Non-woven fabric

Abstract

Provided is a non-woven fabric which exhibits sound-absorbing performance and has excellent sound insulation properties in a wide frequency range in the range of 200 Hz to 2000 Hz. The present invention pertains to: a non-woven fabric containing fibrillated fibers and having a tensile modulus of elasticity of 10 MPa or more; a sound-proof material comprising the non-woven fabric; and a composite sound-proof material obtained by laminating the sound-proof material and a support body.

Description

Technical Field

[0001] The present invention relates to a nonwoven fabric, a sound-absorbing material, and a composite sound-absorbing material using the nonwoven fabric. Background Art

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

[0003] The frequency of noise depends on each sound source, and a sound-absorbing material suitable for each sound source is used. However, although nonwoven fabrics and foams, which are porous sound-absorbing materials commonly used in vehicle applications, show excellent sound absorption rates in the high-frequency band, they tend to have a decreased sound absorption rate on the low-frequency side. In contrast, it is known that the sound insulation performance can be improved in all frequency regions by further providing a layer on the surface of the porous material.

[0004] 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.

[0005] 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 is slightly larger than 10 mm and excellent sound absorption is shown in all frequency bands.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2018-154113.

[0009] Patent Document 2: International Publication No. 2017 / 006993. Summary of the Invention

[0010] Problems to be Solved by the Invention

[0011] However, although the existing technology improves the sound absorption performance by further providing a layer on the porous material, it hardly exerts its effect in terms of sound insulation performance. In addition, in order to cope with noises leaking from the inside of the vehicle to the outside, such as the driving sound of the engine, it is more effective to improve the sound insulation performance than the sound absorption performance of the sound-insulating material.

[0012] In view of the above situation, the problem to be solved by the present invention is to provide a non-woven fabric that exhibits sound absorption performance and excellent sound insulation in a wide frequency range within 200 Hz to 2000 Hz.

[0013] Means for Solving the Problem

[0014] The inventors of the present application conducted dedicated research and repeated experiments to solve this problem, and as a result, unexpectedly found that by including fibrillated fibers and non-fibrillated fibers of a specific length, this problem can be solved, thus completing the present invention.

[0015] That is, the present invention is as follows.

[0016] [1] A non-woven fabric, wherein the non-woven fabric includes fibrillated fibers, and the tensile elastic modulus of the non-woven fabric is 10 MPa or more.

[0017] [2] The non-woven fabric according to the above [1], wherein the non-woven fabric further includes non-fibrillated fibers.

[0018] [3] The non-woven fabric according to the above [1] or [2], wherein the average fiber length of the fibrillated fibers is 25 μm or more.

[0019] [4] The non-woven fabric according to the above [2] or [3], wherein the tensile elastic modulus of the non-fibrillated fibers is 5 GPa or more.

[0020] [5] The non-woven fabric according to any one of the above [1] to [4], wherein the flow resistance per unit thickness of the non-woven fabric is 1400000 Ns / m 4 or more and 5000000000 Ns / m 4 or less.

[0021] [6] The non-woven fabric according to any one of the above [1] to [5], wherein the tortuosity of the non-woven fabric is 1.8 or more and 12.0 or less.

[0022] [7] The non-woven fabric according to any one of the above [1] to [6], 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.

[0023] [8] The non-woven fabric according to any one of the above [1] to [7], wherein the fibrillation rate of the fibrillated fibers is 0.3% or more.

[0024] [9] The non-woven fabric according to any one of the above [1] to [8], 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.

[0025]

[10] The non-woven fabric according to any one of [1] to [9] above, wherein the average fiber length of the fibrillated fiber is 200 μm or less.

[0026]

[11] The non-woven fabric according to any one of [1] to

[10] above, wherein the tensile elastic modulus of the non-woven fabric is 40 MPa or more and 1000 MPa or less.

[0027]

[12] The non-woven fabric according to any one of [2] to

[11] above, wherein the tensile elastic modulus of the non-fibrillated fiber is 500 GPa or more.

[0028]

[13] A soundproof material, wherein the soundproof material is composed of the non-woven fabric according to any one of [1] to

[12] above.

[0029]

[14] A composite soundproof material, wherein the composite soundproof material is a composite soundproof material formed by laminating the soundproof material according to

[13] above and a support.

[0030]

[15] The soundproof material according to

[13] above, wherein the soundproof material is a three-dimensional soundproof material for automobiles.

[0031]

[16] The soundproof material according to

[14] above, wherein the soundproof material is a three-dimensional soundproof material for automobiles.

[0032] Advantages of the Invention

[0033] According to the present invention, by including fibrillated fibers and having a tensile elastic modulus of 10 MPa or more, a non-woven fabric excellent in sound insulation in the range of 200 Hz to 2000 Hz can be provided. Detailed Description of the Invention

[0034] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0035] <Non-woven Fabric>

[0036] A non-woven fabric refers to a structure formed by chemically or physically entangling or bonding a plurality of fibers to each other. In addition, the non-woven fabric of the present embodiment is characterized by containing fibrillated fibers and non-fibrillated fibers described later. In addition, the case where it is composed only of fibrillated fibers is also included in the non-woven fabric of the present embodiment.

[0037] (Thickness of the non-woven fabric)

[0038] The thickness of the non-woven fabric of the present embodiment is preferably 0.05 mm or more. The thickness of the non-woven fabric is measured according to the following steps.

[0039] (1) Five slices with a size of 5 cm × 5 cm are obtained from five different parts of the sample.

[0040] (2) The thickness of each slice is 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 is used for the measuring probe.

[0041] (3) The average value of the five points obtained in step (2) is taken as the thickness of the sample.

[0042] Generally, it is known that the thicker the thickness of a material, the higher its rigidity. In particular, when the rigidity of a soundproof 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 the non-woven fabric, 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, so 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.

[0043] It should be noted that as a method for controlling the thickness, it can be controlled by two methods: control based on the material and control based on the processing method. As a control method based on the material, it can be controlled by the content of fibrillated fibers, the fiber diameter and type of non-fibrillated fibers, etc. For example, by increasing the content of fibrillated fibers, the bonding distance between the short fibers forming the skeleton becomes closer, so the thickness becomes smaller. It should be noted that the thickness of the entire non-woven fabric A can also be increased by laminating two or more non-woven fabrics A.

[0044] (Flow resistance per unit thickness of the non-woven fabric)

[0045] The flow resistance per unit thickness of the non-woven fabric is preferably 1400000 Ns / m 4The above. 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 flow resistance per unit thickness of the non-woven fabric is measured by the following steps using a flow resistance system (manufactured by Nihon Onkyo Engineering company, AirReSys) in accordance with ISO9053. First, a specified number of circular disks with a diameter of φ42 mm are cut out from the non-woven fabric. Then, air with a flow velocity of 0.5 m / s is passed through the cut non-woven fabric, the differential pressure before and after the non-woven fabric is read, and the result is divided by the flow velocity and the thickness of the non-woven fabric for normalization and calculation. 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 7000000 Ns / m 4 or more, further preferably 15000000 Ns / m 4 or more, particularly preferably 42000000 Ns / m 4 or more, extremely 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 air and fibers, vibrations are converted into heat energy, thereby suppressing vibrations. 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 / m 4 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.

[0046] (Porosity of non-woven fabric)

[0047] The porosity of the non-woven fabric is preferably 96% or less. The porosity mentioned here represents the proportion of air per unit volume of the non-woven fabric in percentage. Therefore, the porosity of the non-woven fabric is calculated by the following formula using the bulk density and true density of the non-woven fabric.

[0048] ε[%]=(1 - S1 / S2)×100

[0049] {In the formula, ε: porosity, S1: bulk density, S2: true density}.

[0050] 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 taken as the true density of the nonwoven fabric. The lower the porosity, the smaller the voids in the nonwoven 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 due to the friction between the air and the fibers in the nonwoven fabric can be carried out efficiently, and the sound absorption rate also increases. The porosity of the nonwoven fabric is more preferably 90% or less, and further preferably 88% 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. Therefore, the lower limit is preferably 60% or more, more preferably 70% or more, further preferably 73% or more, particularly preferably 77% or more, and most preferably 82% or more.

