Sound-proof material

Abstract

Provided is a sound insulation material which exhibits sound absorption performance and has excellent sound insulation properties in a wide frequency range of 200 Hz to 2000 Hz. The present invention relates to a sound-proof material in which at least two layers are laminated in which a non-woven fabric A and a porous body B are laminated, the non-woven fabric A being a non-woven fabric comprising fibers, the porous body B being a molded body having a porous structure, and the non-woven fabric A containing 1 mass% or more of fibrillated fibers.

Description

Technical Field

[0001] The present invention relates to a soundproofing material. Background Art

[0002] When an automobile runs, various noises such as noises from an engine / drive system, road noise, and wind noise are generated. Conventionally, in order to suppress these noises and create a comfortable interior space of a vehicle, a sound-absorbing material has been used for the purpose of suppressing noise emission.

[0003] In recent years, with the development of electrification of automobiles, the quietness of the drive system has been improved, and thus sounds that were not recognized as noises in the past are now recognized as noises.

[0004] The frequency of noise depends on each sound source, and a sound-absorbing material suitable for each sound source is used. However, a porous sound-absorbing material generally used for in-vehicle applications, such as nonwoven fabric and foam, shows an excellent sound absorption rate in a high-frequency band, but has a tendency to decrease in sound absorption rate on the low-frequency side. In contrast, it is known that by further providing a layer on the surface of a porous material, soundproofing performance is improved in all frequency regions.

[0005] For example, in Patent Document 1 below, a textile-like composite sound-absorbing material in which a foam layer as a ventilation adjustment layer is provided on a nonwoven fabric obtained by combining fibers having a specific fineness is shown, and excellent sound absorption in the range of 800 Hz to 2000 Hz is described.

[0006] In addition, in Patent Document 2 below, a composite sound-absorbing material in which a spunbond nonwoven fabric is bonded to a melamine foam in a dotted pattern with a hot melt adhesive is shown, and it is described that the thickness exceeds 10 mm and excellent sound absorption is shown in all frequency bands.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2018-154113.

[0010] Patent Document 2: WO 2017 / 006993. Summary of the Invention

[0011] Problems to be Solved by the Invention

[0012] However, although the prior art improves sound absorption by further providing a layer on a porous material, it hardly exhibits its effect in terms of sound insulation. In addition, in order to cope with noises leaking from the inside of the vehicle to the outside, such as the driving sound of an engine, it is more effective to improve sound insulation than the sound absorption of a soundproofing material.

[0013] In view of the above circumstances, the problem to be solved by the present invention is to provide a soundproof material that exhibits sound absorption performance by changing the composition of the layer provided on the porous material and has excellent sound insulation performance in a wide frequency range of 200 Hz to 2000 Hz.

[0014] Means for Solving the Problem

[0015] The inventors of the present application repeatedly conducted dedicated research and experiments to solve the above problems, and as a result, found that by changing the composition of the layer provided on the porous material, it is possible to unexpectedly provide a soundproof material that exhibits sound absorption performance and has excellent sound insulation performance in a wide frequency range of 200 Hz to 2000 Hz, thus completing the present invention.

[0016] That is, the present invention is as follows.

[0017] [1] A soundproof material, characterized in that the soundproof material is a soundproof material formed by laminating at least two layers including a non-woven fabric A and a porous body B, the non-woven fabric A is a non-woven fabric composed of fibers, the porous body B is a molded body having a porous structure, and the non-woven fabric A contains 1% by mass or more of fibrillated fibers.

[0018] [2] The soundproof material according to the above [1], wherein the soundproof material is a soundproof material formed by laminating at least three layers including the non-woven fabric A, the porous body B, and a sound insulation material in the order of the non-woven fabric A, the porous body B, and the sound insulation material, the non-woven fabric A is a non-woven fabric composed of fibers, and the porous body B is a molded body having a porous structure.

[0019] [3] The soundproof material according to the above [2], wherein the sound insulation material is the non-woven fabric A.

[0020] [4] The soundproof material according to any one of the above [1] to [3], wherein the flow resistance per unit thickness of the non-woven fabric A is 1,400,000 Ns / m 4 or more and 5,000,000,000 Ns / m 4 or less.

[0021] [5] The soundproof material according to any one of the above [1] to [4], wherein the porosity of the non-woven fabric A is 60% or more and 96% or less.

[0022] [6] The soundproof material according to any one of the above [1] to [5], wherein the tortuosity of the non-woven fabric A is 1.20 or more and 10.0 or less.

[0023] [7] The soundproof material according to any one of the above [1] to [6], wherein the non-woven fabric A further contains unfibrillated fibers.

[0024] [8] The soundproof material according to any one of the foregoing [1] to [7], wherein the areal density of the porous body B is 10,000 g / m 2 or less, and the thickness is 1 mm or more and 100 mm or less.

[0025] [9] The soundproof material according to any one of the foregoing [1] to [8], wherein the fibrillated fiber is at least one selected from the group consisting of microfibrillated cellulose, acrylic fiber pulp, aramid pulp, chitin nanofiber, chitosan nanofiber, and silk nanofiber.

[0026]

[10] The soundproof material according to any one of the foregoing [1] to [9], wherein the fibrillation rate of the fibrillated fiber is 0.3% or more.

[0027]

[11] The soundproof material according to any one of the foregoing [1] to

[10] , wherein, based on the total mass of the nonwoven fabric, the content of the fibrillated fiber is 3% by mass or more and 30% by mass or less.

[0028] Effect of the Invention

[0029] According to the present invention, it is possible to provide a soundproof material that exhibits sound absorption performance and excellent sound insulation performance in the range of 200 Hz to 2000 Hz. Detailed Description of the Invention

[0030] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0031] <Nonwoven Fabric>

[0032] A nonwoven fabric refers to a structure formed by chemically or physically entangling or bonding a plurality of fibers to each other.

[0033] <Nonwoven Fabric A>

[0034] The soundproof material of the present embodiment is characterized in that the soundproof material includes a nonwoven fabric, and the fibers constituting the nonwoven fabric include the fibrillated fiber described below. Hereinafter, this nonwoven fabric will be referred to as nonwoven fabric A.

[0035] (Thickness of Nonwoven Fabric A)

[0036] The thickness of the nonwoven fabric A of the present embodiment is preferably 0.05 mm or more.

[0037] Generally, the thicker a known material is, the higher its rigidity. In particular, when the rigidity of a soundproofing material is increased, it has high sound insulation in the low-frequency region (referred to as the rigidity law). If the thickness is within this range, since the non-woven fabric has self-supporting properties, the sound insulation is also high. As the thickness of non-woven fabric A, it is more preferably 0.1 mm or more, further preferably 0.5 mm or more, and particularly preferably 0.8 mm or more. In addition, the higher the thickness, the higher the rigidity. Therefore, there is no particular limitation on the upper limit. However, from the viewpoints of workability and post-processing such as pressing, it is preferably 100 mm or less, more preferably 50 mm or less, particularly preferably 10 mm or less, and most preferably 5 mm or less. It should be noted that the overall thickness of non-woven fabric A can also be increased by laminating two or more sheets of non-woven fabric A.

[0038] (Flow resistance per unit thickness of non-woven fabric A)

[0039] The flow resistance per unit thickness of non-woven fabric A is preferably 1400000 Ns / m 4 or more. The flow resistance per unit thickness mentioned here refers to the difficulty of air flow in the material when air flows through a material with a thickness of 1 m. The higher this flow resistance per unit thickness, the more difficult it is for air to pass through, and the sound insulation of the material is improved. As the flow resistance per unit thickness, it is preferably 4300000 Ns / m 4 or more, more preferably 9500000 Ns / m 4 or more, further preferably 15000000 Ns / m 4 or more, particularly preferably 42000000 Ns / m 4 or more, and most preferably 52000000 Ns / m 4 or more. On the other hand, when the flow resistance per unit thickness is large, the sound absorption rate of the material decreases. The sound absorption mechanism of the non-woven fabric is that when air passes through the non-woven fabric, due to the friction between the air and the fibers, the vibration is converted into heat energy, thereby suppressing the vibration. If the flow resistance per unit thickness is too large, it is difficult for air to pass through the non-woven fabric originally, so the sound absorption rate decreases. Therefore, it is preferably 5500000000 Ns / m4 or less, more preferably 4500000000 Ns / m 4 or less, further preferably 3200000000 Ns / m 4 or less, particularly preferably 1500000000 Ns / m 4 or less.

[0040] (Porosity of non-woven fabric A)

[0041] The porosity of non-woven fabric A is preferably 96% or less. The lower the porosity, the smaller the voids in the non-woven fabric. Sound is generated as air particles move. The smaller the gap between the voids, the faster the particle velocity. If the particle velocity is fast, the thermal energy conversion caused by the friction between the air and the fibers in the non-woven fabric can be carried out efficiently, and the sound absorption rate also increases. As the porosity of non-woven fabric A, it is more preferably 90% or less, further preferably 86% or less, particularly preferably 84% or less, and extremely preferably 83% or less. In addition, if the porosity is too low, the flow resistance per unit thickness also becomes high, and the sound absorption rate of the material decreases. The lower limit is preferably 60% or more, more preferably 70% or more, further preferably 73% or more, particularly preferably 77% or more, and extremely preferably 78% or more.

[0042] (Tortuosity of non-woven fabric A)

[0043] The tortuosity of non-woven fabric A is preferably 1.20 or more. The tortuosity mentioned here is a parameter that represents the ratio of the path length of the fluid flowing inside the non-woven fabric to the thickness of the non-woven fabric.

[0044] The higher this tortuosity, the more the sound absorption of the material increases. As described above, the sound absorption of the non-woven fabric is generated by the thermal energy conversion caused by the friction between the fibers and the air vibration. A high tortuosity means that the frequency of friction between the fibers and the air increases, and as a result, the sound absorption rate of the material also increases. As the tortuosity of non-woven fabric A, it is more preferably 1.47 or more, further preferably 2.04 or more, particularly preferably 2.33 or more, extremely preferably 3.00 or more, and most preferably 5.00 or more. In addition, if the tortuosity is too high, the flow resistance per unit thickness also becomes high, and the sound absorption rate of the material decreases. Therefore, it is preferably 12.0 or less, more preferably 11.5 or less, and further preferably 10.0 or less.

[0045] (Constituent fibers of non-woven fabric A)

[0046] Non-woven fabric A contains fibrillated fibers. In addition, preferably, non-woven fabric A contains non-fibrillated fibers in addition to fibrillated fibers. The fibrillated fibers of non-woven fabric A are called fibrillated fibers, and the non-fibrillated fibers are called non-fibrillated fibers.

[0047] (Fibrillated fibers)

[0048] Fibrillated fibers refer to fibers formed by axial cracking, subdivision, and fuzzing of fibers. Fibrillated fibers can generally be divided into two types. One is a fiber formed by destroying a part of the structure of a fiber without a branched structure through physical and chemical methods, and the other is a fiber fibrillated by intentionally creating fluff during the spinning of a high molecular compound. For example, as an example of the former, microfibrillated cellulose (a fiber obtained by refining cellulose fibers using at least one physical and chemical method, which has the same general names as CNF (Cellulose Nanofiber), CeNF (Cellulose NanoFibril), Cellulose Nanofiber, MFC (Microfibrillated Cellulose), cellulose microfibers, microfibrous cellulose, etc.), acrylic fiber pulp (fibrillated fiber of polyacrylonitrile), aramid pulp and other synthetic pulps, chitin nanofibers, chitosan nanofibers, and silk nanofibers can be cited. As an example of the latter, synthetic pulp produced by flash spinning can be cited. Fibrillated fibers generally have a structure in which the fiber diameter is partially thinned compared to ordinary fibers without a branched structure due to their manufacturing method. Therefore, fibrillated fibers tend to have a large surface area and a large number of curved structures. Due to such characteristics, in non-woven fabric A, fibrillated fibers have the effect of acting as an adhesive that binds the non-fibrillated fibers described below through physical entanglement. Depending on the type of fibrillated fiber, the properties of non-woven fabric A will be affected due to differences in the fibrillation rate, fiber diameter, and surface state, but it is preferable that the fibrillated fibers are entangled with each other to increase the flow resistance per unit thickness and the tortuosity. From this perspective, as the fibrillated fiber, it is preferable to use at least one selected from the group consisting of microfibrillated cellulose, acrylic fiber pulp, aramid pulp, chitin nanofibers, chitosan nanofibers, and silk nanofibers.

