Method for producing selective gas separation membrane

Abstract

To provide a method for producing a selective gas separation membrane, which can produce a selective gas separation membrane made of polysiloxane highly selective of carbon dioxides without dependence on cross-linking reaction dependent on heat or light, and can produce a membrane of a large area.SOLUTION: This method for producing the selective gas separation membrane comprises: introducing a polycyclic aromatic compound into a polymer chain of polysiloxane or a polysiloxane derivative; and forming a hydrogen bonding polymer compound into a membrane having a thickness of 0.02-2.0 μm. The membrane formation is carried out by spray-coating a support with a solution of the polymer compound.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a selective gas separation membrane, which is a polymer membrane containing polysiloxane or a polysiloxane derivative in its main chain, and has high carbon dioxide permeability and excellent separation (selectivity) between carbon dioxide and other gases such as nitrogen. In particular, the present invention relates to a method for producing the selective gas separation membrane, which is capable of forming the selective gas separation membrane in a large area. [Background technology]

[0002] Currently, as part of efforts to curb global warming and achieve carbon neutrality, attention is being paid to research and development of carbon dioxide circulation systems that selectively separate and capture carbon dioxide from the atmosphere and use it as a carbon resource, for example as a raw material for synthesizing various carbon compounds. As a technology for selectively separating and capturing carbon dioxide from the atmosphere, attention is being paid to the membrane separation method, which is a carbon dioxide separation technology that does not require thermal energy in principle, that is, a method that uses a membrane that separates dilute carbon dioxide in a gas with high selectivity by allowing the gas to permeate.

[0003] Polysiloxane is a polymer with a skeleton consisting of several tens to several thousand siloxane bonds (Si-O-Si). Polysiloxane, especially polydimethylsiloxane (silicone rubber), has a large gas permeability coefficient for carbon dioxide, and by passing a gas containing carbon dioxide, such as the atmosphere, through a thin film of polydimethylsiloxane, it is possible to separate and extract carbon dioxide from the gas with high selectivity. As such, polysiloxane membranes have excellent selectivity for carbon dioxide, and are therefore expected to be used in applications such as curbing global warming and achieving carbon neutrality.

[0004] Polysiloxane membranes with excellent carbon dioxide selective separation properties have been conventionally produced by crosslinking reaction of polysiloxanes based on heat or light. However, since crosslinking requires heat or light, the additional emission of carbon dioxide in the production of membranes is pointed out as a problem from the viewpoint of energy utilization. In addition, this production method makes it difficult to produce large-area membranes, which are in high demand in society. Therefore, in order to overcome this problem, there is a demand for the development of a method for producing polysiloxane membranes without using crosslinking reaction by heat or light. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3069654 [Non-patent literature]

[0006] [Non-Patent Document 1] Chem.Lett., Vol. 48 (2019) p. 1351 [Non-Patent Document 2] Journal of the Society of Rubber Industry, Japan, Vol. 90, No. 7 (2017), pp. 346-353 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a method for producing a selective gas separation membrane made of polysiloxane and having excellent carbon dioxide selectivity, without requiring a crosslinking reaction dependent on heat or light. Another object of the present invention is to provide a method for producing the selective gas separation membrane, which is capable of producing a large-area membrane. [Means for solving the problem]

[0008] As a result of extensive investigations aimed at solving the above-mentioned problems, the present inventors have found that by introducing a polycyclic aromatic group into a polysiloxane or a polysiloxane derivative, it is possible to prepare a polymer compound that can form a thin membrane without utilizing light or heat, and that by forming a membrane from this polymer compound, it is possible to obtain a selective gas separation membrane that has carbon dioxide permeability and carbon dioxide selectivity equivalent to those of selective gas separation membranes obtained from conventional polymer compounds crosslinked using light or heat.

[0009] The present inventors further discovered that a polymer compound prepared by introducing a polycyclic aromatic group into a polysiloxane or a polysiloxane derivative can be made into a membrane simply by coating, and can be applied by spraying, and therefore a large-area selective gas separation membrane, which is in high demand in society, can be obtained by spray coating, and thus completed the present invention. That is, the above-mentioned problems of the present invention are solved by the invention having the following configuration.

[0010] The first aspect of the present invention is This is a method for producing a selective gas separation membrane, characterized in that a polymer compound having hydrogen bonding properties and a main chain in which a polycyclic aromatic compound is introduced into the polymer chain of a polysiloxane or a polysiloxane derivative is formed into a membrane having a thickness of 0.01 μm or more.

