Selective filtration of cigarette smoke using chitosan derivatives

Abstract

A smoking article filter having a porous resin with a high surface area to mass ratio comprised of a chitosan derivative. Preferred embodiments include chitosan cross-linked with glutaraldehyde and chitosan cross-linked with glyoxal. The chitosan derivative provides for the selective filtration of cigarette smoke, particularly for the removal of aldehydes, hydrogen cyanide, heavy metals and carbonyls.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] Not applicable. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [0002] Not applicable. FIELD OF INVENTION [0003] This invention concerns improvements relating to tobacco smoke filters. More particularly, the invention relates to a cigarette filter that can selectively remove undesirable constituents from tobacco smoke. BACKGROUND OF THE INVENTION [0004] A wide variety of materials have been suggested in the prior art as filters for tobacco smoke. Examples of such filter materials include cotton, paper, cellulose acetate, and certain synthetics. Many of these filter materials, however, are only effective in the removal of particulates, tars and condensable components from tobacco smoke. The art is replete with a myriad of filtration techniques and materials for removing undesirable components in smoke and for causing other reactions as the smoke passes through filtration beds or other reactive media. Among the problems en...

AI Technical Summary

Benefits of technology

[0008] It has been discovered that chitosan can be chemically modified to have the physical attributes of a filter medium and have a chemical composition capable of effectively adsorbing and absorbing undesirable smoke ingredients, yielding superior performance as a cigarette filter.

[0009] Thus, it is an object of the present invention to provide cigarette filter arrangements and, more particularly, cigarette filters that can selectively remove undesirable constituents in the vapor phase of tobacco smoke such as hydrogen cyanide, aldehydes, metals and sulphides without the drawbacks or disadvantages associated with the prior art as previously described.

[0016] A porous chitosan resin may be formed by a phase inversion technique. This is accomplished by dissolving flaked or powdered chitosan in a suitable solvent, such as aqueous acid, and then coacervating in a solution of aqueous base to form water swollen chitosan gel beads. The beads may be cross-linked using glutaraldehyde, and separately with glyoxal, to improve the mechanical strength and reduce the solubility of the beads. The wet beads are then freeze dried to yield a porous cross-linked resin. Drying may also be accomplished by vacuum or air drying.

[0018] The cross-linked resins produced by both methods have a reduced number of reactive amino groups. The reduced number of reactive amino groups is a result of the cross-linking reaction with glutaraldehyde or glyoxal. It has been surprisingly discovered that the described invention, having a reduced number of reactive amino groups, is selective in removing hydrogen cyanide and formaldehyde from tobacco smoke. It has also been surprisingly found that the cross-linked chitosan resin having a reduced number of reactive amino groups exhibits greater selective removal activity than that associated with the prior art where a maximum number of reactive amino groups have been employed.

Problems solved by technology

Many of these filter materials, however, are only effective in the removal of particulates, tars and condensable components from tobacco smoke.

Among the problems encountered with prior filters has been the plugging or clogging with use and the consumption or rendering ineffective of reactive filtering surfaces and materials.

However, they have little or no effect in removing certain gaseous components in the vapor phase of the tobacco smoke such as hydrogen cyanide, aldehydes, carbonyls, metals and sulphides.

Ion-exchange resins of porous structure have been found to be somewhat effective, but their efficiency diminishes during smoking, as does that of carbon and porous minerals.

This may be due to the material becoming saturated and, therefore, increasingly inactive or it may be due to the release of adsorbed material by thermal desorption of retained substances.

Resins which contain major proportions of tertiary amino or quaternary ammonium groups have been found not to be suitable for removing aldehydes from tobacco smoke.

Among the problems encountered with these materials is that they do not provide a filtration media allowing for the continuous flow of smoke at a low pressure differential or gradient.

Other problems with selective filtration medias have been found.

However, it has been discovered that while glycine can reduce the level of formaldehyde in tobacco smoke, it is not stable in the cigarette filter manufacturing process.

Moreover, the use of amino acids causes the release of ammonia odor during storage.