[0049] (Fibrillation rate of fibrillated fiber)

[0050] The fibrillation rate of the fibrillated fibers in nonwoven fabric A is preferably 0.3% or more. The fibrillation rate mentioned here refers to the ratio of the total value of the branched fiber lengths to the trunk length of the fibrillated fibers. If within this range, sufficient effects as an adhesive can be obtained, nonwoven fabric A has self-supporting properties, and the shedding of non-fibrillated fibers from nonwoven fabric A becomes less. In addition, the fibers fibrillated and thinned contribute to sound absorption in the low frequency band. The fibrillation rate of the fibrillated fibers is more preferably 0.5% or more, further preferably 0.9% or more, particularly preferably 1.1% or more, extremely preferably 1.7% or more, and most preferably 2.2% or more. As the upper limit of the fibrillation rate, there is no particular limitation, and it can be 100% or less, 10% or less, or 3% or less.

[0051] The fibrillation rate, average fiber diameter (method A), average fiber length, and area refinement ratio described in the present invention can be measured in the slurry state before obtaining the nonwoven fabric as described in the examples (for example, after obtaining the fibrillated fibers, they can be measured individually). In addition, they can also be measured in a mixed slurry state in which the fibrillated fibers and non-fibrillated fibers are mixed at a specified ratio by sorting the fibrillated fibers using methods such as sieving and centrifugation. Further, the fibrillated fibers and non-fibrillated fibers can be mixed, sheeted, dried to form a nonwoven fabric, and then the nonwoven fabric can be dispersed in water to disintegrate the fibers, and the fibrillated fibers can be sorted by methods such as sieving and centrifugation for measurement.

[0052] For example, the method for sorting fibrillated fibers from the dried nonwoven fabric after mixed sheet forming and measuring the fibrillation rate, average fiber length, average fiber diameter (method A), and area refinement ratio is as follows.

[0053] (1) Introduce 5 g of the nonwoven fabric (dry product) and 300 g of pure water into a squeezing mixer (Vitamix 1200i S), and stir for 3 minutes under the condition of speed level 1. Let the obtained dispersed water flow into a stainless steel sieve (metal mesh diameter: φ150 μm, sieve hole: 300 μm, fabric type: plain weave, inner height: 45 mm), and collect the filtered dispersed water with a receiving vessel to obtain dispersed water containing only the fibrillated fibers extracted.

[0054] (2) Prepare a 1 L aqueous dispersion with the solid component final concentration of 0.004% by mass from the dispersed water obtained in the above (1), and measure it using the above fiber image analyzer (manufactured by TechPap company, Morfi-Neo) under the condition of photographing for 3 minutes. It should be noted that the minimum fiber length as the measurement object is 20 μm. Using this method, the number of fibers measured by the fiber image analyzer is 500 or more as the necessary lower limit. There is no particular limitation for the upper limit, and it can be 1000 or less.

[0055] (Average fiber length of fibrillated fibers)

[0056] The average fiber length of the fibrillated fibers in nonwoven fabric A is preferably 20 μm or more. If it is within this range, sufficient effects as an adhesive can be obtained. In addition, the longer the average fiber length of the fibrillated fibers, the easier it is for the fibrillated fibers to crosslink between the non-fibrillated fibers. Since the crosslinking of the fibrillated fibers improves the rigidity of the nonwoven fabric as an adhesive, the greater the number of crosslinked fibrillated fibers, the higher the rigidity of the nonwoven fabric, and the higher the sound insulation performance in the low-frequency region. In addition, the greater the number of crosslinked fibrillated fibers, the greater the flow resistance per unit thickness and the tortuosity of the nonwoven fabric, and the more the sound insulation performance of the nonwoven fabric is improved. In addition, the uncrosslinked fibrillated fibers exist in a manner of winding around the outer periphery of the non-fibrillated fibers. The contribution of the uncrosslinked fibrillated fibers to improving the sound insulation performance of the nonwoven fabric is smaller than that of the crosslinked fibrillated fibers. The average fiber length of the fibrillated fibers is more preferably 25 μm or more, and further preferably 40 μm or more. As the upper limit of the average fiber length, if it is 200 μm or less, the mixing property with the non-fibrillated fibers is excellent, and a uniform molded body can be obtained, so it is preferred. In addition, in terms of the manufacturing process of the fibrillated fibers, the longer the average fiber length, the larger the average fiber diameter. However, if the average fiber diameter is large, the winding between the fibrillated fibers becomes weak, and the effect as an adhesive also becomes small. As the upper limit of the average fiber length of the fibrillated fibers, it is more preferably 150 μm or less, further preferably 100 μm or less, particularly preferably 90 μm or less, especially preferably 60 μm or less, and most preferably 55 μm or less.

[0057] (Area refinement ratio of fibrillated fibers)

[0058] The area refinement ratio of fibrillated fibers in the nonwoven fabric is preferably 2.0% or more. Here, fine fibers refer to fibers with a fiber length of less than 100 μm, and the area refinement ratio refers to the ratio of the total area of the observed images of fine fibers with a fiber length of less than 100 μm to the total area of the observed images of all fibers (the area of ordinary fibers + the area of fine fibers). As mentioned above, in terms of the production process of fibrillated fibers, the longer the average fiber length, the larger the average fiber diameter. However, if the average fiber diameter is large, the entanglement between fibrillated fibers becomes weak, and the effect as an adhesive also becomes small. If the area refinement ratio is within this range, a sufficient effect as an adhesive can be obtained, the nonwoven fabric has self-supporting properties, and the shedding of non-fibrillated fibers from the nonwoven fabric becomes less. As the area refinement ratio, it is more preferably 3.0% or more, further preferably 8.0% or more, particularly preferably 27.0% or more, and most preferably 30.0% or more. In addition, due to the presence of ordinary fibers with a fiber length of 100 μm or more, the fine fibers form entanglements with the ordinary fibers as the main axis, so it is preferably to contain ordinary fibers to a certain extent. Therefore, as the upper limit of the area refinement ratio, it is preferably 90.0% or less, more preferably 50.0% or less, and further preferably 40.0% or less.

[0059] 〈Average fiber diameter of fibrillated fibers using Method A〉

[0060] Regarding the average fiber diameter of fibrillated fibers in nonwoven fabric A, there are mainly the average fiber diameter corresponding to the main fiber part of the fibrillated fibers (average fiber diameter using Method A) and the average fiber diameter including the fine fiber part up to the fibrillated end (average fiber diameter using Method B). The average fiber diameter using Method A is preferably 50 μm or less. If it is within this range, the pore diameter formed inside the composite molded body will not be too small, and appropriate air permeability can be obtained. As the average fiber diameter of fibrillated fibers using Method A, it is more preferably 20 μm or less, further preferably 15 μm or less, and most preferably 13 μm or less. As the lower limit, in terms of the resolution of the device, it can be 1.5 μm or more. In addition, in the wet papermaking method and the pulp molding method cited as the manufacturing method of nonwoven fabric A described later, from the viewpoint of water filtration properties, it is preferably 2.5 μm or more, more preferably 5 μm or more, and further preferably 10 μm or more.

[0061] (Average fiber diameter of fibrillated fibers using Method B)

[0062] The average fiber diameter of the fibrillated fibers in the nonwoven fabric A using Method B refers to the average fiber diameter including the fine fiber part up to the fibrillated end. The average fiber diameter is preferably 1000 nm or less. If within this range, entanglement with non-fibrillated fibers is likely to occur, and shedding of fibers from the nonwoven fabric A can be suppressed. As the average fiber diameter of the fibrillated fibers as a whole using Method B, it is more preferably 800 nm or less, further preferably 500 nm or less, particularly preferably 400 nm or less, and extremely preferably 300 nm or less. There is no particular limitation on the lower limit, and it is preferably 10 nm or more, more preferably 20 nm or more, further preferably 30 nm or more, and particularly preferably 40 nm or more.

[0063] (Cellulose raw material)

[0064] As the fibrillated fibers for the nonwoven fabric A, microfibrillated cellulose is preferred. As the raw material for this microfibrillated cellulose, as the raw material for type I cellulose, so-called wood pulp such as softwood pulp and hardwood pulp, as well as non-wood pulp can be cited. As the raw material for softwood pulp, fir, hemlock, cedar, larch, Japanese larch, red pine, red Japanese larch, black pine, white pine, king pine, spruce, hinoki cypress, Japanese cypress, cryptomeria, metasequoia, yew, goldenseal, dragon juniper, goldcrest cypress, blue ice cypress, etc. can be exemplified. In addition, as the raw material for hardwood pulp, eucalyptus, poplar, kashi, oak, birch, beech, maple, chestnut, paulownia, birch, elm, aspen, etc. can be exemplified. As the non-wood pulp, cotton linters pulp and other cotton-derived pulp, hemp-derived pulp, bagasse-derived pulp, kenaf-derived pulp, bamboo-derived pulp, and rice straw-derived pulp can be exemplified. Cotton linters pulp, hemp-derived pulp, bagasse-derived pulp, kenaf-derived pulp, bamboo-derived pulp, and rice straw-derived pulp respectively refer to purified pulp obtained from raw materials such as cotton lint or cotton linter, hemp-based abaca (for example, raw materials produced in Ecuador or the Philippines are often used), sisal, bagasse, kenaf, bamboo, rice straw, etc. through a purification process and a bleaching process for the purpose of removing lignin and hemicellulose by cooking treatment. In addition, pure substances such as cellulose derived from bacteria such as acetic acid bacteria, cellulose derived from seaweed, and tunicate cellulose can also be used as raw materials for cellulose microfibrils. As the raw material for type II cellulose, the cut filaments of regenerated cellulose fibers (viscose rayon, lyocell fiber, cuprammonium rayon (Bemberg), etc.) and the cut filaments or pulp of cellulose derivative fibers can also be used as raw materials for cellulose microfibrils. In addition, the cut filaments of extremely fine filaments of regenerated cellulose or cellulose derivatives obtained by electrospinning can also be used as raw materials for cellulose microfibrils or the cellulose microfibrils themselves. In addition, these raw materials can be used alone or in combination of two or more. By mixing a plurality of raw materials, the average fiber diameter can be adjusted.

