JP5853530B2 - Hollow fiber carbon membrane, separation membrane module, and method for producing hollow fiber carbon membrane - Google Patents

Description

  The present invention relates to a hollow fiber carbon membrane, a separation membrane module, and a method for producing a hollow fiber carbon membrane.

  A hollow fiber carbon membrane obtained by carbonizing a polymer formed into a hollow fiber is excellent in heat resistance and chemical resistance, and can separate water from an organic solvent containing water by pervaporation separation. It can be suitably used for an apparatus such as a membrane module.

  For example, Patent Document 1 discloses that a precursor polymer membrane is prepared by extruding a membrane-forming stock solution containing sulfonated polyphenylene oxide into a water coagulation bath from the outer tube of a hollow fiber spinning nozzle having a double-tube annular structure. A hollow fiber carbon membrane obtained by carbonizing the membrane after infusibilizing the membrane is disclosed.

  Patent Document 2 discloses a hollow fiber carbon membrane introduced with metal ions, obtained by introducing metal ions into a precursor polymer membrane containing a hollow fiber-like sulfonated polyphenylene oxide, carbonizing after infusibility treatment. Has been.

  Patent Document 3 discloses a hollow fiber carbon membrane obtained by carbonizing a precursor polymer membrane containing polyphenylene oxide after infusibility treatment.

  A separation membrane formed by providing a carbon membrane on the surface of a porous substrate such as alumina as a support is also known.

  For example, Patent Document 4 discloses a molecular sieve carbon including a carbon film formed by immersing a cylindrical porous alumina tube in a phenol resin solution and drying it to form a phenol resin film and heating the phenol resin film. A membrane is disclosed.

  In Patent Document 5, after forming a base layer precursor arrangement by dip coating a base layer precursor forming solution containing a polyimide resin precursor varnish on a porous base material made of a monolithic alumina porous body, A carbon film laminate formed by dip-coating a separation layer precursor forming solution containing lignin, drying, and carbonizing is disclosed.

JP 2009-34614 A JP 2010-269229 A JP 2006-231095 A Japanese Patent No. 3647985 Special table 2010-510870 gazette

  As a hollow fiber carbon membrane in the case of separating water from an organic solvent containing water by a pervaporation separation method, it is required that the water separation performance and permeation performance of the hollow fiber carbon membrane are both good.

  However, when a hollow fiber carbon membrane was prepared according to Patent Document 1, the water separation performance by the pervaporation separation method is very excellent, but the entire hollow fiber carbon membrane is densified, so the water permeation performance to the hollow portion There was a problem that was not enough.

  Further, as described in the Examples of Patent Document 1, a membrane-forming stock solution containing a sulfonated polyphenylene oxide having a high degree of sulfonation (for example, a degree of sulfonation DS = 45%) is fed from a hollow fiber spinning nozzle into a coagulation bath. When a hollow fiber-like precursor polymer film is produced by extrusion, the precursor polymer film contains a large amount of moisture during the spinning process. As a result, the strength of the precursor polymer film decreases, and the precursor polymer film Difficult handling in mass production. Furthermore, since the precursor polymer membranes are easily bonded to each other in the drying step after the spinning step, there is also a problem that handling at the time of mass production of hollow fiber carbon membranes becomes difficult.

  Even in the hollow fiber carbon membrane described in Patent Document 2, a reduction in water permeation performance due to the densification of the entire structure of the hollow fiber carbon membrane cannot be avoided. Also, when spinning a film-forming stock solution containing a sulfonated polyphenylene oxide having a high degree of sulfonation, the precursor polymer film such that the precursor polymer films are likely to adhere to each other in the drying step after the spinning step, as in Patent Document 1. There arises a problem that handling at the time of mass production of molecular membranes and hollow fiber carbon membranes becomes difficult.

  The hollow fiber carbon membrane described in Patent Document 3 has a relatively large pore diameter and high hydrophobicity in the pores. Therefore, it is considered that the hollow fiber carbon membrane has a structure in which water easily passes through the hollow portion. However, in practice, when water is separated from an aqueous solution containing a low hydrophilic substance as a solvent by pervaporation separation, the low hydrophilic solvent easily enters the pores and adsorbs into the pores. Thus, there is a problem that water does not permeate, resulting in poor water permeation performance. Further, there is a problem that the hollow fiber carbon membrane is easily swelled and damaged by the solvent adsorbed in the pores.

  In addition, since the molecular sieve carbon membrane described in Patent Document 4 and the carbon membrane laminate described in Patent Document 5 each require the use of a porous substrate as a support, the size of an apparatus such as a separation membrane module is increased. Therefore, there was a problem of high cost. Furthermore, the molecular sieving carbon film described in Patent Document 4 and the carbon film laminate described in Patent Document 5 are respectively produced by applying an uncured resin polymer to the surface of a porous substrate and carbonizing it. For this reason, the carbon film is peeled off from the porous base material, or cracks are generated in the carbon film due to the difference in the thermal expansion coefficient between the porous base material and the carbon film. there were.

  In view of the above circumstances, the object of the present invention is a hollow fiber carbon membrane that is easy to manufacture, can be miniaturized, and has excellent water separation performance and permeation performance, and a separation membrane module using the same. An object of the present invention is to provide a method for producing the hollow fiber carbon membrane.

The present invention comprises a hollow fiber-shaped first carbon film and a second carbon film provided on the outer surface of the first carbon film, the second carbon film comprising a metal element, a sulfur element, only containing the metal element content of the second carbon film, more than the metal element content of the first carbon film, a sulfur element content of the second carbon film, elemental sulfur of the first carbon film It is a hollow fiber carbon membrane with more content .

  In the hollow fiber carbon membrane of the present invention, the precursor polymer of the second carbon membrane preferably contains a sulfonic acid group.

  In the hollow fiber carbon membrane of the present invention, the polymer containing a sulfonic acid group has a repeating structure of a repeating unit A represented by the following formula (I) and a repeating unit B represented by the following formula (II). Have

In the formula (I) and the formula (II), m and n each represent a natural number of 1 or more. In the formula (II), R ¹ and R ² are each independently —SO ₃ M, —SO _{3 represents} H or a hydrogen atom, M represents a metal element, R ¹ and R ² do not represent a hydrogen atom at the same time, and the ratio of the percentage of the number of repeating units B to the total number of repeating units A and B is: It is preferably larger than 15% and smaller than 100%.

Further, the hollow fiber carbon membrane of the present invention, within the scope of the scattering vector q of measured X-ray diffraction peaks by wide angle X-ray diffraction method of the second carbon film is 5 nm ^-1 up to 50 nm ^-1, the carbon structure It is preferable that an X-ray diffraction peak other than the X-ray diffraction peak derived from is present.

  In the hollow fiber carbon membrane of the present invention, the thickness of the second carbon membrane is preferably 500 nm or more and 10 μm or less.

  In the hollow fiber carbon membrane of the present invention, the second carbon membrane preferably has higher hydrophilicity than the first carbon membrane.

The present invention also provides a separation membrane module including any one of the hollow fiber carbon membranes described above.
The present invention is also a method for producing any one of the hollow fiber carbon membranes described above, the step of preparing a first precursor polymer that is a precursor polymer of the first carbon membrane, and a second carbon A step of preparing a second precursor polymer that is a precursor polymer of the membrane, a step of forming the first precursor polymer into a hollow fiber shape, and an outer surface of the first precursor polymer formed into a hollow fiber shape A method for producing a hollow fiber carbon membrane comprising a step of forming a hollow fiber carbon membrane precursor by installing a second precursor polymer and a step of carbonizing the hollow fiber carbon membrane precursor.

  Here, in the method for producing a hollow fiber carbon membrane of the present invention, the second precursor polymer preferably contains a sulfonic acid group.

  In the method for producing a hollow fiber carbon membrane of the present invention, the polymer containing a sulfonic acid group includes a repeating unit A represented by the following formula (I) and a repeating unit B represented by the following formula (II): Has a repeating structure of

In the formula (I) and the formula (II), m and n each represent a natural number of 1 or more. In the formula (II), R ¹ and R ² are each independently —SO ₃ M, —SO ₃ H represents a hydrogen atom, M represents a metal element, R ¹ and R ² do not represent a hydrogen atom at the same time, and the ratio of the percentage of the number of repeating units B to the total number of repeating units A and B is 15 It is preferable that it is larger than% and smaller than 100%.

Here, in the method for producing a hollow fiber carbon membrane of the present invention, the first precursor polymer is polyphenylene oxide having no sulfonic acid group , and the second precursor polymer is sulfonated polyphenylene oxide. Is preferred.

  Moreover, it is preferable that the manufacturing method of the hollow fiber carbon membrane of this invention further includes the process of flameproofing a hollow fiber carbon membrane precursor before the process of carbonizing.

  According to the present invention, a hollow fiber carbon membrane that is easy to manufacture, can be miniaturized, and has excellent water separation performance and permeation performance, a separation membrane module using the same, and manufacture of the hollow fiber carbon membrane A method can be provided.

It is typical sectional drawing of an example of the hollow fiber carbon membrane of this invention. (A) is typical sectional drawing along IIa-IIa of FIG. 1, (b) is an example of the fragmentary sectional view of the hollow fiber carbon membrane shown to (a), (c) is It is a figure which shows an example of the relationship between metal element content (mass%) and sulfur element content (mass%) in each film thickness direction of the 1st carbon film and 2nd carbon film which are shown to (b). is there. It is a flowchart of an example of the manufacturing method of the hollow fiber carbon membrane shown in FIG. It is typical sectional drawing of an example of the separation membrane module of this invention. 2 is an SEM (Scanning Electron Microscope) image of the hollow fiber carbon membrane of Example 1. 4 is another SEM image of the hollow fiber carbon membrane of Example 1. FIG. 4 is another SEM image of the hollow fiber carbon membrane of Example 1. FIG. (A) is a figure which shows the area | region where the elemental composition of the hollow fiber carbon membrane of Example 1 was analyzed, (b) is the energy dispersive X-ray spectroscopy of the hollow fiber carbon membrane of Example 1. (C) is a figure which shows the result of each elemental analysis of the 1st carbon film of the hollow fiber carbon film of Example 1, and the 2nd carbon film. X-rays showing X-ray diffraction intensity distributions obtained by the wide-angle X-ray diffraction method of the second carbon membrane of the hollow fiber carbon membrane of Example 1 and the first carbon membrane of the hollow fiber carbon membrane of Comparative Example 1 The example which compared the diffraction profile is shown. It is a typical block diagram of the pervaporation separation apparatus used for evaluation of the water separation performance and permeation performance by the pervaporation separation method of the hollow fiber carbon membranes of Examples 1 to 7 and Comparative Examples 1 to 3.

