Semi-batch Emulsion Polymerization Process Research Articles

Preparation and characterization of high solid content acrylate latex pressure sensitive adhesives with difunctional cross-linker EGDMA

Cross-linked acrylate latex pressure sensitive adhesives (PSAs) were synthesized via unseeded semi-batch emulsion polymerization processes with butyl acrylate (BA), acrylic acid (AA), 2-hydroxyethyl acrylate (HEA) and difunctional cross-linker, ethylene glycol dimethacrylate (EGDMA). The influences of EGDMA on the comprehensive properties of the acrylate latex PSAs were investigated. The results indicated that both viscosity and particle size of the latexes were independent of the amount of EGDMA in the pre-emulsion feed when unseeded semi-batch emulsion polymerization process was employed. It was also found that water resistance of the latex PSA was improved with increasing EGDMA content, further confirmed by water contact angle measurements. DSC and TGA results showed that Tg of the copolymer was elevated, plus thermal stability was increased with introduction of EGDMA. Besides, with the increase of EGDMA content, the gel content of the polymer increased. Moreover, for the cross-linked adhesive film, the shear strength was improved greatly while at the sacrifice of loop tack and peel strength, when compared with the uncross-linked counterparts.

Towards a controllability analysis of multiscale systems: Application of the set-theoretic approach to a semi-batch emulsion polymerization process

This work presents a framework to evaluating the controllability of multiscale systems based on a set-theoretic approach. Calculation of the Controllable Trajectories Set is the core of the set-theoretic approach. From a multi-scale perspective, such calculation is a computationally- intractable problem. Therefore, to overcome the intrinsic curse of dimensionality of the problem, Variance Algebra concepts and a statistical modeling approach are combined to obtain a closed-form allowing to perform an output-controllability analysis for a multiscale system. A semi-batch emulsion polymerization process is adopted as a case study. Results have shown that both, the final Particle Size Distribution (mesoscopic variable) and the secondary particle nucleation rate (microscopic variable) are output-controllable. Evaluating the controllability of lower-scale variables (i.e. below macroscopic) could mitigate the dependency of the current control strategies of on-line measurements at the lower scales as well as help to better understand the process capabilities of achieving the desired product quality specifications.

A reduced-order multiscale model of a free-radical semibatch emulsion polymerization process

Free-radical emulsion polymerization is a heterogeneous process where simultaneous and competitive physicochemical events occur over a wide range of time/length scales. Although a highly accurate representation of the process is possible by multiscale modeling, common approaches face several issues, including the stochastic nature of finer scales, the timely exchange of information between scales, and the high computational load for the model solution. In this work, a reduced-order computationally-tractable multiscale model is proposed while preserving a good predictive capability. The model integrates microscopic-scale calculations based on kinetic Monte Carlo simulations (stochastic), a mesoscopic-scale representation of the particle size distribution through a novel statistical approach and a deterministic description of the macroscopic-scale. The proposed model resulted in faster satisfactory predictions (compared to the model based on the Fokker Planck Equation) of traditional macro and mesoscopic variables, along with the average number of free radicals and secondary nucleation on a microscopic scale.

Plant oil-derived copolymers with remarkable post-polymerization induced mechanical enhancement for high performance coating applications

Polymer coatings have been heavily utilized in many industrial and civil applications where a protective thermoset material with enhanced properties such as chemical and physical resistance, thermal stability, and tailorable mechanical properties is desired. Plant oils are a class of promising biomass toward sustainable polymers, but have yet to be fully harnessed in tailorable thermoset coatings due to the challenging functionalization and extensive crosslinking processes required to achieve desirable thermomechanical properties. In this work, we demonstrated that soybean methacrylate (SBMA) from high oleic soybean oil (HOSO) can be utilized to produce bio-based acrylic thermoset copolymers through an industrially viable semi-batch emulsion polymerization process with various commonly used co-monomers such as methyl methacrylate, styrene, and butyl acrylate. A wide range of monomer feed ratios with SBMA from 0 to 50 wt% was easily achieved with minimal modifications allowing for good tunability of thermal and mechanical properties in the prepared latexes. More importantly, a simple and effective auto-oxidative crosslinking of the latex films provided extreme mechanical enhancements making these thermosets good candidates in ultra-strong, ultra-tough, and high Tg coating applications.

