JPS5851911A - Preparation of aromatic polyether sulfone hollow yarn type semi-permeable membrane - Google Patents

Abstract

PURPOSE:To prepare a polyether sulfone hollow yarn type semipermeable membrane having high water permeability and mechanical properties from a high concn. polymer solution. CONSTITUTION:A solution of an aromatic polyether sulfone containing a glycol in a polar org. solvent is prepared by dissolving a glycol such as ethylene glycol, polyethylene glycol or glycerine in the polar org. solvent such as N-methyl- pyrrolidone or dimethylformamide in which the aromatic polyether sulfone is dissolved in such an amount that a mixed solution remains as a uniform solution and, after extruded from a ring shaped nozzle in a hollow yarn form, the extrudate is contacted with purified water which is miscible with said mixed solution but does not dissolve said aromatic polyether sulfone to prepare a hollow yarn type semi-permeable membrane which has a void-free layer on both surfaces thereof, high water permeability and can be backwashed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aromatic polyether sulfone having a repeating unit represented by the following general formula (I) (wherein x,
x' is, for example, a non-dissociable substituent such as alkyl such as methyl or ethyl, halogen such as chloro or bromine, or -COOH
, -8o, H, etc., and l and m each represent an integer equal to or less than t. ) A method for producing a hollow semipermeable membrane having high water permeability and mechanical properties.

The aromatic polyether sulfone hollow semipermeable membrane according to the manufacturing method of the present invention is basically manufactured by JP-A-Sho! ;'I-/173777
It has a structure similar to that disclosed in the above publication.

The present inventor has developed a hollow aromatic polyether sulfone which has water permeability and mechanical properties equivalent to or better than those of the prior invention by hollow extruding and coagulating a solution of an aromatic polyether sulfone in which glycols coexist. The present inventors have discovered that a similar film can be obtained, and have thus completed the present invention.

The method of the present invention is notable for its ability to produce polysulfone hollow semipermeable membranes with both high water permeability and mechanical properties from highly concentrated polymer solutions. This invention relates to a method for producing a hollow semipermeable membrane, which comprises discharging the membrane into a hollow shape and then removing the solvent by contacting a liquid that is miscible with the mixed solvent but does not dissolve the aromatic polyether sulfone. .

It can be prepared by dissolving the polymer in a polar organic solvent that dissolves well and adding glycols.

The polar organic solvent solution of the polyether sulfone is uniform and transparent, and even when left at 23"C for about 24 hours,
It is stable and does not cause phenomena such as devitrification, clouding, or gelation.

The hollow semipermeable membrane of the present invention is typically obtained by extruding this liquid mixture through an annular nozzle for producing hollow fibers and solidifying it from the inside and outside by ME. When forming a hollow semipermeable membrane, the aromatic polyether sulfone dissolved in a polar organic solvent is penetrated by the coagulating solution from both the inner and outer surfaces, forming a precipitate around the glycol core, which causes the glycols to interact with each other. It is presumed that the contact areas form pores. The presence of glycols is significant as a nucleus for the formation of pores, and greatly contributes to improving water permeability, with water permeability increasing approximately 2 to 10 times compared to when glycols are not used. At the same time, it is estimated that it affects the spread of the polymer chain and has some influence on the membrane structure. The presence of glycol makes the state of aromatic polysulfone in a mixed solution of polar organic solvent and non-solvent unstable, and precipitates are likely to form even in the slightest coagulation solution. Due to the penetration, a layer without cavities can be easily formed on the surface.

As a polar organic solvent, N-methylpyrrolidone is used.

Dimethylformamide and dimethylacetamide are used.

The mixing ratio of glycols may be any ratio as long as the mixed solution can maintain a uniform solution state, but it should be added at least 0.5'% by weight, depending on the concentration of the polymer, type of solvent, and blow moldability. It may be determined by taking into consideration the performance and membrane performance.

