JP4450482B2 - Rubber composition for engine mount - Google Patents

Description

【００２６】
表１で用いた材料は下記の通り。
１）電気化学工業株式会社製、キサントゲン変性クロロプレンゴム(ＤＣＲ−６６)
２）電気化学工業株式会社製、デンカブラック粒状品（Ｌｃ＝３．５ｎｍ、ＤＢＰ吸油量＝２１０ｍｌ／１００ｇ）
３）東海カーボン株式会社製、シーストＳ（Ｌｃ＝１．８ｎｍ以下、ＤＢＰ吸油量＝６８ｍｌ／１００ｇ）
４）旭カーボン株式会社製、アサヒサーマルＦＴ（Ｌｃ＝１．８ｎｍ以下、ＤＢＰ吸油量＝２８ｍｌ／１００ｇ）
５）東海カーボン株式会社製、シースト３（Ｌｃ＝１．８ｎｍ以下、ＤＢＰ吸油量＝１０１ｍｌ／１００ｇ）
６）バイエル（Ｂａｙｅｒ）社（ドイツ）製、エーテル・チオエーテル系可塑剤
【００２７】
【発明の効果】
表１に示すように、クロロプレン系ゴムに結晶子内の層平面のＣ軸方向の平均積み重なり高さＬｃが２ｎｍ以上のカーボンブラックを含有する本発明のエンジンマウント用ゴム組成物は、優れた耐熱性を有し、更に優れた防振特性(低い動倍率)と低圧縮永久ひずみのバランスがとれた加硫物および自動車用エンジンマウントを与える。[0001]
BACKGROUND OF THE INVENTION
The rubber composition for engine mounts needs to reduce the dynamic spring constant in the vicinity of 100 Hz so as not to transmit the vibration of the engine that rotates at the running speed to the vehicle body because it is necessary to reduce the in-vehicle noise during driving. There is. In consideration of the weight of the engine and the like, it is necessary to reduce the dynamic magnification (dynamic spring constant / static spring constant) at the frequency. Furthermore, durability such as heat resistance is high, and in order to support the engine for a long time, it is required that the compression set at a high temperature is small.
The present invention relates to a rubber composition for an engine mount and an engine mount using the rubber composition. More specifically, the heat resistance is remarkably improved, and the vibration resistance is excellent, and the compression set at a high temperature is high. The present invention relates to a rubber composition for an engine mount that gives a small vulcanizate.
[0002]
[Prior art]
Diene rubbers such as natural rubber are often used as rubber compositions for engine mounts. However, the temperature of the engine room is on the rise due to the recent increase in the output of automobiles and exhaust gas regulations, etc., and the heat resistance requirement of the engine mount rubber composition for elastically supporting the engine has become more severe. A material with high heat resistance is desired. Several methods for improving the heat resistance of a chloroprene rubber composition having higher heat resistance than natural rubber have been proposed. For example, in Japanese Patent Laid-Open No. 50-87437, a method for improving heat resistance by adding zinc powder and water to chloroprene rubber, and in Japanese Patent Laid-Open No. 2-34645, zinc powder and thermal black are added. A method for improving heat resistance is disclosed in JP-A-3-81350 in which zinc powder and 4,4 ′-(α, α-dimethylbenzyl) diphenylamine are added to chloroprene rubber. However, the heat resistance is not always satisfied, and an improvement is desired. In addition, these known documents do not mention any anti-vibration characteristics which are important characteristics of the engine mount.
[0003]
[Problems to be solved by the invention]
The present invention solves the above-mentioned problems, improves the heat resistance of the vulcanizate, has excellent vibration-proof characteristics near 100 Hz, and has a low compression set at high temperatures. A composition is provided.
[0004]
[Means for Solving the Problems]
In order to obtain an improved rubber composition for an engine mount, the present inventors have improved the heat resistance of the vulcanized product of the chloroprene-based rubber composition, and further have vibration-proof properties and low compression set at high temperatures. As a result of intensive studies, it was found that this can be achieved by combining chloroprene rubber and carbon black having an average stacking height Lc of 2 nm or more in the C-axis direction of the layer plane in the crystallite. Completed.
