Rubber composition for torsional damper

Information

  • Patent Grant
  • 12281222
  • Patent Number
    12,281,222
  • Date Filed
    Monday, June 22, 2020
    5 years ago
  • Date Issued
    Tuesday, April 22, 2025
    3 months ago
Abstract
A rubber composition for a torsional damper, comprising 10 to 200 parts by weight of carbon black having an iodine adsorption of 100 to 600 mg/g, a DBP oil absorption of 138 to 330 cm3/100 g and a nitrogen adsorption specific surface area of 100 to 530 m2/g, and 5 to 100 parts by weight of a liquid polyolefin oligomer having a number average molecular weight Mn of 3,000 to 4,000, based on 100 parts by weight of at least one of ethylene-propylene-non-conjugated diene terpolymer rubber, ethylene-butene-non-conjugated diene terpolymer rubber and ethylene-propylene copolymer rubber, wherein in the total amount of ethylene and propylene or butene, the content of propylene or butene is 35 to 55 wt. %.
Description
TECHNICAL FIELD

The present invention relates to a rubber composition for a torsional damper. More particularly, the present invention relates to a rubber composition that can provide a torsional damper having excellent damping properties, conductivity and durability.


BACKGROUND ART

For the purpose of reducing engine vibration (reducing torsional vibration of the crankshaft), a torsional damper is attached nearest to the engine at one end of the crankshaft that extends from inside the engine. When interposing a vulcanized rubber layer between the hub part fixed to the crankshaft and the vibration ring (mass part), for example, a function to reduce vibration is exhibited.


Specific examples include a function to reduce the vibration of the crankshaft by matching the natural frequency of the torsional damper with the natural frequency of the crankshaft, and a function to transmit power to auxiliary machinery via the belt.


Rubber materials used for the torsional damper are required to have the following functions.


(1) They should have a hardness variation of about Hs 50 to 85° for natural frequency tuning.


(2) They should have good temperature dependence (E′ temperature dependence) of the spring constant of the rubber materials, since the natural frequency is not required to change much depending on the operating temperature.


(3) They should have high tan δ in a wide temperature range in order to reduce the vibration of the crankshaft.


(4) They should have durability and heat resistance of excellent at high temperatures, since the high temperature use area of torsional dampers exceeds 100° C.


(5) They should have conductivity to prevent static electricity.


The applicant of this application has previously proposed an EPDM composition for a torsional damper, comprising 5 to 30 parts by weight of a liquid polyolefin oligomer having a number average molecular weight Mn of 3,000 to 4,000, and 10 to 120 parts by weight of carbon black having a nitrogen adsorption specific surface area of 100 to 150 m2/g, an iodine adsorption of 110 to 160 mg/g, and a DBP oil absorption of 70 to 135 cm3/100 g, based on 100 parts by weight of EPDM having a propylene content of 35 to 50 wt. % (Patent Document 1).


Such a composition can achieve high damping using specific carbon black; however, on the other hand, the amount (part by weight) of carbon black that can be used needs to be small because the durability of the product tends to deteriorate. As a result, there remains the problem that it is difficult to achieve significantly high damping. Therefore, the above requirements (3) and (4) cannot be satisfied.


In recent years, attention has also been paid to the improvement of conductivity. That is, depending on the type of engine, a large friction is generated between the inner surfaces of the timing belt and the damper pulley groove, thereby causing belt slip and the like, which may cause a charging phenomenon in the damper vibration ring. At that time, since a discharge path cannot be secured with conventional rubber materials, there is a concern, due to electric discharge that noise may be generated and that electronic devices (e.g., sensors) around the engine may be affected.


PRIOR ART DOCUMENT
Patent Document





    • Patent Document 1: WO 2015/012018 A1

    • Patent Document 2: JP-A-2017-183162





OUTLINE OF THE INVENTION
Problem to be Solved by the Invention

An object of the present invention is to provide a rubber composition that is used as a molding material for a torsional damper having improved damping properties (tan δ), conductivity and durability.


Means for Solving the Problem

The above object of the present invention can be achieved by a rubber composition for a torsional damper, comprising 10 to 200 parts by weight of carbon black having an iodine adsorption of 100 to 600 mg/g, a DBP oil absorption of 138 to 330 cm3/100 g and a nitrogen adsorption specific surface area of 100 to 530 m2/g, and 5 to 100 parts by weight of a liquid polyolefin oligomer having a number average molecular weight Mn of 3,000 to 4,000, based on 100 parts by weight of at least one of ethylene-propylene-non-conjugated diene terpolymer rubber, ethylene-butene-non-conjugated diene terpolymer rubber and ethylene-propylene copolymer rubber, wherein in the total amount of ethylene and propylene or butene, the content of propylene or butene is 35 to 55 wt. %.


Effect of the Invention

Since torsional damper rubber, for which the rubber composition compounded with carbon black having a high DBP oil absorption according to the present invention is used, has a high absolute value of tan δ, particularly tan δ at 60° C., at which torsional dampers are commonly used, crankshaft vibration can be reduced; that is, high damping can be achieved.


