Dynamic simulation of primary particle‐size distribution in vinyl chloride polymerization

Abstract

SYNOPSISIn the suspension polymerization of vinyl chloride, colloidally stable primary particles are formed inside the polymerizing monomer droplets. The nucleation, growth, and aggregation of these particles are responsible for the formation of the internal particle morphology and associated properties, such as pore-size distribution, specific surface area, and plasticizer uptake. In the present investigation, a population balance model is derived describing the time evolution of the primary particle-size distribution in the polymerizing monomer droplets. The resulting integrodifferential equation accounts for the coalescence rate of electrically charged colloidal primary particles through the use of the Fuchs modification of the extended Smoluckowski coagulation equation. Simulation studies were carried out to determine both the effects of the model parameters and to afford a direct comparison of model predictions with experimental measurements of the time evolution of the primary particle-size distribution. The dependence of the total number and of the mean diameter of the primary particles on several process variables (i.e., the ionic strength of the medium, total particle charge, temperature, initial initiator concentration, and agitation rate) is quantitatively analyzed. Finally, the predictive capability of the present model is demon- I NTRODU CTl ONPoly (vinyl chloride ) ( PVC ) is one of the oldest polymers and the second largest in volume thermoplastic manufactured in the world.' The enormous expansion of the PVC industry is due to the high versatility of PVC as a plastic raw material. A review of the qualitative and quantitative aspects of PVC polymerization can be found in reviews by Butters,2 B~r g e s s ,~ R a n~e ,~ and Langsam5 and more recently by Tornell, Xie et al., 7,8 and Yuan et al. ' PVC is effectively insoluble in its own monomer; thus, vinyl chloride monomer (VCM) polymerization is a heterogeneous process that involves several physical transitions during the polymerization. As a result, the final particulate product is made up of primary particles and its aggregates. The nucleation,

Kinetics and Mechanism of Bulk Polymerization of Vinyl Chloride in a Polymerization Reactor

“…In light of this, it has been presumed that CSTR includes the gel, solid, and liquid phases. Also assumed is that reactions occur with catalysts during the liquid phrase (Kiparissides et al 1994). In addition to this, it is also observed and identified in the new mathematical model that all three phases take place in controlled conditions.…”

“…Such modeling and comparison will help in assessing the effects of the catalyst flow rate on the reaction's temperature; specifically, the impact of potassium/titanium oxide (Pt/TiO2) must be analyzed. In addition to this, it would also help in determining the variation in the concentration of emulsion reactants with the passage of time (Blazevska and Spasesk 2010;Field 1973;Kiparissides et al 1994;Zuga and Cincu 2006).…”

Part I: Dynamic evolution of the particle size distribution in particulate processes undergoing combined particle growth and aggregation

“…For several polymerization systems, the rate of change of the number density function obeys the following free boundary condition (Kiparissides et al, 1994):…”

“…There is a large number of publications dealing with the application of the PBE in various particulate processes, including aerosol dynamics (Seinfeld, 1979;Landgrebe and Pratsinis, 1990;Friedlander, 2000;Scott, 1968), granulation of solids (Adetayo et al, 1995), crystallization (Randolph and Larson, 1988;Hounslow, 1990), liquid-liquid dispersions (Kronberger et al, 1995), microbial cell cultures (Ramkrishna, 1979;Fredrickson et al, 1967), polymerization (Min and Ray, 1974;Sundberg, 1979;Chen and Wu, 1988;Richards et al, 1989;Alvarez et al, 1994;Kiparissides et al, 1994;Yiannoulakis et al, 2001), fluidized bed reactors (Sweet et al, 1987).…”

A Comprehensive Experimental and Theoretical Investigation of the Styrene/2‐Ethylhexyl Acrylate Emulsion Copolymerization

“…The population balance equation describing the time evolution of the particle size distribution in a batch emulsion copolymerization reactor can take the following general form: [40] @nðV; tÞ @t þ @ðG p nðV; tÞÞ @V…”