Polymers for membranes

Abstract

Membrane comprising a block copolymer comprising polyarylene ether blocks and polyalkylene oxide blocks, wherein said polyalkylene oxide blocks comprise at least one polyethylene oxide segment and at least one segment of at least one polyalkylene oxide that is different from polyethylene oxide.

Claims

1. A process for making a block copolymer comprising a polyarylene ether block and a polyalkylene oxide block, wherein the polyalkylene oxide block comprises a polyethylene oxide segment and a polyalkylene oxide segment different from the polyethylene oxide segment; the process comprises: preparing a mixture of an aromatic bishalogeno compound and an aromatic bisphenol compound, or salts thereof, a polyalkylene oxide comprising a polyethylene oxide segment comprising a number average of 1.5 to 40 units of ethylene oxide per polyethylene oxide segment and a polyalkylene oxide segment different from the polyethylene oxide segment comprising a number average of 40 to 400 units of propylene oxide, butylene oxide, or tetrahydrofuran units per segment of the polyalkylene oxide that is diffirent, a solvent therefore, and a base; and reacting the mixture of the aromatic bishalogeno compound, the aromatic biphenol compound, or salts thereof in the presence of the polyalkylene oxide, the solvent, and the base by heating the mixture; continuously distilling the reacting mixture to remove any water being formed; and maintaining a constant level of the solvent in the reacting mixture.

2. The process of claim 1, wherein the constant level of the solvent is maintained in the reacting mixture by adding further solvent.

3. A process for making a block copolymer comprising a polyarylene ether block and a polyalkylene oxide block, wherein the polyalkylene oxide block comprises: (1) a polyethylene oxide segment comprising a number average of 1.5 to 40 units of ethylene oxide per ethylene oxide segment, and (2) a segment of a polyalkylene oxide that is different from polyethylene oxide comprising a number average of 40 to 400 units of propylene oxide, butylene oxide, or tetrahydrofuran units per segment of a polyalkylene oxide that is different; said process comprises: preparing a mixture of an aromatic bishalogeno compound and an aromatic bisphenol compound, or salts thereof, a polyalkylene oxide comprising a polyethylene oxide segment comprising a number average of 1.5 to 40 units of ethylene oxide and a segment of a polyalkylene oxide that is different from polyethylene oxide segment comprising a number average of 40 to 400 units of propylene oxide, butylene oxide, or tetrahydrofuran units per segment of the polyalylene oxide that is different, a solvent therefore, and a base; and reacting the mixture of the aromatic bishalogeno compound, the aromatic biphenol compound, or salts, thereof, in the presence of the polyalkylene oxide, the solvent, and the base, by heating the mixture; continuously distilling the reacting mixture to remove any water being formed; and maintaining a constant level of the solvent in the reacting mixture.

4. The process of claim 3, wherein the constant level of the solvent is maintained in the reacting mixture by adding further solvent.

5. The process of claim 3, wherein the polyalkylene oxide block comprises a number average in a range of 40 to 300 units of at least one selected from the group consisting of propyleneoxide, butyleneoxide and tetrahydrofuran.

6. The process of claim 3, wherein the polyalkylene oxide block comprises a number average in a range of 2 to 25 ethyleneoxide units per ethylene oxide segment.

7. The process of claim 3, wherein the polyalkylene oxide block comprises an ethyleneoxide segment at the terminal positions of the polyalkylene oxide block.

8. The process of claim 3, wherein the polyalkylene oxide block is of formula (I), formula (II) or formula (III):
R(OCH.sub.2CH.sub.2).sub.m(OCH.sub.2CH.sub.2CH.sub.2CH.sub.2).sub.n(OCH.sub.2CH.sub.2).sub.oO(I)
R(OCH.sub.2CH.sub.2).sub.m(OCH.sub.2CH(CH.sub.3)).sub.n(OCH.sub.2CH.sub.2).sub.oO(II),
R(OCH.sub.2CH.sub.2).sub.m(OCH.sub.2CH(CH.sub.2CH.sub.3)).sub.n(OCH.sub.2CH.sub.2).sub.oO(III), wherein R denotes a hydrogen , an aliphatic group, an aromatic group, or a chemical bond, a number average of m and o ffor the polyalkylene oxide block of formula (I), formula (II), or formula (III) bearing the same R in the block copolymer is independently in a range 2 to 25, and a number average of n for the polyalkylene oxide block of formula (I), formula (II) or formula (III) bearing the same R in the block copolymer is in a range of 40 to 300.

