JP2007085385A - Vibration damping material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide vibration damping material which is vibration damping material not based on a mass low and attenuates vibration, specially effectively low frequency noise. <P>SOLUTION: This vibration damping material contains expanded porous material and expansion magnification of porous material defined as volume after expansion/volume before expansion is 1.2 or higher and less than 5. The porous material contains continuous phase including relatively soft porous structure and relatively hard dispersion substance dispersed in the continuous phase, large number of holes forming a porous structure of the continuous phase do not substantially communicate between a front and a back of the porous material. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vibration damping material, and more particularly to a vibration damping material using a new principle different from the mass law.

  When sound and other mechanical vibrations are blocked by a sound insulating material / damping material, it is more effective that the sound insulating material / damping material is thicker than a material having a large specific gravity such as lead. This is known as sound insulation and vibration suppression using the mass law. In the case of sound insulation, the use is limited when the mass of the sound insulation material is increased, but it has been considered so far that there is no light and sound insulation effect material. Conventionally known as a sound insulation method is a vibration isolation (vibration suppression) technique that suppresses a part of noise caused by sound or mechanical vibration by converting the noise into thermal energy inside the polymer material and attenuating it. . Initially, it was known that a structure in which flake graphite cast iron and flake graphite are dispersed has a characteristic of damping vibration. After that, anti-vibration (vibration control) technology has attracted industrial attention, and anti-vibration alloys based on various principles have been developed. Furthermore, anti-vibration rubber has also been developed and put into practical use as anti-vibration materials. Has reached the point. In addition, these fields of use have expanded to building materials (materials that make up sound barriers), various industrial fields such as home appliances, OA equipment, automobiles, railways, etc. Yes.

  In such a background, research for providing a lightweight and simple vibration-proofing material by using the viscoelasticity of a polymer material has been vigorously conducted. The main thing of these techniques is to obtain a damping effect by using a polymer, particularly an elastomer, as a matrix and adding an organic low molecule or an inorganic filler as an additive thereto. They can be classified as follows according to the anti-vibration mechanism.

(1) Due to the friction effect of additives such as polymers and fillers, such as polyester resin containing an inorganic filler such as cast iron powder (see Patent Documents 1 to 3).
(2) A polymer in which the glass transition temperature of the polymer is adjusted with an organic additive, such as a product obtained by adding a phthalate ester to polyvinyl chloride (see Patent Documents 4 and 5).
(3) What adjusted the dielectric constant of the polymer with the additive, for example, the thing which mix | blended the active ingredient which increases the amount of dipole moments in a resin matrix (refer patent document 6).

  However, these technologies are mainly composed of a polymer, particularly an elastomer, and added with a damping imparting agent that changes the damping function, and the storage elastic modulus and tan δ which are parameters of the damping function are large. There are inconveniences such as being insufficient or having a narrow glass transition temperature and no practical temperature range. Furthermore, there is also a problem that the damping material is bleed out from the polymer matrix and the stability over time is not good.

  On the other hand, a vibration damping material using piezoelectric material has been proposed in search of a material that exceeds the vibration damping method based on the mass law or viscoelasticity. For example, a composition characterized by using at least one substance selected from the group of conductive substances and semiconductive substances and piezoelectric ceramics and meeting impedance matching conditions has been tried (Patent Document). 7). In addition, an attempt to improve the vibration damping effect by setting the diameters of the piezoelectric fine particles and the conductive or semiconductive fine particles within a predetermined range (see Patent Document 8), the piezoelectric particles and the elastic graphite particles in the matrix resin There is an attempt to improve the vibration damping effect by mixing (see Patent Document 9).

  However, these attempts using piezoelectrics are also difficult to design with the size of the damping material that is actually used, and have the disadvantage that the effect of the piezoelectric filler is reduced by the addition of a polymer, and that they are heavy. For example, the electro-mechanical conversion efficiency of a flexible piezoelectric material in which a filler such as barium titanate is combined with a polymer material such as a thermoplastic resin or a synthetic rubber is a fraction of that of the piezoelectric ceramic before composite. (See Non-Patent Document 1), vibration control that does not depend on the mass law or viscoelasticity is impossible.

  In order to eliminate these drawbacks, a piezoelectric dispersion type organic composite vibration damping material has been developed (see Patent Document 10). However, there is a problem in the reproducibility of the performance because the filler of the organic composite material is randomly blended.

  Also, as an attempt based on a different approach from the above, there is a hydrogen bond group or a cyclic structure that bonds to each other by the electron force of π electrons, and forms a continuum by the bond (weaker than a covalent bond). Efforts have been made to improve the materials using such materials (see Patent Document 11). However, their electrical coupling force contributes to structural stabilization and structure formation, but does not contribute much to vibration suppression, and also obtains vibration control performance that exceeds the mass law and energy loss due to viscoelasticity. It was difficult.

