Composite molded body, manufacturing method of the same, and composite sound-absorbing material

Abstract

To provide a composite molded body that can be suitably used as a ventilation adjustment layer that has excellent sound absorption properties in the low to mid frequency bands and also has excellent three-dimensional shaping properties.SOLUTION: According to the present disclosure, there is provided a composite molded body containing fibrillated fibers and short fibers. The composite molded body has an areal density of 30 g / m2 to 1000 g / m2 and an air permeation resistance per unit thickness of 15.0 s / (100 mL.mm) or less. According to the present disclosure, there is also provided a composite sound-absorbing material having a thickness of 10 mm or less, in which a ventilation adjustment layer and a porous material are laminated. In one embodiment, the ventilation adjustment layer has specific sound absorption characteristics in accordance with JIS A 1405. In another embodiment, the ventilation adjustment layer has a total areal density of 100 g / m2 to 1000 g / m2, a total air permeation resistance of 0.1 s / 100 mL to 2.0 s / 100 mL, and a total thickness of 0.50 mm to 5.00 mm, and the thickness of the porous material is 5.00 mm or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a composite molded body, a method for manufacturing the same, and a composite sound-absorbing material.

Background Art

[0002] When an automobile is running, various noises such as noise from the engine and drive system, road noise, and wind noise are generated. Conventionally, in order to suppress these noises and create a comfortable interior space, sound-absorbing materials have been used for the purpose of suppressing noise emission. On the other hand, in recent years, the electrification of automobiles has advanced, and in particular, the quietness of the drive system has improved, and sounds that were not conventionally recognized as noise are now being recognized as noise.

[0003] The frequency of noise depends on each sound source, and it is necessary to use a sound-absorbing material suitable for each sound source. However, porous sound-absorbing materials that are widely used in in-vehicle applications, namely non-woven fabrics and foams, exhibit excellent sound absorption rates in the high-frequency band, but tend to have a decreasing sound absorption rate on the low-frequency side. On the other hand, it is known that by providing a layer for adjusting air permeability (hereinafter referred to as an air permeability adjustment layer) on the surface of the porous material, the sound absorption performance in the low-frequency to mid-frequency band can be improved.

[0004] For example, Patent Document 1 shows a textile-like composite sound-absorbing material in which a foam layer as an air permeability adjustment layer is provided on a non-woven fabric obtained by combining short fibers having a specific fineness, and it is described that the sound absorption performance is excellent in the range of 800 Hz to 2000 Hz.

[0005] Patent Document 2 shows a composite sound-absorbing material in which a spunbond non-woven fabric is adhered in a dotted pattern with a hot melt adhesive on a melamine foam, and it is described that the composite sound-absorbing material has a thickness of slightly more than 10 mm and exhibits excellent sound absorption performance in the entire frequency band.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in the conventional technology, since the function of the ventilation adjustment layer is insufficient, the thickness of the entire sound-absorbing material becomes thick, or although it has excellent function as a ventilation adjustment layer, it has poor formability and cannot follow a complicated three-dimensional shape such as an automotive member.

[0008] One of the objectives of the present disclosure is to provide a composite molded body that can be suitably used as a ventilation adjustment layer excellent in sound absorption in the low-frequency to mid-frequency bands and also has excellent three-dimensional formability.

Means for Solving the Problems

[0009] Examples of embodiments of the present disclosure are listed in the following items [1] to

[10] . [1] A composite molded body containing fibrillated fibers and short fibers, wherein the composite molded body has a basis weight of 30 g / m 2 to 1000 g / m 2 and an air permeability resistance per unit thickness of 15.0 s / (100 mL·mm) or less. [2] The composite molded body according to item [1], wherein the fibrillated fibers are at least one selected from the group consisting of cellulose microfibers, fibrillated fibers of polyacrylonitrile, aramid pulp, chitin nanofibers, chitosan nanofibers, and silk nanofibers. [3] The composite molded body according to item [2], wherein the fibrillated fibers contain cellulose microfibers, and the cellulose microfibers have an average fiber diameter including a microfiber portion up to the fibrillated end of 10 nm or more and 1000 nm or less. [4] The composite molded body according to any one of claims 1 to 3, wherein the short fibers are made of synthetic fibers. [5] A method for manufacturing the composite molded body according to any one of items [1] to [4], the method including a step of three-dimensionally shaping a slurry containing fibrillated fibers and short fibers by a pulp molding method. [6] A sound absorption material including the composite molded body according to any one of items [1] to [4]. [7] A composite sound absorption material including a support body having a thickness of 5 mm or more and the composite molded body according to any one of items [1] to [4] laminated on the support body. [8] The composite sound absorption material according to item [7], wherein the support body is a porous material. [9] A composite sound absorption material having a structure in which a ventilation adjustment layer and a porous material are laminated, wherein the thickness of the composite sound absorption material is 10 mm or less, In the measurement method of normal incidence conforming to JIS A 1405, it has a maximum value of sound absorption at 3000 Hz or less, the sound absorption rate at 1000 Hz is 0.3 or more, the average sound absorption rate from 800 Hz to 2000 Hz is 0.4 or more, and the average sound absorption rate from 500 Hz to 6400 Hz is 0.3 or more.

[10] A composite sound absorption material having a structure in which a ventilation adjustment layer and a porous material are laminated, wherein the thickness of the composite sound absorption material is 10 mm or less, wherein the surface density of the ventilation adjustment layer is 100 g / m 2 or more and 1000 g / m 2 or less, wherein the air permeability resistance of the ventilation adjustment layer is 0.1 s / 100 mL or more and 2.0 s / 100 mL or less, wherein the thickness of the ventilation adjustment layer is 0.50 mm or more and 5.00 mm or less, wherein the thickness of the porous material is 5.00 mm or more.

Advantages of the Invention

[0010] The composite molded body of the present disclosure can be suitably used as a ventilation adjustment layer excellent in sound absorption in the low-frequency to mid-frequency bands, and also has excellent three-dimensional formability.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the present disclosure is not limited to these modes.

[0013] 《Composite Molded Body》 The composite molded body of the present disclosure contains short fibers and fibrillated fibers, has a basis weight of 30 g / m 2 ~1000 g / m 2 and an air permeability resistance per unit thickness of 15.0 s / (100 mL·mm) or less.

[0014] The composite molded body is preferably a structure in which short fibers and fibrillated fibers are mixed and molded in a chemically and physically intertwined or adhered state to each other. The composite molded body has a dense structure with fine fiber gaps and has a very small air permeability resistance. As a result, when sound enters the fiber gaps, the composite molded body can convert the vibration energy of the sound into thermal energy by friction with the ultrafine fibers and further convert it into thermal energy by the membrane vibration of the composite molded body itself, so it has excellent sound absorption characteristics.

[0015] 〈Fibrillated fiber〉 The composite molded body of the present disclosure contains fibrillated fibers. In the present specification, "fibrillated fibers" refer to fibers having a branched structure at least in part thereof. Fibrillated fibers can be roughly classified into two types: those obtained by destroying part of the structure of fibers without a branched structure by physical or chemical means, and those fibrillated by intentionally creating fluff when spinning a polymer compound. For example, examples of the former include microfibrillated cellulose (synonymous with CNF, cellulose nanofibers, cellulose microfibrils, etc.), acrylic pulp (fibrillated fibers of polyacrylonitrile), synthetic pulp such as aramid pulp, chitin nanofibers, chitosan nanofibers, and silk nanofibers. An example of the latter is synthetic pulp made by flash spinning. Fibrillated fibers generally have a structure in which the fiber diameter is partially reduced compared to ordinary fibers without a branched structure due to their manufacturing method. As a result, fibrillated fibers have a large surface area and tend to have many bent structures at the same time. Due to such characteristics, in the composite molded body of the present disclosure, the fibrillated fibers have the effect of acting as a binder that binds the short fibers described later by physical entanglement. Furthermore, the partially thinned fibers contribute to sound absorption in the low frequency band while playing a role in ventilation adjustment of the entire composite molded body. Depending on the type of fibrillated fibers, differences in the fibrillation rate, fiber diameter, and surface state can affect the properties of the composite molded body, but it is preferable that the function as a binder is high and the ventilation resistance is small. From such a viewpoint, as the fibrillated fibers, it is preferable to use at least one selected from the group consisting of microfibrillated cellulose, acrylic pulp, aramid pulp, chitin nanofibers, chitosan nanofibers, and silk nanofibers, and it is more preferable to use at least one selected from the group consisting of microfibrillated cellulose and acrylic pulp composed of polyacrylonitrile. When using microfibrillated cellulose as the cellulose, it is more preferable to use a cellulose having a type II crystal structure as the raw material because the air permeability resistance per unit thickness described later becomes small.

[0016] <Fibrillation rate of fibrillated fibers> The fibrillation rate of the fibrillated fibers in the composite molded body is preferably 0.3% or more. If it is within this range, a sufficient effect as a binder can be obtained, the composite molded body has self-supporting properties, and the dropout of short fibers from the composite molded body is reduced. In addition, the fibrillated and thinned fibers exhibit an effect on sound absorption in the low frequency band. The fibrillation rate of the fibrillated fibers is more preferably 0.5% or more. The upper limit of the fibrillation rate is not particularly limited and may be 100% or less.

[0017] <Area fineness rate of fibrillated fibers> The area fineness rate of the fibrillated fibers in the composite molded body is preferably 3.0% or more and 90% or less. If it is within this range, a sufficient effect as a binder can be obtained, the composite molded body has self-supporting properties, and the dropout of short fibers from the composite molded body is reduced. The area fineness rate of the fibrillated fibers is more preferably 5% or more and 50% or less, and even more preferably 5% or more and 20% or less.

