JPS5850761B2 - Cellulose dialysis membrane and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dialysis membrane formed from cellulose regenerated from cuprammonium solution and in the form of hollow fibers having hollow chambers therethrough.

German Patent No. 736 321 discloses hollow fibers made of regenerated cellulose regenerated from a cuprammonium solution and having hollow chambers passing through them.

It is known from US Pat. No. 3,228,877 that the hollow fibers produced according to the above-mentioned German Patent No. 736,321 are suitable as dialysis membranes and as reverse osmosis membranes.

From U.S. Pat. No. 3,888,771 a hollow fiber formed from cellulose regenerated from cuprammonium solution is known, which fiber has a constant membrane structure and has uniform walls along the entire axis of the fiber. It has a thickness and a precisely annular cross section.

From GB 859,325 a method is known for producing hollow fibers whose cross section varies periodically or non-periodically over the length of the fiber.

Synthetic thermoplastic polymers are used as fiber materials.

The resulting fibers are used as filling materials for polyester, pine tresses, cushions, and the like.

During dialysis, for example hemodialysis, the membrane wall must be thoroughly and unobstructed (cleaned) by the dialysate.

When using a focused dialysis membrane in the form of hollow fibers, the precisely annular hollow fibers have a fiber density of about 500-1000
Similar to the glass plate effect of two plane-parallel glass plates in a bundle of hollow fiber specimens of /cni,
It has the property of easily adhering firmly over its entire length.

This mutual adhesion makes it difficult for the dialysate to flow into the interspace between the hollow fibers, and the area where the hollow fibers adhere to each other remains unused for mass exchange, thereby reducing the efficiency of the hollow fiber module. .

However, mass exchange is also reduced by the flow rate inside the membrane, since in laminar flow a membrane is formed on the membrane wall, and the membrane is poor in metabolites.

This results in a smaller concentration difference governing mass exchange.

The object of the present invention is to form dialysis hollow fibers made of regenerated cellulose in such a way that mutual adhesion of the hollow fibers is sufficiently prevented and the formation of a laminar flow distribution inside the hollow fibers is avoided.

The subject is provided with periodic deformations on its surface in the longitudinal and/or circumferential direction, so that the cross section perpendicular to the fiber axis of the hollow fiber varies over the entire length of the fiber, and/or The solution is a hollow fiber dialysis membrane whose cross section perpendicular to the fiber axis is contoured.

Preferably, the outer wall of the membrane corresponds to two vibration equation curves running at a distance from each other in the longitudinal section of the fiber.

The hollow fibers according to the invention are produced by coagulating in dilute caustic soda solution a cellulose-copper ammonia solution extruded from a hollow fiber nozzle, the spinning solution being extruded from the spinning nozzle in order to avoid stretching and orientation as much as possible. Immediately after that, it is introduced into a coagulation bath.

For the formation of the through-hole cavity, a cavity-forming liquid, for example a halogenated hydrocarbon, a hydrocarbon or an ester, is passed through the central hole in a known manner, with isopropyl myristate proving advantageous.

However, water and aqueous solutions, such as solutions of carboxymethylcellulose salts, have also been shown to be very suitable as cavity-forming liquids.

The formation of hollow fiber shapes according to the present invention is achieved by periodically varying the pumping rate of the spinning solution or the liquid for forming the chambers or the delivery pressure of the pump.

A periodic change in the pumping rate or delivery pressure results in a time-periodically varying cross-sectional variation of the extruded hollow fiber, which resembles a wave in the longitudinal direction.

By a defined change in the pumping rate and/or the delivery pressure of the feed pump, hollow fibers with different shapes are obtained, with the outer wall being periodically excited and damped in the longitudinal section in a particular embodiment of the invention. corresponds to the vibration curve.

Hollow fibers of such a shape can be particularly advantageously grouped together into fiber bundles which can be washed by the dialysate without hindrance, thus ensuring a rapid and effective mass exchange by the membrane.

In another particular embodiment of the invention, the membrane wall corresponds in longitudinal section to a sawtooth curve.

The hollow fibers of such a shape engage each other in forming the hollow fiber bundle and thus create a highly stable, self-supporting fiber bundle with multiple passageways for penetration of dialysate through the fiber bundle. give.

In the dialysis membrane according to the present invention, the cross section of the hollow fibers can be varied within a wide range without causing any trouble to dialysis.

Preferably, the minimum cross-sectional area is 30-85% of the maximum cross-sectional area.

The outer diameter of the hollow fibers according to the invention is between 10 and 1000 μm at the point of greatest cross-sectional area, preferably between 50 and 600 μm.

