FILTERS

摘要

1442631 Tobacco-smoke filters MONSANTO Ltd 28 Jan 1974 [6 Feb 1973 22 May 1973 17 Oct 1973] 5799/73 24427/73 and 48375/73 Addition to 1341400 Heading A2C [Also in Division C3] A cigarette filter comprises an extruded element (see Specification 1341400) of a substantially open-cell (i.e. the majority of the cell walls are perforated) foamed thermoplastic high density polyethylene or polypropylene resin having a cross-section corresponding to that of the relevant cigarette and a microstructure such that the filter has a hardness greater than 50%, #P 10 less than 15cm. water gauge and a TPM filtration efficiency greater than 20% (the hardness, #P 10 and TPM efficiency being as defined), the element containing dispersed therein a physiologically acceptable substance (i.e. presents no known health hazard to a smoker of cigarettes comprising these filters) that alters to the required degree the composition of the gaseous phase of cigarette smoke passing through the filter when a cigarette comprising the filter is smoked. The substance may remove or reduce one or more components of the smoke and may be active charcoal or triacetin, or it may add one or more gaseous components to the smoke and may be menthol. In the examples high-density polyethylene was blended with calcite as nucleating agent and then active charcoal, triacetin or menthol, and the mixture was extruded, using isobutylene as blowing agent, to form a foamed strand which was pulled through a sizing and quenching apparatus to form foamed rods which were cut into elements to act as cigarette filters.