Porous sound-absorbing material and sound-absorbing method

Abstract

The average cell diameter is 100 to 600 μm, and the apparent density is 40 to 140 kg / m 3 A porous sound-absorbing material. A sound-absorbing method using the porous sound-absorbing material.

Description

[Technical Field]

[0001] The present invention relates to a porous sound-absorbing material, a method for manufacturing the same, and a sound-absorbing method. [Background technology]

[0002] Conventionally, fiber materials such as glass wool, and foam materials such as polystyrene foam, polyurethane foam, and polyethylene foam have been used as sound-absorbing materials ("foam" is also called "foamed material"). For example, it is known to use a propylene-based resin containing a propylene-ethylene copolymer and having a melting temperature in the range of 60 to 100°C as a sound-absorbing material (see, for example, Patent Document 1 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5208818 Summary of the Invention [Problem to be solved by the invention]

[0004] The human audible frequency range, although subject to individual differences, is generally said to be from about 20 Hz to about 20,000 Hz. To reduce unpleasant sounds experienced by humans in buildings, vehicles, airplanes, and the like (particularly so-called road noise that invades the interior of a moving automobile), there has been a demand in recent years for sound-absorbing materials to absorb sounds in the low-frequency range (for example, frequencies below 1,000 Hz). While increasing the thickness or weight of the sound-absorbing material (increasing the mass density of the sound-absorbing material) is effective in improving the sound-absorbing properties in the low-frequency range, these methods have the problem of limiting the applications and / or locations of use of the sound-absorbing material. Therefore, there is a demand for sound-absorbing materials to maintain sufficient sound-absorbing properties even when they are made thinner or lighter by improving their sound-absorbing properties.

[0005] One aspect of the present invention aims to provide a porous sound-absorbing material that can achieve excellent sound-absorbing characteristics in the low-frequency range. Another aspect of the present invention aims to provide a sound-absorbing method that uses the porous sound-absorbing material. Another aspect of the present invention aims to provide a manufacturing method for a porous sound-absorbing material that can obtain the porous sound-absorbing material. [Means for solving the problem]

[0006] In one aspect of the present invention, the average cell diameter is 100 to 600 μm and the apparent density is 40 to 140 kg / m 3 The present invention provides a porous sound-absorbing material, which is formed by foaming a foamable composition containing at least one selected from the group consisting of a resin material and an elastomer, and a foaming agent, and then compressing the foam to open up some or all of the closed cells contained in the foam and obtain open cells. Another aspect of the present invention provides a sound-absorbing method using the porous sound-absorbing material. Another aspect of the present invention provides a method for producing the porous sound-absorbing material, which includes foaming a foamable composition containing at least one selected from the group consisting of a resin material and an elastomer, and a foaming agent, to obtain a foam, and then compressing the foam to open up some or all of the closed cells contained in the foam and obtain open cells.

[0007] The porous sound-absorbing material, the manufacturing method thereof, and the sound-absorbing method described above can provide excellent sound-absorbing properties in the low-frequency range. Furthermore, because the excellent sound-absorbing properties can be obtained, sufficient sound-absorbing properties can be maintained even when the sound-absorbing material is made thinner or lighter. [Effects of the Invention]

[0008] According to each aspect of the present invention, excellent sound absorption characteristics can be obtained in the low frequency range. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments and can be practiced with various modifications within the scope of the gist. The materials exemplified in this specification may be used singly or in combination of two or more. In this specification, when multiple substances corresponding to each component are present in the composition, the amount of each component used refers to the total amount of the multiple substances present in the composition, unless otherwise specified. "(Meth)acrylic acid" refers to at least one of acrylic acid and the corresponding methacrylic acid. In this specification, the symbol "to" indicating a numerical range indicates a range from the number immediately preceding "to" to the number immediately following "to". For example, when it is written as "numerical value x to numerical value y" (where x and y are numerical values), it means a range of "x or more and y or less".

[0010] The porous sound-absorbing material according to this embodiment has an average cell diameter (average pore diameter) of 100 to 600 μm and an apparent density of 40 to 140 kg / m 3 By using such a porous sound-absorbing material (low-frequency sound-absorbing material), it is possible to obtain excellent sound-absorbing characteristics (sound absorption properties) in the low-frequency range. According to this embodiment, it is possible to obtain excellent sound-absorbing characteristics in the frequency range of, for example, 1000 Hz or less, and in particular, excellent sound-absorbing characteristics in the frequency range of 500 Hz or less.

[0011] According to this embodiment, excellent sound absorption characteristics can be obtained, and sufficient sound absorption characteristics can be maintained even when the sound-absorbing material is made thinner or lighter. Therefore, according to this embodiment, excellent sound absorption characteristics in the low-frequency range can be achieved while also being made thinner and lighter. Therefore, according to this embodiment, a wide variety of uses and locations for the sound-absorbing material can be ensured. Furthermore, according to this embodiment, excellent sound absorption characteristics can be obtained by using only the porous sound-absorbing material as a single material. According to this embodiment, it is possible to provide applications for porous bodies to absorb sound.

[0012] This embodiment has excellent sound absorption characteristics in the low frequency range, and can therefore be suitably used as a soundproofing material (sound absorbing and insulating material) in vehicles (automobiles, trains, etc.), aircraft, buildings, piping, and the like.

[0013] By having an average cell diameter of 100 μm or more in the porous sound-absorbing material according to this embodiment, excellent sound-absorbing properties can be obtained and size control can be suitably performed during the manufacturing process of the porous sound-absorbing material. From the viewpoint of easily obtaining excellent sound-absorbing properties and easily controlling size during the manufacturing process of the porous sound-absorbing material, the average cell diameter of the porous sound-absorbing material is preferably 150 μm or more, more preferably 200 μm or more, even more preferably 250 μm or more, particularly preferably 300 μm or more, and extremely preferably 350 μm or more. By having an average cell diameter of 600 μm or less in the porous sound-absorbing material according to this embodiment, excellent sound-absorbing properties can be obtained. From the viewpoint of easily obtaining excellent sound-absorbing properties, the average cell diameter of the porous sound-absorbing material is preferably 550 μm or less, more preferably 500 μm or less, even more preferably 450 μm or less, and particularly preferably 400 μm or less. The average cell diameter of a porous sound-absorbing material can be measured by image analysis of an image of any cross section of the porous sound-absorbing material, and even if the porous sound-absorbing material contains open cells as described below, the average cell diameter of the porous sound-absorbing material can be measured in a similar manner.

[0014] The apparent density of the porous sound-absorbing material according to this embodiment is 40 kg / m 3 By satisfying this condition, the amount of air in the porous sound-absorbing material is prevented from increasing, and excellent sound-absorbing properties are obtained. The apparent density of the porous sound-absorbing material is set to 45 kg / m3, which is the most preferable value from the viewpoint of easily obtaining excellent sound-absorbing properties. 3 More than 50 kg / m is preferable. 3 More preferably, 55 kg / m 3 More preferably, 60 kg / m 3 More than 65 kg / m is particularly preferred. 3 More than 70 kg / m is highly preferable. 3 Highly preferred, 75 kg / m 3 More preferably, 80 kg / m 3The above is even more preferable. The apparent density of the porous sound-absorbing material according to this embodiment is 140 kg / m 3 By satisfying the above condition, excellent sound absorbing properties can be obtained. In addition, excellent lightness (e.g., lightness for vehicle use) and secondary processability can be obtained, and suitable open cells can be obtained. From the viewpoint of easily obtaining excellent sound absorbing properties, easily obtaining excellent lightness and secondary processability, and easily obtaining suitable open cells, the apparent density of the porous sound absorbing material is set to 135 kg / m 3 Preferably less than 130 kg / m 3 Less than 120 kg / m is more preferable. 3 More preferably, 110 kg / m or less 3 Particularly preferred is 100 kg / m 3 Less than 90 kg / m is highly preferred 3 Less than 85 kg / m is highly preferred 3 The following is even more preferable: The apparent density of the porous sound-absorbing material can be measured in accordance with JIS K 6767 (1999) "Foamed plastics - Polyethylene - Testing method."

[0015] The average cell diameter and apparent density of the porous sound-absorbing material can be adjusted by the blending ratio of the foaming agent (for example, an organic foaming agent or an inorganic foaming agent) described below, the vulcanization foaming time, the foaming temperature, and the like.

[0016] The porous sound-absorbing material according to this embodiment is a porous body. "Porous" refers to a form (for example, a foam form) in which a large number of holes (voids) are present in a base material, which will be described later, and in this specification, each hole is referred to as a "cell." The cells do not necessarily have to be spherical, and may be irregular in shape.

[0017] The cells contained in the porous sound-absorbing material may be cells of a closed cell structure (closed cells) in which each cell is arranged independently, or may be cells of an open cell structure (open cells) in which a plurality of cells are interconnected. The porous sound-absorbing material may contain at least one of closed cells and open cells, and in this case, there are no particular restrictions on the numerical ratio of the closed cells to the open cells. That is, the porous sound-absorbing material (porous body) may have an open cell structure or a semi-open, semi-closed cell structure. An open cell structure refers to a structure in which the open cell ratio is 100%. A semi-open, semi-closed cell structure refers to a structure in which the lower limit of the open cell ratio exceeds 0% (preferably the open cell ratio is 10% or more) and the upper limit of the open cell ratio is less than 100%.

