JPH0564730A - Hollow yarn for cellulose acetate dialytic membrane and production thereof - Google Patents

Abstract

PURPOSE:To obtain hollow yarn set to specific values in its inner diameter and membrane thickness and excellent in capacity, in the dry and wet type spinning of the hollow yarn for a cellulose acetate dialytic membrane using gas as a hollow yarn forming material, by setting the angle of the hollow yarn before and after a guide in a liquid to 90-below 160 deg.. CONSTITUTION:A cellulose acetate spinning raw solution is downwardly ejected from a double pipe cap 1 and, at the same time, gas is supplied from the center part of the double pipe cap 1 to form a hollow part and, subsequently, the hollow spinning raw solution 4 is allowed to run in air to be guided to a coagulation bath 3. At this time, the advance direction of hollow yarn 4' is altered by the guide 2 in the coagulation bath 3 so that the angle of the hollow yarn 4' before and after the guide 2 is set to 90 deg.-below 160 deg.. By this method, hollow yarn for a cellulose acetate dialytic membrane excellent in capacity wherein the mean inner diameter thereof is 150-250mum, the mean membrane thickness thereof is 10-30mum and the standard deviation of the inner diameter of 100 hollow yarns is 5% of the mean inner diameter is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow fiber for a cellulose acetate dialysis membrane obtained by a dry-wet spinning method and a method for producing the hollow fiber.

[0002]

2. Description of the Related Art Conventional dry-wet spinning of hollow fibers for cellulose acetate dialysis membrane is a non-coagulating liquid as a hollow forming material from the center of a cellulose acetate spinning stock solution when it is discharged from a double tube spinneret. (For example, liquid paraffin or isopropyl alcohol) is introduced to form a hollow portion. By this manufacturing method, it is possible to stably spin a hollow fiber for cellulose acetate dialysis membrane, which has a uniform diameter, a small thickness, and excellent performance.

However, when assembling a hemodialyzer from the hollow fiber for dialysis membrane thus manufactured, the non-coagulable liquid, which is a hollow forming material, must be removed from the hollow fiber for dialysis membrane. That is, a method of removing the hollow forming material from the ends of the bundle-shaped hollow fibers cut at both ends by centrifugation, and a method of washing with an organic solvent after assembling the hemodialyzer have been used, but these methods are extremely difficult. It is complicated and expensive. In addition, there is a case where a specific CFC that partially destroys the ozone layer is used as the organic solvent,
It is also a problem from the viewpoint of global environment protection. Further, in terms of the properties used as a hemodialyzer, it is desirable that the hollow forming material remains as little as possible, but even if various hollow forming material removing means are combined in combination, the hollow forming material can be completely removed from the hollow fiber for dialysis membrane. It is difficult to remove.

Under these circumstances, there is a demand for the development of a spinning method that does not use a hollow forming material. The spinning method using air or gas as the hollow forming material is preferable as the spinning method for the hollow fiber for the dialysis membrane because it does not contain a substance that may be harmful after the hemodialyzer is assembled.

In fact, as a method for producing a hollow fiber for a dialysis membrane using a gas as a hollow forming material, Japanese Patent Laid-Open No. 58-98411 is used.
The method for melt spinning a cellulose acetate hollow fiber membrane of JP-A-53-86834 and the method for wet spinning an ethylene vinyl alcohol copolymer hollow fiber membrane of JP-A-53-86834 are disclosed. Since the principle is fundamentally different from the dry-wet spinning method, it cannot be applied as it is. Further, as an example of using gas as a hollow forming material in dry-wet spinning, there is a method for spinning a regenerated cellulose hollow fiber membrane as shown in Japanese Patent Publication No. 1-44803. When this method was applied to the spinning of cellulose acetate,
It was possible to spin a hollow fiber having a film thickness of 30 μm or more, but if the film thickness is made less than that, unevenness of the yarn diameter occurs in the air running portion,
Stable spinning was not possible. That is, Japanese Patent Publication 1-44
803 is applicable only to regenerated cellulose and cannot be used for cellulose acetate having different polymers.

[0006]

SUMMARY OF THE INVENTION The present invention has been made for the purpose of solving such problems.
That is, the present invention provides a cellulose acetate hollow fiber membrane having a thin film thickness and a small thickness, in which the efficiency of module assembly is improved and the safety to the living body is improved by using gas as the hollow forming material, and a method for producing the same.

