Method for applying porous, metal oxide coatings to relatively nonporous fibrous substrates

Claim 1

A method for the preparation of a catalytically active flexible fibrous element comprised of a porous, catalytically active layer of at least one metal oxide coated on, and disposed as the external surface of, a flexible fibrous substrate of substantially non-porous fibers having surface hydroxyl groups selected from the group consisting of glass and ceramic fibers, said method including the steps of a. preparing a coating solution of at least one substantially unhydrolyzed hydrolyzable metal alkoxide precursor of said at least one catalytically active metal oxide dissolved in a substantially anhydrous organic solvent; b. applying a thin, substantially uniform layer of said coating solution on a contaminant free surface of said non-porous fibrous substrate; c. drying said coated substrate in the presence of water or water vapor in a manner so as to initiate hydrolysis of said metal alkoxide to the corresponding metal hydroxide and condensation thereof to the corresponding metal oxide; and d. curing said coated substrate initially in a microwave oven and thereafter further curing in a thermal oven at a temperature in the range of between about 250° C. and about 500° C. so as to drive said hydrolysis and condensation reactions substantially to completion, and to substantially remove the organic constituents from said coated substrate and form said element, said curing being done at a temperature less than that which will cause a substantial loss of catalytic activity.

Claim 2

A method for the preparation of a catalytically active flexible fibrous element comprised of a porous, catalytically active layer of at least one metal oxide coated on, and disposed as the external surface of, a flexible fibrous substrate of substantially non-porous fibers having surface hydroxyl groups selected from the group consisting of glass and ceramic fibers, said method including the steps of a. preparing a coating solution of at least one substantially unhydrolyzed hydrolyzable metal alkoxide precursor of said at least one catalytically active metal oxide dissolved in a substantially anhydrous organic solvent; b. applying a thin, substantially uniform layer of said coating solution on a contaminant free surface of said non-porous fibrous substrate; c. drying said coated substrate in the presence of water or water vapor in a manner so as to initiate hydrolysis of said metal alkoxide to the corresponding metal hydroxide and condensation thereof to the corresponding metal oxide; and d. curing said coated substrate initially in a microwave oven and thereafter further curing in a thermal oven at a temperature in the range of between about 250° C. and about 500° C. so as to drive said hydrolysis and condensation reactions substantially to completion, and to substantially remove the organic constituents from said coated substrate and form said element, said curing being done at a temperature less than that which will cause a substantial loss of catalytic activity.