US3019794A - Supported protein cigarette filters - Google Patents

Description

Feb. 6, 1962 R. A. WHITMORE \ETAL 3,019,794

SUPPORTED PROTEIN CIGARETTE FILTERS Filed Nov. 25. 1959 Inventors United States Patent SUPPORTED PROTEIN CIGARETTE FILTERS Rehert A. Whitmore, Beverly, and Shu-Tung Tu, Ipswich,

Mass, assignors to United Shoe Machinery Corporation, Flemington, Ni, a corporation of New Jersey Filed Nov. 25, 1959, SenNo. 855,399 2 Claims. (Cl. 131208) This invention relates to a smoke filter and filtering process, and to a method for preparing the medium used for the filter mass. It is well established that tobacco smoke contains ingredients harmful to living tissue, and in order to remove these ingredients during the process of smoking cigarettes or other smoking articles, numerous filtering systems have been proposed and utilized. Tobacco smoke is an aerosol, that is a suspension in air and combustion gases of spherical semisolid particles of tar, nicotine and. other materials generated by the combustion of the tobacco. Conventional smoke filters contain a mass of material which is generally .of cellulosic nature, ranging from tobacco itself to cellulosic material chemically or physically treated to be more receptive to the smoke particles. Generally, a large surface area is required, necessitating a dense filter mass. It has been considered that the density of such a filtering mass, and that the smallness of the intervening spaces within the mass blocked and trapped smoke particles much in the fashion of a sieve to reducethe quantity of all suspended material drawn through the filter. Often these filters are so dense that in an attempt to remove a high portion of harmful components, they offer substantial resistance to the passage of all gases and vapors.

To make such filter systems more efficient treated fibers have been used. have not made the filtering system sufficiently selective in removing undesired components; There has been rather an indiscriminate removal of all components of the smoke, including the important contributors to flavor and taste, as well as the spotty removal of less harmful particles. The net result of this filtering action is often a thin, relatively flavorless smoke, and frequently a hard drawing smoking article. The substances which do pass the filter may still contain a high percentage of the harmful ingredients which are free to become attached to the living tissue of the body in an irritating if not harmful combination.

In an earlier application, Serial No. 707,736, filed January 8, 1958, in the name of Robert A. Whitmore, one of the present inventors, there is disclosed a filter comprising a mass of collagenous fiber material which by reason of its chemical and physico-chemical character was found to be particularly effective in removing the harmful smoke components. The resultant smoke was low in tars and nicotine with a high taste quality.

In general, the treating agents ICE The invention will be describedfurther in connection 7 form ofcoating deposited thereon; and

FIG. 4 is a diagrammatic cross section at the same enlargement of one filament of another form of filter medium showing attached thereto short fibers as used in one aspect of the invention.

Gelatine, like collagen, is a material having a high basic amino-content, and when moist has an afiinity for tannins and aldehydes. Tobacco smoke impinging on a gelatine surface gives up moisture to the gelatine. The moist gelatine surface becomes active for combination of its protein with those components of the smoke including tannins, aldehydes, and others which are irritants for, and would otherwise be free to become attached to, the protein of the living tissue of the body. On the other hand, the volatile flavor components, believed to be essential oils insoluble in water or otherwise unattracted to It is an object of the present invention to provide a I free-drawing, inexpensive, easily prepared smoke filter and filtering process, which by reason of the chemical and physical character of the filter medium employed is selective in removing the harmful protein-attracted components in tobacco smoke.

We have found that the tar and nicotine content of tobacco smoke may be markedly reduced by a filter in which the smoke is caused to impinge on a gelatine surface. The gelatine is preferably carried by a support, suitably a fibrous mass providing passagewaysfor the smoke, and is coated or deposited thereon in a manner providing a high ratio of surface area to mass of the gelatine. The high ratio of surface area to mass may be achieved by special deposition or coating procedure or by the inclusion in the gelatine material to be coated face area.

the moist gelatine, remain in the smoke. However, although-it is believed that the gelatine acts in the above manner to remove certain components from tobacco smoke, it is to be understood that the gelatine surface filter gives superior results and patentability is not dependent upon the correctness of the theory advanced.

Gelatine being a soluble protein has no inherent form, and, for use in the treatment of tobacco smoke, must be disposed in a way to expose a surface to the smoke.

It is possible to prepare pure gelatine in fibrous form. A hot solution of gelatine may be forced through the jet of a spray gun and collected in (dry) air on a screen as hardened fibers. Or the gelatine solution may be spun through a spinneret into a coagulating bath, such as alcohol, and the spun fibers laid down parallel, as are fibers of cellulose acetate. However, these fibers are difficult to assemble into filter plugs, and with absorption of moisture, as from tobacco smoke, tend to shrink to a small mass providing poor contact areas.

The gelatine is preferably sustained on a supporting mass which supports the gelatine in a form providing a high specific area stabilized against shrinking and allowing for free passage of the smoke. This supporting mass for the gelatine deposit may be any one of a number of inert materials which provides a large surface area for impingement of the smoke particles, and which provides surfaces permitting adherence of the gelatine deposit.

