As leading producer of special polyamide fibres filled with abrasive corn (diamond, silicium carbide or ceramic) Hahl Filaments GmbH in Munderkingen, Germany is an important supplier to manufacturers of technical brushes for deburring of components.

Recycled Filaments

The annual production of abrasive filaments is about 800 tons with a process related yield loss of 160 tons.

 Polyamides, commonly known as Nylon, stand out for high mechanical strength, stiffness and toughness. They offer good chemical resistance and processability as well as high abrasion resistance and good slip properties. 
Polyamides (PA6 and PA6.6) are generally twice as expensive as polyolefines or styrene-based polymers and long-chain types like Nylon 6.10, 6.12 or 12 are even more expensive, making recycling of production waste more attractive, especially in times of increasing raw-material prices.

Cost for waste handling and raw-material loss adds up to 1 Million Euros annually and with the CreaSolv® Process an opportunity for the recycling of abrasive grains and the high-value polyamide (PA6.12) carrier polymer as well opened up.

The German Environment Foundation (Deutsche Bundesstiftung Umwelt - BDU) financially supported the transfer from lab into small technical scale process and a sample production of filaments (April 2009 - December 2010).

Convinced by the excellent results and additional tests, Hahl for an industrial implementation in 2012. Because 160 tons do not justify a new plant, it was decided to look for toll-manufacturers. The search for adequate candidates in Germany developed into a difficult exercise because this industry saw quite some concentration over the last decade.

After a lengthy search one company was identified for the CreaSolv® Process and another one for the reconditioning of the polyamide. Both were not in possession of the optimal equipment, but all parties involved felt confident, that a technical implementation should be successful with a few modifications.

After some pretesting it was decided to run a commercial campaign with 3 tons of diamond-filaments at the beginning of 2013. During this campaign 300kg diamond grains were successfully separated from the polymer fraction and re-processed at Hahl to abrasive filaments without problems. However during the separation and drying of the polymer fraction certain processing problem occurred, which were partly related to the available equipment but unfortunately also to lack of professionalism and ignoring existing processing instructions. During the reconditioning of the polyamide at the second toll-converter it turned out, that the existing Know-how in relation to a vacuum extrusion did obviously not fulfill the required qualification.

Despite all that the 3 tons trial confirmed that the recycling of this compound material is technically possible, if one has the appropriate equipment and Know-how and a waste volume that allows for larger campaigns. Because the available volumes are too small for an internal realization at Hahl and the alternative via toll-manufacturing has not been successful, the project was terminated end of 2013.

More Information:

  • Fraunhofer IVV Information from April 2010 – Energy - and Ressource Efficiency Improvement through Recycling of Abrasive Grains and Polyamide from Waste of Abrasive Filament Production with the CreaSolv® Process – Link
  • DBU aktuell Nr. 2 / February 2012 - New Recycling Process for Technical Brushes - Link