WO2021053926A1 - Foam rubber, method for producing same and sound absorbing material - Google Patents

Foam rubber, method for producing same and sound absorbing material Download PDF

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Publication number
WO2021053926A1
WO2021053926A1 PCT/JP2020/025840 JP2020025840W WO2021053926A1 WO 2021053926 A1 WO2021053926 A1 WO 2021053926A1 JP 2020025840 W JP2020025840 W JP 2020025840W WO 2021053926 A1 WO2021053926 A1 WO 2021053926A1
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Prior art keywords
foam rubber
mass
foam
elastomer
less
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PCT/JP2020/025840
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French (fr)
Japanese (ja)
Inventor
正雄 小野塚
貴史 砂田
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デンカ株式会社
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Publication of WO2021053926A1 publication Critical patent/WO2021053926A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R13/00—Elements for body-finishing, identifying, or decorating; Arrangements or adaptations for advertising purposes
    • B60R13/08—Insulating elements, e.g. for sound insulation
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/30—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by mixing gases into liquid compositions or plastisols, e.g. frothing with air
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/34—Silicon-containing compounds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
    • C08L9/10—Latex

Definitions

  • the present invention relates to foam rubber, a method for producing the same, and a sound absorbing material.
  • Sound absorbing materials are widely used in houses, audio equipment, railroad vehicles, aircraft, automobiles, etc.
  • a sound absorbing material as an in-vehicle soundproofing material is used on many of the interior walls of the vehicle.
  • a foam rubber that can be used as a sound absorbing material a foam rubber produced by using a mixture of latex and an emulsifier having a pH of 8.5 or less is known (see, for example, Patent Document 1 below). Further, a sound absorbing material having a high density layer and a low density layer composed of an open cell foam of EPDM rubber and absorbing sound having a frequency of 600 Hz or less is known (see, for example, Patent Document 2 below). ..
  • the sound absorption characteristics in the low frequency region are sufficient for the conventional foam rubber, it is required to improve the sound absorption characteristics in the low frequency region, and in particular, excellent sound absorption at a frequency of 500 Hz. It is required to obtain characteristics (high sound absorption coefficient). Further, foam rubber is required to have excellent moldability for molding into various shapes.
  • One aspect of the present invention is a foam rubber having open cells in which hollow cells are connected to each other, wherein the Heywood diameter defined in JIS Z 8827-1: 2018 of the cells is 180 ⁇ m or less, and the foam rubber has a diameter of 180 ⁇ m or less.
  • Such foam rubber has excellent sound absorption characteristics at a frequency of 500 Hz and also has excellent moldability.
  • Another aspect of the present invention provides a sound absorbing material made of the foam rubber described above.
  • Another aspect of the present invention is a foaming step of foaming an elastomer composition containing a vulcanizing agent to obtain a foam, and a gelling step of adding a gelling agent to the foam to obtain a gelled product.
  • a method for producing a foam rubber which has a gelation time of 2 to 8 minutes after adding the gelling agent in the gelation step.
  • a foam rubber having excellent sound absorbing characteristics at a frequency of 500 Hz and having excellent moldability According to another aspect of the present invention, it is possible to provide a sound absorbing material using the foam rubber. According to another aspect of the present invention, it is possible to provide a method for producing a foam rubber having excellent sound absorbing characteristics at a frequency of 500 Hz and having excellent moldability. According to another aspect of the present invention, it is possible to provide an application of foam rubber for sound absorption (soundproofing), and it is possible to provide an application of foam rubber for sound absorption (soundproofing) in a low frequency region.
  • the numerical range indicated by using “-” indicates a range including the numerical values before and after "-" as the minimum value and the maximum value, respectively. “A or more” in the numerical range means A and a range exceeding A. “A or less” in the numerical range means A and a range less than A.
  • the upper limit value or the lower limit value of the numerical range of one step can be arbitrarily combined with the upper limit value or the lower limit value of the numerical range of another step.
  • the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.
  • "A or B" may include either A or B, or both.
  • each component in the composition means the total amount of the plurality of substances present in the composition when a plurality of substances corresponding to each component are present in the composition, unless otherwise specified.
  • the term "process" is included in this term not only in an independent process but also in the case where the desired action of the process is achieved even if it cannot be clearly distinguished from other processes.
  • the foam rubber according to the present embodiment is a foam rubber having open cells in which hollow cells are connected to each other.
  • the open cells of foam rubber contain a plurality of hollow cells.
  • open cell is meant a structure in which at least a portion of the cells formed in the foam rubber are continuous.
  • the foam rubber may have an open cell structure or a semi-continuous semi-closed cell structure.
  • the open cell structure refers to a structure in which the open cell ratio is 100%. In the semi-continuous semi-closed cell structure, the lower limit of the open cell ratio exceeds 0% and may be 10% or more. In the semi-continuous semi-closed cell structure, the upper limit of the open cell ratio is less than 100% and may be less than 98%.
  • the Heywood diameter defined in JIS Z 8827-1: 2018 of the cell is 180 ⁇ m or less, and the density of the foam rubber is 0.10 to 0.35 g / cm 3 .
  • the foam rubber according to the present embodiment may be a single-layer foam rubber.
  • the foam rubber according to the present embodiment has excellent sound absorption characteristics (high sound absorption coefficient) at a frequency of 500 Hz as sound absorption characteristics in the low frequency region.
  • the foam rubber according to the present embodiment is also excellent in moldability (molding processability, for example, moldability of foam rubber which is a vulcanized product), has excellent sound absorbing characteristics at a frequency of 500 Hz, and has excellent moldability.
  • Moldability molding processability, for example, moldability of foam rubber which is a vulcanized product
  • the foam rubber according to the present embodiment has a sound absorption coefficient of 0.5 or more as a vertically incident sound absorption coefficient at a frequency of 500 Hz, and has a sound absorption coefficient of 0.5 to 0.8 as a vertically incident sound absorption coefficient at a frequency of 500 Hz. You can do it.
  • the foam rubber according to the present embodiment is excellent in sound absorption characteristics in a wide range of low frequencies, and may have excellent sound absorption characteristics in a frequency region of 50 to 1500 Hz, for example.
  • the foam rubber according to the present embodiment may have a maximum value (peak) of the vertical incident sound absorption coefficient in the frequency domain of 50 to 1500 Hz, and the maximum value of the vertical incident sound absorption coefficient in the frequency domain of 50 to 1500 Hz is 0.6 to 0. It may have a sound absorption coefficient of 9.
  • the foam rubber according to the present embodiment may have a high vertical incident sound absorption coefficient in the entire frequency range of 50 to 1500 Hz, and has a minimum value of 0.4 or more vertical incident sound absorption coefficient in the frequency domain of 50 to 1500 Hz. May have a rate.
  • the vertical incident sound absorption coefficient can be measured by JIS A 1405-2: 2007.
  • the vertically incident sound absorption coefficient can be measured by the procedure described in Examples described later.
  • the vertical incident sound absorption coefficient at a frequency of 500 Hz specified by JIS A 1405-2: 2007 may be 0.5 to 0.8, and is specified by JIS A 1405-2: 2007.
  • the vertical incident sound absorption coefficient in the entire frequency range of 50 to 1500 Hz is 0.5 to 1.0.
  • the foam rubber according to this embodiment can achieve excellent sound absorption characteristics with a single layer.
  • the foam rubber according to the present embodiment can be used as a foam rubber for a sound absorbing material, and can be used as a sound absorbing material for various purposes such as automobiles, houses, audio facilities, railway vehicles, and aircraft. By using such foam rubber as a sound absorbing material for automobiles, it is possible to absorb sound in a low frequency region such as motor sound and road noise.
  • the sound absorbing method according to the present embodiment uses the foam rubber according to the present embodiment to absorb sound (for example, absorb sound in a low frequency region).
  • the Heywood diameter defined in JIS Z 8827-1: 2018 of the cell is 180 ⁇ m or less. If the Heywood diameter of the cell exceeds 180 ⁇ m, the sound absorption characteristics in the low frequency region are impaired.
  • the Heywood diameter of the cell exceeds 0 ⁇ m, and from the viewpoint that excellent moldability can be easily obtained, 100 ⁇ m or more is preferable, 110 ⁇ m or more is more preferable, and 120 ⁇ m or more is further preferable.
  • the Heywood diameter of the cell is preferably 170 ⁇ m or less, more preferably 160 ⁇ m or less, further preferably 150 ⁇ m or less, particularly preferably 140 ⁇ m or less, and extremely preferably 130 ⁇ m or less, from the viewpoint that excellent sound absorption characteristics can be easily obtained in the low frequency region. From these viewpoints, the Heywood diameter of the cell is preferably 100 to 180 ⁇ m.
  • the Heywood diameter of the cell may be 130 ⁇ m or more, 140 ⁇ m or more, 150 ⁇ m or more, 160 ⁇ m or more, or 170 ⁇ m or more.
  • the Heywood diameter of the cell may be 120 ⁇ m or less.
  • the gelation time may be adjusted by adjusting the amount of the gelling agent added in the gelation step described later.
  • the amount of the gelling agent may be reduced to lengthen the gelling time.
  • the suitable gelling time for obtaining the foam rubber can be adjusted by using the Heywood diameter of the foam rubber cell as an index.
  • the Heywood diameter of the cell can also be adjusted by the number of revolutions when stirring the elastomer composition in the foaming step described later.
  • the open cells of the foam rubber may include a hollow cell connecting portion (hole of the cell connecting portion) that connects the cells.
  • the Heywood diameter defined in JIS Z 8827-1: 2018 of the cell connecting portion is preferably in the following range.
  • the Heywood diameter of the cell connecting portion is preferably 5 ⁇ m or more, more preferably 8 ⁇ m or more, further preferably 10 ⁇ m or more, particularly preferably 15 ⁇ m or more, extremely preferably 20 ⁇ m or more, and 22 ⁇ m or more from the viewpoint that excellent moldability can be easily obtained. Is very preferable.
  • the Heywood diameter of the cell connecting portion is preferably 50 ⁇ m or less, more preferably 45 ⁇ m or less, further preferably 40 ⁇ m or less, particularly preferably 38 ⁇ m or less, and extremely preferably 35 ⁇ m or less, from the viewpoint that excellent sound absorption characteristics in the low frequency region can be easily obtained.
  • 32 ⁇ m or less is very preferable, and 31 ⁇ m or less is even more preferable.
  • the Heywood diameter of the cell connecting portion is preferably 5 to 50 ⁇ m, more preferably 5 to 35 ⁇ m, further preferably 10 to 35 ⁇ m, and particularly preferably 10 to 30 ⁇ m.
  • the Heywood diameter of the cell connecting portion may be 25 ⁇ m or more, 28 ⁇ m or more, 30 ⁇ m or more, 31 ⁇ m or more, 32 ⁇ m or more, 35 ⁇ m or more, or 38 ⁇ m or more.
  • the Heywood diameter of the cell connecting portion may be 30 ⁇ m or less, 28 ⁇ m or less, 25 ⁇ m or less, 22 ⁇ m or less, 20 ⁇ m or less, 15 ⁇ m or less, or 10 ⁇ m or less.
  • the gelation time may be adjusted in the same manner as adjusting the Heywood diameter of the cell.
  • the density of the foam rubber By adjusting the density of the foam rubber, it is possible to adjust only the Heywood diameter of the cell connecting portion while keeping the Heywood diameter of the cell constant. For example, increasing the density tends to reduce the Heywood diameter of the cell connecting portion.
  • the Heywood diameter of the cell connecting portion can also be adjusted by the number of revolutions when stirring the elastomer composition in the foaming step.
  • the Heywood diameter of the foam rubber cell and cell connecting portion is the diameter defined in JIS Z 8827-1: 2018, and is the diameter of a perfect circle having an area equal to the projected area of the measurement target (cell or cell connecting portion). It shows.
  • the Heywood diameter of the foam rubber cell and the cell connecting portion can be measured by the procedure described in Examples described later.
  • the density of the foam rubber according to the present embodiment is 0.10 to 0.35 g / cm 3 from the viewpoint that excellent moldability can be obtained because the flexibility and mechanical strength of the foam rubber can be maintained.
  • Density of foam rubber from the viewpoint of easy to obtain the formability excellent since the easily maintained flexibility and mechanical strength of the foam rubber, 0.10 g / cm 3 or more preferably, 0.13 g / cm 3 or more preferably , more preferably more than 0.13 g / cm 3, particularly preferably 0.15 g / cm 3 or more, very preferably more than 0.17 g / cm 3, very preferably more than 0.17 g / cm 3, 0.20 g / cm 3 or even more preferably, more preferably more than 0.20 g / cm 3, particularly preferably 0.22 g / cm 3 or higher, 0.24 g / cm 3 or more is very preferred, 0.25 g / Cm 3 or more is very preferable, more than 0.25 g / cm 3 is even more preferable, 0.26 g / cm 3
  • Density of foam rubber from the viewpoint of easy to obtain the formability excellent since the easily maintained flexibility and mechanical strength of the foam rubber is preferably 0.35 g / cm 3 or less, more preferably 0.33 g / cm 3 or less , more preferably 0.30 g / cm 3 or less, particularly preferably 0.29 g / cm 3 or less, 0.28 g / cm 3 or less is very preferable. From these viewpoints, the density of the foam rubber is preferably 0.10 ⁇ 0.35g / cm 3, more preferably 0.15 ⁇ 0.35g / cm 3.
  • the density of the foam rubber is, 0.28 g / cm 3 or more, 0.29 g / cm 3 or more, 0.30 g / cm 3 or more, or, may be at 0.33 g / cm 3 or more.
  • the density of the foam rubber is 0.27 g / cm 3 or less, 0.25 g / cm 3 or less, 0.24 g / cm 3 or less, 0.22 g / cm 3 or less, or 0.20 g / cm 3 or less. Good.
  • the amount of gas taken into the elastomer composition in the foaming step described later, the number of rotations when stirring the elastomer composition in the foaming step, and the like may be adjusted.
  • the density of the foam rubber can be measured by the procedure described in Examples described later.
  • the foam rubber according to this embodiment can contain an elastomer.
  • the elastomer include natural rubber, isoprene rubber, nitrile butadiene rubber, styrene butadiene rubber, chloroprene polymer (chloroprene rubber (a homopolymer of chloroprene), and a copolymer of chloroprene and unsaturated nitrile (for example, a combination of chloroprene and acrylonitrile). Polymers), etc.), ethylene propylene diene rubber, butadiene rubber, butyl rubber and the like.
  • the foam rubber according to the present embodiment may contain a component other than the elastomer, and may contain, for example, an additive described later.
  • the foam rubber according to the present embodiment may contain an elastomer as a main component, and can be obtained by using an elastomer latex as a main raw material.
  • the chloroprene polymer is obtained by polymerizing chloroprene (chloroprene monomer) and has a structural unit derived from chloroprene.
  • the copolymer of chloroprene and unsaturated nitrile is obtained by copolymerizing chloroprene (chloroprene monomer) and unsaturated nitrile (unsaturated nitrile monomer, for example, acrylonitrile monomer), and has a structure derived from chloroprene. It has a unit and a structural unit derived from unsaturated nitrile.
  • unsaturated nitriles examples include acrylonitrile, methacrylonitrile, etacrylonitrile, and phenylacrylonitrile. Unsaturated nitriles can be used alone or in combination of two or more.
  • the unsaturated nitrile preferably contains acrylonitrile from the viewpoint that excellent sound absorbing characteristics in the low frequency region (for example, excellent sound absorbing characteristics at a frequency of 500 Hz) can be easily obtained.
  • the content of the structural unit derived from chloroprene is less than 100% by mass based on the total amount of the copolymer of chloroprene and unsaturated nitrile or the total amount of the structural unit derived from chloroprene and the structural unit derived from unsaturated nitrile. Therefore, the following range is preferable from the viewpoint that excellent sound absorption characteristics in the low frequency region (for example, excellent sound absorption characteristics at a frequency of 500 Hz) can be easily obtained.
  • the content of the structural unit derived from chloroprene is preferably 50% by mass or more, more preferably more than 50% by mass, further preferably 60% by mass or more, particularly preferably 70% by mass or more, and extremely preferably 75% by mass or more.
