POROUS BODY AND SOUND-ABSORBING MATERIAL

Abstract

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

Description

Technical area

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

[0002] Patent Document 1 discloses a multilayer article comprising a support layer and a submicrometer fiber layer on the support layer. The submicrometer fiber layer comprises polymer fibers with an average fiber diameter of less than 1 µm.

[0003] Patent Document 2 discloses a nonwoven textile structure with a fiber body formed from entangled fibers. The fibers comprise resin nanofibers with a fiber diameter of less than 1 µm. The fiber body has a thickness of 10 mm or more and a fiber density of not less than 10 kg / m 3 and less than 50 kg / m 3 . Reference listPatent documents Patent Document 1: Japanese Unexamined Patent Application Publication No. 2014-15042 Patent Document 2: Japanese Unexamined Patent Application Publication No. 2016-121426 Summary of the inventionTechnical problem

[0004] For example, the multilayer article described in Patent Document 1 and the nonwoven fabric structure described in Patent Document 2 can be used as a sound-absorbing material. Porous materials, exemplified by glass wool or urethane foam, have been widely used as sound-absorbing materials. However, such porous materials have poor sound absorption characteristics in the low- to medium-frequency range. For such a porous material to absorb sound, especially in the low-frequency range of 1000 Hz or less, the material must have a large thickness. This poses a space-consumption problem.

[0005] While the multilayer article described in Patent Document 1 and the nonwoven fabric structure described in Patent Document 2 have improved sound absorption characteristics due to the use of nanofibers, their sound absorption characteristics in the low frequency range are still insufficient; there is still room for improvement.

[0006] The present invention was made to solve the above problems. Therefore, an object of the present invention is to provide a porous body that can be used as a sound-absorbing material or the like. Furthermore, an object of the present invention is to provide a sound-absorbing material that, even though it is thin, has excellent sound absorption characteristics in the low-frequency range. Solution to the problem

[0007] The porous body of the present invention has a fiber body layer formed of entangled liquid crystal polymer fibers, wherein the fiber body layer has a fiber diameter of not less than 1 µm and not more than 3 µm and a fiber density of 100 kg / m 3 or more.

[0008] The sound absorbing material of the present invention comprises the porous body of the present invention. Advantageous effects of the invention

[0009] The present invention makes it possible to provide a porous body that can be used as a sound-absorbing material or the like. The present invention also makes it possible to provide a sound-absorbing material that, even if thin, has excellent sound absorption characteristics in the low-frequency range. Brief description of the drawings 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 showing still another example of the porous body of the present invention. Description of the embodiments

[0010] The porous body of the present invention will now be described.

[0011] It should be noted that the present invention is not limited to the features described below, and various changes and modifications may be made thereto within the spirit and scope of the present invention. Two or more preferred features of the present invention as described below may be combined; such a combined feature falls within the scope of the present invention.

[0012] The uses of the porous body of the present invention are not particularly limited; for example, it can be used as a sound-absorbing material. A sound-absorbing material comprising the porous body of the present invention constitutes one aspect of the present invention.

[0013] In one embodiment, the porous body of the present invention can be used in such a manner that it is fixed to a wall surface using an adhesive on one side of the porous body. For example, the porous body can be directly attached to a cover for an automobile or to an inner surface of an electrical device casing. A space (air layer) can be provided behind the porous body fixed to a surface so that when used as a sound-absorbing material, more effective sound absorption characteristics can be achieved.

[0014] The following drawings are schematic; dimensions, aspect ratios, etc., may not be to scale. Throughout the drawings, the same reference numerals are used for the same or equivalent sections. Furthermore, the same elements or components are given the same reference numerals, and duplicate descriptions are omitted.

[0015] Terms indicating a relationship between elements or components (for example, "perpendicular", "parallel" and "orthogonal") and terms indicating the shape of an element or component, as used herein, are not intended to be construed in a strict sense, but in a broad sense that includes a range of substantial equivalence, for example, a difference on the order of a few percent.

