MEMBRANES FOR LIQUID TREATMENT

Abstract

The invention concerns the field of polymer chemistry and relates to membranes, such as those that can be used, for example, for the preparation of aqueous solutions using microfiltration or ultrafiltration.

The object of the present invention is to specify membranes which have improved anti-fouling properties and sliding friction properties.

The object is attained with membranes comprised at least predominantly of multiblock copolymers of the general formula (1)

##STR00001##

where X=connection point E=C.sub.2 to C.sub.4 alkyl ether A=other block component not containing silicone R=C.sub.1 to C.sub.4 alkyl radical and/or phenyl radical m=1<m<500 n=0≤n<100 o=1<o<10 p=1<p<10 z=1<z<25, the molar ratio of the silicone-containing block component and the other block component A in the multiblock copolymer is between 5:1 and 1:5, and wherein the silicon-containing block components are predominantly arranged at the surface of the membranes.

Claims

1. Membranes for liquid treatment, comprised at least predominantly of multiblock copolymers of the general formula (1) ##STR00006## where X=connection point E=C.sub.2 to C.sub.4 alkyl ether A=other block component not containing silicone R=C.sub.1 to C.sub.4 alkyl radical and/or phenyl radical m=1<m<500 n=0≤n<100 o=1<o<10 p=1<p<10 z=1<z<25, the molar ratio of the silicone-containing block component and the other block component A in the multiblock copolymer is between 5:1 and 1:5, and wherein the silicon-containing block components are predominately arranged at the surface of the membranes.

2. The membranes according to claim 1 in which the membranes are comprised 60 to 100 wt %, more advantageously 80 to 100 wt %, of the multiblock copolymers according to the formula (1).

3. The membranes according to claim 1 in which the multiblock copolymers according to the formula (1) comprise at least one silicone-containing block component and at least one other, non-silicone-containing block component A.

4. The membranes according to claim 3 in which polydimethylsiloxane, polydiphenylsiloxane, polymethylphenylsiloxane, poly(alkyl ether)-polysiloxane copolymers or mixtures of these polymers are present as silicone-containing block component.

5. The membranes according to claim 3 in which the silicone-containing block components comprise at least two reactive end groups, advantageously such as OH, NH.sub.2, thiol, isocyanate, carboxylic anhydride, vinyl, allyl, alkyne, azide, halogen, or glycidyl.

6. The membranes according to claim 3 in which polysulfone, polyethersulfone, polyetherethersulfone, polyetherketone, polyetheretherketone, polyester, polycarbonate, polyamide, polyvinylidene fluoride, polyacrylonitrile, or cellulose acetate or a mixture of these polymers are present as other, non-silicone-containing block component A.

7. The membranes according to claim 3 in which the other, non-silicone-containing block components A comprise at least two reactive end groups, such as OH, NH.sub.2, thiol, isocyanate, carboxylic anhydride, vinyl, allyl, alkyne, azide, or glycidyl.

8. The membranes according to claim 1 in which the molecular weights of the silicon-containing block components are 1000 g/mol to 50000 g/mol, and the molecular weights of the other, non-silicon-containing block component A are 5000 g/mol to 25000 g/mol.

9. The membranes according to claim 1 in which aliphatic or aromatic urea groups or urethane groups or amide groups or ester groups or ether groups or thioether groups or amic acid groups or ester acid groups or hydroxy ether groups or imide groups or triazole groups are present as connection point X in the multiblock copolymer according to the formula (1).

10. The membranes according to claim 1 in which, in the multiblock copolymers according to the formula (1), m is between 10 and 200, advantageously between 50 and 150, n is between 0 and 80, advantageously between 0 and 50, o is between 1 and 6, advantageously between 1 and 5, p is between 1 and 8, advantageously between 1 and 5, z is between 5 and 20, advantageously between 8 and 15, the molar ratio of the silicone-containing block component and the other block component A in the multiblock copolymer is between 3:1 and 1:3.

11. The membranes according to claim 1 in which the membranes are present in the form of flat membranes, hollow-fiber membranes, or capillary membranes.

12. The membranes according to claim 1 in which a pore size of 1 nm to 1 μm, advantageously between 5 nm and 0.1 μm, is present.

13. A method for producing membranes for liquid treatment, in which method the membranes are produced by means of a phase inversion method, wherein a solution of 5-30 wt % multiblock copolymer according to formula (1) and 0-10 wt % of a non-silicone-containing polymer and 0-20 wt % of other solution additives and 50-95 wt % of a solvent that is miscible with water and a precipitation bath of 80-100 wt % water and 0-20 wt % other precipitation additives are used.

14. The method according to claim 13 in which N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, acetone, 1,4-dioxane, or tetrahydrofuran or mixtures of these solvents are used as solvents that are miscible with water.

15. The method according to claim 13 in which polysulfone, polyethersulfone, polyetherethersulfone, polyetherketone, polyetheretherketone, polyester, polycarbonate, polyamide, polyvinylidene fluoride, polyacrylonitrile, or cellulose acetate or a mixture of these polymers is used as non-silicone-containing polymer, wherein the non-silicone-containing polymer advantageously has the same chemical structure as the non-silicone-containing block component A according to the formula (1).