[0011] A second aspect of the present invention is a method for producing a selective gas separation membrane, wherein the membrane is formed by spraying a solution of the polymer compound onto a support.

[0012] The present invention further provides a selective gas separation membrane produced by the first or second selective gas separation membrane production method of the present invention, a method for concentrating carbon dioxide in a gas, which is characterized by allowing the gas to permeate through the selective gas separation membrane, and a member for carrying out the method for concentrating carbon dioxide, which is characterized by having a support capable of permeating carbon dioxide and the selective gas separation membrane formed on the support. Effect of the Invention

[0013] According to the first aspect of the present invention, a polymer compound capable of forming a thin membrane can be prepared without the need for crosslinking by light or heat, and by forming this polymer compound into a membrane, a selective gas separation membrane having carbon dioxide permeability and carbon dioxide selectivity equivalent to those of selective gas separation membranes obtained from conventional polymers crosslinked by light or heat can be obtained.

[0014] According to the second aspect of the present invention, a selective gas separation membrane having a large area and having the same carbon dioxide permeability and carbon dioxide selectivity as conventional selective gas separation membranes can be obtained. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic cross-sectional view showing a selective gas separation member of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing a gas permeability measuring device used in measuring gas permeability in Examples 1 and 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, the embodiments for carrying out the present invention will be described in more detail, but the scope of the present invention is not limited to the following embodiments.

[0017] The first aspect of the present invention is This is a method for producing a selective gas separation membrane, characterized in that a polymer compound having hydrogen bonding properties and a main chain in which a polycyclic aromatic compound is introduced into the polymer chain of a polysiloxane or a polysiloxane derivative is formed into a membrane having a thickness of 0.01 μm or more.

[0018] Here, the polysiloxane derivative is, for example, a compound represented by the formula -(Si(Ra) 2 -O-) q- (wherein Ra represents H or an alkyl group, particularly a lower alkyl group having 1 to 4 carbon atoms, which may have a substituent, and q represents a positive integer). Among them, polydimethylsiloxane (hereinafter sometimes referred to as "PDMS") is preferably used because it provides excellent film-forming properties.

[0019] The polymer chain of the polysiloxane or polysiloxane derivative is calculated by size exclusion chromatography (SEC) and 1 The molecular weight determined by HNMR measurement is preferably in the range of 500 to 30,000. The more preferred range of the molecular weight varies depending on the type, particularly the size, of the polycyclic aromatic compound introduced into the polymer chain. For example, when the polycyclic aromatic compound is a compound having perylene as the main skeleton, the molecular weight is more preferably in the range of 5,000 to 20,000, and when it is naphthalene, the molecular weight is more preferably in the range of 500 to 3,000.

[0020] The polycyclic aromatic compound introduced into the polymer chain is an aromatic compound having two or more benzene rings bonded together. For example, naphthalene, anthracene, fluoranthene, pyrene, fluoranthene, perylene, and other compounds having about 2 to 5 benzene rings are used, with naphthalene and perylene being preferred.

[0021] As a method for introducing a polycyclic aromatic compound into a polymer chain, the polymer chain of the polysiloxane or polysiloxane derivative and the polycyclic aromatic compound each have a group for forming a condensation bond at both ends, and the polymer chain and the polycyclic aromatic compound are condensed to form the main chain of the polymer compound. Note that, although the main chain of the polymer compound is formed by the condensation of the polymer chain and the polycyclic aromatic compound, other components may be included within a range that does not impair the gist of the present invention.

[0022] The polymer compound having the condensation product of the polymer chain and the polycyclic aromatic compound as its main chain has π-π interaction or hydrogen bonding between aromatic rings, and is a compound that forms π-π interaction or hydrogen bonds between the polymer compounds. It is considered that the hydrogen bonding property forms (physical) bonds between the polymer compounds, and a membrane having high carbon dioxide permeability and high selectivity can be formed by spray coating. Therefore, the groups forming condensed bonds at both ends of the polymer chain and the polycyclic aromatic compound are preferably those that form a group having hydrogen bonding properties by condensation. For example, when the polymer chain has an alkylamino group at its end and the polycyclic aromatic compound has a carboxylic anhydride group or an α,β-dicarboxylic acid at its end, an imide bond or an amide bond is formed by condensation, and hydrogen bonding properties are obtained by the carbonyl oxygen of the imide group or the amide group, which is preferable.

