JP6334352B2 - SOUND ABSORBING MATERIAL FOR FUEL CELL EXHAUST SYSTEM, FUEL CELL EXHAUST SOUND REDUCTION METHOD, AND FUEL CELL SOUNDER - Google Patents

Description

  The present invention relates to a sound absorbing material for an exhaust system of a fuel cell, a method for reducing the exhaust noise of a fuel cell, and a silencer for a fuel cell, which are not easily deformed even in a humid heat environment and have an excellent sound absorbing effect.

In the automobile industry, in recent years, development of hybrid cars and electric cars has progressed from the viewpoint of energy saving and has already been produced and sold. One of the energy-saving vehicles is a fuel cell vehicle. A fuel cell vehicle or FCV (Fuel Cell Vehicle) generates electricity by reacting oxygen in the air with hydrogen or reformed hydrogen as fuel from the installed fuel cell. Te, because it is the vehicle for driving the electric motor, similarly to the electric vehicle if the reaction only hydrogen, travel during CO ₂ or CO, nO _X, since it does not emit harmful emissions, such as SO _X, the ecology It also attracted attention from a viewpoint. However, the platinum catalyst and other components used as fuel cell materials were also expensive, making them unacceptable in the market. However, in recent years, the cost of materials has been reduced, and future diffusion is expected. Has been.

On the other hand, fuel cell vehicles have various technical problems, and one of them is reduction of exhaust noise. The fuel cell vehicle supplies a large amount of hydrogen gas to the fuel cell to generate electricity that can be used for driving the vehicle, but as the electricity is generated, the gas containing high-temperature water vapor is discharged. For this reason, there is a problem that the noise becomes loud when passing through the discharge port, and a method for reducing such noise has been demanded.
As a countermeasure, for example, Patent Document 1 proposes a sound absorbing material filled with organic fibers.

JP 2004-156555 A

  The present invention has been made in view of the above background, and its object is to provide a sound absorbing material for an exhaust system of a fuel cell and a method for reducing the exhaust noise of a fuel cell, which is not easily deformed even in a humid heat environment and has an excellent sound absorbing effect. The object is to provide a silencer for a fuel cell.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventor uses a sound-absorbing material having a high air permeability and a large compression hardness, so that the fuel cell has an excellent sound-absorbing effect and is not easily deformed even in a humid heat environment. The present inventors have found that a sound absorbing material for a vehicle exhaust system, a method for reducing exhaust noise of a fuel cell vehicle, and a muffler for a fuel cell vehicle can be obtained.

Thus, according to the present invention, “a sound absorbing material for an exhaust system of a fuel cell, wherein the air permeability at a thickness of 25 mm is 1 cm ³ / cm ² · sec or more and the compression hardness is 1 N or more. A sound absorbing material for an exhaust system of a fuel cell is provided.
In that case, it is preferable that the dimensional change rate when the wet heat treatment is performed at a temperature of 80 ° C., a humidity of 100% RH, and 24 hours is 10% or less. Moreover, when the wet heat treatment is performed at a temperature of 80 ° C., a humidity of 100% RH, and 24 hours, it is preferable that the retention ratio of the compression hardness is 40% or more. Moreover, it is preferable that a sound-absorbing material consists of a fiber structure. In addition, the fiber structure is a non-elastic crimped short fiber, and a thermal adhesive property in which a polymer having a melting point lower by 25 ° C. or more than the polymer constituting the non-elastic crimped short fiber is disposed on the surface as a heat fusion component Adhesive bonding obtained by laminating a web blended so that the weight ratio of the composite short fibers is 90/10 to 10/90, and being heat-sealed in a state where the heat-adhesive composite short fibers intersect with each other It is preferable that the fiber structure is formed by interspersing points and / or fixing points thermally fused in a state where the heat-adhesive composite short fibers and the inelastic crimped short fibers intersect. In that case, in the said fiber structure, it is preferable that the said inelastic crimped short fiber and the heat bondable composite staple fiber are arranged in the thickness direction. Moreover, it is preferable that the said fiber structure is a network structure which consists of a three-dimensional random loop joining structure. Moreover, it is preferable that the said fiber structure contains a polyester fiber or polyolefin fiber. Moreover, it is preferable that the average fiber diameter of the fiber which comprises the said fiber structure exists in the range of 27-100 micrometers.

