JP2018146745A - Composite sound absorbing material and method for manufacturing the same, and method for improving sound absorbency - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide composite sound absorbing material improving sound absorbency of sound waves having a wide frequency range, a method for improving sound absorbency, and a method for manufacturing the composite sound absorbing material.SOLUTION: A composite sound absorbing material 13 of the present invention includes a rubber foam 14 and a tabular resin foam 1. The tabular resin foam 1 and the rubber foam 14 have at least continuous bubbles, and the rubber foam 14 is laminated with the tabular resin foam 1.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a composite sound-absorbing material useful for use in vehicles (vehicles such as automobiles, trains, airplanes, ships, etc.), buildings (houses, high-rise buildings, etc.), a method for producing the same, and a method for improving sound absorption About.

  Foam sheets such as polyurethane and soft vinyl chloride resin foam are used as sound-absorbing materials used in vehicles, buildings, etc., and these foam sheets can absorb relatively high frequency sound well. Are known.

Japanese Patent Application Laid-Open No. 2015-199830 (Patent Document 1) has continuous bubbles with an open cell ratio of 50% or more, an apparent density of 600 kg / m ³ or less, and at least one surface of which is continuous cells. A polyolefin resin foam sheet having a concavo-convex structure including a top portion having an opening is described. This document describes that the sound absorption coefficient of the polyolefin resin foam sheet is about 80% in a high frequency range of 5 to 7 kHz. However, the sound absorption coefficient is still low and high sound absorption cannot be obtained. In addition, the sound absorption coefficient shows a sound absorption characteristic that increases to about 0.5 from 1 kHz to 4 kHz and then becomes about 0.8 from 4.5 kHz to 7 kHz. Therefore, the sound absorption cannot be improved in a wide frequency range, and the sound absorption effect is extremely low particularly at 1 kHz to 2 kHz.

  JP 2012-25916 A (Patent Document 2) provides a soft feeling by opening a needle hole shorter than the thickness of the foam in the thickness direction of the foam containing low density polyethylene or the like to form continuous bubbles. An excellent sheet-like foam having excellent cushioning and cushioning properties is described. This document describes a flat sheet-like foam and also describes that it can be used as a sound absorbing material. However, there is no specific description about sound absorption.

  Nichias Technical Time Report No. No. 326 2001 No. 4 “foamed rubber sound absorbing structure” (Non-Patent Document 1), rubber-based foams (EPDM, etc.) are excellent in sound absorption in the middle frequency range (for example, 1.5 to 2.5 kHz). It is described that. However, there is no description about sound absorption in a high frequency range (for example, 4 to 6 kHz).

  JP-A-2006-161844 (Patent Document 3) describes a sound-absorbing material having a low-density layer (foamed EPDM layer) and a high-density layer (metal layer such as SUS). The sound absorbing material can absorb about 60 to 80% of sound in a low to medium frequency range (for example, 100 to 1600 Hz). However, there is no description about sound absorption in the middle to high frequency range (for example, 2000 Hz or more).

  In recent years, for sound absorbing materials used in vehicles, buildings, etc., while maintaining a predetermined strength, the weight is reduced and the peak of the sound absorption coefficient is shifted to the low frequency side, and a wide frequency range (for example, 1500 to 7000 Hz). It is desired to further improve the sound absorption.

Japanese Patent Laying-Open No. 2015-199830 (Claims, Effects of the Invention, FIG. 2) JP 2012-25916 (Claims, industrial applicability, effects of the invention) JP-A-2006-161844 (Claims, Effects of Invention, Table 1)

Nichias Technical Time Report No. 326 2001 No. 4, “Sound Absorbing Structure of Foamed Rubber” (1. Introduction, FIG. 2)

  Accordingly, an object of the present invention is to provide a composite sound-absorbing material capable of shifting the peak of the sound absorption coefficient to the low frequency side and absorbing sound waves in a wide frequency range, a method for manufacturing the same, and a method for improving sound absorption. is there.

  Another object of the present invention is to provide a composite sound-absorbing material having high sound-absorbing properties, a method for producing the same, and a method for improving sound-absorbing properties.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors can shift the peak of the sound absorption coefficient to the low frequency side when laminating or superposing a plate-like resin foam and a rubber-based foam. The present invention has been completed by finding out that the sound absorption of sound waves can be effectively improved over a wide frequency range.

  That is, the composite sound-absorbing material of the present invention has a rubber-based foam and a plate-shaped resin foam. In such a composite sound-absorbing material, the plate-shaped resin foam and the rubber-based foam have at least open cells, and the plate-shaped resin foam is formed by laminating or overlapping the rubber-based foam. ing.

  The plate-like resin foam has a concavo-convex surface on at least one surface, has closed cells together with open cells, penetrates from the surface of the plate-like resin foam to the middle in the thickness direction, and at least a part of the above-mentioned You may have a needle hole which penetrates a closed cell.

  The plate-like resin foam may be arranged with the concavo-convex surface at least outward, and the concavo-convex surface is at least one condition selected from the following (1), (2), (3) and (4) May be satisfied.

(1) The average height difference between the top and valley on the uneven surface is about 1 to 50 mm. (2) The average interval between the tops on the uneven surface is about 1 to 60 mm. (4) Needle holes are provided on at least the uneven surface.

  The depth of the needle hole may be, for example, about 10 to 90% with respect to the entire thickness of the plate-like resin foam. The plate-like resin foam may contain at least one base component selected from an ethylene-based resin and a thermoplastic elastomer, and the plate-like resin foam may have an expansion ratio of about 10 to 100 times.

  The corrugated surface of the plate-like resin foam may be a corrugated surface formed by a protrusion and a groove adjacent to the protrusion.

  The composite sound-absorbing material may have a punched hole penetrating the plate-like resin foam, and the average diameter of the punched hole is larger than the average diameter of the needle hole, for example, about 1 to 20 mm.

  The composite sound absorbing material may satisfy at least one condition selected from the following (5), (6), and (7).

(5) The average cell diameter of the rubber foam is 0.01 to 6 mm (6) The average apparent density of the rubber foam is 0.01 to 0.9 mg / mm ³ (7) Rubber foam The body contains at least ethylene-propylene-diene rubber.

  When the thickness of the plate-like resin foam is 1, the rubber foam may have a thickness of 0.1 to 5.

  The present invention also includes a method of improving sound absorption by making a sound wave incident on the composite sound absorbing material.

  The composite sound-absorbing material of the present invention can be produced by laminating or superposing a plate-like resin foam having open cells on a rubber foam having open cells.

  In the present invention, by laminating a rubber-based foam having open cells and a plate-shaped resin foam having open cells, the sound absorption frequency range can be shifted and the absorption wavelength range can be expanded. Furthermore, sound waves can be absorbed with a wide frequency range and a high sound absorption coefficient.

FIG. 1 is a schematic view of a plate-like resin foam used for the composite sound-absorbing material of the present invention. FIG. 2 is a schematic view for explaining a production process of a plate-like resin foam used for the composite sound-absorbing material of the present invention. FIG. 3 is a schematic view of the composite sound-absorbing material of the present invention. FIG. 4 is a chart showing sound absorption characteristics of the composite sound-absorbing material of Example 1. FIG. 5 is a chart showing sound absorption characteristics of the composite sound-absorbing material of Example 2. FIG. 6 is a chart showing the sound absorption characteristics of the composite sound absorbing material of Comparative Example 1. FIG. 7 is a chart showing the sound absorption characteristics of the composite sound absorbing material of Reference Example 1.

<Plate resin foam>
The plate-like resin foam can be formed of a foamable thermoplastic resin composition containing a soft thermoplastic resin.

  The plate-like resin foam may be soft as a whole, and examples of the thermoplastic resin used for the plate-like resin foam include olefin resins, vinyl chloride resins, vinyl ester resins, and (meth) acrylic resins. Examples thereof include resins, styrene resins (for example, polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer), and thermoplastic elastomers.