[0065] (Crystal form and crystallinity)

[0066] As described above, the crystal form of cellulose is not unique, and there are various crystal forms, which are roughly classified into cellulose type I and type II. Among the two, type I crystal shows high values in terms of rigidity and thermal properties. In particular, it is known that if the soundproof material has high rigidity, it has high sound insulation in the low-frequency region. Therefore, in the crystal form of cellulose of the fibrillated fiber used for non-woven fabric A, it is also preferable to contain type I crystal. It should be noted that, strictly speaking from an academic point of view, cellulose type I crystal contains two types, Iα and Iβ, and the mixing ratio of Iα and Iβ can be ignored here. In addition, the larger the component ratio (crystallinity) of the crystal in cellulose, the greater the rigidity of the microfibrillated cellulose. As the crystallinity, it is preferably 60% or more and can be 100% or less. As the crystallinity, it is more preferably 70% or more, further preferably 80% or more, particularly preferably 85% or more, and most preferably 90% or more. The crystallinity is determined by X-ray diffraction method. The diffraction lines caused by the crystalline matter become peaks, and the scattered light caused by the amorphous matter is detected as a halo. The fitting of the peaks and halos is performed, and the crystallinity is calculated by applying the following formula:

[0067] Crystallinity [%] = 100×Ic / (Ic + Ia)

[0068] {In the formula, Ic: Scattering integral intensity of the peak, Ia: Scattering integral intensity of the halo}

[0069] (Method for producing microfibrillated cellulose)

[0070] The raw materials as described above can be refined to obtain microfibrillated cellulose. In the description of this application, "refinement" means controlling the fiber length, fiber diameter, fibrillation rate, etc. while reducing the size of cellulose. In one mode, a pretreatment process can be performed before the refinement process. In the pretreatment process, it is effective to make the raw material pulp pre-easily refined by autoclave treatment, enzyme treatment, etc. or a combination thereof at a temperature of 100°C to 150°C in water impregnation. These pretreatments not only reduce the load of the refinement process, but also discharge impurity components such as lignin and hemicellulose present on the surface and in the gaps of the microfibrils constituting the cellulose fiber into the aqueous phase. As a result, it also has the effect of increasing the α-cellulose purity of the refined fiber, and thus sometimes is also effective in increasing the heat resistance of the microfibrillated cellulose.

[0071] In the refinement process, the raw material pulp is dispersed in water, and a known refinement device such as a beater, a single-disc refiner, a double-disc refiner, or a high-pressure homogenizer is used for refinement. The appropriate treatment concentration during refinement varies depending on the device used, so it can be set arbitrarily.

[0072] (Multi-stage refinement)

[0073] When refining cellulose in multiple stages, it is effective to combine a refining mechanism or two or more refining devices with different shear rates. Here, as a method of multi-stage refinement, it is preferable to perform multi-stage refinement using disk refiners with different disk structures, or to perform refinement using a high-pressure homogenizer after refinement using a disk refiner. Here, as the disk refiner, any one of a single disk refiner and a double disk refiner can be used.

[0074] (Multi-stage refinement using multiple disk refiners)

[0075] When performing multi-stage refinement using multiple disk refiners, it is preferable to use a refiner having at least two different disk structures. By using refiners with different disk structures, various shape parameters of the microfibrillated cellulose, namely, fibrillation ratio, average fiber length, average fiber diameter, etc., can be variously controlled.

[0076] (Disk structure of disk refiner)

[0077] Adjusting the disk structure of the disk refiner is an effective method for controlling various shape parameters of the microfibrillated cellulose. As structural features of the disk refiner, blade width, groove width, and blade-groove ratio (the value obtained by dividing the blade width by the groove width) are important, and among them, the blade-groove ratio is particularly important in the production of fibrillated fibers. If the blade-groove ratio is small, the effect of cutting fibers is large, so the fiber length becomes small. If the blade-groove ratio is large, the effect of grinding (beating) fibers becomes large, so the fibrillation ratio becomes large. It is important that the non-woven fabric A contains fibrillated fibers, so the blade-groove ratio is preferably 0.2 or more, more preferably 0.4 or more, and most preferably 0.5 or more. It should be noted that if the blade-groove ratio is fixed, the smaller the absolute values of the blade width and groove width, the finer and more uniform the microfibrillated cellulose can be obtained.

[0078] (Distance between blades during disk refiner treatment)

[0079] In the fibrillation using a disk refiner, it is also important to control the distance between the two disks (rotating blade and stationary blade) (hereinafter referred to as "blade gap"). By controlling the blade gap, the average fiber length of microfibrillated cellulose can be controlled, and the smaller the blade gap, the smaller the average fiber length. In addition, in the front-stage treatment, it is preferable to set the blade gap to 0.05 mm or more and 2.0 mm or less, and in the back-stage treatment, it is preferable to set the blade gap to 0.05 mm or more and 1.0 mm or less. In addition, when adjusting the blade gap, it is preferable to gradually reduce it from a wider blade gap to the target blade gap. By controlling in this way, clogging and overload of the device can be prevented, and in addition, microfibrillated cellulose with a narrow distribution of fiber length and fiber diameter and high homogeneity can be obtained.

[0080] (Number of passes in disk refiner treatment)

[0081] The degree of fibrillation can also be controlled by the number of times the cellulose passes through the disk part (hereinafter referred to as "number of passes"). By increasing the number of passes, cellulose fibers with a uniform distribution of fiber diameter and fiber length can be obtained. In the specification of this application, the "number of passes" refers to the number of times the refiner treatment is performed after setting the above-mentioned blade gap to the target value. As the number of passes through the disk refiner, it is preferably 5 or more, more preferably 20 or more, and further preferably 40 or more. As the number of passes increases, the distribution of fiber shape gradually converges to a certain degree, so the more the better. However, considering productivity, the upper limit of the number of passes is 300 or less.

[0082] (Method for controlling the number of passes in disk refiner treatment)

[0083] As a method for controlling the number of passes, there can be mentioned a method of using one tank for one refiner, simply circulating the slurry, and controlling the number of passes according to the flow rate; a method of using two tanks for one refiner and performing refiner treatment while the slurry reciprocates between the tanks, etc. The former can achieve simplification of the equipment. On the other hand, in the latter, since the cellulose reliably passes through the disk part in each treatment, microfibrillated cellulose with higher uniformity can be obtained.

[0084] (Multi-stage fibrillation using a combination of a disk refiner and a high-pressure homogenizer)

[0085] It is also one of the preferred methods to further perform fibrillation treatment on the cellulose fibers fibrillated by a disk refiner using a high-pressure homogenizer. Compared with a disk refiner, the high-pressure homogenizer has a better effect of refining fibers. By combining with the fibrillation using a disk refiner, long and slender microfibrillated cellulose can be obtained.

[0086] (Method for manufacturing synthetic pulp)

[0087] Synthetic pulp can be obtained by methods such as the spinning and stretching method of existing polymers, flash spinning from a solution or emulsion, ribbon fiber method using uniaxial stretching of a membrane, and shear polymerization method of polymerizing monomers under shear stress. In addition, as acrylic fiber pulp, BiPUL (registered trademark, manufactured by Japan Exlan Industry company) can be used, and as aramid pulp, Kevlar (registered trademark, manufactured by DuPont) and Tiara (registered trademark, manufactured by Daicel Miraizu Ltd.) can be used. In addition, it can also be prepared by performing high-pressure homogenizer treatment in the same manner as microfibrillated cellulose.

[0088] (Non-fibrillated fiber)

[0089] Preferably, nonwoven fabric A contains not only fibrillated fibers but also non-fibrillated fibers. In the specification of this application, "non-fibrillated fiber" refers to a fiber without a branched structure as a fibrous substance. As non-fibrillated fibers, any fibers of natural fibers, synthetic fibers, semi-synthetic fibers, and inorganic fibers can be used. Examples of polymers constituting non-fibrillated fibers include thermoplastic resins such as polyolefins, polyesters, polyamides (aromatic or aliphatic), acrylic polymers, polyvinyl alcohol, polylactic acid, polyphenylene ether, polyoxymethylene, and polyphenylene sulfide; thermosetting resins such as epoxy resins, heat-curable modified polyphenylene ether resins, heat-curable polyimide resins, urea-formaldehyde resins, allyl resins, silicone resins, benzoxazine resins, phenolic resins, unsaturated polyester resins, bismaleimide triazine resins, alkyd resins, furan resins, melamine resins, polyurethane resins, and aniline resins; cellulose; chitin; chitosan, etc. In addition, examples of inorganic materials constituting non-fibrillated fibers include glass, ceramics, cement, metals, carbon fibers, slag, and carbon fibers. These non-fibrillated fibers can be used alone or in combination of plural kinds. For non-fibrillated fibers, preferably, based on properties such as heat resistance and chemical resistance, they are selected according to the components to be applied as expected, and examples include polypropylene, polyamide 6, polyamide 66, polyphenylene ether, polyethylene terephthalate, and combinations thereof. If the moldability of nonwoven fabric A is considered, polyethylene terephthalate fibers are particularly preferably included.

[0090] (Average fiber diameter of non-fibrillated fiber)

[0091] The average fiber diameter of non-fibrillated fibers is preferably 0.1 μm or more. The average fiber diameter of non-fibrillated fibers is measured according to the following steps.

[0092] (1) Measure the weight [g] of non-fibrillated fibers with a length of 1000 m as tex.

[0093] (2) Convert the tex into the average fiber diameter by the following formula.

[0094] Average fiber diameter [μm] = 2 × [T × 1000 / (S × π)] 0.5

[0095] {In the formula, T: tex, S: true density of the material [g / cm 3}.

[0096] When the average fiber diameter of the non-fibrillated fiber is less than 0.1 μm, it cannot be uniformly mixed when mixed with the fibrillated fiber, and a non-woven fabric A with sufficient internal refinement cannot be obtained. In addition, the larger the average fiber diameter of the non-fibrillated fiber, the higher the rigidity of the fiber itself, and the higher the rigidity of the non-woven fabric A. Therefore, according to the rigidity law, high sound insulation is exhibited in the low-frequency region. As the average fiber diameter of the non-fibrillated fiber, it is more preferably 1.0 μm or more, further preferably 3.0 μm or more, and particularly preferably 5.0 μm or more.

[0097] In addition, as an example of the manufacturing method of the non-woven fabric A, the wet papermaking method or the pulp molding method described later can be cited. However, if this manufacturing method is used, the fibrillated fibers exist in a manner that they are intricately wound around each other and crosslinked between the fibers of the non-fibrillated fiber. The crosslinking of the fibrillated fibers improves the rigidity of the non-woven fabric A as an adhesive. Therefore, the more the number of crosslinked fibrillated fibers, the higher the rigidity of the non-woven fabric A. According to the rigidity law, higher sound insulation is exhibited in the low-frequency region. In addition, the more the number of crosslinked fibrillated fibers, the greater the flow resistance per unit thickness and the tortuosity of the non-woven fabric A, and the more the sound insulation of the non-woven fabric A is improved. Here, if the average fiber diameter of the non-fibrillated fiber is increased, the number of non-fibrillated fibers per unit volume becomes smaller, and thus the number of fibrillated fibers that can be crosslinked decreases. At this time, the uncrosslinked fibrillated fibers exist in a manner that they are wound around the outer periphery of the non-fibrillated fiber. The contribution of the uncrosslinked fibrillated fibers to improving the sound insulation of the non-woven fabric A is smaller than that of the crosslinked fibrillated fibers. Therefore, as the average fiber diameter of the non-fibrillated fiber, it is preferably 100.0 μm or less, more preferably 30.0 μm or less, further preferably 15.0 μm or less, and particularly preferably 10.0 μm or less.

[0098] (Fiber length of the non-fibrillated fiber)

[0099] The fiber length (also known as the cut length) of the non-fibrillated fiber is preferably 1 mm or more. Within this range, the three-dimensional molding described later becomes easier, a more uniform non-woven fabric can be obtained, and a more uniform sound insulation effect can be obtained. In addition, when the fiber length is long, the rigidity of the non-woven fabric also increases. Therefore, as the fiber length of the non-fibrillated fiber, it is more preferably 3 mm or more, and further preferably 5 mm or more. In addition, as the upper limit, from the viewpoint of the moldability of the non-woven fabric, it is preferably 30 mm or less.

[0100] (Content of fibrillated fiber)

[0101] Preferably, based on the total mass of non-woven fabric A, non-woven fabric A contains 1% by mass or more of fibrillated fiber. Within this range, the fibrillated fiber can contribute to sound absorption in the low frequency band. By containing a large amount of fibrillated fiber, the strength of non-woven fabric A increases, and less fiber falls off from the surface. In addition, since the flow resistance per unit thickness also increases, the sound insulation performance improves. From the above viewpoints, it is further preferably 2.0% by mass or more, particularly preferably 3.0% by mass or more, extremely preferably 5.0% by mass or more, and most preferably 10.0% by mass or more. However, if the content of the fibrillated fiber is too large, it will cause a decrease in workability due to excessive rigidity and a decrease in the sound absorption rate accompanied by excessive flow resistance per unit thickness. Therefore, it is preferably 100% by mass or less, more preferably 90% by mass or less, and further preferably 30% by mass or less.

