Nanoporous molded body and heat exchanger using the same

Abstract

To provide an adsorbent that efficiently adsorbs and desorbs adsorbate and has excellent durability.SOLUTION: Provided is a nanoporous shaped article containing: a nanoporous material in which pore diameter can be changed by applying and releasing stress and that can cause reversible gas-liquid phase transition of adsorbate that is taken in as guest molecule; and a rubber-based material that is a binder.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a nanoporous molded body, and more particularly to a nanoporous molded body that can be used as an adsorbent for an adsorption-type heat exchanger. [Background technology]

[0002] Conventionally, heat exchange devices that heat or cool a target (space or object) by transferring heat have been widely used. For example, Patent Document 1 below discloses an adsorption-type heat exchange device that has an evaporator that vaporizes a medium, an adsorber that includes an adsorbent that desorbs and adsorbs the vaporized medium, and a condenser that condenses the vaporized medium. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-183930 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional adsorption-type heat exchangers, such as those disclosed in Patent Document 1, utilize the latent heat of the adsorbate adsorbed on the adsorbent in the evaporator or condenser to generate cold or hot heat, requiring a large amount of energy for depressurizing and heating / cooling in the evaporator or condenser. Energy is also required for heating to regenerate the adsorbent that has adsorbed the adsorbate. As a result, the coefficient of performance (COP) decreases, and the device tends to become larger. Therefore, there is a demand for an adsorbent that can adsorb and desorb the adsorbate with less energy, particularly for application in heat exchangers such as car air conditioners, which have limited installation space. Furthermore, there is a demand for an adsorbent that is less susceptible to deterioration even when the adsorbate is repeatedly adsorbed and desorbed.

[0005] Therefore, an object of the present invention is to provide an adsorbent that efficiently adsorbs and desorbs an adsorbate and has excellent durability. [Means for solving the problem]

[0006] The present inventors conducted extensive research to solve the above-mentioned problems. In the course of their research, they discovered a nanoporous body that can be mechanically deformed by applying and releasing stress, thereby reversibly desorbing and adsorbing an adsorbate medium. Furthermore, they discovered that desorbing and adsorbing a medium into a nanoporous body can cause a phase change of the medium, generating latent heat. They then attempted to use a nanoporous body containing the nanoporous body and a rubber-based binder as an adsorbent in a heat exchanger. As a result, they found that the latent heat generated by desorption or adsorption can be directly used to cool or heat the body, thereby reducing the energy required for thermal cycling. Furthermore, they discovered that the durability of a nanoporous body can be improved by using a rubber-based binder. This finding led to the completion of the present invention.

[0007] That is, the present invention provides a nanoporous molded body comprising a nanoporous body capable of changing the pore size by applying and releasing stress, thereby causing reversible gas-liquid phase transition of adsorbates incorporated as guest molecules, and a rubber-based binder material. [Effects of the Invention]

[0008] According to the present invention, by applying and releasing stress to a nanoporous molded body to cause it to contract and expand, it is possible to reversibly desorb and adsorb the adsorbate medium, thereby generating latent heat through a phase change. This allows the generated latent heat to be directly used for cold or hot heat. Furthermore, since pressure reduction or heating / cooling is not required in an evaporator or condenser to obtain the latent heat, the energy required for the thermal cycle can be reduced when the nanoporous molded body is used as an adsorbent in a heat exchanger. Furthermore, because rubber-based materials function as binders at relatively low temperatures, using a rubber-based material as a binder reduces degradation during the fabrication of the nanoporous molded body. As a result, the durability of the adsorbent can be improved by using a rubber-based material as a binder to form the nanoporous molded body. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view showing the configuration of a heat exchanger according to one embodiment of the present invention. [Figure 2] FIG. 10 is a diagram showing a state in which stress is applied to a nanoporous body to cause it to shrink and desorb a refrigerant. [Figure 3] FIG. 1 shows XRD spectra of GMS and CMS. [Figure 4] FIG. 1 is a TS diagram of the thermal cycle of a heat exchanger. [Figure 5] 1 is a graph showing the stress-strain curve (first measurement) of the nanoporous molded body produced in Comparative Example 1 and the stress-strain curve (first and tenth measurements) of the nanoporous molded body produced in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0010] One aspect of the present invention is a nanoporous molded body comprising a nanoporous body capable of changing the pore size by applying and releasing stress, thereby causing reversible gas-liquid phase transition of an adsorbate incorporated as a guest molecule, and a rubber-based binder material.

[0011] A typical adsorption heat exchanger has an evaporator that heats and vaporizes a refrigerant under reduced pressure, an adsorber equipped with an adsorbent that desorbs and adsorbs the vaporized refrigerant, and a condenser that condenses the vaporized refrigerant. A typical adsorption heat exchanger uses the latent heat of vaporization in the evaporator for cooling. During desorption / adsorption of the refrigerant onto the adsorbent, the refrigerant remains in a gaseous state without undergoing a phase change, so no latent heat is generated. Desorption / adsorption is used for transporting the refrigerant. Because a typical adsorption heat exchanger uses the latent heat of vaporization in the evaporator for cooling, a large amount of energy is required for depressurizing and heating the evaporator. Energy is also required for heating to regenerate the adsorbent that has adsorbed the medium.

[0012] In contrast, in this embodiment, a nanoporous molded body containing a nanoporous material capable of changing pore size by applying and releasing stress and causing a reversible gas-liquid phase transition of the adsorbate incorporated as guest molecules is used as the adsorbent. This allows the refrigerant to be desorbed by applying mechanical stress to the nanoporous molded body, causing a phase change of the refrigerant and allowing the latent heat of vaporization (heat of desorption) to be used as cold energy. Therefore, there is no need for heating to regenerate the adsorbent or for decompression or heating using an evaporator, and the adsorbent can absorb and generate heat in a short time with little applied energy.