Experimental validation of a mathematical model for the evolution of the particle morphology of waterborne polymer-polymer hybrids: Paving the way to the design and implementation of optimal polymerization strategies

Polymer-polymer composite nanoparticles allow both the improvement of the performance in established applications of waterborne polymer dispersions and targeting new applications that are out of reach of currently available products. The performance of these materials is determined by the particle morphology. To open the way to process optimization and on-line control of the particle morphology, the capability of the recently developed model to predict the evolution of the particle morphology during seeded semibatch emulsion polymerization process was evaluated. Structured polymer particles were synthesized by copolymerization of styrene and butyl acrylate (St-BA) on methyl methacrylate and butyl acrylate (MMA–BA) copolymer seeds of different glass transition temperature (Tgs). The model captured well the effect of process variables on the evolution of the particle morphology, opening the way to the design and implementation of optimal strategies.

Influence of hydrophobic monomers on secondary nucleation of hydroxyl-functionalized latexes

The influence of butyl acrylate (BA) and methyl methacrylate (MMA) on hydroxyl functionalized latexes was investigated. The hydrophobicity of the monomer feed was varied via the BA/MMA ratio. In addition to monitoring the effect of hydrophobic monomer feed on secondary nucleation, the polymerization kinetics and final latex properties were also obtained for comparison. Five different BA to MMA molar ratios were combined with five 2-hydroxyethyl methacrylate (HEMA) concentrations (0, 10, 20, 30 and 40 mol% in monomer composition). All latexes were synthesized through seeded semibatch emulsion polymerization process. Particle size distributions and average particle sizes of the latexes were determined by dynamic light scattering (DLS) and qualitatively compared with transmission electron microscope (TEM) images. The BA to MMA ratio significantly influences the boundary HEMA concentration at which homogeneous secondary nucleation occurs. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017

The application research of environment-friendly reactive surfactants in acrylate emulsion pressure sensitive adhesives

In this article acrylate pressure sensitive adhesive (PSA) latexes were synthesized via a pre-emulsion seeded semi-batch emulsion polymerization process with a conventional nonreactive surfactant (CO-436) and two polymerizable surfactants (traditional surfmer SE-10N and environment-friendly surfmer SR-10). The effects of surfactant contents on the particle size, zeta potential, electrolyte stability of the latexes and gel content, sol molecular weight (Mw, Mn), water absorption of the PSA copolymers were investigated. In addition, X-ray photoelectron spectroscopy (XPS) and contact angle measurements were used to characterize the latex films. The results showed that the particle sizes of latexes prepared with surfmers were smaller than their CO-436 containing counterparts. And the latexes prepared with surfmers had a lower storage stability than the one prepared with CO-436. However, surfmers can improve the electrolyte stability of the latex. Furthermore, the water resistances of the latexes prepared with surfmers were better than that of the latex with CO-436, which can be confirmed by water absorption, contact angle and XPS analysis. The results also indicated that the PSA prepared with SR-10 exhibited the highest gel content among the three surfactants. Finally, the effects of surfactants on the adhesive properties of the PSAs were also evaluated.

Robust Dynamic Optimization of a Semi-Batch Emulsion Polymerization Process with Parametric Uncertainties-A Heuristic Approach -

Optimized exothermic semi-batch emulsion polymerization typically exhibits active arcs of the constraints for the reactor temperature. Given parametric uncertainties in the process model, this might lead to constraint violations which are a safety concern. Therefore, an approach is investigated, such that constraint violations are less likely and is hence robust feasible. The two-model approach is presented as an approximate solution. Therein, two models, the nominal and a worst-case model are optimized simultaneously. Because of the challenges in defining the worst-case, a heuristic method is presented to define the worst-case parameter and its parameter value. The results of the process optimization with the two-model approach are compared with the results of the optimization with the nominal model solely. In addition the feasibility of both optimization strategies is compared by simulating hundred different scenarios with random parameter values from the uncertainty set. The presented approximation does not guarantee robust feasibility, but path constraint violations are less likely due to the introduced conservatism compared to the original optimization.

