JP5966298B2 - Method for producing hollow fiber carbon membrane - Google Patents

Description

  The present invention relates to a hollow fiber carbon membrane obtained by carbonizing a hollow fiber carbon membrane precursor using polyphenylene oxide, which has the advantage of being highly flexible and difficult to break, and as an indicator of flexibility The present invention relates to a hollow fiber carbon membrane excellent in tensile elongation at break. The present invention also relates to a method for producing the hollow fiber carbon membrane and a separation membrane module using the hollow fiber carbon membrane.

  From the viewpoint of environmental problems and energy saving in recent years, membrane separation methods have attracted attention in separation from mixtures such as various gases, and dehydration / purification processes of organic solvents. As the separation membrane to be used, polymer membranes such as polyimide membranes and polysulfone membranes have been proposed, but such polymer membranes have problems in heat resistance and solvent resistance. In addition, it is known to use a zeolite membrane, which is superior in heat resistance as compared with a polymer membrane, as a separation membrane, but the zeolite membrane has a problem of poor acid resistance.

  In recent years, carbon membranes have been developed as separation membranes that are excellent in heat resistance and chemical resistance, and are suitable for gas separation applications in environments containing high temperature or highly corrosive gases. Such a carbon film is composed of a support-type carbon film such as a tubular carbon film or a monolith-type carbon film formed on the surface of a support (porous substrate), and a free-standing carbon film that does not use a support. There are two main types. Typical examples of self-supporting carbon membranes include a flat membrane type and a hollow fiber type.Among them, the membrane area per unit volume can be increased, the apparatus can be downsized, and the manufacturing process is easy. A hollow fiber type (hollow fiber carbon membrane) is considered suitable.

  Regarding a self-supporting hollow fiber carbon membrane excellent in gas separation performance, for example, Japanese Patent Laid-Open No. 2006-231095 (Patent Document 1) carbonizes a precursor polymer membrane containing polyphenylene oxide (PPO) after infusibility treatment. The PPO hollow fiber carbon membrane obtained by this is disclosed.

  Further, for example, in JP 2009-34614 A (Patent Document 2), a film-forming stock solution containing sulfonated polyphenylene oxide (SPPO) is extruded from the outer tube of a hollow fiber spinning nozzle having a double-tube annular structure into a water coagulation bath. An SPPO hollow fiber carbon membrane obtained by producing a precursor polymer membrane, carbonizing the precursor polymer membrane after infusibilizing the precursor polymer membrane is disclosed.

JP 2006-231095 A JP 2009-34614 A

  However, since the PPO hollow fiber carbon membrane disclosed in Patent Document 1 is advantageous in that it is economical and excellent in gas separation performance because PPO is a relatively inexpensive polymer, it has poor flexibility. There was a problem that it was easy to break and the handling property in the manufacturing process of the separation module was difficult.

  In addition, in the SPPO hollow fiber carbon membrane disclosed in Patent Document 2, SPPO having a high degree of sulfonation (for example, the degree of sulfonation described as an example in Patent Document 2 of 45%) is high in hydrophilicity of the polymer. As a result of containing a large amount of moisture in the spinning process, the strength of the membrane is weakened, and the hollow fiber membranes are easily bonded to each other in the drying process, which makes it difficult to handle in the mass production process.

  The present invention has been made in order to solve the above problems, and the object thereof is a hollow fiber carbon membrane obtained by carbonizing a hollow fiber carbon membrane precursor using polyphenylene oxide, In addition to gas separation performance, it is intended to provide a highly practical hollow fiber carbon membrane and a method for producing the same, ensuring flexibility necessary for modularization.

  The present invention is a hollow fiber carbon membrane obtained by carbonizing a hollow fiber carbon membrane precursor using polyphenylene oxide, wherein the elongation at break is 1 to 4%.

The hollow fiber carbon membrane of the present invention preferably has a tensile elastic modulus of 5 GPa or more.
The present invention also provides a separation membrane module using the above-described hollow fiber carbon membrane of the present invention.