[0013] To maintain the shape of the nanoporous compacts when used as adsorbents, they must be bound with a binder to form sheet-like samples. However, the inventors' investigations have revealed that the use of binders such as common Teflon (registered trademark; polytetrafluoroethylene (PTFE)) does not provide sufficient durability.

[0014] While PTFE is resistant to external stimuli such as heat, ultraviolet light, chemicals, and oil, it has weak intermolecular cohesion and tends to be easily worn. Furthermore, its adhesiveness to nanoporous materials is relatively weak, and to obtain strong binding strength, it must be heat-treated at high temperatures, for example, above 370°C, after mixing with the nanoporous material. However, heat treatment causes partial thermal degradation of the PTFE, reducing the durability of the nanoporous molded body. Therefore, it is difficult to obtain a nanoporous molded body with excellent durability when using a common binder such as PTFE.

[0015] In response to this, the present inventors discovered that the durability of nanoporous molded bodies can be improved by using a rubber-based material as a binder. The rubber-based material functions as a binder when heat-treated at a relatively low temperature of about 140 to 160°C. Therefore, it is believed that degradation during the preparation of nanoporous molded bodies is unlikely to occur, resulting in high durability.

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the technical scope of the present invention should be determined based on the description of the claims and is not limited to the following embodiments. Note that the dimensional proportions in the drawings are exaggerated for the convenience of explanation and may differ from the actual proportions.

[0017] <Heat exchange equipment> FIG. 1 shows a heat exchanger 10 according to one embodiment of the present invention. The heat exchanger 10 mechanically deforms a nanoporous body 20 (a first nanoporous body 20A and a second nanoporous body 20B) by applying and releasing stress to the nanoporous body 20, thereby desorbing and adsorbing a refrigerant (medium) 60, which is an adsorbate. The heat exchanger 10 according to this embodiment cools an object by utilizing cold energy obtained from the latent heat of vaporization generated during desorption of the refrigerant (not shown). The heat exchanger 10 can be used, for example, in a car air conditioner (cooling) that cools the interior air of an automobile.

[0018] As shown in FIG. 1, the heat exchange device 10 includes a pair of heat exchange units 30A, 30B (first heat exchange unit 30A and second heat exchange unit 30B) and a control unit 40 that controls the operation of the entire device. The control unit 40 performs swing operation so that while one of the pair of heat exchange units 30A, 30B is in the desorption mode, the other is in the adsorption mode. This allows the heat exchange units 30A, 30B in the desorption mode to continuously generate cold. Here, the "desorption mode" refers to an operation mode in which the refrigerant is desorbed from the nanoporous molded body 20. The "adsorption mode" refers to an operation mode in which the refrigerant is adsorbed into the nanoporous molded body 20.

[0019] The heat exchange device 10 has a pipe 50 that communicates between the first chamber 32A and the second chamber 32B so that the refrigerant 60 can move between them, and a valve 51 that switches between a communication state and a blocked state of the pipe 50. When the valve 51 is opened, the pipe 50 is in a communication state, and when the valve 51 is closed, the pipe 50 is in a blocked state.

[0020] [Heat exchange section 30A, 30B] 1, the first heat exchange unit 30A has a first nanoporous molded body 20A, a first stress-applying unit 31A, a first chamber 32A, and a first air conditioning unit 33A. Similarly, the second heat exchange unit 30B has a second nanoporous molded body 20B, a second stress-applying unit 31B, a second chamber 32B, and a second air conditioning unit 33B.

[0021] The first heat exchange section 30A and the second heat exchange section 30B have the same configuration. In the description herein, the first heat exchange section 30A and the second heat exchange section 30B are collectively referred to as "heat exchange sections 30A, 30B." Similarly, the first stress-applying section 31A and the second stress-applying section 31B are collectively referred to as "stress-applying sections 31A, 31B." The first chamber 32A and the second chamber 32B are collectively referred to as "chambers 32A, 32B." The first air conditioning section 33A and the second air conditioning section 33B are collectively referred to as "air conditioning sections 33A, 33B." The first nanoporous molded body 20A and the second nanoporous molded body 20B are collectively referred to as "nanoporous molded body 20."

[0022] [Nanoporous body 20] The nanoporous molded body 20 includes a nanoporous body and a rubber-based binder. The nanoporous body used in the nanoporous molded body 20 is a nanoporous material that has elasticity and can contract to desorb the refrigerant and expand to adsorb the refrigerant. As a result, the nanoporous molded body 20 contracts and desorbs the refrigerant when stress is applied from the stress-applying parts 31A and 31B, and expands freely to adsorb the refrigerant when the stress is released.

[0023] Here, "elasticity" refers to the property of the nanoporous body 20 being reversibly deformed to a large extent and recovering to approximately its original shape when stress is released, even if it is contracted by external application of stress by the stress-applying units 31A and 31B. The elastic limit of the nanoporous body 20 is preferably designed to be greater than the stress required to desorb the refrigerant. The elastic limit of the nanoporous body 20 is preferably designed appropriately depending on the cooling scale of the target to which the heat exchanger 10 is to be applied, etc.

[0024] Furthermore, "nanoporous" means having a plurality of nano-level pores. Nano-level pores are preferably micropores or mesopores with a diameter of 0.5 to 100 nm, more preferably 0.7 to 50 nm, and even more preferably 0.7 to 6 nm. The International Union of Pure and Applied Chemistry (IUPAC) defines pores with a diameter of 2 nm or less as micropores, pores with a diameter of 2 to 50 nm as mesopores, and pores with a diameter of 50 nm or more as macropores.

[0025] Generally, solid surfaces have high potential energy due to van der Waals forces, which act to condense the molecules of the refrigerant 60. In particular, in the nanoporous molded body 20 according to this embodiment, the refrigerant adsorbed in the nanoporous body is surrounded by tiny pore walls at the nanometer level, resulting in significantly high potential energy due to van der Waals forces (physical adsorption forces) on the solid surface. At this time, the gaseous refrigerant is adsorbed onto the pore walls of the nanoporous body at the density of a liquid. In other words, adsorption into a nanoporous body is a phenomenon similar to a phase change from gas to liquid, and the heat of adsorption is approximately equal to the latent heat of condensation. In the following description, it is assumed that the refrigerant undergoes a phase change from gas to liquid when adsorbed into a nanoporous body, and from liquid to gas when desorbed. It is also assumed that the heat of adsorption is equal to the latent heat of condensation.