Further, according to the present invention, there is provided a method for reducing exhaust noise of a fuel cell vehicle, wherein exhaust gas containing moisture discharged from the fuel cell vehicle is transmitted through the sound absorbing material for the exhaust system to reduce exhaust noise. Is done.
Moreover, according to this invention, the silencer of a fuel cell vehicle which uses the said sound-absorbing material for exhaust systems of a fuel cell vehicle is provided.

  According to the present invention, it is possible to obtain a sound absorbing material for an exhaust system of a fuel cell, a method for reducing exhaust noise of a fuel cell, and a silencer for a fuel cell, which are not easily deformed even in a humid heat environment and have an excellent sound absorbing effect.

  Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited thereto.

First, in a sound absorbing material for an exhaust system of a fuel cell of the present invention (hereinafter sometimes simply referred to as “sound absorbing material”), the air permeability at a thickness of 25 mm is 1 cm ³ / cm ² · sec or more (preferably 5 cm ³ / It is important that it is cm ² · sec or more, more preferably 10 cm ³ / cm ² · sec or more, particularly preferably 100 to 800 cm ³ / cm ² · sec. If the air permeability is less than 1 cm ³ / cm ² · sec, the exhaust gas containing water vapor generated with the generation of electricity in the fuel cell becomes difficult to permeate the sound absorbing material, and noise cannot be reduced. In addition, the gas that could not pass through may diffuse to the surroundings, and the noise may increase. The air permeability is measured by cutting to a thickness of 25 mm when the thickness of the sound absorbing material is larger than 25 mm, and the thickness is 25 mm when the thickness of the sound absorbing material is smaller than 25 mm. It shall be measured by laminating.

  In the sound-absorbing material of the present invention, it is important that the compression hardness is 1N or more (more preferably 5N or more, particularly preferably 5N to 10 kN). However, the compression hardness is the repulsion when a sound absorbing material having a thickness of 25 mm (dimensions of 100 mm × 100 mm × 25 mm) is compressed by 25% (that is, compressed to a thickness of 25 mm × 0.75). It is power. When a large amount of gas containing water vapor generated by the generation of electricity in the fuel cell passes through the sound absorbing material, a predetermined atmospheric pressure is applied to the sound absorbing material. However, the gas pressure cannot be withstood and the shape is deformed, so that the sound absorption effect may be reduced or the gas may be pushed out of the exhaust hole. In addition, the direction which cuts out a sound-absorbing material into the dimension of 100 mm x 100 mm x 25 mm is not specifically limited, Arbitrary directions may be sufficient. In addition, when the dimension of the sound absorbing material is smaller than the dimension 100 mm × 100 mm × 25 mm, it is measured by stacking so that the dimension is 100 mm × 100 mm × 25 mm.

  Further, the sound absorbing material of the present invention has a shape dimension change rate of the sound absorbing material of 10% or less (preferably 5.0% or less, particularly preferably 0) when subjected to wet heat treatment at 80 ° C., humidity 100%, 24 hours. 0.1 to 2.0%). Assuming that gas containing high-temperature water vapor generated with the generation of electricity passes through the sound absorbing material continuously for a predetermined time, if the dimensional change rate of the shape is larger than 10% under the above-mentioned wet heat conditions, the sound absorbing There is a possibility that the shape of the material is greatly deformed and the sound absorption effect is lowered.

Further, when the sound absorbing material is subjected to a wet heat treatment at 80 ° C., humidity 100%, 24 hours, the compression hardness retention is 40% or more (more preferably 50% or more, particularly preferably 60% or more). It is preferable to have a surface. Assuming that gas containing high-temperature water vapor generated with the generation of electricity passes through the sound absorbing material continuously for a predetermined time, if the retention rate of compression hardness is less than 40% under the above-mentioned wet heat conditions There is a possibility that the shape of the sound absorbing material is greatly deformed and a predetermined sound absorbing effect cannot be obtained. The retention rate is calculated by the following formula.
Retention rate = (compression hardness after wet heat treatment / compression hardness before wet heat treatment) × 100

  As the sound-absorbing material of the present invention, for example, those comprising the following fiber structure are preferable. At that time, the fiber constituting the fiber structure is not particularly limited as long as the above air permeability and compression hardness are satisfied. For example, polyester fiber, polyethylene fiber, polypropylene fiber, polyurethane fiber, aramid fiber, vinylon Examples include fibers, polyarylate fibers, polybenzoxazole (PBO) fibers, nylon fibers, acrylic fibers, vinyl chloride fibers, polyketone fibers, cellulose fibers, polyphenyl sulfide fibers, polycarbonate fibers, pulp fibers, and other organic fibers. These can be used alone or in combination of two or more. Of these, polyester fibers, polyethylene fibers, and polypropylene fibers are preferable from the viewpoint of durability and price.

