15. Effect of Silane Compounds on Catalyst Isospecificity-A Plausible Model Based on MO Calculation

Okano, Tamon; Chida, Kosaku; Furuhashi, Hiroshi; Nakano, Akiyuki; Ueki, Satoshi

doi:10.1016/s0167-2991(08)61626-2

Cited by 12 publications

(1 citation statement)

References 7 publications

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“…The desired polypropylene characteristics can be achieved by modifying the supported titanium catalyst systems used for the polymerization with structurally different internal and external donors in addition to the polymerization processes. − Alkoxysilanes are used as external electron donors for supported titanium catalyst systems based on dialkyl phthalate as the internal electron donor. Studies of the relationship among structure, performance, and product properties indicate that the nature and number of alkoxy groups and the steric/electronic nature of the aryl/alkyl group bonded to silicon in the alkoxysilane influences the catalyst activity, as well as the microstructure and molecular-weight characteristics of the resulting polypropylene. − The most effective alkoxysilane external donors for high catalyst stereospecificity are methoxysilanes containing relatively bulky groups in the α position to the silicon atom. − Typical examples include diphenyldimethoxysilane (DDS) and dicyclopentyldimethoxysilane (D-donor). , The latter is less sensitive to H 2 and gives particularly higher molecular weights and broader molecular weight distributions (MWDs) but slightly lower stereospecificity . Most studies in this area have been limited to the use of a single alkoxysilane as the external electron donor for controlling the polymer characteristics.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Combined External Electron Donors on the Structure and Properties of Polypropylene/Poly(ethylene-co-propylene) In-Reactor Alloys Prepared by High-Efficiency Industrial Ziegler–Natta Catalyst

Fan

2013

Ind. Eng. Chem. Res.

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In this work, a series of isotactic polypropylene/ethylene−propylene rubber (iPP/EPR) in-reactor alloys were prepared by high-efficiency industrial Ziegler−Natta catalyst with diphenyldimethoxysilane/dicyclopentyldimethoxysilane (DDS/ D-donor) mixtures as external electron donors. The effects of the external electron donor on the structure and mechanical properties of the iPP/EPR in-reactor alloys were studied. According to the characterization results, the iPP/EPR in-reactor alloys were mainly composed of random poly(ethylene-co-propylene), multiblock poly(ethylene-co-propylene), and highly isotactic PP. For DDS/D-donor mixtures as external electron donors and triethylaluminum (TEA) as the cocatalyst, as the amount of Ddonor in DDS/D-donor mixtures increased, the molecular weight of polypropylene homopolymer and the structural uniformity of multiblock poly(ethylene-co-propylene) increased, whereas when D-donor alone was used as the external electron donor, they decreased. However, the isotacticity of polypropylene homopolymer increased as the amount of D-donor in the DDS/D-donor mixtures increased. Therefore, as the amount of D-donor in the DDS/D-donor mixtures increased, the impact strength of the iPP/EPR in-reactor alloy increased, but when D-donor alone was used as the external electron donor, the impact strength of the alloy decreased. An optimum feed ratio between DDS and D-donor was found, namely, DDS/D-donor = 1:3 (Si/Ti = 5). The iPP/EPR in-reactor alloy prepared under these conditions was the toughest. The influence of the external electron donor on the flexural modulus and flexural strength could be ignored.

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Section: Introductionmentioning

confidence: 99%

Effect of the Combined External Electron Donors on the Structure and Properties of Polypropylene/Poly(ethylene-co-propylene) In-Reactor Alloys Prepared by High-Efficiency Industrial Ziegler–Natta Catalyst

Fan

2013

Ind. Eng. Chem. Res.

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Propylene Polymers

Lieberman¹,

Stewart²

2004

Encyclopedia of Polymer Science and Technology

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Polypropylene is one of the most widely used thermoplastics, accounting for one sixth of total consumption of polymeric materials. Many automobiles, textiles, appliances, and other everyday items contain substantial amounts of these polymers. The ability to manufacture a broad variety of polypropylenes having properties tailored for specific applications is the primary factor in its widespread use. Polypropylene is a polymer whose stereoregularity can be controlled, and it exhibits a spectrum of structural variations, because of the ability to control the manner in which the asymmetrum monomer is incorporated into the growing chain, and through the use of comonomers, usually ethylene, which is often used to provide impact‐modified or lower melting polymers. The types of polymers produced, chain‐structural parameters which can be varied and means to characterize them, morophology, thermodynamic properties, processing methods, end use properties, and applications are discussed. Highly stereoselective Ziegler–Natta catalyst are primarily used to produce polypropylene and are the basis for most modern propylene polymerization processes. The historical development of these catalysts, from the early TiCl 3 systems to the modern, high yield MgCl 2 ‐supported systems, including proposed polymerization mechanisms, are discussed. These catalysts enabled the evolution of these polymerization processes from the early slurry process to the current liquid monomer or gas‐phase processes. Metallocene catalysts have increasingly been an area of emphasis and have provided further commerical advances recently. Most major polymerization process in use today are discussed, with the most notable being the Spheripol and Unipol process. Key input into these polypropylene technologies and economics are the technology and infrastructure associated with propylene monomer. The large expansion in polypropylene production in the late 1980s was facilitated by the availability of this newer, less costly polymerization technology. This expansion, well in excess of growth in consumption, caused a dramatic reduction in polypropylene prices in the 1990s, most dramatically in the Far East, where few polypropylene plants existed outside Japan before 1985. Current economic prospects and associated industry trends are discussed.

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Ziegler–Natta Catalysts

Chadwick

2003

Encyclopedia of Polymer Science and Technology

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This article describes the development and characteristics of Ziegler–Natta catalysts for the polymerization of ethylene, propylene, and other alpha‐olefins. Particular emphasis is given to state‐of‐the‐art MgCl 2 /TiCl 4 /donor catalysts for polypropylene, including current insight into mechanistic aspects of Ziegler–Natta catalysis in relation to catalyst performance and polymer molecular composition and properties. Ziegler–Natta catalysts are multisite systems, in which the nature and the distribution of the active species can be steered to give polymers having different tacticity and molecular weight distributions. MgCl 2 ‐supported catalysts have almost totally replaced the TiCl 3 catalysts used previously and have enabled the development of cost‐efficient bulk and gas‐phase polymerization processes. Spherical particle morphology and controlled particle size and porosity have been achieved and this has played an important role in the widespread application of these catalysts.

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15. Effect of Silane Compounds on Catalyst Isospecificity-A Plausible Model Based on MO Calculation

Cited by 12 publications

References 7 publications

Effect of the Combined External Electron Donors on the Structure and Properties of Polypropylene/Poly(ethylene-co-propylene) In-Reactor Alloys Prepared by High-Efficiency Industrial Ziegler–Natta Catalyst

Effect of the Combined External Electron Donors on the Structure and Properties of Polypropylene/Poly(ethylene-co-propylene) In-Reactor Alloys Prepared by High-Efficiency Industrial Ziegler–Natta Catalyst

Propylene Polymers

Ziegler–Natta Catalysts

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