Nonwoven for sound-absorbing material, and sound-absorbing material

Abstract

In order to provide a nonwoven for a sound-absorbing material having high sound absorption performance throughout a wide range of frequencies from low frequencies to ultra-high frequencies, this nonwoven for a sound-absorbing material is obtained by stacking nonwoven A and nonwoven B, wherein: the nonwoven A and the nonwoven B are stacked alternatingly in eight or more layers independently; the nonwoven A contains fibers A that have an average single fiber diameter of 0.1-5.0 μm, a single peak appears in a 0.1-5.0 μm histogram distribution range for the single fiber diameter, and a nucleating agent constitutes 0.005-1.000 mass%; the nonwoven A has a basis weight of 10-60 g / m2 and an apparent density of 0.100-0.200 g / cm3; the nonwoven B contains fibers B having an average single fiber diameter of 7.0-30.0 μm and has a basis weight of 10-50 g / m2; and the nonwoven for a sound-absorbing material has a basis weight of 150-650 g / m2.

Description

Nonwoven fabrics for sound absorption and sound absorbing materials

[0001] The present invention relates to a nonwoven fabric for sound absorbing material and a sound absorbing material.

[0002] A variety of sound-absorbing materials have been used in vehicles such as automobiles, buildings, home appliances, etc. In recent years, with the spread of electric vehicles, there has been a demand for sound-absorbing materials that achieve even higher levels of quietness in order to make the interior of electric vehicles more comfortable as mobile living spaces than conventional engine-powered vehicles.

[0003] Materials used for such sound-absorbing materials include nonwoven fabrics, foamed resins, films, etc. Nonwoven fabrics, in particular, have a microporous structure inside, and are lightweight yet offer high sound-absorbing performance, making them widely used as sound-absorbing materials for vehicle interiors.

[0004] Various nonwoven fabrics have been proposed for use as sound-absorbing materials for vehicle interiors. For example, Patent Document 1 discloses a fiber board composed of a laminate including a nonwoven material made of polyester fibers, a nonwoven material made of polyolefin fibers, a nonwoven material made of core-sheath composite fibers A having a core component made of a polyester polymer and a sheath component made of a polyolefin polymer, and a nonwoven material made of polyester fibers. Patent Document 2 discloses a fiber laminate structure in which nonwoven fabrics and films or foamed resin sheets having through holes are alternately laminated. Furthermore, in order to achieve sound absorption performance from low to high frequencies, Patent Document 3, for example, discloses a sound-absorbing material in which ultrafine fiber nonwoven fabrics and nonwoven fabrics made of thick fibers are alternately laminated and integrated.

[0005] JP 2022-30954 A JP 2021-172038 A JP 2005-266445 A

[0006] Unlike conventional engine vehicles, electric vehicles require sound absorption performance over a wide frequency range, not only for low frequencies of 1000 Hz to 3000 Hz generated by conventional road noise, but also for sounds up to the ultra-high frequencies of 10,000 Hz caused by inverters, electronic sounds, etc. Conventionally, sound-absorbing materials that can absorb sounds from low to high frequencies of 1000 to 5000 Hz have been known, but sound absorption performance up to ultra-high frequencies such as 10,000 Hz has not been studied.

[0007] For example, the laminated nonwoven fabric for sound absorption in Patent Document 1 has a dense structure, and therefore has poor sound absorption performance at low frequencies such as 1000 Hz. Furthermore, no consideration has been given to sound absorption performance at ultra-high frequencies such as 10000 Hz.

[0008] In addition, in Patent Document 2, by providing through holes in a dense structure, sound absorption performance for low frequency sounds is imparted, but on the other hand, there is no microporous structure formed inside the sound-absorbing material, so there is a problem that sound absorption performance for high frequency sounds is low. Furthermore, no consideration has been given to ultra-high frequencies such as 10,000 Hz.

[0009] Furthermore, in Patent Document 3, the melt-blown nonwoven fabric, which is considered to be a preferred embodiment of the ultrafine fiber nonwoven fabric, has a high density structure, which has the problem of low sound absorption performance for low frequency sounds. Furthermore, as in other documents, no consideration is given to ultra-high frequencies such as 10,000 Hz.

[0010] In view of the above background, an object of the present invention is to provide a nonwoven fabric for sound-absorbing materials and a sound-absorbing material that have excellent sound-absorbing properties for sounds over a wide frequency range from low frequencies to ultra-high frequencies.

[0011] In order to solve the above problems, the present invention has the following configuration: (1) A nonwoven fabric for sound absorption, which is formed by laminating nonwoven fabric A and nonwoven fabric B, wherein the nonwoven fabric A and the nonwoven fabric B are laminated independently and alternately in eight or more layers, the nonwoven fabric A contains fibers A having an average single fiber diameter of 0.1 to 5.0 μm, a single fiber diameter histogram distribution range of 0.1 to 5.0 μm, and a crystal nucleating agent content of 0.005 to 1.000 mass %, and the basis weight is 10 to 60 g / m ２, apparent density is 0.100 to 0.200 g / cm ３ The nonwoven fabric B contains fibers B having an average single fiber diameter of 7.0 to 30.0 μm and a basis weight of 10 to 50 g / m ２ and the basis weight of the nonwoven fabric for sound absorption material is 150 to 650 g / m ２ (2) A nonwoven fabric for sound absorption according to (1) above, in which the single fiber diameter of the fiber A is 0.1 to 10.0 μm. (3) A nonwoven fabric for sound absorption according to (1) or (2) above, in which the nonwoven fabric A is a long-fiber nonwoven fabric. (4) A nonwoven fabric for sound absorption according to any of (1) to (3) above, in which the fiber length of the fiber B is 25 to 100 mm. (5) A nonwoven fabric for sound absorption according to any of (1) to (4) above, in which the fiber A is made of a thermoplastic resin. (6) A nonwoven fabric for sound absorption according to any of (1) to (5) above, in which the fiber B is made of a thermoplastic resin. (7) The nonwoven fabric for sound absorption according to any one of (1) to (6) above, wherein the ratio (X / Y) of the normal incidence sound absorption coefficient (%) X at 1000 Hz to the normal incidence sound absorption coefficient (%) Y at a frequency of 10,000 Hz, as measured by the normal incidence sound absorption measurement method (in-pipe method) of JIS A 1405 (1998), is 0.69 or more. (8) A sound-absorbing material comprising the nonwoven fabric for sound absorption according to any one of (1) to (7) above.