[0018] <Average fiber length of fibrillated fibers> The average fiber length of the fibrillated fibers in the composite molded body is preferably 150 μm or more. If it is within this range, a sufficient effect as a binder can be obtained, and the pore diameter formed inside the composite molded body does not become too small, and appropriate air permeability can be obtained. The average fiber length of the fibrillated fibers is more preferably 200 μm or more, even more preferably 250 μm or more, and particularly preferably 350 μm or more. As the upper limit of the average fiber length, if it is 1000 μm or less, it is preferable because it has excellent mixing properties with short fibers and a uniform molded body can be obtained. More preferably, it is 750 μm or less, and even more preferably 500 μm or less. The average fiber length was measured by a fiber image analyzer (Morfi-Neo, TechPap) with a threshold value of 100 μm for normal fibers and fine fibers.

[0019] <Average fiber diameter of fibrillated fibers by Method A> The average fiber diameter of fibrillated fibers in the composite molded body mainly includes the average fiber diameter corresponding to the trunk fiber part of the fibrillated fibers (average fiber diameter by method A) and the average fiber diameter including the microfiber part up to the fibrillated end (average fiber diameter by method B). The average fiber diameter by method A is preferably 50 μm or less. If it is within this range, the pore diameter formed inside the composite molded body does not become too small, and appropriate air permeability can be obtained. As the average fiber diameter of the fibrillated fibers by method A, more preferably it is 30 μm or less, still more preferably 25 μm or less, and most preferably 15 μm or less. The lower limit is not particularly limited, but it may be 1.5 μm or more due to the resolution of the apparatus.

[0020] 〈Average fiber diameter of fibrillated fibers by method B〉 The average fiber diameter by method B is preferably 1000 nm or less. If it is within this range, entanglement with short fibers is likely to occur, and fiber shedding from the composite molded body can be suppressed. As the average fiber diameter of the entire fibrillated fibers by method B, more preferably it is 800 nm or less, still more preferably 600 nm or less, and most preferably 500 nm or less. The lower limit is not particularly limited, but it may be 10 nm or more, more preferably 20 nm or more, and still more preferably 30 nm or more.

[0021] 〈Microfibrillated cellulose〉 As one of the preferred embodiments of the fibrillated fibers used in the composite molded body, microfibrillated cellulose can be mentioned. Here, cellulose microfibers are those obtained by refining cellulose fibers using at least one physical means, and are synonymous with general names such as cellulose nanofibers, CNF, CeNF, and MFC (microfibrillated cellulose).

[0022] (Cellulose raw material) As raw materials for microfibrillated cellulose, as raw materials for type I cellulose, there may be mentioned so-called wood pulps such as softwood pulp and hardwood pulp, and non-wood pulp. Examples of non-wood pulp include cotton-derived pulp such as cotton linter pulp, hemp-derived pulp, bagasse-derived pulp, kenaf-derived pulp, bamboo-derived pulp, and straw-derived pulp. Cotton-derived pulp, hemp-derived pulp, bagasse-derived pulp, kenaf-derived pulp, bamboo-derived pulp, and straw-derived pulp each mean purified pulp obtained from raw materials such as cotton lint or cotton linter, hemp-based abaca (for example, many are produced in Ecuador or the Philippines), sisal, bagasse, kenaf, bamboo, straw, etc., through a purification process and a bleaching process for the purpose of delignification by cooking and removal of hemicellulose. In addition, purified products such as seaweed-derived cellulose and tunicate cellulose can also be used as raw materials for cellulose microfibrils. As raw materials for type II cellulose, cut yarns of regenerated cellulose fibers and cut yarns of cellulose derivative fibers can also be used as raw materials for cellulose microfibrils, and cut yarns of ultrafine yarns of regenerated cellulose or cellulose derivatives obtained by the electrospinning method can also be used as raw materials for cellulose microfibrils or cellulose microfibrils themselves. These raw materials may be used alone or in combination of two or more. By mixing a plurality of raw materials, the average fiber diameter can be adjusted.

[0023] (Method for producing microfibrillated cellulose) The above raw materials can be refined to obtain microfibrillated cellulose. In the present specification, "refinement" means controlling the fiber length, fiber diameter, area fineness ratio, fibrillation rate, etc. while reducing the size of cellulose. In one aspect, a pretreatment step is carried out before the refinement treatment. In the pretreatment step, it is effective to make the raw material pulp in a state easy to refine by autoclave treatment, enzyme treatment, etc. under impregnation in water at a temperature of 100°C to 150°C, or a combination thereof. These pretreatments not only reduce the load of the refinement treatment, 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 increasing the α-cellulose purity of the refined fibers, and thus may be effective in improving the heat resistance of microfibrillated cellulose.

[0024] In the refinement treatment, the raw material pulp is dispersed in water and refined using a known refinement device such as a beater, single disk refiner, double disk refiner, high-pressure homogenizer, etc. The suitable treatment concentration during refinement may be arbitrarily set because it varies depending on the device used.

[0025] The fibrillation rate, area fineness ratio, average fiber length, and average fiber diameter of microfibrillated cellulose can be controlled by the above-mentioned cellulose raw materials, the conditions of the pretreatment before the refinement treatment (for example, autoclave treatment, enzyme treatment, beating treatment, etc.), the conditions of the refinement treatment (selection of the type of device, operating pressure, number of passes, etc.), or a combination thereof. Here, regarding the cellulose raw materials, pretreatment, refinement, etc., it may also be controlled by combining a plurality of conditions.

[0026] (Multi-stage refinement) When fibrillating cellulose in multiple stages, it is effective to combine a fibrillation mechanism or two or more fibrillation devices with different shear rates. Here, as a method of multi-stage fibrillation, it is preferable to perform multi-stage fibrillation using disk refiners with different disk configurations, or to perform fibrillation with a high-pressure homogenizer after fibrillation with a disk refiner. Here, either a single disk refiner or a double disk refiner may be used for the disk refiner.

[0027] (Multi-stage fibrillation by multiple disk refiners) When performing multi-stage fibrillation using multiple disk refiners, it is preferable to use refiners having at least two different disk configurations. By using refiners with different disk configurations, it is possible to variously control various shape parameters of microfibrillated cellulose, namely, fibrillation rate, area fineness ratio, average fiber length, average fiber diameter, and the like.

[0028] (Disk structure of the disk refiner) Adjusting the disk structure of the disk refiner is an effective means for controlling various shape parameters of microfibrillated cellulose. As structural features of the disk refiner, blade width, groove width, and blade-groove ratio (the value obtained by dividing the blade width by the groove width) are important, and among them, the blade-groove ratio is particularly important in manufacturing fibrillated fibers. When the blade-groove ratio is small, the action of cutting the fibers is large, so the fiber length becomes small. When the blade-groove ratio is large, the action of crushing (beating) the fibers becomes large, so the fibrillation rate becomes large. Since it is important that the composite molded body 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. In addition, if the blade-groove ratio is constant, the smaller the absolute values of the blade width and the groove width, the finer and more uniform microfibrillated cellulose can be obtained.

[0029] (Blade gap distance in disk refiner treatment) In addition, in the refinement with a disk refiner, it is also important to control the distance between two disks (rotating blade and fixed blade) (hereinafter referred to as "blade gap"). By controlling the blade gap, it is possible to control the average fiber length of microfibrillated cellulose. The smaller the blade gap, the smaller the average fiber length. In the previous stage of the process, it is preferable that the blade gap is 0.05 mm or more and 2.0 mm or less, and in the subsequent stage of the process, the blade gap is 0.05 mm or more and 1.0 mm or less. When adjusting the blade gap, it is preferable to gradually narrow it from a wider blade gap to the target blade gap. By controlling in this way, clogging and overload of the device can be prevented, and cellulose fibers with a narrow distribution of fiber length and fiber diameter and high homogeneity can be obtained.

[0030] (Number of passes in disk refiner treatment) The degree of refinement 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 this specification, the "number of passes" means the number of times the refiner treatment is performed after setting the blade gap to the target value. The number of passes of the disk refiner is preferably 5 times or more, more preferably 20 times or more, and even more preferably 40 times or more. As the number of passes increases, the distribution of fiber shapes gradually converges to a certain degree, so a larger number is preferable. However, considering productivity, the upper limit of the number of passes is 300 times or less.

[0031] (Method for controlling the number of passes in disk refiner treatment) As a method for controlling the number of passes, there are methods such as using one tank for one refiner and simply circulating the slurry and controlling the number of passes based on the flow rate, or using two tanks for one refiner and performing refiner treatment while reciprocating the slurry between the tanks. In the former case, simplification of the equipment can be achieved. On the other hand, in the latter case, in each treatment, since cellulose surely passes through the disk part, microfibrillated cellulose with higher uniformity can be obtained.

[0032] (Multi-stage refinement by combination of disk refiner and high-pressure homogenizer) It is also one of the preferred modes to further perform a refinement treatment on the cellulose fibers refined by a disk refiner with a high-pressure homogenizer. Compared with a disk refiner, a high-pressure homogenizer has a greater effect of making the fibers thinner, and by combining with the refinement by a disk refiner, elongated cellulose fibers can be obtained.

[0033] (Synthetic pulp) Synthetic pulp can be obtained by methods such as the spinning and stretching method of existing polymers, the anti-flash method from solutions or emulsions, the strip fiber method by uniaxial stretching of a regulated film, the shear polymerization method of polymerizing monomers under shear stress, etc. Also, as acrylic pulp, BiPUL (registered trademark, manufactured by Nippon Exlan Industry Co., Ltd.) can be used, and as aramid pulp, Kevlar (registered trademark, manufactured by DuPont) or Tiarra (registered trademark, manufactured by Daicel Miraiz Co., Ltd.) can be used. It can also be made by performing high-pressure homogenizer treatment in the same way as microfibrillated cellulose.

