TECHNOLOGY | PET
waste is contamination from spin oil and dust coming from the processing conditions. So there are two important requirements in fibre-to-fibre recycling technology, melt homogeneity and decontamination, both of which BB Engineering has addressed. The VacuFil technology combines gentle
Above: BB Engineering’s VacuFil PET recycling system can process post-production and post- consumer material
with a connected VarioFil spinning plant. Schäfer emphasises the advantage of BB Engineering’s know-how in fibre production in the development of recycling technology. He says the company places a priority on its application know-how, the filament being produced from recycled PET. “We know very well what high-quality filament needs,” he says. While competitors make granule- or flake-to-fibre systems, BB Engineering’s fibre-to-fibre systems are designed to exploit the growth potential of post-production recycling by POY manufacturers using in-house lines. Until recently, yarn producers have avoided
using recycled process waste for two reasons, says Schäfer. The virgin material’s IV reduces from 0.65 dl/g to about 0.6 dl/g during extrusion and spinning, making the scrap material unsuited to going through the processes again without an IV lift. The second deterrent to reusing production
large-scale filtration and targeted IV regulation to maintain consistency in high quality rPET melt. The technology was launched in 2019 but was developed further to integrate it with the company’s VarioFil spinning plant. A key component in the PET recycling system is the patented Visco+ vacuum filter which removes volatile impurities quickly and reliably, says the company. Visco+ is now also available as a separate upgrade component for existing systems. “As a melt filter, the Visco+ operates like a
liquid-state polycondensation [LSP] unit,” says BB Engineering. “A maintenance-intensive reactor or a deposit-prone stirring unit are not required. Moisture is removed from the PET in the filter, which – in conjunction with an adjustable residence time – results in the desired IV increase in the vacuum. This enables a controlled IV build-up of up to 30%.” The IV is continually monitored via an integrated viscosity measurement unit and is adjusted when there are fluctuations. The company says Visco+ “provides an enormous material surface compared to the volume and continuously renews this. To this end, contamination can be removed particularly effectively from the starting material by means of automatically-regulated high-performance vacuum (1-30 mbar)”. (Read more on Visco+ in the feature on Melt Filtration starting on page 45.)
IMAGE: BB ENGINEERING
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