JP6710835B2 - Damping material composition, low-hardness damping material manufacturing method, and low-hardness damping material - Google Patents

Description

The present invention relates to a composition for damping material, a method for manufacturing a low-hardness damping material, and a low-hardness damping material.

Damping materials are used as vibration countermeasures for various devices. The damping material is arranged so as to be in contact with the damping object, and has a function of reducing vibration of the damping object by converting vibration energy into heat energy. Vibrations that are problematic in various devices include vibrations generated from the device itself and vibrations that the device receives from the outside. In any of these cases, a damping material is used to reduce the vibration.

By the way, when a device receives a vibration from the outside, it often receives a large shock at the same time. For example, when a device (for example, a portable device) falls and collides with a floor surface, the device is momentarily subjected to a large force (shock). If a shock is applied to the device, the device may break down. Therefore, as this type of damping material, not only a function of reducing vibration (damping property) but also a material having low hardness is used to absorb or absorb impact (for example, Patent Documents 1 to 3). ).

Patent Document 1 discloses a damping material in which a hydrogenated petroleum resin, a damping filler and the like are added to a thermoplastic elastomer. Further, Patent Document 2 discloses a damping material in which a softening agent or the like is added to a thermoplastic polymer organic material. Further, Patent Document 3 discloses a damping material mainly composed of silicone gel.

JP, 2010-024275, A JP, 2006-225581, A JP2012-102878A

In the vibration damping material described in Patent Document 1, the addition of a vibration damping filler or the like increases the hardness, impairs the flexibility, and may reduce the shock absorbing performance.

In the vibration damping material described in Patent Document 2, the added softening agent may exude from the surface and so-called bleeding may occur.

In the damping material described in Patent Document 3, siloxane gas is generated from the main component silicone gel, and the siloxane gas forms an insulating film, which may cause contact failure in the wiring portion.

An object of the present invention is to provide a low-hardness damping material having low hardness and excellent in damping properties.

The composition for a low-hardness damping material according to the present invention is an acrylic polymer obtained by polymerizing one or more kinds of (meth)acrylate, and an acrylic polymer containing one or more kinds of (meth)acrylate. The acrylic composition having a system composition, a polyfunctional monomer, a crosslinking agent composed of a peroxide, an antioxidant, and a surface-treated filler in which magnesium hydroxide particles are surface-treated with a higher fatty acid. With respect to 100 parts by mass of the product, the polyfunctional monomer is 0.4 to 0.6 parts by mass, the cross-linking agent is 0.8 to 1.2 parts by mass, and the antioxidant is 1.8 to 2.0 parts by mass. Parts and the surface-treated filler are mixed in a proportion of 70 to 90 parts by mass, respectively.

The composition for low-hardness vibration damping material has a surface untreated filler composed of particles of aluminum hydroxide, and the surface untreated filler is 60 to 95 parts by mass with respect to 100 parts by mass of the acrylic composition. It may be mixed in a ratio of parts.

In the composition for low-vibration damping material, the surface-treated filler may have an average particle size of 0.5 μm to 5 μm.

In the composition for a low-vibration damping material, the untreated surface filler comprises particles of low-soda aluminum hydroxide having a soluble sodium content of less than 100 ppm and an average particle diameter of 7 μm to 15 μm. Good.

The method for producing a low-hardness vibration damping material according to the present invention is a method for producing a low-hardness vibration damping material, which comprises manufacturing the low-hardness vibration damping material using the composition for a low-hardness vibration damping material, A coating step of applying the composition for low-damping vibration damping material to the surface of a supporting substrate to form the coating layer comprising the composition for low-hardness vibration damping material, and heating the coating layer to form the coating layer. And a heating step of curing the coating layer to obtain a low-hardness damping material made of a cured product of the coating layer.

The low-hardness vibration damping material according to the present invention comprises a cured product of the composition for a low-hardness vibration damping material, has an Asker C hardness of 10 or less, and a compression set (after heating at 100° C. for 22 hours) of 45%. Hereinafter, the loss coefficient tan σ is 1.0 or more.

According to the present invention, it is possible to provide a low-hardness damping material having a low hardness and excellent vibration damping properties.

