JPH08269269A - Vibrationproof rubber composition - Google Patents

Abstract

PURPOSE: To obtain a vibrationproof rubber compsn. improved in adhesion to a metal and in processibility by mixing and kneading an ethylene-α-olefin- nonconjugated diene terpolymer rubber and a nonmodified liq. polybutadiene in the presence of an org. peroxide. CONSTITUTION: This compsn. contains a rubber component obtd. by mixing and kneading an ethylene-α-olefin-nonconjugated diene terpolymer rubber and a nonmodified liq. polybutadiene in the presence of an org. peroxide. The terpolymer rubber pref. has an ethylene unit content of 60-80mol% and a mol.wt. of 200,000 or higher. The ethylene unit content lower than 60mol% makes the processing of the compsn. difficult, and that higher than 80mol% degrades the low-temp. vibrationproof characteristics. The mol.wt. lower than 200,000 causes the problem of inferior resistances to heat and fatigue. The nonmodified liq. polybutadiene can be easily mixed into the compsn. and facilitates the kneading before cross-linking and the mixing of a carbon black for improving the supporting capability, thus improving the processibility of the compsn.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an anti-vibration rubber composition based on an ethylene-α-olefin-non-conjugated diene copolymer rubber. More specifically, it comprises an EPDM heat-resistant and vibration-damping rubber composition having improved physical properties useful in mounting an automobile engine, etc., particularly adhesion to metal and workability, and the rubber composition. Regarding anti-vibration rubber.

[0002]

2. Description of the Related Art Anti-vibration rubber used when mounting an automobile engine, etc., has anti-vibration properties to reduce engine vibration and accompanying noise, as well as heat resistance to heat generated by the engine. In addition, supporting performance (strength) for mechanically supporting the engine is required. From the standpoint of anti-vibration performance, rubber is generally suitable as soft as it is, but if it is too soft, it will bend due to the weight of the load and its support position will change, adversely affecting the basic performance of the entire structure including the support. Will affect.

Specifically, the vibration isolation performance is better as the spring constant (dynamic spring constant) of the vibration state transmitting the vibration is smaller, while the support performance (strength) is better as the static spring constant showing the support rigidity is larger, Therefore, it can be said that a rubber having a smaller ratio of the dynamic spring constant to the static spring constant, that is, the value of the dynamic magnification (dynamic spring constant / static spring constant) is superior as a vibration-proof rubber.

As such a vibration-proof rubber, at present, natural rubber (NR) and synthetic rubber such as butadiene rubber (BR) and styrene-butadiene rubber (SBR) are used alone or in combination.
These rubbers are used by blending more than one kind, but basically these rubbers have poor heat resistance because they have a double bond in the main chain, and physical properties when used for a long time in a high temperature environment such as an automobile engine room. Is significantly reduced (thermal deterioration and dynamic fatigue (so-called fatigue)). Attempts have been made to solve this problem by controlling the cross-linking state by using a vulcanization accelerator together with a vulcanizing agent, but in the engine room exposed to a high temperature of 120 ° C. or higher for a long time, the rubber cracks. Eventually it may be destroyed.

Many proposals have been made to solve the problem of heat resistance of anti-vibration rubber by using a composition based on a heat resistant ethylene-propylene rubber having no double bond in the main chain. There is. Among them, non-conjugated diene monomer (D
The terpolymer (EPDM) with M) is heat resistant, durable,
Although it has advantages such as low cost and has been widely researched, the fact is that nothing satisfying various properties such as heat resistance, vibration damping properties, moldability and adhesiveness has been obtained.

For example, JP-A-3-227343 discloses that an ethylene content is 60 to 75 mol% and an ethylene-propylene-nonconjugated diene copolymer (EPDM) having a viscosity and an iodine value in a specific range is 100 parts by weight. As disclosed in JP-A-5-86236, there is disclosed a heat-resistant and vibration-resistant rubber composition containing carbon black having excellent dispersibility in which iodine adsorption amount and dibutyl phthalate oil absorption amount are in specific ranges. 90 to 60% by weight of ethylene-propylene-diene copolymer rubber having 60 to 73 mol% and an ethylene content of 50.
Disclosed are ethylene-propylene-diene copolymer rubbers composed of 10 to 40% by weight of a liquid ethylene-propylene copolymer of 78 mol%. In these compositions, a sulfur-based vulcanizing agent is used. In order to be vulcanized, the sag resistance was still insufficient, and it could not be put to practical use as a mounting material for a device such as an engine requiring heat resistance.

