JP7062289B2 - Acrylic rubber-based composition and vibration damping material - Google Patents

Description

The present invention relates to an acrylic rubber-based composition and a vibration damping material.

Vibration damping materials based on silicone rubber and EPDM are known. Although this type of vibration damping material is excellent in heat resistance and cold resistance, it has a problem of poor oil resistance. Therefore, a vibration damping material based on acrylic rubber having excellent oil resistance has been attracting attention (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2005-187772

However, although the conventional vibration damping material based on acrylic rubber has excellent heat resistance, the cold resistance is not sufficient as compared with the case of silicone rubber or the like, and there is room for improvement.

An object of the present invention is to provide a vibration damping material based on acrylic rubber having excellent heat resistance and cold resistance.

The means for solving the above-mentioned problems are as follows. That is,
<1> Ethylene acrylic having a glass transition temperature of -40 ° C or less and 50 to 80 parts by mass of acrylic rubber including a cross-linking point and a glass transition temperature of -40 ° C or less and containing a cross-linking point of the same type as the cross-linking point. 20 to 50 parts by mass of rubber (however, the total of the acrylic rubber and the ethylene acrylic rubber is 100 parts by mass), 15 to 30 parts by mass of the polyether ester-based plasticizer, and 80 to 140 parts by mass of the metal hydroxide. , Acrylic having 5 to 20 parts by mass of a phosphorus-based flame retardant, 5 to 30 parts by mass of a filler composed of flat particles, 0.1 to 5 parts by mass of a cross-linking agent, and 0.1 to 10 parts by mass of a cross-linking aid. Rubber-based composition.

<2> The acrylic rubber-based composition according to <1>, wherein the acrylic rubber and the ethylene acrylic rubber contain a carboxyl group as the cross-linking point.

<3> The acrylic rubber-based composition according to <1> or <2>, wherein the cross-linking agent is made of an aliphatic amine compound and the cross-linking aid is made of a guanidine compound.

<4> A vibration damping material made of a crosslinked product of the acrylic rubber-based composition according to any one of <1> to <3>.

According to the present invention, it is possible to provide a vibration damping material based on acrylic rubber having excellent heat resistance and cold resistance.

Explanatory drawing schematically showing the configuration of the vibration test device

[Acrylic rubber-based composition]
The acrylic rubber-based composition of the present embodiment mainly contains acrylic rubber, ethylene acrylic rubber, a plasticizer, a metal hydroxide, a phosphorus-based flame retardant, flat particles, a cross-linking agent, and a soluble aid.

As the acrylic rubber, one having a glass transition temperature of −40 ° C. or lower is used. Further, as the acrylic rubber, a rubber having a cross-linking point to be cross-linked by using a cross-linking agent and a cross-linking auxiliary is used. Specifically, acrylic rubber having a crosslinkable group (crosslinking point) (for example, acrylic rubber containing a carboxyl group) is used.

Such acrylic rubber is composed of, for example, a polymer of a monomer composition containing at least one (meth) acrylate and a carboxyl group-containing monomer having a carboxyl group. In addition, in this specification, "(meth) acrylate" means "methacrylate and / or acrylate".

Examples of the (meth) acrylate include alkyl (meth) acrylate and alkoxyalkyl (meth) acrylate.

The alkyl (meth) acrylate may be, for example, an alkyl (meth) having a linear or branched alkyl group having 1 to 18 carbon atoms (preferably 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms). ) Acrylate can be mentioned. Examples of such an alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, and 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 and the like.

Examples of the alkoxyalkyl (meth) acrylate include an alkoxyalkyl (meth) acrylate having an alcohol group having 1 to 4 carbon atoms and an alkyl group having 1 to 4 carbon atoms. Examples of such alkoxyalkyl (meth) acrylates include methoxymethyl (meth) acrylate, methoxyethyl (meth) acrylate, methoxypropyl (meth) acrylate, ethoxymethyl (meth) acrylate, ethoxyethyl (meth) acrylate, and ethoxypropyl (meth) acrylate. Examples thereof include meth) acrylate and butoxyethyl (meth) acrylate.

