Multicomponent Polymerization. II. The Effect of Mixing on Copolymerization in Continuous Stirred Tank Reactors

Abstract

Calculations have been carried out to describe the course of three vinyl copolymerizations which typify free-radical copolymerizations. Conversion of monomer to polymer, and copolymer average composition, as well as copolymer composition distribution (CCD), have been calculated for these three systems in batch reactors (BR) and in continuous stirred tank reactors which have perfect. homogeneous micromixing (HCSTR) or imperfect mixing which leads to segregation on the microscopic scale (SCSTR). The results of the calculations indicate that conversion and uceruge composition behavior are not necessarily strongly dependent on mixing in a CSTR. although they are in some systems. However, the CCD is strongly affected by mixing in all systems where the cornposition drifts with csonversion.In the limit a The magnitude of the effect of mixing on CCD increases with conversion. SCSTR gives at high conversion the same CCD as a BR. tions and applications of the calculations are discussed.

Origin of Chemical Composition of Ethylene/Propylene Copolymer Produced with Ziegler–Natta Catalyst

“…In this light, it was reported that the stirring speed during slurry polymerization affected the rate of monomer dissolution from gas phase In many copolymerization systems including Ziegler–Natta copolymerization, monomer concentrations can be non‐uniform in a reaction medium when the mixing is insufficient, thus broadening molecular weight and chemical composition distribution of produced polymer In heterogeneous olefin polymerization, produced polymer covers surfaces of catalyst particles and fills intra‐particle pores, which builds up the diffusion resistance for monomer (and alkylaluminum …”

“…In many copolymerization systems including Ziegler–Natta copolymerization, monomer concentrations can be non‐uniform in a reaction medium when the mixing is insufficient, thus broadening molecular weight and chemical composition distribution of produced polymer …”

“…[24] Kashiwa and Yoshitake reported that Ti 2+ species were active for ethylene homopolymerization and for ethylene/propylene copolymerization while inactive for propylene homopolymerization. [21] The variation of monomer concentrations during copoly merization has been also proposed as (a part of) the origin of the chemical composition, and its distribution of copolymer: [35][36][37][38][39][40][41][42][43][44][45] i) Most of previous studies employed slurry copolymerization either at normal pressure under continuous flow of monomer mixture or at elevated pressure with only one kind of monomer supplied in a semi-batch manner. When the feed rate of monomer supplied from gas phase is lower than the consumption rate by a catalyst, the monomer concentration can deviate from the equilibrium concentration.…”

Modeling of imperfect mixing and its effects on polymer properties

“…1984a1, copolymer composition distribution (CCD) (Atiqullah and Nauman, 1990;Mecklenburgh, 1970;O'Driscoll and Knorr, 1969), and the molecular-weight distribution (MWD) (Tadmor and Biesenberger, 1966;Marini and Georgakis, 1984b;Tosun, 1992). The mean values of CCD and MWD are less affected than the breadth of the distributions, which often increases with poorer mixing.…”

Modern aspects of quantitative theory of free-radical copolymerization

“…In the next paper [328] the authors after comparing the results of theoretical calculations to experimental data on copolymerization of vinyl pyrrolidone with vinyl acetate in CSTR found their good agreement. The further study concerned the various calculation schemes of copolymerization under hydrodynamic regimes different from CSTR [330][331][332][333] and processes with participation of three monomers [330,335]. It is worth noticing the work by Penchev [334] who experimentally proved the reliability of the terminal model to describe the processes of copolymerization of styrene with methyl methacrylate in CSTR.…”