Air separation membrane, method for producing air separation membrane, air separation device and oxygen mask

Abstract

To provide an air separation film that is very thin and has high transmittance as well as high mechanical strength, and allows efficient separation between oxygen and nitrogen in the air, and a method for producing the same.SOLUTION: An air separation film has an air-permeable support 3, and a polymeric thin film 2 that is superimposed on the support 3, separates oxygen and nitrogen in the air, is free of defects, and has a thickness of 100 nm or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an air separation membrane having a thin polymer film that is mainly composed of a polymer material and separates oxygen and nitrogen in the air, a method for producing this air separation membrane, and an air separation device and an oxygen mask that use the air separation membrane. [Background technology]

[0002] Air is composed mainly of 78% nitrogen gas, 21% oxygen gas, and 1% argon gas, carbon dioxide gas, water, and other low-concentration components. The main components, nitrogen gas and oxygen gas, are purified using various technologies and are industrialized for use as useful substances.

[0003] Oxygen gas is produced by removing or reducing the nitrogen gas component from air, and air with an oxygen concentration increased to about 40% higher than normal (oxygen enriched air, hereafter sometimes referred to as "oxygen-enriched air") is used in a variety of fields, including energy, agriculture, and medicine.

[0004] As an example of the industrial use of oxygen gas, for example, in boiler combustion, the use of air with an oxygen concentration higher than normal, up to 40% (hereinafter sometimes referred to as "oxygen-enriched air") has been shown to have the effect of improving combustion efficiency and combustion temperature, leading to energy savings, reducing the amount of exhaust gas, and reducing nitrogen oxides in the exhaust gas. Furthermore, in other fields, oxygen gas is also used to promote aerobic fermentation, treat sewage, and treat respiratory diseases.

[0005] Currently, industrial production of oxygen gas using air as a raw material is often carried out by cryogenic separation, and oxygen is recovered in liquid or gas form. Gaseous oxygen is also produced by adsorption separation, and the PSA (Pressure Swing Adsorption) method is also used. On the other hand, it is said that only about 1% of oxygen gas is produced by electrolysis of water.

[0006] Generally, when high oxygen purity is required, cryogenic separation methods are used to produce products with oxygen purity of up to 99.8%. For lower purities (90-93%), the PSA method is more efficient. While this oxygen may be used at the manufacturing site, it is transported in cylinders as high-pressure gas and diluted to the required concentration depending on the intended use. Therefore, the energy consumption is large throughout the process, from the manufacturing stage to the utilization stage.

[0007] For nitrogen gas, ammonia synthesis under high temperature and pressure conditions using the Haber-Bosch method is widely used. For industrial production of nitrogen gas, the PSA method can be used, as in the case of oxygen gas. Systems that produce nitrogen gas with purity over 99% are commercially available when molecular sieve carbon is used as the adsorbent. For use of nitrogen gas, a PSA separation device is installed on-site to directly supply high purity nitrogen gas, or pure nitrogen gas is pressurized and packed into cylinders, which are then transported and supplied to the consumer. In the following explanation, air with a nitrogen concentration of over 85% may be referred to as "nitrogen-enriched air."

[0008] A lot of research has already been done on oxygen concentration using separation membranes, and representative polymeric materials for oxygen gas separation include silicone (polydimethylsiloxane) and poly-4-methylpentene-1 (for example, "Materials Science of Membranes for Gas and Vapor Separation", Ed. Y. Yampolskii, I. Pinnau, & BDFreeman, John Wiley & Sons Ltd. 2006.).

[0009] However, in these examples, the oxygen gas selectivity (O2 / N2) is about 2-3, and the oxygen gas permeability is only about 700 Barrer (PDMS (Polydimethylsiloxane), 35℃) (Polymer Handbook), and it is thought that they have not yet been used as a practical technology for oxygen production. Of course, gas productivity can be improved by using high-pressure compressed air, but the energy cost naturally increases.

[0010] If an economical "air separation technology using separation membranes" could be put into practical use, which would drastically reduce energy costs and be usable at room temperature under conditions of low energy consumption (for example, a pressure difference between the front and rear of the separation membrane of less than 1 atmosphere), it would be extremely useful as an oxygen and nitrogen enrichment technology, and it is expected that the use of oxygen and nitrogen gas obtained by air separation would expand significantly. For example, by directly connecting the oxygen enrichment process to engines or thermal power generation, it would be possible to greatly improve energy efficiency, and as a new low-carbon technology, its effects would likely extend to a wide range of industries. It is also believed that oxygen enrichment for medical purposes could be achieved with a simpler system.

[0011] Furthermore, if a separation system can be realized with a simple configuration and placed at the site where the gas is used (on-site), there will be no need to transport 100% gas in high-pressure cylinders and the separated gas can be used directly, so there will often be no need for a high level of gas separation purity of over 90%.

[0012] Air separation membranes used for oxygen enrichment are generally made of polymers, which allow oxygen to pass through more easily than nitrogen. Normally, if the required oxygen concentration is 25-40%, the separation membrane does not need to have particularly excellent air separation properties. From the viewpoint of practicality, however, the higher the permeability (permeability rate, permeation speed), the more desirable it is. Thinning the membrane is an effective way to improve permeability, but this can lead to a decrease in the mechanical strength of the membrane. The same situation exists for nitrogen gas. In order to simultaneously achieve these two difficult-to-achieve characteristics of thinning the membrane and ensuring mechanical strength, methods such as multilayer coating, cross-linking, and copolymerization are used, but satisfactory results have not been obtained.

[0013] As a technology relating to a polymer thin film having gas separation properties, there is a gas separation membrane having a gas separation layer containing a crosslinked cellulose resin and cellulose nanofibers, and the crosslinked cellulose resin has, in the crosslinked structure, * -OMO- * , * -SMS- * , * -NR a C(=O)- * , * -NR b C(=O)NR b - * , * -O-CH2-O- * , * -S-(CH2)2-S- * , * -OC(=O)O- * , * -SO3 - N + (R c )3- * and * -P(=O)(OH)O - N + (R d )3- * A gas separation membrane having at least one linking structure selected from the group consisting of: a , R b , R c and R d each independently represents a hydrogen atom or an alkyl group. * indicates a linking site.) is known. (Patent Document 1)

[0014] According to Patent Document 1, by forming a gas separation membrane in which a gas separation layer is formed using a crosslinked cellulose resin having a specific linking structure in the crosslinked structure, it is possible to provide a gas separation membrane that has excellent gas permeability as well as excellent gas separation selectivity, is resistant to plasticization even when used under high temperature, high pressure and high humidity conditions, exhibits excellent gas separation performance, is less susceptible to the effects of toluene and the like, which is an impurity component present in natural gas, has excellent folding resistance, can be processed into various module shapes, can be manufactured with a high yield, and further exhibits stable gas separation performance from the beginning of use. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Patent No. 6349026 DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0016] However, according to the technology described in Patent Document 1, gas separation membranes (composite membranes and asymmetric membranes) can be suitably used for gas separation and recovery and gas separation and purification, and are said to be capable of efficiently separating specific gases from gas mixtures containing, for example, hydrogen, helium, carbon monoxide, carbon dioxide, hydrogen sulfide, oxygen, nitrogen, ammonia, sulfur oxides, nitrogen oxides, hydrocarbons such as methane and ethane, unsaturated hydrocarbons such as propylene, and perfluoro compounds such as tetrafluoroethane. In particular, it is said to be preferable to use a gas separation membrane that selectively separates carbon dioxide from a gas mixture containing carbon dioxide / hydrocarbon (methane), but no preferred configuration or specific characteristics are disclosed for an air separation membrane that separates oxygen and nitrogen in air.

[0017] Furthermore, in the gas separation membrane described in Patent Document 1, in order to construct the gas separation layer from a crosslinked cellulose resin having a specific linking structure in the crosslinked structure, a specific metal complex is used as a crosslinking agent, and a metal bridge is formed by a ligand exchange reaction with the cellulose resin. In this case, the concentration of the cellulose resin and the metal complex as a crosslinking agent in the coating solution is set to a certain level or less to suppress the ligand exchange reaction in the coating solution, and further, by coating this coating solution on a porous support layer as a thin film, the ligand exchange reaction is quickly promoted with the rapid evaporation of the solvent, and a metal bridge structure is formed in the cellulose resin. This makes the microstructure of the gas separation layer complex, and as a result, the manufacturing process is also complicated.

