Emulsion methyl methacrylate

Uses. The a2obisnitriles have been used for bulk, solution, emulsion, and suspension polymeri2ation of all of the common vinyl monomers, including ethylene, styrene vinyl chloride, vinyl acetate, acrylonitrile, and methyl methacrylate. The polymeri2ations of unsaturated polyesters and copolymeri2ations of vinyl compounds also have been initiated by these compounds. 

Acrylics. Acetone is converted via the intermediate acetone cyanohydrin to the monomer methyl methacrylate (MMA) [80-62-6]. The MMA is polymerized to poly(methyl methacrylate) (PMMA) to make the familiar clear acryUc sheet. PMMA is also used in mol ding and extmsion powders. Hydrolysis of acetone cyanohydrin gives methacrylic acid (MAA), a monomer which goes direcdy into acryUc latexes, carboxylated styrene—butadiene polymers, or ethylene—MAA ionomers. As part of the methacrylic stmcture, acetone is found in the following major end use products acryUc sheet mol ding resins, impact modifiers and processing aids, acryUc film, ABS and polyester resin modifiers, surface coatings, acryUc lacquers, emulsion polymers, petroleum chemicals, and various copolymers (see METHACRYLIC ACID AND DERIVATIVES METHACRYLIC POLYMERS). 

Emulsion Polymerization. Emulsion polymerization is the most important industrial method for the preparation of acryhc polymers. The principal markets for aqueous dispersion polymers made by emulsion polymerization of acryhc esters are the paint, paper, adhesives, textile, floor pohsh, and leather industries, where they are used principally as coatings or binders. Copolymers of either ethyl acrylate or butyl acrylate with methyl methacrylate are most common. 

A third source of initiator for emulsion polymerisation is hydroxyl radicals created by y-radiation of water. A review of radiation-induced emulsion polymerisation detailed efforts to use y-radiation to produce styrene, acrylonitrile, methyl methacrylate, and other similar polymers (60). The economics of y-radiation processes are claimed to compare favorably with conventional techniques although worldwide iadustrial appHcation of y-radiation processes has yet to occur. Use of y-radiation has been made for laboratory study because radical generation can be turned on and off quickly and at various rates (61). 

Numerous recipes have been pubUshed which describe the preparation of methacrylate homopolymer and copolymer dispersions (65,66). A typical process for the preparation of a 50% methyl methacrylate, 49% butyl acrylate, and 1% methacrylic acid terpolymer as an approximately 45% dispersion in water begins with the preparation of the monomer emulsion charge. 

MBS polymers are prepared by grafting methyl methacrylate and styrene onto a styrene—butadiene mbber in an emulsion process. The product is a two-phase polymer useful as an impact modifier for rigid poly(vinyl chloride). 

AH-acryHc (100%) latex emulsions are commonly recognized as the most durable paints for exterior use. Exterior grades are usuaHy copolymers of methyl methacrylate with butyl acrylate or 2-ethyIhexyl acrylate (see Acrylic ester polymers). Interior grades are based on methyl methacrylate copolymerized with butyl acrylate or ethyl acrylate. AcryHc latex emulsions are not commonly used in interior flat paints because these paints typicaHy do not require the kind of performance characteristics that acryHcs offer. However, for interior semigloss or gloss paints, aH-acryHc polymers and acryHc copolymers are used almost exclusively due to their exceUent gloss potential, adhesion characteristics, as weU as block and print resistance. 

Recently, Smigol et al. [75] extensively studied emulsifier-free emulsion polymerization of different monomers including styrene, methyl methacrylate, and glycidyl methacrylate in an aqueous medium by using potassium peroxydisulfate as the initiator. In this study. 

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. 

The Emulsion Polymerization Model (EPM) described in this paper will be presented without a detailed discussion of the model equations due to space limitations. The complete set of equations has been presented in a formal publication (Richards, J. R. et al. J. AppI. Poly. Sci . in press). Model results will then be compared to experimental data for styrene and styrene-methyl methacrylate (MMA) copolymers published by various workers. 

Polymerizations conducted in nonaqueous media in which the polymer is insoluble also display the characteristics of emulsion polymerization. When either vinyl acetate or methyl methacrylate is polymerized in a poor solvent for the polymer, for example, the rate accelerates as the polymerization progresses. This acceleration, which has been called the gel effect,probably is associated with the precipitation of minute droplets of polymer highly swollen with monomer. These droplets may provide polymerization loci in which a single chain radical may be isolated from all others. A similar heterophase polymerization is observed even in the polymerization of the pure monomer in those cases in which the polymer is insoluble in its own monomer. Vinyl chloride, vinylidene chloride, acrylonitrile, and methacryloni-trile polymerize with precipitation of the polymer in a finely divided dispersion as rapidly as it is formed. The reaction rate increases as these polymer particles are generated. In the case of vinyl chloride ... 

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. 

The role of water in these reactions is not completely clear since the applied metal complexes are not water-soluble. One reason for using aqueous systems is the possibility of producing aqueous emulsion directly which is a distinct technological benefit. Nevertheless, in polymerizations of methyl methacrylate with [RuCl2(PPh3)3] and PhCOCHCl2, consistently higher reaction rates were observed in the presence of water than in diy toluene [48]. 

