bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Falling Film Reactor for Melt Polycondensation Process
Authors: Xi Zhenghao , Zhao Ling , Liu Zhaoyan 
Published: December 2007

AbstractSummary: A grid falling film tower (GFFT) has been invented as an ideal polycondensation reactor. In this reactor, polymer melt flows through multi‐layers grids from top to bottom to form falling film owing to gravity without agitation and shear; large gas‐liquid interfacial area is generated; the grids are perpendicular between adjacent layers to ensure film renewal and to achieve uniformly flowing. The fluid flow in this reactor has little back‐mixing and dead zone, which is near to plug flow. All melts are under the state of thin film which avoids the negative effect of hydrostatic head on the mass transfer impetus. Furthermore, the GFFT has wide operation flexibility as well as adjustable configuration parameters to meet different demands. A pilot scale GFFT with the height of 4.0 meters has been applied to polyester polycondensation process. The intrinsic viscosity of polyethylene terephthalate increased from 0.45 dl/g to 0.8–0.9 dl/g successfully. GFFT is supposed to be an universal apparatus for many devolatilization processes.
Recent Advances in Modern Static Devolatilization
Authors: Wäckerlin Manfred , Nising Philip 
Published: December 2007

AbstractSummary: The present paper deals with state‐of‐the‐art static devolatilization technology for polymer melts. Recent results obtained by CFD‐studies as well as by experimental testing at pilot scale are presented for the devolatilization of technical thermoplasts like polystyrene, poly (methyl methacrylate) and polycarbonate. It is shown that with the correct design of preheater and devolatilization chamber, volatiles like monomers and solvents can be efficiently removed from the polymer melt, both from the economical and technological point of view. As design criteria for the preheater, maldistribution and heat transfer efficiency are explained in detail.
Process Intensification of Emulsion Polymerization in the Continuous Taylor Reactor
Authors: Rüttgers Dana , Negoita Iuliana , Pauer Werner , Moritz Hans‐Ulrich 
Published: December 2007

AbstractSummary: Process intensification is investigated by the emulsion polymerization of styrene in the continuous Taylor reactor. The result is an increase in space time yield up to a factor 200 in comparison to a semi‐batch polymerization process. This is obtained by a fast emulsion polymerization with a mean residence time, which is reduced to 60 seconds. The article presented the results of the process and the economical aspects of the Taylor reactor plant.
Characterization of Mixing Efficiency in Polymerization Reactors Using Competitive‐Parallel Reactions
Authors: Kunowa Kathrin , Schmidt‐Lehr Sebastian , Pauer Werner , Moritz Hans‐Ulrich , Schwede Christian 
Published: December 2007

AbstractSummary: In this article particular attention is paid to processes of mixing fluids with different viscosities relevant for polymerization where the reaction is fast and mixing is the limiting factor. Apart from this, mixing fluids with different viscosities is still one of the challenging tasks in industrial chemistry. Therefore, the characterization of mixing elements is another important topic.Two different multiple chemical reactions, based on the principle of competitive‐parallel reactions, were used and compared to investigate (micro)mixing efficiency in polymerization reactors. The well‐known Villermaux‐Dushman reaction and the third Bourne reaction were applied. The observed product distribution represents the quantity of segregation of the fluid which gives in turn information about the dependency on certain parameters like type and speed of stirrer, dosing period, feed position, and the viscosity of the fluid.The results from semibatch and continuous stirred tank reactors and two different stirrers, Rushton and INTERMIG® impeller, are discussed.
Model Based Operation of Polymer Processes – What has to be Done?
Authors: Bausa Jens 
Published: December 2007

