Gas filter, gas sensor, and gas detection device

Abstract

The present disclosure addresses the problem of providing a gas filter that can efficiently suppress the flow through of water vapor. A gas filter 1 according to one embodiment of the present disclosure comprises a porous membrane 2. The pore diameter of the porous membrane 2 is not greater than 2 nm. The porous membrane 2 contains a fluoroalkyl group-bearing polysiloxane compound.

Description

Gas filter, gas sensor and gas detection device

[0001] The present disclosure relates to a gas filter, a gas sensor, and a gas detection device, and more particularly to a gas filter that can be provided in a gas sensor, a gas sensor including this gas filter, and a gas detection device including this gas sensor.

[0002] Patent Document 1 discloses a gas separation filter that separates a predetermined gas from a mixed gas, comprising a porous support layer, an intermediate layer formed on the porous support layer and having a pore size smaller than that of the porous support layer, and a separation layer formed on the intermediate layer and having a pore size smaller than that of the intermediate layer, wherein the intermediate layer is a porous body having hydrophobic groups.

[0003] JP 2016-221453 A

[0004] An object of the present disclosure is to provide a gas filter that can efficiently block the passage of water vapor, a gas sensor including this gas filter, and a gas detection device including this gas sensor.

[0005] A gas filter according to one aspect of the present disclosure includes a porous membrane having a pore size of 2 nm or less, and the porous membrane contains a polysiloxane compound having a fluoroalkyl group.

[0006] A gas sensor according to one aspect of the present disclosure includes a gas sensitive portion that changes in response to a component in a gas, and the gas filter through which gas supplied to the gas sensitive portion passes.

[0007] A gas detection device according to one aspect of the present disclosure includes the gas sensor and a detection unit that generates a gas detection result in response to a change in the gas sensitive portion of the gas sensor.

[0008] FIG. 1 is a schematic diagram showing the configuration of a gas filter, a gas sensor, and a gas detection device according to an embodiment.

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to FIG. 1. Note that the following embodiments are merely a portion of various embodiments of the present disclosure. Furthermore, the following embodiments can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. The figures referred to below are schematic diagrams, and the dimensional ratios of the components in the figures do not necessarily reflect the actual dimensional ratios. The mechanism of action of the embodiments shown below is presumed, and the present disclosure is not bound by the following explanation of the mechanism of action.

[0010] The gas filter 1 of the embodiment includes a porous membrane 2, the pore size of which is 2 nm or less, and the porous membrane 2 contains a polysiloxane compound having a fluoroalkyl group.

[0011] The gas filter 1 of the embodiment can effectively inhibit the permeation of water vapor. This is presumably because the polysiloxane compound having a fluoroalkyl group imparts water repellency to the porous membrane 2, and the pore diameter of the porous membrane 2 is 2 nm or less, which significantly inhibits the penetration of water vapor into the pores of the porous membrane 2.

[0012] It may not be possible to sufficiently prevent the passage of water vapor simply by imparting hydrophobicity to the gas filter 1. However, in the embodiment, by imparting high hydrophobicity to the inner surfaces of the pores in the gas filter 1 with a polysiloxane compound having a fluoroalkyl group and setting the diameter of these pores to 2 nm or less, it is believed that the penetration of water vapor into the pores can be effectively prevented, as described above.

[0013] Furthermore, the gas filter 1 can selectively block the permeation of water vapor in particular, thereby preventing excessive blockage of the flow of gases other than water vapor, such as carbon monoxide gas, etc. Therefore, when the gas filter 1 is applied to a gas sensor 8, for example, the flow of water vapor is suppressed while the flow of the gas to be detected can be ensured.

[0014] The gas filter 1 may include only the porous membrane 2. Alternatively, the gas filter 1 may include the porous membrane 2 and one or more layers other than the porous membrane 2, in which the porous membrane 2 and the layers are laminated together. The layer other than the porous membrane 2 may include, for example, a porous substrate 3 described below, or a porous substrate 3 and a porous intermediate layer 4.

[0015] A more specific configuration of the gas filter 1 of the embodiment will be described.