[0018] Methods for producing closed or open cells are not particularly limited. Examples of methods for imparting porosity through foaming include adjusting the type or amount of foaming agent, crosslinking agent, etc., adjusting processing conditions during the foaming process, and mechanically destroying the membranes (cell membranes) between closed cells to connect some or all of the cells. The air permeability and open-cell structure can be improved by, for example, subjecting the resulting porous body (e.g., a sheet-like foam) to compressive deformation using a constant-speed twin roll roller to destroy the cell membranes and thereby interconnect the cells. The interconnection of cells can also be promoted by drilling numerous small holes in the surface of the foam (foam). Small holes can also be drilled in the surface of the foam (foam) by providing numerous small needles on the surface of the constant-speed twin roll roller or by positioning a roll equipped with numerous small needles before and / or after the constant-speed twin roll roller.

[0019] The shape of the porous sound-absorbing material according to this embodiment is not particularly limited, and may be either a fixed shape or an irregular shape. Examples of the shape of the porous sound-absorbing material include a sheet, a columnar shape (a circular cylinder, a polygonal column, etc.), a cone, a polygonal pyramid, a rod, etc.

[0020] The air permeability of the porous sound-absorbing material according to this embodiment is preferably in the following range: The air permeability of the porous sound-absorbing material is preferably in the range of 0.1 cm or less, from the viewpoint that a decrease in viscous friction between sound and air is suppressed and the desired sound absorption characteristics are easily obtained.3 / cm 2 · s or more is preferable, 0.3 cm 3 / cm 2 · s or more is preferable, 0.4 cm 3 / cm 2 · s or more is more preferable, 0.5 cm 3 / cm 2 ·s or more is particularly preferable, 0.8cm 3 / cm 2 ·s or more is highly preferable, 1cm 3 / cm 2 · s or more is highly preferred, 1.2cm 3 / cm 2 · s or more is more preferable, 1.5cm 3 / cm 2 · s or more is more preferable, 1.8 cm 3 / cm 2 The air permeability of the porous sound-absorbing material is particularly preferably 50 cm s or more, from the viewpoint that deterioration of sound absorption characteristics in the low frequency range (for example, deterioration of sound absorption characteristics in the low frequency range due to an increase in the amount of gas in the porous material or an increase in the cell diameter) is easily suppressed. 3 / cm 2 · s or less is preferable, 40 cm 3 / cm 2 · s or less is preferable, 30cm 3 / cm 2 · s or less is more preferable, 20 cm 3 / cm 2 ·s or less is particularly preferable, and 10cm 3 / cm 2 · s or less is highly preferable, 8cm 3 / cm 2 · s or less is highly preferred, 5cm 3 / cm 2 · s or less is more preferable, 3 cm 3 / cm 2 ·s or less is more preferable, 2cm 3 / cm 2 From these viewpoints, the air permeability of the porous sound absorbing material is preferably 0.1 to 50 cm 3 / cm 2 ·s is preferred, 0.1 to 40 cm 3 / cm 2·s is more preferable, 0.5 to 40 cm 3 / cm 2 ·s is even more preferable. The air permeability of a porous sound-absorbing material can be measured by measuring the air flow rate when a certain differential pressure is applied to a test piece, and can be measured in accordance with Method A of JIS L 1096 (2010) "Testing methods for woven and knitted fabrics." The air permeability of a porous sound-absorbing material can be adjusted by the average cell diameter, the degree of open cell formation, the blending ratio of a foaming agent (e.g., an organic foaming agent or an inorganic foaming agent) described below, the vulcanization foaming time, the foaming temperature, etc.

[0021] The thickness of the porous sound-absorbing material according to this embodiment is preferably 5 mm or more, more preferably 8 mm or more, even more preferably 10 mm or more, particularly preferably more than 10 mm, extremely preferably 12 mm or more, very preferably 15 mm or more, even more preferably 18 mm or more, and even more preferably 20 mm or more, from the viewpoint of easily suppressing deterioration in secondary processability and easily suppressing increase in mass, preferably 50 mm or less, more preferably 40 mm or less, even more preferably 30 mm or less, and particularly preferably 25 mm or less. From these viewpoints, the thickness of the porous sound-absorbing material is preferably 5 to 50 mm, more preferably 15 to 40 mm. The thickness of the porous sound-absorbing material can be measured in accordance with ISO 1923 (1981) "Foam plastics and rubber - Measurement of linear dimensions." The thickness of the porous sound-absorbing material may be the thickness of a sheet-shaped porous sound-absorbing material. The thickness of the porous sound-absorbing material may be an average thickness.

[0022] The porous sound-absorbing material according to this embodiment may contain at least one base material selected from the group consisting of resin materials and elastomers.

[0023] Examples of resin materials include polyolefins; polystyrene; acrylic resins such as polymethyl methacrylate and styrene-(meth)acrylic acid ester copolymers; styrene-butadiene copolymers; polyvinyl acetate; polyvinyl alcohol; polyvinyl acetal; polyvinylpyrrolidone; petroleum resins; cellulose; cellulose derivatives such as cellulose acetate, cellulose nitrate, methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose; aromatic polyesters such as saturated alkyl polyesters, polyethylene terephthalate, polybutylene terephthalate, and polyarylate; polyamides; polyacetals; polycarbonates; polyethersulfones; polyphenylene sulfide; polyether ether ketones; and copolymers having structural units derived from vinyl polymerizable monomers and structural units derived from nitrogen-containing vinyl monomers.

[0024] The resin material preferably contains polyolefin, which facilitates obtaining excellent sound absorption properties. Examples of polyolefin include polyethylene (low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, linear very low-density polyethylene, etc.), ethylene-propylene block copolymer, ethylene-propylene random copolymer, ethylene-butene block copolymer, ethylene-butene random copolymer, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, ionomer resin in which ethylene-methacrylic acid copolymer molecules are crosslinked with metal ions, propylene homopolymer, propylene-ethylene random copolymer, propylene-butene random copolymer, propylene-butene block copolymer, polybutene, polypentene, propylene-ethylene-butene terpolymer, propylene-acrylic acid copolymer, propylene-maleic anhydride copolymer, alkylphenol-formaldehyde resin, and melamine-formaldehyde condensate.

[0025] The resin material preferably contains polyethylene, from the viewpoint of easily obtaining excellent sound absorption properties. One type of resin material may be used alone, or two or more types may be used in combination.

[0026] Examples of elastomers include acrylonitrile-butadiene rubber (NBR), hydrogenated acrylonitrile-butadiene rubber (HNBR), carboxylated acrylonitrile-butadiene rubber (XNBR), acrylonitrile-butadiene-isoprene rubber (NBIR), acrylonitrile-isoprene rubber (NIR), chloroprene rubber (CR), isoprene rubber (IR), butyl rubber (IIR), natural rubber (NR), styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), ethylene-propylene-diene rubber (EPDM), urethane rubber, fluororubber, acrylic rubber, and silicone rubber.

[0027] From the viewpoint of excellent foaming properties, the elastomer preferably contains at least one selected from the group consisting of chloroprene rubber, natural rubber, and ethylene-propylene-diene rubber. One type of elastomer may be used alone, or two or more types may be used in combination.

[0028] The content of the base material is preferably in the following range based on the total mass of the porous sound-absorbing material. From the viewpoint of easily obtaining excellent sound-absorbing properties by ensuring sufficient energy attenuation when sound is incident, the content of the base material is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, particularly preferably 25% by mass or more, extremely preferably 30% by mass or more, and very preferably 35% by mass or more. From the viewpoint of easily obtaining excellent sound-absorbing properties, the content of the base material is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, particularly preferably 70% by mass or less, extremely preferably 60% by mass or less, extremely preferably 50% by mass or less, and even more preferably 40% by mass or less. From these viewpoints, the content of the base material is preferably 10 to 90% by mass. From the viewpoint of easily obtaining excellent sound-absorbing properties, the content of at least one selected from the group consisting of polyethylene, chloroprene rubber, and ethylene-propylene-diene rubber is preferably in the above-mentioned range based on the total mass of the porous sound-absorbing material.

[0029] The content of at least one material A selected from the group consisting of polyethylene, chloroprene rubber, and ethylene-propylene-diene rubber is preferably in the following range based on the total amount of the base material (the base material in the porous sound-absorbing material). From the viewpoint of easily obtaining excellent sound-absorbing properties, the content of material A is preferably 50% by mass or more, more preferably 55% by mass or more, even more preferably 60% by mass or more, particularly preferably 65% ​​by mass or more, extremely preferably 80% by mass or more, very preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and particularly preferably 99% by mass or more. The base material in the porous sound-absorbing material may be essentially made up of material A (100% by mass of the base material is essentially material A).

