Emulsion Polymerization Of Vinyl Acetate Research Articles

Nonlinear Geometric Temperature Control of a Vinyl Acetate Emulsion Polymerization Reactor

In this paper, an industrial emulsion polymerization process, which is characterized by exothermic reactions with complex nonlinear dynamics, is addressed. In this process vinyl acetate is used as monomer, potassium persulfate as initiator and polyvinyl alcohol as protective colloid. A model of the system to calculate average molecular weight and dispersity is implemented. A fine and strict temperature control is required in order to guarantee the product quality and safe operation. Nonlinear geometric control based on input/output linearization is used for reactor temperature control. An extended Kalman filter is implemented to estimate unmeasured states. Performance tests of the controller and state estimator are carried out by introducing modeling and estimator errors. It is also verified that the nonlinear controller can work with different initiator feed policies helping to improve the process productivity. Finally, compared to a traditional PID controller, the nonlinear geometric controller is superior in rejecting disturbances and performing set point tracking.

Semi-continuous emulsion copolymerization of vinyl acetate and butyl acrylate in presence of AMPS

The emulsifier-free emulsion polymerization of vinyl acetate (VAc) and butyl acrylate (BA) in the presence of 2-acrylamido-2-methylpropane sulfonic acid (AMPS) was carried out by a semi-continuous process. AMPS was a reactive surfactant in the aqueous emulsion, due to its amphiphilic structure and the unsaturated double bonds. Potassium persulfate (KPS) was used as initiator. The following factors were mainly examined: quantity of AMPS, BA and KPS concentrations, which could significantly affect the particle size and its distribution, conversion, gel content, minimum film-forming temperature, etc. The particle size and its distribution were characterized by dynamic laser particle size analyzer, and morphology of the latex particles was characterized by transmission electron microscopy (TEM). Fourier transform infrared spectroscopy was used to characterize chemical structure of copolymers. The results indicated that AMPS was successfully reacted onto the resulted copolymer of vinyl acetate and butyl acrylate. A hydrophilic sulfonic acid group in the molecular structure of AMPS tended to be distributed in particles surface after polymerization. As a result, an electrostatic repulsion between the particles was produced in order to maintain stability of the system. Thermogravimetric analysis curves suggested that as BA content increased, thermal stability of the polymer increased accordingly. The conversion-time plots with varying AMPS and initiator contents were obtained, which illustrated that the initiator concentration could greatly influence the polymerization rate and the final conversion. The TEM micrographs of the final emulsifier-free latex particles for P(VAc/BA/AMPS) system revealed small particle size in monodisperse polymer latex. The particles of the latex were measured as about 150 nm.

Indomethacin Nanoparticles for Applications in Liquid Ocular Formulations / Наночастицы С Индометацином Для Применения В Жидких Лекарственных Формах Для Глаз

Studies in recent years have consistently shown that polymeric drug nanocarriers can be used in drug release and drug delivery systems to treat eye disorders. To achieve effective control over drug delivery, it is of crucial importance what kind of polymer and which method for drug inclusion in the nanoscale carrier we choose and what conditions are needed for the performance of this process. The aim of this study was to produce poly(vinyl acetate) nanoparticles with indomethacin incorporated in them, assess the effect of time for dialysis of the residual monomer and initiator on the degree of incorporation of indomethacin in the nanoparticles and on the kinetics of its release, to include them in ophtalmic formulations. Poly(vinyl acetate) nanoparticles with indomethacin were obtained by emulsion radical polymerization of vinyl acetate in the presence of indomethacin (in situ inclusion) and the absence of emulsifier. To release the residual monomer and initiator (ammonium persulfate) the obtained latexes were dialysed for 6, 9, 18 and 23 hours and then the nanoparticles were freeze-dried. Structural analysis was performed by transmission electronic microscopy, infrared spectroscopy, differential thermal analysis and thermogravimetry. Release of indomethacin was observed using ultraviolet spectroscopy. We proved the delayed release of indomethacin from the poly(vinyl acetate) nanocarrier and the lack of chemical interaction between the polymer and indomethacin. After 9-hour dialysis the initiator and the residual vinyl acetate were removed from the nanoparticles, while the entrapped indomethacin kept therapeutic concentrations. Dialysis for more than 6 and no more than 9 hours is recommended to remove the residual monomer and initiator when preparing indomethacin nanoparticles by in situ radical emulsion polymerization of vinyl acetate, for inclusion in liquid ocular formulations.

