JP4227074B2 - Sound absorbing material - Google Patents

Description

  The present invention relates to a sound-absorbing material that is used to reduce noise generated, for example, in construction machines, automobile engine rooms, door trims, and the like.

Conventionally, as this type of sound-absorbing material, a sound-absorbing member in which the back surface of a coated porous sound-absorbing material is attached to a substrate is known (for example, see Patent Document 1). As this porous sound-absorbing material, general sound-absorbing materials such as urethane foam, polyethylene foam, and melamine foam are used. Furthermore, a sound-absorbing material is known in which a polyester film or polyethylene film is overlaid on a flame-retardant flexible urethane foam and a release paper is laminated thereon (see, for example, Patent Document 2). As the flame retardant flexible urethane foam, a general flame retardant flexible urethane foam is used.
JP-A-10-8591 (pages 2-4) Japanese Patent No. 33888681 (first page and third page)

  However, the general urethane foam used in Patent Documents 1 and 2 has a large number of cells forming the foam, in other words, individual cells are small. For this reason, the film and the film joined to the urethane foam are not easily vibrated by sound, and there is a problem that the sound absorption effect is low due to insufficient absorption of sound due to vibration of the film or film.

  The present invention has been made paying attention to such problems existing in the prior art. An object of the invention is to provide a sound absorbing material capable of increasing the membrane vibration and exhibiting an excellent sound absorbing effect.

In order to achieve the above-mentioned object, the sound absorbing material of the invention described in claim 1 is a base material made of an open cell foam having 5 to 40 cells / 25 mm width based on JIS K6400. The open-cell foam is made of a soft polyurethane foam, and the cell membrane is removed and the air permeability is 150 to 450 ml / cm ² · sec .

According to a second aspect of the present invention, there is provided the sound absorbing material according to the first aspect, wherein the resin film is a thermoplastic polyurethane film.
The sound-absorbing material according to claim 3 is characterized in that, in the invention according to claim 1 or 2 , an adhesive layer is provided between the substrate and the resin film. .

According to a fourth aspect of the present invention, there is provided the sound absorbing material according to the third aspect , wherein the adhesive layer is formed of a polyurethane-based adhesive.
According to a fifth aspect of the present invention, there is provided the sound absorbing material according to the third aspect, wherein the adhesive layer is formed of a hot melt film.
The sound-absorbing material of the invention according to claim 6 is configured such that the sound-absorbing peak is located in a middle / low frequency range of 200 to 2000 Hz in the invention according to any one of claims 1 to 5 . It is characterized by this.

According to the present invention, the following effects can be exhibited.
In the sound-absorbing material according to any one of claims 1 to 6 , the base material constituting the sound- absorbing material is made of an open-cell foam, and the number of cells based on JISK6400 is 5-40 / 25 mm wide. For this reason, sound is more easily absorbed in the open cell than in the closed cell. Moreover, since the number of cells is small, that is, the cell diameter of each cell is large, the resin film bonded to the base material is resonated to increase the membrane vibration, and the membrane vibration can exhibit an excellent sound absorbing effect. it can.

In addition, since the open-cell foam is a soft polyurethane foam, its elasticity allows good propagation of vibrations, and the viscous friction of air at the bubble part is large, and part of the sound energy is thermal energy. The sound absorption effect can be improved.

Moreover, since the cell membrane of the open-cell foam is removed, the ratio of the opening is increased for each cell. For this reason, even if water permeates into the cell, it is easily discharged and the sound absorbing effect can be further improved.

Further, air permeability of the flexible polyurethane foam is set to a large value of 150~450ml ^/ cm 2 · sec. For this reason, while being able to improve a sound absorption effect, drainage can be improved.

Since the sound-absorbing material of the invention according to claim 3 is provided with an adhesive layer between the base material and the resin film, the vibration of the base material due to sound is sufficiently transmitted to the resin film, and the film of the resin film The sound absorption effect based on vibration is enhanced.