  A porous material is used to reduce the weight of the vibration damping material. However, a fiber aggregate such as a simple foam or glass wool has a drawback that it has good sound absorption but poor sound insulation.

  Although vibration control using an anti-phase using an actuator is highly effective and is often used (see Patent Documents 12 to 14), a device such as a speaker or a vibration generation circuit is required, which must be large.

  In addition, low frequency sound generated from industrial machines, stores, facilities, etc., heavy traffic roads, bridges, railways, etc. has been a problem for some time. It has been pointed out that low-frequency sound induces insomnia, anxiety, headaches, etc. psychologically and physiologically, as well as physical problems such as vibrations of home furniture. In Japan, a range of about 100 Hz or less is considered as a low-frequency sound, and research for prevention and sound insulation is underway. However, since the sound insulation effect due to the law of mass decreases as the frequency of vibration decreases, sound insulation using a sound insulation material is difficult, and in order to isolate low-frequency sound once generated, the sound insulation is heavier and thicker than high-frequency sound waves. It is necessary to use materials. For this reason, there has been no thin and light material having substantial sound insulation against sound waves of 100 Hz or less.

Under such circumstances, the social demand for noise reducing materials has increased as the use of various noise generating devices in and outside the home has increased, and the level of demand for performance has increased. Therefore, development of a material having vibration damping performance that has not been conventionally available is desired. In particular, there is a need for a vibration damping material that is versatile for different types of vibration damping, such as sound absorption, sound insulation and damping, and that does not rely on mass laws and is therefore not heavy. In addition, a light and thin practical sound insulation material capable of effectively insulating the low-frequency side sound that has attracted particular attention in recent years is demanded.
JP-A-6-295182 Japanese Patent Laid-Open No. 10-266390 JP-A-9-242461 JP-A-6-155666 JP-A-6-279645 JP-A-9-302139 JP-A-5-240298 JP-A-6-126909 JP-A-6-85346 Japanese Patent Laid-Open No. 11-68190 JP 2002-146203 A JP 7-26784 A JP-A-6-158747 Japanese Patent Application Laid-Open No. 8-61003 "Ceramic composite", edited by Japan Ceramic Society, Bafukan, pp. 20-24

  The present invention is a vibration damping material that is not based on the law of mass and can be used to attenuate various vibrations such as sound absorption, sound insulation, vibration suppression, vibration insulation, etc. An object of the present invention is to provide a vibration damping material that can be effectively damped.

  The present inventor made various materials for the above purpose and repeatedly studied. As a result, the porous material, which is a foam containing dispersed hard fine particles, has an excellent vibration damping action. Found that there is something. The present invention has been completed based on this finding and further studies. That is, the present invention provides the following.

