Recycling of fluoropolymers and other plastics
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 fluoropolymers 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
Established cycles during production, processing and use of fluoropolymers
Waste incineration with recovery
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 stipulate low-molecular „fragment“ content of less than 25 ppb, are easily complied with.
Mechanical recycling
The thermomechanical degradation of fluoropolymers is particularly environmentally friendly: New, stricter purity regulations, which stipulate 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 highenergy 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.
Chemical recycling
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.
Chemical recycling, also referred to as upcycling in the case of fully fluorinated fluoroplastics, is a new technology (Figure 2). It has been developed on an industrial scale since 2015 in an experimental industrial plant with a capacity of one thousand tons per year. In the meantime, it is ready for market launch. The fully fluorinated polymers, PTFE, modified PTFE, PFA and FEP, as well as some PTFE compounds can be recycled. The monomer recovery rate is around 85 percent.
For the upcycling process, too, the products are collected after reaching the end of their lives, cleaned and then mechanically shredded. This is followed by thermal splitting back into the monomers at over 600 °C. Reaction products are primarily tetrafluoroethylene (TFE) mixed with a little hexafluoropropene (HFP). After purification of the raw gas mixture by distillation and special washing processes, high-purity monomers are recovered. These can be reused for the polymerisation of new fluoropolymers.
Polymers produced with this process show no reduction in quality compared to the original polymers. Upcycling thus transforms „old“ into „new“ materials. The quality is thereby raised to the initial level. Fears that the properties of upcycled products are inferior to those of new products do not apply.
Raw-material saving by upcycling
Polymers produced with this process show no reduction in quality compared to the original polymers. Upcycling thus transforms „old“ into „new“ materials. The quality is thereby raised to the initial level. Fears that the properties of upcycled products are inferior to those of new products do not apply.
Raw-material saving by upcycling
The raw materials for fluoropolymers are fluorspar, crude oil/natural gas, methane and common salt (NaCl). From these, first the fluorocarbon intermediate R22 and finally tetrafluoroethylene (TFE) are produced in a multi-stage process. All fluoropolymers are made from this raw material. Besides a high energy demand, waste products are also produced, especially hydrochloric acid (HCl). These have to be reprocessed or recycled in complex processes. In addition, all the raw materials mentioned are only available in limited quantities. Once these resources are used up, substitute products will be in short supply.
However, if fluoropolymers that have reached the end of their useful life or machining waste are used instead of these finite resources, the raw material and waste savings that can be achieved are enormous. Figure 3 shows the environmental relief per 1,000 tonnes of fully fluorinated polymer returned to the cycle through upcycling. The amounts of „waste acid“ or saved carbon dioxide (CO2) are about ten times the weight of the recycled fluoropolymers. The CO2 footprint („carbon footprint“) of fluoropolymers is thus significantly reduced via the upcycling process to better values.
However, if fluoropolymers that have reached the end of their useful life or machining waste are used instead of these finite resources, the raw material and waste savings that can be achieved are enormous. Figure 3 shows the environmental relief per 1,000 tonnes of fully fluorinated polymer returned to the cycle through upcycling. The amounts of „waste acid“ or saved carbon dioxide (CO2) are about ten times the weight of the recycled fluoropolymers. The CO2 footprint („carbon footprint“) of fluoropolymers is thus significantly reduced via the upcycling process to better values.
Re-use of PE and PP
Two important representatives of the „standard plastics“ are polyethylene (PE) and polypropylene (PP). Due to the comparatively low raw material prices of virgin materials, only low-cost recycling processes are used here; chemical recycling is not possible because of the comparatively high costs.
PE and PP in the production of laboratory supplies are essentially chips or remnants. These are collected, shredded, cleaned and then converted back into new products via thermoplastic processing methods. The preferred recycling method for PE is film production. Recycled PP is reused by means of injection moulding mainly for technical products, for example bumpers or lamp housings for motor vehicles. In these applications, the material cycles can also be passed through several times. About 14 per cent of the plastics currently used in Germany come from such recycling processes.
Plastic mixtures collected via the „yellow bag“, for example, provide a „PE-rich fraction“ and a „PP-rich fraction“ in automated processes. These are then also suitable for further processing by extrusion or injection moulding. Non-separable municipal plastic waste ends up in so-called „energy recycling“ as substitute fuel in coal-fired power plants and thus replaces lignite or hard coal.
PE and PP in the production of laboratory supplies are essentially chips or remnants. These are collected, shredded, cleaned and then converted back into new products via thermoplastic processing methods. The preferred recycling method for PE is film production. Recycled PP is reused by means of injection moulding mainly for technical products, for example bumpers or lamp housings for motor vehicles. In these applications, the material cycles can also be passed through several times. About 14 per cent of the plastics currently used in Germany come from such recycling processes.
Plastic mixtures collected via the „yellow bag“, for example, provide a „PE-rich fraction“ and a „PP-rich fraction“ in automated processes. These are then also suitable for further processing by extrusion or injection moulding. Non-separable municipal plastic waste ends up in so-called „energy recycling“ as substitute fuel in coal-fired power plants and thus replaces lignite or hard coal.
