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Steel Belt Units for Medical Membranes

| By Chemical Engineering

Medical membranes play a key role in certain aspects of healthcare and, with their range of applications now encompassing Covid-19 diagnostic tests, their importance is greater than ever.
Most membranes used for diagnostics or liquid treatment are produced by means of a phase separation process based on steel belt technology. As a supplier of steel belt-based process solutions for many years, IPCO has extensive experience in this area and is a long-term partner to global players in this field.

In common with most equipment designed for pharmaceutical production processes, the phase separation system has to satisfy three key criteria: GMP-compliant design; high standards of precision; and outstanding reliability.

Phase separation

The phase separation process is induced to create a porous structure in a three-dimensional profile. Phase separation occurs by changing the temperature in the applied liquid or adding another solvent. This added solvent is miscible with the solvent in the casting solution, but the polymer does not dissolve in it. As the solubility of the solvent mix is further decreased, phase separation starts.
The polymer is diluted in an appropriate solvent or solvent mixture and applied to the steel belt in a defined liquid layer.

This process is controlled by temperature and the addition of the non-solvent, and the uniformity of the process conditions determines the uniformity of the porous structure.
Narrow tolerances of machine design and process parameters are key to the delivery of high quality products.

Production process

Typically, the casting solution is applied to the steel belt by means of a precision slot die, often positioned at the peak of the drum. In some systems, a coating roller is positioned between the drum and the inlet to the process section.

The endless welded belt runs around two drums and conveys the applied liquid to the process section. The steel belt and the feeding drum must be manufactured to precise tolerances as there is just a small gap between the slot die and the belt. The process also relies on the heat transfer qualities of the steel belt, the efficiency of which depends on its consistency of thickness.
Altogether, this places critical demands on the slot die, the steel belt and the runout tolerances of the selected drums and rollers.

Precision is therefore measured in microns, an extremely fine tolerance for rollers and drums which can be up to 2 m in diameter and more than 2 m wide, and for belts which can easily be more than 150 m².
IPCO’s engineering team has the know how to design equipment and systems capable of fulfilling these requirements and manufacturing products of the required quality.
For some products, the steel belt also must be mirror polished for better release of the product or for a perfect membrane surface. For these high-end belts, maximizing quality starts with the raw material, with production stages such as vacuum melting minimizing any impurities that might otherwise result in defects in the surface polishing.

Integrated system design

Powerful forces need to be applied to ensure that these heavy, high precision belts remain flat and stable during the production process. This requires a robust hydraulic belt tensioning system, together with sophisticated belt tracking to keep the belt within narrow straight run tolerances. IPCO has developed a belt tracking system capable of achieving the necessary straight running tolerances.
The supporting machine frame, drum shafts and bearings must also be suitable for this heavy-duty application if a high quality end product is to be guaranteed; any bending could result in deviation, compromising product quality.

Temperature control

Temperature is another key process parameter, and IPCO has developed high precision temperature control units for steel belt tempering by means of drum heating, impingement heating or water spray zones.

Heating of the feeding drum ensures that the belt reaches precisely the right temperature at the feed point. This requires a maximum of 1 K deviation in surface temperature across the full width of the drum, a real challenge when a typical drum could be 2000 mm wide with a diameter of at least 1200 mm, usually more.

IPCO can also offer air handling process solutions to prepare the process air as required for each process step in the desired temperature and humidity.

In recent decades, the company has broadened its portfolio to enable it to offer a turnkey service encompassing everything from the casting die, steel belt unit and drying system to downstream slitting and winding equipment and all necessary utilities.

IPCO can also provide site supervision or a full site service include system installation and commissioning at production facilities anywhere in the world. Specialised application engineers are available to support projects from first test trials to product qualification after commissioning.

Film casting units – IPCO

Press Contact:
Birgit Rossa
IPCO Germany GmbH
Niederlassung Fellbach
Salierstrasse 35
70736 Fellbach, Germany
Tel. +49 711 5105 208
[email protected]