US2916038A - Tobacco smoke filter - Google Patents

Description

Dec. 8, 1959 W WADE;

TOBACCO SMOKE FILTER Filed Feb. 23, 1954 United States Patent TOBACCO sMoKE FILTER Worth Wade, Rosemont, Pa., assignor to American AViscose Corporation, Philadelphia, Pa., a ycorporation of Delaware Alppiication February 23,1954, Serial No. 411,698

Claims. (Cl. ISI-10) This invention relates in general toY tobacco smoke filters and in particular toa cigarette having a smoke filter incorporated therein and includes correlated improvements in the process of making such filters and in the articles so produced.

Tobacco smoke is made up of a mixture of gaseous compounds and finely divided solids and comprises tar, phenol, acetic acid, acrolein, carbon dioxide, water vapor and sol-id dust particles derived from the disintegration of the tobacco and the paper. Most of the substances contained in tobacco smoke are in the vapor state and are not removed from the smoke by prior filtersthat depend entirely on physical structure for filtration efficiency. Moreover, in prior filters of wood fiber, rayon, cotton, cellulose sponge and the like, theparticles of the smoke are largely deposited on the surface of the filter and soon clog up the surface and increase the draw required -to pull smoke therethrough.

According to the present invention, there is provided a tobacco smoke filter in the form of a mass of organic plastic fibers carrying a substantially permanent electric charge, and preferably in the form of organic fiber elcctrets. The present filter is also characterized by the fact that the fibers which make up the filter mass are not of substantially uniform diameter but, on the contrary, com-prise fibers whose diameters vary Widely over a substantial range of between 10 microns to 0.25 micron, and each individual fiber varies in diameter along itsl length. In the manufacture `of organic plastic fibers in the rayon industry, in which the plastic mass is extruded through a spinneret, the resulting filaments have substantially the same diameters throughout their lengths and the lvariation in the diameter between fibers is only a fraction of the total diameter of either of them. In contrast to these fibers, the present invention utilizes organic fibers in which the variation in the fiber diameter is more than twofold throughout the mass and each fiber tapers substantially at its ends. In a preferred embodiment, the filter comprises at least some fibers which are thermoplastic and thefilter may be heat-treated to bond the thermoplastic fibers to each other or to the other fibers at their points of contact. The filter may comprise an unshaped mass of looserfibers or a shaped mass, the shape being preferably fixed by thermally bonding the thermoplastic fibers on the surface of the filter. It has been found that the variation in the fiber diameter causes the present filter to be effective in depth and not to produce the majority of the deposition at the initial exposed surface of the filter mass.

The variable diameter bers employed in the tobacco smoke filter of the present invention may be produced according to the process disclosed in the copending application of Derek E'. Till and Carl R. Smallman Serial No. 400,252 filed December 24, 1953, now Patent No. 2,810,426, in which an organic plastic material is sprayed from a solution or molten mass into the form of fibers, the spraying taking place in a charged field so that a charge is induced on the fibers during their "ice formation. It would appear that the fibers -so produced actually form miniature fiberelectrets but, in anycase, the mass of fibers so produced is characterizedI by having a strong and substantially permanent electric charge'.4 It is possible by this process to induce upon the fibers either a positive or negative charge but the efiiciency of the filter as a tobacco smoke filter appears to ber substantially independent of the nature of the charge. The reason for this appears to be that the tobacco smoke'particles haver a charge induced upon them as they pass through the filter which is opposite to the charge on the fibers and the particles are then caused to be attracted to the-surface of the bers.

The organic fiber electrets may be formed' from natural or synthetic resins as a class, such as vinyl resins, acrylic resins, polyamide resins, polyethylene resins and the like and from organic fiber-forming cellulose derivatives' as a class such, for example, ascellulose esters, cellulose ethers and cellulose ester-ethers and compatible mixtures of resins and cellulose derivatives.

