HEMODIALYZER FIBER BUNDLE ENCAPSULATION PROCESS

Abstract: A hollow-fiber hemodialyzer (10) is manufactured using an encapsulation process to preliminarily seal the ends (17) of the hollow fiber bundles (14) prior to the potting process. Partially-set quick-setting material (21) is placed in the end caps (18, 19) or potting caps of the hemodialyzer case (11). The caps (18, 19) are then placed over the open ends (12, 13) of the hemodialyzer case (11) so that the ends (17) of the fiber bundles (14) extend into the partially-set material (21) thereby encapsulating the ends (17) of the fiber bundles (14) with partially-set material. After the material is allowed to set, the hemodialyzer (10) is potted using conventional means. As a result of the encapsulation process, maintenance of the bundle fluff to facilitate subsequent potting is achieved and wicking of the high-flux hollow fibers is controlled.

Description: S P E C I F I C A T I O N TITLE "HEMODIALYZER FIBER BUNDLE ENCAPSULATION PROCESS" BACKGROUND OF THE INVENTION The present invention relates generally to hemodialyzers. More specifically, the present invention relates to hemodialyzers having fiber bundles that are encapsulated with a quick-setting material prior to being potted. Still more specifically, the present invention relates to an encapsulation process for hollow fiber bundles that serves to prepare the hollow fiber bundles for the potting step in the hemodialyzer manufacturing process. The use of high-flux hollow-fiber hemodialyzers has become increasingly popular. The future use of super high-flux, medium flux and low flux hemodialyzers is anticipated. Currently, the manufacture of high-flux hollow fiber hemodialyzers presents technical problems during the hemodialyzer manufacturing process . Specifically, high-flux hollow fibers are very porous. The high porosity of the high-flux hollow fibers presents problems during the potting process because the potting compound has the tendency to be drawn up into the inner lumen of the fiber during the potting process due to capillary forces. This phenomenon is referred to in the art as "wicking" . Such wicking has been known to occur to the extent that the inner lumens of the hollow fibers are blocked off rendering the fiber inoperable. As a result, the efficiency of the hemodialyzer is reduced. Further, such severe wicking has been known to occur with enough hollow fibers of a hemodialyzer that the entire hemodialyzer is rendered unusable. Another problem associated with high-flux hollow fiber hemodialyzers is the fact that the high-flux hollow fibers have a greater wall thickness which is required to support the highly porous structure of the high-flux fiber. As a result, high-flux hollow-fiber bundles are denser thereby making it more difficult for the potting material to penetrate into the end of the fiber bundle during the potting process. As a result, while wicking may occur in a number of the hollow fibers thereby reducing the efficiency of the hemodialyzer, the potting process may be adversely affected by the dense fiber bundle which results in some of the fibers not being securely attached to the opposing ends of the hemodialyzer case. As a result, leakage may occur at the ends of the fiber bundles thereby rendering the hemodialyzer defective. Accordingly, there is a need for improved manufacturing processes which will enable high-flux hollow-fiber hemodialyzers to be successfully and reliably manufactured. SUMMARY OF THE INVENTION The present invention satisfies the aforenoted needs by providing a method of encapsulating a hollow fiber bundle of a hemodialyzer prior to the potting step of the hemodialyzer manufacturing process . The method of encapsulating in accordance with the present invention comprises the steps of providing a hollow fiber bundle having a first end and a second end. The fiber bundle is inserted into a hemodialyzer case with a first open end and a second open end. The method further includes the step of fluffing the first and second ends of the fiber bundle and thereafter providing a first potting cap and a second potting cap, both of which are at least partially filled with a quick-setting material in a partially set state. The method then includes the steps of attaching the first potting cap to the first open end of the hemodialyzer case so that the first end of the fiber bundle extends into the quick-setting material disposed in the first potting cap, allowing the quick- setting material in the first cap to set, attaching the second potting cap to the second open end of the hemodialyzer case so that the second end of the fiber bundle extends into the quick-setting material disposed in the second potting cap and allowing the quick-setting material in the second potting cap to set. Now, the hemodialyzer is ready for the potting process. In an embodiment, the first and second open ends of the dialyzer case are respectively fitted with first and second potting collars. The first end of the fiber bundle extends through the first potting collar and the second end of the