Methyl methacrylate reactor

Copolymerization systems offer an even higher degree of d)mamic complexity that involves multiple rates of monomer consumption of the form of eq 2. Pinto and Ray 54) were first to present a comprehensive mathematical model for copolymerization validated with experimental findings. Both experiments and model predictions demonstrated that the stability of such systems is extremely sensitive to small changes in feed composition. For example, when the comonomer feed was switched from pure vinyl acetate to a comonomer mixture containing 0.25 vol% methyl methacrylate, reactor operation changed from stable to oscillatory rapid convergence to stable operation was observed when the feed composition was switched back. 

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. 

This paper presents the physical mechanism and the structure of a comprehensive dynamic Emulsion Polymerization Model (EPM). EPM combines the theory of coagulative nucleation of homogeneously nucleated precursors with detailed species material and energy balances to calculate the time evolution of the concentration, size, and colloidal characteristics of latex particles, the monomer conversions, the copolymer composition, and molecular weight in an emulsion system. The capabilities of EPM are demonstrated by comparisons of its predictions with experimental data from the literature covering styrene and styrene/methyl methacrylate polymerizations. EPM can successfully simulate continuous and batch reactors over a wide range of initiator and added surfactant concentrations. 

Sutterlin 22.), Figures 4,5, and 6, styrene and methyl methacrylate (MMA) homopolymerizations in a batch reactor at 80 °C with various amounts of added surfactant. 

In this work, a comprehensive kinetic model, suitable for simulation of inilticomponent aiulsion polymerization reactors, is presented A well-mixed, isothermal, batch reactor is considered with illustrative purposes. Typical model outputs are PSD, monomer conversion, multivariate distritution of the i lymer particles in terms of numtoer and type of contained active Chains, and pwlymer ccmposition. Model predictions are compared with experimental data for the ternary system acrylonitrile-styrene-methyl methacrylate. 

Model predictions are caipared with experimental data In the case of the ternary system acrylonitrlle-styrene-methyl methacrylate. Ihe experimental runs have been performed with the same recipe, but monomer feed composition. A glass, thermostat ted, well mixed reactor, equipped with an anchor stirrer and four baffles, has been used. The reactor operates under nitrogen atmosphere and a standard degassing procedure is performed Just before each reaction. The same operating conditions have been maintained in all runs tenperature = 50°C, pressure = 1 atm, stirring speed = 500 rpm, initiator (KgSgOg) 0. 395 gr, enulsifier (SLS) r 2.0 gr, deionized water = 600 gr, total amount of monomers = 100 gr. 

A polymer is produced by the emulsion polymerisation of acrylonitrile and methyl methacrylate in a stirred vessel. The monomers and an aqueous solution of catalyst are fed to the polymerisation reactor continuously. The product is withdrawn from the base of the vessel as a slurry. 

Biesenberg, J. S. etal., J. Polym. Eng. Sci., 1976,16, 101-116 Polymerisation of methyl methacrylate initiated by oxygen or peroxides proceeds with a steady increase in velocity during a variable induction period, at the end of which a violent 90°C exotherm occurs. This was attributed to an increase in chain branching, and not to a decrease in heat transfer arising from the increasing viscosity [ 1 ]. The parameters were determined in a batch reactor for thermal runaway polymerisation of methyl methacrylate, initiated by azoisobutyronitrile, dibenzoyl peroxide or di-ferf-butyl peroxide [2],... 

Compositionally uniform copolymers of tributyltin methacrylate (TBTM) and methyl methacrylate (MMA) are produced in a free running batch process by virtue of the monomer reactivity ratios for this combination of monomers (r (TBTM) = 0.96, r (MMA) = 1.0 at 80°C). Compositional ly homogeneous terpolymers were synthesised by keeping constant the instantaneous ratio of the three monomers in the reactor through the addition of the more reactive monomer (or monomers) at an appropriate rate. This procedure has been used by Guyot et al 6 in the preparation of butadiene-acrylonitrile emulsion copolymers and by Johnson et al (7) in the solution copolymerisation of styrene with methyl acrylate. 

Deters (14) grafted acrylonitrile, methyl methacrylate and vinyl chloride on cellulose and cellulose triacetate. The first two monomers were put in the reactor as liquids, the last as a gas. The results are summarized on Table 1. Vinyl chloride did not graft to cellulose (14). 