That is, the present invention relates to carbon black having an average stacking height Lc in the C-axis direction of the layer plane in the crystallite of 2 nm or more on chloroprene-based rubber, and, if necessary, 4,4′-bis (α , Α-dimethylbenzyl) diphenylamine, which is a rubber composition for engine mounts, which improves the heat resistance of the vulcanizate and further has anti-vibration properties.
[0005]
Hereinafter, the present invention will be described in more detail.
The chloroprene rubber in the rubber composition for engine mounts of the present invention is mainly composed of chloroprene rubber. In addition to the chloroprene rubber, natural rubber, SBR, butyl rubber, BR, NBR, EPDM may be used as necessary. Etc. can be contained.
[0006]
The chloroprene rubber of the present invention is obtained by polymerizing a chloroprene homopolymer or a mixture of chloroprene and one or more other monomers copolymerizable with chloroprene (hereinafter referred to as chloroprene monomer). (Hereinafter often referred to as chloroprene rubber).
Examples of the monomer copolymerizable with chloroprene include 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, sulfur, styrene, acrylonitrile, methacrylonitrile, isoprene, butadiene, and Examples thereof include acrylic acid, methacrylic acid, and esters thereof, and can be used within a range that satisfies the object of the present invention.
[0007]
The polymerization method for obtaining the chloroprene rubber used in the present invention is not particularly limited, and a normal polymerization method can be used. A chloroprene monomer is usually used in the presence of a polymerization initiator generally used for chloroprene polymerization. It can be obtained by emulsion polymerization by a method.
The emulsifier for carrying out this emulsion polymerization is not particularly limited, and is generally used for emulsion polymerization of chloroprene, for example, alkali metal salts of saturated or unsaturated fatty acids having 6 to 22 carbon atoms, rosin acid or disproportionate. An alkali metal salt of chlororosin acid, an alkali metal salt of a formalin condensate of β-naphthalenesulfonic acid, or the like is used.
[0008]
Chloroprene-based rubbers are classified into sulfur-modified types, mercaptan-modified types, and xanthogen-modified types, depending on the type of molecular weight regulator. In the sulfur-modified type, a polymer obtained by copolymerizing sulfur and chloroprene is plasticized with thiuram disulfide and adjusted to a predetermined Mooney viscosity. The mercaptan-modified type uses alkyl mercaptans such as n-dodecyl mercaptan, tert-dodecyl mercaptan, and octyl mercaptan as molecular weight regulators. The xanthogen-modified type uses an alkyl xanthogen compound as a molecular weight regulator.
[0009]
Any modified type can be used as the chloroprene rubber of the present invention, but a chloroprene rubber modified by combining sulfur, mercaptan and xanthogen can also be used. However, the sulfur-modified type is inferior in heat resistance of the polymer itself as compared with the mercaptan-modified and xanthogen-modified types. Therefore, when more heat resistance is required, it is preferable to use the mercaptan-modified and xanthogen-modified types. Furthermore, the xanthogen-modified type is particularly preferable because it balances both heat resistance and vibration isolation characteristics.
[0010]
Specific examples of the alkyl xanthogen compound used for the xanthogen-modified type include dimethyl xanthogen disulfide, diethyl xanthogen disulfide, diisopropyl xanthogen disulfide, diisobutyl xanthogen disulfide and the like.
The amount of the alkyl xanthogen compound used is selected so that the molecular weight of the chloroprene polymer (or the Mooney viscosity of the chloroprene rubber obtained by isolating the polymer) is appropriate. Although it varies depending on the structure of the alkyl group and the target molecular weight, it is generally 0.05 to 5.0 parts by weight, preferably 0.3 to 1.0 parts by weight with respect to 100 parts by weight of the chloroprene monomer. Used.
[0011]
As the polymerization initiator, known organic peroxides such as potassium persulfate, ammonium persulfate, sodium persulfate, hydrogen peroxide, and t-butyl hydroperoxide generally used for emulsion polymerization of chloroprene are used.
