To respond to different and rapidly changing market requirements as a medium-sized compounder, all production ranges must be compatible. To achieve this, a complete, globally standardized concept for flexible compounding was developed in partnership with a machinery manufacturer. 

Quality, Efficiency, and Flexibility through Standardized Compounding and Extrusion Technology 

Supply Chain Management

Compound

Extrusion

Compoundieren

Q-Management(system), Strategie

Qualitätssicherung

Compoundeure

Standardized Production Concept Guarantees Quality 

Greater efficiency and flexibility, even in continuous processes such as extrusion, are the orders of the day in plastics processing. At the K 2016, contours of a platform became visible that supports data sharing between process steps all the way to component self-identification.  

A Wealth of Ideas for the Linkage of Work Steps across Processes 

Industrie 4.0

Blasfolienextrusion

Kunststoff-Aufbereitung

Continuously toward Industry 4.0 

The selection of extrusion products at the K 2016 trade fair ranged from new equipment concepts over flexible tool systems to software for equipment networking and process monitoring. 

An Eye for Details to Improve Efficiency 

Werkstoffprüfung

Greater Extrusion Flexibility  

Coperion GmbH, Stuttgart, Germany, is now offering its ZSK Mv Plus twin screw extruder in a best-practice design. The extruder for powder coating production marketed as "ZSK 43 Mv PLUS world proven" comes with 43 mm screw diameter. 

Best-Practice Design 

Extruder

ZSK 43 Mv Plus Twin Screw Extruder 

Due to their modularity, the new Buss compounding systems can be configured specifically to meet the needs of the user and are suitable for processing a wide range of products. Flexible configuration of the process section with kneading flights opens up new compounding possibilities. 

Further Development of Buss Kneader Technology Opens up New Application Fields 

Aufbereitungsmaschinen

Compounding Systems with  Variable Kneading Flights 

The ZRD rotary valve from Coperion GmbH, Stuttgart, Germany, is specially designed for plastics, mineral, chemical and food applications. The valve is engineered for heavy-duty industrial service with pressure differentials up to 21 psi(g) and temperatures up to 212°F; higher temperature options are available. The ZRD is often used as a discharging and metering valve for conveying products in powder and granular form. 

Coperion Manufactures ZRD Rotary Valve in USA 

For Heavy-Duty Industrial Service  

Compounds with long fiber reinforcement are easier to process, but also more expensive than using fibers and granulate separately. Not only can the direct compounding of fibers and plastics during extrusion reduce costs, the characteristics can also be improved due to longer fibers. The secret of a simplified plant concept lies in the screw. 

Improved Characteristics with Lower Costs through the Direct Extrusion of Long Fibers 

Verstärkungsstoffe

Glasfasern / -matten

Fasern

Synergies from the Screw 

The patent on the operating principle of the co-kneader was applied for three quarters of a century ago. Compared to other extruder technologies, it features a clearly higher mixing effect while it processes the raw materials gently. Current applications for its further development range from reactive, shear-sensitive plastics to the compounding of high-performance engineering plastics.

Looking into the process chamber of the current generation of Compeo type co-kneaders we see the position of the stationary kneading pins in the barrel that comb the kneading flights of the modular screw

Gentle Compounding with High Mixing Effect and Good Scalability in the Co-Kneader

Kunststoffverarbeitung: Verfahren

Kunststoffverarbeitung: Maschinen und Komponenten

The One that Shears, Splits,  and Folds Material

Munich-based mechanical engineering group KraussMaffei is repositioning itself and uniting all divisions under a single brand. At a time of accelerated technological change, the company is increasing its efforts to develop new products for digital solutions and new business models – and that includes plastics recycling.

Everything remains different: Dr. Frank Stieler, CEO of KraussMaffei

KraussMaffei Consolidates Three Divisions and the Previous Group Brands under a Single Brand

Spritzgießen

Doriat, Clemens, Dr.

Spritzgießmaschinen, allgemein

Spritzgießmaschinen

Digitale Transformation

Wirtschaft

Innovationen und neue Technologie

Nachhaltigkeit

Umweltmanagement

Industrie 4.0 für die Kunststoffverarbeitung

Kunststoff-Recycling

Ressourcenmanagement

Produktion

Moving with the Times

Innovative leadership through forward-looking technology concepts. ENTEX Rust & Mitschke GmbH is the leading manufacturer of Planetary Roller Extruders. ENTEX owns more than 160 registered property rights for the continuously developed products and additional systems. The product portfolio also includes tempering systems and calander rolls.

ENTEX Rust & Mitschke GmbH  

https://www.entex.de

Biokunststoffe

Kunststoff Werkstoffe

Duroplaste

Hochleistungskunststoffe

Thermoplaste

Polyethylenterephthalat

Silikone

Standardkunststoffe

Technische Kunststoffe

Temperieren

Wärmebehandlung

Verbundwerkstoffe / Werkstoffverbunde

With a newly developed process from Entex it was possible to compound an injection grade compound of PLA with a 50 % wood flour content.