  Embodiments of the present invention will be described below. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts.

<Hollow fiber carbon membrane>
FIG. 1 shows a schematic cross-sectional view of an example of the hollow fiber carbon membrane of the present invention, and FIG. 2 (a) shows a schematic cross-sectional view along IIa-IIa of FIG. As shown in FIG. 1 and FIG. 2 (a), a hollow fiber carbon membrane 10 includes a hollow fiber-shaped first carbon membrane 1 having a hollow portion 3 and a first carbon membrane 1 provided on the outer surface of the first carbon membrane 1. 2 carbon films 2.

  As the first carbon film 1, a porous film containing carbon as a main component can be used. The first carbon film 1 may contain a component other than carbon as long as it contains carbon as a main component. The carbon content in the first carbon film 1 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.

  As the second carbon film 2, a porous film containing carbon as a main component and also containing a metal element and a sulfur element can be used. The second carbon film 2 may also contain components other than carbon, metal elements and sulfur elements as long as it contains carbon as a main component and also contains metal elements and sulfur elements. The carbon content in the second carbon film 2 is preferably 50% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more.

  In the hollow fiber carbon membrane 10, a liquid mixture of an organic solvent and water is brought into contact with the outer second carbon membrane 2, and water is selectively separated by the second carbon membrane 2, thereby the second carbon membrane. 2 is incorporated. Here, the type of the organic solvent is not particularly limited, and examples thereof include ethanol, isopropanol, ethyl acetate, acetone, and tetrahydrofuran. The water taken into the second carbon film 2 diffuses in the second carbon film 2 and moves to the inner first carbon film 1. Then, the water taken into the first carbon film 1 diffuses in the first carbon film 1 and moves from the first carbon film 1 to the hollow portion 3. As described above, in the hollow fiber carbon membrane 10, the second carbon membrane 2 is required to have a performance for efficiently separating water, and the first carbon membrane is required to have a performance for allowing water to efficiently pass through the hollow portion 3. Will be.

  As a result of intensive studies by the present inventors to solve the above-mentioned problems, a hollow fiber carbon membrane 10 having a composite structure of an inner first carbon membrane 1 and an outer second carbon membrane 2 is obtained. By adding a metal element and a sulfur element to the second carbon membrane 2 containing carbon as a main component, the water separation performance and the permeation performance from the mixed solution of the organic solvent and water by the pervaporation separation method are excellent. This is because it has been found that the self-supporting hollow fiber carbon membrane 10 can be easily manufactured and the apparatus can be downsized.

  The constituent components and the content of the hollow fiber carbon membrane 10 can be specified by, for example, energy dispersive X-ray spectroscopy (EDS).

  FIG. 2B shows an example of a partial cross-sectional view of the hollow fiber carbon membrane 10 shown in FIG. As shown in FIG. 2B, the first carbon film 1 has a thickness T1, and the second carbon film 2 has a thickness T2.

  The thickness T1 of the first carbon film 1 is not particularly limited. For example, the thickness T1 can be set to such a thickness that the mechanical strength is high enough to function as a support and the water permeation performance is high. The thickness T2 of the second carbon film 2 is also not particularly limited. For example, the thinness is high enough to increase the water permeation performance, and a defect that may be caused by uneven coating of the second precursor polymer and adhesion of dust described later. However, the thickness can be a thickness that does not affect the water separation performance.

  The thickness T2 of the second carbon film 2 is preferably 500 nm or more and 10 μm or less, more preferably 750 nm or more and 7 μm or less, and further preferably 1 μm or more and 5 μm or less. When the thickness T2 of the second carbon membrane 2 is 500 nm or more and 10 μm or less, particularly when the thickness T2 is 750 nm or more and 7 μm or less, and when the thickness T2 is 1 μm or more and 5 μm or less, water separation of the hollow fiber carbon membrane 10 is performed. Both the performance and the transmission performance tend to be excellent.

  The total film thickness (T1 + T2) of the first carbon film 1 and the second carbon film 2 is preferably 1 μm or more and 50 μm or less, and more preferably 5 μm or more and 20 μm or less. When the total film thickness (T1 + T2) of the first carbon film 1 and the second carbon film 2 is 1 μm or more and 50 μm or less, particularly when the total film thickness is 5 μm or more and 20 μm or less, the water separation of the hollow fiber carbon membrane 10 is performed. Both the performance and the transmission performance tend to be excellent.

  Further, from the viewpoint of making both the water separation performance and the permeation performance of the hollow fiber carbon membrane 10 excellent, the outer diameter of the hollow fiber carbon membrane 10 is preferably 50 μm or more and 500 μm or less, and 100 μm or more and 400 μm or less. More preferably.

  The thickness T1 of the first carbon film 1, the thickness T2 of the second carbon film 2, the total film thickness (T1 + T2) of the first carbon film 1 and the second carbon film 2, and hollow fiber carbon The outer diameter of the film 10 can be measured by, for example, a scanning electron microscope (SEM).

  FIG. 2C shows the metal element content (mass%) and the sulfur element content (mass%) in the film thickness directions of the first carbon film 1 and the second carbon film 2 shown in FIG. %)). The horizontal axis of FIG. 2 (c) shows the film thickness direction from the second carbon film 2 to the first carbon film 1, and the vertical axis of FIG. 2 (c) contains the respective metal elements and sulfur elements. The amount (mass%) is shown. In FIG. 2C, the solid line indicates the metal element content (mass%), and the broken line indicates the sulfur element content (mass%).

  For example, as shown in FIG. 2 (c), in the hollow fiber carbon membrane 10, the metal element content (mass%) of the second carbon membrane 2 is the metal element content (mass%) of the first carbon membrane 1. It is preferable that the sulfur element content (mass%) of the second carbon film 2 is larger than the sulfur element content (mass%) of the first carbon film 1. In this case, the water separation performance and permeation performance of the hollow fiber carbon membrane 10 can be further improved. In the above, the metal element content (mass%) and the sulfur element content (mass%) of the first carbon film 1 may each be 0 (mass%).

  Here, the metal element that can be included in the first carbon film 1 and the second carbon film 2 is not particularly limited, and examples thereof include sodium, potassium, and magnesium. The metal element content of the second carbon film 2 is preferably 0.1% by mass or more and 30% by mass or less, and the metal element content of the first carbon film 1 is the metal of the second carbon film 2 It is preferably less than the element content and 0% by mass or more and 10% by mass or less. In this case, the water separation performance and permeation performance of the hollow fiber carbon membrane 10 tend to be improved.

  The sulfur element content of the second carbon film 2 is preferably 0.1% by mass or more and 30% by mass or less, and the sulfur element content of the first carbon film 1 is the second carbon film 2. It is preferable that the content is less than the sulfur element content. In this case, the water separation performance and permeation performance of the hollow fiber carbon membrane 10 tend to be improved.

  The metal element content of the first carbon film 1, the metal element content of the second carbon film 2, the sulfur element content of the second carbon film 2, and the sulfur element content of the second carbon film 1 are as follows: , Respectively, can be specified by energy dispersive X-ray spectroscopy, for example.

Further, as described later, in the range in which the second scattering vector q of X-ray diffraction peak measured by wide angle X-ray diffraction of the carbon film 2 of the hollow fiber carbon membrane 10 is 5 nm ^-1 up to 50 nm ^-1 It is preferable that an X-ray diffraction peak other than the X-ray diffraction peak derived from the carbon structure exists. In this case, the water separation performance and permeation performance of the hollow fiber carbon membrane 10 can be further improved.

  Furthermore, as a result of intensive studies by the present inventors, a hydrophobic and large pore diameter membrane is used as the first carbon membrane 1 of the hollow fiber carbon membrane 10, and a hydrophilic and small pore size is used as the second carbon membrane 2. It has been found that by using a membrane, a self-supporting hollow fiber carbon membrane having further excellent water separation performance and permeation performance can be obtained. That is, since the outer second carbon film 2 has a small pore diameter and high hydrophilicity in the pores, only water can be efficiently permeated without permeating a solvent having low hydrophilicity. Further, since the inner first carbon membrane 1 has a large pore diameter and high hydrophobicity in the pores, water that has permeated from the second carbon membrane 2 is allowed to pass through the pores of the first carbon membrane 1. It can be quickly permeated into the hollow portion 3 without being adsorbed inside. Thereby, both the water separation performance and the permeation performance of the hollow fiber carbon membrane 10 can be made excellent. In addition, the hollow fiber carbon membrane 10 in which the first carbon membrane 1 and the second carbon membrane 2 are combined does not require a support made of a porous substrate. Manufacture is easy, and downsizing of a device such as a separation membrane module using the hollow fiber carbon membrane 10 is facilitated.

  Therefore, from the above viewpoint, the second carbon membrane 2 is thinner than the first carbon membrane 1 in order to make both the water separation performance and permeation performance of the hollow fiber carbon membrane 10 excellent. It is preferable that the pore diameter is small.

  Note that the pore diameter of the first carbon membrane 1 and the pore diameter of the second carbon membrane 2 are, for example, those of the hollow fiber carbon membrane made of each single component of the first carbon membrane 1 or the second carbon membrane 2. By preparing and evaluating the separation performance of the mixture of organic solvent and water by pervaporation separation, and comparing the permeation amount of organic solvent molecules having a molecular diameter larger than water, that is, pervaporation separation described later It can be evaluated by measuring the separation factor by the method.

  From the above viewpoint, the second carbon membrane 2 is more hydrophilic than the first carbon membrane 1 in order to make both the water separation performance and the permeation performance of the hollow fiber carbon membrane 10 excellent. It is preferable to have properties.

  Since the hollow fiber carbon membrane 10 having the above-described configuration is excellent in both water separation performance and permeation performance, it is particularly suitable for use in removing water from a mixture of an organic solvent and water by pervaporation separation. Can be used. Further, since the hollow fiber carbon membrane 10 is a self-supporting hollow fiber carbon membrane that does not require a support made of a porous substrate, it is easy to manufacture and can be downsized. A separation membrane module can be produced.

<Method for producing hollow fiber carbon membrane>
FIG. 3 shows a flowchart of an example of a method for producing the hollow fiber carbon membrane 10 shown in FIG. Hereinafter, an example of a method for producing the hollow fiber carbon membrane 10 shown in FIG. 1 will be described with reference to FIG.

