Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
  • B01D69/08—Hollow fibre membranes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
  • B01D69/08—Hollow fibre membranes
  • B01D69/082—Hollow fibre membranes characterised by the cross-sectional shape of the fibre
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
  • B01D71/06—Organic material
  • B01D71/08—Polysaccharides
  • B01D71/10—Cellulose; Modified cellulose

Definitions

• the invention relates to a dialysis membrane made of a regenerated cellulosic polymer in the form of a hollow thread with a continuous inner cavity which is essentially filled with a gas, the hollow thread having a porous inner and an outer surface, and a method for producing such a hollow dialysis thread from a solution of cellulose and / or cellulose derivatives and / or chitin; the concentration of polymeric substances being 4-16% by weight, based on the weight of the solution, and the continuous inner cavity being formed by a fluid containing a gas.
• Hollow cellulose filaments in which the cellulose has been regenerated from cuoxam solutions are known, for example, from DE-A-23 28 853.
• DE-C-29 06 576 describes a process for spinning hollow fibers made of regenerated cellulose for semipermeable membranes by squeezing a cellulose-cuoxam solution through the ring slot of a hollow thread spinneret into aqueous Sodium hydroxide solution and a cavity-forming liquid through the inner bore of the hollow fiber spinning nozzle and customary post-treatment known.
• An arrangement of the hollow thread spinneret in the bottom of the coagulation trough is less important due to technical problems with sealing and piecing.
• EP-B-0 076 442 describes a process for producing a hollow fiber from regenerated copper ammonia cellulose with an axially arranged cylindrical bore which extends over the fiber length, the bore being filled exclusively with gas and no contaminating substances contains, became known, with the steps:
• the hollow filaments are made from pure cellulose, the biocompatibility properties are significantly poorer than in the case of membranes which have been modified to a small extent, for example.
• DD-A-261 041 discloses a capillary hollow membrane made of regenerated cellulose (viscose) for the
• Liquid phase permeation the inner cavity being created by a gas or a liquid.
• common viscoses are included High level of coagulation and the use of mildly coagulating precipitation baths.
• EP-A-0 135 593 discloses a hollow dialysis thread made of cuproamraonium cellulose, which has a skin on the outside and no pores on the inside surface. The elongation of the hollow fibers mentioned falls in the range from +1.0 to -5.0%.
• EP-B-0 175 948 describes the production of undrawn hollow fibers for dialysis by coagulating one
• the film structure should be essentially skin-free and essentially pore-free on the inner surface.
• the tolerance of hemodialysis in the patient is influenced by various factors, such as the physical and psychological condition of the patient, the sterile environment and in particular the dialyzer, for which the biocompatibility of the hollow fibers in the dialysis module is an important factor.
• the surface properties of the polymer, the membrane structure and the dialyzer design have a significant influence on the biocorapacity in the dialysis treatment.
• the chemically different structures of the different polymers play an important role in biocompatibility, such as in complement activation (C5a formation), hemolysis and thrombogenicity.
• dialysis membranes made of synthetic or natural polymers when used in artificial kidneys, can very easily cause blood to clot, which is largely prevented by appropriate medication, a further effect often occurs with dialysis membranes made from regenerated cellulose, namely, that in the treatment of a kidney patient with dialyzers with cellulose membranes, a temporary drop in leukocytes can take place in the first period of dialysis treatment.
• This effect is referred to as leukopenia and must at least be largely suppressed or prevented by modifying the membrane.
• the leukopenia during dialysis is most pronounced 15 to 20 minutes after the beginning, whereby the neutrophils (these are the leukocytes that can be stained with neutral or simultaneously with acid and basic dyes) can almost completely disappear. After that, the number of leukocytes recovers to almost the original value or exceeds it within about an hour.
• leukopenia occurs again to the same extent.
• the complement system within the blood serum is a complex, multi-component plasma enzyme system that is used in various ways to ward off damage caused by the invasion of foreign cells (bacteria, etc.). If antibodies against the penetrating organism are present, the complex can be activated in a complement-specific manner by the complex of the antibodies with antigenic structures of the foreign cells, otherwise the complement activation takes place in an alternative way through special surface features of the foreign cells.
• the complement system is based on a large number of plasma proteins. After activation, these proteins react specifically with one another in a certain order and, at the end, a cell-damaging complex is formed, which destroys the foreign cell.
