Sound absorption structure

Abstract

To provide a sound absorption structure having excellent sound absorption performance and excellent recyclability.SOLUTION: Provided is a sound absorption structure including: an inorganic fiber mat that is made of an assembly of inorganic fibers; and an enclosure material that is made of a nonwoven fabric of organic fibers and encloses the inorganic fiber mat. The inorganic fibers are inorganic fibers containing non-fibered fine particles. The inorganic fibers have an average fiber diameter of 30.0 μm or less. The inorganic fiber mat has a bulk density of 10.0 to 200.0 kg / m3. The enclosure material has a flow resistance value of 50 N s / m3 to 3,000 N s / m3.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a sound absorbing structure having an inorganic fiber mat as sound absorbing material. [Background technology]

[0002] Conventionally, sound-absorbing materials have been used in automobiles to reduce noise from outside the vehicle. Currently, sound-absorbing structures having sound-absorbing mats made of an organic fiber assembly are often used in interior trims such as roofs, door trims, luggage sides, pillars, and instrument panels.

[0003] Such sound-absorbing mats made from an organic fiber assembly are made by molding organic fibers such as polypropylene resin, polyester resin, polyethylene resin, nylon resin, and acrylic resin into a mat shape of about 1 to 30 mm, and function as a sound-absorbing material that absorbs sound by converting noise vibrations into vibrational energy of the fibers.

[0004] For example, Patent Document 1 describes a sound absorbing structure having a sound absorbing mat made of an assembly of organic fibers, with an average effective fiber diameter of less than 15 microns, a thickness of at least 0.5 cm, and a density of 50 kg / m 3 Disclosed is a heat stable soundproofing material for attenuation of sound waves comprising a meltblown microfiber polypropylene web having an airflow pressure drop of at least 1 mmH2O at a flow rate of 32 liters / minute as determined using test method ASTM F778-88, wherein the polypropylene microfibers are formed from polypropylene homopolymer, copolymer, or blends thereof, and 0.2-5 wt. % of a non-volatile heat stabilizer or antioxidant is uniformly distributed in the microfibers, and the microfibers are heat stable at 135°C for at least 10 days. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3911548 Summary of the Invention [Problem to be solved by the invention]

[0006] At present, in sound-absorbing structures used in automobiles and the like, organic fibers forming sound-absorbing mats have an average fiber diameter of about 1 to 25 μm. Here, it is known that the smaller the fiber diameter of the organic fibers used in sound-absorbing mats, the greater the number of fibers and voids, and therefore the smaller the fiber diameter of the fibers forming the sound-absorbing mat, the higher the sound-absorbing performance.

[0007] However, in the organic fibers currently used in the manufacture of sound absorbing structures for use in automobiles and the like, there is a problem in that it is difficult to further reduce the average fiber diameter from the standpoint of cost, etc.

[0008] Moreover, from the viewpoint of resource conservation in recent years, there is a demand for recycling the fibers used in the sound absorbing mats of sound absorbing structures.

[0009] Furthermore, sound-absorbing mats made of a combination of two types of thermoplastic resins with different melting points are often used as absorbing structures for automobiles. This sound-absorbing mat is molded in a temperature range where only the resin with the lower melting point softens and melts, allowing the resin with the lower melting point to be used as a binder, and it can be stably molded to a specified thickness and shape. This leads to problems in recycling sound-absorbing mats, such as increased costs due to the time and effort required to separate the two types of thermoplastic resins with different melting points and to separate and remove the surrounding material, and problems in that the composition of the organic fibers in the recycled product changes because the fused surrounding material cannot be completely removed.

[0010] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a sound absorbing structure which has excellent sound absorbing performance and excellent recyclability. [Means for solving the problem]

[0011] The above problem is solved as follows. That is, the present invention (1) comprises an inorganic fiber mat made of an aggregate of inorganic fibers, and an enveloping material made of a nonwoven fabric of organic fibers and enveloping the inorganic fiber mat, the inorganic fibers being inorganic fibers containing non-fiberized fine particles, the average fiber diameter of the inorganic fibers being 30.0 μm or less, and the bulk density of the inorganic fiber mat being 10.0 to 200.0 kg / cm 3 and the flow resistance of the surrounding material is 50N·s / m 3 ~3000N·s / m 3 The present invention provides a sound absorbing structure characterized by:

[0012] The present invention (2) also provides a sound absorbing structure according to (1), characterized in that the inorganic fiber is rock wool, ceramic fiber or glass fiber.