[0016] As described above, the gas filter 1 may include the porous substrate 3, and the porous substrate 3 and the porous membrane 2 may be laminated together. In this case, the porous membrane 2 may be supported by the porous substrate 3. The material of the porous substrate 3 is, for example, porous ceramic, porous glass, or porous resin. Here, the phrase "the porous substrate 3 and the porous membrane 2 are laminated together" means that the porous substrate 3 and the porous membrane 2 are laminated together so that they are in direct contact with each other, or that the porous substrate 3 and the porous membrane 2 are laminated together so that a layer (for example, the porous substrate 3) different from both the porous substrate 3 and the porous membrane 2 is interposed between the porous substrate 3 and the porous membrane 2.

[0017] The pore diameter of the porous substrate 3 is preferably larger than the pore diameter of the porous membrane 2. In this case, the porous substrate 3 is unlikely to excessively inhibit gas permeation through the gas filter 1. The pore diameter of the porous substrate 3 is, for example, 1 nm or more and 100 nm or less. The pore diameter is more preferably 10 nm or more, and even more preferably 50 nm or more. The pore diameter of the porous substrate 3 is an average pore diameter measured by mercury intrusion porosimetry.

[0018] The thickness of the porous substrate 3 is preferably set appropriately so that the porous substrate 3 has a strength sufficient to support the porous membrane 2 and so that the porous substrate 3 does not excessively inhibit gas permeation through the gas filter 1. The thickness of the porous substrate 3 is, for example, 0.1 mm or more and 1 mm or less.

[0019] When the gas filter 1 includes the porous substrate 3, the porous membrane 2 may be directly superimposed on the porous substrate 3. Alternatively, a layer different from both the porous substrate 3 and the porous membrane 2 may be interposed between the porous substrate 3 and the porous membrane 2. For example, as described above, the gas filter 1 may include a porous intermediate layer 4 interposed between the porous substrate 3 and the porous membrane 2. The pore diameter of the porous intermediate layer 4 is preferably smaller than the pore diameter of the porous substrate 3 and larger than the pore diameter of the porous membrane 2. In this case, the pore diameters of the filter decrease in the order of the porous substrate 3, the porous intermediate layer 4, and the porous membrane 2. Therefore, even if there is a difference between the pore diameter of the porous substrate 3 and the pore diameter of the porous membrane 2, the resistance to gas passing through the gas filter 1 can be reduced.

[0020] Furthermore, when the porous membrane 2 is supported only by the porous substrate 3, increasing the thickness of the porous substrate 3 to ensure strength increases the resistance to gas passing through the gas filter 1. However, if the porous intermediate layer 4 is provided instead of increasing the thickness of the porous substrate 3, the porous membrane 2 can be firmly supported by the porous substrate 3 and the porous intermediate layer 4, and an excessive increase in the resistance to gas passing through the gas filter 1 can be suppressed.

[0021] The pore diameter of the porous intermediate layer 4 is, for example, 4 nm to 100 nm, and is an average pore diameter measured by mercury intrusion porosimetry.

[0022] The thickness of the porous intermediate layer 4 is preferably set appropriately so that the porous substrate 3 and the porous intermediate layer 4 have sufficient strength to support the porous membrane 2, and so that the porous intermediate layer 4 does not excessively inhibit gas permeation through the gas filter 1. The thickness of the porous intermediate layer 4 is, for example, 0.1 mm or more and 2 mm or less. The total thickness of the porous substrate 3 and the porous intermediate layer 4 is, for example, 0.2 mm or more and 4 mm or less.

[0023] The material of the porous intermediate layer 4 is, for example, porous ceramic, porous glass, or porous resin. The porous intermediate layer 4 may be made from a hydrolysis polycondensate of a hydrolyzable silane compound, in which case the porous intermediate layer 4 may be made by a sol-gel method. That is, for example, the porous intermediate layer 4 may be made by applying a reactive solution containing a hydrolyzable silane compound, a catalyst, and water to the surface of the porous substrate 3, and then heating the reactive solution to hydrolyze and polycondense the hydrolyzable silane compound. In this case, the porous intermediate layer 4 having a desired thickness may be made by repeating the application and heating of the reactive solution multiple times.