  • the content of the structural unit derived from chloroprene is preferably 99% by mass or less, more preferably 95% by mass or less, further preferably 90% by mass or less, particularly preferably 85% by mass or less, and extremely preferably 80% by mass or less. From these viewpoints, the content of the structural unit derived from chloroprene is preferably 50% by mass or more and less than 100% by mass.
  • the content of the structural unit derived from unsaturated nitrile is 0 mass based on the total amount of the copolymer of chloroprene and unsaturated nitrile, or the total amount of the structural unit derived from chloroprene and the structural unit derived from unsaturated nitrile.
  • the following range is preferable from the viewpoint that it exceeds% and excellent sound absorption characteristics in the low frequency region (for example, excellent sound absorption characteristics at a frequency of 500 Hz) can be easily obtained.
  • the content of the structural unit derived from unsaturated nitrile is preferably 1% by mass or more, more preferably 5% by mass or more, further preferably 10% by mass or more, particularly preferably 15% by mass or more, and extremely preferably 20% by mass or more.
  • the content of the structural unit derived from unsaturated nitrile is preferably 50% by mass or less, more preferably less than 50% by mass, further preferably 40% by mass or less, particularly preferably 30% by mass or less, and extremely preferably 25% by mass or less. , 20% by mass or less is very preferable. From these viewpoints, the content of the structural unit derived from unsaturated nitrile is preferably more than 0% by mass and 50% by mass or less. From the same viewpoint, the content of the structural unit derived from acrylonitrile is based on the total amount of the copolymer of chloroprene and unsaturated nitrile, or the total amount of the structural unit derived from chloroprene and the structural unit derived from unsaturated nitrile. , These ranges are preferable.
  • the amount of the structural unit derived from unsaturated nitrile contained in the copolymer of chloroprene and unsaturated nitrile can be calculated from the content of nitrogen atom in the copolymer. Specifically, the content of nitrogen atoms in the copolymer of 100 mg of chloroprene and unsaturated nitrile was measured using an element analyzer (Sumigraph 220F: manufactured by Sumika Chemical Analysis Service, Inc.), and the content was derived from unsaturated nitrile. The amount of structural units can be calculated. The measurement of elemental analysis can be performed under the following conditions. For example, the electric furnace temperature is set to 900 ° C. for the reactor, 600 ° C. for the reduction furnace, 70 ° C.
  • the calibration curve can be prepared using aspartic acid (10.52%) having a known nitrogen content as a standard substance.
  • the monomer copolymerized with chloroprene is not limited to unsaturated nitriles.
  • Examples of the monomer copolymerizable with chloroprene include 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, styrene, isoprene, butadiene, acrylic acid, acrylic acid esters, and methacrylic acid. Examples thereof include acids, methacrylic acid esters, and sulfur.
  • the elastomer preferably contains a chloroprene polymer from the viewpoint that excellent sound absorption characteristics in the low frequency region (for example, excellent sound absorption characteristics at a frequency of 500 Hz) can be easily obtained.
  • the elastomer does not have to contain ethylene propylene diene rubber.
  • the content of the chloroprene polymer in the foam rubber according to the present embodiment may be larger than the content of the ethylene propylene diene rubber.
  • the content of the chloroprene polymer or the content of the elastomer other than ethylene propylene diene rubber is the total mass of the elastomer from the viewpoint that excellent sound absorbing characteristics in the low frequency region (for example, excellent sound absorbing characteristics at a frequency of 500 Hz) can be easily obtained.
  • the elastomer may be substantially composed of a chloroprene polymer (a mode in which the content of the chloroprene polymer is substantially 100% by mass based on the total mass of the elastomer).
  • the elastomer may be substantially composed of an elastomer other than ethylene propylene diene rubber (a mode in which the content of the elastomer other than ethylene propylene diene rubber is substantially 100% by mass based on the total mass of the elastomer).
  • the content of ethylene propylene diene rubber is 10% by mass or less, 5% by mass or less, 1% by mass or less, 0.5% by mass or less, or 0.1% by mass or less based on the total mass of the elastomer. Good.
  • the content of the elastomer is preferably 50% by mass or more, preferably 50% by mass, based on the total mass of the foam rubber, from the viewpoint that excellent sound absorption characteristics in the low frequency region (for example, excellent sound absorption characteristics at a frequency of 500 Hz) can be easily obtained. More preferably, 60% by mass or more is further preferable, 70% by mass or more is particularly preferable, 80% by mass or more is extremely preferable, and 85% by mass or more is very preferable.
  • the content of the elastomer may be less than 100% by mass, 98% by mass or less, 95% by mass or less, or 90% by mass or less based on the total mass of the foam rubber.
  • the content of the chloroprene polymer or the content of the elastomer other than ethylene propylene diene rubber is the total of the foam rubber from the viewpoint that excellent sound absorption characteristics in the low frequency region (for example, excellent sound absorption characteristics at a frequency of 500 Hz) can be easily obtained.
  • 50% by mass or more is preferable, 50% by mass or more is more preferable, 60% by mass or more is further preferable, 70% by mass or more is particularly preferable, 80% by mass or more is extremely preferable, and 85% by mass or more. Is very preferable.
  • the content of the chloroprene polymer or the content of the elastomer other than ethylene propylene diene rubber is less than 100% by mass, 98% by mass or less, 95% by mass or less, or 90% by mass based on the total mass of the foam rubber. It may be:
  • the method for producing a foam rubber according to the present embodiment includes a foaming step of foaming an elastomer composition containing a vulcanizing agent (a composition containing an elastomer. A foamable composition) to obtain a foam, and a gel on the foam. It has a gelling step of adding an agent to obtain a gelled product.
  • a foaming step of foaming an elastomer composition containing a vulcanizing agent a composition containing an elastomer.
  • a foamable composition a composition containing an elastomer.
  • It has a gelling step of adding an agent to obtain a gelled product.
  • the elastomer composition can contain the above-mentioned elastomer.
  • the elastomer composition preferably contains a chloroprene polymer from the viewpoint that excellent sound absorbing characteristics in the low frequency region (for example, excellent sound absorbing characteristics at a frequency of 500 Hz) can be easily obtained.
  • the elastomer composition may contain an elastomer latex and may contain an elastomer latex as a main raw material.
  • the type of elastomer latex is not particularly limited, and natural rubber latex, isoprene latex, nitrile butadiene latex, styrene butadiene latex, chloroprene latex, chloroprene-acrylonitrile copolymer latex, ethylenepropylene diene latex, butadiene latex, butyl latex and the like are used. Can be mentioned.
  • the elastomer composition is preferably an elastomer latex having a solid content concentration of 55 to 70% by mass as a solid content concentration suitable for producing foam rubber.
  • the solid content concentration is 55% by mass or more, the shrinkage during vulcanization is suppressed to be large, and excellent moldability can be easily obtained.
  • the solid content concentration is 70% by mass or less, it is easy to suppress an increase in the viscosity of the elastomer latex and a decrease in latex stability during foaming.
  • the method for producing a foam rubber according to the present embodiment includes a compounding step of obtaining an elastomer composition (for example, an elastomer latex composition) by mixing an elastomer (for example, elastomer latex) and a vulcanizing agent before the foaming step. You can do it.
  • the method for producing foam rubber according to the present embodiment may include a vulcanization step of vulcanizing the gelled product obtained in the gelation step after the gelation step.
  • the foam rubber manufacturing method according to the present embodiment may include a water washing / drying step of washing and drying the vulcanized product obtained in the vulcanization step after the vulcanization step.
  • the foam rubber manufacturing method according to the present embodiment may include a molding step of molding (molding) the foam rubber.
  • an elastomer composition is obtained by mixing an elastomer and an additive containing a vulcanizing agent.
  • a vulcanization accelerator for example, a vulcanization accelerator, a foaming agent, a bubble stabilizer, an antioxidant, an anti-adhesive agent, a thickener, a water-retaining agent, a colorant, and a dispersant (for example, ⁇ -naphthalene).
  • an additive such as (sodium salt of a sulfonic acid formalin condensate)
  • elastomer for example, an elastomer latex
  • the type of vulcanizing agent is not particularly limited, but examples thereof include sulfur, zinc oxide, and peroxide.
  • the amount of the vulcanizing agent added based on the total amount of the elastomer composition the amount of sulfur added is preferably 0.0 to 2.0% by mass (for example, 0.01 to 2.0% by mass), and zinc oxide is added.
  • the amount is preferably 3.0 to 10.0% by mass, and the amount of peroxide added is preferably 0.0 to 2.0% by mass (for example, 0.01 to 2.0% by mass).
  • the type of vulcanization accelerator is not particularly limited, but is a dithiocarbamate-based accelerator such as zinc diethyldithiocarbamate or sodium dibutyldithiocarbamate; a thiourea-based accelerator such as N, N'-diethylthiourea; Accelerators; thiazole-based accelerators; xanthate-based accelerators and the like can be mentioned.
  • the amount of the vulcanization accelerator added is preferably 0.0 to 8.0% by mass (for example, 0.01 to 8.0% by mass) based on the total amount of the elastomer composition.
  • a plurality of types may be used in combination.
  • the foaming agent has a role of foaming the elastomer composition when a gas is mixed into the elastomer composition.
  • the foaming agent preferably contains an anionic surfactant having C12 to 18 carbon atoms from the viewpoint of good foamability.
  • examples of the foaming agent include fatty acid salts such as sodium laurate, sodium myristate, sodium stearate, ammonium stearate, sodium oleate, potassium oleate, castor oil potassium soap, and coconut oil potassium soap.
  • the amount of the foaming agent added is preferably 0.0 to 2.0% by mass (for example, 0.01 to 2.0% by mass) based on the total amount of the elastomer composition.
  • the bubble stabilizer has a role of stabilizing the foam of the foamed elastomer composition.
  • the bubble stabilizer include trimene base and amphoteric surfactant.
  • amphoteric surfactants include amino acid type, betaine type, amine oxide type and the like.
  • the amount of the bubble stabilizer added is preferably 0.2 to 2.0% by mass based on the total amount of the elastomer composition.
  • the type of antiaging agent is not particularly limited, and examples thereof include monophenol type, bisphenol type, polyphenol type, benzimidazole type, amine type, and phosphoric acid type.
  • Specific examples of the anti-aging agent include 2,2'-methylenebis (4-ethyl-6-tert-butylphenol) and the like.
  • the anti-adhesive agent has a role of preventing the adhesiveness of the obtained foam rubber.
  • Examples of the anti-adhesive agent include wax, petrolatum and the like.
  • an elastomer composition containing a vulcanizing agent is foamed to obtain a foam (for example, a foamed latex composition).
  • the foaming step is a step of mixing a gas with the elastomer composition (taking in air bubbles) to bring the elastomer composition into a foam state.
  • the density of the obtained foam rubber can be adjusted by adjusting the amount of gas mixed in the foaming process.
  • the mass of the elastomer (for example, latex) required at the time of blending is calculated from the desired density of the foam rubber and the volume of the elastomer (for example, latex) to be blended, and at this mass.
  • the amount of the gas to be foamed may be determined so as to have a desired volume.
  • Air, nitrogen, or the like can be used as the gas for foaming the elastomer composition into a foamy state.
  • a mixer can be used, and preferred examples thereof include a hovert mixer, a pin mixer, an oaks mixer, a hand mixer and the like.
  • the gelling step is a step of adding a gelling agent to a foamy elastomer composition (for example, a foamed latex composition) to aggregate and gel the elastomer particles dispersed in the elastomer composition.
  • a foamy elastomer composition for example, a foamed latex composition
  • the elastomer composition gels while maintaining the dispersed state of the bubbles generated by the gas mixed in the elastomer composition, and in the subsequent vulcanization step, the gelled elastomer composition is vulcanized.
  • a latex foam having a uniform cell structure can be obtained.
  • gelling agent examples include sodium silicate, potassium silicate, ammonium sulfate, carbon dioxide and the like.
  • the foaming gas present in the gelled elastomer composition is retained as bubbles, so that the size of the bubbles is the diameter of the cell of the finally obtained foam rubber and / or the cell connecting portion.
  • Tends to determine the diameter depend on the gelation time. If the gelation time is long, the bubbles mixed in the gelled elastomer composition come into contact with each other and coalesce to become large, or are discharged to the outside of the gelled elastomer composition, so that the diameter becomes large. Tends to grow. On the other hand, the shorter the gelation time, the easier it is to obtain a smaller diameter.
  • the gelling time can be adjusted by the amount of the gelling agent added. The larger the amount of the gelling agent added, the shorter the gelling time, and as a result, a foam rubber having a small diameter tends to be obtained.
  • the gelation time after adding the gelling agent in the gelation step is 2 to 8 minutes. In this case, it is possible to obtain a foam rubber having excellent sound absorbing characteristics (for example, excellent sound absorbing characteristics at a frequency of 500 Hz) and excellent moldability.
  • the gelling time is preferably 3 minutes or more from the viewpoint of easily obtaining a foam rubber having excellent sound absorbing properties and excellent moldability.
  • the gelling time is preferably 7 minutes or less, more preferably 6 minutes or less, from the viewpoint of easily obtaining a foam rubber having excellent sound absorbing properties and excellent moldability. From these viewpoints, the gelation time is preferably 3 to 6 minutes.
  • the gelation time may be 4 minutes or more, 5 minutes or more, or 6 minutes or more.
  • the gelation time may be 5 minutes or less, 4 minutes or less, or 3 minutes or less.
  • the "gelling time” is set at 23 ° C. from the time when the gelling agent is added to the foamy elastomer composition obtained in the foaming step until the fluidity disappears (the foamy elastomer composition does not adhere to the hand). Up to) time.
  • the gelled product obtained in the gelation step is vulcanized.
  • vulcanization heat vulcanization
  • the foam obtained by adding a gelling agent is processed into a desired shape by a method such as casting, casting, or extrusion molding, and then depending on the type of vulcanizing agent, elastomer, or the like.
  • This is a step of obtaining a foamed vulcanized product by sufficiently heating the vulcanization to 50 to 200 ° C.
  • the cross-linking reaction may proceed as the vulcanization progresses.
  • the vulcanization method is not particularly limited as long as it can vulcanize the foam, and examples thereof include air vulcanization and steam vulcanization.
  • foam rubber can be obtained by washing and drying the vulcanized product (foam vulcanized product) obtained in the vulcanization step with water.
  • the sound absorbing material according to the present embodiment is, for example, a molded body of the foam rubber according to the present embodiment, and can be obtained by molding (molding) the foam rubber according to the present embodiment.
  • the sound absorbing material according to the present embodiment is made of the foam rubber according to the present embodiment and has excellent sound absorbing characteristics in the low frequency region.
  • the sound absorbing material according to the present embodiment can be used in various applications such as automobiles, houses, audio facilities, railroad vehicles, and aircraft, and is preferably for automobiles (automobile sound absorbing material, in-vehicle soundproofing material). According to the present embodiment, it is possible to provide an automobile, a house, an audio facility, a railroad vehicle, an aircraft and the like provided with the sound absorbing material according to the present embodiment.
  • Example 1> (Making elastomer latex) In a polymerization can with an internal volume of 3 liters equipped with a heating / cooling jacket and a stirrer, 20 parts by mass of chloroprene monomer, 20 parts by mass of acrylonitrile monomer, 150 parts by mass of pure water, potassium disproportionate (Harima Kasei Co., Ltd.) (Manufactured by) 3.3 parts by mass, tall fatty acid (manufactured by Harima Kasei Co., Ltd.) 1.0 part by mass, sodium hydroxide 0.1 parts by mass, and sodium salt of ⁇ -naphthalene sulfonate formalin condensate (manufactured by Kao Co., Ltd.) ) 2.0 parts by mass was added.
  • part by mass indicates the amount of the elastomer latex (A) with respect to 100 parts by mass of the solid content described later.
  • Zinc oxide vulcanization agent 7.5 parts by mass, zinc diethyldithiocarbamate (vulcanization accelerator) 2.0 parts by mass, N, N'-diethylthiourea (vulcanization accelerator) 2.0 parts by mass, 2, 2'-Methylenebis (4-ethyl-6-tert-butylphenol) (anti-aging agent) 2.0 parts by mass, sodium salt of ⁇ -naphthalene sulfonic acid formarin condensate (dispersant, trade name "Demor N", Kao shares A water dispersion containing a vulcanizing agent and a vulcanization accelerator by mixing 0.2 parts by mass and 14.3 parts by mass of water at 20 ° C. for 16 hours using a ceramic ball mill. (Solid content concentration: 48.9% by mass) was prepared.
