CA2645512C - Epdm composition for vibration isolators - Google Patents
Epdm composition for vibration isolators Download PDFInfo
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- CA2645512C CA2645512C CA2645512A CA2645512A CA2645512C CA 2645512 C CA2645512 C CA 2645512C CA 2645512 A CA2645512 A CA 2645512A CA 2645512 A CA2645512 A CA 2645512A CA 2645512 C CA2645512 C CA 2645512C
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- 239000000203 mixture Substances 0.000 title claims abstract description 66
- 229920001971 elastomer Polymers 0.000 claims abstract description 168
- 239000000806 elastomer Substances 0.000 claims abstract description 80
- 229920000181 Ethylene propylene rubber Polymers 0.000 claims abstract description 33
- 239000010445 mica Substances 0.000 claims abstract description 29
- 229910052618 mica group Inorganic materials 0.000 claims abstract description 29
- 229920006285 olefinic elastomer Polymers 0.000 claims abstract description 18
- 150000002978 peroxides Chemical class 0.000 claims abstract description 16
- 239000000470 constituent Substances 0.000 claims abstract description 14
- 239000012968 metallocene catalyst Substances 0.000 claims abstract description 9
- 239000004614 Process Aid Substances 0.000 claims description 14
- 230000005540 biological transmission Effects 0.000 claims description 13
- 239000007795 chemical reaction product Substances 0.000 claims description 10
- 239000002245 particle Substances 0.000 claims description 10
- 239000012763 reinforcing filler Substances 0.000 claims description 10
- 238000000034 method Methods 0.000 claims description 8
- 239000010734 process oil Substances 0.000 claims description 7
- 230000035939 shock Effects 0.000 claims description 4
- 239000006096 absorbing agent Substances 0.000 claims 2
- 229920002943 EPDM rubber Polymers 0.000 description 35
- 238000007906 compression Methods 0.000 description 16
- 230000006835 compression Effects 0.000 description 16
- 238000012360 testing method Methods 0.000 description 12
- 235000019241 carbon black Nutrition 0.000 description 9
- 239000006229 carbon black Substances 0.000 description 9
- -1 cyclic dienes Chemical class 0.000 description 9
- 239000004615 ingredient Substances 0.000 description 8
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 6
- 238000005299 abrasion Methods 0.000 description 6
- 239000000945 filler Substances 0.000 description 6
- 230000002411 adverse Effects 0.000 description 5
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- 229920001577 copolymer Polymers 0.000 description 4
- 150000001993 dienes Chemical class 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 229920000642 polymer Polymers 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 229920005573 silicon-containing polymer Polymers 0.000 description 4
- OJOWICOBYCXEKR-KRXBUXKQSA-N (5e)-5-ethylidenebicyclo[2.2.1]hept-2-ene Chemical compound C1C2C(=C/C)/CC1C=C2 OJOWICOBYCXEKR-KRXBUXKQSA-N 0.000 description 3
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 3
- 239000005977 Ethylene Substances 0.000 description 3
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 description 3
- 238000013016 damping Methods 0.000 description 3
- AFZSMODLJJCVPP-UHFFFAOYSA-N dibenzothiazol-2-yl disulfide Chemical compound C1=CC=C2SC(SSC=3SC4=CC=CC=C4N=3)=NC2=C1 AFZSMODLJJCVPP-UHFFFAOYSA-N 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 239000007924 injection Substances 0.000 description 3
- 238000002955 isolation Methods 0.000 description 3
- 239000003921 oil Substances 0.000 description 3
- 229920003245 polyoctenamer Polymers 0.000 description 3
- 229920001296 polysiloxane Polymers 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 229920005989 resin Polymers 0.000 description 3
- 239000011347 resin Substances 0.000 description 3
- 239000000377 silicon dioxide Substances 0.000 description 3
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 3
- 229920002554 vinyl polymer Polymers 0.000 description 3
- ZNRLMGFXSPUZNR-UHFFFAOYSA-N 2,2,4-trimethyl-1h-quinoline Chemical compound C1=CC=C2C(C)=CC(C)(C)NC2=C1 ZNRLMGFXSPUZNR-UHFFFAOYSA-N 0.000 description 2
- 244000043261 Hevea brasiliensis Species 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 2
- 239000000853 adhesive Substances 0.000 description 2
- 230000001070 adhesive effect Effects 0.000 description 2
- 239000003963 antioxidant agent Substances 0.000 description 2
- 235000014113 dietary fatty acids Nutrition 0.000 description 2
- 239000004205 dimethyl polysiloxane Substances 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 239000000194 fatty acid Substances 0.000 description 2
- 229930195729 fatty acid Natural products 0.000 description 2
- 150000004665 fatty acids Chemical class 0.000 description 2
- 238000009472 formulation Methods 0.000 description 2
- 238000005227 gel permeation chromatography Methods 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 238000001746 injection moulding Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000000465 moulding Methods 0.000 description 2
- 229920003052 natural elastomer Polymers 0.000 description 2
- 229920001194 natural rubber Polymers 0.000 description 2
- 239000010690 paraffinic oil Substances 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 229920000435 poly(dimethylsiloxane) Polymers 0.000 description 2
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 description 2
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 description 2
- 230000000717 retained effect Effects 0.000 description 2
- 230000035882 stress Effects 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 239000011593 sulfur Substances 0.000 description 2
- 238000001721 transfer moulding Methods 0.000 description 2
- XOOUIPVCVHRTMJ-UHFFFAOYSA-L zinc stearate Chemical class [Zn+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O XOOUIPVCVHRTMJ-UHFFFAOYSA-L 0.000 description 2
- RRKODOZNUZCUBN-CCAGOZQPSA-N (1z,3z)-cycloocta-1,3-diene Chemical compound C1CC\C=C/C=C\C1 RRKODOZNUZCUBN-CCAGOZQPSA-N 0.000 description 1
- PRBHEGAFLDMLAL-GQCTYLIASA-N (4e)-hexa-1,4-diene Chemical compound C\C=C\CC=C PRBHEGAFLDMLAL-GQCTYLIASA-N 0.000 description 1
- NALFRYPTRXKZPN-UHFFFAOYSA-N 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane Chemical compound CC1CC(C)(C)CC(OOC(C)(C)C)(OOC(C)(C)C)C1 NALFRYPTRXKZPN-UHFFFAOYSA-N 0.000 description 1
- IPJGAEWUPXWFPL-UHFFFAOYSA-N 1-[3-(2,5-dioxopyrrol-1-yl)phenyl]pyrrole-2,5-dione Chemical compound O=C1C=CC(=O)N1C1=CC=CC(N2C(C=CC2=O)=O)=C1 IPJGAEWUPXWFPL-UHFFFAOYSA-N 0.000 description 1
- XMNIXWIUMCBBBL-UHFFFAOYSA-N 2-(2-phenylpropan-2-ylperoxy)propan-2-ylbenzene Chemical compound C=1C=CC=CC=1C(C)(C)OOC(C)(C)C1=CC=CC=C1 XMNIXWIUMCBBBL-UHFFFAOYSA-N 0.000 description 1
- DQQNMIPXXNPGCV-UHFFFAOYSA-N 3-hexyne Chemical compound CCC#CCC DQQNMIPXXNPGCV-UHFFFAOYSA-N 0.000 description 1
- INYHZQLKOKTDAI-UHFFFAOYSA-N 5-ethenylbicyclo[2.2.1]hept-2-ene Chemical compound C1C2C(C=C)CC1C=C2 INYHZQLKOKTDAI-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- PDQAZBWRQCGBEV-UHFFFAOYSA-N Ethylenethiourea Chemical compound S=C1NCCN1 PDQAZBWRQCGBEV-UHFFFAOYSA-N 0.000 description 1
- 239000004605 External Lubricant Substances 0.000 description 1
- 239000004606 Fillers/Extenders Substances 0.000 description 1
- 239000004610 Internal Lubricant Substances 0.000 description 1
- 241000282320 Panthera leo Species 0.000 description 1
- 239000005662 Paraffin oil Substances 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 1
- 235000021355 Stearic acid Nutrition 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- SXQXMCWCWVCFPC-UHFFFAOYSA-N aluminum;potassium;dioxido(oxo)silane Chemical compound [Al+3].[K+].[O-][Si]([O-])=O.[O-][Si]([O-])=O SXQXMCWCWVCFPC-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 229940053200 antiepileptics fatty acid derivative Drugs 0.000 description 1
- 230000003078 antioxidant effect Effects 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000002902 bimodal effect Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000004927 clay Substances 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000000748 compression moulding Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- LSXWFXONGKSEMY-UHFFFAOYSA-N di-tert-butyl peroxide Chemical compound CC(C)(C)OOC(C)(C)C LSXWFXONGKSEMY-UHFFFAOYSA-N 0.000 description 1
- 229940116901 diethyldithiocarbamate Drugs 0.000 description 1
- LMBWSYZSUOEYSN-UHFFFAOYSA-N diethyldithiocarbamic acid Chemical compound CCN(CC)C(S)=S LMBWSYZSUOEYSN-UHFFFAOYSA-N 0.000 description 1
- 238000010410 dusting Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000006353 environmental stress Effects 0.000 description 1
- 239000005038 ethylene vinyl acetate Substances 0.000 description 1
- 239000003063 flame retardant Substances 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 230000008642 heat stress Effects 0.000 description 1
- QYFRTHZXAGSYGT-UHFFFAOYSA-L hexaaluminum dipotassium dioxosilane oxygen(2-) difluoride hydrate Chemical compound O.[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[F-].[F-].[Al+3].[Al+3].[Al+3].[Al+3].[Al+3].[Al+3].[K+].[K+].O=[Si]=O.O=[Si]=O.O=[Si]=O.O=[Si]=O.O=[Si]=O.O=[Si]=O QYFRTHZXAGSYGT-UHFFFAOYSA-L 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- OFHMODDLBXETIK-UHFFFAOYSA-N methyl 2,3-dichloropropanoate Chemical compound COC(=O)C(Cl)CCl OFHMODDLBXETIK-UHFFFAOYSA-N 0.000 description 1
- 239000012764 mineral filler Substances 0.000 description 1
- 239000003607 modifier Substances 0.000 description 1
- QIQXTHQIDYTFRH-UHFFFAOYSA-N octadecanoic acid Chemical compound CCCCCCCCCCCCCCCCCC(O)=O QIQXTHQIDYTFRH-UHFFFAOYSA-N 0.000 description 1
- OQCDKBAXFALNLD-UHFFFAOYSA-N octadecanoic acid Natural products CCCCCCCC(C)CCCCCCCCC(O)=O OQCDKBAXFALNLD-UHFFFAOYSA-N 0.000 description 1
- 239000012188 paraffin wax Substances 0.000 description 1
- 235000019809 paraffin wax Nutrition 0.000 description 1
- 235000019271 petrolatum Nutrition 0.000 description 1
- 239000004014 plasticizer Substances 0.000 description 1
- 229920001200 poly(ethylene-vinyl acetate) Polymers 0.000 description 1
- 229920001083 polybutene Polymers 0.000 description 1
- 150000004291 polyenes Chemical class 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000010058 rubber compounding Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 229910000077 silane Inorganic materials 0.000 description 1