fiber bundle extends through the second potting collar. In an embodiment, the method of the present invention further includes the step of engaging the first and second ends of the fiber bundles with a pressurized air stream, a brush or by hand to fluff the first and second ends of the fiber bundle prior to the step of attaching the first and second potting caps to the first and second open ends of the hemodialyzer case. In an embodiment, the quick-setting material is polyurethane . In an embodiment, the quick-setting material is selected from the group consisting of epoxy, hot melt adhesive, glue and silicone. In an embodiment, the method of the present invention provides a hemodialyzer that comprises a fiber bundle disposed in a hemodialyzer case whereby the fiber bundle is encapsulated in accordance with the encapsulating method set forth above. In an embodiment, the method of the present invention comprises the steps of providing a hollow fiber bundle having a first end and a second end, providing a hemodialyzer case with a first open end and a second open end, the first and second open ends being respectively fitted with first and second potting collars, placing the fiber bundle in the hemodialyzer case so that the first end of the fiber bundle extends through the first potting collar and the second end of the fiber bundle extends through the second potting collar, fluffing the first and second ends of the fiber bundle, providing a first potting cap at least partially filled with a quick- setting material in a partially set state, attaching the first potting cap to the first open end of the hemodialyzer case so that the first end of the fiber bundle extends into the quick-setting material disposed in the first potting cap, allowing the quick-setting material in the first cap to set, providing a second potting cap at least partially filled with a quick- setting material in a partially set state, attaching the second potting cap to the second open end of the hemodialyzer case so that the second end of the fiber bundle extends into the quick-setting material disposed in the second potting cap, and, allowing the quick- setting material in the second potting cap to set. In an embodiment, the present invention provides a method of manufacturing a hemodialyzer that comprises the steps of providing a hollow fiber bundle having a first end and a second end, providing a hemodialyzer case with a first open end and a second open end, the first and second open ends being respectively fitted with first and second potting collars, placing the fiber bundle in the hemodialyzer case so that the first end of the fiber bundle extends through the first potting collar and the second end of the fiber bundle extends through the second potting collar, fluffing the first and second ends of the fiber bundle with a stream of pressurized air, providing a first potting cap at least partially filled with a quick-setting polyurethane in a partially gelled state, attaching the first potting cap to the first open end of the hemodialyzer so that the first end of the fiber bundle extends into the quick-setting polyurethane disposed in the first potting cap, allowing the quick- setting material in the first potting cap to gel, providing a second potting cap at least partially filled with a quick-setting polyurethane in a partially gelled state, attaching the second potting cap to the second open end of the hemodialyzer case so that the second end of the fiber bundle extends into the quick-setting polyurethane disposed in the second potting cap, allowing the quick-setting polyurethane in the second potting cap to gel fully, and, potting the hemodialyzer. In an embodiment, each potting cap is attached to a collar and each combination potting cap and collar are partially filled with quick-setting material. After a first combination potting cap and collar is attached to the first end of the hemodialyzer and the quick-setting material is allowed to set, the second combination potting cap and collar is attached to the second end of the hemodialyzer and the quick-setting material disposed therein is allowed to set. In an embodiment, the first and second potting caps each comprise a hole for the injection of quick-setting material . The method therefore includes the steps of attaching the first potting cap to the first open end of the hemodialyzer case, injecting quick-setting material through the hole in the first potting cap so the first end of the fiber bundle is immersed in the quick-setting material disposed in the first potting cap and allowing the quick-setting material in the first potting cap to set, attaching the second potting cap to the second open end of the hemodialyzer case, injecting quick-setting material through the hole in the second potting cap so that the second end of the fiber bundle is immersed in the quick-setting material disposed in the second potting cap and allowing the quick-setting material in the second potting cap to set. In an embodiment, a special fitting is employed to inject quick-setting material around the