JPH07258915A - Porous polysulfone hollow yarn - Google Patents

Abstract

PURPOSE:To obtain the subject hollow yarn useful for microfiltration, plasma separation, etc., capable of filtering without damaging a solute component, having sufficient mechanical strength and proper filtration flux density, by specifying the hole shape, the maximum diameter of the hole and the rate of hole area of the hollow yarn of an aromatic polysulfone. CONSTITUTION:The hole shape of fine holes existing in the inner surface of a hollow yarn obtained from an aromatic polysulfone having repeating units of formula I, formula II, etc., is an elliptic shape having a smooth periphery and the maximum diameter of the fine hole is 0.1-10mum. The rate of hole area of circular surface holes having >=0.1mum major axis is 7-23%. In (dry) wet spinning in which a solution containing the polysulfone resin is extruded together with an inner core solution from a ring-shaped nozzle and coagulated with a coagulating solution, affinity for the polysulfone as the inner core solution is controlled to give the objective porous polysulfone hollow yarn.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a porous polysulfone hollow fiber. More specifically, the hollow fiber has an elliptical to circular hole with a smooth circumference on the inner surface, or has no skin layer on the outer surface of the hollow fiber, and is used for medical separation such as microfiltration or plasma separation. The present invention relates to a porous polysulfone hollow fiber that can be effectively used in the field of membranes.

[0002]

2. Description of the Related Art Polysulfone hollow fibers have excellent heat resistance and chemical resistance in addition to their excellent biological safety. Therefore, polysulfone hollow fibers are used in dialysis membranes, plasma separation membranes and double filtration membrane methods. It has come to be widely used for medical applications such as secondary membranes.
Many polysulfone hollow fibers and methods for producing the same have been proposed so far. Of these, aromatic polysulfone hollow fibers which can be used particularly in medical applications such as plasma separation or in the field of microfiltration and the production method thereof are described in JP-A-57-35906 and JP-A-60-2.
22112, JP 59-183761, JP 5
No. 8-91822 and JP-A-58-114702.

[0003]

However, the shapes of the holes present on the inner surface of the hollow fibers described in these publications are slit-like, spindle-like, or indefinite shapes whose shapes cannot be specified. Even from elliptical to circular with a smooth perimeter. As described above, when the shapes and sizes of the pores are significantly different depending on the directions, not only is it difficult to specify the size of the pores, but also the shape of the solute component affects the filtration characteristics in a complicated manner. Therefore, when a liquid containing a plurality of solutes having different shapes as well as sizes is filtered, there arises a problem that a sharp fractionation characteristic is not exhibited. When plasma separation is performed using a hollow fiber having inner surface pores whose pores are different in shape and size depending on the direction and whose circumference is not smooth, the blood on the inner surface of the hollow fiber is brought into contact with blood by contacting the hollow fiber with blood. If the friction between the blood plasma component and the periphery of the pores is increased by increasing the shear rate or increasing the filtration amount, the blood cell component receives local force and is damaged by hemolysis.

Further, for the purpose of separating plasma, in order to obtain an appropriate filtration flux, there is an optimum average pore size and optimum porosity in the cross-sectional direction of the hollow fiber. That is, if the average pore size is too small or the open area ratio is too low, a sufficient filtration flux may not be obtained and the blood cell component may be damaged. On the contrary, if the average pore size is too large, the problem of leakage of blood cell components occurs. On the other hand, if the porosity is too large, the physical strength of the hollow fiber itself will decrease, and if the film thickness is increased to compensate for this, the effective surface area will decrease.

[0005]

Means for Solving the Problems The inventors of the present invention have made intensive studies to overcome the problems in the prior art as described above, and have reached the following conclusions. That is, in order to prevent damage such as hemolysis, a hollow fiber made of aromatic polysulfone is used, and the shape of the pores present on its inner surface is an elliptical to circular shape with a smooth circumference, and the maximum major diameter of the pores is within a specified range. It was found that a polysulfone hollow fiber obtained by adjusting the porosity, which is the ratio of the total open area of the inner surface pores to the inner surface area, within a specific range achieves the above object, and completes the present invention. did.