- 229910052604 silicate mineral Inorganic materials 0.000 description 1
- 239000008117 stearic acid Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229920003051 synthetic elastomer Polymers 0.000 description 1
- 235000012222 talc Nutrition 0.000 description 1
- 229910052714 tellurium Inorganic materials 0.000 description 1
- PORWMNRCUJJQNO-UHFFFAOYSA-N tellurium atom Chemical compound [Te] PORWMNRCUJJQNO-UHFFFAOYSA-N 0.000 description 1
- GJBRNHKUVLOCEB-UHFFFAOYSA-N tert-butyl benzenecarboperoxoate Chemical compound CC(C)(C)OOC(=O)C1=CC=CC=C1 GJBRNHKUVLOCEB-UHFFFAOYSA-N 0.000 description 1
- 229920002725 thermoplastic elastomer Polymers 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
- 230000004580 weight loss Effects 0.000 description 1
- BOXSVZNGTQTENJ-UHFFFAOYSA-L zinc dibutyldithiocarbamate Chemical compound [Zn+2].CCCCN(C([S-])=S)CCCC.CCCCN(C([S-])=S)CCCC BOXSVZNGTQTENJ-UHFFFAOYSA-L 0.000 description 1
- 239000011787 zinc oxide Substances 0.000 description 1
- PIMBTRGLTHJJRV-UHFFFAOYSA-L zinc;2-methylprop-2-enoate Chemical compound [Zn+2].CC(=C)C([O-])=O.CC(=C)C([O-])=O PIMBTRGLTHJJRV-UHFFFAOYSA-L 0.000 description 1
- 239000004711 α-olefin Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/04—Homopolymers or copolymers of ethene
- C08L23/08—Copolymers of ethene
- C08L23/0807—Copolymers of ethene with unsaturated hydrocarbons only containing more than three carbon atoms
- C08L23/083—Copolymers of ethene with aliphatic polyenes, i.e. containing more than one unsaturated bond
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/16—Elastomeric ethene-propene or ethene-propene-diene copolymers, e.g. EPR and EPDM rubbers
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/34—Silicon-containing compounds
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/04—Oxygen-containing compounds
- C08K5/14—Peroxides
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2314/00—Polymer mixtures characterised by way of preparation
- C08L2314/06—Metallocene or single site catalysts
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Compositions Of Macromolecular Compounds (AREA)
Abstract
A rubber composition having (A) an elastomer component in which the primary elastomer constituent is an ethylene-propylene elastomer polymerized in the gas phase with a metallocene catalyst and having a molecular weight of at least about 250,000; (B) a silicon-modified olefinic elastomer in an amount of from about 5 to about 50 parts per hundred parts of the elastomer component; (C) ground mica in an amount of from about 2.5 to about 30 parts per hundred parts of the elastomer component; and (D) a peroxide curative. The composition may be used in a vibration isolator which may be used in a belt drive system.
Description
EPDM COMPOSITION FOR VIBRATION ISOLATORS
Cross Reference to related application [0001] Reference is made to Application Serial Number 11/726,091 filed Mar.
21, 2007 and published as U.S. 2008/0234080A1.
BACKGROUND OF THE INVENTION
Field of the Invention
Cross Reference to related application [0001] Reference is made to Application Serial Number 11/726,091 filed Mar.
21, 2007 and published as U.S. 2008/0234080A1.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] This invention relates generally to an EPDM rubber composition for vibration isolators and such dynamic articles using the composition, more particularly to a rubber composition comprising high-molecular-weight gas-phase metal locene EPDM, ground mica, and silicone-modified EPDM.
Description of the Prior Art
Description of the Prior Art
[0003] Vibrations occur in vehicles, rotating or reciprocating machinery, and the like. Vibrations may be isolated, or absorbed or damped by appropriate placement of rubber members. The term "vibration isolation will be used herein in its most general sense and is intended to encompass isolation, absorption, and damping of any of various modes of vibration, shock, or the like. "Vibration isolator will be used herein for any kind of device for reducing, damping or absorbing vibration, shock, or associated noise or harshness or for isolating or preventing the transmission thereof from its source to another point in a dynamic system or to a user or observer.
[0004] Rubber for dynamic articles such as isolators and other dynamic applications of elastomers, must generally meet demanding physical requirements, such as tear strength, heat resistance, low compression set, flex fatigue, etc.
Some of these properties tend to be in opposition, making improved rubber compounds difficult to achieve. For example, increased crosslink density of cured rubber generally helps reduce compression set, but also results in reduced tear strength. Natural rubber has been a preferred elastomer for isolators because of its high strength, but it is lacking in heat resistance.
Some of these properties tend to be in opposition, making improved rubber compounds difficult to achieve. For example, increased crosslink density of cured rubber generally helps reduce compression set, but also results in reduced tear strength. Natural rubber has been a preferred elastomer for isolators because of its high strength, but it is lacking in heat resistance.
[0005] Ethylene-alpha-olefin elastomers such as ethylene-propylene copolymers and ethylene-propylene-diene terpolymers ("EPDM") are general purpose synthetic elastomers known for good heat resistance, economical, easy to process, but low tear strength and poor dynamic fatigue resistance when compounded for low compression set and heat resistance, for example, by the use of peroxide cure systems. Use of EPDM in dynamic applications has been rather limited, especially for peroxide-cured EPDM.
Peroxide-cured compositions suitable for belts are disclosed by U.S. Pat. No.
5,610,217.
Peroxide-cured compositions suitable for rubber-metal bonded vibration isolators such as crank dampers are disclosed in U.S. Pat. Nos. 7,078,104 and 7,166,678. Sulfur-cured compositions suitable for dynamic applications as a replacement for natural rubber parts are disclosed in U.S. Pat. No. 6,693,145.
Peroxide-cured compositions suitable for belts are disclosed by U.S. Pat. No.
5,610,217.
Peroxide-cured compositions suitable for rubber-metal bonded vibration isolators such as crank dampers are disclosed in U.S. Pat. Nos. 7,078,104 and 7,166,678. Sulfur-cured compositions suitable for dynamic applications as a replacement for natural rubber parts are disclosed in U.S. Pat. No. 6,693,145.
[0006] Silicone-modified EPDM is disclosed for example in U.S. Pat. No.
6,380,312 for use in oil resistant thermoplastic elastomer blends. Elastomeric blends of EPDM with silicone-modified EPDM are disclosed in U.S. Pat. No. 5,985,970 for the purpose of producing a tack-free surface on crosslinked EPDM products.
6,380,312 for use in oil resistant thermoplastic elastomer blends. Elastomeric blends of EPDM with silicone-modified EPDM are disclosed in U.S. Pat. No. 5,985,970 for the purpose of producing a tack-free surface on crosslinked EPDM products.
[0007] Mica is known for general use as a filler, especially in plastics, for specific use as non-conducting or insulating filler in elastomers or plastics, and for use as a dusting agent to prevent sticking of uncured rubber stocks, and the like. Mica is also known to adversely affect the fatigue life of carbon-black-filled or silica-filled elastomeric compounds.
SUMMARY
SUMMARY
[0008] The present invention is directed to compositions which provide a rubber member suitable for use in dynamic applications in general and for vibration isolators in particular. These compositions exhibit high tear strength, low compression set, good fatigue resistance, and heat resistance, and have particularly advantageous abrasion resistance and/or frictional properties which make the inventive compositions particularly advantageous for use as vibration-isolating or vibration-absorbing rubber members in devices having a non-bonded surface or point of contact between the rubber member and a structural member. The invention is also directed to articles and systems incorporating the inventive composition or a rubber member made therefrom.
[0009] Embodiments of the invention are directed to rubber compositions having an elastomer component in which the primary elastomer constituent is an ethylene-propylene elastomer polymerized in the gas phase with a metallocene catalyst and having a molecular weight of at least about 250,000; a silicon-modified olefinic elastomer in an amount of from about 5 to about 50 parts per hundred parts of the elastomer;
ground mica in an amount of from about 2.5 to about 30 parts per hundred parts of the elastomer; and a peroxide curative. The invention is also directed to the crosslinked reaction products of the foregoing composition.
ground mica in an amount of from about 2.5 to about 30 parts per hundred parts of the elastomer; and a peroxide curative. The invention is also directed to the crosslinked reaction products of the foregoing composition.
[0010] In some embodiments, the olefinic elastomer may be silicone-modified ethylene-propylene elastomer. The molecular weight of the primary elastomer constituent may be in the range from about 300,000 to about 350,000. The ground mica may have a particle size such that the majority of particles pass through a number 325 mesh screen.
100111 In other embodiments, the amount of the mica may be from about 2.5 to about 10 parts per hundred parts of the elastomer and the amount of the silicone-modified ethylene-propylene elastomer may be from about 5 to about 20 parts per hundred parts of the elastomer.
[0012] In other embodiments, the rubber composition may include one or more of the following: a minor amount of low-molecular-weight ethylene-propylene elastomer, from about 20 to about 150 parts per hundred parts of the elastomer of reinforcing filler;
from about 20 to about 100 parts per hundred parts of the elastomer of process oil; and from about 1 to about 20 parts per hundred parts of the elastomer of process aid.
[0013] In certain embodiments, the inventive composition is crosslinked to form a rubber member having a cured tear strength of at least about 45 kN/m as determined by the method of ASTM D624 using die C at room temperature and/or a hardness of at least about 75 on the Shore A scale.