[0051] (Tortuosity of nonwoven fabric)

[0052] The tortuosity of the nonwoven fabric is preferably 1.8 or more. The tortuosity mentioned here is a parameter representing the ratio of the path length of the fluid flowing inside the nonwoven fabric to the thickness of the nonwoven fabric. The higher the tortuosity, the higher the sound absorption property of the material. As described above, the sound absorption of the nonwoven fabric is carried out through the thermal energy conversion caused by the friction between the fibers and the air vibration. A high tortuosity means a high frequency of friction between the fibers and the air, and as a result, the sound absorption rate of the material also increases. The tortuosity of the nonwoven fabric is more preferably 2.0 or more, further preferably 2.3 or more, and particularly preferably 3.2 or more. In addition, if the tortuosity is too high, the flow resistance per unit thickness also becomes high, which will instead reduce the sound absorption rate of the material. Therefore, it is preferably 10.0 or less, more preferably 7.0 or less, further preferably 5.0 or less, particularly preferably 4.5 or less, and most preferably 4.0 or less.

[0053] It should be noted that the tortuosity of the nonwoven fabric 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 the nonwoven fabric. Then, the square of the sound velocity ratio between the free space without the nonwoven fabric and the sound velocity of the sound wave passing through the nonwoven fabric is obtained. Specifically, it is obtained by measuring the time required for ultrasonic waves of 300 kHz to reach the receiver from the transmitter. The square of the sound velocity ratio with and without the nonwoven fabric 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 the value corresponding to the y-axis intercept at this time.

[0054] (Fibrillated fiber)

[0055] In the specification of this application, fibrillated fibers refer to fibers formed by axial cracking, subdivision, and fuzzing of fibers. Fibrillated fibers can be generally classified into two types. One is fibers formed by destroying a part of the structure of fibers without a branched structure through physical and chemical methods, and the other is fibers fibrillated by intentionally creating fluff during the spinning of high molecular compounds. For example, as an example of the former, microfibrillated cellulose (which is a fiber obtained by microfibrillating cellulose fibers using at least one physical or chemical method, and has the same general names as CNF (Cellulose Nanofiber), CeNF (Cellulose NanoFibril), Cellulose Nanofiber, MFC (Microfibrillated Cellulose), cellulose microfibers, microfibrillar 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 with a thinner fiber diameter part compared to ordinary fibers without a branched structure due to their manufacturing method. Therefore, fibrillated fibers have a large surface area and tend to have a large number of curved structures. Due to such characteristics, in the non-woven fabric of this embodiment, 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 fibers, due to differences in fibrillization rate, fiber diameter, and surface state, the properties of the non-woven fabric will be affected. However, it is preferred that fibrillated fibers entangle with each other, increasing the flow resistance per unit thickness and tortuosity. From this perspective, as fibrillated fibers, it is preferred 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. Regardless of the above substances, if a fibrous material composed of a polymer and having a melting point higher than the thermal decomposition start temperature is selected, fibrillization is likely to occur, so it is preferred.

[0056] (Fibrillization rate of fibrillated fibers)

[0057] The fibrillation rate of the fibrillated fibers in the nonwoven fabric is preferably 0.3% or more. The fibrillation rate mentioned here refers to the ratio of the total value of the lengths of the branched fibers to the trunk length of the fibrillated fibers. If it is within this range, sufficient effects 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. In addition, the fibers fibrillated and thinned exert an effect on 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 2.1% or more, and most preferably 2.4 or more. As the upper limit of the fibrillation rate, there is no particular limitation, and it may be 100% or less, may be 10% or less, or may be 3% or less.

[0058] In addition, for the fibrillation rate of the fibrillated fibers, the average fiber length and the average fiber diameter (method A), and the area refinement ratio described later, they are measured by the following steps using a fiber image analyzer (manufactured by TechPap company, Morfi-Neo) under the condition of taking pictures for 3 minutes (measuring at least 120,000 or more fibers). It should be noted that the minimum fiber length of the measurement object is 20 μm.

[0059] (1) The fibrillated fibers are dispersed in pure water to prepare a 1 L aqueous dispersion. Here, the final concentration of the solid content of the fibrillated fibers is 0.004% by mass. It should be noted that in the case of an aqueous dispersion of the fibrillated fibers 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, an aqueous 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 conditions of a rotation speed of 25,000 rpm for 5 minutes.

[0060] (2) The aqueous dispersion prepared in step (1) is supplied to an automatic sampler for measurement.

[0061] (3) Based on the measurement results, read the average fiber width (Mean Fibre Width) in μm (or it can also be the average fiber width of the fibers (Fibers Mean Fiber width) in μm), the average length of fines-fibers (Fines-Fibers Meanlength) in μm, the macro fibrillation index (Macro Fibrillation index) in %, (or it can also be the fiber fibrillation index (Fibers Fibrillation index) in %), and the fines content in the area (Fine content in area) in %, (or it can also be the fines content % in area (Fines content%in area)), and respectively use them as the average fiber diameter (Method A), the average fiber length, the fibrillation rate, and the area refinement ratio.

[0062] In the present invention, the fibrillation rate, the average fiber diameter (Method A), the average fiber length, and the area refinement ratio can be measured in the state of the slurry before obtaining the non-woven fabric (for example, after obtaining fibrillated fibers, they can be measured separately). Additionally, after mixing fibrillated fibers and non-fibrillated fibers at a specified ratio, methods such as sieving and centrifugation can be used to separate the fibrillated fibers from the mixed slurry state for measurement. Further, fibrillated fibers and non-fibrillated fibers can be mixed, paper-making can be carried out, dried to form a non-woven fabric, and then the non-woven fabric can be dispersed in water to disintegrate the fibers, and the fibrillated fibers can be separated by methods such as sieving and centrifugation for measurement.

[0063] For example, the method of separating fibrillated fibers from the dried non-woven fabric after mixed paper-making and measuring the fibrillation rate, the average fiber length, the average fiber diameter (Method A), and the area refinement ratio is as follows.

[0064] (1) Introduce 5 g of the non-woven 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 use a receiving vessel to recover the filtered dispersed water to obtain dispersed water that only extracts fibrillated fibers.

[0065] (2) The dispersed water obtained in the above (1) is formulated into a 1-L aqueous dispersion with a final solid content concentration of 0.004% by mass, and the measurement is carried out 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. By 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 on the upper limit, and it can be 1000 or less.

[0066] (Average fiber length of fibrillated fibers)

[0067] The average fiber length of the fibrillated fibers in the non-woven fabric is 25 μm or more. This average fiber length refers to the number-average fiber length (Fines-Fibers Mean length) of the fibers of 20 μm or more when measured by the above fiber image analyzer (manufactured by TechPap company, Morfi-Neo). 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 non-woven fabric as an adhesive, the greater the number of crosslinked fibrillated fibers, the higher the rigidity of the non-woven 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 above non-woven fabric, and the more the sound insulation performance of the non-woven 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 non-woven fabric is smaller than that of the crosslinked fibrillated fibers. The average fiber length of the fibrillated fibers is more preferably 45 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 production 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 is weak, and the effect as an adhesive is also small. As the upper limit of the average fiber length of the fibrillated fibers, it is more preferably 125 μm or less, further preferably 90 μm or less, particularly preferably 65 μm or less, and most preferably 55 μm or less.

[0068] (Area refinement ratio of fibrillated fibers)

[0069] The area refinement ratio of fibrillated fibers in the nonwoven fabric is preferably 2% or more. Here, the area refinement ratio refers to the ratio of the total area of the observation images of fine fibers to the total area of the observation images of all fibers (the area of ordinary fibers + the area of fine fibers). Fine fibers refer to fibers with a fiber length of less than 100 μm. The measurement method of the area refinement ratio of fibrillated fibers is as described above. As described 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% or more, further preferably 7% or more, particularly preferably 8% or more, most preferably 9% or more, and most preferably 30% or more. In addition, due to the presence of ordinary fibers with a fiber length of 100 μm or more, the fine fibers are wound around the ordinary fibers as the main axis. Therefore, it is preferable to contain ordinary fibers to a certain extent. Therefore, as the upper limit of the area refinement ratio, it is preferably 90% or less, more preferably 50% or less, and further preferably 40% or less.