  As a method for producing a fiber structure used as a sound-absorbing material for a fuel cell vehicle of the present invention, as long as it satisfies the dimensional change rate when subjected to the above-mentioned wet heat treatment, air permeability, and compression hardness, For example, in a state where a thermoplastic resin is melted, it is extruded with an extruder from a large number of nozzles, a large number of filaments are spun and allowed to fall naturally, and the mutual filaments are melt-bonded and solidified while still molten. Thus, there is a method for obtaining a three-dimensional fiber structure. In addition, a method for obtaining a normal short fiber nonwoven fabric, for example, using a stapled crimped short fiber, repeating the roller card process and the crosslay process, forming a uniform integrated web state fiber sheet, and three-dimensionally molding it A non-woven fiber structure is used. Here, as a method of three-dimensional molding, a method of fixing the shape by thermally bonding the fiber sheet in the web state obtained as described above as a folded shape, or physical such as needle punching or hydroentanglement It is possible to adopt a method in which fibers are entangled with each other to fix the shape, or a thermoforming method in which a fiber sheet is filled in a mold and molded by heat. As a method of obtaining a fiber sheet in a uniform and integrated web state, it is also preferable to air-lay in the air, and in the air-laying process, it is possible to obtain a web with more random orientation.

  When the fiber structure used as the sound absorbing material for the fuel cell vehicle of the present invention is manufactured using a roller card process, the fiber structure of the fiber structure used preferably includes a main fiber and a heat-adhesive short fiber, Polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyhexamethylene terephthalate, polytetramethylene terephthalate, poly-1,4-dimethylcyclohexane terephthalate, polyethylene naphthalate, polypivalolactone, polylactic acid (PLA), stereocomplex poly Preferable examples include short fibers made of lactic acid, polyester made from biomaterials or copolymer esters thereof, mixed fibers of these fibers, or composite fibers made of two or more of the above polymers.

  The cross-sectional shape of the short fiber may be circular, flat, irregular, or hollow. In particular, short fibers made of polyethylene terephthalate or a copolymer thereof are preferable. Of course, it is also possible to use polyethylene terephthalate that has been material recycled or chemically recycled. Moreover, the polyester obtained using the catalyst containing a specific phosphorus compound and a titanium compound may be sufficient.

The main fibers are polyamides such as nylon 6 and nylon 66, other synthetic fibers such as polyethylene, polypropylene, other polyolefins, acrylic, modacrylic and aramid fibers, inorganic fibers such as carbon fibers and glass fibers, and rayon. , And natural fibers such as silk, cotton, hemp, wool, etc.
The main fiber may be not only a fiber made of a single polymer but also a composite fiber such as a side-by-side type or a core-sheath type. Moreover, the fiber which added the flame retardant and the atypical cross-section fiber may be sufficient. The main fiber may be one type or a combination of a plurality of types.

  In the main fiber, 0.1 dtex or more (more preferably 0.9 to 100 dtex, more preferably 1.7 to 90 dtex, still more preferably 2.2 to 80 dtex, in order to obtain the air permeability and compression hardness described above. Preferably it has a single fiber fineness of 6.6 to 80 dtex, particularly preferably 10 to 60 dtex). If the single fiber fineness is less than 0.1 dtex, the air permeability and compression hardness of the fiber structure may be lowered.

  Moreover, it is preferable that the main fiber is crimped. At that time, the number of crimps is preferably 4 to 25 pieces / 2.54 cm, and the degree of crimp is preferably 20 to 40%. If the number of crimps or the degree of crimp is smaller than the above range, the web may be difficult to be bulked or web formation may be difficult. On the other hand, if the number of crimps or the degree of crimp is too larger than the above range, the entanglement of the fibers becomes strong during web formation, which may cause defects such as streaky irregularities.

In the main fiber, the fiber length is preferably 5 mm or more, more preferably 30 to 100 mm. If the fiber length is less than 5 mm, there is a possibility that sufficient shape retention cannot be obtained. Conversely, if the fiber length is greater than 100 mm, the process stability may be impaired.
As the fiber structure, the main fiber and the heat-adhesive short fiber are mixed so that the weight ratio is 95/5 to 5/95, and the heat-adhesive short fiber is heat-sealed in a state where the heat-adhesive short fibers intersect with each other. It is preferable that the fiber structure is formed by interspersing the fixed fixing points and / or the fixing points thermally fused in a state where the heat-adhesive short fibers intersect with the main fibers.