The present invention is further a method for producing the above-described hollow fiber carbon membrane of the present invention, comprising a step of dissolving polyphenylene oxide in an aprotic solvent, and a polyphenylene oxide from a spinning nozzle at a temperature higher than the temperature-induced phase separation point. A step of discharging and forming a hollow fiber, a step of coagulating the hollow fiber-shaped polyphenylene oxide with water or a mixed solution of water and an organic solvent, and the solidified hollow fiber-like material containing water without performing solvent replacement treatment. There is also provided a method for producing a hollow fiber carbon membrane, comprising a step of drying from a state to obtain a hollow fiber carbon membrane precursor and a step of carbonizing the hollow fiber carbon membrane precursor.

  Since the hollow fiber carbon membrane of the present invention has excellent gas separation performance and flexibility, it is difficult to break, can be easily modularized, and has excellent practicality.

It is a figure which shows typically the sample mount 1 used for the tension test.

  BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the best mode for carrying out the present invention will be specifically described. However, the present invention is not limited to the following embodiment, and is within the scope of the present invention without departing from the spirit of the present invention. It should be understood that design changes, improvements, and the like can be made as appropriate based on the knowledge.

<Hollow fiber carbon membrane>
The hollow fiber carbon membrane of the present invention has a breaking elongation (tensile elongation) of 1 to 4%. According to the present invention, since the elongation at break is in the range of 1 to 4%, the gas separation performance is excellent and the flexibility is excellent. An excellent hollow fiber carbon membrane is provided. When the breaking elongation of the hollow fiber carbon membrane is less than 1%, sufficient flexibility as the hollow fiber carbon membrane is not obtained, and it is easy to break. In addition, when it exceeds 4%, there is a problem that the acidification, chemical resistance, and gas separation performance are not sufficient because the carbonization is not sufficiently advanced. That is, from the reason of ensuring the flexibility as a hollow fiber carbon membrane and improving the acid resistance, chemical resistance, and gas separation performance as a carbon membrane, the breaking elongation of the hollow fiber carbon membrane of the present invention is: It is preferably in the range of 1 to 4%, and more preferably in the range of 1.5 to 3.5%. The elongation at break of the hollow fiber carbon membrane is, for example, a tensile tester technograph (TGI-200N, Minebea Co., Ltd.) in accordance with Japanese Industrial Standard “Testing Method for Tensile Properties of Carbon Fiber-Single Fiber” (JIS R7606). It can be measured by conducting a tensile test using

  The hollow fiber carbon membrane of the present invention having the above elongation at break is obtained by carbonizing a hollow fiber carbon membrane precursor using polyphenylene oxide (PPO). Such a hollow fiber carbon membrane of the present invention must be sufficiently carbonized from the viewpoint of imparting acid resistance, chemical resistance and gas separation performance, and contains carbon as a main component. Provided as a porous membrane. Here, the carbon content in the hollow fiber carbon membrane of the present invention is preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more. In the present specification, the “main component” means a component having the largest content (% by mass) in the constituent components of the film. The constituent components and the content of the hollow fiber carbon membrane can be specified by, for example, energy dispersive X-ray spectroscopy (EDS).

