Asymmetric composite membranes and modified substrates used in their preparation
Durable asymmetric composite membranes consisting of a film of cross-linked poly(ether ether ketone) adhered to a sheet of hydrophilic microporous poly(ethylene) are disclosed. The membranes are suitable for use in the recovery or removal of water from feed streams where repeated clean-in-place protocols are required such as in the processing of dairy products.
1. A method of preparing an asymmetric composite membrane comprising the steps:
irradiating a dispersion comprising sulfonated poly(ether ether ketone) and at least one cross-linking agent in an organic solvent to provide a dispersion of partially cross-linked sulfonated poly(ether ether ketone);
contacting one side of a sheet of microporous polyolefin wetted with a solution of a hydrophilicitizing agent in an aqueous solvent with the dispersion of partially cross-linked sulfonated poly(ether ether ketone);
irradiating the one side of the coated sheet at a wave length and an intensity for a time sufficient to adhere the cross-linked sulfonated poly(ether ether ketone) to the sheet of microporous polyolefin to provide a composite; and then
drying the composite at a temperature and time sufficient to provide the asymmetric composite membrane.
2. The method of claim 1 where the aqueous solvent is 40 to 60% (v/v) acetone in water.
3. The method of claim 2 where the hydrophilicitizing agent is 4-ethenyl-benzenesulfonic acid.
4. The method of claim 1 where the organic solvent is dimethylacetamide.
5. The method of claim 1 where the cross-linking agent is p-divinylbenzene.
6. The method of claim 1 where the dispersion additionally includes 4-ethenyl-benzenesulfonic acid.
7. The method of claim 1 where the dispersion comprises benzophenone.