  First, as shown in step S1, a step of preparing a first precursor polymer is performed. Here, the first precursor polymer is not particularly limited as long as it is a precursor polymer that becomes the precursor of the first carbon film 1, but from the viewpoint of facilitating water permeation, a carbonization treatment step described later is performed. It is preferable that the polymer has a molecular structure in which the first carbon film 1 having a large pore size and high hydrophobicity is formed after the passage. In addition, from the viewpoint of preventing the first carbon film 1 and the second carbon film 2 from being peeled, the first precursor polymer may be a precursor of the second carbon film 2 in a step of performing a flame resistance treatment to be described later. It is preferable to include a polymer having a molecular structure that easily crosslinks with a second precursor polymer, which will be described later.

  As the first precursor polymer, for example, a known carbonizable polymer such as polyphenylene oxide, polyimide, polyamide, polyamideimide, polyarylate, polyacrylonitrile and the like can be used. From the viewpoint of obtaining a hydrophobic first carbon film 1 having a large pore diameter later, polyphenylene oxide is preferable, and polyphenylene oxide having a weight average molecular weight of 5,000 to 100,000 is more preferable. When the weight average molecular weight of the polyphenylene oxide is 5,000 or more and 100,000 or less, the solution viscosity of the polyphenylene oxide in the production process of the hollow fiber carbon membrane precursor becomes appropriate, the handling property in spinning is improved, and the hollow fiber carbon membrane Tends to be easy to manufacture. In order to control the pore diameter of the first carbon film 1, for example, a thermally decomposable polymer and / or a filler may be mixed with the first precursor polymer.

  Next, as shown in step S2, a step of preparing a second precursor polymer is performed. Here, the second precursor polymer is not particularly limited as long as it is a precursor polymer that becomes a precursor of the second carbon film 2, but the second carbon film 2 having a small pore diameter and high hydrophilicity is used. From the viewpoint of obtaining, the second precursor polymer is preferably a polymer containing a sulfonic acid group.

  The polymer containing a sulfonic acid group is not particularly limited. For example, sulfonated polysulfone, sulfonated polyethersulfone, sulfonated polyallyl ether, sulfonated polyimide, or sulfonated polyphenylene oxide is preferably used. Alternatively, it is more preferable to use a sulfonated polyethersulfone, and it is more preferable to use a sulfonated polyphenylene oxide.

  The sulfonated polyphenylene oxide has a repeating structure of a repeating unit A represented by the following formula (I) and a repeating unit B represented by the following formula (II), and is repeated with respect to the total number of the repeating units A and B. Percentage ratio DS of the number of units B (degree of sulfonation: 100 × (number of repeating units B) / (total number of repeating units A and B)) is 15 <DS <100, preferably 30 <DS A sulfonated polyphenylene oxide containing a sulfonic acid group satisfying the relational expression of <100, more preferably 40 <DS <100 is preferable. As the ratio DS of the percentage of the number of repeating units B to the total number of repeating units A and B of the sulfonated polyphenylene oxide increases, the hydrophilicity of the second carbon film 2 obtained through the carbonization treatment step described later. Therefore, the water separation performance tends to be high.

  In the above formulas (I) and (II), m and n are each a natural number of 1 or more, and these are not particularly limited, but m is preferably in the range of 1 to 2000, more preferably It is in the range of 5 to 1000, and n is preferably in the range of 1 to 2000, more preferably in the range of 5 to 1000.

In the above formula (II), R ¹ and R ² each independently represent —SO ₃ M, —SO ₃ H or a hydrogen atom, M represents a metal element, and R ¹ and R ² represent hydrogen atoms simultaneously. Not shown. Here, M represents a metal element, and examples thereof include one or more selected from monovalent metal elements such as lithium, sodium, and potassium, and divalent or higher metal elements such as calcium, magnesium, aluminum, and iron. Among these, when a hollow fiber carbon membrane is produced, the pore diameter of the second carbon membrane 2 suitable for separation by the pervaporation separation method can be obtained, and the hydrophilicity of the second carbon membrane 2 becomes higher. As the metal element, sodium and / or potassium is preferable, and sodium is particularly preferable.

  The structure of the sulfonated polyethersulfone (SPES) has, for example, a repeating unit of a repeating unit C represented by the following formula (III) and a repeating unit D represented by the following formula (IV) and the repeating unit: The percentage DS of the number of repeating units D to the total number of C and repeating units D (degree of sulfonation: 100 × (number of repeating units D) / (total number of repeating units C and repeating units D)) is 15 <DS <100, preferably 30 <DS <100, more preferably sulfonated polyethersulfone containing a sulfonic acid group satisfying the relational expression of 40 <DS <100. As the ratio DS of the percentage of the number of repeating units D to the total number of repeating units C and repeating units D of the sulfonated polyethersulfone increases, the hydrophilicity of the second carbon film 2 obtained through the carbonization treatment step described later is increased. Since the property increases, the water separation performance tends to increase.

  In the above formulas (III) and (IV), k and l are each a natural number of 1 or more, and these are not particularly limited, but k is preferably in the range of 1 to 2000, more preferably It is in the range of 5-1000, and l is preferably in the range of 1-2000, more preferably in the range of 5-1000.

In the above formula (IV), R ³ and R ⁴ each independently represent —SO ₃ M or —SO ₃ H, and M represents a metal element. Here, M which shows a metal element shows 1 or more types chosen from monovalent metal elements, such as lithium, sodium, or potassium, or bivalent or more metal elements, such as calcium, magnesium, aluminum, or iron. Among these, when a hollow fiber carbon membrane is produced, the pore diameter of the second carbon membrane 2 suitable for separation by the pervaporation separation method can be obtained, and the hydrophilicity of the second carbon membrane 2 becomes higher. As the metal element, sodium and / or potassium is preferable, and sodium is particularly preferable.

  The polymer containing the sulfonic acid group has different solubility in a solvent depending on the DS value, but a known solvent is used as a solvent for dissolving the polymer containing the sulfonic acid group. be able to. As such a solvent, for example, a solvent such as dimethylacetamide, N-methyl-2-pyrrolidone, methanol, ethanol, water, or a mixed solvent obtained by mixing at least two of these can be used.

  It is preferable that at least a part of the sulfonic acid group of the polymer containing a sulfonic acid group is neutralized with a metal ion. In this case, the water separation performance of the second carbon membrane 2 tends to be improved.

The metal ion can be, for example, a monovalent metal ion such as lithium, sodium, or potassium, or a divalent or higher metal ion such as calcium, magnesium, aluminum, or iron. From the viewpoint of improving the separation performance, sodium ions or potassium ions are preferable, and sodium ions are more preferable. The polymer containing the sulfonic acid group may contain two or more of the above metal ions. That is, when at least one of R ¹ and R ² of at least one repeating unit B among the repeating units B represented by the above formula (II) of the sulfonated polyphenylene oxide represents —SO ₃ M, M is: The metal which comprises said metal ion will be shown. Further, when at least one of R ³ and R ⁴ of at least one repeating unit D among the repeating units D represented by the above formula (IV) of the sulfonated polyethersulfone represents —SO ₃ M, M Indicates the metal constituting the metal ion.

  The metal ions may be introduced into the raw polymer of the polymer solution used in the spinning process or dip coating process described later, and the hollow fiber carbon membrane precursor after the spinning process or dip coating process is replaced with a desired metal ion. It may be introduced by immersing it in a solution containing it.

  In addition, the order of the step of preparing the first precursor polymer (step S1) and the step of preparing the second precursor polymer (step S2) is not particularly limited, and step S1 may be performed first. Step S2 may be performed first, and Step S1 and Step S2 may be performed in parallel.

  Next, as shown in step S3, a step of forming the first precursor polymer into a hollow fiber shape is performed. The step of forming the first precursor polymer into a hollow fiber shape is not particularly limited. For example, the inner liquid is extruded from the inside of the double cylindrical tube nozzle, and at the same time, the spinning stock solution containing the first precursor polymer is extruded from the outside. Then, after drying in a space (air gap) of a desired length, a dry-wet spinning method in which the spinning stock solution is solidified in a poor solvent coagulation bath to form a first precursor polymer formed into a hollow fiber shape It can be used suitably.

  As a solvent used for dissolving the first precursor polymer when preparing the spinning dope containing the first precursor polymer, for example, when the first precursor polymer contains polyphenylene oxide, polyphenylene oxide A known solvent is used as a good solvent. As a good solvent for polyphenylene oxide, as described in known literature (G. Chowdhury, B. Kruczek, T. Matsuura, Polyphenylene Oxide and Modified Polyphenylene Oxide Membranes Gas, Vapor and Liquid Separation, 2001, Springer), for example, , Benzene, toluene or chloroform can be used, and among them, chloroform can be preferably used. In addition, a known solvent such as acetone, methyl ethyl ketone or tetrahydrofuran that is miscible with the above-mentioned good solvent and is a poor solvent for polyphenylene oxide is added to the spinning dope as long as uniform solubility of polyphenylene oxide is ensured. The solubility of the spinning dope can be changed to control the pore size, pore size distribution, etc. of the first carbon membrane 1.

  The internal liquid is not particularly limited as long as it is a liquid that solidifies the spinning stock solution containing the first precursor polymer extruded into a hollow shape from the inside, and for example, ethanol can be used. The poor solvent for the coagulation bath is not particularly limited, and for example, ethanol can be used. Further, by adding a desired solvent to the poor solvent of the coagulation bath and changing the solvent exchange rate between the spinning solution and the coagulation solution, the pore diameter and pore diameter distribution of the first carbon membrane 1 are controlled. May be. The first precursor polymer formed into a hollow fiber shape by immersion in a coagulation bath is dried and wound up by, for example, a winder device.

  Moreover, the outer diameter, thickness, etc. of the first carbon film 1 can be appropriately adjusted by adjusting the shape of the double cylindrical tube nozzle.

  Next, as shown in step S4, a step of placing the second precursor polymer on the outer surface of the first precursor polymer formed into a hollow fiber shape is performed. The step of placing the second precursor polymer on the outer surface of the hollow fiber-shaped first precursor polymer is not particularly limited. For example, the first precursor polymer formed into a hollow fiber shape is used as the second precursor polymer. After immersing in a dip solution containing a precursor polymer, it can be carried out by lifting and drying.

  The concentration of the second precursor polymer in the dip liquid is preferably 1% by mass or more and 50% by mass or less, and more preferably 5% by mass or more and 20% by mass or less. By making the hollow fiber-shaped first precursor polymer coated with the dip liquid by drying at a predetermined pulling speed, the second precursor polymer is dried at a desired thickness to the first precursor polymer. A hollow fiber carbon membrane precursor placed on the outer surface of the can be prepared.

