JPH10228285A - Acoustical material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an acoustical material which can be recycled and shows equal or higher sound absorbing characteristics than those of a conventional glass fiber as acoustical material by using a PET(polyethylene terephthalate) fiber. SOLUTION: This acoustical material contains 50 to 80wt.% PET fibers 1 having 1 to 2 deniers (D) and 20 to 30wt.% binder fibers 2 comprising PET having 1 to 4 D. This acoustical material is produced by bonding the PET fibers 1 with the binder fibers 2 and formed into a specified shape. By using the binder fiber 2 as a part of the fibers which constitute the acoustical material, such a problem that vacancies among the fibers are filled with fused binders can be suppressed. Thus, the vacancies formed among the fibers are increased in number and the volume of each vacancy is decreased, which gives a dense structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound absorbing material which is disposed in an under cover, a dash outer, an apron side, etc. in an engine room of an automobile and suppresses noise by absorbing engine sound and the like. Sound absorbing material.

[0002]

2. Description of the Related Art In an engine room of an automobile, many devices such as an engine and a fan, which generate noise inside and outside the vehicle, are arranged. Therefore, it is desirable to arrange a sound absorbing material in the engine room in the vicinity of the abnormal sound source. However, since various components are densely arranged in the engine room of a recent automobile, a space for disposing the sound absorbing material is restricted, and the thickness of the sound absorbing material is inevitably reduced. Therefore, conventionally, a sound-absorbing material is formed from a nonwoven fabric mainly composed of glass fiber, shaped into a predetermined shape, and then used by being arranged in a narrow space such as near an engine in an engine room.

[0003] This sound absorbing material is manufactured by shaping a non-woven fabric made of glass fiber to which a thermosetting resin binder is adhered into a predetermined shape by hot pressing or the like. According to this sound absorbing material, sound energy that has entered the holes between the entangled glass fibers gradually attenuates sound energy due to the viscous resistance of air in the vicinity of the fibers and the vibration of the fibers themselves, thereby causing sound absorption. As a result, transmission of sound to the outside can be suppressed.

[0004]

SUMMARY OF THE INVENTION In order to make effective use of the earth's resources, it is necessary to recycle products manufactured from materials that can be melted and reused, such as thermoplastic resin products and glass products. Have been done. Also in automotive parts, names of raw materials are described in various resin members, and recycling is further facilitated.

However, since the conventional sound absorbing material is composed of glass fiber and a thermosetting resin, it is necessary to heat the material to the decomposition temperature of the thermosetting resin when recycling.
In addition, the processing cost of the resin decomposition product increases, and the cost increases. For this reason, the use of new glass is less expensive, so the sound absorbing material is not recycled, and the used sound absorbing material is currently disposed of.

Further, since the specific gravity of the sound absorbing material made of glass fiber is larger than that of the resin, it is contrary to another purpose of reducing fuel consumption by reducing the weight. Therefore, in recent years, sound absorbing materials using polyethylene terephthalate (PET) fibers instead of glass fibers have been studied. Since a recycling law has been established for PET products, recycling can be made possible by using a PET fiber sound absorbing material. Further, since the specific gravity is small, the weight can be reduced as compared with a sound absorbing material made of glass fiber.

The sound absorbing material made of PET fiber is composed of a non-woven fabric made of PET fiber and a thermoplastic resin binder.
The PET non-woven fabric is used by being cold-pressed in a state where the thermoplastic resin binder is melted by heating to form a predetermined shape. By the way, in the case of the fibrous sound absorbing material, when the same weight and the same thickness are used, the smaller the diameter of the constituent fibers, the finer the pores formed between the fibers and the greater the number, the greater the number of the fibers. ing.

[0008] However, the conventional sound absorbing material made of PET fiber has a nonwoven fabric made of PET fiber impregnated with a solution of a thermoplastic resin binder, and then the solvent is removed. It is shaped into a predetermined shape by pressing. For this reason, there is a problem that the molten binder enters between the PET fibers and closes the pores, thereby reducing the number of pores and deteriorating the sound absorbing characteristics.