  Here, the heat-adhesive composite short fiber for fusing the main fiber is a short fiber in which a low-melting-point heat fusing component having a melting point 40 ° C. lower than the melting point of the main fiber is disposed at least on a part of the fiber surface. It is a short fiber that can be fused with the main fiber or the heat-adhesive composite short fiber by melting at least part of its surface by heating. If this difference in melting point is less than 40 ° C., the processing temperature will be close to the melting point of the main fiber, and the physical properties of the main fiber may be lowered, or the shrinkage during molding may be increased.

  Here, as a polymer arranged as a heat-fusion component, polyurethane elastomer, polyester elastomer, inelastic polyester polymer and copolymer thereof, polyolefin polymer and copolymer thereof, polyvinyl alcohol polymer, etc. Examples of polyurethane elastomers include low melting point polyols having a molecular weight of about 500 to 6000, such as dihydroxy polyether, dihydroxy polyester, dihydroxy polycarbonate, dihydroxy polyester amide, and the like, and organic diisocyanates having a molecular weight of 500 or less, such as p, p'-diphenylmethane diisocyanate, tolylene diisocyanate, isophorone diisocyanate hydrogenated diphenylmethane isocyanate, xylylene isocyanate, 2 6-diisocyanate methyl caproate, hexamethylene diisocyanate, molecular weight of 500 or less chain extender, for example a polymer obtained by a reaction between glycol aminoalcohol or triol.

  Among these polymers, particularly preferred is a polyurethane using polytetramethylene glycol, poly-ε-caprolactam or polybutylene adipate as a polyol. Examples of the organic diisocyanate in this case include p, p'-bishydroxyethoxybenzene and 1,4-butanediol.

  In addition, as a polyester-based elastomer, a polyetherester copolymer obtained by copolymerizing thermoplastic polyester as a hard segment and poly (alkylene oxide) glycol as a soft segment, more specifically, terephthalic acid, isophthalic acid, phthalic acid Alicyclic dicarboxylic acids such as naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, diphenyl-4,4′-dicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, succinic acid, oxalic acid, At least one dicarboxylic acid selected from aliphatic dicarboxylic acids such as adipic acid, sebacic acid, dodecanedioic acid, dimer acid, or ester-forming derivatives thereof, 1,4-butanediol, ethylene glycol trimethylene glycol, Tetramethylene glycol, Aliphatic diols such as tamethylene glycol, hexamethylene glycol neopentyl glycol, decamethylene glycol, or alicyclic diols such as 1,1-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tricyclodecane methanol, or the like At least one diol component selected from ester-forming derivatives and the like, and polyethylene glycol, poly (1,2- and 1,3-polypropylene oxide) glycol, poly (tetramethylene oxide) having an average molecular weight of about 400 to 5000 ) Consists of at least one of poly (alkylene oxide) glycols such as glycols, copolymers of ethylene oxide and propylene oxide, copolymers of ethylene oxide and tetrahydrofuran, etc. It can be mentioned terpolymer.

  In particular, from the viewpoint of adhesiveness, temperature characteristics, and strength, a block copolymer polyether ester having polybutylene terephthalate as a hard component and polyoxybutylene glycol as a soft segment is preferable. In this case, the polyester portion constituting the hard segment is polybutylene terephthalate in which the main acid component is terephthalic acid and the main diol component is a butylene glycol component. Of course, part of this acid component (usually 30 mol% or less) may be substituted with another dicarboxylic acid component or oxycarboxylic acid component, and part of the glycol component (usually 30 mol% or less) is also butylene. It may be substituted with a dioxy component other than the glycol component. Further, the polyether portion constituting the soft segment may be a polyether substituted with a dioxy component other than butylene glycol.

  Copolyester polymers include aliphatic dicarboxylic acids such as adipic acid and sebacic acid, aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and naphthalenedicarboxylic acid and / or fats such as hexahydroterephthalic acid and hexahydroisophthalic acid. A co-polymer containing a predetermined number of cyclic dicarboxylic acids and aliphatic or alicyclic diols such as diethylene glycol, polyethylene glycol, propylene glycol, and paraxylene glycol, with addition of oxyacids such as parahydroxybenzoic acid as desired. Polymerized esters and the like can be mentioned. For example, polyesters obtained by adding and copolymerizing isophthalic acid and 1,6-hexanediol in terephthalic acid and ethylene glycol can be used.