10014] The invention is also directed to a dynamic article such as a vibration isolator having a structural member and a crosslinked rubber member formed from an embodiment of the inventive composition. In the dynamic article, the rubber member has a surface engaged with a surface of the structural member, but not bonded thereto, and the rubber member provides advantageous durability including abrasion resistance.
100151 The invention is also directed to a system comprising the inventive dynamic article and a power transmission system in driving relation thereto. The power transmission system may include a toothed belt in driving engagement with the inventive isolator.
[0016] According to an embodiment of the present invention, there is provided a rubber composition comprising: 100 parts of elastomer comprising as its primary elastomer constituent an ethylene-propylene elastomer polymerized in the gas phase with a metallocene catalyst and having a molecular weight of at least about 250,000; a silicone-modified olefinic elastomer in an amount of from about 5 to about 50 parts per hundred parts of the elastomer;
ground mica in an amount of from about 2.5 to about 30 parts per hundred parts of the elastomer; and a peroxide curative, or the crosslinked reaction product of all the components of the composition.
[0016a] According to another embodiment of the present invention, there is provided a dynamic article comprising a structural member and a crosslinked rubber member comprising the reaction product of: 100 parts of elastomer comprising as its primary elastomer constituent an ethylene-propylene elastomer polymerized in the gas phase with a metallocene catalyst and having a molecular weight of at least about 250,000; a silicone-modified olefinic elastomer in an amount of from about 5 to about 50 parts per hundred parts of the elastomer; ground mica in an amount of from about 2.5 to about 30 parts per hundred parts of the elastomer; and a peroxide curative.
[0016b] According to still another embodiment of the present invention, there is provided a system comprising a dynamic article and a power transmission system in driving engagement with said dynamic article, wherein the dynamic article comprises a structural member and a crosslinked rubber member comprising the reaction product of: 100 parts of elastomer comprising as its primary elastomer constituent an ethylene-propylene elastomer polymerized in the gas phase with a metallocene catalyst and having a molecular weight of at least about 250,000; a silicone-modified olefinic elastomer in an amount of from about 5 to about 50 parts per hundred parts of the elastomer; ground mica in an amount of from about 2.5 to about 30 parts per hundred parts of the elastomer; and a peroxide curative.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The accompanying drawings, which are incorporated in and form part of the specification in which like numerals designate like parts, illustrate embodiments of the present invention and together with the description, serve to explain the principles of the invention. In the drawings:
[0018] FIG. 1 is a sectional view of an anti-vibration mount according to an embodiment of the invention;
[0019] FIG. 2 is a perspective view of a vibration isolator according to an embodiment of the invention; and, [0020] FIG. 3 is an exploded view of a wheel isolator according to an embodiment of the invention.
4a DETAILED DESCRIPTION
[0021] In one embodiment the invention is a rubber composition comprising an ethylene-propylene elastomer, a silicon-modified olefinic elastomer, mica, and a peroxide curative, or the crosslinked reaction product thereof. In other embodiments the rubber composition may also have one or more additional ingredients, such as reinforcing filler, process oil, and/or process aid.
[0022] The term ethylene-propylene elastomer, used herein and in the claims, includes rubbery copolymers of ethylene and propylene, optionally copolymerized with at least one polyene, usually a diene. Thus, saturated ethylene-propylene copolymer rubber, commonly called "EPM" rubber or elastomer, can be used. Examples of unsaturated ethylene-propylene-diene elastomer, commonly called "EPDM" rubber or elastomer, which are satisfactory comprise the products from the polymerization of ethylene and propylene, and a lesser quantity of non-conjugated diene. Satisfactory non-conjugated dienes include straight chain dienes such as 1,4-hexadiene, cyclic dienes such as cyclooctadiene, and bridged cyclic dienes such as ethylidenenorbornene ("ENB") or vinylnorbornene.
100231 The ethylene-propylene elastomer used as the primary elastomer constituent in embodiments of the invention is preferably polymerized in the gas phase by means of metallocene catalyst and preferably has a high molecular weight. By molecular weight is meant weight average molecular as determined by gel permeation chromatography ("GPC") for example. Preferably the molecular weight of the primary ethylene-propylene elastomer is greater than 250,000 or greater than about 300,000. The molecular weight of the primary ethylene-propylene elastomer may be in the range from about 300,000 to about 350,000. Such ethylene-propylene elastomer grades are available commercially in a granular form under the trademark NORDEL MG by The Dow Chemical Company.
The granules of NORDEL MG are generally coated with carbon black. When determining the amount of elastomer present in a rubber composition, the amount of carbon black present in the NORDEL MG is generally excluded. A preferred grade is NORDEL MG 47130 which has a molecular weight of 308,000 and came with 30 PHR
of carbon black in the examples reported below.
[0024] The term "primary elastomer constituent" means making up more than half of the total of the elastomeric constituents. Preferably, the primary elastomer constituent makes up 70 to 90 percent or even up to/ 100 percent of the elastomer present in the inventive composition. Additional elastomer constituents may be blended with the primary elastomer for various purposes. For example, other grades of EPM or EPDM
may be blended in minor amounts for example to improve processing. A minor amount means less than half, preferably from 1 to 30 percent.
[0025] The silicon-modified olefinic elastomer component of the composition embodiments of the present invention includes olefinic elastomers which have been modified with a silicon-containing polymer. Suitable olefinic elastomers include EPM
and EPDM elastomers described above, as well as others including ethylene-vinyl acetate copolymer elastomers. The silicon-containing polymer component includes various organopolysiloxanes, methoxy-stopped silicones, silanol-stopped silicones, etc. Each of the foregoing components may be manufactured by conventional techniques, and many are commercially available.
[0026]
Particularly preferred silicon-modified olefinic elastomers include silicone-modified EPDM with polydimethylsiloxane polymers with either vinyl or methyl-terminated polymer chains, preferably methyl-terminated polymer chains. The vinyl content of the polydimethylsiloxane polymer may range between 0 to 4 percent, preferably between 0.1 to 1 weight percent vinyl. The EPDM component of the silicone-modified EPDM may be 10 to 50 weight percent, preferably between 20 to 30 weight percent. Silicone-modified EPDM may be a compatibilized blend of silicone or silicon-containing polymer and EPDM. Examples of useful silicone-modified EPDM
elastomers commercially available include those sold under the ROYALTHERM trademark by Lion Copolymer, LLC. The modified elastomers may also contain additives such as fillers, etc. The amount of silicon-modified olefinic elastomer may be from about 5 to about 50 parts per hundred parts of ethylene-propylene elastomer ("PHR"), or from 5 to about 20 PHR.
[0027] The mica used in the invention is a member of a group of potassium aluminum silicate minerals having a sheet or plate-like crystalline structure.
Mica includes muscovite mica. The mica is preferably ground to a suitable particle size for rubber compounding. A suitable particle size of mica is -325 mesh, meaning most of the particles pass through a number 325 mesh screen. Suitable grades include 160-D
Mica, 325-D Mica, 325 Mesh Mica, 325-MF Mica, and 325-FF Mica available from Harwick Standard Distribution Corporation. These grades range in screen analysis from 74% to 96% passing through a 325 mesh screen, with 1% to 6% retained on a 200 mesh screen and substantially the rest retained on the 325 mesh screen. The mica may, but need not, be treated, for example with a silane or the like for enhanced dispersion in or adhesion to the elastomer matrix. The amount of mica used may be in the range from about 2.5 to about 30 PHR, or from about 2.5 to about 15 PHR, preferably from 2.5 to about 10 PHR.
[0028] The peroxide curative may be one or more of those known in the art.
Exemplary peroxide curatives include, but are not limited to, 1,1-di-(t-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethy1-2,5-di-(t-butylperoxy) 3-hexyne, dicumyl peroxide, oc-a'-bis(t-butylperoxy) diisopropyl benzene, di-t-butyl peroxide, 2,5-dimethy1-2,5-di-t-butylperoxyhexane, and t-butyl perbenzoate. Cure-effective amounts of peroxide may range from 1 to 10 PHR. It should be understood that the inventive composition may conveniently be described by the ingredients used, but then is mixed, formed, crosslinked or cured, usually by the application of heat and possibly pressure in a mold, so that a rubber article formed therefrom becomes a reaction product of those ingredients.
[0029] Reinforcing filler may be used in embodiments of the invention, including one or more carbon blacks, silicas, clays, talcs, or other non-black mineral fillers, treated or untreated, and the like. The amount of reinforcing filler may be in the range from about 20 to about 150 PHR, or from about 50 to about 100 PHR. The amount of reinforcing filler may include amounts of carbon black supplied with the ethylene-propylene elastomer, amounts of silica supplied with the silicon-modified olefinic elastomer, or amounts of fillers supplied with other ingredients.
[0030] Process oil may be used including one or more paraffinic oil, naphthenic oil, synthetic plasticizer, or the like. Paraffinic oil is preferred. Such oils may be included or supplied with an elastomer or other ingredient. The amount of process oil may be in the range from about 20 to about 100 PHR.
[0031] Process aid may be used including one or more internal and/or external lubricants, compatibilizers, dispersion aids, resins, and the like. In particular embodiments of the invention, low-molecular-weight or low-Mooney-viscosity ethylene-propylene elastomer may be used as a process aid. For example, an EPDM
elastomer with Mooney viscosity in the range of from about 15 to about 30, or preferably from about 20 to about 25, may be used to improve the processing of the inventive composition. In other embodiments, process aids such as fatty acids, fatty acid derivatives, polyoctenamers, paraffin waxes, low molecular weight polyethylene and polybutene, and the like, including for example one or more process aids marketed by Struktol Company of America may be used. The amount of process aid used may be from about 1 PHR to about 20 PHR.
[0032] Other ingredients known for use in elastomer compounds may be used. For example, the composition may include one or more additional elastomers, extenders, non-reinforcing fillers, metal oxides, stearates, antioxidants, antiozonants, radical or acid scavengers, coagents, scorch retarders, cure accelerators, colorants, tackifiers, resins, compatibilizers, fire retardants, and the like.
[0033] Thus, in one preferred embodiment the invention is a rubber composition comprising 100 parts of ethylene-propylene elastomer, from about 5 to about 50 parts of silicon-modified ethylene-propylene elastomer, from about 2.5 to about 30 parts of mica, and a peroxide curative, or the crosslinked reaction products thereof.
