Abstract:
A pleated filter paper has activated carbon, fuller's earth, bauxite, diatomaceous earth, magnesium oxide, silica gel, alumina or molecular sieve non-uniformly dispersed throughout the paper, the concentration being preferably smaller towards the surfaces of the paper. In one embodiment, a strip of paper containing equal proportions of cotton linters and activated charcoal is pleated and formed into an annulus for insertion into a filter cartridge in a dry-cleaning machine. The paper may be made by a Fourdrinier process in which a water carbon slurry is introduced over the surface of a partially-settled paper fibre mat. A water-soluble phenolic resin may be added to the beater which coats the paper fibres before carbon is introduced on to the mat.