[0018] Furthermore, in Patent Document 1, the gas separation performance of the gas separation membrane is evaluated by adjusting a mixed gas of carbon dioxide (CO2) and methane (CH4) at a volume ratio of 30:70 to a total pressure of 4 MPa (partial pressure of CO2: 1.2 MPa) on the gas supply side, a flow rate of 500 mL / min, and 45°C, but the carbon dioxide permeability is described as being at most about 90 GPU. According to the study by the applicant of this patent application, it has been found that the CO2 / O2 selectivity ratio in the polymer thin film is about 5, and the CO2 / N2 selectivity ratio is about 11, and it is estimated that the oxygen permeability of the gas separation membrane described in Patent Document 1 is about 90 GPU / 5 = 18 GPU, and the nitrogen permeability is about 90 GPU / 11 = 8.2 GPU. However, with such a permeability, it is practically difficult to apply it to industrial applications that require large amounts of oxygen-enriched air or nitrogen-enriched air.

[0019] The present invention has been devised to solve the problems of the prior art, and has an object to provide an air separation membrane that is extremely thin and therefore has high permeability and high mechanical strength, and that is capable of separating oxygen and nitrogen in the air with high efficiency, as well as a method for manufacturing the same. Another object of the present invention is to provide an air separation device and an oxygen mask to which the air separation membrane is applied. [Means for solving the problem]

[0020] The present invention, made to solve the above problems, is an air separation membrane comprising an air-permeable support and a defect-free thin polymer film having a thickness of 100 nm or less that is overlaid on the support and separates oxygen and nitrogen in the air.

[0021] This makes it possible to separate oxygen and nitrogen in the air with high efficiency.

[0022] In addition, the present invention provides a polymer thin film having an oxygen permeability and a nitrogen permeability of 1000 GPU or more.

[0023] This makes it possible to introduce air separation membranes at low cost even in industrial fields that use large amounts of oxygen-enriched air or nitrogen-enriched air.

[0024] In the present invention, a reinforcing film is superimposed on the support so as to be in close contact with the thin polymer film.

[0025] This allows the thin polymer membrane to be formed in close contact with the reinforcing membrane, greatly improving the mechanical strength of the entire membrane, making it possible to make the thin polymer membrane in the air separation membrane as thin as possible (thin layer).

[0026] In the present invention, the reinforcing membrane contains at least cellulose nanofibers.

[0027] This significantly improves the mechanical strength of the air separation membrane, and because the material cost of cellulose nanofibers is extremely low, it makes it possible to produce air separation membranes at lower cost.

[0028] In addition, the present invention is such that at least cellulose nanofibers are dispersed in the polymer thin film.

[0029] This significantly improves the mechanical strength of the thin polymer film that makes up the air separation membrane, and because the material cost of cellulose nanofiber is extremely low, it makes it possible to manufacture air separation membranes at lower cost.

[0030] In the present invention, the polymer thin film is mainly composed of polysiloxane.

[0031] This allows air separation membranes to be manufactured at lower cost using commonly available materials.

[0032] In the present invention, the polymer thin film is mainly composed of a crosslinkable polymer.

[0033] This makes it possible to obtain an air separation membrane with high functionality and high mechanical strength even by using a crosslinked polymer, which is a more common polymer material.

[0034] The present invention provides an air separation device comprising an intake port, a first outlet, an air separation section including an air separation membrane arranged in a flow path between the intake port and the first outlet, and a second outlet, wherein the first outlet is provided downstream of the air separation section in the flow path and the second outlet is provided upstream of the air separation section in the flow path, and oxygen-enriched air is obtained from the first outlet and nitrogen-enriched air is obtained from the second outlet.

[0035] This makes it possible to obtain oxygen-enriched air having a higher oxygen concentration than air and nitrogen-enriched air having a higher nitrogen concentration than air.

[0036] In the present invention, the air separation section comprises the air separation membranes in multiple stages.

[0037] This makes it possible to increase the oxygen concentration by increasing the number of stages.

[0038] The present invention is also an oxygen mask including an air separation membrane.

[0039] As a result, the oxygen mask itself generates oxygen-enriched air with a high oxygen concentration, eliminating the need for complex equipment such as cylinders and piping to supply oxygen to the oxygen mask.

[0040] The present invention also comprises an air separation unit including the air separation membrane, and a unit support having a generally flat plate shape and a plurality of through holes for supporting a plurality of the air separation units, wherein the total area of ​​the air separation membranes included in the plurality of air separation units is greater than the area of ​​the unit support when the unit support does not have the through holes.

[0041] This increases the area of ​​the air separation membrane, thereby improving the oxygen permeability.

[0042] The present invention also provides a unit support for supporting a plurality of the air separation units, the unit support being configured with a curved surface, and the air separation units being disposed on the unit support configured with the curved surface.

[0043] This increases the area of ​​the air separation membrane, thereby improving the oxygen permeability.

[0044] In addition, the present invention provides an oxygen mask in which an internal space is formed between the oxygen mask and the face of a person wearing the oxygen mask, and which comprises a communication hole that communicates the internal space with an external space, and a valve member that is provided in the communication hole and discharges air from the internal space to the external space when the internal space is under positive pressure, and blocks the internal space from the external space when the internal space is under negative pressure.

[0045] This creates a negative pressure in the internal space when a person inhales, allowing air to be taken in from the external space to obtain oxygen-enriched air, while creating a positive pressure in the internal space when a person exhales, allowing exhaled air to be exhausted to the external space.

[0046] The present invention also provides a method for manufacturing an air separation membrane, comprising: a first step of forming a reinforcing membrane on a substrate; a second step of forming a defect-free polymer thin film having a thickness of 100 nm or less on the reinforcing membrane, which separates oxygen and nitrogen in the air; a third step of separating the reinforcing membrane and the polymer thin film from the substrate; and a fourth step of superimposing the reinforcing membrane and the polymer thin film separated from the substrate on an air-permeable support.

[0047] This makes it possible to form defect-free polymer thin films with thicknesses of 100 nm or less.

[0048] In the present invention, in the first and second steps, the reinforcing film and the thin polymer film are formed on the base material by a spin coating method.

[0049] This allows the reinforcing film and the thin polymer film to be formed in close contact with each other, and further allows the thin polymer film to be formed without defects and with a thickness of 100 nm or less.

[0050] The present invention also includes a preliminary step of forming a sacrificial layer on the substrate, and in the third step, the sacrificial layer formed in the preliminary step is dissolved to separate the reinforcing film and the polymer thin film from the substrate.

[0051] This makes it possible to transfer the film onto the support without applying excessive external force to the reinforcing film and the thin polymer film. Effect of the Invention

[0052] In this way, according to the present invention, it is possible to separate oxygen and nitrogen in the air with high efficiency. [Brief description of the drawings]

[0053] [Figure 1] 1(a) to 1(d) are explanatory diagrams showing the configuration of an air separation membrane 1 according to the present invention. [Diagram 2]Graph showing the relationship between the thickness of the PDMS / CNF membrane of the air separation membrane 1 according to the present invention and the oxygen permeability and nitrogen permeability. [Diagram 3] FIG. 1(a) is an explanatory diagram showing the configuration of an air separation device 10 to which an air separation membrane 1 according to the present invention is applied, and FIG. 1(b) is an explanatory diagram showing a modified example of the air separation device 10. [Figure 4] FIG. 1 is an explanatory diagram showing the configuration of an oxygen mask 30 to which the air separation membrane 1 according to the present invention is applied; [Diagram 5] FIG. 1 is an explanatory diagram showing the configuration of an air separation unit 32a arranged in an oxygen mask 30. [Figure 6] FIG. 1 is an explanatory diagram illustrating a state in which the oxygen mask 30 is used by a user. [Figure 7] FIG. 1(a) is an explanatory diagram showing the configuration of a first modified example of the oxygen mask 30, and FIG. 1(b) is an explanatory diagram showing the configuration of a second modified example of the oxygen mask 30. [Figure 8] FIG. 13 is an explanatory diagram showing the configuration of a third modified example of the oxygen mask 30. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054] (First embodiment) Fig. 1 is an explanatory diagram showing the configuration of an air separation membrane 1 according to the present invention. Hereinafter, an embodiment of the present invention will be described with reference to Fig. 1. As shown in Fig. 1(a), the air separation membrane 1 is composed of a support 3, a polymer thin film 2 superimposed on the support 3, and a reinforcing membrane 4 provided between the support 3 and the polymer thin film 2.

