JPH0150333B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a vibration-proof rubber composition with excellent vibration-absorbing properties and cold resistance. Generally, so-called anti-vibration rubber is used to prevent noise and vibration from transportation means such as automobiles and motorcycles, and industrial machinery. Properties required of anti-vibration rubber include vibration absorption properties and cold resistance. As for the vibration absorption characteristics, (1) it must be hard enough to support a large static load, (2) it must have a small external force transmission coefficient when receiving a dynamic load of 100 Hz or more, and (3) it must have a large loss tangent (tanδ). However, the static dynamic ratio (dynamic spring constant at 100 Hz/static shear modulus; E'100 Hz/Gs) is generally used as a parameter expressing both characteristics (1) and (2). It can be said that the smaller the static-dynamic ratio and the larger the loss tangent, the better the vibration damping characteristics. On the other hand, the temperature at which anti-vibration rubber can be used is expanding, and cold resistance is also a necessary characteristic for anti-vibration rubber. Cold resistance is evaluated, for example, at the temperature (T ₂ ) at which the specific modulus of the JISK6301 low-temperature torsion test is 2, and it can be said that the lower T ₂ is, the better the cold resistance is.
There are limits to how these relationships can be improved by compounding agents, and there has been a desire for the emergence of polymers that have both excellent anti-vibration properties and cold resistance. In order to reduce the static-dynamic ratio, the bound styrene content must be lowered and/
Alternatively, it is necessary to lower the 1.2 bond content of the butadiene moiety, but this also results in a decrease in the loss tangent, so there has been no polymer with a well-balanced static dynamic ratio and loss tangent. . Regarding cold resistance, it is desirable to lower the glass transition temperature, but in this case, the loss tangent becomes smaller, which is not preferable. An object of the present invention is to provide a vibration isolating rubber that has excellent vibration damping properties and excellent cold resistance by reducing the static-dynamic ratio and increasing the loss tangent. The present invention has a bound styrene content of 20 to 50% by weight, and a 1.2 bond content of the butadiene part of 20% or more.60
%, preferably from 30% to less than 60%, and whose glass transition temperature is -55°C or higher, in 100 parts by weight of the rubber component.
The present invention relates to a vibration-proof rubber composition containing at least part by weight. The copolymer rubber of the present invention can be obtained by anionic polymerization using, for example, styrene and butadiene as polymerization initiators, an organolithium compound (e.g., alkyllithium), and a Lewis base such as ether or tertiary amine as a cocatalyst. It will be done.
A solvent is used here if necessary. As the solvent, a solvent inert to the organic lithium compound is used, and toluene, benzene, cyclohexane, heptane, hexane, etc. are preferably used. Such polymerization method and conditions are described in detail in, for example, Japanese Patent Application No. 1983-
No. 162551 (filed on November 20, 1982). The microstructure of the above copolymer can be controlled by changing the type and amount of Lewis base or the polymerization temperature. If the content of bound styrene in the copolymer exceeds 50% by weight, or if the content of 1.2 bonds in the butadiene moiety exceeds 60%, the loss tangent will be large, but the static dynamic ratio will be large and the cold resistance will be poor. When the content of bound styrene is less than 20% by weight and the content of 1.2 bonds in the butadiene portion is less than 20%, the static-dynamic ratio is small, but the loss tangent is also small. If the glass transition temperature is lower than -55°C, the static-dynamic ratio and cold resistance are both good, but the loss tangent is also small, making it impossible to obtain a vibration-proof rubber composition with a well-balanced vibration-proofing property and cold resistance. According to the present invention, a rubber composition having excellent vibration damping properties can be obtained by controlling the bound styrene content, the 1.2 bond content of the butadiene moiety, and the glass transition temperature. By containing therein a polymer having a bond between at least one metal selected from silicon, germanium, and tin and carbon, even more excellent vibration damping properties can be obtained. The proportion is not particularly limited, but is preferably 20% by weight or more. At least one of silicon, germanium, and tin
A polymer having a bond with a species of carbon can be incorporated into the molecular main chain by, for example, a coupling reaction between a halide and the terminal end of a living polymer produced in anionic polymerization using the lithium catalyst. Examples of the halides include tin dichloride, silicon tetrachloride, silicon tetrabromide, tin tetrachloride, tin tetrabromide, and germanium tetrachloride. The styrene-butadiene copolymer rubber of the present invention can be used in combination with other rubbers, and examples of other rubbers include natural rubber and diene-based synthetic rubber. As the diene synthetic rubber, polyisoprene rubber, styrene-butadiene rubber and polybutadiene rubber are preferred. When used in combination with other rubbers, the proportion of the styrene-butadiene copolymer rubber of the present invention in 100 parts by weight of the rubber component is at least 30 parts by weight. If the styrene-butadiene copolymer rubber of the present invention is less than 30 parts by weight, vibration damping properties will not be sufficiently exhibited. The rubber composition of the present invention contains various softeners, plasticizers, and liquid polymers with a number average molecular weight of 2,000 to 100,000 (e.g., low molecular weight polybutadiene, low molecular weight polyisoprene; microstructure does not matter) to improve processability. Can be added.
In addition, it can be used as a vulcanized product containing known additives for various anti-vibration rubber applications. In the examples, the bound styrene content and the microstructure of the butadiene moiety are determined by infrared absorption method, and the content of polymer having metal and carbon bonds is determined by gel permeation chromatography (GPC). It is determined from the peak area on the high molecular weight side. In addition, the glass transition temperature was determined by the differential scanning calorimetry method under a heating rate of 20°C/min _.
was measured by JISK6301 low temperature torsion test, and Mooney viscosity was measured by JISK6300. Anti-vibration properties are based on static shear modulus according to JISK6301
Determine Gs and use a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. to determine the dynamic spring constant (E' ₁₀₀ Hz) and loss tangent at 100 Hz, and calculate the static dynamic ratio (E' ₁₀₀ Hz/
Gs) was calculated and evaluated based on the static-dynamic ratio and the magnitude of the loss tangent. Next, the present invention will be explained in more detail with reference to the following examples and comparative examples. Examples 1 to 8 and Comparative Examples 1 to 6: Styrene of Examples 1 to 5 and Comparative Examples 3 to 6
The butadiene copolymer rubber was obtained under the polymerization conditions shown in Table 1 using a nitrogen-substituted autoclave. Polymers A to G were polymerized without removing the heat of reaction, and polymers H and I were polymerized at constant temperature. For Polymers E and F, after confirming the polymerization conversion rate of 100%, add 5g of butadiene.
and then 0.2 g tin tetrachloride/10 c.c. cyclohexane. After 30 minutes, 5 ml of a methanol solution containing 3 g of 2,4-di-t-butylcatechol was added to stop the reaction. Polymers A to D and G to H
2, immediately after confirming the polymerization conversion rate is 100%.
A solution of 3 g of 4-di-t-butylcatechol in 5 ml of methanol was added to stop the reaction. After desolvation,
A polymer was obtained by drying with a roll at 100°C. Examples 1 to 6 and Comparative Examples 1 to 6 were kneaded using a plastomill and a 6-inch roll machine according to the formulations shown in Table 2 and Examples 7 and 8 in Table 3. Natural rubber is press vulcanized at 150℃ for 10 minutes, others are vulcanized at 150℃ for 30 minutes.
The physical properties of the vulcanized rubber obtained by press vulcanization were measured and the results are shown in Table 4.

