additives feature | PVC stabilizers
no calcium acetylacetonate (CaAA). This additive is traditionally a key ingredient in heat stabilizers for white window profiles, providing good early colour, good colour hold and fast gelation during processing. “CaAA is labelled as toxic, but, within the stabilizer mixture, its concentration is low enough so that it does not affect the labelling of the complete stabilizer,” says IKA. “There is no direct replacement for CaAA within a
stabilizer and so the system containing co-stabilizers, mixed metal soaps and lubricants, needs to be formu-
Fine-tuning formulations
The transition to Ca-based stabilizers in the EU may be almost complete, but formulators’ work continues, says Jörg Fröhlich, technical product manager, PVC additives for window and technical profiles at Baerlocher (which claims to be global leader in Ca-based stabilizer systems). “Up to this point of the story, many
technical issues have been raised and resolved,” he says. Issues tackled by Baerlocher include development of Ca-based stabilizers in dust-free product forms, meeting high-gloss requirements through new lubrication systems, and the development of systems free of calcium acetyl acetonate co-stabilizers to eliminate red deposits in tooling. “You could be forgiven in thinking that
the work for a PVC stabilizer supplier is complete, but that couldn’t be further from the truth,” says Fröhlich. He cites ongoing work to support manufacturers of PVC window profiles who continue to face demanding challenges. “Cost pressure continuously increases, and the needs of the end-markets are always changing. Innovative additives help manufacturers to cope with the challenges and to optimize both their production processes and the quality of the final product. Additive suppliers have to continuously adapt to these requirements.” The formulation of Ca-based stabilizers
is more complex compared to traditional lead-based systems, Fröhlich notes. “A
24 COMPOUNDING WORLD | June 2015
Europe’s shift to Ca-based stabilizers is almost
complete, but formulation work still
continues at Baerlocher
one-pack for white profiles, for example, includes processing aids, external and internal lubricants, metal soaps and inorganic stabilizers. It also contains organic co-stabilizers for thermostability, early colour and colour hold. “In white profiles, colour poses
specific requirements both for the producers as well as for additive suppliers. A window system contains several profiles extruded on different machines. The latest generation of optimized stabilizers ensure consistent colour quality across the different profiles, minimizing the need for time-consuming fine-tuning.” Plate-out on tooling can also be minimized by careful choice of lubrication. “The development effort to achieve this result was considerable, leading to the use of new ingredients, many developed in-house,” Fröhlich says. Coextrusion helps window profile
producers reduce costs without lowering the quality of the final product. “The weatherable outer layer (capstock) must
have the required colour and gloss, but a cost reduction can be achieved by carefully designing the formulation of the core layer,” says Fröhlich. Baerlocher has designed stabilizer systems to allow for the incorporation of raised levels of fillers, such as calcium carbonate, and removal of unnecessary co-stabilizers contributes to cost savings of up to 15%, he claims. Lubrication has also been fine-tuned. Baerlocher collaborated with calcium
carbonate supplier Omya and extrusion technology specialists KraussMaffei Berstorff and Greiner Extrusion to analyse formulations and filler levels. “The results of the study showed that formula- tions for the core layer with calcium carbonate content of up to 20 phr can be processed without problems on standard equipment – provided the optimum combination of extrusion equipment and raw materials is used,” Fröhlich says. ❙
www.baerlocher.com ❙
www.omya.com ❙
www.kraussmaffeiberstorff.com ❙
www.greiner-extrusion.com
www.compoundingworld.com
lated in a new way to ensure that the rheological properties, colour and thermal stability can be matched.” The company says it has now achieved these objectives. “In addition, the outdoor weathering behaviour of the
window profile needed to be verified,” IKA adds. In weathering tests comparing profiles stabilized with its new CaAA-free stabilizer system and various classical Ca-Zn stabilizers, after 8,000 hours (16 GJ/m2
), all the
profiles showed very positive results. IKA has also developed what it says is a new form of
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