Troisdorf, Germany — Blow molding equipment maker W. Müller GmbH (W4180) has developed a new screen changer for processing recyclables with a piston design it says is easy to use, eliminates leaks and doesn't seize. The screen changer absorbs impurities, ensuring the highest melt, which is a factor in product quality.
The WM-030 screen changers are a next-generation product suitable for installation in vertically oriented extruders, according to Mario Jardin, director of aftermarket and service.
Filtering the melt is an essential element of controlled extrusion, he added, especially when using post-consumer recyclate (PCR).
"These new screen changer designs represent a true game-changer in this industry," Jardin said in a news release. "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."
The filtering screen consists of a fixed perforated carrier plate, which 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.
"The screen changer ensures that impurities are kept away from the extrusion head," said Sales Manager Johannes Schwarz, noting PCR can be contaminated with other plastics or particles, such as abrasion from the mill or sections of cable ties.
"Impurities 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," Schwarz said.
W. Müller staff constantly carry out tests with PCR and other recyclates at in-house technical centers in Germany and the United States, company officials said.
The risk of contamination often comes from the used material itself with other sources being snippets of aluminum lids or sleeves of bottles, according to Managing Director Christian Müller.
"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," he said.
The screen changer can be retrofitted, and it does not require special safety precautions because it doesn't have its own drive. It can be operated manually or with a cordless screwdriver without effort.
For processing PCR, W. Müller also offers the ReCo3-brand system for its extrusion units, which consists 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.
"Traditionally, there are no screen changers for such extruders. We are one of the very few suppliers on the market," Müller said. "Normally, the changers are too long to install vertically without risking the stability of the extruder."
A retrofit is possible in most cases without any problems.
"This way, we are able to offer every interested company to get started with PCR processing," Müller said.
A compact design is possible because the screen changer is integrated into the connection piece between the extruder and extrusion head, Schwarz added.
"By retrofitting a screen changer, the extruder is not significantly extended. In addition, it can be installed in any orientation, which further increases flexibility," Schwarz said.
The company has been receiving more inquiries from North, South and Central America about systems for safely processing recyclables, according to Jens Schlueter, president of W. Müller USA Inc.
"I expect a further significant increase here, also because of the changing raw material situation," Schlueter said. "The production of gasoline and diesel is declining. Accordingly, less ethylene and propylene is present for polymerization. This will further drive the demand for alternative materials."
At NPE2024, the company will offer a free three-month trial time for customers.
W. Müller officials said the company currently has more than 100 systems used in customer production within North America.
W. Müller GmbH W4180