JP2008032977A - Sound absorbing material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive sound absorbing material by recycling a waste material, exhibiting excellent sound absorption effect in a low frequency region, which is required in a construction machine and a vehicle or the like. <P>SOLUTION: An absorbing material 30 is constituted by laminating resin films 33 on both faces of a base substance 31 in which small pieces of flexible polyurethane foam with cell membrane removed are connected with a binder, and sound absorption is improved by membrane oscillation of the resin film 33, and it is prevented that the small pieces of the flexible polyurethane foam with cell membrane removed, are fallen off like powder from the base substance 31. It is desirable that the small piece of the flexible polyurethane foam with cell membrane removed has a size of 20 to 50 mm. Moreover, it is desirable that the small piece of the flexible polyurethane foam with cell membrane removed, is composed of a pulverized waste material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sound-absorbing material, and particularly to a sound-absorbing material having good sound-absorbing properties in a low frequency region.

  Conventionally, sound absorbing materials have been used in vehicles, construction machines, and the like for noise prevention. Further, in vehicles and construction machines, noise prevention in a low frequency region is required.

  As a sound absorbing material, a material in which a resin film is laminated on a base made of a flexible polyurethane foam is known (Patent Documents 1 and 2). However, even a sound-absorbing material in which a resin film is laminated on a base made of a soft polyurethane foam cannot be said to have a sufficient sound-absorbing property in a low-frequency region, and further improvement in sound-absorbing property is required. In addition, a sound-absorbing material has been proposed in which a resin film is bonded to a base made of a soft polyurethane foam from which a cell film has been removed to improve sound absorption (Patent Document 3).

  However, since the conventional sound absorbing material uses a new soft polyurethane foam manufactured exclusively for the sound absorbing material, there is a problem that costs increase. Furthermore, when using a soft polyurethane foam from which the cell membrane has been removed, a treatment for removing the cell membrane is required, which further increases the cost.

  The production of soft polyurethane foam from which the cell membrane has been removed involves the continuous production of slab blocks of soft polyurethane foam by discharging the soft polyurethane foam raw material onto the belt conveyor and reacting and foaming on the belt conveyor. Then, the cell film is removed and further cut out to a predetermined size. However, a lot of waste material is generated when cutting out from the slab block, and its reuse is required. In addition, the foam from which the cell membrane has been removed is frequently used in filters and the like in air conditioners, etc., and the waste material from the foam from which the cell membrane has been removed has been generated by the disposal of air conditioners and the like. If it can be used, it is effective in saving resources.

JP-A-10-8591 Japanese Patent No. 3388682 JP 2005-331684 A

  The present invention has been made in view of the above points, and an object of the present invention is to provide an inexpensive sound-absorbing material that has good sound-absorbing properties in a low-frequency region and that can reuse waste materials.

  The invention of claim 1 relates to a sound-absorbing material characterized in that a resin film is laminated on a base body in which small pieces of foam from which cell membranes have been removed are bonded with a binder.

  The invention of claim 2 is characterized in that, in claim 1, the resin film is laminated on both surfaces of the substrate.

  A third aspect of the present invention is characterized in that, in the first or second aspect, the foam from which the cell film has been removed is a soft polyurethane foam from which the cell film has been removed.

  A fourth aspect of the present invention is characterized in that, in any one of the first to third aspects, the foam piece from which the cell film has been removed has a size of 20 to 50 mm.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the small piece of the foam from which the cell film has been removed comprises a foam waste material pulverized product from which the cell film has been removed. .

  According to the present invention, sound absorption in a low frequency region can be improved by a combination of a base body in which small pieces of foam from which a cell film has been removed is bonded with a binder and a resin film laminated on the base body.

  In addition, the foam piece from which the cell membrane has been removed is fragile because it is composed only of the cell skeleton, and even in a base bonded with a binder, a part of the cell skeleton falls off from the surface of the base in powder form (powder). In the present invention, since the resin film is laminated on the substrate, the surface of the substrate can be protected, and part of the cell skeleton is prevented from falling off from the substrate in the form of powder. The performance of the sound absorbing material can be maintained, and the risk of contaminating the usage environment of the sound absorbing material can be eliminated.

  Furthermore, in the present invention, the foam piece from which the cell membrane has been removed is used as the waste material pulverized product of the foam from which the cell membrane has been removed, so that the sound absorbing material can be made inexpensive by recycling the waste material. it can.

  Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 is a cross-sectional view of a sound absorbing material according to an embodiment of the present invention, FIG. 2 is a schematic view of a foam piece from which a cell film has been removed, and FIG. 3 is a schematic view showing an example of a substrate manufacturing process in the present invention. .

  The sound absorbing material 30 shown in FIG. 1 is affixed to a construction machine, a vehicle engine room, or the like, or used as a constituent member of an interior material such as a door trim of a vehicle, and is applied to a predetermined shape according to the application. It is shaped. The sound absorbing material 30 includes a base 31 and a resin film 33.

  The base 31 is made of a foam piece (also referred to as a chip) 10 from which a cell film has been removed as shown in FIG. The foam piece 10 from which the cell membrane has been removed has a three-dimensional network structure by the cell skeleton S1 without the cell membrane, and the portion corresponding to the cell membrane is communicated with the cavity S2, which is high. A foam material that has air permeability and from which the cell membrane has been removed is preferably pulverized by a known pulverizer from the viewpoints of recycling the waste material and reducing the cost of the sound absorbing material 30. The foam from which the cell membrane has been removed is preferably a soft polyurethane foam from which the cell membrane has been removed by a known film removal treatment such as thermal (explosion) treatment, from the viewpoint of sound absorption, availability, cost, and the like. The thickness of the base 31 is preferably 10 to 100 mm. Further, the base 31 may be obtained by slicing a thin plate having a thickness of, for example, 500 to 1000 mm, which is obtained by bonding the small pieces 10 of the foam from which the cell membrane has been removed, to a thickness of 10 to 100 mm. .

  The foam piece 10 from which the cell membrane has been removed preferably has 5 to 20 cells / 25 mm (conforms to JIS K 6400). When the number of cells is less than 5/25 mm, the foam piece 10 from which the cell membrane has been removed becomes too coarse, whereas when the number of cells exceeds 20/25 mm, the cell becomes too fine, In any case, the sound absorbing property of the sound absorbing material 30 is lowered.

  The foam piece 10 from which the cell membrane has been removed preferably has a size d of 20 to 50 mm, more preferably 20 to 40 mm. When the size is smaller than 20 mm, the contact surface area of the cell skeleton between the adjacent small pieces 10 becomes small, and the adhesive force between the small pieces 10 due to the binder becomes insufficient, so that separation becomes easy. Moreover, it causes powder falling and becomes difficult to handle. On the other hand, when the size of the foam piece 10 from which the cell film has been removed is larger than 50 mm, the base 31 has a rough structure and the strength is lowered, and the sound absorbing property of the sound absorbing material 30 is lowered. become.

  Preferable examples of the binder include a polyurethane type composed of a solvent-type polyurethane or a two-component solventless polyurethane that is cured by the presence of moisture, heating, or the like to bond the pieces together. The two-component solventless polyurethane preferably uses an amine curing agent such as triethylamine or N, N-dimethylcyclohexylamine. The polyurethane binder is mainly composed of a high molecular weight material containing an active isocyanate such as toluene diisocyanate (TDI) or diphenylmethane diisocyanate (MDI), and has a high viscosity. Therefore, the polyurethane binder is diluted with various organic solvents. In addition, as said organic solvent, halogenated solvents, such as a methylene chloride, are preferable from a volatile and nonflammable point. The amount of the binder is 5 to 30% by weight, preferably 20% by weight, in 100 parts by weight of the total amount of the foam piece 10 and the binder from which the cell membrane has been removed.

  An embodiment of the method of manufacturing the base 31 will be briefly described with reference to FIG. In the illustrated substrate manufacturing method, the substrate is manufactured by a foam pulverization process (A), a binder adhesion process (B), a mold filling process (C), a pressure curing process (D), and a demolding process (E).

  In the foam crushing process (A), the foam from which the cell membrane has been removed is crushed into small pieces 10 having a required size. The foam from which the cell membrane used in the foam pulverization step (A) has been removed is preferably a waste material. As the waste material of the foam from which the cell membrane has been removed, the waste material made of the foam with the cell membrane is removed, or the foam from which the cell membrane has been removed is used as a filter material, etc. Or a waste material generated when the foam from which the cell film has been removed is cut into a predetermined size by cutting or the like.

  In the binder adhering step (B), a predetermined amount of the binder is applied to the small piece 10 having the required size, or a required amount is blended and kneaded by a mixing device such as a tumbler mixer, a ribbon blender, etc. 11 is attached to obtain a binder-attached piece 12.

