KR20140117174A - Method for manufacturing asymmetric hollow fiber membranes for gas separation using hybrid phase separation and asymmetric hollow fiber membranes for gas separation manufactured thereby - Google Patents

Abstract

Provided is a method for manufacturing asymmetric hollow fiber membranes for gas separation, the method comprising: i) a step of mixing a polymer resin, a solvent, and a cosolvent having a boiling point of 80-150°C, and gaining a dope solution; ii) a step of providing and discharging the dope solution to a dual spinning nozzle of a spinneret and forming hollow fibers; and iii) a step of externally coagulating and winding the hollow fibers formed in the step ii) and manufacturing hollow fiber membranes. The asymmetric hollow fiber membranes for gas separation prepared by the hybrid phase separation improves gas permeability constant and selectivity and has excellent mechanical properties, thereby selectively separating one gas from two or more gas mixtures selected from the group consisting of oxygen, nitrogen, carbon dioxide, hydrogen, and methane.

Description

TECHNICAL FIELD The present invention relates to a method for producing an asymmetric hollow fiber membrane for gas separation using a hybrid phase separation method and an asymmetric hollow fiber membrane for gas separation }

The present invention relates to a method for producing an asymmetric hollow fiber membrane for gas separation using a hybrid phase separation method and to an asymmetric hollow fiber membrane for gas separation produced by the method. More particularly, the present invention relates to a polymer resin, a solvent, To form a dope solution, and spinning the spinning nozzle at a temperature of 80 to 180 占 폚 at a temperature of 20 to 80 占 폚 and a coagulation bath and a spinning bath at a temperature of 20 to 80 占 폚. The present invention relates to a method for producing an asymmetric hollow fiber membrane for gas separation, which is improved at the same time and has excellent mechanical properties.

Currently, the gas separation membrane separates not only oxygen or nitrogen from the air, but also high quality by removing carbon dioxide from biogas, separation of carbon dioxide from natural gas, separation of hydrogen from syngas of petrochemical process and removal of carbon dioxide, And recovery of monomers from the reactants.

However, the hollow fiber membranes developed so far generally have low mechanical strength and are not applicable to processes such as purification of natural gas and synthesis gas, and recovery of monomers of reactants. Particularly, in the device industry such as the separation of carbon dioxide from natural gas and the separation of hydrogen from syngas, the separation process is carried out under high pressure and high temperature conditions where the operating conditions are higher than 25 atm and 100 ° C or higher. A hollow fiber membrane excellent in thermal and mechanical properties and chemical resistance is required.

In order for the polymer separator to selectively separate and concentrate the gas, it is generally required that the separator structure has an asymmetric structure comprising a dense selective separation layer on the membrane surface and a porous support having a minimum permeation resistance at the bottom of the membrane. The selective separation capability of the gas, which is a characteristic of the gas separation membrane, depends on the structure of the separation membrane, and the permeation amount of the selectively separated gas depends on the thickness of the separation layer and the degree of porosity of the porous support, which is a substructure of the asymmetric membrane. In order to selectively separate the mixed gas, the surface of the separation layer should be free of defects and the pore size should be 5 Å or less. In addition, in order to obtain a high gas permeability, the separating layer should be as thin as possible, because the gas permeability is inversely proportional to the effective film thickness. In order to minimize the resistance to gas flow selectively passing through the separation layer, it is advantageous to have a porous structure so as to be a substructure of the asymmetric membrane.

There are two methods for producing a gas separation membrane that meets these requirements. The separation can be divided into Nonsolvent induced phase separation and Thermally induced phase separation.

