JP3395139B2 - Anti-vibration rubber composition - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition mainly used for vibration-proof rubber, and more particularly, it is used for engine mounts, muffler hangers, dampers and the like where the environment temperature is high. It relates to an anti-vibration rubber composition.

[0002]

2. Description of the Related Art Various types of anti-vibration rubber have been used in vehicles as measures against vibration, but in recent years the required characteristics have become more sophisticated. However, a rubber mainly composed of natural rubber (hereinafter referred to as NR) has been used as a vibration isolating rubber since it has excellent vibration isolating performance. However, NR rubber basically lacks heat resistance, and in order to improve it, a method of changing the vulcanization system from sulfur to EV is known. But,
Even with this method, the heat resistance is limited, and the recent severe performance requirement level has not been reached.

Further, ethylene propylene polymer is added to NR.
(Refers to EPM and EPDM, and these are collectively referred to as E
A compounding method in which a small amount of (PR) is added and sulfur is vulcanized has also been proposed, but this is intended to improve the ozone resistance of NR, and NR is the main component, and the vulcanization system is sulfur. Therefore, the heat resistance was also limited.

Among rubber materials other than NR, EPR is excellent in heat resistance and has a track record of being used in parts used in a high temperature environment. For example, this rubber is a muffler
It is applied to hangers, and in order to ensure durability, it is particularly desired that the EPR has a high molecular weight. However, as the molecular weight of this EPR increases, the workability of the rubber decreases remarkably. Therefore, a large amount of oil, carbon black or the like is added to ensure the workability. Here, considering the application as a vibration-proof rubber, since the vibration transmissibility is proportional to the dynamic ratio (= dynamic elastic modulus / static elastic modulus), the compounding amount of carbon should be reduced as much as possible to lower the dynamic ratio. There is a need. However, in the past, it was very difficult to reduce the dynamic magnification because a large amount of carbon was added in order to secure workability.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to an anti-vibration rubber composition containing a high molecular weight EPR as a main component, and it is an anti-vibration rubber composition used particularly at high temperature without impairing processability. Its purpose is to provide things.

[0006]

In order to achieve the above object, the present invention adopts the following characteristic constitution. That is, the gist of the present invention is to use an ethylene propylene-based polymer as a main component, to which natural rubber and carbon black are blended, and to use a peroxide as a crosslinking agent,
An anti-vibration rubber composition having excellent heat resistance, wherein, when the total amount of the polymer is 100 parts, less than 50 parts of natural rubber is added to 50 parts or more of ethylene propylene polymer,
Further, carbon black (part number A) as a reinforcing agent, A ≦
An anti-vibration rubber composition characterized by using only the number of parts calculated by 0.4X + 30 (X is the number of parts of ethylene propylene polymer) and setting the dynamic modulus (= dynamic elastic modulus / static elastic modulus) to 2 or less. It depends on things. And, it is preferable that the ethylene-propylene polymer has a weight average molecular weight of 300,000 or more.

[0007]

The function of the present invention is, as a result of many years of research, high molecular weight EPR.
A system with a small amount of NR added to the
A low filling composition of bon is possible without impairing processability,
Based on the finding that the dynamic ratio, which is important as an anti-vibration rubber, can be remarkably reduced, and because it is crosslinked with peroxide, it has excellent heat resistance, it has high heat resistance, low dynamic ratio, and high durability. It is a compounded product.

In the rubber vibration proof rubber made of EPR type polymer, in order to lower the dynamic ratio and enhance the vibration proof performance, the amount of carbon black must be reduced as compared with the conventional rubber. Workability is reduced. Since the EPR polymer having a higher molecular weight has better durability,
High molecular weight is desirable, but high molecular weight E
It is known that PR has poor workability. E like this
In the PR type polymer, when the amount of carbon black is reduced as described above, there is a big drawback that the workability is extremely poor and mass production is difficult.

According to the present invention, in such an EPR polymer, by blending NR with this EPR polymer, it is possible to suppress deterioration of processability and to reduce the amount of carbon black blended as compared with the prior art. It is a thing. In this case, NR is a high molecular weight EPR polymer with poor processability.
On the other hand, it has the effect of improving the processability, and the amount of such NR may be small, but preferably 10 parts or more.

By increasing the blending amount of NR (Y) and the blending amount of EPR (X), the blending amount of carbon can be further reduced, so that the dynamic magnification can be lowered.
However, since NR contains a double structure in the main chain, it is inferior to EPR in heat resistance. Therefore, N
The compounding amount of R is preferably smaller than that of EPR, and X + Y = 100 parts and Y <50 parts are preferable ranges.

On the other hand, in the vulcanization (crosslinking) system, a peroxide system having a better heat resistance is preferable to a sulfur system.
In the present invention, the crosslinking with the peroxide can minimize the decrease in heat resistance due to the incorporation of NR.

From the viewpoint of workability, when the NR is small, the amount of carbon can be increased, and when the amount of NR is large, the amount of carbon can be decreased. (A) becomes such that A ≦ 0.4X + 30 (part).
If the amount of carbon (A) exceeds this amount, the dynamic magnification becomes large and the vibration damping performance becomes insufficient.

