JP2001131341A - Rubber composition for mounting engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition for mounting an engine, providing a vulcanized rubber having improved heat resistance, excellent damping characteristics in the vicinity of 100 Hz and yet low compression set at a high temperature. SOLUTION: This rubber composition for mounting an engine comprises a chloroprene-based rubber, carbon black having >=2 nm average piled height Lc in C-axis of layer plane in a crystallite and zinc powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The rubber composition for an engine mount is required to reduce the noise inside the vehicle during traveling. It is necessary to reduce the mechanical spring constant. Also, considering the weight of the engine,
It is necessary to reduce the dynamic magnification (dynamic spring constant / static spring constant) at the frequency. Furthermore, in order to have high durability such as heat resistance and to support the engine for a long period of time, it is required that the compression set at high temperatures is small. The present invention relates to a rubber composition for an engine mount and an engine mount using the same. More specifically, the present invention relates to a rubber composition for an engine mount. The present invention relates to a rubber composition for an engine mount that gives a small vulcanizate.

[0002]

2. Description of the Related Art Diene rubbers such as natural rubbers are widely used as rubber compositions for engine mounts. However, the temperature of the engine room has been increasing due to the recent increase in the output of automobiles and emission regulations, and the demand for heat resistance of the rubber composition for engine mounts for elastically supporting the engine has become more severe. Materials with high heat resistance are demanded. Several methods have been proposed for improving the heat resistance of chloroprene rubber compositions having higher heat resistance than natural rubber. For example, JP-A-50-8743
No. 7 discloses a method of improving heat resistance by adding zinc powder and water to chloroprene rubber, and Japanese Unexamined Patent Publication No. 2-34645 discloses a method of improving heat resistance by adding zinc powder and thermal black. And JP-A-3-81350.
Publication No. 4 discloses that chloroprene rubber is mixed with zinc powder and 4,4′-
A method for improving heat resistance by adding (α, α-dimethylbenzyl) diphenylamine is described, but the heat resistance is not always satisfactory, and improvement is desired. Further, these known documents do not mention any vibration damping characteristic which is an important characteristic of the engine mount.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, improves the heat resistance of the vulcanized product, and reduces
An object of the present invention is to provide a rubber composition for an engine mount which has excellent vibration isolation characteristics at around Hz and has a small compression set at high temperatures.

[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 a vulcanized product of a chloroprene-based rubber composition, and further improved the anti-vibration properties. After intensive studies to combine low compression set at high temperature and high temperature, a combination of chloroprene-based 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 and zinc powder was used. As a result, the present inventors have found that this can be achieved and completed the present invention. That is, the present invention provides carbon black and zinc powder having an average stacking height Lc of 2 nm or more in the C-axis direction of the layer plane in the crystallite on the chloroprene rubber, and 4,4′- as an antioxidant if necessary. Screw
A rubber composition for an engine mount containing (α, α-dimethylbenzyl) diphenylamine, wherein the vulcanized product has improved heat resistance and also has anti-vibration properties.

Hereinafter, the present invention will be described in more detail. The chloroprene rubber in the engine mount rubber composition of the present invention is mainly composed of chloroprene rubber. In addition to chloroprene rubber, if necessary, natural rubber, SBR, butyl rubber, BR, NBR, E
PDM and the like can be contained.

The chloroprene rubber of the present invention is obtained by polymerizing a homopolymer of chloroprene or a mixture of chloroprene and at least one other monomer copolymerizable with chloroprene (hereinafter referred to as chloroprene monomer). (Hereinafter often referred to as chloroprene rubber)
It is. Monomers copolymerizable with chloroprene include:
For example, 2,3-dichloro-1,3-butadiene, 1-
Examples thereof include chloro-1,3-butadiene, sulfur, styrene, acrylonitrile, methacrylonitrile, isoprene, butadiene, acrylic acid, methacrylic acid and esters thereof, and can be used within a range satisfying 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 usual polymerization method can be used. The chloroprene monomer is prepared by subjecting the chloroprene monomer to a polymerization initiator generally used for the polymerization of chloroprene. It can be obtained by emulsion polymerization according to a commonly used method. The emulsifier used in the emulsion polymerization is not particularly limited, and is generally an emulsifier used for emulsion polymerization of chloroprene, for example, an alkali metal salt of a saturated or unsaturated fatty acid having 6 to 22 carbon atoms, rosin acid or heterogeneous acid. Alkali metal salts of rosin acids
For example, an alkali metal salt of a formalin condensate of β-naphthalenesulfonic acid is used.

