Method for manufacturing soundproof sheet, and soundproof sheet

Abstract

The present application provides a soundproof sheet manufacturing method for simply controlling internal structure, and a soundproof sheet manufactured by the manufacturing method. The soundproof sheet (S) manufacturing method is characterized by comprising: a first accumulation step (S12) of manufacturing a web (W1) in which a plurality of first fibers (23A) and a plurality of second fibers (23B) are mixed, the first fibers (23A) being natural fibers, and the second fibers (23B) including a first core portion (231) and a first coating layer (232) that coats the first core portion (231) and has a first melting point; a heating step (S13) of heating the web (W1) to melt the first coating layer (232); a pressurization step (S15) of applying a predetermined compression force to the web (W1) in a state in which the first coating layer (232) is melted; and a pressurization cooling step (S16) of cooling the web (W1) to solidify the first coating layer (232) while maintaining the state in which the predetermined compression force is applied.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a soundproof sheet, and the soundproof sheet itself. Background Technology

[0002] Sound-absorbing sheets containing natural fibers such as cellulose fibers and resins have been known for a long time. For example, Patent Document 1 discloses a plate-shaped fiber substrate containing natural fibers and synthetic resins, wherein the content of each material varies in the thickness direction.

[0003] However, in the fiber substrate described in Patent Document 1, there is a problem that it is difficult to easily control the internal structure. Specifically, in order to form a structure in which the content ratio of each material varies, the fiber aggregate is produced by stacking the materials in a manner that gradually changes the content ratio. This method easily leads to increased intervals and increased complexity of the manufacturing process, thus affecting manufacturing costs. Therefore, there is currently a need for a method for manufacturing a sound-damping sheet that allows for easy control of its internal structure.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2017-48475 Summary of the Invention

[0005] The method for manufacturing a sound-absorbing sheet is characterized by comprising: a first stacking step, wherein a first stacked fiber body is formed by mixing a plurality of first fibers and a plurality of second fibers, wherein the first fibers are natural fibers, and the second fibers include a first core and a first coating layer covering the first core and having a first melting point; a heating step, wherein the first stacked fiber body is heated to melt the first coating layer; a pressurizing step, wherein a predetermined compressive force is applied to the first stacked fiber body while the first coating layer is molten; and a pressurizing cooling step, wherein the first stacked fiber body is cooled while maintaining the state of the applied predetermined compressive force, thereby solidifying the first coating layer.

[0006] The manufacturing method of the sound-absorbing sheet is characterized by comprising: a first stacking step, wherein a first stacked fiber body is formed by mixing a plurality of first fibers and a plurality of second fibers, wherein the first fibers are natural fibers, and the second fibers include a first core and a first coating layer covering the first core and having a first melting point; a second stacking step, wherein a second stacked fiber body is formed by mixing a plurality of first fibers and a plurality of third fibers, wherein the third fibers include a second core and a second coating layer covering the second core and having a second melting point higher than the first melting point; and a heating step, wherein the first stacked fiber body and the second stacked fiber body are overlapped and heated, thereby thereby... The first coating layer and the second coating layer melt; in the cooling step, the overlapping first and second stacked fiber bodies are cooled to a temperature above the first melting point and below the second melting point, thereby solidifying the second coating layer without solidifying the first coating layer; in the pressurizing step, a predetermined compressive force is applied to the overlapping first and second stacked fiber bodies and the solidified second stacked fiber bodies; in the pressurizing and cooling step, while maintaining the applied predetermined compressive force, the first and second stacked fiber bodies are cooled to a temperature below the first melting point, so that the first and second coating layers are solidified.

[0007] The soundproof sheet is characterized in that it is manufactured using the aforementioned method for manufacturing soundproof sheets. Attached Figure Description

[0008] Figure 1 This is a schematic enlarged view of the soundproof sheet according to the first embodiment.

[0009] Figure 2 for Figure 1 The cross-sectional view of line segment AA in the diagram.

[0010] Figure 3 for Figure 1 The cross-sectional view of line segment BB in the diagram.

[0011] Figure 4 A flowchart illustrating the manufacturing method of the soundproof sheet.

[0012] Figure 5 This is a schematic diagram illustrating the structure of a device for manufacturing soundproof sheets.

[0013] Figure 6 This is a schematic diagram illustrating the manufacturing method of the soundproof sheet.

[0014] Figure 7 A block diagram showing the structure of the pressurization section and the pressurization cooling section, etc.

[0015] Figure 8 This is a schematic diagram illustrating the manufacturing method of the soundproof sheet.

[0016] Figure 9 This is a schematic diagram illustrating the manufacturing method of the soundproof sheet.

[0017] Figure 10 This is a schematic diagram illustrating the manufacturing method of the soundproof sheet.

[0018] Figure 11 A graph representing the sound insulation properties resulting from the density of the soundproof sheet.

[0019] Figure 12 This is a schematic enlarged view of a low-density area of ​​the soundproof sheet according to the second embodiment.

[0020] Figure 13 for Figure 12 A cross-sectional view of line segment CC in the diagram.

[0021] Figure 14 A flowchart illustrating the manufacturing method of the soundproof sheet.

[0022] Figure 15 This is a schematic diagram illustrating the manufacturing method of the soundproof sheet.

[0023] Figure 16 This is a schematic diagram illustrating the manufacturing method of the soundproof sheet.

[0024] Figure 17 This is a schematic diagram illustrating the manufacturing method of the soundproof sheet.

[0025] Figure 18 This is a schematic diagram illustrating the manufacturing method of the soundproof sheet.

[0026] Figure 19 A graph representing the sound absorption characteristics achieved by the internal structure of the soundproof sheet.

[0027] Figure 20 This is a schematic diagram illustrating the manufacturing method of the soundproof sheet according to the third embodiment.

[0028] Figure 21 This is a schematic diagram illustrating the manufacturing method of the soundproof sheet.

[0029] Figure 22 This is a schematic diagram illustrating the manufacturing method of the soundproof sheet.

[0030] Figure 23 This is a schematic diagram illustrating the manufacturing method of the soundproof sheet.

[0031] Figure 24 This is a schematic diagram illustrating the manufacturing method of the soundproof sheet according to the fourth embodiment.

[0032] Figure 25 This is a schematic diagram illustrating the manufacturing method of the soundproof sheet.

[0033] Figure 26 This is a schematic diagram illustrating the manufacturing method of the soundproof sheet.

[0034] Figure 27 This is a schematic diagram illustrating the manufacturing method of the soundproof sheet. Detailed Implementation

[0035] In the embodiments described below, a sound-absorbing sheet S containing natural fibers, etc., and its manufacturing method are illustrated, and the description is provided with reference to the accompanying drawings. In the following figures, the XYZ axes, serving as coordinate axes, are labeled as needed, and the direction indicated by the arrow is designated as the + direction, and the direction opposite to the + direction is designated as the - direction. Sometimes the +Z direction is referred to as upward, and the -Z direction as downward. Furthermore, in Figure 5 In this diagram, the -Z direction aligns with the vertical direction. Furthermore, for ease of illustration, the sizes of the components are slightly different from the actual dimensions. In the manufacturing apparatus 10 for the sound-damping sheet S, the target side of the conveying direction of the sheet W1, the sound-damping sheet S, etc., which serves as the first stacked fiber body, is sometimes referred to as downstream, and the side in the reverse conveying direction is referred to as upstream. In the sheet W1, etc., or the sound-damping sheet S, thickness refers to the distance along the Z-axis, and the thickness direction refers to the direction along the Z-axis.

