JP2020091339A - Double layer sound absorption material and manufacturing method thereof - Google Patents

Abstract

To provide a double layer sound absorption material excellent in a sound absorption characteristic and in productivity and to provide a manufacturing method of the double layer sound absorption material.SOLUTION: A double layer sound absorption material comprises: an air-permeable base material layer; and a foam layer laminated on the base material layer. The foam layer is constituted of a heated dried body of mechanically foamed (meth)acrylate polymer emulsion, and a ratio of the thickness of the foam layer to the thickness of the base material layer is 20/80 to 85/15. The base material layer is preferably constituted of a nonwoven fabric of thermoplastic organic fibers. A glass transition point of resin constituting the (meth)acrylate polymer emulsion is preferably -45°C to 10°C. Permeability is preferably 5 cm/cms to 40 cm/cms. Density of the foam layer is preferably 60 kg/mto 300 kg/m.SELECTED DRAWING: Figure 1

Description

The present invention relates to a multilayer sound absorbing material and a method for manufacturing the multilayer sound absorbing material.

Sound absorption measures, such as sound absorption, sound insulation, and vibration control, are taken in the passenger compartment of automobiles so that people can live comfortably.For example, sound absorbing materials are used to prevent the sound from reverberating in a closed vehicle interior. It is used. Most of the sound absorbing materials have a structure in which a surface layer and a sound absorbing layer are laminated, and those in which an isocyanate adhesive is used for adhering these (see JP 2005-201191 A) and an aqueous adhesive resin emulsion are used. (See Japanese Patent Laid-Open No. 2010-125096) is known, and a hot melt film or a low-melting resin non-woven fabric is laminated between a fiber layer and a thermoplastic resin sheet layer, and heated and pressed. A laminate integrated structure (Japanese Patent Laid-Open No. 2005-226178) is also under study.

JP, 2005-201199, A JP, 2010-125096, A JP, 2005-226178, A

However, since the above-mentioned conventional sound absorbing material is manufactured by individually manufacturing and bonding each material with an adhesive or the like, the manufacturing is complicated, the productivity is low, and the ventilation by the adhesive or the like is used. There is an inconvenience that the sound absorption characteristic is deteriorated probably because the property is suppressed.

The present invention has been made based on the above circumstances, and an object thereof is to provide a multilayer sound absorbing material having excellent sound absorbing characteristics and excellent productivity, and a method for manufacturing the multilayer sound absorbing material.

In the process of earnestly researching and developing, the present inventors have adopted the sound absorbing material having a layer formed on the surface of the base material using a specific material, and have a specific structure, thereby achieving the above-mentioned problems. The inventors have found that the above can be solved and completed the present invention.

The invention made to solve the above problems comprises an air-permeable base material layer and a foam layer laminated on the base material layer, wherein the foam layer is a mechanically foamed (meth)acrylic acid ester polymer emulsion. Is a heat-dried body, and the ratio of the thickness of the foam layer to the thickness of the base layer is 20/80 or more and 85/15 or less.

Another invention made to solve the above problems is a method for producing the multilayer sound absorbing material, which is obtained by a step of mechanically foaming a (meth)acrylic acid ester polymer emulsion and the mechanical foaming step. A step of applying a mechanically foamed (meth)acrylic acid ester polymer emulsion to one surface of a breathable substrate layer; and a step of heating and drying the coating layer formed by the above-mentioned coating step. Characterize.

The multi-layer sound absorbing material of the present invention has excellent sound absorbing properties and excellent productivity. According to the method for manufacturing a multilayer sound absorbing material of the present invention, the multilayer sound absorbing material having excellent sound absorbing characteristics can be manufactured with high productivity.

It is a typical sectional view of a multilayer sound-absorbing material concerning an embodiment of the present invention.

Hereinafter, embodiments of the multilayer sound absorbing material will be described in detail with reference to the drawings.

<Multilayer sound absorbing material>
The multi-layer sound absorbing material 1 of FIG. 1 includes a breathable base material layer 2 and a foam layer 3 laminated on the base material layer 2. The foam layer 3 is composed of a heat-dried body of mechanically foamed (meth)acrylic acid ester polymer emulsion. The ratio of the thickness of the foam layer 3 to the thickness of the base material layer 2 is 20/80 or more and 85/15 or less.

The multi-layered sound absorbing material has excellent sound absorbing properties and excellent productivity. The reason why the multilayer sound absorbing material has the above-mentioned configuration to achieve the above-mentioned effect is not always clear, but it can be inferred as follows, for example. That is, the multilayer sound absorbing material has a structure in which the foam layer 3 is formed on the surface of the air-permeable base material layer 2. The foam layer 3 is formed by applying a mechanically foamed (meth)acrylic acid ester polymer emulsion and heating and drying it, and is made of a specific material. The multi-layer sound absorbing material includes a breathable base material layer 2 that also contributes to sound absorbing properties and drying properties when forming a foam layer, and the specific foam layer 3, and is different from the conventional sound absorbing material. Differently, the production is simple, and since the ratio of the thickness of the foam layer 3 to the base layer 2 (foam layer/base layer) is not less than the above lower limit, it is considered that the sound absorbing property is excellent. In addition, since the thickness ratio of the multilayer sound absorbing material is not more than the upper limit, the drying property during the formation of the foamed layer becomes better, and the productivity becomes excellent.
Hereinafter, the base material layer and the foamed layer will be described.