[0055] As materials for forming the polymer thin film 2, for example, vinyl polymers, polysiloxanes, and cross-linked polymers can be suitably used. Here, vinyl polymers and polysiloxanes are considered to have low mechanical strength and are unable to ensure self-supporting properties when used alone at a film thickness (for example, 100 nm or less) that can effectively exhibit functionality such as gas (here, air) separation properties. In this case, by forming the polymer thin film 2, which is mainly composed of vinyl polymers or polysiloxane, in close contact with the reinforcing film 4, it becomes possible to achieve both functionality and self-supporting properties.

[0056] That is, when the polymer thin film 2 is composed mainly of a vinyl polymer or mainly of polysiloxane, the air separation membrane 1 is preferably configured as shown in Fig. 1(a), in which case the air separation membrane 1 includes a reinforcing membrane 4 formed between the support 3 and the polymer thin film 2 so as to be in close contact with at least the polymer thin film 2. Alternatively, as shown in Fig. 1(b), the air separation membrane 1 may be configured to include a polymer thin film 2 formed between the support 3 and the reinforcing membrane 4 so as to be in close contact with at least the reinforcing membrane 4.

[0057] That is, air separation membrane 1 is obtained by superposing polymer thin film 2 and reinforcing membrane 4 formed so as to be in close contact with support 3. In the fourth step (transfer step) of the manufacturing process of air separation membrane 1 described below, the configuration of Fig. 1(a) can be selected by contacting reinforcing membrane 4 with support 3, and the configuration of Fig. 1(b) can be selected by contacting support 3 with polymer thin film 2.

[0058] On the other hand, crosslinked polymers are considered to be self-supporting even at a film thickness that allows them to effectively exhibit their functionality (for example, 100 nm or less, similar to vinyl polymers and polysiloxanes). Here, a crosslinked polymer (crosslinked polymer) refers to a polymer that has a three-dimensional network structure (crosslinked structure) formed by bonding multiple linear polymer chains through a chemical reaction, and includes, for example, epoxy resins in which epoxy groups and amino groups as functional groups are crosslinked through a chemical reaction.

[0059] As for epoxy resin, an example of a self-supporting polymer thin film with a thickness of 20 nm is given in "A Large, Freestanding, 20nm Thick Nanomembrane Based on an Epoxy Resin, H. Watanabe T. Kunitake, Advanced Materials Volume 19, Issue 7, Pages 909-912, 2007." (https: / / onlinelibrary.wiley.com / doi / abs / 10.1002 / adma.200601630) It is published in.

[0060] Here, when the polymer thin film 2 is mainly made of a crosslinkable polymer, the polymer thin film 2 has self-supporting properties as described above, so the reinforcing membrane 4 is not an essential component, and the air separation membrane 1 can be configured as shown in Figure 1(d). That is, the air separation membrane 1 can be configured with a support 3 and a polymer thin film 2 superimposed on the support 3. Of course, even when the polymer thin film 2 is made of a crosslinkable polymer, the polymer thin film 2 can be brought into close contact with the reinforcing membrane 4, that is, the configuration shown in Figure 1(a) or Figure 1(b) can be used, and in this case, the air separation membrane 1 can ensure even greater mechanical strength in addition to its air separation function.

[0061] In the first embodiment, the thickness D1 of the polymer thin film 2 is 100 nm or less. By setting the thickness D1 of the polymer thin film 2 to 100 nm or less, it is possible to significantly improve the functionality (here, the air separation characteristics) of the air separation membrane 1.

[0062] The reinforcing membrane 4 has a configuration in which an organic polymer 5 is contained within the membrane. Here, the organic polymer 5 can be, for example, a cellulose nanofiber. The cellulose nanofiber includes an oxidized cellulose nanofiber, and further, a mixture of a cellulose nanofiber and an oxidized cellulose nanofiber (hereinafter, these may be collectively referred to as "CNFs") may be used as the organic polymer 5.

[0063] The CNFs as the organic polymer 5 form fibrils, which are small fibers (fibrous structures). Fibrils have high mechanical strength as a material, and by adhering the reinforcing film 4 made of CNFs to the polymer thin film 2, an extremely high overall mechanical strength is achieved. In addition, CNFs are manufactured at low cost by mechanical defibration from abundant resources such as wood, and are also environmentally friendly materials because they are plant fibers. The CNFs have a diameter (e.g., 4 nm to 90 nm) smaller than the thickness of the polymer thin film 2.

[0064] From the viewpoint of the contribution of the organic polymer 5 to improving the mechanical strength, in addition to the configuration in which the polymer thin film 2 and the reinforcing membrane 4 are superimposed on the support 3, the air separation membrane 1 may be configured so that the organic polymer 5 (here, CNFs) is contained inside the polymer thin film 2 and is uniformly dispersed within the membrane, as shown in Fig. 1(c). Of course, the above-mentioned reinforcing membrane 4 may be adhered closely to the polymer thin film 2 in which the organic polymer 5 is dispersed.

[0065] In Figures 1(a), 1(b) and 1(c), the organic polymers 5 having the same fiber length are shown as if aligned in a specific direction, but this is merely a schematic representation. In reality, the fiber lengths of the organic polymers 5 vary (5 μm or more), and the organic polymers 5 are oriented in all directions and form the reinforcing membrane 4 in a complex entangled state (Figures 1(a) and 1(b)), or are dispersed in the polymer thin film 2 (Figure 1(c)).

[0066] In the first embodiment, the above-mentioned CNFs can be suitably used as the organic polymer 5 constituting the reinforcing membrane 4, but other organic polymers 5 may also be used. Examples of the other organic polymers 5 that can be used include polymers produced by a manufacturing method such as electrospinning, fibrin, which is a protein formed by bundling fine fibers and is involved in blood clotting, peptides, collagen, etc., and further, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) may also be used.

[0067] Here, for example, when DNA is used as the organic polymer 5, since DNA is a fiber with a diameter of 2 nm, the thickness of the reinforcing film 4 may be in the range of, for example, 2 nm to 100 nm. Also, when the organic polymer 5 is CNF, the thickness of the reinforcing film 4 may be in the range of, for example, 4 nm to 100 nm.

[0068] The support 3 is made of, for example, polyacrylonitrile (hereinafter, sometimes referred to as "PAN"). PAN is a plastic whose main component is a base polymer containing 50% or more of acrylonitrile, and has characteristics such as gas barrier properties and high rigidity. On the other hand, by applying tension to a film made of PAN (PAN film), a porous PAN film having countless fine voids and high air permeability can be obtained. In the first embodiment, a porous PAN film having high air permeability is used as the support 3. In the following explanation, the porous PAN film as the support 3 may be referred to as a "PAN support film". EXAMPLES

[0069] Example 1 of the present invention will be described below. First, poly(4-vinylphenol) (Sigma-Aldrich, Mw 11000) was dissolved in ethanol to prepare a 15 wt% poly(4-vinylphenol) / ethanol solution. 1.0 g of cellulose nanofiber (Nanoforest-S (Nanoforest is a registered trademark) manufactured by Chuetsu Pulp Industries, hereinafter sometimes referred to as "CNF") with a solid content of 10 wt% was mixed with 39.0 g of pure water and subjected to ultrasonic treatment for 1 hour to prepare a 0.25 wt% CNF / aqueous dispersion. This dispersion was centrifuged (9000 RPM, 3 min) using a Thermo Fisher Scientific centrifuge. The supernatant was removed to obtain a 0.1 wt% CNF / aqueous dispersion. Pure water was added to this to prepare a 0.05 wt% CNF / aqueous dispersion.

[0070] Separately, a 10v / v% PDMS / hexane solution was prepared from 1mL of A liquid (base material) of polydimethylsilicone (hereinafter sometimes referred to as "PDMS") resin (silicone elastomer kit, Sylgard 184 (SYLGARD is a registered trademark) manufactured by Toray Dow Corning), 0.1mL of B liquid (curing agent), and 9mL of hexane. This was further diluted with hexane to prepare a 0.5v / v% PDMS / hexane solution.

[0071] Next, a sacrificial layer was formed on the glass substrate (base material) that had been treated with oxygen plasma. Specifically, the sacrificial layer was formed by spin coating using an ethanol solution of poly(4-vinylphenol) (preliminary step).

[0072] The surface was made hydrophilic by oxygen plasma treatment (10 W, 30 sec), and then a reinforcing film 4 was formed (on the substrate with the sacrificial layer) by spin coating using a 0.05 wt% CNF / water dispersion (first step), and then a polymer thin film 2 was formed by spin coating using a 0.5 v / v% PDMS / hexane solution (second step).