[0070] (Average fiber diameter of fibrillated fibers using Method A)

[0071] Regarding the average fiber diameter of fibrillated fibers in the nonwoven fabric, 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. The measurement method of the average fiber diameter (Method A) of fibrillated fibers is as described above. 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 methods of the nonwoven fabric described later, from the viewpoint of water filtration property, it is preferably 2.5 μm or more.

[0072] (Average fiber diameter of fibrillated fibers using Method B)

[0073] The average fiber diameter of fibrillated fibers in the non-woven fabric 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 it is within this range, it is easy to entangle with non-fibrillated fibers, and fiber shedding from the non-woven fabric 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 600 nm or less, and most preferably 500 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, and further preferably 30 nm or more.

[0074] The average fiber diameter (Method B) of fibrillated fibers is measured by the following steps using a specific surface area / pore size distribution measuring device (manufactured by Quantachrome Instruments company, USA, model NOVA-4200e). 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.

[0075] [Pretreatment]

[0076] (1) The aqueous dispersion of fibrillated microfibers was filtered to prepare a wet filter cake.

[0077] (2) The obtained wet filter cake was added to tert-butanol and diluted with tert-butanol so that the solid content concentration of the fibrillated fibers became 0.5 wt%, and a high-shear homogenizer (manufactured by IKA company, trade name “Ultra-turrax T18”) was used for dispersion treatment under the treatment conditions of a rotation speed of 25000 rpm for 5 minutes.

[0078] (3) The obtained dispersion was weighed to make its unit area weight 10 g / m 3 , and a sheet was obtained by filtering with filter paper.

[0079] (4) The obtained sheet was not peeled off from the filter paper, and was sandwiched between two larger filter papers together with the filter paper. 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.

[0080] [Measurement of specific surface area and calculation of fiber diameter]

[0081] (1) 0.2 g of the solid component of the fibrillated fibers (the porous sheet prepared by pretreatment) was dried in vacuo at 120 °C for 5 minutes.

[0082] (2) After drying, measure the nitrogen adsorption amount at 5 points (multi-point method) under the boiling point condition of liquid nitrogen within the range where the relative vapor pressure (P / P0) is 0.05 or more and 0.2 or less, and calculate the BET specific surface area (m 2 / g) using the device program.

[0083] (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 fiber, calculate the average fiber diameter (Method B) using the following formula.

[0084] Average fiber diameter (nm) = 1 / (2.5 × ρ × Y × 10 -4 ).

[0085] (Cellulose raw material)

[0086] As the fibrillated fiber for nonwoven fabric, microfibrillated cellulose is preferred. As the raw material of the microfibrillated cellulose, as the raw material of type I cellulose, so-called wood pulp such as softwood pulp and hardwood pulp, and non-wood pulp can be cited. As the raw material of softwood pulp, fir, hemlock, cedar, larch, Japanese red pine, Japanese black pine, Japanese white pine, king pine, spruce, hinoki cypress, Japanese cypress, Japanese cedar, metasequoia, yew, goldenseal, Japanese garden cypress, goldcrest cypress, blue ice cypress, etc. can be cited. In addition, as the raw material of hardwood pulp, eucalyptus, poplar, mizunara oak, oak, birch, beech, maple, chestnut, paulownia, birch, elm, aspen, etc. can be cited. As non-wood pulp, cotton linters pulp and other cotton-derived pulp, hemp-derived pulp, bagasse-derived pulp, kenaf-derived pulp, bamboo-derived pulp, and straw-derived pulp can be cited. Cotton linters pulp, hemp-derived pulp, bagasse-derived pulp, kenaf-derived pulp, bamboo-derived pulp, and straw-derived pulp respectively refer to purified pulp obtained from raw materials such as cotton lint or cotton linter, abaca (e.g., raw materials produced in Ecuador or the Philippines are often used), sisal, bagasse, kenaf, bamboo, straw, etc. through a purification process and a bleaching process for the purpose of removing lignin and hemicellulose by cooking treatment. In addition, purified products 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 of type II cellulose, cut filaments of regenerated cellulose fibers (rayon, lyocell fiber, cuprammonium rayon (Bemberg), etc.) and cut filaments or pulp of cellulose derivative fibers can also be used as raw materials for cellulose microfibrils. In addition, 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 cellulose microfibrils themselves. In addition, these raw materials can be used alone or two or more of them can be mixed and used. By mixing plural raw materials, the average fiber diameter can be adjusted.

[0087] (Crystal form and crystallinity)

[0088] As described above, the crystal forms of cellulose are not unique and there are various crystal forms, which are roughly classified into cellulose type I and type II. Among the two, type I crystals show high values in terms of rigidity and thermal properties. In particular, it is known that if the rigidity of a soundproof material is high, it has high sound insulation in the low-frequency region. Therefore, in the crystal form of cellulose of the fibrillated fibers used in the nonwoven fabric of the present embodiment, it is also preferable to contain type I crystals. It should be noted that, accurately speaking academically, cellulose type I crystals contain two types, Iα and Iβ, and the mixing ratio of Iα and Iβ may not be considered here. In addition, the larger the component ratio (crystallinity) of the crystals 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 form peaks, and the scattered light caused by the amorphous matter is detected as a halo. The peaks and halos are fitted, and the crystallinity is calculated by applying the following formula.

[0089] Crystallinity [%] = 100 × Ic / (Ic + Ia)

[0090] {In the formula, Ic: Scattering integral intensity of the peak, Ia: Scattering integral intensity of the halo}.

[0091] (Method for manufacturing microfibrillated cellulose)

[0092] The raw materials as described above can be refined to obtain microfibrillated cellulose. In the specification of the present 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 pre-treat the raw material pulp to an easily refinable state by autoclave treatment, enzyme treatment, etc. at a temperature of 100°C to 150°C in water containing or a combination thereof. 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 fibers into the aqueous phase. As a result, it also has the effect of improving the α-cellulose purity of the refined fibers, and therefore, it is sometimes effective in improving the heat resistance of the microfibrillated cellulose.

[0093] 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.

[0094] The fibrillation ratio, average fiber length, and average fiber diameter of microfibrillated cellulose can be controlled by the above-mentioned cellulose raw materials, the conditions of pretreatment before micronization (e.g., autoclave treatment, enzyme treatment, beating treatment, etc.), the conditions of micronization (selection of the type of device, operating pressure, number of passes, etc.), or a combination thereof. Here, regarding the cellulose raw materials, pretreatment, micronization, etc., it is also possible to control by combining a plurality of conditions.

[0095] (Multi-stage micronization)

[0096] When micronizing cellulose in multiple stages, it is effective to combine two or more micronization devices with different micronization mechanisms or shear rates. Here, as a method of multi-stage micronization, it is preferable to use a disk refiner with different disk structures for multi-stage micronization, or to use a high-pressure homogenizer for micronization after micronization with a disk refiner. Here, as the disk refiner, any of a single-disk refiner and a double-disk refiner can be used.

[0097] (Multi-stage micronization using multiple disk refiners)

[0098] When using multiple disk refiners for multi-stage micronization, 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 microfibrillated cellulose, namely, fibrillation ratio, average fiber length, average fiber diameter, etc., can be variously controlled.

[0099] (Disk structure of disk refiner)

[0100] Adjusting the disk structure of the disk refiner is an effective method for controlling various shape parameters of microfibrillated cellulose. As structural features of the disk refiner, the 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 manufacturing 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 (retting) fibers becomes large, so the fibrillation ratio becomes large. Since it is important that the non-woven fabric of the present embodiment contains fibrillated fibers, 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 microfibrillated cellulose can be obtained.

[0101] (Distance between blades during disk refiner treatment)

[0102] In addition, in the fibrillation using a disk refiner, it is important to simultaneously 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 the microfibrillated cellulose can be controlled. The smaller the blade gap, the smaller the average fiber length. It should be noted that preferably, in the previous stage of treatment, the blade gap is set to be 0.05 mm or more and 2.0 mm or less, and in the latter stage of treatment, the blade gap is set to be 0.05 mm or more and 1.0 mm or less. It should be noted that when adjusting the blade gap, it is preferably started from a wider blade gap and gradually reduced to the target blade gap. By controlling as described above, cellulose fibers with prevention of device clogging and overload, narrow distribution of fiber length and fiber diameter, and high homogeneity can be obtained.