[0012]
In the present invention, the polymerization temperature and the final conversion rate of the monomer are not particularly limited, but the polymerization temperature is preferably 0 to 50 ° C, more preferably 20 to 50 ° C. Moreover, it is preferable to carry out so that the final conversion rate of a monomer may be in the range of 60 to 90%, and when this conversion rate is reached, a small amount of a polymerization inhibitor is added to stop the polymerization.
As the polymerization inhibitor, for example, usually used inhibitors such as thiodiphenylamine, 4-tertiarybutylcatechol, 2,2-methylenebis-4-methyl-6-tertiarybutylphenol are used.
[0013]
The unreacted monomer can be removed by, for example, a steam stripping method, and then the pH of the latex is adjusted, and the polymer can be isolated by conventional freeze-coagulation, water washing, hot air drying, and the like.
[0014]
Carbon black compounded in the rubber composition for engine mounts of the present invention can be any of thermal black and acetylene black by pyrolysis method, furnace black and channel black by incomplete combustion method. In the carbon black, the average stacking height Lc in the C-axis direction of the layer plane in the crystallite needs to be 2 nm or more, and the average stacking height Lc in the C-axis direction of the layer plane is 2.5 nm or more. Those are particularly preferred.
Further, carbon black having an average particle size of 60 nm or less and a DBP oil absorption of preferably 100 to 350 ml / 100 g, more preferably 120 to 300 ml / 100 g, and particularly preferably 140 to 300 ml / 100 g is preferable.
If the average stacking height Lc in the C-axis direction of the layer plane in the crystallite is smaller than 2 nm, the heat resistance of the vulcanizate obtained by vulcanizing the chloroprene rubber composition is not sufficient.
Furthermore, acetylene black is a carbon black obtained by thermally decomposing acetylene gas, crystallization progresses remarkably, structure is highly developed, and oil absorption is large. Therefore, a chloroprene rubber composition using acetylene black. Is most preferable because of its large effect of improving the heat resistance of the vulcanizate.
The amount of carbon black added is preferably 10 to 70 parts by weight, more preferably 20 to 60 parts by weight, based on 100 parts by weight of the chloroprene rubber. When the added amount exceeds 70 parts by weight, the workability is deteriorated, the exothermic property at the time of kneading is large and scorch is liable to occur, and the embrittlement temperature of the vulcanizate is increased. When the addition amount is less than 10 parts by weight, the tensile strength and modulus of the vulcanizate are lowered, which is not preferable.
[0015]
There are no particular restrictions on the vulcanizing agent used in the present invention, but metal oxides are preferred, specifically zinc oxide, magnesium oxide, lead oxide, trilead tetroxide, iron trioxide, titanium dioxide, calcium oxide, etc. Is mentioned. These may be used in combination of two or more. The addition amount of these vulcanizing agents is preferably 3 to 15 parts by weight with respect to 100 parts by weight of the chloroprene rubber.
Moreover, it can also vulcanize more effectively by using together with the following vulcanization accelerator.
[0016]
As the vulcanization accelerator, thiourea-based, guanidine-based, thiuram-based, thiazole-based, and triazine-based vulcanization accelerators generally used for vulcanization of chloroprene-based rubbers can be used, but thiourea-based ones are preferable. Examples of the thiourea-based vulcanization accelerator include ethylene thiourea, diethyl thiourea, trimethyl thiourea, triethyl thiourea, N, N′-diphenyl thiourea, and trimeryl thiourea is particularly preferable. Also, use a vulcanization accelerator such as 3-methylthiazolidine thione-2 or a mixture of thiadiazole and phenylene dimaleimide, dimethylammonium hydrogen isophthalate or 1,2-dimercapto-1,3,4-thiadiazole derivative. Can do. These vulcanization accelerators may be used in combination of two or more of those listed above. A peroxide vulcanizing agent can also be applied. The addition amount of these vulcanization accelerators is preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of chloroprene rubber.
[0017]
In the rubber composition for engine mounts of the present invention, various additives such as a softening agent, a plasticizer, a processing aid, an anti-aging agent, a lubricant, a filler and the like can be blended as necessary.
