NEW COPOLYMERS SUITABLE FOR MAKING MEMBRANES

Abstract

Copolymer comprising polyarylene ether blocks and hydrophilic-hydrophobic blocks, wherein said hydrophilic-hydrophobic blocks comprise polyisobutene blocks.

Claims

1. A copolymer comprising polyarylene ether blocks and hydrophilic-hydrophobic blocks, wherein said hydrophilic-hydrophobic blocks comprise polyisobutene blocks.

2. The copolymer according to claim 1, wherein said hydrophilic-hydrophobic blocks comprise polyisobutene blocks with terminal ether groups.

3. The copolymer according to claim 1, wherein said hydrophilic-hydrophobic blocks comprise polyisobutene blocks with terminal phenolic ether groups.

4. The copolymer according to claim 1, wherein said hydrophilic-hydrophobic blocks comprise polyisobutene blocks with terminal phenolic ether groups and wherein said phenolic ether groups are etherified with polyalkyleneoxides.

5. The copolymer according to claim 2, wherein said ether groups are obtained by alkoxylation of a hydroxy terminated polyisobutene with ethylene oxide or propylene oxide or mixtures thereof.

6. The copolymer according to claim 1, wherein said hydrophilic-hydrophobic blocks comprise structural units according to formula I ##STR00019## with n=2 to 1000.

7. The copolymer according to claim 1, wherein said hydrophilic-hydrophobic blocks comprise blocks according to formula (II) ##STR00020## wherein n=2 to 1000; m=1 to 300; and wherein said blocks are at least partly covalently bound to polyarylene ether blocks.

8. The copolymer according to claim 1, having a structure (III) ##STR00021## wherein n=2 to 1000; m=1 to 300; and p=0.003 to 0.25.

9. A process for making the copolymer according to claim 1, wherein aromatic bishalogeno compounds and aromatic biphenols or salts thereof are reacted in the presence of at least one suitable base and in the presence of suitable hydrophilic-hydrophobic block copolymers comprising polyisobutene blocks.

10. A membrane comprising a block copolymer comprising polyarylene ether blocks and hydrophilic-hydrophobic blocks, wherein said hydrophilic-hydrophobic blocks comprise polyisobutene blocks.

11. The membrane according to claim 10, wherein said hydrophilic-hydrophobic blocks comprise polyisobutene blocks with terminal ether groups.

12. The membrane according to claim 10, wherein said hydrophilic-hydrophobic blocks comprise polyisobutene blocks with terminal phenolic ether groups.

13. The membrane according to claim 10, wherein said hydrophilic-hydrophobic blocks comprise polyisobutene blocks with terminal phenolic ether groups and wherein said phenol groups are etherified with polyalkyleneoxides.

14. The membrane according to claim 11, wherein said ether groups are obtained by alkoxylation with ethylene oxide or propylene oxide or mixtures thereof.

15. The membrane according to claim 10, wherein said hydrophilic-hydrophobic blocks comprise structural units according to formula I ##STR00022## with n=2 to 1000.

16. The membrane according to claim 10, wherein said hydrophilic-hydrophobic blocks comprise blocks according to formula (II) ##STR00023## wherein n=2 to 1000; m=1 to 300; and wherein said blocks are at least partly covalently bound to polyarylene ether blocks.

17. The membrane according to claim 10, wherein said copolymers have the general having a structure (III) ##STR00024## wherein n=2 to 1000; m=1 to 300; and p=0.003 to 0.25.

18. The membrane according to claim 10, wherein said hydrophilic-hydrophobic blocks are obtained by a process comprising: a) polymerization of isobutene or an isobutene-containing monomer mixture in the presence of a Lewis acid and of an initiator, b) termination of the polymerization with a mixture of at least one phenol and at least one Lewis acid and/or at least one Brnsted acid and c) derivatization of the terminal phenol groups by alkoxylation.

19. The membrane according to claim 10, wherein said polyarylene ether blocks correspond to formula IV ##STR00025## with the following definitions: t, q: each independently 0, 1, 2 or 3, Q, T, Y: each independently a chemical bond or group selected from O, S, SO.sub.2, SO, CO, NN, CR.sup.aR.sup.b where R.sup.a and R.sup.b are each independently a hydrogen atom or a C.sub.1-C.sub.12-alkyl, C.sub.1-C.sub.12-alkoxy or 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, and Ar, Ar.sup.1: each independently an arylene group having from 6 to 18 carbon atoms.

20. The membrane according to claim 10, wherein said polyarylene ether is a polysulfone, polyethersulfone or polyphenylenesulfone.

21. The membrane according to claim 10, comprising said block copolymer in an amount of 0.01% by weight to 100% by weight.