[0023] Therefore, a preferred specific example of the polymer chain is a compound represented by the following formula (a).

[0024] [ka]

[0025] [In the formula, R is an alkyl group having 1 to 4 carbon atoms which may have a substituent, a and b are the same or different and are 1 to 5, n is 7 to 400, and the multiple Rs may be the same or different from each other.]

[0026] Preferable specific examples of the polycyclic aromatic compound include a compound represented by the following formula (b) or a compound represented by the following formula (c).

[0027] [ka]

[0028] Examples of the polymer compound obtained by condensing the polymer chain represented by the formula (a) with the polycyclic aromatic compound represented by the formula (b) include a compound having a divalent group represented by the following general formula (1) as its main chain, and a compound having a divalent group represented by the following general formula (5) as its main chain. The condensation reaction can be carried out in the same manner as known condensation reactions for compounds of similar structure.

[0029] [ka]

[0030] [In the formula, R is an alkyl group having 1 to 4 carbon atoms which may have a substituent, R1 is a divalent group selected from the following formula (2), (3), or (4), a and b are the same or different and are 1 to 5, m is 1 to 10, n is 7 to 270, and the multiple R's and R1's may be the same or different from each other. Note that formula (3) does not limit the orientation of the bond of the imide group and the bond of the amide group.]

[0031] [ka]

[0032] [ka]

[0033] [In the formula, R is an alkyl group having 1 to 4 carbon atoms which may have a substituent, R2 is a divalent group selected from the following formula (6), (7), or (8), a and b are the same or different and are 1 to 5, m is 1 to 60, n is 7 to 40, and the multiple R and R2 may be the same or different from each other. Note that formula (7) does not limit the direction of the bond of the imide group and the bond of the amide group.]

[0034] [ka]

[0035] By forming a membrane from the polymer compound, a selective gas separation membrane that has high carbon dioxide permeability and selectively separates carbon dioxide from gas is produced. The thickness of the selective gas separation membrane is 0.01 μm or more. If the membrane is too thin, the selective separation of carbon dioxide may be insufficient. In addition, the mechanical strength of the membrane decreases, which may lead to durability problems. On the other hand, if the membrane is too thick, the gas is less likely to permeate the membrane, which may lead to problems of reduced productivity. Considering these problems, the thickness of the selective gas separation membrane is preferably 0.02 μm or more and 2.0 μm or less, and more preferably 0.02 μm or more and 1.0 μm or less.

[0036] The membrane is formed, for example, by applying a solution of the polymer compound onto a support for stably holding a thin selective gas separation membrane. The solution of the polymer compound is prepared by dissolving the polymer compound in a solvent, and the solvent is not particularly limited as long as it can uniformly dissolve the polymer compound and can prepare a solution that can be applied to the support in the form of a thin film. Considering the ease of application by spraying, which will be described later, aromatic hydrocarbon solvents such as toluene can be cited as preferred solvents.

[0037] A spin-casting method can also be used as a method for applying the polymer solution onto a support. However, for practical use in society, it is desirable to increase the area of ​​selective gas separation membranes, and the spin-casting method has limitations in terms of the weight and size of the substrate (support, etc.) for forming the membrane. In addition, conventional selective gas separation membranes are also formed by crosslinking using light or heat, so there is a limit to how large the membrane can be. However, the polymer solution can be spray-applied, and a large-area selective gas separation membrane with excellent practical use in society can be produced by spray-applying the polymer solution.

[0038] The selective gas separation membrane produced by the method of the present invention has a higher carbon dioxide permeability than other gases, such as nitrogen. Therefore, by passing a gas containing carbon dioxide through this selective gas separation membrane, the concentration of carbon dioxide in the gas can be increased because carbon dioxide permeates more easily than other gases. In other words, a method for concentrating carbon dioxide is provided.

[0039] The selective gas separation membrane produced by the method of the present invention is thin (0.02 to 2.0 μm), and therefore is usually formed on a support having excellent mechanical strength in order to reinforce its mechanical strength and improve durability. Fig. 1 is a schematic cross-sectional view showing a selective gas separation member in which a thin selective gas separation membrane is laminated on a support. The support is a member that is sufficiently permeable to gases such as carbon dioxide, has a desired mechanical strength, and can be laminated with the selective gas separation membrane, and is usually in the form of a membrane, and is also called a support membrane. EXAMPLES

[0040] The present invention will now be described in more detail with reference to examples, but the scope of the present invention is not limited to these examples.