[0030] The porous sound-absorbing material according to this embodiment may contain a filler. The use of a filler can reinforce the porous sound-absorbing material (porous body). It can also improve the processability when manufacturing the porous sound-absorbing material and the sound-absorbing properties. The shape of the filler is not particularly limited, but it is generally a powder, and examples of such shapes include spherical and plate-like shapes. As the filler, an inorganic filler (inorganic filler) can be used. One type of filler may be used alone, or two or more types may be used in combination.

[0031] Examples of constituent materials of inorganic fillers include metal materials, oxides, nitrides, carbonates, metal hydroxides, carbon-based materials, talc, silicic acid and its salts (e.g., aluminum silicate), clay, mica powder, bentonite, etc. Examples of metal materials include simple metals, metal mixtures, alloys, etc. It is preferable that the inorganic filler contains at least one selected from the group consisting of metal materials, oxides, and carbonates.

[0032] The inorganic filler may be a metal filler containing a metal material. The metal filler may be a filler made of a metal material. Examples of metal materials include zinc (Zn), iron (Fe), tungsten (W), aluminum (Al), silicon (Si), titanium (Ti), copper (Cu), nickel (Ni), tin (Sn), silver (Ag), gold (Au), and alloys containing these metals. Examples of alloys include sendust (Fe-Si-Al alloy), iron alloys (excluding sendust, such as stainless steel), and tungsten alloys. From the viewpoint of easily obtaining excellent sound absorption properties, the inorganic filler preferably contains at least one selected from the group consisting of sendust, zinc alone, iron alloys, and tungsten alloys.

[0033] Examples of oxides include zinc oxide, silicon oxide (silica), lead monoxide, and composite oxides containing these oxides. Examples of nitrides include boron nitride, aluminum nitride, and composite nitrides containing these nitrides. Examples of carbonates include calcium carbonate (e.g., heavy calcium carbonate) and magnesium carbonate. Examples of metal hydroxides include calcium hydroxide, magnesium hydroxide, and aluminum hydroxide. Examples of carbon-based materials include acetylene black and carbon black (furnace black, ketjen black, etc.). From the viewpoint of easily obtaining excellent processability, it is preferable that the inorganic filler contains at least one selected from the group consisting of zinc oxide and calcium carbonate.

[0034] The specific gravity of the inorganic filler (e.g., metal filler) is preferably 4 or more, more preferably 5 or more, even more preferably 6 or more, particularly preferably 7 or more, and extremely preferably 8 or more, from the viewpoint of easily obtaining excellent sound absorption properties. The specific gravity of the inorganic filler is preferably 15 or less, more preferably 12 or less, even more preferably 11 or less, and particularly preferably 10 or less, from the viewpoint of easily obtaining excellent sound absorption properties. From these viewpoints, the specific gravity of the inorganic filler is preferably 4 to 15, more preferably 4 to 10. The specific gravity of the inorganic filler can be measured in accordance with JIS Z 8807 (2012) "Method for measuring density and specific gravity of solids."

[0035] The average particle size of the filler (e.g., inorganic filler such as metal filler) is preferably in the following range. From the viewpoint of easily kneading and dispersing the filler into other components (e.g., base material) during production of the porous body, the average particle size of the filler is preferably 1 μm or more, more preferably 3 μm or more, even more preferably 5 μm or more, particularly preferably 8 μm or more, and extremely preferably 10 μm or more. From the viewpoint of easily suppressing cell size enlargement of the porous body, the average particle size of the filler is preferably 50 μm or less, more preferably 40 μm or less, even more preferably 30 μm or less, particularly preferably 25 μm or less, extremely preferably 20 μm or less, extremely preferably less than 20 μm, even more preferably 15 μm or less, and even more preferably 12 μm or less. From these viewpoints, the average particle size of the filler is preferably 1 to 50 μm, more preferably 5 to 30 μm.

[0036] The content of the filler (e.g., inorganic filler) is preferably in the following range per 100 parts by mass of the base material. From the viewpoint of easily obtaining excellent strength of the porous sound-absorbing material, the content of the filler is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, particularly preferably 50 parts by mass or more, extremely preferably 70 parts by mass or more, very preferably 90 parts by mass or more, even more preferably more than 90 parts by mass, and still more preferably 100 parts by mass or more. From the viewpoint of easily obtaining excellent dispersibility in the base material, processability, and appearance of the porous sound-absorbing material, the content of the filler is preferably 200 parts by mass or less, more preferably 180 parts by mass or less, even more preferably 150 parts by mass or less, particularly preferably 120 parts by mass or less, and extremely preferably 110 parts by mass or less. The content of the filler may be less than 110 parts by mass. From these viewpoints, the content of the filler is preferably 10 to 200 parts by mass.

[0037] The content of the metal material (e.g., metal filler) is preferably within the following ranges per 100 parts by mass of the base material. The content of the metal material is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, particularly preferably 8 parts by mass or more, extremely preferably 10 parts by mass or more, very preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, even more preferably 25 parts by mass or more, and particularly preferably 30 parts by mass or more, from the viewpoint of easily obtaining an open-cell foam with excellent air permeability and easily obtaining excellent sound absorption properties, since the deterioration of secondary processability due to hardening of the porous body is easily suppressed. From these viewpoints, the content of the metal material is preferably 50 parts by mass or less, more preferably 45 parts by mass or less, even more preferably 40 parts by mass or less, and particularly preferably 35 parts by mass or less. From these viewpoints, the content of the metal material is preferably 1 to 50 parts by mass, more preferably 5 to 50 parts by mass. From the viewpoint of easily obtaining excellent sound absorption characteristics, it is preferable that the content of at least one selected from the group consisting of sendust, zinc element, iron alloy, and tungsten alloy be in the above-mentioned range relative to 100 parts by mass of the base material. The porous sound-absorbing material according to this embodiment does not need to contain a metal material (e.g., a metal filler), and the content of the metal material (e.g., a metal filler) may be 0.1 parts by mass or less, 0.01 parts by mass or less, or 0.001 parts by mass or less relative to 100 parts by mass of the base material.

[0038] The content of at least one metal material A selected from the group consisting of sendust, zinc elemental material, iron alloys, and tungsten alloys is preferably in the following range based on the total amount of the metal material (the metal material in the porous sound-absorbing material). From the viewpoint of easily obtaining excellent sound-absorbing properties, the content of metal material A is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, extremely preferably 98% by mass or more, and very preferably 99% by mass or more. The metal material in the porous sound-absorbing material may be essentially composed of metal material A (100% by mass of the metal material is essentially metal material A).

[0039] The oxide content and / or carbonate content (e.g., calcium carbonate) are preferably within the following ranges per 100 parts by mass of the base material. From the viewpoints of easily suppressing deterioration in secondary processability, easily obtaining cells with an open-cell structure excellent in air permeability, and easily obtaining excellent sound-absorbing properties, the oxide content and / or carbonate content is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, particularly preferably 25 parts by mass or more, extremely preferably 30 parts by mass or more, very preferably 50 parts by mass or more, even more preferably 60 parts by mass or more, even more preferably 70 parts by mass or more, particularly preferably 75 parts by mass or more, and extremely preferably more than 75 parts by mass. From the viewpoint of easily obtaining excellent sound-absorbing properties, the oxide content and / or carbonate content is preferably 100 parts by mass or less, more preferably less than 100 parts by mass, even more preferably 95 parts by mass or less, particularly preferably 90 parts by mass or less, extremely preferably 85 parts by mass or less, and extremely preferably 80 parts by mass or less. From these viewpoints, the oxide content and / or carbonate content is preferably 10 to 100 parts by mass.

[0040] The content of calcium carbonate is preferably in the following range based on the total amount of carbonate (carbonate in the porous sound-absorbing material). From the viewpoint of easily obtaining excellent sound-absorbing properties, the content of calcium carbonate is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, extremely preferably 98% by mass or more, and very preferably 99% by mass or more. The carbonate in the porous sound-absorbing material may be in an embodiment consisting essentially of calcium carbonate (100% by mass of the carbonate is essentially calcium carbonate).

[0041] The content of the filler (e.g., inorganic filler) is preferably in the following range based on the total mass of the porous sound-absorbing material. From the viewpoint of easily obtaining excellent sound-absorbing properties, the content of the filler is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, particularly preferably 25% by mass or more, extremely preferably 30% by mass or more, and very preferably 35% by mass or more. From the viewpoint of easily obtaining excellent sound-absorbing properties, the content of the filler is preferably 80% by mass or less, more preferably 70% by mass or less, even more preferably 60% by mass or less, particularly preferably 50% by mass or less, extremely preferably 45% by mass or less, and extremely preferably 40% by mass or less. From these viewpoints, the content of the filler is preferably 10 to 80% by mass.

[0042] The content of the metal material (e.g., metal filler) is preferably in the following range based on the total mass of the porous sound-absorbing material. From the viewpoint of easily obtaining excellent sound-absorbing properties, the content of the metal material is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, particularly preferably 8% by mass or more, and extremely preferably 10% by mass or more. From the viewpoint of easily obtaining excellent sound-absorbing properties, the content of the metal material is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, particularly preferably 20% by mass or less, extremely preferably 15% by mass or less, and extremely preferably 12% by mass or less. From these viewpoints, the content of the metal material is preferably 1 to 50% by mass. The porous sound-absorbing material according to this embodiment does not need to contain a metal material (e.g., a metal filler), and the content may be 0.1% by mass or less, 0.01% by mass or less, or 0.001% by mass or less, based on the total mass of the porous sound-absorbing material.

