Polymeric compositions for membranes

• US 4,207,182 A
• Filed: 11/10/1976
• Issued: 06/10/1980
• Est. Priority Date: 11/14/1975
• Status: Expired due to Term

• Current Assignee: Rhone-Poulenc Industries
• Original Assignee: Rhone-Poulenc Industries
• Inventors: Marze, Xavier
• Primary Examiner(s): Spear, Jr., Frank A.
• Application Number:
  US05/740,656
• Time in Patent Office: 1,308 Days
• Field of Search: 210/500 M, 210/321 R, 210/23 F, 55/16, 55/158, 260/2.2 R, 260/2.5 AY, 23/258.5 M, 428/304, 204/180 P, 521/25, 521/30, 521/27, 264/41, 264/45.1, 264/45.5, 427/244, 427/245, 427/246
• US Class Current: 210/650
• CPC Class Codes: B01D 69/12 Composite membranes; Ultra-thin membranes
• CPC Class Codes: B01D 71/68 Polysulfones; Polyethersulfones
• CPC Class Codes: C08G 65/48 Polymers modified by chemical after-treatment
• CPC Class Codes: C08J 2381/06 Polysulfones; Polyethersulfones
• CPC Class Codes: C08J 5/2218 Synthetic macromolecular compounds
• CPC Class Codes: C08L 81/00 Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing sulfur with or without nitrogen, oxygen or carbon only; Compositions of polysulfones; Compositions of derivatives of such polymers
• CPC Class Codes: C08L 81/06 Polysulfones; Polyethersulfones
• CPC Class Codes: Y10T 428/249978 Voids specified as micro
• CPC Class Codes: Y10T 428/249981 Plural void-containing components

Abstract

A mixture of at least one non-sulphonated polysulphone and at least one sulphonated polysulphone, this mixture consisting of 10 to 30% by weight of a sulphonated polysulphone which has a theoretical exchange capacity of from 500 to 1,200 meq/kg is provided. Such mixtures enable one to obtain semi-permeable membranes using relatively concentrated solutions of the mixtures. The resulting membranes are particularly suitable for use in ultrafiltration.

Claims

1. A membrane-forming composition useful for making ultrafiltration membranes from a polymer solution thereof having a polymer concentration higher than 20%, said composition comprising a mixture of at least one non-sulphonated polysulphone and at least one sulphonated polysulphone, this mixture containing 10 to 30% by weight of a sulphonated polysulphone which has a theoretical exchange capacity of from 500 to 1200 meq/kg.

2. A composition according to claim 1 in which the theoretical exchange capacity of the composition is from 120 to 350 meq/kg.

3. A composition according to claim 1 in which the non-sulphonated polysulphone consists essentially of recurring units of the formula:

##STR4## in which each of E, G and G₁, which are identical or different, represents an aromatic group, each of Q and Q₁ , which are identical or different, represents a substituent which is inert with respect to the sulphonation reactions, each of Q₂ and Q₃, which are identical or different, represents an electron-attracting group, each of r, s, t and u, which are identical or different, is zero or a positive integer from 1 to 4, at least one of which is not greater than 3, m is equal to 0, 1 or 2 and R represents a valency bond or a radical which is selected from the group consisting of --CO--, --O-- and --SO₂ -- and divalent hydrocarbon radicals, and the sulphonated polysulphone consists essentially of recurring units of the formula;

##STR5## alone or in combination with units of formula (I), in which Q, Q₁, Q₂, Q₃, r, s, t, u and m are as defined above and E'"'"', G'"'"' and G'"'"'₁, which are identical or different, are as defined under E, G and G₁, respectively, except that at least one of them contains at least one sulphonic group.

4. A composition according to claim 3 in which the substituent which is inert with respect to sulphonation reactions is selected from the group consisting of alkyl radicals of 1 to 4 carbon atoms and fluorine, chlorine, bromine and iodine atoms.

5. A composition according to claim 3 in which the electron-attracting group is selected from the group consisting of nitro, phenylsulphone, alkylsulphone, trifluoromethyl, nitroso and pyridyl groups.

6. A composition according to claim 3 in which R is selected from the group consisting of alkylene, alkylidene, cycloalkylene and arylene radicals containing less than 7 carbon atoms.

7. A composition according to claim 6 in which R is the ##STR6## radical.

8. A composition according to claim 3 in which r=s=t=u=0, m=1 or 2 and E, G and G₁ are each a para-phenylene radical.

9. A composition according to claim 1 which is in the form of a solution in at least one organic solvent containing at least 20% by weight of the said mixture.

10. A composition according to claim 9 which contains at least 25% by weight of the said mixture.

11. A composition according to claim 9 in which the organic solvent is a polar aprotic solvent.

12. A composition according to claim 11 in which the solvent is N-methylpyrrolidone.

13. A membrane formed from a composition as defined in claim 1.

14. A membrane according to claim 13 which is dense.

15. A membrane according to claim 13 which is screen-reinforced, the screen reinforcement constituting 20 to 80% by weight of the reinforced membrane.

16. A membrane according to claim 13 possessing a dense or microporous layer, and a porous layer.

17. In a method of ultrafiltration of a liquid the improvement in which the ultrafiltration membrane is one defined in claim 13.

18. Process for the preparation of a membrane suitable for ultrafiltration, which comprises casting a composition as defined in claim 1 in the form of a solution having a polymer concentration higher than 20% on a support and immersing the liquid film, on its support, in a coagulation bath.

19. A process for the preparation of a composition comprising a mixture of at least one non-sulphonated polysulphone and at least one sulphonated polysulphone, this mixture containing 10 to 30% by weight of a sulphonated polysulphone which has a theoretical exchange capacity of from 500 to 1200 meq/kg,

said process comprising mixing the non-sulphonated polysulphone with the sulphonated polysulphone in the form of powders or solutions, or combinations thereof.

20. A process according to claim 19 wherein a solution is used, and, after mixing, the solvent of the solution is evaporated.

21. A membrane which is a composite membrane comprising a thin layer of membrane formed from a composition comprising a mixture of at least one non-sulphonated polysulphone and at least one sulphonated polysulphone, this mixture containing 10 to 30% by weight of a sulphonated polysulphone which has a theoretical exchange capacity of from 500 to 1200 meq/kg, and which is supported by a porous layer.

22. Process for the preparation of a membrane suitable for ultrafiltration, which comprises casting on a support a composition comprising a mixture of at least one non-sulphonated polysulphone and at least one sulphonated polysulphone, this mixture containing 10 to 30% by weight of a sulphonated polysulphone which has a theoretical exchange capacity of from 500 to 1200 meq/kg, said composition being in the form of a solution in at least one organic solvent containing at least 20% by weight of the said mixture, and immersing the liquid film, on its support, in a coagulation bath, the coagulation bath being water, alone or in combination with solvent and/or salt, and having a temperature of +10°

to +60°

C.

23. Process according to claim 22 in which the coagulation bath has a temperature of 15°

to 40°

C.