The sound-absorbing material of the invention according to claim 4 can improve the effect of the invention according to claim 3 because the adhesive layer is formed of a polyurethane-based adhesive having excellent adhesive strength.

The sound-absorbing material of the invention according to claim 6 is configured so that the sound-absorbing peak is located in the middle / low frequency range of 200 to 2000 Hz. Therefore, a good sound absorbing effect can be exhibited particularly in the middle / low frequency range.

Hereinafter, embodiments of the present invention will be described in detail.
The sound absorbing material of the present embodiment is configured by bonding a resin film to a base material made of an open cell foam. As the open cell foam, soft polyurethane foam, polyethylene foam, melamine foam and the like are used. Among these, the flexible polyurethane foam is most preferable because it is excellent in vibration propagation performance based on elasticity and sound absorption performance in the bubble portion.

  Therefore, the flexible polyurethane foam will be described. The soft polyurethane foam corresponds to a soft product among polyurethane foams divided into a soft product, a hard product, and a semi-hard product, and has a hardness of 50 to 250 N based on JIS K6400. When the hardness is less than 50N, the polyurethane foam becomes too soft, and when the hardness exceeds 250N, the polyurethane foam becomes too hard and the cushioning property is impaired.

  The raw material of the flexible polyurethane foam is composed of polyols, polyisocyanate compounds, catalysts, foaming agents, foam stabilizers and the like. The polyols are polyether polyols or polyester polyols, and these polyols can be used alone or in combination.

  Polyester polyols include condensed polyester polyols obtained by reacting polycarboxylic acids such as adipic acid and phthalic acid with polyols such as ethylene glycol, diethylene glycol, propylene glycol and glycerin, as well as lactone polyester polyols and polycarbonate polyols. Is mentioned. Examples of the polyether polyol include polypropylene glycol, polytetramethylene glycol, and modified products thereof. These polyols can change the number of functional groups and the hydroxyl value of the hydroxyl group by adjusting the type, molecular weight, condensation degree, and the like of the raw material components.

  The polyisocyanate compound to be reacted with polyols is a compound having a plurality of isocyanate groups, specifically, tolylene diisocyanate (TDI), 4,4-diphenylmethane diisocyanate (MDI), 1,5-naphthalene diisocyanate (NDI), Triphenylmethane triisocyanate, xylylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), dicyclohexylmethane diisocyanate, isophorone diisocyanate (IPDI) and the like are used.

  Here, it is preferable that the isocyanate index of a polyisocyanate compound is 80-130. The isocyanate index represents the equivalent ratio of the isocyanate group of the polyisocyanate compound to the hydroxyl group of the polyol and the foaming agent (water) as a percentage. Therefore, when the value is less than 100, it means that the hydroxyl group is in excess of the isocyanate group, and when it exceeds 100, it means that the isocyanate group is in excess of the hydroxyl group. When the isocyanate index is less than 80, polyols cannot sufficiently react with the polyisocyanate compound, resulting in large flexibility and reduced shape retention. On the other hand, when the isocyanate index exceeds 130, the soft polyurethane foam becomes hard and its physical properties are deteriorated.

  The catalyst is for accelerating the urethanization reaction between polyols and polyisocyanate compounds. As such a catalyst, amines such as N, N, N-trimethylaminoethylpiperazine, triethylenediamine and dimethylethanolamine, organometallic compounds such as tin octylate, acetates, alkali metal alcoholates and the like are used. Among these, in order to obtain a flexible polyurethane foam, it is desirable to use amines or this and a metal-containing catalyst in combination.

  The foaming agent is for foaming polyurethane into a flexible polyurethane foam. As the foaming agent, pentane, cyclopentane, hexane, cyclohexane, dichloromethane, carbon dioxide, etc. are used in addition to water. As a raw material of the flexible polyurethane foam, a foam stabilizer such as a surfactant, a flame retardant such as a condensed phosphate ester, an antioxidant, a plasticizer, an ultraviolet absorber, a colorant, and the like can be added.

