method of manufacturing a filter for tobacco smoke

摘要

1331096 Tobacco-smoke filters BRITISH AMERICAN TOBACCO CO Ltd 4 Oct 1971 [7 Oct 1970] 47707/70 Heading A2C [Also in Divisions B5 and C3] One or more additives is intermittently injected into a cigarette filter rod comprising open cell foamed thermoplastics material, during continuous extrusion of a rod of the material. In the examples (1), a suspension of carbon in triacetin at 170‹C was injected into extruding polyethylene foam; (2), a solution of menthol in triacetin was injected into the polyethylene; (3) a solution of polyethylene glycol in triacetin at 170‹C was injected into polypropylene foam. The foam may also comprise cellulose, or nylon e.g. foamed by a blowing agent or inert gas. The additives may have selective filtration properties, or filtration enhancing properties, and may comprise manganese dioxide, zinc oxide, zeolites, ethylene diamene diacetate, alumina, or finely divided zinc, as solutions, suspensions or slurries, and may also comprise sweetening agents. The additive is injected downstream of the extrusion outlet from a nozzle co-axial therewith, and more than one such outlet may be provided for the separate injection of more than one additive. The injection may be effected via a periodically opened valve, but in the described embodiment, Fig. 1, is injected from an outlet passing through the extrusion die 1, to which the additive is intermittently supplied by a piston pump 4, to within the extruded rod 7 to form spaced additive zones 6. After being drawn by an endless belt traction device 10 through a sizing die 8 and cooling bath 9, the rod 7 is cut midway along the zones, by a device 11, into multiple filter lengths. In the Fig. 2 embodiment (not printed), the additive outlet extends through a cross-head extrusion die, through a support defining with the die an annular extrusion outlet of diameter decreasing in the extrusion direction, the support and/or the outlet being axially adjustable in the die head.