JP2891078B2 - Rubber composition for heat-resistant anti-vibration rubber and vulcanized rubber - 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 for heat and vibration proof rubber, and more particularly to a vulcanized rubber for heat and vibration proof rubber having good fatigue resistance and excellent roll workability. The present invention relates to a rubber composition.

[0002]

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

[0003] When a low unsaturated rubber such as ethylene / α-olefin / non-conjugated diene copolymer rubber (hereinafter sometimes simply referred to as EPDM) is used as a rubber material,
Although an anti-vibration rubber having excellent heat resistance can be obtained, there is a drawback that fatigue resistance when external force is repeatedly applied for a long period of time is poor. The use of a high molecular weight EPDM (which has an intrinsic viscosity [η] of 2.5 dl / g or more, usually measured in xylene at 70 ° C.) solves this drawback. The higher the molecular weight, the more the effect of improving fatigue resistance becomes significant. It is generally known. However, there is a limit in terms of processability before vulcanization to increase the molecular weight, and if the molecular weight is excessively high, there arises a problem that, for example, so-called bagging occurs in which the rubber composition floats from the roll surface during roll processing. Occurs.

Attempts have been made to achieve both workability before vulcanization and excellent vibration-proof rubber properties of vulcanized rubber. For example, JP-A-53-22551 discloses that blending of high molecular weight EPDM with low molecular weight EPDM improves processability. Further, this low molecular weight EPDM acts as a processing aid in an unvulcanized state, and after vulcanization, Is disclosed as contributing to the improvement of dynamic fatigue resistance.

However, with the recent improvement in the performance of automobiles, anti-vibration rubber materials are required to have even lower dynamic magnification and higher durability. In the case of a vibration-proof rubber compound in which the addition amount is more severely restricted, satisfactory roll workability cannot be obtained by the conventional technique alone.

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 intensive studies on 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 were mixed at a constant weight. The rubber composition containing the rubber composition in the ratio is excellent in roll processability, and the vulcanized rubber obtained by vulcanizing such a rubber composition with an organic peroxide has good fatigue resistance and the like. And completed the present invention.

[0007]

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

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. Here, α-olefins include propylene, 1-butene, 1-hexene and the like, and non-conjugated dienes include 1,4-pentadiene, 1,4-hexadiene, divinylbenzene, dicyclopentadiene, methylenenorbornene, ethylidene Norbornene (hereinafter abbreviated as ENB), vinyl norbornene, and the like.

The ethylene / α-olefin / non-conjugated diene copolymer in the present invention is a high molecular weight copolymer having a specific intrinsic viscosity and a low molecular weight having a specific intrinsic viscosity and a molecular weight component concentration ratio as described below. 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 /
g or more of ethylene / α-olefin / non-conjugated diene copolymer, among which [η] is preferably 3 to 5 dl / g, particularly preferably 3.3 to 5 dl / g. The ethylene / α-olefin ratio (molar ratio) of the copolymer is usually from 60/40 to 80/20, preferably from 60/40 to 72/28, from the viewpoint of the temperature dependence of the dynamic magnification. The amount of the non-conjugated diene component in the copolymer is usually 0.5 to 3 mol% of all the monomers constituting the copolymer, from the viewpoint of the heat resistance and the vibration-proof rubber properties of the vulcanized rubber. It is preferred that

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, an 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, in which (η) is 0.8 to 0.8.
Those having 9 dl / g are preferred. In addition, from the viewpoint of processability of the rubber composition, the ethylene component content of the low molecular weight copolymer,
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 concentration [L] of the low molecular weight component and the concentration [H] of the high molecular weight component determined by the C measurement method is 3 or more. That is, the low molecular weight copolymer of the present invention has a bimodal molecular weight distribution and a remarkably large amount of low molecular weight components. If the [L] / [H] of the low molecular weight copolymer is less than 3, the effect of improving the roll processability is not remarkably exhibited.

Here, GPC means gel permeation chromagraphy (gel permeation chromatography).
It is. The GPC measurement is performed according to "Gel Permeation Chromography" published by Takeuchi and published by Maruzen Co., Ltd. The calibration curve is prepared by a standard method using standard polystyrene. In the GPC chart of the copolymer obtained by this GPC measurement method, the horizontal axis represents the logarithm of the molecular chain length in terms of polystyrene, and the vertical axis represents 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 logarithm of the molecular chain length in terms of polystyrene of 3 or less, and the high molecular weight component has a logarithm of the molecular chain length in terms of polystyrene of 4. Refers to 25 or more components.
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 determined.

