Fiber structure body

Abstract

To provide a fiber structure body that is easy to manufacture and recycle and can achieve a specified acoustic performance.SOLUTION: A fiber structure body 200 is a fiber structure body of meltblown fibers made of the same resin material. The fiber structure body 200 has a predetermined thickness between a front surface 201a and a back surface 202a, and a bulk density differs in at least two portions in a thickness direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a fibrous structure used, for example, in sound-absorbing materials and the like.

Background Art

[0002] Conventionally, as a laminate used in sound-absorbing materials and the like, for example, as described in Patent Document 1, a laminate including a surface material containing a fiber aggregate and a base material containing a resin foam molded body is known. The fiber aggregate includes melt-blown fibers having an average fiber diameter of 10 μm or less and binder fibers dispersed in the melt-blown fibers. The surface material and the base material are thermally bonded by heating and softening or melting the resin contained therein and applying pressure. An adhesive or the like may be used separately.

[0003] Also, as described in Patent Document 2, a nonwoven fabric in which at least one layer of ultra-fine fiber layer having an average fiber diameter of 0.3 μm or more and 7 μm or less and at least one layer of continuous long fiber layer having an average fiber diameter of 10 μm or more and 30 μm or less are integrated by adhesion is known. The laminated nonwoven fabric is used as the skin material of a composite sound-absorbing material. The ultra-fine fiber layer is produced by the melt-blown method, and the continuous long fiber layer is produced by the spunbond method. The fiber layer by the melt-blown method is represented by "M", and the fiber layer by the spunbond method is represented by "S". As the laminated structure of the nonwoven fabric, SM type, SMS type, SMMS type, etc. are disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] As described above, a laminate in which different fiber layers are stacked and integrated by adhesion or the like is known. However, since different resin materials are often used in each fiber layer, it requires labor in manufacturing. Further, since different resin materials are integrated, it also requires labor for recycling.

[0006] An object of the present invention is to provide a fiber structure that is easy to manufacture and recycle and can achieve predetermined acoustic performance.

Means for Solving the Problems

[0007] [1] One aspect of the present disclosure is a fiber structure of meltblown fibers made of the same resin material, having a predetermined thickness between the front surface and the back surface, and the bulk density being different in at least two portions in the thickness direction.

[0008] According to the fiber structure of [1], since the fiber structure can be formed only by depositing resin fibers (meltblown fibers) by the meltblown method using the same resin material, there is no need to prepare a plurality of types of resin materials, nor is there a need to bond a plurality of fiber layers. Therefore, the manufacturing is easy. Further, since the fiber structure is made of the same resin material, there is no need for the labor of separating each part of the fiber structure according to the type of resin, and the recycling is also easy. And since the bulk density is different in at least two portions in the thickness direction, respective characteristics are combined, so that predetermined acoustic performance can be achieved.

[0009] [2] In the fiber structure of [1] above, it has a front surface portion including the front surface, a back surface portion including the back surface, and an intermediate portion located between the front surface portion and the back surface portion, and the bulk density of the back surface portion may be larger than the bulk density of the intermediate portion. In this case, the shape retention of the fiber structure can be improved, and the transmitted sound can be reduced.

[0010] [3] In the fibrous structure of [1] above, it has a surface layer including the surface, a back layer including the back, and an intermediate layer located between the surface layer and the back layer, and the bulk density of the surface layer is different from that of the intermediate layer, and the bulk density of the back layer and the intermediate layer may be different. In this case, since the fibrous structure has a multilayer structure, the sound absorption and sound insulation properties can be improved.

[0011] [4] In the fibrous structure of [3] above, the bulk density of the back layer may be greater than that of the intermediate layer. In this case, the shape retention of the fibrous structure can be improved, and the transmitted sound can be reduced.

[0012] [5] In the fibrous structure of [4] above, the intermediate layer may be composed of two or more divided layers having a bulk density smaller than that of the back layer and different from each other. In this case, in the intermediate layer, a first divided layer having a relatively small bulk density and a second divided layer having a relatively large bulk density can be provided. By making the second divided layer adjacent to the back layer, a structure in which the second divided layer is difficult to peel off from the back layer can be obtained. That is, even when the density difference between the back layer and the first divided layer is large, the presence of the second divided layer between them can suppress a sudden change in the density difference. As a result, a structure in which peeling is less likely to occur in the entire fibrous structure can be obtained.

