Study on Immobilized Metallocene and Single-Site Catalysts for the Preparation of Ultra-High Molecular Weight Polyethylene at Various Polymerization Conditions

Abstract

Ultra-high molecular weight polyethylene (UHMWPE) possesses advantages over conventional polyolefins such as excellent mechanical properties. Recent progresses in transition-metal complexes have led to the discovery of highly active catalysts for the preparation of UHMWPE. In this study, Ti with bis(phenoxy-imine) ligand (FI catalyst) and Me₂Si(C₅Me₄)(N-tBu)TiCl₂ (CGC) were immobilized on silica and tested for the preparation of UHMWPE. Results revealed that soluble FI catalyst and CGC can produce polyethylene having relatively high molecular weight above 10⁶ g/mol, which also can be successfully immobilized on carriers for better adaptability to production processes.

Keywords:

• CGC
• FI
• Immobilization
• Ultra-high molecular weight polyethylene (UHMWPE)

ACKNOWLEDGEMENTS

This research was kindly supported by a grant from the Fundamental R & D Program for Core Technology of Materials (10037176) funded by the Ministry of Knowledge Economy, Republic of Korea.

Notes

^a Polymerization conditions: reactor = 250 mL round bottom flask; catalyst concentration = 3 × 10⁻⁵ mol/L; cocatalyst = MAO, 6 × 10⁻² mol/L; [Al]/[cat] = 2000; pressure = 1 bar; temperature = 50°C.

^a Polymerization condition: reactor = 250 mL round-bottom flask; catalyst = FI catalyst, 2.0 × 10⁻⁵ mol/L; MAO, 5.0 × 10⁻² mol/L, [Al]/[FI] = 2500; Ph₃CB(C₆F₅)₄, 4.0 × 10⁻⁵ mol/L, [FI]:[Ph₃CB(C₆F₅)₄]:[TIBAL] = 1: 2: 500; toluene, 125 mL; pressure = 1 bar; time = 20 minutes.

^a Polymerization condition: reactor = 250 mL round bottom flask or 100 mL autoclave; catalyst = FI catalyst, 2.0 × 10⁻⁵ mol/L; MAO, 5.0 × 10⁻² mol/L, [Al]/[FI] = 2500; Ph₃CB(C₆F₅)₄, 4.0 × 10⁻⁵ mol/L, [FI]:[Ph₃CB(C₆F₅)₄]:[TIBAL] = 1: 2: 500; time = 20 minutes; temperature = 40°C.

^b Temperature = 70°C; time = 10 minutes.

^a Polymerization conditions: reactor = 1 L autoclave; temperature = 70°C; polymerization time = 90 minutes; solvent = isobutane, 400 mL.

^b Polymerization temperature was 50°C and solvent was heptanes 100 mL, since isobutane is in gaseous phase at 1 bar.

^c Not determined.

^a Polymerization condition: reactor = 250 mL round-bottom flask; catalyst = immobilized FI catalyst (55 µmol-Ti/g-cat), 1.1 × 10⁻⁵ mol-Ti/L; toluene, 125 mL; pressure = 1 bar; time = 60 minutes; temperature = 70°C.

^a Polymerization condition: reactor = 250 mL round-bottom flask or 100 mL autoclave; catalyst = immobilized FI catalyst (55 µmol-Ti/g-cat), 1.1 × 10⁻⁵ mol-Ti/L; scavenger, TIBAL 150 mg; solvent, 125 mL; time = 60 minutes.

^b Solvent, 40 mL.