Diethylaluminum chloride polymerization

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. 

The diethylaluminum chloride was also a catalyst for the polymerization of ethylene. Very similar products were obtained in parallel polymerizations carried out at 300° with diethylaluminum chloride and with a mixture of aluminum chloride and aluminum. The distillation curves showed marked plateaus for C6, Cs, and Cj0 hydrocarbons with complete absence of C5, C7 and C9. The bromine numbers indicated that these fractions were mixtures of paraffins and olefins. 

The polymerization apparatus (see Fig. 3.2) consists of a 11 three-necked flask, fitted with stirrer, thermometer, gas inlet with tap, and gas outlet.On the inlet side the gas stream passes through three wash bottles one as a safety bottle (A), one for the purification of ethylene, filled with 30 ml of petroleum ether (bp 100-140 °C) and 5 ml of diethylaluminum chloride (B),and one filled with molecular sieves 5 A (C).The last of these dries the ethylene further and also serves to trap aluminum hydroxide carried over from B. On the outlet side there are two wash bottles the first is a safety bottle (D), and the second, (E), is filled with 50 ml of dry bis(2-hydroxyethyl) ether (diglycol), and isolates the apparatus from the external atmosphere. 

Of particular interest are certain ionic graft copolymerizations in which the polymerization reaction is initiated only on the macromolecular framework and no homopolymer is formed. An example is provided by the formation of polymeric carbonium ions from chloride-containing polymers, such as poly(vi-nylchloride), in the presence of diethylaluminum chloride ... 

The actual polymerization takes place in an autoclave under inert atmosphere, where the supernatant liquid of the foregoing step is placed with the dried and rectified monomer and the second catalyst compound, namely diethylaluminum chloride in 1,2-dichloroethane solution (15). The polymerization is conducted at 70°C for 60 min while stirring well. According to this recipe, a series of cyclic monomers can be polymerized. Examples are shown in Table 1.3. 

Hie study of effects of the catalyst components also help clarify the ionic factors in the steric control of isotactic polyvinylethers. Dall Asta and Bassi (15) studied the polymerization of butylvinylether with various alkylaluminum halides. They found that diethylaluminum chloride and ethylaluminum dichloride were the most effective catalysts for the production of isotactic polymer. Ethylaluminum dibromide and ethoxyaluminum dichloride were of questionable effectiveness, while diethylaluminum fluoride was completely ineffective. 

Other effects of the ionicity of the catalyst on its activity has been studied by Natta, PaSQUON, Zambelli and Gatti (66). The polymerization of propylene was carried out with alpha titanium trichloride and diethylberylium or triethylaluminum. They found that catalysts from the alkylberylium were more stereospecific than those from alkyl aluminum. On the other hand their study of titanium trichloride with diethylaluminum iodide, diethylaluminum bromide, diethylaluminum chloride or triethylaluminum showed that the greater stereospecificity was produced by the iodide containing catalyst. The less electrophilic catalyst produced greater crystallinity than the corresponding bromide or chloride component. 

Ziegler, Gellert, Holzkamp, Wilke, Duck and Kroll (72) have shown that the hydride transfer reaction of alkylaluminum occurs much more easily with trialkylaluminum than with the more electrophilic diethylaluminum chloride. Catalysts must be more anionic in order to produce oligomers which involve large amounts of hydride transfer than with polymerization catalysts where hydride chain transfer must be minimized. Thus the oligomerization catalyst employed by Bestian and Clauss was more anionic, or less cationic, than the usual polymerization catalyst where anionic chain transfer is minimized. 

The titanium trichloride-diethylaluminum chloride catalyst converted butadiene to the cis-, trans,-trans-cyclododecatriene. Professor Wilke and co-workers found that the particular structure is influenced by coordination during cyclization between the transition metal and the growing diene molecules. Analysis of the influence of the ionicity of the catalyst shows effects on the oxidation and reduction of the alkyls and on the steric control in the polymerization. The lower valence of titanium is oxidized by one butadiene molecule to produce only a cis-butadienyl-titanium. Then the cationic chain propagation adds two trans-butadienyl units until the stereochemistry of the cis, trans, trans structure facilitates coupling on the dialkyl of the titanium and regeneration of the reduced state of titanium (Equation 14). 

