Untersuchung von Polymerablagerungen während der Synthese in einem Wärmeübertrager

Abstract

Zur Untersuchung der unerwünschten Belagbildung von Polymeren auf wärmeübertragenden Oberflächen (Polymerisationsfouling) wird das Ablagerungsverhalten eines Vinylacetat/Vinylester-Copolymers während der Emulsionspolymerisation untersucht. Hierbei sollen grundlegende Unterschiede zum Ablagerungsverhalten eines bereits reagierten Vinylacetat/Ethylen-Copolymers identifiziert werden. Für einen qualitativen Vergleich wird die Ablagerungstopographie mithilfe eines Digitalmikroskops bestimmt. Für die quantitative Berechnung wird der Foulingwiderstand aus der Masse sowie der Schichthöhe des abgelagerten Materials berechnet. Der Polymerisationsgrad beeinflusst das Ablagerungsverhalten insb. die Topographie. Das bereits ausreagierte Stoffsystem weist eine größere Foulingmasse sowie eine deutlich ausgeprägtere, kraterförmige Ablagerungstopographie auf, wohingegen während des Polymerisationsfoulings eine optisch deutlich andere, tropfenförmige Topographie entsteht.To investigate the unwanted deposition of polymers on heat transfer surfaces (polymerization fouling) the deposition of a vinyl acetate/vinyl ester copolymer during emulsion polymerization is investigated. The aim is to identify fundamental differences to the fouling behavior of an already reacted vinyl acetate/ethylene copolymer. For a qualitative comparison the surface coverage is observed using a digital microscope. For the quantitative examination the fouling resistance is calculated from the mass and the layer height of the deposited material. The degree of polymerization has a significant influence on the deposition behavior. The already reacted material system shows a larger fouling mass and a more pronounced, crater-shaped surface coverage, whereas during polymerization fouling a clearly optically different drop-shaped surface coverage was formed.

Formulation and process determined fouling prediction for the continuous emulsion co polymerisation of vinyl acetate

“…Fouling processes during emulsion polymerisation of vinyl acetate are investigated in literature as well. There are different publications discussing this topic [17,[32][33][34]. Carvalho et al [17] investigated the continuous emulsion copolymerisation of vinyl acetate and n-butyl acrylate in a tubular reactor.…”

“…In these publications the influences of temperature and surface modifications on fouling masses are discussed and it could be shown that higher temperatures lead to higher fouling masses. For surface modifications a general trend could not be observed as it is highly dependent on the other process parameters [32][33][34]. Hohlen et al [33] investigated the differences between fouling of reactive emulsion polymerisation systems compared to the fouling of non-reactive polymer dispersions.…”

“…For surface modifications a general trend could not be observed as it is highly dependent on the other process parameters [32][33][34]. Hohlen et al [33] investigated the differences between fouling of reactive emulsion polymerisation systems compared to the fouling of non-reactive polymer dispersions. Reactive systems cause more fouling than non-reactive so polymerisation fouling is the major part.…”

Ultrasonic and conversion-based inline fouling measurements for continuous emulsion copolymerisation of vinyl acetate in a tubular reactor

“…For surface modifications no general trend could be observed as it is highly dependent on the other process parameters 37 – 39 . Hohlen et al 38 compared fouling of reactive emulsion polymerisation systems with fouling of non-reactive polymer dispersions. Reactive polymerisation systems cause much higher fouling masses than non-reactive so polymerisation fouling is the major part.…”

“…Reactive polymerisation systems cause much higher fouling masses than non-reactive so polymerisation fouling is the major part. Moreover, the morphology of the fouling is given by the pathway of formation so the dominant fouling process can be concluded optically from the fouling morphology 38 .…”