  When the urethanization reaction between the polyols and the polyisocyanate compound is performed, a one-shot method or a prepolymer method is employed. The one-shot method is a method in which a polyol and a polyisocyanate compound are directly reacted. The prepolymer method is a method in which a part of a polyol and a polyisocyanate compound are reacted in advance to obtain a prepolymer having an isocyanate group or a hydroxyl group at a terminal, and the polyol or the polyisocyanate compound is reacted therewith. The one-shot method is a preferable method because the manufacturing process is one step compared to the prepolymer method, and there are few restrictions on the manufacturing conditions, and the manufacturing cost can be reduced.

  The soft polyurethane foam obtained in this way must have an open-cell structure in order to exhibit sound absorbing performance for sucking sound into the cell. In the case of the closed cell type structure, sound is hardly absorbed in the cells of the flexible polyurethane foam. In order to obtain an open-cell structure, it is preferable to set the time for the raw material to exist in the form of cream in the natural foaming stage for 10 to 40 seconds, and then the time for the cell to form 1 to 6 minutes.

  In addition, the flexible polyurethane foam causes the membrane vibration of the resin film to exert a sound absorbing effect, so that the number of cells based on JIS K6400 is formed to 5 to 40 cells / 25 mm width, and 5 to 30 cells / 25 mm width. It is preferable. When the number of cells is less than 5/25 mm width, the sound absorption effect is improved, but it becomes impossible to produce a large flexible polyurethane foam having such a small number of cells. On the other hand, when the number of cells exceeds 40 cells / 25 mm width, each cell becomes too small to improve the sound absorbing effect based on the membrane vibration. Furthermore, the sound absorption peak tends to shift to the high frequency side. Since the cell diameter corresponds to 0.6 to 5.0 mm from the number of cells, the cell diameter can be set within this range instead of the number of cells.

  It is desirable that the cell membrane of the flexible polyurethane foam is removed by a film removal treatment means so that the water can be easily discharged even if water permeates into the cell and the sound absorbing effect is improved. As the film removal processing means, the following method is used. In the first method, a polyester polyol and a polyether polyol are used in combination as a polyol, and a surfactant is further added to manipulate the raw material blend to obtain a foam with less film. The second method is a method of impregnating the foam with water using a penetrant and destroying the cell membrane by volume expansion of water by heating at 100 ° C. or higher. The third method is a method in which combustible materials such as natural gas and hydrogen gas and oxygen are mixed, ignited and exploded within the explosion limit, and the cell membrane is destroyed by the impact.

The air permeability of the flexible polyurethane foam is preferably set to a large value of 150 to 450 ml / cm ² · sec in order to improve the sound absorption effect and improve the drainage. This air permeability is a value measured according to JIS L1069. When the air permeability is less than 150 ml / cm ² · sec, the water drainage property when water penetrates into the foam cell is inferior and the sound absorbing effect is also lowered. On the other hand, when the air permeability exceeds 450 ml / cm ² · sec, it is necessary to make the cell excessively large, and it becomes difficult to produce such a flexible polyurethane foam.

  As such an open-cell foam, either a method of producing a slab foam and cutting it into a constant thickness, or a method of foaming and reacting to a constant thickness is adopted. For example, in the case of a flexible polyurethane foam, the raw material of the flexible polyurethane foam is discharged onto a belt conveyor, and while the belt conveyor moves, the raw material naturally foams at normal temperature and atmospheric pressure, and then reacts in a drying furnace ( A slab foam is obtained by curing and curing. The obtained slab foam is cut out to a certain thickness. Although the thickness of a base material is suitably set according to a use application, it is about 5-50 mm normally. When this thickness is less than 5 mm, the sound absorption effect based on the open-cell foam tends to decrease. On the other hand, when the thickness exceeds 50 mm, the sound absorption effect due to the membrane vibration of the resin film tends to decrease.

