A review of the existing polymerisation processes is proposed, with particular attention to the control of viscosity and heat removal. Up to the present time, different types of reactor have been developed in order to improve the stability of the polymerisation process. A review of these reactors is presented for the heterogeneous and homogeneous polymerisations. The production of solid polymer granules directly in a kneader reactor under evaporative cooling is seen as an efficient and reliable polymerisation technology.

Various types of reactor have been developed to date for improving the stability of the polymerisation process. This review describes a few examples of heterogeneous and homogeneous polymerisation, focusing particularly on viscosity control and heat removal. The production of solid polymer granules directly in a kneader-reactor with evaporative cooling is one efficient and reliable polymerisation technology.

The bulk free radical polymerization of methyl methacrylate (MMA) or the bulk free radical copolymerization of MMA based monomer recipes face a gel effect (Trommsdorff’s effect) and exothermicity. The kneader reactor offers a perfect combination of surface renewal and evaporative cooling to control temperature at high conversion (85 to 95%).

A new type of kneader reactor is proposed for the continuous radical (co-) polymerisation without solvent, based on the proven design of mature (kneader-) dryer technology. The reactor has been developed to satisfy all major aspects required for (co-) polymerisation while maintaining the safety and reliability of the previous mechanical design. The new kneader reactor offers a perfect combination of surface renewal and evaporative cooling to control temperature to high conversion (85 to 95%), even for bulk systems that have a strong gel effect (Trommsdorff’s effect) and high exothermicity.

Batch trials were performed on a kneader reactor where a bulk co-polymerization was carried out. Polymerization conversion, viscosity build, reaction kinetics, and heat transfer calculations were performed using the experimental data from the batch trials. A continuous process was proposed for this bulk copolymerization and the models and results from the batch trials were used in designing the continuous process. Predictions of the continuous process using the batch trial data are compared to the actual continuous process, with a focus on polymer conversion, heat transfer, and torque prediction.

Are you looking for a solvent-free, safe, eco-friendly and energy-efficient way of producing new types of products with new levels of quality? New technology is available to help you do exactly that.

Sie suchen ein lösungsmittelfreies, sicheres, umweltfreundliches und energieeffizientes Herstellungsverfahren, das neue Produkttypen mit neuen Qualitätsmerkmalen hervorbringt? Eine neue Technologie macht’s möglich.

Mit lösemittelfreier Prozessführung, dem sogenannten Dry Processing, lassen sich zwei entscheidende Ziele erreichen: umweltfreundliche Prozesse und eine deutliche Senkung der Investitions- und Betriebskosten. Die Schweizer Firma List konzentriert sich dabei nicht auf einzelne Verfahrensschritte, sondern auf den Prozess als Einheit, um eine ganzheitliche verfahrenstechnische und wirtschaftliche Optimierung zu erreichen.

Converting the polymer industry to solvent-free polymerisation processes and avoiding unnecessary recirculation decreases energy consumption and reduces waste production. This can be achieved with the horizontal large-volume Kneader Reactor with superior mixing and homogenisation performance. The casing, shafts and mixing elements are indirectly heated by heat transfer fluids and dynamically self-cleaning.

Improving Performance in Conversion, Temperature Control, and Reaction Rates.

Summary of the presentation by Daniel Witte during the meeting of the ProcessNet specialist groups Computational Fluid Dynamic, Mixing Processes and Agglomeration and Bulk Solids Technology of DECHEMA in Leipzig, March 16-18, 2022.

Die Sublimation ist ein Verfahren der thermischen Stofftrennung und wird meist als Reinigungsverfahren angewendet, wobei die Knetsublimation unter Vakuum spezielle Vorteile bringt.

The most common application of sublimation is separation of volatile solids and purification of substances. This paper explains the p-T diagram of a pure substance, and discusses existing processes and their operation.

Die Sublimation gehört wie die Destillation, Rektifikation und die Trocknung zu den Verfahren der thermischen Stofftrennung. Sie wird meist als Reinigungsverfahren angewendet, wobei die Sublimation aus einer Trägergasphase als spezielles Verfahren einer stofflichen Gewinnung betrachtet werden kann. Nachfolgend werden die speziellen Vorteile von Knetsublimatoren erläutert.

In diesem Beitrag wird das typische p-T-Diagramm einer reinen Komponente als Ausgangspunkt dargestellt. Danach werden die bisher bekannten Verfahren und Arbeitsweisen mit Nennung der bekanntesten Sublimationsapparate und die speziellen Vorteile der Knetsublimatoren erläutert.

The difference in the production of PA6 in comparison to that of other polymers is the downstream water extraction and drying after the granulation. During these process steps, the monomer and the oligomer contents in the final product are reduced in the 0.2 to 0.6 ww/w range. The installed units for extraction and drying of the final granulated product are characterized by their large energy consumption, which considerably influences manufacturing costs.