[0018]
As the anti-aging agent, general anti-aging agents such as amine-based, imidazole-based, carbamic acid metal salt, phenol-based and wax can be used. Examples of the antioxidant agent having a large effect of improving heat resistance include amine-based 4,4′-bis (α, α-dimethylbenzyl) diphenylamine, octylated diphenylamine and the like. In particular, 4,4′-bis (α, α-dimethylbenzyl) diphenylamine can further improve the heat resistance of the rubber composition for engine mounts of the present invention. The addition amount of the antioxidant is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the chloroprene rubber. The amount of 4,4′-bis (α, α-dimethylbenzyl) diphenylamine added is preferably 1 to 10 parts by weight and more preferably 3 to 10 parts by weight with respect to 100 parts by weight of the chloroprene rubber. When the amount of 4,4′-bis (α, α-dimethylbenzyl) diphenylamine is less than 1 part by weight, the heat resistance of the vulcanizate is not sufficiently improved, and when it is more than 10 parts by weight, 4,4′- Bis (α, α-dimethylbenzyl) diphenylamine is not preferred because it blooms on the surface of the vulcanizate. These anti-aging agents can be used alone or in combination.
[0019]
General softening agents such as lubricating oils, process oils, paraffins, liquid paraffins, petroleum jelly, petroleum asphalt, and other oil-based softeners, rapeseed oil, linseed oil, castor oil, coconut oil and other vegetable oil-based softeners The agent can be used.
[0020]
As the plasticizer, general plasticizers such as dioctyl phthalate and dioctyl adipate can be used. Plasticizers that do not inhibit or improve the heat resistance of the rubber composition for engine mounts of the present invention include ether / thioether plasticizers such as vulcanol OT (trade name, manufactured by Bayer), ester plasticizers. And ether ester plasticizers such as Adekasizer RS-700 and RS-735 (trade name, manufactured by Asahi Denka Kogyo Co., Ltd.). In particular, ether / thioether plasticizers are preferred because they have the effect of improving heat resistance and cold resistance, and are excellent in balance between the two. These plasticizers can be used alone or in combination according to the required properties.
[0021]
As a kneading method and a vulcanizing method of the rubber composition for engine mount in the present invention, a method performed in a normal rubber industry can be used. Generally, it can mix with kneaders, such as a kneader, a Banbury, or a roll, and can shape | mold it into the shape according to the objective, and can obtain a shaping | molding vulcanizate. Specifically, after kneading each component at a temperature lower than the vulcanization temperature, the kneaded product is formed into various shapes and vulcanized. The temperature at the time of vulcanization and the vulcanization time can be appropriately set. The vulcanization temperature is preferably 140 to 190 ° C, and more preferably 150 to 180 ° C.
[0022]
The vulcanizate obtained from the chloroprene-based rubber composition of the present invention is excellent in heat resistance and vibration isolation characteristics in addition to the mechanical characteristics of rubber. And is particularly suitable for engine mounts with stricter heat resistance.
An engine mount can be produced by a known method using the rubber composition for an engine mount of the present invention. The engine mount type is roughly classified into a compression type, a shearing type, and an intermediate inclination type, and the rubber composition of the present invention can be applied to any type.
[0023]
【Example】
EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples.
Example 1, Comparative Examples 1-3
According to the formulation shown in Table 1, kneading was performed using an 8-inch roll to prepare a sheet having a thickness of 2.3 mm. This sheet was subjected to press vulcanization at 150 ° C. for 20 minutes to prepare a vulcanized sheet having a thickness of 2 mm. The physical properties of the vulcanizate were measured using a No. 3 dumbbell and the hardness was measured according to JIS K6253. Further, the compression set test was performed in accordance with JIS K6262.
The evaluation of the anti-vibration property was performed using a cylindrical sample (diameter 29 mm, height 12.5 mm) according to JIS K6394. The dynamic magnification (Kd / Ks) serving as an index of the vibration isolation characteristic is calculated by the ratio of the dynamic spring constant (Kd) and the static spring constant (Ks). The static spring constant is first compressed by 28% in the axial direction, and 2 It calculated from the average stress of 4% and 12% of outward compression. The dynamic spring constant was determined under conditions of an initial strain of 10%, a frequency of 100 Hz, and a dynamic strain of ± 0.4%.
