JPH11116733A - Vibration-proof rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition excellent in vibration proofing performance, resistance to fatigue when subjected to repeated deformations, resistance to flatting under a long-term load, and heat stability by blending a specified rubber polymer component, two specified heat stabilizer compounds and sulfur under specified conditions. SOLUTION: The rubber polymer component comprises singly a butadiene rubber polymerized by using a neodymium catalyst and having a content of cis-1,4 linkages of at least 97%, or its blend with a natural rubber. The composition contains a compound (A) of formula I (wherein x is 0 to 2), a compound (B) of formula II and sulfur for vulcanizing the rubber. BR, the wt.% of butadiene rubber in the rubber polymer component, and a, b and s, which respectively stand for the pts.wt. of the compound A, the compound B and sulfur added based on 100 pts.wt. of the rubber polymer component, satisfy the relations of the formulas: 7<=(a+b+5×s)÷BR×100<=120; a+b<=10; s<=3.0; a, b>=0.5; 10<=BR; and 0.5<=a/b<=2.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for use in a vibration-proof rubber such as an engine mount for an automobile.
In particular, the present invention relates to a vibration damping rubber composition comprising a natural rubber or a diene rubber.

[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 mounts such as engine mounts, strut mounts, body mounts, dampers such as torsional dampers, and various bushes.

[0003] As a rubber polymer component composing the vibration isolating rubber, a diene rubber such as a natural rubber having a vibration isolating performance and a resistance to repeated deformation is generally used. After such a rubber polymer component is mixed with an appropriate filler, an oil agent and the like, it is vulcanized and molded.

[0004] In order to suppress the transmission of vibration and noise generated from the engine of an automobile or the like, the dynamic spring constant (storage spring constant) of the vibration-proof rubber in the frequency range of the vibration and noise is required.
If possible, it is desirable to reduce the value close to the value of the static spring constant. That is, it is required to sufficiently reduce the dynamic magnification (dynamic spring constant / static spring constant). Further, in order to maintain the vibration isolation performance, it is necessary to sufficiently reduce deformation over time (creep) when used under a load for a long time and residual deformation (sag) after release of the load. .

In order to respond to such a demand, Japanese Patent Application No. Hei 8-
In 187873, a rubber polymer component which is obtained by polymerization using a neodymium catalyst and contains 10 to 80% by weight of polybutadiene having a cis-1,4 bond content of 97% or more and the balance of natural rubber or the like is used. That was suggested. Thereby, the dynamic magnification and set were able to be reduced. However, the anti-vibration rubber composition disclosed in Japanese Patent Application No. 8-187873 was not sufficiently heat-resistant and, therefore, did not have sufficient reliability when used for a long period of time under the condition of being continuously heated.

In particular, anti-vibration rubbers for automobiles such as engine mounts are used under severe conditions where they are continuously heated.
Long-term durability and its reliability are required.

[0007] In Japanese Patent Application Laid-Open No. 3-14637, 2-
It has been proposed to use mercaptobenzimidazole in combination with a general amine-based heat stabilizer, and it has been shown that this can significantly improve the heat stability performance.

However, when 2-mercaptobenzimidazole is added to a diene rubber material, the scorch stability is extremely deteriorated, so that it is difficult to use it industrially. There was a problem that permanent deformation (set) was extremely large.

In general, when a heat stabilizer having an excellent effect on diene rubber is used, the resistance of the vibration-proof rubber to sagging is deteriorated. For this reason, it has been difficult to provide sufficient heat stability while maintaining the required vibration-proof properties and resistance to sagging.

On the other hand, as a rubber composition having excellent heat stability and necessary vibration damping properties, recently, Japanese Patent Application No. Hei 8-3238 has been proposed.
Forty-five are proposed. This is based on diene rubber such as natural rubber, zinc salt of 2-mercaptobenzimidazole or a methylated derivative thereof, and 4,4′-
Excellent heat stability by using a combination of bis (α, α'-dimethylbenzyl) diphenylamine and n-tert-butyl-di- (2-benzothiazolesulfenamide) at a specific blending ratio. Is given.

