JP2020189414A - Sound absorber and manufacturing method thereof - Google Patents

Abstract

To provide a sound absorber having a large degree of freedom in sound absorbency and a manufacturing method of a sound absorber with easy work relating to the manufacture.SOLUTION: The sound absorber 10 includes a substrate layer 11 of a melamine resin foam and a surface skin layer 12 of a nonwoven fabric, laminated on the substrate layer 11, wherein a ventilation adjustment part 13 for adjustment of ventilation resistance of the sound absorber 10 is provided between the substrate layer 11 and the surface skin layer 12, and the ventilation adjustment part 13 is formed dot-like with a hot-melt adhesive.SELECTED DRAWING: Figure 1

Description

The present invention relates to a sound absorbing material used in a vehicle such as an automobile or a railroad, an aircraft, a ship, or a building material of a building or a civil engineering structure, and a method for manufacturing the same.

Sound absorbing materials are used for vehicles such as automobiles and railways, aircraft, ships, and building materials for buildings and civil engineering structures to prevent noise from entering from the outside. The main sound absorbing materials are natural fibers such as cotton, wool and linen, synthetic fibers such as polyester, polyamide, acrylic, polyolefin and polyurethane, and inorganic fibers such as glass fiber, rock wool, carbon fiber and metal fiber. Examples thereof include fiber aggregates such as knitted woven fabrics and non-woven fabrics made of, and synthetic resin foams such as polyurethane foam, polyester foam and polyethylene foam.
Usually, the sound absorbing material made of a fiber aggregate or a synthetic resin foam can improve the sound absorbing performance by increasing the thickness. However, since the bulk and weight of the sound absorbing material increase as the thickness increases, it becomes difficult to mount the sound absorbing material on vehicles such as automobiles and railways, aircraft, ships, etc., and to install it on buildings, civil engineering structures, and the like. In particular, recent automobiles and building materials are required to be lighter, and the space for mounting and installation is limited, so it is extremely difficult to increase the thickness of the sound absorbing material to improve the sound absorbing performance. It has become difficult.

Therefore, as disclosed in Patent Documents 1 to 3, a sound absorbing material having improved sound absorbing performance without increasing the thickness has been proposed.
The adhesive sound absorbing sheet described in Patent Document 1 contains 90% by mass or more of porous pulp fibers having a beating degree in the range of 350 to 650 ml (CSF) and having a large number of pores opening on the surface, and is ventilated. Non-breathable adhesive layers are scattered in dots on one or both sides of a fiber sheet base material having a resistance of 0.07 to 2.00 kPa · s / m, and the total area ratio of the non-breathable adhesive layers is By setting it to 5 to 95% of the surface area of the fiber sheet base material, the ventilation resistance is set to 0.30 to 2.50 kPa · s / m.
The soundproofing coating material described in Patent Document 2 includes a first elastic porous body, a porous film having an aperture ratio of 0.1 to 5% and a pore diameter of 50 to 500 μm, and a second elastic porous body. It is characterized in that the plaques are laminated in this order.
The sheet-shaped low-frequency sound absorbing material described in Patent Document 3 includes a sound absorbing layer 1 and a sound absorbing layer 3 made of a fiber or a porous material, and a thin film layer 2 having a meltability between the sound absorbing layer 1 and the sound absorbing layer 3. It has.

International Publication No. 2011/013427 JP-A-2018-141432 JP-A-2019-2996

In the above-mentioned conventional sound absorbing material, a layer such as a non-breathable adhesive layer, a porous film, or a thin film layer having meltability is provided to improve the sound absorbing performance, but the work of providing such a layer is complicated. There was a problem.
Further, in the conventional sound absorbing material, in order to improve the sound absorbing performance, in the case of a non-breathable adhesive layer, the work related to the adjustment of the area ratio, and in the case of the porous film, the work related to the adjustment of the aperture ratio and the pore diameter. This is necessary, and there is a problem that the work related to the adjustment for improving the sound absorption performance is complicated.
Further, in the fiber aggregate used for the elastic porous body, the skin material and the sound absorbing layer in the conventional sound absorbing material, the fiber density tends to be uneven due to the uneven distribution of the fibers, and this uneven fiber density causes the sound absorbing performance to be dense. It is extremely difficult to control the fibers, and even if the above-mentioned complicated work is performed, there is a problem that the produced fiber aggregate may not have the desired sound absorption performance.
That is, the above-mentioned conventional sound absorbing material has a problem that the work related to manufacturing is complicated and the degree of freedom of sound absorbing performance is smaller than expected.

The present invention has focused on such problems existing in the prior art. An object of the present invention is to provide a sound absorbing material having a large degree of freedom in sound absorbing performance, and to provide a method for manufacturing the sound absorbing material, which is easy to carry out.

