JP2894133B2 - Hollow fiber and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow fiber mainly used for blood purification and a method for producing the same.

[0002]

2. Description of the Related Art Hollow fibers currently used for blood purification are inserted in a bundle of several thousands in a cylindrical housing. Among them, particularly in hemodialysis and similar treatments, harmful substances are removed by flowing blood inside the hollow fiber and dialysate outside. In particular, most of urea nitrogen (BUN) in blood, which requires a high removal rate, is removed by diffusion. Therefore, even if the permeation performance of the hollow fiber itself is improved, the removal ability cannot be improved if the contact between the outer surface of the hollow fiber and the dialysate is poor. That is, when the fibers come into close contact with each other, the dialysate cannot sufficiently contact the outer surface of the fiber, so that the performance of the fiber itself cannot be sufficiently exhibited. Therefore, there is a need for a technique for reducing the contact area between the hollow fibers and improving the contact property with the dialysate. As a known technique, a method in which fin-shaped protrusions are provided on the outer surface of a hollow fiber (Japanese Patent Publication No. 2-44)
226), a method in which a spacer is added between hollow fibers (for example, JP-A-3-238027), and a method for meandering the fibers (for example, JP-A-61-5848). Also, a method for forcibly changing the spinning stock solution and the core solution discharge amount for forming the hollow portion during film formation (Japanese Patent Application Laid-Open No. 55-14271).
1, Japanese Patent Publication No. 58-50761) has also been proposed.

[0003]

In these prior arts, special processing nozzles and special processing steps and equipment are required after film formation. Therefore, not only the number of manufacturing steps is increased, but also physical and chemical Susceptible to mechanical damage. Also, when fins or spacers are inserted, the portions where they come into contact with the outer surface of the fiber tend to have low contact with the dialysate, and are not necessarily good. An object of the present invention is to solve the problems of the prior arts possessed by these techniques and to provide a hollow fiber having a high fiber-opening property and a blood processing apparatus using the fibers. Further, in the conventional method for producing hollow fibers, a core liquid composed of an organic liquid is often used to form a hollow portion, but a Freon-based cleaning agent is used for washing and removing the core liquid. However, due to the reduction in the use of CFCs, there is a situation in which they are struggling with such cleaning methods. A second object of the present invention is to provide a method for producing a hollow fiber free of such problems.

[0004]