9. The process of claim 3, wherein the polyarylene ether block is of fornuila (IV): ##STR00009## wherein t, acid q are each independently 0, 1, 2 or 3, Q, T, and Y are each independently a chemical bond or a group selected from the group consisting of O, S, SO.sub.2, SO, CO, NN, and CR.sup.aR.sup.bwhere R.sup.a and R.sup.b are each independently a hydrogen atom, a C.sub.1-C.sub.12-alkyl group, a C.sub.1-C.sub.12-alkoxy group or a C.sub.6-C.sub.18-aryl group, where at least one of Q, T and Y is not O, and at least one of Q, T and Y is SO.sub.2, Ar, and Ar.sup.1 are each independently an arylene group comprising 6 to 18 carbon atoms, and D is a chemical bout or O.

10. The process of claim 9, wherein the polyarylene ether block is of formula (IVk): ##STR00010## wherein t is 1, q is 0, T and Y are each independently a SO.sub.2, Ar is 1,4-phenylene, and D is a chemical bond.

11. The process of claim 9, wherein the polyarylene ether block is of formula (IVk) ##STR00011## wherein t is 1, q is 0, T and Y are each independently a SO.sub.2, Ar is 1,4-phenylene, and D is O.

12. The process of claim 3, wherein the polyarylene ether is a polysulfone, a polyethersulfone, or a polyphenylenesulfone.

Description

EXAMPLES

(1) Abbreviations:

(2) DCDPS 4,4-Dichlorodiphenylsulfone

(3) DHDPS 4,4-Dihydroxydiphenylsulfone

(4) NMP N-methylpyrrolidone

(5) DMAc Dimethylacetamide

(6) PWP pure water permeation

(7) MWCO molecular weight cutoff

(8) The viscosity of copolymers was measured as a 1% by weight solution of the copolymer in NMP at 25 C. according to DIN EN ISO 1628-1.

(9) Copolymers were isolated from their solution by precipitation of solutions of the copolymers in water at room temperature (height of spray reactor 0.5 m, flux: 2.5 l/h). The so obtained beads were then extracted with water at 85 C. for 20 hours (water flow 160 l/h). The beads were then dried to a water content of less than 0.1% by weight.

(10) The molecular weight distribution and the average molecular weight of the copolymers were determined by GPC measurements in DMAc.

(11) GPC-measurements were done using Dimethylacetamide/0.5 wt.-% LiBr as eluent. The concentration of the polymer solution was 4 mg/ml. After filtration (pore size 0.2 m), 100 l of this solution was injected in the GPC system. For the separation 4 different columns (heated to 80 C.) were used (GRAM pre-column, GRAM 30A, GRAM 1000A, GRAM 1000A, separation material: polyester copolymers). The system was operated with a flow rate of 1 ml/min. As detection system a DRI Agilent 1100 was used.

(12) The calibration was done with PMMA-standards with molecular weights (Mn) from 800 to 1820000 g/mol.

(13) The content of polyalkyleneoxide in total or of polyethyleneoxide, polypropyleneoxide or polytetrahydrofurane in the block copolymer was determined using .sup.1H-NMR in CDCl.sub.3. The signal intensity of resonance signals for H-atoms of polyalkylene groups was compared to the signal intensity of resonance signals for H-atoms of aromatic groups comprised in polyarylene ether blocks. This comparison yields the ratio of polyalkylene oxide to polyarylene ether that can be can be used to calculate the content of polyalkylene oxide in the copolymer by weight.

(14) The ratio of polyalkylene oxide incorporated in the block copolymer is the ratio of the mass of polyalkylene oxide comprised in the block copolymer (determined by NMR, see above) to the mass of polyalkylene oxide used as a starting material.

(15) The glass transition temperature of the products was determined by DSC analysis. All DSC-measurements were done using a DSC 2000 of TA Instruments at a heating rate of 20 k/min. About 5 mg material were placed in an Aluminum vessel and sealed. In the first run, the samples were heated to 250 C., rapidly cooled to 100 C. and then in the second run heated to 250 C. The Tg-values given were determined in the second run.