The carboxyl group-containing monomer is not particularly limited as long as it has a carboxyl group and can be copolymerized with the (meth) acrylate, but for example, (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, and the like. Examples thereof include crotonic acid and monoalkyl esters thereof. Further, acid anhydrides of these carboxyl group-containing monomers (for example, acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride) can also be used as the carboxyl group-containing monomers.

For the polymerization of the acrylic rubber, known methods (for example, emulsion polymerization method, suspension polymerization method, bulk polymerization method, solution polymerization method) can be used, and an initiator and a solvent used for the polymerization can be used. Etc. are also appropriately selected from known substances and used.

Examples of commercially available acrylic rubber products include "NOXTITE (registered trademark) PA-524" (glass dislocation temperature: −44 ° C., manufactured by Unimatec Co., Ltd.) and the like.

The blending amount of acrylic rubber in the acrylic rubber-based composition is set to 50 to 80 parts by mass when the total blending amount of acrylic rubber and ethylene acrylic rubber is 100 parts by mass.

As the ethylene acrylic rubber, one having a glass transition temperature of −40 ° C. or lower is used. Further, as the ethylene acrylic rubber, a rubber having a cross-linking point to be cross-linked by using a cross-linking agent and a cross-linking auxiliary is used. Specifically, ethylene acrylic rubber having a crosslinkable group (crosslinking point) of the same type as acrylic rubber (for example, ethylene acrylic rubber containing a carboxyl group) is used.

Such an ethylene acrylic rubber is composed of, for example, a polymer of a monomer composition containing at least one (meth) acrylate, an ethylene monomer, and a carboxyl group-containing monomer having a carboxyl group.

As the (meth) acrylate, for example, the above-mentioned alkyl (meth) acrylate, alkoxyalkyl (meth) acrylate and the like used for acrylic rubber may be used. Further, as the carboxyl group-containing monomer having a carboxyl group, the above-mentioned one used for acrylic rubber may be used.

Also known methods (eg, emulsion polymerization method, suspension polymerization method, bulk polymerization method, solution polymerization method) can be used for the polymerization of the ethylene acrylic rubber, and the initiator used for the polymerization, The solvent and the like are also appropriately selected from known ones and used.

Examples of the commercially available product of the ethylene acrylic rubber include "Vamac (registered trademark) VMX-4017" glass dislocation temperature: −41 ° C., manufactured by DuPont Co., Ltd.).

The blending amount of ethylene acrylic rubber in the acrylic rubber-based composition is set to 20 to 50 parts by mass when the total blending amount of the acrylic rubber and the ethylene acrylic rubber is 100 parts by mass. The blending amount of ethylene acrylic rubber is set to be equal to or lower than the blending amount of acrylic rubber so as not to exceed the blending amount of acrylic rubber.

As the plasticizer, a polyether ester-based plasticizer is used. Examples of the polyether ester-based plasticizer include polyethylene glycol butanoic acid ester, polyethylene glycol isobutanoic acid ester, polyethylene glycol di (2-ethylbutyl acid) ester, polyethylene glycol (2-ethylhexylic acid) ester, and polyethylene glycol decanoic acid ester. Dibutoxyethanol adipate, di (butyl diglycol) adipate, di di (butyl polyglycol) adipate, di di (2-ethylhexyloxyethanol) adipate, di di (2-ethylhexyl diglycol) adipate, di adipate (2-Ethylhexylpolyglycol), dioctoxyethanol adipate, di (octyldiglycol) adipate, di (octylpolyglycol) adipate and the like can be mentioned. These may be used alone or in combination of two or more.

As the freezing point (° C.) of the plasticizer, for example, one having a freezing point (° C.) of −50 ° C. or lower is used. Further, for example, a plasticizer having a molecular weight of 450 or more (preferably 500 or more) is used. When such a plasticizer is used, it does not harden in a low temperature environment (for example, −45 ° C.), and flexibility can be imparted to a base resin containing acrylic rubber or ethylene acrylic rubber. Further, such a plasticizer does not easily volatilize even in a high temperature environment (for example, 150 ° C.) and can stay in the base resin.

The blending amount of the plasticizer in the acrylic rubber-based composition is set to 15 to 30 parts by mass with respect to 100 parts by mass in total of the acrylic rubber and the ethylene acrylic rubber.