  In the mold filling step (C), the binder adhering pieces 12 obtained in the binder attaching step are weighed and filled into the molding apparatus 20. The illustrated mold apparatus 20 includes a frame body 24 having a water vapor inlet 23 formed on the lower surface, a lower mold 21 disposed in the frame body 24, and an upper mold that can be raised and lowered relative to the lower mold 21. 25 (shown in FIG. D), water vapor passages 22 and 27 are formed through the lower mold 21 and the upper mold 25 in the vertical direction, respectively. Furthermore, the upper surface 21a of the lower mold 21 and the lower surface 25a of the upper mold 25 are formed in a shape corresponding to the surface shape of the sound absorbing material.

  In the pressure curing step (D), the upper die 25 is lowered by a press device 26 and a required amount of the binder-attached small piece 12 is pressurized with the lower die 25. The degree of pressurization is adjusted so that the small piece does not collapse completely. Further, during the pressurization, water vapor Vp is supplied into the molding apparatus 20 from an external water vapor supply apparatus (not shown) through the water vapor inlet 23 on the lower surface of the molding apparatus 20. The water vapor Vp supplied in this way enters between the lower mold 21 and the upper mold 25 through the water vapor passage 22 of the lower mold 21, and between the binder adhering small pieces 12 or between the lower mold 21 and the upper mold 25. When passing between the skeletons without small cell membranes, the binder is cured to bond and fix the small pieces together. The water vapor Vp is discharged to the outside through the water vapor passage 27 of the upper mold 25. A formed body 28 shaped in a shape between the lower mold 21 and the upper mold 25 is formed between the lower mold 21 and the upper mold 25 by bonding and fixing the small pieces.

  In the demolding step (E), the molded body 28 is taken out from the molding apparatus 20 and stored in a known drying furnace, or dried by natural drying by the sun to remove moisture in the molded body 28. The drying conditions are appropriately determined in consideration of the drying time. Examples of the drying conditions include 3 to 6 hours at 90 ° C. when a drying furnace is used, and one week in the case of the sun. By completing the demolding step, the target substrate 31 is obtained.

  The resin film 33 is made of a resin film having no air permeability, is laminated on the surface of the base 31 to protect the surface of the base 31, and the small piece 10 made of the foam from which the cell film has been removed is formed from the base 31. While preventing the powder from falling off, the film 31 vibrates on the surface of the base 31 to enhance the sound absorption of the sound absorbing material 30.

  The resin film 33 is provided on one side or both sides of the base 31. In particular, if the resin films 33 are provided on both surfaces of the substrate 31, both surfaces of the substrate 31 can be protected, and the foam piece 10 from which the cell film has been removed falls off from the substrate 31 in powder form. Can be effectively prevented. The material of the resin film 33 is not particularly limited, and examples thereof include resins such as polyurethane, polyester, acrylic resin, and ethylene-vinyl acetate copolymer resin (EVA). In addition, it is more preferable that the resin film 33 is made of a material having good adhesion to the base 31.

  The thickness of the resin film 33 is preferably 10 to 50 μm, and more preferably 20 to 30 μm. When the thickness of the resin film 33 is less than 10 μm, the strength of the resin film 33 is lowered, the surface of the sound absorbing material 30 is easily damaged, and the production of the resin film 33 itself is difficult. On the other hand, if the thickness of the resin film 33 exceeds 50 μm, the resin film 33 cannot sufficiently vibrate in the sound absorbing material 30, and the sound absorbing effect obtained by the membrane vibration is lowered.

  The resin film 33 is bonded to the surface of the base 31 by an adhesive. As the adhesive, various types such as polyurethane, silicone, epoxy, and hot melt are used. In particular, the adhesiveness to both the resin film 33 and the substrate 31 is good.

  Specific examples of the sound absorbing material in the present invention are shown below. The waste foam material from which the cell membrane has been removed, which is generated when cutting the block-shaped foam from which the cell membrane has been removed (7 cells / 25 mm) into a product (filter, etc.) of a predetermined size by cutting. Crushing was performed with a pulverizer (manufactured by Yasuda Tekko Co., Ltd.) to 20 to 50 mm to form foam pieces from which the cell membrane was removed.