[0034] In other preferred embodiments the rubber composition may also have one or more additional ingredients, such as from about 20 to about 150 parts of reinforcing filler, from about 20 to about 100 parts of process oil, and/or from about I
to about 20 parts of process aid. In one embodiment, the process aid may include a low-molecular-weight ethylene-propylene elastomer, which may also be counted as part of the elastomer of the composition.
[0035] In particular for use in various vibration isolating or damping devices, embodiments of the inventive rubber composition may be advantageously compounded to have a predetermined hardness, a predetermined minimum tear strength, low compression set, and generally good physical properties. It is advantageous for cured rubber of the inventive composition to exhibit a hardness of at least about 75 or from about 75 to about 85 on the Shore A scale. It is also advantageous for cured rubber of the inventive composition to exhibit tear strength of at least about 45 kN/m when tested according to ASTM D624 using die C at room temperature. It also may be advantageous for cured rubber of the inventive composition to exhibit compression set of less than 30%, or less than 25%, when tested according to ASTM D395 Method B for 22 hours at 150 C.
In addition to the aforementioned properties, cured rubber members of embodiments of the invention exhibit excellent durability under dynamic, possibly abrasive, conditions as might be found in vibration isolators. These and other advantages will be described in more detail in connection with the examples below.
[0036] According to an embodiment of the invention, FIG. 1 shows a sectional view of vertically adjustable vibration isolation mount 15, having rubber member 34 formed of a rubber composition according to an embodiment of the invention.
Rubber member 34 is mounted on core 32 and preferably bonded at interface 36 between the rubber member and the core. Lower flat surface 30 is adapted to engage a supporting surface such as floor 13. Rubber member 34 and core 32 are housed in cavity 28 which is defined by frame 20, which is a structural member in this device. The dimension of cavity 28 is such as to snugly receive rubber member 34. The cavity sides engage a portion of the side surface of the rubber member at interface 26. There is no bond or adhesive between rubber member 34 and frame 20 at interface 26, so the engagement is frictional and potentially the source of wear or abrasion in use. Bolt 22 is threaded through frame 20 at hole 18 to adjust the height of the mount. Lock nut 24 allows the mount to be locked in position. The inventive rubber composition used in the rubber member insulates the frame 20 from the floor 13 and absorbs, dampens, or isolates vibrations generated by some apparatus, not shown, mounted upon frame 20.
Rubber material present between the side of core 32 and frame 20 permits horizontal vibrations to be damped with excellent resistance to frictional wear at interface 26. Use of an embodiment of the inventive rubber member may also provide excellent durability at surface 30. Floor 13 may also be considered a structural member which contacts or engages a surface of the rubber member without adhesive at the interface.
[0037] According to another embodiment of the invention, FIG. 2 shows isolator for handling torsional vibrations or shock in a belt drive system. Isolator 45 has two structural members, hub 52 and pulley ring 56 defining a shaped gap which is filled by rubber member 54. Rubber member 54 is not bonded at at least one of its two contact surfaces 58 and 60 where it engages with pulley ring 56 and hub 52, respectively. Thus, at the non-bonded interface between the rubber member and a structural member, friction or wear is possible. Also, the rubber member transmits torque between the hub and the pulley ring. In a wheel isolator for a motorcycle or all terrain vehicle, commonly known as a cush drive, for example, the torques that must be transmitted are highly dynamic due to speed shifting, down shifting, engine braking, and the like. Therefore, use of the inventive rubber composition may be advantageous to assure durability of the rubber member.
[0038] According to another embodiment of the invention, FIG. 3 shows an exploded view of a wheel sprocket isolator (or cush drive), more details of which may be found in U.S. Pat. Appl. Pub!. No. 2008/0234080A1.
A sprocket, such as used on a motorcycle final drive, comprises sprocket 600 which cooperatively engages wheel hub 400. Sprocket 600 comprises flat metal projecting members 300 which extend radially from axis of rotation A-A. Wheel hub 400 comprises flat metal projecting members 401 which extend radially from axis A-A.
[0039] Wheel hub 400 may be fastened to a wheel (not shown) using fasteners 402.
Sprocket 600 is engaged with wheel hub 400 only by engagement of each isolating rubber member 10 and projecting members 300 and 401. Projecting members 300 and projecting members 401 interengage in an alternating manner. Receiving portions 601 are disposed within sprocket 600. Blocks 100, 200 make up rubber members 10 and occupy the receiving portions 601. Torque is transmitted from sprocket 600 to wheel hub 400 through compression of isolators 10 as each isolator bears upon projecting members 300 and projecting members 401.
[0040] Axle 500 may be connected to a motorcycle frame swing arm (not shown) in a manner known in the art using mounting nuts 501 and 502. Sprocket 600 rotates about axle 500 on sprocket bearing 700. A toothed power transmission belt B
engages belt bearing surface 602. In operation torque is transmitted from the engine transmission to sprocket 600 through belt B. Belt B applies a tangential force to sprocket surface 602.
The tangential force compresses blocks 100 through projecting members 300.
Blocks 100 in turn press upon projecting members 401 which drive wheel hub 400. In the downshift mode torque is transmitted from the wheel to the engine through blocks 200, thereby allowing engine compression braking. There is potential for relative movement between blocks 100, 200 and projecting members 300 and 401, which may lead to abrasive wear. The stresses on the blocks are also highly dynamic. Therefore, use of the inventive rubber composition may be advantageous to assure durability of the blocks of the rubber members.
[0041] In other embodiments similar to FIG. 3, the rubber member may a chamfer, projecting members or reliefs which result in applied compressive forces causing a bending mode in a rubber member. Such a design may advantageously reduce the isolator torsional stiffness while utilizing a relatively hard and durable rubber composition, for example of Shore A hardness of 75 or more according to an embodiment of the invention.
[0042] FIG. 3 illustrates a system according to an embodiment of the invention.
The system includes power transmission belt B and a dynamic article in the form of the rear wheel or wheel sprocket isolator described above. The system is an example of a cush drive system.
[0043] The examples that follow illustrate embodiments of the inventive composition and embodiments of vibration isolators using the composition.
[0044] Table 1 presents typical characteristics of the various grades of EPDM
used in the following examples. BUNA is a trademark of LANXESS Deutschland GmbH.
VISTALON is a trademark of Exxon Mobil Corporation. Where not readily available in supplier literature, the molecular weight ("Mw") has been estimated ("est.") based on comparing the Mooney viscosity to grades of known Mw.
[0045] Royaltherm 1411 is a silicone-modified EPDM. Royaltherm 650-LF is believed to be a silicone-modified EPDM with graphite filler suggested for use as a primary elastomer in gaskets. Royaltherm grades can be vulcanized with peroxides or sulfur/accelerator systems, provide retention of mechanical strength at elevated temperatures, weather and moisture resistance, electrical stability and compression recovery at low temperatures, and the 650-LF grade is said to offer optimum slip characteristics and freeze release in gaskets. At the levels utilized in embodiments of the present invention, the silicone-modified EPDM is believed to function primarily as a process aid and/or friction modifier, so the elastomer portion of the Royaltherm material is not included as elastomer along with the primary elastomer in the formulation, nor is it factored into the 100 parts elastomer for the PHR calculations. It should be understood that the alternative of including the EPDM portion of the Royaltherm as elastomer or in the PHR calculation is an alternative considered within the scope of the invention.
100111 In other embodiments, the amount of the mica may be from about 2.5 to about 10 parts per hundred parts of the elastomer and the amount of the silicone-modified ethylene-propylene elastomer may be from about 5 to about 20 parts per hundred parts of the elastomer.
[0012] In other embodiments, the rubber composition may include one or more of the following: a minor amount of low-molecular-weight ethylene-propylene elastomer, from about 20 to about 150 parts per hundred parts of the elastomer of reinforcing filler;
from about 20 to about 100 parts per hundred parts of the elastomer of process oil; and from about 1 to about 20 parts per hundred parts of the elastomer of process aid.
[0013] In certain embodiments, the inventive composition is crosslinked to form a rubber member having a cured tear strength of at least about 45 kN/m as determined by the method of ASTM D624 using die C at room temperature and/or a hardness of at least about 75 on the Shore A scale.
10014] The invention is also directed to a dynamic article such as a vibration isolator having a structural member and a crosslinked rubber member formed from an embodiment of the inventive composition. In the dynamic article, the rubber member has a surface engaged with a surface of the structural member, but not bonded thereto, and the rubber member provides advantageous durability including abrasion resistance.
100151 The invention is also directed to a system comprising the inventive dynamic article and a power transmission system in driving relation thereto. The power transmission system may include a toothed belt in driving engagement with the inventive isolator.
[0016] According to an embodiment of the present invention, there is provided a rubber composition comprising: 100 parts of elastomer comprising as its primary elastomer constituent an ethylene-propylene elastomer polymerized in the gas phase with a metallocene catalyst and having a molecular weight of at least about 250,000; a silicone-modified olefinic elastomer in an amount of from about 5 to about 50 parts per hundred parts of the elastomer;
ground mica in an amount of from about 2.5 to about 30 parts per hundred parts of the elastomer; and a peroxide curative, or the crosslinked reaction product of all the components of the composition.
[0016a] According to another embodiment of the present invention, there is provided a dynamic article comprising a structural member and a crosslinked rubber member comprising the reaction product of: 100 parts of elastomer comprising as its primary elastomer constituent an ethylene-propylene elastomer polymerized in the gas phase with a metallocene catalyst and having a molecular weight of at least about 250,000; a silicone-modified olefinic elastomer in an amount of from about 5 to about 50 parts per hundred parts of the elastomer; ground mica in an amount of from about 2.5 to about 30 parts per hundred parts of the elastomer; and a peroxide curative.