[0024] As described above, the porous film 2 contains a polysiloxane compound having a fluoroalkyl group. It is preferable that the surfaces of the pores of the porous film 2 are formed from a polysiloxane compound having a fluoroalkyl group. Therefore, for example, the porous film 2 is a single layer formed from a polysiloxane compound having a fluoroalkyl group. Alternatively, for example, the surfaces of the pores of the porous film 2 may be covered with a layer formed from a polysiloxane compound having a fluoroalkyl group.

[0025] As described above, when the porous membrane 2 contains a polysiloxane compound having a fluoroalkyl group and the pore diameter of the porous membrane 2 is 2 nm or less, the penetration of water vapor into the pores of the porous membrane 2 can be suppressed. In order to further suppress the penetration of water vapor into the pores, it is more preferable that the pore diameter of the porous membrane 2 is 1 nm or less. Furthermore, it is preferable that the pore diameter of the porous membrane 2 is 0.5 nm or more. In this case, the flow of gas in the gas filter 1 is less likely to be excessively inhibited. The pore diameter of the porous membrane 2 is determined by the t-plot method of nitrogen adsorption measurement.

[0026] The polysiloxane compound having a fluoroalkyl group is, for example, a hydrolysis polycondensate of a hydrolyzable silane compound (A) containing a hydrolyzable silane compound (a1) having a fluoroalkyl group.

[0027] The fluoroalkyl group in the hydrolyzable silane compound (a1) is bonded to, for example, a silicon atom in the hydrolyzable silane compound (a1). The hydrolyzable silane compound (a1) has, for example, 1 to 9 fluoroalkyl groups per molecule.

[0028] The hydrolyzable silane compound (a1) contains at least one selected from the group consisting of, for example, fluoroalkyltrimethoxysilane, fluoroalkyltriethoxysilane, fluoroalkylmethyldimethoxysilane, fluoroalkylmethyldiethoxysilane, bis(fluoroalkyldiethoxysilyl)methane, 1,2-bis(fluoroalkyldiethoxysilyl)ethane, 1,4-bis(fluoroalkyldiethoxysilyl)benzene, etc. However, the compounds that the hydrolyzable silane compound (a1) can contain are not limited to the above.

[0029] The number of carbon atoms in the fluoroalkyl group in the hydrolyzable silane compound (a1) is, for example, 1 or more and 3 or less, and the number of fluorine atoms in the fluoroalkyl group is, for example, 3 or more and 9 or less.

[0030] The hydrolyzable silane compound (A) may further contain a hydrolyzable silane compound (a2) that does not have a fluoroalkyl group. The hydrolyzable silane compound (a2) contains at least one selected from the group consisting of, for example, tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, bis(triethoxysilyl)methane, 1,2-bis(triethoxysilyl)ethane, and 1,4-bis(triethoxysilyl)benzene. However, the compounds that can be contained in the hydrolyzable silane compound (a2) are not limited to those listed above.

[0031] The ratio of the hydrolyzable silane compound (a1) to the hydrolyzable silane compound (A) is preferably 2 mol% or more. In this case, the permeation of water vapor through the gas filter 1 can be more efficiently inhibited. This is presumably because the hydrophobicity of the surface of the pores of the porous membrane 2 is sufficiently increased. It is more preferable that this ratio is 5 mol% or more. It is also preferable that the ratio of the hydrolyzable silane compound (a1) to the hydrolyzable silane compound (A) is 20 mol% or less. In this case, the permeation of water vapor through the gas filter 1 can be more efficiently inhibited. It is presumed that when the ratio of the hydrolyzable silane compound (a1) is 20 mol% or less, the variation in the diameter of the pores of the porous membrane 2 is suppressed, and water vapor is prevented from passing through pores with large diameters. It is more preferable that this ratio is 10 mol% or less.

