1

REC YC L ING

Kunststoffe international 4/2013 www.kunststoffe-international.com

THOMAS HOFSTÄTTER

Plastic is becoming an increasingeconomic factor as a valuable sec-ondary raw material. The reasons

are plain to see. Whereas the productionof plastics has increased by 8 % per yearover the last decade, the decline in pri-mary raw material resources is increas-ing on a drastic scale. The fact is that rawmaterial prices are continuing to soar.This means that more and more impor-tance is being attached to high-qualitysecondary raw materials. On theother hand, however, and incontrast to virgin material,plastic ranging from produc-tion to post-consumer waste from col-lection systems poses the problem ofever increasing quality fluctuations. In-fluencing factors here include not onlymixed fractions of varying composi-tions, moisture, viscosity, type and de-gree of contamination but also the widerange of printed and laminated materi-als especially in the packaging sector. Inpractice this is often the limiting factorwhen using recyclates as both the possi-ble applications and the recyclate sharein potential end products are reducedwith fluctuating properties. With its newproduct series Corema, the recycling sys-tem manufacturer Erema GmbH, Ans-felden, Austria, shows how proven recy-cling technology in combination withcompounding technology enables theproduction of better specified recyclates(Fig. 1). Thanks to specific property en-hancement, the materials which areprocessed can once again fulfil exactingrequirements.

How it Works

Corema brings together all the benefits ofrecycling and compounding in a singleprocess step for the first time. Deviationsin starting material quality can be com-pensated by the use of proven recyclingtechnology and the admixing of fillersand/or reinforcing agents, thus realisinga property profile which is in line with theend application. The compounding tech-nology comes from the company Cope-rion GmbH Stuttgart, Germany, a globalmarket leader in this segment.

In the first step, inexpensive recyclingraw material (e.g. PP nonwoven, PE edgetrim, PA fibres etc.) is turned into filteredmelt using the proven, robust Erema tech-nology. The recycling system works to-gether with the patented cutter/com-pactor and a tangentially linked single-screw extrusion system. Feeding is auto-matic: loose material is fed in via a feedconveyor belt and film enters the system

direct on rollers using a roller intake sys-tem. The cutter/compactor shreds andhomogenises the feed material with ro-tating cutter tools. At the same time thefeedstock is dried solely by the processingheat which is generated and compactedready for intake in the extruder. The pre-heated material moves into the direct andtangentially connected single-screw ex-truder and is plastified, homogenised andcleaned in the fully-automatic, self-clean-ing filter. For the second step the preparedand cleaned melt then goes via the meltpump directly to a co-rotating, self-clean-ing twin-screw extruder from Coperion.This flexible part of the system is config-ured in such a modular way that thanksto its excellent mixing and degassingproperties it can be adapted to any indi-vidual task. Besides the dosing of a widevariety of additives, both high amountsof fillers and reinforcing agents (e.g. 75 %CaCO3,70 % talc or 50 % glass fibres) canbe admixed and also virgin material in the

Upcycling. When recycling plastics ranging from production to post-consumer

waste from collection systems, the process always has to cope with quality fluctua-

tions in terms of the feed material. The combination of proven recycling and com-

pounding technology now enables the production of better specified recyclate for

varied and demanding applications.

Fig. 1. Recycling and compounding in a single step (figures: Erema)

Refining Recyclate

Translated from Kunststoffe 4/2013, pp. 52–56Article as PDF-File at www.kunststoffe-international.com; Document Number: PE111304

Spezial rep

rint from

Kunststoffe international 4/2013

2

production of polymer blends. The com-pounded melt is degassed in the gas re-moval zone and sent to the respective tool(Fig. 2).

In particular the short, defined dwelltimes and direct dosing of the melt in thetwin-screw extruder reduce thermal stresson the material enormously. Additional-ly, operating costs are reduced and themodular system concept offers optimumadjustment to the respective application

In summary the Corema system ischaracterized above all through flexibili-ty in terms of possible materials and plantconfigurations and is available for bothsmaller amounts of 300 kg/h and largeamounts of up to 4 t/h.

Highly Filled PP/Talc Recyclates

With an amount of approx. 300,000 t/a,talc, besides calcium carbonate (CaCO3)is one of the most important mineral fillers– primarily for polypropylene (PP) – inEurope. It improves stiffness, hardnessand heat distortion stability and is, fur-thermore, acid-resistant, i.e. practicallychemically inert. Some 600,000 t ofPP/talc compounds with 20 % talc areused in Europe every year which meansaround 120,000 t of talc. It is used main-ly for household goods and in the auto-motive, construction and electronics in-dustries (Fig. 3). Compounders alreadyproduce approx. 60,000 t of this annual

© Carl Hanser Verlag, Munich Kunststoffe international 4/2013

amount based on recycling material.Witha share of over 50 % the automotive in-dustry processes the largest amount ofthese PP/talc recyclates. According toforecasts the overall annual figure is setto rise by another 47,000 t.