[0008] Chloroprene rubbers are sulfur-modified, mercaptan-modified,
It is classified into xanthogen denatured type. In the sulfur-modified type, a polymer obtained by copolymerizing sulfur and chloroprene is plasticized with thiuram disulfide to adjust the polymer to a predetermined Mooney viscosity. Mercaptan-modified type is n-
Alkyl mercaptans such as dodecyl mercaptan, tert-dodecyl mercaptan and octyl mercaptan are used as molecular weight regulators. The xanthogen-modified type uses an alkyl xanthogen compound as a molecular weight regulator.

As the chloroprene rubber of the present invention, any modified type can be used, but those obtained by modifying chloroprene rubber by combining sulfur, mercaptan and xanthogen can also be used. However, the sulfur-modified type
Since the heat resistance of the polymer itself is inferior to the mercaptan-modified and xanthogen-modified types, when more heat resistance is required, it is preferable to use the mercaptan-modified and xanthogen-modified types. Further, the xanthogen-modified type is particularly preferable because both the heat resistance and the anti-vibration properties are balanced.

Specific examples of the alkyl xanthogen compound used in the xanthogen-modified type include dimethyl xanthogen disulfide, diethyl xanthogen disulfide, diisopropyl xanthogen disulfide, diisobutyl xanthogen disulfide and the like. The amount of the alkylxanthogen compound used is selected so that the molecular weight of the chloroprene-based polymer (or the Mooney viscosity of the chloroprene-based rubber obtained by isolating the polymer) is appropriate. Although it depends on the structure of the alkyl group and the target molecular weight, it is generally 0.05 to 5.0 parts by weight, preferably 0.1 to 100 parts by weight, based on 100 parts by weight of the chloroprene monomer.
It is used in the range of 3 to 1.0 part by weight.

As the polymerization initiator, known organic peroxides generally used for emulsion polymerization of chloroprene such as potassium persulfate, ammonium persulfate, sodium persulfate, hydrogen peroxide and t-butyl hydroperoxide are used. .

In the present invention, the polymerization temperature and the final conversion of the monomer are not particularly limited.
° C, more preferably 20 to 50 ° C. The final conversion of the monomer is 60 to 90.
%, And when the conversion is reached, a small amount of a polymerization inhibitor is added to terminate the polymerization. As the polymerization inhibitor, for example, commonly used inhibitors such as thiodiphenylamine, 4-tert-butylcatechol, and 2,2-methylenebis-4-methyl-6-tert-butylphenol are used.

Unreacted monomers are removed, for example, by steam stripping, and then the p
After adjusting H, the polymer can be isolated by a conventional method such as freeze coagulation, washing with water, and drying with hot air.

The carbon black compounded in the rubber composition for an engine mount of the present invention may be any of thermal black and acetylene black by a pyrolysis method, and furnace black and channel black by an incomplete combustion method. However, in these carbon blacks, it is necessary that the average stacking height Lc in the C-axis direction of the layer plane in the crystallite is 2 nm or more, and the average stacking height Lc in the C-axis direction of the layer plane is 2. Those having a thickness of 5 nm or more are particularly preferred. Further, the average particle size is 60 nm or less, and the DBP oil absorption is preferably 100 to 350 ml.
/ 100g, more preferably 120-300ml / 10
It is preferably 0 g, particularly preferably 140 to 300 ml / 100 g of carbon black. 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. Further, acetylene black is a carbon black obtained by thermally decomposing acetylene gas, crystallization is remarkably advanced, and the structure is highly developed, and the oil absorption is large. Is most preferable because the effect of improving the heat resistance of the vulcanizate is large. The addition amount of carbon black is preferably from 10 to 70 parts by weight, preferably from 20 to 60 parts by weight, per 100 parts by weight of the chloroprene rubber.
Part by weight is more preferred. If the added amount exceeds 70 parts by weight, the processability is deteriorated, the heat generation during kneading is large, scorch is easily caused, and the brittle temperature of the vulcanized product is increased. If the amount is less than 10 parts by weight, the tensile strength and modulus of the vulcanized product are undesirably reduced.

The particle size of the zinc powder used in the present invention is 20
Those that have passed 0 mesh are preferred. The amount of zinc powder added is 1 to 20 parts by weight per 100 parts by weight of the chloroprene rubber.
Part by weight is preferable, and 2 to 20 parts by weight is more preferable. 1
When the amount of zinc powder is less than the weight part, the heat resistance of the vulcanized product is not sufficiently improved, and when it is more than 20 parts by weight, the mechanical properties of the vulcanized product are deteriorated.