[0041] Manufacturing Example 1 (Manufacturing of PDMS-PDI) Polymer chain -(Si(CH 3 ) 2 -O) p -Si- (p is a positive integer) has an ethyleneamino group (-CH 2 -CH 2 -NH 2 Three types of PDMS with molecular weights of 1,000, 5,000, and 10,000 were heated to reflux at 140°C in the presence of imidazole and o-dichlorobenzene, and then a hydrochloric acid / ethanol mixed solution was added and the mixture was allowed to react for 30 minutes to form imidized polymers (PDMS-PDI) in which perylene diimide and PDMS were incorporated into the main skeleton.

[0042] Specifically, when the molecular weight of PDMS was 5000, 0.35 g of PTCDA, 6.00 g of PDMS, 1.40 g of imidazole, and 20 mL of o-dichlorobenzene were placed in a flask and reacted at 140°C for 12 hours under an argon atmosphere. After the reaction, 1.2 mL of 6N hydrochloric acid and 50 mL of ethanol were added to the flask and reacted for another hour. The resulting precipitate was collected by filtration and washed with methanol to obtain a rubber-like sample (PDMS-PDI). When the molecular weight of PDMS was 1000 and 10000, the reaction was carried out under the same conditions as above, except that the ratio of PTCDA to PDMS was changed, and then the reaction was similarly collected by filtration and washed with methanol to obtain each sample (PDMS-PDI).

[0043] For each of the three types of PDMS-PDI obtained by the above reaction, 1 HNMR, size exclusion chromatography (SEC), and Fourier transform infrared spectrophotometer (FT-IR) measurements were performed. NMR was performed using CDCl 3 The measurement was performed using THF as the eluent. The measurements were performed for both PDMS-PDIs. 1 In the 1H NMR spectrum, signals assigned to the aromatic ring of perylene diimide were observed, indicating that perylene diimide functions as the main chain skeleton of the polymer.

[0044] According to SEC measurements, the molecular weights of PDMS-PDI prepared from PDMS with number average molecular weights of 1000, 5000, and 10000 were 3000, 24000, and 16000, respectively. In the IR spectrum of both PDMS-PDIs, a peak attributable to the ring-closed perylene diimide was observed at 1700. -1 and 1658 cm -1 was observed. From the above measurement results, it is clear that regardless of which PDMS was used, a polymer containing perylene diimide and PDMS in the main chain skeleton: PDMS-PDI was obtained.

[0045] Example 1 (Production of selective gas separation membrane by spin casting method) For each of the PDMS-PDIs produced in Production Example 1, a 3 wt% chloroform solution was spin-cast onto a glass substrate to prepare a 0.2 μm-thick thin film of PDMS-PDI. The prepared thin film was floated in water to peel it off from the glass substrate, and picked up with a polyacrylonitrile (PAN) support having a diameter of 2.5 cm and a thickness of about 150 to 200 μm to prepare a selective gas separation member having a selective gas separation membrane made of a thin film of PDMS-PDI on the support. In order to hold the membrane at the periphery of the membrane, a 0.1 mm-thick Kapton tape cut into a circle with an inner diameter of 0.5 cm was attached onto the prepared membrane, and a 0.5 cm-thick aluminum cut into a circle was attached on top of that.

[0046] (Gas permeability measurement) For each of the three types of selective gas separation materials fabricated, a gas permeation measurement device, the schematic cross-sectional view of which is shown in Figure 2, was used to measure CO 2 , N 2 Gas permeation measurements were performed and found that N 2 and CO 2 The GPUs of the PDMS films were 405 and 4600, respectively. These GPU values ​​were comparable to those of previously reported PDMS materials, i.e., PDMS films prepared by thermal or light-based crosslinking reactions. This result indicates that the perylene diimide moieties act as physical crosslinking points, allowing the perylene diimide moieties to be easily crosslinked with CO from the atmosphere without the need for light or heat-based crosslinking reactions. 2 This shows that it is possible to create a selective gas separation membrane that can separate CO with high selectivity. 2 , N 2 The selectivity of CO 2 / N 2 =4600 / 405=11.4, which is also comparable to previously reported PDMS materials.

