US3426763A - Tobacco smoke filter having a coated carbon additive - Google Patents

Description

United States Patent Oflice 3,426,763 Patented Feb. 11, 1969 3,426,763 TOBACCO SMOKE FILTER HAVING A COATED CARBON ADDITIVE Cephas H. Sloan and Bobby J. Sublett, Kingsport, Tenn., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Continuation-impart of application Ser. No. 447,093, Apr. 9, 1965. This application July 21, 1965, Ser. No. 473,809 US. Cl. 131-266 2 Claims Int. Cl. A24d 1/06; B01d 27/02 ABSTRACT OF THE DISCLOSURE A new filter for tobacco smoke in which hydrogen cyanide is effectively removed comprises a core or carrier of continuous cellulose acetate filaments which carry as an addition thereon a nonactivated carbon coated with a water soluble salt. Sodium carbonate, potassium carbonate, sodium phosphite, potassium phosphite, sodium phosphate, potassium phosphate, sodium silicate, and potassium silicate constitute the effective water soluble salts. The nonactivated carbon base does not absorb volatile taste producing vapors to the extent that the activated carbons do.

This is a continuation-in-part of our copending application Ser. No. 447,093, filed Apr. 9, 1965.

This invention relates to .a tobacco smoke filtering material for selectively removing deleterious materials from tobacco smoke without removing the desirable smoke vapors which contribute aroma and taste to the smoke. More particularly, this invention concerns a novel cigarette filter tow and filter made therefrom as well as the method for their manufacture. The invention further pertains to a specially coated carbon powder additive for selectively removing certain deleterious materials from tobacco smoke.

In our US. patent application Ser. No. 425,920, filed Ian. 15, 1965, we disclose that the use of certain watersoluble inorganic salts will remove substantial amounts of hydrogen cyanide from tobacco smoke. While such salts have proven to be highly successful hydrogen cyanide removal agents, we have noticed in some instances a tendency of these additives to dust off the filter tow during processing and that they are difiicult to distribute uniformly over the surface of the tow. Thus, in such instances difiiculty in making a uniformly coated tow and tobacco smoke filters from the tow has been experienced. Therefore, both the development and manufacture of a tobacco smoke filter element with improved hydrogen cyanide filtration efiiciency represents a highly desirable result.

After extended investigation we developed various novel additives for a tobacco smoke filter which are described and claimed in our copending application Ser. No. 447,093, filed Apr. 9, 1965, of which this is a continuation-in-part. However, it has now been found that another novel additive for removing substantial amounts of hydrogen cyanide from tobacco smoke can be produced from relatively inexpensive components.

Therefore, one object of this invention is to provide a new and improved type of tobacco smoke filter element. Another object is to provide an additive which may be applied to cigarette filter tow to selectively remove hydrogen cyanide (HCN) from the vapor phase of tobacco smoke. A further object is to provide a method for making an improved tobacco smoke filter. Still another object is to provide an improved additive for use with a cellulose acetate filter tow.

In its broader aspects our invention involves adding to a tobacco smoke filter carbon powders or granules which have water-soluble inorganic salts coated on the surface thereof, especially the salts of Group Ia elements of the Periodic Table. Inorganic salts which we have found particularly useful according to our invention include the sodium and potassium carbonates, phosphites, phosphates, and silicates, or mixtures of these. The salts are coated on the carbon particles by adding a weighed amount of the particles to an aqueous solution of one or more of the aforementioned salts. The inorganic salt solution should contain a sufficient concentration of the salt so that after the water is removed the carbon powder will have deposited on its surface 20 to 40 percent salt by weight. The concentration of salt in solution can be carried to give the desired amount of salt deposit on the carbon. The coated carbon particles are normally carried on a fibrous type filter medium and may be applied thereto by a vibrating device. However, any other suitable method of evenly dispersing a dry powder or granular material onto a filter tow may be employed. The amount of carbon additive coated with salt that may be added to a filter tow according to our invention is between 10 and 30 percent based on the weight of the tobacco smoke filter.