Moreover, due to the excellent conductivity, it is possible to secure a discharge path from the vibration ring to the hub side via the rubber material, and it is also possible to prevent electrical discharge noise and influence on electronic devices around the engine.


Furthermore, since the dispersibility of carbon black in the rubber material is also excellent, durability can be improved, which has the effect of making it possible to provide safe and long-life products.


In addition, the addition of graphite improves kneading-roll processability without impairing physical properties. The addition of an aromatic modified terpene resin, which is well compatible with the target polymer, produces an interaction, making it possible to further enhance the damping performance.


Embodiments for Carrying out the Invention

As the polymer, for the purpose of balancing the heat resistance, cold resistance, durability, temperature dependence of the spring constant and repulsive stress, it is preferable to use at least one member selected from the group consisting of EPM (ethylene/propylene copolymer), EPDM (ethylene/propylene/non-conjugated diene terpolymer), and EBDM (ethylene/butene/non-conjugated diene terpolymer). That is, EPM polymer, EPDM polymer and EBDM polymer may be used singly or as a mixture of two or more of them. Typically, each polymer is solid.


In the present embodiments, in the total amount of ethylene, propylene and butene, the content of propylene and/or butene is preferably 35 to 55 wt. %. The “content of propylene and butene” (C3+C4 content) in each embodiment is shown below.

    • When EPM, EPDM and EBDM are used as polymer:

      C3+C4 content=(amount of propylene in EPM+amount of propylene in EPDM+amount of butene in EBDM)/(total amount of ethylene and propylene in EPM+total amount of ethylene and propylene in EPDM+total amount of ethylene and butene in EBDM)×100
    • When EPM and EPDM are used as polymer:

      C3+C4 content=(amount of propylene in EPM+amount of propylene in EPDM)/(total amount of ethylene and propylene in EPM+total amount of ethylene and propylene in EPDM)×100
    • When EPM and EBDM are used as polymer:

      C3+C4 content=(amount of propylene in EPM+amount of butene in EBDM)/(total amount of ethylene and propylene in EPM+total amount of ethylene and butene in EBDM)×100
    • When EPDM and EBDM are used as polymer:

      C3+C41 content=(amount of propylene in EPDM+amount of butene in EBDM)/(total amount of ethylene and propylene in EPDM+total amount of ethylene and butene in EBDM)×100


Using the above-mentioned polymer makes it possible to achieve a balance between the heat resistance, cold resistance, durability, temperature dependence (E′ temperature dependence) of the spring constant, and repulsive stress. In a more preferred embodiment, the C3+C4 content is 38 to 55 wt. %, preferably 40 to 55 wt. %. If the C3+C4 content is more than this range, the low temperature characteristics and roll processability are deteriorated. In contrast, if the C3+C4 content is less than this range, the low temperature characteristics are deteriorated.


An ethylene-propylene copolymer rubber polymer is used as EPM, and an ethylene-propylene-non-conjugated diene terpolymer rubber polymer is used as EPDM. As the non-conjugated diene, a small amount of dicyclopentadiene, 1,4-hexadiene, dicyclooctadiene, methylene norbomene, vinyl norbomene, ethylidene norbomene, or the like is copolymerized. The Mooney viscosity ML1+4 (125° C.) thereof is about 25 to 80, preferably about 25 to 70.


EBDM is described, for example, in Patent Document 2. As the butene, mainly butene-1 is used. Further, as the non-conjugated diene, cyclic or chain non-conjugated dienes, such as 5-ethylidene-2-norbomene and 5-vinyl-2-norbornene, can be used in addition to the above diene compounds; preferably a cyclic non-conjugated diene is used. Such a non-conjugated diene is used in an amount of about 1 to 20 wt. %, preferably about 3 to 15 wt. %, from the viewpoint of fatigue at low temperature. In practice, commercial products, such as EBT produced by Mitsui Chemicals, Inc., can be used as they are.


EBDM has a copolymer composition comprising 50 to 95 mol %, preferably 65 to 95 mol %, of a structural unit derived from ethylene, 4.9 to 49.9 mol %, preferably 4.9 to 35 mol %, of a structural unit derived from butene and 0.1 to 5 mol %, preferably 0.1 to 3 mol %, of a structural unit derived from non-conjugated diene. EBDM is synthesized using a metallocene-based compound, such as (t-butylamide)dimethyl(η5-2-methyl-s-indacen-1-yl)silanetitanium (II) 1,3-pentadine, as a polymerization catalyst.


Further, EPDM, EBDM and EPM may all contain an oil-extended oil such as a mineral oil, a liquid polyolefin oligomer and the like. The ratio of the oil-extended oil to be added is preferably about 5 to 120 parts by weight based on 100 parts by weight of EPDM, EBDM or EPM.


Carbon black and a liquid polyolefin oligomer are compounded with above polymer to form a rubber composition for a torsional damper.