The metal hydroxide is used for the purpose of imparting flame retardancy, vibration damping, and the like, and is in the form of particles. The metal hydroxide is not particularly limited as long as the object of the present invention is not impaired, and for example, aluminum hydroxide is used. As the aluminum hydroxide, low soda aluminum hydroxide having a soluble sodium content of 100 ppm or less is particularly preferable. As used herein, the amount of soluble sodium is the amount of sodium ions (Na ⁺ ) that dissolve in water when low soda aluminum hydroxide is brought into contact with water.

The average particle size of the metal hydroxide is, for example, preferably 5 μm to 15 μm, more preferably 5 μm to 12 μm.

The blending amount of the metal hydroxide in the acrylic rubber-based composition is set to 80 to 140 parts by mass with respect to 100 parts by mass in total of the acrylic rubber and the ethylene acrylic rubber.

The phosphorus-based flame retardant is a flame retardant containing phosphorus (P) in the compound, and is mainly used for imparting flame retardancy to an acrylic rubber-based composition. The phosphorus flame retardant also contributes to vibration damping. As the phosphorus-based flame retardant, for example, a phosphinic acid metal salt-based flame retardant, an organophosphorus-based flame retardant, ammonium polyphosphate, or the like is used. Of these, phosphinic acid metal salt flame retardants are preferable. Examples of the metal in the phosphinic acid metal salt flame retardant include Al, Mg, Ca, Ti, Zn, Sn and the like.

The blending amount of the phosphorus-based flame retardant in the acrylic rubber-based composition is set to 5 to 20 parts by mass with respect to 100 parts by mass in total of the acrylic rubber and the ethylene acrylic rubber.

As the flat particles, for example, those having an average particle diameter of 1 μm to 100 μm and an average aspect ratio (average particle diameter / average particle thickness) of 10 to 100 are used. When the average particle size and the average aspect ratio of the flat particles are in such a range, the vibration damping performance can be easily ensured. Examples of such flat particles include muscovite, phlogopite and other mica, boron nitride and the like, and mica is preferable. The average particle size is preferably 10 μm to 100 μm, more preferably 20 μm to 80 μm. For the average particle size (weight average particle size), the particle size distribution of the sample (flat particles) was measured by the sieving test described in JIS Z8815 (1994), and the logarithmic probability paper {horizontal axis: particle size, vertical axis. It is obtained by plotting the relationship between the cumulative content and the particle size on the axis: cumulative content (% by weight)} and determining the particle size corresponding to the cumulative content of 50% by weight. For the average particle thickness of the flat particles used when calculating the average aspect ratio, 30 flat particles visible in the image observed by a scanning microscope (SEM) were randomly selected, and the thickness of each flat particle was measured. It is a simple average value obtained.

The blending amount of the flat particles in the acrylic rubber-based composition is set to 5 to 30 parts by mass with respect to 100 parts by mass in total of the acrylic rubber and the ethylene acrylic rubber.

The cross-linking agent is not particularly limited as long as it can cross-link acrylic rubber and ethylene acrylic rubber, and for example, an aliphatic amine compound is used.

Examples of the aliphatic amine compound include aliphatic diamine compounds such as hexamethylenediamine, hexamethylenediamine carbamate, and N, N'-dicinnamylidene-1,6-hexanediamine. Among these, hexamethylenediamine carbamate is preferable.

The blending amount of the cross-linking agent in the acrylic rubber-based composition is 0.1 to 5.0 parts by mass, preferably 0.2 to 3.0 parts by mass with respect to 100 parts by mass of the total of acrylic rubber and ethylene acrylic rubber. Set.

The cross-linking aid is used together with the cross-linking agent and has a function of promoting cross-linking of acrylic rubber and ethylene acrylic rubber. The cross-linking aid is not particularly limited as long as it can cross-link acrylic rubber and ethylene acrylic rubber, but for example, a guanidine compound is used.

Examples of the guanidine compound include guanidine, tetramethylguanidine, dibutylguanidine, 1,3-o-tolylguanidine, 1,3-diphenylguanidine and the like. Among these, 1,3-diphenylguanidine is preferable.

