JP2003335900A - Rubber vibration isolator composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber vibration isolator composition containing a natural rubber as one of essential rubber components which simultaneously realizes thermal aging resistance and mechanical fatigue resistance sufficient for its application to automobile engine mounts, etc. <P>SOLUTION: The natural rubber containing ≤0.05 wt.% foreign matters prescribed in JIS K 6352 is used. As a vulcanizing agent, 0.4-1.5 pts.wt. sulfur is added to 100 pts.wt. rubber components comprising the natural rubber alone or a blend of the natural rubber and a butadiene rubber. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a vibration-proof rubber composition. In particular, the present invention relates to a rubber composition used for a vibration damping member for automobiles such as an engine mount for automobiles.

[0002]

2. Description of the Related Art In order to absorb vibrations of automobiles and vehicles and prevent noise, vibration-proof rubber is used for mount materials such as engine mounts, bush materials, damper materials and the like.

[0003] As a polymer material constituting an anti-vibration rubber for automobiles, a natural rubber (NR) or a blend of a natural rubber and another diene rubber such as a butadiene rubber (BR) is widely used. Styrene-butadiene rubber (SBR), chloroprene rubber (CR), and butyl rubber (IIR) are also used as rubbers to be blended with natural rubber.

Such a natural rubber type vibration damping rubber is suitable for realizing good vibration damping performance and resistance to repeated deformation due to the polymer nature and flexibility of natural rubber. . That is, natural rubber or a blend thereof is easily bent in a relatively high frequency range, is suitable for vibration damping and noise absorption, and has toughness that resists fatigue.

However, vibration-damping rubber for automobiles is required to have a high degree of fatigue resistance because it is subjected to severe repeated deformation over a long period of time. Therefore, it is common knowledge that in a vibration-damping rubber composition for automobiles, which is mainly composed of natural rubber, it is necessary to set the amount of sulfur added to be high and to increase the crosslinking density of the rubber polymer to some extent. There is. By increasing the crosslink density, it is necessary to reduce the effect when the rubber polymer chain is broken due to mechanical deformation.

That is, the amount of sulfur or sulfur donor added to 100 parts by weight of the diene rubber in the natural rubber vibration-damping rubber composition for automobiles is set to at least about 2 parts by weight in a usual system (for example, a special method). Kaihei 8-
269239, JP 2001-240702).

On the other hand, the anti-vibration rubber for automobiles is required to have sufficient supporting rigidity to ensure the steering stability of the automobile. Therefore, carbon black and other reinforcing fillers are added to the anti-vibration rubber composition to impart rubber hardness and supporting rigidity. That is, it is designed to satisfy the contradictory performances of the flexure during dynamic deformation and the supporting rigidity to some extent, and the balance of these required performances is the ratio of the dynamic spring constant to the static spring constant. It is expressed by a certain dynamic magnification. The lower the dynamic ratio,
It is preferable to satisfy both requirements.

In order to keep the dynamic ratio of the anti-vibration rubber low, it has been common knowledge that the amount of sulfur or sulfur donor added should be at least about 2 parts by weight based on 100 parts by weight of the diene rubber (for example, special characteristics). Kaihei 8-26923
9). When the amount of sulfur added is reduced, the rubber hardness decreases when the crosslink density is low.
It is necessary to add a larger amount of the reinforcing filler, and an increase in this reinforcing filler causes an increase in the dynamic ratio. As the amount of the reinforcing filler added increases, the interaction between the filler particles or the interaction between the filler particles and the rubber molecules increases,
Not only the damping coefficient in dynamic deformation but also the dynamic spring constant is significantly increased.

[0009]

However, when the amount of sulfur added is set to a high level, it is difficult to obtain the heat aging resistance required for a vibration proof rubber for automobiles that continues to receive heat from the engine and the like. There was a problem of becoming. In particular, in recent years, the temperature in the engine room tends to become higher due to higher output of the engine, etc., and the demand for heat aging resistance is becoming more severe. In some cases, 12
It is required to have heat aging resistance to withstand the conditions of continuing heating at around 0 ° C.

The inventors of the present invention have made extensive studies in view of the above-mentioned problems, and as a result, when the amount of sulfur added was set to a small amount that is advantageous for heat resistance, a specific natural rubber that has been conventionally used only for a special purpose. It has been found that the use of the above can sufficiently satisfy both the requirements of the mechanical performance and fatigue resistance required for the anti-vibration rubber and the heat aging resistance.

That is, the present invention can simultaneously realize sufficient heat aging resistance and sufficient mechanical fatigue resistance in the anti-vibration rubber composition containing natural rubber as one of the main rubber components.

[0012]

The vibration-proof rubber composition of the present invention has a sulfur content of 0.4 to 0.4 with respect to 100 parts by weight of a rubber component composed of a diene rubber containing 20% by weight or more of natural rubber.
A vibration-proof rubber composition comprising 1.5 parts by weight of:
The value of the amount of dust in the natural rubber specified in JIS K 6352 is 0.
It is characterized in that it is not more than 05% by weight.