As the carbon black, one having an iodine adsorption of 100 to 600 mg/g, preferably 150 to 450 mg/g, more preferably 170 to 450 mg/g, a DBP oil absorption of 138 to 330 cm3/100 g, preferably 140 to 330 cm3/100 g and a nitrogen adsorption specific surface area of 100 to 530 m2/g, preferably 120 to 400 m2/g, more preferably 160 to 400 m2/g, is used at a ratio of about 10 to 200 parts by weight, preferably about 10 to 160 parts by weight, more preferably 10 to 150 parts by weight, particularly preferably 30 to 150 parts by weight, based on 100 parts by weight of the polymer. Even if the above parts by weight of carbon black is added and used in combination with other carbon black, they can be used in combination as long as the object of the present invention is not impaired.


Here, the iodine adsorption, DBP oil absorption and nitrogen adsorption specific surface area are typical indicators showing the characteristics of carbon black. The iodine adsorption is a value measured according to JIS K6221, the DBP oil absorption is a value measured according to JIS K6221 Method A (mechanical method), and the nitrogen specific surface area is a value measured according to JIS K6217.


The nitrogen adsorption specific surface area is, together with the iodine adsorption, an indicator of the total specific surface area including the pores of carbon black. Further, the DBP oil absorption indirectly quantifies the structure by measuring the porosity between the individual aggregates that have a positive correlation with the structure.


If carbon black whose iodine adsorption and nitrogen adsorption specific surface area are lower than those mentioned above is used, it is difficult to achieve high damping. In contrast, if carbon black whose iodine adsorption and nitrogen adsorption specific surface area are higher than those mentioned above is used, the durability is deteriorated. Further, if carbon black whose DBP oil absorption is outside of the above-mentioned range is used, the durability is inferior.


If carbon black is used at a ratio of less than this range, achievement of high damping and securing of conductivity cannot be satisfied, and the dispersibility of carbon black is deteriorated. In contrast, if carbon black is used at a ratio of more than this range, the kneading properties become problematic.


As the liquid polyolefin oligomer, one having a number average molecular weight Mn of 3,000 to 4,000, preferably 3,000 to 3,900, more preferably 3,500 to 3,900, particularly preferably 3,600 to 3,800, is used; preferably from the viewpoint of achieving high damping, an ethylene-α-olefin oligomer is used at a ratio of about 5 to 100 parts by weight, preferably about 10 to 100 parts by weight, based on 100 parts by weight of the polymer. If the liquid polyolefin oligomer is used at a ratio of less than this range, in addition to the difficulty of achieving desired high damping, the kneading properties are deteriorated. In contrast, if the liquid polyolefin oligomer is used at a ratio of more than this range, the tensile strength and kneading properties become problematic.


The rubber composition comprising the above essential components can be further compounded with graphite at a ratio of about 50 parts by weight or less, preferably about 3 to 50 parts by weight, based on 100 parts by weight of the polymer. Examples of graphite include, expanded graphite, expanding graphite, flake graphite, earthy graphite, and the like; of these, flake graphite is preferable. Due to the addition of such graphite, the kneading properties and roll processability can be further improved. However, if graphite is used at a ratio of more than this range, the dispersibility during kneading and mold contamination become problematic, which is not preferable.


Moreover, for the purpose of further improving the damping properties, an aromatic modified terpene resin can be added at a ratio of about 30 parts by weight or less, preferably about 1 to 30 parts by weight, more preferably about 1 to 20 parts by weight, even more preferably about 1 to 10 parts by weight, based on 100 parts by weight of the polymer. If the aromatic modified terpene resin is used at a ratio of less than 1 part by weight, the effect of improving the damping properties is low. If the aromatic modified terpene resin is used at a ratio of more than this range, the kneading properties or low temperature characteristics become problematic. The aromatic modified terpene resins can be used singly or in combination of two or more. In practice, commercial products, such as products of Yasuhara Chemical Co., Ltd., can be used as they are.


As the crosslinking agent, organic peroxides are mainly preferable. Examples of the organic peroxide include t-butyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, 2,5-dimethyl-2,5-di-t-butylperoxyhexine-3, t-butylcumyl peroxide, 1,3-di-t-butylperoxyisopropylbenzene, 2,5-dimethyl-2,5-dibenzoylperoxyhexane peroxyketal, peroxyester, and the like.


Usable examples of peroxyketal include n-butyl-4,4-di(t-butylperoxy)valerate, 2,2-di(t-butylperoxy)butane, 2,2-di[4,4-bis(t-butylperoxy)cyclohexyl]propane, 1,1-di(t-butylperoxy)cyclohexane, di(3,5,5-trimethylhexanoyl)peroxide, 1,1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(t-butylperoxy)-2-methylcyclohexane, and the like.


Further, usable examples of peroxyester include t-butyl peroxybenzoate, t-butyl peroxyacetate, t-hexyl peroxybenzoate, t-butyl peroxy-2-ethylhexyl monocarbonate, t-butyl peroxylaurate, t-butyl peroxyisopropyl monocarbonate, t-butyl peroxy-3,5,5-trimethylhexanoate, t-butyl peroxymaleic acid, t-hexyl peroxyisopropyl monocarbonate, and the like.


