재활용 함량이 높은 블로운 필름 가공
RKW와 Nordson은 생산업체가 재활용 함량이 높은 블로운 필름을 처리할 수 있도록 함으로써 미래를 준비하기 위한 조치를 취하고 있습니다.
지속 가능성은 플라스틱 제품에 있어 점점 더 중요해지고 있으며, 이 메시지는 새로운 법률, 규정 및 요금을 통해 EU와 주 정부 모두에 의해 강화되었습니다. 포장 제품에 사용되는 천연 재료에는 포장재 1kg당 0.23~0.45유로 범위의 국가별 수수료가 적용됩니다. EU 포장법의 이러한 변화는 플라스틱 산업의 순환 경제를 촉진하는 것을 목표로 합니다.
새로운 규정은 영화 제작자에게 심각한 장애물이 됩니다. 그들은 많은 양의 재활용 재료를 수용할 수 있도록 필름 제작 방식을 신속하게 수정해야 합니다.
그러나 이 도전은 잘 준비된 사람에게는 유리할 수 있습니다. 독일 Echte의 RKW에서는 재활용 가능한 재료를 사용하는 것이 오랫동안 논의의 주제였습니다. RKW의 애플리케이션 엔지니어인 Thomas Steffen은 "우리는 수년 동안 필름에 재활용품을 사용해 왔습니다."라고 설명합니다. "이러한 필름은 이후 재활용 소재를 통해 품질 기준을 충족할 수 있는 제품에 사용됩니다."
재활용품을 사용하여 최종 제품의 품질을 유지하려면 효율적인 여과가 중요합니다. 용융 필터는 수년 동안 블로운 필름 라인에서 활용되어 왔지만 과거에는 이러한 필터가 대부분 불연속적이어서 스크린 교체 동안 라인을 폐쇄해야 했습니다. Nordson BKG의 공정 엔지니어인 Stefan Wöstmann은 "깨끗한 순수 재료를 사용하는 공정에서는 이것이 문제가 되지 않습니다. 여기의 필터는 순전히 보호 기능을 수행하며 재료 공급에서 느슨해진 나사나 기타 운송 오염 물질이 들어가지 않도록 보장합니다."라고 말합니다. 프로세스에 들어갑니다. 하지만 오염도가 너무 낮아 화면 교체가 거의 필요하지 않습니다."
소재 품질 차이 보상
더 많은 재활용 재료를 사용함으로써 공정에서는 최종 제품에 많은 영향을 미치는 추가 구성 요소를 처리해야 합니다. “먼지 입자가 포함된 재활용품의 품질은 크게 변동합니다.As a first step, continuous screen changers were implemented. These filters allow operators to change screens without interrupting production and adjust screen fineness for different production batches based on quality requirements. "As a result, we have significantly fewer machine downtimes, and the productivity of our plants has increased distinctively," reports Sven Pastrik. "We can compensate quality differences in the material very well and process high proportions of recyclate, for example, in our FFS bag production."
Thomas Steffen (RKW), Sven Pastrik (RKW), Stefan Wöstmann (Nordson BKG GmbH) presenting a Nordson® BKG® NorCon™ K-SWE continuous screen changer in a blown film line at RKW.
The goal was a system in which high-quality films could be produced in a continuous, automated process. "We needed a plant concept with fast setup and changeover times. We don't want to deal with screen changes and thus line downtimes often and for a long time, but rather ensure an extrusion process that is as uninterrupted as possible."
RKW had a positive experience with Nordson® BKG® screen changers, leading them to approach the filter manufacturer again. Their new five-layer plant is now equipped with continuous BKG® screen changers and has been running successfully since 2021. "We are very satisfied with the performance of the system. Thanks to continuous filtration, we produce high-quality films with high recycled content in an uninterrupted process and can cover a wide application window," explains Sven Pastrik.
At RKW and Nordson, they were certain that the development must go further. "The use of recyclate will continue to increase in the future," explains Stefan Wöstmann. "The EU's Green Deal and national packaging laws are massively increasing the pressure and forcing system- and component manufacturers to act."