[0034] 〈Short fiber〉 The composite molded body of the present disclosure includes short fibers in addition to fibrillated fibers. In the present specification, "short fibers" means fibrous substances having a fiber length of 10 mm or less. As the short fibers, any of natural fibers, synthetic fibers, and semi-synthetic fibers can be used. Examples of the polymers constituting the short fibers include thermoplastic resins such as polyolefin, polyester, polyamide (aromatic or aliphatic), acrylic polymer, polyvinyl alcohol, polylactic acid, polyphenylene ether, polyoxymethylene, and polyphenylene sulfide, epoxy resin, thermosetting modified polyphenylene ether resin, thermosetting polyimide resin, urea resin, allyl resin, silicone resin, benzoxazine resin, phenol resin, unsaturated polyester resin, bismaleimide triazine resin, alkyd resin, furan resin, melamine resin, polyurethane resin, and aniline resin. These short fibers may be used alone or in combination. The short fibers are preferably selected in consideration of properties such as heat resistance and chemical resistance according to the member to which they are to be applied, and examples thereof include polypropylene, polyamide 6, polyamide 66, polyphenylene ether, polyethylene terephthalate, and combinations thereof. In consideration of the moldability of the composite molded body, it is preferable to include at least polyethylene terephthalate fibers.

[0035] 〈Average fiber diameter of short fibers〉 The short fibers preferably have an average fiber diameter of 0.1 μm or more and 10.0 μm or less. By using short fibers having an average fiber diameter within this range, when mixed with fibrillated fibers, they can be uniformly mixed, and a composite molded body with a sufficiently refined interior can be obtained. By using short fibers having a fiber diameter of 10.0 μm or less, the short fibers are likely to vibrate, and an acoustic absorption effect is easily obtained. From the viewpoint of preventing the localization of fibrillated fibers and short fibers inside the composite molded body and preventing the internal structure of the composite molded body from becoming too dense to obtain good air permeability, the average fiber diameter of the short fibers is more preferably 1.0 μm or more and 8.0 μm or less, and even more preferably 1.0 μm or more and 6.0 μm or less. The fiber diameter of the short fibers is usually often expressed in dtex (or T). In this case, a value calculated from the density of the substance constituting the fiber may be considered as the average fiber diameter.

[0036] 〈Fiber length of short fibers〉 The fiber length of the short fibers (also called the cut length) is preferably 5.0 mm or less. Being within this range makes three-dimensional molding easier, a more uniform composite molded body can be obtained, and a more uniform acoustic absorption effect can be obtained. The fiber length of the short fibers is more preferably 4.0 mm or less, and even more preferably 3.0 mm or less.

[0037] 〈Content of fibrillated fibers〉 The composite molded body preferably contains 0.1% by mass or more of fibrillated fibers based on the total mass of the composite molded body. Being within this range allows the fibrillated fibers to contribute to acoustic absorption in the low-frequency band. By containing more fibrillated fibers, the strength of the composite molded body can be improved, and the shedding of fibers from the surface is reduced. Therefore, the content of the fibrillated fibers may be adjusted according to the desired acoustic absorption characteristics. From the viewpoints of the handleability of the composite molded body and preventing fiber shedding, 5.0% by mass or more is more preferable, and 10.0% by mass or more is even more preferable. The upper limit is preferably 50% by mass or less. Within this range, the structure of the composite molded body does not become too dense, appropriate air permeability can be obtained, and the average sound absorption rate at all frequencies is improved. The upper limit is more preferably 40% by mass or less, even more preferably 30% by mass or less, and particularly preferably 20% by mass or less.

[0038] <Short fiber content> The composite molded body preferably contains 50% by mass or more of short fibers based on the total mass of the composite molded body. With the short fiber content in this range, the sound absorption properties in the mid to high frequency bands are excellent. The short fiber content is more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 80% by mass or more. Since the composite molded body must contain fibrillated fibers, the upper limit of the short fiber content is preferably 99.9% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less.

[0039] <Area density of composite molding> The composite molding has an areal density of 30 g / m 2 More than 1000g / m 2 Within this range, it is possible to mold it into a structure without fatal defects, and it is also possible to function as a ventilation adjustment layer. Since a high surface density results in high sound absorption in the low frequency range, and a low surface density results in high sound absorption in the mid to high frequency range, it is preferable to select the surface density according to the object to be sound-absorbed. However, in consideration of the self-supporting property and processability of the composite molded body, and the fact that the ventilation adjustment layer is mainly used for the purpose of absorbing sound in the low to mid frequency range, a surface density of 30 g / m is preferable. 2 More than 500g / m 2 , more preferably 50 g / m 2 More than 500g / m 2 More preferably, 100 g / m 2 More than 300g / m 2 The following is the result.

[0040] <Air permeability resistance per unit thickness of composite molded body> The composite molded body has an air permeability resistance per unit thickness of 15.0 s / (100 mL mm) or less. The air permeability resistance per unit thickness can be calculated using the following formula. Air permeability resistance per unit thickness [s / (100mL mm)] = Air permeability resistance [s / 100mL] / Thickness [mm]

[0041] The measurement method of air permeability resistance (the same concept as air permeability, ventilation rate, flow resistance, etc.) and thickness follows the method described below. In the air permeability adjustment layer, since its structure is often very thin, it may sometimes be discussed in terms of air permeability per unit area while ignoring the thickness. However, in the composite molded body of the present disclosure, although not limited to theory, it is considered that the sound absorption characteristics are controlled by two types of mechanisms: viscous resistance inside the structure and membrane vibration. Therefore, it is important to control the air permeability resistance per unit thickness to be small. If the air permeability resistance per unit thickness is too large, the incidence of sound waves into the composite molded body is significantly restricted at the outermost surface layer of the structure, and sound absorption by viscous resistance cannot be obtained. Therefore, it is required to control within the above range. If it is within this range, it can be preferably used as the air permeability adjustment layer. However, if the air permeability is poor, the sound absorption rate in the high-frequency band decreases. Considering these factors, the air permeability resistance per unit thickness is preferably 10.0 s / (100 mL·mm) or less, and more preferably 5.0 s / (100 mL·mm) or less. If it is within this range, a high sound absorption rate can be obtained in a wide frequency band even when the thickness of the composite molded body is increased. The lower limit of the air permeability resistance per unit thickness is not particularly limited, but is preferably 0.001 s / (100 mL·mm) or more, more preferably 0.01 s / (100 mL·mm) or more, and still more preferably 0.1 s / (100 mL·mm) or more. As described above, the air permeability resistance can be adjusted by the average fiber length, average fiber diameter of fibrillated fibers, average fiber diameter of short fibers, etc.

[0042] 〈Thickness of the composite molded body〉 The thickness of the composite molded body is preferably 100 μm or more and 2000 μm or less. By setting it within this range, it is possible to have excellent sound absorption and reduce the volume of the sound absorption material.

[0043] The thickness of the composite molded body is more preferably 200 μm or more and 1500 μm or less. Here, it should be noted that the thickness cannot be completely independently controlled and largely depends on the areal density. As a method for controlling the thickness, it can be controlled by two methods: control by the material and control by the processing method. As a method for controlling by the material, it can be controlled by the content of fibrillated fibers, the fiber diameter of short fibers, the type of short fibers, etc. For example, by increasing the content of fibrillated fibers, the bonding distance between short fibers forming the skeleton becomes closer, so the thickness becomes smaller.

[0044] As a method for controlling by the processing method, a method of reducing the thickness by pressing when molding the composite molded body can be considered. When controlling the thickness, these methods may be used alone or in combination.

[0045] 〈Bulk density of the composite molded body〉 The bulk density of the composite molded body is preferably 0.05 g / cm 3 or more and 0.50 g / cm 3 or less. When the bulk density is within this range, appropriate air permeability can be obtained and the sound absorption effect can be easily obtained. The bulk density is more preferably 0.1 g / cm 3 or more and 0.4 g / cm 3 or more, and even more preferably 0.15 g / cm 3 or more and 0.35 g / cm 3 or less. Incidentally, the bulk density is calculated by the following formula. Bulk density [g / cm 3 =Areal density [g / m 2 / Thickness [μm] The bulk density can be controlled by adjusting the thickness of the material when the areal density is the same, and the thickness of the material can be adjusted by the method described above.

[0046] 〈Three-dimensional shaping of the composite molded body〉 The composite molded body can be easily formed into a three-dimensional structure, and further, it can be made into a structure with a uniform surface and no joints or gaps. In the present specification, the three-dimensional structure means that the composite molded body does not have a two-dimensional (planar or flat) structure but has at least one bent structure, and is hereinafter also referred to as "three-dimensional" or "three-dimensional structure".

[0047] When applying a planar air-permeability adjustment layer such as a generally 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, it is inevitable that a structure in which the non-woven fabrics partially overlap, gaps, and creases are generated. Therefore, variations in air permeability occur, and uniform sound-absorbing characteristics cannot be obtained on all surfaces. On the other hand, when processing the composite molded body three-dimensionally, since it is a structure with a uniform surface and no joints or gaps, even when applied to sound sources with complex shapes, a certain sound-absorbing property can be obtained on all surfaces of the composite molded body, so it has excellent sound-absorbing properties.