[0007] Therefore, the present applicant has previously used an organic peroxide (dicumyl peroxide) without using a sulfur-based vulcanizing agent, and has ethylene-ethylene having a specific molecular weight and viscosity.
A rubber obtained by crosslinking a composition obtained by blending 100 parts by weight of a propylene-non-conjugated diene copolymer and carbon black having a specific oil absorption amount (dibutyl phthalate absorption amount) in an amount of 30 parts by weight or more (JP-A-6- 63219), and 100 parts by weight of an ethylene-propylene-non-conjugated diene copolymer having a specific molecular weight and viscosity using peroxide and a crosslinking aid (triallyl isocyanurate, ethylene dimethacrylate, trimethylolpropane trimethacrylate). And the like) were cross-linked to form a rubber (JP-A-6-63115).

These rubber compositions have excellent heat resistance at high temperatures (dynamic fatigue resistance and durability) and can be suitably used in the engine room of automobiles, etc. Poor adhesion to metal materials when heated and crosslinked. In addition, when a softening agent (extension oil) is added to improve workability, the static spring constant decreases, and when a filler such as carbon black is added to improve the static spring constant, the dynamic characteristics deteriorate. Therefore, it is difficult to achieve both the dynamic characteristics and workability required for the vibration damping material.

JP-A-56-59853 discloses that the adhesion between EPDM rubber and metallic materials is improved by adding liquid diene rubber. However, sulfur used as a vulcanizing agent is EPDM is difficult to vulcanize because it reacts with liquid diene rubber. Moreover, even when vulcanized, it cannot be used for this purpose because the heat settling property is extremely poor. Therefore, an object of the present invention is to improve the above problems of adhesiveness and processability in a vibration-proof rubber composition based on a heat-resistant EPDM rubber polymer.

[0010]

DISCLOSURE OF THE INVENTION The present inventors
As a result of diligent study on a system in which an organic peroxide is used as a cross-linking agent in order to improve the adhesiveness and the processability without impairing the heat-resistant and vibration-damping property of the DM rubber composition, it was kneaded when a specific unmodified polybutadiene was blended. As a result, it was confirmed that the moldability was improved, and that the adhesive force when heat-crosslinked on the metal material after kneading and molding was also significantly improved, and the present invention was completed.

That is, the present invention provides the following anti-vibration rubber composition. 1) An anti-vibration rubber composition comprising a rubber component obtained by kneading an ethylene-α-olefin-non-conjugated diene copolymer rubber and an unmodified liquid polybutadiene in the presence of an organic peroxide. 2) The antivibration rubber composition as described in 1 above, wherein the unmodified liquid polybutadiene has a 1,2 bond (microstructure) of 70% or less and a viscosity of 600 poise (25 ° C.) or less. 3) The amount of unmodified liquid polybutadiene added is ethylene-
The vibration-insulating rubber composition as described in 1 above, which is 5 to 40 parts by weight with respect to 100 parts by weight of the α-olefin-non-conjugated diene copolymer rubber.

4) The vibration-insulating rubber composition as described in 1 above, wherein the ethylene-α-olefin-non-conjugated diene copolymer rubber has an ethylene content of 60 to 80 mol% and a molecular weight of 200,000 or more. 5) Organic peroxide is 2.5 to 8 per 100 parts by weight of ethylene-α-olefin-non-conjugated diene copolymer rubber.
The vibration-insulating rubber composition as described in 1 above, which is blended in parts by weight. 6) The vibration-insulating rubber composition as described in 1 above, wherein the α-olefin is propylene. 7) An anti-vibration rubber comprising the anti-vibration rubber composition according to any one of 1 to 6 above.

The anti-vibration rubber composition of the present invention will be described in detail below.