Regarding the amount of the crosslinking agent to be compounded, it can be added at a ratio of 0.5 to 10 parts by weight, preferably 0.8 to 5 parts by weight, more preferably 1 to 4 parts by weight, particularly preferably 1 to 3.5 parts by weight, based on 100 parts by weight of the polymer. Within the above range, foaming during vulcanization can be prevented to allow molding. In addition, since the crosslink density is good, products having sufficient physical properties become easy to be obtained.


Further, a crosslinking accelerator may be contained, if necessary. As the crosslinking accelerator, triallyl isocyanurate, triallyl cyanurate, liquid polybutadiene, N,N′-m-phenylenedimaleimide, trimethylolpropane trimethacrylate, and the like can be used. By adding an appropriate amount of crosslinking accelerator, the crosslinking efficiency can be improved, and the heat resistance and mechanical properties can also be improved; thus, the stability as a torsional damper component can also be improved.


In addition to the above components, the rubber composition may contain, if necessary, compounding agents generally used in the rubber industry, such as acid acceptors and antioxidants, as rubber compounding agents.


The rubber composition containing the above components is compounded with a white filler as a reinforcing agent, and a vulcanizing agent, such as sulfur or a sulfur-based vulcanizing agent, as well as, if necessary, zinc oxide as a vulcanization aid, a softener, a plasticizer, an anti-aging agent, and the like. Examples of such other compounding agents are shown below. Examples of the plasticizer include petroleum-based softeners, such as process oil, lubricating oil, and paraffin-based oil; fatty oil-based softeners, such as castor oil, linseed oil, rapeseed oil, and coconut oil; ester-based plasticizers, such as dibutyl phthalate, dioctyl phthalate, dioctyl adipate, and dioctyl sebacate; and the like.


As additives other than the above, anti-aging agents (e.g., polymerized 2,2,4-trimethyl-1,2-dihydroquinoline and 2-mercaptobenzimidazole), auxiliaries (e.g., stearic acid), and acid acceptors, such as hydrotalcite, may be used.


The rubber composition can be prepared by kneading various materials using a kneading machine, such as a single-screw extruder, a twin-screw extruder, a roll, a Banbury mixer, a kneader, or a high shear mixer.


The vulcanization molding thereof is carried out by primary vulcanization performed at about 150 to 200° C. for about 3 to 60 minutes and oven vulcanization (secondary vulcanization) optionally performed at about 120 to 200° C. for about 1 to 24 hours.


Such a rubber composition can be used for a torsional damper, and is vulcanized and molded under the above vulcanization conditions, thereby composing a torsional damper. Such a torsional damper shows a minimum value of tan δ at −30 to 120° C. of 0.11 or more, a volume resistivity of 400 Ω·m or less, and the number of strain of 20000 times or more in a constant strain fatigue test (according to JIS K6270).







EXAMPLES

The following describes the present invention with reference to Examples.


Examples 1 to 17 and Comparative Examples 1 to 7

In addition to the compounding contents of the polymer, carbon black, liquid polyolefin oligomer, graphite, aromatic modified terpene resin, and organic peroxide crosslinking agent shown in Tables 1 to 3, any compounding chemical mentioned above was appropriately added to prepare compositions.


In the present embodiment, to produce a rubber composition for a torsional damper, first, an unvulcanized rubber composition was prepared. The rubber composition was prepared, for example, by kneading predetermined raw materials using a kneading machine, such as an intermix, a kneader or a Banbury mixer, or using an open roll. After that, the prepared rubber compound was subjected to primary vulcanization at 180° C. for 6 minutes and secondary vulcanization at 150° C. for 5 hours using a vulcanization press, a compression molding machine, an injection molding machine, or the like to obtain a test piece with a thickness of 2 mm.


Kneading and roll processability were evaluated according to the following criteria.


Kneading-roll processability: Those satisfying all of the following three items were evaluated as ◯, and those not satisfying any one of these items were evaluated as X.


(1) The kneading machine was not contaminated after discharging the rubber compound.


(2) The rubber compound was in close contact with the roll without separating, and the bank rotated smoothly and had good roll processability.


(3) There was good processability without interruption due to rubber compound adhesion during cutting work to improve dispersibility and rolling work such as sheeting.


Evaluation of each Example and each Comparative Example was ◯.


Using the obtained test pieces, the normal value, vibration characteristics, durability and conductivity were measured and evaluated. The obtained results are shown in Tables 1 and 2 (Examples) and Table 3 (Comparative Examples), together with the compounding contents.


Normal value: according to JIS K6253 (hardness) and JIS K6251 (tensile strength, elongation)


Vibration characteristics: Using a strip-shaped test piece with a width of 6 mm and a thickness of 2 mm, measurement was carried out under the following conditions: gripping tool spacing: 20 mm, average strain: 10%, strain amplitude: ±0.1%, vibration frequency: 100 Hz and tension direction, with reference to JIS K6394 corresponding to ISO 4664-1 using a viscoelastic spectrometer DVE-V4 produced by UBM.


tan δ: In a temperature range of −30° C. to 120° C., tan δ was measured from −30° C. at a heating rate of 2° C./min. Of the measurement points, tan δ values at −30° C., 23° C., 60° C. and 120° C., and the minimum tan δ value in the temperature range of −30° C. to 120° C. were used as representative values.


