Porous body and sound-absorbing material

Abstract

A porous body 1 comprises a fiber body layer 10 in which liquid crystal polymer fibers are intertwined, wherein the fiber diameter of the fiber body layer 10 is 1-3 μm inclusive, and the fiber density of the fiber body layer 10 is 100 kg / m3 or more.

Description

Porous materials and sound-absorbing materials

[0001] The present invention relates to a porous body and a sound-absorbing material.

[0002] Patent Document 1 discloses a multilayer article including a support layer and a submicron fiber layer on the support layer, the submicron fiber layer including polymeric fibers having a median fiber diameter of less than 1 μm.

[0003] Patent Document 2 describes a nonwoven fabric structure having a fibrous body formed by intertwining fibers, the fibers including resin nanofibers having a fiber diameter of less than 1 μm, the thickness of the fibrous body being 10 mm or more, and the fiber density of the fibrous body being 10 kg / m ３ More than 50kg / m ３ A nonwoven structure is disclosed in which the thickness is less than

[0004] JP 2014-15042 A JP 2016-121426 A

[0005] The multilayer article described in Patent Document 1 and the nonwoven fabric structure described in Patent Document 2 can be used, for example, as a sound-absorbing material. Conventionally, porous materials such as glass wool or urethane foam have been widely used as sound-absorbing materials. However, they have poor sound-absorbing properties in the low-to-mid frequency range, and in order to absorb sounds in the low frequency range of 1000 Hz or less, in particular, they require a large thickness, which takes up a lot of space.

[0006] In the multilayer article described in Patent Document 1 and the nonwoven fabric structure described in Patent Document 2, the sound absorption properties are improved by using nanofibers, but there is still room for improvement, such as insufficient sound absorption properties in the low frequency range.

[0007] The present invention has been made to solve the above problems, and aims to provide a porous body that can be used as a sound-absorbing material, etc. Another aim of the present invention is to provide a sound-absorbing material that is thin but has excellent sound-absorbing properties in the low-frequency range.

[0008] The porous body of the present invention includes a fibrous layer formed by entanglement of liquid crystal polymer fibers, the fibrous layer having a fiber diameter of 1 μm or more and 3 μm or less, and a fiber density of 100 kg / m ３ That's all.

[0009] The sound-absorbing material of the present invention comprises the porous body of the present invention.

[0010] According to the present invention, it is possible to provide a porous body that can be used as a sound absorbing material, etc. Furthermore, according to the present invention, it is possible to provide a sound absorbing material that is thin but has excellent sound absorbing properties in the low frequency range.

[0011] Fig. 1 is a cross-sectional view schematically showing an example of the porous body of the present invention. Fig. 2 is a cross-sectional view schematically showing another example of the porous body of the present invention. Fig. 3 is a cross-sectional view schematically showing yet another example of the porous body of the present invention.

[0012] The porous body of the present invention will be described below. However, the present invention is not limited to the following configurations, and can be appropriately modified and applied within the scope of the present invention. Note that the present invention also includes a combination of two or more of the individual desirable configurations of the present invention described below.

[0013] The porous body of the present invention may be used for any purpose, including, but not limited to, a sound absorbing material. Thus, a sound absorbing material comprising the porous body of the present invention is also included in the present invention.

[0014] In one embodiment, the porous body of the present invention can be used by using an adhesive on one side to fix it to a wall surface. For example, it can be used by directly attaching it to the cover of an automobile or the inside of the housing of an electrical appliance. In this case, by providing a space (air layer) behind it, more effective sound absorption properties can be obtained when used as a sound absorbing material.

[0015] The drawings shown below are schematic, and the dimensions or scale of the aspect ratio may differ from those of the actual product. In the drawings, the same or equivalent parts will be designated by the same reference numerals. In addition, the same elements will be designated by the same reference numerals in each drawing, and duplicate explanations will be omitted.

[0016] In this specification, terms indicating the relationship between elements (e.g., "perpendicular," "parallel," "orthogonal," etc.) and terms indicating the shape of elements are not expressions that only express a strict meaning, but are expressions that also include a range of substantial equivalence, for example, a difference of about a few percent.

