JP2794610B2 - Method for producing large-diameter polyethersulfone hollow fiber membrane - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a polyethersulfone hollow fiber membrane. More specifically, the present invention relates to a method for producing a large-diameter polyethersulfone hollow fiber membrane having a high molecular weight cut-off and a high permeation flux and excellent mechanical strength.

[Prior art] Polyethersulfone, one of engineering plastics, has excellent thermal and mechanical properties and also has chemical resistance to acids, alkalis, etc. Widely used in electronic industrial parts.

Also, since polyether sulfone can be easily spun into hollow fibers, it can be used as a hollow fiber membrane for separating gas and liquid. Particularly, it is extremely useful as an ultrafiltration membrane or a microfiltration membrane which is required to be used in a high temperature region or under a strong acid or strong alkaline condition.

A method for producing a polyethersulfone hollow fiber membrane by a so-called phase conversion method is as follows.

The spinning solution (hereinafter referred to as dope) is a mixture of polyethersulfone with a good solvent or a non-solvent mixed with a good solvent.
It is prepared by dissolving 10 to 30% by weight. The dope is extruded from the outer concentric orifice of the double concentric nozzle, and at the same time, a gas or a liquid having a non-solvent property to polyethersulfone is extruded from the central orifice, and the dope is formed into a hollow cylindrical shape, directly or A certain gas-phase space is distanced to enter the coagulation solution, and the dope is transformed into a solid phase to obtain a hollow fiber membrane.

The coagulation liquid has a non-solvent property with respect to polyether sulfone and is a liquid that is mutually miscible with the dope solvent. However, water or an aqueous solution is often used mainly for economic reasons.

With the expansion of separation and purification targets in industrial processes, the development of a membrane having a molecular weight cut off of 100,000 or more has been required along with a further improvement in permeation flux.

In order to increase the permeation flux and increase the molecular weight of the fraction, it is particularly effective to lower the polymer concentration in the dope. However, in order to cause a decrease in spinning stability and a decrease in strength per film thickness of the product due to a decrease in the viscosity of the dope,
There is a limit. Therefore, in addition to lowering the polymer concentration of the dope, the solvent composition of the dope (the type of solvent and non-solvent and the mixing ratio)
In order to increase the water permeation flux by changing the value, various methods have been disclosed, and various methods have been disclosed. Among them, the method of adding a polyhydric alcohol as a non-solvent to be added to the polysulfone-based dope is particularly excellent,
It has been conventionally known that it is effective to increase the addition amount within a limit that the dope maintains a transparent uniform solution at the spinning temperature.

Furthermore, the expansion of the membrane processing target also requires an increase in the inner diameter of the hollow fiber membrane, and a technique for producing a hollow fiber membrane having a high permeation flux or a high permeation flux and a high molecular weight cut-off, and a large diameter is required. Has been studied.

In order to spin the hollow fiber membrane stably, it is necessary that the viscosity of the dope is higher than a certain level, and the desirable viscosity tends to increase as the diameter increases. Although the viscosity of the dope depends largely on the polymer concentration, it is necessary to keep the polymer concentration in the dope as low as possible as described above in order to simultaneously satisfy the demand for a high permeation flux or a high molecular weight cut-off. . This dilemma can be solved by increasing the viscosity of the solvent (mixture of solvent and non-solvent) of the polymer itself and / or by increasing the viscosity of the solvent in which the solution of the polymer is dissolved. From such a viewpoint, polyhydric alcohol is particularly excellent as a non-solvent to be added to the polysulfone-based dope.