Therefore, such a sound absorbing material made of PET fiber has a problem that the sound absorbing performance is low when compared with the conventional sound absorbing material made of glass fiber with the same weight per unit area and the same thickness. The present invention has been made in view of such circumstances, and aims to make it recyclable using PET fibers and to exhibit sound absorption characteristics equal to or higher than that of conventional glass fiber sound absorbing materials. And

[0010]

The sound-absorbing material according to claim 1, which solves the above-mentioned problems, is characterized in that 50 to 80% by weight of PET fibers having a fineness of 1 to 2D and binder fibers having a fineness of 1 to 4D made of PET. 20 to 50% by weight, and the PET fibers are bound to each other by binder fibers and shaped into a predetermined shape.

The sound absorbing material according to the second aspect is characterized in that in the sound absorbing material according to the first aspect, the binder fiber is a polyethylene terephthalate fiber having a fineness of 1 to 2D and a melting point higher than that of the PET fiber. . The feature of the sound absorbing material according to claim 3 is that, in the sound absorbing material according to claim 1, the binder fiber includes a core layer having a high melting point and a surface layer coated on the surface of the core layer and having a lower melting point than the core layer. It has a layer structure.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the sound absorbing material of the present invention, PET fibers are bonded to each other by a binder fiber made of PET and shaped into a predetermined shape. That is, since the binder is in a fiber shape, only the surface of the binder fiber can be melted at the time of heating, and the binder fiber can be used as a part of the fiber constituting the sound absorbing material.

Therefore, the spaces between the fibers are less likely to be filled with the molten binder, the number of the holes formed between the fibers is increased, and the volume of each hole is small and fine. As a result, the sound absorbing characteristics are improved, and when compared with the conventional glass fiber sound absorbing material with the same weight per unit area and the same thickness, sound absorbing characteristics equal to or higher than those can be secured.

As the PET fiber, a PET fiber having a fineness of 1 to 2D (denier) is used. The thickness of the sound absorbing material greatly affects the sound absorbing characteristics, and the thicker the sound absorbing material, the better the sound absorbing characteristics. However, PET with a fineness of less than 1D is extremely expensive, and it is difficult to secure the thickness of the sound absorbing material within a predetermined weight. To secure the predetermined thickness, a large amount of PET fiber is required, resulting in cost and weight. Increase. In addition, since the rigidity is low, there is also a problem that it is difficult to handle the sound absorbing material after shaping. On the other hand, when the fineness exceeds 2D, the sound absorbing properties are reduced as compared with the conventional glass fiber sound absorbing material. Therefore, PET fibers having a fineness of 1 to 2D were used.

The PET fiber contains 50 to 80 in the sound absorbing material.
% By weight. If this content is less than 50% by weight, the volume of each pore between fibers becomes large, and sufficient sound absorbing characteristics cannot be obtained. On the other hand, if the content exceeds 80% by weight, it is difficult to secure a thickness within a predetermined weight, and if the predetermined thickness is to be secured, a large amount of PET fibers is required, which increases cost and weight.

The binder fiber is a fiber made of PET having a lower melting point than the PET fiber. It is desirable to use a fiber made of PET having a melting point of at least 20 ° C. lower than the PET fiber. By heating the nonwoven fabric containing the PET fiber and the binder fiber to a temperature lower than the melting point of the PET fiber and higher than the melting point of the binder fiber, the surface of the binder fiber is melted, and the PET fiber in contact with the binder fiber is fused to the binder fiber. As a result, the PET fibers are bonded to each other via the binder fibers, so that the PET fibers can be easily formed into a predetermined shape.

This binder fiber has a fineness of 1 to 4D. The fineness is preferably smaller, but the above PET
When the diameter is smaller than the fiber, the strength for bonding the PET fibers becomes small, and it becomes difficult to secure the rigidity. On the other hand, if the fineness exceeds 4D, the pores between the fibers may be closed, and the sound absorbing properties may be reduced. This binder fiber is contained in the sound absorbing material in an amount of 20 to 50% by weight. When the amount of the binder fiber is less than 20% by weight, the strength for bonding the PET fibers becomes small, and it is difficult to secure the rigidity.
On the other hand, if it exceeds 50% by weight, the pores between the fibers may be closed, and the sound absorbing properties may be reduced.