[0007]

Means for Solving the Problems The inventors of the present invention have made extensive studies to obtain such a hollow fiber for a cellulose acetate dialysis membrane. As a result, the process of discharging the spinning dope from the spinneret and the running of the hollow spinning dope in the air are carried out. As a result of careful consideration of the process of leading to the coagulation bath, the following manufacturing method was invented. In a cellulose acetate hollow fiber produced by dry-wet spinning using gas as a hollow forming material, the hollow fiber has an average inner diameter of 150 to 250 μm, an average film thickness of the hollow fiber of 10 to 30 μm, and a hollow fiber 1
Hollow fiber for cellulose acetate dialysis membrane, characterized in that the standard deviation of the inner diameter of 00 pieces is 5% or less of the average inner diameter, and the cellulose acetate spinning stock solution are discharged downward from the double tube spinneret, and at the same time, the central part of the spinneret. Gas is supplied to form a hollow part, and then a hollow spinning solution is run in the air and then guided to a coagulating bath located below the spinneret.In dry-wet spinning, the hollow fiber is guided by a submerged guide in the coagulating bath. The method for producing a hollow fiber for a cellulose acetate dialysis membrane is characterized in that the angle of the hollow fiber before and after the submerged guide is 90 degrees or more and less than 160 degrees when changing the traveling direction of.

The present invention is characterized in that the hollow fiber for cellulose acetate dialysis membrane has an average inner diameter of 150 μm to 250 μm. If the inner diameter is smaller than 150 μm, the pressure loss when flowing blood becomes too large,
If the inner diameter is larger than m, there arises a problem that the volume efficiency is lowered.

Further, the present invention is characterized in that the hollow fiber for cellulose acetate dialysis membrane has an average thickness of 10 μm to 30 μm. If the film thickness is thinner than 10 μm, the strength is lowered and the yield in modularization is lowered, and if the film thickness is thicker than 30 μm, it becomes difficult to obtain a hollow fiber membrane having sufficient performance as a dialysis membrane. Further, the present invention is characterized in that the standard deviation of the inner diameter of 100 hollow fibers for cellulose acetate dialysis membrane is 5% or less of the average inner diameter. When the standard deviation is larger than 5% of the average inner diameter, the flow of blood in the hollow fiber is unbalanced, which increases pressure loss, facilitates thrombus formation, and deteriorates bubble removal during priming, which is not preferable.

The first feature of the method for producing a hollow fiber according to the present invention is dry-wet spinning in which a hollow spinning dope is run in the air and then introduced into a coagulating bath located below a spinneret. When changing the traveling direction of the hollow fiber by the submerged guide, the angle of the hollow fiber before and after the submerged guide is set to 90 degrees or more and less than 160 degrees. In normal dry-wet spinning, the angle of the hollow fibers before and after the submerged guide in the coagulation bath is slightly smaller than a right angle. That is, the hollow fiber dropped almost vertically from the spinneret and introduced into the coagulation bath changes the traveling direction upward by the submerged guide and travels again in the air from the liquid surface of the coagulation bath, travels through the rotating roller, and is washed with water or other Proceed to the process. At this time, the angle of the hollow fiber before and after the submerged guide is smaller than 90 degrees. This is because, at an angle of 90 degrees or more, the traveling direction of the hollow fiber is horizontal or downward, and the hollow fiber cannot go out of the coagulation bath liquid surface.

However, the smaller the angle of the hollow fiber before and after the submerged guide, the greater the force the hollow fiber receives when changing the traveling direction at the submerged guide portion. The direction of this force is the direction in which the hollow part of the hollow fiber is crushed, but when gas is used as the hollow forming material, the hollow part is crushed when the force is applied too much because the shape retention force of the hollow fiber is small. I will end up. When the angle before and after the submerged guide is examined, when the angle is smaller than 90 degrees, the shape retaining force of the hollow fiber becomes smaller than the force that the hollow fiber receives at the submerged guide portion, and the hollow portion collapses. I understand. That is, as the angle is larger than 90 degrees, the force applied to the hollow fiber by the submerged guide portion becomes smaller, and the shape of the hollow fiber is easily maintained. On the other hand, as the angle increases, the distance that the hollow fiber travels in the coagulation bath increases. If the angle exceeds 160 degrees, this distance becomes too long, and it is not preferable because practically unnecessary equipment and coagulating liquid are used.

