HYDROPHILIC COPOLYMERS AND MEMBRANES

Abstract

The present invention relates to a process for the preparation of a polyarylethersulfone-polyalkylene oxide block copolymer (PPC) by converting a reaction mixture (R.sub.G) which comprises, among others, at least one aromatic dihalogen sulfone, at least one dihydroxy component comprising trimethylhydroquinone and at least one polyalkylene oxide. The present invention furthermore relates to a polyarylethersulfone-polyalkylene oxide block copolymer (PPC) obtainable by the inventive process and to its use in a membrane (M) and to a membrane (M) comprising the polyarylethersulfone-polyalkylene oxide block copolymer (PPC). Furthermore, the present invention relates to a method for the preparation of a membrane (M).

Claims

1: A process for preparing a polyarylethersulfone-polyalkylene oxide block copolymer (PPC), the process comprising: I) converting a reaction mixture (R.sub.0) comprising: (A1) at least one aromatic dihalogen sulfone, (B1) at least one aromatic dihydroxy component comprising trimethylhydroquinone, (B2) at least one polyalkylene oxide, (C) at least one carbonate component, and (D) at least one aprotic polar solvent, to obtain the polyarylethersulfone-polyalkylene oxide block copolymer.

2: The process according to claim 1, wherein component (A selected from the group consisting of 4,4-dichlorodiphenyl sulfone and 4,4-difluorodiphenyl sulfone.

3: The process according to claim 1, wherein component (B1) comprises at least 50 mol-% of trimethylhydroquinone, based on a total amount of component (B1).

4: The process according to claim 1, wherein component (B2) comprises at least 50% by weight of a polyalkylene oxide obtained by polymerizing ethylene oxide, 1,2-propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide, 1,2-pentene oxide, 2,3-pentene oxide, tetrahydrofuran, or mixtures of two or more of these monomers, based on a total weight of component (B2).

5: The process according to claim 1, wherein component (C) comprises at least 50% by weight of potassium carbonate, based on a total weight of component (C).

6: The process according to claim 1, wherein component (D) is selected from the group consisting of N-methylpyrrolidone, N-dimethylacetamide, dimethylsulfoxide and dimethylformamide.

7: A polyarylethersulfone-polyalkylene oxide block copolymer (PPC) obtained by the process of claim 1 6.

8: A membrane (M), comprising a polyarylethersulfone-polyalkylene oxide block copolymer (PPC) according to claim 7.

9: The membrane (M) according to claim 8, wherein the membrane (M) is asymmetric.

10: The membrane (M) according to claim 8, wherein the membrane (M) is a porous membrane or a dense membrane.

11: A process, comprising forming a membrane (M) from the polyarylethersulfone-polyalkylene oxide block copolymer (PPC) according to claim 7.

12: A method for preparing the membrane (M) of claim 8, the method comprising: i) forming providing a solution (S) comprising the polyarylethersulfone-polyalkylene oxide block copolymer (PPC) and at least one solvent, and ii) separating the at least one solvent from the solution (S) to obtain the membrane (M).

13: The method according to claim 12, wherein the at least one solvent is selected from the group consisting of N-methylpyrrolidone, dimethylacetamide, dimethyl sulfoxide, dimethylformamide, dimethyllactamid and sulfolane.

14: The method according to claim 12, wherein the solution (S) comprises from 0.1 to 30% by weight of the polyarylethersulfone-polyalkylene oxide block copolymer (PPC), based on a total weight of the solution (S).

15: The method according to claim 12, wherein the separating ii) is performed by a phase inversion process.

Description

EXAMPLES

Components Used

[0207] DCDPS: 4,4-dichlorodiphenyl sulfone, [0208] TMH: trimethylhydroquinone, [0209] DHDPS: 4,4-dihydroxydiphenyl sulfone, [0210] Polyethyleneglycol 2000: M.sub.n=2004 g/mol, determined via OH-titration [0211] PEO-PPO-PEO 5500: M.sub.n=5500 g/mol, determined via OH-titration; 50 wt.-% of PPO [0212] Potassium carbonate: K.sub.2CO.sub.3; anhydrous; volume-average particle size of 32.4 m, [0213] NMP: N-methylpyrrolidone, [0214] PESU: polyethersulfone (ULTRASON E 3010) [0215] PVP: polyvinylpyrrolidone; (Luvitec K40) [0216] PEG: polyethyleneglycol [0217] DMAc: dimethylacetamide

General Procedures

[0218] The viscosity number of the polymers is determined in a 1% solution in NMP at 25 C.

[0219] The isolation of the polymers is carried out by dripping a NMP solution of the polymers in demineralized water at room temperature (25 C.). The drop height is 0.5 m, the throughput is about 2.5 l/h. The beads obtained are then extracted with water (water throughput 160 l/h) at 85 C. for 20 h. The beads are dried at 150 C. for 24 h (hours) at reduced pressure (<100 mbar).