fluffed ends of the fiber bundle. Therefore, prior to the attachment of either the first or second potting cap, a fitting is attached to the first open end of the hemodialyzer case and quick-setting material is injected so that the first end of the fiber bundle is immersed in the quick-setting material. After the quick-setting material has been allowed to set, the fitting is removed and the first potting cap is attached to the first open end of the hemodialyzer case. Then, the fitting is mounted to the second open end of the hemodialyzer case and quick- setting material is injected through the fitting so that the second end of the fiber bundle is immersed in the quick-setting material. After the quick-setting material is allowed to set, the fitting is removed and the second potting cap is attached to the second open end of the hemodialyzer case. In the embodiment wherein the first and second potting caps are provided with a hole for the injection of quick-setting material, the quick-setting material serves as a plug for the holes once it is set. In the embodiment which employs the special fitting for the injection of the quick-setting material, the fitting is fabricated from material that does not stick to the quick-setting material which thereby allows for the setting of the quick-setting material prior to the removal of the fitting from the open end of the hemodialyzer case. In an embodiment, the present invention provides a hemodialyzer that comprises a hollow fiber bundle having a first end and a second end. The fiber bundle is accommodated in and extends through a hemodialyzer case having a first open end and a second open end. The first and second open ends of the hemodialyzer case are fitted with first and second potting collars. The fiber bundle extends through the hemodialyzer case so that the first end of the fiber bundle extends through the first potting collar and the second end of the fiber bundle extends through the second potting collar. The first open end of the hemodialyzer case is connected to a first potting cap that is at least partially filled with a first portion of a quick-setting material. The first end of the fiber bundle extends into the first portion of the quick-setting material disposed in the first potting cap. The second open end of the hemodialyzer case is connected to a second potting cap that is at least partially filled with a second portion of the quick-setting material. The second end of the fiber bundle extends into the second portion of the quick-setting material disposed in the second potting cap. It is therefore an advantage of the present invention to provide a means for manufacturing high-flux hollow-fiber hemodialyzers that effectively encapsulates the opposing ends of the fiber bundles thereby facilitating the subsequent potting process. Another advantage of the present invention is that it provides an improved process for manufacturing high- flux, super high-flux, medium flux and low flux hollow- fiber hemodialyzers. Yet another advantage of the present invention is that it provides a means for avoiding wicking of high- flux hollow fibers during the potting step of the hemodialyzer manufacturing process. Yet another advantage of the present invention is that it provides an improved encapsulation process for hollow-fiber hemodialyzers. Yet another advantage of the present invention is that it provides an improved hollow-fiber hemodialyzer. Additional features and advantages of the present invention are described in, and will be apparent from, the detailed description of the presently preferred embodiments and upon reference to the accompanying figures. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a partial exploded view of a hemodialyzer made in accordance with the present invention; Figure 2 is a perspective view of a potting cap used to manufacture the hemodialyzer shown in Figure 1 and particularly illustrating the placement of quick-setting material into the potting cap which is done prior to the attachment of the cap to the dialyzer shown in Figure 1; Figure 3 illustrates an alternative embodiment of the present invention that includes a dialyzer with an inserted fiber bundle and a combination cap and collar that has been filled with quick-setting material; Figure 4 illustrates another alternative embodiment of the present invention, specifically a potting cap with a hole disposed therein for accommodating a nozzle for injecting quick-setting material through the hole in the potting cap; and Figure 5 illustrates yet another alternative embodiment of the present invention which includes the steps of attaching a special fitting to a hemodialyzer with a fiber bundle inserted therein, injecting quick- setting material through the special fitting, allowing the quick-setting material to set, removing the fitting and attaching an empty potting cap onto the end of the hemodialyzer. It should be understood that the drawings are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted. It should be understood, of course, that the invention is not necessarily limited