JPH048522B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Technical Field The present invention relates to a method for producing hollow fibers made of cellulose fibers regenerated using a cuprammonium method. (b) Prior art Hollow fibers made of cellulose fibers regenerated by the copper ammonia method (hereinafter abbreviated as "QYUPRA hollow fibers") are
In recent years, it has been widely used in hemodialysis such as artificial kidneys. Conventionally, in order to manufacture QYUPRA hollow fiber, a copper ammonia cellulose spinning dope is discharged from a circular spinneret, and at the same time, a non-coagulable liquid is introduced into the spinning dope through a liquid introduction tube attached to the center of the annular spinneret. The discharged linear spinning stock solution falls freely into the air and is sufficiently stretched, then led to a coagulation bath, and then wound into a spool or skein shape through a regeneration process, water washing process, and drying process. A method is being used to take it. The hollow part of the QYUPRA hollow fiber manufactured and wound in this manner is filled with liquid introduced from the liquid introduction tube attached to the center of the annular spinneret, and this QYUPRA hollow fiber is used for dialysis. When used in modules, it is necessary to remove these hollow-filling liquids before, during, or after assembly of the module. According to research conducted by the present inventors, it is impossible to completely remove the filling liquid from a hollow fiber with an inner diameter of several tens to hundreds of μ unless the hollow fiber is cut to a length of several tens of centimeters. It's impossible. Therefore, the usual method is to cut the hollow fibers into lengths of several tens of centimeters to form bundles, and then remove the hollow agent in this state. The bundled hollow fibers are treated by physical methods such as gravity, centrifugal force, and vacuum drying, chemical methods such as cleaning with organic solvents, or a combination of these methods to remove the filling liquid. . Both of these methods are very complex and the cost of removal represents a significant proportion of the manufacturing cost. In particular, failure to increase the rate of recovery and reuse of the removed liquid will increase the overall cost throughout the manufacturing of the QYUPRA hollow fiber and the assembly of the dialysis module. On the other hand, even if the above-mentioned removal operation is repeated, a small amount of the liquid filling the hollow space cannot be avoided, but considering that the main application field of QYUPRA hollow fiber is long-term continuous hemodialysis for patients with chronic renal failure. If so, it is desirable that there be no such residue at all. For these reasons, there has been a strong desire to develop a method for manufacturing QYUPRA hollow fibers that does not use any liquid to form hollow portions from the initial stage of spinning.
One possible method for producing QYUPRA hollow fibers with no residue is to use a gas as the hollow filler, but if a compressible gas is used instead of an incompressible liquid, then It was believed that it would be impossible to produce hollow fibers with a uniform circular cross-section and a uniform wall thickness over the entire fiber length of the hollow fiber. The inventors of the present invention dared to take on this difficult challenge in order to break through such conventional fixed ideas, and as a result, they have accomplished the present invention. (c) Object of the Invention The object of the present invention is to provide an industrially advantageous method for manufacturing QYUPRA hollow fibers having a uniform circular cross section and uniform wall thickness over the entire fiber length. (d) Structure of the Invention The method for producing QYUPRA hollow fibers according to the present invention includes discharging a copper ammonia cellulose spinning stock solution from an annular spinneret, and at the same time introducing gas from a gas inlet tube attached to the center of the annular spinneret. Then, when the discharged linear spinning stock solution is allowed to fall freely and guided to the coagulation bath located below, the spinning stock solution moves almost vertically to the surface of the coagulation bath only by the downward force obtained during the free fall. and 30mm larger than 10mm below the liquid surface.
It is characterized by setting the free fall length so that it plunges to the following depth. (E) Preferred Embodiment The hollow fiber obtained by the method of the present invention has a hollow portion that penetrates continuously over the entire fiber length, a circular cross section with an inner diameter of 50 μm to several hundred μm, and a wall thickness of several μm to 60 μm. These are hollow fibers made of regenerated cellulose fibers, and are long hollow fibers whose hollow portions are filled with gas. Here, "long" refers to a length several times to several tens of times longer than the length to be incorporated into a dialysis machine, etc., and usually at least several meters long.