[0017] FIG. 1 is a cross-sectional view schematically showing an example of the porous body of the present invention.

[0018] The porous body 1 shown in Fig. 1 includes a fibrous layer 10. As shown in Fig. 1, the porous body 1 preferably further includes a support layer 20. In the porous body 1 shown in Fig. 1, the fibrous layer 10 is provided on one main surface of the support layer 20. On the other hand, the fibrous layer 10 is not provided on the other main surface of the support layer 20.

[0019] The fibrous layer 10 is made of intertwined liquid crystal polymer (LCP) fibers. For example, when the porous body 1 is used as a sound absorbing material, the high vibration damping properties of the liquid crystal polymer fibers can improve sound absorbing characteristics, particularly in the low frequency range.

[0020] The liquid crystal polymer fiber is preferably a nanofiber liquid crystal polymer (hereinafter also referred to as LCP-NF).

[0021] The LCP-NF includes, for example, a fibrous portion and a lump portion. The fibrous portion may be contained in the LCP-NF as an aggregate portion formed by aggregating fibrous particles, and the lump portion may be contained in the LCP-NF as an aggregate portion formed by aggregating lump particles. Note that the LCP-NF does not necessarily have to include a lump portion.

[0022] The fibrous portion is a fibrous particle. For example, the fibrous particle is a liquid crystal polymer particle having an aspect ratio, which is the ratio of the longitudinal length to the fiber diameter, of 10 or more. The longitudinal length and fiber diameter of the fibrous particle can be measured from image data of the fibrous particle obtained when the fibrous particle is observed with a scanning electron microscope.

[0023] The lumpy portions are LCP-NF that are not substantially fibrous. The lumpy portions may have a flat outer shape. In the LCP-NF, for example, the lumpy portion content is 20% or less. That is, in the LCP-NF, it is preferable that the lumpy portion content is relatively low, and it may not contain any lumpy portions. The lumpy portion content is evaluated by the number of lumpy portions relative to the number of aggregate portions contained in the LCP-NF.

[0024] The liquid crystal polymer fibers such as LCP-NF are preferably made of a thermotropic liquid crystal polymer that exhibits liquid crystallinity in a molten state.

[0025] Among thermotropic liquid crystal polymers, thermotropic liquid crystal polyesters (hereinafter simply referred to as "liquid crystal polyesters") are aromatic polyesters obtained by reacting, for example, an aromatic hydroxycarboxylic acid as an essential monomer with a monomer such as an aromatic dicarboxylic acid or an aromatic diol, and which exhibit liquid crystallinity when melted. Typical examples include Type I synthesized from parahydroxybenzoic acid (PHB), phthalic acid, and 4,4'-biphenol, Type II synthesized from PHB and 2,6-hydroxynaphthoic acid, and Type III synthesized from PHB, terephthalic acid, and ethylene glycol.

[0026] Among them, type I liquid crystal polyester or type II liquid crystal polyester is preferred because of its excellent heat resistance and hydrolysis resistance. In type I liquid crystal polyester, isophthalic acid is preferred as the phthalic acid.

[0027] The fiber diameter of the fibrous layer 10 is 1 μm or more and 3 μm or less.

[0028] The fiber diameter of the fibrous layer 10 can be measured by observing an enlarged image of the fibrous layer 10 .

[0029] The fiber density of the fibrous layer 10 is 100 kg / m ３ That's all.

[0030] The fiber density of the fibrous layer 10 is determined by dividing the basis weight of the fibrous layer 10 by the thickness. The basis weight is the weight of fibers per unit area in the fibrous layer 10. The basis weight can be determined, for example, by calculating the weight per unit area from the weight of the fibrous layer 10.

[0031] Prior art documents Patent Documents 1 and 2 describe examples of nanofiber sound-absorbing materials made from materials with small loss factors. However, to improve the sound absorption coefficient in the low frequency band of, for example, 1000 Hz or less, the thickness needs to be greater than 10 mm, making it difficult to implement noise control measures in the low frequency band for products such as automobiles, where the installation space for sound-absorbing materials is limited.