As described above, the composition of the present invention is one in which heat resistance, vibration resistance and durability are balanced in a high degree and workability is ensured.

[0014]

EXAMPLES Hereinafter, the characteristics of the rubber composition of the present invention will be described in more detail based on examples. Here, all the EPDMs used in Examples and Comparative Examples in Tables 1 to 4 are JSR
T7501EF (40 parts oil-extended) manufactured by K.K., and the compounding number is the number of only the polymer component and does not include the amount of oil-extended oil. Moreover, NR is all RSSI of HADI BARU (Indonesia), and the oil amount is EPDM.
It is the sum of the amount of oil-extended oil corresponding to the number of copies and the amount of SUNPER2280 of SUN OIL. Furthermore, all carbon black (FEF) is Asahi Carbon's Asahi # 60.
And, Perhexin 25B ・ 40 is Nippon Oil's Perhexin 25B ・ 40, ZA is Kawaguchi Chemical Industry's ACTOR.
ZA and sulfur are Z sulfur from Tsurumi Chemical, and polyethylene glycol dimethacrylate is Acryester 4ED from Mitsubishi Rayon. Next, Hd in Table 1 and Table 2 is
Hardness (degree) based on hardness test (JIS K 6301, JIS A), and T _B is tensile test (JIS K 6301).
301) by tensile strength (kg / cm ^2), elongation (% by E _B is the tensile test (JIS K 6301)), △ H
d is hardness change (degree) by air heating aging test (JIS K 6301, aging condition: 120 ° C., 96 hours), ΔT
_B is the rate of change in tensile strength (%) by the same air heating aging test as ΔHd, and ΔE _B is the rate of elongation change (%) by the same air heating aging test as ΔHd. The dynamic characteristics are based on the Toyo Seiki Rheolograph (25 ° C., 15 Hz, extension rate 15%, amplitude 0.2%, test piece size: 2 × 5 × 30 mm), and Es is the static elastic modulus (kg / cm). ² ), Ed15Hz ・ 0.
2% is dynamic elastic modulus (kg / cm ² ), Ed15Hz ・ 0.2% / E
s is a dynamic magnification (dimensionless). In addition, repeated stretching is
Dumbbell-shaped test pieces (DIN53504) at room temperature
The test of 200% elongation was repeated, and the number of repetitions until breakage was measured. The workability was determined by kneading with a roll (diameter 20 cm), and the surface condition of the rubber wrapped around the roll after 5 minutes from the start of kneading. Was evaluated, and ◯ was evaluated as a substantially smooth state, and Δ was evaluated as a state with many holes. Ks in Tables 3 to 4 are static spring constants (kg / mm) in Shimadzu autograph (room temperature), Kd ₁₀₀ is Washimiya dynamic spring tester (room temperature, 100 Hz), Kd ₁₀₀ / K.
s is a dynamic magnification (dimensionless), durability is room temperature under durable vibration conditions, 0 ± 10 mm, breaking life at 2 Hz (10,000 times), durable breaking life is durable vibration conditions at room temperature, 0 ± 20
mm is the breaking life (10,000 times) at 3 Hz. (Examples 1 and 2 and Comparative Examples 1 to 3) Table 1 shows the formulations of Examples 1 and 2 based on the rubber composition of the present invention and Comparative Examples 1 to 3, and the properties of the obtained rubbers are the same. Are shown in Table 1.

[0015]

[Table 1]

In order to apply it to the anti-vibration rubber, it is necessary that the dynamic magnification = dynamic elastic modulus / static elastic modulus = Ed15 Hz · 0.2% / Es (hereinafter referred to as dynamic magnification) is 2 or less, Comparative Example 3 which is a blending system clears this, but Comparative Example 1 and Comparative Example 2 cannot clear this. Further, in terms of heat resistance, it is necessary that the elongation reduction rate after heat aging at 120 ° C. × 96 hours is 30% or less.

Comparative Example 1 is based on high molecular weight EPDM. Further, in Comparative Example 2, EPDM was added in a small amount in order to improve the ozone resistance of NR, and this has a large dynamic ratio and insufficient heat resistance. Furthermore, Comparative Example 3 is an NR type compound, and although it is satisfactory in terms of dynamic magnification, it has the drawback of poor heat resistance. Although Comparative Example 1 is superior in heat resistance to Comparative Example 3, it has a drawback that the dynamic magnification is large.

In Example 1, the high molecular weight EP
It is a mixture of DM with 30 parts of NR, has substantially the same dynamic characteristics as the NR-based comparative example 3, and is at a level applicable to anti-vibration rubber such as engine mounts. The rubber obtained in Example 1 has good heat resistance and durability.

In Example 2, 30 parts by weight of NR was mixed with high molecular weight EPDM, and a small amount of carbon black was added,
This is the case of crosslinking with a peroxide. This is the NR of Comparative Example 3.
It can be seen that the dynamic characteristics and heat resistance are significantly improved compared to the system.

