Continuous stirred tank reactors copolymerization

More recent efforts (primarily at the simulation level) on the optimization of styrene-related systems include Cavalcanti and Pinto [4], suspension reactor for styrene-acrylonitrile, and Hwang et al. [5], thermal copolymerization in a continuously stirred tank reactor (CSTR). 

In addition to the above investigations, free-radical high-pressure polymerizations should also be studied in continuously operated devices for three reasons. (1) Because of the wealth of kinetic information contained in the polymer properties, product characterization is mandatory. Sufficient quantities of polymer, produced under well defined conditions of temperature, pressure, and monomer conversion, are best provided by continuous polymerization, preferably in a continuously stirred tank reactor (CSTR). (2) Copolymerization of monomers that have rather dissimilar reactivity ratios, such as in ethene-acry-late systems, will yield chemically inhomogeneous material if the reaction is carried out in a batch-type reactor up to moderate conversion. To obtain larger quantities of copolymer of analytical value, the copolymerization has to be performed in a CSTR. (3) Technical polymerizations are exclusively run as continuous processes. Thus, in order to stay sufficiently close to the application and to investigate aspects of technical polymerizations, such as testing initiators and initiation strategies, fundamental research into these processes should, at least in part, be carried out in continuously operated devices. 

Using the device in Figure 4.6-4 with only one continuously stirred tank reactor, CSTRl, is sufficient to investigate homo- and copolymerization... 

Hamielec, A. E. and MacGregor, J. F. (1983) Thermal and chemical-initiated copolymerization of styrene/acrylic acid at high temperatures and conversions in a continuous stirred tank reactor, Proc. Internat. Berlin Workshop on Polymer Reaction Engineering, Berlin. 

Liquid monomer is polymerized in continuous stirred tank reactors in a number of processes. The Hypol process, developed by Mitsui Petrochemical, uses a cascaded series of stirred reactors for homopolymerization, followed by fluidized bed gas-phase reactors for copolymerization (274). El Paso (now Himtsman) converted the Rexall liquid monomer process to use high yield catalysts eliminating the sections required for deashing and removal of atactic material (275). Shell (now Basell) developed the LIPP process to produce homopolymers and random copolymers, using their high yield catalysts. 

The styrene and acrylonitrile can be copolymerized by free radical methods using a continuous stirred tank reactor (CSTR). The reactivity ratios r,2 and rj, can be taken as 0.04 and 0.41, respectively. Construct a first-order Markov model using the dyad probabilities derived in Section 11.1. 

In addition to the semi-batch slurry experiments, 9/MAO was used in solution in a continuous stirred tank reactor (CSTR) to further investigate the influence of [ethylene]/[macromonomer] ratio on LCB. Figure 7 shows a quantitative analysis of the C-NMR-based LCB content in polyethylene as a function of the [ethylene]/ [macromonomer] ratio [85]. The LCB content was the highest at low ratios and rapidly decreased with an increase in the [ethylene]/[macromonomer] ratio. This is in line with LCB formation via the copolymerization reaction. 

In practice, the continuous mass polymerization is rather complicated. Because of the high viscosity of the copolymerizing mixture, complex machinery is required to handle mixing, heat transfer, melt transport, and devolatilization. In addition, considerable time is required to establish steady-state conditions in both a stirred-tank reactor and a linear-flow reactor. Thus, system start-up and product grade changes produce some off-grade or intermediate grade products. Copolymerization is normally carried out between 100 and 200°C. Solvents are used to reduce viscosity or the conversion is kept to 40-70%, followed by devolatilization to remove solvents and monomers. Devolatilization is carried out from 120 to 260° C... 

A continuous polymerization train consisting of two stirred tanks in series is used to copolymerize styrene, rx = 0.41, and acrylonitrile, vy = 0.04. The flow rate to the first reactor is 3000 kg/h and a conversion of 40% is expected. Makeup styrene is fed to the second reactor and a conversion of 30% (based on the 3000 kg/h initial feed) is expected there. What should be the feed composition and how much styrene should be fed to the second reactor if a copolymer containing 58 wt% styrene is desired ... 

Reactor designs are characterized as either homogeneous or heterogeneous. Typically, homogeneous reactors are well mixed stirred tanks (either batch or continuous), but can also be tubular reactors. They are widely used in the chemical industry from pilot plant to full-scale production. Examples include decomposition of azomethane, production of ethylene glycol, and the copolymerization of styrene and butadiene. 

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