[0103] (Number of passes in disk refiner treatment)

[0104] 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 the present application, the "number of passes" refers to the number of times the refiner treatment is carried out after setting the above-mentioned blade gap to the target value. As the number of passes of the disk refiner, it is preferably 5 times or more, more preferably 20 times or more, and further preferably 40 times or more. As the number of times increases, the distribution of fiber shapes gradually converges to a certain degree, so the more the better. However, considering productivity, the upper limit of the number of passes is 300 times or less.

[0105] (Method for controlling the number of passes in disk refiner treatment)

[0106] 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 pulp, and controlling the number of passes according to the flow rate; a method of using two tanks for one refiner and carrying out the refiner treatment while the pulp 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.

[0107] (Multi-stage fibrillation using a combination of a disk refiner and a high-pressure homogenizer)

[0108] It is also one of the preferred methods to further carry out fibrillation treatment on the cellulose fibers microfibrillated 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, slender cellulose fibers can be obtained.

[0109] (Method for manufacturing synthetic pulp)

[0110] Synthetic pulp can be obtained by methods such as the spinning and stretching method of existing polymers, the flash spinning method from solution or emulsion, the ribbon fiber method using uniaxial stretching of a membrane, and the 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, synthetic pulp can also be prepared by subjecting it to high-pressure homogenizer treatment in the same manner as microfibrillated cellulose.

[0111] (Non-fibrillated fiber)

[0112] The non-woven fabric of the present embodiment contains not only fibrillated fibers but also non-fibrillated fibers. In the specification of the present application, "non-fibrillated fiber" refers to a fiber without a branched structure as a fibrous material. As the non-fibrillated fiber, any fiber among natural fibers, synthetic fibers, semi-synthetic fibers, and inorganic fibers can be used. Examples of the polymer constituting the non-fibrillated fiber include thermoplastic resins such as polyolefin, polyester, polyamide (aromatic or aliphatic), acrylic polymer, polyvinyl alcohol, polylactic acid, polyphenylene ether, polyoxymethylene, and polyphenylene sulfide; thermosetting resins such as epoxy resin, thermosetting modified polyphenylene ether resin, thermosetting polyimide resin, urea resin, allyl resin, silicone resin, benzoxazine resin, phenolic resin, unsaturated polyester resin, bismaleimide triazine resin, alkyd resin, furan resin, melamine resin, polyurethane resin, and aniline resin; cellulose; chitin; chitosan, etc. In addition, examples of the inorganic material constituting the non-fibrillated fiber include glass, ceramics, cement, metal, carbon fiber, slag, carbon nanotube, graphene, etc. In addition, the higher the rigidity of the non-woven fabric, the higher the sound insulation performance in the low-frequency region. Therefore, it is preferably composed of at least one selected from the group consisting of the aforementioned inorganic materials. Further, from the viewpoint of processability of the fiber shape, glass, metal, and carbon fiber are more preferred. Further, from the viewpoint of ease of compounding with fibrillated fibers, glass is particularly preferred.

[0113] As types of glass, soda-lime glass, borosilicate glass, potash glass, crystal glass, optical glass, quartz glass, polarizing glass, insulating glass (Eco-glass), tempered glass, laminated glass, heat-resistant glass / borosilicate glass, bulletproof glass, glass fiber, photocatalytic self-cleaning glass, water glass, uranium glass, acrylic glass, dichroic glass, aventurine - tektite - sunstone - amethyst, glass-ceramics, low-melting-point glass, metallic glass, sapphire glass, phase-separated glass, porous glass, liquid glass, glass coating, hybrid glass (a silicate compound formed by chemical cross-linking of silicone resin and silanol compound as silicon compounds and a thermoplastic on multiple functional groups, a glassy composite formed by softening at 120 - 180 degrees in the normal temperature range and then quenching), natural glass (obsidian, tektite, Moldavite, meteorite, volcanic glass, fulgurite, nuclear melt glass stone, Pele's hair), etc. can be preferably used. In addition, generally, glass is an amorphous material without a crystalline structure, but by melting at a specified high temperature for a long time, the structure can be split and crystallized, and crystallized glass (glass-ceramics) obtained by homogenizing the crystals can also be exemplified.

[0114] In addition, as the glass fiber that can be used in the present invention, E glass fiber (alkali-free glass), S glass fiber (compared with E glass, contains more alumina (AL2O3), and in addition to alumina, also contains a large amount of magnesium oxide), C glass fiber (alkali-containing glass), ECR glass fiber (does not contain boron (B2O3), fluorine (F2)), AR glass fiber (contains a large amount of zirconia (ZrO2)) can be cited. They can be used alone or in combination of multiple types. From the viewpoint of compounding with fibrillated fibers, as preferred glass fibers, E glass fiber and S glass fiber can be cited. More preferably, it is E glass fiber.

[0115] In addition, as types of carbon fiber, polyacrylonitrile (PAN)-based carbon fiber obtained by carbonizing a polyacrylonitrile precursor (polyacrylonitrile fiber), and pitch-based carbon fiber obtained by carbonizing a pitch precursor (pitch fiber obtained from coal tar or heavy petroleum components) can be exemplified. Among them, in the pitch-based carbon fiber, the carbon layers constituting the fiber have a wide surface and are arranged parallel to the fiber axis, so it has a higher elastic modulus than PAN-based carbon fiber. Therefore, from the viewpoint of improving the elastic modulus of the non-woven fabric itself, pitch-based carbon fiber is preferred.

[0116] These non-fibrillated fibers can be used alone or in combination of multiple types.

[0117] (Average fiber diameter of non-fibrillated fiber)

[0118] The average fiber diameter of the non-fibrillated fiber is preferably 0.1 μm or more. The average fiber diameter of the non-fibrillated fiber is measured according to the following steps.

[0119] (1) Measure the weight [g] of a 1000 m long non-fibrillated fiber as tex.

[0120] (2) Convert tex to the average fiber diameter by the following formula.

[0121] Average fiber diameter [μm] = 2 × [T × 1000 / (S × π)] 0.5

[0122] {In the formula, T: tex, S: true density of the material [g / cm 3}.

[0123] 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 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. 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 μm or more, further preferably 3 μm or more, and particularly preferably 5 μm or more.

[0124] In addition, as an example of the manufacturing method of the non-woven fabric, the wet papermaking method (also called papermaking) 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 as an adhesive. Therefore, the more the number of crosslinked fibrillated fibers, the higher the rigidity of the non-woven fabric, and according to the rigidity law, the higher the sound insulation 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 aforementioned non-woven fabric, and the more the sound insulation of the non-woven fabric 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 non-crosslinked fibrillated fibers exist in a manner that they are wound around the outer periphery of the non-fibrillated fiber. The contribution of the non-crosslinked fibrillated fibers to improving the sound insulation of the non-woven fabric is smaller than that of the crosslinked fibrillated fibers. Therefore, as the average fiber diameter of the non-fibrillated fiber, it is preferably 300 μm or less, more preferably 150 μm or less, and further preferably 30 μm or less.

[0125] (Fiber length of non-fibrillated fiber)

[0126] The fiber length (also referred to 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.

[0127] (Tensile elastic modulus of non-fibrillated fiber)

[0128] The tensile elastic modulus of the non-fibrillated fiber is preferably 1 GPa or more. The tensile elastic modulus (also referred to as Young's modulus) described herein is expressed as the ratio of the tensile stress per unit cross-sectional area to the elongation generated in the stress direction, and refers to the dimensional stability (difficulty in deformation) of the material. If the tensile elastic modulus of the non-fibrillated fiber is high, the rigidity of the non-woven fabric also increases, and high sound insulation is exhibited in the low-frequency region. As the tensile elastic modulus of the non-fibrillated fiber, it is more preferably 5 GPa or more, further preferably 10 GPa or more, particularly preferably 70 GPa or more, extremely preferably 190 GPa or more, and most preferably 300 GPa or more. In addition, there is no particular limitation on the upper limit. As one mode, it is preferably 1000 GPa or less, and more preferably 500 GPa or less. It should be noted that for the tensile elastic modulus, using the fiber length that can be measured for the same material, the following method is used to measure with a Tensilon universal material testing machine (RTG-1250, manufactured by A&D company) (in accordance with JIS L 1013:2010, 8.5.1 (standard test)). In the state of slowly stretching the non-fibrillated fiber, a tensile test is performed by installing the clamping part of the testing machine, and the load and elongation at the time of specimen cutting are measured. The strength and elongation are calculated according to the following formulas respectively, and their arithmetic mean is used as the strength (average strength) and elongation of the sample. In addition, when the cutting strength is less than the strength at the maximum load, the strength at the maximum load and the elongation at this time are measured.

