JPH07173336A - Rubber composition for heat-resistant vibration-proof rubber and vulcanized rubber - Google Patents

Abstract

PURPOSE:To obtain a rubber composition, excellent in roll processability and capable of providing vulcanized rubber for heat-resistant and vibration-proof rubber having good fatigue resistance. CONSTITUTION:This composition is an ethylene.alpha-olefin.nonconjugated diene copolymer rubber which contains 90-60wt.% of a high-molecular weight copolymer consisting of an ethylene.alpha-olefin.-nonconjugated diene copolymer and having >=3dl/g of intrinsic viscosity [eta] measured in xylene at 70 deg.C and a low molecular weight copolymer consisting of an ethylene.alpha-olefin.-nonconjugated diene copolymer having 0.7-1dl/g of intrinsic viscosity [eta] measured in xylene at 70 deg.C. In the rubber composition, the low molecular weight copolymer has >=3 of a ratio of a low molecular weight component concentration [L] to a high molecular weight component concentration [H] obtained by a GPC measuring method, namely, the rubber composition has a bi-modal molecular-weight distribution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for heat and vibration resistant rubber, and more specifically, it provides a vulcanized rubber for heat and vibration resistant rubber having good fatigue resistance and excellent roll processability. The present invention relates to a rubber composition.

[0002]

2. Description of the Related Art Anti-vibration rubbers widely used in the automobile field and the like are required to have excellent properties such as fatigue resistance, heat resistance, dynamic ratio, tensile strength and tear strength. To be done.

When a low unsaturation rubber such as ethylene / α-olefin / non-conjugated diene copolymer rubber (hereinafter sometimes simply referred to as EPDM) is used as the rubber material,
Although an anti-vibration rubber having excellent heat resistance can be obtained, it has a drawback of being inferior in fatigue resistance when an external force is repeatedly applied for a long period of time. Use of a high molecular weight EPDM (usually having an intrinsic viscosity [η] of 2.5 dl / g or more measured in xylene at 70 ° C.) eliminates this drawback, and the higher the molecular weight, the more remarkable the effect of improving fatigue resistance becomes. It is generally known that However, increasing the molecular weight has a limit in terms of processability before vulcanization, and when the molecular weight is excessively high, a problem such as so-called bagging in which the rubber composition floats from the roll surface during roll processing occurs. Occurs.

[0004] Attempts have been made so far to achieve both the processability before vulcanization and the excellent anti-vibration rubber properties of vulcanized rubber. For example, JP-A-53-22551 discloses that if a high molecular weight EPDM is blended with a low molecular weight EPDM, the processability is improved. Further, this low molecular weight EPDM acts as a processing aid in an unvulcanized state, and after vulcanization. Is disclosed to contribute to the improvement of dynamic fatigue resistance.

However, with the recent high performance of automobiles, vibration-proof rubber materials are required to have a lower dynamic ratio and a higher durability, and in order to meet these requirements, softening agents and carbon black are used. With the vibration-proof rubber compounding in which the addition amount is more severely limited, satisfactory roll processability cannot be obtained only by conventional techniques.

Under such circumstances, the present inventors have provided a vulcanized rubber for heat-resistant and vibration-proof rubber having good fatigue resistance, and
As a result of diligently studying a rubber composition having excellent processability, a high-molecular weight copolymer having a specific intrinsic viscosity and a low-molecular weight copolymer having a specific intrinsic viscosity and a concentration ratio of molecular weight components have a constant weight. The rubber composition contained in a ratio is excellent in roll processability, and a vulcanized rubber obtained by vulcanizing such a rubber composition with an organic peroxide is excellent in fatigue resistance and the like. Then, the present invention was completed.