[0073] In this way, the reinforcing film 4 and the polymer thin film 2 are formed in close contact with each other without being mixed with each other by the process of continuously spin-coating a PDMS / hexane solution, which is poorly soluble in water, onto the spin-coated CNF / aqueous dispersion. Furthermore, since the surface smoothness of the CNF-oxidized CNF aqueous dispersion spin-coated onto the hydrophilized sacrificial layer is extremely high, the polymer thin film 2 formed on top of this can be formed without defects and with a thickness of 100 nm or less. Hereinafter, the reinforcing film 4 and the polymer thin film 2 may be collectively referred to as the "PDMS / CNF film."

[0074] The glass substrate on which the sacrificial layer, reinforcing film 4, and polymer thin film 2 were successively formed by the above-mentioned steps was heated and dried, and then immersed in ethanol to dissolve the sacrificial layer, and the PDMS / CNF film (polymer thin film 2 and reinforcing film 4) was peeled off (separated) from the glass substrate (third step).

[0075] This was transferred (superimposed) onto a separately prepared PAN support membrane (UF010104, manufactured by SolSepBV) as an air-permeable support 3 (step 4) to obtain a PDMS / CNF membrane / PAN support membrane, i.e., an air separation membrane 1 having CNF-oxidized CNF as a reinforcing membrane 4 between a PAN support membrane as support 3 and a PDMS layer (hereinafter sometimes referred to as the "PDMS membrane") as a thin polymer film 2.

[0076] When the cross section of the air separation membrane 1 thus obtained was observed with a scanning electron microscope (Hitachi, S-5200), the thickness of the PDMS / CNF membrane excluding the support 3 was approximately 30 nm, of which the thickness of the CNF-oxidized CNF membrane was approximately 10 nm. Hereinafter, the air separation membrane 1 produced in Example 1 is referred to as the "30 nm PDMS / CNF membrane / PAN membrane." EXAMPLES

[0077] Except for changing the concentration of the PDMS / hexane solution, the PDMS / CNF membrane was prepared by the same process as described in Example 1. In Example 2, the thickness of the PDMS membrane was changed by changing the concentration of the PDMS / hexane solution (the same was true for Example 3).

[0078] In Example 2, the thickness of the PDMS / CNF membrane excluding the PAN support membrane in the air separation membrane 1 was 90 nm. Hereinafter, the air separation membrane 1 in Example 2 is referred to as "90 nm PDMS / CNF membrane / PAN membrane." EXAMPLES

[0079] In Example 3, the thickness of the PDMS / CNF membrane excluding the PAN support membrane in the air separation membrane 1 was 54 nm. Hereinafter, the air separation membrane 1 in Example 3 is referred to as "54 nm PDMS / CNF membrane / PAN membrane." EXAMPLES

[0080] Example 4 of the present invention will be described below. A PDMS / CNF membrane was produced using the same process as that described in Example 1. However, unlike Examples 1 to 3 described above, Example 4 had a reinforcing membrane 4 made of CNF and oxidized cellulose nanofibers (hereinafter sometimes referred to as "oxidized CNF"). Oxidized CNF is an isolated nanofiber with a diameter of several nm and a length of several μm or more, and the variation in diameter is also extremely small. It is believed that the use of oxidized CNF reduces the variation in the film thickness and mechanical strength in the planar direction of the reinforcing membrane 4.

[0081] 1.0 g of CNF with a solid content of 10 wt% was mixed with 39.0 g of pure water and ultrasonically treated for 1 hour to prepare a 0.25 wt% CNF / water dispersion. This dispersion was centrifuged using a Thermo Fisher Scientific centrifuge (9000 RPM, 3 min). The supernatant was removed to obtain a 0.1 wt% CNF / water dispersion.

[0082] Separately, a mixture of oxidized CNF with a solid content of 1 wt% and pure water was ultrasonically treated for 1 hour to obtain a 0.1 wt% oxidized CNF / water dispersion.

[0083] The above-mentioned 0.1 wt% CNF / aqueous dispersion and 0.1 wt% oxidized CNF / aqueous dispersion were added in a weight ratio of 1:1 and mixed thoroughly, and pure water was then added to prepare a 0.05 wt% CNF-oxidized CNF / aqueous dispersion.

[0084] Except for using 0.05 wt% CNF-oxidized CNF / aqueous dispersion instead of 0.05 wt% CNF / aqueous dispersion, the other steps were the same as in Example 1 to obtain an air separation membrane 1 having CNF-oxidized CNF as a reinforcing membrane 4. In Example 4, the thickness of the PDMS / CNF-oxidized CNF membrane excluding the PAN support membrane in the air separation membrane 1 was less than 30 nm (from the viewpoint of the reliability of the measurement accuracy, the data in Example 4 are reference values). Hereinafter, the air separation membrane 1 of Example 4 is referred to as "<30 nm PDMS / CNF-oxidized CNF membrane / PAN membrane."

[0085] In Examples 2 and 3, the thickness of the CNF film was 10 to 20 nm. From the measurement results of Examples 1 to 3, the thickness of the CNF-oxidized CNF film in Example 4 is estimated to be 10 to 20 nm. Therefore, in Examples 1 to 4, the thickness of the PDMS / CNF film (or PDMS / CNF-oxidized CNF film) is 100 nm or less (30 nm, 54 nm, 90 nm, <30 nm). Furthermore, considering the thickness of the CNF film (here, 10 nm), it can be said that the thickness of the PDMS film (polymer thin film 2) is 90 nm or less in any case (20 nm, 44 nm, 80 nm <20 nm). Comparative Example 1

[0086] Hereinafter, Comparative Example 1 will be described. Poly(4-vinylphenol) was dissolved in ethanol to prepare a 15 wt% poly(4-vinylphenol) / ethanol solution. Using this, a sacrificial layer was formed by spin coating on a glass substrate that had been subjected to oxygen plasma treatment (10 W, 30 sec).

[0087] Separately, 5 v / v % PDMS / hexane solution was prepared by adding hexane to 1 mL of PDMS A liquid (base material) and 0.1 mL of PDMS B liquid (curing agent), and a film was formed by the spin coating method in the same manner.

[0088] The glass substrate was heated at 100°C for 35 minutes to fully harden the PDMS, and then immersed in ethanol and left to stand, causing the PDMS film to peel off from the substrate. This was transferred to a PAN support membrane to obtain a PDMS / PAN membrane. When the cross section of the membrane was observed with a scanning electron microscope, the thickness of the PDMS membrane excluding the PAN support membrane was approximately 1 μm. Hereinafter, the air separation membrane 1 produced in Comparative Example 1 is referred to as the "1 μm PDMS / PAN membrane." Comparative Example 2

[0089] Hereinafter, a description will be given of Comparative Example 2. First, in the same manner as in Comparative Example 1, a 15 wt % poly(4-vinylphenol) / ethanol solution was prepared.

[0090] Separately, a 10 v / v % PDMS / hexane solution was prepared from 1 mL of PDMS A solution (base material), 0.1 mL of B solution (curing agent), and 9 mL of hexane. A 1.5 v / v % PDMS / hexane solution was also prepared from 1.5 mL of this 10 v / v % PDMS / hexane solution and 8.5 mL of hexane.

[0091] A sacrificial layer was formed on a glass substrate that had been surface-treated with oxygen plasma using a poly(4-vinylphenol) / ethanol solution, and a 1.5 v / v% PDMS / hexane solution was spin-coated onto the upper surface of the sacrificial layer and heated at 100°C for 35 minutes to form a PDMS film. The glass substrate was left in ethanol to peel the PDMS film from the glass substrate and transferred onto a PAN support film to obtain a PDMS / PAN film.

[0092] When the cross section of this film was observed with a scanning electron microscope, the thickness of the PDMS film excluding the PAN support film was 150 nm. Hereinafter, the polymer thin film 2 prepared in Comparative Example 2 is referred to as "150 nm PDMS / PAN film."

[0093] Gas permeation tests were conducted on the air separation membranes 1 obtained in Examples 1 to 4 and Comparative Examples 1 and 2. Table 1 shows the permeabilities of carbon dioxide (CO2), nitrogen (N2) and oxygen (O2), as well as the CO2 / N2 selectivity, CO2 / O2 selectivity and O2 / N2 selectivity of each air separation membrane 1. The "film thickness" shown in Table 1 refers to the film thickness of the PDMS / CNF membrane or PDMS / CNF-oxidized CNF membrane, excluding the thickness of the PAN support membrane from the air separation membrane 1. [Table 1]

[0094] The thicknesses of the PDMS / CNF membranes of the air separation membrane 1 produced in Examples 1 to 3 and the PDMS / CNF-oxidized CNF membrane produced in Example 4 were all 100 nm or less, and were in the range of 30 nm to 90 nm, except for Example 4, where the membrane thickness could not be measured precisely. Furthermore, as described above, if the membrane thicknesses of the CNF membrane and CNF-oxidized CNF membrane are 10 nm, the membrane thickness of the PDMS membrane (polymer thin film 2) is in the range of 20 to 80 nm.