[Base material layer]
The base material layer 2 is a breathable base material layer. The term “air-permeable” means that the base material layer has an air permeability of, for example, 1 cm ³ /cm ² ·s or more, preferably 5 cm ³ /cm ² ·s or more, and more preferably 10 cm ³ /cm ^2.・It means s or more.

Examples of the material forming the base material layer 2 include non-woven fabric, woven fabric, knitted fabric, fiber sheet such as paper; mesh sheet, porous membrane and the like. Of these, a fiber sheet is preferable, and a non-woven fabric is more preferable.

Examples of fibers constituting the fiber sheet include polyolefin fibers such as polyethylene fibers and polypropylene fibers; polyester fibers such as polyethylene terephthalate fibers and polybutylene terephthalate fibers; polyamide fibers such as polyamide 6 fibers and polyamide 6,6 fibers; polycarbonate fibers and the like. Examples of the thermoplastic organic fibers include non-thermoplastic organic fibers such as aramid fibers; natural fibers such as hemp and cotton; inorganic fibers such as glass fibers, carbon fibers, ceramic fibers, and metal fibers.

The lower limit of the average diameter of the fibers constituting the fiber sheet is preferably 0.1 μm, more preferably 1 μm. The upper limit of the average diameter is preferably 100 μm, more preferably 50 μm.

The base material layer 2 is preferably made of a non-woven fabric, more preferably a non-woven fabric of thermoplastic organic fibers. Since the non-woven fabric of thermoplastic organic fiber is excellent in thermoformability, the multilayer sound absorbing material can be thermoformed into an arbitrary shape, and can be applied to uneven surfaces that are not flat surfaces such as automobile interior materials, engine rooms, and trunk rooms. It can be suitably used as a sound absorbing material to be assembled.

The lower limit of the density of the base layer 2, preferably from ^{10kg / m 3, 50kg / m} 3 and more preferably. The upper limit of the density is preferably ^{200kg / m 3, 100kg / m} 3 and more preferably.

The lower limit of the thickness of the base material layer 2 is preferably 1 mm, more preferably 3 mm. The upper limit of the thickness is preferably 10 mm, more preferably 8 mm. "Thickness of base material layer" means an arithmetic mean value of thicknesses measured at three different points in a 10 cm square of the base material layer 2 of the multilayer sound absorbing material.

The lower limit of the weight per unit area of the base material layer is preferably ^{50g / m 2, 100g / m} 2 is more preferable. The upper limit dated the eye, preferably ^{1,000g / m 2, 700g / m} 2 is more preferable.

[Foam layer]
The foam layer 3 is composed of a heat-dried body of mechanically foamed (meth)acrylic acid ester polymer emulsion.

"Heat-dried mechanically foamed (meth)acrylic acid ester polymer emulsion" refers to heat-dried mechanically foamed (meth)acrylic acid ester polymer emulsion obtained by mechanically foaming (meth)acrylic acid ester polymer emulsion. I say what I made. “Mechanical foaming” means dispersing and mixing air bubbles in an emulsion by a mechanical treatment such as stirring and mixing of the emulsion. By heating and drying, the dispersion medium contained in the mechanically foamed (meth)acrylic acid ester polymer emulsion is evaporated and removed.

The mechanically foamed (meth)acrylic acid ester polymer emulsion contains a resin and bubbles of a (meth)acrylic acid ester polymer as a dispersoid, and a dispersion medium in which these are dispersed.
The heat-dried product of the mechanically foamed (meth)acrylic acid ester polymer emulsion includes a coating film derived from the resin in the (meth)acrylic acid ester polymer emulsion, and voids present in the coating film.

The "(meth)acrylic acid ester polymer" refers to a polymer obtained by using at least one kind of acrylic acid ester and methacrylic acid ester as a monomer.

The (meth)acrylic acid ester polymer emulsion contains, for example, one or more kinds of (meth)acrylic acid ester and, if necessary, a monomer other than the (meth)acrylic acid ester, as a polymerization initiator and a necessary monomer. Depending on the presence of an emulsifier or a dispersion stabilizer, it can be obtained by emulsion polymerization in a dispersion medium such as water.

Examples of the (meth)acrylic acid ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, and (meth)acrylic acid. Heptyl, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, octadecyl (meth)acrylate, (meth)acrylic (Meth)acrylic acid hydrocarbon ester such as cyclohexyl acid, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, allyl (meth)acrylate, etc. ;
Glycidyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, glycerol mono(meth)acrylate, ethylene glycol di(meth)acrylate, Examples thereof include (meth)acrylic acid hetero atom-containing esters such as 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate and polypropylene glycol di(meth)acrylate.