(1) A vibration damping material comprising a foamed porous material,
The foaming ratio of the porous material, defined as [volume after foaming / volume before foaming], is 1.2 or more and less than 5,
A continuous phase having a porous structure in which the porous material is relatively soft;
A relatively hard dispersoid dispersed in the continuous phase,
A number of pores forming the porous structure of the continuous phase are not substantially in communication between the front and back of the porous material;
Vibration damping material.
(2) The vibration damping material according to 1 above, wherein the average size of the pores forming the porous structure is 0.1 to 50 μm.
(3) The dispersoid is fine particles or fibers made of a resin having a glass transition region in a temperature range higher than the intended use temperature of the vibration damping material, or inorganic fine particles or fibers, and the continuous phase is The vibration damping material according to 1 or 2 above, which is a resin and has a glass transition region in the intended use temperature range or lower temperature range of the vibration damping material.
(4) The vibration damping material according to any one of 1 to 3 above, wherein the porous material contains 5 to 70% by mass of the dispersoid.
(5) The vibration damping material according to any one of 1 to 4 above, wherein the average aspect ratio of the dispersoid is 2 or more.
(6) The vibration damping material according to any one of 1 to 5 above, wherein the dispersoid is selected from the group consisting of mica, graphite, montmorillonite, ferrite, potassium titanate, layered iron oxide, layered silica, and layered titanium. .
(7) The dispersoid is selected from the group consisting of polyacrylonitrile, polystyrene, polycyclohexyl methacrylate, poly-tert-butyl methacrylate, polydicyclopentenyl acrylate, polydicyclopentanyl methacrylate, polymethyl methacrylate, 1 above Or any one of 6 vibration damping materials.
(8) The continuous phase is a copolymer of (meth) acrylic acid and (meth) acrylic ester, chlorinated polyolefin, polyurethane, synthetic rubber, natural rubber, polysulfide polymer, vinyl acetate polymer, and polyvinyl alcohol polymer. The vibration damping material according to any one of 1 to 7 above, which is selected from the group consisting of:
(9) The vibration damping material according to any one of 1 to 8 above, wherein the shape is a sheet shape.
(10) Vibration damping, characterized in that a relatively hard dispersoid is mixed and dispersed in an emulsion of a relatively soft resin and foamed at a foaming ratio of 1.2 to 5 and cured. A method of manufacturing the material.
(11) The dispersoid is fine particles or fibers made of a resin having a glass transition region in a temperature range higher than the intended use temperature of the vibration damping material, or inorganic fine particles or fibers, and the continuous phase is 10. The manufacturing method according to 10 above, which is a resin and has a glass transition region in the intended use temperature region or lower temperature region of the vibration damping material.
(12) The method according to 10 or 11 above, wherein the porous material contains 5 to 70% by mass of the dispersoid.
(13) The method according to any one of (10) to (12) above, wherein an average aspect ratio of the relatively hard dispersoid is 2 or more.
(14) The production method according to any one of 10 to 13, wherein the dispersoid is selected from the group consisting of mica, graphite, montmorillonite, ferrite, potassium titanate, layered iron oxide, layered silica, and layered titanium. .
(15) The dispersoid is selected from the group consisting of polyacrylonitrile, polystyrene, polycyclohexyl methacrylate, poly-tert-butyl methacrylate, polydicyclopentenyl acrylate, polydicyclopentanyl methacrylate, and polymethyl methacrylate. Thru | or any 14 manufacturing method.
(16) The continuous phase is a copolymer of (meth) acrylic acid and (meth) acrylic ester, chlorinated polyolefin, polyurethane, synthetic rubber, natural rubber, polysulfide polymer, vinyl acetate polymer, and polyvinyl alcohol polymer. 16. The production method according to any one of the above 10 to 15, which is selected from the group consisting of:
(17) The method according to any one of (10) to (16) above, wherein the average particle size of the emulsion particles is 0.8 μm or more.

  According to the present invention configured as described above, a high sound insulation effect can be obtained without depending on the mass law. In particular, according to the present invention, it is possible to obtain a remarkable sound insulation effect even though it is an extremely light and thin material against low frequency sound that has been difficult to sound insulation except by using a heavy and thick material.

  In the present invention, the “porous material” is preferably formed by foaming a resin emulsion containing a dispersoid in a dispersed state. As a resin for this purpose, the glass transition region has a vibration damping material. Those in the intended use temperature range or lower temperature range are preferred. For this purpose, it may be selected from various resins known so far in consideration of the intended use temperature of the vibration damping material in accordance with the object to be sound-insulated and the environment in which it is placed. Candidate resins that can be used include, for example, copolymers of (meth) acrylic acid and (meth) acrylic acid esters, chlorinated polyolefins, polyurethanes, synthetic rubbers, natural rubbers, polysulfide polymers, and vinyl acetate-based poly. It is not limited to. The resin emulsion used preferably has an average particle size of the emulsion particles of 0.8 μm or more.

  The foaming of the resin may be performed using a foaming agent that generates gas by heating and foams, or may be performed by mechanical foaming. In any case, the expansion ratio is preferably adjusted so as to fall within the range of 1.2 to 5, and more preferably adjusted within the range of 2-3. Here, the “foaming ratio” is a value defined as [volume after foaming / volume before foaming].

  For the production of the porous material, for example, a foaming agent is added to the resin emulsion and the dispersoid contained in the resin emulsion, and this is mechanically foamed. It can be carried out by keeping it in a proper shape and drying by heating (for example, at 150 ° C. for 10 minutes). What is necessary is just to use suitably what is conventionally used for mechanical foaming as a foaming agent. For example, soap-based foaming agents, ammonium stearate, sodium dialkylsulfosuccinate and the like can be mentioned. Moreover, in order to erase the foam on the surface of the resin emulsion after mechanical foaming, a conventional antifoaming agent can be used if desired. As the antifoaming agent, various silicon resin-based products are commercially available (for example, BYK-8020, BYK-8070, both manufactured by Big Chemie Japan), and these may be used as appropriate.