Stefan Wöstmann (Nordson BKG GmbH) and Sven Pastrik (RKW) with the new Nordson BKG HiCon K-SWE-HD/RS recycling filter.
The Solution: An Innovative Backflush Screen Changer
To expand the application window and process higher proportions of recyclate and prospectively even highly contaminated materials, e.g., from the yellow bag, without compromising quality, a screen changer with backflush function has now come into play. "We are already seeing that the backflush technology enables the use of recyclate from the PCR area," explains Sven Pastrik."At RKW and Nordson, they were certain that the development must go further. "The use of recyclate will continue to increase in the future," explains Stefan Wöstmann. "The EU's Green Deal and national packaging laws are massively increasing the pressure and forcing system- and component manufacturers to act."
"Melt filters without a backflush function reach their limits when processing recycled material. The degree of contamination is high, and the screens become clogged quickly," explains Stefan Wöstmann. "Screens are expensive, and changing them is time-consuming. Backflushing repeatedly clears the screens of contaminants and deposits, so manufacturers need fewer filter elements, and operators have to change screens less often."
It was necessary to adjust to the conditions to achieve optimal results in blown film lines. Since the film bubble is sensitive to temperature, viscosity, and pressure changes, even minor deviations can negatively impact the final product. Adding recyclates to the process can make it even more challenging. Pressure fluctuations during screen changes, backflushing, and deaeration can significantly reduce film quality or cause downtime. To address this issue, Nordson collaborated with equipment manufacturer Windmöller & Hölscher to develop the Nordson® BKG® HiCon™ K-SWE-HD/RS backflush screen changer. This new filter is specially designed for blown film lines and has a compact design suitable for tight spaces.
Eliminating Even the Slightest Pressure Fluctuations
Maintaining constant pressure is crucial for successfully operating a blown film line. Any material withdrawal for screen changes or backflushing can result in a balancing act in this area of tension. Hence, it is imperative to avoid pressure fluctuations through intelligent solutions in the high-pressure range. Each screen change in the filtration process is a sensitive step since the empty cavity must be refilled with melt after the change. If this is done too quickly, it can lead to pressure fluctuations and quality issues. "This is a major problem with blown film lines, as the film is usually very thin and sensitive to such changes," explains Stefan Wöstmann. "The BKG HiCon K-SWE-HD/RS is equipped with the patented melt pressure-controlled venting start, which fully automates the filling of the screen cavity after the screen change and thus ensures maximum pressure consistency. In addition, filling is so sensitive that no air pockets endanger the process or the end product. Manufacturers can rely on a stable process and high blown film quality."The new BKG HiCon K-SWE-HD/RS was provided to RKW as part of a user test and installed in a 3-layer plant. "The start-up was a complete success. We installed the screen changer and produced film successfully immediately; our machine operators were thrilled," reports Sven Pastrik. "The handling of the screen changer is simple, and due to the high degree of automation, we only have to intervene minimally in the process," explains Detlef Nolte, machine operator. "The fact that a newly developed machine was installed in one of our lines without any complications and then works so well directly is quite remarkable. In addition, it is immediately apparent that the experience gained from the initial joint project has been directly incorporated into the new screen changer.”
Meeting Future Challenges
RKW and Nordson plan to continue working together long-term to meet future challenges. "The shift from virgin material only to recycled material is huge. With the BKG HiCon K-SWE-HD/RS, we offer blown film producers an efficient tool to achieve this goal, says Christian Schröder, Global Segment Manager Recycling at Nordson. "With this machine, we are helping to make plastic packaging more sustainable. We are proud of that."RKW also made a strong commitment to sustainability. Recycling is considered a crucial component of this commitment. Each site has recycling facilities that process internal and external production waste into high-quality recyclate. The company is dedicated to investing in new technologies to further this effort. Sven Pastrik explains, "Our goal is to increase the proportion of recycled material used, depending on the specification, and also incorporate PCR material. We are fortunate to have filtration experts on our team to help achieve this goal."