Optimization styrene polymerization control

Butala et al. [43] applied optimization techniques to styrene polymerization initiated by BPO (dibenzoyl peroxide, 1 h half-life time, 91°C) and TBPB (tert-butyl perbenzoate, 1 h half-life time, 124°C). As mentioned before, the batch time can be minimized by using nonisothermal temperature profiles. Three independent runs with different optimization policies were performed. The detailed control policies are listed in Table 5.1. 

In previous sections we discussed the typical methodologies and practical aspects of the controlled/living carbocationic polymerizations of vinyl ethers, isobutene, styrene, and other monomers. It is possible to select optimal conditions such as the structure and concentrations of initiators, Lewis acids, additives (nucleophiles and salts), solvent, and temperature for each class of monomers in order to control and to prepare well-defined polymers. However, further progress requires a better understanding of the mechanisms of the involved reactions. 

Massebeuf, S., Fonteix, C., Hoppe, S. and Pla, F. (2003). Development of new concepts for the control of polymerization processes multiobjective optimization and decision engineering. I. Application to emulsion homopolymerization of styrene, J. Appl. Polym. Sci, 87, pp. 2383-2396. 

For practical purposes, styrene—DVB copolymers have commonly been obtained by the suspension polymerization method,[53, 54] which is well known to consist of heating and agitating a solution of initiator in monomers with an excess of water containing a stabilizer of the oil-in-water emulsion. Polymerization proceeds in suspended monomer droplets and, in this way, a beaded copolymer is obtained. While looking very simple, this procedure can provide many complications that significantly change the properties of the beaded product as compared to the properties of materials prepared by bulk copolymerization. AU parameters of the suspension copolymerization have to be strictly controlled, since even small deviations from optimal conditions of the synthesis can serve as an additional source of heterogeneity in the copolymer beads. [55]... 

An optimal predictive controller was developed and implemented to allow for maximization of monomer conversion and minimization of batch times in a styrene emulsion polymerization reactor, using calorimetric measiuements for observation and manipulation of monomer feed rates for attainment of control objectives [31]. Increase of 13% in monomer conversion and reduction of 28% in batch time were reported. On-line reoptimization of the reference temperature trajectories was performed to allow for removal of heater disturbances in batch bulk MMA polymerizations [64]. Temperature trajectories were manipulated to minimize the batch time, while keeping the final conversion and molecular weight averages at desired levels. A reoptimization procediue was implemented to remove disturbances caused by the presence of unknown amounts of inhibitors in the feed charge [196]. In this case, temperatiue trajectories were manipulated to allow for attainment of specified monomer conversion and molecular weight averages in minimum time. 

Tailored polymer resins are frequently required for a given application. Fontoura et al. used NIR spectroscopy for in-line and in situ monitoring and control of monomer conversion and polymer average molecular weight during styrene solution polymerization. Two process control strategies, one based on the optimal control theory and the other on model predictive control, were implemented both theoretically and experimentally [67]. 

Optimized concentration of nitroxide in the polymerization lod while preventing thermal initiation in monomer droplets was achieved by the use of a combination of TEMPO and 4-stearoyl-TEMPO that exhibit different water solubility. The polymerization of styrene at 135 C with sodium dodecyl-benzenesulphonate as a surfactant yielded coagulum-free stable latex (D2 = 45nm) with excellent control/livingness. A two-step nitroxide-mediated surfactant-free emulsion polymerization of styrene was also successfully carried out using KPS... 

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