KR101331066B1 - Polyethersulfone hollow fiber membrane and method of manufacturing the same - Google Patents

Abstract

The present invention relates to a polyether sulfone hollow fiber membrane and a method for manufacturing the same, wherein the internal coagulation solution comprising a spinning dope composed of a polyether sulfone polymer, an organic solvent and an organic additive, and a solution containing a glycol compound or a glycol compound is a double tube. In the manufacture of a polyether sulfone-based hollow fiber membrane by discharging into air through a nozzle and solidifying with an external coagulation solution, and subsequently washing, drying and winding, pores formed on the membrane cross-section by adding an inorganic salt to the radiation dope. Polyethersulfone hollow fiber membrane having a sponge structure having a maximum diameter of less than 5 μm, the diameter of the pores gradually increases from the outer surface of the membrane to the inner surface thereof, and the pores having a diameter of 0.2 to 4 μm exist on the outer surface of the membrane. Manufacture.

The present invention has excellent water permeation characteristics and rejection separation performance and at the same time has high mechanical strength.

Inorganic salt, polyether sulfone, hollow fiber, separator, mechanical strength, water permeation characteristics.

Description

Polyethersulfone hollow fiber membrane and method of manufacturing the same

1 is an electron micrograph of a cross section of the polyether sulfone hollow fiber separator according to the present invention

Figure 2 is an enlarged electron micrograph of the inner surface of the polyether sulfone hollow fiber membrane according to the present invention.

Figure 3 is an enlarged electron micrograph of the outer surface of the polyether sulfone hollow fiber membrane according to the present invention.

The present invention relates to a polyether sulfone hollow fiber separator and a method for producing the same, and more particularly, to a polyether sulfone hollow fiber separator and a method for producing the same having excellent water transmittance and separation fraction ability.

Polyether resins are widely used as hollow fiber separator materials for various applications because of their excellent physical properties and performance as separators.

 Polyethersulfone hollow fiber membrane is discharged into the air of constant temperature and humidity with a double tube nozzle by spinning dope consisting of polyethersulfone resin, organic solvent and organic additive, and solidified with external coagulation solution. It is manufactured by winding up.

The pore shape of the hollow fiber membrane thus prepared is mainly circular to elliptical, and depends on various variables such as the thermodynamic stability of the spinning dope, the viscosity of the spinning dope, the solidification speed of the internal coagulation bath, the atmosphere of the discharge air, and the temperature of the external coagulation fluid. The pore size (diameter) and size deviation are determined.

In general, the two most important performances of the membrane are the exclusion separation performance capable of efficiently removing the target material and the water permeability, which is the speed at which the target material can be removed.

However, it is relatively easy to improve the water permeability by controlling the size of the pores in the microfiltration membrane, but it is difficult to improve the technology of reducing the size deviation of the pores, that is, the exclusion fraction separation rate, as the pores become larger.

This is due to the process specificity of the microfiltration hollow fiber membrane, which has a short residence time at the air temperature after being discharged into the air from the double-tubular nozzle, compared to the ultrafiltration hollow fiber membrane.

In other words, in order to increase the pore size, the coagulation force of the internal coagulating solution should be reduced to increase the pore size of the inner surface of the hollow fiber, thereby shortening the residence time in the air. Under these process conditions, not only the cross section of the hollow fiber membrane is dense, but the pore size of the outer surface is also uneven and small, so that it is difficult to expect excellent exclusion fractionation performance.

For the same reason, in particular, the hollow fiber membrane using polyether sulfone system has a disadvantage in that it is difficult to control the phase separation and the process in controlling the pore size, which is the core technology of the membrane, despite the superiority of the material such as contamination resistance and chlorine resistance. It has been used for ultrafiltration and is not widely used in many fields.

Various methods of preparing porous membranes using polyether sulfones are conventionally disclosed in US Pat. Nos. 5,869,174, 5,886,059, 6,017,474, and the like.

However, these are ultrafiltration hollow fiber membranes or microfiltration membranes, and there are no inventions related to microfiltration hollow fiber membranes, and there are few microfiltration hollow fiber membranes produced using polyether sulfones in Korea.

Among them, U.S. Patent No. 5,886,059 proposes a method for facilitating pore size adjustment by making the spinning dope solution thermodynamically unstable, but the membrane type produced by the above method is a flat membrane, and its use value is remarkable compared to that of the hollow fiber membrane It is deteriorated very much, and it cannot be said that the performance as a microfiltration membrane is also excellent.

Therefore, there is a need for a polyether sulfone hollow fiber membrane having excellent water permeability and excellent separation and separation resistance and excellent fouling resistance and chlorine resistance.

The present invention is to provide a polyether sulfone hollow fiber membrane having high mechanical strength and excellent water permeability and separation performance in order to solve these problems.