• the object of the present invention is to provide a dialysis membrane which is distinguished by the fact that its properties can be adapted to as many dialysis parameters as possible and that it can be produced and processed economically.
• the method according to the invention is characterized by the features of one or more of claims 11 to 24.
• Modified celluloses such as those used in:
• FIG. 1 shows the hollow fiber membrane according to the invention in different embodiments.
• FIG. 4 shows a Spinnsche a, in which the essential features of the method according to the invention are shown.
• FIGS. 5 to 10 show FE scanning electron microscope images of the hollow filaments according to the invention.
• FIGS. 1 to 4 which are not to scale, were chosen because the special details of the embodiments would be difficult to see if they were drawn to scale.
• FIG. 1 shows the cross section of a hollow thread 1 according to the invention with a continuous circular inner cavity 2 which is essentially filled with a gas.
• the reference number 3 designates the outer surface of the hollow thread 1, which also has a circular outer cross-section.
• the outer surface 3 is formed by a thin skin and has fine longitudinal grooves.
• the hollow thread 1 has an inner surface 4 which is positively modified by physical and / or chemical means.
• the outer surface 3 of the hollow thread 1 can be arranged concentrically to the inner cavity 2 or, as shown in FIG. 1, eccentrically to the inner cavity 2.
• the centers of the circular inner cavity 2 and the circular surface 3 are arranged at a distance from one another, so that a region of maximum thickness of the hollow fiber wall consisting of cellulosic material continuously changes into a region of minimal wall thickness in a clearly visible manner.
• FIG. 2 shows a further possibility of forming the profile in the dialysis serum according to the invention.
• the membrane wall of the hollow thread 1 consisting of cellulose, which has been regenerated from Cuoxam solutions, has a circular inner cavity 2, while the outer surface has four symmetrically arranged longitudinal ribs 5.
• FIG. 3 shows the cross section of a dialysis membrane consisting of two circular hollow fibers connected by a web.
• the cuoxara spinning solution is fed to the spinning slots of a spinneret 6 by means of a spinning pump.
• the central bore of the spinneret 6 is supplied with at least 80%, preferably at least 90%, of a gas fluid 7 to form the inner cavity.
• the coagulation bath 8 which is present, for example, in a tub 9, the solution jet rising from the spinneret directly into the coagulation bath is coagulated and solidified. After sufficient solidification, the hollow thread 1 which forms can be deflected on rollers 10 in order to ensure a sufficient dwell time in the coagulation bath.
• FIG. 5 shows an FE-SEM image at a magnification of 45,000 times on an outer wall of the hollow thread according to the invention
• FIG. 6 shows the inner wall of the same hollow thread at the same magnification (example 1).
• Figures 7 and 8 are corresponding FE-SEM images at the same magnification, but with the invention Hollow threads that contain a small amount of modified cellulose (Example 3).
• FIG. 9 shows an FE-SEM image of the fracture surface in the vicinity of the inner edge of the hollow thread shown in FIG. 5 in a top view with an enlargement of 27000: 1.
• FIG. 10 shows an FE-SEM image corresponding to FIG. 9, but of the fracture areas in the vicinity of the outer edge of the same hollow thread at the same magnification.
• 2-forming Cuoxam spinning solution of 0.08 mm was used so that the outlet openings pointed vertically upwards and the outlet surface was parallel to the surface of the precipitation bath.
• the precipitation bath contained 140 g / 1 NaOH, 6 g / 1 ammonia and 0.8 g / 1 Cu in water at 20 ° C.
• the bath depth between the nozzle exit surface and the bath surface was 18 cm.
• 6.0 ml / min of Cuoxam spinning solution with a concentration of 9.0% cellulose was passed through the ring slot of the hollow fiber spinning nozzle.
• the wall-forming Cuoxam spinning solution solidified immediately above the outlet opening to form the Norman connection and could then be conveyed on without risk of deformation.
• the gas filling the cavity prevented the collapse of the hollow thread, which was still very soft at the beginning. Since spinning solution and gas emerged from the nozzle at the same time, a very light lump of coagulate formed in relation to the precipitation bath, which lumps after 2 - 5 seconds. detached from the nozzle and rose to the surface of the coagulation bath, as did the following, now correctly dimensioned hollow thread.
• the piecing was made much easier by taking advantage of the buoyancy.
• the coagulate floating on the surface of the bath was passed on through deflections through the second section of the coagulation bath for complete solidification and further through the de-coppering and deacidifying washing baths.
