| 摘要 |
Microfibrous, polymeric filter sheets and filter elements prepared therefrom comprised of a normally hydrophobic, microfibrous, polymeric web, wherein the surfaces of the microfibers making up the web are coated with a cured, precipitated, cationic, thermosetting binder resin or polymer. The filter sheet is further characterized by being hydrophilic and having a positive zeta potential. The process for preparing such filter sheets comprises four steps: (1) applying a first solution or dispersion of a precipitating agent to a hydrophobic web to at least partially wet the web; (2) applying a second solution of the binder resin or polymer to the wetted web of step (1); (3) working the wetted web of step (2) to mix the first and second solutions, thereby facilitating the precipitation of the binder resin or polymer and the distribution of the precipitated binder resin or polymer as a coating on the surface of the microfibers making up the worked web; and (4) drying and curing the coated web of step (3) to form the desired filter sheets. The filter sheets have enhanced mechanical strength, are hydrophilic, have positive zeta potentials over the pH range of from about 3 to about 10 and typically have absolute pore ratings of from about 0.5 to about 80 micrometers.
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