Ethylene catalyst morphology

Since the last edition several new materials have been aimounced. Many of these are based on metallocene catalyst technology. Besides the more obvious materials such as metallocene-catalysed polyethylene and polypropylene these also include syndiotactic polystyrenes, ethylene-styrene copolymers and cycloolefin polymers. Developments also continue with condensation polymers with several new polyester-type materials of interest for bottle-blowing and/or degradable plastics. New phenolic-type resins have also been announced. As with previous editions I have tried to explain the properties of these new materials in terms of their structure and morphology involving the principles laid down in the earlier chapters. 

The simple catalyst embedding technique has been applied to ethylene polymcaization in slurry In this technique, active catalytic components are embedded into styrene polymer matrix. The resulting polyethylene shows better morphology and higher bulk density than those produced by homogeneous catalyst. No activity loss was also observed with the... 

Changes in the morphological and structural characteristics of the carbon deposit resulting from pretreatment of the iron catalyst in H2S were determined from a combination of transmission electron microscopy techniques, X-ray diffraction, surface area measurements and controlled oxidation studies in CO2. Iron powder 200 mesh) was purchased from Johnson Matthey Inc. (99 99% purity) and had a BET surface area of 0.3 m2/g at -196°C, The gases used in this work CO (99 9%), hydrogen (99.999%), ethylene (99.999%), H2S/argon mixtures and helium (99,999%) were obtained from Alphagaz company and used without further purification. 

This process produces a wide melt index range by applying innovative catalyst chemistry combined with a sophisticated polymerization process. An all-round catalyst and simple polymerization operation provide easy product changeover that reduces transition time and yields negligible off-spec product from the transition. Mitsui has also developed new catalyst that contributes better morphology of the polymer powder and ethylene consumption. 

The MAO-activated 138 and 137, effective in the living homopolymerization of ethylene and propylene, also promote their block co-polymerization. This approach broadens remarkably the utility of living catalysts because it allows the preparation of block co-polymers with high glass or melting transition blocks from common commercial monomers such as ethylene and propylene. These materials could have applications as compatibilizers and elastomers.1232,1233 Using complex 138, propylene has been first homopolymerized to sPP for 2h in toluene at 0°C (Mn = 38400 Mw/Mn = 1.11). Then, an ethylene overpressure was applied, and in 1 additional h an sPP-/W< (j -poly(E-r -P) diblock co-polymer was obtained (Mn = 145 100, A/w/A/ = 1.12). The microstructure of this diblock co-polymer is shown in Scheme 48. This co-polymer has a Tm of 131 °C while the ethylene-propylene block (E = 33 mol%) has a TR of —45 °C.1175 A detailed morphological and thermodynamic characterization of these co-polymers has been reported.1234... 

---