[0012] According to the present invention, it is possible to obtain a nonwoven fabric for sound-absorbing material and a sound-absorbing material that have excellent sound-absorbing performance for sounds over a wide frequency range from low frequencies to ultra-high frequencies.

[0013] FIG. 1 is a schematic cross-sectional view of a nonwoven fabric for sound absorption according to one embodiment of the present invention.

[0014] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0015] The nonwoven fabric for sound absorption of the present invention is a nonwoven fabric for sound absorption formed by laminating nonwoven fabric A and nonwoven fabric B, with nonwoven fabric A and nonwoven fabric B being laminated independently and alternately. By laminating the nonwoven fabrics alternately, the surface of each layer of nonwoven fabric has an appropriate porous structure, which makes it possible to suppress a decrease in sound absorption performance due to sound reflection.

[0016] The nonwoven fabric for sound absorption of the present invention is formed by laminating nonwoven fabric A and nonwoven fabric B alternately in a total of eight or more layers. Referring to FIG. 1 , the nonwoven fabric for sound absorption (1) in FIG. 1 is formed by laminating nonwoven fabric A (11) and nonwoven fabric B (12) alternately, and is a nonwoven fabric having a total of 16 layers, including eight layers each of nonwoven fabric A (11) and nonwoven fabric B (12). Furthermore, in the nonwoven fabric for sound absorption of the present invention, the nonwoven fabrics A may be the same or different. For example, 11a to 11h in FIG. 1 may be the same. Similarly, the nonwoven fabrics B may be the same or different. For example, 12a to 12h in FIG. 1 may be the same. From the viewpoints of cost and ease of production, it is preferable that they are the same. By laminating eight or more layers of nonwoven fabric A and nonwoven fabric B alternately, a nonwoven fabric having a laminate structure of eight or more layers of repeated porous and microporous structures in the thickness direction of the nonwoven fabric is obtained. This allows for high sound absorption performance for a wide range of sounds from low frequencies to ultra-high frequencies. If the number of layers is less than 8, the sound absorption performance for low frequencies to ultra-high frequencies decreases, and when used as a sound-absorbing material for automobile interiors, for example, the sound absorption performance required to ensure quietness inside the vehicle is insufficient. Furthermore, sound absorption performance also decreases when nonwoven fabric A and nonwoven fabric B are not alternately laminated. It is sufficient that at least 8 layers are alternately laminated, and the laminate may further include a layer in which nonwoven fabric A and nonwoven fabric B are not alternately laminated. There is no particular upper limit, and the greater the number of layers, the greater the effect tends to be. However, the effect tends to saturate and handling also decreases, so 20 layers or less is preferred, and 15 layers or less is more preferred.

[0017] The nonwoven fabric for sound absorption of the present invention has nonwoven fabric A and nonwoven fabric B laminated independently. By maintaining nonwoven fabric A and nonwoven fabric B in an independent state, voids are created at the interface between each layer, resulting in a structure that does not impair the sound absorption performance of each layer. If nonwoven fabric A and nonwoven fabric B are integrated by fiber entanglement such as needle punching or hydroentanglement, or by heat fusion or adhesion, the interface between each layer of nonwoven fabric A and nonwoven fabric B becomes dense, causing sound reflection and reducing the sound absorption performance of each layer. As long as the above-mentioned eight or more layers are laminated independently and alternately, nonwoven fabrics that are not laminated independently or alternately may be included. In the present invention, the independent state can be confirmed by the following method. (i) Ten measurement samples measuring 1 cm x 1 cm in length x width are taken from any position on the nonwoven fabric for sound absorption. (ii) Using a scanning electron microscope (SEM, for example, "VHX-D500" manufactured by Keyence Corporation), the cross section of the measurement sample is observed at a magnification of approximately 50x. (iii) The cross section of the measurement sample observed at approximately 50x magnification confirms that dense nonwoven fabrics and bulky nonwoven fabrics are alternately laminated. (iv) The image of (iii) above is enlarged to a magnification of 300x to observe the interface between the dense layer and the bulky layer. If it can be observed that the fibers constituting one layer of nonwoven fabric do not penetrate the other layer of nonwoven fabric and are not physically entangled, and that the nonwoven fabric layers are not bonded together by heat fusion or adhesive, it is determined that the layers are independent.

[0018] For example, if nonwoven fabric A and nonwoven fabric B can be easily peeled apart by hand, they are presumed to be in an independent state. In other words, an independent state refers to a state in which nonwoven fabrics A and B are alternately stacked and the layers can be easily peeled apart by hand without using a method to bond each layer together, such as a physical method such as needle punching or hydroentanglement, a thermal bonding method in which the low-melting point components of the fibers are softened by hot air or a heated roll to bond the fibers together, or a chemical bonding method in which a resin is used as a binder to bond the fibers together. Therefore, if a product is manufactured without using any of the above bonding methods and the layers can be easily peeled apart by hand and separated, it can be confirmed that the product is in an independent state.

[0019] As described above, in order to achieve the effects of the present invention, the nonwoven fabric for sound absorption material must simultaneously satisfy the following requirements: nonwoven fabric A and nonwoven fabric B are at least alternately laminated, eight or more layers are laminated, and the layers are independently laminated.

[0020] The nonwoven fabric for sound absorption of the present invention has a basis weight of 150 to 650 g / m ２ The basis weight is 150 g / m ２ or more, preferably 155 g / m ２ More preferably, 160 g / m ２ If the weight is 650 g / m or more, the amount of fiber filled is large when used as a sound absorbing material, and excellent sound absorbing performance can be obtained. ２ Preferably 640 g / m or less ２ or less, more preferably 630 g / m ２ If the thickness is below this, it is excellent in terms of workability into part shapes and light weight.

[0021] In the present invention, the average single fiber diameter of fibers A contained in nonwoven fabric A is 0.1 to 5.0 μm. By setting the average single fiber diameter to 0.1 μm or more, preferably 0.3 μm or more, and more preferably 0.5 μm or more, it is possible to prevent the nonwoven fabric from becoming too dense and to prevent a decrease in sound absorption performance due to reflection of low-frequency sound. By setting the average single fiber diameter to 5.0 μm or less, preferably 4.8 μm or less, and more preferably 4.5 μm or less, a dense microporous structure is formed inside the nonwoven fabric, resulting in a nonwoven fabric with high sound absorption performance for ultra-high frequency sounds.