[0016b] According to still another embodiment of the present invention, there is provided a system comprising a dynamic article and a power transmission system in driving engagement with said dynamic article, wherein the dynamic article comprises a structural member and a crosslinked rubber member comprising the reaction product of: 100 parts of elastomer comprising as its primary elastomer constituent an ethylene-propylene elastomer polymerized in the gas phase with a metallocene catalyst and having a molecular weight of at least about 250,000; a silicone-modified olefinic elastomer in an amount of from about 5 to about 50 parts per hundred parts of the elastomer; ground mica in an amount of from about 2.5 to about 30 parts per hundred parts of the elastomer; and a peroxide curative.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The accompanying drawings, which are incorporated in and form part of the specification in which like numerals designate like parts, illustrate embodiments of the present invention and together with the description, serve to explain the principles of the invention. In the drawings:
[0018] FIG. 1 is a sectional view of an anti-vibration mount according to an embodiment of the invention;
[0019] FIG. 2 is a perspective view of a vibration isolator according to an embodiment of the invention; and, [0020] FIG. 3 is an exploded view of a wheel isolator according to an embodiment of the invention.
4a DETAILED DESCRIPTION
[0021] In one embodiment the invention is a rubber composition comprising an ethylene-propylene elastomer, a silicon-modified olefinic elastomer, mica, and a peroxide curative, or the crosslinked reaction product thereof. In other embodiments the rubber composition may also have one or more additional ingredients, such as reinforcing filler, process oil, and/or process aid.
[0022] The term ethylene-propylene elastomer, used herein and in the claims, includes rubbery copolymers of ethylene and propylene, optionally copolymerized with at least one polyene, usually a diene. Thus, saturated ethylene-propylene copolymer rubber, commonly called "EPM" rubber or elastomer, can be used. Examples of unsaturated ethylene-propylene-diene elastomer, commonly called "EPDM" rubber or elastomer, which are satisfactory comprise the products from the polymerization of ethylene and propylene, and a lesser quantity of non-conjugated diene. Satisfactory non-conjugated dienes include straight chain dienes such as 1,4-hexadiene, cyclic dienes such as cyclooctadiene, and bridged cyclic dienes such as ethylidenenorbornene ("ENB") or vinylnorbornene.
100231 The ethylene-propylene elastomer used as the primary elastomer constituent in embodiments of the invention is preferably polymerized in the gas phase by means of metallocene catalyst and preferably has a high molecular weight. By molecular weight is meant weight average molecular as determined by gel permeation chromatography ("GPC") for example. Preferably the molecular weight of the primary ethylene-propylene elastomer is greater than 250,000 or greater than about 300,000. The molecular weight of the primary ethylene-propylene elastomer may be in the range from about 300,000 to about 350,000. Such ethylene-propylene elastomer grades are available commercially in a granular form under the trademark NORDEL MG by The Dow Chemical Company.
The granules of NORDEL MG are generally coated with carbon black. When determining the amount of elastomer present in a rubber composition, the amount of carbon black present in the NORDEL MG is generally excluded. A preferred grade is NORDEL MG 47130 which has a molecular weight of 308,000 and came with 30 PHR
of carbon black in the examples reported below.
[0024] The term "primary elastomer constituent" means making up more than half of the total of the elastomeric constituents. Preferably, the primary elastomer constituent makes up 70 to 90 percent or even up to/ 100 percent of the elastomer present in the inventive composition. Additional elastomer constituents may be blended with the primary elastomer for various purposes. For example, other grades of EPM or EPDM
may be blended in minor amounts for example to improve processing. A minor amount means less than half, preferably from 1 to 30 percent.
[0025] The silicon-modified olefinic elastomer component of the composition embodiments of the present invention includes olefinic elastomers which have been modified with a silicon-containing polymer. Suitable olefinic elastomers include EPM
and EPDM elastomers described above, as well as others including ethylene-vinyl acetate copolymer elastomers. The silicon-containing polymer component includes various organopolysiloxanes, methoxy-stopped silicones, silanol-stopped silicones, etc. Each of the foregoing components may be manufactured by conventional techniques, and many are commercially available.
[0026]
Particularly preferred silicon-modified olefinic elastomers include silicone-modified EPDM with polydimethylsiloxane polymers with either vinyl or methyl-terminated polymer chains, preferably methyl-terminated polymer chains. The vinyl content of the polydimethylsiloxane polymer may range between 0 to 4 percent, preferably between 0.1 to 1 weight percent vinyl. The EPDM component of the silicone-modified EPDM may be 10 to 50 weight percent, preferably between 20 to 30 weight percent. Silicone-modified EPDM may be a compatibilized blend of silicone or silicon-containing polymer and EPDM. Examples of useful silicone-modified EPDM
elastomers commercially available include those sold under the ROYALTHERM trademark by Lion Copolymer, LLC. The modified elastomers may also contain additives such as fillers, etc. The amount of silicon-modified olefinic elastomer may be from about 5 to about 50 parts per hundred parts of ethylene-propylene elastomer ("PHR"), or from 5 to about 20 PHR.
[0027] The mica used in the invention is a member of a group of potassium aluminum silicate minerals having a sheet or plate-like crystalline structure.
Mica includes muscovite mica. The mica is preferably ground to a suitable particle size for rubber compounding. A suitable particle size of mica is -325 mesh, meaning most of the particles pass through a number 325 mesh screen. Suitable grades include 160-D
Mica, 325-D Mica, 325 Mesh Mica, 325-MF Mica, and 325-FF Mica available from Harwick Standard Distribution Corporation. These grades range in screen analysis from 74% to 96% passing through a 325 mesh screen, with 1% to 6% retained on a 200 mesh screen and substantially the rest retained on the 325 mesh screen. The mica may, but need not, be treated, for example with a silane or the like for enhanced dispersion in or adhesion to the elastomer matrix. The amount of mica used may be in the range from about 2.5 to about 30 PHR, or from about 2.5 to about 15 PHR, preferably from 2.5 to about 10 PHR.
[0028] The peroxide curative may be one or more of those known in the art.
Exemplary peroxide curatives include, but are not limited to, 1,1-di-(t-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethy1-2,5-di-(t-butylperoxy) 3-hexyne, dicumyl peroxide, oc-a'-bis(t-butylperoxy) diisopropyl benzene, di-t-butyl peroxide, 2,5-dimethy1-2,5-di-t-butylperoxyhexane, and t-butyl perbenzoate. Cure-effective amounts of peroxide may range from 1 to 10 PHR. It should be understood that the inventive composition may conveniently be described by the ingredients used, but then is mixed, formed, crosslinked or cured, usually by the application of heat and possibly pressure in a mold, so that a rubber article formed therefrom becomes a reaction product of those ingredients.
[0029] Reinforcing filler may be used in embodiments of the invention, including one or more carbon blacks, silicas, clays, talcs, or other non-black mineral fillers, treated or untreated, and the like. The amount of reinforcing filler may be in the range from about 20 to about 150 PHR, or from about 50 to about 100 PHR. The amount of reinforcing filler may include amounts of carbon black supplied with the ethylene-propylene elastomer, amounts of silica supplied with the silicon-modified olefinic elastomer, or amounts of fillers supplied with other ingredients.
[0030] Process oil may be used including one or more paraffinic oil, naphthenic oil, synthetic plasticizer, or the like. Paraffinic oil is preferred. Such oils may be included or supplied with an elastomer or other ingredient. The amount of process oil may be in the range from about 20 to about 100 PHR.
[0031] Process aid may be used including one or more internal and/or external lubricants, compatibilizers, dispersion aids, resins, and the like. In particular embodiments of the invention, low-molecular-weight or low-Mooney-viscosity ethylene-propylene elastomer may be used as a process aid. For example, an EPDM
elastomer with Mooney viscosity in the range of from about 15 to about 30, or preferably from about 20 to about 25, may be used to improve the processing of the inventive composition. In other embodiments, process aids such as fatty acids, fatty acid derivatives, polyoctenamers, paraffin waxes, low molecular weight polyethylene and polybutene, and the like, including for example one or more process aids marketed by Struktol Company of America may be used. The amount of process aid used may be from about 1 PHR to about 20 PHR.
[0032] Other ingredients known for use in elastomer compounds may be used. For example, the composition may include one or more additional elastomers, extenders, non-reinforcing fillers, metal oxides, stearates, antioxidants, antiozonants, radical or acid scavengers, coagents, scorch retarders, cure accelerators, colorants, tackifiers, resins, compatibilizers, fire retardants, and the like.
[0033] Thus, in one preferred embodiment the invention is a rubber composition comprising 100 parts of ethylene-propylene elastomer, from about 5 to about 50 parts of silicon-modified ethylene-propylene elastomer, from about 2.5 to about 30 parts of mica, and a peroxide curative, or the crosslinked reaction products thereof.
[0034] In other preferred embodiments the rubber composition may also have one or more additional ingredients, such as from about 20 to about 150 parts of reinforcing filler, from about 20 to about 100 parts of process oil, and/or from about I
to about 20 parts of process aid. In one embodiment, the process aid may include a low-molecular-weight ethylene-propylene elastomer, which may also be counted as part of the elastomer of the composition.
[0035] In particular for use in various vibration isolating or damping devices, embodiments of the inventive rubber composition may be advantageously compounded to have a predetermined hardness, a predetermined minimum tear strength, low compression set, and generally good physical properties. It is advantageous for cured rubber of the inventive composition to exhibit a hardness of at least about 75 or from about 75 to about 85 on the Shore A scale. It is also advantageous for cured rubber of the inventive composition to exhibit tear strength of at least about 45 kN/m when tested according to ASTM D624 using die C at room temperature. It also may be advantageous for cured rubber of the inventive composition to exhibit compression set of less than 30%, or less than 25%, when tested according to ASTM D395 Method B for 22 hours at 150 C.
In addition to the aforementioned properties, cured rubber members of embodiments of the invention exhibit excellent durability under dynamic, possibly abrasive, conditions as might be found in vibration isolators. These and other advantages will be described in more detail in connection with the examples below.
[0036] According to an embodiment of the invention, FIG. 1 shows a sectional view of vertically adjustable vibration isolation mount 15, having rubber member 34 formed of a rubber composition according to an embodiment of the invention.
Rubber member 34 is mounted on core 32 and preferably bonded at interface 36 between the rubber member and the core. Lower flat surface 30 is adapted to engage a supporting surface such as floor 13. Rubber member 34 and core 32 are housed in cavity 28 which is defined by frame 20, which is a structural member in this device. The dimension of cavity 28 is such as to snugly receive rubber member 34. The cavity sides engage a portion of the side surface of the rubber member at interface 26. There is no bond or adhesive between rubber member 34 and frame 20 at interface 26, so the engagement is frictional and potentially the source of wear or abrasion in use. Bolt 22 is threaded through frame 20 at hole 18 to adjust the height of the mount. Lock nut 24 allows the mount to be locked in position. The inventive rubber composition used in the rubber member insulates the frame 20 from the floor 13 and absorbs, dampens, or isolates vibrations generated by some apparatus, not shown, mounted upon frame 20.
