JPS61200805A - Polyether sulfone microporous hollow yarn membrane and its production - Google Patents

Abstract

PURPOSE:To obtain a polyether sulfone hollow yarn membrane excellent in the separability of a solute and water transmitting flow flux, by forming a three-layered structure comprising dense layers in the vicinity of both surfaces and an intermediate layer having a reticulated structure so that the void ratio of a membrane as a whole is a specific range and the elongation of the membrane in a wet state is a specific value or more. CONSTITUTION:A raw spinning solution is prepared from polyether sulfone, a solvent such as dimethylsuloxide and water-soluble polyhydric alcohol such as polyethylene glycol to be extruded from the outer ring part of a double tube nozzle and a core solution is simultaneously emitted from the inner ring part to perform the spinning of a hollow yarn while the formed hollow yarn is guided to a water coagulation bath through the open air and subsequently washed with water. By this method, a polyether sulfone microporous hollow yarn membrane, of which the void ratio is 70-90% and the elongation in a wet state is 50% or more, having a three-layered structure is obtained.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is applicable to industrial operations such as concentration of aqueous solutions such as ultrafiltration and separation of substances, bioindustrial operations such as fermentation and cell culture, and filtration type artificial kidneys. , relates to a polyethersulfone microporous hollow fiber membrane suitable for medical applications such as artificial lungs.

[Prior art] In recent years, microporous membranes have been used for the production of ultrapure water for the electronics industry, the treatment of industrial wastewater such as wastewater from paper valves, separation and purification in the sugar industry, filtration-type artificial kidneys, plasma separation, plasma albumin recovery, etc. It has been used in industrial and medical separation and purification techniques such as blood purification, sterilization, and filtration for depyrolysis and diene removal.

For such purposes, microporous materials such as cellulose ester, polycarbonate, and polypropylene have been conventionally used. Porous membrane manufacturing methods include solvent evaporation drying method,
Microphase separation wet method, film stretching method, additive extraction method,
Etching methods after radiation irradiation are known. However, the polymer material, the microporous membrane structure, and its stability are not always satisfactory, especially in terms of permeability, mechanical strength, heat resistance, and solvent resistance.

From this point of view, polysulfone resins, which have excellent properties in terms of mechanical strength, heat resistance, and solvent resistance, have attracted attention, and several techniques have been disclosed regarding microporous membranes thereof. Special Publication No. 50-22508 and Special Publication No. 5
Publication No. 2-29712 is the origin of polysulfone membrane technology, and since then many membrane forming techniques have been disclosed. That is, JP-A-54-16381, JP-A-S4-ZE
2g3 and Japanese Patent Application Laid-open No. 54-143777, polysulfone membranes with an asymmetric membrane structure having a dense layer on the surface and macrovoids (finger type) in the middle layer of the membrane are applied to ultrafiltration, etc. . Japanese Patent Publication No. 55-1062
No. 43, JP-A-57-35906, and JP-A-59-183761 disclose membranes having a microporous membrane structure that are applied to solution separation and the like.

Further, in JP-A-56-81521, an attempt has been made to separate protein solutions using a polysulfone asymmetric membrane.

The polysulfones used in these prior art examples have a repeating unit structure of formula (I).

Further, some polysulfones have a repeating unit structure of the (IF) formula, which is called polyethersulfone.

Polyether sulfone has mechanical strength and heat resistance.

Chemical resistance is also equivalent to polysulfone of formula (I),
Since it is soluble in a polar solvent, a permeable porous membrane can be produced by processing methods such as wet membrane formation and wet spinning. However, there are few technical disclosures regarding membranes specifically using polyether sulfone, such as JP-A-54-16378, JP-A-54-14377, and JP-A-55-106243.
JP-A-56-99422, JP-A-56-99422, JP-A-56-99422
No. 86941, Japanese Unexamined Patent Publication No. 59-112027, etc. The flat membranes and hollow fiber membranes disclosed above for polysulfones of formula (I) and polyethersulfones of formula (n) are used in a wide variety of applications such as ultrafiltration membranes, precision filtration membranes, and support membranes for gas separation. It is. However, they are not always satisfactory in terms of the separation of the solutes to be separated and the permeation flux of the solution or solvent (generally water).