to the particular embodiments illustrated herein. DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS A partial view of a hemodialyzer 10 made in accordance with the method of the present invention is shown in Figure 1. The dialyzer 10 includes a dialyzer case 11 with open ends 12 and 13. A fiber bundle 14 extends through the dialyzer case 11 as shown. The dialyzer case 11 is also equipped with potting collars 15, 16. Prior to the encapsulation process described above and below, the opposing ends (only one of which is shown at 17) of the fiber bundle 14 is fluffed with a stream of pressurized air. After the ends (one of which is shown at 17) of the bundle 14 are sufficiently fluffed, potting caps, shown at 18 in Figure 2 and 19 in Figure 1 are at least partially filled with a quick-setting material 21 through a nozzle 22 or other suitable dispensing device. While the quick-setting material 21 is in a partially-set state, that is, not completely set, gelled, polymerized, or hardened but after the initiation of the setting process, gellation process or polymerization process, the potting caps 18, 19 are attached to the open ends 12, 13 of the dialyzer case 11. As a result, the fluffed ends 17 of the fiber bundle 14 extend into the partially-set, gelled, polymerized, or hardened material 21 disposed in the potting caps 18, 19. Then, the quick-setting material 21 is allowed to set, gel or polymerize. After the material 21 has fully set, gelled or polymerized, the dialyzer 10 is ready for the potting step of the manufacturing process . The encapsulation process described above eliminates the problems associated, with wicking of the high-flux hollow fibers because the material 21 disposed in the potting caps 18, 19 has had a chance to set fully around the fluffed ends 17 of the fiber bundle 14 thereby effectively preventing the creation of capillary forces which would draw the potting material up through the fluffed ends 17 of the fiber bundle 14. Also, the material 21 is preferably provided in a partially-set state which has a relatively high viscosity and which consequently limits wicking. Further, because a measured amount of material 21 is used in the potting caps 18, 19, the degree of wicking of the fibers of the fiber bundle 14 can be tightly controlled. As a result, the manufacturer can control the amount and nature of material 21 disposed in the potting caps 18, 19 and, consequently, can control the wicking problem. In addition, the encapsulation method of the present invention enhances and maintains the end fluff of the fiber bundle 14 which reduces the density of the fiber in the potted volume thereby permitting easier penetration of a potting compound into the fiber bundle. A high degree of fluffing can be achieved by using the potting collars shown at 15, 16. The speed of the process can also be controlled with the temperature of the material 21 disposed in the potting caps 18, 19. With most quick-setting materials, the temperatures of the material, the caps and the collars directly affects the set, gel or polymerization time. The preferred quick-setting material 21 is polyurethane. However, it is anticipated that epoxies, hot melt materials, glues and silicones will be useful as well. Further, a variety of potting collar 15, 16 designs can be used, depending upon the specific manufacturing needs and the physical characteristics of the fiber bundle 14. Figure 3 illustrates an alternative embodiment with a dialyzer 10a that is provided without collars and a combination potting cap and collar 30. The combination potting cap and collar 30 is at least partially filled with quick-setting material prior to its insertion to the open end 31 of the hemodialyzer 10a. Figure 4 illustrates another alternative embodiment whereby the hemodialyzer 10b is equipped with a potting cap 18a that includes a hole 32. The hole 32 accommodates a nozzle 33 which is connected to a supply of quick-setting material (not shown) . The nozzle 33 is inserted into the hole 32 and quick-setting material is injected through the potting cap 18a. After the quick-setting material has set, the nozzle 33 is removed and the process is repeated for the second opposing end 34 of the hemodialyzer 10b. Figure 5 illustrates yet another alternative method whereby a hemodialyzer 10c is provided with a collar 16a. A special fitting 35 is attached to the collar 16a and quick-setting material is injected through the nozzle 36 and through the special fitting 35 into the open end of the hemodialyzer 10c so that a first end of the fiber bundle (not shown) disposed therein is immersed in quick- setting material. After the quick-setting material has set, the fitting 35 and nozzle 36 are removed and a potting cap 18 is attached to the dialyzer 10c. Again, the process is repeated for the second opposing end of the dialyzer 10c. It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the present invention and without diminishing its attendant advantages. It is, therefore, intended that such changes and modifications be covered by the appended claims.

