GB1592157A

GB1592157A - Tobacco-smoke filters

Info

Publication number: GB1592157A
Application number: GB46592/76A
Authority: GB
Original assignee: British American Tobacco Co Ltd
Current assignee: British American Tobacco Investments Ltd
Priority date: 1976-12-09
Filing date: 1976-12-09
Publication date: 1981-07-01
Also published as: BE861704A; ZA777030B; AU512263B2; FI63331C; BR7708174A; FI773676A; DE2754137A1; NL7713585A; AU3107677A; FI63331B; DK547477A

Description

(54) IMPROVEMENTS RELATING TO TOBACCO-SMOKE FILTERS (71) We, BRITISH-AMERICAN TOBACCO COMPANY LIMITED, a Company incorporated under the laws of Great Britain, of Westminster House, 7, Millbank, London, S.W.1, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention concerns improvements relating to filters or filter material for tobacco smoke, especially though not exclusively to cigarette filters.

Filters made from fibrous or filamentary material such as paper or cellulose acetate are known to remove the particulate matter from tobacco smoke. Some other components of tobacco smoke, such as aldehydes, cyanides, sulphides and oxide, can be removed to some extent by absorption or adsorption on a surface or by chemical reaction. One of these vapour-phase constituents which has been found to be difficult to remove from tobacco smoke is nitric oxide. Nitric oxide is a substance which belongs to a group of molecules of an electronic constitution such that there is present an unpaired electron, which gives nitric oxide a free-radical character.

According to the present invention, a tobaccowsmoke filter or filter material-con- tains granules of porous activated carbon to which the nitroxide 4-oxo-2,2,6,6-tetramethylpiperindino-oxy and/or the nitroxide 1 -nitronyl-3 -oxyl-4,4,5,5-tetramethyl-2- phenyldihydroimidazole has been applied. Both compounds are stable, non-volatile, freeradical nltroxides.

By such a filter or material, a considerable filtration efficiency for nitric oxide (NO) in particular and for other constituents which it may be desired to remove, can be obtained without disadvantageous concomitant effects. It is believed that the reduction in nitric oxide may be linked with the porosity of the treated carbon and that, desirably, the pore volume should be at least 0.2 cc/g and the surface area of the said carbon at least 50 m2/g. The preferred compounds 4-oxo-2,2,6,6-tetramethylpiperidino-oxy, has the structural formula:-

The level of loading of the nitroxide carbon expressed as a percentage by weight of the untreated carbon, may be from 0.5 to 25% and is preferably within the range of 1.0 to 15%. In commercial practice, the loading level will probably be within the range of 3 to 10%.

Example 1: 1 g of activated carbon in porous granular form of the type supplied under the trade description " BPL " by the Pittsburg Activated Carbon Co. was added to a solution of 100 mg of 4-oxo-2,2,6,6-tetramethylpiperidino-oxy in 5 ml of ethanol.

The solvent was allowed to evaporate at room temperature until the granular carbon was dry and free-flowing. This gave a loading level of approximately 10%. A triple filter containing a bed composed of 100 mg of this treated carbon disposed between two sections of cellulose acetate, each 5 mm long, was attached to a cigarette having a filling of flue-cured tobacco. On smoking the cigarette through this filter, 72% by weight of nitric oxide was removed from the tobacco smoke.

Tests were carried out with a number of available granular activated carbons and with different loadings of the same nitroxide as in Example 1, using the same application procedure as in that Example. The results are as tabulated below:

NO Filtration NO Filtration LOADING Efficiency (%) Efficiency (%) (% by Carbon with Carbon without CARBON weight) nitroxide nitroxide BPL 10 72 less than 10 BPL 5 60 less than 10 Anthrasorb CC1430/70 10 68 less than 10 MF3 10 57 13 Actibon X 10 45 less than 10 Picatif 60143 7 43 less than 10 Carbomafra GC 7 43 less than 10 207C 10 43 17 The suppliers of the several types of carbon were as follows: BPL Pittsburgh Activated Carbon Co., of Pennsylvania, U.S.A.

Anthrasorb CC1430/70 Cardian Chemical Co., of Cheltenham, England MF3 Chemviron Ltd., of Brussels, Belgium Actibon X Hooker-Mexicana S.A. de C.V., of Mexico Picatif 60143 Pica of Paris, France Carbomafra GC British Traders & Shippers Ltd., of Dagenham, England 207C Sutcliffe-Speakman Ltd., of Leigh, Lancashire, England Actibon X was rendered non-acidic, before application, by treatment with a 0.1 M aqueous solution of sodium hydroxide.

Example 2: 1 -nitronyl-3-oxyl-4,4,5,5-tetramethyl-2-phenyldihydroimidazole was applied to carbon granules of the type BPL referred to above, using the same procedure as in Example 1, but with a loading level of 5%. A triple filter was prepared as des cribed in that example. A filtration efficiency for nitric oxide of 44% was obtained.