[0102] (Bulk density of non-woven fabric A)

[0103] The bulk density of non-woven fabric A is preferably 30 kg / m 3 or more. When the bulk density is within this range, appropriate air permeability can be obtained, and it is easy to obtain a sound absorption effect. The bulk density is more preferably 100 kg / m 3 or more, further preferably 200 kg / m 3 or more, particularly preferably 300 kg / m 3 or more. In addition, if the bulk density of non-woven fabric A is too large, the flow resistance per unit thickness will also be too large, which will instead damage the sound absorption effect. As the upper limit of the bulk density, it is preferably 10000 kg / m 3 or less, further preferably 5000 kg / m 3 or less, particularly preferably 1000 kg / m 3 or less.

[0104] It should be noted that the bulk density of non-woven fabric A is calculated by the following formula.

[0105] Bulk density [kg / m 3 = Areal density [g / m 2 / Thickness [mm]

[0106] For the basis weight of nonwoven fabric A, an electronic balance (GX-8K2, manufactured by A&D company, Japan) was used to measure the weight of nonwoven fabric A cut into a 25 cm square, and it was set to 16 times as the basis weight. The thickness of nonwoven fabric A was calculated by the aforementioned method.

[0107] When the basis weight is the same, the bulk density can be controlled by adjusting the thickness of the material, and the thickness of the material can be adjusted by the aforementioned method.

[0108] (Three-dimensional shaping of nonwoven fabric A)

[0109] Nonwoven fabric A can be easily formed into a three-dimensional structure. Further, a structure with a uniform surface and no seams or gaps can be formed. The three-dimensional structure means that nonwoven fabric A has at least one curved structure instead of a two-dimensional (flat or planar) structure. Hereinafter, it is also referred to as "three-dimensional" or "three-dimensional structure".

[0110] When a planar air-permeability adjusting layer such as a commonly used nonwoven fabric is applied to a three-dimensional structure, the air-permeability adjusting layer is arranged on the surface of the sound-absorbing material by cutting, bending, pasting, etc. At this time, an inevitable structure in which the nonwoven fabric partially overlaps or gaps and creases are generated. Therefore, the air permeability deviates, and uniform sound-absorbing characteristics cannot be obtained on all surfaces. On the other hand, when nonwoven fabric A is three-dimensionally processed, since it is a structure with a uniform surface and no seams or gaps, even when applied to a sound source with a complex shape, a specified sound insulation can be obtained on all surfaces of nonwoven fabric A, and thus the sound insulation is excellent.

[0111] (Manufacturing method of nonwoven fabric A)

[0112] As a method for manufacturing the nonwoven fabric A, there is no particular limitation, and examples thereof include a method of dispersing non-fibrillated fibers and fibrillated fibers in a liquid medium and removing and drying the solvent by filtration, pressing, etc. By mixing non-fibrillated fibers and fibrillated fibers in a liquid medium, a nonwoven fabric A with a more uniform internal structure can be obtained. As the molding method described above, specifically, since it can be processed into any shape, the wet papermaking method and the pulp molding method are preferred. If the wet papermaking method is used, a two-dimensional planar molded body (also referred to as a nonwoven fabric) is obtained. By using the pulp molding method, three-dimensional complex shaping can be performed. For the pulp molding method, there are several different methods depending on the target molded body. There is a thick wall method for obtaining a molded body with a very thick film thickness of 5 mm to 10 mm and high load resistance, a transfer mold method for obtaining a molded body with a film thickness of 3 mm to 5 mm and a smooth surface, a thermoformed mold method for obtaining a molded body with a film thickness of 1 mm to 3 mm and a complex shape, a PIM (Pulp injection mold, pulp injection molding) method for obtaining a more complex shape such as bosses and ribs like ordinary plastic molded products, a PF (Pulp forming, pulp forming) method for obtaining a lightweight and soft molded product by foaming in a mold, etc. Even if it does not belong to these classifications, as long as three-dimensional shaping can be performed, any method can be adopted. During molding, various additives can be added to the liquid medium.

[0113] (Liquid medium during molding)

[0114] As the liquid medium used during molding, there is no particular limitation, and known liquid media such as water and organic solvents can be used. Considering the ease of operation and the environmental load, water is preferably used. However, in order to prevent aggregation during drying and to reduce the air permeability resistance per unit thickness, a non-polar organic solvent with a lower surface tension can also be used. When the liquid medium is water, a surfactant can be added for the purpose of controlling the surface tension.

[0115] (Additives during molding)

[0116] By adding a papermaking dispersant, a binder, and a crosslinking agent as additives during forming, it is possible to control the strength of nonwoven fabric A, operability such as fiber shedding, internal uniformity, surface smoothness, and other structures. The papermaking dispersant refers to a surfactant used to facilitate the fibrillation of fibrillated fibers on a fiber bundle in a liquid medium, and an adhesive used to adjust the viscosity of the liquid medium and prevent fiber aggregation, which can improve surface smoothness and homogeneity and control the air permeability resistance per unit thickness caused by the homogenization of the internal structure. It should be noted that the added surfactant also affects the surface tension of the liquid medium. The binder refers to paste components such as starch, and by bonding the fibers, it is possible to control the strength of the structure and the air permeability resistance per unit thickness. The crosslinking agent refers to isocyanate, polyurethane, etc., and by chemically and physically crosslinking the entanglement points of the fibers, it is possible to prevent fiber shedding or adjust the strength. In addition, when using materials with hydrophilic functional groups such as hydroxyl, carbonyl, carboxyl, and amino groups for the fibrillated fibers and non-fibrillated fibers of nonwoven fabric A, if the moisture absorption / dehumidification of moisture in the air is repeated, sometimes the fibers aggregate and the microstructure of nonwoven fabric A changes. By binding the fibers with a crosslinking agent, this movement of the fibers can be blocked and aggregation can be inhibited. Above all, these additives can be used alone or in combination of two or more.

[0117] (Blackening of nonwoven fabric A)

[0118] As an automotive component, it is better if dirt and the like are less obvious, and black components are preferred. As a method for blackening nonwoven fabric A, examples include dyeing at least one of the fibrillated fibers and non-fibrillated fibers black. As a method for blackening fibrillated fibers and non-fibrillated fibers, there are methods such as coating a black coloring substance on the fibers and methods of pre-including a black coloring substance inside the fibers. As the coloring substance, examples include black powders such as carbon black, titanium-based black pigments, iron oxide powder, titanium nitride powder, and titanium suboxide powder; black fibers such as carbon fibers and carbon nanotubes. In addition, from the perspective of blackening nonwoven fabric A, it is preferable to blacken both fibrillated fibers and non-fibrillated fibers, but considering cost, labor efficiency, etc., it is also possible to consider limited blackening of one of them. In this case, from the perspective of ease of dyeing and content, it is preferable to blacken the non-fibrillated fibers among the fibrillated fibers and non-fibrillated fibers.

[0119] (Imparting a flame retardant to nonwoven fabric A)

[0120] As an automotive component, from the perspective of safety, it is preferable to use a material with high flame retardancy to prevent fires. The flame retardancy can be improved by imparting a flame retardant to the nonwoven fabric A. As a method for imparting a flame retardant to the nonwoven fabric A, methods such as dispersing the flame retardant in a liquid and attaching it by blowing, brushing, coating, casting, dip coating, impregnation, etc. can be cited. In addition, in addition to this, when manufacturing the nonwoven fabric A, by previously dispersing the non-fibrillated fiber, fibrillated fiber, and flame retardant in a liquid medium, it is also possible to form a nonwoven fabric in a state where the flame retardant is attached. In addition, as the types of flame retardants, halogen-based flame retardants, phosphorus-based flame retardants, nitrogen-based flame retardants, and inorganic-based flame retardants can be cited. As specific halogen-based flame retardants, chlorinated paraffin, cyclic aliphatic chlorine compounds (Dechlorane Plus: bis(hexachlorocyclopentadiene) cyclooctane), aliphatic bromine compounds, and aromatic bromine compounds can be cited. As phosphorus-based flame retardants, phosphate esters (monomeric type, condensed type), halogen-containing phosphate esters, metal hypophosphites, intumescent flame retardants (IFR), red phosphorus, APP (ammonium polyphosphate), melamine phosphate, and phosphate ester amides can be cited. As nitrogen-based flame retardants, melamine, melamine derivatives, and guanidine compounds can be cited. As inorganic-based flame retardants, magnesium hydroxide, aluminum hydroxide, antimony compounds (Sb2O3), tin compounds (zinc stannate, zinc hydroxy stannate), boron compounds (zinc borate), montmorillonite (MMT), zirconium compounds, and molybdenum compounds (molybdenum oxide) can be cited. In addition, in addition to the above, silicone-based flame retardants, hindered amine compounds, azoalkane compounds, etc. can also be cited. Among the above, phosphorus-based flame retardants have the characteristic of forming a carbonized coating film (coke) on the material surface through dehydration and blocking oxygen and heat. Therefore, the nonwoven fabric A imparted with a phosphorus-based flame retardant can prevent the spread of fire when a fire occurs inside and outside the vehicle. Therefore, it is preferable to use a phosphorus-based flame retardant.

[0121] 〈Porous body B〉

[0122] Examples of the porous body B include well-known porous materials such as nonwoven fabrics, felts, and foams, but are not limited to these. The nonwoven fabric A has sound insulation, but in the frequency region of the natural vibration frequency of the nonwoven fabric A, the nonwoven fabric A vibrates violently by itself and generates secondary frequency sounds. Therefore, in the frequency region of the natural vibration frequency of the nonwoven fabric A, the sound insulation decreases compared to other frequency regions.

[0123] When laminating the porous body B and the nonwoven fabric A, the porous body B suppresses the vibration of the nonwoven fabric A itself, and the porous body B itself also serves as a sound-absorbing material to contribute to sound insulation. In particular, since it absorbs the frequency sound in the inherent region (sound insulation degradation region) of the nonwoven fabric A, high sound insulation can be exhibited in all frequency regions. The fibers constituting the nonwoven fabric and the felt in the porous body B can be any one of natural fibers, synthetic fibers, semi-synthetic fibers, and inorganic fibers. Examples of inorganic materials include glass, ceramics, cement, metals, carbon fibers, and slag. These fibers can be used alone or in combination of plural kinds.

[0124] Examples of the polymer constituting the porous body B include thermoplastic resins such as polyolefins, polyesters, polyamides (aromatic or aliphatic), acrylic polymers, polyvinyl alcohol, polylactic acid, polyphenylene ether, polyoxymethylene, and polyphenylene sulfide; and thermosetting resins such as epoxy resins, thermosetting modified polyphenylene ether resins, thermosetting polyimide resins, urea-formaldehyde resins, allyl resins, silicone resins, benzoxazine resins, phenolic resins, unsaturated polyester resins, bismaleimide triazine resins, alkyd resins, furan resins, melamine resins, polyurethane resins, and aniline resins.

[0125] In addition, examples of the material of the foam in the porous body B include thermoplastic resins such as polyolefins, polyesters, polyamides (aromatic or aliphatic), acrylic polymers, polyvinyl alcohol, polylactic acid, polyphenylene ether, polyoxymethylene, and polyphenylene sulfide; and thermosetting resins such as epoxy resins, thermosetting modified polyphenylene ether resins, thermosetting polyimide resins, urea-formaldehyde resins, allyl resins, silicone resins, benzoxazine resins, phenolic resins, unsaturated polyester resins, bismaleimide triazine resins, alkyd resins, furan resins, melamine resins, polyurethane resins, and aniline resins.

