SOLUTION OF POLYSULFONE POLYMERS IN GAMMA-VALEROLACTONE FOR THE USE IN MEMBRANES

Abstract

Described herein is a solution including at least one sulfone polymer, at least one water-soluble polymer, and gamma-valerolactone. Also described herein is a process of making a membrane using the solution, and a method of using the membrane for water ultrafiltration and/or dialysis.

Claims

1. A solution comprising: a) at least one sulfone polymer, b) at least one water-soluble polymer, and c) gamma-valerolactone.

2. The solution according to claim 1, wherein said at least one sulfone polymer is a poly(ether sulfone), a polysulfone or a mixture thereof.

3. The solution according to claim 1, wherein the at least one sulfone polymer comprises between 0.02 mol to 2 mol —SO.sub.2— units per 100 g of the at least one sulfone polymer.

4. The solution according to claim 1, wherein the at least one water-soluble polymer is selected from the group consisting of poly(N-vinyl pyrrolidone) and poly(alkylene oxides) with a molecular mass of 8000 g/mol or higher.

5. The solution according to claim 1, wherein the solution further comprises an additive selected from the group consisting of C.sub.2-C.sub.4 alkanol, C.sub.2-C.sub.4 alkanediol, C.sub.3-C.sub.4 alkanetriol, poly(ethylene oxide) with a molar mass of 100 to 1000 g/mol, and mixtures thereof.

6. The solution according to claim 1, wherein the solution comprises 5 to 50 wt.-% of the at least one sulfone polymer based on a total weight of the solution.

7. The solution according to claim 1, wherein the solution comprises 0.1 to 15 wt.-% of the at least one water-soluble polymer based on a total weight of the solution.

8. The solution according to claim 1, wherein the solution comprises 50 to 90 wt.-% of the gamma-valerolactone based on a total weight of the solution.

9. The solution according to claim 5, wherein the solution comprises 0.1 to 25 wt.-% of the additive based on a total weight of the solution.

10. The solution according to claim 1 comprising less than 2.5 wt.-% high-boiling ethers having a boiling point of more than 150° C., esters, ketones, asymmetrically halogenated hydrocarbons, anisole, N,N-dimethylformamide, dimethyl sulfoxide, sulfolane, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N,N-dimethyl-2-hydroxypropanoic amide, N,N-diethyl-2-hydroxypropanoic amide or mixtures thereof based on a total weight of the solution.

11. A process for making a membrane, the process comprising using the solution according to claim 1 when making the membrane.

12. The process of claim 11 comprising the following steps: a) providing the solution, b) b) contacting the solution with at least one coagulant, and c) oxidizing and/or washing the obtained membrane.

13. The process according to claim 12, wherein the at least one coagulant comprises water, water vapor, water-alcohol-, water-poly(alkylene oxide)—and/or water-solvent mixtures, wherein the solvent is selected from the group consisting of high-boiling ethers having a boiling point of more than 150° C., esters, ketones, asymmetrically halogenated hydrocarbons, anisole, N,N-dimethylformamide, dimethyl sulfoxide, sulfolane, N-methyl-2-pyrrolidone, N-ethyl pyrrolidone, N,N-dimethyl-2-hydroxypropanoic amide, N,N-diethyl-2-hydroxypropanoic amide and mixtures thereof.

14. The process according to claim 12, wherein in step c) the membrane is i) washed with water or ii) oxidized with aqueous hypochlorite solution, subsequently washed with water and in a further step washed with aqueous solution of sodium bisulfite.

15. A membrane obtained by the process according to claim 11.

16. The membrane according to claim 15, wherein an average pore size of the membrane is between 0.3 μm and 0.9 μm.

17. A method of using the membrane obtained according to claim 15, the method comprising using the membrane for ultrafiltration and/or dialysis.

18. The solution according to claim 1, wherein the at least one water-soluble polymer has a molecular mass of 8000 g/mol or higher and is selected from the group consisting of poly(ethylene oxide), poly(propylene oxide), poly(ethylene oxide)/poly(propylene oxide) block copolymers, and mixtures thereof.

