Summary: Poly(propylene)/monoalkylimidazolium‐modified montmorillonite (PP/IMMT) nanocomposites were prepared by in situ intercalative polymerization of propylene with TiCl4/MgCl2/MMT catalyst. The PP synthesized possessed high isotacticity and molecular weight. Both wide‐angle X‐ray diffraction (XRD) and transmission electron microscopy (TEM) examinations evidenced the nanocomposite formation with exfoliated MMT homogeneously distributed in the PP matrix. A thermal stability study revealed that the nanocomposites possess good thermal stability.
X‐ray diffraction patterns of PP/IMMT (MMT = 2.2 wt.‐%) nanocomposite before and after processing. 相似文献
The results of studies of the synthesis and properties of supported titanium-magnesium catalysts for propylene polymerization performed at the Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, are considered. The composition of the catalysts is TiCl4/D1/MgCl2-AlEt3/D2, where D1 and D2 are stereoregulating donors. With the use of the procedure proposed for the synthesis of titanium-magnesium catalysts, the morphology of catalyst particles depends on the stage of the preparation of a Mg-containing support. The titanium-magnesium catalysts developed afforded polypropylene (PP) in a high yield; this PP was characterized by high isotacticity and excellent morphology. The controllable fragmentation of the catalyst by the polymer is of crucial importance for the retention of the morphology of titanium-magnesium catalyst particles in PP. The fragmentation of catalyst particles to microparticles occurred in the formation of more than 100 g of PP per gram of the catalyst. The surface complexes were studied by DRIFT and MAS NMR spectroscopy and chemical analysis. It was shown that the role of internal donors is to regulate the distribution of TiCl4 on different MgCl2 faces and, thereby, to influence the properties of PP. It was found that chlorine-containing complexes of aluminum compounds were formed on the catalyst surface by the interaction of the catalyst with AlEt3; these complexes can block the major portion of titanium chloride. Data on the number of active sites and the rate constants of polymer chain propagation (kp) at various sites indicate that donor D1 increases the stereospecificity of the catalyst because of an increase in the fraction of highly stereospecific active sites, at which kp is much higher than that at low-stereospecificity active sites. Donor D2 enhances the role of D1. Similar values of kp at sites with the same stereospecificity in titanium-magnesium catalysts and TiCl3 suggest that the role of the support mainly consists in an increase in the dispersity of titanium chloride. 相似文献
Diphenyl (4-hydroxyphenyl) hexadecyl phosphonium bromide (POH) -modified montmorillonite (POHMMT) was used to prepare a novel TiCl4/MgCl2/POHMMT compound catalyst and exfoliated iPP/POHMMT nanocomposites were prepared by the in situ intercalative polymerization of propylene with the TiCl4/MgCl2/POHMMT compound catalyst. The POH surfactants don’t change the catalytic characteristic of the Z-N catalyst and the obtained PP presents high isotacticity, normal molecular weight and molecular weight distribution. The WAXD, SAXS and TEM results demonstrate the highly exfoliated iPP/POHMMT nanocomposites were produced by the in situ polymerization with this novel catalyst, while the intercalated iPP/Na+MMT nanocomposites were produced with the TiCl4/MgCl2/Na+MMT compound catalyst. Through this approach, in situ propylene polymerization can actually take place between the silicate layers and lead not only to PP with high isotacticity and molecular weight, but also to highly exfoliated PP nanocomposites. 相似文献
Vaporization of MgCl2 and other metal halides results in monomeric gas-phase species. Cocondensation of these species with organic diluents such as heptane yields highly activated solids which are precursors to MgCl2 supported “high-mileage” catalysts for olefin polymerization. These catalysts, prepared by treatment with TiCl4 followed by standard activation with aluminum alkyls display high activity for ethylene and propylene polymerization. MgCl2 can also be evaporated into neat TiCl4 to give a related catalyst. The concentration of MgCl2 in the diluent affects catalyst properties as does the nature of the diluent. TiCl3, 3TiCl3 · AlCl3, VCl3 and other metal halides are subject to similar activation. 相似文献
In‐situ gas phase poly(propylene) (PP) formation over a high activity TiCl4‐MgCl2‐supported Ziegler‐Natta catalyst has been studied by video microscopy combined with ex‐situ light microscopy, SEM, high‐resolution TEM, and STEM/PEELS/EDX for the first time. In‐situ observation revealed rapid formation of poly(propylene) beads 9–10 μm in size (< 1/30 s) as well as growth of significant amounts of polymer within local regions. Catalyst particles containing 2–5 nm‐sized MgCl2 crystalline domains are subjected to transformations during catalysis that form PP/catalyst aggregated structures of 30–50 μm in size. 相似文献
The polymerizations of propylene and ethylene with two postmetallocene catalysts [(4R,5R)-2,2-dimethyl-α,α,α′,α′-tetra(perfluorophenyl)-1,3-dioxolane-4,5-dimethanol]TiCl2 · MgCl2 and [(4R,5R)-2,2-dimethyl-α,α,α′,α′-tetra-(perfluorophenyl-1,3-dioxolane-4,5-dimethanol]TiCl2· (LiCl)2 are studied. The first catalyst shows higher activity in both reactions and forms a lower molecular mass PP. This PP is characterized by a wide molecular-mass distribution that can be described by a set of five or six Flory components with different average molecular masses. Along with heterogeneity with respect to kinetic parameters, there is heterogeneity with respect to stereospecificity. Some of the sites form a high-molecular-mass highly isotactic polymer whose melting point is ≥150°C, whereas other sites produce syndiotactic and atactic PPs. For the most isospecific sites, a stereocontrol mechanism similar to the mechanism typical for metallocene catalysts with C1-symmetry is advanced. The catalysts under study are composed of the [(4R,5R)-2,2-dimethyl-α,α,α′,α′-tetra(perfluorophenyl)-1,3-dioxolane-4,5-dimethanol]TiCl2 complex supported on LiCl and MgCl2, respectively. 相似文献
Monocyclopentadienyl compounds, CpMCl3 (M = Ti, Zr) supported on activated MgCl2 were used for the polymerizations of ethylene in the presence of methylaluminoxane (MAO) or a common alkylaluminium as a cocatalyst. By supporting CpMCl3 on MgCl2, the catalyst activity was increased drastically to show high activity similar to MgCl2‐supported TiCl4 catalysts. The activity of the CpZrCl3 /MgCl2 catalyst was higher than that of the CpTiCl3/MgCl2 one. Both catalysts gave polymers with high molecular weight (Mw) and broad molecular weight distribution (Mw/Mn) in comparison with the corresponding soluble half‐metallocene catalysts. 相似文献