22. The membrane according to claim 10, wherein said membrane is a UF, MF, RO, FO or NF membrane.

23. A process for filtering water, comprising contacting water with the membrane according to claim 10.

24. A membrane element comprising membranes according to claim 10.

25. A membrane module comprising membranes according to claim 10.

26. A filtration system comprising membrane modules according to claim 25.

Description

EXAMPLES

Abbreviations

[0392] DCDPS 4,4-Dichlorodiphenylsulfone [0393] DHDPS 4,4-Dihydroxydiphenylsulfone [0394] NMP N-methylpyrrolidone [0395] DMAc Dimethylacetamide [0396] PWP pure water permeation [0397] MWCO molecular weight cutoff [0398] DMF dimethylformamide

[0399] 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.

[0400] 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.

[0401] The molecular weight distribution and the average molecular weight of the copolymers were determined by GPC measurements in DMAc.

[0402] 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.

[0403] The calibration was done with PMMA-standards with molecular weights (Mn) from 800 to 1820000 g/mol.

[0404] The content of polyisobutene and of polyalkyleneoxide in the block copolymer was determined using .sup.1H-NMR in CDCl.sub.3. The signal intensity of resonance signals for H-atoms of polyisobutene and 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 or polyisobutene to polyarylene ether that can be can be used to calculate the content of polyalkylene oxide and polyisobutene in the copolymer by weight.

[0405] The ratio of polyisobutene and polyethyleneoxide 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.

[0406] 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.

[0407] 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).

[0408] 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.

[0409] For determining the flexibility and the hydrophilicity of the copolymers obtained, a 20% by weight solution of the respective copolymer in DMF was applied onto a glass surface using a casting knife to obtain a coating with a thickness of 300 m. The solvent was left to evaporate and the polymeric films obtained were left to stand for 12 hours at room temperature and 12 hours at 80 C. and 100 mbar. The polymeric films were removed from the glass surface and extracted for 16 hours using water with a temperature of 85 C. The content of organic solvent in the polymeric films so obtained was then below 0.1% by weight (determined by 1H-NMR).

[0410] The polymeric films were then dried for eight hours at 80 C. and a pressure of 100 mbar. Five tensile test samples were cut from the films using a die-cutter to obtain test specimen of the type 5A (ISO 527-2). The tensile strength of the films was determined at an elongation rate of 5 mm/min to determine the elongation at break. The numbers given below are the average values of 5 tests per polymer film.

[0411] To determine the hydrophilicity, samples prepared as described above were stored in demineralized water for five days. The samples were then wiped dry and the weight of the stored samples was determined. The water uptake was calculated relative to the weight of the sample prior to the storage in water.

Example 1

Preparation of Phenol Terminated Polyisobutene: Continuous Polymerization of Isobutene and In Situ Termination with Phenol in a Milli-Reactor

[0412] Liquid isobutene (0.8 mol/h) was mixed continuously with a solution of 1-butyl chloride (2.63 mol/h), phenyltriethoxysilane (10 mmol/h) and 1,3-dicumyl chloride (18 mmol/h) in a micro-mixer, and subsequently mixed homogeneously with a solution of 1-butyl chloride (2.62 mol/h) and TiCl.sub.4 (39 mmol/h) in a second micro-mixer at reaction temperature. The reaction solution formed was subsequently pumped through a temperature-controlled reaction capillary made of Hastelloy (internal diameter 4 mm, length 27 m) with a defined, constant flow rate of 700 g/h. In a third micro-mixer, the polymer solution formed was mixed continuously at ambient temperature with a mixture of phenol (0.5 mol/h), 1-butyl chloride (4.32 mol/h) and aluminum trichloride (50.2 mmol/h) and supplied to a 2 l reaction flask for 30 min. After stirring at room temperature for 2 hours, the reaction was terminated by addition of methanol. The solution was washed three times with methanol/water (80/20) mixture and the hexane phase dried over sodium sulfate, filtered and concentrated by rotary evaporation at 120 C./10 mbar.

[0413] GPC analysis (polystyrene standard, result converted to polyisobutene, ERC-RI-101 detector, tetrahydrofuran eluent, flow rate: 1.2 ml/min): Mn=2200 g/mol, Mw=2750 g/mol, PDI=1.25 1H FT NMR (500 MHz, 16 scans, CD.sub.2Cl.sub.2)

[0414] Aromatic starter in polymer: 7.38 ppm, 1H, s; 7.15 ppm, 3H, mp; phenol functionalization: 7.22 ppm, 2H, d; 6.74 ppm, 2H, d.