  The hollow fiber carbon membrane of the present invention preferably has a tensile elastic modulus of 5 GPa or more, more preferably 10 GPa or more. If the tensile modulus of the hollow fiber carbon membrane is less than 5 GPa, even if the elongation at break is high, the carbonization is not sufficiently advanced, so the acid resistance, chemical resistance, and gas separation performance may not be sufficient. It is. If carbonization proceeds too much, the modulus of elasticity as a carbon membrane increases, but defects increase, resulting in a decrease in elongation, resulting in loss of flexibility, and further deterioration in gas separation performance due to defects. Is likely to occur. For these reasons, the tensile elastic modulus of the hollow fiber carbon membrane is preferably 50 GPa or less, and more preferably 30 GPa or less. The tensile modulus of the hollow fiber carbon membrane is based on the Japanese Industrial Standard “Testing Method for Tensile Properties of Carbon Fiber-Single Fiber” (JIS R7606: 2000), and the tensile test used for the measurement of the elongation at break described above. It can be measured using a machine. At this time, the measurement of the cross-sectional area of the hollow fiber carbon membrane in order to evaluate the tensile elastic modulus is the C method of Japanese Industrial Standard “Testing Method of Diameter and Cross-sectional Area of Carbon Fiber-Single Fiber” (JIS R7607: 2000). In conformity, the surface perpendicular to the fiber axis direction of the hollow fiber carbon membrane embedded in the resin piece was polished, and the cross section was photographed by a scanning electron microscope (Scanning Electron Microscopy: SEM). This is possible by measuring the cross-sectional area and calculating the average value.

  The thickness of the hollow fiber carbon membrane of the present invention is not particularly limited, but is preferably in the range of 1 to 50 μm. When the thickness of the hollow fiber carbon membrane is less than 1 μm, sufficient flexibility cannot be obtained as a self-supporting hollow fiber carbon membrane, and it tends to break, and when the thickness exceeds 50 μm This is because the permeation resistance of gas molecules becomes too large, and there is a tendency that a sufficient permeation flow rate as a gas separation membrane cannot be obtained. That is, it is more preferable that the thickness of the hollow fiber carbon membrane is in the range of 5 to 20 μm because the flexibility as the hollow fiber carbon membrane is secured and the permeation flow rate of gas separation is secured. In addition, the thickness of a hollow fiber carbon membrane can use the method of evaluating the cross section of the hollow fiber carbon membrane embedded in said resin piece by SEM, for example.

  The outer diameter of the hollow fiber carbon membrane of the present invention is not particularly limited, but is preferably in the range of 50 to 500 μm. If the outer diameter of the hollow fiber carbon membrane is less than 50 μm, it becomes difficult to produce the precursor hollow fiber membrane in the discharge step, and the inner diameter of the hollow fiber membrane becomes too small, so that clogging due to foreign matters tends to occur. This is because the minimum bending radius at which the hollow fiber carbon membrane breaks increases as the outer diameter of the hollow fiber carbon membrane exceeds 500 μm and the handleability tends to deteriorate. That is, the outer diameter of the hollow fiber carbon membrane is 100 because it is easy to fabricate, provides a sufficient space in the hollow portion of the hollow fiber carbon membrane, and secures sufficient flexibility as the hollow fiber carbon membrane. More preferably, it is in the range of ˜400 μm. In addition, about the outer diameter of a hollow fiber carbon membrane, the method of evaluating the cross section of the hollow fiber carbon membrane embedded in said resin piece by SEM can be used, for example.

<Method for producing hollow fiber carbon membrane>
The method for producing a hollow fiber carbon membrane of the present invention includes (1) a step of dissolving polyphenylene oxide in an aprotic solvent (dissolution step), and (2) discharging PPO from a spinning nozzle at a temperature equal to or higher than the temperature-induced phase separation point. A hollow fiber-like process (discharge process), (3) a process of coagulating the hollow fiber-shaped PPO with water or a mixed solution of water and an organic solvent (coagulation process), and (4) a solidified hollow fiber-like product, A step of obtaining a hollow fiber carbon membrane precursor by drying from a state containing water without performing a solvent substitution treatment (drying step), and (5) a step of carbonizing the hollow fiber carbon membrane precursor (carbonization) Processing step). The hollow fiber carbon membrane of the present invention described above can be preferably manufactured by such a method of manufacturing the hollow fiber carbon membrane of the present invention, but has the characteristics of the hollow fiber carbon membrane of the present invention as described above. If it is, it will not be limited to what was manufactured with the manufacturing method of the hollow fiber carbon membrane of this invention.