As the binder fiber, it is also preferable to use a two-layer fiber in which the core layer is formed of PET having a high melting point and the surface layer is coated with PET having a low melting point. in this case,
The melting point of the surface layer PET needs to be lower than the melting points of both the PET fibers having a fineness of 1 to 2D and the PET of the core layer, and the difference between the melting points is preferably 20 ° C. or more. When such a two-layer fiber is used, the amount of melting at the time of heating can be significantly reduced, and the pores formed between the fibers are prevented from being closed, so that the sound absorbing properties are further improved.

The sound absorbing material of the present invention has a fineness of 4-6.
PE similar to the PET fiber having a fineness of 1 to 2D and a melting point of D
It is desirable to contain T fibers in a range of less than 20% by weight. By including the PET fiber having such a large diameter, it is easy to secure the thickness within a predetermined weight per unit area, and it is easy to secure the rigidity. If the fineness of the PET fiber is less than 4D, it is difficult to secure a thickness within a predetermined weight per unit area,
If the fineness exceeds 6D, the volume of each hole between the fibers becomes large, and the sound absorbing property is reduced. In addition, this diameter P
Even if the ET fiber is contained in an amount of more than 20% by weight, the volume of each pore between the fibers is increased, and the sound absorbing property is reduced.

It is also preferable to use hollow fibers as PET fibers having a fineness of 4 to 6D. By doing so, it is possible to reduce the weight while securing the above effects. Also, when compared with the same basis weight, the bulk becomes bulky as compared with the case where solid fibers are used, and the thickness and rigidity are easily secured. In addition, it is also preferable to mix about 10 to 20% by weight of a PET fiber or a binder fiber containing a phosphorus-based flame retardant. This enhances the flame retardancy of the sound-absorbing material and enhances the self-extinguishing property in the event of ignition, making it particularly preferable as a sound-absorbing material for automobiles.

[0021]

The present invention will be described more specifically with reference to examples and comparative examples. (Embodiment 1) FIG. 1 shows a sound absorbing material of this embodiment. This sound-absorbing material is formed in a sheet shape having a thickness of 30 mm, and includes a first PET fiber 1 having a small diameter and a second PET fiber 2 having a two-layer structure having a large diameter. The first PET fiber 1 and the second PET fiber 2 are formed.
Are in contact with each other by melting the surface layer of the second PET fiber 2. That is, the second PET fiber functions as a binder. Hereinafter, a method of manufacturing the sound absorbing material will be described, and the detailed description of the structure will be substituted.

First PET having a fineness of 1.5 D and a melting point of 250 ° C.
70% by weight of fiber 1 and 4D fineness and melting point 1 of surface PET
The second PET fiber 2 having a two-layer structure of 60 ° C. and a melting point of the core layer PET of 250 ° C. is mixed with 30% by weight, and the basis weight is 10%.
A non-woven fabric of 00 g / m ² was formed. This non-woven fabric is heated at a temperature of 2
It was kept in a hot air oven at 10 ° C. for 30 seconds, and immediately cold-pressed to form a predetermined shape shown in FIG. 1 to obtain a sound absorbing material having a thickness of 30 mm. At this time, the surface layer portion of the second PET fiber 2 melted and acted as a binder, and the first PET fiber 1 was bonded to complete the shaping.

Example 2 50% by weight of third PET fiber having a fineness of 2D and a melting point of 250 ° C. was 50% by weight, and a melting point of 250 ° C. with a fineness of 6D.
20% by weight of 4th PET fiber and 2D fineness of surface PE
The fifth PET fiber having a two-layer structure having a melting point of 200 ° C. and a core layer PET having a melting point of 250 ° C. was mixed with 30% by weight to form a nonwoven fabric having a basis weight of 1000 g / m ² .

