PET extruder degassing

Special systems

Modern vacuum solutions for extruder degassing

Leybold PET extruder degassing delivers a wide range of product and process benefits and is now used in a wide range of sectors. The main factor behind this is the fact that the material is recyclable, but there are also economic and material criteria.

The requirements for this thermoplastic to develop its full material properties are wrapped up in the PET production process.

Since customers have long relied on our vacuum systems for extruder degassing, we have a massive amount of experience in this application. The manufacturers of PET extruders benefit from our effective solutions for an efficient degassing process. Dry mechanical Leybold pumps are absolutely reliable and ensure that the systems have a long service life.

Extrusion systems are used for preparation of thermoplastic melt during production of plastic components as fibers, sheets, films or tubes. The raw plastic material (usually pellets or bottle flakes) is molten inside single or twin-screw extruders by heat and friction to a viscous liquid.

User advantages

Stable, non-fluctuating vacuum supply

Vacuum level is independent to climate or water temperature

Pressure at venting/degassing dome can be regulated

Minimized maintenance and service demand

Maintenance is reduced to a regular cleaning in parallel to dye cleaning

Full maintenance (incl. pump cleaning) can be executed by trained user

Safe system design, even for expected misuse

As worst-case pumps and system components build up layers

The easy maintenance concept enables the user to help himself, independent from external service

Flexible usage, also for other polymers at multi-purpose extrusion systems

Rising environmental awareness and the increased use of recycled PET are resulting in steadily growing requirements on degassing systems and the vacuum systems used for this purpose. To minimize maintenance requirements, we use dry pumps which require no operating media. Our extruder degassing vacuum solutions are designed so that we achieve above average service lives.

The use of standard pumps in various combinations therefore enables us to meet the highest requirements at low cost. In doing so, we give due consideration to the primary situation facing the customer, namely the ability to complete the cleaning work in-house. The use of dry pre-vacuum pumps with a removable pump chamber means that we can deliver this in user-friendly form.

During the PET degassing, significant amounts of vapors (water, org. solvents, monomers, oligomers) but also pigments particles or solidified melt are extracted out of the extruder and enter the vacuum system. Such vapors could condense and eventually polymerize inside the vacuum pumps. Leybold vacuum system for extruder degassing is designed to withstand these challenges.

Leybold vacuum SCREWLINE pump is a “heavy-duty” pump able to operate even under severe conditions. This allows to design a vacuum system which works with a rough particle trap in front the vacuum pumps only. All gases and vapors extracted out of the extruder can be handled by the vacuum pumps.

Our vacuum PET extruder degassing systems have also been used for extrusion of other polymers (e.g. PS or PLA). Both the pumps are operated with a frequency control, which allows pressure regulation even at pressures rough as 50 mbar. At rough pressures, the roots-pump is mostly not required and could be bypassed. To optimize system usage at multi-purpose extrusion systems, such bypass line could be included in the system design.

The PET extruder vacuum systems maintenance intervals fit to typical campaign lengths of 4-6 weeks, the longest production line uptime. Vacuum system maintenance can be scheduled in parallel to extruder (dye) maintenance.