JPS61296115A - Production of acrylonitrile hollow fiber - Google Patents

Abstract

PURPOSE:To obtain the titled fiber having relatively high tensile strength and breaking strength, by spinning and drawing a nitric acid dope of an AN copolymer through a ring nozzle using a specific fluid as the hollow-forming agent, the coagulation bath and the drawing bath under specific condition. CONSTITUTION:An acrylonitrile copolymer is dissolved in a nitric acid solution, and the obtained dope is introduced into a coagulation bath through a ring nozzle using a hollow-forming agent consisting of a fluid incompatible with the dope. The coagulation bath is a cold nitric acid solution cooled to about -10-0 deg.C, especially preferably -8--3 deg.C. The coagulated fiber is drawn in a nitric acid solution bath maintained at a temperature higher than the coagulation bath, washed with water, drawn in hot atmosphere, dried and wound. The draw ratio is preferably 0.9-6.0 to attain balanced tensile strength and substance permeability.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for continuously producing an acrylonitrile hollow #lim having a substantially homogeneous membrane structure.

(Prior art) There are three known methods for producing hollow fibers from acrylonitrile copolymers: wet, semi-dry, and dry. JP-A-54-34416), method using inorganic acid, method using concentrated salt solution (JP-A-53-10)
6769) and a method of using them in combination (Japanese Patent Application Laid-Open No. 58-98413). The method of manufacturing hollow fibers by dissolving an acrylonitrile copolymer in an inorganic acid solution, especially a nitric acid solution, which is related to the present invention, includes
90616, JP-A-55-103306, JP-A-58-
93708, JP-A No. 58-94862, etc., which also disclose the use of water or a nitric acid solution as a hollow forming agent and a coagulating bath agent.

(Problems to be Solved by the Invention) By the way, when water or a dilute nitric acid solution is used as a hollow forming agent, large cavities are created in the membrane wall of the hollow FPT fiber, resulting in a tilted porous structure toward both surfaces. There is a strong tendency to Therefore, hollow fibers with such large cavities cannot be made thin, resulting in poor dialysis properties and relatively weak tensile strength and breaking strength when used as an artificial kidney.
There are problems such as the need for a lot of time and a large amount of briming liquid to remove air during priming. Therefore, as a means of avoiding the generation of large cavities in the membrane wall of hollow fibers and obtaining a homogeneous membrane structure, a highly concentrated nitric acid solution is used as a hollow forming agent and/or a coagulating bath agent (Japanese Patent Application Laid-Open No. 55-117-1). 906
16).

According to this manufacturing method, hollow fibers with a homogeneous membrane structure and spinning at relatively high speeds can be achieved. On the other hand, in order to dry the obtained hollow fibers, it is necessary to cut them to the required length and then water them with water. Alternatively, it is necessary to dry after washing with alcohol or the like, which has the drawback that drying cannot be performed subsequent to spinning. Furthermore, since the hollow fibers are cut once, the subsequent water washing and drying must be carried out in a free state, resulting in hollow fibers with a low tensile strength and breaking strength as the orientation is close to the #lI fiber orientation. Easy to become fibers. In addition, processing the cut hollow fibers one by one individually is very costly in terms of productivity, so they are bundled into necessary units and processed, but as a result, the central part and the outer part of the bundle are Furthermore, it has the disadvantage that processing unevenness tends to occur at both ends and the center of the bundle.

(Means for Solving the Problems) Therefore, the present inventors produced hollow fibers having a homogeneous membrane structure and relatively high tensile strength and breaking strength from an acrylonitrile copolymer dissolved in a nitric acid solution at high speed. The present invention was completed as a result of studying a manufacturing method using continuous drying and winding.

The gist of the present invention is that when producing hollow fibers using an annular nozzle from a stock solution in which an acrylonitrile copolymer is uniformly dissolved in a nitric acid solution, a fluid that is incompatible with the stock solution is used as a hollow forming agent. Hollow #! from an annular nozzle using a nitric acid solution kept at low temperature as a coagulation bath! The fibers are introduced into a coagulation bath directly or after passing through the air, and then stretched in a nitric acid solution bath maintained at a higher temperature than the coagulation bath, followed by successive washing with water, passing through a hot atmosphere, drying, and rolling. The point is to take action.