In the present invention, the outer diameter of the hollow fiber is changed periodically, especially in a waveform, and the ratio of the outer diameter to the minimum outer diameter / maximum outer diameter (hereinafter referred to as the "outer diameter ratio"). ) In the range of 0.70 to 0.95 and the period of change in the range of 300 to 3,000 μm.
The first object has been achieved. The change in the waveform referred to in the present invention means a change in which the membrane wall is formed in a wavy shape in the longitudinal section of the fiber as shown in FIG. 1, and the cycle of the change means the following from the maximum outer diameter portion to the next. This means that the distance from the maximum outer diameter part or the minimum outer diameter part to the next minimum outer diameter part is used as a unit, and this is periodically repeated. The hollow fiber of the present invention is suitable for use in treating blood by flowing blood therein, and is particularly preferably used as a dialysis membrane. Further, in order to produce such a hollow fiber while achieving the second object, a spinning solution in which the raw material of the hollow fiber is dissolved is prepared so that the viscosity at the time of spinning becomes 500 to 1,000 poise. The mixture is supplied to a double tubular spinning nozzle, extruded into air while supplying gas therein, and then introduced into a coagulation bath to coagulate in a state where little tension is applied. Hereinafter, the hollow fiber-shaped semipermeable membrane of the present invention and a method for producing the same will be specifically described. The hollow fiber of the present invention has an outer diameter ratio of 0.70
０．９0.95, and the cycle (wavelength) of the change is in the range of 300-3,000 μm, but when the outer diameter ratio is larger than 0.95 or the cycle is longer than 3,000 μm, the blood treatment is performed. In this case, the fibers easily adhere to each other, and the effect of the present invention is not sufficiently exhibited. In addition, if the outer diameter ratio is smaller than 0.70 or the cycle is shorter than 300 μm, the fiber is likely to be partially thinned in the manufacturing process, and as a result, blood leakage or fiber crushing occurs in blood processing. It is not preferable because it becomes easier. A more preferred outer diameter ratio is 0.80 to 0.95, and the period is 50.
It is preferably in the range of 0 to 2,000 μm. Further, it is preferable that the thickness of the hollow fiber is substantially constant regardless of the change of the outer diameter in order to obtain excellent membrane performance. When flowing blood inside, the inner diameter of the hollow fiber is 150-250 μm
Is preferably within the range. The thickness of the film is 5 to 10
The range of 0 μm is preferable, and the range of 5 to 50 is more preferable.
μm. In order to produce the hollow fiber of the present invention, first, a spinning solution in which the above-mentioned polymer material is dissolved is prepared so that the viscosity at the time of spinning becomes 500 to 1,000 poise. When the viscosity is smaller than 500 poise, the outer diameter ratio becomes smaller than 0.70, and when the viscosity exceeds 1,000 poise, the outer diameter ratio becomes 0.95.
Larger than. The viscosity varies depending on the concentration of the raw material, the additive, the temperature, and the like, and these are adjusted so that the viscosity during spinning falls within the above range. As a material constituting the hollow fiber used in the present invention, a polymer material such as cellulose acetate and a hydrolyzate thereof, cuprammonium cellulose, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, polysulfone, and polyether sulfone are preferably used. it can. The concentration of the polymer raw material in the spinning solution is 20 to 40% by weight.
Is appropriate. Although the solvent for dissolving the polymer raw materials varies depending on the raw materials, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, N-methyl-2-pyrrolidone, etc. are widely used for various polymers. Can do things. In addition, a third component such as polyethylene glycol, polyvinylpyrrolidone, polyhydric alcohol and inorganic salts having various degrees of polymerization is added to the spinning dope to control membrane performance and adjust the viscosity of the spinning dope. Can be. The spinning solution is supplied to the outer nozzle of a double concentric spinneret, and gas is supplied to the inner nozzle to be extruded into the air from the spinneret. When a liquid is supplied instead of a gas, the outer diameter does not change periodically. The shape of the mold does not necessarily have to be circular,
Other shapes, such as an elliptical shape and other irregular cross-sectional shapes, may be used. As a gas supplied to the inner nozzle, an inert gas such as nitrogen or argon is desirable. The spinning dope is supplied to the spinneret at a constant average flow rate to keep the fiber thickness constant. The spinning solution extruded from the spinneret is introduced into a coagulation bath after passing through the air to form hollow fibers. As the coagulating liquid, water or an aqueous solution is preferable,
The hollow fibers are wound after passing through a coagulation bath. In the present invention, it is necessary to once extrude the spinning solution into the air, and if it is extruded directly into a coagulation bath, it is not possible to obtain hollow fibers whose outer diameter changes periodically. When the viscosity of the spinning dope is set to 500 to 1,000 poise, the reason why a hollow fiber whose outer diameter changes periodically is not clear, but it is extruded into the air while blowing gas inside. If the gas is extruded into the air while the gas is being blown into the inside, the gas inside tends to be rounded due to surface tension, and it is considered that this force and viscosity are appropriately balanced. That is, when the viscosity is less than 500 poise, the force for rounding overcomes the viscosity, the fluctuation of the outer diameter becomes large, and the viscosity becomes 1000
If the poise is larger than the poise, the effect of the rounding force is reduced. If the poise is 500 to 1000 poise, these are balanced to obtain a hollow fiber having a predetermined variation in outer diameter. Then, in order to fix such a periodic change as it is, the solidification is performed in a state where almost no tension is applied.
If any strong tension is applied during solidification, the periodic change in outer diameter disappears. In the present invention, (1) the viscosity of the spinning dope is adjusted to a predetermined range, (2) the gas is supplied to the inner nozzle, and (3) the outer diameter is predetermined by temporarily extruding the air from the nozzle. Hollow fibers that change with the period can be obtained automatically. On the other hand, the prior art described above does not simultaneously satisfy the above conditions (1), (2), and (3), and periodically changes the pressure of the liquid or gas supplied into the fiber. The outer diameter is changed periodically. In the case of such a conventional technique, it is difficult to change the pressure in a very short cycle, so that it is difficult to obtain a fiber whose outer diameter changes in a short cycle as defined in the present invention. The hollow fiber of the present invention,
When the outer diameter fluctuates periodically, the outer surfaces of the fibers are less likely to adhere to each other, and exhibit extremely high spreadability.
Further, by periodically changing the inner diameter, it is difficult to form a boundary film generated when blood, which is a non-Newtonian fluid, flows through the inside of the hollow fiber, and it is also possible to achieve an improvement in diffusion removal ability. In fact, a hemodialyzer using this fiber has a BUN compared with a type having the same membrane area and a constant outer diameter.
In addition to improving the clearance by about 5 to 10%, cleaning after fiber spinning is not required, so the number of manufacturing steps is smaller than before, and the membrane damage rate associated therewith is also reduced.
Residual blood after return was also significantly improved.

