US2881771A - Cigarette filters - Google Patents

Description

April 14, 1959 G. P. TOUEY 2,881,771 CIGARETTE FILTERS Filed Dec. 20, 1954 FIG.]

HYDROPH/LIC CELLULOSE ETHER PARTICLES Geo eR Tone 1y INVENTOR. y

019M jh ATTORNEXS' United States Patent O CIGARETTE FILTERS George P. Touey, Kingsport, Tenn., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Application December 20, 1954, Serial No. 476,549

6 Claims. (Cl. 131-208) The present invention relates to tobacco smoke filtering material and elements thereof suitable for use in cigarettes, pipes, cigarette holders, and cigar holders. More particularly, the invention is concerned with an improvement in filters of the general type disclosed in Crawford and Stevens, U.S. Patents'Nos. 2,794,239 and 2,794,480 granted June 4, 1957.

In the aforementioned patents, newly discovered advantages of a certain type of fibrous tobacco smoke filter are discussed. The filter is prepared from a specially conditioned tow of crimped synthetically spun continuous filaments and comprises a structurally unitary rod-like mass of fibers and a wrapper encircling the mass, each fiber of the mass being substantially coextensive therewith, the fibers as a whole being in substantial alignment longitudinally of the mass but substantially each of the individual fibers having a plurality of short portions thereof crimped into diverging and converging relationship to the main fiber axis, a plurality of the fibers having surface solvation bonds to contiguous fibers at random points of contact. Very good results have been obtained in the use of such filters for the removal of nicotine and tars from tobacco smoke, especially in view of the fact that the filters supply other requirements, such as unitary nature, rigidity, and resiliency, which are equally as necessary to the success of a tobacco smoke filter.

These filters furthermore have a marked processing advantage over other filters known in the art. However, since the fibers in such filters are in general parallel to each other, some channeling of the smoke through the filter may be possible. In other words, while a desirable amount of interference with the smooth flow of combustion products through the channels is provided by the random bonds between adjacent fibers, by the incompleteness of fiber orientation, and by the short fiber portions which are crimped into diverging and converging relationship to the main fiber axis, yet a limited amount of the smoke passing through the filter apparently travels through channels in a smooth, non-turbulent and undisturbed manner and can thereby escape a necessary minimum contact with the fiber surfaces. Experimental investigations have shown that any attempt to reduce the size or shape of detrimentally smooth smoke channels through the filters by an increase in filter density (either by means of greater compaction or by means of the use of finer fibers) generally also results in an intolerable increase in pressure drop through the filter.

In my prior US. patent applications Serial No. 413,950, filed March 3, 1954, Serial No. 432,931, filed May 27, 1954, Serial No. 432,932, filed May 27, 1954, Serial No. 433,287, filed May 28, 1954, and Serial No. 439,123, filed June 24, 1954, it has been shown that the filtering efiiciency of filters of the type described above may be substantially increased without the expected equivalent in crease in pressure drop through the filter by preparing the filter with a deposit of certain finely divided solids dispersed uniformly throughout the smoke channels formed by the spacing of adjacent fibers. As disclosed in my prior applications, certain classes of finely divided solids 2,881,77 l Patented Apr. 14, 1959 have been found to be unusually well suited for this purpose. 7

I now have discovered a new class of chemical compounds which provide finely divided solids of unusual efiiciency for increasing the filtration ability of cigarette filters prepared from a tow of crimped synthetically spun continuous filaments. The capabilities of the new additives are such that their use permits a substantial reduction in the number of filaments which would otherwise be necessary while still providing an improved filtration efiiciency. The present invention has the capacity to afiford substantially greater filtration with relatively little or no increase of pressure drop through the filter.

This invention, therefore, has as one object the production of a novel and more eflicient tobacco smoke filter consisting of a bundle of substantially longitudinally aligned textile fibers infused with finely divided solid powders. Another object is to provide means for increasing the efliciency of a cigarette filter prepared from a textile fiber. A still further object is provision of a filter which is capable of removing nicotine, tars, and other deleterious components of cigarette smoke without causing the smoke to be dry or distasteful. Another object is to increase the efficiency of tobacco smoke filters of the type disclosed in the Crawford and Stevens patents without substantially increasing the pressure drop through the filter. Other objects will be obvious from the present specification and claims.