Rubber material present between the side of core 32 and frame 20 permits horizontal vibrations to be damped with excellent resistance to frictional wear at interface 26. Use of an embodiment of the inventive rubber member may also provide excellent durability at surface 30. Floor 13 may also be considered a structural member which contacts or engages a surface of the rubber member without adhesive at the interface.
[0037] According to another embodiment of the invention, FIG. 2 shows isolator for handling torsional vibrations or shock in a belt drive system. Isolator 45 has two structural members, hub 52 and pulley ring 56 defining a shaped gap which is filled by rubber member 54. Rubber member 54 is not bonded at at least one of its two contact surfaces 58 and 60 where it engages with pulley ring 56 and hub 52, respectively. Thus, at the non-bonded interface between the rubber member and a structural member, friction or wear is possible. Also, the rubber member transmits torque between the hub and the pulley ring. In a wheel isolator for a motorcycle or all terrain vehicle, commonly known as a cush drive, for example, the torques that must be transmitted are highly dynamic due to speed shifting, down shifting, engine braking, and the like. Therefore, use of the inventive rubber composition may be advantageous to assure durability of the rubber member.
[0038] According to another embodiment of the invention, FIG. 3 shows an exploded view of a wheel sprocket isolator (or cush drive), more details of which may be found in U.S. Pat. Appl. Pub!. No. 2008/0234080A1.
A sprocket, such as used on a motorcycle final drive, comprises sprocket 600 which cooperatively engages wheel hub 400. Sprocket 600 comprises flat metal projecting members 300 which extend radially from axis of rotation A-A. Wheel hub 400 comprises flat metal projecting members 401 which extend radially from axis A-A.
[0039] Wheel hub 400 may be fastened to a wheel (not shown) using fasteners 402.
Sprocket 600 is engaged with wheel hub 400 only by engagement of each isolating rubber member 10 and projecting members 300 and 401. Projecting members 300 and projecting members 401 interengage in an alternating manner. Receiving portions 601 are disposed within sprocket 600. Blocks 100, 200 make up rubber members 10 and occupy the receiving portions 601. Torque is transmitted from sprocket 600 to wheel hub 400 through compression of isolators 10 as each isolator bears upon projecting members 300 and projecting members 401.
[0040] Axle 500 may be connected to a motorcycle frame swing arm (not shown) in a manner known in the art using mounting nuts 501 and 502. Sprocket 600 rotates about axle 500 on sprocket bearing 700. A toothed power transmission belt B
engages belt bearing surface 602. In operation torque is transmitted from the engine transmission to sprocket 600 through belt B. Belt B applies a tangential force to sprocket surface 602.
The tangential force compresses blocks 100 through projecting members 300.
Blocks 100 in turn press upon projecting members 401 which drive wheel hub 400. In the downshift mode torque is transmitted from the wheel to the engine through blocks 200, thereby allowing engine compression braking. There is potential for relative movement between blocks 100, 200 and projecting members 300 and 401, which may lead to abrasive wear. The stresses on the blocks are also highly dynamic. Therefore, use of the inventive rubber composition may be advantageous to assure durability of the blocks of the rubber members.
[0041] In other embodiments similar to FIG. 3, the rubber member may a chamfer, projecting members or reliefs which result in applied compressive forces causing a bending mode in a rubber member. Such a design may advantageously reduce the isolator torsional stiffness while utilizing a relatively hard and durable rubber composition, for example of Shore A hardness of 75 or more according to an embodiment of the invention.
[0042] FIG. 3 illustrates a system according to an embodiment of the invention.
The system includes power transmission belt B and a dynamic article in the form of the rear wheel or wheel sprocket isolator described above. The system is an example of a cush drive system.
[0043] The examples that follow illustrate embodiments of the inventive composition and embodiments of vibration isolators using the composition.
[0044] Table 1 presents typical characteristics of the various grades of EPDM
used in the following examples. BUNA is a trademark of LANXESS Deutschland GmbH.
VISTALON is a trademark of Exxon Mobil Corporation. Where not readily available in supplier literature, the molecular weight ("Mw") has been estimated ("est.") based on comparing the Mooney viscosity to grades of known Mw.
[0045] Royaltherm 1411 is a silicone-modified EPDM. Royaltherm 650-LF is believed to be a silicone-modified EPDM with graphite filler suggested for use as a primary elastomer in gaskets. Royaltherm grades can be vulcanized with peroxides or sulfur/accelerator systems, provide retention of mechanical strength at elevated temperatures, weather and moisture resistance, electrical stability and compression recovery at low temperatures, and the 650-LF grade is said to offer optimum slip characteristics and freeze release in gaskets. At the levels utilized in embodiments of the present invention, the silicone-modified EPDM is believed to function primarily as a process aid and/or friction modifier, so the elastomer portion of the Royaltherm material is not included as elastomer along with the primary elastomer in the formulation, nor is it factored into the 100 parts elastomer for the PHR calculations. It should be understood that the alternative of including the EPDM portion of the Royaltherm as elastomer or in the PHR calculation is an alternative considered within the scope of the invention.
11 [0046] TABLE I.
Mooney ENB Ethylene Mw g/
EPDM grade Viscosity content content MWD
( (ML1+4/125 C) (mass %) (mass %) mol) Nordel MG 47130 130 4.9 67 308,000 broad Buna EP T6650 63 6.5 53 ¨200,000 est. not known VistaIon 7800 20 6 79 ¨130,000 est. bimodal Nordel IP 4725P 25 4.9 70 135,000 medium-narrow [0047] A number of compositions were prepared according to the formulations listed in Table 2. Comparative Examples (designated "Comp. Ex.") did not meet the needs of certain isolator designs such as discussed above in connection with Fig's 2 and 3. The inventive examples (designated "Ex.") exhibit suitable properties for use in isolator designs. The compositions were mixed, according to conventional rubber practice, in an internal mixer. Test pieces for physical properties were compression molded. Rubber members for various isolator designs may be formed by any known method, such as injection molding, compression molding, or transfer molding.
In some examples described below, rubber members for motorcycle rear wheel isolators were injection molded.
Mooney ENB Ethylene Mw g/
EPDM grade Viscosity content content MWD
( (ML1+4/125 C) (mass %) (mass %) mol) Nordel MG 47130 130 4.9 67 308,000 broad Buna EP T6650 63 6.5 53 ¨200,000 est. not known VistaIon 7800 20 6 79 ¨130,000 est. bimodal Nordel IP 4725P 25 4.9 70 135,000 medium-narrow [0047] A number of compositions were prepared according to the formulations listed in Table 2. Comparative Examples (designated "Comp. Ex.") did not meet the needs of certain isolator designs such as discussed above in connection with Fig's 2 and 3. The inventive examples (designated "Ex.") exhibit suitable properties for use in isolator designs. The compositions were mixed, according to conventional rubber practice, in an internal mixer. Test pieces for physical properties were compression molded. Rubber members for various isolator designs may be formed by any known method, such as injection molding, compression molding, or transfer molding.
In some examples described below, rubber members for motorcycle rear wheel isolators were injection molded.
12 [0048] TABLE 2.
Comp. Comp. Comp. Comp. Comp. Comp.
Ingredient (parts) Ex. 7 Ex. 8 Ex. 9 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Buna EP T6650 50 40 50 Vistalon 7800 50 60 50 Nordel MG 47130 130 117 117 117 117 117 Nordel IP 4725P 10 10 10 10 10 N550 carbon black 90 105 90 N774 carbon black 50 50 50 50 50 50 N990 carbon black 10 15 10 Silica (HiSil 243LD) 8 8 8 8 8 8 8 8 8 Paraffin Oil 45 45 45 30 30 30 30 30 30 Zinc Oxide 10 10 5 5 5 5 5 5 5 Stearic Acid 2 2 Zinc Stearate 1 1.5 1.5 1.5 1.5 1.5 1.5 Antioxidant 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Mica (-325 mesh) 5 10 5 Royaltherm 650P-LF 10 10 Royaltherm 1411 10 Struktol WB423 4 4 4 4 4 Vestenamer 80124 2 2 2 2 2 2 2 2 2 Zinc Dimethacrylate 10 10 10 10 10 10 Sulfur-70% active 2 2 DPTT-75 6 1.77 1.77 TDEC-70 7 0.2 0.2 ETU-80 8 0.8 0.8 ZDBC-80 9 1.1 1.1 MBTS 1 1.33 1.33 0.3 0.3 0.3 0.3 SR719 " 0.2 0.2 0.2 0.2 0.2 0.2 Peroxider2 4 7 7 7 7 7 7 Total Parts 274.2 304.2 267.5 246.2 247.2 247.5 262.5 267.5 262.5 1 Polymerized 1,2-dihydro-2,2,4-trimethylquinoline.
2 Tackifier resin made from octylphenol and formaldehyde from SI Group, Inc. .
3 Fatty acid derivative blend from Struktol Company of America.
4 Polyoctenamer from Struktol Company of America.
Comp. Comp. Comp. Comp. Comp. Comp.
Ingredient (parts) Ex. 7 Ex. 8 Ex. 9 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Buna EP T6650 50 40 50 Vistalon 7800 50 60 50 Nordel MG 47130 130 117 117 117 117 117 Nordel IP 4725P 10 10 10 10 10 N550 carbon black 90 105 90 N774 carbon black 50 50 50 50 50 50 N990 carbon black 10 15 10 Silica (HiSil 243LD) 8 8 8 8 8 8 8 8 8 Paraffin Oil 45 45 45 30 30 30 30 30 30 Zinc Oxide 10 10 5 5 5 5 5 5 5 Stearic Acid 2 2 Zinc Stearate 1 1.5 1.5 1.5 1.5 1.5 1.5 Antioxidant 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Mica (-325 mesh) 5 10 5 Royaltherm 650P-LF 10 10 Royaltherm 1411 10 Struktol WB423 4 4 4 4 4 Vestenamer 80124 2 2 2 2 2 2 2 2 2 Zinc Dimethacrylate 10 10 10 10 10 10 Sulfur-70% active 2 2 DPTT-75 6 1.77 1.77 TDEC-70 7 0.2 0.2 ETU-80 8 0.8 0.8 ZDBC-80 9 1.1 1.1 MBTS 1 1.33 1.33 0.3 0.3 0.3 0.3 SR719 " 0.2 0.2 0.2 0.2 0.2 0.2 Peroxider2 4 7 7 7 7 7 7 Total Parts 274.2 304.2 267.5 246.2 247.2 247.5 262.5 267.5 262.5 1 Polymerized 1,2-dihydro-2,2,4-trimethylquinoline.