As a means for solving the above-mentioned conventional problems, the invention of the sound absorbing material according to claim 1 has a sound absorbing material having a base material layer made of melamine foam and a skin layer made of a non-woven fabric laminated on the base material layer. A ventilation adjusting portion for adjusting the ventilation resistance of the sound absorbing material is provided between the base material layer and the skin layer of the material, and the ventilation adjusting portion is a hot melt adhesive. The gist is that it is formed in the form of spots.
The gist of the invention according to claim 2 is that, in the invention of the sound absorbing material according to claim 1, the ventilation resistance of the sound absorbing material is 0.2 to 2 kPa · s.
The gist of the invention according to claim 3 is that in the invention of the sound absorbing material according to claim 1 or 2, the surface density of the ventilation adjusting portion is 1 to 20 g / m ² .
The invention according to claim 4 is the invention of the sound absorbing material according to any one of claims 1 to 3, wherein the sound absorbing material has a sound absorbing coefficient with respect to a sound having a frequency of 3150 Hz measured by a vertical incident method. However, the gist is that it is 70% or more.
The invention of the method for producing a sound absorbing material according to claim 5 is to apply a non-woven fabric coated with a hot melt adhesive on the surface of a melamine foam in the sound absorbing material according to any one of claims 1 to 4. The hot melt adhesive is provided with a first step of laminating to obtain a laminate and a second step of heating the laminate. The hot melt adhesive is in the form of a powder having a particle size of 80 to 500 μm by a sieving method. The gist is that things are used.
The gist of the invention according to claim 6 is that in the invention of the method for producing a sound absorbing material according to claim 5, the density of the melamine foam in the first step is 6 to 11 kg / m ³ .
According to the invention of claim 7, in the invention of the method for producing a sound absorbing material according to claim 5 or 6, the texture amount of the nonwoven fabric in the first step is 15 to 150 g / m ^2. It is a summary.
The invention of the method for producing a sound absorbing material according to claim 8 is the invention of the method for producing a sound absorbing material according to any one of claims 5 to 7, wherein the heating temperature is set in the second step. The gist is that the temperature is 180 to 230 ° C.

[Action]
The sound absorbing material of the present invention is provided with a ventilation adjusting portion for adjusting the ventilation resistance of the sound absorbing material between the base material layer made of melamine foam and the skin layer made of non-woven fabric. The ventilation adjusting portion is formed in a spot shape by the hot melt adhesive, and has air permeability by having a gap between the hot melt adhesives forming the spot shape. Therefore, by adjusting the ventilation resistance of the ventilation adjusting portion, the sound absorbing material can set the ventilation resistance to a desired value without being affected by the base material layer and the skin layer, and the ventilation of the ventilation adjusting portion. Since the resistance is adjustable, the degree of freedom in sound absorption performance can be increased.
The speckled shape is not necessarily limited to a shape in which all of the hot melt adhesives forming the spot shape are scattered apart from each other, and includes a shape in which the hot melt adhesives forming the spot shape are partially connected to each other.
When the ventilation resistance of the sound absorbing material is 0.2 to 2 kPa · s, the sound absorbing material used in automobiles, railroads and other vehicles, aircraft, ships, buildings and civil engineering structures, especially in automobiles. It can be suitable as.
When the surface density of the ventilation adjusting portion is 1 to 20 g / m ² , the ventilation resistance of the sound absorbing material can be stably adjusted.
The sound absorbing material can be a sound absorbing material particularly good for use in automobiles when the sound absorbing coefficient for the sound having a frequency of 3150 Hz measured by the vertical incident method is 70% or more.

The method for producing a sound absorbing material of the present invention includes a first step of applying a hot melt adhesive to the surface of a melamine foam, a second step of laminating a non-woven fabric on the surface of the melamine foam to obtain a laminate, and a laminate. It includes a third step of heating. In this first step, as the hot melt adhesive, a powdery one having a particle size of 80 to 500 μm by the sieving method is used, so that the ventilation adjusting portion by the hot melt adhesive is in the form of spots having suitable air permeability. The ventilation resistance of the sound absorbing material can be easily adjusted.
When the density of the melamine foam in the first step is 6 to 11 kg / m ³ , the sound absorption performance can be made suitable while suppressing the penetration of the melted hot melt adhesive into the melamine foam.
When the basis weight of the non-woven fabric is 15 to 150 g / m ² , the sound absorption performance can be made suitable while suppressing the penetration of the melted hot melt adhesive into the non-woven fabric.
When the heating temperature is 180 to 230 ° C. in the second step, the hot melt adhesive is suitably melted so that the melamine foam and the non-woven fabric are suitably bonded, and the ventilation adjusting portion is suitable as a sound absorbing material. It can be speckled.

〔effect〕
According to the present invention, it is possible to provide a sound absorbing material having a large degree of freedom in sound absorbing performance, and to provide a method for producing a sound absorbing material, which is easy to carry out.

(A) is a normal sectional view showing a sound absorbing material of an embodiment, and (b) is a plan sectional view of a ventilation adjusting part. A forward sectional view showing another form of sound absorbing material. A forward sectional view showing another form of sound absorbing material. The explanatory view which shows the manufacturing apparatus of the sound absorbing material of an embodiment. Explanatory drawing which shows the case of compressing a melamine foam. The graph which shows the sound absorption coefficient in the case of the melamine foam with a thickness of 10 mm in an Example. The graph which shows the sound absorption coefficient in the case of the melamine foam with a thickness of 20 mm in an Example. The graph which shows the sound absorption coefficient in the case of the melamine foam with a thickness of 40 mm in an Example.

Embodiments embodying the present invention will be described below with reference to the drawings.
As shown in FIG. 1A, the sound absorbing material 10 has a base material layer 11 and a skin layer 12 laminated on one side of the base material layer 11, and the base material layer 11 and the skin. A ventilation adjusting portion 13 for adjusting the ventilation resistance of the sound absorbing material 10 is provided between the layer 12 and the layer 12.
In the sound absorbing material 10, the base material layer 11 is formed of melamine foam. The skin layer 12 is made of a non-woven fabric. The ventilation adjusting portion 13 is formed of a hot melt adhesive.
As shown in FIG. 1 (b), in the ventilation adjusting unit 13, the hot melt adhesive 13A has a punctate shape in a plan view, and by having a plurality of such punctate hot melt adhesives 13A, the ventilation adjustment The portion 13 is formed in a spot shape in a plan view. The spot-shaped ventilation adjusting portion 13 has a gap 13B between the point-shaped hot melt adhesives 13A.