Materials, preferably fibrous, which may be used include cotton, paper, viscose, cellulose acetate, various synthetic fiber materials, collagen, fibers or asbestos arranged in aggregates to provide free channels for the passage of the smoke. Fibers with a crimp provide. a more effective surface area than those uncrimped. A preferred supporting fibrous material is a crimped tow of continuous filament cellulose acetate of between 3 and 17 denier. v

A cigarette filter plug 2 illustrating one form of the present invention, as shown in FIGS. 1 and 2 of the accompanying drawings, comprises an outer wrapper 4 for the mouthpiece of the filter plug 2, a wrapper 6 for the cylinder of tobacco 8, which extends the length of the cigarette, and a wrapper 10 to contain the filter medium 12. The filter medium 12 comprises a mass of filaments or fibers 14 providing a large surface area as a supporting means for a deposit of gelatine 16, and is arranged to 3 provide numerous passageways for the easy drawing of the smoke.

The gelatine is a commercial, preferably, alkalineprocess product with an isoelectric point between 4 and 5,

and is obtainable commercially without additional purification, but other types of gelatine may be used.

For application to the fibrous supporting material a gelatine solution is made up to a concentration of from 2% to by weight of gelatine in Water based on the weight of the solution. This solution is preferably adjusted to a pH of from 2.5 to 8 by addition of acid or alkali, suit-ably with buffering. For acidifying, hydrochloric, citric, or phosphoric acids may be used, the latter two being preferred since the hydrochloric acid imparts an undesirable taste to the cigarette. It has been observed that gelatine in the desired pH range of 2.5 to 8 is more selective in taking up tars. At a higher pH, the smoke flavor is reduced, while at the preferred medium range of pH it is observed that a greater amount of undesirable smoke components is removed and flavor is more pronounced.

Various methods may be used for applying the gelatine to the fibers. For example, a continuous cellulose acetate tow may be spread apart and fiuffed to expose the fiber surfaces, and the warm gelatine solution, preferably at a temperature between about 80 and 90 C., sprayed on both sides of the tow. The Water content of the sprayed gelatine solution is evaporated, and the gelatine deposited on the fibers. Preferably, the deposit of gelatine when dry will constitute between 1% to 35% of the weight of the fibers. The sprayed gelatine covers the tow with fine droplets and bubbles of gelatine which are retained in these forms on drying. It appears that the gelatine also serves as hinder or matrix for the supporting fiber mass, giving the filter plug a porous but firm character, allowing the fabrication of the fibers into filter plugs. The addition to the gelatine solution of a small percentage of a plasticizer, such as glycerin or sorbitol, or an additional spraying operation with a solution containing the plasticizer alone, further enhances the firm character of th dried fiber bundles.

An alternative procedure is to dip the fibrous material in the solution of warm gelatine, drain it, ship it between the cylinders to remove excess solution, wrap it in paper the moist condition and dry it over a hot metal surface. The spraying method of depositing the gelatine solution on the fibers is perhaps the most economical method for preparing the filter medium. Machinery suitable for this purpose already exists in that used for spraying the conventional cellulose acetate tow medium with a solution of plasticizer. Also a more uniformly coated medium may be obtained by this method.

in a preferred form of the invention, a substantial amount of a water soluble salt is included in the gelatine solution to be sprayed. When this gelatine-salt solution is sprayed on the supporting fibers and dried, the salt efiioresces and forms salt crystals 18 which disrupt the continuity of the gelatine'deposit 16 on the fibers 14, as shown in FIG. 3. The gelatine-salt crystal deposit has a uniform textured, rough surface which is more receptive to taking up suspended matter from the tobacco smoke than is the smooth gelatine coating.

Suitable salts are those which are relatively water soluble and crystallizable, such as sodium chloride, ammonium sulfate, or sodium or ammonium phosphates or citrates. Ordinarily, sodium chloride will be used because of its cheapness and availability. Good results are obtained where sodium chloride is mixed with dry gelatine in an amount equal to 50% of the weight of the dry gelatine before forming the aqueous solution. Alternatively, there may be added an amount of the salt equal to about 10% by volume on the volume of the gelatine solution. Such a solution when sprayed dries on the fibrous material as a frosty, completely opaque coating.

A lower salt concentration, for example in the order of 25% by weight based on the weight of the gelatine, leaves only a slightly opaque coating, whereas a higher concentration, that is, a weight of salt equal to the weight of the gelatine, leaves a very opaque, coarse textured coating which may flake off. However, this flaking may be eliminated by spraying the dried coating with a humectant.