  • the above-mentioned elastomer latex (A) 100 parts by mass as solid content
  • 28 parts by mass of the above-mentioned aqueous dispersion (13.7 parts by mass as solid content)
  • sodium dibutyldithiocarbamate vulcanization
  • the above latex composition is stirred at a rotation speed of 1000 rpm and foamed (23 ° C.) for 5 minutes. It was. Then, while stirring the latex composition with a hand mixer, 3.0 parts by mass of a 20 mass% sodium silicate aqueous solution was added as a gelling agent. The latex composition was further stirred for 2 minutes (23 ° C.) and then cast into a stainless steel mold (23 ° C.). The foamed latex composition lost its fluidity and gelled 2 minutes after casting. The gelation time was 4 minutes in total, 2 minutes for stirring and 2 minutes after casting.
  • the vertical incident sound absorption coefficient specified in JIS A 1405-2: 2007 was measured. Specifically, first, a test piece having a length of 100 mm, a width of 100 mm, and a thickness of 30 mm is cut out from the above-mentioned foam rubber, and then both surface layer portions in the thickness direction of the test piece are cut out by 5 mm to obtain a thickness of 20 mm. A measurement sample was obtained. For this measurement sample, the vertical incident sound absorption coefficient in the frequency range from 10 Hz to 10 Hz was measured using a vertical incident sound absorption coefficient measuring device TYPE10041 (Fprobe tube microphone) manufactured by Denshi Sokki Co., Ltd. The vertical incident sound absorption coefficient of 500 Hz was acquired, and the maximum value and the minimum value in the vertical incident sound absorption coefficient in the frequency domain range of 50 to 1500 Hz were acquired. The results are shown in Tables 1 and 2.
  • Example 2 The foam was the same as in Example 1 except that the amount of the 20 mass% sodium silicate aqueous solution used was changed to 2.5 parts by mass and the gelation time was 6 minutes (2 minutes for stirring and 4 minutes after casting). The rubber was prepared and evaluated.
  • Example 3 The foam was the same as in Example 1 except that the amount of the 20 mass% sodium silicate aqueous solution used was changed to 3.5 parts by mass and the gelation time was 3 minutes (2 minutes for stirring and 1 minute after casting). The rubber was prepared and evaluated.
  • Example 4 Foam rubber was produced and evaluated in the same manner as in Example 1 except that the rotation speed of the hand mixer was changed to 1100 rotations / minute.
  • Example 5 Foam rubber was produced and evaluated in the same manner as in Example 1 except that the rotation speed of the hand mixer was changed to 900 rpm.
  • Elastomer latex (B) chloroprene latex, trade name "LM-61", manufactured by Denka Co., Ltd.
  • LM-61 elastomer latex
  • Foam rubber was prepared and evaluated in the same manner as in Example 1 except that it was changed.
  • Elastomer latex (C) (nitrile butadiene latex, trade name "Nipol LX531B", manufactured by Nippon Zeon Co., Ltd.) was used instead of elastomer latex (A), and the amount of 20 mass% sodium silicate aqueous solution used was 1.5 parts by mass.
  • Foam rubber was prepared and evaluated in the same manner as in Example 1 except that it was changed to.
  • Example 1 The foam was the same as in Example 1 except that the amount of the 20 mass% sodium silicate aqueous solution used was changed to 2.0 parts by mass and the gelation time was 10 minutes (2 minutes for stirring and 8 minutes after casting). The rubber was prepared and evaluated.
  • Example 1 except that the amount of the 20 mass% sodium silicate aqueous solution used was changed to 4.5 parts by mass and the gelation time was 1 minute (0.5 minutes for stirring and 0.5 minutes after casting).
  • a foam rubber was produced in the same manner as in the above. Due to the poor moldability of the foam rubber, a measurement sample could not be prepared, and the foam rubber characteristics and sound absorption characteristics could not be evaluated.
  • Example 3 A foam rubber was produced in the same manner as in Example 1 except that the rotation speed of the hand mixer was changed to 1350 rotations / minute. Due to the poor moldability of the foam rubber, measurement samples could not be prepared except for density measurement, and the foam rubber characteristics and sound absorption characteristics could not be evaluated.
  • Example 4 A foam rubber was produced in the same manner as in Example 1 except that the rotation speed of the hand mixer was changed to 650 rotations / minute. Due to the poor moldability of the foam rubber, measurement samples could not be prepared except for density measurement, and the foam rubber characteristics and sound absorption characteristics could not be evaluated.
  • the foam rubbers of Examples 1 to 7 were excellent in sound absorption coefficient in the low frequency region.
  • Comparative Example 1 since the gelation time was long, the Heywood diameter of the cell was large, and the sound absorption characteristic in the low frequency region was inferior.
  • Comparative Example 2 the gelation time was too short, so that the foam rubber had poor moldability.
  • Comparative Example 3 the density of the foam rubber was less than 0.10 g / cm 3 , the flexibility was poor, and the moldability was poor.
  • the density of the foam rubber exceeded 0.35 g / cm 3 , and the foam rubber was brittle and had poor moldability.
  • Comparative Examples 2 to 4 having poor moldability the measurement sample could not be prepared, and the foam rubber property and the sound absorption property could not be sufficiently evaluated.

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Abstract

A foam rubber which has open cells where hollow cells are connected with each other, wherein: the Heywood diameter of the cells as determined in accordance with JIS Z 8827-1 (2018) is 180 μm or less; and the density of the foam rubber is from 0.10 to 0.35 g/cm3. A method for producing a foam rubber, said method comprising: an expansion step for obtaining a foam by expanding an elastomer composition that contains a vulcanizing agent; and a gelling step for obtaining a gel by adding a gelling agent to the foam. In the gelling step, the gelling time after the addition of the gelling agent is from 2 minutes to 8 minutes.

Description

フォームラバー及びその製造方法並びに吸音材Foam rubber, its manufacturing method, and sound absorbing material
　本発明は、フォームラバー及びその製造方法並びに吸音材に関する。 The present invention relates to foam rubber, a method for producing the same, and a sound absorbing material.
　吸音材は、家屋、音響施設、鉄道車両、航空機、自動車等に幅広く利用されている。特に自動車では、車外又はエンジンルームからの騒音を低減するために、車載用防音材料としての吸音材が車内壁面の多くに使用されている。 Sound absorbing materials are widely used in houses, audio equipment, railroad vehicles, aircraft, automobiles, etc. In particular, in automobiles, in order to reduce noise from the outside of the vehicle or from the engine room, a sound absorbing material as an in-vehicle soundproofing material is used on many of the interior walls of the vehicle.
　一方、昨今のモータ駆動の普及によりエンジン騒音の低減が達成されている一方で、モータ音又はロードノイズの騒音が問題となっており、これらの騒音に対応した吸音材へのニーズが高まっている。これらの騒音はエンジン騒音よりも低周波領域の騒音であることから、低周波領域の吸音特性を従来よりも改善した吸音材の開発が強く望まれている。 On the other hand, while reduction of engine noise has been achieved due to the recent spread of motor drive, the noise of motor noise or road noise has become a problem, and the need for sound absorbing materials corresponding to these noises is increasing. .. Since these noises are noises in a low frequency region rather than engine noises, it is strongly desired to develop a sound absorbing material having improved sound absorbing characteristics in a low frequency region.
　吸音材として使用し得るフォームラバーとしては、ラテックスとｐＨ８．５以下の乳化剤との混合物を用いて作製したフォームラバーが知られている（例えば、下記特許文献１参照）。また、高密度層と、ＥＰＤＭゴムの連続気泡発泡体で構成された低密度層とを有し、周波数６００Ｈｚ以下の音を吸音する吸音材が知られている（例えば、下記特許文献２参照）。 As a foam rubber that can be used as a sound absorbing material, a foam rubber produced by using a mixture of latex and an emulsifier having a pH of 8.5 or less is known (see, for example, Patent Document 1 below). Further, a sound absorbing material having a high density layer and a low density layer composed of an open cell foam of EPDM rubber and absorbing sound having a frequency of 600 Hz or less is known (see, for example, Patent Document 2 below). ..
特開２０１４－１７７５３６号公報Japanese Unexamined Patent Publication No. 2014-177536 特開２０１６－１２２１８７号公報Japanese Unexamined Patent Publication No. 2016-122187
　しかしながら、従来のフォームラバーに対しては、低周波領域の吸音特性がまだ充分であると言えないことから、低周波領域の吸音特性を向上させることが求められ、特に、周波数５００Ｈｚにおける優れた吸音特性（高い吸音率）を得ることが求められる。また、フォームラバーに対しては、各種形状に成形するための優れた成形性が求められる。 However, since it cannot be said that the sound absorption characteristics in the low frequency region are sufficient for the conventional foam rubber, it is required to improve the sound absorption characteristics in the low frequency region, and in particular, excellent sound absorption at a frequency of 500 Hz. It is required to obtain characteristics (high sound absorption coefficient). Further, foam rubber is required to have excellent moldability for molding into various shapes.
　本発明の一側面は、周波数５００Ｈｚにおける優れた吸音特性を有すると共に優れた成形性を有するフォームラバーを提供することを目的とする。本発明の他の一側面は、当該フォームラバーを用いた吸音材を提供することを目的とする。本発明の他の一側面は、周波数５００Ｈｚにおける優れた吸音特性を有すると共に優れた成形性を有するフォームラバーの製造方法を提供することを目的とする。 One aspect of the present invention is to provide a foam rubber having excellent sound absorbing characteristics at a frequency of 500 Hz and also having excellent moldability. Another aspect of the present invention is to provide a sound absorbing material using the foam rubber. Another aspect of the present invention is to provide a method for producing a foam rubber having excellent sound absorbing characteristics at a frequency of 500 Hz and having excellent moldability.
　本発明の一側面は、中空のセル同士が連結した連続気泡を有するフォームラバーであって、前記セルのＪＩＳ　Ｚ　８８２７－１：２０１８で定義されたＨｅｙｗｏｏｄ径が１８０μｍ以下であり、前記フォームラバーの密度が０．１０～０．３５ｇ／ｃｍ３である、フォームラバーを提供する。 One aspect of the present invention is a foam rubber having open cells in which hollow cells are connected to each other, wherein the Heywood diameter defined in JIS Z 8827-1: 2018 of the cells is 180 μm or less, and the foam rubber has a diameter of 180 μm or less. Provided is a foam rubber having a density of 0.10 to 0.35 g / cm 3.
　このようなフォームラバーは、周波数５００Ｈｚにおける優れた吸音特性を有すると共に優れた成形性を有する。 Such foam rubber has excellent sound absorption characteristics at a frequency of 500 Hz and also has excellent moldability.
　本発明の他の一側面は、上述のフォームラバーからなる、吸音材を提供する。 Another aspect of the present invention provides a sound absorbing material made of the foam rubber described above.
　本発明の他の一側面は、加硫剤を含有するエラストマー組成物を発泡させて発泡物を得る発泡工程と、前記発泡物にゲル化剤を加えてゲル化物を得るゲル化工程と、を有し、前記ゲル化工程において前記ゲル化剤を加えた後のゲル化時間が２～８分である、フォームラバーの製造方法を提供する。 Another aspect of the present invention is a foaming step of foaming an elastomer composition containing a vulcanizing agent to obtain a foam, and a gelling step of adding a gelling agent to the foam to obtain a gelled product. Provided is a method for producing a foam rubber, which has a gelation time of 2 to 8 minutes after adding the gelling agent in the gelation step.
　このようなフォームラバーの製造方法によれば、周波数５００Ｈｚにおける優れた吸音特性を有すると共に優れた成形性を有するフォームラバーを得ることができる。 According to such a foam rubber manufacturing method, it is possible to obtain a foam rubber having excellent sound absorption characteristics at a frequency of 500 Hz and excellent moldability.
　本発明の一側面によれば、周波数５００Ｈｚにおける優れた吸音特性を有すると共に優れた成形性を有するフォームラバーを提供することができる。本発明の他の一側面によれば、当該フォームラバーを用いた吸音材を提供することができる。本発明の他の一側面によれば、周波数５００Ｈｚにおける優れた吸音特性を有すると共に優れた成形性を有するフォームラバーの製造方法を提供することができる。本発明の他の一側面によれば、吸音（防音）へのフォームラバーの応用を提供可能であり、低周波領域の吸音（防音）へのフォームラバーの応用を提供できる。 According to one aspect of the present invention, it is possible to provide a foam rubber having excellent sound absorbing characteristics at a frequency of 500 Hz and having excellent moldability. According to another aspect of the present invention, it is possible to provide a sound absorbing material using the foam rubber. According to another aspect of the present invention, it is possible to provide a method for producing a foam rubber having excellent sound absorbing characteristics at a frequency of 500 Hz and having excellent moldability. According to another aspect of the present invention, it is possible to provide an application of foam rubber for sound absorption (soundproofing), and it is possible to provide an application of foam rubber for sound absorption (soundproofing) in a low frequency region.
　以下、本発明を実施するための形態について詳細に説明する。なお、本発明は、以下で説明する実施形態に限定されるものではない。 Hereinafter, a mode for carrying out the present invention will be described in detail. The present invention is not limited to the embodiments described below.
　本明細書において、「～」を用いて示された数値範囲は、「～」の前後に記載される数値をそれぞれ最小値及び最大値として含む範囲を示す。数値範囲の「Ａ以上」とは、Ａ、及び、Ａを超える範囲を意味する。数値範囲の「Ａ以下」とは、Ａ、及び、Ａ未満の範囲を意味する。本明細書に段階的に記載されている数値範囲において、ある段階の数値範囲の上限値又は下限値は、他の段階の数値範囲の上限値又は下限値と任意に組み合わせることができる。本明細書に記載されている数値範囲において、その数値範囲の上限値又は下限値は、実施例に示されている値に置き換えてもよい。「Ａ又はＢ」とは、Ａ及びＢのどちらか一方を含んでいればよく、両方とも含んでいてもよい。本明細書に例示する材料は、特に断らない限り、１種を単独で又は２種以上を組み合わせて用いることができる。組成物中の各成分の含有量は、組成物中に各成分に該当する物質が複数存在する場合、特に断らない限り、組成物中に存在する当該複数の物質の合計量を意味する。「工程」との語は、独立した工程だけではなく、他の工程と明確に区別できない場合であってもその工程の所期の作用が達成されれば、本用語に含まれる。 In the present specification, the numerical range indicated by using "-" indicates a range including the numerical values before and after "-" as the minimum value and the maximum value, respectively. “A or more” in the numerical range means A and a range exceeding A. “A or less” in the numerical range means A and a range less than A. In the numerical range described stepwise in the present specification, the upper limit value or the lower limit value of the numerical range of one step can be arbitrarily combined with the upper limit value or the lower limit value of the numerical range of another step. In the numerical range described in the present specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. "A or B" may include either A or B, or both. Unless otherwise specified, the materials exemplified in the present specification may be used alone or in combination of two or more. The content of each component in the composition means the total amount of the plurality of substances present in the composition when a plurality of substances corresponding to each component are present in the composition, unless otherwise specified. The term "process" is included in this term not only in an independent process but also in the case where the desired action of the process is achieved even if it cannot be clearly distinguished from other processes.
