JPH0819274B2 - Rubber composition for anti-vibration rubber - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rubber composition for vibration isolating rubber, which can be preferably used as a vibration isolating rubber material for engine mounts of automobiles.

[Prior Art] In this type of rubber composition, a filler such as carbon black is blended in order to secure the strength required as a vibration-proof rubber material, and hardness, tensile strength, elongation, tear strength Such physical properties are adjusted.

[Problems to be Solved by the Invention] In recent years, the properties required of a vibration-proof rubber have become extremely strict, and the dynamic properties have been improved, particularly the static-dynamic ratio (dynamic elastic modulus / static elastic modulus is expressed. Reduction) is an important issue. If the static-dynamic ratio is high, the vibration suppressing effect in the high frequency range is reduced, which causes a muffled noise in the vehicle.

In the rubber composition containing carbon black,
It is known that the properties of the carbon black used have a great influence on the properties of the rubber compound, and for example, the use of carbon black having a small iodine adsorption amount can reduce the static-dynamic ratio.

On the other hand, from the standpoint of supporting oscillators such as engines,
It is required to secure a certain degree of static elastic modulus. However, in the conventional compounding, there is a problem that the static elastic modulus is lowered although the static-dynamic ratio is reduced, and it is desired to develop a vibration-proof rubber material satisfying these two characteristics at the same time.

Therefore, an object of the present invention is to provide a rubber composition for a vibration-proof rubber having a low static-dynamic ratio and having a static elastic modulus sufficient for supporting a vibrating body.

[Means for Solving the Problems] The inventors of the present invention have conducted diligent studies in view of the above-mentioned circumstances, and in a raw rubber, an iodine adsorption amount of 10 to 40 mg / g as a filler, a dibutyl phthalate (DBP) oil absorption amount (method A). 100-500ml / 100g
It has been found that a rubber composition obtained by blending carbon black having the above characteristics and vulcanizing it has excellent characteristics as a vibration damping rubber material.

In the present invention, as the raw rubber, for example, natural rubber (NR) or styrene-butadiene rubber (SBR),
Various synthetic rubbers such as butadiene rubber (BR), butyl rubber (IIR) and chloroprene rubber (CR) can be mentioned.

The carbon black blended with the raw rubber has an iodine adsorption of 10 to 40 mg / g and a DBP oil absorption (method A) of 100 to 500 ml / 10.
It is important to be in the range of 0g. When the iodine adsorption amount or DBP oil absorption amount is less than the above range, the static elastic modulus does not improve, and it becomes necessary to increase the amount of carbon black compounded in order to secure the desired static elastic modulus. Sex decreases. Also, fatigue resistance is low. Iodine adsorption capacity is 40
If it is more than mg / g, the effect of reducing the static-dynamic ratio cannot be obtained, and
It is not known at present that the DBP oil absorption (method A) exceeds 500 ml / 100 g.

The blending amount of carbon black varies depending on its use and required properties, but is usually preferably in the range of 10 to 50 parts by weight with respect to 100 parts by weight of the raw rubber.
Generally, since the static elastic modulus and the static-dynamic ratio increase in proportion to the compounding amount, the amount may be appropriately selected within the above range according to the required characteristics. When the amount is less than 10 parts by weight, sufficient strength cannot be obtained, and when the amount is more than 50 parts by weight, the Mooney viscosity increases and the workability decreases.

In the present invention, carbon black having the above-mentioned properties is blended with a commonly used vulcanizing agent in a raw material rubber, and kneading, molding and vulcanization are carried out by a usual method to obtain a product. The rubber composition of the present invention may be added with other compounding agents such as an antioxidant and a vulcanization accelerator.

[Examples] Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples unless the gist thereof is exceeded.

Example 1 A rubber composition having the composition shown in Table 1 below was vulcanized at 160 ° C. for 10 minutes to prepare a test piece, and its vibration characteristics were evaluated.

Carbon black is SRF-HS, Seast S-VHS
(Iodine adsorption amount 30mg / g, DBP oil absorption amount (method A) 137ml / 100g;
Using Tokai Carbon Co., Ltd., trade name, the compounding amount is 10,
The static shear modulus and static-dynamic ratio were measured at 30 and 50 parts by weight. The measuring method was as follows.

Static shear modulus Gs: Gs = 1.639 × 25% Shear modulus of elongation stress Static-dynamic ratio E'100Hz (± 0.5%) / Es: Equipment viscoelastic spectrometer (Iwamoto Manufacturing) Conditions Elongation method 10% static strain, The results of ± 0.5% dynamic strain are shown in Table 2 together with the normal physical properties.

For comparison, the type of carbon black is MA
F (SEAST 116; Tokai Carbon Co., Ltd., trade name), acetylene black (Tenka Black; Denki Kagaku Co., Ltd., trade name), SRF (SEAST S; Tokai Carbon Co., Ltd. trade name) A similar test was performed for the changed case. The results are shown in Table 2 as Comparative Examples 1 to 3, respectively.

Further, for these examples and comparative examples, graphs were prepared by plotting the static shear modulus on the horizontal axis and the static-dynamic ratio on the vertical axis.
As shown in the figure. In addition, in FIG. 1, as Comparative Example 4, Ketjen Black (iodine adsorption amount 850 mg / g, DBP oil absorption amount (A
Method) 350 ml / 100 g) as Comparative Example 5 (thermal absorption (iodine adsorption amount 27 mg / g, DBP oil absorption amount (method A) 28 ml / 100 g))
The case is also described.

As is clear from FIG. 1, when carbon black having a low iodine adsorption amount is used, the static-dynamic ratio is reduced, but when the DBP oil supply amount does not reach the range of the present invention (Comparative Examples 3 and 5), normal carbon is used. Sufficient static shear modulus cannot be obtained with the amount of black used. For example, when applied to an engine mount, it is generally desirable that the static shear elastic modulus is about 8 to 15 kg / cm ^2, but the rubber composition of the present invention retains a sufficient static shear elastic modulus, and It can be seen that the static-dynamic ratio in this range is remarkably reduced as compared with the conventional one.

Next, the elongation fatigue life was measured for each of the formulations of Example 1 and Comparative Examples 1 to 3, and the results are shown in Table 3.
The test method was as follows.

Elongation fatigue life: Sample; No. 3 dumbbell Strain condition; Strain rate between 20 mm marked lines Excitation frequency; 5 Hz Atmosphere temperature; Room temperature Figure 2 shows the relationship between elongation fatigue life and static shear modulus in a graph. As is clear from the figure, the rubber composition of the present invention exhibits elongation fatigue life at the same level as that of the conventional one,
It can be seen that both vibration characteristics and fatigue resistance are excellent. In the case of Comparative Example 3, the elongation fatigue life decreases as the static shear elastic modulus increases.

EFFECTS OF THE INVENTION According to the present invention, it is possible to obtain a well-balanced rubber composition having a low static-dynamic ratio and a sufficient static elastic modulus. Therefore, the vibration damping property in the high frequency range is improved, and the excellent effect in supporting the vibrating body can be exhibited, and it is useful as a vibration damping rubber material such as engine mount.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between static shear modulus and static-dynamic ratio in the examples of the present application, and FIG. 2 is a diagram showing the relationship between extension fatigue life and static shear modulus.

Claims (1)

[Claims] 1. A raw material rubber, as a filler, having an iodine adsorption amount of 10 to 40 mg / g and a dibutyl phthalate oil absorption amount (method A) of 100.
Blended with carbon black having the characteristics of ~ 500ml / 100g,
A rubber composition for anti-vibration rubber obtained by vulcanization.