To this end, in the present invention, when the polyether sulfone hollow fiber membrane is manufactured, the inorganic salt is added to the spinning dope and the internal coagulating solution, respectively, in order to promote the formation of pores when the spinning dope discharged into the air is phase separated from the air. It acts as a pore nucleus to promote pore formation.

In order to achieve the above technical problem, the present invention provides an internal coagulating solution composed of a polyethersulfone polymer, an organic solvent, and an organic coagulant comprising a spinning dope and a glycol compound or a solution containing a glycol compound. In the manufacture of a polyether sulfone-based hollow fiber membrane by solidifying with an external coagulation liquid after discharging, washing, drying and winding continuously, an inorganic salt is added to the radiation dope.

In addition, the polyether sulfone hollow fiber separation membrane of the present invention has a sponge structure in which the maximum diameter of pores formed on the membrane cross-section is less than 5 μm, and the diameter of the pores gradually increases from the outer surface of the membrane to the inner surface thereof, and the diameter is formed on the outer surface of the membrane. It is characterized in that the pores are 0.2 ~ 4㎛.

In general, the structure of the hollow fiber membrane is divided into a sponge structure and a finger structure according to the presence of the macropores present on the cross-section, and as a result of the present invention, the maximum pore size is less than 5 μm and the sponge structure is obtained when the macropores do not exist. Classify. Unlike the finger structure, the sponge structure has a large pore that acts as a defect and thus has a stable film performance.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

First, in the present invention, in preparing a spinning dope by dissolving a polyether sulfone polymer and an organic additive in an organic solvent, a spinning dope is necessarily prepared including an inorganic salt. Inorganic salts added to this spinning dope provide pore cores to promote pore formation when the spinning dope is phase separated in air having a constant temperature and humidity, and strongly absorbs moisture in the air to form pores according to smooth phase separation. Induces a role

As such inorganic salt, mainly alkali metal compound salts or alkaline earth metal salts, such as lithium bromide, sodium chloride, magnesium chloride, etc., are used.

The addition amount of the inorganic salt in the spinning dope is preferably set to 3 to 10% by weight based on the total weight of the spinning dope.

If the addition amount is lower than the above range, the role as a pore-forming agent is insignificant, and it is difficult to expect the effect. If the addition amount is higher than the above range, the viscosity of the spinning dope suddenly rises, making it impossible to manufacture the hollow fiber separator.

As the organic additive in the spinning dope, hydrophilic polymers or oligomers such as polyethylene glycol, polyvinylpyrrolidone, and alcohol compounds may be used.

Spinning dope is preferably 10 to 20% by weight of polyether sulfone, 60 to 75% by weight of organic solvent, 10 to 15% by weight of organic additive, 3 to 10% by weight of inorganic salt, and 1 to 5% by weight of other additives. . However, in the present invention, the composition ratio is not limited to this.

In the present invention, a solution in which an inorganic salt is added to a glycol compound or a solution containing a glycol compound is used as an internal coagulating solution, or a solution containing the above glycol compound or glycol compound without adding an inorganic salt is used. do.

As such inorganic salts, alkali metal compound salts or alkaline earth metal salts such as lithium bromide, sodium chloride, magnesium chloride and the like are used.

As a specific example, in the present invention, sodium chloride is dissolved in a mixed solution of diethylene glycol and water and used as an internal coagulation solution.

Inorganic salts added to the internal coagulating solution precipitate in hydrated form as they pass through the membrane as the inner surface of the spinning dope solidifies, which can act as a pore nucleus to form larger pores.

At this time, the addition amount of the inorganic salt in the internal coagulation solution is preferably 20% by weight or less relative to the total weight of the internal coagulation solution. That is, depending on the composition of the dope, it is possible that the inorganic salt is not added to the internal coagulating solution, but if it exceeds the above range, the radioactive deterioration due to the increase of the viscosity of the coagulating solution and the uneven distribution of the membrane pores due to the precipitation of the inorganic salt may occur. Can be.

As the external coagulant, a non-solvent of polyether sulfone is used. Generally, water is preferably used. As the double tube nozzle, an annular nozzle having an outer diameter of 2.1 to 2.3 mm, an inner diameter of 0.9 to 1.1 mm, and an inner nozzle having a diameter of about 0.5 to 0.7 mm can be used.

Next, spray the spinning dope and internal coagulating solution prepared above through a double-tubular nozzle into air of a certain temperature and humidity, then solidify it with an external coagulating solution, wash it in a washing tank to remove the solvent and additives, and then dry and wind them up. Prepare a separator.

Through the present invention, various physical properties of the polyether sulfone hollow fiber membranes spun by the manufacturing method as described above were evaluated by the following method.