＜フォームラバー＞
　本実施形態に係るフォームラバーは、中空のセル同士が連結した連続気泡を有するフォームラバーである。フォームラバーの連続気泡は、中空の複数のセルを含んでいる。「連続気泡」とは、フォームラバーに形成されるセルの少なくとも一部が連続する構造を意味する。フォームラバーは、連続気泡構造を有してよく、半連続半独立気泡構造を有してもよい。連続気泡構造は、連続気泡率が１００％である構造をいう。半連続半独立気泡構造において連続気泡率の下限は、０％を超えており、１０％以上であってよい。半連続半独立気泡構造において連続気泡率の上限は、１００％未満であり、９８％未満であってよい。本実施形態に係るフォームラバーにおいて、セルのＪＩＳ　Ｚ　８８２７－１：２０１８で定義されたＨｅｙｗｏｏｄ径は１８０μｍ以下であり、フォームラバーの密度は０．１０～０．３５ｇ／ｃｍ３である。本実施形態に係るフォームラバーは、単層のフォームラバーであってよい。 <Foam rubber>
The foam rubber according to the present embodiment is a foam rubber having open cells in which hollow cells are connected to each other. The open cells of foam rubber contain a plurality of hollow cells. By "open cell" is meant a structure in which at least a portion of the cells formed in the foam rubber are continuous. The foam rubber may have an open cell structure or a semi-continuous semi-closed cell structure. The open cell structure refers to a structure in which the open cell ratio is 100%. In the semi-continuous semi-closed cell structure, the lower limit of the open cell ratio exceeds 0% and may be 10% or more. In the semi-continuous semi-closed cell structure, the upper limit of the open cell ratio is less than 100% and may be less than 98%. In the foam rubber according to the present embodiment, the Heywood diameter defined in JIS Z 8827-1: 2018 of the cell is 180 μm or less, and the density of the foam rubber is 0.10 to 0.35 g / cm 3 . The foam rubber according to the present embodiment may be a single-layer foam rubber.
　本実施形態に係るフォームラバーは、低周波領域の吸音特性として、周波数５００Ｈｚにおける優れた吸音特性（高い吸音率）を有している。本実施形態に係るフォームラバーは、成形性（成形加工性。例えば、加硫物であるフォームラバーの成形性）にも優れており、周波数５００Ｈｚにおける優れた吸音特性を有すると共に優れた成形性を有する。本実施形態に係るフォームラバーは、周波数５００Ｈｚの垂直入射吸音率として０．５以上の吸音率を有しており、周波数５００Ｈｚの垂直入射吸音率として０．５～０．８の吸音率を有してよい。 The foam rubber according to the present embodiment has excellent sound absorption characteristics (high sound absorption coefficient) at a frequency of 500 Hz as sound absorption characteristics in the low frequency region. The foam rubber according to the present embodiment is also excellent in moldability (molding processability, for example, moldability of foam rubber which is a vulcanized product), has excellent sound absorbing characteristics at a frequency of 500 Hz, and has excellent moldability. Have. The foam rubber according to the present embodiment has a sound absorption coefficient of 0.5 or more as a vertically incident sound absorption coefficient at a frequency of 500 Hz, and has a sound absorption coefficient of 0.5 to 0.8 as a vertically incident sound absorption coefficient at a frequency of 500 Hz. You can do it.
　本実施形態に係るフォームラバーは、幅広い低周波領域の吸音特性に優れており、例えば、周波数領域５０～１５００Ｈｚにおける優れた吸音特性を有してよい。本実施形態に係るフォームラバーは、周波数領域５０～１５００Ｈｚに垂直入射吸音率の最大値（ピーク）を有してよく、周波数領域５０～１５００Ｈｚにおける垂直入射吸音率の最大値として０．６～０．９の吸音率を有してよい。本実施形態に係るフォームラバーは、周波数領域５０～１５００Ｈｚの全ての範囲において高い垂直入射吸音率を有してよく、周波数領域５０～１５００Ｈｚに垂直入射吸音率の最小値として０．４以上の吸音率を有してよい。 The foam rubber according to the present embodiment is excellent in sound absorption characteristics in a wide range of low frequencies, and may have excellent sound absorption characteristics in a frequency region of 50 to 1500 Hz, for example. The foam rubber according to the present embodiment may have a maximum value (peak) of the vertical incident sound absorption coefficient in the frequency domain of 50 to 1500 Hz, and the maximum value of the vertical incident sound absorption coefficient in the frequency domain of 50 to 1500 Hz is 0.6 to 0. It may have a sound absorption coefficient of 9. The foam rubber according to the present embodiment may have a high vertical incident sound absorption coefficient in the entire frequency range of 50 to 1500 Hz, and has a minimum value of 0.4 or more vertical incident sound absorption coefficient in the frequency domain of 50 to 1500 Hz. May have a rate.
　垂直入射吸音率は、ＪＩＳ　Ａ　１４０５－２：２００７により測定できる。垂直入射吸音率は、後述の実施例に記載の手順により測定することができる。本実施形態に係るフォームラバーでは、ＪＩＳ　Ａ　１４０５－２：２００７で規定される周波数５００Ｈｚの垂直入射吸音率が０．５～０．８であってよく、ＪＩＳ　Ａ　１４０５－２：２００７で規定される周波数領域５０～１５００Ｈｚの全ての範囲の垂直入射吸音率が０．５～１．０である。 The vertical incident sound absorption coefficient can be measured by JIS A 1405-2: 2007. The vertically incident sound absorption coefficient can be measured by the procedure described in Examples described later. In the foam rubber according to the present embodiment, the vertical incident sound absorption coefficient at a frequency of 500 Hz specified by JIS A 1405-2: 2007 may be 0.5 to 0.8, and is specified by JIS A 1405-2: 2007. The vertical incident sound absorption coefficient in the entire frequency range of 50 to 1500 Hz is 0.5 to 1.0.
　本実施形態に係るフォームラバーは、優れた吸音特性を単層で達成することができる。本実施形態に係るフォームラバーは、吸音材向けフォームラバーとして用いることが可能であり、自動車、家屋、音響施設、鉄道車両、航空機等の各種用途の吸音材として用いることができる。このようなフォームラバーを自動車用の吸音材として用いることにより、モータ音、ロードノイズ等の低周波領域の音を吸音することができる。本実施形態に係る吸音方法は、本実施形態に係るフォームラバーを用いて吸音（例えば低周波領域の音を吸音）する。 The foam rubber according to this embodiment can achieve excellent sound absorption characteristics with a single layer. The foam rubber according to the present embodiment can be used as a foam rubber for a sound absorbing material, and can be used as a sound absorbing material for various purposes such as automobiles, houses, audio facilities, railway vehicles, and aircraft. By using such foam rubber as a sound absorbing material for automobiles, it is possible to absorb sound in a low frequency region such as motor sound and road noise. The sound absorbing method according to the present embodiment uses the foam rubber according to the present embodiment to absorb sound (for example, absorb sound in a low frequency region).
　本実施形態に係るフォームラバーにおいて、セルのＪＩＳ　Ｚ　８８２７－１：２０１８で定義されたＨｅｙｗｏｏｄ径は１８０μｍ以下である。セルのＨｅｙｗｏｏｄ径が１８０μｍを超えると、低周波領域の吸音特性が損なわれる。 In the foam rubber according to the present embodiment, the Heywood diameter defined in JIS Z 8827-1: 2018 of the cell is 180 μm or less. If the Heywood diameter of the cell exceeds 180 μm, the sound absorption characteristics in the low frequency region are impaired.
　セルのＨｅｙｗｏｏｄ径は、０μｍを超え、優れた成形性が得られやすい観点から、１００μｍ以上が好ましく、１１０μｍ以上がより好ましく、１２０μｍ以上が更に好ましい。セルのＨｅｙｗｏｏｄ径は、低周波領域において優れた吸音特性が得られやすい観点から、１７０μｍ以下が好ましく、１６０μｍ以下がより好ましく、１５０μｍ以下が更に好ましく、１４０μｍ以下が特に好ましく、１３０μｍ以下が極めて好ましい。これらの観点から、セルのＨｅｙｗｏｏｄ径は、１００～１８０μｍが好ましい。セルのＨｅｙｗｏｏｄ径は、１３０μｍ以上、１４０μｍ以上、１５０μｍ以上、１６０μｍ以上、又は、１７０μｍ以上であってよい。セルのＨｅｙｗｏｏｄ径は、１２０μｍ以下であってよい。 The Heywood diameter of the cell exceeds 0 μm, and from the viewpoint that excellent moldability can be easily obtained, 100 μm or more is preferable, 110 μm or more is more preferable, and 120 μm or more is further preferable. The Heywood diameter of the cell is preferably 170 μm or less, more preferably 160 μm or less, further preferably 150 μm or less, particularly preferably 140 μm or less, and extremely preferably 130 μm or less, from the viewpoint that excellent sound absorption characteristics can be easily obtained in the low frequency region. From these viewpoints, the Heywood diameter of the cell is preferably 100 to 180 μm. The Heywood diameter of the cell may be 130 μm or more, 140 μm or more, 150 μm or more, 160 μm or more, or 170 μm or more. The Heywood diameter of the cell may be 120 μm or less.
　セルのＨｅｙｗｏｏｄ径を調整するには、後述するゲル化工程で添加するゲル化剤の量を調整することによりゲル化時間を調整すればよい。例えば、セルのＨｅｙｗｏｏｄ径を大きくするには、ゲル化剤の量を減らしてゲル化時間を長くすればよい。フォームラバーのセルのＨｅｙｗｏｏｄ径を指標として、フォームラバーを得るための好適なゲル化時間を調整することができる。セルのＨｅｙｗｏｏｄ径は、後述する発泡工程においてエラストマー組成物を撹拌する際の回転数等により調整することもできる。 In order to adjust the Heywood diameter of the cell, the gelation time may be adjusted by adjusting the amount of the gelling agent added in the gelation step described later. For example, in order to increase the Heywood diameter of the cell, the amount of the gelling agent may be reduced to lengthen the gelling time. The suitable gelling time for obtaining the foam rubber can be adjusted by using the Heywood diameter of the foam rubber cell as an index. The Heywood diameter of the cell can also be adjusted by the number of revolutions when stirring the elastomer composition in the foaming step described later.
　フォームラバーの連続気泡は、セル同士を連結する中空のセル連結部（セル連結部分の穴）を含んでよい。セル連結部のＪＩＳ　Ｚ　８８２７－１：２０１８で定義されたＨｅｙｗｏｏｄ径は、下記の範囲であることが好ましい。セル連結部のＨｅｙｗｏｏｄ径は、優れた成形性が得られやすい観点から、５μｍ以上が好ましく、８μｍ以上がより好ましく、１０μｍ以上が更に好ましく、１５μｍ以上が特に好ましく、２０μｍ以上が極めて好ましく、２２μｍ以上が非常に好ましい。セル連結部のＨｅｙｗｏｏｄ径は、低周波領域の優れた吸音特性が得られやすい観点から、５０μｍ以下が好ましく、４５μｍ以下がより好ましく、４０μｍ以下が更に好ましく、３８μｍ以下が特に好ましく、３５μｍ以下が極めて好ましく、３２μｍ以下が非常に好ましく、３１μｍ以下がより一層好ましい。これらの観点から、セル連結部のＨｅｙｗｏｏｄ径は、５～５０μｍが好ましく、５～３５μｍがより好ましく、１０～３５μｍが更に好ましく、１０～３０μｍが特に好ましい。セル連結部のＨｅｙｗｏｏｄ径は、２５μｍ以上、２８μｍ以上、３０μｍ以上、３１μｍ以上、３２μｍ以上、３５μｍ以上、又は、３８μｍ以上であってよい。セル連結部のＨｅｙｗｏｏｄ径は、３０μｍ以下、２８μｍ以下、２５μｍ以下、２２μｍ以下、２０μｍ以下、１５μｍ以下、又は、１０μｍ以下であってよい。 The open cells of the foam rubber may include a hollow cell connecting portion (hole of the cell connecting portion) that connects the cells. The Heywood diameter defined in JIS Z 8827-1: 2018 of the cell connecting portion is preferably in the following range. The Heywood diameter of the cell connecting portion is preferably 5 μm or more, more preferably 8 μm or more, further preferably 10 μm or more, particularly preferably 15 μm or more, extremely preferably 20 μm or more, and 22 μm or more from the viewpoint that excellent moldability can be easily obtained. Is very preferable. The Heywood diameter of the cell connecting portion is preferably 50 μm or less, more preferably 45 μm or less, further preferably 40 μm or less, particularly preferably 38 μm or less, and extremely preferably 35 μm or less, from the viewpoint that excellent sound absorption characteristics in the low frequency region can be easily obtained. Preferably, 32 μm or less is very preferable, and 31 μm or less is even more preferable. From these viewpoints, the Heywood diameter of the cell connecting portion is preferably 5 to 50 μm, more preferably 5 to 35 μm, further preferably 10 to 35 μm, and particularly preferably 10 to 30 μm. The Heywood diameter of the cell connecting portion may be 25 μm or more, 28 μm or more, 30 μm or more, 31 μm or more, 32 μm or more, 35 μm or more, or 38 μm or more. The Heywood diameter of the cell connecting portion may be 30 μm or less, 28 μm or less, 25 μm or less, 22 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.
　セル連結部のＨｅｙｗｏｏｄ径を調整するには、セルのＨｅｙｗｏｏｄ径を調整するのと同様にゲル化時間を調整すればよい。フォームラバーの密度を調整することで、セルのＨｅｙｗｏｏｄ径を一定に保ったままセル連結部のＨｅｙｗｏｏｄ径のみを調整することができる。例えば、密度を高くすることによりセル連結部のＨｅｙｗｏｏｄ径が小さくなる傾向がある。セル連結部のＨｅｙｗｏｏｄ径は、発泡工程においてエラストマー組成物を撹拌する際の回転数等により調整することもできる。 In order to adjust the Heywood diameter of the cell connecting portion, the gelation time may be adjusted in the same manner as adjusting the Heywood diameter of the cell. By adjusting the density of the foam rubber, it is possible to adjust only the Heywood diameter of the cell connecting portion while keeping the Heywood diameter of the cell constant. For example, increasing the density tends to reduce the Heywood diameter of the cell connecting portion. The Heywood diameter of the cell connecting portion can also be adjusted by the number of revolutions when stirring the elastomer composition in the foaming step.
　フォームラバーのセル及びセル連結部のＨｅｙｗｏｏｄ径は、ＪＩＳ　Ｚ　８８２７－１：２０１８で定義される径であり、測定対象（セル又はセル連結部）の投影面積と等しい面積を有する真円の直径を示すものである。フォームラバーのセル及びセル連結部のＨｅｙｗｏｏｄ径は、後述の実施例に記載手順により測定することができる。 The Heywood diameter of the foam rubber cell and cell connecting portion is the diameter defined in JIS Z 8827-1: 2018, and is the diameter of a perfect circle having an area equal to the projected area of the measurement target (cell or cell connecting portion). It shows. The Heywood diameter of the foam rubber cell and the cell connecting portion can be measured by the procedure described in Examples described later.
