JPH0797483A - Rubber vibration insulator composition - Google Patents

Abstract

PURPOSE:To obtain a rubber vibration insulator compsn. improved not only in reversion and thermal permanent set but also in flowability in an unvulcanized state. CONSTITUTION:100 pts.wt. rubber comprising natural rubber or a mixed rubber of natural rubber with a synthetic rubber is blended with 0.1-20 pts.wt. org. unsatd. fatty acid having at least 2 carbon-carbon double bonds in the molecule thereof and contg. at least 5wt.% conjugated dienoic acid having at least 1 set of at least 2 conjugated carbon-carbon double bonds in the molecule thereof.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a vibration-proof rubber composition suitable for a vibration-proof rubber.

[0002]

2. Description of the Related Art Conventionally, anti-vibration rubber has been used to prevent vibration and noise, and anti-vibration effects have been achieved in various places. When a rubber material used for a vibration-proof rubber, especially a vibration-proof rubber for suspension, is required to have excellent fatigue resistance and a small dynamic ratio (dynamic elastic modulus / static elastic modulus ratio). There are many.

In order to improve fatigue resistance, the polymer used is selected from natural rubber (NR) or a blend system of natural rubber and styrene-butadiene rubber (SBR), butadiene rubber (BR), etc., and the vulcanization system is sulfur. Generally, a relatively large amount is used. Further, in order to reduce the dynamic ratio, it is common to increase the crosslink density and reduce the addition amount of the softening agent. As described above, as the rubber material of the conventional anti-vibration rubber, the polymer is a natural rubber type, and the vulcanization type is a composition in which the amount of sulfur is relatively large to increase the crosslink density and the addition of the softening agent is small. Things are used as a selective method.

However, in the case of the anti-vibration rubber composition in which the amount of sulfur is increased to increase the crosslink density, reversion of vulcanization (overcuring lowers the crosslink density and lowers the hardness) increases. A problem occurs in that the settling due to heat (hereinafter, referred to as “heat settling property”) becomes large. That is, when the vulcanization reversion is large, the degree of vulcanization of the product is slightly changed, so that the spring constant of the product is largely changed, which makes it difficult to manufacture a product having a small variation in the spring constant. In addition, since the environment in which the anti-vibration rubber is used is in a much higher temperature environment, heat-induced fatigue is likely to occur. When this heat sag is increased, the function of the vibration-proof rubber as a support is lost.

Further, in the case of the anti-vibration rubber composition in which the addition amount of the softening agent is reduced, the fluidity of the unvulcanized rubber is deteriorated,
In particular, in the case of blending a high amount of a reinforcing agent such as carbon black, there is a problem in workability. Therefore, a processability improver such as a metal salt of an unsaturated fatty acid may be blended, but in that case, the rubber physical properties are deteriorated, that is, the hardness is decreased and the dynamic ratio is increased. Causes a problem.

[0006]

DISCLOSURE OF THE INVENTION The object of the present invention is to provide a problem in the compounding of a vibration isolating rubber which has been generally used in the past, particularly in the case of compounding an antivibration rubber for suspensions, that is, revulcanization, To provide a vibration-insulating rubber composition capable of improving thermal fatigue resistance, maintaining or improving fatigue strength and dynamic ratio, and also improving fluidity in an unvulcanized rubber stage. It is in.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a specific organic compound is not used for a rubber made of natural rubber or a mixed rubber of natural rubber and synthetic rubber. By blending a specific amount of saturated fatty acid, the above-mentioned object of the anti-vibration rubber composition was successfully obtained, and the present invention was completed. That is, the anti-vibration rubber composition of the present invention contains at least one set of two or more carbon-carbon double bonds in a conjugated relationship with 100 parts by weight of a rubber composed of natural rubber or a mixed rubber of natural rubber and synthetic rubber. An organic unsaturated fatty acid containing 2 or more carbon-carbon double bonds in the molecule containing 5% by weight or more of a conjugated dienoic acid containing 0.1 to 2 in the molecule
It is characterized by containing 0 part by weight.

[0008]

The present invention provides an unprecedented anti-vibration rubber composition because the organic unsaturated fatty acid having the above-mentioned properties functions as a compounding agent for a new anti-vibration rubber having various effects. . That is, the present invention is an organic unsaturated fatty acid having the above-mentioned properties, combined with the polymer through sulfur, etc., without deteriorating the physical properties of the anti-vibration rubber such as fatigue resistance and dynamic power, and in other crosslinking reactions. Since it works as a reaction aid, reversion of vulcanization and heat settling property are improved.
In addition, since the organic unsaturated fatty acid having the above properties acts as an internal lubricant when not vulcanized, the fluidity is improved. further,
The improvement in reversion and vulcanization due to heat will be more effective in the compounding with a high sulfur content (these points will be described in detail in Examples and the like).

