Sound-absorbing material

Abstract

To provide a novel sound absorption material suitable for recycling.SOLUTION: A sound absorption material 1 includes: a first layer; and a second layer in which the first layer is stacked and arranged in a thickness direction. The first layer includes short fibers and is arranged in at least one end in the thickness direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to sound-absorbing materials.

Background Art

[0002] Conventionally, sound-absorbing materials used in vehicles have been known (see, for example, Patent Document 1). Such sound-absorbing materials used in vehicles are generally formed by sandwiching a sheet-shaped sound-absorbing layer between sheet-shaped skin layers. As the skin layer, a non-woven fabric such as a melt-blown non-woven fabric or a spunbond non-woven fabric is used. As the sound-absorbing layer, a sheet-shaped material in which thermoplastic long fibers such as polypropylene, polyethylene terephthalate, and nylon are intertwined is used. These skin layer and sound-absorbing layer are joined by entangling the fibers of the skin layer and the sound-absorbing layer by needle punching.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Such sound-absorbing materials are disposed, for example, between various bodies and interior members of a vehicle. For this reason, the sound-absorbing material is processed into various shapes according to the shape of the vehicle body and the shape of the interior member.

[0005] In recent years, there has been a demand to recycle not only sound-absorbing materials attached to vehicles but also sound-absorbing materials that become end materials (waste materials) generated when processing the shape of sound-absorbing materials in the vehicle manufacturing process. Melt-blown nonwoven fabric and spunbond nonwoven fabric are continuous long fibers obtained by stretching molten resin with high-temperature gas. In order to recycle nonwoven fabrics containing such continuous long fibers, a process of separating the skin layer and the sound-absorbing layer and a process of melting the nonwoven fabric used for the skin layer are required. Therefore, for sound-absorbing materials using melt-blown nonwoven fabric or spunbond nonwoven fabric for the skin layer, the recycling process becomes complicated. Furthermore, in the case of fibers combining polyethylene resin and polypropylene resin such as melt-blown nonwoven fabric, it is difficult to separate and melt the polyethylene resin and the polypropylene resin.

[0006] An object of the present disclosure is to provide a novel sound-absorbing material suitable for recycling.

Means for Solving the Problems

[0007] The sound-absorbing material according to the present disclosure includes a first layer and a second layer disposed by overlapping the first layer in the thickness direction. The first layer contains short fibers and is disposed at at least one end in the thickness direction.

[0008] According to this sound-absorbing material, the first layer disposed at the end in the thickness direction is formed of short fibers. The first layer formed of short fibers is easy to unravel the fibers. Therefore, the sound-absorbing material including such a first layer is easy to recycle.

Effects of the Invention

[0009] According to the present disclosure, a novel sound-absorbing material suitable for recycling can be provided.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0011] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.

[0012] (1) Overall configuration As shown in FIG. 1, the sound-absorbing material 1 includes a skin layer (an example of the first layer) 2 and a sound-absorbing layer (an example of the second layer) 3. As shown in FIG. 2, the sound-absorbing material 1 of the present embodiment is disposed, for example, between a pillar (a body member) of the vehicle C and a pillar trim (an interior member). The sound-absorbing material 1 is a member used to absorb sounds such as wind noise that enters the passenger compartment from outside the vehicle C. The sound-absorbing material 1 is disposed such that the skin layer 2 faces the pillar side (the outside of the vehicle C). In addition, the sound-absorbing material 1 may be disposed, for example, between a door panel and a door trim of the vehicle C, between a floor panel and a floor carpet, between a roof panel and a roof liner, and the like.

[0013] As shown in FIG. 1, the skin layer 2 is a wet nonwoven fabric formed by entangling short fibers having a fiber length of less than 20 mm by a wet method into a sheet shape. More preferably, the fiber length of the skin layer 2 is 15 mm or less. The skin layer 2 is disposed so as to overlap the sound-absorbing layer 3 in the thickness direction, and is a layer that forms at least one end portion of the sound-absorbing material 1 in the thickness direction. In the present embodiment, the skin layer 2 is laminated and disposed on one surface of the sound-absorbing layer 3.

[0014] The skin layer 2 has a heat-sealing layer (an example of the first skin layer) 2a and a main material layer (an example of the second skin layer) 2b. The heat-sealing layer 2a is a layer for adhering the skin layer 2 and the sound-absorbing layer 3. The main material layer 2b is a layer formed by including the main material which is the most abundant material among the materials forming the skin layer 2. In the present embodiment, the main material is formed by including short fibers of polyethylene terephthalate resin having a melting point of the second melting point (for example, from 250°C to 280°C). The heat-sealing layer 2a is formed by including short fibers of a resin of a first melting point material having a melting point lower than the second melting point. The first melting point material may be, for example, a low melting point polyethylene terephthalate resin having a melting point of 105°C to 130°C.