[0032] The porous film 2 is produced, for example, by a sol-gel method. In this case, a reactive solution (sol) containing, for example, a hydrolyzable silane compound (A), water, a catalyst, and an organic solvent is prepared. The organic solvent is preferably an amphiphilic solvent that is compatible with both water and the hydrolyzable silane compound (A). The organic solvent is, for example, a lower alcohol such as ethanol. The catalyst is, for example, an appropriate acid catalyst or base catalyst. The acid catalyst is, for example, hydrochloric acid, sulfuric acid, or nitric acid, but is not limited to these.

[0033] The reactive solution is applied, for example, to the porous substrate 3 or the porous intermediate layer 4, and then heated. In this case, in order to suppress defects in the porous membrane 2, it is preferable to heat the reactive solution by heating the porous substrate 3 and then applying the reactive solution. By heating the reactive solution in this manner, the hydrolysis polycondensation reaction of the hydrolyzable silane compound (A) is promoted. This results in the production of a porous membrane 2 formed from a polysiloxane compound having a fluoroalkyl group. By repeating the application and heating of the reactive solution multiple times, the thickness of the porous membrane 2 can be increased, thereby producing a porous membrane 2 having a desired thickness.

[0034] The method for producing the porous film 2 is not limited to the sol-gel method, and the porous film 2 may be produced by, for example, a chemical vapor deposition method.

[0035] The thickness of the porous film 2 is preferably 5 nm or less. In this case, the porous film 2 is less likely to be damaged, such as cracked. A thickness of 2 nm or less is more preferable. Furthermore, the thickness of the porous film 2 is preferably 0.5 nm or more. In this case, the permeation of water vapor through the porous film 2 can be further suppressed. A thickness of 1 nm or more is more preferable.

[0036] The mass per area of ​​the porous membrane 2 is 3 mg / cm ２ In this case, the porous membrane 2 is less likely to be damaged, such as cracked. In addition, the mass per area of ​​the porous membrane 2 is preferably 0.5 mg / cm or less. ２ In this case, the permeation of water vapor through the porous membrane 2 can be further suppressed.

[0037] The gas filter 1 of the embodiment is suitable for use in the gas sensor 8. In this case, the gas filter 1 can effectively suppress the flow of water vapor through the gas sensor 8. Therefore, for example, when the function of the gas sensor 8 is reduced by water vapor, the gas filter 1 can suppress the inflow of water vapor into the gas sensor 8, and when the function of the gas sensor 8 is reduced by dryness, the gas filter 1 can suppress the outflow of water vapor from the gas sensor 8. Furthermore, because the gas filter 1 can selectively suppress the flow of water vapor, it is possible to avoid excessively impeding the flow of the gas to be detected, and therefore the gas filter 1 is less likely to deteriorate the sensitivity of the gas sensor 8.

[0038] However, the gas filter 1 according to the embodiment can be applied to various uses other than the gas sensor 8 in which its characteristics can be utilized.

[0039] A gas sensor 8 including the gas filter 1 of the embodiment and a gas detection device 11 including this gas sensor 8 will now be described.

[0040] The gas sensor 8 includes a gas sensitive part 5 that changes in response to the components in the gas, and a gas filter 1. The gas filter 1 is provided so that the gas supplied to the gas sensitive part 5 can pass through.

[0041] 1 includes a gas sensitive part 5, a sensor chamber 6, a gas flow path 7, and a gas filter 1. The gas sensitive part 5 is disposed in the sensor chamber 6. The gas flow path 7 is a flow path leading to the sensor chamber 6, through which gas supplied to the sensor chamber 6 passes. The gas filter 1 of the embodiment is disposed in the gas flow path 7, and is disposed such that a space within the sensor chamber 6 is interposed between the gas filter 1 and the gas sensitive part 5. In other words, there is a gap between the gas filter 1 and the gas sensitive part 5.

[0042] According to the gas sensor 8 of the embodiment, gas passes through the gas flow path 7 , passes through the gas filter 1 , is supplied to the sensor chamber 6 , and comes into contact with the gas-sensitive part 5 .

[0043] Furthermore, since there is a space in the sensor chamber 6 between the gas-sensitive part 5 and the gas-sensitive part 5, the gas is less likely to be hindered from reaching the gas-sensitive part 5 than when the gas-sensitive part 5 is directly covered by the gas filter 1. Therefore, the sensitivity of the gas-sensitive part 5 is less likely to be impaired by the gas filter 1.