The above-mentioned constitution provides a composition capable of simultaneously achieving sufficient heat aging resistance as an anti-vibration rubber for automobiles and sufficient mechanical fatigue resistance.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber component used in the anti-vibration rubber composition of the present invention comprises a diene rubber, and a natural rubber (NR)
20% by weight or more.

The natural rubber used in the anti-vibration rubber composition of the present invention has a dust amount value of 0.05% by weight specified in JIS K 6352.
The amount is preferably 0.04% by weight or less, more preferably 0.025% by weight or less. On the other hand, the average amount of dust of ribbed smoked sheets (RSS No. 1 to No. 6) used for ordinary rubber products is 0.08 to 2
% By weight. The effect of the present invention is observed for the first time when the amount of dust is in the range of 0.05% by weight or less.

It is considered that the amount of dust in the natural rubber is derived from fine sand, wood debris, etc. mixed in during rubber latex collection and other steps. The amount of garbage is 0.0
Examples of natural rubber products containing 5% by weight or less include those that have undergone strainer treatment with a metal mesh (JP-A-7-48405).

Other diene rubbers to be combined with natural rubber (NR) include isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SB).
R) and butyl rubber (IIR). A rubber blend in which a plurality of these are selected and combined may be used.

The content of natural rubber in the rubber component is preferably set so that the natural rubber forms a continuous phase in the rubber after vulcanization and curing. Therefore, it is generally preferable that the content of natural rubber in the rubber component is 50% by weight or more. A particularly preferred composition as the rubber component is natural rubber alone or a blend of natural rubber and butadiene rubber, which contains 50% by weight or more of natural rubber. However, even if the content of the natural rubber is less than this, if the natural rubber is contained in an amount of at least 20% by weight, more preferably 30% by weight or more, the island-like dispersed natural rubber phase may provide some effect. it can.

The anti-vibration rubber composition of the present invention may contain a relatively small amount of non-diene rubber in the rubber component.

In the anti-vibration rubber composition of the present invention, sulfur is added as a cross-linking agent for diene rubber in an amount of 0.4 to 1.5 parts by weight based on 100 parts by weight of the rubber component. If the amount of sulfur added exceeds 1.5 parts by weight, the heat aging resistance of the rubber obtained after vulcanization and curing becomes insufficient.

On the other hand, when the amount of sulfur added is less than 0.4 parts by weight, it is necessary to increase the amount of reinforcing filler such as carbon black added in order to obtain appropriate supporting rigidity. The dynamic spring constant and dynamic magnification (= dynamic spring constant ÷ static spring constant) in a relatively high frequency region become too large. That is, the anti-vibration performance in the high frequency region is deteriorated.

An appropriate amount of a rubber-reinforcing filler such as carbon black or silica is mixed with the anti-vibration rubber composition of the present invention so as to obtain an appropriate rubber hardness and a static spring constant.

The anti-vibration rubber composition of the present invention is mixed with various kinds of antioxidants, vulcanization accelerators, plasticizers, softeners and the like in appropriate amounts according to the required performance.

The above anti-vibration rubber composition is molded and vulcanized according to a conventional method to produce anti-vibration rubber products for various automobiles such as engine mounts, torsional dampers and strut mounts, and other vehicles. In some cases, anti-vibration rubber for ships or for bridges and other buildings,
It can also be used for seismic isolation rubber.

Examples of the present invention and comparative examples will be described below.

(Test Method) <Kneading> Kneading was carried out according to a general method using a Banbury mixer. Rubber component 1 consisting of various natural rubbers alone or a blend of the natural rubber and butadiene rubber
The following ingredients were sequentially added to 00 parts by weight in this order.

FEF grade (ASTM code N500) carbon black (CB): Amount added as shown in Tables 2 to 6 Aroma oil: 2.0 parts by weight Zinc oxide (ZnO): 5 parts by weight Stearic acid: 1 part by weight ・ Antiaging agent 6C (Ouchi Shinko Chemical Co., Ltd. 6C; N-phenyl-N'-dimethylbutyl-p-phenylenediamine): 2.0
Parts by weight ・ Antiaging agent RD (Sumitomo Chemical Antigen RD; poly (2,
2,4-trimethyl-1,2-di-hydroquinoline)): 2.0 parts by weight Sulfur: Addition amount shown in Tables 2 to 6 Vulcanization accelerator CZ (Sanshin Chemical Co., Ltd. Sanceller CZ) ; N
-Cyclohexyl-2-benzothiazolylsulfenamide): 2.2 parts by weight ・ Vulcanization accelerator D (1,3-diphenylguanidine): 0.3
Parts by weight The amount of dust (% by weight) of the used natural rubber sample is as follows. The amount of dust was determined according to JIS K 6352. The natural rubber of sample number NR-5 is almost equivalent to RSS # 3.

[0028]

[Table 1] Waste amount (% by weight) of natural rubber samples The butadiene rubber used for blending with natural rubber is
B of JSR Corporation with a 1,4 bond content of 96% or more
R01.

