JPS60193504A - Hollow fiber membrane for dialysis - Google Patents

Abstract

PURPOSE:To obtain a hollow fiber membrane for dialysis which is free from deterioration with age in the dialysis performance during storage by consisting the titled membrane of a cellulose ester deriv. and forming said membrane in such a way that the film thickness is of a specific value or below and that the yield strength after a dry heat treatment satisfies the specific equation. CONSTITUTION:The stock liquid for spinning consisting of cellulose ester is extruded from the outside pipe of a spinneret and a core liquid is discharged from the inside pipe by using an annular orifice. The hollow stock liquid emitted from the annular orifice is once traveled in air and is then conducted to an aq. solidifying bath. The hollow liquid is then passed through a glycerol bath after warm rinsing. The fiber is then dried by hot wind and is taken up on a bottin. The bobbin on which the fiber is taken up is heat-treated. The resulted hollow fiber has <=20mu film thickness and a module for dialysis is assembled by using such fiber. The yield strength Sb of the module for dialysis after the dry heat treatment for 20hr at 80 deg.C is measured and the holding rate (Sb/Sa), when determined, satisfies the equation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel hollow fiber membrane, and relates to a cellulose ester dialysis hollow fiber membrane suitable for purifying body fluids by dialysis.

Cellulose esters have traditionally been processed into hollow fiber membranes and used in energy-saving separation processes such as desalination of shrubs and seawater, ultrafiltration of aqueous solutions containing various solutes, etc. It's here.

On the other hand, various research and development efforts have been made on cellulose ester-based hollow fiber membranes as hollow fiber membrane leaf materials used for blood purification of renal failure patients due to their compatibility with living organisms and ease of production. The performance of a hollow fiber membrane when used for blood purification must satisfy the following six items.

■Have excellent dialysis performance ■Have no blood leakage from the hollow fiber membrane ■Have compatibility with blood. In other words, blood coagulation and hemolysis are unlikely to occur. ■ No blood remains in the module after blood purification. ■ There is little eluate from the hollow fiber membrane. ■ Dialysis performance does not change over time during storage. By reducing the membrane thickness, solute diffusion improves, dialysis efficiency improves, and
It is known that this improvement in dialysis efficiency has the great advantage of making it possible to downsize the dialysis module and reducing the need for extracorporeal blood circulation in patients. In contrast to the need to satisfy the above six items, a major problem associated with thinning the membrane is a decrease in the ability to maintain hollow fiber membrane performance as the wall of the hollow fiber membrane becomes thinner. The thickness of the cellulose ester hollow fiber membrane, which does not show any decrease in zero maintenance ability, which is the point at which dialysis performance changes, is approximately 20 mm.
Although it was more than μ, there were still many problems in terms of dialysis performance.

The present inventors have arrived at the present invention as a result of intensive studies to find a hollow fiber membrane that takes advantage of thinning and does not change over time in dialysis performance during storage.

That is, the present invention provides a hollow fiber membrane made of an ester derivative of cellulose, wherein the thickness of the hollow fiber membrane is less than 20 μm and
When subjected to dry heat treatment at 0°C for a fixed length of 20 hours, the yield strength 8b (97 pieces) after heat treatment is a hollow fiber membrane for dialysis that satisfies formula (1).

0.90≦Bb/sa≦1.10 (1) (However, Sa (97 pieces) is the yield strength of the hollow fiber membrane for dialysis before heat treatment.) Used in the cellulose ester-based hollow fiber membrane for dialysis in the present invention The cellulose ester that can be used is a general term for cellulose esters such as cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, and cellulose acetate propionate, or a mixture thereof.