When the value measured at 60° C. was 0.132 or more and the values measured at the other temperatures were 0.110 or more, this case was evaluated as ⊚. When the values measured at all the temperatures were 0.110 or more, this case was evaluated as ◯. When the values measured at all the temperatures were less than 0.110, this case was evaluated as X.


E′ temperature dependence: In a temperature range of −30° C. to 120° C., E′ was measured from −30° C. at a heating rate of 2° C./min. Of the measurement points, E′ values at −30° C., 60° C., and 120° C. were used as representative values.


A value of E′ (−30° C.)/E′ (60° C.) of 10 or less was evaluated as ⊚, 25 or less was evaluated as ◯, 60 or less was evaluated as Δ, and more than 60 was evaluated as X.


A value of E′ (120° C.)/E′ (60° C.) of 0.7 or more was evaluated as ⊚, 0.5 or more was evaluated as ◯, 0.3 or more was evaluated as Δ, and less than 0.3 was evaluated as X.


Durability: Using dumbbell-shaped No. 6 type test pieces according to JIS K6251 as samples, a constant strain fatigue test was carried out for 5 samples in an atmosphere of 120° C. at an vibration frequency of 5 Hz under the extension condition of 0 to 60%, with reference to JIS K6270, using a constant strain fatigue tester FT-3103 produced by Ueshima Seisakusho Co., Ltd. to repeat strain fatigue 50,000 times. Then, the median number of times the sample broke was calculated.


(The number of times the sample broke was set to 50,000 for the unbroken product.)


When the number of times was 30,000 or more, this case was evaluated as ⊚; when the number of times was 20,000 or more and less than 30,000, this case was evaluated as ◯; when the number of times was 10,000 or more and less than 20,000, this case was evaluated as Δ; and when the number of times was less than 10,000, this case was evaluated as X.


Conductivity: Using test pieces with a width (W) of 20 mm, a length (L) of 100 mm and a thickness (T) of 2 mm, a test was carried out under the following conditions: test temperature: 23° C. and voltage between electrodes: 500 V, with reference to JIS K6271-2 (Parallel terminal electrode system). The insulation resistance value was measured using an insulation resistance tester MY40 produced by Yokogawa Test & Measurement Corporation, and the volume resistivity was calculated according to the following formula:

Volume resistivity ρv (Ω·m)=insulation resistivity R(Ω)×WT/L


Those with a volume resistivity of 40 Ω·m or less were evaluated as ⊚.


Those with a volume resistivity of more than 40 Ω·m and 400 Ω·m or less were evaluated as ◯.


Those with a volume resistivity of more than 400 Ω·m and 1000 Ω·m or less were evaluated as Δ.


Those with a volume resistivity of more than 1000 Ω·m were evaluated as X.














TABLE 1









Example 1
Example 2
Example 3
Example 4





Formulation
EPDM (EP33, produced by JSR)
50
50
50
50


(part by
EPDM (EP35, produced by JSR)
50
50
50
50


weight)
EBDM(EBT K-9330M, produced by Mitsui Chemicals, Inc.)







EBDM (EBT K-8370EM, produced by Mitsui Chemicals, Inc.;







containing 30 phr of oil-extended oil (mineral oil))







Conductive carbon black (Tokablack#5500, produced by Tokai
45
70





Carbon Co., Ltd.; iodine adsorption: 254 mg/g, DBP oil







absorption: 155 cm3/100 g, nitrogen adsorption specific surface







area: 225 m2/g)







Conductive carbon black (Mitsubishi 3230B, produced by


45




Mitsubishi Chemical Corporation; iodine adsorption: 243 mg/g,







DBP oil absorption: 140 cm3/100 g, nitrogen adsorption







specific surface area: 220 m2/g)







Conductive carbon black (Mitsubishi 3400B, produced by



45



Mitsubishi Chemical Corporation; iodine adsorption: 184 mg/g,







DBP oil absorption: 175 cm3/100 g, nitrogen adsorption







specific surface area: 165 m2/g)







HAF carbon black (Shoblack N330L, produced by Cabot







Japan K.K.; iodine adsorption: 81 mg/g, DBP oil absorption:







102 cm3/100 g, nitrogen adsorption specific surface area: 76 m2/g)







Liquid polyolefin oligomer (Lucant HC2000, produced by
10
10
10
10



Mitsui Chemicals, Inc.; Mn 3700)







Organic peroxide crosslinking agent (DCP)
3
3
3
3


Polymer
C3 + C4 content (wt. %)
43.4
43.4
43.4
43.4


composition







Oil-extended
Total mineral oil amount (part by weight)
0
0
0
0


content
Total liquid polyolefin oligomer amount (part by weight)
10
10
10
10


Normal value
Hardness (Duro A)
72
84
72
76



Tensile strength (MPa)
18.7
23.8
17.3
20.0



Elongation (%)
240
240
220
220


Vibration
tan δ evaluation






characteristics
tan δ @ −30° C.
0.738
0.484
0.757
0.672



tan δ @ 23° C.
0.155
0.138
0.155
0.139



tan δ @ 60° C.
0.146
0.149
0.147
0.133



tan δ @ 23° C.
0.122
0.149
0.122
0.122



Minimum tan δ @ −30 to 120° C.
0.122
0.137
0.122
0.122



E′ (−30° C./60° C.)