[1] Dissolution Step In the method for producing a hollow fiber carbon membrane of the present invention, first, PPO is dissolved in an aprotic solvent. Solvents for PPO are, for example, benzene, toluene as summarized in known literature (G. Chowdhury, B. Kruczek, T. Matsuura, Polyphenylene Oxide and Modified Polyphenylene Oxide Membranes Gas, Vapor and Liquid Separation, 2001, Springer). , Chloroform such as chloroform has a large environmental load and is harmful to human body. On the other hand, for example, JP-A-3-65227 discloses that PPO is dissolved in an aprotic solvent having a relatively small environmental load at a temperature of about 100 ° C. or higher. As the aprotic solvent used in the present invention, for example, N-methyl-2-pyrrolidone, N, N-dimethylacetamide and the like are used. Among them, the solubility of PPO is particularly excellent. It is preferable to use methyl-2-pyrrolidone.

  When N-methyl-2-pyrrolidone is used as the aprotic solvent, N-methyl-2-pyrrolidone can uniformly dissolve PPO at a temperature of about 100 ° C. or higher. In addition, a desired poor solvent (for example, methanol, ethanol, acetone, tetrahydrofuran, methyl ethyl ketone, ethylene glycol, diethylene glycol, triethylene glycol, glycerin, etc.) is added to N-methyl-2-pyrrolidone as long as the solubility of the polymer is ensured. Thus, the pore size and pore size distribution of the membrane can be changed.

[2] Discharging Step In the subsequent step, a solution (PPO spinning stock solution) in which PPO is dissolved in an aprotic solvent as described above is discharged from a spinning nozzle to form a hollow fiber. The spinning type in the present invention is not particularly limited, and a conventionally known spinning method can be applied. From the viewpoint of precisely controlling the structure of the PPO hollow fiber membrane and from the viewpoint of ease of production. It is preferable to apply a dry and wet spinning method.

  In the method for producing a hollow fiber carbon membrane of the present invention, the PPO spinning stock solution is discharged at a temperature equal to or higher than the temperature-induced phase separation point. Here, the “temperature-induced phase separation point” refers to a temperature at which solidification is not caused by temperature-induced phase separation, for example, temperature induction of a PPO spinning stock solution in which PPO is dissolved in N-methyl-2-pyrrolidone (NMP). The phase separation point varies depending on the spinning dope concentration and the solvent composition, but is generally 80 ° C. (50 to 120 ° C.). Therefore, in this step, spinning is performed together with the internal liquid from a double cylindrical tube nozzle in a state of maintaining a uniform liquid state at a temperature of 80 ° C. or higher, preferably 100 ° C. or higher, more preferably 120 ° C. or higher. It should be noted that the temperature during the discharging step should be set to 200 ° C. or lower from the viewpoint that the viscosity of the stock solution for spinning is not too low and does not impair spinning stability. Is preferable, and it is more preferable to set it as 180 degrees C or less.

  As described above, the hollow fiber PPO spinning stock discharged together with the inner liquid is solidified by non-solvent-induced phase separation from the inner liquid. As the internal solution, one that is discharged inside the PPO spinning solution discharged in the form of a hollow fiber and can coagulate the PPO spinning solution by non-solvent induced phase separation is preferably used. As such an internal solution, a solvent having a boiling point higher than that of water is suitably used when the spinning solution is discharged at 100 ° C. or higher as described above. Examples of such internal liquid include glycerin, ethylene glycol, diethylene glycol and the like. Among them, it is preferable to use ethylene glycol as the internal liquid because the subsequent water washing treatment becomes easy.

[3] Solidification step The spinning dope discharged in the discharge step described above is immersed in a solidification bath filled with a poor solvent in the subsequent solidification step. In addition, from the viewpoint of controlling the membrane structure such as increasing the polymer concentration on the surface of the hollow fiber-like material to make the surface dense, the PPO spinning stock solution formed into a hollow fiber shape after the discharging step partially removes the solvent. It is preferable to use for the said coagulation | solidification process after drying. In the coagulation step, the PPO spinning dope formed into a hollow fiber is coagulated into a hollow fiber by non-solvent induced phase separation.