The second feature is that the angle between the liquid surface of the coagulating bath and the hollow spinning dope when the hollow spinning dope is introduced into the coagulating bath is less than 90 degrees. That is, the angle of the hollow fiber before and after the submerged guide as shown above is 90 degrees or more.
The reason for setting the angle to less than 60 degrees is that the direction of the hollow fiber cannot be changed upward by the submerged guide unless the angle between the liquid surface of the coagulating bath and the hollow spinning dope is less than 90 degrees.

Further, the present invention is characterized in that the distance for running the hollow spinning dope in the air is 1 mm or more and 20 mm or less. When a gas is used as the hollow forming material, the shape retaining force is smaller than that when a liquid is used, so that the yarn diameter unevenness is likely to occur in the air running portion. That is, when the running distance in the air is 20 mm or more, stable spinning cannot be performed due to uneven yarn diameter. Further, when the air travel distance is shorter than 1 mm, it is not preferable because the mouthpiece may come into contact with the coagulation bath liquid surface due to the shaking of the coagulation bath liquid surface, and it may be difficult to adjust the air travel distance.

Further, the present invention is characterized in that the depth of the submerged guide in the coagulation bath is 5 mm or more and 100 mm or less. That is, when the hollow fiber runs in the coagulation bath to a depth of 100 mm or more, the water pressure of the coagulation liquid increases, and the hollow fiber is easily crushed, which is not preferable. The depth of the submerged guide is 5m.
If it is m or less, the coagulation of the spinning dope is insufficient and the running of the hollow fiber in the submerged guide portion may not be stable, which is not preferable.

In the present invention, the gas used as the hollow forming material is not particularly limited as long as it is a gas at room temperature and atmospheric pressure, but examples thereof include air or nitrogen as an air component, oxygen,
Carbon dioxide, argon, etc. may be mentioned, but air or nitrogen is preferable. Needless to say, when air is used, the steam contained therein has a great influence on the coagulability of the spinning dope, so that it is necessary to sufficiently manage the steam.

Further, in the present invention, cellulose acetate refers to a cellulose having hydroxyl groups substituted with acetyl groups, but the substitution rate is not particularly limited, but
Examples include substituted cellulose diacetate and substituted 3 cellulose triacetate. It is also known that the cellulose acetate spinning dope is generally obtained by heating and mixing a system in which cellulose acetate and a non-solvent for controlling the occurrence of phase separation are mixed by heating to remove impurities by a filter. The method is not limited to this. N-methyl 2 as a solvent
-Pyrrolidone, dimethylacetamide, dimethylformamide, etc., and nonsolvents include ethylene glycol, triethylene glycol, polyethylene glycol, glycerin, etc., but are not particularly limited thereto.

[0017]

EXAMPLES The effects of the present invention and more detailed description will be given below with reference to examples, but the present invention is not limited to the examples.

(Example 1) Cellulose triacetate 2
3 parts by weight, N-methyl 2-pyrrolidone 61.6 parts by weight,
15.4 parts by weight of triethylene glycol were heated and mixed at 170 ° C. to dissolve them, and then vacuum defoaming was performed to obtain a spinning dope of cellulose triacetate. This was filtered through a sintered filter having a pore size of 20 μm to remove impurities, and then discharged downward from the double pipe cap at a rate of 1.5 ml / min. On the other hand, 2.6 ml of air from the inside of the double pipe base
/ Min to form a hollow shape. The hollow fiber-shaped spinning solution was discharged from the spinneret, run in the air for 5 mm, and led to a coagulation bath. At this time, the angle between the coagulation bath surface and the hollow fiber spinning stock solution was 60 degrees. The spinning solution introduced into the coagulation bath has a diameter of 16 mm installed 20 mm below the surface of the coagulation bath.
With the satin round bar in liquid guide, change the angle in the liquid surface direction,
It was made to run in the air again from the liquid level of the coagulation bath 50 cm away from the submerged guide. At this time, the angle of the hollow fiber before and after the submerged guide was 118 degrees. After that, guided by the rotating roller,
A second coagulation bath, a washing bath, a glycerin bath, and a drier were run, and finally, it was rolled up into a cheese by a winder.
The winding speed at this time was 75 m / min. When a cross section of 100 hollow fibers thus obtained was observed with a microscope, the average inner diameter of the hollow fibers was 201.3 μm, and the standard deviation of the inner diameters was 5.8 μm. The average film thickness was 14.8 μm. Next, this hollow fiber membrane was cut into a length of 30 cm and 800 bundles were bundled to produce a hollow fiber membrane module for evaluation, and the performance as a dialysis membrane was measured by a known method. The results are shown in Table 1.