AbstractSummary:In the last two decades, simulation technology had a large influence on process industries. Today, modern numerical methods, powerful personal computers and convenient software packages facilitate the solution of complex chemical engineering problems on the basis of rigorous process models at every office workplace. However, although in many cases process models are available from the process design step, model based operation of production plants can only be found rarely. Changing this situation would significantly contribute to the cost effectiveness of many production plants.This contribution focuses on the model based operation of polymer processes which are for some reasons not perfectly suited for model application: Polymer process models tend to be complex, meaningful online measurements are expensive and not always reliable, many polymer processes are performed in batch instead of steady‐state and for most polymer plants, due to the smaller throughput, the economic impact of model application is much smaller than compared to for instance a steam cracker.When model based operation is considered, it has to be recognized that there is not one single approach but many different alternatives of which maybe only a single one will lead to a sustainable economical improvement of the process. From many successfully applied concepts for model based plant operation it can be clearly identified that always trying to implement the most complex solution (e.g. nonlinear closed‐loop online optimization) is neither possible nor reasonable but that plant specific tailor‐made solutions are necessary.
Influence of Reaction Pressure on Semibatch Esterification Process of Poly(ethylene terephthalate) Synthesis
Authors: Patel Himanshu , Feix Gunter , Schomäcker Reinhard 
Published: December 2007

AbstractSummary: Influence of esterification pressure on oligomeric properties was studied by using a semibatch reactor. Esterification model for semibatch process was further improved by considering EG reflux in the column. It was observed that increasing the reaction pressure decreases EG/water ratio in the column while increasing the EG/TPA feed ratio increases EG/water ratio in the column. By controlling the EG reflux in a semibatch reactor, it is possible to generate oligomers with similar oligomeric properties observed at different stages of continuous process.
Estimation of Kinetic Parameters for the Polar‐Modified Anionic Solution Copolymerization of 1,3‐Butadiene and Styrene
Authors: McIntosh W. Carl , Hamann Evemarie , Oertel Ronald , Bartke Michael 
Published: December 2007

AbstractSummary: The application of the terminal copolymerization model to polar modified anionic initiated 1,3‐butadiene/styrene systems in hydrocarbon solvent requires the determination of twelve kinetic model parameters. These include frequency factors (kxY,∞), activation energies (ExY) and live chain end association numbers (nxY) for all four possible combinations of live chain end termini and free monomer. The individual determination of all twelve parameters requires an enormous numerical effort and a large number of experiments. A method for estimating parameters with a minimum number of kinetic batch experiments in an industrial environment will be demonstrated.
Steady State Simulation of Ethylene Polymerization Using Multiple‐Site Coordination Catalysts
Authors: Valencia Francisco Pérez , Soares Joao B.P. 
Published: December 2007

AbstractSummary: Simulation models are important tools for the development and optimization of polymerization processes because they can describe catalyst performance and polymer properties as a function of polymerization kinetics and process conditions. As the polyolefin industry moves towards the production of resins with more complex microstructures, these models become essential for process understanding and product design. A simulation model has been developed for the polymerization of ethylene in a process with n reactors working in series. The model can predict raw material conversions and product properties like the molecular weight distribution (MWD) coupled with short chain branching distribution (SCBD), melt index, density and fluff morphology. Model parameters have been obtained from laboratory data. The model predictions are in good agreement with experimental results.
Modeling Polycondensation of Lactic Acid
Authors: Harshe Yogesh M. , Storti Giuseppe , Morbidelli Massimo , Gelosa Simone , Moscatelli Davide 
Published: December 2007

AbstractSummary: A mathematical model for the polycondensation of lactic acid accounting for water removal by diffusion is developed. The corresponding kinetic parameters are estimated by performing experiments under different sets of reaction conditions in open system. The model results are compared with the experimental ones and, after validating the model, parametric simulations are further carried out to understand the effects of operating conditions such as reaction temperature, catalyst activity, and reaction pressure.
A Novel Production Route for Nylon‐6:. Aspects of Catalysis and Process Development
Authors: Meuldijk J. , van Dijk A. J. M. , Duchateau R. , Koning C. E. 
Published: December 2007

AbstractSummary: A novel production route for nylon‐6 out of 6‐aminocapronitrile has been investigated. Hydrolysis of 6‐aminocapronitrile using a solid porous ZrO2 catalyst is the key step in this novel route. Nylon‐6 with a number average molecular weight of 10 · 103 g · mol−1 can be produced from the hydrolyzed 6‐aminocapronitrile. The reactor set up for the polycondensation can in broad outline be the same as the continuously operated reactor used for the ε‐caprolactam based production of nylon‐6. For the hydrolysis of 6‐aminocapronitrile a number of parallel batchwise operated loop reactors is recommended. A fixed bed of catalyst particles is part of each recirculation loop. Intraparticle mass transport limitation can be avoided by using catalyst particles made of a shell of active ZrO2 and a massive inert core. An annual production of 50 · 106 kg nylon‐6 demands for 5.3 m3 zirconia.
Ethylene/1‐Butene Copolymerization over Heterogeneous Metallocene Catalyst
Authors: van Grieken Rafael , Martín Carlos , Moreno Jovita , Prieto Oscar , Bravo Jose M. 
Published: December 2007