Heat resistance was measured by the above measurement method using a test piece stored in a 140 ° C. gear oven for 9 days in accordance with JIS K6257, and indicated by the amount of change in hardness.
[0024]
The average stacking height Lc (nm) in the C-axis direction of the layer plane in the crystallite was calculated according to the following equation using the (002) diffraction line in the X-ray diffraction method using the Cu—Kα ray. Lc = (180 · K · λ) / (π · β · COSΘ)
K = form factor (using 0.9)
λ = X-ray wavelength (0.154 nm)
Θ = An angle indicating the maximum value in the (002) diffraction line absorption band β = A half width in the (002) diffraction line absorption band expressed in angle
[Table 1]

[0026]
The materials used in Table 1 are as follows.
1) Xanthogen-modified chloroprene rubber (DCR-66) manufactured by Denki Kagaku Kogyo Co., Ltd.
2) Denka Black granular product (Lc = 3.5 nm, DBP oil absorption = 210 ml / 100 g) manufactured by Denki Kagaku Kogyo Co., Ltd.
3) Seast S (Lc = 1.8 nm or less, DBP oil absorption = 68 ml / 100 g) manufactured by Tokai Carbon Co., Ltd.
4) Asahi Thermal FT manufactured by Asahi Carbon Co., Ltd. (Lc = 1.8 nm or less, DBP oil absorption = 28 ml / 100 g)
5) Toast Carbon Co., Ltd., Seast 3 (Lc = 1.8 nm or less, DBP oil absorption = 101 ml / 100 g)
6) Ether / thioether plasticizer manufactured by Bayer (Germany)
【The invention's effect】
As shown in Table 1, the engine mount rubber composition of the present invention containing chloroprene-based rubber containing carbon black having an average stacking height Lc of 2 nm or more in the C-axis direction of the layer plane in the crystallite is excellent in heat resistance. This provides a vulcanizate and an engine mount for automobiles that have a good balance between excellent vibration isolation characteristics (low dynamic magnification) and low compression set.

Claims (10)

10 to 70 parts by weight of carbon black having an average stacking height Lc of 2 nm or more in the C-axis direction of the layer plane in the crystallite with respect to 100 parts by weight of the chloroprene rubber,
The chloroprene rubber is xanthogen-modified chloroprene rubber or a mercaptan-modified chloroprene rubber der is, the engine mount rubber composition characterized by containing an ether-thioether plasticizer.   The rubber composition for an engine mount according to claim 1, wherein the chloroprene rubber is xanthogen-modified chloroprene rubber.
3. The rubber composition for an engine mount according to claim 1 , wherein the carbon black has an average particle diameter of 60 nm or less and a DBP oil absorption of 100 to 350 ml / 100 g.
The rubber composition for an engine mount according to claim 3, wherein the carbon black has a DBP oil absorption of 140 to 300 ml / 100 g.
3. The rubber composition for an engine mount according to claim 1 , wherein the carbon black has an Lc of 2.5 nm or more, an average particle diameter of 60 nm or less, and a DBP oil absorption of 140 to 300 ml / 100 g. .
The rubber composition for an engine mount according to any one of claims 1 to 5 , wherein the carbon black is acetylene black.
1-10 parts by weight of 4,4'-bis to the chloroprene-based rubber 100 parts by weight of (alpha, alpha-dimethylbenzyl) of claims 1 to 6, characterized in that it contains a diphenylamine according to any one of Rubber composition for engine mounts.
A vulcanized product obtained by vulcanizing the rubber composition for engine mounts according to any one of claims 1 to 7 . 10 to 70 parts by weight of carbon black having an average stacking height Lc of 2 nm or more in the C-axis direction of the layer plane in the crystallite with respect to 100 parts by weight of the chloroprene rubber,
The chloroprene rubber is a vulcanized product obtained by vulcanizing a rubber composition for an engine mount which is a xanthogen-modified chloroprene rubber or a mercaptan-modified chloroprene rubber . An automobile engine mount comprising the vulcanized product according to any one of claims 8 and 9 .