JPS63100902A - Aromatic polysulfone hollow yarn membrane and its manufacture - Google Patents

Abstract

PURPOSE:To prepare a membrane to be used effectively in the fields of precision filtration, plasma separation and the like by providing given shapes of pores existing inside an aromatic polysulfone hollow yarn membrane and making the maximum length of diameters of the pores within a given range. CONSTITUTION:The shape of pores existing inside an arromatic polysulfone hollow yarn membrane is arranged as oval-round having a smooth circumference and the maximum length of diameters of said pores is made at least 0.1mum. Said membrane is prepared by extruding aromatic polysulfone solution, preferably 10-20% aromatic polysulfone solution solved with a solvent mixed with a good solvent and a non-solvent, directly out of a double-tube shaped nozzle into a coagulating agent to coagulate aromatic polysulfone, preferably weak coagulation, while feeding gas, preferably air, to its core section. As a result, a membrane to be used effectively in the field of precision filtration, plasma separation and the like is easily prepared.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an aromatic polysulfone hollow fiber membrane and a method for producing the same. In particular, the present invention relates to an aromatic polysulfone hollow fiber membrane that can be effectively used in fields such as microfiltration and plasma separation, and a method for producing the same.

[Prior Art/Problems to be Solved by the Invention] Many aromatic polysulfone hollow fiber membranes and their manufacturing methods are already known. Among these, an aromatic polysulfone hollow fiber membrane that can be used in fields such as precision filtration or plasma separation, and its manufacturing method, is disclosed in Japanese Patent Application Laid-Open No. 58-11470.
Publication No. 2, JP-A-58-91822, JP-A-59
This method is disclosed in Japanese Patent Application Laid-open No. 80-222112, etc.

However, the shapes of the pores existing on the inner surface of the hollow fiber membranes described in these publications are slit-like, spindle-like, or irregular shapes that cannot be specified, and all of them are oval to circular with a smooth circumference. do not have.

In this way, if the pore size differs significantly depending on the direction, it is not only difficult to identify the pore size, but also
Filtration characteristics also change in a complex manner depending on the shape of the solute component. Therefore, when filtering a liquid containing a plurality of solutes that differ not only in size but also in shape, the problem tends to arise that sharp fractionation characteristics are not exhibited.

In addition, when trying to perform plasma separation using a membrane that not only has pore sizes that differ significantly depending on the direction, but also has pores with an uneven circumference, the shear rate of blood on the membrane surface increases. Increasing the friction between the blood cell components and the area around the pores by making them larger or increasing the amount of filtration,
Blood cell components are susceptible to damage such as hemolysis due to local forces.

These problems can be solved by making the pores on the inner surface of the hollow fiber membrane, which are in contact with the liquid to be treated, circular or nearly circular with a smooth circumference. However, an aromatic polysulfone hollow fiber membrane with inner pores having a circular to elliptical shape with a smooth circumference and a predetermined pore diameter has not been obtained.

The reason for this is that aromatic polysulfone is a polymer substance with high crystallinity and relatively strong intermolecular cohesive force, as it is also used as a heat-resistant engineering plastic. When the polymer substance is brought into contact with a liquid that is a non-solvent and is compatible with the solvent, that is, a coagulation liquid, many crystal nuclei of the polymer substance are generated on the contact surface, and each crystal nucleus is centered. As a result of studies conducted by the present inventors, it has been found that this is because the aggregation of the polymeric substances progresses and irregular irregularities of these aggregates occur around the formed pores. In other words, in all conventional hollow fiber membrane manufacturing techniques, hollow fibers are formed using the coagulation liquid as a core liquid, so the periphery of the pores on the inner surface of each hollow fiber membrane has complex irregularities. Hollow fiber membranes with pores on the inner surface of the desired shape have not yet been obtained.

Furthermore, as a result of studies conducted by the present inventors, 1. By using a coagulating liquid with affinity close to that of aromatic polysulfone solution and weak coagulating effect as the core liquid, the number of crystal nuclei generated is reduced and pores with smooth circumferences are formed. As long as the core liquid has a coagulating effect, even if it is a weak one, it is impossible to form pores of this type. Even with a method using a small gas, unless the viscosity of the aromatic polysulfone solution is increased to several thousand cP or more, hollow fibers cannot be formed in the normal dry-wet spinning method. It has been found that hollow fibers with pores of 0.01 μm cannot be obtained.

[Means for Solving the Problems] The present invention has been made to solve the problems in the prior art as described above, and is a hollow fiber membrane made of aromatic polysulfone. The shape of the hole is oval to circular with a smooth circumference, and the maximum major axis of the hole is at least 0. II! While sending gas through the aromatic polysulfone hollow fiber membrane (m) and the nozzle inside the double tubular nozzle, the aromatic polysulfone solution is directly pushed into the coagulating liquid of the solution from the ring-shaped nozzle of the double tubular nozzle. The present invention relates to a method for producing an aromatic polysulfone hollow fiber membrane.

