The SCOPE dynamic model for emulsion polymerization I. Theory

The SCOPE dynamic process model has been developed to treat batch and semibatch emulsion copolymerizations. This computer-based model treats jacketed reactors of arbitrary size. It consists of a coupled set of ordinary differential and algebraic equations that describe material balances for the reacting species and energy balances for both the reactor and the cooling water jacket. The model also includes a feature that allows for proportional integral derivative (PID) control of the monomer emulsion and cooling water feed rates to a reactor temperature set point. The model is based largely upon the kinetic theories developed by Smith, Ewart, and Harkins to treat emulsion homopolymerizations. The SCOPE model improves upon and expands the classic theories by taking advantage of recent theoretical developments in emulsion polymerization. Such phenomena as diffusion-controlled termination and radical desorption—important for predicting accurate polymerization rates—are included in the model. More modern theories of particle nucleation, including both homogeneous and micellar mechanisms, have been incorporated into the model to predict accurate particle size distributions. SCOPE also extends the classic theories to treat the emulsion copolymerization of an arbitrary number of monomers. Output from the model includes species concentrations, residual monomer levels, particle size distributions, molecular weight distributions, instantaneous and cumulative copolymer compositions, and reactor temperatures as a function of time. The SCOPE model can be used to evaluate various process control strategies and to study the effects of process dynamics on polymer properties. In Part II, SCOPE model predictions are compared with experimental data for styrene-methyl methacrylate copolymerizations.     

Modeling poly(vinyl alcohol)-stabilized vinyl acetate emulsion polymerization. II. Comparison with experiment

The mathematical model presented in Part I, accommodating the emulsion polymerization of vinyl acetate stabilized with poly(vinyl alcohol), predicts experimental conversion and particle size data with reasonable accuracy. Model predictions of measurable variables exhibit sensitivity to variables affecting either primary ungrafted particle nucleation of flocculation kinetics, but are relatively insensitive to variables affecting poly(vinyl alcohol) grafting reactions and the resulting primary grafted particle concentration. Semibatch simulations indicate that independent increases in the vinyl acetate, poly(vinyl alcohol), and initiator levels of all increase the primary grafted particle population. It is unlikely, however, that this population exceeds the ungrafted counterpart under most commercial polymerization conditions. This relative insignificance of grafting during particle nucleation is also noted in literature data simulations where, with appropriate parameter adjustments, the model predictions agree well with the batch, thermal initiation data. © 1993 John Wiley & Sons, Inc.     

The modeling of batch and continuous emulsion polymerization reactors. Part II: Comparison with experimental data from continuous stirred tank reactors

A detailed model for emulsion polymerization is compared with extensive data from continuous stirred tank reactors. Model predictions are compared with both steady-state and dynamic data, for polymerization of styrene, methyl methacrylate, and vinyl acetate. Good agreement between model and experiment is achieved with one set of parameters and without any data fitting. The results show that the model is capable of predicting all of the experimentally observed phenomena including steady-state multiplicity, sustained oscillations, ignition and extinction dynamics, and overshoot during start-up.     

新型可聚合乳化剂及其在乳液聚合中应用

综述了可聚合乳化剂的分类、性能与应用,比较了可聚合乳化剂与传统乳化剂在乳液聚合中的优缺点,讨论了可聚合乳化剂的溶液性能,指出了可聚合乳化剂的发展趋势。     

On-line measurement of surface tension and density with applications to emulsion polymerization

Three process sensors are discussed, one for the determination of surface tension and two for the determination of liquid density. All three methods are on-line, compatible with digital data acquisition systems, and capable of monitoring flowing process streams. The instruments are described and calibration data are given. Two mathematical models of the bubble tensiometer are developed. Data showing the application of these instruments to the monitoring of batch and continuous emulsion polymerization are given.     

