1

SPEC I A L

Kunststoffe international 4/2014 www.kunststoffe-international.com

MICHAEL HEITZINGER

With the patented configuration ofthe melt filtration upstream ofextruder degassing, plus the ef-

ficient Laserfilter, the TVEplus systemfrom Erema GmbH of Ansfelden,Austria,enables the manufacture of high-qualityend products with a significantly higheramount of recyclate (Fig. 1). The uniqueconfiguration ensures high degassing per-formance as only thoroughly melted, fil-tered and homogenized material can passthe degassing zone of the extruder. Addi-tionally, the melting procedure takes placewith minimum shearing effect. This pre-vents any contaminants from being fur-

ther reduced in size prior to filtration. Fil-tration efficiency is improved as a result.Erema presented an innovation in plasticrecycling systems last year with thepatented Counter Current system, thecentral core technology of the new Intare-ma plant generation. This also represent-ed a boost in efficiency for the TVEplussystem. Thanks to improved material in-take, it has been possible to increase notonly output but also flexibility in select-ing the optimum operating point (seeKunststoffe international 103 (2013) 12, p. 62).

The Laserfilter is ideal for the process-ing of materials with a high degree of con-taminants such as wood, paper, alu-minum or copper. It fulfills requirementswhich conventional melt filters cannotmeet, especially in the production of re-cycled film-grade recyclates. The technol-ogy of this high-capacity Laserfilter has

now also been enhanced (Fig. 2). The re-sult is immaculate recyclates with top filmquality.

Innovative Scraper Technology

The two significant innovations here arethe new design of the scraper geometryand the new discharge system which re-moves the filtered contaminants morequickly and more thoroughly than in thepast (Fig. 3). Cleaning efficiency, dischargecapacity and thickening thus reach a newlevel. The contaminated plastic melt ispressed through two laser-bored screendiscs in a parallel configuration.A scraperdisc rotates between these screen discs. Itremoves the filtered contaminants fromthe screen immediately and conveys them

Recyclates with Immaculate Film Quality

Melt Filtration. The crucial step in the reclamation of highly contaminated plastic

materials into film-grade recyclate is the ultrafine filtration of the melt. The new

Erema Laserfilter significantly increases the purification efficiency and the separa-

tion capacity.

Fig. 1. Intarema TVEplus withLaserfilter for immaculate recy-clate: with the configuration of themelt filtration upstream of extruderdegassing and the enhancedLaserfilter, the TVEplus system en-ables the manufacture of high-quality end products with a signifi-cantly higher amount of recyclate (figures: Erema)

Fig. 2. The Laserfilter fulfills requirementswhich conventional melt filters cannot meet,especially in the production of recycled film-grade recyclates

Translated from Kunststoffe 4/2014, pp. 21–24Article as PDF-File at www.kunststoffe-international.com; Document Number: PE111645

Spezial rep

rint from

Kunststoffe international 4/2014

2

SPEC I A L

© Carl Hanser Verlag, Munich Kunststoffe international 4/2014

without delay to the discharge system(Fig. 4). This conveying process is contin-uous, thorough and fast. The efficiency ofthe system is increased considerably as aresult. The contaminants are then re-moved under control and with a mini-mum of melt via the likewise optimizeddischarge system. The scraper and dis-charge screw speeds depend on the pres-sure and can be controlled fully automat-ically (“constant pressure operation”).

Unlike many conventional filters theLaserfilter has a rotating scraper ratherthan a rotating screen. Furthermore, thestatic screen is perfectly sealed and pre-vents any items which are filtered outfrom getting into the plastic melt.Anoth-er unique characteristic of the Laserfiltersis the upstream distributor ring whichacts as a preliminary filter and protectsthe core components screen, scraper starand discharge system. This new filter sys-tem increases filtration reliability and, atthe same time, extends the service life ofthe screen discs (Fig. 5). The new Laserfil-

Fig. 3. The new discharge system transports the filtered contaminants more quickly and more thoroughly than before. Cleaning efficiency, discharge capacity and thickening increase as a result

Fig. 4. With the newscraper geometry anycontaminants are lift-ed off the screen im-mediately and for-warded directly tothe discharge system

Fig. 5. Left: Conicalholes are put into thefilter screen usinglaser technology.Right: HardenedLaserfilter screen

3Kunststoffe international 4/2014 www.kunststoffe-international.com

Particle size0

%

-20

-30

-40

-50

-60

Part

icle

red

uctio

n

Fig. 8. The cleaning efficiency was measured by means of optical particle analysis on the films pro-duced from the recyclates of the old and new systems. The diagram compares particle reduction us-ing the new Laserfilter technology in comparison with the old system. A significant reduction of theparticles remaining in the end product can be observed across the entire range of the particle sizesdetected

© Kunststoffe

Fig. 7. These film patterns were produced on an OCS measuring extruder ME25/25D.V3 from a recy-clate of washed PE shreds. Left: Recyclate produced using conventional, commercially availablefilter technology. Right: Recyclate produced with Laserfilter and new scraper technology

ters are available with capacities of 350 to3,500 kg/h and filtration fineness of 90 to800 µm and beyond. Recyclers who al-ready work with Erema Laserfilters canretrofit the new system to existing plants.