[0022] In the present invention, the average single fiber diameter (μm) of a nonwoven fabric is determined by the following method. (i) Ten small sample pieces are randomly collected from the nonwoven fabric. (ii) The surfaces of the collected small sample pieces are photographed using a scanning electron microscope or the like at a magnification of 500 to 10,000 times, allowing the fiber thickness to be measured. (iii) Twenty fibers are randomly selected from each sample, for a total of 200 fibers, and their thicknesses are measured. The fibers are assumed to have circular cross sections with the same cross-sectional area, and this is taken as the single fiber diameter. (iv) The arithmetic mean value of these values ​​is rounded to one decimal place to calculate the average single fiber diameter.

[0023] The fibers constituting the nonwoven fabric A used in the nonwoven fabric for sound absorption of the present invention have one peak between 0.1 and 5.0 μm in the histogram distribution range of the single fiber diameter. By having one peak between 0.1 and 5.0 μm, it is possible to suppress variations in sound absorption performance due to variations in the pore size on the surface of the nonwoven fabric A, etc.

[0024] In the present invention, the histogram of single fiber diameters is prepared based on the data of the diameters (μm) of a total of 200 single fibers measured to calculate the average single fiber diameter described above. The x-axis of the histogram represents the single fiber diameter (μm), and the y-axis represents the percentage frequency. The x-axis ranges from 0.0 μm to 20.0 μm, plotted on a 0.1 μm scale. The number of peaks in the histogram distribution range of single fiber diameters was determined from the plotted data of the prepared histogram.

[0025] The single fiber diameter of fiber A is preferably in the range of 0.1 to 10.0 μm. This range is determined by the same measurement method as for the histogram described above. When the distribution of the single fiber diameter histogram of the fibers is in the range of 0.1 to 10.0 μm, it is possible to further suppress variations in sound absorption performance due to variations in pore size on the surface of nonwoven fabric A.

[0026] From the viewpoint of cost and moldability, fiber A is preferably made of a thermoplastic resin. Examples of thermoplastic resins include polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polylactic acid, polycarbonate resins, polystyrene resins, polyphenylene sulfide resins, fluorine-containing resins, elastomers such as polystyrene elastomers, polyolefin elastomers, polyester elastomers, polyamide elastomers, and polyurethane elastomers, and thermoplastic resins made of copolymers or mixtures thereof. Among these, polypropylene resins and copolymers or mixtures thereof are preferred from the viewpoint of low cost and easy availability, and polypropylene resin homopolymers are more preferred.

[0027] Furthermore, fiber A contains 0.005 to 1.000 mass% of a nucleating agent per 100.000 mass% of fiber A. By incorporating 0.005 mass% or more, preferably 0.006 mass% or more, and more preferably 0.007 mass% or more of a nucleating agent into the fiber, the crystallization temperature of the fiber increases, accelerating the solidification rate of the fiber during spinning, and thereby lowering the apparent density of nonwoven fabric A and weakening the fusion between fibers. This creates a microporous structure within the nonwoven fabric, suppressing the decline in sound absorption performance due to reflection of low-frequency sounds and improving sound absorption performance for ultra-high frequencies. Conversely, if the content of the nucleating agent is less than 0.005 mass%, the apparent density of nonwoven fabric A increases, resulting in increased reflection of low-frequency sounds and a lower sound absorption coefficient. By including a nucleating agent in the fibers in an amount of 1.000% by mass or less, preferably 0.750% by mass or less, and more preferably 0.500% by mass or less, it is possible to suppress the occurrence of shot when spinning the fibers, a decrease in sound absorption performance due to a deterioration in the formation of the nonwoven fabric caused by variations in the average single fiber diameter, etc. Conversely, if the content of the nucleating agent exceeds 1.000% by mass, spinnability deteriorates and the variation in the basis weight of the nonwoven fabric increases, which in turn increases the variation in the sound absorption performance of the nonwoven fabric as a sound-absorbing material.

[0028] The content of the nucleating agent in fiber A, whose content is unknown, can be determined as follows. Fiber A is completely dissolved in a solvent that can dissolve fiber A (for example, in the case of fibers made of an olefin resin such as polypropylene or polyethylene, the fibers are dissolved in a methanol / toluene mixed solution at 110°C for 16 hours). After Soxhlet extraction, the extract is repeatedly fractionated by HPLC, and the structure of each fraction is confirmed by IR measurement, GC measurement, GC / MS measurement, MALDI-MS measurement, 1H-NMR measurement, and 13C-NMR measurement. Next, the masses of the fractions containing the nucleating agent are added together to determine the mass % of the nucleating agent contained in fiber A.

[0029] The crystal nucleating agent is preferably at least one selected from the group consisting of sorbitol-based nucleating agents, nonitol-based nucleating agents, xylitol-based nucleating agents, phosphoric acid-based nucleating agents, triaminobenzene derivative nucleating agents, and metal carboxylate nucleating agents. Two or more of these may be used in combination.

[0030] Examples of sorbitol-based nucleating agents include dibenzylidene sorbitol (DBS), monomethyldibenzylidene sorbitol (e.g., 1,3:2,4-bis(p-methylbenzylidene)sorbitol (p-MDBS)), dimethyldibenzylidene sorbitol (e.g., 1,3:2,4-bis(3,4-dimethylbenzylidene)sorbitol (3,4-DMDBS)), and the like, as well as "Millad" (registered trademark) 3988 (manufactured by Milliken Japan Co., Ltd.) and "Gelall" (registered trademark) E-200 (manufactured by New Japan Chemical Co., Ltd.).

[0031] Examples of nonitol-based nucleating agents include 1,2,3-trideoxy-4,6:5,7-bis-[(4-propylphenyl)methylene]-nonitol, and examples thereof include "Millad" (registered trademark) NX8000 (manufactured by Milliken Japan Co., Ltd.).

[0032] Examples of xylitol-based nucleating agents include bis-1,3:2,4-(5',6',7',8'-tetrahydro-2-naphthaldehyde benzylidene) 1-allyl xylitol.