In the non-solvent-based phase separation method, a spinning solution in which a polymer resin is dissolved in a good solvent is discharged through a spinneret, and the discharged spinning solution is brought into contact with a solution containing non-spinning solvent to induce solidification of spinning solution to produce a film. There is no need to dissolve the polymer resin while increasing the amount of the resin, so that there is an advantage that the energy consumption is small and the manufacturing facility is simple and the manufacturing is easy. However, since the single membrane produced by the non-solvent-derived phase separation method has only an asymmetric sponge structure including macrovoid, the mechanical properties such as tensile strength are not good, and when high pressure is applied, film shrinkage occurs, And the gas permeability is deteriorated (Patent Document 1).

On the other hand, in the heat-induced phase separation method, a spinning solution in which a polymer resin is forcedly dissolved in a poor solvent at a high temperature above a phase separation temperature is discharged through a spinneret, and the discharged spinning solution is contacted with a cooling solution below the phase separation temperature to solidify the spinning solution And has a bead structure that is symmetric with respect to the film thickness direction without including macrovoids, which is advantageous in that the mechanical strength of the film is excellent. However, since the film produced by the heat-induced phase separation method has a low gas permeability, the separation characteristics are deteriorated and the breaking elongation of the film is low, so there is a high possibility that the film is damaged in the course of acidification to suppress fouling (Patent Document 2).

On the other hand, a method of manufacturing an asymmetric hollow fiber membrane having a dense skin layer at room temperature by mixing a high-boiling point solvent and a low-boiling point volatile additive in the production of a polymer solution for spinning is also known However, since this method emits at a room temperature, it is difficult to prepare a hollow fiber membrane in the case of a polymer solution having a very high viscosity. In order to prepare a hollow fiber membrane, a polymer solution having a low viscosity is spun, There is a problem that it is difficult to apply to a high-pressure separation process due to low mechanical strength (Patent Document 3).

Patent Document 1. United States Patent No. 4,399,035 Patent Document 2. Korean Patent Publication No. 2003-0001474 Patent Document 3: U.S. Patent No. 4,902,422

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a method for producing an asymmetric hollow fiber membrane for gas separation having improved gas permeability and selectivity simultaneously, The present invention also provides a hollow fiber membrane for gas separation.

According to an aspect of the present invention, there is provided a method for preparing a dope solution, comprising: i) mixing a polymer resin, a solvent and a cosolvent having a boiling point of 80 to 150 ° C to obtain a dope solution; ii) feeding and discharging the dope solution to a spinning nozzle of a spinneret to form a hollow fiber; And iii) external coagulation and coiling of the hollow fiber formed in the step ii) to produce a hollow fiber membrane. The present invention also provides a method for manufacturing an asymmetric hollow fiber membrane for gas separation.

The polymer resin in step i) is any one selected from the group consisting of polysulfone, polyethersulfone, polyimide, polyetherimide, polyamide, polyacrylonitrile, cellulose acetate, and cellulose triacetate.

The solvent of step i) may be any one selected from the group consisting of N-methylpyrrolidone (NMP), dimethylacetamide (DMAc) dimethylformamide (DMF), dimethylsulfoxide (DMSO), and gamma butyrolactone .

The cosolvent having a boiling point of 80 to 150 DEG C in step i) is any one selected from the group consisting of 1,4-dioxane, butanol, isobutanol, pentanol, and isopentanol.

The dope solution of step i) comprises 15 to 50% by weight of a polymer resin, 30 to 80% by weight of a solvent, and 5 to 20% by weight of a co-solvent having a boiling point of 80 to 150 ° C.

And the spinning nozzle in the step ii) controls the temperature to 80 to 180 ° C.

The method for producing an asymmetric hollow fiber membrane for gas separation may further include treating the surface of the hollow fiber membrane with polydimethylsiloxane.

In addition, the present invention provides an asymmetric hollow fiber membrane for gas separation produced by the method for producing an asymmetric hollow fiber membrane for gas separation.

The asymmetric hollow fiber membrane for gas separation of the present invention is characterized in that any one gas is selectively separated from at least two mixed gases selected from the group consisting of oxygen, nitrogen, carbon dioxide, hydrogen, and methane.