In the low-filling compounding system as in Comparative Examples 1 and 2, workability was greatly reduced, workability was poor, and mass production was very difficult, but in Examples 1 and 2, workability was also good. It turned out to be

(Examples 3 to 5 and Comparative Example 4) Table 2 shows the main formulations of Comparative Example 4 and Examples 3 to 5 according to the present invention and their characteristics.

[0022]

[Table 2]

Comparative Example 4 has a high molecular weight EPDM and an NR of 10
It is a mixture in which a large amount of carbon black is added. With regard to the characteristics of this rubber, the dynamic magnification exceeds the above-mentioned target value, and is insufficient in terms of vibration isolation performance.

In contrast, Example 3 is a low-filling composition in which 40 parts of NR is mixed with high-molecular-weight EPDM and a small amount of carbon black is added, and the dynamic magnification has cleared the target value,
This can be applied to anti-vibration rubber. Also, the reduction rate of elongation after heat aging has reached the above-mentioned target value, and the heat resistance is also good.

In Examples 4 and 5, high molecular weight EPDM and NR
40 parts and 10 parts respectively, and a low-filling composition in which a small amount of carbon black was added. The dynamic characteristics were equal to or higher than those of Comparative Example 3 of NR type, and the heat resistance and durability were You can see that it is significantly superior.

From the above results, it can be seen that by blending EPDM with NR of less than 50 parts, the workability can be significantly improved while maintaining the heat resistance of EPDM.

Conventionally, a large amount of carbon black has been added in order to ensure processability, but in the present invention, a low filling composition is possible by compounding NR. And
In order to achieve antivibration performance that can be applied to antivibration rubber, it is desirable to reduce the amount (A) of carbon black added as much as possible from the above examples, and the above formula A ≦ 0.4x + 30. It can be seen that the range defined by (x is the number of EPDM copies) is good.

(Product Test 1) The rubber compositions having the compositions of Examples 1 and 2 and Comparative Examples 1 and 3 were applied to a muffler hanger. The muffler hanger has a structure as shown in FIG. 1, and is composed entirely of a rubber elastic body 1 and has an H-shaped curls 2
The upper hole 3 is used to hang the muffler, and the lower hole 4 is used to hang the muffler. Each muffler obtained
Table 3 shows the product performance of the hangers.

[0029]

[Table 3]

The product of Comparative Example 1 has good durability after heat aging but is inferior in dynamic characteristics. The product of Comparative Example 3 having only NR has good dynamic characteristics but inferior heat resistance. You can see that On the other hand, the products based on Examples 1 and 2 according to the present invention have good dynamic characteristics and durability, and are found to be optimal for this product.

(Product Test 2) Example 2 and Comparative Example 1,
A rubber composition having the composition of 3 was applied to an engine mount. The structure of the engine mount is as shown in FIG. 2, which is a structure in which a rubber elastic body 7 is bridged between an inner cylinder 5 and an outer cylinder 6, and curls 8 and 9 are formed vertically. . The obtained product performance is shown in Table 4.

[0032]

[Table 4]

Comparative Example 1 in which the polymer is EPDM only
It can be seen that in Comparative Example 3, the dynamic ratio is large and the anti-vibration performance is inferior, while in NR type Comparative Example 3, the durability life after thermal deterioration is low and the heat resistance is inferior. However, it can be seen that the engine mount according to the first embodiment of the present invention has extremely good dynamic characteristics, initial durability, and durability after thermal deterioration.

[0034]

INDUSTRIAL APPLICABILITY As described above, the present invention provides an anti-vibration rubber composition containing EPDM as a main component, which is excellent not only in heat resistance and durability but also in workability in producing a product thereof. The rubber composition provides a rubber composition and has an extremely high industrial utility value.

[Brief description of drawings]

FIG. 1 is a front view of a muffler hanger used for a product test.

FIG. 2 is a front view of an engine mount used for a product test.

[Explanation of symbols]

1 ... rubber elastic body, 2 ... 3 ... the upper hole, 4 ... the lower hole, 5: Inner cylinder, 6 ... Outer cylinder, 7. Rubber elastic body, 8, 9, ...

Claims (2)

(57) [Claims] 1. An anti-vibration rubber composition having an ethylene propylene polymer as a main component, which is blended with natural rubber and carbon black and which uses a peroxide as a cross-linking agent and which has excellent heat resistance, When the total amount of the polymer is 100 parts, less than 50 parts of natural rubber is blended with 50 parts or more of ethylene-propylene polymer, and carbon black (part A) is used as a reinforcing agent, A ≦ 0.4X + 30.
(X is the number of parts of ethylene propylene-based polymer), and a dynamic elastic modulus (= dynamic elastic modulus / static elastic modulus) of 2 or less is used, and a vibration-proof rubber composition is used. 2. The anti-vibration rubber composition according to claim 1, wherein the ethylene-propylene polymer has a weight average molecular weight of 300,000 or more.