Methyl methacrylate batch

Figure 8.1 illustrates the evolution of reaction rates in batch methyl methacrylate (MMA) bulk reactors under limited heat transfer conditions (large reaction vessels without internal refrigerating coils). Acceleration of reaction rates due to positive thermal feedback is... 

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. 

In a second method, a 1 g sample of poly(tri-n-butyltin methacrylate/methyl methacrylate) was dissolved in 4 mL of chloroform. One mL of concentrated HC1 was added dropwise with shaking until no more precipitate appeared. The precipitate was removed and then shaken again with a clean batch of chloroform and HC1. 

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. 

As a medium strength liquid (Table 16.1), THF is commonly used also in the coupled methods of polymer HPLC. It promotes desorption of medium polar polymers such as poly(acrylate)s and poly(methacrylate)s including poly(methyl methacrylate) from the nonmodified silica gel. Other strong(er) solvents widely used in the coupled polymer HPLC methods are acetonitrile that exhibits high UV transparency, and dimethyl formamide. The latter solvent readily decomposes into amine and formic acid and its strength may differ from batch to batch. 

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... 

Kamat et al. (1992) Batch Transesterification of methyl methacrylate by 2-ethylhexanol Lipase from Candida cylindracea... 

Four polymerization examples are presented here to illustrate both available sensitivity, experimental difficulties, and hopefully some interesting aspects of the polymerization processes. The first two examples are the semi-continuous emulsion polymerization of methyl methacrylate (MMA) and styrene, respectively. The third example is a batch charged copolymerization of butyl acrylate (BA) with MMA. The fourth example is a semi-continuous solution polymerization of an acrylic system. In this last example aliquots were taken manually and analyzed at 29.7°C under static conditions. No further polymerization occurred after the samples were cooled to this temperature. 

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. 

Chain addition polymerizations have a typical value of e 4 x 10-2, and for such batch reactions re increase 106 times from 0 = 10 1 to 0 = 10, with the plateau region at 0 values that are 1010 times higher. It is for this reason that chain addition polymerization reactions, although experimentally studied, as with methyl methacrylate (41,42), are rarely carried out in reactive polymer processing equipment. 

Polymerizable surfactants capable of working as transfer agents include thiosulfonates, thioalkoxylates and methyl methacrylate dimer/trimer surfactants. Thioalkoxylates with 17-90 ethylene oxide units were produced from ethoxylated 11 bromo-undecanol by replacing the bromine with a thiol group via the thiazonium salt route [8]. In the presence of water-soluble azo initiator the thio ended Transurfs (used at a concentration above the CMC) gave monodispersed latex particles in emulsion polymerization of styrene. However, the incorporation of the Transurf remained low, irrespective of the process used for the polymerization (batch, semibatch, seeded). The stability of the lattices when the surfactant and the transfer function were incorporated in the same molecule was better than when they were decoupled. 

To synthesize water-soluble or swellable copolymers, inverse heterophase polymerization processes are of special interest. The inverse macroemulsion polymerization is only reported for the copolymerization of two hydrophilic monomers. Hernandez-Barajas and Hunkeler [62] investigated the copolymerization of AAm with quaternary ammonium cationic monomers in the presence of block copoly-meric surfactants by batch and semi-batch inverse emulsion copolymerization. Glukhikh et al. [63] reported the copolymerization of AAm and methacrylic acid using an inverse emulsion system. Amphiphilic copolymers from inverse systems are also successfully obtained in microemulsion polymerization. For example, Vaskova et al. [64-66] copolymerized the hydrophilic AAm with more hydrophobic methyl methacrylate (MMA) or styrene in a water-in-oil microemulsion initiated by radical initiators with different solubilities in water. However, not only copolymer, but also homopolymer was formed. The total conversion of MMA was rather limited (<10%) and the composition of the copolymer was almost independent of the comonomer ratio. This was probably due to a constant molar ratio of the monomers in the water phase or at the interface as the possible locus of polymerization. Also, in the case of styrene copolymerizing with AAm, the molar fraction of AAm in homopolymer compared to copolymer is about 45-55 wt% [67], which is still too high for a meaningful technical application. 

Fig. 16 Copolymer composition during the batch miniemulsion copolymerization of methyl methacrylate with 2-ethylhexyl acrylate (from [104])...

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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