2-methyl-substituted bisindenyl zirconocenes has been further optimized, e.g. by
substitution at the 4-position [52–54] and by pseudo C 2 -symmetric bisindenyl ansazirconocenes with one 2-isopropyl and one 2-methyl substituent [25, 55].
Probably to circumvent the former Hoechst AG’s strong patent position on
bisindenyl-type ansa-metallocenes, alternative structures were developed by
Mitsubishi Chemical Corporation [23, 52] and by former Montell [14, 56], based
on azulenyl and heterocenyl ligands, respectively.
Although ansa-metallocene catalysts are intrinsically homogeneous catalysts,
all industrial polypropylene processes had been developed for heterogeneous
Ziegler–Natta catalysts. Therefore, an absolute requirement for the industrial use
of ansa-metallocenes was their heterogenization on a solid carrier material to avoid
polymer growth on reactor walls and to achieve control over polymer particle
morphology [57, 58]. Fixation of an ansa-metallocene catalyst on a solid support
allows its use as a “drop-in” replacement for traditional Ziegler–Natta solid-state
catalysts in preexisting polyolefin production plants, where it then produces polyolefin materials with properties closely similar to those produced by it in homogeneous solution. The necessity to heterogenize metallocene catalysts was first
recognized by ExxonMobil and patented in 1985 [59]. Since then, suitable recipes
for heterogenized metallocene catalysts, which yield polymer products with controlled spherical morphology, and the elementary processes responsible for this
outcome have been thoroughly researched and described in detailed reviews
[57, 58, 60, 61].
Industrial use of ansa-metallocenes for the production of isotactic polypropylene
had to overcome not only technical hurdles, but has also been restricted by a
complicated and scattered patent landscape. Basic patent rights like the activation
of metallocene complexes by MAO, supported metallocenes [59, 62], silanediylbridges [49] and 2-methyl substitution [50], all of which were required for the use of
ansa-metallocenes in industrial polypropylene production, were owned by different
companies such that no player had the freedom to move. Only in 1995, 5 years after
rac-dimethylsilylenbis(2-methylindenyl)zirconium dichloride had been described
for the first time in a patent [50], did ExxonMobil and the former Hoechst AG
announce independently their first commercial production of metallocenecatalyzed, isotactic polypropylene. Most likely, these 5 years were needed not
only to solve technical problems, but also to gain access to all the necessary patent
rights.
Today, at least five companies are known to use ansa-metallocenes for industrial
production of isotactic polypropylene: TOTAL Petrochemicals & Refining
(Lumicene
® ) [63], LyondellBasell (Metocene) [64], Japan Polypropylene
(WINTEC™), ExxonMobil (Achieve™ PP) and LyondellBasell’s licensee
PolyMirae (Metocene). In addition, technology for the industrial production of
polypropylene by use of ansa-metallocenes is offered for licensing by
LyondellBasell (Metocene) [64] and Lummus Novolen Technology GmbH
(Novocene™) [65]. Although Japan Polypropylene’s WINTEC™ is produced by
a bis-azulenyl-type ansa-metallocene [23, 52] and also uses a MAO-free activator
support, all others are believed to use bis-indenyl-type metallocenes.
36
H.H. Brintzinger and D. Fischer
substitution at the 4-position [52–54] and by pseudo C 2 -symmetric bisindenyl ansazirconocenes with one 2-isopropyl and one 2-methyl substituent [25, 55].
Probably to circumvent the former Hoechst AG’s strong patent position on
bisindenyl-type ansa-metallocenes, alternative structures were developed by
Mitsubishi Chemical Corporation [23, 52] and by former Montell [14, 56], based
on azulenyl and heterocenyl ligands, respectively.
Although ansa-metallocene catalysts are intrinsically homogeneous catalysts,
all industrial polypropylene processes had been developed for heterogeneous
Ziegler–Natta catalysts. Therefore, an absolute requirement for the industrial use
of ansa-metallocenes was their heterogenization on a solid carrier material to avoid
polymer growth on reactor walls and to achieve control over polymer particle
morphology [57, 58]. Fixation of an ansa-metallocene catalyst on a solid support
allows its use as a “drop-in” replacement for traditional Ziegler–Natta solid-state
catalysts in preexisting polyolefin production plants, where it then produces polyolefin materials with properties closely similar to those produced by it in homogeneous solution. The necessity to heterogenize metallocene catalysts was first
recognized by ExxonMobil and patented in 1985 [59]. Since then, suitable recipes
for heterogenized metallocene catalysts, which yield polymer products with controlled spherical morphology, and the elementary processes responsible for this
outcome have been thoroughly researched and described in detailed reviews
[57, 58, 60, 61].
Industrial use of ansa-metallocenes for the production of isotactic polypropylene
had to overcome not only technical hurdles, but has also been restricted by a
complicated and scattered patent landscape. Basic patent rights like the activation
of metallocene complexes by MAO, supported metallocenes [59, 62], silanediylbridges [49] and 2-methyl substitution [50], all of which were required for the use of
ansa-metallocenes in industrial polypropylene production, were owned by different
companies such that no player had the freedom to move. Only in 1995, 5 years after
rac-dimethylsilylenbis(2-methylindenyl)zirconium dichloride had been described
for the first time in a patent [50], did ExxonMobil and the former Hoechst AG
announce independently their first commercial production of metallocenecatalyzed, isotactic polypropylene. Most likely, these 5 years were needed not
only to solve technical problems, but also to gain access to all the necessary patent
rights.
Today, at least five companies are known to use ansa-metallocenes for industrial
production of isotactic polypropylene: TOTAL Petrochemicals & Refining
(Lumicene
® ) [63], LyondellBasell (Metocene) [64], Japan Polypropylene
(WINTEC™), ExxonMobil (Achieve™ PP) and LyondellBasell’s licensee
PolyMirae (Metocene). In addition, technology for the industrial production of
polypropylene by use of ansa-metallocenes is offered for licensing by
LyondellBasell (Metocene) [64] and Lummus Novolen Technology GmbH
(Novocene™) [65]. Although Japan Polypropylene’s WINTEC™ is produced by
a bis-azulenyl-type ansa-metallocene [23, 52] and also uses a MAO-free activator
support, all others are believed to use bis-indenyl-type metallocenes.
36
H.H. Brintzinger and D. Fischer