Solution polymerization continuous flow stirred

In this short initial communication we wish to describe a general purpose continuous-flow stirred-tank reactor (CSTR) system which incorporates a digital computer for supervisory control purposes and which has been constructed for use with radical and other polymerization processes. The performance of the system has been tested by attempting to control the MWD of the product from free-radically initiated solution polymerizations of methyl methacrylate (MMA) using oscillatory feed-forward control strategies for the reagent feeds. This reaction has been selected for study because of the ease of experimentation which it affords and because the theoretical aspects of the control of MWD in radical polymerizations has attracted much attention in the scientific literature. 

In the pre-polymerization vessels, the rubber solution is polymerized to a conversion of 20-30 %. This phase is where the particle structure, the RPS and the RPSD are fixed. In industry, the pre-polymerization is carried out in continuous-flow stirred tank reactors (Shell, Monsanto, Mitsui Toatsu), tower reactors (Dow Chemical), stirred reactor cascades (BASF) or loop reactors with static mixers (Dainippon Ink and Chemicals). 

Styrene polymerizes spontaneously on heating by a free-radical mechanism. Some commercial polystyrene is produced by suspension and emulsion polymerization, but the principal route is solution polymerization. This is carried out either in a continuous plug-flow reactor (CPFR) or a continuous stirred tank reactor (CSTR). 

The effect of physical processes on reactor performance is more complex than for two-phase systems because both gas-liquid and liquid-solid interphase transport effects may be coupled with the intrinsic rate. The most common types of three-phase reactors are the slurry and trickle-bed reactors. These have found wide applications in the petroleum industry. A slurry reactor is a multi-phase flow reactor in which the reactant gas is bubbled through a solution containing solid catalyst particles. The reactor may operate continuously as a steady flow system with respect to both gas and liquid phases. Alternatively, a fixed charge of liquid is initially added to the stirred vessel, and the gas is continuously added such that the reactor is batch with respect to the liquid phase. This method is used in some hydrogenation reactions such as hydrogenation of oils in a slurry of nickel catalyst particles. Figure 4-15 shows a slurry-type reactor used for polymerization of ethylene in a sluiTy of solid catalyst particles in a solvent of cyclohexane. 

Example 4-8 An ideal continuous stirred-tank reactor is used for the homogeneous polymerization of monomer M. The volumetric flow rate is O, the volume of the reactor is V, and the density of the reaction solution is invariant with composition. The concentration of monomer in the feed is [M]o. The polymer product is produced by an initiation step and a consecutive series of propagation reactions. The reaction mechanism and rate equations may be described as follows, where is the activated monomer and P2, . . , P are polymer molecules containing n monomer units ... 

VA, the three copolymers containing 0.37,1.00, and 2.14 mol% AETMC, indicated as PVAcA, PVAcB, and PVAcC, respectively, were prepared by slowly adding a methanol solution of AETMC into a methanol solution of VA at 60°C under nitrogen flow. The polymerization, initiated by AIBN, was continued for 1.5-3 h. Then, the viscous solution was diluted with acetone and poured into excess hexane under stirring. The tacky precipitate was purified by dissolution in methanol and precipitation in cold water. The structure of the three PVAc copolymers is indicated in the scheme below. 

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