Semibatch Emulsion Copolymerization Research Articles

Photon Density Wave spectroscopy to monitor the particle size in seeded semibatch emulsion copolymerization reactions

The performance of Photon Density Wave spectroscopy (PDW) is assessed to inline monitor the particle size during the seeded semibatch emulsion copolymerizations of methyl methacrylate, butyl acrylate, methacrylic acid (MMA/BA/MAA = 51/47/2 wt% composition) with particle size and solids content ranges relevant in industrial formulations. Moreover, the suitability of the technique to early detect some of the most probable deviations, such as particle aggregation and secondary nucleation, is studied. It is shown that the PDW can be successfully used to inline monitor the reduced scattering coefficient, and consequently the particle size evolution in emulsion polymerization reactions for a broad range of particle sizes and solids contents. Nevertheless, for particle sizes higher than 350 nm and solids content above 40 %, the low signal to noise ratio together with the characteristic multiple solutions regime of the theoretical reduced scattering versus the particle size curve, produces uncertainties in the determination of the particle size by PDW.

Online Monitoring of the Particle Size in Semibatch Emulsion Copolymerization Using Spatially Resolved Spectroscopy and Raman Spectroscopy

Spatially resolved spectroscopy (SRS), based on near-infrared, is better adapted to extract physical information (here, particle size) than classical spectroscopy in heterogeneous media (suspension...

High pressure semibatch emulsion and miniemulsion copolymerization of vinyl acetate and ethylene

AbstractThis study presents the experimental study of semibatch emulsion and miniemulsion copolymerization of vinyl acetate (VAc) and ethylene to vinyl acetate‐ethylene (VAE) copolymer at 60°C and 80–300 psig. In the miniemulsion copolymerization, a water‐soluble initiator (K2S2O8) is used and VAc miniemulsion is prepared in presence of surfactant and cosurfactant using a sonicator or a high‐shear homogenizer. Then, ethylene gas is supplied to the reactor at constant partial pressure. In a miniemulsion process, the mass transfer limitations of VAc from monomer droplets to the aqueous phase, and to micelles or polymer latex particles that are present in conventional macro‐emulsion polymerization can be eliminated and the transfer of ethylene dissolved in the aqueous phase to the miniemulsion droplets is the major ethylene transport process for the polymerization. The experimental data show that the amount of ethylene incorporation into the copolymer is higher in miniemulsion polymerization than in emulsion polymerization. The ethylene pressure has been found to have a strong impact on the ethylene incorporation into the copolymer phase in both emulsion and miniemulsion copolymerizations but the increase is more pronounced in miniemulsion case. The VAE copolymer latex particles prepared by miniemulsion polymerization exhibited higher storage stability than those prepared by macro‐emulsion polymerization.

Base case simulation of a semi-batch emulsion copolymerization process: application to styrene/ butadiene system

It has been long recognized that emulsion polymerization is a complex heterogeneous process involving transport of monomers, free radicals, and other species between aqueous phase and organic phase. Though there are a number of models available in the literature, most of them deal only with specific aspects in emulsion polymerization and are far from being general. To simulate this complicated process and to achieve an adequate level of understanding, a Polymers Plus software from Aspen Technology. Inc. was used. The objective of this work is to illustrate the principle of use of Polymers Plus, simulate, and analyze the free-radical seeded emulsion copolymerization of styrene­butadiene process model in a semi-batch reactor. The base case simulation can be used to gain process understanding by analyzing how process variables and operating conditions during the course of a semi-batch reactor affect the product quality.Keywords: Polymers Plus, Emulsion Copolymerization, Simulation, Semi Batch Reactor, Styrene/ butadiene AbstrakTelah diketahui sejak lama bahwa polimerisasi emulsi merupakan sebuah proses heterogen yang kompleks, yang meliputi perpindahan monomer, radikal bebas, dan senyawa lainnya dalam fasa air dan fasa organik. Walaupun dalam literatur terdapat berbagai model, sebagian besar hanya membahas tentang aspek-aspek khusus dalam polimerisasi emulsi yang belurn berlaku umum. Untuk melakukan simulasi serta meningkatkan pemahaman tentang proses yang kompleks ini, digunakan perangkat lunak Polymers Plus dari Aspen Technology, Inc. Penelitian ini bertujuan untuk memberikan ilustrasi tentang prinsip penggunaan Polymers Plus serta melakukan simulasi dan analisis tentang model untuk proses kopolimerisasi emulsi styrene-butadiene dengan free radical seeded dalam reaktor semi batch. Simulasi ini dapat digunakan untuk memperoleh pemahaman proses dengan menganalisis pengaruh variabel-variabel proses dan kondisi operasi dalam reaktor semi batch terhadap kualitas produk.Kata Kunci: Polymers Plus, Kopolimerisasi Emulsi, Simulasi, Reaktor Semi Batch, Stiren/ butadien