[Example] Examples of the aromatic polysulfone used in the present invention include those having the following repeating units.

The hollow fiber membrane of the present invention is a hollow fiber-like membrane manufactured from the above-mentioned aromatic polysulfone, and the pores present on its inner surface are elliptical to circular with a smooth circumference, and the maximum major axis of the pores is at least It is necessary that it is 0.1 coral, preferably 0.1 to 5 coral. Furthermore, if the maximum length of the hole is less than 0.1, even in the conventional method, the dimensions of the unevenness and the size of the hole are close to each other, and there is little difference from the present invention.

Further, it is generally impossible to manufacture a material with sufficient physical properties and the like, and the length of the hole exceeds about 5 times.

Note that the term "elliptical" as used herein refers to shapes such as circular, elliptical, and egg-shaped, and does not necessarily have to be a perfect ellipse, but may include holes whose maximum major axis/minimum minor axis is approximately 3 or less. say something Further, the maximum major diameter of a hole is the largest diameter among the diameters observed at any location on the relevant surface using an electron microscope.

There is no particular limitation on the inner diameter, outer diameter, membrane thickness, membrane density, etc. of the hollow fiber membrane, but from the viewpoint of pressure loss, effective membrane area, mechanical strength, etc., the inner diameter is 200 to 1000ρ, and the outer diameter is 25
0 to 1500 terms, film thickness 20 to 300, film density 0
．． It is preferably about 2 to 0.4 g/cj.

In addition, a skin layer may be present on the outer surface of the hollow fiber membrane, but
Those without a skin layer and having pores with a maximum major axis of at least 0.1 are preferred when used in fields such as precision filtration and plasma separation.

Furthermore, the portion between the inner and outer surfaces of the hollow fiber membrane usually becomes spongy when the hollow fiber membrane is manufactured by the method described below. It is preferable that the maximum major diameter of the pores in this sponge-like portion is at least 0.1 历 from the viewpoint of reducing pressure loss and clogging in this portion.

Next, the method for manufacturing the hollow fiber membrane of the present invention will be explained.

The hollow fiber membrane of the present invention is produced, for example, by directly extruding an aromatic polysulfone solution from a ring-shaped nozzle together with gas from an inner nozzle into a coagulated liquid of the aromatic polysulfone solution.

As a solvent used in the preparation of aromatic polysulfone solutions,
Examples include, but are not limited to, N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, dimethylsulfoxide, and trichloroethane. In addition, to these solvents, for example, non-solvents such as high-boiling alcohols and polyhydric alcohols, water-soluble polymers such as polyethylene glycol and polyvinylpyrrolidone, and inorganic salts are added to prepare the aromatic polysulfone solution used in the present invention. May be used in addition within the range.

There are no particular limitations on the temperature, viscosity, concentration, etc. of the aromatic polysulfone solution during extrusion, but it
A solution of about 00 to 1000 cP is easy to spin when manufacturing a hollow fiber membrane.

Further, it is preferable that the solution concentration is about 10 to 20% from the viewpoint of making the major diameter of the pores on the inner surface of the hollow fibers 0.17a++ or more and obtaining a hollow fiber membrane having practical strength.

In general, as the solution concentration increases, the pore size tends to become smaller, and as the solution concentration decreases, the pore size tends to increase. Become something. However, when hollow fiber membranes are manufactured by the method of the present invention at any concentration, the pores present on the inner surface will have a circular or elliptical shape with a smooth periphery.

Note that the speed at which the aromatic polysulfone solution is extruded is, for example, about 10 to 100 m 2 /min.

Examples of gases sent out from the inner nozzle include air, nitrogen, water vapor, methanol, ethanol,
Examples include, but are not limited to, vapors of organic solvents such as acetone. Furthermore, there are no particular limitations on the temperature of this gas, and any temperature that can be used as a gas may be used. However, it is preferable to use air, which can be used as a gas at room temperature, at room temperature from the viewpoint of cost.

The gas is delivered quantitatively using a metering pump.

The coagulating liquid is used to coagulate the aromatic polysulfone solution extruded from the nozzle from the outside, and is generally a non-solvent for aromatic polysulfone and a solvent that is compatible with a good solvent for aromatic polysulfone. It can be used if Specifically, a mixture of water or water added to adjust the coagulation effect and a good solvent for aromatic polysulfone is usually used.

The structure of the outer surface and cross section of the hollow fiber membrane of the present invention mainly depends on the solvent composition of the aromatic polysulfone solution and the affinity of the coagulating liquid for the aromatic polysulfone solution extruded into the hollow fiber shape.

For example, when the solvent for the aromatic polysulfone solution consists only of a good solvent for aromatic polysulfone, or when using a coagulating liquid such as water, which has a small affinity for aromatic polysulfone and has a strong coagulating effect, the outer surface of the hollow fiber A dense skin layer is formed, and macrovoids having a size of several orders of magnitude to several orders of magnitude are formed following the skin layer.

