Emulsion Polymerization Of Vinyl Acetate Research Articles

Monitoring Polymeric Fouling in a Continuous Reactor by Electrochemical Impedance Spectroscopy

AbstractMonitoring early stages of polymeric deposit formation and its prevention were studied by in‐situ electrochemical impedance spectroscopy (EIS) in a continuously operating reactor employed for polymer production. An EIS flow cell was designed and employed during the emulsion polymerization of vinyl acetate. The electrochemical analysis of the complex impedance at the solution/reactor interface allows the time‐resolved detection of film formation processes. In comparison to oxide‐covered stainless steel, an anti‐adhesive sol‐gel coated alloy showed a significant inhibition of poly(vinyl acetate) fouling. The EIS‐based approach proved to be a valuable tool for monitoring both thin barrier film performance and fouling processes under harsh process conditions.

Scale-up of Emulsion Polymerisation up to 100 L and with a Polymer Content of up to 67 wt%, Monitored by Photon Density Wave Spectroscopy

The scale-up process of the high solid content (up to 67 wt%) emulsion polymerisation of vinyl acetate and Versa®10 from 1 L over 10 L to 100 L was investigated. An emulsion copolymerisation of vinyl acetate and neodecanoic acid vinyl ester in a molar ratio of 9:1 was carried out in a starved-fed semi-batch operation. As a radical source, a redox initiator system consisting of L-ascorbic acid, tert-butyl hydroperoxide and ammonium iron (III) sulphate was used. The process parameters, such as the required stirring speed and heat dissipation, were determined and adjusted beforehand via reaction calorimetry to ensure a successful scale-up without safety issues. In addition, the emulsion polymerisation was monitored inline by Raman (qualitative monomer accumulation), as well as Photon Density Wave spectroscopy (particle size and scattering coefficient) and temperature measurements. The data provided by Raman spectroscopy and temperature measurements revealed mixing difficulties due to an insufficient stirring rate, while the inline measurement with Photon Density Wave spectroscopy offered an insight into the development of the product properties. It proved to be reliable and precise throughout the entire scale-up process, especially compared to conventional offline methods, such as dynamic light scattering or sedimentation analysis by means of a disc centrifuge, both of which encountered issues when using higher polymer contents.

Influence of redox initiator component ratios on the emulsion copolymerisation of vinyl acetate and neodecanoic acid vinyl ester.

Redox initiated emulsion polymerisation of vinyl acetate and neodecanoic acid vinyl ester was investigated at temperatures ranging from −1 °C to 87 °C (initiation temperature between −1 °C and 60 °C), using varying molar ratios of the following redox components: l-ascorbic acid, tert-butyl hydroperoxide and ammonium iron(iii) sulfate dodecahydrate as a catalyst. The high flexibility of redox initiators enables product properties, as well as space-time-yield, to be adjusted as required. Polymers being products by process, it was presumed that modifying the conversion rate would lead to a different product. However, it was shown that the reaction rate is adjustable by varying the catalyst amount without changing the product properties, such as molecular weight, particle size, glass transition temperature and polymer structure, while reducing the overall process time by 40–86% (at equimolar ratios of reducing and oxidising agent). In contrast, variation of the tert-butyl hydroperoxide content resulted in changes of the molecular weight. The influence of the initiation temperature and of the redox system on the reaction rate was determined, enabling control over the reaction rate in the whole temperature range. Meanwhile, overall process times of approximately 2–240 min and high conversions of 90–99% could be achieved. Statistical modelling confirmed the results and facilitated predictions, enabling the conversion rate to be adjusted to the desired properties. The possibility of being able to adjust the conversion rate and product properties independently of each other creates additional degrees of freedom in process design.

Backbone-Degradable Vinyl Acetate Latex: Coatings for Single-Use Paper Products.