Dispersion production by semi-continuous radical vinyl acetate emulsion polymerization with silane co-monomer and characterization of final products

Vinyl acetate radical emulsion polymerization in water with GF51 silane co-monomer was performed by semi continuous way. The GF51 impacts on dispersion rheology as well on films and bonding strength properties were determined. It should be stated that even low quantities of GF51 (up to 6% from VAc) determined high viscosity of dispersions. The GF51 modified films have low water absorption and high affinity to glass. Molecular mass and thermal properties of GF51 modified polymers were determined accordingly.

Emulsion polymerization of vinyl acetate using iodine-transfer and RAFT radical polymerizations

This study deals with control of the molecular weight and molecular weight distribution of poly(vinyl acetate) by iodine-transfer radical polymerization and reversible addition-fragmentation transfer (RAFT) emulsion polymerizations as the first example. Emulsion polymerization using ethyl iodoacetate as the chain transfer agent more closely approximated the theoretical molecular weights than did the free radical polymerization. Although 1H NMR spectra indicated that the peaks of α- and ω-terminal groups were observed, the molecular weight distributions show a relatively broad range (Mw/Mn = 2.2–4.0). On the other hand, RAFT polymerizations revealed that the dithiocarbamate 7 is an excellent candidate to control the polymer molecular weight (Mn = 9.1 × 103, Mw/Mn = 1.48), more so than xanthate 1 (Mn = 10.0 × 103, Mw/Mn = 1.89) under same condition, with accompanied stable emulsions produced. In the Mn versus conversion plot, Mn increased linearly as a function of conversion. We also performed seed-emulsion polymerization using poly(nonamethylene L-tartrate) as the chiral polyester seed to fabricate emulsions with core-shell structures. The control of polymer molecular weight and emulsion stability, as well as stereoregularity, is also discussed. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

Investigation of the Emulsion Polymerisation of Vinyl Acetate, Initiated by Mn(Iii) Trisacetyl Acetonate

The results of investigations in the field of the emulsion polymerisation of vinyl acetate, initiated by Mn(III) trisacetyl acetonate, are analysed. The mechanism of the reaction and the influence of electron donor additives on the kinetics of reactions and the molecular weight of the polymers obtained are examined.

RAFT-mediated emulsion polymerization of vinyl acetate: a challenge towards producing high molecular weight poly(vinyl acetate)

The preparation of poly(vinyl acetate) with well-controlled structure has received a great deal of interest in recent years because of a large number of developments in living radical polymerization techniques. Among these techniques, the use of reversible addition–fragmentation chain transfer (RAFT)-mediated polymerization has been employed for the controlled polymerization of vinyl acetate due to the high susceptibility of this monomer towards chain transfer reactions. Here, a novel water-soluble N,N-dialkyl dithiocarbamate RAFT agent has been prepared and employed in the emulsion polymerization of vinyl acetate. The kinetic results reveal that the polymerization nucleation mechanism changes from homogeneous to micellar and RAFT-generated radicals can change the kinetic behavior from conventional emulsion polymerization to living radical polymerization. At higher concentrations of the modified RAFT agent, as a result of an aqueous phase reaction between RAFT and sulfate radicals, relatively more hydrophobic radicals are generated, which favors entry and propagation into micelles swollen with monomer. This observation was determined from the investigation of the polymerization rate and measurements of the average particle diameter and the number of particles per liter of the aqueous phase. Molecular weight analysis also demonstrated the participation of the RAFT agent in the polymerization in such a way as to restrict chain transfer reactions. This was determined by examining the evolution of polymer chain length and attaining higher molecular weights, even up to 50 % greater than the samples obtained from the conventional emulsion polymerization of vinyl acetate in the absence of the synthesized modified RAFT agent.