One concrete example of use is nonwo-ven material production waste for the con-struction industry, which is processed us-

ing Corema to make highly filled recy-clates with up to 70 % talc. Table 1 showsthe physical property profiles of variousPP/talc recycled pellets based on nonwo-ven waste (with a talc share of up to 40 %).

To evaluate the quality of the disper-sion the highly filled recycled pellets areprocessed to make a sample film on a lab-oratory flat film facility (producer: OCSGmbH, Witten, Germany). Figure 4 docu-ments the dispersion effect for a samplefilm made from recycled pellets with a talcshare of 70 % and PP homopolymer.

The filled recyclates can thus be useddirectly for the production of end appli-cations or as highly filled recycled pelletsin the production of PP/talc compounds.The benefit of using the highly filled ver-sion is that fluctuations in quality of therecycled input material can be compen-sated by the mixing with a large amountof talc (in the example in question the PPnonwoven acts so to speak as the carriermaterial). This means that the use of re-cycling materials can be made more at-tractive, as higher recycled pellet amountscan be admixed to the end product and

compounders can do business in a moresustainable way as a result.

Washed Silage Film and CaCO3

With, according to the British market re-search institute Applied Market Informa-tion (AMI),plastic consumption amount-ing to around 545,000 t in 2011 (EU 27plus Norway and Switzerland),agricultur-al films account for a substantial portionof recycling raw materials. On the otherhand, the mostly very high degree of con-tamination through mineral and organicmaterial (Fig. 7) of these soft and often on-ly 25 to 100 µm films makes processingboth difficult and time-consuming. Asthey consist of high-quality plastics suchas LDPE (low-density polyethylene) andLLDPE (linear low-density polyethylene),however, they are in high demand as re-cyclates and can fetch good prices if thequality is high.

4

56

7

8

9

1

2

3

Fig. 2. Corema system configuration: Automatic feeding (1),cutter/compactor (2), tangentially connected single-screwextruder (3), self-cleaning filter (4), melt pump (5), co-rotat-ing, self-cleaning twin-screw extruder (6), dosing of widevariety of additives plus fillers and reinforcing agents (7),degassing zone (8), tool (9)

© Kunststoffe

White goods,household34 %

Others 10 %

Electro andelectronics 12%

Automotive28 %

Buildingindustry 16 %

Fig. 3. Use of PP/talcin household goodsand in the automo-tive, construction and electronics in-dustries

© Kunststoffe

Fig. 4. Flat film sample (width 60 mm) producedon an OCS measuring extruder ME25/25D-V3;material: 23 % highly filled PP nonwoven/talcrecyclate (talc content 70 % Omya Talco SD 20)+ 77 % PP homopolymer

REC YC L ING

3

REC YC L ING

This recycling raw material is ideal asa carrier polymer, for example, for theproduction of highly filled calcium car-bonate ( CaCO3) recycled pellets. WithCorema technology, filling grades of upto 75 % CaCO3 can be achieved. WashedLLDPE film pieces with a moisture con-tent of up to 8 % serve as starting ma-terials. Through the 2-stage design ofthe Corema system the washed agricul-tural film pieces are processed to makedegassed, filtered melt in the first sec-tion of the system, the cutter/com-pactor-extruder combination. Air flush-ing also supports the process and en-

Kunststoffe international 4/2013 www.kunststoffe-international.com

sures that a major part of the residualmoisture evaporates from the preheat-ed material. The processed melt is sentvia the melt line directly to the secondpart of the system, the co-rotating twin-screw extruder, where it is mixed withup to 75 % CaCO3. The result is highlyfilled LLDPE recycled pellets with nar-rower quality bandwidths and excellentdistribution of the filler thanks to thedispersion performance of the twin-screw extruder. The quality of the dis-persion can be seen in Figure 6 whichshows a film sample made from highlyfilled recycled pellets.

Airbags and Fibreglass

Fibreglass reinforced PA6.6 recyclates areanother field of use for Corema. The inputmaterials can be both fibre productionwaste and also (silicone-coated) fabricwaste which is left over in the productionof airbags, for example (see table of valuesPA6.6 Table 2). The challenge facing the re-cycling technology in the processing of fi-bre waste is the high specific surface of thisinput material. This makes it highly sus-ceptible to contamination and moistureabsorption, making effective drying andmelt filtration essential. In this case Core-

Figure 5. Washed shreds of severely contaminated agricultural film (left) processed with Corema 1108 T (filter system Erema SW 4/134 RTF, 300 µm) tomake recycled pellets with 75 % CaCO3 content