Although activated carbon particles can be used as the carrier material for a salt additive, it has been found that such carbon particles have certain disadvantages. Besides the fact that such activated carbon particles are rather expensive to produce, they are also nonselective in the vapors they absorb. In general, activated carbon absorbs vapors according to their boiling points. Hence, the least volatile vapors will be absorbed and retained more readily than the lower boiling vapors. We have found that certain types of carbon, such as that used in decolorizing and pigmentation work (nonactivated carbon), which have little or no afiinity for tobacco smoke makes a superior carrier for salt additives, and that such salt coated carbon particles when used in a tobacco smoke filter produces .a superior selective filter unit. These nonactivated carbon powders are superior carriers for the inorganic salts since they 1) will not absorb those nondeleterious volatile vapors which give taste to the tobacco smoke, and (2) are relatively inexpensive to produce.

According to one embodiment of the instant invention a crimped tow is spread out to a width of approximately 15 inches as it moves through a cigarette filter-making machine. A vibrating pan adapted to coat the surface of the tow is placed directly above and parallel to the tow. In the pan is placed a nonactivated carbon powder which will pass through a ZO-mesh screen and coated with an inorganic salt. The coating of the nonactivated carbon particles is performed by placing, for example, 6 grams of the particles into 20 ml. of aqueous solution containing 4 grams of a dissolved inorganic salt selected from the group including sodium and potassium carbonates, phosphites, phosphates, and silicates, or mixtures of these. After the nonactivated carbon particles have soaked for a reasonable period of time they are taken from the salt solution and the water remaining in the particles is removed by evaporation thus leaving a dry carbon powder coated with a 40 percent salt coating, based on the dry weight of the powder. The vibrator pan is adjusted to apply the desired amount of additive, and the additive is vibrated onto the filter tow as it moves throuugh the filter-making equipment. If desirable, an adhesive or plasticizer can be added to the tow prior to the addition of the carbon coated additive. As the tow containing the additive moves through the filter-making equipment, the tow is formed into a continuous cylindrical rod and wrapped in paper. This paper encased cylindrical rod may be cut into any desired length and used either alone as a filter unit or in combination with other filter units to make a dual or multiple tobacco smoke filter. While the salt coated carbon particles may be added to the tow as described above, cigarette filters may also be made by positioning a coated carbon mass between filter cylinders made of filaments by methods known in the art.

A further understanding of the invention will be had from a consideration of the following examples which are set forth to illustrate certain preferred embodiments.

Example I A l70-mm. length of 5 denier/filament (d./f.) crimped cellulose acetate filter tow which had 9,000 filments and weighed approximately 1 gram was spread out to a width of 15 inches. Glyceryl triacetate (triacetin) in the amount of 9 percent by weight of the tow was applied to the tow by rollers. A dry nonactivated carbon powder which contained 40 percent by weight of potassium acid carbonate coated on its surface was applied to the tow from a vibrating pan until 30 percent, based on the dry weight of the tow, had been added. The tow was formed into a cylindrical rod, wrapped with a paper tape and allowed to stand until it became firm. The cylindrical rod thus formed, which has a circumference equal to a standard domestic cigarette (25 mm.), was then cut into 20-min. segments. The 20-min segments, which contained approximately 30 mg. of coated carbon, were attached to king-size cigarettes by means of a cellophane tape. The cigarettes were smoked with an automatic smoking device, and the vapors which passed through the filter were collected and analyzed spectrophotometrically and by gas chromatography. These values are recorded in Table 1 below. Also recorded in Table 1 are the amounts of these vapors obtained from the same type filter element containing an untreated nonactivated carbon additive.

TABLE 1 g. found in smoke pg. found in smoke from one cigarette As will be noted from Table l, the salt coated nonactivated carbon filter is much more effective in selectively removing the vapors of hydrogen cyanide from tobacco smoke.

ExampleH A 170-mm. length of 5 d./f. crimped cellulose acetate filter tow which had 9,000 filaments and weighed approximately 1 gram was spread out to a width of 15 inches. Glyceryl triacetate in the amount of 9 percent by weight of the tow was sprayed onto the tow. Dry nonactivated carbon granules which contained 30 percent sodium silicate by weight coated on its surface was uniformly applied to the tow from a vibrating pan until 20 percent total additive, based on the dry weight of the tow, had been added. The tow was formed into a cylindrical rod and wrapped with a paper tape to form a rod. The rod was allowed to become firm and then was cut into 20-min. segments. The 20-mm. segments were attached to king-size cigarettes by means of a cellophane tape and the cigarettes smoked with an automatic smoking device. The vapors which passed through the filter were collected and analyzed spectrophotometrically and by gas chromatography. The amount of hydrogen cyanide and certain other vapor phase components which passed through the filter are shown in Table 2. Also shown in Table 2 are the vapors which passed through the same type 'filter elements containing an amount of activated carbon equivalent to that of the treated carbon which was smoked and analyzed in a similar manner.