　本実施形態に係るフォームラバーの密度は、フォームラバーの柔軟性及び機械強度を維持可能であることから優れた成形性が得られる観点から、０．１０～０．３５ｇ／ｃｍ３である。フォームラバーの密度は、フォームラバーの柔軟性及び機械強度を維持しやすいことから優れた成形性を得やすい観点から、０．１０ｇ／ｃｍ３以上が好ましく、０．１３ｇ／ｃｍ３以上がより好ましく、０．１３ｇ／ｃｍ３を超えることが更に好ましく、０．１５ｇ／ｃｍ３以上が特に好ましく、０．１７ｇ／ｃｍ３以上が極めて好ましく、０．１７ｇ／ｃｍ３を超えることが非常に好ましく、０．２０ｇ／ｃｍ３以上がより一層好ましく、０．２０ｇ／ｃｍ３を超えることが更に好ましく、０．２２ｇ／ｃｍ３以上が特に好ましく、０．２４ｇ／ｃｍ３以上が極めて好ましく、０．２５ｇ／ｃｍ３以上が非常に好ましく、０．２５ｇ／ｃｍ３を超えることがより一層好ましく、０．２６ｇ／ｃｍ３以上が更に好ましく、０．２７ｇ／ｃｍ３以上が特に好ましい。フォームラバーの密度は、フォームラバーの柔軟性及び機械強度を維持しやすいことから優れた成形性を得やすい観点から、０．３５ｇ／ｃｍ３以下が好ましく、０．３３ｇ／ｃｍ３以下がより好ましく、０．３０ｇ／ｃｍ３以下が更に好ましく、０．２９ｇ／ｃｍ３以下が特に好ましく、０．２８ｇ／ｃｍ３以下が極めて好ましい。これらの観点から、フォームラバーの密度は、０．１０～０．３５ｇ／ｃｍ３が好ましく、０．１５～０．３５ｇ／ｃｍ３がより好ましい。フォームラバーの密度は、０．２８ｇ／ｃｍ３以上、０．２９ｇ／ｃｍ３以上、０．３０ｇ／ｃｍ３以上、又は、０．３３ｇ／ｃｍ３以上であってよい。フォームラバーの密度は、０．２７ｇ／ｃｍ３以下、０．２５ｇ／ｃｍ３以下、０．２４ｇ／ｃｍ３以下、０．２２ｇ／ｃｍ３以下、又は、０．２０ｇ／ｃｍ３以下であってよい。 The density of the foam rubber according to the present embodiment is 0.10 to 0.35 g / cm 3 from the viewpoint that excellent moldability can be obtained because the flexibility and mechanical strength of the foam rubber can be maintained. Density of foam rubber, from the viewpoint of easy to obtain the formability excellent since the easily maintained flexibility and mechanical strength of the foam rubber, 0.10 g / cm 3 or more preferably, 0.13 g / cm 3 or more preferably , more preferably more than 0.13 g / cm 3, particularly preferably 0.15 g / cm 3 or more, very preferably more than 0.17 g / cm 3, very preferably more than 0.17 g / cm 3, 0.20 g / cm 3 or even more preferably, more preferably more than 0.20 g / cm 3, particularly preferably 0.22 g / cm 3 or higher, 0.24 g / cm 3 or more is very preferred, 0.25 g / Cm 3 or more is very preferable, more than 0.25 g / cm 3 is even more preferable, 0.26 g / cm 3 or more is further preferable, and 0.27 g / cm 3 or more is particularly preferable. Density of foam rubber, from the viewpoint of easy to obtain the formability excellent since the easily maintained flexibility and mechanical strength of the foam rubber is preferably 0.35 g / cm 3 or less, more preferably 0.33 g / cm 3 or less , more preferably 0.30 g / cm 3 or less, particularly preferably 0.29 g / cm 3 or less, 0.28 g / cm 3 or less is very preferable. From these viewpoints, the density of the foam rubber is preferably 0.10 ~ 0.35g / cm 3, more preferably 0.15 ~ 0.35g / cm 3. The density of the foam rubber is, 0.28 g / cm 3 or more, 0.29 g / cm 3 or more, 0.30 g / cm 3 or more, or, may be at 0.33 g / cm 3 or more. The density of the foam rubber is 0.27 g / cm 3 or less, 0.25 g / cm 3 or less, 0.24 g / cm 3 or less, 0.22 g / cm 3 or less, or 0.20 g / cm 3 or less. Good.
　フォームラバーの密度を調整するには、後述する発泡工程においてエラストマー組成物に取り込む気体の量、発泡工程においてエラストマー組成物を撹拌する際の回転数等を調整すればよい。フォームラバーの密度は、後述の実施例に記載の手順により測定することができる。 In order to adjust the density of the foam rubber, the amount of gas taken into the elastomer composition in the foaming step described later, the number of rotations when stirring the elastomer composition in the foaming step, and the like may be adjusted. The density of the foam rubber can be measured by the procedure described in Examples described later.
　本実施形態に係るフォームラバーは、エラストマーを含有することができる。エラストマーとしては、天然ゴム、イソプレンゴム、ニトリルブタジエンゴム、スチレンブタジエンゴム、クロロプレン重合体（クロロプレンゴム（クロロプレンの単独重合体）、クロロプレンと不飽和ニトリルとの共重合体（例えばクロロプレンとアクリロニトリルとの共重合体）等）、エチレンプロピレンジエンゴム、ブタジエンゴム、ブチルゴムなどが挙げられる。本実施形態に係るフォームラバーは、エラストマー以外の成分を含有してよく、例えば、後述の添加剤を含有してよい。本実施形態に係るフォームラバーは、エラストマーを主成分として含有してよく、エラストマーラテックスを主原料として用いて得ることができる。 The foam rubber according to this embodiment can contain an elastomer. Examples of the elastomer include natural rubber, isoprene rubber, nitrile butadiene rubber, styrene butadiene rubber, chloroprene polymer (chloroprene rubber (a homopolymer of chloroprene), and a copolymer of chloroprene and unsaturated nitrile (for example, a combination of chloroprene and acrylonitrile). Polymers), etc.), ethylene propylene diene rubber, butadiene rubber, butyl rubber and the like. The foam rubber according to the present embodiment may contain a component other than the elastomer, and may contain, for example, an additive described later. The foam rubber according to the present embodiment may contain an elastomer as a main component, and can be obtained by using an elastomer latex as a main raw material.
　クロロプレン重合体は、クロロプレン（クロロプレン単量体）を重合させて得られ、クロロプレン由来の構造単位を有する。クロロプレンと不飽和ニトリルとの共重合体は、クロロプレン（クロロプレン単量体）と不飽和ニトリル（不飽和ニトリル単量体。例えばアクリロニトリル単量体）とを共重合させて得られ、クロロプレン由来の構造単位と不飽和ニトリル由来の構造単位とを有する。 The chloroprene polymer is obtained by polymerizing chloroprene (chloroprene monomer) and has a structural unit derived from chloroprene. The copolymer of chloroprene and unsaturated nitrile is obtained by copolymerizing chloroprene (chloroprene monomer) and unsaturated nitrile (unsaturated nitrile monomer, for example, acrylonitrile monomer), and has a structure derived from chloroprene. It has a unit and a structural unit derived from unsaturated nitrile.
　不飽和ニトリルとしては、アクリロニトリル、メタクリロニトリル、エタクリロニトリル、フェニルアクリロニトリル等が挙げられる。不飽和ニトリルは、１種単独で又は２種以上を組み合わせて用いることができる。不飽和ニトリルは、低周波領域の優れた吸音特性（例えば周波数５００Ｈｚにおける優れた吸音特性）が得られやすい観点から、アクリロニトリルを含むことが好ましい。 Examples of unsaturated nitriles include acrylonitrile, methacrylonitrile, etacrylonitrile, and phenylacrylonitrile. Unsaturated nitriles can be used alone or in combination of two or more. The unsaturated nitrile preferably contains acrylonitrile from the viewpoint that excellent sound absorbing characteristics in the low frequency region (for example, excellent sound absorbing characteristics at a frequency of 500 Hz) can be easily obtained.
　クロロプレン由来の構造単位の含有量は、クロロプレンと不飽和ニトリルとの共重合体の全量、又は、クロロプレン由来の構造単位と不飽和ニトリル由来の構造単位との合計量を基準として、１００質量％未満であり、低周波領域の優れた吸音特性（例えば周波数５００Ｈｚにおける優れた吸音特性）が得られやすい観点から、下記の範囲が好ましい。クロロプレン由来の構造単位の含有量は、５０質量％以上が好ましく、５０質量％を超えることがより好ましく、６０質量％以上が更に好ましく、７０質量％以上が特に好ましく、７５質量％以上が極めて好ましく、８０質量％以上が非常に好ましい。クロロプレン由来の構造単位の含有量は、９９質量％以下が好ましく、９５質量％以下がより好ましく、９０質量％以下が更に好ましく、８５質量％以下が特に好ましく、８０質量％以下が極めて好ましい。これらの観点から、クロロプレン由来の構造単位の含有量は、５０質量％以上１００質量％未満であることが好ましい。 The content of the structural unit derived from chloroprene is less than 100% by mass based on the total amount of the copolymer of chloroprene and unsaturated nitrile or the total amount of the structural unit derived from chloroprene and the structural unit derived from unsaturated nitrile. Therefore, the following range is preferable from the viewpoint that excellent sound absorption characteristics in the low frequency region (for example, excellent sound absorption characteristics at a frequency of 500 Hz) can be easily obtained. The content of the structural unit derived from chloroprene is preferably 50% by mass or more, more preferably more than 50% by mass, further preferably 60% by mass or more, particularly preferably 70% by mass or more, and extremely preferably 75% by mass or more. , 80% by mass or more is very preferable. The content of the structural unit derived from chloroprene is preferably 99% by mass or less, more preferably 95% by mass or less, further preferably 90% by mass or less, particularly preferably 85% by mass or less, and extremely preferably 80% by mass or less. From these viewpoints, the content of the structural unit derived from chloroprene is preferably 50% by mass or more and less than 100% by mass.
　不飽和ニトリル由来の構造単位の含有量は、クロロプレンと不飽和ニトリルとの共重合体の全量、又は、クロロプレン由来の構造単位と不飽和ニトリル由来の構造単位との合計量を基準として、０質量％を超え、低周波領域の優れた吸音特性（例えば周波数５００Ｈｚにおける優れた吸音特性）が得られやすい観点から、下記の範囲が好ましい。不飽和ニトリル由来の構造単位の含有量は、１質量％以上が好ましく、５質量％以上がより好ましく、１０質量％以上が更に好ましく、１５質量％以上が特に好ましく、２０質量％以上が極めて好ましい。不飽和ニトリル由来の構造単位の含有量は、５０質量％以下が好ましく、５０質量％未満がより好ましく、４０質量％以下が更に好ましく、３０質量％以下が特に好ましく、２５質量％以下が極めて好ましく、２０質量％以下が非常に好ましい。これらの観点から、不飽和ニトリル由来の構造単位の含有量は、０質量％を超え５０質量％以下であることが好ましい。同様の観点から、アクリロニトリル由来の構造単位の含有量は、クロロプレンと不飽和ニトリルとの共重合体の全量、又は、クロロプレン由来の構造単位と不飽和ニトリル由来の構造単位との合計量を基準として、これらの範囲であることが好ましい。 The content of the structural unit derived from unsaturated nitrile is 0 mass based on the total amount of the copolymer of chloroprene and unsaturated nitrile, or the total amount of the structural unit derived from chloroprene and the structural unit derived from unsaturated nitrile. The following range is preferable from the viewpoint that it exceeds% and excellent sound absorption characteristics in the low frequency region (for example, excellent sound absorption characteristics at a frequency of 500 Hz) can be easily obtained. The content of the structural unit derived from unsaturated nitrile is preferably 1% by mass or more, more preferably 5% by mass or more, further preferably 10% by mass or more, particularly preferably 15% by mass or more, and extremely preferably 20% by mass or more. .. The content of the structural unit derived from unsaturated nitrile is preferably 50% by mass or less, more preferably less than 50% by mass, further preferably 40% by mass or less, particularly preferably 30% by mass or less, and extremely preferably 25% by mass or less. , 20% by mass or less is very preferable. From these viewpoints, the content of the structural unit derived from unsaturated nitrile is preferably more than 0% by mass and 50% by mass or less. From the same viewpoint, the content of the structural unit derived from acrylonitrile is based on the total amount of the copolymer of chloroprene and unsaturated nitrile, or the total amount of the structural unit derived from chloroprene and the structural unit derived from unsaturated nitrile. , These ranges are preferable.
　クロロプレンと不飽和ニトリルとの共重合体に含まれる不飽和ニトリル由来の構造単位の量は、共重合体中の窒素原子の含有量から算出することができる。具体的には、元素分析装置（スミグラフ２２０Ｆ：株式会社住化分析センター製）を用いて１００ｍｇのクロロプレンと不飽和ニトリルとの共重合体における窒素原子の含有量を測定し、不飽和ニトリル由来の構造単位の量を算出できる。元素分析の測定は次の条件で行うことができる。例えば、電気炉温度として反応炉９００℃、還元炉６００℃、カラム温度７０℃、検出器温度１００℃に設定し、燃焼用ガスとして酸素を０．２ｍＬ／ｍｉｎ、キャリアーガスとしてヘリウムを８０ｍＬ／ｍｉｎフローする。検量線は、窒素含有量が既知のアスパラギン酸（１０．５２％）を標準物質として用いて作成できる。 The amount of the structural unit derived from unsaturated nitrile contained in the copolymer of chloroprene and unsaturated nitrile can be calculated from the content of nitrogen atom in the copolymer. Specifically, the content of nitrogen atoms in the copolymer of 100 mg of chloroprene and unsaturated nitrile was measured using an element analyzer (Sumigraph 220F: manufactured by Sumika Chemical Analysis Service, Inc.), and the content was derived from unsaturated nitrile. The amount of structural units can be calculated. The measurement of elemental analysis can be performed under the following conditions. For example, the electric furnace temperature is set to 900 ° C. for the reactor, 600 ° C. for the reduction furnace, 70 ° C. for the column temperature, and 100 ° C. for the detector temperature. Oxygen is 0.2 mL / min as the combustion gas and helium is 80 mL / min as the carrier gas. Flow. The calibration curve can be prepared using aspartic acid (10.52%) having a known nitrogen content as a standard substance.
　クロロプレンと共重合させる単量体は、不飽和ニトリルに限定されるものではない。クロロプレンと共重合可能な単量体としては、２，３－ジクロロ－１，３－ブタジエン、１－クロロ－１，３－ブタジエン、スチレン、イソプレン、ブタジエン、アクリル酸、アクリル酸のエステル類、メタクリル酸、メタクリル酸のエステル類、硫黄等が挙げられる。 The monomer copolymerized with chloroprene is not limited to unsaturated nitriles. Examples of the monomer copolymerizable with chloroprene include 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, styrene, isoprene, butadiene, acrylic acid, acrylic acid esters, and methacrylic acid. Examples thereof include acids, methacrylic acid esters, and sulfur.
　エラストマーは、低周波領域の優れた吸音特性（例えば周波数５００Ｈｚにおける優れた吸音特性）が得られやすい観点から、クロロプレン重合体を含むことが好ましい。エラストマーは、エチレンプロピレンジエンゴムを含まなくてよい。本実施形態に係るフォームラバーにおいてクロロプレン重合体の含有量は、エチレンプロピレンジエンゴムの含有量より多くてよい。 The elastomer preferably contains a chloroprene polymer from the viewpoint that excellent sound absorption characteristics in the low frequency region (for example, excellent sound absorption characteristics at a frequency of 500 Hz) can be easily obtained. The elastomer does not have to contain ethylene propylene diene rubber. The content of the chloroprene polymer in the foam rubber according to the present embodiment may be larger than the content of the ethylene propylene diene rubber.
　クロロプレン重合体の含有量、又は、エチレンプロピレンジエンゴム以外のエラストマーの含有量は、低周波領域の優れた吸音特性（例えば周波数５００Ｈｚにおける優れた吸音特性）が得られやすい観点から、エラストマーの全質量を基準として、５０質量％以上が好ましく、５０質量％を超えることがより好ましく、６０質量％以上が更に好ましく、７０質量％以上が特に好ましく、８０質量％以上が極めて好ましく、９０質量％以上が非常に好ましく、９５質量％以上がより一層好ましい。エラストマーが実質的にクロロプレン重合体からなる態様（クロロプレン重合体の含有量がエラストマーの全質量を基準として実質的に１００質量％である態様）であってもよい。エラストマーが実質的にエチレンプロピレンジエンゴム以外のエラストマーからなる態様（エチレンプロピレンジエンゴム以外のエラストマーの含有量がエラストマーの全質量を基準として実質的に１００質量％である態様）であってもよい。エチレンプロピレンジエンゴムの含有量は、エラストマーの全質量を基準として、１０質量％以下、５質量％以下、１質量％以下、０．５質量％以下、又は、０．１量％以下であってよい。 The content of the chloroprene polymer or the content of the elastomer other than ethylene propylene diene rubber is the total mass of the elastomer from the viewpoint that excellent sound absorbing characteristics in the low frequency region (for example, excellent sound absorbing characteristics at a frequency of 500 Hz) can be easily obtained. 50% by mass or more, more preferably more than 50% by mass, further preferably 60% by mass or more, particularly preferably 70% by mass or more, extremely preferably 80% by mass or more, and 90% by mass or more. It is very preferable, and 95% by mass or more is even more preferable. The elastomer may be substantially composed of a chloroprene polymer (a mode in which the content of the chloroprene polymer is substantially 100% by mass based on the total mass of the elastomer). The elastomer may be substantially composed of an elastomer other than ethylene propylene diene rubber (a mode in which the content of the elastomer other than ethylene propylene diene rubber is substantially 100% by mass based on the total mass of the elastomer). The content of ethylene propylene diene rubber is 10% by mass or less, 5% by mass or less, 1% by mass or less, 0.5% by mass or less, or 0.1% by mass or less based on the total mass of the elastomer. Good.