Synthesis of high‐molecular weight poly(vinyl alcohol) by low‐temperature emulsifier‐free emulsion polymerization of vinyl acetate and saponification

AbstractHigh‐molecular weight (HMW) poly(vinyl alcohol) (PVA) was prepared via an emulsifier‐free emulsion polymerization of vinyl acetate (VAc) using a redox initiation system in low temperatures, and the subsequent saponification with potassium hydroxide in methanol. The effect of the polymerization conditions on the conversion, molecular weight, and branching degree was investigated. PVA with maximum viscosity‐average degree of polymerization (DP) of 8270 could be prepared by saponification of poly(vinyl acetate) (PVAc), with DP of 10,660 obtained at temperature of 10°C, monomer concentration of 30%, potassium persulfate molar ratio to monomer of 1/2000, agitation speed of 160 rpm. The conversion was above 90%. From the emulsifier‐free emulsion polymerization of VAc in low temperature, PVAc with HMW and high linearity was effectively prepared, which might be useful for the preparation of high‐strength and high‐modulus PVA fiber. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Development of Novel Polymers prepared by vinyl acetate and N-hydroxymethyl acrylamide

To improve the chemical, physical, mechanical and thermal properties of polyvinyl acetate (PVAc), N-hydroxymethyl acrylamide (NMA) was used to polymerize with vinyl acetate (VAc). During the emulsion polymerization of VAc using polyvinyl alcohol as protective colloid and ammonium persulfate as initiator, PVAc-NMA was prepared under the conventional conditions in laboratory. In the polymers, larger PVAc-NMA particles and other smaller NMA-NMA particles randomly dispersed together. Their dispersion was good. PVAc-NMA was a pseudo-plastic non-Newtonian fluid, also possessed the normal stress effect (or Weissenberg effect), the pole-climbing phenomenon. With the change of different synthesis processes and the increase in NMA content in the synthesis system, the molecular weight of PVAc-NMA increased. NMA could lower the glass transition temperature of PVAc, and then improved PVAc’s low temperature resistance, so PVAc-NMA could be applied in more harsh or much lower temperature conditions. The static tensile of PVAc-NMA was better. PVAc and PVAc-NMA all had the cold crystallization. The pyrolysis of PVAc and PVAc-NMA was similar. It was found to consist of eight phases. NMA had no obvious effect on the pyrolysis temperature but mainly delayed the thermal degradation process.

In situ synthesis and characterization of polypropylene/polyvinyl acetate‐organophilic montmorillonite nanocomposite

AbstractA novel polymer‐nanoclay hybrid nanocomposite based on polyvinyl acetate (PVAc)‐organophilic montmorillonite (OMMT) has been reported via an in situ intercalated polymerization technique. The hybrid material was synthesized by one‐step emulsion polymerization of vinyl acetate in the presence of OMMT using polyvinyl alcohol as the stabilizing agent. The intercalated polymerization was characterized by X‐ray diffraction (XRD). The XRD patterns show that the interlayer spacing of OMMT after polymerization increased from 2.64 to 3.78 nm, indicating that the large macromolecular chain of PVAc was formed in the OMMT interlayer space. The Fourier transform infrared spectrum showed the characteristic absorption of PVAc in the OMMT particles separated from the nanocomposite, and the position of peaks shifted to high wave numbers. This showed that there was an interaction between PVAc and OMMT nanoparticles. A two‐fold blend composed of PVAc‐nano‐OMMT/PP was prepared by the melt‐blending technique. XRD and transmission electron microscopy images of the PVAc‐nano‐OMMT/PP composite further confirmed the formation of a partially delaminated nanocomposite structure. Thermogravimetry results showed that the thermal stability of PVAc‐nano‐OMMT/PP was greater than that of either polypropylene (PP) or Nano‐OMMT/PP blend. PVAc‐nano‐OMMT/PP had better toughness, as the mass fraction of OMMT was 5 wt %. The flame retardancy of PP, Nano‐OMMT/PP, and PVAc‐nano‐OMMT/PP composites was also studied. According to the limiting oxygen index (LOI) data and Cone calorimeter test, the addition of PVAc‐OMMT resulted in higher LOI and lower heat release rate, effective heat of combustion, smoke release course, and better flame retardancy and barrier properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Emulsion polymerization of vinyl acetate: Safe optimization of a hazardous complex process

Fast and exothermic discontinuous emulsion polymerization processes are particularly difficult to optimize from both safety and productivity point of view because of the occurrence of side undesired reactions (e.g. chain transfer to monomer, backbiting, propagation of tertiary radicals, termination by disproportion, etc.) and the hazards of boiling phenomena and stable foam formation under atmospheric pressure. Moreover, the relevant number of loading, heating and cooling steps, required before starting the monomer addition (that is, the desired reaction), makes a strict product quality reproducibility very difficult to obtain. Under these operating conditions, it is necessary to employ a suitable combined theoretical and experimental procedure able to detect the optimum process dosing time at both the laboratory and the industrial scale. In this work, it is shown how to use the topological criterion theory together with proper adiabatic calorimeter and RC1 experimental data to safely optimize the synthesis of polyvinyl acetate through the radical emulsion polymerization of vinyl acetate by the means of an indirectly cooled isoperibolic semibatch reactor.