In the sound absorbing material 10, the base material layer 11 and the skin layer 12 are breathable, and the ventilation adjusting portion 13 also has a gap 13B between the plurality of point-shaped hot melt adhesives 13A. Since it has breathability, it exhibits sound absorption performance by acting as a buffering action due to ventilation resistance against noise passing through the inside.
The use of the sound absorbing material 10 is not particularly limited, for example, for vehicles such as automobiles and railways, for aircraft, for ships, or for building materials of buildings and civil engineering structures, but the sound absorbing material 10 of the present application has free sound absorbing performance. It is preferably for automobiles from the viewpoints of high degree, thinness and light weight due to the use of melamine foam described later for the base material layer 11, and excellent flame retardancy.

The ventilation resistance of the sound absorbing material 10 is not particularly limited because it is set according to the frequency of the noise to be absorbed depending on the application. For example, if the sound absorbing material 10 is used for automobiles, the sound having a frequency of 2000 to 6000 Hz is regarded as noise, and if the sound absorbing material 10 is used for building materials, the sound having a frequency of 400 to 2000 Hz is regarded as noise. Therefore, the ventilation resistance of the sound absorbing material 10 is appropriately set according to the frequencies of these noises.
Normally, the ventilation resistance is not limited to the sound absorbing material 10 for a specific purpose, but is widely used for vehicles such as automobiles and railways, aircraft, ships, and building materials for buildings and civil engineering structures. , 0.2 to 4.0 kPa · s.
As described above, the sound absorbing material 10 is preferably used for automobiles, and from the viewpoint of this automobile, the ventilation resistance is such that the sound absorbing performance can be suitably exhibited for noise having a frequency of 2000 to 6000 Hz. Is preferably 0.2 to 2.0 kPa · s, more preferably 0.3 to 2.0 kPa · s, and even more preferably 0.3 to 1.95 kPs · s / m.
If the sound absorbing material 10 is used for building materials, the ventilation resistance is preferably 0.8 to 4.0 kPa · s so that the sound absorbing performance can be suitably exhibited against noise having a frequency of 400 to 2000 Hz. It is more preferably 0.8 to 3.8 kPa · s, still more preferably 0.9 to 3.0 kPs · s / m.
The ventilation resistance (kPa · s / m) of the present invention refers to a value measured by a ventilation tester (product name: KES-F8-AP1, manufactured by Kato Tech Co., Ltd., steady flow differential pressure measurement method). It shall be.

The sound absorbing performance of the sound absorbing material 10 can be expressed by the sound absorbing coefficient measured by the vertical incident method specified or compliant with JIS A 1405-2.
The sound absorption coefficient of the sound absorbing material 10 is not particularly limited because the desired value differs depending on the application, but is used as a sound absorbing material used in vehicles such as automobiles and railroads, aircraft, ships, and building materials of buildings and civil engineering structures. From the viewpoint of exhibiting suitable sound absorption performance, if the sound absorption coefficient for sound having a frequency of 2000 to 2500 Hz is 50% or more, the sound absorption performance suitable for noise of 400 to 6000 Hz is exhibited.
In particular, the sound absorption coefficient of the sound absorbing material 10 when the application is for an automobile is preferably 70% or more for a sound having a frequency of 3150 Hz, and more preferably 80% or more for a sound having a frequency of 4000 Hz.

The sound absorbing material 10 preferably has a flame retardancy of V-0 or higher according to the UL94 standard, especially when the application is for automobiles.
Further, as shown in FIG. 2, the sound absorbing material 10 has a structure including a base material layer 11 and two skin layers 12 laminated on both sides of the base material layer 11, and the base material layer 11 and each skin surface. A ventilation adjusting portion 13 for adjusting the ventilation resistance of the sound absorbing material 10 can be provided between the layer 12 and the layer 12.
The shape of the sound absorbing material 10 may be a shape suitable for the intended use, and is not particularly limited.
The usage pattern of the sound absorbing material 10 is not particularly limited, and the sound absorbing material 10 may be used alone or in combination with a general sound insulating material or another sound absorbing material.

The base material layer 11 constitutes a main part of the sound absorbing material 10, and is formed of melamine foam to make the sound absorbing material 10 thin and lightweight. In particular, melamine foam has an excellent flame retardancy of V-0 according to the UL94 standard, and is suitable for use in automobile applications.
The melamine foam used for the base material layer 11 is not particularly limited to either two or more layers or a single layer, but the bonding between the multiple layers is omitted to facilitate the production. From this point of view, a single layer is preferable.

The ventilation resistance of the melamine foam used for the base material layer 11 is not particularly limited as long as it can exhibit sound absorption performance according to the application, but is not particularly limited, but is used for vehicles such as automobiles and railways, aircraft, ships, buildings and civil engineering structures. From the viewpoint of exhibiting suitable sound absorption performance in the use of building materials, preferably 0.05 to 2.0 kPa · s, more preferably 0.1 to 1.0 kPa · s, still more preferably 0.1 to 0. It is .5 kPa · s.
In particular, the ventilation resistance of the melamine foam when the application is for automobiles is preferably 0.05 to 1.0 kPa · s from the viewpoint of preferably exhibiting sound absorption performance for sounds having a frequency of 2500 to 6000 Hz. It is more preferably 0.1 to 0.5 kPa · s, and even more preferably 0.1 to 0.3 kPa · s.