Glycols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol (molecular weight 200
．． Otsu 00, 2000.6000, etc.), propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol (molecular weight 200.60)
01.2000S Otsu 000, etc.), glycerin, trimethylolpropane, polytetraethylene glycol, and the like.

The concentration of the polymer solution as a membrane forming stock solution is 10 to 3j% by weight, preferably 75 to 30% by weight. If the concentration exceeds 33% by weight, the water permeability of the resulting semipermeable membrane becomes so small that it has no practical meaning, and if the concentration is lower than 10% by weight, a hollow fiber semipermeable membrane with sufficient strength cannot be obtained. I can't do it.

Water is most commonly used as the coagulating liquid, but organic solvents that do not dissolve the polymer may also be used, and these non-solvents may also be used! More than one species may be mixed and used. It is also possible to use different liquids or different liquid compositions as the inner and outer coagulating liquids.

The aromatic polyether sulfone hollow fiber semipermeable membrane obtained by this manufacturing method has pores on both the inner and outer surfaces of the hollow fibers, and has a layer with no cavities, and these intermediate layers also have the same properties. Forms a continuous polymer phase with the surface layer. The diameter of the pores gradually increases from both surfaces of the hollow fiber toward the inside of the membrane, and reaches its maximum inside the membrane at approximately the same distance from both surfaces.

The pore size changes continuously from the membrane surface to the inside, forming a tapered structure. The diameters of the pores on the inner and outer surfaces are in the range of 70 to 10 θA. Its diameter can be estimated by measuring the permeation rejection rate when aqueous dextran solutions with different average molecular weights and aqueous protein solutions are passed through it, and by observing the vicinity of the surface using a transmission electron microscope.

There are no cavities near both surfaces of the hollow fiber over a thickness of about /-j microns from the surface toward the inside, although there are differences depending on the spinning conditions. The inner layer of the membrane, which forms a continuous polymer phase with the layer near the surface without any cavities, contains
Cavities may be present. Cavities are missing parts of the membrane-forming polymer, and their diameter is greater than 10 microns. Therefore, in the heathered yarn t-light, pores with a diameter of 70μ or less are called pores.

In general, the number of cavities decreases when the film thickness is reduced;
When it is less than oμ, hollow fibers with few cavities can be easily produced.

Hollow fiber number J1 has few cavities, has excellent consolidation resistance, mechanical strength, and good water permeability.

Not only when there are no cavities, but also when there are cavities, there are many pores in the inner layer of the membrane, and their diameters gradually increase continuously as they move away from the membrane surface toward the inside. It reaches its maximum at a portion approximately equidistant from the surface, and its average diameter is OO5-70 according to observation using an electron microscope.
μ. The reason why the diameter of the pores increases as you move away from the membrane surface is because solidification occurs from the surface toward the inside, which is faster at the surface and slower toward the inside. Conceivable. therefore,
The radius r of the pores located at a distance l inward from the membrane surface is a function of l - for example, polyether sulfone with a concentration of 750% and 20% by weight is dimethylacetamide, tetraethylene glycol In a hollow fiber with a film thickness of 300 microns spun using the system, /
0-30 m'/m'-D-atm-2! "C" exhibits high water permeability, especially in thin hollow fibers spun with highly concentrated polymers.In general, aromatic polyether sulfone hollow fibers spun under the same conditions have a water permeability of 2. As shown in the figure, it was found that the water permeability is inversely proportional to the membrane thickness and increases as the membrane thickness becomes thinner. The semipermeable membrane of the present invention has water permeability in all layers from the surface to the inside of the hollow membrane, regardless of whether there are cavities or not. It is thought that the entire membrane thickness determines water permeability.Furthermore, the surface pore diameters of aromatic polyethersulfone hollow fibers with different membrane thicknesses spun under the same conditions are almost the same. In addition, the thickness of the layer near the surface where no cavities are present is constant regardless of the film thickness, which improves the rejection rate and electron microscopy for dextran and various proteins, respectively.
The fact that water permeability is inversely proportional to membrane thickness, as confirmed by mirror photography, indicates that the resistance to hydraulic flow through the membrane is due to the entire membrane thickness, and is therefore anisotropic. As with semipermeable membranes, it is not determined only by the surface layer. Furthermore, this is supported by the fact that it has high water permeability despite having layers without cavities on both surfaces.

