Determination of the number of active centers in Ziegler‐Natta polymerization of propene using sulfur‐containing terminating agents 2. Tagging of growing chains during retardation of polymerization by carbon disulfide

Abstract

The CS2-induced retardation of propene polymerization catalyzed by TiCl,/AIEt,Cl and TiCl,/ALEt, systems was investigated. From the two systems, the latter was much more active in polymerization and also exceedingly more susceptible to retardation by CS,. At least for the TiC1,/A1Et2C1-catalyzed polymerization, there is no diffusion limitation imposed on the reaction of growing chain with CS,. It was found that the number of sulfur tags introduced by the above CS, treatment is dominantly related to the ratio of polymerization rates before and after CS2 addition. Monomer plays a dual role during the CS, treatment: on one hand it enhances the CS, insertion into the growing metal-polymer bond, on the other hand it competes with CS2 in the same reaction. CS, reacts preferentially with centers of highest reactivity. It allows, in principle, the determination of the reactivity distribution of activecenters. Several potential side reactions which might lead to an increase of the number of tags in polymer were considered. None of the side reactions play an important role except for a reaction of CS, with chains formed via transfer with the organometal compound in AEt3-cocatalyzed polymerization.

Stereochemistry of Polymerization

“…[C*] is usually determined from experiments in which the active sites are quenched (made inactive) with CH 3 O 3 H, 14 CO, or 14 CO 2 [Jaber and Fink, 1989;Mejzlik et al, 1986Mejzlik et al, , 1988Tait and Watkins, 1989;Vozka and Mejzlik, 1990]. Other methods include the use of number-average molecular weight (combined with polymer yield) and 14 C-labeled group I-III metal component.…”

A new method of active center determination for olefin polymerization with supported Ziegler-Natta catalysts

“…The methods based on quenching the propagating chains with 14 CO or CS 2 are complicated by possible reversibility of the quenching reactions and presence of side reactions. 10,13,17,19,22,25 We have previously used acetyl chloride as a quenching agent to react with the active centers in heterogeneous Ziegler-Natta catalysts. 9,26,27 The reaction of acetyl chloride with TiCl 3 -AlR 3 catalyzed 1-octene polymerization system was found to be very fast and irreversible.…”

“…In the past decades, several methods have been developed for the determination of active center concentration. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] The method using CH 3 OT as a quenching agent to tag the active centers has been proved to be a reliable one for both homogeneous and heterogeneous catalyst systems. 10,11 However, this method suffers from the limitation that only an average value of C p can be estimated.…”

Polymerization of ethylene using high-activity Ziegler-type catalysts: Active center determination

“…However, some side reactions were observed when AlEt 3 was used as metal polymer bonds concentration in mol per mol M T is given by: [MPB] Å KAG/a, where G is the cocatalyst. 16 The purpose of this study is to compare the polymer yield in grmolrM…”