(16) The contact angles between the water and the surface of the films prepared by melt pressing the polymer samples were obtained using a contact angle measuring instrument (Drop shape analysis system DSA 10 MK 2 from Krss GmbH Germany).

(17) For the contact angle measurement a sample of 2 cm.sup.2 was fixed on an object plate. A water drop was put on the samples with a microliter gun. The shape of the droplet was recorded by a CCD-camera. An image recognition software analyzed the contact angle.

(18) Preparation of Copolymers:

Comparative Example 1

PESU-PPO-Copolymer

(19) In a 4 liter glass reactor fitted with a thermometer, a gas inlet tube and a Dean-Stark-trap, 430.62 g of DCDPS, 367.75 g of DHDPS, 136.83 g of polypropylene oxide with a number average molecular mass Mn of 4561 g/mol and 217.68 g of potassium carbonate with a volume average particle size of 32.4 m were suspended in 789.5 ml NMP in a nitrogen atmosphere. 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.

(20) The water that was formed in the reaction was continuously removed by distillation. The solvent level inside the reactor was maintained at a constant level by addition of further NMP.

(21) After a reaction time of eight hours, the reaction was stopped by addition of 1460 ml of NMP with a temperature of 23 C. Nitrogen was bubbled through the mixture for one hour with a rate of 20 l/h and the mixture was let to cool to room temperature. The potassium chloride formed in the reaction was removed by filtration.

Comparative Example 2

PESU-pTHF-Copolymer

(22) In a 4 liter glass reactor fitted with a thermometer, a gas inlet tube and a Dean-Stark-trap, 574.16 g of DCDPS, 475.32 g of DHDPS, 200 g of polytetrahydrofurane with a number average molecular mass Mn of 2000 g/mol and 297.15 g of potassium carbonate with a volume average particle size of 32.4 m were suspended in 1053 ml NMP in a nitrogen atmosphere.

(23) 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.

(24) The water that was formed in the reaction was continuously removed by distillation. The solvent level inside the reactor was maintained at a constant level by addition of further NMP.

(25) After a reaction time of six hours, the reaction was stopped by addition of 1947 ml of NMP with a temperature of 23 C. Nitrogen was bubbled through the mixture for one hour with a rate of 20 l/h and the mixture was let to cool to room temperature. The potassium chloride formed in the reaction was removed by filtration.

Example 3

PESU-(PEO-PPO-PEO)-Copolymer

(26) In a 4 liter glass reactor fitted with a thermometer, a gas inlet tube and a Dean-Stark-trap, 430.62 g of DCDPS, 364.00 g of DHDPS, 90 g of a segmented copolymer with the structure PEO-PPO-PEO with a number average molecular mass Mn of 2001 g/mol and with a number average of two units of ethylene oxide per PEO segment and 217.68 g of potassium carbonate with a volume average particle size of 32.4 m were suspended in 790 ml NMP in a nitrogen atmosphere.

(27) 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.

(28) The water that was formed in the reaction was continuously removed by distillation. The solvent level inside the reactor was maintained at a constant level by addition of further NMP.

(29) After a reaction time of six hours, the reaction was stopped by addition of 1400 ml of NMP with a temperature of 23 C. Nitrogen was bubbled through the mixture for one hour with a rate of 20 l/h and the mixture was let to cool to room temperature. The potassium chloride formed in the reaction was removed by filtration.

Example 4

PESU-(PEO-PPO-PEO)-Copolymer

(30) In a 4 liter glass reactor fitted with a thermometer, a gas inlet tube and a Dean-Stark-trap, 430.62 g of DCDPS, 367.75 g of DHDPS, 87 g of a segmented polymer with the structure PEO-PPO-PEO with a number average molecular mass Mn of 2900 g/mol and with a number average of six units of ethylene oxide per PEO segment and 217.68 g of potassium carbonate with a volume average particle size of 32.4 m were suspended in 790 ml NMP in a nitrogen atmosphere.

(31) 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.

(32) The water that was formed in the reaction was continuously removed by distillation. The solvent level inside the reactor was maintained at a constant level by addition of further NMP.