We report an approach to waterborne and degradable latex polymers. Emulsion polymerization of vinyl acetate (VA) with the cyclic ketene acetal 2-methylene-1,3-dioxepane (MDO) yields polymer particles and latex-based coatings that are hydrolytically degradable due to the presence of backbone ester groups. Polymerization under mildly basic conditions (pH 8) and at low temperature (40 °C) is critical: if the in-process pH is too acidic or the temperature too high, MDO is lost to hydrolysis, but when the media is too alkaline, VA monomer rapidly hydrolyzes. When coated onto commercial paper, films of these degradable particle dispersions show excellent oil and grease resistance as compared to non-degradable, VA-only compositions. This new class of latex is therefore well-suited for the design of next-generation, biodegradable and compostable single-use food service products, as well as for other applications where the erosion or degradation of polymer-based films and coatings is required.

Poly[di(ethylene glycol) vinyl ether]-stabilized poly(vinyl acetate) nanoparticles with various morphologies via RAFT aqueous emulsion polymerization of vinyl acetate

Reversible addition fragmentation chain transfer (RAFT) aqueous emulsion polymerization of vinyl acetate (VAc) is performed using poly[di(ethylene glycol) vinyl ether] (PDEGV) macromolecular chain transfer agents (macro-CTAs) including RAFT end-unfunctionalized PDEGV (up to 32%). Emulsion polymerization directly induces PDEGV-b-PVAc diblock copolymer assemblies in water. This facile formulation enables the production of various particle morphologies, such as spheres, rods (ellipsoids), and vesicles, depending on the composition of the block copolymer. Many other examples of RAFT emulsion polymerization syntheses only result in the formation of kinetically trapped spheres, even when targeting highly asymmetric diblock compositions. However, despite being stabilized only by homopolymer PDEGV macro-CTAs, including PDEGV, PVAc-based nanoparticles with various morphologies can be obtained as PDEGV-b-PVAc assemblies. RAFT aqueous emulsion polymerization owes its success to recent RAFT polymerizations of hydroxy-functionalized vinyl ethers. We investigated the RAFT polymerization of DEGV, analyzed the kinetics of PDEGV-b-PVAc nanoparticle formation, and observed the morphology of resultant particles in detail. We also developed a phase diagram for this RAFT aqueous emulsion polymerization formulation that reliably predicts the precise block compositions associated with well-defined particle morphologies. RAFT aqueous emulsion polymerization of vinyl acetate (VAc) was performed using poly[di(ethylene glycol) vinyl ether] (PDEGV) macromolecular chain transfer agents. The emulsion polymerization directly induced PDEGV-b-PVAc diblock copolymer assemblies in water. Owing to the characteristic PDEGV as a highly hydrophilic steric stabilizer, this facile formulation enables the production of various particle morphologies, such as spheres, rods (ellipsoids), and vesicles, depending on the composition of the block copolymer. Each morphology change in the nanoparticles via RAFT aqueous emulsion polymerization owes its success to the recent RAFT polymerizations of vinyl ethers.

Thermal analysis: an effective characterization method of polyvinyl acetate films applied in corrosion inhibition field

To prepare a commercial product with economic and technical relevance, polyvinyl acetate (PVAc) was synthesized, under our laboratory conditions, updating an industrial prescription by emulsion polymerization of vinyl acetate using polyvinyl alcohol as emulsifier, Fenton reagent as reaction initiator and acetic acid as aqueous phase pH-regulator. A polymeric film (PSYF) was made and comparatively characterized with a standard PVAc film (PSTF) by scanning electron microscopy with energy-dispersive X-ray spectroscopy, Raman spectroscopy and simultaneous thermogravimetry and derivative thermogravimetry analysis. Similar vibration bands for PSTF and PSYF in the Raman spectra were identified which accurately reproduce the values reported in the literature. Thermal analysis was an efficient method to detect the compositional differences between the two polymeric films, precisely indicating that PSYF contained 92% PVAc and a mixture of 8% containing unreacted monomer, polyvinyl alcohol and humidity. Additionally, the PVAc film inhibitive properties on carbon steel corrosion in acid environments were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy. A high inhibition efficiency of PVAc, ranging between 86.0 and 88.0%, was computed from electrochemical measurements, indicating the polymer adsorption ability on carbon steel surface.