(Example 2) Cellulose diacetate 30
By weight, 56 parts by weight of N-methyl-2-pyrrolidone and 14 parts by weight of triethylene glycol were heated and mixed at 120 ° C. to dissolve, and then degassed in vacuum to obtain a cellulose diacetate spinning dope. This was filtered through a sintered filter having a pore size of 20 μm to remove impurities, and then discharged downward from the double tube cap at a rate of 1.3 ml / min. on the other hand,
Air was supplied at 2.6 ml / min from the inner side of the double pipe base to form a hollow shape. The hollow fiber-shaped spinning solution was discharged from the spinneret, run in the air for 3 mm, and led to a coagulation bath. At this time, the angle between the coagulation bath surface and the hollow fiber spinning stock solution was 45 degrees. The spinning stock solution guided to the coagulation bath changes its angle in the direction of the liquid surface by a satin round bar submerged guide with a diameter of 12 mm installed 30 mm below the coagulation bath liquid surface, and from the coagulation bath liquid surface 50 cm away from the submerged guide. I ran again in the air. At this time, the angle of the hollow fiber before and after the submerged guide is about 13
It was twice. Thereafter, the same processing as in the first embodiment is performed, and
It was wound up at a speed of 5 m / min. When the dimension of the obtained aerial yarn was measured, the average inner diameter was 200.9.
μm, the standard deviation of the inner diameter was 3.7 μm, and the average film thickness was 12.4 μm. An evaluation module was prepared in the same manner as in Example 1, and the performance was measured.

Comparative Example 1 The same spinning stock solution of cellulose triacetate as in Example 1 was used. The spinning dope was discharged downward from the double tube spinner at a rate of 1.5 ml / min. On the other hand, 2.6 m of air from the inside of the double pipe base
It was supplied at 1 / min to form a hollow shape. After the hollow fiber-shaped spinning stock solution was discharged from the spinneret, it was run in the air for 30 mm and introduced into the coagulation bath. The spinning stock solution became a pulsating balloon-shaped yarn diameter irregularity in the running section in the air, and stable spinning could not be performed. It was considered that this was because the distance that the hollow fiber spinning solution was run in the air was too long.

Comparative Example 2 The same spinning stock solution of cellulose triacetate as used in Example 1 was used. The spinning dope was discharged downward from the double tube spinner at a rate of 1.5 ml / min. On the other hand, 2.6 m of air from the inside of the double pipe base
It was supplied at 1 / min to form a hollow shape. The hollow fiber-shaped spinning solution was discharged from the spinneret and then run in the air for 5 mm.
Led to the coagulation bath. At this time, the angle between the coagulation bath surface and the hollow fiber spinning stock solution was 45 degrees. The spinning solution introduced into the coagulation bath had a diameter of 12 mm, which was set 150 mm below the surface of the coagulation bath.
The angle was changed in the direction of the liquid surface by means of a liquid guide of a mm satin round bar, and it was made to run again in the air from the liquid surface of the coagulation bath 50 cm away from the liquid guide. At this time, the angle of the hollow fiber before and after the submerged guide was about 130 degrees. Thereafter, the same treatment as in Example 1 was performed and the film was wound at a speed of 75 m / min. When the dimensions of the obtained hollow fiber were measured, the hollow part was crushed in the cross section and it could not be used as a dialysis membrane. It is considered that the cause of the collapse of the hollow portion is that the position of the submerged guide in the coagulation bath portion was too deep, so that the hollow shape could not be maintained by the water pressure.

Comparative Example 3 The same spinning stock solution of cellulose triacetate as in Example 1 was used. The spinning dope was discharged downward from the double tube spinner at a rate of 1.5 ml / min. On the other hand, 2.6 m of air from the inside of the double pipe base
It was supplied at 1 / min to form a hollow shape. The hollow fiber-shaped spinning solution was discharged from the spinneret and then run in the air for 5 mm.
Led to the coagulation bath. At this time, the angle between the coagulation bath surface and the hollow fiber spinning stock solution was 90 degrees. The spinning solution introduced into the coagulation bath has a diameter of 12 m installed 30 mm below the surface of the coagulation bath.
The angle was changed in the direction of the liquid surface by means of the liquid guide for the m. At this time, the angle of the hollow fiber before and after the submerged guide was about 87 degrees. Thereafter, the same treatment as in Example 1 was performed and the film was wound at a speed of 75 m / min. When the dimensions of the obtained hollow fiber were measured, the hollow part was crushed in the cross section and it could not be used as a dialysis membrane. It is considered that the cause of the collapse of the hollow part is that the angle of the hollow fiber before and after the guide in the liquid in the coagulation bath was small, and the hollow shape could not be maintained due to the force applied at the guide part.