Preferably, the length is several tens of meters to several tens of meters or more. The hollow fiber obtained by the method of the present invention is wound in a long length of several meters or more, or in a spool shape, and the hollow portion thereof is filled with gas over the entire fiber length. Therefore, at the stage of cutting the hollow fibers and bundling them,
The gas inside can freely diffuse with the air outside. In the case of conventional hollow fibers that use liquid as a hollow forming agent, the hollow filling liquid is removed using very complicated methods such as gravity, centrifugal force, vacuum drying, or cleaning with chemicals. However, the hollow fiber obtained by the method of the present invention does not require such complicated steps at all, so manufacturing costs can be reduced, the assembly yield of artificial kidneys is high, and dialysis performance is high. The result is obtained. In the case of QYUPRA hollow fibers, compared to synthetic polymer hollow fibers and compared to regenerated cellulose fiber hollow fibers made from cellulose derivatives, the shape and performance of the hollow fibers change due to changes in temperature and humidity. Because of the large As the form of the thread changes,
This is thought to be due to a decrease in performance. For example, when a bundle of QYUPRA hollow fibers is subjected to changes in temperature and humidity, the tips of the hollow fibers curl, which disrupts the shape of the bundle and impedes operations such as insertion into modules during assembly, reducing assembly yield. This phenomenon occurs, but with conventional hollow fibers, this was unavoidable. Since the hollow fiber obtained by the method of the present invention does not require any operation to remove the hollow filling liquid, it can be assembled into an artificial kidney without suffering any such disadvantages. Since the hollow fibers obtained by the method of the present invention are not filled with liquid, they have the very great feature that they can be cut directly and continuously from the long stage to form bundles. are doing. The method of using gas as a hollow forming agent is already known in the production of hollow fibers by melt spinning or dry spinning, and is also known in the production of hollow fibers by wet spinning using synthetic polymers. (For example, see JP-A-53-86834, 54-55623)
There is no known wet spinning method using cellulose as a raw material, especially a wet spinning method using a cuprammonium cellulose solution. The present inventors attempted to manufacture QYUPRA hollow fibers using gas while referring to the conventional manufacturing method for QYUPRA hollow fibers using liquid and the conventional manufacturing method for non-QYUPRA hollow fibers using gas. In the production of hollow fibers, troubles that were not considered problems at all were encountered, and either spinning was not possible at all, or hollow fibers that could withstand practical use could not be obtained. That is, when the spinning stock solution that was free-falling in the air according to the conventional method was drawn into the coagulation bath using a deflection rod, the direction was changed, and the spinning stock solution was run through the coagulation bath. A phenomenon occurred in which pulsation occurred in the direction of the yarn, which eventually led to yarn breakage. On the other hand, if the deflection rod is removed, the spinning solution will run on the surface of the coagulation bath, and in this case, the uncoagulated spinning solution will flow downward, causing eccentricity and making it impossible to obtain hollow fibers with a uniform wall thickness. It turns out there isn't. The problems of "pulsation" and "eccentricity" could not be solved despite various efforts based on conventional techniques. According to the research conducted by the present inventors, the biggest difference between gas hollow agent spinning using other materials and Kyupra hollow fiber is that in the case of other materials, the point of free fall after spinning is The spinning solution quickly gels due to factors such as a decrease in the spinning solution temperature and evaporation of the solvent, generating a force that maintains the shape of the hollow fiber. However, unlike other materials, in the case of Kyupra, gelation does not occur immediately, but only after immersion in a coagulation bath. It was thought that gelation, which maintains its shape against external forces, occurs only after a period of time has passed. Therefore, the pulsation is caused by the free-falling spinning solution entering the coagulation bath, and at the point when gelation has not sufficiently progressed, a large buoyant force acts on the spinning dope from the coagulation bath, causing the spinning solution to become encapsulated in the spinning solution. It was thought that this was caused by gas being pushed upwards. In conventional Kyupra hollow fiber spinning, the discharged spinning solution enters the coagulation bath after undergoing free fall (or without free fall), travels a certain distance downward in the coagulation bath, and then enters the coagulation bath in a horizontal direction. The method used was to be given power and proceed to the next step. When the hollow forming agent is a liquid, buoyancy is hardly a problem, so the spinning dope enters the coagulation bath without much resistance, and in addition to the downward force obtained during free fall, it is The force applied via the deflection rolls allows the coagulation bath to be run downwards over any length. For this reason, the coagulation bath usually travels several centimeters to several tens of centimeters downward through the coagulation bath, then is turned sideways and moves on to the next step. In contrast, the feature of the method of the present invention is that the spinning dope perpendicularly breaks through the surface of the coagulation bath only by the downward force obtained during free fall, and
The goal is to set the free fall length so that the object plunges to a depth of . The present inventors previously discovered that a good spinning condition could be obtained when the depth of penetration of the spinning dope into the coagulation bath surface was 2 to 10 mm, and filed a patent application (Patent Application No.
