Technical Field

The present invention relates to capillary dialyzers for blood purification.

Background of the Invention

Capillary dialyzers are widely used for blood purification in patients suffering from renal insufficiency, i.e., for treatment of the patients by hemodialysis, hemodiafiltra- tion or hemofiltration . A multitude of different models of capillary dialyzers is commercially available.

The devices generally consist of a casing comprising a tub- ular section with end caps capping the mouths of the tubu ^¬ lar section. A bundle of hollow fiber membranes is arranged in the casing in a way that a seal is provided between the first flow space formed by the fiber cavities and a second flow space surrounding the membranes on the outside. Exam- pies of such devices are disclosed in EP 0 844 015 A2, EP 0 305 687 Al, and WO 01/60477 A2.

Hence, commercially available dialyzers at least comprise one housing and two end caps. Generally, they comprise ad- ditional parts like sealing rings, gaskets, and support rings. Production, handling, and subsequent assembly of the individual elements add to the complexity of the production process and the manufacturing cost. It would therefore be desirable to reduce the number of individual parts in the dialyzer. Summary of the Invention

A capillary dialyzer is provided which does not comprise end caps, sealing rings, or support rings. The dialyzer shell is comprised of a single trough-shaped molded part 1 having blood ports 3 and dialysate ports 4; and a cover 2 bonded to the seam of the trough-shaped molded part and sealing the opening of the trough.

Short Description of the Drawings

Fig. 1 shows a perspective view of a capillary dialyzer of the present application;

Fig. 2 shows a partially exploded perspective view of a capillary dialyzer of the present application;

Fig. 3 shows a perspective view of an embodiment of the housing of the capillary dialyzer of the present application;

Fig. 4 shows a perspective view and a cross-sectional view of a bundle of hollow fibers in an embodi ^¬ ment of the housing of the capillary dialyzers of the present invention and a casting mold used during potting of the ends of the bundle of hol ^¬ low fibers;

Fig. 5 shows a detail of a cross-sectional top view and a detail of a longitudinal-sectional perspective view of a bundle of hollow fibers in an embodi ^¬ ment of the housing of the capillary dialyzers of the present invention after potting of the ends of the hollow fibers and before cutting open the ends of the hollow fibers. Detailed Description

Figs. 1 and 2 show a capillary dialyzer comprising:

a) a trough-shaped housing 1 defining a longitudinally extending internal chamber including a first end and a sec- ond end;

b) a cover 2 sealing the opening of the trough of the housing 1;

c) a bundle 5 of semi-permeable hollow fiber membranes disposed within the internal chamber and extending longitu- dinally from the first end of the housing to the second end of the housing, the hollow fiber membranes having an outer surface, and a first end and a second end corresponding to the first end and the second end of the internal chamber; d) end wall means 6 supporting the first and second ends of the hollow fiber membranes within the internal chamber so as to sealingly separate the first and second ends of the hollow fiber membranes from the outer surface of the hollow fiber membranes between the first and second ends thereof;