8.17
7.13
7.74
7.15



E′ (120° C./60° C.)








0.78
0.64
0.79
0.76


Durability
Fatigue life







(median of N = 5)
50000
50000
50000
50000



Number of times of breaking at less than 20,000








0
0
0
0


Conducting
Volume resistivity






property
(Ω · m)
34.8
1.6
36.0
8.0







Example 5
Example 6
Example 7
Example 8





Formulation
EPDM (EP33, produced by JSR)
50
50




(part by
EPDM (EP35, produced by JSR)
50
50
50



weight)
EBDM(EBT K-9330M, produced by Mitsui Chemicals, Inc.)


50




EBDM (EBT K-8370EM, produced by Mitsui Chemicals, Inc.;



130



containing 30 phr of oil-extended oil (mineral oil))







Conductive carbon black (Tokablack#5500, produced by Tokai
100
22.5
45
70



Carbon Co., Ltd.; iodine adsorption: 254 mg/g, DBP oil







absorption: 155 cm3/100 g, nitrogen adsorption specific surface







area: 225 m2/g)







Conductive carbon black (Mitsubishi 3230B, produced by

22.5





Mitsubishi Chemical Corporation; iodine adsorption: 243 mg/g,







DBP oil absorption: 140 cm3/100 g, nitrogen adsorption







specific surface area: 220 m2/g)







Conductive carbon black (Mitsubishi 3400B, produced by







Mitsubishi Chemical Corporation; iodine adsorption: 184 mg/g,







DBP oil absorption: 175 cm3/100 g, nitrogen adsorption







specific surface area: 165 m2/g)







HAF carbon black (Shoblack N330L, produced by Cabot







Japan K.K.; iodine adsorption: 81 mg/g, DBP oil absorption:







102 cm3/100 g, nitrogen adsorption specific surface area: 76 m2/g)







Liquid polyolefin oligomer (Lucant HC2000, produced by
50
10
10
10



Mitsui Chemicals, Inc.; Mn 3700)







Organic peroxide crosslinking agent (DCP)
3
3
3
3


Polymer
C3 + C4 content (wt. %)
43.4
43.4
47.8
46.5


composition







Oil-extended
Total mineral oil amount (part by weight)
0
0
0
30


content
Total liquid polyolefin oligomer amount (part by weight)
50
10
10
10


Normal value
Hardness (Duro A)
79
72
72
66



Tensile strength (MPa)
14.8
19.6
19.6
17.8



Elongation (%)
340
240
240
390


Vibration
tan δ evaluation






characteristics
tan δ @ −30° C.
0.381
0.748
0.724
0.583



tan δ @ 23° C.
0.173
0.155
0.155
0.165



tan δ @ 60° C.
0.197
0.146
0.137
0.143



tan δ @ 23° C.
0.198
0.122
0.116
0.118



Minimum tan δ @ −30 to 120° C.
0.169
0.122
0.116
0.118



E′ (−30° C./60° C.)








7.47
7.96
7.36
5.99



E′ (120° C./60° C.)








0.55
0.79
0.78
0.73


Durability
Fatigue life







(median of N = 5)
50000
50000
50000
50000



Number of times of breaking at less than 20,000








0
0
0
0


Conducting
Volume resistivity






property
(Ω · m)
0.4
33.6
9.2
2.4


























TABLE 2







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Exam-
Exam-
Exam-
Exam-




ple 9
ple 10
ple 11
ple 12
ple 13
ple 14
ple 15
ple 16
ple 17

























Formu-
EPDM (EP33, produced by JSR)
50
50
50




50
50


lation
EPDM (EP35, produced by JSR)
50
50
50




50
50


(part by
EBDM (VNB-EPT PX-008M,



115
115
115
115




weight)
produced by Mitsui Chemicals, Inc.;












containing 15 phr of oil-extended












oil (liquid polyolefin oligomer))












Conductive carbon black
45
45
45
110
110
135
150





(Tokablack#5500, produced by Tokai












Carbon Co., Ltd.; iodine adsorption:












254 mg/g, DBP oil absorption:












155 cm3/100 g nitrogen adsorp-












tion specific surface area: 225 m2/g)












Acetylene black (Denka black Li-435,







45




produced by Denka Co.; iodine adsorp-












tion: 180 mg/g, DBP oil absorption:












220 cm3/100 g, nitrogen adsorp-












tion specific surface area: 133 m2/g)












Ketjenblack (LIONITE EC200L,








45



produced by LION SPECIALTY












CHEMICALS CO., Ltd.; iodine adsorp-












tion: 430 mg/g, DBP oil absorption:












280 cm3/100 g, nitrogen adsorption












specific surface area: 377 m2/g)












Liq. polyolefin oligomer (Lucent
10
10
10
55
55
70
85
10
10



HC2000, produced by Mitsui












Chemicals, Inc.; Mn 3700)












Flake graphite (CPB-3S, produced by

20
10









Chuetsu Graphite Works Co.. Ltd.)