[0044] The gas-sensitive part 5 is, for example, a suitable sensor element that changes in response to the components in the gas when it comes into contact with the gas. The change in the gas-sensitive part 5 is, for example, a change in the physical properties such as the electrical resistance of the gas-sensitive part 5, or the generation of an electromotive force in the gas-sensitive part 5.

[0045] There are no particular limitations on the form of gas flow path 7, as long as it communicates with the interior of sensor chamber 6 and can supply gas from gas flow path 7 to the interior of sensor chamber 6. For example, gas flow path 7 may be a conduit connected to sensor chamber 6, or may be an opening formed in sensor chamber 6.

[0046] The interior of the sensor chamber 6 is preferably sealed except for the portion communicating with the gas flow path 7, and is configured so that all gas flowing through the gas flow path 7 passes through the gas filter 1 before entering the sensor chamber 6. To achieve this, for example, the gas filter 1 is provided so as to block the gas flow path 7, i.e., to divide the gas flow path 7 into an upstream side and a downstream side in the gas flow direction. In this case, particularly when the volume of gas in the sensor chamber 6 decreases during gas detection by the gas sensitive unit 5, a pressure difference occurs between the inside and outside of the sensor chamber 6, which promotes the inflow of gas into the sensor chamber 6 through the gas filter 1. This can improve the efficiency of gas detection. The case in which the volume of gas in the sensor chamber 6 decreases during gas detection by the gas sensitive unit 5 is, for example, when the gas sensitive unit 5 is a catalytic combustion-type sensor element for detecting carbon monoxide. In this case, two molecules of carbon monoxide react with one molecule of oxygen to produce two molecules of carbon dioxide, thereby reducing the gas volume. In the case of a semiconductor sensor element or an electrochemical sensor element, the volume of the gas can be reduced by a chemical reaction, and the inflow of the gas can be promoted.

[0047] In the embodiment, the gas sensitive portion 5 is, for example, a semiconductor sensor element, a catalytic combustion sensor element, or an electrochemical sensor element.

[0048] In particular, when the gas sensing unit 5 is an electrochemical sensor element, the durability of the gas sensing unit 5 can be improved. An electrochemical sensor element generates an electromotive force corresponding to the molecules to be detected in the gas through a water-mediated electrochemical reaction. Therefore, if the electrochemical sensor element dries out in a dry atmosphere and there is a shortage of water in the electrochemical sensor element, the sensitivity decreases. In addition, it is known that the ionic conductivity of electrochemical sensor elements decreases when they dry out, which also contributes to a decrease in sensitivity. However, in the embodiment, the passage of water vapor through the gas filter 1 is suppressed, thereby suppressing the outflow of water from the electrochemical sensor element, which is the gas sensing unit 5. Therefore, the gas sensing unit 5 can have high durability even in a dry atmosphere. Furthermore, in the embodiment, the durability of the gas sensor 8 in a dry atmosphere can be increased without providing a water reservoir, thereby enabling the gas sensor 8 to be miniaturized.

[0049] The structure of the gas sensor 8 is not limited to the above. For example, the gas filter 1 may directly cover the gas sensitive part 5 without any space between the gas filter 1 and the gas sensitive part 5.

[0050] A gas detection device 11 according to an embodiment includes a gas sensor 8 according to the embodiment and a detection unit 9 that generates a detection result in response to a change in the gas sensitive unit 5 in the gas sensor 8. The detection unit 9 is a detection circuit that generates a detection result indicating the type of a component to be measured in a gas based on, for example, a change in the gas sensitive unit 5, or further generates a detection result indicating the concentration of this component in the gas. The gas detection device 11 may also include an alarm unit 10 that notifies the detection result generated by the detection unit 9 by voice, video, or the like. The alarm unit 10 is, for example, a speaker, buzzer, display, or lamp. The gas detection device 11 is configured as, for example, a gas alarm.