[Objective of the invention] In view of the above situation, it is an object of the present invention to utilize the excellent properties of polyether sulfone to impart scale and hydrophilicity to a three-layer microporous membrane to obtain a hollow fiber membrane useful for industrial and medical purposes. With this in mind, we have conducted extensive research and have completed the present invention.

[Structure of the Invention] That is, the present invention provides a membrane consisting essentially of polyether sulfone, which layer includes a dense layer near the outer surface, a dense layer near the inner surface, and a film thickness between the two layers. It has a three-layer structure consisting of an intermediate layer consisting of a network structure with communicating pores that occupies most of the membrane, and the porosity of the entire membrane is 70 to 90%, and the elongation of this layer in a wet state is is 50% or more, and preferably the water ultrafiltration rate of the microporous hollow fiber membrane is within the range of 1 to 600 Id/Td-h'・aIIHg. in,
It is substantially impermeable to afternoon serum albumin.

Furthermore, the present invention prepares a spinning dope consisting of polyether sulfone, a solvent for polyether sulfone, and a water-soluble polyhydric alcohol, extrudes it through a double tube nozzle together with the core liquid, and solidifies after passing through a gas atmosphere. This is a method for producing a polyethersulfone microporous hollow fiber membrane, characterized by coagulating it by introducing it into a bath or directly introducing it into a coagulation bath, and then washing it.

The present invention will be explained in detail below. The polyether sulfone has a repeating unit of the above-mentioned formula (n), and a polymer having a molecular weight of 20,000 to 40,000 is usually easily used. A membrane made essentially of polyether sulfone may contain up to 20% by weight of different polymers, additives, etc. In that case, the physical properties and structure of the membrane are essentially different from those of a membrane made solely of polyether sulfone. It is desirable that there is no such thing.

The membrane of the present invention is characterized by a dense layer near the outer surface, a dense layer near the inner surface, and a network structure with communicating pores occupying most of the film thickness between the two layers. It has a three-layer structure consisting of an intermediate layer and an intermediate layer. Figure 1 (ω
1 shows a cross-sectional photograph taken by a scanning electron microscope of an example of the microporous hollow fiber membrane of the present invention, and +b+ shows an enlarged photograph thereof. In FIG. 1(b), which shows a frozen cross section of the hollow fiber membrane, the three-layer structure can be seen. Most of the middle layer is 0.05~5μ
It consists of a network of pores with a continuous diameter, but the finger-type macrovoids and inclined asymmetric network structure found in conventional asymmetric membranes are not observed.

Further, FIG. 2 shows a photograph of the outer surface of the microporous hollow fiber membrane of the present invention. (ω is an example in which pores of 0.05 times or more are not observed on the surface, and 1) is an example in which pores of about 0.3 μ or less are observed. Figure 3 shows photographs of the inner surface. (B) is an example in which pores of approximately 0.5μ or less are observed in a network structure, and (b) is an example in which oriented pores of approximately 0.2μ or less are observed. This is an acceptable example.

The solute permeability in the membrane of the present invention is controlled by the dense layer near both surfaces. On the other hand, the intermediate layer is composed of a relatively coarse network of communicating pores and can realize high flux permeation of solutions, solvents, and water.

Furthermore, the microporous hollow fiber membrane of the present invention has a porosity of 70
It is characterized by being 90%. The porosity is determined by the following formula using the density of polyether sulfone, 1.37 g/C1j.

If the porosity exceeds 90%, the membrane will be weak, and if it is less than 70%, the entire membrane will become too dense and the membrane properties will be poor.

In addition, the microporous hollow fiber membrane of the present invention has an elongation of 50% or more in a water-wet state measured by a tensile tester.

This indicates that a tenacious film is produced due to the three-layer structure containing no macrovoids of the present invention.

The polymer aggregates in both dense layers and the network structure in the intermediate layer are combined to improve the physical properties of the film. The elongation is preferably 50 to 200%, although it varies depending on the membrane spinning method and developed membrane structure.

