Performance enhancing additives for fiber formation and polysulfone fibers

Abstract

The present invention relates to the use of additives in processes to form polymeric fibers. These fibers can be formed into membranes with improved middle and/or higher molecular weight solute removal.

What is claimed is: 
     
       1. A method of forming a dialysis membrane comprising a plurality of polyarylether polymer fibers, wherein the polyarylether fibers are produced by a method comprising the steps of:
 providing a spin mass comprising at least one polyarylether polymer and at least one organic solvent; 
 providing a bore fluid comprising at least one aqueous solvent and/or at least one organic solvent; 
 combining the spin mass and bore fluid to form the polyarylether polymer fibers; 
 and forming a dialysis membrane from a plurality of said polyarylether polymer fibers; 
 wherein the spin mass or the bore fluid or both comprises at least one additive; 
 wherein the spin mass comprises one medium molecular weight PVP having a K value of from K41 to K54 in an amount of from 0.1 wt % to 8 wt % and 0 wt % low molecular weight (MW) PVP and 0 wt % high molecular weight PVP by weight of the spin mass; 
 wherein the bore fluid comprises 0 wt % low MW PVP by weight of the bore fluid and 0 wt % high MW PVP; and 
 wherein the low MW PVP has a weight average molecular weight of less than about 100 kDa. 
 
     
     
       2. The method of  claim 1 , wherein the at least one additive comprises at least one polyelectrolyte, glycerine, surfactant, vinylpyrrolidone/vinylacetate copolymer, vinylcaprolactam/vinylpyrrolidone/dimethylamino-propylmethacrylamide terpolymer, polyethylene glycol polyester copolymer, or poly(ethyleneimine)-PEI, or any combination thereof, in the spin mass, or the at least one additive comprises at least one polyelectrolyte, glycerine, surfactant, vinylpyrrolidone/vinylacetate copolymer, vinylcaprolactam/vinylpyrrolidone/dimethylamino-propylmethacrylamide terpolymer, polyethylene glycol polyester copolymer, or poly(ethyleneimine)-PEI, or any combination thereof, in the bore fluid. 
     
     
       3. The method of  claim 1 , wherein the at least one additive comprises at least one polyelectrolyte in the bore fluid. 
     
     
       4. The method of  claim 1 , wherein the bore fluid comprises less than 25 wt % medium MW PVP by weight of the bore fluid; and
 wherein the medium MW PVP has a weight average molecular weight of from about 100 kDa to 900 kDa. 
 
     
     
       5. The method of  claim 1 , wherein the at least one additive comprises at least one medium MW PVP. 
     
     
       6. A dialysis membrane produced by the method of  claim 1 . 
     
     
       7. The method of  claim 1 , wherein said at least one additive is present in a sufficient amount so as to achieve at least one of the following properties as compared to the same polyarylether polymer fiber made in the same process, but without said additive being present:
 a) sharpen the sieving curve for improved middle molecule removal; 
 b) remove larger uremic solutes from fluids; 
 c) improve middle molecule removal without a substantial increase in albumin leakage; and 
 d) fully or partially replace PVP or a MW class of PVP or a similar minority polymeric component present in a spin mass, and still obtain the same or similar properties for the produced polyarylether polymer fiber. 
 
     
     
       8. The method of  claim 7 , wherein said polyarylether polymer is a polysulfone and said organic solvent in said spin mass is dimethylacetamide. 
     
     
       9. The method of  claim 1 , wherein the spin mass comprises 4 wt % or less water in the spin mass. 
     
     
       10. The method of  claim 1 , wherein the at least one additive comprises at least one medium molecular weight PVP, and wherein said medium molecular weight PVP is the only PVP type present in said spin mass, and wherein the spin mass contains 4 wt % or less water in the spin mass. 
     
     
       11. The method of  claim 10 , wherein said medium molecular weight PVP comprises a PVP having a K value of from K45 to K53. 
     