[0013] In the present invention (3), the wrapping material has a basis weight of 10.0 to 80.0 g / m 2 The present invention provides a sound absorbing structure according to (1) or (2), characterized in that:

[0014] The present invention (4) provides the sound absorbing structure according to (1) or (2), characterized in that the inorganic fiber mat has a thickness of 1.0 to 30.0 mm.

[0015] The present invention (5) provides a sound absorbing structure according to (1) or (2), characterized in that the surrounding material has a thickness of 0.020 to 3.0 mm.

[0016] The present invention (6) provides a sound absorbing structure according to (1) or (2), characterized in that the inorganic fibers have an average fiber diameter of 3.0 μm or more.

[0017] In addition, the present invention (7) is characterized in that the bulk density of the inorganic fiber mat is 40.0 to 80.0 kg / m 3 The present invention provides a sound absorbing structure according to (1) or (2), characterized in that: Effect of the Invention

[0018] According to the present invention, it is possible to provide a sound absorbing structure that has excellent sound absorbing performance and excellent recyclability. [Brief description of the drawings]

[0019] [Figure 1] FIG. 2 is an end view of an example of a sound absorbing structure of the present invention. [Diagram 2] FIG. 2 is a schematic end view showing an acoustic tube of a Winzac normal incidence sound absorption coefficient measurement system (manufactured by Nihon Onkyo Engineering Co., Ltd.) used in the examples. [Diagram 3] FIG. 2 is a schematic end view of a jig used in testing shot release prevention properties in the examples. [Figure 4] FIG. 1 is a schematic end view showing an acoustic tube of a Winzac normal incidence sound absorption coefficient measurement system (manufactured by Nihon Onkyo Engineering Co., Ltd.) used in a reference example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The sound absorbing structure of the present invention is an inorganic fiber mat formed of an aggregate of inorganic fibers; and an enclosure material made of a nonwoven fabric of organic fibers and surrounding the inorganic fiber mat, The inorganic fibers are inorganic fibers containing non-fiberized fine particles, the average fiber diameter of the inorganic fibers is 30.0 μm or less, and the bulk density of the inorganic fiber mat is 10.0 to 200.0 kg / m 3 and the flow resistance of the surrounding material is 50N·s / m 3 ~3000N·s / m 3 The sound absorbing structure is characterized in that

[0021] That is, the sound absorbing structure of the present invention comprises an inorganic fiber mat made of an aggregate of inorganic fibers, and an enveloping material made of a nonwoven fabric of organic fibers and enveloping the inorganic fiber mat, the inorganic fibers being rock wool, ceramic fiber or glass fiber containing non-fiberized fine particles produced by a melting method, the average fiber diameter of the inorganic fibers being 30.0 μm or less, and the bulk density of the inorganic fiber mat being 10.0 to 200.0 kg / m 3and the flow resistance of the surrounding material is 50N·s / m 3 ~3000N·s / m 3 The sound absorbing structure is characterized in that

[0022] The sound-absorbing structure of the present invention is used in automobiles as interior sound-absorbing members such as roofs, door trims, luggage sides, pillars, instrument panels, etc. for the purpose of absorbing sound, and as exterior sound-absorbing members such as motor rooms, fender liners, etc. for the purpose of absorbing sound.

[0023] The sound absorbing structure of the present invention comprises an inorganic fiber mat made of an assembly of inorganic fibers, and an enveloping material made of a nonwoven fabric of organic fibers and enveloping the inorganic fiber mat.

[0024] The inorganic fiber mat of the sound absorbing structure of the present invention is an assembly of inorganic fibers formed into a mat shape, that is, the inorganic fiber mat is made of inorganic fibers.

[0025] The inorganic fibers forming the inorganic fiber mat are inorganic fibers produced by a melting method, that is, inorganic fibers produced by a melting method. In other words, the inorganic fibers forming the inorganic fiber mat contain non-fiberized fine particles called shots that are generated during production by the melting method, and the inorganic fiber mat is produced using inorganic fibers containing non-fiberized fine particles called shots that are generated during production by the melting method. Therefore, non-fiberized fine particles are present in the inorganic fiber mat. Examples of inorganic fibers forming the inorganic fiber mat include rock wool, ceramic fiber, and glass fiber produced by a melting method. In particular, rock wool is more preferable because it is less flammable and resistant to moisture.

