Metallocene catalysts composition

Walzer JF Jr (1997) Supported metallocene catalyst composition. US Patent 5,643,847... 

EPM [poly(ethylene-co-propylene)] and EPDM [poly(ethylene-co-propylene-co-5-ethylidene-2-norbomene)P can be metallocene catalyst polymerized. Metallocene catalyst technologies include (1) Insite, a constrained geometry group of catalysts used to produce AfiGnity polyolefin plastomers (POP), Elite PE, Nordel EPDM, and Engage polyolefin elastomers (POP) and (2) Exxpol ionic metallocene catalyst compositions used to produce Exact plastomer octene copolymers.2 Insite technology produces EPDM-based Nordel IP with property consistency and predictability (see Sec. 3.2.2). 

More recent inventions are the metallocene catalysts based on zirconium. They offer more uniform catalyst activity and can give a relatively narrow molecular weight distribution. More importantly, they offer better control over structure and copolymer composition distributions. 

It is important to note that the tendency of a monomer towards polymerization and therefore also towards copolymerization is strongly dependent on the nature of the growing chain end. In radical copolymerization the composition of the copolymer obtained from its given monomer feed is independent of the initiating system for a particular monomer pair, but for anionic or cationic initiation this is normally not the case. One sometimes observes quite different compositions of copolymer depending on the nature of the initiator and especially on the type of counterion. A dependence of the behavior of the copolymerization on the used catalyst is often observed with Ziegler-Natta or metallocene catalysts. 

The three-dimensional electron tomographical construction of silica-supported metallocene catalysts using conventional TEM (Steinmetz et al 2000), and a novel method for the automated acquisition of tilt series for electron tomography of nanoparticles using STEM have been reported (Zeisse et al 2000). The HAADE-STEM is shown to be capable of determining the compositions of individual nanoparticle catalysts of a few atoms supported on porous substrates (Vaughan et al 1999). 

Conjugated dienes have been polymerised using supported half-sandwich metallocene catalysts. For instance, catalysts derived by supporting CpTiCl3 on alumina-silica gels, containing—0-Ti(Cp)Cl2 species, displayed activity in isoprene polymerisation without the addition of any other activator. Depending on the alumina-silica gel composition, the kind of polymerisation medium and the temperature, these catalysts exhibited various activities and selectivities polyisoprenes with a predominant 3,4 structure and mixed 1,2/ trans-1,4 structure were obtained [118,119],... 

The rate of polymerization was determined from the amount of polymer obtained per unit of time. The productivity of the metallocene catalyst was calculated from the quantity of polymer and the catalyst metal fed into the reactor. The resulting polymers were investigated by gel permeation chromatography (GPC) to determine the molecular weight distribution together with the average molecular weights. The density was measured on pressed films by means of the suspension method in a mixture of water and isopropanol. 13C-NMR-spectroscopy was applied to analyze the composition of copolymers and to evaluate their structure. 

Isotactic propylene/butene co-polymers have been produced with a much broader array of metallocene catalysts, with greatly differing isotacticities and molecular masses. The melting point/composition relation-... 

The tunable metallocene catalyst with a well-defined polymerization mechanism provides distinctive advantages in the preparation of new polymers with well-controlled molecular structures, especially functional polyolefins that are very difficult to prepare by other methods. Since the discovery of HDPE and i-PP about half a century ago, functionalization of polyolefin has been a scientifically challenging and industrially important area. The constant interest, despite lack of effective functionalization chemistry, is due to the strong desire to improve polyolefin s poor interactive properties. The hydrophobicity and low surface energy of polyolefin has limited its applications, especially in the areas of coating, blends, and composites, in which adhesion, comparability, dispersion, and paintability are paramount. 

In the past decade, our group at Penn State has been focusing on a functionalization approach by the combination of metallocene catalysts and reactive comonomers. The chemistry takes the advantage of metallocene catalyst with a tunable single active site to prepare polyolefin copolymers with narrow molecular weight and composition distributions, high catalyst activities, and predictable tacticities and copolymer compositions. 

Blends of HOPE with long-chain branched polyethylenes (HBPE) prepared from metallocene catalysts have been studied by DSC and their crystal stmcmres interpreted in terms of phase behavior. The HBPE contained long-chain branches and short branches formed form octane comonomer. HBPE with 7.5-12.0% octane exhibited phase separation, whereas HBPE with 2% octane were found to be miscible with HOPE over the whole composition range. Eong branches were few and did not contribute to the immiscibility (16). 

The right choice of supporting material as well as the choice of suitable properties (pore size, specific surface, chemical surface composition) are important factors influencing the immobilization of the metallocene catalyst and the fragmentation of the support during polymerization. Commercially applied porous silica gels are prepared by neutralization of aqueous alkali metal silicate with acid. The pore structure and pore size distribution can be controlled by the type of chemical reaction and experimental conditions. ... 

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