JP2018012784A - Composition for low hardness damping material, method for producing low hardness damping material and low hardness damping material - Google Patents

Abstract

[Problem] To provide a low-hardness vibration-damping material having low hardness and excellent vibration-damping properties. [Solution] The composition for low-hardness vibration-damping material of the present invention comprises an acrylic polymer obtained by polymerizing one or more (meth)acrylates, an acrylic composition containing one or more (meth)acrylates, a polyfunctional monomer, a crosslinking agent consisting of a peroxide, an antioxidant, and a surface-treated filler consisting of magnesium hydroxide particles surface-treated with a higher fatty acid, and the polyfunctional monomer, the crosslinking agent, the antioxidant, and the surface-treated filler are blended in the following proportions relative to 100 parts by mass of the acrylic composition: 0.4 to 0.6 parts by mass, 0.8 to 1.2 parts by mass, 1.8 to 2.0 parts by mass, and 70 to 90 parts by mass, respectively. [Selected Figure] None

Description

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

  Damping materials are used as countermeasures against vibration in various devices. The damping material is disposed in contact with the damping object, and has a function of reducing the vibration of the damping object by converting the vibration energy into heat energy. As vibrations that are problematic in various devices, there are vibrations generated from the devices themselves and vibrations that the devices receive from the outside. In any of these cases, a damping material is used to reduce the vibrations.

  By the way, when a device receives vibration from the outside, it often receives a large impact at the same time. For example, when a device (for example, a portable device) falls and collides with a floor surface, the device receives a large force (impact) instantaneously. If an impact 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 for absorbing or mitigating an impact is used (for example, Patent Documents 1 to 3). ).

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

JP 2010-024275 A JP 2006-225581 A JP 2012-102878 A

  In the damping material described in Patent Document 1, the hardness is increased by adding a damping filler or the like, the flexibility is impaired, and the shock absorbing performance may be lowered.

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

  In the vibration 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 a contact failure of the wiring portion.

  An object of the present invention is to provide a low-hardness vibration damping material having low hardness and excellent vibration 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 (meth) acrylates, and an acrylic containing one or more (meth) acrylates. An acrylic composition comprising: a system composition; a polyfunctional monomer; a crosslinking agent comprising a peroxide; an antioxidant; and 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 2.0 parts by mass with respect to 100 parts by mass of the product. Part and the said surface treatment type filler are respectively mix | blended in the ratio of 70-90 mass parts.

  The low hardness damping material composition has a surface untreated filler composed of aluminum hydroxide particles, and the surface untreated filler is 60 to 95 masses relative to 100 parts by mass of the acrylic composition. You may mix | blend in the ratio of a part.

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

  In the low hardness damping material composition, the surface untreated filler is composed of particles of low soda aluminum hydroxide having an amount of soluble sodium of less than 100 ppm and an average particle size of 7 μm to 15 μm. Also good.

  Further, the method for producing a low hardness damping material according to the present invention is a method for producing a low hardness damping material for producing a low hardness damping material using the low hardness damping material composition, Applying a low-hardness damping material composition on the surface of a supporting substrate, forming a coating layer comprising the low-hardness damping material composition, heating the coating layer, A heating step of curing the coating layer and obtaining a low-hardness damping material made of a cured product of the coating layer.

  The low hardness damping material according to the present invention comprises a cured product of the composition for low hardness damping material, and 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 tanσ is 1.0 or more.

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

Explanatory drawing schematically showing the configuration of the vibration test equipment

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

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

(Acrylic composition)
The acrylic composition is a composition containing at least an acrylic polymer obtained by polymerizing one or more (meth) acrylates and one or more (meth) acrylates. In the present specification, (meth) acrylate means methacrylate and acrylate.

  As the acrylic polymer, a (meth) acrylate having a linear or branched alkyl group having 2 to 18 carbon atoms (hereinafter sometimes referred to as “alkyl (meth) acrylate”) alone is used. Or it consists of what superposed | polymerized combining 2 or more types. 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, 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. The.

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

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

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

(Polyfunctional monomer)
The polyfunctional monomer is 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) acryloxy propoxyphenyl] propane, 2,2-bis [4- (meth) acryloxy tetraethoxy phenyl] propane.

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

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

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

  If the low-hardness damping material composition contains the polyfunctional monomer in the above ratio, the hardness of the damping material manufactured from the low-hardness damping material composition can be kept low (10 or less in Asker C). In addition, the loss coefficient tanσ representing vibration damping is 1.0 or more and the compression set is 45% or less.

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

  In the composition for a low hardness damping material, the crosslinking agent is blended at a ratio of 0.8 to 1.2 parts by mass with respect to 100 parts by mass of the acrylic composition.