In the present invention, a dope solution is formed by mixing a polymer resin, a solvent and a cosolvent having a boiling point of 80 to 150 ° C, and the temperature of the spinning nozzle is adjusted to 80 to 180 ° C, the temperature of the coagulation bath and the coiling machine is changed to 20 to 80 ° C It is possible to provide an asymmetric hollow fiber membrane for gas separation which has both improved gas permeability and selectivity and is also excellent in mechanical properties.

1 shows a process and an apparatus for producing an asymmetric hollow fiber membrane according to the present invention.
2 is a gas permeation testing module for an asymmetric hollow fiber membrane according to the present invention.
3 is a bubble flow meter for measuring the gas permeation amount of an asymmetric hollow fiber membrane according to the present invention.

Hereinafter, an asymmetric hollow fiber membrane for gas separation using the hybrid phase separation method according to the present invention and an asymmetric hollow fiber membrane for gas separation produced by the method will be described in detail. The hybrid phase separation method of the present invention can be understood as a combination of the above two phase separation methods in order to maximize the advantages of the conventional non-solvent-derived phase separation method and the heat induction phase separation method.

The present invention relates to a process for preparing a dope solution, comprising the steps of: i) mixing a polymer resin, a solvent and a cosolvent having a boiling point of 80 to 150 ° C to obtain a dope solution; ii) feeding and discharging the dope solution to a spinning nozzle of a spinneret to form a hollow fiber; and iii) coagulating and coagulating the hollow fiber formed in the step ii) to produce a hollow fiber membrane. FIG. 1 schematically shows a process and an apparatus for producing an asymmetric hollow fiber membrane according to the present invention.

First, as a first step for preparing the asymmetric hollow fiber membrane of the present invention, a dope solution is obtained by mixing a polymer resin, a solvent and a cosolvent having a boiling point of 80 to 150 ° C. Examples of the polymer resin include polysulfone, polyether sulfone, Amide, polyetherimide, polyamide, polyacrylonitrile, cellulose acetate, and cellulose triacetate may be used. Generally, in the case of separating the gas, it is preferable to use the glass-like polymer resin having a high attraction between the polymer chains in view of the fact that a relatively high selectivity can be expected although the permeability is low. Particularly, polyimide excellent in thermal and mechanical properties at high temperature and high pressure is more preferable.

As the solvent, a solvent having a relatively high boiling point (150 DEG C or higher) is preferably used. If the boiling point is low, defects may be generated in the hollow fiber selected layer due to the rapid evaporation of the organic solvent in the high-temperature hollow fiber spinning process. If the boiling point is too high, the evaporation of the organic solvent does not occur during the passage of the spinning solution, The layer can not be obtained. Accordingly, as the solvent, any one selected from the group consisting of N-methylpyrrolidone (NMP), dimethylacetamide (DMAc) dimethylformamide (DMF), dimethylsulfoxide (DMSO) and gamma-butyrolactone Among them, N-methylpyrrolidone (NMP) is more preferable.

As the co-solvent having a boiling point of 80 to 150 ° C, any one selected from the group consisting of 1,4-dioxane, butanol, isobutanol, pentanol, and isopentanol may be used, More preferred is dioxane. In the conventional non-solvent-derived phase separation method, hollow fiber membranes were prepared at low temperatures using low-boiling point non-solvent additives. However, when the concentration of the polymer resin in the dope solution was increased to increase the mechanical strength, It was difficult to apply the heat-induced phase separation method using an expensive extruder. However, according to the present invention, a dope solution is obtained by adding a cosolvent having a boiling point of 80 to 150 DEG C instead of the low-boiling point non-solvent additive used in the conventional non-solvent-derived phase separation method, A hollow fiber membrane can be produced without an extruder. If the boiling point of the cosolvent is less than 80 캜, it evaporates during a high-temperature spinning process and bubbles are generated in the dope solution, thereby causing serious defects on the surface of the hollow fiber membrane and ultimately fail to exhibit the selectivity of the gas separation membrane. On the other hand, if the boiling point of the cosolvent is higher than 150 ° C, evaporation does not occur during the high-temperature spinning process, so that it becomes impossible to form a selective layer, and thus application to a selective gas separation membrane becomes impossible. Therefore, the use of a co-solvent having a boiling point of 80 to 150 ° C is the basis of the technical idea of the present invention.