The PLA compound with 50 % wood flour content was successfully produced on Entex’s planetary roller extruder

16:9

Compounding PLA Formulations with a 50 % Wood Flour Content, without Premixing

Extrusionsanlagen

Kunststoff

Bauwesen

Baustoffe

Direct to Highly Filled Bioplastics

In the second part of the series the digitalization applied in injection molding was presented with examples. The quality of the granulates used, produced in the upstream compounding process, is an important influencing factor via the viscosity. Can consistent granulate quality be achieved through the use of digitalization in compounding? Does comprehensive data recording bring with it further use cases, and what special attention must be paid to a continuous process? The Eastern Switzerland University of Applied Sciences presents the first results of internal projects.

Alex Ramsauer (left) and Prof. Daniel Schwendemann from IWK take a critical look at the data analysis.

Part 3 of the Series: Digitalization in Compounding

Every Unit Counts

A lot has changed since the first look at terahertz in Kunststoffe international [1]. Thanks to advances in system development and system integration, this technique now stands at the threshold of industrial application. The emerging application potential is now ready to be utilized for process and quality control. 

Strahlenmessgeräte

Terahertz Spectroscopy: On the Threshold of Industrial Application 

Compounding engineering focuses on rendering the compounding process more economical. Various approaches are presented for improving the economics, such as the use of more energy-efficient equipment, greater system availability and enhanced throughput. 

Mühlen

Mischer

Compounding, Recycling: Efficiency as Benchmark 

The plastics sector in Israel too, had to suffer severely from the economic crisis. But thanks to high competitiveness and current double-digit growth in exports, the country’s economy is now approaching the former level again. 

Additive

Farbstoffe

Flachfolien- und Plattenextrusion

Country Report: Kibbutz with Cleanroom Production 

Providing Recyclates with Reduced Emissions

Fraunhofer ICT has analyzed stripping agent-assisted and extractive extrusion processes.

Besides chemical recycling technologies, continuous physical material recycling processes offer advanced, economically attractive alternatives for melt purification. Fraunhofer ICT has analyzed stripping agent-assisted and extractive extrusion processes.

Stricter regulative framefork on environmental and health impact require minimum recyclate contents, reduction of CO2 emissions, or the consumer demand for high-quality products from recyclates have led to an increased industry focus on emissions and material purity. Besides chemical recycling technologies, improved continuous physical material recycling processes offer advanced and economical alternatives for melt purification and make it possible to provide recyclates with reduced emissions and contamination.

Fraunhofer ICT has two different continuous technologies available: stripping agent assisted extrusion (stripping) and extractive extrusion. Both processes make use of fluids tailored to the particular separation task during extrusion to improve the cleaning performance. Stripping focuses on the removal of odorous substances and/or of byproducts from preprocessing such as printing inks or adhesion promoters. In contrast to stripping, extractive extrusion is also suitable for the decontamination of undesirable substances that are no longer compliant by regulation. The two methods differ according to the technical effort required to adapt them to an existing twin-screw extruder. Since the stripping agent assisted process can be much more easily integrated compared to the extractive extrusion process, this method should generally be preferred, if the physical material parameters consider it feasible.

In stripping, the polymer is fed into the extruder  via the main hopper. After the melting zone, a melt sealing via a compression must be provided to prevent backflow of the stripping agent. The stripping agent is subsequently mixed into the polymer. In the degassing zone, the stripping agent, with the dissolved, undesirable components, is vacuum degassed and the purified polymer is finally discharged through the nozzle. The key advantage of this method is that, assumed that the plant is correctly configured, only a little shear energy is introduced, and the material is thereby processed with low stress.

Stripping: a Stripping Agent Removes Undesirable Components

For stripping, a wide variety of stripping agents can be chosen depending on the task. Common stripping agents are for example water (H2O), nitrogen (N2) and carbon dioxide (CO2), as well as alcohols. CO2 has proven to be an effective stripping agent as it dissolves very well in polymers and thereby improves the removal of the volatile substances in the degassing step. The common factor of all stripping agents is that, because of the viscosity reduction of the polymer, their addition leads to a continuous renewal of the melt surface and thus to a considerable improvement of the degassing performance in the extruder.

The cleaning performance can be controlled by means of the used proportion of the stripping agent to the polymer. Analysis of the emissions is usually performed according to VDA 277 (headspace GC) or VDA 278 (thermal desorption analysis). Both standards record the concentration of volatile organic compounds (VOCs) and evaluate them using suitable test parameters. In contrast to emissions, the odor reduction, on the other hand, can only be subjectively recorded, since every individual perceives the odor differently. The olfactory impression of a product also only rarely correlates with the data from the emission analysis and can thus only be registered to a limited extent. The success of an odor reduction is therefore evaluated by a test panel (odor test acc. to VDA 270). Alternatively, the first tests at Fraunhofer ICT according to the new standard ISO 16000–28 also indicated its feasibility to plastic pellets. With this method, a specially trained odor panel and the use of comparison standards lead to reproducible results.