Advantages of the Invention

[0013] According to the present invention, it is easy to manufacture and also easy to recycle. Furthermore, predetermined acoustic performance can be achieved.

Brief Description of the Drawings

[0014]

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Mode for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0016] The fiber structure according to an embodiment of the present invention is a fiber structure of melt-blown fibers made of the same resin material. The fiber structure according to an embodiment is used, for example, as a sound-absorbing material. The fiber structure according to an embodiment may be used, for example, as a sound-insulating material. Alternatively, the fiber structure according to an embodiment may be used as a sound-absorbing and sound-insulating material. The applicable uses of the fiber structure are not particularly limited as long as at least one of sound absorption and sound insulation is required. The fiber structure can be applied to any use. The fiber structure is applied, for example, to places where sound insulation (sound pressure reduction) is required in automobiles, electrical products, medical devices, and building structures.

[0017] As shown in FIG. 1, the fiber structure 200 has a front surface 201a and a back surface 202a. The front surface 201a faces, for example, the space on the front surface side A1 where the sound source is located. The back surface 202a faces the space on the back surface side A2 opposite to the front surface side A1. The fiber structure 200 has a predetermined thickness between the front surface 201a and the back surface 202a. In FIG. 1, an example is shown in which the fiber structure 200 has a flat plate shape, and the thickness of the fiber structure 200 is substantially constant. However, the shape of the fiber structure 200 is not limited to a flat plate shape. The thickness of the fiber structure 200 may not be constant and may vary in the plane direction. The shapes of the front surface 201a and the back surface 202a may also be flat, but the front surface 201a and the back surface 202a may have a curved surface or an inclined surface. For example, at least one of the front surface 201a and the back surface 202a may exhibit a wavy curved surface. At least one of the front surface 201a and the back surface 202a may exhibit a zigzag shape having a mountain fold portion and a valley fold portion. The fiber structure 200 may have an appropriate three-dimensional shape according to the place where it is used (such as the shape of the mounting surface or surrounding objects).

[0018] The resin material constituting the fiber structure 200 is preferably a thermoplastic resin, such as polypropylene, polyethylene, polyester, polyurethane, or nylon. The resin material constituting the fiber structure 200 may be thermoplastic polyurethane (hereinafter referred to as TPU in this specification).

[0019] The fiber structure 200 is a nonwoven structure including resin fibers fused to each other. The fiber structure 200 is a nonwoven structure manufactured by the meltblowing method (i.e., a meltblown nonwoven structure). The fiber structure 200 has a structure in which resin fibers F are three-dimensionally deposited in the thickness direction on a base material 50 (see FIG. 2) under normal pressure conditions (for example, atmospheric pressure conditions). The fiber structure 200 is manufactured by three-dimensionally depositing resin fibers using the meltblowing method. By this manufacturing method, in the fiber structure 200, the resin fibers are deposited while maintaining the voids (spaces) between the fibers of the resin fibers. That is, the fiber structure 200 has a porous structure as a whole. Note that the meltblown nonwoven structure may be manufactured by the meltblowing method while applying a suction pressure.

[0020] The average fiber diameter of the resin fibers in the melt-blown nonwoven structure is, for example, 2 μm or more and 100 μm or less. In the melt-blown fiber aggregate, since the voids between the resin fibers are maintained, the average fiber diameter of the resin fibers F discharged from the discharge nozzle of the melt-blown device 1 (see FIG. 2) is maintained as the average fiber diameter of the resin fibers in the melt-blown nonwoven structure. Compared with the nonwoven structure by the spunbond method, the melt-blown nonwoven structure is easy to adjust the fiber diameter and has a wide adjustment range, so it is easy to adjust the acoustic characteristics and strength.