The composition of the dope solution in step i) is 15 to 50% by weight of the polymer resin, 30 to 80% by weight of a solvent, and 5 to 20% by weight of a co-solvent having a boiling point of 80 to 150 ° C.

If the content of the polymer resin in the dope solution is less than 15% by weight, the viscosity of the polymer resin solution is low and it is difficult to obtain the hollow fiber membrane during the high-temperature spinning process. When the content exceeds 50% by weight, the mechanical strength may increase, The content of the polymer resin in the dope solution is preferably adjusted to 15 to 50% by weight. The content of the solvent in the dope solution is preferably 30 to 80% by weight. When the amount of the solvent is less than 30% by weight, the viscosity of the polymer resin solution is very high and the permeability is decreased. It is not easy to obtain a hollow fiber membrane. As a technical feature of the present invention, the content of the cosolvent having a boiling point of 80 to 150 ° C in the dope solution is preferably 5 to 20% by weight. When the content is less than 5% by weight, the skin layer is formed on the surface The content of the cosolvent having a boiling point of 80 to 150 DEG C in the dope solution is preferably 5 to 20 wt.%, More preferably 5 to 20 wt.%, %.

Next, the dope solution obtained in the step i) is supplied to and discharged from the double spinning nozzle of the spinneret to form a hollow fiber. The dope solution removes bubbles, removes foreign matters using a filter, Is supplied to the spinning nozzle's double spinning nozzle. The spinning solution is discharged through the outer nozzle of the double spinning nozzle and the internal coagulant is supplied to the inside of the spinning nozzle through the liquid transfer pump (HPLC pump), so that the phase transition between the internal coagulant and spinning solution starts, Respectively. At this time, the temperature of the spinneret can be adjusted to 80 to 180 ° C. As the internal coagulant, water, isopropanol, ethylene glycol, polyethylene glycol, glycerol, dimethoxyethanol, diethoxyethanol, butoxymethanol, dimethoxybutylenol And diglycidyl dimethyl ether can be used, and it is more preferable to use water.

Next, the hollow fiber formed in the step ii) is coagulated and coagulated to produce a hollow fiber membrane. The hollow fiber formed in the step ii) is introduced into the primary coagulation bath filled with tap water and transformed, and the phase transition is completed in the primary coagulation bath The residual hollow fiber is removed from the secondary coagulation bath and wound in a winding drum at a constant speed. At this time, the temperature of the coagulation bath and the coagulation bath is adjusted to 20 to 80 ° C, the wound hollow fiber is subjected to hydrothermal treatment and solvent substitution to completely remove the residual solvent and then dried to produce a hollow fiber membrane.

The method may further include treating the surface of the hollow fiber membrane with polydimethylsiloxane to remove defects in the hollow fiber membrane produced according to the present invention.

According to the present invention, there is provided an asymmetric hollow fiber membrane for gas separation produced by the above-described method for producing an asymmetric hollow fiber membrane.

The asymmetric hollow fiber membrane for gas separation of the present invention can selectively remove any gas from two or more mixed gases selected from the group consisting of oxygen, nitrogen, carbon dioxide, hydrogen, and methane.

Hereinafter, specific examples will be described in detail.