[0032] In contrast, in the porous body 1, the fiber diameter of the fibrous layer 10 formed by intertwining liquid crystal polymer fibers is set to 1 μm or more and 3 μm or less, and the fiber density of the fibrous layer 10 is set to 100 kg / m ３ By doing so, it is possible to improve the sound absorption characteristics in the low frequency range even if the thickness is small.

[0033] In addition, like the porous body 1, the fiber diameter of the fibrous layer 10 is 1 μm or more and 3 μm or less, and the fiber density of the fibrous layer 10 is 100 kg / m ３ By doing so, the mechanical strength is increased, and therefore collapse due to compression during use can be prevented.

[0034] The upper limit of the fiber density of the fibrous layer 10 is not particularly limited, but is preferably 1000 kg / m ３ Preferably, it is 500 kg / m or less. ３ When the porous body 1 is used as a sound absorbing material, if the fiber density of the fibrous layer 10 is too high and the porosity is too low, the mismatch with the acoustic impedance of air becomes large, and sound waves tend to be reflected on the surface of the material, which tends to reduce the sound absorption coefficient.

[0035] The average pore size of the fibrous layer 10 is preferably 4 μm or less. For example, when the porous body 1 is used as a sound absorbing material, controlling the pore size of the fibrous layer 10 makes it possible to control the sound absorption characteristics in the low frequency range by changing the air permeability.

[0036] From the viewpoint of controlling the sound absorption characteristics in the low frequency range, the average pore diameter of the fibrous layer 10 is preferably 0.5 μm or more, more preferably 1 μm or more, and even more preferably 1.5 μm or more. When the porous body 1 is used as a sound absorbing material, if the average pore diameter of the fibrous layer 10 is too small, the flow resistance per unit thickness becomes too large, resulting in a large mismatch with the acoustic impedance of air, which makes it easier for sound waves to be reflected on the surface of the material, and therefore the sound absorption coefficient tends to decrease.

[0037] The average pore diameter of the fibrous layer 10 can be measured using a mercury porosimeter. In the examples described later, the average pore diameter is determined by measuring the pore distribution using a mercury intrusion porosimeter (AutoPore V9605, manufactured by Micrometrics).

[0038] As shown in Fig. 1, the fibrous layer 10 is preferably supported by a support layer 20. The inclusion of the support layer 20 in the porous body 1 can increase the mechanical strength of the porous body 1 and maintain the shape of the porous body 1. Furthermore, when the porous body 1 is used as a sound-absorbing material, if the porous body 1 is composed of the fibrous layer 10 and the support layer 20, reducing the fiber density or average pore size of the support layer 20 can suppress the reflection of sound waves throughout the porous body 1 while providing the vibration damping effect of the fibrous layer 10, which is thought to improve the sound absorption characteristics throughout the low frequency band.

[0039] The support layer 20 is formed by entangled fibers. The type of fiber constituting the support layer 20 is not particularly limited, but the support layer 20 is preferably formed by entangled polyester fibers such as polyethylene terephthalate (PET).

[0040] Near the interface between the support layer 20 and the fibrous layer 10 , some of the fibers constituting the support layer 20 may be entangled with some of the liquid crystal polymer fibers constituting the fibrous layer 10 .

[0041] The fiber diameter of the support layer 20 is not particularly limited, but is preferably larger than the fiber diameter of the fibrous layer 10 .

[0042] The fiber density of the support layer 20 is not particularly limited, but is preferably lower than the fiber density of the fibrous layer 10 .

[0043] The average pore size of the support layer 20 is not particularly limited, but is preferably larger than the average pore size of the fibrous layer 10 .

[0044] FIG. 2 is a cross-sectional view schematically showing another example of the porous body of the present invention.

[0045] 2, three fibrous layers 10 (10a, 10b, and 10c) are provided on one main surface of the support layer 20. In this way, two or more fibrous layers 10 may be provided on one main surface of the support layer 20. When the porous body 2 is used as a sound absorbing material, if there are two or more fibrous layers 10, adjusting the fiber density or average pore diameter can suppress the reflection of sound waves in the fibrous layers 10, which is thought to have the effect of improving sound absorption characteristics in the low frequency band.

