Trägerfixierte Metallocene: Eine neue Katalysatorgeneration für die Polyolefin‐Produktion

Abstract

Die seit Jahren intensiv untersuchten homogenen Metallocen–Katalysatoren für die Polyolefin‐Produktion weisen gegenüber den konventionellen Ziegler‐Systemen deutliche Vorteile bezüglich der Variationsmöglichkeiten der Mikrostruktur und damit der Eigenschaften der erzeugten Polymere auf. Sie müssen allerdings für den industriellen Einsatz auf Trägermaterialien immobilisiert werden. Welchen Einflüssen dabei Polymerisationskinetik, Polymerwachstum und Polymermorphologie sowie die entscheidende Partikelfragmentierung ausgesetzt sind, wird in diesem Beitrag geschildert und in einem Modell zusammengefaßt

Early Stages of Propylene Bulk Phase Polymerization with Supported Metallocene Catalysts

“…Confirming previous observations for the slurry polymerization process [1][2][3][4][5][6][7] we have shown in this paper that even in bulk polymerization, the shell-by-shell like degradation of silica as catalyst support material is observable, but is proceeding much faster than in case of slurry polymerization. Moreover, SEM micrographs of sectioned particles (Figure 7) reveal a broad variance in the degree of fragmentation between single grains.…”

“…It turned out that the aluminium concentration was much higher for particles that were in an advanced state of fragmentation than for those that remained almost unreacted. To make sure that these differences were not artifacts introduced by the washing procedure with hydrochloric acid in methanol, we verified these results as follows: We repeated the 1.5 min polymerization run, but this time without the washing step with hydrochloric acid in methanol after the polymerization, which is necessary to remove the aluminium residues resulting from the Al(i-Bu) 3 scavenger. All washing steps were carried out with pure methanol only.…”

“…Propylene (350 g) was added to the reactor together with Al(i-Bu) 3 (1 ml). The reactor content was heated to 50 8C.…”

“…The gray particles with a rough looking surface can be assigned to hydrolysis products of the Al(i-Bu) 3 scavenger. Again two EDX spot measurements on two different grains are shown.…”

“…[1][2][3][4][5][6][7] This model was developed with slurry polymerization experiments Full Paper: For the initial steps of propylene bulk phase polymerization with a silica-supported metallocene/MAOcatalyst the processes of polymer growth, particle expansion and carrier fragmentation are investigated. Gravimetric analysis of the kinetics is given.…”