[0006] That is, the present invention is a hollow fiber made of aromatic polysulfone, the pores present on its inner surface are elliptical to circular with a smooth circumference, and the maximum major axis of the pores is 0.1 to 10 µm. A porous polysulfone hollow fiber having a porosity of 7 to 23%, which is the ratio of the total open area of the inner surface pores having a major axis of 0.1 μm or more to the inner surface area, is contained. .

As the aromatic polysulfone used in the present invention, those having the following repeating units are generally known.

[0008]

[Chemical 1]

[0009]

[Chemical 2]

The hollow fiber of the present invention is a hollow fiber membrane produced from the aromatic polysulfone as described above, and the shape of the pores present on the inner surface thereof is elliptical to circular with a smooth circumference, and The maximum major axis is in the range of 0.1-10 μm,
It is necessary that the open area ratio, which is the ratio of the total open area of the inner surface holes having a major axis of 0.1 μm or more to the inner surface area, is 7 to 23%.

If the shape of the pores present on the inner surface of the hollow fiber is not elliptic to circular with a smooth circumference, not only sharp fractionation characteristics cannot be obtained, but, for example, in the case of plasma separation, the blood cell component is localized. Subject to damage such as hemolysis. The elliptical shape and the circular shape referred to in the present invention may be substantially an elliptical shape or a circular shape, and is not limited to a perfect elliptical shape or a circular shape, but the elliptical shape exists on the inner surface of the hollow fiber. The term "arbitrary hole" refers to one having a major axis / minor axis of 3 or less. The major axis and minor axis of the hole are the maximum and minimum lengths of the distance between two parallel lines circumscribing the hole as observed by an electron microscope. Further, the maximum major axis is the maximum major axis described above when an arbitrary place on the inner surface is observed with an electron microscope. In addition, the term “smooth circumference” as used in the present invention means that, when the inner surface of a hollow fiber is observed under an electron microscope at a magnification of about 5000 times, the outer peripheral shape of any hole is continuous toward the outer peripheral direction. It refers to a shape that is drawn with a gentle convex curve, and refers to a shape that does not include wedge-shaped or irregular shapes that are difficult to specify.

The porosity referred to in the present invention means that the inner surface of the hollow fiber is observed with an electron microscope at ten or more places at a magnification of 3000, an average place is photographed, and image processing is performed on a visual field of 8 × 6 cm. Equipment [for example, PIAS Co., P
IAS III type], and is obtained as the ratio of the total open area of pores having a major axis of 0.1 μm or more to the internal surface area. When the maximum major axis of the inner surface pores of the hollow fiber is less than 0.1 μm, a sufficient filtration flux cannot be obtained. Furthermore, due to the increase in pressure loss, blood components are damaged by hemolysis and the like. On the other hand, when the maximum major axis of the inner surface pores of the hollow fiber exceeds 10 μm, the blood cell component leaks out. When the open area ratio of the pores having a major axis of 0.1 μm or more with respect to the inner surface area of the hollow fiber is less than 7%, a sufficient filtration flux cannot be obtained. If the porosity exceeds 23%, a hollow fiber having sufficient physical strength cannot be obtained. If the hole does not have a smooth circumference, the blood cell component receives a local force due to friction between the blood cell component and the periphery of the hole and is damaged by hemolysis.

The inner diameter, outer diameter, film thickness and density of the hollow fiber in the present invention are not particularly limited, but pressure loss,
From the viewpoint of effective membrane area and mechanical strength, the inner diameter is 200 ~
1000 μm, outer diameter 250 to 1500 μm, film thickness 2
It is preferable that the film thickness is 0 to 300 μm and the film density is about 0.2 to 0.4 g / cm ³ . In addition, a skin layer may be present on the outer surface of the hollow fiber, but a skin layer not present and having a maximum major axis of pores present on the outer surface of at least 0.1 μm is suitable for fields such as microfiltration and plasma separation. When used, it is preferable. Furthermore, the part between the inner surface and the outer surface of the hollow fiber is
For example, when a hollow fiber is manufactured by the method described in the below-mentioned example, it usually has a sponge shape. It is preferable that the maximum major axis of the sponge-like portion also has a maximum major axis of at least 0.1 μm in order to reduce pressure loss and reduce clogging in this portion.

