Abstracto

Preparation of rubbery polyethylene and polyethyelene wax using homogeneous late transition metal catalyst

Saman Damavandi, Gholam Hossein Zohuri, Reza Sandaroos, Saeid Ahmadjo, Ali Mohammadi

Rubber formpolyethylene with crystallinity of about 1 to 14%was prepared using a late transition metal catalyst of bis(2,6-isopropyl phenyl) 1,4- diazobutadine Nickel(II) dibromide, [(2,6-i-prph)2 DABMe2]NiBr2. Methylaluminoxan (MAO) and triisobuthylaluminum (TIBA) were used as cocatalyst and scavenger respectively. The optimum activity of the catalyst was observed at [Al]:[Ni]=3333:1 molar ratio and polymerization temperature of 25°C. Higher concentration of MAO than the optimum value not only decreased the activity of the catalyst but also produced polyethylene-wax (PE-Wax). The rate/time profile of the polymerizationwas a decay type with an acceleration period of about 60 min at polymerization temperature of 25°C. However, the higher the temperature to 65°C, the lower the acceleration period and the higher decay rate were observed. The polyethylene produced at temperature up to 55°C showed rubbery form while the reaction at 65°C produced PE-Wax. Activity of the catalyst was increased with monomer pressure to 5 bars. The viscosity average molecular weight (Mv) of the polymer obtained was 7.5 ×104 at the monomer pressure of 3 bars and 35°C temperature.