19. The process according to claim 12, wherein the at least one coagulant comprises a water-gamma-valerolactone mixture, wherein the solvent is selected from the group consisting of high-boiling ethers having a boiling point of more than 150° C., esters, ketones, asymmetrically halogenated hydrocarbons, anisole, N,N-dimethylformamide, dimethyl sulfoxide, sulfolane, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N,N-dimethyl-2-hydroxypropanoic amide, N,N-diethyl-2-hydroxypropanoic amide and mixtures thereof.

Description

FIGURES

[0100] FIG. 1 shows SEM (Scanning-Electron-Microscopy) cross-section of Example 7 (750× magnification)

[0101] FIG. 2 shows SEM (Scanning-Electron-Microscopy) cross-section of Comparative Example 11 (750× magnification)

[0102] FIG. 3 shows the optical appearance of E3010 in NFM (Comparative Example 38)

[0103] FIG. 4 shows the optical appearance of E3010 in GVL (Example 37)

EXAMPLES

[0104] Abbreviations and compounds used in the examples:

PWP pure water permeance
MWCO molecular weight cutoff
GVL gamma-Valerolactone

NMP N-methylpyrrolidone

DMAc N, N-dimethylacetamide

DMF N, N-dimethylformamide

NFM N-formylmorpholine

[0105] Ultrason® E 3010 Poly(ether sulfone) with a viscosity number (ISO 307; in 0.01 g/mol phenol/1,2 orthodichlorobenzene 1:1 solution) of 66; a glass transition temperature (DSC, 10° C./min; according to ISO 11357−1/−2) of 225° C.; a molecular weight Mw (GPC in THF, PS standard): 58000 g/mol, Mw/Mn=3.3

[0106] Ultrason® E 6020 P Poly(ether sulfone) with a viscosity number (ISO 307; in 0.01 g/mol phenol/1,2 orthodichlorobenzene 1:1 solution) of 81; a glass transition temperature (DSC, 10° C./min; according to ISO 11357−1/−2) of 225° C.; a molecular weight Mw (GPC in THF, PS standard): 75000 g/mol, Mw/Mn=3.4

[0107] Ultrason® E 7020 P Poly(ether sulfone) with a viscosity number (ISO 307; in 0.01 g/mol phenol/1,2 orthodichlorobenzene 1:1 solution) of 100; a glass transition temperature (DSC, 10° C./min; according to ISO 11357−1/−2) of 225° C.; a molecular weight Mw (GPC in THF, PS standard): 92000 g/mol, Mw/Mn=3.0

[0108] Ultrason® S 6010 Polysulfone with a viscosity number (ISO 307; in 0.01 g/mol phenol/1,2 orthodichlorobenzene 1:1 solution) of 81; a glass transition temperature (DSC, 10° C./min; according to ISO 11357−1/−2) of 187° C.; a molecular weight Mw (GPC in THF, PS standard): 60000 g/mol, Mw/Mn=3.7

[0109] Luvitec® K30 Poly(N-vinyl pyrrolidone) with a solution viscosity characterised by the K-value of 30, determined according to the method of Fikentscher (Fikentscher, Cellulosechemie 13, 1932 (58))

[0110] Luvitec® K90 Poly(N-vinyl pyrrolidone) with a solution viscosity characterised by the K-value of 90, determined according to the method of Fikentscher (Fikentscher, Cellulosechemie 13, 1932 (58))

[0111] Pluriol® 400E Poly(ethylene oxide) with an average molecular weight of 400 g/mol calculated from the OH numbers according to DIN 53240.

[0112] Pluriol® 9000E Poly(ethylene oxide) with a solution viscosity characterised by the K-value of 33, determined according to the method of Fikentscher (Fikentscher, Cellulosechemie 13, 1932 (58)) and a molecular weight Mw (GPC in water with 0.01 mol phosphate buffer pH 7.4, TSKgel GMPWXL column, Tosoh Bioscience with poly(ethylene oxide) standard 106-1522000 g/mol): 10800 g/mol.