The vulcanizing agent used in the present invention is not particularly limited, but is preferably a metal oxide, specifically, zinc oxide,
Examples include magnesium oxide, lead oxide, trilead tetroxide, iron trioxide, titanium dioxide, calcium oxide and the like. These can be used in combination of two or more. The added amount of these vulcanizing agents is preferably 3 to 15 parts by weight based on 100 parts by weight of the chloroprene rubber. Further, the vulcanization can be more effectively performed by using in combination with the following vulcanization accelerator.

As the vulcanization accelerator, thiourea-based, guanidine-based, thiuram-based, thiazole-based, and triazine-based vulcanization accelerators generally used for vulcanization of chloroprene-based rubber can be used, but thiourea-based vulcanization accelerators are preferred. .
Examples of the thiourea-based vulcanization accelerator include ethylenethiourea, diethylthiourea, trimethylthiourea, triethylthiourea, and N, N'-diphenylthiourea, and trimerylthiourea is particularly preferred.
Also, a vulcanization accelerator such as a mixture of 3-methylthiazolidinethione-2 or thiadiazole and phenylenedimaleimide, dimethylammonium hydrogenisophthalate or a 1,2-dimercapto-1,3,4-thiadiazole derivative is used. Can be. These vulcanization accelerators may be used in combination of two or more of the above. Further, a peroxide vulcanizing agent can also be applied. The addition amount of these vulcanization accelerators is preferably 0.5 to 5 parts by weight based on 100 parts by weight of the chloroprene rubber.

Various additives such as a softener, a plasticizer, a processing aid, an antioxidant, a lubricant, a filler and the like can be incorporated into the rubber composition for an engine mount of the present invention, if necessary. .

As the antioxidant, general antioxidants such as amines, imidazoles, metal salts of carbamic acid, phenols and waxes can be used. As antioxidants having a large effect of improving heat resistance, 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 an engine mount of the present invention. The amount of the antioxidant added is 1 to 100 parts by weight of the chloroprene rubber.
10 parts by weight are preferred. The addition amount of 4,4′-bis (α, α-dimethylbenzyl) diphenylamine is preferably 1 to 10 parts by weight, more preferably 3 to 10 parts by weight, based on 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 vulcanized product is not sufficiently improved. Bis (α, α-dimethylbenzyl) diphenylamine is not preferred because it blooms on the surface of the vulcanizate. These antioxidants can be used alone or in combination.

Examples of the softener include petroleum softeners such as lubricating oil, process oil, paraffin, liquid paraffin, petrolatum, petroleum asphalt and the like, and vegetable oil softeners such as rapeseed oil, linseed oil, castor oil and coconut oil. Softeners can be used.

As the plasticizer, dioctyl phthalate,
General plasticizers such as dioctyl adipate can be used. Examples of the plasticizer that does not impair or improve the heat resistance of the rubber composition for an engine mount of the present invention include ether / thioether plasticizers, for example, Vulkanol OT (trade name, manufactured by Bayer AG), ester plasticizer. Ether-ester plasticizers such as Adekasizer RS-700, RS-73
5 (trade name, manufactured by Asahi Denka Kogyo KK) and the like. In particular,
Ether / thioether plasticizers are preferred because they have the effect of improving heat resistance and cold resistance, and have an excellent balance between the two. One or more of these plasticizers can be used in combination depending on the required properties.

The kneading method and the vulcanizing method of the rubber composition for an engine mount according to the present invention can use the methods commonly used in the rubber industry. Generally, the mixture is mixed by a kneading machine such as a kneader, a Banbury or a roll, and is molded into a shape suitable for the purpose to obtain a molded vulcanizate. Specifically, after each component is kneaded at a temperature equal to or lower than the vulcanization temperature, the kneaded product is formed into various shapes and vulcanized. The temperature and vulcanization time during vulcanization can be set as appropriate. The vulcanization temperature is preferably 140 to 190C,
150-180 ° C is more preferred.

The vulcanizate obtained from the chloroprene rubber composition of the present invention has excellent heat resistance and vibration-proofing properties in addition to the mechanical properties of the rubber, and is therefore suitable for automobiles that require heat resistance and vibration-proofing properties. Suitable for anti-vibration rubber, especially suitable for engine mounts with more severe heat resistance. An engine mount can be manufactured by a known method using the rubber composition for an engine mount of the present invention. The types of engine mounts are roughly classified into a compression type, a shear type, and an intermediate tilt type, and the rubber composition of the present invention can be applied to any type.

