On the Modeling of Acrylic Acid Copolymerization in an Aqueous Solution: A Modular, Integrated Approach (original) (raw)
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European Polymer Journal, 2016
A kinetic model based on method of moments, balance of species and sequences and numerical fractionation was developed for acrylic acid-TMPTA copolymerization. Solution copolymerizations of acrylic acid with trimethylolpropane triacrylate (TMPTA), initiated by sodium persulfate, were carried out at 55°C. The model was compared with a different approach from literature and validated with experimental data from present work. It was a found an acrylic acid propagation rate coefficient at 6000 L mol À1 s À1 for the studied conditions. The simulations were successfully performed with a maximum number of generations in the range 3-5. The model was able to provide fair predictions for the studied experiments and additional information about the dead polymer chains formed, such as gel fraction, molecular weight distribution and concentration of cyclic chains.
The radical polymerization of methacrylic acid, acrylic acid and acrylamide in aqueous solution has been investigated. Detailed kinetic models for both acrylic acid, AA, and methacrylic acid, MAA, have been developed applying the program PREDICI TM. Good representation of experimental conversion vs. time profiles and molar mass distributions as well as, in case of AA, the branching level could be achieved. The polymerization of MAA has been studied at 35 and 50 °C with focus on the influence of 2-mercaptoethanol, ME, as chain transfer agent, CTA, on reaction kinetics. The rate coefficient of transfer to CTA, tr,CTA , k was measured for different monomer levels by the Mayo and the chain length distribution procedure. The ratio of tr,CTA k to the propagation rate coefficient, p k , is independent of monomer to water ratio while both rate coefficients increase by approximately one order of magnitude in passing from bulk to dilute aqueous solution. It was found that addition of CTA reduces the rate of MAA polymerization by two effects on t. k At negligible monomer conversion, t k increases towards higher content of CTA, because average chain length is reduced by the CTA. Chain-length dependent termination may be represented by adopting the composite model, which is a well-established theory to describe chain-length dependency of termination of macroradicals of identical size. The composite model could be applied to average chain length. The reduction of t k towards higher degrees of monomer conversion
Industrial & Engineering Chemistry Research, 2020
The kinetics of batch aqueous-phase solution radical copolymerization of an ionizable monomer acrylic acid (AA) with a cationic monomer 2-(methacryloyloxyethyl)trimethylammonium chloride (TMAEMC) to produce polyelectrolytes is investigated using in situ NMR to follow both overall monomer conversion and comonomer composition. The rate of monomer consumption was dependent on the initial weight fraction of monomer, varied between 0.05 and 0.40, and initial comonomer composition. The unreacted monomer is depleted in TMAEMC with increasing conversion for polymerizations conducted with an initial TMAEMC molar fraction of less than 90%. AA was preferentially incorporated above this level, with the azeotropic behavior dependent on the total monomer concentration in the aqueous solution. Semibatch copolymerizations demonstrate that a constant copolymer composition can be obtained under specific experimental conditions. A model of AA− TMAEMC copolymerization is formulated that predicts polymerization rates and average polymer molar masses, as well as captures the influence of counterion concentration on copolymer composition.
Macromolecules, 2002
In the present study a comprehensive mathematical model for diffusion-controlled freeradical copolymerization reactions is developed. Termination and propagation rate constants as well as initiator efficiency are expressed in terms of a reaction-limited term and a diffusion-limited one. The contribution of the latter term to the apparent rate constants is described in terms of the diffusion coefficients of the corresponding species (e.g., polymer chains, monomers, primary radicals), calculated using the generalized free-volume theory of Vrentas and Duda for a ternary system, and an effective reaction radius. The predictive capabilities of the present model are demonstrated by simulating three free-radical polymerization systems, namely, the bulk copolymerizations of styrene-methyl methacrylate, styrene-acrylonitrile, and p-methylstyrene-methyl methacrylate. It is shown that the model predictions are in excellent agreement with experimental data on monomer conversion, average molecular weights, and copolymer composition, reported in the open literature under various experimental conditions.