[0051] Specific examples are presented below, but the present disclosure is not limited to the following examples.

[0052] 1. Preparation of porous membrane and gas filter A reactive solution was prepared by mixing the hydrolyzable silane compound shown in Table 1 with a 1 mol / L aqueous hydrochloric acid solution, ion-exchanged water, and ethanol. The amount of each raw material used is as shown in Table 1. The proportion of the hydrolyzable silane compound shown in Table 1 (unit: mol%) is the proportion to the total hydrolyzable silane compound.

[0053] As a porous substrate, a porous glass plate (pore diameter: 50 nm) measuring 2 cm x 2 cm x 1 mm was prepared.

[0054] This porous substrate was heated in a dryer for 1 hour and then placed on a hot plate at 180 ° C. In this state, a reactive solution was applied to the porous substrate by a spray method to form a coating film, and this coating film was heated in a dryer at 180 ° C. for 3 minutes. The application of the reactive solution and the heating of the coating film were repeated 10 times. Subsequently, the coating film was heated in a dryer at 180 ° C. for 1 hour. In this way, a gas filter comprising a porous substrate and a porous film overlapping the porous substrate was produced.

[0055] Table 1 shows the mass (adhesion amount) per area of ​​the porous membrane calculated from the amount of reactive solution applied to the porous substrate.

[0056] 2. Measurement of Water Contact Angle The water contact angle (static contact angle) of the porous film was measured using a contact angle meter (product name: DropMaster) manufactured by Kyowa Interface Science Co., Ltd.

[0057] 3. Pore size measurement The pore size of the porous membrane was determined by the t-plot method of nitrogen adsorption measurement.

[0058] 4. Measurement of Specific Surface Area The specific surface area of ​​the porous membrane was determined by the Brunauer-Emmett-Teller method (BET method) of nitrogen adsorption measurement.

[0059] 5. Permeability (1) Carbon monoxide permeability A first chamber and a second chamber, each made from a 5 mm thick acrylic plate and having an inner diameter of 50 mm and a length of 100 mm, were prepared as gas permeation cells. The opening of each chamber had a rim, and with a packing attached to the rim, a sample could be fixed between the openings of the two chambers. The sample was prepared by sandwiching a gas filter between two pieces of aluminum tape with a circular hole of 16 mm diameter and bonding them together. This allowed the carbon monoxide permeation area of ​​the gas filter to be 2 cm². ２ The carbon monoxide gas sensor NAP-508 manufactured by Nemoto Sensor Engineering Co., Ltd. was installed in the second chamber so that the carbon monoxide concentration in the second chamber could be detected at intervals of one second. In this state, the sample was fixed between the two chambers. Carbon monoxide gas was introduced from the carbon monoxide gas cylinder into the first chamber so that the concentration was 150 ppm, and the change in the carbon monoxide concentration in the second chamber was measured with the carbon monoxide gas sensor. From the measurement results by the carbon monoxide gas sensor during the period from the introduction of carbon monoxide gas until one minute had elapsed, the permeability coefficient of carbon monoxide gas (unit: mmol / cm ２ ·h·Pa) was calculated.

[0060] (2) Water Vapor Permeability A cup with an inner diameter of 56 mm and a height of 32 mm, made from a 1 mm thick stainless steel plate, was prepared. The opening of the cup had a rim, to which a packing and a holding lid could be attached to fix the sample. The sample was prepared by sandwiching a gas filter between two pieces of aluminum tape with a circular hole of 16 mm diameter and bonding them together. This resulted in a water vapor permeation area of ​​the gas filter of 2 cm. ２ The standard is defined as follows. A plastic plate containing 10 g of calcium chloride was placed in the cup, and the sample was then fixed to the cup. The initial weight of the cup was measured in this state. The cup was placed in a constant temperature and humidity chamber set at 25°C and 90% humidity, and after 24 hours it was removed and re-weighed. Based on this result, the water vapor permeability coefficient (unit: mmol / cm) was calculated. ２·h·Pa) was calculated.