The present filter may be formed in wholev of the organicv fiber electrets or of a mixture of such electret fibers with non-electret fibers such, for example, as natural or synthetic fibers of any kind. For example, there may be mixed. with the charged fibers such natural` cellulose fibers as are derived from Wood, straw, sisal, hemp and the like,: and regenerated cellulose fibers formed by extrusion of viscose, cuprammonia and solutions of' cellulose in itsv solvents, also protein fibers formed `fromgelatin, casein, zein, and peanut proteins, and mixtures of such classes of fibers. The non-electret fibers may' also comprise mineral fibers such as asbestos, glass and rock wool, but in this embodiment it is advisable that the filter `mass be heat-treated tol bond the thermoplastic organic fibers to the mineral fibers to prevent their escape in the smoke stream: during use. Y

The tobacco smoke filter of the present invention may be used in any tobacco product such as` cigarettes, cigars or in a holder for a cigarette or cigar or in a tobacco pipe stem or in so-called Water pipe smoking apparatus. Also, the filter maybe formed to fit into a refllablefilter holder for use in any smoking article.V

Fora more complete understanding of the nature and objectives of the present invention, referenceshould be had to the accompanying drawing in which Figure l'is a perspective view of one embodiment of the tobacco smoke filter of the invention.

Figure 2 is a representation of a mass of random-sized fibers utilized in the filter of the invention.

Figure 3 is a perspective view illustrating one method of forming the filter shown in Figure l.

Figure 4 is a perspective view of la second method of forming the filter illustratedin Figure l.

Figure 5 is a perspective View ofthe second embodiment of the filter.

Figure 6 is a perspective 'View of a cigarette incorporating the filter in accordance with the lpresent invention.

Referring to Figure l, the present filter comprises, .in its preferred embodiment, a shaped cylindrical-mass 10 of organic fibers 11, carrying an electric charge, the fibers being preferably in random distributionand varying in diameter and length.

Referring to Figure 2, it will be noted that the fibers used in the filter are characterized by the fact that each fiber varies in diameter over a substantial range along its length and with respect to each other. In' the same mass, some of the fibers such as. 11a are of, very large diameter while others such as 11b are of extremely fine diameter. It should also be noted that the individual fiber such as fiber 11C varies in diameter throughout its length and particularly that the ends of the fiber have a pronounced and elongated taper. Thus these fibers differ K 3.. in'their non-uniformity articial fibers which are spinnerets.

of diameter and length from produced by extrusion from The lter Yofitheiinverition ,may b e produced 'in a number of ways, vfor, example by forming the Variablediameter fibers into a web 12 as shown in Figure 3 and i rolling this vweb upon itself to form a cylindrical roll 13. To maintain the cylindrical shape, the roll 13 `may be subjected to heat suicient to cause a substantial number Aof the thermoplastic fibers, preferably those in the surface layers, to bond to 'each other` at their points of contact. Alternatively, there may` be applied yto the surfacev of the roll` a binder, such as a solution ofa resin, cellulose 1 derivative, glue, gelatin, casein, water-soluble cellulose ether or other plastic or adhesive material, to bond the surface fibers. Thereafter, the roll may lbe cut transversely into individual iilter sections as desired.

In Figure 4there is shown another method of forming the cylindrical shape filter `mass in which a web 14 comprising the non-uniform diameter fibers is gathered upon itself by folding, rolling, or twisting to form a cylindrical mass 15 whichis drawn through the central hole of a die 16 having a heating element such -as the electric heating coil 20. In passing through the die, the ibrous mass is` compacted and at least the surface iibers are heated suiiiciently to cause them to fuse together at their points of contact which iixes the cylindrical shape. Thereafter, the cylindrical mass 15 may be cut transversely into ilter sections.

Another method of fixing the shape is shown in Figure 5in which a loose mass of iibers 21 carrying. a charge is enclosed in a collar or cylindrical cover 17 formed of a sheet material such as paper, metal foil, cellophane and the like. lIn the production of the `iilter unit as illustrated in Figure 5,y the assembled unit may be subjected to a suitable treatment such as heat treatment so as to bond together a substantial number of bers at their points of contact and to bond the iibers on the peripheral surface to the. collar thereby preventing displacement of the fibers from the collar. Replaceable filter units ofv this type may be utilized in holders for cigarettes and cigars, pipe stems and any other smoking article.