[0016] Fig.1 is a cross-sectional view schematically showing an example of the porous body of the present invention.

[0017] The Fig. 1 comprises a fiber body layer 10. As shown in Fig. 1, the porous body 1 preferably further comprises a carrier layer 20. In the Fig. In the porous body 1 shown in Figure 1, the fiber body layer 10 is provided on one main surface of the support layer 20. On the other hand, no fiber body layer 10 is provided on the other main surface of the support layer 20.

[0018] The fiber body layer 10 is formed of entangled 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 the sound absorption characteristics, especially in the low-frequency range.

[0019] The liquid crystal polymer fibers are preferably a nanofiber liquid crystal polymer (hereinafter also referred to as LCP-NF).

[0020] For example, the LCP-NF comprises a fiber portion and a piece portion. The fiber portion may be included in the LCP-NF as an aggregate portion, which is a collection of fiber particles. The piece portion may be included in the LCP-NF as an aggregate portion, which is a collection of piece particles. The LCP-NF does not necessarily comprise a piece portion.

[0021] The fiber section comprises fiber particles. The fiber particles are, for example, liquid crystal polymer particles with an aspect ratio (the ratio of the longitudinal length to the fiber diameter) of 10 or more. The longitudinal length and fiber diameter of a fiber particle can be determined from image data of the fiber particle obtained after observing the fiber particles with a scanning electron microscope.

[0022] The chunk portion is essentially a non-fiber portion of the LCP-NF. The chunk portion may have a flattened shape. For example, the chunk portion proportion in the LCP-NF is 20% or less. Thus, it is preferable that the chunk portion proportion in the LCP-NF be relatively low; the chunk portion proportion could even be zero. The chunk portion proportion can be evaluated as the ratio of the number of chunk portions to the number of aggregate portions in the LCP-NF.

[0023] The liquid crystal polymer fibers, such as the LCP-NF, are preferably made of a thermotropic liquid crystal polymer that exhibits liquid crystallinity when in a molten state.

[0024] Among thermotropic liquid crystal polymers, there is a thermotropic liquid crystal polyester (hereinafter simply referred to as "liquid crystal polyester"), such as an aromatic polyester obtained by reacting an aromatic hydroxycarboxylic acid as an essential monomer with a monomer such as an aromatic dicarboxylic acid or an aromatic diol, and which exhibits liquid crystallinity when in a molten state. Representative examples include type I liquid crystal polyester synthesized from parahydroxybenzoic acid (PHB), phthalic acid, and 4,4'-biphenol, type II liquid crystal polyester synthesized from PHB and 2,6-hydroxynaphthoic acid, and type III liquid crystal polyester synthesized from PHB, terephthalic acid, and ethylene glycol.

[0025] Among these, Type I liquid crystal polyester or Type II liquid crystal polyester is preferred because of its superior heat resistance and hydrolysis resistance. For Type I liquid crystal polyester, isophthalic acid is preferred as phthalic acid.

[0026] The fiber diameter of the fiber body layer 10 is not less than 1 µm and not more than 3 µm.

[0027] The fiber diameter of the fiber body layer 10 can be measured by observing a magnified image of the fiber body layer 10.

[0028] The fiber density of the fiber body layer 10 is 100 kg / m 3 or more.

[0029] The fiber density of the fiber body layer 10 can be determined by dividing the basis weight of the fiber body layer 10 by the thickness. The basis weight is the weight of fibers per unit area of ​​the fiber body layer 10. The basis weight can be determined, for example, by calculating the weight per unit area from the weight of the fiber body layer 10.

[0030] Patent Documents 1 and 2, which are prior art documents, describe examples of sound-absorbing materials using nanofibers made of a material with a low loss coefficient. However, in order to improve the sound absorption coefficient of such a sound-absorbing material, for example, in the low-frequency range of not more than 1000 Hz, the thickness of the material must be made greater than 10 mm, making it difficult to implement noise countermeasures in the low-frequency range for an object such as an automobile where the installation space for a sound-absorbing material is limited.