[0129] Strength (cN / dtex) = Strength at the time of cutting or strength at the maximum load (cN) / Fiber fineness of the specimen (dtex).

[0130] Elongation (%) = {Elongation at the time of cutting or elongation at the maximum load (mm) / Clamping interval (mm)} × 100.

[0131] It should be noted that the measurement conditions are as follows:

[0132] Number of measurement samples: 10 points.

[0133] Tensile speed: 300 mm / min (constant speed).

[0134] Load cell type: UR-50N-D.

[0135] Distance between chucks: 300 mm.

[0136] Chuck pressure: 0.20 MPa.

[0137] Ambient temperature: 25 °C.

[0138] Ambient humidity: 55%.

[0139] For the tensile elastic modulus of the above fibrillated fibers, after mixing the fibrillated fibers and non-fibrillated fibers at a specified ratio, the non-fibrillated fibers can be separated from the mixed slurry state by using methods such as sieving and centrifugation for measurement. In addition, the fibrillated fibers and non-fibrillated fibers can be mixed, sheeted, dried to form a non-woven fabric, and then the non-woven fabric can be dispersed in water to disintegrate the fibers, and the non-fibrillated fibers can be separated by using methods such as sieving and centrifugation for measurement. In addition, the non-fibrillated fibers can also be directly extracted from the non-woven fabric with tweezers, adhesive tape, etc. for measurement.

[0140] (Content of fibrillated fibers)

[0141] Preferably, based on the total mass of the non-woven fabric, the non-woven fabric contains 1% by mass or more of fibrillated fibers, and it can also be 100% by mass or less. Within this range, the fibrillated fibers can contribute to sound absorption in the low-frequency band. By containing a large amount of fibrillated fibers, the strength of the non-woven fabric is improved, and less fiber falls off from the surface. In addition, since the flow resistance per unit thickness is also increased, the sound insulation is improved. From the above viewpoints, it is more preferably 1% by mass or more, further preferably 3% by mass or more, particularly preferably 5% by mass or more, and most preferably 10% by mass or more. However, if the content of fibrillated fibers is too high, 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 90% by mass or less, and more preferably 30% by mass or less.

[0142] (Tensile elastic modulus of non-woven fabric)

[0143] The tensile elastic modulus of the non-woven fabric is preferably 10 MPa or more. If the tensile elastic modulus is within this range, then according to the rigidity law, the non-woven fabric exhibits sound insulation in the low-frequency region. As the tensile elastic modulus, it is more preferably 40 MPa or more, further preferably 50 MPa or more, particularly preferably 100 MPa or more, extremely preferably 200 MPa or more, especially preferably 240 MPa or more, and most preferably 300 MPa or more. Additionally, there is no particular limitation on the upper limit. As one embodiment, it may be 100 GPa or less, or it may be 500 MPa. It should be noted that the tensile elastic modulus is calculated using a Tensilon universal material testing machine (RTG-1250, manufactured by A&D company) under the following conditions.

[0144] Number of measurement samples: 10 points.

[0145] Tensile speed: 10 mm / min (constant speed).

[0146] Type of fixture: Parallel clamping type pneumatic chuck.

[0147] Type of load cell: UR-1kN-D.

[0148] Distance between chucks: 100 mm.

[0149] Chuck pressure: 0.48 MPa.

[0150] Ambient temperature: 25 °C.

[0151] Ambient humidity: 50%.

[0152] Shape of test piece: Strip.

[0153] Width of test piece: 15 mm.

[0154] Length of test piece: 150 mm.

[0155] Thickness of test piece: The same as the thickness of the non-woven fabric.

[0156] (Bulk density of non-woven fabric)

[0157] The bulk density of the non-woven fabric is preferably 30 kg / m 3 or more. By having the bulk density 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 3The above. Additionally, if the bulk density of the non-woven fabric is too high, the flow resistance per unit thickness will also be too high, which will instead impair the sound absorption effect. As the upper limit of the bulk density, it is preferably 10,000 kg / m 3 or less, more preferably 5,000 kg / m 3 or less, particularly preferably 1,000 kg / m 3 or less, and most preferably 500 kg / m 3 or less.

[0158] It should be noted that the bulk density of the non-woven fabric is calculated by the following formula:

[0159] Bulk density [kg / m 3 = areal density [g / m 2 / thickness [mm].

[0160] For the areal density of the non-woven fabric, use an electronic balance (GX-8K2, manufactured by A&D company), measure the weight of the non-woven fabric cut into a 25 cm square, and set it to 16 times as the areal density. The thickness of the non-woven fabric is calculated by the aforementioned method.

[0161] When the areal density 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.

[0162] (Three-dimensional shaping of non-woven fabric)

[0163] The non-woven fabric can be easily formed into a three-dimensional structure, and further, a structure with a uniform surface and no seams or gaps can be formed. In the specification of this application, the three-dimensional structure means that the non-woven fabric is not a two-dimensional (planar or flat) structure, but has at least one curved structure. Hereinafter, it is also referred to as "three-dimensional" or "three-dimensional structure".

[0164] When applying a planar air-permeability adjustment layer such as a commonly used non-woven fabric to a three-dimensional structure, the air-permeability adjustment 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 non-woven fabric partially overlaps or gaps and creases are generated will occur. Therefore, the air permeability deviates, and uniform sound absorption characteristics cannot be obtained on all surfaces. On the other hand, when the non-woven fabric 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 fixed sound absorption property can be obtained on all surfaces of the non-woven fabric, so the sound absorption property is excellent.

[0165] (Manufacturing method of non-woven fabric)

[0166] As a method for manufacturing a nonwoven fabric, there is no particular limitation, and examples thereof include a method of dispersing fibrillated fibers and non-fibrillated fibers in a liquid medium and removing and drying a solvent by filtration, pressing, etc. By mixing non-fibrillated fibers and fibrillated fibers in a liquid medium, a nonwoven fabric with a more uniform internal structure can be obtained. As the molding method described above, specifically, since it can be processed into any shape, a wet papermaking method and a 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 a normal plastic molded product, 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.

[0167] (Liquid medium during molding)

[0168] 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 coagulation 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 water is used as the liquid medium, a surfactant can be added for the purpose of controlling the surface tension.

[0169] (Additives during molding)

[0170] By adding a dispersant for papermaking, a binder, and a crosslinking agent as additives during forming, it is possible to control the strength of the nonwoven fabric, the operability such as the fiber shedding property, the internal uniformity, and the structure such as the surface smoothness. The dispersant for papermaking refers to a surfactant that makes it easy for fibrillated fibers on a fiber bundle to defibrillate in a liquid medium, and an adhesive that adjusts the viscosity of the liquid medium and prevents fiber aggregation, which can improve the 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 fibrillated fibers and non-fibrillated fibers of the nonwoven fabric, if the moisture absorption / dehumidification of moisture in the air is repeated, sometimes the fibers aggregate and the microstructure of the nonwoven fabric changes. By binding the fibers with a crosslinking agent, this movement of the fibers can be blocked and aggregation can be suppressed. Above all, these additives can be used alone or in combination of two or more.

[0171] (Blackening of the nonwoven fabric)

[0172] As an automotive component, it is preferable that dirt and the like are less obvious, and black components are preferred. As a method for blackening the nonwoven fabric, there is a method of dyeing at least one of the fibrillated fibers and non-fibrillated fibers black. As a method for blackening the fibrillated fibers and non-fibrillated fibers, there are methods such as coating a black coloring matter on the fibers and pre-including a black coloring matter inside the fibers. As the coloring matter, there are black powders such as carbon black, titanium-based black pigments, iron oxide powder, titanium nitride powder, titanium suboxide powder; black fibers such as carbon fibers and carbon nanotubes. In addition, from the viewpoint of blackening the nonwoven fabric, it is preferable to blacken both the fibrillated fibers and non-fibrillated fibers, but considering costs, labor efficiency, etc., it is also possible to consider limited blackening of either one of them. In this case, from the viewpoints of ease of dyeing and content, it is preferable to blacken the non-fibrillated fibers among the fibrillated fibers and non-fibrillated fibers.