High solids TEMPO‐mediated radical semibatch emulsion polymerization of styrene

ABSTRACTA bicomponent initiation system consisting of 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (TEMPO) and the water soluble initiator potassium persulfate (KPS) was used to develop a robust and versatile semibatch emulsion polymerization process to obtain polystyrene (PS) latexes with solids contents of 5–40 wt %. A window of operating conditions was found that yielded high conversion (>95%) stable latexes and well controlled polymers, overcoming limitations found in previous attempts at developing similar processes using TEMPO. The critical parameters studied were surfactant concentration, monomer concentration in the nucleation step and the monomer feed rate in the semibatch step. Methyl acrylate (MA) was used in the nucleation step to improve the nitroxide efficiency (NEff). Latexes having molecular weight distribution (MWD) with dispersity (Đ) lower than 1.5, average particle size (Dp) from ≈32 to ≈500 nm, nitroxide efficiencies NEff up to ≈1.0 and monomer conversions >90% were obtained in less than 12 h with solids contents up to 40 wt %. These results constitute a significant advance over prior efforts in TEMPO‐mediated polymerization in aqueous dispersions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 49–62

Effect of propyleneimine external cross-linker on the properties of acrylate latex pressure sensitive adhesives

Acrylate pressure sensitive adhesive (PSA) latexes were synthesized via a starved monomer seeded semi-batch emulsion polymerization process with butyl acrylate (BA), methyl methacrylate (MMA), acrylic acid (AA) and 2-hydroxyethyl acrylate (HEA). These PSA polymers were then cross-linked with trifunctional propyleneimine external cross-linker (SAC-100) to study the cross-linking reaction between carboxylic group of the polymer chain and cross-linking agent. It was found that cross-linking provided a significant influence on the film formation process based on the result of SEM analysis. In addition, with the increase of SAC-100 content, the gel content of the polymer increased significantly, while molecular weight between cross-link points (Mc) and the sol molecular weight (Mw, Mn) of the polymer decreased remarkably. The TGA result showed that the addition of the external cross-linker can enhance the thermal stability of the latex film. Moreover, for the cross-linked adhesive film, the shear strength was improved greatly while at the sacrifice of loop tack and peel strength, when compared with the uncross-linked counterparts. Besides, dynamic mechanical analysis (DMA) was also used to evaluate the viscoelastic properties of the acrylate emulsion PSA film.

Evolution of particle morphology during the synthesis of hybrid acrylic/CeO2 nanocomposites by miniemulsion polymerization

ABSTRACTThe evolution of the morphology of an acrylic/CeO2 hybrid latex synthesized by a two step seeded semibatch emulsion polymerization process was investigated. The seed was produced by batch miniemulsion polymerization and in the second step a neat monomer preemulsion was fed to the seed to increase the solids content and encapsulate the inorganic material. The morphology of the hybrid miniemulsion droplets, the seed and the final latex was analyzed by TEM. The morphologies achieved could be explained by theoretical equilibrium morphology maps based on the interfacial tensions of the monomeric, polymeric, inorganic and aqueous phases. © 2014 Wiley Periodicals, Inc. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 792–799

A biodistribution study of PEGylated PCL-based nanoparticles in C57BL/6 mice bearing B16/F10 melanoma

One of the major drawbacks that limits the clinical application of nanoparticles is the lack of preliminary investigations related to their biocompatibility, biodegradability and biodistribution. In this work, biodegradable PEGylated polymer nanoparticles (NPs) have been synthesized by using macromonomers based on poly(ε-caprolaconte) oligomers. More in detail, NPs have been produced by adopting a surfactant-free semibatch emulsion polymerization process using PEG chains as a stabilizing agent. The NPs were also labeled with rhodamine B covalently bound to the NPs to quantitatively study their biodistribution in vivo. NPs were investigated in both in vitro and in vivo preclinical systems to study their biodistribution in mice bearing B16/F10 melanoma, as well as their biocompatibility and biodegradability. The NP concentration was evaluated in different tissues at several times after intravenous injection. The disappearance of the NPs from the plasma was biphasic, with distribution and elimination half-lives of 30 min and 15 h, respectively. NPs were retained in tumors and in filter organs for a long time, were still detectable after 7 d and maintained a steady concentration in the tumor for 120 h. 48 h after injection, 70 ± 15% of the inoculated NPs were excreted in the feces. The favorable tumor uptake, fast excretion and absence of cytotoxicity foster the further development of produced NPs as drug delivery carriers.