[0031] In contrast, by making the fiber diameter of the fiber body layer 10 made of entangled liquid crystal polymer fibers not less than 1 μm and not more than 3 μm and by making the fiber density of the fiber body layer 10 100 kg / m as in the porous body 1 3 or more, it is possible to improve the sound absorption characteristics in the low frequency range even if the porous body is thin.

[0032] Further, by making the fiber diameter of the fiber body layer 10 not less than 1 µm and not more than 3 µm and by making the fiber density of the fiber body layer 10 100 kg / m as in the porous body 1 3 or more, the mechanical strength of the fiber body layer 10 can be improved, making it possible to avoid collapse of the layer due to compression during use.

[0033] While the upper limit of the frequency density of the fiber body layer 10 is not particularly limited, the fiber density is preferably 1000 kg / m 3 or less, more preferably 500 kg / m 3 or less. When the porous body 1 is used as a sound-absorbing material, if the fiber density of the fiber body layer 10 is too high and the porosity is too low, there will be a large mismatch with the acoustic impedance of air. Accordingly, sound waves are likely to be reflected by the surface of the material, and thus the sound absorption coefficient is likely to be low.

[0034] The fiber body layer 10 preferably has an average pore diameter of 4 µm or less. For example, when the porous body 1 is used as a sound-absorbing material, controlling the pore diameter of the fiber body layer 10 makes it possible to control the sound absorption characteristics of the sound-absorbing material in the low-frequency range by changing its air permeability.

[0035] From the standpoint of controlling the sound absorption characteristics in the low-frequency range, the average pore diameter of the fiber body 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 fiber body layer 10 is too small, the flow resistance per unit thickness becomes too high, resulting in a large mismatch with the acoustic impedance of air.

[0036] Accordingly, sound waves are likely to be reflected by the surface of the material and so the sound absorption coefficient is likely to be low.

[0037] The average pore diameter of the fiber body layer 10 can be measured using a mercury porosimeter. In the examples described below, the average pore diameter is determined by measuring a pore distribution using a mercury intrusion porosimeter (manufactured by Micrometrics Instrument Corporation, AutoPore V 9605).

[0038] As in Fig.1, the fiber body layer 10 is preferably supported by the 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, in addition, can maintain the shape of the porous body 1. Furthermore, the porous body 1 composed of the fiber body layer 10 and the support layer 20 can preferably be used as a sound-absorbing material: By reducing the fiber density or the average pore diameter of the support layer 20, the porous body 1 has the vibration-damping effect of the fiber body layer 10 while suppressing reflection of sound waves in the entire porous body 1, resulting in an improvement in sound absorption characteristics in the entire low-frequency band.

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

[0040] In a region around the interface between the carrier layer 20 and the fiber body layer 10, some of the fibers forming the carrier layer 20 may entangle with some of the liquid crystal polymer fibers forming the fiber body layer 10.

[0041] While the fiber diameter of the carrier layer 20 is not particularly limited, it is preferably larger than the fiber diameter of the fiber body layer 10.

[0042] While the fiber density of the carrier layer 20 is not particularly limited, it is preferably lower than the fiber density of the fiber body layer 10.

[0043] While the average pore diameter of the support layer 20 is not particularly limited, it is preferably larger than the average pore diameter of the fiber body layer 10.

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

[0045] In the Fig.In the porous body 2 shown in Figure 2, three fiber body layers 10 (10a, 10b, and 10c) are provided on one main surface of the support layer 20. As in this example, two or more fiber body layers 10 could be provided on one main surface of the support layer 20. When the porous body 2 is used as a sound-absorbing material, the use of two or more fiber body layers 10 suppresses the reflection of sound waves in the fiber body layers 10 by adjusting the fiber density or the average pore diameter, resulting in an improvement in the sound absorption characteristics in the low-frequency band.