[0043] The oxide content and / or carbonate content (e.g., calcium carbonate) are preferably in the following ranges based on the total mass of the porous sound-absorbing material. From the viewpoints of easily suppressing deterioration in secondary processability, easily obtaining cells with an open-cell structure excellent in air permeability, and easily obtaining excellent sound-absorbing properties, the oxide content and / or carbonate content is preferably 5% by mass or more, more preferably 8% by mass or more, even more preferably 10% by mass or more, particularly preferably 15% by mass or more, extremely preferably 20% by mass or more, and very preferably 25% by mass or more. From the viewpoint of easily obtaining excellent sound-absorbing properties, the oxide content and / or carbonate content is preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, particularly preferably 35% by mass or less, and extremely preferably 30% by mass or less. From these viewpoints, the oxide content and / or carbonate content is preferably 5 to 50% by mass.

[0044] The content of the inorganic filler is preferably in the following range based on the total amount of filler (filler in the porous sound-absorbing material). From the viewpoint of easily obtaining excellent sound-absorbing properties, the content of the inorganic filler is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, extremely preferably 98% by mass or more, and very preferably 99% by mass or more. The filler in the porous sound-absorbing material may be in an embodiment where it is essentially composed of inorganic filler (100% by mass of the filler is essentially inorganic filler). From the viewpoint of easily obtaining excellent sound-absorbing properties, the content of the metal material, the content of the oxide, and / or the content of the carbonate (e.g., calcium carbonate) is preferably in the above-mentioned range based on the total amount of the filler.

[0045] From the viewpoint of easily obtaining excellent sound absorption characteristics, the porous sound-absorbing material according to this embodiment preferably contains at least one base material selected from the group consisting of resin materials and elastomers, and a metal filler, the content of the metal filler being 5 to 50 parts by mass per 100 parts by mass of the base material, the specific gravity of the metal filler being 4 to 10, and the average particle size of the metal filler being 5 to 30 μm.

[0046] The porous sound-absorbing material according to this embodiment may contain a softener. The use of a softener can improve processability. Examples of softeners include drying oils or animal and vegetable oils (e.g., linseed oil), petroleum-based oils (paraffinic process oil, naphthenic process oil, aromatic process oil, etc.), asphalts, low-molecular-weight polymers, organic acid esters (e.g., phthalate esters such as di-2-ethylhexyl phthalate (DOP) and dibutyl phthalate (DBP); phosphate esters; higher fatty acid esters; alkyl sulfonates), thickeners, etc. The softener preferably contains a petroleum-based oil, as this facilitates excellent foam processability. One softener may be used alone, or two or more softeners may be used in combination.

[0047] The content of the softener is preferably in the following ranges relative to 100 parts by mass of the base material. From the viewpoint of easily obtaining excellent foaming processability, the content of the softener is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more. The content of the softener may be 10 parts by mass or more, 20 parts by mass or more, 30 parts by mass or more, 40 parts by mass or more, or 50 parts by mass or more, or may even exceed 50 parts by mass. From the viewpoint of easily obtaining excellent foaming processability, the content of the softener is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, even more preferably 80 parts by mass or less, particularly preferably 70 parts by mass or less, and extremely preferably 60 parts by mass or less. The content of the softener may be less than 20 parts by mass. From these viewpoints, the content of the softener is preferably 1 to 100 parts by mass.

[0048] The porous sound-absorbing material according to this embodiment may contain a fatty acid. The fatty acid can be used as a processing aid. The use of a fatty acid can improve processability. The fatty acid can contain at least one selected from the group consisting of saturated fatty acids and unsaturated fatty acids. The number of carbon atoms in the fatty acid is preferably 8 to 30, more preferably 10 to 20, and even more preferably 15 to 18. Examples of the fatty acid include stearic acid, palmitic acid, and oleic acid. From the viewpoint of easily achieving excellent foam processability, the fatty acid preferably contains stearic acid. One type of fatty acid may be used alone, or two or more types may be used in combination.

[0049] The content of the fatty acid is preferably in the following ranges relative to 100 parts by mass of the base material. From the viewpoint of easily obtaining excellent foaming processability, the content of the fatty acid is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more. From the viewpoint of easily obtaining excellent foaming processability, the content of the fatty acid is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less. From these viewpoints, the content of the fatty acid is preferably 1 to 10 parts by mass.

[0050] The porous sound-absorbing material according to the present embodiment may contain any other additives depending on the purpose, such as lubricants, plasticizers, bubble nucleating agents, antioxidants, antioxidants, pigments, colorants, mildew inhibitors, flame retardants, ultraviolet absorbers, and light stabilizers.

[0051] The porous sound-absorbing material according to this embodiment may be a foam, and can be obtained by foaming a foaming composition (foamable composition) using a foaming agent. That is, this embodiment is a porous sound-absorbing material having an average cell diameter of 100 to 600 μm and an apparent density of 40 to 140 kg / m. 3 It is possible to provide a foam composition that gives a porous sound-absorbing material having the following properties. The foam composition according to this embodiment can contain the components of the porous sound-absorbing material and a foaming agent. In this embodiment, by foaming the foam composition, a porous sound-absorbing material having an average cell diameter of 100 to 600 μm and an apparent density of 40 to 140 kg / m can be obtained. 3It is possible to provide a method for producing a porous sound-absorbing material having the above structure. The expansion ratio (ratio of densities before and after foaming; apparent density after foaming) when foaming the foam composition to obtain a foam is preferably 5 to 30 times, more preferably more than 6 times but not more than 25 times, even more preferably 7 to 22 times, and particularly preferably 9 to 20 times, from the viewpoint of balancing weight reduction and average cell diameter of the porous sound-absorbing material. The expansion ratio may be less than 10 times.

[0052] The porous sound-absorbing material according to this embodiment can also be used by being integrated with other materials. For example, the sheet-shaped porous sound-absorbing material can be bonded to a rubber sheet, a resin sheet, a woven fabric, a nonwoven fabric, a gypsum board, a wooden board, a metal plate, or the like to be integrated.

[0053] There are no particular limitations on the method for producing the porous sound-absorbing material according to this embodiment. The method for producing the porous sound-absorbing material according to this embodiment is, for example, a method for producing a porous sound-absorbing material by foaming a foamable composition containing a base material (at least one selected from the group consisting of a resin material and an elastomer) and a foaming agent to obtain a foam (for example, a foam with an expansion ratio of 5 to 30 times), and then compressing the foam to open up some or all of the closed cells contained in the foam to obtain open cells. The foamable composition may contain fillers, processing aids, softeners, crosslinking agents, crosslinking accelerators, foaming aids, etc. as needed. When using a resin material and an elastomer as the base material, operating procedures, devices, etc. suitable for the base material can be appropriately selected.

[0054] The method for manufacturing the porous sound-absorbing material according to this embodiment includes, for example, a foam production step in which a foam is obtained by foaming a foamable composition containing a base material and a foaming agent, and a compression step (communication compression step) in which the foam is mechanically compressed.

[0055] The foam-forming step may include a composition-forming step of mixing a base material and a foaming agent to obtain a foamable composition, and a foaming step of foaming the foamable composition to obtain a foam.

[0056] The composition preparation process may include, in this order, a mastication process of masticating a base material to obtain a masticate (masticated base material), a first kneading process of mixing the masticate with an additive other than a foaming agent (for example, a filler such as a metal filler or calcium carbonate) to obtain a first kneaded product, and a second kneading process of mixing the first kneaded product with a foaming agent to obtain a foamable composition (second kneaded product).

[0057] When kneading the materials in each step, they can be kneaded using a roll kneader (also simply called a "roll"), a Banbury mixer, a kneader, a single-screw or twin-screw extruder, or the like. Furthermore, when forming a sheet, molding may be carried out batchwise using a press, a roll, or the like, or molding may be carried out using a calendar molding machine, an extruder equipped with a T-die, or the like, and a roll. Continuous sheet molding is possible by melt-mixing or dry-blending some or all of the materials to be kneaded in advance and feeding the mixture into a molding machine (for example, an extruder equipped with a T-die).

[0058] The mastication process is a pretreatment process in which a base material (especially an elastomer) is mechanically subjected to shear force using, for example, a mixing roll having three rolls, to appropriately plasticize the base material. The temperature at which mastication is carried out (roll surface temperature) is generally 20 to 200°C, although this depends on the hardness of the base material. The base material does not need to be masticated all at once, and the amount can be gradually increased as it is kneaded. Note that the mastication process may be omitted depending on the type or physical properties of the base material.