<Durability (Repetitive Deformation Resistance) Measurement> 1
A typical shape of strut mount (shown in JP 2001-240702 A) was prepared by vulcanization molding at 60 ° C. for 20 minutes by a conventional method. Then, using a commercially available vibration tester, a load of +8500 to -6900N was applied at 2 Hz at room temperature, and the number of vibrations until the strut mount was broken was measured.

<Measurement of Dynamic Magnification> A cylindrical test piece having a diameter of 8 mm and a height of 4 mm was prepared by vulcanization molding at 160 ° C. for 20 minutes, and a viscoelasticity measuring device (Rheograph Solid manufactured by Toyo Seiki Seisakusho Co., Ltd.) was used. Was used to measure the dynamic spring constant (Kd100) during compression at 100 Hz. In addition, the static spring constant (K
s) was measured and the dynamic magnification (Kd100 / Ks) was calculated. These measurements were performed according to JIS K 6385.

<Measurement of heat aging resistance> Tensile test pieces specified in JIS K 6301 were similarly prepared and subjected to 90 ° C. × 300 hr.
The tensile strength (TB ') after accelerated deterioration of was measured. Then, the retention rate (TB '/ TBo X 100) with respect to the tensile strength (TBo) before accelerated deterioration was obtained.

<Evaluation results> Tables 2 to 5 show the results obtained by the above-mentioned measurements of Examples and Comparative Examples.
In these tables, the evaluation results for durability and heat aging resistance are shown in Sample No. 4 of natural rubber (dust amount 0.073).
%) Is shown by an index value (percentage ratio) based on the result obtained as a percentage.

[0033]

Table 2 Examples and Comparative Examples (1) -Sulfur 0.5 phr

Table 3 Examples and comparative examples (2) -sulfur 1.3 phr As shown in Table 2 above, in Examples 1 and 2, excellent fatigue resistance was obtained even when the amount of sulfur added was set to a low value of 0.5 phr. When seen through Examples 1 and 2 and Comparative Examples 1 to 3, the fatigue resistance increases as the amount of dust in the natural rubber decreases, but especially when it increases significantly before and after 0.05% by weight. it was thought. It should be noted that the heat aging resistance and the dynamic magnification were not significantly affected by the amount of dust.

Further, as is known from the results of Table 2, when the amount of sulfur added is set to 1.3 phr, the same as in Table 1.
Fatigue resistance increases as the amount of garbage in
Especially, it is remarkably increased around 0.05% by weight. Further, as in Table 1, the heat aging resistance and the dynamic magnification were not significantly affected by the amount of dust.

On the other hand, as is known from the results of Table 4 below, when the amount of sulfur added was set to 2.0 phr, the fatigue resistance was sufficient but the heat aging resistance was considerably low.

Further, as is known from the results in Table 5 below, in Comparative Example 14 in which the amount of sulfur added was extremely small, the dynamic ratio exceeded 1.5, which was not preferable. It was considered that the amount of sulfur added should be 0.4 phr or more in order to satisfy the required performance of the anti-vibration rubber for automobiles.

[0037]

Table 4 Example and Comparative Example (3) -Sulfur 2.0 phr (Comparative Example only)

Table 5 Examples and Comparative Examples (4) -Influence of sulfur content Next, Table 6 shows the results obtained for the blends of natural rubber and butadiene rubber.

[0038]

Table 6 Examples and Comparative Examples (5) -Blends with BR As is known from the comparison between Example 5 and Comparative Example 11 and the comparison between Example 6 and Comparative Example 12 in Table 6 above, the amount of dust is small even when a blend with butadiene rubber is used. A remarkable effect was seen by selecting natural rubber. That is, the durability is improved by 10% or more. Regarding the heat aging resistance, no remarkable effect was observed as in the case of natural rubber alone.

The natural rubber content in the rubber component is 10
In Comparative Example 13 in which the content was wt%, the fatigue resistance was equivalent to that in Comparative Example 14, and the effect of using natural rubber with a small amount of dust was not observed. From the results of Table 6, it was considered that the content of natural rubber needs to be 20% by weight or more.

[0040]

The anti-vibration rubber composition containing natural rubber as one of the main rubber components can simultaneously achieve sufficient heat aging resistance and sufficient mechanical fatigue resistance.

Claims (3)

[Claims] 1. Sulfur is added to 100 parts by weight of a rubber component composed of a diene rubber and containing 20% by weight or more of natural rubber.
An anti-vibration rubber composition containing 4 to 1.5 parts by weight, wherein the natural rubber has a dust amount value of 0.05% by weight or less specified in JIS K 6352. Anti-vibration rubber composition. 2. The anti-vibration rubber composition according to claim 1, which has a kinetic magnification (Kd100 / Ks) specified by JIS K 6385 of 1.5 or less after vulcanization and curing. 3. The anti-vibration rubber composition according to claim 1, wherein the added amount of sulfur is 0.4 to 0.9 parts by weight with respect to 100 parts by weight of the rubber component.