Nonwoven waste

Nature Omya Talco SD 20 Lithos Talk LP 10

Properties Test standard Annotation Unity 100 % 20 % 30 % 40 % 20 %

MFR ISO 1133 (230°C/2.16 kg) [g/10 min] 35 31 25 21 51

Tensile Modulus Et ISO 527-2 (1 mm/min) [Mpa] 1,400 2,300 2,900 3,600 2,700

Tensile Strength σM ISO 527-2 (5 mm/min) [Mpa] 34 27 26 26 30

Elongation at break ε ISO 527-2 (5 mm/min) [%] >100 55 31 2 5

Charpy acu ISO 179/1eU (+23°C) [kJ/m2] 95 35 26 19 24

Table 1. Properties of filled PP/talc recyclates from PP nonwoven material production waste with varying talc types

PA6.6 fibre and fabric waste from airbag production

Nature Glass fiber

Properties Test standard Annotation Unity 100 % 15 % 30 %

MFR ISO 1133 (230°C/2.16 kg) [g/10 min] Not reported Not reported Not reported

Tensile Modulus Et ISO 527-2 (1 mm/min) [Mpa] 3,200 5,400 9,500

Tensile Strength σM ISO 527-2 (5 mm/min) [Mpa] 83 120 165

Elongation at break ε ISO 527-2 (5 mm/min) [%] 14 3 2,5

Charpy acu ISO 179/1eU (+23°C) [kJ/m2] 95 39 40

Table 2. Properties of fibreglass reinforced PA6.6 recyclates from airbag production waste with varying fibreglass content

REC YC L ING

ma, with its 2-stage combination consist-ing of the cutter/compactor and a tangen-tially linked single-screw extruder with ef-ficient melt filtration, is the ideal solution.In the first section of the system the cleanedand dried melt is optimally prepared andthen dosed into the second section, thetwin-screw extruder, where up to 50 % fi-breglass can be admixed. Table 2 shows theproperty profile of fibreglass reinforcedPA6.6 recyclates.A Corema 1108 T was usedto recycle fibre and fabric waste from airbagproduction (Fig. 7).The recycled pellets pro-duced with a fibreglass content of 30 % areideal for the production of technical injec-tion molding articles, for example.

Rubber Flour as a SustainableFiller Additive

The following example shows the poten-tial of recycling material: rubber flour canbe used as a sustainable filler additive toimprove elasticity and absorbing prop-erties and reduce costs. Austria alone ac-cumulates over 50,000 t of scrap tyresevery year. Besides thermal disposal and(not yet economical) raw material recy-cling such as depolymerisation or devul-canisation, there are various grindingprocesses in which scrap rubber can beturned into rubber pellets or rubberflour. These scrap tyre pellets are then

reused as material fillers in thermoplas-tic mixtures.

Asamer Plastics in Austria producesthese rubber recyclates under the tradenames AsaBatch and AsaComp. Bothmineral raw materials and recycled rub-ber flour from the group of companiesare used for the specific recycled pelletsof Asamer Plastics. Georg Weigerstorfer,director Erema R&D Centre: “One inter-esting example of how Corema technol-ogy can be used is heavily printed BO-PP(biaxially oriented polypropylene) pro-duction waste in combination with 50%AsaBatch, a highly concentrated rubber

flour material. The recycled pellets pro-duced with Corema is characterizedthrough excellent absorbing propertiesand are suitable for outdoor use in the au-tomotive, sport, leisure and householdsectors plus building applications. Theseand similar, highly filled recycled pelletsare sold under the trade name AsaComp.”An example of the properties is shown inTable 3.

Conclusion

Thanks to the combination of the bene-fits of recycling and compounding tech-nology in a single process stage, togetherwith the particularly energy-saving andenvironment-friendly ecoSAVE design,cost efficiency, responsible use of re-sources, sustainability and thus highervalue added are now possible. The posi-tive aspects are reflected in Erema’s state-ment: We close the loop.�

THE AUTHOR

DI (FH) THOMAS HOFSTÄTTER, born in 1977, isresponsible at Erema for the process engineering de-velopment of Corema.

Figure 6. Light opticalmicroscope image ofa blown film sampleproduced on an OCSmeasuring extruderME25/25D-V3; materi-al: 23 % highly filledLLDPE agriculturalsheeting/ CaCO3 re-cyclate (calcium car-bonate content 75 %Zetafil CST2) + 77 %LLDPE virgin material

Fig. 7. PA6.6 fabric/production waste from airbag production Fig. 8. PA6.6 recyclate with 30 % fibreglass and masterbatch black fromPA6.6 fibres and airbag production waste

Properties Test standard Unity Data

Density ISO 1183 kg/m3 1,116

MFR (190/2.16) ISO 1133 g/10 min 1.4

Young’s modulus ISO 527 MPa 580

Tensile strength ISO 527 MPa 14

Impact strength at roomtemperature ISO 179/1eU kJ/m2 72

Imact strengt hat -20°C ISO 179/1eU kJ/m2 61

Table 3. Properties ofrecyclate compoundAsaComp R10230C-60D

© Carl Hanser Verlag, München 2013. All rights including reprinting, photographic reproduction and translation reserved by the publishers.