[0021] The fiber structure 200 has a surface layer 201 including a surface 201a, a back layer 202 including a back surface 202a, and an intermediate layer 203 located between the surface layer 201 and the back layer 202. The surface layer 201 and the intermediate layer 203, and the intermediate layer 203 and the back layer 202 are adjacent to each other. In other words, the surface layer 201 and the intermediate layer 203, and the intermediate layer 203 and the back layer 202 are in planar contact with each other. Since these multiple layers are continuously formed by the melt-blown method using the same resin material, there is no bonded portion after molding. That is, neither the first interface 210 between the surface layer 201 and the intermediate layer 203 nor the second interface 220 between the intermediate layer 203 and the back layer 202 is an adhesive surface (bonding surface), but a surface where the density of the resin fibers is switched (changed) in the melt-blown method.

[0022] The thicknesses of the surface layer 201, the back layer 202, and the intermediate layer 203 may be set as appropriate.

[0023] In the fiber structure 200, the bulk density of the surface layer 201 is different from that of the intermediate layer 203. The bulk density of the back layer 202 is different from that of the intermediate layer 203. More specifically, the bulk density of the surface layer 201 is preferably greater than that of the intermediate layer 203. The bulk density of the surface layer 201 may be 2 times or more that of the intermediate layer 203. The bulk density of the back layer 202 is preferably greater than that of the intermediate layer 203. The bulk density of the back layer 202 may be 2 times or more, or even 3 times or more that of the intermediate layer 203. By increasing the bulk density of the surface layer 201 and the back layer 202, the strength and shape retention of the fiber structure can be enhanced.

[0024] Next, with reference to FIG. 2, a method for manufacturing a meltblown nonwoven structure will be described. The manufacturing system S forms a fiber structure 200 as a meltblown nonwoven structure by the meltblown method using the same resin material as a raw material. In this specification, the "same resin material" means that any part of the fiber structure is made of the same resin material. That is, the resin composition is uniform throughout the fiber structure. One type of resin material may be used as a raw material, or a plurality of types of resin materials may be mixed and then used as a raw material. The manufacturing system S includes a meltblown device 1 that generates resin fibers F using the resin material as a raw material, and a substrate position control device 40 that holds the substrate 50 so that the fiber structure 200 is formed on the substrate 50 with a desired thickness and shape.

[0025] The meltblown device 1 includes an extrusion part 10 that melts and extrudes the resin material, a discharge part 20 that discharges the resin material, and a blower part 30 that supplies high-temperature air to the discharge part 20. The extrusion part 10 has a tubular screw part 11 that extrudes the resin material in the axial direction, and a motor 12 that gives a rotational driving force to the screw of the screw part 11. A hopper 4 for charging the resin material into the screw part 11 is attached to the upstream side (left side in the figure) end of the screw part 11. The resin material may be, for example, in pellet form or powder form. Also, two or more types of resins may be simultaneously charged into the hopper 4.

[0026] At a plurality of axial positions of the screw portion 11, a plurality of heaters 14 are provided. Alternatively, one large heater 14 extending in the axial direction may be provided. The heater 14 heats and melts the resin material in the screw portion 11. When a plurality of resins are used, different types of resin materials before being introduced into the hopper 4 are melted and mixed with each other in the screw portion 11 and are homogenized (into a mixed resin material). At a plurality of axial positions of the screw portion 11, a plurality of temperature sensors for detecting the temperature of the melted resin material are provided, for example, a first temperature sensor 16, a second temperature sensor 17, a third temperature sensor 18, and a fourth temperature sensor 19. A discharge portion 20 is connected to the downstream end of the screw portion 11.

[0027] The discharge portion 20 includes a spinning pump 21, a die 24, and a discharge pipe portion 22 connecting the spinning pump 21 and the die 24. The spinning pump 21 receives the resin material pumped through the screw portion 11 and discharges it toward the die head 23 on the discharge port side of the die 24. At the center of the lower end of the die head 23, a discharge port 26 for discharging resin X is formed. This discharge port 26 is a discharge nozzle in the melt blow device 1 and has a plurality of holes having a predetermined diameter (hole diameter) corresponding to the desired diameter of the resin fiber F. The die head 23 and the discharge port 26 are provided at the lower end of the discharge portion 20 and are provided downward to discharge a plurality of resin fibers F. At least one of the discharge pressure and the discharge amount of the resin X in the discharge portion 20 can be adjusted as appropriate.