In accordance with the present invention, fibrous filters contain as a finely divided solid additive a hydrophilic cellulose ether or derivative thereof selected from the group consisting of methyl cellulose, hydroxyethyl cellulose, carboxymethyl and sodium carboxymethyl cellulose. More specifically, the invention resides in a tobacco smoke filtering element comprising a mass of mostly oriented fibers aligned substantially longitudinally of the element, the spacing of groups of adjacent fibers providing minute passages for smoke therethrough, said mass carrying therein 1 to 60% by weight of the mass of finely divided particles of a substance selected from the group consisting of methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and sodium carboxymethyl cellulose, said particles occupying positions in and partially blocking said passages whereby substantially all smoke which passes through the filter is impinged either on the fibers or on the finely divided solid particles.

A preferred embodiment of the invention comprises a new tobacco smoke filtering material of synthetically spun continuous filaments and an element made therefrom, the element comprising a structurally unitary rod-like mass of fibers and a wrapper encircling the mass, each fiber of the mass being substantially coextensive there with, the fibers as a whole being in substantial alignment longitudinally of the mass but substantially each of the individual fibers having a plurality of short portions thereof crimped into diverging and converging relationship to the main fiber axis, a plurality of the fibers having surface solvation bonds to contiguous fibers at random points of contact, the mass carrying substantially uniformly dispersed therein a solid hydroxyethyl cellulose of to 300 mesh particle size in the amount of 1 to 60% by weight of the mass. Most advantageously, the invention comprises a filter of cellulose acetate fibers having surface solvation bonds achieved through the application of a plasticizer spray, the filter carrying uniformly dispersed particles of the cellulose ether additive in the amount of about 10 to 40% by weight of the filter, and carrying plasticizer in the amount of about 8 to 20% by weight of the filter.

Any suitable means known to the art for spreading a powder onto a fibrous surface or through a fibrous mass may be employed in preparing filters of the invention.

Thus, for example, the cellulose ether powder can be blown onto the fibers or it can be applied as a slurry in cold water or in an organic solvent or plasticizer. Another method is to apply the powder to the fibers electrostatically, i.e., to induce a charge on the fibers by friction or other suitable means and then to run the fibers through a chamber containing highly concentrated cellulose ether dust. Still another method for applying the powder is to wet the surface of the fibers with an adhesive or a plasticizer before exposing them to a powder spraying device. Preferably, the powder is continuously applied to an opened and banded moving tow formed as described in, the Crawford and Stevens applications. That is to say, tow from a supply roll is opened to debundlize the filaments and provide a larger and more uniform tow cross. section, and the opened tow is. then thinned in one transverse dimension and in another transverse dimension is spread uniformly to a much larger width of e.g. 7 times its original width, thereby exposing substantially all of the filaments to material, i.e. plasticizer, issuing from a dispenser under which the tow passes. The powder may be added before, simulthis spread tow thus assumed an adhesive attitude at their surfaces due to the addition of the plasticizer, the latter having a solvent action on the fibers. The spread tow then was passed through a dusting chamber where both sides were dusted with a fine powder (200 mesh) of hydroxyethyl cellulose containing an average degree of substitution of 1 hydroxyethyl group for every three anhydroglucose units in the polymer. On leaving the dusting chamber the tow of fibers contained 10% plasticizer and, 25% of hydroxyethyl cellulose (based on the total weight of the fiber combination) adhering to its surface. After this spreading and spraying treatment the towwas pulled back to its original shape of a compact taneously with, or after the plasticizer, preferably with or after.