[0059] The first kneading step is a kneading step carried out to add additives other than the foaming agent to the masticated mixture. In the first kneading step, for example, a mixing roll having three rolls can be used. The first kneading step can also be carried out continuously from the mastication step. The temperature at which the first kneading step is carried out (roll surface temperature) is generally 20 to 200°C, depending on the hardness of the base material that is being mixed with additives other than the foaming agent. The additives other than the foaming agent do not need to be added all at once, and the amount of the additives other than the foaming agent can be gradually increased while kneading. Examples of additives other than the foaming agent include fillers, processing aids, softeners, etc.

[0060] After the first kneading step is completed and before the foaming step, a "heating step" can be carried out in which the surface temperature of the mixing roll is temporarily raised to a temperature higher than that at which the first kneading step was carried out, and then the temperature is lowered again to carry out kneading.

[0061] The second kneading step is a kneading step performed to add a blowing agent to the first kneaded material obtained in the first kneading step. The blowing agent does not need to be added all at once and may be added in stages. The blowing agent may be used in part or in its entirety in the form of a masterbatch. In the second kneading step, components that contribute to foaming or crosslinking, as described below, may be added in addition to the blowing agent. For example, a mixing roll having three rolls may be used in the second kneading step. The second kneading step may also be performed continuously from the first kneading step or the heat-up step. The temperature (roll surface temperature) at which the second kneading step is performed is generally 20 to 200°C, depending on the hardness of the second kneaded material that is incorporating the blowing agent. However, it is preferable to perform the second kneading step at as low a temperature as possible within a range that does not interfere with kneading, so as not to cause foaming before the foaming step.

[0062] The foaming step is a step of foaming the foamable composition (second kneaded product) obtained in the second kneading step to obtain a foam. In the foaming step, the foamable composition can be foamed by heating the foamable composition. In the foaming step, at least one of a foaming method in which the foamable composition is foamed in a closed mold frame and a foaming method in which the foamable composition is freely expanded and foamed can be performed. The foamable composition to be foamed may be, for example, a sheet obtained by molding the foamable composition into a sheet shape. As a foaming method in which the foamable composition is foamed in a closed mold frame, a method can be used in which the foamable composition is placed in a metal mold frame and then placed between the hot platens of a heating press to foam the foam. As a foaming method in which the foamable composition is freely expanded and foamed, a method can be used in which the foamable composition is placed directly in an oven and heated to foam.

[0063] The expansion ratio, average cell diameter, apparent density, and air permeability of a foam can be adjusted by the compounding ratio of various base materials, blowing agents, etc., when producing the foam, and by the conditions of kneading, foaming, etc. However, even when the same production method or equipment is used, the foaming phenomenon tends to be easily influenced by subtle factors (for example, the difference in the elapsed time from one step to the next), and also tends to be easily influenced by the size of the equipment, even though the operating principle is the same. Therefore, it may be difficult to obtain foams with exactly the same attributes. In such cases, the compounding composition or processing conditions can be adjusted by an operator with ordinary knowledge in the relevant technical field.

[0064] In the compression step (compression-interconnecting step), the foam is mechanically compressed to convert some or all of the closed cells contained in the foam into interconnected cells. In the compression step, the foam is compressed to mechanically destroy some of the walls of the cells (e.g., closed cells) contained in the foam, thereby interconnecting the cells so that multiple cells are interconnected. The compression step can be carried out by compressing the foam using a press, two-roll machine, or the like. The pressure applied to the foam or the number of presses can be adjusted depending on the desired foam.

[0065] The process from the mastication step to the compression step can be carried out separately for each step, or some or all of the steps may be carried out continuously. When some or all of the steps are carried out continuously, a continuous device capable of carrying out these steps continuously can be used.

[0066] The porous sound-absorbing material can be produced using a kneader and / or an extruder for kneading. For example, instead of previously charging the base material and materials other than the base material into the inlet of an extruder and performing the mastication step, the first kneading step, and the second kneading step using rolls, the steps corresponding to these steps can be essentially combined and continuously performed in a single extrusion kneading operation using an extruder. Alternatively, a resin material can be dry-blended in advance with a filler or the like, and the resulting mixture can be melt-kneaded in an extruder while suppressing foaming to obtain a foamable composition, and the foamable composition can then be subjected to the foam-making step and compression step similar to those for elastomers.

[0067] An example of the porous sound-absorbing material according to the present embodiment can be obtained as a sheet-like sound-absorbing material by a known sheet molding method using a T-die extruder, a calendering machine, or the like. For example, the porous sound-absorbing material can be obtained by adding a crosslinking agent and a blowing agent to polyethylene to obtain a foam composition, and extruding the resulting composition into a sheet at an extrusion temperature of 80 to 150°C. If necessary, additives such as foaming aids, processing aids, pigments, flame retardants, fillers, and softeners (as well as crosslinking accelerators, antioxidants, UV absorbers, light stabilizers, etc.) may be dry-blended in advance, and the resulting mixture may be supplied to the foam composition from the hopper of the T-die extruder. When dry-blending, some or all of the additives may be used in the form of a masterbatch. Furthermore, in the T-die extrusion and calendering, a foam composition may be used that has been previously melt-blended with some or all of the additives and polyethylene using a single-screw extruder, a twin-screw extruder, a Banbury mixer, a kneader, or the like.

[0068] Foaming agents are classified into solid compounds that decompose to generate gas; liquids that vaporize when heated; and inert gases that can be dissolved in a base material under pressure, and any of these can be used. Examples of foaming agents include organic foaming agents and inorganic foaming agents. One type of foaming agent may be used alone, or two or more types may be used in combination.

[0069] Examples of organic foaming agents include azo compounds, N-nitroso compounds, hydrazide compounds, semicarbazide compounds, fluorinated alkanes, and triazole compounds.

[0070] Examples of azo compounds include azodicarbonamide (ADCA), barium azodicarboxylate, azobisisobutyronitrile (AIBN), azocyclohexylnitrile, and azodiaminobenzene. Examples of N-nitroso compounds include N,N'-dinitrosopentamethylenetetramine (DTP), N,N'-dimethyl-N,N'-dinitrosoterephthalamide, and trinitrosotrimethyltriamine. Examples of hydrazide compounds include 4,4'-oxybis(benzenesulfonylhydrazide) (OBSH), paratoluenesulfonylhydrazide, diphenylsulfone-3,3'-disulfonylhydrazide, 2,4-toluenedisulfonylhydrazide, p,p-bis(benzenesulfonylhydrazide) ether, benzene-1,3-disulfonylhydrazide, and allylbis(sulfonylhydrazide). Examples of semicarbazide compounds include p-toluylenesulfonylsemicarbazide and 4,4'-oxybis(benzenesulfonylsemicarbazide). Examples of fluorinated alkanes include trichloromonofluoromethane and dichloromonofluoromethane. Examples of triazole compounds include 5-morpholyl-1,2,3,4-thiatriazole.

[0071] Examples of inorganic foaming agents include hydrogen carbonates such as sodium hydrogen carbonate and ammonium hydrogen carbonate; carbonates such as sodium carbonate and ammonium carbonate; nitrites such as sodium nitrite and ammonium nitrite; borohydrides such as sodium borohydride; and azides.

[0072] From the viewpoint of easily obtaining excellent foaming properties, the foaming agent preferably contains an organic foaming agent, more preferably contains at least one selected from the group consisting of azo compounds and N-nitroso compounds, and even more preferably contains at least one selected from the group consisting of azodicarbonamide (ADCA) and N,N'-dinitrosopentamethylenetetramine (DTP).

[0073] The amount of foaming agent used is preferably within the following ranges per 100 parts by mass of the base material. From the viewpoint of easily obtaining excellent foaming properties, the amount of foaming agent used is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more. The amount of foaming agent used may be 5 parts by mass or more, or 8 parts by mass or more. From the viewpoint of easily suppressing a decrease in rigidity of the porous sound-absorbing material due to excessive foaming, the amount of foaming agent used is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less. From these viewpoints, the amount of foaming agent used is preferably 1 to 20 parts by mass.

[0074] The foamable composition may contain components (excluding foaming agents) that contribute to foaming or crosslinking, and may also contain auxiliary additives. Examples of components that contribute to foaming or crosslinking include foaming aids, crosslinking agents, crosslinking accelerators, and crosslinking retarders. Examples of auxiliary additives include processing aids and softeners.

[0075] Examples of the foaming aid include urea compounds (for example, urea), salicylic acid compounds, and benzoic acid compounds.

[0076] The porous sound-absorbing material and / or the foamable composition according to the present embodiment may contain a crosslinking agent (vulcanizing agent), a crosslinking accelerator (vulcanization accelerator), a crosslinking retarder (vulcanization retarder), etc., from the viewpoint of easily controlling the foaming phenomenon and obtaining the desired average cell diameter. Each of the crosslinking agent, crosslinking accelerator, and crosslinking retarder may be used alone or in combination of two or more. When the porous sound-absorbing material and / or the foamable composition according to the present embodiment contains an elastomer (chloroprene rubber, ethylene-propylene-diene rubber, etc.), the porous sound-absorbing material and / or the foamable composition preferably contains at least one selected from the group consisting of a crosslinking agent and a crosslinking accelerator, and the crosslinking agent may be used in combination with a crosslinking accelerator and / or a crosslinking retarder as necessary.