16. The method according to claim 13 in which water, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, and/or polyvinylpyrrolidone are used as other solution additives.

17. The method according to claim 13 in which methanol, ethanol, propyl alcohol, isopropyl alcohol, ethylene glycol, and/or solvents that are miscible with water are used as other precipitation additives.

18. The method according to claim 13 in which the solvents that are miscible with water for the solution are also used as precipitation additive for the precipitation bath.

19. The method according to claim 13 in which a precipitation bath temperature of 0° C. to 50° C., advantageously of 15° C. to 30° C., is used.

20. A use of membranes according to claims 1 through 12, and produced according to a method according to claims 13 through 19, in the food industry, water treatment, biotechnology, or medical engineering.

Description

COMPARATIVE EXAMPLE 1

[0103] Production of a membrane from pure polysulfone (PSU; Solvay Udel P3500 LCD)

[0104] A non-woven fabric (novatexx 2484; Freudenberg Filtration Technologies SE & Co. KG) is fixed on a glass plate using double-sided adhesive tape. The non-woven fabric is impregnated with a 4:1 mixture of NMP/water. Excess impregnating solution is removed with a doctor blade after 10 min of waiting time. The casting solution, comprised of 20% PSU in 80% NMP, is applied to the non-woven fabric using a doctor blade (gap height of 100 μm) at a drawing speed of 4.7 mm/sec. The protomembrane is immersed in a precipitation bath (water) at 23° C. 15 sec after the drawing process and is left in the precipitation bath for 10 min. The membrane is then detached from the glass plate and washed with DI water at room temperature while the water is changed multiple times. Until further use, the membrane is stored in DI water, to which 0.1% NaN.sub.3 has been added, in a refrigerator.

[0105] The membrane produced in this manner has characteristic values which are indicated in Table 1.

EXAMPLE 2

[0106] a) Production of the other, non-silicone-containing block component A as OH-terminated polysulfone

##STR00004##

[0107] 50 mmol (12.713 g) 4,4′-difluorodiphenyl sulfone and 51 mmol (19.006 g) 4,4′-bis(trimethylsiloxy)bisphenol A are dissolved in 50 mL N-methylpyrrolidone (NMP), and 75 mmol (10.37 g) potassium carbonate are added thereto. The batch is stirred at 175° C. for 8 h under a slight argon flow. The temperature is then increased to 190° C. for 2 h, and an additional 100 mg 4,4′-bis(trimethylsiloxy)bisphenol A is added. After cooling down, the product of the reaction is precipitated in 1000 mL ethanol with the addition of 5 mL of concentrated hydrochloric acid. The product is suctioned off and washed with 250 mL ethanol at 50° C. for 5 h, suctioned off, and dried under vacuum at 100° C. Molecular weights of M.sub.n=9000 g/mol and M.sub.w 24500 g/mol were measured using GPC (CHCl.sub.3; PS standard). The M.sub.n measured using .sup.1H-NMR is 18350 g/mol (x=41).

[0108] b) Synthesis of the multiblock copolymer according to the formula (1) from a silicone-containing block component (PDMS) and another, non-silicone-containing block component A (polysulfone).

##STR00005##

[0109] 4.04 mmol (0.82 g) terephthaloyl dichloride (connection point X) and 8 mmol dry triethylamine are dissolved in 10 mL dry tetrachloroethane. To this solution are added dropwise (over approx. 1 h) 2 mmol (36.7 g) of the polysulfone (polymer A) from (1) and 2 mmol (2.4 g) of a silicon-containing block component (carbinol-terminated polydimethylsiloxane, Fluorochem LTD, DMS-C15) with a molar mass of 1200 g/mol (m=12), dissolved in 50 mL dry THF. The reaction solution is stirred at room temperature for 3 h and at 90° C. for 1 h, wherein a highly viscous solution is produced. The THF is then distilled off, and stirring continues at 90° C. for another 8 h. After cooling down, the reaction mixture is diluted with 10 mL tetrachloroethane and stirred (homogenized) for another 8 h. In a fmal step, the reaction product is precipitated in 1000 mL ethanol, washed multiple times with ethanol, and dried under vacuum at 100° C.

[0110] The values for the multiblock copolymer are:

[0111] NMR: PDMS incorporation rate 128%

[0112] GPC: M.sub.w 49000 g/mol (CHCl.sub.3; PS standard)

[0113] c) Production of a membrane from the multiblock copolymer according to b)

[0114] Producing the Casting Solution:

[0115] 29 g of the polymer produced in (2) is dissolved in a mixture of 70 g dimethylacetamide (DMAc) and 1 g water while being stirred. The solution is degassed at 90° C. for one hour in a convection drying chamber.