Examples of other monomers include unsaturated carboxylic acids such as (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, itaconic acid monoester, maleic acid monoester, maleic anhydride and itaconic anhydride. Compound;
Aromatic vinyl compounds such as styrene and divinylbenzene;
Unsaturated nitrile compounds such as acrylonitrile;
Conjugated diene compounds such as butadiene and isoprene;
Examples thereof include diallyl phthalate and allyl glycidyl ether.

Examples of the dispersion medium of the (meth)acrylic acid ester polymer emulsion include water; alcohols such as ethanol, ketones such as acetone, esters such as ethyl acetate, ethers such as dipropyl ether, glycol ethers such as ethylene glycol monomethyl ether. Examples of organic solvents include Of these, water is preferred.

The (meth)acrylic acid ester polymer emulsion may contain, for example, a surfactant, a silicone compound or the like. The (meth)acrylic acid ester polymer emulsion may be used alone or in combination of two or more.

As a lower limit of the glass transition point (Tg) of the resin constituting the (meth)acrylic acid ester polymer emulsion, −55° C. is preferable, −50° C. is more preferable, −45° C. is further preferable, and −40° C. is particularly preferable. preferable. The upper limit of Tg is preferably 30°C, more preferably 20°C, further preferably 10°C, and particularly preferably 0°C. By setting the Tg of the (meth)acrylic acid ester polymer within the above range, the sound absorbing characteristics of the multilayer sound absorbing material can be further improved.

The lower limit of the average particle size of the dispersoid of the (meth)acrylic acid ester polymer emulsion is preferably 50 nm, more preferably 70 nm, and even more preferably 80 nm. The upper limit of the average particle size is preferably 600 nm, more preferably 500 nm, and even more preferably 400 nm. The average particle diameter is, for example, a volume-based median diameter measured by a laser diffraction type particle size distribution measurement.

As a minimum of solid content concentration of a (meth)acrylic acid ester polymer emulsion, 30 mass% is preferred, 40 mass% is more preferred, and 50 mass% is still more preferred. The upper limit of the solid content concentration is preferably 80% by mass, more preferably 70% by mass, and even more preferably 65% by mass.

The lower limit of the density of the foam layer 3 is preferably 20 kg / ^{m 3,} more preferably 60 kg / ^{m 3,} more preferably ^{80kg / m 3, 100kg / m} 3 is especially preferred. As an upper limit of the density, 400 kg/m ³ is preferable, 350 kg/m ³ is more preferable, 300 kg/m ³ is further preferable, and 250 kg/m ³ is particularly preferable. By setting the density of the foam layer 3 in the above range, it is possible to further improve the sound absorbing characteristics and the productivity of the multilayer sound absorbing material. The “density of the foam layer” means the density of the entire foam layer including voids in the foam layer.

The lower limit of the thickness of the foam layer 3 is preferably 0.1 mm, more preferably 1 mm, further preferably 2 mm. The upper limit of the thickness is preferably 20 mm, more preferably 10 mm, even more preferably 8 mm. By setting the thickness of the foam layer 3 in the above range, it is possible to further improve the sound absorbing characteristics and the productivity of the multilayer sound absorbing material. The “thickness of the foam layer” means the arithmetic mean value of the thickness measured at three different points in a 10 cm square of the foam layer 3.

As a lower limit of the basis weight of the foam layer 3, 100 g/m ² is preferable, 200 g/m ² is more preferable, 300 g/m ² is further preferable, and 400 g/m ² is particularly preferable. The upper limit dated the eye, preferably 2,000 g / ^{m 2,} more preferably 1,800 g / ^{m 2,} more preferably ^{1,600g / m 2, 1,400g / m} 2 is particularly preferred.

The lower limit of the ratio of the thickness of the foam layer 3 to the thickness of the base material layer 2 is 20/80, preferably 30/70, more preferably 35/65, further preferably 40/60, particularly preferably 45/55. preferable. The upper limit of the ratio is 85/15, preferably 80/20, more preferably 75/25, further preferably 70/30, and particularly preferably 65/35. By setting the ratio of the thickness of the foam layer 3 to the base material layer 2 in the above range, the sound absorbing characteristics and the productivity of the multilayer sound absorbing material can be further improved.

As a lower limit of the air permeability of the multilayer sound absorbing material, 1 cm ³ /cm ² ·s is preferable, 2 cm ³ /cm ² ·s is more preferable, 5 cm ³ /cm ² ·s is further preferable, and 8 cm ³ /cm ² -S is particularly preferable. As the upper limit of the air permeability, 50 cm ³ /cm ² ·s is preferable, 45 cm ³ /cm ² ·s is more preferable, 40 cm ³ /cm ² ·s is further preferable, and 30 cm ³ /cm ² ·s is particularly preferable. .. By setting the air permeability of the multilayer sound absorbing material within the above range, the sound absorbing characteristics and productivity of the multilayer sound absorbing material can be further improved.

