JPS588504A - Gas separation membrane comprising polysulfone hollow fiber - Google Patents

Abstract

PURPOSE:To obtain a gas separation membrane having high separation coefficient and high permeation speed, by a method wherein a polysulfone hollow fiber is spun according to a wet process and the obtained hollow fiber is subjected to heat treatment at a temp. corresponding to M.W. of a non-solvent in a dope. CONSTITUTION:A polysulfone resin having repeating units of the formula is dissolved in an aprotic polar solvent such as N, N-dimethylformamide and a non- solvent such as a water-solbule alcohol is added to the resulting solution to prepare a uniform dope. The amount of the aprotic polar solvent is 30-60wt% and that of the non-solvent is 5-20%. From the dope, a hollow fiber is spun by using a hollow fiber spinning nozzle according to a wet process and coagulated in water to be wound up. In the next stage, the obtained fiber is subjected to heat treatment at a temp. range of from 120 deg.C to the m.p. for 0.01sec-60min according to the means of heat treatment, such as superheated steam, heated air, oil bath, contact with a hot plate or microwave irradiation. The obtained hollow fiber can be used in separating and concentrating a low-molecular gaseous compound and excellent in heat and chemical resistances.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a polysulfone hollow membrane for gas separation and a method for producing the same. More details.

High mechanical strength and heat resistance 1. , has chemical resistance.

The present invention relates to a polysulfone hollow fiber membrane for gas separation with excellent separation efficiency and high gas permeation rate, and a method for producing the same.

Conventionally, gas separation is performed using polymer membranes.

It is known that the membrane structure is an asymmetric membrane, the thickness of the dense layer is made as thin as possible, and the gas permeation rate is required to be increased. As a separation membrane that satisfies these requirements to some extent, there is a cellulose acetate asymmetric membrane, and there are also literatures that describe gas separation using this material. However, it has various chemical and physical drawbacks such as heat resistance, chemical resistance, mechanical strength, etc., and has not been commercialized yet.

Various membranes to replace this Q4C have been studied, and one such material, polysulfone-based 1itQ1, which has high mechanical strength, heat resistance, and chemical resistance, has been described in Japanese Patent Application Laid-Open No. 1983-1999.
26283 and JP-A-55-31474 describe methods for producing porous membranes. On the other hand, regarding gas separation, JP-A-51-129880 describes the composition of a polysulfone polymer solution and the composition of a casting liquid as a method for producing an asymmetric membrane, but there is no mention of a method for producing a polysulfone hollow fiber gas separation membrane. Regarding the manufacturing method of hollow fiber membranes, please refer to Journal of Applied Science Vol. 12.
0.2377 pages to 2394 pages (1976)K
However, this relates to porous hollow fibers and composite membranes using the same. According to these previously disclosed documents, when polysulfone hollow fiber membranes are manufactured, the resulting membranes may be porous or hollow fiber membranes may not be obtained due to the membrane manufacturing method of casting onto a support. Therefore, it was difficult to obtain the desired gas separation membrane. As a result of intensive study to overcome this problem, the present inventors found that after spinning polysulfone hollow fibers using the II method, When the hollow fibers are heat-treated at a temperature depending on the molecular weight of the non-solvent, K.

It has been found that a gas separation membrane with high performance separation coefficient and permeation rate can be obtained.

The polysulfone resin used in the present invention includes polysulfone having υ as a repeating unit as a representative example.

According to the present invention I/C, when producing hollow fibers using the above-mentioned polysulfone resin by a daytime method, the production process is particularly limited, but the dope solution adjustment process and the dope solution extrusion process from an annular nozzle are , a solvent evaporation process, a coagulation process, a stretching process, etc.

Polysulfone resin is dissolved in an aprotic polar solvent.
A non-solvent is then added to prepare a uniform dope solution, but as an aprotic polar solvent.