The cellulose ethers of the invention may vary in content of the ether substitutent carried on the cellulose molecule. That is to say, itis not critical to the operability that the average number of substituent groups per anhydroglucose unit be fixed at any particular value. However, I have found that for the purpose of the invention, the less hydrophilic derivatives do not give the same high order of filtering efi'iciencies as the more hydrophilic derivatives. Therefore, for the most advantageous utilization of the invention there should be a sufiicient number of substituent groups present in the cellulose to render the product water soluble, or at least capable of being highly swollen by water. In the case of hydroxyethylcellulose, the average degree of substitution must be at least 3 hydroxyethyl (CH CH OH) groups for every ten anhydroglucose units. The methylcellulose must have at least 5 methyl (-CH groups for every ten anhydroglucose units and the carboxymethylcellulose must have at least 2 carboxymethyl (CH' COOH) groups for every ten units. In the case of carboxymethylcellulose, it is desirable that the product be used as the sodium salt. However, this is only from an economic standpoint since, in preparing this ether, the sodium salt derivative is due to the presence of the sodium hydroxide.

The reason that a strongly hydrophilic cellulose ether gives such high order of filtering efficiencies is not definitely known. However, it is believed that it is due to an aqueous character of many of the areosol particles in the smoke.

The invention is illustrated in the accompanying drawings in which Fig. 1 represents a magnified view of the interior of a mass of filtering material prepared in accordance with the invention, and

Fig. 2 is a view of a cigarette having attached thereto a tip prepared from a filtering material of the invention.

The invention is further illustrated in the following examples:

EXAMPLE 1HYDROXYETHYL CELLULOSE A partially opened tow of cellulose acetate yarn containing 17,000 fibers of five denier per filament was slowly pulled over a compressed air banding. device as disclosed in the aforementioned Crawford and Stevens patents which spread out the fibers to a width of six inches. While the tow was in this spread condition it was sprayed with a plasticizer consisting of 99 parts dimethoxyethyl phthalate and 1 part water. The fibers of bundle or cord by means of a condensing funnel. The condensed tow was fed into a conventional filter-rod making machine which wrapped it with paper and cut it into filter plugs equal in length and diameter to an 85mm. standard cigarette. The plugs were heated for 1. hour at 80 C. to allow the plasticizer to bond the acetate filters. and powder sufficiently to impart rigidity and firmness to the combination and to prevent the powder from, sifting out of the filter plugs. The plugs were then cut into 13 mm. filter tip lengths and attached by means of adhesive tape to ten 85 mm. standard brand cigarettes. shortened by 13 mm. Ten of these cigarettes were smoked to a total butt length of 35 mm. on a smoking machine similar in design and operation to the smoking machine described by J. A. Harlan and H. R. Hanmer in Industrial and Engineering Chemistry, vol. 28, pp. 83'6839 (1936). The smoke which passed through the cigarettes was collected and analyzed for nicotine and tar content.

Control filters without the addition of hydroxyethyl cellulose powder were also prepared from the same cellulose acetate tow containing the same amount of dimethoxyethyl phthalate plasticizer. These filters were attached to the same brand of standard king size cigarettes, shortened by 13 mm. Ten of these cigarettes were also smoked to a total butt length of 35 mm. by means of the smoking machine. The smoke which passed through the 10 cigarettes was collected and analyzed for nicotine and tar content.

Ten unfiltered king size cigarettes (same brand) which were not shortened by 13 mm. were smoked to a butt length of 35 mm. by means of the smoking machine in order to compare the filtering efiiciency of the filters described above to the filtering efiiciency of the tobacco I which they replaced. The smoke which passed through the ten cigarettes was collected and analyzed for nicotine and tar content.

A second set of control filters without the addition of hydroxyethylcellulose was prepared in a similar manner from a cellulose acetate tow containing 30,000 fibers of five denier per filament. These filters were attached to the same brand of standard king size cigarettes shortened by 13 mm. Ten of these cigarettes were smoked to a total butt length of 35 mm. on the smoking machine.

The results obtained from the four sets of 10 cigarettes each are listed in Table I below, from which it can be seen that the filters containing the combination of acetate fibers and hydroxyethyl cellulose powder reduced the amount of tars by 39% and the amount of nicotine by 44%. While the 30,000 filament filter containing no additive gave a tar reduction of 28% and a nicotine reduction of 24%, the pressure drop of 5.3 inches is not in the tolerable range. The control filter reduced the amount of tars collected by 8% and the amount of nicotine collected by 8%. The increase in pressure drop of the filtered' cigarette due to the addition of the hydroxyethyl cellulose was only 5%.

