A Gneuss MRS 70 Extruder, with dosing feeders, vacuum system, automatic Melt Filtration System and Online Viscometer processes PET waste to high quality fibers in Korea.

Recycling line at KTDI technical center with Gneuss MRS Extrusion System, Rotary Filtration System RSFgenius, Online Viscometer VIS

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Gneuss Extruder in Korea

Brückner Maschinenbau has developed mono-material packaging solutions to close the life cycle of plastic packaging as requested by brand owners and legislations.

Examples of monomaterial plastic packaging based on biaxially stretched films of PP, PET or, more recently, PE.

16:9

Messe Interpack

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Blasfolienextrusion

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How Recycling Goals Can Be Achieved

With around EUR 355 million in overall turnover and 350 extruders delivered, Erema Group was able to close the 2022/23 financial year successfully. In June, the company also celebrates its 40th anniversary.

Erema Group Ends Financial Year with Significant Increase in Turnover

TotalEnergies has joined Nextloopp, an initiative bringing together 47 companies from the plastics value chain that aims to create food-grade recycled polymer from advanced mechanical recycling.

Verbände, Institutionen, Messen

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Nextloopp Welcomes TotalEnergies

Interview with David Katz, Founder of Plastic Bank

Plastic Bank promotes recycling in developing countries, thereby combating poverty.

Umweltmanagement

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“We Must Show that Circularity Benefits Everyone“

Plastics Recycling Show Europe expands into second hall, visitor registration for the free-to-attend event is now open.

At the Plastics Recycling Show Europe in 2022.

Plastics Recycling Show Europe: Visitor Registration Is Now Open

The Alpla Group can look back on a successful financial year 2022 in spite of the crisis. Sales of 5.1 billion euros exceeded the previous year’s figure by 27.5 percent.

The packaging specialist will continue to expand its production capacity in injection molding over the coming years.

Verpackungsmittel aus Kunststoffen

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Alpla Achieves Sales Record

Santa Barbara County’s Resource Center efficiently sorts both municipal solid waste and single stream using the same circuit with Tomra‘s Autosort units to successfully reduce landfilling.

The Santa Barbara County Resource Center converts commercial and residential waste into recyclables by recovering recyclable materials, converting organics into landscape nutrients, and generating renewable energy in the process.

Sortierer

Quick-Change Mixed Waste Processing

Berry Global and Werner & Mertz receive the WorldStar Packaging Award 2023.

The design of the head follows a mono-material approach, with over 97% of it produced in polypropylene.

Verpackungsmaterial

International Award for Sustainable Sprayer Design

Evonik is pooling its expertise and integrating its alcoholates business into the Catalysts Business Line.

Chemie

Naturwissenschaften

Unternehmen

Expansion of The Catalysts Business Line

“Forum Plastic Recyclates” to take place on March 29 and 30, 2023 in Darmstadt, Germany. The forum will focus once again on the field of mechanical recycling.

This year´s forum will focus once again on the field of mechanical recycling.

Forum Plastic Recyclates

Borealis provides circular solutions for crosslinked polyethylene for the Wire & Cable and Infrastructure sectors.

Borealis Borcycle C chemical recycling process breathes new life into crosslinked polyethylene (PE) types such as XLPE and PE-X.

Technik Trend

Polyethylen

Kunststoff Werkstoffe

Thermoplaste

Chemical Recycling for Crosslinked Polyethylene

The latest scientific findings of existing and novel packaging features along with state-of-the-art recycling technologies are at the center of the update of both the guidelines protocols.

RecyClass Design for Recycling Guidelines and Recyclability Evaluation Protocols

At Plastindia 2023, Starlinger puts the focus on efficient plastics recycling and sustainable packaging solutions.

Saves costs and energy: the new recoSTAR PET art recycling system for food-grade rPET.

Decontamination at the Highest Level

Plastics Industry Association announces 2023 Recycling Committee Executive Board. Chair: Tory Flynn.

New Recycling Committee’s Executive Board

Glycolic Depolymerization versus Mechanical Bottle-to-Bottle Recycling

Conventional PET recycling lines are based on single-screw extruders with maximum output rates of two and a half tons per hour. Since 2004, KraussMaffei has been researching a process to significantly increase these quantities with the help of glycol and the use of a twin-screw extruder. Given the current high demand for rPET materials, this technology is becoming increasingly important.

The recycling and new production of PET bottles is probably the best-known process in the field of plastics recycling. This process, in which sorted PET plastic bottles are washed, melted, filtered and pelletized before they are used as base material for new PET bottles, has for many years been one of the very few established recycling technologies. In general, a PET reuse rate of over 30 % is currently achieved worldwide.

