Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Patent
1996-10-15
1997-12-02
Seidleck, James J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
528125, 528126, 528128, 528174, 528212, 528218, 528219, 528373, C08G 802, C08G 7523
Patent
active
056937407
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to aromatic polysulphones which are useful particularly, but not exclusively, as membranes for filtration operations.
Composite membranes comprising a thin film of a hydrophilic, sulphonated aromatic polyethersulphone supported on an ultrafiltration membrane are known to have good chemical stability (particularly to extremes of pH and to chlorinated feed waters) and to be usable in reverse osmosis and nanofiltration. Examples of sulphonated polymers which have been used in the past to produce such membranes are shown below as Polymers A, B, and C. ##STR2##
Polymer C has particular advantages in that (i) the presence of the biphenyl linkage in place of an isopropylidene or ether linkage provides a material with significantly improved thermo-mechanical and chemical stability, (ii) the precursor (i.e. non-sulphonated) polymer is readily synthesised at high molecular weight, and (iii) sulphonation of this material to give Polymer C proceeds rapidly and cleanly at room temperature.
However, using polymers of type C, it has not proved possible to fabricate reverse osmosis membranes with an industrially viable combination of salt rejection and water flux. We have found for example that although composite membranes with good fluxes can be readily obtained from polymers of type C, it is difficult to obtain adequate salt rejection.
It is therefore an object of the present invention to provide sulphonated aromatic polysulphones, and membranes fabricated therefrom, which obviate or mitigate the abovementioned disadvantages.
According to a first aspect of the present invention there is provided an aromatic polyethersulphone incorporating the following sub-unit I: ##STR3## where A is an electron withdrawing group, the designation `o,p` represents that the bond is at the ortho or pare position to the A group, and X is selected from; (other than hydrogen) and n is at least 1; are selected from hydrogen, and alkyl, aryl, aminoalkylene or ammonioalkylene groups; and comonomer units.
In the above formula, A is preferably a carbonyl linkage (--CO--) or, more preferably, a sulphonyl linkage (--SO.sub.2 --). If X is --O.sup.- (M.sup.n+).sub.1
then the cation may have a valency of one or more. If the valency is greater than 1 then it will be appreciated that the --O.sup.- moiety is associated with a fraction 1
of the cation. M may for example be an alkali metal, alkaline earth metal, or a higher valency metal ion, eg Al.sup.3+. Preferably M is sodium or potassium.
If X is --NR.sub.1 R.sub.2 then at least one of R.sub.1 and R.sub.2 is preferably other than hydrogen. If R.sub.1 and/or R.sub.2 is alkyl it preferably has less than 4 carbon atoms. A suitable example of an aminoalkylene group for R.sub.1 and R.sub.2 is --(CH.sub.2).sub.m --NH.sub.2 where m is less than 4, preferably 2. Correspondingly a suitable ammonioalkylene group is --(CH.sub.2).sub.m --N.sup.+ R.sub.4 R.sub.5 R.sub.6 where R.sub.4, R.sub.5 and R.sub.6 are independently hydrogen, alkyl or aryl. If X is --OR.sub.3 and R.sub.3 is alkyl it preferably has less than 4 carbon atoms.
Polymers in accordance with the invention are hydrophilic by virtue of the presence of the --SO.sub.2 X groups and are eminently suitable for use as membranes in filtration operations effected in an aqueous environment.
Therefore according to a second aspect of the invention there is provided a porous or non-porous membrane comprising an aromatic polyethersulphone incorporating the sub-unit (I) defined above either alone or in combination wish comonomer units.
Membranes in accordance with the second aspect of the invention may for example be asymmetric membranes, composite membranes or dense films and may be used in a variety of separation processes including reverse osmosis, electrodialysis, nanofiltration, ultrafiltration, microfiltration, gas separation, pervaporation, haemodialysis and haemofiltration.
A particularly preferred form of membrane in accordance with the invention is a composite membrane comprising a thin film of the polymer supported on an u
REFERENCES:
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patent: 4176222 (1979-11-01), Cinderey et al.
patent: 4268650 (1981-05-01), Rose
patent: 4273903 (1981-06-01), Rose
patent: 4320224 (1982-03-01), Rose et al.
patent: 4775738 (1988-10-01), Mayska et al.
patent: 5047496 (1991-09-01), Eckel et al.
Colquhoun Howard Matthew
Lewis David Frank
Seidleck James J.
Truong Duc
United Utilites PLC
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