[0077] The crosslinking agent may be selected appropriately depending on the type of base material, etc. Examples of crosslinking agents include sulfur, sulfur compounds (polysulfide, 4,4'-dithiodimorpholine, etc.), selenium, organic peroxides (cumene hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide, acetylacetone peroxide, etc.), polyamines, oximes (p-quinone dioxime, p,p'-dibenzoylquinone dioxime, etc.), nitroso compounds (e.g., p-dinitrosobenzine), ammonium salts (e.g., ammonium benzoate), and metal oxides (zinc oxide, magnesium oxide, etc.). Zinc oxide may be used as a crosslinking agent or as a filler.

[0078] Examples of crosslinking accelerators include thiazoles (2-mercaptobenzothiazole, dibenzothiazyl disulfide, etc.), dithiocarbamic acids (sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, etc.), guanidines (diphenylguanidine, di-o-tolylguanidine, etc.), sulfenamides (benzothiazyl-2-diethylsulfenamide, N-cyclohexyl-2-benzothiazylsulf benzonamide, etc.), thiurams (tetramethylthiuram monosulfide, tetramethylthiuram disulfide, etc.), xanthogenic acids (sodium isopropyl xanthogenate, zinc isopropyl xanthogenate, etc.), aldehyde ammonias (acetaldehyde ammonia, hexamentylenetetramine, etc.), aldehyde amines (n-butylaldehyde aniline, butylaldehyde monobutylamine, etc.), thioureas (diethylthiourea, trimethylthiourea, etc.).

[0079] The content of the crosslinking agent is preferably in the following ranges relative to 100 parts by mass of the base material. From the viewpoint of balancing foaming and crosslinking, the content of the crosslinking agent is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more. From the viewpoint of balancing foaming and crosslinking, the content of the crosslinking agent is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less. From these viewpoints, the content of the crosslinking agent is preferably 1 to 10 parts by mass.

[0080] The content of the crosslinking accelerator is preferably in the following ranges relative to 100 parts by mass of the base material. From the viewpoint of balancing foaming and crosslinking, the content of the crosslinking accelerator is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and particularly preferably 4 parts by mass or more. From the viewpoint of balancing foaming and crosslinking, the content of the crosslinking accelerator is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less. From these viewpoints, the content of the crosslinking accelerator is preferably 1 to 10 parts by mass.

[0081] The porous sound-absorbing material according to this embodiment may contain a crosslinking retarder (vulcanization retarder) as an additive that delays crosslinking (vulcanization) as opposed to a crosslinking accelerator, as necessary. Examples of crosslinking retarders include organic acids (phthalic anhydride, benzoic acid, salicylic acid, etc.) and amines (N-nitroso-diphenylamine, N-nitroso-phenyl-β-naphthylamine, etc.).

[0082] When a crosslinking retarder is used, the content of the crosslinking retarder is preferably in the following range relative to 100 parts by mass of the base material. From the viewpoint of balancing foaming and crosslinking, the content of the crosslinking retarder is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and particularly preferably 4 parts by mass or more. From the viewpoint of balancing foaming and crosslinking, the content of the crosslinking accelerator is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less.

[0083] The sound absorbing method according to this embodiment uses the porous sound absorbing material according to this embodiment to absorb sound of a target sound absorption. In the sound absorbing method according to this embodiment, sound can be absorbed by placing the porous sound absorbing material in the transmission path of the sound of the target sound absorption. In the sound absorbing method according to this embodiment, sound in a specific frequency range can be absorbed. The frequency range of the target sound absorption may be 1000 Hz or less (for example, 500 to 1000 Hz, or more than 500 Hz to 1000 Hz or less), or may be 500 Hz or less (for example, 300 to 500 Hz). The sound absorption coefficient of sound at 500 Hz or 1000 Hz is preferably 0.4 or more, more preferably 0.5 or more, and even more preferably 0.6 or more. [Example]

[0084] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0085] <Materials used> (Base material) Ethylene-propylene-diene rubber (hereinafter referred to as "EPDM"): "EMB-EPT4021" manufactured by Mitsui Chemicals, Inc. Chloroprene rubber (hereinafter referred to as "CR"): "Skyprene B-30" manufactured by Tosoh Corporation Low-density polyethylene (hereinafter referred to as "LDPE"): "LF640MA" manufactured by Japan Polyethylene Co., Ltd.

[0086] (filler) [Metal filler] Sendust A: Sanyo Special Steel Co., Ltd., Fe-Si-Al alloy powder, specific gravity: 8 g / cm 3 , average particle size: 10μm Sendust B: Sanyo Special Steel Co., Ltd., Fe-Si-Al alloy powder, specific gravity: 8 g / cm 3 , average particle size: 30μm Sendust C: Sanyo Special Steel Co., Ltd., Fe-Si-Al alloy powder, specific gravity: 8 g / cm 3 , average particle size: 5μm Zinc powder: Zinc powder manufactured by Wako Pure Chemical Industries, Ltd. Iron alloy powder: Mitsuwa Chemical Co., Ltd., "sus304L", stainless steel powder Tungsten alloy powder: Tungsten heavy metal powder [Other fillers] Calcium carbonate: "Whiten SB" manufactured by Shiraishi Calcium Co., Ltd. Zinc oxide for filler: Sakai Chemical Industry Co., Ltd., "Zinc Oxide Type 2"

[0087] The specific gravities of Sendust A to C were measured in accordance with JIS Z 8807 (2012) "Method for measuring density and specific gravity of solids."

[0088] The average particle diameters of Sendust A to C were measured using a scanning electron microscope (XL-30S°FEG, manufactured by PHILIPS). Specifically, first, photographs of Sendust were taken at 5,000 to 10,000 magnifications using the scanning electron microscope. The captured images were processed using image analysis software (IP-1000PC, manufactured by Asahi Kasei Engineering Corporation) to determine the circle-equivalent diameters of primary particles within a unit field of view, and then the arithmetic average was calculated. The number of particles observed was 30.

[0089] (processing aids) Stearic acid: NOF Corporation, "Sakura Stearic Acid Powder"

[0090] (softener) Process oil: Idemitsu Kosan Co., Ltd.'s "Diana Process Oil PW-90", a paraffin-based process oil

[0091] (Crosslinking agent) As the crosslinking agent, sulfur was used when the base material was EPDM, zinc oxide (zinc oxide for crosslinking agent) was used when the base material was CR, and organic peroxides were used when the base material was LDEP. Sulfur: Finely divided sulfur S-200 mesh, manufactured by Hosoi Chemical Industry Co., Ltd. Zinc oxide for crosslinking agents: Sakai Chemical Industry Co., Ltd., zinc oxide type 2 Organic peroxides: "Percumyl D" and dicumyl peroxide manufactured by Nippon Oil & Fats Co., Ltd.

[0092] (Crosslinking accelerator) Thiazoles: Ouchi Shinko Chemical Industry Co., Ltd., "Noccela M", 2-mercaptobenzothiazole Thiurams: Ouchi Shinko Chemical Industry Co., Ltd., "Noccela TT", tetramethylthiuram disulfide

[0093] (foaming agent) Azodicarbonamide: Sankyo Kasei Co., Ltd., "CellMic C-1"

[0094] (foaming aid) Urea: Eiwa Chemical Industry Co., Ltd., "Cell Paste 101"

[0095] <Manufacturing porous sound-absorbing materials (foams)> Example 1 100 parts by mass of EPDM (base material) was masticated for 5 minutes using a mixing roll (7 inches, rotation speed: 25 rpm) at a roll temperature of 40°C. Then, 30 parts by mass of Sendust A, 80 parts by mass of calcium carbonate, 1 part by mass of zinc oxide filler, and 3 parts by mass of stearic acid (processing aid) were added to the EPDM and kneaded for 15 minutes. Next, 60 parts by mass of process oil (softener) was added and kneaded for 5 minutes. Subsequently, the roll temperature was raised to 70°C and warmed for 3 minutes. After lowering the roll temperature to 40°C, 1 part by mass of sulfur (crosslinking agent), crosslinking accelerator (2 parts by mass of thiazoles, 1 part by mass of thiurams), 10 parts by mass of azodicarbonamide (foaming agent), and 1 part by mass of urea (foaming aid) were added and kneaded for 10 minutes to obtain a foaming composition (kneaded product) before foaming.

[0096] Next, the foam composition was molded into a sheet having a thickness of 2 mm using a mixing roll (7 inches, rotation speed: 25 rpm) at a roll temperature of 40°C, and then a 70 mm square sheet piece was cut out. Five of these sheet pieces were stacked together and placed at the center of the recess of a mold having a recess (recess shape: 8 mm (height) × 100 mm × 100 mm). The sheet was then pressed at 110°C and 45 kgf / cm using a press. 2 The primary foaming was carried out under the conditions of 100°C, 100°F, 100°C ...

[0097] After removing the primary foam from the mold, it was heated in a hot air circulating oven at 160°C for 30 minutes to cause secondary foaming, resulting in a secondary foam. The secondary foam was passed three times between two rolls with a roll gap of 20 mm to open the cells, and then sliced ​​to a thickness of 20 mm to obtain a sheet-like porous sound-absorbing material.