The prior art for polysulfone-based hollow fiber membrane production was evaluated from the above viewpoint, and the polymer concentration in the dope was 15% by weight.
Above, and the added non-solvent is polyhydric alcohol and its concentration is
If you select a spinning dope from 20% by weight or more,
As an example of high flux, Japanese Patent Publication No. Sho 63-56802 discloses a repeating unit. Polysulfone (hereinafter referred to as PSF) = 20% by weight, polyethylene glycol (hereinafter referred to as PEG) 600 = 36
Wt%, N, N-dimethylformamide (hereinafter referred to as DMF)
= 44 wt% dope, water permeation flux = 1000
Examples and comparative examples in which hollow fiber ultrafiltration membranes (hereinafter referred to as hollow fiber UF membranes) of / m ² · h · atm and 1350 / m ² · h · atm are described. Also, JP-A-1-94902 discloses that PSF =
A hollow fiber UF membrane having a water permeation flux of 840 / m ² · h · atm was obtained from a dope of 20 wt%, PEG 600 = 36 wt%, and N, N-dimethylacetamide (hereinafter referred to as DMAc) = 44 wt%. Examples have been described. JP-A-62-201602 discloses PSF = 17.
Wt%, tetraethylene glycol (hereinafter referred to as TEG)
= 25% by weight, N-methylpyrrolidone (hereinafter referred to as NMP)
= 58% by weight dope to water flux = 970 / m ² .h.at
An example in which a hollow fiber UF membrane of m was obtained was described. JP 6
The publication No. 1-200805 has a repeating unit Polyethersulfone represented by (PES)
= 25 wt%, PEG400 = 25 wt%, dimethyl sulfoxide (hereinafter referred to as DMSO) 50 wt% dope to water permeation flux =
An example in which a hollow fiber UF membrane of 390 / m ² · h · atm was obtained is described. JP-A-59-228017 discloses that a dope of PSF = 17% by weight, diethylene glycol (hereinafter referred to as DEG) = 25% by weight and NMP = 58% by weight has a water permeation flux of 1370 / m ^2.
An example in which a hollow fiber UF membrane of h · atm was obtained is described.

[Problems to be Solved by the Invention] However, in any of the examples, the obtained polysulfone hollow fiber UF membrane has a high water permeation flux even though it has a high water permeation flux.
00 / m ² · h · atm or less.

Insufficient to extend the application of membrane separation technology from the conventional use of relatively expensive solutes, such as electrodeposition paints and oxygen, etc., to the broader industrial processes and wastewater treatment It is. In addition, there is no description of an example in which the inner diameter of the hollow fiber exceeds 0.6 mm, and there is a limitation in expanding the use of a high-viscosity fluid to a suspension.

[Means for Solving the Problems] In order to further improve the water permeation flux and increase the molecular weight of the fractionated molecular weight of the hollow UF membrane having a large diameter of 0.7 mm or more, in addition to contriving the dope composition, the coagulation liquid Ingenuity is also needed. When a separation function layer is formed on the inner surface of a hollow fiber membrane, the higher the coagulation value (weaker coagulation force) of the internal coagulation liquid discharged from the center orifice of the double concentric nozzle during spinning, the higher the water permeation flux is generally. Is known to be. As the internal coagulation liquid, water or an aqueous solution of a non-solvent and / or a solvent is often used. In an aqueous solution, the lower the water content, the higher the water permeation flux generally. However, as the coagulation force of the internal coagulation liquid is weakened, the spinning stability decreases, and the degree increases as the hollow fiber diameter increases. For this reason, if the coagulation force of the internal coagulation liquid is weakened, the spinning conditions are restricted, and as a result, a preferable asymmetric membrane structure cannot be formed, and further, there is a problem that the membrane structure on the inner surface collapses.

The present inventor has solved such a problem, and has a hollow fiber membrane inner diameter of 0.
7 mm or more, tensile strength at break 25 kg / cm ² or more, water permeation flux 1500
In order to obtain a polyethersulfone hollow fiber membrane of not less than / m ² · h · atm (25 ° C.), the relationship between the dope composition and the internal coagulation liquid was studied diligently. As a result, the following method was found to obtain a large-diameter polyethersulfone hollow fiber membrane having a desired high permeation flux and a high molecular weight cut-off, leading to the present invention.

That is, the repeating unit of the material polymer is A method for producing a large-diameter hollow fiber membrane having an inner diameter of 0.7 mm or more, comprising: a spinning solution having 15 to 20% by weight of a polyether sulfone comprising the repeating unit; and 40% by weight or more having 5 or more carbon atoms. And containing at least one non-solvent of the polymer selected from ether alcohol, polyhydric alcohol and derivatives thereof which are liquid at room temperature, has a viscosity of 80 poise or more at 25 ° C., and the internal coagulating liquid has a viscosity of 5 to 5 poise. A large-diameter polyether which is a homogeneous solution comprising at least a three-component mixture of 20% by weight of water, an ether alcohol having 6 or less carbon atoms, and a polyhydric alcohol having 6 or less carbon atoms or a derivative thereof. This is a method for producing a sulfone hollow fiber membrane.