[0005]

【Example】

Example 1 A spinning dope comprising 28 parts of cellulose acetate, 25 parts of polyethylene glycol and 47 parts of dimethylformamide was prepared and heated to 90 ° C. The dope viscosity at this time is 70
It was between 0 and 800 poise. The undiluted solution was discharged from a nozzle outer tube consisting of a double tube and from the inner tube as a core material at room temperature nitrogen gas at a rate of 4 ml / min. After discharging, let it pass through the air layer, then guide it into a water bath and solidify it.
/ Min. The cross section of the obtained hollow fiber is a perfect circle, having a minimum outer diameter of 221 μm and a maximum outer diameter of 265 μm,
The outer diameter ratio was 0.83. Further, in the longitudinal direction of the fiber,
Periodic fluctuation of the outer diameter of 000 to 1,500 μm was observed. The obtained hollow fiber is plasticized with glycerin, dried,
Bundled. At this time, adhesion between the films was not recognized at all, and extremely high opening property was exhibited. When this was used as a module with a membrane area of 1 m ² and the clearance in an aqueous system was measured,
The urea clearance was good at 184 ml / min, and the inorganic phosphorus clearance was good at 130 ml / min. Also,
Flow contrast agent inside the hollow fiber and dialysate outside,
Observation of the flow state of the dialysate by X-ray tomography showed that the dialysate flowed uniformly throughout and was good. Further, a blood circulation test was performed for 4 hours using this module, and the blood was returned. The blood returned was good, and almost no residual blood was observed.

Example 2 A film was formed in the same manner as in Example 1 except that the amount of polyethylene glycol in the spinning solution was changed to 27 parts. The viscosity of the stock solution at this time was about 900 poise. The cross section of the obtained hollow fiber is a perfect circle, the minimum outer diameter is 240 μm, and the maximum outer diameter is 267 μm.
And the outer diameter ratio was 0.90. The outer diameter period variation in the fiber longitudinal direction was 1,200 to 1,500 μm. The urea clearance of a 1 m ² module using this membrane was 175 ml / min.

Example 3 A spinning dope comprising 30 parts of polyether sulfone, 35 parts of polyethylene glycol and 35 parts of dimethyl sulfoxide was prepared and heated to 40 ° C. At this time, the viscosity of the spinning dope was 600 poise. This stock solution was discharged and solidified in the same manner as in Example 1 and wound at 125 m / min. The cross section of the obtained hollow fiber was a perfect circle, having a minimum outer diameter of 275 μm, a maximum outer diameter of 303 μm, and an outer diameter ratio of 0.91. Also,
The period in the fiber longitudinal direction was 1,000 to 1,300 μm. As with Example 1, this hollow fiber also had high openability.

Comparative Example 1 Using the same spinning dope composition as in Example 1, spinning was performed under the same spinning conditions, and the film was wound in a coagulation bath under such a condition that a slight tension was applied. The obtained hollow fiber did not show a periodic change in the outer diameter. When the fibers were bundled in the same manner as in Example 1, adhesion between the fibers was observed. For this reason,
Needed fiber loosening. When a module of 1 m ² was prepared from these fibers and the membrane performance was measured, the urea clearance in an aqueous system was 140 ml / min. In addition, a blood permeation test was performed, and residual blood was observed mainly in the portion that required loosening. Further, the flow state of the dialysate was observed by X-ray tomography in the same manner as in Example 1. As a result, a non-uniform part of the dialysate was observed at several places, and a locally poor flow part was observed.

Comparative Example 2 The same composition as in Example 1 was used and the temperature of the spinning dope was set to 100 to 105.
° C and treated under the same conditions except that the viscosity was reduced. The spinning dope concentration at this time was 100 to 300 poise, the outer diameter ratio of the obtained fiber was 0.5, and the diameter change cycle in the longitudinal direction was 500 μm. These fibers were partially crushed or deformed like glasses, and when assembled into a module and primed, the pressure loss was high, leaks occurred, and the fibers could not be used.

[0010]

The hollow fiber of the present invention has a very high ratio because the outer surface of the fiber is unlikely to adhere to each other because the ratio of the outer diameter to the minimum outer diameter / maximum outer diameter periodically changes within a specific range. Shows spreadability.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of the hollow fiber of the present invention.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ identification code FI D01F 1/08 D01F 1/08 (58) Investigated field (Int.Cl. ⁶ , DB name) D01D 5/24 D01F 1/08 A61M 1 / 14,1 / 18

Claims (5)

(57) [Claims] An outer diameter of a fiber is periodically changed in a waveform in a longitudinal direction of the fiber, and a ratio of a minimum outer diameter to a maximum outer diameter of the outer diameter is in a range of 0.70 to 0.95. And a semi-permeable membrane hollow fiber having a period in the range of 300 to 3,000 μm. 2. The hollow fiber according to claim 1, wherein the fiber has less thickness unevenness. 3. The hollow fiber according to claim 1, wherein the hollow fiber is a dialysis membrane. 4. A blood processing apparatus comprising the hollow fiber according to claim 1, 2 or 3 housed in a housing having an inlet and an outlet for blood. 5. A spinning solution in which a raw material of a hollow fiber is dissolved is prepared so as to have a viscosity of 500 to 1,000 poise during spinning, and this is supplied to a double tubular spinning nozzle to supply a gas therein. 2. The method for producing hollow fibers according to claim 1, wherein the fibers are extruded into air while being introduced into a coagulation bath, and coagulated in a state where little tension is applied.