[0095] Referring to the description in [Table 1], in Comparative Example 1 (1 μm PDMS / PAN membrane) and Comparative Example 2 (150 nm PDMS / PAN membrane), the nitrogen (N2) permeability is 270 GPU and 981 GPU, which does not exceed 1000 GPU, and the oxygen (O2) permeability is 605 GPU and 2075 GPU. On the other hand, in Examples 1 to 4 (30 nm PDMS / CNF membrane / PAN membrane, 90 nm PDMS / CNF membrane / PAN membrane, 54 nm PDMS / CNF membrane / PAN membrane, <30 nm PDMS / CNF-oxidized CNF membrane / PAN membrane), the nitrogen permeability exceeds 1000 GPU and the oxygen permeability exceeds 2500 GPU. That is, the oxygen permeability and the nitrogen permeability of the polymer thin film 2 constituting the air separation membrane 1 according to the present invention are 1000 GPU or more.

[0096] Thus, the PDMS / CNF membranes of Examples 1 to 3 and the PDMS / CNF-oxidized CNF membrane of Example 4 show high oxygen and nitrogen permeabilities. The O2 / N2 selectivity ratio is 2.1 to 2.3, clearly indicating that the PDMS / CNF membrane and the PDMS / CNF-oxidized CNF membrane have an air separation function that separates oxygen and nitrogen in air. In other words, the air separation membrane 1 according to the present invention can increase or decrease the oxygen concentration or nitrogen concentration in air.

[0097] In addition, the O2 / N2 selectivity ratios in Comparative Examples 1 and 2 and Examples 1 to 4 are 2.1 to 2.3, and similar selectivity is observed, so it can be seen that none of the films have defects that cause gas leakage. In addition, the CO2 / N2 selectivity ratios are all about 10 to 11, and the CO2 / N2 selectivity ratio of the PDMS membrane is about 10 to 11 (Reference: Shigenori Fujikawa, Miho Ariyoshi, Roman Selyanchyn, Toyoki Kunitake, Chemistry Letters, 2019, Vol.48, No.11, 1351-1354). Considering this, it is clear that none of the air separation membranes 1 in Examples 1 to 4 contain defects that cause gas leakage (i.e., are defect-free).

[0098] Thus, the air separation membrane 1 of the present invention comprises a support 3 which is air permeable (allowing all gas components contained in air to pass through), and a defect-free polymer thin film 2 having a thickness of 100 nm or less which is superimposed on the support 3 and separates oxygen and nitrogen in the air.

[0099] Fig. 2 is a graph showing the relationship between the membrane thickness of the PDMS / CNF membrane of the air separation membrane 1 according to the present invention and the oxygen permeability and nitrogen permeability. In Fig. 2, the horizontal axis is the membrane thickness [nm] of the PDMS / CNF membrane in the air separation membrane 1 (however, in Comparative Examples 1 and 2, the membrane thickness is the PDMS membrane), and the vertical axis is the gas permeability [GPU] of the air separation membrane 1. Note that Fig. 2 is a graph of the N2 permeability and O2 permeability extracted from Table 1 for Comparative Examples 1 and 2 and Examples 1 to 3.

[0100] Now, in industrial fields that use large amounts of oxygen-enriched air or nitrogen-enriched air (for example, applications to improve combustion efficiency and prevent abnormal combustion), taking into account the cost of introduction, it is desirable for the air separation membrane 1 to have a permeability of 1000 GPU (= 45 liters of gas permeating per minute when a differential pressure of 1 atmosphere is applied to the air pressure on both sides of a 1 square meter membrane) or more.

[0101] As shown in Figure 2, the nitrogen permeability can be considered to exceed 1000 GPU when the thickness of the PDMS / CNF film is thinner than 150 nm (more strictly, 140 nm or less). On the other hand, the oxygen permeability exceeds 2000 GPU when the thickness of the PDMS / CNF film is thinner than 150 nm (more strictly, 140 nm or less).

[0102] Here, the PDMS / CNF membrane includes a CNF membrane (reinforcement membrane 4) that does not contribute to air separation. However, as described above, the thickness of the CNF membrane is 10 to 20 nm. Therefore, if the thickness of the PDMS membrane (i.e., the thin polymer film 2) that constitutes the air separation membrane 1 is set to 130 to 120 nm or less, more preferably 100 nm or less, it is believed that the nitrogen permeability will definitely exceed 1000 GPU and the oxygen permeability will definitely exceed 2000 GPU.

[0103] Now, the air separation function of the PDMS / CNF membrane is exhibited by the PDMS membrane, but as the thickness of the PDMS membrane increases, the permeability decreases, which becomes a practical barrier. However, by forming the PDMS membrane (polymer thin film 2) in close contact with the CNF membrane or CNF-oxidized CNF membrane (reinforcement membrane 4), the mechanical strength of the entire membrane is greatly improved, making it possible to make the PDMS membrane in the air separation membrane 1 as thin as possible (thin layered). EXAMPLES

[0104] Example 5 of the present invention will be described below. A CNF / ethanol dispersion was prepared so that the CNF (Nanoforest-S, manufactured by Chuetsu Pulp Industry Co., Ltd.) was 0.072 weight percent.

[0105] Separately, the base resin and curing agent of commercially available polydimethylsilicone (PDMS) resin (Toray Dow Corning, SYLGARD 184) were mixed in a volume ratio of 10:1, and the previously prepared CNF / ethanol dispersion and hexane were added to this to prepare a 0.5 v / v% CNF / PDMS / hexane solution, which was used in the subsequent operations.

[0106] Next, a polyhydroxystyrene (PHS) / ethanol solution (15 weight percent) was spin-coated (3000 rpm / 1 min) onto a glass substrate, and after forming a PHS layer, the substrate was treated with oxygen plasma to make the surface hydrophilic. The CNF / PDMS / hexane solution prepared above was dropped onto the substrate, and the substrate was rotated at 4000 rpm for 1 min, and then heated at 100°C for 30 min.

[0107] After cooling to room temperature, the substrate was immersed in ethanol, and the polymer thin film 2 with CNF dispersed therein (hereinafter, sometimes referred to as the "PDMS-CNF film") was separated from the substrate. In Example 5, the amount of the above-mentioned CNF / ethanol dispersion was changed to prepare PDMS-CNF films No. 1 to No. 5.

[0108] The PDMS-CNF membrane was transferred (superimposed) onto a separately prepared PAN support membrane (UF010104, manufactured by SolSepBV) as an air-permeable support 3 to produce an air separation membrane 1. Here, the PDMS-CNF membrane of Example 5 is composed of PDMS in which CNF is evenly dispersed, and has the configuration shown in Figure 1(c) unlike the PDMS / CNF membrane described in Example 1 etc. (see Figure 1(a) etc.).

[0109] When the cross sections of the obtained air separation membranes 1 were observed with a scanning electron microscope, the average thickness of the PDMS-CNF membrane excluding the support 3 was about 50 nm. The CO2, N2, and O2 permeabilities of the PDMS-CNF membranes prepared by changing the amount of CNF / ethanol dispersion added are shown in [Table 2] below.

[0110] [Table 2]

[0111] Thus, in Example 5 as well, the O2 / N2 selectivity calculated based on Table 2 was about 2.1 to 2.2, which also clearly shows that the polymer thin film 2 was defect-free. As described above, the measured film thickness of the polymer thin film 2 was about 50 nm (100 nm or less), and the oxygen permeability and nitrogen permeability were 1000 GPU or more.

[0112] Second embodiment Fig. 3(a) is an explanatory diagram showing the configuration of an air separation device 10 to which an air separation membrane 1 according to the present invention is applied, and Fig. 3(b) is an explanatory diagram showing a modified example of the air separation device 10. As shown in Figs. 3(a) and (b), the air separation device 10 is composed of a blower 14, a prefilter 11, a dust collection filter 12, and an air separation section 13, and an air flow path 19 is formed from an intake port 15 to a first outlet 16a (and a second outlet 16b).

