JPS5958042A - Porous polysulfone membrane - Google Patents

Abstract

PURPOSE:To prepare the titled membrane having microscope pores and excellent surface smoothness, and suitable as a membrane filter, a supporting membrane, etc., by the coagulation film-forming of a solution composed of a polysulfone polymer having low content of low-molecular weight component and its solvent in a coagulation bath. CONSTITUTION:A polysulfone solution is prepared by dissolving a polysulfone polymer containing <=0.1wt% of a low-molecular weight component having a molecular weight of 800-1,200, preferably a polymer having a molecular weight of 5,000-300,000 and containing >=50mol% of the recurring unit of formula I or formula II, in a solvent which can dissolve >=5wt% of said polymer at <=50 deg.C (especially N-methyl-pyrrolidone, etc.). The concentration of the polymer in the solution is 5-50wt%. The solution is formed to a flat film or hollow fiber, etc. The formed product is immersed and coagulated in a coagulation bath (water or a mixture or water and an organic liquid) to obtain a porous membrane having an average pore diameter of 100A-5mu and a void volume of the whole membrane of 30-90%.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides polysulfone 1 with a low content of low molecular weight components.
The present invention relates to a polysulfone porous membrane that is formed from coalescence, has uniform pores on its surface, and has particularly excellent surface smoothness.

In recent years, porous membranes have been used in the production of ultrapure water for the electronic industry, etc.2, the treatment of industrial wastewater such as paper and pulp wastewater, and the gas separation process of condensation from the air//) tv1 beam, 1M food industry, such as the sugar industry, etc. Porous membranes have come to be used in a wide range of separation and purification technologies, such as separation and purification in the field, separation of useful components from blood, and medical applications such as microfilters for deprivation.

For this purpose, porous membranes made of cellulose acetate, polypyrene, polycarbonate, and the like have been used.

However, it has been pointed out that it has drawbacks in permeation performance, mechanical strength, heat resistance, solvent resistance, etc.

From this point of view, polysulfone resins that have excellent properties in terms of mechanical strength, heat resistance, and solvent resistance have attracted attention, and a number of techniques related to methods for producing porous membranes have been disclosed.

These porous polysulfone membranes are usually formed using a wet method.
All handling is done in a wet state. If this porous polysulfone membrane is once dried and then re-hydrated when used, its performance will not change at all, which will not only solve the problem of performance changes over time during storage in water, but also reduce transportation costs. It can also be reduced. Furthermore, the porous membrane in a dry state can be used as a support for a gas separation membrane, and its uses are wide.

Conventionally, freeze-drying, glycerin treatment, solvent substitution, etc. are known methods for drying membranes in a water-containing state, but freeze-drying requires a long time to dry, and glycerin treatment does not No lock in use. In addition, when the solvent substitution method is used, low molecular weight components such as oligomers embedded in the polysulfone porous membrane are precipitated on the MU surface.
There was a problem that the surface smoothness was easily lost.

In view of this situation, the present inventors conducted intensive research θ1 with the aim of reliably obtaining a polysulfone porous membrane with excellent surface smoothness. A polysulfone porous membrane formed from a polysulfone polymer in which the content of low molecular weight components is below a certain percentage has uniform micropores on the surface,
They discovered that it also has excellent surface smoothness, leading to the present invention.

That is, the present invention provides a polysulfone polymer formed from a polysulfone polymer in which the content of a component having a molecular weight in the range of about SOO to about 1.200 is 0.1% by weight or less. Oh.

The present invention will be explained in detail below.

The polysulfone resin used in the present invention has the following formula (1) or (2):
...A polymer having 50 mol% or more of the repeating unit represented by curve (2), and preferably has a molecular weight of about 5,000 to about 300,000. These polymers can be used alone or in combination of two or more.

The molecular weight in the present invention is the molecular weight in terms of polystyrene obtained from the detection line (curve of molecular attachment vs. elution count) of a polystyrene standard sample with known molecular properties obtained by GPC (gel permeation chromatography). be.

When forming the polysulfone porous membrane of the present invention, the molecular weight of the low molecular weight component that is preferably not contained in the polysulfone polymer is about 800 to about 1,200, and the preferable allowable amount is 0.1 It is not more than 11 t% by weight, more preferably not more than 0.05 t% by weight.

However, commercially available polysulfone resins preferably do not contain about 1 wt% of the low molecular weight vertical component.
It may contain the following proportions. In such a case, the polystyrene resin is obtained by, for example, a fractional precipitation method to obtain the polysulfone polymer substantially free of the low molecular weight component, that is, the content of the low molecular weight component having a molecular weight of about 800 to 1,200 is 0. It can be a polysulfone polymer having a weight of 1% by weight or less.

The fractional precipitation, which is carried out for the purpose of obtaining a polysulfone polymer in which the content of the low molecular weight component is (), 1 or less, may be carried out using, for example, 6 Experimental Methods for Polymer Synthesis (co-authored by Otsu and Kinoshita, published by Kagaku Doujin) 3.
This can be carried out by the method described on pages 0 to 32. The fractional precipitation method will be explained in more detail.