The shape of the multilayer sound absorbing material is not particularly limited, and may be, for example, a sheet shape, a flat plate shape, a curved plate shape, a concavo-convex plate shape, or the like, for example, according to the structure of the interior of the automobile. It can have various shapes.

<Method for manufacturing multi-layer sound absorbing material>
Next, a method for manufacturing the multilayer sound absorbing material will be described. The method for producing the multilayer sound absorbing material comprises a step of mechanically foaming a (meth)acrylic acid ester polymer emulsion (hereinafter, also referred to as "mechanical foaming step"), and mechanical foaming (meth) obtained by the mechanical foaming step. A step of coating an acrylic ester polymer emulsion on one surface of a breathable base material layer (hereinafter, also referred to as "coating step"), and the coating layer formed by the above coating step is dried by heating. The process (henceforth a "heat-drying process") is provided.

According to the method for manufacturing the multilayer sound absorbing material, the multilayer sound absorbing material having excellent sound absorbing characteristics can be manufactured with high productivity.
Hereinafter, each step will be described.

[Mechanical foaming process]
In this step, the (meth)acrylic acid ester polymer emulsion is mechanically foamed.

Examples of the apparatus used for mechanical foaming include a batch type foaming machine and a continuous type foaming machine.

Examples of the gas introduced by mechanical foaming include air, nitrogen, oxygen and the like.

At the time of mechanical foaming, a thickener, a foam stabilizer, etc. may be added to the (meth)acrylic acid ester polymer emulsion.

The conditions such as the foaming time in the batch type foaming machine and the number of rotations of the mixer are appropriately selected so that the density of the resulting mechanical foaming liquid has a desired value. The lower limit of the mixing time in the batch type foaming machine is preferably 1 minute, more preferably 2 minutes, further preferably 3 minutes. The upper limit of the mixing time is preferably 60 minutes, more preferably 40 minutes, even more preferably 30 minutes.

The conditions such as the liquid flow rate, the gas flow rate, and the mixer rotation speed in the continuous foaming machine are appropriately selected so that the density, the flow rate, etc. of the obtained mechanical foaming liquid have desired values.

[Coating process]
In this step, the mechanically foamed (meth)acrylic acid ester polymer emulsion obtained in the mechanical foaming step is applied to one surface of the air-permeable base material layer.

Examples of the coating method include a casting head method, a roll coating method, an air knife coating method, a gravure roll coating method, a doctor roll coating method, a doctor knife coating method, a curtain flow coating method, a spray method and a brush coating method.

The thickness of the formed coating layer is appropriately selected so that the thickness of the foamed layer formed by heating and drying has a desired value. The lower limit of the thickness of the coating layer is preferably 0.1 mm, more preferably 1 mm. The upper limit of the thickness is preferably 10 mm, more preferably 8 mm.

[Heating and drying process]
In this step, the coating layer formed in the above coating step is heated and dried. That is, the dispersion medium in the mechanically foamed (meth)acrylic acid ester polymer emulsion constituting the coating layer is evaporated by heating. As a result, a foam layer 3 including a film derived from the resin in the (meth)acrylic acid ester polymer emulsion and voids present in the film is formed, and the mechanical foamed (meth)acrylic acid is formed on the base material layer 2. A multilayer sound absorbing material 1 in which a foam layer 3 composed of a heat-dried body of an ester polymer emulsion is laminated is obtained.

Examples of the apparatus for heating and drying the coating layer include an oven, a hot plate, a hot air dryer, and a hot air circulating oven.

Conditions such as temperature and time in the heat drying are appropriately selected so that the dispersion medium is substantially not contained in the foamed layer formed. As a lower limit of the temperature in heat drying, 60°C is preferable, 70°C is more preferable, and 80°C is further preferable. The upper limit of the temperature is preferably 200°C, more preferably 180°C, and even more preferably 160°C. From the viewpoint of improving the productivity of the multilayer sound absorbing material, the upper limit of the time of heating and drying is preferably 70 minutes, more preferably 50 minutes, and even more preferably 40 minutes. The lower limit of the time is, for example, 1 minute, preferably 3 minutes.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. The characteristic values in the examples were measured by the following methods.

[Thickness of base material layer]
The sample was cut into a size of 10 cm×10 cm, left at a temperature of 23° C. and a humidity of 50% RH for 24 hours with no load, and then, using a thickness gauge, according to JIS-L1096, a pressure of 3.7 gf/cm ² was used, which was different. The thickness was measured at three points and the arithmetically averaged value was used as the thickness of the base material layer.