The blending amount of the crosslinking aid in the acrylic rubber-based composition is set to 0.1 to 10 parts by mass, preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the total of acrylic rubber and ethylene acrylic rubber. ..

The acrylic rubber-based composition may contain other components in addition to the above-mentioned components as long as the object of the present invention is not impaired. Specific other components include fillers, processing aids, antiaging agents, tackifier resins, rust inhibitors, antioxidants, corrosion inhibitors, colorants, foaming agents, UV absorbers, surfactants and the like. Can be mentioned.

Examples of the substance constituting the filler include metals such as iron, copper and aluminum or alloys thereof, inorganic materials such as talc, glass and glass, graphite (carbon black) and minerals.

As the processing aid, it is preferable to use, for example, the trade name "Lipomin 18D" (Lion Specialty Chemicals Co., Ltd.), and as the antiaging agent, for example, the trade name "Nocrack CD" (Ouchi). It is preferable to use (manufactured by Shinko Kagaku Kogyo Co., Ltd.).

The acrylic rubber-based composition is uniformly kneaded using a general rubber kneading device.

The acrylic rubber-based composition is heat-press molded into a predetermined shape and further heat-treated in an oven for a predetermined time to proceed with a cross-linking reaction, resulting in vibration of the cross-linked product (cured product) of the acrylic rubber-based composition. A damping material is obtained.

In the acrylic rubber-based composition, a crosslinking reaction (primary crosslinking reaction, amidation reaction) proceeds during heat press molding, and further, a crosslinking reaction (secondary crosslinking reaction, imidization reaction) proceeds during heat treatment. By doing so, a crosslinked product of the acrylic rubber-based composition can be obtained.

[Vibration damping material]
The vibration damping material has heat resistance (for example, can be used at 150 ° C), cold resistance (for example, can be used at -45 ° C), flame retardancy (UL94V standard, equivalent to V-0), and vibration damping (23 ° C). The loss coefficient in is 0.4 or more) is also excellent. Further, the vibration damping material is based on acrylic rubber and ethylene acrylic rubber, and has excellent oil resistance. The hardness of the vibration damping material is preferably A50 or less, and particularly preferably A20 or more and A50 or less. The hardness of the vibration damping material is measured according to JIS K6253.

The vibration damping material is used, for example, in a device having a built-in vibration source such as a motor, or a device having a built-in precision component that wants to block the transmission of vibration from the outside. In particular, the vibration damping material is suitable in a place where the temperature tends to be high, the temperature becomes low in some cases (for example, when used in a cold region), and oil resistance is required, such as an engine room of an automobile. Can be used.

The vibration damping material may be formed in the form of a sheet, or may be formed into a predetermined shape by using a mold or the like.

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

[Examples 1 to 11 and Comparative Examples 1 to 11]
(Preparation of acrylic rubber-based composition)
In each example and each comparative example, acrylic rubber A, ethylene acrylic rubber X, polyether ester plasticizer, aluminum hydroxide, phosphinic acid metal salt flame retardant, carbon black, mica, cross-linking agent and cross-linking aid are used. The mixture was blended at the ratios (parts by mass) shown in Tables 1 and 2, and the mixture thereof was charged in a pressurized kneader and kneaded at 70 ° C. for 5 minutes to obtain an acrylic rubber-based composition.

The materials used in each example are as follows.
"Acrylic rubber A": Product name "NOXTITE (registered trademark) PA-524", Tg = -44 ° C, "Ester acrylic rubber X" manufactured by Unimatec Co., Ltd .: Product name "Vamac (registered trademark) VMX-4017", Tg = -41 ° C, "Polyether ester-based plasticizer" manufactured by DuPont Co., Ltd .: Product name "Adecikaiser (registered trademark) RS-700", molecular weight = approx. 550, freezing point = -53 ° C, manufactured by ADEKA Co., Ltd. "Aluminum hydroxide (Example of metal hydroxide): Low soda aluminum hydroxide, trade name "BF083", average particle size = 10 μm, manufactured by Nippon Light Metal Co., Ltd. "Phosphinic acid metal salt flame retardant" (example of phosphorus flame retardant) : Product name "Exolit (registered trademark) OP1230", phosphorus content = approx. 23% by mass, manufactured by Clarant Chemicals Co., Ltd. "Carbon Black": Product name "Asahi # 35", average particle size = 78 nm, manufactured by Asahi Carbon Co., Ltd. "Mica" (an example of flat particles): trade name "YM-21S", average particle size = 23 μm, aspect ratio = 70, manufactured by Yamaguchi Mica Co., Ltd. "Crosslinking agent": hexamethylenediamine carbamate (an example of an aliphatic diamine compound) ), Product name "CHEMINOX AC-6", "Crosslinking aid" manufactured by Unimatec Co., Ltd .: 1,3-diphenylguanidine (an example of guanidine compound), product name "Noxeller D"