Grafting by in situ Polymerization of Butadiene. The polymerization of butadiene to a high cw-1,4-polybutadiene with a catalyst system containing diethylaluminum chloride and a cobalt compound is now a well established technique (1, 9,15,18, 22). This catalyst system is particularly effective when the cobalt compound is soluble in the reaction medium. 

X-ray structure analysis revealed a 7-coordinate rare-earth metal center with two asymmetrically / -coordinating tetramethylaluminate ligands, an asymmetrically / -coordinating siloxide ligand and one methyl group of a trimethylaluminum donor molecule (Fig. 28). Such heteroleptic complexes can be regarded as molecular models of covalently bonded alkylated silica surface species. Moreover, isoprene was polymerized in the presence of 1-3 equivalents of diethylaluminum chloride, with highest activities observed for (Cl) (Ln) ratios of 2 1 (Table 12) (Fischbach et al., 2006, personal communication) [150]. 

In contrast to the structure-catalyst ratio dependence shown in the AIBU3-TiCl4 system, the polymerization of butadiene with a catalyst prepared by reaction of aluminum triethyl or diethylaluminum chloride with vanadium tetrachloride or oxychloride reportedly yields a polymer whose structure is relatively unaffected by the Al/V ratio—i.e., the polybutadiene obtained in heptane at 15° C. contains 95 to 99% tram-1,4-, 0 to 1% cis-1,4-, and 1 to 5% 1,2- structures at Al/V ratios ranging from 0.5 to 10. After extraction with diethyl ether, diisopropyl ether, and benzene, the residual polymer, constituting 55 to 75% of the total polymer, has 99 to 100% tram- 1,4- structure (15). 

Homogeneous catalysts for the ethylene polymerization based on bis(cyclopenta-dienyl)titanium(IV) compounds [4], tetrabenzyltitanium [14], tetraallylzirconium and hafnium are formed with diethylaluminum chloride, dimethylaluminum chloride or triethylaluminum as co-catalysts. Their activities are poor (less than 200 kg PE/mol catalyst per h), so no industrial application resulted. 

Doi, Y. Suzuki, S. Soga, K. A perfect initiator for living coordination polymerization of pro-pene tris(2-methyl-l,3-butanedionato)vanadium/ diethylaluminum chloride system. Makromol. Chem., Rapid Commun. 1985, 6, 639-642. 

Figure 8.6 illustrates, for example, the complicated equilibria [19] in initiation by alkyl halides which are widely used as initiators in combination with coinitiator such as aluminum alkyl halides or aluminum halide Lewis acids. Each carbocation can initiate polymerization or remove an alkyl (ethyl) group from the counterion to produce a saturated hydrocarbon, REt, and a more acidic Lewis acid. The propagating cation can also terminate by the same process to produce ethyl-capped polymers and new Lewis acids. Thus, even though the coinitiator used is diethylaluminum chloride there may be major contributions to the polymerization from ethylaluminum dichloride or aluminum chloride. 

In the third industrial process, a Ziegler type of ethylene polymerization, the catalyst can be prepared by adding diethylaluminum chloride (activator) and titanium tetrachloride (cocatalyst) to a dry hydrocarbon solvent... 

Coordination polymerization catalysts are complexes of transition metals. The original Ziegler-Natta catalyst, a mixture of titanium tetrachloride and diethylaluminum chloride, has been joined by numerous organometallic complexes such as the widely used bis(cyclopentadienyl)zirconium dichloride. 

Uses Catalyst for Ziegler-Natta polymerization of olefins and dienes reactant in prod, of transition metal catalysts alkylating agent for prod, of organotin compds. and organophosphorus derivs. organic synthesis Manuf./Distrib. Akzo Nobel http //WWW. akzonobei. com Diethylaluminum chloride CAS 96-10-6 EINECS/ELINCS 202-477-2 UN UN 3052... 

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