Energieeinsparung und Qualitätsverbesserung durch indirekte Eindampfung von Polymerlösungen oder direkte Polymerisation und Polykondensation

Devolatilization of solvents from viscous polymer cement is realized through stripping of solvent with steam in stirred vessels or directly by evaporating the solvent from the polymer. The later so-called direct desolventizing is realized in extruders or high volume kneaders. All 3 methods involve additional energy to drive out solvent either by partial pressure through additional steam (steam stripping), building and releasing pressure in order to explode the polymer bulk (extruder) or dynamic surface renewal (kneader).

A concentrated rubber solution (less than 20 % solvent) is fed to a high volume kneader in order to remove the solvent down to ppm level. A simulation program has been developed to describe this devolatilization step. The program predicts final solvent content, the filling level and the mechanical torque build-up. The program can be used to refine process control and the scale-up of this type of process.

Das Fraunhofer-Pilotanlagenzentrum für Polymersynthese und -verarbeitung

Eine konzentrierte Elastomerlösung (weniger als 20 % Lösungsmittel) wird einem großvolumigen Knetreaktor zugeführt, um das Lösungsmittel bis auf ppmGehalte zu entfernen. Um diesen Entgasungsschritt zu beschreiben, wurde ein Simulationsprogramm entwickelt. Das Programm errechnet den Restlösungsmittelgehalt, den Füllgrad und das Drehmoment des Reaktors. Es kann sowohl der Feineinstellung sowie auch dem Scale-up des Prozesses dienen.

Large volume kneaders are designed to handle highly viscous polymer processing. The unitary operations can be compounding, polymerizations, devolatilization or drying. Depending on the polymer viscosity in the kneader, the interaction of kneading elements induce a torque and force evolution on the shaft over one revolution.

How direct devolatisation of an elastomer solution can save time and money

Polymerprozesse – Aufbereitung und Finishing von Polymeren – Knetertechnologie in der Polymeraufbereitung – Wirtschaftlichkeit

Die bestehenden Technologien für die Aufbereitung von Polymeren nach der Polymerisation können in ein-, zwei- und mehrstufige Verfahren unterteilt werden. Dem entsprechend kommen Stripptechnologien mit nachgeschalteter mechanischer und thermischer Entfernung der Hilfsmittel, Extruder in verschiedenen Bauarten und großvolumige Kneter zum Einsatz. Die Knetertechnologie ist vor allem für temperatur- und scherempfindliche Polymermassen geeignet, bei denen die Entgasung diffusionsbestimmt ist.

The synthesis of most elastomers is carried out either by Solution or emulsion polymerization. After the polymcrization step, the polymer is separated from the solvent or emulsifying agents. This separation requires several process steps including coagulation, Stripping, various mechanical separation stages, and finally diying. Beyond that, the existing technologies are energy consuming, waste solvent must be incinerated, and the installation of main and ancillaiy equipment occupies large spaces.

Die Synthese von Kautschuk ist ein wichtiger Prozess: Hersteller von Gummiprodukten – ganz gleich ob Autoreifen oder Kondome – benötigen hochwertigen Kautschuk als Ausgangswerkstoff. Doch die Kautschukerzeugung ist teuer und verschlingt große Mengen an Energie. Forschern des Fraunhofer-Instituts für Angewandte Polymerforschung IAP in Potsdam ist es gemeinsam mit ihren Entwicklungspartnern LIST AG und Dow Olefinverbund GmbH gelungen, den Energiebedarf der Kautschuksynthese um 76 Prozent zu senken.

Synthetic elastomers have been produced for over 50 years. Advances in catalyst systems and polymer formulations have been somewhat diminished by the continued use of the same processing technology. In particular, the use of coagulation, steam stripping, mechanical dewatering, and convective drying for the devolatilization of temperature sensitive elastomeric solutions can be replaced with direct devolatilization using kneader technology. A two-step, direct devolatilization process has demonstrated energy savings and advantages in environmental emissions and process/product flexibility when compared to the conventional steam stripping process.

Kneader reactors are used for combined unitary processing in the polymer industry for devolatilization, compounding or polymerization. In the past, mass transport prediction for devolatilization operations in kneader reactors did not match experimental results, when diffusion was assumed as sole driving force. It was detected that there is an additional concentration and temperature dependent driving force that triggers enhanced transport at finite solvent concentrations by orders of magnitude. The author suggests that the underlying root cause is likely micro bubble formation within the polymer melt. An attempt to model this additional mass transport mechanism is presented.