It is necessary for the hollow fiber membrane according to the present invention to have a thickness of less than 20 μm and to simultaneously satisfy the relationship of the above-mentioned formula (1). It is known that the diffusion of solutes improves as the membrane becomes thinner, but for cellulose ester hollow fiber membranes, hollow fiber membranes with a diameter of approximately 20 μm or more are generally less artificial than artificial membranes due to stability during storage or transportation. It has been used for dialysis. The hollow fiber membrane according to the present invention is unstable in terms of strength when it is used as a thin membrane and at the same time has a rigid membrane structure. In addition, when Bb7B11 exceeds 1.1, the hollow fiber membrane
If it is exposed to high temperatures during storage or transportation, it will tend to become structurally denser, which naturally reduces dialysis performance and prevents it from achieving its original blood purification performance, causing great harm to patients. This will affect the The yield strength of the hollow fiber membrane was measured using a universal tensile tester under the following conditions: hollow fiber membrane length 5Q quantity s, tensile force □□□:l Q nod'/1lfn.
The yield strength was determined from the yield point of the measured stress-strain curve.

The lower limit of the thickness of the hollow fiber membrane according to the present invention is 5μ. With current spinning technology, it is not possible to stably spin a perfectly circular and uniform hollow fiber membrane of less than 6 μm.

Further, the inner diameter of the cellulose ester hollow fiber membrane in the present invention is from 100μ to 400μ, preferably 1
It is 50μ to 300μ. In addition, by making the hollow fiber membrane thinner, it is preferable to add an appropriate amount of ring to the hollow fiber membrane in order to increase the dialysis efficiency of solutes, and also to prevent uneven flow of the dialysate even in the module form. . It is particularly preferred that the shape of the crimps is 10 per 10 CII of the hollow fiber membrane, with a size ranging from 65% of the outer diameter of the hollow fiber membrane to 50 microns plus the outer diameter of the hollow fiber membrane.

If it is within this range, when the hollow fiber membrane is assembled into a module, uneven flow on the dialysate side is prevented, dialysis efficiency is further improved, and in addition to thinning the membrane, it becomes possible to further downsize the module.

Cellulose ester-based dialysis hollow fibers for dialysis of the present invention are extruded through the annular slit of the outer tube of the spinneret, the core liquid is extruded from the inner tube of the spinneret, and the spinning stock solution is once introduced into a gas atmosphere, after which it is coagulated into an aqueous system. The material is introduced into a bath, washed with wet water, passed through a glycerin bath, dried with hot air, wound onto a bobbin, and the wound bobbin is heat-treated.

In order to obtain the hollow fiber membrane according to the present invention, the spinning process described above must satisfy all of the following conditions at the same time. The concentration of cellulose ester in the spinning dope is from 27 weight percent to 37 weight percent, and the water concentration in the coagulation liquid is from 65 weight percent to 90 weight percent, preferably in the range of 70 weight percent to 86 weight percent. The temperature of the hot water washing is 40°C or more and 80°C or less, the glycerin bath conditions are such that the glycerin concentration is 25% to 60% by weight, the warm temperature of the glycerin aqueous solution is 35°C or more and 80°C or less, and the drying temperature is 25% to 60% by weight. The temperature of the hot air in the process is 60°C or higher and 80°C or lower, and the heat treatment temperature of the wound bobbin is 60°C or higher and 10°C or higher.
The temperature is below 0°C.

Furthermore, with the spinning conditions set as described above, as the membrane becomes thinner, residual materials in the hollow fiber membrane tend to move. In other words, considering that residual materials in the hollow fiber membrane move relatively easily to the patient during hemodialysis, it is important to minimize the number of residual materials in the thin hollow fiber membrane as much as possible. For this purpose, we have strengthened the quality control of the raw materials used (i.e. checking for residual raw materials) and hot water washing. In particular, cellulose ester, which is a solid raw material whose quality is difficult to check among raw materials, is extracted with a mixed solvent of acetone and water with a volume ratio of 55 = 45 at a bath ratio of 15 at 20°C for 1 hour. It has been found that it is preferable to use a material with an extraction rate of 0.5 weight percent or less.

Hereinafter, the present invention will be explained in more detail with reference to specific examples, but the present invention is not limited to this range.