Claims: WHAT IS CLAIMED IS; 1. A method of encapsulating a hollow fiber bundle of a hemodialyzer comprising the following steps: providing a hollow fiber bundle having a first end and a second end, inserting the fiber bundle into a hemodialyzer case with a first open end and a second open end, fluffing the first and second ends of the fiber bundle, providing a first potting cap and a second potting cap, both of which are at least partially filled with a quick-setting material in a partially set state, attaching the first potting cap to the first open end of the hemodialyzer case so that the first end of the fiber bundle extends into the quick-setting material disposed in the first potting cap and allowing the quick- setting material in the first potting cap to set, attaching the second potting cap to the second open end of the hemodialyzer case so that the second end of the fiber bundle extends into the quick-setting material disposed in the second potting cap and allowing the quick-setting material in the second potting cap to set. 2. The method of claim 1 wherein the first and second open ends of the dialyzer case are respectively fitted with first and second potting collars, the first end of the fiber bundle extending through the first potting collar and the second end of the fiber bundle extends through the second potting collar. 3. The method of claim 1 wherein the first and second potting caps further comprise a potting collar. 4. The method of claim 1 wherein the fluffing step further comprises : engaging the first and second ends of the fiber bundles with a pressurized air stream. 5. The method of claim 1 wherein the quick-setting material is polyurethane. 6. The method of claim 1 wherein the quick-setting material is selected from the group consisting of epoxy, hot melt adhesive, glue and silicone. 7. A hemodialyzer comprising a fiber bundle that is encapsulated according to the method of claim 1. 8. A method of encapsulating a hollow fiber bundle of a hemodialyzer comprising the following steps: providing a hollow fiber bundle having a first end and a second end, providing a hemodialyzer case with a first open end and a second open end, the first and second open ends being respectively fitted with first and second potting collars, placing the fiber bundle in the hemodialyzer case so that the first end of the fiber bundle extends through the first potting collar and the second end of the fiber bundle extends through the second potting collar, fluffing the first and second ends of the fiber bundle, providing a first potting cap at least partially filled with a quick-setting material in a partially set state, attaching the first potting cap to the first open end of the hemodialyzer case so that the first end of the fiber bundle extends into the quick-setting material disposed in the first potting cap and allowing the quick- setting material in the first potting cap to set, providing a second potting cap at least partially filled with a quick-setting material in a partially set state, attaching the second potting cap to the second open end of the hemodialyzer case so that the second end of the fiber bundle extends into the quick-setting material disposed in the second potting cap and allowing the quick-setting materials in the second potting cap to set fully. 9. The method of claim 8 wherein the quick-setting material is polyurethane. 10. The method of claim 8 wherein the quick-setting material is selected from the group consisting of epoxy, hot melt adhesive, glue and silicone. 11. A hemodialyzer made in accordance with the method of claim 8. 12. A method of manufacturing a hemodialyzer comprising of the following steps: providing a hollow fiber bundle having a first end and a second end, providing a hemodialyzer case with a first open end and a second open end, the first and second open ends being respectively fitted with first and second potting collars, placing the fiber bundle in the hemodialyzer case so that the first end of the fiber bundle extends through the first potting collar and the second end of the fiber bundle extends through the second potting collar, fluffing the first and second ends of the fiber bundle with a stream of pressurized air, providing a first potting cap at least partially filled with a quick-setting polyurethane in a partially gelled state, attaching the first potting cap to the first open end of the hemodialyzer case so that the first end of the fiber bundle extends into the quick-setting polyurethane disposed in the first potting cap and allowing the quick- setting material in the first potting cap to gel, providing a second potting cap at least partially filled with a quick-setting polyurethane in a partially gelled state, attaching the second potting cap to the second open end of the hemodialyzer case so that the second end of the fiber bundle extends into the quick-setting polyurethane disposed in the second potting cap and allowing the quick-setting polyurethane in the second potting cap to gel, potting the hemodialyzer. 13. A hemodialyzer made in accordance with the method of claim 12. 