By selecting the dope composition and the internal coagulating liquid composition to such range, a stable hollow fiber UF membrane or larger diameter inner diameter 0.7mm water permeation rate 1800 / m ² · h · atm or more high flux It can now be manufactured.

The concentration of the polyethersulfone in the dope is preferably 15 to 20% by weight. If the concentration of the polyethersulfone exceeds 20% by weight, the water permeation rate of the obtained hollow fiber membrane is undesirably reduced. On the other hand, when the concentration is less than 15% by weight, the mechanical strength of the obtained hollow fiber membrane decreases, which is not preferable.

D6SO, 2-pyrrolidone (hereinafter referred to as 2)
-PN) and mixtures thereof are preferred, but DMF, D
A polar organic solvent, such as MAc or NMP, which can be freely mixed with water can also be used.

As the non-solvent to be added to the dope, ether alcohols having 5 or more carbon atoms, polyhydric alcohols which are liquid at room temperature and derivatives thereof are preferable, and tetrahydrofurfuryl alcohol, triethylene glycol, tetraethylene glycol, PEG, dipropylene glycol, and tripropylene Glycol, diethylene glycol monomethyl ether or the like alone or a mixture thereof is used.

As the molecular weight of PEG increases, the effect of increasing the viscosity of the dope increases, but the solidification rate of the spun dope decreases, and the effect of disturbing the resulting film structure increases. Therefore, it is not preferable to use PEG 300 or more alone.

PEG is generally regarded as a non-solvent for PES, but PEG having a molecular weight of 300 or more is actually a good solvent for PES (JP-A-2-105).
This is considered to be the main cause of the above phenomenon.

In addition, polyhydric alcohols and derivatives thereof that do not limit the number of carbon atoms to the added non-solvent, for example, ethylene glycol,
Diethylene glycol, glycerin and their monoethers or monoesters may be added in small amounts.

About the addition amount of the non-solvent, the inner diameter of the hollow fiber is 0.7 mm or more, and the water permeation flow rate is 1800 / m ² · h ·
80 for stable spinning of hollow fiber membranes of atm or more
High dope viscosity equal to or higher than poise can be realized.
Further, by adding a second threshold value or more higher than the first threshold value, it is possible to form an asymmetric porous structure having no macrovoids having an equivalent diameter of 20 μm or more in the film cross section.

The preferred range of the amount of the non-solvent varies depending on the composition of the internal coagulating liquid and the spinning conditions, but is preferably 35% by weight or more, more preferably 40% by weight or more of the total amount of the dope. However, it is not preferable to add such a large amount that the dope cannot be maintained as a transparent homogeneous solution at the spinning temperature.

Examples of the internal coagulating liquid include 5 to 20% by weight of water, an ether alcohol having 6 or less carbon atoms such as tetrahydrofurfuryl alcohol, ethylene glycol monoalkyl ether, diethylene glycol monomethyl ether, etc. Mixtures with polyhydric alcohols and derivatives thereof, such as ethylene glycol, diethylene glycol and triethylene glycol, can be used, but in any case the ratio of ether groups to hydroxyl groups is in the range of less than 2, especially in the range of 0.5 to 1.5. Is preferred.

If it is less than 0.5, the water permeation flux may be lower than 1800 / m ² · h · atm, and if it is more than 1.5, the structure of the separation functional layer on the inner surface of the hollow fiber may be broken.

PEG having 8 or more carbon atoms is not preferable because it has a greater risk of coarsening or breaking the separation functional layer on the inner surface of the hollow fiber than polyhydric alcohol containing PEG having 6 or less carbon atoms. In addition, it is possible to substitute a part of the polyhydric alcohol and its derivative with a good solvent used for dope.

