Extrusion Asia Edition 2-2020

I n the past 20 years, total textile production has doubled, and from 2000 to 2016, the use of polyester for clothing alone rose from 8.3 to 21.3 million tonnes worldwide. At the same time, the public's call for the avoidance of plastic waste is be- coming louder and legal directives of the European Union are intended to put a stop to plastic waste. For example, in addi- tion to the collection of plastic, glass, paper and metal, a sepa- rate collection system for textiles is to be implemented in all EU countries by 2025 to enable high-quality recycling. In addition, product manufacturers are being made more responsible through the environmental protection strategy of Extended Producer Responsibility (EPR). They are to ensure the entire life cycle of their product from manufacture to disposal so that goals such as ecological design and resource efficiency can be achieved more quickly. In addition to the recyclability of prod- ucts, the use of recycled materials is one way to achieve these goals. However, this is precisely where problems often arise: The demand for the increased use of recycled materials in tex- tiles requires a sufficient and regular availability of these mate- rials. Well available on the market is the recycled PET from be- verage bottles, which is available in very good quality due to the clean collection systems. However, the increased use of r-PET, especially for packaging applications and textile fiber pro- duction, has led to a strong increase in demand in recent years, so that in addition to the increased market price, other recycled materials must now be used. Possible retrofit of key components Production processes that were previously designed only for the processing of virgin material and thus achieved consistently high qualities under known conditions, are now severely dis- turbed or interrupted by contamination and strongly fluctuat- ing material qualities at a higher recycling rate. Constant me- chanical properties and uniform dyeability of the fibers or spe- cial requirements such as very fine fibers or use in direct body contact can no longer be achieved with the existing production lines. Therefore, plants are required which on the one hand can process recycled material – even in lower quality – and on the other hand can generate a high-quality end product without impurities. This is exactly where the German company Gneuss comes in with its machine components for PET processing. The MRS Extruder with its high degassing and decontamination performance, powerful and automatically operating Rotary Fil- tration Systems, an Online Viscometer as well as the polycon- densation unit Jump, which can ensure a targeted viscosity build-up of the PET melt of up to 0.3 dl/g, are available. Each of these machine components is available individually or in combi- nation and can be retrofitted into an existing production line to adapt it to the changed requirements. In this way an ideal result can be achieved with comparatively low investment costs. Main component MRS Extruder The extruder has a special task when processing PET fiber resi- dues, since the plastic must not only be melted and homoge- nized, but if possible, also dehumidified and freed of volatile components if possible. While post-consumer waste can con- tain mainly moisture and a wide variety of solid dirt particles, production waste from fiber manufacture usually contains spin- ning oils, which are important for processing but make recy- cling more difficult. Regardless of which form of thermal cleaning of the waste material is required, the Multi Rotation System Extruder from Gneuss Kunststofftechnik takes over this task. This is due to its special processing-technical design based on a single-screw extruder. Thanks to the enormously large melt sur- face created in the multi-screw section of the extruder, a high degassing and decontamination performance can be achieved and spinning oils can be effectively removed. No thermal pre- treatment of the residues is necessary. Among others, this was a good reason for the Belarusian processor Mogilevkhimvolo- kno located in Mogilev, one of the largest Eastern European producers of staple fibers, to retrofit an MRS 90 to its existing line. With a capacity of around 350 kg/h, all agglomerated fiber residues arising in production are processed, decontaminated and then re-polymerised to PET with a defined IV value in a po- lycondensation reactor without any further preparation. The si- tuation is similar at the Chinese fiber producer Suzhou Sheng- hong Fiber Co. Ltd which operates an MRS 130 with a capacity of up to 800 kg/h. Here, too, the fiber waste is first shredded, melted in the MRS and thermally cleaned before it is brought back to the desired IV value in the polycondensation reactor and then processed into POY and FDY yarns. For the first time, stretched fibers with a high recycled content can be produced in this way. MRS extruders are in use worldwide for processing PET waste materials. This is also the case with the South American compa- ny Valerio, which operates an MRS 90 with a capacity of 450 kg/h to produce staple fibers from very dirty bottle flakes. Mechanical cleaning indispensable Especially when using heavily contaminated bottle flakes, as is the case with the South American Gneuss customer, mechani- cal melt cleaning is indispensable. Valerio decided in favour of an RSFgenius 90 which, like all melt filtration systems from Gneuss Kunststofftechnik, operates with a rotating filter disc. 40 回收利用 Extrusion Asia Edition 2/2020 用于灵活调整IV数值的聚合反应釜JUMP Polyreactor JUMP for flexible IV increase and adjustment