[0036] 1. First Implementation Method

[0037] The sound-damping sheet S involved in this embodiment is manufactured by the manufacturing method of the sound-damping sheet S described below. Figure 1 As shown, the sound-absorbing sheet S, as a raw material, comprises a plurality of first fibers 23A and a plurality of second fibers 23B. The plurality of first fibers 23A and the plurality of second fibers 23B are not oriented in a specific direction, but are intertwined. The joints of the first fibers 23A and the second fibers 23B, as well as the joints of the second fibers 23B with each other, are bonded together by a first coating layer 232 of the second fibers 23B, which will be described later.

[0038] In the first fiber 23A, there is approximately one or more contact points with the second fiber 23B. In the second fiber 23B, there is also approximately one or more contact points with the first fiber 23A or other second fibers 23B. The contact points of the first fibers 23A with each other are not bonded, but there are also approximately one or more contact points. Thus, in the soundproof sheet S, a plurality of first fibers 23A and a plurality of second fibers 23B are joined together.

[0039] The soundproof sheet S possesses the flexibility and strength derived from the aforementioned methods. Applications of the soundproof sheet S include soundproofing materials for residences, offices, shops, factories, and music studios; and sound insulation materials for vehicles such as automobiles, ships, and airplanes.

[0040] The first fiber 23A is a natural fiber. In this embodiment, cellulose fiber is used as the first fiber 23A. Cellulose fiber is a relatively abundant natural material derived from plants, thus it is relatively inexpensive and readily available.

[0041] Cellulose fibers are obtained by defibrillating raw materials such as paper, corrugated cardboard, pulp, pulp sheets, sawdust, shavings, and wood. Cellulose fibers are substances mainly composed of cellulose, but may also contain components other than cellulose. Examples of components other than cellulose include hemicellulose and lignin.

[0042] The average fiber length of the first fiber 23A is preferably 10 μm or more and 50 mm or less, more preferably 20 μm or more and 5 mm or less. This allows the multiple first fibers 23A and multiple second fibers 23B to be easily wound together, thereby improving the mechanical properties of the sound-absorbing sheet S, such as strength. The average fiber length of the first fiber 23A and the second fiber 23B is measured using a length distribution diagram method.

[0043] like Figure 2 As shown, the second fiber 23B includes a first core 231 and a first coating layer 232 covering the first core 231. The first coating layer 232 is thermoplastic and has a first melting point. The first coating layer 232 is melted by heating during the manufacturing process of the sound-absorbing sheet S, described later. Figure 2 The image shows the state in which the junction of the first fiber 23A and the second fiber 23B is bonded together by the first coating layer 232, which has melted and solidified.

[0044] The first core 231 is made of organic fiber. Examples of organic fibers include natural fibers such as cellulose fibers described above, as well as synthetic fibers such as polyester and rayon. In this embodiment, polyethylene terephthalate (PET) is used as the first core 231. PET has high heat resistance due to its crystallinity, and thus has advantages such as ease of recycling from plastic bottles.

[0045] The first coating layer 232 is a thermoplastic resin. Examples of thermoplastic resins include styrene-butadiene resin, polypropylene, polyvinyl chloride, polyurethane, polystyrene, acrylic resin, and polyvinyl acetate. In this embodiment, polyethylene is used as the first coating layer 232. The average molecular weight of polyethylene can be easily changed during the manufacturing stage, allowing for more flexible setting of its melting point.

[0046] The first melting point of the first coating layer 232 is preferably about 20°C lower than the melting point of the first core 231. Therefore, during the manufacture of the sound-absorbing sheet S, it becomes easier to melt the first coating layer 232 without melting the first core 231. The melting point of the first coating layer 232 is preferably 100°C or higher and 200°C or lower, more preferably 100°C or higher and 150°C or lower. The melting points of the first coating layer 232 and the second coating layer 234, described later, are measured using JIS K0064:1992 (Method for measuring the melting point and melting range of chemical products).

[0047] The average fiber length of the second fiber 23B, i.e. the average fiber length of the first core 231, is preferably 100 μm or more and 5 mm or less, and more preferably about 1 mm. This allows the multiple second fibers 23B to be easily wound with the multiple first fibers 23A, thereby improving the mechanical properties of the soundproof sheet S, such as its strength.

[0048] The ratio of the diameter D1 of the first core 231 to the thickness E1 of the first coating layer 232 is preferably 0.2 or more and 2.0 or less, and more preferably 0.5 or more and 1.5 or less. Therefore, during the heating process in the manufacture of the soundproof sheet S, deformation of the first core 231 can be suppressed, and the first coating layer 232 can be melted and solidified.

[0049] like Figure 3 As shown, the first coating layer 232 also bonds the joints of the second fibers 23B together. The joints of the second fibers 23B are bonded together by the mutual first coating layer 232, which melts and solidifies during the manufacturing process. Since the joints of the first fibers 23A and the second fibers 23B, as described above, and the joints of the second fibers 23B together, are bonded together by the first coating layer 232, the shape of the sound-damping sheet S becomes easier to maintain. Furthermore, the sound-damping properties and strength of the sound-damping sheet S can be improved.

[0050] like Figure 4As shown, the manufacturing method of the sound-damping sheet S according to this embodiment includes a first mixing step S11, a first stacking step S12, a heating step S13, a cooling step S14, a pressurizing step S15, a pressurizing and cooling step S16, and a cutting step S17. In the manufacturing method of the sound-damping sheet S, the sound-damping sheet S is manufactured by performing each step in the above order from the upstream first mixing step S11 to the downstream cutting step S17. In addition, the manufacturing method of the sound-damping sheet of the present invention includes the first stacking step S12, the heating step S13, the pressurizing step S15, and the pressurizing and cooling step S16, and other steps are not limited to the above contents. Furthermore, the sound-damping sheet of the present invention can also be rolled into a roll for storage and sale after the pressurizing and cooling step S16 has been completed and the cutting step S17 has not been completed.

[0051] A specific example of the method for manufacturing the sound-damping sheet S will be described together with the manufacturing apparatus 10 for the sound-damping sheet S. The manufacturing apparatus 10 for the sound-damping sheet S involved in this embodiment is an example and is not limited thereto.

[0052] like Figure 5 As shown, the manufacturing apparatus 10 includes, from upstream to downstream, a mixing section 11, an stacking section 100, a sheet conveying section 120, a humidifying section 130, a heating section 140, a pressurizing and cooling section 160, a cutting section 170, and a tray 180 serving as a storage section. Although the figures are omitted, the manufacturing apparatus 10 also includes a device control section that uniformly controls the operation of each of the above structures. Furthermore, although details will be described later, in the manufacturing apparatus 10, the pressurizing section for performing the cooling process S14 and the pressurizing process S15 is also served by the pressurizing and cooling section 160 for performing the pressurizing and cooling process S16.

[0053] A first mixing process S11 is performed in the mixing section 11. The mixing section 11 mixes the first fiber 23A and the second fiber 23B in air to generate a first mixture. The mixing section 11 includes a tubular main body 60, hoppers 13 and 14 connected to the main body 60, supply pipes 61 and 62, and valves 65 and 66.

[0054] The hopper 13 is connected to the interior of the main body 60 via a supply pipe 61. A valve 65 is disposed between the hopper 13 and the main body 60 in the supply pipe 61. The hopper 13 supplies first fibers 23A into the main body 60. The valve 65 regulates the quality of the first fibers 23A supplied from the hopper 13 to the main body 60.

[0055] The hopper 14 is connected to the interior of the main body 60 via a supply pipe 62. A valve 66 is disposed between the hopper 14 and the main body 60 in the supply pipe 62. The hopper 14 supplies the second fiber 23B into the main body 60. The valve 66 regulates the mass of the second fiber 23B supplied from the hopper 14 to the main body 60. The mixing ratio of the first fiber 23A and the second fiber 23B is thus adjusted via valves 65 and 66.