Explanatory diagram schematically showing the configuration of the vibration test device

(Composition for low hardness damping material)
The composition for low-damping vibration damping material of the present invention is a composition for producing a low-hardness vibration damping material, and is usually in a liquid state at room temperature (23° C.).

The composition for low-hardness vibration damping material mainly includes an acrylic composition, a polyfunctional monomer, a crosslinking agent, an antioxidant, and a surface-treated filler.

(Acrylic composition)
The acrylic composition is a composition containing at least an acrylic polymer obtained by polymerizing one or more kinds of (meth)acrylate and one or more kinds of (meth)acrylate. In addition, in this specification, (meth)acrylate means a methacrylate and an acrylate.

As the acrylic polymer, (meth)acrylate having a linear or branched alkyl group having 2 to 18 carbon atoms (hereinafter sometimes referred to as "alkyl (meth)acrylate") is used alone. Alternatively, it is formed by polymerizing two or more kinds in combination. Examples of the alkyl (meth)acrylate include ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate and n-. Pentyl (meth)acrylate, i-pentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-hexyl (meth)acrylate, octyl (meth)acrylate, i-octyl (meth)acrylate, nonyl (meth)acrylate, i-nonyl (meth)acrylate, i-decyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, i-myristyl (meth)acrylate, stearyl (meth)acrylate, i-stearyl (meth)acrylate, etc. Is mentioned.

The acrylic composition contains a monomer (meth)acrylate together with an acrylic polymer. The (meth)acrylate as the monomer may be the (meth)acrylate (that is, the alkyl(meth)acrylate) exemplified as the material of the acrylic polymer, alone or in combination of two or more kinds. , (Meth)acrylate other than alkyl(meth)acrylate may be used.

The acrylic composition may contain other copolymerizable monomer in addition to the acrylic polymer and (meth)acrylate as a monomer. Other copolymerizable monomers include copolymerizable vinyl monomers having a vinyl group (eg, acrylamide, acrylonitrile, methyl vinyl ether, ethyl vinyl ether, vinyl acetate, vinyl chloride, etc.), aromatic monomers (eg, benzyl (meth)). Examples thereof include acrylates, phenoxyethyl (meth)acrylates, and aromatic esters. These may be used alone or in combination of two or more.

As the acrylic composition, a commercially available one (for example, ACRYCURE (registered trademark) HD-A series manufactured by Nippon Shokubai Co., Ltd.) may be used.

(Polyfunctional monomer)
The polyfunctional monomer comprises a monomer having two or more (meth)acryloyl groups in the molecule. Examples of the bifunctional (meth)acrylate monomer having two (meth)acryloyl groups in the molecule include 1,3-butylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1, 6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, 2-ethyl-2-butyl-propane Diol (meth)acrylate, neopentyl glycol modified trimethylolpropane di(meth)acrylate, stearic acid modified pentaerythritol diacrylate, polypropylene glycol di(meth)acrylate, 2,2-bis[4-(meth)acryloxydiethoxy Phenyl]propane, 2,2-bis[4-(meth)acryloxypropoxyphenyl]propane, 2,2-bis[4-(meth)acryloxytetraethoxyphenyl]propane, and the like.

Examples of the trifunctional (meth)acrylate monomer include trimethylolpropane tri(meth)acrylate and tris[(meth)acryloxyethyl]isocyanurate. Examples of the tetra- or higher functional (meth)acrylate monomer include dimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol ethoxytetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and Examples thereof include pentaerythritol hexa(meth)acrylate.

The polyfunctional monomers may be used alone or in combination of two or more. Among these polyfunctional monomers, 1,6-hexanediol di(meth)acrylate and the like are preferable.

In the composition for low-hardness vibration damping material, the polyfunctional monomer is blended in a proportion of 0.4 to 0.6 parts by mass with respect to 100 parts by mass of the acrylic composition.

When the composition for a low-hardness vibration damping material contains the polyfunctional monomer in the above proportion, the hardness of the vibration-damping material produced from the composition for a low-hardness vibration damping material can be suppressed to a low level (10 or less in Asker C). The loss coefficient tan σ representing the vibration damping property is 1.0 or more, and the compression set is 45% or less.