The hollow fibers obtained in this way can have an extremely high water permeability due to their thinness, and have a structure with a layer without cavities on both surfaces, so they can be backwashed and can be consolidated. This results in fewer changes during various operations, convenience in use, and excellent mechanical strength.

Furthermore, since the hollow fiber with a thin membrane and small inner diameter has a small priming volume and can increase the surface area, it can be used for various medical purposes such as membranes for filtration-type artificial kidneys or protein concentration membranes for ascites. It can also be used as a membrane.

Hereinafter, it will be explained in detail using examples. % is especially 9- Unless otherwise specified, weight will be displayed.

Example: Dimethylacetamide (DMAc) was selected as the solvent, tetraethylene glycol (TEG) was selected as the additive, and +o-()-so2-g)te was selected as the polymer.
6s each of polyethersulfone (hereinafter referred to as polyethersulfone) having a repeating unit represented by
: /s :,! They were mixed at a ratio of 0 (main)) to form a uniform solution.

This polymer solution was extruded from an annular nozzle for producing hollow fibers, and purified water was used as an internal and external coagulating liquid to coagulate the polymer solution from the inner and outer surfaces, thereby spinning a hollow porous membrane. At this time, the hollow fiber spinning conditions were as follows.

Distance from the nozzle to the external coagulating liquid (hereinafter referred to as aerial travel distance)/Sα.

The properties of the obtained hollow fibers were as follows.

Inner diameter 0.7, t ttan, outer diameter iJj; tur, film thickness Q, 3Mn, water permeability/jm'/m'4), atr+
r7. ．． 2.5'c, bursting strength 33 lc9/cr&
, tensile modulus/700 kg/cl, strength 7
0 ky/cl, dextran molecular weight 10', 4ZX
The cut rate for /σ4.7×704 is 20
%, Oj%, ♂, 2%0 Example λ~/j Under the same conditions as in Example 1, various additives were added and hollow fiber spinning was performed. The additives added to the hollow fiber stock solution and the properties of the obtained hollow fibers are shown in Table 1 (not shown).

(Margins below) -l/ - 1/L2- Comparative Example 1 Using the polymer solution of Example 1, it was cast on a glass plate with a Doctor Plaid film thickness of lθθμm at a stock solution temperature of 23'C, and then left for 1 minute, 'C coagulated in water. The properties of the obtained porous flat membrane were as follows. Film thickness 300 μm 1 Water permeability 0.00 ns' I) atm・,
! J'C.

Comparative Example 3 Polyethersulfone 109 and N-methylpyrrolidone were mixed at 30°C to form a uniform solution. The permeate was poured onto a glass plate with a film thickness of 250 using Dr. Plaid.
Casting was carried out in μm. The properties of the obtained porous flat membrane were as follows. Film thickness/OO/'m % water permeability! m'
/m'-D-atm-,2j'c% elastic modulus J, 2/k
g/era, strength/Okg/cwt or less.

This solution was used to spin in the air from a hollow fiber spinning annular nozzle using water as an internal solid-liquid, the polymer was coagulated from the inside of the hollow fiber, and the hollow fiber was spun.

The obtained hollow fiber membrane had an inner diameter of 0.73 film and an outer diameter of 13! ; ran, film thickness OJmm, water permeability, t'/
m'・D-atm −, 23Cs elastic modulus 3231, 73
- Bursting strength was less than /Okg/cJ.

Comparative Example +, j A homogeneous solution was prepared by mixing polyether sulfone 20g as a polymer and dimethylacetamide oxide as a solvent. This solution was cast onto a glass plate at a stock solution temperature of 23° C. to a Dr. Plaid film thickness of 41 OOILm, and then allowed to stand for 1 minute to solidify in 1.2 t'C water.