[0048] 《Manufacturing Method of Composite Molded Body》 As a method for manufacturing the composite molded body of the present disclosure, although not particularly limited, examples include a method including dispersing short fibers and fibrillated fibers in a liquid medium, and removing and drying the solvent by filtration, pressing, or the like. By mixing short fibers and fibrillated fibers in a liquid medium, a composite molded body with a more uniform internal structure can be obtained. As such a molding method, specifically, since it can be processed into an arbitrary shape, a wet papermaking method and a pulp molding method are preferable. When the wet papermaking method is used, a two-dimensional planar molded body (which can also be said to be a non-woven fabric) can be obtained, and by using the pulp molding method, it is possible to impart a three-dimensional complex shape. There are several different methods for the pulp molding method depending on the target molded body. The Thick wall method for obtaining a very thick molded body with a film thickness of 5 mm to 10 mm and high load-bearing properties, the Transfer mold method for obtaining a molded body with a smooth surface and a film thickness of 3 mm to 5 mm, the Thermoformed mold method for obtaining a complex shape with a film thickness of 1 mm to 3 mm, the PIM (Pulp injection mold) method for obtaining a more complex shape such as bosses and ribs like a normal plastic molded product, the PF (Pulp forming) method for obtaining a lightweight and soft molded product by foaming in a mold, and the like. Even if it does not belong to these classifications, any method can be adopted as long as three-dimensional shaping is possible. Various additives may be added to the liquid medium during molding.

[0049] 〈Liquid medium during molding〉 The liquid medium used during molding is not particularly limited, and known liquid media such as water and organic solvents can be used. Considering the ease of handling and the environmental load, water is preferably used, but a non-polar organic solvent with a lower surface tension may be used for the purpose of preventing aggregation during drying and reducing the air permeability resistance per unit thickness. When water is used as the liquid medium, a surfactant may be added for the purpose of controlling the surface tension.

[0050] 〈Additives during molding〉 By adding a papermaking dispersant, binder, and crosslinking agent as additives during molding, it is possible to control the handleability such as the strength of the composite molded body and the fiber shedding property, and the structure such as the internal uniformity and the smoothness of the surface. The papermaking dispersant means a surfactant for easily defibrating short fibers on a bundle in a liquid medium and an adhesive for adjusting the viscosity of the liquid medium and preventing fiber aggregation, and it is possible to control the unit thickness air permeability resistance by improving the surface smoothness and homogeneity and homogenizing the internal structure. Note that the added surfactant also affects the surface tension of the liquid medium. The binder means a paste component such as starch, and by adhering the fibers, it is possible to control the strength of the structure and the unit thickness air permeability resistance. The crosslinking agent means isocyanate, polyurethane, etc., and by chemically and physically crosslinking the fiber entanglement points, it is possible to prevent fiber shedding and adjust the strength. These additives may be used alone or in combination of two or more.

[0051] 《Applications of the Composite Molded Body》 〈Sound Absorbing Material〉 The composite molded body of the present disclosure can be suitably used as a sound absorbing material. The composite molded body of the present disclosure may be used alone or multiple sheets may be stacked and used. When used alone, it mainly exhibits a sound absorption effect due to viscous resistance, and has a sound absorption characteristic in which the sound absorption property is low in the low frequency region and the sound absorption rate increases as the frequency increases. The composite molded body of the present disclosure preferably has a very high air permeability resistance per unit thickness as a sound absorbing material, and thereby also has an effect of blocking some frequencies.

[0052] Examples of objects for use as sound-absorbing materials include buildings, household appliances, automobiles, etc. Since the composite molded body of the present disclosure can be molded into any three-dimensional shape, it can be applied not only to flat surfaces but also to members with complex three-dimensional shapes. Among them, it can be preferably used as a sound-absorbing material for automobiles, especially those with complex shapes of constituent members and constituent devices. Examples of constituent parts and constituent devices of automobiles include instrument panels, doors, roofs, floors, tire houses, engines, compressors, motors, etc. By using the composite molded body of the present disclosure as a sound-absorbing material for these, it is possible to achieve quietness inside the automobile and reduce the noise emitted by the automobile. The same applies to the composite sound-absorbing material and the low-frequency enhanced thin sound-absorbing material described later.

[0053] 〈Composite Sound-Absorbing Material〉 The composite sound-absorbing material of the present disclosure has a structure in which a ventilation adjustment layer is laminated on a support. As the ventilation adjustment layer, the composite molded body of the present disclosure may be used. An air layer may be provided behind the composite molded body (meaning the position opposite to the sound source). Thereby, in addition to viscous resistance, a sound-absorbing effect due to membrane vibration is exhibited. That is, for a specific frequency, sound-absorbing characteristics having a maximum are obtained, and good sound absorption is shown in the entire frequency band. Since it can be made into a composite sound-absorbing material showing more excellent sound-absorbing characteristics by using it as a sound-absorbing material, it is preferable.

[0054] 〈Support〉 As the structure of the support, a structure having air permeability is required. For example, with a columnar structure, a complete void may be provided behind the ventilation adjustment layer, or a porous material such as felt, non-woven fabric, or foam may be used to obtain a composite sound-absorbing material. When a porous material is used for the support and the composite molded body of the present disclosure is laminated thereon, the composite molded body itself has a sound-absorbing effect and can also act as a ventilation adjustment layer. A structure without air permeability, such as a resin plate without a foam structure, is preferably not used as a support.

[0055] 〈Porous Material〉 It is preferable to use a porous material as the support because it is possible to control the sound absorption characteristics. When using a highly breathable material as the porous material, an excellent sound absorption effect can be obtained in a wide frequency range. When using a material with poor breathability, an especially excellent sound absorption effect can be obtained at a specific frequency. The porous material preferably has higher breathability than the composite molded body. As an index of breathability, it is good to use the above-mentioned unit thickness air permeability resistance. Examples of the porous material include, but are not limited to, known porous materials such as non-woven fabrics, felts, and foams.

[0056] 〈Thickness of the support〉 The support preferably has a thickness of 5 mm or more. The thickness of the support means the thickness of the structure having breathability, and the thickness of the structure having no breathability is not considered. When obtaining the sound absorption effect by the membrane vibration effect, the frequency characteristics obtained by the thickness of the air layer behind change greatly. That is, when the thickness of the air layer is small, excellent sound absorption characteristics can be obtained in the high frequency band, and when the thickness of the air layer is large, an excellent sound absorption effect can be obtained in the low frequency band. Therefore, the thickness of the support is preferably 6 mm or more, and most preferably 7 mm or more. Although there is no particular limitation on the upper limit, from the viewpoint of saving space of the sound absorption material, it is preferably 50 mm or less, more preferably 30 mm or less, still more preferably 10 mm or less, and particularly preferably 8 mm or less.

[0057] 〈Laminating method to the support〉 The composite molded body of the present disclosure can be laminated to the support using various means. For example, a method of heating only the surface of the composite molded body with an IR heater or the like and joining by heat fusion, a method of applying a hot melt adhesive to the surface of the composite molded body by a curtain spray method or the like and then heating and heat fusing can be exemplified.

[0058] 〈Thickness of the ventilation adjustment layer in the composite sound absorption material〉 When a porous body is used as the support, by changing the number of laminated composite molded bodies or changing the thickness per layer of the composite molded body (the thickness of the composite molded body described above), the thickness of the air ventilation adjustment layer in the composite sound-absorbing material can be controlled, and the sound-absorbing characteristics can be adjusted. Here, by increasing the thickness of the air ventilation adjustment layer, the air permeability of the entire structure decreases, and a higher sound-absorbing effect is exhibited in the low-frequency band. On the other hand, due to the decrease in air permeability, the sound-absorbing effect in the high-frequency band tends to decrease. The thickness of the air ventilation adjustment is not particularly limited, and it is advisable to adjust it according to the sound source to be absorbed and control the frequency characteristics.

[0059] 〈Method for Controlling the Thickness of the Air Ventilation Adjustment Layer〉 When comparing the method of controlling the thickness of the air ventilation adjustment layer by changing the number of laminated layers and the method of controlling the thickness of the air ventilation adjustment by controlling the thickness per layer of the composite molded body, in the former case, the frequency dependence of sound absorption becomes smaller (the sound absorption rate at the maximum decreases, and the average sound absorption rate in the entire frequency band increases). In the latter case, the frequency dependence becomes larger (the sound absorption rate at the maximum increases, and the average sound absorption rate in the entire frequency band decreases), and at the same time, a high sound-absorbing effect can be obtained at lower frequencies. The thickness and its control method of the air ventilation adjustment layer are preferably adjusted or properly used according to the sound source to be absorbed to control the sound-absorbing characteristics.

[0060] 〈Low-Frequency Reinforced Thin Composite Sound-Absorbing Material〉 By adjusting the thickness of the air ventilation adjustment layer and adjusting the surface density etc. of the air ventilation adjustment layer, a composite sound-absorbing material (hereinafter referred to as "low-frequency reinforced thin composite sound-absorbing material") that shows excellent sound absorption in the low to medium frequency bands and also shows sound absorption in a wide range of frequencies from 500 Hz to 6400 Hz can be obtained while having a very thin structure. Specifically, the low-frequency reinforced thin composite sound-absorbing material has a structure in which the total thickness of the structure is 10 mm or less and the air ventilation adjustment layer and the porous material are laminated, (a) The surface density of the air ventilation adjustment layer is 100 g or more and 1000 g or less, (b) The air permeability resistance of the air ventilation adjustment layer is 0.1 s / 100 mL or more and 2.0 s / 100 mL or less, (c) The thickness of the air permeability adjustment layer is 0.50 mm or more and 5.00 mm or less, and (d) It is preferable that the thickness of the porous material is 5.00 mm or more.