Industrial Production of Poly Vinyl Acetate Dispersions: Relationship Between Latex Properties and Polymerization Start-Up Temperature

An industrial polymerization process for the production of polyvinyl alcohol stabilized polyvinylacetate dispersions has been examined to investigate the influence of the start-up temperature on production process and latex characteristics. The product investigated is a high solids, high viscosity latex, obtained by a semi-batch emulsion polymerization process, initiated with persulfate. The main finding shows that small variations of the start-up temperature affect the reaction kinetics in the first stage of polymerization and have a direct influence on physicochemical and rheological properties of the finished products.

High‐Solids‐Content Hybrid Acrylic/CeO2 Latexes with Encapsulated Morphology Assessed by 3D‐TEM

Hybrid acrylic/CeO2 latexes with solids content as high as 50 wt% and CeO2 content up to 1 wt% are synthesized by a seeded semibatch emulsion polymerization process. TEM images show that CeO2 nanoparticles are randomly located within the polymer particles. The 2D trasmission electron microscopy (TEM) images are not conclusive to elucidate if CeO2 is encapsulated in the hybrid polymer particles. A TEM tomographic analysis is presented here to assess their morphology. The study shows that the latexes synthesized present an encapsulated morphology for CeO2 nanoparticles regardless of whether these are located at the center or borders of the polymer particles. image

The influence of butyl acrylate/methyl methacrylate/2-hydroxy ethyl methacrylate/acrylic acid latex properties on pressure sensitive adhesive performance

Pressure sensitive adhesives (PSAs) were produced using latexes synthesized via a starved seeded semi-batch emulsion polymerization process with butyl acrylate (BA), methyl methacrylate (MMA) and sometimes additional monomers, 2-hydroxy ethyl methacrylate (HEMA) and/or acrylic acid (AA). For the BA/MMA comonomer latexes, the amount of cross-linker (allyl methacrylate), monomer emulsion and initiator solution feeding times, and the BA/MMA weight ratio were manipulated to vary the polymer properties. The performance of PSA films cast from these latexes was evaluated by tack, peel strength and shear strength. The effect of polymer properties on PSA performance was related to the viscoelastic properties of the PSAs. For BA/MMA latexes, it was not possible to greatly improve the peel strength even at great sacrifice of shear strength for PSAs with gel contents of ∼60 wt% or higher. This was because the ratio of the loss modulus at debonding frequency to the storage modulus at bonding frequency did not vary significantly for the conditions studied. The addition of HEMA provided a significant influence on latex polymer properties as well as PSA performance for both high (>60 wt%) and low (∼20 wt%) gel contents. For some cases, tack, peel strength and shear strength were simultaneously and greatly improved by the addition of HEMA. Adding both AA and HEMA while decreasing the amount of emulsifier, also resulted in a PSA with much better performance (i.e., higher tack, peel strength and shear strength) than a BA/MMA PSA with similar gel content (∼60 wt%).

Parameter estimation strategies in batch emulsion polymerization

A new method for correcting a model which simulates the particle size distribution (PSD) has been proposed for a semi-batch emulsion polymerization process involving the copolymerization reaction between vinyl acetate and butyl acrylate. It uses a least squares estimation implemented on the lines of the moving horizon estimation. The work focuses on two important aspects: (i) To see how parameter estimation can be performed without making any assumption on the process or measurement noise. (ii) Using correction factors in the model equations as independent handles for driving the model predictions of the PSD to that of experiments. The approach gives us an insight into the nature of the error present in the model. The results indicate that the parameter estimation can be made effective by using a minimum number of experimental data for estimation purposes.

