TOBACCO SMOKE FILTERS

1,220,086. Tobacco-smoke filters. COURTAULDS Ltd. 18 June, 1968 [30 March, 1967], No. 14534/67. Heading A2C. A tobacco-smoke filter comprises a section of foamed cellulose acetate material having interconnected pores. The foamed material is produced by slurrying finely divided or fibrous cellulose acetate with a solvent or softening agent, subjecting the slurry to heat and pressure sufficient to partially gel the cellulose acetate, and suddenly releasing the pressure to expand and foam the material. Fillers such as natural and synthetic fibres, wood pulp or kaolin, may be included in the slurry before foaming. The filter may form a component of a multiple filter that includes a crimped paper section with or without absorbent additive material such as active carbon, or includes a conventional fibre filter element.