The film thickness ranges from 1 to 100 microns, preferably from 5 to 50 microns.

Since dialysis with dialysis membranes is subject to different and often countercurrent effects upon variations in cross-sectional area, it is often advantageous to offset such effects by a corresponding increase and/or decrease in membrane thickness.

For example, when vibrations are excited by the action of pumping a liquid for forming a hollow chamber, the film thickness decreases at locations with a larger cross-sectional area;
On the other hand, when vibrations are excited by pumping the spinning solution while keeping the pumping of the hollow chamber forming liquid constant, the film thickness at the same location increases.

In this case, the inner cross-section of the hollow fiber is subject to smaller fluctuations than the outer cross-section.

The fibers according to the invention can be produced by periodically varying the withdrawal speed of the hollow fibers as they exit the spinning nozzle and pass through the coagulation bath, the fibers being fed, for example, by means of chamfered rolls.

The profiled cross section preferably extends from 1 to 3 times the membrane thickness of the hollow fibers.

The thickness of the hollow fiber according to the present invention is determined by a method known per se.
00μ door, preferably 5-50μ door.

The inner diameter of the hollow fibers is from 10 to 1000 μm, preferably from 20 to 6
00 μm.

As a rule, the inner cavity cross-section is designed to be annular, since such a fiber cross-section presents fewer difficulties during the spinning of cellulose-copper ammonia solutions.

However, the effectiveness of the dialysis membrane according to the invention can be increased even more significantly by forming the inner cavity cross-section in an oval shape.

This significantly increases the exchange area for the same blood volume in the dialysis membrane according to the invention, which already significantly improves the efficiency of metabolite exchange.

The thin blood film thickness within the dialysis membrane according to the invention further improves the effectiveness of dialysis.

The effect of fiber mutual adhesion known for circular dialysis fibers was no longer observed.

The formation of the hollow fiber shape according to the invention is obtained by using a hollow fiber spinning nozzle with a spinning slit with a correspondingly contoured cross section and a central hole for supplying the liquid for forming the hollow chamber.

In order to obtain the desired shape, the profiled cross-section at the spinning nozzle is deep (
Form.

Regarding the dialysis membrane according to the invention, West German patent application P.
No. 2627858, P2705735 and P270
5733, hollow holes are used to increase leak resistance or to obtain a surface layer containing chemically modified cellulose, or to embed adsorbents within the membrane wall. It is also possible to form the membrane wall of the fibers into two or more layers.

The method according to the present invention has been found to be useful for spinning hollow fibers that have a precise cross-sectional shape given by the shape of the spinning nozzle, have excellent properties as a semipermeable membrane, and have intact mechanical properties. Served.

This method involves immersing a hollow fiber spinning nozzle in an aqueous caustic soda solution, and adjusting the ratio of the take-up speed of the hollow fibers at a first take-up roller to the discharge speed of a cellulose-copper ammonia solution squeezed out from an annular slit of the hollow fiber spinning nozzle. is set to 1.00 to 1.05, and the direction of yarn travel from the hollow fiber nozzle to the first take-up roller forms an acute angle with respect to the axis of the hollow fiber spinning nozzle opening.

When using spinning nozzles for hollow fibers with a profiled cross section, no flattening of the profile cross section occurs, in contrast to the methods of the prior art.

In principle, it is also possible in the method according to the invention to arrange the hollow fiber spinning nozzle at the bottom of the coagulation bath and to spin the yarn upwards.

Owing to the great technical difficulties that arise in such an arrangement during nozzle exchange, backing and spinning start-up, such an embodiment for carrying out the method is less important than in the case of arranging the hollow fiber nozzle at the surface of the coagulation bath. is small.

Preferably, the hollow fiber spinning nozzle is immersed in the aqueous caustic soda solution to a depth of 5 to 107 n11 L during the process of the invention.

This immersion depth is already sufficient to solidify the fibers sufficiently quickly, the hollow fiber spinning nozzle opening being still clearly visible in the caustic soda solution, which is colored deep blue by the cuprammonium solution.

In the method of the present invention, the first take-off roller is arranged so that the spun hollow fibers are not guided vertically downward when exiting the hollow fiber spinning nozzle, that is, from the hollow fiber spinning nozzle to the first take-off roller. The first take-up roller is shifted by the length of the first take-up roller so that the direction of thread travel forms an acute angle with the axis of the hollow fiber spinning nozzle opening.

Advantageously, such an acute angle is between 15° and 70°.

In the method according to the invention, the freshly spun hollow fibers are transported in the coagulation bath only under very low stress.

The circumferential speed of the second take-off roller, which is preferably arranged behind the first take-off roller, is only 90 to 98% of the circumferential speed of the first take-off roller.