　エラストマーの含有量は、低周波領域の優れた吸音特性（例えば周波数５００Ｈｚにおける優れた吸音特性）が得られやすい観点から、フォームラバーの全質量を基準として、５０質量％以上が好ましく、５０質量％を超えることがより好ましく、６０質量％以上が更に好ましく、７０質量％以上が特に好ましく、８０質量％以上が極めて好ましく、８５質量％以上が非常に好ましい。エラストマーの含有量は、フォームラバーの全質量を基準として、１００質量％未満、９８質量％以下、９５質量％以下、又は、９０質量％以下であってよい。 The content of the elastomer is preferably 50% by mass or more, preferably 50% by mass, based on the total mass of the foam rubber, from the viewpoint that excellent sound absorption characteristics in the low frequency region (for example, excellent sound absorption characteristics at a frequency of 500 Hz) can be easily obtained. More preferably, 60% by mass or more is further preferable, 70% by mass or more is particularly preferable, 80% by mass or more is extremely preferable, and 85% by mass or more is very preferable. The content of the elastomer may be less than 100% by mass, 98% by mass or less, 95% by mass or less, or 90% by mass or less based on the total mass of the foam rubber.
　クロロプレン重合体の含有量、又は、エチレンプロピレンジエンゴム以外のエラストマーの含有量は、低周波領域の優れた吸音特性（例えば周波数５００Ｈｚにおける優れた吸音特性）が得られやすい観点から、フォームラバーの全質量を基準として、５０質量％以上が好ましく、５０質量％を超えることがより好ましく、６０質量％以上が更に好ましく、７０質量％以上が特に好ましく、８０質量％以上が極めて好ましく、８５質量％以上が非常に好ましい。クロロプレン重合体の含有量、又は、エチレンプロピレンジエンゴム以外のエラストマーの含有量は、フォームラバーの全質量を基準として、１００質量％未満、９８質量％以下、９５質量％以下、又は、９０質量％以下であってよい。 The content of the chloroprene polymer or the content of the elastomer other than ethylene propylene diene rubber is the total of the foam rubber from the viewpoint that excellent sound absorption characteristics in the low frequency region (for example, excellent sound absorption characteristics at a frequency of 500 Hz) can be easily obtained. Based on the mass, 50% by mass or more is preferable, 50% by mass or more is more preferable, 60% by mass or more is further preferable, 70% by mass or more is particularly preferable, 80% by mass or more is extremely preferable, and 85% by mass or more. Is very preferable. The content of the chloroprene polymer or the content of the elastomer other than ethylene propylene diene rubber is less than 100% by mass, 98% by mass or less, 95% by mass or less, or 90% by mass based on the total mass of the foam rubber. It may be:
＜フォームラバーの製造方法＞
　本実施形態に係るフォームラバーの製造方法は、加硫剤を含有するエラストマー組成物（エラストマーを含有する組成物。発泡性組成物）を発泡させて発泡物を得る発泡工程と、発泡物にゲル化剤を加えてゲル化物を得るゲル化工程と、を有する。 <Manufacturing method of foam rubber>
The method for producing a foam rubber according to the present embodiment includes a foaming step of foaming an elastomer composition containing a vulcanizing agent (a composition containing an elastomer. A foamable composition) to obtain a foam, and a gel on the foam. It has a gelling step of adding an agent to obtain a gelled product.
　エラストマー組成物は、上述のエラストマーを含有することができる。エラストマー組成物は、低周波領域の優れた吸音特性（例えば周波数５００Ｈｚにおける優れた吸音特性）が得られやすい観点から、クロロプレン重合体を含有することが好ましい。 The elastomer composition can contain the above-mentioned elastomer. The elastomer composition preferably contains a chloroprene polymer from the viewpoint that excellent sound absorbing characteristics in the low frequency region (for example, excellent sound absorbing characteristics at a frequency of 500 Hz) can be easily obtained.
　エラストマー組成物は、エラストマーラテックスを含有してよく、主原料としてエラストマーラテックスを含有してよい。エラストマーラテックスの種類としては、特に限定されず、天然ゴムラテックス、イソプレンラテックス、ニトリルブタジエンラテックス、スチレンブタジエンラテックス、クロロプレンラテックス、クロロプレンとアクリロニトリルの共重合ラテックス、エチレンプロピレンジエンラテックス、ブタジエンラテックス、ブチルラテックス等が挙げられる。 The elastomer composition may contain an elastomer latex and may contain an elastomer latex as a main raw material. The type of elastomer latex is not particularly limited, and natural rubber latex, isoprene latex, nitrile butadiene latex, styrene butadiene latex, chloroprene latex, chloroprene-acrylonitrile copolymer latex, ethylenepropylene diene latex, butadiene latex, butyl latex and the like are used. Can be mentioned.
　エラストマー組成物は、フォームラバーの作製に適した固形分濃度として、固形分濃度が５５～７０質量％のエラストマーラテックスであることが好ましい。固形分濃度が５５質量％以上であると、加硫時の収縮が大きくなることが抑制され、優れた成形性が得られやすい。固形分濃度が７０質量％以下であると、エラストマーラテックスの粘度が増大することが抑制され、発泡時のラテックス安定性が低下することを抑制しやすい。 The elastomer composition is preferably an elastomer latex having a solid content concentration of 55 to 70% by mass as a solid content concentration suitable for producing foam rubber. When the solid content concentration is 55% by mass or more, the shrinkage during vulcanization is suppressed to be large, and excellent moldability can be easily obtained. When the solid content concentration is 70% by mass or less, it is easy to suppress an increase in the viscosity of the elastomer latex and a decrease in latex stability during foaming.
　本実施形態に係るフォームラバーの製造方法は、発泡工程の前に、エラストマー（例えばエラストマーラテックス）と加硫剤とを混合することによりエラストマー組成物（例えばエラストマーラテックス組成物）を得る配合工程を有してよい。本実施形態に係るフォームラバーの製造方法は、ゲル化工程の後に、ゲル化工程で得られたゲル化物を加硫する加硫工程を有してよい。本実施形態に係るフォームラバーの製造方法は、加硫工程の後に、加硫工程で得られた加硫物を水洗及び乾燥する水洗・乾燥工程を有してよい。本実施形態に係るフォームラバーの製造方法は、フォームラバーを成形（成形加工）する成形工程を有してよい。用途に応じてフォームラバーに適宜加工を加えることで、各用途に適した所定形状のフォームラバーを得ることができる。 The method for producing a foam rubber according to the present embodiment includes a compounding step of obtaining an elastomer composition (for example, an elastomer latex composition) by mixing an elastomer (for example, elastomer latex) and a vulcanizing agent before the foaming step. You can do it. The method for producing foam rubber according to the present embodiment may include a vulcanization step of vulcanizing the gelled product obtained in the gelation step after the gelation step. The foam rubber manufacturing method according to the present embodiment may include a water washing / drying step of washing and drying the vulcanized product obtained in the vulcanization step after the vulcanization step. The foam rubber manufacturing method according to the present embodiment may include a molding step of molding (molding) the foam rubber. By appropriately processing the foam rubber according to the application, it is possible to obtain a foam rubber having a predetermined shape suitable for each application.
（配合工程）
　配合工程では、エラストマーと、加硫剤を含む添加剤と、を混合することによりエラストマー組成物を得る。例えば、配合工程は、加硫剤に加えて加硫促進剤、起泡剤、気泡安定剤、老化防止剤、粘着防止剤、増粘剤、保水剤、着色剤、分散剤（例えばβ－ナフタレンスルホン酸ホルマリン縮合物のナトリウム塩）等の添加剤（助剤）をエラストマー（例えばエラストマーラテックス）に適宜添加してエラストマー組成物を得る工程であってよい。 (Mixing process)
In the compounding step, an elastomer composition is obtained by mixing an elastomer and an additive containing a vulcanizing agent. For example, in the compounding process, in addition to the vulcanizing agent, a vulcanization accelerator, a foaming agent, a bubble stabilizer, an antioxidant, an anti-adhesive agent, a thickener, a water-retaining agent, a colorant, and a dispersant (for example, β-naphthalene). It may be a step of appropriately adding an additive (auxiliary agent) such as (sodium salt of a sulfonic acid formalin condensate) to an elastomer (for example, an elastomer latex) to obtain an elastomer composition.
　加硫剤の種類としては、特に限定されないが、硫黄、酸化亜鉛、過酸化物等が挙げられる。エラストマー組成物の全量を基準とする加硫剤の添加量として、硫黄の添加量は０．０～２．０質量％（例えば０．０１～２．０質量％）が好ましく、酸化亜鉛の添加量は３．０～１０．０質量％が好ましく、過酸化物の添加量は０．０～２．０質量％（例えば０．０１～２．０質量％）が好ましい。 The type of vulcanizing agent is not particularly limited, but examples thereof include sulfur, zinc oxide, and peroxide. As the amount of the vulcanizing agent added based on the total amount of the elastomer composition, the amount of sulfur added is preferably 0.0 to 2.0% by mass (for example, 0.01 to 2.0% by mass), and zinc oxide is added. The amount is preferably 3.0 to 10.0% by mass, and the amount of peroxide added is preferably 0.0 to 2.0% by mass (for example, 0.01 to 2.0% by mass).
　加硫促進剤の種類としては、特に限定されないが、ジエチルジチオカルバミン酸亜鉛、ジブチルジチオカルバミン酸ナトリウム等のジチオカルバミン酸塩系促進剤；Ｎ，Ｎ’－ジエチルチオ尿素等のチオウレア系促進剤；チウラム系加硫促進剤；チアゾール系促進剤；キサントゲン酸系促進剤などが挙げられる。加硫促進剤の添加量は、エラストマー組成物の全量を基準として０．０～８．０質量％（例えば０．０１～８．０質量％）が好ましい。加硫促進剤として、複数の種類を組み合わせて使用してもよい。 The type of vulcanization accelerator is not particularly limited, but is a dithiocarbamate-based accelerator such as zinc diethyldithiocarbamate or sodium dibutyldithiocarbamate; a thiourea-based accelerator such as N, N'-diethylthiourea; Accelerators; thiazole-based accelerators; xanthate-based accelerators and the like can be mentioned. The amount of the vulcanization accelerator added is preferably 0.0 to 8.0% by mass (for example, 0.01 to 8.0% by mass) based on the total amount of the elastomer composition. As the vulcanization accelerator, a plurality of types may be used in combination.
　起泡剤は、エラストマー組成物に気体を混入させる際にエラストマー組成物を起泡させる役割を有する。起泡剤は、発泡性が良い観点から、炭素数Ｃ１２～１８のアニオン系界面活性剤を含むことが好ましい。起泡剤としては、ラウリン酸ナトリウム、ミリスチン酸ナトリウム、ステアリン酸ナトリウム、ステアリン酸アンモニウム、オレイン酸ナトリウム、オレイン酸カリウム、ひまし油カリウム石鹸、やし油カリウム石鹸等の脂肪酸塩などが挙げられる。起泡剤の添加量は、エラストマー組成物の全量を基準として０．０～２．０質量％（例えば０．０１～２．０質量％）が好ましい。 The foaming agent has a role of foaming the elastomer composition when a gas is mixed into the elastomer composition. The foaming agent preferably contains an anionic surfactant having C12 to 18 carbon atoms from the viewpoint of good foamability. Examples of the foaming agent include fatty acid salts such as sodium laurate, sodium myristate, sodium stearate, ammonium stearate, sodium oleate, potassium oleate, castor oil potassium soap, and coconut oil potassium soap. The amount of the foaming agent added is preferably 0.0 to 2.0% by mass (for example, 0.01 to 2.0% by mass) based on the total amount of the elastomer composition.
　気泡安定剤は、起泡させたエラストマー組成物の泡沫を安定化させる役割を有する。気泡安定剤としては、トリメンベース、両性界面活性剤等が挙げられる。両性界面活性剤としては、アミノ酸型、ベタイン型、アミンオキシド型等の界面活性剤などが挙げられる。気泡安定剤の添加量は、エラストマー組成物の全量を基準として０．２～２．０質量％が好ましい。 The bubble stabilizer has a role of stabilizing the foam of the foamed elastomer composition. Examples of the bubble stabilizer include trimene base and amphoteric surfactant. Examples of amphoteric surfactants include amino acid type, betaine type, amine oxide type and the like. The amount of the bubble stabilizer added is preferably 0.2 to 2.0% by mass based on the total amount of the elastomer composition.
　老化防止剤の種類としては、特に限定されず、モノフェノール系、ビスフェノール系、ポリフェノール系、ベンズイミダゾール系、アミン系、リン酸系等が挙げられる。老化防止剤の具体例としては、２，２’－メチレンビス（４－エチル－６－ｔｅｒｔ－ブチルフェノール）等が挙げられる。 The type of antiaging agent is not particularly limited, and examples thereof include monophenol type, bisphenol type, polyphenol type, benzimidazole type, amine type, and phosphoric acid type. Specific examples of the anti-aging agent include 2,2'-methylenebis (4-ethyl-6-tert-butylphenol) and the like.
　粘着防止剤は、得られるフォームラバーの粘着性を防止する役割を有する。粘着防止剤としては、ワックス、ワセリン等が挙げられる。 The anti-adhesive agent has a role of preventing the adhesiveness of the obtained foam rubber. Examples of the anti-adhesive agent include wax, petrolatum and the like.
（発泡工程）
　発泡工程では、加硫剤を含有するエラストマー組成物を発泡させて発泡物（例えば発泡ラテックス組成物）を得る。発泡工程は、エラストマー組成物に気体を混合し（気泡を取り込み）、エラストマー組成物を泡沫状態とする工程である。得られるフォームラバーの密度は、発泡工程における気体の混入量によって調整できる。エラストマー組成物の密度を調整するためには、所望のフォームラバーの密度と、配合するエラストマー（例えばラテックス）の体積とから、配合時に必要なエラストマー（例えばラテックス）の質量を算出し、この質量において所望の体積となるように発泡させる気体の混入量を決定すればよい。エラストマー組成物を発泡させ泡沫状態とするための気体としては、空気、窒素等を使用することができる。エラストマー組成物を発泡させる方法としては、ミキサーを使用することが可能であり、好ましい例としては、ホバートミキサー、ピンミキサー、オークスミキサー、ハンドミキサー等が挙げられる。 (Foam process)
In the foaming step, an elastomer composition containing a vulcanizing agent is foamed to obtain a foam (for example, a foamed latex composition). The foaming step is a step of mixing a gas with the elastomer composition (taking in air bubbles) to bring the elastomer composition into a foam state. The density of the obtained foam rubber can be adjusted by adjusting the amount of gas mixed in the foaming process. In order to adjust the density of the elastomer composition, the mass of the elastomer (for example, latex) required at the time of blending is calculated from the desired density of the foam rubber and the volume of the elastomer (for example, latex) to be blended, and at this mass. The amount of the gas to be foamed may be determined so as to have a desired volume. Air, nitrogen, or the like can be used as the gas for foaming the elastomer composition into a foamy state. As a method for foaming the elastomer composition, a mixer can be used, and preferred examples thereof include a hovert mixer, a pin mixer, an oaks mixer, a hand mixer and the like.
（ゲル化工程）
　ゲル化工程では、発泡工程で得られた発泡物にゲル化剤を加えてゲル化物を得る。ゲル化工程は、ゲル化剤を泡沫状態のエラストマー組成物（例えば発泡ラテックス組成物）に添加し、エラストマー組成物中に分散しているエラストマー粒子を凝集させてゲル化させる工程である。この際、エラストマー組成物に混入させた気体により発生した気泡の分散状態を維持したままエラストマー組成物がゲル化し、後続の加硫工程において、このゲル化したエラストマー組成物を加硫することで、均一なセル構造を有するラテックスフォームを得ることができる。 (Gelification process)
In the gelling step, a gelling agent is added to the foam obtained in the foaming step to obtain a gelled product. The gelling step is a step of adding a gelling agent to a foamy elastomer composition (for example, a foamed latex composition) to aggregate and gel the elastomer particles dispersed in the elastomer composition. At this time, the elastomer composition gels while maintaining the dispersed state of the bubbles generated by the gas mixed in the elastomer composition, and in the subsequent vulcanization step, the gelled elastomer composition is vulcanized. A latex foam having a uniform cell structure can be obtained.
　ゲル化剤としては、ケイフッ化ナトリウム、ケイフッ化カリウム、硫酸アンモニウム、二酸化炭素等が挙げられる。 Examples of the gelling agent include sodium silicate, potassium silicate, ammonium sulfate, carbon dioxide and the like.