Bringing the On‐Line Control and Optimization of Semibatch Emulsion Copolymerization to the Pilot Plant

Due to hardening competition and increased focus on resource efficiency, efforts are made to develop advanced industrial optimization and control systems with the goal to shift the (semi‐)batch production from recipe‐based to a state‐based approach. This study illustrates the steps needed for the implementation of optimization and on‐line control of semibatch emulsion copolymerization involving the development of process model, its validation and connection with control software, and the realization at pilot plant scale. The process model must be fast and robust enough to provide estimation of the process trajectory reliably and quickly. Moreover, in connection with nonlinear model predictive control (NMPC), the model has to be able to learn from the process and to update parameter values in real time, e.g., due to change of reactor jacket heat transfer. The Cybernetica CENIT software is employed for NMPC. The industrial pilot‐scale semibatch emulsion copolymerization of four comonomers (two of them water soluble) is used for the demonstration of NMPC functionality for: (i) reactor temperature control, (ii) minimization of batch time while preserving product quality, and (iii) minimization of batch duration with desired simultaneous shift in product quality.

Closed-Loop Multitarget Optimization for Discovery of New Emulsion Polymerization Recipes.

Self-optimization of chemical reactions enables faster optimization of reaction conditions or discovery of molecules with required target properties. The technology of self-optimization has been expanded to discovery of new process recipes for manufacture of complex functional products. A new machine-learning algorithm, specifically designed for multiobjective target optimization with an explicit aim to minimize the number of “expensive” experiments, guides the discovery process. This “black-box” approach assumes no a priori knowledge of chemical system and hence particularly suited to rapid development of processes to manufacture specialist low-volume, high-value products. The approach was demonstrated in discovery of process recipes for a semibatch emulsion copolymerization, targeting a specific particle size and full conversion.

Synthesis of a glucose-based surfmer and its copolymerization with n-butyl acrylate for emulsion pressure sensitive adhesives

A glucose-based vinyl surfmer, i.e. butyl polyglucoside maleic acid ester (BGMAH), was synthesized and characterized. Macroemulsion copolymerization of BGMAH with n-butyl acrylate (n-BA) was investigated. The structure of the synthesized BGMAH was confirmed using Fourier transform infrared spectroscopy and a series of 2-D homo- and heteronuclear NMR spectra. Its surfactant properties were confirmed by determination of the critical micelle concentration. The semi-batch emulsion copolymerization was monitored in situ using FTIR spectroscopy. The particle size and its distribution of the emulsions and the gel phase of the polymers were determined. The glass transition temperatures were assessed using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The obtained emulsions were tested for potential application in pressure sensitive adhesives by measuring the adhesion properties of copolymer films (peel strength, tack and shear resistance). It was found that synthetic acrylates could be replaced by the modified glucose in the emulsion polymerization recipe. The adhesion properties were improved when 25wt% of BGMAH was added in reaction mixture.

Film forming hybrid acrylic/ZnO latexes with excellent UV absorption capacity

Acrylic/ZnO hybrid latexes were synthesized through a two-step emulsion polymerization process. First, a hybrid seed was synthesized by miniemulsion polymerization, which contained all the hydrophobically modified ZnO nanoparticles. Subsequently, this hybrid seed was employed in a seeded semibatch emulsion copolymerization yielding high solids content hybrid latexes (40wt%). Cryo-transmission electron microscopy (cryo-TEM) demonstrated that the dispersion of the ZnO nanoparticles in the initial miniemulsion was not homogeneous, which led to a hybrid seed with two populations, polymer particles containing ZnO and pristine polymer particles. After the second step of polymerization barely the same morphology was obtained. Nevertheless, it was proved by electron tomography (3D-TEM) that the ZnO nanoparticles were encapsulated in the polymer particles. The hybrid films containing ZnO presented a superior UV absorption capacity than their counterpart hybrid acrylic/CeO2 prepared following the same strategy.