[0056] In detail, the first mixture comprising the first fiber 23A and the second fiber 23B forms a sheet W1 as the first stacked fiber body in the stacking section 100 described later. In the sheet W1, the content of the second fiber 23B relative to the content of the first fiber 23A is preferably 12.0% by mass or more and 40.0% by mass or less, more preferably 14.0% by mass or more and 25.0% by mass or less. This allows for the suppression of the content of the first coating layer 232 containing the second fiber 23B while improving the mechanical properties of the sound-absorbing sheet S, such as its strength.

[0057] Here, the second fiber 23B is a material produced by another known device and supplied to the hopper 14. Alternatively, a heated mixer or the like can be arranged upstream of the hopper 14, so that the second fiber 23B produced by the heated mixer is supplied to the hopper 14. In the heated mixer, a first coating layer 232 is formed on the first core 231.

[0058] Furthermore, the first core 231 of the first fiber 23A and the second fiber 23B can also be made from fibers produced by defiberizing waste paper or old cloth. Additionally, additives can be supplied from either of the hoppers 13 and 14, thereby containing additives in the sheet W1. Examples of additives include colorants, flame retardants, insect repellents, mildew inhibitors, antioxidants, ultraviolet absorbers, agglomeration inhibitors, and release agents.

[0059] The first fiber 23A and the second fiber 23B are mixed while being conveyed from the main body 60 to the stacking section 100 to form a first mixture. To promote the formation of the first mixture in the main body 60 and improve its conveyability, a blower or similar device for generating airflow may be provided in the main body 60. The first mixture is conveyed from the main body 60 to the stacking section 100. Then, it proceeds to the first stacking process S12.

[0060] The first stacking process S12 is performed in the stacking section 100. The stacking section 100 stacks the first mixture in the air, thereby producing a sheet W1 containing a plurality of first fibers 23A and a plurality of second fibers 23B. The stacking section 100 includes a roller section 101. The stacking section 100 is generally box-shaped with an open bottom, and the roller section 101 is disposed at the top of its interior. The stacking section 100 introduces the first mixture from the main body section 60 into the interior of the roller section 101 and stacks it on the mesh belt 122 in a dry manner.

[0061] Below the stacking section 100, there is a sheet conveying section 120 including a mesh belt 122 and a suction mechanism 110. The suction mechanism 110 is positioned opposite the roller section 101 in the direction along the Z-axis, with the mesh belt 122 in between.

[0062] The drum section 101 is a cylindrical sieve that is driven to rotate by a motor (not shown). A mesh functioning as a sieve is provided on the side of the cylindrical drum section 101. The drum section 101 allows particles such as fibers and the first mixture, which are smaller than the mesh size of the sieve mesh, to pass through from the inside to the outside. Intertwined fibers in the first mixture are untangled by the drum section 101 and dispersed into the air within the accumulation section 100.

[0063] The first fiber 23A and the second fiber 23B are dispersed in the air within the stacking section 100 and randomly stacked on the mesh belt 122. Therefore, in the sheet W1, the first fiber 23A and the second fiber 23B are difficult to orient in a specific direction.

[0064] The sieve of the drum section 101 may not have the function of screening larger fibers in the first mixture. That is, the drum section 101 may also break down the fibers of the first mixture and release the entire first mixture into the interior of the accumulation section 100. The first mixture dispersed in the air within the accumulation section 100 is accumulated above the mesh belt 122 by gravity and suction from the suction mechanism 110.

[0065] The sheet conveying unit 120 includes a mesh belt 122 and a suction mechanism 110. The sheet conveying unit 120 promotes the accumulation of the first mixture on the mesh belt 122 by the suction mechanism 110. In addition, the sheet conveying unit 120 conveys the sheet W1 formed by the first mixture downstream by rotating the mesh belt 122.

[0066] A suction mechanism 110 is disposed below the roller section 101. The suction mechanism 110 draws air from the accumulation section 100 through multiple holes in the mesh belt 122. As a result, the first mixture released to the outside of the roller section 101 is drawn downwards along with the air and accumulates on the surface above the mesh belt 122. A known suction device such as a blower can be used in the suction mechanism 110.

[0067] The mesh belt 122 has multiple holes that allow air to pass through, but makes it difficult for the first fiber 23A and the second fiber 23B contained in the first mixture to pass through. The mesh belt 122 is a seamless belt and is supported by three support rollers 121.

[0068] The mesh belt 122 moves downwards by the rotation of the mounting roller 121. In other words, the mesh belt 122... Figure 5 The conveyor belt 122 rotates clockwise. The conveyor belt 122 is rotated by the support roller 121, causing the first mixture to continuously accumulate and form a sheet W1. The sheet W1 contains a large amount of air, making it soft and inflated. The sheet W1 is conveyed downstream along with the movement of the conveyor belt 122.

[0069] A scraper 123 is attached below the scraper 121 located in the +X direction among the three support rollers 121. The scraper 123 contacts the surface of the conveyor belt 122, which has finished conveying the sheet W1. The conveyor belt 122 removes the first mixture remaining on its surface by contacting the scraper 123 while rotating.

[0070] A humidification section 130 is disposed downstream of the stacking section 100. The humidification section 130 humidifies the sheet material W1 on the conveyor belt 122 by spraying water. This suppresses the scattering or dust generation of the first fiber 23A and second fiber 23B contained in the sheet material W1. Furthermore, the water used for humidification can contain water-soluble additives, thereby allowing the additives to be impregnated into the sheet material W1 in parallel with humidification.

[0071] The sheet W1 is conveyed downstream via the mesh belt 122 and peeled off from the mesh belt 122. Then, the sheet W1 is introduced into the interior of the heat radiation section 143 of the heating section 140 via the conveyor roller 147 of the heating section 140. Then, it proceeds to the heating process S13.

[0072] Preferably, the heating process S13 to the pressurized cooling process S16, as described below, are continuously performed on the sheet W1 produced in the first stacking process S12. The heating process S13 is performed using a heating unit 140. The heating unit 140 heats the sheet W1 introduced into it to a point above the first melting point of the first coating layer 232 of the second fiber 23B, causing the first coating layer 232 to melt. As a result, the sheet W1 becomes a molten fiber body. The heating unit 140 includes a heat source section 141, a heat radiation section 143, and an air supply section 145.

[0073] The heat-radiating section 143 is generally box-shaped, and the heat source section 141 and the air supply section 145 are stored inside it at the upper part. Below the heat-radiating section 143, the material sheet W1 is conveyed from the -X direction to the +X direction.

[0074] The heat source 141 is positioned above the heat radiating section 143 and faces the sheet W1 across the air supply section 145. The heat source 141 radiates heat downward within the heat radiating section 143. The heat source 141 may be a heating device such as an infrared heater. Alternatively, the heating section 140 may be a structure that heats the sheet W1 by contact with it, such as a hot plate, or a constant temperature bath with hot air circulation.

[0075] The air supply unit 145 delivers heat generated by the heat source unit 141 to the sheet W1, which moves downward within the heat radiation unit 143, via air supply. The sheet W1 is heated non-contactly while being conveyed within the heat radiation unit 143. Therefore, uneven temperature distribution is less likely to occur within the sheet W1, thus suppressing deterioration caused by insufficient heating or uneven heat distribution. Alternatively, the sheet W1 can be conveyed within the heat radiation unit 143 using a seamless belt or similar material instead of the conveyor roller 147.