  When foaming a raw material containing dispersoids harder than the continuous phase, the degree of communication between the many pores forming the porous structure of the continuous phase is kept low by keeping the expansion ratio within this range. Thus, a state is created in which a large number of pores of the porous material formed into a sheet shape are not substantially communicated between the front and back surfaces of the material. Here, “substantially not communicating between the front and back” does not mean that there is no communication at all, but the porous material formed into a sheet shape is held horizontally and about 50 mL from above. When water is applied, water does not pass through the sheet immediately (within at least 10 seconds). Since the propagation of sound waves occurs instantaneously, if the sheet does not allow water to pass through immediately, many pores of the porous material are substantially between the front and back of the material as far as the time scale of sound wave propagation is concerned. It is because it can be said that it is not communicating. On the other hand, in the “substantially communicating” sheet, the water immediately reaches the back surface (within at least 10 seconds) and then flows down when operated in the same manner.

  In the present invention, the “aspect ratio” of the dispersoid refers to the longitudinal dimension / shortest dimension of the fine particles or fibers of the dispersoid. The shortest dimension corresponds to, for example, the width (diameter) of a fiber and the thickness of a plate-like fine particle. In the present invention, it is advantageous that the aspect ratio of the dispersoid is large. The aspect ratio is preferably at least 2 or more, more preferably 10 or more, and still more preferably 20 or more. There is no particular upper limit, and it may be 700, 800, 1000, or larger.

  As long as the dispersoid is a material harder than the continuous phase, both organic and inorganic materials can be used. In the case of a dispersoid of an inorganic material, the resin emulsion constituting the continuous phase may be mixed and dispersed before foaming. In the case of dispersoids of organic materials, if the dispersoids are in the form of fine particles or fibers before mixing, they are mixed prior to foaming the resin constituting the continuous phase, similar to the dispersoids of inorganic materials. Can be dispersed. When the dispersoid of the organic material is a monomer that is a constituent material of a resin harder than the continuous phase, a resin that constitutes the continuous phase is manufactured as the first stage (for example, by emulsion polymerization), and the second stage is A mixture of a resin constituting the continuous phase and hard resin fine particles is produced by two-stage polymerization in which the monomer is added and polymerized (for example, while emulsifying), and this is foamed and molded. A porous material may be used. Further, a porous material obtained by adding and mixing a dispersoid of an inorganic material to a mixture of a resin constituting a continuous phase produced by two-stage polymerization and hard resin fine particles, and then foaming and molding the mixture. It is good.

  Among the dispersoids preferably used in the present invention, specific examples of inorganic fine particles include mica, graphite, montmorillonite, ferrite, potassium titanate, layered iron oxide, layered silica, layered titanium and the like. Examples of the inorganic fiber include aluminum borate, carbon fiber, and glass fiber. Mica having various aspect ratios is known, and for example, from about 25 or less to about 1000 can be obtained, and can be suitably used in the present invention.

  When using a hard resin as a dispersoid added to and mixed with a resin that forms a continuous phase as compared to the dispersoid, the hard resin has a glass transition region so that the hardness can be maintained at a normal use temperature. The vibration damping material is preferably in a higher temperature range than the intended use temperature range, and more preferably 100 ° C. or higher. Examples of such resins include polyacrylonitrile (105 ° C.), polystyrene (100 ° C.), polycyclohexyl methacrylate (66 ° C.), poly-tert-butyl methacrylate (107 ° C.), polydicyclopentenyl acrylate (120 ° C.), Examples thereof include polydicyclopentanyl methacrylate (170 ° C.), polymethyl methacrylate (105 ° C.) and the like (in the parentheses are typical glass transition regions of each).

  When a hard resin that becomes an organic dispersoid is produced by polymerization in the same system by two-stage polymerization following polymerization (for example, emulsion polymerization) to obtain a resin for forming a continuous phase of a porous material, organic As the monomer that forms the dispersoid, a monomer that gives a polymer resin having a glass transition region in a higher temperature range is used depending on the intended use temperature range of the vibration damping material. For example, those that polymerize to give a polymer resin having a glass transition temperature of 50 ° C. or higher are preferred, and those that give a polymer resin of 100 ° C. or higher are more preferred. Examples of preferred monomers include acrylonitrile, styrene, cyclohexyl methacrylate, tert-butyl methacrylate, dicyclopentenyl acrylate, dicyclopentanyl methacrylate, methyl methacrylate and the like.