This causes a small shrinkage of the newly spun hollow fibers, whereas in the prior art methods the hollow fibers are already drawn immediately after leaving the spinning nozzle.

Conventionally, in order to produce hollow fibers that are used as semipermeable membranes and have a membrane thickness of 10 to about 200 Itm and a diameter of about 50 to 1000 μm, the dimensions are several times the dimensions of the hollow fibers, e.g. It was thought to be possible only with hollow fiber spinning nozzles that are ~50x.

Within the scope of the invention, hollow fiber spinning nozzles are preferably used in which the dimensions of the annular slit of the hollow fiber spinning nozzle are 2.5 to 6 times the dimensions of the final hollow fiber.

The cellulose content of cellulose-copper ammonia solutions is generally not different from the cellulose content of cellulose-copper ammonia spinning solutions commonly used for regenerating cellulose.

Preferably, however, the cellulose content is between 6 and 10% by weight, based on the weight of the solution.

The NaOH content of the caustic soda solution can be varied within a wide range.

Preferably, however, the NaOH content should be between 10 and 20% by weight in order to ensure a sufficiently rapid formation of Norman cellulose to induce hardening of the hollow fibers.

To the extent that the hollow fibers produced by the method according to the invention are to be or must not be drawn, the drawing is preferably carried out during passage through the aftertreatment bath.

1 to 8 show examples of irregular cross-sections of dialysis membranes according to the present invention.

1' is a membrane wall of hollow fibers 2' made of cellulose, each regenerated from a steel ammonia solution.

1 to 3 are longitudinal cross-sectional views of various embodiments of hollow fibers according to the present invention, and FIGS. 4 to 8 are cross-sectional views of the hollow fibers perpendicular to the fiber axis.

FIG. 1 is a schematic longitudinal section of a dialysis membrane according to the invention, the membrane wall of which corresponds to a sine curve, 1' being the membrane wall of a hollow fiber 2 made of cellulose regenerated from cuprammonium solution.

FIG. 2 is a schematic longitudinal section of a dialysis membrane according to the invention whose membrane wall corresponds approximately to a sawtooth wave, 1' being the membrane wall of a hollow fiber 2' made of cellulose regenerated from a cuprammonium solution. .

FIG. 3 is a schematic longitudinal section of a dialysis membrane according to the invention, the membrane wall of which corresponds approximately to a sinusoidal curve with damping and periodic excitation.

In this example, 1' is also the membrane wall of the hollow fiber 2, which is made of cellulose regenerated from a cuprammonium solution.

FIG. 4 shows a hollow fiber having an annular hollow chamber cross-section with two symmetrically arranged longitudinally extending ribs.

FIG. 5 shows a hollow fiber with an annular hollow chamber cross-section with four symmetrically arranged longitudinally extending ribs.

FIG. 6 shows a hollow fiber with a star-shaped profile with three projections and an annular hollow chamber cross-section.

FIG. 7 shows a hollow fiber with a star-shaped profile with five projections and an annular hollow chamber cross-section.

FIG. 8 shows a hollow fiber having an elliptical hollow chamber cross-section with two longitudinally extending rigs of the hollow fiber symmetrically at the end points of the long axis of the ellipse.

FIG. 9 is a schematic illustration of the method of the invention.

A cellulose-copper ammonia spinning solution 1 and a cavity-forming liquid 2, such as isopropyl myristate or paraffin oil, are fed to the hollow fiber spinning nozzle 3.

The hollow fiber spinning nozzle 3 is immersed in an aqueous caustic soda solution passed through a coagulation tank 4 .

The hollow fibers 5 emerging from the spinning nozzle 3 are deflected by a first take-off roller 6 and sent via a second take-off roller 7 to a post-treatment bath.

The running direction of the fibers forms an acute angle between the first take-up roller 6 and the hollow fiber spinning nozzle 3 and the axis of the hollow fiber spinning nozzle opening.

The aftertreatment bath is preferably designed as a tank, two of which are illustrated in the drawing (8; 14).

A deflection roller 9 is arranged in the aftertreatment bath.

The driven rollers 10, 11, 12 and 13 are driven at a gradient circumferential speed, so that the hollow fibers 5 are drawn to the desired degree.

The washed hollow fibers 5 are led via the last deflection roller into the dryer 15, where they are dried and then taken up in the winding device 1.
It is wound up and made into a reel at step 6.

For after-treatment baths, dilute caustic soda solution, water, dilute sulfuric acid, "oxygenated water" and pure water are generally used in the following order.

The hollow fibers are preferably treated with glycerin before drying.