The effectiveness of some commercial emulsifiers in emulsion polymerization II. Anionic types

The initial polymerization rate of ethyl, butyl, and 2-ethylhexyl acrylate was studied in a thermally insulated polymerization reactor. The monomers were continuously added into the reactor and the effect of concentration of anionic emulsifiers on the temperature increase was investigated. Alkyl(aryl)polyethylenglykolethersulfate were found to be most effective in promoting the initial polymerization rate. An inhibition action of some emulsifiers was found.     

Advances in emulsion polymerization for coatings applications: Latex blends and reactive surfactants

The utilization of latex blends to prepare zero-VOC coatings and the use of reactive surfactants in emulsion polymerization are two advances in waterborne technology that are of increasing interest to coatings formulators. The first part of this paper focuses on an investigation of the influence of the interface between high and low T_g latex particles on the gloss and surface morphologies offilms obtained from model latex blends. Gloss was influenced by the concentration of carboxyl groups present on the surface of the latex particles (optimal concentration for maximum gloss = 13% on the high T_g particles, the degree of neutralization of these groups (higher gloss with increased extent of neutralization), the type and concentration of the neutralizing base (higher gloss for stronger bases), and the presence of added surfactant (higher gloss with added surfactant). Gloss was found to be correlated with the surface smoothness of the film. The kinetics, partide size, molecular weight, and location of the reactive surfactant after polymerization, as well as the contact angle of films prepared from these latexes, are examined in the second part of this paper. The polymerization rate profiles were similar to those obtained using a conventional surfactant; however, the dependency of the rate on the number of particles was significantly lower. The amound bound increased and the molecular weight decreased with increasing surfactant concentration. Presented at the 78th Annual Meeting of the Federation of Societies for Coatings Technology, on October 16–20, 2000, in Chicago, IL. Emulsion Polymers Institute and Department of Chemical Engineering, 111 Research Dr., Bethlehem, PA, 18015-4791.     

Comparison of chemical and enzymatic emulsion polymerization of styrene

For the reasonable comparison of chemical and enzymatic polymerization, manganese(III) acetate and manganese peroxidase (MnP)‐catalyzed synthesis of polystyrenes were chosen and studied with respect to the yield and the polydispersity of polymer particles. MnP allowed the production of polystyrene in a higher yield and higher polydispersity (82.34% and 2.61) than manganese(III) acetate (77.90% and 1.75). This is believed to be due to a gradual supply of initiator radicals via a catalytic cycle in MnP‐catalyzed polymerization, whereas radicals are generated all at once in Mn(III)‐mediated polymerization. NMR spectroscopy revealed that atactic polystyrene was produced by emulsion polymerization using Mn(III) or MnP. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of acrylate polymers by a novel emulsion polymerization for adhesive applications

Pressure‐sensitive adhesives (PSAs) are viscoelastic–elastomeric materials that can adhere strongly to solid surfaces with light contact pressure and a short contact time. Polyacrylates produced by solution polymerization are used widely because of their good adhesive properties. A novel emulsion polymerization was established to improve the low physical properties of PSA on the basis of conventional poly(n‐butyl acrylate) (PBA) by emulsion polymerization. PBA latex was synthesized by the emulsion polymerization of 50 wt % n‐butyl acrylate mixed with 15 wt % ethyl acetate (EA) with Emal‐10P and Emulgen‐920 as anionic and nonionic surfactants, respectively, at 70°C. Potassium persulfate (KPS) or a combination of KPS and dicumyl peroxide (DCP) was used as the initiator. The KPS/DCP system gave a very high‐molecular‐weight PBA of a narrow molecular weight distribution with a weight‐average molecular weight/number‐average molecular weight value of 1.01–1.03 in 15 min. The PSA tape was prepared by the casting of the PSA latex onto a corona poly(ethylene terephthalate) film as an adherent to obtain a 50‐μm‐dry‐thickness film. The PSA tape produced from PBA by the novel emulsion polymerization showed better adhesive properties, such as 180° peel adhesion, shear holding power, and rolling ball tack tests according to JIS and ASTM standards, than PSA tape produced from solution polymerization. The occlusion of a small amount of EA in emulsion particles before polymerization was found to give higher properties than those of PBA prepared by the addition of EA to the PBA latex after polymerization. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100:413–421, 2006     