[0076] Through the above structure, such as Figure 6 As shown, the heat-radiating section 143 is heated to a heating temperature T1. The heating temperature T1 of the sheet W1 in the heating process S13 is appropriately set according to the melting point of the first fiber 23A, the melting point of the first core 231 of the second fiber 23B, and the first melting point of the first coating layer 232. That is, in the heating section 140, the heating temperature T1 of the sheet W1 is set to be above the first melting point of the first coating layer 232, and below the melting point of the first fiber 23A and below the melting point of the first core 231. For example, when the melting point of the first core 231 is 260°C and the melting point of the first coating layer 232 is 125°C, the heating temperature T1 is set to 190°C.

[0077] Here, the sheet W1 is formed by mixing and stacking the first fiber 23A and the second fiber 23B. Therefore, the sheet W1 arriving at the heating section 140 is not pressurized, and is in a state containing more air and with lower density. By heating the sheet W1 in a state of lower density, the heating efficiency can be improved and the energy required for heating can be reduced. Then, it proceeds to the cooling process S14.

[0078] Return to Figure 5 The cooling process S14 is performed using a pressurized cooling unit 160. The pressurized cooling unit 160 has a first pressurized cooling unit 161 and a second pressurized cooling unit 162. The pressurized cooling unit 160 functions to cool and pressurize the sheet W1 by clamping it between the first pressurized cooling unit 161 and the second pressurized cooling unit 162. The pressurized cooling unit 160 is, for example, a stamping device capable of simultaneously cooling and pressurizing the sheet W1.

[0079] The first pressurized cooling section 161 and the second pressurized cooling section 162 are arranged opposite each other in the vertical direction. The downward-facing surface of the first pressurized cooling section 161, i.e., the lower surface, and the upward-facing surface of the second pressurized cooling section 162, i.e., the upper surface, are formed as generally flat surfaces and are cooled to a temperature lower than the ambient temperature by a cooling mechanism (not shown). The sheet W1 is cooled by contacting the lower surface of the first pressurized cooling section 161 and the upper surface of the second pressurized cooling section 162.

[0080] Here, as Figure 7 As shown, the manufacturing apparatus 10 may also include a pressurizing section 150 and a pressurizing and cooling section 160. That is, the cooling process S14 and the pressurizing process S15 may be performed in the pressurizing section 150, and the pressurizing and cooling process S16 may be performed in the separate pressurizing and cooling section 160, which is different from the pressurizing section 150.

[0081] In the above case, the pressurizing unit 150 has a first pressurizing unit 151 and a second pressurizing unit 152. The pressurizing unit 150, like the pressurizing and cooling unit 160, is a stamping device capable of simultaneously cooling and pressurizing the sheet W1.

[0082] The first pressurizing section 151 and the second pressurizing section 152 are arranged in a vertically opposing manner, similar to the pressurized cooling section 160. The downward-facing surface of the first pressurizing section 151 and the upward-facing surface of the second pressurizing section 152 are formed as substantially flat surfaces and are cooled to a temperature lower than the ambient temperature by a cooling mechanism (not shown). The sheet W1 is cooled by contacting the lower surface of the first pressurizing section 151 and the upper surface of the second pressurizing section 152.

[0083] The first pressurizing unit 151 has a first control unit 153, and the second pressurizing unit 152 has a second control unit 154. The first pressurizing cooling unit 161 has a third control unit 163, and the second pressurizing cooling unit 162 has a fourth control unit 164. Although not shown in the figure, the first control unit 153, the second control unit 154, the third control unit 163, and the fourth control unit 164 each include a CPU (Central Processing Unit), a system bus, ROM (Read Only Memory), RAM (Random Access Memory), etc.

[0084] Although not shown in the figures, the first control unit 153, the second control unit 154, the third control unit 163, and the fourth control unit 164 each have a cooling mechanism. Known cooling devices can be used in the cooling mechanism. In this embodiment, a Peltier element is used as the cooling mechanism. Known cooling devices can also be cold air devices.

[0085] The first control unit 153, the second control unit 154, the third control unit 163, and the fourth control unit 164 are electrically connected to the fifth control unit 210 and are uniformly controlled by the fifth control unit 210. The fifth control unit 210 is provided on an external device 200 relative to the manufacturing apparatus 10. That is, the stamping device and cooling mechanism of the pressurizing unit 150, and the stamping device and cooling mechanism of the pressurizing and cooling unit 160 are controlled by the fifth control unit 210 of the external device 200. The external device 200 is, for example, an information terminal device such as a personal computer.

[0086] Therefore, since the first pressurizing unit 151, the second pressurizing unit 152, the first pressurizing cooling unit 161, and the second pressurizing cooling unit 162 are individually controlled by the fifth control unit 210, the stamping pressure and the cooling temperatures T2 and T3, which will be described later, can be precisely and uniformly controlled.

[0087] Furthermore, the first control unit 153, the second control unit 154, the third control unit 163, and the fourth control unit 164 may also have temperature measurement functions. This allows the temperature of the sheet W1 and its respective surface temperature to be sent to the fifth control unit 210, thereby enabling more precise control of the cooling temperatures T2 and T3 of the sheet W1.

[0088] Furthermore, the first control unit 153, the second control unit 154, the third control unit 163, and the fourth control unit 164 may also be equipped with a pressurizing device and a cooling device separately. In this case, a stamping device and a cooling air device may also be used together. In addition, the pressurizing unit 150 or the pressurizing and cooling unit 160 may be a pair of pressurizing rollers equipped with a cooling mechanism.

[0089] As described above, the manufacturing apparatus 10 may also include a pressurizing section 150 and a pressurizing cooling section 160. In this embodiment, the pressurizing section 150 is integrated into the pressurizing cooling section 160 as described above, so that the pressurizing cooling section 160 performs the function of the pressurizing section 150.

[0090] More specifically, such as Figure 8 As shown, sheet W1 is sandwiched between the first pressurized cooling section 161 and the second pressurized cooling section 162. At this time, the lower surface of the first pressurized cooling section 161 contacts the upper surface of sheet W1, and the upper surface of the second pressurized cooling section 162 contacts the lower surface of sheet W1. The first and second pressurized cooling sections 161 and 162 are only in contact with sheet W1, and no compressive force is applied to sheet W1. The heat of sheet W1 is conducted to the first and second pressurized cooling sections 161 and 162, thereby cooling sheet W1.

[0091] In the cooling process S14, the temperature at which the sheet W1 is cooled, i.e., the cooling temperature T2, is set as a lower limit, exceeding the first melting point of the first coating layer 232. That is, the sheet is transferred to the next process, the pressurizing process S15, while maintaining the first coating layer 232 in a molten state. Details will be described later, but if the internal structure of the sound-absorbing sheet S is designed for a higher density, the cooling process S14 can be omitted. Then, the process proceeds to the pressurizing process S15.

[0092] The pressurizing process S15 is also performed using the pressurizing and cooling unit 160. In the pressurizing process S15, a predetermined compressive force is applied to the sheet W1 while the first coating layer 232 of the second fiber 23B is molten. Specifically, as... Figure 9 As shown, a compressive force is applied to the sheet W1 between the first pressurized cooling section 161 and the second pressurized cooling section 162 in a manner that shortens the distance along the Z-axis between the first pressurized cooling section 161 and the second pressurized cooling section 162.

[0093] At this time, the surfaces of the first pressurized cooling section 161 and the second pressurized cooling section 162 that are in contact with the sheet W1 are maintained at a cooling temperature T2. Therefore, the melting of the first coating layer 232 of the second fiber 23B is maintained in the sheet W1.