[0061] By satisfying all of the above (a) to (d), in the measurement method of perpendicular incidence conforming to JIS A 1405, all of the following sound absorption characteristics, that is (1) It has a sound absorption maximum value at 3000 Hz or less, (2) The sound absorption rate at 1000 Hz is 0.3 or more, (3) The average sound absorption rate from 800 to 2000 Hz is 0.4 or more, and (4) The average sound absorption rate from 500 to 6400 Hz is 0.3 or more, It is possible to obtain a low-frequency enhanced thin composite sound absorber. Generally, in a composite sound absorber obtained by air permeability adjustment on the surface, the sound absorption at low frequencies and high frequencies is in a trade-off relationship, and in order to achieve both, the only way is to increase the thickness of the entire structure. However, the low-frequency enhanced thin composite sound absorber of the present disclosure can at least partially eliminate this trade-off while maintaining the thinness. The reason is considered to be that the thickness of the air permeability adjustment layer is extremely large as an air permeability adjustment layer, and further that the air permeability adjustment layer itself has a sound absorption effect due to membrane vibration, which contributes comprehensively. When the composite molded body of the present disclosure is used as the air permeability adjustment layer, the fibrillated fiber, which is a fiber with an extremely thin fiber diameter, and the relatively thick short fiber have a sound absorption effect in different frequency bands due to viscous resistance, so that the above trade-off relationship can be further eliminated.

[0062] 〈Sound Absorption Characteristics of Low-Frequency Enhanced Thin Composite Sound Absorber〉 Despite having a thin structure as described above, the low-frequency enhanced thin composite sound-absorbing material of the present disclosure has excellent sound-absorbing characteristics in the low to mid-frequency bands and further has a sound-absorbing effect in a wide frequency band of 500 Hz to 6400 Hz. Therefore, the sound absorption rate at 1000 Hz is preferably 0.4 or more, and more preferably 0.5 or more. The average sound absorption rate in the range of 800 Hz to 2000 Hz is preferably 0.5 or more, and more preferably 0.6 or more. The average sound absorption rate in the range of 500 Hz to 6400 Hz is preferably 0.4 or more, and more preferably 0.5 or more.

[0063] 〈Structure of the ventilation adjustment layer in the low-frequency enhanced thin composite sound-absorbing material〉 To obtain these preferable sound-absorbing characteristics, the structure of the ventilation adjustment layer, that is, the surface density, air permeability resistance, and thickness of the ventilation adjustment layer may be controlled. The surface density, air permeability resistance, and thickness of the ventilation adjustment layer mean the total values, that is, the values measured in the laminated state when a plurality of composite molded bodies are laminated. In addition, the effect of controlling these values is the same as that in the case of controlling the surface density, unit surface density air permeability resistance, and thickness of the above-described composite molded body. The surface density is preferably 150 g / m 2 or more and 300 g / m 2 or less. The air permeability resistance is preferably 0.5 s / 100 mL or more and 1.5 s / 100 mL or less, more preferably 1.0 s / 100 mL or more and 1.5 s / 100 mL or less. The thickness of the ventilation adjustment layer is preferably 0.75 mm or more and 2.00 m or less, and more preferably 0.75 mm or more and 2.00 m or less. The thickness of the porous material as the support may be arbitrarily adjusted according to the ventilation adjustment layer.

[0064] 〈Thickness of the low-frequency enhanced thin composite sound-absorbing material〉 The low-frequency enhanced thin composite sound-absorbing material has a thickness of 10 mm or less as a whole structure. Similar to general sound-absorbing materials, the sound-absorbing characteristics can also be controlled by controlling the thickness of the whole structure. Since a thick structure is effective for low-frequency sound absorption, it is preferable that the thickness of the whole structure is larger. The lower limit of the thickness is preferably 5.5 mm or more, more preferably 7.0 mm or more, still more preferably 8.0 mm or more, and particularly preferably 9.0 mm or more.

Examples

[0065] Hereinafter, the embodiments of the present disclosure will be specifically described with reference to Examples and Comparative Examples, but the present disclosure is not limited thereto.

[0066] 《Measurement and Evaluation Methods》 〈Average fiber diameter (Method A and Method B) of fibrillated fibers, fibrillation rate, area fineness rate〉 The average fiber diameter (Method A), fibrillation rate, and area fineness rate of the fibrillated fibers were measured using a fiber shape automatic analyzer (Morfi neo manufactured by Technidyne) according to the following procedure. The threshold values of the minimum fiber length and the maximum fiber length during measurement were 100 μm and 1500 μm, respectively. (1) The fibrillated fibers were dispersed in pure water to prepare 1 L of an aqueous dispersion. Here, the final solid content concentration of the fibrillated fibers was 0.003 mass% to 0.005 mass%. When the aqueous dispersion of the fibrillated fibers was 2 mass% or less, the dispersion treatment was performed by simply mixing with a spatula or the like. When it was an aqueous dispersion of 2 mass% or more, a hydrated cake, or a powder, etc., a high-shear homogenizer (manufactured by IKA, trade name "Ultra Turrax T18") was used, and the dispersion treatment was performed under the treatment conditions of a rotation speed of 25,000 rpm for 5 minutes. (2) The aqueous dispersion adjusted in step (1) was supplied to an autosampler for measurement. (3) From the measurement results, Mean Fibre Width, μm, Macro Fibrillation index, %, and Fine content, in area, % were read and used as the average fiber diameter (Method A), fibrillation rate, and area fineness rate, respectively.

[0067] The average fiber diameter (Method B) of fibrillated fibers was measured using a specific surface area and pore size distribution measuring device (manufactured by Quantachrome Instruments, NOVA-4200e) according to the following procedure. For fibrillated fibers that aggregate upon drying, such as fibrillated cellulose microfibers, the following pretreatment was performed before measurement.

[0068] [Pretreatment] (1) The fibrillated microfiber aqueous dispersion was filtered to form a wet cake. (2) The obtained wet cake was added to tert-butanol and diluted with tert-butanol so that the fibrillated fiber solid content concentration was 0.5% by weight. Using a high-shear homogenizer (manufactured by IKA, trade name "Ultra Turrax T18"), dispersion treatment was performed under the treatment conditions of a rotation speed of 25,000 rpm for 5 minutes. (3) The obtained dispersion was weighed to a basis weight of 10 g / m 3 and filtered through filter paper to obtain a sheet. (4) The obtained sheet was not peeled from the filter paper and was sandwiched between two larger filter papers. While pressing the edges of the filter paper with weights from above, it was dried in an oven at 150 °C for 5 minutes to obtain a porous sheet.

[0069] [Measurement of Specific Surface Area and Calculation of Fiber Diameter] (1) 0.2 g of the solid content of the fibrillated fiber (porous sheet prepared by pretreatment) was dried under vacuum at 120 °C for 5 minutes. (2) After drying, the nitrogen gas adsorption amount at the boiling point of liquid nitrogen was measured at 5 points in the range where the relative vapor pressure (P / P0) was 0.05 or more and 0.2 or less (multi-point method), and then the BET specific surface area (m 2 / g) was calculated by the same device program. (3) From the obtained BET specific surface area value Y (m 2 / g), the average fiber length X (nm) and the density ρ (g / cm 3 ) of the fibrillated fiber, the average specific surface area was calculated by the following formula. Average fiber diameter (nm) = 1 / (2.5 × ρ × Y × 10-4 )

[0070] 〈Air permeability of the composite molded body〉 The air permeability of the composite molded body means the result of measuring the permeation time of 100 mL of air using a Gurley densometer (for example, manufactured by Toyo Seiki Seisaku-sho, Ltd., model G-B2C), and was measured according to the following procedure. (1) Sections with a size of 5 cm × 5 cm were obtained from five different locations on the composite molded body. (If the size of the composite molded body is smaller than this, five sections were obtained from a plurality of composite molded bodies.) (2) For each section, the air permeability was measured at five points using a Gurley densometer (manufactured by Toyo Seiki Seisaku-sho, Ltd., model G-B2C). (3) The average value of the five points obtained in step (2) was taken as the air permeability of the composite molded body.

[0071] 〈Thickness of the composite molded body〉 The thickness of the composite molded body was measured according to the following procedure. (1) Sections with a size of 5 cm × 5 cm were obtained from five different locations on the composite molded body. (If the size of the composite molded body is smaller than this, five sections were obtained from a plurality of composite molded bodies.) (2) For each section, the thickness was measured using an ABS digital indicator ID-CX (manufactured by Mitutoyo Corporation). At this time, a flat probe with a diameter of Φ15 mm was used. (3) The average value of the five points obtained in step (2) was taken as the thickness of the composite molded body.