[0026] The refrigerant at liquid density inside the pores adsorbed on the pore walls of the nanoporous molded body 20 is in equilibrium with vapor at a pressure lower than the saturated vapor pressure. That is, the gas adsorbed on the pore walls of the nanoporous molded body 20 becomes liquid at a pressure lower than the saturated vapor pressure.

[0027] As shown in Figure 2, when stress is applied to a nanoporous body 20 containing a nanoporous body and a binder (not shown), the pores of the nanoporous body in the nanoporous body 20 contract, as shown in Figure 2 (A) before stress application and (B) under stress application, and the refrigerant 60 adsorbed to the pore walls is desorbed. At this time, the refrigerant 60 adsorbed at the density of a liquid is released again as a gas to the outside of the nanoporous body 20. The heat exchanger 10 can cool an object by utilizing the latent heat of vaporization generated during this desorption as cold energy.

[0028] On the other hand, when the stress is released in the nanoporous molded body 20, the nanoporous bodies present in the nanoporous molded body 20 freely expand, causing the pores to return to their original size and allowing the refrigerant 60 to be adsorbed again. As described above, the refrigerant 60 is adsorbed at the density of a liquid onto the pore walls of the nanoporous molded body 20. That is, when the refrigerant 60 is adsorbed into the nanoporous molded body 20, it undergoes a phase change from gas to liquid, generating latent heat of condensation.

[0029] The material constituting the nanoporous body is not particularly limited as long as it has elasticity, can contract to desorb the refrigerant 60, and can expand to adsorb the refrigerant 60.

[0030] The BET specific surface area of ​​the nanoporous body is not particularly limited, but is, for example, 800 to 4200 m 2 / g, preferably 800 to 2600m 2 / g range. By using a nanoporous body with a large BET specific surface area within these ranges, the amount of adsorbate adsorbed can be increased. The pore volume of the nanoporous body is not particularly limited, but is preferably 1.0 to 6.0 mL / g, more preferably 1.8 mL / g or more, and particularly preferably 2.0 mL / g or more. A nanoporous body with a pore volume of 1.0 mL / g or more is preferred because the amount of adsorbate adsorbed and desorbed does not become too small even in a relatively high relative vapor pressure region. A pore volume of 6.0 mL / g or less is also preferred because a sufficient BET specific surface area can be secured, increasing the amount of adsorption.

[0031] Such materials include carbon materials that include a single-layer graphene skeleton and have the porosity and elasticity required for desorption and adsorption of the refrigerant 60. Specific examples of such carbon materials include zeolite template carbon (ZTC), graphene meso sponge (GMS), and carbon meso sponge (CMS). Zeolite template carbon (ZTC), graphene meso sponge (GMS), and carbon meso sponge (CMS) all have a single-layer graphene skeleton and have the porosity and elasticity required for desorption and adsorption of the refrigerant 60.

[0032] ZTC is composed of a single graphene sheet. It has uniform pores (diameter approximately 1.2 nm) that are regularly arranged in a three-dimensional manner and interconnected, and has an extremely high BET specific surface area and pore volume (maximum BET specific surface area is 4100 m). 2 It is known that the ordered structure of ZTC is 1.8 mL / g and the pore volume is 1.8 mL / g. The ordered structure of ZTC was analyzed using an X-ray diffraction apparatus (Rigaku Corporation, MiniFlex600, CuK). The BET specific surface area of ​​ZTC was analyzed using liquid nitrogen adsorption (77 K) (Microtrac BEL, BELSORB-max).

[0033] The method for producing ZTC is described in, for example, Nishihara, H. et al., Chemistry-European Journal 15, 5355 (2009). Specifically, a porous material (e.g., zeolite) with pores internally connected in a network structure is prepared as a template. An organic compound (e.g., acetylene, ethylene, etc.) is then introduced to the surface and pores of this porous material under heated conditions, and the organic compound is carbonized by heating, depositing carbon on the porous material. Carbonization of the organic compound and carbon deposition can be achieved, for example, by chemical vapor deposition (CVD). The porous template material is then removed. This method allows for the easy production of a carbon material (i.e., ZTC) that reflects the three-dimensional structure of the template. ZTC produced by the above method has excellent flexibility and elasticity and can reversibly deform elastically from pore diameters of approximately 1.2 nm to approximately 0.7 nm.

[0034] GMS is also a sponge-like mesoporous material with pore walls mostly composed of single-layer graphene and with minute pores of approximately 6 nm in size. Like ZTC, it has an extremely high BET specific surface area (approximately 2000 m) comparable to that of activated carbon. 2 / g). At the same time, unlike activated carbon and carbon black, it contains almost no graphene edges, which cause corrosion, and therefore has excellent corrosion resistance (oxidation resistance). Furthermore, due to the flexible and tough properties of graphene, GMS has excellent flexibility and elasticity, and can reversibly deform from a pore diameter of approximately 5.8 nm to approximately 0.7 nm.

[0035] The manufacturing method of GMS is described in, for example, Nishihara, H. et al., Advanced Functional Materials, Vol. 26, 2016, 6418-6427. Specifically, first, metal oxide nanoparticles made of alumina or the like (e.g., γ-alumina such as SBa-200 (trade name)) are prepared as nano-sized spherical substrates. This material has high catalytic activity for carbon coating by the CVD method described below and excellent sintering resistance.