[0015] In addition, the heat-sealing layer 2a and the main material layer 2b may be formed by including a small amount (for example, from 1% to 6%) of fibers made of pulp. The heat-sealing layer 2a may include polypropylene resin having a melting point lower than that of polyethylene terephthalate resin. More preferably, the heat-sealing layer 2a and the main material layer 2b are formed of short fibers having substantially the same fiber length (for example, short fibers having a fiber length of less than 20 mm, more preferably 15 mm or less as described above). Thereby, the sound-absorbing material 1 is easily recyclable. Also, the heat-sealing layer 2a may have a higher content of the first melting point material than the main material layer 2b. Thereby, the heat-sealing layer 2a melts more easily than the main material layer 2b and easily adheres to the sound-absorbing layer 3.

[0016] The sound-absorbing material 1 is required to absorb sounds between 2 kHz and 4 kHz which are the most audible to humans. For this reason, the skin layer 2 is required to have a function of tuning the frequency of the sound reaching the sound-absorbing layer 3 to 2 kHz to 4 kHz. The tuning of the frequency is performed by adjusting the air permeability of the skin layer 2. Specifically, by using a material with low air permeability for the skin layer 2, the frequency band of the sound transmitted to the sound-absorbing layer 3 is lowered. In the present embodiment, the air permeability of the entire skin layer 2 including the heat-sealing layer 2a and the main material layer 2b is 3 cc / cm 2 / sec to 30 cc / cm 2 / sec, preferably 5 cc / cm2 from 20 cc / cm 2 / sec, more preferably 8 cc / cm 2 / sec to 17 cc / cm 2 / sec. The basis weight of the short fibers of the skin layer 2 is preferably 40 g / m 2 to 80 g / m 2 . The wet nonwoven fabric is easy to change the basis weight and easy to adjust the air permeability. Since the skin layer 2 of this embodiment is formed of such short fibers, it is easier to adjust the air permeability than the conventional skin layer formed of continuous long fibers.

[0017] Also, the heat-sealing layer 2a is formed to be thinner than the main material layer 2b. Specifically, the heat-sealing layer 2a has a thickness of 0.15 percent to 3.0 percent, preferably 0.3 percent to 1.0 percent, relative to the thickness of the main material layer 2b. Thereby, even when the heat-sealing layer 2a is in a melted state, it is difficult to inhibit the air permeability of the entire skin layer 2.

[0018] The sound-absorbing layer 3 is a layer that absorbs the sound that has passed through the skin layer 2. The sound-absorbing layer 3 is disposed on the side of the interior member of the vehicle C with respect to the skin layer 2. The sound-absorbing layer 3 is formed of a material suitable for absorbing sound in the range of 2 kHz to 4 kHz. The sound-absorbing layer 3 is formed by stacking a plurality of sheet-like dry nonwoven fabrics 3a in the thickness direction and bonding these dry nonwoven fabrics 3a to each other. Each dry nonwoven fabric 3a contains a low-melting-point material having a melting point lower than that of the main material most contained among the materials contained in the dry nonwoven fabric 3a.

[0019] In this embodiment, the main material of the dry nonwoven fabric 3a is polyethylene terephthalate resin. The low melting point material of the dry nonwoven fabric 3a is low melting point polyethylene terephthalate resin. The dry nonwoven fabric 3a is formed into a sheet by intertwining long fibers of polyethylene terephthalate resin and long fibers of low melting point polyethylene terephthalate resin by a dry method. The sound absorption layer 3 is formed by stacking a plurality of dry nonwoven fabrics 3a in the thickness direction. Each dry nonwoven fabric 3a is adhered by an adhesion process described later. The fiber length of the long fibers used in the sound absorption layer 3 is 20 mm or more, which is longer than the short fibers of the skin layer 2. More preferably, the fiber length of the long fibers used in the sound absorption layer 3 is 50 mm or more. The basis weight of the sound absorption layer 3 is 100 g / m 2 to 500 g / m 2 , preferably 300 g / m 2 . In this embodiment, the low melting point polyethylene terephthalate resin contained in the dry nonwoven fabric 3a is used for adhering the dry nonwoven fabric 3a. However, for example, an adhesive having the same melting point in the same temperature range as the low melting point polyethylene terephthalate resin may be used.