[Rubber Polymer] The ethylene-α-olefin-nonconjugated diene copolymer rubber used in the present invention is an amorphous random elastic copolymer containing ethylene and α-olefin as main components and a nonconjugated diene component. Examples of α-olefins include propylene, butylene (1-butene), isobutylene (2-methylpropene), 1-pentene and the like. Propylene is particularly preferable. The non-conjugated diene monomer constituting the rubber polymer is a non-conjugated diene having 5 to 20 carbon atoms, and for example, 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 2,5-dimethyl-
1,5-hexadiene and 1,4-octadiene,
Cyclic dienes such as 1,4-cyclohexadiene, cyclooctadiene, dicyclopentadiene, for example, 5
-Ethylidene-2-norbornene, 5-butylidene-2
-Alkenyl norbornene and the like such as norbornene, 2-methallyl-5-norbornene and 2-isopropenyl-5-norbornene. Among the above non-conjugated dienes, dichloropentadiene and 5-ethylidene-2-
Norbornene is preferably used.

The ethylene content of the rubber polymer is 60-8.
It is preferably 0 mol% and has a molecular weight of 200,000 or more. If the ethylene content is less than 60, there is a problem in workability. On the other hand, when it exceeds 80, the anti-vibration property at low temperature deteriorates. When the molecular weight is less than 200,000, there is a problem in heat resistance and fatigue resistance. The rubber polymer exhibiting the above characteristics can be appropriately selected and used from commercial products.

[0015]

[Unmodified Liquid Polybutadiene] When an unmodified liquid polybutadiene and a peroxide are blended with a rubber polymer, the adhesive strength when molded into a predetermined shape on a metal material and crosslinked is significantly improved. The modified polybutadiene instead of the unmodified liquid polybutadiene does not improve the adhesive strength. By blending the unmodified liquid polybutadiene, not only the kneading operation before crosslinking becomes easy, but also the filling and kneading can be easily performed, and the filling and kneading of the carbon black added to further enhance the supporting performance is also easy. Processability is improved.

As the unmodified liquid polybutadiene, the 1,2-bond (microstructure) measured by an infrared spectrophotometer is 70 mol% or less, and the viscosity is 600 poise (25 ° C.).
The following are used: Such liquid polybutadiene can be appropriately selected and used from commercially available products. If the 1,2-bond (microstructure) exceeds 70 mol%, sufficient adhesive force cannot be obtained and the rubber cannot be used as a vibration isolating rubber. If the viscosity exceeds 600 poise, the kneading work is difficult and there is a problem in workability.

[0017]

[Organic peroxide] In the present invention, an organic peroxide (organic peroxide) is mainly used as a crosslinking agent for crosslinking. Specific examples of the peroxide include benzoyl peroxide, dicumyl peroxide, and di-t-
Butyl peroxide, t-butyl cumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5-dimethyl-2,5-di (t
-Butylperoxy) hexane, 2,5-dimethyl-
2,5-di (benzoylperoxy) hexane, 2,5
-Dimethyl-2,5-di (t-butylperoxy) hexyne-3 or 1,3-bis (t-butylperoxypropyl) benzene, di-t-butylperoxy-diisopropylbenzene, t-butylperoxy benzene,
2,4-dichlorobenzoyl peroxide, 1,1-
Examples thereof include di-t-butylperoxy-3,3,5-trimethylsiloxane and n-butyl-4.4-di-t-butylperoxyvalerate. Among these, dicumyl peroxide, t-butylperoxybenzene and di-t-butylperoxy-diisopropylbenzene are preferable.

[0018]

[Component Blending Ratio] In the present invention, the blending ratio of ethylene-α-olefin-non-conjugated diene copolymer rubber and unmodified liquid polybutadiene is ethylene-α-olefin-
40 parts by weight or less of non-modified liquid polybutadiene, preferably 5 to 100 parts by weight of the non-conjugated diene copolymer rubber.
40 parts by weight. If the blending amount of the non-modified liquid polybutadiene exceeds 40 parts by weight, the heat resistance becomes poor and it becomes difficult to use it as a vibration isolating rubber. Further, if the amount is less than 5 parts by weight, the adhesive strength is not improved. The blending amount of peroxide is 100 ethylene-α-olefin-non-conjugated diene copolymer rubber.
It is 2 to 8.5 parts by weight, preferably 2.5 to 7 parts by weight, based on parts by weight. If it is less than 2 parts by weight, sufficient crosslinking does not occur and the dynamic physical properties (deterioration resistance) deteriorate. On the other hand, if it exceeds 8.5 parts by weight, the crosslink density becomes excessive and the physical properties deteriorate, and the durability also decreases accordingly.