[0094] Therefore, the bonding of the joints between the first fiber 23A and the second fiber 23B, as described above, and the bonding of the joints between the second fibers 23B, is difficult to achieve. Consequently, the sheet W1 has low mechanical strength, making it easy to be compressed in the vertical direction by the applied compressive force, thus resulting in a higher density internal structure.

[0095] The compression ratio of the thickness of the sheet W1 in the vertical direction generated by the predetermined compression force is preferably 10% or more. As a result, the density of the sound-damping sheet S increases, thus improving the sound insulation properties. Furthermore, by adjusting the compression ratio, the density of the sound-damping sheet S can be changed. That is, if the compression ratio is increased, the density of the sound-damping sheet S will increase, and if the compression ratio is decreased, the density will decrease. The relationship between the density of the sound-damping sheet S and the sound insulation properties will be described later. Then, the process proceeds to the pressurization and cooling step S16.

[0096] The pressurized cooling process S16 is also performed using the pressurized cooling unit 160. For example... Figure 10 As shown, in the pressure cooling process S16, the sheet W1 is cooled to a cooling temperature T3 while maintaining the predetermined compressive force applied in the pressure process S15. That is, compression force is applied and cooling is performed between the first pressure cooling section 161 and the second pressure cooling section 162. The cooling temperature T3 of the sheet W1 in the pressure cooling process S16 is set to a temperature lower than the first melting point of the first coating layer 232. As a result, the first coating layer 232 solidifies, thereby bonding the joints of the first fiber 23A and the second fiber 23B, as well as the joints of the second fibers 23B to each other, together through the solidified first coating layer 232, thus forming a sound-damping sheet S as a bonded fiber body. The sound-damping sheet S after the pressure cooling process S16 is a continuous sheet shape. Then, it proceeds to the cutting process S17.

[0097] Return to Figure 5 The cutting process S17 is performed using the cutting section 170. The cutting section 170 cuts the continuous, sheet-like soundproof sheet S into the desired shape. Although not shown in the figure, the cutting section 170 includes a longitudinal blade and a transverse blade.

[0098] The longitudinal blade, for example, cuts the continuous, sheet-like sound-damping sheet S along the X-axis. The transverse blade, for example, cuts the continuous, sheet-like sound-damping sheet S along the Y-axis. This produces a roughly rectangular, plate-like sound-damping sheet S, which is then stored in the tray 180.

[0099] Alternatively, in the cooling process S14 described above, the cooling temperature T2 of the sheet W1 can be set to be lower than the first melting point of the first coating layer 232 to manufacture a lower density sheet S. Specifically, the cooling process S14 is continued until the temperature of the sheet W1 becomes lower than the first melting point, thereby solidifying the first coating layer 232. Thus, in the sheet W1, the joints of the first fiber 23A and the second fiber 23B, as well as the joints of the second fibers 23B to each other, are bonded together by the first coating layer 232.

[0100] Therefore, in the subsequent pressurizing step S15 and pressurized cooling step S16 following the cooling step S14, the sheet W1 becomes difficult to compress due to the applied compressive force. Consequently, in the pressurizing step S15 and the like, the compression ratio of the sheet W1's thickness in the vertical direction decreases, thereby enabling the manufacture of a lower-density sound-damping sheet S. That is, by adjusting the cooling temperature T2 of the sheet W1 in the cooling step S14, the density of the sound-damping sheet S can also be easily adjusted.

[0101] Here, the relationship between the density of the soundproof sheet S and the sound insulation properties in the soundproofing characteristics is explained. Figure 11 This illustrates the change in sound transmission loss when sound waves are emitted while the density and thickness of the sound-absorbing sheet S are varied, thus altering the frequency. Figure 11 In the diagram, the horizontal axis represents the frequency of the sound wave [Hz], and the vertical axis represents the transmission loss [dB]. Transmission loss is an indicator of sound insulation performance; the higher the value, the more difficult it is for sound waves to pass through, resulting in superior sound insulation performance.

[0102] exist Figure 11 In the above, levels a and d represent densities set to 0.05 g / cm³. 3 For the sample, levels b and e are defined with a density set to 0.10 g / cm³. 3 The sample, with levels c and f, had a density set to 0.15 g / cm³. 3 The thickness of the samples was set to 20mm for levels a, b, and c, and 40mm for levels d, e, and f.

[0103] The theoretical value 1 is at 1000g / m 2 The line segment calculated under the given conditions has a theoretical value of 2 at 2000 g / m. 2 The line segment calculated under the given conditions has a theoretical value of 3 at 4000 g / m. 2 The line segment calculated under the given conditions has a theoretical value of 4 at 6000 g / m. 2 The line segment calculated under the given conditions.

[0104] like Figure 11 As shown, the sound insulation characteristics varied across different levels between approximately 300Hz and 2000Hz. Overall, it can be observed that the level with higher density and greater thickness exhibits superior sound insulation characteristics.

[0105] According to this embodiment, the following effects can be obtained.

[0106] In the sound-damping sheet S, the internal structure can be easily controlled. Specifically, by adjusting the cooling temperature T2 of the sheet W1, the compression ratio of the sheet W1 can be changed, thereby easily altering the thickness and density of the sound-damping sheet S. That is, a method for manufacturing the sound-damping sheet S with easily controllable internal structure, and a sound-damping sheet S manufactured by this method, are provided.

[0107] 2. Second Implementation Method

[0108] The sound-damping sheet S according to this embodiment is manufactured by the manufacturing method of the sound-damping sheet S of this embodiment described below. The sound-damping sheet S of this embodiment differs from the sound-damping sheet S of the first embodiment in that it is formed from a sheet W1 as a first stacked fiber body and a sheet W2 as a second stacked fiber body. Hereinafter, descriptions of structures repeated in the first embodiment will be omitted. Furthermore, the manufacturing apparatus 10 described above is also used in the manufacturing method of the sound-damping sheet S of this embodiment. In the following description, reference is also made to the first embodiment. Figure 5 .

[0109] The sound-damping sheet S of this embodiment has a high-density region L2 originating from sheet W1 and a low-density region L1 originating from sheet W2, as described later. The high-density region L2 has the same internal structure as the higher-density region in the sound-damping sheet S of the first embodiment.

[0110] like Figure 12 As shown, the low-density region L1 of the sound-absorbing sheet S in this embodiment contains a plurality of first fibers 23A and a plurality of third fibers 23C as raw materials. The plurality of first fibers 23A and the plurality of third fibers 23C are not oriented in a specific direction, but are intertwined. The joints of the first fibers 23A and the third fibers 23C, as well as the joints of the third fibers 23C with each other, are bonded together by a second coating layer 234 of the third fibers 23C, which will be described later.

[0111] In the first fiber 23A, there is approximately one or more contact points with the third fiber 23C. In the third fiber 23C, there is also approximately one or more contact points with the first fiber 23A or other third fibers 23C. The contact points of the first fibers 23A are not bonded to each other, but there are approximately one or more contact points. As described above, in the low-density region L1, multiple first fibers 23A and multiple third fibers 23C are also bonded to each other.

[0112] like Figure 13As shown, the third fiber 23C includes a second core 233 and a second coating layer 234 covering the second core 233. The second coating layer 234 is thermoplastic and has a second melting point. The second coating layer 234 is melted by heating during the manufacturing process of the sound-absorbing sheet S of this embodiment, as described later. Figure 13 The diagram shows the state in which the joints of the first fiber 23A and the third fiber 23C are bonded together by a second coating layer 234 that has melted and solidified. Additionally, although not shown in the diagram, the joints of the third fibers 23C are bonded together by the second coating layer 234.

[0113] The second core 233 is an organic fiber. Examples of organic fibers include the same material as the first core 231 described above. In this embodiment, polyethylene terephthalate is used as the second core 233.