2 Tackifier resin made from octylphenol and formaldehyde from SI Group, Inc. .
3 Fatty acid derivative blend from Struktol Company of America.
4 Polyoctenamer from Struktol Company of America.
13 N,N m-phenylenedimaleimide, from Sartomer Company.
6 =
Dipentamethylenethiuram hexasulfide - 75% active Tellurium diethyldithiocarbamate - 70% active Ethylene thiourea - 80% active Zinc dibutyldithiocarbamate - 80% active Benzothiazyl disulfide.
Scorch retarder from Sartomer Company.
12 a-cC-bis-(t-butylperoxy-diisopropylbenzene) - 40% active on Burgess clay.
[0049] Some properties and characteristics of the example compositions are listed in Table 3. Tensile strength and elongation was tested according to ASTM D412 Method A with die-C dumbbell at room temperature. Rubber hardness was tested according to ASTM D2240 on the Shore A scale. Tear strength was tested according to ASTM
with die C at room temperature. Compression set was tested according to ASTM
Method B. Abrasion resistance was tested according to ASTM D2228, also known as the Pico test. Fatigue or crack growth of a 2-mm crack was tested according to at room temperature with 2-inch stroke at 300 cycles/minute for 30,000 cycles, also known as the DeMattia test. The average crack growth rate was expressed in units of inches per million cycles. Moldability was based on injection and/or transfer molding of rubber members for an isolator like that shown in FIG. 3. The field test result was based on the performance of a rear wheel isolator, like that shown in FIG. 3, on a motorcycle.
[0050] Table 3 shows that Comp. Ex. 1-3, based on conventional grades of EPDM, exhibit insufficient tear strength, resulting in poor performance on field tests in motorcycle wheel isolators. This poor performance was observed for both sulfur and peroxide-cured rubber. On the other hand, Comp. Ex. 4, based on gas-phase metallocene-catalyzed EPDM with very high molecular weight (Nordel MG 47130), exhibit much improved tear strength, but could not be molded without non-fills and/or flow or knit lines. Comp. Ex. 5, also based on Nordel MG 47130, shows some improvement in moldability through the use of process aids such as 4 PHR of Struktol WB42 and of low-Mooney-viscosity EPDM (Nordel IP 4725P). Comp. Ex. 6 was finally capable of producing molded parts worth testing. Moldability in Comp. Ex. 6 was achieved by
6 =
Dipentamethylenethiuram hexasulfide - 75% active Tellurium diethyldithiocarbamate - 70% active Ethylene thiourea - 80% active Zinc dibutyldithiocarbamate - 80% active Benzothiazyl disulfide.
Scorch retarder from Sartomer Company.
12 a-cC-bis-(t-butylperoxy-diisopropylbenzene) - 40% active on Burgess clay.
[0049] Some properties and characteristics of the example compositions are listed in Table 3. Tensile strength and elongation was tested according to ASTM D412 Method A with die-C dumbbell at room temperature. Rubber hardness was tested according to ASTM D2240 on the Shore A scale. Tear strength was tested according to ASTM
with die C at room temperature. Compression set was tested according to ASTM
Method B. Abrasion resistance was tested according to ASTM D2228, also known as the Pico test. Fatigue or crack growth of a 2-mm crack was tested according to at room temperature with 2-inch stroke at 300 cycles/minute for 30,000 cycles, also known as the DeMattia test. The average crack growth rate was expressed in units of inches per million cycles. Moldability was based on injection and/or transfer molding of rubber members for an isolator like that shown in FIG. 3. The field test result was based on the performance of a rear wheel isolator, like that shown in FIG. 3, on a motorcycle.
[0050] Table 3 shows that Comp. Ex. 1-3, based on conventional grades of EPDM, exhibit insufficient tear strength, resulting in poor performance on field tests in motorcycle wheel isolators. This poor performance was observed for both sulfur and peroxide-cured rubber. On the other hand, Comp. Ex. 4, based on gas-phase metallocene-catalyzed EPDM with very high molecular weight (Nordel MG 47130), exhibit much improved tear strength, but could not be molded without non-fills and/or flow or knit lines. Comp. Ex. 5, also based on Nordel MG 47130, shows some improvement in moldability through the use of process aids such as 4 PHR of Struktol WB42 and of low-Mooney-viscosity EPDM (Nordel IP 4725P). Comp. Ex. 6 was finally capable of producing molded parts worth testing. Moldability in Comp. Ex. 6 was achieved by
14 combining the process aids of Comp. Ex. 5 with MBTS, which is believed to function as a scorch retarder for the peroxide cure. The field test results for Comp. Ex.
6 showed that the improved tear strength due to the use of Nordel MG 47130 changed the failure mode from gross failure to abrasive failure along with excessive noise.
[0051] Ex. 7-9 show embodiments of the invention having as the primary elastomer Nordel MG 47130, with mica and Royaltherm added. These embodiments exhibited high tear strength, greater than 45 kN/m, and were easily moldable. They also exhibited improved abrasion resistance based on the Pico test. Ex. 9 showed excellent performance in a motorcycle isolator, with no cracks, wear, or excessive noise. On the other hand, flex fatigue is adversely affected, as indicated by the DeMattia crack growth results.
However, the overall performance of the inventive compound in an isolator is apparently not adversely affected by the adverse crack growth behavior.
[0052] Rubber members for isolators similar to the embodiment of FIG. 3 were then injection molded from inventive composition Ex. 9 and subjected to additional product life testing and field testing. On various motorcycles with various wheel isolator designs, the product life was significantly increased (typically by a factor of 3 or more) over prior rubber member compositions. For example, on one motorcycle application, prior art rubber members were failing at about 5,000 km, a target life of 30,000 km was desired, and rubber members according to the embodiment of Ex. 9 were found to last 90,000 km with no visual signs of wear. On another motorcycle application, field testing of an isolator system in the drive line according to the embodiment of FIG. 3 with Ex. 9 for the rubber member resulted in a significant (approximately double) improvement in bearing life (in particular, sprocket bearing 700 shown in FIG. 3) and overall power transmission system life. At the same time, use of the inventive isolator in the drive system resulted in a significant improvement in rear tire wear, approximately doubling tire life on that motorcycle application.
[0053] The invention is also directed to a system comprising the inventive dynamic article and a power transmission system in driving relation thereto. In a preferred embodiment, the power transmission system may include a toothed belt in driving engagement with the inventive isolator. In other embodiments, the power transmission system could be a chain drive or a shaft drive or any other type of drive.
[0054] TABLE 3.
Comp. Comp. Comp. Comp. Comp. Comp.
Property Ex. 7 Ex.
8 Ex. 9 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Tensile strength 13.44 11.38 15.24 19.23 17.21 18.02 17.28 16.89 17.24 (MPa) Elongation (%) 303 289 345 324 325 312 298 330 319.7 Hardness (Shore A) 75 80 78 79 78 79 80 78 81 Tear strength (kN/m) 24.8 25.2 30.2 52.2 49.8 48.5 50.1 49.8 50.9 Compression set 42.3 44.1 32 21.2 20.5 20.8 22.3 25.8 20.6 Pico Abrasion Index 83 121 Pico weight loss 0.5% 0.2%
DeMattia average crack growth rate 5.66 5.92 7.89 6.06 (in/Mcycle) Moldabilityl OK OK OK
No Poor Fair OK Fair OK
Field test result2 Tear Tear Tear N.T. N.T. Wear N.T.
N.T. Pass Useful Life (km) -5000-30,000 -40,000-90,000 No moldability = molding was very difficult (Non-fill).
Poor moldability = molding was difficult (Flow and/or knit lines appeared).
Fair moldability = some knit lines observed.
2 N.T. = not tested.
Tear = large cracks, compression set, gross failure.
Wear = abrasive wear, lots of rubber particles generated, and noisy.
[0055] Without intending to be limited thereby, it is believed that the inventive compositions work by a combination of mechanisms. It is believed that the isolator applications studied result in both severe stress loads and abrasive forces on a rubber member through contact with a structural member in use. Of course, there are also heat and other environmental stresses during use, which require low compression set, for example. EPDM typically meets the heat stresses without trouble, even at the levels of reinforcing filler and curative required for an 80-durometer hardness rubber compound with low compression set. However, only gas-phase metallocene ethylene-propylene elastomers are capable of also achieving very high tear strength at such filler loadings and curative levels. Even so, high molecular weight alone does not prevent abrasive wear, and processing of these high-viscosity elastomers is very difficult. It appears that the combination of mica with silicone-modified EPDM provides a noticeable reduction in coefficient of friction of the surface of the rubber element. At the same time, it appears that moldability is somewhat improved. At the same time, tear strength, compression set, and heat resistance are not affected in any negative way by mica and silicone-modified EPDM. Although flex fatigue is adversely affected, as indicated by the DeMattia results, the advantages in the application outweigh this negative effect. Thus, the inventive composition provides a moldable, high tear strength, low friction, low wear, rubber member in the desired hardness range of 75 or more, suitable for use in dynamic applications such as vibration isolators.
[00561 The scope of the claims should not be limited by the preferred embodiments set = forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.
6 showed that the improved tear strength due to the use of Nordel MG 47130 changed the failure mode from gross failure to abrasive failure along with excessive noise.
[0051] Ex. 7-9 show embodiments of the invention having as the primary elastomer Nordel MG 47130, with mica and Royaltherm added. These embodiments exhibited high tear strength, greater than 45 kN/m, and were easily moldable. They also exhibited improved abrasion resistance based on the Pico test. Ex. 9 showed excellent performance in a motorcycle isolator, with no cracks, wear, or excessive noise. On the other hand, flex fatigue is adversely affected, as indicated by the DeMattia crack growth results.