  When the low-hardness damping material composition contains the crosslinking agent in the above proportion, the hardness of the damping material manufactured from the low-hardness damping material composition can be kept low (10 or less in Asker C), The loss coefficient tanσ representing vibration damping 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 during sheet production can be suppressed, and as a result, the hardness of the sheet can be suppressed low.

  In the composition for a low hardness damping material, the antioxidant is blended at 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 low hardness damping material contains the antioxidant in the above proportion, the hardness of the damping material manufactured from the composition for low hardness damping material can be kept low (10 or less in Asker C). In addition, the loss coefficient tanσ representing vibration damping is 1.0 or more and the compression set is 45% or less.

(Surface treatment type filler)
The surface-treated filler is made of particles (magnesium hydroxide particles) made of magnesium hydroxide and surface-treated (coating treatment) with higher fatty acids. Examples of higher fatty acids that are 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 diameter of the surface treatment type filler is preferably 0.5 μm to 1.5 μm. The particle diameter is indicated by an average particle diameter D50 obtained by a laser diffraction method or the like.

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

  When the composition for low hardness damping material contains surface-treated filler (surface-treated magnesium hydroxide) in the above proportion, the hardness of the damping material manufactured from the composition for low hardness damping material is low. The loss coefficient tanσ representing vibration damping is 1.0 or more and the compression set is 45% or less.

  The composition for a low hardness damping material may further include a surface untreated filler.

(Untreated surface filler)
The surface untreated filler is made of, for example, aluminum hydroxide particles. In addition, as aluminum hydroxide, the low soda aluminum hydroxide whose soluble sodium amount is less than 100 ppm is preferable. In this specification, the amount of soluble sodium is the amount of sodium ions (Na ⁺ ) dissolved in water when low soda aluminum hydroxide is brought into contact with water.

  Aluminum hydroxide as the surface untreated filler is substantially spherical, and the particle diameter is indicated by an average particle diameter D50 determined 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 a low hardness damping material, the surface untreated filler is blended in a proportion of 60 to 95 parts by mass, preferably in a proportion of 65 to 90 parts by mass with respect to 100 parts by mass of the acrylic composition. The

  When the composition for low hardness damping material contains untreated surface filler (aluminum hydroxide particles) in the above proportion, the pot life of the composition for low hardness damping material becomes longer and the storage stability is excellent. It will be a thing.

  The low-hardness damping material 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.

(Manufacturing method of low hardness damping material)
The method for producing a low hardness damping material of the present invention is a method for producing a low hardness damping material using the above-described composition for low hardness damping material. The manufacturing method of the low hardness damping material is a coating process in which the composition for low hardness damping material is coated on the surface of the support substrate, and a coating layer comprising the composition for low hardness damping material is formed; A heating step of heating the coating layer to cure the coating layer and obtaining a low hardness damping material made of a cured product of the coating layer.

(Coating process)
In the coating process, the low-hardness damping material composition is applied onto a predetermined support substrate using a known coating method (for example, a coating method using a coater or the like). The support substrate is made of, for example, a plastic film such as polyethylene terephthalate, and a coating layer of the low-hardness damping material composition is formed on the surface of the support substrate. In addition, on the surface of a support base material, the peeling process may be performed so that it may be easy to peel the hardened | cured material of an application layer finally.

  There is no restriction | limiting in particular in the thickness of the coating layer of the composition for low-hardness damping materials formed on a support base material, According to the objective, it sets suitably.

  In addition, the supporting base material is finally peeled off when using the low-hardness damping material. In the production process of the low-hardness damping material, one side of the coating layer made of the composition for low-hardness damping material Or you may arrange | position on both surfaces.

  Here, the coating process using a coater will be described. The coater includes a pair of rolls arranged opposite to each other while maintaining a predetermined interval, and a hopper having a lower end opened between the pair of rolls. Also, a plastic film is wound around each of the pair of rolls, and as the rolls rotate, the pair of plastic films are sent out at a predetermined distance in the same direction (the opposite direction of the hopper). It has become.

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

(Heating process)
In the heating process, the coating layer formed on the support substrate is heated to a temperature higher than the curing temperature of the low-hardness damping material composition, and the curing reaction occurs in the low-hardness damping material composition that forms the coating layer. Progresses. In the heating process, radicals are generated from the crosslinking agent (peroxide) in the low-hardness damping material composition, and the coating reaction is cured by the polymerization reaction proceeding in the low-hardness damping material composition. To do.

  In the heating process, 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 a sheet-like coating layer sandwiched between a pair of plastic films may be heated and cured with a heating device.

  Thus, when a coating layer is heat-hardened, the low hardness damping material which consists of a hardened | cured material of a coating layer will be obtained.