[0046] If two or more fiber body layers 10 are provided on one main surface of the carrier layer 20, the fiber body layers 10 (e.g., fiber body layers 10a, 10b, and 10c) may have the same or different fiber diameters and / or fiber densities. At least one of the fiber body layers 10 has a fiber diameter of not less than 1 µm and not more than 3 µm and a fiber density of 100 kg / m 3 or more. Preferably, all fiber body layers 10 have a fiber diameter of not less than 1 µm and not more than 3 µm and a fiber density of 100 kg / m 3 or more.

[0047] If two or more fiber body layers 10 are provided on one main surface of the carrier layer 20, the thicknesses of all fiber body layers 10 may be the same, or the thicknesses of some or all fiber body layers 10 may be different. The average pore diameters of all fiber body layers 10 may be the same, or the average pore diameters of some or all fiber body layers 10 may be different.

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

[0049] In the Fig.In the porous body 3 shown in Figure 3, a fiber body layer 10 is provided on each of the two main surfaces of the support layer 20. The porous body 3 having the structure in which the support layer 20 is sandwiched between the fiber body layers 10 can be advantageously used as a sound-absorbing material: When the fiber density or average pore diameter of the support layer 20 is smaller than that of the fiber body layers 10, the effect of each fiber body layer 10 is multiplied, resulting in an improvement in the sound absorption characteristics throughout the low-frequency band.Furthermore, compared with a structure in which one or more fiber body layers 10 are supported only on one main surface of the support layer 20, the thickness of one fiber body layer 10 per one main surface of the support layer 20 can be made smaller, so that sound waves are more likely to pass through each fiber body layer 10 and reflection of sound waves is less likely to occur.

[0050] If a fiber body layer 10 is provided on each of the two main surfaces of the carrier layer 20, the fiber body layers 10 could have the same or different fiber diameters and / or fiber densities. One or more fiber body layers 10 provided on at least one of the two main surfaces have a fiber diameter of not less than 1 µm and not more than 3 µm and a fiber density of 100 kg / m 3or more. Preferably, the fiber body layers 10 provided on both main surfaces have a fiber diameter of not less than 1 µm and not more than 3 µm and a fiber density of 100 kg / m 3 or more.

[0051] When a fiber body layer 10 is provided on each of the two main surfaces of the support layer 20, the thicknesses of the fiber body layers 10 provided on the main surfaces may be the same or different. The average pore diameters of the fiber body layers 10 provided on the main surfaces may be the same or different.

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

[0053] The carrier layer 20 may consist of a single layer or two or more layers. If the carrier layer 20 consists of two or more layers, the fibers forming the layers of the carrier layer 20 may be the same or different.

[0054] The porous body 1 may comprise one or more layers other than the fiber body layer(s) 10 and the support layer 20. In this case, the fiber body layer(s) 10 is / are preferably arranged as the outermost layer(s) of the porous body 1. Thus, in the porous body of the present invention, one or more fiber body layers formed from entangled liquid crystal polymer fibers and having a fiber diameter of not less than 1 µm and not more than 3 µm and a fiber density of 100 kg / m 3 or more, preferably arranged as the outermost layer(s) of the porous body.

[0055] In the porous body of the present invention, the total thickness is preferably less than 10 mm from the standpoint of size reduction. When the porous body of the present invention is used as a sound-absorbing material, the sound absorption characteristics can be improved without increasing the total thickness. On the other hand, the total thickness may preferably be 1 mm or more. If the porous body is too thin, it is more likely to reflect sound waves and less likely to adsorb low-frequency waves.

[0056] The thickness of the porous body is measured in an appropriate section depending on the shape of the porous body. For example, if the porous body has a sheet-like shape, the thickness may be an average thickness of a flat section of the porous body. If the shape of the porous body includes irregularities, the thickness may be an average thickness of a section corresponding to one or more deepest recesses (i.e., a section where the thickness of the porous body is smallest), or if the area coverage of the deepest recess(es) in the planar direction is low (e.g., less than 50%), it may be a value obtained by averaging the level differences in the surface shape of the porous body.