Der Einsatz von großen Lösungsmittelmengen in Polymerisationsprozessen mit den damit verbundenen Nachteilen muss nicht sein. Ein neues Verfahren beschreitet neue Wege: Kneten statt strippen lautet die Devise.

Der Einsatz von großen Lösemittelmengen in Polymerisationsprozessen mit den damit verbundenen Nachteilen muss nicht sein. Ein optimiertes Verfahren ermöglicht die direkte Entgasung von Lösemitteln, ohne dabei Strippmittel einsetzen zu müssen. Aufwendige Trennschritte werden so vermieden und höhere Produktqualitäten können erreicht werden.

The achievable final volatile content within kneader devolatilization processes is highly dependent on the final melt temperature. For thermosensitive polymers the state of the art process performs poorly. The amount of dissipated energy leads to a heat up of the polymer, limiting the maximal kneader shaft speed and therefore volatile removal rate. This new process uses a suitable additional volatile compound to cool off the dissipated energy by evaporation using the off gas to strip and boost the mass transfer coefficient. A complex multi-parameter study is presented, to predict performance of industrial equipment from pilot scale data.

The achievable final volatile content within kneader devolatilization processes is highly dependent on the final melt temperature. For thermosensitive polymers the state of the art process performs poorly. The amount of dissipated energy leads to a heat up of the polymer, limiting the maximal kneader shaft speed and therefore volatile removal rate. This new process uses a suitable additional volatile compound to cool off the dissipated energy by evaporation using the off gas to strip and boost the mass transfer coefficient. A complex multi-parameter study is presented, to predict performance of industrial equipment from pilot scale data.

Conventional polymerisation in the production of elastomers has been the norm for decades. The time and cost involved in removing and treating solvents in th e final stages of production , for example, were acceptable, but as pressure builds on manufacturers to reduce operating costs, there is greater urgency to develop processes that can help streamline cost and production. One such effort has yielded extremely promising results.

For decades, conventional polymerization in the production of elastomers has been the norm. The time and cost involved in removing and treating solvents in the final stages of production, for example, were acceptable. But as pressure builds on manufacturers to reduce operating costs, there is greater urgency to develop processes that can help streamline cost and production. One such effort by List AG has yielded promising results.

For decades, conventional polymerisation has been the norm in the production of elastomers. The time and cost involved in removing and treating solvents in the final stages of production were acceptable. Yet as pressure builds on manufacturers to reduce operating costs, there is greater urgency to develop processes that can help streamline costs and production techniques. One such effort has yielded extremely promising results.

A new dissolution process for cellulose spinning solution was developed. As Basis for the new process served the classic cellulosic fiber production process. In the last 30 years or so the conventional viscose process became environmentally critical. Evaluated with regard to its environmental viability it was found to create considerable water and air pollution. This conclusion ignited the research and development of new technologies with less environmental impact.

LIST further optimized the cellulose dissolution technology, which was introduced in 1992. This succeeded the production of excellent spinning solution qualities, produced from a variety of low cost raw materials. The technology fulfils the current high safety standards.

Der LYOCELL-Prozess ist eine moderne umweltfreundliche Möglichkeit zur Umwandlung von verschiedensten cellulosischen Rohmaterialien der Natur in Fasern, Filamente und Folien zur weiteren Verarbeitung in der Textilindustrie, der Verpackungsindustrie oder als Strukturbildner in technischen Anwendungen. Die Nassreißfestigkeit der LYOCELL-Faser übertrifft sogar die der Bauwollfaser.

As world consumption of textile fibers expands with the rapid growth of Asia and other developing countries, sources of fibers other than cotton and rayon must be developed and brought to market to meet demand. Cellulose fibers (Lyocell fibers) can meet these expanding needs because of the specific qualities and characteristics of the fiber, as well as the vast availability of the raw materials.

The Iyo cell fiber process is developed to transform cellulose to a man-made cotton-like fiber. The lyocell process includes a number of processing steps. The dissolving step is the most important one. It represents the heart of the lyocell technology. Kneaders developed by List AG, Arisdorf/Switzerland, are successfully applied for the continuous dissolving step whereby raw materials of different origin can be processed and transferred into a spinabie dope.

In conventional spinning dope production, capacity is typically a function of the maximum processing viscosity the spinning plant can handle. Often the prior dissolving process step is limited by this fact. In a typical wet spinning operation, dope viscosity ranges from 500-2500 Pa ·s (zero shear viscosity at 95 °C) can be handled. For processors looking to meet rising demand with world-sca le plants, the limitations imposed by high viscosity dope sol utions are challenging and costly. List AG, Arisdorf/Switzerland, have now adapted the company’s high viscosity processing technology in order to meet the difficult processing challenges of today’s high-production fiber lines. The technology can easily handle 20,000-200,000 Pa·s (zero shear viscosity).