Emulsion polymerization is used for 10-15% of global polymer production, including such industrially important polymers as poly(acrylonitrile-butadiene-styrene) (ABS), polystyrene, poly(methyl methacrylate), and poly (vinyl acetate) [196]. These are made from aqueous solutions with high concentrations of suspended solids. The important components have unsaturated carbon-carbon double bonds. Raman spectroscopy is well-suited to address these challenges, though the heterogeneity of the mixture sometimes presents challenges. New sample interfaces, such as WAI and transmission mode, that have shown promise in pharmaceutical suspensions are anticipated to help here also. 

Bauer et al. describe the use of a noncontact probe coupled by fiber optics to an FT-Raman system to measure the percentage of dry extractibles and styrene monomer in a styrene/butadiene latex emulsion polymerization reaction using PLS models [201]. Elizalde et al. have examined the use of Raman spectroscopy to monitor the emulsion polymerization of n-butyl acrylate with methyl methacrylate under starved, or low monomer [202], and with high soUds-content [203] conditions. In both cases, models could be built to predict multiple properties, including solids content, residual monomer, and cumulative copolymer composition. Another study compared reaction calorimetry and Raman spectroscopy for monitoring n-butyl acrylate/methyl methacrylate and for vinyl acetate/butyl acrylate, under conditions of normal and instantaneous conversion [204], Both techniques performed well for normal conversion conditions and for overall conversion estimate, but Raman spectroscopy was better at estimating free monomer concentration and instantaneous conversion rate. However, the authors also point out that in certain situations, alternative techniques such as calorimetry can be cheaper, faster, and often easier to maintain accurate models for than Raman spectroscopy, hi a subsequent article, Elizalde et al. found that updating calibration models after... 

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. 

Methyl methacrylate is polymerized to poly(methyl methacrylate), which is used in cast and extruded sheet (32%), surface coatings (24%), molding powder and resins (15%), impact modifiers (13%), and emulsion polymers... 

Monomer and initiator must be soluble in the liquid and the solvent must have the desired chain-transfer characteristics, boiling point (above the temperature necessary to carry out the polymerization and low enough to allow for ready removal if the polymer is recovered by solvent evaporation). The presence of the solvent assists in heat removal and control (as it also does for suspension and emulsion polymerization systems). Polymer yield per reaction volume is lower than for bulk reactions. Also, solvent recovery and removal (from the polymer) is necessary. Many free radical and ionic polymerizations are carried out utilizing solution polymerization including water-soluble polymers prepared in aqueous solution (namely poly(acrylic acid), polyacrylamide, and poly(A-vinylpyrrolidinone). Polystyrene, poly(methyl methacrylate), poly(vinyl chloride), and polybutadiene are prepared from organic solution polymerizations. 

Case 3 behavior occurs when the particle size is sufficiently large (about 0.1-1 pm) relative to kt such that two or more radicals can coexist in a polymer particle without instantaneous termination. This effect is more pronounced as the particle size and percent conversion increase. At high conversion the particle size increases and k, decreases, leading to an increase in h. The increase in h occurs at lower conversions for the larger-sized particles. Thus for styrene polymerization it increases from 0.5 to only 0.6 at 90% conversion for 0.7-pm particles. On the other hand, for 1.4-pm particles, n increases to about 1 at 80% conversion and more than 2 at 90% conversion [Chatterjee et al., 1979 Gerrens, 1959]. Much higher values of h have been reported in other emulsion polymerizations [Ballard et al., 1986 Mallya and Plamthottam, 1989]. Methyl methacrylate has a more pronounced Trommsdorff effect than styrene and vinyl acetate, and this results in a more exaggerated tendency toward case 3 behavior for methyl methacrylate. 

The heat of an emulsion polymerization is the same as that for the corresponding bulk or solution polymerization, since AH is essentially the enthalpy change of the propagation step. Thus, the heats of emulsion polymerization for acrylic acid, methyl acrylate, and methyl methacrylate are —67, —77, and —58 kJ mol-1, respectively [McCurdy and Laidler, 1964], in excellent agreement with the AH values for the corresponding homogeneous polymerizations (Table 3-14). 

In a reaction vessel equipped with mechanic propeller stirrer, argon inlet, and reflux condenser an emulsion is prepared of distilled water (300 g), methyl methacrylate (MMA 9.5 g),allyl methacrylate (ALMA 0.5 g) and sodium dodecyl sulfate (5D5 ... 

The emulsion was stabilized with 0.25% block copolymer of starch and methyl methacrylate synthesized by mastication. 

The idea of the preparation of porous polymers from high internal phase emulsions had been reported prior to the publication of the PolyHIPE patent [128]. About twenty years previously, Bartl and von Bonin [148,149] described the polymerisation of water-insoluble vinyl monomers, such as styrene and methyl methacrylate, in w/o HIPEs, stabilised by styrene-ethyleneoxide graft copolymers. In this way, HIPEs of approximately 85% internal phase volume could be prepared. On polymerisation, solid, closed-cell monolithic polymers were obtained. Similarly, Riess and coworkers [150] had described the preparation of closed-cell porous polystyrene from HIPEs of water in styrene, stabilised by poly(styrene-ethyleneoxide) block copolymer surfactants, with internal phase volumes of up to 80%. 

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