JP2008207763A - Sound absorption material and its molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sound absorption material made of foamed resin provided with shock absorbing property and high sound absorbing property. <P>SOLUTION: This sound absorption material 1 has openings on front surface and rear surface, and is made of foamed resin. A film body 3 made of the same resin as that making the sound absorption material 1 is formed as one integral with the sound absorption material 1 between the front surface side opening 2a and the rear surface side opening 2b. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sound-absorbing material made of foamed resin and a molding method thereof, and is not particularly limited, but particularly relates to a sound-absorbing material made of foamed resin suitable as a vehicle interior material such as a floor spacer and a molding method thereof.

  As a sound absorbing material that also serves as a buffer material, a sound absorbing material made of a foamed resin having a plurality of through holes is known. The sound-absorbing material of this form has a sound-absorbing function by the sound being irregularly reflected by the peripheral walls of the plurality of through holes, in addition to the buffer function of the foamed resin. A sound-absorbing material made of foamed resin in which a sound-absorbing member is disposed in a through hole is also known. Patent Document 1 discloses a thickness of 5 to 10 mm in an impact absorbing material such as a rigid urethane foam having a through-hole. A sound-absorbing material (vehicle interior material) in which a sound-absorbing member that is a porous material such as flexible urethane foam, nonwoven fabric, felt, or glass wool is embedded is described. In this sound absorbing material, it is described that sound energy is converted into heat energy in a portion of the sound absorbing member that is a porous material, and a sound absorbing action is exhibited. In the production, the sound absorbing member is preformed in advance, set in a mold, and the urethane material is injected into a cavity in which the sound absorbing member is formed by clamping the mold. The whole is integrated by foaming.

JP 2005-132188 A

  A sound absorbing material made of a foamed resin having a plurality of through holes as described above, in which a sound absorbing member is disposed in the through hole, has a sound absorbing performance as well as a buffer function. However, in the production, a pre-formed sound absorbing member is required in addition to the sound absorbing material main body made of foamed resin, and work such as setting the pre-formed sound absorbing member in a mold is also necessary for molding. It becomes. Therefore, it is inevitable that the manufacturing becomes complicated and expensive.

  The present invention has been made in view of the above circumstances, and provides a sound absorbing material that is made of a foamed resin and has a sound absorbing member disposed in an opening, which can be manufactured by a simpler method. Let it be an issue. It is another object of the present invention to provide a manufacturing method therefor.

  The sound absorbing material according to the present invention is a sound absorbing material made of foamed resin having openings on the front surface and the back surface, and a film body made of the same resin as the resin constituting the sound absorbing material is formed between the front surface side opening and the back surface side opening. It is characterized by being formed integrally with the sound absorbing material.

  The entire sound absorbing material is formed of a single resin and does not use a plurality of members, so that the configuration can be greatly simplified. Even in manufacturing, a foaming resin is filled in a required mold and foamed by a conventional method, or a film body remains in a part of the thickness direction on a pre-formed foamed resin plate. Since a required sound absorbing material can be obtained by a method such as perforating a single opening from both sides, the manufacture thereof is very easy.

  In the sound-absorbing material according to the present invention, in addition to the sound-absorbing effect due to the irregular reflection of sound at the peripheral walls of the front-side opening and the back-side opening, the film body functions as a vibration film and effectively absorbs sound pressure energy by the vibration. . Therefore, a high sound absorption effect can be achieved. The thickness of the film body is preferably in the range of 0.1 to 1.5 mm. A film body having a thickness of less than 0.1 mm is not preferable because it is not easy to integrally form the film body and is easily damaged. A film body thicker than 1.5 mm has a reduced function as a vibrating membrane, and high sound absorption performance cannot be obtained. A more preferable film body thickness is in the range of 0.5 to 1.0 mm.

  In the sound absorbing material according to the present invention, the foamed resin may be a foamed resin such as a styrene-modified polyethylene resin, a styrene-modified polypropylene resin, a polystyrene resin, a polyethylene resin, or a polypropylene resin. Above all, the styrene-modified polyethylene resin foam resin obtained by impregnating and polymerizing polyethylene resin particles with styrene monomer is more dimensionally stable and retains its shape than foam resin of polyethylene resin and polypropylene resin. It is particularly preferable because of its excellent properties and the difficulty of producing powder due to rubbing compared to a polystyrene resin foamed resin. The proportion of the styrene component in the styrene-modified polyethylene resin is 40 to 90% by weight, preferably 50 to 85% by weight, more preferably 55 to 75% by weight.