[0019]

[Other Additives] Further, a crosslinking aid, a filler, and a softening agent may be added to the anti-vibration rubber composition of the present invention. The crosslinking aid is an additive for suppressing radical cleavage of the polymer and improving the crosslinking effect in peroxide crosslinking, and can be used in an amount of about 3 to 10 parts by weight based on 100 parts by weight of the rubber polymer. Examples of cross-linking aids are tetrahydrofurfuryl methacrylate, ethylene dimethacrylate, 1,3-butylene dimethacrylate, 1,4
-Methylene dimethacrylate, 1,6-hexanediol dimethacrylate, polyethylene glycol dimethacrylate, 1,4-butanediol diacrylate,
1,6-hexanediol diacrylate, 2,2'-
Bis (4-methacryloxydiethoxyphenyl) propane, 2,2'-bis (4-acryloxydiethoxyphenyl) propane, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, 3-chloro- Two
-(Meth) acrylates such as hydroxypropyl methacrylate, oligoester acrylate, aluminum (meth) acrylate, zinc (meth) acrylate, magnesium (meth) acrylate, calcium (meth) acrylate, triallyl isocyanurate, triallyl cyanurate, Allyl compounds such as triallyl trimellitate, diallyl phthalate and diallyl chlorendate, divinylbenzene, 2-vinylpyridine, N,
Examples thereof include N'-methylenebisacrylamide, p-quinonedioxime, p, p'-dibenzoylquinonedioxime, dipentamethylenethiuram tetrasulfide and sulfur.

Examples of the filler include carbon black,
Examples include calcium carbonate, talc, silica and the like. These can be used in an amount of about 20 to 100 parts by weight based on 100 parts by weight of the rubber polymer. The softening agent is used up to about 100 parts by weight with respect to 100 parts by weight of the rubber polymer. Examples of softening agents include petroleum-based softening agents such as procell oil, lubricating oil, paraffin, liquid paraffin, petroleum asphalt, and vaseline, and process oil is particularly preferably used. In addition to the above additives, conventional compounding agents such as antiaging agents, plasticizers, stabilizers, processing aids, colorants and the like may be used.

[0021]

[Production Method] The anti-vibration rubber composition of the present invention can be produced by a conventional method using the above rubber polymer, unmodified polybutadiene, organic peroxide and other additives.

The anti-vibration rubber of the present invention has good adhesion to a substrate made of an inorganic material, especially a metal. The type of the base metal is not particularly limited, and the adhesiveness to all ordinary metals such as iron such as steel and cast iron, aluminum, copper and the like is improved. Therefore, the anti-vibration rubber of the present invention is effectively used as a constituent member for anti-vibration rubber used in various vehicles and machines, or structures such as bridges and railway tracks. Especially, engine mounts, body mounts, cab mounts, etc. , Member mount, strut bar cushion, center bearing support, torsional damper, steering rubber coupling, tension rod bush, lower ring bush, arm bush,
Bump strapper, FF engine roll stopper,
It is suitable as a constituent member of various automobile anti-vibration rubbers such as muffler hangers.

[0023]

The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following description. In each of the examples and comparative examples, the following materials were used as raw materials and additives. [Ethylene-α-olefin-non-conjugated diene copolymer] EPDM-1: Ethylene-propylene-non-conjugated diene copolymer (EPDM) ("Esprene 601" manufactured by Sumitomo Chemical Co., Ltd. (ethylene content: 62%, ML _{1 + 3} (121 ° C.): 63) 70 parts by weight of paraffin oil was added to 100 parts by weight and oil-extended. [Unmodified polybutadiene (BR)] Viscosity (2
5 ° C.) and unmodified polybutadiene with 1,2% bond were used. BR-1 to BR-5 in Tables 2 and 3
Symbol.