The resulting porous flat membrane had a thickness of 300 μm and a water permeability of 0.000
3m7m'D-aLm-23'C.

When hollow fibers were spun using this solution under the same hollow fiber spinning conditions as in Example 1, the finger properties of the obtained hollow fibers were as follows:
Inner diameter 0.73, 9/3! ；Scream, film thickness 03, water permeability 0
．． 0/m7m'I) atm-, 2fc, bursting strength 30 kti/cd! Met.

Example/6 Using the same polymer solution as in Example 1, hollow fiber membranes having different inner and outer diameter membrane thicknesses were spun using various annular nozzles.

FIG. 2 shows the relationship between water permeability and membrane thickness of this hollow fiber membrane.

-/l- Comparative Example 6 A 30% aqueous sodium sulfate solution is added to 190 ml of dimethyl sulfoxide to form a homogeneous solution. A repeating unit represented by the formula +Q-so2-Q→L is added to this solution. (J was dissolved to make a polymer solution. The viscosity of this polymer solution was /900 mm (20 ° C.). This polymer solution was extruded from an annular nozzle for producing hollow fibers, and coagulated from the inside and outside using water as a coagulating liquid. Ta.

The inner and outer diameters of the hollow fibers are 0.7311I+I+, 73! ;a
m, the water permeability was 3 mm m'I) atm-, 2, S'C1 bursting strength/3119A+a. Also, the molecule is 1NM
The cut rate for 70,000 dextran was 70%.

Examples 77 to 22 Hollow fiber spinning was carried out in the same manner as in Example 1 using polyether sulfone as the polymer bath liquid, tetraethylene glycol as an additive, and each yuzu solvent.

Table 2 shows the properties of the hollow fibers obtained.

Examples 23-27 Using I) MAc as a polyether sulfone solvent and TEG as an additive, polyether sulfone and DMA
By changing the proportion of c, film-forming stock solutions with different concentrations of polyether sulfone were prepared, and hollow fibers were spun in the same manner as in Example. Table 3 shows the characteristics of the hollow fibers obtained.

Table 3 Effect of polyether sulfone concentration Inside and outside diameter of hollow fiber Q, 73; w, /, 331u+, film thickness 0.3 mm - Example 23 is a comparative example Examples 21 to 3S Polyether sulfone DMAc, TEG , 20", 7/", and 9 (%) respectively to make a uniform solution, extrude the polymer solution from an annular nozzle, and use purified water as the inner 17 part and external coagulation liquid to dissolve the polymer. A hollow porous membrane was spun by solidifying from the inside and outside surfaces.

At this time, the air travel distance from the hollow fiber spinning nozzle to the external coagulation liquid was varied, and the properties of the obtained fibers were examined.

The results are shown in Table 1.

Table G Hollow fiber outer diameter/35I11+++, inner diameter 0.7! ;tm,
Film thickness: 0.3rtrm Examples 3t, 37 Using the same spinning stock solution as in Examples 2 to 3j, the polymer was coagulated using an annular nozzle with an air travel distance of 11i1t, sα, and methanol as the internal and external coagulation liquid. Ta.

The obtained hollow fiber had an inner and outer diameter of 07 m and a diameter of 73! Good results were obtained in terms of mm, bursting strength, water permeability, elastic modulus, and strength.

Similarly, even when methanol was used as the internal coagulating liquid and water was used as the external coagulating liquid, good bursting strength, water permeability, elastic modulus, and strength were obtained.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the radius r of the pore and the distance l from the inner surface of the hollow fiber. FIG. 2 is a graph showing the relationship between water permeability and film thickness. Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] (1) After a polar organic solvent solution of an aromatic polyethersulfone-based polymer containing glycols is discharged from an annular nozzle in the form of a hollow fiber, a liquid that mixes with the mixed solvent but does not dissolve the aromatic polyethersulfone A method for producing an aromatic polyether sulfone hollow semipermeable membrane, the method comprising removing the solvent by contacting the membrane with the aromatic polyether sulfone.