Hollow Fibre Membrane Having Three Dimensional Texturing

Abstract

Hollow-fibre membrane having at least one first curl in the form of a first wave which is characterized by a first oscillation plane and a first wavelength and at least one second curl in the form of a second wave which is characterized by a second oscillation plane and a second wavelength, characterized in that the first oscillation plane and the second oscillation plane confine an angle with one another which is different from zero.

Claims

1. Hollow-fibre membrane having at least one first curl in the form of a first wave which is characterized by a first oscillation plane and a first wavelength and at least one second curl in the form of a second wave which is characterized by a second oscillation plane and a second wavelength, wherein the first oscillation plane and the second oscillation plane confine an angle with one another which is different from zero.

2. The hollow-fibre membrane according to claim 1, wherein the angle is from 70? to 110?.

3. The hollow-fibre membrane according to claim 1, wherein the angle is from 85? to 95?.

4. The hollow-fibre membrane according to claim 1, wherein the angle is 90?.

5. The hollow-fibre membrane according to claim 1, wherein the first wavelength and the second wavelength are different from one another.

6. The hollow-fibre membrane according to claim 1, wherein the wavelength of the first wave is from 3 to 15 mm.

7. The hollow-fibre membrane according to claim 1, wherein the wavelength of the second wave is from 20 to 50 mm.

8. The hollow-fibre membrane according to claim 1, wherein the first wave has a first amplitude within the range from 0.2 to 0.6 mm.

9. The hollow-fibre membrane according to claim 1, wherein the second wave has a second amplitude within the range from 2.0 to 6.0 mm.

10. The hollow-fibre membrane according to claim 1, wherein the first wave and the second wave are sine-shaped.

11. The hollow-fibre membrane according to claim 1, wherein said hollow-fibre membrane has a demoulding force of from 3.4 to 10.0 N based on a hollow-fibre membrane bundle produced therefrom having 16 896 fibres, when the hollow-fibre membrane bundle is demoulded from a cylindrical shell having a diameter of 41.4 mm.

12. The hollow-fibre membrane according to claim 11, characterized in that the demoulding force is from 3.4 to 7.0 N.

13. A hollow-fibre membrane having a demoulding force of from 3.4 to 10.0 N based on a hollow-fibre membrane bundle produced therefrom having 16 896 fibres, when the hollow-fibre membrane bundle is demoulded from a cylindrical shell having a diameter of 41.4 mm.

14. The hollow-fibre membrane according to claim 13 having a fibre diameter of from 170 to 210 ?m.

15. A process for producing the hollow-fibre membrane of claim 1, said process comprising at least steps (a) and (b): (a) providing a hollow fibre having a first curl in the form of a first wave which is characterized by a first oscillation plane and a first wavelength; (b) applying a second curl to the hollow-fibre membrane provided in step (a), in the form of a second wave which is characterized by a second oscillation plane and a second wavelength; wherein the application in step (b) being effected such that, after application, the first oscillation plane and the second oscillation plane confine an angle which is different from zero.

16. The process according to claim 15, wherein the first wavelength and the second wavelength are selected such that the first wavelength is shorter than the second wavelength.

17. The process according to claim 15, wherein the hollow-fibre membrane of step (a) is passed through at least two counter-rotating cog wheels in step (b), the rotation axes of the cog wheels not being aligned perpendicular to the first oscillation plane.

18. A bundle comprising a plurality of the hollow-fibre membrane as defined in claim 1.

19. A filter device for hemodialysis, comprising a housing and the bundle as defined in claim 18 and arranged in said housing.

20. A method to filter a fluid comprising passing the fluid through said filter device of claim 19 to obtain a filtered fluid.

Description

EXAMPLES

[0087] The measure of the filtration efficiency of dialysers that was used was the so-called clearance value, which was determined as described below. Clearance values of hollow-fibre bundles according to the invention were measured according to the requirements of the DIN EN ISO 8637 standard. This involved measuring both the input concentration and the output concentration of a particular guide substance during a simulated dialysis on a dialyser constructed from hollow-fibre bundles and calculating the clearance according to the formula:

[00001]$\mathrm{Cl}=Q_B?\left(1-\frac{C_{B,\mathrm{out}}}{C_{B,\mathrm{in}}}\right)+\frac{C_{B,\mathrm{out}}}{C_{B,\mathrm{in}}}$

TABLE-US-00001 Cl Clearance [ml/min] Q.sub.B Flow rate on blood side [ml/min] Q.sub.F Filtrate flow [ml/min] C.sub.B, in Input concentration, blood side C.sub.B, out Output concentration, blood side

[0088] Altogether, the clearance values were determined on 10 filter modules and the values obtained were averaged.

[0089] The clearance measurement was carried out as follows: A dialyser was produced by moulding of the hollow-fibre bundle to be investigated, by end-side casting of the fibre ends in the housing of the dialyser. The end-side casting separated the dialyser into two flow spaces, a blood-side flow space, which comprises the cavities of the fibres, and a dialysate-side flow space, which comprises the space surrounding the fibres.