[0098] Examples 2 to 4 The same procedure as in Example 1 was carried out except that the types and amounts of metal fillers shown in Table 1 were used, to obtain a sheet-like porous sound-absorbing material.

[0099] Example 5 A secondary foam was obtained in the same manner as in Example 1, except that no metal filler was used and the amount of thiazole used was changed to 2.3 parts by mass. Furthermore, a sheet-like porous sound-absorbing material was obtained in the same manner as in Example 1, except that after the cells were opened, the material was sliced ​​to a thickness of 10 mm.

[0100] Example 6 A secondary foam was obtained in the same manner as in Example 1, except that no metal filler was used and the crosslinking accelerator was changed to 2.3 parts by mass of a thiazole and 1.1 parts by mass of a thiuram. Furthermore, a sheet-like porous sound-absorbing material was obtained in the same manner as in Example 1, except that after the cells were opened, the material was sliced ​​to a thickness of 10 mm.

[0101] Example 7 A secondary foam was obtained in the same manner as in Example 1, except that no metal filler was used and the amount of foaming agent was changed to 15 parts by mass. Also, a sheet-like porous sound-absorbing material was obtained in the same manner as in Example 1, except that the number of times the cells were opened was changed to 8, and the material was sliced ​​to a thickness of 10 mm.

[0102] Example 8 A secondary foam was obtained in the same manner as in Example 1, except that no metal filler was used and the crosslinking accelerator was changed to 2.5 parts by mass of a thiazole and 1.2 parts by mass of a thiuram. Furthermore, a sheet-like porous sound-absorbing material was obtained in the same manner as in Example 1, except that after the cells were opened, the material was sliced ​​to a thickness of 10 mm.

[0103] Example 9 A secondary foam was obtained in the same manner as in Example 1, except that no metal filler was used and the amount of foaming agent was changed to 17 parts by mass. Also, a sheet-like porous sound-absorbing material was obtained in the same manner as in Example 1, except that the number of times the cells were opened was changed to 5, and the material was sliced ​​to a thickness of 20 mm.

[0104] Example 10 The same procedure as in Example 9 was carried out, except that after the cells were opened, the sheet was sliced ​​to a thickness of 30 mm, to obtain a sheet-like porous sound-absorbing material.

[0105] Example 11 100 parts by mass of CR (base material) was masticated for 5 minutes using a mixing roll (7 inches, rotation speed: 25 rpm) at a roll temperature of 40°C. Then, 30 parts by mass of Sendust A, 50 parts by mass of calcium carbonate, and 1 part by mass of stearic acid (processing aid) were added to the CR, and the mixture was kneaded for 5 minutes. Next, 60 parts by mass of process oil (softener) was added, and the mixture was kneaded for 5 minutes. Subsequently, the roll temperature was raised to 70°C, and the mixture was warmed for 5 minutes. After the roll temperature was lowered to 40°C, 5 parts by mass of zinc oxide for crosslinking (crosslinking agent), 15 parts by mass of azodicarbonamide (foaming agent), and 1.5 parts by mass of urea (foaming aid) were added, and the mixture was kneaded for 10 minutes to obtain a foaming composition (kneaded material) before foaming.

[0106] Next, the foam composition was molded into a sheet having a thickness of 2 mm using a mixing roll (7 inches, rotation speed: 25 rpm) at a roll temperature of 40°C, and then a 70 mm square sheet piece was cut out. Five of these sheet pieces were stacked together and placed at the center of the recess of a mold having a recess (recess shape: 8 mm (height) × 100 mm × 100 mm). The sheet was then pressed at 110°C and 45 kgf / cm using a press. 2 The primary foaming was carried out under the conditions of 100°C, 100°F, 100°C ...

[0107] After removing the primary foam from the mold, it was heated in a hot air circulating oven at 160°C for 30 minutes to cause secondary foaming, resulting in a secondary foam. The secondary foam was passed three times between two rolls with a roll gap of 20 mm to open the cells, and then sliced ​​to a thickness of 20 mm to obtain a sheet-like porous sound-absorbing material.

[0108] Example 12 100 parts by mass of EPDM (base material) was masticated for 5 minutes using a mixing roll (7 inches, rotation speed: 25 rpm) at a roll temperature of 40°C. Then, 20 parts by mass of calcium carbonate, 1 part by mass of zinc oxide filler, and 3 parts by mass of stearic acid (processing aid) were added to the EPDM and kneaded for 15 minutes. Next, the rotation speed was changed to 40 rpm (the same rotation speed was used for subsequent kneading operations), and 60 parts by mass of process oil (softener) was added and kneaded for 20 minutes. Subsequently, the roll temperature was raised to 80°C and warmed for 3 minutes. After the roll temperature was lowered to 40°C, 1 part by mass of sulfur (crosslinking agent), crosslinking accelerator (2 parts by mass of thiazoles, 1 part by mass of thiurams), 10 parts by mass of azodicarbonamide (foaming agent), and 1 part by mass of urea (foaming aid) were added and kneaded for 20 minutes to obtain a foam composition (kneaded product) before foaming.

[0109] Next, the foam composition was molded into a sheet having a thickness of 2 mm using a mixing roll (7 inches, rotation speed: 40 rpm) at a roll temperature of 40°C, and then a 70 mm square sheet piece was cut out. Five of these sheet pieces were stacked together and then placed at the center of the recess of a mold having a recess (recess shape: 8 mm (height) × 100 mm × 100 mm). The sheet was then pressed at 110°C and 45 kgf / cm using a press. 2 The primary foaming was carried out under the conditions of 100°C, 100°F, 100°C ...

[0110] After removing the primary foam from the mold, it was heated in a hot air circulating oven at 160°C for 20 minutes to cause secondary foaming, resulting in a secondary foam. The secondary foam was passed three times between two rolls with a roll gap of 20 mm to open the cells, and then sliced ​​to a thickness of 20 mm to obtain a sheet-like porous sound-absorbing material.

[0111] (Examples 13 to 14) The same procedure as in Example 12 was carried out, except that after the cells were opened, the sheet was sliced ​​to a thickness as shown in Table 2, to obtain a sheet-like porous sound-absorbing material.

[0112] Example 15 A sheet-like porous sound-absorbing material was obtained in the same manner as in Example 12, except that the amount of foaming agent used was changed to the amount shown in Table 2 and the cells were not made interconnected.

[0113] Example 16 The same procedure as in Example 12 was carried out except that the amount of foaming agent used was changed to the amount shown in Table 2, to obtain a sheet-like porous sound-absorbing material.

[0114] Example 17 The same procedure as in Example 12 was carried out except that the amounts of the crosslinking accelerator and the foaming agent used were changed to those shown in Table 2, to obtain a sheet-like porous sound-absorbing material.

[0115] Example 18 The same procedure as in Example 12 was carried out except that the amounts of the crosslinking agent, crosslinking accelerator and foaming agent used were changed to those shown in Table 2, to obtain a sheet-like porous sound-absorbing material.

[0116] Example 19 A sheet-shaped porous sound-absorbing material was obtained in the same manner as in Example 12, except that the foaming composition (kneaded material) before foaming was obtained by the following procedure. Specifically, 100 parts by mass of CR (base material) was masticated for 5 minutes using a mixing roll (7 inches, rotation speed: 25 rpm) at a roll temperature of 40°C. Then, 20 parts by mass of calcium carbonate, 1 part by mass of zinc oxide for filler, and 3 parts by mass of stearic acid (processing aid) were added to the CR, and the mixture was kneaded for 15 minutes. Next, the rotation speed was changed to 40 rpm (the same rotation speed was used for the subsequent kneading operations), and 60 parts by mass of process oil (softener) was added, and the mixture was kneaded for 20 minutes. Subsequently, the roll temperature was raised to 80°C, and the mixture was heated for 3 minutes. Then, after lowering the roll temperature to 40°C, 5 parts by mass of zinc oxide for crosslinking (crosslinking agent), 17 parts by mass of azodicarbonamide (foaming agent), and 1.5 parts by mass of urea (foaming assistant) were added, and the mixture was kneaded for 20 minutes to obtain a foaming composition (kneaded material) before foaming.

[0117] (Examples 20 to 21) The same procedure as in Example 19 was carried out except that the amount of crosslinking agent used was changed to the amount shown in Table 2, to obtain a sheet-like porous sound-absorbing material.

[0118] (Comparative Example 1) The same procedure as in Example 12 was carried out except that the amount of the crosslinking accelerator used was changed to the amount shown in Table 3, to obtain a sheet-like porous sound-absorbing material.

[0119] (Comparative Example 2) The same procedure as in Example 12 was carried out except that the amounts of the crosslinking accelerator and the foaming agent used were changed to those shown in Table 3, to obtain a sheet-like porous sound-absorbing material.

[0120] (Comparative Example 3) The same procedure as in Example 19 was carried out except that the amount of foaming agent used was changed to the amount shown in Table 3, to obtain a sheet-like porous sound-absorbing material.