[0028] The air supply unit 30 includes an air supply duct 31 for circulating air and a blower 33 provided in the air supply duct 31. Air is sucked in from the upstream end of the air supply duct 31 and pressure-fed by the blower 33. A connection portion 32, which is the downstream end of the air supply duct 31, is connected to the die 24. The high-temperature air supplied by the air supply unit 30 flows into the die 24 and continuously ejects the resin fiber F from the discharge port 26. One or more heaters 34 are provided around the air supply duct 31. An air temperature sensor 36 for detecting the temperature of the air is provided at an appropriate position of the air supply duct 31. Further, an air volume adjustment valve 37 for adjusting the air volume (the flow rate of air) is provided in the air supply duct 31 on the discharge side of the blower 33.

[0029] In the manufacturing system S and the melt blowing apparatus 1, various operating conditions (or operating parameters) including the air volume, discharge pressure, and nozzle temperature are set in order to achieve a desired fiber diameter in the resin fiber F and desired adhesiveness and bulkiness in the fiber structure 200. Further, the manufacturing system S is provided with a controller and an operation unit (both not shown) for inputting the air volume, discharge pressure, the temperature of the resin material in the screw unit 11, and / or the temperature of the resin material passing through the discharge nozzle and adjusting these numerical values (operating conditions or operating parameters) to predetermined target values.

[0030] The base material position control device 40 may include a robot arm portion 40A that holds the base material 50 and can freely change the position and posture of the base material 50 below the discharge port 26. The base material position control device 40 can adjust the position and posture of the base material 50 by driving and controlling the arm portions 41 to 43.

[0031] The base material 50 that can be used in the manufacturing system S includes a surface corresponding to the shape of the fibrous structure 200 to be manufactured. The base material 50 may be made of resin or metal. The fibrous structure 200 is formed, for example, in a flat plate shape or a flat sheet shape. In that case, the surface of the base material 50 is also flat. When manufacturing a three-dimensional fibrous structure, it is necessary to hold the base material 50 with a robot arm. However, when manufacturing a sheet-like fibrous structure, it is not necessary to hold the base material 50 with a robot arm, and a base material holding device with a simpler movement mechanism may be used.

[0032] Subsequently, the operation method of the melt blowing device 1 will be described. First, in the melt blowing device 1, various operating conditions (or operating parameters) including the air volume, discharge pressure, and nozzle temperature are set. The operator who operates the manufacturing system S turns on the power of the melt blowing device 1 and presses the operation start button or the like of the melt blowing device 1. When each heater is turned on, each part of the melt blowing device 1 is heated up. After the operator confirms that the temperature has risen sufficiently, the resin material is put into the hopper 4. The extrusion part 10 melts the resin material and sends it out by the screw part 11. Air at a predetermined temperature is supplied from the air blowing part 30. The air volume may be set appropriately. However, when it is desired to increase (make denser) the fiber density in the fibrous structure 200, the air volume is set large, and when it is desired to decrease (make coarser) the fiber density in the fibrous structure 200, the air volume is set small. By setting the air volume, the fiber density or softness in the fibrous structure 200 can be controlled. Also, regarding the discharge pressure, similar to the air volume, by setting it large or small, the fiber density or softness in the fibrous structure 200 can be controlled. In the manufacturing system S, the fiber density or softness in the fibrous structure 200 is adjusted by adjusting the air volume and the distance between the discharge port 26 and the base material 50. By controlling the fiber density by the various methods described above, the bulk density in the thickness direction of the formed fibrous structure 200 is adjusted as desired.

