DESALINATION OF POLYARYL ETHERS BY MEANS OF MELT EXTRACTION

Abstract

A method for desalinating a salt-containing polymer (SP) comprising a polyaryl ether having a softening temperature T.sub.S and a salt (S), comprising the steps of a) providing the salt-containing polymer (SP) at a first temperature T.sub.1 above the softening temperature T.sub.S of the polyaryl ether, b) contacting the salt-containing polymer (SP) provided in step a) with an extractant (E) to obtain a desalinated polymer (DP) comprising the polyaryl ether, and a salt-containing extractant (SE) comprising the extractant (E) and the salt (S).

Claims

1.-13. (canceled)

14. A method for desalinating a salt-containing polymer (SP) comprising a polyaryl ether having a softening temperature T.sub.S and a salt (S), comprising the steps of a) providing the salt-containing polymer (SP) at a first temperature T.sub.1 above the softening temperature T.sub.S of the polyaryl ether, b) contacting the salt-containing polymer (SP) provided in step a) with an extractant (E) to obtain a desalinated polymer (DP) comprising the polyaryl ether, and a salt-containing extractant (SE) comprising the extractant (E) and the salt (S), wherein step a) comprises the following steps: i) providing a first salt-containing polymer (SP1) comprising the polyaryl ether and the salt (S), ii) pelletizing the first salt-containing polymer (SP1) provided in step i) to obtain a pelletized first salt-containing polymer (PSP1), iii) contacting the pelletized first salt-containing polymer (PSP1) obtained in step ii) with the extractant (E) to obtain the salt-containing polymer (SP) comprising the polyaryl ether and residues of the salt (S), and a first salt-containing extractant (SE1) comprising the extractant (E) and a portion of the salt (S), iv) heating the salt-containing polymer (SP) obtained in step iii) to a first temperature T.sub.1 above the softening temperature T.sub.S of the polyaryl ether, and wherein step b) comprises the following step: v) contacting the salt-containing polymer (SP) heated in step iv) with the extractant (E) to obtain the desalinated polymer (DP) comprising the polyaryl ether, and a second salt-containing extractant (SE2) comprising the extractant (E) and the residues of the salt (S), wherein the first salt-containing polymer (SP1) is provided in step i) by a melt polymerization method.

15. The method according to claim 14, wherein the salt-containing polymer (SP) is contacted with the extractant (E) in step b) at a second temperature T.sub.2 above the softening temperature T.sub.S of the polyaryl ether.

16. The method according to claim 15, wherein the second temperature T.sub.2 at which the salt-containing polymer (SP) is contacted with the extractant (E) in step b) is in the range from 160 to 300° C.

17. The method according to claim 14, wherein the first temperature T.sub.1 in step a) is within a range from 160 to 300° C.

18. The method according to claim 14, wherein the first temperature T.sub.1 is in the range from 1 to 100° C. above the softening temperature T.sub.S of the polyaryl ether.

19. The method according to claim 14, wherein the softening temperature T.sub.S of the polyaryl ether is in the range from 150 to 230° C.

20. The method according to claim 14, wherein the extractant (E) in step b) comprises water.

21. The method according to claim 14, wherein the desalinated polymer (DP) obtained in step b) comprises not more than 150 ppm by weight of the salt (S), based on the total weight of the desalinated polymer (DP).

22. The method according to claim 14, wherein the first salt-containing polymer (SP1) is pelletized in step ii) to a particle size in the range from 0.3 to 10 mm.

23. The method according to claim 14, wherein the polyaryl ether is a polyaryl ether sulfone.

24. The method according to claim 14, wherein the salt (S) comprises potassium chloride and/or sodium chloride.

25. (canceled)

26. (canceled)

Description

EXAMPLES

Examples 1 and 2

[0251] Polyether sulfone (PESU, Ultrason E) was prepared proceeding from bisphenol S as component (a1) and 4,4″-dihalodiphenyl sulfone as component (a2) in the presence of potassium carbonate as carbonate component (C) in a melt polymerization process.

[0252] The polyether sulfone obtained was pelletized and extracted with water at 80° C. for 24 hours. The salt content of the salt-containing polymer (SP) thus obtained was less than 1% of the original concentration of the salt (S). Subsequently, the salt (5) (potassium chloride) was extracted from the salt-containing polymer (SP) obtained in an autoclave with water at a temperature of 250° C. In each case, 30 g of salt-containing polymer (SP) were extracted with water.

[0253] For the different examples, the water was changed after different periods of time. In example 1, the water was changed after 7, 23, 29 and 48 hours; in example 2, the water was changed every two hours.

[0254] The resulting salt content of the desalinated polymer (eP) as a function of the extraction time from example 1 is reported in table 1, and that from example 2 in table 2. Likewise reported in tables 1 and 2 is the conductivity of the water with which the salt (S) was extracted,

TABLE-US-00001 TABLE 1 Conductivity Chlorine Chloride Potassium Time [h] [mS] [g/100 g] {g/100 g] [g/100 g] 8 16.18 25 1.72 0.24 0.042 0.09 31 0.24 49 0.21 0.17 0.01 0.013

TABLE-US-00002 TABLE 2 Conductivity Chlorine Chloride Potassium Time [h] [mS] [g/100 g] {g/100 g] [g/100 g] 2 16.15 4 4.12 6 0.70 8 0.24 10 0.11 12 0.04 14 0.04 0.17 0.002 0.037