     
       12. A polyarylether polymer fiber comprising at least one polyarylether polymer and at least one polyvinylpyrrolidone (PVP), wherein said at least one PVP consisting consists of at least one medium molecular weight PVP having a K value of from 45 to 53 and present in an amount of from 0.1 wt % to 8 wt % based on weight of said polyarylether polymer fiber, wherein a membrane formed from a plurality of the polyarylether polymer fibers has an ultrafiltration constant (K UF ) of from about 100 ml/hr*mmHg*m 2  to about 600 ml/hr*mmHg*m 2 , and has an albumin sieving coefficient of from about 0.001% to about 0.5%. 
     
     
       13. The polyarylether polymer fiber of  claim 12 , wherein said medium molecular weight PVP is present in an amount of from about 3 wt % to 8 wt %, based on the weight of the polyarylether polymer fiber. 
     
     
       14. The method of  claim 1 , wherein said spin mass comprises from about 0.001 wt % to 3 wt % water, based on the weight of the spin mass. 
     
     
       15. The polyarylether polymer fiber of  claim 12 , wherein the polyarylether polymer fiber has a vitamin B 12  clearance rate, according to DIN 58352, of from about 150 ml/min to about 250 ml/min at Q b /Q d =300/500 ml/min. 
     
     
       16. The polyarylether polymer fiber of  claim 12 , wherein the polyarylether polymer fiber has a creatinine clearance rate, according to DIN 58352, of from about 50 ml/min of creatinine to about 290 ml/min of creatinine with Q b /Q d =300/500 ml/min. 
     
     
       17. The polyarylether polymer fiber of  claim 12 , wherein the polyarylether polymer fiber has a sodium clearance rate, according to DIN 58352, of from about 30 ml/min of sodium to about 300 ml/min of sodium with Q b /Q d =300/500 ml/min. 
     
     
       18. The polyarylether polymer fiber of  claim 12 , wherein the polyarylether polymer fiber has a beta-2-microglobulin clearance rate, according to DIN 58352, of from about 50 ml/min of beta-2-microglobulin to about 250 ml/min of beta-2-microglobulin with Q b /Q d =300/500 ml/min. 
     
     
       19. The polyarylether polymer fiber of  claim 12 , wherein the polyarylether polymer fiber has a middle molecule (lysozyme) clearance rate, according to DIN 58352, of from about 50 ml/min of lysozyme to about 250 ml/min of lysozyme with Q b /Q d =300/500 ml/min. 
     
     
       20. The polyarylether polymer fiber of  claim 12 , wherein the polyarylether polymer fiber has the following fiber geometry: an outside diameter of from about 100 μm to about 0.5 mm, an interior diameter of from about 100 μm to less than 0.5 mm, a thickness of from about 0.001 μm to about 250 μm, and a length of from about 0.01 m to about 1 m, and has a tensile strength of from about 0.1 to about 10 MPa. 
     
     
       21. A dialysis membrane comprising a plurality of polyarylether polymer fibers, said polyarylether polymer fibers comprising at least one polyarylether polymer and at least one polyvinylpyrrolidone (PVP), wherein said at least one PVP consisting of at least one medium molecular weight PVP having a K value of from 45 to 53 and present in an amount of from 0.1 wt % to 8 wt % based on weight of said polyarylether polymer fibers, wherein the dialysis membrane has an ultrafiltration constant (K UF ) of from about 100 ml/hr*mmHg*m 2  to about 600 ml/hr*mmHg*m 2 , and has an albumin sieving coefficient of from about 0.001% to about 0.5%. 
     
     
       22. The method of claim 1, wherein the viscosity of the spin mass is 500 to 10,000 cps (centipoise) at about 25° C. 
     
     
       23. The method of claim 22, wherein the viscosity of the spin mass is 1,000 to 2,500 cps (centipoise) at about 25° C. 
     
     
       24. The dialysis membrane of claim 21, wherein the at least one hydrophilic polymer comprises less than about 10% high molecular weight PVP, less than 10% low molecular weight PVP, or both. 
     
     
       25. The polyarylether polymer fiber of claim 31, wherein the sieving coefficient of myoglobin is from 0.9 to about 1.0. 
     
     
       26. The dialysis membrane of claim 32, wherein the sieving coefficient of insulin is about 0.99. 
     
     
       27. The polyarylether polymer fiber of claim 31, wherein the clearance of lysozyme is from about 75 ml/min. to about 150 ml./min. 
     
