W. Müller targets screen changer to plastic recyclers

Germany-based plastic blow molding equipment provider W. Müller GmbH has developed a new generation of screen changers for extrusion blow molding applications.

The new screen changers have been designed to be space-saving and to address the continuous filtering of melt materials, which the company says is an essential element of controlled extrusion, especially when using postconsumer resin (PCR).

On the space-saving, front W. Müller's new screen changer is suitable for installation in vertically oriented extruders and can be retrofitted and operated safely. The company currently has more than 100 systems in use in North America.

“We are also receiving more and more inquiries from North, South and Central America about systems for safe recyclate processing," says Jens Schlueter, president of Massachusetts-based W. Müller USA Inc. "I expect a further significant increase here also because of the changing raw material situation.

"The production of gasoline and diesel is declining. Accordingly, less ethylene and propylene [PP] is present for polymerization. This will further drive the demand for alternative materials. At NPE 2024, we have a limited offer for a free three-month testing for customers, as we are confident they will be very pleased with the performance."

W. Müller will have information about its products for the plastics recycling sector at the NPE 2024 trade show May 6-10 in Orlando, Florida.

“These new screen changer designs represent a true game changer in this industry,” says Mario Jardin, director of aftermarket and service at W. Müller. “From personal experience in the field, I see how operators frequently struggle with leaks and injuries when trying to operate traditional screen changers, due to the heaviness of these systems, which often tend to jam.

“The operator-friendly piston design of our W. Müller screen changer eliminates the room for leakage and does not seize. This reduces screen changing times significantly.”

Noting that the use of screen changers is highly recommended for companies working with PCR, W. Müller says its filtering screen consists of a fixed perforated carrier plate that is covered by several interchangeable grids with different mesh sizes.

“If the differential pressure on this grid exceeds a certain value, the screen must be changed,” W. Müller says. “The screen changer absorbs impurities ensuring highest melt and end product quality.”

"The screen changer ensures that impurities are kept away from the extrusion head," W. Müller sales manager Johannes Schwarz adds. "In addition to the use of PCR, which can be contaminated with other plastics or particles, abrasion from the mill, degraded plastic material or often sections of cable ties [can] interfere with the process and may lead to interruptions in production. It would be even more problematic if leaking containers were produced and ended up in the filling station.”

The screen changer can be added as a retrofit item and does not require any special safety precautions, as it does not have its own drive, the company says. It can be operated manually or by the use a cordless screwdriver.

Specific to PCR processing, W. Müller is offering the ReCo3 system for its extrusion units, consisting of three independent extruders. The PCR layer is enclosed in the middle by two layers of virgin material. The extruders are mounted vertically for this process.

“In the processing of recycled material, in particular PCR materials, the risk of contamination increases, which does not enter the production process from the outside but from the used material itself," W. Müller Managing Director Christian Müller says. "These can be, for example, snippets of aluminum lids or sleeves of bottles. In operation, the screen is slowly getting clogged and must be changed regularly. How often depends on the quality of the processed material. W. Müller has designed its own system for this change.

“Traditionally, there are no screen changers for such extruders; we are one of the very few suppliers on the market. Normally, the changers are too long to install vertically without risking the stability of the extruder.”

A retrofit of a ReCo3 system with the matching screen changers in most cases is possible without any problems, according to the company. “This way, we are able to offer every interested company to get started with PCR processing,” Christian Müller says.

“The compact design is possible because the screen changer is integrated into the connection piece between extruder and extrusion head," Schwarz adds. "By retrofitting a screen changer, the extruder is not significantly extended. In addition, it can be installed in any orientation, which further increases flexibility.”

W. Müller says it regularly carries out tests with PCR and other recycled-content plastic at its in-house technical centers in Germany and the United States as a way to cultivate its expertise in the growing sector.