  Next, the resin film is bonded to one side or both sides of the open cell foam. As a material of the resin film, for example, polyurethane, polyester, acrylic resin, ethylene-vinyl acetate copolymer resin (EVA) or the like is used. Among these, polyurethane is preferable from the viewpoint of adhesiveness to a soft polyurethane foam as a base material.

  A sound-absorbing material is formed by joining the base material made of the open-cell foam described above and the resin film with an adhesive layer. By strongly bonding the base material and the resin film by the adhesive layer, the vibration of the base material based on sound is sufficiently transmitted to the resin film, and the sound absorption effect based on the membrane vibration of the resin film is enhanced. As the adhesive for forming the adhesive layer, polyurethane adhesive, silicone adhesive, epoxy resin adhesive, etc. are used. A polyurethane-based adhesive that can be increased and has no processing unevenness is preferable. As a bonding method between the base material and the resin film, a hot melt bonding method using a hot melt film, a flame lamination method (flame welding method) without using an adhesive, or the like can also be employed.

  The thickness of the resin film is preferably about 10 to 50 μm, more preferably 20 to 30 μm. When this thickness is less than 10 μm, the strength of the resin film is lowered and its manufacture becomes difficult. On the other hand, when the thickness exceeds 50 μm, the resin film cannot be vibrated sufficiently and the sound absorption effect due to the membrane vibration is lowered.

  When a sound absorbing material is manufactured using, for example, a soft polyurethane foam as an open-cell foam as a base material, the raw material of the soft polyurethane foam is discharged onto a belt conveyor. And while this belt conveyor moves, a raw material naturally foams at normal temperature and atmospheric pressure, and a slab foam is obtained by making polyols and a polyisocyanate compound then react in a drying furnace. The obtained slab foam is cut to a certain thickness to obtain a substrate. A polyurethane film as a resin film is bonded to one side of the substrate using a polyurethane adhesive as an adhesive. In this way, the sound absorbing material is manufactured.

  The obtained sound absorbing material is thin and has a flexible polyurethane film adhered to one side of the flexible polyurethane foam. Therefore, the vibration of the sound with respect to the flexible polyurethane foam becomes the membrane vibration of the polyurethane film due to the resonance action. Thermal energy is dissipated by vibration and sound is attenuated. Furthermore, the cells of the soft polyurethane foam are subjected to film removal treatment, so that the ratio of the openings in each cell is increased, and even if water permeates into the cells, it is quickly discharged.

The effects exhibited by the above embodiment will be described collectively below.
-The base material which comprises the sound-absorbing material of this embodiment consists of open-cell foams, and the cell number based on JISK6400 is formed in 5-40 pieces / 25mm width. For this reason, sound is more easily absorbed in the open cell than in the closed cell. In addition, since the number of cells is small, that is, the cell diameter of each cell is large, the membrane vibration of the resin film bonded to the base material is caused, and the sound absorption effect is exhibited by the membrane vibration.

  ・ The open cell foam is made of soft polyurethane foam, so that the vibration is transmitted well based on its elasticity, and the viscous friction of air in the bubble part is large, and part of sound energy. Can be converted into thermal energy to improve the sound absorption effect.

  ・ In addition, the cell material of the soft polyurethane foam is removed, and the ratio of the opening is increased for each cell, so that the sound absorbing material is easily discharged even if water penetrates into the cell. The sound absorption effect can be improved. Therefore, even when the sound absorbing material is wet due to rain or the like, the drainage is good and water does not accumulate inside the sound absorbing material, so that deterioration of the sound absorbing material is suppressed and the sound absorbing material is attached. The problem of rust and corrosion can be suppressed. Furthermore, it is possible to suppress the generation of a bad odor due to the propagation of spiders and bacteria by the water remaining in the sound absorbing material.

In the sound absorbing material, the air permeability of the flexible polyurethane foam is set to a large value of 150 to 450 ml / cm ² · sec. For this reason, while being able to improve a sound absorption effect, drainage can be made favorable.