  Examples of the polyolefin polymer include low density polyethylene, high density polyethylene, and polypropylene. Of the above heat-sealing components, a copolyester polymer is particularly preferable. In addition, various stabilizers, ultraviolet absorbers, thickening branching agents, matting agents, coloring agents, other various improving agents, and the like may be blended in the above-described polymer as necessary.

  In the heat-bondable composite short fiber, the non-elastic polyester as described above is preferably exemplified as the counterpart component of the heat-sealing component. In that case, it is preferable that the heat fusion component occupies at least a half of the surface area. The weight ratio is suitably in the range of 30/70 to 70/30 in terms of the composite ratio of the heat fusion component and the non-elastic polyester. Although it does not specifically limit as a form of a heat bondable composite staple fiber, It is preferable that a heat-fusion component and inelastic polyester are side-by-side and a core-sheath type, More preferably, it is a core-sheath type. In this core-sheath-type heat-bondable composite short fiber, the non-elastic polyester is the core and the heat-sealing component is the sheath, but the core may be concentric or eccentric.

In such a heat-adhesive composite short fiber, the single fiber fineness is 0.5 to 20 dtex (more preferably 1.7 to 15 dtex, still more preferably 2.2 to 10 dtex, particularly preferably 3.0 to 7.0 dtex). Preferably there is. If the single fiber fineness is less than 0.5 dtex, the air permeability and compressive strength of the fiber structure may be lowered.
Moreover, in the said heat bondable composite staple fiber, fiber length is preferable 5 mm or more, More preferably, it is 30-100 mm. If the fiber length is less than 5 mm, sufficient shape retention may not be obtained. Conversely, if the fiber length is greater than 100 mm, the process stability may be impaired.

By adhering the main fiber and the heat-adhesive composite short fiber and heat-treating, the fixing point and / or the heat-adhesive short fiber heat-sealed in a state where the heat-adhesive short fibers intersect with each other A fiber structure is formed in which the fixing points thermally fused in a state where the main fibers intersect with each other are scattered.
At that time, the weight ratio of the main fiber to the heat-bonding composite short fiber is preferably (main fiber / heat-bonding composite short fiber) 95/5 to 5/95 (more preferably 95/5 to 60/40). . When the ratio of the heat-bonding composite short fibers is less than this range, the fixing points are extremely reduced, and the compression hardness may be lowered. On the other hand, when the ratio of the heat-bonding composite short fibers is larger than this range, the number of bonding points increases, and the air permeability may be lowered.

  In the fiber structure, it is preferable that the main fibers and the heat-bonded composite short fibers are arranged in the thickness direction of the fiber structure because air permeability and compression hardness are improved. Here, “arranged in the thickness direction” means that the total number of fibers arranged in parallel to the thickness direction of the fiber structure is (B) and the thickness direction of the fiber structure is On the other hand, when (A) is the total number of fibers arranged vertically, B / A is 1.5 or more.

  A method for producing such a fiber structure is not particularly limited, and a conventionally known method may be arbitrarily employed. For example, the main fiber and the heat-adhesive composite short fiber are mixed, and uniform by a roller card. After spinning as a web, using a heat treatment machine as shown in FIG. 1 of Japanese Patent Application Laid-Open No. 2008-68799, heat-treating the web while folding it into an accordion, and forming a fixing point by heat fusion, etc. Preferably exemplified. For example, a device disclosed in Japanese Translation of PCT International Publication No. 2002-516932 (for example, commercially available Strut equipment manufactured by Struto Corporation) may be used.

Moreover, as the said fiber structure, the network structure which consists of a three-dimensional random loop joining structure as described in the international publication 2013/168699 pamphlet may be sufficient, for example. That is, a three-dimensional structure in which a continuous linear body made of a thermoplastic resin is twisted to form a random loop, and each loop is brought into contact with each other in a molten state, and most of the contact portion is fused. It is a network structure composed of a random loop bonded structure. In that case, it is preferable that the apparent density of the random loop bonded structure is 0.005 to 0.200 g / cm ³ . Moreover, it is preferable that the number of bonding points per unit weight of the random loop bonded structure is 500 to 1200 pieces / g.