[0007]

That is, the present invention provides 70
A high molecular weight copolymer consisting of an ethylene / α-olefin / non-conjugated diene copolymer having an intrinsic viscosity [η] of 3 dl / g or more measured in xylene at 90 ° C: 90 to 60% by weight;
The intrinsic viscosity [η] measured in 70 ° C xylene is 0.7-
Low molecular weight copolymer consisting of ethylene / α-olefin / non-conjugated diene copolymer of 1 dl / g: 10-40% by weight ethylene / α-olefin / non-conjugated diene copolymer rubber composition In the product, the ratio of the low molecular weight component concentration [L] and the high molecular weight component concentration [H] ([L] /
The present invention provides a rubber composition having a bimodal molecular weight distribution of [H]) of 3 or more, and a vulcanized rubber obtained by vulcanizing the organic peroxide with an organic peroxide. The present invention will be described in detail below.

In the present invention, an ethylene / α-olefin / non-conjugated diene copolymer is used as the rubber material from the viewpoint of heat resistance of the vulcanized rubber. Examples of the α-olefin include propylene, 1-butene, and 1-hexene, and examples of the non-conjugated diene include 1,4-pentadiene, 1,4-hexadiene, divinylbenzene, dicyclopentadiene, methylenenorbornene, and ethylidene. Examples thereof include norbornene (hereinafter abbreviated as ENB) and vinyl norbornene.

The ethylene / α-olefin / non-conjugated diene copolymer in the present invention means a high molecular weight copolymer having a specific intrinsic viscosity described below and a low molecular weight having a specific intrinsic viscosity and a molecular weight component concentration ratio. Refers to a copolymer.

The high molecular weight copolymer used in the present invention is
The intrinsic viscosity [η] measured in xylene at 70 ° C is 3 dl /
It is an ethylene / α-olefin / non-conjugated diene copolymer of g or more, in which [η] is 3 to 5 dl / g, and particularly preferably 3.3 to 5 dl / g. The ethylene / α-olefin ratio (molar ratio) of the copolymer is usually 60/40 to 80/20, preferably 60/40 to 72/28, from the viewpoint of the temperature dependence of the dynamic ratio. The amount of the non-conjugated diene component in the copolymer is usually 0.5 to 3 mol% based on the heat resistance of the vulcanized rubber and the anti-vibration rubber property of all the monomers constituting the copolymer. Is preferred.

The low molecular weight copolymer used in the present invention is
From the viewpoint of the processability of the rubber composition and the heat resistance and fatigue resistance of the vulcanized rubber, the ethylene / α-olefin having an intrinsic viscosity [η] of 0.7 to 1 dl / g measured in xylene at 70 ° C.
It is a non-conjugated diene copolymer, of which [η] is 0.8 to 0.
It is preferably 9 dl / g. From the viewpoint of processability of the rubber composition, the content of ethylene component of the low molecular weight copolymer is
It is preferably in the range of 70 to 85 mol%.

The low molecular weight copolymer in the present invention is GP
It is necessary that the ratio ([L] / [H]) of the low molecular weight component concentration [L] and the high molecular weight component concentration [H] obtained by the C measurement method is 3 or more. That is, it is a characteristic of the low molecular weight copolymer of the present invention that it has a bimodal molecular weight distribution and that it has a remarkably large amount of low molecular weight components. When the [L] / [H] of the low molecular weight copolymer is less than 3, the roll processability is not significantly improved.

GPC means gel permeation chromatography (gel permeation chromatography).
Is. The measurement of GPC is performed according to "Gel Permeation Chromaography" published by Takeuchi, Maruzen Co., Ltd. The calibration curve uses standard polystyrene and is prepared by a conventional method. In the GPC chart of the copolymer obtained by this GPC measurement method, the horizontal axis is the logarithm of the polystyrene equivalent molecular chain length, and the vertical axis is the relative concentration of the copolymer having each molecular chain length. is there.

In the low molecular weight copolymer of the present invention, the low molecular weight component means a component having a polystyrene reduced molecular chain length logarithm of 3 or less, and the high molecular weight component has a polystyrene reduced molecular chain length logarithm of 4. A component of 25 or more.
From the GPC chart obtained by the measurement, the total relative concentration of the low molecular weight component (low molecular weight component concentration) [L] and the relative concentration of the high molecular weight component (high molecular weight component concentration) [H] are obtained.