  Since the adhesion of dust to the second precursor polymer during the dip coating process becomes a defect of the second carbon film 2, the hollow fiber carbon film precursor is produced in an atmosphere with reduced dust. It is preferable. In order to reduce coating unevenness of the dip-coated second precursor polymer and adhesion of dust, the first precursor polymer formed into a hollow fiber shape is immersed in a solvent, or the dip coating process is performed a plurality of times. A pretreatment step may be performed.

  In the above, after the step of forming the first precursor polymer into a hollow fiber shape (step S3), the second precursor is formed on the outer surface of the first precursor polymer formed into a hollow fiber shape. Although the step of installing the polymer (step S4) is performed, step S3 and step S4 may be performed simultaneously. As a method of performing Step S3 and Step S4 simultaneously, using a triple cylindrical tube nozzle, a spinning stock solution containing a first precursor polymer, a spinning stock solution containing a second precursor polymer, and these spinning stock solutions Examples thereof include a method of forming a hollow fiber carbon membrane precursor by extruding the internal solution for coagulation at the same time and using a dry spinning method, a wet spinning method, a dry wet spinning method, or the like.

  Further, if step S3 is performed after step S1, step S3 may be performed before step S2. Further, if step S4 is performed after step S2, step S4 may be performed before step S1.

  Next, as shown in step S5, a process of flameproofing the hollow fiber carbon membrane precursor is performed. Here, the flame-proofing process of the hollow fiber carbon membrane precursor is not particularly limited, and a conventionally known method can be used. For example, the hollow fiber carbon membrane precursor produced as described above is air-treated. In an atmosphere, it can carry out by heating at 150 degreeC-350 degreeC, for example for 30 minutes-4 hours, for example.

  The hollow fiber carbon membrane 10 may be formed by performing the carbonization treatment step described later directly on the hollow fiber carbon membrane precursor produced as described above. However, by performing the carbonization treatment step after the flameproofing treatment step, the cross-linking reaction of the first precursor polymer and the second precursor polymer is promoted, respectively, so that the hollow fiber carbon after the carbonization treatment step Since the membrane 10 can be densified to improve mechanical strength, the water separation performance by the hollow fiber carbon membrane 10 after the carbonization treatment step tends to be improved. Further, in the flameproofing treatment step, the first precursor polymer and the second precursor polymer are cross-linked so that separation between the first carbon film 1 and the second carbon film 2 is difficult to occur. A hollow fiber carbon membrane 10 can be formed.

Next, as shown in step S6, a step of carbonizing the hollow fiber carbon membrane precursor is performed. Here, the step of carbonization treatment is not particularly limited, and a conventionally known method can be used. For example, the hollow fiber carbon membrane precursor is accommodated in a high temperature furnace and the pressure is reduced to 10 ⁻⁴ atm or less. It can be performed by heating the hollow fiber carbon membrane precursor in an air atmosphere or in an inert gas atmosphere such as helium, argon gas or nitrogen gas which is not decompressed. Moreover, the process of carbonizing can also be performed by heat-processing at high temperature in inert gas atmosphere, conveying a hollow fiber carbon membrane precursor continuously, for example in a continuous carbonization furnace.

The heating condition of the hollow fiber carbon membrane precursor in the carbonization treatment step can be appropriately selected depending on the types of polymers constituting the first precursor polymer and the second precursor polymer, but 10 ⁻⁴ atm. It is preferable to heat at 500 ° C. to 850 ° C. for 30 minutes to 4 hours in an atmosphere of reduced pressure or in an inert gas atmosphere that is not decompressed, and in an atmosphere of reduced pressure of 10 ⁻⁴ atm or not. It is more preferable to heat at 550 ° C. to 650 ° C. for 30 minutes to 2 hours in an active gas atmosphere. According to these preferable heating conditions, particularly more preferable heating conditions, the apparatus can be miniaturized, and the hollow fiber carbon membrane 10 excellent in water separation performance and permeation performance tends to be efficiently produced. .

  The hollow fiber carbon membrane 10 produced as described above was subjected to elemental analysis of the cross section and / or outer surface of the second carbon membrane 2 of the hollow fiber carbon membrane 10 by energy dispersive X-ray spectroscopy. In this case, it is detected that the second carbon film 2 contains a metal element and a sulfur element.

  For example, when a polymer containing a sulfonic acid group is used as the second precursor polymer, the sulfonic acid group is thermally decomposed and eliminated in a temperature range of 150 ° C. to 450 ° C. Sulfur should not originally exist in the hollow fiber carbon membrane 10 that has undergone the conversion treatment. However, for example, when the second carbon film 2 is formed using the second precursor polymer in which at least a part of the sulfonic acid group is neutralized with a metal ion, sulfur is contained in the second carbon film 2. The element was found to be present.

Although the details of the structure of the second carbon film 2 containing a metal element and a sulfur element are unknown, the present inventors have examined the second carbon film 2 of the hollow fiber carbon film 10 by X-ray diffraction using a wide angle X-ray diffraction method. the measured ray diffraction peak, in the range of the scattering vector q of X-ray diffraction peak is 5 nm ^-1 up to 50 nm ^-1, X-ray diffraction peaks other than X-ray diffraction peaks derived from the carbon structure was observed. When the present inventors identified this X-ray diffraction peak, it was confirmed that this X-ray diffraction peak was derived from a metal oxide or sulfate.

  Here, the X-ray diffraction peak derived from the carbon structure means two X-ray diffraction peaks and an amorphous halo corresponding to the (002) plane and the (10) plane of the carbon crystal. In addition, the appearance position and / or the half width of the X-ray diffraction peak other than the X-ray diffraction peak derived from the carbon structure varies depending on the heating temperature and / or the heating time in the flameproofing process and / or the carbonization process. To do. In particular, sulfonic acid groups neutralized with metal ions generate highly hydrophilic metal oxides or sulfate microcrystals when thermally decomposed in a flameproofing process and / or a carbonization process. It is considered that the hydrophilicity becomes higher due to the composite with the carbon structure in the second carbon film 2.

  For example, Shujiang Ding et al., Colloid Polymer Science (2008), 286,1093-1096 describes carbon composites made of sulfonated polystyrene. , Sulfonic acid groups can easily take up metal ions, and when carbonized, a composite of metal and carbon is formed, and a hierarchical pore channel structure with high separation selectivity and high permeability can be produced. It has been shown.

  In particular, in the hollow fiber carbon membrane 10, a hydrophilic membrane with a small pore diameter is used as the outer second carbon membrane 2, and a hydrophobic membrane with a large pore diameter is used as the inner first carbon membrane 1. Is a self-supporting hollow that can increase the amount of water permeated because it has excellent separation performance for separating water from a mixture of an organic solvent and water in the pervaporation separation method, and also has excellent water permeation performance. It has been found that a thread carbon film 10 can be obtained.

<Separation membrane module>
FIG. 4 shows a schematic cross-sectional view of an example of the separation membrane module of the present invention. The separation membrane module 20 shown in FIG. 4 has a structure in which a plurality of hollow fiber carbon membranes 10 cut to a predetermined length are bundled and both ends thereof are solidified with an adhesive 11 and an adhesive 12, respectively. doing. The end of the hollow fiber 3 that is solidified with the adhesive 11 in the hollow portion 3 is open, but the end that is solidified with the adhesive 12 is not opened with the adhesive 12. Closed. A cap 14 is attached to the end of the hollow fiber carbon membrane 10 on the adhesive 11 side, and a cap 15 is attached to the end of the adhesive 12 side. Needless to say, the structure is not limited to the above as long as one end of the hollow portion 3 of the hollow fiber carbon membrane 10 is open and the other end is closed. In addition to the structure described above, the end on the side that is hardened with the adhesive 12 is also opened, and the same thing as the cap 14 is attached in place of the cap 15 so that both ends are opened and the separation efficiency is increased. The separation membrane module may be improved.

  The separation membrane module 20 having the above-described configuration is immersed in a mixed solution of an organic solvent and water, and the hollow fiber carbon membrane 10 is in contact with the mixed solution of the organic solvent and water. The gas is extracted in the direction of 13 to make the atmosphere in the cap 14 a reduced pressure atmosphere. Thereby, water is selectively separated and vaporized by the second carbon membrane 2 from the mixed liquid in contact with the outer surface of the second carbon membrane 2 of the hollow fiber carbon membrane 10 and permeates the first carbon membrane 1. The water efficiently permeates from the first carbon membrane 1 to the hollow portion 3. Then, the water molecules that have moved to the hollow portion 3 flow into the cap 14 from the end on the adhesive 11 side, and are taken out from the cap 14 in the direction of the arrow 13.

  The separation membrane module 20 shown in FIG. 4 can be manufactured as follows, for example. First, a plurality of hollow fiber carbon membranes 10 are produced as described above, bundled in a state of being cut into predetermined lengths, and one end of the bundled hollow fiber carbon membranes 10 is bonded to the adhesive 11. And the other end is bonded with an adhesive 12. Then, the hollow part 3 of the hollow fiber carbon membrane 10 on the adhesive 11 side is opened by cutting one end of the hollow fiber carbon membrane 10 on the adhesive 11 side together with the adhesive 11. Thereafter, the cap 14 is attached to the end of the hollow fiber carbon membrane 10 on the adhesive 11 side, and the cap 15 is attached to the end of the adhesive 12 to produce the separation membrane module 20 shown in FIG. it can.

  Since the separation membrane module 20 uses the hollow fiber carbon membrane 10 described above, the separation membrane module is easy to manufacture, can be downsized, and has excellent water separation performance and permeation performance. Can do.

<Example 1>
(Step of preparing the first precursor polymer)
As the first precursor polymer, polyphenylene oxide (PPO) manufactured by Aldrich (No. 181781) was prepared.

(Step of preparing a second precursor polymer)
Moreover, the sulfonated polyphenylene oxide (SPPO) as the second precursor polymer was prepared as follows. First, a mixed solution of chlorosulfuric acid and chloroform was added dropwise at room temperature in a state where PPO manufactured by Aldrich (No. 181781) was dissolved in chloroform, and a sulfonation reaction was advanced to obtain a reaction product. The reaction product thus obtained was reprecipitated and washed with water, and then immersed in a 0.5 M aqueous sodium carbonate solution to neutralize sulfonic acid groups with sodium ions. And the sodium carbonate salt which remained in the reaction material was removed completely by washing the reaction material after immersion in the sodium carbonate aqueous solution with water. Thereafter, the reaction product was dried to obtain SPPO having a sulfonation degree DS = 45% as a target second precursor polymer.

