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Copolymerization of ethylene–propylene using high‐activity bi‐supported Ziegler–Natta TiCl 4 catalyst
Author(s) -
Zohuri G. H.,
Mortazavi M. M.,
Jamjah R.,
Ahmadjo S.
Publication year - 2004
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.20827
Subject(s) - catalysis , copolymer , ethylene , ziegler–natta catalyst , ethylene propylene rubber , monomer , polymer chemistry , polymerization , materials science , natural rubber , alkyl , chemistry , polymer , organic chemistry
Heterogeneous Ziegler–Natta TiCl 4 catalyst using MgCl 2 and SiO 2 as supports was prepared under controlled conditions. Mg(OEt) 2 was used as a starting material and was expected to convert to active MgCl 2 during catalyst preparation. Due to the high surface area and good morphological control, SiO 2 was chosen as well. Slurry copolymerization of ethylene and propylene (EPM) was carried out in dry n ‐heptane by using the catalyst system SiO 2 /MgCl 2 /TiCl 4 /EB/TiBA or TEA/MPT/H 2 at temperatures of 40–70°C, different molar ratios of alkyl aluminum : MPT : Ti, hydrogen concentrations, and relative and total monomers pressure. Titanium content of the catalyst was 2.96% and surface area of the catalyst was 78 m 2 /g. Triisobutyl aluminum (TiBA) and triethyl aluminum (TEA) were used as cocatalysts, while ethyl benzoate (EB) and methyl p ‐toluate (MPT) were used as internal and external donors, respectively. H 2 was used as a chain‐transfer agent. Good‐quality ethylene propylene rubber (EPR) of rubber was obtained at the ratio of [TiBA] : [MPT] : [Ti] = 320 : 16 : 1 and polymerization temperature was 60°C. When TiBA was used as a cocatalyst, a higher and more rubberlike copolymer was obtained. For both of the cocatalysts, an optimum ratio of Al/Ti was obtained relative to the catalyst productivity. Ethylene content of the copolymer obtained increased with increasing TiBA concentration, while inverse results were obtained by using TEA. Addition of H 2 increased the reactivity of the catalyst. The highest product was obtained when 150 mL H 2 /L solvent was used. Increasing temperature from 40 to 70°C decreased the productivity of the catalyst, while irregular behavior was observed on ethylene content. Relative pressure of P P / P E = 1.4 : 1 and total pressure of 1 atm was the best condition for the copolymerization. Polymers with ethylene contents of 25–84% were obtained. Increasing ethylene content of EPR decreased T g of the polymer obtained to a limiting value. Viscosity‐average molecular weight ( M v ) decreased with increasing temperature and TiBA and H 2 concentration. However, increasing the polymerization time increased the M v . © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2597–2605, 2004