[0057] The fibrous body layer constituting the porous body of the present invention has a structure with continuous fine pores. When the porous body of the present invention comprises a support layer, the support layer also has a structure with continuous fine pores. Accordingly, the porous body of the present invention is both air-permeable and liquid-permeable. Therefore, the porous body of the present invention can be used, for example, both in an application requiring specific sound absorption characteristics and in an application requiring these sound absorption characteristics and a specific other function.

[0058] The porous body of the present invention can also be used in an application that only requires this additional function. From this perspective, the porous body of the present invention can advantageously be used as a component element of a nonwoven textile product, for example, a sound-absorbing material, a sound-insulating material, a filter material, an insulating separator, or an air filter.

[0059] This specification discloses the following: 1 A porous body having a fiber body layer formed of entangled liquid crystal polymer fibers, the fiber body layer having a fiber diameter of not less than 1 µm and not more than 3 µm and a fiber density of 100 kg / m 3 or more. 2 Porous body according to 1, in which the average pore diameter of the fiber body layer is 4 µm or less. 3 Porous body according to 2, in which the average pore diameter of the fiber body layer is 0.5 µm or more. 4 Porous body according to 2 or 3, in which the average pore diameter of the fiber body layer is 1 µm or more. 5 Porous body according to any one of 1 to 4, further comprising a support layer formed of entangled fibers. 6 Porous body according to 5, in which the carrier layer is formed from entangled polyester fibers. 7 Porous body according to 5 or 6, in which the fiber body layer is provided on a main surface of the support layer. 8 Porous body according to 5 or 6, in which the fiber body layer is provided on each of the two main surfaces of the support layer. 9 Porous body according to 7 or 8, wherein the fiber body layer consists of two or more layers and is provided on at least one of both main surfaces of the support layer. 10 Porous body according to one of 1 to 9, having a total thickness of less than 10 mm. 11 Sound absorbing material having the porous body according to any one of 1 to 10. EXAMPLES

[0060] The following examples more specifically disclose sound-absorbing materials, each of which is an embodiment of the porous body of the present invention. It should be noted that the present invention is not limited to these examples. [Example 1]

[0061] Liquid crystal polymer (LCP) pellets were coarsely ground using a cutting mill.

[0062] The coarsely crushed LCP was passed through a 3 mm mesh sieve provided at the outlet of the granulator to obtain coarsely crushed LCP.

[0063] The coarsely crushed LCP was finely ground in a liquid nitrogen ball mill and sieved through a 100 µm mesh sieve to obtain finely ground LCP.

[0064] The finely ground LCP was dispersed in a 50 mass% aqueous ethanol solution and subjected to a high-temperature dispersion treatment to obtain liquid crystal polymer fibers (fiber diameter 1 µm). For Example 1, the high-temperature dispersion treatment was performed five times at a pressure of 200 MPa.

[0065] 1,3-butanediol was added to the liquid crystal polymer fibers to obtain a paste.

[0066] The paste was applied to a support layer consisting of PET fibers, which are polyester fibers, and dried at 100°C and then subjected to heat treatment at 120°C for one hour in a nitrogen atmosphere to form a fiber body layer consisting of liquid crystal polymer fibers.

[0067] A sound-absorbing material as a sample of Example 1 was then produced. The melting point of the liquid crystal polymer fibers is preferably controlled according to the melting point of the polyester fibers.

[0068] To evaluate the sound absorption characteristics, the sample was cut to a diameter of 41 mm and the noise reduction coefficient (NRC) was measured using a normal incidence sound absorption coefficient measurement system ("WinZacMTX"). The NRC is the average value of the sound absorption coefficients at 250 Hz, 500 Hz, 1000 Hz, and 2000 Hz.

[0069] Fiber diameters of the fiber body layer were measured at 30 random locations on a scanning electron microscope (SEM) image of the fiber body layer using image processing software ("ImageJ"). The fiber diameter of the fiber body layer was calculated as the average of the measured fiber diameters. The fiber diameter of the carrier layer was determined in the same way.

[0070] The fiber densities of the fiber body layer and the support layer were calculated from measurements of weight, area and thickness of each layer of the sample used to measure the sound absorption coefficient.