[0114] The second coating layer 234 is a thermoplastic resin. Examples of thermoplastic resins include those similar to the first coating layer 232 described above. In this embodiment, polyethylene is used as the second coating layer 234.

[0115] The second melting point of the second coating layer 234 is higher than the first melting point of the first coating layer 232. The difference between the second melting point and the first melting point is preferably 3°C or more, and more preferably 5°C or more. Therefore, during the cooling process of manufacturing the soundproof sheet S as described later, the second coating layer 234 can be easily solidified while keeping the first coating layer 232 in a molten state.

[0116] Furthermore, the second melting point is preferably about 20°C lower than the melting point of the second core 233. Therefore, during the manufacture of the sound-absorbing sheet S, the second coating layer 234 can be easily melted without melting the second core 233. The melting point of the second coating layer 234 is preferably 110°C or higher and 210°C or lower, more preferably 110°C or higher and 160°C or lower.

[0117] The average fiber length of the third fiber 23C, i.e. the average fiber length of the second core 233, is preferably 100 μm or more and 5 mm or less, and more preferably about 1 mm. Therefore, the plurality of third fibers 23C can easily be wound with the plurality of first fibers 23A, thereby improving the mechanical properties of the soundproof sheet S, such as its strength.

[0118] The ratio of the diameter D2 of the second core 233 to the thickness E2 of the second coating layer 234 is preferably 0.2 or more and 2.0 or less, and more preferably 0.5 or more and 1.5 or less. Therefore, during the heating process in the manufacture of the soundproof sheet S, deformation of the second core 233 can be suppressed, and the second coating layer 234 can be melted and solidified.

[0119] like Figure 14 As shown, the manufacturing method of the sound-damping sheet S according to this embodiment includes a first mixing step S11 and a first stacking step S12 for producing sheet W1, and a second mixing step S21 and a second stacking step S22 for producing sheet W2. Furthermore, as subsequent steps after producing sheet W1 and sheet W2, the manufacturing method of the sound-damping sheet S includes a heating step S23, a cooling step S24, a pressurizing step S25, a pressurized cooling step S26, and a cutting step S27. However, the manufacturing method of the sound-damping sheet S is not limited to the above-described structure.

[0120] The first mixing process S11 and the first stacking process S12 are performed in the same manner as in the first embodiment. In this embodiment, the first mixing process S11 described above and the subsequent first stacking process S12 are performed to manufacture the sheet W1, and the second mixing process S21 and the subsequent second stacking process S22 are performed in parallel with or after these processes to manufacture the sheet W2.

[0121] In the manufacturing apparatus 10 described above, the sheet W1 can be either wound into a roll shape near the heating section 140, or it can be processed into a single sheet W1 in the cutting section 170, bypassing the heating section 140 and the pressurized cooling section 160.

[0122] The second mixing step S21 is performed in the mixing section 11. In the second mixing step S21, the second mixing step is performed in the same manner as the first mixing step S11, except that the second fiber 23B in the first mixing step S11 is replaced with the third fiber 23C. Through the second mixing step S21, a second mixture containing a plurality of first fibers 23A and a plurality of third fibers 23C is produced.

[0123] The second mixture is formed in the stacking section 100 into a sheet W2, which serves as a second stacked fiber body. In the sheet W2, the content of the third fiber 23C relative to the content of the first fiber 23A is preferably 12.0% by mass or more and 40.0% by mass or less, more preferably 14.0% by mass or more and 25.0% by mass or less. This allows for the suppression of the content of the second coating layer 234 containing the third fiber 23C while improving the mechanical properties of the sound-absorbing sheet S, such as its strength.

[0124] Here, the third fiber 23C is a material produced by another known device and supplied to the hopper 14. Alternatively, a heated mixer or the like can be arranged upstream of the hopper 14 to supply the third fiber 23C produced by the heated mixer to the hopper 14. In the heated mixer, a second coating layer 234 is formed on the second core 233.

[0125] Furthermore, the second core 233, which is the third fiber 23C, can also be made from fibers produced by defiberizing waste paper or old cloth. Additionally, additives can be supplied from either hopper 13 or 14, and the sheet W2 can contain them. Examples of additives include colorants, flame retardants, insect repellents, mildew inhibitors, antioxidants, UV absorbers, agglomeration inhibitors, and release agents.

[0126] The first fiber 23A and the third fiber 23C are mixed while being conveyed from the main body 60 to the stacking section 100 to form a second mixture. The second mixture is conveyed from the main body 60 to the stacking section 100 via a blower or the like. Then, it proceeds to the second stacking process S22.

[0127] The second stacking process S22 is performed in the stacking section 100. The stacking section 100 stacks the second mixture in the air, thereby producing a sheet W2 containing a plurality of first fibers 23A and a plurality of third fibers 23C. The stacking section 100 introduces the second mixture from the main body section 60 into the interior of the roller section 101 and stacks it on the mesh belt 122 in a dry manner. The second stacking process S22 is performed in the same manner as the first stacking process S12, except that the sheet W2 is produced by the second mixture.

[0128] The produced sheet W2 can be wound into a roll in the same continuous sheet shape as sheet W1, or it can be made into a single sheet at the cutting section 170, etc. Sheets W2 and W1 are overlapped in such a way that their main surfaces are joined together. Alternatively, sheet W2 can be produced on the surface above sheet W1 instead of on the mesh belt 122, thus eliminating the need for overlapping. In this case, a mechanism for unwinding the continuous sheet W1 onto the mesh belt 122 can be provided upstream of the sheet conveying section 120. Then, the process proceeds to the heating step S23.

[0129] The heating process S23 is performed using the heating unit 140. For example... Figure 15 As shown, in the heating step S23, sheet W1 and sheet W2 are overlapped and heated within the heat-radiating section 143 to melt the first coating layer 232 and the second coating layer 234. The heating temperature T1 of sheet W1 and sheet W2 is set to be above the second melting point of the second coating layer 234. Otherwise, it is performed in the same manner as the heating step S13 of the first embodiment. Then, the process proceeds to the cooling step S24.

[0130] The cooling process S24 is performed using a pressurized cooling unit 160. For example... Figure 16As shown, the overlapping sheets W1 and W2 are cooled to a temperature above the first melting point and below the second melting point, i.e., cooling temperature T2. Thus, the second coating layer 234 cures without the first coating layer 232 curing.

[0131] Specifically, sheet W1 and sheet W2 are sandwiched between the first pressurized cooling section 161 and the second pressurized cooling section 162. At this time, the lower surface of the first pressurized cooling section 161 contacts the upper surface of sheet W2, and the upper surface of the second pressurized cooling section 162 contacts the lower surface of sheet W1. The first pressurized cooling section 161 and sheet W2, and the second pressurized cooling section 162 and sheet W1, are only in contact, without applying any compressive force. The heat from sheet W2 is conducted to the first pressurized cooling section 161, and the heat from sheet W1 is conducted to the second pressurized cooling section 162, thereby cooling both sheet W1 and sheet W2.

[0132] Flakes W1 and W2 are cooled to a cooling temperature T2 to maintain the first coating layer 232 in a molten state while the second coating layer 234 is solidified, and then transferred to the next step, the pressure step S25. This allows for the bonding of the joints between the first fiber 23A and the third fiber 23C, as described above, and the bonding of the joints between the third fibers 23C. Furthermore, since the first coating layer 232 is maintained in a molten state during the cooling step S24, the cooling device of the second pressure cooling section 162 can be kept out of operation. Then, the process proceeds to the pressure step S25.