  In addition, since the sound absorbing material has an adhesive layer between the base material and the resin film, the vibration of the base material is sufficiently transmitted to the resin film, and the sound absorbing effect based on the film vibration of the resin film is enhanced. It is done. In particular, when the adhesive layer is formed of a polyurethane-based adhesive having excellent adhesive strength, the adhesive strength is increased, and the sound absorbing effect can be improved.

  In addition, the sound absorbing material is configured such that the sound absorption peak is located in the middle / low frequency range of 200 to 2000 Hz by setting the relationship between the cell diameter of the open cell foam and the thickness of the resin film. Therefore, a good sound absorption effect can be exhibited particularly in the middle / low frequency range.

  As described above, since the sound absorbing material of this embodiment is excellent in sound absorbing performance and drainage performance, it is suitably used for applications to which water adheres, such as construction machines, automobile engine rooms, and door trims.

Hereinafter, the embodiment will be described more specifically with reference to examples and comparative examples.
(Examples 1-4)
A sound absorbing material was prepared by adhering the following resin film with an adhesive to one side of a soft polyurethane foam shown below as a base material. The base material thickness was all 30 mm. About the obtained sound-absorbing material, the normal incidence sound absorption coefficient (%) and the peak value (Hz) of the sound absorption frequency were measured by the following methods, and the results are shown in Table 1.

  Soft polyurethane foam: The following four product numbers manufactured by Inoac Corporation were used. The cell number and density are values measured according to JIS K6400. Further, the air permeability is a value measured in accordance with JIS L1096 (when the thickness is 10 mm).

MF-7 (7 cells / 25 mm, air permeability 450 ml / cm ² · sec, density 30 kg / m ³ )
CFH-13 (13 cells / 25 mm, air permeability 400 ml / cm ² · sec, density 30 kg / m ³ )
CFH-30 (30 cells / 25 mm, air permeability 350 ml / cm ² · sec, density 30 kg / m ³ )
CFH-50 (50 cells / 25 mm, air permeability 200 ml / cm ² · sec, density 30 kg / m ³ )
Resin film: The following two types of thermoplastic polyurethane (TPU) films were used.

Okura Industry Co., Ltd. Silklon ES85, thickness 30μm
PU20-NF20-102 manufactured by Maruyama Kogyo Co., Ltd., thickness 20 μm
Adhesive: A urethane prepolymer (manufactured by Aika Industry Co., Ltd., W651-C80) was used.

Normal incident sound absorption coefficient (%): Measured according to JIS A1405.
Peak value of sound absorption frequency (Hz): The relationship between the sound absorption frequency and the sound absorption rate is shown in a graph, and the peak value is read from the graph.

表１に示したように、実施例１〜４では垂直入射吸音率が７０％以上で吸音率が高く、吸音周波数のピーク値が２５０〜１６００Ｈｚという中・低周波数域であることが示された。
（比較例１〜４）
比較例１においては、セル数が３個／２５ｍｍという非常に少ないセル数の軟質ポリウレタン発泡体を製造しようとしたが、軟質ポリウレタン発泡体のセル数が少なくなり過ぎてフォームの成形ができず、樹脂フィルムを接合することも、吸音率を測定することもできなかった。比較例２では、セル数が１３個／２５ｍｍの軟質ポリウレタン発泡体を用い、樹脂フィルムを接合することなく使用した。比較例３においては、セル数が５０個／２５ｍｍという非常に多いセル数の軟質ポリウレタン発泡体を用い、それに樹脂フィルムを接合して積層体を調製した。比較例４では、セル数が３０個／２５ｍｍの軟質ポリウレタン発泡体を用い、それに樹脂フィルムを接合することなく使用した。基材の厚みは、全て３０ｍｍとした。これらの吸音材について、実施例１〜４と同様にして垂直入射吸音率（％）及び吸音周波数のピーク値（Ｈｚ）を測定し、その結果を表２に示した。