[0033] Examples of phosphoric acid-based nucleating agents include aluminum-bis(4,4',6,6'-tetra-tert-butyl-2,2'-methylenediphenyl-phosphate)-hydroxide, and examples thereof include "ADK STAB" (registered trademark) NA-11 (manufactured by ADEKA CORPORATION) and "ADK STAB" (registered trademark) NA-21 (manufactured by ADEKA CORPORATION).

[0034] Examples of triaminobenzene derivative nucleating agents include 1,3,5-tris(2,2-dimethylpropanamido)benzene, and examples thereof include "Irgaclear" (registered trademark) XT386 (manufactured by BASF Japan Ltd.).

[0035] Further, metal carboxylate nucleating agents include, for example, sodium benzoate and calcium salt of 1,2-cyclohexanedicarboxylate.

[0036] In addition to the above crystal nucleating agent, additives such as a heat stabilizer, a weathering agent, and a polymerization inhibitor may be added to the fiber A.

[0037] The above-mentioned fiber A is preferably contained in an amount of 50% by mass or more, more preferably 80% by mass or more, and even more preferably 95% by mass or more in nonwoven fabric A. The upper limit is preferably 100% by mass, since the interior of the nonwoven fabric has a microporous structure and high sound absorption performance for ultra-high frequency sounds can be obtained.

[0038] In a preferred embodiment, the nonwoven fabric A in the present invention is a long-fiber nonwoven fabric. The method for obtaining the long-fiber nonwoven fabric is not particularly limited, and it can be obtained from fibers obtained by spunbond spinning or meltblown spinning, fibers obtained by ordinary melt spinning, splittable conjugate fibers, islands-in-the-sea conjugate fibers, etc. Ultrafine fibers obtained by spunbond spinning, meltblown spinning, etc. may be accumulated on a support and used as a nonwoven fabric, or they may be directly deposited on nonwoven fabric B. Meltblown spinning, in particular, is a manufacturing method that has the advantage that it does not require complicated steps compared to other nonwoven fabric manufacturing methods such as the spunbond method, and that the single fiber diameter of the fiber A in the present invention can be easily obtained.

[0039] The weight per layer of the nonwoven fabric A used in the nonwoven fabric for sound absorption of the present invention is 10 to 60 g / m ２ The basis weight of nonwoven fabric A is 10 g / m ２ or more, preferably 13 g / m ２ More preferably, 15 g / m ２ By adjusting the nonwoven fabric A to the above value, a microporous structure can be formed in the nonwoven fabric, and high sound absorption performance can be imparted to super-high frequency sounds. ２ Preferably 55 g / m or less ２ or less, more preferably 50 g / m ２ By setting the thickness to the following value, it is possible to prevent the surface of the nonwoven fabric from becoming dense, and to prevent a decrease in sound absorption performance due to reflection of low-frequency sounds.

[0040] The basis weight here refers to the basis weight of one layer of nonwoven fabric A, and is measured in accordance with the mass per unit area (ISO method) of JIS L 1913 (2010). The sample is left to stand under standard conditions of a temperature of 20±2°C and a relative humidity of 65±4%, and when it reaches a constant weight, it is measured at a thickness of 10,000 mm ２ Three samples were taken so that the area was equal to or greater than 100 mm, and the mass of each was measured. The average value (g) of the obtained values ​​was calculated as the unit area (1 m ２ ) and round off to the first decimal place.

[0041] The apparent density of nonwoven fabric A is 0.100 to 0.200 g / cm ３ The apparent density of nonwoven fabric A is 0.100 g / cm ３ or more, preferably 0.105 g / cm ３ More preferably, 0.110 g / cm ３ When the apparent density of nonwoven fabric A is 0.200 g / cm or more, the surface of the nonwoven fabric has a porous structure, and sound reflection can be suppressed. ３ or less, preferably 0.195 g / cm ３ More preferably, 0.190 g / cm or less ３ If the thickness is below this, the inside of the nonwoven fabric will have a microporous structure, and high sound absorption performance for ultra-high frequency sounds can be obtained.

[0042] The method for obtaining the above apparent density is not particularly limited, and examples thereof include a method of increasing the single fiber diameter per fiber A constituting the nonwoven fabric A, a method of increasing the solidification rate of the fiber A during spinning by lowering the melting temperature of the thermoplastic resin in obtaining the fiber A, and a method using the above-mentioned crystal nucleating agent. In the present invention, the above-mentioned method using the crystal nucleating agent is preferred because it can achieve both a microporous structure on the surface of the nonwoven fabric and inside the nonwoven fabric. In the present invention, the apparent density (g / cm) of the nonwoven fabric is ３) shall be a value calculated by the following method. (i) The thickness of the nonwoven fabric shall be measured at 10 equally spaced points in the CD direction using a thickness meter (for example, "TECLOCK" (registered trademark) SM-114 manufactured by Teclock Corporation) in accordance with Method A of the thickness (ISO method) of JIS L 1913 (2010). (ii) The arithmetic mean value shall be rounded to two decimal places to obtain the thickness (mm) of the nonwoven fabric. (iii) The basis weight (g / m2) of the nonwoven fabric shall be calculated by the following method. ２ The apparent density (g / cm) is calculated by the following formula using the thickness (mm) of the nonwoven fabric and the apparent density (g / cm) is rounded to the fourth decimal place. ３ ) = basis weight (g / m ２ ) / thickness (mm) / 1000 Here, in the present invention, the CD direction refers to the sheet conveyance direction during the production of the nonwoven fabric for sound absorption, i.e., the direction perpendicular to the winding direction of the nonwoven fabric roll, and the MD direction refers to the sheet conveyance direction during the production of the nonwoven fabric for sound absorption, i.e., the winding direction of the nonwoven fabric roll. When the nonwoven fabric A is not in a rolled state, for example, because it is cut, the MD and CD directions are determined by the following procedure. (i) Within the plane of the nonwoven fabric A, three samples each measuring 25 mm wide and 200 mm long are taken in the directions of 0°, 30°, 60°, and 90° from any direction at 30° intervals up to 90°. (ii) For example, using a tensile tester "RTG-1250" manufactured by Baldwin Co., Ltd., a test is conducted with a chuck distance of 100 mm and a tensile strength of 100 mm / min, and the breaking strength is measured. (iii) Of the obtained breaking strengths in each direction (S0°, S30°, S60°, S90°), the direction with the highest value is defined as the MD direction, and the value in the direction perpendicular to the direction with the highest value is defined as the CD direction.