Synthesis of cationic binder through surfactant-free emulsion polymerization for textile pigment applications

The cationic P(DMDAAC-BA-MMA-HEA) copolymer latex was prepared with diallyldimethylammonium chloride, butyl acrylate, methylmethacrylate and hydroxyethyl acrylate as monomers via surfactant-free emulsion polymerization. The structures and morphologies of the latex were confirmed by Fourier transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM). The utilization performance of the cationic latex as a binder for pigment dyeing of cotton fabrics was investigated. FT-IR showed that the polymer was prepared successfully. TEM micrograph revealed that the hybrid latex particles were uniform spheres with the diameter ranged from 500 to 600 nm. Cotton fabric dyed with the cationic binder demonstrated 3–4 grade dry and wet rubbing fastness and 4 grade soaping fastness, which were comparable with commercial binders. Moreover, the binder can be used safely in pigment dyeing to give the dyed fabric improved hand feel and excellent elongation at break. It could be said that an efficient way to produce a binder with good performance was developed by the use of cationic emulsifier-free emulsion polymerization.     

The manganic hydroxide–hydrazine system as an initiator of vinyl polymerization. II. The emulsion polymerization of methyl methacrylate

The reaction between hydrazine hydrate and manganic hydroxide has been studied as an initiator for the emulsion polymerization of methyl methacrylate. The system has proved to be effective, and polymerization occurs at favorable rates over a wide temperature range extending from below 10°C to over 50°C. The pH range, however, is rather limited, the most effective value being 9. The main features of the initiator's behavior are similar to those found previously in the corresponding solution polymerization and are explained on the basis of a surface reaction between the hydrazine and the insoluble hydroxide. A complicating feature is the reaction between hydrazine and monomer, which exerts an inhibiting influence.     

Particle coagulation at semicontinuous emulsion polymerization. II. Characterization of surface groups

Semicontinuous emulsion polymerization of acrylic monomers with a monomer emulsion feed has been investigated. The amount of coagulum appearing during the polymerization under conditions of insufficient covering of particle surface by emulsifier was studied from the point of view of particle surface charge. Increasing the surface group concentration via copolymerization of butyl acrylate with acrylic acid or sulfoethyl methacrylate caused increased colloid stability of the system and a rapid decrease in coagulum formation. It was established that during the polymerization acid hydrolysis of ester groups took place, which caused an increase in the carboxyl groups concentration at the particle surface. These carboxyl groups contribute to the colloid stability of the polymerizing system.     

Semibatch emulsion polymerization of butyl acrylate. II. Effects of emulsifier distribution

The effects of emulsifier distribution ratio between the initial charge and the feed on particle formation and kinetics of butyl acrylate emulsion polymerization, using sodium lauryl sulfate as emulsifier and potassium persulfate as initiator, were investigated. The number of particles increased with initial emulsifier concentration in the reactor charge. It was shown that traditional ranking, in terms of number of particles produced, of semibatch emulsion polymerization with monomer emulsion feed is not always justified and a semibatch emulsion polymerization can produce far more particles than a conventional batch emulsion polymerization. The number of polymer particles was found to be practically independent of the emulsifier distribution ratio between the charge and the feed for a high overall emulsifier concentration, while for a low overall emulsifier concentration, the number of particles increased with initial loading of the emulsifier. The polydispersity index (PDI) of the final latexes showed a minimum with emulsifier distribution. A bimodal particle size distribution, and a latex with a large PDI, was obtained when there was no emulsifier in the charge. As the initial emulsifier charge increased, a unimodal PSD with a smaller PDI was obtained. With higher proportions of emulsifier in the initial charge, the PDI rose again due to particle nucleation at monomer‐starved conditions, and a skewed unimodal PSD was obtained. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 582–597, 2001     