[0047] GPU is a unit that expresses the gas permeability of a membrane, and is expressed as 1 m when the differential pressure is 0.1 MPa (1 atm). 2The rate of permeation of 45 L of gas through the membrane in 1 minute is defined as 1000 GPU. In other words, 1 GPU = 45 x 10 -3 m 3 / 1m 2 ×60 seconds ×10 5 Pa = 7.5 × 10 -12 (m / Pa·sec).

[0048] The arrows in Fig. 2 indicate the direction of gas flow, and the gas flows into the gas permeation measuring device from the gas inlet, permeates the selective gas separation member consisting of a support and a selective gas separation membrane formed thereon, and flows out of the device from the gas outlet, where a flow meter is provided to measure the gas flow rate.

[0049] Example 2 (Production of selective gas separation membrane by spray method) Increasing the area of ​​selective gas separation membranes is important for their practical use. Although the spin-casting method enables the preparation of smooth thin films, there are limitations to the preparation of thin films when aiming for large areas due to the weight and size of the substrate. On the other hand, spray coating is said to be independent of the weight and size of the substrate. Therefore, the following experiment was conducted to examine whether the selective gas separation membranes described above can be formed by spray coating.

[0050] Three types of 0.5 wt% toluene solutions of PDMS-PDI produced in the above Production Example 1 were sprayed onto a circular support having the same thickness and diameter of 2.5 cm from a distance of 5 cm using PROFIX's TR-02 PRO, and in each case, a thin film of PDMS-PDI with an average thickness of 0.2 μm was formed over the entire support. In the conventional method of adjusting a film by crosslinking PDMS with light or heat, it is impossible to form a film on a support by spray coating, but the above experiment showed that the PDMS-PDI produced in the above Production Example 1 can be spray-coated to form a large-area film.

[0051] (Gas permeability measurement) The three types of coatings prepared by spray coating as described above were measured using the same gas permeability measuring device as in Example 1. 2 , N 2 Gas permeation measurements were performed and found that N 2 and CO 2 The GPUs are 390 and 3470, respectively, and 2 , N 2 The selectivity of CO 2 / N 2 =3470 / 390=8.9, which is comparable to that of previously reported PDMS materials. In addition, the spray coating method had the same GPU and CO values ​​as the spin casting method in Example 1. 2 / N 2 The selectivity observed indicates that the membrane is not defective.

Claims

1. A method for producing a selective gas separation membrane, comprising forming a polymer compound having hydrogen bonding properties into a main chain in which a polycyclic aromatic compound is introduced into the polymer chain of a polysiloxane or a polysiloxane derivative, into a membrane having a thickness of 0.01 μm or more.

2. 2. The method for producing a selective gas separation membrane according to claim 1, wherein the polysiloxane or polysiloxane derivative is polydimethylsiloxane.

3. 3. The method for producing a selective gas separation membrane according to claim 1, wherein the polymer compound is a polymer compound having a divalent group represented by the following general formula (1) as a main chain: 【Chemistry 1】 [In the formula, R is an alkyl group having 1 to 4 carbon atoms which may have a substituent, R1 is a divalent group selected from the following formula (2), (3) or (4), a and b are the same or different and are 1 to 5, m is 1 to 10, n is 7 to 270, and the multiple R and R1 may be the same or different from each other.] 【Chemistry 2】

4. 3. The method for producing a selective gas separation membrane according to claim 1, wherein the polymer compound is a polymer compound having a divalent group represented by the following general formula (5) as a main chain: 【Chemistry 3】 [In the formula, R is an alkyl group having 1 to 4 carbon atoms which may have a substituent, R2 is a divalent group selected from the following formula (6), (7) or (8), a and b are the same or different and are 1 to 5, m is 1 to 60, n is 7 to 40, and the multiple R and R2 may be the same or different from each other.] 【Chemistry 4】

5. 5. The method for producing a selective gas separation membrane according to claim 1, wherein the membrane is formed by spray coating a solution of the polymer compound.

6. A selective gas separation membrane, which is produced by the method for producing a selective gas separation membrane according to any one of claims 1 to 5.

7. A method for concentrating carbon dioxide in a gas, comprising permeating the gas through the selective gas separation membrane according to claim 6.

8. 7. A selective gas separation member comprising: a support that is permeable to carbon dioxide; and the selective gas separation membrane according to claim 6 formed on the support.

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