The porous polysulfone hollow fiber of the present invention as described above is coagulated, for example, by extruding a solution containing a polysulfone resin together with an inner core liquid through an annular nozzle and immediately or after passing an appropriate dry distance (usually 50 cm or less) from the nozzle. In the method of contacting with a liquid, it can be obtained by adjusting the affinity of the inner core liquid for polysulfone within a specific range. That is, if the affinity is too high, a network of spherical particles is formed, which makes it unsuitable for microfiltration or plasma separation, and if the affinity is too low, it becomes a slit shape or an indefinite shape, resulting in a decrease in fractionation characteristics or blood cells. Causes damage to ingredients. The appropriate affinity as used herein means a solubility in which the concentration of polysulfone dissolved in the solvent is about 0.5 to 5% after 1 hour when the polysulfone is present in the solvent controlled at 80 ° C. .

[0015]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples, but these do not limit the present invention. Example 1 Polysulfone (manufactured by Amoco Co., Udel Polysulfone P-35) in a mixed solvent of 61 parts of N-methyl-2-pyrrolidone (parts by weight, the same applies hereinafter) and 22 parts of propylene glycol.
A solution in which 17 parts of (00) was dissolved was used as a spinning dope. As the core liquid, a mixed liquid of 70 parts of N-methyl-2-pyrrolidone and 30 parts of propylene glycol was used. Inner diameter 0.4 mm,
Using a double nozzle with an annular discharge port with an outer diameter of 0.6 mm and a core liquid discharge port with a diameter of 0.2 mm, 4.0 g / min from the discharge port while maintaining the spinning solution at 55 ° C, 4.5 g of core liquid / Min, and wound at a spinning speed of 50 m / min while coagulating in warm water of 50 ° C located 6 cm below the nozzle, with an inner diameter of 33
A hollow fiber having a diameter of 0 μm and an outer diameter of 430 μm was obtained. Electron micrographs of the shapes of the inner surface and the outer surface of the obtained hollow fiber are shown in FIG. 1 (5000 times) and FIG. 2 (5000 times), respectively. As shown in FIG. 1, the inner surface has a major axis of 0.2 to
Ellipsoidal pores of 1.5 μm were distributed at an opening rate of 16.4%. On the other hand, as shown in FIG. 2, the outer surface of the hollow fiber had holes having a network (sponge) structure of a partial cross section. The cross section of the hollow fiber had a network structure in which the pore diameter increased substantially continuously from the outer surface to the inner surface. The maximum tensile strength of this hollow fiber is 51g
f / mm ² , the maximum elongation was 60%.

Example 2 A spinning dope was prepared by dissolving 15 parts of polysulfone in a mixed solvent of 51 parts of N-methyl-2-pyrrolidone and 34 parts of triethylene glycol. N-methyl-2 as core fluid
-A mixed solution of 59 parts of pyrrolidone and 41 parts of ethylene glycol was used. Using a double nozzle with an inner diameter 0.4 mm, an outer diameter 0.6 mm, and a core liquid discharge outlet having a diameter of 0.2 mm, 4.4 g from the discharge outlet while keeping the spinning solution at 45 ° C.
At a spinning speed of 55 m / min while coagulating in warm water of 50 ° C. located 4 cm below the nozzle, and wound at a spinning speed of 55 m / min, an inner diameter of 340 μm, and an outer diameter of 430 μm.
m hollow fibers were obtained. On the inner surface of the obtained hollow fiber, elliptical pores having a major axis of 0.3 to 1.2 μm and a major axis / minor axis ratio of 1.4 or less, which are close to a circle, are distributed at an opening ratio of 11.2%. It was
The outer surface and the cross-sectional structure of the hollow fiber were almost the same as in Example 1. The maximum tensile strength of this hollow fiber is 42 gf / m
The m ² and the maximum elongation were 53%.