Example 1 Production of a dialysis membrane according to the present invention having periodic fluctuations in the direction perpendicular to the axis of the fibers A cellulose-copper ammonia solution is slit with an annular slit, the slit width of which is reduced to 1/2 of the conventional slit width, The hollow fiber was extruded through an annular nozzle with a ratio of slit width to slit height of approximately 1:20, with the spinning pressure being increased periodically.

The cellulose-copper ammonia solution had a cellulose content of 9% by weight, an ammonia content of 6.5% by weight and a copper content of 4.0% by weight.

The viscosity of the spinning solution was 2300 poise.

At the same time, isopropyl myristate was pumped through the inner hole of the spinning nozzle as a hollow chamber forming liquid.

The extruded spinning solution was led into a caustic soda bath just below the spinning nozzle.

The coagulated fibers were then passed through a longer washing section, which was followed by a water bath, a sulfuric acid bath and then a dryer.

Following dry reeling, winding was performed, with part of the material used as a spool and part of it used as a skein.

The hollow fibers were sized into pieces of fiber approximately 20 CrfL in length.

The diameter at the largest cross section was 305μ door.

The minimum cross-sectional area was 35% of the maximum cross-section.

The waveform has a wavelength of approximately 5 mm and a distance of 27 I as measured from the thickness measurement.
It corresponded to a stationary sine wave of LrIL.

Hollow fibers have a temperature of 2 when measured at 50% atmospheric humidity and 23°C.
It had a tensile strength of 5.10" CN/mA.

The elongation was 25%.

Example 2 Using a dialysis membrane according to the present invention for hemodialysis 6000 hollow fibers produced in Example 1 were bundled together and installed in a hollow fiber test dialyzer.

Ultrafiltration rate 4.1 rrL at standardized solution flow 200 vtl/min·R and dialysate flow 500 m1/min·d
l/) 1-711-7XilHg was measured at a water temperature of 37°C.

The removal of urea in the aqueous solution was 150 TLl/min.

The removal of vitamin B12 in the aqueous solution was 42 verticals/min.

Example 3 Preparation of a dialysis membrane according to the invention A cellulose-copper ammonia solution was placed between two
The hollow fiber was extruded from a spinning nozzle in which the spinning slits on one side expanded symmetrically outward.

The length of the extension is then three times the width of the spinning slit,
The width of the expansion was approximately 1.5 times the width of the spinning slit.

The cellulose content of the cellulose-copper ammonia solution is 9.
It was 2%.

Isopropyl myristate was extruded as a cavity-forming liquid through the inner hole of the hollow fiber nozzle, the diameter of which corresponded to three times the width of the spinning slit.

The nozzle was positioned so that its outlet opening was five orders of magnitude below the surface of the 12.5% NaOH precipitation bath.

The hollow fiber-forming material coming out of the nozzle is sent to a first take-off roller present in the settling bath at an angle of 40° to the axis of the hollow fiber spinning nozzle opening, and after floating up behind the roller, it is sent to a second take-off roller. Guide you through.

In this case, the flow rate of the hollow fiber-forming cellulose material is 30.
The circumferential speed of the first take-up roller was 30.9 m/min, and the circumferential speed of the second take-up roller was 30.26 m/min.

The hollow fibers are then passed through a conventional continuous bath for copper removal.

Another caustic soda bath is followed by a water wash, a sulfuric acid wash and another water wash.

After treatment with glycerin and drying, hollow fibers with an inner diameter of 215 μm and a membrane thickness of 16 μm are obtained.

The fibers have rib-like protrusions each having a width of the hollow fiber membrane thickness and a length 1.5 times the membrane thickness on two opposite sides of the outer wall.
He had an individual.

The inner cross section was annular.

The hollow fibers had a tensile strength of 25.103 cN/rn4 and an elongation of 26%, measured at 50% atmospheric humidity and 23°C.

Example 4 Use of the dialysis membrane according to the invention for hemodialysis The high efficiency of hemodialysis with the dialysis membrane according to the invention produced in Example 3 shows the following results in dialysis tests.

The bundle of fibers 6000 in the contoured dialysis hollow exhibited a very loose configuration even in the wet state.

The fiber bundles were mounted in a hollow fiber testing dialysis machine and tested under standardized conditions.

Solution flow 200TIL/min, 7 and dialysate flow 500r
The following results were obtained in ul/min·m'.