  In the present invention, a resin emulsion produced by emulsion polymerization is preferably used as the resin constituting the continuous phase. Examples of such resin emulsions include, but are not limited to, (meth) acrylic acid and (meth) acrylic ester copolymer emulsions, chlorinated polyolefin emulsions, and the like. These resins may be used as desired. In the emulsion polymerization, for example, an emulsifier having a lipophilic part and a hydrophilic part that give a surface activity in the molecule, such as a carbon-carbon double bond related to a covalent bond with the resin side (generally, a “reactive emulsifier”) Can be suitably used. Examples of reactive emulsifiers include reactive anionic surfactants (Latemul S-180, manufactured by Kao), sodium alkylallylsulfosuccinate (Eleminol JS-2, manufactured by Sanyo Chemical Industries), methacrylic acid AOA sulfate sodium salt ( ELEMINOL RS-30 (manufactured by Sanyo Chemical Industries) is a typical example.

  In the present invention, the continuous phase constituting the porous material is a viscoelastic substance, a hollow filler, a piezoelectric material such as barium titanate, barium lead titanate, and ferrite, a dielectric material, a magnetic material, etc. May further be contained.

  The vibration damping material of the present invention has an excellent vibration damping (sound insulation) property particularly on the low frequency side, and can be used as a thin and light excellent sound insulation material in the form of a sheet or film. In the form of a sheet or film, the thickness may be appropriate depending on the size of the sound insulation effect to be achieved, but may be, for example, 3 mm, 2 mm, 1 mm, or less. In particular, it has been confirmed that for low-frequency sound, for example, sound with a frequency of 100 Hz or lower, an increase in the effect due to the decrease in thickness occurs in the thickness range up to 650 μm (see Examples). Making a sheet (film) thinner than 1 mm has a practical advantage. Moreover, in the case of the form of a sheet (film), the vibration damping material of the present invention may be used by stacking a plurality of sheets in layers, thereby obtaining a sound insulation effect obtained by adding the sound insulation effect by each sheet (film). . Since each sheet (film) can be made extremely thin and light, even if a plurality of sheets are stacked, it is possible to obtain a sound insulating material that is thinner and lighter than the conventional one and has excellent performance as a whole.

  The mechanism of sound insulation by the vibration damping material of the present invention has not yet been elucidated. Although not intending to be bound by theory, when the vibration damping material of the present invention receives a sound wave, a relatively hard dispersoid having an aspect ratio of 2 or more protruding into a large number of pores of the porous material, A sound wave containing a component opposite in phase to the original sound wave is vibrated in a different manner from the relatively soft continuous phase that supports it. It is considered that this may occur secondarily, and this may partially cancel the original sonic vibration.

Hereinafter, the present invention will be described more specifically with reference to examples. However, it is not intended that the present invention be limited to these examples. In the following, “part” indicating the amount represents part by mass.
[Example 1]
Two-stage polymerization emulsion (LC-6525SP, manufactured by High Pressure Gas Industry Co., Ltd.) by adding and polymerizing 10% by mass of methyl methacrylate in a copolymer emulsion of (meth) acrylic acid and (meth) acrylic acid ester ) 4 parts of 35% sodium dialkylsulfosuccinate aqueous solution (Perex TA, manufactured by Kao) as a foaming agent is added to 100 parts of (emulsion average particle size 0.8 μm), and mechanically foamed so that the expansion ratio becomes 3, And dried at 150 ° C. for 10 minutes to obtain a porous material having a thickness of 1 mm. The average diameter of the holes was about 5 μm. The sheet was held horizontally and 50 mL of water was poured from above and observed for 10 seconds, but the water did not reach the back of the sheet.

[Example 2]
100 parts of the same emulsion used in Example 1, 4 parts of 33% aqueous ammonium stearate (DC-100A, manufactured by San Nopco) as a blowing agent, and mica (PDM-5B, aspect ratio 25, Topy Industries, Ltd.) 50 parts were added, mechanically foamed so that the expansion ratio was 3, and formed into a sheet and dried at 150 ° C. for 10 minutes to obtain a porous material having a thickness of 1 mm. The pore diameter was distributed in the range of about 15 to 45 μm. The sheet was held horizontally and 50 mL of water was poured from above and observed for 10 seconds, but the water did not reach the back of the sheet.

Example 3
To 100 parts of the same emulsion as used in Example 1, 2 parts of 35% aqueous sodium dialkylsulfosuccinate solution, 2 parts of 33% aqueous ammonium stearate solution and 50 parts of mica (aspect ratio 1000) were added as foaming agents. Mechanical foaming was performed so that the magnification was 3, and a sheet was formed and dried at 150 ° C. for 10 minutes to obtain a porous material having a thickness of 1 mm. The diameter of the holes was distributed in the range of 20 to 60 μm. The sheet was held horizontally, 50 mL of water was poured from above, and observed for 10 seconds, but the water did not reach the back surface of the sheet.