Online polymer molecular weight and conversion monitoring via calorimetric measurements in RAFT emulsion polymerization

BACKGROUND: Online measurements of key emulsion polymerization attributes, such as conversion and molar mass distribution, are unavailable. Costly offline measurements at low sampling frequencies with time delays usually lead to insurmountable challenges in real-time product quality monitoring and process/product control. RESULTS: We developed an online calorimetric method monitoring the evolution of conversion and molecular weight in complex polymerization reactors. Our experiments were carried out in a 1 L reactor to produce polystyrene homopolymer. Monomer conversion was obtained in real time from polymerization rate, which was estimated from temperature measurements using platinum thermal transducers. The calorimetric model was validated offline for batch and semi-batch emulsion polymerization of styrene with and without transfer agents. The conversion was validated using offline gravimetry. The molecular weights measured offline via size exclusion chromatography with multiple detectors compared well with those estimated online using the calorimetric method. CONCLUSION: We found that a semi-batch emulsion polymerization process can be controlled online to approach living polymerization involving transfer agents. Thus our model is suitable as a ‘soft-sensor’ for real-time control applications. Copyright © 2009 Society of Chemical Industry

Preparation and characterization of the latexes with different particle sizes by semibatch emulsion polymerization and the influence on properties of waterborne pressure‐sensitive adhesives

AbstractIncreasing environmental concerns and regulations are the major driving forces for the development of waterborne pressure‐sensitive adhesives. This article reported the synthesis of a series of poly[(n‐butyl acrylate)‐co‐(acrylic acid)] latexes with different particle sizes using a semibatch emulsion polymerization process. By changing the levels of surfactant (Aerosol Series) at the seed stage, the z‐average particle diameters (dzs) measured with dynamic light scattering varied from 124 to 366 nm. The polymerizations proceeded under monomer‐starved conditions, and the values of dz measured for samples removed during the polymerizations were consistent with theoretical prediction for particle growth spherically without the secondary nucleation. The gel contents of the polymers were determined by Soxhlet extraction, and the molecular parameters were characterized by gel permeation chromatography and dynamic mechanical thermal analysis. The adhesive properties, loop tack, peel force, and shear resistance were measured according to the Fédération Internationale des Fabricants et Transformateurs d′Adhésifs et Thermocollants sur Papiers et Autres Supports (FINAT) test methods. The results were reported and correlated with the latex particle size and molecular parameters. The spatial architecture of gel domains in the dry film and the molecular connectivity between those gel domains play an important role in controlling its adhesive properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Effect of colophony emulsion on the adhesive properties of vinyl acetate/n‐butyl acrylate copolymeric latex

AbstractWe prepared a novel copolymeric latex of vinyl acetate and n‐butyl acrylate (V‐B) using a semibatch emulsion polymerization process. The glass‐transition temperature (Tg), steady viscosity, flow activation energy (Ef), dynamic moduli, and amphiphilic properties of the V‐B latex in the presence of colophony were systematically investigated. The experimental results demonstrate that excellent adhesive behaviors were achieved for the V‐B latex blended with 20 wt % colophony, whereas good adhesive performance was related to the moderate Tg, viscosity, Ef, storage modulus, and low contact angle on the adherent. The debonding mechanisms for V‐B and its colophony‐modified latexes were analyzed. A possible mechanism for the V‐B latex blended with colophony emulsion was determined. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Hybrid model-based approach to batch-to-batch control of particle size distribution in emulsion polymerization

There is an increasing interest in the control of particulate systems, with a focus on the control of distributions (e.g. particle size distribution (PSD)). It is known that such distributions have strong correlations with end-product quality indices, this motivating their tight regulation. This paper addresses the design of a control strategy for control of PSD in a semi-batch emulsion polymerization process. In particular, this work presents a hybrid modeling approach for batch-to-batch optimization in which a fundamental population balance model describing PSD evolution is augmented by a Partial Least Squares (PLS) model. This hybrid model is then embedded in a successive quadratic program (SQP) to design surfactant and initiator input trajectories that drive the process to a target PSD.