However, in the vibration-proof rubber composition of Japanese Patent Application No. 8-323845, reduction of set and creep is not always sufficient, and depending on the use form of the vibration-proof rubber, metal fittings of the vibration-proof rubber may interfere with each other. There was a risk of generating abnormal noise.

[0012]

SUMMARY OF THE INVENTION The above-described conventional vibration-insulating rubber composition cannot provide both resistance to sag and heat stability. For this reason, in recent years,
It has not always been possible to adequately respond to the demand for durability performance of anti-vibration rubber, which is becoming increasingly severe year by year due to intensifying competition between automobile manufacturers for performance.

In view of the above problems, the present invention is a composition which provides a vibration-proof rubber which is excellent in vibration-proofing performance, fatigue resistance to repeated deformation, and resistance to set-down due to long-term load, and is also excellent in heat stability. I will provide a.

In this specification, the terms heat deterioration and heat stabilizer include oxidative deterioration accelerated by heat and a stabilizer against heat deterioration, respectively.

[0015]

According to the first aspect of the present invention, there is provided an anti-vibration rubber composition having the following features (1) to (3).

(1) A blend of a natural rubber and a butadiene rubber having a cis-1,4 bond content of 97% or more, wherein the rubber polymer component is polymerized using a neodymium catalyst, or the butadiene rubber alone. (2) comprising a compound (A) represented by the following general formula (I), a compound (B) represented by the following chemical formula (II), and sulfur for vulcanizing rubber; ) 100 parts by weight of the rubber polymer component, the added parts by weight a, b and s of the compounds (A), (B) and sulfur, and the weight% BR of the butadiene rubber in the rubber polymer component are represented by the following formula ( i) to (v) are satisfied.

7 ≦ (a + b + 5 × s) ÷ BR × 100 ≦ 120 (i) a + b ≦ 10 (ii) s ≦ 3.0 (iii) a, b ≧ 0.5 (iv) 10 ≦ BR (v)

Embedded image The above configuration provides a vibration-proof rubber that is excellent in fatigue resistance against repeated deformation and resistance to sag due to long-term load, and excellent in heat stability.

In the vibration-damping rubber composition according to the second aspect, the compound (B) may be added in an amount by weight of the compound (A).
The ratio a / b to the added parts by weight satisfies the following expression (vi).

0.5 ≦ a / b ≦ 2.0 (vi) In the vibration damping rubber composition according to claim 3, the vibration damping rubber composition according to claim 1 is based on 100 parts by weight of diene rubber. The compounds (A), (B) and the added parts by weight a, b and s of sulfur and the weight% BR of the butadiene rubber in the rubber polymer component satisfy the following formula (vii). .

23 ≦ (a + b + 5 × s) ÷ BR × 100 ≦ 70 (vii)

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber polymer component used in the vibration-proof rubber composition of the present invention is polymerized using a neodymium catalyst.
Butadiene rubber having a cis-1,4 bond content of 97% or more, or a blend of this butadiene rubber and natural rubber.

When a conventional butadiene polymerization catalyst other than the neodymium catalyst is used, for example, a butadiene rubber polymerized using a cobalt catalyst or a nickel catalyst, cis-1,1 is used.
Even if the content of four bonds is 97% or more, a sufficient effect of reducing the dynamic magnification cannot be obtained.

The neodymium (Nd) -based catalyst is neodymium alone or a composite catalyst comprising neodymium and another metal. When a neodymium catalyst is used, the combination of the degree of branching of the rubber polymer, the molecular weight distribution, and the intramolecular distribution of the trans bond, etc., is suitable for reducing the dynamic spring constant of the vibration-isolating rubber and increasing the damping performance. It will be.

The polymerization of butadiene rubber is carried out by solution polymerization or emulsion polymerization, but more preferably by solution polymerization.