[0126] (Thickness of the porous body B)

[0127] It is preferable that the porous body B has a thickness of 1 mm or more. The thickness of the porous body B is measured by the same method as the thickness of the nonwoven fabric A. When the thickness is small, the sound absorption is high only in the high-frequency band, but if the thickness is increased, the sound absorption is improved up to a lower frequency band. Therefore, as the thickness of the porous body B, it is more preferably 5 mm or more. As the upper limit, there is no particular limitation, but from the viewpoint of realizing space saving of the sound insulation material, it is preferably 100 mm or less, more preferably 30 mm or less, further preferably 10 mm or less, and particularly preferably 8 mm or less.

[0128] (Areal density of the porous body B)

[0129] The areal density of the porous body B is preferably 100 g / m 2As described above, the areal density of the porous body B is measured by the same method as that of the nonwoven fabric A. When the areal density is small, the sound absorption is high only in the high-frequency band. However, if the areal density is increased, the sound absorption is improved up to a lower frequency band. As the areal density, it is more preferably 200 g / m 2 or more, and further preferably 250 g / m 2 or more. Additionally, there is no particular limitation on the upper limit, but from the perspective of operability, it is preferably 10000 g / m 2 or less.

[0130] (Porous structure of the porous body B)

[0131] As the porous structure of the porous body B, a continuous bubble structure is preferred compared to a closed-cell structure. Continuous bubbles are in a state where the voids of the porous structure are continuously connected. Therefore, sound penetrates into the interior of the material, contacts the material wall, and the energy of the sound is reduced, resulting in a decrease in the energy of the reflected sound and an increase in the sound absorption rate. On the other hand, the voids of closed cells are independent and not connected. Therefore, in the case of closed cells, sound does not penetrate into the interior of the material, and thus the sound absorption rate is also low. Additionally, as a method for distinguishing between a continuous bubble structure and a closed-cell structure, when gas contacts one side of the sample through a general air permeability test, if it can be confirmed that the gas passes through the voids in the sample and penetrates to the other side, it is a continuous bubble structure; if it cannot be confirmed, it is a closed-cell structure.

[0132] (Flow resistance per unit thickness of the porous body B)

[0133] As described above, it is preferred that the porous body B has a continuous bubble structure. When the flow resistance per unit thickness of the porous body B is large, it is difficult for sound to penetrate into the interior of the material, and the sound absorption rate also decreases. As the flow resistance per unit thickness of the porous body B, it is preferably 5000 NS / m 4 or more, and further preferably 20000 NS / m 4 or more, and further preferably 50000 Ns / m 4 or more. Additionally, as the upper limit, it is preferably 5000000 Ns / m 4 or less, and more preferably 1000000 Ns / m 4 or less.

[0134] (Fiber diameter of the porous body B as a nonwoven fabric)

[0135] As a shape example of the porous material for the porous body B, a nonwoven fabric can be cited. The fiber diameter of the nonwoven fabric is preferably 500 μm or less. As described above, the sound absorption mechanism of the nonwoven fabric is that when air passes through the nonwoven fabric, due to the friction between the air and the fibers, vibrations are converted into heat energy, thereby suppressing vibrations. For a nonwoven fabric of a certain unit volume, the finer the fiber diameter, the greater the proportion of the contact between the air passing through the sound and the fibers, and the greater the conversion amount of heat energy. As a result, the sound absorption property is higher. The fiber diameter is more preferably 100 μm or less, and further preferably 50 μm or less. In addition, if the fiber diameter is too fine, the voids are too small, and it is difficult for sound to penetrate into the material interior, which may instead cause a decrease in the sound absorption rate. Therefore, as the lower limit, 100 nm or more is preferred.

[0136] (Fiber length of the porous body B as a nonwoven fabric)

[0137] The fiber length of the porous body B as a nonwoven fabric is preferably 3 mm or more. If within this range, the porous body B is self-supporting as a nonwoven fabric, and the fiber entanglement and shedding are reduced. The fiber length is preferably 10 mm or more, and further preferably 30 mm or more. In addition, there is no particular limitation on the upper limit. For example, the nonwoven fabric of the porous body B can also be composed of extremely long single fibers like the fibers spun by the electrospinning method or the meltblowing method. It should be noted that as a method for improving the self-supporting property of the nonwoven fabric, methods such as joining the fiber entanglement points like the substrate binder method (Mat Binder) and artificially entangling the fibers like the needling method can be cited.

[0138] 〈Lamination method of nonwoven fabric A and porous body B〉

[0139] The non-woven fabric A can be laminated with the porous body B using various methods. As the lamination method, the non-woven fabric A and the porous body B can be simply overlapped naturally without bonding them. If the two are bonded, the porous body B acts as an adhesive for the non-woven fabric A, suppressing the vibration of the non-woven fabric A and improving the sound insulation property. Therefore, bonding is preferred. In addition, as a method of bonding the two, examples include a method of bonding only by heating the surface of the non-woven fabric A with an infrared (IR) heater or the like and performing heat fusion, a method of applying a hot melt-based adhesive to the surface of the non-woven fabric A by a curtain coating method or the like and then heating and heat-fusing it, and the like. In addition, when using a non-woven fabric as the porous body B, it is also possible to laminate them by preparing aqueous dispersions of the non-woven fabric A and the porous body B respectively and using the wet papermaking method to make a sheet in the order of non-woven fabric A → porous body B (or porous body B → non-woven fabric A). It should be noted that when laminating as a three-dimensional molded body, it is preferable to use the pulp molding method. Specifically, first, bath tanks A and B for dispersing the fibers of the non-woven fabric A and the porous body B with water respectively are prepared. Then, by dipping and sucking a shaping mold with a metal mesh surface in the order of bath tank A → bath tank B (or bath tank B → bath tank A) and laminating the shaping molds, it is possible to fix them in the shape of the shaping mold.

[0140] It should be noted that the higher the bonding strength, the less likely the non-woven fabric A is to peel off from the porous body B due to the vibration caused by sound propagation. As the tensile shear strength (according to JIS K6849), it is preferably 5 MPa or more, more preferably 10 MPa or more. In addition, there is no particular limitation on the upper limit. As one example, it can be 1 GPa or less.

[0141] <Lamination order of non-woven fabric A and porous body B>

[0142] As the lamination order of the non-woven fabric A and the porous body B, from the viewpoint of sound insulation, when observed from the sound source side, the directions of the non-woven fabric A and the porous body B do not change the effect. However, from the viewpoint of sound absorption, the effect varies depending on the lamination order. When it is desired to increase the sound absorption rate in the low-frequency region, since the sound in the low-frequency region is converted into heat energy by the plate film vibration of the non-woven fabric A and can be efficiently absorbed, it is preferable to dispose the non-woven fabric A on the sound source side. At this time, the porous body B functions as an air layer. On the other hand, when it is desired to increase the sound absorption rate in the high-frequency region, since the sound wave penetrates into the interior of the porous body B and the sound in the high-frequency region can be converted into heat energy by fiber friction and can be efficiently absorbed, it is preferable to dispose the porous body B on the sound source side.

[0143] <Lamination structure>

[0144] The soundproof material of this embodiment laminates at least two layers of the non-woven fabric A and the porous body B.

[0145] From the viewpoint of improving the sound insulation performance as a soundproof material, it is preferable to stack the non-woven fabric A, the porous body B, and the soundproof material in the described order to form a structure called a double wall. The soundproof material is not particularly limited, and examples thereof include non-breathable materials such as plastic plates and metal plates. In addition, a woven fabric, non-woven fabric, or foam of continuous bubbles with a low air permeability of 500,000 Ns / m 4 or more can be used as the soundproof material, and the non-woven fabric A can also be used as the soundproof material.

[0146] When the non-woven fabric A and the soundproof material are directly stacked, both the non-woven fabric A and the soundproof material transmit the vibration caused by the sound wave, and the transmission loss of the laminate is significantly lower than the sum of the transmission losses of the individual materials. If the porous body B is inserted between the laminates to make each material completely independent, the transmission loss of the laminate can be made close to the sum of the transmission losses of the individual materials. In particular, in the high-frequency region, the effect is significant.

[0147] In addition, the greater the thickness of the porous body B, the more the vibration transmission between the non-woven fabric A and the soundproof material is suppressed, and the higher the sound insulation performance of the laminate. Therefore, the upper limit of the thickness of the porous body B is not particularly limited, but from a practical viewpoint, it can be 100 mm or less. In addition, as the lower limit, it is preferably 3 mm or more, more preferably 5 mm or more, further preferably 8 mm or more, particularly preferably 10 mm or more, and most preferably 15 mm or more.

[0148] In addition, a film with a thickness of 0.001 mm of the non-woven fabric A and the soundproof material can also exhibit the effect of a double wall, but the greater the thickness, the higher the sound insulation performance of the laminate. Therefore, the upper limit is not particularly limited, but from a practical viewpoint, it can be 100 mm or less. In addition, as the lower limit, it is preferably 0.1 mm or more, more preferably 0.5 mm or more, further preferably 1.0 mm or more, particularly preferably 2.0 mm or more, and most preferably 3.0 mm or more.

[0149] As the stacking order, it is sufficient to arrange the porous body B between the non-woven fabric A and the soundproof material. From the viewpoint of sound insulation, when observed from the sound source side, the directions of the non-woven fabric A and the soundproof material do not change the effect. However, from the viewpoint of sound absorption, considering that the sound wave is more efficiently absorbed when it penetrates into the porous body B, it is preferable to arrange the side with lower air permeability on the sound source side. In addition, even if the porous body B is arranged at the end and the non-woven fabric A and the soundproof material are directly stacked, the effect of a double wall cannot be obtained.

[0150] As a method of laminating the laminate, even if they are simply overlapped naturally, the effect of a double wall can be exhibited. However, by bonding them, the porous body B of the intermediate functions as an adhesive for the non-woven fabric A and the sound insulation material, suppressing the vibration of the non-woven fabric A and the sound insulation material, and improving the sound insulation property. Therefore, bonding is preferred. In addition, as a method of bonding the porous body B as the sound insulation material, hot melt bonding, use of an adhesive, use of an adhesive tape, etc. are considered.

[0151] When applying the lamination of this double wall to a sound source device that requires sound insulation, considering the frame body of the sound source device itself as the sound insulation material, by laminating in the order of non-woven fabric A / porous body B / frame body, the effect of a double wall can be easily obtained.

[0152] 〈Use〉

[0153] The sound insulation material of the present invention can provide a sound insulation material that exhibits sound absorption performance and has excellent sound insulation in a wide frequency range of 200 Hz to 2000 Hz by changing the composition of the layer provided on the porous material. The sound insulation material of the present invention can also be formed into a two-dimensional sheet. However, by further three-dimensionally forming the non-woven fabric A seamlessly using a molding method such as injection molding, it becomes a thin layer with excellent heat resistance and flame retardancy. Therefore, when used for automotive applications, it can also follow the complex mechanical shapes of devices such as sound source devices. The main uses are listed below.

[0154] For automotive applications, it can be applied to large parts such as hood mufflers, outer dashboard mufflers, inner dashboard mufflers (dashboard sound insulation pads), fender liners, wheelhouse liners, fairing inner mufflers, inner dashboard mufflers, side door trims, rear door inner trims, rear trunk side trims, trunk mats, floor mufflers (floor undercovers, floor carpets), engine mufflers, roof liners, rear shelves, rear door trims, sound insulation ducts, melt sheets, transmission sound insulation pads, engine undercovers (motor undercovers in the case of Electric Vehicles, EVs), etc. In addition, as medium and small three-dimensional covers, it can be applied to covers for drive devices such as engines, speed reducers attached to engines, drive shafts, torque converters, gear transmission devices, reduction devices, differential gear devices, differential limiting devices, etc., covers for electrical components such as electric pumps (water, oil circulation), air conditioning electric compressors, air conditioning ducts, electric actuators, inverters, converters, etc. In particular, in the case of EVs, etc., it can be applied to covers for electric drive devices such as electric motors, speed reducers attached to motors, etc. The sound insulation material of the present invention can be three-dimensionally formed into a thin layer and seamlessly, so it is more suitable for medium and small three-dimensional covers and can be used for covers for electrical components such as electric pumps (water, oil circulation), air conditioning electric compressors, air conditioning ducts, electric actuators, inverters, converters, etc. that generate noise and vibration in the range of 200 Hz to 2000 Hz, and covers for electric drive devices such as electric motors, speed reducers attached to motors, etc.