However, the overall performance of the inventive compound in an isolator is apparently not adversely affected by the adverse crack growth behavior.
[0052] Rubber members for isolators similar to the embodiment of FIG. 3 were then injection molded from inventive composition Ex. 9 and subjected to additional product life testing and field testing. On various motorcycles with various wheel isolator designs, the product life was significantly increased (typically by a factor of 3 or more) over prior rubber member compositions. For example, on one motorcycle application, prior art rubber members were failing at about 5,000 km, a target life of 30,000 km was desired, and rubber members according to the embodiment of Ex. 9 were found to last 90,000 km with no visual signs of wear. On another motorcycle application, field testing of an isolator system in the drive line according to the embodiment of FIG. 3 with Ex. 9 for the rubber member resulted in a significant (approximately double) improvement in bearing life (in particular, sprocket bearing 700 shown in FIG. 3) and overall power transmission system life. At the same time, use of the inventive isolator in the drive system resulted in a significant improvement in rear tire wear, approximately doubling tire life on that motorcycle application.
[0053] The invention is also directed to a system comprising the inventive dynamic article and a power transmission system in driving relation thereto. In a preferred embodiment, the power transmission system may include a toothed belt in driving engagement with the inventive isolator. In other embodiments, the power transmission system could be a chain drive or a shaft drive or any other type of drive.
[0054] TABLE 3.
Comp. Comp. Comp. Comp. Comp. Comp.
Property Ex. 7 Ex.
8 Ex. 9 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Tensile strength 13.44 11.38 15.24 19.23 17.21 18.02 17.28 16.89 17.24 (MPa) Elongation (%) 303 289 345 324 325 312 298 330 319.7 Hardness (Shore A) 75 80 78 79 78 79 80 78 81 Tear strength (kN/m) 24.8 25.2 30.2 52.2 49.8 48.5 50.1 49.8 50.9 Compression set 42.3 44.1 32 21.2 20.5 20.8 22.3 25.8 20.6 Pico Abrasion Index 83 121 Pico weight loss 0.5% 0.2%
DeMattia average crack growth rate 5.66 5.92 7.89 6.06 (in/Mcycle) Moldabilityl OK OK OK
No Poor Fair OK Fair OK
Field test result2 Tear Tear Tear N.T. N.T. Wear N.T.
N.T. Pass Useful Life (km) -5000-30,000 -40,000-90,000 No moldability = molding was very difficult (Non-fill).
Poor moldability = molding was difficult (Flow and/or knit lines appeared).
Fair moldability = some knit lines observed.
2 N.T. = not tested.
Tear = large cracks, compression set, gross failure.
Wear = abrasive wear, lots of rubber particles generated, and noisy.
[0055] Without intending to be limited thereby, it is believed that the inventive compositions work by a combination of mechanisms. It is believed that the isolator applications studied result in both severe stress loads and abrasive forces on a rubber member through contact with a structural member in use. Of course, there are also heat and other environmental stresses during use, which require low compression set, for example. EPDM typically meets the heat stresses without trouble, even at the levels of reinforcing filler and curative required for an 80-durometer hardness rubber compound with low compression set. However, only gas-phase metallocene ethylene-propylene elastomers are capable of also achieving very high tear strength at such filler loadings and curative levels. Even so, high molecular weight alone does not prevent abrasive wear, and processing of these high-viscosity elastomers is very difficult. It appears that the combination of mica with silicone-modified EPDM provides a noticeable reduction in coefficient of friction of the surface of the rubber element. At the same time, it appears that moldability is somewhat improved. At the same time, tear strength, compression set, and heat resistance are not affected in any negative way by mica and silicone-modified EPDM. Although flex fatigue is adversely affected, as indicated by the DeMattia results, the advantages in the application outweigh this negative effect. Thus, the inventive composition provides a moldable, high tear strength, low friction, low wear, rubber member in the desired hardness range of 75 or more, suitable for use in dynamic applications such as vibration isolators.
[00561 The scope of the claims should not be limited by the preferred embodiments set = forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.
Claims (23)
1. A rubber composition comprising:
100 parts of elastomer comprising as its primary elastomer constituent an ethylene-propylene elastomer polymerized in the gas phase with a metallocene catalyst and having a molecular weight of at least about 250,000;
a silicone-modified olefinic elastomer in an amount of from about 5 to about 50 parts per hundred parts of the elastomer;
ground mica in an amount of from about 2.5 to about 30 parts per hundred parts of the elastomer; and a peroxide curative, or the crosslinked reaction product of all the components of the composition.
100 parts of elastomer comprising as its primary elastomer constituent an ethylene-propylene elastomer polymerized in the gas phase with a metallocene catalyst and having a molecular weight of at least about 250,000;
a silicone-modified olefinic elastomer in an amount of from about 5 to about 50 parts per hundred parts of the elastomer;
ground mica in an amount of from about 2.5 to about 30 parts per hundred parts of the elastomer; and a peroxide curative, or the crosslinked reaction product of all the components of the composition.
2. The rubber composition of claim 1 wherein the olefinic elastomer is silicone-modified ethylene-propylene elastomer.
3. The rubber composition of claim 1 wherein the molecular weight of the primary elastomer is in the range from about 300,000 to about 350,000.
4. The rubber composition of claim 1 wherein the ground mica has a particle size such that the majority of particles pass through a number 325 mesh screen.
5. The rubber composition of claim 2 wherein the amount of the mica is from about 2.5 to about 10 parts per hundred parts of the elastomer and the amount of the silicone-modified ethylene-propylene elastomer is from about 5 to about 20 parts per hundred parts of the elastomer.
6. The rubber composition of claim 1 wherein the elastomer further comprises a minor amount of low-molecular-weight ethylene-propylene elastomer.
7. The rubber composition of claim 1 further comprising:
from about 20 to about 150 parts per hundred parts of the elastomer of reinforcing filler;
from about 20 to about 100 parts per hundred parts of the elastomer of process oil; and from about 1 to about 20 parts per hundred parts of the elastomer of process aid.
from about 20 to about 150 parts per hundred parts of the elastomer of reinforcing filler;
from about 20 to about 100 parts per hundred parts of the elastomer of process oil; and from about 1 to about 20 parts per hundred parts of the elastomer of process aid.
8. The rubber composition of claim 1 having a cured tear strength of at least about 45 kN/m as determined by the method of ASTM D624 using die C at room temperature.
9. The rubber composition of claim 7 having a cured hardness of at least about 75 on the Shore A scale.
10. A dynamic article comprising a structural member and a crosslinked rubber member comprising the reaction product of:
100 parts of elastomer comprising as its primary elastomer constituent an ethylene-propylene elastomer polymerized in the gas phase with a metallocene catalyst and having a molecular weight of at least about 250,000;
a silicone-modified olefinic elastomer in an amount of from about 5 to about 50 parts per hundred parts of the elastomer;
ground mica in an amount of from about 2.5 to about 30 parts per hundred parts of the elastomer; and a peroxide curative.
100 parts of elastomer comprising as its primary elastomer constituent an ethylene-propylene elastomer polymerized in the gas phase with a metallocene catalyst and having a molecular weight of at least about 250,000;
a silicone-modified olefinic elastomer in an amount of from about 5 to about 50 parts per hundred parts of the elastomer;
ground mica in an amount of from about 2.5 to about 30 parts per hundred parts of the elastomer; and a peroxide curative.
11. The dynamic article of claim 10 wherein the olefinic elastomer is silicone-modified ethylene-propylene elastomer.
12. The dynamic article of claim 10 wherein the ground mica has a particle size such that the majority of particles pass through a number 325 mesh screen.
13. The dynamic article of claim 10 wherein the elastomer further comprises a minor amount of low-molecular-weight ethylene-propylene elastomer.
14. The dynamic article of claim 11 wherein the molecular weight of the primary elastomer is in the range from about 300,000 to about 350,000.
15. The dynamic article of claim 14 wherein the amount of the mica is from about 2.5 to about 10 parts per hundred parts of the elastomer and the amount of the silicone-modified ethylene-propylene elastomer is from about 5 to about 20 parts per hundred parts of the elastomer.
16. The dynamic article of claim 15 further comprising:
from about 20 to about 150 parts per hundred parts of the elastomer of reinforcing filler;
from about 20 to about 100 parts per hundred parts of the elastomer of process oil; and from about 1 to about 20 parts per hundred parts of the elastomer of process aid.
from about 20 to about 150 parts per hundred parts of the elastomer of reinforcing filler;
from about 20 to about 100 parts per hundred parts of the elastomer of process oil; and from about 1 to about 20 parts per hundred parts of the elastomer of process aid.
17. The dynamic article of claim 16 having a cured tear strength of at least about 45 kN/m as determined by the method of ASTM D624 using die C at room temperature.
18. The dynamic article of claim 17 having a cured hardness of at least about 75 on the Shore A scale.
19. The dynamic article of claim 10 in the form of a cush drive, vibration isolator, vibration damper, vibration absorber, or shock absorber.
20. The dynamic article of claim 10 wherein said rubber member has a surface portion in contact with, but not bonded to, a surface portion of said structural member.
21. A system comprising a dynamic article and a power transmission system in driving engagement with said dynamic article, wherein the dynamic article comprises a structural member and a crosslinked rubber member comprising the reaction product of:
100 parts of elastomer comprising as its primary elastomer constituent an ethylene-propylene elastomer polymerized in the gas phase with a metallocene catalyst and having a molecular weight of at least about 250,000;
a silicone-modified olefinic elastomer in an amount of from about 5 to about 50 parts per hundred parts of the elastomer;
ground mica in an amount of from about 2.5 to about 30 parts per hundred parts of the elastomer; and a peroxide curative.
100 parts of elastomer comprising as its primary elastomer constituent an ethylene-propylene elastomer polymerized in the gas phase with a metallocene catalyst and having a molecular weight of at least about 250,000;
a silicone-modified olefinic elastomer in an amount of from about 5 to about 50 parts per hundred parts of the elastomer;
ground mica in an amount of from about 2.5 to about 30 parts per hundred parts of the elastomer; and a peroxide curative.
22. The system of claim 21 wherein the power transmission system comprises a toothed belt and the dynamic article is a vibration isolator in driving engagement with said belt.
23. The system of claim 21 in the form of a cush drive.
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