(Manufacturing of vibration damping material)
Next, the acrylic rubber-based composition was further kneaded with a two-roll mill (distance between rolls: 2 mm) for another 3 minutes, and the subsequent composition was heat-press molded into a plate shape using a heat press machine and a die. At the time of this heat press molding, the primary cross-linking of the composition is performed. The molding temperature was 180 ° C., the molding pressure was 30 MPa, and the molding time was 10 minutes. Further, the composition after heat pressing is allowed to stand in an oven at 175 ° C. for 4 hours for secondary cross-linking, and then taken out from the oven to be a plate-shaped vibration damping material of each Example and each Comparative Example. Got

〔evaluation〕
(Kneader discharge)
In each Example and each Comparative Example, it was evaluated whether or not the acrylic rubber-based composition was easily discharged from the container-shaped kneaded portion of the pressure kneader at the time of producing the acrylic rubber-based composition. The results are shown in Tables 1 and 2. In Tables 1 and 2, the case where the acrylic rubber-based composition is easily discharged from the kneaded portion and has excellent workability is represented by the symbol “〇”, and the acrylic rubber-based composition adheres to the kneaded portion. The case where the product is not easily discharged and the workability is poor is indicated by the symbol "x".

(Roll stickiness)
In each Example and each Comparative Example, when the acrylic rubber-based composition was kneaded with a two-roll mill, the adhesiveness (easiness of sticking) to the roll of the composition was evaluated. The results are shown in Tables 1 and 2. In Tables 1 and 2, the case where the acrylic rubber-based composition has a weak adhesive force to the roll, the acrylic rubber-based composition can be easily peeled off from the roll, and the workability is excellent is represented by the symbol “◯”. On the other hand, the case where the acrylic rubber-based composition has a strong adhesive force to the roll, the acrylic rubber-based composition cannot be easily peeled off from the roll, and the processability is poor is represented by the symbol “x”.

(hardness)
In each Example and each Comparative Example, a test piece having a predetermined size (length 50 mm, width 50 mm, thickness 6 mm) was cut out from the obtained vibration damping material, and the test piece had a hardness in accordance with JIS K6253. (JISA hardness) was measured (constant pressure load within 1 second). The results are shown in Tables 1 and 2.

(Change in hardness after heating)
In each Example and each Comparative Example, the test piece used in the hardness measurement was heated at a temperature condition of 150 ° C. for 24 hours. Then, the hardness (JISA hardness) of the test piece after heating was measured (within a constant pressure load of 1 second) in accordance with JIS K6253 in the same manner as the hardness measurement (hardness measurement before heating). Then, the amount of hardness change (hardness increase amount) before and after heating was obtained from the hardness after heating and the hardness before heating. The results are shown in Tables 1 and 2. When the amount of hardness change (hardness increase amount) is 5 or less, it can be said that the heat resistance is excellent.

(Compressive permanent strain after heating)
In each Example and each Comparative Example, a test piece (diameter 13 mm, thickness 6 mm) having a predetermined size was cut out from the obtained vibration damping material, and the test piece (thickness D) was used to perform compression permanent strain in JIS. Measured according to K6262. Specifically, the heated test piece is compressed by 25% in the thickness direction using a predetermined compression device (compression jig) (thickness D1), and in that state, an environmental tester (constant temperature bath) at 150 ° C. I put it inside and left it there for 22 hours. After that, the test piece is taken out from the environmental tester, the compression device that compresses the test piece is released, and the test piece is allowed to stand on a wooden board at room temperature for 30 minutes or more, and then the thickness (D2) of the test piece is adjusted. The measurement was performed, and the compression set (%) was calculated from (D-D2) / (D-D1) × 100. The results are shown in Tables 1 and 2. When the value of the compression set (%) is 50 or less, it can be said that the heat resistance is excellent.