On the other hand, as a solvent for the aromatic polysulfone solution, a mixed solvent is used, which is a good solvent for aromatic polysulfone with the above-mentioned non-solvents and inorganic salts added to it so that the clouding point is higher than room temperature. When a liquid is used, a dense skin layer is formed on the outer surface of the hollow fiber, but the cross section following the skin layer can have a uniform network structure without macrovoids.

Furthermore, if a coagulating liquid having a weak coagulating effect, such as a concentrated aqueous solution of aromatic polysulfone as a good solvent, is used, the outer surface of the hollow fibers can be made porous without forming a skin layer.

In this way, the inner surface of the hollow fiber membrane has a maximum length of 0.1 m1.
or more, preferably the outer surface also has a maximum major axis of O,i
A hollow fiber membrane having pores larger than am and having a network structure with a preferably uniform cross section, which can be effectively used in fields such as microfiltration and plasma separation, is an aromatic polysulfone solution, preferably an aromatic polysulfone. A 10 to 20% solution of the polysulfone dissolved in a mixed solvent of a good solvent and a non-solvent is placed in a coagulant that has a coagulating effect, preferably a weak coagulating effect, on aromatic polysulfone, and a gas, preferably a gas, is added to the core of the aromatic polysulfone. It is selected by direct extrusion through a double tubular nozzle while blowing air.

Next, the hollow fiber membrane of the present invention and its manufacturing method will be explained based on Examples, but the present invention is not limited thereto.

Example 1 An 86% aqueous solution of dimethyl sulfoxide was kept at 60° C. and used as an outer coagulating liquid for hollow fibers. Inside this is a core diameter of 200A.
A double tubular nozzle with a Bn1 inner diameter of 400 mm and an outer diameter of 800 ρ was immersed in aromatic polysulfone (manufactured by Union Carbide Co., Ltd.,
A 14% solution of P-3500) in dimethyl sulfoxide was extruded directly into the outer coagulation liquid through the tubular nozzle at a flow rate of 6.7 g/min.

At the same time as this extrusion, air is supplied to the core at a rate of 5 ml per minute to form a hollow fiber, which is run through the outer coagulation liquid at a speed of 50 m/min for about m, then wound up in a water bath at 45°C. Ta.

After washing the wound hollow fiber membrane with hot water, it was air-dried at 40°C for a day and night, and then examined using a scanning electron microscope to obtain a
When observed at 0,000 times, the inner diameter is 320 m and the wall thickness is 50 m.
In the outer surface of the hollow fiber, there are many approximately circular holes with a smooth circumference with a maximum length of about 0.5 degrees and a length smaller than this, and the maximum length of the mesh in cross section is about 2J! m
It consisted of a network structure with a substantially uniform degree, and the inner surface had a maximum major axis of about 0.8 mm, and there were many approximately circular pores with smooth circumferences having a maximum major axis of about 0.8 mm or less.

Example 2 A hollow fiber membrane was produced in the same manner as in Example 1 except that a 17% dimethyl sulfoxide solution of aromatic polysulfone was used.

When the cross section, outer surface, and inner surface of this hollow fiber membrane were observed with a scanning electron microscope at a magnification of 100 to 20,000 times, the inner diameter, wall thickness, and cross-sectional structure were the same as those of the hollow fiber membrane of Example 1, but the outer surface has a maximum major axis of 0.3, and there are many approximately circular holes with a smooth circumference that has a major axis of less than this, and the inner surface has a smooth circumference that has a maximum major axis of 0.3- and a major axis of less than this. There were many almost circular holes.

[Effects of the Invention] The polysulfone hollow fiber membrane of the present invention is a novel hollow fiber membrane having circular to elliptical pores having a smooth circumference with a maximum major diameter of 0.1 or more on its inner surface, Since the hollow fiber membrane has the above characteristics, it can be effectively used in fields such as precision filtration and plasma separation.

Further, the hollow fiber membrane can be easily produced by the method of the present invention.

Claims (1)

[Scope of Claims] 1. A hollow fiber membrane made of aromatic polysulfone, in which the pores present on the inner surface are oval to circular with a smooth circumference, and the maximum major axis of the pores is at least 0.1 μm. Aromatic polysulfone hollow fiber membrane. 2. The aromatic polysulfone hollow fiber membrane according to claim 1, which has no skin layer on the outer surface of the hollow fiber membrane and has pores having a maximum major axis of at least 0.1 μm. 3. An aromatic hollow fiber characterized in that an aromatic polysulfone solution is directly extruded from a ring-shaped nozzle of a double-tubular nozzle into a coagulating liquid of the solution while sending gas from an inner nozzle of the double-tubular nozzle. Membrane manufacturing method.