Methacrylates Operating conditions

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. 

Figure 17.3 shows the rate of polymerization plotted versus monomer conversion for the free radical solution polymerization of methyl methacrylate. Unlike a more common reaction in which the rate of reaction falls mono-tonically with conversion, the rate of reaction rises with conversion due to the onset of the gel effect. Thus, the system can be thought of as autocatalytic. At high conversion, the polymerization becomes monomer starved and the rate of polymerization falls to zero. At a fixed residence time, there must be a specific rate of polymerization to produce a given monomer conversion. The mass balance is represented by the dotted lines in Figure 17.3. The slope of the mass balance line will vary with operating conditions bnt it will always pass through the origin since at zero reaction rate the monomer conversion is zero. Inspection of Fignre 17.3 reveals that for mass balances (operating lines) with slopes between the two dotted lines, three steady states exist since an intersection of the reaction rate curve and the operating line defines a steady state.

Porous fibres containing lots of ellipse-like holes on the fibre surface layer have been electrospun from a polylactic acid (PLA)-chloroform solution (Fig. 5.7a). However, when the solution used chloroform-DMF mixture as the solvent, the same operating condition gave a finer nanofibre with a smooth fibre surface (Fig. 5.7b). Porous fibres have also been electrospun from polycarbonate, poly (methyl methacrylate) and polystyrene (Megelski et al., 2002). 

Until 1982, almost all methyl methacrylate produced woddwide was derived from the acetone cyanohydrin (C-3) process. In 1982, Nippon Shokubai Kagaku Kogyo Company introduced an isobutylene-based (C-4) process, which was quickly followed by Mitsubishi Rayon Company in 1983 (66). Japan Methacryhc Monomer Company, a joint venture of Nippon Shokubai and Sumitomo Chemical Company, introduced a C-4-based plant in 1984 (67). Isobutylene processes are less economically attractive in the United States where isobutylene finds use in the synthesis of methyl /i / butyl ether, a pollution-reducing gasoline additive. BASF began operation of an ethylene-based (C-2) plant in Ludwigshafen, Germany, in 1990, but favorable economics appear to be limited to conditions unique to that site. 

Woddwide production capacity is shown in Table 6. Economic conditions in the late 1980s and eady 1990s led to global overcapacity of methyl methacrylate, which caused many plants to be operated at less than optimum levels. 

The purpose of the study was to determine the optimum conditions of operation of pyrolysis equipment by the combined solution of equations relating to the technological and economic analysis of the process. The material considered was poly(methyl methacrylate) one of the most popular types of plastic waste. Articles from this journal can be requested for translation by subscribers to the Rapra produced International Polymer Science and Technology. 

After a steady catalytic behavior was reached, the catalyst was treated in air at 350°C, in order to reoxidize it. Thereafter, the reaction was run again under isobutane-rich conditions (Figure 14.5), in order to understand the role of the POM reduction level on catalytic performance. The reoxidized catalyst exhibited a selectivity to methacrylic acid that was initially around 20%, and approximately 20-30 hours were necessary to recover the original performance of the equilibrated, reduced catalyst. On the contrary, the activity of the catalyst was almost the same as before the oxidizing treatment. This confirms that a partially reduced POM is intrinsically more selective to methacrylic acid than a fully oxidized one, and that one reason for the progressive increase in selectivity to methacrylic acid that occurs during the equilibration period was the increase in the POM reduction level, as a consequence of the operation under isobutane-rich conditions. 

The catalytic performance depends a great deal on the reaction conditions, and specifically on the isobutane-to-oxygen ratio in the feed. Usually isobutane-rich conditions are claimed to be more selective, and the reason for this is that under these conditions the operative POM is a partially reduced one, and a more reduced POM is intrinsically more selective than a fully oxidized one. High isobutane partial pressures help to improve the selectivity, avoiding further oxidation of methacrylic acid. 

Svec et al. also made use of the stability of methacrylate matrices to a very wide pH range and synthesized strong cation-exchange monoliths with sulfonic groups [49], The columns were operated at pH 2.4 and 12, as acidic and, respectively, basic eluents were separated. Figure 8 (from Ref. 49) demonstrates the versatility of one column that, given different conditions, can perform fast and efficient separations on a wide pH range. 

Fig. 25 Hollow particles prepared from SCMs of poly(l,l-dimethyl-2,2-dihexyldisilene)-f -poly(methacrylic acid), (a) AFM image on Pyrex glass plate with operating in the contact mode, (b) vertical profile of the hollow particle shown in part (a), and (c) in the tapping mode under THF wet conditions. Reproduced with permission from [50] Sanji et al. (2000) Macromolecules 33 8524. American Chemical Society...

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