The water ultrafiltration rate of the microporous hollow membrane of the present invention having such a membrane structure is 1 to 600 sd! / rtL -hr・wearH
Within this range, bovine serum albumin with a molecular weight of 6,600 G does not substantially permeate. The ultrafiltration speed of water and solutions is determined by the hollow fiber membrane mini module (membrane area approximately 200Td).
), the recovery rate is 30 ~ under pressure of 100 HQ or less.
Determined by 50% filtration measurement. Ultrafiltration rate 1M1/
If it is less than 7IL-hr-lIIIHg, the water permeability is too low to be practical. On the other hand, 600ai! /rtt-h
Albumin often permeates membranes that exceed r.tm Hg. Preferably 10-600al! /i・
hr 6 s HQ, more preferably 100-600
Id/rd-hr-ml-1 (1. Substantially not permeating albumin means that the solute permeability SC (%) expressed by the following formula is 20% or less, preferably 10% or less.

N-methylpyrrolidone, dimethylacetamide, dimethylformamide, dimethylsulfoxide, and ε-caprolactone are used as solvents for polyethersulfone, but dimethylsulfoxide forms a nearly homogeneous film without macrovoids inside the membrane wall. is preferred. Water-soluble polyhydric alcohols include ethylene glycol,
There are propylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol (abbreviated as PEG) which is liquid at room temperature, etc., but PEG which is liquid at room temperature is particularly preferred and has a molecular weight of 200, 400. and 600 as specific examples.

10 to 35 weight polyether sulfone as spinning dope
A spinning stock solution is prepared from (D lower wt) %, dissolved @ 10 to 85 wt %, and 5 to 90 wt % of polyhydric alcohol. The polymer concentration can be appropriately selected depending on the viscosity of the stock solution and the film properties; if it is too thin, the stock solution viscosity is low and spinning becomes difficult, and if it is too high, the film becomes dense and the film properties are poor. The amount of water-soluble polyhydric alcohol added varies depending on its type; for example, diethylene glycol is about 1wt%, and PEG
400 can add as much as 90W%.

Generally, when the amount added is large, the film properties improve. The stock solution, which has been dissolved and defoamed by heating, is extruded from the outer ring part of the double tube nozzle, and at the same time, the core liquid is discharged from the inner ring part to spin into hollow fibers. The discharged filamentous material passes through the gas or directly into a coagulation bath, where it is coagulated to form a hollow fiber membrane. Next, the solvent, additives, and in some cases the core liquid are removed in a cleaning bath to obtain the hollow fiber membrane of the present invention. Furthermore, the core liquid can be removed and the hollow fiber membranes can be dried with glycerin by known methods.

Water or alcohol can be used in the spinning coagulation bath.

Additionally, the stringiness may be improved by adding a solvent or additive to the core liquid. In any case, when it is necessary to impart microporosity to at least one surface, it is preferable to increase the content of the solvent or additive. Water is generally used in the cleaning bath.

The dimensions of the hollow fiber membrane can be designed as appropriate, but the inner diameter is 10 to 200 mm.
Preferably, the film thickness is 0μ and the film thickness is 5 to 500μ.

[Effects of the Invention] The microporous hollow fiber membrane of the present invention has a three-layer structure consisting of a dense layer near both surfaces and an intermediate layer with a network structure, and is a strong membrane with high elongation, and is able to withstand the limitations of aqueous solutions such as proteins. It has excellent properties as an outer filtration membrane. That is, it does not substantially permeate albumin, but it permeates medium molecular weight substances with a molecular weight of about 10,000, and has a high ultrafiltration rate. Polyether sulfone is thermally stable and can be heat sterilized. In particular, it has a high elongation of 50% or more when wet, so it is highly elastic, difficult to break, easy to handle when manufacturing or incorporating into separators, etc., and is also susceptible to thermal stress during heat sterilization. It is also very stable.

Furthermore, the addition of water-soluble polyhydric alcohol helps to maintain the hydrophilicity of the membrane even after washing. Therefore, the membrane of the present invention can be used in the food industry,
It is useful in the pharmaceutical industry and in medicine as a filtering artificial kidney. In addition, cell culture diaphragms (separation).