[0220] The number average molecular weights (M.sub.n) and the weight average molecular weights (M.sub.w) are determined via GPC in DMAc/LiBr with PMMA (poly(methylmethacrylate)) standards.

[0221] The incorporation rate (incorporation ratio) of PEG and other polyether units and TMH was determined by .sup.1H-NMR in CDCl.sub.3/TMS. In this case the signal intensity of the aliphatic PEG units is considered in relation to the intensity of the aromatic units of the polyarylether. This gives a value for the PEG fraction in mol-% which can be converted into %-by weight with the no molecular weights of the corresponding structured units.

[0222] The contact angle between the water and the surfaces of the films prepared from CDCl.sub.3-solution where obtained using a contact angle measuring instrument (Drop shape analysis system DSA 10 MK 2 from Krss GmbH, Germany). The smaller the contact angle is, the higher is the hydrophilicity of the films.

Example 1: PESU-TMH-co PEO 1

[0223] In a 4 liter glass reactor fitted with a thermometer, a gas inlet tube and a Dean-Stark-trap, 568.59 g (1.98 mol) of DCDPS, 301.33 g (1.98 mol) of TMH, 80.16 g (0.04 mol) Polyethyleneglycol 2000 and 304.06 g (2.20 mol) of potassium carbonate were suspended in 950 ml NMP in a nitrogen atmosphere.

[0224] The mixture was heated to 190 C. within one hour. In the following, the reaction time shall be understood to be the time during which the reaction mixture was maintained at 190 C. The water that was formed in the reaction was continuously removed by distillation.

[0225] After a reaction time of 7 hours, the reaction was stopped by the addition of 2050 ml NMP and cooling down to room temperature (within one hour). The potassium chloride formed in the reaction was removed by filtration. The time to filter the viscous solution in a pressure filter using N.sub.2-pressure of 4 bar and a filter plate with 5 m pore size was recorded. Results of the characterization are summarized in table 1.

Example 2: PESU-TMH-co PEO

[0226] In a 4 liter glass reactor fitted with a thermometer, a gas inlet tube and a Dean-Stark-trap, 568.58 g (1.98 mol) of DCDPS, 298.26 g (1.96 mol) of TMH, 120.24 g (0.06 mol) Polyethyleneglycol 2000 and 304.06 g (2.20 mol) of potassium carbonate were suspended in 950 ml NMP in a nitrogen atmosphere.

[0227] The mixture was heated to 190 C. within one hour. In the following, the reaction time shall be understood to be the time during which the reaction mixture was maintained at 190 C. The water that was formed in the reaction was continuously removed by distillation.

[0228] After a reaction time of 7 hours, the reaction was stopped by the addition of 2050 ml NMP and cooling down to room temperature (within one hour). The potassium chloride formed in the reaction was removed by filtration. The time to filter the viscous solution in a pressure filter using N.sub.2-pressure of 4 bar and a filter plate with 5 m pore size was recorded. Results of the characterization are summarized in table 1.

Example 3: PESU-TMH-co PEO

[0229] In a 4 liter glass reactor fitted with a thermometer, a gas inlet tube and a Dean-Stark-trap, 568.58 g (1.98 mol) of DCDPS, 292.16 g (1.92 mol) of TMH, 200.40 g (0.10 mol) Polyethyleneglycol 2000 and 304.06 g (2.20 mol) of potassium carbonate were suspended in 950 ml NMP in a nitrogen atmosphere.

[0230] The mixture was heated to 190 C. within one hour. In the following, the reaction time shall be understood to be the time during which the reaction mixture was maintained at 190 C. The water that was formed in the reaction was continuously removed by distillation.

[0231] After a reaction time of 7 hours, the reaction was stopped by the addition of 2050 ml NMP and cooling down to room temperature (within one hour). The potassium chloride formed in the reaction was removed by filtration. The time to filter the viscous solution in a pressure filter using N.sub.2-pressure of 4 bar and a filter plate with 5 m pore size was recorded. Results of the characterization are summarized in table 1.

Example 4: PESU-TMH-co-PEO-PPO-PEO

[0232] In a 4 liter glass reactor fitted with a thermometer, a gas inlet tube and a Dean-Stark-trap, 568.58 g (1.98 mol) of DCDPS, 302.79 g (1.99 mol) of TMH, 165.00 g (0.03 mol) PEO-PPO-PEO 5500 (50 wt % PPO) and 304.06 g (2.20 mol) of potassium carbonate were suspended in 950 ml NMP in a nitrogen atmosphere.