When the content of the cis-1,4 bond is less than 97%, even if a neodymium catalyst is used as a polymerization catalyst, a sufficient effect can be obtained in reducing the dynamic magnification and increasing the damping performance. Absent.

Here, the term natural rubber includes synthetic natural rubber (1,4-cis polyisoprene).

The content of butadiene rubber in the rubber polymer component consisting of butadiene rubber and natural rubber is 5 to 60.
%, Preferably 10 to 50% by weight, more preferably 15 to 30% by weight. In rubber blends,
It is preferable in terms of physical properties such as tensile properties that the butadiene rubber is finely dispersed in the form of islands in the continuous phase of natural rubber.

The rubber polymer component includes other diene rubbers,
For example, SBR may be mixed up to 30% by weight.

The heat stabilizer compound used in the rubber composition of the present invention is a compound (A) represented by the following general formula (I).
(A zinc salt of 2-mercaptobenzimidazole or a methylated derivative thereof) and a compound (B) (4,4′-bis (α, α′-dimethylbenzyl) diphenylamine) represented by the following chemical formula (II). is there.

[0030]

Embedded image The amount of addition of these stabilizer compounds is 100
With respect to parts by weight, the total added amount a + b is within the range of 10 parts by weight or less (that is, 10 phr or less), and the added amounts a and b of the stabilizer compounds A and B are at least 0.5 parts by weight. . If the total amount a + b exceeds 10 parts by weight, the processability is difficult because the Mooney scorch time becomes too short. The total added amount a + b is preferably 1 to 8 parts by weight, more preferably 2 to 4 parts by weight. When the amount of any of the stabilizer compounds A and B is 0.
If the amount is less than 5 parts by weight, the thermal stability becomes insufficient.

The ratio of the added amount a of the stabilizer compound A to the added amount b of the stabilizer compound B is 0.5 to 0.5.
2.0 is preferred, and around 1.0 is optimal. this is,
It appears to be related to the synergistic effect of stabilizer compound A and stabilizer compound B.

The rubber composition of the present invention also contains sulfur for vulcanization. Sulfur is a rubber polymer component 10
It is added so that the amount added to 0 parts by weight is 3.0 parts by weight or less. The preferred addition amount is 0.5 to 2 parts by weight, and the optimum addition amount is around 1.0 part by weight. If the added amount of sulfur is too small, vulcanization, that is, three-dimensional formation by crosslinking is not sufficient, and if the added amount of sulfur is too large, physical properties are impaired due to excessive crosslinking.

Each of the compounds (A) and (B) and sulfur are
Addition parts a and b based on 100 parts by weight of rubber polymer component
And s and the weight percent BR of the butadiene rubber in the rubber polymer component are added so as to satisfy the following formula (i).

7 ≦ (a + b + 5 × s) ÷ BR × 100 ≦ 120 (i) If the compounding property value represented by the formula (i) is less than 7, the initial mechanical properties before thermal deterioration are low. .

On the other hand, the blending characteristic value according to the equation (i) is 120
If it exceeds, the retention of the tensile strength and the retention of the elongation after the accelerated deterioration test are lowered, and the sag resistance is reduced. Therefore, when used for an engine mount or the like, the product life is shortened.

The compounding characteristic value according to the formula (i) is preferably 14 to 95, more preferably 23 to 70.

The best example of the formulation is as follows: 100 parts by weight of a rubber polymer component having a butadiene content of 30% by weight is
2 parts by weight of stabilizer compound A, 2 parts by weight of stabilizer compound B, and 1 part by weight of sulfur. With such a formulation, overall performance is optimal. At the time of this blending, the blending characteristic value is 30.

