Semibatch Aqueous‐Solution Polymerization of Acrylic Acid: Simultaneous Control of Molar Masses and Reaction Temperature

Minari, Roque Javier; Caceres, Gerardo; Mandelli, Paola; Yossen, Mariana Matilde; González‐Sierra, Manuel; Vega, Jorge Rubén; Gugliotta, Luis Marcelino

doi:10.1002/mren.201000059

Cited by 22 publications

(15 citation statements)

References 20 publications

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“…Figure compares the experimental and simulated evolutions of x f , pH,

{\overset{M}{true}}_{normaln}

, and

{\overset{M}{true}}_{normalw}

for CR and ME‐based experiments. In CR, bimolecular termination mainly controls the MM . The incorporation of ME contributes to reduce the MM.…”

Section: Resultsmentioning

confidence: 99%

“…The final samples were also characterized by gel phase 13 C NMR (Bruker Advance II 300 spectrometer, 75 MHz) in order to quantify the mean branching degree (BD) and elucidate the main kinetic mechanisms involved in the reactions . NMR characterization was carried out on final PAA liquid samples (0.4 mL) containing D 2 O (0.5–0.1 mL) in 5 mm NMR tubes.…”

Section: Methodsmentioning

confidence: 99%

“…The developed mathematical model is based on that presented by Minari et al, and describes the kinetics of the free radical solution polymerization of AA. An overview of the relevant reactions is presented in Table .…”

Section: Kinetics and Mathematical Modelmentioning

confidence: 99%

“…An overview of the relevant reactions is presented in Table . Inherent assumptions in the polymerization mechanism are: i) thermal decomposition of KPS (Equation (2)), ii) generation of secondary radicals produced by the reaction of the monomer with sulfate radicals [the first and second indexes between brackets in

{normalR}_{\sec}^{•} (s, l)

indicates the number of quaternary carbons linked to a short (s) branch and to a long (l) branch, respectively] (Equation (3)); iii) the generated secondary radicals can propagate with AA (Equation (4)), or can terminate (by combination) between them (Equation (5)), iv) chain transfer reaction between the secondary radicals and the CTA (Equation (6)), v) redox decomposition of the water soluble CTAs containing –SH groups (TGA and ME) with KPS, when they are employed, generating sulfate and mercaptan radicals (

{RS}^{•} or {normalR}_{CTA}^{•}

) (Equation (7)), vi) generation of CTA radicals by reaction of sulfate radicals with CTA (Equation (8)), vii) propagation of CTA radicals produced by Equations (6–9), viii) intramolecular H transfer (backbiting), generating more stable radicals, meaning that the radical end (secondary radical) isomerizes to an internal position (tertiary radical) during propagation, giving place to a new short branch point (Equation (10)); ix) intermolecular transfer to the polymer produced by the abstraction of a tertiary H of PAA, where tertiary radicals are generated in the polymer chain, thus generating a new long branch point (Equation (11)), x) propagation of tertiary radicals with AA (Equation (12)); and xi) termination of SPR and MCR by bimolecular combination (Equation (13)), and termination by disproportionation between two MCR, and (intra and inter‐) abstraction of

{normalR}_{tert}^{normal•}

negligible. Note that in Equation (8) some sulfate radicals are deactivated by transferring the radical function to the –SH ending CTA, thus generating a new radical

{normalR}_{CTA}^{normal•}

that can also initiate propagation by reacting with a monomer molecule in Equation (9) (thiol‐ene reaction).…”

Section: Kinetics and Mathematical Modelmentioning

confidence: 99%

“…In a previous work, an AA feeding strategy was proposed to produce PAA of controlled MM (between 10 and 200 kDa), at complete AA conversion and under safe conditions . With this strategy, a high concentration of potassium persulfate (KPS) was required to produced PAA of relatively low MM, while no significant MM reduction was obtained when the KPS concentration exceeded a limit of 3% weight based on monomer . On the other hand, CTAs are normally used for reducing the MM, but water soluble CTAs have been mainly investigated in batch processes .…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

A Safety Strategy for Producing Poly(Acrylic Acid) of Low Molar Mass

Montenegro

Gutierrez

Vaillard

et al. 2017

Macro Reaction Engineering

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The synthesis of poly(acrylic acid) (PAA) of low molar mass under safe conditions is difficult due to the high polymerization rate of acrylic acid (AA) and the fast heat generation. The aqueous‐solution “semibatch” polymerization of non‐ionized AA in almost starved conditions involves high initiator loads when low molar masses are required. This article proposes the simultaneous feeding of AA and nonconventional chain transfer agents (CTA) as a strategy aimed at controlling both the molar masses and the generated heat rate. Three CTAs are investigated: 2‐mercaptoethanol, thioglycolic acid, and isopropyl alcohol. Even when PAA of relatively low molar mass can be produced by adequately selecting the flow rates and concentrations of both AA and CTA, it is found that the nature of CTA can have a significant effect on the polymerizations kinetics. The mechanisms responsible for these effects are discussed with the help of a representative mathematical model.