( Example  One)

280 g of polyimide, 600 g of N-methylpyrrolidone and 120 g of 1,4-dioxane were added to a 2 L round bottom flask equipped with a stirrer and stirred to obtain a 28 wt% polymer resin solution (dope solution). The polymer resin solution was transferred to a reservoir equipped with a double jacket and allowed to stand at 80 DEG C for 48 hours to completely remove the bubbles generated in the process of obtaining the polymer resin solution. The polymer resin solution was supplied to the double spinning nozzle of the spinneret through the gear pump. The spinning solution was discharged through the outer nozzle of the double spinning nozzle, and water as the inner coagulating agent was injected into the spinning nozzle through the HPLC pump The phase transition between the internal coagulant and the spinning solution started and a hollow fiber was formed. The hollow fiber thus formed was poured into a primary coagulation bath filled with tap water. The hollow fiber finished in phase coagulation in the primary coagulation bath was removed from the secondary coagulation bath and then wound at a constant speed. At this time, the spinning temperature was maintained at 80 ° C, and the temperature of the primary and secondary coagulation baths was maintained at 30 ° C. The wound hollow fiber was subjected to hot water treatment for 4 hours with ethanol and hexane for 1 hour, and the remaining solvent was completely removed, and the hollow fiber membrane was dried at room temperature for 48 hours.

( Example  2)

A hollow fiber membrane was prepared in the same manner as in Example 1, except that 280 g of polyimide, 550 g of N-methylpyrrolidone and 170 g of 1,4-dioxane were used.

( Example  3)

A hollow fiber membrane was prepared in the same manner as in Example 1, except that 280 g of polyimide, 600 g of N-methylpyrrolidone and 120 g of isobutanol were used and the spinning temperature was maintained at 100 占 폚.

( Example  4)

A hollow fiber membrane was prepared in the same manner as in Example 1, except that 250 g of polyimide, 600 g of dimethylacetamide and 150 g of 1,4-dioxane were used.

( Example  5)

A hollow fiber membrane was prepared in the same manner as in Example 1, except that 350 g of polyimide, 580 g of N-methylpyrrolidone and 70 g of 1,4-dioxane were used and the spinning temperature was maintained at 120 캜.

( Comparative Example  One)

A hollow fiber membrane was prepared in the same manner as in Example 1, except that 280 g of polyimide, 600 g of N-methylpyrrolidone and 120 g of tetrahydrofuran were used.

( Comparative Example  2)

A hollow fiber membrane was prepared in the same manner as in Comparative Example 1, except that the spinning temperature was maintained at 20 占 폚.

( Comparative Example  3)

A hollow fiber membrane was prepared in the same manner as in Example 1, except that the spinning temperature was maintained at 20 占 폚. However, since the viscosity of the polymer resin solution (dope solution) was too high, it could not be discharged to the nozzle and the hollow fiber could not be formed.

( Comparative Example  4)

A hollow fiber membrane was prepared in the same manner as in Example 2, except that 280 g of polyimide, 550 g of N-methylpyrrolidone and 170 g of tetrahydrofuran were used.

( Comparative Example  5)

A hollow fiber membrane was prepared in the same manner as in Example 4, except that 250 g of polyimide, 600 g of dimethylacetamide and 150 g of tetrahydrofuran were used.

( Comparative Example  6)

A hollow fiber membrane was prepared in the same manner as in Example 5, except that 350 g of polyimide, 580 g of N-methylpyrrolidone and 70 g of tetrahydrofuran were used.

( Test Example )

To measure the gas permeability of the hollow fiber membranes prepared in Examples 1 to 5 and Comparative Examples 1 to 6, a test module as shown in Fig. 2 was prepared. Using 99.99% oxygen and nitrogen as the mixer, The permeability was measured. The gas permeation amount was measured using a foam flow meter as shown in FIG. 3, and the unit of gas permeability was GPU (Gas Permeation Unit, 10 ^-6 × cm ³ / cm ² · sec · cmHg) The results are shown.