(Function) In the present invention, the substance useful as a hollow-forming agent must be incompatible with the stock solution. That is,
When a fluid that is compatible with the stock solution such as water, an acid solution such as an aqueous nitric acid solution, or an aqueous salt solution is used, water and nitric acid in the stock solution migrate to the hollow forming agent, causing the inner surface layer of the hollow LA fibers to form. is rapidly solidified, and air running and stretching in the coagulation bath cannot keep up with the spinning speed, resulting in yarn breakage. Furthermore, even if the yarn is pulled at a speed just before yarn breakage, a smooth inner surface cannot be obtained due to repeated stretching breakage and solidification. Therefore, the spinning speed must be relatively slow (about 50 m/min). Furthermore, the use of such a compatible solution also has the disadvantage that large cavities tend to form in the hollow fiber membrane wall and the disadvantage that continuous drying is not possible. In addition, even if the hollow forming agent is an incompatible fluid, air, nitrogen, oxygen, carbon dioxide, etc. with small molecular diameters easily pass through the hollow fiber membrane wall in a hot atmosphere and during drying, so it is always constant. Difficult to maintain hollow fiber inner diameter. As the hollow forming agent, carbon tetrafluoride,
Perfluoroethane, perfluoropencune, perfluorohexane, trifluoromethyl-perfluorocyclohexane, 1.2-)lifluoromethyl-perfluorocyclohexane, 2-decafluorobutyl-perfluorotetrahydrofuran or perfluorotetrahydrofuran and Fluorocarbons, carbon tetrachloride, perchloroethane, perchlorethylene, and chlorocarbons, such as substances in which one or two of the fluorines of the substance are replaced with hydrogen, and substances in which one or two of the chlorines of the substance are replaced with hydrogen. Preferably. Next, the hollow fibers led out from the annular nozzle are led to a coagulation bath either directly or after passing through a certain distance in the air.

At this time, when the annular nozzle is directly immersed in the coagulation bath and the hollow fibers are discharged, the hollow fibers are affected by the conditions of the coagulation bath liquid, and the winding speed limit is 50 m/min. If a certain aerial distance is set directly below,
In this region, the hollow fiber is in an uncoagulated state and is easily drawn, so it is possible to obtain a very high winding speed (experimentally more than 200 m/min) after passing through the coagulation bath liquid. It is. Furthermore, it was confirmed that the stability of spinning varies by changing the length of the air travel distance. According to the study results of the present inventors, the aerial travel distance is 0.5 to 50 cm.
is desirable, and 2 to 30 cm is particularly good. The hollow fibers that have passed through the air are then introduced into a coagulation bath. In order to obtain a homogeneous membrane structure, the hollow fibers must be coagulated slowly in a coagulation bath. The temperature of the coagulation bath is -10° to 0°.
C2 is preferably -8 to -3°C. When the coagulation bath temperature is high, large cavities are created in the membrane wall of the hollow fibers.

In order to obtain a more homogeneous membrane structure, it is desirable that the nitric acid concentration in the coagulation bath be 5 to 35% (all percentages by weight hereinafter). If the nitric acid concentration exceeds 38%, the hollow fibers cannot be coagulated in the coagulation bath, making spinning impossible. The semi-gelled hollow fibers obtained in the coagulation bath are then gel-stretched in a nitric acid solution maintained at a temperature substantially higher than the coagulation bath temperature to enhance fiber orientation and tensile strength. The temperature of the stretching bath made of nitric acid solution is 10 to 70°C. In addition, the nitric acid concentration is 5 to 50%.
is desirable. As a result of various studies on the relationship between the temperature and the nitric acid concentration, we found that 20~
A relatively high temperature region of 5-15% at 40°C and a high concentration region of 30-50% at 55-65°C are particularly preferred regions that do not cause large cavities in the S-wall of the hollow fibers. I confirmed something. Furthermore, as a result of various studies regarding the gel stretching ratio, it was found that by increasing the stretching ratio, the degree of orientation of the hollow fibers increases proportionally, and the tensile strength also improves.