  The plate-like resin foam usually contains at least one selected from olefin resins (particularly ethylene resins) and thermoplastic elastomers.

  Examples of the olefin resin include ethylene resins (such as polyethylene and ethylene copolymers), propylene resins (such as propylene copolymers such as polypropylene and propylene-ethylene copolymers), and butene resins. These olefinic resins can be used alone or in combination of two or more. Of these olefin resins (or soft thermoplastic resins), it is preferable to contain at least an ethylene resin.

Among the ethylene resins, examples of the polyethylene include high density polyethylene (HDPE), medium density polyethylene, low density polyethylene (LDPE), and linear low density polyethylene (LLDPE). In addition, high density polyethylene (HDPE) and medium density polyethylene are copolymerization of ethylene and a small amount (for example, about 0.01-5 mol%, especially about 0.1-3 mol%) of copolymerizable α-olefin. Includes coalescence. Linear low density polyethylene (LLDPE) is a copolymerizable α-ethylene with a small amount (for example, 0.01 to 10 mol%, preferably 1 to 8 mol%, particularly about 2 to 7 mol%) of ethylene. Copolymers with olefins (α-olefins other than ethylene) are also included. Examples of copolymerizable α-olefins (α-olefins other than ethylene) include α-C ₃₋ such as propylene, butene-1, hexene-1, 4-methylpentene-1, octene-1, and decene-1. _Ten olefins are preferred. These α-olefins can be used alone or in combination of two or more. LLDPE can be prepared using a metallocene catalyst. These polyethylenes may be used alone or in combination.

Among ethylene resins, ethylene copolymer (ethylene-containing copolymer) is a copolymerizable monomer (non-ethylene copolymerizable monomer or polar copolymerizable monomer) other than ethylene and ethylene. The copolymer may be used. Examples of copolymerizable monomers (or polar copolymerizable monomers) other than ethylene include organic acid vinyl esters such as vinyl acetate, vinyl propionate, and vinyl caproate; propylene, butene-1, and hexene-1. , Α-C _3-10 olefins such as octene-1, decene-1; acidic group-containing copolymerizable monomers such as (meth) acrylic acid, maleic anhydride, fumaric acid; methyl (meth) acrylate, ( (Meth) acrylic acid C _1-12 alkyl esters such as ethyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, Hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate Examples thereof include (meth) acrylic acid esters such as esters and (meth) acrylic acid glycidyl esters; halogen-containing copolymerizable monomers such as vinyl chloride and vinylidene chloride; and cyclic olefins. These copolymerizable monomers other than ethylene (or polar copolymerizable monomers) can be used alone or in combination of two or more.

  The ethylene unit ratio (ethylene content) of the ethylene copolymer is 50 mol% or more (for example, about 60 to 99 mol%), preferably 65 mol% or more (for example, 65 to 65 mol%) with respect to the entire copolymer. About 98 mol%), more preferably about 70 to 97 mol% (for example, about 80 to 95 mol%), or about 60 to 99 mol% (for example, 75 to 98 mol%). . When the ethylene copolymer is a copolymer of ethylene and α-olefin, the ethylene content is in a range different from the ethylene content of the polyethylene (HDPE, LDPE, LLDPE, etc.), for example, 50 to 90 mol% ( For example, it can be selected from the range of about 55 to 87 mol%), preferably about 60 to 85 mol% (for example, 65 to 80 mol%).

Copolymerizable monomers other than ethylene are vinyl acetate, (meth) acrylic acid, (meth) acrylic acid C _1-2 alkyl esters (such as ethyl acrylate), bi- or tricyclic olefins (such as norbornenes). There may be. The ethylene copolymer (ethylene-containing copolymer) may be a random copolymer or an alternating copolymer.

Examples of the ethylene copolymer include ethylene-α-olefin copolymers such as ethylene-propylene copolymer, ethylene-organic acid vinyl ester copolymers such as ethylene-vinyl acetate copolymer, and ethylene- (meth) acrylic acid. Copolymer, ethylene- (meth) acrylic acid C _1-10 alkyl ester copolymer such as ethylene-ethyl acrylate copolymer, ethylene-cycloolefin copolymer such as ethylene-norbornene copolymer, etc. At least one kind can be exemplified, and an organic acid vinyl ester copolymer is preferable, and an ethylene-vinyl acetate copolymer (EVA) is more preferable.

  The number average molecular weight of the olefin resin (for example, ethylene resin) can be selected from the range of, for example, about 8,000 to 500,000, for example, 10,000 to 300,000, preferably 15,000 to 200,000. It may be about 000, more preferably about 20,000 to 150,000 (for example, 25,000 to 100,000). The number average molecular weight of the olefin resin can be measured in terms of standard polystyrene using a gel permeation chromatography method (GPC method) at a measurement temperature of 140 ° C. and orthodichlorobenzene as a solvent.

  The melting point of the olefin resin (for example, ethylene resin) may be, for example, about 65 to 170 ° C., preferably 70 to 160 ° C., and more preferably about 80 to 150 ° C. (for example, 90 to 120 ° C.). The melting point of polyethylene may be, for example, about 90 to 135 ° C, preferably 95 to 132 ° C, and more preferably about 100 to 130 ° C (for example, 105 to 125 ° C). Further, the melting point of the ethylene copolymer may be, for example, 65 to 150 ° C., preferably 70 to 140 ° C., more preferably about 80 to 130 ° C., depending on the type and content of the α-olefin. . In addition, it can replace with melting | fusing point and can also use glass transition temperature, and melting | fusing point and glass transition temperature can be measured with a differential scanning calorimeter.

  Under conditions of a temperature of 190 ° C. and a load of 21.2 N, the melt flow rate of the olefin resin is, for example, 0.05 to 100 g / 10 minutes, preferably 0.08 to 70 g / 10 minutes, and more preferably 0.1 to 0.1 g. It may be about 50 g / 10 minutes. The melt flow rate of polyethylene is, for example, 0.05 to 20 g / 10 minutes (for example, 0.08 to 15 g / 10 minutes) at a temperature of 190 ° C. and a load of 21.2 N, preferably 0.1 to 12.5 g / It may be about 10 minutes (for example, 0.15 to 12 g / 10 minutes), more preferably about 0.2 to 10 g / 10 minutes (for example, 0.25 to 9 g / 10 minutes).

  These olefin resins can be used alone or in combination of two or more. Among these olefin resins, polyethylene [low density polyethylene (LDPE), linear low density polyethylene (LLDPE), etc.] is preferable.

  Examples of thermoplastic elastomers include olefin elastomers (block copolymers having polypropylene, polyethylene, etc. as hard segments and ethylene-propylene rubber, ethylene-propylene-diene rubber, etc. as soft segments), and styrene elastomers (styrene- Butadiene block copolymer (SBS block copolymer), styrene-isoprene block copolymer (SIS block copolymer), styrene-ethylene / butylene block copolymer (SEBS block copolymer), styrene-ethylene / propylene Block copolymers (SEPS block copolymers, etc.), polyester elastomers (polybutylene terephthalate and other aromatic polyesters are used as hard segments, and aliphatic polyesters (polyethylene (Rene adipate glycol, polybutylene adipate glycol, etc.) or aliphatic polyethers (polytetramethylene ether glycol, etc., block copolymers with soft segments), polyamide elastomers (nylon 6, nylon 12 and other polyamides, hard segments) And a block copolymer having the aliphatic polyester or aliphatic polyether as a soft segment), a polyurethane-based elastomer, and the like.

  Examples of the styrene resin include polystyrene (polystyrene for general use (GPPS), high-impact polystyrene (HIPS)), styrene-acrylonitrile copolymer (AS resin), acrylonitrile-butadiene-styrene resin (ABS resin), acrylonitrile- At least selected from acrylic ester-styrene copolymer (AAS resin), acrylonitrile-chlorinated polystyrene-styrene resin (ACS resin), acrylonitrile-ethylene-styrene resin (AES resin), styrene-methyl methacrylate copolymer, etc. 1 type is mentioned, These styrenic resin can be used individually or in combination of 2 or more types. Preferably, polystyrene (general-purpose polystyrene (GPPS), impact-resistant polystyrene (HIPS)), more preferably general-purpose polystyrene (GPPS) is used.