[0113] POLYOX™ WSR-N10 Poly(ethylene oxide) with a solution viscosity characterised by the K-value of 68, determined according to the method of Fikentscher (Fikentscher, Cellulosechemie 13, 1932 (58)) and a molecular weight Mw (GPC in water with 0.01 mol phosphate buffer pH 7.4, TSKgel GMPWXL column, Tosoh Bioscience with, poly(ethylene oxide) standard 106-1522000 g/mol): 102000 g/mol

[0114] POLYOX™ WSR-N80 Poly(ethylene oxide) with a solution viscosity characterised by the K-value of 84, determined according to the method of Fikentscher (Fikentscher, Cellulosechemie 13, 1932 (58)) and a molecular weight Mw (GPC in water with 0.01 mol phosphate buffer pH 7.4, TSKgel GMPWXL column, Tosoh Bioscience with, poly(ethylene oxide) standard 106-1522000 g/mol): 187000 g/mol

[0115] POLYOX™ WSR-N750 Poly(ethylene oxide) with a solution viscosity characterised by the K-value of 109, determined according to the method of Fikentscher (Fikentscher, Cellulosechemie 13, 1932 (58)) and a molecular weight Mw (GPC in water with 0.01 mol phosphate buffer pH 7.4, TSKgel GMPWXL column, Tosoh Bioscience with, poly(ethylene oxide) standard 106-1522000 g/mol): 456000 g/mol

[0116] The pure water permeance (PWP) of the membranes was tested using a pressure cell with a diameter of 74 mm using ultrapure water (salt-free water, filtered by a Millipore UF-system) at 23° C. and 1 bar water pressure. The pure water permeation (PWP) is calculated as follows (equation 1):

[00002]$\begin{array}{cc}\mathrm{PWP}=\frac{m}{A\times P\times t}& \left(1\right)\end{array}$ [0117] PWP: pure water permeance [kg/bar h m.sup.2] [0118] m: mass of permeated water [kg] [0119] A: membrane area [m.sup.2] [0120] P: pressure [bar] [0121] t: time of the permeation experiment [h].

[0122] A high PWP allows a high flow rate and is desired.

[0123] In a subsequent test, solutions of poly(ethylene oxide)—standards with increasing molecular weight were used as feed to be filtered by the membrane at a pressure of 0.15 bar. By GPC-measurement of the feed and permeate, the molecular weight of the permeate of each poly(ethylene oxide)—standard used was determined. The weight average molecular weight (MW) cutoff of the membranes (MWCO) is the molecular weight of the first poly(ethylene oxide) standard which is withhold to at least 90% by the membrane. For example, a MWCO of 18400 means that poly(ethylene oxide) of molecular weight of 18400 and higher are withhold to at least 90%. It is desired to have a MWCO in the range from 10 to 100 kDa.

Preparation of membranes using GVL as polymer solvent (Invention) or other solvent (Comparative Example)

General Procedure

[0124] Into a three-neck flask equipped with a magnetic stirrer there were added 65 to 75 ml of Solvent 51, 19 g sulfone polymer (Ultrason polymer as described in the tables), 6 to 8 g water-soluble polymer (Luvitec® poly(N-vinyl pyrrolidone) or poly(alkylene oxide) as described in the tables with optional second dope additives (Pluriol® 400E) as given in tables 1-6. The mixture was heated under gentle stirring at 60° C. until a homogeneous clear viscous solution, usually referred to as dope solution was obtained. The solution was degassed overnight at room temperature.

[0125] After that the membrane solution was reheated at 60° C. for 2 hours and casted onto a glass plate with a casting knife (300 microns) at 60° C. using an Erichsen Coating machine operating at a speed of 5 mm/min. The membrane film was allowed to rest for 30 seconds before immersion in a water-based coagulation bath at 25° C. for 10 minutes (Table 7). After the membrane had detached from the glass plate, the membrane was carefully transferred into a water bath for 12 h.