Preparation of surfactant-free vinyl polymers by conventional emulsion polymerization using hydrolysable emulsifiers

Emulsion polymerizations of several vinyl monomers, styrene, methyl methacrylate, butyl methacrylate, butyl acrylate, and vinyl acetate, in water using alkali–hydrolysable cationic surfactants with a betaine ester group (1-alkoxycarbonylmethyl)trimethylammonium chlorides, as emulsifiers were carried out and properties of the resulting latices and the polymers recovered by hydrolysis and salting out were investigated. There were little influences of the surfactants and monomers used here on the polymerizations, forming stable and monodisperse latices with a mean diameter of ca. 70 nm and giving a high molecular weight of polymers at high yields. All polymers were precipitated and recovered by adding a small amount of sodium hydroxide into the latex solutions contained little amount of ionic species. Solvent-cast films of the polymers were found to have surfaces as hydrophobic as those for the corresponding pure polymers prepared by bulk polymerization.

무효화 에멀젼 공중합법과 반응염법을 이용한 전기영동 고분자 컬러나노입자에 제조

무유화 에멀젼 공중합법을 이용하여 180-200 nm의 지름을 가지는 단분산성 폴리(스티렌/디비닐벤젠/비닐 아세테이틴) [poly(ST-co-DVB-co-VAc)] 고분자 나노입자를 합성하였으며. 제조된 단분산성 고분자 나노입자의 표면을 비누화반응을 통하여 개질하여 단분산성 폴리(스티렌/디비닐벤젠/비닐알코올) [polyl(ST-co-DVB-co-VA)] 나노입자를 제조하였다 합성된 입자를 반응염료와 반응시켜 적색과 청색 단분산성 폴리(스타렌/디비닐벤젠/비닐알코올 나노입자를 제조하였으며 입자의 형태, 분산성 빛 표면전하를 전자현미경, 시차열분석기, UV/Vis 흡광기 및 제타 전하 측정장치를 이용하여 규명하였다.

Preparation of a novel composite material by emulsion polymerization of vinyl acetate and vinyl polyhedral oligomeric silsesquioxane

A novel material containing polyhedral oligomeric silsesquioxane (POSS) was prepared by semi-continuous emulsion polymerization. Incompletely condensed, phenyl POSS (Na3O12Si7(C6H5)7) with the highly reactive group of trisodium silanolate was used to prepare 1, 3, 5, 7, 9, 11, 13-heptaphenyl-15-vinyl silsesquioxane (vinyl-POSS) by “corner-capping” method. Then this cubic structure molecule was chemically bonded with PVAc chain to synthesize POSS/PVAc composite. The structures of POSS and composite were characterized by FTIR, 1H-NMR and XRD. The results confirmed that vinyl-POSS could be successfully incorporated into the PVAc matrix via emulsion polymerization. Transmission electron microscope (TEM) was used to observe the morphology of copolymers. The thermal properties were investigated by differential scanning calorimetry and thermal gravimetric analysis. Data indicated that the POSS/PVAc composite displayed higher thermal stability than that of the parent PVAc homopolymer.

Some comparative aspects of particle formation and rate of reaction in emulsion polymerization of vinyl acetate and butyl acrylate

AbstractThe comparative study of monomers, in terms of particle formation and rate of polymerization, facilitates the interpretation of the results from the corresponding copolymerization runs and can be considered as a preliminary step toward formulation of copolymerization reactions. Batch emulsion homopolymerization of vinyl acetate (VA) and butyl acrylate (BA), as model monomers with a wide water solubility disparity, were carried out to investigate the effects of variations in the monomer concentration, electrolyte concentration, reaction volume, and surfactant type on the kinetics of polymerization. With sodium lauryl sulfate as surfactant, VA emulsion polymerization produced more particles than BA at a lower monomer concentration, but fewer particles at a higher monomer concentration. At a lower VA concentration, a depressed growth for newly formed particles during interval III contributed to the formation of a large number of particles. The application of aerosol MA and OT surfactants improved the stability of polyvinyl acetate (PVA) particles so that a larger number of polymer particles was obtained for VA, in comparison with BA. BA emulsion polymerization showed little sensitivity to electrolyte concentrations and reaction volumes within the range studied. The colloidal stability of PVA particles was found to be quite sensitive toward the aforementioned variables. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Effects of agitation in emulsion polymerization of vinyl acetate, ethylene, and N-methylol acrylamide