That is, the separation precipitation is a method in which the polysulfone resin is dissolved in a good solvent and then a poor solvent is added to precipitate and separate the desired polysulfone polymer.

A good solvent for the polysulfone resin used in the fractional precipitation of the present invention is one that can dissolve the resin at 5% by weight or more, preferably 10% by weight or more at a temperature of 50°C or lower, such as a halogen solvent, Examples include polar solvents. As a suitable halogen-based numbing agent, g-form 1.2-
Diku I: +p ethane, trichloro-1 diethylene, etc. can be mentioned. Suitable polar solvents include dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, tetramethylurinol, hexamethylphosphoramide, dimethylsulfoxide.

Examples include pyridine, quinoline, aniline, 0-I:+pphenol, and the like. .

The resin concentration used when dissolving the Shima polysulfone resin in the good solvent is 0.5 to 10 cm, more preferably J to 5 cm.

Examples of the poor solvent to be added to the solution obtained by dissolving the resin in the solvent include alcohols and aliphatic hydrocarbons. Suitable alcohols include methanol, ethanol, I-propanol, H-phthanol ethylene glycol, and the like. Suitable aliphatic hydrocarbons include hexane, n-hebutane, ligroin, and the like.

The polysulfone polymer used in the present invention having a molecular weight of about 800 to about 1.200 and a component content of 0.1% by weight or less may be obtained by any method other than the above-mentioned fractional precipitation method.

The polysulfone porous membrane of the present invention formed from the polysulfone polymer is rich in surface smoothness IF and has uniformly woven pores on the surface. The average pore size of the micropores on the surface ranges from about ILIOA to about 5μ, and the entire layer usually has connected pores with a large average pore size on the surface.
The distribution in the cross-sectional direction is uniform or non-uniform.

The overall porosity of the layer is generally in the range of 30-90%.

Examples of membrane forms include flat membranes, tubular membranes, and hollow fiber membranes.

The polysulfone porous membrane formed from the polysulfone polymer of the present invention can be obtained by any method normally used to obtain a polysulfone porous membrane. The general method is to dissolve the polysulfone polymer in
It consists of a step of understanding il+, a step of forming into a desired film shape, a solidifying step, etc. The process will be described more specifically below, but the present invention is not limited thereto.

The melt ill of the polysulfone polymer is preferably t
otf #% or more, such as dimethylacetamide, dimethylborumamide, diethylformamide, diethylacetamide, N-methyl-2-pipridone, tetramethyl [C, hexamethylphosporamide m
-cresol, chlorobenzene, dimethyl sulfoxide, etc., and these can be used alone or in combination of two or more, but among them, N-methyl-2-pyrrolidone and dimethylacetamide, which have higher solubility, are preferably used.

Further, the polymer concentration of the polymer solution used is 5 to 50 polymers.

A non-solvent can be added to the solvent if desired. As the nonsolvent, monohydric or polyhydric alcohols, ethers, or aqueous electrolyte solutions are preferably used. Suitable monohydric alcohols include hexanol, cyclohexanol, cyclohexenol, etc., and polyhydric alcohols include ethylene glycol and polyhydric alcohol.

Examples include butanediol and glycerin.

Suitable ethers include nethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dioxane, and the like. Suitable electrolytic aqueous solutions include organic acid salts such as sodium acetate, inorganic salts such as sodium chloride and sodium nitrate, inorganic acid salts such as sodium polystyrene sulfonate, polymer electrolytes such as sodium polystyrene sulfonate, sodium dioctyl sulfosuccinate, etc. Examples include aqueous solutions of ionic surfactants.

The polysulfone polymer solution dissolved in the above solvent can be formed into the form of a flat membrane, tubular membrane, hollow fiber membrane, etc., as described above, depending on the purpose of use. In the case of flat membranes, tubular membranes, etc., porous materials such as woven fabrics and non-woven fabrics can be used as the supporting base material, if necessary.

In the coagulation process in which a polysulfone polymer solution formed into a desired shape is immersed in a coagulation bath to remove the solvent, the coagulation liquid is water or a small amount of an organic liquid that is freely miscible with water. , or a mixture thereof.

Such organic liquids include monohydric alcohols having 1 to 3 carbon atoms and dihydric alcohols having 2 to 4 carbon atoms.

Glycerin, a ketone having 2 to 4 carbon atoms, an ether having 4 to 6 carbon atoms, a solvent for the polysulfone resin, and a molecular layer 60
0 or less polyx tyrene glycol or the like is used.

More preferably, the organic liquid is methanol.

Ethanol, isopropanol, ethylene glyfur,
Glycerin, dioxane, tetrahydrofuran, dimethylformamide, dimethylacetamide, N-methyl-
2-pyridone, polyethylene glyfur, etc. are used. However, dimethylformamide and dimethyl ocetamide.

The use of a solvent for the resin, such as N-methyl-2-biglidone, as a coagulating liquid is limited to the case where it is mixed with other organic liquids or water.