ㆍ Water transmittance evaluation

A small module having a hollow fiber membrane having an effective length of 15 to 20 cm was added with 1.0 kg / cm 2 pure water at 25 ° C. in an internal pressurizing type to measure the amount of permeate through the hollow fiber membrane for a certain period of time. do.

ㆍ Substance rejection rate evaluation

After preparing the same module as in the water transmittance, the aqueous solution of 0.3ppm, 0.4μm, 0.5μm beads in 1,000ppm was permeated in the same manner as the water transmittance, and the bead concentration ratio in the stock solution and permeated water was measured using UV spectrum. Then it was obtained through the following equation (I).

(Ⅰ)

(I)

ㆍ Microscopic observation

The inside and outside surfaces and fracture surfaces of the hollow fiber membranes were observed by scanning electron microscopy. In particular, the diameter of the micropores present on the cross section was specified by using an image analyzer for the cross-sectional photograph enlarged 1,000 times or more for the observation of the pore on the fracture surface.

The polyethersulfone hollow fiber separator of the present invention has a sponge structure, which does not contain macropores of 5 microns or more inside, that is, the maximum diameter of the pores is less than 5 μm, and the diameter of the pores is from the outer surface of the membrane toward the inner surface. It gradually increases, and has a structure in which pores having a thickness of 0.2 to 4 µm exist on the outer surface of the membrane.

In addition, the hollow fiber membrane of the present invention has an excellent water permeability and separation fraction ability and high mechanical strength by adding inorganic salts to the spinning dope and the internal coagulating solution without the need for a special process operation.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited only to the following examples.

Example  One

16% by weight of polyether sulfone resin (product of E3020P BASF), 15% by weight of polyvinylpyrrolidone, 7% by weight of lithium bromide, and 5% by weight of pure water were added to 57% by weight of dimethylacetamide, followed by stirring and dissolving. To prepare.

This spinning stock solution is discharged at a rate of 11.75 g / min from an annular slit mold having an outer diameter of 2.15 mm, an inner diameter of 1.15 mm, and an inner nozzle diameter of 0.70 mm. At the same time, 64.5% by weight of diethylene glycol and 14.1% by weight of sodium chloride were added to 21.4% by weight of water from the internal nozzle, and dissolved at a rate of 9.55 g / min.

After passing through the air gap of 55cm, the hollow fiber was induced by the coagulation bath (water) of 40 ℃ and washed with coagulation and wound up in a failure shape at a speed of 20m / min. Table 1 shows the results of measuring the water permeability and the material exclusion rate of the prepared polyether sulfone hollow fiber membranes.

Example  2

16 wt% of polyether sulfone resin (product of E3020P BASF), 15 wt% of polyvinylpyrrolidone, 7 wt% of sodium chloride, and 5 wt% of pure water were added to 57 wt% of dimethylacetamide, followed by stirring and dissolving. Manufacture.

This spinning stock solution is discharged at a rate of 11.75 g / min from an annular slit mold having an outer diameter of 2.15 mm, an inner diameter of 1.15 mm, and an inner nozzle diameter of 0.70 mm.

At the same time, 64.5% by weight of diethylene glycol and 14.1% by weight of sodium chloride were added to 21.4% by weight of water from the internal nozzle, and dissolved at a rate of 9.55 g / min. After passing through the air gap of 55cm, the hollow fiber was induced by the coagulation bath (water) of 40 ℃ and washed with coagulation and wound up in a failure shape at a speed of 20m / min. Table 1 shows the results of measuring the water permeability and the material exclusion rate of the prepared polyether sulfone hollow fiber membranes.

Example  3

16% by weight of polyether sulfone resin (product of E3020P BASF), 15% by weight of polyvinylpyrrolidone, 7% by weight of magnesium chloride, and 5% by weight of pure water were added to 57% by weight of dimethylacetamide, followed by stirring and dissolving. To prepare. This spinning stock solution is discharged at a rate of 11.75 g / min from an annular slit mold having an outer diameter of 2.15 mm, an inner diameter of 1.15 mm, and an inner nozzle diameter of 0.70 mm. At the same time, 64.5% by weight of diethylene glycol and 14.1% by weight of sodium chloride were added to 21.4% by weight of water from the internal nozzle, and dissolved at a rate of 9.55 g / min. After passing through the air gap of 55cm, the hollow fiber was induced by the coagulation bath (water) of 40 ℃ and washed with coagulation and wound up in a failure shape at a speed of 20m / min. Table 1 shows the results of measuring the water permeability and the material exclusion rate of the prepared polyether sulfone hollow fiber membranes.

Comparative Example  One

16% by weight of polyether sulfone resin (product of E3020P BASF), 15% by weight of polyvinylpyrrolidone, 7% of polyethylene glycol, and 5% by weight of pure water were added to 57% by weight of dimethylacetamide, followed by stirring and dissolving. Manufacture.