[0026] The composition of the inorganic fibers forming the inorganic fiber mat, calculated as oxides, is such that the Si content calculated as SiO2 is preferably 25.0 to 85.0 mass%, more preferably 30.0 to 80.0 mass%, the Al content calculated as Al2O3 is preferably 0.0 to 70.0 mass%, more preferably 0.0 to 65.0 mass%, the Ca content calculated as CaO is preferably 0.0 to 50.0 mass%, more preferably 0.0 to 45.0 mass%, the Mg content calculated as MgO is preferably 0.0 to 20.0 mass%, more preferably 0.0 to 15.0 mass%, and the Fe content calculated as Fe2O3 is preferably 0.0 to 20.0 mass%, more preferably 0.0 to 15.0 mass%.

[0027] The composition of the rock wool forming the inorganic fiber mat, calculated as oxides, is such that the Si content calculated as SiO2 is preferably 25.0 to 55.0 mass%, more preferably 30.0 to 50.0 mass%, the Al content calculated as Al2O3 is preferably 0.0 to 30.0 mass%, more preferably 5.0 to 25.0 mass%, the Ca content calculated as CaO is preferably 10.0 to 50.0 mass%, more preferably 15.0 to 45.0 mass%, the Mg content calculated as MgO is preferably 0.0 to 20.0 mass%, more preferably 0.0 to 15.0 mass%, and the Fe content calculated as Fe2O3 is preferably 0.0 to 20.0 mass%, more preferably 0.0 to 15.0 mass%.

[0028] The composition of the ceramic fibers forming the inorganic fiber mat, calculated as oxides, is such that the Si content calculated as SiO2 is preferably 30.0 to 70.0 mass%, more preferably 35.0 to 65.0 mass%, and the Al content calculated as Al2O3 is preferably 20.0 to 70.0 mass%, more preferably 25.0 to 65.0 mass%.

[0029] The composition of the glass fibers forming the inorganic fiber mat, calculated as oxides, is such that the Si content calculated as SiO2 is preferably 45.0 to 85.0 mass%, and more preferably 50.0 to 80.0 mass%, the Al content calculated as Al2O3 is preferably 0.0 to 35.0 mass%, and more preferably 0.0 to 30.0 mass%, and the Ca content calculated as CaO is preferably 0.0 to 35.0 mass%, and more preferably 0.0 to 30.0 mass%.

[0030] It is believed that the smaller the average fiber diameter of the inorganic fibers forming the inorganic fiber mat, the better the sound absorption performance. Sound is a compression wave of air, and when sound waves travel through the inorganic fiber mat, the air (voids) between the fibers vibrate, and sound energy is lost mainly due to friction with the fibers. Therefore, it is believed that the smaller the fiber diameter, the more the air between the fibers is subdivided, and the more efficiently the sound wave energy can be absorbed. The average fiber diameter of the inorganic fibers forming the inorganic fiber mat is 30.0 μm or less, preferably 20.0 μm or less, and more preferably 10.0 μm or less. In addition, the lower limit of the average fiber diameter of the inorganic fibers forming the inorganic fiber mat is not particularly limited, but if the average fiber diameter of the inorganic fibers is less than 1.0 μm, the mechanical strength of the inorganic fibers themselves may decrease, and if the fiber diameter is too small and the gap between the fibers is too small, the sound wave will not pass through and the sound absorption performance will decrease. The average fiber diameter of the inorganic fibers forming the inorganic fiber mat is preferably 3.0 μm or more, and more preferably 4.0 μm, in terms of improving sound absorption performance. From the viewpoint of the impact on human health, such as the risk of carcinogenicity, the average fiber diameter of the inorganic fibers is preferably 3.0 μm or more. In the present invention, the average fiber diameter of the inorganic fibers means the arithmetic mean value of the fiber diameters of any 100 inorganic fibers forming the inorganic fiber mat.