(Process of forming the first precursor polymer into a hollow fiber shape)
PPO as a first precursor polymer is added to chloroform so that the first precursor polymer concentration is 27.5% by mass, and stirred at room temperature to dissolve PPO in chloroform. Got.

  Subsequently, the inner liquid ethanol is extruded from the inside of the double cylindrical tube nozzle, and at the same time, the above spinning stock solution is extruded from the outside, dried in an air gap, and then the spinning stock solution is solidified in a coagulation bath filled with ethanol. By doing this, the 1st precursor polymer shape | molded by the hollow fiber shape was produced. Thereafter, the first precursor polymer formed into a hollow fiber shape was dried and wound up with a winder.

(Installing the second precursor polymer on the outer surface of the first precursor polymer)
Methanol and dimethylacetamide were mixed at a mass ratio of 50:50 to prepare a mixed solvent. And so that SPPO density | concentration might be 10 mass%, SPPO as a 2nd precursor polymer was dissolved in the mixed solvent, the dip liquid was produced, and the bathtub was filled with the dip liquid.

  And after immersing the 1st precursor polymer shape | molded in the hollow fiber shape produced as mentioned above in the bathtub satisfy | filled with the dip liquid, it is made to dry while pulling up, A hollow fiber carbon membrane precursor Was made.

(Process for flameproofing)
The hollow fiber carbon membrane precursor produced as described above was placed in a muffle furnace, heated to 260 ° C. at a rate of 2 ° C./min in an air atmosphere, heated at this temperature for 1 hour, and then allowed to cool. As a result, the first precursor polymer and the second precursor polymer of the hollow fiber carbon membrane precursor were crosslinked.

(Process for carbonization)
The hollow fiber carbon membrane precursor after the flameproofing treatment is placed in a high temperature furnace, heated to 600 ° C. at a rate of 10 ° C./min in a nitrogen atmosphere, heated at this temperature for 2 hours, and then allowed to cool. Thus, a hollow fiber carbon membrane of Example 1 composed of a hollow carbon inner first carbon membrane and an outer second carbon membrane was obtained. According to the measurement using SEM described later, the outer diameter of the hollow fiber carbon membrane of Example 1 was 300 μm, and the total thickness of the first carbon membrane and the second carbon membrane was 10 μm.

<Example 2>
Example except that SPPO having a degree of sulfonation DS = 45% as the second precursor polymer was prepared using a magnesium nitrate aqueous solution having a magnesium nitrate concentration of 20% by mass instead of a 0.5 M sodium carbonate aqueous solution. The hollow fiber carbon membrane of Example 2 was obtained using the same method and the same conditions as in Example 1. According to the measurement using SEM described later, the outer diameter of the hollow fiber carbon membrane of Example 2 was 300 μm, and the total thickness of the first carbon membrane and the second carbon membrane was 10 μm.

<Example 3>
A hollow fiber carbon membrane of Example 3 was obtained in the same manner and under the same conditions as in Example 1 except that the SPPO concentration in the dip solution was changed from 10% by mass to 15% by mass. According to the measurement using SEM described later, the outer diameter of the hollow fiber carbon membrane of Example 3 was 300 μm, and the total thickness of the first carbon membrane and the second carbon membrane was 14 μm.

<Example 4>
A hollow fiber carbon membrane of Example 4 was obtained in the same manner and under the same conditions as in Example 1 except that the SPPO concentration in the dip solution was changed from 10% by mass to 6.5% by mass. According to the measurement using SEM described later, the outer diameter of the hollow fiber carbon membrane of Example 4 was 300 μm, and the total thickness of the first carbon membrane and the second carbon membrane was 10 μm.

<Example 5>
The SPPO concentration in the dip solution was changed from 10% by mass to 20% by mass, and the same pulling rate as that of the first precursor polymer formed into a hollow fiber shape from the dip solution was increased. The hollow fiber carbon membrane of Example 5 was obtained using the same method and the same conditions. According to the measurement using SEM described later, the outer diameter of the hollow fiber carbon membrane of Example 5 was 300 μm, and the total thickness of the first carbon membrane and the second carbon membrane was 21 μm.

<Example 6>
The same as Example 1 except that the step of preparing the second precursor polymer and the step of installing the second precursor polymer on the outer surface of the first precursor polymer were changed as follows. The hollow fiber carbon membrane of Example 6 was obtained using the same method and the same conditions. According to the measurement using SEM described later, the outer diameter of the hollow fiber carbon membrane of Example 6 was 300 μm, and the total thickness of the first carbon membrane and the second carbon membrane was 10 μm.

(Step of preparing a second precursor polymer)
As the second precursor polymer, a sulfonated polyethersulfone (SPES) comprising a combination of a repeating unit C and a repeating unit D each having a chemical structure represented by the above formulas (III) and (IV) is as follows: I prepared as follows.

  First, 3,3′-disulfo-4,4′-dichlorodiphenylsulfone disodium salt (abbreviation: S-DCDPS), 2,6-dichlorobenzonitrile (abbreviation: DCBN), 4,4′-biphenol, potassium carbonate , And molecular sieves were weighed into a four-necked flask and flushed with nitrogen. After adding N-methyl-2-pyrrolidone and stirring at 150 ° C. for 50 minutes, the reaction was continued by raising the reaction temperature to 195 ° C. to 200 ° C. and sufficiently increasing the viscosity of the system. Thereafter, the mixture was allowed to cool and then allowed to cool, and the precipitated molecular sieve was removed and the mixture was precipitated in water. The obtained polymer was washed in boiling water for 1 hour and then carefully washed with pure water to completely remove residual potassium carbonate. Thereafter, the polymer after the potassium carbonate was removed was dried to obtain SPES having a sulfonation degree DS = 60% as the second precursor polymer as the target product. The sulfonic acid group was almost neutralized with potassium.

(Installing the second precursor polymer on the outer surface of the first precursor polymer)
Dimethylacetamide and N-methyl-2-pyrrolidone were mixed at a mass ratio of 50:50 to prepare a mixed solvent. Then, a dip solution was prepared by dissolving SPPO as the second precursor polymer in a mixed solvent so that the SPES concentration was 10% by mass, and the bath was filled with the dip solution.

<Example 7>
The step of preparing the second precursor polymer is changed as follows, and the step of installing the second precursor polymer on the outer surface of the first precursor polymer is the same as in Example 6, the same A hollow fiber carbon membrane of Example 7 was obtained in the same manner and under the same conditions as in Example 1, except that the conditions were as described above. According to the measurement using SEM described later, the outer diameter of the hollow fiber carbon membrane of Example 7 was 300 μm, and the total thickness of the first carbon membrane and the second carbon membrane was 10 μm.

(Step of preparing a second precursor polymer)
SPES having a sulfonation degree DS = 60% as a second precursor polymer obtained by the same method and under the same conditions as in Example 6 was dipped in a 0.5 M aqueous sodium carbonate solution, and the sulfonic acid group was converted to sodium. Neutralized. And the sodium carbonate salt which remained in the reaction material was removed completely by washing the polymer after immersion in the sodium carbonate aqueous solution with water. Thereafter, the reaction product was dried to obtain SPES having a sulfonation degree DS = 60% as a target second precursor polymer. The sulfonic acid group was almost neutralized with sodium.

<Comparative Example 1>
A hollow fiber carbon membrane of Comparative Example 1 was obtained by the same method and the same conditions as in Example 1 except that the second precursor polymer was not placed on the outer surface of the first precursor polymer. That is, the hollow fiber carbon membrane of Comparative Example 1 is only a hollow fiber-like first carbon membrane obtained by subjecting the first precursor polymer made of PPO formed into a hollow fiber shape to flame resistance treatment and carbonization treatment. It was a hollow fiber carbon membrane made of According to the measurement using SEM described later, the outer diameter of the hollow fiber carbon membrane of Comparative Example 1 was 290 μm, and the total thickness of the first carbon membrane and the second carbon membrane was 9 μm.

<Comparative Example 2>
The hollow fiber carbon membrane of Comparative Example 2 was produced as follows. First, SPPO having a degree of sulfonation DS of 45% as a second precursor polymer was produced by the same method and the same conditions as in Example 1. Next, this SPPO was added to methanol so that the SPPO concentration would be 27.5% by mass, and the mixture was stirred at room temperature to dissolve SPPO in methanol to obtain a uniform spinning solution.

  Subsequently, an aqueous ammonium nitrate solution having a concentration of 15% by mass of ammonium nitrate as the inner liquid was extruded from the inside of the double cylindrical tube nozzle, and at the same time, the above spinning stock solution was extruded from the outside, dried in an air gap, and then filled with pure water. SPPO formed into a hollow fiber shape was prepared by solidifying the spinning solution in a coagulation bath. Thereafter, the wet SPPO formed into a hollow fiber shape was wound with a winder.

  When the wet SPPO formed in the hollow fiber shape obtained as described above was bundled and dried, the SPPOs were in close contact with each other and were difficult to handle. For this reason, each SPPO was cut to a length of about 1 m and suspended one by one, and a weight of about 1 g was attached to each tip, and dried while removing the internal liquid in the hollow fiber-shaped SPPO.

  After that, the hollow fiber carbon membrane of Comparative Example 2 was obtained by subjecting the hollow fiber-shaped SPPO after drying to flameproofing treatment and carbonization treatment under the same method and the same conditions as in Example 1. That is, the hollow fiber carbon membrane of Comparative Example 2 is a hollow fiber carbon membrane composed only of a hollow fiber-like first carbon membrane obtained by subjecting SPPO molded into a hollow fiber shape to flameproofing treatment and carbonization treatment. It was. According to the measurement using SEM described later, the outer diameter of the hollow fiber carbon membrane of Comparative Example 2 was 260 μm, and the total thickness of the first carbon membrane and the second carbon membrane was 10 μm.

<Comparative Example 3>
The hollow fiber carbon membrane of Comparative Example 3 was produced as follows. First, SPES having a degree of sulfonation DS of 60 as a second precursor polymer was produced by the same method and the same conditions as in Example 6. Next, SPES was dissolved in N-methyl-2-pyrrolidone by adding this SPES to N-methyl-2-pyrrolidone and stirring at 150 ° C. so that the SPES concentration was 27.5% by mass. A uniform spinning dope was obtained.

  Subsequently, an aqueous ammonium nitrate solution having a concentration of 15% by mass of ammonium nitrate as the inner liquid was extruded from the inside of the double cylindrical tube nozzle, and at the same time, the above spinning stock solution was extruded from the outside, dried in an air gap, and then filled with pure water. SPES formed into a hollow fiber shape was prepared by solidifying the spinning solution in a coagulation bath. Thereafter, the wet SPES formed into a hollow fiber shape was wound with a winder.

