Tobacco smoke filter

Details Tobacco smoke filter Tobacco smoke filter

1992-10-14

2001-10-16

Silverman, Stanley S. (Department: 1731)

Tobacco

Tobacco or tobacco substitute product or component part thereof

Cigar or cigarette

C131S361000, C131S362000, C131S342000, C131S331000, C131S200000, C131S202000, C131S203000, C162S139000

Reexamination Certificate

active

06302114

ABSTRACT:

The present invention concerns tobacco smoke filters and filter elements containing particulate smoke-modifying additive.
Suitable particulate additives include sorbents (e.g. selected from activated carbon, silica gel, sepiolite, alumina, ion exchange material etc.), pH modifiers (e.g. alkaline materials such as Na
2
CO
3
, acidic materials), flavourants, other solid additives and mixtures thereof.
The present invention provides a tobacco smoke filter or filter element having a longitudinally extending core and a wrapper engaged around the core, the wrapper having particulate additive adhered to one or more portion(s) of the radially inner face thereof with said wrapper being free of additive around its circumference at one or both ends of the core.
The particulate additive preferably extends only partially around the inner circumference of the wrapper—the wrapper for example having an overlapping longitudinal edge which is free of said additive and provides a lapped and stuck seam holding the wrapper around the core. The particulate additive may cover a single region of the inner surface of the wrapper extending from one end of the core partially towards the other; it may cover a single region which is spaced from both ends of the core; it may be disposed in separate regions spaced longitudinally and/or circumferentially from one another. Any particulate additive used may be a single substance or a mixture, and may be in admixture with other material.
The wrapper is preferably pre-coated with the adhering particulate smoke modifying additive. The core may be pre-formed before application of the coated wrapper, or formation of the core and application of the coated wrapper may occur substantially simultaneously.
The particulate additive is suitably adhered to the wrapper by hot melt adhesive, high m.p. polyethyelene glycol, or emulsion-type adhesive such as PVA. Suitable hot-melt adhesives for use in the invention are various polyester adhesives.
In the filter or element according to the invention the core can be of conventional smoke filtering material (e.g. of filamtentary tow, staple fibre, or creped paper); an open ended tube; or an impermable or low-permeability portion which contributes to the composite filter pressure drop but has little or no filtering effect; the core could be a unitary body, or it could be a composite—e.g. incorporating its own sleeve and/or having longitudinally (and/or radially) adjacent portions. In one type of embodiment the core wrapper is itself surrounded by an outer annular body—which, like the core, could for example be of conventional smoke filtering material or an impermeable or low-permeability portion with little or no filtering effect. The core can be a composite of a central rod and a sleeve. The core, with or without such sleeve, may have external grooves extending longitudinally thereof over part of its length, in which case the particulate additive on the radially inner face of the wrapper may be in register with and extend into these grooves. The grooves may extend from one or each end of the core partially towards the other, or stop short of both ends. In a composite core of a rod with a grooved sleeve, the rod surface may conform to the sleeve grooves.
Filters and elements according to the invention may have an outer containing sleeve e.g. an extruded sleeve or a plugwrap with a lapped and stuck seam; such a plugwrap could be of air-permeable or -impermeable material, and in either case may be perforated. The particulate-coated wrapper could be adhered (e.g. with heat-activatable adhesive) to the core to give a bonded product which is dimensionally stable without a containing sleeve. In another arrangement, one or both longitudinal wrapper edges may be without particulate coating and be used as an adhesive overlap to hold the wrapper around the core. However, even with bonding of the wrapper to itself and/or to the core, it may be preferred to provide a containing sleeve around the wrapper.
The preformed particulate additive-coated wrapper is conveniently applied around a preformed core, or around a core as the core is being formed, using conventional garniture apparatus. In a method according to the invention the supply of the particulate additive-carrying wrapper, the application thereof to the core after or whilst the latter is formed (optionally with application of a surrounding sleeve), and cutting of the resulting elongate product into finite lengths, can be conducted continuously and in-line using conventional filter manufacturing machinery. Where the wrapper is itself to be surrounded by an outer annular body, the latter may be similarly continuously fed and formed around the advancing wrapped core; continuous in-line procedures and apparatus for these operations are known in the cigarette filter art. The finite lengths cut initially from the continuously produced product will usually be multiples of the eventually used individual filters or elements; in this case the initial finite lengths are further subdivided into final unit lengths during or for subsequent formation of filter cigarettes, and are also according to the invention. The wrapper may be coated with adhesive over the restricted regions where particulate additive coating is required (e.g. by a printing wheel), and then with particulate additive (e.g. by drawing through a reservoir, fluidised bed, circulated stream or other supply of the additive whilst the adhesive is active) as part of the above in-line continuous process; instead adhesive-coated strip may be separately produced or obtained from an outside supplier, with activation (e.g. heat-softening) of the adhesive and application of particulate additive being conducted in-line and continuously with filter production. Filters according to the invention may incorporate other material.
Various parameters may vary widely according to product requirements, these including for example weight/unit length of the wrapper used to carry the particulate additive, the particle size of the additive, etc. A suitable particle size for activated carbon is 12/30 British Standard Mesh, and another is 30/70 British Standard Mesh.
The wrapper employed according to the invention may be of any innoxious material. It will usually be a conventional plugwrap, and may be permeable or impermeable to smoke or air, according to the flow requirements in the final product. When intended for a ventilated filter, the wrapper will usually be highly porous. The wrapper may have external grooves extending longitudinally over part of its length, in which case the particulate additive on its radially inner face is preferably at an ungrooved region; the grooves may extend from one or each end of the wrapper partially towards the other, or stop short of both ends; the core surface may conform to the wrapper grooves.
At least some of the particulate additive used may carry (or consist of) flavourant—or other material carrying flavourant may be incorporated.
The invention can provide, without the need for production and subsequent longitudinal alignment and combination of separate elements, a unitary filter element which carries advantageous particulate additive and which yet can present an acceptable, plain, additive-free appearance at the buccal end of a filter cigarette. It also permits incorporation of activated carbon or other particulate additive in tobacco smoke filters using conventional apparatus without introducing production or apparatus problems and in particular with ready achievement of uniform additive loading—and simple and accurate variation of this loading when required. Filters according to the invention allow the particulate additive adhered to the radially inner face of the wrapper to exercise, unhindered or substantially so, its filtering or other effect on the tobacco smoke stream; thus filters according to the invention containing particulate sorbent can give good retention of vapour phase smoke components.
Products according to the invention are generally suitable for use as or in cigarette filters. Cigarette filters a

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