In view of the growing demand for recycled plastics, the requirements in terms of material quantity and quality have also increased substantially. The established processes applied in this field are based on single-screw systems and achieve throughput rates of up to 2.5 t per hour and machine. Against this background and in view of the fact that polymer structures can be rebuilt to achieve the quality level of virgin material, glycolytic decomposition of PET materials is gaining increasing attention. As early as in 2004, KraussMaffei put into operation the first lines designed for this type of process, the interest in which has grown significantly in recent years.

Sustainability Takes Center Stage – Less Focus on Prices

In the past few years, this trend has been further fueled by declining prices for PET virgin material, so that only the use of large-scale machines ensures profitability. While the price for PET virgin material was rising before 2010 and already minor quantities of rPET were considered competitive from a purely economic point of view, the situation has changed drastically since.

Today, PET polymer producers are focusing on the use of rPET also for reasons of sustainability. In PET production, several metric tons of rPET are now added during glycolytic decomposition in the same process, so that twin-screw extruders are further gaining ground.

The process offered by KraussMaffei starts with the feeding system, which then transfers the material to the twin-screw extruder. Here, the washed and dried flakes are melted and homogenized while any adhering moisture and low-boiling contamination are removed via the vacuum degassing dome. Liquid glycol is then injected into the processing section and homogeneously mixed. The chemical reaction thus triggered decomposes and shortens the polymer chains, which results in the formation of oligomers. The PET bottle fraction with an intrinsic viscosity of 0.7 to 0.8 dl/g is thus converted into a low-viscosity melt. The viscosity can be decreased in a controlled manner, with an IV value between 0.5 and 0.2 dl/g being generally required for the subsequent process steps. This is where the exceptional strength of the process becomes apparent: the lower the viscosity, the finer the filters that can be used in the following process step.

Filters with a filter grade of 60 µm or better ensure that even extremely small contaminants are reliably removed from the melt. With the PET production process used in the large-scale petrochemical industry, the recycled low-viscosity melt is subsequently fed into the final reactor together with the material flow coming from the reactor for virgin material. Here, this input material is repolymerized into long-chain polymers with the desired intrinsic viscosity value.

Achieving an IV value of 0.2 dl/g places high demands on the machine and process. The seals and the tolerance values of extruder, melt pumps and filters must be perfectly adapted for this purpose. KraussMaffei achieves this goal through extremely tight manufacturing tolerances and “quality made in Germany”.

In view of the market demand for the use of the finest filter stages, numerous tests were carried out in KraussMaffei’s process laboratories in order to achieve an IV value of 0.2 dl/g and lower. In addition to the lowest possible viscosity, the objective was not to use any additives in order to obtain a high melt quality without any foreign substance. The addition of high amounts of glycol was a major challenge, as there were no downstream reactors available in the process laboratory to repolymerize the material and repelletization was therefore not possible. A viscosity of 0.15 dl/g was achieved in the trials and the melt was discharged by means of a gear pump. The tests confirmed that this viscosity value could be obtained by using 2 to 3 % of glycol and that it is not increased or decreased by adding a higher amount of glycol.

During all these tests involving the handling of ethylene and glycol quantities, special attention must be paid to protective measures in accordance with the Atex directive due to the flash and boiling point. On the one hand, any leaks in the glycol feeding system may cause ignition or deflagration when glycol ignites on hot surfaces of the extruder or vaporizes and subsequently catches fire. On the other hand, the glycol vapors escaping from the melt can also ignite or trigger deflagration. Such a vapor formation is particularly noticeable in the case of higher proportions of glycol (> 5 %).

Thanks to the low viscosity, filters with an even finer mesh width can be used. The melt quality is thus additionally improved, which allows the share of recycled material in the final product to be increased. A further reduction in viscosity is conceivable through the incorporation of additives or the use of new processes in order to install even finer filters, which could possibly remove even coarse color pigments. It is obvious that the twin-screw extruder for this type of process is an excellent alternative to conventional methods. The high output rates and the unparalleled quality achieved by KraussMaffei will further fuel this development.

KraussMaffei Extrusion GmbH  

https://www.kraussmaffei.com/de/startseite

Ausgabenartikel

The above diagram illustrates the operation of the twin-screw extruder during rPET production, where exact metering, extrusion and filtering of the glycol mixture are essential.

Name - Hauptartikel

 Franz-Xaver Keilbach has been Application Owner Circular Economy/Recycling at KraussMaffei since 2020.

Daniel Prizinitzki has been Process Engineer Compounding at KraussMaffei since 2017.

issue 07/2023

issue 06/2023

issue 05/2023

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