[0036] Next, the surface of the spherical substrate (metal oxide nanoparticles) prepared above is coated with carbon by CVD using an organic compound as a carbon source. This CVD carbon coating method allows for the formation of a uniform carbon layer over the entire surface of the spherical substrate (metal oxide nanoparticles). Examples of organic compounds that can be used include methane, acetylene, ethylene, propylene, and benzene. However, methane is preferred as the carbon source, as it allows for a particularly large amount of carbon crystals to be coated. To improve the gas flow during the CVD process, the organic compound may be introduced in a state where a spacer such as quartz sand (silica sand) is mixed with the spherical substrate (metal oxide nanoparticles). An inert gas such as nitrogen may be used as a carrier gas for the introduction of the organic compound. The concentration of the carbon source in the mixed gas of the carrier gas and the carbon source (organic compound) is preferably about 10 to 30% by volume.

[0037] As the CVD process progresses, the color of the sample turns black, while the reaction vessel (e.g., a quartz tube) containing the sample remains transparent, confirming that carbon deposition occurs only on the surface of the spherical substrate (metal oxide nanoparticles). Because the spherical substrate (metal oxide nanoparticles) does not sinter during the CVD process, the shape of the carbon-coated spherical substrate remains virtually unchanged from before carbon coating. The (average) number of carbon layers coated on the surface of the spherical substrate (metal oxide nanoparticles) can be controlled based on the amount of carbon source (organic compound) added during the CVD process, as well as the CVD temperature and time. This corresponds to the (average) number of graphene layers in the final GMS. While the value of this (average) number of layers is not particularly limited, it is preferably 0.90 to 3.0, more preferably 0.95 to 2.0, even more preferably 0.98 to 1.5, and particularly preferably 1.0 to 1.1, in order to exhibit excellent desorption / adsorption properties for the refrigerant 60. The treatment temperature and treatment time in the CVD process are not particularly limited, but the treatment temperature is preferably 800 to 1000° C., more preferably 850 to 950° C. The treatment time is preferably 1 to 10 hours, more preferably 2 to 6 hours.

[0038] The spherical substrate (metal oxide nanoparticles) used as the template is then removed by chemical etching, leaving only the carbon layer coated on the surface of the spherical substrate. An aqueous solution of a strong acid or strong base can be used for this chemical etching. Examples of strong acids include hydrofluoric acid (HF) (in this case, etching can be performed at room temperature). Examples of strong bases include sodium hydroxide (NaOH) (in this case, heating to approximately 200-300°C is preferred). Once the spherical substrate (metal oxide nanoparticles) is removed by chemical etching, a carbon meso sponge (CMS) with spherical mesopores is obtained as a precursor to GMS.

[0039] Finally, the CMS obtained in this manner is washed with water as needed and then heat-treated under reduced pressure at a temperature of approximately 1500 to 2000°C (preferably 1700 to 1900°C) for approximately 30 minutes to 2 hours. This promotes the crystallization of the carbon layers into graphene, yielding GMS. The spherical mesopores of CMS are highly stable even at the high temperatures encountered during the heat treatment described above, so the GMS obtained in this manner retains mesopores similar to those of CMS. Because of these mesopores, GMS can undergo elastic deformation like a sponge. Therefore, it can contract to desorb the refrigerant 60 and expand to adsorb the refrigerant 60, making it suitable for use as a nanoporous body for the nanoporous molded body 20 in the heat exchanger 10.

[0040] When the nanoporous body contains a carbon material, a peak derived from the (10) plane of carbon is preferably observed near 2θ = 44° in an X-ray diffraction spectrum of the nanoporous body using Cu-Kα radiation, with a half-width of 1.2 to 3.2°. Nanoporous bodies having such a structure are preferred because they theoretically exhibit particularly excellent thermal energy. Examples of such nanoporous bodies include GMS and CMS. The inventors measured the X-ray diffraction spectra of GMS and CMS, and as shown in Figure 3, a peak derived from the (10) plane of carbon was observed near 2θ = 44° in these X-ray diffraction spectra, with a half-width of 2.2°. The X-ray diffraction measurement was performed using an XRD-6100 X-ray diffractometer manufactured by Shimadzu Corporation, with a sample mounted on a silicon anti-reflection plate. The radiation source was Cu-Kα, the voltage was 40 kV, and the current was 30 mA.

[0041] The nanoporous molded body of the present invention contains a rubber-based material as a binder. The specific form of the rubber-based material is not particularly limited, but examples include those selected from the group consisting of natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, nitrile-butadiene rubber, chloroprene rubber, ethylene-propylene rubber, butyl rubber, and silicone rubber. From the perspective of particularly excellent durability, the rubber-based material preferably contains natural rubber or styrene-butadiene rubber, and more preferably natural rubber. Note that only one type of rubber-based material may be used alone, or two or more types may be used in combination.

[0042] In addition to the nanoporous body and rubber material described above, the nanoporous molded body of the present invention may contain other components such as compounding agents commonly used in the rubber industry, such as silane coupling agents, crosslinking agents, vulcanization accelerators, polyethylene glycols, softeners, resins, antioxidants, and zinc oxide, selected appropriately within the scope of the present invention.

[0043] Examples of crosslinking agents include sulfur-based crosslinking agents, organic peroxide-based crosslinking agents, inorganic crosslinking agents, polyamine crosslinking agents, resin crosslinking agents, sulfur compound-based crosslinking agents, and oxime-nitrosamine-based crosslinking agents. Among these crosslinking agents, sulfur-based crosslinking agents (vulcanizing agents) are more preferred. The content of the crosslinking agent is preferably 0.1 to 20 parts by mass per 100 parts by mass of the rubber material.

[0044] When sulfur is used as the crosslinking agent, it is preferable to further contain a vulcanization accelerator. Examples of vulcanization accelerators include sulfenamide-based vulcanization accelerators such as TBBS (Nt-butyl-2-benzothiazylsulfenamide), CBS (N-cyclohexyl-2-benzothiazylsulfenamide), and TBSI (Nt-butyl-2-benzothiazylsulfenimide); guanidine-based vulcanization accelerators such as DPG (diphenylguanidine); thiuram-based vulcanization accelerators such as tetraoctylthiuram disulfide and tetrabenzylthiuram disulfide; and zinc dialkyldithiophosphate. The content of the vulcanization accelerator is preferably less than the content of sulfur, and more preferably about 1 to 10 parts by mass per 100 parts by mass of the rubber material.