154808), but the present inventors subsequently conducted a study covering a wider range of spinning conditions and found that a good spinning condition could be obtained even at a plunge depth below the liquid surface that was greater than the above range. This led to the present invention. If the free fall length is shortened and spinning is performed in a state where the surface tension prevents the liquid from breaking through, the spinning solution will run in the lateral direction with insufficient coagulation, causing the spinning solution to flow downward and create an eccentric shape. A hollow fiber with a cross section of . On the other hand, if the free fall length is too high, the spinning dope will sag above the liquid level, making it impossible to break through the liquid level vertically.
It begins to swirl at the interface. In such a state, spinning becomes unstable, fibers are likely to be cut, and the obtained hollow fibers have large dimensional variations. The spinning method of setting the free fall length in this way and obtaining a stable spinning state is a completely new method for spinning hollow fibers using wet spinning, including Kyupra. ,
This was the first time that stable spinning without pulsation was realized. On the other hand, as a prerequisite for setting the free fall length, the spinning dope and gas must be discharged properly, and if the conditions are inappropriate, pulsation will occur during spinning. The discharge amount of the spinning dope is determined by the inner diameter, wall thickness, and winding speed of the target QYUPRA hollow fiber, but the average linear velocity of the spinning dope is preferably 7.
m/min or more, preferably 11 m/min or more. At 7 m/min or less, even if an extremely small amount of gas is discharged, the hollow linear body pulsates violently, causing breakage at the free-falling part, making continuous spinning difficult. It has also been found that even when spinnerets of different dimensions are used, stable spinning can be achieved by setting the average discharge linear velocity to 7 m/min or more, preferably 11 m/min or more, as described above. Incidentally, in conventional spinning of QYUPRA hollow fibers using a liquid as a hollow filler, the average linear discharge speed of the spinning dope is set to about 1 to 2 m/min. The amount of gas to be discharged as a hollow filler is determined by the inner diameter of the target QYUPRA hollow fiber, wall thickness, winding speed, and the amount of gas that passes through the membrane (wall of QYUPRA hollow fiber) during the process up to winding. Determined by the dissipation rate. The gas discharge pressure at this time varies depending on the spindle dimension, but if the discharge pressure is too high, the discharged spinning dope will pulsate, making it impossible to obtain hollow fibers with a stable shape. As a result of research by the present inventors, the discharge pressure is preferably 100% in addition to the external pressure.
It has been found that a stable discharge condition can be obtained by setting the spinneret dimension so that the water column is less than mm, more preferably less than 70 mm. Gas is introduced and filled under such pressure, and then the discharged linear spinning dope is allowed to freely fall into the air, sufficiently stretched, and then led to a coagulation bath located below. The gas used as the hollow space filler can be any substance that is gaseous at room temperature, but it is desirable to use a gas that does not react with the spinning solution and does not coagulate the spinning solution. Furthermore, considering the use of hollow fibers in hemodialysis, it is desirable to use substances with low toxicity, such as various paraffin-based and olefin-based gases, halogenated hydrocarbon-based gases (perfluorocarbons, fluorochlorocarbons, etc.), and various rare gases. Gas etc. can be used. Among them, air and its components or mixtures of its components are easy to handle and are most suitable. Gas is fed using a gas flow rate adjustment device that can supply a small amount of gas. In this way, the hollow fibers are spun under appropriate conditions, allowed to fall freely, guided into a coagulation bath made of caustic soda, and the coagulated hollow fibers are pulled up from the coagulation bath and deposited one by one on a net conveyor. After scouring, it is dried and wound into a skein or spool. The QYUPRA hollow fiber wound into a comb or spool shape has a hollow portion continuously extending through its entire fiber length, and the hollow portion is filled with gas. In addition, when this hollow fiber is used as a dialysis membrane, it has an inner diameter of 50 μm to several hundred μm over the entire fiber length.
Preferably, it has a circular cross section of m and a wall thickness of a few μm to 60 μm. Here, several hundred μm means a maximum of 800 μm, preferably 600 μm, and several μm
means a minimum of 2 μm, preferably 5 μm. When the QYUPRA hollow fiber wound in this manner is cut, the gas filled in the hollow portion mixes and diffuses with the outside atmosphere. In order to use QYUPRA hollow fibers in hemodialysis devices such as artificial kidneys, they are cut into arbitrary lengths of 1 m or less, and thousands to tens of thousands of fibers are tied together to form bundle-like aggregates. In the cutting and binding operations, as with conventional QYUPRA hollow fibers, the hollow portion was crushed, the circular cross section was deformed, and the fibers were easily bent, which were not a practical problem. Furthermore, when an artificial kidney was assembled using the hollow fiber of the present invention, a higher assembly yield was obtained than with conventional hollow fibers, and the dialysis performance was also improved. (F) Examples Hereinafter, the method of the present invention will be specifically explained with reference to Examples. Example 1 Cellulose concentration prepared according to known methods
A cuprammonium cellulose spinning dope having a composition of 10.0%, an ammonia concentration of 7.0%, and a copper concentration of 3.6% and a viscosity of 2000 poise was used, and this was spun into a ring through a circular spinneret. The discharge amount of spinning stock solution is 20.0
ml/min. On the other hand, nitrogen gas was discharged at a rate of 5 ml/min from a gas inlet tube attached to the center of the annular spinneret. The gas discharge pressure at this time was 50 mm of water column pressure in addition to the external pressure. Further, the average linear discharge speed of the spinning dope was set to 17.6 m/min. Next, the discharged linear spinning dope is directly blown into the air.