[0043] The average single fiber diameter of fibers B contained in nonwoven fabric B in the present invention is 7.0 to 30.0 μm. If the average single fiber diameter is 7.0 μm or more, preferably 7.1 μm or more, and more preferably 7.2 μm or more, when nonwoven fabric A and nonwoven fabric B are alternately laminated, sufficient gaps are secured between nonwoven fabric A and nonwoven fabric A via nonwoven fabric B, and a decrease in sound absorption performance due to densification inside the nonwoven fabric can be suppressed. By setting the average single fiber diameter to 30.0 μm or less, preferably 29.5 μm or less, and more preferably 29.0 μm or less, a fine porous structure is formed inside nonwoven fabric B, and high sound absorption performance for low-frequency sounds can be obtained.

[0044] The basis weight of nonwoven fabric B is 10 to 50 g / m ２ The basis weight is 10 g / m ２ or more, preferably 11 g / m ２ More preferably, 12 g / m ２ If the weight is 50 g / m or more, when nonwoven fabric A and nonwoven fabric B are alternately laminated, a sufficient gap is secured between nonwoven fabric A and nonwoven fabric B, and a decrease in sound absorption performance due to densification inside the nonwoven fabric can be suppressed. ２ Preferably 49 g / m or less ２ or less, more preferably 48 g / m ２ If the thickness is below this value, when the nonwoven fabric A and the nonwoven fabric B are laminated together to form a nonwoven fabric for sound absorption, the nonwoven fabric A and the nonwoven fabric B can be easily processed, such as by punching.

[0045] In a preferred embodiment, the fibers contained in nonwoven fabric B in the present invention are made of a thermoplastic resin in terms of cost, moldability, etc. Examples of thermoplastic resins include polyolefin resins such as polyethylene and polypropylene; polyester resins such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polylactic acid; polycarbonate resins, polystyrene resins, polyphenylene sulfide resins, fluorine-containing resins; elastomers such as polystyrene elastomers, polyolefin elastomers, polyester elastomers, polyamide elastomers, and polyurethane elastomers; and copolymers or mixtures thereof. Among these, polyethylene terephthalate resins and copolymers or mixtures thereof are preferred, from the viewpoints that the high rigidity of the fibers can impart a high void ratio to nonwoven fabric B and provide high sound absorption performance for low-frequency sounds, and polyethylene terephthalate resin is more preferred in terms of cost.

[0046] In a preferred embodiment, the fiber length of fiber B is 25 to 100 mm. A fiber length of 25 mm or more, preferably 26 mm or more, more preferably 27 mm or more is preferred from the viewpoint of processability in the production of nonwoven fabrics. A fiber length of 100 mm or less, preferably 90 mm or less, more preferably 80 mm or less ensures that the fibers are uniformly dispersed on the surface of the resulting nonwoven fabric, thereby suppressing variations in sound absorption performance.

[0047] The above-mentioned fiber B is contained in nonwoven fabric B in an amount of preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 95% by mass or more. The upper limit is preferably 100% by mass, since this allows nonwoven fabric B to have a high porosity and provides high sound absorption performance for low-frequency sounds.

[0048] The nonwoven fabric B is preferably a nonwoven fabric such as a carded web or an air-laid web made of short fibers. Among the above-mentioned webs, a carded web made of short fibers has a basis weight of 10 g / m. ２ 50g / m or more ２ The following method for producing the nonwoven fabric is preferred.

[0049] The method for alternately laminating the nonwoven fabric A and the nonwoven fabric B in the nonwoven fabric for sound absorption of the present invention is not particularly limited, and any known method can be used. Among these, it is preferable to obtain the nonwoven fabric for sound absorption by placing the nonwoven fabric A on the nonwoven fabric B made from a carded web, and then alternately laminating the nonwoven fabric A and the nonwoven fabric B using a cross layer.

[0050] The nonwoven fabric for sound absorption of the present invention preferably has a ratio (X / Y) of the normal incidence sound absorption coefficient (%) X at 1000 Hz to the normal incidence sound absorption coefficient (%) Y at 10,000 Hz, as measured by the normal incidence sound absorption measurement method (in-pipe method) of JIS A 1405 (1998), of 0.69 or more, more preferably 0.75 or more, and even more preferably 0.80 or more. By having a ratio above this range, the nonwoven fabric exhibits stable sound absorption performance over a wide range of frequencies, and when used as a sound-absorbing material for automobile interiors, it can absorb a wide range of sounds, from low-frequency sounds such as road noise to ultra-high-frequency sounds caused by inverters, electronic noise, etc. The upper limit is not particularly limited, but is usually 1.00 or less.

[0051] As described above, the nonwoven fabric for sound absorption materials of the present invention has excellent sound absorption performance over a wide range of frequencies from low to ultra-high frequencies, and therefore can be suitably used as a sound absorbing material, particularly as a sound absorbing material for automobile interiors. In particular, it can be suitably used as a sound absorbing material for automobile interiors, which require sound absorption performance for both low-frequency sounds in the range of 1,000 to 3,000 Hz, such as automobile running noise, and high-frequency to ultra-high-frequency sounds in the range of 3,000 to 10,000 Hz, such as electronic sounds.

[0052] The sound-absorbing material of the present invention comprises the nonwoven fabric for sound-absorbing materials of the present invention. The sound-absorbing material of the present invention is preferably obtained by compounding the nonwoven fabric for sound-absorbing materials of the present invention with a surface layer such as a spunbond nonwoven fabric. When this sound-absorbing material is used as a sound-absorbing material for automobile interiors, it is cut or punched to the required shape and size for automobile door panels, instrument panels, headliners, etc., and attached to each part.

[0053] The present invention will be described in further detail below with reference to examples, although the present invention is not limited to these examples.

[0054] [Measurement Methods] The property values ​​in the following examples were measured by the following methods. However, unless otherwise specified, the measurements of each physical property were carried out according to the above-mentioned methods.