Example 3 A spinning dope was prepared by dissolving 15 parts of polysulfone in a mixed solvent of 55 parts of N-methyl-2-pyrrolidone, 10 parts of propylene glycol and 20 parts of triethylene glycol. As the core liquid, a mixed liquid of 68 parts of N-methyl-2-pyrrolidone and 32 parts of propylene glycol was used. Using a double nozzle having an inner diameter of 0.4 mm and an outer diameter of 0.6 mm, and a core liquid discharge outlet of 0.2 mm, 50
While maintaining at ℃, 4.0 g / min from the discharge port, the core liquid 4.5
Extruded with g / min, 50 ° C 4 cm below the nozzle
While being coagulated in warm water, it was wound at a spinning speed of 50 m / min to obtain a hollow fiber having an inner diameter of 350 μm and an outer diameter of 440 μm.
The inner diameter of the obtained hollow fiber has a major axis of 0.3 to 3.2 μm.
The elliptical hole with a major axis / minor axis ratio of 2.1 or less has an open area ratio of 2
It was distributed at 0.8%. The outer surface and the cross-sectional structure of the hollow fiber were almost the same as in Example 1. The maximum tensile strength of this hollow fiber was 39 gf / mm ² , and the maximum elongation was 62%.

Comparative Example 1 A spinning solution was prepared by dissolving 15 parts of the polysulfone used in Example 1 in a mixed solvent of 49 parts of N-methyl-2-pyrrolidone and 36 parts of triethylene glycol. As the core liquid, a mixed liquid of 58 parts of N-methyl-2-pyrrolidone and 42 parts of triethylene glycol was used. Inner diameter 0.4 mm,
Using a double nozzle having an annular discharge port with an outer diameter of 0.6 mm and a core liquid discharge port with a diameter of 0.2 mm, 4.0 g / min from the discharge port while keeping the spinning solution at 35 ° C, 4.5 g of core liquid At a spinning speed of 50 m / min while coagulating in 30 ° C. warm water located 2 cm below the nozzle, and with an inner diameter of 34
A hollow fiber having a diameter of 0 μm and an outer diameter of 460 μm was obtained. An electron micrograph of the shape of the inner surface of the obtained hollow fiber is shown in FIG.
Times). As shown in FIG. 3, a substantially elliptical hole having a major axis of 0.2 to 1.5 μm was formed on the inner surface with a porosity of 5.4.
It was distributed in%. On the other hand, the outer surface of the hollow fiber had the same pores as the outer surface of Example 1. The cross section of the hollow fiber is
It was a network structure in which the pore size increased almost continuously from the outer surface to the inner surface. The maximum tensile strength of this hollow fiber was 31 gf / mm ² , and the maximum elongation was 67%.

Comparative Example 2 A spinning dope was prepared by dissolving 13.5 parts of the polysulfone used in Example 1 in a mixed solvent of 61.7 parts of N-methyl-2-pyrrolidone and 24.8 parts of propylene glycol. As the core liquid, a mixed liquid of 70 parts of N-methyl-2-pyrrolidone and 30 parts of propylene glycol was used. Using a double nozzle having an inner diameter 0.4 mm and an outer diameter 0.6 mm, an annular discharge port and a 0.2 mm diameter core liquid discharge port
Core liquid 5.6 at 5.0 g / min from the discharge port while maintaining at ℃
Extruded with g / min, 60 ° C 2 cm below the nozzle
While being coagulated in warm water, the fiber was wound at a spinning speed of 62.5 m / min to obtain a hollow fiber having an inner diameter of 340 μm and an outer diameter of 460 μm. An electron micrograph of the shape of the inner surface of the obtained hollow fiber is shown in FIG. 4 (2000 times). As shown in FIG. 4, an elliptical hole having a major axis of 1 to 10 μm is formed on the inner surface with a porosity of 2
It was distributed at 9.4%. The outer surface of the hollow fiber had the same holes as in Example 1. The cross section of the hollow fiber had a network structure in which the pore diameter increased substantially continuously from the outer surface to the inner surface. The maximum tensile strength of this hollow fiber was 18 gf / mm ² , and the maximum elongation was 48%.