[0033] According to the fibrous structure 200 of the present embodiment, the fibrous structure 200 can be formed only by depositing resin fibers F (melt blown fibers) by the melt blowing method using the same resin material. Therefore, it is not necessary to prepare a plurality of types of resin materials, nor is it necessary to bond a plurality of fiber layers. Therefore, the production of the fibrous structure 200 is easy. Further, since the fibrous structure 200 is made of the same resin material, it is not necessary to separate each part of the fibrous structure 200 according to the type of resin when recycling. Therefore, the recycling of the fibrous structure 200 is also easy. And since the bulk density is different in at least two parts in the thickness direction, respective characteristics are combined, so that predetermined acoustic performance can be realized.

[0034] Furthermore, the bulk density of the surface layer 201 is different from that of the intermediate layer 203, and the bulk density of the back layer 202 is different from that of the intermediate layer 203. Thereby, since the fibrous structure 200 has a multilayer structure, the sound absorption and sound insulation properties can be improved.

[0035] Also, the bulk density of the back layer 202 is larger than that of the intermediate layer 203. Since the bulk density of the back layer 202 is large, the shape maintainability of the fibrous structure 200 can be improved and the transmitted sound can be reduced.

[0036] Subsequently, the simulation and the results thereof implemented to confirm the acoustic performance of the fibrous structure 200 according to the present embodiment, that is, the sound absorption rate and the transmission loss (sound insulation property), will be described. FIG. 3 is a table showing the simulation results of the sound absorption rate in a TPU-based fibrous structure corresponding to an embodiment of the present invention and glass wool (hereinafter referred to as GW) corresponding to a reference form. FIG. 4 is a table showing the simulation results of the transmission loss in the TPU-based fibrous structure and GW. FIG. 5 is a graph showing the simulation results of the sound absorption rate in FIG. 3, and FIG. 6 is a graph showing the simulation results of the transmission loss in FIG. 4.

[0037] As simulation software, simulation was performed using "Laminated Structure Acoustic Characteristic Prediction Software (STRATI-ARTZ (registered trademark), Nippon Acoustic Engineering Co., Ltd.)". In this simulation software, for the TPU fiber structure, a model (Kato model) that predicts sound absorption and shielding performance using only the parameters of the fiber material (fiber diameter, fiber density, and bulk density) was used. For GW, the Johnson-Champoux-Allard model that deals with the behavior of sound in the material under the assumption that airborne sound and solid-borne sound propagate through the porous elastic material was used. The parameters in GW are Density, Thickness, Flow resistivity, Porosity, Tortuosity, Viscous / Thermal characteristic length, and Elastic Moduli.

[0038] The conditions given in each simulation are as follows. Thickness of the TPU fiber structure: First layer (corresponding to the surface layer 201 of the above embodiment): 6 mm Second layer (corresponding to the intermediate layer 203 of the above embodiment): 3 mm Third layer (corresponding to the back layer 202 of the above embodiment): 2 mm Bulk density of the TPU fiber structure: First layer: 773 kg / m 3 Second layer: 273 kg / m 3 Third layer: 929 kg / m 3 Mass per unit area of the TPU fiber structure: 7.315 kg / m 2 (Thickness 11 mm) Fiber diameter of the TPU fiber structure: First layer: 32.05 μm Second layer: 23.33 μm Third layer: 20 μm Resin density of the TPU fiber structure: 1190 kg / m 3

[0039] Thickness of GW: 11 mm Bulk density of GW: 48 kg / m 3 Mass per unit area of GW: 0.528 kg / m 2 (11 mm)

[0040] As shown in FIGS. 3 to 6, in the simulation results, in both the sound absorption rate and the transmission loss, the effects were shown in the fiber structure of the present embodiment. As shown in FIG. 5, the sound absorption rate was higher for TPU than for GW from 800 Hz to 2 kHz, which is the center frequency of the 1 / 3 octave band. As shown in FIG. 6, the transmission loss was greater for TPU than for GW in the entire frequency range.

[0041] Here, in order to more accurately verify the sound absorption rate, a correction value was determined as shown in FIG. 7 (Table 3) from the measured values and the simulation values. FIG. 7 (Table 4) is a table showing the corrected numerical values of the simulation results in FIG. 3. FIG. 8 is a graph showing the simulation results (after correction) of the sound absorption rate in FIG. 7. As shown in FIG. 8, the sound absorption rate was higher for TPU than for GW from 800 Hz to 2 kHz, which is the center frequency of the 1 / 3 octave band.

