Suspension polymerization of methyl methacrylate

Because the polymerization occurs totally within the monomer droplets without any substantial transfer of materials between individual droplets or between the droplets and the aqueous phase, the course of the polymerization is expected to be similar to bulk polymerization. Accounts of the quantitative aspects of the suspension polymerization of methyl methacrylate generally support this model (95,111,112). Developments in suspension polymerization, including acryUc suspension polymers, have been reviewed (113,114). 

Azad and Fitch (5) investigated the effect of low molecular weight hydrocarbon additives on the formation of colloidafr particles in suspension polymerization of methyl methacrylate and vinyl acetate. It was found that the additives n-octane, n-dodecane, n-octadecane, n-tetracosane and mineral oil exerted a thermodynamic affect depending upon water-solubility and molecular weight. Since these effects on emulsion polymerization have not been considered by the earlier investigators, we have chosen n-pentane and ethyl benzene as additives with limited water-solubility and n-octadecane, and n-tetracosane as water-insoluble ones. Seeded emulsion polymerization was chosen so that the number of particles could be kept constant throughout the experiments and only the effect of the other parameters on the rate could be determined. 

Figure 10.3 Flow sheet for the suspension polymerization of methyl methacrylate. (From Church, J.M., Chem. Eng., p. 79, August 1, 1966.)...

It is noteworthy that both the counterion and the solvent exert a striking effect upon the activity of these catalysts. In addition to their metathesis ability, these cationic Ru-benzylidene complexes are the first Ru-alkylidene catalysts reported so far to perform the controlled radical suspension polymerization of methyl methacrylate, methyl acrylate, and styrene in water, leading to high yields of polymer. 

Suspension polymerization of methyl methacrylate is used mainly for the production of injection moulding and extrusion grades of polymer. Suspension polymer is also used in the preparation of polymer-monomer doughs for dentures. Polymerization is carried out batch-wise in a stirred reactor, jacketed for heating and cooling the reactor is capable of withstanding a pressure of 3—4 atmospheres. A typical basic formulation might be as follows ... 

Reactor configurations other than conventional stirred tanks have been proposed for suspension polymerization. Draft tubes, or internal loops , can be used for suspension polymerization [102], but drop size changes can occur [103] and flow patterns may be complicated [104]. Tanaka et al. [105] used a loop reactor for the suspension polymerization of styrene. They employed a double agitation method to control the transient droplet diameter distribution and the final particle size distribution. Ni et al. [106] developed an oscillatory baffled reactor for batch suspension polymerization of methyl methacrylate. Fluid mixing was achieved by eddies that are generated when a fluid passes through a set of equally spaced, stationary, orifice baffles that are located inside a tube. Periodically formed vortices were con-... 

G. Maschio, T. Bello, C. Scali, Optimization of batch polymerization reactors Modelling and experimental results for suspension polymerization of methyl methacrylate , Chem. Eng. Sci., 1992, 47, 2609. 

Abu-Ayanaa YM, Mohsena RM. Study of some variables affecting particle size and particle size distribution of suspension polymerization of methyl methacrylate. Polym Plast Technol Eng 2005 44 1503-1522. 

FIGURE 12.7 Suspension polymerization of methyl methacrylate. Excerpted by special permission from Reference 11. Copyright 1966 by McGraw-Hill, Inc., New York, NY 10036. 

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