  As the poor solvent used in the coagulation step, water or a mixed solution of water and an organic solvent is used because it is possible to quickly coagulate the PPO polymer in the spinning dope and it is easy to use. In the case of mixing an organic solvent, examples of the organic solvent include methanol, ethanol, glycerin, ethylene glycol, diethylene glycol, acetone, tetrahydrofuran, N-methyl-2-pyrrolidone, N, N-dimethylacetamide and the like. -Methyl-2-pyrrolidone is preferred.

  The temperature of the poor solvent at the time of immersing the PPO spinning dope is not particularly limited, but is preferably in the range of 0 to 50 ° C, more preferably in the range of 0 to 20 ° C. This is because when the temperature of the poor solvent is less than 0 ° C., the liquid in the coagulation bath freezes or the viscosity is too low, and the spinning stability tends to deteriorate, and the temperature of the poor solvent is 50. This is because when the temperature is higher than 0 ° C., the viscosity of the coagulation bath becomes too low, and the membrane structure tends to become unstable or the spinning stability tends to deteriorate. Further, the time for immersing the PPO discharge stock solution in a poor solvent is not particularly limited, but it is 0.1 to 100 seconds from the viewpoint of sufficiently solidifying, maintaining a hollow fiber shape, and not unnecessarily lengthening the process. Is preferably in the range of 1 to 50 seconds, and more preferably in the range of 1 to 50 seconds.

[4] Drying Step After the solidification step, the solidified hollow fiber-like material is dried from a state containing water without performing a solvent replacement treatment to obtain a hollow fiber carbon membrane precursor. In addition, it is preferable to use for the said drying process, after the hollow fiber-like thing which finished phase separation at the coagulation process fully washed with water and removed the remaining solvent.

  The “solvent replacement treatment” not performed in the drying step in the present invention means, for example, that the hollow fiber-like material containing water is gradually made higher in a solvent having a surface tension smaller than that of water such as alcohol and miscible with water. However, this is a method of finally completely replacing the solvent. Further, the hollow fiber-like product substituted with alcohol may be substituted with a solvent having a lower surface tension such as cyclohexane or n-hexane. The hollow fiber-like material dried from a state containing a solvent having a low surface tension is considered to easily maintain the initial pore structure. Further, as a method similar to solvent replacement, the same effect can be obtained when the poor solvent of the coagulation bath in the discharge step is previously made to have a low surface tension, such as alcohol.

  However, such a solvent replacement treatment is not necessary in the method for producing a hollow fiber carbon membrane of the present invention. According to the knowledge of the present inventors, even if such a solvent substitution process is performed, the hollow fiber formed from the PPO discharge stock solution has a porous structure in the flameproofing process and the carbonization process described later. This is because when melted and observed with a scanning electron microscope (SEM), the entire structure becomes a so-called homogeneous film structure that is dense and uniform at first glance. The PPO hollow fiber carbon membrane produced by performing the solvent replacement treatment becomes fragile and less flexible in spite of such a homogeneous membrane structure.

  On the other hand, the inventors of the present invention dried a membrane containing water without subjecting it to solvent substitution treatment to produce a hollow fiber carbon membrane. It was clarified that the flexibility is very excellent as compared with the hollow fiber carbon membrane subjected to the solvent substitution treatment. Further, there was no significant difference in gas separation and permeability between the two. That is, it was found that it is preferable to perform the drying treatment directly from the state containing water without performing the solvent replacement treatment in order to exhibit the excellent flexibility and gas separation performance of the hollow fiber carbon membrane.

