JPS6128409A - Production of aromatic polysulfone separation membrane - Google Patents

Abstract

PURPOSE:To obtain a separation membrane having high mechanical strength and excellent water permeability, by forming an aromatic polysulfone polymer into a membrane according to a wet membrane forming process using an aqueous solution containing polyglycols as a gelling bath. CONSTITUTION:An aromatic polysulfone polymer is dissolved in a solvent such as N-methylpyrrolidone, dimethylformamide or dimethylacetamide in concn. of 10-40% to prepare a stock solution which is, in turn, formed into a membrane according to a wet membrane forming process using an 1-20% aqueous solution of polyethylene glycol and polypropylene glycol as a gelling bath. If glycols with MW of 200 or more are used, water permeability is markedly increased. In a hollow yarn membrane, only the gel solution inside the hollow yarn may be constituted of an aqueous polyglycol solution.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing aromatic polysulfone-based separation membranes, and more specifically relates to aromatic polysulfone separation membranes that have high water permeability and excellent mechanical strength. The present invention relates to a method for manufacturing a group polysulfone separation membrane.

[Prior art]

Generally, methods for separating substances from liquid mixtures such as solutions and emulsions include concentration methods by distillation, fractional precipitation methods, and centrifugation methods, but filtration methods using separation membranes require mild operating conditions. The fact is that the operating cost is low,
It has rapidly developed in recent years due to its high separation efficiency.

Among them, ultrafiltration membranes can separate proteins, colloidal substances, microorganisms, etc., so they can be used to concentrate foods, medicines, etc.
Its use in fields such as refining and factory wastewater treatment is being considered.

Conventionally, such separation membranes have mainly been made of cellulose diaacetate, but they have not been satisfactory in terms of heat resistance, chemical resistance, mechanical strength, etc., and in recent years, there have been many improvements in these respects. Polysulfone resin is attracting attention as an excellent material.

However, although high water permeability is desired from the viewpoint of filtration efficiency, the wet membrane forming method for ordinary polysulfone resin membranes forms a dense structure on the membrane surface, resulting in high water permeability. It is difficult to obtain a film with

Therefore, various inorganic swelling agents or organic swelling agents such as lithium nitrate and lithium chloride are added to the resin stock solution.

Attempts have been made to add ammonium nitrate, ethanol, ethylene glycol, etc., but these have not been sufficiently effective.

It is also possible to increase the amount of water permeation by lowering the resin concentration or increasing the film thickness, but this is not practical because the mechanical strength is low.

[Purpose of the invention]

In view of this situation, the present invention has been made after extensive studies and it has been discovered that a membrane with high water permeability can be obtained by using an aqueous solution of polyglycols instead of the water normally used in gelling baths.The present invention is based on the present invention. The purpose of this invention is to provide a membrane with high mechanical strength and excellent water permeability.

[Structure of the invention]

The present invention relates to a method for producing a partial separation membrane by wet membrane formation using an aromatic membrane polysulfone polymer, which is characterized in that an aqueous solution containing polyglycols is used in a gelling bath. It's a method.

The aromatic polysulfone polymer used in the present invention can be used as long as it has a repeating unit of 1,000-c-8-G-, and among them, the following general formula [■], [old,
Alternatively, one represented by CI[[) is preferably used.

C, H3 alkyl, non-dissociable substituents of halogen such as chlorobenzene, or dissociable substituents such as -〇〇OH, -803H, t, m, n, o are 0 or 4 or less Hail natural numbers. The di-resin stock solution is N-methylpyrrolidone, which is commonly used as a solvent for aromatic polysulfone polymers.

It can be obtained by dissolving an aromatic polysulfone polymer in dimethylformamide, dimethylacetamide, etc. alone or in a combination thereof under heating and stirring, but the concentration of the polymer depends on the required fractionation property and mechanical strength of the membrane. 10 to 4
About 0% is usually used.

In addition, if appropriate, an inorganic swelling agent such as lithium nitrate or ammonium nitrate or an organic swelling agent such as methanol, ethanol or ethylene glycol may be added without causing this problem.

Examples of the polyglycols used in the gel bath include polyethylene glycol, polypyrene glycol, and polytetraethylene glycol, and a suitable concentration thereof is 1% to 20%.

