Process for producing supported celluosic membranes and products

DETAILED DESCRIPTION OF THE INVENTION The supported microporous cellulosic filter according to the present invention comprises an integral support web and a cellulosic polymer coating on either side of the support web.
The support web for the microporous filter is a porous material pervious to a casting lacquer comprised of cellulosic polymers, solvents and non-solvents.
The support web is preferably a non-woven pure polymeric material, for example, nylon, polyester, polypropylene, among others, and has a preferred density of 0.
5 to 1.
5 oz.
per square yard.
Lower density materials are generally weaker and less uniform in thickness, while higher density fabrics require greater amounts of lacquer and increased gelation times for complete encapsulation of the support web.
Depending on the specific application of the microporous filter, the support web may be of any reasonable thickness approximating the desired final filter thickness.
However, it has been found that for most applications structurally preferred filters are obtained from support webs having thicknesses up to about 0.
005 inch.
A support web having a thickness less than 0.
005 inch is generally more flexible while thicker support webs naturally require more polymer and have increased surface area for the same pore size and structure.
It has also been found that support webs having thickness greater than 0.
005 inch are suitable as a solid phase support biotechnology applications.
Specific commerical examples of non-woven materials suitable for use as a support web are Reemay Polyester and Typar Polypropylene, manufactured by Dupont; Hollytex from Filtration Sciences; Webril Polyester, Nomex and nylon from Kendall; Cerex nylon from Monsanto and Chicopee's Kiara polypropylene.
The web supported cellulosic membrane filter is preferably prepared by first coating a casting lacquer containing at least one cellulosic polymer onto the support web in a metered fashion so as to completely saturate the web and to leave a lacquer film of uniform thickness on either side of the support web