Solvent Induced Phase Separation (SIPS)
SIPS is the abbreviation for Solvent Induced Phase Separation technology in which membrane formation is created by the interaction between solvent and non-solvent.
Manufacturing Process Using SIPS
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SIPS Processes for Hollow-Fibre Membranes
The polymer is dissolved in a mixture of solvents and pumped through a ring-shaped spinneret. In the centre of the ring a bore liquid also exits the spinneret. The bore liquid prevents the ring shaped polymer solution from collapsing to a solid fibre and thus creates the lumen. The polymer solution is spun into the precipitation bath, which is mainly composed of a non-solvent to the polymer. The solvent diffuses out into the precipitation bath and the non-solvent into the polymer solution. This causes the polymer to re-solidify and thus a membrane is formed.
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After solidification, the membrane passes several pre-extraction steps (see figure below) and a membrane make-up step like undulation and addition of spacer yarns. Thereafter, it is wrapped into a foil that later aids the incorporation of the membrane bundles into the housing. In a multi-step extraction, the solvent residuals are removed and the membrane is dried and finally packed for delivery.
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SIPS Processes for Flat Sheet Membranes
For flat-sheet production, the polymer solution is not pumped through a spinneret, but cast through a well defined slit onto a chill roll. Like in capillary production, membrane formation takes place when the polymer solidifies inside the precipitation bath. The flat-sheet membrane is then pre-extracted, washed and subjected to stretching, relaxation and post-treatment, before it is cut and packed.
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Applications of Membranes Made by SIPS Processes
Commercial porous membranes formed by SIPS are used both in medical and industrial separation.
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Medical Separation
Typical medical applications for capillary membranes produced via SIPS technique are e.g. haemodialysis and plasma separation.
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Industrial Separation
Microelectronics
SIPS membranes are used extensively in the production of ultra pure water for semi-conductor production.
Industrial power and municipal water
SIPS membranes have even, well defined pores, advantageous for the sensitive application of water treatment.