[5] Carbonization treatment step Finally, the obtained hollow fiber carbon membrane precursor is subjected to carbonization treatment. Preferably, flameproofing treatment is performed as a pretreatment for the carbonization treatment. In the flameproofing treatment, the hollow fiber carbon membrane precursor is heated at 150 to 350 ° C., more preferably 200 to 300 ° C. in an air atmosphere for about 30 minutes to about 4 hours. By applying such a flameproofing treatment, the thermal crosslinking reaction of the polymer is promoted, and the membrane structure after carbonization becomes strong, which is advantageous in improving separation performance and flexibility.

As described above, the hollow fiber carbon membrane precursor preferably subjected to the flameproofing treatment is carbonized by a known method in the carbonization treatment step to obtain a hollow fiber carbon membrane. In the carbonization treatment, for example, the hollow fiber carbon membrane precursor is housed in a high-temperature furnace, and the pressure is reduced under a reduced pressure of 10 ⁻⁴ atm or less or in an inert gas atmosphere substituted with helium, argon gas, nitrogen gas, or the like. The heat treatment is performed without any problems. Moreover, the method of performing a carbonization process with the continuous carbonization furnace processed at high temperature under inert gas atmosphere may be taken, conveying a hollow fiber carbon membrane precursor continuously.

The heating conditions in the carbonization treatment are optimally selected depending on the type of polymer constituting the precursor, but preferably 500 to 850 under a reduced pressure of 10 ⁻⁴ atm or less or in an inert gas atmosphere. 30 minutes to 4 hours at ° C. More preferably, it is 30 minutes to 2 hours at 550 to 650 ° C. Since sufficient carbonization does not occur at temperatures below 500 ° C., the obtained hollow fiber carbon membrane is flexible, but sufficient gas separability cannot be obtained, and chemical resistance and heat resistance are inferior. This is not preferable. On the other hand, when the carbonization treatment, the film after coal hydrogenation becomes brittle unfavorable at temperatures above 850 ° C..

<Separation membrane module>
The present invention also provides a separation membrane module using the above-described hollow fiber carbon membrane of the present invention. The separation membrane module itself is known, and the separation membrane module of the present invention can also be realized by combining conventionally known appropriate materials and structures except that the hollow fiber carbon membrane of the present invention is used. For example, a separation membrane module having a typical structure is exemplified by a separation membrane module in which a plurality of the hollow fiber carbon membranes of the present invention cut to a predetermined length are bundled and both ends thereof are fixed with an adhesive. The At this time, one end of the bundled hollow fiber carbon membrane is hardened with an adhesive so as to open, and a cap having an opening is attached. Further, the other end of the bundled hollow fiber carbon membrane is hardened with an adhesive so as not to open, and a cap having no opening is attached. Note that this is merely an example, and any structure may be used as long as one end of the bundled hollow fiber carbon membrane is open and the other end is closed.

  Also for the method for producing the separation membrane module described above, a known method can be appropriately employed and is not particularly limited. For example, producing a plurality of hollow fiber carbon membranes of the present invention, bundling them in a state where each is cut into a predetermined length, and bonding one end of the bundled hollow fiber carbon membranes with an adhesive, Adhere the other end with an adhesive. Then, it opens by cut | disconnecting the edge part of the one side of the hollow fiber carbon membrane of the bundled state with an adhesive agent. Thereafter, the above-described separation membrane module can be manufactured by attaching a cap as described above to each end.

  The hollow fiber carbon membrane of the present invention and the separation membrane module using the same are particularly useful as a carbon membrane for gas separation. It can be particularly suitably used in fields such as hydrogen production, carbon dioxide separation and recovery, exhaust gas separation and recovery, natural gas separation, gas dehumidification, and production of oxygen from air.