[0020] The sound absorption layer 3 is arranged adjacent to the heat seal layer 2a in the thickness direction. The dry nonwoven fabric 3a of the sound absorption layer 3 and the heat seal layer 2a are formed including at least the same kind of material having substantially the same melting point. In this embodiment, the low melting point polyethylene terephthalate contained in the heat seal layer 2a and the sound absorption layer 3 is the same kind of material. The sound absorption layer 3 and the heat seal layer 2a are adhered to each other not only between the skin layer 2 and the sound absorption layer 3 but also between the dry nonwoven fabrics 3a of the sound absorption layer 3 in one step by melting the low melting point polyethylene terephthalate resin in the adhesion process described later. In other words, in one step, the formation of the sound absorption layer 3 and the adhesion to the skin layer 2 are performed simultaneously.

[0021] (2) Manufacturing process Next, the manufacturing process of the sound-absorbing material 1 according to the present disclosure will be described with reference to FIG. 3. In the present embodiment, a case where the material of the heat-sealing layer 2a is a low-melting-point polyethylene terephthalate resin, the material of the main material layer 2b is a polyethylene terephthalate resin, and the material of the sound-absorbing layer 3 is a polyethylene terephthalate resin and a low-melting-point polyethylene terephthalate resin will be described.

[0022] First, the process of manufacturing the skin layer 2 by the wet method will be described. First, short fibers 5 of polyethylene terephthalate resin (an example of short fibers of the second melting point) with a fiber length of less than 20 mm, and short fibers 6 of low-melting-point polyethylene terephthalate resin (an example of short fibers of the first melting point) with a fiber length of less than 20 mm are prepared. The manufacturing process of the skin layer 2 includes a process of entangling short fibers of polyethylene terephthalate resin by the wet method using a wet nonwoven fabric manufacturing apparatus 7, and a process of entangling short fibers of low-melting-point polyethylene terephthalate resin with the short fibers of polyethylene terephthalate resin by the wet method. In the present embodiment, after dispersing short fibers of polyethylene terephthalate resin in water, a first fleece is formed by lifting and entangling them on a net-like net. Then, short fibers of low-melting-point polyethylene terephthalate resin are dispersed in water, and lifted and entangled on the net-like net together with the first fleece to form a second fleece in which the upper layer is the heat-sealing layer 2a and the lower layer is the main material layer 2b. Then, the second fleece is dehydrated and dried to form a sheet-like skin layer 2.

[0023] Note that the fleece in which the lower layer becomes the heat-sealing layer 2a may be formed by reversing the timing of dispersing the short fibers of polyethylene terephthalate resin and the short fibers of low-melting-point polyethylene terephthalate resin in water.

[0024] Next, the manufacturing process of the sound-absorbing layer 3 will be described. In the present embodiment, an example of manufacturing the dry nonwoven fabric 3a of the sound-absorbing layer 3 separately from the process of manufacturing the skin layer 2 will be described.

[0025] In the process of manufacturing the sound-absorbing layer 3, long fibers 8 of polyethylene terephthalate resin with a fiber length of 20 mm or more and long fibers 9 of low-melting-point polyethylene terephthalate resin with a fiber length of 20 mm or more are prepared. The manufacturing process of the sound-absorbing layer 3 includes a process of intertwining the long fibers 8 of polyethylene terephthalate resin and the long fibers 9 of low-melting-point polyethylene terephthalate resin by a dry method using a dry nonwoven fabric manufacturing apparatus 11. In the present embodiment, the long fibers of polyethylene terephthalate resin and the long fibers 9 of low-melting-point polyethylene terephthalate resin are arranged randomly or in a certain direction in a mixed state. The two types of arranged long fibers are compressed and intertwined to form a sheet-like dry nonwoven fabric 3a.

[0026] Next, the process of bonding the skin layer 2 and the sound-absorbing layer 3 will be described. In the bonding process, a plurality of dry nonwoven fabrics 3a constituting the sound-absorbing layer 3 are laminated in the thickness direction. The skin layer 2 is laminated so that the heat-sealing layer 2a is on the dry nonwoven fabric 3a side on one surface of the laminated dry nonwoven fabrics 3a. In this state, a heat treatment is performed by radiating hot air to the skin layer 2 and the sound-absorbing layer 3 by a heater device 12 to apply heat. The hot air only needs to be at a temperature at which at least the heat-sealing layer 2a, which is the first melting point, and the low-melting-point polyethylene terephthalate resin in the sound-absorbing layer 3 melt. The hot air melts the heat-sealing layer 2a and the low-melting-point polyethylene terephthalate resin contained in the dry nonwoven fabric 3a, bonds the dry nonwoven fabrics 3a of the sound-absorbing layer 3 to each other, bonds the skin layer 2 and the sound-absorbing layer 3, and forms the sound-absorbing material 1. That is, in the bonding process, the formation of the sound-absorbing layer 3 and the bonding of the skin layer 2 and the sound-absorbing layer 3 are performed simultaneously. As a result, the sound-absorbing material 1 can be manufactured in a shorter time compared to the method of fixing the skin layer 2 and the sound-absorbing layer 3 using needle punching.