AbstractSummary: Nowadays, bimodal polyethylene obtained in a two step cascade process is a matter of intensive research in polyolefin field. In the second stage of this process, a high molecular weight ethylene‐α‐olefin copolymer is formed over the homopolymer produced in the first step. In this work, a study of reaction variables on this second step using an heterogeneous metallocene catalyst was carried out. The effect of reaction temperature (70–85 °C) and comonomer concentration (0–0.32 mol/l) was evaluated. Polymerization results showed that activity increases with temperature and 1‐butene initial concentration. Moreover, higher comonomer concentrations and lower temperatures involve higher short chain branching (SCB). Copolymers characterization indicated that melt temperature and density values have a lineal decrease with the SCB content in the polymer, regardless of the reaction temperature. As well, for every temperature, higher comonomer concentrations do not seem to affect to molecular weight, whereas a decrease of crystallinity was observed, which may explain the increase of catalyst activity.
Fe2+ Catalyzed Synthesis of Radiation Grafted Functional Membranes and Application in Fuel Cells and Ion Recovery
Authors: Schmidt Christian , Schmidt‐Naake Gudrun 
Published: December 2007

AbstractSummary: 1‐Vinylimidazole is grafted onto Poly(ethylene‐alt‐tetrafluoroethylen (ETFE) by means of pre‐irradiation technique with electron beam doses between 50 and 150 kGy. The degree of grafting is significantly increased to values of up to 115% by addition of 20‐50 mmol/L of an Fe2+ salt that facilitates the decomposition of the peroxide structures within the irradiated films. The obtained mechanically stable and flexible ETFE‐graft‐poly(1‐vinylimidazole) membranes exhibit a homogenous distribution of the graft polymer for degrees of grafting greater than 50 wt.‐% and show thermal stability up to 250 °C. The applicability of these membranes as anhydrous proton conducting material when doped with phosphoric acid and the complexation capability for Cu2+ ions is demonstrated.
Sorption and Swelling of Poly(D,L‐lactic acid) and Poly(lactic‐co‐glycolic acid) in Supercritical CO2
Authors: Pini Ronny , Storti Giuseppe , Mazzotti Marco , Tai Hongyun , Shakesheff Kevin M. , Howdle Steven M. 
Published: December 2007

AbstractSummary: The equilibrium sorption and swelling behavior in supercritical CO2 of poly(D,L‐lactic acid) and poly(lactic‐co‐glycolic acid) has been studied at a temperature of 35 °C and at pressures up to 200 bar. Sorption was measured through a gravimetric technique and swelling by visualization. From these data, the behavior of the different polymers can be compared. In terms of partial molar volume of CO2 in the polymer matrix, all the polymers exhibit a behavior typical of rubbery systems. The experimental results have been modeled using the Sanchez‐Lacombe equation of state, which is able to represent the actual behavior of the polymer‐CO2 systems with reasonable accuracy.
Dispersion Polymerization of Methyl Methacrylate in Supercritical Carbon Dioxide: Control of Molecular Weight Distribution by Adjusting Particle Surface Area
Authors: Mueller Philipp A. , Storti Giuseppe , Morbidelli Massimo , Mantelis Charalampos A. , Meyer Thierry 
Published: December 2007