The emulsion polymerization of vinyl acetate monomer (VAM), ethylene and N-methylol acrylamide (NMA) was carried out in a high pressure stirred reactor using an Rushton flat blade impeller at a rotational speed of 300 rpm under a semi-batch polymerization process, which was subsequently grown by the continuous addition of monomers (VAM, ethylene, and NMA). The particle diameters of the samples withdrawn during polymerization were determined by using capillary hydrodynamic fractionation (CHDF). Also, the number of particles was calculated from the data obtained by CHDF. Coagulum formation was studied. It was found that coagulum formation increased with increasing conversion and auto-accelerated from ca. 20% conversion. The definition of coagulum in this research was presented. The coagulum formation pattern on the impeller was shown. Also, the flow pattern in the reactor under the same geometrical configuration and operating conditions was simulated.

Characteristics of Continuous Emulsion Polymerization of Vinyl Acetate with a Compartment Reactor

Emulsion polymerization of vinyl acetate with a compartment reactor consisting of 3 well-mixing compartments has been investigated. A step response method revealed that the mixing of this reactor is characterized by a 4 CSTRs-in-series model. Higher conversion of the vinyl acetate monomer is obtained by the compartment reactor than by a single CSTR since the restricted axial dispersion suppresses the effluent of unreacted monomer. The oscillation of the mean particle size induced by the co-presence of small and large particles is inhibited due to narrow residence time distribution of particles, and stable particle size distributions are obtained under steady state operation. Back-mixing causes polymerization with short mean residence time in the first compartment. Since there is little back-mixing, polymerization occurs in the first vessel even when the mean residence time of feed is so low that the polymerization did not occur in a single CSTR. The compartment reactor can be a possible method to convert the batch process into a continuous process.

Modelling the semi-batch vinyl acetate emulsion polymerization in a real-life industrial reactor

A detailed dynamic model of the polymerization reaction of vinyl acetate in a real-life industrial reactor is presented. With the recipe and the operating procedures observed in the factory as inputs, the model predicts with reasonable accuracy the final conversion, the average particle diameter, the solid content and the viscosity. The manual and semi-manual operations, and the decision process followed by the operator, are also modelled in order to replicate closely the process carried out in the factory. The model provides further insight into the reaction kinetics and allows us to make knowledge-based decisions. The model is intended to be used for the optimization of the policy of adding monomer in order to reduce the batch time.

Monitoring of Emulsion Polymerisation Processes using Ion Mobility Spectrometry—A Pilot Study

AbstractOnline monitoring of monomer concentrations in (semi‐) batch emulsion polymerisation reactors is important for safe and cost‐efficient operation of production plants. In the present pilot study, ion mobility spectrometry was applied for monitoring the concentration during emulsion polymerisation of vinyl acetate (VA) using UV light for ionisation of the headspace of a continuous sample flow. Satisfactory sensitivity for online process monitoring of the monomer concentration in the reactor was observed (LOD 400 ng · L−1 air, equivalent to <1%). Furthermore, it is possible to discriminate between VA and other common monomers [butyl acrylate (BA), methyl methacrylate (MMA)]. Using the more efficient β‐radiation ionisation, monomer concentration could be measured even in the final latex as a measure of the final product properties.magnified image

A molecular theory for particle nucleation: Primary particle formation in emulsion polymerization

Homogeneous nucleation is fundamentally important in emulsion polymerization. A molecular theory is proposed to quantify primary particle formation in the process. The proposed model divides a polymerization system into three portions: the domains formed by growing radicals, their surrounding aqueous solution, and dispersed monomer droplets. In general, the total free energy of the domains is contributed from the mixing among the molecules including monomer and water, the elasticity of oligomeric radical chains, and the transferable free energy of electrolytes; while that of the outer solution is from the mixing of monomer and water molecules and the transferable energy of electrolytes. Application of this theory to vinyl acetate emulsion polymerization has shown that the critical degree of polymerization ( j cri ) predicted is in a good agreement with the value derived from experimental data reported in literature. Furthermore, this model can also estimate the concentrations of VAc and water in the domain at the degrees of polymerization around j cri .