  It is preferable that the average fiber diameter of the fiber used for the said fiber structure is 27-100 micrometers. When the average fiber diameter of the fibers used in the fiber structure is smaller than 27 μm, a predetermined air permeability can be obtained when the density of the fiber structure is increased in order to develop a predetermined compressive strength in the fiber structure. There is a possibility of disappearing. On the other hand, if the average fiber diameter of the fibers used in the fiber structure is larger than 100 μm, the specific surface area of the fibers of the fiber structure is small, and the amount of energy in which sound energy due to contact with the fibers is replaced with friction energy is small. Therefore, there is a possibility that a predetermined sound absorption effect cannot be obtained. More preferably, the average fiber diameter of the fiber used for the said fiber structure is 30-80 micrometers, More preferably, it is 30-60 micrometers. The average fiber diameter is calculated by a weighted average.

In the fiber structure, the shape and thickness are not particularly limited due to the shape of the silencer and its space, but the thickness is preferably in the range of 10 to 500 mm in order to obtain excellent sound absorption.
The fiber structure may be added with known functional processing such as water repellent processing, flameproof processing, flame retardant processing, negative ion generation processing, metal deposition, and the like.

The sound-absorbing material of the present invention may be composed only of the fiber structure, or a fabric (woven or knitted fabric or nonwoven fabric) or a metal sheet may be laminated on the fiber structure.
Since the sound absorbing material of the present invention has the characteristics as described above, it is difficult to be deformed even in a humid heat environment and has an excellent sound absorbing effect. Therefore, an exhaust system of a fuel cell such as a fuel cell vehicle, a fuel cell ship, and a household fuel cell. Suitable as a sound absorbing material.

Next, an exhaust noise reduction method for a fuel cell according to the present invention is an exhaust of a fuel cell that reduces exhaust noise by allowing the exhaust gas containing moisture discharged from the fuel cell to pass through the exhaust system sound absorbing material. This is a sound reduction method.
A silencer for a fuel cell according to the present invention is a silencer for a fuel cell using the above-described sound absorbing material for an exhaust system of a fuel cell. Such fuel cells include fuel cells such as fuel cell vehicles, fuel cell ships, and household fuel cells. Further, the structure of the silencer is not particularly limited, but as shown in FIG. 1 of Japanese Patent Application Laid-Open No. 2007-5178, an inner pipe (preferably a plurality of sound transmission holes is provided) that exhausts exhaust gas from the fuel cell. It is preferable to form a sound absorbing chamber between the inner pipe) and the outer shell, and to fill the sound absorbing chamber with the sound absorbing material.

  The present invention will be specifically described below with reference to examples. However, the present invention is not limited thereby. The following evaluations and characteristic values were obtained by the following measurement methods.

(1) Air permeability (cm ³ / cm ² · sec)
The sound absorbing material is cut into 60 x 60 x 25 mm with a thickness direction of 25 mm, used as a test piece, and a ventilation resistance measuring device (manufactured by KATO TECH, KES-F8-AP1) is used to fix the cut sample to the device. It installed in the jig | tool and measured ventilation resistance R (kPa * sec / m). The air permeability of the sample was calculated by substituting the ventilation resistance value thus obtained into the following conversion formula obtained empirically.
Air permeability = 2.17 / Air resistance R

(2) Compression hardness (N)
The sound absorbing material is cut into 100 mm × 100 mm × 25 mm with a thickness direction of 25 mm, used as a test piece, and a compression tester that is larger than one side of the test piece (100 mm × 100 mm), and a speed of 10 mm / min in the thickness direction. , And the load when the test piece was compressed by 25% (thickness 6.25 mm) was measured to obtain the compression hardness. This hardness was defined as “compression hardness before wet heat treatment”.

(3) Shape change rate of sound absorbing material (%) when wet heat treatment is performed at 80 ° C., humidity 100%, 24 hours
First, the sample length (A) before the wet heat treatment in the vertical and horizontal directions of the sample was measured. Subsequently, the sample is placed in a constant temperature and constant temperature drying apparatus in which the inside of the apparatus is in an environment of 80 ° C. and humidity of 100%. After 24 hours, the sample is taken out from the apparatus, and wet heat treatment in the vertical and horizontal directions of the sample is performed. The previous sample length (B) was measured. The shape dimension change rate of the sample was calculated based on the following formula in both the vertical direction and the horizontal direction, and the average value of both was obtained.
Form dimensional change rate (%) = ((A−B) / A) × 100