(Crosslinking agent)
The cross-linking agent is made of a peroxide and generates radicals when heated to a predetermined temperature or higher. Examples of the cross-linking agent include di-(4-t-butylcyclohexyl)peroxydicarbonate, lauroyl peroxide, t-amylperoxy-2-ethylhexanoate, benzoyl peroxide, t-butylperoxy-2. -Ethyl hexanoate, organic peroxide such as 4-(1,1-dimethylethyl)cyclohexanol, and the like. Among the crosslinking agents, di-(4-t-butylcyclohexyl)peroxydicarbonate is preferred. These cross-linking agents may be used alone or in combination of two or more.

In the composition for low-vibration damping material, the crosslinking agent is blended in a proportion of 0.8 to 1.2 parts by mass with respect to 100 parts by mass of the acrylic composition.

When the low-hardness vibration damping composition contains the cross-linking agent in the above proportion, the hardness of the vibration damping material produced from the low-hardness vibration damping composition is suppressed to a low level (10 or less in Asker C), The loss coefficient tan σ representing the vibration damping property is 1.0 or more, and the compression set is 45% or less.

(Antioxidant)
As the antioxidant, for example, a phenolic antioxidant having a radical scavenging action can be used. When such an antioxidant is blended, the polymerization reaction of the acrylic resin at the time of sheet production can be suppressed, and as a result, the hardness of the sheet can be suppressed to a low level.

In the composition for low-vibration damping material, the antioxidant is blended in a ratio of 1.8 to 2.0 parts by mass with respect to 100 parts by mass of the acrylic composition.

When the composition for a low-hardness vibration damping material contains the antioxidant in the above-mentioned proportion, the hardness of the vibration-damping material produced from the composition for a low-hardness vibration damping material can be kept low (10 or less in Asker C). The loss coefficient tan σ representing the vibration damping property is 1.0 or more, and the compression set is 45% or less.

(Surface treatment type filler)
The surface-treated filler is composed of particles of magnesium hydroxide (magnesium hydroxide particles) which have been surface-treated (coated) with a higher fatty acid. Examples of the higher fatty acid coated with magnesium hydroxide particles include palmitic acid, stearic acid, oleic acid, linoleic acid and the like. Of these, oleic acid is preferred. The average particle size of the surface-treated filler is preferably 0.5 μm to 1.5 μm. The particle size is indicated by the average particle size D50 obtained by a laser diffraction method or the like.

In the composition for low-hardness vibration damping material, the surface-treated filler is blended in a proportion of 70 to 90 parts by mass, preferably 75 to 85 parts by mass, relative to 100 parts by mass of the acrylic composition. It

When the low-hardness vibration damping composition contains the surface-treated filler (surface-treated magnesium hydroxide) in the above proportion, the vibration-damping material produced from the low-hardness vibration damping composition has a low hardness. It is suppressed (10 or less in Asker C), the loss coefficient tan σ representing the vibration damping property is 1.0 or more, and the compression set is 45% or less.

The composition for low hardness vibration damping material may further contain a surface-untreated filler.

(Untreated surface filler)
The surface-untreated filler is, for example, aluminum hydroxide particles. The aluminum hydroxide is preferably low-soda aluminum hydroxide having a soluble sodium content of less than 100 ppm. As used herein, the amount of soluble sodium is the amount of sodium ions (Na ⁺ ) that dissolves in water when low-soda aluminum hydroxide and water are brought into contact with each other.

Aluminum hydroxide as a surface-untreated filler has a substantially spherical shape, and its particle size is indicated by an average particle size D50 obtained by a laser diffraction method or the like. The average particle size of aluminum hydroxide is preferably 7 μm to 15 μm.

In the composition for low hardness vibration damping material, the surface-untreated filler is blended in a proportion of 60 to 95 parts by mass, preferably 65 to 90 parts by mass, relative to 100 parts by mass of the acrylic composition. It

When the low-hardness vibration damping composition contains the surface-untreated filler (aluminum hydroxide particles) in the above proportion, the low-hardness vibration damping composition has a long pot life and is excellent in storability. Will be things.

The low hardness vibration damping composition may further contain other components as long as the object of the present invention is not impaired. Examples of other components include colorants (pigments, dyes, etc.), ultraviolet absorbers, flame retardants, plasticizers, preservatives, solvents and the like.