Comparative Example 3 A spinning dope was prepared by dissolving 17 parts of polysulfone used in Example 1 in a mixed solvent of 61 parts of N-methyl-2-pyrrolidone and 22 parts of propylene glycol. As the core liquid, a mixed liquid of 90 parts of dimethylformamide and 10 parts of water was used. Using a double nozzle having an inner diameter 0.4 mm, an outer diameter 0.6 mm, and a core liquid discharge outlet having a diameter of 0.2 mm, 4.0 g / min from the discharge outlet while maintaining the spinning solution at 55 ° C,
Extruded together with 4.5 g / min of core liquid and spinning speed 50 m / m while coagulating in warm water of 50 ° C 6 cm below the nozzle.
It was wound up in minutes to obtain a hollow fiber having an inner diameter of 330 μm and an outer diameter of 430 μm. The inner surface of the obtained hollow fiber has a diameter of 0.5μ.
Fibers in which spherical particles having various particle sizes of m or less were aggregated to form a network structure (sponge structure, open pores of 2 to 5 μm). Since this structure has three-dimensional irregularities, it is difficult to specify the internal surface porosity, but the fibers forming the network themselves include spherical irregularities on the surface of the spherical particles, and therefore do not have apparently smooth perimeters.

Comparative Example 4 A hollow fiber having an inner diameter of 330 μm and an outer diameter of 430 μm was obtained in the same manner as in Comparative Example 3, except that the core liquid was a mixed liquid of 80 parts of dimethylformamide and 20 parts of water. An electron micrograph of the shape of the inner surface of the obtained hollow fiber is shown in FIG. 5 (10000 times). As shown in FIG. 5, slit-shaped holes whose pore diameters were difficult to specify were distributed on the inner surface.

Comparative Example 5 The same operation as in Comparative Example 3 was carried out except that the core liquid was a mixed liquid of 70 parts of N-methyl-2-pyrrolidone and 30 parts of water, and an inner diameter of 330 μm.
m, and an outer diameter of 430 μm was obtained. An electron micrograph of the shape of the inner surface of the obtained hollow fiber is shown in FIG. 6 (3000 times). As shown in FIG. 6, pores of various sizes and irregular shapes were distributed on the inner surface.

Comparative Example 6 Inner diameter was the same as Comparative Example 1 except that the core liquid was a mixed solvent of 85 parts of N-methyl-2-pyrrolidone and 15 parts of propylene glycol, and the distance between the nozzle and the hot water for coagulation was 1 cm. Three
A hollow fiber having a diameter of 30 μm and an outer diameter of 430 μm was obtained. An electron micrograph of the shape of the inner surface of the obtained hollow fiber is shown in FIG.
Times). As shown in FIG. 7, the inner surface had a macrovoid structure in which large cavities (maximum major diameter of 13 μm at a diameter of about 10 μm) were found in a network structure of holes having a diameter of 0.5 to 1 μm. Since the network portion of the inner surface is three-dimensional like Comparative Example 3, it is difficult to specify the porosity. However, the part surrounded by the fibers constituting the network is not a continuous and smooth curve. In addition, minute polymer particles were irregularly accumulated around the macro void portion.

Application Example 1 240 hollow fibers obtained in Example 1 were used, with an inner diameter of 9 mm and an outer diameter of 1
Stored in a 3mm, 21cm long polycarbonate pipe,
An animal plasma separator (module) was produced by potting both ends with urethane resin. This module has a blood inlet and a blood outlet at both ends, and a blood filtrate outlet on the opposite side of the blood inlet and inside the urethane potting portion. The effective length of this module was 18 cm. 3 in this module
When fresh bovine blood kept at 7 ° C was filtered at a flow rate of 5 ml per minute while flowing on the inner surface side of the hollow fiber, the filtration rate was 2.2 per minute.
It was possible to continue the filtration stably at a filtration pressure of 10 mmHg for 2 hours. On the other hand, the filtration rate of fresh bovine blood kept at 37 ° C in the same type module was gradually increased so that the filtration pressure was increased by 10 mmHg in 2 minutes.
The blood pressure was raised to 0 mmHg, but no hemolysis of bovine blood was observed.