Fiber, filament, flies and foil are the final products of a complex process of mixing, dissolving, spinning, washing and drying of raw material. Many specialists believe that the spinning part is the only relevant processing step for the final fiber quality. This belief falls short, as the fiber quality also depends on the dissolving step before the spinning step.

Der zunehmende Kostendruck macht keinen Halt vor der Produktion von Elastomeren. Gefragt sind intensivierte Prozesse, die unnötige Verfahrensschritte ersparen und sowohl Zeitaufwand wie auch Kosten senken. Nun liefert ein innovativer Ansatz aus der Schweiz, die sogenannte Direct Devolatilization (direkte Entgasung) von Polymerlösungen, vielversprechende Ergebnisse.

For decades, conventional polymerisation has been the norm in the production of elastomers. The time and cost involved in removing and treating solvents in the final stages of production were acceptable. Yet as pressure builds on manufacturers to reduce operating costs, there is greater urgency to develop processes that can help streamline costs and production techniques. One such effort has yielded extremely promising results.

This lecture concisely reviews the development and evolution of specialised contact kneaders-dryers, presents the field of their application, defines the selection criteria, describes a basic design procedure, and closes with a list of parameters, that helps one to decide between the implementation of a batch or a continuous operating dryer.

Trocknen und Reagieren kombiniert – Die Verbesserung von Produktionsabläufen konzentriert sich heute weniger auf die Optimierung einzelner Verfahrensschritte, als vielmehr auf eine Vereinfachung des Verfahrensablaufs als Ganzes.

This paper elaborates on the constraints of the drying process of industrial sludges and distillation residues, such as, closed design and product containment, processing of sticky, crusting, or fouling intermediate phases, versatility, low energy demand, and single step drying. It then presents the mechanical, thermal and processing features as well as the operating principles of specialised single-shaft, DISCOTHERM B CONTI/BATCH, and twin-shaft, ORP (Opposite-Rotating Processor) CONTI, kneadersdryers.

Grossvolumige Knettrockner ermöglichen es, Prozessschritte zu kombinieren und damit Vorteile hinsichtlich Wirtschaftlichkeit und Produktqualität zu erzielen, speziell dann, wenn zähpastöse oder krustende Zustände zu bewältigen sind.

In the mid seventies, LIST developed and industrialized a continuous process for the recovery of toluene diisocyanate (further TDI) from distillation residue. The process, which will be highlighted in this document, ensures the Maximum recovery of TDI. The final residue is transformed into a non-toxic (neutral) and easy to handle solid/granular material.

Over time, different types of reacotrs have been developed in order to improve the stability of the polymerization process. This article Reviews those reactors designed for heterogeneous and homogeneous polymerization. It then explorres the production of solid polymer granules directly in a kneader reactor under evaporative cooling, which is seen as an efficient and reliable polymerization Technology.

Bei der Aufbereitung von Industrierückständen, Schlämmen und Sonderabfällen müssen nicht nur gesetzliche Vorschriften beachtet werden. Sinnvoll ist es, die Aufbereitung am Entstehungsort vorzunehmen; darüber hinaus sollte eine maximale Rückgewinnung an Wertstoffen sowie ein Minimum an unvermeidbaren Reststoffen gewährleistet sein.

Consistent with the diversity of chemical-process-industries materials that undergo drying, a wide variety of contact dryers have been brought to the marketplace. However, there is a common set of principles for their process design, and for specifying them.

The increase in the amounts of paint and lacquer sludges from industrial processes combined with more stringent legislation, reduction in available land-fills, escalating costs, and the increasing pressure for residues to be processed at the point of origin has created a tremendous incentive for the development of new and economic concepts and techniques for their minimisation.

Optimizing the recovery of residues in the production of polyurethane: learn how we process hazardous and toxic distillation residues and recover the valuable TDI monomer.

A new dissolution process for cellulose spinning solution was developed. As Basis for the new process served the classic cellulosic fiber production process. In the last 30 years or so the conventional viscose process became environmentally critical. Evaluated with regard to its environmental viability it was found to create considerable water and air pollution. This conclusion ignited the research and development of new technologies with less environmental impact.

LIST further optimized the cellulose dissolution technology, which was introduced in 1992. This succeeded the production of excellent spinning solution qualities, produced from a variety of low cost raw materials. The technology fulfils the current high safety standards.

Der LYOCELL-Prozess ist eine moderne umweltfreundliche Möglichkeit zur Umwandlung von verschiedensten cellulosischen Rohmaterialien der Natur in Fasern, Filamente und Folien zur weiteren Verarbeitung in der Textilindustrie, der Verpackungsindustrie oder als Strukturbildner in technischen Anwendungen. Die Nassreißfestigkeit der LYOCELL-Faser übertrifft sogar die der Bauwollfaser.