  A preferable foamable thermoplastic resin composition contains at least one base component selected from, for example, an ethylene-based resin and a thermoplastic elastomer. In particular, it is preferable to include a base component, an ethylene copolymer, and a styrene resin.

  In the foamable thermoplastic resin composition, the ratio of the base component (for example, the low density polyethylene) to the ethylene copolymer and / or the styrene resin is the former / the latter (weight ratio) = 40/60 to It can be selected from the range of about 100/0 (for example, 50/50 to 100/0), and is usually 55/45 to 98/2, preferably 60/40 to 95/5 (for example, 65/35 to 95/5). ), More preferably 70/30 to 95/5 (for example, 75/25 to 90/10), for example, 50/50 to 80/20, preferably 55/45 to 75/25, More preferably, it may be about 60/40 to 70/30.

  The ratio of the ethylene copolymer and the styrene resin can be selected from the range of the former / the latter (weight ratio) = 0/100 to 100/0 (for example, 10/90 to 90/10). 20/80 to 80/20, preferably 25/75 to 75/25 (e.g. 28/72 to 72/28), more preferably 30/70 to 70/30 (e.g. 32/68 to 68/32). ) Degree.

  The foamable thermoplastic resin composition may contain a foaming agent (or foaming aid) and / or a foam nucleating agent. Examples of the foaming agent include volatile foaming agents used for physical foaming and degradable foaming agents used for chemical foaming. Examples of the volatile blowing agent include inert or nonflammable gases (nitrogen, carbon dioxide, chlorofluorocarbon, chlorofluorocarbon alternative, etc.), water, organic physical blowing agents [for example, aliphatic hydrocarbons (propane, butane (n-butane)). , Isobutane), pentane (n-pentane, isopentane etc.), hexane (n-hexane etc.), aromatic hydrocarbon (toluene etc.), halogenated hydrocarbon (trichloromethane etc.), ethers (dimethyl ether, petroleum ether) Etc.) and ketones (acetone etc.). Examples of decomposable foaming agents include inorganic carbonates such as sodium bicarbonate and ammonium carbonate; organic acids such as citric acid or salts thereof (such as sodium citrate); 2,2'-azobisisobutyronitrile. Azo compounds such as azodicarboxylic acid amide; sulfonyl hydrazide compounds such as benzenesulfonyl hydrazide; nitroso compounds such as N, N′-dinitrosopentamethylenetetramine (DNPT); azide compounds such as terephthalazide. Of these blowing agents, aliphatic hydrocarbons such as butane and pentane, organic acids such as citric acid, or salts thereof (such as sodium citrate) are often used. These foaming agents may be used alone or in combination of two or more.

  The ratio of the foaming agent is 0.1 to 40 parts by weight, preferably 0.3 to 35 parts by weight, more preferably 0.5 to 100 parts by weight of the total amount of the soft thermoplastic resin (or thermoplastic resin). About 30 parts by weight may be used.

  Examples of the foam nucleating agent include inorganic carbonates such as sodium bicarbonate and ammonium carbonate exemplified in the section of the foaming agent; organic acids such as citric acid or salts thereof (such as sodium citrate), and silicic acid compounds (talc). , Silica, zeolite, and the like), metal hydroxides (such as aluminum hydroxide), and metal oxides (such as zinc oxide, titanium oxide, and alumina). These foam nucleating agents may be used alone or in combination of two or more. Among the foam nucleating agents, in particular, when a silicate compound such as talc is used, the cell structure can be made uniform.

  The ratio of the foam nucleating agent is, for example, 0.1 to 10 parts by weight, preferably 0.2 to 8 parts by weight, and more preferably 0 to 100 parts by weight of the total amount of the soft thermoplastic resin (or thermoplastic resin). It may be about 3 to 5 parts by weight.

  The foamable thermoplastic resin composition may contain an anti-shrink agent, for example, an ester of a fatty acid and a polyhydric alcohol, a fatty acid amide, or the like. More specifically, esters of fatty acids (eg, lauric acid, myristic acid, palmitic acid, stearic acid, etc.) and polyhydric alcohols (eg, glycerin, xylitol, sorbitol, mannitol, etc.) include, Examples include triglycerides, monostearic acid triglycerides, and the like. Examples of the fatty acid amide include palmitic acid amide and stearic acid amide. These shrinkage inhibitors may be used alone or in combination of two or more. The proportion of the shrinkage inhibitor is, for example, 0.01 to 30 parts by weight, preferably 0.05 to 20 parts by weight, and more preferably 0.1 to 0.1 parts by weight with respect to 100 parts by weight of the entire soft thermoplastic resin (the whole resin component). It may be about 15 parts by weight, particularly about 0.5 to 10 parts by weight (for example, 1 to 5 parts by weight). The proportion of the shrinkage preventing agent is, for example, 0.01 to 5 parts by weight, preferably 0.02 to 3 parts by weight, more preferably 0.05 to 2 parts by weight with respect to 100 parts by weight of the foaming agent. Part (for example, 0.1 to 1 part by weight).

  The foamable thermoplastic resin composition includes additives such as compatibilizers, bubble regulators, stabilizers [antioxidants (such as hindered phenol antioxidants), ultraviolet absorbers, heat stabilizers, weather stabilizers. Etc.], antistatic agent, antiblocking agent, antifogging agent, organic or inorganic filler (calcium carbonate, carbon fiber, etc.), colorant (dye, pigment etc.), dispersant, lubricant, mold release agent, lubricant, It may contain impact modifiers, plasticizers, surface smoothing agents, flame retardants, biocides (bactericides, bacteriostatic agents, antifungal agents, antiseptics, insecticides, etc.), deodorants and the like. These additives may be used alone or in combination of two or more. The proportion of each additive is, for example, 0.1 to 30 parts by weight, preferably 0.15 to 20 parts by weight (for example, with respect to 100 parts by weight of the total amount of the soft thermoplastic resin (or thermoplastic resin)). 0.2 to 15 parts by weight), more preferably about 0.5 to 10 parts by weight.

  In the foamable thermoplastic resin composition, each component is preliminarily prepared using a conventional method, for example, a mixer (such as a tumbler, V-type blender, Henschel mixer, Nauta mixer, ribbon mixer, mechanochemical apparatus, extrusion mixer). You may mix. Further, the foaming agent, foaming nucleating agent, shrinkage-preventing agent, and additive component may be preliminarily contained in the foamable thermoplastic resin composition (including resin pellets, etc.), respectively. You may add or press-fit into a plastic resin composition.

The expansion ratio of the plate-like resin foam may be, for example, 3 to 120 times (for example, 5 to 110 times), for example, 10 to 100 times (for example, 15 to 95 times), preferably 20 to 90 times. It may be about twice (for example, 25 to 85 times), more preferably about 30 to 80 times (for example, 40 to 75 times). When the expansion ratio is too high, the sound absorption is reduced and the strength of the plate-like resin foam is reduced. If the expansion ratio is too low, the sound absorbing property is lowered and the heat insulating property may be lowered. The expansion ratio can be calculated by measuring the apparent density ρf (g / cm ³ ) of the plate-like resin foam.

The apparent density of the plate-like resin foam can be selected according to the expansion ratio, and is, for example, 0.005 to 0.05 g / cm ³ , preferably 0.007 to 0.03 g / cm ³ (0.008 to 0.00. 02 g / cm ³ ), more preferably about 0.01 to 0.02 g / cm ³ (for example, 0.012 to 0.016 g / cm ³ ), for example, 0.005 to 0.04 g / It may be about cm ³ , preferably about 0.01 to 0.03 g / cm ³ , more preferably about 0.015 to 0.025 g / cm ³ . The apparent density can be measured by an underwater substitution method.