[0155] Example

[0156] Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0157] First, the measurement method and the like will be described.

[0158] <Measurement Method>

[0159] <Average fiber diameter (Method A / Method B), average fiber length, fibrillation rate, area refinement ratio of fibrillated fiber>

[0160] For the average fiber diameter (Method A), average fiber length, fibrillation rate, and area refinement ratio of fibrillated fiber, using a fiber image analyzer (manufactured by TechPap company, Morfi-Neo), under the condition of taking a photo for 3 minutes (measuring at least 120,000 or more fibers), the measurement is carried out through the following steps. It should be noted that the minimum fiber length as the measurement object is 20 μm.

[0161] (1) Disperse the fibrillated fiber in pure water to prepare a 1 L aqueous dispersion. Here, the final concentration of the solid component of the fibrillated fiber is 0.004% by mass. It should be noted that in the case of an aqueous dispersion of fibrillated fiber of 2% by mass or less, the dispersion treatment is carried out by simply mixing with a spatula or the like. In the case of an aqueous dispersion of 2% by mass or more, a water-containing filter cake or powder, etc., a high-shear homogenizer (manufactured by IKA company, trade name "Ultra-turrax T18") is used, and the dispersion treatment is carried out under the treatment condition of a rotation speed of 25,000 rpm × 5 minutes.

[0162] (2) Supply the aqueous dispersion prepared in step (1) to an automatic sampler for measurement.

[0163] (3) According to the measurement results, read the average fiber width (μm), fines-fibers mean length (μm), macro fibrillation index (%), and fine content in area (%) as the average fiber diameter (Method A), average fiber length, fibrillation rate, and area refinement ratio, respectively.

[0164] The average fiber diameter (Method B) of fibrillated fibers was measured using a specific surface area / pore size distribution measuring device (manufactured by Quantachrome Instruments company, model NOVA-4200e) through the following steps. It should be noted that for fibrillated fibers such as fibrillated cellulose microfibers formed by dry aggregation, the measurement was carried out after the following pretreatment.

[0165] [Pretreatment]

[0166] (1) The aqueous dispersion of fibrillated microfibers was filtered to produce a wet filter cake.

[0167] (2) The obtained wet filter cake was added to tert-butanol and diluted with tert-butanol to make the solid content concentration of the fibrillated fibers 0.5 wt%, and dispersion treatment was carried out using a high-shear homogenizer (manufactured by IKA company, trade name “Ultra-turrax T18”) under the treatment conditions of a rotation speed of 25000 rpm for 5 minutes.

[0168] (3) The obtained dispersion was weighed to make the unit area weight 10 g / m 3 , and filtered with filter paper to obtain a sheet.

[0169] (4) The obtained sheet was not peeled off from the filter paper, and was sandwiched between two larger filter papers. While pressing the edge of the filter paper with a heavy object from above, it was dried in an oven at 150 °C for 5 minutes to obtain a porous sheet.

[0170] [Measurement of specific surface area and calculation of fiber diameter]

[0171] (1) 0.2 g of the solid component of the fibrillated fibers (the porous sheet prepared by pretreatment) was dried under vacuum at 120 °C for 5 minutes.

[0172] (2) After drying, the nitrogen adsorption amount under the boiling point conditions of liquid nitrogen was measured at 5 points in the range where the relative vapor pressure (P / P0) was 0.05 or more and 0.2 or less (multi-point method), and the BET specific surface area (m 2 / g) was calculated using the device program.

[0173] (3) Based on the obtained BET specific surface area value Y (m 2 / g), taking the average fiber length X (nm) and the density ρ (g / cm 3 ) of the fibrillated fibers, the average fiber diameter (Method B) was calculated by the following formula.

[0174] Average fiber diameter (nm) = 1 / (2.5 × ρ × Y × 10 -4 ).

[0175] <Thickness of Nonwoven Fabric A and Porous Body B>

[0176] The thickness of the sample was measured according to the following steps.

[0177] (1) Five 5 cm × 5 cm sized slices were obtained from 5 different locations of the sample.

[0178] (2) The thickness of each slice was measured using an ABS digital micrometer ID-CX (manufactured by Mitutoyo Corporation, Japan). At this time, a flat measuring probe with a diameter of Φ15 mm was used for the measuring probe.

[0179] (3) The average value of the 5 points obtained in step (2) was taken as the thickness of the sample.

[0180] <Self-supporting property of Nonwoven Fabric A, Fiber shedding property>

[0181] In each example and comparative example, a 20 cm square sample was prepared, and the self-supporting property of Nonwoven Fabric A and fiber shedding were evaluated according to the following criteria.

[0182] [Self-supporting property]

[0183] 〇: It will not bend or break even with one-handed operation.

[0184] △: It will bend during one-handed operation, but will not break.

[0185] ×: It will break during one-handed operation.

[0186] [Fiber shedding]

[0187] 〇: No shed fibers adhere when touching or rubbing the surface by hand.

[0188] △: Shed fibers will adhere when rubbing the surface by hand, but no shed fibers adhere when only touching.

[0189] ×: Shed fibers adhere when touching the surface by hand.

[0190] <Measurement of Flow Resistance per Unit Thickness of Nonwoven Fabric A>

[0191] The flow resistance per unit thickness of Nonwoven Fabric A was measured using a flow resistance system (manufactured by Nihon Onkyo Engineering company, AirReSys) in accordance with ISO9053 through the following steps. First, a specified number of φ42 mm circular discs were cut out from Nonwoven Fabric A. Then, air with a flow rate of 0.5 m / s was passed through the cut Nonwoven Fabric A, the differential pressure before and after the Nonwoven Fabric A was read, and the result was normalized by the flow rate and the thickness of the Nonwoven Fabric A to calculate.

[0192] <Measurement of the Porosity of Nonwoven Fabric A>

[0193] The porosity of nonwoven fabric A is calculated using the bulk density and true density of nonwoven fabric A according to the following formula.

[0194] ε [%] = (1 - S1 / S2) × 100

[0195] {In the formula, ε: porosity, S1: bulk density, S2: true density}.

[0196] It should be noted that the true density of nonwoven fabric A is calculated using the following material density. In addition, in the case of mixing two materials, the total value obtained by multiplying the true density of each by the volume ratio is used as the true density of nonwoven fabric A.

[0197] Cellulose: 1.50 g / cm 3 .

[0198] Polyethylene terephthalate (PET): 1.38 g / cm 3 .

[0199] Polyacrylonitrile: 1.18 g / cm 3 .

[0200] Nylon 66: 1.14 g / cm 3 .

[0201] Nylon 6: 1.13 g / cm 3 .

[0202] <Measurement of the Tortuosity of Nonwoven Fabric A>

[0203] The tortuosity of nonwoven fabric A is measured using a tortuosity / characteristic length measurement system (manufactured by Nihon Onkyo Engineering company, TORVITH) through the following steps. First, a specified number of φ42 mm circular disks are cut out from nonwoven fabric A. Then, the square of the sound velocity ratio between the free space without nonwoven fabric A and the sound velocity of the sound wave passing through nonwoven fabric A is obtained. Specifically, it is obtained by measuring the time required for ultrasonic waves of 200 - 300 Hz to reach the receiver from the transmitter. The square of the sound velocity ratio with or without this nonwoven fabric A has a frequency characteristic. In particular, in the ultrasonic region, if the reciprocal of the square root of the frequency is taken on the horizontal axis, it becomes a straight line sloping upward to the right. The tortuosity is defined as the limit value when the frequency is set to infinity. Therefore, the tortuosity is obtained as the value corresponding to the y-axis intercept at this time.

[0204] <Sound Insulation Evaluation>

[0205] In each of the examples and comparative examples, the transmission loss of the sample was measured by the double load method using a vertical incidence sound absorption rate / transmission loss measurement system Win Zac (manufactured by Nihon Onkyo Engineering company) to evaluate the sound insulation performance. The inner diameter of the acoustic tube was 40 mm and the measurement was carried out. White noise was used as the sound source. In addition, in the laminate of non-woven fabric A and porous body B, the measurement was carried out in such a way that non-woven fabric A was on the incident side of the sound wave.

[0206] 《Fibrillated Fiber》

[0207] 〈Fibrillated Fiber A〉

[0208] A fibrillated fiber made of polyacrylonitrile (manufactured by Japan Exlan Industry company: BiPUL, solid content 18% by mass) was used as fibrillated fiber A. The evaluation results of the fibrillation rate, area refinement ratio, average fiber length, and average fiber diameter are shown in Table 1 below.

[0209] 〈Fibrillated Fiber B〉

[0210] Lyocell cut fibers (3 mm in length) as regenerated (type II) cellulose fibers obtained from Nisshinbo Holdings, Inc. were placed in a washing net, surfactant was added, and they were washed with water multiple times in a washing machine to remove the sizing agent on the fiber surface. After being simply dispersed using a laboratory pulper (manufactured by Aikawa Iron Works Co., Ltd.), they were transported to a tank. Using a 14-inch single-disc refiner (manufactured by Aikawa Iron Works Co., Ltd.) equipped with a disc having a blade width of 2.5 mm and a groove width of 7.0 mm and connected to the tank, fibrillation was carried out while circulating the pulp. At this time, it was started from a blade gap of 2.0 mm, and while gradually shortening the blade gap, the final blade gap was set to 0.05 mm. After the blade gap reached 0.05 mm, the operation was continued while further confirming the flow rate. When the total amount of the pulp passed through the disc part 30 times, the operation was ended. Then, a high-pressure homogenizer (manufactured by Niro Soavi company, NS015H) was used to carry out a fibrillation treatment. At this time, the pulp was processed in batches and the number of processing times was 5 times. The obtained microfibrillated cellulose was used as fibrillated fiber B. The evaluation results of the fibrillation rate, area refinement ratio, average fiber length, and average fiber diameter are shown in Table 1 below.

[0211] 〈Fibrillated Fiber C〉

[0212] Using cotton linter pulp obtained from Nippon Pulp Trading Co., Ltd. as type I natural cellulose, it was impregnated in water such that the cotton linter pulp became 1.5% by mass. After being simply dispersed using a laboratory pulper (manufactured by Aikawa Iron Works Co., Ltd.), it was transferred to a tank. Using a 14-inch single-disc refiner (manufactured by Aikawa Iron Works Co., Ltd.) equipped with a disc having a blade width of 2.5 mm and a groove width of 7.0 mm and connected to the tank, fibrillation was carried out while circulating the pulp. At this time, it was operated starting from a blade gap of 2.0 mm, and while gradually shortening the blade gap, the final blade gap was set to 0.05 mm. After the blade gap reached 0.05 mm, operation was continued while further confirming the flow rate. When the total amount of the pulp passed through the disc part 30 times, the operation was ended. The obtained microfibrillated cellulose was used as fibrillated fiber C. The results of evaluating the fibrillation ratio, area refinement ratio, average fiber length, and average fiber diameter are shown in Tables 2 and 3 below.

[0213] 〈Fibrillated fiber D〉

[0214] The fibrillated fiber C was further fibrillated using a high-pressure homogenizer (manufactured by Niro Soavi company, NS015H). At this time, the pulp was processed batchwise, and the number of processing times was 10 times. The results of evaluating the fibrillation ratio, average fiber length, and average fiber diameter are shown in Table 2 below.