[Examples] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 18 parts by weight of PES (trade name: Victrex 5200P, manufactured by ICI) was added to 42 parts by weight.
Parts by weight of DMSO (Wako Pure Chemicals, reagent) and 40 parts by weight of PEG200
The mixture was dissolved at 60 ° C. in a mixed solvent composed of (reagents, manufactured by Wako Pure Chemical Industries, Ltd.) to prepare a transparent and uniform dope having a viscosity of 86 poise (25 ° C.).

This dope is composed of 60 wt% of ethylene glycol monomethyl ether (manufactured by Wako Pure Chemical, reagent), 30 wt% of triethylene glycol (manufactured by Wako Pure Chemical), 10 wt% of water, and an internal coagulating liquid having a ratio of ether group to hydroxyl group of 1.0. At the same time, the hollow fiber membrane was extruded from a tube-in-orifice type concentric double nozzle and immersed in 70 ° C. water 10 cm away from the nozzle to obtain a hollow fiber membrane having an inner diameter of about 0.8 mm and an outer diameter of about 1.3 mm.

The obtained hollow fiber membrane has a pure water permeation flux of 2230 / m ² .h.atm.
(25 ° C.), bovine serum albumin (molecular weight: 65,000, hereinafter referred to as BSA) transmittance of about 100%, bovine serum γ-globulin (molecular weight: 1
50,000, hereinafter referred to as BγG) 44% transmittance and high water flux
The molecular weight was high. Solute permeability is 0.01 wt.
% Phosphate buffer solution into the hollow fiber lumen at an average membrane shear rate of 3 ×
The solution was supplied under the conditions of 10 ³ sec ⁻¹ or more and an average diaphragm pressure difference of 0.8 atm, and the solute concentration in the obtained permeate was expressed as a percentage of the average concentration in the feed solution.

The hollow fiber membrane had excellent tensile strength at break of 36 kg / cm ² , elongation at break of 30%, and burst pressure of 17 kg / cm ² .
The result of observing the inner surface of the obtained hollow fiber with a scanning electron microscope (SEM) at a magnification of 10,000 times is shown in FIG.

Comparative Example 1 18 parts by weight of PES were combined with 60 parts by weight of DMSO and 22 parts by weight of PEG200.
Was dissolved at 60 ° C. in a mixed solvent of to prepare a transparent and uniform dope having a viscosity of 41 poise at 25 ° C.

A hollow fiber membrane having an inner diameter of 0.8 mm and an outer diameter of 1.3 mm was spun in the same manner as in Example 1 except that this dope was used as a spinning solution, and the hollow fiber membrane extruded from the nozzle was coagulated in a coagulation bath (70 ° C.).
(Water), the course was not stable and the thread was sometimes broken, so that the hollow fiber membrane could not be manufactured stably.

For reference, inside diameter 0.5mm, outside diameter 0.8mm in this combination
When the hollow fiber membrane was spun, the shaking became small and no yarn breakage occurred. The pure water permeation flux of the obtained hollow fiber membrane having an inner diameter of 0.5 mm was as large as 1930 / m ² · h · atm, but as shown in FIG. 2, the inner surface of the hollow fiber was scanned with a scanning electron microscope (SEM).
Observation at a magnification of 10,000 times showed that a large number of pores having a pore diameter of 0.5 μm or less were scattered unevenly, and the film surface was rough.

Comparative Example 2 A hollow fiber membrane having an inner diameter of 0.8 mm and an outer diameter of 1.3 mm was spun in the same manner as in Example 1 except that a 90 wt% PEG200 aqueous solution (the ratio of ether groups to hydroxyl groups was 1.5) was used as the internal coagulating liquid. The hollow fiber membrane extruded from the nozzle fluctuated in the coagulation bath and was slightly unstable, but did not break.

The pure water permeation flux of the obtained hollow fiber membrane is 1970 / m ² · h · a
Although it was as large as tm, as shown in FIG. 3, when the inner surface of the hollow fiber was observed with a scanning electron microscope (SEM) at a magnification of 10,000 times, many holes having a hole diameter of 0.3 μm or less were scattered.