The thickness of the melamine foam is not particularly limited as long as it can exhibit sound absorption performance according to the application, but is suitable for applications such as automobiles, railways and other vehicles, aircraft, ships, and building materials for buildings and civil engineering structures. From the viewpoint of exhibiting sound absorption performance, it is preferably 10 to 60 mm.
Further, the melamine foam has a property that the sound absorption coefficient for high frequency sound increases as it becomes thinner, while the sound absorption coefficient for low frequency sound increases as it becomes thicker.
Therefore, in the case of the sound absorbing material 10 for automobiles whose noise is a sound having a frequency of 2500 to 6000 Hz, the thickness of the melamine foam is preferably thinned, specifically, preferably 10 to 40 mm, more preferably 10. It is ~ 30 mm, more preferably 10 to 20 mm.

The density of melamine foam varies depending on the above-mentioned ventilation resistance and thickness, and is not particularly limited, but it is suitable for sound absorption performance in applications such as automobiles, railroads and other vehicles, aircraft, ships, and building materials for buildings and civil engineering structures. From the viewpoint of exerting, it is preferably 6 to 11 kg / m ³ .
When the base material layer 11 is formed of compressed melamine foam as described later, the ventilation resistance, thickness and density of the melamine foam are assumed to be the values before compression. Further, the ventilation resistance, thickness and density of the compressed melamine foam are not particularly limited because they vary depending on the compression rate described later.

By forming the base material layer 11 with melamine foam that is compressed by applying pressure in the thickness direction, the sound absorbing performance of the sound absorbing material 10 can be improved.
That is, the melamine foam is a foam having an open cell structure having a large number of uniform and fine pores inside, and when it is pressed and compressed in the thickness direction, the influence of the pressing force in the thickness direction depends on the manufacturing conditions. It has the physical property of being able to stay in the upper layer portion and the lower layer portion and locally compress the upper layer portion and the lower layer portion.
By utilizing the physical properties of this melamine foam and using a single-layer melamine foam, the base material layer 11 has an upper layer portion 14A, an intermediate layer portion 15, and a lower layer portion having different densities as shown in FIG. 14B can be formed.

The upper layer 14A, the intermediate layer 15, and the lower layer 14B are integrated in the base material layer 11, and the boundary between the parts is clear especially when a single layer melamine foam is used for the base material layer 11. It is hard to become. However, in the base material layer 11 using the melamine foam, the upper layer portion 14A, the intermediate layer portion 15, and the lower layer portion 14B have substantially the same thickness by trying to balance the stress generated inside. ..
Therefore, in the sound absorbing material 10 of the present application, the base material layer 11 is divided into three equal parts in the thickness direction, and each portion is referred to as an upper layer portion 14A, an intermediate layer portion 15, and a lower layer portion 14B in order from the surface side.

In the base material layer 11 using the single layer melamine foam, in the upper layer portion 14A, the intermediate layer portion 15, and the lower layer portion 14B, the density of the upper layer portion 14A and the lower layer portion 14B is higher than the density of the intermediate layer portion 15. It gets higher. This is because when the melamine foam is compressed in the thickness direction, the upper layer portion 14A and the lower layer portion 14B are compressed by the influence of the pressing force and the density is locally increased, whereas the intermediate layer portion 15 is due to the fact that compression is suppressed because the influence of the pressing force is almost unaffected.
The upper layer portion 14A, the intermediate layer portion 15, and the lower layer portion 14B have different densities, so that their respective ventilation resistances are also different. Therefore, the base material layer 11 on which the upper layer portion 14A, the intermediate layer portion 15, and the lower layer portion 14B having different densities are formed exhibits suitable sound absorption performance for noise of a wide range of frequencies.
As described above, in the sound absorbing material 10 of the present application, the base material layer 11 is divided into three equal parts in the thickness direction, and each portion is divided into the upper layer portion 14A, the intermediate layer portion 15, and the lower layer portion 14B in order from the surface side. It is said. Therefore, the densities of the upper layer portion 14A, the intermediate layer portion 15, and the lower layer portion 14B in the present application refer to the average densities measured in each of the portions of the base material layer 11 divided into three equal parts in the thickness direction.

The density of the intermediate layer portion 15 is not particularly limited as long as it corresponds to the use of the sound absorbing material 10, but from the viewpoint of automobiles or building materials, the density of the melamine foam before compression is preferably 1.10 times. Below, it is more preferably 1.08 times or less, still more preferably 1.05 times or less.
The densities of the upper layer portion 14A and the lower layer portion 14B correspond to the use of the sound absorbing material 10, and are not particularly limited as long as they are higher than the density of the intermediate layer portion 15, but from the viewpoint of automobiles or building materials, the intermediate layer It is 1.10 to 1.63 times the density of the part 15.
Further, the densities of the upper layer portion 14A and the lower layer portion 14B can be appropriately set according to the use of the sound absorbing material 10 by adjusting the compression rate described later. When the application is for automobiles, the density of the upper layer portion 14A and the lower layer portion 14B is preferably 1.10 to 1.40 times the density of the intermediate layer portion 15. When the application is for building materials, the density of the upper layer portion 14A and the lower layer portion 14B is preferably 1.35 to 1.63 times the density of the intermediate layer portion 15.
Further, the upper layer portion 14A and the lower layer portion 14B are made to have substantially equal densities, for example, by appropriately adjusting the heating temperature at the time of compression of the melamine foam between the upper layer portion 14A side and the lower layer portion 14B side. Although they can be different from each other, it is preferable that the densities of the two are substantially equal to each other because of the simplicity of production.