(Simple low temperature embrittlement test)
In each Example and each Comparative Example, a test piece (length 40 mm, width 6 mm, thickness 2 mm) having a predetermined size was cut out from the obtained vibration damping material, and one end of the test piece was used as a simple low temperature embrittlement test jig. I installed it. The simple low temperature embrittlement test jig is placed in a test environment set to a predetermined temperature for 1 hour, and then taken out, and at the same time, the impact jig is attached to the simple low temperature embrittlement test jig and impacts the free end side of the test piece. Was added, and it was confirmed whether or not the test piece was damaged. The temperature was set at 1 ° C. intervals. The results are shown in Tables 1 and 2. Tables 1 and 2 show the minimum temperature when the test piece did not crack. If it does not crack up to −45 ° C. (when cracked at a temperature lower than −45 ° C.), it can be said that it has excellent cold resistance.

(Loss coefficient)
In each Example and each Comparative Example, four test pieces having a length of 5 mm, a width of 5 mm, and a thickness of 3 mm were cut out from the obtained vibration damping material. Next, the vibration test device 10 shown in FIG. 1 was prepared. FIG. 1 is an explanatory diagram schematically showing the configuration of the vibration test device 10. As the vibration test device 10, "F-300BM / A" (manufactured by EMIC Corporation, fully automatic vibration test device) was used. The vibration test device 10 is a device that generates a frequency of a predetermined frequency to vibrate the vibration table 11. The vibration direction is the vertical direction in FIG. 1 (thickness direction of the test piece S). The vibration test device 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 1000 g. The vibration damping property test using the vibration test device 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, 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 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) showing the peak value (resonance magnification) of the resonance curve and the frequencies f1 and f2 (f1 <f0 <f2) showing the values 3 dB lower than the peak value. , The loss coefficient tan δ was calculated from the following mathematical formula (1) (half-value width method).
tanδ = (f2-f1) / f0 ・ ・ ・ ・ ・ (1)

The loss coefficients tan δ of each example and each comparative example are shown in Tables 1 and 2. When the loss coefficient tan δ is 0.4 or more (23 ° C.), it can be said that the vibration damping property is excellent.

(Flame retardance)
In each Example and each Comparative Example, a test piece (length 125 mm, width 13 mm, thickness 1 mm) having a predetermined size was cut out from the obtained vibration damping material, and the test piece was vertically flame-retardant in accordance with the UL94V standard. The test was conducted. The results are shown in Tables 1 and 2. In Tables 1 and 2, the case where the flame retardancy achieved "V-0" was represented by "V-0", and the case where the flame retardancy could not be achieved was represented by "x".

As shown in Tables 1 and 2, it was confirmed that the acrylic compositions of Examples 1 to 11 had no problem in kneader discharge property and roll adhesiveness, and were excellent in processability. Further, it was confirmed that the vibration damping materials of Examples 1 to 11 are excellent in heat resistance, cold resistance, vibration damping property and flame retardancy.

Comparative Example 1 was a case where the blending amount of mica was too large, and there was a problem in heat resistance and cold resistance. Comparative Example 2 is a case where mica is not blended, the loss coefficient is smaller than 0.4, and there is a problem in vibration damping property. In addition, there is a problem in processability (roll adhesiveness). Comparative Example 3 is a case where the blending amount of the acrylic rubber A is too small, the loss coefficient is smaller than 0.4, there is a problem in vibration damping property, and there is also a problem in processability (kneader discharge property). Comparative Example 4 is a case where ethylene acrylic rubber X is not blended as the base resin, and there is a problem in processability and cold resistance. Comparative Example 5 is a case where acrylic rubber A is not blended as the base resin and only ethylene acrylic rubber X is blended, and there are problems in processability (kneader discharge property) and cold resistance.

