Filter material

A method of producing a self-supporting, non-woven, binder-free cellulose ester fibrous tobacco smoke filter precursor corrugated sheet-like material which comprises preparing a slurry of cellulose ester staple fibers and cellulose ester fibrets in water, said fibrets being precipitated fibrets having a surface area of from 12 to 25 square meters per gram and lengths of less than 1000 microns, mixing the slurry to produce a homogenous mixture of staple fibers and fibrets, depositing the slurry on a porous surface which permits the drainage of water from the deposited fibrous structure, drying the fibrous structure, removing the thus-formed sheet-like material from the porous surface, and then corrugating the sheet-like material whereby a corrugated sheet-like material is obtained having a sheet weight of from 20 to 40 grams per square meter, a surface area in excess of 1 square meter per gram, a sheet breaking strength of from 200 to 1000 g/5 cm. and a porosity through a 1 inch diameter circular sheet of said material or between about 1 millimeter and 70 millimeters at a flow rate of 200 cc. per minute.