(33) After a reaction time of six hours, the reaction was stopped by addition of 1400 ml of NMP with a temperature of 23 C. Nitrogen was bubbled through the mixture for one hour with a rate of 20 l/h and the mixture was let to cool to room temperature. The potassium chloride formed in the reaction was removed by filtration.

Example 5

PESU-(PEO-pTHF-PEO)-Copolymer

(34) In a 4 liter glass reactor fitted with a thermometer, a gas inlet tube and a Dean-Stark-trap, 574.16 g of DCDPS, 485.33 g of DHDPS, 144 g of a segmented polymer with the structure PEO-pTHF-PEO with a number average molecular mass Mn of 2404 g/mol and with a number average of five units of ethylene oxide per PEO segment and 290.24 g of potassium carbonate with a volume average particle size of 32.4 m were suspended in 1333 ml NMP in a nitrogen atmosphere.

(35) 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.

(36) The water that was formed in the reaction was continuously removed by distillation. The solvent level inside the reactor was maintained at a constant level by addition of further NMP.

(37) After a reaction time of six hours, the reaction was stopped by addition of 1667 ml of NMP with a temperature of 23 C. Nitrogen was bubbled through the mixture for one hour with a rate of 20 l/h and the mixture was let to cool to room temperature. The potassium chloride formed in the reaction was removed by filtration.

Example 6

PESU-(PEO-pTHF-PEO)-Copolymer

(38) In a 4 liter glass reactor fitted with a thermometer, a gas inlet tube and a Dean-Stark-trap, 520.94 g of DCDPS, 431.13 g of DHDPS, 218.05 g of a segmented polymer with the structure PEO-pTHF-PEO with a number average molecular mass Mn of 2404 g/mol and with a number average of five units of ethylene oxide per PEO segment and 269.53 g of potassium carbonate with a volume average particle size of 32.4 m were suspended in 1209 ml NMP in a nitrogen atmosphere.

(39) 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.

(40) The water that was formed in the reaction was continuously removed by distillation. The solvent level inside the reactor was maintained at a constant level by addition of further NMP.

(41) After a reaction time of six hours, the reaction was stopped by addition of 1511 ml of NMP with a temperature of 23 C. Nitrogen was bubbled through the mixture for one hour with a rate of 20 l/h and the mixture was let to cool to room temperature. The potassium chloride formed in the reaction was removed by filtration.

Example 7

PESU-(PEO-pTHF-PEO)-Copolymer

(42) In a 4 liter glass reactor fitted with a thermometer, a gas inlet tube and a Dean-Stark-trap, 574.16 g of DCDPS, 474.32 g of DHDPS, 372 g of a segmented polymer with the structure PEO-pTHF-PEO with a number average molecular mass Mn of 3720 g/mol and with a number average of 22 units of ethylene oxide per PEO segment and 297.15 g of potassium carbonate with a volume average particle size of 32.4 m were suspended in 1333 ml NMP in a nitrogen atmosphere.

(43) 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.

(44) The water that was formed in the reaction was continuously removed by distillation. The solvent level inside the reactor was maintained at a constant level by addition of further NMP.

(45) After a reaction time of six hours, the reaction was stopped by addition of 1667 ml of NMP with a temperature of 23 C. Nitrogen was bubbled through the mixture for one hour with a rate of 20 l/h and the mixture was let to cool to room temperature. The potassium chloride formed in the reaction was removed by filtration.

Comparative Example 8

PESU-PEO-Copolymer

(46) In a 4 liter glass reactor fitted with a thermometer, a gas inlet tube and a Dean-Stark-trap, 574.16 g of DCDPS, 475,32 g of DHDPS, 205 g PEO with a number average molecular mass M.sub.n of 2050 g/mol and 290.24 g of potassium carbonate with a volume average particle size of 32.4 m were suspended in 1053 ml NMP in a nitrogen atmosphere.

(47) 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.

(48) The water that was formed in the reaction was continuously removed by distillation. The solvent level inside the reactor was maintained at a constant level by addition of further NMP.

(49) After a reaction time of six hours, the reaction was stopped by addition of 1947 ml of NMP with a temperature of 23 C. Nitrogen was bubbled through the mixture for one hour with a rate of 20 l/h and the mixture was let to cool to room temperature. The potassium chloride formed in the reaction was removed by filtration.

