Page 351 - BOLA Catalogue

350
www.bola.de
TECHNICAL INFORMATION
Recycling of fluoropolymers and other plastics
Dr. Michael Schlipf
With more than 50 percent, polytetrafluoroethylene (PTFE) is the most important representative of the fluoropolymers. For PTFE and other fully fluorinated fluoropolymers, the same applies from the beginning of their use: The material costs are comparatively high and the most important raw material, fluorspar
(CaF2), is one of the finitely available resources. Reasons enough why various recycling cycles for flu- oropolymers were developed early on and integrated into their life cycle. Today, they are general practice (Fig. 1).
Established cycles during production, processing and use of fluoropolymers
Raw material R 22
for monomer production
Processors, Manufacturers of semi-finished products finished parts
Mechanical recycling
End user chemistry, environmental technology, mechanical engineering
Micropowder
Waste incineration with recovery
Grinding
Irradiation
Thermo- mechanical degradation
Second life
Cleaning, crushing
If waste from monomer production and polymerisation is incinerated, integrated lime flue gas purification (Ca(OH)2) enables the recovery of fluorspar. This can then be used again as a raw material for monomer production.
Beginning of a “second life”
It is also possible to extend the life cycle. For this purpose off-spec batches from polymer production are converted into PTFE micropowder by thermomechanical degradation of the molecules. This is then used as an additive in paints, printing inks or lubricants.
The thermomechanical degradation of fluoropolymers is particularly environmentally friendly: New, stricter purity regulations, which stipu- late low-molecular „fragment“ content of less than 25 ppb, are easily complied with.
Machining waste from the production of semi-finished and finished parts is collected, cleaned and ground. This can then be used to produce semi-finished products such as rods, tubes or sheets by means of ram extrusion. It is also possible to break down polymers by high- energy irradiation and reuse the resulting PTFE micro powder.
If products are easy to clean at the end of their life cycle, they too can be ground and used either as a raw material for Ram-extrusion or, after radiation degradation, as PTFE micro powder in additive applications. The reprocessing is done by companies specialised in this. They deliver the recycled products back to their point of origin, where they are processed again.
Fluorothermoplastics such as PFA, FEP, ETFE or PVDF can be used in injection moulding or extrusion after state-of-the-art processes such as grinding, cleaning and reuse. The fact that these thermoplastics are usually marketed without the use of fillers makes recycling particularly easy.
Mechanical recycling
Use of by-products
Monomer production TFE, HEP
Chemical recycling
CLOSED AND RESOURCE-SAVING PRODUCTION CYCLES
Polymerization
PTFE, fluoro- thermoplastics
PTFE, FT reprocessing including compounds
Material recycling
White production waste
Production waste and compounds
White production waste
Processing waste and compounds
End-of-life products and compounds