FlowFree

The Development of a High-Output Processing Method for the Extrusion of Solid Thermoplastic Sheet and Profile

Extrusion and co-extrusion of sheet and profi le are important industrial processes within the EU. A technology developed by two of the FlowFree consortium partners has shown that plastics extrusion equipment can be modified to allow for compressed CO2 to be used as a processing aid for the production of solid extrudate with reduced melt viscosities, thus allowing processing at faster output rates, reduced temperatures or reduced energy.

FlowFree aimed to develop the necessary technologies to allow for industrial-scale, commercially viable extrusion and co-extrusion of solid sheet and profile, either by retro fitting the equipment to current machinery or by fi tting to new extruders.

The main objectives of the project were to:

• Develop a prototype extruder that will allow full industrial and commercial development of the process;
• Develop the process on an industrial scale for small to medium-sized enterprises (SMEs) with different production requirements;
• Demonstrate the technical and commercial viability of the process on full industrial scale;
• Carry out dissemination and training activities that allow for maximum exploitation of the technology.

Organisational Information

Budget: €2.5M
Funding: €1.4M
Start Date: September 2005
Finish Date: February 2009
Duration (in months): 42
Lead Partner (Co-ordinator): Smithers Rapra, UK

Participants

Results – What happened next?

A modified extrusion system was developed to allow a controlled incorporation of supercritical CO2 into polymer melts. Common industrial polymer, PVC (poly(vinyl chloride)) with a K-value of 65 was used to demonstrate the viscosity reducing effect of supercritical CO2. Pressure, motor current, and output were monitored and measured as indicators of change in viscosity and power/energy consumption.

During processing, the CO2 plasticisation effect was demonstrated. A reduction in pressure of up to 30%, a reduction in motor current of up to 10%, and an increase in output rate of up to 50% were observed. These changes are dependent on the amount of CO2 incorporated during the processing. These changes also indicated a reduction in viscosity and power/energy consumption during processing.

The benefits of CO2 assisted polymer extrusion can be summarised as follows:

• Reduced motor current: Reduction in motor current results in power/energy savings. For every 1% reduction in energy achieved by the EU extrusion sector, this would lead to an annual cost reduction of €9 million and an annual CO2 emission reduction of 43,000 tonnes.
• Increased output rate: The energy cost savings and increased output rates lead to reduced production costs.
• Reduced processing pressure and melt viscosity: Reduction in pressure allows processing at a faster rate, thus increasing production. Lowering viscosity means easier processing, resulting in longer machine life. In addition, it also allows easier processing for high viscous materials.
• Lower processing temperature: Processing at a lower temperature allows reduced usage of potentially harmful and expensive additives, such as heavy metal heat stabiliser or antioxidants.