Comparative Example 6 was a case where the amount of the phosphinic acid metal salt flame retardant was too large, and there was a problem in heat resistance and cold resistance. Comparative Example 7 was a case where the phosphinic acid metal salt-based flame retardant was not blended, and there was a problem in flame retardancy. In addition, the loss coefficient is smaller than 0.4, and there is a problem in vibration damping property. In Comparative Example 8, the amount of aluminum hydroxide compounded was too large, and there was a problem in heat resistance and cold resistance. In Comparative Example 9, the amount of aluminum hydroxide compounded was too small, and there were problems in flame retardancy and vibration damping. In Comparative Example 10, the amount of the polyether ester-based plasticizer compounded was too large, and there were problems in heat resistance and vibration damping. Comparative Example 11 is a case where the blending amount of the polyether ester-based plasticizer is too small, and there is a problem in cold resistance.

[Comparative Examples 12 to 17]
Acrylic rubber A, acrylic rubber B, acrylic rubber C, ethylene acrylic rubber X, ethylene acrylic rubber Y, polyether ester plasticizer, aluminum hydroxide, phosphinic acid metal salt flame retardant, carbon black, mica, cross-linking agent and cross-linking The auxiliary agents were blended in the proportions (parts by mass) shown in Table 3, and the mixture thereof was kneaded under the same conditions as in Example 1 and the like to obtain acrylic rubber-based compositions of Comparative Examples 12 to 17.

The details of acrylic rubber B, acrylic rubber C, and ethylene acrylic rubber Y are as follows.
"Acrylic rubber B": Product name "NOXTITE (registered trademark) PA-522HF", Tg = -31 ° C, manufactured by Unimatec Co., Ltd. "Acrylic rubber C": Product name "NOXTITE (registered trademark) PA-521", Tg = -17 ° C, Unimatec Co., Ltd. "Ethethylene acrylic rubber Y": Product name "Vamac (registered trademark) G", Tg = -30 ° C, manufactured by DuPont Co., Ltd.

Next, the acrylic rubber-based composition of each Comparative Example was molded in the same manner as in Example 1 and the like to obtain a vibration damping material of Comparative Examples 12 to 17. Then, the vibration damping material of each comparative example was evaluated in the same manner as in Example 1. The results are shown in Table 3.

As shown in Table 3, Comparative Example 12 was a case where acrylic rubber B having a high glass dislocation temperature was used, and there was a problem in cold resistance. Comparative Example 13 is a case where acrylic rubber A and acrylic rubber B are used as the base resin and ethylene acrylic rubber X is not used, and there are problems in processability and cold resistance. Comparative Example 14 was a case where acrylic rubber C having a high glass dislocation temperature was used, and there was a problem in cold resistance. In addition, the hardness became too high, which caused a problem. Comparative Example 15 is a case where acrylic rubber A and acrylic rubber C are used as the base resin and ethylene acrylic rubber X is not used, and there are problems in processability and cold resistance. Comparative Example 16 is a case where ethylene acrylic rubber X and ethylene acrylic rubber Y are used as the base resin, and there are problems in processability and cold resistance. Comparative Example 17 was a case where ethylene acrylic rubber Y having a high glass dislocation temperature was used, and there was a problem in cold resistance.

[Comparative Examples 18 to 20]
While using a dibasic acid-based plasticizer, an ether ester-based plasticizer, or a polyester-based plasticizer instead of the polyether ester-based plasticizer, together with other components, at the ratio (parts by mass) shown in Table 4. They were blended and the mixture thereof was kneaded under the same conditions as in Example 1 to obtain the acrylic rubber-based compositions of Comparative Examples 18 to 20.

The details of the dibasic acid-based plasticizer, the ether ester-based plasticizer, and the polyester-based plasticizer are as follows.
"Dibasic acid-based plasticizer": di2-ethylhexyl sebacate, trade name "Sun Sizar (registered trademark) DOS", molecular weight = 426, freezing point = -69 ° C, "ether ester-based plasticizer" manufactured by Shin Nihon Rika Co., Ltd. ": Product name" Monosizer (registered trademark) W-260 ", molecular weight = 434, freezing point = -69 ° C, manufactured by DIC Co., Ltd." Ester-based plasticizer ": Product name" Monosizer (registered trademark) W-320 " , Molecular weight = 1000, Freezing point = -35 ° C

Next, the acrylic rubber-based composition of each Comparative Example was molded in the same manner as in Example 1 and the like to obtain a vibration damping material of Comparative Examples 18 to 20. Then, the vibration damping material of each comparative example was evaluated in the same manner as in Example 1. The results are shown in Table 4.

