Norio Kashiwa

FI Catalysts: A New Family of High Performance Catalysts for Olefin Polymerization

This paper reviews a new family of olefin polymerization catalysts. The catalysts, named FI catalysts, are based on non-symmetrical phenoxyimine chelate ligands combined with group 4 transition metals and were developed using “ligand-oriented catalyst design”. FI catalysts display very high ethylene polymerization activities under mild conditions. The highest activity exhibited by a zirconium FI catalyst reached an astonishing catalyst turnover frequency (TOF) of 64,900 s –1 atm –1, which is two orders of magnitude greater than that seen with Cp2ZrCl2 under the same conditions. In addition, titanium FI catalysts with fluorinated ligands promote exceptionally high-speed, living ethylene polymerization and can produce monodisperse high molecular weight polyethylenes (Mw/Mn 400,000) at 50 °C. The maximum TOF, 24,500 min –1 atm –1, is three orders of magnitude greater than those for known living ethylene polymerization catalysts. Moreover, the fluorinated FI catalysts promote stereospecific room-temperature living polymerization of propylene to provide highly syndiotactic monodisperse polypropylene (max. [rr] 98%). The versatility of the FI catalysts allows for the creation of new polymers which are difficult or impossible to prepare using group 4 metallocene catalysts. For example, it is possible to prepare low molecular weight (Mv∼103) polyethylene or poly(ethylene-co-propylene) with olefinic end groups, ultra-high molecular weight polyethylene or poly(ethylene-co-propylene), high molecular weight poly(1-hexene) with atactic structures including frequent regioerrors, monodisperse poly(ethylene-co-propylene) with various propylene contents, and a number of polyolefin block copolymers [e.g., polyethylene-b-poly(ethylene-co-propylene), syndiotactic polypropylene-b-poly(ethylene-co-propylene), polyethylene-b-poly(ethylene-co-propylene)-b-syndiotactic polypropylene]. These unique polymers are anticipated to possess novel material properties and uses.

A new titanium complex having two phenoxy-imine chelate ligands for ethylene polymerization

A new titanium complex having two phenoxy-imine chelate ligands, bis[N-(3-tert-butylsalicylidene)anilinato]titanium(IV)dichloride 1, was synthesized and its structure determined by X-ray analysis. Density functional theory (DFT) calculations and X-ray analysis suggest that complex 1, when activated, possesses two available cis-located sites needed for ethylene polymerization. Complex 1/methylaluminoxane (MAO) in toluene or heptane solvent displayed very high ethylene polymerization activities (2 280-4 150 (kg PE).(mol cat) -1 .h -1 ) with high molecular weight values (M v = 288 000- 881 000) at 25-75 °C under atmospheric pressure. The activity values displayed by complex 1/MAO are some of the highest values exhibited by any titanium complex with no cyclopentadienyl (Cp) ligand(s). Alternatively, complex 1/ i Bu 3 Al/Ph 3 CB(C 6 F 5 ) 4 in toluene solvent displayed high ethylene polymerization activities (190-670 (kg PE).(mol cat) -1 .h -1 ) with exceptionally high molecular weight values (M v = 3 920 000-5 860 000) at 25-75 °C under atmospheric pressure. The molecular weight values displayed by complex 1/ i Bu 3 Al/Ph 3 CB(C 6 F 5 ) 4 are some of the largest values displayed by homogeneous olefin polymerization catalysts including the group 4 metallocenes. The high potential of complex 1 for ethylene polymerization has therefore been demonstrated.

Polymerization of 1-hexene with bis[N-(3-tert-butylsalicylidene)phenylaminato]titanium(IV) dichloride using iBu3Al/Ph3CB(C6F5)4 as a cocatalyst

1-Hexene polymerization was investigated with bis:N-(3-tert-buty salicylidene)phenylamina-to]titanium(IV) dichloride (1) using Bu 3 Al/Ph 3 CB(C 6 F 5 ) as a cocatalyst. This catalyst system produced poly(1-hexene) having a high molecular weight (M a = 445000-884000. 0-60°C). 13 C NMR spectroscopy revealed that the high molecular weight poly(1-hexene) possesses an atactic structure with about 50 mol-% of regioregular units.

Direct modification of polyolefin films by surface-initiated polymerization of a phosphobetaine monomer

The surfaces of polyethylene and polypropylene sheets were modified by grafting with polymeric brushes formed from a phosphobetaine monomer. Pressed sheets of bromo-functionalized polyethylene or polypropylene macroinitiators (PE-MIs and PP-MIs, respectively) were used to initiate the atom-transfer radical polymerization of 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) under mild conditions to form a superhydrophilic grafted surface layer. The grafted polyolefin sheets showed excellent wettability and oil-detachment behaviour in water. Even three years after surface grafting had been performed, the PMPC-g-PP sheet retained a water contact angle of less than 10°. Furthermore, the water contact angle of the PMPC-g-PP sheet remained as low as 12° after it had been annealed at 373 K for 60 min under reduced pressure. Dynamic friction tests performed on the PMPC-g-PE sheet by sliding it against a glass ball revealed a marked reduction in the friction coefficient in water at sliding velocities in the range of 10−5 to 10−1 m s−1, possibly as a result of lubrication by water.

Recent progress on olefin polymerization catalysts

Recent progress on metallocene catalysts is reviewed. This consists for the main part of research activities in metallocene catalysts and their polymerization performances (ethylene polymerization, propylene polymerization, styrene polymerization). In addi-tion, the computational design of metallocene catalysts and the commercial status of metallocene technologies in Japan are described.