Example 4
To 100 parts of the same emulsion used in Example 1, 4 parts of 35% sodium dialkylsulfosuccinate aqueous solution, 30 parts of mica (aspect ratio 25) and 20 parts of barium titanate (aspect ratio 25) are added as a blowing agent. Then, it was mechanically foamed so that the expansion ratio was 3, and was made into a sheet and dried at 150 ° C. for 10 minutes to obtain a porous material having a thickness of 1 mm. The diameter of the holes was distributed in the range of 15 to 30 μm. While this sheet was held horizontally, 50 mL of water was poured from above and observed for 10 seconds, but the water did not reach the back of the sheet.

Example 5
To 100 parts of the same emulsion used in Example 1, 35% 2-alkyl-N-carboxymethyl-N-hydroxymethylimidazolinium betaine aqueous solution and 50 parts of mica (aspect ratio 25) were added as a blowing agent. Then, it was mechanically foamed so that the expansion ratio was 3, and was made into a sheet and dried at 150 ° C. for 10 minutes to obtain a porous material having a thickness of 1 mm. The diameter of the holes was distributed in the range of 5 to 15 μm. While this sheet was held horizontally, 50 mL of water was poured from above and observed for 10 seconds, but the water did not reach the back of the sheet.

Example 6
100 parts of chlorinated polyolefin emulsion (Supermicron E-723, manufactured by Nippon Paper Chemicals Co., Ltd.), 4 parts of 35% sodium dialkylsulfosuccinate aqueous solution, 30 parts of mica (aspect ratio 25), and potassium titanate (Aspect) Ratio 25) 20 parts were added, mechanically foamed so that the expansion ratio would be 3, and formed into a sheet and dried at 150 ° C. for 10 minutes to obtain a porous material having a thickness of 1 mm. The diameter of the holes was distributed in the range of 15 to 30 μm. While this sheet was held horizontally, 50 mL of water was poured from above and observed for 10 seconds, but the water did not reach the back of the sheet.

Example 7
4 parts of thermoplastic microspheres (outer diameter 30 μm) are added to 100 parts of the same emulsion used in Example 1, and foamed at a foaming ratio of about 2 to leave bubbles between the microspheres to form a sheet. It was dried at 150 ° C. for 10 minutes to obtain a 2 mm thick porous material. The hole diameter was about 0.1 μm. While this sheet was held horizontally, 50 mL of water was poured from above and observed for 10 seconds, but the water did not reach the back of the sheet.

Example 8
Two-stage polymerization emulsion (LC-6525SPL, manufactured by High Pressure Gas Industry Co., Ltd.) by adding and polymerizing 10% by mass of methyl methacrylate in a copolymer emulsion of (meth) acrylic acid and (meth) acrylic acid ester ) (Emulsion average particle size 1.1 μm) 4 parts of 35% sodium dialkylsulfosuccinate aqueous solution (Perex TA, manufactured by Kao) as a foaming agent is added to 100 parts, and mechanically foamed so that the expansion ratio becomes 3, And dried at 150 ° C. for 10 minutes to obtain a porous material having a thickness of 1 mm. The average diameter of the holes was about 5 μm. The sheet was held horizontally and 50 mL of water was poured from above and observed for 10 seconds, but the water did not reach the back of the sheet.

[Comparative Example 1]
To 100 parts of a copolymer emulsion of (meth) acrylic acid and (meth) acrylic acid ester (LC-6525, manufactured by High Pressure Gas Industry Co., Ltd.), 4 parts of 35% aqueous sodium dialkylsulfosuccinate solution is added as a foaming agent. 5 was mechanically foamed to form a sheet and dried at 120 ° C. for 12 hours to obtain a porous material having a thickness of 1 mm. The average diameter of the holes was about 10 μm. When this sheet was held horizontally and 50 mL of water was poured from above, the water immediately passed through the sheet.

[Comparative Example 2]
To 100 parts of the same emulsion used in Comparative Example 1, 4 parts of 35% sodium dialkylsulfosuccinate aqueous solution and 50 parts of calcium carbonate are added as a foaming agent, and mechanically foamed so that the foaming ratio is 5 to form a sheet. And dried at 150 ° C. for 10 minutes to obtain a porous material having a thickness of 1 mm. The average diameter of the holes was about 55 μm. When this sheet was held horizontally and 50 mL of water was poured from above, the water immediately passed through the sheet.

[Comparative Example 3]
To 100 parts of the same emulsion used in Comparative Example 1, 4 parts of thermoplastic microspheres (outer diameter 30 μm) are added, formed into a sheet without bubbles and dried at 150 ° C. for 10 minutes, and 1 mm thick A porous material was obtained. While this sheet was held horizontally, 50 mL of water was poured from the top and observed for 10 seconds, but water did not pass through the sheet.

