| 摘要 |
This invention relates generally to low ethylene insertions into alpha -olefin polymers and processes for production of such polymers using unbridged fluxional metallocenes, primarily substituted aryl indenyl metallocenes, and more particularly to use of unbridged, fluxional, cyclopentadienyl or indenyl metallocene catalyst systems in methods of production of high melting point alpha -olefin homo- and co-polymers, particularly elastomeric crystalline and amorphous block homo- and co-polymers of alpha -olefins. The activity of fluxional unbridged metallocene polymerization catalysts containing at least one 2-arylindene ligand is increased 10x or more by the addition of small (typically 0.1-10 wt. %) amounts of ethylene to the polymerization system, which increase is termed the Polymerization Rate-Enhancement effect (PRE), which is measured in terms of an Ethylene Enhancement Factor (EEF) as a dimensionless ratio in the range of from about 1.1 to about 10 or above. A second important aspect of this invention is the ability to use a PRE activity-enhancing amount of ethylene in an olefin polymerization without substantially affecting the physical properties of the elastomer. In a third important aspect of this invention, alpha -olefin elastomers are produced through incorporation of ethylene using unbridged fluxional catalyst systems which may not otherwise produce acceptable elastomeric homopolymers. Preferred polymers of this invention retain sufficient crystallinity to provide a high melting point (by DSC) of about 80 DEG C., preferably above 100 DEG C., including in the range of from about 120 DEG C. to about 140 DEG C. and above. Novel flexible alpha -olefin homo and copolymers having elongation in excess of 600% and substantially no retained force are disclosed. |