[0055] (1) Average Single Fiber Diameter (μm) of Nonwoven Fabric The average single fiber diameter of the nonwoven fabric was calculated by the above-mentioned method using a scanning electron microscope "VHX-D500" manufactured by Keyence Corporation.

[0056] (2) Distribution of Single Fiber Diameters of Nonwoven Fabric and Number of Peaks in the Histogram Distribution Range of 0.1 to 5.0 μm Calculation was performed from the single fiber diameter histogram using a scanning electron microscope "VHX-D500" manufactured by Keyence Corporation according to the method described above.

[0057] (3) Weight of nonwoven fabric (g / m ２ The basis weight of the nonwoven fabric was calculated using the method described above.

[0058] (4) Thickness of Nonwoven Fabric (mm) A "TECLOCK" (registered trademark) SM-114 manufactured by Teclock Corporation was used as a thickness gauge.

[0059] (5) Apparent density of nonwoven fabric (g / cm ３ ) "(3) Weight of nonwoven fabric (g / m ２ ) and "(4) Thickness of nonwoven fabric (mm)" using the method described above.

[0060] (6) Normal Incidence Sound Absorption Coefficient (%) of Nonwoven Fabric Measured in accordance with the normal incidence sound absorption measurement method (in-tube method) of JIS A 1405 (1998). Three test pieces were cut out from a sample of nonwoven fabric for sound absorption material using a 92 mm diameter circular punching blade. An automatic normal incidence sound absorption coefficient measuring instrument (Model 10041A) manufactured by Denshi Sokki Co., Ltd. was used as the test equipment. The test piece was attached to one end of the measurement impedance tube, with a spacer installed to create a 20 mm thick air layer between the test piece and the metal reflector. The sound absorption coefficient for each frequency was calculated by multiplying the measured sound absorption coefficient by 100. The average sound absorption coefficient at 1000 Hz was used as the low-frequency sound absorption coefficient (%), the average sound absorption coefficient at 3000 Hz was used as the high-frequency sound absorption coefficient (%), and the average sound absorption coefficient at 10,000 Hz was used as the ultra-high-frequency sound absorption coefficient.

[0061] (7) Ratio (X / Y) of normal incident sound absorption coefficient (%) of nonwoven fabric at 1000 Hz and 10,000 Hz The sound absorption coefficient (%) at 1000 Hz obtained in "(6) Normal incident sound absorption coefficient (%) of nonwoven fabric" was defined as X, and the sound absorption coefficient (%) at 10,000 Hz was defined as Y, and the ratio (X / Y) was calculated.

[0062] (8) Punching Processability of Nonwoven Fabric The punching processability of nonwoven fabric was evaluated in "(6) Normal Incidence Sound Absorption Coefficient (%) of Nonwoven Fabric" by visually inspecting the edges of test pieces cut out from a nonwoven fabric sample for sound absorption with a circular punching blade having a diameter of 92 mm, and evaluating the processability according to the following criteria: A: No part of the test piece was not cut through by the circular punching blade. B: There was a part of the test piece that was not cut through. C: Almost no part of the test piece was cut through.

[0063] [Example 1] (Nonwoven Fabric A) A polypropylene resin having a melt flow rate of 850 g / 10 min was used as the thermoplastic resin raw material, containing 0.150 mass% of a nucleating agent "Irgaclear" (registered trademark) XT386 (manufactured by BASF Japan Ltd.) and 1.000 mass% of a hindered amine compound "Chimasorb" (registered trademark) 944 (manufactured by BASF Japan Ltd.). The polypropylene resin raw material was charged into the raw material hopper of a spinning machine, and sprayed by a melt-blowing method using a die having a 0.4 mm diameter discharge hole (hole pitch: 1.0 mm) under the conditions of a single-hole discharge rate of 0.29 g / min / hole, a nozzle temperature of 250°C, an air temperature of 260°C, and an air pressure of 0.09 MPa. The collection conveyor speed was adjusted to obtain a nonwoven fabric having a basis weight of 20 g / m. ２ , apparent density is 0.160 g / cm ３ As a result, nonwoven fabric A having an average single fiber diameter of 1.8 μm and one single fiber diameter peak (1.9 μm) was obtained.

[0064] (Nonwoven fabric B) Polyethylene terephthalate having an intrinsic viscosity of 0.65 dl / g was used as the thermoplastic resin, and short fibers having an average single fiber diameter of 23.0 μm and a fiber length of 51 mm were formed. The fibers were then opened in a fiber-opening process. The opened fibers were subjected to a carding process to obtain a fiber having a basis weight of 15 g / m. ２ Nonwoven fabric B was obtained.

[0065] (Laminated Nonwoven Fabric) Nonwoven fabric A was laminated on nonwoven fabric B obtained in the carding process, and nonwoven fabric A and nonwoven fabric B were alternately laminated using a cross wrapper to obtain a laminated nonwoven fabric with a total of 14 layers. The total basis weight of the obtained laminated nonwoven fabric was 490 g / m ２ The laminated nonwoven fabrics A and B could be easily peeled apart by hand, confirming that the layers were independent. The resulting laminated nonwoven fabric had a low-frequency sound absorption coefficient of 84%, a high-frequency sound absorption coefficient of 84%, and an ultra-high-frequency sound absorption coefficient of 97%, with a ratio of the low-frequency to the ultra-high-frequency sound absorption coefficient of 0.87. The results are shown in Table 1.

[0066] [Example 2] A laminated nonwoven fabric was obtained in the same manner as in Example 1, except that in the production process of Example 1, the total number of cross wrapper layers of the laminated nonwoven fabric was changed from 14 to 8. The total basis weight of the obtained laminated nonwoven fabric was 280 g / m ２The laminated nonwoven fabrics A and B could be easily peeled apart by hand, confirming that the layers were independent. The resulting laminated nonwoven fabric had a low-frequency sound absorption coefficient of 65%, a high-frequency sound absorption coefficient of 88%, and an ultra-high-frequency sound absorption coefficient of 94%, with a ratio of the low-frequency to ultra-high-frequency sound absorption coefficients of 0.69. The results are shown in Table 1.