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“…Figure compares the experimental and simulated evolutions of x f , pH,

{\overset{M}{true}}_{normaln}

, and

{\overset{M}{true}}_{normalw}

for CR and ME‐based experiments. In CR, bimolecular termination mainly controls the MM . The incorporation of ME contributes to reduce the MM.…”

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Kinetics and Mathematical Modelmentioning

confidence: 99%

{normalR}_{\sec}^{•} (s, l)

{RS}^{•} or {normalR}_{CTA}^{•}

{normalR}_{tert}^{normal•}

negligible. Note that in Equation (8) some sulfate radicals are deactivated by transferring the radical function to the –SH ending CTA, thus generating a new radical

{normalR}_{CTA}^{normal•}

that can also initiate propagation by reacting with a monomer molecule in Equation (9) (thiol‐ene reaction).…”

Section: Kinetics and Mathematical Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

A Safety Strategy for Producing Poly(Acrylic Acid) of Low Molar Mass

Montenegro

Gutierrez

Vaillard

et al. 2017

Macro Reaction Engineering

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Measuring and modelling the peculiarities of aqueous‐phase radical polymerization

Preusser

Hutchinson

2016

Can J Chem Eng

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The application of specialized pulsed-laser techniques has led to a vastly improved understanding of the kinetics of aqueous phase solution radical polymerization of water-soluble monomers. Propagation rate coefficients vary significantly with monomer concentration, an effect unique to the aqueous environment. In addition, the formation and reaction of mid-chain radicals affects polymerization rates, and thus polymer molar masses, in acrylamide and acrylic acid systems. This perspective provides an overview of these mechanistic peculiarities, which have been captured in kinetic models developed to represent the homopolymerizations of N-vinyl pyrrolidone, N-vinyl formamide, methacrylic acid, acrylic acid, and acrylamide over a wide range of conditions. The batch studies demonstrate the importance of these effects in aqueous polymerization and the validity of the rate coefficients taken from the independent kinetic studies.

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SEC Analysis of Poly(Acrylic Acid) and Poly(Methacrylic Acid)

Lacı́k

Stach

Kasák

et al. 2014

Macro Chemistry & Physics

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The accurate characterization of molar-mass distributions of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) by size-exclusion chromatography (SEC) is addressed. Two methods are employed: direct aqueous-phase SEC on P(M)AA and THF-based SEC after esterifi cation of P(M)AA to the associated methyl esters, P(M)MA. P(M)AA calibration standards, P(M)AA samples prepared by pulsed-laser polymerization (PLP), and PAA samples prepared by reversible addition-fragmentation chain transfer (RAFT) are characterized in a joint initiative of seven laboratories, with satisfactory agreement achieved between the institutions. Both SEC methods provide reliable results for PMAA. In the case of PAA, close agreement between the two SEC methods is only observed for samples prepared by RAFT polymerization with weightaverage molar mass between 80 000 and 145 000 g mol −1 and for standards with peak molar masses below 20 000 g mol −1 . For standards with higher molar masses and for PLP-prepared PAA, the values from THF-based SEC are as much as 40% below the molar masses determined by aqueous-phase SEC. This discrepancy may be due to branching or degradation of branched PAA during methylation. While both SEC methods can be recommended for PMAA, aqueous-phase SEC should be used for molar-mass analysis of PAA unless the sample is not branched.

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Semibatch Aqueous‐Solution Polymerization of Acrylic Acid: Simultaneous Control of Molar Masses and Reaction Temperature

Cited by 22 publications

References 20 publications

A Safety Strategy for Producing Poly(Acrylic Acid) of Low Molar Mass

A Safety Strategy for Producing Poly(Acrylic Acid) of Low Molar Mass

Measuring and modelling the peculiarities of aqueous‐phase radical polymerization

SEC Analysis of Poly(Acrylic Acid) and Poly(Methacrylic Acid)

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