  The sound absorbing material according to the present invention can be used at any place. It can also be used as a part of a wall material or a floor material, and can also be used as an interior material for a vehicle. Among them, it is particularly suitable to use as an interior material for a vehicle because of the moderate buffer function of the foamed resin and the sound absorption characteristics shown in later examples.

  The present invention is also a method for molding the above-described sound absorbing material, comprising a movable mold and a fixed mold as the mold, and the cavity formed by the fixed mold and the movable mold includes the opening on the front surface side and the back surface. The first convex portion and the second convex portion for forming the side opening are provided at corresponding locations, respectively, and the first convex portion and the second convex portion are in a posture in which the fixed mold and the movable mold are clamped. A mold in which a gap is formed between the two convex portions, and the mold is filled with pre-foamed resin particles impregnated with a foaming agent and pre-foamed, and subjected to in-mold foam molding. Also disclosed is a method for forming a sound absorbing material, in which a film body continuous with another portion is integrally formed in the gap between the first and second protrusions. In the above molding method, preferably, as the molding die, in a posture in which a fixed die and a movable die are clamped, a range of 0.1 to 1.5 mm is provided between the first convex portion and the second convex portion. A mold that forms a gap is used.

  The pre-foamed resin particles impregnated with a foaming agent used for molding are pre-foamed, for example, a thermoplastic resin such as the above-mentioned styrene-modified polyethylene resin is impregnated with the foaming agent to produce a foamable thermoplastic resin. Pre-foamed resin particles obtained by pre-foaming the foamable thermoplastic resin with heated steam or the like are used. Such pre-expanded resin particles are filled into the above-described mold, heated steam is supplied and foam-molded according to a conventional method. Preferably, the cracking treatment is performed after filling the pre-foamed resin particles. The filled pre-expanded resin particles enter the gap between the first convex portion and the second convex portion, and are foamed together with other pre-expanded resin particles in the cavity in the process of foam molding and fused together. . Thus, a film body continuous with the other part of the sound absorbing material is integrally formed in the gap.

  ADVANTAGE OF THE INVENTION According to this invention, the sound-absorbing material made from a foaming resin provided with the buffer property and high sound absorption property can be obtained easily.

  Hereinafter, the present invention will be described based on an embodiment with reference to the drawings. FIG. 1 is a perspective view showing an example of a sound-absorbing material 1 according to the present invention, and FIG. 2 is an enlarged cross-sectional view showing a part thereof. FIG. 3 is a view for explaining a method of forming a sound absorbing material according to the present invention.

  A sound absorbing material 1 shown in FIG. 1 is a foamed resin molded product having a thickness of about 10 to 70 mm obtained by, for example, in-mold foam molding of pre-expanded resin particles of styrene-modified polyethylene resin, and has a diameter of about 5 to 30 mm. Are formed at positions where the front surface side opening 2a and the back surface side opening 2b face each other. As shown in FIG. 2, a film body 3 made of the same resin as the resin of the sound absorbing material body is integrally formed between the front surface side opening 2a and the back surface side opening 2b, and the thickness of the film body 3 is Is about 0.1 to 1.5 mm. As shown in the figure, the film body 3 may be integrally formed between the front surface side opening 2a and the back surface side opening 2b facing each other at substantially the center in the thickness direction of the sound absorbing material 1, and may be either in the upper or lower direction. And may be integrally molded.

  Since the sound absorbing material 1 is entirely made of foamed resin, the sound absorbing material 1 has a buffer function and also has a sound absorbing function by sound irregular reflection at the peripheral walls of the front surface side opening 2a and the back surface side opening 2b. Further, since the film body 3 functions as a vibration film and the sound pressure energy is effectively absorbed by the vibration, the sound absorbing function of the sound absorbing material 1 is further improved. Moreover, since the whole is formed from one resin and a plurality of members are not used, the configuration is greatly simplified.