[0042] Although no correction has been made for the transmission loss, from the viewpoint of the mass law, it is obvious that TPU is superior. The mass law is a law that the larger the mass per unit area, the higher the transmission loss (sound insulation amount). The mass per unit area of TPU is 7.315 kg / m 2 (with a thickness of 11 mm), and the mass per unit area of GW is 0.528 kg / m 2 (11 mm), so the above estimation holds.

[0043] As described above, embodiments of the present invention have been explained, but the present invention is not limited to the above embodiments. For example, the intermediate layer 203 of the fibrous structure 200 may be composed of two or more divided layers. In that case, the bulk densities in the two or more divided layers are different from each other. The bulk density in each of the two or more divided layers is smaller than the bulk density of the back layer 202. For example, in the intermediate layer 203, a first divided layer having a relatively small bulk density and a second divided layer having a relatively large bulk density can be provided. By making the second divided layer adjacent to the back layer 202, a structure can be obtained in which the second divided layer is difficult to peel off from the back layer 202. That is, even when the density difference between the back layer 202 and the first divided layer is large, the presence of the second divided layer between them can suppress a rapid change in the density difference. As a result, a structure in which peeling is less likely to occur in the entire fibrous structure 200 can be obtained. The intermediate layer 203 may be composed of only two divided layers, or may be composed of only three or more divided layers.

[0044] The fibrous structure does not necessarily have a plurality of layers having different bulk densities such as the surface layer 201, the intermediate layer 203, and the back layer 202. In other words, the fibrous structure does not necessarily have a distinct boundary surface (a surface where the bulk density changes) such as the first boundary surface 210 and the second boundary surface 220. The bulk density inside the fibrous structure may gradually change in the thickness direction. It is only necessary that the bulk density is different in at least two portions in the thickness direction. Even in that case, the production of the fibrous structure is easy, and the recycling of the fibrous structure is also easy. Furthermore, a predetermined acoustic performance can be realized by the fibrous structure.

[0045] When the bulk density inside the fibrous structure gradually changes in the thickness direction as described above, the bulk density of the surface portion including the surface 201a may be greater than the bulk density of the intermediate portion. The bulk density of the back surface portion including the back surface 202a may be greater than the bulk density of the intermediate portion. In this case, the "surface portion" is, for example, a portion corresponding to a range within 20% from the surface 201a among the total thickness of the fibrous structure. The "back surface portion" is, for example, a portion corresponding to a range within 20% from the back surface 202a among the total thickness of the fibrous structure. The "intermediate portion" is, for example, a portion corresponding to a position exactly in the middle between the surface 201a and the back surface 202a. By increasing the bulk density of the back surface portion, the shape maintainability of the fibrous structure can be improved and the transmitted sound can be reduced.

Explanation of Reference Numerals

[0046] 200... fibrous structure, 201... surface layer, 201a... surface, 202... back surface layer, 202a... back surface, 203... intermediate layer.

Claims

Claim 1 A fibrous structure of meltblown fibers made of the same resin material, having a predetermined thickness between the front and back surfaces, and having different bulk densities in at least two portions in the thickness direction. Claim 2 comprising a front surface portion including the front surface, a back surface portion including the back surface, and an intermediate portion located between the front surface portion and the back surface portion, wherein the bulk density of the back surface portion is greater than the bulk density of the intermediate portion. The fibrous structure according to claim 1. Claim 3 comprising a front surface layer including the front surface, a back surface layer including the back surface, and an intermediate layer located between the front surface layer and the back surface layer, wherein the bulk density of the front surface layer is different from the bulk density of the intermediate layer, and the bulk density of the back surface layer is different from the bulk density of the intermediate layer. The fibrous structure according to claim 1. Claim 4 wherein the bulk density of the back surface layer is greater than the bulk density of the intermediate layer. The fibrous structure according to claim 3. Claim 5 wherein the intermediate layer is composed of two or more divided layers having a bulk density smaller than that of the back surface layer and different from each other. The fibrous structure according to claim 4.

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