US3557802A

US3557802A - Tobacco smoke filter element

Info

Publication number: US3557802A
Application number: US658351A
Authority: US
Inventors: Ernest Marsden
Original assignee: Larus & Brother Co
Current assignee: Larus & Brother Co
Priority date: 1967-08-04
Filing date: 1967-08-04
Publication date: 1971-01-26
Anticipated expiration: 1988-01-26

Abstract

A cigarette smoke filter for removing Polonium 210 contained in cigarette smoke, in which finely divided aluminum particles are uniformly dispersed in a carrier base of high surface area, the particles acting to absorb Polonium 210.

Description

United States Patent [72] inventor Ernest Marsden Lowry Bay, Wellington, New Zealand [21] Appl. No. 658,351 [22] Filed Aug. 4, 1967 [45] Patented Jan. 26, 1971 [73] Assignee Larus & Brother Company Richmond, Va.

[54] TOBACCO SMOKE FILTER ELEMENT 50 Field of Search .l 131/10; 131/261-269. 10.9, 207, (inquired); 55 74, 72

[56] References Cited UNITED STATES PATENTS 3,039,475 6/1962 Neukomm et al. 131 140 Primary ExaminerMelvin D. Rein Attorneys-A. Yates Dowell and A. Yates Dowel], Jr.

ABSTRACT: A cigarette smoke filter for removing Polonium 210 contained in cigarette smoke, in which finely divided alu minum particles are uniformly dispersed in a carrier base of high surface area, the particles acting to absorb Polonium 210.

TOBACCO SMOKE FILTER ELEMENT The present invention relates to smoke filter elements suitable for in cigarettes or cigarette holders.

The object of the present invention is to provide a tobacco smoke filter element which while performing the usual functions of such a filter regarding the removal of, for example tar, is also capable of selectively absorbing the radioactive isotope Polonium 210 (Po2l0) from tobacco smoke to a significant extent.

The basis of the present invention is the discovery that aluminum is highly effective in adsorbing P0210 and that it may be incorporated in tobacco smoke filter materials in a finely divided form to produce a tobacco smoke filter element meeting the criteria set out above.

The invention consists in a tobacco smoke filter element for incorporation in a cigarette or cigarette holder the filter element consisting of a carrier base of high surface area in which particles of finely divided aluminum are substantially uniformly dispersed the average size of the particles being between 5 and 500 microns.

The disclosure describes in a method of making a tobacco smoke filter element wherein a carrier base of high surface area filter material is impregnated with a dispersion of aluminum particles in a liquid, the average size of the particles being in the range of from 5 to 500 microns, the carrier base being formed into a rod of appropriate diameter before or after impregnation.

It is preferred that the carrier base shall be of fibrous material such as cellulose acetate in fibrous form but it may also be of any other material having a high surface area per unit weight suitable for use as a tobacco smoke filter element in which finely divided aluminum particles may be dispersed.

It is further preferred that the aluminum particles be incorporated in the carrier base by immersing the carrier base in a dispersion of aluminum particles in a suitable liquid.

While it has been established that aluminum particles are capable of selectively absorbing P0210, there is no experimental evidence to hand as to whether a particular particle size range is most efficacious for P0210 adsorption, however, it is reasonable tolassume that since the adsorption is a surface area effect it would be inversely proportional to the particle size. it is considered that aluminum particles in the range of from 5 to 500 microns may be used effectively for the purposes of the invention, particles in the size range of from 25 to 150 microns being preferred.

The preferred carrier material is cellulose acetate fiber such as Estron (a registered trade mark of Eastman Chemical Co.) for two reasons (i) the filter-manufacturing technology is well established for such a fiber, and (ii) cellulose acetate itself exhibits a slight selectivity for P0210. However, it could be expected that aluminum would exhibit its selectivity for P0210 irrespective of the carrier material by which it was supported provided that material had a sufficiently high surface area and by virtue of this a sufficient number of spaces to occlude significant quantities of aluminum particles.

The results set out below were obtained with plasticized Estron designated 3.5/44000 where the number 3.5 refers to the denier of the filament (weight in grams of a single filament or fiber 9,000 meters in length) and the 44000 refers to the total denier of the tow. The total number of fibers in the tow is obtained by dividing the total denier by the filament denier. It could be expected that the use of Estron of another denier, e.g. 8.0/70000 would produce a different selectivity when impregnated with aluminum particles by virtue of the reduced number of fibers and consequently the number of interfiber spaces.

Although methods such as dusting and spraying may be used to incorporate the aluminum particles in the fibrous carrier material, the method which has been found most effective for Estron is to immerse, for example, 7.5 mm. X 7.8 mm. diameter plugs of plasticized Estron into a dispersion of the aluminum particles in a suitable liquid such as an organic solvent e.g. n-Hexane. The aluminum particles dispersed in the solvent are rapidly incorporated throughout the plug by virtue of capillary attraction. After drying in air or vacuum no trace of the solvent remains, the plugs retaining only a uniform impregnation of aluminum particles. The characteristics of a suitable liquid are:

i. a sufficiently low boiling point to expedite evaporation;

ii. freedom from noxious nonvolatile residues; and

iii. compatibility with the filter medium so as to cause no dimensional changes.