　ゲル化工程において、ゲル化したエラストマー組成物中に存在する発泡ガスは気泡として保持されるため、この気泡の大きさが、最終的に得られるフォームラバーのセルの径及び／又はセル連結部の径を決定する傾向がある。これらの径はゲル化時間に依存している。ゲル化時間が長ければ、ゲル化したエラストマー組成物中に混合された気泡が互いに接触し合って合一して巨大化したり、ゲル化したエラストマー組成物の外へ排出されたりするため、径が大きくなる傾向がある。一方、ゲル化時間が短いほど小さな径が得られやすい。ゲル化時間はゲル化剤の添加量によって調整することができる。ゲル化剤の添加量が多いほど、ゲル化時間が短くなり、結果として小さな径のフォームラバーが得られる傾向がある。 In the gelling step, the foaming gas present in the gelled elastomer composition is retained as bubbles, so that the size of the bubbles is the diameter of the cell of the finally obtained foam rubber and / or the cell connecting portion. Tends to determine the diameter. These diameters depend on the gelation time. If the gelation time is long, the bubbles mixed in the gelled elastomer composition come into contact with each other and coalesce to become large, or are discharged to the outside of the gelled elastomer composition, so that the diameter becomes large. Tends to grow. On the other hand, the shorter the gelation time, the easier it is to obtain a smaller diameter. The gelling time can be adjusted by the amount of the gelling agent added. The larger the amount of the gelling agent added, the shorter the gelling time, and as a result, a foam rubber having a small diameter tends to be obtained.
　ゲル化工程においてゲル化剤を加えた後のゲル化時間は、２～８分である。この場合、優れた吸音特性（例えば周波数５００Ｈｚにおける優れた吸音特性）を有すると共に優れた成形性を有するフォームラバーを得ることができる。ゲル化時間は、優れた吸音特性を有すると共に優れた成形性を有するフォームラバーを得やすい観点から、３分以上が好ましい。ゲル化時間は、優れた吸音特性を有すると共に優れた成形性を有するフォームラバーを得やすい観点から、７分以下が好ましく、６分以下がより好ましい。これらの観点から、ゲル化時間は、３～６分が好ましい。ゲル化時間は、４分以上、５分以上、又は、６分以上であってもよい。ゲル化時間は、５分以下、４分以下、又は、３分以下であってよい。「ゲル化時間」は、２３℃において、発泡工程で得られた泡沫状態のエラストマー組成物にゲル化剤を加えた時点から流動性がなくなるまで（泡沫状態のエラストマー組成物が手に付着しなくなるまで）の時間である。 The gelation time after adding the gelling agent in the gelation step is 2 to 8 minutes. In this case, it is possible to obtain a foam rubber having excellent sound absorbing characteristics (for example, excellent sound absorbing characteristics at a frequency of 500 Hz) and excellent moldability. The gelling time is preferably 3 minutes or more from the viewpoint of easily obtaining a foam rubber having excellent sound absorbing properties and excellent moldability. The gelling time is preferably 7 minutes or less, more preferably 6 minutes or less, from the viewpoint of easily obtaining a foam rubber having excellent sound absorbing properties and excellent moldability. From these viewpoints, the gelation time is preferably 3 to 6 minutes. The gelation time may be 4 minutes or more, 5 minutes or more, or 6 minutes or more. The gelation time may be 5 minutes or less, 4 minutes or less, or 3 minutes or less. The "gelling time" is set at 23 ° C. from the time when the gelling agent is added to the foamy elastomer composition obtained in the foaming step until the fluidity disappears (the foamy elastomer composition does not adhere to the hand). Up to) time.
（加硫工程）
　加硫工程では、ゲル化工程で得られたゲル化物を加硫する。加硫工程では、ゲル化物を加熱することにより加硫（加熱加硫）することができる。例えば、加硫工程は、ゲル化剤を添加して得られた発泡物を流延、注型、押出し成形等の方法により所望の形状に加工した後、加硫剤、エラストマー等の種類に応じて５０～２００℃に加熱して充分に加硫を進行させて発泡加硫体を得る工程である。加硫の進行に伴い架橋反応が進行してよい。加硫方法としては、発泡物を加硫させ得るものであれば特に限定されず、空気加硫、水蒸気加硫等が挙げられる。 (Vulcanization process)
In the vulcanization step, the gelled product obtained in the gelation step is vulcanized. In the vulcanization step, vulcanization (heat vulcanization) can be performed by heating the gelled product. For example, in the vulcanization step, the foam obtained by adding a gelling agent is processed into a desired shape by a method such as casting, casting, or extrusion molding, and then depending on the type of vulcanizing agent, elastomer, or the like. This is a step of obtaining a foamed vulcanized product by sufficiently heating the vulcanization to 50 to 200 ° C. The cross-linking reaction may proceed as the vulcanization progresses. The vulcanization method is not particularly limited as long as it can vulcanize the foam, and examples thereof include air vulcanization and steam vulcanization.
（水洗・乾燥工程）
　水洗・乾燥工程では、加硫工程で得られた加硫物（発泡加硫体）を水洗及び乾燥することでフォームラバーを得ることができる。 (Washing / drying process)
In the water washing / drying step, foam rubber can be obtained by washing and drying the vulcanized product (foam vulcanized product) obtained in the vulcanization step with water.
＜吸音材＞
　本実施形態に係る吸音材は、例えば、本実施形態に係るフォームラバーの成形体であり、本実施形態に係るフォームラバーを成形（成形加工）して得ることができる。本実施形態に係る吸音材は、本実施形態に係るフォームラバーからなり、低周波領域の吸音特性に優れている。本実施形態に係る吸音材は、自動車、家屋、音響施設、鉄道車両、航空機等の各種用途において使用可能であり、自動車用（自動車用吸音材、車載用防音材料）であることが好ましい。本実施形態によれば、本実施形態に係る吸音材を備える自動車、家屋、音響施設、鉄道車両、航空機等を提供することができる。 <Sound absorbing material>
The sound absorbing material according to the present embodiment is, for example, a molded body of the foam rubber according to the present embodiment, and can be obtained by molding (molding) the foam rubber according to the present embodiment. The sound absorbing material according to the present embodiment is made of the foam rubber according to the present embodiment and has excellent sound absorbing characteristics in the low frequency region. The sound absorbing material according to the present embodiment can be used in various applications such as automobiles, houses, audio facilities, railroad vehicles, and aircraft, and is preferably for automobiles (automobile sound absorbing material, in-vehicle soundproofing material). According to the present embodiment, it is possible to provide an automobile, a house, an audio facility, a railroad vehicle, an aircraft and the like provided with the sound absorbing material according to the present embodiment.
　以下、実施例及び比較例に基づいて本発明をより詳細に説明するが、本発明はこれらの実施例に限定されるものではない。 Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to these Examples.
＜実施例１＞
（エラストマーラテックスの作製）
　加熱冷却ジャケット及び攪拌機を備えた内容積３リットルの重合缶に、クロロプレン単量体２０質量部、アクリロニトリル単量体２０質量部、純水１５０質量部、不均化ロジン酸カリウム（ハリマ化成株式会社製）３．３質量部、トール脂肪酸（ハリマ化成株式会社製）１．０質量部、水酸化ナトリウム０．１質量部、及び、β－ナフタレンスルホン酸ホルマリン縮合物のナトリウム塩（花王株式会社製）２．０質量部を添加した。次に、重合開始剤として過硫酸カリウム０．１質量部を添加し、重合温度４０℃にて窒素気流下で乳化重合を行った。続いて、４０℃における重合液の比重が０．９８４、０．９９１、０．９９８、１．００５、１．０１１、１．０１８、１．０２４、１．０３０、１．０３６、１．０４０、１．０４４及び１．０５３に達した時にクロロプレン単量体をそれぞれ５質量部ずつ合計１２回（合計６０質量部）加えてクロロプレン単量体の分添を行った。クロロプレン単量体及びアクリロニトリル単量体の合計量に対する重合率が８０％となった時点で、重合停止剤であるフェノチアジンを加えて重合を停止させた。そして、減圧下で反応溶液中の未反応単量体を除去及び濃縮することで固形分濃度６５質量％のエラストマーラテックス（Ａ）を得た。 <Example 1>
(Making elastomer latex)
In a polymerization can with an internal volume of 3 liters equipped with a heating / cooling jacket and a stirrer, 20 parts by mass of chloroprene monomer, 20 parts by mass of acrylonitrile monomer, 150 parts by mass of pure water, potassium disproportionate (Harima Kasei Co., Ltd.) (Manufactured by) 3.3 parts by mass, tall fatty acid (manufactured by Harima Kasei Co., Ltd.) 1.0 part by mass, sodium hydroxide 0.1 parts by mass, and sodium salt of β-naphthalene sulfonate formalin condensate (manufactured by Kao Co., Ltd.) ) 2.0 parts by mass was added. Next, 0.1 part by mass of potassium persulfate was added as a polymerization initiator, and emulsion polymerization was carried out at a polymerization temperature of 40 ° C. under a nitrogen stream. Subsequently, the specific gravities of the polymerization solution at 40 ° C. are 0.984, 0.991, 0.998, 1.005, 1.011, 1.018, 1.024, 1.030, 1.036, 1.040. , 1.044 and 1.053, 5 parts by mass of each of the chloroprene monomers were added 12 times in total (60 parts by mass in total) to carry out the addition of the chloroprene monomers. When the polymerization rate with respect to the total amount of the chloroprene monomer and the acrylonitrile monomer became 80%, the polymerization terminator phenothiazine was added to terminate the polymerization. Then, the unreacted monomer in the reaction solution was removed and concentrated under reduced pressure to obtain an elastomer latex (A) having a solid content concentration of 65% by mass.
（フォームラバーの作製）
　以下、「質量部」は、エラストマーラテックス（Ａ）の後述の固形分１００質量部に対する量を示す。 (Making foam rubber)
Hereinafter, "part by mass" indicates the amount of the elastomer latex (A) with respect to 100 parts by mass of the solid content described later.
　酸化亜鉛（加硫剤）７．５質量部、ジエチルジチオカルバミン酸亜鉛（加硫促進剤）２．０質量部、Ｎ，Ｎ’－ジエチルチオ尿素（加硫促進剤）２．０質量部、２，２’－メチレンビス（４－エチル－６－ｔｅｒｔ－ブチルフェノール）（老化防止剤）２．０質量部、β－ナフタレンスルホン酸ホルマリン縮合物のナトリウム塩（分散剤、商品名「デモールＮ」、花王株式会社製）０．２質量部、及び、水１４．３質量部を、陶器製ボールミルを用いて、２０℃で１６時間混合することにより、加硫剤及び加硫促進剤を含有する水分散液（固形分濃度：４８．９質量％）を調製した。 Zinc oxide (vulcanization agent) 7.5 parts by mass, zinc diethyldithiocarbamate (vulcanization accelerator) 2.0 parts by mass, N, N'-diethylthiourea (vulcanization accelerator) 2.0 parts by mass, 2, 2'-Methylenebis (4-ethyl-6-tert-butylphenol) (anti-aging agent) 2.0 parts by mass, sodium salt of β-naphthalene sulfonic acid formarin condensate (dispersant, trade name "Demor N", Kao shares A water dispersion containing a vulcanizing agent and a vulcanization accelerator by mixing 0.2 parts by mass and 14.3 parts by mass of water at 20 ° C. for 16 hours using a ceramic ball mill. (Solid content concentration: 48.9% by mass) was prepared.
　内容積１リットルの容器に、上述のエラストマーラテックス（Ａ）（固形分として１００質量部）、上述の水分散液２８質量部（固形分として１３．７質量部）、ジブチルジチオカルバミン酸ナトリウム（加硫促進剤、商品名「ノクセラーＴＰ」、大内新興株式会社製）２．０質量部、オレイン酸カリウム（起泡剤、商品名「ＦＲ－１４」、花王株式会社製）０．３質量部、ベタイン（気泡安定剤、商品名「アンヒトール２４Ｂ」、花王株式会社製）０．７質量部、及び、粘着防止剤（商品名「ニューエイドＩＡＬ」、精工化学株式会社製）２．０質量部を添加した。各成分を撹拌しつつ混合し、全成分を添加後、５分間撹拌を続けることでラテックス組成物を得た。 In a container with an internal volume of 1 liter, the above-mentioned elastomer latex (A) (100 parts by mass as solid content), 28 parts by mass of the above-mentioned aqueous dispersion (13.7 parts by mass as solid content), and sodium dibutyldithiocarbamate (vulcanization). Accelerator, product name "Noxeller TP", manufactured by Ouchi Shinko Co., Ltd.) 2.0 parts by mass, potassium oleate (foaming agent, product name "FR-14", manufactured by Kao Co., Ltd.) 0.3 parts by mass, 0.7 parts by mass of betaine (bubble stabilizer, trade name "Ancitor 24B", manufactured by Kao Co., Ltd.) and 2.0 parts by mass of anti-adhesive agent (brand name "New Aid IAL", manufactured by Seiko Kagaku Co., Ltd.) Added. Each component was mixed while stirring, and after adding all the components, stirring was continued for 5 minutes to obtain a latex composition.
　付属のバルーンウィスクを取り付けたハンドミキサー（スマートパワーハンドミキサープラスＨＭ－０６０ＳＪ、Ｃｕｉｓｉｎａｒｔ社製）を用いて上述のラテックス組成物を回転数１０００回転／分で撹拌して５分間発泡（２３℃）させた。その後、ハンドミキサーでラテックス組成物を撹拌したまま、ゲル化剤として２０質量％ケイフッ化ナトリウム水溶液を３．０質量部添加した。２分間更にラテックス組成物を撹拌（２３℃）した後、ステンレス製の金型へ注型（２３℃）した。発泡させたラテックス組成物は、注型後２分で流動性がなくなりゲル化した。ゲル化時間は、撹拌２分及び注型後２分を合わせて４分であった。 Using a hand mixer (Smart Power Hand Mixer Plus HM-060SJ, manufactured by Cuisinart) equipped with the attached balloon whisk, the above latex composition is stirred at a rotation speed of 1000 rpm and foamed (23 ° C.) for 5 minutes. It was. Then, while stirring the latex composition with a hand mixer, 3.0 parts by mass of a 20 mass% sodium silicate aqueous solution was added as a gelling agent. The latex composition was further stirred for 2 minutes (23 ° C.) and then cast into a stainless steel mold (23 ° C.). The foamed latex composition lost its fluidity and gelled 2 minutes after casting. The gelation time was 4 minutes in total, 2 minutes for stirring and 2 minutes after casting.
　ゲル化後３０分間室温（２３℃）で静置した。その後、金型ごと空気加硫釜へ移し、１４０℃にて１２０分間加硫を行った。４０℃の温水で冷却洗浄後、脱型し乾燥させることにより、ゴム弾性のあるフォームラバーが得られた。 After gelation, it was allowed to stand at room temperature (23 ° C) for 30 minutes. Then, the mold was transferred to an air vulcanizer and vulcanized at 140 ° C. for 120 minutes. After cooling and washing with warm water at 40 ° C., the mold was removed and dried to obtain a foam rubber having rubber elasticity.
（フォームラバー特性）
［Ｈｅｙｗｏｏｄ径］
　上述のフォームラバーにおけるセル及びセル連結部（セル連結部分の穴）のＨｅｙｗｏｏｄ径（ＪＩＳ　Ｚ　８８２７－１：２０１８で定義されたＨｅｙｗｏｏｄ径）を下記手順により測定した。結果を表１及び表２に示す。
　１）上述のフォームラバーから縦１００ｍｍ、横１００ｍｍ、厚さ２０ｍｍの測定サンプルを切り出した後、測定サンプルの中心を、対向する一対の辺と平行かつ厚さ方向に切断した後、断面の中心部分のＳＥＭ写真（撮影倍率：４５倍）を撮影した。
　２）ＳＥＭ写真を画像解析式粒度分布測定ソフトウエア　Ｍａｃ－Ｖｉｅｗ（株式会社マウンテック）にて解析した。
　３）ＳＥＭ写真における１００個のセル及び１００個のセル連結部を個々にトレースした後に、各セルの径及び各セル連結部の径に関するデータを採取し、セルの平均径及びセル連結部の平均径を求めた。 (Foam rubber characteristics)
[Heywood diameter]
The Heywood diameter (Heywood diameter defined in JIS Z 8827-1: 2018) of the cell and the cell connecting portion (hole of the cell connecting portion) in the above-mentioned foam rubber was measured by the following procedure. The results are shown in Tables 1 and 2.