  The average cell diameter of the plate-like resin foam may be, for example, 0.01 to 3 mm, preferably 0.05 to 2 mm, and more preferably 0.1 to 1 mm. If the average diameter of the bubbles in the plate-like resin foam is too large, the sound absorbing property is lowered and the strength of the plate-like resin foam may be lowered. If the average diameter of the bubbles in the plate-like resin foam is too small, the sound absorbing property is lowered and the heat insulating property may be lowered. In addition, the average diameter of the bubbles in the plate-like resin foam is calculated by measuring the short diameter and the long diameter of n bubbles and calculating the average of the short diameter and the long diameter [(short diameter + long diameter) / 2]. The average value can be obtained.

  The plate-like resin foam is not particularly limited as long as it has at least an open cell structure, and the cell structure may be formed of open cells and / or closed cells. For example, a needle penetrates into closed cells. Or open cells. A skin layer may be formed on the surface of the plate-like resin foam. The thickness of the skin layer is not particularly limited as long as it is a value smaller than the height difference (average height difference) in the thickness direction between the top and valley of the uneven surface, and usually 1 to 50 μm (for example, 5 to 30 μm). ) Degree. Since the plate-like resin foam has closed cells, it also has heat insulation properties. Therefore, the plate-like resin foam can be used not only as a sound absorbing material but also as a soundproofing and heat insulating material in a room, for example.

  The plate-like resin foam has a single layer structure composed of one foam layer, may have a cell structure over the whole, or may have a laminated structure in which a plurality of foam layers are laminated.

  Regarding the form of the plate-like resin foam, the plate-like means a two-dimensional shape, the thickness is not particularly limited, and may be a thin shape such as a film shape or a sheet shape, for example, a block A shape having a large thickness such as a shape may be used. The form of the plate-like resin foam may be, for example, a flat plate shape or may be curved. Further, the thickness of the resin foam may be uniform, may be gradually increased / decreased in a predetermined direction or part (for example, a central part or an intermediate part), and at least one surface is inclined or You may form as a curved surface.

  The average thickness of the plate-like resin foam is 1 to 100 mm (for example, 2 to 50 mm), preferably 3 to 30 mm (for example, 4 to 20 mm), more preferably 5 to 10 mm (from the viewpoint of sound absorption and heat insulation. For example, it may be about 6 to 9 mm). If the thickness of the resin foam is too small or too large, the sound absorbing effect and the heat insulating effect may not be sufficiently exhibited.

  It is sufficient that at least one surface of the plate-like resin foam is formed as an uneven surface (uneven portion), and the other surface may be a flat surface (for example, a smooth flat surface) or an uneven surface. .

  An uneven surface (uneven portion) is formed on at least one surface of the plate-like resin foam. The cross-sectional shape of the concave portion and the convex portion is not particularly limited, and may be, for example, a polygonal shape (triangular shape; a square shape such as a U shape or a rectangular shape, a trapezoidal shape, etc.), a semicircular shape (including a semielliptical shape), A preferable example of the cross-sectional shape of the concave and convex portions is a semicircular shape.

  The concavo-convex pattern on the concavo-convex surface is not particularly limited, and the convex portions and the concave portions in the concavo-convex pattern may be randomly or regularly scattered, or may be adjacent to each other. From the viewpoint of sound absorption, it is preferable that the convex and concave portions are alternately and repeatedly arranged on the concave and convex surface (the concave and convex portion) of the plate-like resin foam. For example, a linearly extending ridge and a ridge Examples thereof include a streak structure formed by adjacent and linearly extending grooves, and a lattice type structure formed by intersecting a plurality of linearly extending protrusions. A preferable structure of the plate-like resin foam includes a streak structure, and more preferably a streak structure (corrugated surface) in which the shape of the convex part and the concave part is curved.

  The shape of the concavo-convex portion may be minute or fine concavo-convex, and may be large concavo-convex (for example, a mountain / valley shape or a ridge shape). The difference in height in the thickness direction (average height difference) between the top and the valley may be, for example, 0.01 to 60 mm (for example, 1 to 55 mm), for example, 3 to 50 mm (for example, 4 to 4 mm). 45 mm), preferably 5 to 40 mm (for example, 8 to 35 mm), more preferably about 10 to 30 mm (for example, 12 to 25 mm), for example, 1 to 50 mm, preferably 1.5 to 40 mm, More preferably, it may be about 2 to 35 mm (for example, 2.5 to 25 mm). If the height difference (average height difference) in the thickness direction between the valley portion and the top portion is too small or too large, the sound absorbing effect may not be sufficiently exhibited. In addition, the difference (average height difference) in the thickness direction between the valley portion and the top portion in the concavo-convex portion can be calculated by measurement using a three-dimensional surface structure analysis microscope.

  In the concavo-convex surface, the average interval (average pitch) of the convex portions (or the top portions) may be, for example, 0.1 to 70 mm (for example, 1 to 65 mm), for example, 2 to 60 mm (for example, 5 to 55 mm). ), Preferably 10 to 50 mm (for example, 12 to 45 mm), more preferably about 15 to 40 mm (for example, 20 to 35 mm), for example, 3 to 45 mm, preferably 6 to 40 mm, more preferably It may be about 8 to 35 mm. If the distance between the tops is too small or too large, the sound absorbing effect may not be sufficiently exhibited.

  In the plate-like resin foam, the uneven surface and / or the flat surface may be a sound wave incident surface, but the uneven surface is preferably a sound wave incident surface. By making the uneven surface having a large surface area the incident surface, the sound absorbing property particularly in a high frequency range (for example, 5000 to 7000 Hz) is improved.

  The plate-like resin foam is formed with a needle hole that penetrates in the thickness direction, and the needle hole may penetrate the plate-like resin foam. It is preferably smaller than the thickness of the body. By forming the needle holes, the surface area of the plate-shaped resin foam is increased, and incident sound waves are easily dispersed and absorbed, and sound absorption in a wide frequency range (for example, 3000 to 7000 Hz) is improved.

  The depth of the needle holes is not particularly limited as long as the plate-like resin foam has a skin layer, and penetrates the skin layer, and further penetrates at least some of the closed cells. 10 to 90% (for example, 20 to 80%), preferably 30 to 70% (for example, 35 to 65%), more preferably 40 to 60% (for example, 45 to 55%) with respect to the entire thickness of the resin foam. %). If the depth of the needle hole is too small, the sound absorption effect may not be sufficiently exerted, and if the depth of the needle hole is too large, the number of closed cells may be reduced and the heat insulation and mechanical strength may be reduced. In addition, when it has a needle hole in the uneven surface of a plate-shaped resin foam, it can calculate about the depth of a needle hole on the basis of the average position of the thickness direction of the top part and trough part of the uneven surface.

  In addition, the needle hole penetrates from the surface of the resin foam, and it is not always necessary to penetrate the needle hole into the convex part of the uneven surface, and any part of the concave part, convex part and flat part regularly or randomly. You may intrude from.

  The needle hole may enter from any one of the uneven surface and the flat surface, but preferably enters at least from the uneven surface. For example, it is preferable to enter from at least one surface (for example, uneven surface) of the plate-like resin foam, and both surfaces (for example, one uneven surface and the other flat surface (and / or) or It is more preferable that the light penetrates from both the concave and convex surfaces.

  The average diameter of the needle holes may be, for example, about 0.1 to 5 mm, preferably 0.2 to 3 mm, and more preferably about 0.25 to 1.5 mm (for example, 0.3 to 1.2 mm). .