Using this nonwoven fabric, cold pressing was performed in the same manner as in Example 1 to obtain a sound absorbing material. At this time, the surface layer of the fifth PET fiber is melted to act as a binder, and the third PET fiber is melted.
The shaping was completed by combining the fiber and the fourth PET fiber. Comparative Example 1 70% by weight of fourth PET fiber having a fineness of 6D and a melting point of 250 ° C. was 70% by weight, and a melting point of surface PET of 110 at a fineness of 6D.
6 ° C., a two-layer structure with a melting point of 250 ° C. of the core layer PET.
PET fiber is mixed with 30% by weight, and the basis weight is 1000g.
/ M ² .

Using this non-woven fabric, cold pressing was performed in the same manner as in Example 1 to obtain a sound absorbing material. At this time, the surface of the sixth PET fiber was melted to act as a binder, and the fourth PET fiber was bonded to complete the shaping. (Comparative Example 2) At the stage of producing glass fiber, a phenolic resin was adhered to the surface of the fiber to form a nonwoven fabric of 1600 g / m ² , which was shaped into a predetermined shape as shown in FIG. 1 by a high-pressure hot press. Thus, a sound absorbing material having a thickness of 30 mm was obtained.

(Test / Evaluation) Each of the sound absorbing materials of Example 1 and Comparative Example 2 was mounted on a normal incidence sound absorption coefficient measuring apparatus (microphone impedance method), and the normal incidence sound absorption coefficient for each frequency was measured. The results are shown in FIG. From FIG. 2, it can be seen that the sound absorbing material of Example 1 shows the same sound absorbing characteristics as Comparative Example 2 although the basis weight is smaller than that of Comparative Example 2. Therefore, assuming the same weight per unit area, the sound absorbing material of Example 1 shows better sound absorbing characteristics than Comparative Example 2. According to the sound absorbing member of Example 1, the conventional sound absorbing material made of glass fiber using PET fiber is used. It is clear that sound absorption characteristics equal to or higher than those obtained are obtained.

The sound absorbing materials of Example 2 and Comparative Example 1 were measured for the normal incidence sound absorption coefficient for each frequency in the same manner as described above. The results are shown in FIG. 3 together with the results of the sound absorbing material of Example 1. FIG. 3 shows that the sound absorbing materials of Example 1 and Example 2 both have substantially the same sound absorbing characteristics. on the other hand,
In the sound absorbing material of Comparative Example 1, the fineness of the PET fiber was large, so that the sound absorbing property was reduced.

[0028]

That is, according to the sound absorbing material of the present invention, there is a great advantage that it exhibits sound absorbing characteristics equal to or higher than that of a conventional sound absorbing material using glass fiber, and is lightweight and can be recycled.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a sound absorbing member according to an embodiment of the present invention and an enlarged explanatory view of a main part thereof.

FIG. 2 is a graph showing the sound absorption coefficient of sound of each frequency of the sound absorbing members of the example and the comparative example.

FIG. 3 is a graph showing a sound absorption coefficient of sound of each frequency of the sound absorbing members of the example and the comparative example.

[Explanation of symbols]

1: 1st PET fiber 2: 2nd PET fiber (binder fiber)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI // B60R 13/08 G10K 11/16 A (72) Inventor Kuniyasu Ito Nagahata 1 Ogai Ochiai, Kasuga-cho, Nishikasugai-gun, Aichi Prefecture Toyoda Gosei (72) Inventor Masamitsu Tsukahara 1 Kasugamachi, Kasuga-cho, Nishi-Kasugai-gun, Aichi Prefecture 1 Nagahata, Toyoda Gosei Co., Ltd.

Claims (3)

[Claims] 1. A 50 to 80% by weight polyethylene terephthalate fiber having a fineness of 1 to 2D and a binder fiber 20 to 50 having a fineness of 1 to 4D made of polyethylene terephthalate.
% By weight, wherein the polyethylene terephthalate fibers are bonded to each other by the binder fibers and shaped into a predetermined shape. 2. The sound-absorbing material according to claim 1, wherein the binder fiber is a polyethylene terephthalate fiber having a fineness of 1 to 2D and a melting point higher than that of the polyethylene terephthalate fiber. 3. The binder fiber according to claim 1, wherein the binder fiber has a two-layer structure comprising a core layer having a high melting point and a surface layer coated on the surface of the core layer and having a lower melting point than the core layer.
The described sound absorbing material.