In the ethylene / α-olefin / non-conjugated diene copolymer consisting of the above-mentioned high molecular weight copolymer and low molecular weight copolymer, the high molecular weight copolymer is 90 to 60% by weight, preferably 80 to It is present in a proportion of 60% by weight and the low molecular weight copolymer is present in an amount of 10-40% by weight, preferably 20%.
Present in a proportion of ˜40% by weight. 1 low molecular weight copolymer
If it is less than 0% by weight, the processability of the rubber composition will not be improved, and if the amount of the high molecular weight copolymer is less than 60% by weight, the fatigue resistance of the vulcanized rubber will be low.

Since the rubber composition according to the present invention contains a low molecular weight copolymer as a component, it is excellent in processability.
To further improve this point, it is also possible to add an extender oil to the high molecular weight copolymer and use it as an oil extended high molecular weight copolymer. Paraffin-based process oil or the like is used as the extender oil, and the amount of the extender oil used is based on the dynamic ratio of the vulcanized rubber.
It is usually 50 parts by weight or less, preferably 10 to 40 parts by weight, per 100 parts by weight of the high molecular weight copolymer.

On the other hand, in order to improve the static properties of the vulcanized rubber, the vulcanized rubber may contain carbon black as a reinforcing filler, the content of which may vary depending on the dynamic ratio. It is usually 50 parts by weight or less, preferably 10 to 50 parts by weight, per 100 parts by weight of the polymer rubber.

In order to obtain a vulcanized rubber excellent in dynamic ratio,
It is important that the rubber composition be organic peroxide vulcanized. Examples of the organic peroxide as a vulcanizing agent include dicumyl peroxide, di-tert-butyl peroxide, tert-butyl cumyl peroxide, 1,1-di- (tert-butylperoxy) -3,3,5-trimethylcyclohexane. , Benzoyl peroxide, lauroyl peroxide, and the like, which are selected in consideration of the compounding of the vulcanizing agent, the temperature during vulcanization, and the like. The amount of the organic peroxide used is the copolymer rubber 1
The amount is usually 0.5 to 10 parts by weight, preferably 2 to 5 parts by weight, based on 00 parts by weight. Also, a small amount of sulfur may be used to improve the dynamic properties of the vulcanized rubber.

The vulcanized rubber may contain additives usually used in rubber applications such as zinc oxide, stearic acid, softening agents, antioxidants, antioxidants, processing aids and vulcanization aids. Examples of the vulcanization aid include sulfur, p-quinonedioxime, p, p-dibenzoylquinonedioxime, ethylene glycol dimethacrylate, triallyl isocyanurate and the like. Further, for the purpose of adjusting the adhesiveness and the like, a small amount of a rubber component other than the ethylene / α-olefin / non-conjugated diene copolymer such as natural rubber or styrene / butadiene rubber may be contained.

The vulcanized rubber of the present invention can be used as a softener, carbon black, organic peroxide in a copolymer rubber under ordinary conditions by using an apparatus used in the production of ordinary rubber products such as Banbury mixer and open roll. It can be produced by compounding the above materials and then vulcanizing them under normal conditions with an apparatus usually used for organic peroxide vulcanization of rubber such as an injection molding machine and a press.

[0021]

The rubber composition according to the present invention contains a high molecular weight copolymer having a specific intrinsic viscosity and a low molecular weight copolymer having a specific intrinsic viscosity and a concentration ratio of molecular weight components in a constant weight ratio. It has excellent roll processability, and since such a rubber composition is vulcanized with an organic peroxide to give a vulcanized rubber with good fatigue resistance, such a vulcanized rubber is used for heat-resistant and vibration-proof rubber. It is useful as rubber. Specifically, anti-vibration rubber for automobiles such as engine mounts, strut mounts, suspension bushes, exhaust mounts,
It is suitable for use as anti-vibration rubber in railway vehicles, construction vehicles, industrial equipment, office automation equipment, and the like.