1) After cutting out a measurement sample having a length of 100 mm, a width of 100 mm, and a thickness of 20 mm from the above-mentioned foam rubber, the center of the measurement sample is cut parallel to a pair of opposite sides in the thickness direction, and then the central portion of the cross section. SEM photograph (photographing magnification: 45 times) was taken.
2) The SEM photograph was analyzed by the image analysis type particle size distribution measurement software Mac-View (Mountech Co., Ltd.).
3) After tracing 100 cells and 100 cell connecting parts individually in the SEM photograph, data on the diameter of each cell and the diameter of each cell connecting part are collected, and the average diameter of the cells and the average of the cell connecting parts are collected. The diameter was calculated.
［密度］
　上述のフォームラバーの密度を下記手順により測定した。結果を表１及び表２に示す。
　１）上述のフォームラバーから縦１００ｍｍ、横１００ｍｍ、厚さ２０ｍｍの試験片Ａを切り出した後、試験片Ａにおける厚さ方向の両表層部分を５ｍｍ切除することにより厚さ１０ｍｍの試験片Ｂを得た。
　２）試験片Ｂの中心部から直径３６ｍｍの円形の測定サンプルを打ち抜き、測定サンプルの質量を秤量した。
　３）下記式より密度を算出した。
　　密度［ｇ／ｃｍ３］＝測定サンプルの質量［ｇ］／測定サンプルの体積（３．２４πｃｍ３） [density]
The density of the above-mentioned foam rubber was measured by the following procedure. The results are shown in Tables 1 and 2.
1) After cutting out a test piece A having a length of 100 mm, a width of 100 mm, and a thickness of 20 mm from the above-mentioned foam rubber, a test piece B having a thickness of 10 mm is obtained by cutting off both surface layers of the test piece A in the thickness direction by 5 mm. Obtained.
2) A circular measurement sample having a diameter of 36 mm was punched out from the center of the test piece B, and the mass of the measurement sample was weighed.
3) The density was calculated from the following formula.
Density [g / cm 3 ] = mass of measurement sample [g] / volume of measurement sample (3.24πcm 3 )
（成形性）
　Ｈｅｙｗｏｏｄ径の上述の測定サンプルの作製可否に基づき成形性（成形加工性）を評価した。結果を表１及び表２に示す。作製可能である場合を「Ａ（良好）」と判定し、作製できない場合を「Ｂ（不良）」と判定した。 (Moldability)
The moldability (molding processability) was evaluated based on the feasibility of producing the above-mentioned measurement sample having a Highwood diameter. The results are shown in Tables 1 and 2. The case where it can be produced was determined as "A (good)", and the case where it could not be produced was determined as "B (defective)".
（吸音特性）
　上述のフォームラバーについて、ＪＩＳ　Ａ　１４０５－２：２００７で規定される垂直入射吸音率を測定した。具体的には、まず、上述のフォームラバーから縦１００ｍｍ、横１００ｍｍ、厚さ３０ｍｍの試験片を切り出した後、当該試験片における厚さ方向の両表層部分を５ｍｍ切除することにより厚さ２０ｍｍの測定サンプルを得た。この測定サンプルについて、電子測器株式会社製の垂直入射吸音率測定器ＴＹＰＥ１００４１（フプローブチューブマイクロホン）を用いて、１０Ｈｚから１０Ｈｚ刻みで２０００Ｈｚまでの周波数領域の垂直入射吸音率を測定した。５００Ｈｚの垂直入射吸音率を取得すると共に、周波数領域５０～１５００Ｈｚの範囲の垂直入射吸音率における最大値及び最小値を取得した。結果を表１及び表２に示す。 (Sound absorption characteristics)
For the above-mentioned foam rubber, the vertical incident sound absorption coefficient specified in JIS A 1405-2: 2007 was measured. Specifically, first, a test piece having a length of 100 mm, a width of 100 mm, and a thickness of 30 mm is cut out from the above-mentioned foam rubber, and then both surface layer portions in the thickness direction of the test piece are cut out by 5 mm to obtain a thickness of 20 mm. A measurement sample was obtained. For this measurement sample, the vertical incident sound absorption coefficient in the frequency range from 10 Hz to 10 Hz was measured using a vertical incident sound absorption coefficient measuring device TYPE10041 (Fprobe tube microphone) manufactured by Denshi Sokki Co., Ltd. The vertical incident sound absorption coefficient of 500 Hz was acquired, and the maximum value and the minimum value in the vertical incident sound absorption coefficient in the frequency domain range of 50 to 1500 Hz were acquired. The results are shown in Tables 1 and 2.
＜実施例２＞
　２０質量％ケイフッ化ナトリウム水溶液の使用量を２．５質量部に変更し、ゲル化時間が６分（撹拌２分及び注型後４分）であったこと以外は実施例１と同様にフォームラバーの作製及び評価を行った。 <Example 2>
The foam was the same as in Example 1 except that the amount of the 20 mass% sodium silicate aqueous solution used was changed to 2.5 parts by mass and the gelation time was 6 minutes (2 minutes for stirring and 4 minutes after casting). The rubber was prepared and evaluated.
＜実施例３＞
　２０質量％ケイフッ化ナトリウム水溶液の使用量を３．５質量部に変更し、ゲル化時間が３分（撹拌２分及び注型後１分）であったこと以外は実施例１と同様にフォームラバーの作製及び評価を行った。 <Example 3>
The foam was the same as in Example 1 except that the amount of the 20 mass% sodium silicate aqueous solution used was changed to 3.5 parts by mass and the gelation time was 3 minutes (2 minutes for stirring and 1 minute after casting). The rubber was prepared and evaluated.
＜実施例４＞
　ハンドミキサーの回転数を１１００回転／分に変更したこと以外は実施例１と同様にフォームラバーの作製及び評価を行った。 <Example 4>
Foam rubber was produced and evaluated in the same manner as in Example 1 except that the rotation speed of the hand mixer was changed to 1100 rotations / minute.
＜実施例５＞
　ハンドミキサーの回転数を９００回転／分に変更したこと以外は実施例１と同様にフォームラバーの作製及び評価を行った。 <Example 5>
Foam rubber was produced and evaluated in the same manner as in Example 1 except that the rotation speed of the hand mixer was changed to 900 rpm.
＜実施例６＞
　エラストマーラテックス（Ａ）に代えてエラストマーラテックス（Ｂ）（クロロプレンラテックス、商品名「ＬＭ－６１」、デンカ株式会社製）を用い、２０質量％ケイフッ化ナトリウム水溶液の使用量を３．５質量部に変更したこと以外は実施例１と同様にフォームラバーの作製及び評価を行った。 <Example 6>
Elastomer latex (B) (chloroprene latex, trade name "LM-61", manufactured by Denka Co., Ltd.) is used instead of elastomer latex (A), and the amount of 20 mass% sodium silicate aqueous solution used is reduced to 3.5 parts by mass. Foam rubber was prepared and evaluated in the same manner as in Example 1 except that it was changed.
＜実施例７＞
　エラストマーラテックス（Ａ）に代えてエラストマーラテックス（Ｃ）（ニトリルブタジエンラテックス、商品名「Ｎｉｐｏｌ　ＬＸ５３１Ｂ」、日本ゼオン株式会社製）を用い、２０質量％ケイフッ化ナトリウム水溶液の使用量を１．５質量部に変更したこと以外は実施例１と同様にフォームラバーの作製及び評価を行った。 <Example 7>
Elastomer latex (C) (nitrile butadiene latex, trade name "Nipol LX531B", manufactured by Nippon Zeon Co., Ltd.) was used instead of elastomer latex (A), and the amount of 20 mass% sodium silicate aqueous solution used was 1.5 parts by mass. Foam rubber was prepared and evaluated in the same manner as in Example 1 except that it was changed to.
＜比較例１＞
　２０質量％ケイフッ化ナトリウム水溶液の使用量を２．０質量部に変更し、ゲル化時間が１０分（撹拌２分及び注型後８分）であったこと以外は実施例１と同様にフォームラバーの作製及び評価を行った。 <Comparative example 1>
The foam was the same as in Example 1 except that the amount of the 20 mass% sodium silicate aqueous solution used was changed to 2.0 parts by mass and the gelation time was 10 minutes (2 minutes for stirring and 8 minutes after casting). The rubber was prepared and evaluated.
＜比較例２＞
　２０質量％ケイフッ化ナトリウム水溶液の使用量を４．５質量部に変更し、ゲル化時間が１分（撹拌０．５分及び注型後０．５分）であったこと以外は実施例１と同様にフォームラバーを作製した。フォームラバーの成形性が悪いことから測定サンプルを作製できず、フォームラバー特性及び吸音特性を評価できなかった。 <Comparative example 2>
Example 1 except that the amount of the 20 mass% sodium silicate aqueous solution used was changed to 4.5 parts by mass and the gelation time was 1 minute (0.5 minutes for stirring and 0.5 minutes after casting). A foam rubber was produced in the same manner as in the above. Due to the poor moldability of the foam rubber, a measurement sample could not be prepared, and the foam rubber characteristics and sound absorption characteristics could not be evaluated.
＜比較例３＞
　ハンドミキサーの回転数を１３５０回転／分に変更したこと以外は実施例１と同様にフォームラバーを作製した。フォームラバーの成形性が悪いことから、密度測定を除き、測定サンプルを作製できず、フォームラバー特性及び吸音特性を評価できなかった。 <Comparative example 3>
A foam rubber was produced in the same manner as in Example 1 except that the rotation speed of the hand mixer was changed to 1350 rotations / minute. Due to the poor moldability of the foam rubber, measurement samples could not be prepared except for density measurement, and the foam rubber characteristics and sound absorption characteristics could not be evaluated.
＜比較例４＞
　ハンドミキサーの回転数を６５０回転／分に変更したこと以外は実施例１と同様にフォームラバーを作製した。フォームラバーの成形性が悪いことから、密度測定を除き、測定サンプルを作製できず、フォームラバー特性及び吸音特性を評価できなかった。 <Comparative example 4>
A foam rubber was produced in the same manner as in Example 1 except that the rotation speed of the hand mixer was changed to 650 rotations / minute. Due to the poor moldability of the foam rubber, measurement samples could not be prepared except for density measurement, and the foam rubber characteristics and sound absorption characteristics could not be evaluated.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　上記表１から明らかなように、実施例１～７のフォームラバーは、低周波領域の吸音率に優れていた。一方、比較例１では、ゲル化時間が長いため、セルのＨｅｙｗｏｏｄ径が大きく、低周波領域の吸音特性が劣っていた。比較例２では、ゲル化時間が短すぎるためフォームラバーの成形性が悪かった。比較例３では、フォームラバーの密度が０．１０ｇ／ｃｍ３未満であり、柔軟性が劣り成形性が悪かった。比較例４では、フォームラバーの密度が０．３５ｇ／ｃｍ３を超えており、フォームラバーが脆く成形性が悪かった。成形性が悪い比較例２～４では、測定サンプルを作製できず、フォームラバー特性及び吸音特性を充分に評価できなかった。 As is clear from Table 1 above, the foam rubbers of Examples 1 to 7 were excellent in sound absorption coefficient in the low frequency region. On the other hand, in Comparative Example 1, since the gelation time was long, the Heywood diameter of the cell was large, and the sound absorption characteristic in the low frequency region was inferior. In Comparative Example 2, the gelation time was too short, so that the foam rubber had poor moldability. In Comparative Example 3, the density of the foam rubber was less than 0.10 g / cm 3 , the flexibility was poor, and the moldability was poor. In Comparative Example 4, the density of the foam rubber exceeded 0.35 g / cm 3 , and the foam rubber was brittle and had poor moldability. In Comparative Examples 2 to 4 having poor moldability, the measurement sample could not be prepared, and the foam rubber property and the sound absorption property could not be sufficiently evaluated.

Claims (13)

  1. 　中空のセル同士が連結した連続気泡を有するフォームラバーであって、
    　前記セルのＪＩＳ　Ｚ　８８２７－１：２０１８で定義されたＨｅｙｗｏｏｄ径が１８０μｍ以下であり、
    　前記フォームラバーの密度が０．１０～０．３５ｇ／ｃｍ３である、フォームラバー。     Foam rubber having open cells in which hollow cells are connected to each other.
    The Heywood diameter defined in JIS Z 8827-1: 2018 of the cell is 180 μm or less.
    A foam rubber having a density of 0.10 to 0.35 g / cm 3 .
  2. 　セル連結部のＪＩＳ　Ｚ　８８２７－１：２０１８で定義されたＨｅｙｗｏｏｄ径が５～３５μｍである、請求項１に記載のフォームラバー。 The foam rubber according to claim 1, wherein the Heywood diameter defined in JIS Z 8827-1: 2018 of the cell connecting portion is 5 to 35 μm.
  3. 　前記セルのＪＩＳ　Ｚ　８８２７－１：２０１８で定義されたＨｅｙｗｏｏｄ径が１００～１８０μｍである、請求項１又は２に記載のフォームラバー。 The foam rubber according to claim 1 or 2, wherein the Heywood diameter defined in JIS Z 8827-1: 2018 of the cell is 100 to 180 μm.
  4. 　前記フォームラバーの密度が０．１０～０．３５ｇ／ｃｍ３である、請求項１～３のいずれか一項に記載のフォームラバー。 The foam rubber according to any one of claims 1 to 3, wherein the density of the foam rubber is 0.10 to 0.35 g / cm 3.
  5. 　エラストマーを含有する、請求項１～４のいずれか一項に記載のフォームラバー。 The foam rubber according to any one of claims 1 to 4, which contains an elastomer.
  6. 　前記エラストマーがクロロプレン重合体を含む、請求項５に記載のフォームラバー。 The foam rubber according to claim 5, wherein the elastomer contains a chloroprene polymer.
  7. 　前記クロロプレン重合体の含有量が、前記エラストマーの全質量を基準として５０質量％を超える、請求項６に記載のフォームラバー。 The foam rubber according to claim 6, wherein the content of the chloroprene polymer exceeds 50% by mass based on the total mass of the elastomer.
  8. 　ＪＩＳ　Ａ　１４０５－２：２００７で規定される周波数５００Ｈｚの垂直入射吸音率が０．５～０．８である、請求項１～７のいずれか一項に記載のフォームラバー。 The foam rubber according to any one of claims 1 to 7, wherein the vertical incident sound absorption coefficient at a frequency of 500 Hz defined by JIS A 1405-2: 2007 is 0.5 to 0.8.
  9. 　ＪＩＳ　Ａ　１４０５－２：２００７で規定される周波数領域５０～１５００Ｈｚの全ての範囲の垂直入射吸音率が０．５～１．０である、請求項１～８のいずれか一項に記載のフォームラバー。 The form according to any one of claims 1 to 8, wherein the vertical incident sound absorption coefficient in the entire range of the frequency domain 50 to 1500 Hz defined by JIS A 1405-2: 2007 is 0.5 to 1.0. rubber.
  10. 　請求項１～９のいずれか一項に記載のフォームラバーからなる、吸音材。 A sound absorbing material made of the foam rubber according to any one of claims 1 to 9.
  11. 　自動車用である、請求項１０に記載の吸音材。 The sound absorbing material according to claim 10, which is for automobiles.
  12. 　加硫剤を含有するエラストマー組成物を発泡させて発泡物を得る発泡工程と、
    　前記発泡物にゲル化剤を加えてゲル化物を得るゲル化工程と、を有し、
    　前記ゲル化工程において前記ゲル化剤を加えた後のゲル化時間が２～８分である、フォームラバーの製造方法。     A foaming step of foaming an elastomer composition containing a vulcanizing agent to obtain a foam, and
    It has a gelling step of adding a gelling agent to the foam to obtain a gelled product.
    A method for producing a foam rubber, wherein the gelation time after adding the gelling agent in the gelation step is 2 to 8 minutes.
  13. 　前記エラストマー組成物がクロロプレン重合体を更に含有する、請求項１２に記載のフォームラバーの製造方法。 The method for producing a foam rubber according to claim 12, wherein the elastomer composition further contains a chloroprene polymer.
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