e) blood ports 3 on the front end and rear end, re ^¬ spectively, of the housing 1; and dialysis fluid ports 4 on the wall of the housing at locations between the first and second end of the bundle 5 of hollow fiber membranes. The housing 1 of the capillary dialyzers of the present in ^¬ vention is a trough-shaped molded part which includes the functionality provided by the end caps in conventional dia ^¬ lyzers. It can be produced in a single step by injection molding of a suitable thermoplastic polymer. Suitable poly- mers include thermoplastic polymers, e.g., polyethylene, polypropylene, polyesters like PET or PBT, polymethylmeth ^¬ acrylate, polystyrene (HIPS) , thermoplastic polyurethane, or polycarbonate. In one embodiment of the present inven ^¬ tion, the housing 1 is transparent. In another embodiment, the housing 1 is opaque. The housing 1 comprises two blood ports 3 on its front end and rear end, respectively. During operation of the dialyz- er, the blood ports 3 are used to feed blood to the dialyz- er and remove blood from the dialyzer, respectively. Two dialysis fluid ports 4 are provided on the wall of the housing at locations between the first and second end of the bundle 5 of hollow fiber membranes. In one embodiment of the invention shown in Fig. 1, both dialysis fluid ports 4 are located on the bottom side of the housing, near the end wall means 6. In another embodiment of the invention, at least one of the dialysis ports 4 is located on a side wall of the housing 1. In still another embodiment of the invention, both dialysis fluid ports 4 are located on the same side wall of the housing 1. In still another embodi ^¬ ment of the invention, one port is located on one of the side walls and the other port is located on the opposite side wall of the housing 1. In one embodiment of the invention, the housing 1 additionally comprises flexible ears 8 located at the upper part of the inside of each side wall of the housing 1 near the trough opening and extending longitudinally along the housing 1, as shown in Figs. 3 and 4. The flexible ears 8 fa- cilitate introduction of the bundle 5 of hollow fiber membranes into the housing 1 by providing additional guidance and act as an additional retainer for the bundle 5 of hol ^¬ low fiber membranes when bent into their final position, as shown in Fig . 4.

In another embodiment of the invention, as shown in Figs. 3 and 5, the housing 1 also comprises circumferential ridges 7 in the part of the housing 1 where the end wall means 6 are located. The circumferential ridges 7 serve as a sup- port for the bundle 5 of hollow fiber membranes and a spac ^¬ er between the ends of the hollow fiber membranes and the inner wall of the housing 1 before the potting step. After completion of the potting step, the circumferential ridges 7 provide an additional anchor for the end wall means 6. In one embodiment, the circumferential ridges 7 have an eleva ^¬ tion, relative to the inner wall surface of the housing (1) , in the range of from 1 to 10 mm, for instance, 2 to 5 mm.

The cover 2 seals the opening of the trough of the housing 1. The cover 2 does not feature any fluid ports such as blood ports or dialysis fluid ports. In one embodiment of the invention, the cover 2 is transparent. In one embodi- ment of the invention, the cover 2 is a sheet of a trans ^¬ parent polymer. Suitable transparent polymers include poly ^¬ ethylene, polypropylene, polyurethane, and polycarbonate. The thickness of the sheet generally is in the range of from 0.1 to 0.5 mm, for instance, 0.15 to 0.3 mm. The cover 2 is bonded to the seam of the trough-shaped molded part, thus sealing the opening of the trough. The cover 2 is bonded to the housing 1 and the end wall means 6 by a suit ^¬ able process, e.g., welding, heat-sealing, or by means of an adhesive. The cover 2 can be equipped with further func- tions. In one embodiment of the dialyzer, a strain gauge is provided on the cover 2, allowing for detection of strain due to the internal pressure in the dialyzer and thus, measurement of the pressure within the dialyzer. In one em ^¬ bodiment, the calibration curve of the strain gauge is rec- orded during the integrity test of the dialyzer and printed on the cover as a Data Matrix code. When the dialyzer is connected to a dialysis monitor, the Data Matrix code can be read by the monitor and used to calculate the pressure within the dialyzer from the observed distortion of the strain gauge. The end wall means 6 supporting the first and second ends of the hollow fiber membranes within the internal chamber are generated by potting the ends of the fiber with a reac- tive polymer. A suitable potting material for the hollow fiber membranes is polyurethane .