  When the wet SPES formed in the hollow fiber shape obtained as described above is bundled and dried, the SPES adheres to each other and is difficult to handle, as in the case of SPPO of Comparative Example 2. Met. Therefore, each SPES was cut to a length of about 1 m and suspended one by one, and a weight of about 1 g was attached to each tip, and the SPES was dried while removing the internal liquid in the hollow fiber-like SPES.

  Then, the hollow fiber carbon membrane of Comparative Example 3 was obtained by subjecting the hollow fiber SPES after drying to flameproofing treatment and carbonization treatment under the same method and the same conditions as in Example 1. That is, the hollow fiber carbon membrane of Comparative Example 3 is a hollow fiber carbon membrane consisting only of a hollow fiber-like first carbon membrane obtained by subjecting SPES formed into a hollow fiber shape to flame resistance treatment and carbonization treatment. It was. According to the measurement using SEM described later, the outer diameter of the hollow fiber carbon membrane of Comparative Example 3 was 270 μm, and the total thickness of the first carbon membrane and the second carbon membrane was 10 μm.

<Evaluation of hollow fiber carbon membrane>
With respect to the hollow fiber carbon membranes of Examples 1 to 7 and Comparative Examples 1 to 3 manufactured as described above, (i) the outer diameter of the hollow fiber carbon membrane, the first carbon membrane, and the second carbon membrane The total thickness of the carbon film, the thickness of the second carbon film, (ii) the metal element content and the sulfur element content, and (iii) the presence or absence of X-ray diffraction peaks other than the X-ray diffraction peak derived from the carbon structure (Iv) Evaluation of water separation performance and permeation performance by the pervaporation separation method was performed.

(Measurement of outer diameter, total thickness and thickness)
The outer diameter of the hollow fiber carbon membranes of Examples 1 to 7 and Comparative Examples 1 to 3, the total thickness of the first carbon membrane and the second carbon membrane, and the second of the hollow fiber carbon membranes of Examples 1 to 7 The thickness of the carbon film was measured with a scanning electron microscope (SEM). In Table 1, the measurement result of the thickness of the 2nd carbon membrane of the hollow fiber carbon membrane of Examples 1-7 is shown. In addition, about the hollow fiber carbon membrane of Comparative Examples 1-3, since the 2nd carbon membrane does not exist, it does not measure about the thickness of a 2nd carbon membrane, but the 1st carbon membrane and the 2nd carbon membrane The total thickness means the thickness of the first carbon film.

  Specifically, each of the hollow fiber carbon membranes of Examples 1 to 7 and Comparative Examples 1 to 3 was cut in a direction orthogonal to the longitudinal direction, and Pt was sputtered on the cut surface. Observation was performed at an acceleration voltage of 5 kV using a scanning electron microscope S-4800 manufactured by Seisakusho. The thickness of the second carbon film of Examples 1 to 7 is based on the fact that a color contrast is generated between the first carbon film and the second carbon film inside the SEM image of the hollow fiber carbon film. Measured. 5-7, the SEM image of the hollow fiber carbon membrane of Example 1 is shown as an example of the SEM image.

  As shown in Table 1, the thicknesses of the second carbon membranes of the hollow fiber carbon membranes of Examples 1 to 7 are 1.2 μm, 1.4 μm, 4.2 μm, 0.4 μm, 13 μm, and 1. 3 μm and 1.3 μm.

(Measurement of metal element content and sulfur element content)
Energy dispersive X-ray spectroscopy of elemental compositions of the first and second carbon films of the hollow fiber carbon membranes of Examples 1 to 7 and the first carbon film of the hollow fiber carbon membranes of Comparative Examples 1 to 3 Analyzed by the method. And the metal element content and sulfur element content were measured from the analysis result, respectively. The results are shown in Table 1.

  Specifically, each of the hollow fiber carbon membranes of Examples 1 to 7 and Comparative Examples 1 to 3 was cut in a direction perpendicular to the longitudinal direction, and the first carbon membrane and the carbon fiber membranes were analyzed by energy dispersive X-ray spectroscopy. The elemental composition of each cut surface of the second carbon film was analyzed. Here, the measurement by energy dispersive X-ray spectroscopy was performed using a scanning electron microscope S-4800 equipped with an energy dispersive X-ray analyzer QUANTAX manufactured by BRUKER under the conditions of an acceleration voltage of 20 kV and an integration time of 300 seconds. .

  FIG. 8A shows a region where the elemental composition of the hollow fiber carbon membrane of Example 1 was analyzed. A region surrounded by a broken line in FIG. 8A is an analysis region of the elemental composition of the second carbon film, and a region surrounded by a solid line is an analysis region of the elemental composition of the first carbon film.

  FIG. 8B shows, as an example of the analysis result of the elemental composition by energy dispersive X-ray spectroscopy, the elemental composition of each of the first carbon film and the second carbon film of the hollow fiber carbon film of Example 1. The analysis results are shown. As shown in FIG. 8B, a peak corresponding to the presence of sodium appears in both the first carbon film and the second carbon film, and the peak is higher than that of the first carbon film. The carbon film was larger. Moreover, although the peak corresponding to the presence of sulfur appeared for the second carbon film, the peak corresponding to the presence of sulfur did not appear for the first carbon film.

  FIG. 8C shows the results of elemental analysis of the first carbon film and the second carbon film of the hollow fiber carbon membrane of Example 1. FIG. As shown in FIG. 8 (c), the content (mass%) of carbon, nitrogen, oxygen, sodium and sulfur in the first carbon membrane of the hollow fiber carbon membrane of Example 1 was 92.60 mass%, respectively. 0.69% by mass, 6.30% by mass, 0.41% by mass and 0% by mass.

  Further, the carbon (carbon), nitrogen, oxygen, sodium and sulfur contents (% by mass) of the second carbon membrane of the hollow fiber carbon membrane of Example 1 were 81.10% by mass, 1.10% by mass and 12%, respectively. They were 0.71 mass%, 3.33 mass%, and 1.76 mass%.

(Measurement of presence or absence of X-ray diffraction peak)
About each of the 2nd carbon membrane of the hollow fiber carbon membrane of Examples 1-7 and the 1st carbon membrane of the hollow fiber carbon membrane of Comparative Examples 1-3, it originates in carbon structure by wide angle X-ray diffraction method The presence or absence of X-ray diffraction peaks other than the line diffraction peaks was measured. The results are shown in Table 1.

Specifically, SmartLab manufactured by Rigaku Corporation was used as an X-ray diffractometer, and 40 kV, 30 mA Cu—Kα ray was used as the X-ray. Wide-angle X-ray diffraction measurement was performed by 2θ-θ scan measurement by the concentration method. As a detector, a high-speed one-dimensional detector D / tex Ultra manufactured by Rigaku Corporation was used. The Cu—Kα ray was monochromatized by using a Kβ filter. The measurement step of wide-angle X-ray diffraction measurement was 0.02 °, and the scan speed was 0.5 deg / min. The measurement range of angles, in a measure of the scattering vector q, and the range of q = 5nm ^-1 ~50nm ^-1.

The scattering vector q is represented by the following formula (V). In equation (V), λ represents the wavelength of X-rays used for measurement, and θ represents a value that is ½ of the Bragg diffraction angle 2θ.
q = (4π / λ) sin θ (V)

  Moreover, the measurement sample of the wide angle X-ray diffraction method was produced as follows. First, each of the hollow fiber carbon membranes of Examples 1 to 7 and Comparative Examples 1 to 3 cut to a length of about 10 cm is immersed in pure water and left for 2 hours while gently stirring with a stirrer bar. Was washed with water. Then, the above water washing was repeated 4 times while exchanging pure water to remove metal salts and / or dirt deposited on the surface of the hollow fiber carbon membrane.

  Next, the hollow fiber carbon membrane was allowed to stand in an atmosphere of 80 ° C. overnight, thereby drying the hollow fiber carbon membrane and removing moisture from the hollow fiber carbon membrane. The wide-angle X is obtained by cutting the hollow fiber carbon membrane from which moisture has been removed by drying to a length that can be accommodated in the glass sample table for the X-ray diffractometer, and laying about 20 to 50 in parallel so as not to overlap. A measurement sample of the line diffraction method was used. The measurement sample thus prepared was attached to the stage of the X-ray diffractometer, and wide-angle X-ray diffraction measurement was performed under the above measurement conditions, and this was used as sample data.

  Next, the air scattering and the scattering of the glass sample stage in the state where the hollow fiber carbon membrane was not spread were measured under the same conditions, and measured under the same conditions as the above measurement conditions, and this was used as background data.

  And by removing the X-ray diffraction intensity distribution of the background data from the X-ray diffraction intensity distribution of the sample data, the second carbon membrane of the hollow fiber carbon membranes of Examples 1 to 7 and Comparative Examples 1 to 3 The X-ray diffraction intensity distribution was measured by wide-angle X-ray diffraction measurement of the first carbon membrane of the hollow fiber carbon membrane. In the operation of removing the X-ray diffraction intensity distribution of the background data from the X-ray diffraction intensity distribution of the sample data, the contribution of X-ray absorption by the sample may be taken into account, but many of the data may be taken without consideration. It is thought that it does not affect.

  FIG. 9 shows, as an example of the X-ray diffraction profile showing the X-ray diffraction intensity distribution obtained by the above-mentioned wide-angle X-ray diffraction method, the second carbon membrane of the hollow fiber carbon membrane of Example 1 and the hollow of Comparative Example 1. The example which compared each X-ray diffraction profile of the 1st carbon film of a thread carbon film is shown. As shown in FIG. 9, in the X-ray diffraction profile of the second carbon membrane of the hollow fiber carbon membrane of Example 1, it is not a location corresponding to the (002) plane and the (10) plane of the carbon crystal (A) X-ray diffraction peaks are observed at the positions (B) and (B), respectively, but such X-ray diffraction peaks are not observed in the X-ray diffraction profile of the first carbon membrane of the hollow fiber carbon membrane of Comparative Example 1. The X-ray diffraction peaks at locations (A) and (B) in the X-ray diffraction profile of the second carbon membrane of the hollow fiber carbon membrane of Example 1 correspond to the (002) plane and the (10) plane of the carbon crystal. The X-ray diffraction peak other than the X-ray diffraction peak derived from the carbon structure is not equivalent to any of the two X-ray diffraction peaks and amorphous halo.