However, on the other hand, the permeability of the substance decreases. A preferred range for achieving a good balance between tensile strength and material permeability is a stretching ratio of 0.9 to 6.0 times. When the stretching ratio exceeds 6.0 times, cracks occur in the hollow fibers, the tensile strength tends to decrease, and the permeability of the substance increases rapidly, and when the stretching ratio is less than 0.9 times. Hollow fibers have drawbacks such as reduced tensile strength and roller wrapping due to bath resistance during production.

Following the drawing process, the hollow fibers are washed with water and then drawn in a hot atmosphere. This treatment completely removes traces of solvent remaining in the hollow fiber membrane walls, and at the same time the hollow fibers undergo shrinkage or stretching, which determines the tensile strength, including permeability and orientation, of the final material. . The conditions for this hot atmosphere include passing through hot water at 60 to 95°C, or passing through steam at 60 to 120°C after passing through the hot water, and further stretching in the hot atmosphere. Magnification is 0.8-2
．． It has been found that the best conditions are 0 times, preferably 0.9 to 1.5 times. Finally, the hollow fibers are dipped in a glycerin solution, dried under constant tension and wound up.

Next, the present invention will be specifically explained using examples.

(Example 1) Acrylonitrile 91.5wt%, methyl acrylate 8
．． 05wt%, sodium methallylsulfonate 0.45
A copolymer having a copolymer concentration of 15.8 wt% was prepared by dissolving the copolymer in a 67.0 wt% aqueous nitric acid solution and degassing it. 4. Apply this stock solution to the annular nozzle.
At the same time, perfluorotetrahydrofuran was introduced into the annular nozzle at a rate of 4.4 mjL/min as a hollow forming agent. The hollow fibers extruded from the annular nozzle were directly introduced into a nitric acid coagulation bath with a temperature of -3°C and a concentration of 31 wt%, and were pulled up in a semi-gel state at a speed of 12 m/min. 3 in a nitric acid drawing bath
Stretched twice. Thereafter, the hollow fibers were washed with water, then stretched twice in 80''O hot water, and then immersed in a glycerin solution.Finally, they were dried in a dryer and rolled up.

The obtained hollow RAM was used as a scanning electron Im microscope (hereinafter SE
M,! = 18) to cut the cut surface [I cut it, it was transparent,
Inner diameter 20011. It had a homogeneous film structure with a film thickness of 30 μm. In addition, the water permeability of the hollow fiber is 13m/hr.
a rrf・m m Hg, urea mass transfer coefficient → is 6.5XlOcm/sec, vitamin B12 mass transfer coefficient is 0, 9X 10-'1'cm/sec, bovine serum U
FR was 4.1 mu/Hrerrf*mmHg.

(Example 2) The hollow fibers that had been subjected to the double stretching treatment in a hot water bath at 80°C in Example 1 were further passed through steam at 100°C, immersed in an aqueous glycerin solution, and then dried. It was dried on a machine and rolled up. As a result of SEM observation, the obtained hollow fibers were transparent, had an inner diameter of 2° Ogm, a film thickness of 28 g, m, and had a homogeneous film structure. In addition, the water permeability of the hollow fiber is l1m
Standing/Hr11rr1″・mmHg, bovine serum UFR is 3
．． 8 mJl/Hr a rn" mm m Hg9 (Example 3) The stock solution prepared in Example 1 was introduced into the annular nozzle for 4.4 m11 minutes, and a permeate was added as a hollow forming agent to the center of the annular nozzle. Chlorethylene was introduced at a rate of 4.4 mu/min. After passing through the annular nozzle and running the hollow fiber with perchlorethylene wrapped in the center for 15 cm in the air, a coagulation bath consisting of a nitric acid solution under various conditions shown in Table 1 was added. It was then pulled up at a speed of 50 m/min to investigate the occurrence rate (number/10 cm) of large cavities with a width of III Bt.