[0072] 〈Air permeability per unit thickness and bulk density of the composite molded body〉 Based on the following definitions, the air permeability, thickness, and areal density of the composite molded body were calculated. Air permeability per unit thickness = Air permeability [s / 100 mL] / Thickness [mm] Bulk density = Areal density [g / m 2 」 / Thickness [mm]

[0073] 〈Self-supporting property and fiber shedding property of the composite molded body〉 The self-supporting property of the composite molded body and fiber shedding were evaluated based on the following definitions. [Self-supporting property of the composite molded body] A: It does not bend or break even when handled with one hand B: When handled with one hand, it easily creases or breaks [Fiber shedding] A: When touching the surface with bare hands, there is no adhesion of shed fibers B: When touching the surface with bare hands, shed fibers adhere

[0074] 〈Evaluation of sound absorption characteristics of the composite sound-absorbing material〉 From the composite molded bodies in each example and comparative example, circular disks with a diameter of 28.8 mm were cut out and naturally laminated with a coarse wool felt having a thickness of 8.0 mm to obtain a composite sound-absorbing material. The sound absorption rate of this composite sound-absorbing material was measured using a perpendicular incidence sound absorption rate measurement system DS-2000 (manufactured by Ono Sokki Co., Ltd.) in accordance with JIS A 1405. At this time, the measurement was carried out so that the composite molded body was on the sound wave incident side. A part of the measurement results is shown in Fig. 1

[0075] 〈Evaluation of sound absorption characteristics of the composite molded body alone〉 From the composite molded body in the example, a circular disk with a diameter of 28.8 mm was cut out, and under the condition of providing a 10.0 mm rear air layer, the sound absorption rate was measured using a perpendicular incidence sound absorption rate measurement system DS-2000 (manufactured by Ono Sokki Co., Ltd.) in accordance with JIS A 1405

[0076] 〈Evaluation of sound absorption characteristics of the low-frequency enhanced thin composite sound-absorbing material〉 From the composite molded bodies in each example and comparative example, a predetermined number of circular disks with a diameter of 28.8 mm were cut out and all of them were naturally laminated with a coarse wool felt having a thickness of 8.0 mm to obtain a low-frequency enhanced thin composite sound-absorbing material. The sound absorption rate of the above composite sound-absorbing material was measured using a perpendicular incidence sound absorption rate measurement system DS-2000 (manufactured by Ono Sokki Co., Ltd.) in accordance with JIS A 1405. At this time, the measurement was carried out so that the composite molded body was on the sound wave incident side. A part of the measurement results is shown in Fig. 2

[0077] 〈Evaluation of sound absorption of the three-dimensional composite sound-absorbing material〉 A schematic diagram of the structure of the three-dimensional composite sound-absorbing material and a schematic diagram of the evaluation method are shown in FIGS. 3 to 5, respectively. A felt (12) with a thickness of 8 mm and a PP plate (11, thickness 1 mm) were attached to the outside of the composite molded body in each example and comparative example using double-sided tape and instant adhesive to form a three-dimensional composite sound-absorbing material (10). The three-dimensional composite sound-absorbing material (10) was arranged to cover the sound source (20) placed on the desk (30). The sound source used a Bluetooth (registered trademark) speaker. The speaker was connected to a smartphone, and sounds of 1045.7 Hz, 1478.9 Hz, and 1974.1 Hz were output using an app (Tuning Fork Pro). Note that at all frequencies, the sound pressure was set to 70 dB in a state without the sound-absorbing material. The ambient sound was in a space of 48 dB. At this time, the evaluator (40) standing at a position 1.0 m away from the side wall of the three-dimensional composite sound-absorbing material (10) was asked to confirm how much the volume had decreased (what percentage of the original volume was felt), and the average value evaluated by the 10 people was used as the evaluation result of the sound absorption performance.

[0078] 《Fibrillated Fiber》 〈Fibrillated Fiber A〉 The fibrillated fiber of polyacrylonitrile (manufactured by Nippon Exlan Co., Ltd.: BiPUL, solid content 18% by mass) was used as fibrillated fiber A. The results of evaluating the fibrillation rate, area fineness rate, average fiber length, and average fiber diameter are shown in Table 1.

[0079] 〈Fibrillated Fiber B〉 Tencel cut yarn (3 mm in length), which is a regenerated (type II) cellulose fiber obtained from Sojitz Corporation, was placed in a washing net, a surfactant was added, and it was washed many times with a washing machine to remove the sizing agent on the fiber surface.

[0080] After simply dispersing this using a Lab Pulper (manufactured by Aikawa Iron Works), it was fed into a tank. The slurry was refined while being circulated by a single disk refiner (front stage) equipped with a disk having a blade width of 2.5 mm and a groove width of 7.0 mm, which was connected to the tank. At this time, with the blade gap set at 1.0 mm, the operation was terminated when the entire amount of the slurry had passed through the disk section 35 times. Subsequently, the slurry was refined while being circulated by a single disk refiner (rear stage) equipped with a disk having a blade width of 0.8 mm and a groove width of 1.5 mm. At this time, the operation was started with a blade gap of 1.0 mm, and while gradually narrowing the blade gap, the final blade gap was set at 0.35 mm. After the blade gap reached 0.35 mm, the operation was continued while checking the flow rate, and the operation was terminated when the entire amount of the slurry had passed through the disk section 120 times. The obtained microfibrillated cellulose was designated as fibrillated fiber B. Table 1 shows the results of evaluating the fibrillation ratio, area fineness ratio, average fiber length, and average fiber diameter.

[0081] 〈Fibrillated Fiber C〉 The fibrillated fiber B was further refined using a high-pressure homogenizer (NS015H manufactured by Niro Soavi, Italy). At this time, the slurry was processed in a batch manner, and the number of processing times was 5. Table 1 shows the results of evaluating the fibrillation ratio, area fineness ratio, average fiber length, and average fiber diameter.

[0082] 〈Fibrillated Fiber D〉 Using linter pulp, a natural cellulose obtained from Nippon Paper Pulp Co., Ltd., it was immersed in water so that the linter pulp was 1.5% by mass, and after being simply dispersed using a lab pulper (manufactured by Aikawa Iron Works), it was fed into a tank. The slurry was refined while being circulated by a single disc refiner (front stage) equipped with a disc having a blade width of 2.5 mm and a groove width of 7.0 mm, which was connected to the tank. At this time, the operation was started with a blade gap of 1.0 mm, and while gradually narrowing the blade gap, the final blade gap was set to 0.05 mm. After the blade gap reached 0.05 mm, the operation was continued while checking the flow rate, and the operation was terminated when the total amount of the slurry had passed through the disc section 10 times. Subsequently, the slurry was refined while being circulated by a single disc refiner (rear stage) equipped with a disc having a blade width of 0.6 mm and a groove width of 1.0 mm. At this time, the operation was started with a blade gap of 1.0 mm, and while gradually narrowing the blade gap, the final blade gap was set to 0.05 mm. After the blade gap reached 0.05 mm, the operation was continued while checking the flow rate, and the operation was terminated when the total amount of the slurry had passed through the disc section 180 times. The obtained microfibrillated cellulose was designated as fibrillated fiber D. Table 1 shows the results of evaluating the fibrillation rate, area fineness rate, average fiber length, and average fiber diameter.

[0083] <<Manufacturing Example of Composite Molded Body>> 〈Example 1-1〉 Using fibrillated fiber A and PET staple fiber A (manufactured by Teijin Ltd.: TA04PN, fineness: 0.1 T, average fiber diameter: 3.0 μm, cut length: 3 mm), a composite molded body was produced by the following procedure.

[0084] The fibrillated fiber and the staple fiber were added to pure water so that the solid content weight ratio was 20:80, the final solid content concentration was set to 0.5%, and the slurry was prepared by stirring with a household mixer for 4 minutes.

[0085] The above-prepared slurry was applied to a batch paper-making machine (manufactured by Kumagai Rikoki Kogyo Co., Ltd., automatic square sheet machine 25 cm × 25 cm, 80 mesh) equipped with a filter cloth (TT35 manufactured by Shima Canvas Co., Ltd.) at a basis weight of 50 g / m 2It was charged so as to achieve [the required state], and then, papermaking (dehydration) was carried out with the degree of vacuum relative to atmospheric pressure set at 50 KPa.

[0086] The above-mentioned filter cloth was placed on the surface of the wet concentrated composition placed on the filter cloth, peeled off from above the wire, and pressed at a pressure of 1 kg / cm 2 for 1 minute. Then, it was dried for about 120 seconds using a drum dryer with the surface temperature set at 130°C to obtain a composite molded body S1. Also, from the obtained composite molded body, a circular disk with a diameter of 28.8 mm was cut out and naturally laminated with a coarse wool felt having a thickness of 8.0 mm to obtain a composite sound-absorbing material. Various physical properties of the obtained composite molded body, sound-absorbing characteristics of the composite sound-absorbing material, etc. are shown in Table 1 below.

[0087] <Example 1-2> A composite molded body S2 was obtained in the same manner as in Example 1, except that PET fiber B (TA04N manufactured by Teijin Co., fineness 0.5 T, average fiber diameter: 7.0 μm, cut length 5 mm) was used for the short fibers. Also, from the obtained composite molded body, a circular disk with a diameter of 28.8 mm was cut out and naturally laminated with a coarse wool felt having a thickness of 8.0 mm to obtain a composite sound-absorbing material. Various physical properties of the obtained composite molded body, sound-absorbing characteristics of the composite sound-absorbing material, etc. are shown in Table 1 below.

[0088] <Example 1-3> A composite molded body S3 was obtained in the same manner as in Example 1, except that the basis weight was set to 100 g / m 2 . Also, from the obtained composite molded body, a circular disk with a diameter of 28.8 mm was cut out and naturally laminated with a coarse wool felt having a thickness of 8.0 mm to obtain a composite sound-absorbing material. Various physical properties of the obtained composite molded body, sound-absorbing characteristics of the composite sound-absorbing material, etc. are shown in Table 1 below.

[0089] <Example 1-4> A composite molded body S4 was obtained in the same manner as in Example 1, except that the solid content weight ratio of fibrillated fibers to short fibers was set to 30:70. Also, from the obtained composite molded body, a circular disk with a diameter of 28.8 mm was cut out and naturally laminated with a coarse wool felt having a thickness of 8.0 mm to obtain a composite sound-absorbing material. Various physical properties of the obtained composite molded body, sound-absorbing characteristics of the composite sound-absorbing material, etc. are shown in Table 1 below.

[0090] <Examples 1-5> The areal density was 150 g / m 2 , and a composite molded body S5 was obtained in the same manner as in Example 1, except that the solid content weight ratio of the fibrillated fiber to the short fiber was 10:90. Also, a circular disk with a diameter of 28.8 mm was cut out from the obtained composite molded body and naturally laminated with a coarse wool felt having a thickness of 8.0 mm to obtain a composite sound absorbing material. Various physical properties of the obtained composite molded body, sound absorption characteristics of the composite sound absorbing material, etc. are shown in Table 1 below.