[0116] Producing the Membrane:

[0117] A non-woven fabric (novatexx 2484; Freudenberg Filtration Technologies SE & Co. KG) is fixed on a glass plate using double-sided adhesive tape. The casting solution is applied to the non-woven fabric using a doctor blade (gap height of 100 μm) at a drawing speed of 4.7 mm/sec. The protomembrane is immersed in a precipitation bath (water) at 23° C. 30 sec after the drawing process and is left in the precipitation bath for 10 min. The membrane is then detached from the glass plate and washed with DI water at room temperature while the water is changed multiple times. Until further use, the membrane is stored in DI water, to which 0.1% NaN.sub.3 has been added, in a refrigerator.

EXAMPLE 3

[0118] A silicone-containing multiblock copolymer according to b) is produced according to Example 2 with the use of a silicone-containing block component (aminopropyl-terminated polydimethylsiloxane; Merck KG aA, Catalog No. 481688) with a molecular weight of M.sub.n=2500 g/mol (m=31) and polysulfone as other, non-silicone-containing block component A with a molecular weight of M.sub.n=10700 g/mol. A membrane is also produced therefrom, likewise according to Example 2.

[0119] The values for the multiblock copolymer are:

[0120] NMR: PDMS incorporation rate 89%

[0121] GPC: M.sub.w 51600 g/mol (CHCl.sub.3; PS standard)

EXAMPLE 4

[0122] A silicone-containing multiblock copolymer is produced according to Example 2 with the use of a silicone-containing block component (succinic acid anhydride-terminated polydimethylsiloxane; ABCR, Germany, Catalog No. AB130292) with a molecular weight of M.sub.n=1200 g/mol and polyethersulfone as other, non-silicone-containing block component A with a molecular weight of M.sub.n=10700 g/mol. A membrane is also produced therefrom, likewise according to Example 2.

[0123] The values for the multiblock copolymer are:

[0124] NMR: PDMS incorporation rate 100%

[0125] GPC: M.sub.w 49000 g/mol (CHCl.sub.3; PS standard)

[0126] The membrane exhibits a significantly improved blood compatibility compared to a membrane of pure polysulfone according to Comparative Example 1.

EXAMPLE 5

[0127] A silicone-containing multiblock copolymer according to b) is produced according to Example 2 with the use of a silicone-containing block component (aminopropyl-terminated polydimethylsiloxane; ABCR, Germany, Catalog No. AB153374) with a molecular weight of M.sub.n=25000 g/mol (m=331) and polysulfone as other, non-silicone-containing block component A with a molecular weight of M.sub.n=17000 g/mol. A membrane is also produced therefrom, likewise according to Example 2, wherein the casting solution contains 18 mass % of the silicone-containing multiblock copolymer and 2 mass% of pure polysulfone (Solvay Udel P3500 LCD).

[0128] The values for the multiblock copolymer are:

[0129] NMR: PDMS incorporation rate 75%

[0130] GPC: M.sub.w 59500 g/mol (CHCl.sub.3; PS standard)

[0131] The membrane exhibits a significantly improved blood compatibility and improved sliding friction properties compared to a membrane of pure polysulfone according to Comparative Example 1.

[0132] Conducting Filtration Tests on the Membranes from Examples 1 through 5

[0133] Membranes each having a size of 23×6 cm.sup.2 from each one of Example 1 through 5 are installed in a cross-flow filtration cell (Simatec, Germany). The active area is 85 cm.sup.2. The permeabilities J are determined using a Simatec LSPa05SPS with the use of a buffer solution (pH 6.8) (J.sub.v before BSA) at a volume flow rate of 30 L/h and a constant permeate volume flow rate of 0.24 L/h, wherein the transmembrane pressure is automatically readjusted. The fouling tests are conducted using a bovine serum albumin (BSA) solution (c=1 g/L in buffer solution; pH 6.8). After the BSA filtration, the membrane is rinsed with buffer solution for 1 h (volume flow rate of 60 L/h, pressureless), and the water permeability is then determined using the buffer solution (value: J.sub.n in Table 2).

[0134] The membranes produced in this manner have characteristic values which are indicated in Table 1.

[0135] In Tables 1 and 2, various characteristic values of the membranes from the Comparative Example and Examples 2 through 5 are indicated, as well as the chemical composition thereof, which were determined via NMR measurements, and the chemical composition thereof for the surface of the membranes, which were determined by means of EDX measurements.

TABLE-US-00001 TABLE 1 Properties of the membranes Contact J.sub.v J.sub.n Sample angle (°) (L/m.sup.2hbar) (L/m.sup.2hbar) Comparative 73 72 62 Example 1 Example 2 92  9  7 Example 3 89  7  2 Example 4 90 10  8 Example 5 95 52 51

TABLE-US-00002 TABLE 2 Comparison of silicone content in the membrane polymer and at the membrane surface S:Si S:Si (bulk) (surface) Enrichment Sample (NMR) (EDX) factor Comparative 0 0 — Example 1 Example 2 1:0.23 1:0.9 3.9 Example 3 1:0.49 1:0.9 1.8 Example 4 1:1.11 1:3.2 2.9 Example 5 1:2.35 1:5.4 2.3