Patent Description:
Unless otherwise stated herein, the statements in this specification merely provide background information related to the present disclosure and do not constitute prior art.

The internal/external noise that enters the interior of a vehicle through various routes during vehicle driving causes discomfort to the driver and the occupants. These noises mainly include noise generated from the engine and noise generated from the vehicle exhaust. As a method of solving the problem of noise entering the interior of a vehicle, sound absorbing materials are applied to various vehicle components, such as a headliner, a door trim, a rear shelf, a truck mat, a car mat, and a bonnet.

For a sound absorber for a vehicle, <CIT> discloses a method including the steps of: cutting a back felt containing low-melting fiber; preheating the back felt; bonding the back felt and a piece of carpet fabric to each other by placing the carpet fabric on the surface of the back felt and inserting the resulting stack of the carpet fabric and the back felt into a mold for molding so that the melted low-melting fiber flows into the carpet fabric during the preheating; and cooling a molded body made of the carpet fabric and the back felt.

According to <CIT>, the felt is separately preheated and then molded and cooled in the mold. Therefore, the appearance quality and sound absorption performance are deteriorated, and the production speed is slow because the production method is complicated.

<CIT> discloses a method of making an acoustical and thermal insulating fibrous panel.

The objective of the present disclosure is to provide a method of molding a sound-absorbing material for automobiles, the method being simple and being capable of producing a sound absorbing member with good surface quality and improved sound-absorbing performance.

Technical problems that can be solved by the present disclosure are not limited to the above-described objective, and other technical problems that are not described herein can also be solved by the present disclosure.

According to one embodiment of the present disclosure, there is provided a method of molding a sound absorbing material for a vehicle, the method including: (a) preparing a first fibrous layer and a second fibrous layer; (b) providing an adhesive member between the first fibrous layer and the second fibrous layer and placing an aggregate of the first fibrous layer, adhesive member, and the second fibrous layer in a molding machine; and (c) pressing an upper mold and a lower mold of the molding machine so that the first fibrous layer and the second fibrous layer are bonded and molded into a molded body.

In addition, in step (a), each of the first fibrous layer and the second fibrous layer includes <NUM>% to <NUM>% by weight of at least one base fiber selected from polyethylene terephthalate, polypropylene, polyacrylate, nylon, and cotton and <NUM>% to <NUM>% by weight of a binder fiber having a melting point of <NUM> or below, the first fibrous layer has an areal density of <NUM> to <NUM>/m<NUM>, and the second fibrous layer has an areal density of <NUM> to <NUM>/m<NUM>, and the second fibrous layer consists of a vertical fiber having a verticality of about <NUM>° to <NUM>°.

In step (c), the upper mold and the lower mold perform different processes, respectively, such that the lower mold performs a steaming process and a vacuuming process at least two times, and, in the steaming process, steam or hot air of <NUM> to <NUM> is supplied for <NUM> to <NUM> seconds at a pressure of <NUM> to <NUM> bar.

In addition, in step (b), the adhesive member is composed of at least one layer, is made of at least one selected from polyethylene, polypropylene, ethylene vinyl acetate copolymer, polyamide, and low-melting-point polyethylene terephthalate, and has a thickness of <NUM> to <NUM>.

In addition, in step (c), the upper mold may perform a vacuuming process for <NUM> to <NUM> seconds under a temperature condition of 10ºC to 100ºC.

In addition, in step (c), the vacuum process may be performed for <NUM> to <NUM> seconds under a temperature condition of 100ºC to 200ºC.

In addition, after step (c), (d) trimming may be performed after removing moisture remaining on the surface of the molded body discharged the molding machine.

In the automobile sound absorber molding method according to one embodiment disclosed in the present specification, the bonding of the first fibrous layer and the second fibrous layer and the molding are performed at the same time. This simplifies the working process and process cycle, thereby improving the production speed and reducing the cost of investment for equipment.

In addition, by processing the first and second fibrous layers at different temperatures with different processes, instead of using a conventional method performing cold pressing after preheating the first and second fibrous layers, the method has the effect of improving the appearance quality and sound absorbing performance while minimizing damage to the surface of the first fibrous layer.

In addition, since vertical fiber is used for the second fibrous layer, the thickness of the second fibrous layer can be reduced, resulting in reduction in weight of a final product (i.e., a sound absorber).

The advantages and features of the present disclosure and the manner of achieving them will become apparent with reference to embodiments described in detail below and the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete and will fully convey the concept of the invention to those skilled in the art. Thus, the invention will be defined only by the scope of the appended claims. Like reference numbers refer to like elements throughout the description herein and the drawings.