The skin layer 12 is for protecting the surface of the base material layer 11 in the sound absorbing material 10. In particular, when the base material layer 11 is formed of compressed melamine foam, the upper layer portion 14A and the lower layer portion 14B having increased densities may become brittle due to the increased hardness. Therefore, at least one surface of the base material layer 11 (Upper layer portion 14A) is preferably protected by the epidermis layer 12.
The material of the skin layer 12 is not particularly limited as long as it can protect the surface of the base material layer 11, and a knitted fabric, a sheet such as a non-woven fabric, a film made of synthetic resin, or the like can be used. Among the materials of the skin layer 12, the non-woven fabric is preferable from the viewpoint of easy availability and sound absorption performance. In particular, when the sound absorbing material 10 is used for automobiles or building materials, the appearance quality of the sound absorbing material 10 can be improved by using a non-woven fabric as the material of the skin layer 12, and the sound absorbing material 10 can be used. It can also be used as a conspicuous member such as an interior material for automobiles and an inner wall material for building materials.

The non-woven fiber is not particularly limited as long as it can protect the surface of the base material layer 11, and is not particularly limited. Polyester fiber, polyethylene fiber, polypropylene fiber, polyamide fiber, acrylic fiber, urethane fiber, polyvinyl chloride fiber, polyvinylidene chloride fiber. , Synthetic fibers such as acetate fibers, biodegradable fibers (polylactic acid fibers) made of starch extracted from plants such as corn and sugar cane, natural fibers such as pulp, cotton, palm fiber, hemp fiber, bamboo fiber, and kenaf fiber. Examples thereof include inorganic fibers such as glass fibers, carbon fibers, ceramic fibers, and asbestos fibers, or recycled fibers obtained by defibrating scraps of textile products using these fibers, and one or two of these. More than seeds are used. Among these fibers, polyester fiber is a preferable fiber from the viewpoint of availability, moldability, and flame retardancy.
The method for producing the non-woven fabric is not particularly limited as long as the surface of the base material layer 11 can be protected, and examples thereof include a spun bond method, a needle punching method, a thermal bond method, a chemical bond method, a stitch bond method, and a span lace method. To. Among these manufacturing methods, the spunbonding method is a preferable manufacturing method from the viewpoint of ease of manufacturing and the thinness of the obtained non-woven fabric and high strength.

The ventilation resistance of the skin layer 12 is not particularly limited as long as it does not affect the adjustment of the ventilation resistance of the sound absorbing material 10 by the ventilation adjusting unit 13. The fact that the ventilation adjusting unit 13 does not affect the adjustment of the ventilation resistance of the sound absorbing material 10 means that the ventilation resistance of the skin layer 12 is sufficiently lower than the ventilation resistance of the ventilation adjusting unit 13. When the ventilation resistance of the skin layer 12 is equal to or higher than the ventilation resistance of the ventilation adjustment unit 13, it is highly possible that the sound absorption performance of the sound absorbing material 10 is determined by the ventilation resistance of the skin layer 12.
Specifically, the ventilation resistance of the skin layer 12 is preferably 0.01 to 0.1 kPa from the viewpoint of improving the sound absorption performance while maintaining the strength and durability that can protect the surface of the base material layer 11. · S / m, more preferably 0.015 to 0.08 kPa · s / m, still more preferably 0.015 to 0.04 kPa · s / m.
When a non-woven fabric is used for the skin layer 12, the basis weight thereof is preferably 10 g / m ^{2 to} 120 g / m ² , more preferably 15 g / m ² from the viewpoint of keeping the airflow resistance of the skin layer 12 within the above range. ~110g / ^{m 2,} more preferably from ^{15g / m 2 ~100g / m 2} .

When a non-woven fabric is used for the skin layer 12, the surface of the base material layer 11 is maintained in strength and durability that can be protected, used for bonding with the base material layer 11, prevents fibers from falling off, and improves appearance quality. It is possible to impregnate a synthetic resin such as a thermoplastic resin or a thermosetting resin from the viewpoint of achieving the above.
The amount of the synthetic resin impregnated into the non-woven fabric is not particularly limited as long as the ventilation resistance of the non-woven fabric can be maintained lower than the ventilation resistance of the base material layer 11. Impregnation amount of specific synthetic resin, preferably 50 g / ^{m 2} or less, more preferably 10 to 50 g / ^{m 2.}

The synthetic resin to be impregnated in the non-woven fabric is preferably a thermosetting resin because the melamine foam is heated when the base material layer 11 is formed and the sound absorbing material 10 is heat-press molded depending on the application.
Examples of thermosetting resins include urethane-based resins, melamine-based resins, and thermosetting acrylic-based resins, especially thermosetting acrylic-based resins, urea-based resins, phenol-based resins, and epoxy-based resins that form ester bonds and cure by heating. Examples thereof include resins and thermosetting polyester resins.
Further, as the thermosetting resin, it is preferable to use an aqueous solution, an aqueous emulsion, or an aqueous dispersion from the viewpoint of easy handling.