[0022]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

Table 1 shows the structures of the ethylene / propylene / ENB copolymers used in the following Comparative Examples and Examples.

The Q value in Table 1 is the weight average molecular weight [Mw] and number average molecular weight [Mn] determined by the GPC measurement method.
And is represented by Q = [Mw] / [Mn]. The larger the Q value, the wider the molecular weight distribution, and the better the processability in general.

The GPC measurement conditions are as follows. Apparatus: Waters 150C type column: Showa Denko KK Shodex 80
MA sample amount: 300 μl (polymer concentration: 0.2% by weight) Flow rate: 1 ml / min Temperature: 135 ° C. Solvent: Trichlorobenzene The calibration curve was prepared by a standard method using standard polystyrene manufactured by Tosoh Corporation. The measurement data was processed using a data processor CP-8 Model II manufactured by Tosoh Corporation.

Comparative Example 1 A BR type Banbury mixer having a volume of 1.7 liters was added to an oil-extended high molecular weight copolymer HEP- (high molecular weight copolymer HEP-shown in Table 1 in xylene at 70 ° C.). The measured intrinsic viscosity [η] is 3.3 dl / g and the ethylene ratio is 70
Molybdenum ML _{1 + 4} 121 ° C = 100 parts by weight of ethylene / propylene / ENB copolymer rubber having an ENB ratio of 1.2% by mole and 40 parts by weight of paraffin-based process oil. 96 parts), MAF carbon black 50 parts by weight, zinc oxide 5 parts by weight, stearic acid 1 part by weight and antioxidant 1 part by weight were added and kneaded to obtain a rubber composition.

The rubber composition was transferred to a 10-inti-pun roll having a roll temperature of 60 ° C. and kneaded to measure the minimum value of the roll gap at which bagging occurs and observe the condition of the sheet skin. did. The results are shown in Table-2. Regarding the minimum value of the roll gap, the larger the value, the less likely bagging occurs. As for the condition of the skin of the sheet, those that are smooth and have no perforations are marked with "○",
Those that were not smooth but had holes were indicated by "x". The results are shown in Table-3.

After the roll temperature was lowered to 40 ° C., 4 parts by weight of organic peroxide and 0.3% of sulfur were added to the rubber composition.
A vulcanizable rubber composition was prepared by blending parts by weight and kneading.

The vulcanizable rubber composition was heat-pressed to 17
It was heated at 0 ° C. for 20 minutes to prepare a vulcanized rubber sheet having a thickness of 2 mm. Regarding the vulcanized rubber sheet, JIS-K63
The tensile test was performed according to 01. Further, the fatigue resistance was measured. The results are shown in Table-3.

The tensile strength and elongation at break are measured according to JIS K63.
According to No. 01, it measured using the JIS-3 dumbbell test piece. The hardness was measured using a spring type hardness tester A type according to JIS K6301. Fatigue resistance is
Using a constant load type rubber fatigue testing machine NRF50 manufactured by Infinite Nishi Co., Ltd., JIS-3 dumbbell test pieces were repeatedly stretched at room temperature at a load value of 3 Kg, and the number of stretches until the number of breaks was measured. It was written by the number of times.

Example 1 A BR type Banbury mixer having a capacity of 1.7 liters was placed on a table.
20 parts by weight of the low molecular weight copolymer LEP- described in 1,
112 parts by weight of oil-extended high molecular weight copolymer HEP-, MA
50 parts by weight of F carbon black, 8 parts by weight of paraffinic process oil, 5 parts by weight of zinc oxide, 1 part by weight of stearic acid and 1 part by weight of antioxidant were kneaded to obtain a rubber composition.