The extraction process is analogous to the stripping process up to the first sealing zone. The supercritical CO2 is metered into the extruder after the sealing zone and is incorporated in the extraction zone parallel to the melt in the free space between the screw, barrel and melt. In the process, some of the CO2 dissolves in the melt. At the end of the extraction zone, the supercritical CO2, together with the contaminants dissolved in the CO2, is removed from the melt again.

After discharge into a flash tank (phase separator), the pressure of the supercritical CO2 is finally reduced. Because of the pressure drop, the solubility in CO2 decreases and the dissolved contaminants are precipitated out. Depending on the profitability and the set CO2 throughput, a reclamation unit for the stripping agent can be used. The extraction process generally uses CO2 in the supercritical state. But other liquids such as water or alcohols are also possible. In a similar way to the stripping process, the extraction performance can be controlled via the amount of supercritical CO2 used, as well as via the amount of an additional contaminant-specific solvent.

In a study, the potential of the stripping process to remove odor-intensive components and volatile organic compounds (VOCs) from recycled polypropylene was investigated. For this, seven stripping agents H2O, CO2, N2, ethanol, isopropanol and two commercial additives were used. For comparison, a reference sample was treated in parallel in a pellet dryer for two weeks to simulate silo degassing. Determination of the VOC emissions and odor notes were performed on pellets and subsequently tensile test bars were produced from them by injection molding.

The evaluation (Fig. 1) shows very good results regarding the odor and emission reduction using the stripping process, on both the pellets and the injection-molded panels. Based on the bag reference sample, the emissions after extrusion and injection molding increased significantly.

A reduction can only be observed when vacuum is applied and it increases with higher vacuum  intensity. High absolute vacuum pressures as well as exclusively atmospheric degassing are practically ineffective. Furthermore, the results show that low absolute vacuum pressures are necessary to obtain low emissions (#14), but lead to unchanged high odor notes. Only the additional introduction of stripping agents promotes a further reduction of the odor values. For the investigated polypropylene, H2O and CO2 proved to be the most effective stripping agents for emission and odor, see Figure 1. The results of degassing in the pellet dryer show good results for VOC and odor; however, they are time consuming and comparatively energetically unfavorable. Fraunhofer ICT coordinates the Europe-sponsored CREAToR project for eliminating today forbidden legacy additives from polymers, so that they can be used again as recyclates.

Reprocessing Waste Streams Contaminated with Illegal Substances

In CREAToR, hazardous and already forbidden brominated flame retardants are eliminated from waste streams such as polystyrene (PS) foam (Fig. 2), using extractive extrusion. The purified polymers are turned back into new high-quality applications, for example in the construction sector, automotive sector and the aeronautic sector.

The first experiments were conducted for insulation panels from the building and construction sector on a batch scale to investigate the extraction efficiency of different solvents under different conditions (temperature, pressure). Then the parameters were transferred to continuous processing. As the project continued, two pilot lines were set up for the extraction, based on the use of environmentally friendly extraction solvents, namely deep eutectic solvents and supercritical CO2. The pilot plant at the Centexbel institute is suitable for performing extraction at up to 150 °C and 700 bar in batch (Fig. 3).

The continuous extractive extrusion line at Fraunhofer ICT is able to treat polymer streams at up to 10 kg/h with a CO2 volume stream of 300 g/h at pressures over 120 bar and temperatures over 160 °C (Title figure). The first results from the extraction trials show promising results.

Fraunhofer Institut für Chemische Technologie ICT  

https://www.ict.fraunhofer.de

Ausgabenartikel

Pilot plant for extractive extrusion at Fraunhofer ICT in Pfinztal, Germany.

Fig. 1. Characteristic values for the VOC emissions and odor after treatment in the stripping process (Comp = after extrusion,  IM = after injection molding, SA = stripping agent).

Fig. 3. The reactor at Centexbel with liquid pump, reaction chamber in the oven and a separator for separating the contamination.

Fraunhofer - Hauptartikel

Bereitstellung von Rezyklaten mit reduzierten Emissionen: Schleppmittelunterstützes Stripping und extraktives Extrusionsverfahren

Extrusion | Schmelze | Physikalisches Recycling

Irma Mikonsaari is a research assistant in the product field of Polymer Engineering at the Fraunhofer Institute of Chemical Technology (ICT) and coordinator of the European-sponsored CREAToR project; <a href="mailto:Irma.Mikonsaari@ict.fraunhofer.de">Irma.Mikonsaari@ict.fraunhofer.de</a>

Dr. Elke van de Walle is a research assistant in the field of “Plastics, Processing & Recycling” at the Belgian textile research institute Centexbel; <a href="mailto:evw@vkc.be">evw@vkc.be</a>

Dr. Kevin Moser is head of the group Material Development and Compounding Technologies in the research area Polymer Engineering at the Fraunhofer Institute of Chemical Technology (ICT); <a href="mailto:Kevin.Moser@ict.fraunhofer.de">Kevin.Moser@ict.fraunhofer.de</a>

The authors dedicate this publication to the memory of their institute director Prof. Dr. Peter Elsner and thereby thank him for his great support and friendly guidance.

The CREAToR project has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement no. 820477