As world consumption of textile fibers expands with the rapid growth of Asia and other developing countries, sources of fibers other than cotton and rayon must be developed and brought to market to meet demand. Cellulose fibers (Lyocell fibers) can meet these expanding needs because of the specific qualities and characteristics of the fiber, as well as the vast availability of the raw materials.

The Iyo cell fiber process is developed to transform cellulose to a man-made cotton-like fiber. The lyocell process includes a number of processing steps. The dissolving step is the most important one. It represents the heart of the lyocell technology. Kneaders developed by List AG, Arisdorf/Switzerland, are successfully applied for the continuous dissolving step whereby raw materials of different origin can be processed and transferred into a spinabie dope.

Fiber, filament, flies and foil are the final products of a complex process of mixing, dissolving, spinning, washing and drying of raw material. Many specialists believe that the spinning part is the only relevant processing step for the final fiber quality. This belief falls short, as the fiber quality also depends on the dissolving step before the spinning step.

For decades, conventional polymerisation has been the norm in the production of elastomers. The time and cost involved in removing and treating solvents in the final stages of production were acceptable. Yet as pressure builds on manufacturers to reduce operating costs, there is greater urgency to develop processes that can help streamline costs and production techniques. One such effort has yielded extremely promising results.

From Lab Testing to Industrialization, discover how LIST helps knead wood into textile with one of the most advanced, environment-friendly cellulose-based fiber production technologies.

Reactors with indirect contact drying under vacuum conditions are often used for a large variety of different production processes. As a typical example for food processing the production of chocolate- or milk-crumb will be explained and discussed. Moreover, the potential for process optimization will be shown in this example.

Für eine ganze Reihe von verfahrenstechnischen Prozessen in der Lebensmittelindustrie werden Reaktoren eingesetzt, die Produkte mit sher hohen Viskositäten verarbeiten.

Optimierter Prozess zur Herstellung von Schoko-Crumb. Für eine Reihe von verfahrenstechnischen Prozessen werden Reaktoren mit indirekter Kontakttrocknung unter Vakuumbedingungen eingesetzt. Ein typisches Anwendungsbeispiel dieses thermischen Verfahrens aus der Lebensmittelindustrie ist die Herstellung von Schoko- oder Milch-Crumb. Anhand von diesem Beispiel werden Optimierungsmöglichkeiten dargelegt.

Discover the LIST approach, methodology and solutions to help solve your challenges, from the Lab to the Plant. And if you wish, rent a Lab-kneader to test and optimize your process in your own laboratory.

Spezielle Knettrockner erbringen den nötigen Wärme- und Stoffaustausch durch intensives Mischen und Kneten in Kombination mit bester Selbstreinigung und ermöglichen so Prozessoptimierungen.

lndustry is under pressure to deve lop susta inab le processing methods. With this in mind, the List kn eader processor provides an alternative to the stirred-tank reactor for the production of po lymers, allowing so lven ts to be eliminated from the reac tion step. The kneader processor is also an alternative to the extruder for polymer devolatilization.

Kneader reactors are used for combined unitary processing in the polymer industry for devolatilization, compounding or polymerization. In the past, mass transport prediction for devolatilization operations in kneader reactors did not match experimental results, when diffusion was assumed as sole driving force. It was detected that there is an additional concentration and temperature dependent driving force that triggers enhanced transport at finite solvent concentrations by orders of magnitude. The author suggests that the underlying root cause is likely micro bubble formation within the polymer melt. An attempt to model this additional mass transport mechanism is presented.

Torrefaction is a thermochemical treatment of the biomass, carried out at temperatures between 200 and 300 C in the absence of O2. This treatment produces beneficial changes on the biomass fuel, such as the improvement in milling behavior, the increase of calorific value, reduction of Cl, N and S content, reduction of equilibrium moisture content and the improved resistance to biological degradation.

La parte principal del agua se atribuye al almacenamiento, pero también a su mezcla con el lodo para el transporte de éste. Solo una pequeña parte del agua podría considerarse como de reacción directa.

Bei der Erdölförderung, in Raffinerien, bei der Teerdestillation, in Steinkohle- und braunkohlekokereien genauso wie in zahlreichen anderen Industriebereichen entstehen übelriechende Schlämme. Ihre Zusammensetzung ergibt sich aus der Herkunft der Produkte, wobei die Eigenschaften stark schwanken. Solche Teer-Öl-Schlämme werfen bei ihrer Verwertung zahlreiche Probleme auf. Der Beitrag beschreibt Lösungen und Verwertungsmöglichkeiten.

