Effect of the internal/external donor pair in high‐yield catalysts for propylene polymerization, 1. Catalyst‐cocatalyst interactions

Abstract

The chemistry of the catalyst-cocatalyst interaction was investigated in systems containing different internaVexterna1 donor pairs. Qualitatively similar results were obtained with the ethyl benzoate/methyl p-toluate (EB/MFT) and dibutyl phthalate/triethoxy(henyl)silane (DBPIEPS) systems, which thus were assumed to follow the same model. Quantitative differences were accounted for by assuming a different basic strength of the two donor pairs towards MgC12 and AIEt,.-Catalyst C: containing DBP as internal donor.(EB = ethyl benzoate, DBP = dibutyl phthalate). 0 1991, Huthig & Wepf Verlag, Basel CCC 0025-1 16)</91/$03.00 1116 L. Noristi, P. C. Barbk, G. BaruzziThe catalysts were used in combination with triethylaluminium (TEA) as cocatalyst and either MPT or EPS as external donors (MPT = methylp-toluate, EPS = triethoxy(pheny1)silane).This paper deals with the chemical changes occurring in the catalyst upon contact with the cocatalyst and the external donor under the polymerization conditions.The polymerization results and their relationships with the chemical changes observed will be the subject of a subsequent paper. Experimental part Catalysts synthesisThe general procedure for the catalysts preparation was as follows: 50 g of anhydrous MgCl, were put under dry N, in a 1 dm3 stainless steel jar containing 650 mL of stainless steel balls having a diameter of 15,s mm, and ground for 25 h in a vibratory mill. 10 g of ground MgCI, were then contacted twice with 100 cm3 of pure TiCI, at 100°C for 2 h. For the catalysts B and C, 0,125 moles of ethyl benzoate (EB) and dibutyl phthalate (DBP), respectively, per mole of MgCI, were added during the first treatment with TiCI,.The mixture was then filtered, the solid washed with hexane and then treated once with 1,2-dichloroethane (100 g solid/dm3 of DCE) under reflux for 2 h, in order to remove any inactive TiCI,-Lewis base complex. The catalyst was then filtered, washed with hexane, and finally dried mder vacuum. Catalyst-cocatalyst contactThe typical procedure for the contact experiments was as follows: a flask immersed in a thermostatting bath was charged under a stream of dry N, with 1 OOO cm3 of hexane. The temperature was raised (50 "C), then the proper amounts of triethylaluminium (TEA) and external donor were added, followed by a catalyst amount corresponding to 0,3 mmol of Ti. The mixture was kept at 50 "C with stirring for the selected time, then the catalyst was recovered by filtration, thoroughly washed with hexane, and finally dried under vacuum. Catalyst analysisThe content of Ti, Mg and A l was measured by atomic absorption spectroscopy, C1 by potentiometric titration. The content of Lewis base was determined by gas chromatography after dissolution of the catalyst in properly selected solvents so as to avoid any degradation of the component investigated (suitable solvents were: acetone for DBP, CH30H for methyl p-toluate (MPT), C,H,OH for EB and ethoxysilanes).Experimental errors expressed as confidence limits at 95% probability were * 5 % for Ti, Mg and Al, ...

The discovery and progress of MgCl2‐supported TiCl4 catalysts

“…Through enormous evaluation of electron donors, we eventually reached a very effective combination of dialkyl phthalates and alkoxysilanes as IDs and EDs, respectively. 19 -21 It was confirmed [22][23][24][25][26] that a dialkyl phthalate as ID was displaced from the catalyst surface, and an alkoxysilane as ED was fixed on the catalyst surface as a stereospecificity improver instead of ID. The function of alkoxysilanes in enhancing not only the stereospecificity but also the molecular weight of the resulting PP also was reported.…”

Stopped-Flow Techniques in Ziegler Catalysis

“…(2) in ref. [58] c) Crystallinity (v c ) was calculated from Equation (1) in ref. [58] tion of properties versus molecular weight is scarcely reported in the literature.…”

“…[58] c) Crystallinity (v c ) was calculated from Equation (1) in ref. [58] tion of properties versus molecular weight is scarcely reported in the literature. Therefore, the high-pressuretype stopped-flow polymerization system was established mainly as further efforts to develop an olefin block copolymer PP-block-(PE-co-PP) with a well-defined structure and excellent properties.…”

Effects of external electron donor on catalyst active sites in propylene polymerization

“…Accordingly, role of electron donor are reported. [7][8][9][10][11][12][13][14] any doubts of mixing effect can be eliminated. All As discussed above, there is not any consisof the polymerization results adopted in this study tency in the external electron donor addition efare the average values of five trials.…”