Although the detail of the Example of this invention is shown below, this invention is not restrict | limited.
<Example 1>
36.25 g of N-methyl-2-pyrrolidone is added to 13.75 g of polyphenylene oxide (PPO) (No. 181781, manufactured by Aldrich) and kneaded to prepare a uniform suspension. A uniform spinning dope was obtained by heating while kneading at a temperature in the range of ° C. The obtained spinning dope was kept at 150 ° C., filled in a spinning dope extruder that was also heated and kept at 130 ° C., and the spinning dope was quantitatively extruded from the slit portion of the double cylindrical tube nozzle. From the inner hole of the double cylindrical tube nozzle, a constant amount of ethylene glycol is discharged as the inner liquid, and phase separation is induced in the inner layer portion of the spinning raw liquid extruded into a hollow shape, while the surface layer of the spinning raw liquid is at a 50 mm air gap. Part of the mixture was dried, and then phase separation was allowed to proceed completely in a coagulation bath filled with 30% aqueous N-methyl-2-pyrrolidone kept at 10 ° C. The solidified hollow fiber-like material was sufficiently washed with water and then dried in an oven at 80 ° C. while containing water.

  The obtained hollow fiber-like material is cut into a length of 50 cm, heated at a rate of 10 ° C./min in an air atmosphere in a muffle furnace, reached 280 ° C., and heated at the same temperature for 1 hour. Then, it was allowed to cool.

  The hollow fiber-like material subjected to air oxidation treatment is heated at a rate of 10 ° C./min in a high-temperature firing furnace at a rate of 10 ° C./min. After reaching 600 ° C., it is heated at the same temperature for 2 hours and then released. It cooled and obtained the PPO hollow fiber carbon membrane.

<Example 2>
A PPO hollow fiber carbon membrane was obtained in the same manner as in Example 1 except that the coagulation bath composition was changed to pure water kept at 10 ° C.

<Example 3>
A PPO hollow fiber carbon membrane was obtained in the same manner as in Example 1 except that the temperature in the carbonization treatment was changed to 700 ° C.

<Example 4>
A PPO hollow fiber carbon membrane was obtained in the same manner as in Example 1 except that the temperature in the carbonization treatment was changed to 500 ° C.

<Comparative Example 1>
The solidified hollow fiber membrane was thoroughly washed with water, then immersed in a 50 wt% ethanol aqueous solution for 2 hours, further immersed in ethanol overnight, then immersed in hexane overnight, and then dried at room temperature. Obtained a PPO hollow fiber carbon membrane in the same manner as in Example 1.

<Comparative example 2>
To 13.75 g of polyphenylene oxide (PPO) (No. 181781, manufactured by Aldrich), 36.25 g of chloroform was added and kneaded to prepare a uniform spinning stock solution, which was then filled into a spinning stock solution extruder. The spinning solution was quantitatively extruded from the slit part of the double cylindrical tube nozzle under normal temperature conditions. From the inner hole of the double cylindrical tube nozzle, ethanol is quantitatively discharged as an inner liquid, and a phase separation is induced in the inner layer portion of the spinning stock solution extruded in a hollow shape, while the spinning stock solution surface layer is dried, Thereafter, phase separation was allowed to proceed completely in a coagulation bath filled with ethanol kept at 10 ° C. The solidified hollow fiber was dried and wound up to obtain a hollow fiber. The hollow fiber-like material thus obtained was subjected to flameproofing treatment and carbonization treatment under the same conditions as in Example 1 to obtain a PPO hollow fiber carbon membrane.

  The evaluation methods of the samples (PPO hollow fiber carbon membrane or PPO hollow fiber) obtained in Examples and Comparative Examples are shown below.

(Flexibility evaluation method 1)
Based on JIS R7606: 2000, a tensile test was performed using a tensile tester technograph (TG-200NB, load cell type TT3D-10N, manufactured by Minebea Co., Ltd.). The cross-sectional area of the hollow fiber carbon membrane sample was measured according to the JIS R7607: 2000 C method. In order to prevent the end portion from being cut off at the gripping portion of the sample, the sample 2 is placed on both ends of the square frame-shaped sample mount 1 as shown in FIG. 1 and the both ends of the sample 2 are bonded to each other with the two-component epoxy resin 3. , Solidified. The chuck holding portions 5 at both ends of the prepared sample mount 1 are held and fixed by a chuck of a tensile tester. Subsequently, after disconnecting the connection portion 4, the tensile test of the sample 2 is started. The sample length was 25 mm. The pulling speed was 5 mm / min. The number of measurements was 20 and the average value was evaluated. Table 1 shows the elongation at break and the tensile modulus of elasticity for each sample.