AbstractSummary: Experiments of methyl methacrylate dispersion polymerization are carried out in a reaction calorimeter using PDMS‐mMA as surfactant. Different stabilizer concentrations from 0 to 10 wt% with respect to monomer have been considered in order to control particle morphology. The analysis by scanning electron microscopy reveals a definite decrease of the total particle surface area at decreasing stabilizer concentration. At the same time, the analysis of the polymer microstructure by gel permeation chromatography shows a trend of the average molecular weight towards smaller values. In particular, a second mode at low molecular weights has been observed leading to bimodal molecular weight distributions. The experimental results are compared with simulation results obtained through a detailed kinetic model developed in previous studies.1 The key role of the radical exchange between continuous and dispersed phases is confirmed.
Effect of 1‐Hexene Comonomer on Polyethylene Particle Growth and Kinetic Profiles
Authors: van Grieken Rafael , Carrero Alicia , Suarez Inmaculada , Paredes Beatriz 
Published: December 2007

AbstractSummary: The polymer growth and the microstructure of the final polymer are greatly affected by mass transfer, especially in the early stages of polymerization. In the present work, the catalytic system (nBuCp)2ZrCl2/MAO immobilized over SiO2‐Al2O3 has been tested in ethylene‐1‐hexene copolymerizations using different amounts of comonomer. The catalytic activity shows a positive comonomer effect up to 1‐hexene concentration of 0.724 mol/L since larger amounts of 1‐hexene lead to a decrease in the activity. Copolymer properties analyzed by 13C NMR, GPC, CRYSTAF and DSC point to the presence of important amorphous regions in the growing polymer chains as the 1‐hexene concentration increases.In order to study the incorporation of 1‐hexene during ethylene polymerization, several experiments were performed with 0.194 mol/L of 1‐hexene, 5 bar of ethylene pressure and different polymerization times. The incorporation of 1‐hexene decreases slightly at polymerization times above 20 minutes. From cross‐sectioned SEM images it can be concluded that the presence of 1‐hexene helps catalyst fragmentation which could be related with the filter effect proposed by Fink.
Adaption of the Mechanism of Emulsion Polymerization to New Experimental Results
Authors: Tauer Klaus , Hernández Hugo F. , Kozempel Steffen , Lazareva Olga , Nazaran Pantea 
Published: December 2007

AbstractSummary: New experimental investigations of the 'classical' batch ab‐initio emulsion polymerization of styrene reveal the important role of monomer droplets for the whole process. Monomer droplets with a size between a few and some hundreds of nanometers, which are formed by spontaneous emulsification as soon as styrene and water are brought into contact, have a strong influence on the particle nucleation, the particle morphology, and the swelling of the particles. Experimental results confirm that micelles of low molecular weight surfactants are not a major locus of particle nucleation. Brownian dynamics simulations show that the capture of matter by the particles (monomer or radicals) strongly depends on the polymer volume fraction and the size of the captured species (primary free radicals, oligomers, single monomer molecules, or clusters).
Nucleation in Emulsion Polymerization: Another Step towards Non‐Micellar Nucleation Theory
Authors: Nazaran Pantea , Tauer Klaus 
Published: December 2007

AbstractSummary: Comprehensive experimental results of the nucleation stage of styrene emulsion polymerization in the absence as well as in the presence of emulsifier at different concentrations are presented. In addition, the influence of initiator type and presence of seed particles are studied. The nucleation mechanism is verified by means of on‐line monitoring of the optical transmission and the conductivity of the aqueous phase. Results prove that micelles do not alter the nucleation mechanism which comprises the initiation of water soluble oligomers in the aqueous phase followed by their aggregation into colloidally stable latex particles. Surfactants assist with nucleation as they lower the activation free energy of particle formation. Contrary, in the presence of seed particles above a critical volume fraction the formation of new particles can be suppressed.
Brownian Dynamics Simulation Studies on Radical Capture in Emulsion Polymerization
Authors: Hernández Hugo F. , Tauer Klaus 
Published: December 2007