(Method of manufacturing low hardness damping material)
The method for producing a low-hardness vibration damping material of the present invention is a method for producing a low-hardness vibration damping material using the composition for a low-hardness vibration damping material described above. The method for producing a low-hardness vibration damping material includes a coating step of applying the composition for a low-hardness vibration damping material to the surface of a supporting substrate to form a coating layer made of the composition for a low-hardness vibration damping material, And heating the coating layer to cure the coating layer to obtain a low-hardness damping material made of a cured product of the coating layer.

(Coating process)
In the coating step, the composition for low-vibration damping material is coated on a predetermined supporting substrate by using a known coating method (for example, a coating method using a coater or the like). The supporting base material is made of, for example, a plastic film such as polyethylene terephthalate, and a coating layer of the composition for low-hardness vibration damping material is formed on the surface of the supporting base material. The surface of the supporting substrate may be subjected to a peeling treatment so that the cured product of the coating layer can be finally peeled off easily.

The thickness of the coating layer of the composition for low-vibration damping material formed on the supporting substrate is not particularly limited and is appropriately set according to the purpose.

Further, the supporting substrate is what is finally peeled off when the low-hardness vibration damping material is used, and in the manufacturing process of the low-hardness vibration damping material, one surface of the coating layer made of the composition for the low-hardness vibration damping material Alternatively, they may be arranged on both sides.

Here, a coating process using a coater will be described. The coater is provided with a pair of rolls which are arranged to face each other in the vertical direction while keeping a predetermined distance, and a hopper whose lower end is opened between the pair of rolls. In addition, the plastic films are wound around the pair of rolls respectively, so that as the rolls rotate, the pair of plastic films are sent out in the same direction (opposite to the hopper) at a predetermined distance. It has become.

The composition for low hardness vibration damping material prepared in advance is extruded between a pair of plastic films to form a sheet-shaped coating layer. As will be described later, the sheet-shaped coating layer sandwiched between the pair of plastic film openings is heated and cured in the heating step.

(Heating process)
In the heating step, the coating layer formed on the supporting substrate is heated to a temperature higher than the curing temperature of the composition for low-damping vibration-damping material, and a curing reaction occurs in the composition for low-hardness vibration-damping material forming the coating layer. Progresses. In the heating process, radicals are generated from the cross-linking agent (peroxide) in the composition for low-damping vibration damping material, and the polymerization reaction proceeds in the composition for low-damping vibration damping material, thereby curing the coating layer. To do.

In the heating step, a known heating device such as a heater is used. For example, a heating device (heater) may be installed on the downstream side of the coater, and the sheet-shaped coating layer sandwiched between the pair of plastic films may be heated and cured by the heating device.

When the coating layer is heat-cured in this way, a low-hardness damping material made of a cured product of the coating layer is obtained.

(Low hardness damping material)
The low-hardness vibration damping material of the present invention has vibration damping properties, and also has flexibility (low hardness) capable of absorbing or mitigating impact during a drop or collision. More specifically, the loss coefficient tan σ regarding damping properties is 1.0 or more, the Asker C hardness is 10 or less, and the compression set (after heating at 100° C. for 22 hours) is 45% or less.

Further, the low-hardness vibration damping material has flame retardancy equivalent to HB in the horizontal burning test of UL94HB. Further, the low-hardness vibration damping material is excellent in workability, durability, adhesion to an adherend and the like.

Low-hardness damping materials are used for various purposes such as handy terminals, LED printers, projectors, digital single-lens cameras, HDDs, LCDs, car navigation systems, etc. for the purpose of shock absorption, vibration absorption, etc. Device, mobile device, etc.). The low-hardness vibration damping material is used, for example, in a form of being interposed between the object to be protected and another object (for example, a housing).

[Preparation of composition for low hardness damping material]
(Example 1)
0.4 parts by mass of a polyfunctional monomer, 1.0 part by mass of a cross-linking agent, 81.8 parts by mass of surface-treated magnesium hydroxide, 1.83 parts by mass of an antioxidant, and hydroxylation based on 100 parts by mass of an acrylic composition. 90 mass of aluminum was added and mixed to obtain a composition for low hardness vibration damping material of Example 1.