[Comparative Example 4]
Polyethylene foam (calp material, manufactured by Taisei Co., Ltd.) in which individual bubbles are independent from each other and do not communicate (expansion ratio is about 9).

[Performance evaluation]
1. Evaluation of dynamic viscoelasticity Dynamic viscoelasticity was measured at 0.1 Hz using a dynamic viscoelastic spectrometer DMS100 (Seiko Instruments). As a measurement sample, a 1 mm thick sheet of each vibration damping material of the example and the comparative example was cut into a length of 30 mm and a width of 10 mm.

2. Sound insulation evaluation <Sound insulation effect measuring device, etc.>
As shown in FIGS. 1 and 2, a slate plate having a size of 60 cm × 60 cm and a thickness of 1 cm is set up on a table 2 as a partition 1, and a 10 cm × 10 cm square window 4 (shown by a broken line in FIG. 1) is placed on the center line. The base was provided so that it was 10 cm above the surface of the table. The microphones 5 and 6 were suspended from the front and rear surfaces along the center line of the screen 1 by strings 7 and 8 so as to be at the same height as the center of the window. A speaker 9 (Multimedia Speaker, frequency characteristics: 30 Hz to 20 kHz, manufactured by Sanwa Supply Co., Ltd.) was installed behind the microphone 2. AUDIO TEST CD-1 of Japan Audio Association was used as a sound source. As the sound level meter, two digital sound level meters (SM-325) manufactured by AS ONE Corporation were used. The measurable frequency range of the sound level meter is 31.5 Hz to 8 kHz, and the resolution is 0.1 dB. Med (50-100 dB) was used as the measurement range.

(Vibration damping material)
Each of the vibration damping materials 15 to be tested is a slightly vertically long rectangle that is large enough to cover the window 4, and the window 1 is attached to the front surface of the partition 1 just above the window 4 and hung. Was entirely covered on the front surface of the screen 1.
The vibration damping material 15 of Examples 1 to 8 and Comparative Examples 1 to 4 was tested for sound waves having various frequencies. Further, the porous material of Example 2 was formed into sheets having a thickness of 650 μm, 850 μm, 1000 μm, and 2000 μm, and the sound insulation at 100 Hz was evaluated. Moreover, about the porous material of Example 2, the normal incidence sound absorption coefficient in various wavelengths was measured over 100 Hz-5000 Hz about what was shape | molded into the sheet | seat of 1200 micrometers thickness.

3. Evaluation Results Table 1 shows the measurement results tan δ of dynamic viscoelasticity as an index of vibration damping properties of the samples of Examples and Comparative Examples.

  As is apparent from Table 1, the sheets of Examples 1 to 6 have a larger tan δ value than the sheets of Comparative Examples 1 to 3, and thus have excellent vibration damping action, and are particularly remarkable in Examples 2 to 6. is there. As is clear from Example 8, when the emulsion particle size was large, a large tan δ value was obtained.

  Table 2 shows the measurement results of the sound insulation of each sheet and the 3 mm-thick slate plate of Examples and Comparative Examples at 250 Hz.

  As shown in Table 2, at 250 Hz, each sheet of the example shows significantly higher sound insulation than the sound insulation of each sheet of Comparative Examples 1, 2, and 4. Moreover, each sheet of the example shows much greater sound insulation than the sheet of Comparative Example 4 and the 3 mm-thick slate plate having a much higher surface density. This is a result that cannot be predicted at all from the prediction based on the law of mass, and the sheet of the example expresses the sound insulating property due to factors other than the mass of the sound insulating material.

  Table 3 shows the sound insulation measurement results at 100 Hz of the samples of the examples and comparative examples.

  As shown in Table 3, each sheet of the example shows significantly higher sound insulation than the sheets of Comparative Examples 1, 2, and 4 as in the case of 100 Hz and 250 Hz. Even when compared with a 3 mm thick slate plate having a high thickness, the sound insulation is remarkably large. This represents a distinguishing feature of the example sheet, as well as the result at 250 Hz.

  Table 4 shows the results obtained when the sheet of 650 μm, 850 μm, 1000 μm, and 2000 μm in thickness was prepared in the porous material of Example 2 and the sound insulation property was measured at 100 Hz.

As can be seen from Table 5, in the sheet thickness range from 650 to 2000 measured in this example, the sound insulation of the sheet increases conversely as the surface density decreases, which is 650 μm thickness (surface density 220 g / m ² ). The thinness shows a high value of 7 dB. This result cannot be explained by any known mechanism for the magnitude of the sound insulation of the material.