[0233] The mixture was heated to 190 C. within one hour. In the following, the reaction time shall be understood to be the time during which the reaction mixture was maintained at 190 C. The water that was formed in the reaction was continuously removed by distillation.

[0234] After a reaction time of 8 hours, the reaction was stopped by the addition of 2050 ml NMP and cooling down to room temperature (within one hour). The potassium chloride formed in the reaction was removed by filtration. The time to filter the viscous solution in a pressure filter using N.sub.2-pressure of 4 bar and a filter plate with 5 m pore size was recorded. Results of the characterization are summarized in table 1.

Comparative Example 5: PESU-co-PEO

[0235] In a 4 liter glass reactor fitted with a thermometer, a gas inlet tube and a Dean-Stark-trap, 574.32 g (2.00 mol) of DCDPS, 490.55 g (1.96 mol) of DHDPS, 80.16 g (0.04 mol) Polyethyleneglycol 2000 and 304.06 g (2.20 mol) of potassium carbonate were suspended in 950 ml NMP in a nitrogen atmosphere.

[0236] The mixture was heated to 190 C. within one hour. In the following, the reaction time shall be understood to be the time during which the reaction mixture was maintained at 190 C. The water that was formed in the reaction was continuously removed by distillation.

[0237] After a reaction time of 7 hours, the reaction was stopped by the addition of 2050 ml NMP and cooling down to room temperature (within one hour). The potassium chloride formed in the reaction was removed by filtration. The time to filter the viscous solution in a pressure filter using N.sub.2-pressure of 4 bar and a filter plate with 5 m pore size was recorded. Results of the characterization are summarized in table 1.

Comparative Example 6: PESU-co-PEO

[0238] In a 4 liter glass reactor fitted with a thermometer, a gas inlet tube and a Dean-Stark-trap, 574.32 g (2.00 mol) of DCDPS, 485.54 g (1.94 mol) of DHDPS, 120.24 g (0.06 mol) Polyethyleneglycol 2000 and 304.06 g (2.20 mol) of potassium carbonate were suspended in 950 ml NMP in a nitrogen atmosphere.

[0239] The mixture was heated to 190 C. within one hour. In the following, the reaction time shall be understood to be the time during which the reaction mixture was maintained at 190 C. The water that was formed in the reaction was continuously removed by distillation.

[0240] After a reaction time of 7 hours, the reaction was stopped by the addition of 2050 ml NMP and cooling down to room temperature (within one hour). The potassium chloride formed in the reaction was removed by filtration. The time to filter the viscous solution in a pressure filter using N.sub.2-pressure of 4 bar and a filter plate with 5 m pore size was recorded. Results of the characterization are summarized in table 1.

Comparative Example 7: PESU-co-PEO

[0241] In a 4 liter glass reactor fitted with a thermometer, a gas inlet tube and a Dean-Stark-trap, 574.32 g (2.00 mol) of DCDPS, 475.53 g (1.90 mol) of DHDPS, 200.40 g (0.10 mol) Polyethyleneglycol 2000 and 304.06 g (2.20 mol) of potassium carbonate were suspended in 950 ml NMP in a nitrogen atmosphere.

[0242] The mixture was heated to 190 C. within one hour. In the following, the reaction time shall be understood to be the time during which the reaction mixture was maintained at 190 C. The water that was formed in the reaction was continuously removed by distillation.

[0243] After a reaction time of 7 hours, the reaction was stopped by the addition of 2050 ml NMP and cooling down to room temperature (within one hour). The potassium chloride formed in the reaction was removed by filtration. The time to filter the viscous solution in a pressure filter using N.sub.2-pressure of 4 bar and a filter plate with 5 m pore size was recorded. Results of the characterization are summarized in table 1.

Comparative Example 8: PSU-Co-PEO

[0244] In a 4 liter glass reactor fitted with a thermometer, a gas inlet tube and a Dean-Stark-trap, 574.32 g (2.00 mol) of DCDPS, 447.44 (1.96 mol) Bisphenol A, 80.16 g (0.04 mol) of Polyethyleneglycol 2000 and 304.06 g (2.20 mol) of potassium carbonate were suspended in 950 ml NMP in a nitrogen atmosphere.

[0245] The mixture was heated to 190 C. within one hour. In the following, the reaction time shall be understood to be the time during which the reaction mixture was maintained at 190 C. The water that was formed in the reaction was continuously removed by distillation. After a reaction time of 10 hours, the reaction was stopped by the addition of 2050 ml NMP and cooling down to room temperature (within one hour). The potassium chloride formed in the reaction was removed by filtration. The time to filter the viscous solution in a pressure filter using N.sub.2-pressure of 4 bar and a filter plate with 5 m pore size was recorded for the different batches.