Desirable thermosetting resins are phenolic resins, which are more desirable from the viewpoints of being easily available, easily forming an aqueous solution, an aqueous emulsion, and an aqueous dispersion, having adhesiveness, and having flame retardancy. Is a phenol-alkylresorcin cocondensate. The phenol-alkylresorcin cocondensate has the advantages that the aqueous solution of the initial condensate is stable and can be stored at room temperature for a long period of time as compared with the initial condensate composed of phenol alone.
In particular, by impregnating the non-woven fabric with an aqueous solution of a phenol-alkylresorcin cocondensate to bring it into a semi-cured state (B stage), stability is improved and moldability can be maintained even after long-term storage.

The ventilation adjusting portion 13 is a main portion for adjusting the overall ventilation resistance of the sound absorbing material 10. The ventilation adjusting portion 13 is formed in a spot shape by heat-melting the hot melt adhesive 13A in a state of being scattered on the surface of the base material layer 11 in a spot shape, and has a large number of gaps 13B. (See FIG. 1 (b)).
More specifically, the surface of the base material layer 11 formed by the melamine foam is not uneven due to the uneven density of fibers such as non-woven fabric, and the bubbles of the melamine foam are very dense and fine. The unevenness is also very fine and fine, so it is very smooth. Therefore, the hot melt adhesive is dispersed substantially uniformly on the surface of the melamine foam (base material layer 11) without being unevenly dispersed or heat-melted and permeating the surface. Heat melt. The hot melt adhesive, which is heat-melted in a state of being substantially uniformly dispersed on the surface of the melamine foam, exerts a suitable adhesive force in a small amount, and the ventilation adjusting portion 13 is formed into a thin film having a substantially uniform gap 13B. It is said.
The thin film-shaped ventilation adjusting portion 13 having a substantially uniform gap 13B allows the sound of the base material layer 11 to pass only through the gap 13B, and the portion other than the gap 13B (dot-shaped hot melt adhesive). (Part 13A) inhibits. As a result, the overall ventilation resistance of the sound absorbing material 10 becomes higher than the ventilation resistance of the base material layer 11, and the sound absorbing performance of the sound absorbing material 10 is improved.
The ventilation adjusting portion 13 is adhered to and integrated with the base material layer 11, and it is difficult to measure the ventilation resistance of only the ventilation adjusting portion 13, but the ventilation adjusting portion 13 provides the entire ventilation resistance of the sound absorbing material 10. It is considered that the ventilation resistance of the ventilation adjusting unit 13 is substantially equal to the ventilation resistance of the sound absorbing material 10 from the viewpoint of being adjusted and determined.
Further, the ventilation adjusting unit 13 is formed in a spot shape by the hot melt adhesive 13A that is heat-melted in a state of being scattered in dots, but the hot melt adhesive 13A that is heat-melted in a state of being scattered in dots is formed. , Not all of them are necessarily separated from each other, but may be partially connected.

The type of hot melt adhesive is not particularly limited, and one or more selected from polyethylene type, polyester type, polyamide type, ethylene-vinyl acetate copolymer type, acrylic type, synthetic rubber type and the like shall be exemplified. Can be done. Among these, the polyamide-based hot melt adhesive has suitable flame retardancy, and is suitable when the sound absorbing material 10 is used especially for automobile applications.
The form of the hot melt adhesive is not particularly limited, such as powder or aqueous emulsion, but the powder is preferable from the viewpoint of ease of use and easy adjustment of ventilation resistance.
The method of applying the powdered hot melt adhesive is not particularly limited, and the powdered material is sprayed and applied as it is, such as electrostatic spray coating, or a dispersion liquid dispersed in water or the like is used. Examples thereof include a method of applying by a spray method, a roll method, a spin method, a dip method and the like. Among these, the method of applying the dispersion liquid containing the powdered hot melt adhesive by the spray method is preferable from the viewpoints of simpleness, short working time, and easy adjustment of the amount of the hot melt adhesive applied. The method.
The particle size of the powdery hot melt adhesive is not particularly limited as long as the base material layer 11 and the skin layer 12 can be adhered to each other, but from the viewpoint of forming the airflow adjusting portion 13 in a speckled shape and preferably forming the gap 13B. The particle size according to the sieving method is preferably 80 to 500 μm, more preferably 100 to 300 μm, and even more preferably 100 to 150 μm.

The ventilation resistance of the sound absorbing material 10 can be adjusted by the ventilation adjusting unit 13 by adjusting the surface density of the ventilation adjusting unit 13. That is, as the surface density of the ventilation adjusting unit 13 increases, the overall ventilation resistance of the sound absorbing material 10 increases, and as the surface density of the ventilation adjusting unit 13 decreases, the overall ventilation resistance of the sound absorbing material 10 decreases.
The surface density of the ventilation adjusting unit 13 is not particularly limited as long as the ventilation resistance of the sound absorbing material 10 can be adjusted to a value according to the application, but is preferable from the viewpoint of exhibiting sound absorbing performance particularly suitable for automobile applications. Is 1 to 20 g / m ² , more preferably 5 to 10 g / m ² .

