Copolymerization of ethylene/propylene elastomer using high‐activity Ziegler–Natta catalyst system of MgCl₂ (ethoxide type)/EB/PDMS/TiCl₄/PMT

Abstract

Abstract A high‐activity Ziegler–Natta catalyst of TiCl 4 ‐supported MgCl 2 (ethoxide type) was prepared. Ethyl benzoate (EB) and polydimethylsiloxane (PDMS) were used as internal donors, while p ‐methyl toluate (MPT) and triethylaluminum (TEA) were used as the external donor and cocatalyst, respectively. Suspension copolymerization of ethylene–propylene (EPM) was carried out in n ‐heptane using the catalyst system. The relative pressures of 1.5 : 1 and 2 : 1 atmosphere of propylene‐to‐ethylene (P P /P E ) gave a polymer with elastomeric properties. The relative pressure of propylene‐to‐ethylene higher and lower than the above values, however, gave a homopolymer or copolymer without elastomeric properties. The effect of the TEA concentration, H 2 concentration, temperature, and pressure of P P /P E on the yield of the polymer obtained was investigated. The effects of these factors on the glass transition temperature (T g ) and ethylene content of the polymer were studied. The content of ethylene in EPM was determined using the FTIR technique. The molar ratio of Al : MPT : Ti = 355 : 107 : 1 gave a polymer with an ethylene content of about 32%. However, a ratio lower than AL : MPT : Ti = 355 : 107 : 1 did not give a good elastomeric polymer. The highest productivity of the catalyst was obtained at a molar ratio of AL : MPT : Ti = 355 : 107 : 1. Increasing the temperature from 45 to 70°C caused a slight increase of Et % content and a decrease of the T g of the copolymer obtained, while the highest productivity of the catalyst was obtained at 55°C with good elastomeric properties using an AL : MPT : Ti = 497 : 107 : 1 molar ratio. Increasing the pressure of propylene from 1.5 to 2.5 atm caused a sharp decrease in the T g and ethylene content of the polymer. When the ethylene content in the copolymer was increased, the T g value had a tendency to be closer to the polyethylene T g . © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 84: 785–790, 2002; DOI 10.1002/app.10330