[Basis weight of base material layer]
The sample was cut into a size of 10 cm×10 cm, left at a temperature of 23° C. and a humidity of 50% RH for 24 hours without load, and then W: mass (g) was measured to determine the basis weight (g/m ² ) of the base material layer. )=W/0.01

[Thickness of foam layer]
The sample was cut into a size of 10 cm x 10 cm, left at no load for 24 hours at a temperature of 23°C and a humidity of 50% RH, and the thickness of the foam layer on the cross section was measured at three different points using a caliper, and the arithmetic mean was calculated. The value obtained was taken as the thickness of the foam layer. When the mechanically foamed emulsion permeates into the surface layer of the base material layer, the portion formed by this corresponds to the base material layer and not the foamed layer.

[Fabric layer weight]
The sample was cut into a size of 10 cm×10 cm, left at a temperature of 23° C. and a humidity of 50% RH for 24 hours without load, and then W: mass (g) was measured, and basis weight (g/m ² )=W/ By 0.01, A: the basis weight (total basis weight: g/m ² ) when the foam layer was laminated on the base material layer was obtained, and B: the basis weight of the base material layer when the foam layer was not laminated was measured above. from (g / ^{m 2),} the basis weight of the foam layer ^{(g /} m 2) = determined by a-B.

[Density of foam layer]
Divide the W: mass (g) of the foamed layer measured in the above "Basis weight of the foamed layer" by the sample area (0.01 m ² ) x the sample volume (m ³ ) obtained by the thickness (m) of the foamed layer. It was calculated by

[Air permeability of multi-layer sound absorbing material]
The sample was cut into a size of 10 cm×10 cm, left at a temperature of 23° C. and a humidity of 50% RH for 24 hours without a load, and then subjected to a Frazier breathability tester (“Takayama Reed Co., Ltd.” according to the method A shown in JIS-L1096. FX3300-IV").

[Glass transition point]
A dry film was obtained by thinly stretching 1 to 10 g of resin on a glass plate and drying at 25° C. for 3 days. About the obtained dry film, using a differential scanning calorimeter (“DSC2910 type” manufactured by TA Instruments Co., Ltd.), using a sample of 5 to 10 mg, under a nitrogen atmosphere, a temperature rising rate: 20° C./min, Temperature range: Measurement was performed at -100°C to 100°C. The temperature at the midpoint between the starting point and the ending point of the inflection of the differential curve of the differential scanning calorimetry obtained by the measurement was taken as the glass transition temperature (Tg).

<Manufacture of multi-layer sound absorbing material>
The base material layer and the (meth)acrylic acid ester polymer emulsion used for the production of the multilayer sound absorbing material are shown below.

[Base material layer]
Non-woven fabric: Non-woven fabric made of polyester fiber of 6 denier (thread diameter of about 27 μm) produced by the needle punch method N-1: Density: 75 kg/m ³ , thickness: 5.2 mm
N-2: Density: 72 kg/m ³ , Thickness: 7.7 mm
N-3: Density: 68 kg/m ³ , Thickness: 3.3 mm
N-4: Density: 70 kg/m ³ , thickness: 9.8 mm
N-5: Density: 73 kg/m ³ , Thickness: 1.1 mm

[(Meth)acrylic acid ester polymer emulsion]
(Meth)acrylic acid ester polymer emulsions (E-1) to (E-3) were synthesized as follows.

[Synthesis Example 1] (Synthesis of (meth)acrylic acid ester polymer emulsion (E-1))
Monomer a: 62 parts by mass of butyl acrylate, Monomer b: 37 parts by mass of methyl methacrylate, Monomer c: 1 part by mass of acrylic acid (80% by mass acrylic acid aqueous solution) (actual amount of acrylic acid), Emulsifier: 4 parts by mass of "NeoPerex G-25" manufactured by Kao Co., Ltd. and 27 parts by mass of deionized water were charged and emulsified by stirring for 10 minutes.
Separately from this, 37.2 parts by mass of deionized water and 0.15 parts by mass of an emulsifier (“NeoPerex G-25” manufactured by Kao Corporation) are used with respect to 100 parts by mass of the total amount of the monomers a to c. The mixture was charged, the mixture was stirred, the atmosphere was replaced with nitrogen, and the temperature was raised to 75°C. Next, 0.28 parts by mass of a radical polymerization initiator: sodium persulfate (Fuji Film Wako Pure Chemical Industries, Ltd.) was added to 100 parts by mass of the total amount of the monomers a to c. The emulsion of the above-mentioned monomers a to c was continuously added dropwise to this mixture over 4 hours, and the polymerization was carried out at a polymerization temperature of 80°C. After completion of the dropping, aging reaction was performed for 2 hours to obtain a (meth)acrylic acid ester polymer emulsion (E-1). The solid content concentration of this (meth)acrylic acid ester polymer emulsion (E-1) was 60% by mass, and the glass transition temperature of the resin was -12°C.