[0024]

[Table 1] Symbol Viscosity (poise) 1, 2 bond% Modified BR-1 15 65 None BR-2 500 65 〃 BR-3 350 90 90 〃 BR-4 200 90 Glycol modified BR-5 3000 65 Epoxy modified

Carbon black: FEE carbon black (manufactured by Asahi Carbon Co., Ltd.), zinc white (ZnO) (manufactured by Mitsui Metal Industry Co., Ltd.), stearic acid (manufactured by Kao Corporation), anti-aging agent: 2-mercaptobenzimidazole ( Table 2
.About.3 and represented by MB in the following text) 2,2,4-trimethyl-1,2-dihydroquinoline polymer (represented by RD in Table 2 and the following text), crosslinking agent: dicumyl peroxide (NOF Corporation) "Park Mill D")

Example 1 The above oil-extended EPDM-1 (170 parts by weight) was added to unmodified polybutadiene BR-1 (10 parts by weight), zinc white (5 parts by weight), stearic acid (1 part by weight), MB (1 part by weight). Part),
RD (0.25 parts by weight) and FEF carbon black (50
(Parts by weight) was added and kneaded with a Banbury mixer. The kneaded material thus obtained was cooled to 70 ° C. or lower, dicumyl peroxide (6 parts by weight) was added, and the mixture was further kneaded at 50 to 60 ° C. with a roll to obtain a compounded rubber composition. The obtained compounded rubber composition was molded and crosslinked as described below to give a test piece, and the normal state characteristics (blank physical properties), aging property, adhesiveness, and dynamic characteristics were measured using this. An evaluation test of roll processability was also conducted. The results are shown in Tables 2-3.

1) Physical properties of blank A compounded rubber composition was molded, heated at 170 ° C. for 20 minutes and crosslinked to obtain a dumbbell-shaped test piece (JIS K6301). Using this test piece, the measuring temperature is 25 according to the method described in JIS K6301.
Tensile test was carried out under conditions of ℃ and tensile speed of 500 mm / min., 100% modulus (M100), tensile strength (T
B) (kgf / cm ² ) and elongation at break (EB) (%)
Was measured. The hardness (HS) is also JIS
The spring hardness was measured with a JIS A hardness meter according to the method described in K6301.

2) Aging property A test piece prepared in the same manner as in the blank physical property test was used as 120
After holding at 240 ° C. for 240 hours, 100% modulus (M100), tensile strength (TB) (kgf / cm ² ), elongation at break (EB) (%) and hardness (HS) after the test were measured in the same manner. The results are shown in Tables 2-3. In the table, TB, EB
After the measured value of, the rate of change (%) of each physical property value due to heating is enclosed in parentheses. With respect to HS, the increase and decrease in hardness due to heating is added.

3) Adhesiveness Two disc-shaped metal fittings (having a handle extending in the axial direction on one side) having a diameter of 40.5 mm were prepared, and each test surface (the surface without the handle) was degreased and polished. After treatment, a halogenated rubber adhesive for undercoating was applied and dried. After the undercoat surface was dried, a topcoat adhesive (halogenated rubber adhesive) was further applied thereon and dried. Next, the test surfaces of the two metal fittings were faced in parallel, the compounded rubber composition was sandwiched, and vulcanized and adhered at 165 ° C. for 40 minutes. The vulcanized rubber part has a thickness of 14.8 mm and a diameter of 35.7 mm.
It had a cylindrical shape of mm. This test piece was fixed by the handle of one of the metal fittings, and the handle of the other metal fitting was pulled in the axial direction to break or peel the rubber. The maximum load required at this time was taken as the adhesive force, and the adhesiveness was evaluated together with the state of the fracture surface. In the table, the symbols of the fracture surface state have the following meanings. R: rubber rupture (%), RC: rupture (%) between the rubber and the top coating surface.

4) Dynamic characteristics A compounded rubber composition was heated at 170 ° C. for 30 minutes to prepare a cross-linked columnar test piece having a diameter of 50 mm and a height of 25 mm, and the upper surface and the lower surface thereof had a diameter of 60 mm and a thickness of 6 mm. Each of the circular metal fittings was attached, the static spring constant (Ks) and the dynamic spring constant (Kd100) were measured, and the dynamic magnification (Kd100 / Ks) was obtained. The static spring constant is 1.5 mm and 3.5 mm from the second load deflection curve obtained by compressing the cylindrical test piece in the axial direction of the cylinder by 7 mm in the axial direction.
The load at the time of bending was read and calculated. The dynamic spring constant is that the test piece is compressed 2.5 mm in the axial direction, and the amplitude is ± 0.
A constant displacement harmonic vibration of 05 mm was applied, the dynamic load was measured with a load cell attached above the test piece, and calculation was performed according to JIS K6394. Dynamic magnification is the ratio of these values.