Aromatic modified terpene resin
20

10









(TO-115, produced by Yasuhara












Chemical Co., Ltd.)












Organic peroxide crosslinking
3
3
3
3
2
3
3
3
3



agent (DOP)











Polymer
C3 + C4 content (wt. %)
43.4
43.4
43.4
39.1
39.1
39.1
39.1
43.4
43.4


composi












tion












Oil-
Total mineral oil amount
0
0
0
0
0
0
0
0
0


extended
(part by weight)











content
Total liquid polyolefin oligomer
10
10
10
70
70
85
100
10
10



amount (part by weight)











Normal
Hardness (Duro A)
65
78
71
73
71
77
76
80
81


value
Tensile strength (MPa)
17.2
19.7
19.9
13.2
10.5
10.7
8.4
19.2
20.6



Elongation (%)
440
250
350
320
400
310
330
203
229


Vibration
tan δ evaluation











character-
tan δ @ −30° C.
0.569
0.680
0.716
0.326
0.316
0.273
0.267
0.597
0.584


istics
tan δ @ 23° C.
0.214
0.160
0.183
0.185
0.182
0.170
0.179
0.138
0.131



tan δ @ 60° C.
0.177
0.156
0.170
0.207
0.209
0.199
0.209
0.126
0.131



tan δ @ 120° C.
0.171
0.139
0.156
0.195
0.202
0.196
0.209
0.122
0.122



Minimum tan δ @ −30 to 120° C.
0.171
0.139
0.156
0.176
0.173
0.159
0.167
0.122
0.122



E' (−30° C./60° C.)
Δ












42.3
9.13
18.1
7.32
7.55
6.97
7.56
7.34
7.00



E' (120° C./60° C.)













0.70
0.72
0.70
0.58
0.57
0.54
0.50
0.68
0.70


Durability
Fatigue life












(median of N = 5)
50000
50000
50000
50000
50000
50000
50000
50000
50000



Number of times of breaking at less







Δ




than 20,000
0
1
0
0
0
0
0
2
1


Conducting
Volume resistivity











property
(Ω · m)
174.0
9.6
43.6
0.8
0.8
0.4
0.4
3.6
1.2
























TABLE 3







Compar-
Compar-
Compar-
Compar-
Compar-
Compar-
Compar-




ative
ative
ative
ative
ative
ative
ative




Exam-
Exam-
Exam-
Exam-
Exam-
Exam-
Exam-




ple 1
ple 2
ple 3
ple 4
ple 5
ple 6
ple 7























Formu-
EPDM(EP33, produced by JSR)
50
50
50
50
50
50
50


lation
EPDM (EP35, produced by JSR)
50
50
50
50
50
50
50


(part by
Conductive carbon black (Tokablack#5500,




5
45



weight)
produced by Tokai Carbon Co., Ltd.;










iodine adsorption: 254 mg/g.










DBP oil absorption: 155 cm3/100 g, nitrogen










adsorption specific surface area: 225 m2/g)










HAF carbon black (Shoblack N330L, produced
45



40





by Cabot Japan KK; iodine adsorption:










81 meg, DBP oil absorption: 102 cm3/100 g,










nitrogen adsorption specific surface area: 76 m2/g)










ISAF-LS Seasto00, produced by Tokai Carbon Co.,

45








nitrogen Ltd.; Iodine absorption: 111 mg/g,










DBP oil absorption: 75 cm3/100 g, adsorption










specific surface area: 106 m2/g)










Carbon black (Tokablack #8300, produced by


45







Tokai Carbon Co., Ltd.; for coloring; iodine










adsorption: 236 mg/g, DBP oil absorption:










76 cm3/100 g, nitrogen adsorption specific










surface area: 244 m2/g)










Conductive carbon black (Tokablack#4500,



45






produced by Tokai Carbon Co.. Ltd.;










iodine adsorption: 63 mg/g, DBP oil










absorption: 168 cm3/100 g, nitrogen adsorption










specific surface area: 58 m2/g)










Conductive carbon black (Ketjen black EC300J,






45



produced by LION SPECIALTY










CHEMICALS CO., Ltd.; iodine adsorption: 800










mg/g, DBP oil absorption: 365 cm3/100 g, nitrogen










adsorption specific surface area: 800 m2/g)










Liquid polyolefin oligomer (Lucant HC2000,
10
10
10
10
10

10



produced by Mitsui Chemicals. Inc.; Mn 3700










Organic peroxide crosslinking agent (DCP)
3
3
3
3
3
3
3


Polymer
C3 + C4 content (wt.%)
43.4
43.4
43.4
43.4
43.4
43.4
43.4


composi-










tion










Oil-
Total mineral oil amount (part by weight)
0
0
0
0
0
0
0


extended
Total liquid polyolefin oligomer
10
10
10
10
10
0
10


content
amount (part by weight)