[0071] The average pore diameters of the fiber body layer and the support layer were measured using a mercury porosimeter. Specifically, the average pore diameter of each layer was determined by measuring the pore distribution using a mercury intrusion porosimeter (manufactured by Micrometrics Instrument Corporation, AutoPore V 9605). [Example 2]

[0072] A sound-absorbing material as a sample of Example 2 was prepared in the same manner as in Example 1 except that the heat treatment temperature was changed to 140°C. [Example 3]

[0073] A sound-absorbing material as a sample of Example 3 was prepared in the same manner as in Example 1 except that the heat treatment temperature was changed to 160°C. [Example 4]

[0074] A sound-absorbing material as a sample of Example 4 was prepared in the same manner as in Example 1, except that the high-pressure dispersion treatments were carried out twice to obtain liquid crystal polymer fibers (fiber diameter 2 µm) and that the heat treatment temperature was changed to 140°C. [Example 5]

[0075] A sound-absorbing material as a sample of Example 5 was prepared in the same manner as in Example 1, except that the high-pressure dispersion treatments were carried out 30 times to obtain liquid crystal polymer fibers (fiber diameter 0.7 µm) and that the heat treatment temperature was changed to 140°C. [Example 6]

[0076] A sound-absorbing material as a sample of Example 6 was prepared in the same manner as in Example 1, except that the high-pressure dispersion treatments were carried out 30 times to obtain liquid crystal polymer fibers (fiber diameter 0.7 µm) and that the heat treatment temperature was changed to 120°C. [Example 7]

[0077] A sound-absorbing material as a sample of Example 7 was prepared in the same manner as in Example 1, except that no support layer was used and that an LCP fiber mat was prepared from a slurry of liquid crystal polymer fibers using a suction filtration device and a nonwoven polyester microfiber fabric (basis weight: 14 g / m 2 ) was manufactured. [Example 8]

[0078] A sound-absorbing material as a sample of Example 8 was prepared in the same manner as in Example 7 except that the heat treatment temperature was changed to 140°C. [Example 9]

[0079] A sound-absorbing material as a sample of Example 9 was prepared in the same manner as in Example 7 except that the heat treatment temperature was changed to 160°C. [Example 10]

[0080] A sound-absorbing material as a sample of Example 10 was prepared in the same manner as in Example 7, except that the high-temperature dispersion treatments were carried out twice to obtain liquid crystal polymer fibers (fiber diameter 2 µm) and that the heat treatment temperature was changed to 140°C. [Example 11]

[0081] A sound-absorbing material as a sample of Example 11 was prepared in the same manner as in Example 7, except that the high-temperature dispersion treatments were carried out 30 times to obtain liquid crystal polymer fibers (fiber diameter 2 µm) and that the heat treatment temperature was changed to 140°C. [Example 12]

[0082] A sound-absorbing material as a sample of Example 12 was prepared in the same manner as in Example 7, except that the high-temperature dispersion treatments were carried out 30 times to obtain liquid crystal polymer fibers (fiber diameter 2 µm) and that the heat treatment temperature was changed to 120°C. [Example 13]

[0083] A sound-absorbing material as a sample of Example 13 was prepared in the same manner as in Example 1, except that after applying the paste to one surface of the support layer and then drying the paste, the same paste was applied to the other surface of the support layer, followed by drying the paste. [Example 14]

[0084] A sound-absorbing material as a sample of Example 14 was prepared in the same manner as in Example 13 except that the heat treatment temperature was changed to 140°C. [Example 15]

[0085] A sound-absorbing material as a sample of Example 15 was prepared in the same manner as in Example 13 except that the heat treatment temperature was changed to 160°C. [Example 16]

[0086] A sound-absorbing material as a sample of Example 16 was prepared in the same manner as in Example 13, except that the high-temperature dispersion treatments were carried out twice to obtain liquid crystal polymer fibers (fiber diameter 2 µm) and that the heat treatment temperature was changed to 140°C. [Example 17]

