This invention relates generally to low
ethylene insertions into I-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 I-olefin homo- and co-polymers, particularly elastomeric crystalline and amorphous block homo- and co-polymers of I-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. The amount of
ethylene included in the
reaction system can be selected and controlled to be so small as to result in essentially minimal (<2 mole %) incorporation of ethylene units into the resulting elastomeric
polymer and the molecular weight may be increased. Amounts of ethylene to generate the PRE effect may be greater than 0.1 wt. % and preferably range up to about 2 wt. %. However, if a
polymer with more ethylene is desired, additional ethylene may be incorporated into the
polymerization feed, including up to 10 to about 50 mole % based on olefin units. 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, I-olefin elastomers are produced through incorporation of ethylene using unbridged fluxional catalyst systems which may not otherwise produce acceptable elastomeric homopolymers. This effect is termed the EPE effect, for Elastomeric Property-Enhancing effect. The EPE amount of ethylene required to produce such elastomers typically overlaps the PRE activity-enhancing amount. Incorporation of up to about 5 mole % or more of ethylene typically will produce an elastomeric
polymer using such catalyst systems. Typical useful amounts of incorporated ethylene include about 1 to 3 mole %. Preferred polymers of this invention retain sufficient
crystallinity to provide a high
melting point (by DSC) of about 80° C., preferably above 100° C., including in the range of from about 120° C. to about 140° C. and above. Novel flexible alpha-olefin homo and copolymers having elongation in excess of 600% and substantially no retained force are disclosed.