(Low hardness damping material)
The low-hardness vibration damping material of the present invention has vibration damping properties and flexibility (low hardness) that can absorb or relax an impact at the time of dropping or collision. More specifically, the loss coefficient tanσ relating to vibration damping 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 damping material has flame resistance equivalent to HB in the horizontal combustion test of UL94HB. The low hardness damping material is also 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. Devices, portable devices, etc.). The low-hardness damping material is used, for example, in a form that is interposed between the object to be protected and another object (for example, a housing).

[Preparation of composition for low hardness damping material]
Example 1
With respect to 100 parts by mass of the acrylic composition, 0.4 part by mass of the polyfunctional monomer, 1.0 part by mass of the crosslinking agent, 81.8 parts by mass of the surface-treated magnesium hydroxide, 1.83 parts by mass of the antioxidant, hydroxylated 90 masses of aluminum was added, and they were mixed to obtain the composition for low hardness damping material of Example 1.

  As the acrylic composition, “ACRYCURE (registered trademark) HD-A218” (manufactured by Nippon Shokubai Co., Ltd.) was used. 1,6-hexanediol diacrylate was used as the polyfunctional monomer. As the cross-linking agent, “Perkadox 16” (manufactured by Kayaku Akzo Corporation, di- (4-tert-butylcyclohexyl) peroxydicarbonate, 4- (1,1-dimethylethyl) cyclohexanol) was used. As the surface-treated magnesium hydroxide, magnesium hydroxide having an average particle diameter of about 1 μm and treated 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 damping material 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 damping material composition of Example 3 was produced in the same manner as Example 1 except that aluminum hydroxide was not added.

(Comparative Examples 1-15)
With respect to 100 parts by mass of the acrylic composition, the polyfunctional monomer, the crosslinking agent, the surface-treated magnesium hydroxide, the antioxidant, and the surface untreated filler are added in the addition amount shown in Table 1, and they are mixed. And the composition of Comparative Examples 1-15 was produced.

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

(Comparative Examples 1-15)
Each composition of Comparative Examples 1 to 15 was applied onto the surface of the PET substrate that had been subjected to a release treatment in the same manner as in Example 1 above, to form a coating layer of each composition, and then each coating The layer was heated at 100 ° C. for 6 minutes to try to produce a sheet made of each composition of Comparative Examples 1-15. Among Comparative Examples 1 to 15, for Comparative Examples 1 to 10 and Comparative Examples 12 to 15, sheets (thickness 2 mm) were obtained. However, about the comparative example 11, the composition did not harden | cure to the extent which can hold | maintain a shape, and the sheet | seat was not obtained.

[Evaluation]
(hardness)
The hardness of the sheet of each example and each comparative example was measured using a constant pressure loader for rubber hardness tester (manufactured by Elastron Co., Ltd.) and Asker C hardness tester. Specifically, the test piece cut out from the sheet of each example and each comparative example was brought into contact with a push pin of a hardness meter, and the value after 30 seconds was read from a state where all the loads were applied. The results are shown in Table 1.

(Compression set)
Three test pieces (diameter 13 mm, thickness 2 mm) were cut out from the sheets of each example and each comparative example, and the compression set was measured according to JIS K6262 using a three-layer test piece. Specifically, the test piece (3 sheets, thickness D) is compressed 25% in the thickness direction (thickness D1) using a predetermined compression device (compression jig) (in this state, 100 ° C. environmental test). It put in the machine (constant temperature bath) and left to stand in an environmental test machine for 22 hours. After that, take out the test piece (3-layer stack) from the environmental testing machine, release the compression device that compresses the test piece (3-layer stack), and let it stand on the wooden board for 30 minutes or more at room temperature. After that, the thickness (D2) of the test piece (three sheets) 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 the sheets of each Example and each Comparative Example. Next, a 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. In addition, as the vibration test apparatus 10, "F-300BM / A" (Emic Co., Ltd. full automatic vibration test apparatus) was used. The vibration test apparatus 10 is an apparatus that generates a vibration frequency of a predetermined frequency and vibrates the vibration table 11. The excitation 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 in addition to the vibration table 11. The mounting plate 12 has a square shape in plan view and a mass of 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 respectively disposed at the four corners of the mounting plate 12 and are disposed 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 where it is supported at four points by the test piece S on the vibration table 11.

  In such a state, the vibration 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) indicating the peak value (resonance magnification) of the resonance curve and the frequencies f1 and f2 (f1 <f0 <f2) indicating values 3 dB lower than the peak value. The loss coefficient tan δ was calculated from the following formula (1) (half-value width method).
tan δ = (f2−f1) / f0 (1)

  The loss factor tan δ of each example and each comparative example is shown in Table 1. Note that 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 the sheet of each example and each comparative example, and the flame retardancy was evaluated based on the horizontal combustion test of UL94HB using the test piece. As a result, it was confirmed that each of the sheets of Examples and Comparative Examples (excluding Comparative Example 11) had an HB grade flame retardancy. The results are shown in Table 1.