无皂乳液制备PMMA动力学及其模型

以甲基丙烯酸甲酯(MMA)为单体、过硫酸钾(KPS)为引发剂进行无皂乳液聚合反应,考察了单体MMA浓度、引发剂KPS用量及聚合温度对其动力学行为的影响。建立了转化率-时间关系曲线的模型函数———Gamm a积分函数,用它拟合了转化率-时间关系曲线,获得了聚合过程的重要特征参数,如平均成核速率,聚合最大速率和平稳期平均聚合速率及成核结束和聚合进入完成期对应的转化率。同时对聚合速率与以上各聚合参数的关系数据进行了非线性拟合,得到了它们之间的关系式。拟合相关系数非常接近于1,平均拟合误差很小,成核结束时转化率在15%以内,聚合速率随以上参数增大而增大,反应温度在聚合过程中起决定作用。     

Kinetics of multimonomer emulsion polymerization. The pseudo-homopolymerization approach

By generalizing the Smith–Ewart theory, a system of polymer particle population balances is developed for describing the kinetics of emulsion polymerization processes involving any number of monomer species. Each population is characterized by the number of active radicals of each type present inside each particle, and described through a size distribution function. An approximation procedure is proposed for reducing the original system to that typical of homopolymerization processes, thus characterizing each population-only through the overall number of radicals, without any significant loss of accuracy. The reliability of such “pseudo-homopolymerization approach” is tested by comparison with polymer composition vs. monomer conversion experimental data for the ternary system acrylonitrile–styrene–methyl methacrylate.     

Soapless emulsion polymerization of methyl methacrylate. II. Simulation of polymer particle formation

In this work, a generalized mathematical model was developed to estimate the variation of particle concentration during the entire course of soapless emulsion polymerization of methylmethacrylate (MMA). All of the factors, such as oligomeric radical absorption or desorption by polymer particles, coagulation between polymer particles, and the termination effect on the formation mechanism of polymer particles, were considered and included in this model. When appropriate parameters were selected, this model could be successfully used to interpret the experimental behavior of particle concentration during the entire reaction. Under different conditions, the rate of polymerization, the number of radicals in each particle, the instantaneous average molecular weight of polymers, and the rate constant of termination were also calculated. All of them coincided with the experimental results quite well. © 1996 John Wiley & Sons, Inc.     

Continuous emulsion polymerization of vinyl acetate. Part: II Parameter estimation and simulation studies

Conversion data obtained over a wide range of operation of a continuous latex reactor for vinyl acetate polymerization were used to estimate the unknown kinetic parameters of a transient CSTR reactor model. Conversion-time histories were adequately fitted by models of two levels of sophistication: a comprehensive model which solves for the age distribution function of polymer particles, and a simplified model that neglects the effect of particle size distribution for the case of continuous particle nucleation. These models were then used for simulation and control studies in an attempt to devise a practical control strategy⁽¹¹⁾. The existence of sustained oscillations was investigated by examining the behavior of the state variables in the phase-plane.     

Miniemulsion vs. conventional emulsion polymerization for pressure-sensitive adhesives production

A systematic study of the production of poly(2-ethyl hexyl acrylate/methyl methacrylate/acrylic acid) pressure-sensitive adhesives (PSAs) via conventional emulsion and miniemulsion polymerization was carried out in order to discern and compare the influence of copolymer composition, chain transfer agent (CTA) and surfactant concentrations on the kinetics and microstructure of the resulting adhesive films. The results showed that miniemulsion polymerization proceeded solely under droplet nucleation for a certain set of initial reaction conditions. The miniemulsion-based latexes presented a polymer microstructure that was different to that found in latexes produced by conventional emulsion polymerization, as observed in the frequency master curves and PSA performance analysis. Batch miniemulsion polymerization was able to produce films with entanglement densities (M_w/M_e) from 2 up to 11, which were strongly correlated with loop tack, peel strength and shear strength. Conversely, under the same reaction conditions, batch conventional emulsion polymerization was only able to produce M_w/M_e ratios below 2.