Centerpiece Filter Screen

The centerpiece of the Laserfilter is thefilter screen. It features very fine boreholeswhich are drilled into the hardened spe-cial steel of the screen discs using lasertechnology.The conical shape of the holescauses a self-cleaning effect. The numberof holes on the filter screen of the en-hanced Laserfilter is approx. 15 % high-er, thus improving filtration perform-ance. The screen discs are made by 3SGmbH in Roitham, Austria. The Eremasubsidiary worked together with the Uni-versity of Erlangen, Germany, to developthe laser technology required to producethese screens (see box).

41 % Thickening with WashedPE Shreds

Around 46 million tonnes of plastic areconsumed in Europe, thereof some 8 mil-lion tonnes of LDPE and LLDPE. Thesematerials are used primarily in the packag-ing sector and as agricultural films. Whenrecycling the washed post-consumer filmflakes, not only the moisture content butalso the high degree of contamination is a

challenge.Special contaminants in soft ma-terials such as aluminum, paper, wood orcopper place very high demands on the fil-tering technology used in the recyclingprocess.The demand for LDPE and LLDPErecyclates processed in high quality, how-ever, is quite high and they generate goodprices.With the newly developed filter tech-nology, heavily contaminated recoveredmaterial can be reprocessed to make high-quality PE recyclate – a much sought-after raw material in the plastic film indus-try.

In the filtration of washed PE shredsfrom post-consumer collections with 2 to3 % residual contamination through PET,aluminum, paper and wood, a thickeningof 41 % is achieved on an Intarema 2021TVEplus with Laserfilter LF 4/350 in aparallel configuration (filtration fineness

Fig. 6. The LF 4/350 achieves a thickening of41 % in the filtration of washed PE shreds fromthe post-consumer collection system

130 µm) at a throughput of 2,300 kg/h(Fig. 6). The output material is PE recyclatein film quality. The film samples in Fig-ure 7 from a wide variety of recyclates doc-ument the increase in quality through thenew Laserfilter.

This result is due to the fact that withthe new Laserfilter technology, contami-nants are lifted off the screen immediate-ly and passed on to the discharge system.This process has two additional benefits.Firstly, the active screen area lasts longeras the boreholes in the laser screen cannotbe clogged by contaminant plating (e.g.aluminum). Secondly, the service life ofthe screen is also longer as friction is re-duced. As a result the entire active screenarea is available over a longer period.Clemens Kitzberger, Process Engineer atErema,describes the concrete result of this

Rec y c l i ng SPEC I A L

4 © Carl Hanser Verlag, Munich Kunststoffe international 4/2014

application from the post-consumer sec-tor: “The service life of the screens hasdoubled, to be exact,and the scrapers needreplacing only half as often.”

Particle Reduction in LDPEFilms from Trade and Industry

Processing LDPE stretch films from tradeand industry which have adhesive labelsto make film-grade recyclates previouslyrepresented a major challenge for recy-clers.Particles of paper and adhesive stuckto the film cause problems especially inthe area of filtration. Trials in the courseof developing the new Laserfilter systemled to remarkable results here.

The previous filter system and the newLaserfilter system with the new scraperstar were compared in the trials on anIntarema 1514 TVEplus. The input ma-terial was recycled under the same condi-tions at a throughput of 1,300 kg/h fortest purposes. The Laserfilter LF 2/350with a filter fineness of 110 to 130 µm wasused for the filtration. The thickeningwith the new system was 42 %. The clean-ing efficiency was measured by means of

optical particle analysis using the filmsproduced from the recyclates of the oldand new systems. Figure 8 compares theparticle distribution measures and showsthe particle reduction using the new

Laserfilter technology in comparison withthe old system. A significant reduction ofthe particles remaining in the end prod-uct can be observed across the entirerange of the particle sizes detected. Be-tween 30 and 60 % more particles wereremoved from the material compared tothe previous model.

Conclusion

Thanks to the redesign of the scrapergeometry and discharge system, the high-performance filtration system of the newLaserfilters can remove contaminantseven more quickly and more thoroughlythan before. The cleaning efficiency, dis-charge capacity and thickening are thusincreased considerably. The result: recy-clates with immaculate film quality. Withthe new system, the service life of both thescreens and the scrapers is increased andservicing is also reduced.�

THE AUTHORMICHAEL HEITZINGER, born in 1967, is Chief

Technical Officer (CTO) at Erema GmbH, Ansfelden,Austria.

3S GmbH of Roitham, Austria, specializesin the manufacture of core parts for the ex-trusion branch. These include screws, bar-rels and intake parts. 3S produces screws,screen changer blocks and pistons forErema.

Working together with the University ofErlangen, Germany, 3S developed a newlaser technology for the production ofscreens. In this process, 280,000 conicalholes with a diameter of between 90 and800 µm are made. The laser pulse is every10 ms and the spaces are checked usingspecial computer software. 3S has particu-larly high-performing machines for the pro-duction of Laserfilter screens which enablehigh quantities and maximum precision.> www.3s-gmbh.at

3S GmbH!

© Carl Hanser Verlag, München 2014. All rights including reprinting, photographic reproduction and translation reserved by the publishers.

SPEC I A L