[0173] (Imparting a flame retardant to the nonwoven fabric)

[0174] 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 of the present embodiment. As a method of imparting a flame retardant to the nonwoven fabric, methods such as dispersing the flame retardant in a liquid and attaching it by blowing, brushing, coating, casting coating, dip coating, impregnation, etc. can be cited. In addition, in addition to this, when manufacturing the nonwoven fabric, 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, condensed), 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 hydroxystannate), 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 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.

[0175] <Lamination of Nonwoven Fabric and Support>

[0176] The nonwoven fabric of the present embodiment exhibits higher sound insulation by being laminated with a support. The nonwoven fabric has sound insulation, but in the frequency region of the natural vibration frequency of the nonwoven fabric, the nonwoven fabric itself vibrates violently and generates secondary frequency sounds. Therefore, in the frequency region of the natural vibration frequency of the nonwoven fabric, the sound insulation decreases compared to other frequency regions.

[0177] Therefore, when the support body is laminated with the non-woven fabric, since the support body suppresses the vibration of the non-woven fabric itself, high sound insulation can be maintained in all frequency regions. As the types of support bodies, a plate film body and a porous body can be cited. For the plate film body, compared with the porous body, the effect of suppressing the vibration of the non-woven fabric is high. In addition, the plate film body itself also functions as a sound insulation material, so it becomes a laminate specifically for sound insulation. On the other hand, although the porous body has lower sound insulation than the plate film body, it has higher sound absorption. Therefore, when the porous body is laminated, the porous body contributes to sound prevention as a sound absorption material, and becomes a composite laminate having both sound absorption and sound insulation properties.

[0178] In addition, preferably, when the plate film body is laminated as the support body, the non-woven fabric is disposed inside the sound source with respect to the plate film body. The plate film body itself has almost no sound absorption, but the non-woven fabric has sound absorption. Therefore, by using the non-woven fabric and the plate film body to insulate the sound emitted from the sound source, and using the non-woven fabric inside to absorb the sound, a laminate with high sound insulation is obtained.

[0179] <Material types of the support body>

[0180] As described above, the support body of the present embodiment is roughly divided into a plate film body and a porous body. As the materials constituting the plate film body, thermoplastic resins such as polyolefin, polyester, polyamide (aromatic or aliphatic), acrylic polymer, polyvinyl alcohol, polylactic acid, polyphenylene ether, polyoxymethylene, and polyphenylene sulfide can be cited; thermosetting resins such as epoxy resin, thermosetting modified polyphenylene ether resin, thermosetting polyimide resin, urea resin, allyl resin, silicone resin, benzoxazine resin, phenolic resin, unsaturated polyester resin, bismaleimide triazine resin, alkyd resin, furan resin, melamine resin, polyurethane resin, and aniline resin, etc. In addition, inorganic materials such as glass, ceramics, cement, metal, and slag can also be cited. In addition to this, rubber materials, cellulose, fiber-reinforced resins (reinforcing materials: cellulose fiber, glass fiber, aramid fiber, carbon fiber), particle-reinforced resins, etc. can also be cited.

[0181] In addition, the fibers constituting the non-woven fabric and felt in the porous body can be any of natural fibers, synthetic fibers, semi-synthetic fibers, and inorganic fibers. Examples of the polymer constituting the porous body 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. In addition, examples of the inorganic material constituting the non-fibrillated fiber include glass, ceramics, cement, metals, carbon fibers, and slag. These fibers can be used alone or in combination of multiple types. Examples of the material constituting the foam in the porous body 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.

[0182] <Tensile Elastic Modulus of the Plate Membrane Body>

[0183] The tensile elastic modulus of the plate membrane body in the support body of the present embodiment is preferably 0.5 GPa or more. If it is within this range, the plate membrane body is self-supporting, and thus, the effect of the support body as a non-woven fabric is exhibited. The higher the tensile elastic modulus of the plate membrane body, the more the vibration of the non-woven fabric can be suppressed, and thus, the sound insulation of the laminate is also improved. The tensile elastic modulus of the plate membrane body is more preferably 1 GPa or more, further preferably 5 GPa or more, and particularly preferably 10 GPa or more. In addition, there is no particular limitation on the upper limit, and as one example, it can be 1000 GPa.

[0184] <Method of Laminating the Non-Woven Fabric with the Support Body>

[0185] The non-woven fabric of this embodiment can be laminated with the support by various methods. As the lamination method, the non-woven fabric and the support can be naturally overlapped without bonding them. However, if the two are bonded, the support acts as an adhesive for the non-woven fabric, suppressing the vibration of the non-woven fabric and improving the sound insulation. 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 with an infrared (IR) heater or the like by heat fusion, a method of applying a hot melt adhesive to the surface of the non-woven fabric by a curtain coating method or the like and then heating and heat fusing, a method of fixing with a commercially available tape, and the like.

[0186] It should be noted that the higher the bonding strength, the less likely the non-woven fabric is to peel off from the porous body due to the vibration when the non-woven fabric vibrates due to sound propagation. As the tensile shear strength (based on JIS K6849), it is preferably 1 MPa or more, more preferably 5 MPa or more. In addition, there is no particular limitation on the upper limit. As one embodiment, it can be 1 GPa or less.

[0187] <Usage>

[0188] The use of a two-dimensional sheet-like non-woven fabric as a sound-absorbing material exists as a well-known technique. However, by using the fibrillation fiber or non-fibrillation fiber of this embodiment to perform seamless three-dimensional molding by a method such as the pulp molding method, a three-dimensional non-woven fabric having both sound insulation and sound absorption properties can be provided. In particular, by using cellulose as the fiber material, it can be three-dimensionally molded into a thin layer and also exhibits a high elastic modulus. Therefore, it can be used as a three-dimensional soundproof material having high sound insulation particularly in the low frequency region. In addition, due to its high formability, it can also follow the complex mechanical shapes of devices such as sound sources. In addition, since it also has excellent heat resistance, it is particularly useful for automotive applications. The main applications are listed below.

[0189] For automotive applications, it can be applied to large components such as hood silencers, dashboard outer silencers, dashboard inner silencers (dashboard sound insulation pads), fender liners, wheelhouse liners, fairing inner silencers, dashboard inner silencers, side door trims, tailgate inner trims, trunk sidewall trims, trunk mats, floor silencers (floor bottom covers, floor carpets), engine silencers, roof liners, rear shelves, tailgate trims, sound insulation ducts, melt sheets, transmission sound insulation pads, engine bottom covers (motor bottom covers in the case of Electric Vehicles (EVs)), etc. Additionally, as a small and medium-sized three-dimensional cover, it can be applied to covers for drive devices such as engines, reducers attached to the engine, drive shafts, torque converters, gear shifting devices, reduction devices, differential gear devices, differential limiting devices, etc., covers for electrical components such as electric pumps (water and 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, reducers attached to the motor, etc. The sound insulation material of the present invention can be three-dimensionally formed in a thin layer and seamlessly, so it is more suitable for small and medium-sized three-dimensional covers and can be used for covers for electrical components such as electric pumps (water and oil circulation), air conditioning electric compressors, air conditioning ducts, electric actuators, inverters, converters, etc., which generate noise and vibration in the range of 200 Hz to 2000 Hz, and covers for electric drive devices such as electric motors, reducers attached to the motor, etc.

[0190] Examples

[0191] Hereinafter, the present invention will be specifically described based on examples and comparative examples, but the present invention is not limited to these examples.

[0192] First, the measurement methods, etc. will be described.

[0193] <Self-supporting property of non-woven fabric, fiber shedding property>

[0194] In each example and comparative example, a 20 cm square sample was prepared, and the self-supporting property of the non-woven fabric and fiber shedding were evaluated according to the following criteria.

[0195] [Self-supporting property]

[0196] 〇: It will not bend or break even with one-handed operation.

[0197] △: It will bend during one-handed operation, but will not break.

[0198] ×: It will break during one-handed operation.

[0199] [Fiber shedding]

[0200] 〇: No detached fibers adhere when touching or rubbing the surface by hand.