  Next, an embodiment for forming the above-described sound absorbing material 1 will be described by taking as an example an embodiment in which pre-foamed resin particles impregnated with a foaming agent and pre-foamed are filled into a mold and subjected to in-mold foam molding. . FIG. 3 shows an embodiment of the mold in a clamped state. The mold 10 is generally composed of a box-shaped fixed mold 11 that opens upward and a box-shaped movable mold 12 that opens downward. A cavity space is formed.

  As shown in the drawing, convex portions 13 and 14 are provided as corresponding first and second convex portions at corresponding positions of both the fixed mold 11 and the movable mold 12. When the mold is clamped, the convex portions 13 and 14 are provided. A predetermined gap G is formed between the two. Preferably, the gap G is in the range of 0.1 to 1.5 mm. In the illustrated mold 10, only two sets of convex portions 13 and 14 are shown. However, in an actual mold, the number of the front surface side opening 2a and the back surface side opening 2b formed in the sound absorbing material 1 is shown. Only convex portions 13 and 14 are provided.

  When the sound absorbing material 1 is molded, for example, a pre-foamed particle R is produced by pre-foaming a styrene-modified polyethylene resin at a foaming ratio of 30 times with heated steam or the like, and the pre-foamed particle R is placed in the mold 10. After filling, if necessary, after performing a cracking process, the mold is clamped as shown in FIG. By pre-clamping, the pre-expanded particles R also enter the gap G formed between the convex portions 13 and 14.

  After clamping, the mold 10 is heated for several seconds, one surface of the molded body is steam-heated for about 5 seconds, the other surface is steam-heated for about 5 seconds, and both surfaces are further heated for about 10 seconds. Thereby, the filled pre-expanded particles R are thermally fused together with the foam, and the sound absorbing material 1 is formed in the cavity. In the process, the pre-expanded particles R that have entered the gap G between the convex portions 13 and 14 are simultaneously expanded and thermally fused, and the film body 3 integrated with the other parts of the sound absorbing material 1 is integrated simultaneously. Molded. Finally, it is allowed to cool for about 150 seconds, and is released from the mold while opening the mold, whereby the sound-absorbing material 1 made of foamed resin having openings on the front and back surfaces shown in FIGS. A sound absorbing material 1 is obtained in which a film body 3 made of the same resin as that constituting the sound absorbing material 1 is formed between the sound absorbing material 1 and the back surface side opening 2b. In addition, the time etc. which each process requires are suitably adjusted so that it may become a desired sound-absorbing material.

  Next, although this invention is demonstrated based on an Example and a comparative example, naturally this invention is not restricted to this Example.

[Example 1]
Using the mold having the shape described with reference to FIG. 3, pre-expanded resin particles of styrene-modified polyethylene resin impregnated with a foaming agent and pre-expanded 30 times are filled into the mold and subjected to in-mold foam molding. Thus, the sound absorbing material 1 having the form shown in FIGS. 1 and 2 was obtained. However, the expansion ratio of the sound absorbing material 1 was 30 times, the thickness of the sound absorbing material 1 was 30 mm, and the diameters of the front surface side opening 2a and the back surface side opening 2b were 20 mm. The film body 3 was integrally formed at the central position in the thickness direction of the sound absorbing material 1, and the thickness of the film body 3 was set to 0.5 mm.

  The sound absorption coefficient of the molded sound absorbing material was measured according to ISO10534-2 and ASTME1050. That is, using a normal incident sound absorption coefficient measurement system 4206 type acoustic impedance tube (manufactured by Prüel & Care) and measurement software MS1020 type (manufactured by Matsushita Techno Trading Co., Ltd.), measurement conditions are a temperature of 20 ° C. and a sample thickness of 30 mm. Measured without the back air layer of the sample.

  The results are shown as curve A in the graph of FIG.

[Example 2]
A sound absorbing material was molded in the same manner as in Example 1 except that the thickness of the film body 3 was changed to 1 mm, and the sound absorption rate was measured in the same manner as in Example 1. The results are shown as curve B in the graph of FIG.