[0121] Comparative Example 4 The same procedure as in Example 19 was carried out except that the amounts of the crosslinking agent and the foaming agent used were changed to those shown in Table 3, to obtain a sheet-like porous sound-absorbing material.

[0122] Example 22 A mixture was obtained by dry blending 100 parts by mass of LDPE (base material), 30 parts by mass of Sendust C (metal filler), 10 parts by mass of calcium carbonate, 0.2 parts by mass of zinc oxide for filler, 5 parts by mass of stearic acid (processing aid), 0.7 parts by mass of dicumyl peroxide (crosslinking agent), 10 parts by mass of azodicarbonamide (foaming agent), and 1 part by mass of urea (foaming aid), and the mixture was melt-kneaded using a kneader for 15 minutes to obtain a foamable composition (irregular shape) before foaming.

[0123] Next, a foamable composition was weighed out in an amount equivalent to 110% of the mold volume, calculated from the density and blending ratio of each raw material, and filled into the recess of a mold (recess shape: 8 mm (height) × 100 mm × 100 mm). The foam was pressed at 140°C and 45 kgf / cm using a press. 2 The primary foaming was carried out under the conditions of 100°C, 100°F, 100°C ...

[0124] After removing the primary foam from the mold, it was heated in a hot air circulating oven at 180°C for 30 minutes to carry out secondary foaming, obtaining a secondary foam. The secondary foam was passed three times between two rolls with a roll gap of 20 mm to open the cells, and then sliced ​​to a thickness of 20 mm to obtain a sheet-like porous sound-absorbing material.

[0125] Example 23 A sheet-shaped porous sound-absorbing material was obtained in the same manner as in Example 22, except that Sendust A was used as the metal filler.

[0126] Example 24 A sheet-like porous sound-absorbing material was obtained in the same manner as in Example 22, except that Sendust B was used as the metal filler.

[0127] (Examples 25 to 26) The same procedure as in Example 22 was carried out except that Sendust A was used as the metal filler and the amount of metal filler used was changed to the amount used in Table 4, to obtain a sheet-like porous sound-absorbing material.

[0128] Example 27 A sheet-shaped porous sound-absorbing material was obtained in the same manner as in Example 22, except that iron alloy powder was used as the metal filler.

[0129] Example 28 A sheet-shaped porous sound-absorbing material was obtained in the same manner as in Example 22, except that tungsten alloy powder was used as the metal filler.

[0130] Example 29 A mixture was obtained by dry blending 100 parts by mass of LDPE (base material), 10 parts by mass of calcium carbonate, 0.2 parts by mass of zinc oxide for filler, 5 parts by mass of stearic acid (processing aid), 0.7 parts by mass of dicumyl peroxide (crosslinking agent), 2.5 parts by mass of azodicarbonamide (foaming agent), and 1 part by mass of urea (foaming aid), and the mixture was melt-kneaded using a kneader for 15 minutes to obtain a foamable composition (irregular shape) before foaming.

[0131] Next, a foamable composition was weighed out in an amount equivalent to 110% of the mold volume, calculated from the density and blending ratio of each raw material, and filled into the recess of a mold (recess shape: 8 mm (height) × 100 mm × 100 mm). The foam was pressed at 140°C and 45 kgf / cm using a press. 2 The primary foaming was carried out under the conditions of 100°C, 100°F, 100°C ...

[0132] After removing the primary foam from the mold, it was heated in a hot air circulating oven at 180°C for 30 minutes to cause secondary foaming, resulting in a secondary foam. The secondary foam was passed three times between two rolls with a roll gap of 20 mm to open the cells, and then sliced ​​to a thickness of 14 mm to obtain a sheet-like porous sound-absorbing material.

[0133] Examples 30 to 33 The same procedure as in Example 29 was carried out except that the amount of foaming agent used was changed to the amount shown in Table 5, to obtain a sheet-like porous sound-absorbing material.

[0134] (Examples 34 to 35) The same procedure as in Example 30 was carried out, except that the number of times the cells were opened was changed to 5, and the sheet was finished to the thickness shown in Table 5 by slicing, to obtain a sheet-like porous sound-absorbing material.

[0135] (Comparative Examples 5 to 8) The same procedure as in Example 29 was carried out except that the amounts of calcium carbonate and foaming agent used were changed to those shown in Table 6, to obtain a sheet-like porous sound-absorbing material.

[0136] <Evaluation of porous sound-absorbing materials> The physical properties of the porous sound-absorbing material (foam) were evaluated by the following methods. The results are shown in Tables 1 to 6.

[0137] (Expansion ratio) The expansion ratio of the porous sound-absorbing material was measured by the following procedure. Specifically, a test piece measuring 1 cm thick, 5 cm long, and 5 cm wide was cut out from the foamable composition before foaming, and the mass of the test piece was measured to determine the density before foaming. The expansion ratio was then calculated by dividing the density before foaming by the apparent density (density after foaming) of the porous sound-absorbing material described below.

[0138] (average cell diameter) The average cell diameter of the porous sound-absorbing material was measured. Specifically, an image of one of the bubbles in the porous sound-absorbing material was captured using a tabletop scanning electron microscope (JCM6000Plus Neoscope, manufactured by JEOL Ltd.), and the cell diameter (μm) was calculated by image analysis (conversion to a circular equivalent diameter) using image analysis software (Mac-View, manufactured by Mountec Co., Ltd.). After obtaining the cell diameters of 100 bubbles in the porous sound-absorbing material, the arithmetic mean value of the 100 cell diameters was calculated as the average cell diameter (μm).

[0139] (apparent density) The apparent density of the porous sound-absorbing material was measured in accordance with JIS K 6767 (1999) "Foam plastics - Polyethylene - Test method." Specifically, after adjusting the thickness of the porous sound-absorbing material to 10 mm, a plate-shaped test piece measuring 5 cm in length and 5 cm in width was cut out, and the mass of the test piece was measured to calculate the mass per unit volume (apparent density).

[0140] (breathability) Air permeability of porous sound absorbing material (cm 3 / cm 2 The air permeability of a 5 mm thick sample was measured using a Frazier-type air permeability tester (Fragile Permeability Meter, manufactured by Toyo Seiki Seisakusho Co., Ltd.) in accordance with Method A of JIS L 1096 (2010) "Testing Methods for Woven and Knitted Fabrics."

[0141] (Thickness) The thickness of the porous sound-absorbing material was measured in accordance with ISO 1923 (1981) "Foam plastics and rubber - Measurement of linear dimensions." Specifically, the measurement area was approximately 10 cm. 2 The thickness of the porous sound-absorbing material was measured using a dial gauge.

[0142] <Sound absorption coefficient evaluation> The sound absorption coefficient was measured according to the method described in JIS A 1405:1998, "Acoustics - Measurement of sound absorption coefficient and impedance using an impedance tube - Standing wave ratio method." The sound absorption coefficient was measured at 500 Hz and 1000 Hz using a normal incidence sound absorption coefficient measuring instrument (TYPE10041, manufactured by Denshi Sokki Co., Ltd.) equipped with a probe tube microphone. Specifically, a porous sound-absorbing material was adjusted to a diameter of 29 mm to obtain a test piece, which was then placed in close contact with the back panel of a sample holder for measurement. The higher the sound absorption coefficient, the better the sound absorption characteristics. A sound absorption coefficient of 0.6 or greater was evaluated as "A," a sound absorption coefficient of 0.4 or greater but less than 0.6 was evaluated as "B," and a sound absorption coefficient of less than 0.4 was evaluated as "C."

[0143] [Table 1]

[0144] [Table 2]

[0145] [Table 3]

[0146] [Table 4]

[0147] [Table 5]

[0148] [Table 6]

[0149] From the above results, it is confirmed that by using a porous sound-absorbing material having a specific average cell diameter and apparent density, excellent sound-absorbing properties can be obtained in the low-frequency range.

Claims

1. The adhesive composition contains at least one base material selected from the group consisting of a resin material and an elastomer, and a carbonate, The content of the carbonate is 10 to 100 parts by mass relative to 100 parts by mass of the base material, The average cell diameter is 100 to 600 μm, Apparent density 40 to 140 kg / m ３ and Breathability is 0.3 cm ３ / cm ２ - Porous sound-absorbing material having a thickness of s or more.

2. Air permeability is 0.3 to 40 cm ３ / cm ２ 3. The porous sound-absorbing material according to claim 1, wherein s is a value of s.

3. 3. The porous sound-absorbing material according to claim 1, which is in the form of a sheet having a thickness of 15 to 40 mm.

4. Further containing a metal filler, The content of the metal filler is 5 to 50 parts by mass relative to 100 parts by mass of the base material, The specific gravity of the metal filler is 4 to 10, The porous sound-absorbing material according to any one of claims 1 to 3, wherein the metal filler has an average particle size of 5 to 30 µm.

5. A sound absorbing method, comprising absorbing sound using the porous sound absorbing material according to any one of claims 1 to 4.

6. The sound absorbing method according to claim 5, wherein sounds of 1000 Hz or less are absorbed.

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