Propylene, polymerization

Since the previous titanium-based catalyst was not able to perform a-olefin polymerization, it was obviously interesting to investigate other soluble active systems to further study the problem of stereoregulation. That was done by Zambelli [Makromol Chemie, 112, 160 (1968)] with the complex obtained from VCI4 and AIR2CI (Fig. 21) in the presence of either an excess of A1 derivative or a Lewis base ligand, e.g. anisole. 

Finally, it is worthwhile stressing that these catalytic systems have the abihty, under well-controlled conditions, to ensure living polymerizations of propene, as described by Keii and Doi [9]. 

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Eastman Chemical has utilized a unique, high temperature solution process for propylene polymerization. Polymerization temperatures are maintained above 150°C to prevent precipitation of the isotactic polypropylene product in the hydrocarbon solvent. At these temperatures, the high rate of polymerization decreases rapidly, requiring low residence times (127). Stereoregularity is also adversely affected by high temperatures. Consequentiy, the... 

Polypropylene. One of the most important appHcations of propylene is as a monomer for the production of polypropylene. Propylene is polymerized by Ziegler-Natta coordination catalysts (92,93). Polymerization is carried out either in the Hquid phase where the polymer forms a slurry of particles, or in the gas phase where the polymer forms dry soHd particles. Propylene polymerization is an exothermic reaction (94). 

There are other methods of preparation that iavolve estabhshing an active phase on a support phase, such as ion exchange, chemical reactions, vapor deposition, and diffusion coating (26). For example, of the two primary types of propylene polymerization catalysts containing titanium supported on a magnesium haUde, one is manufactured usiag wet-chemical methods (27) and the other is manufactured by ball milling the components (28). 

The syndiotactic polymer configuration is not obtained in pure form from polymerizations carried out above 20°C and, thus has not been a serious concern to most propylene polymerization catalyst designers. Eor most commercial appHcations of polypropylene, a resin with 96+% isotacticity is desired. Carbon-13 nmr can be used to estimate the isotactic fraction in a polypropylene sample. Another common analytical method is to dissolve the sample in boiling xylene and measure the amount of isotactic polymer that precipitates on cooling. 

Erom 1955—1975, the Ziegler-Natta catalyst (91), which is titanium trichloride used in combination with diethylaluminum chloride, was the catalyst system for propylene polymerization. However, its low activity, which is less than 1000 g polymer/g catalyst in most cases, and low selectivity (ca 90% to isotactic polymer) required polypropylene manufacturers to purify the reactor product by washing out spent catalyst residues and removing unwanted atactic polymer by solvent extraction. These operations added significantly to the cost of pre-1980 polypropylene. 

Supported Catalysts for Propylene Polymerization. Although magnesium haUde supported titanium catalysts for propylene... 

Most of the propylene polymerized by this process is used in motor gasoline ("Polymer Gasoline"). However, an appreciable portion of the C7, C, and C,2 olefins find use as feedstocks for production of Oxo alcohols. 

The three different stereochemical forms of polypropylene all have somewhat different properties, and all can be made by using the right polymerization catalyst. Propylene polymerization using radical initiators does not work well, but polymerization using Ziegler-Natta catalysts allows preparation of isotactic, syndiotactic, and atactic polypropylene. 

In propylene polymerization by TiCl2 the addition of aluminumorganic compounds results in a fall of the polymerization rale and a concurrent increase of the isotactic fraction content in the polymer (158). A similar effect occurred when triphenylphosphine was added to TiCl2. The content of the isotactic fraction decreased in the series AlEt3 > AlEt2Cl > AlEtCl2. The catalytic activity also decreases in the same row (159). 

It was found 158,159) that the fall of the rate observed when aluminum-organic compound was added to TiCl2 during ethylene polymerization was due to the decrease in the number of propagation centers. The propagation rate constant remained unchanged. In propylene polymerization the number of atactic propagation centers sharply diminished when the aluminum-... 

The processes of reversible adsorption of the coordination" inhibitors (including the adsorption of organometallic compounds) result in an increase in the lifetime of the transition metal-carbon bond. It is possible that due to this, in the case of propylene polymerization by two-component catalysts based on TiCU, at low temperatures a long-term increase of molecular weight with time was observed (192,193). 

The propylene polymerization is very complicated. Figure 12 illustrates some conceivable reactions which make clear the complicity of the reaction and the numerous compounds in TPB. 

Propylene Polymerization Kinetics in Gas Phase Reactors Usii Titanium Trichloride Catalyst... 

Figure I. Gas Phase Propylene Polymerization (batch reactor, 1 L, 80°C, 441...

Figure 3. Resistance increase during semibatch gas phase propylene polymerization (80°C, 441 psia, 50 mg TiCls loading, 99% pure CgHe, kg° = 0.00638 cm/sec)...

The semibatch model GASPP is consistent with most of the data published by Wisseroth on gas phase propylene polymerization. The data are too scattered to make quantitative statements about the model discrepancies. There are essentially three catalysts used in his tests. These BASF catalysts are characterized by the parameters listed in Table I. The high solubles for BASF are expected at 80 C and without modifiers in the recipe. The fact that the BASF catalyst parameters are so similar to those evaluated earlier in slurry systems lends credence to the kinetic model. 

BASF CATALYST PARAMETERS AT REFERENCE TEMPERATURE OF 80 C GAS PHASE PROPYLENE POLYMERIZATION... 

They have shown it to fit propylene polymerization rate data well, when using a MgCl supported TiCl /triethylaluminum (TEA)... 

Fink and Babik reported that propylene polymerization was achieved by a bis (imino)pyridine iron complex with Ph3C[B(C6p5)]4] and ttialkylaluminium as additives [127]. Both 3-methyl-"butyl and "butyl endgroups were observed by NMR spectrum when ttiisobutylaluminium as an activator was used, whereas the only "propyl endgroup was formed in case of triethylaluminium activation. In addition, this polymerization proceeds two times faster with than without a hydrogen atmosphere, but the value decreases and the M IM value rises up. 

The model catalysts prepared according to the above-mentioned procedures were active for ethylene and propylene polymerization without additional cocatalyst present in the gas phase [21,23]. The TiClx/MgCl2-based catalysts have been proven catalytically active at 300 K and an ethylene pressure above... 

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