[0031] The inorganic fibers forming the inorganic fiber mat are inorganic fibers produced by a melting method. The method for producing the inorganic fibers is not particularly limited, and may be any method capable of adjusting the average fiber diameter to 30.0 μm or less, preferably 20.0 μm or less, more preferably 10.0 μm or less. For example, the inorganic fiber raw material is melted at about 1500 to 1600 ° C. in an electric furnace or the like to prepare a molten liquid, and the molten liquid is collided with a spinner rotating at high speed to produce the inorganic fibers, that is, the melting method. Such a method for producing inorganic fibers makes it easy to obtain inorganic fibers with a small average fiber diameter, and the average fiber diameter can be adjusted by the rotation speed of the spinner, etc.

[0032] The inorganic fiber mat may contain a binder for binding the inorganic fibers together in addition to the inorganic fibers. Examples of the binder used in the inorganic fiber mat include organic binders such as phenol resin, acrylic resin, and urea-melamine resin. The organic binder is preferable because it disappears by oxidative decomposition when the inorganic fiber mat is melted during recycling.

[0033] When the inorganic fiber mat contains a binder, the content of the binder in the inorganic fiber mat is preferably 20.0 parts by mass or less, more preferably 1.0 to 10.0 parts by mass, per 100.0 parts by mass of the inorganic fibers. By having the content of the binder in the inorganic fiber mat within the above range, the inorganic fiber mat can be stably molded to a desired thickness while maintaining flexibility.

[0034] The bulk density of the inorganic fiber mat is 10.0 to 200.0 kg / m 3 , preferably 20.0 to 100.0 kg / m 3 , more preferably 40.0 to 80.0 kg / m 3When the bulk density of the inorganic fiber mat is within the above range, the sound absorbing structure has high sound absorbing performance and also has sound insulation performance. On the other hand, if the bulk density of the inorganic fiber mat is less than the above range, the inorganic fiber mat is damaged when a worker picks up the inorganic fiber mat during production or handling, resulting in poor handling properties and a reduced amount of fiber in the inorganic fiber mat, resulting in reduced sound absorbing performance. If the bulk density of the inorganic fiber mat is less than the above range, the sound insulation performance is also reduced. Furthermore, if the bulk density of the inorganic fiber exceeds the above range, the amount of fiber in the inorganic fiber mat increases, the weight of the inorganic fiber mat itself increases, and the sound waves penetrating into the inorganic fiber mat are prevented from traveling, resulting in reduced sound absorbing performance. In the present invention, the bulk density of the inorganic fiber mat means a value calculated by dividing the weight of the inorganic fiber mat to be a measurement sample by the volume of the inorganic fiber mat measured with a micrometer or the like.

[0035] In the inorganic fiber mat, the higher the bulk density, the smaller the gap between the fibers, and therefore the smaller the fiber diameter, the more the air between the fibers is divided, and it is considered that the energy of the sound waves can be absorbed efficiently. However, if the gap between the fibers becomes too small, the sound waves do not pass through the inorganic fiber mat, and the sound waves do not progress into the inorganic fiber mat. In addition, the sound waves are reflected on the surface of the inorganic fiber mat, and the energy of the sound waves is not absorbed, and the sound absorption performance decreases. On the other hand, the sound insulation performance increases as the mass of the inorganic fiber mat increases. And, since the effect of reducing transmitted sound is the combined effect of the sound absorption performance and the sound insulation performance, there is a trade-off between the sound absorption performance and the sound insulation performance when adjusting the amount of inorganic fibers forming the inorganic fiber mat. Therefore, there is a problem in achieving both the sound absorption performance and the sound insulation performance by adjusting the amount of inorganic fibers forming the inorganic fiber mat. Under such circumstances, the inorganic fibers adjusted to a predetermined fiber diameter by the melting method according to the sound absorption structure of the present invention, preferably 3.0 μm or more, more preferably 4.0 μm, are used to produce a sound absorbing structure having a predetermined bulk density range, preferably 40.0 to 80.0 kg / m 3 By forming an inorganic fiber mat having a bulk density of 100%, a good balance between sound absorption performance and sound insulation performance is achieved, thereby enhancing the sound insulation effect of reducing transmitted sound.

[0036] The thickness of the inorganic fiber mat is preferably 1.0 to 30.0 mm, and more preferably 5.0 to 20.0 mm.