[0126] Optionally afterwards the membrane was transferred into a bath containing 2000 ppm NaOCl in water at 60° C. and pH9.5 for 2 h. The membrane was then washed with water at 60° C. and one time with a 0.5 wt.-% aqueous solution of sodium bisulfite to remove active chlorine (Posttreatment A).

[0127] Or optionally the membrane was washed with water at 60° C. three times (Posttreatment B).

[0128] After several washing steps with water the membrane was stored wet until characterization regarding pure water permeability (PWP) and minimum pore size (MWCO) started.

[0129] Tables 1 to 6 summarize the membrane properties.

[0130] Membranes produced with GVL according to the invention show improved separation characteristics over membranes known from the art. Membranes produced with GVL show higher water permeability values in combination with MWCO values in the ultrafiltration range (10-100 kDa) compared to membranes known from the art.

TABLE-US-00002 TABLE 1 Compositions and properties of Ultrason ® E 3010 membranes prepared with Luvitec ® K90 and Pluriol ® E400; MWCO in [Da], PWP in [kg/h m.sup.2bar], Posttreatment A. Coagulation W Water- soluble Sulfone Coagulation polymer polymer Additive bath Luvitec ® Ultrason ® Pluriol ® Bath Solvent Examples K90 E3010 E400 (cf. Table 7) S1 PWP MWCO Example 1 6 g 19 g — W 75 g GVL 970 29300 Comparative 6 g 19 g — W 75 g NMP 530 17200 Example 2 Example 3 6 g 19 g 10 g X 65 g GVL 990 28400 Comparative 6 g 19 g 10 g X 65 g NMP 440 21900 example 4

TABLE-US-00003 TABLE 2 Compositions and properties of Ultrason ® E 3010 membranes prepared; MWCO in [Da], PWP in [kg/h m.sup.2bar], Posttreatment A. Coagulation W Water- Sulfone soluble polymer polymer Solvent Examples E3010 Polyox S1 PWP MWCO Example 5 19 g 6 g N10 65 g GVL 800 68000 Example 6 19 g 3 g N750 + 65 g GVL 610 10700 3 g E9000 Example 7 19 g 6 g N80 65 g GVL 370 10800 Example 8 19 g 6 g N750 65 g GVL 280 17200 Comparative 19 g 6 g N10 65 g NMP 250 10000 Example 9 Comparative 19 g 3 g N750 + 65 g NMP 180 12000 Example 10 3 g E9000 Comparative 19 g 6 g N80 65 g NMP 280 10750 Example 11 GM 19 g 6 g N750 65 g NMP 260 9500 Comparative Example 12

TABLE-US-00004 TABLE 3 Compositions and properties of Ultrason ® E 3010 membranes prepared; MWCO in [Da], PWP in [kg/h m.sup.2bar], Posttreatment B. Coagulation W Water- Sulfone soluble polymer polymer Solvent Examples E3010 Polyox S1 PWP MWCO Example 13 19 g 6 g N10 65 g GVL 210 14000 Example 14 19 g 3 g N750 + 65 g GVL 220 10800 3 g E9000 Example 15 19 g 6 g N80 65 g GVL 250 15500 Example 16 19 g 6 g N750 65 g GVL 210 14300 Comparative 19 g 6 g N10 65 g NMP 76 50700 Example 17 Comparative 19 g 3 g N750 + 65 g NMP 29 13200 Example 18 3 g E9000 Comparative 19 g 6 g N80 65 g NMP 29 10700 Example 19 Comparative 19 g 6 g N750 65 g NMP 19 12900 Example 20

TABLE-US-00005 TABLE 4 Compositions and properties of Ultrason ® E 6020 and Ultrason ® E 7020 membranes prepared; MWCO in [Da], PWP in [kg/h m.sup.2bar], Posttreatment A. Coagulation W Water- soluble Sulfone Sulfone polymer polymer polymer Solvent Examples K90 E6020 E7020 S1 PWP MWCO Example 21 6 g 19 g — 75 g GVL 750 17700 Comparative 6 g 19 g — 75 g NMP 300 13300 Example 22 Example 23 6 g — 19 g 75 g GVL 470 23700 Comparative 6 g — 19 g 75 g NMP 210 9550 Example 24