[0067] [Example 3] In the production process of Example 1, the amount of the crystal nucleating agent "Irgaclear" (registered trademark) XT386 (manufactured by BASF Japan Ltd.) contained in the thermoplastic resin raw material of nonwoven fabric A was changed from 0.150 mass% to 0.600 mass%, and the apparent density was 0.170 g / cm ３ A laminated nonwoven fabric was obtained in the same manner as in Example 1, except that nonwoven fabric A was obtained having an average single fiber diameter of 1.9 μm, a single fiber diameter distribution range of 1.1 to 8.0 μm, and one peak at 2.1 μm. The total basis weight of the obtained laminated nonwoven fabric was 490 g / m ２ The laminated nonwoven fabrics A and B could be easily peeled apart by hand, confirming that the layers were independent. The resulting laminated nonwoven fabric had a low-frequency sound absorption coefficient of 87%, a high-frequency sound absorption coefficient of 88%, and an ultra-high-frequency sound absorption coefficient of 99%, with a ratio of the low-frequency to the ultra-high-frequency sound absorption coefficient of 0.88. The results are shown in Table 1.

[0068] [Example 4] In the manufacturing process of Example 1, the basis weight of nonwoven fabric A was 20 g / m ２ to 40 g / m ２ A laminated nonwoven fabric was obtained in the same manner as in Example 1, except that the speed of the collecting conveyor was adjusted so that the total number of layers of the cross wrapper in the laminated nonwoven fabric was changed from 14 to 10. The total basis weight of the obtained laminated nonwoven fabric was 650 g / m ２ The laminated nonwoven fabrics A and B could be easily peeled apart by hand, confirming that the layers were independent. The resulting laminated nonwoven fabric had a low-frequency sound absorption coefficient of 66%, a high-frequency sound absorption coefficient of 81%, and an ultra-high-frequency sound absorption coefficient of 94%, with a ratio of the low-frequency to the ultra-high-frequency sound absorption coefficient of 0.70. The results are shown in Table 1.

[0069] Example 5 A laminated nonwoven fabric was obtained in the same manner as in Example 1, except that in the production process of Example 1, the content of the crystal nucleating agent "Irgaclear" (registered trademark) XT386 (manufactured by BASF Japan Ltd.) contained in the thermoplastic resin raw material of nonwoven fabric A was changed from 0.150 mass% to 0.010 mass%, resulting in a nonwoven fabric A having an average single fiber diameter of 1.9 μm, a single fiber diameter distribution range of 0.4 to 7.0, and one peak at 1.9 μm, and that the average single fiber diameter of the staple fibers of nonwoven fabric B was changed from 23 μm to 20 μm. The total basis weight of the obtained laminated nonwoven fabric was 490 g / m ２ The laminated nonwoven fabrics A and B could be easily peeled apart by hand, confirming that the layers were independent. The resulting laminated nonwoven fabric had a low-frequency sound absorption coefficient of 70%, a high-frequency sound absorption coefficient of 80%, and an ultra-high-frequency sound absorption coefficient of 91%, with a ratio of the low-frequency to the ultra-high-frequency sound absorption coefficient of 0.77. The results are shown in Table 1.

[0070]

[0071] The properties of the obtained nonwoven fabrics for sound absorption are as shown in Table 1. The nonwoven fabrics for sound absorption in Examples 1 to 5 all had a low frequency sound absorption coefficient of 65% or more, a medium frequency sound absorption coefficient of 80% or more, a superhigh frequency sound absorption coefficient of 91% or more, and a ratio of the low frequency to the superhigh frequency sound absorption coefficient of 0.69 or more, meaning that they were nonwoven fabrics for sound absorption with excellent sound absorption performance at all frequencies, including low, high, and superhigh frequencies. Furthermore, the punching processability of the nonwoven fabrics was also good, scoring B or higher.

[0072] [Comparative Example 1] In the production process of Example 1, the amount of the crystal nucleating agent "Irgaclear" (registered trademark) XT386 (manufactured by BASF Japan Ltd.) contained in the thermoplastic resin raw material of nonwoven fabric A was changed from 0.150 mass% to 0.000 mass%, and the apparent density was 0.220 g / cm ３ A laminated nonwoven fabric was obtained in the same manner as in Example 1, except that nonwoven fabric A was obtained having an average single fiber diameter of 1.8 μm, a single fiber diameter distribution range of 0.3 to 11.0 μm, and one peak at 1.8 μm. The total basis weight of the obtained laminated nonwoven fabric was 490 g / m ２The laminated nonwoven fabrics A and B could be easily peeled apart by hand, confirming that the layers were independent. The low-frequency sound absorption coefficient of the resulting laminated nonwoven fabric was 63%, the high-frequency sound absorption coefficient was 77%, and the ultra-high-frequency sound absorption coefficient was 92%, with a ratio of the low-frequency to the ultra-high-frequency sound absorption coefficient of 0.68. The results are shown in Table 2.

[0073] [Comparative Example 2] A laminated nonwoven fabric was obtained in the same manner as in Example 1, except that in the production process of Example 1, the total number of cross wrapper layers of the laminated nonwoven fabric was changed from 14 to 6. The total basis weight of the obtained laminated nonwoven fabric was 210 g / m ２ The laminated nonwoven fabrics A and B could be easily peeled apart by hand, confirming that the layers were independent. The resulting laminated nonwoven fabric had a low-frequency sound absorption coefficient of 32%, a high-frequency sound absorption coefficient of 63%, and an ultra-high-frequency sound absorption coefficient of 94%, with a ratio of the low-frequency to ultra-high-frequency sound absorption coefficients of 0.34. The results are shown in Table 2.

[0074] [Comparative Example 3] In the manufacturing process of Example 1, the basis weight of nonwoven fabric A was 20 g / m ２ to 70 g / m ２ A laminated nonwoven fabric was obtained in the same manner as in Example 1, except that the speed of the collecting conveyor was adjusted so that the total basis weight of the obtained laminated nonwoven fabric was 1,190 g / m ２ The laminated nonwoven fabrics A and B could be easily peeled apart by hand, confirming that the layers were independent. The resulting laminated nonwoven fabric had a low-frequency sound absorption coefficient of 40%, a high-frequency sound absorption coefficient of 65%, and an ultra-high-frequency sound absorption coefficient of 89%, with a ratio of the low-frequency to ultra-high-frequency sound absorption coefficients of 0.45. The results are shown in Table 2.