(Testing Method) <Kneading> Natural rubber (RSS # 3, ie, ribbed smoked sheet No. 3) and butadiene rubber (BUN manufactured by Bayer AG) were mixed on a mixing roll adjusted to a surface temperature of 50 ° C.
ACB22) and sufficiently mixed at a predetermined weight ratio. Thereafter, zinc salt of 2-mercaptobenzimidazole (stabilizer compound A, Ouchi Shinko Chemical Co., Ltd.) was used as a heat stabilizer with respect to 100 parts by weight of the blend rubber material.
1-5 parts by weight of Nocrack MBZ manufactured by Nissan Co., Ltd. and 1-5 parts by weight of 4,4′-bis (α, α′-dimethylbenzyl) diphenylamine (stabilizer compound B). Stabilizer compound B
In Examples, Nocrack CD manufactured by Ouchi Shinko Chemical Industry Co., Ltd. was used, and in Comparative Examples, Antigen FR manufactured by Sumitomo Chemical Co., Ltd. was used. Next, 30 parts by weight of FEF grade carbon black (CB) and zinc oxide (Zn)
O) 3 parts by weight, 2 parts by weight of stearic acid, 1 part by weight of microcrystalline wax, 2 parts by weight of Santocure TBSI manufactured by Flexis Corporation as a vulcanization accelerator, and 1 part by weight of Noxeller TS manufactured by Ouchi Shinko Chemical Industry Co., Ltd. ,as well as,
0.5 to 3.5 parts by weight of sulfur were sequentially added in this order.

<Mooney scorch time> With respect to the unvulcanized rubber after the completion of kneading, using SMV-200 manufactured by Shimadzu Corporation at 125 ° C. in accordance with JIS K 6300.
, The time (minute) until the viscosity increased from the minimum viscosity by 5 points (mooney unit) was measured.

<Tensile Test> The unvulcanized rubber after the completion of kneading was formed into a sheet with a roll, and heated at 150 ° C. for 30 minutes with a hot press to obtain a 2 mm thick vulcanized rubber sheet. A tensile test was performed on a test piece obtained by punching out this sheet with a No. 3 dumbbell using a strograph R manufactured by Toyo Seiki Seisaku-sho, Ltd. These were performed in accordance with JIS K6301.

<Accelerated Deterioration Test> A test specimen for a tensile test was left for 1000 hours in a thermostatic dryer adjusted to 90 ° C.
Thereafter, the tensile test was performed, and the retention (%) with respect to the value before the accelerated deterioration was calculated.

Further, the unvulcanized rubber after completion of kneading was compression-molded by a hot press at 150 ° C. for 30 minutes to form a cylindrical sample (diameter 29 m).
mx 12.7 mm in height), and after accelerated deterioration in the same manner as above, the compression set (%) was measured in accordance with JIS K6301.

<Engine Mount Product Creep Test> Using the unvulcanized rubber after the completion of kneading, a two-liquid chamber / one air chamber type engine mount shown in a longitudinal sectional view of FIG. 1 was prepared. Each rubber member was vulcanized by heating at 150 ° C. for 30 minutes. Here, the dimension between the upper and lower mounting brackets 11 and 13 of the engine mount is 140 mm, and the diameter of the main body rubber portion 2 at the upper end bent portion of the main body bracket 1 (the overhang portion 1 for the stopper).
b) is 150 mm. The thickness at the center of the rubber body 2 is 45 mm. FIG. 1 is drawn so that the dimensional relationship is accurate except for the thicknesses of the rubber film and the metal plate.

For such an engine mount, J
According to the heat aging test described in IS K 6385, 9
After a constant compression load of 5 kg was applied at 90 ° C. for 1000 hours, the amount of set (residual strain after creep and after release of load) was measured.

<Engine Mount Product Fatigue Resistance Test> The engine mount after the creep test described above was subjected to JI
Based on the constant load durability test described in SK 6385,
A sinusoidal tensile load in the range of 95 kg ± 95 kg was repeatedly applied at a cycle of 5 Hz, and the number of times to break was measured.