Further, in describing embodiments of the present disclosure, well-known functions or constructions will not be described in detail since they may unnecessarily obscure the gist of the present disclosure. The following terms are defined in consideration of the functions in the embodiments of the present disclosure and thus may vary according to the intentions of users, operators, or the like. Therefore, the definition of each term should be interpreted based on the contents throughout this specification.

Hereinafter, a method of molding a sound absorbing material for a vehicle according to the present disclosure will be described in detail with reference to the accompanying drawings.

<FIG> is a process flowchart illustrating a method of molding a sound absorbing material for a vehicle according to an embodiment of the present disclosure, and IG. <NUM> is a schematic view illustrating a method of molding a sound absorbing material for a vehicle according to an embodiment of the present disclosure.

Referring to <FIG> and <FIG>, first, a first fibrous layer <NUM> and a second fibrous layer <NUM> are prepared (S10).

Each of the first fibrous layer <NUM> and the second fibrous layer <NUM> may contain <NUM>% to <NUM>% by weight of at least one base fiber selected from polyethylene terephthalate (PET), polypropylene (PP), polyacrylate (PA), nylon (nylon), and cotton and <NUM>% to <NUM>% by weight of a binder fiber having a melting point of <NUM> or below. Here, as the binder fibers, polyethylene (PE), polypropylene (PP), ethylene-vinyl acetate copolymer (EVA), polyamide (PA), and low melting point polyethylene terephthalate (LM PET) may be used.

In the present disclosure, the term "nylon" refers to synthetic polymer based on aliphatic or semi-aromatic polyamide, and the term "cotton" refers to raw cotton, cotton cloth, and cotton fibers obtained by processing cotton as a raw material.

Specifically, in this embodiment, the first fibrous layer <NUM> is composed of <NUM>% to <NUM>% by weight of the base fiber and <NUM>% to <NUM>% by weight of the binder fiber. Preferably, the first fibrous layer <NUM> includes <NUM>% to <NUM>% by weight of the base fiber and <NUM>% to <NUM>% by weight of the binder fiber. The first fibrous layer may be manufactured by any one method selected from a needle punching method, an air-laid method, a fiber blow injection molding (FBIM) method, and a vertical method. The areal density of the first fibrous layer <NUM> may be in the range of <NUM> to <NUM>/m<NUM>, and preferably in the range of <NUM> to <NUM>/m<NUM>.

On the other hand, on one surface of the first fibrous layer <NUM>, any one selected from elastic rubber such as latex, a polyethylene coating layer, compressed fiber, breathable film, non-woven fabric, and adhesive powder may be provided according to the desired function such as shaping, sound absorbing, insulating, or adhesion.

The second fibrous layer <NUM> is composed of <NUM>% to <NUM>% by weight of the base fiber and <NUM>% to <NUM>% by weight of the binder fiber. The Second fibrous layer may be manufactured by any one method selected from a needle punching method, an air-laid method, a fiber blow injection molding (FBIM) method, and a vertical method. The second fibrous layer <NUM> consists of a vertical fiber having a verticality of about <NUM>° to <NUM>° which has excellent elasticity and breathability, thereby facilitating a molding process to be described later. The second fibrous layer <NUM> has an areal density in the range of <NUM> to <NUM>/m<NUM> and preferable in the range of <NUM> to <NUM>/m<NUM>. In addition, unlike a conventional method in which the second fibrous layer has to have a thickness larger than or equal to the maximum thickness of an application component for good adhesion with the first fibrous layer <NUM>, according to the present disclosure, sufficient adhesive strength between the second fibrous layer and the first fibrous layer <NUM> can be obtained even when the second fibrous layer is thin. Since the thickness of the second fibrous layer is reduced, the weight of the sound absorbing member, which is the final product, can be reduced.

Next, the adhesive member <NUM> is provided between the first fibrous layer <NUM> and the second fibrous layer <NUM> and then an aggregate of the first fibrous layer <NUM>, the adhesive member, and the second fibrous layer <NUM> is placed in a molding machine <NUM> (S20).

That is, an object in which the adhesive member <NUM> is provided between the first fibrous layer <NUM> and the second fibrous layer <NUM> is placed in the molding machine <NUM>. In this case, the aggregate may be a stacked structure in which the second fibrous layer <NUM>, the adhesive member <NUM>, and the first fibrous layer <NUM> are stacked in this order from the bottom.

The adhesive member <NUM> is not significantly limited in specific material as long as the material has a melting point of <NUM> or below, but any at least one material selected from polyethylene (PE), polypropylene (PP), ethylene vinyl acetate copolymer (EVA), polyamide (PA), and low-melting polyethylene terephthalate (LM PET) may be used. Preferably, either polyethylene (PE) or polyamide (PA) is used. The adhesive member <NUM> may be applied in various forms such as a film, a liquid adhesive, a fiber, a hot melt, an adhesive fiber, a powder, a coating layer, etc. to facilitate adhesion of the first fibrous layer <NUM> and the second fibrous layer <NUM>. As the film, a breathable film may be used.