[0037] The surrounding material in the sound absorbing structure of the present invention is a material that surrounds the inorganic fiber mat. The surrounding material is formed of a nonwoven fabric of organic fibers. In the sound absorbing structure of the present invention, the surrounding material can improve the sound absorbing performance at low frequencies by adjusting the flow resistance value, and can prevent the emission of unfiberized fine particles called shots from the inorganic fiber mat made of an aggregate of inorganic fibers.

[0038] The flow resistance of the enclosure material is 50N·s / m 3 ~3000N·s / m 3 , preferably 100 to 2500 N·s / m 3 , more preferably 140 to 2000 N·s / m 3 , more preferably 159 to 1408 N·s / m 3 In the sound absorbing structure of the present invention, the flow resistance value of the surrounding material is an index of the size and amount of inter-fiber gaps formed in the surrounding material. When the flow resistance value of the surrounding material is within the above range, the low frequency sound absorbing performance is improved and the release of non-fiberized fine particles called shots from the inorganic fiber mat made of an aggregate of inorganic fibers can be prevented. On the other hand, if the flow resistance value of the surrounding material is less than the above range, fine powder is released from the inorganic fiber mat, and if it exceeds the above range, the propagation of sound waves into the inorganic fiber mat is hindered, resulting in a decrease in the low frequency sound absorbing performance. The flow resistance value of the surrounding material can be adjusted by selecting the average fiber diameter of the organic fibers forming the surrounding material, the basis weight of the surrounding material, and the thickness of the surrounding material. In the present invention, the flow resistance value is a value measured using a flow resistance measuring system AirReSys (manufactured by Nihon Onkyo Engineering Co., Ltd.). The relationship between flow resistance and basis weight and fiber diameter is described, for example, in "Development of agricultural insect-proof knitted fabric with fine mesh, Karaki Yusuke and Horie Satoru, Tokyo Metropolitan Industrial Technology Research Center Research Report, No. 8, pp. 144-145, 2013."

[0039] The material of the organic fiber forming the envelope material is not particularly limited, but examples thereof include thermoplastic resins such as polypropylene, polyethylene terephthalate, polyethylene, nylon, acrylic, polyamide, and aramid, cotton, hemp, and silk.

[0040] The average fiber diameter of the organic fibers forming the packaging material is preferably 0.50 to 30.0 μm, more preferably 1.0 to 20.0 μm, and more preferably 2.0 to 10.0 μm. By having the average fiber diameter of the organic fibers in the above range, the flow resistance value of the enveloping material can be reduced to 50 N·s / m 3 ~3000N·s / m 3 , preferably 100 to 2500 N·s / m 3 , more preferably 140 to 2000 N·s / m 3 , more preferably 159 to 1408 N·s / m 3 Since it becomes easier to adjust the thickness of the inorganic fiber mat to 100 mm, the sound absorbing performance at low frequencies is improved and the effect of preventing the release of fine powder from the inorganic fiber mat is enhanced. In the present invention, the average fiber diameter of the organic fibers means the arithmetic mean value of the fiber diameters of 100 arbitrary organic fibers forming the enclosure material.

[0041] When the encapsulating material contains a binder, the content of the binder in the encapsulating material is preferably 50.0 parts by mass or less, more preferably 1.0 to 25.0 parts by mass, per 100.0 parts by mass of the organic fiber. When the content of the binder in the encapsulating material is within the above range, the propagation of the sound waves to the inorganic fiber mat is not hindered, and the falling off of fine powder such as shot can be prevented.

[0042] The weight of the envelope material is preferably 10.0 to 400.0 g / m 2 , more preferably 10.0 to 80.0 g / m 2 , more preferably 40.0 to 80.0 g / m 2 When the mass per unit area of ​​the surrounding material is within the above range, the propagation of sound waves to the inorganic fiber mat is not impeded, and the fine powder can be prevented from falling off.

[0043] The thickness of the envelope material is preferably 0.020 to 3.0 mm, and more preferably 0.10 to 1.0 mm.

[0044] In the sound absorbing structure of the present invention, the enveloping material is disposed so as to surround the periphery of the inorganic fiber mat. Fig. 1 shows an end view of an example of the sound absorbing structure of the present invention. In Fig. 1, the sound absorbing structure 1 comprises an inorganic fiber mat 2, an enveloping material 3a disposed on one side of the inorganic fiber mat 2, and an enveloping material 3b disposed on the other side of the inorganic fiber mat 2. An end 4a of the enveloping material 3a and an end 4b of the enveloping material 3b are bonded by fusion or the like. In the sound absorbing structure 1, the entire periphery of the inorganic fiber mat 2 is surrounded by the enveloping material 3 (3a, 3b), so that the fine powder is prevented from being released to the outside from the inorganic fiber mat 2.