division Dope solution composition
(Polymer / solvent / co-solvent)
(weight%) Radiation temperature
(° C) N ₂ transmittance
(GPU) O ₂ transmission
(GPU) O ₂ / N ₂
Selectivity Example 1 28/60/12 80 25.2 138.4 5.5 Example 2 28/55/17 80 14.5 80.6 5.6 Example 3 28/60/12 100 16.3 85.7 5.3 Example 4 25/60/15 80 17.4 102.4 5.9 Example 5 35/58/7 120 14.1 77.3 5.5 Comparative Example 1 28/60/12 80 40.2 82.4 2.0 Comparative Example 2 28/60/12 Room temperature 5.3 24.8 5.76 Comparative Example 3 28/60/12 Room temperature - - - Comparative Example 4 28/55/17 80 18.4 28.8 1.6 Comparative Example 5 25/60/15 80 25.7 32.4 1.3 Comparative Example 6 35/58/7 120 123.2 114.6 0.9

As can be seen from Table 1, using the cosolvent having a boiling point of 80 to 150 ° C according to Examples 1 to 5 of the present invention, it is possible to obtain a polymer solution having a very high level Even when having a viscosity, it can be confirmed that the asymmetric hollow fiber membrane is stably manufactured by the method of mixing the non-solvent induction phase separation method and the heat induction phase separation method at a relatively high temperature of 80 to 120 ° C, and it is confirmed that the mechanical property is excellent .

The asymmetric hollow fiber membranes prepared by the hybrid phase separation method according to Examples 1 to 5 of the present invention had permeability and selectivity of the conventional gas separation membranes were in a trade-off relationship, And it can be applied not only to a mixed gas of oxygen / nitrogen but also to selective separation of carbon dioxide / methane, steam / natural gas, or steam / air.

Claims (9)

i) mixing a polymer resin, a solvent and a cosolvent having a boiling point of 80 to 150 DEG C to obtain a dope solution;
ii) feeding and discharging the dope solution to a spinning nozzle of a spinneret to form a hollow fiber; And
and iii) coagulating and coagulating the hollow fiber formed in step ii) to produce a hollow fiber membrane. The method according to claim 1, wherein the polymer resin in step i) is selected from the group consisting of polysulfone, polyethersulfone, polyimide, polyetherimide, polyamide, polyacrylonitrile, cellulose acetate, and cellulose triacetate Of the asymmetric hollow fiber membrane for gas separation. The method of claim 1, wherein the solvent in step i) is selected from the group consisting of N-methylpyrrolidone (NMP), dimethylacetamide (DMAc) dimethylformamide (DMF), dimethylsulfoxide (DMSO), and gamma butyrolactone Wherein the method comprises the following steps: The cosolvent as claimed in claim 1, wherein the cosolvent having a boiling point of 80 to 150 ° C in step i) is any one selected from the group consisting of 1,4-dioxane, butanol, isobutanol, pentanol and isopentanol Method of manufacturing asymmetric hollow fiber membrane for gas separation. The method according to claim 1, wherein the dope solution in step i) comprises 15 to 50% by weight of a polymer resin, 30 to 80% by weight of a solvent and 5 to 20% by weight of a co- solvent having a boiling point of 80 to 150 ° C Method of manufacturing asymmetric hollow fiber membrane for gas separation. The method as claimed in claim 1, wherein the spinning nozzle in step ii) adjusts the temperature to 80 to 180 占 폚. The method of claim 1, wherein the asymmetric hollow fiber membrane for gas separation further comprises treating the surface of the hollow fiber membrane with polydimethylsiloxane. An asymmetric hollow fiber membrane for gas separation produced by the method of any one of claims 1 to 7. The asymmetric hollow fiber membrane for separating gas according to claim 8, wherein the asymmetric hollow fiber membrane for separating gas selectively separates any gas from at least two mixed gases selected from the group consisting of oxygen, nitrogen, carbon dioxide, hydrogen, and methane Asymmetric hollow fiber membrane for.

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