In this embodiment, the adhesive member <NUM> may be formed as at least one layer. Preferably polyamide, the adhesive member <NUM> may be a three-layer film in which polyethylene is provided as an intermediate layer and polyamide is provided on and under the polyethylene. In this case, the thickness of the adhesive member <NUM> may be in the range of <NUM> to <NUM>. Preferably, the thickness is <NUM>. When the thickness of the adhesive member <NUM> is smaller than <NUM>, the adhesive strength can be easily lost. On the other hand, when the thickness exceeds <NUM>, the thickness of the final molded body <NUM> becomes excessively thick, which is not preferable in terms of its use.

Next, an upper mold <NUM> and a lower mold <NUM> of the molding machine <NUM> are pressed against each other to bond and mold the first fibrous layer <NUM> and the second fibrous layer <NUM> to each other (S30).

The molding machine <NUM> is composed of the upper mold <NUM> for molding the first fibrous layer <NUM> and the lower mold <NUM> for molding the second fibrous layer <NUM>, and the upper mold <NUM> and the lower mold <NUM> has at least one hole serving as an air intake passage on the surface thereof. The upper mold <NUM> and the lower mold <NUM> of the molding machine <NUM> hot presses the first fibrous layer <NUM> and the second fibrous layer <NUM> in a direction perpendicular to the ground surface for <NUM> to <NUM> seconds, and more preferably for <NUM> seconds to perform bonding and molding simultaneously.

On the other hand, the upper mold <NUM> and the lower mold <NUM> each perform different processes, but the upper mold <NUM> performs a vacuuming process, and the lower mold <NUM> performs a steaming process and a vacuuming process at least two times.

The vacuuming process performed by the upper mold <NUM> is a process of continuously suctioning air for <NUM> to <NUM> seconds and preferably for <NUM> to <NUM> seconds through the hole(s) formed on the surface of the upper mold <NUM>. This vacuuming process may be carried out at a temperature in the range of <NUM> to <NUM>°-C, preferably in the range of 30ºC to 70ºC, and most preferably in the range of 40ºC to 60ºC, so that the temperature of the upper mold <NUM> is not excessively high because the excessively high temperature may cause damage to the surface of the first fibrous layer <NUM>. As described above, since the first fibrous layer <NUM> is molded in the vacuuming process under a low temperature condition, damage to the surface of the first fibrous layer <NUM> is minimized. Therefore, the appearance quality and the sound absorption performance of the product are improved.

The vacuuming process performed by the lower mold <NUM> is a process of continuously suctioning air for <NUM> to <NUM> seconds and preferably for <NUM> to <NUM> seconds through the hole(s) formed on the surface of the lower mold <NUM>. This vacuuming process may be carried out at a temperature in the range of <NUM> to 200ºC and preferably in the range of 130ºC to 170ºC so that damage to the surface of the second fibrous layer <NUM> can be prevented and the adhesive member <NUM> can be melted.

The steaming process performed by the lower mold <NUM> is performed by supplying steam or hot air of 100ºC to 200ºC, preferably 130ºC to 170ºC, and most preferably 140ºC to 160ºC at a pressure of <NUM> to <NUM> bar and preferably <NUM> to <NUM> bar for a period of <NUM> to <NUM> seconds.

In the present embodiment, the lower mold <NUM> may sequentially perform a first steaming process, a first vacuuming process, a second steaming process, and a second vacuuming process.

For example, the first steaming process may be carried out by ejecting steam or hot air of <NUM> to <NUM> at a pressure of <NUM> to <NUM> bar for <NUM> to <NUM> seconds, and the first vacuuming process may be performed for <NUM> to <NUM> seconds. The second steaming process may be performed by ejecting steam or hot air of <NUM> to <NUM> at a pressure of <NUM> to <NUM> bar for <NUM> to <NUM> seconds, and the second vacuuming process may be performed for <NUM> to <NUM> seconds. The first vacuuming process and the second vacuuming process may be performed in a temperature range of <NUM> to <NUM>, and specifically, the temperature of the lower mold <NUM> may be in the range of <NUM> to <NUM>.

In the process of bonding and molding the fiber with the above-described molding machine <NUM>, the first fibrous layer <NUM> placed in the molding machine <NUM> is seated and molded by the vacuuming process performed by the upper mold <NUM>, and the second fibrous layer <NUM> is bonded to the first fibrous layer and molded by the lower mold <NUM> in a manner that the adhesive material <NUM> is melted by the steaming process of the lower mold <NUM> to be bonded the first fibrous layer <NUM> and the second fibrous layer <NUM> is molded by the vacuuming process. In addition, during the vacuuming process, the second fibrous layer <NUM> heated by the steaming process may be cooled.