[Table] Table-2 Formulation table (parts by weight) Polymer 100 FEF carbon 30 Zinc white 5 Stearic acid 1 Vulcanization accelerator CZ ^* 2 Sulfur 2 *Cyclohexyl-benzothiazolesulfenamide Table-3 Formulation table (parts by weight) Polymer 100 FEF carbon 30 Plasticizer or liquid polymer 10 Zinc white 5 Stearic acid 1 Vulcanization accelerator CZ 2 Sulfur 2

【table】

【table】

[Table] From the results shown in Table 4, the styrene-butadiene copolymer rubber of the present invention has a higher static dynamic ratio, loss tangent, and It can be seen that a vibration-proof rubber composition with excellent balance of cold resistance is provided.

Claims (1)

[Claims] 1. The bound styrene content is 20 to 50% by weight, the 1.2 bond content of the butadiene moiety is 20% or more and less than 60%,
Styrene-butadiene copolymer rubber with a glass transition temperature of -55℃ or higher is added to 100 parts by weight of the rubber component.
A vibration-proof rubber composition characterized by containing 30 parts by weight or more. 2 The 1.2 bond content of the butadiene moiety is 30% or more,
The anti-vibration rubber composition according to claim 1, characterized in that the anti-vibration rubber composition is less than 60%. 3. Claim 1, wherein the styrene-butadiene copolymer rubber contains at least 20% by weight of a copolymer having in its molecular chain a bond between at least one metal selected from silicon, germanium, and tin and carbon. Or the anti-vibration rubber composition according to item 2.