Kinetic studies of semibatch emulsion copolymerization of methyl methacrylate and styrene in the presence of high intensity ultrasound and initiator

The present work deals with kinetic studies of copolymerization of methyl methacrylate and styrene using ultrasound assisted semibatch emulsion copolymerization in the presence of sodium dodecyl sulfate (emulsifier) and potassium persulfate (external initiator). The effect of temperature, acoustic intensity, initiator loading, surfactant concentration and monomer concentration on the extent of conversion has been investigated. The extent of polymerization was observed to increase with an increase in the temperature, and concentrations of initiator, monomer and surfactant. Further, the initial polymerization rate increased with an increase in the acoustic intensity from 11.2 to 23.1Wcm−2 and then it was found to decrease with a further increase to 33.80Wcm−2. The novelty of this work lies in the fact that there have been only limited kinetic studies for the approach of ultrasound assisted emulsion copolymerization. It has been also established in the present work that the formation of fine and stable monomer droplets, due to the cavitational activity at/near the interface of immiscible monomer phase and subsequent disruption by micro jets, leads to the smaller final polymer particle size and under optimized conditions, it was found to be about 40nm.

Analysis of optimal operation of a fed-batch emulsion copolymerization reactor used for production of particles with core–shell morphology

In this paper dynamic optimization of a lab-scale semi-batch emulsion copolymerization reactor for styrene and butyl acrylate in the presence of a chain transfer agent (CTA) is studied. The mathematical model of the process, previously developed and experimentally validated, is used to predict the glass transition temperature of produced polymer, the number and weight average molecular weights, the monomers global conversion, the particle size distribution, and the amount of residual monomers. The model is implemented within gPROMS environment for modeling and optimization. It is desired to compute feed rate profiles of pre-emulsioned monomers, inhibitor and CTA that will allow the production of polymer particles with prescribed core–shell morphology with high productivity. The results obtained for different operating conditions and various additional product specifications are presented. The resulting feeding profiles are analyzed from the perspective of the nature of emulsion polymerization process and some interesting conclusions are drawn.

Seeded Semibatch Emulsion Copolymerization of Styrene, Butadiene, and Carboxylic Acids in a Pilot Plant Reactor

The seeded semibatch emulsion terpolymerization of styrene–butadiene–acrylic acid is investigated in a pilot plant scale reactor of 151 L. The effect of the styrene–butadiene ratio (S/BD ratio), amount of tertiary-dodecyl mercaptan as chain transfer agent (CTA), and two temperature profiles on the kinetics of the process (solids content, styrene conversion, particle size, and acid partitioning), by-product formation (4-phenyl cyclohexane, 4-PCH, and 4-vinyl cyclohexane, 4-VCH) and the molar mass distribution of the sol and the fraction of gel are studied.

Preparation, properties, and applications of acrylic–polyurethane hybrid emulsions in extinction electrophoresis

ABSTRACTAqueous acrylic–polyurethane hybrid emulsions (PUA) were fabricated by semibatch emulsion copolymerization using a mixture of acrylic (AC) monomers in the presence of an isocyanate terminated polyurethane (PU). The effects of PU content on the morphology of the hybrid emulsions and film properties were here investigated in detail using FT‐IR, UV, TEM, and SEM. TEM images clearly showed that hybrid emulsions exhibited a core‐shell structure before neutralization. However, after neutralization with N,N‐dimethylethanolamine, the typical particles exhibited phase inversion, producing particles with irregular hemispheres shapes and diameters about 0.5 μm. SEM images showed that the film surface became rougher as PU content increased, peaking at 10 wt %, the gloss of this film was 23.1 (60°). The UV transmittance spectra of the PUA hybrid emulsion within a wavelength range 700–200 nm decreased as PU content increased. This was consistent with the changes in the surface roughness of the film. Electrophoresis took place on an aluminum alloy surface and the product was dried at 120°C. The film exhibited excellent mechanical performance due to curing reaction between the NCO group on PU and hydroxyl group on the AC copolymer. The gloss of the film was found to be as low as 4.0 after electrophoresis testing. These films may be useful in practical extinction electrophoresis. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40078.