The average density (pieces / cm ² ) of the needle holes can be selected according to the density of closed cells, for example, 1 to 200 pieces / cm ² (for example, 3 to 150 pieces / cm ² ), preferably 5 to 100 pieces. / Cm ² (for example, 7 to 90 pieces / cm ² ), more preferably about 8 to 50 pieces / cm ² (for example, 10 to 40 pieces / cm ² ), for example, 10 to 90 pieces / cm ^2. It may be about cm ² (for example, 15 to 45 / cm ² ), preferably about 20 to 40 / cm ² (for example, 25 to 35 / cm ² ), for example, 50 to 500 / cm ^2. (e.g., 60 to 250 pieces / ^cm 2), preferably 70 to 150 pieces / cm ² (e.g., 80 to 120 pieces / cm ²⁾ may be about. If the density of the needle holes is too small or too large, the sound absorbing effect may not be sufficiently exhibited.

  The plate-like resin foam has an open cell layer (open cell region) having an open cell structure on at least one surface side, and an open cell layer (closed cell region) having an open cell structure on the other surface side. May be formed. Moreover, the open cell layer and the closed cell layer may be formed adjacent to each other in the thickness direction of the plate-like resin foam. In addition, the open cell layer can form a needle hole, for example, by breaking a needle into the closed cell layer and drilling (or penetrating) the closed cell wall of the closed cell.

  The thickness ratio of the open cell layer and the closed cell layer can correspond to the depth of the needle hole, and the range of the former / the latter = 10/90 to 90/10 (for example, 20/80 to 80/20). For example, the former / the latter = 25/75 to 75/25, preferably 30/70 to 70/30 (for example, 35/65 to 65/35), and more preferably 40/60 to 60/40 ( For example, it may be about 45/55 to 55/45). Note that the boundary between the open cell layer and the closed cell layer is a mixture of closed cells and open cells, which may not be clear, but it can be calculated as an approximate average thickness ratio by observing the cross section, and the penetration degree of the needle Based on the above, the thickness ratio may be calculated. About the thickness ratio of an open cell layer and a closed cell layer, it can calculate on the basis of the average position of the thickness direction of the top part and trough part of an uneven surface. In addition, closed cells may be mixed in the open cell layer.

  The plate-like resin foam may be formed with a punched hole penetrating the plate-like resin foam in the thickness direction. By forming the punched hole, the incident sound wave is easily dispersed, and the sound absorption in a wide frequency range is improved.

  The average diameter of the punched holes is larger than the average diameter of the needle holes, and is, for example, about 1 to 30 mm (for example, 1.5 to 25 mm), preferably about 2 to 20 mm (for example, 2.5 to 15 mm). For example, 1-20 mm (for example, 3-12 mm), preferably 3-10 mm (for example, 3.5-8 mm), more preferably about 4-8 mm (for example, 4.5-7.5 mm). There may be. If the average diameter of the punched holes is too small or too large, the sound absorbing effect may not be sufficiently exhibited. The average diameter of the punched holes is determined by measuring the minor axis and the major axis for n punched holes, and calculating the average of the minor axis and major axis [(minor axis + major axis) / 2]. Can be requested. The average diameter of the punched holes can be measured using a three-dimensional surface structure analysis microscope.

The average density of the punching holes, for example, 0.1 to 50 pieces / 10 cm ² (e.g., 0.3 to 30 pieces / 10 cm ^2), preferably 0.5 to 20 pieces / 10 cm ² (e.g., 0.7 10 pieces / 10 cm ² ), more preferably about 0.8 to 5 pieces / 10 cm ² (for example, 1 to 3 pieces / 10 cm ² ), for example, 1 to 4 pieces / 10 cm ² , preferably 2 It may be about ˜3.5 / 10 cm ² . If the number of punched holes is too small or too large, the sound absorbing effect may not be sufficiently exhibited.

  FIG. 1 is a schematic view showing an example of a plate-like resin foam. The plate-like resin foam 1 is provided with ribs 2 having a corrugated structure on one surface where a top 3 and a valley 4 are alternately repeated. In addition, a large number of needle holes 5 are formed only on one surface (rib surface) of the plate-like resin foam 1 so as to enter half of the plate-like resin foam 1 in the thickness direction. That is, an open cell layer 6 mainly having an open cell structure is formed on one surface (rib surface) side of the plate-like resin foam 1 where the needle holes 5 are formed, and the other surface (flat surface) side. The closed cell layer 7 mainly having closed cells is formed. Further, the plate-like resin foam 1 has a plurality of punched holes 8 penetrating in the thickness direction.

<Method for producing plate-like resin foam>
The plate-like resin foam is obtained by undergoing a foaming process in which a foamable resin composition containing a soft thermoplastic resin is foamed to form a foam having a closed cell structure and a perforating process in which closed cells are made into continuous cells. Can be manufactured.

[Foaming process]
A plate-like resin foam can be obtained by supplying the resin composition to a melt kneader in the form of a mixture of each component or in the form of pellets and foam molding. For melt kneading, a conventional melt kneader, for example, a single screw or vent type twin screw extruder can be used. As the foam molding method, a conventional method such as an extrusion molding method (for example, a T-die method, an inflation method, etc.), an injection molding method, or the like can be used. The foam having a concavo-convex shape on at least one surface may be embossed according to the concavo-convex shape. It is often produced by an extrusion foaming method in which the composition is extruded and foamed. The foaming temperature may be, for example, 70 to 300 ° C, preferably 80 to 280 ° C, and more preferably about 85 to 260 ° C.

  In addition, the foam of the closed cell structure in which closed cells are mainly formed has the resin melt extrusion temperature (based on the melting point or glass transition temperature T of the resin component whose content in the resin composition exceeds 50% ( It can prepare by adjusting in the range of about T-20)-(T-5) degreeC.

[Punching process]
In the drilling process, a large number of needles shorter than the thickness of the foam having the closed cell structure generated in the foaming process are inserted (or pierced) in the thickness direction of the foam to make the closed cells continuous. This drilling process may be performed after the foamed foam is cooled, but is foamed (or extruded), and the foam is hot (or fluidity or melted state, bubble formation process) In many cases, the needle penetrates (or pierces) the foam during the bubble growth process. In particular, immediately after foaming or subsequent to foaming (for example, within 1 minute after discharge from the die), that is, while foaming (or extruding the foam), the needle is allowed to enter the foam ( Or stab). At that time, the needle may be heated, but in order to efficiently form open cells, it is advantageous to allow the needle to enter (or pierce) the foam in the foaming step (after the foaming step) without heating the needle. It is. A preferred method is a method in which a needle is inserted (or stabbed) in the thickness direction of the foam while rotating a roll (needle roll or pin roll) having a large number of needles (or pins) on the surface.

The length of the needle (or pin) can be selected according to the thickness ratio of the open cell layer (first cell layer), and usually the thickness of the closed cell layer and the open cell layer of the foam when the needle enters. The length corresponds to the ratio. The foam may be compressed to allow the needle to enter. Moreover, you may make a needle penetrate | invade into a foam over multiple times. For example, the foam may be sequentially punched with a plurality of needle rolls or pin rolls that are rotatably arranged at intervals in the direction of travel of the foam. The thickness of the needle (or pin) may be, for example, about an average diameter of 0.1 to 5 mm (for example, 0.2 to 3 mm, preferably 0.25 to 1.5 mm). The density of the needle (or pin) (lines / cm ² ) can be selected according to the density of closed cells, and is usually 1-60 lines / cm ² (for example, 2-55 lines / cm ² ), preferably It may be about 3 to 50 / cm ² (for example, 4 to 45 / cm ² ), more preferably about 5 to 40 / cm ² (for example, 6 to 35 / cm ² ). The number may be about 1 / cm ² (for example, 2 to 200 / cm ² ), preferably 70 to 150 / cm ² (for example, 80 to 120 / cm ² ). In addition, the density (lines / cm ² ) of the needles is 0.1 to 1 / cm ^{2 on} average (for example, 0.2 to 0.8 / cm ² ) per one closed cell (closed cell having an average cell diameter). ² , preferably about 0.25 to 0.6 / cm ² , more preferably about 0.3 to 0.5 / cm ² ).

