Polymerization continued batch

Manufacturing Processes. The three manufacturing processes already mentioned (continuous mass polymerization, batch suspension and emulsion polymerization) continued to compete with each other after 1945. Whereas the third one gradually decreased in importance, the other two were given preference in... 

As in any type of polymerization, a batch reaction is not as commercially attractive as a continuous polymerization process that can produce larger quantities of polymer in the same amount of time. The first continuous polymerizations in C02 were reported (Charpentier et al., 1999) with the monomers acrylic acid and vinylidene fluoride. The vinylidene fluoride polymerization was extensively studied at 75 °C, 275 bar. The polymerizations were run with residence times that varied between 15 and 40 min in a continuous-stirred-tank reactor before collection in a filter. The maximum rate of polymerization was determined to be 19 x 10 5 mol L-1s-1. Future research will move toward continuous removal of polymer, recycling of unreacted monomer and C02, and expansion to other monomers. 

While vinyl acetate is normally polymerized in batch or continuous stirred tank reactors, continuous reactors offer the possibility of better heat transfer and more uniform quality. Tubular reactors have been used to produce polystyrene by a mass process (1, 2), and to produce emulsion polymers from styrene and styrene-butadiene (3 -6). The use of mixed emulsifiers to produce mono-disperse latexes has been applied to polyvinyl toluene (5). Dunn and Taylor have proposed that nucleation in seeded vinyl acetate emulsion is prevented by entrapment of oligomeric radicals by the seed particles (6j. Because of the solubility of vinyl acetate in water, Smith -Ewart kinetics (case 2) does not seem to apply, but the kinetic models developed by Ugelstad (7J and Friis (8 ) seem to be more appropriate. 

Polystyrene can be easily prepared by emulsion or suspension techniques. Harkins (1 ), Smith and Ewart(2) and Garden ( ) have described the mechanisms of emulsTon polymerization in batch reactors, and the results have been extended to a series of continuous stirred tank reactors (CSTR)( o Much information on continuous emulsion reactors Ts documented in the patent literature, with such innovations as use of a seed latex (5), use of pulsatile flow to reduce plugging of the tube ( ), and turbulent flow to reduce plugging (7 ). Feldon (8) discusses the tubular polymerization of SBR rubber wTth laminar flow (at Reynolds numbers of 660). There have been recent studies on continuous stirred tank reactors utilizing Smith-Ewart kinetics in a single CSTR ( ) as well as predictions of particle size distribution (10). Continuous tubular reactors have been examined for non-polymeric reactions (1 1 ) and polymeric reactions (12.1 31 The objective of this study was to develop a model for the continuous emulsion polymerization of styrene in a tubular reactor, and to verify the model with experimental data. 

Good mixing is important to ensure uniform temperatures and prevent the occurrence of localized inhomogenieties. It is difficult to generalize about mixing in bulk polymerizations in batch reactors, because the viscosity and density of the reaction medium is continuously changing as the reaction proceeds. The... 

A continuous process may include batch make-up of minor reagents, such as the catalyst for a polymerization process. Batch flows into a continuous process are usually labeled Normally no flow and show the flow rates that will be obtained when the stream is flowing. It is these instantaneous flow rates that govern the equipment design, rather than the much lower time-averaged flow rates. 

Dube, M.A. Soares, J.B.P. Penlidis, A. Hamielec, A.E. Mathematical modeling of multicomponent chain-growth polymerizations in batch, semibatch, and continuous reactors a review. Ind. Eng. Chem. Res. 1997, 36, 966-1015. 

Continuous solvent casting Batch in situ polymerization Continuous in situ polymerization... 

Polymerization is performed in solution either batchwise or continuously. Batch reaction takes place in a variety of ways. The batch may be mixed and held at a constant temperature while running for a given time, or for a time dictated by tests made during the progress of the run. Alternatively, termination is dictated by a predetermined decrease in pressures following monomer consumption. A continuous reaction train, on the other hand, consists of a number of reactors, usually up to about ten, with the earlier ones overflowing into the next and the later ones on level control, with transfer from one to the next by pump. 

