Tobacco Smoke Filter

What is this patent about?

'279 is related to the field of tobacco smoke filters, specifically those used in cigarettes, pipes, and cigar holders. The background acknowledges the presence of harmful substances like aldehydes, ketones, nicotine, and tar in tobacco smoke, and the ongoing efforts to remove these without sacrificing the taste and flavor. Existing filters often use cellulose acetate filaments with regular, I-shaped, or Y-shaped cross-sections, each having trade-offs between filtration efficiency and flavor retention.

The underlying idea behind '279 is to use cellulose acetate filaments with a C-shaped cross-section in a tobacco smoke filter. This specific geometry is intended to provide an improved balance between filtering out harmful substances and preserving the desired tobacco flavor. The inventors discovered that this shape offers a unique combination of effective filtration and minimal flavor impairment.

The claims of '279 focus on a tobacco smoke filter made of cellulose acetate filaments, where at least a portion of the filaments have a C-shaped cross-section. The shape is further defined by a shape factor (A/T²), where A is the cross-sectional area and T is the thickness in the center of the cross-section. This shape factor is preferably between 3 and 10, and more preferably between 4 and 10, to achieve a larger blocking area.

In practice, the C-shaped filaments are manufactured by spinning a solution of cellulose acetate through a spinneret. The resulting filter achieves filtration through mechanisms like inertia, diffusion, and blocking, with the effectiveness increasing with the size of the blocking area perpendicular to the smoke flow. The C-shape provides a large area of projection for a given weight, leading to effective filtering. Thin-walled C-shaped filaments maximize the blocking area and result in a higher pressure drop, enhancing the filtering action.

The use of C-shaped filaments allows for a highly effective filter with a relatively small filling density, saving on cellulose fibers. While filters with regular cross-sections are generally considered better at retaining flavor than I-shaped or Y-shaped ones, the C-shaped filter surprisingly surpasses even the regular cross-section in flavor retention. The filter can be made entirely of C-shaped filaments or a mixture, with at least 10% C-shaped filaments to achieve the desired flavor benefits. The filaments typically have a denier of 0.8-16 and 20-32 crimps per 25 mm, and a plasticizer like triacetin can be used.