(4) Retention rate (%) of compression hardness when the thickness is reduced by 25% when wet heat treatment is performed at 80 ° C., humidity 100%, 24 hours
The sample subjected to the wet heat treatment used to calculate the shape dimensional change rate of the sound absorbing material when subjected to the wet heat treatment for 24 hours at 80 ° C., 100% humidity, 100 × 100 × 25 mm, assuming that the thickness direction is 25 mm. The test piece is cut into two pieces, and is compressed at a speed of 10 mm / min in the thickness direction by means of a compressor larger than the test piece with a compression tester, and the load when compressed for 25% of the thickness of the test piece is measured, Compressive hardness. This hardness was defined as “compressed hardness after wet heat treatment”.
And the retention rate of the compression hardness of the sample was calculated based on the following formula.
Compression hardness retention (%) = (Compression hardness after wet heat treatment / Compression hardness before wet heat treatment) × 100

(5) Sound absorption φ50mm, 500mm long iron pillars, with one mouth left open, the other mouth with two φ10mm, 50mm long iron bars installed in a cross , Fixed by welding.
Next, the sound absorbing material was cut into a diameter of 50 mm and a thickness of 25 mm, inserted into the iron pillar prepared in the above procedure from the open mouth, and pushed into the iron bar installed in the cross until the sound absorbing material was grounded.
Subsequently, 80 degreeC vapor | steam was poured in by the gas amount of 1 m < ³ > / min from the side where the opening of the iron pillar was vacant, and the noise was measured with the noise meter. At this time, the sound level meter is measured at a distance of 10 cm from the steam outlet side, and if noise reduction of 5 dB or more is confirmed compared to the case where no sound absorbing material is installed, the sound absorbing property ○ (pass). If noise reduction of 5 db or more was not confirmed, it was set as sound absorptivity x (failed).

(6) Thickness Measured according to JIS L 1913.

(7) Weight per unit area Measured according to JIS L 1913.

[Example 1]
As a main fiber, polyethylene terephthalate (PET) short fiber (single fiber fineness 13 dtex, fiber diameter 40 μm, fiber length 51 mm, crimp number 9 / 2.54 cm) manufactured by Teijin Ltd. is 60% by weight as a heat-adhesive short fiber Coated polyethylene terephthalate short fiber (single fiber fineness 4.4 dtex, fiber diameter 25 μm, fiber length 51 mm, crimped number 11 pieces / 2.54 cm) manufactured by Teijin Ltd. The card web was obtained through equipment carding and cross-layering.
Next, a card web having a predetermined weight is placed in a mold through which hot air can pass, subjected to heat treatment at 160 ° C. for 20 minutes, and a fiber structure having a basis weight of 1000 g / m ² , length × width × thickness of 500 × 500 × 25 mm. A body (average fiber diameter 34 μm) was obtained.
The fiber structure thus obtained is used as a sound absorbing material for a fuel cell vehicle,
(A) Air permeability when the thickness of the fiber structure in the direction of air passage is 25 mm (b) Compression hardness (c) 80 when the fiber structure having a thickness of 25 mm is compressed by 25% of the thickness Dimensional change rate of shape of fiber structure when subjected to wet heat treatment at ℃, humidity 100%, 24 hours (d) Fiber structure having a thickness of 25 mm when subjected to wet heat treatment at 80 ° C, humidity 100%, 24 hours The body was compressed for 25% thickness, the compression hardness retention rate and sound absorption were evaluated, and the evaluation results are summarized in Table 1.

[Example 2]
“Breath Air” (trade name) manufactured by Toyobo (weight per unit: 500 g / m ² , thickness: 40 mm, average fiber diameter 60 μm) was prepared,
(A) Air permeability when the thickness of the fiber structure in the direction of air passage is 25 mm (b) Compression hardness (c) 80 when the fiber structure having a thickness of 25 mm is compressed by 25% of the thickness Dimensional change rate of shape of fiber structure when subjected to wet heat treatment at ℃, humidity 100%, 24 hours (d) Fiber structure having a thickness of 25 mm when subjected to wet heat treatment at 80 ° C, humidity 100%, 24 hours The body was compressed for 25% thickness, the compression hardness retention rate and sound absorption were evaluated, and the evaluation results are summarized in Table 1.