(Examples and Comparative Examples) The compounding of the vibration-proof rubber composition used in the test, and the physical properties and durability of the obtained vibration-proof rubber are summarized in Table 1. In particular, the weight percent BR of butadiene rubber in a rubber polymer component comprising a blend of natural rubber and butadiene rubber, and the added parts by weight a of the heat stabilizer compounds (A), (B) and sulfur with respect to the rubber polymer component, The relationship between the compounding characteristic value (a + b + 5 × s) ÷ BR × 100 and the durability of the vibration damping rubber when b and s are changed will be described.

[0047]

[Table 1] Endurance test results and blending characteristic values (a + b +) in Table 1 above
5 × s) ÷ BR × 100 is shown graphically in FIGS. 2 to 6 show the relationship between the tensile strength retention, the elongation retention, the compression set, the set after creep, and the fatigue resistance and the compounding property values, respectively.

In these figures, the outline plots correspond to the equations (ii) to (v) (a + b ≦ 10, s ≦
3.0, a, b ≧ 0.5, and 10 ≦ BR), and the filled plot is out of this range.

The durability test results shown in FIGS. 2 to 6 change uniformly with the increase of the above-mentioned compounding characteristic values, especially when the above-mentioned formulas (ii) to (v) are satisfied.
In the range markedly increased or decreased.

The retention ratio of the tensile strength shown in Table 1 and FIG. 2 is 56 to 63% in the region where the blending characteristic value is up to 100, but decreases to 50% at the blending characteristic value of 120, and further decreases. At 145, it has dropped to 42%.

The required values of the initial physical properties are a tensile strength of 17 MPa or more and an elongation of 400% or more. All of the examples and comparative examples shown in Table 1 satisfy the required values.

Similarly, the retention of elongation during the tensile test shown in Table 1 and FIG. 3 is 57 to 63% or more in the region where the compounding characteristic value is up to 100 (Examples 1 to 4). The characteristic value is reduced to 51% at the characteristic value 120 (Example 13), and further reduced to 41% at the compounding characteristic value 145 (Comparative Example 1).

The retention rate of tensile strength and the retention rate of elongation are currently required to be 50% or more, and those having a compounding characteristic value of up to about 120 can be used. The lower the blending property value, the higher these retention rates, but on the other hand, the tensile strength is somewhat reduced. Therefore, in consideration of the strength and elongation retention and the initial strength, Example 8 (with a compounding characteristic value of 30) is considered to be the most preferable.

The compression set shown in Table 1 and FIG. 4 is 38 to 44% in the region up to the blending characteristic value of 100, but becomes 45% at the blending characteristic value of 120. It has increased to 53%. The compression set is required to be 45% or less, and the one having a compounding characteristic value of up to 120 can be used.

In the set after creeping as shown in Table 1 and FIG.
Although it is 5.6 mm, it rises to 6.0 mm at the blending characteristic value 120, and further rises to 6.3 mm at the blending characteristic value 145. 5. For set after creep.
0 mm or less, and the blending characteristic value 1
Up to 30 can be used.

The number of repetitive deformations before fracture (index of fatigue resistance) shown in Table 1 and FIG. 6 is 215 to 2.3 million in the region where the compounding characteristic value is up to 100. 2 million times, and compounding property value 1
Forty-five, the number has dropped to 1.75 million times. The number of repetitive deformations before breaking is required to be 2,000,000 times or more, and those having a compounding characteristic value of up to 120 can be used.

As with the above-mentioned retention and compression set, fatigue resistance and sag resistance are better as the compounding property value is lower.

In consideration of the initial values of strength and elongation shown in the middle part of Table 1 and the durability performance shown in FIGS.
The one in Example 8 having a blending characteristic value of 30 can be said to be optimal. Therefore, the most preferable range of the compounding characteristic value is 2
It is considered to be about 3 to 70.

As described above, if the compounding property value is in an appropriate range, the vibration-proof rubber is excellent in fatigue resistance against repeated deformation, resistance against set-down due to long-term load, and excellent heat resistance stability. Is obtained.