This spinning stock solution is discharged at a rate of 11.75 g / min from an annular slit mold having an outer diameter of 2.15 mm, an inner diameter of 1.15 mm, and an inner nozzle diameter of 0.70 mm. At the same time, 64.5% by weight of diethylene glycol and 14.1% by weight of sodium chloride were added to 21.4% by weight of water from the internal nozzle, and dissolved at a rate of 9.55 g / min.

After passing through the air gap of 55cm, the hollow fiber was induced by the coagulation bath (water) of 40 ℃ and washed with coagulation and wound up in a failure shape at a speed of 20m / min. Table 1 shows the results of measuring the water permeability and the material exclusion rate of the prepared polyether sulfone hollow fiber membranes.

Comparative Example  2

16% by weight of polyether sulfone resin (product of E3020P BASF), 15% by weight of polyvinylpyrrolidone, 7% by weight of lithium bromide, and 5% by weight of pure water were added to 57% by weight of dimethylacetamide, followed by stirring and dissolving. To prepare.

This spinning stock solution is discharged at a rate of 11.75 g / min from the annular slit mold having an outer diameter of 2.15 mm, an inner diameter of 1.15 mm, and an inner nozzle diameter of 0.70 mm. At the same time, 64.5% by weight of diethylene glycol was added and dissolved in 35.5% by weight of water from the internal nozzle, and was injected at a rate of 9.55 g / min.

After passing through the air gap of 55cm, the hollow fiber was induced by the coagulation bath (water) of 40 ℃ and washed with coagulation and wound up in a failure shape at a speed of 20m / min. Table 1 shows the results of measuring the water permeability and the material exclusion rate of the prepared polyether sulfone hollow fiber membranes.

Comparative Example 3

16% by weight of polyether sulfone resin (product of E3020P BASF), 15% by weight of polyvinylpyrrolidone, 7% of polyethylene glycol, and 5% by weight of pure water were added to 57% by weight of dimethylacetamide, followed by stirring and dissolving. Manufacture.

This spinning stock solution is discharged at a rate of 11.75 g / min from an annular slit mold having an outer diameter of 2.15 mm, an inner diameter of 1.15 mm, and an inner nozzle diameter of 0.70 mm. At the same time, 64.5% by weight of diethylene glycol was added and dissolved in 35.5% by weight of water from the internal nozzle, and was injected at a rate of 9.55 g / min.

After passing through the air gap of 55cm, the hollow fiber was induced by coagulation bath (water) of 40 ℃ and washed with coagulation and wound up in a failure shape at a speed of 20m / min. Table 1 shows the results of measuring the water permeability and the material exclusion rate of the prepared polyether sulfone hollow fiber membranes.

division Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Transmittance
(Ml / kgf · cm · min) 58.42 32.74 33.56 17.48 13.72 8.95 ship
ashes
rate
(%) 0.3 μm 2.34 11.44 17.94 94.65 97.85 99.75 0.4 μm 15.31 85.69 77.53 99.08 99.47 99.56 0.5 탆 95.38 98.67 98.43 99.14 99.99 99.99

The present invention is excellent in water permeation characteristics and exclusion separation ability and at the same time has a high mechanical strength.

As a result, the present invention is useful in the field of sewage treatment, pharmaceutical field, domestic / industrial water treatment field and other fine filtration fields.

Claims (8)

The internal coagulating solution composed of a polyethersulfone polymer, a spinning dope composed of an organic solvent and an organic additive, and a glycol compound or a solution containing a glycol compound is discharged into the air through a double-tubular nozzle, and then solidified into an external coagulating solution. In the preparation of the polyether sulfone-based hollow fiber membrane by washing, drying and winding by using, an inorganic salt is added to both the spinning dope and the internal coagulating solution, and the amount of the inorganic salt in the spinning dope is 3 to 10% by weight based on the total weight of the spinning dope. The method of producing a polyether sulfone hollow fiber separator, characterized in that the addition amount of the inorganic salt in the internal coagulation solution is 20% by weight or less relative to the total weight of the internal coagulation solution. delete The method for producing a polyether sulfone hollow fiber separator according to claim 1, wherein the inorganic salt is an alkali metal compound salt or an alkaline earth metal compound salt. The method for producing a polyether sulfone hollow fiber separator according to claim 3, wherein the inorganic salt is one or two or more selected from lithium bromide, sodium chloride, and magnesium chloride. delete delete The method of producing a polyether sulfone hollow fiber separator according to claim 1, wherein the organic additive is a hydrophilic polymer or a hydrophilic oligomer. The maximum diameter of the pores formed on the membrane cross-section has a sponge structure of less than 5㎛, the diameter of the pores gradually increases from the outer surface of the membrane to the inner surface, and the outer surface of the membrane has pores with a diameter of 0.4 ~ 0.5㎛ Polyether sulfone hollow fiber separator.

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