JPS61141907A - Preparation of hollow fibrous separation membrane - Google Patents

Abstract

PURPOSE:To obtain a hollow yarn membrane reduced in the adhesion of scale, by using a solution prepared by dissolving a polyether sulfone resin in a solvent prepared by adding an additive of an org. acid, an org. acid anbydride or an org. acid ester type to a polar org. solvent dissolving said resin. CONSTITUTION:Polyether sulfone is dissolved in a solvent mixture consisting of a solvint for polyether sulfone and at least one additive selected from an org. acid type, an org. acid anhydride type and an org. acid ester type in an amount of 10-25wt.% at room temp. or under heating to prepare a spinning raw solution. At this time, it is necessary to set the mixing wt. ratio of additive/ solvent in a range of 1/99-1/4. As the solvent, dimethylformamide or N- methyl-2-pyrrolidone is used. Spinning is performed by wet spinning method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hollow fibrous separation membrane. More specifically, the present invention relates to a method for producing a polyethersulfone hollow fiber separation membrane that has both excellent mechanical strength and filtration properties. The aim is to create a polyether sulfone hollow fiber separation membrane that has excellent mechanical strength and stable filtration properties that can withstand long-term continuous filtration by using a spinning dope with a specific composition. The purpose is to provide a manufacturing method.

[Prior art]

Separation membranes made of polyether sulfone are known to have excellent properties mainly in the ultrafiltration range. In addition, polyether sulfone originally has excellent heat resistance, chemical resistance, and safety, and for this reason, its uses are wide-ranging, such as in the food industry, the medical field, and as a support material for reverse osmosis membranes.

On the other hand, Japanese Patent Publication No. 50-22508 is known as a method for manufacturing a separation membrane that has been commonly used in the past. When this method is followed, liquid flow through the barrier layer on the surface and the membrane following this. A polymer membrane consisting of a support layer having a porous structure with small pores and a small resistance against the pores is obtained. A separation membrane with this structure has a high filtration flow rate per unit membrane area, but its drawbacks include low mechanical strength and the fact that the filtration flow rate is too high. It has been mentioned that the concentration polarization in the filtrate is significant, and therefore the adhesion and deposition of scale etc. on the surface increases, resulting in a rapid decrease in the filtration flow rate during continuous filtration.

[Purpose of the invention]

The present inventors have solved the above-mentioned drawbacks of conventional separation membranes, and have obtained a method for producing a separation membrane that has a high filtration flow rate, allows stable filtration for a long time, and has mechanical strength. As a result of intensive research, we found that polyether sulfone, its solvent, and certain additives such as organic acids,
An extremely excellent method involves forming a resin stock solution containing either organic acid anhydride-based or organic acid ester-based solvent into a film shape by casting or spinning, and then coagulating it by contact with a non-solvent of the resin. As a result of various studies based on this knowledge, we have completed the present invention.

[Structure of the invention]

That is, the present invention provides a wet spinning method in which a hollow fiber manufacturing nozzle with a double tube structure is used, and a spinning dope is discharged from an outer annular port and a coagulating liquid is discharged from a core into a coagulating bath and coagulated.
The spinning stock solution contains polyether sulfone, a polar organic solvent that dissolves the resin, and at least one solvent selected from an organic acid type, an organic acid anhydride type, and an organic acid ester type as an additive, and the additive/ The mixing weight ratio of the solvent is 1/99 to 1
This is a method for producing a hollow fibrous separation membrane characterized in that:

To explain the present invention in more detail, the spinning stock solution contains 10 to 25% by weight of polyether sulfone, preferably 12 to 2% by weight.
It is obtained by dissolving 0% by weight of polyethersulfone in a mixed solvent consisting of a solvent of polyether sulfone and at least one type of additive selected from organic acids, organic acid anhydrides, and organic acid esters at room temperature or by heating. Here, polyether sulfone is used, and the solvent is dimethylformamide, N-methyl-2
-pyrrolidone, etc., but is not limited to these as long as polyether sulfone can be dissolved therein.

Examples of organic acid additives include formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, trimethylacetic acid, caproic acid, 2-ethyl acetic acid, caprylic acid, 2-ethylhexanoic acid, oleic acid, and monochloroacetic acid. , dichloroacetic acid, trichloroacetic acid, lactic acid, maleic acid, fumaric acid, tartaric acid,
Examples include, but are not limited to, stearic acid, succinic acid, benzoic acid, phthalic acid, and the like. Examples of organic acid anhydride additives include, but are not limited to, acetic anhydride, propionic anhydride, butyric anhydride, maleic anhydride, succinic anhydride, benzoic anhydride, phthalic anhydride, and the like.