[0201] △: Fibers that adhere and fall off when the surface is rubbed by hand, but no fibers adhere when only in contact.

[0202] ×: Fibers fall off and adhere when the surface is contacted by hand.

[0203] <Sound insulation evaluation>

[0204] In each example and comparative example, the transmission loss of the sample was measured and the sound insulation was evaluated by the double load method using a vertical incidence sound absorption rate / transmission loss measurement system Win Zac (manufactured by Nihon Onkyo Engineering company). 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 the nonwoven fabric and the porous body, the measurement was carried out with nonwoven fabric A on the incident side of the sound wave.

[0205] 《Fibrillated fiber》

[0206] <Fibrillated fiber A>

[0207] The fibrillated fiber using 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.

[0208] <Fibrillated fiber B>

[0209] The fibrillated fiber using aramid pulp (manufactured by DuPont: Kevlar) 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.

[0210] <Fibrillated fiber C>

[0211] Using the 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 2% by mass, and after being simply dispersed using a laboratory pulper (manufactured by Aikawa Iron Works Co., Ltd.), it was transferred to a tank and diluted to 1.5% by mass. 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, it was continued to be operated while further confirming the flow rate, and the operation was ended at the stage where the total amount of the pulp passed through the disc part 30 times. 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.

[0212] <Fibrillated Fiber D>

[0213] 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 obtained fibrillated fiber was used as fibrillated fiber D. The results of evaluating the fibrillation ratio, area refinement ratio, average fiber length, and average fiber diameter are shown in Table 3 below.

[0214] <Fibrillated Fiber E>

[0215] Using the 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 2% by mass, and after being simply dispersed using a laboratory pulper (manufactured by Aikawa Iron Works Co., Ltd.), it was transferred to a tank and diluted to 1.5% by mass. 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 0.15 mm. After the blade gap reached 0.15 mm, it was continued to be operated while further confirming the flow rate, and the operation was ended at the stage where the total amount of the pulp passed through the disc part 30 times. 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 2 below.

[0216] <Fibrillated Fiber F>

[0217] 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 2% by mass. After being simply dispersed using a laboratory pulper (manufactured by Aikawa Iron Works Co., Ltd.), it was transferred to a tank and diluted to 1.5% by mass. 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, microfibrillation 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 0.30 mm. After the blade gap reached 0.30 mm, it was continued to be operated 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 F. The results of evaluating the fibrillation ratio, area refinement ratio, average fiber length, and average fiber diameter are shown in Table 2 below.

[0218] <Fibrillated fiber G>

[0219] 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 G. The results of evaluating the fibrillation ratio, area refinement ratio, average fiber length, and average fiber diameter are shown in Table 2 below.

[0220] <<Manufacturing Example of Soundproof Material>>

[0221] <Example 1>

[0222] Using fibrillated fiber A as a fibrillated fiber and glass fiber A as a non-fibrillated fiber (manufactured by Central Glass fiber Co., Ltd.: ECS 03-670, average fiber diameter: 13 μm, cut length: 3 mm), non-woven fabric 1 was produced 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 made 0.5%. The above-prepared slurry was stirred for 4 minutes using a household mixer to prepare a slurry. The above-prepared slurry was made to have a basis weight of 300 g / m 2It 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). 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 nonwoven fabric 1. Various physical properties, sound insulation properties, etc. of the obtained nonwoven fabric 1 are shown in Table 1 below.

[0223] <Example 2>

[0224] Except that fibrillated fiber B is used as the fibrillated fiber, nonwoven fabric 2 is obtained by the same method as in Example 1. Various physical properties, sound insulation properties, etc. of the obtained nonwoven fabric 2 are shown in Table 1 below.

[0225] <Example 3>

[0226] Fibrillated fiber C is used as the fibrillated fiber, and glass fiber B (manufactured by Nippon Electric Glass Co., Ltd.: ECS 03T - 289DE, average fiber diameter: 6.5 μm, cut length: 3.2 mm) is used as the non - fibrillated fiber, and the solid - component weight ratio is set to 20:80. Except for this, nonwoven fabric 3 is obtained by the same method as in Example 1. Various physical properties, sound insulation properties, etc. of the obtained nonwoven fabric 3 are shown in Table 1 below.

[0227] <Example 4>

[0228] Fibrillated fiber C is used as the fibrillated fiber, and glass fiber B is used as the non - fibrillated fiber, and the solid - component weight ratio is set to 30:70. Except for this, nonwoven fabric 4 is obtained by the same method as in Example 1. Various physical properties, sound insulation properties, etc. of the obtained nonwoven fabric 4 are shown in Table 1 below.

[0229] <Example 5>

[0230] Except that fibrillated fiber C is used as the fibrillated fiber, nonwoven fabric 5 is obtained by the same method as in Example 1. Various physical properties, sound insulation properties, etc. of the obtained nonwoven fabric 5 are shown in Table 1 below.

[0231] <Example 6>

[0232] For the fibrillated fiber, fibrillated fiber C is used, and the fibrillated fiber and the non-fibrillated fiber are set at a solid component weight ratio of 15:85. Except for this, the non-woven fabric 6 is obtained by the same method as in Example 1. Various physical properties, sound insulation properties, etc. of the obtained non-woven fabric 6 are shown in Table 1 below.

[0233] <Example 7>

[0234] For the fibrillated fiber, fibrillated fiber C is used, and the fibrillated fiber and the non-fibrillated fiber are set at a solid component weight ratio of 20:80. Except for this, the non-woven fabric 7 is obtained by the same method as in Example 1. Various physical properties, sound insulation properties, etc. of the obtained non-woven fabric 7 are shown in Table 1 below.

[0235] <Example 8>

[0236] For the fibrillated fiber, fibrillated fiber C is used, and the fibrillated fiber and the non-fibrillated fiber are set at a solid component weight ratio of 30:70. Except for this, the non-woven fabric 8 is obtained by the same method as in Example 1. Various physical properties, sound insulation properties, etc. of the obtained non-woven fabric 8 are shown in Table 2 below.

[0237] <Example 9>

[0238] For the fibrillated fiber, fibrillated fiber C is used. As the non-fibrillated fiber, carbon fiber (manufactured by Mitsubishi Chemical Corporation: TR03CM, average fiber diameter: 7μm, cut length: 3mm) is used, and the solid component weight ratio is set at 30:70. Except for this, the non-woven fabric 9 is obtained by the same method as in Example 1. Various physical properties, sound insulation properties, etc. of the obtained non-woven fabric 9 are shown in Table 2 below.

[0239] <Example 10>

[0240] For the fibrillated fiber, fibrillated fiber C is used. As the non-fibrillated fiber, glass fiber C (manufactured by Central Glass Fiber Co., Ltd.: ECS 06-670, average fiber diameter: 13μm, cut length: 6mm) is used, and the solid component weight ratio is set at 30:70. Except for this, the non-woven fabric 10 is obtained by the same method as in Example 1. Various physical properties, sound insulation properties, etc. of the obtained non-woven fabric 10 are shown in Table 2 below.

[0241] <Example 11>

[0242] For the fibrillated fiber, fibrillated fiber C is used. As the non-fibrillated fiber, stainless steel fiber (commercial stainless steel wool cut into 20mm in length, average fiber diameter: 150μm, cut length: 20mm) is used. Except for this, the non-woven fabric 11 is obtained by the same method as in Example 1. Various physical properties, sound insulation properties, etc. of the obtained non-woven fabric 11 are shown in Table 2 below.

[0243] <Example 12>

[0244] Except that fibrillated fiber E is used as the fibrillated fiber, nonwoven fabric 12 is obtained by the same method as in Example 1. Various physical properties, sound insulation properties, etc. of the obtained nonwoven fabric 12 are shown in Table 2 below.

[0245] <Example 13>

[0246] Except that fibrillated fiber F is used as the fibrillated fiber, nonwoven fabric 13 is obtained by the same method as in Example 1. Various physical properties, sound insulation properties, etc. of the obtained nonwoven fabric 13 are shown in Table 2 below.

[0247] <Example 14>

[0248] Except that fibrillated fiber G is used as the fibrillated fiber, nonwoven fabric 14 is obtained by the same method as in Example 1. Various physical properties, sound insulation properties, etc. of the obtained nonwoven fabric 14 are shown in Table 2 below.