[0113] First, the configuration of the air separation unit 10 of the second embodiment will be described with reference to Fig. 3(a). The blower 14 is composed of, for example, an air compressor. By driving the blower 14, air is sucked in from an inlet 15, and passes through a flow path 19 as an airflow AF, in the order of the prefilter 11, the dust collection filter 12, and the air separation section 13. The air that has passed through the air separation section 13 is discharged as an airflow AFO from a first blowing outlet 16a provided downstream of the air separation section 13. On the other hand, the air that has not passed through the air separation section 13 is discharged as an airflow AFN from a second blowing outlet 16b provided upstream of the air separation section 13.

[0114] Here, in order to perform air separation, a predetermined pressure difference is required between the space on the upstream side (first space S1) and the space on the downstream side (here, the external space S0) across the air separation section 13. In the air separation device 10 of the second embodiment, in order to ensure the pressure difference, an air cock 17 is connected to the second blowing port 16b to restrict the outflow amount of the air flow AFN, and compressed air is sent out by the blower 14 to adjust the first space S1 to a positive pressure relative to the external space S0 (1 atmosphere). Note that, although it depends on the application of the oxygen-enriched air or nitrogen-enriched air, since the permeability of the air separation membrane 1 mounted in the air separation section 13 is very high, the air pressure in the first space S1 can also be set to a gentle value, for example, about 2 atmospheres (pressure difference between the first space S1 and the external space S0 = 1 atmosphere).

[0115] The prefilter 11 is the filter through which the air sucked in by the blower 14 first passes, and captures relatively large dust particles contained in the airflow AF. The dust collection filter 12 is the filter through which the air that has passed through the prefilter 11 passes next, and is preferably, for example, a HEPA (High Efficiency Particulate Air) filter. The HEPA filter has a capture rate of 99.97% or more for particles with a particle size of 0.3 μm contained in the air, and captures microparticulate matter such as bacteria and PM2.5.

[0116] The air separation section 13 is provided therein with an air separation membrane 1 according to the present invention. As shown in Table 1 and Fig. 2, the air separation membrane 1 according to the present invention has a higher oxygen permeability than nitrogen, so the air flow AFO that passes through the air separation section 13 and is discharged from the first air outlet 16a has a higher oxygen concentration than normal air (i.e., oxygen-enriched air). On the other hand, the air flow AFN that does not pass through the air separation section 13 and is discharged from the second air outlet 16b has a higher nitrogen concentration than normal air (i.e., nitrogen-enriched air).

[0117] When the air separation unit 10 is intended to have only an air separation function, the prefilter 11 and the dust collection filter 12 are not essential components. However, it is desirable to provide the prefilter 11 and the dust collection filter 12 upstream of the air separation section 13 to prevent the air separation membrane 1 from becoming clogged.

[0118] The air flow AFO discharged from the air separation unit 10 is used in fish farms that utilize oxygen-enriched air (air with reduced nitrogen concentration), oxyfuel combustion power plants, oxyfuel combustion boilers, and the like.

[0119] On the other hand, airflow AFN can be used for fire extinguishing, for example. Three elements are necessary for combustion: combustible material, oxygen supplier, and ignition source. In air, combustion of combustible material will not continue unless the oxygen concentration is above the critical level. If the nitrogen concentration is above 85% (oxygen concentration is below 14%), combustion of most combustible materials can be suppressed. In other words, fire can be extinguished by covering the burning material with nitrogen-enriched air. Water is often used as a fire extinguishing agent, but when this is difficult, water can be replaced with oxygen-diluted air.

[0120] Furthermore, the airflow AFN (nitrogen-enriched air) can be used in corrosion and decay prevention systems (preservation systems) that prevent the deterioration of food, artworks, etc. due to oxidation.

[0121] In addition, in thermal power plants where fossil fuels such as coal, oil, and LNG gas are burned in boilers and the heat produced by the combustion creates steam that turns turbines to generate electricity, AFO (oxygen-enriched air) airflow is normally used to improve combustion efficiency, while in the event that the boiler becomes abnormally hot due to a malfunction, AFN (nitrogen-enriched air) airflow can be supplied to prevent fires.

[0122] Specifically, the airflow AFO and the airflow AFN discharged from the air separation unit 10 are connected to a thermal power plant or the like using pipes each equipped with a shutoff valve, and the control device monitors the temperature of the boiler, and when the temperature of the boiler is normal, the control device opens the shutoff valve for the airflow AFO and shuts off the shutoff valve for the airflow AFN (at this time, the airflow AFN is discharged to the outside). In this way, oxygen-enriched air is supplied to the boiler. On the other hand, when the control device detects that the temperature of the airflow boiler is abnormally high, the control device shuts off the shutoff valve for the airflow AFO (at this time, the airflow AFO is discharged to the outside) and opens the shutoff valve for the airflow AFN. In this way, nitrogen-enriched air is supplied to the boiler.

[0123] As described above, the O2 / N2 selectivity of the air separation membrane 1 is 2.1 to 2.3 (approximately 2.2), but the air separation section 13 may have a multi-stage configuration in which multiple air separation membranes 1 are arranged in series. If the number of stages of the air separation membranes 1 is P, the O2 / N2 selectivity of the entire air separation section 13 is 2.2^P, and it is possible to increase the oxygen concentration by increasing the number of stages. Of course, when P is increased, the gas permeability of the air separation section 13 decreases. In this case, it is possible to deal with the problem by increasing the capacity of the air compressor that constitutes the blower 14.

[0124] Among polysiloxanes, PDMS is known to have a particularly large free volume ratio. In fact, the cavity radius inside the polymer estimated by positron annihilation spectroscopy is said to be less than 1 nm (see Yampolskii, Pinnau, Freeman, p.125). Therefore, so-called nanoparticles that exceed this size have difficulty penetrating the PDMS membrane, and the oxygen-enriched air that forms the airflow AFO is clean air that does not contain nanoparticles.

[0125] In this way, the air separation unit 10 equipped with the air separation membrane 1 of the present invention not only has high permeability, but also has the function of removing nano-sized particles that cannot be removed even by the above-mentioned dust collecting filter 12.By applying the air separation membrane 1, it is possible to realize a clean room system (air purifier) ​​with extremely high levels of cleanliness.

[0126] A modified example of the air separation unit 10 shown in Fig. 3(b) will be described below. In the modified example, the prefilter 11, the dust collecting filter 12, the air separation section 13, and the blower 14 are arranged in this order from the air inlet 15 toward the first outlet 16a. In the above-mentioned second embodiment, the space (first space S1) upstream of the air separation section 13 is set to a positive pressure, but in the modified example, the space (second space S2) downstream of the air separation section 13 is set to a negative pressure. This causes a pressure difference between the upstream space (third space S3) and the downstream space (second space S2) across the air separation section 13.

[0127] Here, for example, a sirocco fan can be used as the blower 14. Also, a second blowing outlet 16b is provided in the first space S1 between the dust collecting filter 12 and the air separating section 13, and a second blower 18 is provided at the second blowing outlet 16b.

[0128] The second blower 18 is provided to discharge to the outside the nitrogen-enriched air remaining in the third space S3 without passing through the air separation section 13. This makes it possible to make the air composition in the third space S3 equivalent to that of normal air and maintain the oxygen and nitrogen separation performance of the air separation section 13. Since the prefilter 11 and the dust collection filter 12 are substantially in communication with the external space S0 and the pressure loss is small, the air pressure in the third space S3 can be considered to be close to 1 atmosphere. In addition, since the second space S2 is not made into a vacuum by the blower 14, the pressure difference between the third space S3 and the second space S2 is less than 1 atmosphere.

[0129] The air separation membrane 1 according to the present invention has an extremely high oxygen and nitrogen permeability of over 1000 GPU, so that even if the pressure difference between the space upstream of the air separation membrane 1 (third space S3) and the space downstream of the air separation membrane 1 (second space S2) is less than 1 atmosphere, as in the modified example, it is possible to obtain oxygen-enriched air or nitrogen-enriched air with a simple configuration and at low cost. Specifically, the second space S2 is maintained at, for example, 0.5 to 0.8 atmospheres, and the pressure difference between the third space S3 and the second space S2 is 0.5 to 0.2 atmospheres. Thus, the air separation membrane 1 according to the present invention has high permeability, so air separation is fully possible even when negative pressure is used.

[0130] As described above, the air separation device 10 of the present invention comprises an intake port 15, a first outlet 16a, an air separation section 13 including an air separation membrane 1 arranged in a flow path 19 between the intake port 15 and the first outlet 16a, and a second outlet 16b, the first outlet 16a being provided downstream of the air separation section 13 in the flow path 19 and the second outlet 16b being provided upstream of the air separation section 13 in the flow path 19, and oxygen-enriched air is obtained from the first outlet 16a and nitrogen-enriched air is obtained from the second outlet 16b.