(50) TABLE-US-00001 TABLE 1 Analytical data of block copolymers prepared in experiments 1 to 7 1 2 3 4 5 6 7 8 viscosity number [ml/g] 47.7 33.9 61.0 85.3 71.9 73.6 60.2 75.4 PEO content (% by 0.5 1.9 2.3 3.5 13.7 18.2 weight) PPO content (% by 9.7 11.2 9.0 weight) pTHF content (% by 7.0 10.6 16 12.6 weight) Ratio incorp. polyalkylene 58 38 98 98 95 92 90 99 oxide [%] Mw/Mn 3.1 2.9 2.8 2.9 3.0 2.8 2.9 2.9 Tg [ C.] 73/ n.d./ 67/ 66/ 66/ 67/ 67/ 129 188 165 211 179 197 189 142 contact angle with water 67 69 38 31 35 31 27 56 []

(51) Block copolymers according to the invention showed a higher viscosity number than comparative examples. The ratio of polyalkyleneoxide incorporated into the block copolymer over the polyalkyleneoxide use as the starting material is very high.

(52) Block copolymers according to the invention showed a reduced contact angle with water over comparative examples.

(53) Block copolymers according to the invention had two distinct glass transition temperatures and show a phase separated structure.

(54) Block copolymers according to the invention showed high upper glass transition temperatures.

(55) Preparation of Membranes

Example M1

Preparation of PESU Flat Sheet Membranes

(56) Into a three neck flask equipped with a magnetic stirrer 80 ml of N-methylpyrrolidone (NMP), 5 g of polyvinylpyrrolidone (PVP, Luvitec K40) and 15 g of polyethersulfone (PESU, Ultrason E 6020P) were added. The mixture was heated under gentle stirring at 60 C. until a homogeneous clear viscous solution was obtained. The solution was degassed overnight at room temperature. 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 bath at 25 C. for 10 minutes.

(57) After the membrane has detached from the glass plate, the membrane was carefully transferred into a water bath for 12 h. Afterwards the membrane was transferred into a bath containing 2000 ppm NaOCl at 50 C. for 4.5 h to remove PVP. After that process the membrane was washed with water at 60 C. and then one time with a 0.5 wt.-% solution of NaBisulfite to remove active chlorine. After several washing steps with water the membrane was stored wet until characterization started.

(58) A flat sheet continuous film with micro structural characteristics of UF membranes having dimension of at least 1015 cm size was obtained. The membrane comprised a top thin skin layer (1-3 microns) and a porous layer underneath (thickness: 100-150 microns).

Example M2

Flat Sheet Membranes Based on Copolymer 1

(59) Into a three neck flask equipped with a magnetic stirrer 80 ml of N-methylpyrrolidone (NMP), 5 g of polyvinylpyrrolidone (PVP, Luvitec K40) and 15 g of the block copolymer obtained in example 1 were added. The mixture was heated under gentle stirring at 60 C. until a homogeneous clear viscous solution was obtained. The solution was degassed overnight at room temperature. 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 bath at 25 C. for 10 minutes.

(60) After the membrane has detached from the glass plate, the membrane was carefully transferred into a water bath for 12 h. Afterwards the membrane was transferred into a bath containing 2000 ppm NaOCl at 50 C. for 4.5 h to remove PVP. After that process the membrane was washed with water at 60 C. and then one time with a 0.5 wt.-% solution of NaBisulfite to remove active chlorine. After several washing steps with water the membrane was stored wet until characterization started.

(61) A flat sheet continuous film with micro structural characteristics of UF membranes having dimension of at least 1015 cm size was obtained. The membrane comprised a top thin skin layer (1-3 microns) and a porous layer underneath (thickness: 100-150 microns).

Example M3

Flat Sheet Membranes Based on Copolymer 4

(62) Into a three neck flask equipped with a magnetic stirrer 80 ml of N-methylpyrrolidone (NMP), 5 g of polyvinylpyrrolidone (PVP, Luvitec K40) and 15 g of the block copolymer obtained in example 46 were added. The mixture was heated under gentle stirring at 60 C. until a homogeneous clear viscous solution was obtained. The solution was degassed overnight at room temperature. 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 bath at 25 C. for 10 minutes.

