RUBBER COMPOSITION FOR TORSIONAL DAMPER

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 cm.sup.3/.sub.100 g and a nitrogen adsorption specific surface area of 100 to 530 m.sup.2/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. %.

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 cm.sup.3/100 g and a nitrogen adsorption specific surface area of 100 to 530 m.sup.2/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 cm.sup.3/100 g and a nitrogen adsorption specific surface area of 120 to 400 m.sup.2/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 cm.sup.3/100 g and a nitrogen adsorption specific surface area of 160 to 400 m.sup.2/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.

Description

EXAMPLES

[0053] The following describes the present invention with reference to Examples.

Examples 1 to 17 and Comparative Examples 1 to 7

[0054] 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.

[0055] 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.

[0056] Kneading and roll processability were evaluated according to the following criteria.

[0057] Kneading-roll processability: Those satisfying all of the following three items were evaluated as O, and those not satisfying any one of these items were evaluated as X .

[0058] (1) The kneading machine was not contaminated after discharging the rubber compound.

[0059] (2) The rubber compound was in close contact with the roll without separating, and the bank rotated smoothly and had good roll processability.

[0060] (3) There was good processability without interruption due to rubber compound adhesion during cutting work to improve dispersibility and rolling work such as sheeting.

[0061] Evaluation of each Example and each Comparative Example was O.

[0062] 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.

[0063] Normal value: according to JIS K6253 (hardness) and JIS K6251 (tensile strength, elongation)

[0064] 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.

[0065] 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.

[0066] 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 O. When the values measured at all the temperatures were less than 0.110, this case was evaluated as X .

[0067] 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.

[0068] A value of E′ (−30° C.)/E′ (60° C.) of 10 or less was evaluated as ⊚, 25 or less was evaluated as O, 60 or less was evaluated as Δ, and more than 60 was evaluated as X.

[0069] A value of E′ (120° C.)/E′ (60° C.) of 0.7 or more was evaluated as ⊚, 0.5 or more was evaluated as O, 0.3 or more was evaluated as Δ, and less than 0.3 was evaluated as X .

[0070] 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 O; 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 .

[0071] 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 (n.m)=insulation resistivity R(Ω)×WT/L

[0072] Those with a volume resistivity of 40 Ω.m or less were evaluated as ⊚.

[0073] Those with a volume resistivity of more than 40 Ω.m and 400 Ω.m or less were evaluated as O.

[0074] Those with a volume resistivity of more than 400 Ω.m and 1000 Ω.m or less were evaluated as Δ.

[0075] Those with a volume resistivity of more than 1000 Ω.m were evaluated as X .

TABLE-US-00001 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 .Math. 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 .Math. m) 0.4 33.6 9.2 2.4

TABLE-US-00002 TABLE 2 Exam- Exam- Exam- Exam- Exam- 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 .Math. m) 174.0 9.6 43.6 0.8 0.8 0.4 0.4 3.6 1.2

[0076] M

TABLE-US-00003 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 .Math. m) 1120 0 156.0 16.8 68.0 424.0 6.8 0.4