[0045] In addition to the rubber-based material, a known binder used for binding nanoporous bodies together in nanoporous bodies may be used in combination as the binder. However, since the effects of the present invention can be more significantly obtained, the binder used in the nanoporous body is preferably 95% by mass or more, more preferably 98% by mass or more, even more preferably 99% by mass or more, and most preferably 100% by mass, of the rubber-based material.

[0046] (binder content) The binder content in the nanoporous compact is not particularly limited, but is preferably 10 to 60% by mass, more preferably 15 to 40% by mass, and particularly preferably 15 to 25% by mass, relative to the total mass of the nanoporous compact (100% by mass). A binder content of 10% by mass or more enhances the retention of the nanoporous compact, resulting in a more durable nanoporous compact. On the other hand, a binder content of 60% by mass or less can prevent the binder from penetrating the nanoporous compact and reducing the amount of adsorbate adsorbed. Furthermore, a binder mass ratio of 15 to 40% by mass is preferable, as this further improves durability and prevents a decrease in the amount of adsorption. In this specification, the "binder content" also includes the amounts of compounding agents such as crosslinking agents, vulcanizing agents, and vulcanization accelerators.

[0047] (Method for preparing nanoporous compact) The method for preparing the nanoporous molded body is not particularly limited. For example, the nanoporous molded body can be prepared by mixing the nanoporous body or its raw material with a rubber-based binder material, and then heat-treating the mixture, preferably by hot pressing.

[0048] The conditions for the heat treatment are not particularly limited. For example, a pressure of 200 to 400 MPa is applied for 10 minutes to 1 hour at a temperature of approximately 140 to 160°C under reduced pressure. This allows the rubber-based material to function as a binder, strongly binding the nanoporous bodies together or between the nanoporous body and the rubber-based material, resulting in a nanoporous body with excellent durability. A heating temperature of 140°C or higher ensures high binding strength, while a heating temperature of 160°C or lower reduces the risk of deterioration of the nanoporous body during production. That is, according to another aspect of the present invention, there is also provided a method for producing a nanoporous body, comprising heat-treating a mixture at 140 to 160°C containing a nanoporous body capable of changing its pore size by applying and releasing stress, thereby causing a reversible gas-liquid phase transition of an adsorbate incorporated as a guest molecule, and a rubber-based binder.

[0049] In this case, pressure may be applied at room temperature before hot pressing. The pressure applied here is preferably lower than the pressure conditions used in hot pressing, for example, 100 to 300 MPa. The pressure application time is not particularly limited, but is, for example, 10 seconds to 1 minute. By applying heat and pressure in stages in this way, a stronger bonding force can be achieved.

[0050] For the same reason, the hot pressing step may be carried out in two or more steps under different heating and pressing conditions so that heating and pressing are gradually applied in stages.

[0051] The content of the rubber-based material in the nanoporous molded body can be controlled to a desired content by measuring the weight loss of the rubber-based material under heating conditions equivalent to those used to prepare the nanoporous molded body, and adjusting the feed ratio based on the weight loss. In a preferred embodiment, the feed ratio of the rubber-based material is 13 to 29 mass% in terms of solid content relative to the total amount of the mixture (100 mass%). This allows for the production of a nanoporous molded body with a high adsorption mass and excellent durability.

[0052] (BET specific surface area of ​​nanoporous compact) The BET specific surface area of ​​the nanoporous molded body is not particularly limited, but is, for example, 900 to 3200 m 2 / g, preferably 900 to 1899 m 2 / g. The BET specific surface area is 900m 2 / g or more, the amount of adsorbate adsorbed can be increased. 2 / g or less, especially 1899m 2 / g or less. The BET specific surface area of ​​the nanoporous body can be adjusted by appropriately selecting the BET specific surface area of ​​the nanoporous body constituting the nanoporous body and the amount of binder added. The BET specific surface area of ​​the nanoporous body and the nanoporous body can be analyzed using liquid nitrogen adsorption (77K) (Microtrac BEL, BELSORB-max).

[0053] (Pore volume of nanoporous compact) The pore volume of the nanoporous body is not particularly limited, but is preferably 1.0 to 6.0 mL / g, and more preferably 1.3 to 6.0 mL / g. The nanoporous body of the present invention generates heat by undergoing a gas-liquid phase transition of the adsorbate associated with the compression and expansion of the nanoporous body in a relatively high relative vapor pressure range. A pore volume of 1.0 mL / g or greater is preferred because the amount of adsorbate adsorbed and desorbed is not too small even in a relatively high relative vapor pressure range. A pore volume of 6.0 mL / g or less is also preferred because a sufficient BET specific surface area can be secured, resulting in a high adsorption capacity. The pore volume of the nanoporous body can be adjusted by appropriately selecting the pore volume of the nanoporous body constituting the nanoporous body and the amount of binder added. The pore volume of the nanoporous body and the nanoporous body can be analyzed using liquid nitrogen adsorption (77 K) (Microtrac BEL, BELSORB-max).

[0054] [Stress applying portions 31A, 31B] The stress-applying units 31A and 31B apply stress to the nanoporous body 20 to cause it to contract, and release the applied stress to allow the nanoporous body 20 to freely expand. In this way, the stress-applying units 31A and 31B can control the pore size of the nanoporous body 20 by external stress.

[0055] The configuration of the stress-applying units 31A and 31B is not particularly limited as long as they can reciprocate in a direction toward and away from the nanoporous molded body 20 to apply and release stress to the nanoporous molded body 20. As the stress-applying units 31A and 31B, for example, a mechanical press that uses the rotational motion of a motor or a hydraulic press that uses fluid pressure such as oil pressure can be used.

