The Effect of Oxygen on the Kinetics and Particle Size Distribution in Vinyl Chloride Emulsion Polymerization

Abstract

A comprehensive mathematical model is developed to quantify the effect of the oxygen concentration on the polymerization rate and particle size distribution in an unseeded vinyl chloride batch emulsion polymerization reactor. Particle formation is assumed to proceed by both the homogeneous and micellar nucleation mechanisms. Dynamic species mass balances are derived to follow the evolution of the polymerization rate and particle size distribution (PSD) in the batch reactor. It is shown that, at low initial oxygen concentrations, the polymerization rate increases with the oxygen concentration. On the other hand, the average latex particle size exhibits a U-shaped behavior with respect to the initial oxygen concentration. The experimental observations on the polymerization rate and the average particle size are explained by the combined role of oxygen as an inhibitor and a radical generator through the formation and subsequent decomposition of vinyl polyperoxides. The predictive capabilities of the present model are demonstrated through the successful simulation of experimental data on monomer conversion and PSD obtained from an industrial pilot-plant batch PVC reactor operated with various initial oxygen and initiator concentrations.

Modeling particle size distribution in emulsion polymerization reactors

“…A number of models based on the (classical and extended) DLVO theory [83,84] have been proposed to predict the coagulation rate coefficients of latex particles stabilized both by anionic surfactants (Coen et al [8,22], Fortuny et al [85], Kiparissides et al [86], and Melis et al [87,88]), or of non-ionic surfactants (Immanuel et al [13], Kammona et al [48], and Lazaridis [89]). Next, we will take a look at the key steps of the DLVO approach, followed by a discussion of its major limitations.…”

“…A number of authors [85,86,89] followed the approach given by Coen et al [8] and used the Debye-Huckel or the Gouy-Chapman equations to relate 0 σ to the surface potential 0 ψ , and then a Stern layer model to compute d ψ from 0 ψ . However, as noted by Melis et al [88], such a procedure seems to be incorrect since the Debye-Huckel and Gouy-Chapman equations cannot be used to relate 0 σ to the surface potential 0 ψ .…”

“…Some researchers have applied a logarithmic transformation to the particle size domain (e.g. [86,127]). This kind of transformation improves the description of nucleation, since it expands the small particle region, but it tends to perform poorly as particles grow by polymerization and coagulation [128].…”

Modeling Particle Size Distribution in Heterogeneous Polymerization Systems Using Multimodal Lognormal Function

“…Furthermore, the understanding of the dynamics of PSD is very important for process monitoring and final quality control of heterogeneous polymerization processes (Hosseini et al, 2013). Therefore, PSD modeling has received great attention with the proposal of models such as Population Balance Equations (PBE) (Machado et al, 2000;Araújo et al, 2001;Kiparissides et al, 2002;Immanuel et al, 2002;Coen et al, 2004). However, according to Vale and McKenna (2005), even when these difficulties in coagulation modeling are overcome, the PBEs are difficult to solve if they include kinetic and/or hydrodynamic complete models.…”

Modelagem De Distribuições De Tamanho De Partículas, Usando Função Lognormal Multimodal Em Processos De Polimerização Em Meio Heterogêneo

“…Uma alternativa é a modelagem fenomenológica fazendo uso das equações de balanço populacional (Kiparissides et al 2002;Araújo et al 2001;Coen et al 2004), sendo que estes modelos permitem uma estrutura que pode relacionar a DTP à cinética de reação, à nucleação e crescimento das partículas, bem como a coagulação. No entanto, de acordo com Vale e McKenna (2005), mesmo quando superadas as dificuldades relativas à modelagem da coagulação, as equações de balanço populacional são difíceis de resolver se as mesmas incluírem modelos cinéticos e ou hidrodinâmicos completos.…”