Rubber composition and vibration damper using the rubber composition
View Patent ↗A torsional vibration damper or other vibration damping device with a rubber vibration absorbing element. The rubber element is a peroxide-cured composition comprising 100 parts of ethylene-alpha-olefin elastomer, and 20 to 100 parts of substantially isobutylene or butene polymer having a viscosity average molecular weight greater than about 5000. The polymer may also be a copolymer of isobutylene and isoprene. The addition of the isobutylene polymer to the ethylene-alpha-olefin elastomer composition increases the vibration damping character of the rubber.
1. A vibration absorbing device comprising a rubber vibration absorbing element, said rubber element comprising: 100 parts of ethylene-alpha-olefin elastomer, and 20 to 100 parts of substantially isobutylene or butene polymer having a viscosity average molecular weight in the range from about 50,000 to about 1,250,000 and having less than about 1 mole per cent unsaturation.
2. The device of claim 1 wherein said device is a crankshaft torsional vibration dampener.
3. The device of claim 1 wherein said rubber element is cured by a free-radical-producing material.
4. The device of claim 3 wherein said free-radical-producing material is selected from the group consisting of organic peroxides and ionizing radiation.
5. The device of claim 4 wherein said elastomer is selected from the group consisting of ethylene-propylene copolymers, ethylene-propylene-diene terpolymers, ethylene-octene copolymers, ethylene-octene-diene terpolymers, ethylene-butene copolymers, ethylene-butene-diene terpolymers, and blends thereof.
6. The device of claim 5 wherein said polymer is polyisobutylene or polybutene.
7. A torsional vibration damper comprising a free-radical-cured rubber vibration absorbing element, wherein said rubber element comprises: 100 parts of ethylene-alpha-olefin elastomer; and 20 to 100 parts of one or more polymers having a viscosity average molecular weight in the range from about 50,000 to about 1,250,000 selected from the group consisting of polybutylene, polyisobutylene, polybutene; and polyisobutylene-co-isoprene having less than about 1 mole per cent isoprene.
8. A cured rubber composition comprising: 100 parts of ethylene-alpha-olefin elastomer; and an amount of substantially isobutylene or butene polymer having a viscosity average molecular weight above about 50,000 effective for substantially increasing the vibration damping character of the composition as indicated by an increase in tan δ of at least about 100 percent at 120° C.
9. The composition of claim 8 further comprising: a metal-adhesive adjuvant.
10. The composition of claim 8 wherein said polymer is a copolymer of isobutylene and isoprene having less than about 1 mole per cent isoprene.
11. The composition of claim 10 wherein said polymer has a viscosity average molecular weight in the range from about 50,000 to about 1,250,000.
12. The composition of claim 11 wherein said composition is peroxide cured.
13. An article selected from the group consisting of a belt, a hose and a vibration control device; comprising: molded or extrusion-formed, free-radical-cured, ethylene-alpha-olefin rubber, said rubber comprising: substantially isobutylene or butene polymer having less than about 1 mole per cent isoprene and having a viscosity average molecular weight greater than about 50,000 in an amount effective for at least doubling the damping character of the rubber as indicated by measurement of tan δ at 120° C.
14. The article of claim 13 wherein said polymer has a viscosity average molecular weight in the range from about 50,000 to about 1,250,000.