[0056] [Chambers 32A and 32B] The chambers 32A and 32B are containers having a space therein for accommodating the nanoporous body 20. The interiors of the chambers 32A and 32B are maintained at a vacuum or a low pressure close to a vacuum, so that the refrigerant 60 can change phase from liquid to gas at a relatively low temperature.

[0057] [Air conditioning units 33A and 33B] The air conditioning units 33A, 33B switch between a cooling state in which heat is conducted between the chambers 32A, 32B and low-temperature air, and a heat rejection state in which heat is conducted between the chambers 32A, 32B and high-temperature air. Because the heat exchange device 10 is a device for cooling an object, the low-temperature air corresponds to the atmosphere of the object to be cooled. The air conditioning units 33A, 33B are in the cooling state to extract the cold energy required to cool the object from the heat exchange units 30A, 30B. The air conditioning units 33A, 33B are also in the heat rejection state to reject the heat generated from the heat exchange units 30A, 30B.

[0058] When the heat exchanger 10 is applied to an automobile air conditioner (cooling), for example, the low-temperature air can be the air inside the vehicle cabin (inside air) and the high-temperature air can be the air outside the vehicle cabin (outside air). For example, the outside air temperature is about 303 K (30°C), and the inside air temperature is about 298 K (25°C). In the following description, the low-temperature air will be referred to as the "inside air" inside the vehicle cabin, and the high-temperature air will be referred to as the "outside air" outside the vehicle cabin.

[0059] [Control unit 40] The control unit 40 is composed of, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), and a computer-readable recording medium (not shown). The control unit 40 controls the operation of the stress applying units 31A, 31B and the air adjusting units 33A, 33B. The control unit 40 switches the operation mode of the heat exchange units 30A, 30B between a desorption mode in which the refrigerant 60 is desorbed from the nanoporous molded body 20 and an adsorption mode in which the refrigerant 60 is adsorbed into the nanoporous molded body 20.

[0060] [Refrigerant 60] It is preferable to use water or an alcohol such as methanol or ethanol as the refrigerant 60. In general vapor compression heat exchangers, the fluorocarbon HFC-134a is widely used as a refrigerant, but water has approximately 16 times the latent heat of vaporization of HFC-134a, so theoretically, the amount of cold that can be obtained is 16 times greater. In addition, water and alcohol are preferable because they do not have a negative impact on the global environment.

[0061] <Thermal cycle of the heat exchange device 10> Next, the heat cycle of the heat exchanger 10 will be described with reference to FIG. 4. FIG. 4 shows a TS diagram of the heat cycle of the heat exchanger 10. In this case, the refrigerant 60 is considered to be divided into the following four types. The first type is the portion that remains permanently adsorbed in the nanoporous molded body 20. The second type is the portion that desorbs and adsorbs due to the application of stress to the nanoporous molded body 20 or free expansion, but is not involved in cooling the inside air. The third type is the portion that desorbs and adsorbs due to the application of stress to the nanoporous molded body 20 or free expansion, but is involved in cooling the inside air. The fourth type is the portion that is not adsorbed in the nanoporous molded body 20 and remains permanently in the gas phase. Note that only the third type of refrigerant is considered in FIG. 4.

[0062] The heat cycle of the heat exchange device 10 is a reverse Carnot cycle. The reverse Carnot cycle changes the state of the third type of refrigerant in the order of State 1 → State 2 → State 3 → State 4. In Figure 4, the process from State 1 to State 2 represents heating, the process from State 2 to State 3 represents isobaric and isothermal adsorption, the process from State 3 to State 4 represents cooling, and the process from State 4 to State 1 represents isobaric and isothermal desorption. Here, the third type of refrigerant is saturated vapor at low temperature T1 in State 1, superheated vapor at high temperature T2 in State 2, liquid at high temperature T3 in State 3, and liquid at low temperature T4 in State 4. Here, temperatures T1 and T4 are equal and are expressed as T L and temperatures T2 and T3 are equal to T H is.

[0063] From State 1 to State 2, the third type of refrigerant is at a low temperature T L is heated from saturated steam at high temperature T H At this time, the temperature of the third type of refrigerant rises without changing phase as a gas. At the same time, the temperature of the first type of refrigerant and the nanoporous molded body 20 is raised to T L From T H To raise the sensible heat Q sh1-2[J] is absorbed. Note that the third type of refrigerant is a gas, and its sensible heat is small compared to that of the first type of refrigerant, which is a liquid, and can therefore be ignored. In the thermal cycle of the heat exchange device 10, "sensible heat" includes not only the amount of heat required to change the temperature of the first type of refrigerant, but also the amount of heat required to change the temperature of the nanoporous molded body 20.

[0064] From State 2 to State 3, the contracted nanoporous body 20 expands freely, and the third type of refrigerant is adsorbed into the pores of the nanoporous body 20. Due to the adsorption, the third type of refrigerant changes phase from gas (water vapor) to liquid (water). The phase change generates the latent heat of condensation Q H [J] is dissipated heat.

[0065] From State 3 to State 4, the third type of refrigerant is heated to a high temperature T H is cooled from the liquid to a low temperature T L At this time, the first type of refrigerant and the third type of refrigerant remain liquid and do not change phase, but their temperatures decrease. The temperatures of the first type of refrigerant, the third type of refrigerant, and the nanoporous molded body 20 are set to T H From T L In order to reduce the sensible heat Q sh [J] is released as heat. In states 3 and 4, the third type of refrigerant is adsorbed into the pores. In addition, during the transition from state 3 to state 4, the second type of refrigerant, which is a gas, is adsorbed into the nanoporous body 20 as the temperature drops, causing the gas phase pressure of the system to temporarily decrease. However, the nanoporous body 20 contracts, causing the second type of refrigerant to desorb, thereby restoring the gas phase pressure of the system to its original state and reaching state 4.