[0075] Comparative Example 4 A laminated nonwoven fabric was obtained in the same manner as in Example 1, except that the layers of the laminated nonwoven fabric obtained by the cross wrapper were entangled by needle punching in the production process of Example 1. The total basis weight of the obtained laminated nonwoven fabric was 490 g / m ２ The laminated nonwoven fabrics A and B could not be easily peeled apart by hand, and needle punching confirmed that the layers were entangled. The resulting laminated nonwoven fabric had a low-frequency sound absorption coefficient of 15%, a high-frequency sound absorption coefficient of 62%, and an ultra-high-frequency sound absorption coefficient of 95%, with a ratio of the low-frequency and ultra-high-frequency sound absorption coefficients of 0.16. The results are shown in Table 2.

[0076] [Comparative Example 5] In the manufacturing process of Example 1, the basis weight of nonwoven fabric A was 20 g / m ２ to 8 g / m ２ The speed of the collection conveyor was adjusted so that the apparent density was 0.190 g / cm ３ The nonwoven fabric A was obtained, and the basis weight of the nonwoven fabric B was 15 g / m ２ to 27 g / m ２ A laminated nonwoven fabric was obtained in the same manner as in Example 1, except that the total basis weight of the obtained laminated nonwoven fabric was 490 g / m ２ The laminated nonwoven fabrics A and B could be easily peeled apart by hand, confirming that the layers were independent. The resulting laminated nonwoven fabric had a low-frequency sound absorption coefficient of 27%, a high-frequency sound absorption coefficient of 88%, and an ultra-high-frequency sound absorption coefficient of 78%, with a ratio of the low-frequency to high-frequency sound absorption coefficients of 0.35. The results are shown in Table 2.

[0077] Comparative Example 6 In the production process of Example 1, a die having discharge holes of 0.4 mm and 0.7 mm diameter (hole pitch: 1.2 mm) was used to obtain nonwoven fabric A, and a nonwoven fabric having an average single fiber diameter of 1.7 μm to 3.7 μm, a single fiber diameter distribution range of 0.3 to 11.7 μm, two peaks of single fiber diameter at 2.4 μm and 8.1 μm, and an apparent density of 0.15 g / cm ３ A laminated nonwoven fabric was obtained in the same manner as in Example 1, except that the total basis weight of the obtained laminated nonwoven fabric was 490 g / m ２ The laminated nonwoven fabrics A and B could be easily peeled apart by hand, confirming that the layers were independent. The resulting laminated nonwoven fabric had a low-frequency sound absorption coefficient of 53%, a high-frequency sound absorption coefficient of 75%, and an ultra-high-frequency sound absorption coefficient of 79%, with a ratio of the low-frequency to high-frequency sound absorption coefficients of 0.67. The results are shown in Table 2.

[0078] Comparative Example 7 A laminated nonwoven fabric was obtained in the same manner as in Example 1, except that in the production process of Example 1, a die having discharge holes with a diameter of 0.7 mm (hole pitch: 1.2 mm) was used as the die for obtaining nonwoven fabric A, and the average single fiber diameter was 1.8 μm to 6.1 μm, the fiber diameter distribution range was 1.3 to 11.8 μm, and the peak single fiber diameter was 6.3 μm. The total basis weight of the obtained laminated nonwoven fabric was 490 g / m２ The laminated nonwoven fabrics A and B could be easily peeled apart by hand, confirming that the layers were independent. The resulting laminated nonwoven fabric had a low-frequency sound absorption coefficient of 56%, a high-frequency sound absorption coefficient of 58%, and an ultra-high-frequency sound absorption coefficient of 69%, with a ratio of the low-frequency to high-frequency sound absorption coefficients of 0.81. The results are shown in Table 2.

[0079]

[0080] The properties of the obtained nonwoven fabric for sound absorption material are as shown in Table 2, but Comparative Examples 1 to 7 all had low and inferior sound absorption coefficients at low and high frequencies. Furthermore, Comparative Examples 1 to 7 had low sound absorption coefficients at low and ultra-high frequencies, and their sound absorption performance for sounds over a wide range of frequencies was inferior. Comparative Examples 3 and 7 also had inferior punching processability.

[0081] 1: Nonwoven fabric for sound absorbing material 11a, b, c, d, e, f, g, h: Nonwoven fabric A 12a, b, c, d, e, f, g, h: Nonwoven fabric B

Claims

1. A nonwoven fabric for sound absorption material, which is formed by laminating nonwoven fabric A and nonwoven fabric B, wherein the nonwoven fabric A and the nonwoven fabric B are laminated independently and alternately in eight or more layers, the nonwoven fabric A contains fiber A having an average single fiber diameter of 0.1 to 5.0 μm, a single fiber diameter histogram distribution range of 0.1 to 5.0 μm with one peak, and a crystal nucleating agent content of 0.005 to 1.000 mass%, and the basis weight is 10 to 60 g / m ２ , apparent density is 0.100 to 0.200 g / cm ３ The nonwoven fabric B contains fibers B having an average single fiber diameter of 7.0 to 30.0 μm and a basis weight of 10 to 50 g / m ２ and the basis weight of the nonwoven fabric for sound absorption material is 150 to 650 g / m ２ This is a nonwoven fabric for sound absorption.

2. The nonwoven fabric for sound absorption according to claim 1, wherein the single fiber diameter of said fiber A is 0.1 to 10.0 μm.

3. A nonwoven fabric for sound absorption according to claim 1 or 2, wherein said nonwoven fabric A is a long-fiber nonwoven fabric.

4. The nonwoven fabric for sound absorption according to claim 1 or 2, wherein the fiber length of said fiber B is 25 to 100 mm.

5. A nonwoven fabric for sound absorption according to claim 1 or 2, wherein said fiber A is made of a thermoplastic resin.

6. A nonwoven fabric for sound absorption according to claim 1 or 2, wherein said fiber B is made of a thermoplastic resin.

7. The nonwoven fabric for sound absorption materials according to claim 1 or 2, wherein the ratio (X / Y) of the normal incidence sound absorption coefficient (%) X at 1,000 Hz to the normal incidence sound absorption coefficient (%) Y at a frequency of 10,000 Hz, as measured by the normal incidence sound absorption measurement method (in-pipe method) of JIS A 1405 (1998), is 0.69 or more.

8. A sound-absorbing material comprising the nonwoven fabric for sound-absorbing materials according to claim 1 or 2.

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