The rubber composition was transferred to a 10-inti-pun roll having a roll temperature of 60 ° C. and kneading operation was carried out to measure the minimum value of roll gap where bagging occurs and observe the condition of the sheet skin. did. The results are shown in Table-2. Regarding the minimum value of the roll gap, the larger the value, the less likely bagging occurs. As for the condition of the skin of the sheet, those that are smooth and have no perforations are marked with "○",
Those that were not smooth but had holes were indicated by "x".

After the roll temperature was lowered to 40 ° C., 4 parts by weight of Sunperox DCP-98 and 0.3 part by weight of sulfur were blended and kneaded with the rubber composition to obtain a vulcanizable rubber composition. I adjusted things.

The vulcanizable rubber composition was heat-pressed to 17
It was heated at 0 ° C. for 20 minutes to prepare a vulcanized rubber sheet having a thickness of 2 mm. Tensile test and fatigue resistance of the vulcanized rubber sheet were measured in the same manner as in Comparative Example 1, and the results are shown in Table-3.

Example 2 In Example 1, the low molecular weight copolymer LEP-
The same procedure as in Example 1 was performed, except that 91 parts by weight of the oil-extended high molecular weight copolymer HEP- and 14 parts by weight of the paraffinic process oil were used. Table 3 shows the physical properties of the rubber composition and the physical properties of the vulcanized rubber sheet.

Example 3 Example 3 was repeated except that 36 parts by weight of MAF carbon black was used and no paraffinic process oil was used. Table 3 shows the physical properties of the rubber composition and the physical properties of the vulcanized rubber sheet.

Comparative Example 2 Example 3 was repeated except that the low molecular weight copolymer LEP- was replaced by the low molecular weight copolymer LEP-. Table 3 shows the physical properties of the rubber composition and the physical properties of the vulcanized rubber sheet.

[0038]

[0039]

[0040]

[Brief description of drawings]

FIG. 1 is a GPC of the low molecular weight copolymer LEP- used in Examples and the low molecular weight copolymer LEP- used in Comparative Examples.
It is a chart. The horizontal axis is the logarithm of the polystyrene equivalent molecular chain length, and the vertical axis is the relative concentration of the copolymer having each molecular chain length. Further, in the case of LEP-, the total relative concentration [L] of the low molecular weight component is indicated by the right diagonal line, and the total relative concentration [H] of the high molecular component is indicated by the left diagonal line.

[Explanation of symbols] GPC chart of low molecular weight copolymer LEP- GPC chart of low molecular weight copolymer LEP-

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Claims (5)

[Claims] 1. A high molecular weight copolymer comprising an ethylene / α-olefin / non-conjugated diene copolymer having an intrinsic viscosity [η] of 3 dl / g or more measured in xylene at 70 ° C .: 9
Low molecular weight copolymer consisting of 0-60% by weight and an ethylene / α-olefin / non-conjugated diene copolymer having an intrinsic viscosity [η] of 0.7-1 dl / g measured in xylene at 70 ° C: Ethylene-α-containing 10 to 40% by weight
In the olefin / non-conjugated diene copolymer rubber composition, the ratio of the low molecular weight component concentration [L] and the high molecular weight component concentration [H] of the low molecular weight copolymer ([L] / [H] ]) Has a bimodal molecular weight distribution of 3 or more. 2. A high-molecular copolymer, the high-molecular copolymer 10
The rubber composition according to claim 1, which is used as an oil-extended high molecular weight copolymer containing 10 to 50 parts by weight of an extender oil based on 0 part by weight. 3. A vulcanized rubber obtained by vulcanizing the rubber composition according to claim 1 with an organic peroxide. 4. A vulcanized rubber obtained by vulcanizing the rubber composition according to claim 2 with an organic peroxide. 5. Containing 10 to 50 parts by weight of carbon black per 100 parts by weight of the rubber composition according to claim 1,
A vulcanized rubber obtained by vulcanizing an organic peroxide.