[0415] Mn from 1H-NMR: 1760 g/mol

Example 2

Preparation of PEO-polyisobutene-PEO

[0416] 7.4 g of potassium tert.-butylate were dissolved in 760 g of the phenol terminated polyisobutene obtained in example 1. The tert.-butanol that was formed was removed by distillation at 130 C. and 50 mbar. 700 g of the mixture obtained was filled into a 2 liter reactor and heated to 100 C. To the reactor, ethylene oxide was added until the pressure inside the reactor was 5 to 6 bar. This pressure was maintained at a constant level by constant addition of ethylene oxide over 8 hours. After eight hours an amount of 730 g of ethylene oxide was consumed. The reactor was cooled to ambient temperature and the pressure was released. The product mixture was dissolved in 2 l of n-hexane and washed three times with 1 l of hydrochloric acid (5% by weight in water) and 1 l of demineralized water. The product was dried over sodium sulfate. The solvent was removed at 120 C. and 5 mbar to obtain 1200 g of polymer.

[0417] .sup.1H-NMR: (500 MHz, 16 scans, CD.sub.2Cl.sub.2): 7.25 d; 6.75 d; 3.75-3.25 multiplet; 1.8 s; 1.5 s; 1.2 s/d; 0.8 s.

[0418] M.sub.n (from NMR): 3070 g/mol

[0419] According to the 1H-NMR, the product comprised an average of 39 units of isobutene (ca. 2200 g/mol) and two blocks with an average of 11 units of von ethylene oxide (ca. 500 g/mol).

Example 3

[0420] In a 4 liter glass reactor fitted with a thermometer, a gas inlet tube and a Dean-Stark-trap, 574.16 g of DCDPS, 490.33 g of DHDPS, 70.4 g of the phenol terminated polyisobutene obtained in example 1 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.

[0421] 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.

[0422] 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.

[0423] After a reaction time of eight 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 4

[0424] 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, 105.6 g of the phenol terminated polyisobutene obtained in example 1 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.

[0425] 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.

[0426] 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.

[0427] After a reaction time of eight 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 5

[0428] In a 4 liter glass reactor fitted with a thermometer, a gas inlet tube and a Dean-Stark-trap, 574.16 g of DCDPS, 490.33 g of DHDPS, 122.0 g of the PEO terminated polyisobutene obtained in example 2 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.

[0429] 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.

[0430] 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.

[0431] After a reaction time of eight 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

[0432] In a 4 liter glass reactor fitted with a thermometer, a gas inlet tube and a Dean-Stark-trap, 574.16 g of DCDPS, 474.53 g of DHDPS, 183.0 g of the phenol terminated polyisobutene obtained in example 1 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.

[0433] 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.

[0434] 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.

[0435] After a reaction time of eight 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 7

[0436] Commercially available polyethersulfone with a viscosity number of 65.0 ml/g.

TABLE-US-00001 TABLE 1 Analytical data of block copolymers prepared in experiments 3 to 7 3 4 5 6 7 viscosity number [ml/g] 62.1 63.3 75.2 75.4 65 PIB content (% by 6.8 9.7 6.3 9.0 n/a weight) Mw [kg/mol] (GPC) 67.1 68.5 75.1 76.3 62.7 Tg [ C.] 219 218 212 209 226 Elongation at Break [%] 56 78 62 85 23 Water Uptake [% by 1.4 1.4 5.1 7.2 1.8 weight]

[0437] Block copolymers according to the invention showed an improved elongation at break over comparative examples.

Examples M1 to M5

Preparation of PESU Flat Sheet Membranes

[0438] Into a three neck flask equipped with a magnetic stirrer, 75 g of N-methylpyrrolidone (NMP), 5 g of polyvinylpyrrolidone (Mw=1.3*10.sup.6 g/mol, Kollidon K90) and 20 g of a copolymer according to examples 3 to 7 were added. The composition of the membranes prepared is given in table 2. The mixture was kept at 60 C. under gentle stirring until a homogeneous clear viscous solution was obtained. The solution was degassed overnight at room temperature at a pressure of 100 mbar. After that the membrane solution was reheated at 60 C. for 2 hours and casted onto a glass plate with a casting knife (200 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.

[0439] After the membrane has detached from the glass plate, the membrane was carefully transferred into a water bath for 24 h. Afterwards the membrane was transferred into a bath containing 2500 ppm NaOCl at 60 C. for 2 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.

[0440] 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).

Membrane Characterization:

[0441] Using a pressure cell with a diameter of 60 mm, the pure water permeation (PWP) 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.

TABLE-US-00002 TABLE 2 Characterization of membranes obtained in examples M1 to M5 Sample M1 M2 M3 M4 M5 Polymer 3 4 5 6 7 PWP 890 930 1350 1500 750 [l/m.sup.2 * h * bar] MWCO 86 105 94 92 88

[0442] The membranes comprising block copolymers according to the invention show higher water permeability than reference membranes. Furthermore, the membranes comprising copolymers according to the invention show high tensile strengths and elongation at break.