[Comparative Example 1]
Prepare a commercially available polystyrene foam (manufactured by Kasahara Kogyo Co., Ltd.), then
(A) Air permeability when the thickness of the fiber structure in the direction of air passage is 25 mm (b) Compression hardness (c) 80 when the fiber structure having a thickness of 25 mm is compressed by 25% of the thickness Dimensional change rate of shape of fiber structure when subjected to wet heat treatment at ℃, humidity 100%, 24 hours (d) Fiber structure having a thickness of 25 mm when subjected to wet heat treatment at 80 ° C, humidity 100%, 24 hours The body was compressed for 25% thickness, the compression hardness retention rate and sound absorption were evaluated, and the evaluation results are summarized in Table 1.

[Comparative Example 2]
3M “Synthrate” (trade name) (weight per unit: 442 g / m ² , thickness: 26 mm, average fiber diameter 12 μm) was prepared,
(A) Air permeability when the thickness of the fiber structure in the direction of air passage is 25 mm (b) Compression hardness (c) 80 when the fiber structure having a thickness of 25 mm is compressed by 25% of the thickness Dimensional change rate of shape of fiber structure when subjected to wet heat treatment at ℃, humidity 100%, 24 hours (d) Fiber structure having a thickness of 25 mm when subjected to wet heat treatment at 80 ° C, humidity 100%, 24 hours The body was compressed for 25% thickness, the compression hardness retention rate and sound absorption were evaluated, and the evaluation results are summarized in Table 1.

  As is clear from these results, the sound-absorbing material for fuel cells of the present invention has a specific air permeability, compression hardness, and durability under wet heat conditions, so that moisture generated in the process of generating electricity in the fuel cell can be obtained. It has been recognized that the exhaust gas containing can be a material that can reduce the exhaust noise by passing through the sound absorbing material.

  According to the present invention, there are provided a sound absorbing material for an exhaust system of a fuel cell, a method for reducing exhaust noise of a fuel cell, and a silencer for a fuel cell, which are not easily deformed even in a humid heat environment and have an excellent sound absorbing effect. The value is tremendous.

Claims (11)

A sound absorbing material for an exhaust system of a fuel cell, wherein the air permeability at a thickness of 25 mm is 1 cm ³ / cm ² · sec or more, and the compression hardness is 1 N or more. Sound absorbing material.   2. The sound absorbing material for an exhaust system of a fuel cell according to claim 1, wherein a dimensional change rate when subjected to a wet heat treatment at a temperature of 80 ° C. and a humidity of 100% RH for 24 hours is 10% or less.   The sound-absorbing material for an exhaust system of a fuel cell according to claim 2, wherein the retention of compression hardness is 40% or more when a wet heat treatment is performed at a temperature of 80 ° C and a humidity of 100% RH for 24 hours.   The sound absorbing material for an exhaust system of a fuel cell according to any one of claims 1 to 3, wherein the sound absorbing material comprises a fiber structure.   The fiber structure is composed of a non-elastic crimped short fiber and a heat-adhesive composite short in which a polymer having a melting point 25 ° C. lower than that of the polymer constituting the non-elastic crimped short fiber is arranged on the surface as a heat fusion component. Fixing points obtained by laminating webs blended so that the weight ratio of fibers becomes 90/10 to 10/90, and heat-sealed in a state where the heat-adhesive composite short fibers intersect with each other; and 5. The fuel cell according to claim 4, which is a fiber structure in which the heat-bonding composite short fibers and the inelastic crimped short fibers intersect with heat-bonded fixing points. Sound absorber for exhaust system.   The sound absorbing material for an exhaust system of a fuel cell according to claim 5, wherein in the fiber structure, the inelastic crimped short fibers and the heat-bonding composite short fibers are arranged in the thickness direction.   The sound absorbing material for an exhaust system of a fuel cell according to claim 4, wherein the fiber structure is a network structure made of a three-dimensional random loop joint structure.   The sound absorbing material for an exhaust system of a fuel cell according to any one of claims 4 to 7, wherein the fiber structure includes a polyester fiber or a polyolefin fiber.   The sound absorbing material for an exhaust system of a fuel cell according to any one of claims 1 to 8, wherein an average fiber diameter of fibers constituting the fiber structure is in a range of 27 to 100 µm.   An exhaust noise reduction method for a fuel cell, wherein exhaust gas containing moisture discharged from the fuel cell is allowed to pass through the exhaust system sound absorbing material according to any one of claims 1 to 9 to reduce exhaust noise.   A silencer for a fuel cell, comprising the sound absorbing material for an exhaust system of a fuel cell according to any one of claims 1 to 9.