"Acrycure (registered trademark) HD-A218" (manufactured by Nippon Shokubai Co., Ltd.) was used as the acrylic composition. As the polyfunctional monomer, 1,6-hexanediol diacrylate was used. As the cross-linking agent, "Percadox 16" (manufactured by Kayaku Akzo Co., Ltd., di-(4-tert-butylcyclohexyl)peroxydicarbonate, 4-(1,1-dimethylethyl)cyclohexanol) was used. As the surface-treated magnesium hydroxide, one obtained by treating the surface of magnesium hydroxide having an average particle diameter of about 1 μm with oleic acid was used. Tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane was used as the antioxidant.

(Example 2)
A low-hardness vibration damping composition of Example 2 was produced in the same manner as in Example 1 except that the addition amount of the polyfunctional monomer was changed to 0.54 parts by mass.

(Example 3)
A low-hardness vibration damping composition of Example 3 was produced in the same manner as in Example 1 except that aluminum hydroxide was not added.

(Comparative Examples 1 to 15)
To 100 parts by mass of the acrylic composition, the polyfunctional monomer, the cross-linking agent, the surface-treated magnesium hydroxide, the antioxidant, and the surface-untreated filler were added in the amounts shown in Table 1 and mixed. Thus, the compositions of Comparative Examples 1 to 15 were produced.

[Production of sheet]
(Examples 1 to 3)
Each composition for low-damping vibration damping materials of Examples 1 to 3 is applied onto the surface of a PET substrate that has been subjected to a release treatment to form a coating layer of each composition for low-vibration damping material, and then Then, each coating layer was heated at 100° C. for 6 minutes to prepare a sheet (an example of a low hardness vibration damping material, a thickness of 2 mm) made of each composition for low vibration damping materials of Examples 1 to 3.

(Comparative Examples 1 to 15)
Each composition of Comparative Examples 1 to 15 was applied on the surface of the PET substrate subjected to the release treatment in the same manner as in the above Example 1 to form a coating layer of each composition, and then each coating. The layers were heated at 100° C. for 6 minutes to try to make sheets of each composition of Comparative Examples 1-15. In Comparative Examples 1 to 10 and Comparative Examples 12 to 15 of Comparative Examples 1 to 15, sheets (thickness 2 mm) were obtained. However, in Comparative Example 11, the composition was not cured to the extent that the shape could be retained, and a sheet could not be obtained.

[Evaluation]
(hardness)
The hardness of each of the sheets of Examples and Comparative Examples was measured using a constant pressure loader for rubber hardness tester (Elastron Co., Ltd.) and an Asker C hardness tester. Specifically, the test needles cut out from the sheets of Examples and Comparative Examples were brought into contact with a pressing needle of a hardness meter, and the value after 30 seconds was read from the state where all the loads were applied. The results are shown in Table 1.

(Compression set)
From each of the sheets of Examples and Comparative Examples, three test pieces (diameter 13 mm, thickness 2 mm) were cut out, and the compression set was measured according to JIS K6262 using the test pieces of three layers. Specifically, a test piece (three stacked, thickness D) is compressed by 25% in the thickness direction using a predetermined compression device (compression jig) (thickness D1), and in that state, an environmental test at 100° C. It was placed in a machine (a constant temperature bath) and left in the environmental test machine for 22 hours. After that, remove the test pieces (3 sheets stacked) from the environment tester, further release the compression device that is compressing the test pieces (3 sheets stacked), and let them stand on the wooden board at room temperature for 30 minutes or more at room temperature. After that, the thickness (D2) of the test piece (three sheets stacked) was measured, and the compression set (%) was calculated from (D-D2)/(D-D1)×100. The results are shown in Table 1.