N,N-dimethylformamide, 2-dimethylacetamide, dimethylsulfoxide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-methyl-2-piperidone, sulfofun, 5-tylurea, chloride Examples include methylene and mixtures thereof. The amount of aprotic polar solvent added is usually 20 to 80% by weight (hereinafter, all - represents weight).
, preferably ti is 30 to 60%. If the concentration of the dope solution becomes too low, stable spinning becomes difficult and the separation coefficient of the separation membrane deteriorates.

On the other hand, if the concentration of the dope solution is too high, the amount of gas permeation through the separation membrane will decrease, which is not preferable. The hollow fiber membrane obtained by spinning must have a porous structure with a relatively small pore size, and the non-solvent may be water or a water-soluble alcohol represented by the general formula R-(OH)n. 1 Typical examples include methyl alcohol, ethyl alcohol, isopropyl alcohol, butyl alcohol, 1,3-furopanediol, '!
, 3-butanediol, 1,4-butanediol, 2,
Examples include 3-butanediol, ethylene glycol, glycerin 1,2,3.4-butanetetraol, and pentaerythritol. Preferably, Fi and R have 1 to 4 carbon atoms. n is 1-2.

Alternatively, representative examples of glycols represented by the general formula HO+CH*·CRY-)rnOH include Fi, diethylene glycol, lJ ethylene glycol, and fluoropylene gelylcol. Preferably ei and m are 2-4. It may also be a mixture of two or more selected from these. If the molecular weight of the non-solvent increases, the pore size of the hollow fiber membrane obtained after spinning increases, and even if heat treatment is performed, the amount of gas permeation will increase, but good separation performance will not be obtained, which is not preferable.

The amount of non-solvent added is θ~20%, preferably 5~20%. If the amount added is too large, the polysulfone resin will precipitate, so care must be taken.

The concentration of the polysulfone resin in the dope solution is inevitably determined by the concentration of the aprotic polar solvent and the concentration of the non-solvent, but it is from 1.0 to 70, preferably from 30 to 60.

The process of spinning hollow fibers from the dope solution prepared as described above is carried out using the I1 method. After spinning using a hollow fiber yarn and evaporating a part of the fibers at an appropriate spatial distance, , coagulate in water or a mixture of water and an organic solvent, and wind up. Stretch if necessary. The resulting hollow fibers are surface skin IIIK porous membranes with relatively small pore sizes;
It is necessary to adjust various KFi conditions to meet this requirement.1 For example, in addition to the dope solution adjustment conditions already mentioned, adjustment of dope solution temperature, solvent evaporation time, spatial distance, coagulation bath composition, coagulation bath temperature, stretching ratio, etc. is necessary.

Furthermore, in detail 1111, the temperature of the dope solution is set at 20 to 100°C.
, solvent evaporation time θ seconds ~ 30 seconds, spatial distance 0 ■ ~ 10 seconds
It is desirable to adjust the coagulation temperature to θ°C to 50°C and the grinding ratio to 0.8 to 2 times.

Next, the obtained hollow fiber membrane is heat-treated by any method. For example, treatment with saturated steam or superheated steam, heat treatment with air - heat treatment in an oil bath, heat treatment by contact with a hot plate, etc. ? ! ll treatment and other heat treatments using infrared rays or microwaves are also possible. It is also possible to perform the heat treatment once after the hollow fiber is wound up, or it is also possible to perform the heat treatment while the hollow fiber is running after spinning and before being wound up.

The temperature of heat treatment is 120℃ or higher and 0.0 for 1 hour below the melting point.
A range of 1 second or more and 60 minutes or less is desirable.

Preferably, the temperature is 170°C or higher and lower than the melting point. A hydrophilic non-solvent is added to slow down the coagulation rate and make the skin layer denser. However, when the molecular weight of the non-solvent used in the dope is large, the pore size of the hollow fiber membrane before heat treatment is large, and the non-solvent When the molecular weight of the non-solvent is small, a film with a relatively small pore size can be obtained.
When the heat treatment temperature is low, only the skin layer on the very surface of the hollow fiber membrane is dense and the separation efficiency is high.