[0045] The sound-absorbing structure of the present invention has excellent sound-absorbing performance because the sound-absorbing mat can be formed from fine fibers having an average fiber diameter of 30.0 μm or less, preferably 20.0 μm or less, and more preferably 10.0 μm or less, by using inorganic fibers produced by a melting method as the material for forming the sound-absorbing mat.

[0046] Inorganic fiber mats, which are made of an aggregate of inorganic fibers produced by the melting method, have the problem of releasing fine powder. Therefore, in the sound-absorbing structure of the present invention, the inorganic fiber mat is surrounded by an enveloping material, thereby preventing the release of fine powder from the inorganic fiber mat to the outside. In this case, if the gaps between the organic fibers that form the enveloping material are too small, the progression of sound waves to the inorganic fiber mat will be hindered, resulting in reduced sound absorption performance, while on the other hand, if the gaps between the organic fibers that form the enveloping material are too large, fine powder will be released from the gaps between the fibers. Therefore, in the sound-absorbing structure of the present invention, the flow resistance value of the enveloping material is set to 50 N·s / m 3 ~3000N·s / m 3 , preferably 100 to 2500 N·s / m 3 , more preferably 140 to 2000 N·s / m 3 , more preferably 159 to 1408 N·s / m 3 This improves the sound absorbing performance and prevents the fine powder from being released to the outside from the inorganic fiber mat.

[0047] Since organic fibers are completely oxidized and decomposed at high temperatures of about 1500 to 1600°C and disappear, the sound absorbing structure of the present invention, which is made of an inorganic fiber mat formed of inorganic fibers and an enveloping material formed of organic fibers, can be recycled by heating it at about 1500 to 1600°C without separating the enveloping material from the inorganic fiber mat, so that the enveloping material made of organic fibers disappears and the inorganic fibers forming the inorganic fiber mat can be melted. Therefore, the sound absorbing structure of the present invention does not need to separate the enveloping material made of organic fibers when recycled, and the composition of the recycled raw material does not change even if the inorganic fiber mat is melted as it is. Therefore, the sound absorbing structure of the present invention has excellent recyclability.

[0048] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples in any way. EXAMPLES

[0049] Examples and Comparative Examples <Inorganic fiber mat> Inorganic fiber mat 1 Rock wool produced by the melting method (average fiber diameter: 4.4 μm, oxide equivalent: SiO2: 40.0 mass%, MgO: 4.0 mass%, Al2O3: 16.0 mass%, CaO: 35.0 mass%, Fe2O3: 1.0 mass%), inorganic fiber mat (Felt N, manufactured by Nichias Corporation), bulk density: 65.0 kg / m 3 , Thickness: 10.4mm, Flow resistance: 175N·s / m 3

[0050] <Enclosure material> Enclosure 1 Organic fiber nonwoven fabric (manufactured by Unicel), organic fiber material: polyethylene terephthalate, basis weight: 40.0 g / m 2 , Thickness: 0.10mm, Flow resistance: 159N·s / m 3 Enclosure 2 Organic fiber nonwoven fabric (manufactured by Unicel), organic fiber material: polyethylene terephthalate, basis weight: 61.0 g / m 2 , Thickness: 0.20mm, Flow resistance: 1155N·s / m 3 Enclosure 3 Organic fiber nonwoven fabric (manufactured by Unicel), organic fiber material: polyethylene terephthalate, basis weight: 70.0 g / m 2 , Thickness: 0.20mm, Flow resistance: 1408N·s / m 3 Enclosure 4 Organic fiber nonwoven fabric (manufactured by Asahi Kasei Corporation), organic fiber material: polyethylene terephthalate, basis weight: 74.0 g / m 2 , Thickness: 0.20mm, Flow resistance: 2179N·s / m 3 Enclosure 5 Organic fiber nonwoven fabric (manufactured by Unicel), organic fiber material: polyethylene terephthalate, basis weight: 23.0g / m 2 , Thickness: 0.10mm, Flow resistance: 28N·s / m 3

[0051] (Method of measuring flow resistance) The flow resistance was measured using a flow resistance measurement system, AirReSys (manufactured by Nihon Onkyo Engineering Co., Ltd.).