Examples of organic acid ester additives include methyl formate, ethyl formate, propyl formate, butyl formate, amyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, amyl acetate, ethyl propionate, butyl propionate,
Amyl propionate, ethyl butyrate, butyl butyrate, isoamyl butyrate, butyl stearate, ethyl acetoacetate, methyl lactate, ethyl lactate, butyl lactate, amyl lactate, methyl benzoate, ethyl benzoate, propyl benzoate, methyl salicylate, Schella acid Examples include, but are not limited to, diethyl, dibutyl tartrate, dimethyl phthalate, diethyl phthalate, and the like.

Furthermore, if the mixing weight ratio of the additive/solvent is 1/99 or less, the effect of the additive cannot be obtained, and therefore it is insufficient to achieve the mechanical strength and filtration stability that are the objectives of the present invention. If it exceeds 9.1/4, it is difficult to obtain a spinning stock solution with a homogeneous phase because the amount of additive is too large, and even if a stock solution can be obtained, the solution becomes highly viscous and the hollow fiber cannot be stabilized. spinning becomes difficult.

The composition of the internal coagulating liquid that is discharged from the nozzle core and coagulates the spinning dope inside, and the coagulating bath that coagulates the spinning solution externally, is preferably composed of water alone from the viewpoint of operability. By adding/or a polyether sulfone solvent and/or a polyether sulfone non-solvent, it is possible to change the structure of the intermediate layer of the separation membrane.

Here, metal salts that can be added to the coagulation liquid include Lict, Li
Br.

NaCl, NaBr, KC4%KBr, MgC
42, MgBr2, CaCl2, CaBr2, etc., but are not limited to these, and a combination of two or more metal salts is also possible. Further, the polyether sulfone solvent that can be added to the coagulation bath includes dimethylformamide, N-methyl-2-pyrrolidone, etc., but is not limited to these, and a combination of two or more solvents is also possible. Non-solvents for polyether sulfone that can be added to the coagulation bath include, but are not limited to, alcohol-based and ketone-based solvents, and it is also possible to combine two or more types of non-solvents.

When spinning hollow fibers, temperature control is the main important factor in the discharge conditions, that is, the film forming conditions.It is usually carried out around room temperature, but if the composition of the spinning stock solution is unstable at room temperature, heated spinning is performed. The spinning temperature is suitably in the range of room temperature to 100°C. Furthermore, since the obtained membrane may contain additives that are insoluble in water, it is effective to immerse the membrane in ethanol or the like to remove solvent and additives, and then replace the water with water.

〔Effect of the invention〕

The structure of the polyether sulfone hollow fiber separation membrane obtained by the method of the present invention has pores of 0.05μ or less on the inner surface and pores of 15μ or less on the outer surface, and the inner surface has smoothness. Therefore, there is less scale adhesion during filtration. Furthermore, when the filtered liquid is blood, there is less deposition of blood cell components and the like. The intermediate layer sandwiched between the inner and outer surface layers is formed by combining the compositions of the spinning solution and coagulation solution.
A wide variety of membrane structures, from void structures to sponge structures, can be made of PL, and the membrane has excellent mechanical strength because it has a relatively dense internal structure. Furthermore, both the relatively dense internal structure and the small pores on the outer surface provide appropriate resistance to the filtrate fluid, and can suppress concentration polarization at the surface layer, which normally tends to occur with high-flow membranes. This indicates that stable continuous filtration is possible.

Although the reason why the above-mentioned excellent characteristics are expressed in the present invention is not clear, the spinning dope comes into contact with the coagulation solution, the exchange of water and solvent progresses, and the polynylon sulfone coagulates to form the fine structure of the membrane. It is presumed that during the process, the additive acts on the exchange of water and solvent, and as a result of appropriately controlling the rate, a distinctive film structure is produced.

Examples of the present invention will be described below.

Example 1 Polyether sulfony/(manufactured by IC1, Vlctrex
300P) and N-methyl-2 as a solvent.
-78% by weight of pyrrolidone and 7% by weight of propionic acid as an additive were mixed, and heated and stirred at 80'C for 3 hours to obtain a homogeneous solution. Water was discharged from the outer annular opening of the hollow fiber manufacturing nozzle and from the core, and the spinning dope was introduced into a water coagulation bath for coagulation, and then wound up at a speed of 30 m/min. Here, the spinning temperature, that is, the temperature of the spinning dope and the internal coagulation liquid, was 40°C. The obtained hollow fibrous separation membrane had an inner diameter of 250 μm and a membrane thickness of 45 μm.

Next, 1000 membranes each having an effective length of 20 cm were bundled, both ends fixed with adhesive, and then cut to obtain a membrane module having openings at both ends. The performance of the membrane module was evaluated by adding 2 tons of a 1% aqueous solution of dextran (Pharmacia Fine Chemicals, Inc., T2O) with a weight average molecular weight of about 70,000 to 200 m (7
The pump circulates at a flow rate of
At this time, changes over time in the filtration rate and dextran rejection rate were measured.

The terminology can be explained as follows.