TABLE-US-00001 TABLE 1 Example Comp. Comp. Comp. Comp. Ex. 1 Ex. 2 Ex.3 Ex. 4 Ex 5 Ex. 6 Ex. 7 Ex. 8 Product PESU-TMH- PESU-TMH- PESU-TMH- PESU-TMH- co-PEO- PESU- PESU- PESU- PSU- co-PEO co-PEO co-PEO PPO-PEO co-PEO co-PEO co-PEO co-PEO V.N. [ml/g] 64.9 62.9 59.9 64.8 65.2 73.5 74.1 63.8 content 8.8 14.0 21.1 17.2 7.9 11.4 17.9 8.1 PEO/PPO [wt. %] Tg [ C.] 189 176 153 65/191 178 157 131 141 Contact 54 48 40 36 61 57 53 n.b. Angle [] Filtration 7 7.2 8.5 9 12.5 16.0 21.5 19 time [h]

[0246] Surprisingly, the solutions of the inventive polyarylethersulfone-polyalkylene oxide block copolymer (PPC) can be filtered much better than the ones of the comparative PESU-co-PEO products. At a given PEO-content, the inventive copolymers have much higher hydrophilicity, as can be seen from the contact angles.

Preparation of Membranes:

[0247] Membranes were prepared by adding 78 ml of NMP, 5 g of PVP and 17 g of polymer into a three neck flask equipped with a magnetic stirrer. This mixture is then heated under gentle stirring at 60 C. until a homogeneous clear viscous solution is obtained. The solution is degassed over night at room temperature. After that, the solution is re-heated at 60 C. for 2 h and casted onto a glass plate with a casting knife (300 microns) at 60 C. at a speed of 5 mm/min. The obtained film is then rest for 30 sec and subsequently immersed into a water bath at 25 C. for 10 min. After the membrane is detached from the glass plate, the membrane is carefully transferred into a water bath for 12 h. Afterwards, the membrane is transferred into a bath containing 250 ppm NaOCl at 50 C. for 4.5 h. The membrane is washed with water at 60 C. and a 0.5 weight-% solution of Na-bisulfit to remove active chlorine. A membrane having a dimension of at least 1015 cm size is obtained.

[0248] To test the pure water permeation (PWP) of the membranes, ultrapure water (salt-free water filtered by a Millipore UF-system) using a pressure cell with a diameter of 60 mm, is used. In a subsequent test a solution of different PEG standards is filtered at a pressure of 0.15 bar. By GPC-measurements of the feed and the permeate, the molecular weight cut-off (MWCO) is determined.

[0249] The gel fraction of the membranes was determined by dissolving 0.5 g of dry membrane material in 50 ml of NMP (24 h, room temperature, stirring). This solution was then filtered through a pre-weighed (m.sub.0) filter paper. The filter paper was tried in the vacuum for 24 h at 100 C. cooled to room temperature and weighed again (m.sub.g). The gel-content was calculated as:

Gel-Fraction=(m.sub.gm.sub.0)/m.sub.0*100

Reference Polymer for the Membrane Trials

Comparative Example 8: PESU-TMH

[0250] In a 4 liter glass reactor fitted with a thermometer, a gas inlet tube and a Dean-Stark-trap, 574.34 g (2.00 mol) of DCDPS, 304.38 g (2.00 mol) of TMH and 290.24 g (2.10 mol) of potassium carbonate were suspended in 950 ml NMP in a nitrogen atmosphere.

[0251] The mixture was heated to 190 C. within one hour. In the following, the reaction time shall be understood to be the time during which the reaction mixture was maintained at 190 C. The water that was formed in the reaction was continuously removed by distillation.

[0252] After a reaction time of eight hours, the reaction was stopped by the addition of 2050 ml NMP and cooling down to room temperature (within one hour). The potassium chloride formed in the reaction was removed by filtration. The viscosity number was 65.8 ml/g.

[0253] Furthermore, neat PESU having a viscosity number of 66 ml/g was used.

[0254] The results are shown in table 2.

TABLE-US-00002 TABLE 2 Comp. Comp. Comp. M1 M2 M3 M4 M5 PESU [g] 17 Comp. 17 Ex. 8 (PESU-TMH) [g] Ex. 1 (PESU-TMH-co-PEO) 17 [g] Comp. 17 Ex. 6 (PESU-PEO) [g] Ex. 3 (PESU-TMH-co-PEO) 17 [g] PVP [g] 5 5 5 5 5 NMP [g] 78 78 78 78 78 PWP [l/m.sup.2*h*bar] 630 330 690 870 950 MWCO [kD] 73 16 23 89 23 Gel-Fraction [wt %] 0 9 10 0 9

[0255] The membranes prepared from the new copolymers show excellent filtration performance. Surprisingly, the membranes are not completely soluble in NMP, indicating improved solvent resistance, which will be useful to filter produced water, containing organic contaminants.