[0052] <Sound absorbing structure> Enveloping materials 1 to 4 were placed on both sides of inorganic fiber mat 1, respectively, and the ends were bonded to produce the sound absorbing structures shown in Fig. 1 (Examples 1 to 4). In addition, as Comparative Example 1, a sound absorbing structure was prepared consisting of only inorganic fiber mat 1 without being surrounded by any enveloping material. In addition, an enveloping material 5 was placed on the sound wave incident surface side of inorganic fiber mat 1, and the sound absorbing structure shown in Fig. 1 (Comparative Example 2) was produced. The normal incidence sound absorption coefficient of the obtained sound absorbing structure was then measured. The results are shown in Table 2.

[0053] (Measurement of normal incidence sound absorption coefficient) A Winzac normal incidence sound absorption coefficient measurement system (manufactured by Nihon Onkyo Engineering Co., Ltd.) was used as a measuring device for the normal incidence sound absorption coefficient of a sound absorbing structure, and the sound absorbing structure to be measured was placed in the acoustic tube of the Winzac normal incidence sound absorption coefficient measurement system shown in Figure 2, as shown in Figure 2, and the normal incidence sound absorption coefficient was measured as the frequency was changed from 160 Hz to 4000 Hz. When the frequency was 2500 Hz or higher, a sound absorption coefficient of 0.70 or higher was judged as pass (◯), and a coefficient of less than 0.70 was judged as fail (×).

[0054] Figure 2 is a schematic end view showing the sound tube of the Winzac normal incidence sound absorption coefficient measurement system. In Figure 2, a sound source 12 is installed on the left side of the sound tube 11, and during measurement, a measurement target 13 is placed on the right side of the sound tube 11, and sound waves 14 are emitted from the sound source 12 toward the measurement target 13 to measure the sound absorption coefficient.

[0055] (Shot release prevention) Rock wool felt (Homemat, manufactured by Nichias Corporation) was fired in an electric furnace at 600°C to burn off the binder, and then crushed and sieved through a sieve with a mesh size of 45 μm to obtain shot that remained on the sieve. Next, the surrounding material and shot to be evaluated were placed on a jig 31 shown in FIG. Next, after vibration, the transmittance of the shot particles was calculated using the following formula (1). The lower the transmittance of the shot particles, the higher the shot release prevention performance. The results are shown in Table 3. Shot particle transmittance (%) = (particle weight (g) in the lower part of the jig after vibration / particle weight (g) in the upper part of the jig before vibration) × 100 (1) A shot particle transmittance of 1.0% or less was rated as pass (◯), and a shot particle transmittance of more than 1.0% was rated as fail (×). As shown in Figure 3, jig 31 consists of an upper jig 32 and a lower jig 33. With simulated shot particles 35 placed on surrounding material 36, the outer edge of surrounding material 36 is sandwiched between upper jig 32 and lower jig 33, and upper jig 32 and lower jig 33 are fixed together with fixing tape 34.

[0056] [Table 1]

[0057] [Table 2]

[0058] [Table 3]

[0059] In order to understand the transmission loss when rock wool is used as the inorganic fiber forming the inorganic fiber mat, the following Reference Examples 1 to 3 were carried out.

[0060] (Reference examples 1~3) <Inorganic fiber mat> Inorganic fiber mat 2 Rock wool produced by the melting method (average fiber diameter: 4.7 μm, oxide equivalent: SiO2: 40.0 mass%, MgO: 4.0 mass%, Al2O3: 16.0 mass%, CaO: 35.0 mass%, Fe2O3: 1.0 mass%), inorganic fiber mat (Felt N, manufactured by Nichias Corporation), bulk density: 50.0 kg / m 3 , Thickness: 18.0mm Inorganic fiber mat 3 Rock wool produced by the melting method (average fiber diameter: 4.7 μm, oxide equivalent: SiO2: 40.0 mass%, MgO: 4.0 mass%, Al2O3: 16.0 mass%, CaO: 35.0 mass%, Fe2O3: 1.0 mass%), inorganic fiber mat (Felt N, manufactured by Nichias Corporation), bulk density: 107.0 kg / m 3 , Thickness: 18.0mm Inorganic fiber mat 4 Rock wool produced by the melting method (average fiber diameter: 4.7 μm, oxide equivalent: SiO2: 40.0 mass%, MgO: 4.0 mass%, Al2O3: 16.0 mass%, CaO: 35.0 mass%, Fe2O3: 1.0 mass%), inorganic fiber mat (Felt N, manufactured by Nichias Corporation), bulk density: 126.0 kg / m 3, Thickness: 18.0mm