AbstractSummary: A computer simulation method based on the solution of the equations of Brownian motion is used to study the process of radical capture in emulsion polymerization. The effect of the size of the radical was studied, showing that as the radical grows its mobility is reduced (its diffusion coefficient decreases), and this leads to lower collision rates. The distance between the radicals and the surface of the particles at the moment of radical generation was found to be a very important factor in radical capture, with an increase of several orders of magnitude in the collision rate as the radical is generated closer to the particle surface. The effect of process temperature and interfacial barriers to radical capture on the collision rate and on the collision efficiency, defined as the ratio of successful radical captures to the total number of radical‐particle collisions, is also analyzed. In the presence of an energy barrier, multiple collisions are observed, having an important effect on capture kinetics. The results obtained evidence the complexity involved in emulsion polymerization and demonstrates the capability of Brownian Dynamics simulation as a powerful tool for the study and understanding of such complex systems.
Kinetic Study of the Copolymerisation of Ethylene with a Single Site Catalyst in Propane Slurry Polymerisation
Authors: Kröner Sebastian , Eloranta Kirsi , Bergstra Michiel F. , Bartke Michael 
Published: December 2007

AbstractSummary: The kinetic behaviour of a supported metallocene catalyst in slurry polymerisation of ethylene with 1‐hexene under industrially relevant reaction conditions has been studied. Polymerisation experiments were carried out in a 5‐litre stirred tank reactor in a temperature range from 60 to 80 °C and ethylene partial pressures from 5 to 15 bar. Comonomer and hydrogen amounts were varied as well. The catalyst showed pronounced activation and slow deactivation during runtimes of about 1 hour. Strong influences of 1‐hexene (“hexene effect”) and hydrogen (“hydrogen effect”) on the activity profiles were observed. Based on the experimental results, a kinetic model has been derived in order to describe and predict important polymerisation data such as activity profile, comonomer content and molecular weight distributions with respect to the reaction conditions. The presented kinetic model is able to describe the observed effects of 1‐hexene and hydrogen on the activity profiles, as well as the comonomer incorporation across a broad range of polymerisation conditions. The molecular weight distributions can be simulated with good qualitative agreement to the experimental data.
High‐Solids Content Waterborne Polymer‐Clay Nanocomposites
Authors: Diaconu Gabriela , Asua José M. , Paulis Maria , Leiza Jose R. 
Published: December 2007

AbstractSummary: Waterborne polymer clay nanocomposites (WPCN) were prepared by emulsion and miniemulsion copolymerization of butyl acrylate and methyl methacrylate with enhanced mechanical, thermal and barrier properties for coating applications. Emulsion polymerization was used to synthesize WPCN using pristine Na‐MMT (sodium montmorillonite) and miniemulsion polymerization to prepare the WPCNs when the pristine clay was organically modified and hence its incorporation into the polymerization loci was not guaranteed by the conventional emulsion polymerization technique. Both techniques allowed preparing stable nanocomposite latexes of BA/MMA copolymers with partially exfoliated morphologies as demonstrated by wide X‐ray difraction (WAXD) and transmission electron microscope (TEM) measurements. Furthermore, latexes with solids contents up to 45 wt% and manageable viscosities were prepared for the first time using seeded semibatch emulsion polymerization.
Sorption and Diffusion of Propylene and Ethylene in Heterophasic Polypropylene Copolymers
Authors: Bartke Michael , Kröner Sebastian , Wittebrock Annette , Reichert Karl‐Heinz , Illiopoulus Ilias , Dittrich Christoph Johannes 
Published: December 2007

AbstractSummary: Sorption experiments of ethylene and propylene in different polypropylene powder samples, both homopolymer and heterophasic copolymers with different rubber content, have been carried out in a high‐pressure magnetic suspension balance at 10 bars pressure and 70 °C. The gross solubilities measured can be well correlated with the rubber content of the polymer samples. Solubility of ethylene and propylene in the rubber phase differ from solubility in the amorphous fraction of the homopolymer, especially the concentration ratio of propylene to ethylene differs significantly between rubber phase and amorphous fraction of the homopolymer. From the slope of monomer uptake, information on kinetics of mass‐transfer can be gained. No significant differences were observed in terms of mass‐transfer for ethylene and propylene. With increasing rubber content, effective diffusion coefficients increased slightly. By combined sorption studies with powder samples and compressed films, information about both effective diffusion coefficients and the effective length scale of diffusion could be gained. It could be shown, that the particle radius is not the characteristic length of diffusion in the studied powder samples. Mass transfer of nearly all samples could be described by a constant diffusion length of 120 to 130 µm, independently on particle size. This indicates that the effective scale of diffusion in polymer particles is in between microparticle and macroparticle scale used in classical particle modeling.