According to another modification of the invention, a 10% suspension of a particulate filler such as short wood cellulose fiber, ground wood, starch granules, phenolformaldehyde micro-balloons, mineral granules and so on may be added to a warm solution of gelatine, and the filler particles dispersed evenly throughout the warm solution. The particle-containingsuspension is sprayed on the supporting fiber as shown in FIG. 4, and coats the supporting fibers Us with a deposit of gelatine l6 and short fibers 2d of wood cellulose held by the gelatine on the supporting fibers at randomly disposed angles. The short fibers 20, themselves also have a coating of gelatine 22. Supporting fibers and short fibers thus coated present a very large surface area for the physical trapping of smoke particles, as well as a large number of sites actively receptive to gaseous elements in the smoke. The gelatine, as well as holding the short fibers to the supporting fibers of the tow, holds this aggregate in -a firm bundle.

While a small quantity of gelatine per se may trap a high percentage of volatile ingredients, difierences are observed in the taste of the smoke under various conditions. The amount of gelatine used is important, as well as the specific agent used to adjust the pH of the gelatine solution, and the inclusion of the salt or particulate filler in the solution. The inclusion of and kinds of humectants and plasticizers must also be noted as affecting flavor. The taste is also affected depending on what is used for the substrate on which the gelatine is deposited, and how it is deposited, such as dip coating or spraying of fibers. A selection of these variable conditions alone or in combination depends on the taste and flavor desired.

The following examples are given for a better understanding of the invention and are not to be construed as limitations of the use of gelatine as a filter medium for tobacco smoke.

Example 1 A 20% by weight solution of gelatine in water was prepared and its pH adjusted to about 3. The solution was heated to a temperature between 80 and 90 C. It was then sprayed on a tow of continuous filament of 5 denier cellulose acetate having a total denier to 70,000 which has been opened to a width of from 14 to 18 inches and flufied to expose the individual fibers. Both sides'of the relatively fiat array of opened fibers were sprayed in a quantity to provide after drying a gelatine content of 5% based on the weight of the fibers. Moisture was evaporated from the sprayed-on material leav- 1 on the surface of the fibers.

to cylindrical shape and cut into filter plugs approxiing the gelatine deposited as dried beads and bubbles The tow was then brought mately 17 mm. in length, 24.7 mm. in'circumference and weighing approximately 0.222 mgm.

In the ensuing comparison with conventional filter plugs of the same brand of cigarette, a darker coloration from tars and other undesirable components was observed while an excellent taste and flavor was retained.

' Example 2 A solution was prepared as in Example 1 of 20% by weight of gelatine, but in this instance an amount of sodium chloride equal to 50% by weight of the dry gelatine was mixed with the dry gelatine before dissolving. The gelatine salt solution was sprayed on the cellulose acetate tow, and the moisture evaporated from it. Upon examination, the coating on the tow was a chalky, com-.

pletely opaque layer comprised of fine crystals of salt and gelatine. When tested as a filter media for tobacco smoke it was found to have a comparatively high retentive capacity for the tars contained in the smoke passing through it.

Example 3 A solution of 2% by weight of gelatine in water was prepared and adjusted to a pH of 3, and 10% by weight of Solka Floc which is a purified short-fiber wood cellulose flock sold by the Brown Co., was added with sufiicient stirring to disperse the short fibers evenly throughout the solution. The fiber suspension in gelatine solution was warmed to 80-90 C. and sprayed on a denier cellulose tow of 50,000 denier, prepared as in Example 1. The moisture was evaporated from the treated tow and upon examination the gelatine coated short fibers adhered at random angles to the tow fibers which were themselves intermittently coated with gelatine. The fiber-gelatine coated tow was then brought to cylindrical shape with a circumference of approximately 25 mm. and cut into filter plugs approximately 17 mm. in length. Upon comparison with the commercial filter of the same brand of cigarette, the tested fibergelatine coated tow filter plug was found to remove undesirable harmful components, while the taste and flavor were retained.

Having thus described our invention what we claim as new and desire to secure by Letters Patent of the United States is:

1. A tobacco smoke filtering system for removing undesired components from tobacco smoke, said filtering system comprising a passageway for said smoke, a mass of supporting fibers disposed substantially to fill a crosssection of said passageway and arranged to define paths for said tobacco smoke through said mass, and a coating on said fibers comprising a mixture of gelatine at a pH between 2.5 and 8.0 and between 10% and by weight of a water soluble salt based on the weight of said gelatine, said salt being in the form of crystals formed in situ in said gelatine on the surfaces of fibers of said mass, said salt crystals interrupting the continuous surface of said gelatine, to provide a high ratio of surface area to mass of said gelatine and salt mixture.

2. A tobacco smoke filtering system as in claim 1, in which the gelatine deposited on the surface of said supporting fibers is at least 1% by weight of the weight of said fibers.

References Cited in the file of this patent UNITED STATES PATENTS 2,774,680 Hackney et a1 Dec. 18, 1956 2,805,671 Hackney et a1 Sept. 10, 1957 2,883,990 Nichols Apr. 28, 1959 2,908,280 Touey Oct. 13, 1959 2,928,399 Touey Mar. 15, 1960 FOREIGN PATENTS 329,353 Switzerland June 14, 1958

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