[0046] When two or more fibrous layers 10 are provided on one main surface of the support layer 20, the fibrous layers 10 (for example, fibrous layers 10a, 10b, and 10c) may have the same or different fiber diameters and / or fiber densities. In addition, at least one fibrous layer 10 has a fiber diameter of 1 μm or more and a fiber density of 100 kg / m or less. ３ However, it is sufficient that the fiber diameter of all the fibrous layers 10 is 1 μm or more and 3 μm or less, and the fiber density is 100 kg / m ３ It is preferable that this is equal to or greater than this.

[0047] When two or more fibrous layers 10 are provided on one main surface of the support layer 20, the thicknesses of the fibrous layers 10 may all be the same, or some or all of them may be different. In addition, the average pore diameters of the fibrous layers 10 may all be the same, or some or all of them may be different.

[0048] FIG. 3 is a cross-sectional view schematically showing yet another example of the porous body of the present invention.

[0049] In the porous body 3 shown in Fig. 3, a fibrous layer 10 is provided on each of the main surfaces of the support layer 20. When the porous body 3 is used as a sound-absorbing material, by sandwiching the support layer 20 between the fibrous layers 10, if the fiber density or average pore diameter of the support layer 20 is smaller than that of the fibrous layer 10, the effects of the fibrous layer 10 are synergistically enhanced, and it is thought that the sound absorption characteristics of the entire low frequency band are improved. Furthermore, compared to a configuration in which the fibrous layer 10 is overlaid on one main surface of the support layer 20, by reducing the thickness of the fibrous layer 10 per one main surface of the support layer 20, sound waves are more easily transmitted and reflection of sound waves is less likely to occur.

[0050] When the fibrous layers 10 are provided on both main surfaces of the support layer 20, the fibrous layers 10 provided on each main surface may have the same or different fiber diameter and / or fiber density. ３ However, the fiber diameter of the fibrous layers 10 provided on both main surfaces is 1 μm or more and 3 μm or less, and the fiber density is 100 kg / m ３ It is preferable that this is equal to or greater than this.

[0051] When the fibrous layers 10 are provided on both main surfaces of the support layer 20, the thicknesses of the fibrous layers 10 provided on each main surface may be the same or different. The average pore sizes of the fibrous layers 10 provided on each main surface may be the same or different.

[0052] When a fiber layer 10 is provided on each of the main surfaces of the support layer 20, two or more fiber layers 10 may be provided on one main surface of the support layer 20, and two or more fiber layers 10 may be provided on the other main surface of the support layer 20. In this case, the number of fiber layers 10 provided on one main surface of the support layer 20 may be the same as or different from the number of fiber layers 10 provided on the other main surface of the support layer 20.

[0053] The support layer 20 may be a single layer or may be two or more layers. When the support layer 20 is two or more layers, the fibers constituting the support layer 20 of each layer may be the same or different.

[0054] The porous body 1 may include layers other than the fibrous layer 10 and the support layer 20. In this case, the fibrous layer 10 is preferably disposed as the outermost layer of the porous body 1. In this manner, the porous body of the present invention is formed by entanglement of liquid crystal polymer fibers, has a fiber diameter of 1 μm or more and 3 μm or less, and has a fiber density of 100 kg / m ３ The above-mentioned fibrous layer is preferably disposed as the outermost layer of the porous body.

[0055] In the porous body of the present invention, the overall thickness is preferably less than 10 mm from the viewpoint of miniaturization. In particular, when the porous body of the present invention is used as a sound absorbing material, the sound absorbing characteristics can be improved without increasing the overall thickness. On the other hand, the overall thickness is preferably 1 mm or more. If it is too thin, it will be prone to reflection and will have difficulty absorbing low frequencies.

[0056] The thickness of the porous body is measured at an appropriate portion depending on the shape of the porous body. For example, if the porous body is sheet-shaped, it is the average thickness of the flat portion of the porous body. If the shape of the porous body includes irregularities, it is the average thickness of the deepest recess (the portion where the thickness of the porous body is smallest). Alternatively, if the area occupancy of the recess in the planar direction is low (for example, less than 50%), it is the value obtained by smoothing out the height differences of the surface shape of the porous body.

