Textile & Clothing

Ecologically sound, solvent-free production process for filter membranes

The membrane production process developed by the project facilitates production of open-celled foam channels without employing solvents or softeners. This provides the foundations for a new, ecologically sound production method for filter membranes. The membranes have a broad scope of application in the manufacture of insulation materials, noise damping and sports articles as well as in vehicle production and the packaging industry.



The production of medical, pharmaceutical and foodstuff products often necessitates several microfiltration steps for purification of the precursor products. The filter media used are usually made of cellulose acetate (CA). The primary process for the production thereof is the evaporation process. This process, however, employs highly volatile halogenated hydrocarbons as solvents. As these present a substantial health and environmental hazard, this research project pursues two approaches to avoid them. While the first sub-project aims to replace the halogen-based solvent with an ecologically sound solvent, the second sub-project examines the development of a solvent-free production process for filter membranes. The porous membranes are produced through extrusion directly from the melt. Suitable alternative solvents to the climate and health hazard dichloromethane are methyl formate and methyl acetate.


  • Sub-project 1: The new solvents achieve asymmetric membrane structures with service lives that have so far been achieved on CA basis only by using complex double-coating technology
  • On a methyl-formate base, the CA membrane used for sterile filtration passed all process and test steps up to the end product successfully.
  • Sub-project 2: No softeners, solvents or coagulants were used during the foam extrusion. Further, the method facilitates process speeds of up to several 100 m/min.
  • The energy-intensive drying process as well as disposal, reconditioning and recovery of the solvents is no longer necessary.
  • The membranes made of pure polymer are excellently suited for applications in the bio-medical and pharmaceutical sector.
  • The open-celled foams display special insulating properties, high mechanical impact resistance and rapid substance exchange with their environment.

Project Participants

Implementing Institution

Sartorius AG

More Project Informations

Project title:  Verbundprojekt: Entwicklung neuer umweltfreundlicher Herstellungsverfahren für Filtrationsmembranen

Project number:  01RV9901/0

Project period:  1999 - 2003

Project region:  Germany (Lower Saxony)

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Source: German National Library of Science and Technology Hannover (TIB)