A particular advantage of this technique in contrast to the dusting and spraying techniques is that the filter is impregnated after plasticizing of the Estron fiber whereas the reverse procedure may significantly reduce the surface activity of the aluminum particles. Other advantages of this technique are its economy, simplicity, and suitability for continuous operation in contrast with, for example, the vacuumspluttering technique.

However, this liquid dispersion technique is only applicable to aluminum particles whose diameters are smaller than the interfiber distances and when larger particles are being used, dusting and sieving of the particles into the fibrous carrier material, or the use of a technique known as the Eastman S|urry Additive Process, is necessary.

The weight of aluminum per unit volume of the filter can be altered by changing the quantity of aluminum being dusted or sieved onto a moving band of fibrous carrier material such as Estron tow, or in the case of the liquid dispersion technique by the quantity of aluminum dispersed per unit volume of the bath.

For example, in the liquid dispersion technique, if the dispersion bath contained l5 g. aluminum powder per liter, approximately 5 mg. aluminum was deposited in a 7.5 mm. X 7.8 mm. diameter 3.5/44000 Estron plug; if 30 g. per liter than approximately 10 mg. per plug; if 60 g. per liter then approximately 13 mg. per plug. The proportionally lower deposition at the highest dispersion concentration indicates saturation or an approaching saturation for that denier Estron.

Test results are set out below in connection with one particular form of filter according to the invention the construction of which is described by way of example only.

The test results set out below s were obtained from smoking tests of cigarettes fitted with two 7.5 mm. X7 .8 mm. diameter 3.5/44000 Estron plugs in series. The Estron plugs were either plan plain or impregnated with aluminum particles of a total weight as stated. Smoking tests were performed according to the recommendations of the CORESTA Scientific Commission, Smoke Study Group, Jan. 1966. Eight groups of 10 cigarettes were smoked for P0210 analysis and eight groups of five cigarettes were smoked for tar and nicotine analysis. Both the cigarette filters and the Cambridge filters were analyzed for the relevant smoke components. Filtration efficiencies were calculated according to the formula.

f F H where F= amount of smoke component retained on cigarette filter and H= amount of smoke component retained on Cambridge filter.

The total P0210 content of cigarettes smoked was of the order of 0.50 Ci per cigarette.

Filtration Efiiciency percent.

Filtration etficieney, percent Nicotine N0'1E.= Error terms are 1 standard deviation limits.

The test results set out above are only examples of a typical degree of selectivity obtained. Depending on the particular requirements e.g. whether increased tar filtration is required multiples or submultiples of these filters may be used. Different results could be expected from filters made from Estron of a different denier or from filters of different lengths. It is estimated for example that a filter element having a length of 22.5 mm. and containing about 38 mg. A1 would have a filtration efficiency for P02 l of about 66 percent.

It will be seen that the aluminum impregnated filter elements show a significant improvement in their capacity to remove P0210 as compared with the unimpregnated filter elements.

A matter of some practical significance is that whereas the pressure drop of an unimpregnated filter was l1.8 cms. of water this was increascd'only to I22 cms. of water in the case of the third impregnated filter containing about 26 mg. A1.

in the practical application of a tobacco smoke filter element according to the invention it is preferred that the filter element be followed by a length of plain unimpregnated filter material to prevent the possible ingestion of any loosely held aluminum particles.

lclaim: 1 y

l. A tobacco smoke filter element for incorporation in a cigarette or cigarette holder to remove Polonium 2l0, said filter element consisting of a carrier base of high surface area in which particles of finely divided aluminum aresubstantially uniformly dispersed, the average size of the particles being between 5 and 500 microns.

2. A tobacco smoke filter element as claimed in claim I wherein the carrier base is of fibrous material and the aluminum particles are retained in the interfiber spaces.

3. A tobacco smoke filter element as claimed in claim .2 wherein the fibrous material is cellulose acetate fiber.

4. A tobacco smoke filter as claimed in claim 3 wherein the average size of the aluminum particles is in the range of from 25 to microns.

Claims

1. A tobacco smoke filter element for incorporation in a cigarette or cigarette holder to remove Polonium 210, said filter element consisting of a carrier base of high surface area in which particles of finely divided aluminum are substantially uniformly dispersed, the average size of the particles being between 5 and 500 microns.

2. A tobacco smoke filter element as claimed in claim l wherein the carrier base is of fibrous material and the aluminum particles are retained in the interfiber spaces.

3. A tobacco smoke filter element as claimed in claim 2 wherein the fibrous material is cellulose acetate fiber.

4. A tobacco smoke filter as claimed in claim 3 wherein the average size of the aluminum particles is in the range of from 25 to 150 microns.