[Comparative Example 1]
By changing the lengths of the convex portions 13 and 14 in the mold having the shape described based on FIG. 3, a mold was prepared in which the gap G was not formed when the mold was clamped. Using this, a sound absorbing material was foam-molded under the same conditions as in Example 1. In the molded sound absorbing material, the front surface side opening 2a and the back surface side opening 2b are continuous, and the film body 3 is not provided therebetween. The sound absorption coefficient of the obtained sound absorbing material was measured in the same manner as in Example 1. The result is shown as curve C in the graph of FIG.

[Comparative Example 2]
A molding die without the convex portions 13 and 14 in the molding die having the shape described based on FIG. 3 was prepared. Using this, a sound absorbing material was foam-molded under the same conditions as in Example 1. The molded sound absorbing material does not include the front surface side opening 2 a, the back surface side opening 2 b, and the film body 3. The sound absorption coefficient of the obtained sound absorbing material was measured in the same manner as in Example 1. The result is shown as curve D in the graph of FIG.

[Discussion]
The sound absorbing material without the front surface side opening 2a, the back surface side opening 2b, and the film body 3 has a sound absorption coefficient (perpendicular incident sound absorption coefficient%) as low as about 10% in all frequency bands as shown by the curve D. . As shown in curve C, the sound absorbing material in which the front surface side opening 2a and the back surface side opening 2b are continuous and not including the film body 3 is compared with the sound absorbing material without the front surface side opening 2a and the back surface side opening 2b. It shows a high sound absorption rate. The sound absorbing material according to the present invention, that is, the sound absorbing material including the film body 3 made of the same resin as the resin constituting the sound absorbing material between the front surface side opening 2a and the back surface side opening 2b, as shown by curves A and B, The sound absorption coefficient is higher than that in which the front surface side opening 2a and the back surface side opening 2b are continuous through holes. In particular, the sound absorption coefficient in the frequency band of 1000 to 3000 Hz is improved, which shows the superiority of the sound absorbing material according to the present invention and the superiority of using it as an interior material for vehicles.

The perspective view which shows an example of the sound-absorbing material by this invention. Sectional drawing which expands and shows a part of sound-absorbing material. The figure for demonstrating the shaping | molding method of the sound-absorbing material by this invention. The graph which shows the sound absorption rate in an Example and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Sound absorption material, 2a ... Front surface side opening, 2b ... Back surface side opening, 3 ... Film body, 10 ... Molding die, 11 ... Fixed type | mold, 12 ... Movable type | mold, 13, 14 ... 1st and 2nd convex part, G: Gap formed between convex portions, R: Pre-expanded particles

Claims (5)

  A sound-absorbing material made of foamed resin having openings on the front and back surfaces, and a film body made of the same resin as the resin constituting the sound-absorbing material is integrated with the sound-absorbing material between the front-side opening and the back-side opening. A sound-absorbing material characterized by being formed.   The sound absorbing material according to claim 1, wherein the thickness of the film body is in a range of 0.1 to 1.5 mm.   The sound absorbing material according to claim 1 or 2, wherein the sound absorbing material is an interior material for a vehicle. A sound absorbing material made of foamed resin having openings on the front and back surfaces, and a film body made of the same resin as the resin constituting the sound absorbing material is formed integrally with the sound absorbing material between the front surface side opening and the back surface side opening. A method of forming a sound absorbing material,
The mold includes a movable mold and a fixed mold, and a cavity formed by the fixed mold and the movable mold has a first convex portion and a second convex portion for molding the front surface side opening and the rear surface side opening. Are provided at corresponding locations, and in a posture in which the fixed mold and the movable mold are clamped, a molding die in which a gap is formed between the first convex portion and the second convex portion is used. The mold is filled with pre-foamed resin particles impregnated with a foaming agent and pre-foamed, and is subjected to in-mold foam molding. In the process, a gap is formed between the first convex portion and the second convex portion. A method for forming a sound-absorbing material, wherein a continuous film body is integrally formed with another portion.   As the molding die, a molding die in which a gap of 0.1 to 1.5 mm is formed between the first convex portion and the second convex portion in a posture in which the fixed die and the movable die are clamped is used. The method for molding a sound-absorbing material according to claim 4.

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