EXAMPLE 2SODIUM CARBOXY METHYL CELLULOSE The procedures described in Example 1 were repeated using the same tow of, cellulose acetate and the same plasticizer but using a powdered (200 mesh) sodium carboxymethyl cellulose in the dusting chamber. The cellulose ether contained an average degree of substitution of 7 carboxymethyl groups for every 10 anhydroglucose units in the polymer. The tow of fibers prepared in this case had 14% plasticizer and 30% carboxymethyl cellulose powder (based on the total weight) as it left the dusting chamber. The baked plugs were cut into 13 mm. filter tips and attached to the standard king size cigarettes which had been shortened by 13 mm. Ten of these filtered cigarettes were smoked to total butt lengths of 35 mm. on the smoking machine and the smoke which passed through the cigarettes was collected and analyzed for nicotine and tar content. From Table I it will be seen that, relative to the tobacco which it replaced, the sodium carboxymethyl cellulose filter gave a reduction in tar of 33% and a reduction in nicotine of 36%. More important, the filter which contained the powdered hydrophilic cellulose ether additive gave a 27% tar reduction and a 30% nicotine reduction relative to the filtered cigarette containing no finely divided ether.

EXAMPLE 3METHYL CELLULOSE The procedures described in Example 1 were repeated using the same tow of cellulose acetate and the same plasticizer but using a powdered (200 mesh) methyl cellulose in the dusting chamber. The cellulose ether contained an average degree of substitution of 2.3 methyl groups for every anhydroglucose unit in the polymer. The tow of fibers prepared in this case had 13% plasticizer and 32% methyl cellulose powder (based on the total weight) as it left the dusting chamber. The baked plugs were cut into 13 mm. filter tips and attached to 10 standard king size cigarettes which were smoked to a total butt length of 35 mm. on the smoking machine. The smoke which passed through the 10 cigarettes was collected and analyzed for nicotine and tar content.

As will be seen from Table I, the tar and nicotine content of the collected smoke corresponds to a reduction in tar of 36% and a reduction in nicotine of 36%.

Table 1 Mg. Tars Mg. Average Found in Nicotine Type of Filter on Cigarettes Pressure the Smoke Found in Smoked Drop 1 from 10 the Smoke Cigarettes from 10 Cigarettes 1. Unfiltered control 3. 2 163 25 2. 17,000 filament tow with no solid additive 3. 6 150 23 3. 30,000 filament tow with no solidadditive 5. 3 118 19 4. 17,000 filament tow containing hydroxyethyl cellulose (Exampie 1) 3. 8 100 14 5. Containing sodium carboxymethyl cellulose (Example 2). 3. 8 110 16 6. Containing methyl cellulose (Example 3) 3.9 105 16 1 Pressure drop in inches of water at an air flow rate of 17.5 cc./second through the cigarette.

While unusually good results have been obtained with filters prepared from a crimped continuous filament tow of cellulose acetate fibers sprayed with a plasticizer, e.g. dimethoxyethylphthalate or methylphthalylethyglycollate, it will be recognized by those skilled in the art that the usefulness of the invention extends to other fibrous filters, including those prepared from fibers such as for example, those of viscose, cotton, nylon, polyamides and polyesters, particularly where the fibers are in substantial alignment longitudinally of the filter and are coextensive with the body of the filter. While it is preferred to accomplish bonding with a plasticizer which has a solvent action on the composition of the filaments, the invention will be found to have merit also where other types of bonding agents, eg film-forming agents, latex emulsions, and resins are employed with cellulosic or other types of 6 fibers, either plasticized or nonplasticized. Best results generally will be obtained by the use of a strand, e.g. tow of 4000 to 35,000 filaments, of 16 to 3 denier per filament and having 4 to 10 crimps per inch.

I claim:

1. A tobacco smoke filtering element comprising a structurally unitary rod-like mass of cellulose acetate fibers and a wrapper encircling the mass, each fiber of the mass being substantially coextensive therewith, the fibers as a whole being in substantial parallelism longitudinally of the mass but substantially each of the individual fibers having a plurality of short portions thereof crimped into diverging and converging relationship to the main fiber axis, a plurality of the fibers having surface solvation bonds to contiguous fibers at random points of contact, the mass carrying substantially uniformly dispersed therein a solid finely divided substance selected from the group consisting of hydroxyethyl cellulose, methyl cellulose, sodium carboxymethyl cellulose, and carboxymethyl cellulose in the amount of 160% by weight of the mass.