The present disclosure also relates to processes for pro ^¬ ducing the dialyzer of the invention. An exemplary process comprises the steps of

i) providing a trough-shaped housing 1 defining a longitudinally extending internal chamber including a first end and a second end; and having blood ports 3 on its front end and rear end wall, respectively; and dialysis fluid ports 4 on its bottom wall and/or side walls;

ii) introducing a bundle 5 of hollow fiber membranes into the internal chamber of the housing 1, so that the fi ^¬ bers extend longitudinally from the first end of the hous ^¬ ing 1 to the second end of the housing 1;

iii) introducing a casting mold 9 into the housing 1 which completely covers the trough opening of the housing 1 and seals off compartments at the first end and at the sec ^¬ ond end, respectively, of the interior chamber;

iv) potting the ends of the hollow fiber membranes to produce end wall means 6 supporting the ends of the hollow fiber membranes within the internal chamber;

v) removing the casting mold 9 from the housing 1; vi) cutting the part of the end wall means 6 facing the blood ports 3 to open the ends of the hollow fiber mem- branes; and

vii) bonding the cover 2 to the trough opening of the housing 1.

It is expedient to close the ends of the hollow fiber mem- branes before the potting step in order to prevent the pot- ting material from permeating into the fibers. The fiber ends can be closed by processes known in the art, e.g., by melting or by means of an adhesive. In one embodiment of the process the ends of the hollow fiber membranes are closed before the bundle 5 of hollow fiber membranes is in ^¬ troduced into the housing 1.

After the bundle 5 of hollow fiber membranes has been in ^¬ troduced into the housing 1, a casting mold 9 is introduced into the housing 1. As shown in Fig. 4 for an exemplary embodiment, the casting mold 9 in its final position com ^¬ pletely covers the trough opening of the housing 1 and seals off compartments at the first end and at the second end, respectively, of the interior chamber, so that potting material introduced through one or both of the dialysis ports 4 cannot penetrate into these compartments.

In one embodiment of the process, the casting mold 9 also provides spacers between a part of the end wall means 6 on the side facing the blood port 3 and the side walls of the housing 1, as shown in Fig. 4. As a result, gaps are pro ^¬ vided between a portion of the end wall means 6 and the side walls of the housing 1, as shown in Fig. 5. In an embodiment of the invention where the housing 1 addi ^¬ tionally comprises flexible ears 8, the casting mold 9 also bends the flexible ears 8 into their final position during its introduction into the housing 1, simultaneously pushing peripheral hollow fiber membranes into the housing 1 and further compacting the bundle 5 of hollow fiber membranes, as illustrated by Fig. 4.

With the casting mold 9 in its final position, the ends of the hollow fiber membranes are potted to produce end wall means 6. Potting material, for instance polyurethane, is introduced into the housing via one or both of the dialysis fluid ports 4. The potting material is distributed within the housing 1 of the dialyzer by centrifugation, i.e., ro- tating the dialyzer at high speed perpendicular to its longitudinal axis. The potting material is allowed to cure; thereby forming end wall means 6 on both ends of the bundle 5 of hollow fiber membranes. After the potting material has hardened, the casting mold 9 is removed.

The ends of the hollow fiber membranes are subsequently opened, for instance by cutting the part of the end wall means 6 facing the blood ports 3 with a blade 10. The end wall means 6 are cut diagonally, as shown in Fig. 5. In one embodiment of the process, the angle and the starting posi ^¬ tion of the blade 10 are selected to have the blade 10 cut through the face of the end wall means 6 at a position above the bottom wall of the housing 1, e.g., at a distance in the range of from 0.5 to 2 mm. The cutting angle, rela- tive to a plane perpendicular to the bottom wall of the housing 1, is in the range of from 2 to 10°. As the result ^¬ ing wedge-shaped section does not adhere to the bottom wall of the housing 1, it can easily be removed from the housing 1. This is even more so for embodiments where a gap is pro- vided between the section to be cut off from the end wall means 6 and the side walls of the housing 1, as shown in Fig. 5. In one embodiment of the process, the cuts at both end wall means 6 of the dialyzer are mirror-symmetrical to each other.

After the ends of the hollow fiber membranes have been opened, the cover 2 is mounted on the housing 1 of the dia ^¬ lyzer to close the trough opening of the housing 1. The cover 2 is bonded to the housing 1 and the end wall means 6 by a suitable process, e.g., welding, heat-sealing, or by means of an adhesive, for instance, a polyurethane adhe ^¬ sive .