Comparative Examples 18 to 20 are cases where another plasticizer is used as the plasticizer without using the polyether ester-based plasticizer. Comparative Example 18 had a problem in heat resistance and vibration damping, Comparative Example 19 had a problem in heat resistance, and Comparative Example 20 had a problem in cold resistance.

(Cold heat impact test)
A thermal shock test was performed on the test piece of Example 3 used in the measurement of the loss coefficient. Specifically, a total of 1 hour cycle of exposing the test piece to −40 ° C. and 150 ° C. for 30 minutes was executed for 1000 cycles. Then, after 500 cycles and after 1000 cycles, the loss coefficient tan δ was measured by using the above-mentioned method, respectively. As a result, it was 0.52 after 500 cycles and 0.56 after 1000 cycles. As described above, the vibration damping material of Example 3 did not show a decrease in the loss coefficient even after the thermal shock test.

(Oil resistance test: mass change, volume change)
Three test pieces (length 20 mm, width 20 mm, thickness 3 mm) having a predetermined size were cut out from the vibration damping material of Example 3, and the test pieces 1a to 3a were immersed in gasoline. The mass (g) and volume (cm ³ ) of each of the test pieces 1a to 3a were measured before the immersion, 100 hours after the immersion, and 500 hours after the immersion. The results of mass change (%), volume change (%), etc. of each test piece 1a to 3a are shown in Table 5.

As shown in Table 5, even after being immersed in gasoline for 500 hours, the mass change and volume change were within 5%, confirming that the oil resistance was excellent.

(Oil resistance test: tensile strength, elongation)
Three test pieces having a predetermined shape (No. 2 dumbbell shape) were cut out from the vibration damping material of Example 3, and the test pieces 1b to 3b were immersed in gasoline. Before immersion, 100 hours after immersion, and 500 hours after immersion, the maximum test force (tensile strength) was used for each test piece using an autograph (product name "AGS-X 5NX type", manufactured by Shimadzu Corporation). ) And elongation was measured (crosshead 40 m / min). The results of the tensile strength (MPa) and the elongation rate (%) of each test piece 1b to 3b are shown in Table 6.

As shown in Table 6, even after being immersed in gasoline for 500 hours, no decrease in tensile strength and elongation was observed, and it was confirmed that the oil resistance was excellent.

10 ... Vibration test device, 11 ... Vibration table, 12 ... Mounting plate, 13 ... Accelerometer pickup, S ... Test piece (vibration damping material)

Claims (4)

Acrylic rubber with a glass dislocation temperature of -40 ° C or less and 50 to 80 parts by mass of acrylic rubber including a cross-linking point.
20 to 50 parts by mass of ethylene acrylic rubber having a glass transition temperature of −40 ° C. or lower and containing a cross-linking point of the same type as the cross-linking point (however, the total of the acrylic rubber and the ethylene acrylic rubber is 100 parts by mass).
15 to 30 parts by mass of a polyether ester-based plasticizer,
With 80 to 140 parts by mass of aluminum hydroxide ,
Phosphorus flame retardant 5 to 20 parts by mass and
5 to 30 parts by mass of a filler composed of flat particles,
With 0.1 to 5 parts by mass of the cross-linking agent,
An acrylic rubber-based composition having 0.1 to 10 parts by mass of a cross-linking aid. The acrylic rubber-based composition according to claim 1, wherein the acrylic rubber and the ethylene acrylic rubber contain a carboxyl group as the cross-linking point. The acrylic rubber-based composition according to claim 1 or 2, wherein the cross-linking agent is made of an aliphatic amine compound, and the cross-linking aid is made of a guanidine compound. A vibration damping material made of a crosslinked product of the acrylic rubber-based composition according to any one of claims 1 to 3.

Images