  The roll diameter of the needle roll (or pin roll) is, for example, about 50 to 250 mmφ (for example, 70 to 200 mmφ, preferably 80 to 170 mmφ), and the pitch of the needle (or pin) is 0.5 to 20 mm (for example, 0.8 to 15 mm, preferably 1 to 12 mm, more preferably 1.5 to 10 mm, and the rotation speed of the roll is 10 to 170 rpm (for example, 25 to 150 rpm, preferably 50 to 130 rpm, more preferably 75 to 125 rpm).

  FIG. 2 is a schematic view for explaining a production process of a plate-like resin foam. A resin foam (a foam having a closed cell structure) 9 extruded from the die of the extruder is guided to the support guide roll 10 while bubbles are growing, and on the surface of a roll (needle roll) 11 that can rotate on the surface. A plurality of needles 12 having a predetermined length are pierced, and the closed cells on one surface side (surface layer portion) are made into continuous cells. That is, among the resin foams 9, the open cell layer 6 mainly having an open cell structure is formed on one surface side into which the needle 12 has entered, and the closed cell layer 7 mainly having closed cells is formed on the other surface side. Forming.

  By the above method, a plate-like resin foam in which needle holes having an open cell layer are formed can be continuously produced. Such a corrugated plate-like resin foam can be easily produced, mass-produced, and manufacturing costs can be reduced.

<Rubber foam>
A rubber-based foam (such as a plate-like rubber-based foam) can be formed of a rubber-based polymer having at least an open cell structure.

  Examples of rubber polymers include olefin elastomers (ethylene-propylene-diene rubber (EPDM), ethylene-propylene rubber (EPM), etc.), styrene elastomers (styrene-butadiene copolymer rubber (SBR), styrene-butadiene block copolymer). Rubber (SBS), styrene-isoprene block copolymer (SIS block copolymer rubber), styrene-ethylene / butylene block copolymer (SEBS block copolymer rubber), etc., butyl elastomer (butyl rubber, isoprene rubber (IR)) , Isobutylene rubber, etc.), vinyl chloride elastomer (polyvinyl chloride (PVC), etc.), butadiene rubber (BR), chloroprene rubber (CR), polyurethane rubber, polyamide rubber, acrylic rubber, silicone rubber, natural Beam (NR), and fluorine rubbers.

  These rubber polymers can be used alone or in combination of two or more. Preferred are olefin elastomers, more preferred are ethylene-propylene-diene rubber (EPDM) and ethylene-propylene rubber (EPM).

  The rubber-based foam may contain a foaming agent (or foaming aid), a foam nucleating agent, a shrinkage preventing agent, or an additive, like the plate-like resin foam. As the foaming agent (foaming aid, shrinkage-preventing material or additive) used for the rubber foam, the same one used for the plate-like resin foam can be used. The addition amount of the foaming agent, foaming nucleating agent, shrinkage-preventing agent, or additive can be appropriately selected within a range that does not impair the formation of bubbles and the like, and the addition amount used for ordinary rubber-based foams can be adopted.

  As a method for forming the cell structure in the rubber-based foam, it can be formed by the same method as the method for preparing the cell structure of the plate-like resin foam. The rubber-based foam may have a skin layer and usually does not have a skin layer in many cases.

The average apparent density of the rubber foam is, for example, 0.01 to 0.9 g / cm ³ (for example, 0.03 to 0.7 g / cm ³ ), preferably 0.04 to 0.5 g / cm ³ ( For example, it may be about 0.05 to 0.3 g / cm ³ ). If the density of the rubber foam is too small or too large, the sound absorption of the rubber foam will be reduced.

  The average cell diameter of the rubber foam is, for example, 0.01 to 6 mm (for example, 0.05 to 6 mm), preferably 0.1 to 5 mm (for example, 0.2 to 4.5 mm), and more preferably 0. .About 3-4 mm (for example, 0.5-3.5 mm) may be sufficient. If the average cell diameter of the rubber foam is too small, the sound absorption is reduced, and if the average cell diameter of the rubber foam is too large, the sound absorption is decreased and the strength of the rubber foam is decreased.

  The rubber-based foam is not particularly limited as long as it has at least an open-cell structure, and the entire rubber-based foam may have an open-cell structure, or even if closed cells and open-cells are mixed. Good.

  The rubber-based foam has a single-layer structure composed of one foam layer, may have a cell structure over the whole, or may have a stacked structure in which a plurality of layers are stacked.

  The form of the rubber-based foam is not particularly limited, and may be, for example, a two-dimensional shape, and the thickness is not particularly limited, and may be a flat plate shape. The average thickness of the rubber-based foam is, for example, 1 to 50 mm (for example, 2 to 25 mm), preferably 3 to 20 mm (for example, 4 to 18 mm), and more preferably 5 to 15 mm (for example, 6 to 12 mm). May be. If the thickness of the rubber foam is too small or too large, the sound absorption of the rubber foam will be reduced.

  In addition, when the average thickness of the plate-like resin foam is 1, the average thickness of the rubber-based foam is, for example, 0.1 to 5 (for example, 0.2 to 3), preferably 0.3 to 2 ( For example, it may be 0.25 to 2), more preferably 0.5 to 1.5 (for example, 0.8 to 1.2).

  The composite sound-absorbing material (soundproofing material or silencing material) of the present invention can be formed by laminating a plate-like resin foam and a rubber-based foam in a predetermined order or in layers.

  The average thickness of the composite sound-absorbing material provided with the plate-like resin foam and the rubber foam is, for example, 3 to 100 mm (for example, 5 to 70 mm), preferably 7 to 50 mm (for example, 10 to 30 mm), Preferably, it may be 12 to 25 mm (for example, 15 to 20 mm).

<Sound absorption characteristics of composite sound absorbing material>
Based on the normal incidence method according to JIS A 1405, the composite sound-absorbing material exhibits the following sound-absorbing characteristics when measured in a frequency range of 0 to 6500 Hz using a thin tube.

  The rubber-based foam exhibits a high sound absorption coefficient peak in the frequency range of 1500 to 2500 Hz. Therefore, the rubber-based foam alone cannot improve the sound absorption coefficient in the frequency range of 2500 Hz or higher.

  More specifically, for example, the sound absorption coefficient of the rubber foam gradually rises from around 500 Hz to around 2000 Hz, and is 1500 to 2500 Hz, 0.55 to 0.85, preferably 0.6 to 0.8, More preferably, it may show a peak at about 0.65 to 0.75. Thereafter, as the frequency increases, the sound absorption coefficient decreases to about 0.4 to 0.5, and at 3000 Hz or higher, 0.35 to 0.65, preferably 0.4 to 0.6, and more preferably 0.45. It may be stable at about .about.0.55.

  On the other hand, the plate-shaped resin foam has a high sound absorption coefficient peak in the frequency range of 4500 to 5500 Hz even if the needle hole is formed on the uneven surface on the upstream side with respect to the incident direction of the sound wave and the punched hole is formed. It is not possible to improve the sound absorption coefficient in a frequency range of 4500 Hz or less.

  More specifically, for example, the sound absorption coefficient of the plate-shaped resin foam gradually rises from around 500 Hz to around 4500 Hz, and is around 0.85 to 1, preferably 0.9 to 1, around 4500 to 5500 Hz. Preferably, it may show a peak at about 0.95 to 1. Thereafter, as the frequency range increases, the sound absorption rate may gradually decrease.

  In the present invention, sound absorption characteristics can be improved by laminating a plate-like resin foam on a rubber foam. For example, in the aspect (Aspect A) in which the rubber foam is disposed on the upstream side with respect to the incident direction of the sound wave, the frequency shifts to a lower frequency range (for example, 800 to 1500 Hz) than the peak of the sound absorption coefficient of the rubber foam. Can be made. That is, sound absorption can be improved in a low frequency range that is not found in rubber and plate-like resin foam. Therefore, the composite sound-absorbing material of aspect A is suitable for applications that absorb sound waves of low frequency.