[0091] <Examples 1-6> A composite molded body S6 was obtained in the same manner as in Example 1, except that fibrillated fiber B was used for the fibrillated fiber and PET short fiber C (manufactured by Teijin Ltd.: TA04PN, fineness: 0.3 T, average fiber diameter: 5.3 μm, cut length: 3 mm) was used for the short fiber. Also, a circular disk with a diameter of 28.8 mm was cut out from the obtained composite molded body and naturally laminated with a coarse wool felt having a thickness of 8.0 mm to obtain a composite sound absorbing material. Various physical properties of the obtained composite molded body, sound absorption characteristics of the composite sound absorbing material, etc. are shown in Table 1 below.

[0092] <Examples 1-7> A composite molded body S7 was obtained in the same manner as in Example 1, except that fibrillated fiber C was used for the fibrillated fiber and the areal density was 100 g / m 2 . Also, a circular disk with a diameter of 28.8 mm was cut out from the obtained composite molded body and naturally laminated with a coarse wool felt having a thickness of 8.0 mm to obtain a composite sound absorbing material. Various physical properties of the obtained composite molded body, sound absorption characteristics of the composite sound absorbing material, etc. are shown in Table 1 below.

[0093] <Examples 1-8> A composite molded body S8 was obtained in the same manner as in Example 1, except that fibrillated fiber B was used for the fibrillated fiber, the areal density was 100 g / m 2 , and the solid content weight ratio of the fibrillated fiber to the short fiber was 5:95. Also, a circular disk with a diameter of 28.8 mm was cut out from the obtained composite molded body and naturally laminated with a coarse wool felt having a thickness of 8.0 mm to obtain a composite sound absorbing material. Various physical properties of the obtained composite molded body, sound absorption characteristics of the composite sound absorbing material, etc. are shown in Table 2 below.

[0094] <Example 1-9> Using fibrillated fiber B for the fibrillated fiber, except that the areal density was 300 g / m 2 , and the solid content weight ratio of the fibrillated fiber to the short fiber was 5:95, a composite molded body S9 was obtained in the same manner as in Example 1. Further, a circular disk with a diameter of 28.8 mm was cut out from the obtained composite molded body and naturally laminated with a coarse hair felt having a thickness of 8.0 mm to obtain a composite sound absorbing material. Various physical properties of the obtained composite molded body, sound absorption characteristics of the composite sound absorbing material, etc. are shown in Table 2 below.

[0095] <Example 1-10> Using fibrillated fiber B for the fibrillated fiber and PP fiber (AIRYMO manufactured by Ube Eximo Co., fineness 0.2 T, average fiber diameter: 5.3 μm, cut length 2 mm) for the short fiber, except that the areal density was 300 g / m 2 , and the solid content weight ratio of the fibrillated fiber to the short fiber was 5:95, a composite molded body S10 was obtained in the same manner as in Example 1. Further, a circular disk with a diameter of 28.8 mm was cut out from the obtained composite molded body and naturally laminated with a coarse hair felt having a thickness of 8.0 mm to obtain a composite sound absorbing material. Various physical properties of the obtained composite molded body, sound absorption characteristics of the composite sound absorbing material, etc. are shown in Table 2 below.

[0096] <Example 1-11> Using fibrillated fiber B for the fibrillated fiber, except that the solid content weight ratio of the fibrillated fiber to the short fiber was 30:70, a composite molded body S11 was obtained in the same manner as in Example 1. Further, a circular disk with a diameter of 28.8 mm was cut out from the obtained composite molded body and naturally laminated with a coarse hair felt having a thickness of 8.0 mm to obtain a composite sound absorbing material. Various physical properties of the obtained composite molded body, sound absorption characteristics of the composite sound absorbing material, etc. are shown in Table 2 below.

[0097] <Example 1-12> Regarding the composite molded body S1 created in Example 1, the sound absorption characteristics were evaluated alone. As a result of evaluating the sound absorption characteristics, the peak frequency was 3990 Hz, the sound absorption rate at the peak frequency was 0.91, and the average sound absorption rate from 500 Hz to 6400 Hz was 0.73.

[0098] <Comparative Example 1-1> Using fibrillated fiber B for the fibrillated fiber, except that the basis weight was 25 g / m 2 A composite molded body R-1 was obtained in the same manner as in Example 1. Also, from the obtained composite molded body, a circular disk with a diameter of 28.8 mm was cut out and naturally laminated with a coarse wool felt having a thickness of 8.0 mm to obtain a composite sound absorbing material. Various physical properties of the obtained composite molded body, sound absorption characteristics of the composite sound absorbing material, etc. are shown in Table 1 below.

[0099] <Comparative Example 1-2> Using fibrillated fiber D for the fibrillated fiber, except that the basis weight was 100 g / m 2 A composite molded body R-2 was obtained in the same manner as in Example 1. Also, from the obtained composite molded body, a circular disk with a diameter of 28.8 mm was cut out and naturally laminated with a coarse wool felt having a thickness of 8.0 mm to obtain a composite sound absorbing material. Various physical properties of the obtained composite molded body, sound absorption characteristics of the composite sound absorbing material, etc. are shown in Table 1 below.

[0100] <Comparative Example 1-3> Using fibrillated fiber B for the fibrillated fiber, with a basis weight of 100 g / m 2 and a solid content weight ratio of fibrillated fiber to short fiber of 50:50, a composite molded body R-3 was obtained in the same manner as in Example 1. Also, from the obtained composite molded body, a circular disk with a diameter of 28.8 mm was cut out and naturally laminated with a coarse wool felt having a thickness of 8.0 mm to obtain a composite sound absorbing material. Various physical properties of the obtained composite molded body, sound absorption characteristics of the composite sound absorbing material, etc. are shown in Table 1 below.

[0101] <<Manufacturing Example of Composite Sound Absorbing Material>> <Example 2-1> Three circular disks with a diameter of 28.8 mm were cut out from the composite molded body S1, and all were naturally laminated on a coarse wool felt having a thickness of 8.0 mm to obtain a low-frequency enhanced thin composite sound absorbing material. The sound absorption characteristics of the obtained composite sound absorbing material, etc. are shown in Table 3 below.

[0102] <Example 2-2> From the composite molded body S1, four circular disks with a diameter of 28.8 mm were cut out, and all of them were naturally laminated on a coarse wool felt with a thickness of 8.0 mm to obtain a low-frequency enhanced thin composite sound-absorbing material. The sound-absorbing characteristics and the like of the obtained composite sound-absorbing material are shown in Table 3 below.

[0103] <Example 2-3> From the composite molded body S2, two circular disks with a diameter of 28.8 mm were cut out, and all of them were naturally laminated on a coarse wool felt with a thickness of 8.0 mm to obtain a low-frequency enhanced thin composite sound-absorbing material. The sound-absorbing characteristics and the like of the obtained composite sound-absorbing material are shown in Table 3 below.

[0104] <Example 2-4> From the composite molded body S2, three circular disks with a diameter of 28.8 mm were cut out, and all of them were naturally laminated on a coarse wool felt with a thickness of 8.0 mm to obtain a low-frequency enhanced thin composite sound-absorbing material. The sound-absorbing characteristics and the like of the obtained composite sound-absorbing material are shown in Table 3 below.

[0105] <Example 2-5> From the composite molded body S3, two circular disks with a diameter of 28.8 mm were cut out, and all of them were naturally laminated on a coarse wool felt with a thickness of 8.0 mm to obtain a low-frequency enhanced thin composite sound-absorbing material. The sound-absorbing characteristics and the like of the obtained composite sound-absorbing material are shown in Table 3 below.

[0106] <Example 2-6> From the composite molded body S3, three circular disks with a diameter of 28.8 mm were cut out, and all of them were naturally laminated on a coarse wool felt with a thickness of 8.0 mm to obtain a low-frequency enhanced thin composite sound-absorbing material. The sound-absorbing characteristics and the like of the obtained composite sound-absorbing material are shown in Table 3 below.

[0107] <Example 2-7> From the composite molded body S5, one circular disk with a diameter of 28.8 mm was cut out and naturally laminated on a coarse wool felt with a thickness of 8.0 mm to obtain a low-frequency enhanced thin composite sound-absorbing material (the same as the composite sound-absorbing material in Example 1-5). The sound-absorbing characteristics and the like of the obtained composite sound-absorbing material are shown in Table 3 below.

[0108] <Example 2-8> From the composite molded body S6, three circular disks with a diameter of 28.8 mm were cut out, and all were naturally laminated on a coarse wool felt with a thickness of 8.0 mm to obtain a low-frequency enhanced thin composite sound-absorbing material. The sound-absorbing characteristics, etc. of the obtained composite sound-absorbing material are shown in Table 3 below.

[0109] 〈Example 2-9〉 From the composite molded body S8, two circular disks with a diameter of 28.8 mm were cut out, and all were naturally laminated on a coarse wool felt with a thickness of 8.0 mm to obtain a low-frequency enhanced thin composite sound-absorbing material. The various physical properties of the obtained composite molded body and the sound-absorbing characteristics, etc. of the composite sound-absorbing material are shown in Table 4 below.

[0110] 〈Example 2-10〉 From the composite molded body S8, three circular disks with a diameter of 28.8 mm were cut out, and all were naturally laminated on a coarse wool felt with a thickness of 8.0 mm to obtain a low-frequency enhanced thin composite sound-absorbing material. The sound-absorbing characteristics, etc. of the obtained composite sound-absorbing material are shown in Table 4 below.

[0111] 〈Example 2-11〉 From the composite molded body S9, one circular disk with a diameter of 28.8 mm was cut out and naturally laminated on a coarse wool felt with a thickness of 8.0 mm to obtain a low-frequency enhanced thin composite sound-absorbing material (the same as the composite sound-absorbing material in Example 1-9). The sound-absorbing characteristics, etc. of the obtained composite sound-absorbing material are shown in Table 4 below.