Finally, after removing moisture remaining on the surface of the molded body <NUM> in the molding machine <NUM>, the surface of the molded body <NUM> is trimmed (S40).

In step S30, a hot air blower <NUM> may blow room temperature air or mildly heated air to remove the moisture remaining on the surface of the molded body <NUM> obtained in step S30, and then the molded body <NUM> is trimmed into a desired shape. The molded body <NUM> may be a sound-absorbing member for use in the interior of a vehicle.

After mixing <NUM>% by weight of polyethylene terephthalate (PET) and <NUM>% by weight of a binder fiber, a needle punching process was performed on the mixture to produce a first fibrous layer having an areal density of <NUM>/m<NUM>.

After mixing <NUM>% by weight of polyethylene terephthalate (PET) and <NUM>% by weight of a binder fiber, an air laid process was performed on the mixture to produce a second fibrous layer having an areal density of <NUM>/m<NUM>.

Polyethylene (PE), polyamide (PI), and polyethylene (PE) were laminated and pressed to prepare an adhesive member in the form of a three-layer film having a thickness of <NUM>.

The first fibrous layer, the second fibrous layer, and the adhesive member prepared in Preparation Examples <NUM> to <NUM> were mounted in a hot forming mold without being preheated. Then, the upper mold was heated to <NUM> and a vacuuming process was performed for <NUM> seconds. At the same time, a steaming process was performed such that the lower mold was heated to <NUM>, and then steam of <NUM> was applied at a pressure of <NUM> bar for <NUM> seconds, and then a vacuuming process was performed for <NUM> seconds. Next, another steaming process was performed such that steam of <NUM> was applied at a pressure of <NUM> bar for <NUM> seconds, and then another vacuuming process was performed. Thus, a sound absorbing member with a double layer structure shown in <FIG> was obtained.

As shown in <FIG>, first, a second fibrous layer was preheated in a hot air oven at <NUM> for about <NUM> seconds and then pressed and molded in a cold forming machine at <NUM> for <NUM> seconds. The molded second fibrous layer was placed in a cold forming mold having a temperature of 25ºC. The first fibrous layer and the adhesive member were preheated for about <NUM> seconds in a hot air oven at <NUM>, and then laminated on the second fibrous layer and pressed for <NUM> seconds to prepare a sound absorbing member having a double layer structure shown in <FIG>.

An experiment was conducted according to ISO <NUM>-<NUM> using a vertical incident sound absorption coefficient tester (Two-microphone Impedance Measurement Tube) to evaluate the sound absorption performance of the sound absorption member of Example <NUM>.

The sound absorption performance was measured from the side of the first fibrous layer of the sound absorption member, and the results are shown in Table <NUM> and <FIG>.

Referring to Table <NUM> and <FIG>, it was confirmed that the sound absorbing member of Example <NUM> was significantly superior to the sound absorbing member of Comparative Example <NUM> at all frequencies. Therefore, it was found that the surface damage of the first fibrous layer attributable to heating affects the sound absorption performance.

Claim 1:
A method of producing an automobile sound absorbing member through molding, the method comprising:
(a) preparing a first fibrous layer and a second fibrous layer;
(b) providing an adhesive member between the first fibrous layer and the second fibrous layer and placing an aggregate of the first fibrous layer, the adhesive member, and the second fibrous layer in a molding machine; and
(c) pressing the aggregate with an upper mold and a lower mold of the molding machine so that the first fibrous layer and the second fibrous layer are bonded and molded at the same time,
wherein in step (a), each of the first fibrous layer and the second fibrous layer comprises <NUM>% to <NUM>% by weight of at least one base fiber selected from polyethylene terephthalate, polypropylene, polyacrylate, nylon and cotton and <NUM>% to <NUM>% by weight of a binder fiber having a melting point of <NUM> or below, the first fibrous layer has an areal density in a range of <NUM> to <NUM>/m<NUM>, the second fibrous layer has an areal density in a range of <NUM> to <NUM>/m<NUM>, and the second fibrous layer consists of a vertical fiber having a verticality of about <NUM>° to <NUM>°,
wherein in step (c), the upper mold and the lower mold perform different processes, respectively, such that the lower mold performs a steaming process and a vacuuming process at least two times, and, in the steaming process, steam or hot air of <NUM> to <NUM> is supplied for <NUM> to <NUM> seconds at a pressure of <NUM> to <NUM> bar.