WO1999065983A1 - Rubber composition for power transmission belts - Google Patents

Abstract

This invention relates to power transmission belts and to a rubber composition for use therein. The composition contains from 90 to 10 phr alkylated chlorosulfonated polyethylene and 10 to 90 phr ethylene vinyl acetate.

Description

RUBBER COMPOSITION FOR POWER TRANSMISSION BELTS Technical Field This invention relates to power transmission belts and to a rubber composition for use therein. Background Art

Continually increasing temperatures in the engine compartment of motor vehicles has resulted in conventional compounds such as neoprene becoming obsolete due to insufficient heat resistance. In many instances, a change has been made to hydrogenated nitrile butadiene rubber (HNBR) . However, HNBR is a very expensive rubber. See e.g. U.S. Patent No. 5,599,246. More recently, the use of alkylated chlorosulfonated polyethylene (ACSM) has been suggested as a lower cost alternative to HNBR. See e.g. U.S. Patent No. 5,711,734; 5,408,007 and 5,626,953. While the ACSM polymer suffer some deficiencies, such as retention of properties at elevated temperatures and oil resistance, when used by itself, we have found that blending the ACSM with ethylene vinyl acetate (EVM) and curing the blends with an organic peroxide and a cure co- agent overcome those deficiencies. Summary of the Invention

In accordance with the practice of the present invention, there is provided a rubber composition comprising:

a. from 90 to 10 parts by weight per 100 parts of rubber (phr) of ACSM; b. from 10 to 90 phr of EVM; c. from 20 to 75 phr of carbon black; and d. from 2 to 10 phr of an organic peroxide.

There is also disclosed a power transmission belt produced from a rubber composition comprising:

a. from 90 to 10 phr of ACSM; and b. from 10 to 90 phr of EVM. The ACSM used in the present invention is available from DuPont-Dow as ACSIUM HPR 6367.. The EVM is available from Bayer as LEVAPREN 500HV.

Typical of the peroxide cure co-agents are trimethylolpropane trimethacrylate, trifunctional organosiloxanes, triallyl cyanurate and triallyl isocyanurate, 1,3-butylene glycol dimethacrylate, ethylene glycol dimethacrylate, and n, n' -m-phenylene-dimaleimide-1, 2-cis- polybutadiene. While from 0.5 to 10 phr of the co-agent can be used, 1 to 4 phr are preferred.

Typical of the organic peroxides which can be used with invention are 1, 3-bis (t-butylperoxy-1-propyl) benzene, dicumyl peroxide, α,α-bis (t-butylperoxy) valerate, α,α-bis(t- butylperoxy) diisopropyl benzene, 2, 5-dimethyll-2, 5-di (t- butylperoxy) hexane, 1, 1-bis (t-butylperoxy) -3, 3, 5- trimethylcyclohexane, n-butyl-4, 4-bis (t-butylperoxy) valerate, and ethyl-3, 3-bis (t-butylperoxy) butyrate.. While 0.5 to 10 phr of the peroxide can be used, 1.5 to 4.5 phr are preferred. While 20 to 75 phr of carbon black can be used, we prefer a mixture of from 15 to 45 phr of a N550 carbon black from Cabot and from 5 to 30 phr of an SRF/N762 carbon black available from Cabot.

Experimental

1. ACSIUM HPR 6367.

2. LEVAPREN 500HV. 3. Poly-Dispersion VC-60, Rhein Chemie.

4. PLASTOMAG 170, Akrochem

5. PE 200, Hercules

Original physicals, compression modulus, oven-aged physicals and oil immersion physicals were run on the blends and are shown in Table 2.

As the data indicate, the blends of ACSM/EVM exhibit better retention of modulus at elevated temperatures and improved resistance to oil.

A series of blends of ACSM/EVM were compared to an all ACSM compound, an all EVM compound and three compounds known to be used in positive drive belts comprising a sulfur cured HNBR, a peroxide cured HNBR and a Neoprene for: a) percent of torque S' at 38°C which is retained at 135°C; b) oil resistance as percent volume swell after aging seventy hours at 100°C in IRM 903 oil; and c) the change in 10% modulus of each compound after being in oven for 168 hours @ 135°C. The results are shown in Tables 3, 4 and 5 respectively.

As the data indicate, significant improvement in retention of modulus at elevated temperatures and oil resistance versus ACSM can be achieved via an ACSM/EVM blend. The modulus retention results further show an unexpected synergistic effect between the ACSM and EVM, such that the %S' retained for certain blend ratios is higher than for ACSM or EVM alone.

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 spirit or scope of the invention.

Claims

1. A rubber composition comprising parts by weight per 100 parts of rubber (phr) :

a. from 90 to 10 phr of an alkylated chlorosulfonated polyethylene; b. from 10 phr to 90 phr of an ethylene vinyl acetate copolymer; c. from 20 phr to 75 phr of carbon black; and d. from 2 phr to 10 phr of an organic peroxide.

2. A power transmission belt produced from a rubber composition comprising parts by weight per 100 parts or rubber (phr) ;

a. from 90-10 phr of an alkylated chlorosulfonated polyethylene; and b. from 10-90 phr of an ethylene vinyl acetate copolymer.

3. The rubber composition of claim 1 further comprising from .5 to 10 phr of a peroxide cure co-agent.

4. The belt according to claim 2 further comprising from 20-75 phr of carbon black and from 2-10 phr of an organic peroxide.

5. The belt according to claim 4 further comprising from 0.5 to 10 phr of a peroxide cure co-agent.