[0060]

According to the present invention, an anti-vibration rubber having excellent resistance to fatigue due to repeated deformation and resistance to sag due to long-term load and excellent heat resistance stability is provided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an engine mount used for a creep test and a fatigue resistance test.

FIG. 2 shows the blending characteristic values ((a +
9 is a graph showing the relationship between (b + 5 × s) ÷ BR × 100) and the retention of tensile strength after the accelerated deterioration test.

FIG. 3 shows blending characteristic values ((a +
6 is a graph showing the relationship between (b + 5 × s) ÷ BR × 100) and the retention of tensile elongation after the accelerated deterioration test.

FIG. 4 shows blending characteristic values ((a +
9 is a graph showing the relationship between (b + 5 × s) ÷ BR × 100) and the compression set after the accelerated deterioration test.

FIG. 5 is a graph showing blending characteristic values ((a + b +) in Examples and Comparative Examples when the engine mount product of FIG. 1 was prepared.
5 is a graph showing the relationship between 5 × s) ÷ BR × 100) and set after a creep test.

FIG. 6 is a graph showing blending characteristic values ((a + b +) in Examples and Comparative Examples when the engine mount product of FIG. 1 was prepared.
5 is a graph showing the relationship between (5 × s) ÷ BR × 100) and the number of repetitive deformations leading to fracture.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Cylindrical main-body fitting 1a Projecting piece part of main-body fitting 1b Projecting part of main-body rubber part in which protruding piece part of main-body fitting is embedded 2 Main-body rubber part 2a Cylindrical rubber part connected to the inner periphery of main-body fitting 2b Seal rubber part Reference Signs List 3 Lower mounting bracket 4 Diaphragm made of rubber film 4a Ring-shaped auxiliary bracket for fastening buried in the periphery of diaphragm 4b Seal rubber section 5 Partition metal fitting also used as stopper 6,7 Filled liquid chamber 8 Air chamber 9 Filled liquid chamber 10 Mounting bolts for lower mounting brackets 11 Upper mounting brackets 12 Mounting bolts for upper mounting brackets 12a Anchor portions of upper mounting bolts 13 Stabilizers 13a, 13b made of substantially L-shaped metal plates Stabilizer stopper

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F16F 1/36 F16F 1/36 C

Claims (3)

[Claims] An anti-vibration rubber composition having the following features (1) to (3): (1) a rubber polymer component is polymerized using a neodymium-based catalyst, and is composed of a blend of butadiene rubber having a cis-1,4 bond content of 97% or more and natural rubber, or this butadiene rubber alone; (2) a compound (A) represented by the following general formula (I), a compound (B) represented by the following chemical formula (II), and sulfur for vulcanizing rubber; Addition parts by weight of each of the compounds (A), (B) and sulfur relative to 100 parts by weight of the molecular components a, b and s
And the weight% BR of the butadiene rubber in the rubber polymer component satisfies the following formulas (i) to (v). 7 ≦ (a + b + 5 × s) ÷ BR × 100 ≦ 120 (i) a + b ≦ 10 (ii) s ≦ 3.0 (iii) a, b ≧ 0.5 (iv) 10 ≦ BR (v) 2. The vibration damping rubber composition according to claim 1, wherein the ratio a / b of the added parts by weight of the compound (A) to the added parts by weight of the compound (B) satisfies the following formula (vi). An anti-vibration rubber composition comprising: 0.5 ≦ a / b ≦ 2.0 (vi) 3. The anti-vibration rubber composition according to claim 1, wherein the compounds (A), (B) and sulfur are added in parts by weight, a, b and s, based on 100 parts by weight of the diene rubber,
A vibration-proof rubber composition characterized in that the weight% BR of the butadiene rubber in the rubber polymer component satisfies the following formula (vii). 23 ≦ (a + b + 5 × s) ÷ BR × 100 ≦ 70 (vii)