Filtration rate (m'tanHgφ time・m) Rejection rate (%) As a result of measurement, the filtration rate 5 minutes after the start of circulation was 510 (m17
1eIHg・time-m), then 30 minutes, 1 hour, 2
The values for time and 3 hours are 490.485.475.
The value remained high at 470 (me/tasHg/hour am), and the decrease was extremely small. The inhibition rate of dextran was 33% at 5 minutes and stable at 35 to 39 hours thereafter.

Comparative Example 1 15% by weight of polyether sulfone and 85% by weight of N-methyl-2-pyrrolidone were dissolved in the same manner as in Example 1.
When we formed a membrane and evaluated the performance of the obtained membrane with the same dimensions, we found that the 5-minute filtration rate was 650 (ml/lxx+
Hg・time・a) was high, but after that the value decreased significantly to 560.480 and 340.180 (m1/wnHg・time・a) at 30 minutes, 1 hour, 2 hours, and 3 hours, respectively. decreased almost linearly. On the other hand, the inhibition rate of dextran was 39%, 43%, 47%, 55%, and 64% for 30 minutes, 1 hour, 2 hours, and 3 hours, respectively, from the 5-minute value.
It showed a tendency to increase.

Example 2 Polyether sulfone (manufactured by ICI, Vlctrex
300P), 70% by weight of dimethylformamide as a solvent, and 13% by weight of benzoic anhydride as an additive.
were mixed and stirred at 80°C for 3 hours to obtain a homogeneous solution. At a spinning temperature of 30° C., the material was subjected to HM in the same manner as in Example 1, and further immersed in ethanol for 5 hours to remove solvent and additives. The inner diameter and thickness of the membrane were 250μ and 45μ, respectively. Next, a module was prepared in the same manner as in Example 1, and a filtration test of an aqueous dextran solution was conducted. Changes in filtration rate and rejection rate were stable as shown in Table 1.

Example 3 Polyether sulfo 7 (manufactured by ICI, Victrex)
300P) 14% by weight, N-methyl-2-pyrrolidone 82% by weight, 11% by weight, ethyl lactate 4 = 4% by weight as an additive.
were mixed and stirred at 80°C for 3 hours to obtain a homogeneous solution.

Example 1 This was used as a spinning dope and the spinning temperature was 40°C.
A module was produced by forming a film in the same manner as described above. In addition, a filtration test of an aqueous dextran solution was conducted in the same manner. The results are shown in Table 1.

Example 4 Polyether sulfone (manufactured by Natsu CI Co., Ltd., Victrex)
300P) 14% by weight, N-methyl-2-pyrrolid/8
1% by weight, 5% by weight of trimethylacetic acid as an additive, 8% by weight of trimethylacetic acid as an additive.
The mixture was stirred and dissolved at 0° C. for 3 hours, and this was used as a spinning stock solution to form a film in the same manner as in Example 1. However, the winding speed is 45m/
It was a minute. The wound membrane was immersed in ethanol for 5 hours, and then replaced with water. The obtained one has an inner diameter of 200μ and a film thickness of 3.
It was 5μ.

The effective length of the membrane module is 16crIt, and the number of membranes per membrane is 2000.
I made it into a book. To this, 2 tons of physiological saline solution containing 0.2- human albumin was pumped and circulated at a flow rate of 200 ml/min.
Changes in filtration rate and rejection were measured. As a result, the filtration rate was 470.450.445.430.420.410 (
mffi/mHg・time・a), and the rejection rate is about 90~
It remained almost constant at 959g.

Examples 5 to 8 Polyether sulfo 7 (manufactured by IC1, Victrec
300P) 14% by weight, 2.7.12.17% by weight of ethyl benzoate as an additive, and 84.79.74.6% of N-methyl-2-pyrrolid/solvent corresponding to the amount of additive.
It was set at 9% by weight and designated as Examples 5 to B, respectively. These were stirred and dissolved at 80° C. for 3 hours to obtain a spinning stock solution. Furthermore,
A module was produced by forming a film in the same manner as in Example 4.

Evaluation of the module was also carried out in the same manner as in Example 4, and the results were as shown in Table 2.

Claims (3)

[Claims] (1) In a wet spinning method in which a hollow fiber manufacturing nozzle with a double tube structure is used, the spinning stock solution is discharged from the outer annular port and the coagulation solution is discharged from the core into a coagulation bath and coagulated. , a polar organic solvent that dissolves the resin;
and at least one type of solvent selected from an organic acid type, an organic acid anhydride type, and an organic acid ester type as an additive, and the mixing weight ratio of the additive/the solvent is 1/99 to 1/4. A method for producing a hollow fibrous separation membrane, characterized by: (2) The hollow space according to claim (1), wherein the composition of the coagulating liquid and the coagulating bath is water, or water and a metal salt and/or a solvent for the resin, and/or a non-solvent for the resin. A method for producing a fibrous separation membrane. (3) A method for producing a hollow fibrous separation membrane according to claim (1), wherein the polyether sulfone is made of a polymer having a repeating unit as shown in the formula, chemical formula, table, etc.