Infrared spectral characterization of supported propene polymerization catalysts: A link to catalyst performance

Magnesium dichloride supported titanium catalyst system: dimethoxypropane as an external lewis base☆

Various ideas on the mechanism of stereoregulation by complex catalysts in the polymerization processes of the olefins are discussed. Two possibilities of stereocontrol of the polymer chain are examined: enantiomorphous mechanism and the mechanism of control by the end group. Quantitative methods of evaluating the microstructure of the chain and the stereoregulating capacity of catalytic systems are described. An analysis is made of the published data on the influence of various parameters of polymerization and the nature of the catalyst on the stereospecificity of the macromolecule formed and the stereoregulating capacity of the catalytic system. The question of the heterogeneity of the active centres and their distribution by stereoregulating capacity and activity is discussed. Data are presented on current homogeneous and supported catalytic systems with high stereoregulating capacity.

Current aspects of stereospecific polymerization of olefins—review☆

New, highly active supported propene polymerization catalysts are prepared by activating supports derived from Mg dialkyl complexes with sterically hindered aromatic esters, such as ethyl 2,6-dimethylbenzoate (6a), ethyl 2,4-6-trimethylbenzoate (7), or isopropyl benzoate (2b). The support is precipitated by reacting a hexane solution of the Mg dialkyl complex with SiCl4 and then activated by treatment with TiCl4 and diisobutylphthalate in chlorobenzene. Optimized catalysts of this type prepared from Mg dialkyl complex with 7 realize yields of 16–17 kg polypropylene/g catalyst in 2 h hexane slurry polymerizations at 70°C, 10,2 atm, with less than 1% boiling hexane extractables and 0,41–0,43 g/ml polymer powder bulk density. The cocatalyst-external modifier package used consists of Al(C2H5)3-dimethoxydiphenylsilane. The polymer produced is characterized by a narrow particle size distribution, which renders the title catalysts suitable for use in both slurry and solventless propene polymerization processes.

Supported propene polymerization catalysts, 1. Supports derived from magnesium dialkyl‐sterically hindered aromatic ester complexes

Following the earlier development of highly active supported propene polymerization catalysts prepared by activating supports derived from Mg dialkyl complexes with the rare and very expensive ethyl esters of 2,6-dimethyl- (1) or 2,4,6-trimethylbenzoic acid (2), research was undertaken to uncover low-cost and commercially available substitutes for 1 and 2. Several phosphonate, phosphate, and phosphite alkyl esters, as well as ethers and amines, were investigated. Dibutyl butylphosphonate (5b) adducts with Mg dialkyl were found to produce catalysts with comparable activity, improved, narrower particle size distribution, and only slightly lower stereospecificity and polymer powder bulk density relative to catalysts made using MgR2 adducts with 1 or 2 as starting materials (R = n-C4H9). Optimized catalysts based on MgR2 · 5b adducts, prepared by precipitating the support by reaction of a solution of the adduct with SiCl4 and subsequent activation by treatment of the support with TiCl4 and diisobutyl phthalate in chlorobenzene, realize yields of 16–17 kg polypropylene/g catalyst in 2-h hexane slurry polymerizations at 70°C, 10,2 atm, with 1,2–1,5 wt.-% boiling hexane extractables and 0,40–0,41 g/ml polymer powder bulk density. The cocatalyst-external modifier package used consists of Al(C2H5)3-dimethoxydiphenylsilane. The narrow particle size distribution of the polymer powder produced renders the new catalysts suitable for use in both slurry and solventless propene polymerization processes, while the low cost and ready availability of 5b make the catalyst preparation commercially feasible.

Charles R. Hoppin

Papers

Supported propene polymerization catalysts, 1. Supports derived from magnesium dialkyl‐sterically hindered aromatic ester complexes

Supported propene polymerization catalysts, 2. Supports derived from dialkylmagnesium/dibutyl butylphosphonate complexes