It is preferable to adjust the heat treatment conditions so that a film with a large gas permeation rate can be obtained. In addition, the hollow fibers wound up after spinning are heat treated at relatively low temperatures for a long period of time.

The running hollow fibers undergo a short heat treatment near their melting point. It is desirable to apply

As described above, the present invention has excellent heat resistance and chemical resistance.

It is possible to obtain a novel polysulfone hollow fiber membrane for gas separation that has high mechanical strength, high separation coefficient, and high permeation rate.

The polysulfone hollow fiber membrane for gas separation obtained by the present invention can be used to separate oxygen, nitrogen, helium, argon, neon, carbon dioxide, -carbon oxide, and hydrogen sulfide.

Sulfur dioxide gas, nitrogen dioxide, methane, main thane, propane,
It can be applied to the separation and concentration of Noshiro molecular gaseous compounds such as ethylene, propylene, butylene, and so on, as well as gas separation in gas-liquid mixtures and other purposes.

The present invention will be explained in more detail with reference to the following examples, but the present invention is not limited to these examples at all.

Example 1 Polyarylether sulfone (UDEL P3500
(manufactured by Union Carbide Co., Ltd.) was dissolved in 50 parts of the mixed solvent shown in Table 1 and defoamed to prepare a uniform dope solution. This dope was maintained at 95°C and spun through a sheath core type spinneret, and then spun in air at 200°C.
(2) After running, it was introduced into an aqueous solution containing 30 g of a mixed solvent adjusted to the proportions shown in Table 1 and adjusted to a temperature of 10°C in advance to remove the solvent and solidify it. An aqueous solution containing the above mixed solvent was introduced into the scoring section. The solidified hollow fiber membrane is then pulled out of the coagulation bath and continuously washed with water.

Dry.

The obtained hollow fiber membrane was subjected to the conditions shown in Table 1.

Heat treated in saturated steam. The bubbling point of the obtained hollow fiber was 30 kf/d or more.

The resulting hollow fiber membranes were cut into 2m ICs, 150 pieces were bundled together, bent into a U shape, and the open ends were glued with epoxy resin. Permeation experiments were conducted under an applied pressure of 1.0 kr/d.

Air was supplied from the outside of the hollow fiber, and the permeated gas was taken out from the hollow part of the fiber, and the flow rate and composition were measured to evaluate the gas permeation performance. Example 2 Polyarylether sulfone (UDEL P3500)
A homogeneous dope solution was prepared by dissolving 50 parts of Unit Card <4 (manufactured by Do Co., Ltd.) in a mixed solvent consisting of 47 parts of N-methylpyrrolidone and 3 parts of ethylene glycol and defoaming. This was spun under the same conditions as in Example IK and heat treated in saturated steam at 180° C. for 10 minutes to obtain a hollow fiber membrane with a bubbling point of 30 kF/cIA or higher. The gas permeation performance of this hollow fiber membrane was measured in the same manner as in Example 1. The results are shown in Table 2.

Table 2 13-

Claims (7)

[Claims] (1) It has an asymmetric structure with a dense surface layer. A polysulfone hollow fiber gas separation membrane having a puzzle point of 20-/- or more. (2) Polysulfone resin is dissolved in an aprotic polar solvent, a non-solvent is added to it to make a homogeneous solution, and the solution is poured into a hollow l! Separation membrane 6 according to claim (1), which is treated after being made into a fibrous membrane. (3) Scope No. (2) of the patent application in which the polysulfone resin is expressed in folded units
Separation membrane described in section. (4) Claim No. 2 in which the aprotic polar solvent is = NtN-dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-furkylpyrrolidone, sulfolane, tetramethylurea, methylene chloride
Separation membrane described in section. (5) The non-solvent is R-(OH)n A separation membrane according to claim (2). (6) The separation membrane according to claim (2), wherein the non-solvent is represented by HO+CHs -CHY-0+mH. (7) The separation membrane according to claim 1, wherein the heat treatment temperature is 120° C. or higher and lower than the melting point.