Comparative Example 3 An inner diameter of 0.8 m was made in the same manner as in Example 1 except that a 90 wt% aqueous solution of diethylene glycol monomethyl ether (the ratio of ether groups to hydroxyl groups was 2.0) was used as the internal coagulating liquid.
When a hollow fiber membrane having an outer diameter of 1.3 mm and a diameter of 1.3 mm was spun, the hollow fiber membrane extruded from the nozzle fluctuated in the coagulation bath and was slightly unstable, but did not break.

The pure water permeation flux of the obtained hollow fiber membrane is 2170 / m ² · h · a
Although it was as large as tm, the inner surface of the hollow fiber was observed with a scanning electron microscope (SEM) at a magnification of 10,000 times, and as shown in FIG. 4, it had a collapsed porous structure with a pore diameter of 0.5 μm or less.

Examples 3 to 5 Three types shown in Table 1 were prepared as internal coagulating liquids.

A hollow fiber membrane having an inner diameter of 0.8 mm and an outer diameter of 1.3 mm was spun in the same manner as in Example 1 except that these were used as the internal coagulating liquid.

As a result of evaluating the membrane performance of the obtained hollow fiber membrane, all were high performance as shown in Table 1.

Examples 6-9 18 parts by weight of PES were combined with 37 parts by weight of DMSO and 45 parts by weight of PEG200.
Was dissolved at 60 ° C. in a mixed solution of the above to prepare a transparent uniform dope having a viscosity of 105 poise.

 Four types shown in Table 2 were prepared as internal coagulating liquids.

A hollow fiber membrane having an inner diameter of 0.8 mm and an outer diameter of 1.3 mm was spun in the same manner as in Example 1 except that these dopes and the internal coagulation liquid were used.

As a result of evaluating the membrane performance of the obtained hollow fiber membrane, all were high performance as shown in Table 2.

Example 2 18 parts by weight of PES were replaced by 40 parts by weight of DMSO, 40 parts by weight of PEG200
And a mixed solvent consisting of 2 parts by weight of glycerin was dissolved at 69 ° C. to prepare a transparent and uniform dope having a viscosity of 110 poise.

A hollow fiber membrane having an inner diameter of 1.0 mm and an outer diameter of 1.5 mm was spun in the same manner as in Example 1 except that this dope was used as a spinning solution.

The obtained hollow fiber membrane has a pure water permeation flux of 2160 / m ²
m, BSA transmittance 100%, BγG transmittance 0%, and high performance.

[Effect of the Invention] According to the present invention, the repeating unit is Polyethersulfone consisting of a membrane material with a hollow fiber inner diameter of 0.7 mm or more and a water permeation flux of 1800 / m ² · h
-It is possible to stably produce a hollow fiber UF membrane having a high permeation flux and a high molecular weight cut-off having an atm of at least or more and a molecular weight cut-off of 70,000 or more and excellent in thermal and mechanical properties.

[Brief description of the drawings]

1 is Example 1, FIG. 2 is Comparative Example 1, FIG. 3 is Comparative Example 2, and FIG. 4 is a magnification of 10,000 showing the shape of the inner surface of the fibrous hollow fiber obtained in Comparative Example 3, respectively. It is a scanning electron microscope photograph of the magnification.

Claims (2)

(57) [Claims] (1) The repeating unit of the material polymer is A method for producing a large-diameter hollow fiber membrane having an inner diameter of 0.7 mm or more, comprising: a spinning solution having 15 to 20% by weight of a polyether sulfone comprising the repeating unit; and 40% by weight or more having 5 or more carbon atoms. And containing at least one non-solvent of the polymer selected from ether alcohol, polyhydric alcohol and derivatives thereof which are liquid at room temperature, has a viscosity of 80 poise or more at 25 ° C., and the internal coagulating liquid has a viscosity of 5 to 5 poise. A large-diameter polyether which is a homogeneous solution comprising at least a three-component mixture of 20% by weight of water, an ether alcohol having 6 or less carbon atoms, and a polyhydric alcohol having 6 or less carbon atoms or a derivative thereof. A method for producing a sulfone hollow fiber membrane. 2. The method for producing a large-diameter polyethersulfone hollow fiber membrane according to claim 1, wherein the pure water permeation flux is 1800 / m ² .h.atm or more.