Polymerization batch bulk

For the copolymerization of ethene and vinyl acetate, solution polymerization, suspension polymerization, emulsion polymerization and bulk polymerization may be used, but solution polymerization is preferred (1). A method of either continuous type or batch type may be employed. Methanol is generally used as the solvent. 

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... 

Polymerization in bulk (or in block) under normal pressure in the temperature range from room temperature to about 15CUC. The batch polymerization of methylmethacrylate to give Lucite" or Plexiglass" and the continuous polymerization of styrene to give the various types of polystyrene can be quoted as examples. 

Data on a thermal batch bulk polymerization at 150°C (run in a two-litre bench-scale reactor) are presented in Table III and compared with computer predictions. Here, the computer prediction of molecular weight is good (almost independent of conversion) while the predicted conversions are slightly low. Comparison of the model predictions with thermal polymerization data of Hui and Hamielec 6) and Husain and Hamielec (J7) also indicate that the... 

An optimal predictive controller was developed and implemented to allow for maximization of monomer conversion and minimization of batch times in a styrene emulsion polymerization reactor, using calorimetric measiuements for observation and manipulation of monomer feed rates for attainment of control objectives [31]. Increase of 13% in monomer conversion and reduction of 28% in batch time were reported. On-line reoptimization of the reference temperature trajectories was performed to allow for removal of heater disturbances in batch bulk MMA polymerizations [64]. Temperature trajectories were manipulated to minimize the batch time, while keeping the final conversion and molecular weight averages at desired levels. A reoptimization procediue was implemented to remove disturbances caused by the presence of unknown amounts of inhibitors in the feed charge [196]. In this case, temperatiue trajectories were manipulated to allow for attainment of specified monomer conversion and molecular weight averages in minimum time. 

The batch suspension polymerization system considered in the present study, is schematically shown in Figure 1. It consists of a well mixed jacketed vessel. In the suspension polymerization process, liquid styrene is dispersed in the continuous aqueous phase by the combined action of stirring and the use of suspending agents. The reaction takes place in the monomer droplets. For modelling purposes, each droplet can be treated as a small batch bulk polymerization reactor. The heat of polymerization is transferred from the dispersed droplets to the aqueous phase and then to the coolant flowing through the reactor s jacket. 

The predictive capabilities of the new kinetic model were demonstrated by a direct comparison of model predictions with experimental measurements on monomer conversion, number and weight average molecular weights and molecular weight distribution. The polymerization was carried at different temperatures in a batch, bulk polymerization system. In the temperature range of 100 - 150 °C, a chemical initiator (e.g., Dicumyl Peroxide, DCP) was employed in combination with the thermal initiation of styrene. On the other hand, at higher temperatures (150 - 180 °C), the polymerization was initiated exclusively by the thermal initiation mechanism. 

The most common way to use ANN modeling is direct modeling, when output variables are correlated with inputs of the network. For instance, in the batch bulk free radical polymerization of methyl methacrylate, using (a,a -azobis(isobutyronitrile) as initiator, monomer conversion, polymerization degrees, and reaction viscosity are related to the working conditions (temperature, initial concentrations of reactants, and initiator and time) (Figiue 12.3a). 

The preform-drawing method is a batch process where a polymeric preform is fabricated first, which is then followed by thermal drawing of the preform into the fiber. A schematic diagram of the process is shown in Figure 5.1. In this method, a cylindrical polymer rod consisting of a core and cladding layers, usually prepared by radical polymerization in bulk under a clean environment, is positioned vertically in the middle of the furnace where its lower portion is heated locally to the drawing temperature. The furnace temperature appropriate for the preform is... 

Lousberg HHA, Boelens HFM, Le Comte EP, Hoefsloot HCJ, Smilde AK. On-line determination of the conversion in a styrene bulk polymerization batch reactor using near-infrared spectroscopy. J Appl Polym Sci 2002 84 90-98. 

Example 12.1 The maximum possible temperature rise in a polymerizing batch may be calculated by assuming that no heat is transferred from the system (adiabatic assumption). Estimate the adiabatic temperature rise for the bulk polymerization of styrene, given that Af/p = — 16.4kcal/mol and monomer molecular weight = 104. 

It is necessary to use the weak inhibitor method for controlling the molecular weight of polymethyl methacrylate in batch bulk polymerization. At 60°C kp is 580 L/mol sec, whereas the value of for terephthonitrile is 31.2. Assume that [I2] = lO mol/L and find in problem. 

Three bulk polymerization processes are commercially important for the production of methacrylate polymers batch cell casting, continuous casting, and continuous bulk polymerization. Approximately half the worldwide production of bulk polymerized methacrylates is in the form of molding and extmsion compounds, a quarter is in the form of cell cast sheets, and a quarter is in the form of continuous cast sheets. 

Solution Polymerization. In this process an inert solvent is added to the reaction mass. The solvent adds its heat capacity and reduces the viscosity, faciUtating convective heat transfer. The solvent can also be refluxed to remove heat. On the other hand, the solvent wastes reactor space and reduces both rate and molecular weight as compared to bulk polymerisation. Additional technology is needed to separate the polymer product and to recover and store the solvent. Both batch and continuous processes are used. 