The amount of treated carbon to be provided in a filter will depend upon the filtration efficiency required as well as upon the nitroxide used. The effect of variation of the weight of treated carbon is illustrated by the table below: The results tabulated were obtained with the Anthrasorb type of granular carbon, referred to above, treated as described in Example 1 but with a loading level of 7% of the 4-oxo-2,2,6,6-tetra methylpiperidino-oxy nitroxide. The treated carbon was incorporated in triple filters as described in that Example.

WEIGHT OF CARBON FILTRATION EFFICIENCY ( 10) (mg) For NO 25 29 50 50 75 50 100 61 150 75 200 81 The efficiency of filtration for nitric oxide can be enhanced by so called " ventilation" of the filter, for example by use of a perforated or porous filter wrapper. Thus, if, in a triple filter whose centre section comprises a bed of the treated carbon, either the tobacco-end section or the said centre section is ventilated in known manner, the filtration efficiency of the filter is significantly increased. For example, a triple filter of this kind with ventilation holes in the wrapping of the centre section was attached to cigarettes of flue-cured tobacco.There were 3 rows of holes 1 mm apart, the holes being rectangular (0.1 mm x 0.5 mm) and the first row being 7 mm from the end of the tobacco rod. 100 mg of carbon of the Anthrasorb type with 10% loading of the 4-oxo-2,2,6,6-tetramethylpiperidino-cxy nitroxide was employed as the aforesaid bed.

With the ventilation holes closed by covering with non-porous tape, the overall reduction of nitric oxide was found to be 67% whereas, with the holes uncovered, the overall reduction was 89%.

WHAT WE CLAIM IS: 1. A tobacco-smoke filter or filter material containing granules of porous activated carbon to which the nitroxide 4-oxo-2,2,6,6-tetramethylpiperidino-oxy and/or the nitroxide l-nitronyl-3-oxyl-4,4,5,5-tetramethyl-2-phenyldihydroimidazole has been applied.

2. A filter or filter material according to daim 1, wherein the carbon is loaded with 0.5 to 25 O/o by weight of the nitroxide.

3. A filter or filter material according to claim 1, wherein the carbon is loaded with 1.0 to 15% by weight of the nitroxide.

4. A filter according to any one of claims 1 to 3, wherein a bed of carbon forms one section of the filter which has at least one other section of different smokefiltering material.

5. A filter according to claim 4, wherein the said bed is located between two other sections of smoke-filtering material.

6. A filter according to claim 4 or 5, wherein the smoke-filtering material of the said other section or sections is fibrous or filamentary.

7. A filter according to claim 4, 5 or 6, wherein the said smo,ke-filtering material of at least one said other section is cellulose acetate.

8. A filter according to any one of cralmsl to 7 and having provision for filter ventilation.

9. A filter according to claim 8, being a triple filter of which the centre section contains the treated carbon, wherein the said centre section and/or the section upstream thereof is ventilated.

10. A tobacco-smoke filter or filter material containing granules of activated carbon substantially as hereinbefore described.

11. A smoking article provided with a filter or filter material according to any oneof the preceding claims.

12. A method for improving a tobacco-smoke filter or filtration material containing granules of porous activated carbon which comprises applying to the said carbon the nitroxide 4-oxo-2,2,6,6-tetramethylpiperidino-oxy and/or the nitroxide 1-nitronyl-3- oxyl-4,4,5,5-tetramethyl-2-phenyldihydroimidazole.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. The efficiency of filtration for nitric oxide can be enhanced by so called " ventilation" of the filter, for example by use of a perforated or porous filter wrapper. Thus, if, in a triple filter whose centre section comprises a bed of the treated carbon, either the tobacco-end section or the said centre section is ventilated in known manner, the filtration efficiency of the filter is significantly increased. For example, a triple filter of this kind with ventilation holes in the wrapping of the centre section was attached to cigarettes of flue-cured tobacco.There were 3 rows of holes 1 mm apart, the holes being rectangular (0.1 mm x 0.5 mm) and the first row being 7 mm from the end of the tobacco rod. 100 mg of carbon of the Anthrasorb type with 10% loading of the 4-oxo-2,2,6,6-tetramethylpiperidino-cxy nitroxide was employed as the aforesaid bed. With the ventilation holes closed by covering with non-porous tape, the overall reduction of nitric oxide was found to be 67% whereas, with the holes uncovered, the overall reduction was 89%. WHAT WE CLAIM IS:

1. A tobacco-smoke filter or filter material containing granules of porous activated carbon to which the nitroxide 4-oxo-2,2,6,6-tetramethylpiperidino-oxy and/or the nitroxide l-nitronyl-3-oxyl-4,4,5,5-tetramethyl-2-phenyldihydroimidazole has been applied.