The increase in the amounts of paint and lacquer sludges from industrial processes combined with more stringent legislation, reduction in available land-fills, escalating costs, and the increasing pressure for residues to be processed at the point of origin has created a tremendous incentive for the development of new and economic concepts and techniques for their minimisation.

Allphasen-Knettrockner in geschlossener Bauweise sind gut geeignet, krustende oder zähe Zwischenphasen ohne Trockengutrückführung direkt zu trocknen.

Für die Trocknung von Klär-/Lackschlamm, Destillationsrückständen und Waschlösungen sind Knettrockner besonders gut einsetzbar.

Der zunehmende Kostendruck macht keinen Halt vor der Produktion von Elastomeren. Gefragt sind intensivierte Prozesse, die unnötige Verfahrensschritte ersparen und sowohl Zeitaufwand wie auch Kosten senken. Nun liefert ein innovativer Ansatz aus der Schweiz, die sogenannte Direct Devolatilization (direkte Entgasung) von Polymerlösungen, vielversprechende Ergebnisse.

For decades, conventional polymerisation has been the norm in the production of elastomers. The time and cost involved in removing and treating solvents in the final stages of production were acceptable. Yet as pressure builds on manufacturers to reduce operating costs, there is greater urgency to develop processes that can help streamline costs and production techniques. One such effort has yielded extremely promising results.

For decades, conventional polymerization in the production of elastomers has been the norm. The time and cost involved in removing and treating solvents in the final stages of production, for example, were acceptable. But as pressure builds on manufacturers to reduce operating costs, there is greater urgency to develop processes that can help streamline cost and production. One such effort by List AG has yielded promising results.

Conventional polymerisation in the production of elastomers has been the norm for decades. The time and cost involved in removing and treating solvents in th e final stages of production , for example, were acceptable, but as pressure builds on manufacturers to reduce operating costs, there is greater urgency to develop processes that can help streamline cost and production. One such effort has yielded extremely promising results.

Polymerization of lactide to polylactic acid (PLA) can be performed using conventional reactor technology such as stirred tank reactors, but the conversion and/or final molecular weight may have to be controlled to a lower level. At higher conversion and/or molecular weight, the reaction mass will become very viscous, which limits the ability of conventional reactor technology to provide adequate mixing, minimize mass transfer effects on reaction kinetics, remove exothermic heat of reaction and ensure proper heat transfer in order to eliminate hotspots/thermal degradation.

Converting the polymer industry to solvent-free polymerisation processes and avoiding unnecessary recirculation decreases energy consumption and reduces waste production. This can be achieved with the horizontal large-volume Kneader Reactor with superior mixing and homogenisation performance. The casing, shafts and mixing elements are indirectly heated by heat transfer fluids and dynamically self-cleaning.

The achievable final volatile content within kneader devolatilization processes is highly dependent on the final melt temperature. For thermosensitive polymers the state of the art process performs poorly. The amount of dissipated energy leads to a heat up of the polymer, limiting the maximal kneader shaft speed and therefore volatile removal rate. This new process uses a suitable additional volatile compound to cool off the dissipated energy by evaporation using the off gas to strip and boost the mass transfer coefficient. A complex multi-parameter study is presented, to predict performance of industrial equipment from pilot scale data.

The achievable final volatile content within kneader devolatilization processes is highly dependent on the final melt temperature. For thermosensitive polymers the state of the art process performs poorly. The amount of dissipated energy leads to a heat up of the polymer, limiting the maximal kneader shaft speed and therefore volatile removal rate. This new process uses a suitable additional volatile compound to cool off the dissipated energy by evaporation using the off gas to strip and boost the mass transfer coefficient. A complex multi-parameter study is presented, to predict performance of industrial equipment from pilot scale data.

In der Polymerhers tellung und -verarbeitung werden traditionell kontinuierlich arbeitende Rührkessel, Extruderschnecken und Dünnschichtapparate eingesetzt. Immer öfter kommen jedoch großvolumige, so genannte Knetreaktoren zum Einsatz. Die Bereitschaft zu fundamentalem Umdenken vorausgesetzt, verschaffen sie dem Betreiber Wettbewerbsvorteile.

Der Einsatz von großen Lösemittelmengen in Polymerisationsprozessen mit den damit verbundenen Nachteilen muss nicht sein. Ein optimiertes Verfahren ermöglicht die direkte Entgasung von Lösemitteln, ohne dabei Strippmittel einsetzen zu müssen. Aufwendige Trennschritte werden so vermieden und höhere Produktqualitäten können erreicht werden.

Der Einsatz von großen Lösungsmittelmengen in Polymerisationsprozessen mit den damit verbundenen Nachteilen muss nicht sein. Ein neues Verfahren beschreitet neue Wege: Kneten statt strippen lautet die Devise.