• the hollow fiber which now consisted of pure cellulose, passed through a plasticizer bath with 10 g / 1 glycerin and 400 g / 1 isopropyl alcohol in water and was then dried on a drum dryer at a contact temperature of 75-80 ° C. to a water content of 10%.
• winding was carried out as required on a package or, after applying an undulation, on a bundle winding machine.
• the finished hollow thread showed the desired concentric shape, but more uniform than when using an air gap and spinning from top to bottom, since the negative effects of viscosity differences, air movements and surface tension were avoided.
• the hollow thread produced in this way had a wall thickness of 8 ⁇ m and an inner diameter of 200 ⁇ m.
• the breaking strength was 110 cN, the elongation at break was 52% dry and 102% wet.
• a nozzle was placed in a spinning device according to Example 1
• Spinning solution with the concentrations: 6.35% cellulose, 8.0% ammonia and 2.65% Cu.
• the amount of extruded spinning solution was 6.5 ml / min, the amount of gas was 1.6 ml / min at a pressure of 22 mbar.
• the immersion depth was unchanged at 18 cm and the concentration of the precipitation bath was 140 g / 1 NaOH, 6 g / 1 ammonia and 0.8 g / 1 Cu in water at 20 ° C.
• the exit speed at the nozzle was 59.2 m / min, the speed of the first deflection was 50.2 m / min.
• the hollow thread was again transported through the further treatment baths with the least possible tension.
• the aftertreatment bath contained 80 g / 1 glycerin and 400 g / 1 isopropyl alcohol in water and the drying temperature was 75-95 ° C.
• Example 1 The final presentation is as in Example 1.
• the hollow fiber obtained in this way had a breaking strength of 70 cN and an elongation at break of 56% dry or 110% wet.
• the wall thickness was 16 ⁇ m and the inside diameter was 205 ⁇ m.
• the following performance data were measured on this hollow fiber:
• Dialysis performance vitamin B 12 14.8 cm / min * 10
• the sieving coefficient for cytochrome C was 0.86, for albumin 0.06.
• a spinning solution was used in a spinning device according to Example 2, the cellulose of which comprised 95% pure linter cellulose, but 5% diethylaminoethyl cellulose with a DS of 0.4.
• the nitrogen content of the regrind was 0.14%.
• the other conditions remained unchanged.
• the hollow fiber produced in this way showed the following data:
• Dialysis performance vitamin B ⁇ 2 14 ⁇ 8 cm / min . 1Q -3
• a hollow fiber membrane was produced which, unlike conventional HF membranes, contained a discrete layer of higher consistency on its inside.
• Example 3 This effect was achieved under the conditions of Example 3, but with an inner filling gas which consisted of 80% by volume of nitrogen and 20% by volume of sulfur dioxide. The amounts of gas used and the wall-forming spinning solution remained unchanged, as did the further post-treatment steps.
• the sulfur dioxide supplied with the nitrogen acted as a sulphurous acid on the inner wall. While in conventional processes the precipitation begins on the outer wall and creates a denser layer there, with the rest of the wall remaining of a relatively uniform porous structure, in this case such a layer of 1-3 ⁇ m thickness could also be produced on the inner wall.
• the total wall thickness decreased by 1 ⁇ m to 15.5 ⁇ m, the
• the inside diameter remained at 200 ⁇ m. 2
• Cytochrome C decreased to 0.77, that for albumin to 0.004.
• the deformed hollow thread on the other hand, can be safely assembled into loose, evenly filled bundles and thus guarantees optimal dialyzer performance.
• This necessary loose bundling can also be achieved if contact-preventing profiles are applied to the hollow thread on the outside, e.g. webs extending in the longitudinal direction and pointing outwards.
• the speed of the first deflection was 52.1 m / min.
• the hollow thread created under these conditions actually showed the desired profile of four webs evenly distributed over the circumference with rounded edges of 4 - 5 ⁇ m heights with a wall thickness of 9 ⁇ m on the free sections of the membrane wall and an inside diameter of 198 on its cross-sectional area ⁇ m. These dimensions and the said profile remained constant to any desired extent over any endless length.
• bundles for test modules were produced from these hollow fibers in such a way that an additional change in the hollow fiber shape due to pressure points was excluded.
• the bundles showed a loose structure with an even distribution over the bundle cross-section.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Separation Using Semi-Permeable Membranes (AREA)
• External Artificial Organs (AREA)

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Citations (8)

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• 1992
  • 1992-08-07 WO PCT/EP1992/001801 patent/WO1993003829A1/de not_active Application Discontinuation
  • 1992-08-07 JP JP5504064A patent/JPH06509746A/ja active Pending
  • 1992-08-07 DE DE59205365T patent/DE59205365D1/de not_active Revoked
  • 1992-08-07 EP EP92916710A patent/EP0600932B1/de not_active Revoked
  • 1992-08-07 ES ES92916710T patent/ES2083757T3/es not_active Expired - Lifetime
  • 1992-08-07 US US08/196,100 patent/US5505859A/en not_active Expired - Fee Related

Patent Citations (8)

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