The reason for the increase in water permeability when an aqueous polyglycol solution is used in a gel bath is thought to be that it becomes the nucleus for gelation of aromatic polysulfons and phonols.

Glycols with a small molecular weight such as ethylene glycol, propylene glycol, etc. have no effect, and have a molecular weight of 200.
By using the above polyethylene glycol, water permeability is significantly increased. Furthermore, when polyethylene glycol with a molecular weight of 20,000 is used at the same concentration as polyethylene glycol with a molecular weight of 200, water permeation tends to decrease when the concentration exceeds 20%, but this is because the viscosity of the gel bath solution is too high. This is thought to be due to the fact that the exchange of the solvent and gel bath solution becomes slower.

In addition, membrane shapes include flat membranes, hollow fiber membranes, and tubular membranes.
Although any shape of membrane can be applied, especially in the case of hollow fiber membranes, water permeation can be increased by making only the gel solution inside the hollow fibers an aqueous polyglycol solution.

〔Effect of the invention〕

According to the present invention, it is possible to increase water permeability without reducing the mechanical strength of the membrane, and the water permeability can also be adjusted, making it possible to manufacture membranes that suit the purpose using the same resin stock solution. If this is possible, it is extremely suitable as an industrial membrane manufacturing method.

〔Example〕

Example 1 CH3+0-o-C-o-O-o-8O2-◎÷.

Polysulfone with 9 repeat units (Udel P-17
00UCC) was heated and dissolved in 82 parts of N-methylpyrrolidone to form a uniform solution.

This solution was cast at a speed of 5 crn/sec using a doctor blade with a gap of 180 μm on a horizontally placed smooth glass plate as a casting substrate. The membrane was immersed in a 5% aqueous solution of polyethylene glycol having an average molecular weight of 3000 to gel the polymer. The produced film was peeled off from the substrate and film performance was measured.

As a result, the water permeation rate was 857t/hr-mt @ Kf
/di (25°C) showed excellent water permeability.

Example 2 The resin stock solution used in Example 1 was extruded from an annular nozzle for manufacturing hollow fibers, and the internal coagulation liquid was made of polyethylene glycol with an average molecular weight i of 3000, the same as that used in Example 1.
% aqueous solution, and using purified water as an external coagulation liquid, the polymer solution was coagulated from the inner and outer surfaces to obtain a hollow fiber membrane.

The obtained hollow fiber had an inner diameter of 1.0 mφ, an outer diameter of 1.6 mm, a membrane thickness of 0.3 mm, and a water permeation rate of 760 L/h.
r-n?・Kf/d (25℃), 25Kf/ff
It had a bursting strength of 1 or more. The results are shown in Table 1.

Examples 3 to 6 Hollow fiber membranes were obtained in the same manner as in Example 1, except that the type of internal coagulation liquid was changed. Table 1 shows the composition of the internal coagulation liquid and the properties of the hollow fiber membrane obtained.

Comparative Example 1 A hollow fiber membrane was obtained in the same manner as in Example 2 using the same resin stock solution as in Example 1 and using purified water as the coagulation liquid.

The water permeation rate of this membrane is 270 t/hr--Kf/i (
25°C).

Examples 7 to 9 Poly/l/water having a repeating unit represented by mo0-cFSOdoO→ (Victrex 300p I
(manufactured by CI Corporation) was heated and dissolved in 84 parts of N-methylpyrrolidone to form a homogeneous solution. This solution was used as a coagulation liquid using polyethylene glycol or an aqueous solution of polyethylene glycol, and a hollow fiber membrane was spun.

Table 2 shows the composition of the coagulation liquid and the properties of the hollow fiber membrane obtained.

Comparative Example 2 A hollow fiber membrane was spun using the resin stock solution used in Examples 7 to 9 in the same manner except that purified water was used as the coagulation liquid.

The water permeability of this membrane obtained was 53 (1/hr・-・K4/
-It was.

Claims (2)

[Claims] (1) A method for producing an aromatic polysulfone-based separation membrane using an aromatic polysulfone-based polymer by wet membrane formation, the method comprising using an aqueous solution containing polyglycols in the gelling bath. . (2) The method for producing an aromatic polysulfone-based separation membrane according to claim 1, wherein an aqueous solution containing polyethylene glycol having a molecular weight of 200 to 8,000 is used in the gelling bath.