[0061] <Sound absorbing structure> A polyethylene terephthalate envelope material was placed on both sides of each of the inorganic fiber mats 2 to 4, and the ends were bonded to prepare the sound absorbing structure shown in FIG. The normal incidence sound transmission loss of the resulting sound absorbing structure was then measured, and the results are shown in Table 4.

[0062] (Measurement of normal incidence transmission loss) A Winzac normal incidence sound absorption coefficient measurement system (manufactured by Nihon Acoustic Engineering Co., Ltd.) was used as a measurement device for the normal incidence sound transmission loss of a sound absorbing structure. The sound absorbing structure to be measured was placed in the acoustic tube of the Winzac normal incidence sound absorption coefficient measurement system shown in Figure 4, as shown in Figure 4, and the normal incidence sound transmission loss (dB) was measured as the frequency was changed from 160 Hz to 4000 Hz.

[0063] Fig. 4 is a schematic end view showing the sound tube of the Winzac normal incidence sound absorption coefficient measurement system. In Fig. 4, a sound source 22 is installed on the left side of the sound tube 21, and during measurement, a measurement target 23 is placed in the sound tube 21 so as to separate a pre-transmission space 25 and a post-transmission space 26. A sound wave 24 is emitted from the sound source 22 toward the measurement target 23, and the intensity I of the incident sound on the measurement target 23 is measured. i and the intensity of the transmitted sound I transmitted through the measurement object 23 t The transmittance τ was calculated by the formula: t / I i ) and the normal incidence transmission loss TL (dB) was calculated using the following formula: Normal incidence transmission loss TL(dB)=10log 10 (1 / τ)

[0064] [Table 4]

[0065] Generally, sound insulation materials follow the mass law, so that the transmission loss depends on the mass of the sound absorbing structure. In Table 4, the transmission loss values ​​for the bulk density at a frequency of 4000 Hz in Reference Example 2 and Reference Example 3 are approximately equal, 0.11 and 0.12, respectively. In contrast, the transmission loss value for the bulk density at a frequency of 4000 Hz in Reference Example 1 is 0.21, which is approximately twice as high as Reference Examples 2 and 3. From this, it can be seen that Reference Example 1 has a higher efficiency in reducing transmitted sound than Reference Examples 2 and 3. Therefore, it is presumed that Reference Example 1 has a higher effect of reducing transmitted sound by sound absorption than Reference Examples 2 and 3.

Claims

1. an inorganic fiber mat formed of an aggregate of inorganic fibers; and an enclosure material made of a nonwoven fabric of organic fibers and surrounding the inorganic fiber mat, The inorganic fibers are inorganic fibers containing non-fibered fine particles, the average fiber diameter of the inorganic fibers is 30.0 μm or less, and the bulk density of the inorganic fiber mat is 10.0 to 200.0 kg / m ３ and the flow resistance of the surrounding material is 50 N·s / m ３ ~3000N・s / m ３ A sound absorbing structure characterized by:

2. 2. The sound absorbing structure according to claim 1, wherein the inorganic fiber is rock wool, ceramic fiber or glass fiber.

3. The wrapping material has a basis weight of 10.0 to 80.0 g / m ２ 3. The sound absorbing structure according to claim 1, wherein

4. 3. The sound absorbing structure according to claim 1, wherein the inorganic fiber mat has a thickness of 1.0 to 30.0 mm.

5. 3. The sound absorbing structure according to claim 1, wherein the surrounding material has a thickness of 0.020 to 3.0 mm.

6. 3. The sound absorbing structure according to claim 1, wherein the inorganic fibers have an average fiber diameter of 3.0 μm or more.

7. The bulk density of the inorganic fiber mat is 40.0 to 80.0 kg / m ３ 3. The sound absorbing structure according to claim 1, wherein

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