The results are shown in Table 1.

(Left below) (Example 4) In the experiment conducted in Example 1, the coagulation bath had a concentration of 15 wt%.
Two conditions were used: temperature -5°C and concentration 25wt% and temperature -5°C.The hollow fibers were further treated using a drawing bath consisting of nitric acid solution under various conditions, and then 100m/
The rate of occurrence of large cavities (pcs/locm) was investigated. The results are shown in Tables 2 and 3.

(Example 5) Example! The stock solution prepared above was introduced into the annular nozzle at a rate of 4.4 mIL/min, and perchlorethylene was introduced as a hollow forming agent at a rate of 4.4 mIL/min. After the hollow fibers extruded from the annular nozzle were run in the air, the concentration was 15 wt% and the temperature was -
After being immersed in a nitric acid solution coagulation bath at 5°C, it was rolled up at a speed of R1,
Thereafter, it was immersed in a nitric acid solution stretching bath with a temperature of 30° C. and a temperature of 10 wt%, and was pulled up at a speed of R2. After washing with water, the degree of orientation was investigated. The results are shown in the graph.

(Example 6) Pour 4.4ml of the stock solution prepared in Example 1 into an annular nozzle.
/min, and perchlorethylene was introduced as a hollow forming agent at a rate of 4.4 ml/min. The lifting speed of the hollow fibers extruded from the annular nozzle after immersion in the coagulation bath was investigated with and without air travel. In the case of aerial travel, it was possible to perform a single pull at a speed of 250 m/min or more, but without aerial travel, it was possible to perform a single pull at a speed of 32 m/min or more.
Yarn breakage occurred at an extremely low speed of m/min. Moreover, when the air travel distance exceeded 50 cm, the dimensional variation of the hollow fibers became extremely large.

(Example 7) The stock solution prepared in Example 1 was introduced into the annular nozzle at a rate of 4.4 mu/min, and perchlorethylene as a hollow forming agent was introduced at a rate of 4.4 mm/min. After the hollow fiber extruded from the annular nozzle traveled 15 cm in the air, the concentration was 15 wt%,
It was immersed in a nitric acid solution coagulation bath at a temperature of -5°C and pulled up at a speed of R1. Thereafter, the hollow MIU fibers were added at a concentration of 10 wt%.
It was immersed in a nitric acid solution stretching bath at a temperature of 30'0 and pulled out at a speed of R2.

The hollow fibers were then washed with water, immersed in a hot water bath at 80°C, pulled up at a speed of R3, immersed in a glycerin solution, dried in a hot air dryer, and wound up at a speed of R4. All of the obtained hollow fibers were perfectly circular and had a homogeneous membrane structure as a result of SEM observation. In addition, other performance values are
As shown in Table 4, the dimensions of the hollow fibers were 200gm in inner diameter and 25~25mm in wall thickness.
It was 30m at the end.

(Effects of the Invention) As described above, according to the present invention, hollow fibers having a homogeneous membrane structure and relatively strong tensile strength and breaking strength can be manufactured continuously at high speed. In addition, the hollow fibers obtained in this way are useful for dialysis-type or oral dialysis-type artificial kidneys, and because they can be continuously dried and rolled up, they are cost-effective and quality-friendly. It also has great advantages.

BRIEF DESCRIPTION OF THE DRAWINGS The figure is a graph showing the relationship between the degree of orientation and manufacturing conditions of the hollow fibers obtained in Example 5.

Claims (1)

[Claims] In a method for producing hollow fibers using an annular nozzle from a stock solution in which an acrylonitrile copolymer is uniformly dissolved in a nitric acid solution, a fluid that is incompatible with the stock solution is used as a hollow forming agent and is kept at a low temperature as a coagulation bath. Using the nitric acid solution, the hollow fibers are introduced into the coagulation bath directly or after passing through the air through an annular nozzle, and then stretched in a nitric acid solution bath maintained at a higher temperature than the coagulation bath, and then continuously stretched. Rinse with water,
A method for producing acrylonitrile hollow fibers, which comprises passing through a hot atmosphere, drying, and winding.