[0249] <Example 15>

[0250] Fibrillated fiber C is used as the fibrillated fiber, and PET fiber (manufactured by Teijin Limited, TA04PN, average fiber diameter: 3 μm, cut length 3 mm) is used as the non-fibrillated fiber, and it is set to 5:95 by weight ratio of solid components. Except for this, nonwoven fabric 15 is obtained by the same method as in Example 1. Various physical properties, sound insulation properties, etc. of the obtained nonwoven fabric 15 are shown in Table 3 below.

[0251] <Example 16>

[0252] Fibrillated fiber C is used as the fibrillated fiber, and PET fiber (manufactured by Teijin Limited, TA04PN, average fiber diameter: 3 μm, cut length 3 mm) is used as the non-fibrillated fiber. Except for this, nonwoven fabric 16 is obtained by the same method as in Example 1. Various physical properties, sound insulation properties, etc. of the obtained nonwoven fabric 16 are shown in Table 3 below.

[0253] <Example 17>

[0254] Fibrillated fiber C is used as the fibrillated fiber, and PP fiber (manufactured by Ube Exsymo Inc., AIRYMO, average fiber diameter: 5.3 μm, cut length 2 mm) is used as the non-fibrillated fiber. Except for this, nonwoven fabric 17 is obtained by the same method as in Example 1. Various physical properties, sound insulation properties, etc. of the obtained nonwoven fabric 17 are shown in Table 3 below.

[0255] <Example 18>

[0256] A nonwoven fabric 18 was obtained by the same method as in Example 1 except that fibrillated fiber D was used as the fibrillated fiber. The various physical properties, sound insulation properties, etc. of the obtained nonwoven fabric 18 are shown in Table 3 below.

[0257] <Example 19>

[0258] The nonfibrillated fiber was not used, and only fibrillated fiber G (the solid weight ratio of fibrillated fiber: nonfibrillated fiber = 100:0) was used. Then, a nonwoven fabric 19 was obtained by the same method as in Example 1. The various physical properties, sound insulation properties, etc. of the obtained nonwoven fabric 19 are shown in Table 3 below.

[0259] <Comparative Example 1>

[0260] 10 g of dry bleached kraft pulp (Machenzie, manufactured by Fletcher Challenge Canada ltd.) and 500 mL of ion-exchanged water were put into a 2-L glass beaker and allowed to stand overnight to swell the pulp. Its temperature was adjusted to 30.0 °C by a water bath with temperature control, 0.1 g of TEMPO (2,2,6,6-tetramethylpiperidine-N-oxide) (manufactured by Tokyo Chemical Industry Co., Ltd., 98%) and 1 g of sodium bromide (manufactured by Wako Pure Chemical Industries, Ltd.) were added and stirred to obtain a pulp suspension. Further, while stirring, sodium hypochlorite (manufactured by Wako Pure Chemical Industries, Ltd., Cl: 5%) at 5 mmol / g relative to the mass of each cellulose was added. At this time, an approximately 1 M aqueous sodium hydroxide solution was added to maintain the pH of the pulp suspension at approximately 10.5. Then, the reaction was carried out for 2 hours, and the pulp was washed thoroughly with ion-exchanged water to obtain TEMPO-oxidized cellulose. This TEMPO-oxidized cellulose is a nonfibrillated fiber.

[0261] A nonwoven fabric 20 was obtained by the same method as in Example 1 except that TEMPO-oxidized cellulose and glass fiber A were used at a solid component weight ratio of 10:90. The various physical properties, sound insulation properties, etc. of the obtained nonwoven fabric 20 are shown in Table 3 below. It should be noted that the fiber diameter of the TEMPO-oxidized cellulose is below the measurement limit of a fiber image analyzer (Morfi-Neo, manufactured by TechPap company), so it cannot be observed. Therefore, for the average fiber length, the average value of 100 TEMPO-oxidized cellulose fibers was calculated using a scanning electron microscope. The average fiber diameter was only calculated by Method B.

[0262] <Comparative Example 2>

[0263] Without using fibrillated fibers and using only glass fiber A as the non-fibrillated fiber, nonwoven fabric 21 was obtained by the same method as in Example 1. Various physical properties, sound insulation properties, etc. of the obtained nonwoven fabric 21 are shown in Table 3 below.

[0264] <Example 20>

[0265] A 2V gear reduction electric motor (manufactured by Uster (FastUU), 12V 250W heavy-duty DC gear reduction brushed motor with a 9-tooth sprocket) was fixed to a 10mm 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 5mm air gap to follow the shape of the electric motor and the reducer, a 1mm thick molded cover A was made using fibrillated fiber G by the pulp molding method. This cover was set and rotated at 2950 rpm, and the noise B after 5 minutes was measured. The transmission loss was calculated from noise A and B, and the result was 7 dB.

[0266] <Example 21>

[0267] A 2V gear reduction electric motor (manufactured by Uster (FastUU), 12V 250W heavy-duty DC gear reduction brushed motor with a 9-tooth sprocket) was fixed to a 10mm 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 5mm air gap to follow the shape of the electric motor and the reducer, a 1mm thick molded cover A was made by the pulp molding method with the composition of nonwoven fabric 16 in Example 16. This cover was set and rotated at 2950 rpm, and the noise B after 5 minutes was measured. The transmission loss was calculated from noise A and B, and the result was 10 dB.

[0268] <Comparative Example 4>

[0269] A 2V gear reduction electric motor (manufactured by Uster (FastUU), 12V 250W heavy-duty DC gear reduction brushed motor with a 9-tooth sprocket) was fixed to a 10mm 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 5mm air gap to follow the shape of the electric motor and the reducer, a 1mm thick molded cover A was made using PET fiber (manufactured by Teijin, TA04PN, average fiber diameter: 3μm, cut length 3mm) by the pulp molding method. This cover was set and rotated at 2950 rpm, and the noise B after 5 minutes was measured. The transmission loss was calculated from noise A and B, and the result was 2 dB.

[0270] Table 1

[0271]

[0272] Table 2

[0273]

[0274] Table 3

[0275]

[0276] Industrial applicability

[0277] The nonwoven fabric of the present invention exhibits sound absorption performance and excellent sound insulation in a wide frequency range within the range of 200 Hz to 2000 Hz. Therefore, it suppresses various noises such as engine / drive system noise, road noise, and wind noise in automobiles and the like, and can be suitably used as a sound absorption material for creating a comfortable in-vehicle space.

Claims

1. A non-woven fabric, wherein, The non-woven fabric contains fibrillated fibers, and the tensile elastic modulus of the non-woven fabric is 10 MPa or more.

2. The non-woven fabric according to claim 1, wherein, The non-woven fabric further contains non-fibrillated fibers.

3. The non-woven fabric according to claim 1 or 2, wherein The average fiber length of the fibrillated fibers is 25 μm or more.

4. The non-woven fabric according to claim 2, wherein, The tensile elastic modulus of the non-fibrillated fibers is 5 GPa or more.

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

6. The non-woven fabric according to claim 1 or 2, wherein, The tortuosity of the non-woven fabric is 1.8 or more and 12.0 or less.

7. The non-woven fabric 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.

8. The non-woven fabric according to claim 1 or 2, wherein The fibrillation rate of the fibrillated fibers is 0.3% or more.

9. The non-woven fabric 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.

10. The non-woven fabric according to claim 1 or 2, wherein, The average fiber length of the fibrillated fibers is 200 μm or less.

11. The non-woven fabric according to claim 1 or 2, wherein, The tensile elastic modulus of the non-woven fabric is 40 MPa or more and 1000 MPa or less.

12. The non-woven fabric according to claim 2, wherein, The tensile elastic modulus of the non-fibrillated fibers is 500 GPa or more.

13. A soundproof material, wherein, The sound insulation material is composed of the non-woven fabric according to claim 1 or 2.

14. A composite soundproof material, wherein, The composite sound insulation material is a composite sound insulation material obtained by laminating the sound insulation material according to claim 13 and a support.

15. The soundproof material according to claim 13, wherein, The sound insulation material is a three-dimensional sound insulation material for automobiles.

16. The soundproof material according to claim 14, wherein, The sound insulation material is a three-dimensional sound insulation material for automobiles.

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