[0215] 〈Fibrillated fiber E〉

[0216] Using cotton linter pulp obtained from Nippon Pulp Trading Co., Ltd. as type I natural cellulose, it was impregnated in water such that the cotton linter pulp became 1.5% by mass. After being simply dispersed using a pressing mixer (manufactured by Transgate company: HBH450) under the conditions of high-speed mode and 5 minutes, the obtained microfibrillated cellulose was used as fibrillated fiber E. The results of evaluating the fibrillation ratio, area refinement ratio, average fiber length, and average fiber diameter are shown in Table 3 below.

[0217] <<Manufacturing Example of Soundproof Material>>

[0218] 〈Example 1〉

[0219] Nonwoven fabric A1 was produced using fibrillated fiber A as a fibrillated fiber and PET staple fiber A (manufactured by Teijin Limited: TA04PN, fineness: 0.1 T, average fiber diameter: 3.0 μm, cut length: 3 mm) as a non-fibrillated fiber through the following steps. The fibrillated fiber and the non-fibrillated fiber were added to pure water such that the weight ratio of the solid components was 10:90, and the final concentration of the solid components was 0.5%. The prepared slurry was stirred using a household mixer for 4 minutes to prepare a slurry. The above-prepared slurry was made to have a basis weight of 300 g / m2 It is put into a batch paper machine (manufactured by Kumagai Riki Kogyo Co., Ltd., automatic angular sheet machine 25 cm × 25 cm, 80 mesh) equipped with a filter cloth (manufactured by Shikishima Canvas Co., Ltd., TT35) in such a manner, and then, papermaking (dehydration) is carried out by setting the degree of vacuum relative to atmospheric pressure to 50 KPa. The filter cloth is covered on the surface of the wet concentrated composition placed on the filter cloth, peeled off from the wire, and pressed at a pressure of 1 kg / cm 2 for 1 minute. Then, it is dried for about 120 seconds using a drum dryer with the surface temperature set at 130°C to obtain non-woven fabric A1.

[0220] In addition, the obtained non-woven fabric A1 and a commercially available thick felt with a thickness of 8.0 mm as the porous body B are naturally laminated as a soundproof material. Various physical properties of the obtained non-woven fabric A1 and porous body B, the soundproof characteristics of the soundproof material, etc. are shown in Table 1 below.

[0221] 〈Example 2〉

[0222] Except that fibrillated fiber B is used as the fibrillated fiber, non-woven fabric A2 is obtained by the same method as in Example 1. In addition, the obtained non-woven fabric A2 and a thick felt with a thickness of 8.0 mm as the porous body B are naturally laminated as a soundproof material. Various physical properties of the obtained non-woven fabric A2 and porous body B, the soundproof characteristics of the soundproof material, etc. are shown in Table 1 below.

[0223] 〈Example 3〉

[0224] Fibrillated fiber C is used as the fibrillated fiber, and the fibrillated fiber and non-fibrillated fiber are set to a solid content weight ratio of 5:95. Except for this, non-woven fabric A3 is obtained by the same method as in Example 1. In addition, the obtained non-woven fabric A3 and a thick felt with a thickness of 8.0 mm as the porous body B are naturally laminated as a soundproof material. Various physical properties of the obtained non-woven fabric A3 and porous body B, the soundproof characteristics of the soundproof material, etc. are shown in Table 1 below.

[0225] 〈Example 4〉

[0226] Except that fibrillated fiber C is used as the fibrillated fiber, non-woven fabric A4 is obtained by the same method as in Example 1. In addition, the obtained non-woven fabric A4 and a thick felt with a thickness of 8.0 mm as the porous body B are naturally laminated as a soundproof material. Various physical properties of the obtained non-woven fabric A4 and porous body B, the soundproof characteristics of the soundproof material, etc. are shown in Table 1 below.

[0227] 〈Example 5〉

[0228] Nonwoven fabric A5 was obtained by the same method as in Example 4, except that the fibrillated fiber and the non-fibrillated fiber were set at a solid component weight ratio of 20:80. In addition, the obtained nonwoven fabric A5 was naturally laminated with a thick felt having a thickness of 8.0 mm as the porous body B to be used as a soundproof material. Various physical properties of the obtained nonwoven fabric A5 and the porous body B, and the soundproof characteristics of the soundproof material are shown in Table 1 below.

[0229] <Example 6>

[0230] Nonwoven fabric A6 was obtained by the same method as in Example 4, except that the fibrillated fiber and the non-fibrillated fiber were set at a solid component weight ratio of 30:70. In addition, the obtained nonwoven fabric A6 was naturally laminated with a thick felt having a thickness of 8.0 mm as the porous body B to be used as a soundproof material. Various physical properties of the obtained nonwoven fabric A6 and the porous body B, and the soundproof characteristics of the soundproof material are shown in Table 1 below.

[0231] <Example 7>

[0232] Nonwoven fabric A7 was obtained by the same method as in Example 4, except that the non-fibrillated fiber used was PET fiber B (manufactured by Teijin Limited, TA04N, fineness 0.5 T, average fiber diameter: 7.0 μm, cut length 5 mm). In addition, the obtained nonwoven fabric A7 was naturally laminated with a thick felt having a thickness of 8.0 mm as the porous body B to be used as a soundproof material. Various physical properties of the obtained nonwoven fabric A7 and the porous body B, and the soundproof characteristics of the soundproof material are shown in Table 1 below.

[0233] <Example 8>

[0234] Nonwoven fabric A8 was obtained by the same method as in Example 4, except that the non-fibrillated fiber used was PET fiber B and the fibrillated fiber and the non-fibrillated fiber were set at a solid component weight ratio of 20:80. In addition, the obtained nonwoven fabric A8 was naturally laminated with a thick felt having a thickness of 8.0 mm as the porous body B to be used as a soundproof material. Various physical properties of the obtained nonwoven fabric A8 and the porous body B, and the soundproof characteristics of the soundproof material are shown in Table 1 below.

[0235] <Example 9>

[0236] The non-fibrillated fiber used is PET fiber C (manufactured by Teijin Limited, TT04N, fineness 1.7 T, average fiber diameter: 12.0 μm, cut length 5 mm). The fibrillated fiber and the non-fibrillated fiber are set at a solid component weight ratio of 20:80. Except for this, non-woven fabric A9 is obtained by the same method as in Example 4. In addition, the obtained non-woven fabric A9 and a thick felt with a thickness of 8.0 mm as the porous body B are naturally laminated to be used as a soundproof material. Various physical properties of the obtained non-woven fabric A9 and the porous body B, the soundproof characteristics of the soundproof material, etc. are shown in Table 2 below.

[0237] 〈Example 10〉

[0238] The non-fibrillated fiber used is PET fiber D (manufactured by Teijin Limited, TA04N, fineness 8.0 T, average fiber diameter: 30.0 μm, cut length 5 mm). The fibrillated fiber and the non-fibrillated fiber are set at a solid component weight ratio of 2:98. Except for this, non-woven fabric A10 is obtained by the same method as in Example 4. In addition, the obtained non-woven fabric A10 and a thick felt with a thickness of 8.0 mm as the porous body B are naturally laminated to be used as a soundproof material. Various physical properties of the obtained non-woven fabric A10 and the porous body B, the soundproof characteristics of the soundproof material, etc. are shown in Table 2 below.

[0239] 〈Example 11〉

[0240] The non-fibrillated fiber used is PET fiber D (manufactured by Teijin Limited, TA04N, fineness 8.0 T, average fiber diameter: 30.0 μm, cut length 5 mm). The fibrillated fiber and the non-fibrillated fiber are set at a solid component weight ratio of 1:99. Except for this, non-woven fabric A11 is obtained by the same method as in Example 4. In addition, the obtained non-woven fabric A11 and a thick felt with a thickness of 8.0 mm as the porous body B are naturally laminated to be used as a soundproof material. Various physical properties of the obtained non-woven fabric A11 and the porous body B, the soundproof characteristics of the soundproof material, etc. are shown in Table 2 below.

[0241] 〈Example 12〉

[0242] Except that the fibrillated fiber and the non-fibrillated fiber are set at a solid component weight ratio of 3:97, non-woven fabric A12 is obtained by the same method as in Example 4. In addition, the obtained non-woven fabric A12 and a thick felt with a thickness of 8.0 mm as the porous body B are naturally laminated to be used as a soundproof material. Various physical properties of the obtained non-woven fabric A12 and the porous body B, the soundproof characteristics of the soundproof material, etc. are shown in Table 2 below.

[0243] 〈Example 13〉

[0244] For the non-fibrillated fiber, PET fiber C is used. The fibrillated fiber and the non-fibrillated fiber are set at a solid component weight ratio of 40:60. Except for this, nonwoven fabric A13 is obtained by the same method as in Example 4. In addition, the obtained nonwoven fabric A13 and a thick felt with a thickness of 8.0 mm as porous body B are naturally laminated to be used as a soundproof material. The various physical properties of the obtained nonwoven fabric A13 and porous body B, the soundproof characteristics of the soundproof material, etc. are shown in Table 2 below.

[0245] 〈Example 14〉

[0246] For the fibrillated fiber, fibrillated fiber D is used. The fibrillated fiber and the non-fibrillated fiber are set at a solid component weight ratio of 100:0. Except for this, nonwoven fabric A14 is obtained by the same method as in Example 4. In addition, the obtained nonwoven fabric A14 and a thick felt with a thickness of 8.0 mm as porous body B are naturally laminated to be used as a soundproof material. The various physical properties of the obtained nonwoven fabric A14 and porous body B, the soundproof characteristics of the soundproof material, etc. are shown in Table 2 below.

[0247] 〈Example 15〉

[0248] Except that the fibrillated fiber and the non-fibrillated fiber are set at a solid component weight ratio of 100:0, nonwoven fabric A15 is obtained by the same method as in Example 4. In addition, the obtained nonwoven fabric A15 and a thick felt with a thickness of 8.0 mm as porous body B are naturally laminated to be used as a soundproof material. The various physical properties of the obtained nonwoven fabric A15 and porous body B, the soundproof characteristics of the soundproof material, etc. are shown in Table 2 below.

[0249] 〈Example 16〉

[0250] Except that fibrillated fiber D is used for the fibrillated fiber, nonwoven fabric A16 is obtained by the same method as in Example 4. In addition, the obtained nonwoven fabric A16 and a thick felt with a thickness of 8.0 mm as porous body B are naturally laminated to be used as a soundproof material. The various physical properties of the obtained nonwoven fabric A16 and porous body B, the soundproof characteristics of the soundproof material, etc. are shown in Table 2 below.

[0251] 〈Example 17〉

[0252] Except that fibrillated fiber E is used for the fibrillated fiber, nonwoven fabric A17 is obtained by the same method as in Example 4. In addition, the obtained nonwoven fabric A17 and a thick felt with a thickness of 8.0 mm as porous body B are naturally laminated to be used as a soundproof material. The various physical properties of the obtained nonwoven fabric A17 and porous body B, the soundproof characteristics of the soundproof material, etc. are shown in Table 3 below.

[0253] 〈Example 18〉

[0254] Nonwoven fabric A18 was obtained by the same method as in Example 4. In addition, the obtained nonwoven fabric A18 was naturally laminated with a commercially available polyester nonwoven fabric with a thickness of 11.0 mm as the porous body B to be used as a soundproof material. Various physical properties of the obtained nonwoven fabric A18 and the porous body B, and the soundproof characteristics of the soundproof material are shown in Table 3 below.

[0255] 〈Example 19〉

[0256] Nonwoven fabric A19 was obtained by the same method as in Example 4. In addition, the obtained nonwoven fabric A19 was naturally laminated with a commercially available polyurethane foam with a thickness of 11.0 mm as the porous body B to be used as a soundproof material. Various physical properties of the obtained nonwoven fabric A19 and the porous body B, and the soundproof characteristics of the soundproof material are shown in Table 3 below.