  For the hollow fiber carbon membranes of Examples 2 to 7 and Comparative Examples 1 to 3, X-ray diffraction profiles were obtained in the same manner as described above, and other than the X-ray diffraction peaks derived from the carbon structure based on the same criteria as described above. The presence or absence of an X-ray diffraction peak was determined.

If the second carbon membrane of the hollow fiber carbon membrane is thin and sufficient X-ray diffraction intensity cannot be obtained with the laboratory apparatus as described above, for example, in a large synchrotron radiation facility such as SPring8 may be a wide-angle X-ray diffraction measurement in the same range of the scattering vector q = 5nm ^-1 ~50nm ^-1 and above (e.g. measured by transmission method) is performed.

(Evaluation of separation performance and permeation performance)
In FIG. 10, the typical block diagram of the osmosis | evaporation separation apparatus used for evaluation of the water separation performance by the osmosis | evaporation separation method of the hollow fiber carbon membrane of Examples 1-7 and Comparative Examples 1-3 and permeation | permeation performance is shown. . A plurality of hollow fiber carbon membranes 10 of Examples 1 to 7 and Comparative Examples 1 to 3 are bundled in the same number, and the opening at one end of the bundled hollow fiber carbon membranes 10 is sealed with an adhesive and closed. The separation membrane module 20 was produced by opening the opening at the other end and fitting caps at both ends. Then, the separation membrane module 20 produced in this way was attached to one end of the stainless tube 44 covered with the heat insulating tape 39 so as to keep an airtight state. A stop valve 40 was attached between the ends of the stainless tube 44.

  In addition, an ethyl acetate aqueous solution 32 having a water content of 3% by mass as a supply liquid was poured into the container 33, and a stirrer 35 was installed at the bottom of the container 33. And the container 33 was installed in the thermostat 34, the thermostat 34 was installed on the stirrer 31, and the thermometer 38 was inserted in the ethyl acetate aqueous solution 32. FIG. The stirrer 35 is rotated by the stirrer 31 while the ethyl acetate aqueous solution 32 is stirred by keeping the ethyl acetate aqueous solution 32 in the container 33 at a constant temperature by the thermostatic bath 34, and the separation membrane module 20 is immersed in the ethyl acetate aqueous solution 32. It was.

  Further, the other end of the stainless steel tube 44 was inserted in an airtight state into a cooling trap 36 cooled with liquid nitrogen 37 (−196 ° C.) together with one end of the other stainless steel tube 45. The other end of the stainless steel tube 45 was attached to the vacuum pump 43, and a pressure gauge 41 and a stop valve 42 were attached between the ends of the stainless steel tube 45 in this order from the cooling trap 36 side.

Then, the vacuum pump 43 was operated to set the pressure on the supply liquid side of the ethyl acetate aqueous solution 32 of the separation membrane module 20 to atmospheric pressure, and the pressure on the permeate side to 1 Pa. Then, after a predetermined time has elapsed from the start of the evaluation, the permeation flux (kg · m ⁻² · h ⁻¹ ) is obtained from the mass of the permeate trapped by the cooling trap 36 by the following formula (VI). It was. The results are shown in Table 1.
Permeation flux [kg · m ⁻² · h ⁻¹ ] = (mass of permeate [kg]) ÷ {area of hollow fiber carbon membrane [m ² ] × time [h]} (VI)

Further, the permeate trapped by the cooling trap 36 was analyzed by a TCD (Thermal Conductivity Detector) gas chromatograph to obtain the ethyl acetate concentration in the permeate and the separation factor was calculated by the following equation (VII). The results are shown in Table 1.
Separation factor = {water concentration in permeate [mass%] / ethyl acetate concentration in permeate [mass%]} ÷ {water concentration in feed liquid [mass%] / ethyl acetate concentration in feed liquid [mass%]} VII)

<Relative comparison of pore size>
Moreover, the pore diameter of the 1st carbon membrane of the hollow fiber carbon membrane of Examples 1-7 and the 2nd carbon membrane 2 and the pore diameter of the 1st carbon membrane of the hollow fiber carbon membrane of Comparative Examples 1-3 are the same. The relative comparison between large and small was evaluated by the value of the separation coefficient in the separation performance test by the above-described pervaporation separation method. That is, for example, when the separation factor is higher, it means that ethyl acetate molecules having a larger molecular diameter than water molecules can be effectively prevented from entering the carbon membrane, which means that the pore diameter is small. .

  As a result, as is clear from Table 1, the separation factors of the hollow fiber carbon membranes of Examples 1 to 7 were 320,000, 220,000, 540000, 20000, 820000, 230000, and 320,000, respectively. On the other hand, the separation factor of the first carbon membrane of the hollow fiber carbon membrane of Comparative Example 1 was 645. The separation factor of the hollow fiber carbon membranes of Examples 1 to 7 greatly exceeds the separation factor of the first carbon membrane of the hollow fiber carbon membrane of Comparative Example 1, and the separation factor of the first carbon membranes of Examples 1 to 7 It was confirmed that the pore diameter of the second carbon film installed above was smaller than the pore diameter of the first carbon film, and that the structure was favorable for blocking organic solvent molecules.

<Evaluation results>
(Evaluation of Hollow Fiber Carbon Membrane of Example 1)
In the hollow fiber carbon membrane of Example 1, the presence of sodium element and sulfur element was confirmed in the second carbon membrane, and the sodium element content and the sulfur element content in the second carbon membrane were respectively More than the sodium element content and the sulfur element content in one carbon film. Further, the second carbon membrane having a small pore diameter and made of SPPO and having a high hydrophilicity prevents permeation of ethyl acetate, and water is selectively separated to permeate the second carbon membrane, thereby reducing the fineness. In the first carbon membrane formed from PPO having a relatively large pore diameter and having low hydrophilicity, water can permeate efficiently and rapidly dissipate into the hollow portion of the hollow fiber carbon membrane, resulting in permeation flow rate and separation. Each coefficient increased and the ethyl acetate concentration in the permeate decreased. In the second carbon film of the hollow fiber carbon membrane of Example 1, in the range of the scattering vector q of X-ray diffraction peak measured by wide angle X-ray diffraction method is 5 nm ^-1 up to 50 nm ^-1, X-ray diffraction peaks other than the X-ray diffraction peak derived from the carbon structure were confirmed.

(Evaluation of hollow fiber carbon membrane of Example 2)
In the hollow fiber carbon membrane of Example 2, the presence of magnesium element and sulfur element was confirmed in the second carbon membrane, and the magnesium element content and the sulfur element content in the second carbon membrane were respectively More than the magnesium element content and the sulfur element content in one carbon film. Further, the second carbon membrane having a small pore diameter and made of SPPO and having a high hydrophilicity prevents permeation of ethyl acetate, and water is selectively separated to permeate the second carbon membrane, thereby reducing the fineness. In the first carbon membrane formed from PPO having a relatively large pore diameter and having low hydrophilicity, water can permeate efficiently and rapidly dissipate into the hollow portion of the hollow fiber carbon membrane, resulting in permeation flow rate and separation. Each coefficient increased and the ethyl acetate concentration in the permeate decreased. Also in the second carbon layer of the hollow fiber carbon membrane of Example 2, within the range of the scattering vector q of X-ray diffraction peak measured by wide angle X-ray diffraction method is 5 nm ^-1 up to 50 nm ^-1, X-ray diffraction peaks other than the X-ray diffraction peak derived from the carbon structure were confirmed.

(Evaluation of Hollow Fiber Carbon Membrane of Example 3)
In the hollow fiber carbon membrane of Example 3, the presence of sodium element and sulfur element was confirmed in the second carbon membrane, and the sodium element content and the sulfur element content in the second carbon membrane were respectively More than the sodium element content and the sulfur element content in one carbon film. Further, the second carbon membrane having a small pore diameter and made of SPPO and having a high hydrophilicity prevents permeation of ethyl acetate, and water is selectively separated to permeate the second carbon membrane, thereby reducing the fineness. In the first carbon membrane formed from PPO having a relatively large pore diameter and having low hydrophilicity, water can permeate efficiently and rapidly dissipate into the hollow portion of the hollow fiber carbon membrane, resulting in permeation flow rate and separation. Each coefficient increased and the ethyl acetate concentration in the permeate decreased. Also in the second carbon layer of the hollow fiber carbon membrane of Example 3, within the range of the scattering vector q of X-ray diffraction peak measured by wide angle X-ray diffraction method is 5 nm ^-1 up to 50 nm ^-1, X-ray diffraction peaks other than the X-ray diffraction peak derived from the carbon structure were confirmed.

(Evaluation of Hollow Fiber Carbon Membrane of Example 4)
In the hollow fiber carbon membrane of Example 4, the presence of sodium element and sulfur element was confirmed in the second carbon membrane, and the sodium element content and the sulfur element content in the second carbon membrane were respectively More than the sodium element content and the sulfur element content in one carbon film. Further, the second carbon membrane having a small pore diameter and made of SPPO and having a high hydrophilicity prevents permeation of ethyl acetate, and water is selectively separated to permeate the second carbon membrane, thereby reducing the fineness. In the first carbon membrane formed from PPO having a relatively large pore diameter and having low hydrophilicity, water can permeate efficiently and rapidly dissipate into the hollow portion of the hollow fiber carbon membrane, resulting in permeation flow rate and separation. Each coefficient increased and the ethyl acetate concentration in the permeate decreased. Also in the second carbon layer of the hollow fiber carbon membrane of Example 4, in the range of the scattering vector q of X-ray diffraction peak measured by wide angle X-ray diffraction method is 5 nm ^-1 up to 50 nm ^-1, X-ray diffraction peaks other than the X-ray diffraction peak derived from the carbon structure were confirmed.

  However, in the hollow fiber carbon membrane of Example 4, the permeate flow rate and the separation factor were lower than in the hollow fiber carbon membranes of Examples 1 to 3, and the ethyl acetate concentration in the permeate was also higher. This is because the SPPO concentration in the dip solution is too low, resulting in uneven coating of the second precursor polymer, the thickness of the second carbon film is reduced, and the thickness of the second carbon film is 500 nm or more and 10 μm. This is thought to be due to the fact that it no longer exists within the following range.