In the above-mentioned ethylene / α-olefin / non-conjugated diene copolymer comprising a high molecular weight copolymer and a low molecular weight copolymer, the high molecular weight copolymer is 90 to 60% by weight, preferably 80 to 60% by weight. It is present in a proportion of 60% by weight, the low molecular weight copolymer being 10 to 40% by weight, preferably 20% by weight.
It is present in a proportion of ４０40% by weight. 1 low molecular weight copolymer
If the amount is less than 0% by weight, the processability of the rubber composition is not improved, and if the amount of the high molecular weight copolymer is less than 60% by weight, the fatigue resistance of the vulcanized rubber becomes low.

Although the rubber composition according to the present invention contains a low molecular weight copolymer as a component, it has excellent processability.
To further improve this point, extender oil may be added to the high molecular weight copolymer to use it as an oil-extended high molecular weight copolymer. As the extender oil, a paraffin-based process oil or the like is used.
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. 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 having excellent dynamic magnification,
It is important that the rubber composition be vulcanized with an organic peroxide. Examples of the organic peroxide as a vulcanizing agent include dicumyl peroxide, di-tert-butyl peroxide, tert-butylcumyl peroxide, 1,1-di- (tert-butylperoxy) -3,3,5-trimethylcyclohexane. Benzoyl peroxide, lauroyl peroxide, and the like, and are selected in consideration of the blending of the vulcanizing agent, the temperature during vulcanization, and the like. The amount of the organic peroxide used is as follows.
It 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, a softener, an antioxidant, an antioxidant, a processing aid, and a vulcanization aid. Examples of the vulcanization aid include sulfur, p-quinone dioxime, p, p-dibenzoylquinone dioxime, 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 and styrene / butadiene rubber, may be contained.

The vulcanized rubber of the present invention can be prepared by adding a softening agent, carbon black, organic peroxide to a copolymer rubber under ordinary conditions using an apparatus commonly used in the production of rubber products such as a Banbury mixer and an open roll. And then vulcanizing it under ordinary conditions using an apparatus generally used in organic peroxide vulcanization of rubber, such as an injection molding machine or 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 at a constant weight ratio. In addition, such a rubber composition is vulcanized with an organic peroxide to form a vulcanized rubber having good fatigue resistance. Useful as rubber. Specifically, anti-vibration rubber for automobiles such as engine mount, strut mount, suspension bush, exhaust mount, etc.
It is suitable for use as an anti-vibration rubber in railway vehicles, construction vehicles, industrial equipment, OA equipment, and the like.

[0022]

EXAMPLES The present invention will be described below in more detail 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 values in Table 1 are the weight average molecular weight [Mw] and the number average molecular weight [Mn] determined by the GPC measurement method.
And Q = [Mw] / [Mn]. The larger the Q value, the wider the molecular weight distribution, and generally the better the processability.

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

Comparative Example 1 An oil-extended high molecular weight copolymer HEP- (high molecular weight copolymer HEP- described in Table 1: xylene at 70 ° C.) was placed in a 1.7-liter BR type Banbury mixer. The measured intrinsic viscosity [η] is 3.3 dl / g, and the ethylene ratio is 70.
100% by weight of an ethylene / propylene / ENB copolymer rubber having an ENB ratio of 1.2% by mole and 40 parts by weight of a paraffinic process oil, and Mooney viscosity ML _{1 + 4} 121 ° C. = 96 parts), 140 parts by weight of MAF, 50 parts by weight of MAF carbon black, 5 parts by weight of zinc oxide, 1 part by weight of stearic acid and 1 part by weight of an antioxidant were kneaded to obtain a rubber composition.

The rubber composition was transferred to a 10-inch roll with a roll temperature of 60 ° C. and kneaded to measure the minimum value of the gap between the rolls at which bagging occurs and to observe the condition of the sheet skin. did. Table 2 shows the results. Regarding the minimum value of the roll gap, the larger the value, the less the occurrence of bagging. Regarding the condition of the sheet skin, if it is smooth and no perforation is recognized,
Those that are not smooth but have holes are indicated by “x”. The results are shown in Table-3.

After lowering the roll temperature to 40 ° C., 4 parts by weight of an organic peroxide and 0.3 parts of sulfur were added to the rubber composition.
Parts by weight were blended and kneaded to prepare a vulcanizable rubber composition.

