(R6)2-, in which R6 is hydrogen or a (C1-C6)-alkyl or (C1-C4)-fluoroalkyl group, or b) is -Y-Ar1-Y-, in which -Y- is the radical -O- or -C(CH3)2-, or c) is -O-Ar1-Q-Ar2-O-, in which Q has the meaning given under Xa).

5. A semipermeable membrane as claimed in claim 2 or 3, wherein the carrier material and the semipermeable layer both comprise the same polyether ketone or different polyether ketones having the recurring units of the formula (Ia) or (Ib), or comprise the same polyaramid or comprise different polyaramids of the formula (II).

6. A semipermeable membrane as claimed in claim 1, wherein the carrier material is a non-woven or a woven fabric based on a polymer having the recurring units of the formula (Ia) or (Ib) or of the formula (II).

7. A semipermeable membrane as claimed in claim 1, wherein the carrier material is a polyphenylene sulfide having the recurring structural units of the formula (III) ( III )

8. A process for the production of a semipermeable membrane as claimed in claim 1, which comprises first dissolving the polymer in a solvent and filtering and degassing the solution, and, in a subsequent step, producing a membrane by the phase inversion process, and employing H2SO4, CF3-SO3H, HF, Cl2HC-COOH or a mixture of Cl2HC-COOH and H2SO4 as the solvent for a polyether ketone and N-methyl-pyrrolidone, dimethylacetamide or dimethylformamide as the solvent for a polyaramid.

9. A semipermeable membrane as claimed in claim 1, which is a flat or tubular membrane.