TABLE-US-00006 TABLE 5 Compositions and properties of Ultrason ® S 6010 membranes prepared; MWCO in [Da], PWP in [kg/h m.sup.2bar], Posttreatment A. Coagulation W Water- Water- soluble soluble Sulfone Polymer Polymer Polymer Solvent K90 K30 S6010 S1 PWP MWCO Example 25 3 g 3 g 19 g 75 g GVL 400 42400 Comparative 3 g 3 g 19 g 75 g DMAc 290 10900 Example 26 Example 27 6 g — 19 g 75 g GVL 410 69400 Comparative 6 g — 19 g 75 g DMAc 260 12100 Example 28 Comparative 3 g 3 g 19 g 75 g NFM 135 8300 Example 35 Comparative 6 g 19 g 75 g NFM 120 9600 Example 36

TABLE-US-00007 TABLE 6 Compositions and properties of Ultrason ® E 3010 membranes prepared; MWCO in [Da], PWP in [kg/h m.sup.2bar], Posttreatment PT. Coagulation W Water- soluble Sulfone Polymer polymer Solvent K90 E3010 PT S1 PWP MWCO Example 29 6 g 19 g A 75 g GVL 820 46800 Comparative 6 g 19 g none 75 g GVL 27 3180 Example 30 Comparative 6 g 19 g A 75 g NMP 570 21500 Example 31 Comparative 6 g 19 g none 75 g NMP 60 4400 Example 32 Example 33 8 g 19 g A 73 g GVL 970 73400 Comparative 8 g 19 g A 73 g NMP 380 14700 Example 34

TABLE-US-00008 TABLE 7 Compositions of the coagulation bath employed for membrane preparation content composition Coagulation bath W Water   100 wt.-%/wt.-% Coagulation bath X Water/Pluriol ® 400E 90/10 wt.-%/wt.-%

[0131] Membranes according to the invention are showing a well formed nano porous filtration layer on the top supported by a sponge-type substructure with increasing pore sizes from top to bottom. No defects or macrovoids are visible in the cross-section (cf. FIG. 1). Membranes from comparative examples showing numerous macrovoids which could partially penetrate the filtration layer on the top (cf. FIG. 2). Membranes produced with GVL according to the invention show improved separation characteristics over membranes known from the art. Membranes produced with GVL show higher water permeability values in combination with MWCO values in the ultrafiltration range (10-100 kDa) compared to membranes known from the art prepared with other solvents.

Turbidity Measurement:

[0132] The polymer solution turbidity was measured with a turbidimeter 2100AN (Hach Lange GmbH, Dusseldorf, Germany) employing a filter of 860 nm and expressed in nephelometric turbidity units (NTU). The turbity measurement shows solubility of a polymer in a solvent. Low NTU values are preferred.

TABLE-US-00009 TABLE 7 Compositions and properties of polymer solutions; turbidity@RT [NTU], Visco@60° C. [Pas], example polymer Solvent S1 Visco NTU (0 d) Example 37 25 g E3010 75 g GVL 2.3 1.3 Comparative Exam- 25 g E3010 75 g NFM * >7500 ple 38 Example 39 25 g S6010 75 g GVL 15.0 0.8 Comparative Exam- 25 g S6010 75 g NFM 55.0 3.2 ple 40 Comparative Exam- 25 g S6010 75 g DMF 2.4 1.5 ple 41 * no solution could be manufactured

[0133] Polyethersulfone (E3010) solutions produced with GVL according to the invention have low solution turbidity (FIG. 4) in contrast to NFM where only a turbid paste (no solution) could be obtained (FIG. 3). Polysulfone (E6010) solutions produced with GVL have also lower turbidity than NFM and DMF (cf. Table 7).