  In FIG. 3, the measurement result of the normal incident sound absorptivity about the sheet | seat of 1200 micrometers thickness consisting of the porous material of Example 2 is shown with a graph. As for the sound absorption coefficient, an effect is recognized at 500 to 5000 Hz.

  The present invention is applied directly to machinery and equipment as a light and thin vibration damping material, and as a sound absorbing material and a sound insulating material, particularly as a sound insulating material that is particularly effective against sound waves having a relatively low frequency, such as factories and commercial facilities. Can be used for houses, fences around roads and railways, vehicles, aircraft, etc.

Front schematic diagram showing the configuration of the sound insulation effect measuring device Side schematic diagram showing the configuration of the sound insulation effect measuring device Graph showing normal incident sound absorption rate measurement results

Explanation of symbols

1 = partition 2 = table 4 = window 5 = microphone 6 = microphone 7 = string 8 = string 9 = speaker 15 = sound insulating material

Claims (17)

A vibration damping material comprising a foamed porous material,
The foaming ratio of the porous material, defined as [volume after foaming / volume before foaming], is 1.2 or more and less than 5,
A continuous phase having a porous structure in which the porous material is relatively soft;
A relatively hard dispersoid dispersed in the continuous phase,
A number of pores forming the porous structure of the continuous phase are not substantially in communication between the front and back of the porous material;
Vibration damping material.   The vibration damping material according to claim 1, wherein the average size of the pores forming the porous structure is 0.1 to 50 μm. The dispersoid is fine particles or fibers made of a resin having a glass transition region in a temperature range higher than the intended use temperature of the vibration damping material, or inorganic fine particles or fibers, and the continuous phase is made of resin. The vibration damping material according to claim 1, wherein the vibration damping material has a glass transition region in a target temperature range of use of the vibration damping material or a lower temperature range.   The vibration damping material according to any one of claims 1 to 3, wherein the porous material contains 5 to 70 mass% of the dispersoid.   The vibration damping material according to any one of claims 1 to 4, wherein an average aspect ratio of the dispersoid is 2 or more.   6. The vibration damping material according to claim 1, wherein the dispersoid is selected from the group consisting of mica, graphite, montmorillonite, ferrite, potassium titanate, layered iron oxide, layered silica, and layered titanium.   The dispersoid is selected from the group consisting of polyacrylonitrile, polystyrene, polycyclohexyl methacrylate, poly-tert-butyl methacrylate, polydicyclopentenyl acrylate, polydicyclopentanyl methacrylate, and polymethyl methacrylate. Any vibration damping material.   The continuous phase is a group consisting of a copolymer of (meth) acrylic acid and (meth) acrylic ester, chlorinated polyolefin, polyurethane, synthetic rubber, natural rubber, polysulfide polymer, vinyl acetate polymer, and polyvinyl alcohol polymer. The vibration damping material according to any one of claims 1 to 7, wherein the vibration damping material is selected.   The vibration damping material according to claim 1, wherein the shape is a sheet shape.   Production of a vibration damping material characterized by mixing and dispersing a relatively hard dispersoid in a relatively soft resin emulsion, and foaming and curing the mixture at a foaming ratio of 1.2 to 5. Method.   The dispersoid is fine particles or fibers made of a resin having a glass transition region in a temperature range higher than the intended use temperature of the vibration damping material, or inorganic fine particles or fibers, and the continuous phase is made of resin. The method according to claim 10, wherein the vibration damping material has a glass transition region in a target use temperature region or a temperature region lower than the intended use temperature region.   The production method according to claim 10 or 11, wherein the porous material contains 5 to 70 mass% of the dispersoid.   The method according to any one of claims 10 to 12, wherein the relatively hard dispersoid has an average aspect ratio of 2 or more.   The method according to any one of claims 10 to 13, wherein the dispersoid is selected from the group consisting of mica, graphite, montmorillonite, ferrite, potassium titanate, layered iron oxide, layered silica, and layered titanium.   The dispersoid is selected from the group consisting of polyacrylonitrile, polystyrene, polycyclohexyl methacrylate, poly-tert-butyl methacrylate, polydicyclopentenyl acrylate, polydicyclopentanyl methacrylate, and polymethyl methacrylate. Any manufacturing method of. The continuous phase is a group consisting of a copolymer of (meth) acrylic acid and (meth) acrylic ester, chlorinated polyolefin, polyurethane, synthetic rubber, natural rubber, polysulfide polymer, vinyl acetate polymer, and polyvinyl alcohol polymer. The production method according to any one of claims 10 to 15, which is selected from the above. The method according to any one of claims 10 to 16, wherein the average particle size of the emulsion particles is 0.8 µm or more.

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