[0061] (3) Evaluation For Example 2, Example 7, and Comparative Example 1, the carbon monoxide permeability and water vapor permeability were measured. From the results, the ratio of the water vapor permeability coefficient to the carbon monoxide gas permeability coefficient (H ２ The ratio (O permeability coefficient / CO permeability coefficient) was calculated. The results are shown in Tables 1 and 2. The smaller this value, the more the gas filter can be evaluated as inhibiting the permeation of water vapor.

[0062] In Examples 2 and 7, the ratio values ​​are small, and therefore it can be evaluated that the gas filter sufficiently inhibits the permeation of water vapor. It can be similarly inferred that the gas filter can sufficiently inhibit the permeation of water vapor in Examples other than Examples 2 and 6. On the other hand, in Comparative Example 1, the ratio value is large compared to Examples 2 and 7. Therefore, it can be determined that the gas filter in Comparative Example 1 cannot sufficiently inhibit the permeation of water vapor compared to the Examples.

[0063]

[0064]

[0065] [Aspects] A gas filter (1) of a first aspect includes a porous membrane (2). The porous membrane (2) has a pore size of 2 nm or less. The porous membrane (2) contains a polysiloxane compound having a fluoroalkyl group.

[0066] In this embodiment, the gas filter (1) can efficiently prevent the passage of water vapor.

[0067] In a second aspect, the gas filter (1) of the first aspect further comprises a porous substrate (3). The pore size of the porous substrate (3) is larger than the pore size of the porous membrane (2). The porous substrate (3) and the porous membrane (2) are laminated together.

[0068] In this embodiment, the porous membrane (2) is supported by the porous substrate (3), which further suppresses damage such as cracking of the porous membrane (2) and ensures gas permeability in the gas filter (1).

[0069] In a third aspect, the gas filter (1) of the second aspect further comprises a porous intermediate layer (4) interposed between the porous substrate (3) and the porous membrane (2). The pore size of the porous intermediate layer (4) is smaller than the pore size of the porous substrate (3) and larger than the pore size of the porous membrane (2).

[0070] In this embodiment, the gas permeability of the gas filter (1) can be better ensured.

[0071] In a fourth aspect, the gas filter (1) in any one of the first to third aspects is used for a gas sensor (8).

[0072] In this embodiment, the gas filter (1) can effectively suppress the flow of water vapor through the gas sensor (8).

[0073] A gas sensor (8) of the fifth aspect comprises a gas sensitive part (5) that changes in response to a component in a gas, and a gas filter (1) of any one of the first to fourth aspects through which gas supplied to the gas sensitive part (5) passes.

[0074] In this embodiment, the gas filter (1) can effectively suppress the flow of water vapor through the gas sensor (8).

[0075] A gas detection device (11) of a sixth aspect includes the gas sensor (8) of the fifth aspect and a detection section (9) that generates a gas detection result in response to a change in the gas sensitive section (5) in the gas sensor (8).

[0076] REFERENCE SIGNS LIST 1 Gas filter 2 Porous membrane 3 Porous substrate 4 Porous intermediate layer 5 Gas sensitive part 8 Gas sensor 11 Gas detection device

Claims

1. Equipped with a porous membrane, The pore size of the porous membrane is 2 nm or less. The porous membrane contains a polysiloxane compound having a fluoroalkyl group. Gas filter.

2. Further comprising a porous substrate, The pore diameter of the porous substrate is larger than the pore diameter of the porous membrane. The porous substrate and the porous membrane are laminated together. The gas filter according to claim 1.

3. The porous intermediate layer is further interposed between the porous substrate and the porous membrane, The pore diameter of the porous intermediate layer is smaller than the pore diameter of the porous substrate and larger than the pore diameter of the porous membrane. The gas filter according to claim 2.

4. It is for gas sensors. A gas filter according to any one of claims 1 to 3.

5. A gas-sensitive part that changes in response to components in the gas, The gas filter according to any one of claims 1 to 3 through which the gas supplied to the gas sensing unit passes, is provided. Gas sensor.

6. The gas sensor according to claim 5, The gas sensor comprises a detection unit that generates a gas detection result in response to changes in the gas-sensitive part of the gas sensor, Gas detection device.