5) Roll processability When the compounded rubber composition (before crosslinking) was kneaded and wound around a roll (outer diameter: 8 inches), it was tested whether or not the rubber composition floats from the roll. The result was evaluated as workability. The ones that did not float from the roll are ○, the ones that are slightly floating are △, and the ones that are completely floating are ×.
And

[0032]

[Table 2]

[0033]

[Table 3]

Examples 2 to 4 and Comparative Examples 1 to 5 The compounded rubber composition was prepared in the same manner as in Example 1 except that the type and amount of polybutadiene added were changed, and the physical property values were the same as in Example 1. Was measured. The results are also shown in Tables 2 and 3. As shown in the table, in the example in which the unmodified polybutadiene was added to the EPDM, the adhesion was improved by about 10 times as compared with the control example (Comparative Example 1) in which the polybutadiene was not added. Further, when the modified polybutadiene was used, even if the viscosity was at the same level as that of the example (Comparative Example 2), the adhesiveness was hardly improved, and when the viscosity was increased (Comparative Example 3), the adhesiveness was slightly increased. However, the workability is significantly reduced. Even with unmodified polybutadiene, 1,2 bond% is 9
When more than 0% is used (Comparative Example 4), the adhesiveness is low and the elongation at break is low. Further, since the breaking elongation decreases as the 1,2-bond% of the unmodified polybutadiene increases, the practical upper limit of the 1,2-bond% is about 70% (Example 4). Further, when the unmodified polybutadiene is blended in an amount of 40 phr or more (Comparative Example 5), the elongation at break and the static spring constant are low and are not suitable for practical use in terms of dynamic characteristics.

[0035]

EFFECTS OF THE INVENTION The heat and vibration resistant rubber composition of the present invention has a heat aging resistance which cannot be realized by the natural rubber vibration proof rubber. Further, the heat and vibration resistant rubber composition of the present invention, as a result of using a combination of peroxide cross-linking with peroxide and a predetermined amount of liquid polybutadiene, not only heat aging resistance and dynamic fatigue resistance, but also to metal. Excellent properties are also realized in terms of adhesiveness, processability and vibration resistance. Therefore, the EPDM-based anti-vibration rubber of the related art is not effective enough to obtain a sufficiently satisfactory result. It is also highly effective as a constituent material of a high-vibration anti-vibration rubber for automobiles such as engine mounts. .

Claims (7)

[Claims] 1. An anti-vibration rubber comprising a rubber component obtained by kneading an ethylene-α-olefin-non-conjugated diene copolymer rubber and a non-modified liquid polybutadiene in the presence of an organic peroxide. Composition. 2. The anti-vibration rubber composition according to claim 1, wherein the unmodified liquid polybutadiene has a 1,2 bond content of 70 mol% or less and a viscosity of 600 poise (25 ° C.) or less. 3. The antivibration rubber composition according to claim 1, wherein the amount of the unmodified liquid polybutadiene added is 5 to 40 parts by weight based on 100 parts by weight of the ethylene-α-olefin-nonconjugated diene copolymer rubber. Stuff. 4. The ethylene-α-olefin-non-conjugated diene copolymer rubber has an ethylene content of 60 to 80 mol%.
The anti-vibration rubber composition according to claim 1, having a molecular weight of 200,000 or more. 5. An organic peroxide based on 100 parts by weight of an ethylene-α-olefin-non-conjugated diene copolymer rubber.
The anti-vibration rubber composition according to claim 1, which is compounded in an amount of 2.5 to 8 parts by weight. 6. The anti-vibration rubber composition according to claim 1, wherein the α-olefin is propylene. 7. An anti-vibration rubber comprising the anti-vibration rubber composition according to any one of claims 1 to 6.