Cellulose nanocrystal as ecofriendly stabilizer for emulsion polymerization and its application for waterborne adhesive

Soap-free emulsion polymerization of vinyl acetate (AVM) in the presence of cellulose nanocrystals (CNCs) was performed using persulfate/metabisulfite as initiator. The effect of the addition of MPEG comonomer on the locus of CNCs with respect to polymer particles was investigated. It was shown that the presence of MPEG strongly favors the accumulation of CNCs on the polymer particle thus contributing to a stabilization of polymer particle through Pickering effect. The rheological properties of the dispersion as well as the reinforcing effect of CNCs were also meaningfully affected by the presence of MPEG. For purpose of application, the polyvinyl acetate (PVA)/CNC nanocomposite dispersion was used as binder to produce PVA-based waterborne adhesive for wood. This open the way to produce high-value one pot nanocomposite dispersion ready for use, free from any surfactant likely to be used for waterborne adhesive or coating with higher mechanical performance.

Dynamic optimization and experimental validation of a pilot scale emulsion polymerization reactor

Dynamic optimization of the emulsion polymerization of vinyl acetate in a pilot scale stirred-tank reactor was studied. The objective function was defined in order to minimize the reaction time. The polymerization reactor was modeled concluding that the effect of the heat removal is decisive to regulate the quality characteristics of the product. The optimization was performed offline using an optimal control dynamic optimization method, selecting as manipulated variables the heat exchange fluid rate and the feeding flow rates of initiator and monomer. The objective function was subjected to several constraints: the heating time until the system reached the activation temperature, final solids content, final product viscosity and final monomer conversion. As a result, it was determined that the polymer could be produced with a maximum time reduction of 29%. The reduction of time affected the polymer final viscosity dropping it, due to an increase in the number of free radicals which intensified the termination reaction rate. Finally, an experimental validation at pilot scale reactor was made showing good results in terms of the polymer end-properties, in accordance to those obtained via dynamic optimization.

Синтез водостойких и биостойких поливинилацетатных дисперсий

The characteristics of the emulsion polymerization of vinyl acetate in the presence of inorganic compounds such as silicon dioxide, titanium dioxide and polyhexamethylene guanidine hydrochloride are studied. It was found that, under the same synthesis conditions, inorganic additives affect the polymerization mechanism of vinyl acetate. The highest conversion of vinyl acetate can be obtained with the introduction of 0.5 wt% silicon dioxide. Polyhexamethylene guanidine hydrochloride also accelerates the reaction rate at the initial moment of time. However, the combined use of silicon dioxide and polyhexamethylene guanidine hydrochloride also reduces the reaction rate in comparison with the syntheses of vinyl acetate, carried out in the presence of each additive separately. The introduction of titanium dioxide, on the contrary, inhibits the reaction. However, when titanium dioxide and polhexamethylene guanidine hydrochloride are used together, the curve of the dependence of vinyl acetate conversion on time is close in process speed to the polymerization process of vinyl acetate without additives. The introduction of silicon dioxide and titanium dioxide makes it possible to increase by 1.5 times the water resistance of the resulting dispersions after short-term keeping glued samples in the water. At the same time, an increase in the water resistance of the samples after long-term contact with water allows only silica. The joint introduction of polyhexamethylene guanidine hydrochloride and silicon dioxide also led to improve the water resistant of adhesive joints, but not as significantly as in the case of the separate introduction of only silica. Polyhexamethylene guanidine hydrochloride increases the fungicidal activity of the resulting dispersions, and its combined use with titanium dioxide made it possible to improve the water resistance of the dispersion during long-term contact with water, in contrast to samples modified only with titanium dioxide. In addition, these samples showed greater fungicidal activity than samples containing silica and polymethylene guanidine hydrochloride.