Acrylic Acid/Vinyl Acetate Suspension Copolymerizations. 2. Modeling and Experimental Results
Industrial & Engineering Chemistry Research, 2004
The present work presents experimental and modeling results for both vinyl acetate (VAc) homopolymerizations and VAc/acrylic acid (AA) copolymerizations performed in suspension. It is shown that the VAc homopolymerization presents a maximum conversion limit that cannot be surpassed with additional feed of an initiator. This maximum conversion limit is believed to be due to viscosity effects that characterize the well-known gel effect. A correlation based on the free-volume theory is then proposed for the gel effect. Because the molecular weight averages obtained for samples of the produced poly(vinyl acetate) are very high, the existence of strong diffusion limitations in the reaction medium is very likely. A mathematical model is developed and shown to describe very well the dynamic conversion and molecular weight profiles obtained experimentally. The model is then extended to describe VAc/AA copolymerizations, considering the AA partition between the organic and aqueous phases, which is a fundamental point for the successful description of both dynamic conversion and copolymer composition profiles. The monomer reactivity ratios and the AA partition coefficients between the organic and aqueous phases are evaluated experimentally. The proposed model is validated with experimental data obtained for monomer conversion, copolymer composition, and molecular weight averages of polymer samples.
Optimal estimation of reactivity ratios for acrylamide/acrylic acid copolymerization
Journal of Polymer Science Part A: Polymer Chemistry, 2013
Reactivity ratios for the important acrylamide (AAm)/acrylic acid (AAc) copolymerization system exhibit considerable scatter in previously published literature, and therefore, there is a need for more definitive values for these reactivity ratios. An appropriate methodology, based on the error-in-variables-model (EVM) framework along with a direct numerical integration procedure, is applied in order to determine reliable reactivity ratios. The reliability of the results is confirmed with extensive and independent replication. Furthermore, via an EVM-based criterion for the design of experiments using mechanistic models, optimal feed compositions are calculated, and from these optimal reactivity ratios are estimated for the first time (r AAm 5 1.33 and r AAc 5 0.23) based on information from the full conversion range. V
Processes
The radical homopolymerization kinetics of 3-(methacryloylaminopropyl) trimethylammonium chloride (MAPTAC) and its batch copolymerization with nonionized acrylic acid (AA) in aqueous solution are investigated and modeled. The drift in monomer composition is measured during copolymerization by in situ NMR over a range of initial AA molar fractions and monomer weight fractions up to 0.35 at 50 °C. The copolymer becomes enriched in MAPTAC for monomer mixtures containing up to 60 mol% MAPTAC, but is enriched in AA for MAPTAC-rich mixtures; this azeotropic behavior is dependent on initial monomer content, as electrostatic interactions from the cationic charges influence the system reactivity ratios. Models for MAPTAC homopolymerization and AA-MAPTAC copolymerization are developed to represent the rates of monomer conversion and comonomer composition drifts over the complete range of experimental conditions.
Advanced manufacturing, 2015
The interest for models on a polymerization plant of acrylonitrile is (a) to predict the maximum capacity of an industrial reactor, (b) to increase the robustness of the process by defining stable operational conditions, and (c) to help the development of new copolymers. Using design of experiments (DOE), the copolymerization and terpolymerization of acrylonitrile with vinyl acetate and methyl-2 propene-1 sodium sulfonate were studied in aqueous suspension initiated by the redox system KClO 3 /NaHSO 3 /Fe 2þ. The molar fraction of the copolymers and terpolymers produced ranged from 93.0 to 98.2% for acrylonitrile, from 1.7 to 7.0% for vinyl acetate, and from 0.0 to 0.5% for sodium sulfonate. The mass molecular weight ranged from 76 000 to 419 000 g/gmol. Experiments were done in a pilot plant, consisting of 227 L of continuously stirred tank reactor, stripping and recycle systems, drum filter, and band dryer. The experiments were conducted according to a fractioned factorial 2 823 matrix with five central points. A statistic kinetic model was built, which explains well the copolymerization and terpolymerization of acrylonitrile. This model was applied with success on an industrial polymerization reactor, showing the potential of production increase, confirming the robustness of the process, and supporting the development of new copolymers of acrylonitrile. The focus of this paper is the development of a kinetic statistical polymerization model, the criteria to interrupt the regression analysis, and its application in the understanding of the polymerization phenomena.