[0087] A sound-absorbing material as a sample of Example 17 was prepared in the same manner as in Example 13, except that the high-temperature dispersion treatments were carried out 30 times to obtain liquid crystal polymer fibers (fiber diameter 2 µm) and that the heat treatment temperature was changed to 140°C. [Example 18]

[0088] A sound-absorbing material as a sample of Example 18 was prepared in the same manner as in Example 13, except that the high-temperature dispersion treatments were carried out 30 times to obtain liquid crystal polymer fibers (fiber diameter 2 µm) and that the heat treatment temperature was changed to 120°C. [Example 19]

[0089] The sample of Example 19 was prepared in the same manner as Example 1, except that the sample of Example 3 was used as the support layer. [Comparison example 1]

[0090] A sound-absorbing material as a sample of Comparative Example 1 was prepared in the same manner as in Example 1 except that the heat treatment temperature was changed to 170°C. [Comparison example 2]

[0091] The sample of Comparative Example 2, which is a sound-absorbing material, was formed only from the polyester fibers described in Example 1. [Comparison example 3]

[0092] A sound-absorbing material as a sample of Comparative Example 3 was prepared in the same manner as in Example 7, except that the high-temperature dispersion treatments were performed once to obtain liquid crystal polymer fibers (fiber diameter 2.6 µm) and that the heat treatment temperature was changed to 120°C.

[0093] The evaluation results for Examples 1 to 19 and Comparative Examples 1 to 3 are shown in Table 1 below. [Table 1] Layer structure Fiber diameter [µm] Fiber density [kg / m 3 ] Average pore diameter [µm] Total thickness [mm] NRC[-] 1st shift 2nd layer 3rd layer 1st shift 2nd shift 3rd shift 1st shift 2nd shift 3rd shift 1st shift 2nd shift 3rd shift Example 1 Liquid crystal polymer fibers Polyester fibers - 1,1 16,1 - 140 82 - 1,8 125,7 - 7 0,48 Example 2 Liquid crystal polymer fibers Polyester fibers - 1,8 16,8 - 281 88 - 2,1 128,9 - 7 0,46 Example 3 Liquid crystal polymer fibers Polyester fibers - 2,5 15,9 - 421 83 - 3,4 127,3 - 7 0,51 Example 4 Liquid crystal polymer fibers Polyester fibers - 2,1 16,4 - 213 85 - 4,4 127,4 - 7 0,32 Example 5 Liquid crystal polymer fibers Polyester fibers - 1,2 16,4 - 412 84 - 0,8 127,4 - 7 0,38 Example 6 Liquid crystal polymer fibers Polyester fibers - 1,0 16,2 - 482 83 - 0,4 128,8 - 7 0,30 Example 7 Liquid crystal polymer fibers - - 1,1 - - 140 - - 1,8 - - 7 0,37 Example 8 Liquid crystal polymer fibers - - 1,8 - - 281 - - 2,1 - - 7 0,38 Example 9 Liquid crystal polymer fibers - - 2,5 - - 421 - - 3,4 - - 7 0,40 Example 10 Liquid crystal polymer fibers - - 2,1 - - 213 - - 4,4 - - 7 0,28 Example 11 Liquid crystal polymer fibers - - 1,2 - - 412 - - 0,8 - - 7 0,32 Example 12 Liquid crystal polymer fibers - - 1,0 - - 482 - - 0,4 - - 7 0,27 Example 13 Liquid crystal polymer fibers Polyester fibers Liquid crystal polymer fibers 1,1 16,1 1.1 140 82 140 1,8 125,7 1,8 7 0,58 Example 14 Liquid crystal polymer fibers Polyester fibers Liquid crystal polymer fibers 1,8 16,8 1.8 281 88 281 2,1 128,9 2,1 7 0,59 Example 15 Liquid crystal polymer fibers Polyester fibers Liquid crystal polymer fibers 2,5 15,9 2,5 421 83 421 3,4 127,3 3,4 7 0,61 Example 16 Liquid crystal polymer fibers Polyester fibers Liquid crystal polymer fibers 2,1 16,4 2,1 213 85 213 4,4 127,4 4,4 7 0,43 Example 17 Liquid crystal polymer fibers Polyester fibers Liquid crystal polymer fibers 1,2 16,4 1,2 412 84 412 0,8 127,4 0,8 7 0,44 Example 18 Liquid crystal polymer fibers Polyester fibers Liquid crystal polymer fibers 1,0 16,2 1,0 482 83 482 0,4 128,8 0,4 7 0,42 Example 19 Liquid crystal polymer fibers Liquid crystal polymer fibers Polyester fibers 1,1 2,5 16,1 140 421 82 1,8 3,4 125,7 7 0,54 Comparison example 1 Liquid crystal polymer fibers Polyester fibers - 3,6 16,2 - 980 86 - 4,6 127.4 - 7 0,24 Comparison example 2 Polyester fibers - - 16,2 - - 85 - - 127,7 - - 7 0,22 Comparison example 3 Liquid crystal polymer fibers - - 2,8 - - 82 - - 5,3 - - 7 0,21