[Synthesis Example 2] (Synthesis of (meth)acrylic acid ester polymer emulsion (E-2))
Monomer a: 82 parts by mass of butyl acrylate, monomer b: 17 parts by mass of methyl methacrylate, monomer c: 1 part by mass of acrylic acid (80% by mass acrylic acid aqueous solution) (acrylic acid actual amount conversion), Emulsifier: 4 parts by mass of "NeoPerex G-25" manufactured by Kao Co., Ltd. and 27 parts by mass of deionized water were charged and emulsified by stirring for 10 minutes.
Separately from this, 37.2 parts by mass of deionized water and 0.15 parts by mass of an emulsifier (“NeoPerex G-25” manufactured by Kao Corporation) are used with respect to 100 parts by mass of the total amount of the monomers a to c. The mixture was charged, the mixture was stirred, the atmosphere was replaced with nitrogen, and the temperature was raised to 75°C. Next, 0.28 parts by mass of a radical polymerization initiator: sodium persulfate (Fuji Film Wako Pure Chemical Industries, Ltd.) was added to 100 parts by mass of the total amount of the monomers a to c. The emulsion of the above-mentioned monomers a to c was continuously added dropwise to this mixture over 4 hours, and the polymerization was carried out at a polymerization temperature of 80°C. After the dropwise addition was completed, a maturing reaction was performed for 2 hours to obtain a (meth)acrylic acid ester polymer emulsion (E-2). The solid content concentration of this (meth)acrylic acid ester polymer emulsion (E-2) was 60% by mass, and the glass transition temperature of the resin was -36°C.

[Synthesis Example 3] (Synthesis of (meth)acrylic acid ester polymer emulsion (E-3))
Monomer a: 81 parts by mass of ethyl acrylate, Monomer b: 18 parts by mass of methyl methacrylate, Monomer c: 1 part by mass of acrylic acid (80% by mass aqueous acrylic acid solution) (acrylic acid actual amount conversion), Emulsifier: 4 parts by mass of "NeoPerex G-25" manufactured by Kao Co., Ltd. and 27 parts by mass of deionized water were charged and emulsified by stirring for 10 minutes.
Separately from this, 37.2 parts by mass of deionized water and 0.15 parts by mass of an emulsifier (“NeoPerex G-25” manufactured by Kao Corporation) are used with respect to 100 parts by mass of the total amount of the monomers a to c. The mixture was charged, the mixture was stirred, the atmosphere was replaced with nitrogen, and the temperature was raised to 75°C. Next, 0.28 parts by mass of a radical polymerization initiator: sodium persulfate (Fuji Film Wako Pure Chemical Industries, Ltd.) was added to 100 parts by mass of the total amount of the monomers a to c. The emulsion of the above-mentioned monomers a to c was continuously added dropwise to this mixture over 4 hours, and the polymerization was carried out at a polymerization temperature of 80°C. After the dropwise addition was completed, a maturing reaction was performed for 2 hours to obtain a (meth)acrylic acid ester polymer emulsion (E-3). The solid content concentration of this (meth)acrylic acid ester polymer emulsion (E-3) was 60% by mass, and the glass transition temperature of the resin was -5°C.

[Manufacture of multi-layer sound absorbing material]
[Example 1]
The multilayer sound absorbing material (S-1) was manufactured by the following procedure.
(Mechanical foaming process)
To the (meth)acrylic acid ester polymer emulsion (E-1), 1% by mass of a thickening agent ("PG-13" manufactured by E-Tech) and a foam stabilizer ("Nopco DC-100-A" manufactured by San Nopco). 4% by mass was added, and the mixture was stirred uniformly with a stirrer for 10 minutes.
Next, using a batch type foaming machine (“Mixing stirrer 5DM-r” manufactured by Dalton, stirrer: whipper), foaming was performed for 5 minutes at a stirring rotation speed of 125 rpm in the atmosphere at room temperature of about 23° C., and a specific gravity of 0. A mechanical foaming liquid of the (meth)acrylic acid ester polymer emulsion (E-1) of 3 was obtained.

(Coating process)
A spacer frame (thickness: 5 mm) for thickness setting is placed on the surface of the non-woven fabric (N-1) as a base material layer, the mechanical foaming liquid of the emulsion (E-1) obtained above is poured, and then a stainless steel ruler. Excessive foaming liquid was scraped off along with the thickness of the spacer by using to coat it with a thickness of 5 mm.

(Heating and drying process)
By using a hot air circulation type oven (“DH611” manufactured by Yamato Scientific Co., Ltd.), the laminate including the formed coating layer is heated and dried for 20 minutes at a temperature of 150° C. and a damper opening of 50%. A multilayer sound absorbing material (S-1) was obtained. The foam layer thus formed had a thickness of 4.9 mm and a density of 161 kg/m ³ .