[0066] From State 4 to State 1, the nanoporous body 20 contracts and the third type of refrigerant is desorbed. The sum of the external work required to contract the nanoporous body 20 from State 3 to State 4 and the external work required to contract the nanoporous body 20 from State 4 to State 1 is defined as W ns [J]. Also, due to desorption, the third type of refrigerant changes phase from liquid (water) to gas (water vapor). The phase change results in the latent heat of vaporization QL The heat exchanger 10 absorbs the latent heat of vaporization Q L [J] can be used as cold energy to cool objects.

[0067] As a control method for the heat exchange device 10, a method similar to the control method for a heat exchange device described in JP 2019-138620 A can be adopted.

[0068] Although the heat exchanger of this embodiment has been described above as being applied to a cooling device that cools an object by utilizing cold heat obtained from the latent heat of evaporation during desorption, it may also be applied to a heating device (heat pump) that heats an object by utilizing warm heat obtained from the latent heat of condensation during adsorption. Also, while the heat exchanger has been described as a batch-type heat exchanger having a pair (two) heat exchange sections, the present invention is not limited to this and may be configured with one heat exchange section or with three or more heat exchange sections. [Example]

[0069] The present invention will be described in more detail below with reference to examples, although the technical scope of the present invention is not limited to the following examples.

[0070] [Example 1] 1.6309 g of natural rubber (NR) (TSR20) and 0.111 g of a crosslinker mixture consisting of stearic acid (50S stearic acid, New Japan Chemical Co., Ltd.), zinc oxide (Hakusui Tech Co., Ltd., zinc oxide type 2), TBBS (Suncerer NS-G, Sanshin Chemical Industry Co., Ltd.), and sulfur (Sulfax 5, Tsurumi Chemical Industry Co., Ltd.) (mixing ratio: stearic acid:zinc oxide:TBBS:sulfur = 1:3:1:1.8 (mass ratio)) were weighed and added to 183 mL of tetrahydrofuran (THF) and stirred overnight. As some THF evaporated, an additional 50 mL was added. 22.0265 g of carbon-coated alumina particles (SBa-200) were then added and stirred at 50 °C for 1 hour. Finally, the mixture was heated with stirring at 60 °C for 3 hours to evaporate the THF, yielding 24.2649 g of solid. 50-100 mg of this was placed in a carbide jig (inner diameter 10 mm, interior mirror finish) and heated and molded by applying a pressure of 300 MPa at 145°C to obtain pellets. The resulting pellets were immersed in 30% by mass hydrofluoric acid for 5 hours to dissolve and remove the alumina (SBa-200), yielding the nanoporous molded body of this example. The nanoporous molded body thus obtained has a structure in which the nanoporous CMS is firmly bound by the binder natural rubber. The binder (natural rubber) content was 20% by mass relative to the total mass of the nanoporous molded body (100% by mass).

[0071] [Example 2] The nanoporous body of this example was obtained in the same manner as in Example 1, except that the blending amounts of natural rubber (NR), the crosslinking agent mixture, and the alumina particles were changed so that the binder (natural rubber) content was 10 mass% relative to the total mass of the nanoporous body (100 mass%). The blending ratio of natural rubber (NR) to the crosslinking agent mixture was the same as in Example 1.

[0072] [Example 3] The nanoporous body of this example was obtained in the same manner as in Example 1, except that the blending amounts of natural rubber (NR), the crosslinking agent mixture, and the alumina particles were changed so that the binder (natural rubber) content was 15% by mass relative to the total mass of the nanoporous body (100% by mass). The blending ratio of natural rubber (NR) to the crosslinking agent mixture was the same as in Example 1.

[0073] [Example 4] The nanoporous body of this example was obtained in the same manner as in Example 1, except that the blending amounts of natural rubber (NR), the crosslinking agent mixture, and the alumina particles were changed so that the binder (natural rubber) content was 40 mass% relative to the total mass of the nanoporous body (100 mass%). The blending ratio of natural rubber (NR) to the crosslinking agent mixture was the same as in Example 1.

[0074] [Example 5] The nanoporous molded body of this example was obtained in the same manner as in Example 1, except that the blending amounts of natural rubber (NR), the crosslinking agent mixture, and the alumina particles were changed so that the binder (natural rubber) content was 60 mass% relative to the total mass of the nanoporous molded body (100 mass%). The blending ratio of natural rubber (NR) to the crosslinking agent mixture was the same as in Example 1.

[0075] [Comparative Example 1] (Preparation of nanoporous materials (CMS)) CMS was prepared according to the method described in Advanced Functional Materials, Vol. 26, 2016, 6418-6427. Specifically, alumina nanoparticles (Taimei Chemicals, TM300) were placed in an electric furnace and heated to 1173 K (900 °C) in a nitrogen stream. Once the temperature reached 900 °C, the nitrogen gas was switched to 20 vol% methane and 80 vol% nitrogen, and carbon was deposited on the surface of the alumina nanoparticles by CVD for 2 hours. The nitrogen flow was then switched to nitrogen only, and the alumina nanoparticles were cooled to room temperature. The resulting carbon-coated alumina nanoparticles were immersed in hydrofluoric acid (47% by mass, Fujifilm Wako Pure Chemical Industries, Ltd.) to remove the alumina nanoparticles, yielding CMS.

[0076] (Preparation of nanoporous compacts) The CMS prepared above was mixed with a PTFE binder so that the PTFE binder content was 10% by mass relative to the total mass of the final nanoporous molded body (100% by mass), and the mixture was kneaded at room temperature using an agate mortar to form a composite.

[0077] The composite material was then pelletized by hot pressing to obtain a nanoporous compact for this comparative example. Hot pressing was performed using a dedicated device manufactured by Izumi Tech Co., Ltd., and pressure application and pressure control were performed using an autograph manufactured by Shimadzu Corporation. Pressurization was performed in two stages: 160°C for 28 minutes, followed by 300°C for 60 minutes.

