Cellulose filter materials - having a high proportion of pores of uniform size

摘要

Filter materials based on cellulose-contg. raw materials are claimed which contain pores of 0.1 to 120 mu m. The material contains 60-85 vol. % pores of 5 to 40 mu m whose diameters differ from each other by at most 5 mu m. The materials are made e.g. by milling a previously comminuted cellulosic raw material in an air medium in a concn. of at least >=80% (on dry material) until the average length of the cellulose fibres is 0.3-2.5 mm. The resulting fibres are dispersed in water at a concn. of 1.5 - 6% to form a homogeneous suspension, and natural and/or chemical fibres and substances and hydrophobing agents are added. The resulting mixt. is cast and formed into a web, pressed and dried to form the filter material. The high proportion of pores of homogeneous size gives filters with excellent retention properties coupled with high permeability. The filters are useful in internal combustion engines, dust traps, air conditioning units, purification of oil, filtration of edible liquids and chemical products, etc.