     
       28. The dialysis membrane of claim 32, wherein the clearance of vitamin B 12  is from about 150 ml/min. to about 250 ml/min. 
     
     
       29. The polyarylether polymer fiber of claim 31, wherein the polyarylether polymer fiber exhibits a water absorption capacity of from 1% to 10%. 
     
     
       30. The polyarylether polymer fiber of claim 31, wherein the polyarylether polymer fiber exhibits an ultrafiltration constant K UF  of from about 100 ml/hr*mmHg*m 2  to about 600 ml/hr*mmHg*m 2 . 
     
     
       31. A polyarylether polymer fiber formed from a solution comprising at least one polyarylether polymer, at least one polyvinylpyrrolidone (PVP), and a solvent, wherein said at least one PVP has a K value that is below 40 or above 55 or both;
 wherein said polyarylether polymer fiber has a high sieving coefficient for molecules of molecular weight of about 65 kDa or less while maintaining a sieving coefficient of 1% or less for proteins with molecular weights greater than about 65 kDa, and   wherein said high sieving coefficient includes a sieving coefficient of 1.0 for Vitamin B 12 , about 0.99 for inulin, and from about 0.9 to about 1.0 for myoglobin.   
     
     
       32. A dialysis membrane prepared from a solution comprising:
 10 to 30 wt. % of at least one polyarylether polymer,   1 to 10 wt. % of at least one hydrophilic polymer that is other than a polyvinylpyrrolidone having a K value of from 40 to 55,   and at least one solvent, wherein the dialysis membrane has:   a molecular weight cut off of 60 kDa to about 65 kDa such that a molecule or protein having about the size of albumin has a sieving coefficient of about 10% or less according to DIN 58352.   
     
     
       33. The dialysis membrane of claim 32, wherein the dialysis membrane further has a middle molecule (lysozyme) clearance rate of from about 50 ml/min of lysozyme to about 250 ml/min of lysozyme with Q b /Q d =300/500 ml/min. 
     
     
       34. The dialysis membrane of claim 32, wherein the at least one hydrophilic polymer includes at least one polyvinylpyrrolidone having a K value of K80 or higher. 
     
     
       35. The dialysis membrane of claim 32, wherein the at least one hydrophilic polymer includes at least one polyvinylpyrrolidone having a K value of K36 or lower. 
     
     
       36. The dialysis membrane of claim 32, wherein the at least one hydrophilic polymer includes at least one polyvinylpyrrolidone having a K value of from K80 to K105. 
     
     
       37. The dialysis membrane of claim 32, wherein the at least one hydrophilic polymer includes at least one polyvinylpyrrolidone having a K value of from K1 to K36. 
     
     
       38. The polyarylether polymer fiber of claim 31, wherein the at least one PVP is at least one polyvinylpyrrolidone having a K value of K80 or higher. 
     
     
       39. The polyarylether polymer fiber of claim 31, wherein the at least one PVP is at least one polyvinylpyrrolidone having a K value of K36 or lower. 
     
     
       40. The polyarylether polymer fiber of claim 31, wherein the at least one PVP is at least one polyvinylpyrrolidone having a K value of from K80 to K105. 
     
     
       41. The polyarylether polymer fiber of claim 31, wherein the at least one PVP is at least one polyvinylpyrrolidone having a K value of K1 to K36. 
     
     
       42. The polyarylether polymer fiber of claim 31, wherein the at least one PVP is at least one polyvinylpyrrolidone having a K value of K36 or lower and at least one polyvinylpyrrolidone having a K value of K80 or higher. 
     
     
       43. The dialysis membrane of claim 32, wherein the at least one hydrophilic polymer is at least one polyvinylpyrrolidone having a K value of K36 or lower and at least one polyvinylpyrrolidone having a K value of K80 or higher. 
     
     
       44. The polyarylether polymer fiber of claim 31, wherein the at least one PVP comprises at least one polyvinylpyrrolidone having a K value of K36 or lower in an amount of from 4 wt % to 10 wt % based on said solution. 
     
     
       45. The dialysis membrane of claim 32, wherein said at least one hydrophilic polymer is at least one polyvinylpyrrolidone having a K value of K36 or lower in an amount of from 4 wt % to 10 wt % based on said solution.