The vulcanizable rubber composition is hot-pressed to 17
By heating at 0 ° C. for 20 minutes, a vulcanized rubber sheet having a thickness of 2 mm was prepared. The vulcanized rubber sheet is JIS-K63
A tensile test was carried out in accordance with No. 01. Further, the fatigue resistance was measured. The results are shown in Table-3.

The tensile strength and the elongation at break were measured according to JIS K63.
The measurement was performed using a JIS-3 dumbbell test piece in accordance with No. 01. The hardness was measured using a spring type hardness tester A type in accordance with JIS K6301. Fatigue resistance is
Using a constant load type rubber fatigue tester NRF50 manufactured by Infinite Nishi Co., Ltd., a JIS-3 dumbbell test piece was repeatedly stretched at room temperature at a load value of 3 kg, and the number of stretches until breaking was measured. And the number of times.

Example 1 A 1.7-liter BR type Banbury mixer was prepared as shown in Table 1.
20 parts by weight of the low molecular weight copolymer LEP- according to 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 an antioxidant were added and kneaded to obtain a rubber composition.

The rubber composition was transferred to a 10-inch roll with a roll temperature of 60 ° C. and kneaded to measure the minimum value of the gap between rolls at which bagging occurs and to observe the condition of the sheet skin. did. Table 2 shows the results. Regarding the minimum value of the roll gap, the larger the value, the less the occurrence of bagging. Regarding the condition of the sheet skin, if it is smooth and no perforation is recognized,
Those that are not smooth but have holes are indicated by “x”.

After lowering the roll temperature to 40 ° C., 4 parts by weight of Samperox DCP-98 and 0.3 part by weight of sulfur were mixed and kneaded with the rubber composition to form a vulcanizable rubber composition. I adjusted things.

The vulcanizable rubber composition was hot-pressed to 17
By heating at 0 ° C. for 20 minutes, a vulcanized rubber sheet having a thickness of 2 mm was prepared. For the vulcanized rubber sheet, a tensile test and fatigue resistance 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-
Example 1 was repeated except that 91 parts by weight of the oil-extended high molecular weight copolymer HEP- and 14 parts by weight of the paraffin-based process oil were used. Table 3 shows the physical properties and the like of the rubber composition and the physical properties of the vulcanized rubber sheet.

Example 3 The procedure of Example 2 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 and the like of the rubber composition and the physical properties of the vulcanized rubber sheet.

Comparative Example 2 The procedure of Example 3 was repeated, except that the low-molecular-weight copolymer LEP- was used instead of the low-molecular-weight copolymer LEP-. Table 3 shows the physical properties and the like of the rubber composition and the physical properties of the vulcanized rubber sheet.

[0038]

[0039]

[0040]

[Brief description of the drawings]

FIG. 1 GPC of low molecular weight copolymer LEP- used in Examples and low molecular weight copolymer LEP- used in Comparative Examples
It is a chart. The horizontal axis is the logarithm of the molecular chain length in terms of polystyrene, 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 shown by oblique lines on the right, and the total relative concentration [H] of the high molecular component is shown by oblique lines on the left.

[Description of Symbols] GPC chart of low molecular weight copolymer LEP- GPC chart of low molecular weight copolymer LEP-

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-62-101615 (JP, A) JP-A-5-86236 (JP, A) JP-A-61-264035 (JP, A) JP-A-3-3 200854 (JP, A) JP-A-53-22551 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08L 23/00-23/36

Claims (5)

(57) [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
A low molecular weight copolymer comprising an ethylene / α-olefin / non-conjugated diene copolymer having an intrinsic viscosity [η] of 0.7 to 1 dl / g as measured in 0 to 60% by weight and 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 [L] to the high molecular weight component [H] determined by the GPC measurement method ([L] / [H ]) Having a bimodal molecular weight distribution of 3 or more. 2. A polymer copolymer, comprising:
2. The rubber composition according to claim 1, wherein the rubber composition is used as an oil-extended high molecular weight copolymer containing 10 to 50 parts by weight of extender oil per 0 parts 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 subjecting the rubber composition according to claim 2 to organic peroxide vulcanization. 5. A rubber composition according to claim 1, comprising 10 to 50 parts by weight of carbon black per 100 parts by weight of the rubber composition.
A vulcanized rubber obtained by vulcanizing with an organic peroxide.