[0057] The fibrous layer constituting the porous body of the present invention has a structure with continuous fine voids. Furthermore, when the porous body of the present invention has a support layer, the support layer also has a structure with continuous fine voids. Therefore, the porous body of the present invention has both breathability and liquid permeability. Therefore, the porous body of the present invention can be used, for example, in both applications requiring specific sound absorption properties and applications requiring both the sound absorption properties and other functions.

[0058] The porous body of the present invention can also be used solely for the other functions described above. From this perspective, the porous body of the present invention is suitably used as a constituent member of nonwoven fabric products such as sound absorbing materials, sound insulating materials, filtering materials, insulating separators, and air filters.

[0059] The present specification discloses the following:

[0060] <1> A fiber layer formed by intertwining liquid crystal polymer fibers, wherein the fiber diameter of the fiber layer is 1 μm or more and 3 μm or less, and the fiber density of the fiber layer is 100 kg / m ３ That's it, porous body.

[0061] <2> The porous body according to <1>, wherein the average pore diameter of the fibrous layer is 4 μm or less.

[0062] <3> The porous body according to <2>, wherein the average pore diameter of the fibrous layer is 0.5 μm or more.

[0063] <4> The porous body according to <2> or <3>, wherein the average pore diameter of the fibrous layer is 1 μm or more.

[0064] <5> The porous body according to any one of <1> to <4>, further comprising a support layer formed by entangled fibers.

[0065] <6> The porous body according to <5>, wherein the support layer is formed by entangling polyester fibers.

[0066] <7> The porous body according to <5> or <6>, wherein the fibrous layer is provided on one main surface of the support layer.

[0067] <8> The porous body according to <5> or <6>, wherein the fibrous layer is provided on each of the main surfaces of the support layer.

[0068] <9> The porous body according to <7> or <8>, wherein two or more of the fibrous layers are provided on at least one main surface of the support layer.

[0069] <10> The porous body according to any one of <1> to <9>, having an overall thickness of less than 10 mm.

[0070] <11> A sound-absorbing material comprising the porous body according to any one of <1> to <10>.

[0071] Examples will be given below that more specifically disclose the sound-absorbing material, which is one embodiment of the porous body of the present invention, but the present invention is not limited to these examples.

[0072] [Example 1] Liquid crystal polymer (LCP) pellets were coarsely pulverized using a cutter mill. The coarsely pulverized LCP was passed through a 3 mm diameter mesh provided at the outlet of the cutter mill to obtain coarsely pulverized LCP. The coarsely pulverized LCP was finely pulverized using a liquid nitrogen bead mill and sieved through a 100 μm mesh to obtain finely pulverized LCP. The finely pulverized LCP was dispersed in a 50% by mass aqueous ethanol solution and subjected to high-pressure dispersion treatment to obtain liquid crystal polymer fibers (fiber diameter 1 μm). In Example 1, the pressure of the high-pressure dispersion treatment was 200 MPa, and the treatment was repeated 5 times.

[0073] Liquid crystal polymer fibers were added to 1,3-butanediol to obtain a paste. The paste was applied to a support layer made of PET fibers, which are polyester fibers, and then dried at 100°C. After that, the support layer was heat-treated at 120°C for 1 hour in a nitrogen atmosphere to form a fibrous layer made of liquid crystal polymer fibers.

[0074] A sound absorbing material was produced in this manner, to obtain a sample of Example 1. It is preferable to control the melting point of the liquid crystal polymer fiber so as to match the melting point of the polyester fiber.

[0075] To evaluate the sound absorption properties, samples were cut to a diameter of 41 mm and the noise reduction coefficient (NRC) was measured using a normal incidence sound absorption coefficient measurement system ("WinZac MTX"). The NRC is the average value of the sound absorption coefficients at 250 Hz, 500 Hz, 1000 Hz, and 2000 Hz.

[0076] The fiber diameter of the fibrous layer was calculated by measuring the fiber diameter at any 30 points on a scanning electron microscope (SEM) image of the fibrous layer using image processing software (ImageJ), and calculating the average value of the measured fiber diameters. The fiber diameter of the support layer was also calculated in the same manner.