[0133] The pressurization process S25 is also implemented using the pressurization and cooling unit 160. For example... Figure 17 As shown, a predetermined compressive force is applied to sheet W1, which is overlapped and in a state where the first coating layer 232 is molten, and sheet W2, which is in a state where the second coating layer 234 is solidified. In detail, sheet W1 and sheet W2 are compressed in a manner that shortens the distance along the Z-axis between the first pressurized cooling section 161 and the second pressurized cooling section 162.

[0134] At this point, because the first coating layer 232 is in a molten state, it is difficult to bond the joints of the first fiber 23A and the second fiber 23B, as well as the joints of the second fibers 23B to each other. Therefore, the sheet W1 has low mechanical strength and will be compressed in the vertical direction by the applied compressive force, thus forming a high-density internal structure.

[0135] In contrast, because the second coating layer 234 is cured, the joints of the first fiber 23A and the third fiber 23C, as well as the joints of the third fibers 23C with each other, are bonded together. Therefore, the sheet W2 has high mechanical strength and is difficult to compress in the vertical direction by applied compressive force, thus resulting in a lower density internal structure.

[0136] The compression ratio of the thickness of sheet W1 and sheet W2 in the vertical direction generated by the predetermined compression force is preferably 10% or more in total. As a result, the density of sheet W1 increases, thus improving sound insulation. Then, the process proceeds to the pressurization and cooling step S26.

[0137] The pressurized cooling process S26 is also implemented using the pressurized cooling unit 160. For example... Figure 18 As shown, in the pressurized cooling process S26, the sheet materials W1 and W2 are cooled to a cooling temperature T3 while maintaining the state of applying a predetermined compressive force as in the pressurized process S25. That is, compressive force is applied and cooling is performed between the first pressurized cooling section 161 and the second pressurized cooling section 162. The cooling temperature T3 of sheet materials W1 and W2 in the pressurized cooling process S26 is set to a temperature lower than the first melting point of the first coating layer 232.

[0138] Thus, the first coating layer 232, in addition to the second coating layer 234, also becomes cured, thereby bonding the joints of the first fiber 23A and the second fiber 23B, as well as the joints of the second fibers 23B to each other, together through the cured first coating layer 232. Then, a sound-damping sheet S is formed, comprising a higher-density region L2 originating from sheet W1 and a lower-density region L1 originating from sheet W1. Then, the process proceeds to the cutting process S27.

[0139] The cutting process S27 is performed using the cutting section 170. The sound-damping sheet S can also be rolled up while maintaining a continuous, sheet-like shape without performing the cutting process S27. Through these methods, the sound-damping sheet S of this embodiment is manufactured.

[0140] Here, the sound absorption characteristics of the soundproofing properties are explained in the soundproofing sheet S, which includes a low-density region L1, a high-density region L2, and a region with intermediate density in its internal structure. Figure 19 This paper shows the change in sound absorption rate when a sample with altered configuration of the three regions in the sound-absorbing sheet S is subjected to perpendicular incidence of sound waves onto one side of the main surface, while simultaneously changing the frequency [Hz]. Figure 19 In the diagram, the horizontal axis represents the frequency of the sound wave [Hz], and the vertical axis represents the absorption rate of the incident sound wave, i.e., the perpendicular incidence absorption rate. The absorption rate is an indicator of sound absorption characteristics; the higher the value, the better the sound absorption characteristics.

[0141] Furthermore, the aforementioned region with intermediate density can be formed by shortening the time of the cooling process S24 so as to transfer it to the pressurization process S25 before the second coating layer 234 has been cured, or by reducing the applied compressive force.

[0142] In each sample, three sound-damping sheets S with different densities were overlapped one on top of the other. A density of 0.15 g / cm³ was used as the high-density region L2. 3 Thin sheets H were used as low-density regions L1 with a density of 0.05 g / cm³. 3 Thin sheets L were used, and a density of 0.10 g / cm³ was used as a region with intermediate density. 3 Thin sheet M. Thin sheets H, L, and M are each 20 mm thick.

[0143] Levels g1 and g2 represent samples where thin sheet L is placed on the surface where sound is incident, and thin sheets H and M are placed behind thin sheet L. Levels h1 and h2 represent samples where thin sheet M is placed on the surface where sound is incident, and thin sheets L and H are placed behind thin sheet M. Levels f1 and f2 represent samples where thin sheet H is placed on the surface where sound is incident, and thin sheets L and M are placed behind thin sheet H.

[0144] like Figure 19 As shown, differences in sound absorption characteristics are observed across different levels within a frequency range of approximately 500Hz to 4000Hz. Within this range, sound absorption characteristics are improved at levels h1 and h2 compared to levels f1 and f2, and are even more superior at levels g1 and g2. In other words, generally speaking, the lower the density of the surface on which sound waves are incident, the better the sound absorption characteristics. Therefore, when considering the relationship between density and sound insulation characteristics described above, configuring a low-density region L1 on the incident side of the sound wave and a high-density region L2 on the emitting side of the sound wave can improve both sound absorption and sound insulation characteristics.

[0145] Therefore, when used on the exterior walls of residences, for example, by configuring a low-density area L1 on the interior side, sound absorption of sounds generated inside the room can be achieved. Furthermore, by configuring a high-density area L2 on the exterior side, sound insulation against external noise can be achieved.

[0146] According to this embodiment, the following effects can be obtained.

[0147] In the sound-damping sheet S, the internal structure can be easily controlled. Specifically, by performing the pressure process S25 while the first coating layer 232 is melted and the second coating layer 234 is solidified, compression by pressure is easily achieved in the sheet W1, resulting in a higher density internal structure. In contrast, compression by pressure is difficult to achieve in the sheet W2, resulting in a lower density internal structure. Thus, a high-density region L2 and a low-density region L1 can be easily formed in the sound-damping sheet S. That is, a method for manufacturing a sound-damping sheet S with easily controllable internal structure and a sound-damping sheet S manufactured by this method are provided.

[0148] 3. Third Implementation Method

[0149] The sound-damping sheet S according to this embodiment is manufactured by the manufacturing method of the sound-damping sheet S of this embodiment, which will be described later. The sound-damping sheet S of this embodiment has an internal structure in which a lower density region L1 originating from sheet W2 is sandwiched between a higher density region L2 originating from sheet W1. That is, the sound-damping sheet S of this embodiment differs from the sound-damping sheet S of the second embodiment in that it is manufactured from two sheets W1 and one sheet W2.

[0150] Hereinafter, descriptions of structures repeated in the above embodiments will be omitted. Furthermore, in the manufacturing method of the sound-damping sheet S in this embodiment, the manufacturing apparatus 10 described above is also used. In the following description, reference will also be made to the first embodiment. Figure 5 and the second embodiment Figure 14 .

[0151] Sheets W1 and W2 are manufactured in the same manner as in the above embodiment and proceed to the heating step S23. In the heating step S23, as... Figure 20 As shown, within the heat-radiating section 143, sheet W1, sheet W2, and sheet W1 are stacked vertically in this order and heated to melt the first coating layer 232 and the second coating layer 234. The heating temperature T1 of sheet W1 and sheet W2 is set to be above the second melting point of the second coating layer 234. Otherwise, it is performed in the same manner as the heating step S13 of the first embodiment. Then, it proceeds to the cooling step S24.

[0152] In the cooling process S24, such as Figure 21 As shown, the two overlapping sheets W1 and one sheet W2 are cooled to a temperature above the first melting point and below the second melting point, i.e., cooling temperature T2. Thus, the second coating layer 234 solidifies before the first coating layer 232 has solidified. Then, the process proceeds to the pressurization step S25.