[0131] Third embodiment Fig. 4 is an explanatory diagram showing the configuration of an oxygen mask 30 to which air separation membrane 1 according to the present invention is applied, and Fig. 5 is an explanatory diagram showing the configuration of an air separation unit 32a disposed in oxygen mask 30. Fig. 4 shows a schematic cross section of oxygen mask 30.

[0132] The oxygen mask 30 is composed of a mask body 31, an air separation cartridge 32, and an air introduction section 33. A mask body first opening 31a is provided on the side of the mask body 31 that is attached to a person's face (face side), and a mask body second opening 31b is provided on the side that is farther from the face when the mask body 31 is attached to the person's face. Here, the outer edge of the mask body first opening 31a forms a shape that conforms to the person's face, and the outer edge of the mask body second opening 31b forms a substantially rectangular shape. However, when the oxygen mask 30 is used, the outer edge of the mask body first opening 31a does not need to be in close contact with the person's face.

[0133] In addition, a mask body third opening 31c is provided on the side surface of the mask body 31. When the oxygen mask 30 is worn on the face, the mask body third opening 31c allows the first space S1 formed between the face and the oxygen mask 30 to communicate with the outside.

[0134] The air separation cartridge 32 is a cylindrical member made of resin, and includes an air separation unit 32a inside the cylinder, and a unit support 32b that is fitted into the air separation cartridge 32 to support the air separation unit 32a. The air separation cartridge 32 is formed with a cartridge first opening 32d on the upstream side through which the air flow AF passes, and a cartridge second opening 32e on the downstream side. This cartridge second opening 32e fits snugly into the mask body second opening 31b of the mask body 31.

[0135] The unit support body 32b is made of, for example, resin and has a generally flat plate shape with, for example, a large number of mesh-like voids formed therein (with a plurality of through holes formed in the thickness direction), and is provided with a holder (not shown) that supports the air separation unit 32a in an inclined state relative to the generally flat unit support body 32b. That is, the air separation unit 32a is stored in the air separation cartridge 32 in a state in which it is sandwiched between the two unit support bodies 32b from the front and rear.

[0136] 5, air separation unit 32a includes frame 32aa and filter 32ab made of nonwoven fabric or the like that covers the front and back of the surface formed by frame 32aa, and the above-mentioned air separation membrane 1 is disposed between the two filters 32ab. Air separation membrane 1 disposed in air separation unit 32a provides the air separation function of oxygen mask 30.

[0137] Continuing the explanation by returning to Figure 4. As described above, by supporting the air separation units 32a in an inclined state relative to the unit support body 32b, the total area of ​​the air separation membranes 1 of the multiple air separation units 32a is made larger than the area of ​​the cartridge first opening 32d (cartridge second opening 32e).

[0138] From another perspective, the total area of ​​the air separation membranes 1 included in the multiple air separation units 32a is made larger than the area of ​​the unit support 32b (the area of ​​the main surface forming a substantially flat plate) when the unit support 32b, which is configured in a substantially flat plate shape, does not have through holes penetrating from the front to the back. This increases the area of ​​the air separation membrane 1, making it possible to improve the permeability of oxygen (and nitrogen).

[0139] The air separation cartridge 32 is a replaceable component that combines the components that perform the air separation function, and the user can always maintain the air separation function of the oxygen mask 30 in good condition by replacing the air separation cartridge 32, for example, once a day.

[0140] The air introduction part 33 is a cup-shaped member made of, for example, resin, and is attached to the front (external side) of the air separation cartridge 32. When the air introduction part 33 is attached to the air separation cartridge 32, a second space S2 is formed by the air introduction part 33 and the air separation cartridge 32. The air introduction part 33 is provided with a cylindrical protrusion 33a that protrudes forward. A tube 35 is attached to the tip of the cylindrical protrusion 33a. The air introduction part 33 is also provided with an air introduction part opening 33b, which communicates with the second space S2 and the external space S0.

[0141] The above-mentioned mask body 31, air separation cartridge 32, and air inlet 33 are made of resin, such as polyester, polyethylene, polypropylene, and acrylic. It is preferable that these members are made transparent so that the breathing state of the patient using the oxygen mask 30 can be visually observed.

[0142] 6 is an explanatory diagram illustrating a state in which a user uses the oxygen mask 30. The other end of the tube 35 connected to the cylindrical protrusion 33a of the air inlet 33 is connected to an air pump 36. Air (air flow AF) discharged by the air pump 36 flows into the air inlet 33 via the cylindrical protrusion 33a.

[0143] Of the air that has flowed into the air introduction section 33, a portion of it passes through the air separation cartridge 32 and flows into the first space S1, while the remainder is discharged to the outside through the air introduction section opening 33b. As described above, the O2 / N2 selectivity ratio of the air separation membrane 1 housed in the air separation cartridge 32 is about 2.2, and since it selectively permeates oxygen over nitrogen, the air that has permeated the air separation cartridge 32 (air flow AFO) is oxygen-enriched air. In this way, the air separation membrane 1 functions as a so-called oxygen-enriched membrane.

[0144] Conversely, the air (air flow AFN) that does not pass through the air separation cartridge 32 and is discharged to the outside from the air inlet opening 33b is nitrogen-enriched air in which the oxygen concentration is reduced compared to normal air and the nitrogen concentration is increased.

[0145] When the user breathes, air with a high oxygen concentration is inhaled, while the user's exhaled air is discharged to the outside through the mask body third opening 31c (air flow AFE). The mask body third opening 31c has a sufficient opening area to quickly discharge the exhaled air to the outside.

[0146] Here, the driving force of the air pump 36 and the opening size of the air introduction opening 33b provided in the air introduction part 33 are adjusted so that the air pressure in the second space S2 formed between the air introduction part 33 and the air separation cartridge 32 is higher than the air pressure in the first space S1 (internal space) formed between the air separation cartridge 32 and the face.

[0147] By making the opening area of ​​the mask body third opening 31c sufficiently large, the air pressure in the first space S1 is substantially maintained at 1 atmosphere. Therefore, by controlling the driving force of the air pump 36, the air pressure in the second space S2 and the first space S1 can be adjusted to Air pressure in the second space S2 > air pressure in the first space S1 (= 1 atmosphere) Equation (1) By adjusting the air pressure in the second space S2 so as to satisfy the above relationship, it is possible to generate a desired air pressure difference between one surface and the other surface of the air separation membrane 1.

[0148] Here, the opening area of ​​the air inlet opening 33b is appropriately determined in consideration of the air compression performance of the air pump 36, etc. Of course, it is also possible to adjust the air pressure in the second space S2 by connecting an air cock or the like to the air inlet opening 33b. The air pressure in the second space S2 (the air pressure difference between the second space S2 and the first space S1) can be adjusted according to the amount of oxygen required by a user such as a patient, for example.

[0149] As described above, according to the oxygen mask 30 of the present invention, the oxygen mask 30 itself generates oxygen-enriched air, so that complicated equipment such as cylinders and piping for supplying oxygen to the oxygen mask 30 is not required.

[0150] In addition, the oxygen mask 30 according to the third embodiment is particularly useful for medical purposes, in that oxygen-enriched air is supplied to the first space S1 on the face side regardless of the breathing condition of the user. Of course, even if the user is healthy, the mask can be used for so-called refreshing purposes such as recovering from fatigue.

[0151] 7(a) is an explanatory diagram showing the configuration of a first modified example of the oxygen mask 30, and (b) is an explanatory diagram showing the configuration of a second modified example of the oxygen mask 30. In the above-mentioned third embodiment, the air inlet 33 was provided at the front of the oxygen mask 30, but the first and second modified examples differ from the third embodiment in that the oxygen mask 30 does not include the air inlet 33 as a component, and further, the thickness of the combined film (PDMS / CNF film) of the polymer thin film 2 and the CNF film that constitute the above-mentioned air separation membrane 1 is formed to be very thin, for example, 30 nm or less.

[0152] As shown in Table 1 above, when the PDMS / CNF film has a thickness of 30 nm, the oxygen permeability exceeds 7600 GPU, and when it is less than 30 nm, it approaches 10000 GPU. When the oxygen permeability reaches this level, the air pump 36 that delivers compressed air described in the third embodiment is no longer an essential component, and in the first and second modified examples, oxygen-enriched air is taken into the first space S1 by the small pressure difference that occurs between the outside side of the air separation unit 32a (external space S0:1 atmospheric pressure) and the face side of the air separation unit 32a (first space S1: less than 1 atmospheric pressure) when a person inhales air.