Mit lösemittelfreier Prozessführung, dem sogenannten Dry Processing, lassen sich zwei entscheidende Ziele erreichen: umweltfreundliche Prozesse und eine deutliche Senkung der Investitions- und Betriebskosten. Die Schweizer Firma List konzentriert sich dabei nicht auf einzelne Verfahrensschritte, sondern auf den Prozess als Einheit, um eine ganzheitliche verfahrenstechnische und wirtschaftliche Optimierung zu erreichen.

Sie suchen ein lösungsmittelfreies, sicheres, umweltfreundliches und energieeffizientes Herstellungsverfahren, das neue Produkttypen mit neuen Qualitätsmerkmalen hervorbringt? Eine neue Technologie macht’s möglich.

Are you looking for a solvent-free, safe, eco-friendly and energy-efficient way of producing new types of products with new levels of quality? New technology is available to help you do exactly that.

Kneader reactors are used for combined unitary processing in the polymer industry for devolatilization, compounding or polymerization. In the past, mass transport prediction for devolatilization operations in kneader reactors did not match experimental results, when diffusion was assumed as sole driving force. It was detected that there is an additional concentration and temperature dependent driving force that triggers enhanced transport at finite solvent concentrations by orders of magnitude. The author suggests that the underlying root cause is likely micro bubble formation within the polymer melt. An attempt to model this additional mass transport mechanism is presented.

Synthetic elastomers have been produced for over 50 years. Advances in catalyst systems and polymer formulations have been somewhat diminished by the continued use of the same processing technology. In particular, the use of coagulation, steam stripping, mechanical dewatering, and convective drying for the devolatilization of temperature sensitive elastomeric solutions can be replaced with direct devolatilization using kneader technology. A two-step, direct devolatilization process has demonstrated energy savings and advantages in environmental emissions and process/product flexibility when compared to the conventional steam stripping process.

Die Synthese von Kautschuk ist ein wichtiger Prozess: Hersteller von Gummiprodukten – ganz gleich ob Autoreifen oder Kondome – benötigen hochwertigen Kautschuk als Ausgangswerkstoff. Doch die Kautschukerzeugung ist teuer und verschlingt große Mengen an Energie. Forschern des Fraunhofer-Instituts für Angewandte Polymerforschung IAP in Potsdam ist es gemeinsam mit ihren Entwicklungspartnern LIST AG und Dow Olefinverbund GmbH gelungen, den Energiebedarf der Kautschuksynthese um 76 Prozent zu senken.

The synthesis of most elastomers is carried out either by Solution or emulsion polymerization. After the polymcrization step, the polymer is separated from the solvent or emulsifying agents. This separation requires several process steps including coagulation, Stripping, various mechanical separation stages, and finally diying. Beyond that, the existing technologies are energy consuming, waste solvent must be incinerated, and the installation of main and ancillaiy equipment occupies large spaces.

Batch trials were performed on a kneader reactor where a bulk co-polymerization was carried out. Polymerization conversion, viscosity build, reaction kinetics, and heat transfer calculations were performed using the experimental data from the batch trials. A continuous process was proposed for this bulk copolymerization and the models and results from the batch trials were used in designing the continuous process. Predictions of the continuous process using the batch trial data are compared to the actual continuous process, with a focus on polymer conversion, heat transfer, and torque prediction.

Die bestehenden Technologien für die Aufbereitung von Polymeren nach der Polymerisation können in ein-, zwei- und mehrstufige Verfahren unterteilt werden. Dem entsprechend kommen Stripptechnologien mit nachgeschalteter mechanischer und thermischer Entfernung der Hilfsmittel, Extruder in verschiedenen Bauarten und großvolumige Kneter zum Einsatz. Die Knetertechnologie ist vor allem für temperatur- und scherempfindliche Polymermassen geeignet, bei denen die Entgasung diffusionsbestimmt ist.

Polymerprozesse – Aufbereitung und Finishing von Polymeren – Knetertechnologie in der Polymeraufbereitung – Wirtschaftlichkeit

How direct devolatisation of an elastomer solution can save time and money

Large volume kneaders are designed to handle highly viscous polymer processing. The unitary operations can be compounding, polymerizations, devolatilization or drying. Depending on the polymer viscosity in the kneader, the interaction of kneading elements induce a torque and force evolution on the shaft over one revolution.

Eine konzentrierte Elastomerlösung (weniger als 20 % Lösungsmittel) wird einem großvolumigen Knetreaktor zugeführt, um das Lösungsmittel bis auf ppmGehalte zu entfernen. Um diesen Entgasungsschritt zu beschreiben, wurde ein Simulationsprogramm entwickelt. Das Programm errechnet den Restlösungsmittelgehalt, den Füllgrad und das Drehmoment des Reaktors. Es kann sowohl der Feineinstellung sowie auch dem Scale-up des Prozesses dienen.