[0153] In the pressurization process S25, such as Figure 22 As shown, a predetermined compressive force is applied to two sheets W1, where the first coating layer 232 is molten, and to one sheet W2, where the second coating layer 234 is solidified. As a result, sheet W1 becomes a higher-density internal structure, while sheet W2 becomes a lower-density internal structure. Then, the process proceeds to the pressurization and cooling step S26.

[0154] In the pressurized cooling process S26, such as Figure 23 As shown, the two sheets W1 and one sheet W2 are cooled to a cooling temperature T3 while maintaining the state of applying a predetermined compressive force in the pressurizing process S25. The cooling temperature T3 in the pressurizing and cooling process S26 is set to a temperature lower than the first melting point of the first coating layer 232.

[0155] Thus, the first coating layer 232, in addition to the second coating layer 234, also becomes cured. Then, a sound-damping sheet S is formed, comprising a higher-density region L2 originating from sheet W1 and a lower-density region L1 originating from sheet W2. The sound-damping sheet S can also be appropriately cut using a cutting process S27.

[0156] According to this embodiment, in addition to the effects of the above-described embodiments, a three-layer structure can be easily formed.

[0157] 4. Fourth Implementation Method

[0158] The sound-damping sheet S according to this embodiment is manufactured by the manufacturing method of the sound-damping sheet S of this embodiment, which will be described later. The sound-damping sheet S of this embodiment differs from the sound-damping sheet S of the first embodiment in that it is formed from a single sheet W1, creating an internal structure including a lower-density region L1 and a higher-density region L2. Hereinafter, descriptions of structures repeated in the above embodiments will be omitted. Furthermore, the manufacturing apparatus 10 described above is also used in the manufacturing method of the sound-damping sheet S of this embodiment. In the following description, reference will also be made to the first embodiment. Figure 4 , Figure 5 .

[0159] The sheet W1 is manufactured in the same manner as in the first embodiment and proceeds to the heating step S13. In the heating step S13, as... Figure 24 As shown, the sheet W1 is heated within the heat-radiating section 143, causing the first coating layer 232 to melt. The heating temperature T1 of the sheet W1 is set above the first melting point of the first coating layer 232. Then, the process proceeds to the cooling step S14.

[0160] In the cooling process S14, such as Figure 25 As shown, the sheet W1 is cooled to a cooling temperature T2, which is below the first melting point. At this time, the sheet W1 is assumed to contain areas below the first melting point and areas above the first melting point. That is, the areas that are closer to the first pressure cooling section 161 and the second pressure cooling section 162 and where the first coating layer 232 has solidified, and the areas that are farther away from the first pressure cooling section 161 and the second pressure cooling section 162 and where the first coating layer 232 has melted, are mixed together. Therefore, the pressing process S15 is advanced before the internal temperature of the sheet W1 has completely and uniformly decreased to the cooling temperature T2.

[0161] In the pressurization process S15, such as Figure 26 As shown, a predetermined compressive force is applied to the sheet W1. This creates regions of varying densities within the sheet W1. Then, the process proceeds to the pressurization and cooling step S16.

[0162] In the pressurized cooling process S16, such as Figure 27 As shown, the sheet W1 is cooled to a cooling temperature T3 while maintaining the state of applying a predetermined compressive force in the pressurizing step S15. The cooling temperature T3 of the sheet W1 in the pressurizing cooling step S16 is set to a temperature lower than the first melting point of the first coating layer 232.

[0163] Therefore, in the soundproof sheet S, the region below the first melting point becomes the lower density region L1, and the region above the first melting point becomes the higher density region L2.

[0164] According to this embodiment, in addition to the effects of the first embodiment, it is also possible to easily form an internal structure with a density tilt in a sheet W1.

[0165] Symbol Explanation

[0166] 10… Manufacturing apparatus; 23A… First fiber; 23B… Second fiber; 23C… Third fiber; 150… Pressurizing section; 151… First pressurizing section; 152… Second pressurizing section; 153… First control section; 154… Second control section; 160… Pressurized cooling section; 161… First pressurized cooling section; 162… Second pressurized cooling section; 163… Third control section; 164… Fourth control section; 210… Fifth control section; 231… First core; 232… First coating layer; 233… Second core; 234… Second coating layer; S… Soundproof sheet; S12… First stacking process; S13, S23… Heating process; S16, S26… Pressurized cooling process; S22… Second stacking process; S24… Cooling process; S25… Pressurized process; W1… Sheet as the first stacked fiber body; W2… Sheet as the second stacked fiber body.

Claims

1. A method for manufacturing a sound-absorbing sheet, characterized in that, have: The first stacking process involves producing a first stacked fiber body composed of a mixture of multiple first fibers and multiple second fibers, wherein the first fibers are natural fibers, and the second fibers include a first core and a first coating layer that coats the first core and has a first melting point. The second stacking process involves fabricating a second stacked fiber body composed of a mixture of a plurality of first fibers and a plurality of third fibers, wherein the third fibers include a second core and a second coating layer that coats the second core and has a second melting point that is higher than the first melting point. The heating process involves overlapping and heating the first and second stacked fiber bodies to melt the first and second coating layers. The cooling process cools the overlapping first and second stacked fiber bodies to a temperature above the first melting point and below the second melting point, thereby curing the second coating layer without curing the first coating layer. In the pressurization process, a predetermined compressive force is applied to the first stacked fiber body and the second stacked fiber body that has been coated and cured. The pressurized cooling process, while maintaining the state of the applied predetermined compressive force, cools the first and second stacked fiber bodies to a temperature below the first melting point, so as to set the first and second coating layers to a solidified state.

2. The method for manufacturing the sound-absorbing sheet as described in claim 1, wherein, The first fiber is a cellulose fiber. The average fiber length of the first fiber is 10 μm or more and 50 mm or less. In the second fiber, the first core is polyethylene terephthalate, and the first coating layer is polyethylene. In the third fiber, the second core is polyethylene terephthalate, and the second coating layer is polyethylene. The average fiber length of the second fiber and the third fiber is more than 100 μm and less than 5 mm.

3. The method for manufacturing the sound-absorbing sheet as described in claim 2, wherein, The difference between the first melting point and the second melting point is greater than 3°C.

4. The method for manufacturing the sound-absorbing sheet as described in claim 3, wherein, In the first stacked fiber body, the content of the second fiber is 12.0% by mass or more and 40.0% by mass or less relative to the content of the first fiber. In the second stacked fiber body, the content of the third fiber is 12.0% by mass or more and 40.0% by mass or less relative to the content of the first fiber.

5. The method for manufacturing the sound-absorbing sheet as described in claim 1, wherein, In the pressurization process, the compression rate achieved by the predetermined compression force is 10% or more.

6. The method for manufacturing the sound-absorbing sheet as described in claim 5, wherein, The pressurization process is carried out using a pressurization unit. The pressurizing section has a first pressurizing section and a second pressurizing section. The compressive force is applied between the first pressurizing part and the second pressurizing part. The pressurized cooling process is implemented using a pressurized cooling unit. The pressurized cooling section includes a first pressurized cooling section and a second pressurized cooling section. The compression force is applied and the cooling is performed between the first pressurized cooling section and the second pressurized cooling section.

7. The method for manufacturing the sound-absorbing sheet as described in claim 6, wherein, The first pressurizing unit has a first control unit. The second pressurizing unit has a second control unit. The first pressurized cooling unit has a third control unit. The second pressurized cooling unit has a fourth control unit. The first control unit, the second control unit, the third control unit, and the fourth control unit are controlled by the fifth control unit.

8. A soundproof sheet, characterized in that, It is manufactured using the method for manufacturing the soundproof sheet as described in claim 1.

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