Example L 33 parts by weight of cellulose diacetate and 5 parts by weight of N-methyl-2-pyrrolidone have an extraction rate of 0.32% by weight with a mixed solvent of acetone/water 55/45 (volume ratio).
4 parts by weight and 13 parts by weight of ethylene glycol were mixed and dissolved, this was used as a spinning stock solution, and spinning was performed using an annular orifice nozzle. A spinning dope was supplied from the outer tube, while liquid paraffin was discharged as a core liquid. The hollow stock solution that came out of the annular oliice was run in 5 c + a air, then introduced into a coagulation bath containing 75 parts by weight of water and coagulated, and then thoroughly washed with 50°C hot water, and then washed with 45 parts of glycerin by weight. % in an aqueous solution at 40° C., and then a zone of dry air at 60° C. was passed through the hollow fiber in countercurrent to the drying air and wound onto a bobbin by a winder.

The wound bobbin was treated in a hot air dryer at 70° C. for 15 hours.

The obtained cellulose diacetate hollow fibers were perfectly circular, had an inner diameter of 200 μm, and a membrane thickness of 15 μm. Using this hollow fiber membrane, a 1.1 d dialysis module was assembled. The performance of this dialysis module was measured according to the dialyzer performance evaluation standards of the Japanese Society for Artificial Organs, and the ultrafiltration rate was υ, 9d/hr H9, and the blood side flow company was 720.
When 0 d/ll1n, the clearance of urea is 17
It was 4 d/lrm.

The yield strength Shioka+ of the dialysis module was measured before and after dry heat treatment at 80° C. for 20 hours, and the retention rate (Sb/8a) was found to be 1.03. When a dialysis module using this hollow fiber was stored for 15 days at 55°C, the highest temperature it could be exposed to in a single transportation vehicle, the retention rate of ultrafiltration rate, which is an indicator of dialysis performance, was 93%. It was fun.

Comparative Example 1 A hollow fiber membrane with an inner diameter of 200 μm and a membrane thickness of 27 μm was obtained under the same conditions as in Example 1 by changing the discharge bar and spinning speed of the spinning dope. Using this hollow fiber membrane 1. The dialysis module II was assembled. The retention rate (81)/Sa) of the yield strength structure before and after the dry heat treatment at 80° C. for 20 hours was 1.01. However, when the performance of the dialysis module was measured in the same manner as in Example 1, the ultra-excess amount was 3.5 sd/hr-1.
11LH9 and urea clearance was 140. This performance is insufficient for a dialysis module.

Comparative Example 2 Using the same spinning dope and core solution as in Example 1, spinning was carried out using an annular orifice. The hollow stock solution exiting the annular orifice was allowed to travel 5 cm into the air, and then introduced into a coagulation chamber containing 60 layers of water, allowed to coagulate, and thoroughly washed at room temperature. The hollow fibers were passed through an aqueous solution, then passed through a dry air zone of 60° C., and wound onto a bobbin using a winder.

The obtained cellulose diacetate hollow fibers had an inner diameter of 1
The film thickness was 15μ. Using this hollow fiber membrane, 1.
A 1 d dialysis module was assembled.

The yield strength Ihu retention rate (Fll)/8a) before and after dry heat treatment at 80° C. for 20 hours was 1.15. When this dialysis module was stored at 56° C. for 15 days, the ultra-excess retention rate was 83%, which is unsuitable as a hollow fiber membrane for dialysis.

Patent applicant: Toyobo Co., Ltd.

Claims (1)

[Scope of Claims] A hollow fiber membrane made of an ester derivative of cellulose, the thickness of which is less than 20 μm, and when dry heat treated at 80° C. for 20 hours, the yield strength after heat treatment is 5b ( 9
/ book) satisfies formula (I).A hollow fiber membrane for dialysis. However, B & (97 pieces) is the yield strength (g/piece) of hollow fiber membrane for dialysis before heat treatment.