(Vibration control)
Four test pieces each having a length of 5 mm, a width of 5 mm and a thickness of 2 mm were cut out from each of the sheets of Examples and Comparative Examples. Next, the vibration test apparatus 10 shown in FIG. 1 was prepared. FIG. 1 is an explanatory diagram schematically showing the configuration of the vibration test apparatus 10. As the vibration test device 10, "F-300BM/A" (manufactured by Emic Co., Ltd., fully automatic vibration test device) was used. The vibration test apparatus 10 is an apparatus that vibrates the vibration table 11 by generating a frequency of a predetermined frequency. The vibration direction is the vertical direction in FIG. 1 (the thickness direction of the test piece S). The vibration test apparatus 10 includes a mounting plate 12 and the like in addition to the vibration table 11. The mounting plate 12 has a square shape in a plan view and has a mass set to 400 g. The vibration damping test using the vibration test apparatus 10 was performed in a room temperature environment of 23°C.

As shown in FIG. 1, the four test pieces S are arranged at the four corners of the mounting plate 12, respectively, and are arranged so as to be sandwiched between the mounting plate 12 and the vibration table 11. That is, the mounting plate 12 is in a state of being supported at four points by the test piece S on the vibration table 11.

In such a state, the vibrating table 11 was vibrated under the conditions of an acceleration of 0.4 G, a frequency of 5 Hz to 1000 Hz, and a sweep speed of 1 oct/min. Then, the vibration of the mounting plate 12 was detected by the acceleration pickup 13 mounted on the mounting plate 12, and a resonance curve was created based on the detection result.

Next, based on the resonance frequency f0 (Hz) showing the peak value (resonance magnification) of the resonance curve and the frequencies f1 and f2 (f1<f0<f2) showing the value 3 dB lower than the peak value. The loss coefficient tan δ was calculated from the following mathematical expression (1) (half-width method).
tan δ=(f2-f1)/f0 (1)

The loss coefficient tan δ of each example and each comparative example is shown in Table 1. When the loss coefficient tan δ is 1 or more, it can be said that the vibration damping property is excellent.

(Flame retardance)
A test piece having a length of 125 mm, a width of 13 mm, and a thickness of 2 mm was cut out from each of the sheets of Examples and Comparative Examples, and the flame retardancy was evaluated based on the horizontal burning test of UL94HB. As a result, it was confirmed that each of the sheets of Examples and Comparative Examples (excluding Comparative Example 11) had HB grade flame retardancy. The results are shown in Table 1.

(viscosity)
The viscosities (initial viscosity of materials before sheet molding) of the compositions of Examples and Comparative Examples were measured using a BH type viscometer (manufactured by Tokyo Keiki Co., Ltd.) and a rotor No. 7 was used. As a result of the measurement, the case where the viscosity was 50,000 cps or more was “good”, and the case where the viscosity was less than 50,000 cps was “bad”. The results are shown in Table 1. In Table 1, “good” is shown by “◯”, and “bad” is shown by “x”.

(Pot life)
The composition of each Example and each Comparative Example (before sheet molding) was put into a 200 cc disposable cup up to a height of about 75 mm, and it was allowed to stand under a temperature condition of about 25°C. Then, every hour, a spoon was put in the composition in the cup, and the composition in the cup was scooped up from the bottom side of the cup to confirm whether or not the composition was cured. Before the start of the test, each of the compositions of Examples and Comparative Examples was in a liquid state, and the composition became jelly-like, or the time when the solid matter was caught in a spoonful had a pot life. And As a result of the test, a case where the pot life is 7 hours or more is “good”, a case where the pot life is 6 hours is “normal”, and a case where the pot life is 5 hours or less is “poor”. And The results are shown in Table 1. In Table 1, “good” is shown by “◯”, “normal” is shown by “Δ”, and “bad” is shown by “x”.

The sheets (damping materials) produced from the compositions of Examples 1 to 3 have excellent technical effects (Asker C hardness, compression set, vibration damping (loss coefficient), flame retardancy). It was confirmed. Therefore, in Examples 1 to 3, the comprehensive judgment is “good (when excellent in Asker C hardness, compression set, vibration damping (loss coefficient) and flame retardancy)”, and in Table 1, “ ◯”.

On the other hand, the sheets produced from the compositions of Comparative Examples 1 and 4 to 6 had a compression set of more than 45% and a loss coefficient of less than 1.0.

Further, the sheets produced from the compositions of Comparative Examples 2, 3, 7, and 8 had an Asker C hardness of more than 10, a compression set of more than 45%, and a loss coefficient of less than 1.0.