In Figure 6, there Vis shown the cigarette of the invention comprising a paper wrapper 18 closing the granulated tobacco 19 and having disposed at one end the filter 10 of this invention. The iilter unit 10 may be a mass of tibers, or it may consist of a preformedbody i Vment such as a heat treatment so as to bond the surface iibers to the Wrapper 18. Where the iilter unit has not been previously-processed to bond the fibers together, the heat treatment may be suiiicient also to bond together a substantial number of iibers. The iibers are thereby bonded into a coherent porous mass and the mass bonded to the wrapper so as to 'securely tix the unit within the clgarette.

I claim: I

1. A tobacco; smoke filter formed of a mass of randomly arranged organic fibers each of which has more than a two-fold variation in diameter, terminates in elongated tapered ends and carries a substantial permanent electric charge.

2. A tobacco smoke filter as defined in claim 1 wherein the maximum diameter of the bers is between 0.25 micron and 10 microns.

3. A tobacco smoke filter formed of a mass of randomly arranged thermoplastic fibers each of which has a maximum diameter between 0.25 micronand 10 microns, has more than a two-fold variation in diameter, terminates in elongated tapered ends and carries a substantially permanent electric charge, a substantial number of the fibers being bondedV together at their points of contact.

4. As an article of manufacture, a tobacco smoke iilter comprising a collar and a ilter body within the collar formed of a mass of randomly arranged organic fibers each of which has a maximum diameter between 0.25 micron and 10 microns, has more than a two-fold variation in diameter, terminates in elongated tapered ends and carries a substantially permanent electric charge.

5. An article ofrmanufac'ture as defined in claim 4 wherein the iibers are thermoplastic'iibers and are bonded together at their points of contact.

6. An article of manufacture as definedin claim 4 wherein the iibers are thermoplastic iibers and the fibers in contact with the collar are bonded to the collar.y

7. As an article of manufacture, a cigarette comprising a tobacco smoke filter formed of a mass of randomly arranged organic bers eachrof which has a maX- imurn diameter between 0.25 micron and 10 microns, has more than a two-fold variation in diameter, terminates in elongated tapered ends and carries a substantially permanent electric charge.

8. An article of manufacture as deiined in claim 7 wherein the libers are formed of a synthetic resin.

9. An article of manufacture as definedin claim 7` wherein the fibers are thermoplastic synthetic resin iibers and a substantial number of the iibers are bonded together at their pointsof contact.

10. As an article of manufacture, a cigarette having at one end a cylindrical smoke lter, said filter having an outer casing formed of a non-thermoplastic liber and a smoke filter within said casing formed of a mass of randomly arranged organic iibers each of which has a maximum diameter between 0.25 micron and 10 microns, has more' than a two-fold variation in diameter, terminates in elongated tapered ends and carries a substantially permanent electric charge, a substantial number of said tibers being bonded together at their points of contact and the` fibers in contact with said casing being bonded y thereto.

d References Cited in the file of this patent UNITED STATES PATENTS Y 2,126,422 Tarrant Aug. 9, 1938 2,159,121 Alley May 23, 1939 2,161,766 f Rugeley et al. June 6, 1939 2,219,491 'Podmore Oct. 29, 1940 2,336,745 Manning ,Dec. 14, 1943 2,355,822 Rugeley Aug. 15, 1944 2,411,660 Manning Nov. 26, 1946 2,459,804 Francis Jan. 25, 1949 2,464,301 Francis Mar. 15, 1949 2,476,582 Browne July 19, 1949 V2,483,406 Francis Oct. 4, 1949 2,502,545 Wellborn Apr. 4, 1950 2,520,124 Chaney Aug. 29, 1950 2,688,380 MacHenry Sept. 7, 1954 FOREIGN PATENTS 121,414 Australia 'May 16, 1946 Great Britain June 13, 1929

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