(63) After the membrane has detached from the glass plate, the membrane was carefully transferred into a water bath for 12 h. Afterwards the membrane was transferred into a bath containing 2000 ppm NaOCl at 50 C. for 4.5 h to remove PVP. After that process the membrane was washed with water at 60 C. and then one time with a 0.5 wt.-% solution of NaBisulfite to remove active chlorine. After several washing steps with water the membrane was stored wet until characterization started.

(64) A flat sheet continuous film with micro structural characteristics of UF membranes having dimension of at least 1015 cm size was obtained. The membrane comprised a top thin skin layer (1-3 microns) and a porous layer underneath (thickness: 100-150 microns).

Example M4

Flat Sheet Membranes Based on Copolymer 6

(65) Into a three neck flask equipped with a magnetic stirrer 80 ml of N-methylpyrrolidone (NMP), 5 g of polyvinylpyrrolidone (PVP, Luvite K40) and 15 g of the block copolymer obtained in example 6 were added. The mixture was heated under gentle stirring at 60 C. until a homogeneous clear viscous solution was obtained. The solution was degassed overnight at room temperature. 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 bath at 25 C. for 10 minutes.

(66) After the membrane has detached from the glass plate, the membrane was carefully transferred into a water bath for 12 h. Afterwards the membrane was transferred into a bath containing 2000 ppm NaOCl at 50 C. for 4.5 h to remove PVP. After that process the membrane was washed with water at 60 C. and then one time with a 0.5 wt.-% solution of NaBisulfite to remove active chlorine. After several washing steps with water the membrane was stored wet until characterization started.

(67) A flat sheet continuous film with micro structural characteristics of UF membranes having dimension of at least 1015 cm size was obtained. The membrane comprised a top thin skin layer (1-3 microns) and a porous layer underneath (thickness: 100-150 microns).

Example M5

Flat Sheet Membranes Based on Copolymer 8

(68) Into a three neck flask equipped with a magnetic stirrer 80 ml of N-methylpyrrolidone (NMP), 5 g of polyvinylpyrrolidone (PVP, Luvitec K40) and 15 g of the block copolymer obtained in example 46 were added. The mixture was heated under gentle stirring at 60 C. until a homogeneous clear viscous solution was obtained. The solution was degassed overnight at room temperature. 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 bath at 25 C. for 10 minutes.

(69) After the membrane has detached from the glass plate, the membrane was carefully transferred into a water bath for 12 h. Afterwards the membrane was transferred into a bath containing 2000 ppm NaOCl at 50 C. for 4.5 h to remove PVP. After that process the membrane was washed with water at 60 C. and then one time with a 0.5 wt.-% solution of NaBisulfite to remove active chlorine. After several washing steps with water the membrane was stored wet until characterization started.

(70) A flat sheet continuous film with micro structural characteristics of UF membranes having dimension of at least 1015 cm size was obtained. The membrane comprised a top thin skin layer (1-3 microns) and a porous layer underneath (thickness: 100-150 microns).

(71) Membrane Characterization:

(72) Using a pressure cell with a diameter of 60 mm, the pure water permeation of the membranes was tested using ultrapure water (salt-free water, additionally filtered by a Millipore UF-system). In a subsequent test, a solution of different PEG-Standards was filtered at a pressure of 0.15 bar. By GPC-measurement of the feed and the permeate, the molecular weight cut-off (MWCO) was determined. The data obtained is summarized in table 2.

(73) To simulate thermal stress occuring during steam sterilization, the membranes were put into a preheated oven set at 120 C. for 5 minutes. The shrinkage of the membranes with respect to initial sample size (40 mm*40 mm) and the appearance are also given in table 2.

(74) TABLE-US-00002 TABLE 2 Characterization of membranes obtained in examples M1 to M5 M1 M2 M5 (refer- (refer- (refer- Sample ence) ence) M3 M4 ence) PWP 490 >2500 850 940 620 [l/m.sup.2*h*bar] (defects) MWCO 90 >1000 100 100 95 [kg/mol] Shrinkage 5 >50, 12 9 27 [%] wrinkled

(75) The membranes comprising block copolymers useful according to the invention show higher water permeability at a comparable or slightly improved separation performance than the reference membrane. Furthermore, the membranes comprising copolymers useful according to the invention show much higher thermal stability than other hydrophilic copolymers.