High modulus belt composition and belts made therewith

Abstract: A high modulus composition based on a mixture of a hydrogenated acrylonitrile butadiene rubber which has been modified with either zinc methacrylate or a combination of zinc oxide and methacrylic acid and an unmodified hydrogenated acrylonitrile butadiene rubber for use in high load-bearing synchronous drive belts and belts made therewith.

Description: Field of the Invention This invention relates to a high modulus elastomeric composition particularly suited for use in high load-bearing synchronous drive belts. Background The use of hydrogenated acrylonitrile-butadiene (HNBR) rubber in belts, particularly for automotive use, has been suggested in the past. See e.g. articles by Trevor A. Brown: "Compounding for Maximum Heat Resistance and Load Bearing Capacity in HNBR Belts", Rubber World magazine, October 1993, page 53, and "Using HNBR to Improve Belt Compounds", Rubber & Plastics News, June 7, 1993, page 45. See also US-A- 5,405,690. There are, however, no suggestions on what the composition should be. Fujiwara, in US-A- 5,599,246 (& EP-A-674 121), discloses using a modified HNBR, specifically using the ZSC-2295, in a belt composition. The modified HNBR is blended with unmodified HNBR, blending 10-40 ppw of the modified HNBR with 90-60 ppw of unmodified HNBR so that the amount of zinc methacrylate is between 4 to 20 percent of the rubber compound. Fujiwara teaches that if the amount of zinc methacrylate becomes greater than 20 ppw of the total rubber composition, fatigue of the tensile body occurs. Summary of the Invention In accordance with the practice of the present invention, there is provided an elastomeric composition and a power transmission belt produced from such as defined in the claims. A typical example of an HNBR modified with zinc oxide and methacrylic acid is commercially available as Zetpol ZSC2295 from Nippon Zeon Co. An unmodified HNBR is available as Zetpol 2020, also from Nippon Zeon Co. Typical of the peroxide cure co-agents are trimethylolpropane trimethacrylate, trifunctional organosiloxanes, triallyl cyanurate and triallyl isocyanurate. While from 0.5 to 10 phr of the co-agent can be used, 3 to 6 phr are preferred. Typical of the organic peroxides which can be used with the invention are 1,3-bis(t-butylperoxy-1-propyl) benzene, dicumyl peroxide and α,α-bis(t-butylperoxy) valerate. While 0.25 to 20 phr of the peroxide can be used, 1.5 to 4.5 phr are preferred. Typical of the phenolic resins which can be used are phenol formaldehyde resins. Preferred is an oil-modified thermosetting phenol formaldehyde resin. While from 1 to 20 phr of the phenolic resin can be used, from 6 to 12 phr are preferred. It is believed that the phenolic resin provides a high level of adhesion to the reinforcement in the cured belts as well as allows the belts to be built on conventional elastomer processing equipment without the use of solvents. In addition to those ingredients listed above, the composition can contain other materials customarily used in rubber compounding such as fillers, antioxidants, antiozonants, processing aids, etc. Particularly preferred is from 5 to 50 phr of a N330 carbon black. The composition of the invention has been found to provide synchronous drive belts with teeth having sufficient rigidity without the use of fiber reinforcement. As a measure of this property, it is preferred that the modulus at 10% elongation be from 5.2 to 7.25 MPa. While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in this art that various changes and modifications may be made therein without departing from the scope of the claims.

Claims: An elastomeric composition comprising: (a) from 50 to 95 parts by weight per 100 parts of rubber of an HNBR modified with either zinc methacrylate or a combination of zinc oxide and methacrylic acid; b) from 5 to 50 parts by weight per 100 parts of rubber of an unmodified HNBR; c) from 0.5 to 10 parts by weight per 100 parts of rubber of a peroxide cure co-agent; d) from 0.25 to 20 parts by weight per 100 parts of rubber of an organic peroxide; and e) from 5 to 50 parts by weight per 100 parts of rubber of carbon black, wherein the composition is characterized by the addition of from 1 to 20 parts by weight per 100 parts of rubber of a phenolic resin. The composition according to claim 1 wherein the peroxide cure co-agent is trimethylolpropane trimethacrylate. The composition according to claim 1 wherein the peroxide is α,α-bis(t-butylperoxy) valerate. The composition according to claim 1 having a modulus at 10% elongation of 5.2 to 7.25 MPa. A power transmission belt produced from an elastomeric composition comprising: (a) from 50 to 95 parts by weight per 100 parts of rubber of an HNBR modified with either zinc methacrylate or a combination of zinc oxide and methacrylic acid; b) from 5 to 50 parts by weight per 100 parts of rubber of an unmodified HNBR; c) from 0.5 to 10 parts by weight per 100 parts of rubber of a peroxide cure co-agent; d) from 0.25 to 20 parts by weight per 100 parts of rubber of an organic peroxide; and e) from 5 to 50 parts by weight per 100 parts of rubber of carbon black; wherein the composition is characterized by the addition of from 1 to 20 phr of a phenolic resin.

Inventors: GRANATOWICZ DANIEL STANLEY, MORRIS MATTHEW THOMAS, PILKINGTON MERVIN VICTOR, TOMPKIN GARY RICHARD, GRANATOWICZ, DANIEL STANLEY, MORRIS, MATTHEW THOMAS, PILKINGTON, MERVIN VICTOR, TOMPKIN, GARY RICHARD
Applicants: GOODYEAR TIRE & RUBBER, THE GOODYEAR TIRE & RUBBER COMPANY
Application year: 1998
Main classification: C08L15
IPC codes: B29D29, C08K5, C08L15, C08L61, F16F9, C08L9, C08K3, F16G1