Normal
Hardness (Duro A)
70
68
70
73
70
78
88


value
Tensile strength (MPa)
16.8
17.7
19.4
18.9
18.7
20.2
21.3



Elongation (%)
200
240
360
200
210
190
222


Vibration
tan δ evaluation
X


X
X
X



character-
tan δ @ −30° C.
0.857
0.811
0.647
0.828
0.844
0.707
0.397


istics
tan δ @ 23° C.
0.157
0.164
0.170
0.146
0.156
0.128
0.121



tan δ @ 60° C.
0.130
0.143
0.169
0.123
0.132
0.117
0.136



tan δ @ 120° C
0.107
0.117
0.135
0.104
0.109
0.104
0.137



Minimum tan δ @ −30 to 120° C.
0.107
0.117
0.135
0.104
0.109
0.104
0.121



E' (−30° C./60° C.)











8.21
8.86
9.37
8.33
8.20
9.94
6.74



E' (120° C./60° C.)











0.86
0.82
0.74
0.85
0.85
0.80
0.60


Durability
Fatigue life

X
X



X



(median of N = 5)
33140
2035
6186
50000
50000
50000
1375



Number of times of breaking at less than 20,000
Δ
X
X

Δ

X




2
5
5
0
2
1
5


Conducting
Volume resistivity
X



Δ




property
(Ω · m)
1120 0
156.0
16.8
68.0
424.0
6.8
0.4








Claims
  • 1. A rubber composition for a torsional damper, comprising 10 to 200 parts by weight of carbon black having an iodine adsorption of 100 to 600 mg/g, a DBP oil absorption of 138 to 330 cm3/100 g and a nitrogen adsorption specific surface area of 100 to 530 m2/g, and 5 to 100 parts by weight of a liquid polyolefin oligomer having a number average molecular weight Mn of 3,000 to 4,000, based on 100 parts by weight of at least one of ethylene-propylene-non-conjugated diene terpolymer rubber, ethylene-butene-non-conjugated diene terpolymer rubber and ethylene-propylene copolymer rubber, wherein in the total amount of ethylene and propylene or butene, the content of propylene or butene is 35 to 55 wt. %.
  • 2. The rubber composition for a torsional damper according to claim 1, wherein carbon black having an iodine adsorption of 150 to 450 mg/g, a DBP oil absorption of 138 to 330 cm3/100 g and a nitrogen adsorption specific surface area of 120 to 400 m2/g is used.
  • 3. The rubber composition for a torsional damper according to claim 1, wherein carbon black having an iodine adsorption of 170 to 450 mg/g, a DBP oil absorption of 140 to 330 cm3/100 g and a nitrogen adsorption specific surface area of 160 to 400 m2/g is used.
  • 4. The rubber composition for a torsional damper according to claim 1, wherein 50 parts by weight or less of graphite is further comprised.
  • 5. The rubber composition for a torsional damper according to claim 1, wherein 30 parts by weight or less of aromatic modified terpene resin is further comprised.
  • 6. A torsional damper comprising a vulcanization molding of the rubber composition for a torsional damper according to claim 1.
  • 7. The torsional damper according to claim 6, wherein the minimum value of tan δ at −30 to 120° C. is 0.110 or more and a volume resistivity is 400 Ω·m or less and a constant strain fatigue is 20,000 times or more.
  • 8. A torsional damper comprising a vulcanization molding of the rubber composition for a torsional damper according to claim 4.
  • 9. A torsional damper comprising a vulcanization molding of the rubber composition for a torsional damper according to claim 5.
Priority Claims (1)
Number Date Country Kind
2019-127089 Jul 2019 JP national
PCT Information
Filing Document Filing Date Country Kind
PCT/JP2020/024298 6/22/2020 WO
Publishing Document Publishing Date Country Kind
WO2021/006018 1/14/2021 WO A
US Referenced Citations (3)
Number Name Date Kind
20150001434 Nagata Jan 2015 A1
20160177076 Negami Jun 2016 A1
20200048446 Negami Feb 2020 A1
Foreign Referenced Citations (11)
Number Date Country
104854189 Aug 2015 CN
2 810 985 Dec 2014 EP
3 613 806 Feb 2020 EP
2006-257334 Sep 2006 JP
2014-024929 Feb 2014 JP
2017-183162 Oct 2017 JP
2018071703 May 2018 JP
2013114869 Aug 2013 WO
2013114869 Aug 2013 WO
2015012018 Jan 2015 WO
2018079076 May 2018 WO
Non-Patent Literature Citations (2)
Entry
International Search Report issued in International Patent Application No. PCT/2020/024298, dated Sep. 8, 2020, along with an English translation thereof.
International Preliminary Report on Patentability in International Application No. PCT/2020/024298, dated Sep. 8, 2020, along with an English translation thereof.
Related Publications (1)
Number Date Country
20220275185 A1 Sep 2022 US