  More specifically, in the aspect A, the sound absorption rate suddenly rises, for example, from around 500 Hz to around 800 to 1300 Hz, and around 800 to 1500 Hz, 0.6 to 0.9, preferably 0.65 to 0.00. 85, more preferably about 0.7 to 0.8.

  In addition, in aspect A, the plate-like resin foam may be arranged with the concavo-convex surface facing outward, but in many cases it is arranged with the rubber-based foam.

  Further, in the present invention, in the aspect (Aspect B) in which the plate-shaped resin foam is disposed on the upstream side with respect to the incident direction of the sound wave, the sound wave is compared with the rubber-based foam, the plate-shaped resin foam, or the aspect A. The frequency range to be absorbed can be expanded and the sound absorption rate can be improved. That is, in the aspect B, the frequency range where the sound absorption coefficient is low in the rubber-based foam and the plate-shaped resin foam alone (for example, the frequency range of 2000 Hz or more for the rubber-based foam and 1500 to 4500 Hz for the plate-shaped resin foam). In many cases, the sound absorption rate in the frequency range) can be greatly improved, and the sound absorption rate in the frequency range where the sound absorption rate is low (for example, a frequency range of 1500 Hz or more) can be improved. Moreover, the sound absorption can be improved at a high level in a wide frequency range. Furthermore, sound absorption can be improved even in a frequency range (3000 to 4000 Hz) that is not found in rubber-based foams and plate-like resin foams. Therefore, the composite sound-absorbing material of aspect B is suitable for applications that absorb sound waves in a wide frequency range. For example, in the aspect B, the sound absorption frequency range can be expanded to 1500 Hz or more (for example, 1500 to 6500 Hz), and the sound absorption rate can be improved. Note that the sound absorption coefficient of the composite sound-absorbing material has peaks at, for example, 1500 to 2500 Hz (for example, about 0.75 to 0.98) and 3500 to 4500 Hz (for example, about 0.8 to 1). The sound absorption rate at 3000 to 4000 Hz may be improved.

  More specifically, for example, the sound absorption coefficient of the aspect B suddenly rises from around 500 Hz to around 1500 Hz, 0.75 to 0.98, preferably 0.8 to 0.95, around 1500 to 2500 Hz. Preferably, it may show a peak at about 0.85 to 0.9. Thereafter, the sound absorption coefficient decreases to about 0.65 to 0.85 (for example, 0.7 to 0.8) near 2500 Hz, and gradually increases when it exceeds about 2500 Hz, for example, near 3500 to 4500 Hz. There may be a peak at about 0.8 to 1, preferably about 0.85 to 0.99, and more preferably about 0.9 to 0.95. Thereafter, as the frequency increases, the sound absorption coefficient gradually decreases, and the sound absorption coefficient may be 0.6 to 0.7 (for example, 0.55 to 0.65) in the vicinity of 6500 Hz.

  In aspect B, the plate-like resin foam may be arranged with the concavo-convex surface facing the rubber-based foam, but is often arranged outward.

  In the aspect A and the aspect B, the plate-like resin foam may be positioned with any surface (for example, a flat surface or an uneven surface) facing the sound wave incident side. In the aspect (for example, aspect B), the uneven surface of the plate-shaped resin foam is disposed facing the flat surface of the plate-shaped resin foam relative to the incident side of the sound wave. Then, the sound absorption coefficient that was about 0.7 to 0.9 in the frequency range of 3000 to 5000 Hz may be improved to about 0.8 to 1.

  Furthermore, in the aspect A and the aspect B, a sound wave may be incident without forming a needle hole, and one surface (for example, an uneven surface) or both surfaces (for example, one uneven surface) of the plate-like resin foam, A sound wave may be incident from a surface (needle hole forming surface) in which a needle hole is formed on the other flat surface or both of the uneven surface. In the said aspect (for example, aspect B), if a sound wave is injected from a needle hole formation surface after forming a needle hole, the sound absorption coefficient in a frequency range of 1500 Hz or more can be improved. When a needle hole is formed on one surface (for example, an uneven surface) of the plate-like resin foam and a sound wave is incident from the needle hole forming surface, for example, about 0.7 to 0.9 in a frequency range of 3000 to 5000 Hz. The sound absorption coefficient may be improved to about 0.8 to 1. Furthermore, when needle holes are formed on both surfaces of the plate-shaped resin foam (for example, both the one uneven surface and the other flat surface or the uneven surface), for example, 0.65 in the frequency range 1500 to 2500 Hz. In some cases, the sound absorption coefficient, which was about 0.85, can be further improved to about 0.75-0.98.

  Furthermore, in the said aspect A and the said aspect B, a sound wave may be incident after forming a punched hole in the plate-like resin foam. In the above aspect (for example, aspect B), when a sound wave is incident after forming a punched hole, for example, the sound absorption coefficient that is about 0.65 to 0.85 in the frequency range 1500 to 2500 Hz is set to 0.75 to 0.00. In some cases, it can be improved to about 98.

  From these facts, in the composite sound-absorbing material, when the rubber-based foam is disposed on the downstream side with respect to the incident direction of the sound wave, the sound-absorbing property can be improved in a wide frequency range (for example, 1500 to 6500 Hz). Furthermore, the sound wave is incident from the uneven surface of the plate-shaped resin foam, the needle hole is formed on at least one surface (one surface or both surfaces, particularly the uneven surface) of the plate-shaped resin foam, By forming the punched hole, it is possible to further improve the sound absorption.

  FIG. 3 is a schematic view showing an example of the composite sound absorbing material of the present invention. In this example, the composite sound absorbing material 13 is arranged in a layered manner in the order of the plate-like resin foam 1 and the rubber foam 14. Further, at least one surface of the plate-like resin foam 1 is formed as an uneven surface, and the uneven surface is disposed as a sound wave incident surface. Further, needle holes 5 are formed on the uneven surface, and punched holes 8 penetrating the plate-like resin foam 1 are formed.

  In the present invention, a plate-like resin foam and a rubber-based foam may be provided, and the middle of the plate-shaped resin foam and the rubber-based foam or the inside of the plate-shaped resin foam and the rubber-based foam. / Adjacent to the outside, non-woven fabric and / or woven fabric (for example, non-woven fabric and / or woven fabric (for example, glass wool) of fibers such as organic fiber, inorganic fiber, etc.), porous material (for example, urethane sponge, etc.) A soft resin foam; a foam other than the rubber foam and / or a resin foam other than the plate-like resin foam), a sheet and / or a thin film (for example, a metal such as aluminum, a plastic, etc.), You may laminate | stack a net | network or a mesh (for example, net | networks, such as the said fiber and a foam).

<Method for producing composite sound absorbing material>
As described above, the composite sound-absorbing material of the present invention can be produced by laminating or laminating a rubber-based foam and a plate-shaped resin foam. The members do not necessarily have to be joined to each other, and can be installed according to the application location and the shape thereof. Each member may be joined or bonded to each other, for example, a double-sided tape, an adhesive, etc. It may be sutured and fastened. In addition, even if it adhere | attaches and joins, it does not seem to affect the sound absorption property of a composite sound-absorbing material.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

  As the sound absorption coefficient, a normal incident sound absorption coefficient based on JIS A 1405 was measured. The sound absorption coefficient was measured in a frequency range from a frequency of 0 Hz to 6500 Hz using a thin tube with a normal incidence transmission loss measurement unit (transmission loss tube kit, Type 4206-T (manufactured by Brüel & Kjær)).

  The following plate-like resin foam and rubber foam were used.