The polysulfone porous membrane of the present invention has uniform micropores on the surface and has a smooth surface, and can be used as a membrane filter used for sterilization, separation and purification of proteins, etc., or for blood separation etc. As a blood processing membrane to separate specific components from blood, or as a support membrane for membranes for these purposes.

Furthermore, in a dry state, it can be used as a support for ultra-thin membranes for gas separation. In particular, the polysulfone porous membrane of the present invention has excellent surface smoothness, and has the great advantage that when forming a permselective membrane using this layer as a support, a membrane with excellent permselective performance can be easily obtained. are doing.

The present invention will be described in detail below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 (Removal of low molecular weight components) Polysulfone resin (Ul) FLP-3500)
Dissolve in form to make triple 11% popform solution,
Furthermore, methanol was added to make 28 volumes to obtain a cloudy solution. The cloudy white solution was heated and stirred to become a transparent solution again, and then slowly cooled to precipitate the polysulfone polymer in the form of a gel. This gel-like polymer was separated by centrifugation (16,000 G, 30 m),
A polysulfone polymer from which low molecular weight components were removed was obtained by thoroughly washing with a large amount of methanol and drying under vacuum (first fraction). Evaporate the supernatant after centrifugation,
A residue consisting of low molecular weight components was obtained (second fraction). The GPC chart of the polysulfone polymer obtained as the first fraction is shown in FIG. 1, and the GPC chart of the low molecular weight component obtained as the second fraction is shown in FIG.

Example 2 (film formation) 72.8 parts of dimethylformamide, 11.2 parts of ethylene glycol dimethyl ether, 1 part of benzoguanamine,
Polysulfone polymer obtained in Example 1 (first fraction) 1
5 parts were placed in a dissolution tank, stirred and dissolved at room temperature under a phonetic air stream, and the obtained polysulfone solution was applied to a thickness of 200 μm on a polysulfone nonwoven fabric at 25°C, and immediately immersed in water at 15°C to solidify and flatten. A membrane-like polysulfone porous membrane was obtained.

Example 3 The hydrated polysulfone porous membrane obtained in Example 2 was
It was immersed in 1-purpanol for 2 hours and then in cyclohexane for 2 hours, washed under a stream of dry air, and air-dried in the evening to obtain a dry polysulfone porous membrane. As a result of observation using an electron microscope, this polysulfone porous membrane had a very smooth surface. Two ultra-thin films of poly(4-methylpentene-1) with a film thickness of approximately 0.045μ obtained by water surface development method 1 were laminated on top of this polysulfone porous membrane, and the gas separation performance was measured. The membrane was evaluated as a support.The results are shown in Table 1.

The gas component 11 film obtained by laminating an ultra-thin film of poly(4-methylpentene-1) on the polysulfone porous film of the present invention exhibits selective permselectivity inherent to poly(4-methylpentene-1),
This shows that the polysulfone porous membrane of the present invention has excellent surface smoothness and is useful as a support for gas separation membranes.

Comparative Example 1 In Example 2, a commercially available polysulfone resin (UDgr, p-350
0) is all 4a! This polysulfone porous membrane was obtained using Kl and polysulfone porous membrane in Example 3 and all (
Evaluation as a support was conducted in the same manner, and the results are shown in Table 1. As a result of observation and observation using an electron microscope, 4 to 8 precipitates/d of 2 to 5 microns were observed at W4 degrees in a field of view with a magnification of 500 times.

Table 1

[Brief explanation of drawings]

FIG. 1 shows a GPC chart of the first fraction of the polysulfone polymer in Example 1, and FIG. 2 shows a GPC chart of the second fraction of the haborisulfone polymer. Procedural amendment dated October 75, 1980, Commissioner of the Japan Patent Office 2 Name of the invention Polysulfone porous membrane 3 Person making the amendment Relationship to the case Patent applicant Representative of Teijin Ltd., 1-11 Minamihonmachi, Higashi-ku, Osaka (300) Toku Sue Tomo Teijin Co., Ltd. ``Brief explanation of the drawings'' in the in-house specification 6. Contents of amendment (1) Insert the following sentence at the end of page 15 of the specification. The measurement conditions for Figure 1 are as follows: Apparatus: Toyo Soda 11LC-802UR Column: 2 3/8 inch x 2 feet G2000L, 1 G4000H. Solvent: Chloroform Flow rate: 1.0 m/Total Measuring temperature Room temperature detection UV 254 nm The measurement conditions in Figure 2 are as follows: Columns 3/8 inch x 2 feet G200Q, 3 columns, G3000H, 1 column, etc.
It is similar to the Noya case. In addition, elution count 3 in Figure 2
9. The peak near o+j corresponds to a component with a molecular weight of 800 to 1200. "that's all

Claims (1)

[Claims] A polysulfone porous membrane formed from a polysulfone polymer in which the content of a component having a molecular weight in the range of about 800 to about 1,200 is 0.1% by weight or less.