[0077] The fiber densities of the fibrous layer and the support layer were calculated by measuring the weight, area and thickness of the sample used to measure the sound absorption coefficient.

[0078] The average pore diameters of the fibrous layer and the support layer were measured using a mercury porosimeter. Specifically, the average pore diameter was determined by measuring the pore distribution using a mercury intrusion porosimeter (AutoPore V9605, manufactured by Micrometrics).

[0079] Example 2 A sound-absorbing material was produced in the same manner as in Example 1, except that the heat treatment temperature was changed to 140° C., to obtain a sample of Example 2.

[0080] Example 3 A sound-absorbing material was produced in the same manner as in Example 1, except that the heat treatment temperature was changed to 160° C., to obtain a sample of Example 3.

[0081] [Example 4] A sound-absorbing material was produced in the same manner as in Example 1, except that the number of high-pressure dispersion treatments was increased to two, liquid crystal polymer fibers (fiber diameter 2 μm) were obtained, and the heat treatment temperature was changed to 140°C, thereby obtaining a sample of Example 4.

[0082] [Example 5] A sound-absorbing material was produced in the same manner as in Example 1, except that the number of high-pressure dispersion treatments was increased to 30, liquid crystal polymer fibers (fiber diameter 0.7 μm) were obtained, and the heat treatment temperature was changed to 140°C, thereby obtaining a sample of Example 5.

[0083] [Example 6] A sound-absorbing material was produced in the same manner as in Example 1, except that the number of high-pressure dispersion treatments was increased to 30, liquid crystal polymer fibers (fiber diameter 0.7 μm) were obtained, and the heat treatment temperature was changed to 120°C, thereby obtaining a sample of Example 6.

[0084] [Example 7] A suction filtration device and a polyester microfiber nonwoven fabric (basis weight: 14 g / m) were used without using a support layer. ２ A sound-absorbing material was produced in the same manner as in Example 1, except that a liquid crystal polymer fiber slurry was obtained by weaving up the LCP fiber mat using the above-mentioned cellulose acetate cellulose.

[0085] Example 8 A sound-absorbing material was produced in the same manner as in Example 7, except that the heat treatment temperature was changed to 140°C, to obtain a sample of Example 8.

[0086] Example 9 A sound-absorbing material was produced in the same manner as in Example 7, except that the heat treatment temperature was changed to 160° C., to obtain a sample of Example 9.

[0087] [Example 10] A sound-absorbing material was produced in the same manner as in Example 7, except that the number of high-pressure dispersion treatments was increased to two, liquid crystal polymer fibers (fiber diameter 2 μm) were obtained, and the heat treatment temperature was changed to 140°C, thereby obtaining a sample of Example 10.

[0088] [Example 11] A sound-absorbing material was produced in the same manner as in Example 7, except that the number of high-pressure dispersion treatments was increased to 30, liquid crystal polymer fibers (fiber diameter 0.7 μm) were obtained, and the heat treatment temperature was changed to 140°C, thereby obtaining a sample of Example 11.

[0089] [Example 12] A sound-absorbing material was produced in the same manner as in Example 7, except that the number of high-pressure dispersion treatments was increased to 30, liquid crystal polymer fibers (fiber diameter 0.7 μm) were obtained, and the heat treatment temperature was changed to 120°C, thereby obtaining a sample of Example 12.

[0090] [Example 13] A sound-absorbing material was prepared in the same manner as in Example 1, except that after applying and drying a paste to one side of the support layer, a similar paste was applied and dried to the other side of the support layer, and a sample of Example 13 was obtained.

[0091] Example 14 A sound-absorbing material was produced in the same manner as in Example 13, except that the heat treatment temperature was changed to 140° C., to obtain a sample of Example 14.

[0092] Example 15 A sound-absorbing material was produced in the same manner as in Example 13, except that the heat treatment temperature was changed to 160°C, to obtain a sample of Example 15.

[0093] [Example 16] A sound-absorbing material was produced in the same manner as in Example 13, except that the number of high-pressure dispersion treatments was increased to two, liquid crystal polymer fibers (fiber diameter 2 μm) were obtained, and the heat treatment temperature was changed to 140°C, thereby obtaining a sample of Example 16.

