Extrusion Asia Edition 2-2021

37 Extrusion Asia Edition 2/2021 面质量。它由 MAS 锥形双螺杆挤出机、高效熔体过滤器和下 游挤出设备中串联式最佳的熔体脱气装置组成。在循环经济 中，这种技术显著地扩大了回收再生薄膜的应用范围。 T he MAS components used for this include the DRD (Double Rotary Disc) film flake cleaning system and a downstream extrusion system. The latter consists of the MAS-specific co-ro- tating conical twin-screw extruder, a continuous MAS melt fil- ter and a single-screw degassing cascade ( Picture 1 ). Incorporated special features of the DRD dry cleaner include ele- ments that completely dispense with the use of water as a was- hing medium operating via the principle of an air cyclone. In it, film flakes are dried by friction in a heated air vortex. In the pro- cess, adhering contaminants such as sand, dust and soil are se- parated and discharged by centrifugal forces. The advantage of waterless operation includes lower energy input for the cleaning process, resulting in a significantly smaller CO 2 -footprint. For subsequent extrusion, the MAS twin-screw extruder is also well suited to low-bulk-density feed materials thanks to its con- ceptually large feed opening. Due to modular, co-rotating screws and short processing length, plasticizing is designed to be me- chanically efficient and simultaneously as gentle as possible. A key goal of the joint development work was to increase the surface quality and thus, the printability of the film by minimiz- ing the specks (dust and dirt particles, as well as cross-linked polymer agglomerations) still contained in the recycling film. The functional principle of the MAS extruder are the keys to its success The basis of this system is a co-rotating MAS twin-screw extru- der designed to optimize the entire extrusion process. The short and gentle melting phase in the MAS extruder reduces the for- mation of polymer cross-links to a minimum. A screw geometry developed directly for processing LDPE films with an increased LLDPE content, together with an adjustable screw speed, en- ables the shear forces required for ultra-fine homogenization to be applied with pinpoint accuracy. With this, the foreign bodies contained in the melt, as well as already existing cross-linkages, are broken up, crushed and evenly incorporated. This signifi- cantly minimizes the effect of specks on the smoothness and optical properties of the film. This results in substantially improv- ed printability of the film, a significant improvement in the print image and a reduction in the amount of ink required ( Picture 2 ). Process technology honored with "Plastics Recycling Award 2020” This process technology, developed by MAS and Caroda BV, re- ceived an award at the "Plastics Recycling Awards Europe 2020". During this event, which traditionally takes place in Amsterdam, both companies were awarded the main prize in the category "Recycling Machinery Innovation" ( Picture 3 ). Summary Through cooperation between plant manufacturer and plant operator, MAS and Caroda BV have developed a process tech- nology that significantly increases the surface quality of recy- cled films. It consists of the MAS conical twin-screw extruder, efficient melt filtration and optimum melt degassing in the downstream extrusion cascade. In a circular economy, this opens up significantly expanded application possibilities for re- cycling films. 图4: 来自MAS的设备安装在Caroda B.V ，生产回收再生产品 (图片:Caroda BV) Picture 4: From Caroda B.V. with the MAS equipment recycling goods (Picture: Caroda BV) ➠ 作者: / The Author: Reinhard Bauer - TECHNOKOMM office@technokomm.at ➠ MAS Maschinen- und Anlagenbau Schulz GmbH A-4055 Pucking, Austria www.mas-austria.com 图5：回收再生技术获奖 (图片:MAS) Picture 5: Recycling- Technology-Award (Picture: MAS)