TABLE 2 pg. Found in smoke from one pg. Found in smoke from one It should be noted that the filter containing the nonactivated coated carbon additive is highly selective in the vapor it removes, and that some of the volatile vapors which give the desired taste and flavor to the tobacco smoke were permitted to pass in large quantities.

Example III A 170-mm. length of 5 d./ f. crimped cellulose acetate filter tow which had 9,000 filaments and weighed approximately 1 gram was spread out to a width of 15 inches. Glyceryl triacetate in the amount of 9 percent by weight of the tow was sprayed uniformly over the surface of the tow. Treated nonactivated carbon granulars (20 X 50 mesh) containing 20 percent sodium acid carbonate on their surfaces were dusted on the thus treated tow from a vibrating pan until 30 percent of the additive, based on the dry weight of the tow, had been added. The tow was then formed into a cylindrical rod and wrapped with paper to form a filter rod with a circumference equal to that of a standard commercial cigarette. The rod was allowed to stand until it became rigid and then was cut into 20-min. segments. The 20-mm. segments or filter elements, which contained approximately 30 mg. of treated carbon, were attached to king-size cigarettes by means of a cellophane tape and the cigarettes smoked with an automatic smoking device. The vapors passing through the filter were collected and analyzed spectrophotometrically for hydrogen cyanide. The amount of hydrogen cyanide found was 35 ,ug. The amount of hydrogen cyanide found by similarly analyzing a king-size cigarette with a plain cellulose acetate filter containing no treated carbon was 225 g. From this it can be seen that the hydrogen cyanide content of the tobacco smoke which passes through a filter containing the salt coated nonactivated carbon additive is reduced by over percent from that which is permitted to pass through a fibrous filter unit containing no such additive.

From the foregoing description it is readily apparent that the coated carbon additive of this invention offers numerous advantages over those previously known. Not only is carbon of the nonactivated type an excellent carrier medium, but it is both inexpensive to produce and can be handled by existing filter forming equipment. Furthermore, the nonactivated carbon does not remove any of the highly volatile vapors which gives the desired flavor to tobacco smoke as would occur if an activated material like activated carbon were used as the carrier medium.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

What is claimed and desired to be secured by United States Letters Patent is:

1. A vapor-permeable rod-shaped element comprising a core of compacted substantially horizontally aligned cellulose acetate filaments contained in a close-fitting wrapper, said filaments containing as a tar and hydrogen cyanide removing additive 10 to 30 percent by weight of said element of nonactivated carbon granules coated with 5 20 to 40 percent by weight of a water-soluble inorganic salt selected from the group consisting of sodium carbonate, potassium carbonate, sodium phosphite, potassium phosphite, sodium phosphate, potassium phosphate, so-

dium silicate, and potassium silicate.

2. A tow adapted for being formed into a tobacco smoke filter comprising a continuous cellulose acetate carrier medium having as an additive thereon nonactivated carbon particles coated with at least one Watersoluble inorganic salt selected from the group consisting of sodium carbonate, potassium carbonate, sodium phosphite, potassium phosphite, sodium phosphate, potassium phosphate, sodium silicate, and potassium silicate.

References Cited UNITED STATES PATENTS 2,172,946 9/1935 Sutter 131265 2,815,760 10/1957 Schrens et a1 131262 X 8/1963 Seligman et al. 131266 4/1959 Tovey 131266 5/1966 Keith et a1. 131-10.9 X 10/1967 Lloyd 131266 5/1967 Hughes et a1. 13l-267 9/1958 Spaulding et a1. 256-446 2/1968 Avedekian 1319 X FOREIGN PATENTS 10/ 1930 Great Britain. 11/ 1956 Great Britain.

US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,426,763 February 11, 1969 Cephas H. Sloan et a1.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 70, after "element" insert useable as a tobacco smoke filter Signed and sealed this 31st day of March 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer WILLIAM E. SCHUYLER, JR.