(viscosity)
The viscosity (material initial viscosity before sheet molding) of the composition of each example and each comparative example was measured using a BH viscometer (manufactured by Tokyo Keiki Co., Ltd.) and rotor No. 7 was measured. As a result of the measurement, the case where the viscosity was 50,000 cps or more was determined as “good”, and the case where the viscosity was less than 50,000 cps was determined as “bad”. The results are shown in Table 1. In Table 1, “good” is indicated by “◯” and “bad” is indicated by “x”.

(Pot life)
The composition of each example and each comparative example (before sheet molding) was placed in a 200 cc disposable cup up to a height of about 75 mm and allowed to stand at a temperature of about 25 ° C. Thereafter, every 1 hour, a medicine spoon was put into 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. The composition of each example and each comparative example was in a liquid state before the start of the test, and the time during which such a composition became jelly-like or a solid matter was caught in a spoon was pot life. It was. As a result of the test, the case where the pot life is 7 hours or more is determined as “good”, the case where the pot life is 6 hours is determined as “normal”, and the case where the pot life is 5 hours or less is determined as “bad”. It was. The results are shown in Table 1. In Table 1, “good” is indicated by “◯”, “normal” is indicated by “Δ”, and “bad” is indicated by “x”.

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

  On the other hand, the sheet | seat produced from the composition of the comparative examples 1 and 4-6 exceeded 45% of compression set, and the loss factor was less than 1.0.

  In addition, the sheets prepared 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 factor of less than 1.0.

  Moreover, the sheet | seat produced from the composition of Comparative Examples 9-10, 12-15 exceeded 45% of compression set.

  In addition, crosslinking inhibition occurred from the composition of Comparative Example 11, and a sheet could not be produced. Thus, in Comparative Examples 1 to 15, at least one of Asker C hardness, compression set, vibration damping (loss coefficient), and flame retardancy is “bad”, and the overall determination result is “bad (Table 1). In this case, it is expressed as “×”).

  Of 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.

  In addition to the surface-treated magnesium hydroxide, the compositions of Examples 1 and 2 contain aluminum hydroxide as a surface untreated filler. In contrast, the composition of Example 3 does not contain aluminum hydroxide. In Examples 1 and 2, by containing aluminum hydroxide, the concentration of surface-treated magnesium hydroxide (surface treated filler) in the composition is higher than that in the case where aluminum hydroxide is not included (Example 3). It can be said that it is relatively low.

  The pot life of each composition is presumed to be influenced 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 When it is low (Examples 1 and 2), it can be said that the composition is hardly cured.

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

  DESCRIPTION OF SYMBOLS 10 ... Vibration test apparatus, 11 ... Excitation table, 12 ... Mounting plate, 13 ... Accelerometer, S ... Test piece (low hardness damping material)

Claims (6)

An acrylic polymer obtained by polymerizing one or two or more (meth) acrylates, an acrylic composition containing two or more (meth) acrylates, a polyfunctional monomer, and a peroxide. A cross-linking agent, an antioxidant, and a surface-treated filler obtained by surface-treating magnesium hydroxide particles 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 with respect to 100 parts by mass of the acrylic composition. A composition for a low-hardness vibration damping material, in which 2.0 parts by mass and the surface treatment type filler are respectively blended at a ratio of 70 to 90 parts by mass. It has a surface untreated filler made of aluminum hydroxide particles,
The composition for low hardness damping materials according to claim 1, wherein the surface-untreated filler is blended at a ratio of 60 to 95 parts by mass with respect to 100 parts by mass of the acrylic composition.   The composition for a low hardness damping material according to claim 1 or 2, wherein the surface-treated filler has an average particle size of 0.5 to 5 µm.   The low hardness according to any one of claims 1 to 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. Composition for damping material. A method for producing a low hardness damping material for producing a low hardness damping material using the composition for low hardness damping material according to any one of claims 1 to 4,
A coating step of coating the low-hardness damping material composition on the surface of a support substrate and forming a coating layer comprising the low-hardness damping material composition;
A method for producing a low hardness damping material comprising: a heating step of heating the coating layer to cure the coating layer and obtaining a low hardness damping material made of a cured product of the coating layer. A cured product of the composition for low hardness damping material according to any one of claims 1 to 4,
Asker C hardness is 10 or less,
Compression set (after heating at 100 ° C. for 22 hours) is 45% or less,
A low hardness damping material having a loss coefficient tan σ of 1.0 or more.

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