[0112] 〈Example 2-12〉 From the composite molded body S10, one circular disk with a diameter of 28.8 mm was cut out and naturally laminated on a coarse wool felt with a thickness of 8.0 mm to obtain a low-frequency enhanced thin composite sound-absorbing material (the same as the composite sound-absorbing material in Example 1-10). The sound-absorbing characteristics, etc. of the obtained composite sound-absorbing material are shown in Table 4 below.

[0113] 〈Example 2-13〉 From the composite molded body S1, one circular disk with a diameter of 28.8 mm was cut out and naturally laminated on a coarse wool felt with a thickness of 8.0 mm to obtain a composite sound-absorbing material (the same as the composite sound-absorbing material in Example 1-1). The sound-absorbing characteristics, etc. of the obtained composite sound-absorbing material are shown in Table 4 below.

[0114] <Example 2-14> Two circular disks with a diameter of 28.8 mm were cut out from the composite molded body S1, and all were naturally laminated on a coarse wool felt with a thickness of 8.0 mm to obtain a composite sound-absorbing material. The sound-absorbing characteristics and the like of the obtained composite sound-absorbing material are shown in Table 4 below.

[0115] <Example 2-15> Six circular disks with a diameter of 28.8 mm were cut out from the composite molded body S6, and all were naturally laminated on a coarse wool felt with a thickness of 8.0 mm to obtain a composite sound-absorbing material. The sound-absorbing characteristics and the like of the obtained composite sound-absorbing material are shown in Table 4 below.

[0116] <Example 2-1> Six circular disks with a diameter of 28.8 mm were cut out from the composite molded body S8, and all were naturally laminated on a coarse wool felt with a thickness of 8.0 mm to obtain a composite sound-absorbing material. The sound-absorbing characteristics and the like of the obtained composite sound-absorbing material are shown in Table 4 below.

[0117] <Comparative Example 2-1> One circular disk with a diameter of 28.8 mm was cut out from the composite molded body R1, and it was naturally laminated on a coarse wool felt with a thickness of 8.0 mm to obtain a composite sound-absorbing material. The sound-absorbing characteristics and the like of the obtained composite sound-absorbing material are shown in Table 4 below.

[0118] <Comparative Example 2-2> One circular disk with a diameter of 28.8 mm was cut out from the composite molded body R2, and it was naturally laminated on a coarse wool felt with a thickness of 8.0 mm to obtain a composite sound-absorbing material. The sound-absorbing characteristics and the like of the obtained composite sound-absorbing material are shown in Table 4 below.

[0119] <Comparative Example 2-3> One circular disk with a diameter of 28.8 mm was cut out from the composite molded body R3, and it was naturally laminated on a coarse wool felt with a thickness of 8.0 mm to obtain a composite sound-absorbing material. The sound-absorbing characteristics and the like of the obtained composite sound-absorbing material are shown in Table 4 below.

[0120] <<Manufacturing Example of Composite Sound-Absorbing Material by Pulp Molding Method>> <Example 3-1> Using fibrillated fiber A and PET staple fiber A (manufactured by Teijin Ltd.: TA04PN, fineness: 0.1 T, average fiber diameter: 3.0 μm, cut length: 3 mm), a composite molded body was produced according to the following procedure.

[0121] The fibrillated fiber and the staple fiber were added to pure water so that the solid content weight ratio was 10:90, the final solid content concentration was 0.5%, and the slurry was prepared by stirring with a household mixer for 4 minutes.

[0122] As schematically shown in FIG. 6, the above slurry (60) was placed in a material tank (50). By depressurizing in the depressurizing direction (80), the surface density was 150 g / m on the surface of a cage (a cube with one side open) - shaped metal mesh (70). 2 It was adsorbed so as to obtain a slurry concentrate (60). The obtained slurry concentrate (60) was pressed against a mold, further dehydrated, and then dried in an oven heated to 130 °C for 10 minutes. The obtained three - dimensional composite molded body had a uniform surface and was a structure without folds, joints or cuts. Further, as schematically shown in FIGS. 3 and 4, a felt (12) with a thickness of 8 mm and a PP plate (11, thickness 1 mm) were attached to the outside using double - sided tape and instant adhesive to form a three - dimensional composite sound - absorbing material (10). The evaluation results of various physical properties and sound - absorbing properties of the composite molded body are shown in Table 5.

[0123] 〈Example 3 - 2〉 A planar composite molded body S5 was attached to a felt with a thickness of 8.0 mm using an adhesive, and further assembled into a cage shape using cellophane tape and an adhesive. At this time, it was confirmed that there were gaps between the composite molded bodies in part. On this surface, a PP plate (thickness 1 mm) was further pasted using double - sided tape and an adhesive to create a three - dimensional composite sound - absorbing material imitating Example 3 - 1. The evaluation results of various physical properties of the used composite molded body and the sound - absorbing properties of the three - dimensional composite sound - absorbing material are shown in Table 5.

[0124] 〈Comparative Example 3 - 1〉 Similar to the composite molded body R1, fibrillated fiber B was used for the fibrillated fiber, and the surface density was 25 g / m. 2A composite molded body was obtained in the same manner as in Example 3-1 except for [specific conditions]. The evaluation results of various physical properties and sound absorption properties of the composite molded body are shown in Table 5.

[0125] <Comparative Example 3-2> Similar to the composite molded body R2, fibrillated fiber D was used for the fibrillated fiber, and the areal density was 100 g / m 2 A composite molded body was obtained in the same manner as in Example 3-1 except for [specific conditions]. The evaluation results of various physical properties and sound absorption properties of the composite molded body are shown in Table 5.

[0126] <Comparative Example 3-3> Similar to the composite molded body R3, fibrillated fiber B was used for the fibrillated fiber, and the areal density was 100 g / m 2 A composite molded body was obtained in the same manner as in Example 3-1 except that the solid content weight ratio of the fibrillated fiber to the short fiber was 50:50. The evaluation results of various physical properties and sound absorption properties of the composite molded body are shown in Table 5.

[0127] [Table 1]

[0128] [Table 2]

[0129] [Table 3]

[0130] [Table 4]

[0131] [Table 5] [Industrial Applicability]

[0132] The composite molded body of the present disclosure can be suitably used as a ventilation adjustment layer of a sound-absorbing material, and since it can be easily three-dimensionally molded, it can be suitably used particularly as a composite sound-absorbing material used in buildings, automobiles, and home appliances.

Explanation of Signs

[0133] 10 Three-dimensional composite sound-absorbing material 11 PP plate 12 Felt 13 Composite molded body 20 Sound source 30 Desk 40 Evaluator 50 Material tank 60 Slurry 61 Slurry concentrate 70 Metal mesh 80 Reducing pressure direction

Claims

1. A composite molded body containing fibrillated fibers and short fibers, wherein the composite molded body has a basis weight of 30 g / m ２ to 1000 g / m ２ and an air permeability resistance per unit thickness of 15.0 s / (100 mL·mm) or less.

2. The composite molded body according to claim 1, wherein the fibrillated fiber is at least one selected from the group consisting of cellulose microfibers, fibrillated fibers of polyacrylonitrile, aramid pulp, chitin nanofibers, chitosan nanofibers, and silk nanofibers.

3. The composite molded body according to claim 2, wherein the fibrillated fiber contains cellulose microfibers, and the cellulose microfibers have an average fiber diameter including a microfiber portion up to the fibrillated end of 10 nm or more and 1000 nm or less.

4. The composite molded body according to any one of claims 1 to 3, wherein the short fiber is made of a synthetic fiber.

5. A method for manufacturing the composite molded body according to any one of claims 1 to 3, the method including a step of three-dimensionally shaping a slurry containing a fibrillated fiber and a short fiber by a pulp molding method.

6. A method for manufacturing the composite molded body according to claim 4, the method including a step of three-dimensionally shaping a slurry containing a fibrillated fiber and a short fiber by a pulp molding method.

7. A sound absorption material including the composite molded body according to any one of claims 1 to 3.

8. A sound absorption material including the composite molded body according to claim 4.

9. A composite sound absorption material including a support having a thickness of 5 mm or more and the composite molded body according to any one of claims 1 to 3 laminated on the support.

10. A composite sound absorption material including a support having a thickness of 5 mm or more and the composite molded body according to claim 4 laminated on the support.

11. The composite sound absorption material according to claim 9, wherein the support is a porous material.

12. The composite sound absorption material according to claim 10, wherein the support is a porous material.

13. A composite sound absorption material having a structure in which a ventilation adjustment layer and a porous material are laminated, wherein the thickness of the composite sound absorption material is 10 mm or less, and having a maximum sound absorption value at 3000 Hz or less, a sound absorption rate of 0.3 or more at 1000 Hz, an average sound absorption rate of 0.4 or more from 800 Hz to 2000 Hz, and an average sound absorption rate of 0.3 or more from 500 Hz to 6400 Hz in a measurement method of vertical incidence conforming to JIS A 1405.

14. A composite sound absorption material having a structure in which a ventilation adjustment layer and a porous material are laminated, wherein the thickness of the composite sound absorption material is 10 mm or less, The areal density of the ventilation adjustment layer is 100 g / m ２ or more and 1000 g / m ２ or less, and The air permeability resistance of the air ventilation adjustment layer is 0.1 s / 100 mL or more and 2.0 s / 100 mL or less, the thickness of the air ventilation adjustment layer is 0.50 mm or more and 5.00 mm or less, and the thickness of the porous material is 5.00 mm or more, a composite sound-absorbing material.

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