ADDITIVES | FILM PRODUCTION
Right: Clariant’s AddWorks PKG 906 Circle stabiliser
allows higher levels of recycled
content to be incorporated into polyolefin films
reintroduced without affecting quality or process- ing, according to the company, which says the stabiliser reduces gel and black speck formation, allows manufacturers to maintain high line speeds, and minimises film breakage. It reports that up to 20% BOPP regrind could be added in one com- mercial trial, with up to 30% shown to be possible in Clariant’s own in-house testing.
Easier processing Processing aids are also an effective additive tool to improve processing of film formulations contain- ing recycled resins and can help ensure a good film surface and, in some cases, can reduce die build- up, according to David Seiler, Americas Business Manager, Industrial and Fluoropolymers Global Advisor at Arkema, which manufactures the Kynar line of polyvinylidine fluoride (PVDF) polymer processing aids (PPAs). Seiler says PPAs lessen start-up and processing variability, which are potential problems with reprocessed resin due to the variability in recycled material streams. “Before considering processing aids, the manufacturers often added large amounts of virgin LDPE to make the films. Now, with process- ing aids, they can use no or less virgin resin and can run faster at higher shear rates,” he explains.
Films made from recycled resins often run more slowly than virgin resins, but the addition of a PPA can improve this. “If converters are pressure-limit- ed, using a PPA, which reduces melt pressure, improves their output,” says Robert Lowrie, Field Sales Engineer at Arkema. Trials performed in Arkema’s processing labs have evaluated Arkema’s PPA in three representa- tive samples of recycled LLDPE from a commercial film converter. They found that PPAs helped relieve processing variation and also reduced degradation and discolouring problems. “Melt fracture is really flow instability,” says Lowrie. “PPAs can eliminate melt fracture and improve flow stability and surface finish.” Lowrie will present results of the company’s studies at the upcoming AMI Polyethylene Films conference in the US. PPAs are typically added by the film converter as a pelletised masterbatch containing 1-6% of the additive. Alternatively, they can be dosed using a liquid masterbatch. Seiler says that having some residual PPA content in the recycled resin itself is not a concern when adding PPA to a film formula- tion. “There is no harm in having 300ppm of PPA in the material versus 1,200ppm,” he says. However, he does add that levels above 2,500ppm may result in blooming. Seiler also says that Arkema eliminated the use
of PFAS (perfluorinated alkylated substance) in its production of Kynar PPA fluoropolymers several years ago. PFAS use is being regulated or phased out in many regions of the world due to its persis- tence in the environment.
CLICK ON THE LINKS FOR MORE INFORMATION: �
www.basf.com �
www.kafrit.com �
www.ampacet.com �
www.tosaf.com �
www.clariant.com �
www.arkema.com
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IMAGE: CLARIANT
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