(Evaluation of Hollow Fiber Carbon Membrane of Example 5)
In the hollow fiber carbon membrane of Example 5, the presence of sodium element and sulfur element was confirmed in the second carbon membrane, and the sodium element content and the sulfur element content in the second carbon membrane were More than the sodium element content and the sulfur element content in one carbon film. Further, the second carbon membrane having a small pore diameter and made of SPPO and having a high hydrophilicity prevents permeation of ethyl acetate, and water is selectively separated to permeate the second carbon membrane, thereby reducing the fineness. In the first carbon membrane formed from PPO having a relatively large pore diameter and having low hydrophilicity, water can permeate efficiently and rapidly dissipate into the hollow portion of the hollow fiber carbon membrane, resulting in permeation flow rate and separation. Each coefficient increased and the ethyl acetate concentration in the permeate decreased. Also in the second carbon layer of the hollow fiber carbon membrane of Example 5, in the range of the scattering vector q of X-ray diffraction peak measured by wide angle X-ray diffraction method is 5 nm ^-1 up to 50 nm ^-1, X-ray diffraction peaks other than the X-ray diffraction peak derived from the carbon structure were confirmed.

  However, in the hollow fiber carbon membrane of Example 5, the separation factor was higher than in the hollow fiber carbon membranes of Examples 1 to 3, and the ethyl acetate concentration in the permeate was low, but the permeate flow rate was low. It was. This is presumably because the SPPO concentration in the dip solution was too high and the thickness of the second carbon film became too thick to be no longer in the range of 500 nm to 10 μm.

(Evaluation of Hollow Fiber Carbon Membrane of Example 6)
In the hollow fiber carbon membrane of Example 6, the presence of potassium element and sulfur element was confirmed in the second carbon membrane, and the potassium element content and the sulfur element content in the second carbon membrane were respectively More than the potassium element content and the sulfur element content in one carbon film. In addition, the second carbon membrane formed from SPES, which has a small pore diameter and is highly hydrophilic, prevents permeation of ethyl acetate, and water is selectively separated and permeated through the second carbon membrane. In the first carbon membrane formed from PPO having a relatively large pore diameter and having low hydrophilicity, water can permeate efficiently and rapidly dissipate into the hollow portion of the hollow fiber carbon membrane, resulting in permeation flow rate and separation. Each coefficient increased and the ethyl acetate concentration in the permeate decreased. Also in the second carbon layer of the hollow fiber carbon membrane of Example 6, in the range of the scattering vector q of X-ray diffraction peak measured by wide angle X-ray diffraction method is 5 nm ^-1 up to 50 nm ^-1, X-ray diffraction peaks other than the X-ray diffraction peak derived from the carbon structure were confirmed.

(Evaluation of hollow fiber carbon membrane of Example 7)
In the hollow fiber carbon membrane of Example 7, the presence of sodium element and sulfur element was confirmed in the second carbon membrane, and the sodium element content and the sulfur element content in the second carbon membrane were respectively More than the sodium element content and the sulfur element content in one carbon film. In addition, the second carbon membrane formed from SPES, which has a small pore diameter and is highly hydrophilic, prevents permeation of ethyl acetate, and water is selectively separated and permeated through the second carbon membrane. In the first carbon membrane formed from PPO having a relatively large pore diameter and having low hydrophilicity, water can permeate efficiently and rapidly dissipate into the hollow portion of the hollow fiber carbon membrane, resulting in permeation flow rate and separation. Each coefficient increased and the ethyl acetate concentration in the permeate decreased. Also in the second carbon layer of the hollow fiber carbon membrane of Example 7, in the range of the scattering vector q of X-ray diffraction peak measured by wide angle X-ray diffraction method is 5 nm ^-1 up to 50 nm ^-1, X-ray diffraction peaks other than the X-ray diffraction peak derived from the carbon structure were confirmed.

(Evaluation of Hollow Fiber Carbon Membrane of Comparative Example 1)
Compared with the hollow fiber carbon membranes of Examples 1 to 7, the hollow fiber carbon membrane of Comparative Example 1 had a low permeation flow rate and a separation factor and a high ethyl acetate concentration in the permeate. Further, the hollow fiber carbon membrane after evaluation by the pervaporation separation method was greatly swollen by the adsorption of ethyl acetate. This adsorbed ethyl acetate hinders the permeation of water, so it seems that the permeate flow rate showed a low value. In the hollow fiber carbon membrane of Comparative Example 1, the presence of metal elements and sulfur elements was not confirmed. Furthermore, within the scope of the scattering vector q of X-ray diffraction peak measured by wide angle X-ray diffraction method is 5 nm ^-1 up to 50 nm ^-1, confirmed the X-ray diffraction peaks other than X-ray diffraction peaks derived from the carbon structure Was not.

(Evaluation of Hollow Fiber Carbon Membrane of Comparative Example 2)
Since the hollow fiber carbon membrane of Comparative Example 2 is made of SPPO, the pore size is relatively small and the hydrophilicity is relatively high, so the separation factor is high and the ethyl acetate concentration in the permeate is low. The flow rate was very small. In the hollow fiber carbon membrane of Comparative Example 2, the presence of metal elements and sulfur elements was confirmed. Furthermore, within the scope of the scattering vector q of X-ray diffraction peak measured by wide angle X-ray diffraction method is 5 nm ^-1 up to 50 nm ^-1, confirmed the X-ray diffraction peaks other than X-ray diffraction peaks derived from the carbon structure It was done.

(Evaluation of Hollow Fiber Carbon Membrane of Comparative Example 3)
Since the hollow fiber carbon membrane of Comparative Example 3 is formed of SPES, the pore size is relatively small and the hydrophilicity is relatively high, so the separation factor is high and the ethyl acetate concentration in the permeate is low. The flow rate was the smallest. In the hollow fiber carbon membrane of Comparative Example 3, the presence of metal elements and sulfur elements was confirmed. Furthermore, within the scope of the scattering vector q of X-ray diffraction peak measured by wide angle X-ray diffraction method is 5 nm ^-1 up to 50 nm ^-1, confirmed the X-ray diffraction peaks other than X-ray diffraction peaks derived from the carbon structure It was done.

(Summary)
From the above results, it was confirmed that the hollow fiber carbon membranes of Examples 1 to 7 were superior in both water separation performance and permeation performance as compared with the hollow fiber carbon membranes of Comparative Examples 1 to 3. Moreover, since the hollow fiber carbon membranes of Examples 1 to 7 are self-supporting hollow fiber carbon membranes that do not use a support made of a porous substrate, they can be easily manufactured, and separation membrane modules, etc. It is possible to reduce the size of the apparatus.

  Further, the hollow fiber carbon membranes of Examples 1 to 3 and Examples 6 to 7 in which the thickness of the second carbon membrane is in the range of 500 nm to 10 μm are within the range of the thickness of the second carbon membrane. Compared to the hollow fiber carbon membranes of Examples 4 to 5 which are not present, it was confirmed that both separation performance and permeation performance can be achieved.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be used for a hollow fiber carbon membrane, a separation membrane module, and a method for producing a hollow fiber carbon membrane.

  DESCRIPTION OF SYMBOLS 1 1st carbon membrane, 2nd 2nd carbon membrane, 3 hollow part, 10 hollow fiber carbon membrane, 11,12 adhesive, 13 arrow, 14,15 cap, 20 separation membrane module, 31 stirrer, 32 ethyl acetate aqueous solution , 33 container, 34 constant temperature bath, 35 stirrer, 36 cooling trap, 37 liquid nitrogen, 38 thermometer, 39 heat insulating tape, 40 stop valve, 41 pressure gauge, 42 stop valve, 43 vacuum pump, 44, 45 stainless steel tube.

Claims (12)

A hollow fiber-shaped first carbon membrane;
A second carbon film provided on the outer surface of the first carbon film,
Said second carbon film, seen containing a metal element, a sulfur element,
The metal element content of the second carbon film is greater than the metal element content of the first carbon film,
The hollow fiber carbon membrane , wherein the sulfur element content of the second carbon membrane is greater than the sulfur element content of the first carbon membrane. The hollow fiber carbon membrane according to claim 1, wherein the precursor polymer of the second carbon membrane contains a sulfonic acid group. The polymer containing a sulfonic acid group has a repeating structure of a repeating unit A represented by the following formula (I) and a repeating unit B represented by the following formula (II):
In the formula (I) and the formula (II), m and n each represent a natural number of 1 or more, and in the formula (II), R ¹ and R ² are each independently —SO ₃ M, —SO ₃ H or a hydrogen atom, M represents a metal element, R ¹ and R ² do not simultaneously represent a hydrogen atom,
The hollow fiber carbon membrane according to claim 2 , wherein a ratio of the percentage of the number of repeating units B to the total number of repeating units A and B is larger than 15% and smaller than 100%. Within the scattering vector q of the second X-ray diffraction peak measured by wide angle X-ray diffraction of the carbon film is 5 nm ^-1 up to 50 nm ^-1, X other than X-ray diffraction peaks derived from the carbon structure The hollow fiber carbon membrane according to any one of claims 1 to 3 , wherein a line diffraction peak is present. The hollow fiber carbon membrane according to any one of claims 1 to 4 , wherein a thickness of the second carbon membrane is 500 nm or more and 10 µm or less. The hollow fiber carbon membrane according to any one of claims 1 to 5 , wherein the second carbon membrane has higher hydrophilicity than the first carbon membrane. A separation membrane module comprising the hollow fiber carbon membrane according to any one of claims 1 to 6 . A method for producing the hollow fiber carbon membrane according to any one of claims 1 to 6 ,
Providing a first precursor polymer that is a precursor polymer of the first carbon film;
Providing a second precursor polymer that is a precursor polymer of the second carbon film;
Forming the first precursor polymer into a hollow fiber shape;
Forming a hollow fiber carbon membrane precursor by placing a second precursor polymer on the outer surface of the first precursor polymer shaped into a hollow fiber;
A process for carbonizing the hollow fiber carbon membrane precursor. The method for producing a hollow fiber carbon membrane according to claim 8 , wherein the second precursor polymer contains a sulfonic acid group. The polymer containing a sulfonic acid group has a repeating structure of a repeating unit A represented by the following formula (I) and a repeating unit B represented by the following formula (II):
In the formula (I) and the formula (II), m and n each represent a natural number of 1 or more, and in the formula (II), R ¹ and R ² are each independently —SO ₃ M, —SO ₃ H or a hydrogen atom, M represents a metal element, R ¹ and R ² do not simultaneously represent a hydrogen atom,
The method for producing a hollow fiber carbon membrane according to claim 9 , wherein a ratio of a percentage of the number of repeating units B to a total number of repeating units A and B is larger than 15% and smaller than 100%. . The first precursor polymer is polyphenylene oxide having no sulfonic acid group ,
The method for producing a hollow fiber carbon membrane according to any one of claims 8 to 10 , wherein the second precursor polymer is a sulfonated polyphenylene oxide. The method for producing a hollow fiber carbon membrane according to any one of claims 8 to 11 , further comprising a step of flameproofing the hollow fiber carbon membrane precursor before the carbonizing treatment.