A cardanol-based surface-active dithiocarbamate and its application in emulsion polymerization

A surface-active dithiocarbamate is synthesized in three steps from the renewable cardanol. Structures of the intermediates are characterized and confirmed by 1H-NMR spectra. This functional cardanol-based dithiocarbamate is further used in RAFT emulsion polymerization of vinyl acetate without adding any other emulsifier.

Kinetics of waterborne fluoropolymers prepared by one-step semi-continuous emulsion polymerization of chlorotrifluoroethylene, vinyl acetate, butyl acrylate and Veova 10

Due to using gaseous fluorine monomer with toxicity, waterborne fluoropolymers are synthesized by semi-continuous high-pressure emulsion polymerization method which differs from free-pressure emulsion polymerization. To dates, the research on preparing process and kinetics for high-pressure emulsion polymerization is reported relatively less, which hinders researchers from understanding of mechanisms for monomer-fluorinated emulsion polymerization. The paper also provides a new method by element auxiliary analysis to calculate kinetics parameters of high-pressure emulsion polymerization. Based on aforementioned consideration, waterborne fluoropolymers were prepared by copolymerization of chlorotrifluoroethylene (CTFE), vinyl acetate (VAc), butyl acrylate (BA) and vinyl ester of versatic acid (Veova 10) using potassium persulfate as initiator and mixed surfactants. The kinetics of emulsion polymerization of waterborne fluoropolymers was then investigated. Effects of emulsifier concentration, initiator concentration, and polymerization temperature on polymerization rate (Rp) were evaluated, and relationship was described as Rp∝[I]0.10 and Rp∝[E]0.12. The apparent activation energy was determined to be 33.61 kJ·mol-1. Moreover, the relative conversion rate of CTFE with the other monomers was observed, and results indicated that CTFE monomer more uniformly copolymerized with the other monomers. The resulting emulsion properties and pressure change in an autoclave were evaluated at different stirring rates. The initial reaction time, defined as the beginning time of dropwise addition, was determined by the change in solid content and particle size of emulsion.

The effects of feeding ratio on final properties of vinyl acetate-based latexes via semi-continuous emulsion copolymerization

Semi-continuous emulsion polymerization of vinyl acetate and dioctyl maleate (VAc/DOM) (60/40, w/w) was carried out with pre-emulsion feeding using potassium persulfate as an initiator. The influence of emulsifier type and its initial ratio were studied and the mixture of non-ionic emulsifiers; 30 and 10 mol ethoxylated nonylphenol (NP30 and NP10) at a ratio of 50/50 (w/w) provided better pre-emulsion and polymerization stability, and also final latex stability. In addition, two series of experiments were conducted to determine the effect of initiator and reactive surfactant, oligomeric N-methylol acrylamide (o-NMA) amount in the initial reactor charge on the latex properties. By increasing the initial initiator amount from 10 to 50 wt%, the average particle size of the latexes decreased from 203 to 143 nm. As expected, the amount of initiator strongly affected the particle charge and the highest zeta potential value was obtained when 50 wt% of the initiator was initially present in the reactor, showing the increased latex stability. On the other hand, it was detected that the colloidal properties of the copolymer latexes were significantly affected by the change of initial charge of o-NMA. The o-NMA amount exceeding 50 wt% caused coagulation. When all o-NMA was initially fed, the highest viscosity value, 9878 cP; lowest zeta potential value, − 5 mV; and the highest surface tension value, 37.5 mN m−1, were obtained. Consequently, the change in the initial charge of emulsifier, initiator, and reactive surfactant has played an important role on the colloidal stability of VAc/DOM latexes.

Synthesis and Characterization of Waterborne Fluoropolymers Prepared by the One-Step Semi-Continuous Emulsion Polymerization of Chlorotrifluoroethylene, Vinyl Acetate, Butyl Acrylate, Veova 10 and Acrylic Acid.