[0078] (Measurement of displacement when stress is applied to nanoporous compacts) Stress was applied to the nanoporous bodies prepared in each Example and Comparative Example, and the resulting displacement was measured. A stress of 76 MPa was applied to the sample of Comparative Example 1, while a stress of 50 MPa was applied to the samples of each Example.

[0079] Specifically, each nanoporous body sample prepared in each Example and Comparative Example was first vacuum-dried at 150°C and placed in a chamber for in situ measurement of a press chamber device. To ensure a sufficient amount of sample for measurement, the pellet-shaped sample was sandwiched between stainless steel metal plates and placed in the chamber. Prior to the in situ measurement, the stacked sample was pressed several times to stabilize the elastic deformation of the sample.

[0080] The relationship between the torque of the linear feedthrough and the stress applied to the laminated sample was confirmed in advance through the following experiment. A ratchet with an attached torque sensor (Kyoto Tool Co., Ltd., GEK085-W36) was attached to the linear feedthrough, allowing the torque applied to turn the linear feedthrough to be measured. With the tip of the linear feedthrough fixed so that it was in contact with the load cell of the testing machine (Shimadzu Corporation, AG-50kNXplus), the ratchet was turned to investigate the relationship between the torque applied to the handle and the stress applied to the load cell. Using the above relationship, the stress applied to the laminated sample was controlled by the torque of the linear feedthrough.

[0081] During the in-situ measurements, stress-strain curves were measured at room temperature using a testing machine manufactured by Shimadzu Corporation. The nanoporous molded body produced in Comparative Example 1 was only able to measure its stress-strain curve once; measurements were impossible from the second time onward due to sample damage. The nanoporous molded body produced in Example 2 was able to measure its stress-strain curve up to the fifth time, but was unable to measure its stress-strain curve from the sixth time onward due to sample damage. The nanoporous molded bodies produced in the other Examples were able to measure their stress-strain curves up to the tenth time. Figure 5 shows the stress-strain curves of the nanoporous molded body produced in Comparative Example 1 (first measurement) and the nanoporous molded body produced in Example 1 (first and tenth measurements).

[0082] Next, the stress application energy was calculated by integrating the polynomial approximation curve of the stress-strain curve obtained above with respect to the displacement. From the adsorption isotherm when methanol was used as a refrigerant, the theoretical value of the heat of adsorption that can be extracted by applying stress to the nanoporous compact using methanol as a refrigerant was calculated to be 1725 J / g-CMS (1100 mg (STP) / g-CMS as the amount of methanol adsorbed and desorbed) at an applied pressure of 76 MPa (Comparative Example 1) and 1121 J / g-CMS (724 mL (STP) / g-CMS as the amount of methanol adsorbed and desorbed) at an applied pressure of 50 MPa (each Example). The efficiency was calculated by dividing these values ​​by the value of the applied stress energy calculated above. The results are shown in Table 1 below. In Table 1, the nanoporous compact is referred to as a "CMS composite."

[0083] [Table 1]

[0084] The results shown in Table 1 show that the nanoporous molded bodies of Examples 1 to 5, in which the nanoporous bodies were bound together using a rubber-based binder, were able to efficiently adsorb and desorb methanol by applying and releasing stress, and were therefore highly durable. In particular, Examples 1 and 3 to 4, in which the binder content was 15 to 40 mass% relative to 100 mass% of the nanoporous molded body, exhibited particularly excellent durability. On the other hand, the nanoporous molded body of Comparative Example 1, in which PTFE was used as the binder, exhibited excellent initial efficiency but significantly lower durability. [Explanation of symbols]

[0085] 10 heat exchange equipment, 20 Nanoporous compacts, 20A first nanoporous body, 20B second nanoporous body, 30A 1st heat exchange section (heat exchange section), 31A first stress applying portion (stress applying portion), 32A First Chamber (Chamber), 30B 2nd heat exchange section (heat exchange section), 31B second stress applying portion (stress applying portion), 32B Second chamber (chamber), 33A First air conditioning unit, 33B second air conditioning unit, 40 control section, 50 piping, 51 valves, 60 Refrigerant (medium).

Claims

1. a nanoporous body capable of changing the pore size by applying and releasing stress, and of causing a reversible gas-liquid phase transition of an adsorbate incorporated as a guest molecule; a rubber-based material as a binder; A nanoporous formed body comprising:

2. 2. The nanoporous molded body according to claim 1, wherein the rubber-based material comprises one or more selected from the group consisting of natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, nitrile-butadiene rubber, chloroprene rubber, ethylene-propylene rubber, butyl rubber, and silicone rubber.

3. 3. The nanoporous compact according to claim 1, wherein the content of the binder is 15 to 40% by mass relative to 100% by mass of the total amount of the nanoporous compact.

4. The nanoporous molded body according to any one of claims 1 to 3, wherein the nanoporous body contains a carbon material, and the half-width of the peak derived from the (10) plane of carbon in an X-ray diffraction spectrum of the nanoporous body using Cu-Kα radiation is within a range of 1.2 to 3.2°.

5. The BET specific surface area of ​​the nanoporous body is 800 to 2600 m ２ The nanoporous molded body according to any one of claims 1 to 4, wherein the surface roughness is 1 / g.

6. The nanoporous molded body according to any one of claims 1 to 5, wherein the pore volume of the nanoporous body is 2.0 mL / g or more.

7. The nanoporous molded body according to any one of claims 1 to 6, a stress applying unit that applies stress to the nanoporous body to contract the nanoporous body and releases the applied stress to expand the nanoporous body; A heat exchange device comprising:

8. A method for producing a nanoporous molded body, comprising heat-treating a mixture containing a nanoporous body or its raw material, which can change the pore size by applying and releasing stress, thereby causing a reversible gas-liquid phase transition of an adsorbate taken in as a guest molecule, and a rubber-based binder material, at 140 to 160°C.

9. The manufacturing method according to claim 8, wherein the rubber material is added in an amount of 13 to 29% by mass in terms of solid content relative to the total mass of the mixture.

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