The contents of the present invention will be described below. Examples of the rubber used in the anti-vibration rubber composition of the present invention include rubber made of natural rubber (NR) or a mixed rubber of natural rubber and synthetic rubber. Examples of the synthetic rubber include various synthetic rubbers that are usually used as a vibration-proof rubber. For example, butadiene rubber (BR) and synthetic isoprene rubber (I
R), styrene-butadiene rubber (SBR) and the like. Two or more kinds of synthetic rubber may be used at the same time.

The organic unsaturated fatty acid used in the present invention contains 5% by weight or more of conjugated dienoic acid containing at least one set of two or more carbon-carbon double bonds in a conjugated relationship in the molecule. It is composed of an organic unsaturated fatty acid containing two or more double bonds. In the organic unsaturated fatty acid used in the present invention, the “conjugated dienoic acid” refers to an organic unsaturated monocarboxylic acid containing at least one pair of carbon-carbon double bonds having a conjugated relationship in its molecule, and the conjugated relationship It is preferable that the carbon-carbon double bond in 1 is one pair, but there may be two or more pairs. The organic unsaturated fatty acid containing two or more carbon-carbon double bonds in the molecule containing 5% by weight or more of the conjugated dienoic acid (hereinafter, simply referred to as “organic unsaturated fatty acid”) naturally contains the conjugated dienoic acid, Other organic unsaturated fatty acids contain two or more carbon-carbon double bonds, but differ in that they are in a non-conjugated relationship with each other.

The content of the conjugated dienoic acid in the organic unsaturated fatty acid needs to be 5% by weight or more, preferably 20% by weight or more, and 100% by weight, that is, the organic unsaturated fatty acid is all conjugated dienoic acid. It may be. If the content of the conjugated dienoic acid is less than 5% by weight, the effect of the present invention cannot be sufficiently exhibited. Further, when the content of the conjugated dienoic acid is 20% by weight or more, the effect of the present invention can be further improved.

Examples of the conjugated dienoic acid include 2,4-
Pentadienoic acid, 2,4-hexadienoic acid, 2,4-decadienoic acid, 2,4-dodecadienoic acid, 9,11-octadecadienoic acid, α-eriostearic acid, 9,11,
13,15-octadecatetraenoic acid, 9,11,13
-Octadecatrienoic acid and the like.

Preferred examples of the organic unsaturated fatty acid used in the present invention include dehydrated castor oil fatty acid. This dehydrated castor oil fatty acid is obtained by dehydrating castor oil. The content of the conjugated dienoic acid can be changed depending on the dehydration method, and for example, 35% by weight and 60% by weight can be obtained. In the case of this dehydrated castor oil fatty acid, the conjugated dienoic acid is mainly 9,11-octadecadienoic acid, and other organic unsaturated fatty acids mainly include non-conjugated octadecadienoic acid, and other ricinoleic acid,
Linoleic acid, linoleic acid and the like are also included. Further, in addition to the organic unsaturated fatty acid used in the present invention, conventionally used fatty acids represented by stearic acid may be used in combination.

The compounding amount of the organic unsaturated fatty acid used in the present invention is 0.1 to 20 parts by weight, preferably 0.5 to 100 parts by weight of rubber composed of natural rubber or a mixed rubber of natural rubber and synthetic rubber. It is necessary to mix 10 to 10 parts by weight. The amount of the organic unsaturated fatty acid used in the present invention is 0.
If it is less than 1 part by weight, the effect of the present invention cannot be exhibited, and
Even if the amount is more than 20 parts by weight, the effect of the present invention does not change so much and the effect over the compounding cost is not exhibited.

In the present invention, the improvement of reversion to vulcanization and the heat settling property are more effectively exhibited by the compounding with high sulfur content. The content of sulfur in this case is 1.5 to 5 parts by weight, preferably 1.8 to 4 parts by weight, relative to 100 parts by weight of the rubber.
Parts by weight.

In the present invention, in addition to the above-mentioned rubber and organic unsaturated fatty acid, it is usually used as a compounding agent for anti-vibration rubber, for example, a reinforcing agent, a softening agent, an antiaging agent, a vulcanization accelerator, Vulcanization accelerating aids, dispersants, processing aids and the like can be added as appropriate.

[0017]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

(Blanks 1-2, Examples 1-5, Comparative Examples 1-3) Vibration-proof rubber compositions were prepared according to the blending compositions (blending units: parts by weight) shown in Tables 1 and 2 below. The Mooney viscosity (ML _{1 + 4} ) of the anti-vibration rubber composition, the dynamic ratio (Ed / Es) of the rubber after vulcanization of the rubber composition, the fatigue resistance, the thermal fatigue resistance, and the hardness were measured. It shows in Table 1 and Table 2. Mooney viscosity (ML _{1 + 4} ), dynamic magnification (Ed / E)
s), fatigue resistance, thermal fatigue resistance, and hardness were measured by the following methods.