(It can also serve as a carrier) and can also be stressed. It can also be used for gas separation and filtration cleaning.

The present invention will be explained below using Examples, but the present invention is not limited to these Examples.

Example 1 Polyether sulfone (hereinafter abbreviated as PES) was made by IC1 (manufactured by Sumitomo Chemical), Victrex (LT Rokusho 1, 4800P (formerly known as Grate 300P) was used, and polyethylene glycol was made using NOF PEG400. ,
PES 25wt% (weight% based on the total amount, the same applies hereinafter).

A spinning stock solution containing 50 wt% of PEG 400 and 50 wt% of dimethyl sulfoxide E (abbreviated as DMSO) was prepared by heating and dissolving. PEG40 in core liquid
Hollow fiber spinning was performed using a mixed solution of 0/methanol (3/1), the atmosphere was passed through 6cIR into a water coagulation bath, and then washed in a water washing bath to obtain a hollow fiber membrane. The hollow fiber membrane had a three-layer structure with an outer diameter of 450 μm and an inner diameter of 270 μm, and no macrovoids larger than 10 μm were observed. The porosity of the membrane is 8
2%, wet strength was 0.11 g/de, and elongation was 198%.

The membrane performance is shown in Table 1, and an ultrafiltration membrane with an excellent molecular weight fraction was obtained, and in particular, albumin did not permeate at all.

Example 2 PE520wt%, PEG 400; 70wt%,
Using a spinning dope consisting of 10 wt% Oyo UDMSO, the spinning was carried out in the same manner as in Example 1 except that the porosity was 78%, the strength was o, 1
A hollow fiber membrane with an elongation of 49/de and an elongation of 53% was obtained. Performance comes first
As shown in the table, it had excellent filtration characteristics.

(Margin below) Table 1 (Margin below)

[Brief explanation of the drawing]

FIG. 1 shows a cross section of the polyethersulfone microporous hollow fiber membrane of the present invention, FIG. 2 shows its outer surface, and FIG. 3 shows a scanning electron micrograph of its inner surface. Sparrow f 1, 3 (a) (Bn whistle 2 diagram (a) (b) Kaku 31 diagram (a) (b) Procedural amendment (com) 1. Case indication patent application No. 1986-38681 2. Invention Name of Polyether Sulfone Microporous Hollow Fiber Membrane and Process for Producing the Same 3, Relationship with the Amendment Case Patent Applicant 1-11 Minamihonmachi (300), Higashi-ku, Osaka-shi, Osaka Prefecture Representative of Teijin Limited Sasuke Okamoto Department 4, Agent 2-1 Uchisaiwaicho, Chiyoda-ku, Tokyo
No. 1 No. 7, contents of amendment

Claims (1)

[Scope of Claims] 1) A membrane consisting essentially of polyether sulfone, the membrane comprising a dense layer near the outer surface, a dense layer near the inner surface, and a majority of the film thickness between the two layers. The membrane has a three-layer structure consisting of an intermediate layer consisting of a network structure with communicating pores occupying the entire membrane, the porosity of the entire membrane is 70 to 90%, and the elongation of the membrane in a wet state is 50%. % or more of polyethersulfone microporous hollow fiber membranes. 2) The water ultrafiltration rate of the membrane is 1 to 600 ml/m^2.
The microporous hollow fiber membrane according to claim 1, which is substantially impermeable to bovine serum albumin within the range of hr/mmHg. 3) Prepare a spinning dope consisting of polyether sulfone, a solvent for polyether sulfone, and a water-soluble polyhydric alcohol, extrude it through a double tube nozzle along with the core liquid, pass through gas, and then introduce it to a coagulation bath. Alternatively, a method for producing a polyethersulfone microporous hollow fiber membrane, characterized in that it is coagulated by introducing it directly into a coagulation bath, and then washed. 4) The method for producing a microporous hollow fiber membrane according to claim 3, wherein the solvent is dimethyl sulfoxide. 5) The method for producing a microporous hollow fiber membrane according to claim 3, wherein the water-soluble polyhydric alcohol is polyethylene glycol that is liquid at room temperature.