Bead Polymerization Bulk reaction proceeds in independent droplets of 10 to 1,000 [Lm diameter suspended in water or other medium and insulated from each other by some colloid. A typical suspending agent is polyvinyl alcohol dissolved in water. The polymerization can be done to high conversion. Temperature control is easy because of the moderating thermal effect of the water and its low viscosity. The suspensions sometimes are unstable and agitation may be critical. Only batch reaciors appear to be in industrial use polyvinyl acetate in methanol, copolymers of acrylates and methacrylates, polyacrylonitrile in aqueous ZnCh solution, and others. Bead polymerization of styrene takes 8 to 12 h. 

Polylactides, 18 Poly lactones, 18, 43 Poly(L-lactic acid) (PLLA), 22, 41, 42 preparation of, 99-100 Polymer age, 1 Polymer architecture, 6-9 Polymer chains, nonmesogenic units in, 52 Polymer Chemistry (Stevens), 5 Polymeric chiral catalysts, 473-474 Polymeric materials, history of, 1-2 Polymeric MDI (PMDI), 201, 210, 238 Polymerizations. See also Copolymerization Depolymerization Polyesterification Polymers Prepolymerization Repolymerization Ring-opening polymerization Solid-state polymerization Solution polymerization Solvent-free polymerization Step-grown polymerization processes Vapor-phase deposition polymerization acid chloride, 155-157 ADMET, 4, 10, 431-461 anionic, 149, 174, 177-178 batch, 167 bulk, 166, 331 chain-growth, 4 continuous, 167, 548 coupling, 467 Friedel-Crafts, 332-334 Hoechst, 548 hydrolytic, 150-153 influence of water content on, 151-152, 154... 

Classification of Processes and Reactors. Most styrene polymers are produced by batch suspension or continuous mass processes. Some are produced by batch mass processes. Mass in this sense includes bulk polymerization of the polymer... 

The second large-scale process was the batch mass suspension process. Monsanto did the pioneer work on this (41). In this process, prepolymerization is carried out in bulk and main polymerization in suspension the latter is taken to conversions of over 99%. In contrast to the continuous mass process, peroxide starters are used in order to achieve a high conversion at tolerable reaction times. Figure 3 shows a basic flow diagram of such a plant. A detailed discussion of advantages and disadvantages of the two processes can be found in R. Bishop s monograph published in 1971 (42), and it is continued in a paper by Simon and Chappelear in 1979 (43). It was a decisive factor for the economic success of impact polystyrene that these processes had been completely developed and mastered in theory and practice. 

This was derived assuming uniform concentration because good mixing is important for this relationship to hold. It also assumes a constant temperature. Both these assumptions are only approached in most batch systems. Further, stirring becomes more difficult as conversion increases so that both control of localized temperature and concentration become more difficult. In reality, this relationship holds for only a few percentage points of conversion. Overall, temperature is a major concern for vinyl polymerizations because they are relatively quite exothermic. This is particularly important for bulk polymerizations. This, coupled with the general rapid increase in viscosity, leads to the Trommsdorff-like effects. 

A bnlk polymerization reactor can be as simple as a tube into which the reactants are fed and from which the polymer mixture emerges at the end it can be more of a traditional, continnons stirred-tank reactor (CSTR), or even a high-pressure autoclave-type reactor (see Figure 3.21). A bulk polymerization process need not be continuous, but it should not be confnsed with a batch reaction. There can be batch bnlk polymerizations jnst as there are continnons bulk polymerizations processes. 

Although the bulk of chemical manufacture is done on a continuous basis, there are sectors of the industry in which batch reactors are essential, notably for fermentations and polymerizations. Such plants may employ as many as 100 batch reactors. The basic processing steps include the charging of several streams, bringing up to reaction temperature, the reaction proper, maintenance of reaction temperature, discharge of the product, and preparation for the next batch. Moreover, the quality of the product depends on the accuracy of the timing and the closeness of the control. 

The production of vinyl chloride monomer is only a part of PVC production. Polymerization of the monomer completes the process. Commercially, it is a batch operation by one of three methods suspension, emulsion, or bulk. In all three methods, the chemical reaction is a free radical-initiated chain reaction. Peroxides or redox systems generally are used to provide the initial free radicals. 

Example 13.6 The following data were obtained using low-conversion batch experiments on the bulk (solvent-free), free-radical copolymerization of styrene (X) and acrylonitrile (Y). Determine the copolymer reactivity ratios for this polymerization. 

Emulsion Polymerization in a CSTR. Emulsion polymerization is usually carried out isothermally in batch or continuous stirred tank reactors. Temperature control is much easier than for bulk or solution polymerization because the small (. 5 Jim) polymer particles, which are the locus of reaction, are suspended in a continuous aqueous medium as shown in Figure 5. This complex, multiphase reactor also shows multiple steady states under isothermal conditions. Gerrens and coworkers at BASF seem to be the first to report these phenomena both computationally and experimentally. Figure 6 (taken from ref. (253)) plots the autocatalytic behavior of the reaction rate for styrene polymerization vs. monomer conversion in the reactor. The intersection... 

The rational design of a reaction system to produce a desired polymer is more feasible today by virtue of mathematical tools which permit one to predict product distribution as affected by reactor type and conditions. New analytical tools such as gel permeation chromatography are beginning to be used to check technical predictions and to aid in defining molecular parameters as they affect product properties. The vast majority of work concerns bulk or solution polymerization in isothermal batch or continuous stirred tank reactors. There is a clear need to develop techniques to permit fuller application of reaction engineering to realistic nonisothermal systems, emulsion systems, and systems at high conversion found industrially. A mathematical framework is also needed which will start with carefully planned experimental data and efficiently indicate a polymerization mechanism and statistical estimates of kinetic constants rather than vice-versa. 

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