The surface density of the ventilation adjusting unit 13 can be adjusted by the amount of the hot melt adhesive applied per unit area. That is, as the coating amount of the hot melt adhesive per unit area increases, the surface density of the ventilation adjusting unit 13 increases, so that the ventilation resistance of the sound absorbing material 10 increases, and as the coating amount per unit area decreases, the ventilation adjustment As the surface density of the portion 13 becomes lower, the ventilation resistance of the sound absorbing material 10 becomes lower.
Specifically, the amount of the hot melt adhesive applied per unit area corresponds to the surface density of the ventilation adjusting portion 13, and is applied to the surface of the base material layer 11 (melamine foam 11A) or the surface of the epidermis layer 12 (nonwoven fabric 12A). The coating amount per unit area is preferably 1 to 20 g / m ² , more preferably 5 to 10 g / m ² .
Further, the target to which the hot melt adhesive is applied may be either melamine foam or non-woven fabric, and is not particularly limited, but the heat-melted hot melt adhesive permeates the surface of the melamine foam and closes the bubbles of the melamine foam. From the viewpoint of preventing the above, it is preferable to use a non-woven fabric.
In particular, when a powdered hot melt adhesive is applied to a non-woven fabric, the hot melt adhesive is temporarily fused to the surface of the non-woven fabric by spraying the hot melt adhesive at the above-mentioned surface density and then heating the non-woven fabric. Therefore, it is more preferable because it is possible to prevent the hot melt adhesive from seeping into the surface of the melamine foam while maintaining the surface density.

The above-mentioned sound absorbing material 10 is a first step of obtaining a laminated body 10A by laminating a non-woven fabric 12A coated with a hot melt adhesive 13A on the surface of a melamine foam 11A using an apparatus 20 as shown in FIG. It is manufactured through S1 and a second step S2 for heating the laminated body 10A.
In the apparatus 20, a non-woven fabric 12A coated with the hot-melt adhesive 13A in a predetermined coating amount is prepared in advance in a separate step, and the non-woven fabric 12A is in a state where the coated surface of the hot-melt adhesive 13A is facing upward. It is placed on the conveyor 21 and transported from the upstream side to the downstream side.
In the first step S1, the melamine foam 11A is laminated on the surface of the non-woven fabric 12A coated with the hot melt adhesive 13A to obtain a laminated body 10A.
In the second step S2, the laminated body 10A is conveyed onto the base 24, and the heating plate 25 arranged above the base 24 heats the laminated body 10A on the base 24 to absorb sound. Material 10 is manufactured.

In the second step S2, the heating temperature is not particularly limited as long as it is less than 240 ° C., which is the heat resistant temperature of the melamine foam 11A, but from the viewpoint of suppressing the melamine foam 11A from returning to the original density due to elasticity or the like. It is preferably 180 to 230 ° C, more preferably 180 to 220 ° C, and even more preferably 200 to 220 ° C.
In the second step S2, when the laminated body 10A is heat-pressed by the heating plate 25 for a predetermined pressing time, the melamine foam 11A can be compressed in the thickness direction as described above to improve the sound absorbing performance. This pressing time is not particularly limited as long as the base material layer 11 can be formed from the melamine foam 11A, but is preferably within the range of the compression ratio described later and from the viewpoint of improving work efficiency, preferably from 1 second to 1. 1 minute.

In the second step S2, when the base material layer 11 having the upper layer portion 14A, the intermediate layer portion 15 and the lower layer portion 14B is formed by compressing the melamine foam 11A in the thickness direction as described above, the heating plate 25 is used. It is necessary to adjust the pressing force.
This pressing force can be adjusted by adjusting the compression ratio of the melamine foam 11A. The compression ratio of the melamine foam 11A is such that the thickness of the melamine foam 11A before compression is T ₀ (see FIG. 5), and the thickness of the melamine foam 11A after compression, that is, the thickness of the base material layer 11 is T. In this case (see FIG. 5), it can be calculated by the calculation formula: (1-T / T ₀ ) × 100.
The compressibility of the melamine foam 11A is preferably 10 to 30% from the viewpoint of preferably forming the upper layer portion 14A, the intermediate layer portion 15 and the lower layer portion 14B.

Hereinafter, examples in which the present invention is further embodied will be described, but the present invention is not limited to these examples.
[Preparation of sample]
The melamine foam has a thickness of 10 mm and a ventilation resistance of 0.11 kPa · s / m (Sample No. 1), and a thickness of 20 mm and a ventilation resistance of 0.12 kPa · s / m (Sample No. 1). 7), three types were used, one having a thickness of 40 mm and a ventilation resistance of 0.18 kPa · s / m (Sample No. 13).
As the hot melt adhesive, a polyamide copolymer having a particle size of 100 to 150 μm by a sieving method and a softening temperature of 150 ° C. was used.
The non-woven fabric was made of polyester fiber and had a basis weight of 20 g / m ² by the spunbond method.

The amount of the hot melt adhesive applied (surface density of the ventilation adjusting part) to one side of the non-woven fabric is 1 g / m ² , 5 g / m ² , 10 g / m ² , 20 g / m ² , and 30 g / m ^2. Then, the non-woven fabric was heated in a heating furnace at 160 ° C. to temporarily fuse the hot-melt adhesive to the non-woven fabric to obtain a non-woven fabric coated with the hot-melt adhesive.
Next, the non-woven fabric coated with the hot-melt adhesive was subjected to Sample No. 1 so that the coated surface of the hot-melt adhesive was in contact with the non-woven fabric. It was laminated on the surface of 1, 7 and 13 melamine foams to obtain a laminate.
Then, the laminate was heated at 180 ° C., and the non-woven fabric and the melamine foam were adhered with a hot melt adhesive to obtain Sample No. Samples of 2-6, 8-12 and 14-18 were obtained.

