Metallorganische Titan‐Verbindungen als Polymerisationskatalysatoren

Abstract

Aus Mischungen von Titantetrachlorid und Alkylaluminium‐Verbindungen lassen sich Organotitanhalogenide RTiCl3 und R2TiCl2 isolieren. Die reinen aluminium‐freien Verbindungen sind in Gegenwart ihrer Zersetzungsprodukte TiCl3 und TiCl2 wirksame Katalysatoren für die Polymerisation von α‐Olefinen. ‐ Beim Polymerisationsprozeß wird das Monomere zwischen die TiC‐Bindung eingelagert, so daß Organotitan‐Verbindungen mit hochmolekularem Organo‐Rest entstehen. Daneben bilden sich ungesättigte Kohlenwasserstoffe durch Übertragungsreaktion mit dem Monomeren. Die reduzierten Viscositäten dieser Produkte liegen zwischen 0,4 und 1. ‐ Die Polymerisation mit dem Katalysatorsystem RTiCl3TiCl3 tritt als wichtiger Teilprozeß bei der Verwendung von Mischkatalysatoren aus TiCl4 und Alkylaluminium‐halogeniden auf.

Probing the Coordinative Unsaturation and Local Environment of Ti3+ Sites in an Activated High‐Yield Ziegler–Natta Catalyst

“…[5] Thei nfluence of certain Lewis bases and at al ater stage the AlR 3 cocatalyst [1] on the system is still largely unestablished and seminal experimental [3,[6][7][8][9] and theoretical [5,[10][11][12][13][14] investigations have failed to account for all knownf acts.A ctivation is usually performed by reacting the precatalyst with aluminum alkyl compounds (typically triethyl aluminum, TEA). In this process tetravalent Ti 4+ ions assume alower oxidation state [15] and both Ti 3+ and Ti 2+ ions have been proposed. Ti 3+ centers are believed to play an important role in ZN catalysis,h owever their exact role and nature is still uncertain.…”

Thermal Decomposition of Methyl Titanium Chlorides

“…The experiments in this paper were carried out to provide a background of such knowledge against which more detailed and specific experiments could be judged. As such, they permit, when considered with the data of others (3,4), postulation of a set of reactions which, while not entirely proven, provides a consistent explanation of both kinetic and polymerization observations.…”

“…1-3 indicate that the equilibrium constant for reaction 4 is very small. Consequently, the rapid decline in CH3TiC13 concentration cannot be explained on the basis of the equilibrium [4] operating to replace decomposed (CH,),TiCl,, since the latter is at all times in much greater concentration than in the cases shown in Figs. 1-3.…”

“…Liquid volumes were Studies of the decomposition of alkyl titanium chlorides have yielded a diversity of views on the mechanism involved. The proposition that decomposition involved a radical attack upon the solvent (1,2) has been effectively disproven as a general theory by de Vries (3), although radical attack may occur under special conditions (4). However the theory of de Vries leads to awkward explanations for the decomposition of methyl titanium halides, particularly the postulated existence of either CH, or CH,TiCl, without supporting evidence.…”

“…It is suggested that CH, formation is, at least in part, the product of (CH3),TiC1, which has been formed through the equilibrium [4]. I41 2CH3TiC13 =(CH3)2TiCI, + TiCI, Such a route is supported by the slight reduction in CH, production observed at low Zn/Ti ratios (where TiCl, is present in excess) and by the observation (3) that CH, is reduced relative to C2H6 and CH3Cl by addition of TiCl, to CH3TiC13 in n-heptane.…”