2. A tobacco smoke filtering element as defined in claim 1 wherein the solid finely divided substance is hydroxyethyl cellulose.

3. A tobacco smoke filter comprising a mass of substantially parallel, substantially longitudinally disposed continuous cellulose acetate fibers, a content of plasticizers dispersed on said fibers, and l60% by Weight of l50300 mesh particles of compounds from the group consisting of hydroxyethyl cellulose, methyl cellulose, sodium carboxymethyl cellulose, and carboxyrnethyl cellulose dispersed throughout the fiber mass.

4. The tobacco smoke filter in accordance with claim 3 wherein the plasticizer is from the group consisting of dimethoxyethylphthalate and methylphthalylethylglycollate.

5. A tobacco smoke filter comprising a mass of substantially parallel, substantially longitudinally disposed continuous cellulose acetate fibers made up of a tow having 4,000 to 35,000 filaments of 3-16 denier per filament and having at least 4 crimps per inch, a plasticizer distributed over said fibers, l-60% by weight of fine particles of a compound from the group consisting of hydroxyethyl cellulose, methyl cellulose, sodium carboxymethyl cellulose, and carboxymethyl cellulose dispersed throughout the fiber mass and partially blocking the spaces between the aforesaid substantially parallel fibers.

6. A tobacco smoke filter element comprising a structurally unitary rod-like mass of cellulose acetate fibers and a wrapper encircling the mass of fibers as a whole, the fibers being generally parallel, continuous and co-extensive with the wrapper, a plurality of the fibers having surface solvation bonds to contiguous fibers at random points of contact, said solvation bonds being produced by a content of plasticizers carried on said fibers, and 160% by weight of l50300 mesh particles from the group consisting of hydroxyethyl cellulose, methyl cellulose, sodium carboxymethyl cellulose, and carboxymethyl cellulose dispersed throughout the fiber mass and partially blocking the spaces between the aforesaid substantially parallel fibers.

References Cited in the file of this patent UNITED STATES PATENTS 2,228,383 Berl Jan. 14, 1941 2,325,386 Frank July 27, 1943 2,707,308 Taylor et al. May 3, 1955 2,739,913 Lieser Mar. 27, 1956 2,774,680 Hackney et al. Dec. 18, 1956 2,780,228 Touey Feb. 5, 1957 2,789,563 Taylor et al Apr. 23, 1957 FOREIGN PATENTS 435,168 Great Britain Sept. 16, 1935 665,278 Great Britain Jan. 23, 1952 813,324 France May 31, 1937 1,081,215 France June 9, 1954

Claims (1)

1. A TOBACCO SMOKE FILTERING ELEMENT COMPRISING A STRUCTURALLY UNITARY ROD-LIKE MASS OF CELLULOSE ACETATE FIBERS AND A WRAPPER ENCIRCLING THE MASS, EACH FIBER OF THE MASS BEING SUBSTANTIALLY COEXTENSIVE THEREWITH, THE FIBERS AS A WHOLE BEING IN SUBSTANTIALLY PARALLELISM LONGITUDINALLY THE MASS BUT SUBSTANTIALLY EACH OF THE INDIVIDUAL FIBERS HAVING A PLURALITY OF SHORT PORTIONS THEREOF CRIMPED INTO DIVERGING AND CONVERGING RELATIONSHIP TO THE MAIN FIBER AXIS, A PLURALITY OF THE FIBERS HAVING SURFACES SOLVATION BONDS TO CONTIGUOUS FIBERS AT RANDOM POINTS OF CONTACT, THE MASS CARRYING SUBSTANTIALLY UNIFORMLY DISPERSED THEREIN A SOLID FINELY DIVIDED SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF HYDROXYETHYL CELLULOSE, METHYL CELLULOSE, SODIUM CARBOXYMETHYL CELLULOSE, AND CARBOXYMETHYL CELLULOSE IN THE AMOUNT OF 1-60% BY WEIGHT OF THE MASS.

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