[0094] As shown in Table 1, the samples of Examples 1 to 19 comprising a fiber body layer formed of entangled liquid crystal polymer fibers, and wherein the fiber body layer has a fiber diameter of not less than 1 µm and not more than 3 µm and a fiber density of 100 kg / m 3 or more, is excellent in sound absorption characteristics in the low frequency range even if the total thickness is small.

[0095] As can be seen from a comparison between Examples 1 to 3 and Examples 4 to 6, the sound absorption characteristics in the low-frequency range are superior when the average pore size of the fiber body layer is 4 µm or less. The comparison also shows that the average pore diameter of the fiber body layer is preferably 0.5 µm or more, and more preferably 1 µm or more. The same applies to a comparison between Examples 7 to 9 and Examples 10 to 12, as well as to a comparison between Examples 13 to 15 and Examples 16 to 18.

[0096] As can be seen from a comparison between Examples 1 to 6 and Examples 7 to 12, the inclusion of the support layer in addition to the fiber body layer improves the sound absorption characteristics in the low frequency range.

[0097] As can be seen from a comparison between Examples 1 to 6 and Examples 13 to 18, the sound absorption characteristics in the low frequency range are superior when the fiber body layer is provided on each of both main surfaces of the support layer.

[0098] The information for Example 19 shows that the sound absorption characteristics in the low frequency range are superior when two or more fiber body layers are provided on the main surface of the support layer. List of reference symbols 1, 2, 3 porous body 10, 10a, 10b, 10c Fibrous body layer 20 Carrier layer QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2014-15042

[0003] JP 2016-121426

[0003]

Claims

[1] A porous body having a fiber body layer formed of entangled liquid crystal polymer fibers, wherein the fiber body layer has a fiber diameter of not less than 1 µm and not more than 3 µm and a fiber density of 100 kg / m 3 or more. [2] The porous body according to claim 1, wherein the average pore diameter of the fiber body layer is 4 µm or less. [3] The porous body according to claim 2, wherein the average pore diameter of the fiber body layer is 0.5 µm or more. [4] A porous body according to claim 2 or 3, wherein the average pore diameter of the fiber body layer is 1 µm or more. [5] A porous body according to any one of claims 1 to 4, further comprising a support layer formed of entangled fibers. [6] A porous body according to claim 5, wherein the support layer is formed from entangled polyester fibers. [7] A porous body according to claim 5 or 6, wherein the fiber body layer is provided on a main surface of the support layer. [8] A porous body according to claim 5 or 6, wherein the fiber body layer is provided on each of both main surfaces of the support layer. [9] A porous body according to claim 7 or 8, wherein the fiber body layer consists of two or more layers and is provided on at least one of both main surfaces of the support layer. [10] Porous body according to one of claims 1 to 9, which has a total thickness of less than 10 mm. [11] A sound-absorbing material comprising the porous body according to any one of claims 1 to 10.

Images