As shown in Table 1, in Examples 1 to 4, the normal incident sound absorption coefficient is 70% or higher, the sound absorption coefficient is high, and the peak value of the sound absorption frequency is in the middle / low frequency range of 250 to 1600 Hz. .
(Comparative Examples 1-4)
In Comparative Example 1, an attempt was made to produce a flexible polyurethane foam having a very small number of cells of 3 cells / 25 mm, but the number of cells of the flexible polyurethane foam was too small to form a foam. Neither the resin film was bonded nor the sound absorption coefficient could be measured. In Comparative Example 2, a soft polyurethane foam having 13 cells / 25 mm was used, and the resin film was used without bonding. In Comparative Example 3, a soft polyurethane foam having a very large cell number of 50 cells / 25 mm was used, and a resin film was bonded thereto to prepare a laminate. In Comparative Example 4, a flexible polyurethane foam having 30 cells / 25 mm was used without using a resin film bonded thereto. The base material thickness was all 30 mm. For these sound absorbing materials, the normal incident sound absorption rate (%) and the peak value (Hz) of the sound absorption frequency were measured in the same manner as in Examples 1 to 4, and the results are shown in Table 2.

表２に示すように、比較例２では樹脂フィルムを接合しなかったので、垂直入射吸音率が４５％と低く、吸音周波数のピーク値が４０００Ｈｚという高周波数域であった。比較例３ではセル数が５０個／２５ｍｍという非常に多いセル数の軟質ポリウレタン発泡体を用いたため、垂直入射吸音率が３８％と低く、吸音周波数のピーク値が３１５０Ｈｚという高周波数域であった。比較例４では樹脂フィルムを接合しなかったので、垂直入射吸音率が５５％と低く、吸音周波数のピーク値が３１５０Ｈｚという高周波数域であった。

As shown in Table 2, since the resin film was not bonded in Comparative Example 2, the normal incident sound absorption coefficient was as low as 45%, and the peak value of the sound absorption frequency was a high frequency range of 4000 Hz. In Comparative Example 3, a soft polyurethane foam having a very large cell number of 50 cells / 25 mm was used, so that the normal incident sound absorption coefficient was as low as 38% and the peak value of the sound absorption frequency was a high frequency range of 3150 Hz. . In Comparative Example 4, since the resin film was not bonded, the normal incident sound absorption coefficient was as low as 55%, and the peak value of the sound absorption frequency was a high frequency range of 3150 Hz.

In addition, the said embodiment can also be changed and actualized as follows.
-The communication rate of the open cell foam can be set to 80% or more. Also in this case, it is possible to improve sound absorption and water drainage.

-An adhesive layer between the substrate and the resin film can be formed of a hot melt film, and the hot melt film can have a function of membrane vibration.
-A flexible polyurethane foam can be obtained by a molding method, an on-site spray molding method, or the like.

The sound absorbing material of the embodiment can be used for noise prevention of a hard disk drive of a computer such as a personal computer.
Further, the technical idea that can be grasped from the embodiment will be described below.

- the resin film is film Der Ru intake sound material of polyurethane. According to this sound absorbing material, the adhesiveness of the resin film to the soft polyurethane foam can be improved.

Claims (6)

A base material made of an open-cell foam having 5 to 40 cells / 25 mm width based on JIS K6400 is composed of a resin film bonded ,
The open cell foam is made of a soft polyurethane foam, the cell membrane is removed, and the air permeability is 150 to 450 ml / cm ² · sec . The sound absorbing material according to claim 1, wherein the resin film is a thermoplastic polyurethane film . The sound absorbing material according to claim 1, wherein an adhesive layer is provided between the base material and the resin film . The sound absorbing material according to claim 3 , wherein the adhesive layer is formed of a polyurethane-based adhesive . The sound absorbing material according to claim 3 , wherein the adhesive layer is formed of a hot melt film . The sound absorbing material according to any one of claims 1 to 5, wherein the sound absorbing peak is configured to be located in a middle / low frequency range of 200 to 2000 Hz .