Multimodal ethylene, alpha-olefin and diene polymers, processes for making and devices comprising such compositions

#This invention relates generally to multimodal ethylene, alpha-olefin and diene polymer compositions, processes for making them and to devices comprising such compositions. These compositions have been found to have an improved balance of processability, resilience and durability.

#Elastomers useful in applications requiring high resilience have in general a high elasticity in the medium to high frequency range (typically between 5 and 600 rad/sec) which results in low loss tangent (tan δ), at temperatures ranging from approximately room temperature to over 100° C. Natural rubber is an elastomer of this type.

#Ethylene elastomers contain sufficient copolymerised alpha-olefin to produce amorphous to semi-crystalline compounds of density generally below 0.9. In the class of ethylene based elastomers, such as EPDM elastomers, polymers of very high molecular weight (as measured by their Mooney viscosity) are usually required for high resilience applications. Although high molecular weight EPDM elastomers are commercially available, their inherently very high viscosity (Mooney viscosity in general greater than 200) creates difficulties in processability which requires them to be produced with the addition of extender oil to reduce their apparent viscosity. Very high molecular weight polymers are not only difficult to separate from their polymerization solvent without inducing significant macromolecular chain breakage, but they are difficult to mix and compound. The addition of extender oil to the elastomer eases processability in terms of production process recovery, elastomer mixing and compounding.

#FIGS. 1, 2 and 3 are graphs of the tan delta versus frequency of several comparative and inventive compositions.

#The polymer compositions of this invention comprise units derived from ethylene, alpha-olefin and diene. Such “EPDM-type” or “EODM” terpolymers are well known in the art. The alpha olefin is preferably one or more C3 to C8 alpha olefins, more preferably propylene or butene, most preferably propylene. The diene is preferably a non-conjugated diene selected from the group consisting of 5-ethylidene-2-norbornene (ENB), 1,4-hexadiene, 1,6 octadiene, 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene, dicyclopentadiene (DCPD), norbornadiene, 5-vinyl-2-norbornene (VNB), and combinations thereof, most preferably ENB.

#In a preferred embodiment, the maximum amount of ethylene derived units is 90 mole percent (corresponding to 85 wt % in EPDM), more preferably 80 mole percent and most preferably 75 mole percent based on the total moles of monomer. The preferred minimum amount of ethylene derived units is 35 mole percent, more preferably 40 mole percent, even more preferably 50 mole percent based on the total moles of monomer. The diene content maximum is preferably 5.0 mole percent (15 wt %), more preferably 3.0 mole percent even more preferably 2.5 mole percent, with the preferred minimum being 0.2 mole percent (0.7 wt %), more preferably 0.3 mole percent, and even more preferably 0.5 mole percent. The balance of the polymer units is preferably made up of alpha olefin. Ethylene content is determined by FTIR, ASTM D3900, and is not corrected for diene content. ENB content is determined by FTIR, ASTM D6047. Other dienes can be measured via 1H NMR. All ranges disclosed herein are inclusive unless otherwise noted.

#One well known measure of resiliency is tan (δ) which denotes the ratio of the loss modulus G″, to the elastic modulus G′. This quantifies the ability of a material to dissipate mechanical energy into heat versus the purely elastic storage of mechanical motion during one cycle of oscillatory movement. The measurement of tan (δ) can be made by a dynamic analyzer, and may be made by a sweep of frequencies at a fixed temperature, then repeating that sweep of frequencies at several other temperatures, followed by the development of a master curve of tan (δ) versus frequency by curve alignment. An alternate method is to measure tan (δ) at constant frequency and strain over a temperature range. As used herein tan (δ) is measured at 10.4 rad/sec and 13.95 % strain using A Rubber Processing Analyzer RPA 2000 (by Alpha Technologies Co).