[0257] 〈Example 20〉

[0258] Nonwoven fabric A20 was obtained by the same method as in Example 4. In addition, the obtained nonwoven fabric A20 was naturally laminated with a foam (manufactured by Asahi Kasei Corporation, SunForce) of polyamide 666 (copolymer of polyamide 66 and polyamide 6) with a thickness of 6.0 mm as the porous body B to be used as a soundproof material. Various physical properties of the obtained nonwoven fabric A20 and the porous body B, and the soundproof characteristics of the soundproof material are shown in Table 3 below.

[0259] 〈Comparative Example 1〉

[0260] Using a carding machine, sea-island type fibers of 180 g / m 2 and polyethylene terephthalate staple fibers (Toray Industries, Inc., "Tetoron") with an average fiber length of 51 mm and a single fiber fineness of 2.2 dtex of 180 g / m 2 were opened to form a double-layer structure, and then a web was made using a cross-lapper. The web was processed with a needle loom to obtain a nonwoven fabric with a basis weight of 323 g / m 2 and a thickness of 0.75 mm. Then, the above nonwoven fabric was treated with a 1% sodium hydroxide aqueous solution at a temperature of 95°C and a liquor ratio of 1:40 (mass ratio) to dissolve polylactic acid, and a nonwoven fabric S1 with a basis weight of 234 g / m 2 and a thickness of 1.6 mm composed of N6 nanofibers with an average fiber diameter of 150 nm and polyethylene terephthalate filaments was obtained. In addition, the obtained nonwoven fabric S1 was naturally laminated with a thick felt with a thickness of 8.0 mm as the porous body B to be used as a soundproof material. Various physical properties of the obtained nonwoven fabric S1 and the porous body B, and the soundproof characteristics of the soundproof material are shown in Table 3 below.

[0261] <Comparative Example 2>

[0262] A nonwoven fabric S2 composed of nylon 66 nanofibers with an average fiber diameter of 320 nm was produced by the electrospinning method (electrostatic spinning method). In addition, the obtained nonwoven fabric S2 was naturally laminated with a thick felt with a thickness of 8.0 mm as the porous body B to be used as a soundproof material. Various physical properties of the obtained nonwoven fabric S2 and the porous body B, the soundproof characteristics of the soundproof material, etc. are shown in Table 3 below.

[0263] <Comparative Example 3>

[0264] A nonwoven fabric S3 was obtained by the same method as in Example 4. In addition, for the obtained nonwoven fabric S3, lamination with the porous body B was not performed. Various physical properties of the obtained nonwoven fabric S3, the soundproof characteristics of the soundproof material, etc. are shown in Table 3 below.

[0265] <Comparative Example 4>

[0266] PET fiber D was used as the non-fibrillated fiber, and the fibrillated fiber and the non-fibrillated fiber were set at a solid component weight ratio of 0:100. Except for this, a nonwoven fabric S4 was obtained by the same method as in Example 4. In addition, the obtained nonwoven fabric S4 was naturally laminated with a thick felt with a thickness of 8.0 mm as the porous body B to be used as a soundproof material. Various physical properties of the obtained nonwoven fabric S4 and the porous body B, the soundproof characteristics of the soundproof material, etc. are shown in Table 3 below.

[0267] <Example 21>

[0268] A 2V gear reduction electric motor (manufactured by Uster (FastUU), 12V 250W electric motor heavy-duty DC gear reduction brushed motor, with a 9-tooth sprocket) was fixed to a 10 mm stainless steel (Steel Use Stainless, SUS) table and rotated at 2950 rpm, and the noise A (600 Hz) after 5 minutes was measured. Then, in the form of setting a 5 mm air gap to follow the shapes of the electric motor and the reducer, a molded cover A with a thickness of 1 mm was made by the pulp molding method using the composition of the nonwoven fabric 1 in Example 1. This cover was set and rotated at 2950 rpm, and the noise B after 5 minutes was measured. The transmission loss was calculated based on the noise A and B, and the result was 10 dB.

[0269] <Example 22>

[0270] In Example 21, after covering the electric motor and the reducer with the molded cover A, it was covered with an 8 mm thick miscellaneous felt on the outside. This cover was set and rotated at 2950 rpm, and the noise C after 5 minutes was measured. The transmission loss was calculated based on the noise A and C, and the result was 15 dB.

[0271] <Example 23>

[0272] In Example 22, after covering the electric motor and the reduction gear with the forming cover A and the felt waste, it was covered with a 1-mm thick polypropylene outer shell on the outside. This cover was set and rotated at 2950 rpm, and the noise D after 5 minutes was measured. The transmission loss was obtained from the noises A and D, and the result was 20 dB.

[0273] <Example 24>

[0274] A 12-V electric compressor (manufactured by NEKPOKKA company) was fixed to a 10-mm thick SUS table, driven, and the noise E (600 Hz) after 5 minutes was measured. Then, in a form where a 5-mm air gap was set to follow the shape of the electric compressor, a 1-mm thick forming cover B was made by the pulp molding method with the composition of the nonwoven fabric 1 of Example 1. This cover was set and driven, and the noise F after 5 minutes was measured. The transmission loss was obtained from the noises E and F, and the result was 10 dB.

[0275] <Example 25>

[0276] In Example 24, after covering the electric compressor with the forming cover B, it was covered with an 8-mm thick felt waste on the outside. This cover was set and driven, and the noise G after 5 minutes was measured. The transmission loss was obtained from the noises E and G, and the result was 15 dB.

[0277] <Example 26>

[0278] In Example 25, after covering the electric compressor with the forming cover B and the felt waste, it was covered with a 1-mm thick polypropylene outer shell on the outside. This cover was set and driven, and the noise H after 5 minutes was measured. The transmission loss was obtained from the noises E and H, and the result was 20 dB.

[0279] <Example 27>

[0280] In the order of the nonwoven fabric A4 (thickness 1.0 mm) / coarse felt (thickness 8.0 mm) / polypropylene plate (thickness 1.0 mm) of Example 4, they were naturally laminated, cut into a size of 1000 m × 1000 m for each sample, and the transmission loss was evaluated. The measurement method was based on the sound intensity method according to JIS A 1441. In addition, as the measurement equipment, a small reverberation chamber - anechoic chamber (reverberation chamber capacity: 8.9 m 3 ) of the Second Acoustics Research Institute of Nihon Onkyo Engineering company was used. The reverberation chamber side was set as the sound source chamber, and the anechoic chamber side was set as the receiving chamber. The transmission loss was calculated by the following formula.

[0281] Transmission loss = (i) Sound power level incident on the specimen - (ii) Sound power level transmitted through the specimen.

[0282] (i) Sound power level incident on the specimen: Calculated from the average sound pressure levels at 5 points in the reverberation chamber.

[0283] (ii) Sound power level transmitted through the specimen: Calculated from the average sound intensity level on the sound wave transmission surface (7 points x 7 points = 49 points).

[0284] It should be noted that an open clamp with a side length of 900 mm is used as the clamping range for the specimen, and the outer periphery of the four sides is clamped 50 mm. In addition, the position of the sound intensity probe is maintained 170 mm from the sample surface.

[0285] The results of the transmission loss of the obtained non-woven fabric are shown in Table 4.

[0286] <Example 28>

[0287] In Example 27, they were naturally laminated in the order of non-woven fabric A4 (thickness 1.0 mm) / coarse felt (thickness 16.0 mm) / polypropylene plate (thickness 1.0 mm), and the transmission loss was evaluated. The side of the sound receiving chamber was set as a polypropylene plate, and the results of the transmission loss are shown in Table 4.

[0288] <Example 29>

[0289] In Example 27, they were naturally laminated in the order of non-woven fabric A4 (thickness 1.0 mm) / coarse felt (thickness 8.0 mm) / non-woven fabric A4 (thickness 1.0 mm), and the transmission loss was evaluated. The side of the sound receiving chamber was set as a polypropylene plate, and the results of the transmission loss are shown in Table 4.

[0290] <Comparative Example 5>

[0291] In Example 27, the same transmission loss test was carried out using only non-woven fabric A4. The results of the transmission loss are shown in Table 4.

[0292] <Comparative Example 6>

[0293] In Example 27, the same transmission loss test was carried out using only a coarse felt with a thickness of 8.0 mm. The results of the transmission loss are shown in Table 4.

[0294] <Comparative Example 7>

[0295] In Example 27, the same transmission loss test was carried out using only a polypropylene plate with a thickness of 1.0 mm. The results of the transmission loss are shown in Table 4.

[0296] <Comparative Example 8>

[0297] In Example 27, a coarse felt with a thickness of 8.0 mm and a polypropylene plate with a thickness of 1.0 mm were naturally laminated, and the transmission loss was evaluated. The side facing the sound recording room was the polypropylene plate, and the results of the transmission loss are shown in Table 4.

[0298] <Comparative Example 9>

[0299] In Example 27, a non-woven fabric A4 with a thickness of 1.0 mm and a polypropylene plate with a thickness of 1.0 mm were naturally laminated, and the transmission loss was evaluated. The side facing the sound recording room was the polypropylene plate, and the results of the transmission loss are shown in Table 4.

[0300] Table 1

[0301]

[0302] Table 2

[0303]

[0304] Table 3

[0305]

[0306] Table 4

[0307]

[0308] Industrial Applicability

[0309] The soundproofing material of the present invention exhibits sound absorption performance and excellent sound insulation in the range of 200 Hz to 2000 Hz. Therefore, it can suppress various noises such as engine noise, drive system noise, road noise, and wind noise in automobiles, etc., and can be suitably used as a sound absorption material for creating a comfortable interior space of a vehicle.

Claims

1. A soundproof material, characterized in that, the soundproof material is a soundproof material formed by laminating at least two layers including non-woven fabric A and porous body B, the non-woven fabric A is a non-woven fabric composed of fibers, and the porous body B is a molded body having a porous structure, the non-woven fabric A contains 1% by mass or more of fibrillated fibers.

2. The soundproof material according to claim 1, wherein, the soundproof material is a soundproof material formed by laminating at least three layers in the order of non-woven fabric A, porous body B, and sound insulation material, laminating non-woven fabric A, porous body B, and sound insulation material, the non-woven fabric A is a non-woven fabric composed of fibers, and the porous body B is a molded body having a porous structure.

3. The soundproof material according to claim 2, wherein, the sound insulation material is the non-woven fabric A.

4. The soundproof material according to claim 1 or 2, wherein, The flow resistance per unit thickness of the non-woven fabric A is 1,400,000 Ns / m 4 or more and 5,000,000,000 Ns / m 4 or less.

5. The soundproof material according to claim 1 or 2, wherein, the porosity of the non-woven fabric A is 60% or more and 96% or less.

6. The soundproof material according to claim 1 or 2, wherein, the tortuosity of the non-woven fabric A is 1.20 or more and 10.0 or less.

7. The soundproof material according to claim 1 or 2, wherein, the non-woven fabric A further contains non-fibrillated fibers.

8. The soundproof material according to claim 1 or 2, wherein, The areal density of the porous body B is 10,000 g / m 2 or less, and the thickness is 1 mm or more and 100 mm or less.

9. The soundproof material according to claim 1 or 2, wherein, the fibrillated fibers are at least one selected from the group consisting of microfibrillated cellulose, acrylic fiber pulp, aramid pulp, chitin nanofibers, chitosan nanofibers, and silk nanofibers.

10. The soundproof material according to claim 1 or 2, wherein, the fibrillation rate of the fibrillated fibers is 0.3% or more.

11. The soundproof material according to claim 1 or 2, wherein, based on the total mass of the non-woven fabric, the content of the fibrillated fibers is 3% by mass or more and 30% by mass or less.

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