Synthesis of core–shell acrylic–polyurethane hybrid latex as binder of aqueous pigment inks for digital inkjet printing

Acrylic–polyurethane (PUA) hybrid aqueous emulsion with core–shell structure was prepared via semibatch emulsion copolymerization of the acrylate monomers (AC) in the presence of a commercial polyurethane dispersion as seeds. The core–shell structure of the emulsion was observed by TEM. The particle size and distribution of the emulsion was found to vary drastically with the core–shell ratio. The thermal response properties of emulsion films were measured by DSC, and the results indicated the good compatibility between PA and PU moieties in PUA hybrids. The chemical structures of emulsion films were studied by FTIR, and the surface properties were tested by contact angle measurement. The results supported the idea that the surface of the cast films was rich in polyurethane component. The water resistance of the cast films became better by increasing the AC fraction. The rheological properties of the latex and its utilization as a binder for aqueous pigment inks of digital inkjet printing were thoroughly investigated, indicating that the prepared hybrid emulsion could be used safely for aqueous pigment inks of digital ink jet printing.

Semi-batch emulsion copolymerization of styrene and butyl acrylate for production of high solids content latexes: Experiments and mathematical model

Polymer latexes with high solids content exhibit several advantages such as lower costs of transport and storage and shorter drying and film formation times. To keep the apparent viscosity at satisfactory levels, the particle size distributions should be either broad or multimodal. In the present work, the production of high solid content latexes by emulsion copolymerization of styrene and butyl acrylate was studied in a semi-batch process in which the nucleation of a second population of particles is promoted by the instantaneous (shot) feeding of an additional charge of emulsifiers. Latexes of about 64 wt% of solids with bimodal particle size distributions and reasonably low apparent viscosity were produced. A representative mathematical model for the copolymerization processes that accounts for the changes in the particle size distribution that occurred in the process is presented, tested and validated with the experimental data measured during the experiments.

Semi-Continuous Emulsion Copolymerization of Styrene-Butyl Acrylate with Methacrylic Acid: Screening Design of Experiments

A fractional factorial screening design of experiments was conducted to identify the effects of five variables, i.e., styrene/butyl acrylate ratio, methacrylic acid content, pH, emulsifier content, and chain transfer agent content on various product properties in the monomer-starved semi-batch emulsion copolymerization of styrene/butyl acrylate. The impact of these variables on the methacrylic acid (MAA) distribution in the latex, the average latex particle diameter, the molecular weight and distribution of the polymer products, the glass transition temperature (Tg) of the polymer, and the coating adhesion to a plastic substrate was studied.

Semibatch emulsion copolymerization of butyl acrylate and glycidyl methacrylate: Effect of operating variables

AbstractSemibatch emulsion copolymerization was carried out to prepare poly(butyl acrylate‐co‐glycidyl methacrylate) latexes at 75°C, using potassium persulfate as an initiator, sodium dodecylbenzene sulfonate as an emulsifier and sodium bicarbonate as a buffer. The reaction was conducted in three stages; a further stage (called the steady stage, 2 h) was added to the traditionally stages (i.e., feed and seed stages) to improve considerably the monomer conversion. The monomer conversion and particle size distribution were studied by gravimetric and laser light scattering methods, respectively. The effects of variables such as agitation speed, emulsifier concentration, initiator concentration, feeding rate and comonomers ratio were fully investigated based on the monomer conversion‐time profiles and the particle size distribution to find the optimized copolymerization conditions. Increasing the agitation speed had a negative effect on the monomer conversion, but reduced coagulation of polymer particles. Monomer conversion could be improved by increasing the initiator or emulsifier contents. Feeding rate increased the polymer particle size sharply; however, it showed no significant effect on conversion. The final conversions were as high as 97–99% and they were recognized to be independent of the comonomers ratios employed. Morphological studies by scanning electron microscopy showed nano‐sized isolated particles which were partially aggregated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Batch‐to‐batch control of characteristic points on the PSD in experimental emulsion polymerization