  Using MDI prepolymer as the binder, 20 parts by weight of the binder was sprayed onto the 80 parts by weight of the foam piece from which the cell membrane had been removed with a coating device (air mix type spray gun, manufactured by Meiji Machinery Co., Ltd.). The removed foam pieces and the binder were mixed with a mixer (manufactured by Kuroki Kogyo Co., Ltd.) to obtain binder-attached pieces. 1300 g of this binder-attached small piece was filled in a molding apparatus having a molding space having an inner bottom surface of 400 × 400 mm and pressed to a predetermined thickness. The degree of pressing was set such that in Example 1, the deposition thickness (height of the molding space) of the binder-attached small pieces filled in the molding space was 10 mm, whereas in Example 2, it was 50 mm. Further, water vapor was supplied into the molding apparatus, and the binder was cured by continuing the supply of the water vapor and the pressing for 7 minutes to form a molded body. Thereafter, the molded body was taken out from the molding apparatus and naturally dried at room temperature to obtain a substrate of the example. A polyethylene terephthalate (PET) resin film having a thickness of 30 μm was adhered to both surfaces of the substrate thus obtained by hot lamination resin (product name: Dyna Sheet LNS, manufactured by Kureha Tech Co., Ltd.) at 150 ° C. by dry lamination. 1 and 2 sound absorbing materials were obtained.

Further, Comparative Example 1 which is composed only of a soft polyurethane foam (product name: Calm Flex F-2, with cell membrane, manufactured by Inoac Corporation) marketed as a foam for sound absorbing material, and in which a resin film is not laminated. And the sound absorbing materials of Comparative Examples 2 and 3 in which the resin film is eliminated from the sound absorbing materials of Examples 1 and 2, respectively. Table 1 shows the configurations of the sound absorbing materials of Examples 1 and 2 and Comparative Examples 1 to 3. The basis weight (g / m ² ) in Table 1 represents the weight per unit area of the entire sound absorbing material.

  For the sound absorbing materials of Examples 1 and 2 and Comparative Examples 1 to 3, the normal incident sound absorption coefficient (%) is expressed in JIS A 1405 Appendix I. Measured based on acoustics. Table 2 shows the measurement results. The total in Table 2 is the sum of the normal incidence sound absorption coefficient at each measurement frequency. The larger the total value, the better the sound absorption performance.

Table 3 shows the normal incidence sound absorption coefficient of low frequency 500 Hz and 1000 Hz among the measurement results of the normal incidence sound absorption coefficient shown in Table 2, and in the sound absorbing materials of Examples 1 and 2 and Comparative Examples 1 to 3. It is a table | surface which shows the sound absorption property of a low frequency area | region.

  As can be understood from the total value of the normal incidence sound absorption coefficient shown in the bottom row of Table 2 and the normal incidence sound absorption coefficients of 500 Hz and 1000 Hz shown in Table 3, Comparative Example 1 consisting of only a flexible polyurethane foam, a resin film is laminated. Compared with Comparative Example 2 and Comparative Example 3 that are not performed, the sound absorbing materials of Example 1 and Example 2 have good sound absorbing performance, particularly good sound absorbing properties at low frequencies (500 Hz, 1000 Hz).

  In addition, since the sound absorbing materials of Example 1 and Example 2 were provided with a resin film on the surface of the base, there were few drops of the foam pieces from which the cell film constituting the base was removed. On the other hand, since the sound absorbing materials of Comparative Examples 2 and 3 were not provided with a resin film on the surface of the base, the small pieces of foam from which the cell film constituting the base was removed were often dropped.

It is sectional drawing of the sound-absorbing material in one Embodiment of this invention. It is the schematic of the small piece of the foam from which the cell membrane was removed. It is the schematic which shows the example of the manufacturing process of the base | substrate in this invention.

Explanation of symbols

30 Sound Absorbing Material 31 Base 33 Resin Film

Claims (5)

  A sound-absorbing material comprising a resin film laminated on a substrate in which small pieces of foam from which cell membranes have been removed are bonded with a binder.   The sound absorbing material according to claim 1, wherein the resin film is laminated on both surfaces of the base.   The sound absorbing material according to claim 1 or 2, wherein the foam from which the cell film has been removed is a soft polyurethane foam from which the cell film has been removed.   The sound absorbing material according to any one of claims 1 to 3, wherein the foam piece from which the cell film has been removed has a size of 20 to 50 mm. The sound absorbing material according to any one of claims 1 to 4, wherein the foam piece from which the cell film has been removed is made of a pulverized waste material of the foam from which the cell film has been removed.

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