| 摘要 |
A ventilated tobacco smoke filter reduces tar yield mainly by air dilution rather than mechanical filtration (and/or which enhances reduction of CO yield in comparison to that of tar yield), whilst maintaining a relatively high pressure drop, wherein the filtering material forms a layer around a denser flow-obstructing fibrous or filamentary core and is itself surrounded by an air-permeable wrapper. The filtering material is suitably of bonded crimped cellulose acetate filaments and the flow- obstructing core is suitably a zero or low permeability drawn-down rod of bonded substantially uncrimped filaments, e.g. of cellulose acetate. The filter is incorporated in a filter cigarette by means of a ventilating (e.g. perforate) tipping overwrap, which may constitute said wrapper. Also provided is a tobacco smoke filter rod comprising a layer of tobacco smoke filtering material around a denser flow-obstructing drawn-down core of bonded filaments. <IMAGE> |