(Flexibility evaluation method 2)
In addition to the tensile test described above, the flexibility of the PPO hollow fiber carbon membranes of Examples and Comparative Examples was also evaluated for the minimum bending radius when the hollow fiber carbon membrane was broken. Winding the hollow fiber carbon membrane 180 ° or more around a cylinder of various diameters different in 1 mm increments to check whether the hollow fiber carbon membrane breaks, the minimum bending radius is in the cylinder where the hollow fiber carbon membrane does not break, The flexibility of the film was evaluated by obtaining a cylinder having the minimum radius and showing the value by the value of the radius of the cylinder. The results are shown in Table 1.

(Evaluation of breakage rate of hollow fiber carbon membrane)
Using the PPO hollow fiber carbon membranes of Examples and Comparative Examples, 10 separation membrane modules each consisting of 100 hollow fiber carbon membranes were produced, and when gas separation evaluation was performed, The percentage of the number when the hollow fiber carbon membrane was broken and when the leak occurred during the gas permeation test was evaluated as the percentage of breakage. The results are shown in Table 1.

(Evaluation of gas separation performance of hollow fiber carbon membrane)
Using a test gas (He, CO ₂ , N ₂ ), the gas separation performance of the hollow fiber carbon membrane was measured. Each sample (PPO hollow fiber carbon membrane or PPO hollow fiber-like material) is mounted on a self-made hollow fiber gas permeability measuring device, and a test gas is supplied to the inner surface of each sample at a constant pressure, and the permeate gas flow rate is measured by a flow meter. Measured with At this time, the gas separation performance was evaluated by a gas permeation rate Q (10 ⁻⁶ cm ³ (STP) · cm ⁻² · s ⁻¹ · cmHg ⁻¹ (= GPU)) obtained by the following formula. Further, the ideal separation factor of the gas was obtained from the ratio of Q.

Q = {gas permeation flow rate (cm ³ · STP)} ÷ {membrane area (cm ² ) × time (seconds) × pressure difference (cmHg)}
The results are shown in Table 2.

  As is apparent from Tables 1 and 2, in Examples 1 to 4, it was found that PPO hollow fiber carbon membranes having high elongation at break and excellent handleability were obtained. Further, it can be seen that the minimum bending radius is as small as 4.5 to 9.0 mm, which is rich in flexibility. Furthermore, the damage rate at the time of module production is zero, and it can be seen that modularization is easy. On the other hand, Comparative Examples 1 and 2 have a remarkably low breaking elongation and a very small minimum bending radius of 30 mm, which is easily damaged. As a result, there was a problem in handling at the time of modularization, and the breakage rate was very high.

  1 sample mount, 2 samples, 3 epoxy resin, 4 connection part, 5 chuck gripping part.

Claims (2)

A method for producing a hollow fiber carbon membrane obtained by carbonizing a hollow fiber carbon membrane precursor using polyphenylene oxide and having a breaking elongation of 1 to 4%,
Dissolving polyphenylene oxide in an aprotic solvent;
Discharging polyphenylene oxide from the spinning nozzle at a temperature equal to or higher than the temperature-induced phase separation point to form a hollow fiber;
A step of solidifying the hollow fiber-shaped polyphenylene oxide with water or a mixed solution of water and an organic solvent;
A step of drying the solidified hollow fiber-like material from a state containing water without performing a solvent substitution treatment to obtain a hollow fiber carbon membrane precursor;
And a step of carbonizing the hollow fiber carbon membrane precursor. The method for producing a hollow fiber carbon membrane according to claim 1, wherein the tensile elastic modulus is 5 GPa or more .

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