[0027] Thereafter, the sound-absorbing material 1 is processed into various shapes according to the shapes of the body members and interior members of the vehicle C.

[0028] (3) Function and effect The sound-absorbing material 1 formed in this way has a skin layer 2 formed of short fibers. For this reason, the fibers can be easily unraveled. For example, it is desirable to recycle the end materials (waste materials) generated when processing the sound-absorbing material 1 into various shapes. According to the sound-absorbing material 1 of the above embodiment, it can be cut in a state where the skin layer 2 and the sound-absorbing layer 3 are integrated, put into a fiber-disentangling device composed of a drum or the like, and the fibers can be unraveled. As a result, the fibers can be unraveled and recycled without separating the skin layer 2 and the sound-absorbing layer 3 in advance. Also, in the sound-absorbing material 1, the skin layer 2 is formed of short fibers and the sound-absorbing layer 3 is formed of long fibers. As a result, a process of heating and melting the skin layer, such as a skin layer formed of continuous long fibers, is unnecessary. As a result, the sound-absorbing material 1 is suitable for recycling.

[0029] Furthermore, according to this sound-absorbing material 1, the heat-sealing layer 2a contains a first melting-point material having a lower melting point than the main material layer 2b and is formed of a wet nonwoven fabric. For this reason, by applying heat to such an extent that the first melting-point material is welded, it is possible to form the sound-absorbing material 1 to which the skin layer 2 is adhered without impairing the physical properties of the main material layer 2b. As a result, regardless of the thickness and shape of the sound-absorbing material 1, it is possible to form the sound-absorbing material 1 to which the skin layer 2 is adhered. As a result, it is possible to obtain the sound-absorbing material 1 whose adhesiveness can be easily enhanced.

[0030] Furthermore, according to the manufacturing method of this sound-absorbing material 1, it includes an adhesion step of forming the sound-absorbing layer 3 and adhering the skin layer 2. As a result, in one step, it is possible to form the sound-absorbing layer 3 and adhere the skin layer 2 to the sound-absorbing layer 3. For this reason, the sound-absorbing material 1 can be easily formed.

[0031] (4) Other embodiments As described above, the embodiments of the present disclosure have been described. However, the present disclosure is not limited to the above embodiments, and various modifications are possible without departing from the gist of the invention. In particular, a plurality of modification examples described in this specification can be arbitrarily combined as needed.

[0032] For example, in the above embodiment, the sound absorption layer 3 is formed at one end of the skin layer 2, but the present invention is not limited thereto. For example, the sound absorption material 1 may be formed by sandwiching the sound absorption layer 3 with the skin layer 2.

Explanation of Reference Numerals

[0033] 1: Sound absorption material 2: Skin layer (an example of the first layer) 2a: Heat seal layer (an example of the first skin layer) 2b: Main material layer (an example of the second skin layer) 3: Sound absorption layer (an example of the second layer) 3a: Dry nonwoven fabric 5: Short fibers of polyethylene terephthalate resin 6: Short fibers of low melting point polyethylene terephthalate resin 7: Wet nonwoven fabric manufacturing apparatus 8: Long fibers of polyethylene terephthalate resin 9: Long fibers of low melting point polyethylene terephthalate 11: Dry nonwoven fabric manufacturing apparatus 12: Heater apparatus

Claims

1. a first layer and a second layer disposed overlapping the first layer in the thickness direction; comprising: the first layer includes short fibers and is disposed at at least one end in the thickness direction; The basis weight of the first layer is 40 g / m ２ to 80 g / m ２ and a sound-absorbing material, wherein the fiber length of the short fibers is less than 20 mm.

2. a first layer and a second layer disposed overlapping the first layer in the thickness direction; comprising: the first layer includes short fibers and is disposed at at least one end in the thickness direction; consisting only of the same kind of material; a sound-absorbing material, wherein the fiber length of the short fibers is less than 20 mm.

3. The first layer has a ventilation rate of 3 cc / cm ２ / sec to 30 cc / cm ２ / sec, The sound-absorbing material according to Claim 1 or 2.

4. a sound-absorbing structure in which a sound-absorbing material is disposed between a body member and an interior member of a vehicle, wherein the sound-absorbing material comprises a first layer and a second layer disposed overlapping the first layer in the thickness direction; the first layer includes short fibers; is disposed at at least one end in the thickness direction; the first layer is disposed facing the body member side; a sound-absorbing structure, wherein the fiber length of the short fibers is less than 20 mm.

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