WO1996010929A1 - Cigarette filters and the like - Google Patents

Abstract

A filter for tobacco smoke comprises a free-radical inhibitor, particularly an O-alkylated derivative of 2,4-monofufurylidene sorbitol, together with an antioxidant to reduce the content of polycyclic aromatic hydrocarbons in the smoke.

Description

CIGARETTE FILTERS AND THE LIKE

The present invention is concerned with the treatment of filters for tobacco smoke particularly cigarette filters, to limit the carcinogenic effect of the smoke passed by them to the consumer

Tobacco smoke particularly that from cigarettes, is well-known to contain various components which are either carcinogens or pro-carcinogens One particular class of compounds falling within this category comprises the polycyclic aromatic hydrocarbons (PAH) which are converted by the cytochrome P450 enzyme system in the liver or the lung into oxygenated derivatives which have been shown to be carcinogenic A considerable amount of literature now exists in this field, for example Pryor, et al Science 220:425-427 Pryor. et al Cancer and Free-Radicals in Antimutagenesis and Anticarcinogenesis Mechanisms, Ed D Shankel. et a l ; Plenum Press, New York NY. pages 45-59. Janoff. et a l 1987 Am Rev Respir Dis 1361058-1064 and many others The effect of free-radicals in the smoke has been extensively discussed, for example by Church and Pryor Environ Hea lth Perspect 64111-126 (1985)

GB-A-1044434 discloses the use of 2,4-monofurfurylιdene sorbitol in cigarette filters to reduce the content of PAH in the smoke

In situations where free-radicals are known to cause harm, for example in the skin, the use of free-radical inhibitors is well-known For example EP-B-0 345 362 discloses the use of a particular type of free-radical inhibitor in skin cosmetics The inhibitor in question is chosen from a group of furfurylidene derivatives of sorbitol. in particular 2.4-monofurfurylidene sorbitol and the tetra-O-alkyl derivatives thereof A method for preparing 2,4-monofurfurylιdene sorbitol was disclosed in US-A-3.383.279 comprising gradual addition of furfurol to acidified sorbitol thus forming the 2,4-O-furfurylιdene derivative

We have now investigated the effect of these sorbitol derivatives in other areas Surprisingly, we have now found that the furfurylidene sorbitol derivatives of EP-B-0 345 362. in combinations with certain other components, can be used to impregnate tobacco smoke filters to achieve smoke which has a dramatically reduced content of PAH The mechanism of this action is unknown and unexpected: on the model of previous uses of free- radical inhibitors, it would be expected that the inhibitor must be present at the site of absorption by the body and not at a remote location The compounds appear to remove mutagenic or carcinogenic compounds from the smoke, but other explanations are possible.

According to the present invention there is thus provided a filter for tobacco smoke comprising means forming a passageway for smoke, characterised in that on a surface of the passageway arranged to contact the smoke there is provided an O-alkylated derivative of 2.4-monofurfurylιdene sorbitol together with an antioxidant. The O-alkylated derivative is desirably a C_1-5-alkyl derivative, e.g. the methyl derivative, and the tetra-O-alkyl derivative is preferred.

The filter according to the invention is particularly represented by a cigarette filter, which may have any conventional construction arranged to provide a very large surface area in contact with the smoke passing through, for example packed filaments, open-cell foams, etc.

The free-radical inhibitor may be incorporated in the filter at any effective level, but typically at 2.5-30 mg per filter, especially about 5-20 mg, particularly when tetra-0-methyl 2,4-monofurfurylιdene sorbitol is used

The filter also contains an antioxidant and the ratio by weight of the sorbitol derivative to the antioxidant is desirably from about 1.5:1 to 31, especially, about 2.1 Particularly preferred antioxidants comprise phenolic antioxidants such as tert-butyl-hydroxyanisole (BHA) or tert-butyl-hydroxytoluene (BHT). It appears that there is synergy between the sorbitol derivative and the antioxidant. and both components are necessary for maximum activity

The active components can be added to the cigarette filter by any convenient method, for example by dosing with a solution of the components and allowing the solvent to evaporate. Alternatively, the packing material for the filter can be pre-impregnated with the active component before the filter is constructed.

The following Example illustrates the invention further. EXAMPLE - Measurement of benzo[α]pyrene and tar levels

In a series of tests, standard cigarettes were used - either Kentucky Reference 1R3F or commercial cigarettes containing no additives in the filter The following additives were investigated

2,4-monofurfurylidene sorbitol tetra-O-methyl ether (FT)

tert-butyl-hydroxyanisole (BHA) The results are summarised in the following table The stated additive dissolved in 40-60 μl diethyl ether, was added in six to ten aliquots using a microsyπnge to inject through the end of the filter Control cigarettes were prepared using diethyl ether only The cigarettes were stored in conditions of controlled humidity and temperature for twenty-four hours and were tested to check that there had been no change in the pressure drop across the filter

The test methods were standard in the industry for the investigation of cigarette smoking and analysis of tobacco smoke The cigarettes were "smoked" in a smoking machine conforming to the standard US Federal Trade Commission smoking protocol and the smoke was passed through a Cambridge filter, which was weighed before and after the smoking The increase in weight of the filter is the total particulate matter (TPM) Nicotine was extracted from the filter by washing with alkaline methanol and estimated using gas chromatography using a nitrogen-phosphorus detection The water content of the TPM was measured by extracting the filter with ethanol followed by gas chromatography with conductivity detection Tar is calculated by deducting the nicotine and water contents from the TPM Benzo[α]pyrene (BaP) is taken as a representative carcinogen for tobacco smoke and was measured by HPLC analysis (with fluorescence detection) of a cyclohexane extract Cambridge filter

As can be seen from the last column, for a 2:1 combination of FT and BHA, a highly significant reduction in BaP was noted. Similar applications in other smoke filters can be envisaged, for example filter cartridges in tobacco pipes. An expert in the art will be able to foresee several modifications and variations, which will be considered all included within the scope of the present specification.

Claims

1 A filter for tobacco smoke comprising means forming a passageway for smoke, characterised in that on a surface of the passageway arranged to contact the smoke there is provided an O-alkylated derivative of 2,4-monofurfurylidene sorbitol together with an antioxidant

2 A filter according to Claim 1 in which the antioxidant is a phenolic antioxidant

3 A filter according to Claim 2, in which the antioxidant comprises tert-butyl-hydroxyanisole (BHA) or tert-butyl-hydroxytoluene (BHT).

4 A filter according to any of Claims 1 to 3, in which the O-alkylated derivative comprises 24-monofurfurylidene-1,3,5,6-tetra-0-methyl sorbitol

5 A filter according to any of Claims 1 to 4. in which the ratio by weight of the free-radical inhibitor to the antioxidant is from 1.5 1 to 3 1

6 A filter according to Claim 5, in which the ratio is about 21

7 A filter according to any of Claims 1 to 6 in the form of a cigarette filter

8 A filter according to Claim 7 containing 25 to 30 mg of the free-radical inhibitor

9 A filter according to Claim 8 containing about 5 to 20 mg of the free-radical inhibitor