[0153] A first space S1 (internal space) is defined between the oxygen mask 30 (mask body 31) and the face of the person wearing it, and a valve member 31e is provided in a communication hole (here, the mask body third opening 31c) that communicates the first space S1 with the external space S0. The valve member 31e exhausts air in the first space S1 to the external space S0 when the first space S1 is under positive pressure, and blocks the first space S1 from the external space S0 when the first space S1 is under negative pressure.

[0154] Here, the outer edge of the mask body first opening 31a is shaped to fit the face of a person, and the outer edge of the mask body first opening 31a is adapted to fit closely to the face of a person. In particular, it is preferable to configure the mask body first opening 31a so that the outer edge of the mask body first opening 31a fits closely to the face of a person when the person inhales air. Specifically, the outer edge of the mask body first opening 31a may be covered with, for example, soft plastic or silicone rubber to improve the degree of fit with the face.

[0155] When a person inhales air, the first space S1 becomes negative pressure, and the valve member 31e blocks the first space S1 from the outside space S0. When the first space S1 becomes negative pressure, a pressure difference occurs between the first space S1 and the outside space S0, and some of the air on the outside side passes through the air separation unit 32a and is taken into the first space S1 (air flow AFO).

[0156] On the other hand, when a person exhales, the first space S1 becomes positive pressure, the valve member 31e is opened, and the exhaled air containing a large amount of carbon dioxide is discharged to the outside space S0 (air flow AFE).

[0157] This makes it possible, when a person inhales, to create negative pressure in the first space S1 (internal space) and take in air from the external space S0 to obtain oxygen-enriched air, while, when a person exhales, to create positive pressure in the internal space and exhaust the exhaled air to the external space S0.

[0158] In the first modified example, of the unit supports 32b mounted on the air separation cartridge 32, a plurality of slits 32f are formed in the external unit support 32b, and the air separation unit 32a is exposed to the external space S0 in the area facing the slits 32f. This prevents the nitrogen-enriched air that has not passed through the air separation unit 32a from remaining on the external side of the air separation unit 32a, which would result in a decrease in air separation efficiency.

[0159] In the second modified example, the air separation unit 32a is formed to have the same dimensions as the unit support 32b, and these are superimposed inside the air separation cartridge 32. In the first and second modified examples, the air separation cartridge 32 is detachable from the mask body 31.

[0160] 8 is an explanatory diagram showing the configuration of a third modified example of the oxygen mask 30. In the third modified example, the oxygen mask 30 is composed of a mask body 31, a unit support 32b, and an air separation unit 32a. The unit support 32b is detachable from the front opening (mask body second opening 31b) of the mask body 31. The unit support 32b is composed of a curved surface as shown in the figure, and the air separation unit 32a is disposed on the unit support 32b composed of a curved surface.

[0161] In the third modified example as well, when a person inhales air, the first space S1 becomes negative pressure, and the valve member 31e blocks the first space S1 from the external space S0. The negative pressure in the first space S1 creates a pressure difference with the external space S0, and some of the air on the external side passes through the air separation unit 32a and is taken into the first space S1 (air flow AFO). On the other hand, when a person exhales air, the first space S1 becomes positive pressure, the valve member 31e becomes open, and the exhaled air containing a large amount of carbon dioxide is discharged to the external space S0 (air flow AFE).

[0162] In addition, the oxygen masks 30 according to the first to third modifications take in oxygen-enriched air into the first space S1 by utilizing the negative pressure generated by the user's inhalation, so the user is assumed to be a healthy person with normal respiratory function, and it is considered that the masks are applied to refreshing purposes such as recovering from fatigue. In addition, the oxygen masks 30 according to the first to third modifications involve a load when breathing in, so that continuous use of the masks induces the user to breathe abdominally, and further leads to training so-called inner muscles such as the diaphragm, multifidus, transverse abdominis, and pelvic floor muscles. Here, even if the physical load during inhalation increases, the amount of oxygen supplied to the body will not be insufficient because oxygen-enriched air is supplied to the user. [Industrial Applicability]

[0163] The air separation membrane 1 of the present invention is capable of separating oxygen and nitrogen in the air with high efficiency, and therefore can be suitably applied to oxygen enrichment devices that increase the concentration of oxygen in the air, oxygen masks, plant factories, oxyfuel combustion power plants, oxyfuel combustion boilers, etc., nitrogen enrichment devices that increase the concentration of nitrogen in the air, inert gas fire extinguishing equipment, etc. [Explanation of symbols]

[0164] 1. Air separation membrane 2 Polymer thin film 3 Support 4 Reinforced membrane 5 Organic polymers 10 Air Separation Unit 13 Air Separation Section 14 Blower 15 Intake port 16a 1st outlet 30 Oxygen Mask 31 Mask body 31 32 Air Separation Cartridge 32a Air Separation Unit 33 Air intake section 36 Air Pump

Claims

1. A support composed of a porous membrane; a polymer thin film having an oxygen permeability higher than its nitrogen permeability and a thickness of 100 nm or less; A reinforcing membrane containing at least cellulose nanofibers; Equipped with the polymer thin film and the reinforcing film are formed to be in close contact with each other, The support, the reinforcing film, and the polymer thin film are (a) The support, the reinforcing film, and the polymer thin film in this order. or, (b) the support, the polymer thin film, and the reinforcing film in this order 1. An air separation membrane comprising:

2. A support composed of a porous membrane; a polymer thin film laminated on the support, the polymer thin film having an oxygen permeability higher than a nitrogen permeability and a thickness of 100 nm or less; Equipped with An air separation membrane, characterized in that at least cellulose nanofibers are dispersed in the thin polymer film.

3. 3. The air separation membrane according to claim 1, wherein the oxygen permeability and nitrogen permeability of the thin polymer membrane are 1000 GPU or more.

4. 4. The air separation membrane according to claim 1, wherein the thin polymer film is mainly composed of polysiloxane.

5. 4. The air separation membrane according to claim 1, wherein the thin polymer film is mainly composed of a crosslinkable polymer.

6. A suction port, A first air outlet; an air separation section including the air separation membrane according to any one of claims 1 to 5, which is disposed in a flow path between the suction port and the first air outlet; A second air outlet, The first air outlet is provided downstream of the air separation section in the flow path, The second air outlet is provided upstream of the air separation section in the flow path, An air separation unit comprising: an air separator configured to obtain oxygen-enriched air from said first outlet and nitrogen-enriched air from said second outlet.

7. 7. The air separation unit according to claim 6, wherein the air separation section comprises multiple stages of the air separation membranes.

8. An oxygen mask comprising the air separation membrane according to any one of claims 1 to 5.

9. an air separation unit comprising the air separation membrane; a unit support body having a substantially flat plate shape and a plurality of through holes for supporting a plurality of the air separation units; 9. The oxygen mask according to claim 8, wherein the total area of ​​the air separation membranes included in the plurality of air separation units is greater than the area of ​​the unit support when the unit support does not have the through hole.

10. an air separation unit comprising the air separation membrane; 9. The oxygen mask according to claim 8, further comprising a unit support for supporting a plurality of said air separation units, said unit support being configured with a curved surface, and said air separation units being disposed on said unit support configured with a curved surface.

11. An internal space is created between the oxygen mask and the wearer's face, A communication hole that communicates the internal space with an external space; a valve member that is provided in the communication hole and that exhausts air from the internal space to the external space when the internal space is under positive pressure and isolates the internal space from the external space when the internal space is under negative pressure; The oxygen mask according to any one of claims 8 to 10, further comprising:

12. A first step of forming a reinforcing membrane containing at least cellulose nanofibers on a substrate; a second step of forming a polymer thin film on the reinforcing film, the polymer thin film having an oxygen permeability higher than a nitrogen permeability and a thickness of 100 nm or less; a third step of separating the reinforcing film and the thin polymer film from the substrate; a fourth step of laminating the reinforcing membrane and the thin polymer film separated from the substrate on a support made of a porous membrane; A method for producing an air separation membrane, comprising the steps of:

13. 13. The method for producing an air separation membrane according to claim 12, wherein in the first and second steps, the reinforcing membrane and the thin polymer film are formed on the substrate by a spin coating method.

14. A preliminary step of forming a sacrificial layer on the substrate, The method for manufacturing an air separation membrane according to claim 12 or 13, characterized in that in the third step, the reinforcing membrane and the polymer thin film are separated from the substrate by dissolving the sacrificial layer formed in the preliminary step.

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