[0024]

EXAMPLES The present invention will be described in detail with reference to the following examples, but the present invention is not limited to the following examples. Examples 1 and 2, Comparative Examples 1 to 4 Kneading was carried out using an 8-inch roll according to the compounding recipe shown in Table 1 to produce a 2.3 mm thick sheet. This sheet was subjected to press vulcanization under the conditions of 150 ° C. × 20 minutes to produce 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.
Performed according to K6253. The compression set test was performed in accordance with JIS K6262. The evaluation of the vibration isolation characteristics is based on JIS K6394.
(29 mm diameter, 12.5 mm height). The dynamic magnification (Kd / Ks), which is an index of the vibration isolation characteristics, is calculated by the ratio of the dynamic spring constant (Kd) to the static spring constant (Ks). Second compression 4
% And the average stress in the outward path of 12%. The dynamic spring constant was determined under the conditions of an initial strain of 10%, a frequency of 100 Hz, and a dynamic strain of ± 0.4%. Heat resistance is JIS K
Using a test piece stored in a gear oven at 140 ° C. for 9 days in accordance with 6257, the hardness was measured by the above-mentioned measuring method, and the change in hardness was indicated.

The average stacking height Lc (nm) of the layer plane in the crystallite in the C-axis direction was calculated from the (002) diffraction line in the X-ray diffraction method using Cu-Kα ray according to the following equation. Lc = (180 · K · λ) / (π · β · COSΘ) K = shape factor (using 0.9) λ = wavelength of X-ray (0.154 nm) Θ = (002) in diffraction line absorption band Angle of maximum value β = (002) half-width in diffraction line absorption band expressed as angle

[0026]

[Table 1]

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 / 10) manufactured by Denki Kagaku Kogyo Co., Ltd.
0g) 3) Seat S (Lc = 1.
8 nm or less, DBP oil absorption = 68 ml / 100 g) 4) Asahi Thermal FT (Lc manufactured by Asahi Carbon Co., Ltd.)
= 1.8 nm or less, DBP oil absorption = 28 ml / 100
g) 5) Tokai Carbon Co., Ltd., Seast 3 (Lc = 1.
8 nm or less, DBP oil absorption = 101 ml / 100 g) 6) Bayer (Germany), ether / thioether plasticizer

[0028]

As shown in Table 1, the chloroprene rubber has an average stacking height L in the C-axis direction of the layer plane in the crystallite.
The rubber composition for an engine mount of the present invention, which contains carbon black having zinc of 2 nm or more and zinc powder, has excellent heat resistance, and further has excellent vibration isolation properties (low dynamic magnification) and low compression set. Provides a balanced vulcanizate and automotive engine mount.

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[Procedure amendment]

[Submission date] May 23, 2000 (2005.2
3)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 3/22 C08K 3/22 5/18 5/18 C09K 3/00 C09K 3/00 PF term (reference ) 3D035 CA04 4F070 AA09 AB09 AC04 AC06 AC13 AC14 AC15 AC46 AE01 AE03 AE08 GA08 GB09 GC01 4J002 AC091 AE032 DA036 DA107 DE089 DE099 DE109 DE119 DE139 EJ018 EN078 EU118 EV138 FD010 FD016 FD020 FD030 FD03 FD03FD

Claims (5)

[Claims] 1. A rubber composition for an engine mount, comprising: chloroprene-based rubber; carbon black having an average stacking height Lc of 2 nm or more in a C-axis direction of a layer plane in a crystallite; and zinc powder. 2. 100 parts by weight of chloroprene rubber, 10 to 70 parts by weight of carbon black and 1 part of zinc powder.
The rubber composition for an engine mount according to claim 1, wherein the rubber composition is blended in an amount of from 20 to 20 parts by weight. 3. An antiaging agent, 4,4'-bis (α, α
3. The rubber composition for an engine mount according to claim 1, comprising 1 to 10 parts by weight of (dimethylbenzyl) diphenylamine based on 100 parts by weight of the chloroprene rubber. 4. 4. A vulcanizate obtained by vulcanizing the rubber composition for an engine mount according to claim 1, 2 or 3. 5. An automotive engine mount, comprising the vulcanizate according to claim 4.