A reactor was charged with the step 3 product (1.0 g), methyl methacrylate (8.0 g),... 

Bulk Polymerization. This involves only monomer, initiator, and perhaps chain-transfer agent. It gives the greatest polymer yield per unit of reactor volume and a very pure polymer. However, in large-scale batch form, it must be run slowly or in continuous form with a lot of heat-transfer area per unit of conversion to avoid mnaway. Objects are conveniendy cast to shape using batch bulk polymerization. Poly(methyl methacrylate) glazing sheets are produced by batch bulk polymerization between glass plates. They are also made by continuous bulk polymerization between polished stainless steel... 

The most favorable conditions for reactive processing of monolithic articles are created when the frontal reaction occurs at a plane thermal front. For example, a frontal process can be used for methyl methacrylate polymerization at high pressure (up to 500 MPa) in the presence of free-radical initiators. The reaction is initiated by an initial or continuous local increase in temperature of the reactive mass in a stationary mold, or in a reactor if the monomer is moving through a reactor. The main method of controlling the reaction rate and maintaining stability is by varying the temperature of the reactive mass.252... 

The available data from emulsion polymerization systems have been obtained almost exclusively through manual, off-line analysis of monomer conversion, emulsifier concentration, particle size, molecular weight, etc. For batch systems this results in a large expenditure of time in order to sample with sufficient frequency to accurately observe the system kinetics. In continuous systems a large number of samples are required to observe interesting system dynamics such as multiple steady states or limit cycles. In addition, feedback control of any process variable other than temperature or pressure is impossible without specialized on-line sensors. This note describes the initial stages of development of two such sensors, (one for the monitoring of reactor conversion and the other for the continuous measurement of surface tension), and their implementation as part of a computer data acquisition system for the emulsion polymerization of methyl methacrylate. 

Figure 2. Isothermal polymerization of methyl methacrylate in a CSTR (1 5). a. Predicted steady-state monomer conversion vs. reactor residence time for the solution polymerization of MMA in ethyl acetate at 86 °C. h. Steady-state and dynamic experiments for the isothermal solution polymerization of MMA in ethyl acetate (solvent fraction O.k) ( ) steady states,...

The key problems in a polymerization CSTR are the determination and characterization of micro- and macromixing, and the possibility of multiple steady states due to the exothermic nature of the reactions. Recent studies of CSTRs for bulk or solution free-radical polymerization indicate the possibility of multiple steady states due to the large heat evolution and difficult heat transfer that are characteristic of the reactors. Furthermore, even in simple solution polymerization (for example, in methyl methacrylate polymerization in ethyl acetate solvent), autocatalytic kinetics can lead to runaway conditions even with perfect temperature control for certain combinations of solvent concentration and reactor residence time. In practice, the heat evolution can be an additional source of autocatalytic behavior. 

Additional attemps in the polymerization of methyl-methacrylate (MMA) and styrene (S) with AIBN lead to a thin film on the walls of the reactor, which was caused by a low conversion rate. Copolymerization attempts of AA with MMA resp. S led to undefined waxkind products. 

By means of the spatially intermittent reactor, Ito and O Driscoll determined, for example, the absolute rate constant of termination, fct, for methyl methacrylate copolymerization with butyl or dodecyl methacrylate. The value of /ct is a function of the monomer mixture composition [89]. 

A container was charged with a solution of Vazo 52 catalyst and 2,2 -azobis(2,4-dimethyl pentane nitrile) (4.5 g) dissolved in acetone (600 g) a second container was charged with methyl methacrylate (540 g) and 2-hydroxy ethyl methacrylate (180 g). The first and second containers were uniformly fed into a reactor for 330 and 240 minutes, respectively, and then refluxed for 1 hour. After standard workup the product was isolated in 100% yield, having aMn of 30,308 daltons, Mw of93,195 daltons, and a PDI of 3.07. 

Although theoretical models seem to be quite adequate for styrene emulsion polymerization in either batch reactors or CSTR s, such is not the case with other monomers like vinyl acetate, methyl acrylate, methyl methacrylate, vinyl chloride, etc. One of the early papers to discuss scane of the important mechanisms involved with these other moncaners was written by Priest ( ). He studied the emulsion polymerization of vinyl acetate and identified most of the key mechanisms involved. Priest s paper has been largely overlooked, however, perhaps because of the success of the Smith-Ewart approach to styrene. 

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