[0094] [Example 17] A sound-absorbing material was produced in the same manner as in Example 13, except that the number of high-pressure dispersion treatments was increased to 30, liquid crystal polymer fibers (fiber diameter 0.7 μm) were obtained, and the heat treatment temperature was changed to 140°C, thereby obtaining a sample of Example 17.

[0095] [Example 18] A sound-absorbing material was produced in the same manner as in Example 13, except that the number of high-pressure dispersion treatments was increased to 30, liquid crystal polymer fibers (fiber diameter 0.7 μm) were obtained, and the heat treatment temperature was changed to 120°C, thereby obtaining a sample of Example 18.

[0096] Example 19 In Example 1, the sample prepared by the method of Example 3 was used as the support layer to obtain a sample of Example 19.

[0097] Comparative Example 1 A sound-absorbing material was produced in the same manner as in Example 1, except that the heat treatment temperature was changed to 170° C., to obtain a sample of Comparative Example 1.

[0098] Comparative Example 2 A sample of Comparative Example 2 was obtained using only the polyester fiber described in Example 1 as the sound absorbing material.

[0099] [Comparative Example 3] A sound-absorbing material was produced in the same manner as in Example 7, except that the number of high-pressure dispersion treatments was set to one, liquid crystal polymer fibers (fiber diameter 2.6 μm) were obtained, and the heat treatment temperature was changed to 120°C, thereby obtaining a sample of Comparative Example 3.

[0100] The evaluation results for Examples 1 to 19 and Comparative Examples 1 to 3 are shown in Table 1.

[0101]

[0102] As shown in Table 1, the liquid crystal polymer fiber is provided with a fibrous layer formed by intertwining the fibers, the fiber diameter of the fibrous layer is 1 μm or more and 3 μm or less, and the fiber density of the fibrous layer is 100 kg / m ３ It can be confirmed that in Examples 1 to 19 described above, even if the overall thickness is thin, the sound absorption characteristics are excellent in the low frequency range.

[0103] When Examples 1 to 3 are compared with Examples 4 to 6, it is confirmed that when the average pore diameter of the fibrous layer is 4 μm or less, the sound absorption characteristics in the low frequency range are excellent. Furthermore, it is confirmed that the average pore diameter of the fibrous layer is preferably 0.5 μm or more, and more preferably 1 μm or more. The same is true when Examples 7 to 9 are compared with Examples 10 to 12, and when Examples 13 to 15 are compared with Examples 16 to 18.

[0104] When Examples 1 to 6 are compared with Examples 7 to 12, it can be seen that when a support layer is provided in addition to a fibrous layer, the sound absorption characteristics in the low frequency range are excellent.

[0105] When comparing Examples 1 to 6 with Examples 13 to 18, it can be confirmed that when a fibrous layer is provided on each of the main surfaces of the support layer, the sound absorption characteristics in the low frequency range are excellent.

[0106] Furthermore, it can be confirmed that when two or more fibrous layers are provided on the main surface of the support layer as in Example 19, the sound absorption characteristics are excellent in the low frequency range.

[0107] 1, 2, 3: Porous body 10, 10a, 10b, 10c: Fibrous layer 20: Support layer

Claims

1. A fiber layer is provided in which liquid crystal polymer fibers are entangled, The fiber diameter of the fibrous layer is 1 μm or more and 3 μm or less, The fiber density of the fibrous layer is 100 kg / m ３ That's all, The porous body has an average pore size of the fibrous layer of 1 μm or more and 4 μm or less.

2. The porous body according to claim 1 , further comprising a support layer formed of intertwined fibers.

3. The porous body according to claim 2 , wherein the support layer is made of entangled polyester fibers.

4. The porous body according to claim 2 or 3, wherein the fibrous layer is provided on one main surface of the support layer.

5. 4. The porous body according to claim 2, wherein the fibrous layer is provided on each of the main surfaces of the support layer.

6. 4. The porous body according to claim 2, wherein two or more of the fibrous layers are provided on at least one main surface of the support layer.

7. The porous body according to any one of claims 1 to 3, having an overall thickness of less than 10 mm.

8. A sound-absorbing material comprising the porous body according to any one of claims 1 to 3.