(1) Mooney viscosity (ML _{1 + 4} ) It was measured at 130 ° C. using a Mooney viscometer manufactured by Shimadzu Corporation. The test method is based on JIS K6300 and ML.
_{1 + 4} (after 1 minute preheating, Mooney value after 4 minutes of operation) was determined. The smaller the value, the better the fluidity of the unvulcanized rubber. (2) Dynamic Magnification The dynamic magnification was calculated from Ed (dynamic elastic modulus) / Es (static elastic modulus). The smaller the value of the dynamic magnification, the better. In addition, Ed and Es are as follows. Ed: Calculated from the stress when a sinusoidal amplitude of ± 0.2% and a frequency of 15 Hz was applied in a stretched state of 15%. Es: Calculated from the stress when stretched by 15%.

(3) Fatigue The anti-vibration rubber fitting 1 (material: SPCC-SD) shown in FIG.
Adhesion treatment [blast treatment, undercoat as adhesive: Chemlok 205, overcoating: Chemloc 220 [all manufactured by Lord Co.]] was performed, and each shape rubber composition was used to provide a standard shape anti-vibration rubber A (length 40 mm, diameter). 36 mm) was vulcanized. The fatigue test was carried out in a normal temperature atmosphere using a hydraulic anti-vibration rubber fatigue tester. The initial strain was not given, and the cyclic strain was tested at a constant shear strain of ± 50% at 3 Hz, and the number of repetitions (times) until abnormalities such as rubber cracks occurred was determined. The larger the number of repetitions (times),
Shows good fatigue.

(4) Thermal sag property The test method was conducted at 100 ° C. for 22 hours in accordance with JIS K6301 (compression set). The smaller the number,
It shows that the heat settling property is good. (5) Hardness The test method was based on JIS K6301 (hardness). The measurement sample has two levels of vulcanization time (160 ° C x 10 minutes, 1
It was vulcanized at 60 ° C. for 30 minutes. The hardness is for evaluating reversion, and the smaller the difference between the hardness of the 10-minute vulcanized product and the hardness of the 30-minute vulcanized product, the better the vulcanization reversion.

[0022]

[Table 1]

[Discussion of Table 1] In Examples 1 to 4, organic unsaturated fatty acids (dehydrated castor oil fatty acids) were varied. It was found that these improve vulcanization reversion and heat settling property, and improve the fluidity (Moonie viscosity) of the unvulcanized rubber. Further, it was found that the fatigue property was similar to that of the blank 1, and the dynamic magnification was maintained or improved.
On the other hand, Comparative Examples 1 to 3 are examples in which no organic unsaturated fatty acid (dehydrated castor oil fatty acid) is used. In Comparative Example 1, the amount of the vulcanization accelerator was increased instead of increasing the amount of sulfur in order to improve the crosslink density, and although the reversion and heat settability were slightly improved, the fatigue property was deteriorated. understood. In Comparative Example 2, NR / BR / LIR is 60 /
It was set to 35/5, and it was found that the fluidity of the unvulcanized rubber was only slightly improved and the thermal fatigue resistance and fatigue resistance were deteriorated. In Comparative Example 3, a processability improver was added, and although the thermal fatigue resistance and the fluidity of the unvulcanized rubber were slightly improved, it was found that the fatigue property was deteriorated and the dynamic ratio was also increased. . According to the results of Examples 1 to 4 and Comparative Examples 1 to 3 described above, by using the organic unsaturated fatty acid of the present invention, the fatigue resistance required for the anti-vibration rubber for suspension and the like is excellent, and It has been found that the characteristics of low dynamic ratio are maintained or improved, and reversion to vulcanization and heat settling, which have been problems so far, and fluidity of unvulcanized rubber are improved.

[0024]

[Table 2]

[Discussion of Table 2] Table 2 evaluates the effect of the organic unsaturated fatty acid (dehydrated castor oil fatty acid) in the composition further filled with sulfur. That is, Example 5
Is a mixture of an organic unsaturated fatty acid (dehydrated castor oil fatty acid) and a high sulfur content (3 parts by weight), and it has been found that even a high sulfur content improves vulcanization reversion and heat settling properties. . Further, from the comparison with blank 1 / Example 3 in Table 1, it was found that the improvement of reversion to vulcanization and heat settling effect is more significant in the high sulfur content.

[0026]

EFFECTS OF THE INVENTION According to the present invention, there is provided a vibration-insulating rubber composition capable of improving reversion and vulcanization of heat and improving fluidity when unvulcanized. Further, in the present invention, reversion to vulcanization and heat settling property are more effectively exhibited by the compounding with high sulfur content.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a standard shape vibration-proof rubber used in a fatigue test.

[Explanation of symbols]

 A Standard shape anti-vibration rubber 1 Anti-vibration rubber bracket

Claims (1)

[Claims] 1. A conjugated diene containing in the molecule at least one set of two or more carbon-carbon double bonds in a conjugated relationship with 100 parts by weight of a rubber composed of natural rubber or a mixed rubber of natural rubber and synthetic rubber. Organic unsaturated fatty acid containing 2 or more carbon-carbon double bonds in the molecule containing 5% by weight or more of acid 0.1-
An anti-vibration rubber composition containing 20 parts by weight.