Process-related requirements for polymer filtration

The special properties of polymer melts place high demands on the filter elements used.

High viscosity and differential pressure

Polymer melts have a significantly higher viscosity than liquid media. In order to ensure a constant volume flow through the filter element, correspondingly high differential pressures are required. The porous structure must permanently absorb this load without compacting or changing its filtration properties.

Continuous thermal load

Filtration takes place at temperatures above the melting temperature of the respective polymer. The filter material must remain dimensionally stable under these conditions and must not be mechanically or structurally impaired.

Even load on the filter surface

A homogeneous pore structure is crucial in order to avoid preferential flow channels. Uneven flow quickly leads to local overloads, pressure peaks or blockages in melts.

Process stability and service life

Polymer filtration is often designed as a continuous process. Fluctuations in pressure loss or flow rate have a direct effect on process control. The requirements for stable filtration performance over longer service lives are correspondingly high.

Suitable SIPERM® materials for polymer filtration

In polymer filtration, the focus is not on the general choice of material, but on the reliability of filtration under melting conditions. The decisive factors here are the mechanical stability of the porous structure, the uniform flow of the melt and the behavior of the filter element under permanently high differential pressure and elevated temperature.

SIPERM® R – porous stainless steel for melt filtration

Porous filter elements made of SIPERM® R are predominantly used for the filtration of polymer melts. The material meets the requirements for temperature resistance and strength that are necessary for use in extrusion and spinning systems.

The porous structure of SIPERM® R enables a defined separation of solid impurities from the melt with a uniform flow. This prevents the formation of preferential flow channels that could lead to local overloading or premature clogging.

In addition to pure separation, filtration with porous stainless steel contributes to the homogenization of the polymer melt. The melt is distributed over the entire filter surface, reducing local inhomogeneities. Inclusions such as gel particles can be separated within the porous structure, which has a positive effect on further processing and the resulting product quality.

These properties make SIPERM® R particularly suitable for applications where high purity requirements are placed on films, fibers or technical plastic products and a stable, continuous process is required at the same time.

Typical filter elements and filter structures

In practice, different filter concepts are used in polymer filtration, which are adapted to the respective process control.

A frequently used concept is multi-layer disc filters, in which several porous filter elements are stacked on top of each other. This arrangement enables graduated filtration and a more even load on the individual filter layers. At the same time, service life can be extended without significantly impairing the flow rate.

In addition, porous filter elements made of SIPERM® R are also used as:

• Disc filter

• Panel elements

• Customized molded parts

are used. The design of the geometry depends on the throughput, melt properties, available installation length and desired service life.