Eine Vielzahl der heute im Einsatz befindlichen Polymersynthesen verarbeiten Stoffe und Stoffgemische, die zur besseren Handhabung der Roh-, Zwischen- und Endprodukte sowie zur Verhinderung von Temperaturschädigungen mit großen Mengen organischem Lösungsmittel, in der Regel Aliphaten oder Aromaten, verdünnt werden. Der technische, technologische und ökonomische Aufwand für die nachfolgend notwendige Aufarbeitung, die Entfernung dieses Lösungsmittels oder anderer Stripphilfsmittel, ist dabei sehr hoch. Einen möglichen Lösungsansatz stellt die Nutzung von großvolumigen Knetern für die Polymersynthese und die direkte Eindampfung von Polymerlösungen in einem Hochviskosprozess dar.

Das Fraunhofer-Pilotanlagenzentrum für Polymersynthese und -verarbeitung

A concentrated rubber solution (less than 20 % solvent) is fed to a high volume kneader in order to remove the solvent down to ppm level. A simulation program has been developed to describe this devolatilization step. The program predicts final solvent content, the filling level and the mechanical torque build-up. The program can be used to refine process control and the scale-up of this type of process.

Devolatilization of solvents from viscous polymer cement is realized through stripping of solvent with steam in stirred vessels or directly by evaporating the solvent from the polymer. The later so-called direct desolventizing is realized in extruders or high volume kneaders. All 3 methods involve additional energy to drive out solvent either by partial pressure through additional steam (steam stripping), building and releasing pressure in order to explode the polymer bulk (extruder) or dynamic surface renewal (kneader).

Energieeinsparung und Qualitätsverbesserung durch indirekte Eindampfung von Polymerlösungen oder direkte Polymerisation und Polykondensation

Grossvolumige Knettrockner ermöglichen es, Prozessschritte zu kombinieren und damit Vorteile hinsichtlich Wirtschaftlichkeit und Produktqualität zu erzielen, speziell dann, wenn zähpastöse oder krustende Zustände zu bewältigen sind.

The increase in the amounts of paint and lacquer sludges from industrial processes combined with more stringent legislation, reduction in available land-fills, escalating costs, and the increasing pressure for residues to be processed at the point of origin has created a tremendous incentive for the development of new and economic concepts and techniques for their minimisation.

Bei der Aufbereitung von Industrierückständen, Schlämmen und Sonderabfällen müssen nicht nur gesetzliche Vorschriften beachtet werden. Sinnvoll ist es, die Aufbereitung am Entstehungsort vorzunehmen; darüber hinaus sollte eine maximale Rückgewinnung an Wertstoffen sowie ein Minimum an unvermeidbaren Reststoffen gewährleistet sein.

This paper elaborates on the constraints of the drying process of industrial sludges and distillation residues, such as, closed design and product containment, processing of sticky, crusting, or fouling intermediate phases, versatility, low energy demand, and single step drying. It then presents the mechanical, thermal and processing features as well as the operating principles of specialised single-shaft, DISCOTHERM B CONTI/BATCH, and twin-shaft, ORP (Opposite-Rotating Processor) CONTI, kneadersdryers.

A dryer designed for pasty materials handles solvent Evaporation problems

Synthetic fibers facility uses thermal evaporation Technology to recover waste solvent and minimize residues.

Ölschlämme sind meist ein Gemisch unterschiedlicher Rückstände und die physikalischen Eigenschaften dieser schwankt in weiten Grenzen. Daher stellt die Aufarbeitung dieser Ölschlämme hohe Anforderungen an Trockner.

Knettrockneranlagen zur Lösemittelrückgewinnung und Wertstoffverwertung ermöglichen die betriebssichere und umweltfreundliche Entsorgung feststoffhaltiger, hochviskoser Rückstände am Entstehungsort.

Allphasen-Knettrockner in geschlossener Bauweise sind gut geeignet, krustende oder zähe Zwischenphasen ohne Trockengutrückführung direkt zu trocknen.

Für die Trocknung von Klär-/Lackschlamm, Destillationsrückständen und Waschlösungen sind Knettrockner besonders gut einsetzbar.

“Hands-On”-Science for Successful High Viscosity Process Trials.

Torrefaction is a thermochemical treatment of the biomass, carried out at temperatures between 200 and 300 C in the absence of O2. This treatment produces beneficial changes on the biomass fuel, such as the improvement in milling behavior, the increase of calorific value, reduction of Cl, N and S content, reduction of equilibrium moisture content and the improved resistance to biological degradation.