[Example 2]
(Mechanical foaming process)
In the same manner as in Example 1 above, a mechanical foaming liquid of the (meth)acrylic acid ester polymer emulsion (E-1) was obtained.
(Coating process)
A non-woven fabric (N-2) was used as the base material layer, and a 2 mm thick coating was applied in the same manner as in Example 1 except that the spacer frame had a thickness of 2 mm.
(Heating and drying process)
A multilayer sound absorbing material (S-2) was obtained in the same manner as in Example 1 except that the heating and drying time was 10 minutes. The foam layer thus formed had a thickness of 2.1 mm and a density of 158 kg/m ³ .

[Example 3]
(Mechanical foaming process)
In the same manner as in Example 1 above, a mechanical foaming liquid of the (meth)acrylic acid ester polymer emulsion (E-1) was obtained.
(Coating process)
A non-woven fabric (N-3) was used as the base material layer, and a 7 mm thick coating was applied in the same manner as in Example 1 except that the spacer frame had a thickness of 7 mm.
(Heating and drying process)
A multilayer sound absorbing material (S-3) was obtained in the same manner as in Example 1 except that the heating and drying time was 30 minutes. The formed foam layer had a thickness of 6.9 mm and a density of 155 kg/m ³ .

[Example 4]
(Mechanical foaming process)
A mechanical foaming liquid of the (meth)acrylic acid ester polymer emulsion (E-2) was prepared in the same manner as in Example 1 except that the (meth)acrylic acid ester polymer emulsion (E-2) was used. Obtained.
(Coating process)
A 5 mm-thick coating was carried out in the same manner as in Example 1 except that the mechanical foaming liquid of the (meth)acrylic acid ester polymer emulsion (E-2) was used.
(Heating and drying process)
A multilayer sound absorbing material (S-4) was obtained in the same manner as in Example 1 above. The foam layer thus formed had a thickness of 5.2 mm and a density of 165 kg/m ³ .

[Example 5]
(Mechanical foaming process)
A mechanical foaming liquid of the (meth)acrylic acid ester polymer emulsion (E-3) was prepared in the same manner as in Example 1 except that the (meth)acrylic acid ester polymer emulsion (E-3) was used. Obtained.
(Coating process)
It was applied to a thickness of 5 mm in the same manner as in Example 1 except that the mechanical foaming liquid of the (meth)acrylic acid ester polymer emulsion (E-3) was used.
(Heating and drying process)
A multilayer sound absorbing material (S-5) was obtained in the same manner as in Example 1 above. The foam layer thus formed had a thickness of 4.9 mm and a density of 161 kg/m ³ .

[Example 6]
(Mechanical foaming process)
A (meth)acrylic acid ester polymer emulsion (E-1) having a specific gravity of 0.17 was prepared in the same manner as in Example 1 except that foaming was carried out for 6 minutes at a stirring rotation speed of 250 rpm in a batch type foaming machine. A mechanical foaming liquid of
(Coating process)
A 5 mm-thick coating was performed in the same manner as in Example 1 except that the mechanical foaming liquid having a specific gravity of 0.17 of the (meth)acrylic acid ester polymer emulsion (E-1) was used.
(Heating and drying process)
A multilayer sound absorbing material (S-6) was obtained in the same manner as in Example 1 above. The foam layer thus formed had a thickness of 5.0 mm and a density of 98 kg/m ³ .

[Example 7]
(Mechanical foaming process)
A (meth)acrylic acid ester polymer emulsion (E-1) having a specific gravity of 0.45 was prepared in the same manner as in Example 1 except that foaming was carried out for 3 minutes at 125 rpm with a batch type foaming machine. A mechanical foaming liquid of
(Coating process)
A 5 mm-thick coating was carried out in the same manner as in Example 1 except that the mechanical foaming liquid having a specific gravity of 0.45 of the (meth)acrylic acid ester polymer emulsion (E-1) was used.
(Heating and drying process)
A multilayer sound absorbing material (S-7) was obtained in the same manner as in Example 1 except that the heating and drying time was 40 minutes. The foamed layer thus formed had a thickness of 4.9 mm and a density of 263 kg/m ³ .

[Example 8]
(Mechanical foaming process)
A (meth)acrylic acid ester polymer emulsion (E-1) having a specific gravity of 0.12 was prepared in the same manner as in Example 1 except that the foaming was performed for 8 minutes at 250 rpm with a batch type foaming machine. A mechanical foaming liquid of
(Coating process)
A 5 mm-thick coating was carried out in the same manner as in Example 1 except that the mechanical foaming liquid having a specific gravity of 0.12 of the (meth)acrylic acid ester polymer emulsion (E-1) was used.
(Heating and drying process)
A multilayer sound absorbing material (S-8) was obtained in the same manner as in Example 1 except that the heating and drying time was 15 minutes. The foam layer thus formed had a thickness of 5.1 mm and a density of 71 kg/m ³ .