Waterborne fluoropolymer emulsions were synthesized using the one-step semi-continuous seed emulsion polymerization of chlorotrifluoroethylene (CTFE), vinyl acetate (VAc), n-butyl acrylate (BA), Veova 10, and acrylic acid (AA). The main physical parameters of the polymer emulsions were tested and analyzed. Characteristics of the polymer films such as thermal stability, glass transition temperature, film-forming properties, and IR spectrum were studied. Meanwhile, the weatherability of fluoride coatings formulated by the waterborne fluoropolymer and other coatings were evaluated by the quick ultraviolet (QUV) accelerated weathering test, and the results showed that the fluoropolymer with more than 12% fluoride content possessed outstanding weather resistance. Moreover, scale-up and industrial-scale experiments of waterborne fluoropolymer emulsions were also performed and investigated.

Controlled synthesis of poly(vinyl acetate) by traditional radical emulsion polymerization

AbstractA new redox initiation system, potassium persulfate/N,N‐dimethylethanolamine, was used to initiate traditional radical emulsion polymerization of vinyl acetate at low temperature. Polymers were characterized using gel permeation chromatography, scanning electron microscopy and dynamic light scattering. The results showed that poly(vinyl acetate) with high molar mass and small dispersity (Đ) was successfully synthesized. © 2016 Society of Chemical Industry

Economic production of VAc and VEOVA 10 emulsion polymer using factorial design

Emulsion polymerisation of vinyl acetate (VAc) and vinyl ester of versatic acid (VEOVA 10) was carried out using different feed composition ratios. The copolymer emulsion was characterised by measuring the morphological properties (average particle diameter, D) by using the transmission electron microscope (TEM), minimum film forming temperature (MFFT) and filtration residue (ppm). The results of the study indicate that the average particle diameter of emulsion (D) decreases with the increase of the amount of VEOVA 10 content (and subsequently decreases the amount of VAc), also the ppm and the MFFT is decreased. These results were illustrated using response surface methodology and contour plots. In this paper, the economic production of VAc and VEOVA 10 emulsion polymer was studied to ensure the best performance of all properties at minimum cost utilising multi-objective optimisation methodology.

Emulsion Polymerization of Vinyl Acetate in the Presence of Different Hydrophilic Polymers Obtained by RAFT/MADIX

The surfactant-free emulsion polymerization of vinyl acetate (VAc) was achieved using RAFT/MADIX-mediated polymerization-induced self-assembly (PISA) process in water. First, well-defined hydrophilic macromolecular RAFT agents (macroRAFT) bearing a xanthate chain end were synthesized by RAFT/MADIX polymerization of N-vinylpyrrolidone (NVP) and N-acryloylmorpholine (NAM) or by post-modification of commercial poly(ethylene glycol). Chain extension of the macroRAFT with VAc in water led to the block copolymer nanoscale organization and the subsequent formation of stable and isodisperse PVAc latex nanoparticles with high solids content (35–37 wt %). The influence of various parameters, including the nature and functionality of the macroRAFT agent precursor, on the polymerization kinetics and particle morphology was also studied.

Synthesis of ABA Type Block Copolymers of Poly(Ethylene Glycol) and Poly(Dodecyl Vinyl Ether) and Its Using as Surfactant in Emulsion Polymerization

A poly(ethylene glycol) (PEG) based macroinitiator (MI) with terminal chloride atom at both ends was prepared by the reaction of PEG-400 with chloroacetyl chloride and used for the cationic polymerization of dodecyl vinyl ether (DVE) yielding ABA type block copolymer. The block copolymer was then used as the surfactant for the emulsion polymerization of vinyl acetate and styrene in the presence of potassium persulfate as an initiator. The effects of new polymeric emulsifier on the physicochemical properties of obtained latexes were investigated depending on surfactant percentage in homopolymerizations.

Emulsion Polymerization of Vinyl Acetate in the Presence of a New Cationic Surfactant

In this study, the emulsion homopolymerization system containing vinyl acetate, potassium persulfate, a new cationic polymeric surfactant and water was studied by the applying semi-continuous emulsion polymerization process. The effects of new polymeric emulsifier on the physicochemical properties of obtained vinyl acetate latexes were investigated depending on vinyl acetate percentage in the polymerization recipe, and two thermal initiators in homopolymerization.

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.