[Sound absorption test]
Sample No. For each of the samples 1 to 18, the ventilation resistance was measured using a ventilation tester (product name: KES-F8-AP1, manufactured by Kato Tech Co., Ltd., steady flow differential pressure measurement method). The results are shown in Table 1.
In addition, sample No. The sound absorption coefficient of each of the samples 1 to 18 was measured by the vertical incident method according to JIS A 1405-2. The results were presented in Sample No. with a melamine foam thickness of 10 mm. 1 to 6 are the graphs of FIG. 6, and the sample No. 1 having a melamine foam thickness of 20 mm. 7 to 12 are the graphs of FIG. 7, and sample Nos. With a melamine foam thickness of 40 mm. 13 to 18 are shown in the graph of FIG.

As a result of the sound absorption test, the sample No. having a surface density of 1 to 20 g / m ^{2 in the} ventilation adjusting part was set. Nos. 2 to 5 are sample Nos. In which the ventilation adjusting portion is not formed. Compared with 1, the sound absorption performance was clearly improved in almost the entire frequency range where the sound absorption coefficient was measured, and the sound absorption coefficient was about 80% or more particularly at the frequency of 2000 to 5000 Hz.
Similarly, the sample No. having a surface density of 1 to 20 g / m ² in the ventilation adjusting portion. Nos. 8 to 11 are sample Nos. Compared with No. 7, the sound absorption performance was clearly improved in almost the entire frequency range where the sound absorption coefficient was measured, and the sound absorption coefficient was about 85% or more particularly at the frequency of 2000 to 5000 Hz.
Similarly, the sample No. having a surface density of 1 to 20 g / m ² in the ventilation adjusting portion. Nos. 14 to 17 are sample Nos. No. 14 to 17 in which the ventilation adjusting portion is not formed. Compared with No. 13, the sound absorption performance was clearly improved in almost the entire frequency range where the sound absorption coefficient was measured, and the sound absorption coefficient was about 90% or more particularly at the frequency of 2000 to 5000 Hz.
From the above, it was shown that when the surface density of the ventilation adjusting portion is 1 to 20 g / m ² , it is a particularly preferable sound absorbing material for automobiles.

In addition, the sample No. has a surface density of 30 g / m ² in the ventilation adjustment section. No. 6 has a sound absorption coefficient for a sound of 1000 to 1500 Hz, and the sample No. Compared to 1, it was rising.
Similarly, the sample No. having a surface density of 30 g / m ² in the ventilation adjusting portion. No. 12 has a sound absorption coefficient for a sound of 1000 to 1500 Hz, and the sample No. Compared to 7, it was rising.
Similarly, the sample No. has a surface density of 30 g / m ² in the ventilation adjusting portion. No. 18 has a sound absorption coefficient for a sound of 1000 to 1500 Hz, and the sample No. Compared to 13, it was rising.
From the above, when the surface density of the ventilation adjusting part is set to 30 g / m ² , it is not suitable for automobile applications, but sound absorption performance against noise of 1000 to 1500 Hz such as for building materials is required. It has been shown to be suitable for use.

According to the sound absorbing material and the method for producing a sound absorbing material of the present invention, it is possible to obtain a sound absorbing material having a large degree of freedom in sound absorbing performance, and it is easy to adjust the density and ventilation resistance of the sound absorbing material. It is possible.

10 Sound absorbing material 10A Laminated body 11 Base material layer 11A Melamine foam 12 Skin layer 12A Non-woven fabric 13 Ventilation adjustment part 13A Hot melt adhesive 13B Gap 14A Upper layer 14B Lower layer 15 Intermediate layer 20 Equipment 21 Conveyor 24 Base 25 Heating board S1 1st process S2 2nd process

Claims (8)

A sound absorbing material having a base material layer made of melamine foam and a skin layer made of a non-woven fabric laminated on the base material layer.
A ventilation adjusting portion for adjusting the ventilation resistance of the sound absorbing material is provided between the base material layer and the skin layer.
The ventilation adjusting portion is a sound absorbing material characterized in that it is formed in a spot shape by a hot melt adhesive. The sound absorbing material according to claim 1, wherein the ventilation resistance of the sound absorbing material is 0.2 to 2 kPa · s. The sound absorbing material according to claim 1 or ² , wherein the surface density of the ventilation adjusting portion is 1 to ²⁰ g / m ² . The sound absorbing material according to any one of claims 1 to 3, wherein the sound absorbing material has a sound absorbing coefficient of 70% or more with respect to a sound having a frequency of 3150 Hz measured by a vertical incident method. The method for producing a sound absorbing material according to any one of claims 1 to 4.
The first step of laminating the non-woven fabric coated with the hot melt adhesive on the surface of the melamine foam to obtain a laminate, and
It is provided with a second step of heating the laminate.
A method for producing a sound absorbing material, wherein a powdery material having a particle size of 80 to 500 μm by a sieving method is used as the hot melt adhesive. The method for producing a sound absorbing material according to claim 5, wherein the density of the melamine foam in the first step is 6 to 11 kg / m ³ . The method for producing a sound absorbing material according to claim 5 or 6, wherein the weight of the nonwoven fabric in the first step is 15 to 150 g / m ² . The method for producing a sound absorbing material according to any one of claims 5 to 7, wherein in the second step, the heating temperature is 180 to 230 ° C.

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