(A) Plate-like resin foam A polyolefin foam (manufactured by DM Nova Foam Co., Ltd.) was used. This foam has an average thickness of 8 cm, an expansion ratio of 40 times, and an apparent density of 0.021 g / cm ³ . It has a rib surface (curved uneven surface; pitch 10 mm, height 3 mm) on one surface, needle holes (needle hole density 12 / cm ² ) are formed only on the rib surface, and punched holes (average diameter: 5 mmΦ) , Average density: 1.5 pieces / 10 cm ² ).

  The plate-like resin foam is prepared in Example 7 of Patent Document 2 except that a foamable resin composition is extruded into a sheet shape from a die in which one of the opposing inner walls is formed in an uneven shape. It produced according to. The foamable resin composition comprises 65 parts by weight of polyethylene, 20 parts by weight of polystyrene, 15 parts by weight of an ethylene-vinyl acetate copolymer, 2 parts by weight of talc and a foaming agent (butane / pentane (weight ratio) = 50/50). Contains 0 parts by weight.

(B) Rubber-based foam It is formed of EPDM, has an apparent density of 0.196 g / cm ³ and a thickness of 8 mm, and no skin layer is formed.

Comparative Example 1
(B) The sound absorption coefficient of the rubber-based foam was measured. The results are shown in FIG.

  As is clear from FIG. 6, in Comparative Example 1, a peak (sound absorption rate of about 0.7) was shown in the frequency range near 2000 Hz, and the sound absorption rate was low in the frequency range of 3000 Hz or more (sound absorption rate of 0.55 or less). .

Reference example 1
(A) With respect to the plate-like resin foam, a sound wave was incident from the rib surface and the sound absorption coefficient was measured. The results are shown in FIG.

  As is clear from FIG. 7, in Reference Example 1, a peak (sound absorption rate of 0.95 to 1) was shown in the frequency range near 5000 Hz, and the sound absorption rate was low in the frequency range of 3000 Hz or less (sound absorption rate of 0.4 or less). ).

Example 1
A plate-shaped resin foam and a rubber-based foam were stacked in the following order, and each was bonded with a double-sided tape to obtain a composite sound-absorbing material.

(B) Rubber-based foam / (A) Plate-shaped resin foam The rib surface of the plate-shaped resin foam was disposed toward the rubber-based foam side. The obtained composite sound-absorbing material had a thickness of 16.5 mm (measured with a thickness gauge). About the obtained composite sound-absorbing material, a sound wave was incident from a rubber-based foam and the sound absorption rate was measured. The results are shown in FIG.

  As is clear from FIG. 4, in Example 1, the peak near 1000 Hz (sound absorption ratio 0.7 to 0.8) is shifted to a low frequency range, that is, in Example 1 (FIG. 4), a comparative example is provided. 1 (FIG. 6) and Reference Example 1 (FIG. 7), the peak frequency region can be shifted to the low frequency side that did not appear.

Example 2
A plate-like resin foam and a rubber foam were stacked in the following order and bonded with a double-sided tape to obtain a composite sound absorbing material.

(A) Plate-like resin foam / (B) Rubber-based foam The rib surface (uneven surface) of the plate-like resin foam was arranged facing outward. The thickness of the obtained composite sound absorbing material was 16.7 mm (measured with a thickness gauge). About the obtained composite sound-absorbing material, a sound wave was incident from the rib surface and the sound absorption rate was measured. The results are shown in FIG.

  As is clear from FIG. 5, in Example 2 (FIG. 5), the sound absorption frequency range is set to a wide frequency range (1500 to 6500 Hz) that was not found in Comparative Example 1 (FIG. 6) and Reference Example 1 (FIG. 7). In addition to being able to expand, the sound absorption rate can be improved, and even in the low frequency range (around 3000 to 4000 Hz) where the sound absorption effect is small even if the measurement data of Comparative Example 1 and Reference Example 1 are weighted average, Can be improved.

  The composite sound-absorbing material of the present invention is a composite sound-absorbing material having a rubber-based foam and a plate-shaped resin foam, wherein the plate-shaped resin foam and the rubber-based foam have open cells, Since the plate-like resin foam is arranged on the most upstream side with respect to the incident direction of the sound wave, a composite sound absorbing material having a high sound absorbing property can be obtained in a wide frequency range of medium to high frequency (for example, 1500 to 6500 Hz). Can be obtained. Therefore, the present invention includes vehicles (cars, vehicles such as trains, aircraft, ships, etc.), buildings (houses, apartment houses, condominiums, factories, libraries, hospitals, school buildings, gymnasiums, auditoriums, movie theaters, concert venues, Parking lots, high-rise buildings such as buildings), electrical appliances (toys, household appliances, etc.), industrial machinery (construction machinery, agricultural machinery, etc.), piping (exhaust pipes, supply pipes, drain pipes, water absorption pipes, etc.) It is useful as a sound-absorbing material and a sound-absorbing heat insulating material. In particular, it can be used for automobiles, trains and other car bodies, building walls, floors, ceilings, etc. that require sound absorption.

DESCRIPTION OF SYMBOLS 1 ... Plate-shaped resin foam 2 ... Rib 3 ... Top part (convex part)
4 ... Valley (concave)
DESCRIPTION OF SYMBOLS 5 ... Needle hole 6 ... Open cell phase 7 ... Closed cell phase 8 ... Punching hole 9 ... Resin foam 10 ... Support guide roll 11 ... Roll 12 ... Needle 13 ... Composite sound-absorbing material 14 ... Rubber foam

Claims (13)

A composite sound absorbing material having a plate-like resin foam and a rubber foam,
The plate-like resin foam and the rubber foam have at least open cells,
A composite sound absorbing material in which the plate-like resin foam is laminated on the rubber-based foam. The plate-like resin foam has an uneven surface on at least one surface, has closed cells together with open cells,
The composite sound-absorbing material according to claim 1, wherein the composite sound-absorbing material has a needle hole that penetrates from the surface of the plate-like resin foam partway through the thickness direction and penetrates at least some of the closed cells.   The composite sound-absorbing material according to claim 2, wherein the plate-like resin foam is disposed with the uneven surface facing at least the outside. The composite sound-absorbing material according to claim 2 or 3, wherein the uneven surface satisfies at least one condition selected from the following (1), (2), (3) and (4).
(1) The average height difference between the top and the valley on the concavo-convex surface is 1 to 50 mm. (2) The average interval between the tops on the concavo-convex surface is 1 to 60 mm. (4) Needle holes at least on the uneven surface   The composite sound-absorbing material according to any one of claims 2 to 4, wherein the depth of the needle hole is 10 to 90% with respect to the entire thickness of the plate-like resin foam.   The plate-like resin foam contains at least one base component selected from an ethylene-based resin and a thermoplastic elastomer, and the expansion ratio of the plate-like resin foam is 10 to 100 times. The composite sound-absorbing material described in 1.   The composite sound-absorbing material according to any one of claims 2 to 6, wherein the uneven surface is a corrugated surface formed by a protrusion and a groove adjacent to the protrusion.   The composite sound-absorbing material according to any one of claims 1 to 7, which has a punched hole penetrating the plate-like resin foam.   The composite sound-absorbing material according to claim 8, wherein an average diameter of the punched holes is larger than an average diameter of the needle holes and is 1 to 20 mm. The composite sound-absorbing material according to any one of claims 1 to 9, wherein at least one condition selected from the following (5), (6) and (7) is satisfied.
(5) The average cell diameter of the rubber foam is 0.01 to 6 mm (6) The average apparent density of the rubber foam is 0.01 to 0.9 mg / mm ³ (7) Rubber foam Body comprises at least ethylene-propylene-diene rubber   The composite sound-absorbing material according to any one of claims 1 to 10, wherein the thickness of the rubber foam is 0.1 to 5 when the thickness of the plate-like resin foam is 1.   A method for improving the sound absorption of the composite sound absorbing material according to claim 1, wherein a sound wave is incident on the composite sound absorbing material to improve the sound absorption.   The method for producing a composite sound-absorbing material according to any one of claims 1 to 11, wherein a rubber foam having open cells is laminated with a plate-like resin foam having open cells.

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