[Example 9]
(Mechanical foaming process)
A (meth)acrylic acid ester polymer emulsion (E-1) having a specific gravity of 0.55 was prepared in the same manner as in Example 1 except that foaming was carried out for 2 minutes at a stirring rotation speed of 125 rpm in a batch type foaming machine. A mechanical foaming liquid of
(Coating process)
A 5 mm-thick coating was performed in the same manner as in Example 1 except that the mechanical foaming liquid having a specific gravity of 0.55 of the (meth)acrylic acid ester polymer emulsion (E-1) was used.
(Heating and drying process)
A multilayer sound absorbing material (S-9) was obtained in the same manner as in Example 1 except that the heating and drying time was 60 minutes. The foam layer thus formed had a thickness of 4.8 mm and a density of 331 kg/m ³ .

[Comparative Example 1]
(Mechanical foaming process)
In the same manner as in Example 1 above, a mechanical foaming liquid of the (meth)acrylic acid ester polymer emulsion (E-1) was obtained.
(Coating process)
A non-woven fabric (N-4) was used as the base material layer, and a 1 mm-thick coating was performed in the same manner as in Example 1 except that a spacer frame having a thickness of 1 mm was used.
(Heating and drying process)
A multilayer sound absorbing material (CS-1) was obtained in the same manner as in Example 1 except that the heating and drying time was 10 minutes. The foam layer thus formed had a thickness of 1.0 mm and a density of 163 kg/m ³ .

[Comparative example 2]
(Mechanical foaming process)
In the same manner as in Example 1 above, a mechanical foaming liquid of the (meth)acrylic acid ester polymer emulsion (E-1) was obtained.
(Coating process)
A non-woven fabric (N-5) was used as a base material layer, and a spacer frame having a thickness of 9 mm was used, and applied in a thickness of 9 mm in the same manner as in Example 1 above.
(Heating and drying process)
A multilayer sound absorbing material (CS-2) was obtained in the same manner as in Example 1 except that the heating and drying time was 80 minutes. The foam layer thus formed had a thickness of 9.2 mm and a density of 165 kg/m ³ .

<Evaluation>
The sound absorption characteristics and the productivity of the obtained multilayer sound absorbing material were evaluated by the following methods. The evaluation results are also shown in Table 1 below.

[Sound absorption characteristics]
The sound absorption characteristics of the multilayer sound absorbing material were measured according to JIS-A1405-2 using an acoustic tube. The frequency was measured at 315 Hz to 5000 Hz, and the sound absorption coefficient of 3000 Hz was used for the sound absorption characteristic determination.
The sound absorption characteristics are "A (good)" when the sound absorption rate (3000 Hz) is 70% or more, "B (somewhat good)" when 30% or more and less than 70%, and "C" when less than 30%. (Defective)" can be evaluated.

[Productivity]
Regarding the productivity of the multilayer sound absorbing material, the time required in the heating and drying process was evaluated. The necessary time in the heating and drying step means the time required until the dispersion medium is substantially not contained in the foam layer.
Productivity is "A (good)" when the required time is 50 minutes or less, "B (somewhat good)" when the required time is more than 50 minutes and 70 minutes or less, and "C (poor) when the required time is more than 70 minutes. )” was evaluated.

From the results in Table 1, it was shown that the multilayer sound absorbing materials of Examples had excellent sound absorbing properties and excellent productivity. On the other hand, the multi-layered sound absorbing material of the comparative example has insufficient sound absorbing properties or low productivity.

The multi-layer sound absorbing material of the present invention has excellent sound absorbing properties and excellent productivity. According to the method for manufacturing a multilayer sound absorbing material of the present invention, the multilayer sound absorbing material having excellent sound absorbing characteristics can be manufactured with high productivity.

1 Multi-layer sound absorbing material 2 Base material layer 3 Foaming layer

Claims (6)

A breathable substrate layer,
A foam layer laminated on the base material layer,
The foamed layer is composed of a heat-dried body of mechanically foamed (meth)acrylic acid ester polymer emulsion,
A multilayer sound-absorbing material, wherein the ratio of the thickness of the foam layer to the thickness of the base layer is 20/80 or more and 85/15 or less. The multilayer sound absorbing material according to claim 1, wherein the base material layer is formed of a nonwoven fabric of thermoplastic organic fibers. The multi-layered sound absorbing material according to claim 1 or 2, wherein a glass transition point of the resin constituting the (meth)acrylic acid ester polymer emulsion is -45°C or higher and 10°C or lower. The multi-layer sound absorbing material according to claim 1, claim 2 or claim 3, having an air permeability of 5 cm ³ /cm ² ·s or more and 40 cm ³ /cm ² ·s or less. The multilayer sound absorbing material according to any one of claims 1 to 4, wherein the foam layer has a density of 60 kg/m ³ or more and 300 kg/m ³ or less. A method for producing a multilayer sound absorbing material according to any one of claims 1 to 5,
A step of mechanically foaming a (meth)acrylic acid ester polymer emulsion,
A step of applying the mechanically foamed (meth)acrylic acid ester polymer emulsion obtained by the mechanical foaming step to one surface of the breathable base material layer;
And a step of heating and drying the coating layer formed by the coating step described above.

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