Application Examples 2 and 3 Using the hollow fibers obtained in Examples 2 and 3, a bovine blood filtration test was conducted in the same manner as in Application Example 1, and the same results were obtained.

Application Comparative Example 1 A bovine blood filtration test was conducted in the same manner as in Application Example 1 using the hollow fiber obtained in Comparative Example 1. The filtration rate was 1.5 ml / min.
The filtration pressure was 10 mmHg, and the filtration could be stably continued for 2 hours. However, when a module of the same type was used and the filtration rate was set to 2.2 ml / min, the filtration pressure continued to increase from the beginning of filtration, and bovine blood filtration could not be performed under certain conditions. On the other hand, using the same type of module, the initial filtration rate was 1.5 ml / min, and the filtration pressure was 1 minute in 2 minutes.
The filtration rate was gradually increased so as to increase by 0 mmHg and the filtration pressure was increased to 35 mmHg, but hemolysis of bovine blood was not observed.

Application Comparative Example 2 An attempt was made to make a module similar to Application Example 1 using the hollow fiber obtained in Comparative Example 2, but the mechanical strength of the hollow fiber was insufficient and a module could be made. There wasn't.

Application Comparative Examples 3 and 4 A bovine blood filtration test was conducted in the same manner as in Application Example 1 using the hollow fibers obtained in Comparative Examples 4 and 5, and the filtration rate was 2.2 per minute.
ml, and the filtration pressure was 10 mmHg, and the filtration could be continued stably for 2 hours. However, using the same type of module,
When the filtration rate was gradually increased so that the filtration pressure was increased by 10 mmHg in 2 minutes, hemolysis occurred at about 100 mmHg.

Regarding the hollow fibers produced in Comparative Examples 3 and 6, it is feared that foreign matter (fine particles, etc.) may be mixed into the hollow fiber during filtration or in the undiluted solution of the filtration. We judged that it was unsuitable for fields such as separation and did not carry out a comparative study using bovine blood filtration.

[0030]

INDUSTRIAL APPLICABILITY Since the hollow fiber having a specific inner surface structure of the present invention has the inner surface pores changed from a smooth elliptical shape to a circular shape, it can be filtered without damaging the solute component. Further, the hollow fiber of the present invention has a maximum major axis of pores and a porosity of a specific range, and thus has sufficient mechanical strength and an appropriate filtration flux. Thus, the porous polysulfone hollow fiber of the present invention has a high utility value as a filtration membrane for microfiltration or blood filtration.

[Brief description of drawings]

FIG. 1 is an electron micrograph showing the shape of fibers on the inner surface of a hollow fiber of Example 1.

FIG. 2 is an electron micrograph showing the shape of fibers on the outer surface of the hollow fiber of Example 1.

3 is an electron micrograph showing the shape of fibers on the inner surface of the hollow fiber of Comparative Example 1. FIG.

FIG. 4 is an electron micrograph showing the shape of fibers on the inner surface of the hollow fiber of Comparative Example 2.

5 is an electron micrograph showing the shape of fibers on the inner surface of the hollow fiber of Comparative Example 4. FIG.

6 is an electron micrograph showing the shape of fibers on the outer surface of the hollow fiber of Comparative Example 5. FIG.

FIG. 7 is an electron micrograph showing the shape of fibers on the outer surface of the hollow fiber of Comparative Example 6.

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Claims (2)

[Claims] 1. A hollow fiber made of aromatic polysulfone, wherein the pores present on its inner surface are elliptical to circular with a smooth circumference, and the maximum major axis of the pores is in the range of 0.1 to 10 μm. The open area ratio, which is the ratio of the total open area of the inner surface holes having a major axis of 0.1 μm or more to the inner surface area, is 7 to 2
3% porous polysulfone hollow fiber. 2. The porous polysulfone hollow fiber according to claim 1, wherein there is no skin layer on the outer surface of the hollow fiber, and the maximum major axis of the pores present on the outer surface is at least 0.1 μm.