14. A hemodialyzer comprising: a hollow fiber bundle having a first end and a second end, the fiber bundle being accommodated in a hemodialyzer case having a first open end and a second open end, the first and second open ends being respectively fitted with first and second potting collars, the fiber bundle extending through the hemodialyzer case so that the first end of the fiber bundle extends through the first potting collar and the second end of the fiber bundle extends through the second potting collar, the first open end of the hemodialyzer case being connected to a first potting cap that is at least partially filled with a first portion of a quick-setting material, the first end of the fiber bundle extending into the first portion of the quick-setting material disposed in the first potting cap, the second open end of the hemodialyzer case being connected to a second potting cap that is at least partially filled with a second portion of the quick-setting material, the second end of the fiber bundle extending into the second portion of the quick-setting material disposed in the second potting cap. 15. The hemodialyzer of claim 14 wherein the quick- setting material is polyurethane. 16. The hemodialyzer of claim 14 wherein the quick- setting material is selected from the group consisting of epoxy, hot melt adhesive, glue and silicone. 17. The hemodialyzer of claim 14 wherein the first and second ends of the fiber bundle are fluffed. 18. A method of encapsulating a hollow fiber bundle of a hemodialyzer comprising the following steps: providing a hollow fiber bundle having a first end and a second end, inserting the fiber bundle into a hemodialyzer case with a first open end and a second open end, fluffing the first and second ends of the fiber bundle, providing a first potting cap and a second potting cap, the first and second potting caps each comprising a hole for the injection of quick-setting material, attaching the first potting cap to the first open end of the hemodialyzer case, injecting quick-setting material through the hole in the first potting cap so the first end of the fiber bundle is immersed in the quick-setting material disposed in the first potting cap and allowing the quick-setting material in the first potting cap to set, attaching the second potting cap to the second open end of the hemodialyzer case, injecting quick-setting material through the hole in the second potting cap so that the second end of the fiber bundle is immersed in the quick-setting material disposed in the second potting cap and allowing the quick-setting material in the second potting cap to set. 19. A method of encapsulating a hollow fiber bundle of a hemodialyzer comprising the following steps: providing a hollow fiber bundle having a first end and a second end, inserting the fiber bundle into a hemodialyzer case with a first open end and a second open end, fluffing the first and second ends of the fiber bundle, attaching a fitting to the first open end of the hemodialyzer case, the fitting being connected to a supply of quick-setting material, injecting quick-setting material into the first open end of the hemodialyzer case so that the first end of the fiber bundle is immersed in the quick-setting material, allowing the quick-setting material around the first end of the fiber bundle to set, removing the fitting from the first open end of the hemodialyzer case and attaching a first potting cap to the first open end of the hemodialyzer case, attaching the fitting to the second open end of the hemodialyzer case, injecting quick-setting material into the second open end of the hemodialyzer case so that the second end of the fiber bundle is immersed in the quick-setting material, allowing the quick-setting material around the second end of the fiber bundle to set, removing the fitting from the second open end of the hemodialyzer case and attaching a second potting cap to the second open end of the hemodialyzer case. 20. A method of encapsulating a hollow fiber bundle of a hemodialyzer comprising the following steps: providing a hollow fiber bundle having a first end and a second end, inserting the fiber bundle into a hemodialyzer case with a first open end and a second open end, fluffing the first and second ends of the fiber bundle, providing a combination first potting cap and collar and a combination second potting cap and both of which are at least partially filled with a quick-setting material in a partially set state, attaching the first combination potting cap and collar to the first open end of the hemodialyzer case so that the first end of the fiber bundle extends into the quick-setting material disposed in the first combination potting cap and collar and allowing the quick-setting material in the first combination potting cap and collar to set, attaching the second combination potting cap and collar to the second open end of the hemodialyzer case so that the second end of the fiber bundle extends into the quick-setting material disposed in the second combination potting cap and collar and allowing the quick-setting material in the second combination potting cap and collar to set.

Inventors: MARR DENNIS, SMITH TINA, MARR, DENNIS, SMITH, TINA
Applicants: BAXTER INT, BAXTER INTERNATIONAL INC.
Application year: 1999
Main classification: A61M1
IPC codes: A61M1, B01D61, B01D63