Ultrafiltration rate: 2,7rI'Ll/hm'・'IfLr
/LHg urea removal: 138ml/min Vitamin B12 removal: 28rIll/min

[Brief explanation of drawings]

1 to 8 show embodiments of a modified cross-section of the dialysis membrane according to the invention, and FIG. 9 is a schematic diagram for carrying out the method according to the invention. 11...Membrane wall, 2...Hollow fiber, 1.
...Cellulose-copper ammonia solution, 2...
... Liquid for hollow chamber formation, 3 ... Hollow fiber spinning nozzle, 4 ... Coagulation bath, 6 ... First take-up roller, 7 ... Second take-up roller , 9... Direction changing roller, 8, 14... Post-treatment bath.

Claims (1)

[Claims] 1. A dialysis membrane manufactured from cellulose regenerated from a cupric ammonia solution and in the form of a hollow fiber having a hollow chamber passing through, the surface of which is periodically deformed in the longitudinal and/or circumferential direction. This means that the cross section perpendicular to the fiber axis of the hollow fiber varies over the length of the fiber and/or that the cross section perpendicular to the fiber axis is irregularly shaped. Characteristic cellulose dialysis membrane. 2. The dialysis according to claim 1, which corresponds to a vibration equation curve in which two outer membrane walls symmetrical with respect to the fiber axis run at a distance in the longitudinal section of the fiber. film. 3. The dialysis membrane according to claim 1 or 2, wherein the membrane wall corresponds to a curve of vibrations that are periodically excited and damped in a longitudinal section. 4. The dialysis value according to any one of claims 1 to 3, wherein the membrane wall corresponds to a sawtooth curve in a longitudinal section. 5. The dialysis membrane according to any one of claims 1 to 4, wherein the minimum cross-sectional area is 30 to 85% of the maximum cross-sectional area. 6 Claims 1 to 5, wherein the thickness of the hollow fiber increases and/or decreases in accordance with periodic variations in the cross section.
The dialysis membrane according to any of paragraphs. 7. The dialysis membrane according to claim 1, wherein the hollow fibers have one or more ridge-like protuberances on the outside along the fiber axis. 8. The dialysis membrane according to any one of claims 1 to 7, wherein the cross section of the hollow fiber has an irregular cross section corresponding to a star shape having three or more protrusions on the outside. 9 Claim 7, wherein the hollow chamber has an annular cross section
Or the dialysis membrane according to any one of Item 8. 10. The dialysis membrane according to any one of claims 7 to 9, wherein the hollow chamber has an oval cross section. 11 Pass the cellulose-copper ammonia solution through the annular slit of the hollow fiber spinning nozzle into the aqueous caustic Noda solution;
and the surface thereof is subjected to periodic deformation in the longitudinal direction and/or circumferential direction by forcing out the hollow chamber forming liquid through the inner hole of the hollow fiber spinning nozzle and subjecting it to a conventional post-treatment, For this purpose, the hollow fibers are regenerated from a copper ammonia solution, in which the cross-section perpendicular to the fiber axis varies over the entire length of the fiber and/or the cross-section perpendicular to the fiber axis is formed with irregular shapes. In a method for manufacturing a dialysis membrane made of cellulose in the form of hollow fibers having hollow chambers passing through, the hollow fiber spinning nozzle is immersed in an aqueous caustic soda solution, and the hollow fibers are taken up at a first take-up roller at a The ratio of the discharge speed of the cellulose-copper ammonia solution extruded from the annular slit of the hollow fiber spinning nozzle to the discharge speed is set to 1.00 to 1.05, and the direction of yarn running from the hollow fiber spinning nozzle to the first take-up roller is the same as that of the hollow fiber. A method for manufacturing a dialysis membrane, characterized by forming an acute angle with the axis of a spinning nozzle opening. 12. The method according to claim 11, wherein the hollow fiber spinning nozzle is immersed in an aqueous caustic soda solution to a depth of 5 to 10 mm. 13. The method according to claim 11 or 12, wherein the direction of travel from the hollow fiber spinning nozzle to the first take-up roller forms an angle of 15° to 70° with respect to the axis of the opening of the hollow fiber spinning nozzle. . 14. The method according to any one of claims 11 to 13, wherein the circumferential speed of the second take-up roller disposed behind the first take-up roller is set to 90 to 98% of the circumferential speed of the first take-up roller. . 15. Method 616 according to any of claims 11 to 14, wherein the dimensions of the annular slit of the hollow fiber spinning nozzle are 2.5 to 6 times the dimensions of the finished hollow fibers.
The cellulose content of the cuprammonium solution is 6-10% by weight based on the weight of the solution and the NaO content of the aqueous caustic soda solution is
The H content is 10-20% by weight relative to the weight of the solution.
The method according to any one of claims 11 to 15. 17. The method according to any one of claims 11 to 16, characterized by hollow fibers during passage through the after-treatment bath.