AbstractAn integrated batch‐to‐batch and in‐batch control algorithm to regulate the endpoint particle size distribution (PSD) in an experimental semibatch emulsion copolymerization reactor is presented. Partial least squares (PLS) models of the process are utilized in a model predictive control (MPC) framework to regulate the PSD. The high dimensionality of the PSD is reduced through the use of a new approach, where the heights and positions of the characteristic points on the distribution are used to represent the whole distribution. This approach enables one to shift control priorities on the positions of the modes of a distribution with respect to the heights of the modes as well as efficiently reducing the dimensionality of the problem. The proposed algorithm is first tested on the simulation of the plant and showed success in regulating the PSD both in set point changes and against persistent disturbances. The experimental validation of the algorithm included two case studies where the controller was found to be effective. © 2008 American Institute of Chemical Engineers AIChE J, 2008

Semibatch emulsion copolymerization in the presence of n‐methylol acrylamide: effects of emulsifier type and concentration

AbstractTwo types of emulsifier were studied to compare the colloidal and physicochemical properties of vinyl acetate (VAc)/(BuA) emulsions. Emulsions were prepared by varying the composition and the concentration of the anionic and nonionic emulsifiers. An increase in the total emulsifier concentration of anionic and nonionic emulsifier percentage leads to dispersions with smaller particles and higher viscosities. Using anionic and nonionic emulsifiers in copolymer latexes, it was observed that the viscosity goes through a maximum which is located at total emulsifier concentration of about 3.6 wt% The surface tension of the copolymers shows a drastic increase at a concentration above 3.5% for mixed emulsifier systems. Copyright © 2008 John Wiley & Sons, Ltd.

Synthesis of a latex with bimodal particle size distribution for coating applications using acrylic monomers

Multipart emulsion polymerization of methyl methacrylate (MMA) and butyl acrylate (BA) was carried out in this work. The target was to achieve stability during the polymerization and to determine the proper hydrophilic–lipophilic balance (HLB) value for the stable system, using different types of non-ionic emulsifiers, sodium lauryl sulphate and their combinations. After determination of proper value of HLB (36.2), the best emulsifier combination on the basis of minimization of coagulum level was determined. This combination was 20 wt.% of KENON30 to SLS. The effect of monomer feed composition on the dry latex film properties was investigated to approach a monomer feed composition dealt with a proper T g. The prepared latex showed a bimodal particle size distribution, due to the proper feeding policy in semibatch emulsion copolymerization process. The monomer feed composition of 45 wt.% MMA and 55 wt.% BA with a proper T g was selected for the final improvement of coating properties such as UV resistance and adhesion. Adding acrylic acid (AA) and N-methylol acrylamide (NMA) to the reaction mixture improved the UV resistance and adhesion property of dry latex film. The flow and leveling, gloss, adhesion, UV resistance and water resistance of the produced bimodal latex showed good quality in comparison with the similar commercial resins used in coating applications.

Reduced-order methodologies for feedback control of particle size distribution in semi-batch emulsion copolymerization

Within-batch feedback control strategies are developed for the regulation of the particle size distribution (PSD) in a semibatch vinyl acetate (VAc)/butyl acrylate (BuA) emulsion copolymerization system. These strategies are also applicable for regulation of distributions in other particulate systems governed by population balances. In the first strategy, PID controllers are employed for regulating nucleation and growth events through tracking the nominal trajectories of total number of particles and the solids content by manipulating the feed-rates of the more reactive monomer, BuA, and the surfactant. The second control strategy is based on tracking nominal trajectories of the moments of the distribution with a quadratic dynamic matrix controller (QDMC). To determine the appropriate number of moments to describe the PSD during various stages of a nominal batch, a maximum-entropy approach is utilized. In the final and most complex approach, a nonlinear model predictive controller is designed utilizing the detailed population balance model of the system. The ill-conditioning resulting from the high-dimensionality of the resulting dynamical system is removed by principal component analysis (PCA)-based model order reduction and a multi-rate estimator is designed to compensate for the measurement delay associated with the PSD measurements.