[0090] The dialyser had an inlet port and outlet port on the blood side in order to introduce liquid into the fibre interior and to remove it at the other end of the fibres. Furthermore, the dialyser had an inlet port and an outlet port on the dialysate side in order to allow liquid to flow along the fibres on the dialysate side.

[0091] To carry out the clearance measurement, the dialysate side was flushed with a 1% aqueous potassium chloride solution at 37? C. at a flow rate of 500 ml/min. The test liquid adjusted to a temperature of 37? C. flowed through the blood side at a flow rate of 300 ml/min.

[0092] For the measurement of sodium clearance, the test liquid used was a 154 mmol/l sodium chloride solution. For the measurement of vitamin B12 clearance, a 36.07 ?mol/l test solution was used. After the respective liquids had flowed through both flow sides for 10 minutes, the concentration of the analyte at the output of the blood side and at the output of the dialysate side was determined.

[0093] For the measurement of demoulding force, a fibre bundle driven into an HDPE film is used as a test body. In this case, the hollow-fibre membrane bundle inserted into the film assumes a cylindrical shape.

[0094] The fibre bundle is then slid out of the film cover, such that the hollow-fibre bundle freely towers above the film cover by 2 cm. With the aid of an adhesive strip, the free bundle end is wrapped and fixed on a receiver unit of a tensile tester. The thus enclosed bundle end then has the same diameter as the bundle driven into the film. The fibre bundle prepared in this manner is positioned horizontally on a test bench. The film is fixed with appropriate holding devices.

[0095] With the aid of the tensile tester, the fibre bundle was pulled out of the film shell. The pulling speed was 1 cm/sec. After 50% of the length of the fibre bundle had been pulled out of the film shell, the force value of the demoulding process was recorded on the tensile tester. The thus measured force value indicated the demoulding force of the fibre bundle.

Example 1

[0096] A fibre bundle according to the invention with double curl was moulded into a commercially available F60S filter housing from Fresenius Medical Care. Specifications relating to fibre number, active membrane area, fibre diameter, wall thickness of the hollow-fibre membrane and length of the hollow-fibre membrane in the dialyser housing are shown in Table 1. The fibres of the hollow-fibre membrane bundle according to the invention had a first curl having a wavelength of 3 mm and a second curl having a wavelength of 30 mm. The oscillation planes of the two curls were in a 90? angle in relation to one another.

[0097] The clearance values for sodium and vitamin B12 were determined according to the method described above. The sodium clearance was 253 ml/min. The vitamin B12 clearance was 135 ml/min.

Comparative Example 1

[0098] Fibres of the comparative example were obtained according to the same spinning process as the fibres of the exemplary embodiment. Fibre dimensions and pore structure were therefore identical to those of the fibres of the exemplary embodiment. The fibres of the example were then provided with a single curl having a wavelength of 30 mm. The fibres were combined to form bundles and moulded and casted into a commercially available F60S filter housing from Fresenius Medical Care according to the same method as in example 1.

[0099] The clearance values for sodium and vitamin B12 were determined according to the method described above. The sodium clearance was 238 ml/min. The vitamin B12 clearance was 127 ml/min.

TABLE-US-00002 TABLE 1 Comparative Example 1 example 1 Housing inner diameter 39 mm 39 mm Number of fibres 9216 9216 Fibre inner diameter 200 ?m 200 ?m Wall thickness 40 ?m 40 ?m Fibre length in the filter module 227 mm 227 mm Active membrane area 1.31 m.sup.2 1.31 m.sup.2 1st curl wavelength 7 mm Amplitude of the 1st wavelength 0.4 mm 2nd curl wavelength 30 mm 30 mm Amplitude of the 2nd wavelength 3.5 mm 3.5 mm Sodium clearance 253 ml/min 238 ml/min Vit. B12 clearance 135 ml/min 127 ml/min

Example 2

[0100] For the measurement of demoulding force, fibre bundles consisting of 16896 fibres having a length of 280 mm were produced. The fibre inner diameter of the fibres was 183 ?m and the wall thickness of the fibres was 38 ?m. The fibres were inserted into an HDPE film to form a cylindrical fibre bundle having a diameter of 41.4 mm. The demoulding force was determined according to the method described above. The demoulding force was measured on each of 30 fibre bundles with the inventive double curl having a first wavelength of 7 mm and an amplitude of 0.4 mm and a second wavelength of 30 mm with an amplitude of 3.5 mm.

[0101] For comparison, the demoulding force was measured on 30 fibre bundles which differed from the fibre bundles according to the invention only in the nature of the curl. The fibres had a single curl having a wavelength of 30 mm and an amplitude of 3.5 mm.

[0102] From 30 measurements, an averaged demoulding force of 4.2 N was found for the fibre bundles according to the invention. An averaged demoulding force of 3.4 N for fibre bundles was found for the fibre bundles with the singly curled fibres.