The sheets made from the compositions of Comparative Examples 9 to 10 and 12 to 15 had a compression set of more than 45%.

In addition, from the composition of Comparative Example 11, a sheet could not be produced due to inhibition of crosslinking. As described above, in Comparative Examples 1 to 15, at least one of Asker C hardness, compression set, vibration damping (loss coefficient), and flame retardancy is “poor”, and the comprehensive determination result is “poor (Table 1 Then, it is written as “×”).

Moreover, among the compositions of Examples 1 to 3, the compositions of Examples 1 and 2 were excellent in both viscosity and pot life. The pot life of the composition of Example 3 was 6 hours, which was inferior to the compositions of Examples 1 and 2.

The compositions of Examples 1 and 2 include aluminum hydroxide as a surface-untreated filler in addition to the surface-treated magnesium hydroxide. In contrast, the composition of Example 3 does not contain aluminum hydroxide. In Examples 1 and 2, by including aluminum hydroxide, the concentration of the surface-treated magnesium hydroxide (surface-treated filler) in the composition was higher than that in the case where aluminum hydroxide was not included (Example 3). , Relatively low.

It is speculated that the pot life of each composition is affected by the surface treated magnesium hydroxide in the composition. Therefore, when the concentration of the surface-treated magnesium hydroxide in the composition is high as described above (Comparative Example 3), the composition is easily cured, and conversely, the concentration of the surface-treated magnesium hydroxide in the composition is high. When it is low (Examples 1 and 2), it can be said that the composition is hard to cure.

The sheet (damping material) made of the composition of Example 3 has the same technical effect as the sheet (damping material) made of the composition of Examples 1 and 2 as described above. (Asker C hardness, compression set, vibration damping property, flame retardancy) was confirmed.

10... Vibration test device, 11... Excitation table, 12... Mounting plate, 13... Acceleration pickup, S... Test piece (low hardness damping material)

Claims (6)

An acrylic polymer obtained by polymerizing a (meth)acrylate having a linear or branched alkyl group having 2 to 18 carbon atoms, alone or in combination of two or more kinds, and a straight chain having 2 to 18 carbon atoms Acrylic composition containing (meth)acrylate having a linear or branched alkyl group, and aromatic esters,
A polyfunctional monomer comprising a bifunctional (meth)acrylate monomer having two or more (meth)acryloyl groups in the molecule,
A crosslinking agent composed of peroxide,
A phenolic antioxidant,
Having a surface-treated filler in which magnesium hydroxide particles are surface-treated with a higher fatty acid,
The polyfunctional monomer is 0.4 to 0.6 parts by mass, the crosslinking agent is 0.8 to 1.2 parts by mass, and the antioxidant is 1.8 to 100 parts by mass of the acrylic composition. 2.0 parts by mass, and a composition for a vibration damping material in which the surface-treated filler is mixed in a proportion of 70 to 90 parts by mass, respectively . Having a surface untreated filler composed of particles of aluminum hydroxide,
The composition for a vibration damping material according to claim 1, wherein the surface-untreated filler is mixed in a proportion of 60 to 95 parts by mass with respect to 100 parts by mass of the acrylic composition. The composition for damping material according to claim 1 or 2, wherein the average particle diameter of the surface-treated filler is 0.5 µm to 5 µm . The composition for a vibration damping material according to claim 2 or 3 , wherein the surface-untreated filler comprises particles of low-soda aluminum hydroxide having an amount of soluble sodium of less than 100 ppm and an average particle diameter of 7 µm to 15 µm . A method for producing a low-hardness vibration-damping material, which comprises manufacturing a low-hardness vibration-damping material having an Asker C hardness of 10 or less using the composition for a vibration-damping material according to any one of claims 1 to 4.
A coating step of the damping material composition was coated on the surface of the support substrate to form a coating layer made of the damping material composition,
A heating step of curing the coating layer by heating the coating layer to obtain a low hardness damping material having an Asker C hardness of 10 or less, which is a cured product of the coating layer. Production method. A cured product of the composition for vibration damping material according to any one of claims 1 to 4,
Asker C hardness is 10 or less,
45% or less of compression set (after heating at 100°C for 22 hours)
A low hardness damping material having a loss coefficient tan σ of 1.0 or more.

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