500mm free fall and sufficient stretching, then continue to increase the density.
It was introduced into a coagulation bath filled with an 11% (hereinafter "%" represents weight percentage) aqueous caustic soda solution. At this time, the linear spinning stock solution was once submerged to a depth of 18 mm below the surface of the coagulation bath. After giving a coagulation effect in a coagulation bath and forming a thread, the thread is naturally turned sideways by the force derived from winding, and is lifted out of the coagulation bath and transferred to a net conveyor using a shake-off roller. The yarn is shaken off, and as it moves along the net conveyor, the yarn is pickled with a dilute 3% sulfuric acid aqueous solution to regenerate the yarn. After washing thoroughly with water, the yarn is pulled up from the top of the net conveyor and run in a straight line. The film was run through a tunnel dryer to be thoroughly dried, and then wound into a spool using a winder. The winding speed was set at 80 m/min.
The hollow part of the wound QYUPRA hollow fiber was filled with nitrogen gas, and the hollow part did not collapse even when located inside the spool. Next, the QYUPRA hollow fibers wound into a spool shape were cut into a length of 200 mm, and 10,000 pieces were bundled to obtain a bundle of QYUPRA hollow fibers. The obtained Kyupra hollow fiber is
The outer diameter was 234 μm, the inner diameter was 192 μm, and the wall thickness was 21 μm. Further, a hollow portion was formed that continuously penetrated the entire fiber length, and the fiber had a uniform circular cross section in the fiber axis direction. Next, the performance of the hollow fiber of the present invention was compared with that of a conventional product (using a non-coagulable organic liquid as a hollowing agent,
It was manufactured according to the manufacturing method described in Publication No. 134920. )
The comparison is shown in Table 1. The measurement items are albumin and urea removal rate in model liquid dialysis,
This is an extreme overspeed.

【table】

[Table] Example 2 Inner diameter according to the manufacturing method described in Example 1
A 150 μm Kyupra hollow fiber was manufactured. A cuprammonium cellulose spinning stock solution was used and discharged through a circular spinneret. The discharge amount was 21.0 ml/min. Meanwhile, air was discharged from the center of the spinneret at a rate of 2.7 ml/min. The gas discharge pressure at this time was set to 26 mm of water column pressure in addition to the external pressure. Further, the average linear discharge speed of the spinning dope was set at 35.7 m/min. Next, the discharged linear spinning dope was allowed to freely fall directly into the air, sufficiently stretched, and then introduced into a caustic soda aqueous solution bath having a concentration of 11%. At this time, the linear spinning dope was stabilized once submerged to a depth of 23 mm.
Thereafter, the material was wound into a spool on a winder through the same steps as in Example 1. Winding speed is 80
m/min. Next, the Kyupura hollow fibers wound into a spool were cut into lengths of 300mm and 10,000 pieces were tied together.
An aggregate of bundled Kyupra hollow fibers was obtained. The obtained QYUPRA hollow fiber has an outer diameter of 203 μm and an inner diameter of
The wall thickness was 27 μm. Further, a hollow portion was formed that continuously penetrated the entire fiber length, and had a uniform circular cross section in the fiber axis direction.

Claims (1)

[Claims] 1. Discharge the copper ammonia cellulose spinning stock solution from the annular spinneret, and at the same time introduce and fill gas from the gas introduction tube attached to the center of the annular spinneret. Then, let the discharged linear spinning solution fall freely. When the spinning dope is led to the coagulation bath located below, the spinning stock solution breaks through the coagulation bath surface almost perpendicularly and plunges to a depth of more than 10 mm and less than 30 mm below the liquid surface only by the downward force obtained during free fall. A method for producing hollow fibers made of regenerated cellulose using the copper ammonia method, which is characterized by setting the free fall length as follows.