Before considering the two classes of batchwise process in detail, it is important to have a clear understanding of the simple distinction between them. In batch processes all reactants are completely added to the reaction vessel at the start of the polymerization, whereas in semi-batch processes (also referred to as semi-continuous batch processes) only part of the total reaction formulation is introduced at the beginning of the reaction, the remainder being added, according to a predetermined schedule, during the course of the polymerization. Batch processes are of limited versatility for manufacture of latexes and mainly find use in academic studies and simple evaluations of reaction formulations. By comparison, semi-batch processes are very versatile and are widely used, both industrially and in academic laboratories. 

Caprolactam for use as fibers is hydrolytically polymerized in batches as 80%-90% aqueous solutions with 0.2%-0.5% acetic acid and ethylene diamine at 250-280° C. The acetic acid acts as chain stabilizer (see above). The ethylene diamine increases the amine equivalent of PA 6 so that mixed weaves of Perlon and wool can be evenly dyed. The water is removed as steam in the polymerization progresses. Caprolactam is also polymerized continuously by what is known as the VK process (vereinfacht-A ontinuierliche, or simplified continuous, process). This process is carried out without pressure with, for example, 6-amino caproic acid or AH salt as initiator. In contrast to the production of nylon 6,6, this process can proceed continuously the melt can be directly spun from the reactor. Polyamide 6 fibers have good properties but they yellow slowly since pyrrole structures are formed at the chain ends. 

For commercial PBT polymerization, both batch process and continuous process can be used. When a variety of different grades of PBT are needed, a batch process is preferred however, for large commercial production of PBT of more than 20,000 metric ton capacities, a continuous process is more economical. 

Many solution polymerizations are batch processes. Contrary to this, reactive extrusion is a continuous process. An important economic advantage of a continuous process is its relative simplicity, resulting in less operator units necessary to run the plant. Moreover, continuous processes require no large storage vessels as they are necessary for a batch process. 

VF can be polymerized by a number of techniques, including suspension, bulk, and emulsion polymerizations in batch and continuous modes. Graft and radiation-induced polymerizations of VF have also been reported. 

Table IX gives the recipe used for these pol3nnerizations. The polybutyl acrylate seed latex was prepared by heating the ingredients for 24 hours at 70° the styrene, water, and potassium persulfate were then added and polymerized for another 8 hours at 70°. Three methods of adding the styrene monomer were used in the second-stage polymerization (i) batch polymerization (ii) equilibrium swelling of the seed latex particles followed by batch pol3nneriza-tion (iii) starved semi-continuous pol3nnerization. The particle growth was essentially stoichiometric, i.e., no new particles were initiated. All three latexes formed transparent continuous films upon drying, whereas a 50 50 mixture of polybutyl acrylate and...

Emulsion Polymerization in Batch Generally, it comprises of three stages [40,41] interval I, in which free radicals generated in the aqueous phase enter micelles and form polymer particles, interval II where particles grow as they absorb monomer from monomer droplets, until their depletion, and interval III, where polymerization continues within the particles until the monomer consumption. 

Hamielec AE, MacGregor IF, Penlidis A. Multicomponent free-radical polymerization in batch, semi-batch and continuous reactors. Macromol Chem Macromol Symp 1987 10/11 521-570. 

Example 9.11 Which type of isothermal reactor would produce the narrowest possible distribution of chain lengths in a free-radical addition polymerization continuous stirred tank reactor (CSTR, or backmix), batch (assume perfect stirring in each of the previous), plug-flow tubular, or laminar-flow tubular ... 

Owing to the broad interest of such particles not just for specialty applications, a huge amount of work has been developed in order to elaborate surface functionalized latex particles. In that purpose, it is possible to deal with the use of molecular or macromolecular species (bearing the functionality) along with the polymerization protocol (batch, semi-continuous, core-sheU, shot-growth etc.) (Pichot, 1995 Pichot Delair, 1999). 

The emulsion polymerization process (batch or continuous) is widely used for producing ABS because various grades of ABS resins can be manufactured. In a continuous process, two to six reactors are used in series with rubber latex feed added either to the first reactor or the first two reactors. In a typical ABS emulsion process, the styrene/acrylonitrile copolymer (SAN) and polybutadiene (PBL) are separately prepared by emulsion pro-... 

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