Comparative Example 4 The same spinning stock solution of cellulose triacetate as in Example 1 was used. In Comparative Example 1, spinning could not be performed. Therefore, when the discharge amount of the spinning dope was increased to 4.0 ml / min, the length of the hollow running portion was 30 mm.
However, stable spinning was possible. On the other hand, air was supplied at 2.6 ml / min from the inside of the double pipe die to form a hollow shape, and the same operation as in Example 1 was performed thereafter. When observing the cross section of 100 hollow fibers with a microscope, the average inner diameter of the hollow fibers was 202.5 μm, and the standard deviation of the inner diameter was 4.3 μm. The average film thickness is 3
It was 5.2 μm. Next, when an evaluation module was prepared and the performance was measured in the same manner as in Example 1, the performance as a dialysis membrane was lower than that in Example 1. It is considered that this is because the hollow fiber membrane had a large thickness and had a large resistance to permeation of the solute.

(Comparative Example 5) The same spinning stock solution of cellulose triacetate as in Example 1 was used. Since spinning was not possible in Comparative Example 1, the discharge rate of the spinning dope was increased to 2.0 ml / min, and air was fed from the inner side of the double tube spinneret to 2.6.
It was supplied at a rate of ml / min to form a hollow shape. When the length of the air running portion was set to 25 mm, vibration of the hollow fiber was observed in the air running portion, but spinning was possible. Thereafter, the same operation as in Example 1 was performed. When observing the cross section of 100 hollow fibers with a microscope, the average internal system of the hollow fibers was 2
The average film thickness was 02.5 μm and the average film thickness was 22.4 μm. However, the standard deviation of the inner diameter is 25.3 μm (12.5
%), And it was unsuitable for use as a dialyzer due to a drift in the bovine blood test. It was considered that the reason why the standard deviation of the inner diameter became large was that the hollow fiber vibrated in the aerial running part because the length of the aerial running part of the hollow fiber was too long.

[0025]

EFFECTS OF THE INVENTION The hollow fiber membrane for cellulose acetate dialysis of the present invention improves the efficiency of assembly of the module as well as the safety to the living body by using gas as the hollow forming material, and since the yarn diameter is small and the film thickness is thin. By using the hollow fiber membrane, it becomes possible to obtain a dialyzer having excellent performance.

[Brief description of drawings]

FIG. 1 is a diagram showing a spinning method in the present invention. The numbers in the figure are as follows. 1 double pipe spinneret 2 angle 7 hollow spinning dope angle 6 coagulating bath surface and a hollow fiber of the hollow fiber in a coagulation bath in liquid guide 3 coagulating bath 4 hollow fiber spinning solution 4 ^'hollow fiber 5 liquid guide before and after In-air travel distance of filamentous spinning dope 8 Depth of liquid guide in coagulation bath

[Table 1]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Watanabe Politics 1-1-1, Katata, Otsu City, Shiga Prefecture Toyobo Co., Ltd.

Claims (2)

[Claims] 1. A cellulose acetate hollow fiber produced by dry-wet spinning using a gas as a hollow forming material, wherein the hollow fiber has an average inner diameter of 150 to 250 μm, and the hollow fiber has an average film thickness of 10 to 30 μm. A hollow fiber for a cellulose acetate dialysis membrane, wherein the standard deviation of the inner diameter of 100 hollow fibers is 5% or less of the average inner diameter. 2. A cellulose acetate spinning dope is discharged downward from a double tube spinneret, at the same time a gas is supplied from the center of the spinneret to form a hollow portion, and then a hollow spinning dope is run in the air. In the dry-wet spinning method of guiding to the coagulation bath located below the spinneret, when changing the traveling direction of the hollow fiber by the submerged guide in the coagulation bath, the angle of the hollow fiber before and after the submerged guide is 90 degrees or more. A method for producing a hollow fiber for a cellulose acetate dialysis membrane, characterized in that it is less than 100 degrees.